Influence of Processing on the Nature of the Precipitates in a Microalloyed Line Pipe Steel

小学上册英语第二单元期末试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The capital city of Nigeria is __________.2.My uncle loves to __________. (旅行)3. A frog can change its color based on its ______ (环境).4.What is the name of the famous scientist known for his contributions to the field of genetics?A. Gregor MendelB. Charles DarwinC. Louis PasteurD. Albert EinsteinA5.The _______ (猪) will oink when happy.6.What is the name of the first living creature in space?A. LaikaB. BelkaC. StrelkaD. Yuri7.We have _____ (a/an) apple for snack.8.What do we call the time when the sun rises?A. MorningB. NoonC. EveningD. Midnight9.Kale is a type of ______ (绿叶菜).10.Dolphins are very _______ and friendly.11.My friend is very ____.12. A _______ is a type of solution that contains more solute than it usually can at a given temperature.13.How many wheels does a bicycle have?A. OneB. TwoC. ThreeD. Four14.What do you call a person who sings songs?A. DancerB. MusicianC. SingerD. PerformerC15.We measure temperature in degrees ______.16.What is the name of the famous clock tower in London?A. Big BenB. Eiffel TowerC. Leaning TowerD. Tower of PisaA17.My toy dinosaur is very ______.18.In a chemical equation, the products are shown on the _____ side.19.I like to _______ (jump) rope.20.This boy, ______ (这个男孩), loves to ride his bike.21.What do we call a person who repairs cars?A. DoctorB. MechanicC. PilotD. Chef22.The ______ is the part of a flower that produces seeds.23.We should respect all _____ (自然环境).24.At the pet shop, I saw a _______ (小仓鼠) running in a wheel.25.I enjoy _______ (参加) community service.26.I want to ________ (visit) my grandma.27.The soup is ___ (hot/cold) today.28.What is the name of the famous American singer known for "All of Me"?A. John LegendB. Ed SheeranC. Sam SmithD. Michael BubléA29.All matter is made up of tiny particles called ______.30.What is the name of the famous American singer known for "Jolene"?A. Reba McEntireB. Dolly PartonC. Carrie UnderwoodD. Miranda LambertB31.Which of these is NOT a type of fruit?A. AppleB. OrangeC. CarrotD. BananaC32.The country known for its multicultural societies is ________ (以多元文化社会闻名的国家是________).33.The parrot can _________ words. (模仿)34.The Earth's atmosphere is made up of different ______ gases.35.My sister likes to sing __________. (歌曲)36. A covalent bond is formed when atoms __________ electrons.37.I have a collection of miniature ________ (玩具类型).38.Chemical changes can result in the release of ________.39.My uncle is a fantastic ____ (storyteller).40.The country that is famous for pyramids is __________.41.They are _______ (building) a sandcastle.42.I made a ______ (贺卡) for my friend's birthday. She was very ______ (感动).43. A ____ is a small animal that loves to forage for food.44. A lion is a brave _______ that roams the savanna.45.Orbiting space debris poses a risk to ______.46.What is the main ingredient in a salad?A. RiceB. VegetablesC. MeatD. Bread47.The __________ (历史的启示性探讨) foster understanding.48. A solid has a definite ______ and volume.49.Polyatomic ions consist of multiple ______.50.The _______ (小浣熊) washes its food before eating.51. A seahorse is a type of ______ (鱼).52._____ (花园) can be enjoyed by everyone.53. A ________ (水獺) loves to swim and catch fish.54.What do we call a person who studies the past?A. HistorianB. ArchaeologistC. AnthropologistD. SociologistA55.What do we call the process of taking care of plants?A. GardeningB. FarmingC. CultivationD. All of the aboveD All of the above56.She is a _____ (作家) writing for various platforms.57.The __________ (社会变革) can lead to progress.58. A chemical reaction that releases heat is called an ________ reaction.59.Which of these is a warm-blooded animal?A. FishB. BirdC. LizardD. FrogB60.What do we call a piece of furniture we sit on?A. TableB. ChairC. BedD. Couch61.The chemical symbol for scandium is ______.62.The _____ (章鱼) can squeeze into tight spaces.63.My favorite dish is ______ (沙拉).64.The Earth's surface is shaped by a combination of internal and ______ forces.65.What is the main ingredient in lemonade?A. WaterB. SugarC. LemonD. All of the aboveD66.My mom is a __________ (会计师).67.The _______ (猪) rolls in mud.68.I saw a _______ (小鸟) perched on a tree.69.The __________ (历史的共同创造) enriches narratives.70.What do we call a person who studies the effects of climate change?A. ClimatologistB. MeteorologistC. Environmental ScientistD. EcologistA71.The quokka is known as the world's ________________ (最快乐) animal.72.What is the name of the spacecraft that took humans to the moon?A. DiscoveryB. ApolloC. GeminiD. Voyager73.What is the main source of energy for all living things?A. WaterB. FoodC. SunlightD. AirC Sunlight74.The __________ (历史的深刻) inspires thought.75.I enjoy cooking ________ with my dad.76.She is a great ___. (helper)77.The cake is _____ with icing. (covered)78.The __________ (印度独立) movement was led by Mahatma Gandhi.79.小老鼠) nibbles on cheese. The ___80.The __________ is a famous mountain range in Asia. (喜马拉雅山)81.The __________ is the process of breaking down large molecules into smaller ones.82.The cake is very ______ (sweet).83.Which day comes after Monday?A. SundayB. TuesdayC. WednesdayD. ThursdayB84.What do we call the act of studying the past?A. ArchaeologyB. HistoryC. AnthropologyD. Paleontology85.What do we call the device used to look at distant objects?A. MicroscopeB. TelescopeC. PeriscopeD. Kaleidoscope86.The ant works together in a _______ (群体).87.The chemical formula for -pentanol is ______.88.In winter, I wear ______ (靴子) to keep my feet warm.89.What is the capital of Mexico?A. Mexico CityB. GuadalajaraC. MonterreyD. PueblaA90.What is the capital of Sweden?A. OsloB. CopenhagenC. HelsinkiD. StockholmD91.What do we call the application of mathematics to solve real-world problems?A. AlgebraB. GeometryC. CalculusD. Applied MathematicsD92.I want to _____ (learn/teach) English.93.What is the capital of China?A. BeijingB. ShanghaiC. Hong KongD. TaipeiA94.The painter, ______ (画家), creates beautiful art.95.My family has a ______ (小狗) and a ______ (小猫). They are best ______ (朋友).96.I want to _______ (学习) how to fish.97.Which fruit is known for having seeds on the outside?A. AppleB. StrawberryC. BananaD. CherryB98.The ____ is often seen fluttering around flowers.99.I want to learn how to ________ (做手工艺).100.My school has a big ________ (图书馆) filled with many interesting ________ (书籍).。

