Ice force spectrum on narrow conical structures
冷冻干燥法制备纤维素基多孔材料的研究
•纤维素基多孔材料研究论文作者简介：马珊珊女士，在读硕士研究生；主要 从事高性能纤维纸基功 能材料研究。
冷冻干燥法制备纤维素基多孔材料的研究马珊珊-，7张美云-，！杨斌1苏治平1宋顺喜1(1.陕西科技大学轻工科学与工程学院，中国轻工业纸基功能材料重点实验室，陕西西安，710021; 2.轻化工程国家级实验教学示范中心（陕西科技大学），陕西西安，710021)摘要：以植物纤维为原料，研究了利用冷冻干燥法制备纤维素基多孔材料过程中纤维悬浮液浓度 和冷冻温度对多孔材料微观结构和性能的影响，并探讨了冷冻过程中冰晶对纤维的作用方式和多孔 材料微观结构的形成机制。
结果表明，随着纤维悬浮液浓度的升高，冰晶的结构从平面状演变为层 状，导致多孔材料的X向微观形貌从各向同性转变为各向异性层状孔隙结构，有助于提高其抗欧拉 失稳能力，使应力-应变曲线平压区缩短，密实化区向低应变点偏移。
随着冷冻温度降低，冰晶凝固 前沿处纤维受到的黏滞阻力增大，从而使其被冰晶吞没而均匀分散，材料两面差减少；另外，降低 冷冻温度可降低层状冰晶的厚度，使多孔材料X向孔隙尺寸减小，有助于提高其抵抗应力变形的能 力，使应力-应变曲线中的密实化区向低应变点偏移。
关键词：植物纤维；冷冻干燥；多孔材料；悬浮液浓度；冷冻温度中图分类号：TS767 文献标识码： A D O I：10. 11980/j. issn. 0254-508X. 2017. 11. 006Study on the Preparation of Cellulose-lbased Porous Material by Freeze-drying ProcessM A Shan-shan1，2Z H A N G Mei-yun1，*Y A N G Bin1S U Z h i-ping1S O N G S h u n-C1(1. Colle^ye of Bioresources Chemical and Materials Engineering，Shaanxi University of Science & Technology，Key Lab Paper BasedFunctional Materials，China National Light Industry，X ia n，Shaanxi Province，710021 %2. National Demonstration Center forExperimental Light Chemistry Engineering Educatioo( Shaanxi University 〇o Science & Technolog^y)，X i'an，Shaanxi Province，710021)(!E-m ail: myzhang@sust. edu. cn )Abstract: In this study， a cellulose-based porous material was prepared from plant fibers by freeze-dryig technique. The effect of the solidcontent of fiber suspension and freeze-temperature on the microstructure and properties of the prepared porous materials was investigated.M eanwhile，the action and formation mechanisms of ice crystal on the fillers during freezing process and the microstructure of final porous material were discussed. The results revealed that the increase of solid content of fiber suspension could transform the Z direction microstructureof final porous material from an isotropic architecture to an anisotropic lamellar porous structure which could prevent Euler buckling of porousm aterials，leading to the shortening of plateau curve and the shiftment of densification curve to lower strain percentage in stress-strain curve.With the decreasing of freeze-tem perature，the viscous resistance acting on the fibers at the solidification front of ice crystal was enhanced，thus the fibers had uniform distribution as it were swallowed by ice crystal and resulting in the porous materials with less two-sidedness. Inaddition，porous material produced at lower freeze-temperature owned smaller pores due to the thickness of lamellar ice crystal was reduced，whichimproved its ability to resist stress and deformation，leading to the densification region in stress-strain c u Key words ：plant fib ers; freeze-drying; porous m aterial; the solid content of fiber suspension; freeze-temperature多孔材料是一种具有丰富孔隙结构[1]和气体通道的功能化材料[2]，其广泛应用于过滤分离[3]、气 体吸附等方面。
新教材2024年高中英语本册综合学业质量检测新人教版选择性必修第三册
本册综合学业质量检测选择题部分第一部分：听力(共两节，满分30分)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．Who is the woman raising money for？ __A__A．The old. B．The poor. C．The homeless.2．What does the man’s house have？ __B__A．A pool. B．A garden. C．A garage.3．When should the speakers start to work？ __C__A．At 2:30．B．At 2:00．C．At 1:30．4．Where does the conversation probably take place？ __B__A．In an office. B．At home. C．At the airport.5．What does the woman think of her own job？ __B__A．It’s boring.B．It’s unsatisfying.C．It’s exciting.其次节(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。
每段对话或独白后有几个小题，从题中所给的A、B、C三个选项中选出最佳选项。
听每段对话或独白前，你将有时间阅读各个小题，每小题5秒钟；听完后，各小题将给出5秒钟的作答时间。
每段对话或独白读两遍。
听第6段材料，回答第6和第7两个小题。
6．What kind of concert will the speakers attend？ __A__A．Jazz. B．Rock. C．Classical.7．Which is right about the concert this Saturday？ __C__A．It is through the night. B．It is held indoors.C．It is free of charge.听第7段材料，回答第8至第10三个小题。
causes for ice ages托福阅读
Causes for Ice AgesIce ages are long periods of low global temperatures, characterized by the expansion of ice sheets and glaciers. These extreme cold periods are believed to have occurred multiple times throughout Earth’s history. Scientists have proposed various theories to explain the causes of ice ages. In this document, we will explore some of these theories.Orbital VariationsOne widely accepted theory suggests that variations in the Earth’s orbit around the sun, known as orbital variations, play a significant role in the onset of ice ages. These variations occur due to changes in the planet’s eccentricity, axial tilt, and precession. Eccentricity refers to the shape of Earth’s orbit, which can vary from a more circular shape to a more elongated one over a period of 100,000 years. Axial tilt refers to the tilt of Earth’s axis of rotation, which oscillates between approximately 22.1 and 24.5 degrees over a cycle of 41,000 years. Precession refers to the wobbling motion of Earth’s axis, which completes a full cycle in abou t 26,000 years.These orbital variations can affect the distribution of solar energy received by the Earth’s surface. For example, when the Earth’s orbit is more elongated (higher eccentricity), the amount of solar radiation reaching the planet’s surface d ecreases, leading to colder global temperatures. This decrease in solar radiation, in combination with other factors, can trigger the onset of an ice age.Solar OutputAnother proposed cause for ice ages is variations in solar output. The Sun is the primary source of heat for our planet, and its energy output is not constant. Over time, the Sun undergoes cyclic changes in activity, resulting in variations in the amount of radiation it emits. These variations in solar output are known as solar cycles or solar flares.During periods of lower solar activity, the amount of energy received by Earth decreases, leading to cooler temperatures. This decrease in solar output can potentially contribute to the onset of an ice age. However, it is important to note that while solar variations may play a role in ice age triggers, they are likely only one contributing factor among several.Atmospheric CompositionThe composition of the Earth’s atmosphere can also influence the onset of ice ages. Scientists believe that fluctuations in greenhouse gas concentrations, such as carbon dioxide (CO2) and methane (CH4), can impact global temperatures. Thesegases act as a “blanket” around the Earth, trapping heat and preventing it from escaping into space.During ice ages, the atmospheric concentration of greenhouse gases is thought to decrease. This reduction can lead to a cooling effect, as less heat is trapped in the atmosphere. The decrease in greenhouse gas concentration can be caused by various factors, including changes in volcanic activity, shifts in ocean circulation patterns, and the growth of ice sheets themselves, which can alter the exchange of gases between the atmosphere and the ocean.Geological ProcessesGeological processes, such as the movement of tectonic plates and the formation of mountain ranges, can also influence ice age occurrence. These processes can alter the circulation patterns of ocean currents, affecting the distribution of heat around the globe. Additionally, the growth of mountain ranges can impact atmospheric circulation patterns and create barriers that restrict the flow of air masses, leading to localized cooling.ConclusionIce ages are complex phenomena influenced by a combination of factors. Orbital variations, solar output fluctuations, atmospheric composition changes, and geological processes all contribute to the onset and duration of ice ages. Understanding these causes and their interactions can provide valuable insights into past ice ages and help predict future climatic changes on our planet.。
极地航行船舶防覆冰涂层研究进展
第53卷第6期表面技术2024年3月SURFACE TECHNOLOGY·1·研究综述极地航行船舶防覆冰涂层研究进展张祎轩1，刘涛2，刘耀虎3，刘杰1*，王健君4（1.中国科学院化学研究所，北京 100190；2.上海海事大学，上海 201306；3.中国科学院 前沿科学与教育局，北京 100864；4.中国科学院理化技术研究所，北京 100190）摘要：两极地区是未来重要的能源和资源基地。
然而，极地长年低温多冰，极大限制了我国对两极地区的科学考察、商业航运和能源开发进程。
因此，发展长效稳定的防覆冰技术是推进极地发展战略的关键。
系统阐明了船舶在极地航行过程中面临的结冰困境，分析了船舶积冰的类型，总结了目前解决船舶覆冰问题的多种防除冰技术及发展现状，包括主动防除冰技术（机械除冰、超声导波除冰、加热除冰、化学熔融除冰等）和被动防覆冰涂层技术（气体润滑防覆冰涂层、液体润滑防覆冰涂层、“类液体”润滑防覆冰涂层、界面可控断裂防覆冰涂层等），同时对各技术在极地船舶防冰应用中的优缺点和可行性进行了深入分析。
展望了船舶装备对特种防冰涂层的关键需求，提出主、被动协同除冰技术是实现极地船舶防覆冰的重要策略。
关键词：极地；船舶；防冰；涂层材料；冰黏附中图分类号：TQ050.4 文献标志码：A 文章编号：1001-3660(2024)06-0001-10DOI：10.16490/ki.issn.1001-3660.2024.06.001Research Progress on Anti-icing Coatings for Polar ShipsZHANG Yixuan1, LIU Tao2, LIU Yaohu3, LIU Jie1*, WANG Jianjun4(1. Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; 2. Shanghai Maritime University,Shanghai 201306, China; 3. Bureau of Frontier Sciences and Education, Chinese Academy of Sciences, Beijing 100864, China; 4. Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China)ABSTRACT: The polar regions are strategically important for the sustainable development of the global economy due to their abundant natural resources and special geographical location. However, the prolonged low temperature and heavy icing in the polar regions have greatly restricted the process of scientific research, commercial shipping, and energy development. Therefore, the icing problem of various types of equipment has become a hot topic of research and the development of long-lasting and stable anti-icing technology is crucial to advancing the polar development strategy.The icing dilemma faced by ships during polar navigation was systematically expounded. Types of ice accretion on ships were analyzed according to the origin of ice. Various anti-icing technologies were summarized, including active anti-icing technologies (mechanical de-icing, ultrasonic de-icing, heating de-icing, chemical de-icing, etc.) and passive anti-icing coating technologies (gas lubrication, liquid lubrication, "liquid-like" lubrication, interface-controlled fracture, etc.).The gas lubrication is mainly composed of micro/nanocomposite structure in the surface and low surface energy hydrophobic layer, which effectively inhibits the icing process by reducing the attachment of water droplets. However, the收稿日期：2023-03-29；修订日期：2023-10-23Received：2023-03-29；Revised：2023-10-23基金项目：国家自然科学基金面上项目（52273220）Fund：National Natural Science Foundation of China (52273220)引文格式：张祎轩, 刘涛, 刘耀虎, 等. 极地航行船舶防覆冰涂层研究进展[J]. 表面技术, 2024, 53(6): 1-10.ZHANG Yixuan, LIU Tao, LIU Yaohu, et al. Research Progress on Anti-icing Coatings for Polar Ships[J]. Surface Technology, 2024, 53(6): 1-10.*通信作者（Corresponding author）·2·表面技术 2024年3月disadvantage of it is liquid generally slipping into a hierarchical scale and adhering to the surface, resulting in the Cassie-Baxter state converting into the Wenzel state. Water freezing in the Wenzel state will cause mechanical interlocking forces and invalid deicing capabilities. Subsequently, the surface can be worn away after repeatedly de-icing. Although certain special structures have been proven to reduce the transition to the Wenzel state, the complex fabrication process is almost impossible to cover on a large scale. Liquid lubrication and "liquid-like" lubrication can greatly reduce the adhesion strength of ice on the solid surface by effectively reducing the strong physical interaction between ice and surface. Liquid lubrication is built through the overfilling lubricating liquid to the micro/nanopores substrate. Despite adhering within the substrate, lubrication becomes invalid over time by evaporation, erosion, and is contaminated. "Liquid-like" lubrication, covalently attached on one end of a flexible macromolecule onto a smooth substrate, determines the lubricating property. The high mobility and small intermolecular force of polymer enable it to function as a lubricating layer. "Liquid-like" lubrication has been considered a promising coating for its extreme uniformity, low adhesion, transparency, and safety. Interface-controlled fracture makes the crack nucleation and growth at the specific position of the interface quickly, accelerates the interface fracture process, and then makes the ice desorb quickly under the action of low shear stress. Under the action of shear stress, the interface between ice and substrate is not uniform, and macroscopic cracks are preferentially generated in the low shear modulus region. The cracks propagate rapidly, making the ice easier to break away from the substrate surface. The current development of anti-icing technologies in solving the icing problem is summarized. The feasibility of each technology to be applied in polar ships is discussed in depth according to their advantages and disadvantages.In the last section, the work emphasizes the key requirements for special anti-icing coatings for ship equipment, and the importance of active and passive cooperative de-icing strategies in polar ship protection technology is proposed.KEY WORDS: polar; ships; anti-icing; coating materials; ice adhesion极地地区具备丰富的自然资源和特殊的地理位置，对全球经济的可持续发展具有重要的战略意义。
雅思阅读机经真题解析之南极气候
雅思阅读机经真题解析之南极气候雅思阅读机经真题解析-南极气候Antarctica-in from the cold?A A little over a century ago, men of the ilk of Scott, Shackleton and Mawson battled against Antarctica's blizzards, cold and deprivation. In the name of Empire and in an age of heroic deeds they created an image of Antarctica that was to last well into the 20th century - an image of remoteness, hardship, bleakness and isolation that was the province of only the most courageous of men. The image was one of a place removed from everyday reality, of a place with no apparent value to anyone.B As we enter the 21st century, our perception of Antarctica has changed. Although physically Antarctica is no closer and probably no warmer, and to spend time there still demands a dedication not seen in ordinary life, the continent and its surrounding ocean are increasingly seen to an integral part of Planet Earth, and a key component in the Earth System. Is this because the world seems a little smaller these days, shrunk by TV and tourism, or is it because Antarctica really does occupy a central spot on Earth's mantle? Scientific research during the past half century has revealed - and continues to reveal - that Antarctica's great mass and low temperatureexert a major influence on climate and ocean circulation, factors which influence the lives of millions of people all over the globe.C Antarctica was not always cold. The slow break-up of the super-continent Gondwana with the northward movements of Africa, South America, India and Australia eventually created enough space around Antarctica for the development of an Antarctic Circumpolar Current (ACQ, that flowed from west to east under the influence of the prevailing westerly winds. Antarctica cooled, its vegetation perished, glaciation began and the continent took on its present-day appearance. Today the ice that overlies the bedrock is up to 4km thick, and surface temperatures as low as - 89.2deg C have been recorded. The icy blast that howls over the ice cap and out to sea - the so-called katabatic wind - can reach 300 km/hr, creating fearsome wind-chill effects.D Out of this extreme environment come some powerful forces that reverberate around the world. The Earth's rotation, coupled to the generation of cells of low pressure off the Antarctic coast, would allow Astronauts a view of Antarctica that is as beautiful as it is awesome. Spinning away to the northeast, the cells grow and deepen, whipping up the Southern Ocean into the mountainous seas so respected by mariners. Recent work is showing that the temperature of the ocean may be a better predictor of rainfall in Australia than is the pressure difference between Darwin and Tahiti - the Southern Oscillation Index. By receiving moreaccurate predictions, graziers in northern Queensland are able to avoid overstocking in years when rainfall will be poor. Not only does this limit their losses but it prevents serious pasture degradation that may take decades to repair. CSIRO is developing this as a prototype forecasting system, but we can confidently predict that as we know more about the Antarctic and Southern Ocean we will be able to enhance and extend our predictive ability.E The ocean's surface temperature results from the interplay between doep- wa,ter temperature, air temperature and ice. Each winter between 4 and 19 million square km of sea ice form, locking up huge quantities of heat close to the continent.Only now can we start to unravel the influence of sea ice on the weather that is experienced in southern Australia. But in another way the extent of sea ice extends its influence far beyond V Antarctica. Antarctic krill - the small shrimp-like crustaceans that are the staple diet for baleen whales, penguins, some seals, flighted sea birds and many fish - breed well in years when sea ice is extensive and poorly when it is not. Mary species of baleen whales and flighted sea birds migrate between the hemispheres and when the krill are less abundant they do not thrive.F The circulatory system of the world's oceans is like a huge conveyor belt, moving water and dissolved minerals and nutrients from one hemisphere to the other, and from the ocean's abyssal depths to thesurface. The ACC is the longest current in the world, and has the largest flow. Through it, the deep flows of the Atlantic, Indian and Pacific Oceans are joined to form part of a single global thermohalinc circulation. During winter, the howling katabatics sometimes scour the ice off patches of the sea's surface leaving Large ice- locked lagoons, or 'polynyas'. Recent research has shown that as fresh sea ice forms, it is continuously stripped away by the wind and may be blown up to 90km in a single day. Since only fresh water freezes into ice, the water that remains bccom.cs increasingly salty and dense, sinking until it spills over the continental shelf. Cold water carries more oxygen than warm water, so when it rises, well into the