皮皮学,免费搜题
登录
logo - 刷刷题
搜题
【简答题】
Last week I visit one of my old neighborhoods in Washington D.C. I had not been there for twenty years and as I walked along the street, my mind was flooded by memories of the past. I saw the old apartment building where I had lived and the playground where I had played. As I viewed these once familiar surroundings, images of myself as a child there came to mind. However, what I saw and what I remembered were not the same. I sadly realized that the best memories are those left untouched. My old apartment building, as I remember, was bright and alive. It was more than just a place to live. It was a movie house, a space station, or whatever my young mind could imagine. I would steal away with my friends and play in the basement. This was always exciting because it was cool and dark, and there were so many things there to hide among. There was a small river in the back of the building. We should go there to lie in the shade of trees and enjoy ourselves. However, what I saw was completely different. The apartment building was now in disrepair( 失修,破损 ). What was once more than a place to live looked hardly worth living in. The windows were all broken. The once clean walls were covered with dirty marks. The river was hardly recognizable. The water was polluted( 污染 )and the trees flowers were all dead. The once sweet smelling river now smelled terrible. It was really heartbreaking to see all this. I do not regret( 后悔 )having seen my old neighborhood. However, I do not think my innocent childhood memories can ever be the same. I suppose it is true when they say,“You can never go home again.”
手机使用
分享
复制链接
新浪微博
分享QQ
微信扫一扫
微信内点击右上角“…”即可分享
反馈
参考答案:
举一反三
【简答题】模拟信号是指信号的参量可 取值的信号。
【简答题】用电源等效变换求图中的电流I= A;若用叠加定理求解,电压源单独作用时电流分量I'= A,电流源单独作用时 电流分量I'’= A;若用戴维宁定理或诺顿定理求解电流I,将1Ω电阻看作外电路,剩下的一端口含源网络如图所示,则开路电压Uoc= V,短路电流Isc= A,等效电阻Ro= Ω。
【单选题】在所有配水点关闭后,整个热水系统与大气隔绝,其优点是水质不易受外界传染,但缺点是若设计运行不当会出现由于温升引起的压力升高而造成超压事故,故必须设置安全阀或膨胀水罐的系统称为(  )。
A.
自然循环热水供应系统
B.
机械循环热水供应系统
C.
开式热水供应系统
D.
闭式热水供应系统
【简答题】分析下列成语的内部结构关系。 (1)一衣带水 (2)自怨自艾 (3)正本清源 (4)流芳百世 (5)风雨飘摇 (6)中饱私囊 (7)满载而归 (8)兼收并蓄 (9)波澜壮阔 (10)莫衷一是 (11)源远流长 (12)处之泰然
【简答题】模拟信号是指信号的参量( __ )取值的信号,数字信号是指信号的参量可( __ )取值的信号。(离散 / 连续)
【单选题】关于电子支付的特点,下列说法正确的是()
A.
电子支付的工作环境是一个封闭的系统平台
B.
电子支付具有方便、快捷、低效和经济的优势
C.
电子支付使用的是最先进的通信手段,如因特网
D.
电子支付比传统支付安全
【单选题】关于电子支付的特点,下列说法正确的有( )。
A.
电子支付比传统支付安全
B.
电子支付具有方便、快捷、低效和经济的优势
C.
电子支付的工作环境是一个封闭的系统平台
D.
电子支付使用的是最先进的通信手段,如因特网
【多选题】用戴维宁定理计算下 图中的电流 I ,以下阐述正确的是:
A.
解题思路是:先将下面左图中的框内电路等效成右图中电压源,最后再计算I。
B.
计算开路电压,将电流源化成电压源,如下图。 计算: ,对Uoc和12V电源支路列KVL方程得: U OC =-2+12-6×2/3=6 (V)
C.
计算开路电压,将电流源化成电压源,如下图。 计算: ,对Uoc和6V电源支路列KVL方程得: U OC =-2+6-3×2/3= 2 (V)
D.
计算内阻的方法是,断开待求支路,对剩下的电路去源,然后计算两端的等效电阻,如下图,则Ro=Rab Ro=1-1+3//6=4Ω
E.
采用电源等效的办法计算开路电压和内阻: Uoc=2-8=-6V,Ro=1+1+2=4Ω
F.
经过计算,I=-1A
G.
经过计算,I=1A
【简答题】模拟信号是指信号的参量可 取值的信号,数字信号是指信号的 取值的信号。
【判断题】模拟信号是指信号的参量可连续取值的信号,数字信号是指信号的参量可离散取值的信号。
A.
正确
B.
错误
相关题目:
参考解析:
知识点:
题目纠错 0
发布
创建自己的小题库 - 刷刷题