The economic costs of noise to society are several. Airports are currently operating at less than capacity because of noise regulations which restrict their hours of operation. For instance, at Washington's National Airport no jet traffic is allowed from 11 pm to 7 am. Other airports restrict the use of certain runways. One estimate is that noise restrictions reduce possible airport use by 20 percent. The profitable cargo trade is especially affected by night restrictions. In the case of airports, jet engines may be modified to reduce their noise level, or insulation(隔音)from air traffic noise may be provided by the purchase of land around airports or the insulation of buildings. One estimate is that $ 5. 7 billion would be required to equip all existing jet engines with noise control devices. However, considering the current state of the art, even taking this step will not reduce noise levels at all points to acceptable values. Some combination of methods is probably necessary. If all aircraft were made quieter by existing methods, there would be a number of economic benefits. An increase in airport capacity would occur. Property values near airports might rise. Transportation costs to and from airports could be reduced since the airports now could be located closer to population centers. Much research still needs to be done on the economic aspects of noise reduction and noise effects. Although some of the effects of noise pollution are known, more must be discovered about its effects on health, productivity, property values and the quality of life. Furthermore, the cost of noise pollution to the economy as a whole needs to be investigated. The public must be alerted to the dangers and economic costs of noise pollution so that people may make intelligent choices and exert appropriate pressures.

31． There is no jet traffic at Washington's National Airport from 11 pm to 7 am because______.

79． 当那个贼意识到警察认出了他时，便向门口走去。(realize)

80． 没有多少人能比得上像牛顿和爱因斯坦那样的天才。(approach)

76． 每次我去上海，都能看到这个城市的巨大变化。(each time)

78． 客户服务已经是并将继续是一个主要的竞争因素。(competitive factor)

77． 如果遇到生词，最好查字典。(come across)

74． 【T4】

73． 【T3】

75． 【T5】

E-procurement, also known as e-purchasing, is the process of requisitioning direct or indirect materials using the Internet as the primary medium.【T1】With online catalogs and purchasing systems , companies can save time and money at order time as well as when dealing with accounts payable and receivable.By some estimates, an automated order and approval system reduces the cost of purchase orders by as much as $ 75 to $ 150 each. Engaging in e-procurement requires two major steps; First, your company must become an e-business. Once you've embraced the Internet as a way of doing business(or if you already have), you must deploy the actual e-procurement system. 【T2】In white paper entitled"Reap Rewards with an Efficient E-procurement Strategy", you learn about the big picture issues of setting up an e-procurement system as well as specific steps.In tacking the opportunity of engaging in e-business, companies must take several steps; Build the infrastructure. Doing business on the Internet requires servers that can handle enterprise demands, as well as building blocks for securing load balancing of Internet traffic. This infrastructure can be built in house or outsourced. Modify business processes.【T3】This is perhaps the most difficult phase because it requires changing the way you do things in order to streamline processes and implement technology uniformly.Evaluate your customers' perspective. Once you hour have new processes and technologies in place, you must get feedback from your customers to find out how well you're meeting their needs and expectations. As an e-business, you're ready to reap the benefits of an e-procurement system. The steps to deploying such a system fall into four areas; Understand and automate the workflow. You must fully understand requisition, approval and acquisition process as it now.【T4】As you move to automate it, you shouldn't stray too far from the current practice or employees may resist the change.Create an electronic catalog. Pull together electronic catalogs from your suppliers to create a single catalog. Also, determine what electronic payments your suppliers can accept. Design and test the system. Generic company described in the white paper required 20 person weeks, or 800 hours, to set up its system. The paper delves deeper into spew civic steps. Implement the system.【T5】Once the system works, you need to launch it on an enterprise class architecture. The white paper provides details, including configurations and topologies.

71． 【T1】

72． 【T2】