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文胸罩杯与胸部形态的适体度研究张龙琳(西南大学纺织服装学院,重庆400716)摘 要:以文胸的主体部分 罩杯为研究对象,根据标准人体胸部模型,结合文胸基本纸样设计方法制作一系列罩杯白坯布样,通过拟合标准人体胸部模型与罩杯白坯布样的实验,针对文胸罩杯的不同样板因素对文胸适体度的影响进行了相应的研究。
分别以下杯缘和下杯高为定量进行两组实验,从正面和侧面对人体胸部模型着装效果进行对比,研究了下杯高、罩杯省以及下杯缘对文胸罩杯与胸部形态适体度的影响,指出在文胸罩杯的结构设计过程中,三者间存在一定的非线性数量影响关系。
关键词:罩杯;下杯高;下杯缘;罩杯省;适体度中图分类号:T S941.2 文献标识码:A文章编号:1673-0356(2009)03-0084-04收稿日期:2009-03-03;修回日期:2009-04-12基金项目:西南大学实验室创新项目(2008)19号作者简介:张龙琳(1976-),男,工学硕士,服装系主任,主要研究方向为数字化服装技术、纺织服装产业经济。
文胸是由罩杯、前侧片、后拉片、鸡心、肩带、调整环、钢圈、捆条和钩扣几部分组成[1](如图1所示),并且每个组成部分都有其独特的功能。
罩杯是文胸的主体部位,除了包容乳房,还具备推胸、隆胸、方便运动等功能。
由于乳房是形成女性整体胸部形态的最复杂部分,文胸罩杯的适体性设计进而成为影响文胸适体度的最关键部分。
本论文选取了影响文胸罩杯适体度的样板因素[2] 下杯高、下杯缘与罩杯省进行相应的实验设计分析。
图1文胸的基本结构1 标准人体胸部模型的建立1 1 人体胸部形态分析1 1 1生理特征分析乳房是女性上体唯一没有骨骼支撑的器官,也是女性身体最丰满、最能体现女性魅力的部位,主要由乳腺、脂肪以及皮肤组成,而胸部的脂肪中心带则是文胸结构设计的主要依据(如图2所示)。
脂肪带的形态直接决定文胸罩杯的外部形态和内部结构。
1 1 2形态特征分析女性乳房的外观形态大致可以用高度、宽度、朝向和位置来描述,但很难做到精确。
1.Bill of lading 提单Definition:Bill of lading is a document given by a shipping company,representboth a receipt for thegoods siped and a contract for shipment between the shipping companyand the sipper.it is also adocument of title to the goods,giving the holder or the assigne theright to possessionof the goods.2.Marketing 市场营销Definition:Marketing is the process of planning and executing the conception,pricing,promouon ,and distribution of goods and services to create exchanges that satisfy individual and organizational objectives.3.D/P 付款交单Definition:D/P is short for"document against payment.Under this payment method,the exporter is to ship the goods ordered and delivered the relative shipping documents to thebuyer abroad through the remitting bank and the collecting bank with instructions not torelease the documents to the buyer until the payment lorthe goods is made.4.QA 品质/质量保证Definition:QA is short for quality assurance,it is about how a business can design the way a pro duct or services is produced or delivered to minimize the chances that output will beup-standard.5.Flexible exchange rates 浮动汇率Definition:A flexible exchange rate means the government does not enter the foreign exchange markets and leaves the determination of exchange rates up to currency trades.The price of its currency is allowed to rise and fall as market forces dictate.1.Parternship；合作关系A parternship is a legal relationship between persons arising on apofi-motivated business.a cooperative relationship between people or groups who agree to share responsibility for achieving some specific goal2.manegement 管理人员Definition:Management is defined as the application of planning,organizing,directing,and Controlling functions in the most effient manner possible to accomplish meaningful organizational objectives.3.HR management 人力资源管理Definition:The human resource management is an ongoing procedure that tries to keep the Organization suplied with the right people in the right positions.4.Documentary Credit 跟单信用证A Documentary Letter of Credit is a written undertaking given by a bank on behalf of an Importer to pay the Exporter a given sum of money with in a specified time,providing thatthe Exporter presentsdocuments which comply with the terms laid down in the Letter of Credit. 5.Draft 汇票Defnition:A draft is simply an order write by an exporter intruting an importer,or importer' sagent,to pay a specified amount of money at a specified time.Shipping document：运输单据(运输单证）shipping documents also as transport documents,are legal documents that are utilized in the process of transporting goods from one location to another.2.certificate of origin：原产地证书（证明）is document used in international trade,completed by the exporter,and certificated by a recognized issuing body,attesting that the goods in a particular export shipment have beenproduced,manufactured or processed in a particular country.3.insurance policy：保单(保险合同/大保单)is a formal contract-document between the insurer and the insured,known as the policy holder, which determines the claims which the insurer is legally required to pay.5.customer equity：顾客资产is the value of potential future revenue generated by a company's customers in a lifetime.l.sole/individual proprietorship:独资经营Detnition:It is a type of enterprise that is owned and run by one natural person.The owner is in Direct control of all elements and is legally accountable for the finances of such business and this may include debts,loans,loss,etc.2.Productivity:生产力It is the rate at which goods are produced.(or having thẻpower to produce)3.broker：代理/中介：A broker is a person whose job is to buy and sell shares,foreign money,or goods for other people.4.Fixed assets：固定资产are assets which a company uses on a continuous basis,such as properly and machinery.5.Cash on delivery:货到付款Collecting the charges upon delivery.1.anti-dumping duty:反倾销税is an extra duty levied temporarily on the imported commodity in dumping to protect home industry and market against the import commodity in large quantity and cheap price.2.Transnational corporation跨国公司refers to large international enterprise consisting of entities in two ormore countries,that operates manufacturing,sales and other business.3.Invisible trade:无形贸易trade of services rather than actual goods,for example,banking,insurance,and professional service,etc.4.Balance of payment:国际收支A statement that summarizes an economy's transactions with the rest of the world for a specified time period.1.CPI,消费价格指数消费物价指数Consumer price index measures changes in the price level of market basket of consumer goods and services purchased by households.2.LLC, 有限责任公司Limited liability company a business structure that combines the pass-through taxation of apartner ship or sole proprietorship with the limited liability of a corporation.3.FOB,离岸价格/船上交货价格Free On Board is a shipping term which indicates that the supplier pays the shipping costs(and usually also the insurance costs)from the point of manufacture to a specified destination,at Which point the buyer takes responsibility.4.B2B,企业对企业的电子商务模式Business-To-Business is a transaction that occurs between two companies,as opposed to a transaction involving a consumer.The term may also describe a company that provides goods or s ervices for another company.5.Definition:借记卡/提款卡Debit card is a card which allows customers to access their funds immediately electronically.With a debit card,you can immediately take money out of your checking account either through purcha ses at a store or through an ATM.1.A CEO首席执行官(chief executive fficer)is the position of the most senior corporate officer,executive,leader or administrator in charge of managing an organization.2.Human resource:人力资源In a company or other organization,the department of human resources is the department take on ponsibility for the recruiting,training,and welfare of the staff.bor market劳动力市场is the market in which workers compete for jobs and employers compete for workers.3.V AT增值税(value added tax)is a tax that is added to the price of goods or services.4.A balance sheet is a written statement of the amount of money and property that a company op erson has,including amounts of money that are owed or are owing.