人对自然的影响英语作文1. The impact of human activities on nature is undeniable. From deforestation to pollution, we have significantly altered the natural environment.2. Our industrial activities have led to the release of harmful chemicals and greenhouse gases into the atmosphere, contributing to climate change and global warming.3. The overexploitation of natural resources, such as water, minerals, and fossil fuels, has led to depletion and degradation of ecosystems, affecting the balance of the natural world.4. Urbanization and infrastructure development have resulted in habitat loss for many species, leading to a decline in biodiversity and the extinction of certain plant and animal species.5. Agricultural practices, including the use ofpesticides and fertilizers, have contaminated soil and water, posing a threat to the health of both humans and wildlife.6. The introduction of invasive species, either intentionally or unintentionally, has disrupted native ecosystems and caused harm to indigenous plants and animals.7. Our waste generation, from plastic pollution to electronic waste, has had a detrimental impact on the environment, affecting marine life, soil quality, and air and water pollution.8. Our recreational activities, such as hiking, camping, and wildlife tourism, have also put pressure on natural areas, leading to soil erosion, habitat disturbance, and wildlife disturbance.9. The demand for energy, water, and food has put a strain on natural resources, leading to unsustainable practices and the need for conservation and sustainable management.10. Despite these negative impacts, there is still hope for the restoration and preservation of nature through conservation efforts, sustainable practices, and the collective action of individuals, communities, and governments.。

八年级科技前沿英语阅读理解25题1<背景文章>Artificial intelligence (AI) has been making remarkable strides in the medical field in recent years. AI - powered systems are being increasingly utilized in various aspects of healthcare, bringing about significant improvements and new possibilities.One of the most prominent applications of AI in medicine is in disease diagnosis. AI algorithms can analyze vast amounts of medical data, such as patient symptoms, medical histories, and test results. For example, deep - learning algorithms can scan X - rays, CT scans, and MRIs to detect early signs of diseases like cancer, pneumonia, or heart diseases. These algorithms can often spot minute details that might be overlooked by human doctors, thus enabling earlier and more accurate diagnoses.In the realm of drug development, AI also plays a crucial role. It can accelerate the process by predicting how different molecules will interact with the human body. AI - based models can sift through thousands of potential drug candidates in a short time, identifying those with the highest probability of success. This not only saves time but also reduces the cost associated with traditional trial - and - error methods in drug research.Medical robots are another area where AI is making an impact.Surgical robots, for instance, can be guided by AI systems to perform complex surgeries with greater precision. These robots can filter out the natural tremors of a surgeon's hand, allowing for more delicate and accurate incisions. Additionally, there are robots designed to assist in patient care, such as those that can help patients with limited mobility to move around or perform simple tasks.However, the application of AI in medicine also faces some challenges. Issues like data privacy, algorithmic bias, and the need for regulatory approval are important considerations. But overall, the potential of AI to transform the medical field is vast and holds great promise for the future of healthcare.1. What is one of the main applications of AI in the medical field according to the article?A. Designing hospital buildings.B. Disease diagnosis.C. Training medical students.D. Managing hospital finances.答案：B。

As a high school student with a keen interest in environmental science, I have always been fascinated by the intricate relationship between organisms and their environment. One of the most intriguing aspects of this relationship is the impact of mushrooms on the land. Mushrooms, as part of the fungi kingdom, play a crucial role in the ecosystem, and their influence extends far beyond what meets the eye.Growing up in a rural area, I was fortunate enough to have ample opportunities to observe nature firsthand. During my walks through the woods, I noticed the abundance of mushrooms, especially after a rainfall. These fungi, with their diverse shapes, sizes, and colors, caught my attention, and I became curious about their role in the ecosystem.Mushrooms are the fruiting bodies of fungi, and they are essential for the decomposition process. As decomposers, they break down organic matter, such as dead plants and animals, into simpler compounds. This process releases nutrients back into the soil, making them available for other organisms. Without mushrooms and other decomposers, the cycle of life would be disrupted, and the land would become saturated with decaying matter.One of the most significant impacts of mushrooms on the land is their ability to improve soil structure. As they grow, their threadlike structures, known as mycelium, penetrate the soil, creating a network that helps to bind particles together. This network not only strengthens the soil but also increases its waterholding capacity. As a result, the land becomes more resistant to erosion and better equipped to handle drought conditions.Moreover, mushrooms have a symbiotic relationship with many plants. Through a process called mycorrhizal association, fungi form a partnership with plant roots, exchanging nutrients and water. This relationship benefits both parties, as the plant receives essential nutrients, while the fungi get carbohydrates produced by the plant. This mutualistic interaction contributes to the overall health and productivity of the land.However, the influence of mushrooms on the land is not always