The Size Distribution of Farms and International Productivity Differences
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。
《英美文化概论》期末考试20
一、单项选择题〔题数：50，共50.0 分〕1Why did the French consortium gave up to build the canal?( )〔1.0分〕1.0 分A、Because it was too expensive.B、Because many people died.C、Because the topography in Panama was difficult to build a canal.D、Because the American government decidded to buld it by themselves.正确答案：C 我的答案：C2The most popular pets in America is ( ).〔1.0分〕1.0 分A、DogB、FishC、BirdD、Cat正确答案：D 我的答案：D31 kilogram is ( ) pounds.〔1.0分〕1.0 分A、0.6B、1.7C、2.1D、2.2正确答案：D 我的答案：DWhich one of following is polite in western culture?( )〔1.0分〕1.0 分A、Throwing paper on the groundB、Smoking in restaurantC、Spitting in the streetD、Waiting bus in a queue正确答案：D 我的答案：D5Which car company has the most market in America?( )〔1.0分〕1.0 分A、GMB、FordC、ToyotaD、Honda正确答案：A 我的答案：A6According to the 2010 Pew Survey, ( ) of Chinese believe folk religion.〔1.0分〕1.0 分A、18.2%B、5.1%C、13.8%D、21.9%正确答案：D 我的答案：D7Which one of following is wrong about the GFC Recession? ( )〔1.0分〕A、Banks stopped lending.B、Companies cut jobs.C、Stock market crashed.D、People got more job opportunity.正确答案：D 我的答案：D8( ) was the state with the highest crime rate in America.〔1.0分〕1.0 分A、FloridaB、TexasC、New YorkD、Georgia正确答案：A 我的答案：A9( ), Missouri, Iowa, Oklahoma and California have the most farms in the USA.〔1.0分〕1.0 分A、ArizonaB、MarylandC、TexasD、Nevada正确答案：C 我的答案：C10Which one is right about George Washington?( )〔1.0分〕1.0 分He was graduated from college.B、He had three children.C、He had no experience in military action.D、He was revered as the "Father of the United States".正确答案：D 我的答案：D11The Great Depression started in ( ).〔1.0分〕1.0 分A、1929B、1932C、1933D、1939正确答案：A 我的答案：A12Which one is wrong about 9/11?( )〔1.0分〕1.0 分A、About 3000 people were killed.B、It happened in 2002.C、The World Trade Centre and Pentagon were attacked.D、It was the first attack on mainland USA since 1812.正确答案：B 我的答案：B13Which was wrong about the Civil War?( )〔1.0分〕1.0 分A、America was kept as one country.Slavery was abolished.C、After the Battle of Gettysburg, the North started to win.D、The South was strong in "hard power".正确答案：D 我的答案：D14The Democratic Party is also called ( ).〔1.0分〕1.0 分A、Enlightened PartyB、Judicial PartyC、Conservative PartyD、Liberal Party正确答案：D 我的答案：D15Bernie Madoff's clients lost about ( ) billion dollars.〔1.0分〕1.0 分A、10B、20C、30D、40正确答案：A 我的答案：A16Which one is wrong about the American political system?( )〔1.0分〕1.0 分A、The government is small.B、Leaders are educated.There are many traditions.D、The society is classless.正确答案：C 我的答案：C17Which is right about American college?( )〔1.0分〕1.0 分A、Many American college students have part time jobs.B、There is only one chance to do college entrance exam.C、There are many classed even at night.D、Friends and classmates will help you to study.正确答案：A 我的答案：A18Voting can not be ( ).〔1.0分〕1.0 分A、In personB、AbsenteeC、Making a phone callD、By mail正确答案：C 我的答案：C19Which is not the major environment issues of America?( )〔1.0分〕1.0 分A、Air pollutionB、Water shortageC、Loss of agricultural landdesertification正确答案：C 我的答案：C2068% of the 79 inventors with more than 300 utility paten families are from ( ).〔1.0分〕1.0 分A、AustraliaB、JapanC、GermanyD、USA正确答案：D 我的答案：D21The biggest religion by followers is ( ).〔1.0分〕1.0 分A、IslamB、HinduismC、ChristianityD、Buddhism正确答案：C 我的答案：C22Which one of following is not an American company?( )〔1.0分〕1.0 分A、GoogleB、CocaColaC、FacebookD、Airbus正确答案：D 我的答案：D23Which one is wrong about Franklin Delano Roosevelt?( )〔1.0分〕1.0 分A、He was also known as FDR.B、He give American people confidence during the Great Depression.C、He was elected as president for 3 times.D、He started many government programs to provide work to people.正确答案：C 我的答案：C24Why don't many people in New York City want a car?( )〔1.0分〕1.0 分A、Because car is expensive in New York City.B、Because traffic is bad in New York City.C、Because there is no place to park cars in New York City.D、Because the number of cars is limited by government.正确答案：C 我的答案：C25World Series is held in ( ) every year.〔1.0分〕1.0 分A、JulyB、AugustC、SeptemberD、October正确答案：D 我的答案：D26Who is the most powerful person according to the 2013 Forbes List?( )〔1.0分〕1.0 分A、Vladimir PutinB、Barack ObamaC、Xi JinpingD、Pope Francis正确答案：A 我的答案：A27Which one is wrong about Benjamin Franklin?( )〔1.0分〕1.0 分A、He was also a Doctor.B、He loved reading.C、He started the first public library in Philadelphia.D、He was 81 when he went to the Constitutional Convention.正确答案：A 我的答案：A28In ( ), Barack Obama was elected as the 44th President of the USA.〔1.0分〕1.0 分A、2006B、2007C、2008D、2009正确答案：C 我的答案：C29Which one of following is wrong about Abraham Lincoln?( )〔1.0分〕1.0 分A、He was the 16th president of America.B、He was killed in 1865 when the Civil War was just finished.C、He was a businessman and then became politician.D、He was born in a poor farm family.正确答案：C 我的答案：C30In American countries, ( ) has the highest homicide rate.〔1.0分〕1.0 分A、USAB、BrazilC、JamaicaD、Honduras正确答案：D 我的答案：D31The amendments to the Constitution must be supported by ( ) of the States.〔1.0分〕1.0 分A、72%B、73%C、74%D、75%正确答案：D 我的答案：D32Christopher Columbus was the first person to cross the ( ) Ocean.〔1.0分〕1.0 分A、B、IndianC、ArcticD、Atlantic正确答案：D 我的答案：D33George Washington declared ( )〔1.0分〕1.0 分A、Thanksgiving DayB、ChristmasC、HalloweenD、New Year's Day正确答案：A 我的答案：A34( ) is most used for the electricity production in the USA and China.〔1.0分〕1.0 分A、WaterB、NuclearC、WindD、Coal正确答案：D 我的答案：D35The new Constitution was singed in ( ).〔1.0分〕1.0 分A、1787B、C、1785D、1784正确答案：A 我的答案：A36Michael Phelps won ( ) Olympic medals.〔1.0分〕1.0 分A、18B、20C、22D、25正确答案：C 我的答案：C37Which one is wrong, about the geography of America and China?( )〔1.0分〕1.0 分A、China has more railways than America.B、America has two neighbour countries, Canada and Mexico.C、Both America and China's climates vary greatly.D、America's land is less than China's, but water in America is more than China.正确答案：A 我的答案：A38Which statement of following is wrong?( )〔1.0分〕1.0 分A、There were many cold conflicts in the cold war, such as weapon competition and spying.B、Germany reunited in 1990.C、The USSR was dissolved in 1990.D、After the USSR dissovled, 15 new countries were created.正确答案：C 我的答案：C39Which one is wrong about housing in western countries?( )〔1.0分〕1.0 分A、Apartment is preferred by young and old people.B、Couples get mortgage from bank to buy a house or an apartment.C、Real estate is cheap in Australia.D、More people live in houses than in high buildings.正确答案：C 我的答案：C40The New York magzine called Bernie Madoff ( ).〔1.0分〕1.0 分A、VillainB、HeroC、MonsterD、Saviour正确答案：C 我的答案：C41Registering to vote costs ( ).〔1.0分〕1.0 分A、＄5B、＄10C、＄20D、No cost正确答案：D 我的答案：D42In ( ), the first humans walked on the moon.〔1.0分〕1.0 分A、1967B、1968C、1969D、1970正确答案：C 我的答案：C43The Panama Canal was finally built by a ( ) consortium.〔1.0分〕1.0 分A、FranceB、ItalyC、BritainD、America正确答案：D 我的答案：D44The American Bill of Rights was effective in ( ).〔1.0分〕1.0 分A、1787B、1786C、1791D、1792正确答案：C 我的答案：C45Which one is wrong about Thomas Edison?( )〔1.0分〕1.0 分A、He was educated in school.B、His first job is telegraph operator.C、He had many patents.D、He invented electric light bulb.正确答案：A 我的答案：A46Bill is the short version of ( ).〔1.0分〕1.0 分A、WilliamB、StevenC、RobertD、Richard正确答案：A 我的答案：A47The capital city of Australia is ( ).〔1.0分〕1.0 分A、SydneyB、CanberraC、MelbourneD、Brisbane正确答案：B 我的答案：B48What does "When in Rome, do as the Romans do." mean?( )〔1.0分〕1.0 分A、When travelling in Rome, do what the Roman people do.B、When you are staying in another place, you should respect local culture.C、If you are in another place, you should act like the local people.D、When living in Rome, you should do what the Roman people do.正确答案：C 我的答案：C49The Super Bowl is usually held ( ).〔1.0分〕1.0 分A、AT the end of JanuaryB、In MarchC、In MayD、In November正确答案：A 我的答案：A50Which is the largest states by population?( )〔1.0分〕1.0 分A、TexasB、New YorkC、CaliforniaD、Florida正确答案：C 我的答案：C二、判断题〔题数：50，共50.0 分〕1There is only one given name in western name.( )〔1.0分〕1.0 分正确答案：×我的答案：×2Each State has the same Constitution.( )〔1.0分〕1.0 分正确答案：×我的答案：×3"Tiger Woods" is the real name of Woods.( )〔1.0分〕1.0 分正确答案：×我的答案：×4The British Parliamentary System, the Legislative Branch, Executive Branch and Judicial Branch are separated.( )〔1.0分〕1.0 分正确答案：×我的答案：×5There is no Christianity in China.( )〔1.0分〕1.0 分正确答案：×我的答案：×6Now services in China grows very fast.( )〔1.0分〕1.0 分正确答案：√我的答案：√7Over the lasr few years, guns are becoming more and more popular in America.( )〔1.0分〕1.0 分正确答案：×我的答案：×8British people migrated to America with the ship called Mayflower in 1620.( )〔1.0分〕1.0 分正确答案：√我的答案：√9In America, president can not veto legislation.( )〔1.0分〕1.0 分正确答案：×我的答案：×10Henry Ford was the first man in the world using moving assembly line in factory.( )〔1.0分〕1.0 分正确答案：√我的答案：√11Senators are elected for 5 year.( )〔1.0分〕正确答案：×我的答案：×12The first telephone line was built in 1877.( )〔1.0分〕1.0 分正确答案：√我的答案：√13Only the north tower of the World Trade Centre was attacked.( )〔1.0分〕1.0 分正确答案：×我的答案：×14Warren Buffett was born in a rich family.( )〔1.0分〕1.0 分正确答案：×我的答案：×15Boston is on the West Coast of America.( )〔1.0分〕1.0 分正确答案：×我的答案：×16In 2008, most of American agriculture imports were from China.( )〔1.0分〕1.0 分正确答案：×我的答案：×1710% of people in America use left hand.( )〔1.0分〕1.0 分正确答案：√我的答案：√18Thomas Paine was born in France.( )〔1.0分〕1.0 分正确答案：×我的答案：×192014 AD means 2014 Before the Birth of Jesus Christ.( )〔1.0分〕1.0 分正确答案：×我的答案：×20Before America purchased it,Alaska was belong to Mexico.( )〔1.0分〕1.0 分正确答案：×我的答案：×21In 2013, the Seattle Seahawks was the best defensive team during the season.( )〔1.0分〕1.0 分正确答案：√我的答案：√22Agnostic is 100% certain that there is no god.( )〔1.0分〕正确答案：×我的答案：×23In America and Australia, people prefer to big motorbikes.( )〔1.0分〕1.0 分正确答案：√我的答案：√24The Declaration of Independence was made in 1775.( )〔1.0分〕1.0 分正确答案：×我的答案：×25American president can be elected for 3 terms.( )〔1.0分〕1.0 分正确答案：×我的答案：×26It's expensive to have a horse.( )〔1.0分〕1.0 分正确答案：√我的答案：√27The Constituional Convention was held in Philadelphia.( )〔1.0分〕1.0 分正确答案：√我的答案：√28The total area of China is bigger than America.( )〔1.0分〕1.0 分正确答案：×我的答案：×29Many western students go on a gap year after finishing high school.( )〔1.0分〕1.0 分正确答案：√我的答案：√30In western countries, people don't always say thank you to other people.( )〔1.0分〕1.0 分正确答案：×我的答案：×31The Communist Party in the USA is not legal.( )〔1.0分〕1.0 分正确答案：×我的答案：×32The Cold War continued for only a few years.( )〔1.0分〕1.0 分正确答案：×我的答案：×33Both American and Chinese governments have significant direct involvement in the economy.( )〔1.0分〕1.0 分正确答案：×我的答案：×34Because the northern America is cold, James Naismith invented basketball which is a good sport for winter.( )〔1.0分〕1.0 分正确答案：√我的答案：√35The Great Depression only happened in America.( )〔1.0分〕1.0 分正确答案：×我的答案：×36America's population growth rate is lower than China's.( )〔1.0分〕1.0 分正确答案：×我的答案：×37The aim to build the Panama Canal was to connect America and Panama.( )〔1.0分〕1.0 分正确答案：×我的答案：×3896% of the farmers are black people.( )〔1.0分〕1.0 分正确答案：×我的答案：×39Benjamin Franklin was born in a rich family and well educated.〔〕〔1.0分〕1.0 分正确答案：×我的答案：×40The Pew Global Attitudes Project shows that rich countries have stronger belief in religion, but the poor countries have lower belief in religion.( )〔1.0分〕1.0 分正确答案：×我的答案：×41Because many West Germans fled to the East, the West Germany government built the Berlin Wall.( )〔1.0分〕1.0 分正确答案：×我的答案：×42In western countries, eye contact is important.( )〔1.0分〕1.0 分正确答案：√我的答案：√43Per capita means a person.( )〔1.0分〕1.0 分正确答案：√我的答案：√44Gambling is legal in western countries.( )〔1.0分〕1.0 分正确答案：√我的答案：√45Women never won the Nobel Prize.( )〔1.0分〕1.0 分正确答案：×我的答案：×46The membership of the Democratic Party is hard.( )〔1.0分〕1.0 分正确答案：×我的答案：×47There are no catholics in China.( )〔1.0分〕1.0 分正确答案：×我的答案：×48China was not affected much by the GFC Recession.( )〔1.0分〕1.0 分正确答案：√我的答案：√49Originally, the Christians were called Catholics.( )〔1.0分〕1.0 分正确答案：√我的答案：√50A senator and a representative can only be elected for two times.( )〔1.0分〕1.0 分正确答案：×我的答案：×学习文档仅供参考。
北师大版高中英语选择性必修第一册精品课件 UNIT 3 CONSERVATION Section C
Part 1 Reading comprehension Part 2 Language points
Part 1 Reading comprehension
第一步速读课文 理清脉络 Task 1 Read the email quickly and find out what the email’s main purpose is. A.The definition of factory farming. B.The advantages of factory farming. C.The disadvantages of factory farming. D.The pros and cons of factory farming. 答案 D
仿写训练
另一方面,人工智能也引发了许多担忧。例如,存在失业的风险,因为人工
智能变得更有能力执行传统上由人类执行的任务。除此之外,过度依赖人
工智能可能会对人类的独立思考和发现能力构成潜在威胁,因为有些人会
停止思考,在做出决策时完全依赖人工智能。
On the other hand
,AI also raises a number of concerns.