资产负债表5.Brand loyalty 品牌忠诚:The tendency to always buy a particular brand.2.Joint venture合资公司A business activity in which2or more companies have invested together.3.Quota:定额Quanttative restrictions imposed by one country on imports of a certain type from another country.4.marketing mix:营销组合A comprehensive plan or strategy covering product price,promotion and place,usually summarized as the4Ps".of marketing.5.Acqusition :收购Getting control of a company bitiony buying over50%of its shares. Definition:Lredit card is a small plastic card that you can use to buy goods and services and pay for the market.2.Depeciatiton贬值means decrease in value of assets.3.Brand preference品牌偏好is measure of brand loyalty in which a consumer will choose a paticular brand in presence of competing brands,but will accept substitutes if that brand is not available.4.Corporate Culture公司文化is a broad term used to define the unique personality or character of a particularcompany or organization,and includes such elements as core values and beliefs,corporate ethics,and rules of behavior.5.:Fringe benefit额外福利is an incidental or additional advantage,a benefit provided by an employer to supplement an employee's regular pay,such as a pension,company car,luncheon voucher,insurance,vacation 1.overcapacity:生产能力过剩If there is overcapacity in a particularindustry, more goods have been produced than areneed and the industry is therefore less profitable thanit could be.2.A free trade zone(FTZs):自由贸易区A free-trade area is a trade bloc whose member countries have signed a free-trade agreement(FT A),which eliminates tariffs,import quotas,and preferences on most(if not all)goods and services traded between them.If people are also free to move between the countries,in addition to FTA,it would also be considered an open border.4.A non-performing loan,or NPL,is a loan that is in default or close to being in default.Manyloans become non-performing after being in default for90days,but this can depend on the contract terms.不良贷款4..外债Definition:Foreign debt is the total debt a country owes to foreign creditors,complemented by int ernaldebtowed to domestic lenders.The debtors can be the government,corporations or citizens o f that country.The debt includes money owed to privale commercial banks,other governments,or international financialinstitutions such as the International(IMF)and World Bank5.Translation:风险投资家A venture capitalist is an investor who either provides capilal lo slartup ventures or supports small companiesthat wish to expand but do not have access to equities markets.V enture capitalists are willing toinvest in such companies because they can earn a massive return on their investments if these companies are asuccess.1.Translation:授权经营Definition:Licensing is an arrangement in which the owner of intellectual property grants another firm theright to use that property for a specified period of time in exchange for royalties or other compensation.2.Translation:间接投资，证券投资made with theexpectation of earning a return.Thisexpected retum'is'diretly orrelated with theion snen"cpeted ik Pofoioo ioene dainet fom dica muene whidh no uinesiable sake in a target compa ny and posbly being ivolvede wilh is day body mngeme 3.Translation:反向贸易、对等贸易Counter trade is a sale that encompases more than an exhane of god,erices or iesformoney.4.乘数效应Definition:The multiplier efect is the expansion of a country's money supply that results from banks beingable to lend.The size of the multiplier effect depends on the percentage of deposits that banks are required tohold as reserves.In other words,it is the money used to create more money and is calculated by dividing total bank deposits by the reserve requirement.5.Definition:Initial public ffering(IPO)is a type of public ofringn in which shares of a company usually aresold to nstitutional investors that in turn,sell to the general public,on a secrities excha nge,for the firsttime. 首次公开发行股票1.Break-even point is the point at which toal cost and toalrevenue are equal.Tanslaion:盈亏平衡点/盈亏临界2.Onder cydle time is a peindbetween placing5an order and receiving the ordered item. Translation:汀貨周期3.by the bank to the importer according to his demand upon receiving the billsunder the letter of credited and the impotterTranslation:进ロ押汇4.Maker share is the amo thata company sells of itspoduets or serices compared wih oher companies selling the same things. 市场份额5.Definition:Brand positioning is an activity of creating a brand offer in such a manner that it occ upies adistinctive place and value in the target customers'mind.Translation:品牌定位1.Defnition:Itis the right to buy or sell property at an agreed price;rithe ght is purchased and15 notexercised by a stated date,the money is forfeited.期权2.It is a fraudulent investment operation that pays returns to its investors from thelr own money0 1the money paid by subsequent investors,rather than from profit earned by the individual or orga nizationrunning the operation.庞氏骗局3.Definition:It is a stock market index and one of the several indices created by W all Street Jour nal editors and Dow Jones&Company co- founder Charles Dow.The industrial averagewas first calculated on May26,1896.Translation:道琼斯工业平均指数4.Definition:It is a company or person that supplies shops and companies with goods. Translation:经销商5.Definition:It is a process of judging officially how an argument should be settled. Translation:仲裁1.Barriers to trade are any action by a govermment to limit or prevent the free flow of goods in an dout of its country.贸易壁垒4.Definition:V enture capital is money made available for investment in innovative enterprises or research.especially in high technology,in which both the risk of loss and the potential for profit may be considerable.Also called risk capital.Translation:风险资本5.Definition:Insurable interest holds that no one may insure anything unless he has and interest i n it.(Whichmeans that if the thing insured is preserved he will derive a benefit from its preservati on,but if it is any way_damaged or lost the assured will be -adversely afet.-)Translation:可保利益2.Definition:Contracting party isаcountry or firm that signs a legalagreement.缔约国3.Definition:Sight draft calls for immediate payment on presentation to the drawee. Translation:及期汇票4.It is a reply to an ofter which conains aditions or other modietaons还盘2.Definition;lt is a kind of standard used to indicate that the quality of the product ffe is about equal to theaverage quality level of the same crop within a certain period of time. Translation:良好平均品质3.Definition:The act of the transferor in transferring a draft to the transferee by making a signatu re on the backof the draft. 背书4.Definition:It is a delivery situation in which when the seller delivers the buyer does not physic ally receive thegoods.This kind of delivery is proved by the submission of transport document by the seller to the buyer.Translation:象征性交货5.Goods are transported directly from the production country to the consuming country.In this ca se,onlv two parties are involved in the transaction,namely the exporter and the importer. Translation:直接贸易。
2016年3⽉13⽇托福阅读真题词汇题汇总：dramatically=striking perplexing=puzzlingtending=taking 挀愀爀攀 of conducive=favorable 琀漀quest＝search prevail＝dominantgenerally＝usually thereby＝consequentlyexceptional＝extraordinary suitable=appropriate 3⽉13⽇托福阅读真题第⼀篇 题材划分：地质类 主要内容：北美海⾯某种 dramatically heat 的现象。
这种先现象还导致海⾯上升(有题问为什么上升)。
然后⽤洋流来解释，但是这解释有问题，因为科学家发现洋流带来30%热才能增温。
但是不管是表层海⽔还是底层海⽔的检测都发现根本没这么多热，所以就进⼊第⼆段⽐较了厄尔尼诺和拉尼娜，厄尔尼诺是太平洋⾚道带海洋和⼤⽓互相作⽤后失去平衡的⽓候现象，还说暖流移动，使cool area变暖，还和Indian⽐较，Indian ocean 是 cool area，有 deep sea和sea surface。
史前距今五百万年的Eocene 时期在极地仍然会出现温暖的季节.厄尔尼诺还和 trade wind减弱相关。
拉尼娜是海⾯温度异常偏冷的现象，拉尼娜和wind trade增强相关，主要是tropical ocean和atmosphere的共同作⽤。
最后还讲了 greenhouse gas也可能是造成heat的原因，但是要测五百万年前的⼆氧化破浓度的挑战性就超级难，所以证据不⾜不确定。
有个题问了第三段和第四段的作⽤还是关系。
相似TPO练习推荐： TPO-23 Urban Climates TPO-10 Variations in the Climate 相关背景知识： El Ni漀 is the warm phase of the El Ni漀 Southern Oscillation (commonly called ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (between approximately the International Date Line and 120°W), including off the Pacific coast of South America. El Ni漀 Southern Oscillation refers to the cycle of warm and cold temperatures, as measured by sea surface temperature, SST, of the tropical central and eastern Pacific Ocean. El Ni漀 is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific. The cool phase of ENSO is called "La Ni愀" with SST in the eastern Pacific below average and air pressures high in the eastern and low in western Pacific. The ENSO cycle, both El Ni漀 and La Ni愀, causes global changes of both temperatures and rainfall. Mechanisms that cause the oscillation remain under study. La Ni愀 is a coupled ocean-atmosphere phenomenon that is the counterpart of El Ni漀 as part of the broader El Ni漀–Southern Oscillation climate pattern. The name La Ni愀 originates from Spanish, meaning "the girl", analogous to El Ni漀meaning "the boy". It has also in the past been called anti-El Ni漀, and El Viejo (meaning "the old man"). During a period of La Ni愀, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3–5°C. In the United States, an appearance of La Ni愀 happens for at least five months of La Ni愀 conditions. It has extensive effects on the weather in North America, even affecting the Atlantic Hurricane Season. A La Ni愀 often, though not always, follows an El Ni漀. 3⽉13⽇托福阅读真题第⼆篇 题材划分：经济发展史 主要内容： 16or17世纪的英国经济发展问题，讲英国农业如何在欧洲其他各国的农业发展之前独⾃发展⾄⼩康⽔平。
