Applied Mechanics and Materials Vols. 670-671

Abstract: This paper uses the vibration method to diagnose the mechanical state of transformer winding,directed against the fact that the accuracy of the mechanical fault diagnosis in transformer winding is not high. It collects the load test vibration signal of transformer winding in normal and abnormal state, analyzes the vibration signals in different states, and use the vibration frequency and load current matching to judge the winding condition. By setting the different faults to the actual transformer winding of S11-M-500/35 type, it uses the vibration method to do the diagnosis analysis. And the research content is of great significance for the promotion and application of vibration analysis method.

Abstract: In order to study the vibration and seismic performance of K8 triangular cone partial double layer spherical reticulated shell and analyze the factors that impact its self-vibration and seismic performance, this paper used parametric design language APDL of ANSYS to establish the shell model,then used 3D El-Centro seismic waves to analyze the influencing factors of its self-vibration and seismic performance by changing the ratio of rise to span, the ratio of thickness to span, bar section area and other parameters. Therefore this paper get some conclusions with engineering significance.

Abstract: This paper presents a prototype of a new flextensional transducer with PVDF (Polyvinylidene Fluoride) piezoelectric film instead of metallic shell. Resonance frequency, bandwidth, transmitting voltage response, and horizontal directivity of the flextensional transducer with PVDF piezoelectric film were respectively measured by using laser-scanning vibrometer, and underwater acoustic measurement system. Experimental results showed that the new transducer features effectively conversion from longitudinal vibration of piezoelectric stack into radial vibration of PVDF piezoelectric film.

Abstract: This paper describes a quality power module design for Biological Electrical Impedance Tomography (BEIT) system based on FPGA. As the electrical signals on the boundary of subject are too weak to measure effectively, it is essential to design a data acquisition system with high SNR and extremely low noise. This paper is focus on the power module design because the quality of the power module impacts the performance of the data acquisition system directly. The BEIT system needs several kinds of power supply to work effectively, such as 12V, 5V. In this paper, the power module is supplied by DC18V, using Buck-type DC/DC and LDO technologies, a set of independent power supply scheme is carried out, and provides stability and low noise power sources. The expected powers with ripple less than 20mV are achieved, which can preferably meet the BEIT system power supply requirements.

Abstract: A sensitive cataluminescence-based detecting technology using nanosized Mo₄V₆Ti₁₀O₄₇ as a probe was proposed for determination of formaldehyde in air. Trace formaldehyde was firstly absorbed on active carbon at room temperature to concentrate, then desorbed at 75°C to determine. The method showed high selectivity to formaldehyde at wavelength of 575nm, satisfying activity at temperature of 260°C and good stability at carrier flow rate of 145 ml/min. The linear range of CTL intensity versus concentration of formaldehyde was 0.04~78 mg/m³, and the detection limit (3σ) was 0.02 mg/m³. The recovery of artificial sample was 96.8%-103.4% by this method. There was no response to CO, CO₂, SO₂, NH₃, methanol, ethanol, benzene, toluene and xylenes.

Abstract: A inverse identification method is proposed to deal with the nonlinear boundary parameter identification problem. The boundary condition is modeled as unknown equivalent substructure applied on the initial linear structure and the parameter identification inverse problem is translated into a linear-model based equivalent force identification problem. Based on a given multi-point approximations method, the time history of the equivalent force is identified using the measured dynamic response. The unknown dynamic forces due to substructure are parameterized by combination the base functions on a series of space-time points. Using the moving least squares method, a matrix is derived to extract the force time history from the measured dynamic response. Then, the boundary stiffness and damping are identified using the input-output data of the equivalent substructure. The proposed approach has been demonstrated by some numerical examples and the boundary parameters are successfully identified.

Abstract: This paper proposes a method of the fault detection and diagnosis for the railway circuit of ZPW-2000 system based on the main track voltage curve. Exact curve matching fault detection method and SVM-based fault diagnosis method are adopted. Based on envelope algorithm, exact curve matching method is used to match the detected current curve with the reference curve so as to predict whether the curve would have fault or not. Then, the SVM-based fault diagnosis method is used to make sure that the fault classification could be diagnosed intelligently. The experiment results show that the proposed method can accurately identify the track circuit fault state, and the accuracy rate in the diagnosis of the fault location is above 99%, which verify the effectiveness of the method in the fault detection and diagnosis.

Abstract: Combined with the power system fault diagnosis current situation, fault diagnosis methods are important to shorten fault outage time, prevent accident expanding and restore power quickly. We summed up expert system, artificial neural network, Petri network and Bayesian network fault diagnosis methods. The diagnosis principle, advantages and disadvantages of different methods were discussed.

Abstract: Nowadays, digital front-end devices are widely used in large number of fields such as electronic appliances. Signals must be presented in an appropriate format, for example, the original analog signals must be converted into digital formats that can be recognized and used by digital equipment. In this paper, the random sampling technique is implemented by original design of a Pseudorandom Signal Sampler circuit for controlling ADC to relax constraints of receiver circuits supporting multiband signal processing. This new idea of using non-uniform sampling technique for multiband signals sampling allows the main advantage of suppressing spectral aliases at integer multiples of sampling frequency produced by conventional uniform sampling technique. This approach could reduce the constraints on the anti-aliasing filter, relax the automatic gain control dynamic range, and decrease the ADC dynamic power consumption. Experiments show that this approach achieve good performance and it could be implemented in FPGA in signal processing successfully.

Abstract: In engineering practice, geotechnical particle vibration speed is usually regarded as stability criterion of explosion seismic wave. However, when using explosion seismic wave to evaluate damage effect of shock wave, it is needed to study characteristics on other physical quantities of explosion seismic wave. By establishing test system of explosion seismic wave, seismic acceleration signals of 4 rounds of ammunition in air explosions are measured in three directions. The results show that the test system is reliable and effective.