A team of engineers at Harvard University has been inspired by Nature to create the first robotic fly. The mechanical fly has become a platform for a series of new high-tech integrated systems. Designed to do what a fly does naturally, the tiny machine is the size of a fat housefly. Its mini wings allow it to stay in the air and perform controlled flight tasks.

    “It's extremely important for us to think about this as a whole system and not just the sum of a bunch of individual components (元件),” said Robert Wood, the Harvard engineering professor who has been working on the robotic fly project for over a decade. A few years ago, his team got the go-ahead to start piecing together the components. “The added difficulty with a project like this is that actually none of those components are off the shelf and so we have to develop them all on our own,” he said.

    They engineered a series of systems to start and drive the robotic fly. “The seemingly simple system which just moves the wings has a number of interdependencies on the individual components, each of which individually has to perform well, but then has to be matched well to everything it's connected to,” said Wood. The flight device was built into a set of power, computation, sensing and control systems. Wood says the success of the project proves that the flying robot with these tiny components can be built and manufactured.

    While this first robotic flyer is linked to a small, off-board power source, the goal is eventually to equip it with a built-in power source, so that it might someday perform data-gathering work at rescue sites, in farmers' fields or on the battlefield. “Basically it should be able to take off, land and fly around,” he said.

    Wood says the design offers a new way to study flight mechanics and control at insect-scale. Yet, the power, sensing and computation technologies on board could have much broader applications. “You can start thinking about using them to answer open scientific questions, you know, to study biology in ways that would be difficult with the animals, but using these robots instead,” he said. “So there are a lot of technologies and open interesting scientific questions that are really what drives us on a day to day basis.”

    Do you ever dream about climbing Mount Everest, which is 8,848 meters high? If so, you're not alone. Every year, thousands of people try to climb the world's highest mountains or walk across deserts. Let's take a look at some of the 21st century's greatest adventurers (冒险家).

    Ed Stafford

    Ed Stafford from the UK is the first person to walk along the Amazon River from the mountains of Peru to the mouth of the river in Brazil. There are many dangerous animals in the rainforest, but he was only bitten by ants and mosquitoes. On his trip, Ed had to find fruit and nuts or catch fish each morning. He used a radio to ask the people of the rainforest for food and help. Many people came to meet him and guide him through the rainforest. While he walked, Ed wrote a blog to tell the world about climate change and destruction (破坏) of the rainforest.

    Gerlinde Kaltenbrunner

    Gerinde Kaltenbrunner from Austria is one of the world's greatest climbers and has climbed all the world's mountains over 8,000 metres. It's very difficult to climb in the cold weather and storms, but Gerlinde loves it. Now she spends her time climbing and helping a charity for poor children in Nepal.

    Meagan Mcgrath

    Some adventurers are always looking for a new challenge. Meagan Mcgrath from Canada has climbed mountains, ridden a bike across Canada and run races in the desert to raise money for the disabled.

    Erik Weihenmayer

    Erik Weihenmayer from the United States has climbed mountains and ridden a bike through deserts. Amazingly, Erik is blind and he wants other blind people to have active lives too. He has taken groups of young blind people climbing in Nepal.

    Healthy eating doesn't just mean what you eat, but how you eat. Here is some advice on healthy eating.

    Eat with others. It can help you to see others' healthy eating habits. If you usually eat with your parents, you will find that the food you eat is more delicious.

    Listen to your body. Ask yourself if you are really hungry. Have a glass of water to see if you are thirsty—sometimes you are just thirsty, you need no food. Stop eating before you feel full.

    Eat breakfast. Breakfast is the most important meal of the day. After you don't eat for the past ten hours, your body needs food to get you going. You will be smarter after eating breakfast.

    Eat healthy snacks like fruits, yogurt or cheese. We all need snacks sometimes. In fact, it's a good idea to eat two healthy snacks between your three meals. This doesn't mean that you can eat a bag of chips instead of a meal.

    Don't eat dinner late. With our busy life, we always put off eating dinner until the last minute. Try to eat dinner at least 3 hours before you go to bed. This will give your body a chance to digest most of the food before you rest for the next 8—10 hours.