Diamonds 鑽石Diamonds are rare, beautiful, and also quite useful. They are the hardest substance found in nature. That means a diamond can cut any other surface. And only another diamond can make a slight cut in a diamond.Diamonds are made from carbon. Carbon is found in all living things, both plant and animal. Much of the carbon in the earth comes from things that once lived.Scientists know that the combination of extreme heat and pressure changes carbon into diamonds. Such heat and pressure exist only in the hot, liquid mass of molten rock deep inside the earth. It is thought that millions of years ago this liquid mass pushed upward through cracks in the earth's crust. As the liquid cooled, the carbon charged into diamond crystals.There are only four areas where very many diamonds have been found.The first known area was in India, where diamonds were found thousands of years ago. In the 1600's, travelers from Europe brought back these beautiful stones from India. Diamonds became very popular with the kings and queens of Europe.In the 1720's, diamonds were discovered in Brazil. This discovery came at a good time, too. India's supply of diamonds was finally running out after 2,500 years of mining the stones.In the 1800's, two other important areas were found in Russia and South Africa. Today, most diamonds used in industry come from Russia. Most diamonds used as gems come from South Africa. Only 25 percent of all diamonds mined are good enough for cutting into gems.Most of the diamonds in India were found in stream beds. People would pick up handfuls of gravel from the bottom of the streams and sort out the diamonds. These diamonds were probably carried from where they were formed to India by great sheets of moving ice that covered parts of the earth 20,000 years ago.Most diamonds today are not found in stream beds, however. They are mined from rock formations deep inside the earth called pipes. Scientists believe that these are parts of volcanoes that were formed when molten rock pushed upward through the earth's crust. The hand rock in which diamonds are found is called blue ground.鑽石既珍貴稀缺，又美麗晶瑩，也用途很廣。
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6. Just as glass windows offer building both light and insulation, certain atmospheric gases ______ incoming sunlight and ______ heat radiated from the ground, preventing warmth from escaping.答案:B F解析:类比结构;顺承结构A使偏斜B允许C 抵制D 释放E 分发F 控制翻译:就像玻璃墙提供给建筑物阳光和隔离一样,一种特定的大气层气体可以(允许阳光的射入而且可以(控制从地面反射的热,从而阻止热扩散出去。
7. No longer considered ______, the belief that all of Puerto Rico's indigenous Taino people perished centuries ago appears to be a ______ now that modern Taino descendants have come forward.答案:BE解析:时间反义A 神话的B 可靠的C 错误的D 现实E 误解翻译:波多黎各所有土生土长的Taino人已经在几个世纪前灭绝了的理论已经不再(站得住脚,而成为了一个(误解,因为现在Taino人的后代又出现了。
8. In many cases, the formerly______ origins of diseases have now been identified through modern scientific techniques.A. insightfulB. mysteriousC. cruelD. notableE. useful答案:B解析:时间反义A 有洞察力的B 神秘的C 治疗的D 能看到的E 可用的翻译:在很多事例中,早前来源不明的疾病现在已经通过现代科学技术明确身份。
小学上册英语第四单元真题试卷(含答案)考试时间：80分钟（总分:100）A卷一、综合题(共计100题共100分)1. 填空题：I can play the ______.2. 填空题：I love to ________ (聚会) with friends.3. 填空题：My grandma bakes ________ (饼干) for me.4. 选择题：What do you call a story that explains how things came to be?A. LegendB. MythC. FableD. Tale答案:B5. 听力题：A hot spring is a natural feature that occurs when groundwater is heated by ______.6. 听力题：The pH scale measures how ______ a substance is.7. 听力题：The sun is shining ___ (brightly) today.8. ers have a sweet __________ (香味). 填空题：Some flo9. 填空题：I enjoy playing _____ (桌面游戏) with my family.We go to school _____ (in/on) the morning.11. 听力题：The _____ is a group of stars that form a picture in the night sky.12. 填空题：Did you see a _______ (小猴子) swinging from a branch?13. 选择题：What is the main diet of omnivores?A. PlantsB. MeatC. Both plants and meatD. Fruits答案:C14. 听力题：The cat loves to nuzzle its _______.15. 填空题：The __________ (历史的交互作用) enhance learning experiences.16. 听力题：A chemical reaction can change the ______ of a material.17. 听力题：The ______ helps with the storage of energy in plants.18. 听力题：I found a ______ in my pocket. (button)19. 听力题：Plants can be very _______ and grow quickly.20. 选择题：What do you call a baby rabbit?A. KitB. PupC. CalfD. Chick答案:A21. n Tea Party was a protest against ______ (税收). 填空题：The BostChemical bonds can be broken and formed during a ______ reaction.23. 填空题：I saw a _____ (鳄鱼) at the zoo.24. 听力题：The girl is very ________.25. 填空题：The ______ (植物的生长速度) can vary based on conditions.26. 填空题：The turtle is a symbol of _______ (长寿).27. 填空题：My pet fish swims in a _____.28. 选择题：How many legs does a spider have?A. 6B. 8C. 10D. 1229. 填空题：My favorite stuffed animal is a _________ (小狗) named Fluffy.30. 选择题：Which of these is a type of cloud?A. CumulusB. MountainC. ValleyD. Desert答案:A31. 听力题：The _____ (road) is busy.32. 听力题：My dad loves to play ____ (poker) with friends.33. 听力题：A homogeneous mixture has a _____ composition throughout.The _____ (cypress) tree is often seen in swamps.35. 填空题：I can ______ (保持) good grades.36. 选择题：What is the capital of Mexico?A. CancunB. GuadalajaraC. Mexico CityD. Monterrey答案: C. Mexico City37. 填空题：People love to hike in the __________ (国家公园).38. 选择题：What is the capital of Angola?a. Luandab. Benguelac. Huambod. Lubango答案:a39. 填空题：We have a ______ in our backyard.40. 听力题：The process of heating a substance to remove water is called _______.41. 选择题：What is the main ingredient in tofu?A. SoybeansB. WheatC. RiceD. Corn42. 选择题：What do we call the person who cuts hair?A. DoctorB. BarberC. ChefD. Teacher答案：BI enjoy ________ in the garden.44. 填空题：A ______ (自然保护区) protects plants and wildlife.45. 选择题：What is the term for the gradual cooling of the universe after the Big Bang?A. Cosmic CoolingB. Universal ExpansionC. Dark AgesD. Cosmic Microwave Background46. 选择题：What do we call a person who studies the history of science?A. Science HistorianB. SociologistC. AnthropologistD. Philosopher答案: A47. 听力题：The dog is ___ (barking/growling).48. 选择题：What do we call a baby cow?A. CalfB. KidC. LambD. Foal答案:A49. 听力题：Some _______ can be used for making perfumes.50. 选择题：What is the capital of the United States?A. New YorkB. Washington, D.C.C. Los AngelesD. Chicago51. 听力题：The ____ has a thick fur coat and loves to stay warm.What is the name of the famous American author known for writing "The Adventures of Tom Sawyer"?A. Mark TwainB. Ernest HemingwayC. F. Scott FitzgeraldD. John Steinbeck答案：A53. 听力题：The cat's whiskers help it navigate in the _______.54. 填空题：A caribou migrates during the ________________ (季节).55. 听力题：The chemical formula for ammonium thiocyanate is __________.56. 听力题：The __________ is a famous area known for its traditional medicine.57. 选择题：What is the opposite of open?A. CloseB. ShutC. BlockD. Both A and B答案:D58. 填空题：My best friend loves to _______ (动词) during summer vacation. 她觉得 _______ (形容词).59. 填空题：The _____ (花坛) is full of blooming flowers.60. 选择题：What is the smallest unit of life?A. CellB. TissueC. OrganD. Organism答案:AI want to learn to ________ (驾驶).62. 填空题：A ________ (生态平衡) ensures diversity.63. 选择题：What is the name of the famous statue in New York Harbor?A. DavidB. LibertyC. Christ the RedeemerD. The Thinker64. 选择题：How many colors are in the national flag of the USA?A. 2B. 3C. 4D. 5答案:B65. 选择题：What do you use to cut paper?A. PencilB. GlueC. ScissorsD. Tape答案:C66. 填空题：I love _______ (冬天) because of the snow.67. 听力题：A __________ can affect human development.68. 选择题：What is the value of 6 ÷ 2 + 3?A. 5B. 6C. 8D. 9答案:A69. 选择题：What is the main purpose of a calendar?A. To tell timeB. To show datesC. To measure distanceD. To calculate70. 填空题：My sister has a collection of ______.71. 选择题：What do we call the process of learning how to swim?A. DivingB. FloatingC. Swimming lessonsD. Water sports答案:C72. 填空题：Planting trees along streets can provide ______ from the sun. (在街道上种植树木可以提供遮阳。