positive. Some species of fungi can be detrimental to the environment. For instance, certain types of mushrooms can cause diseases in plants, leading to a decline in plant health and productivity. Additionally, some mushrooms can be toxic to animals and humans if consumed, posing a risk to the ecosystems balance.Furthermore, the presence of mushrooms can be an indicator of environmental health. A diverse range of mushroom species suggests a healthy ecosystem, while a lack of diversity may signal an imbalance or disturbance. By monitoring the types and numbers of mushrooms in a particular area, scientists can gain valuable insights into the overall health of the land.In conclusion, mushrooms have a profound impact on the land, affecting its structure, nutrient availability, and overall health. As a high school student, I am inspired by the complexity of these relationships and the importance of understanding and preserving the delicate balance of our ecosystems. By studying the role of mushrooms and other organisms, wecan learn more about the interconnectedness of life and work towards a more sustainable future.。

The Impact of Urbanization on theEnvironmentUrbanization refers to the process of population concentration in cities and towns, leading to the expansion of urban areas. This phenomenon has become increasingly prevalent in recent years, with more and more people moving fromrural areas to urban centers in search of better opportunities and a higher standard of living. While urbanization has undoubtedly brought about economic growth and development, it has also had a significant impact on the environment. This essay will explore the various ways in which urbanization has affected the environment, taking into account both the positive and negative aspects of this process. One of the most significant environmental impacts of urbanization is the loss of natural habitats and biodiversity. As cities expand and develop, theyoften encroach upon previously untouched areas, leading to the destruction of forests, wetlands, and other ecosystems. This loss of habitat can have devastating consequences for wildlife, pushing many species to the brink of extinction. In addition, urbanization can also disrupt natural migration patterns and food chains, further endangering the delicate balance of ecosystems. Furthermore, urbanization is often accompanied by increased pollution levels, as a result of industrial activities, transportation, and waste disposal. The concentration of people and resources in urban areas leads to higher levels of air and water pollution, which can have serious health consequences for both humans and wildlife. Air pollution,in particular, has been linked to respiratory diseases, cardiovascular problems, and even premature death. Water pollution, on the other hand, can contaminate drinking water sources and harm aquatic ecosystems, leading to a decline in water quality and biodiversity. Another environmental impact of urbanization is the depletion of natural resources. As cities grow and expand, they require more and more resources to sustain their populations, leading to increased extraction of minerals, fossil fuels, and water. This overexploitation of natural resources can have long-term consequences, depleting finite reserves and causing irreversible damage to ecosystems. In addition, the production and consumption patterns associated with urbanization often lead to high levels of waste generation,further straining the environment and contributing to pollution and resource depletion. On a more positive note, urbanization can also have some beneficial effects on the environment. For example, the concentration of people in cities can lead to more efficient land use, as urban areas are typically more compact and densely populated than rural areas. This can help to preserve natural habitats and reduce urban sprawl, minimizing the impact of development on ecosystems. In addition, the density of urban areas can promote the use of public transportation and non-motorized modes of transport, reducing greenhouse gas emissions and alleviating traffic congestion. Moreover, urbanization can also provide opportunities for sustainable development and environmental conservation. Many cities around the world are implementing green initiatives and sustainable practices to minimize their environmental footprint and promote a more eco-friendly way of life. This includes measures such as green building design, renewable energy sources, waste reduction and recycling programs, and green spaces and parks. By incorporating these practices into urban planning and development, cities can mitigate the negative impacts of urbanization on the environment and create more livable and sustainable urban environments for future generations. In conclusion, urbanization has both positive and negative impacts on the environment, depending on how it is managed and implemented. While urbanization can lead to habitat destruction, pollution, and resource depletion, it can also promoteefficient land use, sustainable development, and environmental conservation. It is essential for policymakers, urban planners, and residents to work together to address the environmental challenges associated with urbanization and strive towards creating more sustainable and resilient cities that prioritize the well-being of both people and the planet.。