4.How does the author present opponents’ viewpoint according to the third paragraph? A.By listing facts. B.By giving definitions. C.By comparing different views. D.By making a comparison. 答案 A
(三)赏逻辑之巧 On the other hand,opponents of factory farming say that it is cruel to the animals.For instance,many farm animals are kept in small spaces...People who fight for animal rights claim that these animals suffer terrible stress.In addition to this,factory farming has a negative impact on the environment because it creates a lot of waste products... 赏析:作者使用“On the other hand”和“For instance”以及“In addition to”介绍 了反方观点:工业化养殖对于动物过于残忍。理由有:动物被关闭的空间小, 动物精神压力大;不环保。这些过渡词使得结构条理,表述清晰。文章还使 用其他过渡词:According to,apart from,Moreover,To sum up,In my opinion等。
试题英文数理统计
一、填空（一）各章节的introduction1、Continuous variables or interval data can assume any value in some interval of real numbers.连续变量或间隔数据可以假设在某个实数间隔中的任意值。
（measurement）Discrete variables assume only isolated values.离散变量只假定孤立的值。
(counting)11、The lower or first quartile is the 25th percentile and the upper or third quartile is the 75th percentile.12、The fist qurtile Q1 is the median of the observations falling below the median of the entire sample and the third quartile Q3 is the median of the observations falling above the median of the entire sample.The interquartile range is defined as IQR=Q3-Q1.第一个四分位数Q1是低于整个样本中位数的观测值的中位数，第三个四分位数Q3是高于整个样本中位数的观测值的中位数。
四分位数范围定义为IQR=Q3-Q1。
2、Statistics applied to the life sciences in often called biostatistics or biometry.统计学应用于生命科学，通常称为生物统计学或生物计量学。
3、A descriptive measure associated with a random variable when it is considered over the entire population is called a parameter.当在整个总体中考虑一个随机变量时，与它相关的描述性度量称为参数4、One is forced to examine a subset or sample of the population and make inferences about the entire variable of a sample is called a statistic.人们被迫检查总体中的一个子集或样本，并对样本中的整个变量做出推断，这被称为统计量。
高考英语四级试卷真题
Part I Writing (30 minutes)Directions: For this part, you are allowed 30 minutes to write a short essay on the topic of "The Importance of Environmental Protection". You should write at least 120 words and you should base your essay on the outline given below:1. The current situation of environmental pollution in China.2. The negative effects of environmental pollution on human life and nature.3. Your suggestions on how to protect our environment.---Part II Reading Comprehension (40 minutes)Section ADirections: There are 4 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A), B), C) and D). You should decide on the best choice and mark the corresponding letter on Answer Sheet 2 with a single line through the centre.Passage 1The digital revolution has transformed the way we communicate, work, and live. It has brought us unprecedented convenience and opportunities, but it has also raised serious concerns about privacy and security. One of the most significant impacts of the digital revolution is the massive amount of data generated and collected by companies and governments. This data can be a valuable resource for improving our lives, but it also poses significant risks if it falls into the wrong hands.The following questions are based on the passage above:1. What is the main topic of the passage?A) The benefits of the digital revolution.B) The challenges of the digital revolution.C) The privacy issues in the digital age.D) The security risks in the digital world.2. According to the passage, what is one of the most significant impacts of the digital revolution?A) Increased communication.B) Enhanced privacy.C) Expanded security.D) More data generation and collection.Section BDirections: There are 2 passages in this section. Each passage is followed by some multiple-choice questions. For each question or unfinished statement, there are four choices marked A), B), C) and D). You should decide on the best choice and mark the corresponding letter on Answer Sheet 2 with a single line through the centre.Passage 2The traditional way of farming, often referred to as "conventional farming," involves the use of chemical fertilizers, pesticides, and other synthetic inputs. While this method has increased crop yields and helped feed a growing global population, it has also had negative consequences for the environment and human health. Organic farming, on the other hand, emphasizes the use of natural processes and substances to grow food. It is gaining popularity as more people become aware of the health and environmental benefits of organic produce.The following questions are based on the passage above:3. What is the main difference between conventional farming and organic farming?A) The use of chemicals.B) The focus on yields.C) The reliance on natural processes.D) The cost of production.4. Why is organic farming becoming more popular?A) It is more cost-effective.B) It is more convenient.C) It offers health and environmental benefits.D) It requires less labor.---Part III Listening Comprehension (25 minutes)Section ADirections: In this section, you will hear 10 short conversations between two speakers. At the end of each conversation, a question will be asked about what was said. Both the conversation and the question will be spoken only once. After each question, there will be a pause. During the pause, you must read the four choices marked A), B), C) and D), and decide which is the best answer. Then mark the corresponding letter on Answer Sheet 2 with a single line through the centre.Example:You will hear:Man: When shall we go to the new museum?Woman: It opens at 9 o'clock and we can leave at 8:45.You will read:A) 9:00.B) 8:45.C) 9:15.D) 8:30.Choose B) 8:45.---Section BDirections: In this section, you will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A), B), C) and D). Then mark the corresponding letter on Answer Sheet 2 with a single line through the centre.Passage 3The following questions are based on the passage above:5. What is the main topic of the passage?A) The benefits of healthy eating habits.B) The challenges of maintaining a healthy diet.C) The importance of exercise in maintaining health.D) The role of sleep in recovery and health.6. According to the passage, what is one of the most common health issues related to poor diet?A) Heart disease.B) Cancer.C) Mental health issues.D) All of the above.---Part IV Translation (30 minutes)Directions: For this part, you are allowed 30 minutes to translate a passage from Chinese into English. You should write your answer on Answer Sheet 2.In recent years, the concept of "green living" has gained increasing attention. People are becoming more aware of the importance ofprotecting the environment and living a sustainable lifestyle. From using reusable bags and water bottles to reducing energy consumption, there are many simple ways to contribute to a greener world. The government is also taking steps to promote environmental protection, such as implementing stricter regulations on pollution and encouraging the use of renewable energy sources. It is our collective responsibility to ensure a healthy and sustainable future for generations to come.。
风电综述
A Comprehensive Overview on Reactive Power Compensation Technologies for Wind PowerApplicationsAhmed Faheem Zobaa1, and Milutin Jovanovic21Cairo University, Giza, Egypt2Northumbria University, Newcastle upon Tyne, United KingdomAbstract— The size and number of wind farms contributing to the energy production is continuously growing. The rating of wind turbines has increased from less than 1 MW a few years ago to 2- to 3-MW being installed today with 5-MW machines under development. The interaction of the wind farm, reactive power compensators, and the associated power network is being investigated. Because the loads and the wind farms' output fluctuate during the day, the use of reactive power compensation is ideal for the power system network. The purpose of this study is to provide wind farm developers and interested researchers with some valuable insights into the reactive power compensation techniques for wind farm power systems.I. I NTRODUCTIONind energy is a rapidly expanding industry.Global installed capacity has increased from 2,500 MW in 1992 to just over 40,000 MW at the end of 2004, at an annual growth rate of nearly 30%. Almost three quarters of this capacity has been installed in Europe. The European Wind Energy Association (EWEA) scenarios show that the future prospects of the global wind industry are promising and the total wind power installed worldwide could quadruple to 160,000 MW by 2012 [1,2]. For example, penetration levels in the electricity sector have reached 20% in Denmark. The German state of Schleswig-H olstein has 1,800 MW of installed wind capacity, enough to meet 30% of the region’s total electricity demand, while in Navarra (Spain), 50% of consumption is met by wind power.A reactive power compensator is a very important component of the wind generation system in the wind farms. Most of the wind turbines currently operating in the area are based on conventional cage induction generators (fixed speed, constant frequency ‘Danish’ concept) [1]. An induction generator requires reactive power to be supplied from the grid. It is therefore necessary to provide this power locally, and as close as possible to the demand levels. In the early days of wind farm development, the wind farm operators were supposed to compensate each wind turbine operated under no-load conditions. H owever, the induction generator requires an increasing amount of reactive power with load, and without proper compensation, the output voltage of the wind farm would oscillate with the wind speed variations. The aim of this paper is to review the reactive power compensation methods currently employed to tackle this and similar problems in wind farm power systems [1]-[18].II. O VERVIEWWind Energy Conversion Systems (WECS) are site specific and an intermittent source of power due to the nature of the wind velocity instantaneous and seasonal variations. This entails a high degree of precision in allocating a suitable site and sophistication in controlling the generated voltage and frequency produced by the WECS generating part.The WECS are used to either supply power to remote areas [3] or into the nearby distribution network (at the point of common coupling) incorporated as distributed generation ‘DG’ or bulk producing wind farms [4]. In order to supply power to remote areas as shown in Fig. 1, the generating system, operated in the so-called stand-alone mode, has to be equipped with its own ancillary units, such as voltage regulation and power factor correction devices and must also have sufficient storage capacity to meet the load demand, otherwise a second source of energy such as a diesel/alternator generating set need to be integrated in parallel with the system. On the other hand, grid-connected WECS use either inland or offshore large wind turbine ‘WT’ generators (10KW to 2MW units). The grid integrated WECS must meet the hosting utility integration requirements and adhere to the strict safety and protection regulations [5]. Once the integration is established, the WECS are considered to be a viable contribution and increase the utility’s reserve capacity. If the WECS are connected to the distribution network, grid integrated ancillary services are likely to be supplied by the hosting utility, which can impose stress, additional cost and pronounced network vulnerability to instabilities.The grid integrated WECS, as shown in Fig. 2, come in two categories; fixed speed and variable speed. The key advantages of variable speed WECS generators compared to their fixed-speed counterparts are the reduced mechanical stresses and higher conversion efficiency but at the expense of increased capital and maintenance cost [6]-[8]. The fixed speed WECS normally use a cage induction generator, coupled to theWwind turbine shaft through a fixed ratio gearbox, and therefore operate in a narrow range above the synchronous speed (so that the speed is virtually constant) with the wind turbine rotational speed being regulated by mechanical means (pitch control) at high winds. Variable speed WECS, however, allow the turbine to rotate at different rotational speeds ‘to match the maximum allowable wind velocity/power path’ thus maximizing the wind energy capture. The generator is usually a conventional induction generator with a gearbox, or a multi-pole wound rotor or permanent magnet synchronous generator directly coupled to the wind turbine rotor (the so called direct or gearless drive) [7,9]. In general, the generated voltage and frequency are electronically controlled using a bi-directional power converter connected either at the stator side (in this case, it must be fully-rated) or at the rotor side of a doubly-fed slip ring induction generator (DFIG) in a slip power recovery system where it can be partially-rated (due to limited speed ranges around the synchronous speed) with obvious cost reduction implications. Additional power factor correction capacitors are normally connected across the generator terminal once the load power factor is at low level.Voltage Electric DCloadFig. 1. Wind Energy Conversion System for off-grid applicationsP o in t o f C o m m o n P W M Fig. 2. Wind Energy Conversion System for grid integrationWind farms are arrays of WECS’s interconnected electrically so as to deliver cumulative power to the utility grid [10] as shown in Fig. 3. The electrical power output is considerably smoothed relative to that of a single turbine. The degree of smoothing depends on thegeographical extent of the wind farm, average wind speed, the control characteristics of the wind turbines and, finally, details of the terrain and how they influence the distribution of wind speeds across the wind farm. From an electrical power flow perspective, the wind farm acts in parallel with the utility's conventional generating capacity to supply the power demands of the connected load. Wind farms are made of tens to hundreds of turbines and have overall power rating of thousands to tens of megawatts. Usually, however, the power rating of a wind farm is but a small fraction of the conventional generation capacity on the grid, typically known as the wind penetration ratio. In general the ratio of wind generating capacity to the total system capacity (wind plus conventional sources) serving utility load at any given moment is measured by the wind penetration which currently does not exceeds 15% for most wind farms.To the distribution gridFig. 