A Theoretical Analysis of the Road not Taken by the Use of the ＂Sound of Sense＂

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------Lateral Dynamics of Commercial Vehicle Combinations-A Literature Survey(Vehicle System Dynami

As compared with single vehicle units, the road vehicle trains are characterized by some specific features among which particularly the following should be noted (Fig. 2): a ) jackknifing b) trailer swing c ) trailer lateral oscillations Under conditions of high vehicle velocities the articulated vehicles tend to yaw oscillations causing large amplitudes of lateral trailer oscillations. The combinations truck-trailer are more prone to lateral oscillations than the tractorsemitrailer sets. Under braking conditions on wet slippery roads the blocking of one or more wheels causes jackknifing or a swing of the semitrailer or trailer. The combination TS (tractor-semitrailer) appears to be more sensitive to these effects. The tractor has to transmit a part of the mass of the semitrailer and, consequently, also a part of the braking power indispensable for braking the semitrailer, and thus considerable forces are exerted at the kingpin connecting the tractor and the trailer. When the tractor rear wheels are blocked, the tractor swings around the kingpin. In case the semitrailer wheels get blocked, the semitrailer starts to yaw by skidding around the axis of the connecting mechanism (i.e. the fifth wheel). The lateral stability and braking performance of articulated vehicles are problematic, in particular for the following reason: owing to forces in the connection

2015年12月大学英语六级考试真题(第3套)

2015 年12 月大学英语六级考试真题及答案（第3 套）Part I Writing (30 minutes)Directions: For this part, you are allowed 30 minutes to write an essay based on the picture below. You should focus on the harm caused by misleading information online. You are required to write atleast 150 words but no more than 200 words.注意：此部分试题请在答题卡1 上作答。

Part III Reading Comprehension (40 minutes)Section AQuestions 36 to 45 are based on the following passage.It seems to be a law in the technology industry that leading companies eventually lose their positions, often quickly and brutally. Mobile phone champion Nokia, one of Europe’s biggest technology success stories, was no 36 losing its market share in just a few years.In 2007, Nokia accounted for more than 40% of mobile phone sales 37 . But consumers’ preferences were already 38 toward touch-screen smartphones. With the introduction of Apple’s iPhone in the middle of that year, Nokia’s market share 39 rapidly and revenue plunged. By the end of 2013, Nokia had sold its phone business to Microsoft.What sealed Nokia’s fate was a series of decisions made by Stephen Elop in his position as CEO, which he 40 in October 2010. Each day that Elop spent in charge of Nokia, the company’s market value declined by $23 million, making him, by the numbers, one of the worst CEOs in history.But Elop was not the only person at 41 .Nokia’s board resisted change, making it impossible for the company to adapt to rapid shifts in the industry. Most 42 , orma Ollila, who had led Nokia’s transition from an industrial company to a technology giant, was too fascinated by the company 43 success to recognize the change that was needed to sustain its competitiveness. The company also embarked on a 44 cost cutting program, which included the elimination of thousands of jobs. This contributed to the 45 of the company’s once-spirited culture, which had motivated employees to take risks and make miracles. Good leaders left the company, taking Nokia’s sense of vision and direction with them. Not surprisingly, much of Nokia's most valuable design and programming talent left as well.注意：此部分试题请在答题卡2 上作答。

英语公示翻译技巧

IntroductionInternational communication is becoming popular now. China, with the rapid development of economy and society, has maintained increasingly close ties with other countries around the world. In recent years, more and more people come to Chengde City to have a visit or study. Chengde is famous for the Summer Mountain Resorts. There are all kinds of public signs in the Summer Mountain Resorts. It brings convenience to the visitors and improves the culture taste of the city. However, there are also many errors of public signs, including: lexical errors, spelling errors, grammar errors, unclear description, cultural confusion and Chinglish. In this situation, the paper will try to give a theoretical and practical analysis of C-E translation of public signs from the perspective of functionalist translation. The paper offers some suggestions for the public signs translation by utilizing the three principles of skopos theory and analyzing many examples. “The end justified the means”means that the translation strategies and methods are determined by acceptability and effectiveness of translation.Public signs translation has great significance to both our country and the foreigners. English translations of Chinese public signs belong to publicity materials. Proper translations not only bring precise information to foreigners but also help build a good communication and good understanding. So the research on the translation of public signs is very important.Chapter One A Brief Introduction of Public signsBefore an exploration of translation public signs, some information about public signs needs to be provided. This chapter will introduce the definition, function, classification of public signs and the language style of public signs.1.1 The definition of public signsAs we known the public signs is a logo shown to some groups of people in particular place in order to have the function of communication. Public signs have become an academic term since 2000. “Si gn are anything from the simplest way finding or information maker to the technically sophisticated communication of a message”（Wang & Lv, 2007: 4）. “Signing affects everybody---travelers, shoppers, visitors, and drivers etc. whether in the course of business or pleasure”（Cheng，2000：104）.Basic literal information that are publicly shown to the public, tourists, oversea guest, foreigners in China and the Chinese in other countries to satisfy their behavior and needs in food, dwelling, travel and entertainment, are all within the category of signs (Lv, 2005:22).Some websites also pay close attention to public signs translation, such as, “”, “”and “”. “”provides the following definition: “literal information for public in public places”.According to the definition above, public signs have the following features: First they convey warning, instructional, restrictive, prohibitive or advocating information. Second, they are expressed in literal. Third they are not aimed at individuals but groups of people.1.2 The function of public signsPublic signs are widely used in daily life, such as airport, ticket office, high way, gas station, subway, taxi, museums, docks, emergency, school, tourist site, park, restaurant, street, cinema, etc.They are greatly informative. They can give us great help and facility. All the signs have four principal functions in application: directing, prompting, restricting, compelling effects.Directing signs convey the information to the public, without any restricting or compelling indication. It does not require the public to take actions, but give them an instruction or direction. For example: At the sight of “Information”（问询中心）people will know they can ask some questions and get answers. From “P et Hotel”（宠物旅馆）people will know their pets can be taken care in this place.Prompting signs are widely used although they do not have any special meaning. They just have prompting functions. For example, “S old Out”（售完）“P reserved”（预留席位）“B eware of Dog”（当心犬只）“F ull Booked”（客满）“M aximum Height”（限高）, etc.Restricting signs order the audience to restrict the behavior. The language used is straightforward but not rude. For example, “E mergency Passage Way, Please Not Hand Luggage on the Floor” （紧急通道，请勿将手提物品搁置地上）,“Give Way”（让路）,“Ticket Only”（凭票进场）,etc.Compelling signs ask the public to take some actions or not, otherwise they would be punished. For example, “Police Line Do Not Pass”（警戒线，勿超越）“Don‟t Walk”（禁止通行）, “No Smoking”（禁止吸烟）,“No Overnight Parking”（严禁过夜停车）.From the discussion above, we know the function of public signs. This is one of the ways of dividing the functions of public signs. We can also divide the functions into directing, reminding and ordering.1.3 The classification of public signsGenerally speaking, we have different ways to classify public signsaccording to different criteria.1.3.1 Informative and evocativePublic signs can be divided into “informative” (content focused) and “evocative” (appeal focused). Informative public signs provide information or describe a situation. The readers do not need to take some actions. They are widely used in scenic spots, such as, facilities, the name of the park, introduction, etc.Evocative public signs are designed to present information with a particular perspective. According to Nord, “…evocative‟is called …appellative‟”:the use of language to make the receivers do something corresponding (Nord, 2006:40). e.g. “No Fishing Here, 禁止垂钓”“Wet Floor, 小心地滑”and “Free for Children under 12, 十二岁以下儿童免费”.1.3.2 Slogans and advertisementsPublic signs include “slogans” and “advertisements” according to the purpose of usage.Slogans are used for publicity. For example, create a new situation, modernize in all fields （全面开创社会主义现代化建设新局面）. The later is shown in written form outside. For example, “we care to provide service above and beyond the call of duty”（殷勤有加，风雨不改，UPS联合快递公司）.1.3.3 Public signs in scenic spots and other placesAccording to the place where the public signs appear we can classify the public signs as the following:Public signs in scenic spots: signs in the scenic spots are designed to give the travelers some help or instruction. e.g.: Please Protect Facilities（保护公共设施, State Protect Historic Site（国家级文物保护单位）.There are also some traffic signs and road signs, for example, Xin Hua Road（新华路）, No Parking（禁止停车）.All above are the classifications of public signs.1.4 The language style of public signsAll the public signs have special features because they are mainly used in public places and their functions are communicative. Understanding the language style of public signs is very important. The main language features of public signs are conciseness and directness.1.4.1 ConcisenessPublic signs must be short and they must express the meaning clearly with right structures because the functions of public signs are to arouse readers‟ attention, and then, they can give readers warning or notice. Besides, they are usually written on the billboards or posters, which have limited writing space. Wordy public signs can‟t convey the effective information to the readers but make the readers confused. For example, “H and Off, 请勿触摸”, which means “please don‟t touch the exhibits”, “C losed during Repairs,停业整顿” which means “the store is being repaired, suspensions of business”1.4.2 DirectnessTo be direct means the public signs should be expressed directly. Public signs should be written in the simple words so that everybody can understand it. Obscure terms should be avoided in signs. For example, Staff Only, which means if you are not the staff, please doesn‟t enter.Chapter Two Problems of C-E Public Signs Translations inSummer Mountain ResortsNow we know the important function and situation of public signs for people but the translation errors still exist in public signs, even in the Summer Mountain Resorts. It is unfortunate that there are a lot of problems such as lexical errors, spelling errors, grammar errors, literal translation, and cultural differences, against convention and so on. All of that have harmful effect on the society.2.1 Lexical errorsErrors coming from lexical mistranslation account for the biggest percentage of the total linguistic errors according to the relevant statistic material. This phenomenon exists because the translators only know the vocabulary of formal equivalence, and ignore vocabulary dynamic equivalence. A word is the smallest unit of language. Translators should use the proper words in translation on the basis of accurate comprehension of the original. So the translators should make sure to understand the correct comprehension of each word in is source text, and express the correct expression in target language. How to choose a proper word is the key step.Example (1): there is a big public signs in the gate of the Summer Mountain Resorts: “W ay Out”, which refers to the place from which you can go out of a building in British English and in the scenic spots we should use “E xit” instead.Example (2): “请在此排队Join the Main Line”. It should write “Please Queue”.Example (3): “请注意安全Please Pay Attention to Safety”. It should write “Caution: Risk of Danger”.2.2 Spelling errorsSpelling errors are apparent and easy to be avoided. In the Summer Mountain Resorts we find out lots of spelling errors. For example, “芳园居fragrant Garden”. I t should be capitalized. “观莲所Lotus view PA VILION”, the word on the board are confused. They should be written in uniform format. Spelling errors also include the misuse of Chinese pinyin. Pinyin is often mixed with English in nonstandard ways. Like “西岭晨霞Xilingchenxia Chamber”. The foreigners can‟t understand its meaning. “云帆月航a tower in the shape of boat , the …seneryis‟ a boat-shaped chamber with two floors.” “S ceneryis” should be written as“scenery is”.2.3 Grammar errorsChinese and English have two different grammar rules and grammar errors are likely to happen because of the differences. Grammar errors refer to the system of inflection, syntax and word formation of a language. For example:“It was built in 1703, was over the palace area before 1771, after the formal palace had been completed, the island becomes a major scenic attraction in the landscape area.”“如意洲建于1703年，1771年之前竣工，在正宫完成之后，如意洲成为景区的主要景点。

考驾驶证的英语作文

考驾驶证的英语作文英文回答：As an integral component of modern transportation, the acquisition of a driving license signifies a pivotal milestone in an individual's life. The process of obtaining a driving license entails a rigorous and comprehensive examination that serves to evaluate an applicant's capabilities and adherence to established traffic regulations.To embark on this journey, aspiring drivers must meticulously prepare by studying the prescribed curriculum, which encompasses both theoretical and practical elements. Theoretical knowledge forms the foundation of safe driving practices and covers topics such as traffic laws, defensive driving techniques, and vehicle maintenance. Practical training provides hands-on experience behind the wheel under the guidance of a qualified instructor. This encompasses maneuvering the vehicle in various trafficscenarios, perfecting basic driving skills, and gaining confidence on the road.Upon successful completion of the preparatory phase, applicants are eligible to take the driving license examination. The examination comprises two components: a written test and a practical road test. The written test assesses an applicant's comprehension of traffic rules and regulations, while the road test evaluates their ability to operate a vehicle safely and effectively in real-world traffic conditions.Passing the driving license examination symbolizes the attainment of a significant level of competence and responsibility. License holders are entrusted with the privilege of operating a motor vehicle on public roads, a privilege that must be exercised with the utmost care and adherence to established regulations. The possession of a driving license not only enhances personal mobility but also contributes to the smooth and efficient flow of traffic, ultimately promoting public safety.中文回答：驾驶执照考试是现代交通中不可或缺的一部分，也是个人生活中具有里程碑意义的一个步骤。

马克思英文简介_英文简历模板

马克思英文简介卡尔·海因里希·马克思,马克思主义的创始人之一，被称为全世界无产阶级和劳动人民的伟大导师。

下面是小编为你整理的马克思英文简介，希望对你有用!卡尔·海因里希·马克思简介Karl Heinrich Marx (German: Karl Heinrich Marx, May 5, 1818 - March 14, 1883), one of the founders of Marxism, the organizer and leader of the first international A great mentor for the proletariat and working people all over the world. The spiritual leader of the proletariat, the pioneer of the international communist movement.Marx is a great German thinker, politician, philosopher, economist, revolutionist and sociologist. The main works are "Capital", "Communist Manifesto" and so on.Marx founded the well-known philosophical thought as historical materialism, its greatest wish is for the individual's comprehensive and free development. Marx founded the great economic theory. In his personal terms, his great work is "Capital", and Marx established his principles of elaboration as "Critique of Political Economy". Marx believes that this is the "political economy principle" thing, this is the "essence", and later people can continue to study on this basis.Marx argues that the demise of the bourgeoisie and the victory of the proletariat are equally unavoidable. He and Engels co-founded the Marxist doctrine, is considered to guide the working people around the world to achieve the socialist and communist great ideals of the struggle of the theoretical weapons and action guide.卡尔·海因里希·马克思人物生平Early schoolMarx was born on May 5, 1818 in the German Federal Prussian kingdom Rhine province (belonging to the German Rhineland-Palatinate) Terry City, a lawyer family. His grandfather Rabbin Marc Levy was a Jewish law jurist, his father, Hirsch Karl Marx, later renamed Heinrich Marx, born in 1782, with Dutch Jewish woman Henriette Presborck married, gave birth to many children, but found in a document of the heir, only Karl Marx and three daughters Sofia, Emir, Luisa survived.In October 1830, Marx entered Trier Middle School. After graduating from high school, enter the University of Bonn, 18 years after the transfer to the University of Berlin to study the law, but most of his focus is on the philosophy and history. In 1840, the Prussian New King Frederick William IV ascended the throne, persecuted Liberal Democrats, demanding that all publications must pass a rigorous review, the university lost academic freedom, and the new king appointed the University of Berlin professor FWvon Schelling would review the , But the position of Marx's scholar in philosophy is higher than the theological position can not be accepted by the anti-Hegelian professor, so Marx will be sent to the doctoral thesis to the Saxony - Weimar - Eisenach Grand Duchy of the University of Jena ( Jena) examines doctoral qualifications. In 1841 Marx applied for a degree from the distinction between the natural philosophy of Democritus and the natural philosophy of Epicurus, and successfully received the PhD in the University of Jena from the unanimous approval of the committee. After graduation as "Rheinland" editor, met in the history of Marx thought quite famous "forest theft problem".Revolutionary careerAt the beginning of the nineteenth century, the industrialrevolution swept through Germany, which promoted the development of the economy of the country's Junke landlords, and also exacerbated the extreme poverty of the lower working people. Hunger drives the poor to pick up dead branches in the forest, picking wild fruits, and some even break the hunting grounds and ranches. Although the 1826 "Prussian Penal Code" on the unauthorized logging and theft of trees severely punished, but the incident is still increasing. And many people do so in order to be sent to the detention center to receive a prison rations, it is hunger and homeless to force people to violate the forest management regulations.In 1836, there were 150,000 people who were subject to criminal penalties in Prussia, accounting for 77 per cent of all criminal cases. In the face of this rather serious social situation, the Prussian rulers did not find the root of the problem and the solution to the problem from the social system level. Instead, it introduced a tougher bill that would pick up dead branches in the forest, Some other violations of the forest management regulations have also been upgraded to theft and criminal penalties. According to the record of the Sixth Rheinland Parliament in 1841, in October the following year, the article "Debate on the Forest Burglary Law" was written to condemn the legislature's favor of the interests of the owners of the trees, to deprive the poor of the right to pick up dead branches, To put forward their own view of forest legislation.The Prussian government was very angry at the views expressed by the Rheinische Zeitung, who immediately sent a seizure of the Rheinland newspaper to force it to stop printing. Marx angrily resigned from the editorial duties of the newspaper. Marx did not regret his own actions, on the contrary, herecognized the government's ugly. He is looking for the opportunity to continue to resolutely fight against the government.1843 "Rheinische" issue license was revoked by King Prussia, because Marx published in the newspaper criticized the Russian czar article, triggering the dissatisfaction of the Russian Tsar Nicholas I, King of Prussia received a protest after the arrest of the ban Reported that Marx was unemployed. During this period, Marx met Friedrich Engels. Engels is the owner of the factory owner is very much appreciate the idea of Marx, often money to sponsor Marx's activities and life, Marx to do learning seriously serious but life with nature, often delayed to the newspaper to the manuscript, Engels often help Marx's work and pens Some articles.married familyFebruary 14, 1814, Yanni Marx was born in Teller a famous family. Yanni Marx (February 12, 1814 - December 2, 1881, formerly known as Johanna "Jenny" · Bernard Jolie von Weston Warren (Johanna "Jenny" Bertha Julie von Westphalen) is A German sociologist, who is only a few minutes away from the home of Marx.In the late summer of 1836, at the University of Bonn, the first year of the study of Marx, back to Terrier to his girlfriend to marry him. Yanni and 18-year-old Marx agreed for life. In accordance with the custom at that time, this is unprecedented. Aristocratic birth, the daughter of Yan Ni, was recognized as the most beautiful girl and the "Queen of the Queen", many handsome aristocratic youth dumping, suitors who lack some people, no doubt, you can conclude a glory Wealthy marriage. But she is contempt for all the traditional concept of society,without the knowledge of their parents to promise to a citizen of the community, she can not predict and Marx's future life how to live. Marx thought that he could not marry Yanni in front of his father, Yan Ni's father, as a temporary adviser. So at first he could only reveal his secret to his father. He believes that his father will be in front of the parents of Jenny for a successful pro-ready for a variety of preparations.In October 1836, Marx moved from the University of Bonn at home near the University of Berlin at home, which meant that they were to be loyal to each other for a long time. In Berlin, because of the feelings of the mind and "love" and the love and the suspense and anxiety, once influenced the Marx wholeheartedly into learning. He had told his father frankly that he had "fallen into the real tranquility" because he was far from the Moose Valley and was far from his "infinite beauty of Jenny". Troubled him is not a guessing heart, because he had never had the slightest doubt on the love of Jenny, but because of the thought of her and long years in the long years of separation, so that he felt very heavy mood.So, 18-year-old Marx wrote writing poetry, poems to express their feelings and feelings. Most of Marx's poems are singing Yanni and pouring himself into her, but there are many of them that express their own thoughts and aspirations and desire to make a difference.On April 15, 1841, Marx received a Ph.D. degree in advance. Young philosopher had just arrived in Trill, hastened to his most beloved home, the doctoral thesis personally sent to the hands of Jenny's father. Yan Ni and Marx after years of separation, had intended to immediately get married. But there is a doctoral thesis and can not be used as a basis for subsistence, so he andYanni had to cancel the idea of marriage, continue to wait. Beginning in April 1842, Marx began writing for the "Rheinische Zeitung". In October 1842, the shareholders of the Rheinland newspaper appointed Marx as editor, and in March 1843, Marx was forced to withdraw from the editorial board of the Rheinburger. And then with Arnold Luger in consultation with the work on the joint publication of the plan. Then on June 19, 1843 he went to Croznach (Yanni after her father died in March 1842 and his mother moved to this place), and waited for him for seven years, was born 1814 born in the German aristocratic (Baron) family of Jenny von Westphalia married. From their private agreement to life together, Yanni waited for a long seven years. In the past seven years, in addition to her had a few times with the fiance of Marx had a few times together, only from the distant with their thoughts and letters to accompany him. She wrote in a letter to Marx: "How brilliant is your image in front of me, how magnificent it is! How far is it from my heart that you can always be by my side, my heart, How is the joy of joy for your beating, my heart, what is anxious to follow you on the way you follow ... ... everywhere I am with you, walking in front of you, but also with you I hope that I can fill the road where you are going, and clear all the obstacles that will stop you from moving forward. "At the same time, she has to struggle with her aristocratic relatives.After the wedding, Marx and Jenny then set off a short wedding trip. In the autumn of 1843, the young Marx and his wife set foot on the exile journey to Paris. During this period he proceeded to study political economy, the French social movement and the French history, and eventually led to its becoming a communist.At the end of October 1843, Marx and Yanni came to Paristogether, and they came to Luga for two months earlier to organize and publish the magazine "German and French Yearbook". At this point, they opened a life full of hardship and self-sacrifice.Because of Marx's outstanding contribution to the cause of communism and to the landlords and bourgeoisians ruthlessly expose and criticize, so that all the conservative forces to exclude him, expelled him. He had to carry a small home around the transfer of their difficulties sometimes difficult to imagine the point of life. At the end of March 1850, with the death of London in London, Jenny wrote a letter to a friend Joseph Weiderme, depicting her life at that time: "Because here the nurse is too high wages, although I often have a bad chest , But still their own children to feed the poor children from my body sucked so much sadness and anxiety, so he has been frail, day and night to endure severe pain.He has been born since the night, Can fall asleep for two or three hours, and recently with violent ventilation, so the child struggles all day on the death line, because of these pains, he desperately sucked milk, so that my breasts were injured and cracked; blood often flow One day, I was holding him sitting, suddenly the female landlord came, I paid her five pounds of arrears, but we have no money at hand.Then came the two bailiffs, Will be my meager home - bed clothes and so on - and even my poor children's cradle and the better toys are seized. They threatened me to say two hours later to all West and I have to sleep with the shivering children sleep light board. "Marx and Yanni symbiotic four women and two children, for the above reasons, only three daughters (ie eldest daughter Jenny Marx, second daughter Laura Marx, Three daughter Elena Marx) grew up [at that time thanks to Helen de Mute Lin Heng, Yanni if thereis no such a loyal assistant, it is difficult to imagine her and her children later how to go down] TheIn this situation, Yan Ni is still deeply in love with Marx. In addition to her mother and housewife's responsibility, in addition to worry about the daily life, but also take on a lot of other work. Yanni is an indispensable secretary to Marx, and almost all manuscripts of Marx - most of which are hard to recognize - must be clearly written by her before being sent to a printing or publishing house.And publishers and editorial office negotiations, some cumbersome procedures, it is difficult to deal with the affairs, must write the situation, many by her agent. Marx was not the kind of person who was easily present in his mouth, but when Yanni left him for a few months because of his mother's death, he wrote in her letter: "Deep passion Because of the close proximity of its object The performance of the daily habits, and in the next resort under the influence of magic will grow up and re-have its inherent strength of my love is the case.As long as we are forced for the space, I immediately understand that time in my Love is like a sun and rain in the plant - to grow.I love you, as long as you stay away from me, it will show its true colors, like a giant face. In this love focused on all my energy and all the feelings. ... ... if I can put your gentle and pure heart close to his heart, I will be silent, not for a cry. I can not kiss you with lips, but have to resort to the text, to the text to convey the kiss. "The love of Marx and Jenny's dusk is more intense. 1880, may suffer from liver cancer, she with amazing restraint ability, endured great pain. In this scared of the years, Marx took care of his wife, not left or right in order to make her happy, Marx in 1881in July and August, accompanied her to France to see the eldest daughter and a few grandson. In the fall of 1881, due to anxious and insomnia, excessive physical exertion, Marx was ill. He is suffering from pneumonia, life is dangerous, but he still can not forget the yanni. Their little daughter talked about her parents' life, "I will never forget the scene of the morning." He felt that he was much better and had gone to the mother's room. Young people, like a pair of young men and women who are beginning to live together, are not like a sick man and a dying old woman, unlike a man who is about to farewell.December 2, 1881, Yan Ni sleepy. This is the biggest blow that Marx has never suffered. On the day of his death, Engels said: "Moore (from India, who describes the dark skin) is also dead." In the next few months, he accepted the doctor's advice, to the mild climate to rest. But no matter where they can not forget Yan Ni, could not stop grief. He wrote to the best friend, "By the way, you know that few people are more disgusted than I am sad, but if I do not admit that I miss my wife at all times - she is the best of my life Everything is inseparable - that 's how I'm lying. "How awesome these words are.January 11, 1883, came the sudden death of the eldest daughter of the bad news, Marx's condition increased. At noon on March 14, 1883, Marx resigned peacefully. On March 17, 1883, Marx was buried next to the grave of Haget's Cemetery, Jenny.Great friendshipIn 1844 September, Engels visited Paris, the two sides began to study the scientific socialism, and formed a deep friendship. Marx wrote the "Economic Philosophy Manuscript", the manuscript until 1933 was discovered and published, known as the "1844 economic philosophy manuscript." In 1845, Marxparticipated in the preparation of "forward magazine", in which the authoritarianism of Germany made a sharp criticism. The Prussian government was very dissatisfied and asked the French government to expel Marx. In the autumn of the same year, Marx was beaten by the French government rogue, deported, forced to come to Brussels, Belgium. In December 1845, Marx declared his departure from Prussian nationality.And then Engels completed with the "German ideology." The book criticizes Hegel's dialectics and analyzes the incompleteness of Feuerbach materialism, which for the first time systematically expounded the historical materialism they founded and made clear that the proletariat seized power The historical task laid the initial theoretical foundation for socialism from fantasy to science. At the beginning of 1846, Marx and Engels established the Brussels Communist Communications Commission. In 1847, Marx and Engels were invited to the righteous alliance. In June 1847, the reorganization of the alliance and renamed the communist alliance, Marx and Engels drafted the alliance program "Communist Manifesto." Since then the revolution of 1848 swept through Europe, also spread to Belgium. In March 1848, Marx was expelled by the Belgian authorities. At the invitation of the French new government, the Marxist couple returned to Paris, France, Engels arrived in Paris.In April 1848, under the auspices of the German proletariat, Marx and Engels returned to Prussia Cologne and founded the "New Rheinische Zeitung". Followed by almost all editors or judicial arrests, or deportation. On May 16, 1849, Marx received a deportation order from the Prussian authorities. May 19, published in the red ink published "New Rheinische" the last one No. 301 published. In early June, Marx came to Paris. He wasforced to choose or be imprisoned in Brittany, France, or was forced to expel again. In August, Marx was expelled from the French government to London, England. From the Prussian stationed in the British spy report that Marx seems to never scratch the beard, Marx is still in the UK by the Prussian government to monitor.In London, Marx spent the most difficult day of his life. In five years, Marx because of economic and debt problems, mental anxiety, suffering from the poor mood of the disease, four children in three deaths. But during this period, Marx wrote his most important work - "Capital" (Volume 1). Marx is thought to be rich, economically poor and poor, and the great economist who has a thorough study of the capitalist economy is itself poor, and his life is almost in poverty. Marx did not have a fixed job, and the family's economic origins was mainly due to his extremely unstable and extremely meager royalties, coupled with the persecution and blockade of the bourgeoisie, which had always plagued the Marxist family with hunger and survival. To death. In the life of the displaced, he is often empty, clean clothes, struggling in the dilemma of the struggle. If not Engels in economic long-term selfless assistance, Marx can not engage in leading the international proletarian movement and concentrate on theoretical creation.From the letter to Engels on February 27, 1852, we saw the plight of the world famous theorist, Marx wrote: "A week I have reached the point of great pain: because the coat into the pawn shop, I can not And then go out, because not to credit, I can not eat meat. "Soon wrote to Engels talked:" My wife is sick, little Yanni disease, Linheng suffering from a nerve heat, the doctor I can not please , And now can not please, because there is nomoney to buy medicine. Eight to ten days since the home to eat bread and potatoes, whether today can get these, but also a problem. "Hungry poverty and housework trivia, troubled Marx, he Feeling angry and irritable, unable to concentrate and wisdom to carry out theoretical creation. On the plight of Marx, Engels as their own difficulties. "I will send you five pounds in early February," he wrote in a letter to Marx. "You can receive this number every month, even if I do not have a debt to the new year." ... of course, you do not because I promised to pay 5 pounds a month in the difficult time no longer write to me to ask for money, because as long as possible, I must do so. "At this time Engels in the door - Engels The company is just an ordinary small clerk, the income is very low.Engels later made the company's care, the monthly salary has improved. From 1860 onwards, the support of Marx increased to 10 pounds per month, but also often "other" to give some funding. From 1851 to 1869, Marx received a total of £ 3121 remittances of Engels. For Engels at the time, it was a matter of course. It is precisely because of the generosity of Engels, so that Marx relentlessly survived, to be engaged in long-term scientific writings, writing for the "capital" for extensive and in-depth economic research. Just as Lenin said: "If not Engels sacrificed himself and continue to give funding, Marx not only can not be written as" capital "and is bound to die from poverty." Engels's selfless dedication, Marx was very moved, and very disturbed, in 1867 Wrote to Engels' letter: "frankly told you that my conscience is often as heavy as the dream of the devil, because your excellence is mainly for me to waste in business, only to let them deserted, and But also to share all my trivial worries. "This is the words of Marx's heart. The concern of Marx and his family life,Engels is meticulous. Marx's life is suffering from hardships, whenever Marx suffered setbacks and blows, thoughts and feelings with grief and depression, Engels always think of ways to soothe, he has become a Marx to avoid the storm of life in the harbor, Marx arrived in this harbor, Quiet and happy. Poverty and suffering have claimed the four children of Marx.In April 1855, Marx's favorite son, Edgar, died, which gave Marx a heavy blow, and he felt he could not support it. In the letter to Engels, Marx talked about the infinite sadness: "In these days, I have been able to bear all this terrible pain, because always miss you, miss your friendship, always hope that the two of us also To make some meaningful things together in the world. "Engels brought the couple to Manchester, in Engels's careful arrangements and care, the Marx and the couple spent the most difficult moments of life. Engels is a "supernumerary" member of Marx's house, and every time he goes to Marx's house, the whole family is as happy as the holidays, and Marx's daughters see Engels as "the second father". Of course, the Marx family of Engels on the health concerns, it is worrying. In 1857 July, when Engels was sick, Marx wrote a letter of comfort: "Dear Engels, you can believe that no matter how unfortunate we are, my wife and I are more concerned about your recent health situation than our own. "Two old comrades in the work of different places, often communicate with each other ideas, without reservation to talk about personal life and political life in the emotions, in their more than 1,000 communications, we see the two comrades Deep Yi Benedict, a few days can not get each other letters, each other to each other up. In his letter to Engels, Marx wrote, "Dear Engels, are you crying or laughing, sleeping or awake? In the last three weeks, I sent a variety of letters to Manchester, but Did notreceive a reply, but I believe are sent to. "Similarly, if you can not hear a few days of Marx's audio, Engels will be issued" even the gun "like questioning" old Moore, old Moore, big beard old Do you have anything to do? What are you doing, what are you doing? Are you sick or falling into the abyss of your political economy? "They are doing nothing Said, nothing to talk about. And the friendship between Engels, Marx made a high degree of evaluation, February 20, 1866 to Engels in the letter said: "This friendship between us is how happy, you have to know that I am any relationship Have not made such a high evaluation. "Engels and Marx's noble friendship, for the human to establish a brilliant example, the two great great friendship to tell the world: based on common faith and the pursuit of the foundation of friendship, is evergreen, unbreakable.Old age and deathSeptember 28, 1864, Marx participated in the first international congress, was elected to the leadership committee. He drafted the Declaration on the Establishment of the International, the Provisional Constitution and other important documents. September 14, 1867, "Capital" first volume published. After the two volumes for the death of Marx, by Engels finishing its legacy, respectively, in 1885, published in 1894. In October 1870 Marx reunited with Engels in London. As many countries were expelled and exiled everywhere, he claimed to be "the world's citizens".On December 2, 1881, Yanni Marx died. March 14, 1883 at 2:33 pm, the great thinker of Marx died in London, at the age of 65 years old. And later with Yanni buried in the northern suburbs of London Haget cemetery. Engels published the tomb speech, about 20 people attended the funeral.。

