问题 问答题

电业工人创造了具有世界先进水平的超高压带电作业法,利用“绝缘梯”使输电线间的电势差逐渐变小,直到最后使人体的电势与输电线电势相等,试问:

(1)人与输电线电势相等时,为什么没有危险?

(2)超高压输电线周围存在强电场,人靠近输电线时,人体会有什么现象发生?

(3)工人带电作业时穿着由金属丝和棉纱织成的均压服,有什么作用?

答案

(1)人与输电线电势相等时,即任意两点间的电势差U=0,电荷不会发生定向移动,不会产生电流,因此无危险

(2)人体靠近超高压输电线周围的强电场时,由于静电感应,人体中的自由电荷重新分布,瞬时间负电荷向E的反方向移动,如图那样形成了瞬时电流

(3)由金属丝和绵纱织成的均压服有静电屏蔽的作用

阅读理解

Have you heard of the scandal that happened in one of Great Britain’s biggest supermarket chains called Tesco? The British love Tesco as it sells very cheap products and it can be found on almost every corner of a British city or town.

On January 15th 2013 food inspectors discovered 30 % horsemeat in a certain brand of frozen beefburgers that were mostly sold by Tesco in the UK and Ireland.

In times of social media like Facebook and Twitter the news has spread fast and customers have been very concerned about what the food they buy actually contains. Tesco said it had taken away the burgers from the shop shelves immediately, and apologized to their customers. They also promised that they would find out what exactly happened and that they would work harder than ever so this would never happen again. Customers are also able to return the beefburgers and get a refund, that is, their money back.

However, it will be hard for Tesco to get the people’s trust back. Just imagine buying lovely beefburgers that you fry at home and suddenly you find out that you have actually eaten horsemeat! In this case not only horse lovers will be upset!

By the way, why are British people so shocked about eating horsemeat? In history, horses have played great roles as working animals and as an important means of transport. When Britons of today think of horses, they think of majestic animals or cute pets rather than meat.

But this is not the only reason for the protest: Customers also want to be sure that the products they buy contain what it says on the label. Hopefully, supermarkets can avoid mistakes like that in the future. Maybe there should be stricter regulations and more controls of our food? Otherwise we will soon find ourselves eating panda meat instead of pork and parrot instead of chicken. So the next time you are in a supermarket maybe check the ingredients of your food before you buy it or you could get a nasty surprise …

小题1:What is the scandal?

A.Tesco’s products were much more expensive than they are supposed to be.

B.Tesco didn’t react immediately to a food quality issue.

C.Tesco sold expired food.

D.Horsemeat was found in burgers sold in Tesco.小题2:What didn’t Tesco do in response to the scandal?

A.It withdrew the beefburgers.

B.It made an apology to the public.

C.It investigated and found out the cause and effect of the scandal.

D.It returned money to customers who bought the beefburgers.小题3:Which statement isn’t among the reasons why customers are furious?

A.People trusted Tesco so much that they never expected a scandal like this.

B.Everyone can call himself or herself a horse lover in the UK.

C.Sellers shouldn’t cheat customers.

D.The horse is humans’ friend.

问答题

请编制程序PROG1.ASM,其功能是:内存中连续存放的20个8位有符号数(补码)是由一个8位A/D转换器采集的双极性信号(Xn),现要求对该信号作如下限幅处理(处理后的信号记为Yn):
a) Yn=-100Xn<-100
b) Yn=Xn∣Xn∣≤100
c) Yn=100Xn>100
例如:
Xn:68H,60H,8EH,38H,…
Yn:64H,61H,9CH,38H,…
部分程序已在PROG1.ASM中给出,请填空BEGIN和END之间已给出的源程序使其完整(空白己用横线标出,每行空白一般只需一条指令,但功能相当的多条指令亦可)或删除 BEGIN和END之间原有的代码并自行编写程序片段来完成要求的功能。
原始数据由过程LOAD从文件INPUT1.DAT中读入SOURCE开始的内存单元中,结果要求从RESULT开始存放,由过程SAVE保存到文件OUTPUT1.DAT中。
对程序必须进行汇编,并与IO.OBJ链接产生PROG1.EXE执行文件,最终运行程序产生结果(无结果或结果不正确者均不得分)。
试题程序:
EXTRN LOAD:FAR, SAVE:FAR
N EQU20
M EQU100
DSEGSEGMENT
SOURCE DWN DUP()
RESULT DWN DUP(0)
NAME0 DB’INPUTI.DAT’,0
NAME1 DB’OUTPUT1.DAT’,0
DSEGENDS
SSEGSEGMENT STACK
DB128 DUP()
SSEGENDS
CSEGSEGMENT
ASSUME CS:CSEG, DS:DSEG, SS:SSEG
START PROC FAR
PUSH DS
XORAX,AX
PUSH AX
MOVAX,DSEG
MOVDS,AX
LEADX,SOURCE; 数据区起始地址
LEASI,NAME0; 原始数据文件名起始地址
MOVCX,N ; 字节数
CALL LOAD ; 从INPUT1.DAT中读取数据
; **** BEGIN ****
LEASI,SOURCE
LEADI,RESULT
(1)
NEXT: MOVAX,[SI]
CMPAX,-M
(2) L1
CMPAL,M
(3)
MOVAL,M
JMPL2
L1:MOVAL,-M
L2:MOV[DI],AL
(4)
(5)
(6)
; **** END ****
LEA DX,RESULT ; 结果数据区首址
LEA SI,NAME1 ; 结果文件名起始地址
MOV CX,N ; 字节数
CALL SAVE ; 保存结果到OUTPUT1.DAT文件中
RET
START ENDP
CSEGENDS
END START