3. WECS grid integrated Wind FarmsIII. P ARALLEL C OMPENSATIONParallel compensation is a common practice in wind turbine generation systems and is used to increase the power factor of each turbine. Some wind turbines employ more than one value of the capacitor at their terminals to compensate reactive power at different wind speeds. The advantage of an improved power factor is the reduction of total current loading, which, in turn, reduces transmission loss and improves voltage regulation.Based on the equivalent circuit diagram in Fig. 4, the voltage and current equations in a vector form can be written as:E S = V S + n (R S + j X S ) I S (1) I S = I IM + I C (2)To keep the terminal voltage constant, it is necessary to adjust the amount of generated reactive power to follow the fluctuation in output power and to compensate for different number of turbines on-line.Fig. 4. Per-turbine, per–phase equivalent circuit of an induction machine (simplified) in a wind farm with n turbines Various sizes of capacitors or Static VAR Compensators (SVCs) can be used where the reactive power can be adjusted continuously at a different slip or power level. Ideally, a small-sized capacitor can be used during low wind speed to raise the voltage to an appropriate level, and a larger capacitor can be used in a high wind speed region to raise the voltage and the electromagnetic torque above the peak of aerodynamic torque.IV. S ERIES C OMPENSATIONFor series compensation, as the name implies, the capacitor is installed in series with the transmission line. The size of the capacitor is chosen to compensate for the line impedance, i.e., to reduce the effective reactance in the line impedance.The series capacitors are often used to improve the power transfer capability of transmission lines. Variable series capacitance is usually implemented by using thyristor control series (TCSC).Fig. 5 shows a per-phase, per-turbine equivalent circuit of a series-compensated system. Note that although the circuit is simplified, the actual calculations used to draw phasor diagrams are based on the complete circuit.The equations corresponding to the equivalent circuit in Fig.5 are:E S = V S + V Zs + V C (3)V Zs + V C = n (R S + j X S) I S- j n X C I S (4)Fig. 5. Series compensation of an induction machine (simplified) ina wind farm with n turbinesWith capacitor compensation, a small size of AC capacitor means a high reactance.Although the compensation improves the voltage conditions and the torque profile of the generator, there is an increase in the stator current in comparison to the uncompensated system for the same situation (300 turbines on-line). Parallel compensation improves the effective power factor of the wind farm seen from the PCC, thus reducing the transmission line current and the corresponding losses. Series compensation reduces the voltage drop across the transmission line, thus improving the electromagnetic torque of the induction generator.The effective power factor of the wind farm is not affected by series compensation. In a parallel compensation, the level of compensation decreases if the voltage across the capacitor decreases. On the other hand, in series compensation, the level of compensation increases with the increase of the line current. It is necessary to investigate the variation of terminal voltage at different slip and with different number of turbines on-line to determine the range of voltage on the PCC at different conditions.V. P ARALLEL A ND S ERIES C OMBINATION It is apparent that we can take advantage of both parallel and series compensation abilities of an AC capacitor. In a parallel compensation, the capacitor is used to compensate the individual induction generator, and for series compensation, to compensate the line impedance. Fig. 6 shows the per-phase equivalent circuitof a wind turbine connected to an infinite bus.Fig. 6. Series and parallel compensation of an induction machine(simplified)The equations for parallel and series combination can be written as:E S = V S + V Zs + V C (5)V Zs + V C = n (R S + j X S) I S - j n X C I S (6)I S = I IM + I C (7)VI. D YNAMIC C OMPENSATIONTwo kinds of dynamic compensation of reactive power will be highlighted below: SVC (Static Var Compensator) and SVC Light. The former is based on thyristor-controlled reactors and thyristor switched capacitors, whereas the latter is VSC (Voltage Source Converter) based.A Thyristor-Controlled Reactor (TCR) consists of a fixed reactor in series with a bi-directional thyristor valve. TCR reactors are by default of air core type, glassfiber insulated, and epoxy resin impregnated.A Thyristor-Switched Capacitor (TSC) consists of a capacitor bank in series with a bi-directional thyristor valve and a damping reactor, which also serves to de-tune the circuit to avoid parallel resonance with the network. The thyristor switch acts to connect or disconnect the capacitor bank for an integral number of half-cycles of the applied voltage. The TSC is not phase controlled, which means it does not generate any harmonic distortion. A complete SVC based on TCR and TSC may be designed in a variety of ways, to satisfy a number of criteria and requirements for its grid operation.SVC characteristics: Usually, the terminal voltage is allowed to vary in proportion with the compensating current, in accordance to a set slope. The SVC of TCR / TSC type is very useful as a means of dynamic voltage control in a number of situations such as mitigation of not too rapid voltage fluctuations and preventing voltage collapses in conjunction with grid faults as discussed above. Its dynamic response is limited by the maximum switching frequency of ordinary grid commutated power thyristors, i.e. 100 Hz.SVC control: The main objective of the control system is to determine the SVC susceptance needed at the point of connection to the power system, in order to keep the system voltage as close as possible to some desired value. This function is realised by measuring and comparing the system voltage with the set (reference) value. In case of a discrepancy between the measured and reference values, the controller makes sure that necessary changes are made in the susceptance until equilibrium is attained. The desired susceptance value is determined by the voltage regulator of the controller, and is achieved by generating appropriate firing signals for each thyristor. The overall active SVC susceptance is given by the sum of susceptances of the harmonic filters, the continuously controllable TCR, and the TSC if switched into operation. The control system also includes supervision of currents and voltages in different branches. If needed, protective actions are taken.Thyristor valves: The thyristor valves consist of single-phase assemblies. The thyristors are electrically fired. The energy for firing is taken from snubber circuits, also being part of the valve assembly. The order for firing the thyristors is communicated via optical light guides from the valve control unit located at ground potential. Between thyristors, heat sinks are located. The heat sinks are connected to a water piping system. The cooling media is a low conductivity mixture of water and glycol. The TCR and TSC valves each comprise a number of thyristors in series, to obtain the voltage blocking capability needed for the valves.Bi-Directional Control Thyristors:H igh power thyristors are normally able to conduct in one direction only, which is acceptable for most applications. In the SVC case, however, thyristors conducting in both directions of the current cycle would definitely offer possibilities for cost as well as space savings. In the most recent SVCs supplied, the thyristor valves are equipped with so-called Bi-Directional Control Thyristors (BCT). In such devices, two thyristors are actually integrated into one wafer with separate gate contacts. The two component thyristors of the BCT function completely independently of each other under static and dynamic operating conditions, and each of them has performance similar to a separate conventional device of the same current carrying capability. The valves comprise only one thyristor stack in each phase instead of two this resulting in a more compact design.SVC Light: With the advent of fully controllable semiconductor devices of high power rating, high performance voltage source converters have become feasible far into the tens of MVA range. With the SVC Light concept, the VSC (Voltage Source Converter) and IGBT (Insulated Gate Bipolar Transistor) technologies have been brought together to create a tool offering possibilities hitherto unseen for power quality improvement in industry and power distribution. This opens up completely new options for power quality control in areas so far unattainable or only partly manageable, such as active filtering and far-reaching mitigation of voltage flicker in sub transmission and distribution grids. The SVC Light technology is being implemented at present for flicker mitigation at a couple of different locations within European electric power industry.SVC Light is a flicker-mitigating device. It achieves this by tackling the root of the problem, the erratic flow of reactive power through the supply grid down into the loads. The reactive power consumption is measured, and corresponding amounts are generated in the SVC Light and injected into the system, thereby decreasing the net reactive power flow to an absolute minimum. As an immediate consequence, voltage flicker is decreased to a minimum, as well.Voltage Source Converters: The function of the VSC is to match the bus voltage in phase and frequency, and with amplitude, which can be continuously and rapidly controlled, so that it can be used as an effective tool for reactive power control.To this controlled reactive power branch, an offsetting capacitor bank is usually added in parallel, enabling the overall control range of the SVC Light to be capacitive. The reactive power supplied to the network is controlled at high rates by appropriately changing the switching pattern of the converter power devices. The response time is limited mainly by the switching frequency and the size of the reactor.The controllability of IGBTs also facilitates series connection of devices with safeguarded voltage sharing across each IGBT. This enables the SVC Light to be directly connected to voltages of tens of kV. Thanks to this, it becomes unnecessary to parallel converters in order to achieve the power ratings needed for wind power farms of the order of tens of MVA or larger.Pulse Width Modulation: The input of the Voltage Source Converter is connected to a capacitor, which is acting as a DC voltage source. At the output, the converter is creating a variable AC voltage by connecting the positive pole or the negative pole of the capacitor directly to any of the converter outputs. In converters thatutilize Pulse Width Modulation (PWM), the input DC voltage is normally kept constant and sinusoidal output voltage waveforms having only high switching harmonics are generated. The amplitude, frequency and phase of the fundamental output voltage is controlled by changing the switching pattern of the inverter legs.The VSC of the SVC Light has a switching frequency greater than 1 kHz. The voltage across the reactor at full reactive power is only a small fraction (typically 15%) of the output voltage. This makes the SVC Light nearly an ideal tool for fast reactive power compensation.IGBT: This power device has been chosen as the most appropriate for the SVC Light since it allows series connections owing to the low delay times for turn-on and turn-off. The IGBT has low switching losses and can thus be used at high switching frequencies. Nowadays, devices are available with both high power handling capability and high reliability, making them suitable for high power converters.As only a small power is needed for gate control of the IGBT, this can be taken from the main circuit. This is highly advantageous in high voltage converters, where many devices are connected in series. In addition, each IGBT module is equipped with an over-voltage monitoring system, which makes it possible to detect any operating abnormalities during the delivery test so that faulty devices could be replaced.The converter valve: The converter topology for the SVC Light is a three-level configuration. In such a converter the output of each phase can be connected to either the positive pole, the mid-point or the negative pole of the capacitor. The DC side of the converter is floating, or in other words, insulated relative to ground. Using the PWM, the converter will produce a very smooth phase current, with low harmonic content. The three-level topology also features low switching losses this implying high converter efficiency and high current capability.VII. C ONCLUSIONSCapacitor compensation can help boost the voltage at the PCC, thus improving the torque-speed capability of an individual induction generator.Ideal parallel compensation requires a variable reactive power as the output power and power factor fluctuate. A Static VAR Compensator can serve for this purpose.Series compensation can be used to offset the voltage drop across the line impedance. The capacitance value can be computed given the required compensation. TSCS can be considered to provide an adjustable series capacitor compensation.A combination of parallel and series compensation can improve the overall system. With a correct choice of capacitor sizes, fixed capacitors can be employed for both series and parallel compensation.Dynamic compensation of reactive power is an effective means of preserving power quality as well as voltage stability. It can be implemented by using thyristor-controlled reactors and thyristor-switched capacitors in parallel with the grid (SVC). An alternative is the voltage source converter (VSC) based shunt compensation. Here, the SVC Light combines VSC and IGBT technologies to attain high dynamic response, a prerequisite for effective flicker mitigation.R EFERENCES[1] European Wind Energy Association (EWEA), Press Release, London 23rd November 2004.[2] P. Weis-Taylor, “Implementing Agreement for Co-operation in the Research and Development of Wind Turbine Systems,” International Energy Agency ‘IEA’ 26th Wind Energy Annual Report 2003. PWT Communications in Boulder, Colorado, United States, April 2004.[3] T. F. Chan, K. A. Nigim, and L. I. Lai, “Voltage and frequency control of self excited slip ring induction generators,” IEEE Trans. on Energy Conversion, vol.19, no.1, March 2004, pp.81 – 87.[4] C. Jauch, P. Sørensen and B. Bak-Jensen, “International Review of Grid Connection Requirements for Wind Turbines,” NORDIC wind power conference, March 1-2, 2004, Chalmers University of Technology, Sweden.[5] J. Matevosyan, T, Ackermann, S.Bolik and L. Söder, “Comparison of International Regulations for Connection of Wind Turbines to the Network,” NORDIC wind po wer co nference, Chalmers University of Technology. Sweden , March 1-2, 2004,.[6] G. A. Smith and K. A. Nigim, “A multi function electrical generator for a wind turbine,” Wind Engineering Jo urnal, vol.VII, UK, spring 1989.[7] S. Muller, M. Eeicke & R. W. De Doncker, “Doubly fed induction generator systems for wind turbines,” IEEE Industry Applicatio n Magazine, May/June 2002.[8] L.H. H ansen, F. Blaabjerg, H.C. Christensen and U. Kindhard “Generators and power electronics technology for wind teurbines,” 27th Annual c o nference o f the IEEE Industrial Electr o nics S o ciety, IECON’01, Denver, Colorado, USA, 2001.[9] D. Schreiber, “State of the Art of Variable Speed Wind Turbines,” 11th Internatio nal Sympo sium o n Po wer Electro nics, Ee2001, NOVI SAD, YUGOSLAVIA, OCT. 31 – NOV. 2, 2001[10] E. G. Potamianakis and C. D. Vournas, “Aggregation of wind farms in distribution networks,” European Wind Energy Conference and Exhibition, Madrid, June, 2003.[11] W.Q. Jeffries, “Analysis and Modeling of Wind/Diesel Systems Without Storage”, Ph.D. Thesis, Department of Mechanical Engineering, University of Massachusetts, 1994.[12] M.P. Papadopoulos, et al., “Penetration of Wind Turbines in Islands with Diesel Power Stations”, Proc. EWEC 1988, pp. 512-517. [13] J.T.G. Pierik, and De Bonte, “Quasi Steady State Simulation of Autonomous Wind Diesel Systems” (Status Report), Report No. ECN-85-091, Netherlands Energy Research Foundation, Petten, May 1985. [14] K. Uhlen, and O. Skarstein, “A Short Term Dynamic Simulation Model for Wind/Diesel Systems”, Proc. 10 BWEA Conference, pp. 239-242, 1988.[15] P.M. Anderson, A. Bose, “Stability Simulation on Wind Turbine Systems”, IEEE Transactions on Power Apparatus and Systems, Vol. PAS-102, No. 12, December 1983, pp. 3791-3795.[16] E.N. H inrichsen, P.J. Nolan, “Dynamic of Single and Multi Unit Wind Energy Conversion Plants Supplying Electric Utility Systems”, OE/ET/20466 - 78/1 Report.[17] R. Grunbaum, B. H alvarsson, A. Wilk-Wilczynski, “FACTS and HVDC Light for Power System Inter- 11 connections”, Power Delivery Conference, Madrid, Spain, September 1999.[18] Mid-Continent Area Power Pool (MAPP), Regional Reliability Handbook, MAPP, St. Paul, Mn. 1999.。
[大学英语考试复习资料]大学英语四级分类模拟题523
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2．如果当选，你将为同学做什么? 答案:A Campaign Speech Ladies and Gentlemen,
Good evening! Thank you for coming to this election campaign today. With the trust and complete support of my team, I am delighted to announce that I am running for chairman of the Student Union. There are some reasons, I think, to join the activity. As a
该段第二句中指出种植这些作物的农场主已经发现自1980年以来随着气温的升高作物产量的增长速度逐渐放缓尽管其他政策和经济因素对此也有一定影响
[大学英语考试复习资料]大学英语四级分类模拟题 523
[大学英语考试复习资料]大学英语四级分类模拟题 523
大学英语四级分类模拟题 523
Part Ⅰ Writing 问题:1. Directions: For this part, you are allowed 30 minutes to write a campaign speech in support of your election to the post of chairman of the Student Union. You should write at least 120 words following the outline given below in Chinese.
