整流柜内所设的保护有？

为了测量玩具遥控汽车的额定功率，某学习小组用天平测出小车质量为0.5kg，小车的最大速度由打点计时器打出的纸带来测量（如图所示）．主要实验步骤有：

A．给小车尾部系一条长纸带并让纸带穿过打点计时器；

B．接通打点计时器电源（电源频率50Hz），使小车以额定功率沿水平地面直线加速到最大速度，继续运行一段时间后关闭小车发动机，使其沿地面直线向前滑行直至停止；

C．学习小组分析后选择了认为符合要求的一段纸带，从某点开始每5个连续点标为一个记数点，并将表示每两个相邻记数点间距离的字母和测量数据在纸带上做了记录．（所有结果均保留2位有效数字）

①相邻两记数点间的时间间隔T=______s，由纸带知遥控汽车的最大速度为v=______m/s；

②实验小组在计算关闭发动机后的遥控汽车滑行过程的加速度时，选择了纸带上后5段数据，经过分析又舍掉了一段不合理数据．请你判断哪段数据不合理______（用字母表示），舍掉了不合理数据后加速度的计算表达式为a=______（请用时间间隔T及纸带上表示记数点间距离的字母表示），计算出的加速度大小为______m/s²；

③遥控汽车滑行过程的阻力大小为f=______N，其额定功率P=______W．

已开具的发票存根联和发票登记簿应当保存( )年。

A．1

B．5

C．10

D．15

Passage Two

The value of heat for the preservation of food has been known for thousands of years, but it was not realized until the nineteenth century that a very mild heat treatment far below the boiling point, made liquid foods such as milk keep much longer. The discovery followed the work of the French scientist Louis Pasteur on wine and beer.

The process, called after him "pasteurization", is a carefully controlled mild heat treatment. It was found that the process served two purposes, it prevented the souring of milk, and it destroyed the dangerous disease germs which sometimes occur in this product.

It has long been known to bacteria experts that the tubercle bacillus is the germ in milk which host ply resists heat treatment. To destroy this organism it is necessary to heat milk to about 60 degrees centigrade for 15 minutes, and its destruction has always been taken as a way of testing the efficiency of pasteurization. A heat treatment of this kind destroys about 99 percent of the common bacteria in milk, including nearly all those which cause milk to turn sour.

To ensure the certain destruction of tuberculosis and other disease germs in milk, it must be held at a fixed temperature for a fixed time. In Britain, for example, these conditions were defined-coy law in 1923 as 63-66 degrees centigrade for 30 minutes. This became known as the "holder" process, since the raw milk had to be pumped into a large tank, heated to just over 63 degrees centigrade, held in the tank for half an hour and then pumped out and cooled. This was a slow process and required a very large plant, so scientists worked for many years to produce a simpler, more convenient method, with less large equipment.

The latest method, officially approved in Britain in 1949, is known as the high-temperature-short-time, or H. T. S. T. method. It has now almost entirely replaced the "holder" process. In the H. T. S. T. system, the milk flows continuously through many sections of thin stainless steel pipes, During the process, the milk is held at 72 degrees centigrade for at least 15 seconds then, as it-cools, the heat is used, in part, to raise the temperature of the incoming milk in a device called a "wheat exchanger".

Efficient pasteurization may reduce the bacteria in raw milk from, say, one million to only a few thousand per cubic centimeter. The bacteria left are chemically mostly of the inert type, thatis, they either do not.

According to the passage, pasteurization refers to （）.

A．the heat treatment of milk

B．heating liquid to 100 degrees centigrade

C．the heat treatment to destroy all the common bacteria

D．heating objects to a fixed temperature for a fixed time

我国提出建立医院伦理委员会的主张是哪一年代（）

A.20世纪20年代

B.20世纪60年代

C.20世纪80年代

D.20世纪90年代

E.21世纪初

（）负责500kV主干网、部分220（330）kV跨省联络线和直调电厂的调度运行管理。

A.地调；

B.省调；

C.网调；

D.国调。