Leonardo da Vinci, one of the greatest thinkers in the world, began his career as an artist. Very little is known about Leonardo's early life. He was born in 1452 in the town of Vinci. As a boy, Leonardo showed a great interest in drawing, sculpting and observing nature.

    However, because Leonardo was born to parents who were not married to each other, he was barred from some studies and professions. He trained as an artist after moving to Florence with his father in the 1460s. It was an exciting time to be in Florence, one of the cultural capitals of Europe. Leonardo trained with one of the city's very successful artists, Andrea del Verrocchio. He was a painter, sculptor and gold worker. Verrocchio told his students that they needed to understand the body's bones and muscles when drawing people.

    Leonardo took the teacher's advice very seriously. He spent several periods of his life studying the human body by taking apart and examining dead bodies. While training as an artist, Leonardo also learned about and improved on relatively new painting methods at the time. One was the use of perspective(透视) to show depth. A method called “sfumato” helped to create a cloudy effect to suggest distance. “Chiaroscuro” is a method using light and shade as a painterly effect.

    Leonardo's first known portrait now hangs in the National Gallery in Washington, D. C. He made this painting of a young woman named Ginevra de' Benci around 1474. The woman has a pale face with dark hair. In the distance, Leonardo painted the Italian countryside.

    He soon received attention for his extraordinary artistic skills. Around 1475 he was asked to draw an angel in Verrocchio's painting “Baptism of Christ.” One story says that when Verrocchio saw Leonardo's addition to the painting, he was so amazed by his student's skill that he said he would never paint again.

    The BeiDou Navigation Satellite System（BDS）is a Chinese satellite navigation system. It consists of two separate satellite constellations（星座）. The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System and also known as BeiDou-1, consists of three satellites, which since 2000 has offered limited coverage and navigation services, mainly for users in China and neighboring regions. Beidou-1 was decommissioned at the end of 2012.

    The second generation of the system, known as COMPASS or BeiDou-2, became operational in China in December 2011 with a partial constellation of 10 satellites in orbit. Since December 2012, it has been offering services to customers in the Asia-Pacific region.

    In 2015, China started the build-up of the third generation BeiDou system（BeiDou-3）in the global coverage constellation. The first BDS-3 satellite was launched on 30 March 2015. Up to January 2018, nine BeiDou-3 satellites have been launched. BeiDou-3 will eventually consist of 35 satellites and is expected to provide global services upon completion in 2020. So far, China has sent 27 BeiDou satellites into space. When fully completed, BeiDou, the world's fourth navigation satellite system, following GPS in the United States, GLONASS in Russia and Galileo in the European Union, will provide an alternative global navigation satellite system to the United States owned Global Positioning System（GPS）, and is expected to be more accurate than the GPS. It was claimed in 2016 that BeiDou-3 will reach millimeter-level accuracy（with post-processing）, which is ten times more accurate than the finest level of GPS.

    According to China Daily, in 2015, fifteen years after the satellite system was launched, it was generating a turnover of $31.5 billion annually for major companies such as China Aerospace Science and Industry Corp, AutoNavi Holdings Ltd, and China North Industries Group Corp.

    In 1812, the year Charles Dickens was born, there were 66 novels published in Britain. People had been writing novels for a century—most experts date the first novel to Robinson Crusoe in 1719—but nobody wanted to do it professionally. The steam-powered printing press was still in its early stages; the literacy（识字） rate in England was under 50%. Many works of fiction appeared without the names of the authors, often with something like “By a lady.”Novels, for the most part, were looked upon as silly, immoral, or just plain bad.

    In 1870, when Dickens died, the world mourned him as its first professional writer and publisher, famous and beloved, who had led an explosion in both the publication of novels and their readership and whose characters — from Oliver Twist to Tiny Tim— were held up as moral touchstones. Today Dickens' greatness is unchallenged. Removing him from the pantheon（名人堂） of English literature would make about as much sense as the Louvre selling off the Mona Lisa.

    How did Dickens get to the top? For all the feelings readers attach to stories, literature is a numbers game, and the test of time is extremely difficult to pass. Some 60,000 novels were published during the Victorian age, from 1837 to1901; today a casual reader might be able to name a half-dozen of them. It's partly true that Dickens' style of writing attracted audiences from all walks of life. It's partly that his writings rode a wave of social, political and scientific progress. But it's also that he rewrote the culture of literature and put himself at the center. No one will ever know what mix of talent, ambition, energy and luck made Dickens such a singular writer. But as the 200th anniversary of his birth approaches, it is possible — and important for our own culture—to understand how he made himself a lasting one.