Moore pointed out that the biggest issues are often how quickly farmers in Europe will adapt to climate change (adaptation uncertainty) and how crop yields will respond to climate change (response uncertainty).
人工智能原理MOOC习题集及答案北京大学王文敏课件
正确答案：A、B 你选对了Quizzes for Chapter 11 单选(1 分)图灵测试旨在给予哪一种令人满意的操作定义得分/ 5 多选(1 分)选择下列计算机系统中属于人工智能的实例得分/总分总分A. Web搜索引擎A. 人类思考B.超市条形码扫描器B. 人工智能C.声控电话菜单该题无法得分/1.00C.机器智能 1.00/1.00D.智能个人助理该题无法得分/1.00正确答案：A、D 你错选为C、DD.机器动作正确答案： C 你选对了6 多选(1 分)选择下列哪些是人工智能的研究领域得分/总分2 多选(1 分)选择以下关于人工智能概念的正确表述得分/总分A.人脸识别0.33/1.00A. 人工智能旨在创造智能机器该题无法得分/1.00B.专家系统0.33/1.00B. 人工智能是研究和构建在给定环境下表现良好的智能体程序该题无法得分/1.00C.图像理解C.人工智能将其定义为人类智能体的研究该题无法D.分布式计算得分/1.00正确答案：A、B、C 你错选为A、BD.人工智能是为了开发一类计算机使之能够完成通7 多选(1 分)考察人工智能(AI) 的一些应用，去发现目前下列哪些任务可以通过AI 来解决得分/总分常由人类所能做的事该题无法得分/1.00正确答案：A、B、D 你错选为A、B、C、DA.以竞技水平玩德州扑克游戏0.33/1.003 多选(1 分)如下学科哪些是人工智能的基础？得分/总分B.打一场像样的乒乓球比赛A. 经济学0.25/1.00C.在Web 上购买一周的食品杂货0.33/1.00B. 哲学0.25/1.00D.在市场上购买一周的食品杂货C.心理学0.25/1.00正确答案：A、B、C 你错选为A、CD.数学0.25/1.008 填空(1 分)理性指的是一个系统的属性，即在_________的环境下正确答案：A、B、C、D 你选对了做正确的事。
得分/总分正确答案：已知4 多选(1 分)下列陈述中哪些是描述强AI (通用AI )的正确答案？得1 单选(1 分)图灵测试旨在给予哪一种令人满意的操作定义得分/ 分/总分总分A. 指的是一种机器，具有将智能应用于任何问题的A.人类思考能力0.50/1.00B.人工智能B. 是经过适当编程的具有正确输入和输出的计算机，因此有与人类同样判断力的头脑0.50/1.00C.机器智能 1.00/1.00C.指的是一种机器，仅针对一个具体问题D.机器动作正确答案： C 你选对了D.其定义为无知觉的计算机智能，或专注于一个狭2 多选(1 分)选择以下关于人工智能概念的正确表述得分/总分窄任务的AIA. 人工智能旨在创造智能机器该题无法得分/1.00B.专家系统0.33/1.00B. 人工智能是研究和构建在给定环境下表现良好的C.图像理解智能体程序该题无法得分/1.00D.分布式计算C.人工智能将其定义为人类智能体的研究该题无法正确答案：A、B、C 你错选为A、B得分/1.00 7 多选(1 分)考察人工智能(AI) 的一些应用，去发现目前下列哪些任务可以通过AI 来解决得分/总分D.人工智能是为了开发一类计算机使之能够完成通A.以竞技水平玩德州扑克游戏0.33/1.00常由人类所能做的事该题无法得分/1.00正确答案：A、B、D 你错选为A、B、C、DB.打一场像样的乒乓球比赛3 多选(1 分)如下学科哪些是人工智能的基础？得分/总分C.在Web 上购买一周的食品杂货0.33/1.00A. 经济学0.25/1.00D.在市场上购买一周的食品杂货B. 哲学0.25/1.00正确答案：A、B、C 你错选为A、CC.心理学0.25/1.008 填空(1 分)理性指的是一个系统的属性，即在_________的环境下D.数学0.25/1.00 做正确的事。
三层宾州筛检测标准
College of Agricultural Sciences • Cooperative Extension Evaluating particle size of forages and TMRs using the Penn State Particle Size SeparatorJud HeinrichsDepartment of Dairy and Animal ScienceThe Pennsylvania State University324 Henning BuildingUniversity Park, PA 16802(814) 865-5491 • FAX (814) 865-7442/teamdairy/––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––Include:TopicsIntroductionGuidelines on particle sizeParticle size separator instructionsParticle size effects on the dairy cowRecommended fiber intakesINTRODUCTION___________________________________________________________________________________________________________________________________Having the proper particle size distribution of forages is an important part of a total ration formulation program. Until recently this has been difficult to measure on farms. Many dairy nutritionists have put subjective measures on this aspect of the diet and most have been quite effective in making ration changes in respect to this measure.The new Penn State Forage Particle Size Separator is currently available to quantitatively determine the forage particle size of various components. The concept of forage particle size analysis and having a standard method for this is not new. The American Society of Agricultural Engineers' standard for particle size analysis and distribution has been available for many years. The objective in developing the easy to handle Penn State separator was to mimic the cumbersome laboratory method for measuring forage and total mixed ration (TMR) particle sizes.Forage particle size analysis begins with harvesting forages at the proper stage of maturity. Chopping the crop at the proper length allows the forages that can be combined in a total ration to achieve the desired ration particle length.Measuring the particle length of individual forages is only one part of the solution. In fact, measuring single forages for particle size is similar to analyzing that forage for crude protein. There are recommended ranges for individual forages, but the real use of the measurement is in combining forages to achieve the proper particle size in the total ration, much like combining feeds to achieve the proper protein level in the ration.The main goal in analyzing the particle size of the total ration is to measure the distribution of feed and forage particles that the cow actually consumes. Examine not only the particles greater than a particular size, but also the overall distribution of feed particles being consumed by the dairy cow. It is recommended that a TMR be measured from fresh samples taken from the feed bunk before the cows eat or sort the feed. Mixing and distribution equipment can reduce particle size of feeds and forages and needs to be accounted for when evaluating the diet.GUIDELINES ON PARTICLE SIZE___________________________________________________________________________________________________________________________________Achieving adequate ration particle size requires using recommended guidelines for forages and TMRs (Table 1). Particle size guidelines have been obtained from field data consisting of a large number of farms and samples studied over several months. The results of forage and TMR particle size distribution can be a tool in formulating rations, especially for forage neutral detergent fiber (NDF) intake, total NDF intake, and forage dry matter intake. Corn silageCorn silage can be quite variable and depends largely on the amount fed in the diet. If corn silage is the sole forage, then some longer particle size is suggested. At least 5 to 10 percent of the particles should be in the upper sieve of the separator (> 0.75 inches). When corn silage is not the sole forage, then 2 to 4 percent of the particles in the top sieve may be adequate.___________________________________________________________________________________________________________________________________It is more critical to chop corn silage so that a good fermentation can occur yet not be pulverized. This means that about 40 to 50 percent of the silage material measured is in both the middle (<0.75 and >0.31 inches) and bottom (<0.31 inches) pans of the separator. As corn silage makes up a greater proportion of the ration, the more that should be in the middle sieve and less in the bottom pan.The newer systems of harvesting corn silage that includes chopping and rolling in one process can create a silage with 10 percent or more of the forage material having long particles without large pieces of whole cobs or stalks. This forage can still be excellent quality because adequate fermentation can occur in the silo due to packing characteristics.More conventional choppers that are operated to create such long particle size in corn silage would create a forage material that would be predisposed to mold formation due to poor silo compaction. The material usually has large pieces of cob, dry stalks and leaves that have poor palatability and may often be refused by high producing cows.HaylageThere is a lot of variability with haylage due to the type and use of machinery, sward type and density, and most of all, the dry matter of the crop harvested. Ten to 25 percent of the crop should be in the top sieve of the particle separator. This means that 10 to 25 percent of the forage particle size is greater than 0.75 inches. If the distribution of forage particles is determined, then the amount of forage particles greater than 1 inch can be approximated.The type of silo structure may require altering the particle size distribution recommended. Forages stored in upright sealed silos would likely fall at the lower end of the range (10 to 15 percent). Bunker silos can have appreciably longer material ranging from 15 to 25 percent. The middle pan should contain 30 to 40 percent of the material and the bottom pan 40 to 50 percent.TMRField investigations conducted at Penn State have found that there is a high degree of variability in overall rations. Feeding management plays an important role in the particle length needs of the cow. Ideally 10 percent or more of the material should be greater than 0.75 inches (top sieve). It was observed that many rations have only 3 to 8 percent of the TMR particles in the top sieve (> 0.75 inches). This extrapolates to many rations having less than 1 percent of the particles as being greater than 1.5 inches. While this goes against many old thumb rules, there are many farms feeding these types of rations with obvious success.Feeding management, balanced rations, and attention to total ration NDF and forage NDF levels are likely a large part of their success. Some generally preferred guidelines to follow for TMRs are 6 to 10 percent of the particles in the top sieve, 30 to 50 percent in the middle sieve, and 40 to 60 percent in the bottom pan in rations for high producing dairy cows.___________________________________________________________________________________________________________________________________PARTICLE SIZE SEPARATOR INSTRUCTIONS___________________________________________________________________________________________________________________________________The Penn State Particle Size Separator is currently available from Nasco. For their free phone order service dial 1-800-558-9595. The data sheet and Weibull paper to use with the particle size separator are attached to the back of this publication. An accurate scale is also needed for weighing the samples and the boxes.Using the separatorStack the three plastic separator boxes on top of each other in the following order: sieves with the large holes (upper sieve) on top, the smaller holes (middle sieve) in the center and the pan on the bottom. Place approximately 3 pints of forage or TMR in the upper sieve.On a flat surface, shake the sieves in one direction 5 times. There should be no vertical motion during shaking. This process should be repeated 7 times for a total of 8 sets or 40shakes with the sieves rotated 1/4 turn after each set of 5 shakes. See sieve shaking pattern shown in Figure 1.Weigh the material on the sieves and on the bottom pan. Note that the material above the upper sieve is greater than 0.75 inches long, the material on the middle sieve is between 0.31 and 0.75 inches, and the material on the bottom pan is less than 0.31 inches. See Table 2 for data entry and how to compute percentages under each sieve.PARTICLE SIZE SEPARATOR INSTRUCTIONS (CONTINUED) ___________________________________________________________________________________________________________________________________Using Weibull paperWeibull paper is used to graph the distribution of forage and TMR particles of the sample using the three weighed fractions from the sieves. The number of forage and TMR particles in a sample do not follow a normal distribution population, however they can be plotted as a straight-line distribution using the unique Weibull graphing paper.Plotting the sample allows one to extrapolate beyond the measured points (.75 and .31 inches). It should be noted that the accuracy of these values decrease as the line is extended beyond these two points. Therefore the line should not be drawn beyond .2 and 1.5 inches.Referring to Table 2, value [e] refers to 0.75 inches and value [f] to 0.31 inches. These percentages are plotted on Weibull paper and an appropriate line drawn between the two points (Figure 2).On Weibull paper, the horizontal axis is for particle size and the vertical axis is for cumulative percent undersized. The axesare not linear. For the example given in Table 2, the following deductions or statements can be made:- approximately 8% of the feed is > 0.75inches- approximately 30% of the feed fallsbetween 0.31 and 0.75 inches- approximately 62% of the feed are <0.31 inchesAnother interpretation could be:- approximately 97% of the feed are < 1.0inch- approximately 80% of the feed are<0.50inches- approximately 48% of the feed are < 0.22inchesThis example would indicate a typical, well cut corn silage. This material can be used as a component of a forage-feeding program where another longer forage material is also used.PARTICLE SIZE SEPARATOR INSTRUCTIONS (CONTINUED) ___________________________________________________________________________________________________________________________________Figure 2. Weibull paperPARTICLE SIZE EFFECTS ON THE DAIRY COW___________________________________________________________________________________________________________________________________The dairy cow's need for increasingly higher levels of energy have led to diets relatively high in concentrates. All silage diets have replaced diets high in long hay in today's larger herds and more mechanized farms. However, cows still require adequate fiber in the ration to function properly. When the minimum fiber levels are not met, cows often show one or more of the following metabolic disorders: reduced total dry matter digestibility, reduced milk fat percentage, displaced abomasum, and an increase in the incidence of rumen parakeratosis, laminitis, acidosis, and fat cow syndrome. Cows consuming sufficient NDF with finely chopped forage can also exhibit the same metabolic disorders as a diet deficient in fiber.Adequate forage particle length is necessary for proper rumen function. Reduced forage particle size has been shown to decrease the time spent chewing and cause a trend toward decreased rumen pH . When cows spend less time chewing, there is a decrease in the volume of saliva produced needed to buffer the rumen.It has been shown that insufficient particle size will decrease the rumen acetate to propionate ratio and pH, which will lower milk fat percent. When rumen pH falls below 6.0, the growth of the cellulolytic organisms are depressed, allowing for an increase in the propionate producing microbes decreasing the acetate to propionate ratio.Reduced forage particle size increases dry matter intake, decreases digestibility, and results in less rumen solid retention time. Diets that have a smaller forage particle size enter the rumen at a smaller size after initial chewing and swallowing, and therefore leave the rumen at a faster rate. The result is an increase in the rumen turn over rate allowing for an increase in dry matter intake. Smaller forage particles spend less time in the rumen for microbial digestion, thereby reducing digestibility, particularly fiber digestion.If rations or forages are too fine in particle size a small amount of long hay or balage can make improvements in achieving some long particles in the ration. Farms feeding 5 or more pounds of long hay per cow daily would not likely have problems with overall particle size. Many farms, however, do not have long hay as an option. In these situations, the distribution of the total ration particle size is likely more important than particles greater than a certain length.Particle size analysis is not the end all for ration problems. It does give a way to measure this variable and to improve upon the overall nutrition of the dairy cow. Feeding a ration containing extremely fine particle size length with a small amount being greater than 0.75 inches is not recommended. Diets containing very fine particle size can predispose cows to rumen acidosis and other associated problems.RECOMMENDED FIBER INTAKES___________________________________________________________________________________________________________________________________Adequate NDF intake by the dairy cow is necessary for normal rumen function, production, and health. A majority of the NDF in the ration must be in the form of forage NDF along with sufficient ration particle size to maintain a healthy rumen environment.Under conditions where particle size is marginal, special attention must be paid to maintaining adequate levels of total NDF and forage NDF intakes (Table 3 and 4).The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities. The Pennsylvania StateUniversity does not discriminate against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, or veteran status. Direct all inquiries regarding thenondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 201 Willard RECOMMENDED FIBER INTAKES (CONTINUED )___________________________________________________________________________________________________________________________________Suggested ranges for total NDF should be at least 1.10 to 1.20 percent of body weight. Forage NDF intake can range from .75 to 1.10 percent of body weight.However, if the forage or TMR particle length is too fine, then a higher minimum (> 0.85 percent of body weight) should be used in the ration.Table 3. Guidelines for forage NDF intake.Forage NDF as % of body weight 1 Intake level.75%2 Minimum if ration provides 1.30-1.40% total NDF by use of byproduct feeds. .85%2 Minimum if ration provides 1.00-1.20% total NDF by use of grains or starchy feeds. .90% Moderately low .95% Average 1.00 % Moderately low 1.10% Maximum1Forage dry matter intake should range between 1.40% to 2.40% of body weight regardlessof forage NDF intake parameters. 