Many years ago, people relied on the sun, the moon and stars to find their way around. Later, the compass was introduced. And now, we have satnav（卫星导航）systems to guide us. A satnav system uses groups of satellites to show the user's location. They send information to a receiver, such as a smart phone, to show us where we are.

    The earliest built satnav system is the Global Positioning System, which belongs to the US. Then there is Russia's Global Navigation（导航）Satellite System, the European Union's Galileo and China's own satellite navigation system, BeiDou.

    On October 14, 2017, an ARJ21-700 plane, which was the first domestically-produced jet equipped with the BeiDou navigation system, successfully completed a test flight. The results showed the performance of the system developed by China matches that of similar systems produced abroad, according to the Commercial Aircraft Corporation of China.

    Since its introduction in 2000, the Beidou navigation system has seen increasing numbers of applications linked to everyday life, from shared bikes to farming.

    When it comes to shared bikes, smart locks that support BeiDou chips offer more accurate positioning than others, making it easier to find a bike.

    Farmers can use BeiDou-enabled tractors to plow（犁）the soil and use unmanned aircraft with BeiDou to sow seeds, which can improve efficiency and make better use of resources. BeiDou's farming applications have spread from Heilongjiang province to Beijing, Liaoning, Shanxi, Hubei and other regions across China.

    With its many uses, the Beidou navigation system is even playing a big role in the Belt and Road Initiative（— 带—路）. “To date, the BeiDou system has covered most parts of the Asia-Pacific region, as well as counties along the Silk Road Economic Belt and the 21^st Century Maritime Silk Road” said Yang Changfeng, Chief designer of the BeiDou system.

    Today, there are more than 20 BeiDou satellites above our heads, and China plans to launch even more this year to expand the BeiDou network to better serve the Belt and Road Initiative.

    “As BeiDou expands its overseas reach, it will be increasingly popular in the logistics （物流）industry,” said Miao Qianjun, secretary-general of the navigation services association. “Ships, for example, can use it to position themselves while sailing across oceans to European countries, no longer limited to Southeast Asian regions in the near future.”

    Off-Peak fares are cheaper tickets for traveling on trains that are less busy, offering good value for money. The tickets may require you to travel at specific times of day, days of the week or on a specific route. Where there is more than one Off-Peak fare for a journey, the cheaper fare is called Super Off-Peak.

    You can buy Off-Peak tickets any time before you travel, either online or at a local station. The travel restrictions for your Off-Peak ticket will depend on the journey you are making. The tickets must be used on the date shown on the ticket. For Off-Peak return tickets, related journeys must be made on the date shown on your ticket as well.

    Children aged five to fifteen get a 50% discount for all Off-Peak fares. Up to 2 children under 5years can travel free with each fare paying adult. Railcard holders get 1/3 off all Standard Class Off-Peak fares. Senior, and disabled Railcard holders also get I/3 off all First Class Off Peak fares. Please note that minimum fares and time restrictions may apply to tickets bought with a Railcard.

    If you plan on a train trip with friends or your family, you may get group travel discounts. Three or four can travel for the price of just two adults—leaving everyone more money to spend on the day out! If you are traveling in a group of ten or more at Off-Peak times, you may be able to obtain a further discount through the train company you are traveling with. Contact the train company directly and be aware that you may need to book tickets in advance.

    For more information, please visit www. nationalrail. co. uk

    Some inventions are so useful, but seem so simple, that we wonder why no one thought of them long ago. Post-it Notes, the pieces of paper that you can stick almost anywhere and then remove without leaving any sign that they are there, are an example of such an invention.

    Post-it Notes were invented about twenty years ago by Art Fry, a scientist at 3M Corporation. The idea for the product came from an upsetting experience he often had while singing in his church choir. Fry used pieces of paper as bookmarks to mark the places in his book of songs, but these bookmarks were always falling out. He knew he needed a bookmark that would stay where he put it, but that he could remove without damaging the pages.

    Around that time, Fry heard about a new adhesive(粘合剂) that a colleague, Dr. Spence Silver had created. This adhesive was special because it was sticky, but not too sticky. It was strong enough to hold papers together, but weak enough not to tear the paper when it was removed. Fry saw that the new adhesive could help solve his bookmark problem. One morning, Fry put some of the adhesive on the edge of a piece of paper. Just as he hoped, it made a perfect bookmark.

    A short time later, Fry realized that his new invention had even more uses than being a great bookmark. He came to this realization when he wrote a note on one of his new “bookmarks” and attached it to a report he was going to give to a colleague. Soon, co-workers were asking Fry for more sample of his invention so that they could use the new type of notes themselves.

