You have never seen him,but they're with you every time you fly.They record where you are going,how fast you're traveling and whether everything on your airplane is functioning normally.Their ability to withstand（经受得住）almost any disaster makes them seem like something out of a magic book.They're known as the black box.

    When planes fall from the sky,as a Yemeni airliner did on its way to Comoros Islands in the India ocean June 30,2009,the black box is the best bet for identifying what went wrong.So when a French submarine（潜水艇）detected the device's homing signal five days later,the discovery marked a huge step toward determining the cause of a tragedy in which 152 passengers were killed.

    In 1958,Australian scientist David Warren developed a flight-memory recorder that would track basic information like altitude and direction.That was the first mode for a black box,which became a requirement on all U.S.commercial flights by 1960.Early models often failed to withstand crashes,however,so in 1965 the device（装置）was completely redesigned and moved to the back of the plane-the area least affected bu impact-from its original position in the landing wells（起落架舱). The same year, the Federal Aviation Authority required that the boxes,which were never actually black,be painted orange or yellow to aid visibility.

    Modern airplanes have two black boxes: a voice recorder,which tracks pilots' conversations,and a flight-data recorder,which monitors fuel levels,engine noises and other operating functions that help investigators reconstruct the aircraft's final moments.Placed in an insulated ( 隔绝的) case and surrounded by a quarter-inch-thick panels of stainless steel,the boxes can withstand massive force and temperatures up to 2,000℉.When in deep water,they're also able to emit signals from depths of 20,000 ft.Experts believe the boxes from Air France Flight 447,which crashed near Brazil on June 1,2009,are in water nearly that deep,but statistics say they're still likely to turn up.In the approximately 20 deep-sea crashes over the past 30 years,only one plane's black boxes were never recovered.

    Friends are important to children．Research shows that children who have no friends can suffer from difficulties later in life．Friendship provides children with more than just fun．In making friends，children learn how to get in touch with others and solve problems．Having friends even does good to children for they can help each other during class.

    If the parents are concerned about whether their children make many friends，what matters is that the child is comfortable and happy with his friends．Parents need to understand the steps children take in building friendships．First of all，be a friend to your child．Good friendships start at home．Children begin to develop the necessary ability to go out and meet others through getting along with their parents. Greet the child warmly and let him know you are glad to see him．Children learn a lot from how their parents stay with them and other people.

    Teach children how to solve conflicts(争端)．Being able to work out conflicts is an important skill in getting along with others．If parents know the children have a conflict，let them work it out on their own．Only step in if it is really necessary，for example，an argument is getting physical.

    Give children chances to practice staying together．Have children play games that require cooperation. For example，races are fun and provide plenty of practice in teamwork．“In what ways didn't you work well together? What might you do differently next time?” For these ideas，see books such as Games Book by Telly Orlick and Team—Building by Alanna Jones.

    Encourage children to show thanks to others．The parents can encourage children to do this by setting the example for them．

    It is quite apparent that competition surrounds every aspect of human life whether in the United States or the Amazon Rain Forest. Without it we would not have grown into primates(灵长类动物). Or we would probably still be struggling to sharpen a bronze tool while crawling around on four legs in search of meat. Without competition, Columbus wouldn't have discovered America and Edison would never have invented the light bulb.

    Friendship, like all relationship between two people, involves competition. It isn't competition in a traditional sense because there are no goals to be scored and no prize. Perhaps the ecological definition—the simultaneous (同时的)demand by two or more organisms for limited environmental resources, such as nutrients， living space, or light- better explain it.

    As in nature, high school life is governed by a set of laws, similar to a shortened version of Darwin's theory of evolution, overpopulation, and competition. There is an abundance of high school students and to distinguish them, ranking and categorizing(分类)take place. In high school, friendships learn to co-exist with competition even though at times the relationship is rough. In fact, in some circumstances, competition is too much of a burden for a friendship to bear, causing it to fall apart. College admission is the final high school objective. Four years of hard work is to achieve good grades, and a student's fate is determined not only by these achievements, but by the records of thousands of other seniors trying to achieve a similar recognition.

    Nevertheless, by necessity, competition between students exists in all aspects of high school life. It sets and improves the standards in everything from sports to school work. A healthy, friendly competition can have only benefits, but when it becomes too fierce, jealousy can tear friendships apart. Yet, despite all this, without competition, we would be lost.

