Knickpoints within the Suoshui watershed and the implication in Zhangjiajie, China

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托福阅读TPO26原文

智课网TOEFL备考资料托福阅读TPO26原文摘要：托福TPO是曾经考过的托福考试真题的汇集，提前认真做好托福TPO题集能够让我们准确了解托福考题最新动向，出题点在哪里？今天小编就来接着为大家介绍托福阅读TPO26原文:Energy and the Industrial Revolution，希望对大家会有一定的帮助。

托福阅读TPO26原文:Energy and the Industrial Revolution托福阅读 TPO26原文：The Formation of Volcanic IslandsEarth’s surface is not made up of a single sheet of rock that forms a crust but rather a number of “tectonic plates” that fit closely, like the pieces of a giant jigsaw puzzle. Some plates carry i slands or continents others form the seafloor. All are slowly moving because the plates float on a denser semi-liquid mantle, the layer between the crust and Earth’s core. The plates have edges that are spreading ridges (where two plates are moving apart and new seafloor is being created), subduction zones (where two plates collide and one plunges beneath the other), or transform faults (where two plates neither converge nor diverge but merely move past one another). It is at the boundaries between plates t hat most of Earth’s volcanism and earthquake activity occur.Generally speaking, the interiors of plates are geologically uneventful. However, there are exceptions. A glance at a map of the Pacific Ocean reveals that there are many islands far out at sea that are actually volcanoes----many no longer active, some overgrown with coral----that originated from activity at points in the interior of the Pacific Plate that forms the Pacific seafloor.How can volcanic activity occur so far from a plate boundary? The Hawaiian Islands provide a very instructive answer. Like many other island groups, they form a chain. The Hawaiian Islands Chain extends northwest from the island of Hawaii. In the 1840s American geologist James Daly observed that the different Hawaii islands seem to share a similar geologic evolution but are progressively more eroded, and therefore probable older, toward the northwest. Then in 1963, in the early days of the development of the theory of plate tectonics. Canadian geophysicist Tuzo Wilson realized that this age progression could result if the islands were formed on a surface plate moving over a fixed volcanic source in the interior. Wilson suggested that the long chain ofvolcanoes stretching northwest from Hawaii is simply the surface expression of a long-lived volcanic source located beneath the tectonic plate in the mantle. Today’s most northwest island would have been the first to form. They as the plate moved slowly northwest, new volcanic islands would have forms as the plate moved over the volcanic source. The most recent island, Hawaii, would be at the end of the chain and is now over the volcanic source.Although this idea was not immediately accepted, the dating of lavas in the Hawaii (and other) chains showed that their ages increase away from the presently active volcano, just as Daly had suggested. Wilson’s analysis of these data is now a central part of plate tectonics. Most volcanoes that occur in the interiors of plates are believed to be produced by mantle plumes, columns of molten rock that rise from deep within the mantle. A volcano remains an active “hot spot” as long as it is over the plume. The plumes apparently originate at great depths, perhaps as deep as the boundary between the core and the mantle, and many have been active for a very long time. The oldest volcanoes in the Hawaii hot-spot trail have ages close to 80 million years. Other islands, including Tahiti and Easter Islands in the pacific, Reunion and Mauritius in the India Ocean, andin deed most of the large islands in the world’s oceans, owe their existence to mantle plumes.The oceanic volcanic islands and their hot-spot trails are thus especially useful for geologist because they record the past locations of the plate over a fixed source. They therefore permit the reconstruction of the process of seafloor spreading, and consequently of the geography of continents and of ocean basins in the past. For example, given the current position of the Pacific Plate, Hawaii is above the Pacific Ocean hot spot. So the position of The Pacific Plate 50 million years ago can be determined by moving it such that a 50-million-year-oil volcano in the hot-spot trail sits at the location of Hawaii today. However because the ocean basins really are short-lived features on geologic times scale, reconstruction the world’s geography by backtracking along the hot-spot trail works only for the last 5 percent or so of geologic time.Paragraph 1:1.The author mentions “spreading ridges”, “subduction zones”, and “transform faults” in order toO illustrate that the boundaries of tectonic plates are neat, thin linesO explain why some tectonic plates carry islands or continents while others form the seafloorO explain the complex nature of the edges of tectonic platesO provide examples of areas of tectonic plates where little geologic action occurs2. The word “converge” in the passage is closest in meaning toO expandO formO riseO move closerParagraph 2: 3.which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential informationO Volcanic activity is responsible for the formation of the Pacific seafloor in the interior of the Pacific Plate.O Many volcanoes in the Pacific Ocean are no longer active and have become islands that support coral.O There are many islands in the Pacific Ocean that originated as volcanoes in the interior of the Pacific Plate.O The map of the Pacific Ocean reveals fewer volcanic islands than there truly are because many are no longer active and some are completely overgrown with coral.Paragraph 3:4. The word “instructive” in the passage is closest in meaning toO clearO detailedO informativeO familiar5. The word “eroded” in the passage is closest in meaning toO worm downO scatteredO developedO deserted6.In paragraph 3, what is the relationship between the scientific contribution of James Daly and Tuzo Wilson?O Wilson provided an explanation for the observations made by Daly.O Wilson challenged the theory proposed by Daly.O Wilson found numerous examples of island chains that supported Daly’s theory.O Wilson popularized the explanation of volcanic island formation formulated by Daly.Paragraph 4: 7.Why does the author provide the information that “the dating of lavas in the Hawaii (and other) chains showed that their ages increase away from the presently active volcano”?O To point out differences between the Hawaii island chain and other volcanic island chainsO To question the idea that all the islands in an island chain have been formed by volcanic activityO To explain why Wilson hypothesis was initially difficult to acceptO To prov ide evidence in support of Daly’s and Wilson’s ideas about how the Hawaii islands were formed8.According to paragraph 4, which of the following is true of mantle plumesO They exist close to the surface of tectonic plates.O They cause most of the volcanic activity that occurs in the interiors of plates.O They are rarely active for long period of time.O They get increasingly older away from the present hot spots.Paragraph 5:9.According to paragraph 5, volcanic islands help geologists toO reconstruct past geographyO detect changes in mantle plumesO measure the rigidity of tectonic platesO explain why the seafloor spreads10.What can be inferred about the Pacific Plate from paragraph 5?O The hot spots on the Pacific Plate are much older than the ones located on the other tectonic plates.O Most of the volcanic sources beneath the Pacific Plate have become extinct.O The Pacific Plate has moved a distance equal to the length of the Hawaiian Island chain in the past 80 million years.O The Pacific Plate is located above fewer mantle plumes than other plates are.11. The word “current” in the passage is closest in meaning toO originalO idealO relativeO present12.According to paragraph 5, why are geologists unable to trace back the entire geologic ofcontinents from hot-spot trails?O Hot spots have existed for only about 5 percent of geologic time.O Hawaii did not exist 50 millions years ago.O Oceanic basins that contained old hot-spot trails disappeared a long time ago.O Hot-spot trails can be reconstructed only for island chains.Paragraph 3: 13.Look at the four squares [] that indicate where the following sentence could be added to the passage.This pattern remained unexplained for a long time.Where would the sentence best fit?14 Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.Although volcanic activity is concentrated on the edge of tectonic plates, such activity can occur in the interiors of plates as well.Answer ChoicesO Our understanding of islands comes from Daly’s and Wilson’s observations of the Hawaiian Islands, which was later confirmed by plate-tectonic theory.O The hot-spot trails formed by volcanic island chains indicate the positions of tectonic plates as for back as the present ocean basins have existed.O Whereas volcanic islands formed by mantle plumes are typically small, most of the world’s largest islands are formed at the edges of tectonic plates.O It has only recently been discovered that tectonic plates are closely fitting rather than loosely constructed, as geologist previously believed.O Volcanic island chains such as the Hawaiian Islands form in the interior of a tectonic plate as the plate moves over a fixed volcanic source in the mantle.O The Pacific Plate has existed for as long as the Hawaiian Islands have existed, namely for more than 80 million years.托福阅读TPO26原文:参考答案1.○32.○43.○34.○35.○16.○17.○48.○29.○1 10.○3 11.○4 12.○3 13.○414. Our understanding of islands comes…Whereas volcanic islands…It has only recently been…托福阅读TPO26原文:答案解析：第一题，C，修辞目的题。

雅思模拟试题1-阅读(学术类)

Academic ReadingALL ANSWERS MUST BE WRITTEN ON THE ANSWER SHEET.The test is divided as follows:Reading Passage 1 Questions 1 to 13Reading Passage 2 Questions 14 to 27Reading Passage 3 Questions 28 to 40Start at the beginning of the test and work through it. You should answer all the questions. If you cannot do a particular question leave it and go on to the next one. You can return to it later.TLME ALLOWED: 60 MINUTESNUMBER OF QUESTIONS: 40Reading Passage 1You should spend about 20 minutes on Questions 1-14, which are based on Reading Questions 1-5Reading Passage 1 has seven paragraphs A-G.Choose the correct heading for paragraphs B-E and G from the list of headings below. Write the correct number (i-x) in boxes 1-5 on your answer sheet.Example Paragraph A Answer iv1 Paragraph B2 Paragraph C3 Paragraph D4 Paragraph EExample Paragraph F Answer ii5 Paragraph GSpace travel AND healthASpace biomedicine is a relatively new area of research both in the USA and in Europe. Its main objectives are to study the effects of space travel on the human body, identifying the most critical medical problems and finding solutions to those problems. Space biomedicine centres are receiving increasing direct support from NASA and/or the European Space Agency (ESA).BThis involvement of NASA and the ESA reflects growing concern that the feasibility of travel to other planets, and beyond, is no longer limited by engineering constraints but by what the human body can actually withstand. The discovery of ice on Mars, for instance, means that there is now no necessity to design and develop a spacecraft large and powerful enough to transport the vast amounts of water needed to sustain the crew throughout journeys that may last many years. Without the necessary protection and medical treatment, however, their bodies would be devastated by the unremittingly hostile environment of space.CThe most obvious physical changes undergone by people in zero gravity are essentially harmless; in some cases they are even amusing. The blood and other fluids are no longer dragged down towards the feet by the gravity of Earth, so they accumulate higher up in the body, creating what is sometimes called ‘fat face’,together with the contrasting ‘chicken legs’ syndrome as the lower limbs become thinner.DMuch more serious are the unseen consequences after months or years in space. With no gravity, there is less need for a sturdy skeleton to support the body, with the result that the bones weaken, releasing calcium into the bloodstream. This extra calcium can overload the kidneys, leading ultimately to renal failure. Muscles too lose strength through lack of use. The heart becomes smaller, losing the power to pump oxygenated blood to all parts of the body, while the lungs lose the capacity to breathe fully. The digestive system becomes less efficient, a weakened immune system is increasingly unable to prevent diseases and the high levels of solar and cosmic radiation can cause various forms of cancer.ETo make matters worse, a wide range of medical difficulties can arise in the case of an accident or serious illness when the patient is millions of kilometres from Earth. There is simply not enough room available inside a space vehicle to include all the equipment from a hospital’s casualty unit, some of which would not work properly in space anyway. Even basic things such as a drip depend on gravity to function, while standard resuscitation techniques become ineffective if sufficient weight cannot be applied. The only solution seems to be to create extremely small medical tools and ‘smart’ devices that can, for example, diagnose and treat internal injuries using ultrasound. The cost of designing and producing this kind of equipment is bound to be, well, astronomical.FSuch considerations have led some to question the ethics of investing huge sums of money to help a handful of people who, after all, are willingly risking their own health in outer space, when so much needs to be donea lot closer to home. It is now clear, however, that every problem of space travel has a parallel problem on Earth that will benefit from the knowledge gained and the skills developed from space biomedical research. For instance, the very difficulty of treating astronauts in space has led to rapid progress in the field of telemedicine, which in turn has brought about developments that enable surgeons to communicate with patients in inaccessible parts of the world. To take another example, systems invented to sterilize waste water on board spacecraft could be used by emergency teams to filter contaminated water at the scene of natural disasters such as floods and earthquakes. In the same way, miniature monitoring equipment, developed to save weight in space capsules, will eventually become tiny monitors that patients on Earth can wear without discomfort wherever they go.GNevertheless, there is still one major obstacle to carrying out studies into the effects of space travel: how to do so without going to the enormous expense of actually working in space. To simulate conditions in zero gravity, one tried and tested method is to work under water, but the space biomedicine centres are also looking at other ideas. In one experiment, researchers study the weakening of bones that results from prolonged inactivity. This would involve volunteers staying in bed for three months, but the centre concerned is confident there should be no great difficulty in finding people willing to spend twelve weeks lying down. All in the name of science, of course.Questions 6 and 7Answer the question below using NO MORE THAN THREE WORDS for each answer.6 Where, apart from Earth, can space travellers find water ........................7 What happens to human legs during space travel ..........................Questions 8-12Do the following statements agree with the writer’s views in Reading Passage 1In boxes 8-12 on your answer sheet writeYES if the statement agrees with tile views of the writerNO if the statement does not agree with the views of the writer NOT GIVEN if there is no information about this in the passage8 The obstacles to going far into space are now medical, not technological.9 Astronauts cannot survive more than two years in space.10 It is morally wrong to spend so much money on space biomedicine.11 Some kinds of surgery are more successful when performed in space.12 Space biomedical research can only be done in space.Questions 13 and 14Complete the table belowChoose NO MORE THAN THREE WORDS from the passage for each answer. Write your answers in boxes 13 and 14 on your answer sheet.Reading Passage 2You should spend about 20 minutes on Questions 15-27, which are based on Reading Passage 2.Cannes. Monte Carlo. St Tropez. Magic names all. And much of the enchantment comes from the deep blue water that laps their shores. But what if somebody pulled the plug Suppose the Mediterranean Sea were to vanish, leaving behind an expanse of salt desert the size of India. Hard to imagine It happened.‘It would have looked like Death Valley,’ says Bill Ryan, from the Lamont-Doherty Earth Observatory in New York, one of the leaders of the team that discovered the Mediterranean had once dried up, then refilled in a deluge of Biblical proportions. Between five and six million years ago, the great desiccation touched off what scientists call me Messinian Salinity Crisis-a global chemical imbalance that triggered a wrenching series of extinctions and plunged the Earth into an ice age.The first indications of some extraordinary past events came in the 1960s, when geologists 20 discovered that major rivers flowing into the Mediterranean had eroded deep canyons in the rock at the bottom of the sea. River erosion of bedrock cannot occur below sea level, yet somehow the River Rhone in the South of France had managed to create a channel1000 metres deep in the sea floor, while the Nile had cut nearly 1500 metres into the rock off the North African coast. There was more: despite the fact that the formation of caves can only take place above water, scientists 30 discovered a whole network beneath the island of Malta that reached an astonishing depth of 2000 metres below sea level.Further evidence came to light in 1970, when an international team chugged across the Mediterranean in a drilling ship to study the sea floor near the Spanish island of Majorca. Strange things started turning up in core samples: layers of microscopic plants and soil sandwiched between beds of salt more than two kilometres below today’s sea level. The plants had grown in sunlight. Also discovered inside the rock were fossilized shallow-water shellfish, together with salt and silt: particles of sand and mud that had once been carried by river water. Could the sea floor once have been near a shorelineThat question led Ryan and his fellow team leader, Kenneth Hsǖ, to piece together a staggering chain of events. About million years ago, they concluded, the Mediterranean was gradually cut off from the Atlantic Ocean when continental drift pinned Morocco against Spain. As the opening became both narrower and shallower, the deep outward flow from sea to ocean was progressively cut off, leaving only the shallow inward flow of ocean water into the Mediterranean. As this water evaporated, the sea became more saline and creatures that couldn’t handle the rising salt content perished. ‘The sea’s interior was dead as a door nail, except for bacteria,’ says Ryan. When the shallow opening at Gibraltar fin ally closed completely, the Mediterranean, with only rivers to feed it, dried up and died.Meanwhile, the evaporated water was falling back to Earth as rain. Whenthe fresh water reached the oceans, it made them less saline. With less salt in it to act as an antifreeze, parts of the ocean that would not normally freeze began to turn to ice. ‘The ice reflects sunlight into space,’ says Ryan. 'The planet cools. You drive yourself into an ice age.’Eventually, a small breach in the Gibraltar dam sent the process into reverse. Ocean water cut a tiny channel to the Mediterranean. As the gap enlarged, the water flowed faster and faster, until the torrent ripped through the emerging Straits of Gibraltar at more than 100 knots. ‘The Gibraltar Falls were 100 times bigger than Victoria Falls and a thousand times grander than Niagara,’ Hsǖwrote in his book The Mediterranean was a Desert (Princeton University Press, 1983).In the end the rising waters of the vast inland sea drowned the falls and warm water began to escape to the Atlantic, reheating the oceans and the planet. The salinity crisis ended about million years ago. It had lasted roughly 400,000 years.Subsequent drilling expeditions have added a few wrinkles to Ryan and Hsǖ’s scenario. For example, researchers have found salt deposits more than two kilometres thick - so thick, some believe, that the Mediterranean must have dried up and refilled many times. But those are just geological details. For tourists the crucial question is, could it happen again Should Malaga start stockpiling dynamiteNot yet, says Ryan. If continental drift does reseal the Mediterranean, it won’t be for several million years. ‘Some future creatures may face the issue of how to respond to nature’s closure. It’s not something our species has to worry about.’Questions 15-19Complete the summary below.Choose NO MORE THAN THREE WORDS from the passage for each answer. Write your answers in boxes 15-19 on your answer sheet.The 1960s discovery of 15.......................... in the bedrock of the Mediterranean, as well as deep caves beneath Malta, suggested something strange had happened in the region, as these features must have been formed16 ......................... sea level. Subsequent examination of the17.......................... off Majorca provided more proof. Rock samples from 2000 metres down contained both vegetation and 18.......................... that could not have lived in deep water, as well as 19.......................... originally transported by river.Questions 20-22Complete each of the following statements with the best ending from the box below.Write the appropriate letters A-G in boxes 20-22 on your answer sheet.20 The extra ice did not absorb the heat from the sun, so...21 The speed of the water from the Atlantic increased as...22 The Earth and its oceans became warmer when...Questions 23-27Choose the appropriate letters A, B, C or D and write them in boxes 23-27 on your answer sheet.23 What, according to Ryan and Hsǖ, happened about million years agoA Movement of the continents suddenly closed the Straits of Gibraltar.B The water level of the Atlantic Ocean gradually fell.C The flow of water into the Mediterranean was immediately cut off.D Water stopped flowing from the Mediterranean to the Atlantic.24 Why did most of the animal and plant life in the Mediterranean dieA The water became too salty.B There was such a lot of bacteria in the water.C The rivers did not provide salt water.D The sea became a desert.25 According to the text, the events at Gibraltar led toA a permanent cooling of the Earth.B the beginning and the end of an ice age.C the formation of waterfalls elsewhere in the world.D a lack of salt in the oceans that continues to this day.26 More recent studies show thatA Ryan and Hsǖ’s theory was correct in every detail.B the Mediterranean was never cut off from the Atlantic.C it may have been cut off more than once.D it might once have been a freshwater lake.27 At the end of the article, Ryan suggests thatA the Mediterranean will never dry up again.B humans will have the technology to prevent it drying up again.C the Mediterranean is certain to dry up again one day.D humans will never see the Mediterranean dry up.Reading Passage 3onAGenetic studies show that dogs evolved from wolves and remain as similar to the creatures from which they came as humans with different physical characteristics are to each other, which is. to say not much different at all, ‘Even in the most changeable mitochondrial DNA markers - DNA handed down on the mother’s side- dogs and wolves differ by not’ much more tha n one per cent’ says Robert Wayne, a geneticist at the University of California at Los Angeles.BWolf-like species go back one to two million years, says Wayne, whose genetic work suggests dogs of some sort began breaking away about 100,000 years ago. Wolf and early human fossils have been found close together from as far back as 400,000 years ago, but dog and human fossils date back only about 14,000 years, all of which puts wolves and/or dogs in the company of man or his progenitor’s before the developm ent of farming and permanent human settlements, at a time when both species survived on what they could scratch out hunting or scavenging.CWhy would these competitors cooperate The answer probably lies in the similar social structure and size of wolf packs and early human clans, the compatibility of their hunting objectives and range, and thewillingness of humans to accept into camp the most suppliant wolves, the young or less threatening ones.DCertain wolves or protodogs may have worked their way close to the fire ring after smelling something good to eat, then into early human gatherings by proving helpful or unthreatening. As wandering packs of twenty- five or thirty wolves and clans of like- numbered nomadic humans roamed the landscape in tandem, hunting big game, the animals hung around campsites scavenging leftovers, and the humans might have used the wolves’ superior scenting ability and speed to locate and track prospective kills. At night, wolves with their keen senses could warn humans of danger approaching.ETimes might not have been as hard back then as is commonly thought, in many instances food would have been plentiful, predators few, and the boundaries between humans and wildlife porous. Through those pores slipped smaller or less threatening wolves, which from living in packs where alpha bosses reigned would know the tricks of subservience and could adapt to humans in charge. Puppies in particular would be hard to resist, as they are today. Thus was a union born and a process of domestication begun.FOver the millennia, admission of certain wolves and protodogs into human camps and exclusion of larger, more threatening ones led to the development of people-friendly breeds distinguishable from wolves by size, shape, coat, cars and markings. Dogs were generally smaller than wolves, their snouts proportionally reduced. They would assist in the hunt cleanup camp by eating garbage, warn of danger, keep humans warm, and serve as food. Native Americans among others ate puppies, and in some societies it remains accepted practice.GBy the fourth millennium BC Egyptian rock and pottery drawings show dogs being put to work by men. Then, as now, the relationship was not without drawbacks. Feral dogs roamed city streets, stealing food from people returning from market. Despite their penchant for misbehaviour, and sometimes because of it, dogs keep turning up at all the important junctures in human history.HIn ancient Greece, 350 years before Christ, Aristotle described three types of domesticated dogs, including speedy Laconians used by the rich to chase and kill rabbits and deer. Three hundred years later, Roman warriors trained large dogs for battle. The brutes could knock an armed man from his horse and dismember him.IIn seventeenth-century England, dogs still worked, pulling carts, sleds, and ploughs, herding livestock, or working as turn-spits, powering wheels that turned beef and venison over open fires. But Working dogs were not much loved and were usually hanged or drowned when they got old. ‘Unnecessary’ dogs meanwhile gained status among English royalty. King James I was said to love his dogs more than his subjects. Charles Ⅱ was famous for playing with his dog at Council table, and his brother James had dogs at sea in 1682 when his ship was caught in a storm. As sailors drowned, he allegedly cried out, ‘Save the dogs and Colonel Churchill!’JBy the late nineteenth century the passion for breeding led to the creation of private registries to protect prized bloodlines. The Kennel Club was formed in England in 1873, and eleven years later the American Kennel Club (AKC) was formed across the Atlantic. Today the AKC registers 150 breeds, the Kennel Club lists 196, and the Europe-based Fédération Cynologique Internationale recognizes many more. Dog shows sprouted in the mid- 1800s when unnecessary dogs began vastly to outnumber working ones, as they do to this day. Unless, that is, you count companionship as a job.Questions 28-31Reading Passage 3 has ten paragraphs labelled A-J.Write the correct letters A-J in boxes 28-31 on your answer sheet.28 Which paragraph explains how dogs became different in appearance from wolves29 Which paragraph describes the classification of dogs into many different types30 Which paragraph states the basic similarity between wolves and dogs31 Which paragraph gives examples of greater human concern for animals than for peopleQuestions 32-35Which FOUR of the following statements are made in the textChoose FOUR letters from A-H and write them in boxes 32-35 on your answer sheet.A In a typical camp there were many more wolves than humans.B Neither the wolves nor the humans lived in one place for long.C Some wolves learned to obey human leaders.D Humans chose the most dangerous wolves to help them hunt.E There was very little for early humans to eat.F Wolves got food from early humans.G Wolves started living with humans when agriculture began.H Early humans especially liked very young wolves.Questions 36-40Write the correct letters A-F in boxes 36-40 on your answer sheet. NB You may use any letter more than once.36 in war37 as a source of energy38 as food39 to hunt other animals40 to work with farm animals。