小学上册英语第四单元测验卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The ________ is a small animal that hops and plays.2.The cake is ________ for the party.3.What is 10 7?A. 1B. 2C. 3D. 4C4.What is the name of the famous wall in China?A. Great WallB. Berlin WallC. Hadrian's WallD. Walls of Jericho5. A pharaoh ant is a common ______ (蚂蚁).6.The ________ (公路) connects different cities.7.What do you call a baby donkey?A. FoalB. CalfC. PupD. Kit8.What is the capital of Greece?A. AthensB. RomeC. IstanbulD. Cairo9.________ (植物生长调控) is studied in labs.10.What do you call a small, round fruit?A. AppleB. OrangeC. GrapeD. All of the aboveD11.The process of crystallization involves forming __________ from a solution.12.The first book printed using movable type was the _______. (古登堡圣经)13.What do we call a young seal?A. PupB. CubC. KidD. Calf14.All living things are made of ______.15. A _______ can be used for herbal remedies.16.I love spending holidays with my ____.17.Which of these animals can swim?A. DogB. CatC. FishD. Bird18.His favorite sport is ________.19.The Earth's crust is thicker under ______ than under oceans.20.They are ___ a treasure hunt. (having)21. A ____ has a soft, fluffy coat and enjoys being around people.22.The cat chases _______ (光点) from a laser.23.environmental monitoring) tracks ecosystem health. The ____24.The chemical formula for -butanol is ______.25.ssance was a revival of _____ and learning. The Rena26.What is the main ingredient in sushi?A. NoodlesB. RiceC. BreadD. PotatoesB27. A molecule is made of two or more ______ bonded together.28.What do you call the person who writes stories?A. ArtistB. AuthorC. ChefD. Scientist29.The chemical symbol for gold is _____.30.My dad drives a _____ car. (blue)31.How many letters are in the word "banana"?A. FiveB. SixC. SevenD. Eight32.The symbol for zinc is _____.33.I enjoy _______ (看电视) after dinner.34.What do we call the time of day when we go to sleep?A. MorningB. EveningC. NightD. Afternoon35.The first successful test of an atomic bomb was in _______.36. A ______ (花卉展) showcases beautiful blooms.37. A reaction that absorbs heat energy is called an ______ reaction.38.What is the name of the largest volcano in the solar system?A. Olympus MonsB. Mauna KeaC. Mount EverestD. Kilauea39.I like to ______ on sunny days. (play outside)40.What is the capital of Ethiopia?A. Addis AbabaB. NairobiC. AsmaraD. DjiboutiA41.The __________ is a large natural area of trees and plants.42.I help my sister with __________. (学习)43. A chemical reaction may produce a gas, solid, or ______.44.The process of burning is called ______.45.What do you call a sweet, baked good made with flour?A. CookieB. BrownieC. CakeD. All of the aboveD46.I enjoy reading mystery ________ (小说) and trying to solve the puzzles in them.47. A strong acid has a pH less than ______.48.The lizard can shed its _______ (尾巴) to escape.49.I have a toy _______ that glows in the dark and lights up my room.50.The sun is _______ (很亮).51.My brother is a big fan of _______ (运动). 他喜欢 _______ (动词).52.The bee gathers nectar from _______.53.What is the name of the place where we go to watch movies?A. TheaterB. MuseumC. Concert HallD. LibraryA54.What do you call a large group of animals living together?A. FlockB. HerdC. ColonyD. All of the above55.How many eyes does a typical human have?A. OneB. TwoC. ThreeD. Four56.The __________ (建筑风格) reflects local traditions.57.The _______ (鲸鱼) is one of the largest animals.58.What do we call the process of converting waste into energy?A. Waste-to-energyB. Energy recoveryC. IncinerationD. Biomass conversionA Waste-to-energy59.We are friends with the ______ (neighbors).60.The rabbit loves to dig _______ (洞) for fun.61.What do we call the animal that is often kept as a pet and purrs?A. DogB. CatC. RabbitD. Hamster62.What do we call the movement of water in the oceans?A. WavesB. CurrentsC. TidesD. RipplesB63.I believe that friendship is one of the most ________ (重要的) things in life.64.What is the term for a written account of someone's life written by someone else?A. BiographyB. MemoirC. AutobiographyD. NovelA65.The country known for its spices is ________ (以香料闻名的国家是________).66.We are studying for the ________ (考试).67.The _______ (The Industrial Revolution) began in Britain and spread worldwide.68.The __________ is a major river that flows through Nigeria. (尼日尔河)69.What is the capital of Turkey?A. IstanbulB. AnkaraC. IzmirD. BursaB70.What type of animal is a dolphin?A. FishB. ReptileC. MammalD. AmphibianC71.The ______ (青蛙) lives in wet environments.72.My cousin is a great __________ (志愿者).73.We are going to ______ (visit) the aquarium.74.Do you think __________ (玩具名) is too __________ (形容词)?75.What do we call the study of insects?A. EntomologyB. ZoologyC. BotanyD. AnthropologyA Entomology76.The chemical reaction that occurs during cooking is an example of a _______ change.77.My brother is a ______. He wants to be a pilot.78.What is the opposite of 'happy'?A. JoyfulB. SadC. ExcitedD. AngryB79.The capital city of Iceland is _____.80.The _____ (zucchini) is a popular vegetable.81.The __________ can reveal patterns in sediment deposition and erosion.82.Which planet is known for having a big red spot?A. MarsB. VenusC. JupiterD. SaturnC83.My dad bought me a new _____.84.The __________ (历史的传递) conveys wisdom.85.What do we call a large waterfall?A. CascadeB. RapidsC. FallsD. Torrent86.The chemical formula for linoleic acid is ______.87.How do you say "please" in French?A. S'il vous plaîtB. Por favorC. BitteD. Per favore88.I want to ________ my friends.89.I love to plant _____ (花) in my garden.90.can Civil War was fought from ______ (1861到1865年). The Amer91.What do we call the science of matter and energy?A. BiologyB. ChemistryC. PhysicsD. AstronomyC92.What is the largest land animal?A. LionB. GiraffeC. ElephantD. Rhino93.An alkaline solution has a pH greater than ______.94.War was a period of tension between the United States and ________. The Cold95.What is the name of the famous American author known for "The Road"?A. Cormac McCarthyB. Don DeLilloC. Philip RothD. Toni MorrisonA96.My cousin is very __________ (活泼).97.My ________ (玩具名称) is a fun way to practice sharing.98.The ________ (baby) is sleeping.99.My friend has a toy ____ that can do flips. (玩具名称)100.The ______ helps with the detection of sound.。

