题目内容
举例说明P、V操作为什么要求设计成原语(即对同一信号量上的操作必须互斥)。P(S)操作： S.value--: If(S.value＜0) Add this process to S.L; Block( ): V(S)操作 S.value++; If(S.value＜=0) Remove a process P from S.L; Wakeup(P):
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Questions 51 to 55 are based on the following passage. Canadian authorities relayed that suspicion to the U. S. Coast Guard, which dispatched a cutter to intercept the vessel. After a two-week chase, the cutter’s crew finally boarded the Cao Yu 6025, a stateless ship, south of Japan. In the hold, they found damning evidence: 110 tons of tuna and shark fins, and a drift gillnet almost 20 kilometers long--an indiscriminate killer of marine life banned on high seas under an international agreement. Out of sight, and mostly out of mind, the oceans are under siege. Scientists from around the world are reporting global disturbances in the seas that threaten to bring Richard Cashin’s grim warning home to every Canadian household. From the polar seas to the tropics, fish populations have collapsed or teeter on the brink. In a third of the Pacific, plankton that form the foundation of the marine food chain are vanishing. In every corner of the planet, increasing temperatures are obliterating some species, while driving others into unfamiliar waters. As science scrambles to make sense of uneven data, evidence points to an alarming conclusion, the sea, the cradle of life, is dying. The killers are numerous. The most obvious, global over fishing, harvests 70 per cent of the world’s species faster than they can reproduce themselves. But the scientific community is not even sure that is the worst menace to the seas. Other major threats: human pollution, including an estimated 700 million gallons of toxic chemicals dumped into the sea each year, and global warming, widely attributed to industrial production of so-called greenhouse gases, which appears to be affecting ocean temperatures. Sharply pricier seafood is only the mildest consequence; others are far more serious. In many parts of the world, fishing jobs have disappeared. On Canada’s East Coast, 26,000 unemployed former fish workers drew income from the federal government’s Atlantic Ground fish Strategy--15,000 from Newfoundland alone--until its $1.9 billion in funding ran out in August. Far worse, developing countries dependent on marine protein confront the risk of mass starvation. In many regions, rival national claims to the seas’ diminishing harvest hold potential for armed conflict. More terrifying still is the specter of ecological Armageddon, as the oceans lose the capacity to generate the oxygen on which life itself depends. For too many species, extinction has already come. Half a century ago, 600,000 barn door skate swam North America’s Atlantic seaboard. Never intentionally fished, they nonetheless frequently became ensnared in nets or on hooks. By the 1970s, scientists could find no more than 500 skate throughout its previous range. Now, they can’t find any. "If bald eagles were as common as robins and then disappeared, someone would notice," says biologist Ransom Myers of Hallifax’s Dalhousie University. "In the ocean, no one knows. No one cares. " Belatedly, a handful of governments and others have begun to notice, to care and to act, moving tentatively to rein in the worst abuses of the seas. The patrol that spotted the Cao Yu was one of six that Canada donates each year to enforce an international ban on drift nets, blamed for killing dolphins, sharks, turtles, and seabirds, in addition to their intended catch. On September 1, the federal government designated two protected marine habitats at Race Rocks and Gabriola Passage, British Columbia--the first in a promised chain of preserves in Canadian waters where fishing will be banned. On the same day, an international commission concluded three years of study by urging coastal nations to bury their differences and form a world authority to regulate fishing beyond the 200-mile (370-killometer) economic zones of individual states. Questions : ______ are regarded as the foundation of the marine food chain.
Passage 3
Flora: Billy, would you like to join our ride-sharing group to and from work Billy: Why not It’ll save me some money, and the company would welcome it. Flora: ______. Billy: I’ll be waiting, and thanks.
小龙今年10岁，上小学四年级，与开批发部做生意的爸爸、妈妈生活在一起。爸爸、妈妈每天除了忙于店里的生意之外，还担心小龙的学习。小龙平时不爱读书，上课经常做小动作，还喜欢接老师的话、抄袭同学的作业。为了让小龙能认真学习，爸爸、妈妈每天挤出时间检查和监督小龙的学习，并且为小龙报了绘画班。这样，小龙每天做完作业后还要画画，他总是抱怨没有玩的时间，对学习越来越反感。爸爸、妈妈看到小龙这样非常生气，经常打骂小龙。妈妈总是抱怨为什么小龙不能像别的孩子一样爱学习，除了不爱学习，小龙平时嘴巴很甜，遇见邻居和亲戚都会主动而且礼貌地打招呼，这点让大家都很喜欢他。 问题：1.从上述案例可以发现，父母与小龙之间的冲突都是围绕着小龙的学习，小龙的学习问题主要有哪些针对这一问题，社会工作者应以怎样的服务目标介入
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