搜题请搜索小程序“爱下问搜题”
问题 填空题

海水是一种重要的自然资源。以下是我市对海水资源的部分利用。

（1）从海水中获取淡水。常用的操作方法是               ；

（2）从海水中获得氯化钠。将海水进行             可得到粗盐；

（3）从海水中得到金属镁。下图是从海水中提取镁的简单流程。

上述过程中，沉淀B与试剂C发生的是中和反应，则沉淀B的化学式为               ；由无水MgCl2制取Mg的化学方程式为                          。海水本身就是含有MgCl2的溶液，它与通过步骤①、②得到的MgCl2溶液有何不同：                           。

答案

(1)蒸馏法

(2)蒸发结晶

(3)Mg(OH)2； MgCl2Mg+Cl2↑；后者是经过富集和分离后的溶液(或海水中含有氯化钠等多种溶质，氯化镁的浓度很低)

单项选择题

Questions 16～20


It is already common knowledge, on the beaches and in the cafes of mainland Europe, that Americans work too hard—just as it is well known on the other side of the Atlantic that Europeans, above all the French and the Germans, are slackers who could do with a bit of America’s vigorous work ethic.
But a new survey suggests that even those vacations American employees do take are rapidly vanishing, to the extent that 40 per cent of workers questioned at the start of the summer said they had no plans to take any holiday at all for the next six months, more than at any time since the late 1970s.
It is probably mere coincidence that George W. Bush, one of the few Americans who has been known to enjoy a French-style month off during August, cut back his holiday in Texas to a fortnight. But the survey by the Conference Board research group, along with other recent statistics, suggests an epidemic of overwork among ordinary Americans.
A quarter of people employed in the private sector in the US get no paid vacation at all, according to government figures. Unlike almost all other industrialized nations, including Britain, American employers do not have to give paid holidays.
The average American gets a little less than four weeks of paid time off, including public holidays, compared with 6.6 weeks in the UK—where the law requires a minimum of four weeks off for full-time workers—and 7.9weeks for Italy. One study showed that people employed by the US subsidiary of a London-based bank would have to work there for 10 years just to be entitled to the same vacation time as colleagues in Britain who has just started their jobs.
Even when they do take vacations, overworked Americans find it hard to switch off. One in three find not checking their email and voicemail more stressful than working, according to a study by the Travelocity website, while the traumas of travel take their own toll. "We commonly complain we need a vacation from our vacations," the author Po Bronson wrote recently. "We leave home tired; we come back exhausted "
Christian Schneider, a German-born scholar at the Wharton business school in Philadelphia, argues that there is "a tendency to really relax in Europe, to disengage from work. When an American finally does take those few days of vacation per year they are most likely to be in constant contact with the office. "
Mindful that well-rested workers are more productive than burnt-out ones, the accounting firm PricewaterhouseCoopers has started closing all its US offices completely twice a year, for 10 days over Christmas and about five around Independence Day. "We wanted to create an environment where people could walk away and not worry about missing a meeting, a conference call or 300 emails," Barbara Kraft, a partner at the company, told the New York Times.
Left to themselves, Americans fail to take an average of four days of their vacation entitlement—an annual national total of 574 million unclaimed days.

According to the first paragraph, what do the people in America think of Europeans ______

A. They work less vigorously except the French and the Germans.
B. They work almost as vigorously as Americans.
C. They should work with some more vigor as Americans do.
D. They could work a bit more vigorously than Americans.
查看答案
多项选择题

RRU上行通道定标异常时通常会表现出下列哪些现象？（）

A.LMT上查询到某个通道的某个载波出现上行通道通道一致性差异过大告警；

B.出现射频通道故障—发射功率过高或过低告警；

C.同一通道在不同载波的上行校正结果幅度有较大差别；

D.查看上行通道增益分布，通道在不同载波上线缆增益Gcable值差别较大。
查看答案