Becoming a Scientist The Role of Undergraduate Research in Students ’ Cognitive, Personal,

Becoming a Scientist:The Roleof Undergraduate Research in Students’Cognitive,Personal, and Professional DevelopmentANNE-BARRIE HUNTER,SANDRA URSEN,ELAINE SEYMOUR Ethnography&Evaluation Research,Center to Advance Research and Teaching in the Social Sciences,University of Colorado,Campus Box580,Boulder,CO80309,USAReceived9November2005;revised2May2006;accepted2June2006DOI10.1002/sce.20173Published online12October2006in Wiley InterScience().ABSTRACT:In this ethnographic study of summer undergraduate research(UR)expe-riences at four liberal arts colleges,where faculty and students work collaboratively on aproject of mutual interest in an apprenticeship of authentic science research work,analysisof the accounts of faculty and student participants yields comparative insights into thestructural elements of this form of UR program and its beneﬁts for parison ofthe perspectives of faculty and their students revealed considerable agreement on the nature,range,and extent of students’UR gains.Speciﬁc student gains relating to the process of “becoming a scientist”were described and illustrated by both groups.Faculty framed these gains as part of professional socialization into the sciences.In contrast,students emphasizedtheir personal and intellectual development,with little awareness of their socialization intoprofessional practice.Viewing studyﬁndings through the lens of social constructivist learn-ing theories demonstrates that the characteristics of these UR programs,how faculty practiceUR in these colleges,and students’outcomes—including cognitive and personal growth and the development of a professional identity—strongly exemplify many facets of these theo-ries,particularly,student-centered and situated learning as part of cognitive apprenticeshipin a community of practice.C 2006Wiley Periodicals,Inc.Sci Ed91:36–74,2007Correspondence to:Anne-Barrie Hunter;e-mail:abhunter@Contract grant sponsor:NSF-ROLE grant(#NSF PR REC-0087611):“Pilot Study to Establish the Nature and Impact of Effective Undergraduate Research Experiences on Learning,Attitudes and Career Choice.”Contract grant sponsor:Howard Hughes Medical Institute special projects grant,“Establishing the Processes and Mediating Factors that Contribute to Signiﬁcant Outcomes in Undergraduate Research Experiences for both Students and Faculty:A Second Stage Study.”This paper was edited by former Editor Nancy W.Brickhouse.C 2006Wiley Periodicals,Inc.BECOMING A SCIENTIST37INTRODUCTIONIn1998,the Boyer Commission Report challenged United States’research universities to make research-based learning the standard of students’college education.Funding agencies and organizations promoting college science education have also strongly recommended that institutions of higher education provide greater opportunities for authentic,interdis-ciplinary,and student-centered learning(National Research Council,1999,2000,2003a, 2003b;National Science Foundation[NSF],2000,2003a).In line with these recommen-dations,tremendous resources are expended to provide undergraduates with opportunities to participate in faculty-mentored,hands-on research(e.g.,the NSF-sponsored Research Experience for Undergraduates[REU]program,Howard Hughes Medical Institute Science Education Initiatives).Notwithstanding widespread belief in the value of undergraduate research(UR)for stu-dents’education and career development,it is only recently that research and evaluation studies have produced results that begin to throw light on the beneﬁts to students,faculty,or institutions that are generated by UR opportunities(Bauer&Bennett,2003;Lopatto,2004a; Russell,2005;Seymour,Hunter,Laursen,&DeAntoni,2004;Ward,Bennett,&Bauer, 2002;Zydney,Bennett,Shahid,&Bauer,2002a,2002b).Other reports focus on the effects of UR experiences on retention,persistence,and promotion of science career pathways for underrepresented groups(Adhikari&Nolan,2002;Barlow&Villarejo,2004;Hathaway, Nagda,&Gregerman,2002;Nagda et al.,1998).It is encouraging toﬁnd strong convergence as to the types of gains reported by these studies(Hunter,Laursen,&Seymour,2006).How-ever,we note limited or no discussion of some of the stronger gains that we document,such as students’personal and professional growth(Hunter et al.,2006;Seymour et al.,2004) and signiﬁcant variation in how particular gains(especially intellectual gains)are deﬁned. Ongoing and current debates in the academic literature concerning how learning occurs, how students develop intellectually and personally during their college years,and how communities of practice encourage these types of growth posit effective practices and the processes of students’cognitive,epistemological,and interpersonal and intrapersonal de-velopment.Although a variety of theoretical papers and research studies exploring these topics are widely published,with the exception of a short article for Project Kaleidoscope (Lopatto,2004b),none has yet focused on intensive,summer apprentice-style UR experi-ences as a model to investigate the validity of these debates.1Findings from this research study to establish the nature and range of beneﬁts from UR experiences in the sciences,and in particular,results from a comparative analysis of faculty and students’perceptions of gains from UR experiences,inform these theoretical discussions and bolsterﬁndings from empirical studies in different but related areas(i.e.,careers research,workplace learning, graduate training)on student learning,cognitive and personal growth,the development of professional identity,and how communities of practice contribute to these processes. This article will presentﬁndings from our faculty andﬁrst-round student data sets that manifest the concepts and theories underpinning constructivist learning,development of professional identity,and how apprentice-style UR experience operates as an effective community of practice.As these bodies of theory are central tenets of current science education reform efforts,empirical evidence that provides clearer understanding of the actual practices and outcomes of these approaches inform national science education pol-icy concerns for institutions of higher learning to increase diversity in science,numbers of students majoring in science,technology,engineering,or mathematics(STEM)disci-plines,student retention in undergraduate and graduate STEM programs and their entry 1David Lopatto was co-P.I.on this study and conducted quantitative survey research on the basis of our qualitativeﬁndings at the same four liberal arts colleges.Science Education DOI10.1002/sce38HUNTER ET AL.into science careers,and,ultimately,the production of greater numbers of professional scientists.To frame discussion ofﬁndings from this research,we present a brief review of theory on student learning,communities of practice,and the development of personal and professional identity germane to our data.CONSTRUCTIVIST LEARNING,COMMUNITIES OF PRACTICE,AND IDENTITY DEVELOPMENTApprentice-style URﬁts a theoretical model of learning advanced by constructivism, in which learning is a process of integrating new knowledge with prior knowledge such that knowledge is continually constructed and reconstructed by the individual.Vygotsky’s social constructivist approach presented the notion of“the zone of proximal development,”referencing the potential of students’ability to learn and problem solve beyond their current knowledge level through careful guidance from and collaboration with an adult or group of more able peers(Vygotsky,1978).According to Green(2005),Vygotsky’s learning model moved beyond theories of“staged development”(i.e.,Piaget)and“led the way for educators to consider ways of working with others beyond the traditional didactic model”(p.294).In social constructivism,learning is student centered and“situated.”Situated learning,the hallmark of cultural and critical studies education theorists(Freire,1990; Giroux,1988;Shor,1987),takes into account students’own ways of making meaning and frames meaning-making as a negotiated,social,and contextual process.Crucial to student-centered learning is the role of educator as a“facilitator”of learning.In constructivist pedagogy,the teacher is engaged with the student in a two-way,dialog-ical sharing of meaning construction based upon an activity of mutual ve and Wenger(1991)and Wenger(1998)extended tenets of social constructivism into a model of learning built upon“communities of practice.”In a community of practice“newcomers”are socialized into the practice of the community(in this case,science research)through mutual engagement with,and direction and support from an“old-timer.”Lave and Wenger’s development of the concept and practice of this model centers on students’“legitimate pe-ripheral participation.”This construct describes the process whereby a novice is slowly,but increasingly,inducted into the knowledge and skills(both overt and tacit)of a particular practice under the guidance and expertise of the master.Legitimate peripheral participation requires that students actively participate in the authentic practice of the community,as this is the process by which the novice moves from the periphery toward full membership in the community(Lave&Wenger,1991).Similar to Lave and Wenger’s communities of practice, Brown,Collins,and Duguid(1989)and Farmer,Buckmaster,and LeGrand(1992)describe “cognitive apprenticeships.”A cognitive apprenticeship“starts with deliberate instruction by someone who acts as a model;it then proceeds to model-guided trials by practition-ers who progressively assume more responsibility for their learning”(Farmer et al.,1992, p.42).However,these latter authors especially emphasize the importance of students’ongoing opportunities for self-expression and reﬂective thinking facilitated by an“expert other”as necessary to effective legitimate peripheral participation.Beyond gains in understanding and exercising the practical and cultural knowledge of a community of practice,Brown et al.(1989)discuss the beneﬁts of cognitive ap-prenticeship in helping learners to deal capably with ambiguity and uncertainty—a trait particularly relevant to conducting science research.In their view,cognitive apprenticeship “teaches individuals how to think and act satisfactorily in practice.It transmits useful, reliable knowledge based on the consensual agreement of the practitioners,about how to deal with situations,particularly those that are ill-deﬁned,complex and risky.It teachesScience Education DOI10.1002/sceBECOMING A SCIENTIST39‘knowledge-in-action’that is‘situated”’(quoted in Farmer et al.,1992,p.42).Green(2005) points out that Bowden and Marton(1998,2004)also characterize effective communities of practice as teaching skills that prepare apprentices to negotiate undeﬁned“spaces of learning”:“the‘expert other’...does not necessarily‘know’the answers in a traditional sense,but rather is willing to support collaborative learning focused on the‘unknown fu-ture.’In other words,the‘inﬂuential other’takes learning...to spaces where the journey itself is unknown to everyone”(p.295).Such conceptions of communities of practice are strikingly apposite to the processes of learning and growth that we have found among UR students,particularly in their understanding of the nature of scientiﬁc knowledge and in their capacity to confront the inherent difﬁculties of science research.These same issues are central to Baxter Magolda’s research on young adult development. The“epistemological reﬂection”(ER)model developed from her research posits four categories of intellectual development from simplistic to complex thinking:from“absolute knowing”(where students understand knowledge to be certain and view it as residing in an outside authority)to“transitional knowing”(where students believe that some knowledge is less than absolute and focus onﬁnding ways to search for truth),then to“independent knowing”(where students believe that most knowledge is less than absolute and individuals can think for themselves),and lastly to“contextual knowing”(where knowledge is shaped by the context in which it is situated and its veracity is debated according to its context) (Baxter Magolda,2004).In this model,epistemological development is closely tied to development of identity. The ER model of“ways of knowing”gradually shifts from an externally directed view of knowing to one that is internally directed.It is this epistemological shift that frames a student’s cognitive and personal development—where knowing and sense of self shift from external sources to reliance upon one’s own internal assessment of knowing and identity. This process of identity development is referred to as“self-authorship”and is supported by a constructivist-developmental pedagogy based on“validating students as knowers, situating learning in students’experience,and deﬁning learning as mutually constructed meaning”(Baxter Magolda,1999,p.26).Baxter Magolda’s research provides examples of pedagogical practice that support the development of self-authorship,including learning through scientiﬁc inquiry.As in other social constructivist learning models,the teacher as facilitator is crucial to students’cognitive and personal development:Helping students make personal sense of the construction of knowledge claims and engagingstudents in knowledge construction from their own perspectives involves validating thestudents as knowers and situating learning in the students’own perspectives.Becoming socialized into the ways of knowing of the scientiﬁc community and participating in thediscipline’s collective knowledge creation effort involves mutually constructing meaning.(Baxter Magolda,1999,p.105)Here Baxter Magolda’s constructivist-developmental pedagogy converges with Lave and Wenger’s communities of practice,but more clearly emphasizes students’development of identity as part of the professional socialization process.Use of constructivist learning theory and pedagogies,including communities of practice, are plainly evident in the UR model as it is structured and practiced at the four institutions participating in this study,as we describe next.As such,the gains identiﬁed by student and faculty research advisors actively engaged in apprentice-style learning and teaching provide a means to test these theories and models and offer the opportunity to examine the processes,whereby these beneﬁts are generated,including students’development of a professional identity.Science Education DOI10.1002/sce40HUNTER ET AL.THE APPRENTICESHIP MODEL FOR UNDERGRADUATE RESEARCH Effective UR is deﬁned as,“an inquiry or investigation conducted by an undergraduate that makes an original intellectual or creative contribution to the discipline”(NSF,2003b, p.9).In the“best practice”of UR,the student draws on the“mentor’s expertise and resources...and the student is encouraged to take primary responsibility for the project and to provide substantial input into its direction”(American Chemical Society’s Committee on Professional Training,quoted in Wenzel,2003,p.1).Undergraduate research,as practiced in the four liberal arts colleges in this study,is based upon this apprenticeship model of learning:student researchers work collaboratively with faculty in conducting authentic, original research.In these colleges,students typically underwent a competitive application process(even when a faculty member directly invited a student to participate).After sorting applications, and ranking students’research preferences,faculty interviewed students to assure a good match between the student’s interests and the faculty member’s research and also between the faculty member and the student.Generally,once all application materials were reviewed (i.e.,students’statements of interest,course transcripts,grade point averages[GPA]), faculty negotiated as a group to distribute successful applicants among the available summer research advisors.Students were paid a stipend for their full-time work with faculty for 10weeks over summer.Depending on the amount of funding available and individual research needs,faculty research advisors supervised one or more students.Typically,a faculty research advisor worked with two students for the summer,but many worked with three or four,or even larger groups.In most cases,student researchers were assigned to work on predetermined facets of faculty research projects:each student project was open ended,but deﬁned,so that a student had a reasonable chance of completing it in the short time frame and of producing useful results.Faculty research advisors described the importance of choosing a project appropriate to the student’s“level,”taking into account their students’interests,knowledge, and abilities and aiming to stretch their capacities,but not beyond students’reach.Research advisors were often willing to integrate students’speciﬁc interests into the design of their research projects.Faculty research advisors described the intensive nature of getting their student re-searchers“up and running”in the beginning weeks of the program.Orienting students to the laboratory and to the project,providing students with relevant background information and literature,and teaching them the various skills and instrumentation necessary to work effectively required adaptability to meet students at an array of preparation levels,advance planning,and a good deal of their time.Faculty engaged in directing UR discussed their role as facilitators of students’learning.In the beginning weeks of the project,faculty advisors often worked one-on-one with their students.They provided instruction,gave “mini-lectures,”explained step by step why and how processes were done in particular ways—all the time modeling how science research is done.When necessary,they closely guided students,but wherever possible,provided latitude for and encouraged students’own initiative and experimentation.As the summer progressed,faculty noted that,based on growing hands-on experience,students gained conﬁdence(to a greater or lesser degree)in their abilities,and gradually and increasingly became self-directed and able,or even eager, to work independently.Although most faculty research advisors described regular contact with their student researchers,most did not work side by side with their students everyday.Many research advisors held a weekly meeting to review progress,discuss problems,and make sure students(and the projects)were on the right track.At points in the research work,facultyScience Education DOI10.1002/sceBECOMING A SCIENTIST41 could focus on other tasks while students worked more independently,and the former were available as necessary.When students encountered problems with the research,faculty would serve as a sounding board while students described their efforts to resolve difﬁculties. Faculty gave suggestions for methods that students could try themselves,and when problems seemed insurmountable to students,faculty would troubleshoot with them toﬁnd a way to move the project forward.Faculty research advisors working with two or more student researchers often used the research peer group to further their students’development.Some faculty relied on more-senior student researchers to help guide new ones.Having multiple students working in the laboratory(whether or not on the same project)also gave student researchers an extra resource to draw upon when questions arose or they needed help.In some cases,several faculty members(from the same or different departments)scheduled weekly meetings for group discussion of their research monly,faculty assigned articles for students to summarize and present to the rest of the group.Toward the end of summer, weekly meetings were often devoted to students’practice of their presentations so that the research advisor and other students could provide constructive criticism.At the end of summer,with few exceptions,student researchers attended a campus-wide UR conference, where they presented posters and shared their research with peers,faculty,and institution administrators.Undergraduate research programs in these liberal arts colleges also offered a series of seminars andﬁeld trips that explored various science careers,discussed the process of choosing and applying to graduate schools,and other topics that focused on students’professional development.We thus found that,at these four liberal arts colleges,the practice of UR embodies the principles of the apprenticeship model of learning where students engage in active,hands-on experience of doing science research in collaboration with and under the auspices of a faculty research advisor.RESEARCH DESIGNThis qualitative study was designed to address fundamental questions about the beneﬁts (and costs)of undergraduate engagement in faculty-mentored,authentic research under-taken outside of class work,about which the existing literature offers fewﬁndings and many untested hypotheses.2Longitudinal and comparative,this study explores:•what students identify as the beneﬁts of UR—both following the experience,and inthe longer term(particularly career outcomes);•what gains faculty advisors observe in their student researchers and how their view of gains converges with or diverges from those of their students;•the beneﬁts and costs to faculty of their engagement in UR;•what,if anything,is lost by students who do not participate in UR;and•the processes by which gains to students are generated.This study was undertaken at four liberal arts colleges with a strong history of UR.All four offer UR in three core sciences—physics,chemistry,and biology—with additional programs in other STEMﬁelds,including(at different campuses)computer science,engi-neering,biochemistry,mathematics,and psychology.In the apprenticeship model of UR practiced at these colleges,faculty alone directed students in research;however,in the few2An extensive review and discussion of the literature on UR is presented in Seymour et al.(2004). Science Education DOI10.1002/sce42HUNTER ET AL.instances where faculty conducted research at a nearby institution,some students did have contact with post docs,graduate students,or senior laboratory technicians who assisted in the research as well.We interviewed a cohort of(largely)“rising seniors”who were engaged in UR in summer2000on the four campuses(N=76).They were interviewed for a second time shortly before their graduation in spring2001(N=69),and a third time as graduates in 2003–2004(N=55).The faculty advisors(N=55)working with this cohort of students were also interviewed in summer2000,as were nine administrators with long experience of UR programs at their schools.We also interviewed a comparison group of students(N=62)who had not done UR. They were interviewed as graduating seniors in spring2001,and again as graduates in 2003–2004(N=25).A comparison group(N=16)of faculty who did not conduct UR in summer2000was also interviewed.Interview protocols focused upon the nature,value,and career consequences of UR experiences,and the methods by which these were achieved.3After classifying the range of beneﬁts claimed in the literature,we constructed a“gains”checklist to discuss with all participants“what faculty think students may gain from undergraduate research.”Dur-ing the interview,UR students were asked to describe the gains from their research experience(or by other means).If,toward the end of the interview,a student had not mentioned a gain identiﬁed on our“checklist,”the student was queried as to whether he or she could claim to have gained the beneﬁt and was invited to add further com-ment.Students also mentioned gains they had made that were not included in the list. With slight alterations in the protocol,we invited comments on the same list of possi-ble gains from students who had not experienced UR,and solicited information about gains from other types of experience.All students were asked to expand on their an-swers,to highlight gains most signiﬁcant to them,and to describe the sources of any beneﬁts.In the second set of interviews,the same students(nearing graduation)were asked to reﬂect back on their research experiences as undergraduates,and to comment on the rel-ative importance of their research-derived gains,both for the careers they planned and for other aspects of their lives.In theﬁnal set of interviews,they were asked to of-fer a retrospective summary of the origins of their career plans and the role that UR and other factors had played in them,and to comment on the longer term effects of their UR experiences—especially the consequences for their career choices and progress, including their current educational or professional engagement.Again,the sources of gains cited were explored;especially gains that were identiﬁed by some students as arising from UR experiences but may also arise from other aspects of their college education.The total of367interviews represents more than13,000pages of text data.We are currently analyzing other aspects of the data and will reportﬁndings on additional topics, including the beneﬁts and costs to faculty of their participation in UR and longitudinal and comparative outcomes of students’career choices.This article discussesﬁndings from a comparative analysis of all faculty and administrator interviews(N=80),withﬁndings from theﬁrst-round UR student interviews(N=76),and provides empirical evidence of the role of UR experiences in encouraging the intellectual,personal,and professional development of student researchers,and how the apprenticeship modelﬁts theoretical discussions on these topics.3The protocol is available by request to the authors via abhunter@.Science Education DOI10.1002/sceBECOMING A SCIENTIST43METHODS OF DATA TRANSCRIPTION,CODING,AND ANAL YSISOur methods of data collection and analysis are ethnographic,rooted in theoretical work and methodological traditions from sociology,anthropology,and social psychol-ogy(Berger&Luckman,1967;Blumer,1969;Garﬁnkel,1967;Mead,1934;Schutz& Luckman,1974).Classically,qualitative studies such as ethnographies precede survey or experimental work,particularly where existing knowledge is limited,because these meth-ods of research can uncover and explore issues that shape informants’thinking and actions. Good qualitative software computer programs are now available that allow for the multiple, overlapping,and nested coding of a large volume of text data to a high degree of complexity, thus enabling ethnographers to disentangle patterns in large data sets and to reportﬁndings using descriptive statistics.Although conditions for statistical signiﬁcance are rarely met, the results from analysis of text data gathered by careful sampling and consistency in data coding can be very powerful.Interviews took between60and90minutes.Taped interviews and focus groups were transcribed verbatim into a word-processing program and submitted to“The Ethnograph,”a qualitative computer software program(Seidel,1998).Each transcript was searched for information bearing upon the research questions.In this type of analysis,text segments referencing issues of different type are tagged by code names.Codes are not preconceived,but empirical:each new code references a discrete idea not previously raised.Interviewees also offer information in spontaneous narratives and examples,and may make several points in the same passage,each of which is separately coded.As transcripts are coded,both the codes and their associated passages are entered into“The Ethnograph,”creating a data set for each interview group(eight,in this study). Code words and their deﬁnitions are concurrently collected in a codebook.Groups of codes that cluster around particular themes are assigned and grouped by“parent”codes.Because an idea that is encapsulated by a code may relate to more than one theme,code words are often assigned multiple parent codes.Thus,a branching and interconnected structure of codes and parents emerges from the text data,which,at any point in time,represents the state of the analysis.As information is commonly embedded in speakers’accounts of their experience rather than offered in abstract statements,transcripts can be checked for internal consistency;that is,between the opinions or explanations offered by informants,their descriptions of events, and the reﬂections and feelings these evoke.Ongoing discussions between members of our research group continually reviewed the types of observations arising from the data sets to assess and reﬁne category deﬁnitions and assure content validity.The clustered codes and parents and their relationships deﬁne themes of the qualita-tive analysis.In addition,frequency of use can be counted for codes across a data set, and for important subsets(e.g.,gender),using conservative counting conventions that are designed to avoid overestimation of the weight of particular opinions.Together,these frequencies describe the relative weighting of issues in participants’collective report. As they are drawn from targeted,intentional samples,rather than from random samples, these frequencies are not subjected to tests for statistical signiﬁcance.They hypothesize the strength of particular variables and their relationships that may later be tested by random sample surveys or by other means.However,theﬁndings in this study are un-usually strong because of near-complete participation by members of each group under study.Before presentingﬁndings from this study,we provide an overview of the results of our comparative analysis and describe the evolution of our analysis of the student interview data as a result of emergentﬁndings from analysis of the faculty interview data.Science Education DOI10.1002/sce。

