下载文档原格式
杭州电子科技大学《民航服务英语二》2023-2024学年第一学期期末试卷院(系)_______ 班级_______ 学号_______ 姓名_______1、“Made in China 2025” aims to transform China from a product-making factory into a product-making power, ______________ driven by innovation and emphasizing quality over quantity.A．the one that B．one thatC．one D．the one2、—What did she want to know, Tom?—She wondered we could complete the experimentA．when was it that B．it was when thatC．it was when D．when it was that3、What is your main reason for choosing one restaurant another?A．over B．ofC．from D．for4、Generally speaking, ________according to the directions, the medicine has no side effect.A．when taken B．when taking C．when to take D．when to be taken 5、Yesterday is history, tomorrow is a mystery, only today is a gift, and that is ______ we call it present.A．how B．when C．why D．where6、The cost of living in big cities ________ steadily for many years，and it has led some youths to drop out of the big city race.A．is climbing B．is being climbedC．has been climbing D．has been climbed7、______ his love, Chris sent his mom a thank-you note on Mother’s Day. A．Expressing B．Expressed C．To express D．Having expressed8、By doing so, you can ________ more information and details about the topic, and better understand it.A．keep up with B．do away withC．have access to D．get down to9、________ the program, they have to stay there for another two weeks.A．Not completing B．Not completedC．Not having completed D．Having not completed10、---When shall we start the reconstruction of the historic building?--- Not until our program ______ by the authority.A. will approveB. will be approvedC. has approvedD. has been approved第二部分阅读理解（满分20分）阅读下列短文，从每题所给的A、B、C、D 四个选项中，选出最佳选项。
2024学年第一学期奉贤区高三英语练习卷考生注意：1. 考试时间105分钟,试卷满分115分。
2. 本次考试设试卷和答题纸两部分。
所有答题必须涂（选择题）或写（非选择题）在答题纸上,做在试卷上一律不得分。
3. 务必在答题纸上填写准考证号和姓名,并将核对后的条形码贴在指定位置。
I. Grammar and vocabularySection A (10分)Directions:After reading the passage below, fill in the blanks to make the passage coherent and grammatically correct. For the blanks with a given word, fill in each blank with the proper form of the given word; for the other blanks, use one word that best fits each blank.The Best Music to Boost ProductivityHow many times have you put on your headphones to help you concentrate on your tasks? Various studies have tried to address the question of (1)________ music in the workplace can be helpful or not. The short answer seems to be yes, but it depends on the job and the music.In one study, machine operators at a clothes manufacturer became (2)________ (productive) when they listened to relaxing music; the researchers therefore suggested trying music with a faster pace instead. However, in another study (3)________ (conduct) among surgeons who operated on patients while listening to classical music, it showed that they were both faster and more accurate in performance. In this case, the researchers advised against high pace or loud music (4)________ it could be distracting.According to some scientists, no matter what task you’re engaged in, lyrics in music (5)________ negatively impact your attention. However, if (6)________ (listen) to lyric-less or classical tunes annoys you, you’re probably not going to be very productive, so it ultimately depends on your personal preference.There might be a link between ‘emotional use’ of music at work and performance, too. Essentially, if your mood improves, so does your work. To some extent, then, you may be best off playing music (7)________ makes you happy. Interestingly, though, one 2023 study, which surveyed 244 people who listened to music at work, revealed no benefit when music (8)________ (use) for cognitive thinking or just played in the background.But if you’re just here for the best tracks (9)________ (boost) your productivity, we’ve got some recommendations for you. The top three songs most often included in work-related Spotify lists (10)________ (be): ‘Drops of Jupiter’ (Train), ‘Dreams’ (Fleetwood Mac) and ‘Don’t Stop Believin’ (Journey). Integrate these songs into your workday and experience the boost in productivity they can provide.Section B (10分)Directions:Fill in each blank with a proper word chosen from the box. Each word can be used only once. Note that there is one word more than you need.A. enterB. echoC. physicalD. linkedE. supposedF. initialG. literally H. diverse I.weather J. alternative K. effectivelySkyquakeIf you’ve ever heard a loud, distant booming noise with no obvious explanation like a thunderstorm or a car backfiring, then you might have experienced a skyquake. Skyquakes have been reported around the world and locals have ___11___ names for them in different regions. Near Seneca Lake in New York State, they’re known as ‘Seneca guns’; in Belgium they’re called ‘mistpoeffers’; and the Japanese refer to them as ‘uminari’, which ___12___ means ‘cries from the sea.’ Some scientists have suggested that a type of meteor(流星)could be the cause. These space rocks explode when they ___13___ Earth’s atmosphere. If this occurred above thick cloud, the sound could ___14___ across a wide area. However, there is no ___15___ evidence reaching the ground.A(n) ___16___ explanation is the gas coming out of the bottom of the lake. Several hot spots for skyquake activity are close to large, deep lakes, such as Seneca. But skyquakes have also been reported away from such water bodies.Researchers at the University of North Carolina compared local news reports with information from ___17___ sensors and earthquake detectors. They were unable to identify any earthquake activity that coincided with the strange noises, ___18___ ruling out ground shaking as the cause of it. They concluded that this phenomenon is ___19___ to the atmosphere. Possible reasons could include meteors exploding in the sky or the sound of big waves getting louder because of special weather conditions near the ocean. Over the years, many of these ___20___ mystery noises have turned out to be caused by military planes flying faster than the speed of sound.Given the diversity of locations and explanations, it’s possible that skyquakes in different parts of the world have different causes. But for now, their true cause remains mysterious.II. Reading Comprehension (45分)Section A (15分)Directions: For each blank in the following passage there are four words or phrases marked A, B, C and D. Fill in each blank with the word or phrase that best fits the context.The rigid corridors of Welton Academy carried the weight of tradition and conformity (循规蹈矩). John Keating, an English teacher with a(n) ___21___ of mystery and passion, stepped into the academy like a breath of freshness in a dull room. His very presence was a(n) ___22___ to the long-established norms of the school.He was not one to simply stand at the front of the classroom and lectured about Shakespeare’s poetry or the rules of grammar. ___23___, he had a unique way of making the words come alive. In his first class, he walked into the room, a twinkle in his eye, and led the boys out into the hallway.Pointing at the old, faded pictures of former students, he said, “Carpe diem, boys. Seize the day. Make your lives ___24___. These men were once just like you, with dreams and potential. Don’t let this place bury your ambitions.”His special haven, the “Whispers of the Bard,” was a magical place hidden away from the ___25___ eyes of the school authorities. Here, under the open sky, Keating would gather the students around him. He would recite poetry with such enthusiasm that the words seemed to ___26___in the air. “Poetry,” he told them, “is not just about rhymes and meters. It’s the language of the ___27___. It’s the way we express the deepest desires and the wildest dreams that we hold ___28___us.”He encouraged each student to find their own voice between the lines of the great poets. To Neil Perry, who had a hidden passion for the ___29___ burning like a small fire in his heart, Keating was like a guiding star. He saw the potential in Neil’s eyes and said, “Neil, the stage is waiting for you. Don’t let anyone even your father ___30___ your light. Your dreams are precious, and you have the talent to make them come true.” He helped Neil practice his lines, showing him how to ___31___ his emotions through every word. Under Keating’s guidance in every session, Neil grew more confident, believing that he could