Fe K_alpha line A tool to probe massive binary black holes in Active Galactic Nuclei
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trimAl: a tool for automated alignment trimming in large-scale phylogenetics analyses Salvador Capella-Gutiérrez, Jose M. Silla-Martínez and Toni GabaldónTutorialVersion 1.2trimAl tutorialtrimAl is a tool for the automated trimming of Multiple Sequence Alignments. A format inter-conversion tool, called readAl, is included in the package. You can use the program either in the command line or webserver versions. The command line version is faster and has more possibilities,so it is recommended if you are going to use trimAl extensively.The trimAl webserver included in Phylemon 2.0 provides a friendly user interface and the opportunity to perform many different downstream phylogenetic analyses on your trimmed alignment. This document is a short tutorial that will guide you through the different possibilities of the program.Additional information can be obtained from where a more comprehensive documentation is available.If you use trimAl or readAl please cite our paper:trimAl: a tool for automated alignment trimming in large-scale phylogenetic analyses.Salvador Capella-Gutierrez;Jose M.Silla-Martinez;Toni Gabaldon.Bioinformatics 2009 25: 1972-1973.If you use the online webserver phylemon or phylemon2, please cite also this reference:Phylemon:a suite of web tools for molecular evolution,phylogenetics and phylogenomics.Tárraga J, Medina I, Arbiza L, Huerta-Cepas J, Gabaldón T, Dopazo J, Dopazo H. Nucleic Acids Res. 2007 Jul;35 (Web Server issue):W38-42.1. Program Installation.If you have chosen the trimAl command line version you can download the source code from the Download Section in trimAl's wikipage.For Windows OS users, we have prepared a pre-compiled trimAl version to use in this OS. Once the user has uncompressed the package, the user can find a directory,called trimAl/bin, where trimAl and readAl pre-compiled version can be found.Meanwhile for the OS based on Unix platform, e.g. GNU/Linux or MAC OS X, the user should compile the source code before to use these programs. To compile the source code, you have to change your current directory to trimAl/source and just execute "make".Once you have the trimAl and readAl binaries program, you should check if trimAl is running in appropriate way executing trimal program before starting this tutorial.2. trimAl. Multiple Sequence Alignment dataset.In order to follow this tutorial, we have prepared some examples. These examples have been taken from and you can use the codes from these files to get more information about it in this database.You can find three different directories called Api0000038, Api0000040 and Api0000080 with different files. The directory contains these files:A file .seqs with all the unaligned sequences.A file .tce with the Multiple Sequence Alignment produced by T-Coffee1.A file .msl with the Multiple Sequence Alignment produced by Muscle2.A file .mft with the Multiple Sequence Alignment produced by Mafft3.A file .clw with the Multiple Sequence Alignment produced by Clustalw4.A file .cmp with the different names of the MSAs in the directory. This file would be used by trimAl to get the most consistent MSA among the different alignments.You can use any directory to follow the present tutorial.3. Useful trimAl's features.Among the different trimAl parameters, there are some features that can be useful to interpret your alignment results:-htmlout filename. Use this parameter to have the trimAl output in an html file. In this way you can see the columns/sequences that trimAl maintains in the new alignment in grey color while the columns/sequences that have been deleted from the original alignment are in white color.-colnumbering. This parameter will provide you the relationship between the column numbers in the trimmed and the original alignment.-complementary. This parameter lets the user get the complementary alignment, in other words,when the user uses this parameter trimAl will render the columns/sequences that would be deleted from the original alignment.-w number. The user can change the windows size, by default 1, to take into account the surrounding columns in the trimAl's manual methods. When this parameter is fixed, trimAl take into account number columns to the right and to the left from the current position to compute any value, e.g. gap score, similarity score, etc. If the user wants to change a specific windows size value should use the correspond parameter-gw to change window size applied only a gap score assessments, -sc to change window size applied only to similiraty score calculations or -cw to change window size applied only to consistency part.4. Useful trimAl's/readAl's features.Both programs, trimAl and readAl, share common features related to the MSA conversion. It is possible to change the output format for a given alignment, by default the output format is the same than the input one, you can produce an output in different format with these options: -clustal. Output in CLUSTAL format.-fasta. Output in FASTA format.-nbrf. Output in PIR/NBRF format.-nexus. Output in NEXUS format.-mega. Output in MEGA format.-phylip3.2. Output in Phylip NonInterleaved format.-phylip. Output in Phylip Interleaved format.5. Getting Information from Multiple Sequence Alignment.trimAl computes different scores, such as gap score or similarity score distribution, from a given MSA. In order to obtain this information, we can use different parameters through the command line version.To do this part,we are going to use the MSA called Api0000038.msl.This file is in the Api0000038 directory.$ cd Api0000038$ trimal -in Api0000038.msl -sgt$ trimal -in Api0000038.msl -sgc$ trimal -in Api0000038.msl -sct$ trimal -in Api0000038.msl -scc$ trimal -in Api0000038.msl -sidentYou can redirect the trimAl output to a file. This file can be used in subsequent steps as input of other programs, e.g.gnuplot,,microsoft excel,etc,to do plots of this information.$ trimal -in Api0000038.msl -scc > SimilarityColumnsFor instance, in the lines below you can see how to plot the information generated by trimAl using the GNUPLOT program.$ gnuplotplot 'SimilarityColumns' u 1:2 w lp notitleset yrange [-0.05:1.05]set xrange [-1:1210]set xlabel 'Columns'set ylabel 'Residue Similarity Score'plot 'SimilarityColumns' u 1:2 w lp notitleexitIn this other example you can see the gaps distribution from the alignment. This plot also was generated using GNUPLOT$ trimal -in Api0000038.msl -sgt > gapsDistribution$ gnuplotset xlabel '% Alignment'set ylabel 'Gaps Score'plot 'gapsDistribution' u 7:4 w lp notitleexit6. Using user-defined thresholds.If you do not want to use any of the automated procedures included in trimAl (see sections 7 and 8) you can set your own thresholds to trim your alignment. We will use the parameter -htmlout filename for each example so differences can be visualized. In this example, we will use the Api0000038.msl file from the Api0000038 directory.Firstly, we are going to trim the alignment only using the -gt value which is defined in the [0 - 1] range. In this specific example, those columns that do not achieve a gap score, at least, equal to 0.190, meaning that the fraction of gaps on these columns are smaller than this value, will be deleted from the input alignment.$ trimal -in Api0000038.msl -gt 0.190 -htmlout ex01.htmlYou can see different parts of the alignment in the image below.This figure has been generated from the trimAl's HTML file for the previous example.In this other example, we can see the effect to be more strict with our threshold. An usual consequence of higher stringency is that the trimmed MSA has fewer columns. Be careful so you do not remove too much signal$ trimal -in Api0000038.msl -gt 0.8 -htmlout ex02.htmlTo be on the safe side, you can set a minimal fraction of your alignment to be conserved. In this example,we have reproduced the previous example with the difference that here we required to the program that, at least, conserve the 80% of the columns from the original alignment. This will remove the most gappy 20% of the columns or stop at the gap threshold set.$ trimal -in Api0000038.msl -gt 0.8 -cons 80 -htmlout ex03.htmlSecondly,we are going to introduce other manual threshold-st value.In this case,this threshold,also defined in the[0-1]range,is related to the similarity score.This score measures the similarity value for each column from the alignment using the Mean Distance method, by default we use Blosum62 similarity matrix but you can introduce any other matrix (see the manual). In the example below, we have used a smaller threshold to know its effect over the example.$ trimal -in Api0000038.msl -st 0.003 -htmlout ex04.htmlIn this example, similar to the previous example, we have required to conserve a minimum percentage of the original alignment in a independent way to fixed by the similarity threshold.A given threshold maintains a larger number of columns than the cons threshold, trimAl selects this first one.$ trimal -in Api0000038.msl -st 0.003 -cons 30 -htmlout ex05.htmlThirdly, we are going to see the effect of combining two different thresholds. In this case, trimAl only maintains those columns that achieve or pass both thresholds.$ trimal -in Api0000038.msl -st 0.003 -gt 0.19 -htmlout ex06.htmlFinally, we are going to see the effect of combining two different thresholds with the cons parameter. In this case, if the number of columns that achieve or pass both thresholds is equal or greater than the percentage fixed by cons parameter, trimAl chose these columns. However, if the number of columns that achieve or pass both thresholds is less than the number of columns fixed by cons parameter, trimAl relaxes both to thresholds in order to retrieve those columns that lets to achieve this minimum percentage.$ trimal -in Api0000038.msl -st 0.003 -gt 0.19 -cons 60 -htmlout ex07.html7. Selection of the most consistent alignment.trimAl can select the most consistent alignment when more than one alignment is provided for the same sequences (and in the same order) using the -compareset filename parameter. To do this part, we are going to move to Api0000040 directory, we can find there a file calledApi0000040.cmp listing the alignment paths. Using this file, we execute the instruction below to select the most consistent alignment among the alignment provided$ trimal -compareset Api0000040.cmpAs in previous section, once trimAl has selected the most consistent alignment, we can get information about the alignment selected using the appropriate parameters. For example, we can use the follow instructions to know the consistency value for each column in the alignment or its consistency values distribution$ trimal -compareset Api0000040.cmp -sct$ trimal -compareset Api0000040.cmp -sccAlso, we can trim the selected alignment using a specific threshold related to the consistency value. To do that, we should use the -ct value where the value is a number defined in the [0 - 1] range. This number refers to the average conservation of residue pars in that column with respect to the other alignments.$ trimal -compareset Api0000040.cmp -ct 0.6 -htmlout ex08.htmlOn the same way than the previous section, we can define a minimum percentage of columns that should be conserve in the new alignment. For this purpose, we have to use the cons parameter as we explained before.$ trimal -compareset Api0000040.cmp -ct 0.6 -cons 50 -htmlout ex09.htmlFinally, we can combine different thresholds, in fact, we can use all of them as well as we can define a minimum percentage of columns that should be conserve in the output alignment. In the line below, you can see an example of this situation.$ trimal -compareset Api0000040.cmp -ct 0.6 -cons 50 -gt 0.8 -st 0.01-htmlout ex10.html8. Applying automated methods.One of the most powerful aspects of trimAl is that it provides you with several automated options.This option will automatically select the most appropriate thresholds for your alignment after examining the distribution of various parameters along your alignment. Among the alignment features that trimAl takes into account to compute these optimal cut-off are the gap distribution, the similarity distribution, the identity score, etc.You can find a complete explanation about all of these methods in the trimAl's Publications Section.Here,we provide some examples on how to use these methods.The automated methods, gappyout, strict and strictpus, can be used independently if you are working with one or more than one alignment, in the last case, for the same sequences.In the lines below, you can see how to use the gappyout method in both ways. This method will eliminate the most gappy fraction of the columns from your alignment. For this, we are going to continue using the same directory than the previous section.$ trimal -compareset Api0000040.cmp -gappyout -htmlout ex11.html$ trimal -in Api0000040.mft -gappyout -htmlout ex12.htmlIn this case, we are going to use the same files than in the example before but we have changed the method to trim the alignmnet. Now, we are using strict and strictplus methods. These two methods combine the information on the fraction of gaps in a column and their similarity scores, being strictplus for more stringent than strict method.$ trimal -compareset Api0000040.cmp -strict -htmlout ex13.html$ trimal -in Api0000040.clw -strictplus -htmlout ex14.htmling an heuristic method to decide which is the best automated method for a given MSA.Finally, we implemented an heuristic method to decide which is the best automated method to trim a given alignment. The heuristic method takes into account alignment features such as the number of sequences in the alignment as well as some measures about the identity score among the sequences in the alignment or among the best pairwise sequences in that MSA. According to these characteristics trimAl will decide upon one of the two automated methods (gappyout or strictplus).To illustrate how to use this method, we provide a couple of example using the same directory than the section before. First, we used trimAl to selecte the most consistent alignment and then we trimmed that alignmnet using our heuristic method.$ trimal -compareset Api0000040.cmp -automated1 -htmlout ex15.htmlThen, we trim a single MSA using the previously mentioned method.$ trimal -in Api0000040.msl -automated1 -htmlout ex16.html10. Getting more information.We hope that this short introduction to trimAl's features has been useful to you.We advise you to visit periodically the trimAl's wikipage()where you could get the latest news about the program as well as more information, examples, etc, about trimAl's package. You can also subscribe to the mailing list if you want to be updated in new trimAl developing.11. References.1.T-Coffee: A novel method for fast and accurate multiple sequence alignment.Notredame C, Higgins DG, Heringa J. J Mol Biol. 2000 Sep 8;302(1):205-17.2.MUSCLE:multiple sequence alignment with high accuracy and highthroughput. Edgar RC.Nucleic Acids Res. 2004 Mar 19;32(5):1792-7.3.MAFFT: a novel method for rapid multiple sequence alignment based on fastFourier transform. Katoh K, Misawa K, Kuma K, Miyata T. Nucleic Acids Res. 2002 Jul 15;30(14):3059-66.4.CLUSTAL W:improving the sensitivity of progressive multiple sequencealignment through sequence weighting,position-specific gap penalties and weight matrix choice. Thompson JD, Higgins DG, Gibson TJ. Nucleic Acids Res. 1994 Nov 11;22(22):4673-80.。
关于中国天眼的英文作文英文回答:The Five-hundred-meter Aperture Spherical Telescope (FAST), also known as China's "Eye of the Sky," is a colossal astronomical marvel that has revolutionized the study of the cosmos. Situated in a remote karst depression in Pingtang County, Guizhou Province, FAST is the world's largest and most sensitive radio telescope, surpassing the Arecibo Observatory in Puerto Rico.With a massive dish measuring an impressive 500 meters in diameter, FAST boasts an enormous collecting area that gives it unparalleled sensitivity and resolving power. Its design is based on a novel concept known as the "active surface," where the entire dish surface is adjustable, enabling it to focus on specific regions of the sky with high precision.FAST's construction, spanning over a decade, was atestament to China's technological prowess and scientific ambitions. The telescope began scientific operations in September 2016 and has since made numerous groundbreaking discoveries. Among its most notable contributions are the detection of pulsars, the study of interstellar gas, and the investigation of extragalactic objects.One of FAST's most significant achievements is its discovery of an enormous number of millisecond pulsars, rapidly rotating neutron stars that emit precise pulses of radio waves. These pulsars serve as invaluable probes for studying the evolution of binary systems, testing theories of gravity, and exploring the enigmatic nature of dark matter.FAST has also played a crucial role in mapping the distribution of interstellar gas, the raw material from which stars form. By observing the faint hydrogen radiation emitted by these gas clouds, astronomers have gained insights into the formation and evolution of galaxies, including our own Milky Way.Moreover, FAST has extended our astronomical reach beyond our galaxy, enabling the detection and characterization of extragalactic objects. Its sharp resolution has allowed astronomers to probe the structure and dynamics of distant galaxies, unveil the nature ofblack holes, and search for signs of extraterrestrial life.The scientific community worldwide has embraced FAST as a valuable asset, providing access to this cutting-edge instrument through open calls for observing proposals. Researchers from various countries have utilized FAST's capabilities to pursue transformative research projects, leading to advancements in our understanding of the universe.中文回答:中国天眼又称“天眼”,坐落在贵州平塘县的一个喀斯特洼地,是世界上最大、最灵敏的射电望远镜,超过了波多黎各的阿雷西博天文台。
May 21, 2018: Technicians ready the Queqiao relay satellite for launch at the Xichang Satellite Launch Center in the Liangshan Yi Autonomous Prefecture, Sichuan Province. That same day, a Long March-4C rocket carrying the relay satellite was successfully launched from the satellite launch center. VCG Technology, the Ministry of Environmental Protec-tion, jointly released guidance on collaborative promotion of green packaging in the express delivery industry.According to industry experts, the Chinese government still needs to formulate national stan-dards on green logistics to ensure the compati-bility and interoperability of logistics technology, products and services among different enterpris-es to encourage them to strengthen cooperation in research and development of new technologies and new models and provide services that are more environmentally friendly. Edited by Li Zhuoxi Relay Satellite satellite of satellites,” is a kind of communication satellite used to transmit massive volumes of data. By providing data relay, telemetry, tracking and command (TT&C) services for spacecraft and satellites, it greatly improves the efficiency and emergency response capabilities of various satellites. The technology enables real-time data transmission of resources satellites and environ-mental satellites, earning more warning time for major natural disasters.Early on the morning of May 21, 2018, China successfully launched the world’s first relay sat-ellite named Queqiao (“Magpie Bridge”) in orbit around the moon, which will provide a commu-nication link between the earth and the planned Chang’e-4 lunar probe that will soft-land on and explore the moon’s mysterious far side at the end of 2018. The relay satellite will solve a major difficulty in lunar exploration. The tidal forces of the earth slowed the moon’s rotation to the point where the same side always faces the earth. The other side, most of which is never visible from the earth, is known as the “dark side” of the moon.Due to shielding from the moon itself, the detector landing on the far side of the moon cannot directly realize TT&C communication and data transmission with the earth.The Queqiao relay satellite will assist the control center on the earth to enhance control of the lunar probe to ensure a smooth landing.Chinese e-commerce giant Alibaba recently launched the “Green Logistics 2020” plan across all its platforms, promising that by 2020, all of its express bags will be biodegradable and all boxes recyclable. And other e-commerce and logistics companies will follow suit to launch similar green logistics plans.China has clearly become a big country for express delivery. The nation handled a total of 40.06 billion express deliveries in 2017, up by 28 percent from the previous year, consuming 19.2 bil-lion boxes, 5.8 billion woven bags, 15 billion plastic bags and about 30 billion meters of packing tape.In the process of building an ecologicalChina, the express delivery industry has become a major area for improvement. In August 2016, the State Post Bureau issued a plan to advance green packaging in the express delivery industry.In November 2017, ten ministerial-level government departments of China, including the State Post Bureau, the National Development and Reform Commission, the Ministry of Science and Version 2.0 of the sharing express box, jointly de-veloped by Suning Logistics and Shenzhen Huidu Technology Co., Ltd., can be reused over 60 times, with each-time usage price 30 percent lower than that of an ordinary carton. IC The word “relay” in “relay satellite” refers to expanding the distance of network transmission by sending or forwarding data signals. A relay satellite, sometimes referred to as “the Edited by Li Zhuoxi Green Logistics C H I N A P I C T O R I A L 11B U Z Z W O R D SCopyright ©博看网. All Rights Reserved.。