ReliabilityEngineeringandSystemSafety91(2006)992–1007

Reliability Engineering and System Safety 91(2006)992–1007Multi-objective optimization using genetic algorithms:A tutorialAbdullah Konak a,Ã,David W.Coit b ,Alice E.Smith caInformation Sciences and Technology,Penn State Berks,USA bDepartment of Industrial and Systems Engineering,Rutgers University cDepartment of Industrial and Systems Engineering,Auburn UniversityAvailable online 9January 2006AbstractMulti-objective formulations are realistic models for many complex engineering optimization problems.In many real-life problems,objectives under consideration conﬂict with each other,and optimizing a particular solution with respect to a single objective can result in unacceptable results with respect to the other objectives.A reasonable solution to a multi-objective problem is to investigate a set of solutions,each of which satisﬁes the objectives at an acceptable level without being dominated by any other solution.In this paper,an overview and tutorial is presented describing genetic algorithms (GA)developed speciﬁcally for problems with multiple objectives.They differ primarily from traditional GA by using specialized ﬁtness functions and introducing methods to promote solution diversity.r 2005Elsevier Ltd.All rights reserved.1.IntroductionThe objective of this paper is present an overview and tutorial of multiple-objective optimization methods using genetic algorithms (GA).For multiple-objective problems,the objectives are generally conﬂicting,preventing simulta-neous optimization of each objective.Many,or even most,real engineering problems actually do have multiple-objectives,i.e.,minimize cost,maximize performance,maximize reliability,etc.These are difﬁcult but realistic problems.GA are a popular meta-heuristic that is particularly well-suited for this class of problems.Tradi-tional GA are customized to accommodate multi-objective problems by using specialized ﬁtness functions and introducing methods to promote solution diversity.There are two general approaches to multiple-objective optimization.One is to combine the individual objective functions into a single composite function or move all but one objective to the constraint set.In the former case,determination of a single objective is possible with methods such as utility theory,weighted sum method,etc.,but theproblem lies in the proper selection of the weights or utility functions to characterize the decision-maker’s preferences.In practice,it can be very difﬁcult to precisely and accurately select these weights,even for someone familiar with the problem pounding this drawback is that scaling amongst objectives is needed and small perturbations in the weights can sometimes lead to quite different solutions.In the latter case,the problem is that to move objectives to the constraint set,a constraining value must be established for each of these former objectives.This can be rather arbitrary.In both cases,an optimization method would return a single solution rather than a set of solutions that can be examined for trade-offs.For this reason,decision-makers often prefer a set of good solutions considering the multiple objectives.The second general approach is to determine an entire Pareto optimal solution set or a representative subset.A Pareto optimal set is a set of solutions that are nondominated with respect to each other.While moving from one Pareto solution to another,there is always a certain amount of sacriﬁce in one objective(s)to achieve a certain amount of gain in the other(s).Pareto optimal solution sets are often preferred to single solutions because they can be practical when considering real-life problems/locate/ress0951-8320/$-see front matter r 2005Elsevier Ltd.All rights reserved.doi:10.1016/j.ress.2005.11.018ÃCorresponding author.E-mail address:konak@ (A.Konak).since theﬁnal solution of the decision-maker is always a trade-off.Pareto optimal sets can be of varied sizes,but the size of the Pareto set usually increases with the increase in the number of objectives.2.Multi-objective optimization formulationConsider a decision-maker who wishes to optimize K objectives such that the objectives are non-commensurable and the decision-maker has no clear preference of the objectives relative to each other.Without loss of generality, all objectives are of the minimization type—a minimization type objective can be converted to a maximization type by multiplying negative one.A minimization multi-objective decision problem with K objectives is deﬁned as follows: Given an n-dimensional decision variable vector x¼{x1,y,x n}in the solution space X,ﬁnd a vector x* that minimizes a given set of K objective functions z(x*)¼{z1(x*),y,z K(x*)}.The solution space X is gen-erally restricted by a series of constraints,such as g j(x*)¼b j for j¼1,y,m,and bounds on the decision variables.In many real-life problems,objectives under considera-tion conﬂict with each other.Hence,optimizing x with respect to a single objective often results in unacceptable results with respect to the other objectives.Therefore,a perfect multi-objective solution that simultaneously opti-mizes each objective function is almost impossible.A reasonable solution to a multi-objective problem is to investigate a set of solutions,each of which satisﬁes the objectives at an acceptable level without being dominated by any other solution.If all objective functions are for minimization,a feasible solution x is said to dominate another feasible solution y (x1y),if and only if,z i(x)p z i(y)for i¼1,y,K and z j(x)o z j(y)for least one objective function j.A solution is said to be Pareto optimal if it is not dominated by any other solution in the solution space.A Pareto optimal solution cannot be improved with respect to any objective without worsening at least one other objective.The set of all feasible non-dominated solutions in X is referred to as the Pareto optimal set,and for a given Pareto optimal set,the corresponding objective function values in the objective space are called the Pareto front.For many problems,the number of Pareto optimal solutions is enormous(perhaps inﬁnite).The ultimate goal of a multi-objective optimization algorithm is to identify solutions in the Pareto optimal set.However,identifying the entire Pareto optimal set, for many multi-objective problems,is practically impos-sible due to its size.In addition,for many problems, especially for combinatorial optimization problems,proof of solution optimality is computationally infeasible.There-fore,a practical approach to multi-objective optimization is to investigate a set of solutions(the best-known Pareto set)that represent the Pareto optimal set as well as possible.With these concerns in mind,a multi-objective optimization approach should achieve the following three conﬂicting goals[1]:1.The best-known Pareto front should be as close aspossible to the true Pareto front.Ideally,the best-known Pareto set should be a subset of the Pareto optimal set.2.Solutions in the best-known Pareto set should beuniformly distributed and diverse over of the Pareto front in order to provide the decision-maker a true picture of trade-offs.3.The best-known Pareto front should capture the wholespectrum of the Pareto front.This requires investigating solutions at the extreme ends of the objective function space.For a given computational time limit,theﬁrst goal is best served by focusing(intensifying)the search on a particular region of the Pareto front.On the contrary,the second goal demands the search effort to be uniformly distributed over the Pareto front.The third goal aims at extending the Pareto front at both ends,exploring new extreme solutions.This paper presents common approaches used in multi-objective GA to attain these three conﬂicting goals while solving a multi-objective optimization problem.3.Genetic algorithmsThe concept of GA was developed by Holland and his colleagues in the1960s and1970s[2].GA are inspired by the evolutionist theory explaining the origin of species.In nature,weak and unﬁt species within their environment are faced with extinction by natural selection.The strong ones have greater opportunity to pass their genes to future generations via reproduction.In the long run,species carrying the correct combination in their genes become dominant in their population.Sometimes,during the slow process of evolution,random changes may occur in genes. If these changes provide additional advantages in the challenge for survival,new species evolve from the old ones.Unsuccessful changes are eliminated by natural selection.In GA terminology,a solution vector x A X is called an individual or a chromosome.Chromosomes are made of discrete units called genes.Each gene controls one or more features of the chromosome.In the original implementa-tion of GA by Holland,genes are assumed to be binary digits.In later implementations,more varied gene types have been introduced.Normally,a chromosome corre-sponds to a unique solution x in the solution space.This requires a mapping mechanism between the solution space and the chromosomes.This mapping is called an encoding. In fact,GA work on the encoding of a problem,not on the problem itself.GA operate with a collection of chromosomes,called a population.The population is normally randomly initia-lized.As the search evolves,the population includesﬁtterA.Konak et al./Reliability Engineering and System Safety91(2006)992–1007993andﬁtter solutions,and eventually it converges,meaning that it is dominated by a single solution.Holland also presented a proof of convergence(the schema theorem)to the global optimum where chromosomes are binary vectors.GA use two operators to generate new solutions from existing ones:crossover and mutation.The crossover operator is the most important operator of GA.In crossover,generally two chromosomes,called parents,are combined together to form new chromosomes,called offspring.The parents are selected among existing chromo-somes in the population with preference towardsﬁtness so that offspring is expected to inherit good genes which make the parentsﬁtter.By iteratively applying the crossover operator,genes of good chromosomes are expected to appear more frequently in the population,eventually leading to convergence to an overall good solution.The mutation operator introduces random changes into characteristics of chromosomes.Mutation is generally applied at the gene level.In typical GA implementations, the mutation rate(probability of changing the properties of a gene)is very small and depends on the length of the chromosome.Therefore,the new chromosome produced by mutation will not be very different from the original one.Mutation plays a critical role in GA.As discussed earlier,crossover leads the population to converge by making the chromosomes in the population alike.Muta-tion reintroduces genetic diversity back into the population and assists the search escape from local optima. Reproduction involves selection of chromosomes for the next generation.In the most general case,theﬁtness of an individual determines the probability of its survival for the next generation.There are different selection procedures in GA depending on how theﬁtness values are used. Proportional selection,ranking,and tournament selection are the most popular selection procedures.The procedure of a generic GA[3]is given as follows:Step1:Set t¼1.Randomly generate N solutions to form theﬁrst population,P1.Evaluate theﬁtness of solutions in P1.Step2:Crossover:Generate an offspring population Q t as follows:2.1.Choose two solutions x and y from P t based ontheﬁtness values.ing a crossover operator,generate offspringand add them to Q t.Step3:Mutation:Mutate each solution x A Q t with a predeﬁned mutation rate.Step4:Fitness assignment:Evaluate and assign aﬁtness value to each solution x A Q t based on its objective function value and infeasibility.Step5:Selection:Select N solutions from Q t based on theirﬁtness and copy them to P t+1.Step6:If the stopping criterion is satisﬁed,terminate the search and return to the current population,else,set t¼t+1go to Step2.4.Multi-objective GABeing a population-based approach,GA are well suited to solve multi-objective optimization problems.A generic single-objective GA can be modiﬁed toﬁnd a set of multiple non-dominated solutions in a single run.The ability of GA to simultaneously search different regions of a solution space makes it possible toﬁnd a diverse set of solutions for difﬁcult problems with non-convex,discon-tinuous,and multi-modal solutions spaces.The crossover operator of GA may exploit structures of good solutions with respect to different objectives to create new non-dominated solutions in unexplored parts of the Pareto front.In addition,most multi-objective GA do not require the user to prioritize,scale,or weigh objectives.Therefore, GA have been the most popular heuristic approach to multi-objective design and optimization problems.Jones et al.[4]reported that90%of the approaches to multi-objective optimization aimed to approximate the true Pareto front for the underlying problem.A majority of these used a meta-heuristic technique,and70%of all meta-heuristics approaches were based on evolutionary ap-proaches.Theﬁrst multi-objective GA,called vector evaluated GA (or VEGA),was proposed by Schaffer[5].Afterwards, several multi-objective evolutionary algorithms were devel-oped including Multi-objective Genetic Algorithm (MOGA)[6],Niched Pareto Genetic Algorithm(NPGA) [7],Weight-based Genetic Algorithm(WBGA)[8],Ran-dom Weighted Genetic Algorithm(RWGA)[9],Nondomi-nated Sorting Genetic Algorithm(NSGA)[10],Strength Pareto Evolutionary Algorithm(SPEA)[11],improved SPEA(SPEA2)[12],Pareto-Archived Evolution Strategy (PAES)[13],Pareto Envelope-based Selection Algorithm (PESA)[14],Region-based Selection in Evolutionary Multiobjective Optimization(PESA-II)[15],Fast Non-dominated Sorting Genetic Algorithm(NSGA-II)[16], Multi-objective Evolutionary Algorithm(MEA)[17], Micro-GA[18],Rank-Density Based Genetic Algorithm (RDGA)[19],and Dynamic Multi-objective Evolutionary Algorithm(DMOEA)[20].Note that although there are many variations of multi-objective GA in the literature, these cited GA are well-known and credible algorithms that have been used in many applications and their performances were tested in several comparative studies. Several survey papers[1,11,21–27]have been published on evolutionary multi-objective optimization.Coello lists more than2000references in his website[28].Generally, multi-objective GA differ based on theirﬁtness assign-ment procedure,elitisim,or diversiﬁcation approaches.In Table1,highlights of the well-known multi-objective with their advantages and disadvantages are given.Most survey papers on multi-objective evolutionary approaches intro-duce and compare different algorithms.This paper takes a different course and focuses on important issues while designing a multi-objective GA and describes common techniques used in multi-objective GA to attain the threeA.Konak et al./Reliability Engineering and System Safety91(2006)992–1007 994goals in multi-objective optimization.This approach is also taken in the survey paper by Zitzler et al.[1].However,the discussion in this paper is aimed at introducing the components of multi-objective GA to researchers and practitioners without a background on the multi-objective GA.It is also import to note that although several of the state-of-the-art algorithms exist as cited above,many researchers that applied multi-objective GA to their problems have preferred to design their own customized algorithms by adapting strategies from various multi-objective GA.This observation is another motivation for introducing the components of multi-objective GA rather than focusing on several algorithms.However,the pseudo-code for some of the well-known multi-objective GA are also provided in order to demonstrate how these proce-dures are incorporated within a multi-objective GA.Table1A list of well-known multi-objective GAAlgorithm Fitness assignment Diversity mechanism Elitism ExternalpopulationAdvantages DisadvantagesVEGA[5]Each subpopulation isevaluated with respectto a differentobjective No No No First MOGAStraightforwardimplementationTend converge to theextreme of each objectiveMOGA[6]Pareto ranking Fitness sharing byniching No No Simple extension of singleobjective GAUsually slowconvergenceProblems related to nichesize parameterWBGA[8]Weighted average ofnormalized objectives Niching No No Simple extension of singleobjective GADifﬁculties in nonconvexobjective function space Predeﬁned weightsNPGA[7]Noﬁtnessassignment,tournament selection Niche count as tie-breaker in tournamentselectionNo No Very simple selectionprocess with tournamentselectionProblems related to nichesize parameterExtra parameter fortournament selectionRWGA[9]Weighted average ofnormalized objectives Randomly assignedweightsYes Yes Efﬁcient and easyimplementDifﬁculties in nonconvexobjective function spacePESA[14]Noﬁtness assignment Cell-based density Pure elitist Yes Easy to implement Performance depends oncell sizesComputationally efﬁcientPrior information neededabout objective spacePAES[29]Pareto dominance isused to replace aparent if offspringdominates Cell-based density astie breaker betweenoffspring and parentYes Yes Random mutation hill-climbing strategyNot a population basedapproachEasy to implement Performance depends oncell sizesComputationally efﬁcientNSGA[10]Ranking based onnon-dominationsorting Fitness sharing bynichingNo No Fast convergence Problems related to nichesize parameterNSGA-II[30]Ranking based onnon-dominationsorting Crowding distance Yes No Single parameter(N)Crowding distance worksin objective space onlyWell testedEfﬁcientSPEA[11]Raking based on theexternal archive ofnon-dominatedsolutions Clustering to truncateexternal populationYes Yes Well tested Complex clusteringalgorithmNo parameter forclusteringSPEA-2[12]Strength ofdominators Density based on thek-th nearest neighborYes Yes Improved SPEA Computationallyexpensiveﬁtness anddensity calculationMake sure extreme pointsare preservedRDGA[19]The problem reducedto bi-objectiveproblem with solutionrank and density asobjectives Forbidden region cell-based densityYes Yes Dynamic cell update More difﬁcult toimplement than othersRobust with respect to thenumber of objectivesDMOEA[20]Cell-based ranking Adaptive cell-baseddensity Yes(implicitly)No Includes efﬁcienttechniques to update celldensitiesMore difﬁcult toimplement than othersAdaptive approaches toset GA parametersA.Konak et al./Reliability Engineering and System Safety91(2006)992–10079955.Design issues and components of multi-objective GA 5.1.Fitness functions5.1.1.Weighted sum approachesThe classical approach to solve a multi-objective optimization problem is to assign a weight w i to each normalized objective function z 0i ðx Þso that the problem is converted to a single objective problem with a scalar objective function as follows:min z ¼w 1z 01ðx Þþw 2z 02ðx ÞþÁÁÁþw k z 0k ðx Þ,(1)where z 0i ðx Þis the normalized objective function z i (x )and P w i ¼1.This approach is called the priori approach since the user is expected to provide the weights.Solving a problem with the objective function (1)for a given weight vector w ¼{w 1,w 2,y ,w k }yields a single solution,and if multiple solutions are desired,the problem must be solved multiple times with different weight combinations.The main difﬁculty with this approach is selecting a weight vector for each run.To automate this process;Hajela and Lin [8]proposed the WBGA for multi-objective optimization (WBGA-MO)in the WBGA-MO,each solution x i in the population uses a different weight vector w i ¼{w 1,w 2,y ,w k }in the calculation of the summed objective function (1).The weight vector w i is embedded within the chromosome of solution x i .Therefore,multiple solutions can be simulta-neously searched in a single run.In addition,weight vectors can be adjusted to promote diversity of the population.Other researchers [9,31]have proposed a MOGA based on a weighted sum of multiple objective functions where a normalized weight vector w i is randomly generated for each solution x i during the selection phase at each generation.This approach aims to stipulate multiple search directions in a single run without using additional parameters.The general procedure of the RWGA using random weights is given as follows [31]:Procedure RWGA:E ¼external archive to store non-dominated solutions found during the search so far;n E ¼number of elitist solutions immigrating from E to P in each generation.Step 1:Generate a random population.Step 2:Assign a ﬁtness value to each solution x A P t by performing the following steps:Step 2.1:Generate a random number u k in [0,1]for each objective k ,k ¼1,y ,K.Step 2.2:Calculate the random weight of each objective k as w k ¼ð1=u k ÞP K i ¼1u i .Step 2.3:Calculate the ﬁtness of the solution as f ðx Þ¼P K k ¼1w k z k ðx Þ.Step 3:Calculate the selection probability of each solutionx A P t as follows:p ðx Þ¼ðf ðx ÞÀf min ÞÀ1P y 2P t ðf ðy ÞÀf minÞwhere f min ¼min f f ðx Þj x 2P t g .Step 4:Select parents using the selection probabilities calculated in Step 3.Apply crossover on the selected parent pairs to create N offspring.Mutate offspring with a predeﬁned mutation rate.Copy all offspring to P t +1.Update E if necessary.Step 5:Randomly remove n E solutions from P t +1and add the same number of solutions from E to P t +1.Step 6:If the stopping condition is not satisﬁed,set t ¼t þ1and go to Step 2.Otherwise,return to E .The main advantage of the weighted sum approach is a straightforward implementation.Since a single objective is used in ﬁtness assignment,a single objective GA can be used with minimum modiﬁcations.In addition,this approach is computationally efﬁcient.The main disadvan-tage of this approach is that not all Pareto-optimal solutions can be investigated when the true Pareto front is non-convex.Therefore,multi-objective GA based on the weighed sum approach have difﬁculty in ﬁnding solutions uniformly distributed over a non-convex trade-off surface [1].5.1.2.Altering objective functionsAs mentioned earlier,VEGA [5]is the ﬁrst GA used to approximate the Pareto-optimal set by a set of non-dominated solutions.In VEGA,population P t is randomly divided into K equal sized sub-populations;P 1,P 2,y ,P K .Then,each solution in subpopulation P i is assigned a ﬁtness value based on objective function z i .Solutions are selected from these subpopulations using proportional selection for crossover and mutation.Crossover and mutation are performed on the new population in the same way as for a single objective GA.Procedure VEGA:N S ¼subpopulation size (N S ¼N =K )Step 1:Start with a random initial population P 0.Set t ¼0.Step 2:If the stopping criterion is satisﬁed,return P t .Step 3:Randomly sort population P t .Step 4:For each objective k ,k ¼1,y K ,perform the following steps:Step 4.1:For i ¼1þðk 21ÞN S ;...;kN S ,assign ﬁt-ness value f ðx i Þ¼z k ðx i Þto the i th solution in the sorted population.Step 4.2:Based on the ﬁtness values assigned in Step 4.1,select N S solutions between the (1+(k À1)N S )th and (kN S )th solutions of the sorted population to create subpopulation P k .Step 5:Combine all subpopulations P 1,y ,P k and apply crossover and mutation on the combined population to create P t +1of size N .Set t ¼t þ1,go to Step 2.A similar approach to VEGA is to use only a single objective function which is randomly determined each time in the selection phase [32].The main advantage of the alternating objectives approach is easy to implement andA.Konak et al./Reliability Engineering and System Safety 91(2006)992–1007996computationally as efﬁcient as a single-objective GA.In fact,this approach is a straightforward extension of a single objective GA to solve multi-objective problems.The major drawback of objective switching is that the popula-tion tends to converge to solutions which are superior in one objective,but poor at others.5.1.3.Pareto-ranking approachesPareto-ranking approaches explicitly utilize the concept of Pareto dominance in evaluatingﬁtness or assigning selection probability to solutions.The population is ranked according to a dominance rule,and then each solution is assigned aﬁtness value based on its rank in the population, not its actual objective function value.Note that herein all objectives are assumed to be minimized.Therefore,a lower rank corresponds to a better solution in the following discussions.Theﬁrst Pareto ranking technique was proposed by Goldberg[3]as follows:Step1:Set i¼1and TP¼P.Step2:Identify non-dominated solutions in TP and assigned them set to F i.Step3:Set TP¼TPF i.If TP¼+go to Step4,else set i¼iþ1and go to Step2.Step4:For every solution x A P at generation t,assign rank r1ðx;tÞ¼i if x A F i.In the procedure above,F1,F2,y are called non-dominated fronts,and F1is the Pareto front of population P.NSGA[10]also classiﬁes the population into non-dominated fronts using an algorithm similar to that given above.Then a dummyﬁtness value is assigned to each front using aﬁtness sharing function such that the worst ﬁtness value assigned to F i is better than the bestﬁtness value assigned to F i+1.NSGA-II[16],a more efﬁcient algorithm,named the fast non-dominated-sort algorithm, was developed to form non-dominated fronts.Fonseca and Fleming[6]used a slightly different rank assignment approach than the ranking based on non-dominated-fronts as follows:r2ðx;tÞ¼1þnqðx;tÞ;(2) where nq(x,t)is the number of solutions dominating solution x at generation t.This ranking method penalizes solutions located in the regions of the objective function space which are dominated(covered)by densely populated sections of the Pareto front.For example,in Fig.1b solution i is dominated by solutions c,d and e.Therefore,it is assigned a rank of4although it is in the same front with solutions f,g and h which are dominated by only a single solution.SPEA[11]uses a ranking procedure to assign better ﬁtness values to non-dominated solutions at underrepre-sented regions of the objective space.In SPEA,an external list E of aﬁxed size stores non-dominated solutions that have been investigated thus far during the search.For each solution y A E,a strength value is deﬁned assðy;tÞ¼npðy;tÞN Pþ1,where npðy;tÞis the number solutions that y dominates in P.The rank r(y,t)of a solution y A E is assigned as r3ðy;tÞ¼sðy;tÞand the rank of a solution x A P is calculated asr3ðx;tÞ¼1þXy2E;y1xsðy;tÞ.Fig.1c illustrates an example of the SPEA ranking method.In the former two methods,all non-dominated solutions are assigned a rank of1.This method,however, favors solution a(in theﬁgure)over the other non-dominated solutions since it covers the least number of solutions in the objective function space.Therefore,a wide, uniformly distributed set of non-dominated solutions is encouraged.Accumulated ranking density strategy[19]also aims to penalize redundancy in the population due to overrepre-sentation.This ranking method is given asr4ðx;tÞ¼1þXy2P;y1xrðy;tÞ.To calculate the rank of a solution x,the rank of the solutions dominating this solution must be calculatedﬁrst. Fig.1d shows an example of this ranking method(based on r2).Using ranking method r4,solutions i,l and n are ranked higher than their counterparts at the same non-dominated front since the portion of the trade-off surface covering them is crowded by three nearby solutions c,d and e. Although some of the ranking approaches described in this section can be used directly to assignﬁtness values to individual solutions,they are usually combined with variousﬁtness sharing techniques to achieve the second goal in multi-objective optimization,ﬁnding a diverse and uniform Pareto front.5.2.Diversity:ﬁtness assignment,ﬁtness sharing,and nichingMaintaining a diverse population is an important consideration in multi-objective GA to obtain solutions uniformly distributed over the Pareto front.Without taking preventive measures,the population tends to form relatively few clusters in multi-objective GA.This phenom-enon is called genetic drift,and several approaches have been devised to prevent genetic drift as follows.5.2.1.Fitness sharingFitness sharing encourages the search in unexplored sections of a Pareto front by artiﬁcially reducingﬁtness of solutions in densely populated areas.To achieve this goal, densely populated areas are identiﬁed and a penaltyA.Konak et al./Reliability Engineering and System Safety91(2006)992–1007997。

