In early 2004 eight tiny sensors were dropped from a plane near a military base in California. After hit ting the ground, the sensors—also known as smart dust sensors organized themselves into a network and quickly detected a fleet of military vehicles on the ground. They determined the direction, speed and size of a series of military vehicles traveling along the road and later transmitted the data to a computer at a nearby base camp. Smart dust sensors are minicomputers—as small as a grain of rice in some cases—that can monitor and evaluate their physical environment and can relay the information via wireless, communication. They can monitor elements such as temperature, moisture, humidity, pressure, energy use, vibration, light, motion, radiation, gas, and chemicals. These devices will soon have many applications, such as use in emergency rescue. Software has been developed to run these minicomputers. A key feature of the software is the ability of the sensors to automatically organize themselves into a communications network and talk to each other via wireless radio signals. If any one connection is interrupted, the sensors will self-correct and pass the information on to the next available sensor. Each sensor has a chip that does the computing work recording things like temperature and motion at its location. Each sensor also has a tiny radio transmitter that allows it to talk to other sensors within 100 feet or so. With a single network of 10,000 sensors—thought to be the biggest array(排列) of sensors currently possible, you could cover 9 square miles and get information about each point along the way. The data finally works its way to a base station that can send the information to a computer or to a wireless network. The scientists who are working with this technology say smart dust sensors can be used to detect the location or movement of enemy troops in areas too dangerous or remote for soldiers to operate. Scattering hundreds of self-networking sensors from a manned or unmanned plane onto the battlefield, in theory, could produce critical information and lead to strategic advantage. Sensors could also be used to detect the presence of chemical weapons and could give troops the time needed to put on protective gear.

Human beings are animals. We breathe, eat and digest, and reproduce the same life【B1】common to all animals. In a biological laboratory, rats, monkeys, and humans seem very much the same. However, biological understanding is not enough:【B2】itself, it can never tell us what human beings are.【B3】to our physical equipment—the naked human body—we are not an【B4】animal. We are tropical creatures,【B5】hairless and sensitive to cold. We are not fast and have neither claws nor sharp teeth to defend ourselves. We need a lot of food but have almost no physical equipment to help us get it. In the purely physical【B6】, our species seems a poor【B7】for survival. But we have survived—survived and multiplied and【B8】the earth. Some day we will have a【B9】living on the moon, a place with neither air nor water and with temperatures that turn gases into solids. How can we have done all these things? Part of the answer is physical.【B10】its limitations, our physical equipment has some important potentials. Inhabitants of our eventual moon colony will bring their own food and oxygen and then create an artificial earth environment to supply necessities.

Your hair wants ______. You"d better have it done tomorrow.

Change, or the ability to【B1】oneself to a changing environment is essential【B2】evolution. The farmer whose land is required for housing or industry must adapt himself: he can transfer to another place and master the problems【B3】to it; he can change his occupation, perhaps【B4】a period of training; or he can starve to death. A nation which can"t adapt its trade or defense requirements to【B5】world conditions faces an economic and military disaster. Nothing is fixed and permanently stable.【B6】must be movement forward, which is progress of a sort, and movement backward, which is decay and deterioration. In a changing world, tradition can be a force for good or for evil.【B7】long as it offers a guide, it helps the ignorant and the uninformed to take a step【B8】and, thereby adapt themselves to【B9】circumstances. But if we make an idol of tradition, it ceases to be a guide. It becomes an obstacle【B10】on the path of course. Man is to accept the help which tradition can give but to be well aware of its limitations in a changing world.

Fueled by weather, wind, and dry undergrowth, uncontrolled wildfires can burn acres of land—and consume everything in their way—in mere minutes. 【C1】______, more than 100, 000 wildfires clear 4 million to 5 million acres of land in the U. S. every year. A wildfire moves at speeds of up to 23 kilometers an hour, consuming everything— trees, bushes, homes, even humans—in its【C2】______. There are three conditions that need to be【C3】______in order for a wildfire to burn: fuel, oxygen, and a heat source. Fuel is any material【C4】______a fire that will burn quickly and easily, including trees, grasses, bushes, even homes. Air supplies the oxygen a fire【C5】______to burn. Heat sources help spark the wildfire and bring fuel to【C6】______hot enough to start burning. Lightning, burning campfires or cigarettes, hot winds, and even the sun can all provide【C7】______heat to spark a wildfire. 【C8】______often harmful and destructive to humans, naturally occurring wildfires play a positive role in nature. They【C9】______nutrients to the soil by burning dead or decaying matter. They remove diseased plants and harmful insects from a forest ecosystem(生态系统). And by burning【C10】______thick trees and bushes, wildfires allow sunlight to reach the forest floor, enabling a new generation of young plants to grow.