23年高考英语外刊阅读训练——阅读理解:行业主导的风险逼近AI变革——改编自Risk of ‘industrial capture’looms over AI revolution Artificial intelligence is going through a massive change, but not the one that people might expect. Advanced language-generating systems and chatbots have dominated headlines, but private AI companies have quietly entrenched their power. Recent developments mean that a few individuals and corporations now control most of the resources and knowledge in the industry and will ultimately shape its impact on our collective future.This phenomenon, known as industrial capture by AI experts, was quantified in a paper published in the journal Science by researchers from the Massachusetts Institute of Technology earlier this month, calling on policymakers to pay closer attention. The data is becoming increasingly crucial as generative AI technology is being embedded into software used by billions of people.The MIT research found that almost 70 per cent of AI PhDs went to work for companies in 2020, compared to 21 per cent in 2004. Similarly, there was an eightfold increase in facultybeing hired into AI companies since 2006, far faster than the overall increase in computer science research faculty.Many researchers have abandoned certain research trajectories because they feel they cannot compete with industry as they do not have the computing power or engineering talent. Academics are unable to build large language models like GPT-4, which require enormous amounts of data and computing power primarily available only to large technology companies like Google, Microsoft and Amazon. In fact, companies' share of the biggest AI models has gone from 11 per cent in 2010 to 96 per cent in 2021.A lack of access means researchers cannot replicate the models built-in corporate labs. Therefore, they can neither probe nor audit them for potential harms and biases very easily. Public alternatives to corporate AI tech such as models and data sets are scarce, and new applications are likely to be commercially driven through corporate interests rather than the broader public interest.Researchers agree that governments should not turn a blind eye and must take steps against this shift. Policy experts suggest various solutions, from setting up academia-only datacentres to running experiments to further concentrate power among those who own infrastructure like cloud services.The consequences of this shift are manifold and need closer attention. The policymakers must take steps to ensure a more level playing field for AI research that benefits the public interest rather than becoming a tool for corporations.【重点词汇】1. artificial [ɑːtɪˈfɪʃl] adj. 人工的,虚假的2. intelligence [ɪnˈtelɪdʒəns] n. 智能,智慧3. massive [ˈmæsɪv] adj. 巨大的,大量的4. change [tʃeɪndʒ] n. 变化,变革;v. 变化,改变5. advanced [ədˈvænst] adj. 先进的,高级的6. language-generating [ˈlæŋɡwɪdʒ-ˈdʒenəreɪtɪŋ] adj. 能够生成语言的7. system [ˈsɪstəm] n. 系统,制度8. chatbot [tʃætbɒt] n. 聊天机器人9. dominate [ˈdɒmɪneɪt] v. 支配,控制10. headline [ˈhedlaɪn] n. 头条新闻11. private [ˈpraɪvət] adj. 私有的,私营的12. company [ˈkʌmpəni] n. 公司,企业13. quietly [ˈkwaɪətli] adv. 安静地,悄悄地14. entrench [ɪnˈtrentʃ] v. 巩固,确立15. power [ˈpaʊə(r)] n. 力量,权力16. recent [ˈriːsnt] adj. 最近的,近来的17. development [dɪˈveləpmənt] n. 发展,开发18. individual [ˌɪndɪˈvɪdʒuəl] n. 个人,独立的19. corporation[ˌkɔːpəˈreɪʃn] n. 公司,企业20. control [kənˈtrəʊl] v. 控制,支配21. resource [rɪˈsɔːs] n. 资源,财富22. knowledge [ˈnɒlɪdʒ] n. 知识,学问23. sector [ˈsektə(r)] n. 部门,行业24. ultimately [ˈʌltɪmətli] adv. 最终地,最后25. shape [ʃeɪp] v. 形成,塑造26. impact [ˈɪmpæk t] n. 影响,冲击;v. 影响,影响到27. collective [kəˈlektɪv] adj. 集体的,共同的28. future [ˈfjuːtʃə(r)] n. 未来,前途29. phenomenon [fɪˈnɒmɪnən] n. 现象,事件30. refer to [rɪˈfɜː(r) tuː] 提到,指的是31. industrial [ɪnˈdʌstriəl] adj. 工业的,产业的32. capture [ˈkæptʃə(r)] v. 捕获,俘获33. expert [ˈekspɜːt] n. 专家,权威34. quantified [ˈkwɒntɪfaɪd] adj. 可以量化的35. paper [ˈpeɪpə(r)] n. 论文,报纸,文件36. publish [ˈpʌblɪʃ] v. 发布,出版37. researcher [rɪˈsɜːtʃə(r)] n. 研究员,调查者38. Massachusetts Institute of Technology [mæsəˈtʃu:sɪts ˌɪnstɪtju:təv əv tehˈnɒlədʒi] 麻省理工学院39. journal [ˈdʒɜːnl] n. 期刊,杂志【阅读理解练习题】1. What is the main topic of the article?A. The development of AI language-generating systems and chatbots.B. The increasing power of private AI companies in the industry.C. The impact of AI on our collective future.D. The need for policymakers to pay closer attention to AI.Answer: B中文解析:文章主要讲述的是私营AI 公司在行业中的增强力量。
Candidate name__________________________________________________________________ INTERNATIONAL ENGLISH LANGUAGE TESTING SYSTEM 0381/1Academic ReadingPRACTICE MATERIALS 1hourAdditional materials:Answer sheet for Listening and ReadingTime 1hourINSTRUCTIONS TO CANDIDATESDo not open this question paper until you are told to do so.Write your name and candidate number in the spaces at the top of this page.Read the instructions for each part of the paper carefully.Answer all the questions.Write your answers on the answer sheet. Use a pencil.You must complete the answer sheet within the time limit.At the end of the test, hand in this question paper and your answer sheet.INFORMATION FOR CANDIDATESThere are 40 questions on this question paper.Each question carries one mark.READING PASSAGE 1You should spend about 20 minutes on Questions 1-13, which are based on Reading Passage 1 on pages 3 and 4.Questions 1-6Reading Passage 1 has six paragraphs, A-F.Choose the correct heading for each paragraph from the list of headings below.Write the correct number, i-ix, in boxes 1-6 on your answer sheet.1Paragraph A2Paragraph B3Paragraph C4Paragraph D5Paragraph E6Paragraph FSeaweeds of New ZealandA Se aweed is a particularly wholesome food, which absorbs and concentrates traces of a wide variety of minerals necessary to the body’s health. Many elements may occur in seaweed-aluminum, barium, calcium, chlorine, copper, iodine and iron, to name but a few-traces normally produced by erosion and carried to the seaweed beds by river and sea currents. Seaweeds are also rich in vitamins; indeed, Inuits obtain a high proportion of their bodily requirements of vitamin C from the seaweeds they eat. The health benefits of seaweed have long been recognized. For instance, there is a remarkably low incidence of goiter among the Japanese, and also among New Zealand’s indigenous Maori people, who have always eaten seaweeds, and this may well be attributed to the high iodine content of this food. Research into historical Maori eating customs shows that jellies were made using seaweeds, nuts, fuchsia and tutu berries, cape gooseberries, and many other fruits both native to New Zealand and sown there from seeds brought by settlers and explores. As with any plant life, some seaweeds are more palatable than others, but in a survival situation, most seaweeds could be chewed to provide a certain sustenance.B New Zealand lays claim to approximately 700 species of seaweed, some of which have no representation outside that country. Of several species grown worldwide, New Zealand also has a particularly large share. For example, it is estimated that New Zealand has some 30 species of Gigartina, a close relative of carrageen of Irish moss. These are often referred to as the New Zealand carrageens. The substance called agar which can be extracted from these species gives them great commercial application in the production of seameal, from which seameal custard (a food product) is made, and in the canning, paint and leather industries. Agar is also used in the manufacture of cough mixtures, cosmetics, confectionery and toothpastes. In fact, during World War II, New Zealand Gigartina were sent to Australia to be used in toothpaste.C New Zealand has many of the commercially profitable red seaweeds, several species of which are a source of agar ( Pterocladia, Gelidium, Chondrus, Gigartina). Despite this, these seaweeds were not much utilized until several decades ago. Although distribution of the Gigartina is confined to certain areas according to species. And even then, the east coast, and the area around Hokianga, have a considerable supply of the two species of Pterocladia from which agar is also made. New Zealand used to import the Northern Hemisphere Irish moss ( Chondrus crispus) from England and ready-made agar from Japan.D Seaweeds are divided into three classes determined by colour-red, brown and green-and each tends to live in a specific position. However, expect for the unmistakable sea lettuce (Ulva), few are totally one colour; and especially when dry, some species can change color significantly-a brown one may turn quite black, or a red one appear black, brown, pink or purple. Identification is nevertheless facilitated by the fact that the factors which determine where a seaweed will grow are quite precise, and they tend therefore to occur in very well-defined zones. Although there are exceptions, the green seaweeds are mainly shallow-water algae; the browns belong to the medium depths; and the reds are plants of thedeeper water, furthest from the shore. Those shallow-water species able to resist long periods of exposure to sun and air are usually found on the upper shore, while those less able to withstand such exposure occur nearer to, of below, the low-water mark. Radiation from the sun, the temperature level, and the length of time immersed also play a part in the zoning of seaweeds. Flat rock surfaces near mid-level tides are the most usual habitat of sea-bombs, Venus’ necklace, and most brown seaweeds. This is also reddis h-purple lettuce. Deep-water rocks on open coasts, exposed only at very low tide, are usually the site of bull-kelp, strapweeds and similar tough specimens. Kelp, or bladder kelp,has stems that rise to the surface from massive bases or holdfasts, the leafy branches and long ribbons of leaves surging with the swells beyond the line of shallow coastal breakers or covering vast areas of calmer coastal water.E Propagation of seaweeds occurs by seed-like spores, or by fertilization of egg cells. None have roots in the usual sense; few have leaves; and none have flowers, fruits or seeds. The plants absorb their nourishment through their leafy fronds when they are surrounded by water; the holdfast of seaweeds is purely an attaching organ not an absorbing one.F Some of the large seaweeds stay on the surface of the water by means of air-filled floats; others, such as bull-kelp, have large cells filled with air, often reduce dehydration either by having swollen stems that contain water, or they may (like Venus’ necklace) have swollen nodules, or they may have a distinctive shape like a sea-bomb. Others, like the sea cactus, are filled with a slimy fluid or have a coating of mucilage on the surface. In some of the larger kelps, this coating is not only to keep the plant moist, but also to protect it from the violent action of waves.5Questions 7-10Complete the flow-chart below.Choose NO MORE THAN THREE WORDS from the passage for each answer.Write your answers in boxes7-10 on your answer sheet.Gigartina seaweed(other name:7 )↓Produces↓8Is used to make is used to make9 --medicines, suchAs 10Is used to make ---cosmeticsA type of custard ----sweets-----toothpastesQuestions 11-13Classify the following characteristics as belong toA brown seaweedB green seaweedC red seaweedWrite the correct letter, A, B or C, in boxes 11-13 on your answer sheet.11 can survive the heat and dryness at the high-water mark12 grow far out in the open sea13 share their site with karengo seaweed6READING PASSAGE 2You should spend about 20 minutes on Questions 14-26, which are based on Reading Passage 2 on pages 6 and 7.TWO WINGS AND A TOOLKITA research team at Oxford University discover the remarkable toolmaking skills of NewCaledonian crownsBetty and her mate Abel are captive crows in the care of Alex Kacelnik, an expert in animal behavior at Oxford University. They belong to a forest-dwelling species of bird (Corvus moneduloides) confined to two islands in the South Pacific. New Caledonian crows are tenacious predators, and the only birds that habitually use a wide selection of self-made tools to find food.One of the wild crows’ cleverest tools in the crochet hook, made by detaching a side twig from a larger one, leaving enough of the larger twig to shape into a hook. Equally cunning is a tool crafted from the barbed vine-leaf, which consists of a central rib with paired leaflets each with a rose-like thorn at the top, which remains as a ready-made hook to prise out insects from awkward cracks.The crows also make an ingenious tool called a padanus probe from padanus tree leaves. The tool has a broad base, sharp tip, a row of tiny hooks along one edge, and a tapered shape created by the crow nipping and tearing to form a progression of three or four steps along the other edge of the leaf. What makes this tool special is that they manufacture it to a standard design, as if following a set of instructions. Although it is rare to catch a crow in the act of clipping out a padanus probe, we do have ample proof of their workmanship: the discardedle aves from which the tools are cut. The remarkable thing that these ‘counterpart’ leaves tell us is that crows consistently produce the same design every time. With no in-between or trail versions. It’s left the researchers wondering whether, like people, t hey envisage the tool before they start and perform the actions they know are needed to make it. Research has revealed that genetics plays a part in the less sophisticated toolmaking skills of finches in the Galapagos islands. No one knows if that’s also the case for New Caledonian crows, but it’s highly unlikely that their toolmaking skills are hardwired into the brain. “The picture so far points to a combination of cultural transmission-from parent birds to their young-and individual resourcefulness”, say s Kacelnik.In a test at Oxford, Kacelnik’s team offered Betty and Abel an original challenge-food in a bucket at the bottom of a ‘well’. The only way to get the food was to hook the bucket out by its handle. Given a choice of tools- a straight length of wire and one with a hooked end- the birds immediately picked the hook, showing that they did indeed understand the functional properties of the tool.But do they also have the foresight and creativity to plan the construction of their tools?It appears they do. In one bucket-in-the-well test. Abel carried off the hook, leaving Betty with nothing but the straight wire. ‘What happened next was absolutely amazing’, says Kacelnik. She wedged the tip of the wire into a crack in a plastic dish and pulled the other end to fashion her own hook. Wild crows don’t have access to pliable, bendable material that retains its shape, and Betty’s only similar experience was a brief encounter with some pipe cleaners a year earlier. In nine out of ten further tests, she again made hooks and retrieved the bucket. The question of what’s going on in a crow’s mind will take time and a lot more experiments to answer, but there could be a lesson in it for understanding our own evolution. Maybe our ancestors, who suddenly began to create symmetrical tools with carefully worked edges some 1.5 million years ago, didn’t actually have the sophisticated mental abilities with which we credit them. Close scrutiny of the brains of New Caledonian crows might provide a few pointer s to the special attributes they would have needed. ‘If we’re lucky we may find specific developments in the brain that set these animals apart,’ says Kacelnik.One of these might be a very strong degree of laterality-the specialization of one side of the brain to perform specific tasks. In people, the left side of the brain controls the processing of complex sequential tasks, and also language and speech. One of the consequences of this is thought to be right-handedness. Interestingly, biologists have noticed that most padanus proves are cut from the left side of the leaf, meaning that the handedness. The team thinks this reflects the fact that the left side of the crow’s brain is specialized to handle the sequential processing required to make complex tools.Under what conditions might this extraordinary talent have emerged in these two species? They are both social creatures, and wide-ranging in their feeding habits. These factors were probably important but, ironically, it may have been their shortcomings that triggered the evolution of toolmaking. Maybe the ancestors of crows and humans found themselves in a position of where they couldn’t make the physical adaptations required for survival – so they had to change their behavior instead. The stage was then set for the evolution of those rare cognitive skills that produce sophisticated tools. New Caledonian crows may tell us what those crucial skills are.Questions 14-17Label the diagrams below.Choose NO MORE THAN TWO WORDS from the passage for each answer. Write your answers in boxes 14-17 on your answer sheet.THREE TOOLS MADE BY CROWSQuestions 18-23Do the following statements agree with the information given in Reading Passage 2?In boxes 18-23 on your answer sheet, writeTRUE if the statements agree with the informationFALSE if the statements contradicts the informationNOT GIVEN if there is no information on this18 there appears to be a fixed patter for the padanus probe’s const ruction.19 there is plenty of evidence to indicate how the crows manufacture the padanus prove20 crows seem to practice a number of times before making a usable padanus probe21 the researchers suspect the crows have a mental images of the padanus probe beforethey create it.22 research into how the padanus probe is made as helped to explain the toolmakingskills of many other bird species.23 the researchers believe the ability to make the padanus probe is passed down to thecrows in their genesQuestions 24-26Choose THREE letters, A-GWrite the correct letters in boxes 24-26 on you answer sheet.According to the information in the passage, which THREE of the following features are probably common to both New Caledonian crows and human beings?A keeping the same mate for lifeB having few natural predatorsC having a bias to the right when workingD being able to process sequential tasksE living in extended family groupsF eating a variety of foodstuffsG being able to diverse habitatsREADING PASSAGE 3You should spend about 20 minutes on Questions 27-40, which are based on Reading Passage 3 on pages 10 and 11.How did writing begin?Many theories, few answersThe Sumerians, an ancient people of the Middle East, had a story explaining the invention of writing more than 5000 years ago. It seems a messenger of the king of Uruk arrived at the court of a distant ruler so exhausted that he was unable to deliver the oral message. So the king set down the words of his next messages on a clay tablet. A charming story, whose retelling at a recent symposium at the university of Pennsylvania amused scholars. They smiled at the absurdity of a letter which the recipient would not have been able to read. They also doubted that the earliest writing was a direct rendering of speech. Writing more likely began as a separate, symbolic system of communication and only later merger with spoken language.Yet in the story the Sumerians, who lived in Mesopotamia, in what is now southern Iraq, seemed to understand writing’s transforming function. As Dr Holly Pittman, director of the University’s Center for Ancient Studies, observed, writing ‘ arose out of the need to store and transmit information…over time and space’.In exchanging interpretations and information, the scholars acknowledged that they still had no fully satisfying answers to the questions of how and why writing developed. Many favourated an explanation of writing’s origins in the visual arts, pictures becoming increasingly abstract and eventually representing spoken words. Their views clashed with a widely held theory among archaeologists writing developed from the pieces of clay that Sumerian accountants used as tokens to keep track of goods.Archaeologists generally concede that they have no definitive answer to the question of whether writing was invented only once, or arose independently in several places, such as Egypt, the Indus Valley, China, Mexico and Central America. The preponderance of archaeological data shows that the urbanizing Sumerians were the first to develop writing, in 3200 or 3300 BC. These are the dates for many clay tablets in an early form of cuneiform, a script written by pressing the end of a sharpened stick into wet clay, found at the site of the ancient city of Uruk. the baked clay tablets bore such images as pictorial symbols of the names of people, place and things connected with government and commerce. The Sumerian script gradually evolved from the pictorial to the abstract, but did not at first represent recorded spoken language.Dr Peter Damerow, a specialist in Sumerian cuneiform at the Mac Planck Institute for the History of Science i n Berlin, said, “It is likely that there were mutual influences of writing systems around the world. However, their great variety now shows that the development of writing, once initiated, attains a considerable degree of independence and flexibility to adapt to specific characteristics of the sounds of the language to be representation of words by pictures. New studies of early Sumerian writing, he said, challenge this interpretation. The structures of this earliest writing did not, for example, match the structure of spoken language, dealing mainly in lists and categories rather than in sentences and narrative.For at least two decades, Dr Denise Schmandt-Besserat, a University of Texas archaeologist, has argued that the first writing grew directly out of a system practiced by Sumerian accountants. They used clay tokens, each one shaped to represent a jar of oil, a container of grain of a particular kind of livestock. These tokens were sealed inside clay spheres, and then then number and type of tokens inside was recorded on the outside using impressions resembling the tokens. Eventually, the token impressions were replaced with inscribed signs, and writing had been invented.Though Dr Schmandt-Besserat has won much support, some linguists question her thesis, and others, like Dr Pittman, think it too narrow. They emphasise that pictorial representation and writing evolved together. ‘There’s no question that the token system is a forerunner of writing,’ Dr Pittman said, ‘but I have an argument with her eviden ce for a link between tokens and signs, and she doesn’t open up the process to include picture making.’Dr Schmandt-Besserat vigorously defended her ideas. ‘My colleagues say that pictures were the beginning of writing,’ she said, ‘but show me a single pic ture that becomes a sign in writing. They say that designs on pottery were the beginning of writing, but show me a single sign of writing you can trace back to a pot- it doesn’t exist.’ In its first 500 years, she asserted, cuneiform writing was used almost solely for recording economic information, and after that its uses multiplied and broadened.Yet other scholars have advanced different ideas. Dr Piotor Michalowski, Professor of Near East Civilizations at the University of Michigan, said that the proto-writing of Sumerian Uruk was ‘so radically different as to be a complete break with the past’. It no doubt served, he said, to store and communicate information, but also became a new instrument of power. Some scholars noted that the origins of writing may not always have been in economics. In Egypt, most early writing is high on monuments or deep in tombs. In this case, said Dr Pascal Vernus from a university in Paris, early writing was less administrative than scared. It seems that the only certainty in this field is that many questions remain to be answered.Questions 27-30Choose the correct letter, A,B,C or D.Write the correct letter in boxes 27-30 on your answer sheet.27 The researchers at the symposium regarded the story of the King of Uruk as ridiculousbecauseA writing probably developed independently of speech.B clay tablets had not been invented at that time.C the distant ruler would have spoken another language.D evidence of writing has been discovered from an earlier period.28 According to the writer, the story of the King of UrukA is a probable explanation of the origins of writing.B proves that early writing had a different function to writing today.C provides an example of symbolic writing.D shows some awareness amongst Sumerians of the purpose of writing.29 There was disagreement among the researchers at the symposium aboutA the area where writing began.B the nature of early writing materials.C the way writing began.D the meaning of certain abstract images.30 The opponents of the theory that writing developed from tokens believe that itA grew out of accountancy.B evolved from pictures.C was initially intended as decoration.D was unlikely to have been connected with commerce.Questions 31-36Look at the following statements (questions 31-36) and the list of people below.Match each statement with the correct person, A-EWrite the correct letter, A-E, in boxes 31-36 on your answer sheet.NB You may use any letter more than once.31 There is no proof that early writing is connected to decorated household objects.32 As writing developed, it came to represent speech.33 Sumerian writing developed into a means of political control34 Early writing did not represent the grammatical features of speech.35 There is no convincing proof that tokens and signs are connected.36 The uses of cuneiform writing were narrow at first, and later widened.Questions 37-40Complete the summary using the list of words, A-N, below.Write the correct letter, A-N, in boxes 37-40 on your answer sheet.The earliest form of writingMost archaeological evidence shows that the people of 37 invented writing in around 3300 BC. Their script was written on 38 and was called39 . Their script originally showed images related to political power and business, and later developed to become more40 .。
