In this paper the realization approach of X-band four-frequency multiplier microstrip structure is discussed mainly.

本文主要讨论x波段四倍频器微带结构的实现途径。

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An analog signal is composed of four basic components: DC and AC magnitudes, frequency, and phase.

模拟信号由直流和交流分量、频率和相位四部分组成。

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Four white LEDs on the interface pulse at different frequencies, and the system can use the frequency of the brainwave evoked to determine at which LED the user is staring.

四个白色led在不同频率上闪烁，系统可以通过脑电波确定是看着哪个频率的led。

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A food frequency--by the way, you also have the issue of whether the particular twenty-four hours that a person is interviewed is representative of their diet overall, because you can imagine how much your food intake varies from day to day.

食物摄取频率,顺便说下,还有一个问题,就是在选取的24小时里,测试者,是不是对总体有代表性,因为你可以想象,每天事物的摄入量都是不同的

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

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