tpo45三篇托福阅读TOEFL原文译文题目答案译文背景知识

tpo45三篇托福阅读TOEFL原文译文题目答案译文背景知识阅读-1 (2)原文 (2)译文 (5)题目 (7)答案 (15)背景知识 (16)阅读-2 (16)原文 (16)译文 (19)题目 (23)答案 (30)背景知识 (31)阅读-3 (32)原文 (32)译文 (35)题目 (37)答案 (45)背景知识 (45)阅读-1原文The Beringia Landscape①During the peak of the last ice age,northeast Asia(Siberia)and Alaska were connected by a broad land mass called the Bering Land Bridge.This land bridge existed because so much of Earth’s water was frozen in the great ice sheets that sea levels were over100meters lower than they are today.Between25,000and10,000years ago,Siberia,the Bering Land Bridge,and Alaska shared many environmental characteristics.These included a common mammalian fauna of large mammals,a common flora composed of broad grasslands as well as wind-swept dunes and tundra,and a common climate with cold,dry winters and somewhat warmer summers.The recognition that many aspects of the modern flora and fauna were present on both sides of the Bering Sea as remnants of the ice-age landscape led to this region being named Beringia.②It is through Beringia that small groups of large mammal hunters, slowly expanding their hunting territories,eventually colonized North and South America.On this archaeologists generally agree,but that is where the agreement stops.One broad area of disagreement inexplaining the peopling of the Americas is the domain of paleoecologists,but it is critical to understanding human history:what was Beringia like?③The Beringian landscape was very different from what it is today. Broad,windswept valleys;glaciated mountains;sparse vegetation;and less moisture created a rather forbidding land mass.This land mass supported herds of now-extinct species of mammoth,bison,and horse and somewhat modern versions of caribou,musk ox,elk,and saiga antelope.These grazers supported in turn a number of impressive carnivores,including the giant short-faced bear,the saber-tooth cat,and a large species of lion.④The presence of mammal species that require grassland vegetation has led Arctic biologist Dale Guthrie to argue that while cold and dry, there must have been broad areas of dense vegetation to support herds of mammoth,horse,and bison.Further,nearly all of the ice-age fauna had teeth that indicate an adaptation to grasses and sedges;they could not have been supported by a modern flora of mosses and lichens. Guthrie has also demonstrated that the landscape must have been subject to intense and continuous winds,especially in winter.He makes this argument based on the anatomy of horse and bison,which do not have the ability to search for food through deep snow cover.They needlandscapes with strong winds that remove the winter snows,exposing the dry grasses beneath.Guthrie applied the term“mammoth steppe"to characterize this landscape.⑤In contrast,Paul Colinvaux has offered a counterargument based on the analysis of pollen in lake sediments dating to the last ice age.He found that the amount of pollen recovered in these sediments is so low that the Beringian landscape during the peak of the last glaciation was more likely to have been what he termed a"polar desert,"with little or only sparse vegetation,in no way was it possible that this region could have supported large herds of mammals and thus,human hunters. Guthrie has argued against this view by pointing out that radiocarbon analysis of mammoth,horse,and bison bones from Beringian deposits revealed that the bones date to the period of most intense glaciation.⑥The argument seemed to be at a standstill until a number of recent studies resulted in a spectacular suite of new finds.The first was the discovery of a1,000-square-kilometer preserved patch of Beringian vegetation dating to just over17,000years ago—the peak of the last ice age.The plants were preserved under a thick ash fall from a volcanic eruption.Investigations of the plants found grasses,sedges,mosses,and many other varieties in a nearly continuous cover,as was predicted by Guthrie.But this vegetation had a thin root mat with no soil formation,demonstrating that there was little long-term stability in plant cover,a finding supporting some of the arguments of Colinvaux.A mixture of continuous but thin vegetation supporting herds of large mammals is one that seems plausible and realistic with the available data.译文洞察白令地貌①在上一次冰期的高峰，东北亚地区（西伯利亚）和阿拉斯加曾由一片广阔的陆地相连，这片土地被叫做白令陆桥。

Kink Structure in the Quasiparticle Band of Doped Hubbard Systems

a r X i v :c o n d -m a t /0507564v 1 [c o n d -m a t .s u p r -c o n ] 25 J u l 2005Typeset with jpsj2.cls <ver.1.2>LetterKink Structure in the Quasiparticle Band of Doped Hubbard SystemsYoshiro Kakehashi 1∗and Peter Fulde 2†1Department of Physics and Earth Sciences,Faculty of Science,University of Ryukyus,1Senbaru,Nishihara,Okinawa903-0213,Japan2Max-Planck-Institut f¨u r Physik komplexer Systeme,N¨o thnitzer Str.38,D-01187Dresden,GermanyBy making use of the self-consistent projection operator method with high-momentum and high-energy resolutions,we ﬁnd a kink structure in the quasiparticle excitation spectrum of the two-dimensional Hubbard model in the underdoped regime.The kink is caused by a mixing between the quasiparticle state and excitations with short-range antiferromagnetic order.We suggest that this might be the origin of the strong concentration dependence of the ’kink’found in La 2−x Sr x CuO 4(x =0.03−0.07).KEYWORDS:kink,quasiparticle excitations,Hubbard model,ARPES,cuprate,LSCORecent high-resolution photoemission experiments show that there is a well-deﬁned ’kink ’in the quasipar-ticle band dispersion of high-T c cuprates,whose energy scale is ωkink =60−70meV in both the normal and superconducting states.1–3The kink along the nodal di-rection was found to have a universal feature,2i.e.,the Fermi velocity v F in the low-energy region (|ω|<ωkink )is not sensitive to the type of cuprates,doping concen-tration,and isotope substitution,4although v F in the high-energy regime (|ω|>ωkink )strongly depends on the latter.Various theoretical explanations for the kink have been attempted from two diﬀerent points of view.One type of theory relies on the coupling of an electronic quasiparticle to the spin ﬂuctuation resonance mode ob-served in inelastic neutron scattering experiments.5,6An-other relies on a coupling to phonons,particularly to the longitudinal optical phonon mode found in neutron ex-periments.2,3The latter approach raised again the fun-damental question on the mechanism underlying high-T c superconductivity in cuprates,i.e.,electron-or phonon-mediated.Although the reliability of these theories is un-der debate and the improvements of these theories are in progress,7,8it has not yet been seriously studied whether or not the kink in the quasiparticle state can be solely of electronic origin.We deal with this problem in the present letter and report the appearance of a kink due to long-range electron correlations in the two-dimensional (2D)Hubbard model for small doping concentrations.The diﬃculty in the present problem is that the per-turbation approach is not applicable to cuprates be-cause of strong electron correlations.Therefore,ad-vanced theories such as the Lanczos method,9the quan-tum Monte-Carlo (QMC)method,10–12and dynamical cluster approximation (DCA),13,14have been applied to the cuprate system.They clariﬁed the global structure of the single-particle excitation spectrum in the 2D Hub-bard model.A detailed structure of the low-energy ex-citations at low temperatures,however,has not been derived because of the limited resolutions in both mo-mentum and energy and the limited range of intersitez −ǫk −Λk (z ).(1)Here,z =ω+iδ,where δis a positive inﬁnitesimal number,and ǫk is the Hartree-Fock one-electron energy dispersion measured from Fermi energy.In the SCPM,the momentum-dependent self-energy Λk (z )is calcu-lated from the Fourier transform of nonlocal memory functions M ij asΛk (z )=U2jM j 0(z )exp(i k ·R j ).(2)Note that R j is the position vector of site j .High-momentum and high-energy resolutions are achieved bytaking into account the oﬀ-diagonal terms M ij (z )up to inﬁnity.We calculate M ij (z )by means of an incremental cluster expansion in an eﬀective medium with a co-herent potential ˜Σ(z ).Within the two-site approxima-tion,the M ij (z )are given by M ii (z )=M (i )ii (z )+ l =i M (il )ii (z )−M (i )ii (z ) and M i =j (z )=M (ij )i =j (z ).M (i )ii (z )and M (ij )i =j (z )are the matrix elements of the clus-ter memory matrices deﬁned by M (c )lm (z )= ˆM(c ) 1−L (c )·ˆM(c )−1lm(c =i,ij ).Here,L (c )(z )is a 1×1-15-10-5051015ΓXMΓωkδh = 0.14 U=8Fig.1.Excitation spectra along high symmetry line calculated at hole concentration δh =0.14,U =8,and T =0.Γ=(0,0),X =(0,π),and M =(π,π)in units of the lattice constant.The energy unit is chosen so that the nearest-neighbor transfer integral is one.Open circles with error bars are the results obtained by the QMC method 12at T =0.33.The dashed curve shows the Hartree-Fock contribution ǫk .(for c =i )or (2×2)(c =(ij ))cluster Liouvillean,whose diagonal matrix elements are given by L (i )(z )=U (1−2 n i −σ )/[ n i −σ (1− n i −σ )]using an average elec-tron number n iσ with spin σon site i .The screenedmemory matrix element ˆM (c )ij(z )is obtained using renor-malized perturbation theory 15asˆM (c )ij(z )=A ij dǫdǫ′dǫ′′˜ρ(c )ij (ǫ)˜ρ(c )ij (ǫ′)˜ρ(c )ji (ǫ′′)χ(ǫ,ǫ′,ǫ′′)vFδhFig.4.Fermi velocity along nodal direction as function of hole concentration.Closed circles denote the velocity in the marginal Fermi liquid state,while open circles indicate the velocity in the normal Fermi liquid state.The dashed line is the result for a noninteracting system.range magnetic order(i.e.,a precursor of the gap for-mation due to antiferromagnetic correlations).11,13The kink atωkink=−0.8|t|is caused by a mixing between the quasiparticle state and magnetic excitations.Re-cently,we have reported that a marginal Fermi liquid17 (MFL)-like behavior is found in the underdoped region (δh<∼0.03)away from half-ﬁlling because of a pinning of Fermi energy to the van Hove anomaly due to a trans-fer of spectral weight from the lower Hubbard band to the upper one.18Antiferromagnetic correlations should be enhanced in this region because of nesting.The kink behavior appears in this regionδh<∼0.03.On the other hand,the lower Hubbard band collapses whenδh>∼0.03. The MFL-like state with antiferromagnetic correlations changes to a normal Fermi liquid state and the kink dis-appears,as noted in Fig.3.The calculated Fermi velocity along theΓ-M line is presented in Fig.4.The velocity shows a weak concentration dependence,and the renor-malization factor of the Fermi velocity is about1.8from the underdoped region to the overdoped one.We have also examined in detail excitations alongΓ-X-M.Because of the van Hove singularity,the quasipar-ticle band around the X point is quiteﬂat.We do not ﬁnd a kink behavior in thisﬂat band region.The mix-ing between the quasiparticle band and the band of the magnetic excitations takes place away from the linear dispersion regime near the Fermi level,i.e.,(|k|,ω)= (0.5π,−1.2)on theΓ-X line.Because both bands are ﬂat,it is not clear whether this region contains a kink. The present model is too simple for attempting a comparison with the experimental data.Nevertheless, it is plausible that the kink is enhanced with decreas-ing doping concentration because of the development of short-range antiferromagnetic order.We speculate that the strong concentration dependence of the kink in La2−x Sr x CuO4(LSCO)3,19may be caused by the present mechanism.In fact,we obtain for the charac-teristic kink energyωkink=70meV when we choose the transfer integral so that the calculated Fermi veloc-ity along the nodal direction agrees with the observed one(1.8eV·˚A).The value forωkink agrees well with the experimental one(60-70meV).19In summary,we have investigated the quasiparticle band in the doped2D Hubbard model on the basis of the SCPM with high-momentum and high-energy resolutions.Weﬁnd a kink along the nodal direction (0,0)−(π,π)in the range of doping concentrations 0<δh<∼0.03where the MFL behavior persists.It is caused by a mixing between the quasiparticle excitations and magnetic excitations with short-range antiferromag-netic order.The kink decays rapidly with the decrease in antiferromagnetic correlations.We speculate that the kink in the underdoped regime of LSCO may be due to the present mechanism.AcknowledgementsThe authors would like to thank Drs.J.Fink and O. Gunnarsson for valuable discussions.1)P.V.Bodanov,nzara,S.A.Keller,X.J.Zhou,E.D.Lu,W.J.Zheng,G.Gu,J.-I.Shimoyama,K.Kishio,H.Ikeda, R.Yoshizaki,Z.Hussain and Z.X.Shen:Phys.Rev.Lett.85 (2000)2581.2) nzara,P.V.Bogdanov,X.J.Zhou,S.A.Keller,D.L.Feng,E.D.Lu,T.Yoshida,H.Eisaki,A.Fujimori,K.Kishio, J.-I.Shimoyama,T.Noda,S.Uchida,Z.Hussain and Z.-X.Shen:Nature412(2001)510.3)T.Cuk,D.H.Lu,X.J.Zhou,Z.-X.Shen,T.P.Devereax andN.Nagaosa:Phys.Stat.Sol.(b)242(2005)11.4)G.-H.Gweon,T.Sasagawa,S.Y.Zhou,J.Graf,H.Takagi,D.-H.Lee and nzara:Nature430(2004)187.5)M.Eschrig and M.R.Norman:Phys.Rev.Lett.85(2000)3261;Phys.Rev.Lett.89(2002)277005.6)P.D.Johnson,T.Valla,A.V.Fedorov,Z.Yusof,B.O.Wells,Q.Li,A.R.Moodenbaugh,G.D.Gu,N.Koshizuka,C.Kendziora, Sha Jian and D.G.Hinks:Phys.Rev.Lett.87(2001)177007.7) E.Schachinger,J.J.Tu and J.P.Carbotte:cond-mat/0304029.8)S.Ishihara and N.Nagaosa:Phys.Rev.B69(2004)144520.9) E.Dagotto:Rev.Mod.Phys.66(1994)763.10)N.Bulut,D.J.Scalapino and S.R.White:Phys.Rev.Lett.73(1994)748;72(1994)705;Phys.Rev.50(1994)7215. 11)R.Preuss,W.Hanke and W.von der Linden:Phys.Rev.Lett.75(1994)1344.12) C.Gr¨o ber,R.Eder and W.Hanke:Phys.Rev.B62(2000)4336.13)M.Jarrell,Th.Maier,C.Huscroft and S.Moukouri:Phys.Rev.B64(2001)195130.14)Th.A.Maier,Th.Pruschke and M.Jarrell:Phys.Rev.B66(2002)075102.15)Y.Kakehashi and P.Fulde:Phys.Rev.B70(2004)195102.16)Y.Kakehashi:Adv.Phys.53(2004)497.17) C.M.Varma,P.B.Littlewood,S.Schmitt-Rink,E.Abrahamsand A.E.Ruckenstein:Phys.Rev.Lett.63(1989)1996.18)Y.Kakehashi and P.Fulde:Phys.Rev.Lett.94(2005)156401.19)X.J.Zhou,J.Shi,T.Yoshida,T.Cuk,W.L.Yang,V.Brouet,J.Nakamura,N.Mannella,S.Komiya,Y.Ando,F.Zhou,W.X.Ti,J.W.Xiong,Z.X.Zhao,T.Sasagawa,T.Kakeshita,E.Eisaki,S.Uchida,A.Fujimori,Z.Zhang,E.W.Plummer,R.ughlin,Z.Hussain and Z.-X.Shen:cond-mat/0405130.。

Halsey Taylor 水晶瓶礁水槽说明书（模型号：97878C）

TUBE IS SECURED IN POSITIONSIMPLY PUSH IN TUBE TO ATTACHPUSH IN COLLET TO RELEASE TUBEPUSHING TUBE IN BEFORE PULLING IT OUT HELPS TORELEASE TUBEFIG. 2FIG. 1NOTE: WATER FLOWDIRECTIONSERVICE STOP (NOT FURNISHED)INSTALLATION INSTRUCTIONS1.Install remote chiller. Remove front panel of chiller. Remove and discard cardboard inner pack frombetween compressor and side panel. Slide chiller onto the shelf and position it to the left within the guides on the shelf. NOTE: Building construction must allow for adequate air flow on both sides, top, and back of chiller.A minimum of 4" (102mm) on both sides and top is required. See chiller instructions for additional instructions.2. Make water supply connections. The inlet port is marked on the chiller (1/4" O.D. copper tube). Bend thecopper tube (provided) at an appropriate length from chiller to opening in frame. Install the in-line strainer(provided with chiller) by pushing it in until it reachs a positive stop, approximately 3/4" (19mm) on the marked chiller inlet port. Attach an unplated and deburred copper water inlet line and a service stop (not provided) to the in-line strainer. Turn on the water supply and flush the line thoroughly. DO NOT SOLDERTUBES WHILE INSERTED INTO THE STRAINER AS DAMAGE TO THE O-RINGS MAY RESULT.3. Hang the upper panel on the mounting frame hanger. Align holes in the panel with the holes in the mountingframe. Be sure that panel is engaged with hanger at top of frame before releasing it.4. Install fountain. Remove access cover plate on underside of fountains and save the screws. Mount thefountains to the upper panel and the wall frame with (4) 5/16" x 1-1/4" (32mm) long bolts, washers, and nuts.Tighten securely, but do not overtighten. Over tightening will crack the Marblyte Fountain.NOTE: The short fountain should be mounted to the upper left hand side of the panel.5. Remove elbow from end of p-trap and attach it to drain tube. Re-attach elbow to p-trap and cut waste tube torequired length using plumbing hardware and trap as a guide.6. Make connection between remote chiller outlet tube and fountain(s). Outlet port is marked on the chiller (1/4"O.D. copper tube). Install a 1/4" union/tee (provided) on the marked chiller outlet port. Insert the 1/4" poly tubing coming from the fountain(s) into the union/tee. Turn on water supply and check for leaks.DO NOT SOLDER TUBES WHILE INSERTED INTO THE STRAINER AS DAMAGE TO THE O-RINGS MAYRESULT. (See figure 5 or 6).7. These products are designed to operate on 20-105 PSI supply line pressure. If inlet pressure is above 105 PSI,a pressure regulator must be installed in the supply line. Any damage caused by reason of connecting theseproducts to supply line pressures lower than 20 PSI or higher than 105 PSI is not covered by warranty.8. Make electrical connections to the chiller. See chiller instructions.9. Check stream height from bubbler. Stream height is factory set at 35-40 PSI. If supply pressure varies greatlyfrom this, adjust the screw on regulator item 2 by using a small screwdriver through the small hole in the push button item 5 (See Fig.8). Clockwise adjustment will raise stream height and counter-clockwise adjustment will lower stream height. For best adjustment stream height should be approximately 1-1/2" (38mm) above the bubbler guard (See Figure 7, Page 5).10. Mount lower panel. Loosen the (2) #10-24 x 5/8" (16mm) screws at frame bottom lip. Slide upper tongue oflower panel under lower edge of already installed upper panel. Tighten previously loosened screws securely. 11. Replace bottom access panel to fountain basin using screws provided. Tighten securely.Care and Maintenance of Halsey Taylor Marblyte FountainsMarblyte provides an exremely durable, nonporous surface which resists staining. Care is very simple. Routine cleaning with a soft sponge or cloth, or with water or non-abrasive aerosol foam cleaner, is all that is normally needed to give many years of trouble free service. Cleaners left standing on the fountain surface can dull the surface finish. Be certain to rinse all cleaning agents completely and polish with a soft cloth.Harsh abrasive cleaners are not required and should not be used.Mild abrasives such as liquid automotive cleaning compound or baking soda paste will remove simple scratchesand stains. Cigarette burns can normally be removed without noticeable effect. Deeper scratches or gouges can be corrected with fine grit sandpaper (240 grit then 400 grit) or a green Scotchbrite pad.To maintain or regain luster and make cleaning easier, periodic applications of automobile wax or like products will keep the finish looking like new.TROUBLE SHOOTING & MAINTENANCEOrifice Assy: Mineral deposits on orifice can cause water flow to spurt or not regulate. Mineral deposits may be removed from the orifice with a small round file not over 1/8" diameter or small diameter wire. CAUTION: DO NOT file or cut orifice material. Stream Regulator: If orifice is free of material deposits, regulate flow as instructions on page 4 (Step 9). If replacement is necessary, see parts list for correct regulator part number.Actuation of Quick Connect Water Fittings: Cooler is provided with lead-free connectors which utilize an o-ring water seal. To remove tubing from the fitting, relieve water pressure, push in on the gray collar while pulling on the tubing(see Fig 2, Page 1). To insert tubing, push tube straight into fitting until it reaches a positive stop, approximately 3/4".1-1/2"(38mm)CHILLER INLET2112CHILLER OUTLET20TO BUBBLERHRFG - ER / SR TUBE ROUTINGFIG. 5HRFG - SER TUBE ROUTINGTO BUBBLER16CHILLER OUTLETCHILLER INLET12FIG. 621TO BUBBLER212222 CAMDEN COURTOAK BROOK, IL 60523630.574.3500PRINTED IN U.S.A.。

