What subject do you worry about the most at school? Many students worry about math. Some students can’t sleep well the day before a math exam. Others may feel very nervous during the exam itself. But there might be a way to make the subject less stressful.

“For people who are anxious about math, posture (姿势) makes a big difference,” Erik Peper from San Francisco State University told the Daily Mail. That’s right—sitting up straight can help you do better on math exams.

Scientists tested 125 college students. They asked them to do a simple math quiz (测试) while siting in a slumped-over (趴倒的) position, or sitting up straight. After the test, 56 percent of students said the exam was easier to do if they were sitting up straight.

Slumping over is a defensive (防御的) posture. It can trigger (激发) negative memories in the body and brain. This can stop you from thinking clearly, Peper said.

Students who were not nervous about taking the math exam did not necessarily benefit from better posture. But they did find that doing math while slumped over was more difficult, Science Daily reported.

Good posture isn’t just helpful for taking math exams. Athletes, musicians and public speakers can all benefit from better posture. When you feel stressed out, you can also try to sit up straight or stand tall. It can help you feel more positive and focus better.

China has completed its BeiDou Navigation Satellite System (卫星导航系统), or BDS, becoming another one in the world with a global (全球的) navigation network, the other three being GPS of the US, GLONASS of Russia and Galileo of the European Union.

As the name suggests, the global navigation satellite system provides navigation and location services 24 hours a day. From what we have known so far, building a good satellite system costs a lot. Why does China have a new one if there is nothing special?

The other three systems have 24 satellites in MEO. Besides the 24 satellites, China’s new global navigation satellite system BeiDon-3 also has three satellites in GEO and three in IGSO. What’s special about these six satellites is that they have a relatively fixed area of activity. This can improve BDS’ accuracy (精准度) in China and the Asia-Pacific region to 5 meters, compared with a 10-meter accuracy in other areas.

BDS has another advantage - the short message service. It allows users to have a two-way communication. In areas not covered by communication signals (信号), BDS can make the short message service available in uninhabited areas, such as deserts, forests, mountainous and polar areas. With this service, users who are in danger can tell the rescue team (救援队) their location and condition.

In fact, BDS is also good business. According to the official report, China’s satellite industry has kept a 20% annual growth since 2012. And BDS contributes (贡献) about 80% of it. BDS has also created countless high-paying jobs. And with continuous improvement, it will have much more to offer in the future.

Your handshake is a part of your first impression (印象). Do you want your handshake to say good things about you? Here are some ways to help you learn how to shake hands correctly.

Know who to start. The person in a higher position or who is older should be the first one to reach out a hand. For example, if you are interviewed for a job, the interviewer should be the one to take the lead.

Don’t offer an unannounced handshake. If you offer someone your hand when they aren’t paying attention, they may not shake hands with you. It doesn’t mean the person doesn’t want to shake your hand. So start with a greeting to let others know that you’re here.

The handshake often lasts about 2 to 5 seconds. Most people don’t spend more time shaking hands. If the other person holds your hand for more than five seconds, politely withdraw (撤回) your hand.

Don’t show a sweaty (出汗的) hand. If you hand someone a sweaty hand, you may make them uncomfortable. Before shaking their hand, dry your own hand. If you’re holding a drink, hold it in your left hand so that it won’t make your right hand wet or sweaty because we often use our right hand to shake hands with others.

Shake hands in an up-and-down direction. Don’t go back and forward or side to side. Don’t swing the other person’s hand more than three times. It may make the other person uncomfortable.

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