northern hemisphere, it reoxygenates and revitalises the ocean. The state of the northern oceans, and their biological productivity, owe much to what happens in the Antarctic.Question 14-18The reading Passage has ten paragraphs A-J.Which paragraph contains the following information?Write the correct letter A-F, in boxes 14-18 on your answer sheet.14. introduction of a millman under awards15. the definition of an important geographical term16. a rival against Harrison’s invention emerged17. problems of sailor encountered in identifying the postion on the sea18. economic assist from another counterpartQuestion 19-21SummaryPlease match the natural phenomenon with correct determined factor Choose the correct answer from the box; Write the correct letter A-F in boxes 19-21 on your answer sheet.19. Globally, mass Antarctica’s size and _________ influence the climate change.20. __________ contributory to western wind.21. Southern Oscillation Index based on air pressure can predict__________ in Australia.A Antarctic Circumpolar Current (ACC)B katabatic windsC rainfallD temperatureE glaciersF pressureQuestion 22-26Choose the correct letter, A,B,C or D.Write your answers in boxes 22-26 on you answer sheet.22 In the paragraph B, the author want to tell which of thefollowing truth about Antarctic?A To show Antarctica has been a central topic of global warming in Mass mediaB To illustrate its huge see ice brings food to million lives to places in the worldC To show it is the heart and its significance to the global climate and currentD To illustrate it locates in the central spot on Earth geographically23 Why do Australian farmers Keep an eye on the Antarctic ocean temperature ?A Help farmers reduce their economic or ecological lossesB Retrieve grassland decreased in the overgrazing processC Prevent animal from dyingD A cell provides fertilizer for the grassland24 What is the final effect of katabatic winds?A Increase the moving speed of ocean currentB Increase salt level near ocean surfaceC Bring fresh ice into southern oceansD Pile up the mountainous ice cap respected by mariners25 The break of the continental shelf is due to theA Salt and density increaseB Salt and density decreaseC global warming resulting a rising temperatureD fresh ice melting into ocean water26 The decrease in number of Whales and seabirds is due toA killers whales arc more active aroundB Sea birds are affected by high sea level saltyC less sea ice reduces productivity of food sourceD seals fail to reproduce babies篇章结构体裁说明文题目南极洲的自然环境及其对全球气候和水循环等的影响结构A段：之前的南极洲被人类遗忘，毫无价值B段：21世纪，人类对南极洲有了新的认识，发现它对气候，海洋环流有重大影响C段：南极洲气候变化是如何形成的D段：关于南极洲气候的预测对澳大利亚农业的影响E段：南澳大利亚的海冰对海洋生态（动物）的影响F段：南极海冰为北半球带来积极影响G段：南极洲的强大影响力得到人类肯定试题分析Question14-18题目类型：段落信息配对题Question19-21题目类型：填空题Question22-26题目类型：选择题题号定位词文中对应点题目解析14Weather prediction, agricultureD段第五，六句D段第五六两句提到“通过接收更为准确的预测，放牧人能够·······。
极地破冰船操纵设计需求分析及研究方法综述
1232023年·第3期·总第204期极地破冰船操纵设计需求分析及研究方法综述刘小健１， ３ 刘 义２， ３ 魏跃峰１， ３（１． 喷水推进技术重点实验室 上海 ２０００１１； ２． 上海市船舶工程重点实验室 上海 ２０００１１；３． 中国船舶及海洋工程设计研究院 上海 ２０００１１）摘 要：…船舶在极地地区航行时的操纵问题远比常规水域复杂，使得船舶在极地的航行十分危险，而目前关于极地破冰船特点及操纵性设计需求等方面的分析研究较少。
该文介绍了与破冰船操纵性相关的风、浪、流、浅水、狭窄水道、低温和能见度等极地环境条件，分析了俄罗斯等国破冰船的分类及特征，总结了吊舱、多桨多舵破冰船操纵装置操纵性标准相关需求。
为满足操纵设计的需要，介绍了破冰船操纵性模型试验、实船试验和数值模拟等操纵性研究方法，提出船-冰相互作用力的计算方法，如经验公式法、有限元法和离散元法等。
通过以上分析与总结，为极地破冰船的操纵性设计提供了思路和参考。
关键词：极地；破冰船；操纵性；研究设计；数值模拟法；试验研究法中图分类号：U661.3………文献标志码：A………DOI ：10.19423/ki.31-1561/u.2023.03.123Requirement Analysis and Research Methods of ManeuverabilityDesign for IcebreakerLIU Xiaojian 1, 3 LIU Yi 2, 3 WEI Yuefeng 1, 3(1. Science and T echnology on Water Jet Propulsion Laboratory, Shanghai 200011, China ；…2. Shanghai Key Laboratory on Ship Engineering, Shanghai 200011, China ；…3. Marine Design & Research Institute of China, Shanghai 200011, China)Abstract: The maneuvering of ships sailing in Polar Regions is much more complex than those in conventional waters, imposing hazards on ships sailing in Polar Regions. However, there are currently few analysis and research on the characteristics and maneuverability design requirements of polar icebreakers. This study introduces the polar environment related to the maneuverability of icebreakers, such as the wind, wave and current, shallow water, narrow waterway, low temperature and low visibility. It also analyzes the classification and ship characteristics of the icebreakers in Russia and other countries, and summarizes the relevant requirements of maneuverability standards for maneuvering devices on ice breakers with pod, multi-propeller and multi-rudder. In order to meet the requirement of maneuverability design, it introduces the maneuverability research methods such as the model test, full-scale test and numerical simulation of ice breakers, and the calculation methods for the ship-ice interaction forces such as the empirical formula method, finite element method and discrete element method. The above analysis and summary can provide references for the maneuverability design of icebreakers.Keywords:…polar region; icebreaker; maneuverability; design and research ；numerical simulation; experimental research收稿日期：2022-09-24；修回日期：2022-10-21作者简介：刘小健（1979-），男，博士，研究员。
2024学年山西省晋城市陵川一中高考冲刺押题(最后一卷)英语试卷(含解析)
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第一部分（共20小题，每小题1.5分，满分30分）1．Whitney Houston’s sudden death suggests that dr ug abuse is such a serious problem ________ we should deal with it appropriately.A．as B．that C．which D．where2．If they throw stones at you，don’t throw e them to build your own foundation ________.A．somehow B．anywayC．instead D．nevertheless3．--- Do you think I should join the singing group, Mary?--- ______ If I were in your shoes, I certainly would.A．None of your business．B．It depends.C．Why not? D．I don’t think so.4．— What great changes have taken place in our city in the last few years!— Indeed, many high buildings have _______all over the city.A．wound up B．sprung up C．held up D．made up5．In my driving lesson, a traffic rule that impressed me most is that in no time ________ when the traffic lights turn red. A．all vehicles should stop B．should all vehicles stopC．should stop all vehicles D．should stop all vehicles6．So far, only one man has ________ a theory that seems to fit all the facts.A．come up with B．put up withC．lined up with D．caught up with7．The new product is beyond all praise and has quickly taken over the market ________ its superior quality.A．in terms of B．on account ofC．on behalf of D．on top of8．Countries which continue importing huge quantities of waste will have to____ the issue of pollution.A．maintain B．simplify C．overlook D．address9．Nobody can go back and start a new beginning, ______ anyone can start now and make a new ending.A．for B．andC．but D．so10．If you sleep less than seven hours, you are three times more to catch a cold．A．possible B．certainly C．probable D．likely11．We believe ________ you have been devoted to ________ naturally of great necessity.A．that; being B．all that; beC．that all; are D．what; is12．—I’m afraid I couldn’t go to your birthday party.I have a test next Monday.—Oh，！You’re my best friend and you must be there！A．go ahead B．come on C．you needn’t D．it doesn’t matter13．She is quite____to office work.You had better offer her some suggestions when necessary．A．familiar B．freshC．similar D．sensitive14．Time is pressing．You cannot start your task _____ soon．A．too B．very C．so D．as15．－Do you really mean it when you say he will a good president?A．judge B．duit C．turn D．Serve16．---We want someone to design the new art museum for me.---_____ the young fellow have a try?A．Shall B．May C．Will D．Need17．Last December China _____ 100 Chinese and 10 foreigners for their outstanding contributions to the country’s reform and opening-up.A．distinguished B．sponsoredC．acknowledged D．evaluated18．— Did you go to last night’s concert?— Y es. And the girl playing the violin at the concert _______ all the people present with her excellent ability.A. impressed B．compared C．conveyed D．observed19．If I can help , I don’t like working late into the night.A．so B．that C．them D．it20．—Sorry, I didn’t hear the door bell ring.—Your bell . Perhaps it needs repairing.A．never worked B．is never workingC．never works D．had never worked第二部分阅读理解（满分40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。
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History of infrared detectorsA.ROGALSKI*Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Str.,00–908 Warsaw, PolandThis paper overviews the history of infrared detector materials starting with Herschel’s experiment with thermometer on February11th,1800.Infrared detectors are in general used to detect,image,and measure patterns of the thermal heat radia−tion which all objects emit.At the beginning,their development was connected with thermal detectors,such as ther−mocouples and bolometers,which are still used today and which are generally sensitive to all infrared wavelengths and op−erate at room temperature.The second kind of detectors,called the photon detectors,was mainly developed during the20th Century to improve sensitivity and response time.These detectors have been extensively developed since the1940’s.Lead sulphide(PbS)was the first practical IR detector with sensitivity to infrared wavelengths up to~3μm.After World War II infrared detector technology development was and continues to be primarily driven by military applications.Discovery of variable band gap HgCdTe ternary alloy by Lawson and co−workers in1959opened a new area in IR detector technology and has provided an unprecedented degree of freedom in infrared detector design.Many of these advances were transferred to IR astronomy from Departments of Defence ter on civilian applications of infrared technology are frequently called“dual−use technology applications.”One should point out the growing utilisation of IR technologies in the civilian sphere based on the use of new materials and technologies,as well as the noticeable price decrease in these high cost tech−nologies.In the last four decades different types of detectors are combined with electronic readouts to make detector focal plane arrays(FPAs).Development in FPA technology has revolutionized infrared imaging.Progress in integrated circuit design and fabrication techniques has resulted in continued rapid growth in the size and performance of these solid state arrays.Keywords:thermal and photon detectors, lead salt detectors, HgCdTe detectors, microbolometers, focal plane arrays.Contents1.Introduction2.Historical perspective3.Classification of infrared detectors3.1.Photon detectors3.2.Thermal detectors4.Post−War activity5.HgCdTe era6.Alternative material systems6.1.InSb and InGaAs6.2.GaAs/AlGaAs quantum well superlattices6.3.InAs/GaInSb strained layer superlattices6.4.Hg−based alternatives to HgCdTe7.New revolution in thermal detectors8.Focal plane arrays – revolution in imaging systems8.1.Cooled FPAs8.2.Uncooled FPAs8.3.Readiness level of LWIR detector technologies9.SummaryReferences 1.IntroductionLooking back over the past1000years we notice that infra−red radiation(IR)itself was unknown until212years ago when Herschel’s experiment with thermometer and prism was first reported.Frederick William Herschel(1738–1822) was born in Hanover,Germany but emigrated to Britain at age19,where he became well known as both a musician and an astronomer.Herschel became most famous for the discovery of Uranus in1781(the first new planet found since antiquity)in addition to two of its major moons,Tita−nia and Oberon.He also discovered two moons of Saturn and infrared radiation.Herschel is also known for the twenty−four symphonies that he composed.W.Herschel made another milestone discovery–discov−ery of infrared light on February11th,1800.He studied the spectrum of sunlight with a prism[see Fig.1in Ref.1],mea−suring temperature of each colour.The detector consisted of liquid in a glass thermometer with a specially blackened bulb to absorb radiation.Herschel built a crude monochromator that used a thermometer as a detector,so that he could mea−sure the distribution of energy in sunlight and found that the highest temperature was just beyond the red,what we now call the infrared(‘below the red’,from the Latin‘infra’–be−OPTO−ELECTRONICS REVIEW20(3),279–308DOI: 10.2478/s11772−012−0037−7*e−mail: rogan@.pllow)–see Fig.1(b)[2].In April 1800he reported it to the Royal Society as dark heat (Ref.1,pp.288–290):Here the thermometer No.1rose 7degrees,in 10minu−tes,by an exposure to the full red coloured rays.I drew back the stand,till the centre of the ball of No.1was just at the vanishing of the red colour,so that half its ball was within,and half without,the visible rays of theAnd here the thermometerin 16minutes,degrees,when its centre was inch out of the raysof the sun.as had a rising of 9de−grees,and here the difference is almost too trifling to suppose,that latter situation of the thermometer was much beyond the maximum of the heating power;while,at the same time,the experiment sufficiently indi−cates,that the place inquired after need not be looked for at a greater distance.Making further experiments on what Herschel called the ‘calorific rays’that existed beyond the red part of the spec−trum,he found that they were reflected,refracted,absorbed and transmitted just like visible light [1,3,4].The early history of IR was reviewed about 50years ago in three well−known monographs [5–7].Many historical information can be also found in four papers published by Barr [3,4,8,9]and in more recently published monograph [10].Table 1summarises the historical development of infrared physics and technology [11,12].2.Historical perspectiveFor thirty years following Herschel’s discovery,very little progress was made beyond establishing that the infrared ra−diation obeyed the simplest laws of optics.Slow progress inthe study of infrared was caused by the lack of sensitive and accurate detectors –the experimenters were handicapped by the ordinary thermometer.However,towards the second de−cade of the 19th century,Thomas Johann Seebeck began to examine the junction behaviour of electrically conductive materials.In 1821he discovered that a small electric current will flow in a closed circuit of two dissimilar metallic con−ductors,when their junctions are kept at different tempera−tures [13].During that time,most physicists thought that ra−diant heat and light were different phenomena,and the dis−covery of Seebeck indirectly contributed to a revival of the debate on the nature of heat.Due to small output vol−tage of Seebeck’s junctions,some μV/K,the measurement of very small temperature differences were prevented.In 1829L.Nobili made the first thermocouple and improved electrical thermometer based on the thermoelectric effect discovered by Seebeck in 1826.Four years later,M.Melloni introduced the idea of connecting several bismuth−copper thermocouples in series,generating a higher and,therefore,measurable output voltage.It was at least 40times more sensitive than the best thermometer available and could de−tect the heat from a person at a distance of 30ft [8].The out−put voltage of such a thermopile structure linearly increases with the number of connected thermocouples.An example of thermopile’s prototype invented by Nobili is shown in Fig.2(a).It consists of twelve large bismuth and antimony elements.The elements were placed upright in a brass ring secured to an adjustable support,and were screened by a wooden disk with a 15−mm central aperture.Incomplete version of the Nobili−Melloni thermopile originally fitted with the brass cone−shaped tubes to collect ra−diant heat is shown in Fig.2(b).This instrument was much more sensi−tive than the thermometers previously used and became the most widely used detector of IR radiation for the next half century.The third member of the trio,Langley’s bolometer appea−red in 1880[7].Samuel Pierpont Langley (1834–1906)used two thin ribbons of platinum foil connected so as to form two arms of a Wheatstone bridge (see Fig.3)[15].This instrument enabled him to study solar irradiance far into its infrared region and to measure theintensityof solar radia−tion at various wavelengths [9,16,17].The bolometer’s sen−History of infrared detectorsFig.1.Herschel’s first experiment:A,B –the small stand,1,2,3–the thermometers upon it,C,D –the prism at the window,E –the spec−trum thrown upon the table,so as to bring the last quarter of an inch of the read colour upon the stand (after Ref.1).InsideSir FrederickWilliam Herschel (1738–1822)measures infrared light from the sun– artist’s impression (after Ref. 2).Fig.2.The Nobili−Meloni thermopiles:(a)thermopile’s prototype invented by Nobili (ca.1829),(b)incomplete version of the Nobili−−Melloni thermopile (ca.1831).Museo Galileo –Institute and Museum of the History of Science,Piazza dei Giudici 1,50122Florence, Italy (after Ref. 14).Table 1. Milestones in the development of infrared physics and technology (up−dated after Refs. 11 and 12)Year Event1800Discovery of the existence of thermal radiation in the invisible beyond the red by W. HERSCHEL1821Discovery of the thermoelectric effects using an antimony−copper pair by T.J. SEEBECK1830Thermal element for thermal radiation measurement by L. NOBILI1833Thermopile consisting of 10 in−line Sb−Bi thermal pairs by L. NOBILI and M. MELLONI1834Discovery of the PELTIER effect on a current−fed pair of two different conductors by J.C. PELTIER1835Formulation of the hypothesis that light and electromagnetic radiation are of the same nature by A.M. AMPERE1839Solar absorption spectrum of the atmosphere and the role of water vapour by M. MELLONI1840Discovery of the three atmospheric windows by J. HERSCHEL (son of W. HERSCHEL)1857Harmonization of the three thermoelectric effects (SEEBECK, PELTIER, THOMSON) by