托福阅读tpo70R-2原文+译文+题目+答案+背景知识

托福阅读tpo70R-2Nineteenth-Century Theories of Mountain Formation原文 (1)译文 (5)题目 (8)答案 (16)背景知识 (17)原文Nineteenth-Century Theories of Mountain Formation①One of the central scientific questions of nineteenth-century geology was the origin of mountains.How were they formed?What process squeezed and folded rocks like bread dough?What made Earth's surface move?Most theories invoked terrestrial contraction as a causal force.It was widely believed that Earth had formed as a hot,incandescent body and had been steadily cooling since the beginning of geological time.Because most materials contract as they cool,it seemed logical to assume that Earth had been contracting as it cooled,too.As it did,its surface would have deformed,producing mountains.②In Europe,Austrian geologist Eduard Suess(1831-1914)popularized the image of Earth as a drying apple:as the planet contracted,its surface wrinkled to accommodate the diminished surface area.Suess assumed that Earth’s initial crust was continuous but broke apart as the interior shrank.The collapsed portions formed the ocean basins, the remaining elevated portions formed the continents.With continued cooling,the original continents became unstable and collapsed to form the next generation of ocean floor,and what had formerly been ocean now became dry land.Over the course of geological history,there would be a continual interchange of land and sea,a periodic rearrangement of the landmasses.③The interchangeability of continents and oceans explained a number of other perplexing geological observations,such as the presence of marine fossils on land(which had long before puzzled Leonardo da Vinci)and the extensive interleaving of marine and terrestrial sediments in the stratigraphic record.Suess's theory also explained the striking similarities of fossils in parts of Africa and South America. Indeed,in some cases the fossils seemed to be identical,even though they were found thousands of miles apart.These similarities had beenrecognized since the mid-nineteenth century,but they had been made newly problematic by Darwin's theory of evolution.If plants and animals had evolved independently in different places within diverse environments,then why did they look so similar?Suess explained this conundrum by attributing these similar species to an early geological age when the continents were contiguous in an ancient supercontinent called Gondwanaland.④Suess’s theory was widely discussed and to varying degrees accepted in Europe,but in North America geologist James Dwight Dana(1813-1895)had developed a different version of contraction theory.Dana suggested that the continents had formed early in Earth history,when low-temperature minerals such as quartz and feldspar had solidified.Then the globe continued to cool and contract,until the high-temperature minerals such as olivine and pyroxene finally solidified—on the Moon,to form the lunar craters,on Earth,to form the ocean basins.As contraction continued after Earth was solid,its surface began to deform.The boundaries between continents and oceans were most affected by the pressure,and so mountains began to form along continental margins.With continued contraction came continued deformation,but with the continents and oceans always inthe same relative positions.Although Dana's theory was a version of contraction,it came to be known as permanence theory,because it viewed continents and oceans as globally permanent features.⑤In North America permanence theory was linked to the theory of subsidence(or sinking)of sedimentary basins along continental margins.This idea was developed primarily by paleontologist James Hall(1811-1898),who noted that beneath the forest cover,the Appalachian Mountains of North America were built up of folded layers of shallow-water sedimentary rocks,thousands of feet thick.How did these sequences of shallow-water deposits form?How were they folded and uplifted into mountains?Hall suggested that materials eroded off the continents accumulated in the adjacent marginal basins, causing the basins to subside.Subsidence allowed more sediment to accumulate,causing more subsidence,until finally the weight of the pile caused the sediments to be heated,converted to rock,and then uplifted into mountains.Dana modified Hall's view by arguing that thick sedimentary piles were not the cause of subsidence but the result of it.Either way,the theory provided a concise explanation of how thick sequences of shallow-water rocks could accumulate,but was vague on the question of how they were transformed into mountainbelts.译文19世纪山脉形成理论①十九世纪地质学中的一个核心科学问题是山脉的起源。

multiple scales on river water chemistry in the Tiaoxi Basin, China

Contents lists available at ScienceDirectEcological Indicatorsjournal homepage:/locate/ecolindIdentifying the in ﬂuence factors at multiple scales on river water chemistry in the Tiaoxi Basin,ChinaLijuan Cui a ,b ,1,⁎,Wei Li a ,b ,1,Changjun Gao a ,b ,c ,Manyin Zhang a ,b ,Xinsheng Zhao a ,b ,Zheng Yang d ,Yinru Lei a ,b ,Di Huang a ,b ,Wu Ma eaInstitute of Wetland Research,Chinese Academy of Forestry,Beijing 100091,China bBeijing Key Laboratory of Wetland Services and Restoration,Beijing 100091,China cGuangdong Academy of Forestry,Guangzhou 510520,China dSchool of Geographical Sciences,University of Bristol,United Kingdom eSchool of Natural Resources,West Virginia University,USAA R T I C L E I N F OKeywords:Redundancy analysis Multi-scale PhysiographyHuman disturbance Tiaoxi riverA B S T R A C TThe catchment environment and landscape is widely used as a predictor of stream-ecosystem condition,and the extent of its in ﬂuence is closely linked to spatial scale.The aim of this study was to identify the in ﬂuence factors on river water chemistry at multiple scales in a basin,namely the catchment,riparian corridor,and river reach rmation about the catchment and riparian corridor landscapes,reach-scale river properties,and catchment environments and river water chemistry data were collected monthly from 31streams across the Tiaoxi Basin from July 2011to June 2012.We used redundancy analysis to identify the relative in ﬂuences of multi-scale variables on nine water quality indexes over both the whole study period and three sub-periods (before,during,and after rainy seasons).Results showed that all the selected factors helped to explain variations in water chemistry,although the relative e ﬀects of these factors changed considerably with variation in the spatial and temporal scales.Stream water chemistry across the entire study period was more sensitive to phy-siography and landscape variable at the catchment scale than at the reach and riparian corridor scales.From dry seasons to the rainy season,the in ﬂuence of physiography and landscape variable at the catchment scale de-creased slightly,while the e ﬀects of variables at the reach and riparian corridor scales increased noticeably.Besides,the in ﬂuence of variables at the catchment scale was relatively strong and stable while the impacts of variables at the local scale were relatively weak and ﬂuctuated widely with seasons.The ﬁndings from this study may improve our understanding of the main drivers of variations in stream water chemistry in di ﬀerent spatial and temporal scales,and will help managers protect and restore stream water environments using a basin-scale perspective.1.IntroductionLandscape patterns in catchments have important in ﬂuences on the processes that control di ﬀerent forms of carbon (C),nitrogen (N),and phosphorus (P)discharged in river water (Ahearn et al.,2005;Allan,2004).Basin landscape pattern was generally characterized by some geographical factors,such as climate,topography,sur ﬁcial geology,and land use or land cover types (Frissell et al.,1986;Schoonover et al.,2005).In addition,hydrological processes within a basin can a ﬀect the water quality of rivers through changing the supply,transport,and transformations of C,N,and P in the river water column (Hynes,1975;Sheldon et al.,2012;Allan,2004).Also,the hydrological processes were dominantly a ﬀected by basin landscape pattern,which have scale-dependent and seasonally variable in ﬂuences on river ecosystems (Buck et al.,2004).Most early studies of the relationships between watershed land-scapes and river ecosystems were limited in their spatial scale,such as the areas that were either directly connected with rivers and streams or within a few hundred meters of the river.Less consideration has been given to the importance of elements at larger spatial-scales (Allan,2004;Marzin et al.,2013).With increasing human disturbance in catchments and riparian zone corridors,later studies related to the/10.1016/j.ecolind.2017.08.053Received 20November 2016;Received in revised form 22August 2017;Accepted 22August 2017⁎Corresponding author at:Institute of Wetland Research,Chinese Academy of Forestry,Beijing 100091,China,and Beijing Key Laboratory of Wetland Services and Restoration,Beijing 100091,China.1These authors contributed equally to this work.E-mail addresses:wetlands108@ ,lkyclj@ (L.Cui),wetlands207@ (W.Li).Ecological Indicators xxx (xxxx) xxx–xxx1470-160X/ © 2017 Published by Elsevier Ltd.Please cite this article as: Lijuan, C., Ecological Indicators (2017), /10.1016/j.ecolind.2017.08.053eﬀects of landscape patterns on river ecosystems,such as biodiversity (Sandin and Johnson,2004;Weijters et al.,2009),water quality (Johnson et al.,1997;Tong and Chen,2002)and nutrients in rivers (Udy et al.,2006),have attracted increasing attention(Allan,2004). Studies examined the importance of the inﬂuence of landscape patterns at diﬀerent spatial scales on nutrient dynamics and variations in river water,however have produced inconsistent results(Buck et al.,2004; Dow et al.,2006;Johnson et al.,1997;Sliva and Dudley Williams, 2001).Some scholars believe that the variations in nutrients and river habitat conditions should be examined using catchment-scale landscape patterns due to their inﬂuence on driving the geomorphic processes of a catchment,e.g.,shaping channel network,supplying water and sedi-ments(Esselman and Allan,2010;Frissell et al.,1986;Johnson et al., 1997;Roth et al.,1996),while the others consider that the relationships between river habitat and riparian zone landscape patterns on both sides of a river are much more signiﬁcant.For examples,Peterson et al. (2011)indicated that upstream land use was more inﬂuential in larger streams,while local land use and other factors might be more important in smaller streams;and Sandin and Johnson(2004)concluded that local physical(24.4%)and local chemical(20.4%)variables explained the largest part of the among-site variability of river community assem-blages.Moreover,most of these studies have not highlighted the eﬀects of or seasonal variations in,the natural and anthropogenic factors at multi-scale on river habitat.Multi-scale studies of factors that aﬀect river water chemistry var-iation are mostly focused on reach,local and catchment scale(Frissell et al.,1986;Esselman et al.,2010;Kings et al.,2005;Marzin et al., 2013).For the purposes of this study,reach-scale factors were selected to reﬂect local habitat conditions within≤500m sections of the river channel.Catchment-scale factors were deﬁned as the integrated con-ditions in the landscape upstream of a given sampling location(e.g., percentage of diﬀerent landscape types in a catchment),the geomor-phology condition or the position relative to the sampling location(e.g., mean slope,distance from the river mouth etc.).Local-scale factors were restricted in the river riparian zone indicating the hydrological connectivity or the potential resource/sink for nutrient export from upland to downstream.The present study identify the relative im-portance of reach-,riparian-and catchment-scale landscape factors to variation in water chemistry in Tiaoxi River,one of the main tributaries to Taihu Lake.We then identiﬁed the variables that have most inﬂuence on the river habitat for individual spatial scales,and their combina-tions.By acknowledging the inﬂuence variables on nutrient dynamics at multiple scales and in diﬀerent seasons(before,during,and after rainy seasons),we examined the hypothesis that the impacts of selected variables on nutrients varied seasonally.We anticipated that theﬁnd-ings from this study help basin water resource managers optimize the timing of special management measures,which will eﬀectively control the supply,transport,and transformations of nutrients in catchments.2.Material and methods2.1.Study areaThe Tiaoxi Basin is located in the southwest of the Taihu Lake Basin (E:119°10′–120°11′;N:30°04′–120°02′)(see Fig.1),and is divided into the east and west tributaries.Two tributaries converge at Bai quetang Bridge(hereinafter referred to as the Tiaoxi River)in Huzhou City and then pour into Taihu Lake(Huzhou City Water District,2004).The main channel of Tiaoxi River is157.4km long,and the basin area covers4576.4km2,accounting for12.54%of the total area of the Taihu Lake Basin(36500km2).Tiaoxi River has a large annual runoﬀ(14.93×109m3)and is one of the main tributaries toTaihu Lake (Huzhou Water Resource Bureau,2004).2.2.Sampling sites and water chemistry dataThirty-one river sections(see Fig.1)were selected as sampling sites in the main channels and tributaries of the Tiaoxi River.Sampling sites were distributed across the entire study area so that,as far as possible, all the characteristics of the natural geographical environment and the spatial layout of all land use types in the study area were included.We identiﬁed and sampled a reference site1000m upstream of the sam-pling area before formal sampling began where there were no impacts of industrial sewage outlets,livestock excrement,and a domestic waste disposal site.Sampling was completed monthly from July2011to June 2012.Two methods were used to collect water samples,depending on the nature of the river channel at the sampling site.A water collector with a volume of2.5L was used to collect water samples from non-wade able rivers in the middle and lower reaches where the water depth in the center of the river was greater than1.5m.At these sites,the samples were collected from a depth of0.5m and water surface in the center of the channel.The samples were mixed on collection and stored in acid-washed1000mL polyethylene bottles.For wadeable rivers in the upper reaches,water samples were collected using plastic cups from water at the surface on both sides of the river.Once collected,the samples were immediately placed in a portable fridge at4°C and transported to the laboratory,where they were processed and analyzed within48h of collection.The samples were analyzed for total nitrogen (TN),total phosphorus(TP),nitrate nitrogen(NO3e N),and soluble phosphate using the National Standard Methods(Editorial board of Water and wastewater monitoring analysis method,2002).The dis-solved organic carbon(DOC)concentrations were measured with a total organic carbon analyzer(Shimadzu TOC-V).Samples wereﬁltered and the suspended solids on theﬁlter paper were dried for24h at60°C, weighed,fumigated with concentrated hydrochloric acid for24h,and ground.Particulate organic carbon(POC)concentrations were de-termined after a series of treatments in an element analyzer(EA3000 CHNS/O Analyzer).The sum of the POC and DOC concentrations was taken as the total organic carbon(TOC)concentration.The samples were analyzed in the State Key Laboratory of Lakes and Environment, Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences.Based on the multi-year precipitation and runoﬀin the Tiaoxi Watershed(Huzhou Municipal Water Conservancy Bureau,2004),the study period was divided into three periods:before the rainy season from March and May,during the rainy season from June to August,and after the rainy season in November,December and January.All the water quality data were normalized by log10transformations.Results from normality analysis using the non-parametric K-S test showed all the indexes were normally distributed.2.3.Selections of variable2.3.1.Environmental variablesSix natural environmental variables,including altitude,average slope,river discharge,annual precipitation,catchment area,and dis-tance to the river source were used to represent the geomorphic pro-cesses of the sampling location and to determine their potential eﬀects on nutrient dynamics in water(see Table1).Elevation,mean slope, catchment area,and distance to the river source,were derived from spatial analysis of the1:50,000DEM(see Fig.1)of the study area and its derived data using ArcGIS9.3and ARCSWAT software.Annual precipitation data from42hydro-meteorological stations located in and around the Tiaoxi Basin were provided by the Hydrological Bureau of Huzhou City and were processed by the Kriging interpolation method in the geostatistical analysis module of ArcGIS9.3.River discharge data for the middle and lower reaches of the main channel were supplied by the Huzhou Hydrological Bureau,while discharge data for the upstream source streams and other streams were collected using a portableﬂow meter(SonTek/YSI-Tracker).All environmental variable data were log10-transformed before data analysis to ensure that they met the2assumptions of the normal distribution.2.3.2.Reach-scale river propertiesA channel segment is the area between two de ﬁned cross-sections and is the smallest study scale in the study of a riparian zone.To achieve the objectives of this study,the river range was limited to the riparian zone that is within 30m of both sides of the river channel and extends for a distance of up to 500m along the bank.Bank slope,river vegetation type,type of tra ﬃc in the river,water conservation facilities were recorded with a tape measure and GPS instrument.The river types were identi ﬁed using a combination of ﬁeld observation and visual interpretation of high resolution images provided by the Google Earth platform (Quickbird and SPOT images,acquisition date:4July 2003and 4October 2010;resolution of 0.61m and 5m).After ﬁeld investigation and expert judgement,six indicators were selected to indicate the hydrogeomorphic (e.g.,instream habitat,channel form modi ﬁcations)and hydro-connectivity (e.g.,dam,lock)of modi ﬁcations river characteristics (Table 1).Arti ﬁcial embankment refers to the degree of arti ﬁcial hardening of the riparian zone,and re ﬂects the land-use intensity of the near shore.This indicator was classi ﬁed into three types;namely natural (no hardening),semi-natural (partially hardened),and arti ﬁcial (fully hardened).The degree of in-terference of vegetation on the bank slope re ﬂects the vegetation cov-erage on the bank slope,and was divided into four classes,namely 3(<10%),2(10–45%),1(45–85%),and 0(≥85%).The downstream sluice gate re ﬂects the degree of connectivity of river water bodies on the vertical spatial scale,and it was categorized into three classes,de-pending on the type of sluice (Table 1).The river bed habitat dis-turbance re ﬂects the degree of damage to the morphology and vege-tation of the river bed.A good river bed habitat can,to a certain extent,decrease and impede the transport of nutrients in a water body.The main channels in the middle and lower reaches of the Tiaoxi River are rge cargo ships a ﬀect the transportation of nutrients in the water body by disturbing bottom sediment,changing the river bed habitat,and in ﬂuencing the direction of ﬂow.ndscape at the riparian corridor and catchment scalesRiparian corridor refers to the riparian zone within 1000m from both sides of the river channel and extends for a distance of up to 10,000m along the sampling site.Because of its unique spatial struc-ture and ecological functions,the riparian corridor is able to coordinate lateral (from land to water)and longitudinal (upstream to downstream)ﬂows of material and energy by intercepting and ﬁltering sediments,water,and nutrients (Meng et al.,2011)The term catchment-scale refers to the complete basin upstream,including the tributaries,of the stream sampling site.Changes in land use and landscape patterns in catchment areas are a concentrated ex-pression of the integrated action of large-scale human activities (such as the expansion of urbanization,agricultural development,and forest harvesting)and natural factors,and they give rise to a variety of complex interactions between river hydrology,water quality,biological habitat,and aquatic organisms (King et al.,2005;Meng et al.,2011;Ou et al.,2012).Therefore,the catchment landscape pattern can be used as an important proxy of the e ﬀects of natural factors and human activities on the river water chemistry.In this study we used a Landsat TM image that covered the study area (Path/Row:119/39;Date:24May 2010).The images were cali-brated,cropped,and classi ﬁed into six categories:forestland,urban land,cropland,bareland,water,and grassland (see Fig.2).An accuracy assessment showed that the total accuracy was 88.46%,which met the requirements of this study.In this study,the percentage of each land-scape type area was used as a variable to describe land use (see Table 1).The area of the landscape type was calculated with ArcGIS 9.3,and the data from the attribute table of each layer were exported into Excel 2010.The percentages of all the landscape types on both spatial scales were normalized with an inverse sine root-to-square transformation to ensure the data conformed to the normal distribution.2.4.Data analysisSpearman (ordinal variables)and Pearson correlations (quantitative variables)were calculated in SPSS 16.0to determine therelationshipsFig.1.The Tiaoxi River basin.3among catchment physiography,landscape variables at three scales (reach,riparian and catchment),and water quality indices.PCA ana-lysis was also used to describe the spatial distribution of the selected water quality indexes in CANOCO software(version4.5,Plant Research International,the Netherlands).RDA wasﬁrst carried out using CANOCO4.5to determine which multiple scale landscape variables(reach,riparian and catchment)were statistically suitable for explaining variations in the nine selected water quality indices.Statistically important correlations between ex-planatory(e.g.,each possible factor)and response(e.g.,variations of water chemistry)variables were determined using a Monte Carlo per-mutation test(with499permutations in the reduced model;Sadyśet al.,2015).In this case,RDA was applied to evaluate the relative inﬂuence of multi-scale inﬂuence factors on variations of each water quality index for the four periods(the whole study period,before the rainy season,during the rainy season,and after the rainy season).RDA results are presented graphically on biplots,where variations in each water quality index and landscape factor for each spatial scale are shown as arrows and their abbreviated names;the former are pre-sented in gray,most of the latter are indicated in black,and the six physiography variables are indicated by black triangles.The sig-niﬁcance of the correlation between the distribution of changes in the water quality indexes and landscape factors is shown by the length of the arrows.A longer arrow indicates a stronger correlation between them(Sadyśet al.,2015).A vector of relationships(directly propor-tional or inversely proportional)was interpreted from the position of the changed water quality index relative to the end of the arrow.If the water quality indexes were close to the end of the arrows,the corre-lation was positive.If they were on the opposite site,then the corre-lation was negative(Sadyśet al.,2015).3.Results3.1.Variations in water quality variables in the Tiaoxi BasinSummary information on C,N,and P in the Tiaoxi Basin is presented in Table2.During the monitoring period,the TN concentrations in the Tiaoxi River ranged from0.94to9.23mg/L,and the average con-centration was3.59mg/L,1.795times greater than the water quality standard(2mg/L).The average ammonium nitrogen(NH4e N)con-centration was0.38mg/L,which was10.58%of the TN concentration, and was lower than the Class II NH4e N threshold(0.5mg/L).The average concentration of nitrate nitrogen(NO3e N)was2.03mg/L,the maximum concentration was less than7.0mg/L.For all components of TN,NO3e N represented56.55%,and was the main form of TN.The mean concentration of TP was0.11mg/L.Concentrations ranged from 0.01to1.36mg/L and were close to the limit(class II)for phosphorus (1mg/L).The mean POC concentration was200.63mg/L,while that of DOC was only2.39mg/L.Therefore,POC was the main component of TOC.In contrast,the ecological stoichiometric ratios(N:P,C:N,and C: P)of C,N,and P in the Tiaoxi River were much higher than those in the sediments of Taihu Lake,which reﬂected the classic Redﬁeld ratio(Liu et al.,2011;Qu et al.,2001;Redﬁeld,1958;Xu et al.,2010).This in-dicates that there is more C and N in the Tiaoxi River relative to P.As shown in Table2,the ranges of the standard deviation and variability in the water quality variables of the Tiaoxi Basin were wide, indicating that there were large spatial diﬀerences in the concentrations of C,N,and P in river water.Fig.3shows the relationship between the water quality variables and quadrat samples in the Tiaoxi Basin.The ﬁrst principal component mainly reﬂected the characteristics of DOC, TP,NH4e N,and POC,and the C:P and N:P ratios,while the second principal component mainly reﬂected NO3e N and the C:N ratio.There were strong correlations among some water quality variables, e.g., between DOC and TP or between POC and C:N ratio,indicating similar sources and input paths of these water quality variables to the water body.Theﬁgure also demonstrates that water quality variables varied within the diﬀerent quadrats.When the rays of the water quality variables are extended,31squares are vertically projected onto the ray. Using the relative distance from the projection point to the solid arrow as the standard,the value increases in the direction of the arrow and decreases in the opposite direction.For example,the values for TN were largest in quadrats X1,X15,D5,D7,and D10.The squares of X4,X5, D3,and D4were near the origin,which shows that the TN degree was approximately equal to the mean value and the TN degrees for X9,X10, X11and X13were the smallest.These samples roughly correspond to the spatial characteristics from downstream to upstream(Fig.1),but these results also show that the water environment in the lower reaches of the Tiaoxi Basin has gradually deteriorated,the proportion of man-made landscapes has increased slightly,and human disturbance has gradually increased.3.2.Correlations between water quality and variablesTable3shows the correlation coeﬃcients between natural en-vironment characteristics,diﬀerent landscape scales,and water quality variables.Almost all of the environmental variables were signiﬁcantly correlated with TN,and with the N:P and C:P ratios.Correlations with TP,NO3e N,and the C:N ratio were weakest.Out of the variables,the catchment area(CA)was least able to explain the water quality vari-ables,and was only signiﬁcantly and positively correlated with the TN concentrations.The average annual precipitation(AP)was negatively correlated with TN,PO4-P,DOC,and POC,but was positively correlated with the N:P and C:P ratios.The distance to the source(DS)wasTable1Summary statistics of inﬂuence factors at diﬀerent scales.Variable Unit DatatransformationVariable statistics aPhysiographyAltitude(Alti)m Log(x)157.01(14.06–697.00) Mean slope(Slope)%Log(x)25.05(3.97–56.59) River discharge(RD)m3/s Log(x) 5.16(0.38–80.25)Annual precipitation (AP)mm Log(x)1526.15(1316.54–1872.21)Catchment area(CA)km2Log(x)130.20(23.59–355.18) Distance to thesource(DS)km Log(x)0.55(0.19–1.91) Reach-scale variableArtiﬁcial embankment(AE)–No(4)/Partial(13)/Yes(14)Reservoir upstream(RU)–No(18)/Yes(13)Barrier downstream(BD)No(18)/Partial(6)/Yes(7)In-stream freighter (ISF)–No(15)/Slight(5)/Intermediate(6)/High(5)Riparian vegetation modiﬁed(RVM)–No(4)/Slight(8)/Intermediate(13)/High(6)Subﬂuvial habitat modiﬁed(SHM)–No(3)/Partial(17)/Yes(11)Riparian corridor zone landscape%forestland(FOR)%√(arcsin(x))34.67(1.2–85.4)%urban land(URB)%√(arcsin(x))16.28(2.0–61.7)%cropland(CROP)%√(arcsin(x))40.58(10.5–85.1)%grassland(GRAS)%√(arcsin(x))11.00(0.0–13.8)%water(WAT)%√(arcsin(x)) 6.53(0.0–16.4)%bareland(BAR)%√(arcsin(x))0.56(0.0–4.7)Catchment landscape%forestland%√(arcsin(x))57.53(10.77–92.89)%urban land%√(arcsin(x))9.08(1.09–39.22)%cropland%√(arcsin(x))28.09(4.05–67.39)%grassland%√(arcsin(x))0.99(0.05–5.25)%water%√(arcsin(x)) 3.44(0.03–13.03)%bareland%√(arcsin(x))0.81(0.00–4.51)a Modalities for qualitative variables(number of sites)and ranges for quantitative variables(median(min–max)).4positively correlated with both TN and DOC concentrations,and was negatively correlated with the N:P and C:P ratios.The annual average discharge (RD)of the river was positively correlated with TP,NO 3e N,PO 4-P,and POC,and negatively correlated with the N:P and C:P ratios.The TN and DOC concentrations were negatively correlated,the N:P and C:P ratios were positively correlated,and the mean slope (slope)and altitude (Alti)were negatively correlated.The di ﬀerent correlations indicate that the POC concentrations were not correlated with Slope,but were negatively correlated with Alti.There were signi ﬁcant correlations between TP,PO 4-P,and POC and the C:N ratios of all the river reach-scale variables.The arti ﬁcial bank (AE)and cargo ships in the river channel (ISF)were strongly correlated with most of the water quality variables,and were positively correlated with TP,PO 4-P,DOC,and COD and negatively correlatedwith the N:P and C:P ratios.The di ﬀerence between the correlations for AE and ISF possibly means that the AE was also positively correlated with the NO 3e N concentrations,but that the ISF were not correlated with the NO 3e N concentrations.The correlations between the up-stream reservoir and downstream dam were theweakest.Fig.2.Distribution of land use types in the Tiaoxi River Basin.Table 2Summary information of water quality variables in the Tiaoxi Basin.Water quality index Unit Mean Standard deviation Min Max TN mg/L 3.59 1.720.949.23TPmg/L 0.110.140.00 1.36NO 3e N mg/L 2.03 1.300.05 6.99NH 4e N mg/L 0.380.130.140.66DOC mg/L 2.39 2.010.1419.24POCmg/L 200.63137.5341.42928.45N:P (TN:TP)mg/mg 61.9864.21 4.54499.63C:N (TOC:TN)mg/mg 66.7648.048.06346.28C:P (TOC:TP)mg/mg2817.551938.10399.199908.09Note:TOC equals to the sum of DOC andPOC.Fig.3.Biplots from relationships between water quality variables and sampling sites.Note:Arrows with italic letters indicate the nine selected water quality variables.Shallow black dots indicate the 31sampling sites (D1–D15,X1–X16).5At the riparian corridor and the catchment scales,most of the landscape variables were positively correlated with TN,DOC,and the N:P and C:P ratios,but were not correlated with TP,NO3e N,PO4-P, POC,and C:N.The area occupied by woodland was negatively corre-lated with the concentrations of C,N,and P,while the other land use type variables were positively correlated with the concentrations of C, N,and P.3.3.Inﬂuences of multi-scale landscape variables on water chemistry indiﬀerent seasons3.3.1.Through the whole study periodAs shown in Fig.4,at the natural environment,river reach,riparian corridor,and catchment scales,the landscape variables were able to explain39%,36%,38%and39%of the entire variation,respectively, in C,N,and P.The environment and catchment scale variables ex-plained most of the variation,variables at the riparian corridor scale followed,and reach-scale variables explained the lowest percentage of the variation.The inﬂuence of the various landscape variables on the variability of nutrients in the water body is focused on theﬁrst two ordinal axes.At the river reach scale,the original ordinal axis explained 25.8%(permutation F test,P=0.002)of the variation in river water quality caused by ISF and SHM.The correlation coeﬃcients of ISF and SHM with the axis were0.72and0.67,respectively.At the riparian corridor scale,the basic ordinal axis explained30.21%of the variation in the water quality(permutation F test,P=0.002).The water body and grassland,with correlation coeﬃcients of−0.97and−0.84, respectively,were most closely related to the axis.Forestland followed with a correlation coeﬃcient of0.73.At the catchment scale,theﬁrst ordinal axis explained44.39%of the variability in water quality(per-mutation F test.P=0.012)with correlation coeﬃcients of−0.75and 0.79,respectively,between forestland,water and the axis.Out of the river basin environment variables,36.98%of the variability in water quality was explained by the environmental variables in the initial or-dinal axis(permutation F test,P=0.012).The correlation coeﬃcients between AP and DS were the highest,and were−0.75and0.73re-spectively.In addition,the elevation and slope variables were also linked to this axis,with a correlation coeﬃcient of−0.66between the two variables and the axis.3.3.2.Before the rainy seasonAs shown in Fig.5,before the rainy season,the landscape variables were able to explain48%,28%,40%,and39%of the entire variation in C,N,and P at the natural environment,river reach,riparian corridor, and catchment area scales,respectively.Natural environment variables had the greatest inﬂuence on variability of nutrients in river water, followed by the riparian corridor scale and the catchment scale,the inﬂuences of which were similar.The river scale had least inﬂuence. Before the onset of the rainy season,the inﬂuence of the various landscape variables on nutrient variability in the water body was con-centrated on theﬁrst ordination axis,such as the river scale,and the various landscape variable categories can explain13.83%of the water quality variation on theﬁrst ordination axis(permutation F test, P=0.002).The correlations between ISF and SHM and theﬁrst ordinal axis were the strongest,with correlation coeﬃcients of0.59and0.44, respectively,followed by AM with a correlation coeﬃcient of0.41.At the riparian corridor scale,the landscape variables in the initial ordinal axis were able to explain27.15%of the variation in water quality (permutation F test,P=0.002),with correlation coeﬃcients of−0.68, 0.67,and0.65,respectively.At the catchment scale,the landscape variables in theﬁrst ordination axis were together able to explain45% of the variability in water quality(permutation F test,P=0.002).The correlations were strongest between the landscape variables and the areas of cultivated land and water bodies,with correlation coeﬃcients of0.71and0.70,respectively.The natural environment variables (permutation F test,P=0.002)are reﬂected on theﬁrst ordinal axis, and,out of all the environmental variables,the correlations were strongest with DS(r=−0.80),AP(r=0.78),and Alti(r=0.75).Table3Relationships between water quality and selected variables at diﬀerent scales.Variable TN TP NO3PO4DOC POC N:P C:N C:P PhysiographyCA0.44––––––––AP−0.64––−0.35−0.59−0.400.62−0.330.62 DS0.61–––0.62–−0.590.32−0.66 RD–0.330.300.32–0.32−0.37–−0.44 Slope−0.54–––−0.66–0.50–0.65 Altitude−0.53–––−0.60−0.310.53–0.62 Reach-scaleAE0.530.700.540.600.370.44−0.37–−0.57 RU–––––––––BD−0.30––––––––ISF0.600.68–0.370.540.48−0.40–−0.69 RVM–0.670.380.49–0.38–––SHF0.580.640.370.360.560.55––−0.47 Riparian-scale%forestland0.61–––0.660.31−0.50−0.61 %urban land–––0.320.61––––%cropland0.32–––––−0.49–−0.50 %grassland−0.45−0.630.48–0.64 %bareland–––––––––%water0.850.31–0.310.69–−0.57–−0.64 Catchment-scale%forestland0.51–––0.63–––−0.42 %urban land0.59–––0.640.31−0.42–−0.64 %cropland0.64–––0.65–−0.60–−0.69 %grassland−0.62–––−0.64−0.340.64–0.68 %bareland0.51–––0.32–−0.38–−0.39 %water0.780.32––0.660.32−0.60–−0.64 Note:“–”means no signiﬁcant correlations(P>0.05).Listed numbers mean signiﬁcant correlations(P<0.05).Pearson correlations were computed for quantitative variables and Spearman correlations for ordinal variables.6。