By the time you have completed the essential training, you ______exposed to virtually every new feature of the course.

Many people wrongly believe that when people reach old age, their families place them in nursing homes. They are left in the hands of strangers for the rest of their lives. Their【B1】children visit them only occasionally, but more often, they do not have any【B2】visitors. The truth is that this idea is an unfortunate myth imaginary story. In fact, family members provide over 80 percent of the care【B3】elderly people need. Samuel Preston, a sociologist, studied【B4】the American family is changing. He reported that by the time the【B5】American couple reaches 40 years of age, they have more parents than children.【B6】because people today live longer after an illness than people did years ago, family members must provide long term care. More psychologists have found that all caregivers share a common characteristic: All caregivers believe that they are the best people for the job. In other words, they all felt that they【B7】do the job better than anyone else. Social workers interviewed caregivers to find out why they took on the responsibility of caring for an elderly relative. Many caregivers believed they had【B8】to help their relative. Some stated that helping others would【B9】them feel more useful. Others hoped that by helping【B10】now, they would deserve care when they became old and dependent. Caring for the elderly and being taken care of can be a mutually satisfying experience for everyone who might be involved.

Wood carving refers to the art of creating or decorating objects of wood by carving with a sharp, hand-held tool. This form of art has a history of over 1,000 years and a unique artistic style. The following is some introduction about wood carving in America. Wood carving began as a necessity in America and developed into an art. Because of the lack of other materials, early settlers were forced to make tools and utensils out of wood. At first, these articles were whittled with a knife, but when pioneer craftsmen set up their primitive shops most of them were fashioned on a lathe--a machine which holds an object and rotates it while it is being shaped by a tool. However, even after Massachusetts-born Thomas Blancard designed a lathe which could turn irregular shapes--an innovation that made possible mass production of gunstocks, shoe lasts, oblong and square wooden wares--craftsmen who could use knife and chisel skillfully were still in demand. Some found ready employment in shops of cabinetmakers, while others, carved decoy. Still others specialized in creating shop signs, ship figureheads, or in decorating interior woodwork. A few even accepted commissions to make busts of prominent citizens.

So long as teachers fail to distinguish between teaching and learning, they will continue to undertake to do for children that which only children can do for themselves. Teaching children to read is not passing reading on to them. It is certainly not endless hours spent in activities about reading. Douglas insists that "reading cannot be taught directly and schools should stop trying to do the impossible. " Teaching and learning are two entirely different processes. They differ in kind and function. The function of teaching is to create the conditions and the climate that will make it possible for children to devise the most efficient system for teaching themselves to Learning to read involves all that each individual does to make sense of the world of printed language. Almost all of it is private, for learning is an occupation of the mind, and that process is not open to public scrutiny. If teacher and learner roles are not interchangeable, what then can be done through teaching that will aid the child in the quest (探索) for knowledge? Smith has one principal rule for all teaching instructions. "Make learning to read easy, which means making reading a meaningful, enjoyable and frequent experience for children. " When the roles of teacher and learner are seen for what they are, and when both teacher and learner fulfill them appropriately, then much of the pressure and feeling of failure for both is eliminate& Learning to read is made easier when teachers create an environment where children are given the opportunity to solve the problem of learning to read by reading.

Regular child care provided outside home or by someone other than the mother does not in itself undermine healthy emotional connections between mothers and their 15-month-old infants, according to a long-term national study. The finding holds even if care begins during the first 3 months after birth and runs for 30 hours or more per week. Among infants who receive unkind and unresponsive care from their mothers, however, the mother-child relationship may be damaged. "This research helps us put apart complexities regarding child care that have not previously been studied in detail", contends Jay Belsky, a psychologist. The investigation consists of 1,153 children and their families living in or near Boston. The youngsters, no more than 1 month old when they entered the study in 1991, will be tracked until the age of 7. Experimenters administered questionnaires to mothers in their homes and videotaped baby caretakers interacting with the kids at ages 1, 6, and 15 months. Independent observers rated the quality of each child care efforts and noted infant nervousness. Unlike most previous studies, this one allows researchers to observe each caretaker"s personality at child nursing, and kids" emotional reaction by the equipment.