2Higher minimum may be necessary if forage is chopped too fine.Table 4. Guidelines for total NDF and forage NDF intakes as a percent of the total ration drymatter when using low NDF concentrates.Milk production Total NDF intake Forage NDF intake High (> 80 pounds) 28-32% 21-27% Medium (60-80 pounds) 33-37% 25-32% Low (< 60 pounds)38-42%29-36%。
托福TPO36综合写作阅读原文+听力原文+满分范文
为了帮助大家高效备考托福，为大家带来托福TPO36综合写作阅读原文综合写作阅读原文++听力原文听力原文++满分范文，希望对大家备考有所帮助。
托福TPO36综合写作阅读原文文本：Hail—pieces of ice that form and fall from clouds instead of snow or rain—has Hail—pieces of ice that form and fall from clouds instead of snow or rain—has always been a problem for farmers in some areas of the United States. Hail pellets can fall with great force and destroy crops in the field. Over the last few decades,a method of reducing hail, called "cloud seeding," has been tried. In cloud seeding,the chemical silver iodide is sprayed on storm clouds from an airplane. This makes the clouds produce harmless rain or snow instead of hail. Several pieces of evidencesuggest that cloud seeding has been effective in protecting crops from hail.Laboratory experiments Experiments in the laboratory support the idea that cloud seeding is effective. Hail usually forms water vapor that is close to the freezing point However, when experimenters added silver iodide to cold water vapor in the laboratory, they often observed light snow forming instead of hail pellets. Evidencefrom Asia There is evidence about the effectiveness of cloud seeding from several countries around the world. In some Asian countries, for example, cloud seeding hasbeen successfully used to control precipitation in urban areas. These positive results suggest that cloud seeding should also be effective in protecting fields andfarms in the United States. Local studies A few local studies also support the valueof cloud seeding. One study conducted in a farming region in the central United States,for example, directly monitored crop damage due to hail. The study found that in an area where cloud seeding was used there was reduced hail damage compared to previousyears.托福TPO36综合写作听力原文文本：It’s not clear that cloud seeding is all that effective and there are reasons It’s not clear that cloud seeding is all that effective and there are reasons to question each of the arguments you just read. First, it may be true that under laboratory conditions silver iodide creates snow instead of hail. However, in real life, silver iodide can actually prevent any precipitation at all from forming in the cloud, snow, rain or hail. This is a bad thing. Because if you seed all the cloudsin areas where it doesn’t rain very often, you ran the risk of causing a drought. In this case the crops simply get damaged for a different reason: lack of water.Second,it's not clear that positive result of cloud seeding in Asia can be repeated in the United States. The reason is that cloud seeding in Asia was tried in urban areas, in cities. And cities tend to have a high level of air pollution, from car, factory,etc. Surprisingly, pollution particles can create favorable conditions for cloud seeding because they interact with clouds and seeding chemicals. Such favorable conditions for cloud seeding may not occur in an unpolluted area. This means that the cloud seeding method that works in polluted cities may not work in unpolluted farming regions in the United States.Third, the local study mentioned in the passageisn’t very convincing either. That’s because the study found that hail damagedecreased not just in the area where the cloud seeding actually took place, but also in many of the neighboring areas to the east, south and north of the area. So the fact that the whole region was experiencing a reduce number of hail storms that particular year makes it more likely that this was a result of natural variation in local weather, and has nothing to do with cloud seeding.托福TPO36综合写作满分范文：The Theauthor discussed that although hail makes crops suffer a lot, there has always been a method called cloud seeding which can protect crops from this disaster. He listed three facts supporting this approach. However, the speaker holds acontradictory view that all these three ways are not reliable. First, the writer proposes that laboratory experiments has already proved that cloud seeding iseffective in eliminating hail. But the professor points out that although the hail can be turned into rain and snow in experimental movement, but it is also possible that hail, snow and rain can be all prevented by cloud seeding. Consequently, it willcause drought. Crops will still be damaged as a result of lack of water. The writer’sfirst argument is refuted. Second, the passage indicates that cloud seeding has an Asia evidence. To render this disproof, the lecturer reveals that this successful application in Asia probably will not get a similar outcome in America. High air pollution offers favorable conditions for cloud seeding process because thosepolluted air can interact with cloud and seeding chemicals. So this method which canbe used in cities area may not be effective in unpolluted farming area. The second idea in the passage is also retorted. Third, the essay says that local studies in central United States also attain a satisfying result. Nevertheless, the speaker rebuts this idea. He thinks it unconvincing because hail damage in whole America notonly decreases just in central of America, but also in the east, south and north partof country. So it is hard to say cloud seeding is the exact factor causes all those good things. Natural variation and local weather can also contribute to theelimination of hail disaster. This overturns the writer’s concept. (294 words) 以上是给大家整理的托福TPO36综合写作阅读原文综合写作阅读原文++听力原文听力原文++满分范文，希望对你有所帮助帮助!!。
雅思阅读长难句分析
雅思阅读长难句分析我们先来看几个例子1. 题目：Research completed in 1982 found that in the United States soil erosion……C3T2P2A reduced the productivity of farmland by20 per centB was almost as severe as in India and ChinaC was causing significant damage to 20 per cent of farmlandD could be reduced by converting cultivated land to meadow or forest原文：The United States, where the most careful measurements have been done, discovered in 1982 that about one-fifth of its farmland was losing topsoil at a rate likely to diminish the soil’sproductivity.很明显，原文是一个长句，而对于长句的处理就是找出主干，我们可以看出来，这个句子的主干是The United States discovered in 1982 that about one-fifth of its farmland was losingtopsoil。
所以答案就非常明显应该选择C。
所以你会发现很多考生都会选的A项经过对此长句的分析，它根本就不在此长句的主干，也就是说这是对作者要表达的意思的补充说明。
从这里我们可以看出，出题者对干扰项的出题思路，干扰项所在的位置都是定位句子的非主干部分。
2. 题目：Paragraph B How the port changes a city’s infrastructure C2T2P3原文：Port cities become industrial, financial and service centers and political capitals because of their water connections and the urban concentration which arises there and later draws to itrailway, highways and air routes. Water transport means cheap access, the chief basis of all port cities. Many of the world’s biggest cities, for example, London, New York, Shanghai, Istanbul,Buenos Aries, Tokyo, Jakarta, Calcutta, Philadelphia and San Francisco began as ports—that is, with land-sea exchange as their major function—but they have since grown disproportionately inother respects, so that their port functions are no longer dominant.They remain different kinds of places from non-port cities and their port functions account for that difference.做这一道题的时候，考生只要知道出题者的出干扰项的思路，就不会选How the port changes a city’s inf rastructure这个小标题。
2021年高中英语(新教材)人教版选择性必修一课时素养评价 十五 Unit 5 Using Language (含解析)
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课时素养评价十五Unit 5Using LanguageⅠ. 单句语法填空1. What some scientists have found is that their long-term use can sometimes harm both the land and people’s health.2. Pesticides can damage the land by killing not only harmful bacteria and insects, but also helpful ones.3. Organic farming is simply farming without using (use) any chemicals.4. Organic farmers also use many other methods (method) to produce rich soil.5. The goal of using different organic farming methods is to grow good food while avoiding(avoid) damage to the environment or to people’s health.6. Some people would prefer to stop the use of man-made chemicals in agriculture entirely (entire).7. What keeps them from doing so is the fact that chemical farming serves the high demand for food around the world.Ⅱ. 完成句子1. When they were first introduced, many farmers welcomed them as a great way to fight crop disease and increase production.当它们被首次推广时, 许多农民欢迎它们, 把它们作为抗击作物疾病和增加产量的好方法。
博世汽车SPC
4th Edition, 07.20053rd Edition dated 06.19942nd Edition dated 05.19901st Edition dated 09.19872005 Robert Bosch GmbHTable of ContentsIntroduction (5)1. Terms for Statistical Process Control (6)2. Planning .........................................................................................................................................................8 2.1 Selection of Product Characteristics .................................................................................................8 2.1.1 Test Variable ........................................................................................................................8 2.1.2 Controllability ......................................................................................................................9 2.2 Measuring Equipment .......................................................................................................................9 2.3 Machinery .........................................................................................................................................9 2.4 Types of Characteristics and Quality Control Charts ......................................................................10 2.5 Random Sample Size ......................................................................................................................11 2.6 Defining the Interval for Taking Random Samples (11)3. Determining Statistical Process Parameters ................................................................................................12 3.1 Trial Run .........................................................................................................................................12 3.2 Disturbances ....................................................................................................................................12 3.3 General Comments on Statistical Calculation Methods ..................................................................12 3.4 Process Average ..............................................................................................................................13 3.5 Process Variation . (14)4. Calculation of Control Limits ......................................................................................................................15 4.1 Process-Related Control Limits ......................................................................................................15 4.1.1 Natural Control Limits for Stable Processes ......................................................................16 4.1.1.1 Control Limits for Location Control Charts .........................................................16 4.1.1.2 Control Limits for Variation Control Charts ........................................................18 4.1.2 Calculating Control Limits for Processes with Systematic Changes in the Average .........19 4.2 Acceptance Control Chart (Tolerance-Related Control Limits) .....................................................20 4.3 Selection of the Control Chart .........................................................................................................21 4.4 Characteristics of the Different Types of Control Charts . (22)5. Preparation and Use of Control Charts ........................................................................................................23 5.1 Reaction Plan (Action Catalog) .......................................................................................................23 5.2 Preparation of the Control Chart .....................................................................................................23 5.3 Use of the Control Chart .................................................................................................................23 5.4 Evaluation and Control Criteria ......................................................................................................24 5.5 Which Comparisons Can be Made? (25)6. Quality Control, Documentation .................................................................................................................26 6.1 Evaluation .......................................................................................................................................26 6.2 Documentation .. (26)7. SPC with Discrete Characteristics ...............................................................................................................27 