    A year after graduation, I was offered a position teaching a writing class. Teaching was a profession I had never seriously considered, though several of my stories had been published. I accepted the job without hesitation, as it would allow me to wear a tie and go by the name of Mr. Davis. My father went by the same name, and I liked to imagine people getting the two of us confused. "Wait a minute," someone might say, "are you talking about Mr. Davis the retired man, or Mr. Davis the respectable scholar?"

    The position was offered at the last minute, and I was given two weeks to prepare, a period I spent searching for briefcase and standing before my full-length mirror, repeating the words, "Hello, class. I'm Mr. Davis." Sometimes I would give myself an aggressive voice. Sometimes I would sound experienced. But when the day eventually came, my nerves kicked in and the true Mr. Davis was there. I sounded not like a thoughtful professor, but rather a 12-year-old boy.

    I arrived in the classroom with paper cards designed in the shape of maple leaves. I had cut them myself out of orange construction paper. I saw nine students along a long table. I handed out the cards, and the students wrote down their names and fastened them to their breast pockets as I required.

    "All right then,'' I said." Okay, here we go." Then I opened my briefcase and realized that I had never thought beyond this moment. I had been thinking that the students would be the first to talk, offering their thoughts and opinions on the events of the day. I had imagined that I would sit at the edge of the desk, overlooking a forest of hands. Every student would shout. "Calm down, you'll all get your turn. One at a time, one at a time!"

    A terrible silence ruled the room, and seeing no other opinions, I asked the students to pull out their notebooks and write a brief essay related to the theme of deep disappointment.

    Every festival has its own meaning. Labor Day, for example, celebrates the value of hard work. Thanksgiving is about showing thanks to people around you. And Valentines' Day is a time when you express love to your loved ones, But somehow it now seems that all festivals we just about one thing-shopping. And that can be a big problem.

    "In a way, over -consumption(过度消费) is the mother of all our environmental problems" Kalle Lasn once told CNN. Lasn is the organizer of Buy Nothing Day, a day set up in Canada in 1992 to fight against unhealthy spending habits, and has now become an international event. It's hel on the day, which is known as Black Fridny -a famous shopping day in the US and Canada. You can see the irony(讽刺)here.

    Even though the idea of Buy Nothing Day was brought up 26 years ago, we seem to need it now more than ever, It's just as Lasn said, all the different kinds of pollution in our lives today bad air quality, the reduction of forest area, endangered animal species, and plastic bags found in the ocean-seem to be the same cause: over-consumption.

     The latest example is the Singles' Day shopping craze of Nov 11, which saw a new sales record, But as Nie Li, a campaigner at Greenpeace, told Reuters. "Record-setting over-consumption means record-setting waste." And it was reported that last year the Singles' Day packages left more than 160,000 tons of waste, including plastic and cardboard. The Collins dictionary has also just named "single-use" its Word of the Year, pointing out the problem that there're too many things we tow out after only using them once.

    So, Buy Nothing Day might only be here for one day a year, but it's not just to remind us to the a break from shopping on that day, but to change our lifestyle completely, focusing on fun "with people we care about" rather than wasting money on useless things.

    Self-driving cars have been backed by the hope that they will save lives by getting involved in fewer crashes with fewer injuries and deaths than human-driven cars. But so far, most comparisons between human drivers and automated vehicles have been unfair. Crash statistics for human-driven cars arc gathered from all sorts of driving situations and all types of roads. However, most of the data on self-driving cars' safety have been recorded often in good weather and on highways, where the most important tasks are staying in the car's own lane and not getting too close to the vehicle-ahead. Automated cars are good at those tasks, but so are humans.

    It is true that self-driving cars don't get tired, angry, frustrated or drunk .But neither can they yet react to uncertain situations with the same skill or anticipation of an attentive Unban driver. Nor do they possess the foresight to avoid potential dangers. They largely drive from moment to moment, rather than think ahead to possible events literally down the road.

    To a self-driving car, a bus full of people might appear quite similar to an uninhabited field. Indeed, deciding what action to take in an emergency is difficult for humans, but drivers have sacrificed themselves for the greater good of others. An automated system's limited understanding of the world means it will almost never evaluate (评估)a Situation the same way a human would. And machines can't be programmed in advance to handle every imaginable set of events.

    Some people may argue that the promise of simply reducing the number of injuries and deaths is enough to support driverless cars. But experience from aviation(航空)shows that as new automated systems are introduced, there is often an increase in the rate of disasters.

    Therefore, comparisons between humans and automated vehicles have to be performed carefully. To fairly evaluate driverless cars on how well they fulfill their promise of improved safety, it's important to ensure the data being presented actually provide a true comparison. After all, choosing to replace humans with automation has more effects than simply a one-for-one exchange.