安德鲁鱼叉系统（中英对照）

安德鲁鱼叉系统（中英对照）安德鲁鱼叉系统Andrews’ Pitchfork is an instrument consisting of three parallel Trend Lines. This instrument was developed by Dr. Alan Andrews.3 条平行直线的趋势线，由安德鲁博士最先发现。

The first trend line starts in a selected extreme left point (it is an important peak or trough) and is drawn exactly between two extreme right points. This line is the "handle" of pitchfork. Then, the second and the third trend line issuing from two above-mentioned extreme right points (important peak and trough) is drawn parallel to the first one. These lines are "tines" of the pitchfork.左边的峰谷或者峰顶发展出的趋势线是叉把，右边的临近峰值发展出叉的两个尖齿。

In our discussion of Andrews Pitchforks, the terms “price pivot,” and “pivot point” will be used quite often. A pivot point is the location of a price reversal. At a pivot point, price bars change direction. When price changes from an upward to a downward direction, a “top pivot” is formed.When price changes from a downward to an upward di rection, a “bottom pivot” is formed. The following chart gives examples of pivots.Multi-Pivot linesStandard pivot lines (or trend lines) can be drawn by connecting two pivots. However, connecting several pivots creates a multi-pivot line. When drawing a multi-pivot line, it is not necessary to run through the exact high or low of each pivot. It is only necessary to be as close to each pivot as possible. Looking for trend lines that can be drawn through alarge number of pivots is important. The more pivots through which the trend line passes, the more accurate the trend line will be in predicting future support and resistance.一大段英文就一句话：短期的极值点叫做轴心点（附近价格运动受其附近轴心影响），轴心点的连线就是我们常说的趋势线了。

CURRENTS AND THEIR COUPLINGS IN THE WEAK SECTOR OF THE STANDARD MODEL

(4)
which is eﬀective four-fermion interaction with the Fermi constant given √the familiar 2 2 h ℓ by GF / 2 = g /(8mW ). Here Jµ and Jµ are known as the hadron and lepton currents, where
(2)
1 where t3L (i) is the weak isospin of fermion i ( + 1 2 for ui and νi ; − 2 for di and ℓi ) and qi is the charge of ψi in units of e. The three terms in the interaction Lagrangian of Eq. 1 represent the chargedcurrent weak interaction, the electromagnetic interaction and the neutral-current weak interaction respectively. Note that the Lorentz structure involves only vectors and axial vectors; there is no compelling experimental evidence for scalars, pseudoscalars or tensor constructions. The minimal Standard Model as described by Eq. 1 successfully3 explains W and Z decays, neutrino-hadron scattering, neutrino-electron scattering and parity-violating electron-hadron neutral-current experiments, providing that radiative corrections to order α, the ﬁne-structure constant, are applied. In this chapter we will focus our discussion on the charged-current weak interaction in semi-leptonic decays involving quarks and leptons from the ﬁrst family. As an example, consider the decay d → ue− ν e , for which the T -matrix is2

电子水泵系统说明说明书

LNNote,a system may take 24 hours to vent all the air in the system to atmosphere.ATTENTION DO NOT run the pump dry as this will result in bearing failure.Speed RegulatorOutput of the CP range of domestic circulators is by 3 speed control.(Single speed versions are also available)Speed regulator adjustment should only be made with electrical supply switched off.1.It is always preferable to use the lowest performance where this gives circulationsufficient to heat all the heat emitters evenly (uneven distribution of heat may be due to the need to balance the flow of water in each heat emitter).2.If the pump performance requirement is not known start with the lowest pumpsetting.If heat emitters remain cold,or if the boiler inlet and outlet temperature differential (specified by the manufacturers of the boiler) is not achieved increase the flow by adjusting the speed control as shown in fig.7.ATTENTION too high a speed setting may result in pumping over or drawing in air.Important - DO NOT use pump isolating valves for performance control.6.MaintenanceNo routine maintenance is necessary,however,during prolonged shutdown e.g.summer months,it is advisable to run the pump for a few minutes every few weeks.Locked PumpShould the pump fail to start,switch to maximum setting.If the pump still does not start,the manual restart knob can be used to free a locked pump (see manual restart procedure - section 5).Once the pump is running the regulator should be reset to its original position.7.Trouble Shooting GuideFaults and Remedies Pump Fails to Start Check power supply fuses.Check voltage at pump terminals (see pump nameplate data).Check electrical connection wiring procedure (see section 4.3).Check rotor free to rotate (see section 6).Pump Starts but Provides Incorrect Circulation Check pump valves open.Check pump case and system adequately vented (see section 5).Check correct electrical regulator setting (see section 5).NoiseCheck electrical regulator setting and readjust as required (see section 5).Noise due to cavitation can be subdued by increasing the system pressure within the permissible limits.Pump may require 48 hours to attain normal quiet operation.8.Relevant DocumentationSpare PartsNo non-approved replacement parts may be used.Publication CPUK 10/02.Printed in the U.K.PART NO.6479433 (230V)In accordance with our policy of continual product improvement,we reserve theright to amend the specification of these products without prior notice.COMPACTDOMESTICCIRCULA TOR PUMPInstallation and Operating InstructionsCirculating Pumps Ltd,Oldmedow Road,Kings Lynn,EnglandT echnical Helplines (01553) 7648214.3 Electrical Connections ATTENTIONElectrical work to be carried out by competent qualified and licensed electricians in strict conformity to ruling national conditions and local regulations.All wiring and external switchgear to comply with the ruling local regulations in accordance with the latest edition of IEE wiring regulations.Observe pump name plate data.For pump fuse protection use a 3 Amp fuse.A means of disconnection from the power supply having a contact separation of at least 3mm in all poles must be provided.If the pump already has a cable fitted to it,ensure the pump is isolated from the mains before removing the terminal cover.Wiring Proceduree heat resisting 3 x 0.75mm 2 core cable with rubber insulation rated at110ºC minimum.2.Cut cable to required length.3.Remove terminal cover.4.Thread cable through grommet.5.Depress levers to open cable clamps.Connect cable - Brown to L,Blue to N,Y ellow/Green to see Fig 6.6.See Fig 6.7.Refit terminal cover,locating cover onto motor and tighten screws.The cable must not come in contact with the pump body or pipework.W ARNING - ‘THIS PUMP MUST BE EARTHED’missioning/Operation ATTENTIONOpen both valves either side of the pump.In normal operation the pump surface can be hot (up to 125ºC) creating a risk of being burnt.Manual Restart (First Commissioning)During this operation be aware of the risk of scalding from escaping hot water or steam.Before switching the pump on the manual restart Fig 7 should be unscrewed and withdrawn to engage in the motor shaft.Check that the shaft rotates freely ,and that the knob can be seen rotating on initial start up of the circulator.Screw manual restart back in.(CP23/CP43/CP53/CP63 only).V entingWhen the system is filled with water the pump will normally self vent air within a short while of switching on.In cases where the pump venting is slow (identified by pump noise) the pump bearings may be quickly vented by using the manual restart knob.During this operation ensure the pump is switched off.Once the system has filled,switch off the pump,unscrew the manual restart knob applying sideways pressure to the screw until water emerges from it.Screw the manual restart knob back in.Switch pump back on.Fig 6 Plan view of T erminal Arrangement1.General Safety RulesThese instructions are of fundamental importance for the installation,use andmaintenance of these products and must therefore be read before commencing work and then carried out accurately by the installer and end user.Installation and maintenance must be carried out by qualified personnel only .Failure to comply with these safety instructions will cause risk to people and equipment and may invalidate the guarantee.Danger from general causes:Instructions which if ignored could cause damage or impair the function of the pump are highlighted by the word:ATTENTION1.1 Field of ApplicationThe CP range is suitable for open vented or pressurised domestic central heating systems only.1.2 Product DataW eight CP21/23/41/43/51/53 2.8Kg (6.3lbs)W eight CP61/632.9Kg (6.5lbs)Maximum water temperature 110ºC (230ºF)Maximum Ambient temperature 55ºC Maximum static pressure 10 bar(147p.s.i.)(102m water gauge)Max system pressure =Max head m wg from Fig 1 to Fig 4 + Max static pressure 102mwg Minimum recommended flow rate5 l/minOperating conditions - When pumping water at 110ºC the minimumdynamic head should be 11 meters water gauge to avoid cavitation and ensure quiet running.Minimum static head - open vented systems CP pumps may be fitted tosystems with a minimum static head of 300mm provided the pump inlet is adjacent to the neutral point and the water temperature does not exceed 80o C.Fig 1 CP21/23 Performance Curve - 230V ~ 50HzW ater T emperature - 20ºC.For CP21 use speed 3.Fig 2 CP41/43 Performance Curve - 230V ~ 50HzW ater T emperature - 20ºC.For CP41 use speed 3.Fig 3 CP51/53 Performance Curve - 230V ~ 50HzW ater T emperature - 20ºC.For CP51 use speed 3.Fig 4 CP61/63 Performance Curve - 230V ~ 50HzW ater T emperature - 20ºC.For CP61 use speed 3.Supply voltage 230V ~ 50Hz Model Speed Speed W atts Amps SettingRPM Input CP212600600.28CP411950710.30CP5118501040.45CP6118001100.48CP2332600600.2822450450.2012100350.16 CP4331950710.3021550550.2411150400.18CP53318501040.4521400780.351950560.26CP63318001100.4821400830.3711050600.27Dimensions2.Packaging & Handling2.1 Transport and Storage ATTENTIONThe pump must be protected from moisture,and must not be subjected to temperatures outside -10ºC and 50ºC.2.2 Handling ATTENTIONCare must be taken when handling and installing the pump to avoid damaging components.If damage occurs the pump must not be used.Abnormal handling may invalidate the warranty.3.Description of Pump3.1 General DescriptionThe pumps are of a drum motor design using hard coated shaft and bearings supporting a moulded impeller and rotor.Motor cooling and bearing lubrication is carried out by the pumped water.Models offer a single or variable speed setting to allow system requirements to be accurately met.Design and Function/Safety DevicesThe motor windings are impedance protected.A provision for earthing the outer casing is provided.Prohibited Use ATTENTIONThe pump must not be used on secondary hot water services or handling drinking water or handling food related liquids.4.Installation4.1 Electrical Connection Block PositioningIf the electrical connection block is not in a convenient position when the circulator is delivered,the motor head may be rotated prior to fitting.Release the screws on the pump casing and rotate the motor head to its new position.If this is done please check the following :-1.Take care not to remove or damage the ‘O’ring seal between motor headand pump casing.2.Tighten the fixing screws in a diagonal pattern in stages to a final torque of25Kg cm (22lb in).3.Check the motor is still moving freely by loosening the Manual RestartKnob (fig.7) and then withdrawing until it engages in the motor shaft.The motor should then be free to turn with the finger tips.N.B.After use the Manual Restart Knob should be screwed back finger tight into its original position.4.2 System ATTENTIONThe pump must not be installed against wood or any other material which may be effected by heat from the pump.Before installing the circulator ensure all soldering/welding adjacent to the pump is complete,the system has been thoroughly flushed out to remove any foreign matter and that vent and feed pipes are positioned so that the pump will not draw in air or pump over.It is advisable to ensure the impeller is free by rotating manually through the outlet.The pump should not be installed in either a high point in the system where air could collect or a low point where sediment could build up.Pipes on both sides of the pump should be supported to reduce strain and must be correctly aligned prior to installing the pump to reduce the risk of scalding.The pump must be installed with the rotating shaft horizontal (see fig.5)Fig 5 Pump Installation PositionsCheck the direction of flow indicated by an arrow on the pump casing and install the pump between the isolating valves.When replacing a pump maintain the same direction of flow.Use approved makes of additives with corrosion inhibitors only and follow manufacturer’s instructions.Do not leave system empty without protection from corrosion inhibitor.Ensure no fluid drips onto the pump motor or its electrical connections during installation,venting or operation as when the pump is energised this may create a risk of electric shock.76.78046.6105.4130/1801”/1.5”/2”BSP 1200123456712345Q(m /h)H (m )PC1394CP21132112345672345Q(m /h)H (m )PC1393123CP4100123456712345Q(m 3/h)H (m )PC1392123CP510.0012345670.51.01.52.0 2.53.03.54.04.5Q(m /h)H (m )PC1372123CP6112.0 S L O T。

