The question of what children learn, and how they should learn it, is continually being debated and redebated. Nobody dares any longer to defend the old system, the parrot-fashion（way of learning by repeating what others say）of learning lessons, the grammar-with-a-whip（鞭子）system, which was good enough for our grandparents. The theories of modern psychology have stepped in to argue that we must understand the needs of our children. Children are not just small adults; they are children who must be respected as such.

    Well, you may say, this is as it should be, and a good idea. But think further. What happens? “Education” becomes the responsibility not of teachers, but of psychologists. What happens then? Teachers worry too much about the psychological implications（暗示） of their lessons, and forget about the subjects themselves. If a child dislikes a lesson, the teacher feels that it is his fault, not the child's. So teachers worry whether history is “relevant” to modern young children. And do they dare to recount stories about violent battles? Or will this make the children themselves violent? Can they tell their classes about children of different races, or will this encourage racial hatred? Why teach children to write grammatical sentences? Oral expression is better. Sums? Arithmetic? No; real-life mathematical situations are more understandable.

    You see, you can go too far. Influenced by educational theorists, who have nothing better to do than write books about their ideas, teachers leave their teaching-training colleges filled with grand, psychological ideas about children and their needs. They make complicated preparations and try out their “modern methods” on the long-suffering children. Since one “modern method” rapidly replaces another, the poor kids will have well been fed up by the time they leave school. Frequently the modern methods are so complicated that they fail to be understood by the teachers, let alone the children; even more often, the relaxed discipline so necessary for the “informal” feeling the class must have, prevents all but a handful of children from learning anything.

    The U. S. Postal Service (USPS) is losing billions of dollars a year. The government company that delivers "small mail" is losing out to email and other types of electronic communication. First-class mail amount fell from a high point of 104 million pieces in 2000 to just 64 million pieces by 2014.

    Congress permits the 600.000-empIoyee USPS to hold a monopoly (垄断) over first-class and standard mail. The company pays no federal, state or local taxes; pays no vehicle fees; and is free from many regulations on other businesses. Despite these advantages, the USPS has lost $52 billion since 2007, and will continue losing money without major reforms.

    The problem is that Congress is preventing the USPS from reducing costs as its sales decline, and is blocking efforts to end Saturday service and close unneeded post office locations. USPS also has a costly union-dominated workforce that slows the introduction of new ideas or methods down. USPS workers earn significantly higher payment than comparable private-sector workers. The answer is to privatize the USPS and open postal markets to competition. With the rise of the Internet, the argument that mail is a natural monopoly that needs government protection is weaker than ever.

    Other countries facing declining letter amounts have made reforms Germany and the Netherlands privatized their national postal companies over a decade ago, and other European countries have followed suit. Britain floated shares of the Royal Mail on its stock exchange in 2013. Some countries, such us Sweden and New Zealand, have not privatized their national postal companies, but they have opened them up to competition.

    These reforms have driven efficiency improvements in all of these countries. Additional number of workers have been reduced, productivity has risen and consumers have benefited. Also, note that cost-cutting measures—such as closing tone post offices—are good for both the economy and the environment.

    Privatization and competition also encourage new changes. When the USPS monopoly over "extremely urgent" mail was stopped in 1979, we saw an explosion in efficient overnight private delivery by firms such as FedEx.

    The government needs to wake up to changing technology, study postal reforms abroad and let businessmen reinvent our out-of-date postal system.

    Self-driving vehicles(车辆) will rely on cameras, sensors and artificial intelligence (人工智能) to recognize and respond to road and traffic conditions, but sensing is the most effective for objects and movement in the neighborhood of the vehicle. Not everything important in a car's environment will be caught by the vehicle's camera. Another vehicle approaching at high speed on a collision (碰撞) track might not be visible until it's too late. This is why vehicle-to-vehicle communication is undergoing rapid development. Our research shows that cars will need to be able to chat and cooperate on the road, although the technical challenges are still great.

    The usages of vehicle-to-vehicle communication contain vehicles driving together in a row, as well as safety messages about nearby emergency vehicles. Vehicles could alert each other to avoid collisions or share notices about passers-by and bicycles. From as far as several hundred metres away, vehicles could exchange messages with one another or receive information from roadside units（RSUs）about nearby incidents or dangerous road conditions through 4G network. A high level of AI seems required for such vehicles, not only to self-drive from A to B, but also to react intelligently to messages received. Vehicles will need to plan, reason, strategize and adapt according to information received in real time and to carry out cooperative behaviors. For example, a group of autonomous vehicles might avoid a route together because of possible risks, or a vehicle could decide to drop someone off earlier due to messages received, a foreseen crowding ahead.

    Further applications(应用) of vehicle-to-vehicle communication are still being researched, including how to perform cooperative behavior.

