Advanced Materials Research Vols. 706-708

Abstract: In this paper, a mathematical analysis of the EMI(Electromagnetic Interference) for a 20kHz/10kV capacitor charging power supply in frequency-domain is presented, and a related circuit model considering the transient switching interference is proposed. Due to the high working frequency and the device-switching transitions, the conducted EMI caused by the charging circuit which includes the harmonics of grid frequency, working frequency and device-switching transition frequencies. Thus under certain working situations or loads parallel power supply, the interference may cause charging failure. To solve this problem, a high frequency transformer modeled with stray capacitances and an approximation of the device-switching transition is applied in the Pspice-based simulation model, and a mathematical analysis in frequency-domain is presented.

Abstract: PEM Fuel Cell (PEMFC) system plays an important role in a future hydrogen economy. Numerical modeling is useful to evaluate and optimize PEM fuel cell system. Therefore, this paper developed an integrated numerical model for predicting the power output of PEMFC system and optimizing system operation parameters to achieve the maximal output power. The developed numerical model integrated the models of fuel cell stack itself and its auxiliary systems, which were quantitatively described and analyzed with calculation equations. Furthermore, the newly developed numerical model was applied to a PEMFC powered scooter to estimate the output power a PEMFC system and optimize the operation conditions parameters of its auxiliary systems based on optimization algorithm. This validates that the developed integrated numerical model is useful and reliable for predicting the net output power and achieving maximal net output power through optimizing the operating parameters of a PEMFC system.

Abstract: The special atmospheric environment accelerats the corrosion process of electrical connectors in southeast coastal areas. It causes the failure probability increased and the reliability level declined. This paper discussed the most kinds of electrical connector corrosions in southeast coastal areas. The corrosion characters of the metal material used on the electrical connectors are expounded, and environmental factors in the corrosion of electrical connectors are introduced at length.

Abstract: The prediction of mine Gas Emission Amount is an important part of helping to make rational gas control measures. In order to improve the accuracy of mine gas emission prediction, this paper introduced the grey theory into the Elman artificial neural network theory, and combined the gray prediction model GM (1,1) with the Elman neural network model,established a gray Elman artificial neural network prediction model of gas emission, and carried on the simulation through software Matlab. Practice and experiment showed that this method compared well, and is superior to the traditional Grey prediction model, moreover this method also applied to the situation of original data was few or the historical data had transition. The forecasting results from this method can be more reliable and accurate, so it can instruct the practice accurately

Abstract: DC transformer with high frequency and efficiency under a fixed duty cycle is widely used in dc distributed generations. In this paper, the topologies and equivalent circuits of single /bidirectional full-bridge non-resonant DC transformers are presented. And the configurations of the input-series output-parallel and input-parallel output-series DC transformers are also proposed for reducing voltage stress of power devices. The example consisting of DC transformers in a distributed generation system based on DC grid is shown. Finally, simulation results verify the feasibility.

Abstract: In the digital signal processing process, the length of signal that we can get is limited, so should be infinite long time sequence limit in a certain interval, only choose one of the segment signal to carry on the analysis, namely cut off the signal, and this process is equivalent to add a window function to the signal is, using the window function truncation infinite unit sampling response sequence. This article in accordance with the principles of window function design method, based on analysis spectrum of the measured signal, design and analysis that add different window function on filter performance effect while signal intercept, and ultimately chose a suitable window function for the measured signal to the design of filter. Through the MATLAB simulation shows that the choice of window function can meet the measured signal filtering.

Abstract: The de-noising principle using wavelet was discussed and the de-noising property was compared with that of using general threshold strategy. The steps of the per-level de-noising method were then given and the experimental study with a vibration model was carried out. The results prove that the method is advantageous to de-noising, which is more suitable to recover the interest mutations signal buried in intensive background noise. The application of the method in the bearing vibration was presented and the results show that it can inhibit the background noise effectively and recover the interest information satisfactorily.

Abstract: The relationship between the installment and machining errors and the follower displacement error for a translating roller follower plate cam was studied. The formulae of the follower displacement error were derived. These expressions can be used to calculate the follower displacement error. The follower displacement error of a translating roller follower cam system is closely related to the cam geometric error and offset distance error. By taking the values and signs of the cam geometric error and offset distance error properly, we can minimize the roller follower displacement error and design the high precision translating roller follower plate cam

Abstract: Intelligent diagnosis is the development direction of mechahnical condition monitoring and fault diagnosis.Conbined improved EEMD with SVM in fault intelligent diagnosis is researched in this paper.To bearing normal and fault as an example,impove EEMD decomposed 9D normalized energy for characteristic vector applied to the binary classification and identification.Compared to the SVM classification accuracy using different kernel functions that is linear,polynomial,RBF and Sigmoid kernel function.In the same parameters,SVM classification accuracy based on linear and polynomial kernel function is a hundred percent.Bearing normal and fault two kinds of state is completely correct apart. And the normal and fault state of the binary classification and identification using RBF and Sigmoid kernel function appeared wtong points.

Abstract: Currently, expended polystyrene (EPS) are widely used as liner material in bicycle helmet. Due to its characteristics is excellent performance, lightweight, low cost of manufacturing. However, EPS has some disadvantage as difficulty to optimize energy absorbing in different areas of head and inferior effect of heat dissipation and a brittle characteristic. This study focuses on to find a replacement material for EPS foam to improve liner of bicycle helmet. Impaxx energy absorbing (EA) foams present strong potential in overcoming such problems of EPS foam. To make certain that all bicycle helmets reach efficiency, the helmets are required to pass shock absorption test of EN1078 standard. This study performs finite element analyses of helmet impact tests using LS-DYNA software. Simulation results indicate Impaxx foams are suitable for shock absorption test according to the EN1078 standard. Therefore these results encouraged the authors to extend the manufacturing work to cover the creating helmet design and performance experimental tests.