题目内容
（请给出正确答案）
A small dam of height h=2.0m is constructed of vertical wood beams AB of thickness t = 120 mm , as shown in the figure. Consider the beams to be simply supported at the top and bottom. Determine the maximum bending stress
in the beams, assuming that the weight density of water is
.
安装简答题APP，拍照搜题省时又省心！
更多“A small dam of height h=2.0m i…”相关的问题
【M1】
Part Ⅱ Reading Comprehension (Skimming and Scanning)
Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1. For questions 1-7, choose the best answer from the four choices marked [A], [B], [C] and [D]. For questions 8-10, complete the sentences with the information given in the passage.
Hydroelectric Power
Hydroelectric power is America's leading renewable energy resource. Of all the renewable power sources, it's the most reliable, efficient and economical. Water is needed to run a hydroelectric generating unit. It's held in a reservoir or lake behind a dam, and the force of the water being released from the reservoir through the dam spins the blades of a turbine. The turbine is connected to the generator that produces electricity. After passing through the turbine, the water re-enters the river on the downstream side of the dam.
Hydroelectric plants convert the kinetic energy within falling water into electricity. The energy in moving water is produced in the sun, and consequently is continually being renewed. The energy in sunlight evaporates water from the seas and deposits it on land as rain. Land elevation differences result in rainfall runoff, and permit some of the original solar energy to be harnessed as hydroelectric power. Hydroelectric power is at present the earth's chief renewable electricity source, generating 6% of global energy and about 15% of worldwide electricity. Hydroelectric power in Canada is plentiful and provides 60% of their electrical requirements. Usually regarded as an inexpensive and clean source of electricity, most big hydroelectric projects being planned today are facing a great deal of hostility from environmental groups and local people.
The earliest recorded use of water power was a clock, constructed around 250 BC. Since then, people have used falling water to supply power for grain and saw mills, as well as a host of other uses. The earliest use of flowing water to generate electricity was a waterwheel on the Fox River in Wisconsin in 1882.
The first hydroelectric power plants were much more dependable and efficient than the plants of the day that were fired by fossil fuels. This led to a rise in number of small to medium sized hydroelectric generating plants located wherever there was an adequate supply of falling water and a need for electricity. As demand for electricity soared in the middle years of the 20th century, and the effectiveness of coal and oil power plants improved, small hydro plants became less popular. The majority of new hydroelectric developments were focused on giant mega-projects.
Hydroelectric plants harness energy by passing flowing water through a turbine. The water turbine rotation is delivered to a generator, which generates electricity. The quantity of electricity that can be produced at a hydroelectric plant relies upon two variables. These variables are (1) the vertical distance that the water falls, called the "head", and (2) the flow rate, calculated as volume over time. The amount of electricity that is produced is thus proportional to the head product and the flow rate.
So, hydroelectric power stations can normally be separated into two kinds. The most widespread are "high head" plants and usually employ a dam to stock up water at an increased height. They also store water at times of rain and discharge it during dry times. This results in reliable and consistent electricity generation, capable of meeting demand since flow can be rapidly altered. At times of excess electrical system capacity, usually available at night, these plants can also pump water from one reservoir to another at a greater height. When there is peak electrical demand, the higher reservoir releases water throu
A．6%.
B．9%.
C．15%.
D．60%.
听力原文： Villages in developing countries often lack many things--books, clean water, electricity. These shortages are easy to see. But a different kind of shortage is not easy to see. That is a shortage of experts. Many villages have no doctors, engineers or scientists. They have no one who knows how to treat unusual medical problems or design a new expert system. There's a way to ease these problems. They can do it with computers. In the past few years, computer scientists around the world have developed what they call expert systems. An expert system is a special kind of computer program. In some situations, it can take the place of a human expert. For example, an expert in medical system can help care for a sick person. A question appears on the computer screen, "Is the person hot？" You tell the computer either yes or no. The computer asks other questions. "Has the person lost any blood？" "Can the person move normally？" You answer. The computer continues to ask questions until it has enough information to make a decision. Then it tells what medicine or other treatment is needed. In this way the expert system takes the place of a doctor. Another kind of expert system takes the place of an engineer. It measures the flow of water in a river. It tells if a dam can be built on the river. It also tells how much electricity can be produced. Still other kinds of expert systems help solve problems for farmers and owners of small businesses.
(23)
A．Lack of electricity.
B．Shortage of books.
C．Lack of clean water.
D．Shortage of experts.
