A cellphone is one of the few things that we hold close to our faces all the time, and yet it could possibly explode - this is what made the recent Samsung's Galaxy Note 7 smart-phone accidents so shocking.

   According to technology news website The Verge, flawed（有瑕疵的）phone batteries might be to blame.

    Even if you are not a science student, you probably know that it is common sense that the anode (the negative（负的）end of the battery) and the cathode (the positive end) should never touch. If they do, the battery will short-circuit（短路）, causing a powerful electrical reaction that can destroy the battery and cause a fire.

    This is why all lithium-ion（锂离子）batteries - the kind that can be found in many of our devices like tablets and cameras - have a separator layer inside to stop the two ends from touching one another.

    But somehow, the separators in some of the Samsung phones broke, causing explosions.

    Overcharging is another problem that can make batteries heat up quickly. Fortunately, most batteries are designed to be able to automatically stop charging once they are fully charged. But again, this somehow failed to happen in some of the Samsung phones.

    The two “somehows” may sound random（随机的）and hard to explain. But they actually both come from the fact that phone producers have been pushing the limits of batteries to meet customers' demand for a longer battery life.

    According to Lynden Archer, a materials scientist at Cornell University, US, we have already achieved 90 percent of the battery life possible from a lithium-ion battery. Customers' demand that their devices get thinner has also given producers little choice but to try to put more power into thinner batteries.

     “The more energy you put into a box, the more dangerous it's going to be,” Billy Wu, a lecturer at Imperial College London, told The Guardian.

    A thinner battery also means producers have to use thinner material for separators, and thinner material has more chance of breaking.

    Bees in a colony work with each other to gather food, and they try to find the most nectar (花蜜)in the least amount of time possible. A small number of bees work as searchers, but when a good flower patch (花丛) is found, how do they tell other bees where to find it?

    Bees communicate flower location using special dances inside the hive, where bees live. One bee dances while the other bees watch. The dancing bee smells like the flower patch, and also gives the watching bees a taste of the nectar she has gathered. Smell and taste helps other bees find the correct flower patch. Bees use two different kinds of dances to communicate information: the waggle (摇摆) dance and the circle dance.

    Waggle dance

    The waggle dance tells the watching bees two things about a flower patch's location: the distance and the direction away from the hive.

A. Distance

    The dancing bee waggles back and forth as she moves forward in a straight line, then circlesaround to repeat the dance. The length of the middle line, called the waggle run, shows roughly how far it is to the flower patch.

B. Direction

    Bees know which way is up and which way is down inside their hive, and they use this to show direction. How? Bees dance with the waggle run at a specific angle away from straight up. Outside the hive, bees look at the position of the sun, and fly at the same angle away from the sun.

    Circle dance

    The circle dance tells the watching bees only one thing about the flower patch's location: that it is somewhere close to the hive.

    In this dance, the bee walks in a circle, turns around, then walks the same circle in the opposite direction. Sometimes, the bee includes a little waggle as she's turning around. The duration of this waggle is thought to indicate the quality of the flower patch.

    When Kevin Durant gave his tearful MVP speech in 2014, the NBA star made sure to thank one person who had been there with him from the very beginning: his mother. His heartfelt words about the sacrifices she made for Durant and his brother led to a lifetime movie about her journey as a single parent, The Real MVP: The Wanda Durant Story.

    Today, the NBA superstar's mom travels the country as a motivational speaker and philanthropist (慈善家). On Monday, she spoke at Thomson Reuters' in New York about her personal struggles to achieve financial stability and shared the financial advice she gave her son when he entered the league with CNBC.

    “I wanted him to realize he has worked hard," she says, "And it is OK for him to enjoy himself because of his hard work. But it is also imperative that he prepares for his future.” While she advised him to enjoy the rewards of his labor, she also wanted to make sure that her son knew the importance of financial planning.

    She told the audience that when she found herself a single parent to two children at 21, she couldn't follow the financial principles. Rather than planning for the future, she focused only on how her money could make ends meet for that moment.

Recently, Durant has teamed up with Laurene Powell Jobs for a new philanthropic program called College Track which is aimed at helping disadvantaged kids attend college. As part of the program, Durant has committed to donating $10 million to his hometown's public school system.

    Durant's mom says that in addition to his financial decisions, she is proud of his philanthropic work and his desire to help the community. “I thought giving back was always very important, and so we talked about that and he had seen that from us as a family and it's one of the things that I taught him," she says.