All the people who went to the new supermarket had one great hope: to be the lucky customer who did not have to pay for his shopping. For this was what the notice just inside the entrance promised. It said, "Remember, once a week, one of our customers gets free goods. This may be your lucky day!" For several weeks Mrs. White hoped, like many of her friends, to be the lucky customer. Unlike her friends, however, she never lost heart. Her kitchen was full of things which she did not really need. Her husband tried again and again to persuade her to give it up, but she just wouldn"t listen. She dreamed of the day when the manager of the supermarket would come up to say, "Madam, this is your lucky day. Everything in your basket today is free". One Friday morning, after she had finished her shopping and had taken it to her car, she found that she had forgotten to buy some tea. She rushed back to the supermarket, got the tea and went to the desk to pay for it. As she was walking, she saw the manager of the supermarket coming up. "Madam", he said warmly, holding out his hand, "I want to congratulate you! You are our lucky customer today. Everything you"ve got in your basket is free".

How much sleep does a person need?【B1】the physiological bases of the need for sleep remain conjectural(猜想), rendering conclusive answers to this question impossible, much evidence has been gathered on how much sleep people do in fact obtain. Perhaps the most important conclusion to be【B2】from this evidence is【B3】there is great variability among individuals in total sleep time. For adults,【B4】between six and nine hours of sleep as a nightly average is not unusual, and 7.5 hours probably best expresses the norm. Such norms, of course, forms inevitably vary with the criteria of sleep employed. The most【B5】and reliable figures on sleep time, including those cited here, come from studies in sleep laboratories, where EEG criteria are employed. 【B6】consistently has been associated with the varying amount, quality, and pattern of electrophysiologically defined sleep. The newborn infant may spend an average of about 16 hours of each 24-hour period in sleep,【B7】the sleep time drops sharply; by two years of age, it may【B8】from nine to 12 hours. Decreases to approximately six hours have been observed among the elderly. 【B9】will be discussed from below, EEG sleep studies have indicated that sleep can be considered to consist of several different stages. Developmental changes in the relative proportion of sleep time【B10】in these sleep stages are as striking as age-related changes in total sleep time.

Peter: Why not join us this Saturday and tell us about your adventures in Russia? Keith: ______.

Sporting activities are essentially modified forms of hunting behavior. Viewed biologically, the modern foot-bailer is in reality a member of a hunting group. His killing weapon has turned into a harmless football and his prey(猎物) into a goalmouth. If his aim is accurate and he scores a goal, he enjoys the hunter"s triumph of killing his prey. To understand how this transformation has taken place we must briefly look back at our forefathers. They spent over a million years evolving as cooperative hunters. Their very survival depended on success in the hunting-field. Under this pressure their whole way of life, even their bodies, became greatly changed. They became chasers, runners, jumpers, aimers, throwers and prey-killers. They cooperated as skillful male-group attackers. Then about ten thousand years ago, after this immensely long period of hunting their food, they became farmers. Their improved intelligence, so vital to their old hunting life, was put to a new use—that of controlling and domesticating their prey. The hunt became suddenly out of date. The food was there on the farms, awaiting their needs. The risks and uncertainties of the hunt were no longer essential for survival.

Manager: First, I"d like the reservations made for my trip to Tokyo. Secretary: ______.

This country, as Lincoln said, belongs to the people. So do the natural resources which make it rich. They supply the basis of our prosperity now and hereafter. In preserving them, which is a national duty, we must not forget that monopoly is based on the control of natural resources and natural advantages, and that it will help the people little to conserve our natural wealth unless the benefits which it can yield are given back to the people. Let us remember, also, that conservation does not stop with the natural resources. The principle of making the best use of all we have requires that we stop the waste of human life in industry and prevent the waste of human welfare which flows from the unfair use of concentrated power and wealth in the hands of men whose eagerness for profit blinds them to the cost of what they do. We have no higher duty than to promote the efficiency of the individual. There is no surer road to the efficiency of the nation.