2023年12月英语六级考试真题及答案详解和听力原文第二套

12月英语六级考试真题第二套Part I Writing （30minutes）Directions: For this part, you are allowed 30 minutes to write a short essay based on the picture below. You should focus on the difficulty in acquiring useful information in spite of advanced information technology. You are required to write at least 150 words but no more than 200 words．Part ⅡListening Comprehension (30 minutes)Section ADirections : In this section, you will hear 8 short conversations and 2 long conversations. At the end of each conversation, one or more questions will be asked about what was said. Both the conversation and the questions 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 1 with a single line through the centre.1. A. The restaurant offers some specials each day.B. The restaurant is known for its food varieties.C. The dressing makes the mixed salad very inviting.D. The woman should mix the ingredients thoroughly.2. A. He took over the firm from Mary. C. He failed to foresee major problems.B. He is running a successful business. D. He is opening a new consulting firm.3. A. Someone should be put in charge of office supplies.B. The man can leave the discs in the office cabinet.C. The man may find the supplies in the cabinet.D. The printer in the office has run out of paper.4. A. He has to use a magnifying glass to see clearly.B. The woman can use his glasses to read.C. He has the dictionary the woman wants.D. The dictionary is not of much help to him.5. A. Redecorating her office.B. Majoring in interior design.C. Seeking professional advice.D. Adding some office furniture.6. A. Problems in port management.B. Improvement of port facilities.C. Delayed shipment of goods.D. Shortage of container ships.7.A. Their boss. B. A colleague. C. Their workload. D. A coffee machine.8. A. Call the hotel manager for help.B. Postpone the event until a later date.C. Hold the banquet at a different place.D. Get an expert to correct the error.Questions 9 to 11 are based on the conversation you have just heard.9 .A. He shares some of the household duties.B. He often goes back home late for dinner.C. He cooks dinner for the family occasionally.D. He dines out from time to time with friends.10. A. To take him to dinner.B. To talk about a budget plan.C. To discuss an urgent problem.D. To pass on an important message.11. A. Foreign investors are losing confidence in India's economy.B. Many multinational enterprises are withdrawing from India.C. There are wild fluctuations in the international money market.D. There is a sharp increase in India's balance of payment deficit. Questions 12 to 15 are based on the conversation you have just heard.12. A. They have unrealistic expectations about the other half.B. They may not be prepared for a lifelong relationship.C. They form a more realistic picture of life.D. They try to adapt to their changing roles.13. A. He is lucky to have visited many exotic places.B. He is able to forget all the troubles in his life.C. He is able to meet many interesting people.D. He is lucky to be able to do what he loves.14.A. It is stressful. B. It is full of time. C. It is all glamour. D. It is challenging15. A. Bothered. B. Amazed. C. Puzzled. D. Excited.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 I with a single line through the centre.Passage OneQuestions 16 to 18 are based on the passage you have just heard.16. A. Maintain the traditional organizational culture.B. Learn new ways of relating and working together.C. Follow closely the fast development of technology.D. Learn to be respectful in a hierarchical organization.17. A. How the team integrates with what it is supposed to serve.B. How the team is built to keep improving its performance.C. What type of personnel the team should be composed of.D. What qualifications team members should be equipped with.18. A. A team manager must set very clear and high objectives.B. Teams must consist of members from different cultures.C. Team members should be knowledgeable and creative.D. A team manager should develop a certain set of skills.Passage TwoQuestions 19 to 22 are based on the passage you have just heard.19. A. It is a platform for sharing ideas on teaching at the University of Illinois.B. It was mainly used by scientists and technical people to exchange text.C. It started off as a successful program but was unable to last long.D. It is a program allowing people to share information on the Web.20. A. He visited a number of famous computer scientists.B. He met with an entrepreneur named Jim Clark.C. He sold a program developed by his friends.D. He invested in a leading computer business.21. A. They had confidence in his new ideas.B. They trusted his computer expertise.C. They were very keen on new technology.D. They believed in his business connections.Passage ThreeQuestions 22 to 25 are based on the passage you have just heard.22. A. Prestige advertising.B. Institutional advertising.C. Word of mouth advertising.D. Distributing free trial products.23. A. To sell a particular product.B. To build up their reputation.C. To promote a specific service.D. To attract high-end consumers.24. A. By using the services of large advertising agencies.B. By hiring their own professional advertising staff.C. By buying media space in leading newspapers.D. By creating their own ads and commercials.25. A. Decide on what specific means of communication to employ.B. Conduct a large-scale survey on customer needs.C. Specify the objectives of the campaign in detail.D. Pretest alternative ads or commercials in certain regions.Section CDirections: In this section, you will hoar a passage three times. When the passage is read for the first time, you should listen carefully for its general idea. When the passage is read for the second time, you are required to fill in the blanks with the exact words you have just hoard. Finally, when the passage is read for the third time, you should chock what you have written.Extinction is difficult concept to grasp. It is an（26）concept. It's not at all like the killing of individual life forms that can be renewed through normal processes of reproduction. Nor is it simply（27）numbers. Nor is it damage that can somehow be remedied or for which some substitute can be found. Nor is it something that simply affects our own generation. Nor is it something that could be remedied by some supernatural power. It is rather an（28）and final act for which there is no remedy on earth or in heaven. A species once extinct is gone forever. However many generations （29)us in coming centuries, none of them will ever see this species that we extinguish. Not only are we bringing about the extinction of life（30）, we are also making the land and the air and the sea so toxic that the very conditions of life are being destroyed.（31）basic natural resources, not only are the nonrenewable resources being（32）in a frenzy ( 疯狂) of processing, consuming, and（33）, but we are also mining much of our renewable resources, such as the very soil itself on which terrestrial (地球上旳) life depends.The change that is taking place on the earth and in our minds is one of the greatest changes ever to take place in human affairs, perhaps the greatest, since what we are talking about is not simply another historical change or cultural （34）, but a change of geological and biological as well as psychological order of（35).Part ⅢReading Comprehension (40 minutes)Section ADirections: In this section, there is a passage with ten blanks. You are required to select one word for each blank from a list of choices given in a word bank following the passage. Read the passage through carefully before making yourchoices. Each choice in the bank is identified by a letter. Please mark the corresponding letter for each item on Answer Sheet 2 with a single line through the centre. You may not use any of the words in the bank more than once.Questions 36 to 45 are based on the following passage.It seems to be a law in the technology industry that leading companies eventually lose their positions, often quickly and brutally. Mobile phone champion Nokia, one of Europe's biggest technology success stories, was no（36）, losing its market share in just a few years.In , Nokia accounted for more than 40% of mobile phone sales（37）But consumers'preferences were already（38）toward touch-screen smart phones. With the introduction of Apple's phone in the middle of that year, Nokia's market share（39）rapidly and revenue plunged. By the end of , Nokia had sold its phone business to Microsoft.What sealed Nokia's fate was a series of decisions made by Stephen Elop in his position as CEO, which he（40）in October . Each day that Elop spent in charge of Nokia, the company's market value declined by $ 23 million, making him, by the numbers, one of the worst CEOs in history. But Elop was not the only person at（41）Nokia's board resisted change, making it impossible for the company to adapt to rapid shifts in the industry. Most（42）, Jorma Ollila, who had led Nokia's transition from an industrial company to a technology giant, was too fascinated by the company's（43）success to recognize the change that was needed to sustain its competitiveness. The company also embarked on a（44）cost-cutting program, which included the elimination of thousands of jobs. This contributed to the(45) of the company’s once-spirited culture.which had motivated employees to take risks and make miracles. Good leaders left the company, taking Nokia's sense of vision and directions with them. Not surprisingly, much of Nokia's most valuable design and programming talent left as well.A. assumedB. biasC. desperateD. deteriorationE. exceptionF. faultG. incidentallyH. notablyI. previousJ. relayedK. shiftingL. shrankM. subtleN. transmittingO. worldwideSection BDirections : In this section, you are going to read a passage with ten statements attached to it. Each statement contains information given in one of the paragraphs. Identify the paragraph from which the information is derived. You may choose a paragraph more than once.Each paragraph is marked with a letter. Answer the questions by marking the corresponding letter on Answer Sheet 2.First-Generation College-Goers: Unprepared and Behind Kids who are the first in their families to brave the world of higher education come on campus with little academic know—how and are much more likely than their peers to drop out before graduation.[ A] When Nijay Williams entered college last fall as a first—generation student and Jamaican immigrant, he was academically unprepared for the rigors of higher education. Like many first—generation students, he enrolled in a medium-sized state university many of his high school peers were also attending, received a Pell Grant, and took out some small federal loans to cover other costs.Given the high price of room and board and the closeness of the school to his family, he chose to live at home and worked between 30 and 40 hours a week while taking a full class schedule.[ B] What Nijay didn't realize about his school—Tennessee State University—was its frighteningly low graduation rate: a mere 29 percent for its first-generation students. At the end of his first year, Nijay lost his Pell Grant of over $ 5,000 after narrowly missing the 2.0 GPA cut-off, making it impossible for him to continue paying for school.[ C ]Nijay represents a large and growing group of Americans: first—generation college students who enter school unprepared or behind. To make matters worse, these schools are ill-equipped to graduate these students—young adults who face specific challenges and obstacles. They typically carry financial burdens that outweigh those of their peers, are more likely to work while attending school, and often require significant academic remediation (补习).[ D ] Matt Rubinoff directs I'm First, a nonprofit organization launched last October to reach out to this specific population of students. He hopes to distribute this information and help prospective college-goers fad the best post-secondary fit. And while Rubinoff believes there are a good number of four—year schools that truly care about these students and set aside significant resources and programs for them, he says that number isn't high enough.[ E ] "It's not only the selective and elite institutions that provide those opportunities for a small subset of this population," Rubinoff said, adding that a majority of first-generation undergraduates tend toward options such as online programs, two—year colleges, and commuter state schools."Unfortunately, there tends to be a lack of information and support to help students think bigger and broader. "[ F] Despite this problem, many students are still drawn to these institutions--and two-year schools in particular. As a former high school teacher, I saw students choose familiar, cheaper options year after year. Instead of skipping out on higher education altogether, they chose community colleges or state schools with low bars for admittance.[ G]"They underestimate themselves when selecting a university," said Dave Jarrat, a marketing executive for InsideTrack, a for—profit organization that specializes in coaching low-income students and supporting colleges in order to help students thrive. "The reality of it is that a lot of low-income kids could be going to elite universities on a full ride scholarship and don't even realize it. "[ H] "Many students are coming from a situation where no one around them has the experience of successfully completing higher education, so they are coming in questioning themselves and their college worthiness," Jarrat continued. That helps explain why, as I'm First's Rubinoff indicated, the schools to which these students end up resorting can end up being some of the poorest matches for them. The University of Tennessee in Knoxville offers one example of this dilemma. A flagship university in the South, the school graduates just 16 percent of its first—generation students, despite its overall graduation rate of 71 percent. Located only a few hours apart, The University of Tennessee and Tennessee State are worth comparing. Tennessee State's overall graduation rate is a tiny 39 percent, but at least it has a smaller gap between the outcomes for first—generation students and those of their peers.[ I] Still, the University of Tennessee deserves credit for being transparent. Many large institutions keep this kind of data secret—or at least make it incredibly difficult to find The University of North Carolina at Chapel Hill, for instance, admits only that the graduation rate for its first—generation pupils is "much lower" than the percentage of all students who graduate within four years (81 percent).[ J] It is actually quite difficult to freed reliable statistics on the issue for many schools. Higher education institutions are, under federal law, required to report graduation rates, but these reports typically only include Pell recipient numbers —not necessarily rates specific to first—generation students. Other initiatives fail to break down the data, too. Imagine how intimidating it can be for prospective students unfamiliar with the complexities of higher education to navigate this kind of information and then identify which schools are the best fit.[ K] It was this lack of information that prompted the launch of I'm First in , originally as an ann. of its umbrella organization, the Center For Student Opportunity."If we can help to direct students to more of these types of campuses and help students to understand them to be realistic and accessible places, have them apply to these schools at greater frequency and ultimately get in and enroll, we are going to raise the success rate," Rubinoff said, citing a variety of colleges ranging from large state institutions to smaller private schools.[ L] Chelsea Jones, who now directs student programming at I'm First, was a first—generation college student at Howard. Like other student new to the intimidating higher—education world, she often struggled on her path to college, "There wasn't really a college—bound culture at my high school," she said. "I wanted to go to college but I didn't reallyknow the process. " Jones became involved with a college—access program through Princeton University in high school. Now, she attributesmuch of her understanding of college to that: "But once I got to campus, it was a completely different ball game that no one really prepared me for. "[ M] She was fortunate, though. Howard, a well—regarded historically black college, had an array of resources for its first—generation students, including matching kids with counselors, commenting first—generation students to one another, and TRIO, a national program that supported 200 students on Howard's campus. Still, Jones represents a small percentage of first-generation students who are able to gain entry into more elite universities, which are often known for robust financial aid packages and remarkably high graduation rates for first—generation students.(Harvard, for example, boasts a six—year graduation rate for underrepresented minority groups of 98 percent. ) [ N]Christian Vazquez, a first—generation Yale graduate, is another exception, his success story setting him far apart from students such as Nijay. "There is a lot of support at Yale, to an extent, after a while, there is too much support," he said, half—joking about the countless resources available at the school. Students are placed in small groups with counselors ( trained seniors on campus) ;they have access to cultural and ethnic affinity (联络) groups, tutoring centers and also have asummer orientation specifically for first—generation students ( the latter being one of the most common programs for students).[ O]"Our support structure was more like : ' You are going to get through Yale; you are going to do well,' " he said, hinting at mentors (导师), staff, and professors who all provided significant support for students who lacked confidence about "belonging" at such a top institution.46. Many first—generation college—goers have doubts about their abilities to get a college degree.47. First—generation college students tend to have much heavier financial burdens than their peers.48. The graduation rate of first—generation students at Nijay's university was incredibly low.49. Some top institutions like Yale seem to provide first—generation students with more support than they actually need.50. On entering college, Nijay Williams had no idea how challenging college education was.51. Many universities simply refuse to release their exact graduation rates for first-generation students.52. According to a marketing executive, many students from low-income families don't know they could have achance of going to an elite university.53. Some elite universities attach great importance to building up the first—generation students' serf—confidence.54. I'm First distributes information to help first-generation college-goers find schools that are most suitable for them.55. Elite universities tend to graduate fan’s-generation students at a higher rate.Section CDirections: There are 2 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 OneQuestions 56 to 60 are based on the following passage.Saying they can no longer ignore the rising prices of health care, some of the most influential medical groups in the nation are recommending that doctors weigh the costs, not just the effectiveness of treatments, as they make decisions about patient care. The shift, little noticed outside the medical establishment but already controversial inside it, suggests that doctors are starting to redefine their roles, from being concerned exclusively about individual patients to exerting influence on how healthcare dollars are spent. In practical terms, the new guidelines being developed could result in doctors choosing one drug over another for cost reasons or even deciding that a particular treatment—at the end of life, for example—is too expensive. In the extreme, some critics have said that making treatment decisions based on cost is a form of rationing. Traditionally, guidelines have heavily influenced the practice of medicine, and the latest ones are expected to make doctors more conscious of the economic consequences of their decisions, even though there's no obligation to follow them. Medical society guidelines are also used by insurancecomoanies to help determine reimbursement (报销) policies. Some doctors see a potential conflict in trying to be both providers of patient care and facial.Overseers. "There should be forces in society who should be concerned about the budget, but they shouldn't be functioning simultaneously as doctors," said Dr. Martin Samuels at a Boston hospital. He said doctors risked losing the trust of patients if they told patients, "I'm not going to do what I think is best for you because I think it's bad for the healthcare budget in Massachusetts. " Doctors can face some grim trade—offs. Studies have shown, for example, that two drugs are about equally effective in treating macular degeneration, and eye disease. But one costs $ 50 a dose and the other close to $ 2,000. Medicare could save hundreds of millions of dollars a year if everyone used the cheaper drug, Avastin, instead ofthe costlier one, Lucentis. But the Food and Drug Administration has not approved Avastin for use in the eye. and using it rather than the alternative, Lucentis, might carry an additional, although slight, safety risk. Should doctors consider Medicare's budget in deciding what to use?"I think ethically (在道德层面上) we are just worried about the patient in front of us and not trying to save money for the insurance industry or society as a whole," said Dr. Donald Jensen. Still, some analysts say that there's a role for doctors to play in cost analysis because not many others are doing so. "In some ways," said Dr. Daniel Sulmasy, "it represents a failure of wider society to take up the issue. "56. What do some most influential medical groups recommend doctors do?A. Reflect on the responsibilities they are supposed to take.B. Pay more attention to the effectiveness of their treatments.C. Take costs into account when making treatment decisions.D. Readjust their practice in view of the cuts in health care.57. What were doctors mainly concerned about in the past?A. Specific medicines to be used.B. Effects of medical treatment.C. Professional advancement.D. Patients' trust.58. What may the new guidelines being developed lead to?A. The redefining of doctors' roles.B. Overuse of less effective medicines.C. Conflicts between doctors and patients.D. The prolonging of patients' suffering.59. What risk do doctors see in their dual role as patient care providers and financial overseers?A. They may be involved in a conflict of interest.B. They may be forced to divide their attention.C. They may have to use less effective drugs.D. They may lose the respect of patients.60. What do some experts say about doctors' involvement in medical cost analysis?A. It may add to doctors' already heavy workloads.B. It will help to save money for society as a whole.C. It results from society's failure to tackle the problem.D. It raises doctors' awareness of their social responsibilities.Passage TwoQuestions 61 to 65 are based on the following passage.Economic inequality is the "defining challenge of our time," President Barack Obama declared in a speech last monthto the Center for American Progress. Inequality is dangerous, he argued, not merely because it doesn't look good to have a large gap between the rich and the poor, but because inequality itself destroys upward mobility, making it harder for the poor to escape from poverty. "Increased inequality and decreasing mobility pose a fundamental threat to the American Dream," he said. Obama is only the most prominent public figure to declare inequality Public Enemy No. 1 and the greatest threat to reducing poverty in America. A number of prominent economists have also argued that it's harder for the poor to climb the economic ladder today because the rungs (横档) in that ladder have grown farther apart.For all the new attention devoted to the 1 percent, a new dam set from the Equality of Opportunity Project at Harvard and Berkeley suggests that, if we care about upward mobility overall, we're vastly exaggerating the dangers of the rich—poor gap. Inequality itself is not a particularly strong predictor of economic mobility, as sociologist Scott Winship noted in a recent article based on his analysis of this data. So what factors, at the community level, do predict if poor children will move up the economic ladder as adtdts? what explains, for instance, why the Salt Lake City metro area is one of the 100 largest metropolitan areas most likely to lift the fortunes of the poor and the Atlanta metro area is one of the least likely?Harvard economist Raj Cherty has pointed to economic and racial segregation, community density, the size of a community's middle class, the quality of schools, commitments religiosity, and family structure, which he calls the "single strongest correlate of upward mobility. " Chetty finds that communities like Salt Lake City, with high levels of two-parent families and religiosity, are much more likely to see poor children get ahead than communities like Atlanta, with high levels of racial and economic segregation. Chetty has not yet issued a comprehensive analysis of the relative predictive power of each of these factors. Based on my analyses of the data. of the factors that Chetty has highlighted, the following three seem to be most predictive of upward mobility in a given community.1. Per-capita (人均) income growth2. Prevalence of single mothers ( where correlation is strong, but negative)3. Per-capita local government spending In other words, communities with high levels of per-capita income growth, high percentages of two-parent families, and high local government spending-which may stand for good schools-are the most likely to help poor children relive Horatio Alger's rags-to-riches story.61. How does Obama view economic inequality?A. It is the biggest obstacle to social mobility.B. It is the greatest threat to social stability.C. It is the No. 1 enemy of income growth.D. It is the most malicious social evil of our time.62. What do we learn about the inequality gap from Scott Winship's data analysis?。