    Anyone who cares about what schools and colleges teach and how their students learn will be interested in the memoir (回忆录) of Ralph W. Tyler, who is one of the most famous men in American education.

    Born in Chicago in 1902, brought up and schooled in Nebraska, the 19-year-old college graduate Ralph Tyler became hooked on teaching while teaching as a science teacher in South Dakota and changed his major from medicine to education.

    Graduate work at the University of Chicago found him connected with honorable educators Charles Judd and W. W. Charters, whose ideas of teaching and testing had an effect on his later work. In 1927, he became a teacher of Ohio State University where he further developed a new method of testing.

    Tyler became well-known nationally in 1938, when he carried his work with the Eight-Year Study from Ohio State University to the University of Chicago at the invitation of Robed Hutchins.

    Tyler was the first director of the Center for Advanced Study in the Behavioral Sciences at Stanford, a position he held for fourteen years. There, he firmly believed that researchers should be free to seek an independent spirit in their work.

    Although Tyler officially retired (退休) in 1967, he never actually retired. He served on a long list of educational organizations in the United States and abroad. Even in his 80s he traveled across the country to advise teachers and management people on how to set objectives (目标) that develop the best teaching and learning within their schools.

A 293-million-mile journey of the NASA Perseverance rover (探测器) to Mars: ended successfully on February 18, 2021, with a picture-perfect landing inside the Jezero Crater. The car-sized, six-wheeled rover, nicknamed Percy is the US space agency's biggest and most advanced explorer to date. Its primary mission is to search for signs of ancient microbial (微生物的) life on Mars.

Landing on Mars is extremely tricky. The Red Planet's gravitational pull causes approaching spacecraft to go faster to high speeds, while its thin atmosphere-just 1 percent that of Earth's-does little to help slow it down as it approaches the surface.

The scientists had to reduce Percy's 12,000 mph speed to a safe landing speed of less than five mph-in just six and a half minutes. The target entry angle also had to be a precise 12 degrees-any steeper, and the spacecraft would burn up; any flatter, and it would get lost in space. It is no wonder that the final approach is often referred to as the "seven minutes of terror. "

Upon attaining a manageable speed, Percy briefly flew over the Martian surface to seek out the perfect landing spot. Its complex map-reading system rapidly scanned the area and matched it with maps in its database to find the best location.

The NASA scientists will spend the next two months testing Percy's scientific instruments. Once ready, the rover will begin to carry out its mission.

"Perseverance is the smartest robot ever made, but confirming that microbial life once existed carries an unusually large burden of proof," said Lori Glaze, director of NASA's Planetary Science Division. "While we'll learn a lot with the great instruments we have aboard the rover, it may very well require the far more well-equipped laboratories and delicate instruments back here on Earth to tell us whether our samples (样本) carry evidence that Mars once harbored life. "

Yunnan offers exciting experiences of unique customs. If you are already planning to visit Yunnan, see our festival tours.

The Torch (火把) Festival

Date: July /August (24th to 26th of the sixth lunar month)

Location: Lijiang

It is a traditional festival among the Yi, Naxi, and Bai minority (少数民族) groups. According to the ancient rule of the Naxi people, the Torch Festival should last three days, and every family should light a big torch in front of their doors for the three days.

Recommended Tour: 3-Day Ancient Lijiang Tour

The Water Splashing (泼酒) Festival

Date: April 13th to 15th

Location: Xishuangbanna

It is the most important festival observed by the Dai people of Xishuangbanna in southern Yunnan. It involves splashing water, lantern floating and other joyful activities.

Recommended tour: 6-Day Xishuangbanna Tour

The Horse Race Festival

Date: May/June (5th of the fifth lunar month)

Location: Shangri-La

Falling on the same date as the Dragon Boat Festival, it is the biggest gathering of Tibetans in Yunnan and usually lasts about 3 days. During the celebrations, traditional performances and competitions like horse racing and wrestling(摔跤) will be held.

Recommended tour: 8-Day Yunnan Tour of the Nu River and Tengchong

The Third Month Fair of the Bai Group

Date: April /May (15th to 21th of the third lunar month)

Location: Dali

It is one of the most important festivals celebrated by the Bai people in Dali in western Yunnan. During the March Fair, the streets of Dali Ancient Town are packed with people selling amazing minority items.

Recommended tour: 6-Day Yunnan Minorities Tour