Materials Chemistry and Physics98(2006)90–94Influence of heat treatment conditions on the structure and magnetic properties of barium ferrite BaFe12O19hollow microspheres of low densityPing Ren a,b,JianGuo Guan b,∗,XuDong Cheng ba Department of Energy Sources and Environment Engineering,Shanghai University of Electric Power,Shanghai200093,PR Chinab State Key Laboratory of Advanced Technology for Materials Synthesis,Wuhan University of Technology,Wuhan430070,PR ChinaReceived22May2005;received in revised form28August2005;accepted28August2005AbstractBarium ferrite BaFe12O19hollow microspheres of low density(about2.50g cm−3)were synthesized without BaFe2O4or other intermediate phase by spray pyrolysis technique,combined with co-precipitation precursor and followed further heat treatment.The relationships between the microstructure,magnetic properties and the sintering temperature,time were investigated.Hollow microspheres,constituted by nanometer particles,showed a broad particle distribution of2–15␮m.When the sample was sintered at900◦C for3h or at1100◦C for2h,pure BaFe12O19 ferrite was formed.With the increase of the sintering temperature or time,the grain size and preferential growth orientation were influenced,the saturation magnetization(M s)had a small increase,and the coercive force(H c)decreased obviously.©2005Elsevier B.V.All rights reserved.Keywords:Barium ferrite;Hollow microspheres;Spray pyrolysis;Microstructure;Magnetic properties1.IntroductionBarium ferrite(BaFe12O19)has been well-known for perma-nent magnets since its development by Philips researchers in the beginning of the1950s because of their high-coercivity,high-saturation magnetization,high resistance,low cost,associated with their excellent chemical stability and resistance to corrosion [1–3].In recent years,hexagonal ferrite has also caused wide interest in high-density recording media and radar-absorbing coatings[4,5].Its frequency of resonance absorption in the range of GHz is more than one thousand times as high as that of spinel ferrite.Therefore,it is promising for a kind of absorption mate-rial in thefield of high frequency.However,they are quite heavy, which restricts their applications requiring lightweight mass. Moreover,they have difficulties in increasing the permeability in GHz region because of Snoek limit[6,7].As one of the ways to overcome these problems,hollow microspheres of low den-sity are suggested.At the same time hollow microspheres also exhibit different catalytic,optical,electric and magnetic prop-erties and have important applications in materials,chemistry, catalysis and biologyfield[8].It is expected that microwave ∗Corresponding author.Tel.:+862787218832;fax:+862787879468.E-mail address:guanjg@(J.G.Guan).absorbing ability can be improved by adjusting the diameter and wall thickness of hollow microspheres or composition and grain size of ferrite nanometer particles.A number of fabrication methods have been used to produce hollow microspheres which are comprised of polymer,metal and ceramic materials,including nozzle reactor approaches (spray drying or pyrolysis)[9,10],emulsion/phase separation techniques(often combined with sol–gel processing)[11], emulsion/interfacial polymerization strategies[12],deposition method on sacrificial cores[13]and self-assembly process [14,15].Among these routes,spray pyrolysis technique was considered simplest and suitable for the synthesis of inorganic ferrite hollow microspheres,and large quantity production is likely by using the route.In this paper,we synthesized ferrite precursor with co-precipitation method and obtained BaFe12O19 hollow microspheres by spray pyrolysis technique followed fur-ther heat treatment,and reported the influence of heat treatment conditions on thefinal structure and magnetic properties of the samples.2.ExperimentalBarium ferrite hollow microspheres were produced by three steps,the inves-tigated variables were:calcination temperature(T)and calcination time(t). Firstly,an aqueous solution of Fe(NO3)3·6H2O and Ba(NO3)3·2H2O(Fe/Ba0254-0584/$–see front matter©2005Elsevier B.V.All rights reserved. doi:10.1016/j.matchemphys.2005.08.070P.Ren et al./Materials Chemistry and Physics98(2006)90–9491atomic ratio equal to12)was added to a stirring aqueous solution of NaOH and Na2CO3(OH−/CO32−ion ratio equal to5).After they reacted for2h,the resulting precipitates standed for24h,were then washed with deionized water and dried at110◦C.The dry precipitate was grinded in order to obtainfine and uniform barium ferrite precursor powder.Secondly,fine barium ferrite precursor powder was atomized into small particles by negative pressure of the FS-4Flame Spray Dryer.At the same time they were heated quickly at the high temperature flame,which was produced by acetylene and oxygen as combustion gas.They passed the different holes of the Flame Spray Dryer respectively,mixed and burnt in the nozzle.Therefore,spherical droplets,caused by surface tension, decomposed to obtain hollow microspheres.Finally,the hollow microspheres were colleted and further calcined to form BaFe12O19phase or promote crystal-lization under air for3h at several different temperatures(600,800,1000,1100, 1200◦C)and at1100◦C for different time(2,3,4h).X-ray diffraction with Cu K␣radiation(XRD)was used for phase analysis. The surface morphology and size of the grains were studied by scanning electron microscope(SEM).The thermal curves were presented by thermo gravimetric analysis(TG)and differential scanning calorimeter(DSC).The magnetic mea-surements are performed using a vibrating sample magnetometer(VSM)to an appliedfield of16000Oe,hysteresis loops are measured at room temperature.3.Results and discussion3.1.Structural analysis of pyrolysis products without heat treatmentFig.1shows the micrograph,phase constitution and the thermal curves for the pyrolyzed sample by SEM,XRD,TG and DSC.Spherical particles with a broad particle distribu-tion of2–15␮m were observed in Fig.1(a).This was prob-ably related to uneven solid ferrite precursor powder from co-precipitation method or the uniform atomization of the equip-ment.It demonstrated microspheres could be formed by spray pyrolysis method.Although hollow structure could not directly be seen in Fig.1(a),the average density of the sample(about 2.50g cm−3),which represented a50%decrease of hollow microspheres compared to solid powder of(about5.31g cm−3), could explain it to some extent.A small number of slight diffrac-tion peaks␣-Fe2O3and BaCO3were observed in Fig.1(b), which indicated the sample was constituted by a mixture of␣-Fe2O3and BaCO3phase of low crystallinity and also implied time of pyrolysis was not long enough to completely decom-pose iron hydroxide and barium carbonate or to form BaFe12O19 phase.Therefore,its necessary for further heat-treatment to form ferrite phase.Fig.1(c)was evident,an endothermic reaction accompanying with5.2%weight loss was observed at the tem-perature between78and138◦C,which showed the precursor did not decompose completely during the pyrolysis process. Between838and938◦C,the sample undergone exothermic reaction without weight loss.At the temperature range by com-paring XRD patterns of the samples after being heated at600 and1200◦C,it revealed that this change could be ascribed to the reaction of oxides to form barium ferrite.3.2.Influence of the heating temperature on the structureand magnetic propertiesThe phase constitution of the samples heat-treated at differ-ent temperatures for3h with a heating rate of5K min−1was obtained by XRD and is shown in Fig.2.At600◦C,a small number of␣-Fe2O3diffraction peaks and some slight peaks of BaFe12O19phase were observed.Single phase barium fer-rite had started to form by800◦C(except for the only slight peak at2.69˚A which corresponded to␣-Fe2O3).At900◦C,the sample presented a series of peaks all assigned to BaFe12O19 Fig.1.