W. THOMSON (Lord KELVIN)1859Relationship between absorption and emission by G. KIRCHHOFF1864Theory of electromagnetic radiation by J.C. MAXWELL1873Discovery of photoconductive effect in selenium by W. SMITH1876Discovery of photovoltaic effect in selenium (photopiles) by W.G. ADAMS and A.E. DAY1879Empirical relationship between radiation intensity and temperature of a blackbody by J. STEFAN1880Study of absorption characteristics of the atmosphere through a Pt bolometer resistance by S.P. LANGLEY1883Study of transmission characteristics of IR−transparent materials by M. MELLONI1884Thermodynamic derivation of the STEFAN law by L. BOLTZMANN1887Observation of photoelectric effect in the ultraviolet by H. HERTZ1890J. ELSTER and H. GEITEL constructed a photoemissive detector consisted of an alkali−metal cathode1894, 1900Derivation of the wavelength relation of blackbody radiation by J.W. RAYEIGH and W. WIEN1900Discovery of quantum properties of light by M. PLANCK1903Temperature measurements of stars and planets using IR radiometry and spectrometry by W.W. COBLENTZ1905 A. EINSTEIN established the theory of photoelectricity1911R. ROSLING made the first television image tube on the principle of cathode ray tubes constructed by F. Braun in 18971914Application of bolometers for the remote exploration of people and aircrafts ( a man at 200 m and a plane at 1000 m)1917T.W. CASE developed the first infrared photoconductor from substance composed of thallium and sulphur1923W. SCHOTTKY established the theory of dry rectifiers1925V.K. ZWORYKIN made a television image tube (kinescope) then between 1925 and 1933, the first electronic camera with the aid of converter tube (iconoscope)1928Proposal of the idea of the electro−optical converter (including the multistage one) by G. HOLST, J.H. DE BOER, M.C. TEVES, and C.F. VEENEMANS1929L.R. KOHLER made a converter tube with a photocathode (Ag/O/Cs) sensitive in the near infrared1930IR direction finders based on PbS quantum detectors in the wavelength range 1.5–3.0 μm for military applications (GUDDEN, GÖRLICH and KUTSCHER), increased range in World War II to 30 km for ships and 7 km for tanks (3–5 μm)1934First IR image converter1939Development of the first IR display unit in the United States (Sniperscope, Snooperscope)1941R.S. OHL observed the photovoltaic effect shown by a p−n junction in a silicon1942G. EASTMAN (Kodak) offered the first film sensitive to the infrared1947Pneumatically acting, high−detectivity radiation detector by M.J.E. GOLAY1954First imaging cameras based on thermopiles (exposure time of 20 min per image) and on bolometers (4 min)1955Mass production start of IR seeker heads for IR guided rockets in the US (PbS and PbTe detectors, later InSb detectors for Sidewinder rockets)1957Discovery of HgCdTe ternary alloy as infrared detector material by W.D. LAWSON, S. NELSON, and A.S. YOUNG1961Discovery of extrinsic Ge:Hg and its application (linear array) in the first LWIR FLIR systems1965Mass production start of IR cameras for civil applications in Sweden (single−element sensors with optomechanical scanner: AGA Thermografiesystem 660)1970Discovery of charge−couple device (CCD) by W.S. BOYLE and G.E. SMITH1970Production start of IR sensor arrays (monolithic Si−arrays: R.A. SOREF 1968; IR−CCD: 1970; SCHOTTKY diode arrays: F.D.SHEPHERD and A.C. YANG 1973; IR−CMOS: 1980; SPRITE: T. ELIOTT 1981)1975Lunch of national programmes for making spatially high resolution observation systems in the infrared from multielement detectors integrated in a mini cooler (so−called first generation systems): common module (CM) in the United States, thermal imaging commonmodule (TICM) in Great Britain, syteme modulaire termique (SMT) in France1975First In bump hybrid infrared focal plane array1977Discovery of the broken−gap type−II InAs/GaSb superlattices by G.A. SAI−HALASZ, R. TSU, and L. ESAKI1980Development and production of second generation systems [cameras fitted with hybrid HgCdTe(InSb)/Si(readout) FPAs].First demonstration of two−colour back−to−back SWIR GaInAsP detector by J.C. CAMPBELL, A.G. DENTAI, T.P. LEE,and C.A. BURRUS1985Development and mass production of cameras fitted with Schottky diode FPAs (platinum silicide)1990Development and production of quantum well infrared photoconductor (QWIP) hybrid second generation systems1995Production start of IR cameras with uncooled FPAs (focal plane arrays; microbolometer−based and pyroelectric)2000Development and production of third generation infrared systemssitivity was much greater than that of contemporary thermo−piles which were little improved since their use by Melloni. Langley continued to develop his bolometer for the next20 years(400times more sensitive than his first efforts).His latest bolometer could detect the heat from a cow at a dis−tance of quarter of mile [9].From the above information results that at the beginning the development of the IR detectors was connected with ther−mal detectors.The first photon effect,photoconductive ef−fect,was discovered by Smith in1873when he experimented with selenium as an insulator for submarine cables[18].This discovery provided a fertile field of investigation for several decades,though most of the efforts were of doubtful quality. By1927,over1500articles and100patents were listed on photosensitive selenium[19].It should be mentioned that the literature of the early1900’s shows increasing interest in the application of infrared as solution to numerous problems[7].A special contribution of William Coblenz(1873–1962)to infrared radiometry and spectroscopy is marked by huge bib−liography containing hundreds of scientific publications, talks,and abstracts to his credit[20,21].In1915,W.Cob−lentz at the US National Bureau of Standards develops ther−mopile detectors,which he uses to measure the infrared radi−ation from110stars.However,the low sensitivity of early in−frared instruments prevented the detection of other near−IR sources.Work in infrared astronomy remained at a low level until breakthroughs in the development of new,sensitive infrared detectors were achieved in the late1950’s.The principle of photoemission was first demonstrated in1887when Hertz discovered that negatively charged par−ticles were emitted from a conductor if it was irradiated with ultraviolet[22].Further studies revealed that this effect could be produced with visible radiation using an alkali metal electrode [23].Rectifying properties of semiconductor−metal contact were discovered by Ferdinand Braun in1874[24],when he probed a naturally−occurring lead sulphide(galena)crystal with the point of a thin metal wire and noted that current flowed freely in one direction only.Next,Jagadis Chandra Bose demonstrated the use of galena−metal point contact to detect millimetre electromagnetic waves.In1901he filed a U.S patent for a point−contact semiconductor rectifier for detecting radio signals[25].This type of contact called cat’s whisker detector(sometimes also as crystal detector)played serious role in the initial phase of radio development.How−ever,this contact was not used in a radiation detector for the next several decades.Although crystal rectifiers allowed to fabricate simple radio sets,however,by the mid−1920s the predictable performance of vacuum−tubes replaced them in most radio applications.The period between World Wars I and II is marked by the development of photon detectors and image converters and by emergence of infrared spectroscopy as one of the key analytical techniques available to chemists.The image con−verter,developed on the eve of World War II,was of tre−mendous interest to the military because it enabled man to see in the dark.The first IR photoconductor was developed by Theodore W.Case in1917[26].He discovered that a substance com−posed of thallium and sulphur(Tl2S)exhibited photocon−ductivity.Supported by the US Army between1917and 1918,Case adapted these relatively unreliable detectors for use as sensors in an infrared signalling device[27].The pro−totype signalling system,consisting of a60−inch diameter searchlight as the source of radiation and a thallous sulphide detector at the focus of a24−inch diameter paraboloid mir−ror,sent messages18miles through what was described as ‘smoky atmosphere’in1917.However,instability of resis−tance in the presence of light or polarizing voltage,loss of responsivity due to over−exposure to light,high noise,slug−gish response and lack of reproducibility seemed to be inhe−rent weaknesses.Work was discontinued in1918;commu−nication by the detection of infrared radiation appeared dis−tinctly ter Case found that the addition of oxygen greatly enhanced the response [28].The idea of the electro−optical converter,including the multistage one,was proposed by Holst et al.in1928[29]. The first attempt to make the converter was not successful.A working tube consisted of a photocathode in close proxi−mity to a fluorescent screen was made by the authors in 1934 in Philips firm.In about1930,the appearance of the Cs−O−Ag photo−tube,with stable characteristics,to great extent discouraged further development of photoconductive cells until about 1940.The Cs−O−Ag photocathode(also called S−1)elabo−History of infrared detectorsFig.3.Longley’s bolometer(a)composed of two sets of thin plati−num strips(b),a Wheatstone bridge,a battery,and a galvanometer measuring electrical current (after Ref. 15 and 16).rated by Koller and Campbell[30]had a quantum efficiency two orders of magnitude above anything previously studied, and consequently a new era in photoemissive devices was inaugurated[31].In the same year,the Japanese scientists S. Asao and M.Suzuki reported a method for enhancing the sensitivity of silver in the S−1photocathode[32].Consisted of a layer of caesium on oxidized silver,S−1is sensitive with useful response in the near infrared,out to approxi−mately1.2μm,and the visible and ultraviolet region,down to0.3μm.Probably the most significant IR development in the United States during1930’s was the Radio Corporation of America(RCA)IR image tube.During World War II, near−IR(NIR)cathodes were coupled to visible phosphors to provide a NIR image converter.With the establishment of the National Defence Research Committee,the develop−ment of this tube was accelerated.In1942,the tube went into production as the RCA1P25image converter(see Fig.4).This was one of the tubes used during World War II as a part of the”Snooperscope”and”Sniperscope,”which were used for night observation with infrared sources of illumination.Since then various photocathodes have been developed including bialkali photocathodes for the visible region,multialkali photocathodes with high sensitivity ex−tending to the infrared region and alkali halide photocatho−des intended for ultraviolet detection.The early concepts of image intensification were not basically different from those today.However,the early devices suffered from two major deficiencies:poor photo−cathodes and poor ter development of both cathode and coupling technologies changed the image in−tensifier into much more useful device.The concept of image intensification by cascading stages was suggested independently by number of workers.In Great Britain,the work was directed toward proximity focused tubes,while in the United State and in Germany–to electrostatically focused tubes.A history of night vision imaging devices is given by Biberman and Sendall in monograph Electro−Opti−cal Imaging:System Performance and Modelling,SPIE Press,2000[10].The Biberman’s monograph describes the basic trends of infrared optoelectronics development in the USA,Great Britain,France,and Germany.Seven years later Ponomarenko and Filachev completed this monograph writ−ing the book Infrared Techniques and Electro−Optics in Russia:A History1946−2006,SPIE Press,about achieve−ments of IR techniques and electrooptics in the former USSR and Russia [33].In the early1930’s,interest in improved detectors began in Germany[27,34,35].In1933,Edgar W.Kutzscher at the University of Berlin,discovered that lead sulphide(from natural galena found in Sardinia)was photoconductive and had response to about3μm.B.Gudden at the University of Prague used evaporation techniques to develop sensitive PbS films.Work directed by Kutzscher,initially at the Uni−versity of Berlin and later at the Electroacustic Company in Kiel,dealt primarily with the chemical deposition approach to film formation.This work ultimately lead to the fabrica−tion of the most sensitive German detectors.These works were,of course,done under great secrecy and the results were not generally known until after1945.Lead sulphide photoconductors were brought to the manufacturing stage of development in Germany in about1943.Lead sulphide was the first practical infrared detector deployed in a variety of applications during the war.The most notable was the Kiel IV,an airborne IR system that had excellent range and which was produced at Carl Zeiss in Jena under the direction of Werner K. Weihe [6].In1941,Robert J.Cashman improved the technology of thallous sulphide detectors,which led to successful produc−tion[36,37].Cashman,after success with thallous sulphide detectors,concentrated his efforts on lead sulphide detec−tors,which were first produced in the United States at Northwestern University in1944.After World War II Cash−man found that other semiconductors of the lead salt family (PbSe and PbTe)showed promise as infrared detectors[38]. The early detector cells manufactured by Cashman are shown in Fig. 5.Fig.4.The original1P25image converter tube developed by the RCA(a).This device measures115×38mm overall and has7pins.It opera−tion is indicated by the schematic drawing (b).After1945,the wide−ranging German trajectory of research was essentially the direction continued in the USA, Great Britain and Soviet Union under military sponsorship after the war[27,39].Kutzscher’s facilities were captured by the Russians,thus providing the basis for early Soviet detector development.From1946,detector technology was rapidly disseminated to firms such as Mullard Ltd.in Southampton,UK,as part of war reparations,and some−times was accompanied by the valuable tacit knowledge of technical experts.E.W.Kutzscher,for example,was flown to Britain from Kiel after the war,and subsequently had an important influence on American developments when he joined Lockheed Aircraft Co.in Burbank,California as a research scientist.Although the fabrication methods developed for lead salt photoconductors was usually not completely under−stood,their properties are well established and reproducibi−lity could only be achieved after following well−tried reci−pes.Unlike most other semiconductor IR detectors,lead salt photoconductive materials are used in the form of polycrys−talline films approximately1μm thick and with individual crystallites ranging in size from approximately0.1–1.0μm. They are usually prepared by chemical deposition using empirical recipes,which generally yields better uniformity of response and more stable results than the evaporative methods.In order to obtain high−performance detectors, lead chalcogenide films need to be sensitized by oxidation. The oxidation may be carried out by using additives in the deposition bath,by post−deposition heat treatment in the presence of oxygen,or by chemical oxidation of the film. The effect of the oxidant is to introduce sensitizing centres and additional states into the bandgap and thereby increase the lifetime of the photoexcited holes in the p−type material.3.Classification of infrared detectorsObserving a history of the development of the IR detector technology after World War II,many materials have been investigated.A simple theorem,after Norton[40],can be stated:”All physical phenomena in the range of about0.1–1 eV will be proposed for IR detectors”.Among these effects are:thermoelectric power(thermocouples),change in elec−trical conductivity(bolometers),gas expansion(Golay cell), pyroelectricity(pyroelectric detectors),photon drag,Jose−phson effect(Josephson junctions,SQUIDs),internal emis−sion(PtSi Schottky barriers),fundamental absorption(in−trinsic photodetectors),impurity absorption(extrinsic pho−todetectors),low dimensional solids[superlattice(SL), quantum well(QW)and quantum dot(QD)detectors], different type of phase transitions, etc.Figure6gives approximate dates of significant develop−ment efforts for the materials mentioned.The years during World War II saw the origins of modern IR detector tech−nology.Recent success in applying infrared technology to remote sensing problems has been made possible by the successful development of high−performance infrared de−tectors over the last six decades.Photon IR technology com−bined with semiconductor material science,photolithogra−phy technology developed for integrated circuits,and the impetus of Cold War military preparedness have propelled extraordinary advances in IR capabilities within a short time period during the last century [41].The majority of optical detectors can be classified in two broad categories:photon detectors(also called quantum detectors) and thermal detectors.3.1.Photon detectorsIn photon detectors the radiation is absorbed within the material by interaction with electrons either bound to lattice atoms or to impurity atoms or with free electrons.The observed electrical output signal results from the changed electronic energy distribution.The photon detectors show a selective wavelength dependence of response per unit incident radiation power(see Fig.8).They exhibit both a good signal−to−noise performance and a very fast res−ponse.But to achieve this,the photon IR detectors require cryogenic cooling.This is necessary to prevent the thermalHistory of infrared detectorsFig.5.Cashman’s detector cells:(a)Tl2S cell(ca.1943):a grid of two intermeshing comb−line sets of conducting paths were first pro−vided and next the T2S was evaporated over the grid structure;(b) PbS cell(ca.1945)the PbS layer was evaporated on the wall of the tube on which electrical leads had been drawn with aquadag(afterRef. 38).。