The biggest safety threat facing airlines today may not be a terrorist with a gun, but the man with the portable computer in business class. In the last 15 years, pilots have reported well over 100 incidents that could have been caused by electromagnetic interference. The source of this interference remains unconfirmed, but increasingly, experts are pointing the blame at portable electronic devices such as portable computers, radio and cassette players and mobile telephones. RTCA, an organization which advises the aviation(航空) industry, has recommended that all airlines ban(禁止) such devices from being used during "critical" stages of flight, particularly take-off and landing. Some experts have gone further, calling for a total ban during all flights. Currently, rules on using these devices are left up to individual airlines. And although some airlines prohibit passengers from using such equipment during take-off and landing, most are reluctant to enforce a total ban, given that many passengers want to work during flights. The difficulty is predicting how electromagnetic fields might affect an aircraft"s computers. Experts know that portable devices emit radiation which affects those wavelengths which aircraft use for navigation and communication. But, because they have not been able to reproduce these effects in a laboratory, they have no way of knowing whether the interference might be dangerous or not. The fact that aircraft may be vulnerable(易受损的) to interference raises the risk that terrorists may use radio system in order to damage navigation equipment. As worrying, though, is the passenger who can"t hear the instructions to turn off his radio because the music"s too loud.

Before high school teacher Kimberly Rugh got down to business at the start of a recent school week, she joked with her students about how she"d had to clean cake out of the comers of her house after her 2-year-old son"s birthday party. This friendly combination of chitchat took place not in front of a blackboard but in an E-mail message that Rugh sent to the 135 students she"s teaching at the Florida Virtual School, one of the nation"s leading online high schools. The school"s motto is "any time, any place, any path, any pace". Florida"s E-school attracts many students who need flexible scheduling, from young tennis stars and young musicians to brothers Tobias and Tyler Heeb, who take turns working on the computer while helping out with their family"s clam-farming business on Pine Island, off Florida"s southwest coast. Home-schoolers also are well represented. Most students live in Florida, but 55 hail from West Virginia, where a severe teacher shortage makes it hard for many students to take advanced classes. Seven kids from Texas and four from Shanghai round out the student body. The great majority of Florida Virtual Schoolers—80 percent are enrolled in regular Florida public or private high schools. Some are busy overachievers. Others are retaking classes they barely passed the first time. The school"s biggest challenge is making sure that students aren"t left to sink or swim on their own. After the school experienced a disappointing course completion rate of just 40 percent in its early years, Executive Director Julie Young made a priority out of what she calls "relationship-building", asking teachers to stay in frequent E-mail and phone contact with their students. That personal touch has helped: The completion rate is now 80 percent. Critics of online classes say that while they may have a limited place, they are a poor substitute for the face-to-face contact and socialization that take place in brick-and-mortar classrooms. Despite opportunities for online chats, some virtual students say they"d prefer to have more interaction with their peers. Students and parents are quick to acknowledge that virtual schooling isn"t for everyone. "If your child"s not focused and motivated, I can only imagine it would be a nightmare", says Patricia Hay good of Orlando, whose two daughters are thriving at the Florida school. For those who have what it takes, however, virtual learning fills an important niche. "I can work at my own pace, on my own time", says Hackney. "It"s the ultimate in student responsibility".

In the United States elementary education begins at the age of six. At this stage nearly all the teachers are women, mostly married. The atmosphere is usually very friendly, and the teachers have now accepted the idea that the important thing is to make the children happy and interested. The old authoritarian (要绝对服从的) methods of education were discredited (不被认可) rather a long time ago—so much so that many people now think that they have gone too far in the direction of trying to make children happy and interested rather than giving them actual instruction. The social education of young children tries to make them accept the idea that human beings in a society need to work together for their common good. So the emphasis is on cooperation rather than competition throughout most of this process. This may seem curious, in view of the fact that American society is highly competitive; however, the need for making people sociable in this sense has come to be regarded as one of the functions of education. Most Americans do grow up with competitive ideas, and obviously quite a few as criminals, but it is not fair to say that the educational system fails. It probably does succeed in making most people sociable and ready to help one another both in material ways and through kindness and friendliness.

The museum has been temporarily closed______the public.