Hummingbirds(蜂鸟) are one of nature's most energetic fliers and the only birds to hover(盘旋) in the air by relying on their strength alone.

    Now scientists have found that it is the ratio(比值) of the bird's wing length to its width that makes them so efficient. The discovery is helping experts compete with 42 million years of natural selection to build helicopters that are increasingly efficient.

    David Lentink, an assistant professor at Stanford University in California, tested wings from 12 different species of hummingbirds, which he sourced from museums. He placed them on a machine used to test the aerodynamics(气力学) of the helicopter blades(桨叶). Professor Lentink's team used the same machine to test the blades from an advanced micro-helicopter used by the UK's army. They found that the micro-helicopter's blades are as efficient at hovering as the average hummingbirds.

    But while the micro-helicopter's blades kept pace with the average hummingbird wings, they could not keep up with the most efficient hummingbird's wing. The wings of Anna's hummingbird were found to be about 27 percent more efficient than the man-made micro- helicopter's blades.

    While Professor Lentink wasn't surprised at nature's superiority, he said that helicopter blades have come a long way. “The technology is at the level of an average hummingbird,” he said. “A helicopter is really the most efficient hovering device that we can build. The best hummingbirds are still better, but I think it's amazing that we're getting closer. It's not easy to match their performance, but if we build better wings with better shapes, we might match hummingbirds.”

    Professor Lentink said that we don't know how hummingbirds maintain their flight in a strong wind, how they navigate(确定方向) through branches, or how they change direction so quickly. He thinks that great steps could be made by studying wing aspect ratios-the ratio of wing length to wing width. Understanding these abilities and characteristics could be a benefit for robotics and will be the focus of future experiments.

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China is a land of bicycles. At least it was back in 1992 when I traveled the country. Back then everyone seemed to be riding a bicycle. Millions of them, all black. Cars were rare. Yet since my arrival in Beijing last year, I've found the opposite is true. There are millions of cars. However, people still use their bicycles to get around. For many, it's the easiest and cheapest way to travel today. Bicycles also come in different colors — silver, green, red, blue, yellow, whatever you want.

    It's fun watching people biking. They rush quickly through crossroads, move skillfully through traffic, and ride even on sidewalks. Bicycles allow people the freedom to move about that cars just can't provide.

    Eager to be part of this aspect of Chinese culture, I decided to buy a bicycle. Great weather accompanied my great buy. I immediately jumped up on my bicycle seat and started home.

    My first ride home was orderly (守秩序的). To be safe, I stayed with a “pack” of bikers while cars on the streets came running swiftly out of nowhere at times. I didn't want to get hit. So I took the ride carefully.

    Crossing the streets was the biggest problem. It was a lot like crossing a major highway back in the United States. The streets here were wide, so crossing took time, skill and a little bit of luck.

    I finally made it home. The feeling on the bicycle was amazing. The air hitting my face and going through my hair was wonderful. I was sitting on top of the world as I passed by places and people. Biking made me feel alive.

    One evening at a busy crossroads, I noticed a sister struggling to keep her little kid under control while she talked on the pay phone. She wanted him to stay still next to her, but he wanted to run and play by the road, close to rushing buses and taxis. One could sense the woman's frustration, that she was pulled in too many directions: She was angry at the person on the telephone and shouting at the younger that she would “snap（折断）his leg” if he moved again. As I waited for the traffic light to change, the child began to complain and struggle to free himself from the woman's grasp. She dropped the phone, seized（抓住）the neck of his tiny. T-shirt and gave him a back-hand blow across the face that I know made his little head spin.

    The light changed, and passers-by continued on their way. But I stood there, fixed to the pavement. I knew this extremely upset woman would carry through on her threat of violence to the child. Before, I had wanted to get close to her and offer to watch the youngster while she dealt with the troubling situation on the phone. Now I wanted to comfort the little boy. I also wanted to speak to the sister to calm her and to caution（告诫）her, as I wish someone had cautioned me when I was passing my pain on to my daughter and causing her emotional suffering. But I was chicken. I thought, she may think I'm out of line, or I may be her next target.

    Often I've thought about that child and the many others abused（虐待）by adults. I wonder how they will internalize（使……藏在心底）their pain, and if it will crush their spirits. Will this little boy grow up to be an abusive man? Will he be gloomy（阴郁的，沮丧的）and withdrawn（孤僻，内向的）? Will he find it hard to communicate with women, with other men? Or will he survive and be sensitive, caring and determined not to continue the cycle?

    There is too much cruelty（残忍）in the world, too much cruelty between people. I tremble at the increasing verbal（言语的）bitterness and violence among Black girls, and among young mothers trying to discipline their children. This behavior isn't class-or age-related: I hear sharp words from Black women from all walks of life who are overworked and stressed out and have grown impatient. At times I, too, become impolite to others, or, like the sister on the phone, strike out at（抨击）those closest to me.

    Often we're tired because we've made the wrong choices. Young girls who still need mothering are loaded with children. We sisters easily get hurt and annoyed when we don't compromise with our own sense of self. Our personal fulfillment requires knowing what is best for us, setting our boundaries（界限）and keeping them undamaged. We will always be asked to do more than we are comfortable doing. When we know our boundaries, we can decline comfortably. People—and we ourselves—will act in ways we don't like. But they, like us, are still worthy of love.

    Whatever irritates（激怒）us about a person should be examined. Is the person reflecting behavior in us that needs to be changed? Often, when I find people irritating, I find they mirror something about me that I need to correct.