GRE阅读考试资料During experiments at the Bimini Biological Research Station in the Bahamas， researchers Eric Stroud and Michael Hermann dropped a small mag in the water beside a shark。
The presence of the mag elicited a distinct reaction from the fish －－ they darted away from it。
Why the intense reaction？ The interaction of salt water and charged metals produces a weak electrical field。
When a shark es close to that field， the field seems to disrupt the sharks‘ special sixth sense，electroreception。
Many shark species have pores dotted around their snouts called ampullae of Lorenzinithat detect minute changes of electricity in the seawater， up to one－billionth of a volt。
These electrical impulses e from the tiniest muscle contractions of other aquatic life forms －－ or people －－ and are carried through the ions in the salt water。
As a national platform for global technological in-novation and cooperation, t he 2023 E x h ibit ion of the ZGC Forum recently closed in Beijing. The forum witnessed many dark technologies including low-car-bon cycling, space interaction, data display across whole screens, and the metaverse. Artificial intelligence becomes the focus Robots equipped with AI mod-els can sense human needs before re-ceiving instructions; medical devices featuring AI technology can generate medical images within 5 minutes; the IQ test scores of the AI big model are even higher than those of talents from top universities... In the “Artificial In-telligence” exhibition area of the 2023 Exhibition of the ZGC Forum, more than 30 scientific and technological innovation companies displayed the latest AI research results, showing the extraordinary capabilities of artificial intelligence in various fields.At the exhibition stand of the Beijing Academy of Artificial Intel-ligence, the visual model SegGPT that can segment things in context through visual technology is show-ing what it can do on a big screen. According to the staff, SegGPT has the automatic power to segment and track videos. People just need to mark an object on a first frame image, and SegGPT is able to segment it out in later videos.The staff from the Beijing In-stitute for General Artificial Intelli-gence introduced mathematical log-ic to a model with human cognitive intelligence capabilities, referring to it as the “intelligent model”. As introduced, this model outperforms large models of deep learning in IQ tests and is a vivid case for “small data for a big task”. This marks a step in the direction towards artifi-Cutting-edge High-tech Congregates at Zhongguancun ForumBy Lily Wang 30cial intelligence.A huge medical robot in the ex-hibition area was surrounded by the audience. This robot consists of three parts: the main control trolley, the robotic arm, and the tracker. Before surgery, a doctor will make an AI 3D scan of the patient’s bones through the main control trolley to work out an optimal plan for the next step of the surgery. “Traditional 3D medical image reconstruction usually takes two weeks, but with AI, you only need five minutes.” The staff also stat-ed that after quickly obtaining clear medical images, doctors do not need to rely on “experience” to perform surgery, and orthopedic joint replace-ment surgery has become an easy test, which will shorten the learning curve for young doctors. During surgery, the robotic arm will do its work. As the main control trolley has inputted key parameter marker points into the robotic arm, it will generate a three-dimensional control boundary. “Once there is an operational mistake that exceeds the range of parameter markers, the robotic arm will stop within 0.1 seconds.” The staff also said that as of now, this technology covers 30 provinces and cities across the country, and has been used in more than 600 grade-A tertiary hos-pitals across the country.UAVs attract attentionPresently, that scope of U AV (unmanned aerial vehicle) applica-tion has surpassed imagination. At the exhibition stand of the U AV industry, a red unmanned plane is enchanting to behold. The plane is equipped with two f ire monitors either side of the body and t wo spiral blades on the top. It’s cool appearance has attracted a large group of visitors. According to staff members from United Aircraft, this unmanned drone can take off and land vertically, fly up to an altitude of 3500 meters above the ground, and can withstand winds of up to force 6. Fire drones can be used for firefighting and rescue work in situations where fire ladders cannot access high-rise buildings that have caught fire.Nex t to it, there is a la rgerwhite drone. “This drone can fly toan altitude of 6,500 meters above theground and has a faster flight speedof up to 180 kilometers per hour.”The staff explained that this dronehas been playing an important role invarious fields such as transportationand emergency rescue.New energy drones are also amajor attraction in the exhibitionarea. A solar powered drone called“Cygnus” has a large solar panel onits wing. Although it looks simple,its functions are powerful and itcan be charged while flying. Astaff member from BeijingChangyuan TechnologyCo., Ltd. said, “the droneis able to fly at a max-imum altitude of 10kilometers, with anendurance of 55 fly-ing hours.” It is saidthat solar-powereddrones rely on solarpa nels to capt u relight energy, makethe motors drive thepropellers to providethe f light power andcharge energy storagebat ter ie s. At n ight,drones rely on the energystored in energy storagebatteries to maintain flight.It is said that the dronecluster exhibition area gathers 13research institutes and enterprises,including Beihang, Beiyou, Qing-hang Equipment, and Zhonghangzhi,highlighting their research achieve-and products in different applicationscenarios such as emergency rescues,communication support, firefighting,and material transportation.When quantum computing isloaded onto the cloudThe 2023 ZGC Forum sets up aquantum information exhibition areafor displaying cutting-edge informa-tion technology. The best exhibitionspace is reserved for quantum com-puting cloud platforms.“This is the number of bitsd i s p l a ye d, w it h t h r e e o p t i o n savailable: 10 bits, 18 bits, and 136bits.” In front of the exhibitionstand, Yang Zhipeng, a postdoc-tora l scholar from the quant umcomputing cloud platform team atthe Beijing Academy of QuantumInformation Sciences, showcasesThe 2023 ZGCForum sets up aquantum informationexhibition area fordisplaying cutting-edgeinformation technology.31the operation process of the cloud platform to interested audiences. U n l i ke t he comple x operat ions seen i n t he l aborator y, he on ly needs to connect to the internet and click the mouse.Wang Zheng’an, a founding member of the “Quafu” team and a postdoctoral fellow at the Beijing Academy of Quantum Information Sciences, explained that in reality, the superconducting quantum com-puter is a very complex machine, and there are many specific problems to be solved. “For example, before con-ducting experiments, the whole set of equipment needs to be calibrated to a relatively good operating state, which may take several days or even months. After a period of time, due to the impact of environmental noise, its state will gradually deteriorate, and it will finally reach an unusable condition. If this happens, it needs to be recalibrated. In addition, we have done a lot of work on the control over superconducting quantum computers, compiling quantum programs and correcting errors,” he said.