Applied Mechanics and Materials Vols. 130-134

Abstract: This paper presents principles of a down-converted mixer for four sub-harmonic designed by ADS software. The LO and RF frequencies are 23GHz, 92-94GHz respectively. The structure of ridge waveguide to microstrip transitions is optimized by CST simulation software, and W-band signals are directed to mixer RF side. The simulation results show that this mixer achieves higher 1 dB compression point, loss of frequency conversion less than 15 dB and good linearity.

Abstract: Taking three phase PWM rectifier as the research object, according to interference mechanism of the rectifier bridge, this paper describes the equivalent circuit of AC side differential mode interference and calculates the interference source voltage and differential mode interference voltage of the three phase PWM rectifier AC side in 150KHz-30MHz frequency band. Then we analyze the model of the equivalent circuit diagram using the Saber software and verify the validity of the model and the accuracy of the calculation through experiments.

Abstract: Time division multiplier was widely used in high-precision industrial frequency AC power measurements.The poor stability of zero point was caused by the switch leakage and amplifier offset voltage. Based on the experimental study of the time division multiplier circuit designed in the article, the mathematical model of zero point compensation was established, and then the appropriate calibration method was proposed. Considered the amplifier offset voltage, the error model of the time division multiplier was analyzed and the error expression was obtained. These can provide theoretical guidance for choosing amplifiers of the no-beat time division multiplier.

Abstract: The compounds of Fe substitution of Cr in nanotructured Sr₂Fe_1-xCr_xMoO₆ (0≤x≤0.3) double perovskite have been prepared by sol-gel method. The x-ray diffraction patterns of the samples show that the samples are in nanometer range. And the average grain size D for these samples is 39.7, 37.1, 33.4, 31.9, and 31.2nm, respectively, decreases with the increasing of Cr ion. The saturation magnetization and the magnetoresistance of the samples decrease with the increasing of Cr for the disorder defects which increase for the close ionic radii of Mo and Cr.

Abstract: The effects of tungsten doping in La₂Mo_2–yW_yO₉ (y =0, 0.25, 0.5, 1.0, 1.4) samples were studied using dielectric relaxation measurements. The results indicate that the solubility of W⁶⁺ in La₂Mo₂O₉ sample is about 25mol%, W⁶⁺ can suppress the α/β phase transition in the La₂Mo₂O₉. Additional to the low-temperature relaxation peak P_d associated with oxygen ion diffusion, a new dielectric loss peak P_h associated with a phase transition from the static disordered state to the dynamic disordered state of oxygen ion distribution was observed around 740 K. The conductivity of La₂Mo_1.9W_0.1O₉ sample is higher than that of the pure La₂Mo₂O₉, and then decrease with the increasing of the tungsten doping in La₂Mo_2–yW_yO₉ (y = 0.5, 1.0) samples in the whole measurement temperature.

Abstract: Visual tracking is a key issue for autonomous navigation, intelligent monitoring system and so on. While a Particle Filter for tracking is designed, the target in image may be out of range, and the tracked target will be lost since the target image size keeps changing. A method for tracking a mobile target with visual image, Particle Filter with multi-path particles (PFWMP), is proposed to solve the above problem in this paper. Here, the method is based on the wavelet transform incorporated in traditional Particle Filter, and particles are made to move in original image and the image processed by wavelet transform. The results show that the improved approach using multiple particles can enhance the robustness of tracking algorithm and improve tracking accuracy.

Abstract: A CUDA accelerated Quasi-Monte Carlo Gaussian particle filter (QMC-GPF) is proposed to deal with real-time non-linear non-Gaussian problems. GPF is especially suitable for parallel implementation as a result of the elimination of resampling step. QMC-GPF is an efficient counterpart of GPF using QMC sampling method instead of MC. Since particles generated by QMC method provides the best-possible distribution in the sampling space, QMC-GPF can make more accurate estimation with the same number of particles compared with traditional particle filter. Experimental results show that our GPU implementation of QMC-GPF can achieve the maximum speedup ratio of 95 on NVIDIA GeForce GTX 460.

Abstract: In this paper, a nonlinear numerical model of laser melting of crystalline silicon solar cells and phosphorus diffusion has been established by finite difference method implemented in MATLAB. Based on the features of liquid-phase diffusion of phosphorus atoms in melting silicon, theoretical simulation for phosphorus concentration profiles and explanation for the mechanism of laser doping are achieved. The theoretical phosphorus concentration profile is in good agreement with the experimental SIMS data.

Abstract: Recently, high frequency short pulse electrochemical machining is a focus engineering of national research, its mechanism of research must established in the foundation of correct mathematics model, capacitance model is a ideal model to analysis high frequency short pulse, this article is based on capacitance model, make a detailed formula deduction on the main factors for high frequency short pulse electrochemical machining, eventually, acquired high frequency narrow pulse electrolysis processing gap between poles formula which is based on capacitance model.

Abstract: Intravascular Ultrasound (IVUS) is one of interventional imaging modalities widely used in clinical diagnosis of vascular diseases, especially coronary artery diseases. Segmentation of IVUS images to extract vessel wall boundaries is of importance for quantitative analysis and 3D vessel reconstruction. A 3D parallel method for segmenting IVUS image sequence is proposed in this paper. Firstly, original images are preprocessed to reduce possible noises and eliminate ring-down artifacts. Then, several longitudinal cuts are obtained and intima-lumen and media-adventitia boundaries are detected. Once these boundaries are mapped onto each cross-sectional slice, initial plan of vessel wall boundaries in each frame is obtained. Finally, these initial contours evolve continuously until stop at target contours. Consequently, segmentation of each IVUS tomographic frame isimplemented simultaneously and the efficiency is greatly raised compared with 2D sequential approaches.