2023-2024学年广东省华附 省实 广雅 深中四校高二下学期期末联考英语试题
2023-2024学年广东省华附省实广雅深中四校高二下学期期末联考英语试题1. After months of hard work and preparation, the company finally saw its business ________, attracting numerous investments.A．take up B．take over C．take off D．take in2. ________ in the planning process for the group project will leave team members feeling disconnected and unproductive.A．Not involving B．Not involvedC．Not having involved D．Not being involved3. It is reported that a new wildlife conservation area has been established in ________ was once known for deforestation to protect endangered species.A．what B．which C．how D．where4. ________ a healthy eating habit, and you can feel more energetic and improve your well-being.A．Have B．To have C．Having D．Had5. ________ unique project, ________ of a series of experiments, is designed to investigate the potential of AI in identifying medical conditions.A．An; consists B．A; consists C．An; consisting D．A; consisting 6. The thrilling moment ________ Susan cherishes most is ________ she reached the peak of the mountain and appreciated the untouched wilderness below.A．that; when B．which; why C．where; when D．what; why7. The new Guangzhou Cultural Museum, ________ a collection of historical relics from various dynasties, ________ visitors with its rich cultural heritage.A．housing; collects B．featuring;attracts C．displayed;gathersD．contained;fascinates8. By the time she ________ next year, Sarah ________ three internships, giving her a strong foundation for her career in finance.A．graduate; will complete B．graduates; will have completedC．graduated; will be completed D．graduating; will be completing9. ________ mutual understanding, cultural exchange programs ________ among the countries participating in the meeting currently.A．Strengthening; is introduced B．Strengthened; is being introducedC．Having strengthened; are introduced D．To strengthen; are being introduced10. ________ the weather is like, the marathon will continue as planned, with participants ________ to prepare for rain or shine.A．Whatever; advised B．However; advisedC．No matter what; being advised D．No matter how; being advised11. A recent survey ________ 60% of US respondents believed social media platforms were evolving too fast, ________ 80% urged caution in introducing new features.A．shows, since B．has shown, so C．showed, while D．had shown, as12. ________ data leaks have become more common, worries about privacy are growing, and the chance ________ a person’s private details are at risk is getting higher.A．Given that; whether B．Now that; thatC．But that; whether D．Except that; that13. The information board ________ that all drones (无人机) under 250 grams must be registered with the local flight agency before ________ in public areas.C．reads; flying D．read; flying A．reads; flew B．read; beingflown14. ________ governments have addressed the problem of affordable housing ________ their commitment to providing accessible living options for all citizensA．What; reflects B．That; reflects C．There; reflected D．Whether;reflected15. Novels by authors such as Dickens and Austen are widely read, some of ________ works, however, are sometimes difficult ________.A．which, to comprehend B．whose, to comprehendC．which, to be comprehended D．whose, to be comprehendedThere are many scientific breakthroughs made by women in the Antarctic. Here are four landmarks in Antarctica and the female pioneers they’re named after.Jones TerraceThe ice-free terrace in easter n Antarctica’s Victoria Land bears Jones’ name. In 1969, geochemist Lois M. Jones led the first all-female research team from the U. S. to work in Antarctica. Jones and her team studied chemical weathering in the McMurdo Dry Valleys, an ice-free area of Antarctica. Through chemical analyses of rocks they had collected, Jones and her team discovered many geochemical characteristics of the valley’s ice-covered lakes.Mount Fiennes8,202-foot-high Mount Fiennes, located on Antarctica’s largest island—Alexander Island—is named after Ginny Fiennes. She established and maintained 80-foot-tall radio towers in the Antarctic with her colleagues. In 1985, Fiennes became the first female invited to join the Antarctic Club, a British supper club open to individuals who have spent extended time in the Antarctic region.Francis Peak The 3,727-foot-tall peak on Antarctica’s Adelaide Island is named after Dame Jane Francis, who is the first female director of the British Antarctic Survey, the national polar research institute of the UK. Her collection of fossils on Seymour Island helped conclude in a 2021 paper that Antarctica’sabundant plant fossils indicate the continent once had a much warmer climate than it currently does.Peden CliffsPeden Cliffs near Antarctica’s Marie B yrd Land are proof of the labor of Irene Peden. She was the first American female scientist to both live and work in the Antarctic, where she used radio waves to study ice sheets. Peden and her team determined how very low frequency radio wave spread over long polar distances by measuring pathways in the ice. They also used varying radio wave frequencies to measure the thickness of Antarctica’s ice sheets.16. What do the first two pioneers have in common?A．They analyzed different chemicals of rocks in Antarctica.B．They both worked with their own team in Antarctica.C．They conducted the research in the ice-free areas in Antarctica.D．They joined the Antarctic Club for their stay in Antarctica.17. Who proved the previous higher temperatures of the Antarctic?A．Lois M. Jones. B．Ginny Fiennes.C．Dame Jane Francis. D．Irene Peden.18. What is the scientific breakthrough of Irene Peden?A．She was the first American scientist to explore the Antarctic.B．She measured the spreading frequencies of radio waves.C．She found out the thickness of Antarctica’s ice sheets.D．She discovered a lot of ice-covered lakes in the Antarctic.Canadian author Alice Munro, a master of the contemporary short story, passed away on May 13, 2024, at 92.Munro’s texts featured depictions of everyday but decisive events, pulling vast themes out of ordinary settings. Her characters often mirrored her own rural Ontario lifestyle. In an interview after winning the Nobel Prize, she said that living in a small town gave her t he freedom to write. “I don’t think I could have been so brave if I had been living in a city, competing with people on what can be called a generally higher cultural level,” she said. “As far as I knew, at least for a while, I was the only person I knew w ho wrote stories.”Munro’s first short story was published when she was 37, a college dropout squeezing in writing time around her children’s naps. By the time she was in her 60s, she had become one of the most celebrated short-story writers in the world. Throughout her long career, she hardly ever failed to wow readers and critics with her quietly powerful language. In reviewing her last collection, Dear Life, NPR critic Alan Cheuse wrote “A Munro story gives us so much life within the bounds of a single tale that it nourishes (滋养) us almost as much as a novel does.”In a literary culture that tends to celebrate novels over shorter fiction, Munro has been a constant advocate for the power of the short story. In the interview, Munro emphasized the significance of her win not f or herself, but for her art form: “I really hope this would make people see the short story as an important art, not just something you play around with until you get a novel written.”When asked “Do you want young women to be inspired by your books and feel inspired to write?” Munro replied, “I don’t care about that. I want people to find not so much inspiration as great joy. I want them to think of my books as related to their own lives in ways.”19. Why did Munro feel free to write while living in rural areas?A．She was inspired by rural landscape and lifestyles.B．She was free from stress of a more cultured setting.C．She had more courage to compete with urban writers.D．She had access to ordinary people and decisive events.20. What did Alan Cheuse say about Munro’s stories in Dear Life?A．They promote readers’ mental well-being.B．They have broken the length limit of short stories.C．They impress readers with quietly powerful language.D．They offer richness and depth in shorter format.21. How did Munro view the short story in literary culture?A．It is more powerful than novels. B．It is a way of entertainment for youngwriters.C．It is as important an art form as novels. D．It is an inspiration for young writers. 22. What did Munro want readers to get by reading her books?A．Inspiration to become writers themselves.B．Enjoyment and connection to their own lives.C．Pleasure and motivation to change their lives.D．Information about art forms and literary culture.Handwriting notes in class might seem old-fashioned as digital technology affects nearly every aspect of learning. But a recent study in Frontiers in Psychology suggests that taking notes with pen and paper is still the best way to learn, especially for young children.The new research builds on a 2014 study that suggested people may type notes quickly, without thinking much about what they’re writing-but writing by hand is slower and makes them activelypay attention to and process the incoming information. This conscious action of building on existing knowledge can make it easier for students to stay engaged and grasp new concepts.To understand specific brain-activity differences during the two note-taking approaches, the authors of the new study sewed 256 electrodes (电极) into a hairnet. These sensors let the scientists record 36 students’ brain activity as they wrote or typed words displayed on a screen. When students wrote by hand, the sensors picked up widespread brain connectivity throughout visual regions that receive and process sensory information, and the motor cortex (运动皮层) that helps the brain use environmental inputs to inform a person’s next action. Typing, however, resulted in minimal activity in these brain regions.Vanderbilt University educational neuroscientist Sophia Vinci-Booher says the recent study highlights the clear tie between physical actions and concept understanding, “As you’re writing a word, you’re taking this continuous understanding of something and using motor system to create it.” That creation then affects the visual system, where it’s processed again-strengthening the connection between an action and the words associated with it.Vinci-Booher notes that the new findings don’t mean technology is always a disadvantage in the classroom. Digital devices can be more efficient for writing essays and offer more equal access to educational resources. However, there’s a growing trend of relying on digital devices to perform cognitive (认知的) tasks, such as taking photos instead of memorizing information. Yadurshana Sivashankar, an researcher at the University of Waterloo says, “If we’re not actively using these areas, then they are going to become worse over time, whether it’s memory or motor skills.”23. Why does the author mention the 2014 study?A．To present different research findings. B．To make the new research moreconvincingC．To compare two note taking approaches. D．To show the advantage of writing slowly 24. What can be learned from the experiment in Paragraph 3?A．Sensors were used to process visual information.B．Electrodes were connected to students’ hair directly.C．Writing by hand activated more brain activity than typing.D．Typing stimulated the motor cortex to inform following action.25. What would Sophia Vinci-Booher probably advise students to do?A．Make better use of motor system. B．Take advantage of digital devices.C．Adopt a new approach to taking notes. D．Memorize words by writing essays.26. What is the main idea of the text?A．Technology is not a disadvantage in classroom.B．Writing by hand comes with learning benefits.C．Taking notes enhances students’ brain activity.D．Two note-taking approaches have clear differences.The more scientists investigate the microbes (微生物) living inside us, the more they learn about the surprising impact of the tiny organisms on how we look, act, think, and feel. Are our health and well-being really driven by the bacteria, viruses and fungi that live in our intestines (肠), in our lungs, on our skin, on our eyeballs? What a weird concept-that the bugs we carry around appear to be essential to establishing the basic nature of who we are.The effects of the microbiome, the microorganisms that exist in human body, can be profound and can start incredibly early. In a study, scientists showed that something supposedly as natural as a child’s character might be related to the bacteria in an infant’s digestive system; the more Bifidobacterium (双歧杆菌) there are, the sunnier the baby is. This observation, from the University of Turku in Finland, is based on an analysis of samples from 301 babies. Those with the highest proportion of Bifidobacterium organisms at two months old were more likely to exhibit a trait the researchers called “positive emotionality” at six months old.Microbiome science is still relatively young. Most studies so far have been initial and small-scale, involving only a dozen or so mice or humans. Scientists have found associations between the microbiome and disease but can’t yet draw clear cause-and-effect conclusions about our extensive collection of microorganisms and their effects on us as hosts. Still, the collection itself is mind-boggling—it’s now thought to be around 38 trillion microbes for a typical young adult male, slightly more than the number of actual human cells. And the prospects for putting that collection to use are more than promising.In the not-too-distant future, according to the most enthusiastic researchers, it might be a routine for us to take a dose of healthy microbes in various forms. Hopefully, with the help of new medical advances, we will be able to achieve our full potential by functioning at peak levels internally and externally.27. What can we learn about microbiome?A．The development of microbiome is quite mature nowadays.B．The more Bifidobacterium an adult has, the healthier one is.C．More microbes than human cells are present in young men.D．Microbes have little influence on shaping our identity28. What docs the underlined word “mind-boggling” in Paragraph 3 probably mean?A．Weakening. B．Astonishing. C．Disturbing. D．Misleading.29. What can be inferred from the text?A．It’s necessary to remove certain fungi from our body.B．2-month-old babies are often more positive than 6-month-old ones.C．New supplements related to microbiome are likely being developedD．The relationship between microorganisms and disease remains unclear.30. Which of the following can be the best title for the text?A．How microbes benefit our healthB．How microbes shape our lives.C．What affects early childhood personality.D．What Turku University reveals about microbes.On a large scale, making the world a better place can seem challenging. 31 As a leader, your perspectives and ideas can directly impact your community for the better. Here are some ways to make an impact and grow your leadership through emotional intelligence.32 Being able to provide a safe space through deep listening creates trust, which lays the foundation for meaningful relationships and fruitful partnerships. As a result, people are more likely to share openly and honestly. Empathy and listening will increase the quality of your relationships and skyrocket your results.Making a positive impact can also be as simple as taking the time to acknowledge and inspire someone into action. Taking time to acknowledge someone by letting them know you see their efforts and talents. 33 An example of what this could sound like is, “Wow! I am blown away by your project. What I see possible for you is to share with the rest of the team how to do it too.”Get involved with your already existing communities and networking circles. Start by connecting with your peers and ask them about causes they’re already involved in. 34 There is almost no limit to the impact you can create contributing to a cause that matters to you and your peers. With a little time, you can make a big differenceSharing your knowledge and strengths is another essential skill. When you share with others, you’re teaching them something special about you and your journey. Imagine what would be possible if your community was in the mode of cooperation and contribution. This approach creates new ideas and opportunities. 35At one night in July 2020 in Reykjavik, Halli was wandering around the city’s main street with his wife and two kids. During their walk, his three-year-old son was ______ and wanted a drink from the corner store. But Halli soon discovered he couldn’t help with the ______ request: A 20-centimetre step ______ his access to the store.The barrier was all too ______. Born with muscular dystrophy (肌肉萎缩), which causes progressive ______ and loss of muscle, Halli, now 46, has been using a wheelchair since he was 25.As be, ______ his wife and children outside the shop, he recalls, “I thought about how very strange it is that we always ______ families in this way.”Living all over the world as a creative director and digital designer, Halli had ______ first hand how different cities consider and plan for accessibility, from ramps (坡道) and sidewalks to public transportation. He decided to start with a project to make Iceland wheelchair ______.Ramp Up Reykjavik launched as a non-profit in 2021 with a ______ to build 100 ramps within 1 year. Unlike temporary solutions in other cities, these ramps are ______ structures that match the beauty of buildings.With the help of government funding and other sponsors, the Ramp Up team finished ahead of schedule and has ______ its scope to all of Iceland. In three short years, Hali has become a ______ in his hometown. Halli is proud that Ramp Up has ______ others to act “Equal access to society is ______ not something that is a reality yet,” says Hali. But as he’s learned, change starts with just one person.36.A．anxious B．thirsty C．exhausted D．hungry37.A．special B．funny C．simple D．childish38.A．replaced B．ruined C．supported D．blocked39.A．surprising B．familiar C．unique D．complex40.A．weakness B．depression C．strength D．trouble41.A．waited for B．listened to C．worried about D．searched for 42.A．reject B．protect C．separate D．connect43.A．ignored B．recorded C．questioned D．witnessed44.A．accessible B．attractive C．effective D．practical45.A．treatment B．limitation C．goal D．rule46.A．convenient B．permanent C．formal D．useful47.A．broadened B．hidden C．narrowed D．deepened48.A．master B．legend C．success D．expert49.A．prevented B．persuaded C．forced D．motivated50.A．fortunately B．definitely C．eventually D．regularly语法填空When discussing global education systems, Finland stands out for 51 (it) high-ranking performance in international assessments and holistic (全面的) approach to education. The Finnish curriculum prioritizes essential life skills such as 52 (creative), cooperation, critical thinking, and communication. Additionally, Finnish schools 53 (emphasis) social and emotional skills like empathy and self-confidence, ensuring students are well-rounded and prepared for real-world challenges.Finland’s education system values cooperation 54 competition, fostering a cooperative learning environment 55 students learn from and support each other. Meanwhile, Finnish teachers enjoy freedom to design their course, which allows them 56 (tailor) their teaching methods to meet their students’ unique needs. This trust in teachers, combined with the cooperative learning environment,57 (promote) innovation, continuous improvement, and collective responsibility for student success.58 , to imitate Finland’s success requires careful consideration of contextual factors and systemic differences. Finland’s model shows that comprehensive education, 59 (profession) trust, and cooperation are key to 60 (secure) long-term student success.61. 上周六，你校组织了“走进社区”实践活动。
