首页 > 大学本科> 工学

网友您好，请在下方输入框内输入要搜索的题目：

请输入或粘贴题目内容搜题

搜题

拍照、语音搜题，请扫码下载APP

题目内容（请给出正确答案）

[主观题]

A group of particles is described by the log-normal distribution by weight, asshown in Fig.2, please

calculate D_mean=______, and logarithmic standdeviations σ_g=______.

答案

查看答案

发布时间：2020-07-09

更多“A group of particles is described by the log-normal distribution by weight, asshown in Fig.2, please”相关的问题

第1题

An alkaline earth element is radioactive. It and its daughter elements decay by emitting three alpha

particles in succession. In what group should the resulting element be found？

点击查看答案

第2题

听力原文： How many teeth have you had failed in the past two years？ If you follow the advi

ce of Dr Forsdic, you may be able to reduce the number of your visits to dentist. Dr Forsdic conducted a two-year survey to find out how to prevent or reduce dental decay. 946 students took part in the experiment. 523 students cleaned their teeth within 10 minutes of eating. When possible, they used the tooth- brush. When this was impossible, they washed their mouth thoroughly with water. The remaining 423 students merely cleaned their teeth when they went to bed and when they got up in the morning. All the students had their teeth X-rayed at the end of the first and second years. At the end of the first year, the night-and-morning group had 3 times as many decayed teeth as the clean-after-each- meal group. At the end of the second year, the latter group had 53% fewer decayed teeth than the former group. Dr Forsdic has cleaned his teeth after every meal for 13 years and has not had a single decayed tooth. He pointed out that sugar is a major agent in dental decay. Particularly the sugar in sweets, cakes and soft drinks. Ideally, you should keep a toothbrush in your pocket and use it immediately after you have finished eating. When this is impractical, you can at least make sure that you have a drink of water and let the water through your teeth to force out any particles of food. Seven out of ten people lose at least half their teeth by the time they are 50. Many have a complete set of false teeth by that time. In any case, neither toothache nor a visit to a dentist is very pleasant. So it is worthwhile making an effort to keep your own teeth as long as possible. The main preventative agent is simply water.

According to the passage ,what type of food/drink is most likely to cause dental decay？

A．Coca Cola

B．Sausage.

C．Milk.

D．Fried chicken.

点击查看答案

第3题

听力原文：How many teeth have you had filled in the past two years？ If you follow the advic

听力原文： How many teeth have you had filled in the past two years？ If you follow the advice of Dr. Faustick 'you may be able to reduce the number of your visits to a dentist. Dr. Faustick conducted a twoyear survey to find out how to prevent or reduce dental decay. 946 students took part in an experiment. 523 students cleaned their teeth within ten minutes of eating when possible they used a tooth brush, when this was impossible they washed their mouth thoroughly with water. The remaining 423 students merely cleaned their teeth when they went to bed and when they got up in the morning. All the students had their teeth X rayed at the end of the first and second years. At the end of the first year, the night and morning group had three times as many decayed teeth as the dean after each meal group. At the end of the second year the latter group had 53 percent fewer decayed teeth than the former group. Dr. Fausstick has cleaned his teeth after meal for thirteen years and has not had a single decayed tooth. He pointed out that sugar is a major agent in dental decay. Particularly the sugar in sweets, cakes, and soft drinks. Ideally you should keep a tooth brush in your pocket and use it immediately after you have finished eating. When this is impractical you can at least make sure that you have a drink of water and let the water through your teeth to force out any particles of food. 7 of out 10 people loose at least half of their teeth by the time they are fifty. Many have a complete set of false teeth by that time. In any case neither toothache nor a visit to a dentist is very pleas ant. So it is worthwhile making an effort to keep you own teeth as long as possible. The main preventative agent is simply water.

(23)

A．Coca Cola.

B．Sausage.

C．Milk.

D．Fried chicken.

点击查看答案

第4题

Sandstorms blow 300,000 tons of dust into Beijing. The severe sandstorm that was hovering

over Beijing for the past few days finally moved out of the city yesterday morning, leaving a heavy layer of dust and sand on the ground. Experts with the State Environmental Protection Administration said some 30,000 tons of fine sand and dust were blown into the capital. In an earlier sandstorm last weekend, some 26,000 tons of sand and dust also landed on Beijing.

Dong Xuhui, director of the sandstorm research group under the administration, said the sandstorm that invaded Beijing this week was the most severe since the group began conduction sandstorm research in 1995. "In some sandstorms in the Inner Mongolia Autonomous Region, visibility had been lowered to less than 1 meter," Dong said.