7.1 General ............................................................................................................................................27 7.2 Defect Tally Chart for 100% Testing . (27)8. Tables (28)9. Example of an Event Code for Mechanically Processed Parts ....................................................................29 9.1 Causes .............................................................................................................................................29 9.2 Action ..............................................................................................................................................29 9.3 Handling of the Parts/Goods ...........................................................................................................30 9.4 Action Catalog .. (30)10. Example of an x -s Control Chart (32)11. Literature (33)12. Symbols (34)Index (35)IntroductionStatistical Process Control (SPC) is a procedure for open or closed loop control of manufacturing processes, based on statistical methods.Random samples of parts are taken from the manufacturing process according to process-specific sampling rules. Their characteristics are measured and entered in control charts. This can be done with computer support. Statistical indicators are calculated from the measurements and used to assess the current status of the process. If necessary, the process is corrected with suitable actions.Statistical principles must be observed when taking random samples.The control chart method was developed by Walter Andrew Shewhart (1891-1967) in the 1920´s and described in detail in his book “Economic Control of Quality of Manufactured Product”, published in 1931.There are many publications and self-study programs on SPC. The procedures described in various publications sometimes differ significant-ly from RB procedures.SPC is used at RB in a common manner in all divisions. The procedure is defined in QSP0402 [1] in agreement with all business divisions and can be presented to customers as the Bosch approach.Current questions on use of SPC and related topics are discussed in the SPC work group. Results that are helpful for daily work and of general interest can be summarized and published as QA Information sheets. SPC is an application of inductive statistics. Not all parts have been measured, as would be the case for 100% testing. A small set of data, the random sample measurements, is used to estimate parameters of the entire population.In order to correctly interpret results, we have to know which mathematical model to use, where its limits are and to what extent it can be used for practical reasons, even if it differs from the real situation.We differentiate between discrete (countable) and continuous (measurable) characteristics. Control charts can be used for both types of characteristics.Statistical process control is based on the concept that many inputs can influence a process.The “5 M´s” – man, machine, material, milieu, method – are the primary groups of inputs. Each “M” can be subdivided, e.g. milieu in temperature, humidity, vibration, contamination, lighting, ....Despite careful process control, uncontrolled, random effects of several inputs cause deviation of actual characteristic values from their targets (usually the middle of the tolerance range).The random effects of several inputs ideally result in a normal distribution for the characteristic.Many situations can be well described with a normal distribution for SPC.A normal distribution is characterized with two parameters, the mean µ and the standard deviation σ.The graph of the density function of a normal distribution is the typical bell curve, with inflection points at σµ− and σµ+.In SPC, the parameters µ and σ of the population are estimated based on random sample measurements and these estimates are used to assess the current status of the process.1. Terms for Statistical Process ControlProcessA process is a series of activities and/or procedures that transform raw materials or pre-processed parts/components into an output product.The definition from the standard [3] is: “Set of interrelated or interacting activities which trans-forms inputs into outputs.”This booklet only refers to manufacturing or assembly processes.Stable processA stable process (process in a state of statistical control) is only subject to random influences (causes). Especially the location and variation of the process characteristic are stable over time (refer to [4])Capable processA process is capable when it is able to completely fulfill the specified requirements. Refer to [11] for determining capability indices. Shewhart quality control chartQuality control chart for monitoring a parameter of the probability distribution of a characteristic, in order to determine whether the parameter varies from a specified value.SPCSPC is a standard method for visualizing and controlling (open or closed loop) processes, based on measurements of random samples.The goal of SPC is to ensure that the planned process output is achieved and that corresponding customer requirements are fulfilled.SPC is always linked to (manual or software supported) use of a quality control chart (QCC). QCC´s are filled out with the goal of achieving, maintaining and improving stable and capable processes. This is done by recording process or product data, drawing conclusions from this data and reacting to undesirable data with appropriate actions.The following definitions are the same as or at least equivalent to those in [6].Limiting valueLower or upper limiting valueLower limiting valueLowest permissible value of a characteristic (lower specification limit LSL)Upper limiting valueHighest permissible value of a characteristic (upper specification limit USL)ToleranceUpper limiting value minus lower limiting value:LSLUSLT−=Tolerance rangeRange of permissible characteristic values between the lower and upper limiting valuesCenter point C of the tolerance rangeThe average of the lower and upper limiting values:2LSLUSL C +=Note: For characteristics with one-sided limits (only USL is specified), such as roughness (Rz), form and position (e.g. roundness, perpen-dicularity), it is not appropriate to assume 0=LSL and thus to set 2/USLC= (also refer to the first comment in Section 4.1.1.1).PopulationThe total of all units taken into considerationRandom sampleOne or more units taken from the population or from a sub-population (part of a population)Random sample size nThe number of units taken for the random sample Mean (arithmetic)The sum of theix measurements divided by the number of measurements n:∑=⋅=niixnx11Median of a sampleFor an odd number of samples put in order from the lowest to highest value, the value of the sample number (n+1)/2. For an even number of samples put in order from the lowest to highest value, normally the average of the two samples numbered n/2 and (n/2)+1. (also refer to [13])Example: For a sample of 5 parts put in order from the lowest to the highest value, the median is the middle value of the 5 values.Variance of a sampleThe sum of the squared deviations of the measurements from their arithmetic mean, divided by the number of samples minus 1:()∑=−⋅−=niixxns12211Standard deviation of a sampleThe square root of the variance:2ss=RangeThe largest individual value minus the smallest individual value:minmaxxxR−=2. PlanningPlanning according to the current edition of QSP 0402 “SPC”, which defines responsibilities. SPC control of a characteristic is one possibility for quality assurance during manufacturing and test engineering.2.1 Selection of Product CharacteristicsSpecification of SPC characteristics and their processes should be done as early as possible (e.g. by the simultaneous engineering team). They can also, for example, be an output of the FMEA.This should take• Function,• Reliability,• Safety,•Consequential costs of defects,•The degree of difficulty of the process,• Customer requests, and•Customer connection interfaces, etc.into account.The 7 W-questions can be helpful in specifying SPC characteristics (refer to “data collection” in “Elementary Quality Assurance Tools” [8]): Example of a simple procedure for inspection planning:Why do I need to know what, when, where and how exactly?How large is the risk if I don’t know this? Note: It may be necessary to add new SPC characteristics to a process already in operation. On the other hand, there can be reasons (e.g. change of a manufacturing method or intro-duction of 100% testing) for replacing existing SPC control with other actions.SPC characteristics can be product or process characteristics.Why?Which or what? Which number or how many?Where? Who?When?With what or how exactly?2.1.1 Test VariableDefinition of the “SPC characteristic”, direct or indirect test variable. Note: If a characteristic cannot be measured directly, then a substitute characteristic must be found that has a known relationship to it.2.1.2 ControllabilityThe process must be able to be influenced (controlled) with respect to the test variable. Normally manufacturing equipment can be directly controlled in a manner that changes the test variable in the desired way (small control loop). According to Section 1, “control” in the broadest sense can also be a change of tooling, machine repair or a quality meeting with a supplier to discuss quality assurance activities (large control loop).2.2 Measuring EquipmentDefinition and procurement or check of the measuring equipment for the test variable.Pay attention to:• Capability of measuring and test processes, • Objectiveness,• Display system (digital),• Handling. The suitability of a measurement process for the tested characteristic must be proven with a capability study per [12].In special cases, a measurement process with known uncertainty can be used (pay attention to [10] and [12]).Note: The units and reference value must correspond to the variables selected for the measurement process.2.3 MachineryBefore new or modified machinery is used, a machine capability study must be performed (refer to QSP0402 [1] and [11]). This also applies after major repairs.Short-term studies (e.g. machine capability studies) register and evaluate characteristics of products that were manufactured in one continuous production run. Long-term studies use product measurements from a longer period of time, representative of mass production. Note: The general definition of SPC (Section 1) does not presume capable machines. However, if the machines are not capable, then additional actions are necessary to ensure that the quality requirements for manufactured products are fulfilled.2.4 Types of Characteristics and Control Charts This booklet only deals with continuous anddiscrete characteristics. Refer to [6] for these andother types of characteristics.In measurement technology, physical variables are defined as continuous characteristics. Counted characteristics are special discrete characteristics. The value of the characteristic is called a “counted value”. For example, the number of “bad” parts (defective parts) resulting from testing with a limit gage is a counted value. The value of the characteristic (e.g. the number 17, if 17 defective parts were found) is called a “counted value”.SPC is performed with manually filled out form sheets (quality control charts) or on a computer.A control chart consists of a chart-like grid for entering numerical data from measured samples and a diagram to visualize the statistical indices for the process location and variation calculated from the data.If a characteristic can be measured, then a control chart for continuous characteristics must be used. Normally the sx− chart with sample size 5=n is used.2.5 Random Sample SizeThe appropriate random sample size is a compromise between process performance, desired accuracy of the selected control chart (type I and type II errors, operation characteristic) and the need for an acceptable amount of testing. Normally 5=n is selected. Smaller random samples should only be selected if absolutely necessary.2.6 Defining the Interval for Taking Random SamplesWhen a control chart triggers action, i.e. when the control limits are exceeded, the root cause must be determined as described in Section 5.4, reaction to the disturbance initiated with suitable actions (refer to the action catalog) and a decision made on what to do with the parts produced since the last random sample was taken. In order to limit the financial “damage” caused by potentially necessary sorting or rework, the random sample interval – the time between taking two random samples – should not be too long.The sampling interval must be individually determined for each process and must be modified if the process performance has permanently changed.It is not possible to derive or justify the sampling interval from the percentage of defects. A defect level well below 1% cannot be detected on a practical basis with random samples. A 100% test would be necessary, but this is not the goal of SPC. SPC is used to detect process changes.The following text lists a few examples of SPC criteria to be followed.1. After setup, elimination of disturbances orafter tooling changes or readjustment, measure continuously (100% or with randomsamples) until the process is correctly centered (the average of several measure-ments/medians!). The last measurements canbe used as the first random sample for furtherprocess monitoring (and entered in the control chart). 