even ___32___ what his father expected of him.For Todd Anderson, who was shy and often ___33___ by his brother seemingly excellent at everything, Keating noticed his talent for seeing the deeper meaning in literature. “Todd,” he said, “your mind is a treasure chest. Open it and share your thoughts with the world. Don’t be afraid to ___34___. Your interpretations are as valuable as any other’s.” With Keating’s encouraging words, Todd started to come out of his ___35___, finding the courage to speak up and express himself.Keating’s encouragement was like a gentle wind that blew through the lives of these students, fanning the flames of their dreams and giving them the strength to pursue what they truly loved.21. A.air B.gesture C.mood D.outlook22. A.threat B.barrier C.challenge D.opportunity23. A.However B.Therefore C.Instead D.Moreover24. A.mysterious B.extraordinary C.practical D.specific25. A.caring B.shining C.wandering D.watching26. A.dance B.float C.move D.slide27. A.insight B.innocence C.soul D.sense28. A.between B.upon C.into D.within29. A.poetry B.stage C.match D.music30. A.dim B.adjust C.flash D.fuel31. A.conceal B.project C.stimulate D.sustain32. A.fall within B.persist in C.keep off D.go beyond33. A.overseen B.overshadowed C.overestimated D.overlooked34. A.step away B.fit in C.stand out D.push forward35. A.routine B.shell C.circle D.spaceSection B (22分)Directions:Read the following three passages. Each passage is followed by several questions or unfinished statements. For each of them there are four choices marked A, B, C and D. Choose the one that fits best according to the information given in the passage you have just read.AIn the year 1669, a German trader named Hennig Brand set out on an unusual quest that would lead to one of the most fascinating discoveries in the history of chemistry. Brand, driven by the age-old alchemists’ dream of magically turning base metals into gold, conducted a series of experiments that would forever change our understanding of elements.Brand’s journey began with an assumption that the key to creating “gold” resided in human urine (尿液). This seemingly strange idea was fueled by the observation that urine shared a similar yellow color with the precious metal. Acting on this belief, Brand collected an astonishing 5000 liters of urine and allowed it to stand and ferment (发酵).After weeks of fermentation, Brand boiled the urine down to a thick, sticky substance. He then mixed this paste with sand and heated the mixture to an extreme temperature. What emerged from this process was a substance that was entirely new to the world of science – a white solid that shone with a soft light in the dark.Brand named this glowing material “phosphorus,” originating from the Greek words for “light bearer.” The discovery of phosphorus was not just a scientific breakthrough; it captured the imagination of the public and the scientific community alike. Its ability to give off light in the darkness was both fascinating and mysterious.The implications of Brand’s discovery were far-reaching. Phosphorus was not only a novelty but also a substance with practical applications. It would later become an essential component in the production of matches, fertilizers, and various chemicals.Hennig Brand’s accidental discovery of phosphorus in 1669 was more than just finding a new element; it marked the end of the era of the period of magic chemistry and the beginning of modern chemistry. Brand’s phosphorus, once sought as a means to wealth, became a cornerstone in the field of science, a clear demonstration of power of curiosity and the unexpected paths that can lead to enlightenment.36.What is the main idea of the passage?A. The fall of ancient alchemists and the rise of modern chemists.B. The accidental discovery of phosphorus and its scientific impact.C. The importance of human urine in scientific experiments.D. The transformation of base metals into gold through magic.37.What was Hennig Brand’s initial goal when he started his experiments?A. To turn human urine into gold.B. To discover a new element.C. To produce a glowing substance.D. To reform modern chemistry.38.The underlined word “cornerstone” in the last paragraph is closest in meaning to ______.A.mysteryB.symbol C.obstacle D.foundation39.What can be inferred about Hennig Brand from the passage?A. He was a serious chemist who followed established scientific methods.B. He was a visionary scientist who predicted the future of chemistry.C. He was a curious individual willing to explore unconventional ideas.D. He was a wealthy trader with a deep understanding of chemistry.BGoing underground?The Subway is the easiest way to get around the City Centre and West End of Glasgow. Running every four minutes at peak times, it takes just 24 minutes to complete a circuit of the 15 stations and costs from as little as £1.80 for an adult single to travel anywhere else on the system.First Trains Last TrainsOuter CircleMon. to Sat. Sun. Outer Circle Mon. to Sat. Sun. From Govan06:30 10:00 From Govan 23:16 17:50 From St Enoch06:34 10:03 From St Enoch 23:30 18:03 Inner CircleMon. to Sat. Sun. Inner Circle Mon. to Sat. Sun. From Govan06:30 10:00 From Govan 23:16 17:50 From St Enoch 06:32 10:00 From St Enoch23:28 18:00 Subway ticketsType Adult Child*** unlimited travel for one day ** Applies to children under 16 years old. Children under five travel for free if accompanied by a fare paying adult.Single£1.80 £0.85 Return£3.40 £1.60 All day* £4.30 £2.1540. According to the notice board, which of the following is TRUE ?A. The subway is the only way to travel in the city.B. The subway runs every 4 minutes any time of the day.C. An entire journey of 24 stations takes 15 minutes.D. An adult ticket for a full circuit costs only £1.80.41. To arrive at Kelvinbridge on a weekday morning as soon as possible, you can take the earliesttrain from St Enoch at ____________.A. 6:34B. 6:32C. 10:00D. 10:0342. A couple taking a 15-year-old and a newborn on a ONE-DAY trip in Glasgow can maximize theirsubway experience by paying ____________.A. £6.45B. £8.40C. £10.75D. £12.90CFor the first time, scientists have observed the brain throughout the pregnancy (怀孕) timeline. Sex hormones, like estrogen and testosterone, are powerful players in the brain, affecting mood, memory, and more. Some of the most dramatic hormonal changes that humans experience happen during pregnancy, and yet those nine months have been a black box for human neuroscience until now.A new study published this week in Nature Neuroscience provides the most extensive look inside that black box yet. Researchers scanned the brain of one woman 26 times over the entire course of her pregnancy – before, during and after. Brain scans show that tracks of white matter get stronger during pregnancy. Previous brain imaging studies from before and after pregnancy have shown that pregnancy shrinks (缩小) parts of the brain, specifically its gray matter. These outer layers of the brain are responsible for most of sensation, learning and other great things the brain does.Shrinking gray matter may sound scary, but it happens to all of us throughout development to fine-tune our neural processing and make our brains more efficient. Though the term “mommy brain” is often used to refer to the brain fog and forgetfulness some people feel during pregnancy, the brain changes are likely adaptive. For example, you may be forgetting where your keys are, but you are way more focused on what is happening to your baby. Researchers are particularly interested in changes within brain regions that help with social cognition by allowing us to take on others’ perspectives.The scale and pattern of brain changes during pregnancy are similar to what other researchers have seen in adolescent brains during puberty (青春期), also driven by hormones. Other researchers have been able to detect whether someone had been pregnant based only on neuro imaging data from decades later. So despite the common saying that our brains stop developing in our mid-20s, hormones seem to drive big, long-lasting changes throughout adulthood.From studying the woman’s brain, researchers confirmed gray matter decreased by four percent over the course of pregnancy and that decrease persisted throughout the end of the study two years after giving birth. And it wasn’t just one area or network – 80% of brain regions shrunk. While certain areas and networks changed faster than others, the team doesn’t yet know what the implications are.43. The passage mainly tells us __________________.A. how pregnancy impacts women’s memoryB. how brain scans lead to a breakthroughC. how puberty differs from pregnancyD. how brain changes during pregnancy44. Based on the research, a pregnant woman should ______ changes accompanying “mommy brain”?A. peacefully acceptB. consciously avoidC. completely ignoreD. eagerly expect45. We can learn from the last two paragraphs that ________________________.A. researchers have figured out why certain areas of brain change fasterB. despite similarity, brain changes in puberty aren’t driven by hormonesC. hormones are likely to cause brain changes beyond adolescenceD. the shrinkage of gray matter in brain stops shortly after child birth46. What is the structure of this passage? A.B.C. Introducing a topic Providing examples Stating a problem Proposing solutionsEvaluating the solutions Presenting a finding Explaining Relating with other findingsSummarizing the main pointsD.Describing a phenomenon Analyzing the causesSection C (8分)Directions: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.A.Previously, they’ve trained packs of hero rats to detect dangerous bacteria.B.Then they were introduced to common scents used to mask illegal wildlife trade.C.This effort aims to provide a low-cost detection system to prevent illegal hunting.D.However, there are concerns that the rats might be distracted by some common scents.E.Existing screening tools are expensive and time intensive, necessitating a new approach.F.For this purpose, these trained rats will be expected to work in likely hotspots for illegalwildlife trade.Ratting on Crimes“You are never more than six feet away from a rat,” goes the saying. Though it has been concluded that this estimate is incorrect, it might soon be accurate for those involved in the illegal wildlife trade.A team of researchers have trained African rats to pick up the scents (气味) of endangered animal products, such as elephant ivory and rhino horn. 47.__________The rat pack can even identify these items when concealed among other substances, and have been shown to remember the smells after months of non-exposure. This isn’t the first time APOPO, a Tanzania-based non-profit, have recognized a potential for a super-rat workforce. 48.__________ The organization looks to provide low-tech, cost-efficient solutions to pressing challenges throughout Africa.The rats in the new study went through several demanding stages of training. They first learned to smell a target scent for several seconds to earn a flavoured reward. 49.__________ The final step was memory consolidation training, where they were reintroduced to scents they’d not encountered for five and eight months, respectively. Despite the months of non-exposure, the rats showed perfect memory scores, suggesting that their cognitive memory performance is similar to that of dogs.Illegal capture, killing, and harvesting of animals and plants have increased dramatically in recent years. For example, 55 African elephants are killed for their tusks every day, over 20,000 a year. This has to be stopped immediately.50.__________ They will be armed with custom-made vests (马甲). With their front paws, they will be able to pull a small ball attached to the chest of their vest, which gives out a beeping sound. This way rats will be able to alert handlers when they detect a target. Once fully trained and prepared, these giant rats could become illegal hunters’ worst enemy.III. Summary Writing (10分)51. Directions: Read the following passage. Summarize the main idea and the main point(s) of the passage in no more than 60 words. Use your own words as far as possible.The Significance of Cattle in Maasai SocietyCattle are the traditional partners of the Maasai people of East Africa. The traditional Maasai diet is heavily centered around cattle products. Milk is a fundamental component of the Maasai diet, consumed daily and in various forms. Fresh milk, known as “enkirowua”, is often drunk straight or mixed with herbs for added flavor and medicinal benefits. Processed milk, or “mokore”, is a popular variation, providing rich source of nutrition. Cattle’s meat is another important part of the Maasai diet, consumed during special occasions and ceremonies. Every part of the animal is used, reflecting the Maasai’s resourcefulness and respect for their livestock. It represents strength and the community’s collective wealth.Cattle hold significant value in Maasai social life. An individual’s social status is heavily influenced by cattle ownership. The number of cattle one possesses directly relates with his standing in the community. This is particularly evident during traditional ceremonies, such as weddings, where the exchange of cattle as gifts signifies the strong bond between families and a shared commitment to the future. Families there share responsibilities in cattle care and their collective management promotes unity and teamwork. For example, the process of milking is a shared activity, involving both men and women and strengthening social bonds. It is especially vital during challenging times, such as droughts or other hardships when the well-being of the cattle is crucial.Cattle also play a big role in Maasai rituals and ceremonies, accompanying individuals from birth to death. For example, the sacrifice of a cow during naming ceremonies or funerals not only celebrates the occasion but also strengthens the community’s spiritual connection with their livestock. These rituals highlight the spiritual importance of cattle, seen as a link between the physical and spiritual worlds, thus firmly establishing their central role in Maasai culture.IV. Translation (15分)Directions: Translate the following sentences into English, using the words given in the brackets.52. 农忙季节,这个偏远的小村子显得空荡荡的。
2022年考研考博-考博英语-电子科技大学考试全真模拟易错、难点剖析AB卷（带答案）一.综合题(共15题)1.单选题I recommend that the planning（）until all the materials have been supplied.问题1选项A.is not startedB.will not be startedC.not be startedD.is not to be started【答案】C【解析】句意:我建议应该在所有的材料己被提供后才启动这个计划。
语法题。
考查虚拟语气。
句子谓语为recommend,表示要求建议,这类动词所接的宾语从句一般用虚拟语气: (should) +原形动词，且should —般会省略,故选C。
2.单选题This is not the right（）to ask for my help; I am far too busy even to listen.问题1选项A.timeB.opportunityC.chanceD.case 【答案】A【解析】句意:这不是向我寻求帮助的恰当吋机，我太忙了，甚至没时间倾听。
考查固定搭配。
it is the right time to do sth. 是做某事的恰当时机。
故选A。
3.单选题She was so fat that she could only just（）through the door.问题1选项A.assembleB.appearC.squeezeD.gather【答案】C【解析】句意:她如此胖，以至于只能挤过这扇门。
考查动词辨析。
assemble 聚集，集合，收集;appear 出现，显得，似乎，看来；squeeze 挤，紧握，勒索；squeeze through 挤过，勉强通过;gather 收集，收割，使……聚集。
故C符合句意。
4.单选题The government（）to approve the use of wide-spread surveillance when the Justice Department took objections.问题1选项A.is goingB.had beenC.was aboutD.is coming【答案】C【解析】句意:政府即将同意采取广泛监督的手段吋，却遭到了司法部的反对。
2022年考研考博-考博英语-北京航空航天大学考试全真模拟易错、难点剖析B卷（带答案）一.综合题(共15题)1.单选题Email is a convenient, highly democratic informal medium for conveying messagesthat（）well to human needs.问题1选项A.adheresB.conformsC.satisfiesD.reflects【答案】B【解析】动词辨析。
adheres坚持，黏附；conforms符合；satisfies满足，使满意；reflects反射，考虑。
句意：电子邮件是方便的、高度大众化的用于传递信息的非正式媒介，它（）人们的需求。
从语义上来说，B项和C项都可以,但是satisfy是及物动词，排除。
conform to意为“符合，遵照，顺应”，因此正确答案是B选项。
2.单选题All the ceremonies at the 2000 Olympic games had a unique Australian flavor, （）of their multicultural communities.问题1选项A.noticeableB.indicativeC.conspicuousD.implicit【答案】B【解析】形容词辨析。
noticeable明显的；indicative表示的，象征的；conspicuous明显的，惹人注目的；implicit不言明的，含蓄的，无疑问的。
句意：2000年奥运会所有的仪式都带有一种独特的澳大利亚风情，（）他们是多元文化的社会。
B选项indicative在此符合句意,意为“表明他们是多元文化的社会”。
3.单选题While typing, Kathy had a habit of stopping（）o give her long and flowing hair a smooth. 问题1选项A.promptlyB.simultaneouslyC.eventuallyD.occasionally【答案】D【解析】副词辨析。
英语试卷注意事项：1.答题前，考生务必用黑色碳素笔将自己的姓名、准考证号、考场号、座位号在答题卡上填写清楚。
2.每小题选出答案后，用2B 铅笔把答题卡上对应题目的答案标号涂黑。
如需改动，用橡皮擦干净后，再选涂其他答案标号。
在试题卷上作答无效。
3.考试结束后，请将本试卷和答题卡一并交回。
满分150分，考试用时120分钟。
第一部分听力（共两节，满分30分）注意，听力部分答题时，请先将答案标在试卷上。
听力部分结束前，你将有两分钟的时间将答案转涂到答题卡上。
第一节（共5小题；每小题1.5分，满分7.5分）听下面5段对话。
每段对话后有一个小题，从题中所给的A 、B 、C 三个选项中选出最佳选项，并标在试卷的相应位置。
听完每段对话后，你都有10秒钟的时间来回答有关小题和阅读下一小题。
每段对话仅读一遍。