(a)SEM image,(b)XRD pattern and(c)TG and DSC curves of the sample after spray pyrolysis without heat treatment.92P.Ren et al./Materials Chemistry and Physics98(2006)90–94Fig.2.XRD patterns of the samples calcined at different temperature for3h: (a)600◦C,(b)800◦C,(c)900◦C,(d)1100◦C,(e)1200◦C.phase.When the temperature increased further,the values of diffraction peak intensities improved obviously,which could be associated with the amount and grain coarsening of BaFe12O19 phase.There was a slight change between thefirst and second strongest peaks at1200◦C due to preferential grain growth.In this work,pure barium ferrite BaFe12O19was formed directly from iron oxides and barium oxides as the onlycomponents Fig.4.Static magnetic properties of the samples calcined at different tempera-tures for3h.detected.Other intermediate phase such as␣-BaFe2O4,␥-Fe2O3 were never observed during the heat treatment.This is consistent with the results obtained in the previous work[16].As expected from XRD data,change in grain morphology with temperature was observed,which is presented in Fig.3. Hollow microspheres had kept intact during the calcination pro-cess.The surface of the sample without heat treatment was relatively smooth.The surface became rougher with the increase of sintering temperature.By1100◦C,the spheres were consti-tuted by crystals for hexagonal like platelet of about several hundred nanometer.These clearly indicated heat treatment was beneficial for ferrite formation and crystallization.Fig.4shows the effect of the sintering temperature on the magnetic properties between600and1200◦C for3h.The sat-uration magnetization(M s)increased obviously from600to 1000◦C,increased slightly between1000and1200◦C,and reached a maximum of55emu g−1at1200◦C.The value is lower than the theoretical limit(72emu g−1)[17],which might be associated with the density and porosity of hollow micro-spheres.A drastic increase of M s between800and1000◦Cwas Fig.3.SEM images of the samples calcined at different temperatures for3h:(a)without heat treatment,(b)800◦C,(c)1000◦C,(d)1100◦C.P .Ren et al./Materials Chemistry and Physics 98(2006)90–9493related to the increasing amount of BaFe 12O 19phase and a small increase from 1000to 1200◦C for grain coarsening according to XRD and SEM results.The hematite formation in the samples reduced the volumetric fraction of barium ferrite and conse-quently reduced M s before 800◦C.This result is in accordance with that previously described in literature [18].The rema-nent magnetization (M r )reached a maximum of 28emu g −1at 1000◦C,decreasing slightly for higher temperature.The intrin-sic coercive force (H c )basically showed a contrary behavior as M s ,increased obviously before 800◦C due to the increas-ing amount of BaFe 12O 19phase,decreased slightly from 3.4to 3.2kOe between 800and 1000◦C which is close to the coer-civity value of typical hard magnetic materials,and decreased drastically from 3.2to 1.3kOe between 1000and 1200◦C owing to grain coarsening.This indicated the coercive force exhibited strong dependency on the sintering temperature.Similar results were reported by Joonghoe et al.[19],who studied effects of the grain boundary on the coercivity of barium ferrite BaFe 12O 19.The results were also supported by Janasi et al.[18]who con-ducted an investigation on the effect of heat treatment conditions and routes on the magnetic properties of co-precipitated ferrite powders.3.3.Influence of the heating time on the structure and magnetic propertiesFig.5shows XRD patterns of the samples calcined at 1100◦C for different heat treatment times.In all cases,the samples were virtually single phase BaFe 12O 19ferrite.With the extending of sintering time,the relative intensities of diffraction peaks increased.At the same time the average grain size,measured from the full-width at half-maximum (FWHM)of (107)peak using Scherrer formula,was found to increase from about 450nm for the heated powder for 2h,520nm for 3h,to 550nm for 4h.According to the XRD intensity formulaI =I 0λ3e 432πR 3m 2c 4 Vq V 20|F h k l |2 1+cos 22θsin 2θcos θFig.5.XRD patterns of the samples calcined at 1100◦C for different times:(a)2h,(b)3h,(c)4h.Fig.6.Hysteresis curve of the samples calcined at 1100◦C for different time.where V is the grain volume of (h k l )plain-oriented,q thegrain number of (h k l )plain-oriented,V 0the volume of unit cell,the relative intensities of diffraction peaks were consis-tent with the calculated intensities for the powder heat treated at 1100◦C for 3h.However,when the sintering time was 4h,(107)diffraction peak were dominant whereas relative intensity of (114)diffraction peak was diminished because the grain size of (107)plain-oriented increased quicker than that of (114)plain-oriented based on the above formula and Scherrer for-mula.These implicated that preferential grain growth probably occurred when the samples were sintered at long time.Fig.6shows the magnetization hysteresis loops at room tem-perature of the samples sintered at 1100◦C between 2and 4h.All the samples had almost identical saturation magnetization and remanent magnetization values,indicating that M s and M r are independent on the sintering time,because the samples were all pure BaFe 12O 19phase and their densities are basically same.On the other hand,the coercivity was changed with the sinter-ing time,which decreased initially from 3.0kOe for 2h and then recovered to 2.5kOe for 4h and reached the minimum of 1.9kOe for 3h because of grain size and preferential grain growth according to the XRD results