On a Saturday morning earlier this September, the world got its first look at the Strati. This electric vehicle is unlike any other currently on the road. It rolls on four wheels, but its body and chassis(底盘) weren't built in a factory. Instead, Strati's designers used a technology called 3-D printing. It created those parts of the car in one piece, from the ground up.

    “Compared to a typical vehicle on the road, the Strati definitely looks different,” says Greg Schroeder, a senior research engineer at the Center for Automotive Research in Ann Arbor, Mich. He did not work on the new car. His organization studies trends and changes in th e auto industry.

    It took 44 hours to print the new car at the International Manufacturing Technology Show in Chicago. Over the next few days, the car's designers installed additional parts. These included the car's engine, brakes and tires. Then, early on September 13, Jay Rogers climbed into the car, started its engine and drove the vehicle onto the street. Rogers helped found Local Motors. It's the Arizona-based company behind the Strati. Two weeks later, his team printed a second Strati, and just as fast, at a fair in New York City.

    Justin Fishkin, a local Motors official, sees the Strati as a window into the future. Today, car buyers are limited in their choice of a vehicle. They can order only what car companies have already designed. But in the future, he says, you may be able to design your own car online and then get it printed to order.

    Manufacturing experts say 3-D printing has begun to revolutionize how they make things. The technology has been around for decades. But these machines used to be so expensive that only large companies could afford them. In the last few years, though, that has changed. Many of the machines are now inexpensive enough for small companies—or even individuals —to own. Some local libraries make them available to the public. High Schools are beginning to use them in classrooms. Wide access to these printers means people can now design and print a wide variety of new things.

    The car's printer is a one-of-a-kind device.

    The technology behind the 3-D printer used in Chicago is an example of additive manufacturing. This proce ss builds solid objects, slice by slice, from the bottom up. (“Strati” means layers, in Italian.) A mechanical arm moves a nozzle from one side to another, back and forth. As it moves, the nozzle deposits a liquid—often melted plastic or metal (but it could be food, concrete or even cells) —that quickly hardens or bonds to become solid or semi-solid. This creates a single, thin layer. Once a layer is complete, the printer starts depositing the next one.

    “There's a lot of interest in 3-D printing in the auto industry,” says Schroeder. Right now, the technology is particularly useful for building models of cars or car parts.

    To compete with current auto manufacturers, the 3-D printer would have to increase in a hurry, Schroeder says. By contrast, he notes, a Ford F-150 pickup truck rolls off an assembly line at a rate of roughly one per minute. To print as many Stratis would require many more printers. Schroeder says he doesn't see 3-D printing soon taking over for such high-volume manufacturing. But, he adds, “Who knows what will h appen in the long term?”

    Scientists at Oak Ridge National Laboratory in Tennessee designed the 3-D printer used in Chicago. Lonnie Love, a research scientist at the lab, led the effort.

    Additive manufacturing often is slow and expensive. It also may produce materials that are unreliable, Love says. So for two years, his team searched for ways to make 3-D printing better. They built new machines and tested them over and over.

    All of that work paid off: their new machine is fast and uses less expensive material than earlier printers. In addition, it prints a plastic embedded with fibers of carbon to produce a stronger material. This helps ensure the material won't crack or break under pressure.

    Batteries can power anything from small sensors to large systems. While scientists are finding ways to make them smaller but even more powerful, problems can arise when these batteries are much larger and heavier than the devices themselves. University of Missouri(MU) researchers are developing a nuclear energy source that is smaller, lighter and more efficient.

    “To provide enough power, we need certain methods with high energy density (密度)”，said Jae Kwon, assistant professor of electrical and computer engineering at MU. “The radioisotope (放射性同位素) battery can provide power density that is much higher than chemical batteries.”

    Kwon and his research team have been working on building a small nuclear battery, presently the size and thickness of a penny, intended to power various micro/nanoelectromechanreal systems (MNEMS) Although nuclear batteries can cause concerns, Kwon said they are safe.

    “People hear the word 'nuclear' and think of something very dangerous,” he said, “However, nuclear power sources have already been safely powering a variety of devices, such as pace-makers, space satellites and underwater systems.”

    His new idea is not only in the battery's size, but also in its semiconductor(半导体). Kwon's battery uses a liquid semiconductor rather than a solid semiconductor.

    “The key part of using a radioactive battery is that when you harvest the energy, part of the radiation energy can damage the lattice structure(晶体结构) of the solid semiconductor,” Kwon said, “By using a liquid semiconductor, we believe we can minimize that problem.”

    Together with J. David Robertson, chemistry professor and associate director of the MU Research Reactor, Kwon is working to build and test the battery, In the future, they hope to increase the battery's power, shrink its size and try with various other materials. Kwon said that battery could be thinner than the thickness of human hair.

阅读理解

    Although computers used to be large, expensive and difficult to use, they have been made smaller, cheaper and easier to use. As a result, more people have been buying computers for their homes and businesses. They are used to record information and make difficult things easy.

    Let's look at some of the many ways computers may affect(影响) your life.