1.How does the man feel?A.Cold.B.Warm.C.Hot.2.What is the woman doing?A.Working on the marketing plan.B.Writing a monthly report.C.Playing computer games.3.Where does the woman want to go?A.The Art Gallery. B.Beijing Road.4.What is the man going to do next?A.Stop for a rest.B.Keep handling the problem alone.C.Make a phone call.5.What does the woman want the man to do?A.Apologize to her.B.Lower the volume.C.Put on the headset.第二节（共15小题；每小题1.5分，满分22.5分）听下面5段对话或独白。
2023年全国硕士研究生招生考试（英语二）参考答案及解析Section Ⅰ Use of EnglishHere’s a common scenario that any number of entrepreneurs face today: you’re the CEO of a small business and though you're making a nice 1 , you need to find a way to take it to the next level. what you need to do is 2 growth by establishing a growth team. A growth team is made up of members from different departments within your company, and it harnesses the power of collaboration to focus 3 on finding ways to grow.Let's look at a real-world 4 . Prior to forming a growth team, the software company BitTorrent had 50 employees.Working in the 5 departments of engineering, marketing and product development. This brought them good results until 2012, when their growth plateaued. The 6 was that too many customers were using the basic, free version of their product. And 7 improvements to the premium, paid version, few people were making the upgrade.Things changed, 8 , when an innovative project marketing manager came aboard, 9 a growth team and sparked the kind of 10 perspective they needed. By looking at engineering issues from a marketing point of view, it became clear that the 11 of upgrades wasn't due to a quality issue. Most customers were simply unaware of the premium version and what it offered.Armed with this 12 , the marketing and engineering teams joined forces to raise awareness by prominently 13 the premium version to users of the free version. 14 ,upgrades skyrocketed, and revenue increased by 92 percent.But in order for your growth, team to succeed, it needs to a have a strong leader. It needs someone who can 15 the interdisciplinary team and keep them on course for improvement.This leader will 16 the target area, set clear goals and establish a time frame for the 17 of these goals. This growth leader is also 18 for keeping the team focus on moving forward and steer them clear of distractions. 19 attractive, new ideas can be distracting, the team leader must recognize when these ideas don’t 20 the current goal and need to be put on the back burner.1.A. purchase B. profit C. connection D. bet2.A. define B. predict C. prioritize D. appreciate3.A. exclusively B. temporarily C. potentially D. initially4.A. experiment B. proposal C. debate D. example5.A. identical B. marginal C. provisional D. traditional6.A. rumor B. secret C. myth D. problem7.A. despite B. unlike C. through D. besides8.A. moreover B. however C. therefore D. again9.A. inspected B. created C. expanded D. reformed10.A.cultural B. objective C. fresh D. personal11.A. end B. burden C. lack D. decrease12.A. policy B. suggestion C. purpose D. insight13.A. contributing B. allocating C. promoting D. transferring14.A. As a result B. At any rate C. By the way D. In a sense15.A. unite B. finance C. follow D. choose16.A. share B. identify C. divide D. broaden17.A. announcement B. assessment C. adjustment D. accomplishment18.A. famous B. responsible C. available D. respectable19.A. Before B. Once C. While D. Unless20.A. serve B. limit C. summarize D. alter【1】B. profit 原文提到“小公司的CEO也挣到了大钱”。
Protective RelayingModern, time-efficient, and interactive hands-on training Protective relaying providesdetection of abnormal operatingconditions in electrical systemsand is needed in order to actquickly to protect circuits, equip-ment, and the general public.The theoretical background, aswell as practical application, ofthese protective devices and theirprotection functions are animportant part of the education ofpower systems for electrical engi-neers.Power-utility-grade equipment,Siemens’ newest generation theSIPROTEC 5 series, is used in thisinnovative teaching approach.Example scenarios are created inthe accompanying professionalprogramming tool, DIGSI 5, whichallows users to create differentsetups and simulate possiblefaults using the built-in relay test-ing unit. The response of the relayis then analyzed with the relaydisplay and the fault record.This customizable solution allowsperfect alignment for individualteaching needs. The availablerange of relays and manuals pro-vide coverage of these generaltopics:• Overcurrent/OverloadProtection• Directional Protection• Differential Protection• Distance ProtectionDidactic Short InformationDID1052ENCustomizationIndividual, cost-effective learning solutions are created by combining a maximum of two hardware relays with the corresponding courseware.Comprehensive CoursewareTheoretical knowledge and hands-on training exercises teach students the basic and advanced relay protection functions.The courseware provides the follow-ing topic coverage:Overcurrent/Overload Protection • Evolution of protective relays• Overcurrent protection• Overcurrent and overload protec-tion of AC machines and power transformers• Overcurrent protection of radial feedersDirectional Protection• Protection of parallel power lines using overcurrent relays• Directional overcurrent protection • Directional comparison protection • Directional power protection Differential ProtectionBasic implementation of differentialprotection:• Effect of the current measuring erroron the sensitivity of current differ-ential protection• Percentage restrained differentialprotection• Application of differential protectionDistance Protection• Simplified diagram of a powersystem• Conventional time-stepped distanceprotection• Distance relay impedance charac-teristic• Fault impedance vs. load imped-ance• Line protection• Generator loss-of-excitation protec-tion• Distance protection using communi-cation-assisted tripping schemesState of the art HardwareThe front display and keypad of therelays allow direct user interactionwhile communication with the PCsoftware is through USB or Ethernet.The units can be used table-top or inan A4 frame. The hardware providesthe following ANSI/IEEE protectionfunctions:Numerical Overcurrent Relay• Directional phase overcurrent (67)• Directional ground overcurrent(67N)• Directional power (32)• Instantaneous phase overcurrent(50)• Instantaneous ground overcurrent(50N)• Phase overcurrent (51)• Ground overcurrent (51N)Numerical Distance Relay• Phase distance (21)• Ground distance (21N)• Directional phase overcurrent (67)• Directional ground overcurrent(67N)• Directional power (32)• Instantaneous phase overcurrent(50)• Instantaneous ground overcurrent(50N)• Phase overcurrent (51)• Ground overcurrent (51N)Numerical Differential Relay• Numerical Differential Relay• Transformer differential (87T)• Instantaneous phase overcurrent(50)• Instantaneous ground overcurrent(50N)• Phase overcurrent (51)• Ground overcurrent (51N)DID152EN©216FestoDidacticSE.Protective RelayingFesto Didactic SERechbergstraße 373770 DenkendorfGermanyPhone: +49/711/3467-0Fax: +49/711/34754-88500************.com。
Are you an experienced pilot with a passion for helping others in need? Do you have the skills and dedication required to perform highstress rescue missions? If so, we are looking for you to join our team of elite rescue pilots!Our organization specializes in providing rapid and effective assistance to those in distress, whether it be in the form of medical evacuations, search and rescue operations, or disaster relief efforts. As a rescue pilot, you will play a crucial role in these missions, utilizing your expertise and skill to navigate challenging environments and deliver lifesaving aid.Key qualifications for this position include:1. Certified Pilot License: A valid and current pilots license with appropriate ratings for the type of aircraft you will be flying.2. Experience: Prior experience in flying rescue missions or similar highstress environments is highly desirable.3. Physical Fitness: The ability to meet the physical demands of the role, including long hours, high altitudes, and potential exposure to extreme weather conditions.4. Calm Under Pressure: The capacity to remain focused and make clear decisions in highstakes situations.5. Team Player: A strong sense of teamwork and the ability to coordinate effectively with ground crews, medical personnel, and other pilots.6. Excellent Communication Skills: The ability to communicate clearly and concisely with all team members and control centers.7. Adaptability: The flexibility to adjust to changing conditions and mission parameters quickly and efficiently.8. Technical Knowledge: A thorough understanding of aircraft systems and the ability to perform preflight checks and troubleshooting as needed.Responsibilities of the role will include:Conducting preflight inspections and ensuring the aircraft is in optimal condition for each mission.Flying rescue missions, including but not limited to medical evacuations, search and rescue, and disaster relief.Collaborating with mission coordinators to plan and execute rescue operations.Maintaining accurate and detailed records of all flight activities and mission outcomes. Participating in regular training exercises to maintain proficiency and update skills.If you are ready to take on the challenge of a rewarding career as a rescue pilot, we encourage you to apply. Together, we can make a difference in the lives of those who need us most. Please submit your application along with your resume and any relevant certifications to our recruitment team.。