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Network impacts of a road capacity reduction:Empirical analysisand model predictionsDavid Watling a ,⇑,David Milne a ,Stephen Clark baInstitute for Transport Studies,University of Leeds,Woodhouse Lane,Leeds LS29JT,UK b Leeds City Council,Leonardo Building,2Rossington Street,Leeds LS28HD,UKa r t i c l e i n f o Article history:Received 24May 2010Received in revised form 15July 2011Accepted 7September 2011Keywords:Trafﬁc assignment Network models Equilibrium Route choice Day-to-day variabilitya b s t r a c tIn spite of their widespread use in policy design and evaluation,relatively little evidencehas been reported on how well trafﬁc equilibrium models predict real network impacts.Here we present what we believe to be the ﬁrst paper that together analyses the explicitimpacts on observed route choice of an actual network intervention and compares thiswith the before-and-after predictions of a network equilibrium model.The analysis isbased on the ﬁndings of an empirical study of the travel time and route choice impactsof a road capacity reduction.Time-stamped,partial licence plates were recorded across aseries of locations,over a period of days both with and without the capacity reduction,and the data were ‘matched’between locations using special-purpose statistical methods.Hypothesis tests were used to identify statistically signiﬁcant changes in travel times androute choice,between the periods of days with and without the capacity reduction.A trafﬁcnetwork equilibrium model was then independently applied to the same scenarios,and itspredictions compared with the empirical ﬁndings.From a comparison of route choice pat-terns,a particularly inﬂuential spatial effect was revealed of the parameter specifying therelative values of distance and travel time assumed in the generalised cost equations.When this parameter was ‘ﬁtted’to the data without the capacity reduction,the networkmodel broadly predicted the route choice impacts of the capacity reduction,but with othervalues it was seen to perform poorly.The paper concludes by discussing the wider practicaland research implications of the study’s ﬁndings.Ó2011Elsevier Ltd.All rights reserved.1.IntroductionIt is well known that altering the localised characteristics of a road network,such as a planned change in road capacity,will tend to have both direct and indirect effects.The direct effects are imparted on the road itself,in terms of how it can deal with a given demand ﬂow entering the link,with an impact on travel times to traverse the link at a given demand ﬂow level.The indirect effects arise due to drivers changing their travel decisions,such as choice of route,in response to the altered travel times.There are many practical circumstances in which it is desirable to forecast these direct and indirect impacts in the context of a systematic change in road capacity.For example,in the case of proposed road widening or junction improvements,there is typically a need to justify econom-ically the required investment in terms of the beneﬁts that will likely accrue.There are also several examples in which it is relevant to examine the impacts of road capacity reduction .For example,if one proposes to reallocate road space between alternative modes,such as increased bus and cycle lane provision or a pedestrianisation scheme,then typically a range of alternative designs exist which may differ in their ability to accommodate efﬁciently the new trafﬁc and routing patterns.0965-8564/$-see front matter Ó2011Elsevier Ltd.All rights reserved.doi:10.1016/j.tra.2011.09.010⇑Corresponding author.Tel.:+441133436612;fax:+441133435334.E-mail address:d.p.watling@ (D.Watling).168 D.Watling et al./Transportation Research Part A46(2012)167–189Through mathematical modelling,the alternative designs may be tested in a simulated environment and the most efﬁcient selected for implementation.Even after a particular design is selected,mathematical models may be used to adjust signal timings to optimise the use of the transport system.Road capacity may also be affected periodically by maintenance to essential services(e.g.water,electricity)or to the road itself,and often this can lead to restricted access over a period of days and weeks.In such cases,planning authorities may use modelling to devise suitable diversionary advice for drivers,and to plan any temporary changes to trafﬁc signals or priorities.Berdica(2002)and Taylor et al.(2006)suggest more of a pro-ac-tive approach,proposing that models should be used to test networks for potential vulnerability,before any reduction mate-rialises,identifying links which if reduced in capacity over an extended period1would have a substantial impact on system performance.There are therefore practical requirements for a suitable network model of travel time and route choice impacts of capac-ity changes.The dominant method that has emerged for this purpose over the last decades is clearly the network equilibrium approach,as proposed by Beckmann et al.(1956)and developed in several directions since.The basis of using this approach is the proposition of what are believed to be‘rational’models of behaviour and other system components(e.g.link perfor-mance functions),with site-speciﬁc data used to tailor such models to particular case studies.Cross-sectional forecasts of network performance at speciﬁc road capacity states may then be made,such that at the time of any‘snapshot’forecast, drivers’route choices are in some kind of individually-optimum state.In this state,drivers cannot improve their route selec-tion by a unilateral change of route,at the snapshot travel time levels.The accepted practice is to‘validate’such models on a case-by-case basis,by ensuring that the model—when supplied with a particular set of parameters,input network data and input origin–destination demand data—reproduces current mea-sured mean link trafﬁcﬂows and mean journey times,on a sample of links,to some degree of accuracy(see for example,the practical guidelines in TMIP(1997)and Highways Agency(2002)).This kind of aggregate level,cross-sectional validation to existing conditions persists across a range of network modelling paradigms,ranging from static and dynamic equilibrium (Florian and Nguyen,1976;Leonard and Tough,1979;Stephenson and Teply,1984;Matzoros et al.,1987;Janson et al., 1986;Janson,1991)to micro-simulation approaches(Laird et al.,1999;Ben-Akiva et al.,2000;Keenan,2005).While such an approach is plausible,it leaves many questions unanswered,and we would particularly highlight two: 1.The process of calibration and validation of a network equilibrium model may typically occur in a cycle.That is to say,having initially calibrated a model using the base data sources,if the subsequent validation reveals substantial discrep-ancies in some part of the network,it is then natural to adjust the model parameters(including perhaps even the OD matrix elements)until the model outputs better reﬂect the validation data.2In this process,then,we allow the adjustment of potentially a large number of network parameters and input data in order to replicate the validation data,yet these data themselves are highly aggregate,existing only at the link level.To be clear here,we are talking about a level of coarseness even greater than that in aggregate choice models,since we cannot even infer from link-level data the aggregate shares on alternative routes or OD movements.The question that arises is then:how many different combinations of parameters and input data values might lead to a similar link-level validation,and even if we knew the answer to this question,how might we choose between these alternative combinations?In practice,this issue is typically neglected,meaning that the‘valida-tion’is a rather weak test of the model.2.Since the data are cross-sectional in time(i.e.the aim is to reproduce current base conditions in equilibrium),then in spiteof the large efforts required in data collection,no empirical evidence is routinely collected regarding the model’s main purpose,namely its ability to predict changes in behaviour and network performance under changes to the network/ demand.This issue is exacerbated by the aggregation concerns in point1:the‘ambiguity’in choosing appropriate param-eter values to satisfy the aggregate,link-level,base validation strengthens the need to independently verify that,with the selected parameter values,the model responds reliably to changes.Although such problems–ofﬁtting equilibrium models to cross-sectional data–have long been recognised by practitioners and academics(see,e.g.,Goodwin,1998), the approach described above remains the state-of-practice.Having identiﬁed these two problems,how might we go about addressing them?One approach to theﬁrst problem would be to return to the underlying formulation of the network model,and instead require a model deﬁnition that permits analysis by statistical inference techniques(see for example,Nakayama et al.,2009).In this way,we may potentially exploit more information in the variability of the link-level data,with well-deﬁned notions(such as maximum likelihood)allowing a systematic basis for selection between alternative parameter value combinations.However,this approach is still using rather limited data and it is natural not just to question the model but also the data that we use to calibrate and validate it.Yet this is not altogether straightforward to resolve.As Mahmassani and Jou(2000) remarked:‘A major difﬁculty...is obtaining observations of actual trip-maker behaviour,at the desired level of richness, simultaneously with measurements of prevailing conditions’.For this reason,several authors have turned to simulated gaming environments and/or stated preference techniques to elicit information on drivers’route choice behaviour(e.g. 1Clearly,more sporadic and less predictable reductions in capacity may also occur,such as in the case of breakdowns and accidents,and environmental factors such as severe weather,ﬂoods or landslides(see for example,Iida,1999),but the responses to such cases are outside the scope of the present paper. 2Some authors have suggested more systematic,bi-level type optimization processes for thisﬁtting process(e.g.Xu et al.,2004),but this has no material effect on the essential points above.D.Watling et al./Transportation Research Part A46(2012)167–189169 Mahmassani and Herman,1990;Iida et al.,1992;Khattak et al.,1993;Vaughn et al.,1995;Wardman et al.,1997;Jou,2001; Chen et al.,2001).This provides potentially rich information for calibrating complex behavioural models,but has the obvious limitation that it is based on imagined rather than real route choice situations.Aside from its common focus on hypothetical decision situations,this latter body of work also signiﬁes a subtle change of emphasis in the treatment of the overall network calibration problem.Rather than viewing the network equilibrium calibra-tion process as a whole,the focus is on particular components of the model;in the cases above,the focus is on that compo-nent concerned with how drivers make route decisions.If we are prepared to make such a component-wise analysis,then certainly there exists abundant empirical evidence in the literature,with a history across a number of decades of research into issues such as the factors affecting drivers’route choice(e.g.Wachs,1967;Huchingson et al.,1977;Abu-Eisheh and Mannering,1987;Duffell and Kalombaris,1988;Antonisse et al.,1989;Bekhor et al.,2002;Liu et al.,2004),the nature of travel time variability(e.g.Smeed and Jeffcoate,1971;Montgomery and May,1987;May et al.,1989;McLeod et al., 1993),and the factors affecting trafﬁcﬂow variability(Bonsall et al.,1984;Huff and Hanson,1986;Ribeiro,1994;Rakha and Van Aerde,1995;Fox et al.,1998).While these works provide useful evidence for the network equilibrium calibration problem,they do not provide a frame-work in which we can judge the overall‘ﬁt’of a particular network model in the light of uncertainty,ambient variation and systematic changes in network attributes,be they related to the OD demand,the route choice process,travel times or the network data.Moreover,such data does nothing to address the second point made above,namely the question of how to validate the model forecasts under systematic changes to its inputs.The studies of Mannering et al.(1994)and Emmerink et al.(1996)are distinctive in this context in that they address some of the empirical concerns expressed in the context of travel information impacts,but their work stops at the stage of the empirical analysis,without a link being made to net-work prediction models.The focus of the present paper therefore is both to present theﬁndings of an empirical study and to link this empirical evidence to network forecasting models.More recently,Zhu et al.(2010)analysed several sources of data for evidence of the trafﬁc and behavioural impacts of the I-35W bridge collapse in Minneapolis.Most pertinent to the present paper is their location-speciﬁc analysis of linkﬂows at 24locations;by computing the root mean square difference inﬂows between successive weeks,and comparing the trend for 2006with that for2007(the latter with the bridge collapse),they observed an apparent transient impact of the bridge col-lapse.They also showed there was no statistically-signiﬁcant evidence of a difference in the pattern ofﬂows in the period September–November2007(a period starting6weeks after the bridge collapse),when compared with the corresponding period in2006.They suggested that this was indicative of the length of a‘re-equilibration process’in a conceptual sense, though did not explicitly compare their empiricalﬁndings with those of a network equilibrium model.The structure of the remainder of the paper is as follows.In Section2we describe the process of selecting the real-life problem to analyse,together with the details and rationale behind the survey design.Following this,Section3describes the statistical techniques used to extract information on travel times and routing patterns from the survey data.Statistical inference is then considered in Section4,with the aim of detecting statistically signiﬁcant explanatory factors.In Section5 comparisons are made between the observed network data and those predicted by a network equilibrium model.Finally,in Section6the conclusions of the study are highlighted,and recommendations made for both practice and future research.2.Experimental designThe ultimate objective of the study was to compare actual data with the output of a trafﬁc network equilibrium model, speciﬁcally in terms of how well the equilibrium model was able to correctly forecast the impact of a systematic change ap-plied to the network.While a wealth of surveillance data on linkﬂows and travel times is routinely collected by many local and national agencies,we did not believe that such data would be sufﬁciently informative for our purposes.The reason is that while such data can often be disaggregated down to small time step resolutions,the data remains aggregate in terms of what it informs about driver response,since it does not provide the opportunity to explicitly trace vehicles(even in aggre-gate form)across more than one location.This has the effect that observed differences in linkﬂows might be attributed to many potential causes:it is especially difﬁcult to separate out,say,ambient daily variation in the trip demand matrix from systematic changes in route choice,since both may give rise to similar impacts on observed linkﬂow patterns across re-corded sites.While methods do exist for reconstructing OD and network route patterns from observed link data(e.g.Yang et al.,1994),these are typically based on the premise of a valid network equilibrium model:in this case then,the data would not be able to give independent information on the validity of the network equilibrium approach.For these reasons it was decided to design and implement a purpose-built survey.However,it would not be efﬁcient to extensively monitor a network in order to wait for something to happen,and therefore we required advance notiﬁcation of some planned intervention.For this reason we chose to study the impact of urban maintenance work affecting the roads,which UK local government authorities organise on an annual basis as part of their‘Local Transport Plan’.The city council of York,a historic city in the north of England,agreed to inform us of their plans and to assist in the subsequent data collection exercise.Based on the interventions planned by York CC,the list of candidate studies was narrowed by considering factors such as its propensity to induce signiﬁcant re-routing and its impact on the peak periods.Effectively the motivation here was to identify interventions that were likely to have a large impact on delays,since route choice impacts would then likely be more signiﬁcant and more easily distinguished from ambient variability.This was notably at odds with the objectives of York CC,170 D.Watling et al./Transportation Research Part A46(2012)167–189in that they wished to minimise disruption,and so where possible York CC planned interventions to take place at times of day and of the year where impacts were minimised;therefore our own requirement greatly reduced the candidate set of studies to monitor.A further consideration in study selection was its timing in the year for scheduling before/after surveys so to avoid confounding effects of known signiﬁcant‘seasonal’demand changes,e.g.the impact of the change between school semesters and holidays.A further consideration was York’s role as a major tourist attraction,which is also known to have a seasonal trend.However,the impact on car trafﬁc is relatively small due to the strong promotion of public trans-port and restrictions on car travel and parking in the historic centre.We felt that we further mitigated such impacts by sub-sequently choosing to survey in the morning peak,at a time before most tourist attractions are open.Aside from the question of which intervention to survey was the issue of what data to collect.Within the resources of the project,we considered several options.We rejected stated preference survey methods as,although they provide a link to personal/socio-economic drivers,we wanted to compare actual behaviour with a network model;if the stated preference data conﬂicted with the network model,it would not be clear which we should question most.For revealed preference data, options considered included(i)self-completion diaries(Mahmassani and Jou,2000),(ii)automatic tracking through GPS(Jan et al.,2000;Quiroga et al.,2000;Taylor et al.,2000),and(iii)licence plate surveys(Schaefer,1988).Regarding self-comple-tion surveys,from our own interview experiments with self-completion questionnaires it was evident that travellersﬁnd it relatively difﬁcult to recall and describe complex choice options such as a route through an urban network,giving the po-tential for signiﬁcant errors to be introduced.The automatic tracking option was believed to be the most attractive in this respect,in its potential to accurately map a given individual’s journey,but the negative side would be the potential sample size,as we would need to purchase/hire and distribute the devices;even with a large budget,it is not straightforward to identify in advance the target users,nor to guarantee their cooperation.Licence plate surveys,it was believed,offered the potential for compromise between sample size and data resolution: while we could not track routes to the same resolution as GPS,by judicious location of surveyors we had the opportunity to track vehicles across more than one location,thus providing route-like information.With time-stamped licence plates, the matched data would also provide journey time information.The negative side of this approach is the well-known poten-tial for signiﬁcant recording errors if large sample rates are required.Our aim was to avoid this by recording only partial licence plates,and employing statistical methods to remove the impact of‘spurious matches’,i.e.where two different vehi-cles with the same partial licence plate occur at different locations.Moreover,extensive simulation experiments(Watling,1994)had previously shown that these latter statistical methods were effective in recovering the underlying movements and travel times,even if only a relatively small part of the licence plate were recorded,in spite of giving a large potential for spurious matching.We believed that such an approach reduced the opportunity for recorder error to such a level to suggest that a100%sample rate of vehicles passing may be feasible.This was tested in a pilot study conducted by the project team,with dictaphones used to record a100%sample of time-stamped, partial licence plates.Independent,duplicate observers were employed at the same location to compare error rates;the same study was also conducted with full licence plates.The study indicated that100%surveys with dictaphones would be feasible in moderate trafﬁcﬂow,but only if partial licence plate data were used in order to control observation errors; for higherﬂow rates or to obtain full number plate data,video surveys should be considered.Other important practical les-sons learned from the pilot included the need for clarity in terms of vehicle types to survey(e.g.whether to include motor-cycles and taxis),and of the phonetic alphabet used by surveyors to avoid transcription ambiguities.Based on the twin considerations above of planned interventions and survey approach,several candidate studies were identiﬁed.For a candidate study,detailed design issues involved identifying:likely affected movements and alternative routes(using local knowledge of York CC,together with an existing network model of the city),in order to determine the number and location of survey sites;feasible viewpoints,based on site visits;the timing of surveys,e.g.visibility issues in the dark,winter evening peak period;the peak duration from automatic trafﬁcﬂow data;and speciﬁc survey days,in view of public/school holidays.Our budget led us to survey the majority of licence plate sites manually(partial plates by audio-tape or,in lowﬂows,pen and paper),with video surveys limited to a small number of high-ﬂow sites.From this combination of techniques,100%sampling rate was feasible at each site.Surveys took place in the morning peak due both to visibility considerations and to minimise conﬂicts with tourist/special event trafﬁc.From automatic trafﬁc count data it was decided to survey the period7:45–9:15as the main morning peak period.This design process led to the identiﬁcation of two studies:2.1.Lendal Bridge study(Fig.1)Lendal Bridge,a critical part of York’s inner ring road,was scheduled to be closed for maintenance from September2000 for a duration of several weeks.To avoid school holidays,the‘before’surveys were scheduled for June and early September.It was decided to focus on investigating a signiﬁcant southwest-to-northeast movement of trafﬁc,the river providing a natural barrier which suggested surveying the six river crossing points(C,J,H,K,L,M in Fig.1).In total,13locations were identiﬁed for survey,in an attempt to capture trafﬁc on both sides of the river as well as a crossing.2.2.Fishergate study(Fig.2)The partial closure(capacity reduction)of the street known as Fishergate,again part of York’s inner ring road,was scheduled for July2001to allow repairs to a collapsed sewer.Survey locations were chosen in order to intercept clockwiseFig.1.Intervention and survey locations for Lendal Bridge study.around the inner ring road,this being the direction of the partial closure.A particular aim wasFulford Road(site E in Fig.2),the main radial affected,with F and K monitoring local diversion I,J to capture wider-area diversion.studies,the plan was to survey the selected locations in the morning peak over a period of approximately covering the three periods before,during and after the intervention,with the days selected so holidays or special events.Fig.2.Intervention and survey locations for Fishergate study.In the Lendal Bridge study,while the‘before’surveys proceeded as planned,the bridge’s actualﬁrst day of closure on Sep-tember11th2000also marked the beginning of the UK fuel protests(BBC,2000a;Lyons and Chaterjee,2002).Trafﬁcﬂows were considerably affected by the scarcity of fuel,with congestion extremely low in theﬁrst week of closure,to the extent that any changes could not be attributed to the bridge closure;neither had our design anticipated how to survey the impacts of the fuel shortages.We thus re-arranged our surveys to monitor more closely the planned re-opening of the bridge.Unfor-tunately these surveys were hampered by a second unanticipated event,namely the wettest autumn in the UK for270years and the highest level ofﬂooding in York since records began(BBC,2000b).Theﬂooding closed much of the centre of York to road trafﬁc,including our study area,as the roads were impassable,and therefore we abandoned the planned‘after’surveys. As a result of these events,the useable data we had(not affected by the fuel protests orﬂooding)consisted ofﬁve‘before’days and one‘during’day.In the Fishergate study,fortunately no extreme events occurred,allowing six‘before’and seven‘during’days to be sur-veyed,together with one additional day in the‘during’period when the works were temporarily removed.However,the works over-ran into the long summer school holidays,when it is well-known that there is a substantial seasonal effect of much lowerﬂows and congestion levels.We did not believe it possible to meaningfully isolate the impact of the link fully re-opening while controlling for such an effect,and so our plans for‘after re-opening’surveys were abandoned.3.Estimation of vehicle movements and travel timesThe data resulting from the surveys described in Section2is in the form of(for each day and each study)a set of time-stamped,partial licence plates,observed at a number of locations across the network.Since the data include only partial plates,they cannot simply be matched across observation points to yield reliable estimates of vehicle movements,since there is ambiguity in whether the same partial plate observed at different locations was truly caused by the same vehicle. Indeed,since the observed system is‘open’—in the sense that not all points of entry,exit,generation and attraction are mon-itored—the question is not just which of several potential matches to accept,but also whether there is any match at all.That is to say,an apparent match between data at two observation points could be caused by two separate vehicles that passed no other observation point.Theﬁrst stage of analysis therefore applied a series of specially-designed statistical techniques to reconstruct the vehicle movements and point-to-point travel time distributions from the observed data,allowing for all such ambiguities in the data.Although the detailed derivations of each method are not given here,since they may be found in the references provided,it is necessary to understand some of the characteristics of each method in order to interpret the results subsequently provided.Furthermore,since some of the basic techniques required modiﬁcation relative to the published descriptions,then in order to explain these adaptations it is necessary to understand some of the theoretical basis.3.1.Graphical method for estimating point-to-point travel time distributionsThe preliminary technique applied to each data set was the graphical method described in Watling and Maher(1988).This method is derived for analysing partial registration plate data for unidirectional movement between a pair of observation stations(referred to as an‘origin’and a‘destination’).Thus in the data study here,it must be independently applied to given pairs of observation stations,without regard for the interdependencies between observation station pairs.On the other hand, it makes no assumption that the system is‘closed’;there may be vehicles that pass the origin that do not pass the destina-tion,and vice versa.While limited in considering only two-point surveys,the attraction of the graphical technique is that it is a non-parametric method,with no assumptions made about the arrival time distributions at the observation points(they may be non-uniform in particular),and no assumptions made about the journey time probability density.It is therefore very suitable as aﬁrst means of investigative analysis for such data.The method begins by forming all pairs of possible matches in the data,of which some will be genuine matches(the pair of observations were due to a single vehicle)and the remainder spurious matches.Thus, for example,if there are three origin observations and two destination observations of a particular partial registration num-ber,then six possible matches may be formed,of which clearly no more than two can be genuine(and possibly only one or zero are genuine).A scatter plot may then be drawn for each possible match of the observation time at the origin versus that at the destination.The characteristic pattern of such a plot is as that shown in Fig.4a,with a dense‘line’of points(which will primarily be the genuine matches)superimposed upon a scatter of points over the whole region(which will primarily be the spurious matches).If we were to assume uniform arrival rates at the observation stations,then the spurious matches would be uniformly distributed over this plot;however,we shall avoid making such a restrictive assumption.The method begins by making a coarse estimate of the total number of genuine matches across the whole of this plot.As part of this analysis we then assume knowledge of,for any randomly selected vehicle,the probabilities:h k¼Prðvehicle is of the k th type of partial registration plateÞðk¼1;2;...;mÞwhereX m k¼1h k¼1172 D.Watling et al./Transportation Research Part A46(2012)167–189。

