Applied Mechanics and Materials Vols. 571-572

Abstract: To solve the problem of image information transmission delay in the network multimedia teaching system, the compression and multicast solutions are put forward on the basis of usual screen blocking skill of data. According to the characteristics of the multimedia teaching system, the screen changes typically little at smaller intervals. It means that only a few screen blocks, which are changing, are needed to be transferred by screen blocking skill. At the same time, the network video data transmission volume is further curtailed through compression and multicast so that the multimedia information network transmission delay is decreased. The minimal buffer size for allocation is determined to ensure the smooth transmission of video data in the multimedia teaching system.

Abstract: Sonobuoy is used as aviation antisubmarine device to detect submarines, and its wireless communication mechanism would introduce radio interference. The speech signal needs to be identified from the submarine noise in order to facilitate sonar signal processing system to do further processing of the signal. This paper presents a TS-201 based dual-DSP sonobuoy signal processing system, and proposes an algorithm using Cubic Spline Interpolation and Pearson correlation coefficient to identify the speech signal from submarine radiated noise signal. This article describes the specific signal processing algorithm of the system, the hardware and software design of the system. This article uses a large number of data from experiments to test the hardware and software systems separately. The results of tests are analyzed, which indicate that the system function well in identifying speech signal from submarine radiated noise signal to, with a percentage of 98% correct rate.

Abstract: A high speed and high resolution semi-digital DLL (Delay Locked Loop) circuit will be discussed. The circuit is composed of three blocks: delay line, phase detector and digital finite-state machine (FSM). The delay line consists of two steps: the coarse tuning by tapping and the fine delay using interpolation to enable a resolution as high as 2 picoseconds. With the two steps approach and configuration of delay line, 3 GHz speed and picoseconds-level resolution can be achieved.

Abstract: The adjustable high-power distributed DC power supply controlled by DSP presented in this article is a new type of electronic power supply. Considering the features of modern power system, this article discusses and compares the principles of technical design and application of the adjustable high-power distributed DC power supply controlled by DSP with those of traditional DC power supply. The result suggests that the adjustable high-power distributed DC power supply controlled by DSP is easy to install, energy-saving and environment-friendly. It also has the characteristics of lower cost and higher performance.

Abstract: In order to keep the stability of the control circuit of electric vehicle, a flyback switching power supply was designed in this paper. The flyback switching power supply adopting current control mode PWM chip UC3842, and the output power of flyback switching power supply is 25W. In the design process of flyback switching power supply, the component parameters of control loop are worked out thoroughly. The flyback transformer was designed by considering the maximum pressure value of power switch. From the experimental results, the flyback switching power supply can work stably in the full load condition. The flyback switching power supply has excellent stability and dynamic characteristics.

Abstract: Aiming at reducing standby power consumption of switching power supply, a low standby power consumption control circuit for switching power supply is designed. The control circuit is composed of power switches, the driving circuit, the load detection circuit and the low power supply circuit. The control circuit effectively closed the input of switching power supply when the switching power supply is without load. The control circuit ensures the normal work of switching power supply when the switching power supply is with load. From the experiment results, the control circuit can effectively reduce standby power consumption of switching power supply.

Abstract: In order to achieve symmetry of the drive signal and suppress the magnetic bias, a novel dead-time control method for the double end converter is put forward in this paper, which can generate two independent and complementary PWM waveforms by configuring EPWM (Enhanced Pulse Width Modulator) module. The magnetic bias problems of the double end converter, principle of EPWM module and adjustment process of the dead-time control method are analyzed. Two different dead-times can de realized by setting the rising edge delay and falling edge delay of the corresponding registers in Dead-band (DB) module in one cycle to meet the requirement of drive signals. Experimental research on the novel dead-time control method is done on the push-pull forward circuit and the experiment results verify the feasibility of the proposed method.

Abstract: Based on Maxwell's equations and the time-varying plasma constitutive equation, electromagnetic scattering characteristics by a sudden-created plasma slab can be analyzed. According to one-dimensional numerical analysis, a modified NPML(M-NPML) absorbing boundary condition (ABC), by which the transient plasma can be truncated, was validated. The frequency drift phenomenon for electromagnetic wave in a transient plasma slab and some other useful conclusions are obtained.

Abstract: In order to reduce the power consumption of the synchronous rectification model buck converter, a current zero crossing detection circuit is designed in this paper. The detection circuit determines the freewheeling current of the synchronous rectification power switch is zero or not by detecting the drain voltage of synchronous rectification power switch. Due to use transistors instead of resistors in the voltage conversion, the accuracy of the detection circuit is less affected by temperature and process corner. From the experimental results, the detection circuit can make accurate current zero crossing detection in different temperatures and process corners, and the detection circuit has strong robustness.

Abstract: A knowledge reasoning based on-line infrared image monitoring system of the power equipments in substation is designed. The function, feature and structure of the system are introduced. Compare with the usual on-line infrared imaging monitoring system, a knowledge base is added and a knowledge reasoning method is used to diagnose the fault mode of operating equipments. The representation method of knowledge and processing of knowledge reasoning engine are introduced. Our research demonstrates that fault can be diagnosed correctly.