适用范围:19级本科山东科技大学2019—2020学年第一学期《大学英语》考试试卷(A卷)注意:1.请将第一、二、三部分的答案涂在答题卡上,做在试卷上无效;2.请将第四、五、六部分的答案写在答题纸上,写在试卷上无效;3.请把后面的答题纸单独交,答题卡和试卷也单独交;4.听力部分放音时间:2:30,放音频段:调频96MHz.5.请务必填好个人信息,答题卡上填涂准考证号,试卷类型涂A,科目代号涂英语,请用2B铅笔和和黑色中性笔答题。
Part I Listening Comprehension(15%)Section A (4%)Directions: In this section you will hear 4 short conversations. At the end of each conversation, a question will be asked about what was said. Both the conversation and the question will be spoken only once. After each question there will be a pause. During the pause, you must read the four choices marked A), B), C) and D), and decide which is the best answer. Then write the corresponding letter on the Answer Sheet.1. A) A teacher and a student. B) A shop assistant and a customer.C) A receptionist and a client. D) A boss and a worker.2. A) He went to bed too late.B) His mother forgot to wake him up.C) He gets up late because he feels tired these days.D) He doesn’t have an alarm clock to wake him up.3. A) He is taking care of his twin brother. B) He has been in perfect condition.C) He is worried about Rods’ health.D) He has been feeling ill all week.4. A) Travel in different countries.B) Look for some similar topics.C) Make comparisons of festivals in different countries.D) Go to some countries with similar culture.Section B (4%)Directions: In this section, you will hear one long conversation. At the end of the conversation,you will hear four questions. Both the conversation and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A), B), C) and D). Then write the corresponding letter on the Answer Sheet.Questions 5 to 10 are based on the passage you have just heard.5. A) He misses Laura very much. B) He hasn’t got the invitation to the party.C) He wants to make sure of the time. D) He can’t attend the party.6. A) Some of his relatives from Scotland. B) Some of his friends from Scotland.C) Some of his colleagues from Ireland. D) Some of his former classmates from Ireland.7. A) Take his relatives to the party. B) Take his colleagues to his home.C) Take his friends out to dinner. D) Take his classmates to a hotel.8. A) He can drop in later with his friends. B) He can come to the party to meet James.C) He can send her an email about his plan. D) He can come with his relatives.Section CDirections: In this section, you will hear 2 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A), B), C) and D). Then write the corresponding letter on the Answer Sheet.Questions 9 to 12 are based on the passage you have just heard.9. A) How fire moves. B) How fire starts.C) What fire needs and does. D) What fire is made of.10. A) Fire is matter. B) Fire is smoke.C) Fire is a spot. D) Fire is an activity.11. A) Fuel and glass. B) Glass and wind.C) Fuel and gas. D) Heat source and fuel.12. A) It burns very quickly. B) It burns slowly at a high heat.C) It’s easy to light.D) I t’s very smoky.Questions 13 to 16 are based on the passage you have just heard.13. A) The best medical care maintains good health.B) It’s too late to see the doctor when you feel sick.C) Good health results largely from good habits.D) Doctors are responsible for maintaining people’s health.14. A) One should try to avoid being overweight.B) One should keep fit acco rding to one’s own conditions.C) Easier exercise is preferable.D) Sweaty, competitive games are more helpful.15. A) Accidents and disease. B) Being sick or getting overweight.C) Developing bad habits. D) Neglecting common health rules.Part II Vocabulary (20%)16. It was about 30 seconds before Alex ______ from the water.17. It is well known that China is a country with rich natural __________.18. The committee’s decision will be _______ to all employees.19. Consumers say they are ________ about using their credit cards over the internet.A. resourcesB. notifiedC. emergedD. uneasy20. When you do yoga, try to _____ your breathing.21. People are beginning to realize that to _______ nature at will is the biggest mistake.22. My favorite store is the one that _____ in hand-made chocolates.23. He always drinks a _____ amount of alcohol to get himself drunk.A. massiveB. transformC. regulateD. specializes24. I had to ____ one of my email accounts as it was filled with junk email.25. The power station was moved further away from the living areas to _______ the pollution.26. He was _______ with his business matters and didn’t have time to think about a holiday.27. Du e to increased ______ , the past decade saw great economic growth in China.A. decreaseB. productivityC. abandonD. occupied28. He________ the dangers of the trip to the mountain.29. She was _______ by her failure in applying for the post.30. The ______ tick of the clock got on my nerves.31. I think the scientist is ______ of the high praise.A. worthyB. exaggeratedC. continualD. frustrated32. Children display great_____ about every new thing they see.33. The room only has a ____ for 100 people.34. Discipline is _____ to anyone who wants to be successful.35. Keeping a ______ attitude to get the job.A. essentialB. curiosityC. positiveD. capacityPart III Reading Comprehension (30%)Passage 1The flowers are blooming and the birds are singing as Melinda sits in the rose garden of the nursing home. She is recalling old times as she waits for her family's arrival. The nursing home has been Melinda's new settlement ever since Thomas passed away a week ago. Thomas had fought a long and hard battle against lung cancer for three years. Unfortunately, he has broken the promise that he and Melinda had made: to be with each other for every birthday. Melinda knew this was unrealistic but agreed to the promise for Thomas’s sake.“Thomas, you are completely a dreamer!” Melinda shouted to Thomas as h e dragged on about living on an island with his beautiful wife. That s what she loved about him most—he had a vivid imagination. They got married at age eighteen and began having children right away. Mary came within the year,followed by Thomas Benjamin II, Lilly-Ann, and Joseph “Little Joey' George. The family lived an exultant life filled with laughter and love.“Mom!” Lilly shouted, but it really sounded like a howl. Melinda had lost herself in thinking about the life she had shared with her late husband. Lilly pushed her down the long dark halls of the nursing home until they arrived at the recreational room.When the doors opened, Melinda put her hand over her mouth and was completely speechless. The room was crowded with the people nearest and dearest to her and the warmth and love was felt instantly. The night went on; stories and cocktails were shared and everything was perfect. However, when Melinda caught a moment to herself she looked around at her family. With a smi le on her face, she raised her Manhattan and called out for a toast. “This one is for you, Thomas,though you are not here.”36. Why did Thomas break his promise?A. He was busy with his work.B. He died of lung cancer.C. He had to serve in the army.D. He stopped loving Melinda.37. Which of the following best explains “exultant” underlined in Paragraph 2?A. Peaceful.B. Simple.C. Stressful.D. Happy.38. What can we infer from the last paragraph?A. Melinda,children forgot their father.B. Melinda was tired of noise.C. Melinda missed her husband badly.D. Melinda liked to drink alcohol,39. What can be a suitable title for the text?A. A Particular BirthdayB. A Woman at a Nursing HomeC. Memories of Old DaysD. A Big Surprise for MelindaPassage BSpotify can tell if you’re sad. Here’s why that should scare you. Want to figure out if someone is a patient with a mental disability? Ask them what their favorite song is. A New York University study last year found that people who loved Eminem's Lose Yourself and Justin Bieber's What Do You Mean? were more likely to have trouble with mental disabilities than people who were into Dire Straits.Over the past few years,Spotify has been improving the ability to analyze information to help businessmen target consumers with advertisements made specially for their needs. They conclude this from the sort of music you’re listening to, combined with where and when you’re listening to it, along with third-party data that might be available.Now, to be clear, there’s nothing significantly illegal about what Spotify is doing with your information. I certainly don't think that they are working with shadowy consulting firms to serve you ads selling a culture struggle while you're listening to music that suggests you might be in a terrible situation. However, I find it disappointing that our personal, private moments with music are increasingly being turned into information points and offered to advertisers.You can see where this could go,can’t you? As ad targeting gets ever more accurate, businessmen will have the ability to target our feelings in potentially improper ways. According to one study, you are more likely to spend more on a product if you’re feeling sad. You can imagine some companies might take advantage of that. And on that note,I’m feeling a littledown about all this. Head off to treat myself to something expensive.40. What's the purpose of the first paragraph?A. To introduce a new song.B. To draw readers’ attention.C. To help more patients.D. To promote a new medium.41. Spotify improves its ability to analyze information to______.A. provide services for the governmentB. work with shadowy consulting firmsC. get listeners' personal informationD. help businessmen attract consumers42. What s th e author’s attitude towards Spo tify?A. Uncertain.B. Supportive.C. Positive.D. Dissatisfied.43. Who is the text probably designed for?A. Internet users.B. Officials.C. Researchers.D. Managers.Passage CAn exciting landing process of Chang'e-4 lunar probe (月球探测器)was seen through the monitor at Beijing Aerospace Control Center in Beijing,Jan. 3, 2019. It touched down on the far side of the moon at 10:26 a.m. Beijing Time, becoming the first spacecraft soft-landing on the moon’s unknown side nev er visible from Earth.China’s Chang'e-4 probe has started the exploration on the far side of the moon thanks to the relay satellite that provides a communication link with ground control. The relay satellite, named Queqiao, meaning Magpie Bridge, after a Chinese legend, was launched on May 21,2018,and became the first communication satellite operating in the halo orbit, nearly 500,000 km from the earth. It can also provide communication for probes from other countries. The relay satellite will also be used for scientific and technological experiments. The maximum distance between the satellite and the Chang'e-4 probe on the far side of the moon is 79,000 km. The satellite processes data from the probe and sends it to Earth.The satellite can stay in its orbit for a long time due to its relatively low fuel consumption, as the earth’s and moon's gravity balances its orbital moving. While in orbit, it can “see” both the earth and the far side of the moon.The concept of using a relay satellite in the halo orbit was first put forward by U.S. space expertsin the 1960s, but was realized by Chinese space engineers.Researchers hope to use the cameras on the satellite to record asteroids (小行星)hitting the far side of the moon. To control the cost of the Chang'c-4 probe, the relay satellite was designed to be relatively small, weighing about 400 kg.Researchers had just 30 months to develop the satellite, putting them under high pressure. To promote public interest in space exploration, the China National Space Administration invited people to write down their wishes for lunar and space exploration, and the relay satellite carries the names of tens of thousands of participants and their messages.44. What do we learn from the second paragraph?A. The relay satellite was launched on Jan. 3, 2019.B.Chang'e-4 probe was the first communication satellite.C. The relay satellite only explores the far side of the moon.D. The relay satellite can handle data from Chang'e-4 probe.45. Why was the size of the relay satellite relatively small?A. To reduce the cost as much as possible.B. To make it circle Moon for a longer time.C. To avoid being crashed by other satellites.D. To follow American space experts,advice.46. What made researchers suffer from great stress?A. Few people interested in the exploration on the moon.B. The relay satellite carrying too much equipment.C. Their lacking enough time to develop the relay satellite.D. People’s never being optimistic about the relay satellite47. What is the main idea of the text?A. China is a new space power after the USA.B.Change-4 probe lands on Moon’s far side.C. Chinese space engineers make much progress.D. Space exploration is a dangerous challenge.Passage DLast year marked the 100th anniversary of the end of World War I. There were events around theworld in memory of those who died in the conflict. We have picked out three of them in European countries. Let's take a look.BelgiumIn a park, the famous Belgian artist Koen Vanmechelen had an exhibition called Coming World, Remember Me. The work consisted of 600,000 individual(单独的)clay sculptures, one for exhibition was a big egg made of clay each person killed during the World War. In the center of the exhibition was a big egg made of clay, symbolizing a new world.UKIn a small town called Aldridge. almost 100 houses in one street were covered with 24,000poppies and statues of sold.They stood for the men from the area who had been killed in the war. The flowers were chosen because of a poem written by the Canadian doctor John McCrea in1915. They made people think of fields of blood.FranceThe British artist Guy Denning arrived in La Feuille,a small town in the northwest of France, to stick life-size drawings of soldiers who never came back home. Armed with glue and a brush, Denning stuck his drawings carefully on walls. Before long 112 men, ma.nly young adults, were brought back to mind, if not to life.48. What do we know about Coming World. Remember Me?A. It's the name of an exhibition.B. It's a film about World War I.C. It's a work standing for peace.D. It's a sculpture made of clay.49. Why were poppies chosen to symbolize the dead soldiers?A. The British people preferred them.B. They showed the cruelty of war.C. A Canadian doctor suggested them.D. The fields were filled with them.50. How was the end of World War I marked in France?A. A memorial to the dead soldiers was built.B. 112 wounded soldiers in the war were helped.C. Drawings of some dead soldiers were put up.D. Young adults were encouraged to join the army.Part IV Skimming and Scanning (10%)Technology in education: Current trendsA)Computers and Internet connections are becoming widely available in schools and classrooms. In 1999, 99 percent of teachers in the United States had access to a computer in their schools, and 84 percent had one or more computers in their classrooms. At the same time, Internet connections were also widespread, with 95 percent of schools and 63 percent of classrooms having access. Worldwide, many countries are making the creation and diffusion of information and communications technology (ICT) an important priority.The use of technology to find educational resourcesB) In the past, teachers attempting a problem-based curriculum felt the need to limit problems to those for which they had expertise or the local library had resources. Now the World Wide Web brings a seemingly endless amount of information on almost any subject, and it is possible for students to choose topics based on personal interest rather than availability of resources.C) Internet research projects are gaining popularity. In the spring of 1998, 30 percent of teachers surveyed (and 70 percent of those with high-speed Internet connections) reported they had assigned Internet research tasks to their students during the school year. Use of the Internet to gather information for solving problems sometimes resembles a modern version of library research, in which students gather and synthesize information from published reports. Despite the fact that the task seems traditional, the characteristics of this new medium require special skills for students. The sheer volume of information allows students to study almost any topic, but also makes it more difficult to locate precisely the right information from among the thousands, or even millions, of sites. In addition, the ease of publishing materials on the Internet increases the likelihood that students will encounter inaccurate or biased information. As a result, students must learn new strategies for conducting searches and evaluating the information thatthey retrieve.D) Students carrying out scientific investigations can use the Internet to make observations and collect data. For example, the fourth and fifth graders in California collected insects and sent them to San Diego State University. Using two-way audio and video connecting the school and the university, scientists guided the students in using an electron microscope to examine their specimens. Technology has made it possible to collect data from places students could never visit. In recent projects, high school students explored the floor of the Monterey Bay by studying the video from remotely operated robots, and middle school students were given time to use the Hubble telescope. Students also use technology to collect data in their schools and communities. For example, using handheld computers outfitted with various types of probes (探测仪),students can monitor the water quality at various locations in nearby streams or lakes. By transmitting their individual readings to a laptop computer in a field laboratory they can quickly graph their data and visually compare readings.The use of technology to summarize and present findingsE) In the past, students memorized and used formulas and models created by others to solve problems. Students often used these formulas, especially in the early stages of learning, with little understanding. In the early 21st century computer tools provide the opportunity for students to construct and test their own models using tools such as spreadsheets (电子制表软件)or concept maps (概念图). This type of instruction deepens students' understanding of abstract concepts and allows these concepts to be taught at an earlier age.F) Once students have summarized their data and other information, they typically communicate their findings to others. Writing reports is still the most widespread use of ICT, with 61 percent of US teachers assigning students word-processing tasks. In addition to text, students also use computer-created graphics, videos, and animations to communicate their ideas.G) The teacher is not the only audience for students' presentations. Students frequently expect to present their work to and receive feedback from their peers and the world outside their classroom. Whether they are using presentation software to accompany a face-to也cepresentation or developing materials to put on the Web, the trend is for students to be able to communicate their work to a broad audience. This increases students' perception that problem-based learning is real work for real audiences.The use of technology for collaboration and distance educationH) There are many opportunities for individual students to use technology to enhance their learning. These include online courses that provide students in remote locations with opportunities for customized curriculum and advanced placement courses (先修课程). These courses are conducted entirely online and offer asynchronous (异步的)interaction among faculty and students. Because they allow students to participate anytime and from anywhere, online courses are becoming increasingly popular among postsecondary (高等教育)students whose job and personal commitments do not allow them to meet a regular class schedule.I) Opportunities for interaction with peers from other countries can also contribute to knowledge and understanding of other cultures. ICT makes this type of communication possible for anyone with Internet access. For example, the Kidlink project encourages students up to age 15 to use the Internet to build a global network of friends. Kidlink participants discuss issues ranging from how to make and keep friends to war and peace.J) Monitoring students' independent learning in these flexible environments will be supported by sophisticated new assessment technologies that will help teachers collect and analyze students' data and make instructional decisions. These tools will continually assess students' work and provide feedback to them and their teachers. Such assessment has the potential to make time-consuming standardized testing unnecessary and to personalize the curriculum for every student. Ubiquitous,well-integrated technology tools will bring educators closer to redefine the educational enterprise and provide customized, just-in-time solutions for the learning needs of students.____1 Students find it more difficult to locate the right information from among a large number of websites.____2 Teachers will use sophisticated new technologies to assess students' learning in flexible environments and make instructional decisions.____3 Collecting information from the Internet is similar to that in the library as students obtain published reports and process the information in both cases.____4 While teachers had to limit problems to those with resources in the process of teaching in the past, students nowadays can make their own interest-based choices because of a large amount of information available on many subjects.____5 Students of higher education prefer online courses to those given at fixed time and in fixed places due to their other businesses.____6 The Kidlink project encourages students up to 15 to make foreign friends and have discussions about a wide range of issues on the Internet.____7 Many countries around the world prioritize the creation and spread of ICT.____8 By means of two-way audio and video, scientists in San Diego State University instructed the fourth- and fifth-grade students in California to observe specimens with electronic devices. ____9 Face-to-face presentations accompanied by software indicate the trend that students can communicate their work with more people.____10 Because of computer tools, abstract concepts can be better understood by students and be taught at an earlier age.Part V Translation (10%)1. 孔子的许多思想,尤其是教育思想,对中国社会产生了深远的影响。