海底一艘沉船的英文作文

海底一艘沉船的英文作文英文回答：Deep beneath the cerulean waves, where sunlight surrenders to darkness, lies a sunken vessel, a relic of a bygone era. Its once-proud hull, now encrusted with marine life, has become a haunt for enigmatic creatures of the deep.The ship's identity remains shrouded in mystery, its secrets swallowed by the unforgiving sea. Was it a merchant vessel laden with exotic goods, or a warship that met its fate in battle? Perhaps it was an intrepid explorer, venturing into uncharted waters in search of new frontiers. Whatever its purpose, the ship's final resting place is a testament to the indomitable spirit of those who sailed before us.Time has taken its toll on the vessel, its wooden structure slowly being consumed by the relentless tide. Yet,amidst the decay, there lies a haunting beauty, a silent symphony of nature reclaiming what once belonged to man. Marine life has made the wreck its home, creating a vibrant ecosystem that teems with life.Schools of silvery fish dart and gleam through the shadowy interior, their scales shimmering like a thousand tiny mirrors. Sponges, anemones, and other colorful invertebrates cling to the ship's hull, adding splashes of color to the otherwise somber surroundings. Curious crustaceans scuttle across the deck, their antennae twitching with anticipation.The wreck has also become a refuge for larger marine creatures. Giant squid hide within its shadowy depths,their tentacles reaching out to ensnare unsuspecting prey. Curious sharks circle the vessel, their sleek bodies casting ominous silhouettes against the dim light. And occasionally, a majestic whale glides past, its mournful song echoing through the water.For the adventurous diver, exploring the sunken wreckis a thrilling experience. It is a journey into a hidden world, where the past and present intertwine in an enchanting dance. As they navigate the ship's labyrinthine corridors, divers can almost hear the echoes of those who once sailed these waters. They can imagine the laughter and camaraderie of the crew, the tension and excitement of battle, and the silent solitude of a solitary voyage.中文回答：在湛蓝的海浪深处，阳光向黑暗投降的地方，坐落着一艘沉船，这是过去时代的一个遗迹。

Evaluation of thermo-mechanical and thermal behavior of full-scale energy foundations

RESEARCH PAPEREvaluation of thermo-mechanical and thermal behavior of full-scale energy foundationsKyle D.Murphy •John S.McCartney •Karen S.HenryReceived:20September 2013/Accepted:12December 2013/Published online:27May 2014ÓSpringer-Verlag Berlin Heidelberg 2014Abstract Eight full-scale energy foundations were con-structed for a new building at the US Air Force Academy.The foundations are being used to demonstrate this tech-nology to the United States Department of Defense and have several experimental features in order to study their thermal–mechanical behavior.Three of the foundations are instrumented with strain gages and thermistors,and their thermo-mechanical response during a heating and cooling test was evaluated.For a temperature increase of 18°C,the maximum thermal axial stress ranged from 4.0to 5.1MPa,which is approximately 25%of the compressive strength of concrete (estimated at 21MPa),and the maximum upward displacement ranged from 1.4to 1.7mm,which should not cause angular distortions sufﬁcient enough to cause structural or aesthetic damage of the building.The end restraint provided by the building was observed to change depending on the location of the foundation.The heat ﬂux per meter was measured by evaluating the tem-peratures and ﬂow rates of a heat exchanger ﬂuid entering and exiting the foundations.The heat ﬂux values were consistent with those in the literature,and the foundation with the three continuous heat exchanger loops was found to have the greatest heat ﬂux per meter.The transientthermal conductivity of the subsurface measured using the temperatures of the subsurface surrounding the foundation ranged from 2.0to 2.3W/mK,which is consistent with results from thermal response tests on energy foundations reported in the literature.Keywords Deep foundations ÁGeothermal heat exchange ÁThermal response test ÁThermo-mechanical behavior1IntroductionHeating and cooling of buildings comprises nearly 50%of the total building energy usage in the USA (Energy Information Administration)[8].Ground-source heat exchange (GSHE)systems are an approach to reduce the energy demand of heating and cooling systems compared with conventional air-source heat pump systems.The most common GSHE system involves the use of a closed-loop heat exchanger to transfer heat between the subsurface soil or rock and an overlying structure,taking advantage of the relatively constant natural ground temperature below the depth of seasonal variation [6].The subsurface below a depth of 4m generally has a relatively constant tempera-ture approximately equal to the mean annual air tempera-ture at a given location which contributes to making the efﬁciency of a GSHE system higher than that of an air-source heat exchange system [13].Although conventional ground-source heat exchange (GSHE)systems have been used for many years,the additional cost of drilling deep boreholes for the sole purpose of exchanging heat with the ground has rendered this technology cost-prohibitive in some situations [12].Energy foundations are a feasible approach to enhance implementation of GSHE systems by reducing installationK.D.Murphy ÁJ.S.McCartney (&)Department of Civil,Environmental,and ArchitecturalEngineering,University of Colorado Boulder,428,Boulder,CO 80309,USAe-mail:john.mccartney@ K.D.Murphye-mail:kyle.murphy@K.S.HenryDepartment of Civil Engineering,United States Air Force Academy,Colorado Springs,CO 80840-6232,USA e-mail:karen.henry@Acta Geotechnica (2015)10:179–195DOI 10.1007/s11440-013-0298-4costs through taking advantage of initial construction activities[1,6].In this study,energy foundations refer to drilled shaft foundations constructed with a set of closed-loop heat exchangers attached to the inside of the rein-forcement cage so that they can serve the dual purposes of providing structural support and providing access to ground thermal energy.While energy foundations are gaining popularity throughout the world,further research is required to fully understand their performance in terms of thermal response and thermo-mechanical behavior in dif-ferent soil proﬁles.This paper focuses on the character-ization of a series of eight energy foundations installed in an unsaturated sandstone deposit.2Background2.1Thermo-mechanical BehaviorAs a deep foundation is loaded mechanically,the axial stress is expected to be highest at the head and decrease with depth as side shear resistance is mobilized at the soil–foundation interface.The axial stress will decrease to zero if the side shear resistance is sufﬁcient to support the building load;if not,it will decrease to a nonzero value, and there will be end-bearing resistance in the material underlying the toe of the foundation.As an energy foun-dation is heated or cooled,the reinforced concrete will tend to expand or contract axially about a point referred to as the ‘‘null point’’[14].The null point is the point of zero axial displacement during heating or cooling,and its location depends on the stiffness of the end boundaries imposed by the overlying superstructure and the material beneath the toe,as well as the distribution of mobilized side shear resistance[2,4].It is also likely that radial expansion of the foundation will occur as the foundation is heated[15], which may result in a net increase in ultimate side shear resistance[21,26].The upper limit on the thermal axial strain e T in an energy foundation is the free-expansion(i.e.,unrestrained) thermal axial strain e T,free,deﬁned as follows:e T;free¼a c D Tð1Þwhere a c is the coefﬁcient of linear thermal expansion of reinforced concrete and D T is the change in temperature. For geotechnical engineering purposes,the thermal axial strain is deﬁned as positive during compression. Accordingly,a c is deﬁned as negative because structural elements expand during heating(i.e.,positive D T).For the case that an energy foundation is restrained from moving such that the actual thermal axial strain e T is less than that predicted by Eq.1,the thermal axial stresses r T can be calculated as follows:r T¼Eðe TÀa c D TÞð2Þwhere E is the Young’s modulus of reinforced concrete. For energy foundations,soil–structure interaction mecha-nisms will restrict the movement of the foundation during heating.The side shear resistance,end bearing,and building restraint will inﬂuence the distribution in ther-mally induced stresses and strains[22].Soil–structure interaction mechanisms of energy foundations have been studied in centrifuge-scale tests for simpliﬁed soil proﬁles Table1Results of previous studies on thermo-mechanical behavior of energy foundationsCase Laloui et al.[15]Bourne-Webbet al.[4]McCartneyand Murphy[20];Murphy[23]Site stratigraphy Alluvial soil,sand,andgravel,founded insoftsandstone,groundwatertable nearsurfaceGranularﬁlland sand,founded instiffﬁssuredsilty clay,groundwatertable at adepth of3mUrbanﬁll,sand,andgravel,founded inshale,locations ofperchedgroundwaterLoadmechanism atfoundationheadFreeexpansion,buildingdead loadLoad frame Building deadloadFoundationdiameter(m)0.880.560.91Foundationlength(m)25.82314.8(A),13.4(B) Mechanical loadduring heatingtest(s)(kN)0,130012003840(A),3640(B)Range of D T(°C)?20.9,?13.4-19.0to?29.4-5.0to?14.0Depth ofminimumthermal axialstrain duringheating(m)21.017.011.6Minimum/maximumthermal axialstress(MPa)2.1-0.8to1.9-1.0to4.0Maximumincrease inthermal axialstress withtemperature(kPa/°C)104192285Range in headdisplacements(negative isupward)(mm)-4.2,notmeasured4.0to-2.00.4to-0.8[21,30].However,evaluation of full-scale foundations imposes a set of real boundary conditions and soil strata. Several full-scale energy foundations have been evaluated to study the thermo-mechanical stresses and strains during mechanical loading,heating,and cooling[2,4,15,16,20] (Table1).The thermal axial stress ranges from-1to 5MPa,and the thermal axial displacement of the founda-tion head ranges from-4.2mm upward to?4.0downward. The axial stresses are well within the compressive strength of reinforced concrete,and the axial displacements of the foundation would not lead to signiﬁcant angular distortions to cause architectural damage for most buildings.2.2Thermal behaviorThe thermal behavior of energy foundations depends on many factors,including the thermal properties of individual materials in the GSHE,site stratigraphy,groundwater and itsﬂow,heat exchanger conﬁguration within foundation and dimensions of the energy foundation,and thermal demands of the building[6].To optimize the design of GSHE,the system thermal conductivity,speciﬁc heat capacity,borehole resistance,and heat exchange rate must be evaluated accurately[27].For the purposes of this study, the primary mode of heat transport in the soil surrounding energy foundations is assumed by conduction.There is little to no groundwater present in the soil proﬁle of the foundation installations;hence,groundwaterﬂow(and convective heat transfer)is considered to be negligible. The heatﬂux from an inﬁnitely long cylindrical source is given by:Q¼À2p Rl k d Td rð3Þwhere Q is the heatﬂux in Watts being supplied to the energy foundation,R is the radius of the energy foundation, l is the length of the energy foundation,k is the thermal conductivity of the medium in contact with the cylindrical source,and d T/d r is the temperature gradient in the radial direction.As theﬂuidﬂow rate through the heat exchanger pipes is sufﬁcient to lead to a turbulentﬂow pattern,con-vection is assumed to be the predominant mechanism of heat transfer within theﬂuid.Conduction is assumed to be dominant through the heat exchanger pipe walls,concrete, and into the ground.As it is difﬁcult to measure the thermal properties of the individual soil layers and materials in energy foundations,they are typically characterized using a system value.Thermal response tests(TRTs)are the most common method of determining thermal properties of the subsurface and energy foundation system[6].Thermal response test-ing of geothermal borehole heat exchangers has been in use for several years[28]and involves circulating aﬂuid through a heat exchanger while supplying a constant amount of power to theﬂuid.During a TRT,the temper-atures of theﬂuid entering and exiting the foundation are monitored over a period of several days.The measured values of theﬂuid supply and return temperatures and the massﬂow rate through each foundation can be used to calculate the input heatﬂux in Watts,as follows:Q¼D T fluid_V q fluid C fluidð4Þwhere D Tﬂuid is the difference between the supply and returnﬂuid temperatures in K(T supply and T return,respec-tively),_V is theﬂuidﬂow rate in m3/s,qﬂuid is the mass density of theﬂuid kg/m3,and Cﬂuid is the speciﬁc heat capacity of theﬂuid in J/(kgK).The heatﬂux density can be calculated by dividing Eq.(4)by the cross-sectional area of the heat exchanger tubing.Several studies have used simple analytical solutions to investigate the thermal behavior of full-scale energy foundations in different soil types with various heat exchanger loop conﬁgurations and foundation geometries [7,9,10,17,25].The results of these studies are sum-marized in Table2.The system thermal conductivity val-ues reported in these studies range from2.4to6.0W/mK, which is much higher than the thermal conductivity of most geological and structural materials,suggesting that the thermal conductivity values may incorporate the effects of the heat capacity of the concrete and may not represent steady-state conditions[18].In these studies,the TRT was performed at the head of the foundation before the building has been constructed.However,there has not been a thorough evaluation of TRT results on foundations after construction and plumbing is complete.The fact that the tubing used to connect the energy foundation to the heat pump is often not insulated for practical construction pur-poses means that the heat exchange response of the energy foundation system may be affected by ambient surface ﬂuctuations.3Project description3.1Building descriptionA one-story,shower-shave building was constructed at the Field Engineering and Readiness Laboratory(FERL)of the US Air Force Academy(USAFA)beginning in March 2012.The building provides restrooms,showers,and laundry facilities for100people.The building will also be used to evaluate the performance of energy-efﬁcient tech-nologies to aid in the development of‘‘net zero’’-energy-consuming structures for the US Department of Defense (DoD).These technologies include energy foundations,a radiant in-ﬂoor heating system,solar photovoltaic panels,and a solar water heating system.Each component will be continuously monitored to evaluate the energy usage or output of each technology.In addition to the ground-source heat pump coupled with the energy foundations,the building contains a natural gas boiler heating system. Having both conventional and ground-source HVAC sys-tems permits comparison of their energy efﬁciencies under similar environmental conditions.3.2Subsurface conditionsA site investigation was performed in September2011by Hernandez[11],which consisted of two102-mm-diameter borings located within the building footprint,extending12 and7m below the ground surface.At selected intervals, disturbed samples were obtained by driving split-spoon with a622.75N hammer falling762mm.Penetration resistance measurements were made during driving. Exploration results from both boreholes were similar and showed three prominent strata,and relevant data are shown in Table3.The thermal conductivity values were measured on the split-spoon samples of soil using a thermal needle and provide a preliminary estimate of the thermal con-ductivity of the subsurface strata.The top layer is approximately1m thick and consists of sandyﬁll.Beneath theﬁll is a very dense1-m-thick sandy gravelly layer.The bedrock is Dawson–Arkose(sandstone)extending to the maximum depth explored.No groundwater was encoun-tered during the site investigation or foundation installa-tion,so it is assumed to be at a depth greater than16m.3.3Energy foundation descriptionsEight drilled shafts,each15.2m deep by0.61m diameter, provide the foundation support for the structure,as shown in Fig.1a.The one-story building could have been con-structed with a shallow foundation,so the main purpose of incorporating the deep drilled shafts into the building was to evaluate the thermo-mechanical response of the energy foundations for this research project.Each foundation contains a0.46-m-diameter steel reinforcing cage that extends the full length of the shaft.The reinforcing cages are composed of six#7longitudinal bars with#5radial hoops spaced at0.3m on center throughout the length of the cage.The top of the shafts is spliced into a0.91m deep by0.61m wide grade beam that extends around the perimeter of the building.Each foundation contains a heat exchanger loop consisting of19-mm-diameter HDPE tub-ing.At the top of each foundation(i.e.,1m below grade), the heat exchanger loop is connected with tubing,which is routed through the grade beam(Fig.1b)into a manifold within the mechanical room of the building(Fig.1c).Table2Summary of TRT results from previous studiesCase Hamadaet al.[10]Ookaet al.[25]Gao et al.[9]Lennon et al.[17]Brettmann andAmis[7]Foundation type269DP29DS19DS49DP39ACIP Foundation length(m)9202512-1718.3 Foundation diameter(mm)300(square)1500600244(round),270(square)300-450#Heat exchanger loops1,2,Indirect/Direct Pipe81-312TRT analysis method N/A N/A Num.method Line source Line source Thermal conductivity(W/mK)N/A N/A 5.8–6.0 2.4–2.6 2.5–2.6 Heat exchange rate(W/m)54–69(ext.)100–120(rej.)44–52(ext.)57–108(rej.)N/A73–80(rej.) DS drilled shaft,ACIP auger cast in place pile,DP driven pile,Rej heat rejection into foundation,Ext heat extraction from foundationTable3Summary of stratigraphy encountered during subsurface exploration at USAFALayer Depth to bottomof stratum(m)MaterialencounteredGravimetric watercontent(%)Dry unit weight(kN/m3)SPT N-Value(blows/300mm)Thermal Conductivity(W/mK)11Sandyﬁll w/silt,gravel518.470 1.11822Dense sands,silt,gravel719.2850.785 312?Sandstone N/A N/A50/25.4mm 1.233The heat exchange tubing was attached to the inside of the reinforcing cages such that the inlet and outlet tubes were separated diametrically by at least 90°,which minimizes thermal short circuiting from the inlet to outlet tubes.The reinforcing cages were lifted with a 3-point pick to minimize bending,and the cages were lowered into the hole with a crane and were suspended on wooden beams to ensure that the top of the cage was at the base of the grade beam.A concrete pump truck was used to place high-slump concrete with a compres-sive strength (f 0c )of 21MPa in the holes following placement of the reinforcing cages.A tremie pipe was used to avoid excessive segregation of the concrete during free fall.The use of the tremie also minimized therisk of damage to the heat exchanger loops and embed-ded instrumentation.Each shaft has one,two,or three heat exchanger loops conﬁgured in different ways (Fig.1a).Foundations 1through 4have identical heat exchanger conﬁgurations,with two continuous heat exchanger loops attached to the inside of the steel reinforcement cage.Foundation 5has three individual loops,each having a supply and return line running to the mechanical room;this permits any combi-nation of the loops to be operational in order to evaluate the efﬁciency of multiple loops in a single foundation.Foun-dation 6has three continuous heat exchanger loops with only one supply and return line extending to the manifolds.Foundation 7contains one loop connected to the interior of the reinforcing cage.Foundation 8has a single loop in the center of the foundation to simulate a retroﬁt where a heat exchanger would be inserted into a core hole bored into an existing foundation.This was constructed with a 100-mm-diameter plastic sleeve in the center of the foundation.After curing,a single heat exchanger loop was inserted into the plastic sleeve and the hole was grouted with sand bentonite grout.3.4InstrumentationInstrumentation was incorporated into three of the eight energy foundations to capture the distribution of axial strain and temperature with depth.Foundations 1and3Fig.1a Plan view of the building with the locations of the different energy foundations;b heat exchanger tubing conﬁguration in grade beam prior to concrete placement;c manifold detail prior to installation ofinsulationFig.2Measurements from Foundation 4during building construc-tion:a proﬁle of seasonal temperature variations;b proﬁles of axial strain during foundation curing and building loading,with strains due to mechanical loadingcontain six Geokon Model4200vibrating wire strain gauges(VWSGs),while Foundation4contains twelve,at the depths shown in the legend of Fig.4.Foundation4has twice the number of gauges to capture detailed strain and temperature distribution.At three locations within Foun-dation4,gauges were located at the same depth on oppo-site sides of the reinforcing gage to gain redundancy in temperature and strain readings and to capture any differ-ential strain measurements across the width of the shaft. All of the gauges were oriented vertically and attached to brackets welded to longitudinal steel reinforcing bars.The sensor cables were routed to the mechanical room where they are connected to the data acquisition system.Tem-perature variations in the soil surrounding the energy foundations are monitored using a series of ten Geokon model3810thermistor strings that each has six thermistors spaced equally over the same length as the foundation, installed in boreholes that were then backﬁlled with CETCO high thermal conductivity grout at the locations shown in Fig.1a.The temperatures around Foundations3 and4are monitored using four thermistor strings each, with additional thermistor strings located beneath theﬂoor slab and outside the building footprint.3.5Ambient ground temperatures and constructionstrainsSeasonal temperature versus depth in Foundation4was recorded at various times over the course of a year (Fig.2a),as were the axial strains(Fig.2b).The depths in thisﬁgure(and otherﬁgures)are measured from the bot-tom of the grade beam,which is0.91m below the ground surface.Ground temperaturesﬂuctuate between5and 16°C near the surface and then become relatively stable at a temperature of9°C at depths below4m.The axial strains measured in July2012reﬂect the impact of concrete curing,with some tensile strains observed near the head of the foundation.Construction of theﬂoor slab,walls,and roof occurred in Fall2012,reﬂected in the increase in axial strain at the head of the foundation.The difference in the strain proﬁles between February2013and July2012was assumed to be equal to the mechanical strain in the foun-dation due to the majority of the building load.The strain decreases with depth as expected,with a maximum strain corresponding to an axial load of833kN.Similar behavior was noted from the temperatures and strains measured in Foundations1and3.3.6Testing schemeA series of thermal response tests were performed on individual and groups of foundations after the building was constructed.Speciﬁcally,an11kW thermal response test unit was used to circulate and heat a20%propylene glycol–water mixture through the foundations.The TRT unit is comprised of four heaters,two rated at2.5kW and two at3kW.A combination of heaters may be activated to achieve a nominal heat input to the heat exchangeﬂuid ranging from2.5to11kW.Fluid properties of the glycol mixture are shown in Table4.The heatedﬂuid passed into the supply header,circulated through the foundations,and then passed out of return header back to the test unit.The ﬂow rate of each foundation was measured at one instance during the test on each foundation from the pressure/tem-perature ports(P/T ports)using a differential pressure meter at aﬂuid temperature of30°C.The differential pressure was then used to compute theﬂow.During the test,the inlet and outlet temperatures of the heat exchanger ﬂuid for each foundation were continuously monitored using pipe plug thermistors installed within ports on the manifold.A series of seven test stages were performed to investigate the thermal response of various components of the energy foundation system at USAFA,as summarized in Table5.In each stage,a nominal heat input was selected to avoid heating any foundation component too rapidly.Stage1involved heating Foundations1–4 simultaneously.Since each of these foundations has an identical loop conﬁguration within the foundation itself, the effects of the horizontal length of tubing required to connect each foundation to the manifold(called‘‘run-out length’’)were documented[24].Stage1operated for 498h with the intent of allowing sufﬁcient time to increase the temperature of the soil surrounding the foundations and to observe the temperature rise in the boreholes3–10.Stages2–4were conducted on Founda-tions6–8individually with a nominal heat input to the ﬂuid of5kW and duration of approximately1week for each stage.Stages5–7were conducted on Foundation5, which has three individual loops that can be turned on and off at the manifold.Stage5operated on only Loop5A. During stage6,Loop5B was activated while continuing to passﬂuid through Loop5A.In stage7,all three loops in Foundation5were switched open so thatﬂow was permitted to pass through all three loops.Stages5–7uti-lized a2.5-kW heater in the thermal response test unit. The input heatﬂux was calculated using Eq.(4)for each heat exchanger loop during each stage.Table4Heat exchangeﬂuid propertiesWater-to-propyleneglycol ratioMolar heatcapacity(J/molK)Molecularweight(g/mol)Speciﬁc heatcapacity(J/kgK)Fluiddensity(g/ml) 5:198303267 1.0084Thermal response test resultsTheﬂuid temperatures versus elapsed time plots are shown in Fig.3.The differences inﬂuid temperatures,D Tﬂuid,are also plotted on the right vertical axis for each foundation. In all cases,a relatively rapid rise in temperature was observed in theﬁrst25h.At one segment during stage1, the data acquisition system malfunctioned and is repre-sented by a gap in the data(Fig.3a–d).A constant D Tﬂuid value reﬂects uniform heat input energy into the system, and these conditions prevailed after about100h of testing in each stage.Note that the differential temperature is greater for longer horizontal run-out lengths,indicating that heat exchange occurs in the grade beam and can have an impact on heat exchange performance.The temperatures of the three instrumented foundations at different depths are shown in Fig.4a–c.The thermistor at the bottom of each of the foundations showed a sub-stantially lower increase in temperature than in the rest of the foundation.This may be due to denser rock at the toe of the foundation,potential rises in the water table at the time of testing,or the geometry of how the heat exchangers were routed to the U-connector at the base of the founda-tion.After approximately498h of heating,ﬂuid circula-tion in Foundations1–4was stopped,and the temperatures in the foundation were monitored during the cooling pro-cess.The deeper portions of the foundations cooled more rapidly,as they were not inﬂuenced by the warm ambient air temperature at the ground surface.The foundations returned to their original temperatures after approximately 700–1,000h after the end of heating.Fluctuations in the uppermost thermistors during cooling reﬂect the impact of the seasonal ground temperatureﬂuctuations.Foundation heating led to an increase in ground tem-peratures measured by the thermistor strings.The temper-atures measured in Borehole1,located at a distance of 4.6m outside of the building footprint,are shown in Fig.5a.The temperatureﬂuctuations occur only near the surface and appear to be due to hot weather.The temper-atures measured in Borehole2,located under the building slab in the center of Foundations1–4,are shown in Fig.5b. Although some changes in temperature near the top of the borehole appear to correspond with the increase in surface temperature during the summer,the temperature of the subsurface at the bottom of the borehole experienced an increase in temperature by about2°C below a depth of 8m likely due to the heating of the subsurface due to the operation of Foundations1–4.After stage1ended,the borehole temperature slightly decreased and remained nearly unchanged from8/15/13to9/4/13.The temperatures measured in Boreholes3through6, which are located at different radial distances from Foun-dation4,are shown in Fig.6.The temperatures at1.2m from the center of Foundation4(Fig.6a,b)increase more rapidly than those located at2.4m from the center of the foundation(Fig6c,d).The temperatures under the build-ing slab were affected less by changes in the surface temperature than those that were not under the building slab.This suggests that theﬂoor slab acts as an insulator. This effect may be enhanced after the heating system in the building is used to maintain a constant temperature within the building envelope.Although the results shown in Table 6provide a preliminary evaluation of the thermal response of energy foundations,a more in-depth analysis of the thermal resistance of the different energy foundations will be investigated in the future using the concepts of thermalTable5Summary of thermal response testing stages and heat input detailsTesting stage Foundation Testing dates Approximate duration(hours)Nominal heatﬂux applied(kW)Measured heatﬂux Q(kW)112346/18/13–7/9/1349811.0 3.1332.6962.1802.081267/11/13–7/18/13175 5.0 4.534 377/18/13–7/25/13167 5.0 4.431 487/25/13–8/1/13165 5.0 4.075 55A8/1/13–8/5/13119 2.5 2.28565A5B 8/5/13–8/28/13530 2.5 1.1641.15075A5B5C 8/28/13–9/4/13163 2.50.7970.8031.201。