“The most critical thing is that only having the equipment is not enough. It requires professional per-sonnel to operate it, which involves al o t o fe x p e r tk n o w l-e d g e a n de x p e r ie n c e,and such talentsa r e a l s o s c a r c ei n C h i n a.” Wa n gZheng’an also said thatin order to do well in thecomplex basic parts of quantumto operate such machines in a simpleway will be one of the original pur-poses of the cloud platform project.Yang Zhipeng introduced thetopic further: “the quantum comput-ing cloud platform means that usersonly need to connect to our serverthrough the network, and the servercan use the quantum computing de-vices and return corresponding cal-culation results. Researchers are thusable to use the quantum computer tosolve their issues.”At present, the “Quafu” quan-tum computing cloud platformhas been open to users fortesting, and users onlyneed to register for anaccount to use it forfree. It is reportedthat the numberof registered us-enterprises, andr epractical reason behind simplifyingoperations is reducing costs. It isunderstood that the low-tempera-ture environment and supportingmeasurement and control equipmentrequired for quantum chips are veryexpensive. Sharing quantum resourc-es and providing research methodsthrough cloud platforms is a relativelysimple way to reduce costs.Smart life is within reachWith the advancement of tech-nology, scenes of intelligent livinghave sta r ted to mushroom. Theaudience are able to experience theforefront of this technology at the ex-hibition site.A spider-shaped drone is sus-pended above the exhibition stand,with a gas detection device installedbelow. “With the detection device,gas sampling and detection can becarried out,” explained the workingstaff.There are also small and exqui-site gas detection vehicles that canachieve unmanned operation. “Thetesting vehicle is equipped with an ul-trasonic anemometer, which can per-form instantaneous detection withina range of 150 meters and accuratelyidentify the source of gas.” The staffalso noted that the small vehicle canplay a significant role. As of now,the testing vehicle has completed thetesting of over 1 million kilometers of32gas pipelines.great souvenir.” tive robot has been applied in multiple industries such as automotive parts, healthcare, and logistics.Immersive experiences of the metaverseThe metaverse has become a super hot topic at present. At the metaverse stand in the cutting-edge technology and future industry exhibition area, actors perform various dance movements, and vir-tual humans on the screen dance almost without delay. The actions of people in both the virtual and real world cor-respond exactly 1:1, including facial expressions.There are four positioning light towers on site, which can cap-ture 15 large bone joint points on the actor’s body and 12 joint points on recognize the absolute position of the joints by identifying the six degrees of freedom of the laser and inertial com-ponents, thereby providing feedback on the position of the virtual charac-ter in the software.According to Zhang Zhenhua, senior vice president of STEPVR, this virtual dance is realized through a motion capture device based on the world’s only laser plus inertia solu-tion. Such device has been widely used in movie animation produc-tion, live broadcasts on short video output platforms, mov-ie and game shooting and the convenience and low cost of inertial motion cap-ture. Due to its low cost, this system can be provided for personal workers and voice actors, with a virtual live streaming market share nlike cam-, t h i s system can stably r 5 For example, “cosmic spec-ulation” is committed to creating a unified urban metaverse entrance, with over 120 city level digital twin assets, providing irreplaceable support for the implementation of metaverse application scenarios. It builds a city level spatial digital base that can shut-tle freely to any meta space, creating a digital parallel world that belongs to everyone. The company’s product matrix covers metaverse super apps, interstellar exploration, and a series of technological interaction solutionsthat have been innovated around metaverse scenes.Besides this, in the “metaverse” e x h i b i t i o n a r e a , t h e a u d i e n c e may also experience technologi-cal achievements such as physical garbage sorting, AR magic brush 33。
托福阅读备考之长难句分析：地球上的二氧化碳下面给大家分享托福阅读备考之长难句分析：消失的化石记录的相关内容，希望你们喜欢。
托福阅读备考之长难句分析：地球上的二氧化碳The answer to the first question is that carbon dioxide is still found in abundance on Earth, but now, instead of being in the form of atmospheric carbon dioxide, it is either dissolved in the oceans or chemically bound into carbonate rocks, such as the limestone and marble that formed in the oceans. ( TPO41, 53) abundance /?'b?nd(?)ns/ n. 丰富，充裕atmospheric /?tm?s'fer?k/ adj. 大气的dissolve /d?'z?lv/ v. 溶解limestone /?la?m?st??n/ n. 石灰石marble /'mɑ?b(?)l/ n. 大理石大家自己先读，不回读，看一遍是否能理解The answer to the first question is ( that carbon dioxide is still found in abundance on Earth), but now, (instead of being in the form of atmospheric carbon dioxide), it is either dissolved in the oceans or chemically bound into carbonate rocks, (such as the limestone and marble) (that formed in the oceans.) ( TPO41, 53) 托福阅读长难句分析：这个句子的主干是：The answer to the first question is 从句 , but now, it is either dissolved in the oceans or chemically bound into carbonate rocks 修饰一：(that carbon dioxide is still found in abundance on Earth) ，从句中文：在地球上二氧化碳依然可以大量被找到修饰二：(instead of being in the form of atmospheric carbon dioxide) ，介词短语中文：它不是以大气中的二氧化碳的形式出现修饰三：(such as the limestone and marble that formed in the oceans.) ，介词短语中文：例如在海洋中形成的石灰石和大理石修饰四：(that formed in the oceans.) ，从句中文：在海洋中形成的参考翻译：第一个问题的答案是，在地球上二氧化碳依然可以大量被找到，但是现在，它不是以大气中的二氧化碳的形式出现，它溶解在海洋里或者通过化学作用进入碳酸盐岩中，例如在海洋中形成的石灰石和大理石。
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a r X i v :q u a n t -p h /0002040v 2 22 F eb 2000Heating of trapped ions from the quantum ground state ∗Q.A.Turchette,†D.Kielpinski,B.E.King,a D.Leibfried,b D.M.Meekhof,C.J.Myatt,c M.A.Rowe,C.A.Sackett,C.S.Wood,d W.M.Itano,C.Monroe,and D.J.Wineland Time and Frequency Division,National Institute of Standards and Technology,Boulder,CO80303(February 1,2008)We have investigated motional heating of laser-cooled 9Be +ions held in radio-frequency (Paul)traps.We have measured heating rates in a variety of traps with different geometries,electrode materials,and characteristic sizes.The results show that heating is due to electric-field noise from the trap electrodes which exerts a stochastic fluctuating force on the ion.The scaling of the heating rate with trap size is much stronger than that expected from a spatially uniform noise source on the electrodes (such as Johnson noise from external circuits),indicating that a microscopic uncorrelated noise source on the electrodes (such as fluctuating patch-potential fields)is a more likely candidate for the source of heating.I.INTRODUCTIONCold trapped ions have been proposed as a physical implementation for quantum com-putation (QC)[1],and experiments on one [2–5]and two [6,7]ions have demonstrated proof of the principle.Work is currently underway to extend these results.In ion trap QC,ion-laser interactions prepare,manipulate and entangle atomic states in ways dependent on the quantum motional state of the ions.A limiting factor in the fidelity of an operation is uncontrolled heating of the motion during manipulations.Heating leads to decoherence of the quantum superposition states involved in the computation [8,9],and can ultimately limit the number of elementary gate operations which can be strung together.Speculationshave been made about the mechanisms that lead to heating[8,10–14],but measurements are scarce since the necessary sensitivity can be achieved only through laser cooling to near the ground state of motion.Additionally,systematic studies of the dependence of heating rate on various trap properties are difficult,since often this requires the construction and operation of an entirely new trap apparatus which may have different values of properties not under study.Indeed,the data presented here pose several interpretational difficulties for this reason.Heating of a single trapped ion(or the center-of-mass motion of a collection of trapped ions)occurs when noisy electricfields at the position of the ion couple to its charge,giving rise tofluctuating forces.If the