Applied Mechanics and Materials Vols. 397-400

Abstract: Antenna is all important part of GPS receivers，there is a great need for the design and production of new antennas which are fully compatible with modernized signals. Because of their advantages such as low cost, compact size, low profile，ability to support dual-frequency and circular polarization operation, microstrip patch antennas have become widely used in GPS antenna designs. A circular polarization patch antennas are proposed in the paper. The antenna designed to operate at L1(1575.42MHz) and L5(1176.45MHz)frequency bands. Initially, a comer-truncated patch antenna for GPS L1 operation was designed to validate simulation in Ansoft High Frequency Structure Simulator(HFSS), the results obtained for this antenna were used to design the two proposed antennas,and designed antennas are presented．

Abstract: An adaptive web information extraction approach is presented in this paper. Most of the traditional web information extraction approaches depend on the templates of web sites. If the templates are changed, the information extraction rules should be redesigned. To reduce the maintenance costs and improve the adaptability of information extractors, an adaptive web information extraction approach is proposed based on the STU-DOM tree. The webpage is parsed into DOM Trees based on HTML Parser. Then DOM trees are filtered into STU-DOM trees to confirm blocks which contain keywords of a certain topic. The proposed approach is applied to webpages and the results show that the approach not only extracts information efficiently, but also is irrelevant to site structures.

Abstract: This paper addresses the enhanced power allocation (PA) and relay selection scheme (RS) in two-way relaying cognitive radio networks consisting of multiple user-pairs and multiple relays. In order to reduce the computational complexity for practical scenario, we propose a branch and bound based (BnB-based) power allocation and relay selection scheme and a greedy power allocation and relay selection scheme to maximize the system throughput. Simulation results show that the proposed BnB-based PA and RS scheme can achieve better tradeoff of system throughput and complexity.

Abstract: In this paper the fundamental characteristics of fiber Bragg grating was described. The important parameters such as the length of fiber gratinggrating periodwhich strongly affected the characteristics of fiber Bragg grating were analyzed.

Abstract: Various kinds of household appliances have been widely deployed in the low-voltage grid. They inject conducted noise into the power line system, which may cause a detrimental effect on the Power-line Communications (PLC) channel. This paper examines a new measurement method of conducted Electromagnetic Interference (EMI) on the PLC channel. The proposed method is to facilitate the noise characteristic research, which overcomes the potential difficulties when the measurement is performed according to CISPR 16-2-1. In particular, taking the hairdryer as an example, the conducted noises when the motor is deemed as the noise source are measured by employing the presented method. Moreover, this paper also analyzes the conducted noise of the hairdryer both in the time domain and in the frequency domain, and interprets the noise generating mechanisms with the working principle of the motor in detail. The central issue in all these studies is to research the conducted electromagnetic noise characteristics on the PLC channel.

Abstract: To meet the requirements of planning and to improve accuracy and stability of traffic prediction model in the communication network for electric power, a traffic prediction method based on grey model optimized by buffer operator and particle swarm optimization (PSO) is proposed in this paper. Variable weights buffer operators are implemented for preprocessing traffic data to enhance the adaptability of gray prediction model. Taking the maximum grey correlation degree between prediction series and true series as objective function, based on the search ability of PSO, the fitness function is founded, which can determine the optimal parameters of gray model. Applying the improved model to traffic prediction in communication network for electric power, a new prediction result is drawn. The prediction result shows that the improved model has higher prediction accuracy compared with the traditional GM (1, N) model.

Abstract: By cryptanalysis of a strong designated-verifier proxy signature scheme, it is found that this scheme has security leaks: original signer can forge the proxy signers valid proxy signature for any message; not only the designated-verifier but also proxy signer can verify the signature and proxy signer can misuse it. An improvement is given, and the security analysis shows that it can resist the spiteful forgery attacks by original signer and prevent the misuse of proxy signature by proxy signer.

Abstract: The design on the system of low-voltage power line carrier-current communication based on OFDM was finished in this paper. Then model of the system was simulated and the modulation and demodulation of OFDM were realized. The results show that the integral performance can be enhanced with channel code. And the bit error ratio (BER) of the system is different with several sub-carrier wave modulation modes. This system could satisfy the requirement of power line communication basically.

Abstract: With the rapid development of modern communication, more and more new communication systems are invented. In this treatise, the author mainly describes the significance of computer simulation in the field of communication system modeling, analyzes the technologies and principles of communication system simulation, and summaries basic methods and general technologies for communication system simulation and model construction.

Abstract: According to the issue of tag collision in the radio frequency identification technology, this paper proposes a binary tree search anti-collision algorithm, which takes different processing methods according to how many continuous collision. Compared with the dynamic binary tree search algorithm, the improved algorithm reduces the query information send by the reader. At the same time,the algorithm in the process of identifying tags reduces the query information, the query number and tag response times, so as to shorten the recognition time, further improve the search performance.