上海市部分区2024届高三二模英语试题汇编六选四2024届上海市长宁区高三下学期二模英语试卷Section CDirections:Read the passage carefully. Fill in each blank with a proper sentence given in the box. Each sentence can be used only once. Note that there are two more sentences than you need.Martha Stewart was charged, tried and convicted of a crime in 2014. As she neared the end of her prison sentence, a well-known columnist wrote that she was “paying her dues,”and that “there is simply no reason for anyone to attempt to deny her right to start anew. ”67 Unfortunately, many federal and state laws impose post-conviction restrictions ona shockingly large number of Americans, who are prevented from ever fully paying their debt to society.At least 65 million people in the United States have a criminal record. This can result in severe penalties (惩罚) that continue long after punishment is completed.Many of these penalties are imposed regardless of the seriousness of the offense or the person’s individual circumstances. 68 They can affect a person’s ability to get a job and qualification for benefits.In all, more than 45, 000 laws and rules serve to exclude vast numbers of people from fully participating in American life. Some laws make senses. No one advocates letting someone convicted of pedophilia (恋童癖) work in a school. 69 Should a woman who possessed a small amount of drugs years ago be permanently unable to be licensed as a nurse?These laws are also counterproductive (适得其反), since they make it harder for people with criminal records to find housing or a job, two key factors that reduce backsliding. A recent report makes several recommendations, including the abolition of most post-conviction penalties, except for those specifically needed to protect public safety. 70 .The point isn’t to excuse or forget the crime. Rather, it i s to recognize that in America’s vast criminal justice system, and second chances are crucial. It is in no one's interest to keep a large segment of the population on the margins of society.2024届上海市徐汇区高三二模考试英语试题Section CDirections: Read the passage carefully. Fill in each blank with a proper sentence given in the box. Each sentenceAstronomers are eagerly anticipating a celestial (天体的) event that promises to be a once-in-a-lifetime sight: the appearance of a "new star" in the night sky, expected to occur sometime between now and September, as reported by NASA. This event, known as a nova (新星), is projected to take place within the T Coronae Borealis system, nestled in the constellation(星座) Corona Borealis, situated between the Boötes and Hercules constellations.In contrast to the explosive demise of a massive star seen in a supernova, a nova is characterized by a sudden, brief explosion originating from a collapsed star, specifically a white dwarf. The T Coronae Borealis system is affectionately called the "Blaze Star." (67) _______________________ These stars orbit closely enough to interact violently, leading to periodic explosive events, with the last eruption observed in 1946.(68) _______________________ Over time, the red giant becomes increasingly unstable, shedding its outer layers onto the white dwarf. This exchange of matter eventually triggers a "runaway thermonuclear reaction," resulting in the nova phenomenon, according to NASA.While the precise timing of the upcoming nova event remains uncertain, astronomers are closely monitoring the T Coronae Borealis system, which has been dimming since March of the previous year. William J. Cooke, lead of NASA's Meteoroid Environments Office, notes that while most novae occur unexpectedly, T Coronae Borealis is one of the 10 recurring novae in the galaxy, offering some predictability to its eruptions.Located approximately 3,000 light-years away from Earth, the T Coronae Borealis system is typically too faint to be seen with the naked eye. (69) _______________________Once the nova reaches its peak brightness, it will appear as if a new star has emerged in the night sky, remaining visible for a few days without any equipment and slightly over a week with binoculars before gradually fading from view over the course of about 80 years.(70) _______________________ As an effective observing approach, they provide valuable insights into the dynamics of recurrent novae and the processes occurring within these stellar systems.The NASA Universe account on X will provide regular updates on the nova event, allowing enthusiasts and researchers alike to stay informed about this captivating astronomical phenomenon. Reflecting on past experiences, including witnessing the 1975 Nova Cygni, which inspired his career in astronomy, Cooke underscores the significance of these celestial events in shaping our understanding of the cosmos.2024届上海市上海市闵行区高三二模英语试题Section CDirections: Read the following passage. Fill in each blank with a proper sentence given in the box. Each sentence can be used only once. Note that there are two more sentences than you need.Childhood Media Shaping FuturesMuch of the media we consume during our formative years shapes us into the people we are today. Reflect on a particular piece of media from our childhood—perhaps it’s the TV show we eagerly awaited every weekend during visits to our grandmother’s house. 67 It shapes our dreams and fears and even drives us to future careers.68 Older children may have had a lot more restrictions, like TV shows, movies, and social media access. And because of these, they were able to be a child for longer compared to their siblings (兄弟姐妹). Ch ildren who have older siblings tend to show more mature tendencies and can appear to “grow up quicker” than other children their age.While they might have been restricted from social media accounts until a certain age, once given access, they tend to be more prepared. The media exposure of our generation has undoubtedly led to an increased maturation at younger ages. 69 9Simply looking back at previous generations and the rate of consumption and processing of information that we experience every day, the effects of such are only beginning.As soon-to-be or current adults, we are already facing issues such as depression, anxiety, and delays in certain learning and social skills, just to name a few. Are we “more mature?” or are we o verexposed and at risk for exceptional mental, physical, and emotional consequences?In conclusion, childhood media consumption significantly influences our lives. 70Striking a balance between media exposure and mental well-being is essential fo r our growth in today’s media-rich world.2024届上海市静安区高三下学期二模英语试题Section CDirections: Read the following passage. Fill in each blank with a proper sentence given in the box. Each sentenceTime to end Santa’s ‘naughty list’?Many of us have magical memories of Santa secretly bringing gifts and joy to our childhood homes — but is there a darker side to the beloved Christmas tradition?I was —and I’m happy to admit it — a loyal believer of Santa. I absolutely loved the magic of Christmas, especially Santa Claus, and my parents went above and beyond to encourage it. However, as I begin to construct my own Santa Claus myth for my daughter, I can’t help but feel guilty. Could it undermine her trust in me?__67__ Back in 1978, a study published in the American Journal of Orthopsychiatry(矫正精神医学) found that 85% of four-year-olds said they believed in Santa. In 2011, research published in the Journal of Cognition and Development found that 83% of 5-year-olds claimed to be true believers.I guess it’s not all that surprising. __68__ He features in every Christmas TV show and movie. Each year the North American Aerospace Defence Command (NORAD) allows you to track Santa’s journey on Christmas Eve. To reassure children during the pandemic in 2020, the World Health Organization issued a statement declaring that Santa was “immune” from Covid 19. And it’s precisely this effort on behalf of parents, and society in general, to create such seemingly overwhelming evidence for the existence of Santa Claus that David Kyle Johnson, a professor of philosophy at King’s College in Pennsylvania, describes as ‘The Santa Lie’ in his book The Myths That Stole Christmas. He highlights how we don’t simply ask children to imagine Santa, but rather to actually believe in him. __69__The ‘Santa lie’ can reduce trust between a parent and a child. __70__ It is the creation of false evidence and convincing kids that bad evidence is in fact good evidence that discourages the kind of critical thinking we should be encouraging in children in this era. “The ‘Santa lie’ is part of a parenting practice that encourages people to believe what they want to believe, simply because of the psychological reward,” says Johnson. “That’s really bad for society in general.”2024届上海市浦东新区高三下学期二模英语试题Section CDirections:Read the following passages. Fill in each blank with a proper sentence given in the box. Each sentence can be used only once. Note that there are two more sentences than you need.What motivates you to work or study harder? Is it the thought of success and all the amazing things that you can achieve, or is it the fear of failure and worry about all the things that can go wrong for you? _____67_____ But is one better than the other?A recent study looked at the effect of fear-based strategies on British secondary school students. As is so often the case, it’s complicated. They fou nd that if a test is seen as important, and students are optimistic that they can succeed, then the fear of failure can be used successfully by teachers to motivate these learners. _____68_____ It can in turn lead them to do worse on the test than they would have done otherwise. The study also found that if students are disengaged and don’t care about the test in the first place, then, unsurprisingly, the fear of failure is not likely to motivate them.Entrepreneurs often run the risk of failure. It’s a fac t that most new companies will fail. _____69_____ The personal consequences of failure can be significant, and so founders may be motivated to work harder to avoid them. A study carried out on British and Canadian entrepreneurs found that fear of failure can improve problem solving, as people are motivated to anticipate and resolve potential issues. However, the study also showed that it can lead to increased procrastination as people focus too much on what they personally fear, rather than what would be best for the business. If someone is less confident about their business idea, then they may find their decision-making negatively affected by their fears._____70_____ It can drive confident people to do better, but it can also increase our doubts and turn them into barriers.参考答案2024届上海市长宁区高三下学期二模英语试卷Section C 评分标准:每小题2分。
高中高考英语单词以下是一份包含高中高考英语常见单词大全。
这些单词被广泛使用于高中英语教学以及高考考试中。
为了方便学习,按照字母顺序进行了分类。
A1. Abandon2. Abbreviation3. Abolish4. Abstract5. Accelerate6. Accommodate7. Accumulate8. Accuracy9. Acquire10. Adapt11. Adequate12. Administer13. Adversity14. Advocate15. Affect16. Aggregate17. Agriculture18. Alleviate19. Alternative20. AmbiguousB21. Barrier22. Bias23. Bizarre24. Brevity25. Budget26. Bureaucracy27. BystanderC28. Calculate29. Caption30. Categorize31. Causality32. Cease33. Certainty34. Challenge35. Circumstance36. Civilize37. Clarify38. Coherent39. Coincide40. Collaborate41. Commission42. Compatible43. Compile44. Complement45. Comprehend46. Conceive47. Concentrate48. Conclude49. Conducive50. ConformD51. Decline52. Dedicate53. Deficit54. Deliberate55. Demonstrate56. Denote57. Depict58. Derive59. Detect60. Deviate61. Devise62. Differentiate63. Diffuse64. Dilemma65. Diligent66. Diminish67. Discern68. Discrepancy69. Disperse70. Distinct71. Diverse72. Divert73. Document74. Domestic75. DominantE76. Economical77. Ecosystem78. Elicit79. Eligible80. Embrace81. Empirical82. Enable83. Encourage84. Endorse85. Enhance86. Enrich87. Ensure88. Entail89. Entity90. Entrench91. Equate92. Equivalent93. Eradicate94. Erode95. Ethical96. Evaluate97. Evoke98. Evolution99. Excel 100. ExcerptF101. Facilitate 102. Factor 103. Famine 104. Feedback 105. Feasible 106. Federal 107. Fertilize 108. Fluctuate 109. Focus 110. Forecast 111. Format 112. Formulate 113. Framework 114. Friction115. FundamentalG116. Generate 117. Globalization 118. Gradual 119. Graph 120. Grant 121. Grasp 122. Guarantee 123. GuidelineH124. Halt125. Hazard 126. Hierarchy 127. HypothesisI128. Identical 129. Ideology 130. Ignite132. Immigrate 133. Impair 134. Implement 135. Impose 136. Impulse 137. Incentive 138. Incidence 139. Incline 140. Incorporate 141. Indicate 142. Individual 143. Induce 144. Infer 145. Inflation 146. Influence 147. Inherent 148. Initiate 149. Innovation 150. Input 151. Inquiry 152. Insert154. Inspire 155. Install 156. Integrate 157. Integrity 158. Intelligence 159. Intensive 160. Intention 161. Interaction 162. Interfere 163. Interpret 164. Interval 165. Intervene 166. Intrinsic 167. Intuition 168. Invariably 169. Investigate 170. InvokeJ171. JustifyK172. KineticL173. Laborious 174. Lament 175. Latitude 176. Legislative 177. Literacy 178. Livelihood 179. LogicalM180. Magnitude 181. Maintain 182. Manifest 183. Manipulate 184. Margin 185. Massive 186. Mature 187. Maximum 188. Measurable189. Mediate 190. Medium 191. Melancholy 192. Merchandise 193. Merge 194. Metaphor 195. Methodology 196. Mimic 197. Minimum 198. Minor 199. Mode 200. ModifyN201. Narrative 202. Navigate 203. Neutral 204. Nevertheless 205. Norm 206. Notion 207. NurtureO208. Objective 209. Obstacle 210. Occupy 211. Omit212. Orientation 213. Origin 214. Outweigh 215. Overcome 216. Overtake 217. OzoneP218. Paradox 219. Parameter 220. Participate 221. Passive 222. Perception 223. Persist 224. Perspective 225. Pervasive 226. Phenomenon227. Philosophy 228. Pioneer 229. Policy 230. Portray 231. Postulate 232. Potential 233. Precede 234. Precise 235. Predict 236. Prejudice 237. Preliminary 238. Prescribe 239. Preserve 240. Presume 241. Prevail 242. Previous 243. Prioritize 244. Probe 245. Proceed 246. Process 247. Profound 248. Prohibit249. Prominent 250. PromptQ251. Qualitative 252. Quantitative 253. QuotaR254. Radical 255. Random 256. Rationale 257. Rationalize 258. React 259. Recede 260. Reciprocal 261. Reconcile 262. Rectify 263. Reflect 264. Refrain 265. Regime 266. Regulate268. Reject 269. Relate 270. Relevant 271. Reluctant 272. Remove 273. Render 274. Renew 275. Repetition 276. Repress 277. Require 278. Resemble 279. Reside 280. Resolve 281. Resort 282. Resource 283. Respond 284. Restore 285. Restrict 286. Retain 287. Retrieve 288. Reveal290. Revise 291. Revolutionize 292. Rigid293. RouteS294. Satellite 295. Saturate 296. Scenario。
0707 ©2006 Titan Tool Inc. All rights reserved. Form No. 313-2459CPrinted in the U. S. A.Do not use this equipment before reading this manual!440ixAirless SprayerOwner’s ManualFor professional use onlyNOTE:This manual containsimportant warnings and instructions.Please read and retain for reference.X-Lock Theft Deterrent SystemSecurity Code————Serial # __________Model Numbers:Skid Basic 700-3030Skid Loaded700-3035High Rider Basic 700-3040High Rider Loaded700-30452©Titan Tool Inc. All rights reserved.©Titan Tool Inc. All rights reserved.34©Titan Tool Inc. All rights reserved.Trigger the gun into the metal waste container until the oldsolvent is gone and fresh solvent is coming out of the gun.knob slowly clockwise into the green zone.Procedure” in this manual before tightening any fittings or Follow the “Pressure Relief Procedure” in this manualTrigger lock in locked position.container while flushing. Failure to Trigger the gun into the metal waste container until all air and solvent is flushed from the spray hose and paint is unless the tip is in either the spray or the unclog position. Always engage the gun trigger lock before removing, replacing or cleaning tip.Trigger lock in locked position.©Titan Tool Inc. All rights reserved.56©Titan Tool Inc. All rights reserved.©Titan Tool Inc. All rights reserved.78©Titan Tool Inc. All rights reserved.container until the paint is flushed out of the hose and Continue to trigger the spray gun into the waste containeruntil the solvent coming out of the gun is clean.Follow the “Pressure Relief Procedure” found in theUnplug the unit and store in a clean, dry area.For long-term or cold weather storage, pumpmineral sprits through the entire system.For short-term storage when using latex paint,pump water mixed with Titan Liquid Shieldthrough the entire system (see the Accessories section of this manual for part number).©Titan Tool Inc. All rights reserved.910©Titan Tool Inc. All rights reserved.©Titan Tool Inc. All rights reserved.1112©Titan Tool Inc. All rights reserved.