希望拥有瞬间移动英语作文Title: The Phenomenon of Teleportation: A Scientific Exploration。
Teleportation, the instantaneous movement of objects or individuals from one location to another, has captured the imagination of humanity for decades. While it has been a staple in science fiction narratives, the prospect of real-life teleportation raises profound questions about the nature of space, time, and the limits of human understanding. In this essay, we will delve into the concept of teleportation, its potential implications, and the current state of scientific research in this field.Teleportation, in its essence, involves the disassembly of an object or person into data, which is then transmitted to another location and reassembled. This process bypasses conventional modes of transportation and seemingly defies the constraints of distance and time. The allure of teleportation lies in its promise of near-instantaneoustravel, eliminating the need for lengthy commutes and transcending geographical boundaries.One of the most prominent theories underlying teleportation is quantum entanglement, a phenomenon observed at the subatomic level where particles become interconnected regardless of the distance between them.This interconnectedness suggests the possibility of transmitting information instantaneously across vast distances, laying the groundwork for teleportation. However, harnessing quantum entanglement for practical teleportation remains a formidable challenge due to the delicate natureof quantum states and the technical hurdles involved in controlling them.Another approach to teleportation involves quantum teleportation, a process that relies on the principles of quantum mechanics to transfer the state of one particle to another instantaneously. While experiments havesuccessfully demonstrated quantum teleportation over short distances in controlled environments, scaling up this technology to teleport macroscopic objects, let alonehumans, presents significant obstacles. The fidelity of teleportation, ensuring that the object arrives intact and unaltered at its destination, is a paramount concern that must be addressed.Furthermore, ethical considerations surrounding teleportation abound. The prospect of deconstructing and reconstructing living organisms raises profound questions about identity, consciousness, and the sanctity of life. Would a teleported individual retain their memories, personality, and sense of self? Or would they be reduced to mere copies, devoid of the essence that defines their humanity? These ethical quandaries underscore the need for careful deliberation and ethical oversight in the pursuit of teleportation technology.Despite these challenges, recent advancements in quantum computing, nanotechnology, and materials science have reignited interest in teleportation research. Breakthroughs in quantum teleportation protocols, such as the development of more robust quantum error correction codes, offer glimpses of progress toward practicalteleportation systems. Furthermore, interdisciplinary collaborations between physicists, engineers, andbiologists are shedding light on the fundamental principles underlying teleportation and its potential applications in fields ranging from medicine to space exploration.In conclusion, teleportation represents a tantalizing frontier in scientific inquiry, promising to revolutionize the way we perceive and interact with the world. While the realization of practical teleportation remains a distant prospect, ongoing research endeavors hold the promise of unraveling the mysteries of instantaneous travel. As we navigate the complexities of teleportation, we must remain vigilant in our ethical considerations and mindful of the profound implications that this technology may hold for humanity's future.。
Purposeful mobility for relaying and surveillance in mobilead-hoc sensor networksR.Rao and G.Kesidis∗†October30,2004AbstractIn this paper,we consider a mobile ad-hoc sensor network.The mobility of the sensor nodes is designed with the cost of communication and mobility in mind along with consid-eration of the possible scanning tasks of the nodes.Our mobility algorithm is developedin the context of a distributed system where,for any single mobile node,only local infor-mation about associated energy costs is known.We use a distributed simulated annealingframework to govern the motion of the nodes and prove that,in a limiting sense,a globalobjective function comprising mobility and communication energy costs will be minimized.This paper concludes with a simulation study focusing on mobile sensors with dual roles ofscanning and relaying higher priority tracking traffic from tracking nodes.keywords:sensor networks,MANET,mobility strategy,communication,Energy-awaresystems1IntroductionTraditional mobile ad hoc networks(MANETs)typically treat node mobility as an uncontrolled factor.In sensor MANETs,the nodes have a communal surveillance(tracking/scanning)mission and mobility in some cases can be designed to help achieve the mission.In addition,mobility can be used to provide logistical support by,for example,facilitating network connectivity and achieving better communication,in general,between the sensors and data repository(cache or larger database)or,in a real-time setting,the command-and-control entities of the network. Also,node mobility makes the network more robust against node failure events.We consider the real-time,command-and-control context of a sensor MANET deployed in battlefield environment to perform surveillance tasks.Each node is a robot carrying one or more sensors.These sensors collect information and transmit it to a data sink:base-station(satellite up-link)or command-and-control center.The nodes are required to track any hostile targets they sense,perform local scans(explore local surrounding that are not covered by any other nodes) and forward data from neighboring nodes towards the base station.The specific goal of communal-mission-oriented(i.e.,“purposeful”)mobility is to decide where2to move a node so that it can perform any one or all the tasks better.We assume that a node at any given time can be a tracking node or a scanning node.The data generated by the tracking nodes is considered latency-critical since we are looking to provide detailed information on tracked targets in real time.The scanning node generates lower volume,non-latency-critical data about its local surroundings.The scanning node also relays traffic,i.e.it forwards,in particular,latency-critical data towards the base station node.Other kinds of communication are possible in such a sensor MANET including that required for coordination of target tracking and overhead for communication route establishment and maintenance.In the somewhat more simplified setting of this paper,we target a single network“time-scale”and focus on scanning nodes moving to scan a new area and/or reduce the total transmission power used by the network for high-priority tracking traffic.We are interested in distributed mobility algorithms relying only on information local to the node.For terrestrial vehicles(nodes),the cost of mobility may be high depending on their weight and on