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【单选题】
How does E-mail travel on the Internet to reach someone far away? When Jennifer, Who lives in Pasadena, Calif. wants to send an E-mail message from her home computer to her mother in Washington, D. C., she uses a local Internet service provider (ISP) such as EarthLink Network Inc. (ELNK). EarthLink gives Jennifer access to the Internet, much in the way that a ramp puts a driver on the national highway system. After Jennifer's computer makes a local telephone call to EarthLink's local bank of modems, Jennifer types in her E-mail message and hits 'send.' Based on Mom's E-mail address, EarthLink will recognize that Mom is a customer of an ISP in Washington called Erols Internet Inc. (RCNC). EarthLink will then send the E-mail to an Internet backbone provider, such as GTE Corp. (GTE), to route it along its way What is a backbone provider and why is it important on the Internet? Backbone providers are the Internet players that typically own and lease long-haul fiber-optic cables spanning a large region. They also own the communications gear that directs traffic over the Internet. There are only a handful of major backbone providers, including MCI, WorldCom, Sprint Corp. , GTE, and PSINet Inc. (PSIX). Backbone providers connect to each other to exchange data between their customers. They also pick up and deliver traffic for a fee from the 7,000 or so smaller ISPs, who give residential and small-business users access to the Internet. Backbone carriers are like the highway system over which most of the freight of the Internet travels to reach its destination. How did the current backbone providers come to be? When the Internet was still a government-run system, there was only a single Internet backbone: the NSFNET, operated by the National Science Foundation, which connected the regional government-funded Internet networks that were run by various research universities. When the government privatized the NSFNET in 1995, companies such as MCI, UUNET Technologies (now owned by Worldcom), BBN (now owned by GTE), and PSINet stepped into the breach by setting up commercial Internet backbone services. Now, instead of one NSFNET backbone, there are many of them that link together to provide the global connectivity, that is the Internet. How do Internet companies connect to each other? When the NSFNET was privatized, the government set up three locations in the U. S. where various Internet backbone companies could place their communications gear side by side and connect to each other. These so-called 'public peering points' are in Chicago, Palo Alto, Calif., and Pennsauken, N.J.. Later, the government sanctioned two industry-run public peering points called Metropolitan Access Exchange East and West — MAE-East, in Vienna, Va., and MAE- West in San Jose, Calif.. The problem was, as the Internet grew, the public points became overburdened and traffic slowed at these bottlenecks. So backbone providers started making arrangements with each other, called 'private peering.' These are direct, bilateral connections between two carriers in which no fees are charged. Do the largest backbone providers charge each other? Backbone providers aren't charging peers now, but there is a lot of discussion about whether they should. Most industry experts say the Internet needs to develop some payment scheme. After all, it is now a commercial, profit-making business, not a government freebie. But the industry has not figured out how to calculate who owes what to whom. Without an industry standard or government regulation, smaller companies fear that larger ones will set these charges in an arbitrary and discriminatory fashion. America's first backbone Internet Service provider was ______.
A.
EarthLink
B.
MCI
C.
GTE Corp
D.
NSFNET
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【多选题】下列各项属于建设项目基本预备费组成内容的是
A.
竣工验收时为鉴定工程质量,对隐蔽工程进行必要挖掘和修复的费用
B.
一般自然灾害造成的损失的费用
C.
利率、汇率调整所增加费用
D.
预防自然灾害所采用的措施费
E.
设计变更、局部地基处理等增加的费用
【多选题】乳状液中的分散相又被称为()。
A.
内相
B.
外相
C.
连续相
D.
不连续相
【单选题】创建单位时,提示单位名重复怎么办?
A.
找微服务产品将已有单位转移至自己账号下
B.
换个单位名字(用简称、别称)创建
C.
根据页面指引填写申诉材料并提交,或联系客服处理
D.
自行联系已有单位的管理员协商解决
【单选题】输入输出设备工作过程中,使用CPU控制时间最少的I/O控制方式为( )。
A.
循环测式方式
B.
 中断方式
C.
DMA 方式
D.
通道方式
【单选题】若“学生”表中存储了学号、姓名、成绩等字段,则“删除所有姓孙的学生记录”的SQL语句是_____________。
A.
DELETE FROM 学生 WHERE 姓名 LIKE “孙%”
B.
DELETE FROM 学生 WHERE 姓名=孙
C.
DELETE FROM 学生 WHERE 姓名=孙%
D.
DELETE * FROM 学生 WHERE 姓名 LIKE “”孙%”
【单选题】满清时期军机处位于以下哪一区域附近:()
A.
天坛
B.
明堂
C.
南书房
D.
养心殿
【单选题】一个4输入端与非门,使其输出为0的输入变量组合有( )种。
A.
2
B.
3
C.
1
D.
6
【判断题】一个4输入端与非门,使其输出为0的输入变量取值组合共有15种:
A.
正确
B.
错误
【多选题】单跨对称结构在对称荷载作用下,对称轴上的截面
A.
沿对称轴方向上的位移为零
B.
垂直对称轴方向上的位移为零
C.
角位移为零
D.
弯矩为零
E.
剪力为零
【多选题】奇数跨对称结构在对称荷载作用下,对称轴上的截面( )。
A.
水平线位移为零
B.
竖向线位移为零
C.
角位移为零
D.
弯矩为零
E.
剪力为零
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