In traditional thinking, when the elastic problems are solved, we need to repeatedly plot element grids and analyze computing results according to diverse precision requirement. Against the malpractice exists in the above process, a new method of error estimation was suggested on H-R adaptive boundary element method in this paper. Based on the discrete meshes that are generated for the process of H-R adaptive refinement, the solution error was estimated by the interpolation residue. In addition, this method is easy to programming, which is carried out in the program by automatically creating new adaptive data files. Then a great deal of fore-disposal and post-disposal can be saved. Its validity and effectiveness have been confirmed by numerical example.

Network information poses great threats from malicious attacks due to the openness and virtuality of network structure. Traditional methods to ensure infor- mation security may fail when both integrity and source authentication for information are required. Based on the security of data broadcast channel, a novel Trusted Com- puting Model (TCM) of network security authentication is proposed to enhance the security of network information. In this model, a method of Uniform content locator security Digital Certificate (UDC), which is capable of fully and uniquely index network information, is developed. Standard of MPEG-2 Transport Streams (TS) is adopted to pack UDC data. Additionally, a UDC hashing algorithm (UHA512) is designed to compute the integrity and security of data infor- mation . Experimental results show that the proposed model is feasible and effective to network security authentication.

The use of multi-channel MAC protocols for mobile ad hoc networks has been seen as a very potent method of improving the throughput capacity of such networks. In recent past, a number of multi-channel MAC protocols have been proposed for mobile ad hoc networks that have increased the overall network throughput by quite some margin compared to their single channel counterparts. However, there are still many issues with these protocols that need to be resolved. Clock synchronization is one of the major overhead in a majority of the proposed multi-channel MAC protocols. In this paper we propose a new asynchronous multi-channel MAC protocol that does not require clock synchronization between mobile nodes. Our proposed protocol is an asynchronous solution that uses multiple channels for data transmission. In our proposed protocol, nodes use a single base channel when the network load is considerably lower and migrates to other channels when the network load increases beyond a threshold value. Also, nodes share multi-channel cooperation messages with their neighbors to further improve throughput. We have conducted extensive simulations to compare the performance of our protocol against the traditional IEEE 802.11b single channel and MMAC protocol. Simulation results show that our proposed protocol outperforms both IEEE 802.11b and MMAC protocol.

Coordinated Multi-Point transmission/reception (CoMP) can increase the performance of the cell edge users, the spectrum efficiency and mitigate the inter-cell interference among cells. In the CoMP scenario, several base stations which usually need satisfy the cooperating condition serve a single or several cell-edge users cooperatively. As we know, the CoMP techniques can be characterized into many classes. For the joint transmission system which is a classical CoMP system, a large number of data sharing and channel information exchange will be needed, where the system inevitably become comparatively complex. However, in this paper, the coordinated beam forming system will be considered, where several base stations cope with the inter-cell interference among cells, and all the base stations will only exchange the channel information. Further, the downlink multi-cell coordinated beam forming system is considered in this paper. In this downlink multi-cell coordinated beam forming system, it is crucial to design appropriate pre-coding schemes that are able to mitigate the inter-cell interference. In obtainable pre-coding schemes, the Signal-to-leakage-and-noise ratio (SLNR) pre-coding scheme is a promising pre-coding scheme in downlink multi-cell coordinated beam forming system, which makes closed-form solution accessible. Moreover, the problem in designing the pre-coding vectors is not a coupled problem since the cooperative base stations need not optimize the pre-coding vectors jointly, which are responsible for their own design of pre-coding vectors, that is, they will just carry out independent optimization. In this paper, we proposed a novel pre-coding scheme based on the SLNR scheme, which will determine the pre-coding vectors via iteration. The simulation results show that, the proposed method outperforms the conventional SLNR pre-coding scheme in bit error rate performance.