建设社会主义核心价值体系_英文_

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Social Sciences in China
spirit of the socialist system. Socialism is a theory and spirit as well as a road and system. The socialist road finds its expression in the establishment, steady improvement and maturity of the socialist system while the socialist spirit serves as the theoretical basis of and ideological support for the socialist road and system. Socialism differs from capitalism and other social forms in that it takes a different road and adopts a different system, the essence being a different social theory and spirit. In a sense, only a progressive social theory and spirit can give rise to a progressive social road and progressive social system. The degree of scientific understanding and grasp of social theory and spirit determines the degree of perfection and maturity of the social road and system. Throughout human history, each society has had its own unique social spirit and temperament, which is formed by its mode of production, political ideas and cultural traditions, reflecting its value needs, value objectives and value pursuits, covering its ideals, convictions, ethos and moral standards, and constituting its system of core values. Each society has its system of core values, which has an overriding position in that society’s ideology and plays a guiding role in its economic and social construction, social progress and human development. This is the basic spiritual support for the proper operation of a given social system and the maintenance of a given social order. A progressive system of social core values is a spiritual bond for maintaining social unity and harmony, a spiritual force for promoting all-round social development and a spiritual banner for directing social progress, exerting a direct and profound influence over society’s vitality, cohesion and creativity. The system of socialist core values is linked with the basic system and essential nature of socialism. It reveals the driving force for socialist economic, political, cultural and social development and reflects the requirements of the socialist modernization drive for prosperity, democracy, civilization and harmony. The “Decision of the Central Committee of the Chinese Communist Party on Some Major Issues concerning Structuring a Harmonious Socialist Society” clearly pointed out that the Marxist guiding principle, the common ideal of socialism with Chinese characteristics, a patriotism-centered national spirit, a spirit of the times centering on reform and innovation and the socialist concept of honor and disgrace are the basic contents of the system of socialist core values. All these are the most important parts of Chinese socialist ideology and the ideological foundation of the Chinese socialist system; at no time should we waver in our conviction about any of them. II The theme of the system of socialist core values is the common ideal of socialism with Chinese characteristics. This system is an organic whole with clear unity and coherence and a wellorganized structure. The common ideal of socialism with Chinese characteristics is both a basic part of socialist core values and the main theme of the whole system. It is the common ideal of the whole Party and all ethnic groups to follow the road of socialism with Chinese characteristics and realize the great rejuvenation of the Chinese nation under the leadership of the Communist Party; it is their common cause at present to build socialism with Chinese characteristics. To

Migration and the search for a better way of life a critical exploration of lifestyle migration

Migration and the search for a betterway of life:a critical exploration of lifestyle migrationMichaela Benson and Karen O’ReillyAbstractFor the past few years,the term‘lifestyle migration’has been used to refer to an increasing number of people who take the decision to migrate based on their belief that there is a more fulﬁlling way of life available to them elsewhere.Lifestyle migration is thus a growing,disparate phenomenon,with important but little under-stood implications for both societies and individuals.This article outlines and explores in detail a series of mobilities that have in common relative afﬂuence and this search for a better lifestyle.We attempt to deﬁne the limits of the term lifestyle migration,the characteristics of the lifestyle sought,and the place of this form of migration in the contemporary world.In this manner,we map the various migra-tions that can be considered under this broad rubric,recognising the similarities and differences in their migration trajectories.Further to this,drawing on the sociologi-cal literature on lifestyle,we provide an initial theoretical conceptualisation of this phenomenon,attempting to explain its recent escalation in various guises,and investigating the historical,sociological,and individualised conditions that inspire this migration.This article is thus theﬁrst step in deﬁning a broader programme for the study of lifestyle migration.We contend that the study of this migration is especially important in the current era given the impact such moves have on places and people at both ends of the migratory chain.IntroductionIn this article,we explore the usefulness of‘lifestyle migration’as an analytical tool in explaining a budding sociological phenomenon:the relocation of people within the developed world searching for a better way of life.We outline the unique characteristics of this form of migration,locating this migratory trend as a consequence of particular historical,sociological,and individualised condi-tions.In this manner,we present a new way of conceptualising a trend that runs counter to the most important or numerically dominant streams as identiﬁed by most migration researchers(eg Bommes and Morawska,2005;Castles and Miller,2003;Papastergiadis,2000),yet appears to be a historical continuation of earlier mobilities including the Grand Tour,adventure travel,and voluntary, The Sociological Review,57:4(2009)©2009The Authors.Journal compilation©2009The Editorial Board of The Sociological Review.Published by Blackwell Publishing Inc.,9600Garsington Road,Oxford OX42DQ,UK and350Main Street,Malden,02148, USA.Migration and the search for a better way of life temporary,and‘love’migration(King,2002).While it is recognised that,broadly speaking,the search for a better way of life is meaningful for all migrants,this paper examines a growing range of contemporary mobilities that intimate the growing interest in lifestyle within sociology.The migration of relatively afﬂuent individuals has been largely overlooked in the more general literature on migration.Where afﬂuent migrants have been studied,the major focus has been on professional expatriates(see for example Amit,2001,2002;Amit-Talai,1998;Beaverstock,2002;Cohen,1977; Fechter,2007;Iredale,2001;Nowicka,2006)or International Retirement Migration,with a particular focus on policy implications(see for example Casado-Díaz,2006;Helset et al.,2005;Rodríguez et al.,2005;Schriewer and García,2005).As Aledo Tur(2005)has noted,a policy focus tends to exclude relatively afﬂuent migrants who do notﬁt the stereotypical idea of a migrant in the given destinations,do not compete for jobs,and tend not to be racialised as other immigrants.Despite the signiﬁcant and increasing number of afﬂuent individuals migrating in search of a better way of life(with an increasing number of locations involved as both sending communities and destinations), in general they remain poorly understood and conceptualised.We contend that the study of these relatively afﬂuent migrants is especially important in the current era given the impact such moves has on places and people at both ends of the migratory chain(Mantecón,2008).Since this phenomenon of moving for a better way of life has rarely been covered by standard migration typologies(but see King,2002),researchers have attempted to link their studies to wider phenomena using umbrella concepts such as,inter alia,retirement migration,leisure migration,(inter-national)counterurbanisation,second home ownership,amenity-seeking and seasonal migration.None of these conceptualisations,however,is fully inclu-sive in grasping the complexity of this trend and uniting its various elements. In all these cases,research shows a common narrative through which respon-dents render their lives meaningful(Cortazzi,2001)–the search for a different lifestyle,a signiﬁcantly better quality of life which underlies migration.We argue here that despite the peculiarity of each case,these common lifestyle concerns demonstrate that these different migrations can be considered as a single phenomenon–lifestyle migration.As we perceive it,lifestyle migrants are relatively afﬂuent individuals of all ages,moving either part-time or full-time to places that,for various reasons, signify,for the migrant,a better quality of life.Ethnographic accounts espe-cially have revealed a narrative of escape permeating migrants’accounts of the decision to migrate,further emphasised by their negative presentations of life before migration.Migration is thus often described using language like ‘getting out of the trap’,‘making a fresh start’,‘a new beginning’(eg Helset et al.,2005;Karisto,2005;SalváTomás,2005).The fundamental features of the different lifestyles sought thus include the re-negotiation of the work-life balance,quality of life,and freedom from prior constraints.Through these strategies of reorientation,the migrants seek the greater good in life,however609©2009The Authors.Journal compilation©2009The Editorial Board of The Sociological ReviewMichaela Benson and Karen O’Reillythat might be perceived.Lifestyle migration is thus a search,a project,rather than an act,and it encompasses diverse destinations,desires and dreams. The search for a better way of lifeThe search for the good life as a comparative project is a consistent theme in lifestyle migration.Migrants retrospectively explain their speciﬁc relocation contrasting the merits of the host community–the slow pace of life;the relative cost of living(including cheap property prices);the climate and health beneﬁts;a feeling of community–with the shortcomings of home–rising levels of crime and unemployment;lack of community spirit;high-pressured lifestyles(or the ‘rat race’);and low quality of life(eg O’Reilly,2000;Sunil et al.,2007).These narrativesofdeclinehavebeenremovedfromtheindividualandhistoriographic contexts,rather than being analysed as narrative(eg Buller and Hoggart,1994; King,Warnes and Williams,2000).As retrospective stories,they may not reﬂect objective reality;the presented advantages of life in the destination are often romanticised accounts,while the migrants’representations of the ills of their home society are often overstated.However,the exaggerated comparison between life before and after migration provides a rationalisation of this form of migration extending beyond the discussion of economic privilege.Through such narrative accounts,the migrants challenge their depiction as consumers, emphasising instead their substantial,personal reasons for migrating.Migration stories thus additionally emphasise individualised,self-realisation narratives of the decision to migrate.Many stress the particular events and circumstancesleadinguptotheirmigration,orexplaintheirmigrationinrelation to one watershed event(Benson,2007;Hoey,2005;O’Reilly,2000).This might be redundancy,a change in working status(eg retirement),or a bereavement, each of which is experienced as traumatic in some way.Migration is presented as a way of overcoming the trauma of these events,of taking control of their lives,or as releasing them from ties and enabling them to live lives more‘true’to themselves.Life after migration is thus presented as the antithesis of life before migration,not only generally,but also on a more personal level.Because the fundamental features of the different lifestyles sought by such migrants include the good life,escape from past individual and community histories,and the opportunity for self-realisation,strategies post migration often include the re-negotiation of the work-life balance,maintaining quality of life and freedom from prior constraints.However,in order to achieve and maintain their new,preferable lifestyles,many migrants still need to generate income following migration,and it is common toﬁnd that they run small businesses as‘self-employed expatriates’(Stone and Stubbs,2007).Their choice of enterprise varies and,while many work within tourism or providing services for other migrants,the advances in communications technology make the possibilities endless.Importantly,these lifestyle migrants use their businesses as a means to an end;they use them to fund their new lifestyles 610©2009The Authors.Journal compilation©2009The Editorial Board of The Sociological ReviewMigration and the search for a better way of life (Befus et al.,1988;Madden,1999;Stone and Stubbs,2007).For example,when small business owners on the Costa del Sol were asked why they moved,they listed climate,quality of life,and lifestyle ahead of business opportunities. Lifestyle remains the main priority(Madden,1999).Individuals often seek self-employment not because they cannotﬁnd work locally,but because they prefer being their own boss.As Stone and Stubbs argue,‘working for others ...was not part of the new life that they had envisaged’(2007:438).Self-employed,the migrants have a greater degree of control over how much they work,and thus maintain what they perceive as an acceptable work-life balance.There is thus often a limit to how much the migrants will engage in the expansion–both in size and pecuniary terms–of their businesses,for fear that it will disturb the work-life balance they have established.Importantly,entrepreneurial activities undertaken by these migrants are most often a departure from their careers in life before migration;Hoey’s (2005)discovery that‘the pie guy’had previously worked as an engineer is perhaps the best example of the contrast between life before and after migra-tion.It is often the case that many lifestyle migrants have little or no previous experience of establishing and running businesses,but many of them take the opportunity of migrating to follow their dreams(some more successfully than others).In this respect,it can be seen that this form of migration does have a liberatory potential,instilling into people the idea that they can do anything they want.However,when viewed more clearly within the context of people’s lives before migration,this apparent disjuncture is not so clear-cut.The migrants take transferable skills from their jobs before migration,which they then put to use in their new businesses.As we have described in this section,the search for a better way of life is necessarily a comparative project.Presenting their migration within a compara-tive frame,the migrants provide an easily understandable justiﬁcation for their migration.However,what is often understated is the effort migrants invest in making their dreams a reality,and achieving an appropriate work-life balance. The search for idyllic placesThe destinations chosen by lifestyle migrants tell us a lot about the lives they aspire to lead.The different or better way of life sought is diverse,and,to some extent,and is speciﬁc to the destination chosen,reﬂecting individual prefer-ences and aspirations.This speciﬁcity warrants further investigation,but we can suggest a typology of lifestyle migration based upon the choice of desti-nation.We therefore present three different types of lifestyle migrant:the residential tourist,the rural idyll seeker,and the bourgeois bohemian. Residential tourismThe most renowned of lifestyle migrants have chosen destinations in coastal resorts or islands in the sun.1Reﬂecting the extensive public interest in these611©2009The Authors.Journal compilation©2009The Editorial Board of The Sociological ReviewMichaela Benson and Karen O’Reillymigrants,academic research on this‘heliotropic’migration has been relatively extensive,especially in relation to North-South migration,and with Spain as a favoured destination.2Migrants are attracted to places such as the Algarve, Malta and the Costa del Sol with their characteristic‘Mediterranean lifestyle’, incorporating cuisine,wine,a slow pace of life,and outdoor living(Casado-Díaz,2006;King et al.,2000),features analogous to those mentioned by those seeking the rural idyll and the bohemian ideal,discussed below.Although these sun-seeking migrants could be portrayed as hedonistic‘residential tour-ists’(Aledo Tur,2005),the health beneﬁts of the weather and the coast,as well as the relaxation and tranquillity associated with tourist destinations,act as a greater pull than any desire to be with other tourists(eg Sunil et al.,2007). Nevertheless,the imaginings and desires of these coastal migrants are difﬁcult to distinguish from the social construction of the spaces associated with mass tourism(O’Reilly,2003,2007b).Coastal lifestyle migration emphasises escape, leisure,relaxation,and‘tourism as a way of life’.The rural idyllRural locations are imagined to offer lifestyle migrants a sense of stepping back in time,getting back to the land,the simple or good life,as well as a sense of community spirit.While it is often the case in lifestyle migration that destinations are depicted as having the characteristics of rurality,the narra-tives of those who move to the countryside,whether at home or abroad, additionally stress the unique and embodied relationship that they have with the landscape(see for example Benson,2007;Geoffrey,2007).The everyday lives of migrants in these rural retreats are relatively understudied.There are, however,an increasing number of researchers studying the British and North European populations in France(see for example Deschamps,2006;Benson, 2007,forthcoming;Geoffrey,2007;Smallwood,2007;Drake and Collard,forth-coming).And we know that more and more people are seeking rural desti-nations;Spain has seen an increase in international buyers seeking rural properties,and new markets across Europe are opening up with,for example as Nagy(2006)argues,the Romanian countryside attracting European city dwellers with its relatively low-costs.And on the other side of the Atlantic, Hoey(2005)spearheads the interest in the relocation of middle-class migrants to non-metropolitan areas in an attempt to‘start over’.Further aﬁeld,there are North American communities in the highlands of Panama and Costa Rica who have yet to be studied,destinations that are equally marketed to migrants on the grounds that they offer escape.It will be interesting to explore the extent to which these unstudied migrations can also be considered forms of lifestyle migration.Bourgeois BohemiansFinally,there are migrants who seek alternative lifestyles in spaces that signify what we might deﬁne as bohemian ideals.These destinations are characterised 612©2009The Authors.Journal compilation©2009The Editorial Board of The Sociological ReviewMigration and the search for a better way of life by certain spiritual,artistic,or creative aspirations and unique‘cultural’expe-rience.The terms spiritual and‘cultural’in our rendering are intended in the widest sense.Jacqueline Waldren’s(1996)accounts of the outsiders–literary personalities,artists and musicians–of Deía,Mallorca is the seminal text on these bohemian ideals and the way that they intersect with the daily lives led in this particular Mediterranean village.More recently,Pola Bousiou (2008)presents an account of the Mykoniots d’élection,a group of people whose lives are characterised by their‘constant return to the island of Mykonos,Greece,and their insistence on living,acting,working and creating in a tourist space offers them an alternative identity’(2008:3).For these self-ascribed‘nomads’,this Greek island is a place on which they can inscribe their own alternative lifestyle.There are also a number of texts in preparation that equally concentrate on the perception that a bohemian form of living is available(see for example Korpela forthcoming;Trundle forthcoming), exploring diverse destinations such as Florence,Italy and Varanasi,India.These disparate destinations are not in any sense mutually exclusive in what they putatively provide for the lifestyle migrant.We offer their description as a framework for examining the similarities and differences in lifestyle migra-tion narratives.This framework reﬂects our efforts to consider what might be included in the deﬁnition of an emergent trend and what the uniqueness of each destination(or imagining)might offer to the paradigm.As there is,to date,comparatively little literature on lifestyle migration,there is plenty of scope for theﬁeld to expand.There are many migration trends which could be thus categorised and which have,to our knowledge,not yet been examined.Narratives that emphasise the value of particular places and landscapes highlight that how individuals perceive destinations is the result of a complex interaction between their prior experiences of a location,wider culturally-speciﬁc imaginings(distributed primarily through the media and‘property pornography’),certain historical and material conditions,and their individual circumstances(including cultural,educational,and economic capital)at the point of migration.The choice of destination,while also an intentional choice about how to live,is thus the product of both structural constraints and individual agency.We will now consider some of these wider circumstances, beginning with a critical look at two ways these migrations have been con-ceptualised to date:as(residential)tourism and as counter-urbanisation. Conceptualising Lifestyle MigrationTourismMuch lifestyle migration is a clear case of what Williams and Hall(2002)have called tourism-informed mobility.In this rendering,migrants develop a taste for a particular way of life while on holiday in an area,and subsequently decide to migrate,encouraged by their imaginings of the place as offering a613©2009The Authors.Journal compilation©2009The Editorial Board of The Sociological ReviewMichaela Benson and Karen O’Reillybetter lifestyle.Simply,tourist destinations(for example the Costa del Sol, the Algarve,the Dordogne)become migration destinations.In some cases,the migration destination continues to be socially constructed in terms of holiday and its concomitant meanings(Shields,1991),with lifestyle migrants seeming loth to have their lives structured and routinised(O’Reilly,2000).Therefore, in terms of the lifestyle sought and the destination chosen,there is a partial overlap between lifestyle migration and tourism,(O’Reilly,2003and2007b). But to apply a persistent‘holiday feel’to the lives of all lifestyle migrants would,in our opinion,do an injustice to these populations,many of whom actively strive to show that they are different from tourists who are often negatively stereotyped(see for example Benson,2007;Oliver,2008;Waldren, 1996,1997).From another angle,the study of tourism as a phenomenon can inform our exploration of lifestyle migration(O’Reilly,2003).Tourism,of course,is based on all those distinctions Urry(1990)recognised between leisure and work, home and away,everyday and holiday.It is about escaping the drudgery of the routine in order to‘gaze’on the exotic and other;the perfect foundation for an anti-modern migration in search of community,security,leisure,and tranquil-lity.The pursuit of a better way of life that characterises lifestyle migration is the tourist’s pursuit of authentic experience(MacCannell,1976)made epic, an embedded feature of daily life within the destination(cf.Benson,2007; O’Reilly,2007b).Tourism facilitates this form of migration by constructing and marketing ideals.Through this process,these ideals become feasible and attainable lifestyle choices.Despite the links between the two,it is important not to reduce lifestyle migration to tourism as this undermines the diverse motivations and experi-ences of the migrants.Not all lifestyle migration began as tourism,and there has yet to be an adequate explanation of why people might want to turn their experiences from tourism into a way of life.CounterurbanisationThe study of counterurbanisation may also shed some light on lifestyle ed to describe and account for the physical movement of populations out of cities and metropolitan areas towards more rural areas,counterurbani-sation has tended to focus on trends andﬂows(Halliday and Coombes,1995). However,researchers are increasingly adding a motivational element to their deﬁnition(Mitchell,2004).While there are various motivations that might drive people to move to rural areas,including house prices,overcrowding, retirement,and the green movement,the most-documented motivation listed in the counterurbanisation literature is the rural idyll–that is the pull of the countryside as a way of life.The essential elements that the rural idyll incor-porates are a less hurried lifestyle,peace and quiet,space,and greenness(van Dam et al.,2002).The countryside is thus constructed or(mis)represented as somewhere people have more time for each other,with a more close-knit 614©2009The Authors.Journal compilation©2009The Editorial Board of The Sociological ReviewMigration and the search for a better way of life community,somewhere children can grow up in safety(Matthews et al.,2000), a stress-free environment away from the excesses and constraints of the city. There is an additional sense that this kind of move is motivated in part by more extreme anti-urban motivations,with counterurbanisation operating as an escape from high crime levels,taxes,congestion and pollution.Counterurban migrations can therefore include‘back to the land’moves,quality of life moves to smaller communities,and even amenity-driven,retirement migration (Mitchell,2004).In the perception of the counterurbanising population,their destinations offer them the antithesis of the lives that they are leaving behind.Indeed,this attraction to the countryside has already been well documented in the case of the British in rural France(Buller and Hoggart,1994;Barou and Prado,1995; Benson,2007).However,it is the case that the interpretations and meanings of a place,refracted through a range of media,matter more to migrants than the actual qualities that can be objectively described(Halliday and Coombes, 1995).As a result,the concrete attributes and characteristics labelled‘rural’means the term does not actually have to coincide with the countryside as such;rurality can be constructed,sought,or created elsewhere(see Boyle et al.,1998,van Dam et al.,2002).Bearing in mind this social construction of rurality,when once the countryside was marketed as offering an alternative way of life,an escape from the ills of modernity and the city,now distant lands hold the same meanings;in other words,they are being constructed in the same ways.Lifestyle migration shares the motivations characteristic of counter-urbanisation with migrants commonly stressing their anti-modern and anti-urban sentiments.Within the counterurbanisation discourse,it has been concluded that all destinations signify the same thing to individuals:a different and better way of life to that led before migration.How this then translates into their everyday experiences of life following migration is,however,some-thing that remains overlooked within the counterurbanisation discourse. Explaining Lifestyle MigrationFrom the preceding discussion,it is apparent that both tourism and counterur-banisation offer a speciﬁc lens through which this migration might be better perceived.However,their explanations do not look at how the act of migration intersects with life more generally.By encapsulating this form of migration within the term lifestyle,we shift the focus from the movement itself to the lifestyle choices inherent within the decision to migrate.In this manner,we re-place migration in the context of the lives led before and after migration and drawattentionawayfromthemovementasasingularevent.Theinitialmigration therefore emerges as one point of the journey en route to a better way of life (Benson,2007).Lifestyle migration is thus intrinsic to the lifestyle trajectories of individuals,a part of their reﬂexive project of the self(or the search for a615©2009The Authors.Journal compilation©2009The Editorial Board of The Sociological ReviewMichaela Benson and Karen O’Reillypotential self as Hoey(2005)describes it,whereby migrants escape disillu-sionment through seeking an alternative lifestyle.Studies of this phenomenon should concentrate,therefore,not only on the reasoning and circumstances leading to migration,but also on how these inform experiences of life within the destination.Lifestyle migration,as a conceptualisation,thus holds at its core a commitment to a more nuanced insight into individual circumstances (including phase in the life course,Oliver,2008)and their inﬂuence on the trajectory of lives following migration,while also recognising that there are various historical and material prerequisites for this form of migration. Lifestyle and habitusThe relocation of lifestyle migrants can broadly be deﬁned as indicative of a fundamental change in lifestyle,signifying a break,a contrast,a turning point, and a new beginning.In this respect,the decision to migrate is a lifestyle choice.But what do we mean by lifestyle in this case and what is the impact of these choices?Many of the previous studies on this search for a better way of life emphasise its links to consumption(see for example King et al.,2000;Sunil et al.,2007;Williams and Hall,2002).With this in mind,we consider the insights offered by sociological theorists who make explicit the link between consump-tion and lifestyle(eg Beck,1992;Bauman,2000;Giddens,1991).Common to these accounts is the notion that society has now entered post,late,second, or liquid modernity(depending on the author),characterised by the demise of traditional social structures and divisions of labour,and a greater degree of consumer choice.Lifestyle,within this contemporary consumer society,is a life project for the individual,part of the reﬂexive project of the self(Giddens, 1991),in which we unremittingly,but never routinely,engage,in order to make sense of who we are and our place in the world.The lifestyle choices that individuals make thus,‘give material form to a particular narrative of self-identity’(Giddens,1991:81).Consumption enables individuals to sustain a coherent lifestyle reﬂecting their self-identity.These approaches to the study of lifestyle thus argue that,‘engaging in a particular lifestyle no longer reﬂects our already existing status as members of a particular class,for example,but says something about who we–as individuals–have decided we want to be’(Sweetman,2003:529original italics).While there is undoubtedly something appealing about the idea that we have such extensive freedom of choice,the pervading criticism of this empha-sis on the individual is that it fails to account for the persisting inﬂuence of social structures on the individual.For example,it remains unclear why the ‘goods’people seek(community,security,tranquillity)seem to remain so consistent.In contrast to these approaches,Bourdieu(1984)presents a more structurally aware description of lifestyle,linking consumption practices, lifestyle,and social position.In this rendering,lifestyles emerge as the result of particular material circumstances and a speciﬁc class habitus;all lifestyle choices are thus mediated through our habitus,our embodied class-culture. 616©2009The Authors.Journal compilation©2009The Editorial Board of The Sociological Review。

