皮皮学，免费搜题
登录
搜题
【单选题】
关于电力电子装置过电流保护，表述正确的是下面哪一个？A.
如果电力电子装置中已经安装了快速熔断器，则不需要其它过电流保护措施。
B.
对重要的、且易发生短路的晶闸管设备或器件，需采用电子电路进行过电流保护，响应最快。
C.
快速熔断器仅用于部分区段的过载保护。
D.
快速熔断器仅用于短路保护。
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【多选题】Which two are true concerning a multitenant container database with three pluggable database?（）
A.
All administration tasks must be done to a specific pluggable database.
B.
The pluggable databases increase patching time.
C.
The pluggable databases reduce administration effort.
D.
The pluggable databases are patched together.
E.
Pluggable databases are only used for database consolidation.
【单选题】About Database, which of the following is WRONG?
A.
Relational model is an obsolete database model now
B.
DBMS means database-management system.
C.
A query is a request to see information from a database that matches specific criteria
D.
A record is a collection of related fields in a database and also called a row
【单选题】Which statement is true about a whole consistent database backup on a database running in ARCHIVELOGmode（）
A.
The backup will consist of used data blocks only.
B.
The database must be shut down to accomplish the backup.
C.
The backup can be accomplished without shutting down the database.
D.
The backup will contain all database files that have never been backed up
【简答题】（1）化简： sin( π 2 +α)?cos( π 2 -α) cos(π-α) + sin(π-α)?sin(-α) sin(π+α) ； （2）设两个非零向量 e 1 和 e 2 不共线，且 AB = e 1 +2 e 2 ， BC =-2 e 1 +3 e 2 ， CD =5 e 1 +3 e 2 ，求证：A，B，D三点在同一直线上．
【简答题】证明 e(φ)×e1(φ)=k； (2)证明 e(φ+α)=e(φ)cos α+e1(φ)sin α．
【单选题】I would rather apologize to my boss for being late without an explanation than ______ an excuse.
A.
fabricate
B.
fake
C.
forge
D.
pretend
【简答题】已知A(r，θ，φ)=r 2 sinφe r +2rcosθe θ +sinθe φ ，求 ． (ρ，φ，z)为柱面坐标，(r，θ，φ)为球面坐标．
相关题目：