Applied Mechanics and Materials Vols. 543-547

Abstract: IEC 61400-25 is a series of international standards on communication of wind power plants. The service defined by information exchange models in wind power plants communicates through being mapped to web service. Web service is described by WSDL, but with the limitation of WSDL itself, web service can not realize the semantic description, the automatic discovery and composition of service. So semantic web service is introduced, the service is described by OWL-S to realize the interconnection of wind power plant hardware devices from different manufacturers, to facilitate the sharing and reuse of devices function and to realize the sharing of wind power plant knowledge in semantic level.

Abstract: Halbach magnet array has advantages of its small size and yokeless, so it has been widely used in various areas. In this paper, two Halbach permanent magnet arrays for small-size NMR with cube and octagonal shape, respectively, were compared in parameters of average magnetic field strength, field homogeneity and volume with the same material consumption. It was found that the octagonal shape magnet has better performance than the cube one. Then the field homogeneity optimization for octagonal magnet was performed. By analysis of magnetic field strength, the best homogeneity in 5mm DSV (Diameter of Spherical Volume) with 133.4ppm was achieved when the height of magnetic blocks is 16.25mm. After optimization, the magnetic field homogeneity has been significantly improved when the shape of magnet has small volume. This result laid a foundation for the design and manufacture of the octagonal Halbach permanent magnet array in small size.

Abstract: By analyzing the two lightning accidents happening to a 500kV substation situated in the lightning-prone northeastern Guangdong Province, I conclude as follows, there should be some problem in the equipotential earthing of the secondary system of this substation. Specifically, the existing potential difference in the secondary equipment gave rise to the meltdown of it which finally caused the accident. In the context,I build the one-point earthing parallel system simulation model according to ATP graphic pretreatment program, then by using slope-ramp simulation I study the lightning current which leaked into the grounding grids of the substation.In conclusion, the application of high frequency signal mixed low frequency signal earth system in the secondary system and the equipotential bonding is key to preventing accidents.

Abstract: In the fuzzy evaluation process of the power quality, different membership function scan lead to different results, which affect the credibility of the evaluation. In order to avoid subjectivity of choosing membership function, a combined membership function based on the Variance-covariance optimized combination method is proposed. Firstly, five typical member-ship function is selected after the deeply analysis of the power quality data. Secondly, weights of each function are calculated by the variance-covariance optimized combination method, and then a combined membership function of general applicability is constructed according to the weights. Thirdly, the fuzzy evaluation is performed by using this combined membership function. Finally, an application of this combined membership function in the fuzzy evaluation of power quality of a power supply bureau shows that this function can improve credibility of three valuation result.

Abstract: Single-Sideband (SSB) modulation is now widely used for its high band efficiency and low power consumption. In anolog SSB systems, it is usually hard to achieve high performance due to many nonideal factors of anolog components and circuits, such as the I/Q channel mismatch and temperature drift. To overcome these disadvantages, a digtal SSB modulation system based on the Weaver method is designed in this paper. In this system we creatively use the onchip ADC of the ARM processor for audio sampling. Besides, the CORDIC algorithm and the folding transformation are also utilized to reduce hardware costs in the FPGA implemention. This paper mainly discusses the theory and implemention of the Weaver SSB modulation system, and shows the experimental results on actual hardware.

Abstract: . Based on the formulation of conventional operational rule, a scenario clustering method for extracting TTC operational rules of transmission corridors with the integration of wind power is presented in more detail. The scenario clustering for the network state is obtained on the basis of the output-load level of wind farm; in a certain scenario, the rules can be utilized to provide decision support for the dispatchers. The formation of the rule is proposed by using the data mining techniques, consisting of sample generation, feature selection and rule extraction. IEEE-RTS79 system simulation results indicate that the relationship between operation state and TTC can be better reflected by the dispatching information based on the scenario clustering.

Abstract: The process of a power reactor spent fuel reprocessing pilot plant had been completed after many years of scientific research experiment and engineering construction, while the commissioning results indicated that some technological problems exist in a few key equipments, especially the shearing machine. As the main design basis it is needed to obtain accurate shear force so as to improve research of shearing machine. In this paper, shearing fracture process and shear force have been simulated in ABAQUS software, also a sample type of shear machine has been realize to do the shearing experiment. Through the study, simulation result is verified reliable comparing with the experimental data and the research method using computer simulation combined with experiment verification is significance to the research of spent fuel reprocessing.

Abstract: On the basis of expounding the necessity of establishing power distributing system fault diagnosis visualization systems, the outage situation automatic notification and equipment failure query plan of distribution network is proposed based on database. Firstly, the information of electrical diagrams of distributing system should be input into database. Secondly, the information in the form of a tree structure will be displayed in WPF by programming. Meanwhile, we can add annotation to electrical diagrams by programming. When the distribution system malfunctions, dispatching operation control personnel enter the point of failure, the cause and outage time and the details of the regional head of a power outage will be shown. Then he responsible person will be informed by SMS. In this way, we can reduce blackout time and achieve the standardized management of distribution network. When needing the working condition of any device, just enter its name and the information will be shown.

Abstract: In order to test new type self-propelled Gun's power generate and supply system, based on modular structure and distributed control design method, using variable frequency control and dual-model control technique, the laboratory equipment was designed according to the technical requirements. Firstly, the structure of the laboratory equipment was build. Based on design of hybrid multimode synchronous teeth belt transmission, programmable load unit, programmable power source and data fusion operator, main composition of the laboratory equipment are developed. Distributed control is used to ensure the laboratory equipment work orderly. To improve ability of anti-electromagnetic interference, three methods are used. Practically use, the synthetically laboratory equipment is proved to being high stability, strong comprehensiveness, good generality.

Abstract: In this paper, an expectation maximization (EM) algorithm based iterative receiver is utilized in the underwater acoustic OFDM system to improve the spectrum efficiency. A relatively smaller number of pilots are used to determine the initial value for the EM-based channel estimation process. The intermediate estimates of the channel state information generated by the EM algorithm are fed forward to the BCJR decoding unit to achieve the a posterior probability of the transmitted bit sequence. The a posterior probability is then fed back to the EM algorithm to estimate channel state information. The iterative receive process is expected to realize a better channel estimate and bit error rate (BER) performance. Simulation results demonstrate that the EM-based iterative underwater acoustic OFDM system has a fast convergence property, and can achieve a low mean square error (MSE) for the channel estimation and a near optimal BER performance.