    When you choose a friend, you should be very careful. A good friend can help you study. You can have fun together and make each other happy. Sometimes you will meet fair weather friends. They will be with you as long as you have money or luck, but when you are down, they will run away. How do I know when I have found a good friend? I look for certain qualities of character, especially understanding, honesty and reliability (可靠).

    Above all else, I look for understanding in a friend. A good friend tries to understand how another person is feeling. He is not quick to judge. Instead, he tries to learn from others. He puts himself in the other person's place, and he tries to think of ways to be helpful. He is also a good listener.

    At the same time, however, a good friend is honest. He does not look for faults (过错) in others. He notices their good points. In short, good friends will be honest to each other and accept each other.

    Another quality of a friend is reliability. I can always depend on a good friend. If he tells me he will meet me somewhere at a certain time, I can be sure that he will be there. If I need a favor, he will do his best to help me. If I am in trouble, he will not run away from me.

    There is a fourth quality that makes a friend special. A special friend is someone with whom we can have fun. We should enjoy our lives, and we would enjoy our friendship. That is why I especially like friends who are fun to be with. A good friend likes the same things I like. We share experience and learn from each other. A good friend has a good sense of humor, too. He likes to laugh with me. That is how we share in the joy of being friends. And I know that he is looking for the same quality in me.

    When I meet someone who is reliable, honest, and understanding, I know I've found a friend!

    Judy Wright and her husband decided to move closer to their son, Chris, who lived in Georgia. About a month after the move, Judy fell ill, suffering from her ongoing (不间断的) battle against Parkinson disease.

    Her condition worsened rapidly and she required medical care at home. The family hired a nursing aid who canceled at the last minute. Instead, a woman named TunDe Hector showed up in her place.

    One day, TunDe shared a story with Judy and her family. She remembered a particularly difficult day in 2014, when a stranger had helped her with a kind gesture. She had run out of gas, and with only $5 in her pocket, was walking to a gas station. A man saw her walking and turned his car around. He paid for her gas and gave her all the cash left in his wallet. Upon hearing the story, Judy's son, Chris, took off his hat and said, "That was me!" He was the stranger that had helped TunDe on that difficult day.

    During the care of Judy, the Wright family learned about TunDe's family and her own dream. The nursing aid, TunDe hoped that one day she could become an OB-GYN nurse. Her tuition was past due (逾期) and she had a family to care for, but she was determined to achieve that goal for herself and her family.

    Judy died on July 9,2017. Instead of flowers, her family asked mourners (悼念者) to donate to TunDe's education, to assist her in paying for her nursing school. In less than a week, they raised more than $8,000 and presented her with the surprise check.

    Learning is so complex that there are many different psychological theories to explain how people learn. A psychologist named Albert Bandura suggested a social learning theory which shows that observation, imitation (模仿), and modeling play a primary role in this process.

    In Albert Bandura's opinion, people can learn through observation. Observational learning doesn't even necessarily require watching another person join in an activity. We can also learn by reading, hearing, or watching the actions of characters in books and films. However, just observing someone else's actions isn't always enough to lead to learning. Your own mental state also plays an important role in determining whether a behavior is learned or not. In addition, though in many cases, learning can be seen immediately when the new behavior is displayed, yet sometimes we can learn things even though that learning might not be immediately obvious, which means people can learn new information without showing new behaviors.

    Not all observed behaviors are effectively learned. Certain requirements need to be related to the observational learning process. For example, you need to be paying attention. Also your retention is an important part of observational learning as you need to pull up information later and act on it during the process. Once you've paid attention to the model and kept the information, it's time to actually perform the behavior you observed. Further practice of the learned behavior leads to improvement. Finally, you have to be motivated to imitate the behavior that has been modeled.

    Social learning theory have many real-world applications. For example, researchers employ it to look into and understand ways that positive role models can be used to encourage desirable behaviors. Besides, it's also applied in the field of education, and today, both teachers and parents recognize how important it is to model appropriate behaviors.