Zhang L.,Beijing Information Science and Technical University
Sheng wu yi xue gong cheng xue za zhi = Journal of biomedical engineering = Shengwu yixue gongchengxue zazhi | Year: 2012
EEG Synchronization is considered the conformity of the brain functional areas. Advanced brain function requires many nervous systems with a specific function in relevant brain regions (areas) to achieve integration and coordination at different levels. In this paper, a new method for phase synchronization analysis-Mutually Approximate Entropy is proposed to process different frequency band of EEG signal during audio-visual stimulation and get Similar results with the method of Synchronization Index and Mutual Information Entropy. This showed that the Mutually Approximate Entropy can lead to a good indication of the phase synchronization between two leads. The paper also explored the brain reaction zone by the results of the phase synchronization analysis. The research work lays the foundation for the brain-computer interface design. Source
Beijing Information Science and Technical University | Date: 2014-10-08
A gas detection system with an inner ring cavity fiber laser using saturated absorption optical fiber is provided. The system comprising a ring fiber laser consisted of a pump source, a wavelength division multiplexer, a first active optical fiber, a first coupler, a fiber Bragg grating and a second coupler connected successively; an optical isolator coupled between said first active optical fiber and said first coupler; a second active grating connected between said fiber Bragg grating and said first coupler; a detection gas chamber connected between said first coupler and said second coupler; a first photoelectric detector for detecting the laser intensity outputted from said ring fiber laser to generate a first light intensity signal; a second photoelectric detector for receiving the intensity measuring beam passing through the detection gas chamber to generate a second light intensity signal; and a feedback control unit.
Beijing Information Science and Technical University | Date: 2014-10-01
The present invention provides a fiber laser gas detection system using active feedback compensation by a reference cavity, said system comprising: an optical fiber laser consists of a laser diode pump source, a wavelength division multiplexer, an active optical fiber and a fiber Bragg grating connected successively; an optical isolator coupled with said wavelength division multiplexer for blocking a reverse light transmission in said active fiber; a coupler connected with said optical isolator for dividing the laser light after being isolated by the optical isolator into a reference beam, a detecting beam and an intensity measuring beam according a certain ration power. The gas detection system according to the present invention can take advantages of the unique superiority of compact structure and narrow linewidth of the laser output of the fiber laser, and achieve a gas detection method with high sensitive and high precision by feedback controlling.
Wang J.,Beijing Information Science and Technical University |
Mu X.,Beijing Jiaotong University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2015
Aiming at that current control strategies of voltage source PWM rectifier under unbalanced voltage conditions at home and abroad exist complicated control structure and unsatisfactory control performances, hybrid passivity based control strategy by DC voltage loop(PI) and passivity based current controller is proposed in the paper. Based on EL model of the PWM rectifier, passivity based current controller is designed by damping injection method. According to passivity based current controller, switch function that can compensate unbalanced voltage conditions is obtained. All harmonics in input current of rectifier can be eliminated or restrained and DC output voltage of rectifier is kept constant by hybrid passivity based controller based on the real time value of voltage and current. Hybrid passivity based controller can make rectifier having good performances, and has simple control structure. Hybrid passivity based control of voltage source PWM rectifiers under unbalanced voltage conditions is proved feasible by simulation and experimental results. ©, 2015, Chinese Machine Press. All right reserved. Source
Li L.,Shenyang University of Chemical Technology |
Wang L.-K.,Beijing Information Science and Technical University |
Qin L.,Beijing Information Science and Technical University
Chuan Bo Li Xue/Journal of Ship Mechanics | Year: 2016
A ceramic disk plastered at the bottom of the metal shell constitutes the piezoelectric disk resonator with barrel shell. Vibration frequency of the resonator is deduced by Rayleigh-Ritz energy equation and elastic boundary conditions. Influence of the resonator structure on the resonant frequency is analyzed. The result shows that the resonant frequency (f) increases with the raise of thickness ratio (α) and radius ratio (β). The frequency changes little during α is the range of 0.5~0.75, but the frequency is rising rapidly when α is bigger than 0.75. The rake ratio of f/β increases a bit with the raise of β in the range of 0.4~0.9. The analysis result could be the reference about the design and manufacture of the piezoelectric disk resonator. © 2016, China Ship Scientific Research Center. All right reserved. Source