©Titan Tool Inc. All rights reserved.13Troubleshooting14©Titan Tool Inc. All rights reserved.Solution1.Plug the unit in.2.Reset the breaker.3.Turn the pressure control knob clockwise to supply power to the unit and increase the pressure setting.4.Inspect or take to a Titan authorized service center.5.Allow motor to cool.6.Replace the ON/OFF switch.1.Rotate the PRIME/SPRAY valve clockwise to the PRIME position.2.Check the siphon tube/suction set connection and tighten or re-tape the connection with PTFE tape.3.Remove the pump filter element and clean.Remove the inlet screen and clean.4.Remove the siphon tube/suction set and clean.1.Replace the spray tip following theinstructions that came with the spray gun.2.Replace the spray tip with a tip that has a smaller orifice following the instructions that came with the spray gun.3.Turn the pressure control knob clockwise to increase the pressure setting.4.Remove the pump filter element and clean.Remove the gun filter and clean. Remove the inlet screen and clean.5.Clean or replace the PRIME/SPRAY valve.6.Check the siphon tube/suction set connection and tighten or re-tape the connection with PTFE tape.7.Check for external leaks at all connections.Tighten connections, if necessary.8.Clean the valves and service the fluid section following the “Servicing the Fluid Section” procedure in the Maintenance section of this manual.9.Reverse or replace the valve seatsfollowing the “Servicing the Fluid Section”procedure in the Maintenance section of this manual.10.Take unit to a Titan authorized servicecenter.1.Repack the pump following the “Servicing the Fluid Section” procedure in the Maintenance section of this manual.2.Replace the piston rod following the“Servicing the Fluid Section” procedure in the Maintenance section of this manual.1.Replace hose with a minimum of 50’of 1/4”grounded textile braid airless paint spray hose.2.Replace the spray tip following theinstructions that came with the spray gun.3.Rotate the pressure control knob counterclockwise to decrease spray pressure.Cause1.The unit is not plugged in.2.Tripped breaker.3.The pressure is set too low (pressure control knob set at minimum setting does not supply power to unit).4.Faulty or loose wiring.5.Excessive motor temperature.6.ON/OFF switch is defective.1.The PRIME/SPRAY valve is in the SPRAY position.2.Air leak in the siphon tube/suction set.3.The pump filter and/or inlet screen is clogged.4.The siphon tube/suction set is clogged.1.The spray tip is worn.2.The spray tip is too large.3.The pressure control knob is not set properly.4.The pump filter,gun filter,or inlet screen is clogged.5.Material flows from the return hosewhen the PRIME/SPRAY valve is in the SPRAY position.6.Air leak in the siphon tube/suction set.7.There is external fluid leak.8.There is an internal fluid section leak (packings are worn and/or dirty,valve balls are worn).9.Worn valve seats10.Motor powers but fails to rotate1.The upper packing is worn.2.The piston rod is worn.1.Wrong type of airless spray hose.2.The spray tip worn or too large.3.Excessive pressure.ProblemThe unit will not run.The unit will not prime.The unit will not build or maintain pressure.Fluid leakage at the upper end of the fluid section.Excessive surge at the spray gun.TroubleshootingProblemPoor spray pattern. The unit lacks power.Cause1.The spray tip is too large for thematerial being used.2.Incorrect pressure setting.3.Insufficient fluid delivery.4.The material being sprayed is tooviscous.1.The pressure adjustment is too low.2.Improper voltage supply.Solution1.Replace the spray tip with a new or smallerspray tip following the instructions thatcame with the spray gun.2.Rotate the pressure control knob to adjustthe pressure for a proper spray pattern.3.Clean all screens and filters.4.Add solvent to the material according to themanufacturer's recommendations.1.Rotate the pressure control knob clockwiseto increase the pressure setting.2.Reconnect the input voltage for 120V AC.20©Titan Tool Inc. All rights reserved.Parts ListMain AssemblyItem Part #Description Quantity 1704-181Screw (includes washer and grommet) (4)2704-232Motor cover (1)3700-681Screw (4)4704-499Power cord (skid) (1)704-553Power cord (high rider)5704-229Ground screw (1)6704-486Screw (4)7704-488Pressure control knob (1)8704-469Xact Digital Control System assembly(optional) (1)9704-467Xact Digital Control system cover(optional) (1)10704-487Screw (2)11704-300Siphon/Return assembly (skid) (1)12704-599Dust cover (for sprayers without XactDigital Control System) (1)13704-473Control panel cover (for sprayers withoutXact Digital Control System).......................1Item Part #Description Quantity 14765-063Strain relief (skid). (1)704-369Strain relief (high rider)15704-331Gasket (1)16761-178Hex screw (4)17----------Skid assembly (1)18704-470Control panel (1)19704-538Fluid section assembly (skid) (1)704-571Fluid section assembly (high rider)20704-117Socket screw (2)21704-304Pail hook (high rider) (1)22763-552Lock washer (high rider) (2)23710-033Hex screw (high rider) (2)24702-239Return hose (high rider) (1)25755-225Siphon tube (high rider) (1)26730-334Hose clip (high rider) (1)27710-046Inlet screen (high rider) (1)28800-929Fuse, 15A(not shown) (1)Fluid Section Assembly (Skid P/N 704-538, High Rider 704-571)98111210712345141315161718196Item Part #Description Quantity 1730-508Retainer nut (1)2700-587Piston guide (1)3704-564Upper packing assembly with tool (1)4704-532Pump block (1)5227-006Outlet fitting (1)6704-547Lower packing assembly (1)7704-551Piston rod (1)8704-642Outlet cage (includes item 9 (1)9704-612Crush washer (1)10762-144Outlet valve ball (1)11704-558Outlet valve seat (1)12704-587Outlet valve retainer (1)13755-186Piston bushing (1)14700-821Foot valve seal (1)15730-510Inlet cage (1)16762-145Foot valve ball (1)17762-137Foot valve seat (1)18762-058O-ring, PTFE (1)19704-054Foot valve housing (skid) (1)730-511Foot valve housing (high rider)20700-421Filter housing..............................................1Item Part #Description Quantity 21540-030Filter (1)22560-038Seal (1)23700-258PRIME/SPRAY valve assembly (1)24700-697Valve handle (1)25700-759Groove pin (1)26700-252Cam base (1)27700-721Valve stem o-ring, Viton (1)700-897Valve stem o-ring, PTFE (optional)28221-012O-ring, Viton (1)29222-012O-ring, PTFE (1)30700-537Gasket (1)31762-202Packing tool (not shown) (1)704-560Piston assembly (includes items 7–12)704-586Repacking kit (includes items 2, 3, 6, 8, 9,10, 14, 16, and 18. Also included arepacking grease P/N 700-203 and pistonguide tool P/N 700-793.)3 145 2Item Part#Description Quantity 1704-380ON/OFF Switch (1)2700-139Screw (8)3704-019Front cover (1)4704-492Transducer assembly (includes item 5) (1)5704-584Transducer o-ring (1)6704-588Electronic pressure control (EPC) (1)7704-589Motor (without EPC) (1)8704-173Crankshaft/gear assembly (1)9704-174Thrust washer.............................................1Item Part #Description Quantity 10704-1762nd stage gear.. (1)11704-510Pump housing (1)12700-2060Slider assembly (1)13704-548Transducer jumper wire (not shown) (1)15730-260Electronic pressure controlmounting screw (not shown) (4)16704-126Electronic pressure controllock washer (not shown) (4)TransducerElectrical SchematicHigh Rider Cart Assembly (P/N 704-574)Item Part #Description Quantity 1704-573Cart weldment (includes item 5).................12704-355Cap.............................................................23704-354Spacer ........................................................44704-353Wheel..........................................................25710-199Plug. (4)12354LabelsPart #Description313-1638Front cover label 313-1629Motor cover label 313-1673Warning label(injection/explosion)313-1847Shock hazard label 313-1906Infinity motor label 313-2324X-Lock label313-2327Xact Digital Control System label 313-2328Xact Instruction label 313-2430Transducer warning labelNotesNotesTitan Tool, Inc., (“Titan”) warrants that at the time of delivery to the original purchaser for use (“End User”), the equipment covered by this warranty is free from defects in material and workmanship. With the exception of any special, limited, orextended warranty published by Titan, Titan’s obligation under this warranty is limited to replacing or repairing without charge those parts which, to Titan’s reasonable satisfaction, are shown to be defective within twelve (12) months after sale to the End User. This warranty applies only when the unit is installed and operated in accordance with the recommendations and instructions of Titan.This warranty does not apply in the case of damage or wear caused by abrasion, corrosion or misuse, negligence, accident,faulty installation, substitution of non-Titan component parts, or tampering with the unit in a manner to impair normal operation.Defective parts are to be returned to an authorized Titan sales/service outlet. All transportation charges, including return to the factory, if necessary, are to be borne and prepaid by the End User. Repaired or replaced equipment will be returned to the End User transportation prepaid.THERE IS NO OTHER EXPRESS WARRANTY . TITAN HEREBY DISCLAIMS ANY AND ALL IMPLIED WARRANTIESINCLUDING, BUT NOT LIMITED TO, THOSE OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, TO THE EXTENT PERMITTED BY LAW. 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UNIT1mood /mu:d/ n.心情circus /'sɜːkəs/ n.马戏团amusement /ə'mju:zmənt/ n.娱乐,消遣amusement park游乐场* curly /'kɜːli/ adj.卷曲的* wig /wɪg/n.假发* badge /bædʒ/n.微章ankle /'ænk(ə)l/n.脚踝* clown /klaʊn/ n.小丑entertain /,entə'teɪn/ v.使快乐health care医疗保健cheer up (使)高兴起来,(使)振作起来do the trick奏效,达到预期效果examine /ɪg'zæmɪn/v.检查(身体) advertisement /ad'vɜːtɪsmənt/n.广告employer /ɪm'pɪɔɪə/n.雇用者,雇主essential /r'senʃ(ə)/ adj.极其重要的,必不可少的impress /ɪm'pres/ v.使钦佩,使留下深刻印象* grin /grɪn/v. 露齿而笑,咧着嘴笑deserve /dɪ'zɜːv/v.应得,应受到long face愁眉苦脸laughing stock笑料,笑柄crack a smile 笑了起来practical joke恶作剧* fame /feɪm/n.名声,名誉* linguist /'lɪŋgwɪst/ n.语言学家* witty /'wɪti/ adj. 说话风趣的;妙趣横生的* medieval /,medi'i:v(ə)l/ adj.中世纪的,中古时期的* emotive /ɪ'məʊtɪv/ adj. 使情绪激动的* mischievous /'mɪstʃɪvəs/ adj.调皮的,淘气的* remark /rɪ'mɑːk/n. 言论;意见,评论interaction /,ɪntər'ækʃ(ə)n/ n.交流* barber /bɑːbə/ n.男理发师shave /ʃeɪv/n.刮脸,刮胡子fellow /'feləʊ/ n.男人;家伙* brand /brænd/n.品牌,牌子brand of humour某种类型的幽默concept /'kɒnsept/n.概念,观念spot /spɒt/n.地点,处所put sb on the spot(故意提出难以回答或尴尬的问题)使某人难堪cruel /'kru:ə1/ adj.残忍的whisper /'wɪspə/ v.悄声说,低语* roar/rɔ:/v. 哄笑,大笑* gently /'dʒentli/ adv. 温和地;轻柔地tell off斥责,责骂* illuminate /ɪ'lu:mɪneɪt/ v.照亮,照明* equation /ɪ'kweɪʒ(ə)n/n.等式,方程式complicated /'kɒmplɪkeɪtɪd adj.难处理的;难懂的conclude /kən'klu:d/v.结束,终止composer /kəm'pəʊzə/n.作曲家fall behind不能按时完成(工作)UNIT 2debt /det/n.债务,欠款pace /peɪs/n.速度;进度* inform /ɪn'fɔ:m/v.通知,告知* dread /dred/v.畏惧,惧怕rarely /'reəli/ adv.很少,难得* overnight /,əuvə'naɪt/ adv. 突然,一下子rejection /rɪ'dʒekʃ(ə)n/n.拒绝,否决nevertheless /,nevəðə'les/ adv.然而,不过* persevere /psstvsa/u锲而不舍,坚持不懈criticism /'krɪtɪsɪz(ə)m/n.批评;指责* manuscript /'mænjʊskrɪpt/n. 手稿,底稿* rye/raɪ/n.黑麦*best seller /,best'selə/ n. 畅销书;畅销产品* Victorian /vɪk'tɔ:riən/adj. 英国维多利亚(女王)时代的*laureate /lɔ:riət/ n. 重要奖项获得者Poet Laureate桂冠诗人classic /'klæsɪk/n.名著;经典作品*endurance /ɪn'djʊrəns/n. (忍)耐力guarantee /,gærən'ti:/v.保证;确保delighted /dɪ'laɪtɪd/ adi.愉快的,高兴的outcome /'aʊtkʌm/n.结果,后果worthwhile /,wɜːθ'waɪl/ adj.重要的:值得做的blanket /'blæŋkɪt/n.毯子,毛毯* beaver /'bi:və/n. 河狸,海狸* cucumber /'kju:kʌmbə/n.黄瓜enthusiastic /ɪn,θju:zi'æstɪk/ adj.热心的,热衷的contest /'kɒntest/n.比赛,竞赛upset /,ʌp'set/ adi.心烦意乱的,烦恼的elect /ɪ'lekt/v.选举,推选blessing /'blesɪŋ/n.幸事,幸运appreciative /ə'pri:ʃətɪv/ adj.感激的worthy /wɜːði/ adj.值得尊敬的;值得赞赏的worthy of值得...的mere /mɪə/ adj.仅仅,只不过gentleness /'dʒentlnɪs/n.和蔼,温和*companionship /kəm'pænjənʃɪp/n. 友谊;友好交往* fingertip /fɪŋgə,tɪp/n.指尖outline /'aʊtlaɪn/n.外形,轮廓* intoxicate /ɪn'tɒksɪkeɪt/v.使兴奋,使陶醉* pageant /'pædʒ(ə)nt/n. 盛大的(露天)演出the pageant of (历史事件的)缤纷场景* probe /prəʊb/v.调查;探究* dawn /dɔ:n/n.黎明,破晓* delight /dɪ'laɪt/ n.使人高兴的事* revelation /,revə'leɪʃ(ə)n/n.展现,显示* workaday /wɜːkədeɪ/ adj. 平凡的;平淡的* amid /ə'mɪd/ prep. ....之中* haunt /hɔ:nt/n. (某人)常去的地方permanent /'pɜːmənənt/ adj.长久的; 永久的* descend /dɪ'send/v.降临;来临*mighty /'maɪti/ adi.强有力的;雄伟的strains of音乐的曲调或旋律* orchestra /'ɔ:kɪstrə/n. ( 大型的)管弦乐队* tactile /'tæktaɪl/ adj. 触觉的* perfume /pɜːfju:m/n. 香味* relish /'relɪʃ/n. 享受,乐趣* morsel /mɔ:s(ə)l/n. (尤指食物的)一小片,一小块* delightful /dɪ'laɪtf(ə)l/ adj.令人愉快的,讨人喜欢的literary /'lɪt(ə)rəri/ adj.文学的embarrassed /ɪm'bærəst/ adj.难堪的,尴尬的UNIT 3a far cry from ...不相同* shiny /'ʃaɪni/ adj. 光滑发亮的,闪光的association /ə,səʊsɪ''ɪʃ(ə)n/n.协会,社团muddy /'mʌdi/ adj.沾满泥的,泥泞的* shot /ʃɒt/n.投球,射球,击球* backboard /'bækbɔ:d/n.篮板give way倒塌,向下垮bump /bʌmp/n.隆起之处bounce /baʊns/v. (使)弹起,(使)反弹* sharpen /'ʃɑːpən/ v.使提高,使改进* teammate /'ti:mmeɪt/n. 队友footstep /'fʊtstep/n.脚步声;足迹follow in one's footsteps仿效某人;继承某人(尤指家人) 的事业carry on继续* warrior /'wɒriə/n. 武士,战士Expectation/,ekspek'teɪʃ(ə)n/n.预料,预期beyond one's expectations超出某人的预期ina row连续地philosophy /fɪ'lɒsəfi/n.人生哲学* self-belief /,selfrbɪi:f/ n. 自信* hoop /hu:p/n. (篮球中的)篮圈cheat /tʃi:t/v.欺骗,作弊* yoga /'jəʊgə/n.瑜伽roller skating滑旱冰remarkable /rɪ'mɑːkəb(ə)l/ adj.非凡的:不寻常的net /net/n.球网* spiker /'spaɪkə/ n. (排球队的)扣球队员,主攻手* burst /bɜːst/ v. 突然出现burst onto突然出现.... (指突然成功)vivid /'vɪvɪd/ adj.生动的,逼真的assign /ə'saɪn/v.分配,分派opponent /ə'pəʊnənt/n. (竞争、比赛等的)对手*quarter final /,kwɔ:tə'faɪnl/n. 四分之一决赛* preliminary /prɪ'lɪmɪn(ə)ri/ adj. 初步的;预备的surgery /'sɜːdʒ(ə)ri/n.外科手术pay off取得成功* comeback /'kʌmbæk/ n.东山再起defeat /dɪ'fi:t/v.战胜,打败*semi-final /,semi'faɪnl/ n.半决赛steely /'sti:li/ adj.钢铁般的;坚定的nerve /nɜːv/ n.意志力seize /si:z/ v.夺取cooperation /kəʊ,ɒpə'reɪ(ə)n/n.合作,协作* ingredient /ɪn'gri:diənt/n. (完成某事的)要素,因素* teamwork /'ti:mwɜːk/ n.合作,协作* podium /'pəʊdiəm/n. 表演台,讲台tournament /'tʊənəmənt/ n.锦标赛intense /ɪn'tens/ adj.紧张的,激烈的UNIT 4quote /kwəʊt/n.引文,引语*Dutch /dʌtʃ/ adj. 荷兰的*float /fləʊt/v.浮,漂folk /fəʊk/ adj.民间的,民俗的tale /teɪl/ n.故事folk tale民间故事motion /'məʊʃ(ə)n/n.动,运动set... in motion ......始compose /kəm'pəʊz/v.作(曲)* crouch /kraʊtʃ/v. 蹲下;蹲伏peacock /'pi:kɒk/n. (雄)孔雀princess /,prɪn'ses/n. 公主*ethnic /'eθnɪk/ adj. 民族的abstract /'æbstrækt/ adj.抽象(派)的*awe-inspiring /'ɔ:ɪn,spaɪərɪŋ/ adj. 令人起敬的,令人钦佩的* installation /,ɪnstə'leɪʃ(ə)n/ n.现代雕塑装置(除物体外还包括光、声等)wire /waɪə/n.金属丝;电线* cable /'keɪb(ə)l/ n.电缆innovative /'ɪnəvətɪv/ adj.新颖的,创新的trend /trend/n.趋势,动向wire fence铁丝网,铁丝栅栏contrast /'kɒntɑːst/ n.反差,对比* Greek /gri:k/ adj.希腊的literally /'lɪt(ə)rəli/ adv.根据字面意思*technician /tek'nɪʃ(ə)n/ n. 巧匠* animation /,ænɪ'meɪʃ(ə)n/ n. 动画片distinct /dɪ'stɪŋkt/ adj.清晰的;明显不同的innovation /,ɪnə'veɪʃ(ə)n/n.革新,创新UNIT 5seed /si:d/n.种子,籽distant /'dɪstənt/ adj.遥远的answer the call响应号召* disgrace /dɪs'greɪs/n. 丢脸,耻辱be a disgrace是耻辱,是丢脸的事* geologist /dʒi'ɒlədʒɪst/n. 地质学家sample /'sɑːmp(ə)l/n.样本* evolve /ɪ'vɒlv/v.进化* finch /fɪntʃ/n. 雀科鸣禽beak /bi:k/n.鸟嘴,喙suspect /sə'spekt/v.猜想,怀疑,觉得ancestor /'ænsəstə/n. ( 动物的)原种,祖先evolution /,i:və'lu:ʃ(ə)n/n.进化(论) generate /'dʒenəreɪt/v.产生,创造characteristic /,kærɪktə'rɪstɪk/ n.特征,特性decline /dɪ'klaɪn/v.减少tortoise /'tɔ:təs/ n.陆龟blame /bleɪm/v.责怪,指责;把...归咎于goat /gəʊt/n.山羊be native to源于...的,原产于...... primitive /'prɪmɪtɪv/ adj.原始的,低等的* worldwide /,wɜːld'waɪd/ adv.遍及全世界* giant /'dʒaɪənt/ adj. 巨大的,特大的giant tortoise巨型陆龟*mangrove /'mæŋgrəʊv/n. 红树(一种热带树木,生于水中或水边,并从树枝上长出新根须)* iguana /ɪ'gwɑːnə/n. 鬣蜥( -种大型热带美洲蜥蜴)* comb-like /'kəʊmlaɪk/ adj.梳状的* spine /spaɪn/n. ( 动植物的)刺,刺毛* myth /mɪθ/n. ( 古代的)神话* legend /'ledʒ(ə)nd/n. 传说,传奇(故事)detect /dɪ'tekt/v.发现,察觉(尤指不易觉察到的事物)* wasp /wɒsp/n.黄蜂pesticide /'pestɪsaaɪd/n.杀虫剂,农药root /ru:t/ n.根* chilli /'tʃɪli/n.辣椒ink /lɪŋk/v. 把...联系起来;连接* fungus /'fʌŋgəs/n.真菌(复数fungi )fungal /'fʌnŋg(ə)I/ adj.真菌的*cybercrime /'saɪbəkraɪm/ n.网络犯罪centimetre /'sentɪ,mi:tə/n.厘米UNIT 6* steadily /'stedɪli/ adv.平稳地massive /'mæsɪv/ adj.巨大的delicate /'delɪkɪt/ adj.脆弱的* landmark /'lændmɑːk/ n.地标splendid /'splendɪd/ adj.壮丽的* permafrost /'pɜːməfrɒst/n. 永久冻土层* Tibetan /tɪ'bet(ə)n/ adj.西藏的* antelope /'æntɪləʊp/n. 羚羊leisure /leʒə/n.空闲,闲暇at one's leisure空闲时* wetland /'wetlənd/ n.湿地* grassland /'grɑːslænd/n.草原radiation /,reɪdi'eɪʃ(ə)n/ n.辐射mirror-like /'mɪrə,laɪk/ adj.如镜面般的wander /'wɒndə/ v.徘徊* scenery /'si:nəri/n. 风景,景色* plateau /'plætəʊ/n. 高原economy /ɪ'kɒnəmi/ n.经济jungle /'dʒʌŋg(ə)l/n. (热带)丛林disturb /dɪ'stɜːb/ v.干扰,扰乱* emission /ɪ'mɪʃ(ə)n/n. 散发物,排放物operator /'ɒpəreɪtə/ n.经营者conservationist /,kɒnsə'veɪʃ(ə)nɪst n. ( 动植物或古旧建筑的)保护工作者;环境保护主义者* via /'vaɪə/ prep.通过(某人、某机器等)传送(某物);借助于candidate /'kændɪdɪt/ n.申请者applicant /'æplɪkənt/n.申请人favour /'feɪvə/n.支持,赞同in favourof支持,赞同advertise /'ædvətaɪz/v. (为.....做广告(宣传)genuine /'dʒenjuɪn/ adj.真的,真正的salary /'sæləri/n.薪金,工资negotiable /nɪ'gəʊʃiəb(ə)l/ adj.可协商的preference /'pref(ə)rəns/n.优先(权)qualification /,kwɒlɪfɪ'keɪʃ(ə)n/ n.技能条件,资格waist /weɪst/n.腰,腰部。
Femtosecond pulse shaping using spatial light modulatorsA. M. WeinerCitation: Rev. Sci. Instrum. 71, 1929 (2000); doi: 10.1063/1.1150614View online: /10.1063/1.1150614View Table of Contents: /resource/1/RSINAK/v71/i5Published by the American Institute of Physics.Related ArticlesNote: Self-characterizing ultrafast pulse shaper for rapid pulse switchingRev. Sci. Instrum. 83, 046111 (2012)Application of a transmission crystal x-ray spectrometer to moderate-intensity laser driven sourcesRev. Sci. Instrum. 83, 043104 (2012)Fractional high-order harmonic combs and energy tuning by attosecond-precision split-spectrum pulse control Appl. Phys. Lett. 100, 121104 (2012)Time-resolved single-shot imaging of femtosecond laser induced filaments using supercontinuum and optical polarigraphyAppl. Phys. Lett. 100, 111107 (2012)Fragment momentum distributions obtained from coupled electron-nuclear dynamicsJ. Chem. Phys. 136, 104306 (2012)Additional information on Rev. Sci. Instrum.Journal Homepage: Journal Information: /about/about_the_journalTop downloads: /features/most_downloadedInformation for Authors: /authorsREVIEW ARTICLEFemtosecond pulse shaping using spatial light modulatorsA.M.Weiner a)School of Electrical and Computer Engineering,Purdue University,West Lafayette,Indiana47907-1285͑Received17August1999;accepted for publication20January2000͒We review thefield of femtosecond pulse shaping,in which Fourier synthesis methods are used to generate nearly arbitrarily shaped ultrafast optical wave forms according to user specification.An emphasis is placed on programmable pulse shaping methods based on the use of spatial light modulators.After outlining the fundamental principles of pulse shaping,we then present a detailed discussion of pulse shaping using several different types of spatial light modulators.Finally,new research directions in pulse shaping,and applications of pulse shaping to optical communications, biomedical optical imaging,high power laser amplifiers,quantum control,and laser-electron beam interactions are reviewed.©2000American Institute of Physics.͓S0034-6748͑00͒02005-0͔I.INTRODUCTIONSince the advent of the laser nearly40years ago,there has been a sustained interest in the quest to generate ul-trashort laser pulses in the picosecond(10Ϫ12s)and femto-second(10Ϫ15s)range.Reliable generation of pulses below 100fs in duration occurred for thefirst time in1981with the invention of the colliding pulse modelocked͑CPM͒ring dye laser.1Subsequent nonlinear pulse compression of pulses from the CPM laser led to a series of even shorter pulses,2–6 culminating in pulses as short as6fs,a record which stood for over a decade.Six femtoseconds in the visible corre-sponds to only three optical cycles,and therefore such pulse durations are approaching the fundamental single optical cycle limit.Further rapid progress occurred following the demonstration of femtosecond pulse generation from solid-state laser media in the1990time frame.7Femtosecond solid-state lasers bring a number of important advantages compared to their liquid dye laser counterparts,including substantially improved output power and stability and new physical mechanisms for pulse generation advantageous for production of extremely short pulses.Femtosecond solid-state laser technology has now advanced to the point that pulses below6fs can be generated directly from the laser.8–14Equally important,the use of solid-state gain media has also led to simple,turn-key femtosecond lasers,and many researchers are now setting their sights on practical and low cost ultrafast laser systems suitable for real-world applications͑in addition to the scientific applications for which femtosecond lasers have been used extensively͒.De-tailed information on the current status of femtosecond tech-nology and applications can be found in several recent jour-nal special issues,15–17books,18–21and in another recent review article in this journal.22The focus of this article is femtosecond pulse shaping,a topic complementary to femtosecond pulse generation.Over the past decade powerful optical waveform synthesis͑or pulse shaping͒methods have been developed which allow generation of complicated ultrafast optical waveforms ac-cording to user specification.Pulse shaping systems have already demonstrated a strong impact as an experimental tool providing unprecedented control over ultrafast laser wave-forms for ultrafast spectroscopy,nonlinearfiber optics,and high-field physics.Coupled with the recent advances and re-sulting widespread availability of femtosecond lasers,as well as advances in femtosecond pulse characterization tech-niques,femtosecond pulse shaping is poised to impact many diverse and additional applications.In the terminology of electronic instrumentation,femtosecond lasers constitute the world’s best pulse generators,while pulse shaping is the short pulse optical analog to electronic function generators, which widely provide electronic square waves,triangle waves,and indeed arbitrary user specified waveforms.A number of approaches for ultrafast pulse shaping have been advanced.Here we concentrate on the most successful and widely adopted method,in which waveform synthesis is achieved by spatial masking of the spatially dispersed optical frequency spectrum.A key point is that because waveform synthesis is achieved by parallel modulation in the frequency domain,waveforms with effective serial modulation band-widths as high as terahertz and above can be generated with-out requiring any ultrafast modulators.We will be particu-larly interested in pulse shaping using spatial light modulators͑SLMs͒,where the SLM allows reprogrammable waveform generation under computer control.A review ar-ticle by Froehly describes a variety of pulse shaping tech-niques investigated prior to1983for picosecond pulses.23A more recent review by Weiner provides a broad account of femtosecond pulse shaping as well as related pulse process-ing techniques,including both the pulse shaping technique which is the focus of the current article as well as other approaches.27Other useful reviews include Ref.24,whicha͒Electronic mail:amw@REVIEW OF SCIENTIFIC INSTRUMENTS VOLUME71,NUMBER5MAY200019290034-6748/2000/71(5)/1929/32/$17.00©2000American Institute of Physicsdescribes early results on femtosecond pulse shaping using fixed masks and related experiments on picosecond pulse shaping performed in the context of nonlinear pulse com-pression,and Refs.25and26,which include citations to recent results on pulse shaping as well as holographic and nonlinear pulse processing.This review article is organized as follows.In Sec.II we discuss the basics of femtosecond pulse shaping,including a description of the apparatus,examples of pulse shaping re-sults usingfixed spatial masks,important results from the theory of pulse shaping,and instrument control,alignment, and pulse measurement issues.In Secs.III and IV we discuss programmable pulse shaping using liquid crystal SLMs and acoustic-optic modulators,respectively;these are the two types of SLMS which are most widely applied for femtosec-ond pulse shaping.Section V summarizes the relative advan-tages and disadvantages of liquid crystal and acousto-opticSLMs for pulse shaping.Section VI covers developments indeformable,movable,and micromechanical mirrors for pulseshaping applications.These special mirror based approachesfor programmable pulse shaping,while important,are not yetas completely developed as the liquid crystal or acousto-optic approaches,and for this reason are not included forcomparison in Sec.V.In Sec.VII we discuss further direc-tions in femtosecond pulse shaping,including shaping of in-coherent light,integration,direct space-to-time pulse shap-ing,and generalized pulse shapers for holographic andnonlinear pulse processing.We conclude in Sec.VIII by sur-veying some of the applications of femtosecond pulse shap-ing,including optical communications,dispersion compensa-tion,laser control of terahertz radiation,coherent control ofquantum mechanical processes,and laser-electron beam in-teraction physics.II.FEMTOSECOND PULSE SHAPING BASICSA.LinearfilteringThe femtosecond pulse shaping approach described inthis article is based on the linear,time-invariantfilter,a con-cept well known in electrical engineering.Linearfiltering iscommonly used to process electrical signals ranging fromlow frequencies͑audio and below͒to very high frequencies ͑microwave͒.Here we apply to linearfiltering to generate specially shaped optical waveforms on the picosecond andfemtosecond time scale.Of course,the hardware needed forprogrammable linearfiltering of femtosecond laser pulseslooks very different from the familiar resistors,capacitors,and inductors used for linearfiltering of conventional elec-trical signals.Linearfiltering can be described in either the time do-main or the frequency domain,as depicted in Fig.1.27In thetime domain,thefilter is characterized by an impulse re-sponse function h(t).The output of thefilter e out(t)in re-sponse to an input pulse e in(t)is given by the convolution ofe in(t)and h(t)e out͑t͒ϭe in͑t͒*h͑t͒ϭ͵dtЈe in͑tЈ͒h͑tϪtЈ͒,͑2.1͒where*denotes convolution.If the input is a delta function, the output is simply h(t).Therefore,for a sufficiently short input pulse,the problem of generating a specific output pulse shape is equivalent to the task of fabricating a linearfilter with the desired impulse response.Note that instead of the term‘‘impulse response function,’’which is common in electrical engineering,h(t)may also be called a Green func-tion,which is a common terminology in some otherfields.In the frequency domain,thefilter is characterized by its frequency response H().The output of the linearfilter E out()is the product of the input signal E in()and the frequency response H()—i.e.,E out͑͒ϭE in͑͒H͑͒.