CREATING KLEIN BOTTLES BY SURGERY ON KNOTS

2. Slopes
Throughout this paper, we will assume that K is a knot in S 3 , which is not cabled. b Suppose that K (r) contains a Klein bottle P for some slope r. We can assume b intersects the attached solid torus J in a disjoint union of meridian disks of that P b b J , and that P is chosen so that p = jP \ J j is minimal among all such Klein bottles b \ E (K ) is a punctured Klein bottle properly embedded in in K (r). Then P = P E (K ) with j@P j = p. Note that p is odd. If not so, E (K ) would contain a closed non-orientable surface obtained by attaching suitable annuli in @E (K ) to P along @P , a contradiction. P E (K ) Assume that P is compressible in E (K ). Let D be a disk in E(K ) with @D is essential in P . Note that @D is an orientation-preserving loop in P . There are two cases.

蜿蜒式鱼道与竖缝式鱼道的水力特性对比分析

第43卷第6期2020年11月河北农业大学学报JOURNAL OF HEBEI AGRICULTURAL UNIVERSITYVol.43 No.6Nov.2020蜿蜒式鱼道与竖缝式鱼道的水力特性对比分析刘辉，郄志红，吴鑫淼（河北农业大学城乡建设学院，河北保定 071001）摘要：为分析1种新型近自然型鱼道——蜿蜒式鱼道的水力特性，分别对新型蜿蜒式鱼道和工程型竖缝式鱼道进行了CFD数值模拟计算，对比了2类鱼道结构在不同水深处流态、流速及紊动能等水力学方面的特性。

结果表明：2种鱼道均主流明确，流态分区明显，区别是主流所处位置不同，蜿蜒式鱼道结构主流最大流速轨迹线明显靠近池壁，增大了低流速区与回流区面积；在相同坡降J下，竖缝式鱼道池室内在横向上表现为中间流速高两侧流速偏低，而蜿蜒式鱼道表现出右侧区域近靠壁位置流速高左侧区域流速偏低规律；在竖缝式鱼道中，不同水深处的紊动能分布基本相似，蜿蜒式鱼道也有此规律，但池室紊动能值明显偏小，蜿蜒式鱼道最大紊动能值仅为竖缝式鱼道的61.3%，降低了对鱼类上溯的影响。

关键词：蜿蜒式鱼道；竖缝式鱼道；水力因子；CFD数值模拟中图分类号：TV131开放科学（资源服务）标识码（OSID）：文献标志码：AComparison and analysis of the hydraulic characteristics between themeandering fishway and the vertical slit fishwayLIU Hui, QIE Zhihong, WU Xinmiao(College of Urban and Rural Construction, Hebei Agricultural University, Baoding 071001, China) Abstract：In order to analyze the hydraulic characteristics of a new type of near-natural fishway—meanderingfishway, the CFD numerical simulation was carried out for the new meandering fishway and the engineering verticalslit fishway respectively. The hydraulic characteristics of the two kinds of fishway structures in different depths, flowpattern, velocity and turbulent kinetic energy, were compared. The results show that: the main stream of the two kindsof fishway is clear and the flow pattern has obvious zonal phenomenon, but the position of the mainstream is different.The maximum velocity trajectory of the mainstream in the meandering fishway is obviously close to the pool wall,which increases the area of low velocity zone and recirculation zone. On the condition of the same slope J, theflow velocity in the vertical slit fishway is higher in the middle area and lower in the two sides area, while the flowvelocity in the meandering fishway is higher in the right area and lower in the left area. In the vertical slit fishway,the distribution of turbulent kinetic energy in different depths is similar, and the same rule exists in the meanderingfishway. However, the turbulent kinetic energy value of the meandering fishway is obviously smaller than that of thevertical slit fishway. The maximum turbulent kinetic energy value of the meandering fishway is only 61.3% that ofthe vertical slit fishway, which reduces the impact on upstream swimming of fishes.Keywords: meandering fishway；vertical slit fishway；hydraulic factor；CFD numerical simulation文章编号：1000-1573(2020)06-0126-06DOI：10.13320/ki.jauh.2020.0122收稿日期：2020-04-30基金项目：河北省自然科学基金项目（E2017204125）；河北省教育厅在读研究生创新能力培养资助项目（CXZZSS2019057）；河北省水利科研和推广计划项目（2018-29）.第一作者：刘辉（1994-），男，河北张家口人，硕士研究生，主要从事水工结构优化设计. E-mail:*****************通信作者：郄志红（1969-），男，河北徐水人，博士，教授，主要从事水工结构工程研究. E-mail:******************本刊网址：http: // hauxb. hebau. edu. cn: 8080 /CN/ volumn / home. shtml127第6期鱼道是1种能够使被拦河建筑（如水闸、大坝等）阻断的江河重新连通，为鱼类提供洄游路径的专门水工建筑物，具有维系江河上下游水生态的作用。

基于设定用水模式的小型热水系统计算

1引言建筑热水系统的核心计算问题是系统设计小时耗热量及水加热设施储热量(为简化分析起见,本文只涉及闭式热水罐,不涉及开式热水箱),系统的供水能力是由二者耦合作用决定的。

水加热设施储热量按GB 50015—2019《建筑给水排水设计标准》[1](以下简称《建水标》)第6.5.11条取值。

一般公建类工程耗热量按《建水标》中公式(6.4.1-1)计算:Q h =K h mq r C (t r -t 1)p r C y /T(1)式中,Q h 为设计小时耗热量,kJ/h ;m 为用水计算单位数(人数或床位数);q r 为热水用水定额,L/(人·d )或L/(床·d );C 为水的比热,kJ/(kg ·℃);t r 为热水温度,℃,t r =60℃;t 1为冷水温度,按《建水标》表6.2.5取用;p r 为热水密度,kg/L ;T 为每日使用时间,h ,按《建水标》表6.2.1-1取用;C y 为热水供应系统的热损失系数,取1.10~1.15;K h 为小时变化系数,可按表1取用。

规范规定“使用人(床)数小于或等于下限值及大于或等于上限值时,K h 就取上限值及下限值,中间值可用定额与人(床)数的乘积作为变量内插法求得。

”如宾馆类项目,即使使用人数很少,K h 值最大为3.33。

2019版《建水标》没有说明该值的来源。

查阅2003版《建水标》,宾馆类项目K h 值最大为6.84,与2019版《建水标》的K h 值相差巨大,规范对其也没有解释。

根据分析,K h 值应该具有经验数据性质。

从定性角度看,系统设计小时耗热量及水加热设施储热量公式为半理论半经验公式,具有与用水过程无关联的特点,对于较大的建筑热水系统,该公式计算逻辑合理,经过大量的工程实践,其计算结果可靠,可以满足使用要求。

小型热水系统用水人数少,用水差异性大,有可能在较短时间内完成洗浴用水过程。

如别墅式客房,只有几间客房,有【作者简介】曾杰（1968~），男，浙江德清人，高级工程师，从事建筑给水排水、建筑消防给水及高级住宅设计与研究。

Karl Fischer水分定量法简介说明书

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The Temperature Scan func-tionality speeds up the analysis of unknown samples by deter-mining, in just one single run, the optimum temperature for heating the sample.Improved productivity in less spaceThis approved applicationallows easy and accurate water determination of solid or viscous samples, for example:• Substances releasing water only at elevated temperatures: plas-tics in powder or granular form • Substances causing side reac-tions with Karl Fischer reagents: oxidizing inor g anic salts• Substances causing problems in the titration vessel due to their consistency: fibrous or pasty substances• Substances poorly soluble or insoluble: lubricants, wool, dough, tar or coalGas phase extraction11Precise and efficientThe InMotion KF Oven Autosampler allows for up to 26 samples to be analyzed using the gas extraction technique. Sample preparation is simplified by the innovative one-piece cap, which does not necessitate the use of extra tools or adhesive membranes. Gas flow is controlled elec -tronically, allowing you to monitor the amount of dried gas entering the titration cell. Together with LabX ® software, which ensures full data traceability, these attributes help laboratories meet the most demanding regulatory standards.12G TP™Good Titration Practice ™Reliable ResultsThrough the Entire Life CycleThe foundation for reliable results is laid out long before operation starts: evaluation and selection of the correct system, as well as proper installation and training, is essen-tial. Regular maintenance and calibration means ongoing accuracy and repeatability, and supports the increasing demands of regulatory requirements. For every step of the way, METTLER TOLEDO accompanies you and offers competent support with the right tools to ensure that your investment is secure and the risks are minimized.Evaluation and Selection• Which is the parameter of interest: moisture or water content or dynamic vapor sorption analysis?• Is volumetric or coulometric titration appropriate?• Is combination with general titration needed?• Which application, which method?• How many samples: is automation necessary?• What are the best reagents for the sample?• Which accessories make sense?METTLER TOLEDO has expert knowledge in moistureand water content determination, and offers the right products to fulfill every analytical task.Moisture determination by loss on drying method Moisture determination by Halogene Moisture Analyzers Water determination by Karl Fischer Titration Dynamic vapor sorption by TGA Sorption Analyzer SystemG o o d T i t r a t i o n P r a c t i c e ™13Installation and QualificationProfessional installation and appro-priate user training are key factors in achieving good titration results from day one. Our equipment qualification and software valida -tion products ensure that both your equipment and operators have the perfect start, and that your regula-tory needs are properly fulfilled.• Comprehensive Qualification: The EQPac service supports the highest level of regulatory com-pliance providing IQ, OQ, PQ recommendations, maintenance proposals and initial calibra-tion. Comprehensive documen-tation fulfills all your auditory requirements.• Standard Qualification: The IPac service provides professional installation including IQ, OQ, PQ recommendations, maintenance proposals and system perfor-mance tests. Our standard docu-mentation supports regularly requirements.• Software Validation: The LabX ® validation service provides com-plete and comprehensive software validation. The documentation contains all the evidence required to satisfy any regulatory body.Routine OperationAchieving good titration results re-lies on three key para m eters: the instrument, correct operation and regular service. With the support of METTLER TOLEDO, you've selected the best instrument. Now let us support you in correct operation and regular service:• EduPac: Supplement the Quali-fication Pacs with our EduPac training. The professional training material provides easy-to-follow guidance and practical exercises to support the correct operation of your KF titrator. Together with the expert tuition of a special-ist, learn how to perform routineanalysis with confidence! In ad-dition, the publication "Good Titration Practice ™ in Karl Fischer Titration" gives valuable tips and tricks.• Preventive Maintenance and Calibration: Regular service means confidence in your re-sults, as well as fulfilling quality requirements. Our fully-compliant calibration procedures are docu-mented with professional, easy-to-read certificates. Combined with our Preventive Maintenance service, pre-planned periodic cal-ibration ensures reliable perfor-mance, regulatory compliance, avoids unexpected downtime and protects your budget.14For Every Purpose the Perfect Match Model OverviewM o d e l s & A c c e s s o r i e s15••••TTL TTL RS / TTL RS / TTL ••••••••PC softwareLabX ® Titration Server LabX ® Titration ExpressUSB-P25compact paper roll printerXPE or XSE series analytical balancesUSB printerDV1000 series with volumes of 1, 5, 10 or 20 mLDO308manual ovenTBox DR42for use of a homoge-nizer controlled by TTLAdapter Setfor Kinematica or IKA HomogenizersInMotion KFOven AutosamplersVisco Spoon ™for viscous samplesFor KF titration at elevated or reduced temperatureIncluding Solvent Manager, titration stand, vessel, sensor, tubes and all accessories (only for Titration Excellence)Accessories OverviewSoftwarePrinterBurettesGas phase extraction ovensHomogenizerSampling deviceThermostatable vesselTitrationExcellence Karl Fischer kit(Volumetric or Coulometric)External Dosing Unit to add auxiliary reagentsLogStraightFingerprint ReaderSecurityLevelSensPrevents from waste overflow and warns the user when bottles run dry./titrationFor more informationService and SupportFeel secure in the knowledge that your TitrationExcellence system is installed and qualified according to the quality standards that apply in your company. Ask for one of the qualification products offered by your local METTLER TOLEDO representative in the form of service and accompanying documentation.Titration AutomationTitration puts a high demand on automation due to the large range of sample types and numbers. METTLER TOLEDO automation solutions can run the entire analysis process automatically – from sample preparation to the titration itself and then finally through cleaning/conditioning of the sensor and accessories.LabX ® PC softwareThis market-approved titration software offers full control over your titration systems, secure database archiving, efficient result management with control charts and individual search filters, rapid and clear method development for new applications, andcomplete traceability by providing user management, audit trail, method history and electronic signature.One Click is a Registered Trademark of METTLER TOLEDO in Switzerland, the European Union, Russia and bX is a Registered Trademark of METTLER TOLEDO inSwitzerland, USA, China, Germany and a further 13 countries.METTLER TOLEDO Group Laboratory DivisionLocal contact: /contactSubject to technical changes.© 07/2017 METTLER TOLEDO. All rights reserved. 30265527BMarketing Titration / MarCom Analytical。

布料缩水测试英语

布料缩水测试英语Fabric Shrinkage Testing: An Essential Process for Quality Assurance.Fabric shrinkage testing is a crucial process in the textile industry, ensuring the quality and durability of fabrics. Shrinkage occurs when fabrics undergo changes in moisture, temperature, or both, resulting in dimensional alterations. This can lead to issues such as fit problems in clothing, distortion of patterns, and overall dissatisfaction with the product. Therefore, it is essential to conduct shrinkage testing to assess thefabric's behavior under various conditions and ensure it meets the required standards.The process of fabric shrinkage testing involves several steps. Firstly, it is crucial to select the appropriate testing method based on the type of fabric and its intended use. Common methods include washing test, drying test, and steaming test. Each method simulatesdifferent conditions that fabrics may encounter duringtheir lifecycle.In the washing test, the fabric is washed with water at a specific temperature and then dried. This simulates the shrinkage that occurs when fabrics are washed and dried at home. The drying test involves exposing the fabric to heat in a dryer or oven, simulating the shrinkage that occurs when fabrics are tumble-dried. Finally, the steaming test involves steaming the fabric to simulate the shrinkage that occurs during pressing or ironing.During the testing process, it is important to measure the fabric's dimensions accurately before and after each test. This allows for the calculation of shrinkage percentage, which is essential for comparing different fabrics and assessing their performance. Additionally, itis crucial to follow standard test conditions and procedures to ensure consistent and reliable results.Fabric shrinkage testing not only benefits manufacturers but also consumers. Manufacturers can use thetest results to improve their products, ensuring that they meet the required standards and providing customers with a better experience. Consumers can also benefit from this testing as it helps them make informed decisions when purchasing clothing or other textile products.Moreover, fabric shrinkage testing is essential for environmental sustainability. By ensuring that fabrics shrink to a minimal amount, manufacturers can reduce waste and improve the overall efficiency of production processes. This, in turn, helps reduce the impact of the textile industry on the environment.In conclusion, fabric shrinkage testing is a crucial process in the textile industry. It ensures the quality and durability of fabrics, provides manufacturers with valuable insights into product performance, and helps consumers make informed decisions. Additionally, it promotes environmental sustainability by reducing waste and improving production efficiency. Therefore, it is essential to conduct shrinkage testing regularly and follow standard procedures to ensure consistent and reliable results.。

测量拳头的体积作文英语

测量拳头的体积作文英语Title: Measuring the Volume of a Fist。

Measuring the volume of a fist might seem like a straightforward task, but upon closer examination, it reveals intriguing insights into both the principles of measurement and the intricacies of human anatomy. In this exploration, we embark on a journey to understand the methodologies and considerations involved in quantifying the volume of a fist.To begin with, it's essential to establish a systematic approach to measurement. One common method is displacement, which involves immersing the fist in a container of water and measuring the volume of water displaced. This principle is based on Archimedes' principle, which states that the buoyant force acting on an object submerged in a fluid is equal to the weight of the fluid displaced by the object.The process starts with selecting a suitablecontainer—a graduated cylinder or a beaker with volume markings would be ideal. Care must be taken to ensure that the container is of adequate size to accommodate the fist without overflowing. 。