the environmental conditions(terrain).If we consider unmanned aerial vehicles(UAVs), there is a roughlyfixed power cost to keep the UAV airborne.The power cost of motion for scanning and relaying(the focus of this paper)would the additional cost needed to maneuver the UAV in the necessary directions.This cost may be relatively low compared to that required to keep the UAV airborne.For unmanned underwater vehicles(UUVs),the cost of motion may be significantly lower than that of terrestrial vehicles in certain environments.If there is afixed power cost for necessary mobility,we can include it together with that of computation and communication-reception under onefixed costπ.The available energy of a node at any time3t>0will then beE t=E0−πt−M t−C twhere M t is the cumulative energy required for additional motion and C t is the cumulative energy required for communication-transmission.Two cases are considered in this paper both assuming statically positioned tracking nodes generating latency critical data that is forwarded by mobile“intermediate”nodes to the single data sink.In thefirst case,the intermediate nodes only relay the tracking information to the sink.The intermediate nodes move so that the total transmission power is reduced.For example if a node is relaying a large volume of data between two nodes,it will obviously save energy in transmission if it is closer to them.The cost of motion to a chosen location will be amortized against the savings in communication energy at that location as predicted by the node(again, using only local information).To this optimization problem,we can apply a greedy approach to select the optimum position of nodes.This may result in a optimal solution locally,but could potentially give rise to sub-optimal placement globally.To prevent this,we employ simulated annealing wherein a node,with a positive probability,accepts a“bad move”locally because the move could benefit the network globally in the longer run.This is explained in greater detail in Section3.Note how the use of“randomized”motion is,at least in part,motivated by the distributed nature of the problem we have formulated.Alternative motivations for random motion of sensor nodes were articulated in[8].In the second case,the intermediate nodes are assigned both scanning and relaying tasks.To reiterate,we assume that data volume generated by intermediate nodes is of lower priority and of4negligible volume compared to the data from the tracking nodes.The goal here is tofind optimal node paths to conserve power and to cover areas not explored by any nodes.An intermediate node could move either to save communication energy or to perform local scans.This mobility strategy is explained in greater detail in Section4.The remainder of the paper is organized as follows.A survey of related literature is given in Section2.In Section5,our simulation study is described.The paper concludes with a summary and discussion of future work in Section6.2Related WorkIssues of surveillance coverage and communication connectivity for random static positioning of sensors were explored in[5]and,more recently,in[13].In[13],the nodes are active with certain probability with a given sensing and communication radius.They have derived results to prove connectivity and coverage is maintained even if the probability of a node being active and communication radius are low.This may give the communication radius for coverage and connectivity but only for a static network.It is not possible to extend this framework to include mobility as the nodes are assumed to be uniformly arranged.Clearly,a basic motivation of node mobility is that the nodes are not deployed with sufficient density in the region under surveillance to make mobility of the nodes unnecessary.In this paper, we assume that the sensors deployed are somewhat sophisticated and costly so that very dense deployment is infeasible.In[11],the effect of mobility on a position detection algorithm was considered.They suggested5the use of hop-counts from reference nodes tofind relative positions of all nodes.Nodes are moved to neighborhoods where accurate information is not available.Mobility helps to increase accuracy of information regarding node positions but does not help tofind best position for coverage or connectivity.Flocking properties of platoons of UAVs were studied in[14].Specifically,they explored local mobility laws that keep formation(velocity and heading).In[8],the authors evaluate the distribution of the time until detection of a point-target under purely random(diffusion)mobility per node.Given an associated Bessel process describing the distance between any two given nodes,there also exist expressions for the distribution of the time between successive contact of any two nodes assuming each of their communication ranges is bounded,see p.297of[1].In[10],the authors look at navigating across a vehicle across a sensor grid.The nodes in the sensor interacts with the vehicle giving it local information about the terrain.The vehicle then decides where to move next.In[16],the authors consider a scenario where mobility assists the nodes in sensor deployment. The goal is to maximize coverage while not compromising connectivity by intuitively enacting local repulsion of nodes(to minimize redundancy of coverage)along with long-range attraction of nodes so as not to compromise network connectivity.[17]and[6]also consider virtual forces between the nodes for sensor deployment.Again,the mobility assists only in the deployment of a static network.Finally,simulated annealing mechanisms have been proposed in the past for other networking6purposes.For example,in[15],a(centralized)simulated annealing algorithm was used for clusterhead selection based on weights assigned to nodes.3Deterministic and random mobility for relay network-ingIn this section we assume a single task per node.For example,in response to target detection, certain nodes(proximal to the target)are assigned logistical target-tracking tasks while others are assigned tasks supporting communication.We focus herein on mobility for the latter category of nodes and,for those nodes,state that a goal of node mobility is to maximize the life-time of the MANET and,at the same time,perform the required relaying tasks satisfactorily.Our specific objective is to incrementallyfind the node positions that minimize the total required transmission power for all the activeflows in the MANET while suitably“penalizing”for the energy cost of motion in order tofind these positions.For a node to move from one position to another,there must be a significant resulting reduc-tion in communication power compared to the power consumed for motion.This would vary significantly depending on the environment of the moving vehicle operates in.For example,the relative cost for UAVs will be significantly less than UUVs which will be significantly less that terrestrial vehicles.In the following,we assume that nodes make such decisions based only on local information(traffic and neighbor positions)as appropriate for a highly decentralized and distributed sensor MANET.We will devise a distributed mobility strategy based on the simu-7lated annealing algorithm,see,e.g.,[9].The randomness introduced in the strategy will allow the sensor MANET to avoid positions that are suboptimal local minima of its objective.3.1Basic network model assumptions and a“greedy”mobility strat-egyWe need to define the following terms for our problem formulation:•N is the number of intermediate relay nodes;•F is the number offlows each of constant rateλpackets/s(fixed length packets assumed herein);•x is a vector of the positions of the intermediate relay nodes(so,in3-dimensions,x is actually an N×3matrix);•r is the set of F routes(each assigned to oneflow)where a route through the network is determined by a series of nodes beginning with a source and ending with a data sink;•V(x,r)is the total power required from the network to transmit the Fflows using routes r when the intermediate nodes are in positions x;the optimal choice of routes at position x isR(x)≡arg minV(x,r)r∈R(x)where R(x)is the set of feasible routes connecting those nodes when in positions x.8The quantity R(x)is the objective of a distributed routing algorithm(like Bellman-Ford[2]) and its determination is assumed to occur on a much faster time-scale than that of the mobility of the nodes.Further assume that all nodes have an associated clock cycling every T seconds (clocks are not necessarily synchronized).Once every cycle,a node decides with probability p whether it should attempt to move.Under a deterministic“greedy”mobility strategy,node k at position x k will move to position z that minimizesV((x−k;z),R(x))−V(x,R(x))+c|z−x k|/T(1)≡∆k V(x,z)+c|z−x k|/Twhere(x−k;z)represents the vector x with x k replaced by z,and c|z−x k|represents the amount of energy required for the move that we have chosen to amortize over a clock cycle-time(c is a fixed parameter of the assumed“constant”terrain).Movement according to(1)may be velocity v constrained,i.e.,|z−x k|≤vT.For a simple illustrative example,consider a relay node k that forwards twoflows from its tributary nodes i and j to node l.Suppose that the power required to transmit over distance d(again,at rateλpackets/s)is given by KdαWatts where K is a constant andα≥2is a transmission attenuation factor[4].So,for this example,∆k V(x,z)=K[|z−x i|α+|z−x j|α+2|z−x l|α−|x k−x i|α−|x k−x j|α−2|x k−x l|α].