【推荐1】In the past 200 years,the earth's temperature has increased greatly.It's reported that a marked increase in the temperature of about 0.7℃ appeared at the end of last century.Some scientists think mini-umbrellas(微型伞)might reduce the global(全球的)temperature.

Building a single umbrella,which is big enough to cover the whole earth,seems to be impossible.Roger Angel,a scientist from the USA,has carried out research to deal with this problem.He came up with an idea of mini-umbrellas.In fact,each mini-umbrella is made up of two parts,a spaceship and a sunshade(遮阳篷).A spaceship weighing about 1g would carry a sunshade that is half a meter long.It would be mostly transparent.That means light can pass it directly to reach the earth,with lands and oceans clearly in view.

Pressure(压力)from the sunlight would keep the little spaceships in position around the earth at a distance of about 1.5 million kilometers.As a result,sending over 1,000 billion mini-umbrellas into space would reduce the amount of sunlight reaching the earth.This allows sunlight to be reflected(反射)back to space easily,causing the temperature of the earth's ground to fall off.Covering large areas of the earth,mini-umbrellas together could reflect 1.8 percent of sunlight back.In Roger's plan,scientists will send up 800,000 mini-umbrellas at a time,20 million times in all during ten years.Scientists suggest the earliest launch could be in just 16 years.

Not all the scientists agree with the idea.Some suppose there should be easier and much cheaper ways to prevent the earth from getting too hot,such as to slow down the pollution people bring and to reduce the human activities.Whatever the result of the argument is,this idea of mini-umbrellas in space is certainly creative.

【推荐2】Chinese Internet search company Baidu Inc opened Apllo Go Robotaxi, its self-driving taxi service, to the public in Beijing, becoming the first company to carry passengers in self-driving cars in the capital.

With 40 taxis, the service covers the largest total area and the longest road distance of about 700 kilometers for an autonomous（自动化）driving test area in China. It has nearly 100 pick-up and drop-off stations in residential（住宅的）and business areas in the Yizhuang area, Haidian and Shunyi districts of Beijing. Passengers in Beijing can now take free self-driving taxis through Baidu Maps or Apoll Go apps.

Before this move, the company opened its robotaxi service to the public in Cangzhou, Hebei province, in August, when such service appeared in the downtown area of a city for the first time in China.

In April, Baidu opened its self-driving taxi service in Changsha, Hunan province, where robotaxi provides free rides to passengers across an area of 130 square kilometers.

China is planning to realize the scale（规模）production of self-driving cars and commercialization （商业化）of highly autonomous self-driving cars in certain situations by 2025.

"The self-driving technology is expected to see wide application （应用）in the next five years," said Robin Li, CEO of Baidu. According to him, intelligent infrastructure（基础设施）built for self-driving will improve traffic and bring in economic growth.

"China is taking the lead in self-driving around the world," said Li Zhenyu, vice president of Baidu. He said that Baidu Apollo would continue to push forward self-driving. "Self-driving is the future development direction of the car industry. It not only solves traffic safety problems and greatly improves the transportation, but also frees people from repetitive driving," said Jiang.

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【推荐3】Competition is good for businesses. In the world of positioning systems, however, competition is also a must.     1     Now, China is building its own positioning system. It’s called Beidou.

China is only the third country in the world to own a positioning system. Only the United States and Russia have already developed their GPS or Glonass.

    2    With it, the country no longer has to rely on foreign systems. It also shows the world that China has made much technological progress.

Work on the Beidou project began in 1994. However, the first two Beidou satellites were not sent into space until 2000.     3    These satellites have formed a global network. They began operations at the end of 2018. To further improve the system, China will send ten more Beidou satellites into space. It plans to complete the system before 2020.

    4    It will provide a positioning accuracy of within ten centimeters for the Chinese military. The United States’ GPS only has an accuracy of around 30 centimeters.

The Beidou system offers services to ordinary users, too. In big cities like Shanghai, thousands of buses have been using the Beidou system.     5    

Moreover, most smartphones today can already receive Beidou signals. A phone salesperson in Beijing jokes, “Many people are used to saying, ‘I am using GPS.’ In fact, however, their phones have been using Beidou.”