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问题 单项选择题

在晶闸管触发电路中，若使控制电压UC=0，改变（）的大小，可使直流电动机负载电压Ud=0，使触发角α=90º。达到调定移相控制范围，实现整流、逆变的控制要求。

A.同步电压

B.控制电压

C.偏移调正电压

答案

参考答案：C

单项选择题 B1型题

每于经期头痛，甚或巅顶掣痛，烦躁易怒，口苦咽干，中医辨证为（）

A.血瘀

B.肝肾阴虚

C.血虚

D.肝火

E.肾虚肝郁
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单项选择题

Prior to the UML, there was no clear leading （） language. Users had to choose from among many similar modeling languages with minor differences in overall （） power. Most of the modeling languages shared a set of commonly accepted concepts that are expressed slightly differently in various languages. This lack of （） discouraged new users from entering the OO market and from doing OO modeling, without greatly expanding the power of modeling. Users longed for the industry to adopt one, or a very few, broadly supported modeling languages suitable for （） usage. Some vendors were discouraged from entering the OO modeling area because of the need to support many similar, but slightly different, modeling languages. In particular, the supply of add-on tools has been depressed because small vendors cannot afford to support many different formats from many different （） modeling tools. It is important to the entire OO industry to encourage broadly based tools and vendors, as well as niche products that cater to the needs of specialized groups.

many different （） modeling tools

A．internal

B．external

C．front-end

D．back-end
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