All over the world the need for more laptops and computers increases each year. Networks have been part of our life. Probably everyone with a portable device （移动设备）has once logged on to a public WiFi network without paying for it, while they are having a coffee, on a train, in a shopping mall or at a hotel. However, is this kind of public WiFi network safe?

    Some networks are better protected than others because encryption （加密）methods are used. Therefore, they are safer than others. But a survey in 2015 showed that more than 950 million records were not protected, including addresses, emails, birth dates, phone numbers, passwords and so on. These open WiFi networks are really not safe, because it is very easy for hackers （黑客） to break into the operating system and get people's private information.

    Most smartphones and laptops, by themselves, search and connect to WiFi networks. They usually prefer a network with a connection that has been used before. Hackers' devices are able to record these searches and look like the trusted WiFi networks. When these smartphones and laptops log on to the networks which are not real, hackers can easily steal their private information.

    So next time, when we want to use our laptops or our smartphones in public places which offer free WiFi networks, please think it twice or take safe measures before using them.

    Today some people call Amsterdam the "City of Bicycles" because it is a city which is flat and convenient（方便）for bicycles.

    In the 1960s, a group of cycling fans1an idea . They believed that it would be better for everybody if only bicycles were allowed in the city centre. They were2that this would help to save energy, reduce pollution and provide free public transport. The group painted hundreds of bicycles3and placed them in public places around Amsterdam for people to use.4was allowed to take them and use them for short journeys, whether he was a local or a foreigner, Wherever someone finished a journey, they would5the bike there for someone else to use. The problem was that it didn't work-thieves took all the bicycles6 weeks!

    7,more than thirty years later, the "white bike" is back in town-this time with a computer chip(芯片)to8 its every move! To take a bicycle, you have to put a special card inside. The new "White bike" is not white any more but is an unusual9with bright colours. The bikes are parked at special parking places and people who want to use them have to take them to another place that has enough room.

    There is already less traffic in central Amsterdam, 10 both locals and tourists have been using the white bikes. Thanks to the good ideas of lots of people, like the cycling fans in the 1960s, many people around the world have been enjoying city centre streets without cars for many years.

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    Last week, scientists said they discovered a new birdlike dinosaur. With feathers, a beak (鸟嘴) and long legs, it looked pretty funny. This kind of dinosaur was 3 meters (10 feet) long, and it was higher than most humans. It also had sharp claws (爪子).

    Fossil hunters dug out the bones of this species in a rocky place of southwest North Dakota. The scientists nicknamed this dinosaur the "Chicken from Hell". They also gave it a more formal name: Anzu Wyliei. Anzu was a mythical (神秘的) fire-breathing bird. Wylie is the dinosaur-loving grandson of a man who supports the Carnegie Museum of Natural History in Pittsburgh, Pa. Scientists at that museum were part of the team that told the new dinosaur in a paper published on March 19 in the journal PLOS ONE. "The Anzu dinosaur is based on a surprisingly nice specimen(样品), and past digs turned up this animal," a scientist told Science News for Students.

    The idea of being able to walk on water has long interested humans greatly. Sadly, biological facts prevent us ever accomplishing such a thing without artificial aid-we simply weigh too much, and all our mass pushes down through our relatively small feet, resulting in a lot of pressure that makes us sink.

    However, several types of animals can walk on water. One of the most interesting is the common basilisk Basilicus basilicus, a lizard(蜥蜴) native to Central and South America. It can run across water for a distance of several meters, avoiding getting wet by rapidly hitting the water's surface with its feet. The lizard will take as many as 20 steps per second to keep moving forward. For humans to do this, we'd need huge feet that we could bring up to our ears in order to create adequate "hitting."

    But fortunately there is an alternative: cornflour. By adding enough of this common thickening agent to water (and it does take a tot), you can create a "non-Newtonian" liquid that doesn't behave like normal water. Now, if the surface of the water is hit hard enough, particles(粒子) in the water group together for a moment to make the surface hard. Move quickly enough and put enough force into each step, and you really can walk across the surface of an adequately thick liquid of cornflour.

    Fun though all this may sound, it's still rather messy and better read about in theory than carried out in practice. If you must do it, then keep the water wings handy in case you start to sink and take a shower afterward!

    Wind power is a very clean source of energy. This is how wind power works. Wind makes windmills spin (旋转). When the windmills spin, they make electricity. Then we can use the electricity.

    A lot of people think that wind power is new, but that's not true.

    For thousands of years, people have used wind to sail boats and move water. We still do those things today, but these days we mostly use wind power to make electricity.windmills

    Wind power is a very popular source of energy. Most people think that we should use it more and more. First of all, it's clean. Windmills don't pollute the environment at all. Second, we can use wind power forever. After all, we will always have wind. Also, wind power is cheap, and it's getting even cheaper.

    A lot of people don't understand wind power very well. They believe that there are problems with wind power, but many of those problems are not real. For example, some people say that windmills are dangerous for birds. They used to be true, but it isn't true anymore. Old windmills killed birds because they spun very fast. New windmills spin slowly, and they aren't dangerous for birds.

    However, there are real problems with windmills. One problem is that many people think windmills are very ugly. This is a problem for people, because windmills are often in very pretty areas. Also, wind doesn't blow all the time, so we can't use wind power all the time. Finally, windmills are noisy.

    Wind power is becoming more and more common. Right now, more than 80 countries use wind power. About 2.5 percent of the world's power comes from the wind. For some countries, that number is a lot higher. Wind power gives Denmark more than 25 percent of its electricity.