Applied Mechanics and Materials Vols. 220-223

Abstract: In this paper, we propose a Taylor expansion method for solving (approximately) linear Volterra integral equations with weakly singular kernel. By means of the nth-order Taylor expansion of the unknown function at an arbitrary point, the Volterra integral equation can be converted approximately to a system of equations for the unknown function itself and its n derivatives. This method gives a simple and closed form solution for the integral equation. In addition, some illustrative examples are presented to demonstrate the efficiency and accuracy of the proposed method.

Abstract: Fault or health condition prediction of complex system equipments has attracted more and more attention in recent years. Complex system equipments often show complex dynamic behavior and uncertainty, it is difficult to establish precise physical model. Therefore, the time series of complex equipments are often used to implement the prediction in practice. In this paper, in order to improve the prediction accuracy, based on grey system theory, accumulated generating operation (AGO) with raw time series is made to improve the data quality and regularity, and then inverse accumulated generating operation (IAGO) is performed to get the prediction results with the sequence, which is computed by LS-SVR. The results indicate preliminarily that the proposed method is an effective prediction method for its good prediction precision.

Abstract: The hardware structure and the data-processing flow of FPGA based Time to Digital Converter (TDC) are introduced firstly in the essay. Then, according to the issue of inaccuracy in arriving time of external triggers, a correction method is proposed to enhance the accuracy of starting time. In the end, by contrast experiment, it is shown that this correction method could improve the accuracy of starting time effectively. In addition, the minimum time resolution is 400ps, which makes the TDC be adequate for applications in the fields which require high-resolution time measurement, for example, in the application of time-of-flight mass spectrometer (TOF-MS).

Abstract: A Software filter technique based on Haar wavelet is proposed for effectively suppressing the noise components in the signal of electromagnet flow transducer. It is proved with computer simulation based on MATLAB Wavelet Toolbox that the proposed filter technique is well matched with the feature of the signal of the electromagnetic flow transducer in effectiveness and efficiency. A prototype flowmeter was developed based on the proposed technique, experimental result with the prototype shows that the proposed Haar wavelet filter technique is well suitable for de-noising the signal of electromagnetic flow meter.

Abstract: The helicopter Maintenance, Repair and Overhaul/Operations (MRO) system enables the best sharing of the maintenance resources and maintenance ability in a wide area, so as to promote the specialization of the helicopter maintenance organizations. Information acquisition is an important and difficult part of the helicopter MRO system. This paper systematically analyzes the condition monitoring methods which are used to monitor the rotational speed, temperature, pressure, vibration and flight parameter in different parts of a helicopter, and then it puts forward some improved ways for information acquisition. Considering the helicopter’s features, the process of information acquisition is illustrated. In addition, this paper presents the basic requirements of data sampling, and it also shows a detailed discussion on data format and data transmission in the helicopter MRO system. At the end of the paper, a system mode and architecture of helicopter MRO system are proposed.

Abstract: In this paper, the wireless communication at 433 MHz with different polarization modes in a rectangular tunnel has been analyzed. Based on the theoretical analysis, it is found that if the height of the rectangular tunnel H is greater than the width W, the performance of the wireless communication by means of vertical polarization is better than that of horizontal polarization, but when H < W, horizontal polarization is better than vertical polarization. To prove this point, a measurement has been carried out in a rectangular tunnel. The height of the tunnel is 3 meters and the width is 2 meters. In the experiment, the transmitting power is from -30 dBm to -25 dBm, the receiving sensitivity is -105 dBm, the gain of the linear polarization antenna is 2dBi, and the transmitted data is uncoded. The experimental results show that communication distance of the vertical polarization is better than that of horizontal polarization in the tunnel.

Abstract: Dielectric loss angle is the effective means to determine the status of the high voltage equipment.Influenced by power grid frequency fluctuation and white noise, the measurement accuracy of traditional method of dielectric loss angle such as harmonic analysis method, cannot meet the demand.A new methodbased on wavelet threshold denoising and least squares is presented in this paper. Firstly, harmonic wave and white noise are eliminated by improved wavelet thresholddenoising, Second, the fundamental wave of voltage and current signal is extracted by mean of least square method, then we can get dielectric loss angle.Simulation and calculation are validated in the different values of frequency fluxion and whtie noise.Comparing with harmonic analysis method,the result show the feasibility and effectiveness of this method.

Abstract: Aiming at many uncertain factors in the reliability assessment of aircraft, a new approach to reliability assessment combining D-S theory of evidence and fuzzy theory was discussed. The concepts of inclusion degree and intersection degree of fuzzy sets were redefined, and fuzzy evidence theory was extended to the circumstance when the framework of discrimination is a continuous and in finite set. Finally, the practical assessment process was given in an illustrative example of aircraft system. The results show that the method is effective and reliable.

Abstract: The information modeling of mold enterprises which based on Teamcenter product lifecycle management software platform is put forward, according to the analysis to the characteristics of injection mold manufacturing enterprises. User management model, product structure model and workflow management model have been established and implemented in the system management platform. It is not only enhance management level to data of mold enterprises, but also the scientific and effective methods of modeling and implementing can be provided for the other mold enterprises to carry out system platform of product lifecycle management.

Abstract: On the basis of analyzing the process of passive thermal imaging in subdivision mid-wave infrared thoroughly, the paper makes clear the factors which influence imaging in subdivision bands of mid-wave infrared(SBMWIR). The forming models for images in SBMWIR are set up，and some simulation experiments on these models are done, from which the formation mechanism of the characteristic differences of imaging in SBMWIR are shown. There exist three differences in SBMWIR imaging, relating to the gray scale, environment effects on the target, and the contrast of target-background, which provide the foundation for extracting characteristics from images in SBMWIR, formulating fusion rules, and determining fusion weights.