Scaling of excitons in carbon nanotubes
a r X i v :c o n d -m a t /0402091v 2 [c o n d -m a t .m t r l -s c i ] 30 A p r 2004Scaling of excitons in carbon nanotubesVasili Perebeinos,J.Tersoff,and Phaedon Avouris ∗IBM Research Division,T.J.Watson Research Center,Yorktown Heights,New York 10598(Dated:February 2,2008)Light emission from carbon nanotubes is expected to be dominated by excitonic recombination.Here we calculate the properties of excitons in nanotubes embedded in a dielectric,for a wide range of tube radii and dielectric environments.We find that simple scaling relationships give a good description of the binding energy,exciton size,and oscillator strength.PACS numbers:78.67.Ch,71.10.Li,The optical properties of carbon nanotubes have re-ceived increasing experimental and theoretical atten-tion.Optical absorption and emission spectra of car-bon nanotubes have been studied by a number of groups [1,2,3,4,5,6];and electro-optical devices have already appeared [7,8].Initial attempts to explain the experi-mental observations naturally took independent-electron theory as their starting point.However,theoretically it is now clear that emission is dominated by excitonic re-combination [9,10,11,12].A number of theoretical approaches have been used to describe these excitons.One approach involves vari-ational calculations [10,11].While valuable,these have been limited to an effective-mass approximation,and do not address issues of spectral weight.The most accu-rate description is provided by an ab initio solution of the Bethe-Salpeter equation using GW-corrected quasi-particle energies [12].However,it is not currently feasi-ble to apply this computationally intensive approach to a wide range of nanotube sizes or environments.Here we use an intermediate level of theory to provide a broad overview of the exciton properties.We calculate the excitonic properties of nanotubes embedded in di-electric media,for the range of tube radii and dielectric constants most relevant to potential applications.We find that the exciton size,binding energy,and oscillator strength all exhibit robust (though approximate)scaling relationships.The relationships obtained for the exci-tonic properties can be used to better understand and optimize the operation of nanotube opto-electronic de-vices.The proper procedure for the calculation of excitons has been described in detail in Ref.[13].It involves solv-ing the Bethe-Salpeter equation,∆k A S k+k ′K k,k ′A S k ′=ΩS A Sk (1)where the kernel K k,k ′describes the interaction between all possible electron-hole pairs of total momentum q exc ,and ∆k is the quasiparticle energy for a non-interacting electron and hole with wavevector k and q exc −k .The exciton momentum q exc is equal to that of the exciting photon,and is hereafter approximated by q exc =0.We approximate the quasiparticle energies by eigenvalues ofthe tight-binding Hamiltonian [14,15](t =3.0eV),withany additional self-energy corrections restricted to the so-called “scissors operator”,in which the self-energy is approximated by a rigid shift of the conduction band rel-ative to the valence band.Since the quasi-particle band-structures are not well known for nanotubes of varying diameters and embedding media,we report only proper-ties that are not affected by the magnitude of this shift.For the optically active singlet excitons,the interaction has two contributions,direct (K d )and exchange (K x ):K k,k ′=K d k,k ′+2K xk,k ′(2)where the direct (exchange)term is evaluated with thescreened (bare)Coulomb interactions [13].The un-screened Coulomb interaction between carbon p z orbitals is modelled by the Ohno potential,which realistically de-scribes organic polymer systems:V (r ij )=U4πε2E b 1 (e V )m R 2E b (e V )m R /εFIG.1:(a)Binding energy of first optically active exciton,vs.ε,in four semiconducting zig-zag tubes:(13,0),(19,0),(25,0),and (31,0).(b)Scaling of binding energy of first and second exciton (red dots)in semiconducting tubes with all possible chirality (156tubes with d =1.0−2.5nm,ε=2−15).Here R and m are in a.u.The black solid line is the best fit to Eq.(7)for ε=4−15(3%RMS error over this range),corresponding to α=1.40and A b =24.1eV.imaginary part of the dielectric function for light polar-ized along the nanotube axis [17]:ǫ2(ω)=8π2e 2∆k2δ( ω−ΩS )(4)where P is the dipole matrix element [18].The optical response Eq.(4)is the same as derived in the presence of the GW non-local potential [17].ε2(ω)obeys a sum rule,where ε2dω∝ k P 2cv (k )/∆2k is a constant independent of the strength of the screened interaction e 2/ε.We solve the BSE equation (1)by direct diagonaliza-tion,choosing a k sample sufficient to converge the low-energy optical spectra (and a fortiori the binding ener-gies).We calculate the binding energy,size,and spectral function for singlet excitons.The binding energy of the first optically active exciton vs.εis shown on Fig.1a for four zig-zag tubes with diameters d =1.0−2.5nm.(There is another singlet state 3-5meV lower in energy,but it is optically silent by symmetry.)The dependence of binding energy E b 1on εin Fig.1can be fitted well with a power law,with the exponent being almost independent of the tube diameter.This suggests a more general power law scaling,which we can motivate in an effective mass approximation as follows.Given a variation wavefunction described by a single pa-rameter L that scales the size along the tube axis,the exciton binding energy is:E L ∝2ǫR fL mR 2g L ε (5)Here the first term is the kinetic energy,and m is theeffective mass.The second term is the potential energy,which depends on the exciton size via the dimensionless function f (L/R ).Then the exciton binding energy isE b =min L (E L )= 2ε(6)E b ≈A b R α−2m α−1ǫ−α(7)where we approximate the function h by a power law overthe range of interest,with empirical parameters αand A b .The effective mass m depends on the tube indices [14](i.e.on radius and chirality).In 3D semiconductors,the potential energy is ∝1/L ,and the energy is minimized when the exciton size L S ∝ε/m ,so the binding energy scales as E b ∝m/ǫ2.This corresponds to true scaling,with a power law α=2in Eq.(7).In the case of nanotubes,the power-law scaling is only an approximation.Nevertheless,for the most im-portant range of tube sizes and dielectric constants,the behavior is rather well described by a power-law scaling in R and εwith a single value of α.Indeed,all the binding energies for the first and second excitons in semiconduct-ing tubes,with all possible chiralities,(d =1.0−1.5nm)collapse onto a single curve shown in Fig.1b.Similar energy scaling was reported by Pedersen [10]in a varia-tional effective-mass model.In the range ε 4,where our approach is most reliable,we obtain the best fit with α=1.40.The second exciton that is optically active derives pri-marily from the second band of the nanotube.It falls within the continuum of the first band,and so becomes a resonance with a finite lifetime [12].By artificially turn-ing offthe interband coupling,we determine that this coupling has very little effect on the exciton energy.Considerable attention has been focused on the ra-tio E b 2/E b 1between the binding energies of the first and second excitons [11,12].(E b 2is defined relative to the second-band quasiparticle gap.Note that the exciton formation energies involve also the quasiparti-cle bandgaps.)The scaling relation of Eq.(7)predicts E b 2/E b 1=(m 2/m 1)α−1,where m 2and m 1are the effec-tive masses of the first and second bands.In the case of zig-zag tubes:m 1=2∆12t−1m 2= 2∆22t −1(8)Here ∆1and ∆2are the tight-binding bandgaps;a is the graphene lattice constant;and for tube indeces (n,0),σ=1if mod(n,3)=1and σ=-1if mod(n,3)=2.It is common to treat the gap values in the infinite-radius limit,∆∞2=2∆∞1=2ta/√3mass ratio m2/m1varies from3.4to1.3,approaching the infinite-radius limit m2/m1→2much more slowly than the gap ratio.Thus caution must be used in discussing available experimental data in terms of the R→∞limit [11].In particular,for the(8,0)tube m2/m1=0.96, and according to Eq.(7)the binding energies of thefirst two excitons should be very similar.Indeed,the accu-ratefirst-principles calculations by Spataru et.al.[12]find the binding energies of thefirst and second exci-tons(A’1and C’1in[12])to ing ε=1.93to best reproduce this,our calculations give E b1=0.99eV and E b2=1.05eV.In contrast,the(10,0) tube has m2/m1=4.14,and for the sameε=1.93we find E b2/E b1=1.41.[The simple mα−1scaling is not accurate for such smallε.]It is important to note that effective mass dependence similar to Eq.(8)holds also for chiralities other from zig-zag tubes.Thus we expect exciton properties in tubes of index(m,n)to depend pri-marily on whether mod(n-m,3)=1or2,independent of the chiral angle.To quantify the exciton size,we use the root-mean-square(RMS)distance between electron and hole,L S. The size L1of thefirst exciton is shown in Fig.2a as a function ofε,for four different tube diameters.The size is approximately linear inε.From Eq.(5),L S/R is expected to be a function of mR/ε.Combining this with the observed linear dependence onε,we anticipate that the exciton size will obey the scaling relationship:L1Rm1(9)This is confirmed in Fig.2b,which shows a linear de-pendence of L1/R onε/m1R in all semiconducting tubes with d=1.0−2.5nm,for all chiralities.The exciton size directly affects observable quantities such as the exciton oscillator strength and the radiative lifetime.The exciton oscillator strength is proportional to the probability tofind an electron and a hole at the same position[19].In3D semiconductors this is inversely proportional to the exciton volume1/L3.In the case of nanotubes the electron and hole wavefunctions are confined in two dimensions and therefore the oscillator strength should be inversely proportional to the exciton size L1.Typical optical absorption spectra are shown on Fig.3a-c,calculated for a(19,0)tube in different di-electric media.Asεincreases,the spectral function con-verges to the non-interacting limit.Forε=10,the spec-tral weight transfer to thefirst and second excitons,as a fraction of the total spectral weights forfirst and second bands in the non-interacting limit,are71%and55%re-spectively.The second exciton resonance is more bound than thefirst,by63meV vs.43meV.The higher spectral weight transfer to thefirst exciton is due not to stronger binding,but rather to the smaller band gap∆1.L1(nm)L1/Rε/m RFIG.2:(a)First exciton RMS e-h separation L1in four zig-zag tubes(13,0),(19,0),(25,0),and(31,0).The solid lines are the best linearfits.The slope k scales approximately as m−1:the product km1(in a.u.)equals0.167,0.160,0.157, and0.155for tubes with diameter1.0,1.5,2.0,and2.5nm, respectively.(b)The linear scaling of L1/R withε/mR in semiconducting tubes of all possible chirality with d=1.0−2.5nm,andε=2−15.The solid line is the bestfit to Eq.(9)to the results in the rangeε≥4,giving A L=2.13 and B L=0.174(for m and R in a.u.).The RMS discrepancy between thefit and the full calculations is2%for the subset of data havingε≥4orε/mR2≥9.5.The probability argument[19]along with Eq.(4)sug-gest the following scaling relation for the exciton oscilla-tor strength:I1∆2L1R 1−B I R4ε2 (a r b . u .)I 1/I 0∆12L 12L 1/RFIG.3:Absorption spectra ε2in (19,0)tube in dielectric environment (a)ε=∞(equivalent to no e-h interaction),(b)ε=10,(c)ε=4.(E s is the unknown self-energy shift.)Note expanded scales for dotted lines in continuum region in (b)and (c).The fractional spectral weight transfer to the first exciton is I 1/I 0=0,0.71,and 0.95respectively.Spec-tra are broadened with a Gaussian width of 0.0125eV.(d)The scaling of spectral weight transfer to the first exciton,I 1,according to Eq.(10),in all semiconducting tubes with d =1.0−2.5nm and ε=2−15and all possible chiralities.The best fit to Eq.(10)(RMS difference 3.5%)is obtained with A I =1.22eV 2nm 2and B I =1.61.length in the nanotube,which in turn depends on en-vironment and temperature.(If the coherence length is sufficiently large,other lengthscales such as tube length or photon wavelength can become important.)Another important factor is that electrons and holes are rela-tively unlikely to form optically active excitons,because there are far more excitons that are optically inactive.These include triplet and other dipole-forbidden excitons at lower energy than the optically active exciton.Most importantly,only a tiny fraction of excitons have a total momentum compatible with photon emission,so phonon scattering plays an important role [22].In conclusion,we have calculated optical spectra of carbon nanotubes including the electron-hole Coulomb interaction by solving the Bethe-Salpeter equation (1)in a tight-binding wavefunction basis set.We find scaling relations with respect to the tube radius and dielectric constant ε,for the binding energy Eq.(7),exciton size Eq.(9),and oscillator strength Eq.(10).Thus the ab-sorption and emission properties depend on the dielectric media in which the nanotube is placed.We find a strong dependence on tube index (chirality),but only via the ef-fective mass.This depends strongly on whether mod(n-m,3)=1or 2,but is otherwise insensitive to the chiral angle.The authors thank M.Freitag,T.Heinz,M.Hybert-sen,S.G.Louie,G.Mahan,and F.Wang for helpfuldiscussions.[*]Electronic address:avouris@[1]Z.M.Li,Z.K.Tang,H.J.Liu,N.Wang,C.T.Chan,R.Saito,S.Okada,G.D.Li,J.S.Chen,N.Nagasawa,and S.Tsuda,Phys.Rev.Lett.87,127401(2003).[2]M.J.O’Connell,S.M.Bachilo,C.B.Huffman,V.C.Moore,M.S.Strano,E.H.Haroz,K.L.Rialon,P.J.Boul,W.H.Noon,C.Kittrell,J.Ma,R.H.Hauge,R.B.Weisman,and R.E.Smalley,Science,297,593(2002).[3]S.M.Bachilo,M.S.Strano,C.Kittrell,R.H.Hauge,R.E.Smalley,R.B.Weisman,Science,298,2361(2002).[4]A.Hagen and T.Hertel,Nano Lett.3,383(2003)[5]S.Lebedkin,F.Hennrich,T.Skipa,and M.M.Kappes,J.Phys.Chem.B 107,1949(2003).[6]J.Lefebvre,Y.Homma,and P.Finnie,Phys.Rev.Lett.90,217401(2003)[7]J.A.Misewich,R.Martel,Ph.Avouris,J.C.Tsang,S.Heinze,J.Tersoff,Science 300,783(2003).[8]M.Freitag,Y.Martin,J.A.Misewich,R.Martel,andPh.Avouris,Nano Lett.3,1067(2003).[9]T.Ando,J.Phys.Soc.Japan 66,1066(1996).[10]T.G.Pedersen,Phys.Rev.B 67,073401(2003).[11]C.L.Kane and E.J.Mele,Phys.Rev.Lett.90,207401(2003).[12]C.D.Spataru,S.Ismail-Beigi,L.X.Benedict,and S.G.Louie,cond-mat/0310220,Applied Physics A[13]M.Rohlfing and S.G.Louie,Phys.Rev.B 62,4927(2000).[14]R.Saito and H.Kataura,in Carbon Nanotubes:Syn-thesis,Structure,Properties and Application ,edited by M.S.Dresselhaus,G.Dresselhaus,P.Avouris (Springer-Verlag,Heidelberg 2001),Vol.80.[15]This approach neglects s-p hybridization,which becomesincreasingly important for narrower tubes.Fortunately,the associated error is small for the entire range of tubes and excitation energies considered here [except perhaps for the (8,0)and (10,0)tubes which are mentioned in the text but not including in the scaling analysis];see X.Blase,L.X.Benedict,E.L.Shirley,and S.G.Louie,Phys.Rev.Lett.72,1878(1994).[16]If the exciton binding energy is much smaller the op-tical phonon energy in the dielectric medium,then the static dielectric constant ε0should be used in the scal-ing relations obtained here;but if much larger,then the screening ε∞(i.e.for frequencies well above the phonon frequency)is used.A general treatment would require explicit inclusion of exciton-phonon coupling.[17]R.Del Sole and R.Girlanda,Phys.Rev.B 48,11789(1993).[18]L.G.Johnson and G.Dresselhaus,Phys.Rev.B 7,2275(1973).[19]R.J.Elliott,Phys.Rev.108,1384(1957).[20]F.Stern,in Solid State Physics ,edited by F.Seitz andD.Turnbull (Academic Press Inc.,New York,1963),Vol.15,Sec.36.[21]E.Hanamura,Phys.Rev.B 38,1228(1988).[22]D.S.Citrin,Phys.Rev.Lett.69,3393(1992).。