(2)9A basic assumption herein is that the quantity in(1)is computable by node k requiring,in par-ticular,knowledge of the location of its neighbors[12].Note that what makes this“distributed”computation of∆k V(x,z)is the fact that V is an additive function of the transmission power required at each node.The existing routes(at x)are used in the term V((x−k;z),R(x))because, in this distributed setting,the node k does not know the consequences its move will have on the routes.When multiple nodes can move simultaneously,the uncertainty in the benefit of a move is significantly larger;to reduce the likelihood of this,one may set p=1/N for this case of static sources and sinks.3.2Mobility by distributed annealingThis greedy method may converge to a“suboptimal”solution because:V(x,R(x))may have local minima;simultaneous motion of multiple nodes;and/or suboptimal local movement,i.e.,∆k V(x,z)+c|z−x k|/T≥minzminV((x−k;z),R((x−k;z)))z−V(x,R(x))+c|z−x k|/T.So,we propose a randomized motion on a lattice resulting in a kind of distributed simulated annealing algorithm.Motion is restricted to a lattice and a node k(currently at x k)selects a neighboring position z at random and accepts the move to z according to a“heat bath”probability(c.f.,(5)).Many other kinds of motion randomization could be used[8]but we chose annealing on a lattice because it is tractable in the following sense:Assuming no simultaneous10motion of nodes,we show in the following theorem that limit of this annealing motion tends to the(assumed unique)state x that minimizesU(x)≡V(x,R(x))+cT−1Nk=1|x k|(3)≡V(x,R(x))+cT−1||x||.(4) In this function,we clearly see the total cost of transmission power combined with the amortized cost of motion to positions x from the origin over a constant terrain.Consider the framework of,e.g.,[9]with potential function(Hamiltonian)U(x)given by(3) over all states x∈D where D is a lattice.We can define a time-reversible discrete-time annealing Markov chain on D with associated transition-probability matrix(TPM)P and stationary distri-butionπ.More specifically,consider an aperiodic,irreducible and time-reversible Markov chain with TPM Q and stationary distributionµ,i.e.,detailed balance holds:µx Q x,y=µy Q y,x for all states x,y∈D and Q x,y>0implies that x and y are neighboring points in D,e.g.,y=(x−k,z) for some k and z as above.Define the annealing chain using the heat bath acceptance probability rule:for states x=y,P x,y≡Q x,y min{1,exp(−β(U(y)−U(x)))}whereβ>0is interpreted as inverse temperature and,for our purposes herein,a constant.So, the TPM P inherits aperiodicity and irreducibility from Q.The TPM is also time-reversible with Gibbs stationary distribution:πx=µx e−βU(x)where Zβis the normalizing constant(partition function).Now define a TPM for the distributed annealing process:ˆPx,y≡Q x,y min{1,exp(−β[V(y,R(x))−V(x,R(x))+c||y−x||/T])}.(5) The TPMˆP continues to be irreducible and aperiodic,thereby yielding a unique stationary distributionˆπ[3],but is no longer time-reversible.Lemma1P x,y≥ˆP x,y for all x=y,and P x,x≤ˆP x,x for all x.Proof:By the definition of R and the triangle inequality,V(y,R(x))−V(x,R(x))+c||y−x||/T≥V(y,R(y))+c||y||/T−[V(x,R(x))+c||x||/T]=U(y)−U(x).Thefirst statement of the lemma directly follows from the definitions of P andˆP.The second statement is an immediate corollary of thefirst because both P andˆP are row-stochastic matrices. Now,sinceπis Gibbs,lim β→∞πx(β)=0for all x∈Ω≡arg minx∈DU(x)(6)12where we have explicitly shown the dependence ofπonβ(β→∞is interpreted as“cool-ing”).The following result states that the distributed annealing chain,ˆP,also has a stationary distribution with this“Gibbs like”property.Theorem1IfΩis a singleton set,i.e.,Ω≡{x∗},thenˆπ(β)=1x∗limβ→∞where1x∗=0if y=x∗and1x∗x∗=1.yProof:First note that[(1x∗)′ˆP(β)]y=ˆP x∗,y(β).If y=x∗then by Lemma1,ˆP(β)≤P x∗,y(β)→0asβ→∞.x∗,yOtherwise,if y=x∗then again by Lemma1,ˆPx∗,x∗(β)≥P x∗,x∗(β)→1asβ→∞.Therefore,(1x∗)′ˆP(β)=(1x∗)′.(7)limβ→∞Now recall thatˆπ(β)is the unique solution toˆπ(β)′(I−ˆP(β))=0andˆπ(β)′1D=113where1D is a vector all of whose entries are1.LetˆV(β)be the matrix obtained by replacing a column of I−ˆP(β),say column n,by1D.Thusˆπ(β)is the unique solution toˆπ(β)′ˆV(β)=(1n)′.Uniqueness implies that the null space ofˆV(β)must be just the zero vector;this,in turn,implies thatˆV(β)is nonsingular giving,for allβ>0:ˆπ(β)′=(1n)′[ˆV(β)]−1.Beginning with(7)and using the same argument,(1n)′[ˆV(β)]−1=(1x∗)′.limβ→∞The theorem statement follows from the last two equations.A straight-forward extension to this theorem(using condition(6))follows for optimal setsΩin which no two states are directly connected by the TPM Q.In summary,we have demonstrated that randomized annealing motion of the sensor nodes, distributed in the sense that only local information is used,nevertheless retains a Gibbs-like property,i.e.,a natural composite utility of communication and mobility costs(3)is minimized as the temperatureβ−1cools.144Dual tasking:scanning and relayingIn this section we look at combining the two tasks of scanning and relaying for the intermediate nodes in greater detail.The goal of the scanning task is to move to a location in the surveillance area not visited before or not visited by a scanning node in a long time.To quantify this,we partition the surveillance area with a grid.A node selects a“scanning move”with probability p s and“relaying move”with probability p r=p−p s where0<p s,p r<1.A simple method of scanning involves maintenance of a“taboo list”of,say,the last10points visited by the node.When considering a scanning move,points on the taboo list are excluded and the remaining choices are chosen uniformly at random.Alternatively,the taboo list can also maintain the time of the last visit so that the list could be implemented as a sliding time-window. For both of the approaches above,the taboo lists or lists of time-stamps can be exchanged by neighboring nodes and merged to create a more up-to-date table(at each node),where we note that the latter will require some kind of time time-synchronization among the nodes.5Simulation StudyWe considered a MANET with seven nodes,including four mobile relays,operating within a 40m×40m square area(for the following simulations,the units of distance can be scaled-up by suitable modification of the following mobility and communication parameters).We assumed there are two stationary(immobile)source(tracking)nodes and a single stationary data-sink (base station)node.Source nodes generated data at a constant bit rate of100kbps with50-byte15packets.We chose the following communication and mobility parameters for our simulation study.The relative motion constant c of the global utility function(3)was assumed to be determined by thefigure50mJ/m;i.e.,a node weighing1kg required about5mJ to move a distance of0.1m. The value of the parameter K from Equation(2),determining communication power required to transmit a packet over a distance of1m,was assumed to be1mW.Also for this equation, the communication attenuation parameter was assumed to beα=2.5.Finally,the intermediate nodes involved in forwarding traffic from sources to sink made a movement decision every T=10 seconds.Initially,the positions x(0)of the