    As global temperatures rise, trees around the world are experiencing longer growing seasons, sometimes as much as three extra weeks a year. All that time helps trees grow faster. For the past 100 years, trees have been experiencing fast growth in temperate regions from Maryland to Finland, to Central Europe, where the growth rate of some trees has even sped up nearly 77% since 1870. Assuming wood is just as strong today, those gains would mean more timber(木材) for building, burning, and storing carbon captured from the atmosphere. But is wood really as dense as it used to be?

    Hans Pretzsch, a forest scientist at the Technical University of Munich in Germany, and his colleagues wanted to find an answer. They carried out a study of the forests of Central Europe. They started with 41 experimental plots in southern Germany, some of which have been continuously monitored since 1870. Pretzsch and his team took core samples from the trees—which included Norway spruce, sessile oak, European beech, and Scots pine—and analyzed the tree rings using a high-frequency probe.

    They found that in all four species, wood density has decreased by 8% to 12%, they report online in Forest Ecology and Management. “We expected a trend of the wood density like this, but not such a strong and significant decrease,” Pretzsch says. Increasing temperatures, and the faster growth they spur, probably account for some of the drop. Another factor, Pretzsch says, is more nitrogen in the soil from agricultural fertilizer(化肥) and vehicle exhaust. Previous studies have linked increased fertilizer use to decreased wood density. Above all, the study suggests that the higher temperatures—combined with pollution from auto exhaust and farms—are making wood weaker, resulting in trees that break more easily and wood that is less durable.

    “I am getting worried,” says Richard Houghton, an ecologist at the Woods Hole Research Center in Falmouth, Massachusetts, who was not part of the new study. As the density of the samples dropped, so did their carbon content, by about 50%. That means forests may suffer more damage from storms and may be less efficient at soaking up the greenhouse gas carbon dioxide (CO2) than scientists had thought, Houghton says.

    Lima, the capital of Peru (秘鲁), has countless museums that tourists can't afford to miss. Now start packing up and prepare for your perfect Peruvian history exploration at these wonderful museums.

    ◆Larco Museum

    Stepping inside, visitors get to learn the 5,000-year history of Peru through an unbelievable collection of objects. The best thing about the museum is that it keeps the door to the storeroom open to visitors so that they can admire its collection closely.

    ◆Gold Museum of Peru

    If you like shiny objects or precious metals, then plan a trip to the Gold Museum of Peru. In ancient times, the Peruvian people were celebrated for their skills in metals. And the museum is aimed at preserving this heritage.

    ◆Lima Art Museum

    Art experts are much pleased as the city is also home to the Lima Art Museum. Its permanent exhibit of over 1, 200 pieces is merely a small part of its amazing collection of more than 17, 000 artifacts. The highlight of the museum is its collection of Carlos Baca-Flor's masterpieces, which is considered to be the most complete set in the world.

    ◆Museum of Italian Art

    The only museum dedicated to European art in Peru, the Museum of Italian Art is a storehouse of classical and contemporary paintings and sculptures belonging to the 20th century. The property is easily accessible by a short walk from the Lima Art Museum.

    ◆Museum of Natural History

    Last but certainly not least is the Museum of Natural History. Giving a glimpse into the rich biodiversity in Peru, the museum has on display the skeletons of a sperm whale and fossils of several mammals.

Benjamin West, the father of American painting, showed his talent for art when he was only six years of age. But he did not know about brushes before a visitor told him he needed one. In those days, a brush was made from camel's hair. There were no camels nearby. Benjamin decided that cat hair would work instead. He cut some fur from the family cat to make a brush.

The brush did not last long. Soon Benjamin needed more fur. Before long, the cat began to look ragged(蓬乱). His father said that the cat must be sick. Benjamin was forced to admit what he had been doing.

The cat's lot was about to improve. That year, one of Benjamin's cousins, Mr. Pennington, came to visit. He was impressed with Benjamin's drawings. When he went home, he sent Benjamin a box of paint and some brushes. He also sent six engravings (版画) by an artist. These were the first pictures and first real paint and brushes Benjamin had ever seen.

In 1747, when Benjamin was nine years old, Mr. Pennington returned for another visit. He was amazed at what Benjamin had done with his gift. He asked Benjamin's parents if he might take the boy back to Philadelphia for a visit.

In the city, Mr. Pennington gave Benjamin materials for creating oil paintings. The boy began a landscape (风景) painting. William Williams, a well-known painter, came to see him work. Williams was impressed with Benjamin and gave him two classic books on painting to take home. The books were long and dull. Benjamin could read only a little, having been a poor student. But he later said, "Those two books were my companions by day, and under my pillow at night." While it is likely that he understood very little of the books, they were his introduction to classical paintings. The nine-year-old boy decided then that he would be an artist.