    Fry and some other people at 3M believed so much in the new product that they persuaded the company to give away thousands of the sticky pieces of paper for trial use. When some salespeople at 3M went to offices and showed workers just how helpful the new type of notes could be, they immediately received many orders. As more and more people discovered how useful Post-it Notes could be, the product took off.

    I was desperately nervous about becoming car-free. But eight months ago our car was hit by a passing vehicle and it was destroyed. No problem, I thought: we'll buy another. But the insurance payout didn't even begin to cover the costs of buying a new car－I worked out that, with the loan, we'd need plus petrol, insurance, parking permits and tax, we would make a payment as much as £600 a month.

    And that's when I had my fancy idea. Why not just give up having a car at all? I live in London. We have a railway station behind our house, a tube station 10 minutes' walk away, and a bus stop at the end of the street. A new car club had just opened in our area, and one of its shiny little red Peugeots was parked nearby. If any family in Britain could live without a car, I reasoned, then surely we were that family.

    But my new car-free idea, sadly, wasn't shared by my family. My teenage daughters were horrified. What would their friends think about our family being "too poor to afford a car"? (I wasn't that bothered what they thought, and I suggested the girls should take the same approach.)

    My friends, too, were astonished at our plan. What would happen if someone got seriously ill overnight and needed to go to hospital? (an ambulance) How would the children get to and from their many events? (buses and trains) People smiled as though this was another of my mad ideas, before saying they were sure I'd soon realize that a car was a necessity.

    Eight months on, I wonder whether we'll ever own a car again. The idea that you "have to" own a car, especially if you live in a city, is all in the mind. I live—and many other citizens do too—in a place that has never been better served by public transport, and yet car ownership has never been higher. We worry about rising car costs, but we'd be better off asking something much more basic: do I really need a car? Certainly the answer is no, and I'm a lot richer because I dared to ask the question.

    American high school students are terrible writers, and one education reform group thinks it has an answer: robots. Or, more accurately, robot-readers—computers programmed to scan students' essays and spit out a grade.

    Mark Shermis, professor of the College of Education at the University of Akron, is helping to hold a contest, set up by the William and Flora Hewlett Foundation (WFHF), which promises $ 100,000 in prize money to programmers who write the best automated grading software. "If you're a high school teacher and you give a writing task, you're walking home with 150 essays," Shermis said. "You're going to need some help."

    Automated essay grading was first proposed in the 1960s, but computers back then were not up to the task. In the late 1990s, as technology improved, several textbooks and testing companies jumped into the field. Today, computers are used to grade essays on South Dakota's student writing assessments and a handful of other exams, including the TOEFL test of English fluency, taken by foreign students.

    The Hewlett contest aims to show that computers can grade as well as English teachers—only much more quickly and without all that depressing red ink. "Automated essay scoring is objective," Shermis said. "And it can be done immediately. If students finish an essay at 10 pm, they will get a result at 10: 01 pm."

    Take, for instance, the Intelligent Essay Assessor, a web-based tool marketed by Pearson Education, Inc. Within seconds, it can analyze an essay for spelling, grammar, organization, and help students to make revisions. The program scans for key words and analyzes semantic (语义的) patterns, and Pearson claims that it can understand the meaning of text much the same as a human reader.

    Polish President Andrzej Duda has signed a bill into law that largely limits trade on Sundays, saying it will benefit family life.

    The legislation（立法）, worked out by the government and the Polish trade union, is expected to draw protests from large western supermarket chains that are the main target of the law. A large part of their profit is earned on weekends.

    As of March 1, shops and markets are closed on two Sundays per month; in 2019 only one Sunday a month will be open for shopping; and starting in 2020, there will be no Sunday shopping with a few exceptions.

    Duda praised the law as giving children a chance to be with parents and giving shop workers some needed time off. He also said big traders will need to adjust their practices to the new system and asked them for "understanding". But critics say some of them make employees work long hours for modest pay.

    "A family should be together on Sundays," Olszewska said after buying some food at a local Biedronka, a large discount supermarket chain. She said that before she retired she served cold cuts in a grocery store, and was grateful she never had to work on Sundays.

    There are some exceptions to the ban. For instance, gas stations, cafes, pharmacies and some other businesses are allowed to keep operating on Sundays.

    Anyone breaking the new rules faces a fine of up to 100,000 zlotys （$ 29,500）, while repeat offenders may face a prison sentence. Polish trade union appealed to people to report any violators to the National Labor Inspectorate, a state body.