HYDRUS Model Use, Calibration, and Validation

Submitted for review in September 2011 as manuscript number SW 9401; approved for publication by the Soil & Water Division of ASABE in April 2012. The authors are Jiří Šimůnek, Professor and Hydrologist, Department of Environmental Sciences, University of California, Riverside, California; Martinus Th. van Genuchten, Professor, Department of Mechanical Engineering, Federal University of Rio de Janeiro, Brazil; and Miroslav Šejna, Director, PC-Progress s.r.o., Prague, Czech Republic. Corresponding author: Jiří Šimůnek, Department of Environmental Sciences, University of California-Riverside, Riverside, CA 92521; phone: 951-8277854; e-mail: Jiri.Simunek@.
HYDRUS: MODEL USE, CALIBRATION, AND VALIDATION
J. n, M. Šejna
ABSTRACT. The HYDRUS numerical models are widely used for simulating water flow and solute transport in variably saturated soils and groundwater. Applications involve a broad range of steady-state or transient water flow, solute transport, and/or heat transfer problems. They include both short-term, one-dimensional laboratory column flow or transport simulations, as well as more complex, long-duration, multi-dimensional field studies. The HYDRUS models can be used for both direct problems when the initial and boundary conditions for all involved processes and corresponding model parameters are known, as well as inverse problems when some of the parameters need to be calibrated or estimated from observed data. The approach to model calibration and validation may vary widely depending upon the complexity of the application. Model calibration and inverse parameter estimation can be carried out using a relatively simple, gradient-based, local optimization approach based on the Marquardt-Levenberg method, which is directly implemented into the HYDRUS codes, or more complex global optimization methods, including genetic algorithms, which need to be run separately from HYDRUS. In this article, we provide a brief overview of the HYDRUS codes, discuss which HYDRUS parameters can be estimated using internally built optimization routines and which type of experimental data can be used for this, and review various calibration approaches that have been used in the literature in combination with the HYDRUS codes. Keywords. Calibration, HYDRUS-1D, HYDRUS (2D/3D), Numerical model, Optimization methods, Parameter estimation, Solute transport, Unsaturated soils, Validation, Water flow.

科技文翻译英汉对照

Ross Gregory WRc Swindon Frankland Road,Blagrove Swindon,Wiltshire England罗斯格雷戈里斯文顿弗兰克兰路,布拉格罗夫斯温顿英格兰，威尔特郡Thomas F. Zabel WRc Medmenham Medmenham,Oxfordshire England托马斯·f·扎贝尔汽车拉力英格兰牛津郡James K. Edzwald Professor,Department of Civil and Environmental Engineering University of Massachusetts Amherst,Massachusetts U.S.A.詹姆斯·k.爱德华教授,土木与环境工程系马萨诸塞大学阿默斯特,美国马萨诸塞州Sedimentation and flotation are solid-liquid separation processes used in water treatment mostly to lower the solids concentration,or load,on granular filters. As a result,filters can be operated more easily and cost effectively to produce acceptablequality filtered water. Many sedimentation and flotation processes and variants of them exist, and each has advantages and disadvantages. The most a ppropriate process for a particular application will depend on the water to be treated as well as local circumstances and requirements.水处理中的固液分离过程中使用沉降和浮选流程主要是为了降低固体颗粒浓度、颗粒过滤器或负载。

Reading Comprehension

Practice Test #1 Reading Comprehension(18 Essays, 61 Questions)Essay #1. 019 (21201-!-item-!-188;#058&00019-00)During the nineteenth century, occupational information about women that was provided by the United States census--a population count conducted each decade--became more detailed and precise in response to social changes. Through 1840, simple enumeration by household mirrored a home-based agricultural economy and hierarchical social order: the head of the household (presumed male or absent) was specified by name, whereas other household members were only indicated by the total number of persons counted in various categories, including occupational categories. Like farms, most enterprises were family-run, so that the census measured economic activity as an attribute of the entire household, rather than of individuals.The 1850 census, partly responding to antislavery and women's rights movements, initiated the collection of specific information about each individual in a household. Not until 1870 was occupational information analyzed by gender: the census superintendent reported 1.8 million women employed outside the home in "gainful and reputable occupations." In addition, he arbitrarily attributed to each family one woman "keeping house." Overlap between the two groups was not calculated until 1890, when the rapid entry of women into the paid labor force and social issues arising from industrialization were causing women's advocates and women statisticians to press for more thorough and accurate accounting of women's occupations and wages.Question #1. 019-01 (21247-!-item-!-188;#058&000019-01)The primary purpose of the passage is to(A) explain and critique the methods used by early statisticians(B) compare and contrast a historical situation with a current-day one(C) describe and explain a historical change(D) discuss historical opposition to an established institution(E) trace the origin of a contemporary controversyQuestion #2. 019-02 (21293-!-item-!-188;#058&000019-02)Each of the following aspects of nineteenth-century United States censuses is mentioned in the passage EXCEPT the(A) year in which data on occupations began to be analyzed by gender(B) year in which specific information began to be collected on individuals in addition to the head of the household(C) year in which overlap between women employed outside the home and women keeping house was first calculated(D) way in which the 1890 census measured women's income levels and educational backgrounds(E) way in which household members were counted in the 1840 censusQuestion #3. 019-04 (21339-!-item-!-188;#058&000019-04)The passage suggests which of the following about the "women's advocates and women statisticians" mentioned in the highlighted text?(A) They wanted to call attention to the lack of pay for women who worked in the home.(B) They believed that previous census information was inadequate and did not reflect certaineconomic changes in the United States.(C) They had begun to press for changes in census-taking methods as part of their participation in the antislavery movement.(D) They thought that census statistics about women would be more accurate if more women were employed as census officials.(E) They had conducted independent studies that disputed the official statistics provided by previous United States censuses.Essay #2. 066 (21346-!-item-!-188;#058&00066-00)The general density dependence model can be applied to explain the founding of specialist firms (those attempting to serve a narrow target market). According to this model, specialist foundings hinge on the interplay between legitimation and competitive forces, both of which are functions of the density (total number) of firms in a particular specialist population. Legitimation occurs as a new type of firm moves from being viewed as unfamiliar to being viewed as a natural way to organize.At low density levels, each founding increases legitimation, reducing barriers to entry and easing subsequent foundings. Competition occurs because the resources that firms seek--customers, suppliers, and employees--are limited, but as long as density is low relative to plentiful resources, the addition of another firm has a negligible impact on the intensity of competition. At high density levels, however, competitive effects outweigh legitimation effects, discouraging foundings. The more numerous the competitors, the fiercer the competition will be and the smaller will be the incentive for new firms to enter the field.While several studies have found a significant correspondence between the density dependence model and actual patterns of foundings, other studies have found patterns not consistent with the model. A possible explanation for this inconsistency is that legitimation and competitive forces transcend national boundaries, while studies typically restrict their analysis to the national level. Thus a national-level analysis can understate the true legitimation and competitive forces as well as the number of foundings in an industry that is internationally integrated. Many industries are or are becoming international, and since media and information easily cross national borders, so should legitimation and its effects on overseas foundings. For example, if a type of firm becomes established in the United States, that information transcends borders, reduces uncertainties, and helps foundings of that type of firm in other countries. Even within national contexts, studies have found more support for the density dependence model when they employ broader geographic units of analysis--for example, finding that the model's operation is seen more clearly at the state and national levels than at city levels.Question #4. 066-02 (21392-!-item-!-188;#058&000066-02)According to the passage, which of the following may account for the inconsistency between the general density dependence model and the evidence provided by certain studies of foundings?(A) Such studies have overemphasized the impact of preexisting firms on the establishment of new firms.(B) Such studies have not focused strongly enough on the role of competition among newly established firms operating at the city and state levels.(C) Such studies fail to differentiate among specialist firms with regard to the degree to which they deviate from familiar forms of organization.(D) Such studies have not taken into account the fact that many industries are internationally integrated.(E) Such studies have neglected to investigate firms that attempt to serve only a narrow target market.Question #5. 066-04 (21438-!-item-!-188;#058&000066-04)In the second paragraph, the author is primarily concerned with(A) noting various exceptions to a certain general finding(B) examining the impact of one type of industry on another(C) proposing a possible explanation for an inconsistency(D) providing specific examples of a particular phenomenon(E) defending the validity of a particular study's conclusionsQuestion #6. 066-06 (21484-!-item-!-188;#058&000066-06)The passage suggests that when a population of specialist firms reaches a high density level, which of the following is likely to occur?(A) Foundings will decline despite legitimation that has occurred in these industries.(B) Increasing competition will encourage many firms to broaden their target market.(C) Competition for resources will become stabilized and thus foundings will be encouraged.(D) Many customers will abandon their loyalty to older firms as more innovative firms enter the market.(E) Firms will begin to cross national borders in an attempt to gain a competitive advantage. Question #7. 066-08 (21530-!-item-!-188;#058&000066-08)The primary purpose of the passage is to(A) question the validity of an economic model(B) point out some inconsistencies within an economic model(C) outline an economic model and suggest revisions to it(D) describe an economic model and provide specific examples to illustrate its use(E) explain why an economic model remains valid despite inconsistent research resultsEssay #3. 075 (21535-!-item-!-188;#058&00075-00)In its 1903 decision in the case of Lone Wolf v. Hitchcock, the United States Supreme Court rejected the efforts of three Native American tribes to prevent the opening of tribal lands to non-Indian settlement without tribal consent. In his study of the Lone Wolf case, Blue Clark properly emphasizes the Court's assertion of a virtually unlimited unilateral power of Congress (the House of Representatives and the Senate) over Native American affairs. But he fails to note the decision's more far-reaching impact: shortly after Lone Wolf, the federal government totally abandoned negotiation and execution of formal written agreements with Indian tribes as a prerequisite for the implementation of federal Indian policy. Many commentators believe that this change had already occurred in 1871 when--following a dispute between the House and the Senate over which chamber should enjoy primacy in Indian affairs--Congress abolished the making of treaties with Native American tribes. But in reality the federal government continued to negotiate formal tribal agreements past the turn of the century, treating these documents not as treaties with sovereign nations requiring ratification by the Senate but simply as legislation to be passed by both houses of Congress. The Lone Wolf decision ended this era of formal negotiation and finally did away with what had increasingly become the empty formality of obtaining tribal consent.Question #8. 075-03 (21581-!-item-!-188;#058&000075-03)According to the passage, the congressional action of 1871 had which of the following effects?(A) Native American tribal agreements were treated as legislation that had to be passed by both houses of Congress.(B) The number of formal agreements negotiated between the federal government and Native American tribes decreased.(C) The procedures for congressional approval and implementation of federal Indian policy were made more precise.(D) It became more difficult for Congress to exercise unilateral authority over Native American affairs.(E) The role of Congress in the ratification of treaties with sovereign nations was eventually undermined.Question #9. 075-06 (21627-!-item-!-188;#058&000075-06)According to the passage, which of the following resulted from the Lone Wolf decision?(A) The Supreme Court took on a greater role in Native American affairs.(B) Native American tribes lost their legal standing as sovereign nations in their dealings with the federal government, but their ownership of tribal lands was confirmed.(C) The federal government no longer needed to conclude a formal agreement with a Native American tribe in order to carry out policy decisions that affected the tribe.(D) The federal government began to appropriate tribal lands for distribution to non-Indian settlers.(E) Native American tribes were no longer able to challenge congressional actions by appealing to the Supreme Court.Question #10. 075-07 (21673-!-item-!-188;#058&000075-07)The author of the passage is primarily concerned with(A) identifying similarities in two different theories(B) evaluating a work of scholarship(C) analyzing the significance of a historical event(D) debunking a revisionist interpretation(E) exploring the relationship between law and social realityEssay #4. 094 (21680-!-item-!-188;#058&00094-00)Some historians contend that conditions in the United States during the Second World War gave rise to a dynamic wartime alliance between trade unions and the African American community, an alliance that advanced the cause of civil rights. They conclude that the postwar demise of this vital alliance constituted a lost opportunity for the civil rights movement that followed the war. Other scholars, however, have portrayed organized labor as defending all along the relatively privileged position of White workers relative to African American workers. Clearly, these two perspectives are not easily reconcilable, but the historical reality is not reducible to one or the other.Unions faced a choice between either maintaining the prewar status quo or promoting a more inclusive approach that sought for all members the right to participate in the internal affairs of unions, access to skilled and high-paying positions within the occupational hierarchy, and protection against management's arbitrary authority in the workplace. While union representatives often voiced this inclusive ideal, in practice unions far more often favored entrenched interests. The accelerating development of the civil rights movement following the Second World War exacerbated the unions'dilemma, forcing trade unionists to confront contradictions in their own practices.Question #11. 094-01 (21726-!-item-!-188;#058&000094-01)The "unions' dilemma" mentioned in the highlighted text can best be described as the question of whether or not to(A) pressure management to create more skilled and high-paying positions(B) fight for greater union participation in management decisions(C) include minority workers in their membership(D) extend full rights and benefits to all their members(E) emphasize the recruitment of new members over serving the needs of current members Question #12. 094-02 (21772-!-item-!-188;#058&000094-02)According to the passage, the historians mentioned in the first highlighted portion of text and the scholars mentioned in the second highlighted portion disagree about the(A) contribution made by organized labor to the war effort during the Second World War(B) issues that union members considered most important during the Second World War(C) relationship between unions and African Americans during the Second World War(D) effect of the Second World War on the influence of unions in the workplace(E) extent to which African Americans benefited from social and political changes following the Second World WarQuestion #13. 094-06 (21818-!-item-!-188;#058&000094-06)The passage is primarily concerned with(A) providing a context within which to evaluate opposing viewpoints about a historical phenomenon(B) identifying a flawed assumption underlying one interpretation of a historical phenomenon(C) assessing the merits and weaknesses of a controversial theory about a historical phenomenon(D) discussing the historical importance of the development of a wartime alliance(E) evaluating evidence used to support a particular interpretation of a historical phenomenonEssay #5. 118 (21825-!-item-!-188;#058&00118-00)Historians have identified two dominant currents in the Russian women's movement of the late tsarist period. "Bourgeois" feminism, so called by its more radical opponents, emphasized "individualist" feminist goals such as access to education, career opportunities, and legal equality. "Socialist" feminists, by contrast, emphasized class, rather than gender, as the principal source of women's inequality and oppression, and socialist revolution, not legal reform, as the only road to emancipation and equality.However, despite antagonism between bourgeois feminists and socialist feminists, the two movements shared certain underlying beliefs. Both regarded paid labor as the principal means by which women might attain emancipation: participation in the workplace and economic self-sufficiency, they believed, would make women socially useful and therefore deserving of equality with men. Both groups also recognized the enormous difficulties women faced when they combined paid labor with motherhood. In fact, at the First All-Russian Women's Congress in 1908, most participants advocated maternity insurance and paid maternity leave, although the intense hostility between some socialists and bourgeois feminists at the Congress made it difficult for them to recognize these areas ofagreement. Finally, socialist feminists and most bourgeois feminists concurred in subordinating women's emancipation to what they considered the more important goal of liberating the entire Russian population from political oppression, economic backwardness, and social injustice.Question #14. 118-03 (21871-!-item-!-188;#058&000118-03)The passage suggests that socialists within the Russian women's movement and most bourgeois feminists believed that in Russia(A) women would not achieve economic equality until they had political representation within the government(B) the achievement of larger political aims should take precedence over the achievement of women's rights(C) the emancipation of women would ultimately bring about the liberation of the entire Russian population from political oppression(D) women's oppression was more rooted in economic inequality than was the case in other countries(E) the women's movement was more ideologically divided than were women's movements in other countriesQuestion #15. 118-05 (21917-!-item-!-188;#058&000118-05)The passage is primarily concerned with(A) identifying points of agreement between two groups(B) advocating one approach to social reform over another(C) contrasting two approaches to solving a political problem(D) arguing that the views espoused by one political group were more radical than those espoused by another group(E) criticizing historians for overlooking similarities between the views espoused by two superficially dissimilar groupsQuestion #16. 118-06 (21963-!-item-!-188;#058&000118-06)According to the passage, Russian socialists within the women's movement and most bourgeois feminists disagreed about which of the following?(A) Whether legal reform was central to the achievement of feminist goals(B) Whether paid employment was important for the achievement of equality(C) Whether maternity insurance was desirable for working mothers(D) Whether working mothers faced obstacles(E) Whether women's emancipation should be subordinated to the liberation of the Russian population Essay #6. 145 (21972-!-item-!-188;#058&00145-00)Colonial historian David Allen's intensive study of five communities in seventeenth-century Massachusetts is a model of meticulous scholarship on the detailed microcosmic level, and is convincing up to a point. Allen suggests that much more coherence and direct continuity existed between English and colonial agricultural practices and administrative organization than other historians have suggested. However, he overstates his case with the declaration that he has proved "the remarkable extent to which diversity in New England local institutions was directly imitative of regional differences in the mother country."Such an assertion ignores critical differences between seventeenth-century England and New England. First, England was overcrowded and land-hungry; New England was sparsely populated andlabor-hungry. Second, England suffered the normal European rate of mortality; New England, especially in the first generation of English colonists, was virtually free from infectious diseases. Third, England had an all-embracing state church; in New England membership in a church was restricted to the elect. Fourth, a high proportion of English villagers lived under paternalistic resident squires; no such class existed in New England. By narrowing his focus to village institutions and ignoring these critical differences, which studies by Greven, Demos, and Lockridge have shown to be so important, Allen has created a somewhat distorted picture of reality.Allen's work is a rather extreme example of the "country community" school of seventeenth-century English history whose intemperate excesses in removing all national issues from the history of that period have been exposed by Professor Clive Holmes. What conclusion can be drawn, for example, from Allen's discovery that Puritan clergy who had come to the colonies from East Anglia wereone-third to one-half as likely to return to England by 1660 as were Puritan ministers from western and northern England? We are not told in what way, if at all, this discovery illuminates historical understanding. Studies of local history have enormously expanded our horizons, but it is a mistake for their authors to conclude that village institutions are all that mattered, simply because their functions are all that the records of village institutions reveal.Question #17. 145-03 (22018-!-item-!-188;#058&000145-03)According to the passage, which of the following was true of most villages in seventeenth-century England?(A) The resident squire had significant authority.(B) Church members were selected on the basis of their social status within the community.(C) Low population density restricted agricultural and economic growth.(D) There was little diversity in local institutions from one region to another.(E) National events had little impact on local customs and administrative organization.Question #18. 145-05 (22064-!-item-!-188;#058&000145-05)The passage suggests that Professor Clive Holmes would most likely agree with which of the following statements?(A) An understanding of seventeenth-century English local institutions requires a consideration of national issues.(B) The "country community" school of seventeenth-century English history distorts historical evidence in order to establish continuity between old and new institutions.(C) Most historians distort reality by focusing on national concerns to the exclusion of local concerns.(D) National issues are best understood from the perspective of those at the local level.(E) Local histories of seventeenth-century English villages have contributed little to the understanding of village life.Question #19. 145-07 (22110-!-item-!-188;#058&000145-07)It can be inferred from the passage that the author of the passage considers Allen's "discovery" (see highlighted text) to be(A) already known to earlier historians(B) based on a logical fallacy(C) improbable but nevertheless convincing(D) an unexplained, isolated fact(E) a new, insightful observationQuestion #20. 145-08 (22156-!-item-!-188;#058&000145-08)The author of the passage is primarily concerned with(A) substantiating a claim about a historical event(B) reconciling two opposing ideas about a historical era(C) disputing evidence a scholar uses to substantiate a claim about a historical event(D) analyzing two approaches to scholarly research and evaluating their methodologies(E) criticizing a particular study and the approach to historical scholarship it representsEssay #7. 146 (22165-!-item-!-188;#058&00146-00)The United States government has a long-standing policy of using federal funds to keep small business viable. The Small Business Act of 1953 authorized the Small Business Administration (SBA) to enter into contracts with government agencies having procurement powers and to arrange for fulfillment of these contracts by awarding subcontracts to small businesses. In the mid-1960's, during the war on poverty years, Congress hoped to encourage minority entrepreneurs by directing such funding to minority businesses. At first this funding was directed toward minority entrepreneurs with very low incomes. A 1967 amendment to the Economic Opportunity Act directed the SBA to pay special attention to minority-owned businesses located in urban or rural areas characterized by high proportions of unemployed or low-income individuals. Since then, the answer given to the fundamental question of who the recipients should be--the most economically disadvantaged or those with the best prospects for business success--has changed, and the social goals of the programs have shifted, resulting in policy changes.The first shift occurred during the early 1970's. While the goal of assisting the economically disadvantaged entrepreneur remained, a new goal emerged: to remedy the effects of past discrimination. In fact, in 1970 the SBA explicitly stated that their main goal was to increase the number of minority-owned businesses. At the time, minorities constituted seventeen percent of the nation's population, but only four percent of the nation's self-employed. This ownership gap was held to be the result of past discrimination. Increasing the number of minority-owned firms was seen as a way to remedy this problem. In that context, providing funding to minority entrepreneurs in middle- and high-income brackets seemed justified.In the late 1970's, the goals of minority-business funding programs shifted again. At the Minority Business Development Agency, for example, the goal of increasing numbers of minority-owned firms was supplanted by the goal of creating and assisting more minority-owned substantive firms with future growth potential. Assisting manufacturers or wholesalers became far more important than assisting small service businesses. Minority-business funding programs were now justified as instruments for economic development, particularly for creating jobs in minority communities of high unemployment.Question #21. 146-01 (22211-!-item-!-188;#058&000146-01)The primary purpose of the passage is to(A) discuss historical changes in a government policy(B) describe the role of Congress in regulating the work of the SBA(C) contrast types of funding sources used by minority businesses(D) correct a misconception about minority entrepreneurship(E) advocate an alternative approach to funding minority entrepreneursQuestion #22. 146-05 (22257-!-item-!-188;#058&000146-05)It can be inferred that the "ownership gap" (see highlighted text) would be narrowed if which of the following were to occur?(A) Minority entrepreneurs received a percentage of government contracts equal to that received by nonminority entrepreneurs.(B) Middle- and high-income minority entrepreneurs gave more assistance to their low-income counterparts in the business community.(C) Minority entrepreneurs hired a percentage of minority employees equal to the percentage of minority residents in their own communities.(D) The percentage of self-employed minority persons rose to more than ten percent of allself-employed persons.(E) Seventeen percent of all persons employed in small businesses were self-employed.Question #23. 146-06 (22303-!-item-!-188;#058&000146-06)According to the passage, in 1970 funding to minority entrepreneurs focused primarily on which of the following?(A) Alleviating chronic unemployment in urban areas(B) Narrowing the ownership gap(C) Assisting minority-owned businesses with growth potential(D) Awarding subcontracts to businesses that encouraged community development(E) Targeting the most economically disadvantaged minority-owned businessesQuestion #24. 146-09 (22349-!-item-!-188;#058&000146-09)Which of the following best describes the function of the second paragraph in the passage as a whole?(A) It narrows the scope of the topic introduced in the first paragraph.(B) It presents an example of the type of change discussed in the first paragraph.(C) It cites the most striking instance of historical change in a particular government policy.(D) It explains the rationale for the creation of the government agency whose operations are discussed in the first paragraph.(E) It presents the results of policies adopted by the federal government.Essay #8. 147 (22358-!-item-!-188;#058&00147-00)In terrestrial environments, gravity places special demands on the cardiovascular systems of animals. Gravitational pressure can cause blood to pool in the lower regions of the body, making it difficult to circulate blood to critical organs such as the brain. Terrestrial snakes, in particular, exhibit adaptations that aid in circulating blood against the force of gravity.The problem confronting terrestrial snakes is best illustrated by what happens to sea snakes when removed from their supportive medium. Because the vertical pressure gradients within the blood vessels are counteracted by similar pressure gradients in the surrounding water, the distribution of blood throughout the body of sea snakes remains about the same regardless of their orientation in space, provided they remain in the ocean. When removed from the water and tilted at various angles。

