In self-mixing dual-frequency laser Doppler velocimetry, the self-mixing Doppler frequency shift of the optical frequency difference is a linear function of the velocity of an external dynamic object; however, it is always ultralow for signal processing. Therefore, an ultralow frequency extraction method based on artificial neural networks (NNs) is presented because NNs can accurately create a fitting function for a Doppler signal and extend the signal to the DC value, increasing the signal length and sampling points without yielding unnecessary influences on the Doppler frequency. We precisely measured Doppler frequencies in the frequency domain with a low sampling rate and calculated the velocities for a target with longitudinal movements. Compared to time-domain extraction, frequency-domain extraction can reflect the complete information of the original Doppler signal. This feature potentially contributes to the signal processing of velocimetry in practical engineering applications.

In the internet era, the college student groups are internet users who use the internet more widely and deeply than the ordinary internet users. However, college students have insufficient social experience and live in a relatively simple living environment for a long time, which makes them have low ability to distinguish the true from the false, so they are easily targeted by cyber scammers. This paper analyzes the causes and the basic types of online fraud cases that happened to college students; the fraud case data are classified and sorted to extract the salient features of the telecom network fraud cases of college students and the common features of the victims. The paper provides suggestions for guiding college students to learn to screen online fraud and self-protect and to cultivate more comprehensive high-quality talents.

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In the Internet era, the college student groups are Internet users who use the Internet more widely and deeply with more frequency than the ordinary Internet users. However, college students have insufficient social experience and they have been living in a relatively simple living environment for a long time, which makes them have low ability to distinguish the true from the false and become the targeted by cyber scammers easily. This paper analyzes the causes and the basic types of online fraud cases happened on college students through studying the current situation of online fraud cases happened on college students so as to guide college students to learn to screen and self-protect, and to cultivate more comprehensive high-quality talents.