͑2.2͒Here e in(t),e out(t),and h(t)and E in(),E out(),and H(),respectively,are Fourier transform pairs—i.e.,H͑͒ϭ͵dt h͑t͒eϪit͑2.3͒andh͑t͒ϭ12͵dH͑͒e it.͑2.4͒For a delta function input pulse,the input spectrum E in()is equal to unity,and the output spectrum is equal to the fre-quency response of thefilter.Therefore,due to the Fourier transform relations,generation of a desired output waveform can be accomplished by implementing afilter with the re-quired frequency response.Our pulse shaping approach is described most naturally by means of this frequency domain point of view.B.Pulse shaping apparatus and pulse shaping examples usingfixed masksFigure2shows the basic pulse shaping apparatus,which consists of a pair of diffraction gratings and lenses,arranged in a configuration known as a‘‘zero dispersion pulse com-pressor,’’and a pulse shaping mask.28The individual fre-quency components contained within the incident͑usually but not always bandwidth limited͒ultrashort pulse are angu-larly dispersed by thefirst diffraction grating,and then fo-cused to small diffraction limited spots at the back focal plane of thefirst lens,where the frequency componentsare FIG.1.Pulse shaping by linearfiltering.͑a͒Time-domain view.͑b͒Fre-quency domain view.1930Rev.Sci.Instrum.,Vol.71,No.5,May2000 A.M.Weinerspatially separated along one dimension.Essentially the first lens performs a Fourier transform which coverts the angular dispersion from the grating to a spatial separation at the back focal plane.Spatially patterned amplitude and phase masks ͑or a SLM ͒are placed in this plane in order to manipulate the spatially dispersed optical Fourier components.After a sec-ond lens and grating recombine all the frequencies into a single collimated beam,a shaped output pulse is obtained,with the output pulse shape given by the Fourier transform of the patterned transferred by the masks onto the spectrum.In order for this technique to work as desired,one re-quires that in the absence of a pulse shaping mask,the output pulse should be identical to the input pulse.Therefore,the grating and lens configuration must be truly free of disper-sion.This can be guaranteed if the lenses are set up as a unit magnification telescope,with the gratings located at the out-side focal planes of the telescope.In this case the first lens performs a spatial Fourier transform between the plane of the first grating and the masking plane,and the second lens per-forms a second Fourier transform from the masking plane to the plane of the second grating.The total effect of these two consecutive Fourier transforms is that the input pulse is un-changed in traveling through the system if no pulse shaping mask is present.Note that this dispersion-free condition also depends on several approximations,e.g.,that the lenses are thin and free of aberrations,that chromatic dispersion in passing through the lenses or other elements which may be inserted into the pulse shaper is small,and that the gratings have a flat spec-tral response.Distortion-free propagation through the ‘‘zero dispersion compressor’’has been observed in many experi-ments with pulses down to roughly 50fs—see for example Refs.28and 29.For much shorter pulses,especially in the 10–20fs range,more care must be taken to satisfy these approximations.For example,both the chromatic aberration of the lenses in the pulse shaper and the dispersion experi-enced in passing through the lenses can become important effects.However,by using spherical mirrors instead of lenses,these problems can be avoided and dispersion-free operation has been obtained.30The first use of the pulse shaping apparatus shown in Fig.2was reported by Froehly,who performed pulse shap-ing experiments with input pulses 30ps in duration.23Re-lated experiments demonstrating shaping of pulses a few pi-coseconds in duration by spatial masking within a fiber and grating pulse compressor were performed independently by Heritage and Weiner;31–33in those experiments the gratingpair was used in a dispersive configuration without internal lenses since grating dispersion was needed in order to com-press the input pulses which were chirped through nonlinear propagation in the fiber.The dispersion-free apparatus in Fig.2was subsequently adopted by Weiner et al.for ma-nipulation of pulses on the 100fs time scale,initially using fixed pulse shaping masks 28and later using programmable SLMs.34,35With minor modifications,namely,replacing the pulse shaping lenses with spherical mirrors,pulse-shaping operation has been successfully demonstrated for input pulses on the 10–20fs time scale.30,36–38A fiber-pigtailed pulse shaper,with fiber-to-fiber insertion loss as low as 5.3dB,has also been reported for 1.55m operation for optical communications applications.39–41The apparatus of Fig.2͑without the mask ͒can also be used to introduce dispersion for pulse stretching or compression by changing the grating-lens spacing.This idea was introduced and analyzed by Martinez 42and is now extensively used for high-power fem-tosecond chirped pulse amplifiers.22,43Pulse shaping using programmable SLMs will be dis-cussed beginning in Sec.III.Here we present several ex-amples using fixed spatial masks,the masking technology employed in early femtosecond pulse shaping experiments.Fixed masks can provide excellent pulse shaping quality and have been employed in experimental applications of pulse shaping in nonlinear fiber optics,fiber communications,and ultrafast spectroscopy.Disadvantages of fixed masks are that they do not easily provide continuous phase variations ͑bi-nary phase variations are fine ͒and that a new mask must be fabricated for each experiment.Figure 328shows intensity cross-correlation traces of waveforms generated by using an opaque mask with two isolated slits,resulting in a pair of distinct and isolated spec-tral peaks.Note that the intensity cross-correlation traces ap-proximately provide a measurement of optical intensity ver-sus time—see Sec.II G for further explanation.The two frequencies interfere in the time domain,producing a high-frequency optical tone burst.The 2.6THz period of the in-tensity modulation is identical to the separation of the se-lected frequency components and corresponds to a period of only 380fs.We have also performed experiments using an additional phase mask to impose a phase shift between the two spectral components.The resulting waveform is shown in Fig.3as the dotted line.The two distinct frequencies still interfere to produce a tone burst.However,the phaseshiftFIG.2.Basic layout for Fourier transform femtosecond pulseshaping.FIG.3.Intensity cross-correlation traces of optical tone bursts resulting from a pair of isolated optical frequency components.Solid:optical frequen-cies in phase.Dotted:optical frequencies phase shifted by .1931Rev.Sci.Instrum.,Vol.71,No.5,May 2000Femtosecond pulse shapingis expected to lead to an interchange in the positions of the peaks and nulls of the time domain,and this effect is clearly seen in the data.It is worth noting that this effect,namely the shift in the time-domain interference features reflecting spec-tral phase variations,demonstrated here in the context of pulse shaping,has also been developed into a powerful pulse characterization tool for measuring the spectral phase pro-files of unknown ultrashort pulses.44It is also worth noting that the data in Fig.3represent a time-domain analog of the well known Young’s double slit interference experiment. This is one manifestation of the close analogy which exists between time-domain Fourier optics discussed here and the well known and activefield of spatial domain Fourier optics.We also consider generation of ultrafast square pulses usingfixed masks.28The spectrum of a square pulse of du-ration T is shaped as a sinc function,given byE͑f͒ϭE0T sin͑f T͒f T.͑2.5͒The corresponding mask is specified byM͑x͒ϭsin͑x/x0͒x/x0,͑2.6͒where M(x)is the masking function,x0ϭ(Tץf/ץx)Ϫ1,and ץf/ץx is the spatial dispersion at the masking plane.In order to implement the desiredfiltering function,both a phase and an amplitude mask are needed.The phase mask is used to impart the required alternating sign to thefilter.The trans-mission function of the amplitude mask varies continuously with position.Furthermore,due to the combination of fast and slow temporal features͑Ͻ100fs rise and fall times, pulse duration in the picosecond range͒,the amplitude mask must be capable of producing a series of sidelobes over a large dynamic range.The required phase and amplitude masks were fabricated on fused silica substrates using mi-crolithographic patterning techniques,and the two masks were placed back to back at the masking plane of the pulse shaper.Phase masks were fabricated by using reactive ion etching to produce a relief pattern on the surface of the fused silica.Amplitude masks consisted of a series offine opaque metal lines deposited onto the substrate with linewidths and spacings varied in order to obtain the desired transmission. This approach to forming a variable transmission amplitude mask is related to diffractive optics structures utilized for spatial manipulation of laser beams via computer generated holography.Figure4shows a semilog plot of a power spec-trum produced in this way.The data correspond to a mask containing15sidelobes on either side of the central peak.A dynamic range approaching104:1,as well as excellent signal-to-noise ratio,are evident from the power spectrum. The dotted line,which is an actual sinc function,is in good agreement with the data,although the zeroes in the data are washed out due to thefinite spectral resolution of the mea-surement device Figure5͑a͒shows an intensity cross-correlation measurement of a2ps square pulse produced by using masks truncated afterfive sidelobes on either side of the main spectral peak.The rise and fall times of the square pulse are found to be on the order of100fs.The ripple present on the square pulse arises because of the truncation of the spectrum and is in good qualitative agreement with the theoretical intensity profile͓Fig.5͑b͔͒.Square pulses with reduced ripple have also been obtained,by avoiding trunca-tion of the spectrum and instead using a more gentle spectral apodization.An experimental example of such a‘‘smooth’’square pulse is plotted in Fig.5͑c͒.45FIG.4.Semilog plot of power spectrum of an optical squarepulse.FIG.5.Optical square pulses.͑a͒Measurement of a2ps optical square pulse.͑b͒Corresponding theoretical intensity profile.͑c͒Measurement of a square pulse with reduced ripple.1932Rev.Sci.Instrum.,Vol.71,No.5,May2000 A.M.WeinerAt this point we also discuss pulse shaping using phase-only filters.Phase-only filters have the advantage,in situa-tions where they are adequate,of no inherent loss.Here we discuss two examples of useful pulse shaping via lossless,phase-only filtering using fixed phase masks.There are also many examples of phase-only filtering using SLMs;these will be discussed later.One interesting example is encoding of femtosecond pulses by utilizing pseudorandom phase patterns to scramble ͑encode ͒the spectral phases.28,29An example is shown in Fig.6.29The clear aperture of the mask is divided into 44equal pixels,each of which corresponds to a phase shift of either zero or .Figure 6͑a ͒shows a measurement of the intensity profile of the encoded waveform.Spectral encoding spreads the incident femtosecond pulses into a complicated pseudonoise burst within an ϳ8ps temporal envelope.The peak intensity is reduced to ϳ8%compared to that of an uncoded pulse of the same optical bandwidth.For compari-son,the theoretical intensity profile,which is the square of the Fourier transform of the spectral phase mask,is shown in Fig.6͑b ͒.The agreement between theory and experiment is excellent.Similar coding and decoding has been demon-strated with longer phase codes ͑up to 127pixels ͒28and also using programmable SLMs.41An important feature is that because the phase-only filtering is lossless,by using a second pulse shaper with a conjugate phase mask,the spectral phase modulation can be undone,with the result that the pseud-onoise burst is decoded ͑restored ͒back to the original ul-trashort pulse duration.This forms the basis of a proposed ultrashort pulse code-division multiple-access ͑CDMA ͒com-munications concept,in which multiple users share a com-mon fiber optic channel on the basis of different minimally interfering code sequences assigned to different transmitter-receiver pairs.41,46In some cases only the temporal intensity profile of an output pulse is of interest,and this greatly increases the de-grees of freedom available for filter design.In particular,phase-only filters can be designed to yield the desired tem-poral intensity profile.An important example is the use of periodic phase-only spectral filters to produce high quality pulse trains.47,48As in Fig.3,where spectral amplitude fil-tering is used for pulse train generation,the repetition rate of the pulse train is equal to the periodicity of the spectral filter.However,unlike the spectral amplitude filtering case,the envelope of the pulse train depends on the structure of the phase response within a single period of the phase filter.It turns out that by using pseudorandom phase sequences with sharp autocorrelation peaks ͑similar to those used in CDMA and other forms of spread spectrum communication ͒49as the building blocks of the phase filter,one can generate pulse trains under a smooth envelope.The intensity cross-correlation measurement of a resulting experimental pulse train with 4.0THz repetition rate,generated using 75fs input pulses and binary phase masks based on periodic repetitions of the so-called M ͑or maximal length ͒sequences,49is shown in Fig.7͑a ͒.47The pulse train is clean,and the pulses are well separated.Pulse trains with similar intensity profiles ͑not shown ͒have been produced by spectral amplitude filtering,but with substantially reduced energies.Note that the optical phase is constant from pulse to pulse in trains produced by amplitude filtering,unlike the phase filtering case,where the optical phase varies.Pulse trains such as that in Fig.7͑a͒FIG.6.Ultrafast pseudonoise bursts generated by using a pseudorandom spectral phase filter ͑shown as inset ͒.͑a ͒Intensity cross-correlation trace.͑b ͒Corresponding theoretical intensityprofile.FIG.7.Pulse trains generated by phase-only filtering.͑a ͒Pulse train under a smooth envelope.͑b ͒and ͑c ͒Pulse trains under a square envelope.1933Rev.Sci.Instrum.,Vol.71,No.5,May 2000Femtosecond pulse shapinghave been utilized for experiments demonstrating selective amplification of coherent optical phonons in crystals,50,51la-ser control over coherent charge oscillations in multiple quantum well semiconductor structures,52,53and enhance-ment of terahertz radiation emitted from photoconducting antennas.54Similar pulse trains have also been generated us-ing input pulses below20fs,both withfixed masks30and with SLMs,36and with repetition rates in the vicinity of20 THz.36Pulse trains with different envelopes can be generated by varying the details of the phase response within a single pe-riod of the periodic phasefilter.47,48For example,flat-topped pulse trains have been generated by usingfilters based on the so-called Dammann gratings.55–57Damman gratings are computer generated holograms that have previously been used to split an individual laser beam into an equally spaced, equal intensity array of beams in space.The structure for a Dammann grating consists of a periodic binary phase func-tion,where the period of the phase modulation is selected to yield the desired beam separation in the spatial output array and the phase structure within a single modulation period is designed using numerical global optimization techniques to provide the desired number of beams,with as little energy as possible outside the target array area.In spatial optics,the output beam array can be obtained by passing a single input beamfirst through the Dammann grating and then through a lens,which takes the spatial Fourier transform.Pulse se-quences in the time domain can be formed by placing similar masks at the Fourier plane of a pulse shaper.One example of time domain data,obtained by placing a binary phase mask fabricated according to a Dammann grating design into a femtosecond pulse shaper,is shown in Fig.7͑b͒.The wave-form consists of a relatively uniform sequence of eight pulses,with one central pulse missing.Waveforms with the missing central pulse restored have been obtained by adjust-ing the phase difference on the mask to be less than—see Fig.7͑c͒.These time domain results,achieved by using a phasefilter originally designed for spatial beam forming ap-plications,underscores again the close analogy between time domain and space domain Fourier optics.It is worth noting that design of Dammann phase grat-ings for spatial array generation is usually accomplished through numerical optimization techniques.New phase-only filters designed to generate other femtosecond waveforms can also be found using numerical optimization codes.Sev-eral authors have employed simulated annealing algorithms to design either binary48or gray-level58–60phase-onlyfilters, which were tested in pulse shaping experiments using either binary phase masks or liquid crystal modulators,respec-tively.Binary͑0-͒phasefilters produce waveforms with symmetrical intensity profiles,while gray-level phasefilters ͑typically with four or more phase levels͒can be used for generating pulse trains and other waveforms with asymmet-ric intensity profiles.We emphasize that phase-onlyfiltering is generally sufficient only when the target time-domain waveform is not completely specified,e.g.,when the time-domain intensity is specified but the temporal phases are left free.C.Results from pulse shaping theoryIt is important to have a quantitative description of the shaped output waveform e out(t).In terms of the linearfilter formalism,Eqs.͑2.1͒–͑2.4͒,we wish to relate the linearfil-tering function H()to the actual physical masking function with complex transmittance M(x).To do so,we note that thefield immediately after the mask can be writtenE m͑x,͒ϳE in͑͒eϪ͑xϪ␣͒2/w02M͑x͒,͑2.7͒where␣ϭ2f2cd cos͑d͒͑2.8a͒andw0ϭcos͑in͒cos͑dͩfw inͪ.͑2.8b͒Here␣is the spatial dispersion with units cm͑rad/s͒Ϫ1,w0is the radius of the focused beam at the masking plane͑for any single frequency component͒,w in is the input beam radius before thefirst grating,c is the speed of light,d is the grating period,is the wavelength,f is the lens focal length,andin andd are the input and diffracted angles from thefirst grat-ing,respectively.Note that Eq.͑2.7͒is in general a nonseparable function of both space͑x͒and frequency͑͒.This occurs because the spatial profiles of the focused spectral components can be altered by the mask—e.g.,some spectral components may impinge on abrupt amplitude or phase steps on the mask, while others may not.This leads to different amounts of diffraction for different spectral components and results in an outputfield which may be a coupled function of space and time.This space-time coupling has been analyzed by several authors.61–63On the other hand,one is usually interested in generating a spatially uniform output beam with a single prescribed temporal profile.In order to obtain an outputfield which is a function of frequency͑or time͒only,one must perform an appropriate spatialfiltering operation.Thurston et al.64ana-lyze pulse shaping by expanding the maskedfield into Hermite–Gaussian modes and assuming that all of the spatial modes except for the fundamental Gaussian mode are elimi-nated by the spatialfiltering.In real experiments the Gauss-ian mode selection operation could be performed by focusing into afiber͑for communications applications͒or by coupling into a regenerative amplifier͑for high power applications͒. This can be also be performed approximately by spatialfil-tering or simply by placing an iris after the pulse shaping setup.In any case,if one takes thefilter function H()to be the coefficient of the lowest Hermite–Gaussian mode in the expansion of E m(x,),one arrives at the following expression:27,64H͑͒ϭͩ2w02ͪ1/2͵dx M͑x͒eϪ2͑xϪ␣͒2/w02.͑2.9͒Equation͑2.9͒shows that the effectivefilter in the frequency domain is the mask function M(x)convolved with the inten-sity profile of the beam.The main effect of this convolution is to limit the full width at half maximum͑FWHM͒spectral resolution␦of the pulse shaper to␦Х(ln2)1/2w0/␣.1934Rev.Sci.Instrum.,Vol.71,No.5,May2000 A.M.Weiner。
职称英语核心词汇汇总职称英语考试备考技巧一、词汇:需要考生在最后阶段练习查字典,建议一天练习查60对,而且一个词汇题要反、正查,同时也要进行职称考试中常考词汇的记忆,这样可以在考试时提高速度,节省时间。
词汇题一般情况下仅凭字典一般也能做对,因此考生对自己不认识、不熟悉或没有绝对把握的题一定要通过字典来确认,从而确保词汇题100%的正确率。
特别提醒考生,考试时要带上一本带有同义词的词典。