spectrum offluctuations overlaps the trap secular motion frequency or its micro-motion sidebands,thefluctuating forces can impart significant energy to the secular motion of the ion.Here,we express the heating rate as the average number of quanta of energy gained by the secular motion in a given time.There are several candi-dates worth considering for sources of the noisyfields which give rise to heating.Some of these are[8]:Johnson noise from the resistance in the trap electrodes or external circuitry (the manifestation of thermal electronic noise or black body radiation consistent with the boundary conditions imposed by the trap electrode structure),fluctuating patch-potentials (due,for example,to randomly oriented domains at the surface of the electrodes or adsorbed materials on the electrodes),ambient electricfields from injected electronic noise,fields gen-erated byfluctuating currents such as electron currents fromfield-emitter points on the trap electrodes,and collisions with background atoms.Only thefirst two mechanisms will be considered here since the remaining mechanisms(and others)are unlikely contributers[8]or can be eliminated by comparing the measured heating rates of the center-of-mass and differ-ential modes of two ions[6].As will be shown below,the Johnson-noise and patch-potential mechanisms give rise to heating rates which scale differently with the distance between the ion and the trap electrodes.II.TWO MODELS FOR SOURCES OF HEATINGA.PreliminariesThe heating rate caused by afluctuating uniformfield can be derived as in Savard,et al.[15]and agrees with a classical calculation[8].The Hamiltonian for a particle of charge q and mass m trapped in an harmonic well subject to afluctuating,uniform(non-gradient) electricfield driveǫ(t)isH(t)=H0−qǫ(t)x,(1)where H0=p2/2m+mω2m x2is the usual,stationary harmonic oscillator Hamiltonian with trap frequencyωm.Fromfirst order perturbation theory,the rate of transition from the ground state of the well(|n=0 )to thefirst excited state(|n=1 )is[15]Γ0→1=1m¯hωmS E(ωm)(3)where S E(ω)≡ ∞−∞dτe iωmτ ǫ(t)ǫ(t+τ) is the spectral density of electric-fieldfluctuations.For an ion trapped by a combination of(assumed noiseless)static and inhomogeneous rffields(Paul trap)the heating rate can be generalized to[11]:˙¯n=q 22Ω2TS E(ΩT±ωm) ,(4)where˙¯n is the rate of change of the average thermal occupation number,ωm is now the secular frequency of the mode of motion under consideration andΩT is the trap rf-drive frequency.The second term on the rhs of Eq.4is due to a cross-coupling between the rf and noisefields;it will not be present for the axial motion of a linear trap which is confined only by staticfields.Even for motion confined by rf pondermotive forces,this second termwill be negligible in the absence of spurious resonances in S E(ω)or increasing S E(ω)(since ω2m/Ω2T∼10−4)and is neglected in what follows[8].We differentiate two sources of the noise that gives rise to heating.Thefirst is thermal electronic noise in the imperfectly conducting trap electrodes and elsewhere in the trap circuitry.Though this source of noise is ultimately microscopic in origin,for our purposes here it can be treated adequately by use of lumped circuit models.Thermal noise has been considered in the context of ion-trap heating in several places[8,11–14].The second source of noise considered here is due to“microscopic”regions of material(small compared to the size of the trap electrodes)withfluctuating,discontinuous potentials established,for example, at the interface of different materials or crystalline domains.We call this patch-potential noise,and its microscopic origin leads to manifestly different heating behaviour from that for the thermal electronic noise case.Static patch-potentials are a well-known phenomenon, but little is known about the high-frequency(MHz)fluctuating patches which are required to account for our observed heating rates[16–18].B.Thermal electronic noiseHeating rates in the case of thermal electronic noise(Johnson noise)can be obtained simply through the use of lumped-circuit models,which are justified by the fact that the wavelength of the relevantfields(at typical trap secular or drive frequencies)is signifi-cantly larger than the size of the trap electrodes.Such an analysis has been carried out elsewhere[8,11,19],and only the major results will be quoted here.Resistances in the trap electrodes and connecting circuits give rise to an electricfield noise spectral density S E(ω)=4k B T R(ω)/d2where d is the characteristic distance from the trap electrodes to the ion,T is the temperature(near room temperature for all of our experiments),k B is Boltzmann’s constant,and R(ω)is the effective(lumped-circuit)resistance between trap electrodes.The heating rate is given byq2k B T R(ωm)˙¯nR=A numerical estimate of the heating rate for typical trap parameters gives0.1/s<˙¯n R<1/s [8,11],which is significantly slower than our observed rates.As afinal note,the lumped circuit approach is convenient,but not necessary.In the Appendix,we present a microscopic model that is valid for arbitrary ion-electrode distances and reproduces Eq.5for all the traps considered here(and for all realistic traps where d≫δ,whereδis the skin depth of the electrode material at the trap secular frequency).C.Fluctuating patch-potential noiseTo derive the heating rate for the case of microscopic patch-potentials we use the following approximate model.We assume that the trap electrodes form a spherical conducting shell of radius a around the ion.Each of the patches is a disc on the inner surface of the sphere with radius r p≪a and electric potential noise V p(ω).Alternatively,each patch is assumed to have power noise spectral density S V(ω).The electricfield noise at the ion due to a single patch is E p(ω)=−3V p(ω)r2p/4a3in the direction of the patch.There are N≈4Ca2/r2p such patches distributed over the sphere with coverage C≤1.Averaging over a random distribution of patches on the sphere,wefind that the power spectral density of the electric field at the ion(along a single direction)isS E(ω)=N ∂E p(ω)4a4.(6) This gives a heating rate3q2Cr2p S V(ωm)˙¯nP=III.MEASUREMENTSA.Measuring the heating rateTo determine the heating rate,wefirst cool the ion to near the ground state.In suf-ficiently strong traps,this is achieved simply by laser cooling with light red-detuned from a fast cycling transition(γ≈ωm,whereγis the radiative linewidth of the upper state) propagating in a direction such that its k-vector has a component along the direction of the mode of interest.In weaker traps,additional sideband Raman cooling is utilized to cool to the ground state[3].Typical starting values of¯n,the average number of thermal phonons in the mode of interest,are between0and2.After cooling and optically pumping the ion to its internal ground state(denoted|↓ ), we drive Raman transitions between atomic and motional levels[2–4].Tuning the Raman difference frequency∆ωto the k th motional blue sideband(bsb)at∆ω=ω0+kωm drives the transition|↓ |n ↔|↑ |n+k where|↑ ,|↓ refer to the internal(spin)states of the atom that are separated byω0.The k th red sideband(rsb)at∆ω=ω0−kωm drives |↓ |n ↔|↑ |n−k .The measurement utilizes asymmetry in the strengths of the red and blue motional sidebands to extract¯n.The strengths of the sidebands are defined as the probability of making a transition|↓ ↔|↑ ,which depends on the occupation number of the motional levels.The strengths are probed by a Raman pulse of duration t tuned to either k th sideband.The probability P↓of remaining in|↓ after probing is measured and the strengths I rsb k=1−P↓,rsb and I bsbk=1−P↓,bsb are extracted.For thermal motional states,the strengths of the red and blue sidebands are related by[3,8]I rsb k=∞m=k P m sin2Ωm,m−k t(8)= ¯n1+¯n k I bsb k(10) whereΩm+k,m=Ωm,m+k is the Rabi frequency of the k th sideband between levels m andm+k,and P m=¯n m/(1+¯n)m+1is the probability of the m th level being occupied foris a thermal distribution of mean number¯n.The ratio of the sidebands R k≡I rsb k/I bsbk