抗结冰涂层相关英文书籍
抗结冰涂层相关英文书籍1. Anti-Ice: A Strategy for Roadway and Airport Pavement Maintenance by Jerry A. DiMaggio2. Anti-Ice Techniques for Highway Pavements by Transportation Research Board3. Icephobic Coatings and Surfaces edited by Victor P. Kleshchev4. Icephobicity of Bi-Continuous Structured Surfaces edited byJúlio R.S. Bastos5. Ice Formation and Anti-Icing Technology edited by Victor G. Kossenko and Alexander N. Lagunov6. Icing of Structures by Dr. Jan W. F. Mulder7. Advanced Coatings for Transportation Infrastructure: A Technical Guide by Oleg Figovsky and Dmitry Beilin8. Handbook of Winter Service: Anti-icing, De-icing, and Road Maintenance by Gunther Leonhardt9. Icing on the Lake: International Journal on Ice Breaking and Ice Operations edited by Camila Albertsen10. Cold formation and anti-icing materials edited by Albert V. Prochorov and Yury L. Fradkov这些书籍涵盖了抗结冰涂层技术的不同方面，包括道路和机场路面的维护，冰抗性涂层和表面的开发，以及结构上的结冰和抗冰技术。
211127352_核动力破冰船国内外设计规范研究
100核动力破冰船国内外设计规范研究吴 俊 吴 刚（中国船舶及海洋工程设计研究院 上海 ２０００１１）摘 要：…该文从破冰船的设计需求出发，介绍了核动力破冰船适用的规范，并从极地低温、多冰以及地理位置偏远等风险要素分析破冰船设计规范的要点。
首先对比不同船级社规范关于低温环境的定义，并从主机进气、液舱防冻以及脱险通道等方面解读防寒规范的设计要点；其次从防火安全、堆舱安全和防寒防冻要求，梳理总布置的相关要求；同时总结了结冰对完整稳性的影响、骑冰稳性以及破舱稳性等规范要求；最后对冰级舵系和冰级轴桨的强度校核规范进行分析。
通过对以上规范的总结和对比，为今后核动力破冰船的设计研发提供规范参考。
关键词：核动力破冰船；设计规范；防寒设计；总布置；稳性；机械装置中图分类号：U674.21；U674.921………文献标志码：A………DOI ：10.19423/ki.31-1561/u.2023.02.100On Design Rules for Nuclear-Powered Icebreakers at Home and AbroadWU Jun WU Gang(Marine Design & Research Institute of China, Shanghai 200011, China)Abstract: The applicable rules of nuclear-powered icebreakers at home and abroad are introduced from the design requirements of icebreakers. And the key points of icebreaker design rules are analyzed from polar risks such as low temperature, excessive ice and remote geographical location. Firstly, the definitions of low-temperature environment in different classification society rules have been compared, and the design points of winterization rules are interpreted from the aspects of engine intake, cold protection for liquid tank and escape passage. Secondly, the relevant requirements of the general arrangement are sorted out from the requirements of fire safety, nuclear safety and winterization. The influence of icing on the requirements of intact stability, riding ice stability and damaged stability in rules are also summarized. Finally, the strength check rules of ice class rudder system and ice class propeller are analyzed. The above comparison and analysis of rules can provide references for future design of nuclear-powered icebreakers with practical significance.Keywords:…nuclear-powered…icebreaker;…design…rule;…winterization…design;…general…arrangement;…stability;…mechanical…device收稿日期：2022-09-26；修回日期：…2022-12-12作者简介：吴…………俊（1990-），男，硕士，工程师。
英语六级巅峰阅读附详解 第30期-自然科学
英语六级巅峰阅读附详解第30期:自然科学Icebergs are among nature's most spectacular creations,and yet most people have never seen one.A vague airof mystery envelops them.They come into being-somewhere-in faraway,frigid waters,and thunderous noise and splashing turbulence,which in most cases no one hears or sees. They exist only a short time and then slowly waste away just as unnoticed.Objects of sheerest beauty,they have been called.Appearing in an endless variety of shapes,they may be dazzlingly white,or they may be glassy blue,green,or purple,tinted faintly of darker hues（颜色）.They are graceful,stately（宏伟的）,inspiring in calm,sunlit seas.But they are also called frightening and dangerous,and that they are-in the night,in the fog,and in storms.Even in clear weather one is wise to stay a safe distance away from them.Most of their bulk is hidden below the water,so their underwater parts may extend out far beyond the visible top.Also,they may roll over unexpectedly,churning（剧烈搅动）the waters around them.Icebergs are parts of glaciers that break off,drift intothe water.float about awhile and finally melt.Icebergs afloat today are made of snowflakes that have fallen over long ages of time.They embody snows that drifted down hundred,or many thousand,or in some cases,maybe a million years ago.The snows fell in polar-regions and on cold mountains,where they melted only a little or not at all and so collected to great depthsover the years and centuries.As each year's snow accumulation lay on the surface,evaporation and melting caused the snowflakes slowly to lose their feathery points and become tiny grains of ice.When new snow fell on top of the old,it too turned into icy grains.So blankets of snow and ice grains mounted layer upon layer and were of such great thickness that the weight of the upper layers compressed the lower ones.With time and pressure from above,themany small ice grains joined and changed to larger crystals,and eventually the deeper crystals merged intoa solid mass of ice.冰山是大自然最壮观的杰作之一，而大多数人却从未见过。
英语制冷词汇概述(1)
AA-weighted sound pressure level||A声级absolute humidity||绝对湿度absolute roughness||绝对粗糙度absorbate 吸收质absorbent 吸收剂absorbent||吸声材料absorber||吸收器absorptance for solar radiation||太阳辐射热吸收系数absorption equipment||吸收装置absorption of gas and vapor||气体吸收absorptiong refrige rationg cycle||吸收式制冷循环absorption-type refrigerating machine||吸收式制冷机access door||检查门acoustic absorptivity||吸声系数actual density||真密度actuating element||执行机构actuator||执行机构adaptive control system||自适应控制系统additional factor for exterior door||外门附加率additional factor for intermittent heating||间歇附加率additional factor for wind force||高度附加率additional heat loss||风力附加率adiabatic humidification||附加耗热量adiabatic humidiflcation||绝热加湿adsorbate||吸附质adsorbent||吸附剂adsorber||吸附装置adsorption equipment||吸附装置adsorption of gas and vapor||气体吸附aerodynamic noise||空气动力噪声aerosol||气溶胶air balance||风量平衡air changes||换气次数air channel||风道air cleanliness||空气洁净度air collector||集气罐air conditioning||空气调节air conditioning condition||空调工况air conditioning equipment||空气调节设备air conditioning machine room||空气调节机房air conditioning system||空气调节系统air conditioning system cooling load||空气调节系统冷负荷air contaminant||空气污染物air-cooled condenser||风冷式冷凝器air cooler||空气冷却器air curtain||空气幕air cushion shock absorber||空气弹簧隔振器air distribution||气流组织air distributor||空气分布器air-douche unit with water atomization||喷雾风扇air duct||风管、风道air filter||空气过滤器air handling equipment||空气调节设备air handling unit room||空气调节机房air header||集合管air humidity||空气湿度air inlet||风口air intake||进风口air manifold||集合管air opening||风口air pollutant||空气污染物air pollution||大气污染air preheater||空气预热器air return method||回风方式air return mode||回风方式air return through corridor||走廊回风air space||空气间层air supply method||送风方式air supply mode||送风方式||air supply (suction) opening with slide plate||插板式送（吸）风口||air supply volume per unit area||单位面积送风量||air temperature||空气温度air through tunnel||地道风||air-to-air total heat exchanger||全热换热器air-to-cloth ratio||气布比air velocity at work area||作业地带空气流速air velocity at work place||工作地点空气流速air vent||放气阀air-water systen||空气—水系统airborne particles||大气尘air hater||空气加热器airspace||空气间层alarm signal||报警信号ail-air system||全空气系统all-water system||全水系统allowed indoor fluctuation of temperature and relative humidity||室内温湿度允许波动范围ambient noise||环境噪声ammonia||氨amplification factor of centrolled plant||调节对象放大系数amplitude||振幅anergy||x||angle of repose||安息角ange of slide||滑动角angle scale||热湿比angle valve||角阀annual [value]||历年值annual coldest month||历年最冷月annual hottest month||历年最热月anticorrosive||缓蚀剂antifreeze agent||防冻剂antifreeze agent||防冻剂apparatus dew point||机器露点apparent density||堆积密度aqua-ammonia absorptiontype-refrigerating machine||氨—水吸收式制冷机aspiation psychrometer||通风温湿度计Assmann aspiration psychrometer||通风温湿度计atmospheric condenser||淋激式冷凝器atmospheric diffusion||大气扩散atmospheric dust||大气尘atmospheric pollution||大气污染atmospheric pressure||大气压力（atmospheric stability||大气稳定度atmospheric transparency||大气透明度atmospheric turblence||大气湍流automatic control||自动控制automatic roll filter||自动卷绕式过滤器automatic vent||自动放气阀available pressure||资用压力average daily sol-air temperature||日平均综合温度axial fan||轴流式通风机azeotropic mixture refrigerant||共沸溶液制冷剂Bback-flow preventer||防回流装置back pressure of steam trap||凝结水背压力back pressure return余压回水background noise||背景噪声back plate||挡风板bag filler||袋式除尘器baghouse||袋式除尘器barometric pressure||大气压力basic heat loss||基本耗热量hend muffler||消声弯头bimetallic thermometer||双金属温度计black globe temperature||黑球温度blow off pipe||排污管blowdown||排污管boiler||锅炉boiller house||锅炉房boiler plant||锅炉房boiler room||锅炉房booster||加压泵branch||支管branch duct||(通风) 支管branch pipe||支管building envelope||围护结构building flow zones||建筑气流区building heating entry||热力入口bulk density||堆积密度bushing||补心butterfly damper||蝶阀by-pass damper||空气加热器）旁通阀by-pass pipe||旁通管Ccanopy hood ||伞形罩capillary tube||毛细管capture velocity||控制风速capture velocity||外部吸气罩capturing hood ||卡诺循环Carnot cycle||串级调节系统cascade control system||铸铁散热器cast iron radiator||催化燃烧catalytic oxidation ||催化燃烧ceilling fan||吊扇ceiling panelheating||顶棚辐射采暖center frequency||中心频率central air conditionint system ||集中式空气调节系统central heating||集中采暖central ventilation system||新风系统centralized control||集中控制centrifugal compressor||离心式压缩机entrifugal fan||离心式通风机||check damper||(通风)止回阀||check valve||止回阀||chilled water||冷水chilled water system with primary-secondary pumps||一、二次泵冷水系统chimney||(排气)烟囱circuit||环路circulating fan||风扇circulating pipe||循环管circulating pump||循环泵clean room||洁净室cleaning hole||清扫孔cleaning vacuum plant||真空吸尘装置cleanout opening||清扫孔clogging capacity||容尘量close nipple||长丝closed booth||大容积密闭罩closed full flow return||闭式满管回水closed loop control||闭环控制closed return||闭式回水closed shell and tube condenser||卧式壳管式冷凝器closed shell and tube evaporator||卧式壳管式蒸发器closed tank||闭式水箱coefficient of accumulation of heat||蓄热系数coefficient of atmospheric transpareney||大气透明度coefficient of effective heat emission||散热量有效系数coficient of effective heat emission||传热系数coefficient of locall resistance||局部阻力系数coefficient of thermal storage||蓄热系数coefficient of vapor||蒸汽渗透系数coefficient of vapor||蒸汽渗透系数coil||盘管collection efficiency||除尘效率combustion of gas and vapor||气体燃烧comfort air conditioning||舒适性空气调节common section||共同段compensator||补偿器components||(通风〕部件compression||压缩compression-type refrigerating machine||压缩式制冷机compression-type refrigerating system||压缩式制冷系统compression-type refrigeration||压缩式制冷compression-type refrigeration cycle||压缩式制冷循环compression-type water chiller||压缩式冷水机组concentratcd heating||集中采暖concentration of narmful substance||有害物质浓度condensate drain pan||凝结水盘condensate pipe||凝结水管condensate pump||凝缩水泵condensate tank||凝结水箱condensation||冷凝condensation of vapor||气体冷凝condenser||冷凝器condensing pressure||冷凝压力condensing temperature||冷凝温度condensing unit||压缩冷凝机组conditioned space||空气调节房间conditioned zone||空气调节区conical cowl||锥形风帽constant humidity system||恒湿系统constant temperature and humidity system||恒温恒湿系统constant temperature system 恒温系统constant value control 定值调节constant volume air conditioning system||定风量空气调节系统continuous dust dislodging||连续除灰continuous dust dislodging||连续除灰continuous heating||连续采暖contour zone||稳定气流区control device||控制装置control panel||控制屏control valve||调节阀control velocity||控制风速controlled natural ventilation||有组织自然通风controlled plant||调节对象controlled variable||被控参数controller||调节器convection heating||对流采暖convector||对流散热器cooling||降温、冷却（、）cooling air curtain||冷风幕cooling coil||冷盘管cooling coil section||冷却段cooling load from heat||传热冷负荷cooling load from outdoor air||新风冷负荷cooling load from ventilation||新风冷负荷cooling load temperature||冷负荷温度cooling system||降温系统cooling tower||冷却塔cooling unit||冷风机组cooling water||冷却水correcting element||调节机构correcting unit||执行器correction factor for orientaion||朝向修正率corrosion inhibitor||缓蚀剂coupling||管接头cowl||伞形风帽criteria for noise control cross||噪声控频标准cross fan||四通crross-flow fan||贯流式通风机cross-ventilation||穿堂风cut diameter||分割粒径cyclone||旋风除尘器cyclone dust separator||旋风除尘器cylindrical ventilator||筒形风帽Ddaily range||日较差damping factot||衰减倍数data scaning||巡回检测days of heating period||采暖期天数deafener||消声器decibel(dB)||分贝degree-days of heating period||采暖期度日数degree of subcooling||过冷度degree of superheat||过热度dehumidification||减湿dehumidifying cooling||减湿冷却density of dust particle||真密度derivative time||微分时间design conditions||计算参数desorption||解吸detecting element||检测元件detention period||延迟时间deviation||偏差dew-point temperature||露点温度dimond-shaped damper||菱形叶片调节阀differential pressure type flowmeter||差压流量计diffuser air supply||散流器diffuser air supply||散流器送风direct air conditioning system 直流式空气调节系统direct combustion 直接燃烧direct-contact heat exchanger 汽水混合式换热器direct digital control (DDC) system 直接数字控制系统direct evaporator 直接式蒸发器direct-fired lithiumbromide absorption-type refrigerating machine 直燃式溴化锂吸收式制冷机direct refrigerating system 直接制冷系统direct return system 异程式系统direct solar radiation 太阳直接辐射discharge pressure 排气压力||discharge temperature 排气温度dispersion 大气扩散district heat supply 区域供热district heating 区域供热disturbance frequency 扰动频率dominant wind direction 最多风向double-effect lithium-bromide absorption-type refigerating machine 双效溴化锂吸收式制冷机double pipe condenser 套管式冷凝器down draft 倒灌downfeed system 上分式系统downstream spray pattern 顺喷drain pipe 泄水管drain pipe 排污管droplet 液滴drv air 干空气dry-and-wet-bulb thermometer 干湿球温度表dry-bulb temperature 干球温度dry cooling condition 干工况dry dust separator 干式除尘器dry expansion evaporator 干式蒸发器dry return pipe 干式凝结水管dry steam humidifler 干蒸汽加湿器dualductairconing ition 双风管空气调节系统dual duct system 双风管空气调节系统duct 风管、风道dust 粉尘dust capacity 容尘量dust collector 除尘器dust concentration 含尘浓度dust control 除尘dust-holding capacity 容尘量dust removal 除尘dust removing system 除尘系统dust sampler 粉尘采样仪dust sampling meter 粉尘采样仪dust separation 除尘dust separator 除尘器dust source 尘源dynamic deviation||动态偏差Eeconomic resistance of heat transfer||经济传热阻economic velocity||经济流速efective coefficient of local resistance||折算局部阻力系数effective legth||折算长度effective stack height||烟囱有效高度effective temperature difference||送风温差ejector||喷射器ejetor||弯头elbow||电加热器electric heater||电加热段electric panel heating||电热辐射采暖electric precipitator||电除尘器electricradian theating 电热辐射采暖electricresistance hu-midkfier||电阻式加湿器electro-pneumatic convertor||电—气转换器electrode humidifler||电极式加湿器electrostatic precipi-tator||电除尘器eliminator||挡水板emergency ventilation||事故通风emergency ventilation system||事故通风系统emission concentration||排放浓度enclosed hood||密闭罩enthalpy||焓enthalpy control system||新风)焓值控制系统enthalpy entropy chart||焓熵图entirely ventilation||全面通风entropy||熵environmental noise||环境噪声equal percentage flow characteristic||等百分比流量特性equivalent coefficient of local resistance||当量局部阻力系数equivalent length||当量长度equivalent[continuous A] sound level||等效〔连续A〕声级evaporating pressure||蒸发压力evaporating temperature||蒸发温度evaporative condenser||蒸发式冷凝器||evaporator||蒸发器excess heat||余热excess pressure||余压excessive heat ||余热cxergy||xexhaust air rate||排风量exhaust fan||排风机exhaust fan room||排风机室exhaust hood||局部排风罩exhaust inlet||吸风口exhaust opening||吸风口exhaust opening orinlet||风口exhaust outlet||排风口exaust vertical pipe||排气〕烟囱exhausted enclosure||密闭罩exit||排风口expansion||膨胀expansion pipe||膨胀管explosion proofing||防爆expansion steam trap||恒温式疏水器expansion tank||膨胀水箱extreme maximum temperature||极端最高温度extreme minimum temperature||极端最低温度Ffabric collector||袋式除尘器face tube||皮托管face velocity||罩口风速fan||通风机fan-coil air-conditioning system||风机盘管空气调节系统fan-coil system||风机盘管空气调节系统fan-coil unit||风机盘管机组fan house||通风机室fan room||通风机室fan section||风机段feed-forward control||前馈控制feedback||反馈feeding branch tlo radiator||散热器供热支管fibrous dust||纤维性粉尘fillter cylinder for sampling||滤筒采样管fillter efficiency||过滤效率fillter section||过滤段filltration velocity||过滤速度final resistance of filter||过滤器终阻力fire damper||防火阀fire prevention||防火fire protection||防火fire-resisting damper||防火阀fittings||(通风〕配件fixed set-point control||定值调节fixed support||固定支架fixed time temperature (humidity)||定时温（湿）度flame combustion||热力燃烧flash gas||闪发气体flash steam||二次蒸汽flexible duct||软管flexible joint||柔性接头float type steam trap||浮球式疏水器float valve||浮球阀floating control||无定位调节flooded evaporator||满液式蒸发器floor panel heating||地板辐射采暖flow capacity of control valve||调节阀流通能力flow characteristic of control valve||调节阀流量特性foam dust separator||泡沫除尘器follow-up control system||随动系统forced ventilation||机械通风forward flow zone||射流区foul gas||不凝性气体four-pipe water system||四管制水系统fractional separation efficiency||分级除尘效率free jet||自由射流free sillica||游离二氧化硅free silicon dioxide||游离二氧化硅freon||氟利昂frequency interval||频程frequency of wind direction||风向频率fresh air handling unit||新风机组resh air requirement||新风量friction factor||摩擦系数friction loss||摩擦阻力frictional resistance||摩擦阻力fume||烟〔雾〕fumehood||排风柜fumes||烟气Ggas-fired infrared heating 煤气红外线辐射采暖gas-fired unit heater 燃气热风器gas purger 不凝性气体分离器gate valve 闸阀general air change 全面通风general exhaust ventilation (GEV) 全面排风general ventilation 全面通风generator 发生器global radiation||总辐射grade efficiency||分级除尘效率granular bed filter||颗粒层除尘器granulometric distribution||粒径分布gravel bed filter||颗粒层除尘器gravity separator||沉降室ground-level concentration||落地浓度guide vane||导流板Hhair hygrometor||毛发湿度计hand pump||手摇泵harmful gas andvapo||有害气体harmful substance||有害物质header||分水器、集水器（、）heat and moisture||热湿交换transfer||热平衡heat conduction coefficient||导热系数heat conductivity||导热系数heat distributing network||热网heat emitter||散热器heat endurance||热稳定性heat exchanger||换热器heat flowmeter||热流计heat flow rate||热流量heat gain from lighting||设备散热量heat gain from lighting||照明散热量heat gain from occupant||人体散热量heat insulating window||保温窗heat(thermal)insuation||隔热heat(thermal)lag||延迟时间heat loss||耗热量heat loss by infiltration||冷风渗透耗热量heat-operated refrigerating