问题 问答题 简答题

测定比表面积的注意事项

答案

参考答案:

1、试样捣实。捣实试样时,一定要使试样均匀分布在筒中,然后捣实,这样制备的水泥层,空隙分布比较均匀。2、空隙率的影响。对硅酸盐水泥,空隙率采用0.500±0.005,其他水泥或粉料的空隙率选用0.530±0.005。当上述的要求不能满足试料层制备的要求时,则允许改变空隙率。空隙率的调整以2000g砝码(5等砝码)将试样压实至规定的位置为止。

3、水泥密度对结果计算有影响,因此一定要测准。

4、仪器的液面应保持一定的刻度上。

5、要保证实验过程中仪器不漏气。

6、点在圆孔板上的滤纸大小应与圆筒内径一致,不能太大也不能太小。

7、捣器捣实水泥层时捣器的边必须与圆筒上边接触,以保持料层到一定高度。

8、用抽气瓶抽气时,应保持让液面徐徐上升,以免损失液体。

阅读理解

阅读理解。

     If you live in a place like Britain, you could not help thinking that the weather is random (随意的). This

is because the weather there seems to change daily if not hourly. In fact the weather is controlled (控制) by

systems which move around areas of the earth. In the UK the weather depends on depressions, often called

"lows", and anticyclones, also known as "highs". These systems start in the Atlantic Ocean, and make their

way across the British Isles from the west to the east. Highs bring sunny weather, while lows bring rain and

wind.

     The weather systems in tropical climates are very different from those in mid and high latitudes (纬度).

Tropical storms develop from depressions, and often build into cyclones, violent (猛烈的) storms, great

hurricanes and torrential rain.

     In modern times, human activity seems to be changing weather patterns. Gases or smoke produced by

heavy industry (工业) change the temperature of the earth's surface, and affect cloud formation (形成).

Some researchers say that factories in Europe and North America may have been one of the causes of the

droughts in Africa in the 1980s.

根据短文内容,判断下列句子正(T)误(F)。

( )1. The weather in Britain is very changeable.

( )2. Violent storms are common in mid and high latitudes.

( )3. Anticyclones bring fine weather.

( )4. The word torrential in Paragraph 2 means very heavy.

( )5. Climate changes as a rule and can't be affected by man.

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