Applied Mechanics and Materials Vols. 220-223

Abstract: The electromagnetic pulse simulator designed in this paper consists of an adjustable direct current high voltage source, a capacitor for energy-storage, an air spark gap switch, a resistive divider for measurement and a GHz transversal electromagnetic wave (GTEM) cell. The analysis model is constructed based on the theory of transmission line. Influencing factors, such as self-load and impedance mismatch of the transmission line (as well as the cell), were analyzed using Pspice. The self-load has the effect of parallel connection with the load of GTEM cell. It may increase the rise-time, decrease the fall time and reduce the voltage peak. The sudden change of the transmission line impedance will make the waveform of pulse contain reflected oscillation. Four types of resistance divider link were also simulated using Pspice. Improper connection of the resistance divider will cause the waveform of pulse oscillation and lengthen the rise-time, which can be reduced by shorting the high voltage lead, using system structure with gradually changing resistance or connecting a damping resistance at the end.

Abstract: This paper puts forward the design of communication system based on FPGA. USB controller CY7C68013 is widely used for its faster data transmission rate and diverse interface way which provide a simple and seamless connecting interface for the ATA, FPGA and DSP . This paper introduces the basic working principles of the controllers, and uses its affiliate FIFO method in order to produce corresponding control signal in FPGA with VHDL. It realizes fast data transmission between PC and FPGA through USB. Test results shows that the scheme transmission speed fast, data accurate, and can be extended to other need through the USB fast data transmission system.

Abstract: Analog circuits are of great importance in electronic system design. Recent evolutionary design results are usually small-scale analog circuits. This paper proposes a real-coded mechanism and uses it in the large-scale analog circuit evolutionary design. The proposed scheme evolves the circuit topology and size to a uniformed continuous space, in which the circuit representation is closed and of causality. Experimental results show that the proposed scheme can work successfully on many analog circuits with different kinds of characteristics. Comparing with other evolutionary methods before, the proposed scheme performs better on large-scale problems of circuit synthesis with higher search efficiency, lower computational complexity, and less computing time.

Abstract: The data acquisition system for mine's dynamic rail track scale is designed based on embedded technology. The automatic motion direction judge of the tramcar could be achieved by the staggered installation of the weight sensors without installing additional direction sensors. Each pair of tracks are installed with a data collector and all data collectors carry out a two-way data exchange with the same measurement controller. A video monitor is installed near the coal mines to get video monitoring. Only one video server is required for all video monitors. The measurement controller is used to receive and deal with both the weight data from the data collector and the video data from video server. The data is computed in measurement controller and transmitted to the remote monitoring center server, in which the final results are presented.

Abstract: Although intensified charge coupled device (ICCD) is conventionally used to investigate the breakdown mechanism in gas discharge. ICCD can not be used to study the long plasma column because it is hard to be imaged. For solving this problem, a novel optical system is proposed which consists of several elements. Each element is composed of one collimator and a photomultiplier tube. Using this system, spatial resolved emission signal can be obtained. Results show that the light emission signal from each area shows a pulse with a width of about 3μs. It is interesting that the time lag in each half cycle increases with the increase of distance away from the dielectric barrier discharge (DBD). This phenomenon implies that the plasma bullet always leaves DBD at the rising edge of the applied voltage. The time lag versus the distance from DBD is used to calculate the propagation velocity of the discharge.

Abstract: In photovoltaic grid-connected system, the method of adding voltage feed-forward to improve the shape of grid-connected current wave is presented, the reason for the introduction of the net voltage feed-forward decreasing the phasic difference between grid-connected current and net voltage and reducing the THD of grid-connected current is analyzed. It is confirmed that the net voltage feed-forward compensation can improve grid-connected current availably by the results of simulations and experiments, keep the current frequency and phase synchronous to the grid.

Abstract: This paper puts forward a dielectric barrier discharge detection system using PMT for photoelectric element. According to faint light signal characteristics and testing purpose of dielectric barrier discharge, this system is designed, including three parts: optical fiber transmission, photoelectric conversion and signal processing circuit. This paper introduces design and ideas of the system framework and presents circuit design parameter. Results in atmospheric pressure of dielectric barrier discharge detection experiment show that the system has high sensitivity, fast response, can effectively distinguish discharge and interference signals, gather more signals in different areas.

Abstract: Phase-match in degenerate four-wave mixing (DFWM) is not automatically achieved in the forward folded boxcars geometry. In this paper, we first design a simple image aligning system composed of an optical system, CCD camera and the related software. We can feasibly obtain well overlapped spot in the sample cell without moving the sample cell under this system. Also, we have proven the three pumping light beams are well overlapped in the sample cell when the three pumping light beams are on the same spot on CCD camera. This method minimizes the deviation by our eyes aligning. We can easily and timely know the effect of the pointing stability on the optical path by monitoring facula changing with the laser beam pointing and disturbs of the environment. So, this is a good choice for fast adjusting the light path and finding the overlapped spot. Finally, Steady DFWM signals have been obtained in the iodine vapor. This system makes it feasible that the potential application of FG-DFWM is used as a diagnostic tool in combustion research and environment monitoring.

Abstract: The projectile’s shooting accuracy measurement is an important content during the target measurment, based on the analysis of the various test principles of existing accuracy test equipment, i.e. accuracy optical target,a new-type test technology of accuracy optical target ,which is based on intersection laser principle, has been designed. In the design, the optical path is reasonable, and the circuit is simple without amplifier circuit but can realize digital signal processing and it has made experimental verification on the core technologies of the sensitivity and frequency response etc. in the signal acquisition circuit.

Abstract: LEDs for lighting application are becoming widely adopted due to economic, energy and environmental reasons. LEDs are conventionally powerd by low-voltage DC sources. More and more recent research works have been focusing on an integrated LED chip directly driven by high-voltage DC power supply (HV-LED). The chip structure, the key manufacturing processes and its driving technologies are discussed respectively in this paper, which indicates the advantages of HV-LED including higher luminous efficiency, lower cost and enhanced reliability, and base on this, a HV-LED flip chip is proposed.