    What's needed in our personal relationships is a return to gentleness and tolerance（容忍）. We must allow one another our learning experiences. Just as violence results to violence, verbal violence—the hard words and sharp tones we use to release inner stress—adds to the distance between us.

    What we people of African root must do to become, and continue to be strong begins with love, sensitivity and our ability to work together. We Black women have these spiritual resources in abundance（丰富）. Now we must encourage them to create a peaceful place—for ourselves, our children, our men.

    Ottawa is the capital of Canada. It is the second largest city in Ontario and the fourth largest city in the country.

    The Centre Block is the main building on Parliament Hill (国会山). There also stand several ceremonial spaces, such as the Hall of Honor and the Memorial Chamber. The present Centre Block is the second copy of the building, after the first was undermined by a big fire in 1916, and it is one of the most recognizable buildings in Canada.

    Downtown Ottawa is the commercial and economic centre of the city. Most of the buildings are office towers. While most of Ottawa's high tech industry is based elsewhere, it has an important presence in the downtown center. The downtown also contains a number of apartments, hotels, and the older single family homes and townhouses along its edges (边缘).

    The National Gallery of Canada is one of Canada's earliest art galleries. The Gallery has a large and varied collection of paintings, drawings, sculpture and photographs. Although its focus is on Canadian art, it also holds works by some well-known American and European artists.

    The Rideau Canal is the oldest continuously operated canal (运河) system in North America. At the very beginning, it was used to provide a safe supply and communication route between Montreal and the British naval (海军的) base in Kingston. It remains in use today mainly for people to boat and enjoy themselves, with most of its original structures undamaged. The locks on the system open for navigation (航海) in mid-May and close in mid-October.

    Experts say there are about 6, 500 languages spoken throughout the world. But the United Nations estimates that about half of these languages are in danger of disappearing.

    One non-profit organization seeking to save world languages is a New York-based group called Wikitongues. Officials from Wikitongues say the organization has a simple goal: to provide the tools and support that people need to save their languages.

    Udell is the co-founder of Wikitongues. He said when a language disappears, many other things can go away as well. For example, parts of a community's culture, knowledge and identity can also be lost. Because of this. Udell believes the process of bringing languages back must be done by community members themselves, “from the ground up,” he said.

    “There is no way an outside organization can save someone's language for them.”

    Wikitongues was launched in 2016 as an open internet collection of world languages. The self-described “community” is operated by volunteers from around the world. The collection is in the form of language videos that people add to the Wikitongues website.

    There are currently more than 400 languages and dialects represented on Wikitongues' YouTube channel. Udell says more than 1,500 people from 70 different countries have added videos to the system.

    “We have people from India who record dozens of languages, which is beyond their own.” he said.

    One of Wikitongues'volunteers is Kolokwe, who lives in Namibia. His native language is Subiya, however, he does not get the chance to speak his native language every day. Like many other educated people from his area, he speaks a lot of English and Afrikaans.

    Kolokwe is hoping his involvement with Wikitongues call help keep Subiya and other African languages from going extinct. He wants the world to know about his language. But his goal goes beyond just sharing his language with others through video. He is also working to create a dictionary and language teaching materials that can be used in schools.

The Rapid Rise and Fall of Robot Babysitters

    During the winter of 2017, an 18-year old college student named Canon Reeves spent much of his time trailing a knee-high robot around Fayetteville, Arkansas, as it delivered Amazon packages to students. The robot, created by a start-up called Starship Technologies in 2014, is basically a cooler on wheels; it uses radars, sensors, and nine cameras to make deliveries. Reeves's job was to monitor how it handled various grounds, field comments from the public, and press the off switch if necessary. He said, "People would also ask if it could deliver beer." It couldn't.

    Broadly speaking, jobs of caring for robots fall under the umbrella of careers in automation, which include maintenance, engineering and programming. The demand for people with this skill set is considerable, with 20 million to 50 million new jobs to be expected in this category by 2030, according to the Mckinsey Global Institute. In the year that ended in June 2018, Indeed.com had almost three times the number of positions on the recruitment committee that ended in June 2016.

    Over the last year, a 34-year-old businessman named David Rodriguez spent hundreds of hours following a machine called the KiwiBot around UC Berkeley's campus while it delivered Red bull and other drinks to students. To retrieve (检索) orders, the app encourages students to give the robot a wave; the robot's digital eyes will roll depending on its mood. Rodriguez, who heads business development for the start-up, was tasked, early on, with monitoring the KiwiBot for problems – even carrying it, should the motors fail. Since April 2018, though, the KiwiBot has largely been left unattended, and the majority of human interactions involve technical checks and loading food into the robot. To eliminate the boring work, the team is developing a restaurant robot to collect and load orders – which could happen in 2020. However, Rodriguez assured me that his staff won't be out of work. Everyone holds double roles in the company. Greater robot self-governing just means employees will shift their focus to accounting, engineering, and design.

    Mckinsey estimates that millions of jobs globally could be lost to automation by 2030. "A huge number of jobs will be produced as autonomous vehicles are released into the environment," Ramsey said. In 2016, Bosch started training students from Schoolcraft College, a community college in Michigan, in autonomous-vehicle repair; Toyota has trained students in maintenance as well. "We might even see a return to low-level jobs where people come and fuel the car for you," Ramsey said. "Until we can wirelessly charge, someone needs to refuel them." The hardest-to-automate industries, as it happens, are the ones that require looking after humans, such as childcare, education and health care. Robot babysitters might feel like they have scored the job of the future, but in fact, they might be better positioned.