independent of drive time t and immediately gives the mean occupation number¯n,(R k)1/k¯n=on either side of the electrode,centered with the hole,similar to the trap shown in Fig.2. In trap1,the ring and endcap electrodes are at the same average potential;in traps2and 3a static biasfield could be added between the fork and ring to change the distribution of binding strengths along the three principle axes of the trap.The size of these traps is stated as the hole radius,with the endcaps spacing approximately70%of the hole diameter.For the elliptical ring trap(trap2)the stated size is the radius along the minor axis and the aspect ratio is3:2;the fork tines are parallel to the major axis of the ellipse.Traps3a and3b were drilled into a singleflat electrode with a single graded fork electrode(see Fig.2).The rings are circular and the size stated is the radius.This was the trap used for the size-scaling measurements.The heating in all of the ring traps was measured in a direction in the plane of the ring electrode,parallel to the tines of the fork electrode.Traps4,5and6are similar linear traps with geometry indicated in Fig.3.Trap6was made slightly larger than traps4 and5by increasing the space between the two electrode wafers.Heating was measured along the axial direction,which has only a static confining potential.The size quoted in Table I for the linear traps is the distance between the ion and the nearest electrode.All traps are mounted at the end of a coaxialλ/4resonator for rf voltage buildup[21].Typical resonator quality factors are around500and rf voltage at the open end is approximately500V with a few watts of input power.In all traps except for trap3a and3b the resonator is inside the vacuum chamber with the trap.In traps3a and3b,the resonator is outside the chamber, with the high-voltage rf applied to the trap through a standard vacuum feedthrough.Since we believe that surface effects are an important factor in heating,we cleaned the electrode surfaces before using a trap.When trap electrodes were recycled,they werefirst cleaned with HCl in order to remove the Be coating deposited by the atomic source.For the molybdenum traps an electro-polish in phosphoric acid was then used.For the beryllium electrodes electro-polishing in a variety of acids was ineffective,so abrasive polishing was used.Finally,the traps were rinsed in distilled water followed by methanol.The gold electrodes of the linear traps were cleaned with solvents after being evaporatively deposited on their alumina substrates.The time of exposure of clean trap electrodes to the atmospherebefore the vacuum chamber was evacuated was typically less than one day.The traps were then vacuum baked at∼350◦C for approximately three days.C.DataOur longest-term heating measurements were made on trap1.In Figure4we plot the heating rate as a function of date of data acquisition for afixed trap frequency(11MHz). The heating rate is on the order of1quantum per millisecond with a basic trend upwards of∼1quantum per millisecond per year.Over this time the electrodes were coated with Be from the source ovens,but beyond this,nothing was changed in the vacuum envelope, which was closed for this entire period of time.The cause of the increase in heating rate is unknown,but may be related to increased Be deposition on the electrodes.Be plating on the trap electrodes could be a source of patch-potential noise.Figure5shows heating rates in the linear traps(trap4,5and6)and the elliptical ring trap(trap2)as a function of trap secular frequency.The frequency dependence of the heating rate is expected to scale as S E(ωm)/ωm(Eq.4).For example,a trap electrode with aflat noise spectrum(S E(ω)=constant)will have a heating rate that scales asω−1m.The actual spectrum offluctuations is impossible to know a priori,but in principle the data can be used to extract a spectrum over a limited frequency range given the model leading to Eq.4.For the three linear traps,the heating rate data are most consistent with aω−2m scaling, implying S E∝ω−1.This does not greatly assist in identifying a physical mechanism for the heating.For example,pure Johnson noise will have aflat spectrum,low-pass-filtered Johnson noise will have a spectrum that decreases with increasing frequency,and the spectrum of fluctuations in the patch-potential case is entirely unknown.In addition to the theoretical ambiguity,there is evidence in other data sets of different frequency scalings(though they are always power-law scalings).This measurement certainly cannot be used to pinpoint a heating mechanism;it is presented here only for completeness.The data of Figure5b provide afirst indication of the scaling of the heating rate withtrap size.Trap6is about1.3times larger than trap5,while its heating rate(at10MHz) was a factor of3slower.This indicates that the dependence of heating rate on trap size is stronger than d−2,but is consistent with d−4.Of course,this comparison is to be taken with some caution,since these are two separate traps measured several weeks apart,and therefore likely had different microscopic electrode environments.However,a comparison is warranted since the traps were identical apart from their sizes.In particular,all the associated electronics was the same and the rf drive voltage was very nearly the same.In fact,the rf voltage was slightly larger for the measurements on trap6,which showed the lower heating rate.This is important to note because we observe a slight dependence of the heating rate on the applied rf trapping voltage.Though we have only a qualitative sense of this dependence at present,it seems that heating rates increase with rf voltage, up to a point,at which the effect levels off.This rf-voltage dependence is observed along directions where the ion is confined both by staticfields and by pondermotivefields.It may not be unreasonable that the increased rf voltage increases the intensity of the noise source (possibly due to an increase of temperature of the electrodes),even when it does not affect the trap secular frequency,as in the axial direction of the linear traps.Trap3was designed to give a controlled measure of the heating rate as a function of trap size,while all other parameters were heldfixed.The trap electrodes were made from the same substrates,the electrodes were subjected to the same pre-use cleaning,the traps were in the same vacuum envelope,driven by the same rf electronics(simultaneously)and data for both traps were acquired with minimal delay.For direct comparison at the same secular frequency in both traps,it was necessary to change the applied rf voltage sinceωm∝1/d2.(A static bias between ring and endcap can be added,as discussed above,but this was not sufficient to measure heating at identical secular frequencies for the same rf drive.)There are two data sets to be discussed for this trap,shown in Figure6.In thefirst set,shown in Figure6a,we have data points at two different secular frequen-cies for the“small trap”(trap3a)and one point for the“big trap”(trap3b).The heating rates of the small trap are comparable to the heating rates for other traps and show aω−1mscaling of the heating rate.The single point on the big trap is at a lower secular frequency, yet has a much slower heating rate.In fact,if we extrapolate the data from the small trap to the same secular frequency(usingω−1m),the heating rate is over an order of magnitude lower in the big trap.The ratio of the heating rate in the small trap to that of the big trap is20±6.This is a much stronger scaling than that predicted by a Johnson noise heating mechanism(Eq.5predicts a d2∼4.8scaling),but is consistent with the scaling in the patch-potential case(Eq.7predicts a d4∼23scaling).When these data are used to predict an exponent for the size-scaling,the result is d3.8±0.6.For the second data set,shown in Figure6b,the trap was removed from the vacuum enclosure,given the usual cleaning(as discussed above),and replaced for the measurements. In this data set,the trap behaved quite differently from all other traps,with heating rates