且词典不能含有职称、考试等字样,更不能带电子词典。
二、阅读判断:答题时需掌握一条原则,就是在文章中有明确提出的才能确定为对。
题目中若出现must、only、all、always等时,答案一般不会是对的。
除上面的原则外,一般根据下列原则和规律也可以确定正确答案。
选择A、B或C的三种情况:选A的情况:如果某题干与原文信息完全一致或基本一致选B的情况:如果某题干与原文信息完全相反选C的情况:如果某题干部分或局部信息在原文中未提到三、概括大意和完成句子:概括大意要先看选项,寻找关键词,确定所考段落。
完成句子则要根据所给的短句进行选择,比较好的方法是找同类动词。
同时读每段话时,要抓住该段话的主题句和核心词汇,正确答案常常是主题句的改写。
读每段话时,并不是该段话全要仔细阅读。
这样,既浪费时间,也不容易抓住重点。
应该抓住该段话的主题句。
四、阅读理解:首先要重点掌握教材上的阅读理解的重点文章的背诵,来抓住出自教材上的分数,这是顺利通过考试很关键的一步。
同时充分利用老师在课上讲的解题技巧,如大标题做题法、红花绿叶原则、顺序出题原则、关键词回归定位法通过做模拟试题来进行解题技巧的演练和应用。
在做题时要注意:搞清主旨题、细节题、推理题、逻辑关系题、观点态度题。
注意标题、首尾段、首尾句、逻辑关系处、细节处等出题点;在阅读时见到日期、数量等要先做好标记,这样有重点有理有节的解题,才有可能取得满意的成绩。
五、补全短文:要先看标题定文体,再看选项,观察选项时应注意抓主干,猜大意,弄清选项大意是表示定义、因果、例子还是措施;不要放过代词、专用名字、连接词、数字等特征词;然后回头再去看课文,明确1-5的位置。
大学校园里最难忘的一件事英语作文全文共5篇示例,供读者参考篇1The Most Unforgettable Thing That Happened at UniversityHey guys! I want to tell you about the craziest, most awesome thing that happened when I went to university. You're not gonna believe this story!It was my first year at Cornerstone University. I was finally living on my own in the dorms and loving every minute of it. No parents to tell me when to go to bed or make me eat gross vegetables. I could stay up all night playing video games if I wanted! The dining halls had chicken nuggets and pizza every day. It was the best!My roommate David and I became best friends right away. We came from the same city and had known each other a little bit from high school. Now we were rooming together and doing everything together - going to parties, pulling pranks, you name it. We were having so much fun!One night, we were up late playing Call of Planetary Battlefields 9 in our dorm room. We were screaming at eachother and rage quitting every five minutes like idiots. But we were having a blast.Suddenly, there was a huge rumbling sound. The ground started shaking like crazy! Our game controllers went flying out of our hands."Whoa, what's happening?" I yelled. I thought maybe there was an earthquake or something.David's eyes got really wide. "Dude...I think a spaceship just landed on campus!"I started cracking up. "Yeah right, you idiot! There's no such thing as spaceships."But David was already running to the window. I followed him and looked outside. And there it was - a massive glowing spaceship bigger than a football field, hovering silently over the campus quad!"Oh my gosh!" I shouted. "You were right! There IS a spaceship!"We just stood there for a minute, our mouths hanging open like a couple of dummies. Neither of us could believe our eyes.Then the spaceship started shooting zillions of colorful lights out in every direction. Red, green, blue, purple lights were flashing everywhere. It looked like the craziest laser show ever!"Let's go check it out!" David said, pulling on his shoes."What? Are you nuts?" I said. "What if it's aliens? What if they try to probe us or something?"David just laughed. "Don't be a wuss! This is the coolest thing that's ever happened. We have to go see!"Well, I didn't want to be a chicken, so I got my shoes on too and we ran outside. Turns out, there were about a zillion other students flooding out of the dorms too. I guess the entire campus was awake from all the shaking and lights!We all just stood there on the quad, staring up at the massive spaceship in awe. It was so bright, with those laser lights flashing everywhere. Some people looked terrified, some people looked thrilled. A bunch of dudes were chanting "Aliens! Aliens!" like morons.Suddenly, the lights on the spaceship stopped flashing. A loud voice spoke words that I didn't understand. Some kind of alien language, I guess.Then the voice switched to English. "Greetings, people of planet Earth! We come in peace from the planet Zyglon in the galaxy of Andromeda."A hatch opened on the spaceship and a ramp extended down to the ground. Three giant alien beings slowly came walking down the ramp. They looked like upright lizards with scaly green skin and these weird tentacle arms.Everyone on the quad started screaming and running in every direction. I'm not gonna lie, I was pretty darn scared. These things looked like real live monsters!The aliens must have noticed everyone freaking out, because they stopped and put their tentacle arms up. "Please, do not be afraid," the alien voice said from the ship. "We mean you no harm. We come in peace and simply wish to study your world for educational purposes."Well, I didn't know whether to believe them or not. But the aliens certainly didn't seem mad or hostile or anything. They were just standing there, almost like they were waiting for something.Then the strangest thing happened. A girl came walking out from the crowd towards the aliens. It was Jennifer Sims, this supersmart science nerd who lived on our floor.Jennifer walked right up to the aliens without a bit of fear. She stuck her hand out and said loudly, "Hi there! My name's Jennifer. Welcome to our planet!"One of the aliens reached out with its tentacle arm and shook Jennifer's hand. A bunch of people gasped."We are pleased to meet you, Jennifer," the alien voice said. "We have come millions of light years through篇2The Most Unforgettable Thing in CollegeWow, you want me to tell you about the most unforgettable thing that happened to me in college? That's a really big ask since college was just a total blast from start to finish! There were so many amazing experiences crammed into those four years that it's honestly quite tricky to pick just one.But I'll give it a shot because you asked so nicely. Let me think here...maybe I should start at the very beginning? Yeah, that makes sense!So on my very first day of college, I was a teensy bit nervous if I'm being perfectly honest. I'd gone to the same small school with the same friends since kindergarten, and now I was being thrown into this enormous campus with thousands of new faces. It was all a bit intimidating at first!My parents helped me move my stuff into the tiny little dorm room I'd be calling home. Once we got all my belongings situated, they gave me a big hug goodbye. I'll never forget the proud smiles on their faces as they left me to start the next chapter of my life.In the days and weeks that followed, I started settling into my new routine. My roommate and I hit it off right away - we came from completely different backgrounds but it was like we had been besties forever. We'd stay up late every night chatting, watching movies, studying together, and getting way too little sleep!The classes themselves were intense compared to high school, but I was determined to work as hard as I could. I'd go to the library for hours prepping for exams and writing papers. I ended up joining a study group for my trickiest classes, and those buddies truly became like a second family.Of course, it wasn't all work and no play! There were always fun activities happening on campus. I went to comedy shows, sporting events, movie screenings in the plaza, you name it. My personal favorite was anything involving free food - you could find me first in line at every campus BBQ or ice cream social!I also got involved in a few clubs that really spoke to my interests. I joined the creative writing club and a few of us would get together every week to share our latest poems or short stories. I met some of my closest friends through that group. We'd provide feedback on each other's work in a really supportive, uplifting environment.Looking back now, I can definitely say that joining that creative writing group was the single most unforgettable part of my college experience. Those people helped me discover my passion for storytelling and played a huge role in building my confidence as a writer. We'd laugh together, cry together, and lean on each other through all the ups and downs.One particular moment that will forever be etched into my memory was the night we all travelled off-campus to attend a live poetry reading in the city. It was my first time reading my work in front of a real audience, and I was an absolute wreck beforehand! My hands were shaking, my voice was quivering,and I'm pretty sure I was doing a very unattractive sweating situation too.But as soon as I got up on that stage and saw the warm, encouraging faces of my friends in the audience, a sense of calmness just washed over me. I took a deep breath and began sharing some of my favorite poems that I had worked so hard on. With every line I spoke, I could feel my confidence growing.When I finished and heard the roar of cheers and applause from the audience, it was easily one of the proudest, most incredible moments of my entire life up until that point. My creative writing friends rushed up to hug me afterward, gushing about how brilliant and moving my performance was. Just typing about it now gives me goosebumps!That special night kicked off many more opportunities to share my writing and perform. Before long, I was being invited to other open mic events and even published a few pieces in literary journals. Looking back, those early experiences with my college creative writing group gave me the bravery to pursue my wildest dreams as an artist.So while I definitely have a million other amazing memories from college - from game days to spring breaks to graduation itself - nothing will ever quite top the feeling of finding mycalling and my people through that group. Those years shaped me into the person I am today in more ways than I can count. I'm so grateful I took that initial leap and joined.Well, there you have it! The story of my most unforgettable college experience. Thanks for letting this rambling writer reminisce on such a meaningful time in my life. I hope you enjoyed listening to my tale as much as I enjoyed revisiting those special moments and incredible people. College really was the best!篇3The Most Unforgettable Thing at UniversityWow, you guys won't believe the totally awesome and crazy thing that happened to me at university! It was the craziest day ever. I'm still shocked just thinking about it!It all started on a sunny Saturday morning. I was visiting my older brother Jake at his university. He's a super smart guy studying lots of difficult subjects like mathematics and physics. I always look up to him and think he's the coolest.Anyway, that morning I was hanging out in the student lounge playing video games while Jake was in one of his classes. The lounge had these massive flat screen TVs and the latestgame consoles. It was paradise for a kid like me! I was battling through an intense level when suddenly the whole building started shaking like crazy!At first I thought maybe there was a huge monster stomping around outside or something. But then I realized it must be an earthquake! The floor was moving beneath my feet and objects were falling off the shelves all around me. I heard students screaming from the hallways. It was total pandemonium!I froze up because I had no idea what to do. I'd never experienced an earthquake before. Should I hide under a table? Run outside? I just stood there paralyzed with fear until the shaking finally stopped after what felt like an eternity but was probably only a minute or so.When it was over, I raced outside to find Jake. The campus was in chaos with debris scattered everywhere. Fire alarms were blaring and thick clouds of dust filled the air. I could hardly breathe! Students were frantically running in all directions, scared out of their minds.Finally, I spotted my brother looking frazzled but unharmed. We hugged each other super tight, relieved that we were both okay. The earthquake turned out to be a major one, measuring7.2 magnitude! It was one of the biggest quakes to hit the area in decades according to the news reports later.Luckily, the university buildings were constructed to strict safety codes for earthquakes. While there was a lot of damage, like crumbled walls and shattered windows, the structures remained standing. Only a few people suffered minor injuries, which was miraculous considering how powerful the shaking was.The rest of the day was just surreal. The entire campus had to be evacuated for safety inspections. Thousands of students, faculty, and staff were stranded outside on the lawns and quadrangles. It felt more like a weird outdoor festival than a university!Jake and I hung out with his friends, sharing snacks and playing card games to pass the time. We heard lots of crazy stories from people about where they were when the quake hit - in class, at the gym, even in the bathroom! Some of the tales were pretty hilarious when you thought about it.There were also some touching moments. I saw students embracing and comforting each other after such a terrifying experience. Despite being strangers, everyone felt connected bygoing through that earthquake together. The campus community really came together in a remarkable way.By nightfall, emergency crews determined it was safe for us to re-enter the dorms and dining halls. But all academic buildings remained closed until further structural testing could be done. Essentially, we all got an unexpected extra-long weekend off from classes!Over the next few days, the clean-up and repairs began across campus. There was lots of construction equipment and work crews removing debris and fixing up the cracked walls. It looked like a total mess but everyone carried on like normal, going to classes in temporary locations.I'll never forgot that powerful earthquake for as long as I live. It was one of the most intense, scary, but also amazingly cool experiences ever! The sheer force of nature was mind-blowing. But it showed me how strong humans can be too in coming together after a disaster.I have so much respect now for my brother and all university students after seeing how calmly and bravely they handled the whole situation. They didn't panic but just rolled with the punches! I can't wait until I'm old enough to go to universitymyself and maybe even experience another earth-shaking adventure.For now, the memory of that shocking earthquake will stick with me forever. It was easily the most unforgettable day during my visit to Jake's campus. I'll definitely be telling my own kids and grandkids the crazy story about the time the ground started moving under my feet at university! What an epic tale to share for the rest of my life.篇4The Most Unforgettable Thing at UniversityOne day, my big sister Sarah took me to visit her at university.I was so excited because I had never been to a university before! When we got there, I couldn't believe how big everything was. The buildings were huge and there were lots of people walking around carrying books and backpacks.Sarah showed me around the campus first. We saw the library which had more books than I had ever seen in my whole life! Sarah said students come here to study and do their homework. It was a very quiet place with lots of people reading or typing on computers.Next, we went to the student center where there were lots of places to eat like pizza places, sandwich shops, and even a Starbucks! Sarah got us two hot chocolates and we sat down at a table. She told me that's where she hangs out with her friends between classes. It was a loud, busy place with students hanging out and talking to each other.After that, we went outside and walked around the huge grassy areas in the middle of campus. Sarah said they were called "quads" and that's where students relax, study, play sports, or have picnics when it's nice out. We saw students throwing frisbees, kicking soccer balls, and even doing cartwheels on the grass! I wished I could join in but Sarah said I was too little.The last place we went was the sports center which had huge gym areas for basketball, swimming pools, workout rooms, and even a rock climbing wall! Sarah said all the students can use it whenever they want for exercise or just fun. I couldn't believe how many cool things were inside. We didn't go in but I could see through the glass walls and it looked amazing.After the long tour, I was getting pretty tired. We stopped to get a snack from one of the food trucks parked on campus. I got a big pretzel and Sarah got some french fries and we sat on abench to eat them. While we were sitting there, the strangest thing happened...A huge group of students came running across the quad, screaming and yelling at the top of their lungs! I got really scared and hugged Sarah tight. But she just laughed and said, "Don't worry, that's just the engineering students. They do that every year after their final exams are over to celebrate."More and more students joined in, running across the grass and cheering loudly. Some of them were even dressed in crazy costumes like banana suits or toilet paper mummies! I couldn't believe what I was seeing. Sarah explained it was a tradition at the university for engineering graduates to do that after turning in their last assignments.At first, I thought it was scary with all the yelling and running around. But after watching for a little while, I realized they were just really happy and excited to be done with a very difficult program. They had worked so hard for years and years, and now they could finally celebrate.Some of the students were tackling each other and rolling around in the grass, completely covered in mud and dirt but not caring one bit because they were having so much fun! Otherswere spraying whipped cream on each other or throwing water balloons. It was the craziest thing I had ever seen!Sarah and I just sat there watching the chaos for a long time, laughing at how silly they all looked. At one point, a group of students dressed as trees came running by and one of the tree branches whacked me in the head accidentally! I started crying at first, but then I realized it was just a costume and I couldn't help but laugh. How could anyone be scared when there were trees running around a university?Finally, after what seemed like forever, the celebration started to wind down and the students went back to the dorms, still cheering but calmer than before. Sarah gave me a big hug and said, "See? That's what univerisity is all about - having fun after working really hard."As we walked back to the car, I felt so happy seeing how much fun the students were having. University seemed like a crazy, overwhelming place, but also exciting and full of adventure around every corner. I knew that no matter how old I got, I would never forget the day I saw trees running across campus throwing whipped cream!That has to be the most unforgettable, ridiculous thing I've ever witnessed. But it just showed me that university isn't justabout studying and exams - it's about making amazing memories with friends that will last forever. I can't wait until I'm old enough to go to university myself! Who knows what kind of unbelievable, unforgettable experiences I'll have?篇5The Most Unforgettable Thing at UniversityWow, you want me to tell you about the most unforgettable thing that happened at university? That's a tough one! University was soooo much fun and there were a ton of crazy things that happened. But I'll try my best to tell you the craziest story of them all!It was my second year and I was living in the dorms on campus. My roommate was this really funny guy named Mark. Mark and I became best buds pretty much right away. We were like two peas in a pod! We loved playing video games, watching movies, and causing a little bit of trouble here and there. Not too much trouble though, I promise!Anyway, one night Mark and I were feeling really bored. We had already beaten the hardest level on our favorite video game and watched all the good movies on Netflix. We were like "Man, what should we do tonight? I'm sooooo bored!" That's whenMark had this brilliant, crazy idea. His eyes got all big and he said "Dude, you'll never believe what I was just thinking!"I asked him what his crazy plan was and he told me with the biggest smile ever. Mark said we should sneak into the university's sports stadium and play an epic game of laser tag in the middle of the night! At first I thought he was kidding, but nope - he was totally serious! I tried to be the responsible one and talk him out of it, but Mark can be really persuasive when he wants to be. Before I knew it, we were suiting up in our darkest clothes and grabbing our laser tag gear.It was around 2am when we snuck onto the huge stadium field under the cover of darkness. The place was absolutely massive and completely empty - it was just me, Mark, and thousands of empty seats. We turned on our laser tag vests and guns and the game was on! We ran around like crazy people, diving behind benches and bleachers to avoid getting tagged. We were shouting and screaming at the top of our lungs, not caring at all that it was the middle of the night. This went on for probably two hours of the most intense laser tag battle ever!Just when we thought the night couldn't get any crazier, the stadium's huge floodlights suddenly turned on, blasting us with this crazy bright light. Mark and I both froze in our tracks,completely stunned and blinded. Then we heard a voice over the loudspeaker: "Hey you two knuckleheads! What do you think you're doing out there?!"It was the stadium security guard! He had spotted us on the security cameras and turned on the floodlights to get a better look. We were so busted! Mark and I just looked at each other, unsure whether to make a run for it or not. But before we could decide, the security guard was walking across the field towards us. This guy was HUGE - like a bodybuilder or wrestler or something. He was fuming mad!When he got up to us, the first thing he said was "Didn't your parents ever teach you two any manners? Playing laser tag in the middle of the night? At the stadium?! You kids have a lot of nerve!" Mark and I were scared out of our minds - this dude looked like he could snap us like twigs if he wanted to! We just stood there trembling and mumbling "S-s-sorry sir...we werej-just messing around. We didn't mean any harm!"The security guard stared us down for what felt like forever. Then, he did the craziest thing - he started laughing Like, full on belly laughs! He told us that we had guts for doing something so bold and silly. He admired our youthful spirit and sense ofadventure. But he also reminded us never to do something so stupid again, otherwise we'd be in serious trouble next time.The guard decided not to get us in any trouble this time, as long as we got out of the stadium right away and went straight back to our dorms. Phew, we were so relieved! Mark and I couldn't stop saying "Thank you sir, thank you!" over and over again. We gathered up our laser tag gear as fast as we could and made a beeline for the exit before the guard could change his mind.As we walked home, Mark and I recounted the whole crazy experience, still in disbelief at what had happened. We felt like we were on top of the world - we had pulled off the most epic, unforgettable prank ever and lived to tell the tale! Sure, we came very close to getting in huge trouble. But somehow we managed to get off with just a warning from a surprisingly cool security guard.From that night on, Mark and I made a pact - we would tone it down a notch on the pranks and just focus on being typical university guys: studying hard, attending。