in Fig.5.This clearly illus-trated the well-known fact that the coercivity strongly depended on the calcining time.4.ConclusionsWe had prepared barium ferrite BaFe 12O 19hollow micro-spheres mainly distributed between 2and 15␮m by spray pyrolysis technique,combined with co-precipitation precursor and followed further calcinations,and studied the effect of heat treatment conditions.We found that hollow microspheres kept unbroken and the average density nearly kept unchange-able (about 2.50g cm −3)during the heat treatment.When the sample was sintered at 900◦C for 3h or at 1100◦C for 2h,the single phase BaFe 12O 19ferrite was formed,directly by iron oxide and barium oxide without BaFe 2O 4or ␥-Fe 2O 3intermediate phase.Increasing the temperature was beneficial in increasing the crystalline,improving the saturation mag-netization and eliminating the coercive force.The saturation94P.Ren et al./Materials Chemistry and Physics98(2006)90–94magnetization(M s)increased obviously before1000◦C,and increased slightly between1000and1200◦C and reached the maximum of55emu g−1at1200◦C.Increasing the heat treat-ment time influenced grain size,preferential grain growth ori-entation and magnetic properties.H c reached a minimum of 1.9kOe for3h and a maximum of3.0kOe for2h,whereas M s was little affected.In a conclusive manner we can say that H c was strongly dependent on heat treatment conditions owing to grain size and preferential growth and M s was closely related to the materials composition.Preparation of narrow distribution of smaller hollow microspheres and study of their structure and properties will be our following work.AcknowledgementThis work is supported by863HI-TECH project of China (no.2002AA305302).References[1]J.Smit,H.P.J.Wijn,Ferrites,Philips Technical Library,Eindhoven,1959.[2]T.Fujiwara,IEEE Trans.Magn.21(1985)1480.[3]P.Campbell,Permanent Magnet Materials and their Application,Cam-bridge University Press,Cambridge,1994.[4]N.Ichnose,Super Particle Technology,Springer-Verlag,1992.[5]K.J.Viney,R.M.Jha,Radar Absorbing Materials,Kluwer AcademicPublishers,1996.[6]K.Hatakeyama,T.Inui,IEEE Trans.Magn.20(1984)1261.[7]M.Matsumoto,Y.Miyata,IEEE Trans.Magn.33(1994)4459.[8]D.L.Wilcox,T.Bernat,D.Kellerman,J.K.Cochran,Materials ResearchSociety Proceedings,vol.375,Pittsburgh,1995.[9]M.Iida,T.Sasaki,M.Watanabe,Chem.Mater.10(1998)3780.[10]K´a roly Zolt´a n,Sz´e pv¨o lgyi J´a nos,Powder Technol.132(2/3)(2003)211.[11]T.Z.Ren,Z.Y.Yuan, B.L.Su,Chem.Phys.Lett.374(1/2)(2003)170.[12]J.Hotz,W.Meier,Langmuir14(1998)1031.[13]J.L.Yin,X.F.Qian,J.Yin,M.W.Shi,G.T.Zhou,Mater.Lett.57(24/25)(2003)3859.[14]R.A.Caruso,A.Susha,F.Caruso,Chem.Mater.13(2001)400.[15]F.Caruso,R.A.Caruso,H.Mohwald,Science282(6)(1998)1111.[16]R.C.Pullar,A.K.Bhattacharya,Mater.Lett.57(2002)537–542.[17]B.T.Shirk,W.R.Buessem,J.Appl.Phys.40(1969)1294.[18]S.R.Janasi,M.Emura,ndgraf,D.Rodrigues,J.Magn.Magn.Mater.238(2002)168–172.[19]Joonghoe Dho,E.K.Lee,J.Y.Park,N.H.Hur,J.Magn.Magn.Mater.285(2005)164–168.。

英语托福试题及答案一、听力部分1. 问题：What is the main topic of the lecture?答案：The main topic of the lecture is the impact of industrialization on the environment.2. 问题：According to the professor, what is the primarycause of air pollution?答案：The primary cause of air pollution, according to the professor, is the burning of fossil fuels.3. 问题：What is the student's suggestion to reduce pollution?答案：The student suggests using renewable energy sourcesto reduce pollution.二、阅读部分1. 问题：What does the author argue about the role of technology in education?答案：The author argues that technology has the potentialto enhance learning experiences but also emphasizes the importance of its proper integration into the curriculum.2. 问题：What evidence does the author provide to support the benefits of technology in education?答案：The author provides evidence such as increasedstudent engagement, access to a wider range of resources, and the ability to personalize learning.3. 问题：What is the author's view on the challenges of integrating technology into education?答案：The author believes that challenges include the need for teacher training, the digital divide, and the risk of distraction.三、口语部分1. 问题：Describe a memorable event from your childhood.答案：One memorable event from my childhood was my first visit to a zoo, where I was amazed by the variety of animals and learned about their habitats.2. 问题：Why do you think it is important to learn a second language?答案：Learning a second language is important because it opens up opportunities for communication, broadens cultural understanding, and enhances cognitive abilities.3. 问题：What are some ways to improve your English speaking skills?答案：Some ways to improve English speaking skills include practicing with native speakers, joining language exchange groups, and using language learning apps.四、写作部分1. 问题：Do you agree or disagree with the following statement? University education should be free for all students.答案：[Your response should be a well-organized essay that includes an introduction, body paragraphs with supporting arguments, and a conclusion.]2. 问题：Some people believe that the government should spend more on art and culture, while others think that this money should be used for other public services. Discuss both views and give your opinion.答案：[Your response should be a well-organized essay that presents the arguments for both views, provides your own opinion, and includes a conclusion.]3. 问题：Describe a person who has had a significant influence on your life and explain why this person is important to you.答案：[Your response should be a descriptive essay that outlines the person's characteristics, the impact they have had on you, and the reasons for their significance.]。