system||热力制冷系统heat-operated refrigetation||热力制冷heat pipe||热管heat pump||热泵heat pump air conditioner||热泵式空气调节器heat release||散热量heat resistance||热阻heat screen||隔热屏heat shield||隔热屏heat source||热源heat storage||蓄热heat storage capacity||蓄热特性heat supply||供热heat supply network||热网heat transfer||传热heat transmission||传热heat wheel||转轮式换热器heated thermometer anemometer||热风速仪heating||采暖、供热、加热（、、）heating appliance||采暖设备heating coil||热盘管heating coil section||加热段heating equipment||采暖设备heating load||热负荷heating medium||热媒heating medium parameter||热媒参数heating pipeline||采暖管道heating system||采暖系统heavy work||重作业high-frequency noise||高频噪声high-pressure ho twater heating||高温热水采暖high-pressure steam heating||高压蒸汽采暖high temperature water heating||高温热水采暖hood||局部排风罩horizontal water-film syclonet||卧式旋风水膜除尘器hot air heating||热风采暖hot air heating system||热风采暖系统hot shop||热车间hot water boiler||热水锅炉hot water heating||热水采暖hot water system||热水采暖系统hot water pipe||热水管hot workshop||热车间hourly cooling load||逐时冷负荷hourly sol-air temperature||逐时综合温度humidification||加湿humidifier||加湿器humididier section||加湿段humidistat||恒湿器humidity ratio||含湿量hydraulic calculation||水力计算hydraulic disordeer||水力失调hydraulic dust removal||水力除尘hydraulic resistance balance||阻力平衡hydraulicity||水硬性hydrophilic dust||亲水性粉尘hydrophobic dust||疏水性粉尘Iimpact dust collector||冲激式除尘器impact tube||皮托管impedance muffler||阻抗复合消声器inclined damper||斜插板阀index circuit||最不利环路indec of thermal inertia (valueD)||热惰性指标（D值）indirect heat exchanger||表面式换热器indirect refrigerating sys||间接制冷系统indoor air design conditions||室内在气计算参数indoor air velocity||室内空气流速indoor and outdoor design conditions||室内外计算参数indoor reference for air temperature and relative humidity||室内温湿度基数indoor temperature (humidity)||室内温（湿）度induction air-conditioning system||诱导式空气调节系统induction unit||诱导器inductive ventilation||诱导通风industral air conditioning||工艺性空气调节industrial ventilation||工业通风inertial dust separator||惯性除尘器infiltration heat loss||冷风渗透耗热量infrared humidifier||红外线加湿器infrared radiant heater||红外线辐射器inherent regulation of controlled plant||调节对象自平衡initial concentration of dust||初始浓度initial resistance of filter||过滤器初阻力imput variable||输入量insulating layer||保温层integral enclosure||整体密闭罩integral time||积分时间interlock protection||联锁保护intermittent dust removal||定期除灰intermittent heating||间歇采暖inversion layer||逆温层inverted bucket type steam trap||倒吊桶式疏水器irradiance||辐射照度isoenthalpy||等焓线isobume||等湿线isolator||隔振器isotherm||等温线isothermal humidification||等温加湿isothermal jet||等温射流Jjet||射流jet axial velocity||射流轴心速度jet divergence angle||射流扩散角jet in a confined space||受限射流Kkatathermometer||卡他温度计Llaboratory hood||排风柜lag of controlled plant||调节对象滞后large space enclosure||大容积密闭罩latent heat||潜热lateral exhaust at the edge of a bath||槽边排风罩lateral hoodlength of pipe section||侧吸罩length of pipe section||管段长度light work||轻作业limit deflection||极限压缩量limit switch||限位开关limiting velocity||极限流速linear flow characteristic||线性流量特性liquid-level gage||液位计liquid receiver||贮液器lithium bromide||溴化锂lithium-bromide absorption-type refrigerating machine||溴化锂吸收式制冷机lithium chloride resistance hygrometer||氯化锂电阻湿度计load pattern||负荷特性local air conditioning||局部区域空气调节local air suppiy system||局部送风系统local exhaustventilation (LEV)||局部排风local exhaust system||局部排风系统local heating||局部采暖local relief||局部送风local relief system||局部送风系统local resistance||局部阻力local solartime||地方太阳时local ventilation||局部通风||local izedairsupply for air-heating||集中送风采暖local ized air control||就地控制loop||环路louver||百叶窗low-frequencynoise||低频噪声low-pressure steam heating||低压蒸汽采暖lyophilic dust||亲水性粉尘lyophobic dust||疏水性粉尘Mmain ||总管、干管main duct||通风〕总管、〔通风〕干管main pipe||总管、干管make-up water pump||补给水泵manual control||手动控制mass concentration||质量浓度maximum allowable concentration (MAC)||最高容许浓度maximum coefficient of heat transfer||最大传热系数maximum depth of frozen ground||最大冻土深度maximum sum of hourly colling load||逐时冷负荷综合最大值mean annual temperature (humidity)||年平均温（湿）度mean annual temperature (humidity)||日平均温（湿）度mean daily temperature (humidity)||旬平均温（湿）度mean dekad temperature (humidity)||月平均最高温度mean monthly maximum temperature||月平均最低温度mean monthly minimum temperature||月平均湿（湿）度mean monthly temperature (humidity)||平均相对湿度mean relative humidity||平均风速emchanical air supply system||机械送风系统mechanical and hydraulic||联合除尘combined dust removal||机械式风速仪mechanical anemometer||机械除尘mechanical cleaning off dust||机械除尘mechanical dust removal||机械排风系统mechanical exhaust system||机械通风系统mechanical ventilation||机械通风media velocity||过滤速度metal radiant panel||金属辐射板metal radiant panel heating||金属辐射板采暖micromanometer||微压计micropunch plate muffler||微穿孔板消声器mid-frequency noise||中频噪声middle work||中作业midfeed system||中分式系统minimum fresh air requirmente||最小新风量minimum resistance of heat transfer||最小传热阻mist||雾mixing box section||混合段modular air handling unit||组合式空气调节机组moist air||湿空气||moisture excess||余湿moisure gain||散湿量moisture gain from appliance and equipment||设备散湿量||moisturegain from occupant||人体散湿量motorized valve||电动调节阀motorized (pneumatic)||电（气）动两通阀-way valvemotorized (pneumatic)-way valve||电（气）动三通阀movable support||活动支架muffler||消声器muffler section||消声段multi-operating mode automtic conversion||工况自动转换multi-operating mode control system||多工况控制系统multiclone||多管〔旋风〕除尘器multicyclone||多管〔旋风〕除尘器multishell condenser||组合式冷凝器Nnatural and mechanical combined ventilation||联合通风natural attenuation quantity of noise||噪声自然衰减量natural exhaust system||自然排风系统natural freguency||固有频率natural ventilation||自然通风NC-curve[s]||噪声评价NC曲线negative freedback||负反馈neutral level||中和界neutral pressure level||中和界neutral zone||中和界noise||噪声noise control||噪声控制noise criter ioncurve(s)||噪声评价NC曲线noisc rating number||噪声评价NR曲线noise reduction||消声non azeotropic mixture refragerant||非共沸溶液制冷剂non-commonsection||非共同段non condensable gas ||不凝性气体non condensable gas purger||不凝性气体分离器non-isothermal jet||非等温射流nonreturn valve||通风〕止回阀normal coldest month||止回阀normal coldest month||累年最冷月normal coldest -month period||累年最冷三个月normal hottest month||累年最热月（３）normal hottest month period||累年最热三个月normal three summer months||累年最热三个月normal three winter months||累年最冷三个月normals||累年值nozzle outlet air suppluy||喷口送风number concentration||计数浓度number of degree-day of heating period||采暖期度日数Ooctave||倍频程/ octave||倍频程octave band||倍频程oil cooler||油冷却器oill-fired unit heater||燃油热风器one-and-two pipe combined heating system||单双管混合式采暖系统one (single)-pipe circuit (cross-over) heating system||单管跨越式采暖系统one(single)-pipe heating system||单管采暖系统pne(single)-pipe loop circuit heating system||水平单管采暖系统one(single)-pipe seriesloop heating system||单管顺序式采暖系统one-third octave band||倍频程on-of control||双位调节open loop control||开环控制open return||开式回水open shell and tube condenser||立式壳管式冷凝器open tank||开式水箱operating pressure||工作压力operating range||作用半径opposed multiblade damper||对开式多叶阀organized air supply||有组织进风organized exhaust||有组织排风organized natural ventilation||有组织自然通风outdoor air design conditions||室外空气计算参数outdoor ctitcal air temperature for heating||采暖室外临界温度outdoor design dry-bulb temperature for summer air conlitioning||夏季空气调节室外计算干球温度outdoor design hourly temperature for summer air conditioning||夏季空气调节室外计算逐时温度outdoor design mean daily temperature for summer air conditioning||夏季空气调节室外计算日平均温度outdoor design relative humidityu for summer ventilation||夏季通风室外计算相对湿度outdoor design relative humidity for winter air conditioning||冬季空气调节室外计算相对湿度outdoor design temperature ture for calculated envelope in winter冬季围护结构室外计算温度outdoor design temperature ture for heating||采暖室外计算温度outdoor design temperature for summer ventilation||夏季通风室外计算温度outdoor design temperature for winter air conditioning||冬季空气调节室外计算温度outdoor design temperature for winter vemtilation||冬季通风室外计算温度outdoor designwet-bulb temperature for summer air conditioning夏季空气调节室外计算湿球温度outdoor mean air temperature during heating period||采暖期室外平均温度outdoor temperature(humidity)||室外温（湿）度outlet air velocity||出口风速out put variable||输出量overall efficiency of separation||除尘效率overall heat transmission coefficient||传热系数ouvrflow pipe||溢流管overheat steam||过热蒸汽overlapping averages||滑动平均overshoot||超调量Ppackaged air conditioner||整体式空气调节器packaged heat pump||热泵式空气调节器packed column||填料塔packed tower||填料塔panel heating||辐射采暖parabolic flow character||抛物线流量特性isticparallel multiblade damperin||平行式多叶阀parameter detection||参数检测part||通风〕部件partial enclosure||局部密闭罩partial pressure of water vapor||水蒸汽分压力particle||粒子particle counter||粒子计数器particle number concentration||计数浓度particle size||粒径particle size distribution||粒径分布particulate||粒子particulate collector||除尘器particulates||大气尘passage ventilating duct||通过式风管penetration rate||穿透率percentage of men，women and children||群集系数and childrenpercentage of possible sunshine||日照率percentage of return air ||回风百分比cerforated ceiling air suppyl||孔板送风perforated plate tower||筛板塔periodic dust dislodging||定期除灰piece||(通风〕部件pipe fittings||管道配件pipe radiator||光面管散热器pipe section||管段pipe coil||光面管放热器pitot tube||皮托管plate heat exchanger||板式换热器plenum chamber||静压箱plenum space||稳压层plug||丝堵plume||烟羽plume rise height||烟羽抬升高度PNC-curve[s]||噪声评价PNC曲线pneumatic conveying||气力输送pueumatic transport||气力输送pneumatic valve||气动调节阀pneumo-electrical convertor||气-电转换器positioner||定位器positive feedback||正反馈powerroof ventilator||屋顶通风机preferred noise criteria curve[s]||噪声评价PNC曲线pressure drop||压力损失pressure enthalpy chart||压焓图pressure gage||压力表pressure of steam supply||供汽压力pressure reducing valve||减压阀pressure relief device||泄压装置pressure relief valve||安全阀pressure thermometer||压力式温度计pressure volume chart||压容图primary air fan-coil system||风机盘管加新风系统primary air system||新风系统primary retirn air||一次回风process air conditioning||工艺性空气调节program control||程序控制proportional band||比例带proportional control||比例调节proportional-integral (PI)control||比例积分调节proportional-integralderivative(PID)control||比例积分微分调节protected(roof)monitor||避风天窗psychrometric chart||声级计pulvation action||干湿球温度表push-pull hood||焓湿图pulvation action||尘化作用push-pull hood||吹吸式排风罩Qquick open flow characteristic||快开流量特性Rradiant heating||辐射采暖radiant intensity||辐射强度sadiation intensity||辐射强度radiator||散热器radiator heating||散热器采暖radiator heating system||散热器采暖系统radiator valve||散热器调节阀rating under air conditioning condition||空调工况制冷量rcactive muffler||抗性消声器receiver||贮液器receiving hood||接受式排风罩reciprocating compressor||活塞式压缩机recirculation cavety||空气动力阴影区recording thermometer||自记温度计reducing coupling||异径管接头reducing valve||减压阀reentrainment of dust ||二次扬尘refrigerant||制冷剂[refrigerating] coefficient of performance (COP)||(制冷)性能系数refrigerating compressor||制冷压缩机refrigerating cycle||制冷循环refrigerating effect||制冷量refrigerating engineering||制冷工程refrigerating machine||制冷机refrigerating medium||载冷剂refrigerating planttoom||制冷机房refrigerating station||制冷机房refrigerating system||制冷系统refrigeration ||制冷regenerative noise||再生噪声register||百叶型风口regulator||调节器reheat air conditioning system||再热式空气调节系统relative humidity||相对湿度relay||继电器remote control||遥控resistance of heat transfer||传热阻resistance thermometer||电阻温度计resistance to water vapor permeability蒸汽渗透阻resistance to water vapor permeation||蒸汽渗透阻resistive muffler||阻性消声器resistivity||比电阻resonance||共振resonant frequency||共振频率response curve of controlled plant||调节对象正升曲线teturn air||回风return air inlet||回风口return branch of radiator||散热器回水支管return fan||回风机return flow zone||回流区return water temperataure||回水温度reverse Carnot cycle||逆卡诺循环reversed return system||同程式系统reversible cycle||可逆循环rim exhaust||槽边排风罩rim ventilation||槽边通风riser||立管roof ventilator||筒形风帽room absorption||房间吸声量room air conditioner||房间空气调节器rotameter||转子流量计rotary dehumidifier||转轮除湿机rotary heat exchanger||转轮式换热器rotary supply outlet||旋转送风口rotating air outlet with movable guide vanes||旋转送风口roughness factor||相对粗糙度rubber shock absorber||橡胶隔振器running means||滑动平均Ssafety valve||安全阀samling hole||测孔sampling port||测孔saturated steam||饱和蒸汽saturation humidity ratio||饱和含湿量screw compressor||螺杆式压缩机screwnipple||丝对screwed plug||丝堵scondary refrigerant||载冷剂secondary return air||二次回风selective control system||选择控制系统selector||选择器self-contained cooling unit||冷风机组self learning system||自学习系统sensible cooling||等湿冷却sensible heat||显热sensible heating||等湿加热sensing element||敏感元件sensor||传感器sequence control||程序控制set point||给定值settling chamber||沉降室setting velocity||沉降速度shading coefficient||遮阳系数shell and coil condenser||壳管式冷凝器shell and tube condenser ||壳管式冷凝器shell and tube evaporator||壳管式蒸发器sholder nipple||长丝shutter||百叶窗sidehood||侧吸罩sidewall air supply||侧面送风sieve-plate column||筛板塔single duct air conditioning system||单风管空气调节系统。
2014高考英语阅读能力(2)--科普类
2014高考英语阅读能力（2）—-科普类温暖的海水使南极大部分冰架消融Ocean waters melting the undersides of Antarctic ice shelves, not icebergs calving into the sea，are responsible for most of the continent’s ice loss, a study by UC Irvine and others has found. The first comprehensive survey of all Antarctic ice shelves discovered that basal melt, or ice dissolving from underneath, accounted for 55 percent of shelf loss from 2003 to 2008 —— a rate much higher than previously thought。
Ice shelves, floating extensions of glaciers，fringe 75 percent of the vast，frozen continent。
The findings，to be published in the June 14 issue of Science, will help scientists improve projections of how Antarctica, which holds about 60 percent of the planet’s fresh water locked in its massive ice shee t，will respond to a warming ocean and contribute to sea level rise。
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Ice force spectrum on narrow conical structuresQianjin Yue a,⁎,Yan Qu b ,Xiangjun Bi a ,KärnäTuomo caDalian University of Technology,Dalian,ChinabResearch center of CNOOC,China cKarna Research and Consulting,FinlandReceived 2December 2006;accepted 6February 2007AbstractThis paper presents an ice force spectrum model for narrow conical offshore structures deployed in ice infested areas.The force spectrum is developed from a spectral analysis of ice load data that was obtained in full-scale tests on the JZ20-2platform in Bohai Bay.The results show that the power spectral density (PSD)function of the ice force has characteristics of both a narrow band and a wide band random process when the ice sheets fail by bending and the broken ice pieces are totally cleared up.The PSD function of the ice force can be approximated by the Neumann spectrum.This spectrum is the basis for the ice force model that is presented in this paper.This model can be used in a dynamic analysis of narrow,conical offshore structures that are exposed to the action of drifting ice floes.©2007Published by Elsevier B.V .Keywords:Oil platform;Ice induced vibration;Ice load spectrum;Conical structures1.IntroductionThe concept of adding ice-breaking cones on cylindrical structures was proposed in 1970's.It has been demonstrated by many researchers that the ice force on a conical structure is smaller than the force on a cylindrical structure of similar size (Ralston,1977;Frederking and Schwarz,1982;Sodhi et al.,1987;Hirayama and Obara,1986;Wessels and Kato,1988;Shkhinek et al.,1996;Matskevitch,2002;Barker et al.,2005;Gravesen et al.,2005).The main reason for the reduction in the ice force is that a well-designed cone can change the ice failure mode from crushing tobending.Encouraged by this advantage,ice-breaking cones have been installed on offshore structures such as piers of the Confederation bridge in the Southern Gulf of St Lawrence,offshore wind turbine foundations in Denmark and oil platforms in the Bohai Bay,China.Ice force measurements have been carried out on some full-scale structures.Test results published by Määttänen (1996),Brown (1997),Yue and Bi (1998,2000)show that the ice force has been reduced by the cone as the failure mode of the level ice changes from crushing to bending and higher ice load could also be caused when the ice ridge interaction is concerned.Brown and Määttänen (2002)state that besides reducing the peak values of the ice force caused by the level ice,a cone also almost completely eliminates ice induced vibrations,especially continuous resonant vibrations.However a different phenomenon was found in full-scale tests that were carried out in the BohaiBay.Cold Regions Science and Technology 49(2007)161–169/locate/coldregions⁎Corresponding author.E-mail addresses:yueqj@ (Q.Yue),quyan@ (Y .Qu),bixj@ (X.Bi),tuomo.karna@ (K.Tuomo).0165-232X/$-see front matter ©2007Published by Elsevier B.V .doi:10.1016/j.coldregions.2007.02.002Measurements show that after cones were installed on some structures,the steady state vibration known as self-excited vibration was avoided.However,another kind of cyclic ice force appeared and ice induced vibrations still prevailed(Yue and Bi,1998,2000, 2003).This has been a problem for the structures concerned.The vibration has loosened flanges and caused gas leaks in pipelines of the platforms.Compared to other dynamic environmental forces such as wave and wind,ice force is the most serious environmental action on the platforms of the Bohai Bay.Both experimental and theoretical researches have been conducted to better understand the dynamic excitation mechanisms.Yue and Bi(2000)developed a deterministic ice force function based on the analysis of ice force data and the failure process of the icesheet.Qu et al.