驾校学车的英语作文带翻译

Benefits of Learning to Drive in English:
1. Improved Language Skills
Learning to drive in English not only provides practical driving skills but also improves overall language proficiency.It helps learners develop their listening, speaking, reading, and writing skills in English. This can be valuable for individuals who are non-native English speakers and want to enhance their language abilities.
The driving school provided comprehensive theoretical classes where John learned about road signs, traffic laws, and safe driving practices. The instructors patiently explained the concepts in English, ensuring that John understood everything. John also had the opportunity to practice driving in various road conditions, including highways and urban areas.
2. Familiarity with Traffic Rules and Regulations

练车everydaylife英语作文范文模板

练车everydaylife英语作文范文模板As you embark on the journey of mastering everyday life English through the lens of learning to drive, it's crucial to have a well-structured framework to guide your writing. Here's a template to aid you in crafting your essay:---**Title: The Everyday Adventures of Learning to Drive**Driving, an essential skill in today's fast-paced world, embodies both practicality and adventure. From navigating bustling city streets to embarking on serene countryside roads, the journey of learning to drive intertwines with the fabric of everyday life. Let's explore this narrative through a personal lens.**Introduction:**The prospect of learning to drive often evokes a mix of excitement and apprehension. It marks a significantmilestone, symbolizing newfound independence and mobility. However, it also presents a daunting challenge, requiring mastery of both theoretical knowledge and practical skills.**Body Paragraph 1: The Classroom Experience**The journey begins in the classroom, where theoretical knowledge lays the groundwork for practical application. Here, learners delve into traffic rules, road signs, and safety regulations. Through interactive lessons and engaging discussions, students grasp the intricacies of driving etiquette and legal obligations.**Body Paragraph 2: Behind the Wheel**Transitioning from theory to practice, the driving seat becomes both a sanctuary and a battlefield. With the guidance of a patient instructor, learners confront real-world scenarios, from mastering parallel parking to navigating roundabouts. Each session is a symphony of adrenaline and concentration, as learners synchronize foot pedals and hand controls with precision.**Body Paragraph 3: The Road to Mastery**As proficiency grows, so does confidence. The once-intimidating highway transforms into a canvas of possibilities, beckoning drivers to explore beyond their comfort zones. With each milestone - from obtaining a learner's permit to conquering the driving test - learners inch closer to mastery, armed with experience and resilience.**Conclusion:**Learning to drive is more than a practical skill; it's a transformative journey that shapes one's perception of the world. Through perseverance and determination, learners navigate the twists and turns of the road, emerging not only as competent drivers but also as confident individuals ready to embrace life's adventures.---This template serves as a scaffold, providing a framework for organizing your thoughts and experiences into a cohesive narrative. Remember to infuse your essay with personal anecdotes and reflections to enrich the storytelling. Happy writing!。

身体残疾励志故事名人英文作文

身体残疾励志故事名人英文作文全文共3篇示例，供读者参考篇1Title: Inspiring Stories of Disabled Public FiguresIntroduction:Disability is not the end of the road for many individuals. In fact, there are numerous public figures who have overcome their physical disabilities to achieve great success in their respective fields. Their stories serve as an inspiration to many, proving that nothing is impossible if one is determined and motivated. In this article, we will take a look at some of these remarkable individuals and how they have overcome their challenges.Stephen Hawking:Stephen Hawking, a renowned theoretical physicist and cosmologist, was diagnosed with amyotrophic lateral sclerosis (ALS) at a young age. Despite being confined to a wheelchair and losing his ability to speak, Hawking continued his groundbreaking research on black holes and the origin of the universe. His book "A Brief History of Time" became a bestseller and he became a household name in the scientific community.Hawking's perseverance and determination in the face of adversity serve as a beacon of hope for many people with disabilities.Nick Vujicic:Nick Vujicic was born without arms and legs, a condition known as tetra-amelia syndrome. Despite facing countless challenges and ridicule from others, Vujicic never gave up on his dreams. He became a motivational speaker and author, inspiring millions of people around the world with his message of hope and positivity. Vujicic travels the globe, spreading his message of resilience and courage to audiences of all ages.Marlee Matlin:Marlee Matlin is an Academy Award-winning actress who has been deaf since childhood. She has starred in numerous films and television shows, breaking barriers for deaf actors in Hollywood. Matlin's talent and determination have earned her critical acclaim and respect from her peers. She is also a strong advocate for the deaf community, raising awareness about deaf culture and the importance of inclusion.Sudha Chandran:Sudha Chandran is an Indian actress and classical dancer who lost her leg in a tragic accident. Despite her disability, Chandran continued to pursue her passion for dance and became a prominent figure in the Indian entertainment industry. She has performed in numerous dance shows and acted in several films and television series. Chandran's resilience and talent have inspired many people with disabilities to follow their dreams.Conclusion:These are just a few examples of how individuals with physical disabilities have overcome their challenges to achieve great success. Their stories remind us that disability does not define a person and should not limit their potential. By sharing their stories, these public figures have inspired countless people to never give up on their dreams and to believe in themselves. Their journeys serve as a testament to the power of determination, resilience, and hope in the face of adversity.篇2Title: Inspirational Stories of Famous Figures with Physical DisabilitiesIntroduction:Physical disabilities can present significant challenges in life, but there are many examples of individuals who have overcome their disabilities to achieve great success. In this article, we will explore the stories of several famous figures who have shown incredible resilience and determination in the face of adversity.1. Helen Keller:Helen Keller was born in 1880 in Alabama, USA. At the age of 19 months, she fell ill and lost her sight and hearing. Despite her disabilities, Helen Keller went on to become a renowned author, lecturer, and political activist. With the help of her teacher, Anne Sullivan, Keller learned to communicate through touch and went on to graduate from Radcliffe College. She became an advocate for the blind and deaf community and traveled the world to speak about disability rights.2. Stephen Hawking:Stephen Hawking was a world-renowned theoretical physicist who was diagnosed with amyotrophic lateral sclerosis (ALS) at the age of 21. Despite being confined to a wheelchair and losing the ability to speak, Hawking continued his research and made groundbreaking contributions to our understanding of the universe. He wrote several best-selling books, including "ABrief History of Time," and became a household name for his work in physics.3. Frida Kahlo:Frida Kahlo was a Mexican artist who suffered from polio as a child and later survived a near-fatal bus accident that left her with lifelong physical pain. Despite her injuries, Kahlo channeled her struggles into her art and became known for her colorful and emotional self-portraits. Kahlo's work explored themes of identity, disability, and femininity and has inspired generations of artists and activists.4. Nick Vujicic:Nick Vujicic was born in Australia with a rare disorder called tetra-amelia syndrome, which left him without arms and legs. Despite facing bullying and discrimination as a child, Vujicic learned to adapt and thrive with his disabilities. He became a motivational speaker, author, and founder of the nonprofit organization Life Without Limbs. Vujicic travels the world sharing his message of hope and encouraging others to embrace their differences.5. Marlee Matlin:Marlee Matlin is an Academy Award-winning actress who is deaf. Matlin lost her hearing at the age of 18 months due to a fever-related illness. Despite her disability, Matlin pursued a career in acting and became the youngest person to win the Best Actress Oscar for her role in "Children of a Lesser God." Matlin has since appeared in numerous film and television roles and has used her platform to advocate for deaf and disability rights.Conclusion:The stories of Helen Keller, Stephen Hawking, Frida Kahlo, Nick Vujicic, and Marlee Matlin are just a few examples of individuals who have overcome physical disabilities to achieve great success. Their resilience, determination, and creativity serve as an inspiration to us all, showing that with perseverance and a positive attitude, anything is possible. These famous figures have not only broken barriers in their respective fields but have also raised awareness and changed attitudes towards disability. As we celebrate their accomplishments, let us remember that disability does not define a person's worth or potential. With the right support and mindset, individuals with physical disabilities can accomplish incredible things and make a lasting impact on the world.篇3Title: Inspirational Stories of Famous People with Physical DisabilitiesIntroductionPhysical disabilities can present unique challenges for individuals, but many famous people have overcome these obstacles to achieve remarkable success. In this article, we will explore the inspirational stories of several well-known individuals who have not let their disabilities define them.Stephen HawkingPerhaps one of the most famous examples of a person who overcame a physical disability is Stephen Hawking. Diagnosed with a rare form of motor neuron disease at the age of 21, Hawking was told he only had a few years to live. Despite the grim prognosis, he went on to become one of the most brilliant theoretical physicists of his time. Using a wheelchair and a speech synthesizer to communicate, Hawking made groundbreaking contributions to our understanding of the universe and became an international icon of scientific excellence.Helen KellerHelen Keller lost her sight and hearing at a very young age due to an illness, but she did not let her disabilities hold her back. With the help of her dedicated teacher, Anne Sullivan, Keller learned to communicate through sign language and went on to become a renowned author and activist. She was the firstdeaf-blind person to earn a bachelor's degree and dedicated her life to advocating for the rights of people with disabilities.Nick VujicicNick Vujicic was born without arms or legs, a condition known as tetra-amelia syndrome. Despite facing numerous challenges growing up, including bullying and depression, Vujicic refused to let his disability define him. He became a motivational speaker, author, and founder of the nonprofit organization Life Without Limbs, inspiring millions of people around the world with his message of hope and resilience.Marlee MatlinMarlee Matlin lost her hearing at the age of 18 months due to a genetic disorder, but she has not let her disability stop her from pursuing her dreams. Matlin became the first deaf actress to win an Academy Award for her role in the film "Children of a Lesser God" and has since appeared in numerous movies andtelevision shows. She is also an advocate for the deaf community and a prominent spokesperson for deaf rights.ConclusionThese are just a few examples of the many famous people who have overcome physical disabilities to achieve greatness. Their stories serve as a reminder that with determination, perseverance, and a positive attitude, anything is possible. By sharing these inspirational stories, we can encourage others to embrace their own challenges and strive for excellence, no matter what obstacles they may face.。

驾照考试英语作文

Driving a car has become a fundamental skill in modern society,and obtaining a drivers license is the first step towards this independence.The process of acquiring a drivers license involves several stages,each of which is crucial for ensuring that drivers are wellprepared and safe on the road.Theoretical Knowledge:The journey to obtaining a drivers license begins with studying the rules of the road, traffic signs,and safety regulations.This theoretical knowledge is tested in a written exam,which is the first major hurdle for aspiring drivers.The exam typically consists of multiplechoice questions that assess a candidates understanding of traffic laws,road signs, and safe driving practices.Practical Lessons:After passing the theoretical exam,the next step is to learn the practical aspects of driving. This involves taking driving lessons with a certified instructor.During these lessons, students learn how to operate a vehicle,including starting,stopping,turning,and parking. They also practice essential driving skills such as reversing,lane changing,and responding to various traffic situations.Practical Exam:Once a candidate feels confident in their driving abilities,they can schedule their practical exam.This exam is conducted by a licensed examiner and assesses the candidates ability to drive safely and efficiently.The exam includes various maneuvers, such as parallel parking,hill starts,and emergency stops.Additionally,the candidate must demonstrate their ability to follow traffic rules and respond appropriately to traffic signs and signals.Road Test:The road test is the final stage of the drivers license examination process.During this test, the candidate drives on public roads under the supervision of an examiner.The candidate must demonstrate a thorough understanding of traffic laws,show proficiency in various driving situations,and exhibit a high level of safety awareness.The road test is designed to ensure that new drivers are capable of handling realworld driving conditions.Importance of Safety:Throughout the entire process,safety is of paramount importance.Candidates are taught to anticipate potential hazards,maintain a safe following distance,and always be aware of their surroundings.Defensive driving techniques are emphasized to prepare drivers for the unexpected and to reduce the risk of accidents.Continuous Learning:Even after obtaining a drivers license,the learning process does not end.Safe driving requires ongoing practice and adaptation to new situations and environments.Drivers should always be open to learning and improving their skills to ensure they remain safe on the road.In conclusion,the process of obtaining a drivers license is comprehensive and designed to produce responsible and competent drivers.It involves a combination of theoretical knowledge,practical skills,and a strong emphasis on safety.By successfully navigating this process,individuals gain not only the ability to drive but also the confidence and skills necessary to do so safely.。

考驾照英语作文

考驾照英语作文As I embarked on the quest to obtain my driver's license, I was filled with a mixture of excitement and anxiety. The process, though daunting, was an essential rite of passagethat would grant me the freedom of the open road and the independence that comes with it.Theoretical Knowledge:The first step in my journey was to absorb the theoretical knowledge required to pass the written test. I spentcountless hours poring over the driver's manual, learning about traffic regulations, road signs, and safety precautions. The manual was a comprehensive guide, but it was also dry and dense with information. To aid my learning, I used mnemonic devices and online quizzes to reinforce my understanding ofthe rules of the road.Practical Lessons:Once I felt confident in my theoretical knowledge, I moved on to the practical lessons. My driving instructor, a patientand experienced individual, taught me how to operate the vehicle safely. We started with the basics: adjusting the mirrors, fastening the seatbelt, and understanding the controls. Gradually, I progressed to more complex maneuvers such as parallel parking, hill starts, and defensive driving techniques.Behind-the-Wheel Training:The behind-the-wheel training was both thrilling and nerve-wracking. My instructor accompanied me on various road types, from quiet residential streets to bustling highways. Each session was an opportunity to apply what I had learned and to receive feedback on my performance. The more I practiced, the more my confidence grew, and the less intimidating the road seemed.The Written Test:When the day of the written test arrived, I was as prepared as I could be. The test was a comprehensive evaluation of my knowledge of traffic laws and safe driving practices. With a deep breath, I began the test, methodically working through each question. To my relief, my diligent study paid off, and I passed the test on my first attempt.The Driving Test:The ultimate challenge was the driving test. This was the moment where all my lessons and practice would be put to the test. The examiner was stern but fair, observing my every move as I navigated through the designated route. I focused on maintaining a safe following distance, signaling my intentions clearly, and demonstrating smooth control of the vehicle. The test was nerve-wracking, but I managed to complete it without any major errors.Receiving the License:Upon successfully passing the driving test, I was elated to receive my driver's license. It was a symbol of my hard work, determination, and newfound responsibility. The license not only allowed me to drive legally but also represented thebeginning of a new chapter in my life where I could explore the world with a greater sense of autonomy.In conclusion, the process of obtaining a driver's license was a significant personal achievement. It required dedication, patience, and a commitment to learning. The journey was not without its challenges, but the reward of being able to drive was well worth the effort. With my license in hand, I was ready to hit the road, eager to explore the horizons that lay ahead.。

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