A.＜applet code=Test.class age=33 width=100 heigh=100＞
B.＜param name=age value=33＞
C.＜applet code=Test.class name-age value=33 width=100 height=100＞
D.＜applet Test 33＞
听力原文： Villages in developing countries often lack many things: books, clean water and electricity. These shortages are easy to see, but a different kind of shortage is not easy to see. That is the shortage of experts.
Many villages have no doctors, engineers, or scientists. They have no one who knows how to treat unusual medical problems or design a new energy system. There is a way to solve these problems. They can do it with computers. In the past few years, computer scientists around the world have developed what they call expert system.
An expert system is a special kind of computer program. In some situations, it can take the place of human expert. For example, an expert medical system can help care for a sick person. A question appears on the computer screen "Is this person hot？" You tell the computer either "Yes" or "No". The computer asks other questions, "Has the person lost any blood？" "Can the person move normal[y？" you answer. The computer continues to ask questions until it has enough information to make a decision. Then it tells what medicine or other treatment is needed. In this way, the expert system takes the place of a doctor. Another kind of expert system takes the place of an engineer. It measures the flow of water in the river. It tells if a dam can be built on the river. It also tells how much electricity can be produced. Still other kinds of expert systems help solve problems for farmers and owners of small business.
(26)
A．Lack of clean water.
B．Lack of electricity.
C．Shortage of experts.
D．Shortage of books.
听力原文： Villages in developing countries often lack many things. Books, clean water, electricity. These shortages are easy to see. But a different kind of shortage is not easy to see. That is a shortage of experts. Many villages have no doctors, engineers or scientists. They have no one who knows how to treat unusual medical problems or design a new energy system. Them' s a way to ease these problems. They can de it with computers. In the past few years, computer scientists around the world have developed what they call expert systems. An expert system is a special kind of computer program. In some situations, it can take the place of a human expert. For example, an expert in medical system can help care for a sick person. A question appears on the computer screen, "Is the person hot？" You tell the computer either yes or no. The computer asks other questions. "Has the person lest any blood？" "Can the person move normally？" You answer. The computer continues to ask questions until it has enough information to make a decision. Then it tells what medicine or other treatment is needed. In this way the ex pert system takes the place of a doctor. Another kind of expert system takes the place of an engineer. It measures the flow of water in a river. It tells if a dam can be built on the river. It also tells how much electricity can be produced. Still other kinds of expert systems help solve problems for farmers and owners of small businesses.
(30)
A．Lack of electricity.
B．Shortage of books.
C．Lack of clean water.
D．Shortage of experts.
第二节 完型填空
阅读下面短文，从短文后所给各题的四个选项(A、B、C和D)中选出能填入相应空白处的最佳选项。
Villages in developing countries often lack many things. Books, clean water, electricity. These shortages are【B1】to 【B2】. But a【B3】kind of shortage is not easy to see. That is a shortage of 【B4】 Many villages have no doctors, engineers or scientists. They have no one who know【B5】to treat unusual medical problems or design a new expert system. There's a way to ease these problems. They can do it with【B6】. In the past few years, computer scientists around the world【B7】 【B8】they call expert systems. An expert system is a special kind of computer program. In some 【B9】, it can take the place of a human expert. For example, an expert in 【B10】system can help【B11】a sick person. A question appears on the computer screen, "Is the person hot7" You tell the computer either yes or no. The computer asks【B12】questions. "Has the person lost any blood？" Can the person move normally？" You【B13】. The computer continues to ask questions【B14】it has enough【B15】to make a decision. Then it tells what【B16】or other treatment is needed. In this way the expert system takes the place of a【B17】. Another kind of expert system takes the place of an engineer. It 【B18】the flow of water in the river. It tells if a dam can be built【B19】the river. It also tells【B20】electricity can be produced. Still other kinds of expert systems help solve problems for farmers and owners of small businesses.
【B1】
A．difficult
B．easy
C．unable
D．easier
China's Three Gorges Dam ______
A．is the first hydroelectric dam in the world
B．is of the same size as the US's Hoover Dam.
C．can generate around 3% of world electricity.
D．is the largest hydroelectric dam in the world
(ii) An evaluation of the environmental and sustainability implications of the Giant Dam Project; (8 marks)
为了保护您的账号安全，请在“简答题”公众号进行验证，点击“官网服务”-“账号验证”后输入验证码“”完成验证，验证成功后方可继续查看答案！
微信搜一搜
简答题
微信搜一搜
简答题
如搜索结果不匹配，请 