2. Random sample intervals for ongoingprocess control can be defined in the following manner, selecting the shortest interval appropriate for the process.Definition corresponding to the expected average frequency of disturbances (as determined in the trial run or as is knownfrom previous process experience).Approximately 10 random samples within this time period.Definition depending on specified preventivetooling changes or readjustment intervals.Approximately 3 random samples within thistime period.Specification of tooling changes or readjust-ment depending on SPC random samples.Approximately 5 random samples within theaverage tooling life or readjustment interval.But at least once for the production quantitythat can still be contained (e.g. delivery lot,transfer to the next process, defined lots forconnected production lines)!3. Take a final random sample at the end of aseries, before switching to a different producttype, in order to confirm process capabilityuntil the end of the series.Note: The test interval is defined based on quantities (or time periods) in a manner that detects process changes before defects are produced. More frequent testing is necessary for unstable processes.3. Determining Statistical Process Parameters3.1 Trial RunDefinition of control limits requires knowledge or estimation of process parameters. This is determined with a trial run with sampling size and interval as specified in Sections 2.5 and 2.6. For an adequate number of parts for initial calculations, take a representative number of unsorted parts, at least 25=m samples (with n = 5, for example), yielding no fewer than 125 measured values. It is important to assess the graphs of the measured values themselves, the means and the standard deviations. Their curves can often deliver information on process performance characteristics (e.g. trends, cyclical variations).3.2 DisturbancesIf non-random influences (disturbances) occur frequently during the trial run, then the process is not stable (not in control). The causes of the disturbances must be determined and elimi-nated before process control is implemented (repeat the trial run).3.3 General Comments on Statistical Calculation MethodsComplicated mathematical procedures are no longer a problem due to currently available statistics software, and use of these programs is of course allowed and widespread (also refer to QSP0402 [1]).The following procedures were originally developed for use with pocket calculators. They are typically included in statistics programs.Note: Currently available software programs allow use of methods for preparing, using and evaluation control charts that are better adapted to process-specific circumstances (e.g. process models) than is possible with manual calculation methods. However, this unavoidably requires better knowledge of statistical methods and use of statistics software. Personnel and training requirements must take this into account.Each business division and each plant should have a comprehensively trained SPC specialist as a contact person.Parameter µ is estimated by:Example (Section 10): samplesof number valuesx the of total mxx mj j===∑=1ˆµ3622562862662.......x ˆ=+++==µor:samplesof number mediansthe of total mxx m j j===∑=1~~ˆµ46225626363....x ~ˆ=+++==µIf µˆ significantly deviates from the center point C for a characteristic with two-sided limits, then this deviation should be corrected by adjusting the machine.Parameter σ is estimated by:Example (Section 10):a) ∑=⋅=m j j s m 121ˆσ41125552450550222.......ˆ=+++=σsamplesof number variancesthe of total =σˆNote: s =σˆ is calculated directly from 25 individual measurements taken from sequential random samples (pocket calculator).or b) na s=σˆ, where27125552450550.......s =+++=samplesof number deviationsdard tan s the of total ms s mj j==∑=1351940271...a s ˆn ===σnn a3 0.89 5 0.94 See Section 8, Table 1 7 0.96 for additional valuesor c) ndR =σˆ, with96225611....R =+++= samplesof number rangesthe of total mR R mj j==∑=1271332962...d R ˆn ===σn n d3 1.69 5 2.33 See Section 8, Table 1 7 2.70 for additional values Note: The use of table values n a and n d pre-supposes a normal distribution!Some of these calculation methods were originally developed to enable manual calculation using a pocket calculator. Formula a) is normally used in currently available statistics software.4. Calculation of Control Limits4.1 Process-Related Control LimitsThe control limits (lower control limit LCL andupper control limit UCL) are set such that 99% of all the values lie within the control limits in the case of a process which is only affected by random influences (random causes).If the control limits are exceeded, it must there-fore be assumed that systematic, non-random influences (non-random causes) are affecting the process.These effects must be corrected or eliminated by taking suitable action (e.g. adjustment).Relation between the variance (standard deviation x σ) of the single values (original values, individuals) and the variance (standard deviation x σ) of the mean values: nxx σσ=.4.1.1 Natural Control Limits for Stable Processes4.1.1.1 Control Limits for Location Control Charts (Shewhart Charts)For two-sided tolerances, the limits for controlling the mean must always be based on the center point C. Note: C is replaced by the process mean x =µˆ for processes where the center point C cannot be achieved or for characteristics with one-sided limits.* Do not use for moving calculation of indices!Note: Use of the median-R chart is onlyappropriate when charts are manually filled out, without computer support.n*A E C n c'E EE E3 1.68 1.02 1.16 2.93 1.73 5 1.230.59 1.20 3.09 1.337 1.020.44 1.21 3.19 1.18Estimated values µˆ and σˆ are calculated per Sections 3.4 and 3.5.Refer to Section 8 Table 2 for additional values.Comments on the average chart: For characteristics with one-sided limits (or in general for skewed distributions) and small n , the random sample averages are not necessarily normally distributed. It could be appropriate to use a Pearson chart in this case. This chart has the advantage compared to the Shewhart chart that the control limits are somewhat wider apart. However, it has the disadvantage that calculation of the control limits is more complicated, in actual practice only possible on the computer.Control charts with moving averagesThe x chart with a moving average is a special case of the x chart. For this chart, only single random samples are taken.n sample measurements are formally grouped as a random sample and the average of these n measurements is calculated as the mean.For each new measurement from a single random sample that is added to the group, the first measurement of the last group is deleted, yielding a new group of size n , for which the new average is calculated.Of course, moving averages calculated in this manner are not mutually independent. That is why this chart has a delayed reaction to sudden process changes. The control limits correspond to those for “normal” average charts:σˆn .C LCL ⋅−=582 σˆn.C UCL ⋅+=582Calculate σˆ according to Section 3.5 a)Control limits for )3(1=n :σˆ.C LCL ⋅−=51 σˆ.C UCL ⋅+=51Example for )3(1=n :3 74 741.x = 3 7 4 9 762.x = 3 7 4 9 2 053.x = 3 7 4 9 2 8 364.x =This approach for moving sample measurements can also be applied to the variation, so that an s x − chart with a moving average and moving standard deviation can be used.After intervention in the process or process changes, previously obtained measurements may no longer be used to calculate moving indices.4.1.1.2 Control Limits for Variation Control ChartsThe control limits to monitor the variation (depending on n ) relate to σˆ and s and like-wise R (= “Central line”).s charta) generally applicable formula(also for the moving s x − chart)Example (Section 10):σˆB UCL 'Eob⋅= 62351931...UCL =⋅=σˆB LCL 'Eun ⋅= 30351230...LCL =⋅=b) for standard s x − chartNote: Formula a) must be used in the case ofmoving s calculation. Calculation of σˆ per Section 3.5 a).s B UCL *Eob ⋅= 62271052...UCL =⋅=s B LCL *Eun ⋅=30271240...LCL =⋅=R chartR D UCL Eob ⋅=2696212...UCL =⋅=R D LCL Eun ⋅=70962240...LCL =⋅=Tablen 'Eun B 'Eob B *Eun B *Eob B Eun D Eob D3 5 70.07 0.23 0.34 2.30 1.93 1.76 0.08 0.24 0.35 2.60 2.05 1.88 0.08 0.24 0.34 2.61 2.10 1.91See Section 8, Table 2 for further values4.1.2 Calculating Control Limits for Processes with Systematic Changes in the AverageIf changes of the mean need to be considered as a process-specific feature (trend, lot steps, etc.) and it is not economical to prevent such changes of the mean, then it is necessary to extend the “natural control limits”. The procedure for calculating an average chart with extended control limits is shown below.The overall variation consists of both the “inner” variation (refer to Section 3.5) of the random samples and of the “outer” variation between the random samples.Calculation procedure Control limits for the mean。
关于农场的英语作文
A farm is a place where agriculture is practiced,and it is often a source of fascination for many people,especially those who live in urban environments.Here are some key points to consider when writing an essay about a farm in English:1.Introduction to the Farm:Begin your essay by introducing the farm.Describe its location,size,and the type of landscape it is situated in.For example,is it a small family farm nestled in the countryside,or a large commercial operation in a flat,fertile plain?2.Types of Crops and Livestock:Discuss the variety of crops grown on the farm and the types of livestock raised,if any.Mention the primary crops like wheat,corn,or soybeans, and any secondary crops that might be grown for local markets or personal use.If the farm has animals,describe the breeds of cows,pigs,or chickens,and what they are used fordairy,meat,or eggs.3.Seasonal Activities:Describe the different activities that take place on the farm throughout the year.This could include planting and harvesting crops,caring for animals, and maintaining the farms infrastructure such as fences and barns.4.Farm Equipment and Technology:Talk about the machinery and tools used on the farm.Modern farms often use advanced technology for planting,harvesting,and monitoring crop health.Mention any specific equipment like tractors,combines,or drones that are used.5.Farmers Daily Life:Give insight into the daily life of a farmer.Discuss the hard work and dedication required to manage a farm,including early mornings,physical labor,and the responsibility of caring for animals.6.Economic and Environmental Impact:Consider the economic impact of the farm on the local community and the environment.Discuss how the farm contributes to the local economy through jobs and the sale of its products.Also,touch on any sustainable practices the farm might employ to reduce its environmental footprint.7.Challenges and Opportunities:Address the challenges that farmers face,such as weather conditions,pests,and market fluctuations.On the other hand,discuss the opportunities for growth and innovation in farming,such as organic farming,agritourism, or the use of new technologies.8.Conclusion:Conclude your essay by summarizing the main points and reflecting on the importance of farms in providing food and contributing to the economy and culture of a region.Remember to use descriptive language to paint a vivid picture of the farm and its activities.This will help engage your readers and give them a clear understanding of what life on a farm is like.。
陕西省西安市牛羊养殖场职业暴露高危人群布鲁氏菌感染相关风险因素分析
2021年第38卷第5期陕西省西安市牛羊养殖场职业暴露高危人群布鲁氏菌感染相关风险因素分析王 新1，徐 琨2，张靖飞1，冯 鹏1，高 娴1，赵 康3（1. 西安市动物疫病预防控制中心，陕西西安 710018；2. 西安市疾病预防控制中心，陕西西安 710054；3. 灞桥区动物疾病预防控制中心，陕西西安 710024）摘 要：为掌握陕西省西安市牛羊养殖场职业暴露人群布鲁氏菌感染风险因素，做好高危人群布鲁氏菌病防控工作，2019年对西安市39个布鲁氏菌病阳性养殖场及346位职业暴露高危人群进行流行学调查，并采用单因素分析及多因素logistic 回归分析，找出养殖场高危人群感染风险因素。
结果显示：畜间布鲁氏菌病在养殖方式上主要发生于散养场（27/39），时间上发生于4月、7—8月、10月，在畜种上以羊群为主（28/39）。
对从业人员主观潜在风险因素的单因素分析发现，感染从业人员与未感染高危人员在挤奶、喝生牛羊乳、接生、免疫、接触流产畜（流产物及粪便）病差异均有统计学意义（P＜0.05）；多因素logistic回顾分析发现，挤奶（OR=2.435，95%CI=1.137~5.071）、喝生牛羊乳（OR=2.893，95%CI=1.218~7.569）、接生（OR=3.217，95%CI=1.382~8.036）、接触流产畜（流产物及粪便，OR=2.439，95%CI=1.175~5.209）是从业人员感染的风险因素。
同时，对养殖场客观潜在风险因素的单因素分析及多因素logistic回顾分析显示，场区消毒（OR=0.694，95%CI=0.307~1.043）、流产病死畜无害化处理（OR=0.549，95%CI=0.325~1.105）也是从业人员感染的风险因素。
结果表明，挤奶、喝生牛羊乳、接生、接触流产畜（流产物及粪便）是从业人员感染的主观性风险因素，场区消毒、流产病死畜无害化处理是从业人员感染的客观风险因素。
小农户数据画像说明书
A data portrait of smallholder farmers An introduction to a dataset on small-scale agricultureThe Smallholder Farmers’ Dataportrait is a comprehensive, systematic and standardized data set on the profile of smallholder farmers across the world. It can generate an image on how small family farmers in both emerging and developing countries live their lives. It is about putting in numbers, the constraints they face, and the choices they make so that policies can be informed by evidence to meet the challenge of agricultural development. The family farm as a firmAcross all levels of development, family farms are the dominant type of firm in agriculture. For many crops, farming over a large area requires hired labour, and hired labour requires supervision. For a family that runs a farm, supervision costs can be high relative to the benefits of operating at a greater scale. This makes the small family farm optimal as a firm.The size of family farms, their production patterns and factor use depend on agro-ecological and soil conditions, technology, the relative prices of inputs and outputs, as well as the size of the family. Family farms are, in general, small, as high supervision costs contain the farm size. Indeed, the concepts underpinning the definitions of smallholders and family farms coincide.In developed countries, where farmers facelower capital transaction costs and can1spread capital over large areas, some family farms can be relatively large. In developing countries, families farm small plots of land: they face low transaction costs in labour, engage more workers per hectare, who being family, are motivated to work. This gives them a productivity advantage over larger farms. In some regions, such as Latin America and East Europe, family farms coexist with large corporate farms. Today’s smallho lder farm unwrappedThe success of the Green Revolution in Asia put small family farms, or smallholders, firmly on the development agenda. Productivity growth in smallholder farms contributes towards growth not only by reducing the price of staple food, but also by increasing the demand for labour in rural areas, generating jobs for the poor and raising the unskilled labour wage rate. However, i n today’s modern markets, smallholder farmers must overcome considerable constraints. Sales through sophisticated channels, such as supermarkets, require greater managerial skills and an ability to provide continuity of supply and meet food safety, certification and quality requirements. Agricultural research is becoming increasingly private, focusing on technologies which are knowledge intensive, being developed for larger, commercial farms. This renders technology adoption by small farmers difficult. Smallholder farms face considerable difficulties in accessing credit, as banks are often reluctant to lend due to poor collateral and lack of information. These market failures potentially offset any advantage small farmers may have in productivity. Smallholder farms and development from one region to anotherThe differences in family farms between countries are significant. Equally significant are the differences in the stages of structural transformation across regions. Africa has been bypassed by the Green Revolution and a share of its people experience extreme poverty and hunger. Paradoxically, Africa has been urbanizing fast, but labour productivity in agriculture is low and farm sizes decline. The development agenda highlights the need to stimulate labour productivity in smallholder farms through technical change and promote market participation.Latin America is now urbanized and in many countries smallholder farms coexist with larger commercial farming enterprises. Within the family farm sector, the inequality is pronounced, in spite past land reform policies. Extra efforts may be needed not to bypass or squeeze out smallholder farmers. Some policy prescriptions for growth incline towards increasing smallholder competitiveness, or expanding their asset base through