The administration's satellite sandstorm supervision system showed that sand and dust drifted at about 2,500 to 3,500 meters above the ground, affecting Beijing for 51 consecutive hours. "The sand and dust particles in the air are relatively small, so they could easily invade people's breathing systems." Dong said, "So it is better to stay indoor in such weather."

Unfortunately, there are no effective ways to stop or decrease the frequency of sandstorms in the near future. Gao Jixi, a researcher with the China Environmental Science Institute, suggested that the government address that the overall problem as part of its environmental protection policy.

Though protective forests in North China are expected to grow soon, Gao said that drifting sands at high altitudes could still invade most cities. "We should consider the environment in northern and western China as a whole when adopting related environmental protection policies," Gao suggested.

He said governments in the relevant provinces and autonomous regions should speed up their industrial restructuring and firmly put a stop to industrial practices that harm the environment. Gao said some hasty tree planting activities should also be stopped because many of tree species have now been found not to match the local soil. "Planting more trees does not mean the improvement of the environment," he said.

Gao was invited to present an environmental report to premier Zhu last year. Gao had advocated the building of a large ecological system in northern and western China to resist sandstorm.

He objected to environmental stress caused by humans interfering with nature. "We should respect nature's rules by restoring the original ecological systems in those regions." Gao said. Following that principle would be the best way to fight sandstorms, he added.

What's the main idea of this article？

A．Sandstorms blow 300,000 tons of dust into Beijing.

B．Sandstorms are threatening human's life.

C．There is no effective way to stop sandstorms in the near future.

D．B and C.

点击查看答案

第5题

The particles of electromagnetic radiation given off by matter are known as ______.A．quant

The particles of electromagnetic radiation given off by matter are known as ______.

A．quantums

B．atoms

C．electrons

D．valences

点击查看答案

第6题

Small particles mainly damage ______.A．lungsB．eyesC．bloodstreamD．heart

Small particles mainly damage ______.

A．lungs

B．eyes

C．bloodstream

D．heart

点击查看答案

第7题

Poisonous particles, such as lead compounds, are cumulative and can build up slowly in the

body.

A．Y

B．N

C．NG

点击查看答案

第8题

One of the Price's findings （Paragraph 2) about the particles of the air is that ______.A．

One of the Price's findings (Paragraph 2) about the particles of the air is that ______.

A．they contain more pollutants than normal particles

B．they move much faster in high altitudes than in low altitudes

C．they are finer and lighter than normal particles

D．their ability to reflect light is much than stronger

点击查看答案

第9题

The turbulence detector can tell the severity of the turbulence by measuring A

The turbulence detector can tell the severity of the turbulence by measuring

A．the speed of the plane.

B．the speed of the light.

C．the number of particles in the air.

D．the changes of the particles' speed.

点击查看答案

第10题

To find Kim Hyung Gyoon’ s office in Samsung’s R&D complex, just follow the baskets of

dirt clothes. No, Kim is not running the company laundry. As chief of Samsung’s Washing & Cleaning Technology Group(WCTG), he’s the man behind a new washing machine that deposits tiny silver particles(small pieces of things) —about 1 / 10,000 the thickness of a human hair— onto clothes to make them germ-and-odor-free without the need of hot water. The device represents the first mass-produced application of this tape of nanotechnology — the science of very small structures—to home appliances. "In summer of 2002, I asked everyone in the office to take off their socks," says Kim. "took one sock from each person and placed it in a regular washing machine; the others were washed in a machine with the Ag+ Nano System. The next day, I asked everyone to check the odor of their socks after a day’s wear. One began produce a strong unpleasant smell, and the other was odorless."

Kim says he came up with the idea five years ago while on a business trip to Japan, where he learned of a brand of socks that retained their freshness even after many days of unwashed wear and tear. Tiny sticks of sliver with germ-killing chemicals were woven into the fabric. When he got back to Seoul, Kim applied the principle to washing machines.

According to the Korea Testing & Research Industry, Samsung’s device kills 99.9% of germs. Kim says garments stay germ-free for up to a month after being laundered. The Ag+ Nano device went on sale in March 2003 and costs around $1,150; the revolutionary technology is also being used in Samsung’s refrigerators and air conditioners.

No wonder: consumers seem to a little sliver in their spin cycles. Since Samsung’s nano-armed products were first launched, they have brought in an estimated $779 million in revenue. Overall, nanotech has been one of science’s fastest-growing fields in recent years, with potential applications in fields as diverse as energy production and toothpaste manufacture. The nanotech market is projected to be worth $1 trillion by 2015.

Which of the following best describes the nature of Kim Hyung Gyoon’s work？

A．Product development.

B．Market investigation.

C．Research designing.

D．Sales promotion.

点击查看答案