2024北京高三二模英语汇编：阅读理解C篇及答案

2024北京高三二模英语汇编阅读理解C篇（2024北京顺义高三二模）As biologist Nicola Foster and her colleagues guided a remote-controlled monitor through the coral reefs(珊瑚礁)of the Indian Ocean’s Chagos Archipelago,they saw corals full of color near the surface. But nearly300feet below,in the darker and colder waters of what oceanographers call the“twilight zone,”some corals had turned terrible white,leaving them vulnerable(脆弱的)to disease and death.“It wasn’t something we were expecting to see,”says Foster,who studies deeperwater coral ecosystems called mesophotic reefs.Mesophotic reefs would seem to be protected from rising sea-surface temperatures that white n higher-up corals.But this team’s2019observations show the deepest instance of bleaching(变白)ever recorded—suggesting similar reefs are more vulnerable than previously believed.Bleaching often happens when warming water boosts corals to remove the colorful algae(水藻)that live in their tissues and help to sustain them.Although surface waters weren’t typically warm when Foster and her team took their measurements,the twilight zone waters neared84degrees Fahrenheit(华氏度)—far above the68-to75-degree range in which mesophotic corals are used to.The researchers realized that bleaching is related to the timing of the Indian Ocean Dipole.This phenomenon shifts the region’s surface winds and ocean currents,says study co-author Phil Hosegood.Wind and waves shake the upper ocean, keeping it relatively warm and uniform in temperature.But the2019dipole deepened this well-mixed upper layer;the thermocline(the slice of ocean that separates warm upper waters from the cold depths)had become deeper than normal. Then,those corals were exposed to temperatures that are normally found at the surface.This observation suggests mesophotic reefs elsewhere could also be bleaching.Fortunately,the corals in this study had largely recovered their color by2022,Foster notes.But each bleaching stresses the corals and,if extended,can starve them.Future Indian Ocean Dipole patterns are likely to be more severe,Hosegood says,noting that data suggest“that these natural cycles are becoming increased climate change.”1．What are the first two paragraphs mainly about?A．Corals in twilight zone become vulnerable because of bleaching.B．Corals normally found at the surface were found in twilight zone.C．Mesophotic reefs are much more vulnerable than higher-up reefs.D．Mesophotic reefs and higher-up reefs need different temperature.2．According to the passage,which group of pictures can describe the changes caused by the Indian Ocean Dipole?A．B．C．D．3．Regarding the future of mesophotic reefs,Hosegood probably feels______.A．excited B．worried C．curious D．hopeful（2024北京丰台高三二模）In the United Arab Emirates(UAE),water is more valuable than oil.To support its citizens,the nation relies on expensive campaigns of cloud seeding from aircraft,which spray particles(喷洒微粒)into passing clouds to make rainfall.But according to Oliver Branch,a climate scientist,there may be another method to stir up a rainmaker:with city-size solar farms that create their own weather.The heat from dark solar panels can cause updrafts that sometimes lead to rainstorms,providing water for local people.“Maybe it’s not science fiction that we can produce this effect,”says Branch, who led the work.Few studies have examined how renewable energy might shift weather patterns.In2020,Branch found that incredibly large solar farms,taking up more than1million square kilometers in the Sahara desert,could boost local rainfall. But the reward would come with a cost,the researchers found:By altering wind patterns,the solar farms would push tropical rain bands north.That’s not good news for the Amazon areas.To find more,researchers turned to a weather model that can account for land surface changes.They modeled the solar farms as nearly black fields that absorbed95%of the sunlight,surrounded by relatively reflective sand.When the solar farms reached15square kilometers,they found,the increased heat they absorbed appreciably increased the updrafts,or convection,that drive cloud formation.Hacking convection wasn’t enough,however:damp air was also needed.When conditions were ripe,the model also found,a20-square-kilometer solar field would increase a storm’s total rainfall by nearly600,000cubic meters.If such rainstorms occurred10times in one summer,they would provide enough water to support more than30,000people for a year.Solar farms in China and elsewhere are nearly big enough,Branch says.If they were built in the right spots,it wouldn’t take much to darken the panels and to plant dark crops between panel rows.Still they’re trying to improve the realism of their solar panel simulations by cross-checking them with field measurements at existing solar farms.The UAE“is committed to studying the potentially dynamic strategies,such as optimizing convection,”says Alya Al, director of the UAE’s Research Program.For now,she adds,the UAE is deeply committed to its cloud seeding program, carrying out some300missions each year.4．In his study,Branch attempts to produce rainfall________.A．by way of updrafts formed on solar farms B．by spraying particles into passing cloudsC．by means of relatively reflective sand D．by planting dark crops5．The model is designed to find out________.A．the ripe conditions for building a solar farmB．the realistic size of a solar farm for rainfall increaseC．the annual amount of water consumption in the UAED．the heat absorption rate of the solar panels in the black fields6．What can we learn about Branch’s method?A．It is not supported by the director.B．It needs great investment if applied.C．It remains to be further tested in practice.D．It has promoted cloud seeding in the UAE.（2024北京昌平高三二模）Baleen whales play a vital role in ecosystems.To communicate across vast distances and find each other,baleen whales depend critically on the production of sounds that travels far in dark oceans.However,since whale songs were first discovered more than50years ago,it remained unknown how baleen whales produce their complex vocalizations（发音）.A new study in the journal Nature reports that baleen whales developed unique structures in their larynx（喉）that enable their low-frequency vocalizations,but also limit their communication range.The study was led by voice scientists Professor Coen Elemans and Professor Tecumseh Fitch.“The toothed whales and baleen whales were initially land animals that had a larynx serving two functions:protecting the airways and sound production.However,their switching to living in the water placed new and strict demands on the larynx to prevent choking underwater,”says Tecumseh Fitch.The study shows that baleen whales nevertheless can still produce sound with their larynx,but they have developed new structures to do so,which only exists in baleen whales.“This is probably to keep a rigid open airway when they have to move huge amounts of air in and out during explosive surface breathing,”states Fitch.“We found that this U-shaped structure pushes against a big fatty cushion（垫）on the inside of the larynx.When the whales push air from their lungs past this cushion,it starts to shake and this generates very low frequency underwater sounds,”says Elemans.To understand how muscle activity could change the calls,the researchers built a computational model of the entire whale larynx.The model predicted the natural vocalizations of the whales very well.However,these newly discovered features that allowed whales to successfully communicate in the vast oceans also poses huge physiological（生理的）limits for many baleen bining experiments and models,the researchers provide the first evidence that baleen whales are physiologically incapable of escaping noise caused by humans,because it covers up their voices,and thus limits their communication range.“Unfortunately,the main frequency and depth of man-made noise caused by shipping traffic cover the frequency range and maximum communication depth of100meters that we predicted,”Elemans says.The first voice recordings of a certain whale song by Roger and Katy Payne in1970attracted global interest in sea conservation efforts.The Payne’s made people aware how quiet the seas were before humans started the widespread use of machine ships.Elemans adds:“Compared to the seventies,our oceans are now even more filled with human-made noise, which affects the whales,because they are dependent on sound for communication.Now we show that despite their amazing physiology,they literally cannot escape the noise humans make in the oceans.”7.What can we know about baleen whales’vocalization system?A.Their airways are closed during explosive surface breath.B.Their larynx has difficulty preventing choking underwater.C.Their vocalization system changed when they were land animals.D.Their fatty cushion shakes to make low frequency underwater sounds.8.The researchers’experiments and models show that______.A.baleen whales are incapable of recognizing humans’noiseB.the muscle activity is related to the vocalizations of the whalesC.human-made noises disturb baleen whales’communication rangeD.the bodily features in baleen whales limit their communication depth9.What can we infer from the last paragraph?A.Sea conservation efforts used to be better than now.B.The special structure protects Baleen whales from noises.C.Actions should be taken to regulate human activities at sea.D.The application of technology contributes to sea conservation.（2024北京朝阳高三二模）Science begins with mystery.Arguably,the two greatest mysteries are the universe and awareness—the vast world out there and the powerful world within.Scientists attracted by one can be called to study the other,led by the thought that these mysteries are connected.Science writer George Musser’s book Putting Ourselves Back in the Equation(方程)reviews their progress:Can physics unlock the mystery of awareness?Does awareness form the basis of fundamental physics?The result is an ambitious but ultimately disappointing tour,filled with breathless encounters with well-known scientists.Representative of the cast is MIT’s Max Tegmark,who tells Musser,“If you look at the problems that were still difficult to answer in fundamental physics,pretty much all of them trace back to awareness.”The book shows how physicists are contributing to understanding the mind,continuing a longhistory of physicists exploring other fields.Musser integrates physics with neuroscience,economies,mathematics and more. Yet a key source of local knowledge is obviously absent—psychology.An early example:Musser rightly applauds physicists’contributions to artificial neural networks but is overly trustful of their implications,declaring that“ChatGPT”is already starting to demonstrate a generalized intelligence like that of humans.Interviewing more psychologists could have exposed the considerable gap remaining.What about awareness itself?Why are some states associated with felt experience,such as the pain of a headache and the sight of a sunset,but others not?Musser’s focus is integrated information theory(IIT).IIT begins with five self-evident principles of awareness:awareness exists,and it is structured,specific,unified,and definite.It then concludes assumptions concerning the causal structure of awareness systems,identifying awareness with integrated information.Finally,IIT offers a mathematical measure of this quantity:an equation for awareness.However,despite its enthusiasts,IIT has significant problems.Its working basis is unfounded,and serious doubts surround its testability and definability.Of course,a theory of awareness must detail when,why,and to what degree we are aware of ourselves.Here,psychology’s absence is most obvious.Over the last century,psychological research has revealed countless phenomena of awareness,from models that alter awareness to methods that stimulate unawareness;from extraordinary disorders of awareness to careful studies of metacognition(元认知).Although questionable,such phenomena are the data that any scientific theory of awareness must account for.Yet these phenomena and ideas are almost nowhere in the book.Of course,psychology has not solved awareness,but one cannot hope to explain awareness without confronting these data.Awareness is genuinely mysterious.So is fundamental physics.But hoping that physics can solve awareness while excluding other approaches is only a recipe for more mystery,not less.10.What can we learn from Musser’s book?A.IIT is acknowledged for its testability and definability.B.Musser underestimates the impact of artificial intelligence.ing psychology is a trend for physicists exploring other fields.D.Musser highlights physicists’efforts to uncover the secret of awareness.11.What can be inferred from the passage?A.The link between physics and awareness has been established.B.There is no doubt about the principles of an equation for awareness.C.A multidisciplinary approach is essential to understanding awareness.D.Study of awareness needs to ignore related psychological phenomena.12.Regarding Musser’s view in his book,the author is______.A.neutralB.disapprovingC.supportiveD.uncertain（2024北京东城高三二模）Neuroscientists usually investigate one brain at a time.They observe how neurons（神经元）fire as a person reads certain words,for example,or plays a video game.As social animals,however,those same scientists do much of their work together—brainstorming hypotheses,puzzling over problems and fine-tuning experimental designs.Increasingly,researchers are bringing that reality into how they study brains.Collective neuroscience,as some practitioners call it,is a rapidly growing field of research.An early,consistent finding is that when people converse or share an experience,their brain waves synchronize.Neurons in corresponding locations of the different brains fire at the same time,creating matching patterns,like dancers moving together.The experience of“being on the same wavelength”as another person is real,and it is visible in the activity of the brain.Such work is beginning to reveal new levels of richness and complexity in sociability.In classrooms where students are engaged with the teacher,for example,their patterns of brain processing begin to synchronize with that teacher’s—and greater synchrony may mean better learning.Couples exhibit higher degrees of brain synchrony than non-romantic pairs,as do close friends compared with more distant acquaintances.But much about the phenomenon remains mysterious—even scientists occasionally use the word“magic”when talking about it.One straightforward explanation could be that synchrony between brains is a result of shared experience or simply a sign that we are hearing or seeing the same thing as someone else.But the newest research suggests that synchrony is more than that—or can be.Researchers are discovering synchrony in humans and other species,and they are mapping its choreography—its rhythm,timing and undulations（波动）—to better understand what benefits it may give us.Given that synchronized experiences are often enjoyable,researchers suspect this phenomenon is beneficial:it helps us interact and may have facilitated the evolution of sociality.This new kind of brain research might also cast light on why we don’t always“click”with someone or why social isolation（孤立）is so harmful to physical and mental health.With synchrony and other levels of neural interaction,humans teach and learn,forge friendships and romances,and cooperate and converse.We are driven to connect,and synchrony is one way our brains help us do it.13.According to the passage,collective neuroscience______.A.collects and refines research on neuronsB.analyses activities of one brain at a timeC.promotes connections among neuroscientistsD.focuses on studying brains in interactive groups14.What can we infer about brain synchrony from Paragraph4?A.It can benefit other species.B.Its mechanism has changed.C.It demands further investigations.D.Findings about it are contradictory.15.Which of the following may result from brain synchrony?A.Increasing popularity among peers.B.Better cooperation among teammates.C.Improved techniques for conversations.D.More shared experiences between a couple.（2024北京海淀高三二模）The idea that aging reduces adults’ability to imagine,a common theme in children’s literature,is contradicted by psychological research.While children are often portrayed as more imaginative,research indicates that adults not only keep this ability but sometimes surpass children in imaginative thinking.Children are frequently celebrated for boundless imagination.Yet,research reveals that their make-believe games often center around realistic scenarios,such as cooking and cleaning,as demonstrated in a2020study published in Journal of Cognition and Development.Another study,lasting for four decades,also suggests that children are not naturally more imaginative than adults;their limitations result from a lack of knowledge and expertise to effectively use their imaginative capacity as adults.Imagination may have evolved for considering alternatives to reality,but we use it most naturally to explore close alternatives,like preparing a different meal,rather than far alternatives,like riding on clouds.When we use imagination to envision far alternatives—to innovate or invent—we’re not digging into an inborn appreciation of the extraordinary;we’re using a tool designed to explore the ordinary.When considering alternatives to reality,we fix our attention on possibilities that are physically reasonable,statistically probable,socially conventional and morally permissible.When told about possibilities that violate such regularities,we usually deny they could happen.Generally speaking,our ideas about what could happen are firmly rooted in what we expect to happen.This mindset is also particularly apparent in young children.In a2018study I co-designed with psychologist Jonathan Phillips,4-year-olds were asked to help a distressed girl who disliked going to school due to missing her mother.Among all the solutions given,they perceived the only possible solution was for her mother to do something special after school to ease her concerns.Unexpected alternatives,such as snapping fingers and making it Saturday,wearing pajamas to school or lying about school being closed,were all regarded impossible.From this,we can conclude that children’s earliest intuitions (直觉力)about possibility confuse what could happen with what should happen.Historically,the improbable event of traveling faster than a horse was considered impossible,as was traveling by air or traveling into space.Before the arrival of trains and planes,there were good reasons to think that people could travel only so far and only so fast.But these reasons were empirical(经验主义的),not logical.Imagination,on its own,lumps the improbable with the impossible,but we can combine imagination with other abilities—namely,knowledge and reflection—to separate the two.While imagination in children often subjects to expectation,adults can control their imaginative capacity for innovation by integrating it with accumulated knowledge and reflective thinking.16.According to the first two paragraphs,we know that.A.children develop imagination through gamesB.children face limitations in acquiring knowledgeC.adults are as good as children in imaginative thinkingD.adults’imaginative ability is likely to stay constant with age17We can infer from the passage that.A.expectation results from imaginative capacityB.certain practical concerns can limit imaginationC.breaking regularities may lead to close alternativesD.far alternatives are more important than close alternatives18.The2018study shows that children.A．came up with a wide range of alternatives B．were quicker to figure out solutionsC．took what should happen as possibilities D．used imagination in a reasonable way19.The underlined word“lump”in the last paragraph probably means.A.mix B．match C．compare D．replace（2024北京西城高三二模）When people hear“artificial intelligence,”many envision“big data.”There’s a reason for that:some of the most important AI breakthroughs in the past decade have relied on enormous data sets.But AI is not only about large data sets,and research in“small data”approaches has grown extensively over the past decade—with so-called transfer learning as an especially promising example.Also known as“fine-tuning,”transfer learning is helpful in settings where you have little data on the task of interest but abundant data on a related problem.The way it works is that you first train a model using a big data set and then retrain slightly using a smaller data set related to your specific problem.Research in transfer learning approaches has grown impressively over the past10years.In a new report for Georgetown University’s Center for Security and Emerging Technology(CSET),we examined current and projected progress in scientific research across“small data”approaches.Our analysis found that transfer learning stands out as a category that has experienced the most consistent and highest research growth on average since2010.This growth has even outpaced the larger and more established field of reinforcement learning,which in recent years has attracted widespread attention.Small data approaches such as transfer learning offer numerous advantages over more data-intensive methods.By enabling the use of AI with less data,they can bolster progress in areas where little or no data exist,such as in forecasting natural disasters that occur relatively rarely or in predicting the risk of disease for a population set that does not have digital health records.Another way of thinking about the value of transfer learning is in terms of generalization.A recurring challenge in the use of AI is that models need to“generalize”beyond their training data.Because transfer learning models work by transferring knowledge from one task to another,they are very helpful in improving generalization in the new task,even if only limited data were available.Moreover,by using pretrained models,transfer learning can speed up training time and could also reduce the amount of computational resources needed to train algorithms(算法).This efficiency is significant,considering that the process of training one large neural(神经系统的)network requires considerable energy.Despite the growth in research,transfer learning has received relatively little visibility.The existence of techniques such as transfer learning does not seem to have reached the awareness of the broader space of policy makers and business leaders in positions of making decisions about AI funding and adoption.By acknowledging the success of small data techniques like transfer learning—and distributing resources to support their widespread use—we can help overcome some of the common misconceptions regarding the role of data in AI and facilitate innovation in new directions.20.What does the underlined word“bolster”in Paragraph3probably mean?A.Promote.B.Seek.C.Track.D.Monitor.21.In which of the following settings can transfer learning be best applied?A.Predicting the frequency of floods in Amazon rainforest.B.Designing a program that can read handwritten documents.C.Forecasting the number of people infected with an unknown illness.D.Predicting house prices based on basic features like area and location.22.What is the writer’s attitude towards transfer learning?A.Doubtful.B.Optimistic.C.Critical.D.Unconcerned.23.Which would be the best title for the passage?A.Transfer Learning:Where Does It Best Fit?B.Small Data Are Also Crucial for Advancing AIC.Transfer Learning Powers Technological AdvancesD.Big Data vs.Small Data:Which Is the Future of AI?参考答案1．A2．D3．B【导语】本文为一篇说明文，介绍了印度洋的中孔珊瑚的白化现象十分严重，且未来的气候变化会加大这种现象。

