突出煤层掘进工作面局部通风机的通风方式是()。A、压入式通风 B、抽出式通风 C、混合式

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问题:

突出煤层掘进工作面局部通风机的通风方式是()。

A、压入式通风

B、抽出式通风

C、混合式通风

D、压入式或混合式通风

考点:煤矿防突工煤矿防突工综合练习煤矿防突工综合练习题库
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采用邻接表存储的图的深度优先遍历算法类似于树的 (22) ,用邻接表存储的图的广度优先遍历算法类似于树的 (23) ,判断有向图是否存在回路,除了可以利用拓扑排序方法外,还可以利用 (24)

A.中序遍历

B.先序遍历

C.后序遍历

D.按层次遍历

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America’s population hit the 300 million mark yesterday—at 7:46 a.m. Eastern time, according to Census Bureau estimates. Nobody knows exactly who became America’s 300 millionth citizen.
But demographers are summing up the milestone as a turning point that signals several trends to watch as the US—in contrast with Europe and Japan—deals with a steadily growing population.
Politically and demographically, experts say, the shifts will begin to have an impact on regions of the country not yet used to the new diversity provided by the influx of Hispanics and Asians, which has already transformed California, Arizona, Texas, Florida, and New York.
In coming years, Midwesterners, those in the Great Plains, rural areas, and small towns everywhere will begin to deal with the challenges of new ethnic and racial residents, says William Frey, a population expert at the Brookings Institution in Washington. And the country as a whole will begin to be more dominated by a young/old divide than the current liberal/conservative model that dominates political discourse.
"This means we are going to transform the current, red/blue political dichotomy to one where the nation is separated by age ... young vs. old," says Mr. Frey. "The issues of younger generations dealing with children and opportunities for minorities will clash with those of the aging baby boomers whose voters are concerned with issues of aging and Social Security and Medicare," he adds. "Both parties will have to adjust to this new dichotomy. "
The new milestone hasn’t generated much hoopla. That’s in sharp contrast to 1967, when President Johnson hailed the 200 millionth American, and Life magazine dispatched a cadre of photographers to find a baby born at the exact moment. One reason is that population growth has become controversial, especially in an election year when immigration is a hot-button issue and politicians are wary.
Commerce Secretary Carlos Gutierrez says the Bush administration is not playing down the milestone, though he had no plans for Tuesday. "I would hate to think that we are going to be low-key about this," he says, since growth helps the economy.
While it’s hard to prove that population growth spurs economic growth, the two often go hand in hand, according to experts quoted in the Monitor’s recently published series: "US population. 300 million." For example, a nation with a rising population can support its retirees far more easily than one with a declining population. That’s an advantage for the US, which is virtually the only developed nation expected to grow this century. But population growth has less rosy implications, the Monitor series points out. Some experts worry that the land can’t sustain the extra 100 million people expected by 2043. Another challenge is sprawl, the dominant model of development, which gobbles up forest and prairie.

Why does the author say that the nation’s reaction to the new milestone of 300 million is "in sharp contrast to 1967" (para. 5)

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脊髓空洞症最常见于下列哪种疾病()

A.小脑扁桃体下疝畸形

B.颅底陷入

C.颈椎分节不全

D.寰枕融合

E.扁平颅底

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物证区别于其他证据的最显著的特点是()

A.物证具有客观性

B.物证具有相关性

C.物证以其存在及外部特征证明案件事实

D.物证不可能单独反映案件主要事实

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土方开挖前需做好准备工作,包括()等。

A.清除障碍物

B.设置排水设施

C.设置测量控制网

D.修建临时设施

E.地基验槽

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