DC bus capacitors of Medium Voltage Cascaded STATCOM are independent. DC side voltage balance control method is the key influencing factor of current control. The imbalance of DC bus voltage increases harmonic current and affects the safety of device. In this paper, the unbalance mechanism of DC side capacitor voltage is analyzed. Based on the unipolar dual frequency and carrier phase-shifted SPWM (CPS-SPWM) modulation algorithms, the distributed control algorithms, which need multi- FPGA structure, are proposed. By changing the instantaneous active power input of single module, the voltage balance control strategies of DC bus capacitors are realized. The strategy can be applied in each inverter, respectively. Simulation and experiment results show the feasibility and effectiveness of the strategy

In this study, a new handoff strategy to improve the performance of wireless mobile networks is presented. It has been found form this study that the dropping probability of handoff calls is drastically reduced compared to the existing method of channel reservation strategy of handoff calls and the performance of new calls can be improved. The strategy is that the new call should be delayed then it can use the last idle channel. The time that all the channels are holding has been shortened. Opportunities of the new call and handoff call occupancy channel are increased; the scheme also takes into account the priority of different data types, and only when the high-priority data packets queue is empty, the data packets in low-priority data queue can be transmitted. Simulation results show that, to let the new voice call delay in the allowable range, can effectively reduce the dropping probability of handoff call and the blocking probability of high-priority data while improving the probability of new call to enter into the systems

Honor-based trust mechanism is an important means to evaluate the behavior of the P2P network node, and it is used to ensure the health of the P2P network application. Trust mechanisms need to evaluate a node to other node local trust value and local trust value because they do not consider the policy node and human evaluation error of two important factors. The calculation is difficult to accurately reflect the characteristics of the nodes of the network. Evaluation models of the behavior of a P2P network neighbor. The PeerBehavior model has used a deterministic finite state machine (DFA) depicts the continuous behavior of the neighbor state changes cause a negative evaluation of any continuous behavior by focusing neighbors almost died, both able to more accurately discover policies node in the network, but also be able to tolerate a certain degree of human evaluation error simulation experiment showed that this model was significantly improve the accuracy of the local trust value, and reducing the estimation error of the global trust value, was significantly superior to the calculation method of the current value of the other local trust

Aiming at that there are some heterogeneous nodes in special applications, time synchronization algorithm for heterogeneous WSNs based on cluster (TSBC) is proposed in this paper. In every round of TSBC, time synchronization is started by sink node, every heterogeneous node sends cluster head request message to sink node when it receives the time synchronization start message, and take itself as a cluster head when it receives the acknowledgement sent by sink node. Then, every cluster head broadcasts elected message in the net, common nodes select the nearest cluster head as their cluster head and join the cluster. Time synchronization begins firstly between sink node and cluster heads, and then begins between cluster heads and common nodes. The components of transmitting delay of synchronization message between sender and receiver are analyzed and computed, consequently, the time offset of nodes are obtained, and the frequency drift are computed by linear regression method. Simulation results indicate that TSBC has higher synchronization ratio and synchronization precision, longer lifetime and lower energy consumption than FTSP in heterogeneous WSNs.

Wind power is sustainable, renewable and clean energy. There are abundant wind resources in Yunnan province, China. In recent years, wind power integration has developed rapidly in Yunnan province. With the first batch of the wind farm being built and a part of them going into production in Yunnan, the wind power resources will be large-scale developed and utilized in the future. Based on the wind power planning of Yunnan, the impacts of security and stability after wind power are studied in this paper. The major researches are made on the capacity analysis for accessing high-capacity wind farm, the analysis for power system voltage stability and comparison of different wind-generator model structures, thus finding out the most suitable choice for fan selection in Yunnan Power Grid.

Since the energy supply of a sensor node is limited, energy optimization should be considered as the key objective when studying the wireless sensor networks (WSN). Facing these challenges, clustering is one of the methods used to manage network energy consumption efficiently, and plays an important role in prolonging network lifetime and reducing energy consumption. The improved clustered routing algorithm based on distance and energy is proposed, which efficient improve the rate of data aggregation, thus greatly decrease the energy consumed. Experimental results show that the proposed routing algorithm has higher efficiency and can effectively prolong the lifetime in WSN