    Top 5 smart wearable vendors in the world

    Market research company IDC's latest data showed that a total of 21 million smart wearables were shipped in the third quarter of 2015, up by 197.6% year-on-year.

    As a rather new area, market players change positions frequently. China's BBK, owner of a children's phone watch brand Xiaotiancai, outperformed Samsung and broke into the top five clubs, gaining a market share of 3.1 percent.

    Let us have a look at the top 5 vendors.

    No 5 BBK

    Shipment volume: 0.7 million

    Market share: 3.1%

    People can watch a video on the website of Guangdong Xiaotiancai Tech Company Limited to know more about its phone watches.

    No 4 Garmin

    Shipment volume: 0.9 million

    Market share: 4.1%

    Garmin's new fenix 3 multi-sport GPS training watch is displayed at the 2015 International CES, a trade show of consumer electronics, in Las Vegas, Nevada, Jan 7, 2015.

    No 3 Xiaomi

    Shipment volumes: 3.7 million

    Market share: 17.4%

    The Mi Bands, developed by Xiaomi's ecosystem company Huami Co Ltd, has a function to track the user's heart beat while in motion.

    No 2 Apple

    Shipment volume: 3.9 million

    Market share: 18.6%

    Customers try to use an Apple Watch in an Apple retail store in Hangzhou city, East China's Zhejiang province, April 24, 2015. The watch went on sale on April 24 around the world.

    No 1 Fitbit

    Shipmen volume: 4.7 million

    Market share: 22.2%

    Various Fitbit devices were displayed outside the New York Stock Exchange on Jun 18, 2015, when the company got listed.

    Franz Boas was born in Minden, Germany, in 1858. After studying at the Universities of Heidelberg, Bonn, and Kiel, he received a doctor's degree in physics from the University of Kiel in 1881. His first fieldwork experience was among the Eskimo in Baffinland, Canada, in 1883-1884. In 1886, on his way back from a visit to the Kwakiutl Indians of British Columbia, Canada, he stopped in New York and decided to settle.

    Boas's first teaching position in America was at the newly founded Clark University in 1888. Eleven years later, he became professor of anthropology(人类学) at Columbia University. From 1896 to 1905 he was also curator(馆长) of anthropology at the American Museum of Natural History in NY. There he organized and took part in the Jesup North Pacific Expedition of 1902, which suggested the possibility of a strong relationship between northern Asian and northwestern Native American cultures. After guiding the Columbia Anthropology Department for 41 years, Boas became Professor Emeritus(荣誉退休教授) in 1937.

    Boas's anthropological studies have become classics in the field. He showed the necessity of studying a culture in all its aspects, including art, history, dance, language as well as the characteristics of the people. He pointed out that the differences in peoples were the results of historical, social and geographic conditions and all populations had complete and equally developed culture. He argued that no truly pure race exists, and that no race is superior to any other.

    In 1911 Boas published the Mind of Primitive Man, a series of lectures on culture and race. In the 1930s the Nazis in Germany burned the book. Boas revised the book in 1937 and put his anthropological ideas about racism into popular magazine articles. In 1942, Boas died, having founded anthropology as a recognized social science.

    On the very first day, God created the cow and said to him, "As a cow, you must go to the field, working under the sun all day long! And I will give you 40 years to live." The cow objected, "What? You want me to live such a tough life for 40 years? Let me have 20 years, and I'll give the rest back to you." So God agreed.

    On the second day, God created the dog and said, "You'll be man's best friend, guarding his house and eating his leftovers. I'll give you a life span of 30 years." The dog shook his head. "Eating leftovers for 30 years? No way! I'll give half back to you!" So God agreed.

    Then, God created the monkey, saying, "Your job is to entertain people. You've got to do monkey tricks and make them laugh. And you'll live 20 years."" Do monkey tricks to make them laugh? 10 years will do." the monkey said. So God agreed.

    Finally, God created the man. "You will be the man. All you need to do is to sleep, eat, and play, simply enjoying your life. And I'll give you 20 years to live." Thinking for a while, the man replied, "I can be the man, but I want to take all the years that the cow, the dog and the monkey didn't want." So God agreed.

    Since then, man eats, sleeps and plays in the first 2 decades, marries and spends the next 2 decades like a cow, working very hard to support his family. Then when he has children, he lives 15 years like a dog, taking care of the house and eating whatever is given to him. And when he is old, he retires and lives 10 years like a monkey, doing tricks to amuse his grandchildren.