当野外抽水试验设备缺乏时,可采用试坑渗水试验法,测定包气带非饱和岩层的渗透 系数。有条件可采用单环法或双环法以提高精度。 试坑法是在表层干土中挖一试坑,坑底要离潜水位3~5m以上,向试坑内注水,必须 使试坑中的水位始终高出坑底约10cm,为便于观测坑内水位,在坑底设一标尺

1.设z=u2-v2,而u=x+y,v=x-y,求 2.设z=u2m,而u=x,v=3x-2y,求 3.设z=ex-2y,而x=sint,y=,求 4.设zarcsinr-y),而x+3t,y=4t2,求

提出了GF(3m)上3次方程根的判别方法,讨论了有限域GF(pm)(p ≥ 3)上3pl次方程根的状况,给出了GF(pm)上p次和pl+1次方程根的判别方法

流射沸腾冷却强化的核心是利用常压水形成的水柱,以一定的速度贯穿水层,与钢板表面直接接触,产生核沸腾区,引起了强烈沸腾,通过对射流出口速度、高度、直径及水柱间距的优化的实验研究,达到了在整个钢板横截面上获得极强冷却区的效果,对于20mm厚的钢板,冷却速度可达45.2℃/s,板形精度可达3mm/m

1已知质点沿x轴作直线运动,其运 动方程为:x=2+6t2-2t3,式中x的单位 为m,t的单位为s.求:(1)质点在运动 开始后4.0s内位移的大小;(2)质点在该 时间内所通过的路程;(3)t=4s时质点的 速度和加速度

Uint IL. Basic Listening Practice 1. Script W: Did you see the paper today? There was an earthquake in brazil M: Yes, but it only measured 3. 5 on the Richter scale. I dont think there were any casualties

Inti I. Basic listening practice 1. Script W: Ok. It's your turn to pay the bill. I paid last time M: What? You have a selective memory. You tried to pay last turn, but your credit card failed; so I ended up paying! It's definitely your turn Q: What is true according to the conversation? 2. Script

Uinta I. Basic listening practice 1. Script M: Did you pick up the paper for me today? i really want to check the job vacancies W: I know, it's over there. There's not much happen though. I had a look already Maybe you should look on the Net instead

Unit 6 I. Basic listening practice 1. Script W: Are those cigarettes yours? I thought you quit. If you go back to it, your teeth and fingers will be nicotine-Stained; your breath and clothes will smell smoky M: I didnt. I swear. Ads showing diseased lungs kept me from starting again. Believe

Ⅱ. Listening skills Understanding Times and dates w: Oh, look at the clock It's 5: 15. I'll be late for Jennifer's birthday party! I was supposed to leave at 5 o'clock M: Don't worry! You still have some time. The clock is twenty minutes fast Q What time is it now?