    Want to get the best treatment at hospitals? Your doctors at hospitals have been greatly helped by computers to get information about patients. It is possible for doctors from different hospitals to read the records of patients, discuss them and make decisions on the best treatment. It would, at one time, take them hours and days to do so.

    Want to talk to your friends both at home and abroad? Then it's necessary to connect your computer to the Internet and set up your own e-mail letter box. You can then collect and send mails in seconds. It will be a waste of time and money to post your letters.

    Want to get advice from Michael Jordan on how to play basketball like a NBA super star? Now it is possible to find out what it is on the Internet.

    But if you think you have entered the information age because you have the chance to use the Internet, you are wrong. The reason is quite a simple one: over 98 percent of the information on the Internet is in English. The information on-line won't be helpful to you unless you can use English freely.

    Teachers' Day is, interestingly, not celebrated on the same day all over the world. In some countries it is marked by a holiday, in others it is a working day.

    International Teachers' Day is celebrated on October 5. Being held ever since 1994, it is in honor of teachers' organizations worldwide. Its aim is to encourage supports for teachers and to meet the needs of students.

    China   In 1939, Teachers' Day was set for August 27, Confucius' birthday. In1951, the celebration was stopped. However, it was founded again in 1985, and the day was changed to September 10.

    India   Teachers' Day is celebrated on September 5 in honour of Dr. Sarvepalli Radhakrishnan, the second president of India, whose birthday falls on that day.

    Russia   In Russia, Teachers' Day was celebrated on the first Sunday of October between 1965 and 1994. Since 1994, the day is observed on the October 5, just the same day as World Teachers Day.

    The US   In the US, Teachers' Day is non-official holiday. It is celebrated on the Tuesday of the first full week of May. A number of activities are organized in schools to honor teachers. The celebrations can continue for the whole week of May.

    Thailand   In Thailand, National Teachers' Day is celebrated every year on January 16. The first Teachers' Day was held in 1957. The day is a holiday in schools.

    Teachers say the digital age has had a good influence and a not-so-good influence on this generation of American teenagers. More than 2,000 middle and high school teachers took an online survey. Researchers also spoke with teachers in focus groups.

    Three-quarters of the teachers said the Internet and digital search tools have had a "mostly positive" effect on their students' research habits and skills. But 87 percent agreed that these technologies are creating an "easily distracted generation with short attention spans (持续时间)". And 64 percent said the technologies "do more to distract students than to help them academically(学业上)". Many students think "doing research" now means just doing a quick search on Google.

    The Pew Internet Project did the survey with the College Board and the. National Writing Project. Most of the teachers came from Advanced Placement classes, which provide college-level work for high school students.

    Judy Buchanan is director of the National Writing Project and a co-author of the report. Ms. Buchanan says digital research tools are helping students learn more, and learn faster. Teachers really welcome these tools because they are ways to make some of learning exciting and engaging. Young people welcome these tools. And the goal is to really help them become creators of content, and meaningful content, and not just sort of consumers.

    But one problem the survey found is that many students are lacking in digital literacy. In other words, they trust too much of the information they find on the Internet. Another problem the survey found is blamed on something that might not seem like a problem at all: being able to quickly find information online.

    Teachers say the result is a reduction in the desire and ability of their students to work hard to find answers. They say students are depending too much on search engines and do not make enough use of printed books or libraries. Many teachers are also concerned that the Internet makes it easy for students to copy work done by others instead of using their own abilities.

 "A moth (飞蛾) to a flame" is often used to indicate an inescapable attraction, yet it is a strange example of animal behavior that continues to confuse people today. Scientists have raised a number of theories over the years to explain why. One holds that insects flying at night are following their nature to fly toward the brightest spot in their field of vision, which they mistake for the sky. Another suggests that insects are trying to warm themselves with the heat produced by the light. The most popular theory, though, is that insects are confusing lights with the moon or other celestial bodies (天体) that they normally use to navigate (导航).

To find out the real reason, the team carried out a first set of experiments in an insect flight area. The researchers used eight high-speed infrared (红外线) cameras equipped with motion-capture technologies to track 30 insects from three moth and two dragonfly species. They also flew lab-raised insects from six different insect orders that were too small for motion-capture technology, including fruit flies and honeybees, to make sure different insects all showed similar responses to light. Working with co-author Pablo Allen of the Council on International Educational Exchange in Monteverde, Costa Rica, the researchers put heavy cameras, lights and tripods in two field sites to gather behavioral data from insects in the wild.

The team was able to confirm that insects were not beelining to the light but rather circling it as they tilted (倾斜) in an attempt to turn their backs toward it. This behavior, known as a "dorsal light response", normally helps insects to remain in an unchanging path of flight that is properly lined to the horizon (地平线). Artificial light that arrives from a point source causes them to fly in unpredictable patterns as they try to turn their backs to what they are mistaking for the sky.

Now research might have finally solved the mystery mentioned first: artificial light confuses insects' ability to turn themselves to the horizon, confusing their sense of what is up and down and causing them to fly in circles.