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Alluvial terrace systems in Zhangjiajie of northwest Hunan,China:Implications for climatic change,tectonic uplift and geomorphic evolutionGuifang Yang a ,*,Xujiao Zhang a ,Mingzhong Tian a ,Gary Brierley b ,Anze Chen c ,Yamin Ping a ,Zhiliang Ge a ,Zhiyun Ni a ,Zhen Yang aaSchool of Earth Sciences and Resources,China University of Geosciences,No.29Xueyuan Road,Beijing 100083,China bSchool of Environment,University of Auckland,Private Bag 92019,Auckland,New Zealand cChinese Academy of Geological Sciences,Beijing 100037,Chinaa r t i c l e i n f oArticle history:Available online 12June 2010a b s t r a c tThis paper reports the latest details from two comprehensive investigations of alluvial terrace sequences in Zhangjiajie,northwest Hunan Province,China.Seven alluvial terrace units along the Maoxi River and four terrace sequences along the Suoxi River record signi ﬁcant regional geomorphic history.Rates of regional Quaternary uplift and climate change are reconstructed using topographic and stratigraphic evidence from terrace and adjacent cave deposits,along with Electron Spin Resonance (ESR)and Thermo-luminescence (TL)dating controls.Between 928ka and 689ka the time-averaged uplift rate (or incision rate)was 0.16m/ka.The rate decreased to 0.05m/ka between 689ka and 347ka,and then increased slightly to 0.11e 0.14m/ka after 347ka.The inferred incision rate increased roughly from 0.21e 0.32m/ka to 0.51m/ka from the Late Pleistocene to present.The seven alluvial phases (T 7ÀT 1)and their associated chronology are consistent with climatic variations at regional and/or global scales,suggesting that these terraces represent climate-driven pauses imprinted atop the record of long-term tectonically induced incision by rivers.Insights from these alluvial terrace staircases and cave features indicate that the spectacular sandstone peak forest landscape of the study area has emerged since the middle period of the Middle Pleistocene.Ó2010Elsevier Ltd and INQUA.All rights reserved.1.IntroductionStepped surfaces along river courses re ﬂect river responses to external and internal forces which operate over variable temporal and spatial scales (e.g.,Schumm and Lichty,1965;Maddy et al.,2001a;Wegmann and Pazzaglia,2002).Tectonic and climatic factors induce systematic adjustments to river systems,while local scale factors such as uplift along a fault line,volcanic input of sediment,or land use changes are superimposed upon these broader-scale controls (e.g.,Bull and Knuepfer,1987;Formento-Trigilio et al.,2003;Clement and Fuller,2007).Shifts in the ﬂow/sediment balance induce aggradational/degradational phases on valley ﬂoors (i.e.,Merritts et al.,1994;Bridgland,2000;Vandenberghe and Maddy,2001).This generates alluvial terraces,as former ﬂoodplain deposits become perched above the contem-porary channel such that they are no longer inundated by ﬂood events.These features provide excellent geomorphological,ecological and sedimentary archives that re ﬂect the different conditions experienced during their formation (Vandenberghe,2002).External (exogenous)controls upon terrace formation refer primarily to tectonic activities,climate variations and eustatic changes.Sustained tectonic uplift and associated river incision form and preserve ﬂights of alluvial terraces.Climatic controls upon sediment availability and discharge are imprinted atop these geological controls (e.g.,Bridgland,2000;Vandenberghe and Maddy,2001;Bridgland and Maddy,2002;Suresh et al.,2007).Typically,episodes of alluviation are associated with periods of long-term cooling,while incision is more intensive during glacial-interglacial transitions (Bridgland,2000;Maddy et al.,2001b;Bridgland and Westaway,2008).Terraces in lowland reaches are often produced by base-level adjustments driven by glacioeustatic sea level ﬂuctuations (Maddy,1997;Maddy et al.,2001b;Bridgland and Westaway,2008).Incision tends to occur in downstream rea-ches progressing upstream via knickpoint recession,as responses to lower sea level conditions.This situation is reversed during warmer intervals,often inundating and/or burying former terrace surfaces.Typically this occurs in association with regional subsidence.*Corresponding author.Tel.:þ861082329979;fax:þ861082322264.E-mail address:yangguifang@ (G.Yang).Contents lists available at ScienceDirectQuaternary Internationaljournal h omepage:w ww.else/locate/quaint1040-6182/$e see front matter Ó2010Elsevier Ltd and INQUA.All rights reserved.doi:10.1016/j.quaint.2010.05.019Quaternary International 233(2011)27e 39However,sea level change may have a limited inﬂuence on terrace formation in some lowland settings(Litchﬁeld and Berryman, 2005).In areas that were not subjected to glacial activity,the imprint of climate change may be relatively minor,and terrace formation is largely controlled by intermittent uplift(Melton,1959; Molnar and England,1990;Li et al.,1997;Zhang et al.,2007). Terrace formation is also inﬂuenced by endogenous controls upon the balance ofﬂow/sediment interactions in a catchment(e.g., Womack and Schumm,1977).As terraces reﬂect the imprint of conditions from the past,they represent a form of geological, climatic or anthropogenic memory,or combinations thereof (Brierley,2010).The relative inﬂuence of tectonic,climatic and anthropogenic factors varies markedly in differing settings.River terraces and karst caves are often used to signify long-term uplift of landscapes and/orﬂuvial incision(e.g.,Molnar et al., 1994;Maddy et al.,2001b;Piccini et al.,2003;Bridgland et al., 2004;Litchﬁeld and Berryman,2007;Bridgland and Westaway, 2008;Litchﬁeld,2008;Carcaillet et al.,2009;Claessens et al., 2009;Robustelli et al.,2009;Strasser et al.,2009;Westaway, 2009).Terraces have long been used to interpret the synchroneity of landscape responses to glacial and interglacial cycles(Schumm, 1977;Chatters and Hoover,1992;Li et al.,1997;Bridgland,2000; Pan et al.,2003;Bridgland and Westaway,2008;Gao et al.,2008). In recent decades,the evolutionary history of alluvial terraces has also been related to allocyclic mechanisms,with detailed inter-pretations of depositional systems providing valuable insights into changes in basin geometry that reﬂect factors such as widespread planation or valley development(Antoine,1994;Fuller et al.,1998; Li et al.,2001;Macklin et al.,2002;Robustelli et al.,2009).Despite their unique natural and scientiﬁc importance,the formation and age structure of the sandstone peak forest land-scapes of Zhangjiajie,in the Lishui River Basin of northwest Hunan Province,remains poorly understood(Hunan Geo-environmental Monitoring Center,1988;Chen,1993;Zhou,1995;Wu and Zhang, 2002;Zhou et al.,2004).The widespread distribution of distinc-tive stepped landforms(including alluvial terraces and karst caves) in the middle and lower catchment enable detailed assessment of the geological and geomorphic evolution of this region.This manuscript combines geomorphologic,sedimentologic and strati-graphic evidence to characterize the alluvial terrace sequences in this region,correlating these features with karst cave systems. Analysis of mechanisms of terrace formation is used to unravel the relative controls played by tectonics and climatic changes.2.Study areaRelative topography in the study area of9563km2 (28 520e29 480N,109 400e111 200E)extends over around1000m, ranging from200e300m above sea level(a.s.l.)on valleyﬂoors to 1500m a.s.l.on mountain peaks(Hunan Geo-environmental Monitoring Center,1988;Fig.1).The area is dominated by moist monsoonal(subtropical)climatic conditions with an annual average temperature of17 C.Average annual precipitation is around1400mm,and is highest in summer.Notable alluvial terraces and karst landscapes have formed in Zhangjiajie,located in the Wuling Range between the Yun-Gui Plateau to the north-east and the mountainous area of northwest Hunan Province. Topography decreases to the southeast.The lithostratigraphy within this area is comprised of Silurian,Devonian,Permian, Triassic and Quaternary strata.Silurian and Devonian strata account for most of the total area.Carboniferous strata are typi-cally absent,indicating tectonic movement around390e250Ma (Hunan Bureau of Geology and Mineral Resources,1988).The sandstone peak forest landform developed primarily in the Upper and Middle Devonian.Karst landforms formed primarily within Permian or Triassic strata(Hunan Bureau of Geology and Mineral Resources,1988;Hunan Geo-environmental Monitoring Center, 1988;Hunan Bureau of Land and Resource,2003).Quaternary deposits are relatively limited in this region,withﬂuvial and diluvial materials dominant.The study area extends across twoﬁrst-order tectonic units, Jiangnan ancient land and Yangtze paraplatform(Hunan Bureau of Geology and Mineral Resources,1988;Hunan Bureau of Land and Resource,2003).In general terms,these relatively stable blocks are characterized by typical up-and-down tectonic movement.The fold and fracture movement is not strong and magmatic activity is absent.Fault activity is restricted to the two major tectonic-joint sites,along the Lishui River Valley(Fig.2).3.MethodsComprehensive surveys were undertaken in October2008and May2009as part of the analysis of geological heritage protection for Zhangjiajie Sandstone Peak Forest Geopark(or Zhangjiajie World Geopark).Emphasis here is placed upon alluvial terraces along the Lishui River and its tributaries of the middle Yangtze catchment.Dated deposits and associated sedimentary character-istics provide minimum estimates of the incision rate of river systems and the timing of sandstone landform development in Zhangjiajie.Terrace thickness and elevation above the present river bed were measured by combining GPS data with1:50000topo-graphic maps.More than10bulk samples were taken from sedi-ment lenses in the alluvial gravel layers from different terraces in the Maoxi,Suoxi and Loushui River basins.As noted in previous studies elsewhere,terrace age control was derived from careful application of Thermo-luminescence(TL)and Electron Spin Reso-nance(ESR)analysis of siliceous-rich samples(e.g.,Forman,1989; Laurent et al.,1998;Chaivari et al.,2001;Wray et al.,2001; Bahain et al.,2007;Blain et al.,2007;Tissoux et al.,2008).The samples comprising of silty-sand materials were collected from around10e15cm below the exposure wall.Proximity to boulders was avoided by at least20cm to minimize contamination of the sample material.During sampling,10cm wide sample tins were wedged directly into the alluvial deposits and were sealed imme-diately after sample collection.ESR analyses were performed at the laboratory of the Institute of Geology,China Earthquake Adminis-tration(CEA),whilst TL analyses were completed by the Institute of Crustal Dynamics,CEA.The general principles and experimental protocols of the ESR dating methods for terrace sediments are based on previous publications that assert that these procedures are well-established for dating Pleistoceneﬂuvial terraces(Bahain et al.,2007;Yin et al.,2007).Based on prior works,the system-atic error of ESR dating was estimated to be within10%(Bahain et al.,2007;Yin et al.,2007).The TL samples wereﬁrst treated with warm HCL to remove carbonates and to break up aggregates. Fine grains(4e11m m)were then collected by sedimentation in distilled water,with procedures being repeated3e4times.Samples for TL measurements were prepared followingﬁnal sedimentation from acetone onto aluminum ing Beijing(e40 N)late fall to early winter(November and December)sun,bleaching experi-ments were carried out on a large number of discs ofﬁne grains. The determination of equivalent dose(ED)was carried out using methods outlined by Lu et al.(1987,1988).The systematic error of TL dating was estimated to be within10%.Statistical analysis of gravels was completed from the wide-spread and continuous3rd order terrace for further age veriﬁcation. Weathering rinds and sedimentary features for widespread terrace (T3)were incorporated into this study to support relative-dating estimation.Additionally,detailed studies of the karst system along the Suoxi River are used to provide relative-dating determination.G.Yang et al./Quaternary International233(2011)27e39 284.Alluvial terraces and karst caveDespite displacements in response to neotectonic movement and river erosion,a series of stepped landforms are clearly evident in the study area (Fig.3).Based on interpretations of large-scale topographic maps,chronologic analysis,and ﬁeld investigations,seven terraces are identi ﬁed in the Maoxi River Basin,while three terraces are evident in the Loushui River and four terraces in its tributary,the Suoxi River.These terraces units are labeled according to their topographic position from the highest (T 7)to the present-day riverbed (Fig.3).4.1.Maoxi River terracesAlluvial terraces are best preserved in the Maoxi River Basin from the Lishui catchment (Figs.3and 4).In the lower reaches of the Maoxi catchment,terraces converge downstream as the valley widens into broad ﬂoodplains.Altogether,seven terraces (T 7ÀT 1,in descending order from oldest to the youngest)were identi ﬁed in the Maoxi River Basin.T 7is up to 136m above the contemporary channel (Figs.4and 5,Table 1).Gravel layers in the higher terraces (T 7ÀT 6)are usually overlain by ﬂuvial successions,with clay coatings and prominent red (iron)staining (Fig.5).T 5is a cut or strath terrace (Fig.5a and b)characterized by little (<20cm)or no clay cover,with 40e 60cm thick sand/gravel ﬂuvial deposits resting on bedrock (Fig.5b).The composition of T 4varies markedly,from comparatively thick gravel to no gravel in some instances (Fig.5).T 3is the most developed and continuous terrace,and it is especially well preserved in the middle and lower catchment.T 2is up to 28e 33m above the contemporary river level.The most recently abandoned feature,T 1,is 10e 15m above the present-day riverbed.Of note,most terraces of different heights showcommonFig.1.(a)Sketch map of China with speci ﬁc indicating of Hunan Province;(b)Map of Hunan Province showing the location of our study area,Zhangjiajie,and associated Middle Yangtze water system;(c)Geographical sketch map of Zhangjiajie with speci ﬁc emphasis on major alluvial terrace localities we investigated in the study area.G.Yang et al./Quaternary International 233(2011)27e 3929Fig.2.Geological sketch map of Zhangjiajie World Geopark (modi ﬁed from Hunan Geo-environmental Monitoring Center,1988).Fig.3.An overview of the alluvial terrace sequences indenti ﬁed in the lower Maoxi River of the Lishui River BasinG.Yang et al./Quaternary International 233(2011)27e 3930characteristics:they are typically characterized by channel facies overlain by ﬁne-grained sand and silt;the gravel bodies are comprised of resistant sandstone/siltstone with diverse colors,indicating that they are entirely composed of local Devonian rocks.Terrace chronology,on the basis of ESR and TL dating,is shown in relation to elevation in Fig.5and Table 1.Age estimates from ESR dating indicate that T 7ÀT 4terraces in the Maoxi catchment date back to 928Æ92ka,574Æ57ka,689Æ68ka,and 347Æ34ka,respectively.These can be considered as minimum age estimates of terrace abandonment.The dating control of T 6is the most dia-chronous.This is considered to re ﬂect the weakly developed nature of these materials along with some human disturbance at the sample site.T 3and T 2were dated at 151.05Æ12.84ka/201.24Æ17.11ka and 60.95Æ5.18ka based on TL control (Table 1).The gravel composition of the most extensive terrace,T 3,was compared from several sites to validate age determinations (cf.Colman,1981;Colman et al.,1987;Knuepfer,1988;Tian and Cheng,2009;Fig.6).Terrace T 3consists of channel facies overlain by facies of layered sand and silt.A prominent gravel layer,up to150e 200cm thick,crosses much of this terrace,showing an almost imbricate structure.Within this distinct bed,the axis of gravels is typically 15e 20cm,with a maximum of 40cm and a minimum of 3e 5cm.These relatively well-sorted and well-rounded gravels have consistent orientation and are weakly weathered (Fig.6).These gravels show a characteristic and relatively simple admixture of resistant sandstone/siltstone,being comparatively loose and only differing notably in their color.In ﬁlling ﬁne-grained sand,silt and even clay of matrix materials are uncemented and very loose,highlighting the distinctive and consistent bimodal nature of this sediment layer.4.2.Loushui River terracesTerraces are less prominent along the Loushui River,probably because the intense tectonic uplift and hard,resistant sedimentary rocks (mainly limestone)have impeded terrace development by favoring vertical incision over lateral migration.This has created a narrow valley with limited space for deposition of riversedimentsFig.4.Alluvial terraces from T 7to T 2in the Maoxi River;(a)indicates the highest terrace T 7and topographic as well as sedimentary features;(b)shows the poor preserved and relatively thin gravel layer of T 6;(c)denotes the surface of T 5;(d)and (e)present the T 4with thin gravel layer and relative ﬂat surface;(f)shows the gravel layer of T 2.G.Yang et al./Quaternary International 233(2011)27e 3931and preservation of alluvial landforms.In addition,the land surface has been extensively modi ﬁed by human activities.Three weakly developed and poorly preserved terraces are evident.Older and higher terraces are less well preserved,probably due to tectonic activity,while younger and lower surfaces are widespread and better preserved.4.3.Suoxi River terracesThree stepped ﬂuvial formations are evident along the lower reaches of the Suoxi catchment,a tributary of the Loushui River (Fig.7a).T 1terrace is 173m a.s.l.(7m above the contemporary channel bed).It is comprised of thick and fertile sediments atop which many crops are grown.T 2terrace is a small tread that ranges from 178to 183m a.s.l.,becoming more continuous in downstream areas at an elevation of 180m a.s.l.The 1e 1.5m thick sediment is composed of round,well-sorted gravel.T 3,the higher terrace level along this river,is locally represented in part of the Suoxi River by a 1m thick conglomerate (Fig.7a).In the middle segment of the Suoxi River,the alluvial terraces have similar characteristics in terms of relative height and sedimentary features,though they arefound at a higher absolute height (Fig.7b).Some small relics of alluvial deposits are evident at a higher elevation associated with the peak summits along the middle Suoxi River (Fig.7b),potentially representing a 4th (strath)terrace.Two samples from different pro ﬁles in T 3terrace yielded TL age estimates of 104.45Æ8.88ka and 117.62Æ9.99ka (Table 1).4.4.Typical karst cave:Huanglong CaveHuanglong Cave,located 10km east of Jundiping village on the north ﬂunk of the Suoxi Valley,is the core sightseeing spot of Zhangjiajie Sandstone Peak Forest Geopark.The cave network ranges from 260to 400m a.s.l.,with exit standing approximately 5Æ2m above the present Suoxi River.It is comprised of almost all types of stalactite,stalagmite,stone columns,stone waterfall,and stone valance (Cheng,1988;Hunan Geo-environmental Monitoring Center,1988;Yang,2007;Fig.8).There are four primary layers,aligned approximately east-west direction,with a total length of 13km,vertical height of 140m,and an area of more than 20million m 2(Ge et al.,2009;see Fig.8and Table 1).A 60cm thick bed of rudimental clayey sand and well-rounded gravels in theuppermostFig.5.Transverse section through the terraces of the lower Maoxi River Basin;(a)shows an overall 7terraces in lower Maoxi River;(b)indicates 5-order terrace sequence in the lower Maoxi RiverG.Yang et al./Quaternary International 233(2011)27e 3932layer is considered to be indicative of an imprint from ancient river deposits.ESR dating of these materials indicates that the cave initially formed more than 463Æ46ka ago (Table 1).5.Discussion5.1.Terrace ages and relation to karst caveEvidence from previous studies indicated that the ages of terraces T 7ÀT 1in the middle Yangtze catchment extend from 1.16Ma to 0.01e 0.03Ma (Xie,1991;Tian et al.,1996;Li et al.,2001;Xiang et al.,2005),almost encompassing the entire period from the late Early Pleistocene to the Holocene.ESR and TL dates derived from T 7ÀT 2terraces in this study are consistent with these ﬁnd-ings (Table 1).The comparable chronology indicates that timing for initial incision of the Lishui River began at least in the late phase of Early Pleistocene,at a time when the Yangtze River was adjusting its drainage network to form alluvial terraces (Yang and Chen,1988;Li et al.,2001).Variability in age control is most pronounced for T 6(574Æ57ka).This may be attributed,in part,to the poorly devel-oped and relatively thin nature of the most diachronous deposits that make up this strath terrace unit,as well as human disturbance to this surface (Figs.3and 4).The dating control of T 6,therefore,can be considered ‘too young ’according to the terrace position in regional comparison with those of adjoining middle Yangtze Gorges,with an age dating back to e 0.86Ma (Li et al.,2001;Yang,2006).Its greater height indicates that it must be older,consis-tent with the weathering-dominant red sediments.The lackofTable 1Fig.6.The widespread T 3from the Maoxi River Basin (shown in a and b)and associated gravel statistical graphs;(c)Weathering degree:1.No weathering,2.Weak weathering;3.Strong weathering;4.Entirely Weathered;(d)Roundness:1.Well-rounded,2.Subrounded,3.Subangular,4.Angular.G.Yang et al./Quaternary International 233(2011)27e 3933Fig.7.Alluvial terrace pro ﬁles along the lower (a)and middle (b)SuoxiRiver.Fig.8.Horizontal (a)and vertical (b)structure of Huanglong Cave Cave in the middle Suoxi River (shaded colors indicate the differentiation of multi-levels)(modi ﬁed from Hunan Geo-environmental Monitoring Center,1988).G.Yang et al./Quaternary International 233(2011)27e 3934alluviation materials and later anthropogenic disturbance post-date the deposition.This age therefore is not employed in the subsequent discussion.The Huanglong Cave initially emerged more than463Æ46ka ago during interglacial conditions dominated by the wettest climate.Four horizontal or slightly inclining cave passages provide signiﬁcant evidence with which to reconstruct the former groundwater table and its relation to the regionalﬂuvial base level (Palmer,1987).This conforms to the ensuing T4formation from the adjacent Maoxi River and middle Yangtze River(0.46Æ0.046Ma, 0.347Æ0.034Ma,and0.3e0.5Ma,respectively;see Li et al.,2001; Xiang et al.,2005;Yang,2006;Table1).The strongly cemented gravel layer and red inﬁll feature in the highest level of Huanglong Cave are indicative of warm and humid climatic conditions at this time.When viewed together,this is considered to provide a repre-sentative and accurate estimate of river incision and cave formation in the entire Lishui River Basin,in a manner that is broadly consistent with age estimates for terraces elsewhere in the middle Yangtze catchment(Li et al.,2001;Xiang et al.,2005;Yang,2006). For example,Xie(1991)derived an age estimate of0.31e0.54Ma for the fourth river terrace in the Three Gorges of the Yangtze River. Interestingly,comparative studies of terrace reveal the origin of T4 along the Yellow River and the Weihe River at approximately 0.3e0.5Ma(Li et al.,1997;Xiang et al.,2005;Liu and Di,2007;Gao et al.,2008).The good correlation between terrace and cave features indicates that the formation of the Huanglong cave initially occurred in the middle Mid-Pleistocene or earlier.A signiﬁcant base-level standstill is likely to have occurred during the Middle Pleistocene,at which time a new karst feature emerged at elevation approximately80e90m above the contemporary river level at Zhangjiajie,followed by the aggradation of T4terrace during a cold period(Table1).TL dating ages of samples from the Suoxi and the Maoxi Rivers indicate minimum ages for T3and T2of0.1e0.2Ma and0.06Ma, respectively(Table1).Rock weathering rinds and sedimentary diagnoses also provide a reliable means of age estimations for Quaternary stream terraces(e.g.,Chinn,1981;Colman,1981; Colman et al.,1987;Knuepfer,1988;Li et al.,1996;Oguchi,2004; Tian and Cheng,2009).Given the abundance of surface cobbles observed,the relatively weak weathering rinds of the gravel(with a mean thickness of approximately0.57cm)in the most extensive terrace(T3)should not have undergone the consolidation process within a relatively short time in the region,a pattern comparable with an overall relative-dating determination of previous studies (Li et al.,1996;Oguchi,2004;Tian and Cheng,2009;Fig.6). Consideration of the regional correlations leads us now to suggest that terrace T3aggraded in MIS6,with relatively loose and lighter color inﬁlled sediments seemingly occurring in response to a cool and dry periodicity(Fig.6).These conditions likely resulted in the deposition of coarse sedimentary units(Fig.6).Aggradation ofﬁne-grained materials(majorly silt and clay)atop these coarser units has produced the dual structure of these sediments.These age controls and sedimentary features indicate that T3was initially formed during the Late Pleistocene in both Maoxi and Suoxi Rivers, broadly contemporaneous with MIS6or‘Typ-Riss’(Chappell and Shackleton,1986;Chappell et al.,1996;Zhao et al.,2009).5.2.Terraces as a record of Quaternary climatic changeMany previous studies have provided support for the notion that terraces have been formed in tune with,and therefore prob-ably in response to,Milankovitch-scale climatic oscillation (Antoine,1994;Bibus and Wesler,1995;Li et al.,1997;Bridgland, 2000;Maddy et al.,2001b;Vandenberghe and Maddy,2001;Pan et al.,2003;Starkel,2003;Vandenberghe,2003;Bridgland and Westaway,2008).This thinking relates phases of aggradation and incision to variations in sediment and water supply due to major climate oscillation,perhaps in response to glacial-interglacial cycles.During glacial periods,cold climatic conditions triggered sparse vegetation cover,promoting the generation and deposition of abundant coarse sediment because of the limited transport capability of river systems.At the glacial/interglacial transition, slopes are stabilized by colonizing vegetation,restricting mass-movement processes and thereby limiting sediment supply to the valleyﬂoor.High rainfall events and release of considerable melt-water facilitate increases in stream power,enhancing prospects for incision by‘hungry’rivers.This process creates the accommodation space for subsequent inﬁlling and reworking of deposits.During interglacial times,relatively stable climatic conditions and thor-ough weathering may enhance the availability ofﬁne-grained sediments.Therefore,episodes of coarser andﬁner alluviation can be associated with periods of glacial and interglacial,while river incision is more intensive during glacial/interglacial transitions (Bridgland,2000;Maddy et al.,2001b;Vandenberghe,2003;Chang et al.,2005;Westaway et al.,2006;Bridgland and Westaway,2008).As noted in many other studies,a climatic imprint associated with glacial-interglacial cycles can be discerned atop the longer-term record of uplift-induced rejuvenation from the terraces at Zhangjiajie(cf.,Penck and Brückner,1909;Li,1991;Mather et al., 1995;Saucier,1996;Li et al.,2001;Pan et al.,2003).A transverse section through the terraces of the Maoxi River reveals differing orders of cyclical adjustment in the study area(Fig.5).The age controls presented here for T7to T1indicate that terrace sequences were broadly contemporaneous with previous cold glacial/stadial periods.On the basis of regional correlations,these terraces(T7and T5ÀT2terrace levels)have been thought to represent MIS24,18,10, 6and4respectively.The attribution of terrace5to MIS18is based on the presence in sediments as a corresponding position in adjoining middle Yangtze River of deposits dated back to0.73Ma (Li et al.,2001;Xiang et al.,2005;Yang,2006).Similarly,the assignment of T3to MIS6is according to the sedimentary diagnoses and dating constraint occurring at a near-equivalent height in the neighboring middle Yangtze River that has been dated back to 0.1e0.2Ma(Xie,1990,1991;Tian et al.,1996;Li et al.,2001;Xiang et al.,2005;Yang,2006).From the late Early Pleistocene(e928ka)to Late Pleistocene,the Lishui River has predominantly been incising into bedrock in synchrony with Milankovitch cycles,forming cut or base terraces. The highest identiﬁed unit of T7was formed since the late period of Early Pleistocene during MIS24when the cold climate created conditions that promoted alluviation.The position and dating control of T5suggest that this feature most likely developed during MIS18,while T4,T3and T2were established during MIS10,6and4, respectively.The terrace aggradation periods,therefore,invariably correspond with cold stages,as indicated by occurrence of gravels (Bridgland,2000;Bridgland and Westaway,2008).Terrace erosion occurred under strongly increased water discharge rates and rela-tively low sediment supply.This took place,in particular,during a warming limb of the glacial-interglacial transition(Bridgland, 2000;Maddy et al.,2001b;Monecke et al.,2001;Litchﬁeld and Berryman,2005;Westaway et al.,2006;Bridgland and Westaway, 2008).Importantly,T6was identiﬁed at an intermediate topo-graphical level,with an age control that lies between two cooling periods(928and689ka,respectively),at a time when changing climatic conditions altered rates ofﬂuvial processes(Raymo et al., 1997;Clark and Pollard,1998;Wang et al.,2000).The onset of a relatively frigid-arid climate probably increased the hillslope sediment yields.The subsequent return of humid and mesic climatic conditions decreased sediment yields and induced river incision.G.Yang et al./Quaternary International233(2011)27e3935。