significantly below those of other traps.Also,S E must have been a strong function ofωfor this trap since the scaling with trap frequency was rather pronounced.The scaling with size was also strong:the heating rate was16,000times smaller in the big trap.When these data are used to predict an exponent for the size-scaling,the result is d12±2.Needless to say,it is difficult to draw general conclusions from the data for this particular trap,but the difference in heating rates between the two traps seems to strongly indicate,again,that Johnson noise is not the source of the heating.We cannot be sure why this trap had such anomalous heating behaviour,but we speculate that it is due to a less-than-usual deposition of Be on the trap electrodes prior to the measurements,because the trap loaded with minimal exposure to the Be source atomic beam.At this point it is useful to compare the present results to heating rates in other ex-periments.There are two other measurements.Thefirst was done with198Hg+[10].For that experimentωm/2π≈3MHz and d≈450µm and the heating rate was0.006/ms. Accounting for scalings with trap frequency(ω−1m)[23]and mass(m−1),these results are consistent with the present results for a size-scaling of d−4.Another measurement has been made with40Ca+[5].For that experimentωm/2π≈4MHz and d≈700µm and the heating rate was0.005/pared to the present experiments and the Hg experiment,this isalso consistent with a d−4scaling,although it is certainly unlikely that all systems had the same patchfield environment.IV.CONCLUSIONS AND OUTLOOKWe have measured heating from the ground state of trapped ions in different traps.The magnitude of heating rates and the results of the size-scaling measurements are inconsistent with thermal electronic noise as the source of the heating.The results do not indicate any strong dependence on trap-electrode material or on the type of trap potential(pondermotive or static).The rf voltage applied to the electrodes may play a role in heating,in as much as it may have an influence on patch-potentials.Since we have not identified the mechanism for the observed heating,it is difficult to say what path should be taken to correct it.Iffluctuating patch-potentials on the surface of the electrodes are the cause,then further cleaning may be appropriate.Additionally,better masking of the the trap electrodes from the Be source ovens may help.The results coupled with those of other experiments[10,5],strongly indicate that bigger traps have smaller heating rates.This is not a surprise,but the strength of the scaling may be.With little sacrifice in the trap secular frequency(which ultimately determines the fastest rate of coherent manipulation)a dramatic decrease in the heating rate vs.logic gate speed appears possible using larger traps.We acknowledge support from the U.S.National Security Agency,Office of Naval Re-search and Army Research Office.We thank Chris Langer,Pin Chen,and Mike Lombardi for critical readings of the manuscript.V.APPENDIX:THERMAL ELECTRIC FIELDS We are interested in the thermal electricfield power spectral density S E(r,ω)generatedifrom a specified volume of conductor.The conductor can be decomposed into a web of resistors each carrying current spectral density S I=4k B T/R i(where we assume k B T≫i¯hω).The resistance along the ith direction of an infinitesimal volume element is R i= dl/(σdA),whereσis the conductivity,dl is the length along i and dA is the cross-sectional area.A Fourier component of current I i(ω)through the volume dV=dldA gives rise to an electric dipole P i(ω)=I i(ω)dl/ω,thus the equivalent spectral density of electric dipole of the infinitesimal resistor is isotropic:S Pi(ω)=4k B TσdV/ω2.The electricfield from an electric dipole P(r′,ω)oscillating at frequencyωand position r′isE i(r,ω)= j=x,y,z P j(r′,ω)G ij(r,r′,ω).(12) In this expression,G ij(r,r′,ω)is a Green function matrix,representing the ith component of electricfield at position r due to the jth component of a point dipole at r′which satisfies the appropriate boundary conditions of the geometry.The electricfield spectral density at position r is an integral over the dipoles in the conductor volume:S Ei (r,ω)=4k B Tω j=x,y,zℑm G ij(r,r,ω).(14)Agarwal solved Maxwell’s equations for G ij(r′,r,ω)for the simple geometry of an infinite sheet of conductorfilling the space z≤0with the conductor-vacuum interface in the z=0 plane[25].Although this idealized geometry is far from any real ion trap electrode structure, rough scalings of the thermalfields can be relevant to real ion trap geometries.From Ref.[25],the Green function matrix for this problem is diagonal with axial(z)and radial(ρ) componentsG zz(z,z,ω)=G free(ω)+i ∞0q3w0ε+w e2iw0z dq(15)Gρρ(z,z,ω)=G free(ω)−iw0ε+w +k2w+w0e2iw0z dq,(16)In the above expressions,ε(ω)=ε0+iσ/ε0ωis the dielectric function of the conductor (in the low frequency limit),k=ω/c,and wavevectors w0and w(generally complex)are defined by w20=k2−q2and w2=k2ε−q2withℑm w0≥0andℑm w≥0.The free space Green’s function G free(ω)has imaginary partℑm G free(ω)=k3/6πε0and gives rise to the isotropic free space blackbody electricfieldfluctuations when substituted into Eq.(14).The above integrals are significantly simplified in the“quasi-static”limit,where kz≪1 and the conductivity is sufficiently high so that kδ≪1,whereδ=3πε0c3+k B T11δ4(17)S Eρ(z,ω)=k B T11δ4.(18)These expressions show that the thermal electricfield noise scales as1/z3for z≪δ[14], but scales as1/z2for z≫δ[8,11].At large distances z>This result is also reported in Ref.[26].The behavior is shown in Fig.7,where Eqs.(17) and(18)have been substituted into Eq.4,giving the expected thermal heating rate for a 9Be ion trapped with molybdenum electrodes at room temperature.Note that the predicted heating rate at trap sizes typical in our experiments is significantly slower than the0.1-1 quanta/s rate predicted in[8,11].This difference comes from the choice of the value of the resistance in Eq.5,which was chosen in[8,11]as an absolute upper limit.When interpreting these results,only the rough scaling should be considered.Realistic ion trap electrode geometries are more complicated than a single infinite conducting plane, involving a more closed electrode structure.This generally requires a full numerical solution to the relevant boundary value problem.Moreover,we are usually interested in the electric fieldfluctuations at the center of the trap,where thesefluctuations will be substantially different from those above an infinite plate.[4]D.M.Meekhof,C.Monroe,B.E.King,W.M.Itano,D.J.Wineland,Phys.Rev.Lett.76,1796(1996).[5]Ch.Roos,Th.Zeiger,H.Rohde,H.C.N¨a 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J.E.Thomas,Phys.Rev.A56,R1095(1997).[16]J.B.Camp,T.W.Darling,R.E.Brown,J.Appl.Phys.69,7126(1991).[17]C.Kleint,Annalen der Physik10,309(1963).[18]G.W.Timm and A.Van der Ziel,Physica32,1333(1966).[19]D.J.Wineland and H.G.Dehmelt,J.Appl.Phys.46,919(1975).[20]S.Stenholm,Rev.Mod.Phys.58,699(1986).[21]S.R.Jefferts,C.Monroe,E.W.Bell,and D.J.Wineland,Phys.Rev.A51,3112(1995).[22]C.A.Sackett,D.Kielpinski,B.E.King,nger,V.Meyer,C.J.Myatt,M.Rowe,Q.A.Turchette,W.M.Itano,D.J.Wineland,and C.Monroe,unpublished(2000).[23]There is no way to know ifω−1m is the proper way to scale for trap frequency,but it is areasonablefirst assumption.[24]ndau and E.M.Lifshitz,Statistical Physics,3rd edition Part I(Pergamon,Oxford,1980),Chapter XII.[25]G.S.Agarwal,Phys.Rev.A11,230(1975).[26]C.Henkel,S.Potting,M.Wilkens,Appl.Phys.B69,379(1999).43210<n >0.200.150.100.050.00t [ms]FIG.1.An example of heating rate data.The main graph shows ¯n (≡ n )vs t ,the delay between cooling and probing.The insets show Raman spectra from which ¯n is extracted,according to Eq.11.For the insets,P ↓is the probability that the ion remains in the |↓ state after application of a Raman probe of fixed duration with difference frequency ∆ω;rsb:red motional sideband,bsb:blue motional sideband.The sidebands shown are the 1st sidebands.The data are for trap 5fromTable I at 5MHz secular frequency and ˙¯n =12±2/ms.。