小学上册英语第3单元真题(含答案)考试时间：100分钟（总分:140）A卷一、综合题(共计100题共100分)1. 听力题：The ____ is a small rodent that likes to nibble on seeds.2. 填空题：I believe that laughter is the best _______ (良药). It makes every situation better.3. 选择题：How many sides does a hexagon have?A. 4B. 5C. 6D. 7答案:C4. 填空题：My grandmother has a __________ flower garden. (美丽的)5. 选择题：Which planet is known as the "Blue Planet"?A. EarthB. MarsC. VenusD. Neptune6. 听力题：The chemical symbol for molybdenum is __________.7. 听力题：The chemical symbol for neon is ____.8. 选择题：What do we call the part of the plant that absorbs water and nutrients?A. StemB. LeafC. RootD. Flower答案: C9. 听力题：The chemical formula for sulfur trioxide is _____.10. 填空题：The __________ (社会参与) strengthens communities.11. 填空题：The frog's skin is _______ (湿润).12. 填空题：I watched a _______ (小黄鹂) build its nest in the tree.13. 选择题：What is the capital of Bangladesh?A. DhakaB. ChittagongC. KhulnaD. Sylhet答案:A. Dhaka14. 填空题：I have a ________ (魔方) that I try to solve every day.15. ts need _____ (湿润的) conditions to thrive. 填空题：Some pla16. 听力题：The capital of Albania is __________.17. 选择题：What is the name of the famous wizard in "Harry Potter"?A. DumbledoreB. VoldemortC. SnapeD. Harry Potter18. 听力题：Some _______ are edible and used in cooking.19. 选择题：What is the name of the famous scientist known for his work on radioactivity?A. Marie CurieB. Albert EinsteinC. Louis PasteurD. Isaac Newton答案: A20. 选择题：What do we call the movement of the Earth around the sun?A. RotationB. RevolutionC. OrbitD. Spin答案:B21. 填空题：The playground is _______ during recess.22. 填空题：My sister loves to create __________ (艺术品) at home.23. 选择题：What is the first letter of the alphabet?A. AB. BC. CD. D答案:A24. 填空题：The ________ was a major turning point in World War I.25. 填空题：The _____ (自然环境) is important for biodiversity.26. 听力题：The process of crystallization involves forming ______ from a solution.27. 填空题：I have a toy _______ that dances and sings my favorite songs.28. 选择题：What do we call a scientist who studies the Earth?A. GeologistB. MeteorologistC. ZoologistD. Biologist答案: A29. 选择题：What is the capital of Argentina?A. Buenos AiresB. CórdobaC. MendozaD. Rosario30. 选择题：Which of these is a type of measurement?A. LengthB. ColorC. ShapeD. Size31. 选择题：Which fruit is red and often mistaken for a vegetable?A. AppleB. TomatoC. StrawberryD. Cherry答案:B32. 听力题：The ______ is a layer of rock that lies directly beneath the Earth's surface.33. 听力题：A __________ is a group of islands.34. 听力题：He likes to __________ football after school.35. 选择题：How many fingers are on one hand?A. FourB. FiveC. SixD. Seven答案:B36. 填空题：The first successful face reconstruction was performed in ________.37. 选择题：Which word means "happy"?A. SadB. JoyfulC. AngryD. Tired答案: B38. 听力题：The frog is _____ (jumping/sitting) on the lily pad.39. 选择题：What do we call the study of how people interact with each other?A. SociologyB. PsychologyC. AnthropologyD. Economics答案: A40. 填空题：My ________ (玩具名称) is a fun way to learn about cultures.41. 听力题：A ______ is a geological feature that rises sharply.42. 选择题：What do you call the person who directs a movie?A. ProducerB. DirectorC. ActorD. Writer答案:B43. 听力题：A hypothesis is an educated _____ about a scientific question.44. 选择题：What is the name of the famous river that runs through Egypt?A. NileB. AmazonC. YangtzeD. Mississippi答案：A45. 选择题：What do you call the person who fixes cars?B. TeacherC. MechanicD. Chef答案:C46. 填空题：The ______ (触感) of leaves can vary widely.47. 填空题：The ancient Greeks practiced _____ as a form of government.48. 听力题：Chemical reactions often produce energy in the form of _____ or light.49. 填空题：The _____ (金色的鱼) swims gracefully in its aquarium. 金色的鱼在它的水族箱中优雅地游动。

The Influence of Music on Our EmotionsMusic possesses an extraordinary power to evoke emotions,shape our moods,and influence our mental states.From the stirring sounds of a symphony to the simple strumming of a guitar,music can transport us to different emotional landscapes,offering comfort,joy,or catharsis.This essay explores how music affects our emotions,the psychological mechanisms behind its impact,and the ways in which it enriches our emotional experiences.Emotional Impact of MusicMusic can elicit a wide range of emotions,from happiness and excitement to sadness and nostalgia.The emotional response to music can be immediate and profound,affecting not just our mood but also our physical state.For instance,an upbeat song can energize us, quickening our heartbeat and motivating us to move,while a melancholy melody might slow our breathing and induce a reflective state.Psychological MechanismsThe influence of music on emotions can be attributed to several psychological mechanisms:Brain Activation:Music stimulates various areas of the brain,including those involved in emotion,memory,and sensory processing.This activation can trigger emotional responses,connecting the music we hear to our past experiences,memories,and feelings.Rhythm and Melody:The rhythm and melody of music can directly affect our emotional state.Upbeat,fast-paced music tends to evoke feelings of happiness and excitement,while slow,minor-key music can elicit sadness or contemplation.Expectation and Surprise:Music often plays with our expectations through tension and release,anticipation,and surprise.These elements can provoke emotional responses,as we react to the fulfillment or violation of our musical expectations.Personal Associations:The emotional impact of music is also shaped by personal associations.A song that reminds us of a specific event or period in our life can evoke the emotions we experienced at that time.Music and Emotional RegulationMany people use music as a tool for emotional regulation,choosing songs that match or alter their mood.For example,someone feeling down might listen to upbeat music to improve their mood,while another might choose sad music to process feelings of grief or loneliness. Music therapy leverages this principle,using music to help individuals explore and express their emotions in a therapeutic setting.Social and Cultural DimensionsThe emotional influence of music extends beyond the individual to social and cultural contexts.Music can foster a sense of unity and collective identity,as seen in national anthems,protest songs,or religious hymns. Cultural background also shapes our emotional responses to music,as different cultures may associate specific musical elements with particular emotions.ConclusionThe influence of music on our emotions is a testament to its profound power and universal appeal.Through its ability to activate the brain, evoke memories,and engage with our expectations,music can profoundly shape our emotional experiences.Whether used for personal enjoyment,emotional regulation,or social connection,music remains an essential part of the human experience,enriching our lives with its emotional depth and complexity.。