(2003)studied the random features of the ice force and developed a random ice force function as a simple representation of the real time-varying ice force.Dynamic environmental forces can be characterized either in the time domain or in the frequency domain.A frequency domain method is often used for stochastic environmental forces.Sundararajan and Reddy(1973) initiated the application of a frequency domain analysis of dynamic ice actions.Ou and Duan(1996)studied a spectral density function and its parameters in the case where ice forces act on vertical structures.Kärnäet al. (2004)derived a formula for spectral density functions of the crushing ice force on vertical structures.Time–frequency domain analysis has also been made to the full-scale test data obtained at lighthouse in the Baltic Sea(Bjerkås,2006).The nonstationary state of the ice loads was considered in the analysis.The present paper presents a spectral model for dynamic ice forces on narrow conical structures.The model is developed using results of spectral analyses of ice force data collected in full-scale test in the Bohai Bay.2.Ice force measurementsThe results of this paper are largely based on the full-scale test data that were measured in five winters from 2000to2004on the JZ20-2oil platform.The platform is a four legs jacket platform located in the Bohai Bay (Fig.1).In common winters,the sea area is covered by first year level ice and rubble ice for2months.The thickness of the parent ice sheets varies from5cm to20cm. Driven by the wind and current,the ice sheets move at variable velocities that can amount up to1m s−1.Ice loads measurement on the JZ20-2MUQ platform (Fig.2)is part of the Sea Ice Management project funded by China National Oil Bohai Company.The objective of the project is to evaluate how the sea ice affects oil platforms.In the test,dynamic response of the platform is measured by several accelerometers placed on decks of different elevations.Ice forces are recorded using ice force panels designed by Dalian University of Technology.Ice conditions and ice failure processes are recorded by3video cameras and direct site observation.The detailed arrangements of the full-scale test have been described by Yue and Bi(1998, 2000).Ice-breaking cones on the JZ20-2MUQ platform (Fig.3)are acting either upward or downward depending on the phase of the tidal current.The slopes of these two cones are60°and45°as shown in Fig.3. Six force panels,each covering an area of8°of the cone surface are installed on one of the upward cones.The load area of the panel is about0.27m by0.7m.The load panels are instrumented with two2strain gauge load cells under a rigid cover.In the tests,ice forces and the response signals of the structure are recorded synchronously and continuously. Every10min the data are saved as a file on a computer throughout the winter.The sampling rate of the data is 64Hz.Video records showing ice-cone interactions are stored on another PC.This data has been used to study the ice failure mechanisms and to evaluate the ice thickness as well as ice velocity.3.Analysis of ice forces in time domainThe ice failure process observed on the MUQ platform has been described by Yue and Bi(1998).A typical feature of the ice failure mechanism isthat Fig.1.Map of the Bohai sea with the location of the JZ20-2oil platform.162Q.Yue et al./Cold Regions Science and Technology49(2007)161–169broken ice pieces are cleared up in each circle and do not ride-up and pile up on the cone.A similar phenomenon was found by Izumiyama et al.(1991)in the model tests. Fig.4shows a time-window of an ice force time series recorded by six load panels during a typical ice failure process.The figure shows the normal component of the ice force.It should be noticed that the load panels worked well in this test.Accordingly,a large amount of data has been recorded.Yue and Bi(1998)proposed that the ice force can be simplified as a series of pulses with constant ice force amplitudes and periods.Qu et al.(2006)discussed how to use the load panel data to derive a random total ice load model on the narrow cone.In the present work both of these parameters are random variables.The defini-tions of the force amplitudes and periods are shown in Fig.5.In this figure,the periods of the ice force are shown as T(i)and the force amplitudes as F(i).Lau et al.(1999)and Li et al.(2003)describe a method to determine the period as a function of the breaking length and the ice velocity.The present study concerns narrow cones where the ice rubble created by the failure process is cleared away in each loading cycle.Therefore,the ice force fluctuates between the zero level and a random peak value F0.If the cone is wider,the forces would drop after each failure to a certain level that is unequal to zero.This is caused by frictional and gravity forces associated with the post-failure behavior of the broken ice(Wessels and Kato,1988).Qu et al.(2003)analyzed the statistical distributions of the periods and amplitudes of the ice force.This information was used to determine the power spectral density function(PSD)of the ice force.To derive the PSD function of the ice load,54events from the field test were selected for the analysis.The time durationof Fig.3.Ice-breaking cone on MUQ platform and loadpanels.Fig.2.JZ20-2MUQ&MNW platform and sketch of the measurement system on the platforms.163 Q.Yue et al./Cold Regions Science and Technology49(2007)161–169those events varies from 3to 10min.The ice thickness,ice velocity,ice strength and water level were almost constant during each of these events.Therefore,the ice failure process of each event was stable and ice force was a stationary random process during each event.It should be noticed that the period T and,accord-ingly,the time function F (t )depend on the ice thickness and ice velocity.Therefore,the 54events were categorized into different groups in accordance with the ice thickness and velocity in the analysis.It was then assumed that the ice failure process is ergodic (Kajaste-Rudnitski,1995).This assumption implies that a time signal obtained in an event with fixed ice thickness and ice velocity represents a full ensemble of events with the same values of thickness and velocity.Accordingly,the random characteristics of the ice action process were obtained for a limited number of thickness and velocity by analyzing one or a few time signals that belonged to a specific group.The assumption of ergodicity was necessary here because the number of recorded loading events was limited.4.Spectral analysis of ice forcesConsider a general case where an offshore structure is subjected to a random dynamic force.The time-varying force can be expressed as the sum of the average force level and a time-varying force component.Assume that G F (f )denotes the power spectral density function of the time-varying force component and G Y (f )is the power spectral density of the dynamic component of the response.The response G Y (f )term can be obtained by the equation G Y ðf Þ¼H ðf ÞG F ðf ÞH ⁎T ðf Þð1Þwhere H (f )is a complex valued frequency response function that accounts for the dynamic properties of the structure (Newland,1975).This equation shows,in the frequency domain,the relationship between the time-varying component of the ice force and the correspond-ing response.The total response is obtained by combining the static and dynamic response.In this paper,the determination of the power spectral density function of the excitation in the case where a level ice is acting on a conical structure will be discussed.When such a function is available,the dynamic response of an offshore structure is obtained from Eq.(1).Fig.6shows the PSD function of the ice force obtained in one event.The PSD function was obtained by applying Welch's averaged modified periodogram method to the ice force record (Bendat and Piersol,2000).The force signals were divided into their mean components and the time-varying components firstly.Then the time-varying components of the force data was segmented into sections comprising 1024samples,each with a 50%overlap.As the sample frequency of the ice force data is 64Hz,the time duration of eachdataFig.4.Ice forces recorded by the load panels on JZ20-2platform at 08:14Jan 4,2003.The ice thickness and drift speed is about 12cm and 40cm s −1respectively.The data in different channels are correspond-ing to ice forces recorded by different loadpanels.Fig.5.Ice forces recorded by the load panels and definition of periods and amplitudes of the ice force.164Q.Yue et al./Cold Regions Science and Technology 49(2007)161–169section is 16s.Each section is windowed by a Hamming window of 0.5segment's length.It can be seen from Fig.6that the energy of the ice force is concentrated in a frequency range of 0.3Hz to 3Hz.The first natural frequencies of most jacket leg structures in the Bohai Bay are in this range.Therefore,those structures with ice-breaking cones in Bohai bay are sensitive to the dynamic ice forces.Several mathematical formulas can be used to approximate the PSD function shown in Fig.6.In this paper,the formula developed by Neumann (1952)is used.This spectrum was originally developed to simulate sea wave spectra.The Neumann spectrum is expressed asG F ðf Þ¼A f p exp −B 1f q ð2Þwhere G F (f )is the PSD function of the ice force.Thecoefficients A ,B ,p and q are experimental parameters.By using the Neumann spectrum as trial formula to the ice load PSD,a curve fitting method can be used to obtain values of the model parameters.Fig.6shows a comparison between the PSD curves obtained from the test data and from the results of curve fitting.It can be seen that the Neumann's formula agrees well with the force spectrum result obtained from the test data.It should be noted that some minor peaks of the PSD can be detected in the spectral analysis for some force records due to the natural energy distribution of the periodic impulse-like signals.However those minor peaks will become weak when the length of the force records increased as well as the signal become more random.In this paper,those minor peaks were ignored by using the Neumann's formula as mathematical represen-tation of the ice load spectrum in order to cover the more general load condition and simplify the application of the load spectrum model.5.Parameters of the ice load spectrumTo apply the ice load spectrum for different structures exposed to variable ice actions,some parameters that consider both the ice and structure should be involved in the load spectrum.It is noticed that parameters of the ice force could be incorporated into the spectrum formula by studying relationships between the spectrum para-meters and ice force parameters.The basic features of a one-sided spectral density function G F (f )can be characterized by using spectral moments,which are defined asm r ¼Z lf r G F ðf Þd f r ¼0;1;2;N nð3Þwhere m r is the r th spectral moment.However,higher order spectral moments are difficult to be analyzed in practice.Therefore a simplified method is adopted in this paper to determine the load spectrum parameters.The simplified method is based on slope coefficients,peak frequency and the 0th-order spectral moment of the ice load spectrum.5.1.Slope coefficient of the ice load spectrum The Neumann spectrum is composed of two parts,A /f p and exp(−B /f q ),which correspondingly deter-mine the shapes of the high frequency and low frequency parts of the spectrum.The parameters p and q are slope coefficients of these two parts.As p and q have only a minor effect on the frequency range of the ice load's energy distribution,the mean values obtained from the curve fitting result of the test data can be used as the values of p and q in the spectral model.Fig.7shows histograms of p and q obtained from the curve fitting result.The mean values were determine as p ¼3:5ð4:2Þq ¼0:64ð4:1Þ5.2.Peak frequency of the ice load spectrum Peak frequency of the ice load spectrum is defined as the frequency point where the spectrum curve achieves its maximum value.It determines position of the load spectrum in frequency domain.If the peakfrequencyFig.6.One-sided PSD functions of ice force obtained from load panel data and Neumann's formula.165Q.Yue et al./Cold Regions Science and Technology 49(2007)161–169approaches the natural frequency of the structure,thedynamic response will increase.In the time domain,periods of the ice force are distributed around the mean period.Therefore,the peakfrequency f m and the mean period T¯are the correspond-ing parameters in the frequency and time domains.They are related to each other as f m ¼1Tð5ÞThe relationship shown in Eq.(5)was verified by the test data as shown in Fig.8.In Neumann's formula,the peak frequency can be obtained by setting the derivative of Eq.(2)equal to zero.Hence,the equation d G F (f )/d f =0yieldsf m ¼Bq p 1=q ð6ÞInserting Eq.(5)into Eq.(6)and considering the results shown in Eqs.(4.1),(4.2)we can express the model parameter B as B ¼5:47¯T−0:64ð7Þ5.3.The 0th-order spectral momentThe 0th-order spectral moment m 0defined in Eq.(3)when r =0is an important parameter for the spectralanalysis of a random excited linear system.According to the definition,0th-order spectral moment is also variance of the ice force time series.m 0¼Z lG F ðf Þd x ¼D ½F ðt Þ ð8Þwhere D [F (t )]is variance of the ice force time series.Itis of interest to study the relationship between the variance of the ice forces and ice force parameters.The result can be used to determine the ice load spectrum parameters.As discussed by Qu et al.(2003),ice forces of narrow conical structures are composed of similar ice force pulses with random parameters.The ice force F (t )can be expressed as F ðt Þ¼X N i ¼1f i ðt −t 0i Þð9Þwhere N represents the length of the loading function,t 10=0and t 01¼P i ¼1j ¼1T j for i >1.The function f i (t )is an ice force model for one event of ice failure.One of the plausible possibilities to define this function is given byf i ðt Þ¼6F 0i T i t 0<t <T i 62F 0i −6F 0i T i t T i 6<t <T i30T i <t <T i 8>>>>><>>>>>:ð10Þwhere F 0i (i =1,2,3,…,n )denotes the random ice force amplitudes and T i is the random ice force period.Experiments show that the force amplitude and the period have only a weak correlation with each other (Qu et al.,2003).The data also shows that the period and the amplitude can be assumed to follow two independent normaldistributions.Fig.7.(a).Distribution of parameter p .(b).Distribution of parameter q.Fig.8.The mean value T¯of the ice force period as a function of the peak frequency f m of the PSD function of the ice force.166Q.Yue et al./Cold Regions Science and Technology 49(2007)161–169The variance of the ice force is defined in time domain asD ½F ðt Þ ¼EF 2ðt ÞÄÅ−E 2½F ðt Þð11Þwhere E [·]is the expectation operator.Under the assumption that the period and the force magnitude are independent and normally distributed,Eq.(10)can be used to show that the two components of the right side of Eq.(11)are given byE 2½F ðt Þ ¼¯F2036ð12:1ÞE ½F 2ðt Þ ¼¯F209þr 2F 09ð12:2Þwhere F ¯0and σF 02are correspondingly the mean and variance of the force amplitudes F 0.Inserting Eq.(12.1),(12.2)in to Eq.(11)yieldsD ½F ðt Þ ¼¯F 2012þr 2F09ð13ÞStatistical analysis of the field data in Bohai bayshows that the standard deviation of the ice force amplitude is about 0.4times the mean of the ice force amplitude (Qu et al.,2006).Therefore,m 0¼D ½F ðt Þ c 0:1¯F20ð14ÞFig.9compares the Eq.(14)with the field data.The 0th-order spectral moment can be calculated for the Neumann spectrum as m 0¼A q C ½ðp −1Þ=qB ðp −1Þ=qð15ÞWhere Γ(x )is the gamma function.Inserting the obtained values on the constants p and q into (Eq.(15))yieldsm 0¼8:33AB −3:9ð16ÞInserting Eqs.(7)and (14)into Eq.(16)yields A ¼10¯F20¯T −2:5ð17ÞTherefore,the parameter A of the ice load PSDmodel can be determined by the ice force parameters F¯0and T¯.6.Spectral model for the ice force on a cone The results obtained above can be combined to obtain a spectral model for the ice force action on a cone.Inserting Eqs.(4.1),(4.2),(7)and (17)in to Eq.(2)yields,G F ðf Þ¼10¯F 20¯T −2:5f exp −5:47¯T −0:641f ð18ÞEq.(18)gives the ice load PSD model as a one-sidedspectral density function.The mean values F¯0and T ¯of the force magnitude and period are used as the parameters of this equation.They depend on the geometry of the cone,ice thickness and ice strength.Eq.(18)is a dimensional expression.When the frequency,time and force are inserted correspondingly in the dimensions [Hz],[s]and [kN],the spectral density function has the dimension [kN 2/Hz].Fig.10shows a comparison between the PSD function obtained from test data and as determined by Eq.(18).The comparison shows that Eq.(18)agrees well with the PSD function obtained from the testdata.Fig.9.The relationship between the ice force variance and theamplitudes of the iceforce.Fig.10.The PSD function obtained from test data and from Eq.(18).167Q.Yue et al./Cold Regions Science and Technology 49(2007)161–169Eq.(18)in connection with Eq.(1)can be used to obtain the dynamic component of the total structural response.The total response can be obtained by combining the dynamic component with the static component that corresponds to the mean level of the time-varying ice force.Fig.11shows comparisons between the responses measured in the filed tests and the responses calculated by using the PSD function as input to the finite element model of the platform.It can be found from the figure that the responses obtained from the PSD function agree well with the test data for the 1st and 4th events.However,the response calculated in the 2nd and 3rd events is bigger than the test data.The overestimation of the response may be induced by many reasons such as the ice is not as uniform as we expected.As the main parameters used in the load spectral model are mean magnitudes and periods of the ice force,the improve-ment of the ice load spectrum model can be expected by improving the study to the relationship between the ice failure process and the ice load characteristics.This is not intended to be solved in this paper because it is more fundamental to this paper.7.ConclusionWhen ice acts on the ice-breaking cones of the JZ20-2platform in the Bohai Bay,the broken ice pieces are cleared up and seldom pile up on the cone.Under these conditions the ice force is periodic and creates vibrations in the structure.Field measurements of the ice forces have been analyzed both in 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