further redistributive interventions. Other measures focus on longer run solutions, and tend to favour enhancing human capital and managing rural poverty through cash transfers.Asia offers many positive lessons on agricultural development but rural poverty remains a problem. In spite of agricultural productivity increases and the fast-growing industrial sector, many Asian countries have undergone a structural transformation characterized by a slow rate of urbanization. Although farmers close to urban centres are becoming increasingly commercial due to strong demand by consumers – who are rapidly diversifying and enriching their diets– more and more smallholder farmers are cut off from modern supply chains. Rural population growth, in conjunction with slow urbanization, also means that policy makers should pay attention to the rural non-farm sector through the creation of a large number of jobs outside agriculture.The need for informationAcross the development policy fora, there is no clear consensus on the likely future direction of small family farm agriculture. Smallholders are the centre of interest by many, but opinions differ on where it is best for them to be in the future. The focus on the importance of structural transformation is weak.This lack of focus is strongly reflected on the availability of information on small-scale agriculture. In spite of the wealth of data, in the form of censuses and household surveys, a comprehensive, systematic and standardized data set on the profile of smallholder farmers across the world has still to be developed. There is need to know, how much and what food is produced by smallholder farmers, how much of their income is generated by farming, how much produce they sell, which is their asset base and much more.Such information will generate an array of benefits: first, it will underline the strengths but also the weaknesses of small-scale family agriculture in many countries, highlighting its linkages with the rural and wider economies and help assess the potential for development; second, it will uncover the main constraints to agricultural development and underscore their importance across countries and regions; third, it will provide valuable insights for the formulation of policy options at national, regional and global levels; and, fourth, it will serve as a platform for advocacy for the role of smallholder farms in growth, emphasizing the fact that their evolution is both the cause and the effect of development.This note introduces a systematic data set for smallholders covering many countries across the world, both developing and emerging. The dataset – being developed in FAO – estimates the number of smallholders and with eight concise indicator groups draws a portrait of smallholder agriculture. In other words, the data ‘take stock’ of smallholder farmers across countries, identify their characteristics in terms of production, technologies, capital assets, access to markets, contribution to rural income, well being, food security and poverty, and, to some extent, highlight the effects of policies and programmes. Who and how manyThere is no unique and unambiguous definition of a smallholder. Often scale, measured in terms of farm size is used to classify farmers. Often, households with less than a threshold land size may be characterized as smallholder. For example, smallholders are often those who farm less than a threshold size of 2 hectares. However, across countries, the distribution of farm sizes depends on a number of agro-ecological and demographic conditions and economic and technological factors.An effort to identify smallholders and vary the threshold size from one country to another, thus taking into consideration agro-climatic conditions was made for a limited number of countries by FAO.1 The Data1FAO (2010). Policies and institutions to support smallholder agriculture. Committee on Agriculture, 22nd Session, 2010.Portrait for Smallholder Farmers does utilize thresholds that take into consideration country-specific factors. The middle-sized farm is one such threshold.2 It is determined by the hectare weighted median and is calculated by ordering farms from smallest to largest and choosing the farm size at the middle hectare as the threshold to choose smallholders and non smallholders in each country.This threshold for smallholder farms and the indicators, are estimated utilizing household surveys, such as the FAO Rural Income Generating Activities database and the Living Standards Measurement Surveys, in combination with agricultural censuses and other information.The Data PortraitThe Smallholder Farmers’Data Portrait has a number of attributes. First, it is being developed t be as ‘global’ as possible. Second, it provides a clear picture of smallholder agriculture, bringing out its strengths and weaknesses: Scale, productivity, technology, commercialization and well-being. Third, it is designed in such a way as to reveal differences between countries and regions in terms of structural transformation; and fourth, it includes policies and programmes to any extent possible.About 30 indicators are adequate to draw a clear portrait of smallholder agriculture. Table 1 shows these indicators, organized in 8 groups, which through the data, depict the main characteristics of smallholders. General indicators, such as the average smallholding size and the number of smallholders, provide an overall idea about farm structure in each 2Key, N. and M. Roberts (2007). Measures of trends in farm size tell differing stories. Amberwaves, November. country. Production indicators take into account food and non food commodities, as well as productivity. Income and pluri-activity indicators show how income is generated on- and off-farm and assess whether smallholder farm households are classified as poor or non poor. They also underscore the importance of farm and non-agricultural activities.Data on labour highlight the importance of family farm as a firm, but also that of the rural economy in supporting livelihoods, by illustrating both the demand and the supply of rural labour. Capital and inputs reflect the base of productive capital of smallholder farms, together with irrigation investments and mechanization. Innovation and technology are covered by data on the use of improved seeds, which reflects the adoption of technology, together with the use of extension services.Access to output and input markets describe the extent of commercialization of small farms. Information on the access to credit also provides a pointer for investment. Transport and communication infrastructure are also portrayed. The inclusion of policies and programmes in the data portrait, when available, can support the assessment of their effectiveness. Demographic indicators also introduce gender and youth dimensions in underpinning both food security, but also investment.Table 1 – Indicators of the smallholder farmers’ data portraitNotes:1.Farm size refers to average land operated by the family for crop production in hectares. Minimum and maximum farm sizes for smallholder and otherfarms are also reported.2.Value of crop production includes all crops produced on the farm. Value of food produced excludes cash crops.3.Household income refers to gross annual earnings from all income generating activities (i.e. on-farm, agricultural wages, off-farm self-employment orwage earning, transfers and other).4.Family labour days on-farm supplied over a day refer to the total number of person-days family members spend on- farm during one working day. Hiredlabour days on-farm and family labour days in off-farm activities are computed similarly.5.All animals are included in the calculation of livestock in Tropical Livestock Units. Depending on the country, these refer to horses, donkeys, oxen, cows,sheep, goats, lambs, pigs, chicken, and ducks.6.% of improved to total seeds is the ratio between quantity of improved seeds to the total quantity of seeds.7.% of expenditure for inputs on value of production refers to the ratio between the total value of inputs to the value of agricultural production.8.The average years of education at school is reported for the head of the household.6。
国开理工英语4形考参考答案
一、选择填空：阅读下面的对话或句子，从A、B、C三个选项中选出一个能填入空白处的最佳选项。
试题1正确得分10.00/10.00 分未标记标记试题试题正文—Do you mind my using my mobile phone here?—________________.选择一项：a.Yes, use it please.b.No, of course not反馈你的回答正确解析：本题考核征求意见的交际用语。
Do you mind...意为“介意不介意”。
A的意思是“介意，请做吧”，C的意思是“不介意，你不能在这里用移动电话”，都前后矛盾。
因此选B.试题2正确得分10.00/10.00 分未标记标记试题试题正文2.—Thank you ever so much for the Apple Watchyou sent me.—________________选择一项：a.No thanks.b.I’m glad you like it.c.Please don’t say so.反馈你的回答正确解析：本题考核回答感谢的交际用语。
A和C两项都是中式英语。
因此选择B.试题3正确得分10.00/10.00 分未标记标记试题试题正文—Oh. Dear! I’ve lost my new watch.—_________________选择一项：a.I’m sad.b.That’s all right.c.What a pity!反馈你的回答正确解析：本题考核表达遗憾的交际用语。
What a pity在这里用来对对方丢失了新手表这件事情表示遗憾，意为“真可惜”。
所以C是正确答案。
试题4正确得分10.00/10.00 分未标记标记试题试题正文They are _______ make an announcement later on today.选择一项：a.wish tob.expected toc.looking forward to反馈你的回答正确译文：预计他们今天晚些时候会宣布一项通告。
after the peak year of1957 推断题
after the peak year of1957 推断题例一：Both the number and the percentage of people in the United Statesinvolved in nonagricultural pursuits expanded rapidly during the half century following the Civil War,with some of the most dramatic increases occurring in the domains of transportation,manufacturing, and trade and distribution. The development of the railroad and telegraph systems during the middle third of the nineteenth century led to significant improvements in the speed, volume, and regularity of shipments and communications, making possible a fundamental transformation in the production and distribution of goods.What can be inferred from the passage about the agricultural sector of the economy after the Civil War?(A) New technological developments had little effect on farmers.(B) The percentage of the total population working in agriculture declined.(C) Many farms destroyed in the war were rebuilt after the war.(D) Farmers achieved new prosperity because of better rural transportation.例二：After the peak year of 1957, the birth rate in Canada began todecline. It continued falling until in 1966 it stood at the lowest level in 25 years. Partly this decline reflected the low level of births during the depression and the war, but it was also caused by changes in Canadian society. Young people were staying at school longer, more women were working, young married couples were buying automobiles or houses before starting families, rising living standards were cutting down the size of families. It appeared that Canada was once more falling in step with the trend toward smaller families that had occurred all through theWestern world since the time of the Industrial Revolution.It can be inferred from the passage that before the Industrial Revolution(A) families were larger(B) population statistic were unreliable(C) the population grew steadily(D) economic conditions were bad例三：Accustomed though we are to speaking of the films made before 1927 as "silent", the film has never been, in the full sense of the word, silent. From the very beginning, music was regarded as an indispensable accompaniment; when the Lumiere films were shown at the first public film exhibition in the United States in February 1896, they were accompanied by piano improvisations on popular tunes. At first, the music played bore no special relationship to the films; an accompaniment of any kind was sufficient. Within a very short time, however, the incongruity of playing lively music to a solemn film became apparent,and film pianists began to take some care in matching their pieces to the mood of the film.What can be inferred that the passage about the majority of films made after 1927?(A) They were truly "silent".(B) They were accompanied by symphonic orchestras.(C) They incorporated the sound of the actors' voices.(D) They corresponded to specific musical compositions.例四：Eighteenth-century houses showed great interior improvementsover their predecessors. Windows were made larger and shutters removed. Large, clear panes replaced the small leaded glass of the seventeenth century. Doorways were larger and more decorative. Fireplaces became decorative features of rooms. Walls were made of plaster or wood, sometimes elaborately paneled. White paint began to take the place of blues, yellows, greens, and lead colors, which had been popular for walls in the earlier years. After about 1730, advertisements for wallpaper styles in scenic patterns began to appear in colonial newspapers.What does the author imply about the use of wallpaper before 1730?(A) Wallpaper samples appeared in the architectural manuals.(B) Wallpaper was the same color as the wall paints used(C) Patterned wallpaper was not widely used.(D) Wallpaper was not used in stone house.例五：This was before the steam locomotive, and canal building was at itsheight. The companies building the canals to transport coal needed surveyors to help them find the coal deposits worth mining as well as to determine the best courses for the canals. This job gave Smith an opportunity to study the fresh rock outcrops created by the newly dugcanal. He later worked on similar jobs across the length and breadth of England, all the while studying the newly revealed strata and collecting all the fossils he could find. Smith used mail coaches to travel as much as 10,000 miles per year. In 1815 he published the firstmodern geological map, “A Map of the Strata of England and Wales with a Part ofScotland,”a map so meticulously researched that it can still be used today.Which of the following can be inferred from paragraph 2 about canal building?(A) Canals were built primarily in the south of England rather than in other regions.(B) Canal building decreased after the steam locomotive was invented.(C) Canal building made it difficult to study rock strata which often became damaged in the process.(D) Canal builders hired surveyors like Smith to examine exposed rock strata.。
Increasing Returns and Economic Geography翻译
报酬递增和经济地理保罗•克鲁格曼这篇论文构建了一个简单的模型用以说明一个国家如何内生地成为一个以制造业为核心农业为外围的国家。
为了实现规模经济最大、运输成本最小，制造业厂商会倾向于在市场规模较大的区域选址。
而需求定位本身又往往取决于生产分布。
核心一外围模型的出现依赖于运输成本、规模经济和制造业在GDP中所占的份额。
地理经济学的研究集中在生产选址因索的分析上。
传统的国际贸易理论习惯性的把国家当作无量纲的点，也就是说通常假设在国家之间不存在运输成本。
实际上，这种疏忽是令人惊讶的。
至少对外行来说，地理经济学的事实是包含在现实世界经济的各种显著特征中的。
这篇论文的写作目的在于：通过模型和从理论制造业组织中获得的技术的应用使得我们可以重构地理经济学。
现在我们试图将运输成本这一长期以来就有并且非正式的因素加入到规范模型中。
为了实现这一点，这篇论文构造了一个简单的解释模型来阐明选址的关键问题之一：在什么时候为什么制造业在一些地区集中，从而使其他一些地方相对没有发展。
我们应该看到建立一个基于规模经济的相互影响和传输成本的制造业地理集聚的简单模型是可能的。
这个并不稀奇，因为从近年来文献所得到的结果中可以看出。
这种在某一地点的制造业集聚并不总是发生，而且它的发生是否以某种有趣的方式下依赖一些关键因素，这些事实都是很有趣的。
这篇论文可以分成四个部分。
第一部分通过对这个问题的非规范的讨论来提供条件。
第二部分给出分析模型。
第三部分将分析短期均衡和动态的测量结果。
第四部分分析制造业集聚是否出现的条件。
第一部分地区分化的基础关于决定某种制造业选址的外部性特征的广泛讨论历时已久。
实际上，最初马歇尔的外部经济性概念的阐述就是通过制造业选址的例子说明的。
这个领域的大部分文献都接受马歇尔关于选址因索的认定。
首先，在某一地的企业集聚为具有制造业所需专业技能的工人提供了一个共享的市场，从而保障了该地区的低失业率，降低了劳动力短缺的可能性。