Applied Mechanics and Materials Vols. 48-49

Abstract: The Gui-Guang HVDC system in south china scheme with interconnections to the 500kV transmission to Guizhou and to Guangdong can exhibits, under certain operating conditions, the percussion of the dc filters impedance resonance problems. The analysis explains the dc filters impedance resonance. The influence of changing the dc filter parameters is also studied. Finally, an assessment is made for improve the dc filter performance

Abstract: Knowledge acquisition is the bottleneck of construction expert system, to provide an accurate inference of knowledge is the key decision-making plan. This article use the rough sets theory, through the rough sets reduction eliminate redundant condition attribute, to achieve the streamlining of the knowledge library. First study the knowledge acquisition, in exposition knowledge hierarchical structure foundation, has given the conceptualization, formal, the knowledge library refinement and so on three knowledge acquisition; and then study attributes reduction algorithms, in the research sets difference and the attribute importance, the reduction algorithms inferential reasoning process's foundation, has given the attribute reduction algorithms six steps. Finally, according to the attributes reduction algorithms and the steps, to estimate the expert system to the function analytic method construction software cost, the composition technology complexity factor of 14 factors reduction. The results showed that the use of rough sets theory to reduce the attributes, can simplify the structure of complex systems, and can effectively maintain the knowledge library structure and performance.

Abstract: To establish the uniform situation map, the platforms’ low-precision navigation information and the location information measured mutually are used to carry out the sensor data alignment for martime multi-platforms. This method can avoid the dependences on high-precision navigation equipments and the errors introduced by assuming the earth’s surface to be the plane. The models of coordinate conversion for aligning are presented. Then the measure equations and the state equations with regard to navigation systematic error and sensor systematic error are built respectively, and a registration algorithm based on Unscented Kalman filtering is designed for estimating online and compensating those two systematic errors. Consequently, the error registration for martime multi-platforms is achieved, and the higher precision information can be provided for the subsequent data association and data fusion. The simulation results demonstrate the correctness and validity of the algorithm.

Abstract: Fuzzy modeling is discussed in many literatures and there are numerous algorithms are proposed. Back-propagation algorithm is an efficient algorithm for fuzzy modeling and many papers proposed the usage of such method. But there exists potential risk of dead zone, abrupt inference surface and decreasing sensitivity for normal back-propagation algorithm in fuzzy modeling. This paper analysis the potential problems of normal algorithm and suggest a reformative back-propagation algorithm for fuzzy modeling. A complete algorithm is presented in the paper and some simulate result is discussed

Abstract: This paper proposed a matching algorithm FBMH(Fast Boyer Moor Horspool),which made an improvement on the BMH(Boyer Moor Horspool) and BMHS(Boyer Moor Horspool Sundy) matching algorithm based on the study of several typical pattern matching algorithms used in intrusion detection. The result shows that, the FBMH algorithm has less intrusion detection matching time than BMH and BMHS algorithm. The FBMH algorithm accelerated the speed of pattern matching effectively, therefore enhanced the efficiency of the intrusion detection system.

Abstract: Partial discharge (PD) pulses recognition, which is directly related to the credibility of PD online measurement results, is the key technology of the high-voltage (HV) equipment PD online monitoring. In this paper, a pulses recognition method during PD online measurement was put forward to extract PD pulses buried in external interferences, the method adopted three key steps to identify PD pulses: (a) Firstly, two pretreatments, including discrete spectrum interferences (DSI) suppression and single pulse boundaries determination, are used to convert several consecutive power cycles on-site monitoring signal to plenty of pulse - time sequences; (b) Then, an optimized adaptive clustering algorithm is adopted to classify all pulses into certain categories (c) Finally, the three-dimensional distribution of each category which indicated the pulses phase distribution with power cycles was calculated, and the PD pulses were identified by the statistics characteristics of their three-dimensional distribution. At present, the PD pulses recognition method has been used in industrial application, and on-site monitoring signal processing results has proved the effectiveness of the method.

Abstract: Inter-harmonic wave is one of most important factors to influence power quality in power system, which is harmful to the power system and power equipment. Db5 wavelet, sym4 wavelet and Fourier transform have been applied to analyze the inter-harmonic of power system, respectively. The simulation results show that Fourier transform fails to analyze the inter-harmonic, while db5 wavelet and sym4 wavelet can separate the fundamental wave from inter-harmonic wave. By Comparison, db5 wavelet is more precise and effective than sym4 wavelet to separate the fundamental wave.

Abstract: In this paper, we take flame optical radiation signal in low-frequency on a gas combustion test-bed as research objects, multi-fractal spectrum can analyze the micro structures and characteristic of flame optical radiation time series is corroborated through computing. We research the trend of the sharps and key parameters of the multi-fractal spectrum under different scales. Result shows that as one of the most important parameters of multi-fractal spectrum, the width of the multi-fractal spectrum has the significant correlation with variance, which reflects the status of the combustion stability, and the accuracy of the combustion stability judgement is increased further through multi-scale and multi-fractal analysis. As a developmental assisted analysis method, the multi-scale and multi-fractal analysis method can effectively reveal the dynamic process of the flame radiation, which provides to the operation staff with multi-angle supplementary method in judging the combustion stability.

Abstract: In order to research the motion precision reliability of hydraulic support when the influence of the bar length error and gap error is considered, the motion trace mathematical model for the top beam of hydraulic support is established, with the calculation method of motion precision reliability and the effective length of bar based on continuous contact model. Taking some type of hydraulic support as an example, its motion precision reliability is calculated and analyzed. The Monte Carlo simulation is also used to verify the model, and the T-R curve of the gap error and the reliability is plotted. The results from simulation accord with those from the theoretical calculation, which verifies the model established and can provide some valuable reference for the related future research.

Abstract: This paper describes how to calculate stiffness reliability for bus body frame in the specified case. The principle of the Response Surface Method and solving process of reliability calculation are presented. Designing response surface by central index method and solving undetermined coefficients of unknown function by interpolation technique, the fitted response surface placed on check point is founded. Then failure probability of bus frame is got by Monto Carlo method and corresponding reliability is obtained. The calculation results of a specified bus body show that stiffness reliability of frame is 100% and it is necessary that the structure should be improved because of strong stiffness.