nodes are chosen independently and uniformly at random in the area under consideration.In the simulation,we also assume all active relay nodes move at all times,i.e.,p=1instead of p=1/N as advised in the end of section3.1.A transmission power-based(distributed Bellman-Ford with dαas metric)routing algorithm was assumed to be in effect determining the routes R(x)at node-positions x(again,assumed to operate at a time-scale much faster than that of node movement,T).As we are using power based routing algorithm,we assume nodes can communicate with all nodes in the given region.A node wishing to communicate with a farther node can do so by increasing its transmission power.Finally,from each set of simulation trials we determined an empirical mean and95%confidence interval;in the following graphs,the confidence interval is indicated by a vertical bar centered at the mean.165.1Single task per nodeIn this set of simulations,we assumed that the intermediate nodes have a single task,i.e.,that of relaying source-node tracking-data transmissions to the sink-node.That is,the relay nodes did not generate any scanning data of their own.Figure1:Total transmission power over time for differentfixedβIn Figure1we plot the total transmission power of the network over time for different values of theβparameter in the annealing algorithm(i.e.,the inverse temperature).Note thatβwas a fixed constant for each simulation run.Asβincreased(temperature decreased or cooled),note that the variance in total transmission power decreased.For lower values ofβ,the nodes accepted “bad”moves with higher probability,hence the higher variance in total transmission power.The increased variance at the beginning of each set of simulation trials was due to the randomly chosen initial positions for each simulation run.This variance reduces as the nodes move closer to the optimal position.Since we average over different initial positions,the reduction in total transmission power might not appear significant.But for cases where nodes have a bad initial position,we observed a reduction in total transmission power by as much as a factor of3.Theβ17value also controls the rate of convergence.For largerβ,the nodes move to an optimal position more quickly.We note this difference in the total transmission plot forβ=50andβ=500. Forβ=50the total transmission power reaches the optimal value after700s and continues to change around the optimal value.Forβ=500,the total transmission power reaches the optimal value after450s and remains relatively unaltered.Figure2:Total transmission power whenβincreased dynamically(cooling)In Figure2,we“cooled”the temperature during each simulation run in order to trap the nodes into optimal positions from the perspective of communication power.More specifically, every10s,βwas increased in increments of20from an initial value of200.As theβincreases, the variance in the transmission power predictably decreased.Such a cooling schedule makes sense in the context of constant bit-rate and stationary source nodes,stationary data sinks,and with no scanning motion,but would not make sense in a more dynamic networking environment, c.f.,Sections5.2and6.Figure3shows the initial andfinal position of the intermediate nodes of a representative sample path of a single simulation run.Note how the relay nodes have basically formed a line18Figure3:Inital andfinal node positionsbetween the sources and sink to reduce transmission distance.Figure4:Mobility and transmission energyFigure4shows the transmission energy saved compared to the energy spent in moving from the initial node-positions,for different values ofβ.The energy saved in transmission was on the order of a few tens of Joules while the energy spent in moving the nodes was of the order of few hundred mJ clearly demonstrating the worth of mobility in the context of our selected parameters.For largeβ,mobility is typically restricted to moves that deterministically reduce transmission19energy.The result is both a reduction of transmission energy and a small amount of energy is spent on mobility,but poor local minimas may occur.Under the annealing policy,as the value of βdecreases,the nodes have greater freedom to move.This ultimately reduces the energy saved in transmisson because poor local minima are avoided as the nodes make more“bad”moves to better explore the space of relay node-positions(i.e.,a greater breadth of search).5.2Dual tasking per nodeIn this set of simulations,we assumed that the intermediate nodes had both a scanning and relaying function,as described in Section4.The simple method involving a taboo list of the last10points visited by the node was simulated.Taboo lists of neighboring nodes were not exchanged.Finally,we assumed that the transmission energy for scanning(passive surveillance) traffic was negligible compared to that of the tracking traffic and the former was not accounted for.Figure5:Total transmission power over timeFor two values of the scanning-decision probability parameter,p s∈{0.4,0.6},the commu-20nication energy is plotted in Figure5.One can also compare with the second graph of Figure 1in which p s=0.Note that the effect of increasing p s(i.e.,a greater propensity for scanning moves)has an effect on communication energy similar to that of increasing temperature for singly tasked(relay)nodes as indicated in Figure1.Of course,the advantage of increasing p s is that the nodes cover(scan)more of the area under surveillance.Defining coverage as the total number of different points visited by all of the scan-relay intermediate nodes over a sliding time-window of twenty seconds,the p s=0.6trials depicted in Figure5achieved25%more coverage on average than the trials using p s=0.4.Indeed both p s and the temperatureβ−1affect coverage which significantly increased with decreasingβfor the trials of Figure1.6Discussion and future workWe demonstrated that motion based on our distributed annealing method results in the maxi-mization of the desired objective(3)accounting for both total transmission power and the energy required for motion.When assuming only a relaying task for intermediate nodes and stationary tracking nodes and data sink,the annealing algorithm can be allowed to“cool”(βincreased) to trap the relay nodes in optimal positions.However,if the tracking nodes themselves move or the tracking tasking is dynamic,cooling would make the relay network less responsive to this change.Such change is part of more general“volatility”in networking conditions that may be experienced by the relay nodes.When such conditions change slowly,an alternate cooling(over a period of stable conditions)and heating up(over a period of volatile conditions)of the annealing algorithm may be beneficial.During periods of sustained change,there may be no advantage to21cooling at all.Clearly,if an additional scanning task was added,cooling may make little sense as it would tend to cluster nodes about their optimal positions for relaying.In our algorithm,node responsiveness is p/T(the average number of moves per second).Sources of network“volatil-ity”include:finite-lifetime batteries,traffic,source/sink node mobility,changing environmental conditions affecting the channel and terrain,enemy activity targeting the network itself,etc.In general,local perceptions of increasing volatility require increased node responsiveness;i.e.,a node’s p-value could increase(more likely to move)and/or its clock cycle-time T could decrease. Such p/T-adaptation also results in smoother motion.Increased responsiveness may,however, result in annealing motion based on cruder estimates of the change in the objective function, U,due to,e.g.,more simultaneous movement,and a convergence of time-scales for routing(to determine R(x))and mobility.We are currently exploring our distributed annealing framework for motion together with dynamic node responsiveness for volatile network conditions.Also,we are considering more het-erogeneous terrain and networking contexts.Finally,we are developing suitable dual-priority routing algorithms in order to more accurately manage the energy required for joint commu-nicaiton of tracking(high priority)and scanning(low priority)traffic,particularly for volatile network conditions[7].References[1]A.N.Borodin and P.Salminen.Handbook of Brownian Motion-Facts and Formulae.Birkhauser,Boston,1996.22。
