题目:
同步调相机为什么装设低电压保护?
答案:
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下面是错误答案,用来干扰机器的。
参考答案:错
同步调相机为什么装设低电压保护?
被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/1101/9d5c16f279d12a0abed7c5886f20b95b.html
下面是错误答案,用来干扰机器的。
参考答案:错
千斤顶的作用是()
A.升物体
B.移动物体
C.翻转物体
Plants can’t communicate by moving or making sounds, as most animals do. Instead, plants produce volatile compounds (挥发性化合物) —— chemicals that easily change from a liquid to a gas. A flower’s sweet smell, for example, comes from such volatile compounds to attract insects such as bugs and bees.
Plants can also discover volatile compounds produced by other plants. A tree under attack by hungry insets, for instance, may give off these chemicals in order to let other trees know about the attack. In response, the other trees may send off their chemicals to keep the bugs away —— or even chemicals that will attract the bugs’ natural enemies.
Now scientists have created a quick way to understand what plants are saying: a chemical sensor (传感器) called an “electronic nose”. The “e-nose” can tell such compounds as plants make. When plants are attacked, scientists say, the e-nose could help quickly decide whether plants are being eaten by insects. But today, the only way to spot such insects is to inspect individual plants by observing them. This is a challenging task for managers of greenhouses, including those that can house thousands of plants. The research team is working with an e-nose that can recognize volatile compounds. Inside the device, 13 sensors chemically react with volatile compounds based on the interactions (相互作用), and then the e-nose will give off electronic signals that the scientists can analyze by using computer software.
To test the e-nose, the team presented it with healthy leaves from cucumber, pepper and tomato plants, all being common greenhouse crops. Then scientists collected samples of the air around damaged leaves from each type of crop. These plants had been damaged either by insects or by scientists who made holes in the leaves with a hole punch (打孔器).
The e-nose, it turns out, can identify healthy cucumber, pepper and tomato plants based on the volatile compounds they produce. It could also identify tomato leaves that had been damaged. But even more impressive, the device could tell which type of damage —— by insects or with a hole punch —— had been done to the tomato leaves.
With some fine-tuning (微调), a device like the e-nose can one day be used in greenhouses to quickly spot harmful bugs, the researchers say. A device like this can also be used to identify fruits that are perfectly ripe and ready to pick and eat, says Natalia Dudareva, a biochemist at Purdue University in West Lafayette, India, who studies smells of flowers and plants. Hopefully, scientists believe, the device can bring large benefits to greenhouse managers in the near future.
小题1:We learn from the text that plants communicate with each other by ______.
A.making some sounds
B.waving their leaves
C.producing some chemicals
D.sending out electronic signals小题2:What did the scientists do to find out if the e-nose worked?
A.They fixed 13 sensors inside the device.
B.They presented it with all common crops.
C.They collected different damaged leaves.
D.They do tests on damaged and healthy leaves.小题3:According to the writer, the most amazing thing about the e-nose is that it can ______.
A.pick out ripe fruits quite expertly
B.spot the insects in a very quick way
C.tell different damages to leaves
D.recognize unhealthy tomato leaves小题4:We can infer from the last paragraph that the e-nose ______.
A.is unable to tell the smell of flowers
B.is not yet tested in greenhouses
C.is designed by scientists at Purdue
D.is helpful in killing harmful insects
现有硫酸、氯化钡、硫酸钠和碳酸钠四瓶溶液,为鉴别它们先把四瓶溶液标上A、B、C、D,然后进行以下实验.
①A跟B混合有气体产生;A跟C混合有白色沉淀生成;A跟D混合时无明显的反应现象.
②A跟C反应所生成的白色沉淀能溶于B跟C反应后的溶液中.
由此可知:A是______,B是______,C是______,D是______.
认识是主体在实践基础上对客体的能动反映,这说明
A.主体和客体的关系是改造和被改造的关系
B.主体和客体的关系是反映和被反映的关系
C.实践是认识的来源与途径
D.不仅客体决定认识,而且主体(包括主观)也制约、规范认识.
简述工地现场临时用电相关检查要素及规范。