题目内容
Networks can be interconnected by different devices．In the physical layer，networks can be connected by (66) or Hubs, which just move the bits from one network to an identical net-work. One layer up we find bridgas and swiehes, which operate at data link layer. They can accept (67) , examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two netwoks. If two networks have (68) network layer, the router may be able to translate between the packet formats. In the transport layer we find transport gateway, which can interface between the two transport connections. Finally, in the application layer, application gateways translate message (69) . As an example, gateways between Internet e-mail and X.400 e-mail must (70) the e-mail message and change various header fields.
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4 The crucial years of the Depression, as they are brought into historical focus, in creasingly emerge as the decisive decade for American art, if not for American culture in general. For it was during this decade that many of the conflicts which had blocked the pro gress of American art in the past came to a head and sometimes boiled over. Janus-faced, the thirties look backward, sometimes as far as the Renaissance; and at the same time for ward, as far as the present and beyond. It was the moment when artists, like Thomas Hart Benton, who wished to turn back the clock to regain the virtues of simpler times came into direct conflict with others, like Stuart Davis and Frank Lloyd Wright, who were ready to come to terms with the Machine Age and to deal with its consequences. America in the thirties was changing rapidly. In many areas the past was giving way to the present, although not without a struggle. A Predominantly rural and small town society was be ing replaced by the giant complexes of the big cities; power was becoming increasingly centralized in the federal government and in large corporations. Many Americans, deeply attached to the old way of life, felt disinherited. At the same time, as immigration decreased and the population became more homogeneous, the need arose in art and literature to commemorate the ethnic and regional differences that were fast disappearing. Thus, paradoxically, the conviction that art, at least, should serve some purpose or carry some message of moral uplift grew stronger as the Puritan ethos lost its contemporary reality. Often this elevating message was a sermon in favor of just those traditional American virtues, which were now threat ened with obsolescence in a changed social and political context. In this new context, the appeal of the paintings by the regionalists and the American Scene painters often lay in their ability to recreate an atmosphere that glorified the traditional American values—self-reliance tempered with good-neighborliness, independence modified by a sense of community, hard work rewarded by a sense of order and purpose. Given the actual temper of the times, these themes were strangely anachronistic, just as the rhetoric supporting political isola tionism was equally inappropriate in an international situation soon to involve America in a second world war. Such themes gained popularity because they filled a genome need for a comfortable collective fantasy of a God-fearing, white-picketfence America, which in retrospect took on the nostalgic appeal of a lost Golden Age. In this light, an autonomous art-for-art’s sake was viewed as a foreign invader liable to subvert the native American desire for a purposeful art. Abstract art was assigned the role of the villainous alien; realism was to personify the genuine American means of ex pression. The arguments drew favor in many camps: among the artists, because most were realists; among the politically oriented intellectuals, because abstract art was apoliti cal; and among museum officials, because they were surfeited with mediocre imitations of European modernism and were convinced that American art must develop its own distinct identity. To help along this road to self-definition, the museums were prepared to set up an artificial double standard, one for American art, and another for European art. In 1934, Ralph Flint wrote in Art News, "We have today in our midst a greater array of what may be called second-, third-, and fourth-string artists than any other country. Our big annuals are marvelous outpourings of intelligence and skill~ they have all the diversity and anima tion of a fine-ring circus. \ According to the passage, the best word to describe America in the 1930s would be______.
局域网中使用的传输介质有双绞线、同轴电缆和光纤等。10BASE-T采用3类UTP，规定从收发端到有源集线器的距离不超过 (44) m。100BASE-TX把数据传输速率提高了10倍，同时网络的覆盖范围 (45) 。假设tPHY表示工作站的物理层时延，c表示光速，s表示网段长度，tR表示中继器的时延，在IOBASE-5最大配置的情况下，冲突时槽约等于 (46) 。光纤分为单模光纤和多模光纤，与多模光纤相比，单模光纤的主要特点是 (47) ，为了充分利用其容量，可使用 (48) 技术同时传输多路信号。
Write an essay in no tess than 200 words with the title "What Can I Offer to Sciety" First, write an outline for your essay, and then according to your outline, write your essay. Both your outline and your essay should be written clearLy on your ANSWER SHEET.
2007年10月16日15时20分，C市地铁1号线B站工段施工工地(露天开挖作业)发生地面塌陷事故，造成长约100m、宽约50m的正在施工区域塌陷，施工现场西侧路基下陷达6m左右，将施工挡士墙全部推垮，自来水管、排污管断裂，大量污水涌出，同时东侧河水及淤泥向施工塌陷地点溃泻，导致施工塌陷区域逐渐被泥水淹没。事故造成在此处行驶的11辆汽车下沉陷落(车上员2人轻伤，其余人员安全脱险)，施工人员17人死亡、4人失踪。经抢险人员全力搜救，未发现生还人员。据初步调查，C市地铁1号线B站工段建设单位为A地铁集团有公司，设计单位为C城建设计研究总院，施工单位为中国中铁股份有限公司中铁某分局，监理单位为D工程项目监理咨询有限公司。 根据以上场景，回答下列问题： 特别重大事故的事故调查组的职责有( )。
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