a r X i v :a s t r o -p h /0105256v 1 15 M a y 2001Fe K αline:A tool to probe massive binary black holes in Active GalacticNuclei?Qingjuan YuPrinceton University Observatory,Princeton,NJ 08544-1001,USAEmail:yqj@and Youjun Lu Center for Astrophysics,Univ.of Sci.&Tech.of China,Hefei,Anhui 230026,P.R.China Email:lyj@ ABSTRACT Hierarchical mergers of galaxies can form binary black holes (BBHs)since many or most galaxies have central massive black holes (BHs).It is possible that some BBHs exist in active galactic nuclei (AGNs).We argue that each BH may be surrounded by an accretion disc with a different inclination angle to the line of sight (due to different BH spin directions and the Bardeen-Petterson effect).The observed Fe K αline profile from a BBH system is a combination of the lines from the inner regions of the two discs,which is significantly affected by the inclination angles of the two discs.The Fe K αline profile associated with BBHs may have an unusual shape with double or more peaks as well as short-term variability,which can be distinguished from the Fe K αline properties of some other possible models.We suggest that with the improvement of resolution in X-ray astronomy,Fe K αline profiles be a potential tool to probe the existence of massive BBHs in AGNs.The Fe K αline profile associated with BBHs may also provide a tool to investigate the dynamics in strong gravitation field (e.g.providingevidence of the Bardeen-Petterson effect).Subject headings:Black hole physics–Accretion–Line profile–galaxies:active1.IntroductionMuch evidence indicates that massive black holes (BHs)reside in the centers of many or most galaxies (e.g.Magorrian et al.1998).Mergers of galaxies are likely to form massive binary black holes (BBHs).Theoretical estimation shows that the BBH lifetime is not much shorter than the Hubble time and many BBHs should be still in the centers of galaxies (Begelman,Blandford &Rees 1980).The existence of BBHs in the universe will not only provide a laboratory to test gravitationradiation theory and BH physics,but also probe of the hierarchical structure model of galaxy and large-scale structure formation.Currently,there is no systematic and unambiguous method to identify BBHs.BBHs stay at a separation in the range1016−1019cm(e.g.10−4−10−1arcsec at10Mpc)during the slowest evolution period(Begelman,Blandford&Rees1980,Yu2002),and thus it is hard to resolve a BBH —two very close galactic nuclei in the image—with current telescope resolution.The shallow cusps in the inner surface brightness profiles of some nearby giant galaxies may be produced from steep cusps by ejecting stars from their inner regions during the hardening of BBHs(Faber et al.1997,Quinlan&Hernquist1997),but there is still no proof of a currently existing BBH in those galaxies.To identify a BBH,we have tofind some other effect of BBHs on their nearby environment and/or some manifestation of the motion in a two-body system,such as jet precession (Begelman,Blandford&Rees1980),double-peaked Balmer lines(Gaskell1996),or quasi-periodic radio,optical,X-ray orγ-ray variation(e.g.OJ287:Sillanp¨a¨a et al.1988,Valtaoja et al.2000; Mkn501:Rieger&Mannheim2000).Some active galactic nuclei(AGNs)have been claimed to be detected as BBH candidates by those methods,but all of them are controversial because of other explanations for the same phenomena or some inconsistency with other observational evidence.If there is sufficient gas with some angular momentum close to a BBH,we may expect that the gas in the vicinity of each BH is accreting onto the BH in the form of a disc rather than in the form of spherical accretion,which may make the system appear as an AGN.If the binary separation is small(say,much less than the scale of the broad line region),the two accretion discs may be warped at outer parts and connected with an outer large circumbinary accretion disc.If the separation is large enough,each BH is probably accompanied by its own disc and broad line region.The spin axes of the two BHs are very likely to be misaligned(Rees1978,Begelman,Blandford&Rees 1980)and the discs in this two-accretion-disc(TAD)system associated with the BBH can also have different inclination angles to the line of sight.AGNs are observed to be copious X-ray emitters.This X-ray emission is believed to originate from the very inner accretion disc around a massive BH.The broad skewed iron Kαline profile found by GINGA and confirmed by ASCA is believed to result from a combination of gravitational broadening and Doppler shift in an accretion disc(Tanaka et al.1995).So far,alternative models have failed to account for this profile(Fabian et al.1995,Fabian et al.2000),which offers one of the strongest lines of evidence for the existence of massive BHs.X-ray spectroscopy also promises a powerful tool to detect strong-gravitation-field relativistic effects in the vicinity of a massive BH. The observed Fe Kαline profile is significantly affected by the inclination angle of the disc to the observers line of sight(Fabian et al.1989,Laor1991).In a BBH system,the observed Fe Kαline profile can be a combination of the line profiles from two discs with very different inclination angles to the line of sight.Motivated by this observation,we propose a method to probe BBHs in AGNs by Fe Kαline profiles.We expect that Fe Kαline profiles will become an efficient way to probe BBHs in AGNs.2.Two accretion discs in BBH systemsConsider a BBH containing BHs of mass m1and m2rotating around their center of mass(Fig.1), the relative orbit of the two BHs is assumed to be circular with separation a.The Keplerian orbital period of the binary isP orb=210 a m1+m2 1/2yr(1) and their maximum orbital velocities relative to the center of mass in the line of sight are |v i|=1.5×103km/s 0.1pc2×108M⊙ 1/2 2m1m2Gm1/ac2if m1>m2), the spins will precess in a cone with the orbital angular momentum as axis.Their precession periods are given by:P prec∼6×106 a2×108M⊙ 1/2 108M⊙m iiobserverFig.1.—Schematic diagram of a BBH and its accretion discs:the BBH containing BHs m1and m2is rotating around the center of mass‘O’in circular orbits.A distant observer is located in the z-axis direction.The inclination angles of the two discs to the line of sight areθ1andθ2, respectively.An example of Fe Kαline profile is plotted in the upper-right of thisfigure by setting θ1=60o,θ2=5o,the emissivity ratioǫ02/ǫ01=0.6(or equivalently the mass ratio m2/m1=0.6 by assuming the two discs have almost the same dimensionless accretion rates),and p=2.5(the exponent of the emissivity law in§3).The dashed line represents the component from the disc of the BH m1and the dotted line represents the component from the disc of the BH m2.The solid line is the observed line profile,which is a combination of the two components.The precession may cause the two accretion discs to be tilted to their BHs equatorial plane,but the two disc inclination angles to our line of sight will not change in a short time.Detailed study of the dynamics and stability of the TADs in BBHs is beyond the scope of this paper.3.Emergent Fe Kαline profiles from BBH systemsWe have argued that there are good reasons for the existence of TADs with different inclination angles to the line of sight in BBHs.We shall assume that both discs are cold thin accretion discs. The observed Fe Kαline profile is then the summation of the two components from the TADs.The combined line profile is mainly controlled by the inclination angles of the TADs and the relative strength of the two components.The relative strength is related to the mass ratio of the two BHs and the accretion rates onto them(if the two accretion systems have almost the same dimensionless accretion rate˙m=˙M/˙M Edd,where˙M is the accretion rate and˙M Edd is Eddington accretion rate, the relative strength of the two components will be given by the mass ratio m1/m2).Using the ray-tracing technique and elliptic integrals(Rauch&Blandford1994),we follow the photons from each accretion disc to a distant observer,and calculate the corresponding redshift of the photons and the resulting line profiles.The spins of BHs are both set to be a/M=0.998.The Fe Kαline photons are assumed to be isotropically emitted in the frame moving with the accretion disc material,and the surface emissivity is given by the power-lawǫi(r)=ǫ0i r−p for the region r in i≤r≤r outi.We adopt the averaged line emissivity exponent index of p=2.5which is obtained from thefitting of Fe Kαline profiles for a sample of AGNs observed by ASCA(Nandra et al.1997). We set the inner radius to be the marginally stable orbit r ms(few Fe Kαline photons come from the region inside the marginally stable orbit for Kerr BH with spin0.998),and the outer radiusr out i =160Gm i/c2(the line profiles are not sensitive to the value of r outisince most line photonscome from the inner region for a typical line emissivity law with p=2.5).An example of the resulting spectral line is shown in Figure1,for discs with inclination anglesθ1=60o andθ2=5o, andǫ02/ǫ01∼m2/m1∼0.6.This unusual line profile is double-peaked,asymmetric and has two ‘edge’-like feature.The peak with the smaller central energy,near the rest frame energy of Fe Kαline–6.4keV,(or less than6.4keV due to gravitational redshift for extremely low inclination disc), comes from disc D2with a small inclination angle,has the characteristic features of emission from a relativistic accretion disc:a skewed red wing and a sharp“blue”edge(note that the energy of the “blue”edge is mainly determined by the inclination of a disc,and the red wing extent is sensitive to the inner radius of the line emission region).The peak with the smaller central energy is narrower than the broad component,which comes from disc D1with a high inclination angle.If the spin of the BH m1is smaller,the“narrow component”can be even narrower.The“narrow”component can be stronger or weaker than the broad component depending on the relative emissivity.Another important feature is that these two components should both have short-term variability of intensity and shapes on the timescale of104s,as suggested by the variation in some Seyfert galaxies(Iwasawa et al.1996,Nandra et al.1999),and their variation patterns can be totally different and unrelatedwith each other since they come from two different discs.All of the above features make it easy to distinguish the BBH model from the other alternative models producing a two-component line shape.Not all of the emergent Fe Kαline profiles from TAD systems are so distinguishable from the profiles produced by only one disc.If the relative emissivity of the two discs is too small or too large,the component emitted from one accretion disc in TADs system will be drowned by the other.Only whenǫ02/ǫ01is about in the range0.2−2(or m2/m1is in a similar range if luminosity is proportional to Eddington luminosity)will the line profiles from TADs be significantly different from the one emitted by a single BH–accretion disc system.Ifǫ02/ǫ01is a little less than0.2,the line profile may be misunderstood as a relativistic line from a single disc plus an absorption feature; and ifǫ02/ǫ01is a little larger than2,the line profile may be misunderstood as a relativistic line from a single disc plus a high ionization line(e.g.Fe Kβor Ni Kαline).If the difference betweenθ1and θ2is too small,the two line components will be blended,and thus difficult to distinguish from the profile produced by a single BH–accretion disc system.The line profiles in TAD systems can be very complicated with double peaks,three peaks and even four peaks depending on the inclination angles of the two accretion discs and the relative emissivity(Fig.2).Whenθ1∼45o−70o and θ2∼0o−20o,the emergent line profile will clearly exhibit two distinct components(see Fig.2; note that the line from a disc with very high inclination angle(say,>70o)may be strongly affected by the limb-darkening effect of the outer layer of accretion disc).If the inner disc is somewhat ionized,or the emissivity law is somewhat different,the line profile should remain similar.The probability that the combined line from two randomly oriented equal discs is in the shape similar to those shown in Figure2,is about20%(the difference between the inclination angles is larger than 30o and both the disc inclination angles are not larger than70o).The amounts of AGN sources expected to harbor BBH systems with comparable BH masses,which could be identified by Fe Kαline profiles,are relevant to the process of structure formation and the merger history of galaxies.The line shapes from the TAD systems shown in Figure1and Figure2are examples chosen from many idealizations.We have neglected such complication as the actual dynamics of the system, the possible warp of the outer disc,the ionization of the accretion discs,the real line emissivity law,contamination from non-disc emitters,the irradiation of one disc by the X-ray photons from the other,and the absorption of intervening gas and dust etc.The complication certainly affects the line profile quantitatively,but will not make much difference qualitatively.4.Differentiating the BBH model from other possible modelsThere are other possible models that can produce two-component line profiles,but they are not difficult to differentiate from the BBH model.First,off-axis X-rayflares above a single disc can strongly affect the line profiles(off-axis-flare model;c.f.Yu&Lu2000).In§3,the disc emissivity is assumed to be axisymmetric.In reality,Fig.2.—Fe Kαline combined profiles from TADs in BBHs.The exponent index of the emissivity law p is2.5.In panels(a)and(b)ǫ02/ǫ01=0.6,θ1=50o(dotted line),60o(solid line),70o(dashed line),butθ2=5o in(a)andθ2=20o in(b).In panels(c)and(d)ǫ02/ǫ01=1.5(dotted line),0.7(solid line),0.2(dashed line),θ1=60o,butθ2=5o in(c)andθ2=20o in(d).X-rayflares can be offthe disc rotation axis and the emissivity law of the disc is non-axisymmetric because the disc region just under theflares generally receive more illumination.Thus,the non-axisymmetric emissivity may strongly affect the Fe Kαline profiles since different energy parts of Fe Kαline profiles stem from different regions of a disc.For example,a cold accretion disc is illuminated by two localflares:one is atop the approaching side of the disc,where the energy of Fe Kαline photons are blue shifted by Doppler effect;and the other is atop the disc region towards or backwards us which corresponds to the line emission around6.4keV.This situation can make line shapes like the one from TADs.The X-rayflares are probably produced by some thermal instability in the disc or magnetic reconnection and their locations should be randomly distributed. The appearance of the line profile arising fromflares can be very complex.However,the average line profile over severalflares should be consistent with the profile from a single disc(with a single inclination angle),as suggested by the observations of MCG-6-30-15(Iwasawa et al.1996,Iwasawa et al.1999),which is quite different from the combined line profiles from TADs.Second,a two-component line shape can be produced if a narrow line component is emitted from a molecular torus or broad line region(BLR)clouds,and a broadened line component is emitted from the inner region of a highly inclined accretion disc(BLR/Torus-AD model,c.f.Yaqoob et al.2001).In this scenario,the central energy of the narrow component should be around 6.4keV or a little blue-shifted by the outflow motion,and the line width caused by the velocity dispersion of the clouds should be several thousand km/s.1In contrast,in the BBH model,the “narrow”component is redshifted to energies less than6.4keV if the inclination is very low(due to gravitational redshift).With higher inclination,the narrow component is centered around6.4keV or higher,but with a large width.More importantly,in the BLR/Torus-AD model,the narrow component should remain constant on the timescale of several days or more(the light-travel time across the BLR or the torus)rather than varying on timescales<104s,as predicted by the BBH model.Third,a two-component line shape can also be produced by the combination of a broadened iron line from a highly inclined accretion disc plus a component which is scattered into our line of sight by an efficient electron-scattering material(Scatter-AD model,c.f.Wang et al.1999). It is unlikely that this electron-scattering material is close to the disc because this configuration is unlikely to produce a line with two distinct components:first,the scattered line component shape will be different from the one observed from a disk with a small inclination angle;second, Fe Kαphotons from the inner accretion disc cannot be seen directly because the disc is covered by the scattering material.If the scattering layer is high enough above the disc,the scattered line profile would be somewhat like the one observed at a small inclination angle;however,the covering factor would normally be small and the equivalent width of this component should therefore bemuch smaller than the broad one since the scattered photons are redistributed in all directions. In contrast,in the BBH model,the equivalent width of the“narrow”component can be larger than that of the broad component.Furthermore,the temporal variations of the two components in the Scatter-AD model must be strongly correlated with a time delay which reflects the distance between the scattering material and the disc.5.ProspectsTo use Fe Kαprofiles to identify a BBH with TADs,we need to resolve both the narrow component and broad component of the line profiles and study the variation of the line profiles and intensity with time.Over the past decade,a number of Seyfert galaxies and QSOs have been shown to have broad Fe Kαlines(Nandra et al.1997,Yaqoob&Serlemitsos2000).The Fe Kαline profile of NGC4151isfitted by two disc components with inclinations of0o and58o better than by a one-disc line model(Wang et al.1999).The component with inclination0o was explained by being scattered into our line of sight;however,those two components can also be explained as coming from possible TADs.Future observations with higher resolution are needed to check if NGC4151is a possible BBH candidate.The unique Fe Kαprofile of MARK205(see Fig.2in Reeves et al.2000),recently revealed by XMM-Newton,is somewhat like the line shape established in Figure1.Its broad line component can befitted by an accretion-disc line with a high inclination.Unfortunately,the narrow component is not fully resolved.The present observations can be explained by assuming that the narrow component comes from neutral matter at large distant from a central BH and the broad one is emitted from a highly ionized relativistic accretion disc(Reeves et al.2000).So,further observations and variability studies are needed to check if this object is a BBH candidate or not.Stimulated by those special line shapes observed in some objects,we believe that some BBHs in AGNs,if any,can be identified by searching the unusual iron line profile with current and future X-ray satellites,such as XMM-Newton,Constellation-X and XEUS.If any one of AGNs is revealed to have the typical line shapes shown in Figure2as well as short-term variability,it will provide one of the strongest lines of evidence for the existence of BBHs and a laboratory to investigate the dynamics in strong gravitationfield(e.g.the Bardeen-Petterson effect).We are grateful to Scott Tremaine for a careful reading of an early draft with many insightful comments and suggestions.We thank Jeremy Goodman and David N.Spergel for helpful discus-sions.YL acknowledges the hospitality of the Department of Astrophysical Sciences,Princeton University.REFERENCESBardeen J.M.,Petterson J.A.,1975,ApJL,195,65Begelman M.C.,Blandford R.D.,Rees M.J.,1980,Nature,287,307Fabian A.C.,Rees M.J.,Stella L.,White N.E.,1989,MNRAS,238,729Fabian A.C.,Nandra K.,Reynolds C.S.,Brandt W.N.,Otani C.,Tanaka Y.,Inoue H.,Iwasawa K.,1995,MNRAS,277,L11Fabian A.C.,Iwasawa K.,Reynolds C.S.,Young A.J.,2000,PASP,112,1145Faber S.M.et al.,1997,AJ,114,1771Gaskell C.M.,1996,ApJL,464,107Ivanov P.B.,Papaloizou J.C.B.,Polnarev A.G.,1999,MNRAS,307,79Iwasawa K.et al.,1996,MNRAS,282,1038Iwasawa K.,Fabian A.C.,Young A.J.,Inoue H.,Matsumoto C.,1999,MNRAS,306,L19Laor A.,1991,ApJ,376,90Magorrian J.et al.,1998,AJ,115,2285Nandra K.,George I.M.,Mushotzky R.F.,Turner T.J.,Yaqoob T.,1997,ApJ,477,602 Nandra K.,George I.M.,Mushotzky R.F.,Turner T.J.,Yaqoob T.,1999,ApJL,523,17 Natarajan P.,Pringle J.E.,1998,ApJ,506,L97Nelson R.P.,Papaloizou J.C.B.,2000,MNRAS,315,570Quinlan G.D.,Hernquist L.1997,New Astron.,2,533Rauch K.P.,Blandford R.D.,1994,ApJ,421,46Rees,M.J.1978,Nature,275,516Reeves J.N.,Turner M.J.L.,Pounds K.A.,O’Brien P.T.,Boller Th.,Ferrando P.,KendziorraE.,Vercellone S.,2000,A&A,365,L134Rieger F.M.,Mannheim K.,2000,A&A,359,948Sillanp¨a¨a A,Haarala S.,Valtonen M.J.,Sundelius B.,Byrd G.G.,1988,ApJ,325,628Sulentic J.W.,Marziani P.,Dultzin-Hacyan D.,2000,ARA&A,38,521Tanaka Y.et al.,1995,Nature,375,659Valtaoja E.,Ter¨a sranta H.,Tornikoski M.,Sillanp¨a¨a A.,Aller M.F.,Aller H.D.,Hughes P.A., 2000,ApJ,531,744–11–Wang J.,Zhou Y.,Wang T.,1999,ApJL,523,129Yaqoob T.,Geroge I.M.,Nandra K.,Turner T.J.,Serlemitsos P.,Mushotzky R.F.,2001,ApJ, 546,759Yaqoob T.,Serlemitsos P.,2000,ApJL,544,L95Yu Q.,Lu Y.,2000,MNRAS,311,161Yu Q.,2002,Chapter1in Ph.D.Thesis(Princeton University),in preparation。