Applied Mechanics and Materials Vols. 397-400

Abstract: In the technology of temperature measurement, the sensor is an important part of system. But with the increase of the number of sensors, it will undoubtedly bring with a lot of data cable. Compared with wired communication technology, wireless communications technology has the advantages of low cost, simple structures, low impact of environment. So the wireless communication technology meeting with the requirements of data communications has become a more practical, fast and efficient way. This paper describes a multi-channel temperature monitoring system using nRF905 wireless transmission module, STC89C52RC MCU and DS18B20 temperature sensor as core. Functions such as sampling, analysis, display, alarm and others can be done automatically by the system, dates transmitted by wireless module, and the system can realize the function of real-time monitoring of temperature.

Abstract: Based on new ship isolated power system, the models of power station, loads and hybrid energy storage system (HESS) are built. Fuzzy control theory is adopted to control different energy storage modules (ESM) coordinately, effectively level the fluctuation of loads and improve system stability. Simulations in Matlab/Simulink investigate the impact of different control filter parameters on compensation effect of HESS, and the impact of ESMs performance on HESS compensation.

Abstract: Aiming at the AC excitation control and speed governing of high water-head impulse hydroelectric generating unit, and in order to realize unit optimization adjustment and obtain desirable comprehensive control performance, a variable structure and variable parameter coordination control idea, including designing coordination control module and constructing coordination control mechanism, is proposed. By the management of coordination control module, the dynamic switching between no load operation and grid-connected generation control, and the dynamic matching between AC excitation control and rotational speed control can be realized. Thanks to the dynamic coordination control of AC excitation and hydraulic governing, on the one hand, power regulation is rapid and precise, improving stability of power system; on the other hand, unit nozzle twitching is reduced, decreasing difficulty in speed governing, and realizing maximum efficiency tracking control. The simulation of grid-connected operation shows that: AC excitation and coordination control strategy can make doubly-fed asynchronous generating unit acquire much better control performance than conventional unit.

Abstract: The differential protection for transformer is main protection , the unbalance current is the main factor affecting the behavior of the protection. The unbalance current caused many reasons, generally can be divided into steady state and transient state, the transient unbalance current is mainly under the circumstance of exciting inrush current, Containing a lot of harmonic component and harmonic component, based on this the paper studied the harmonic component in the application of power transformer differential protection, and through the simulation analysis.

Abstract: The security in e-mail protocol has received significant research attention. In this paper, an e-mail protocol, GSEP, using improved generalized signcryption scheme is proposed. GSEP can send private e-mail, public e-mail safely, and using key trace to solve the problem of key escrowing, using identity authentication to solve the problem of junk e-mail. The proposed protocol not only improves the information processing capability of e-mail system for its multi-function, but also guarantees the security of transmitting information.

Abstract: Application-layer distributed denials of service (DDoS) attacks are becoming ever more challenging to internet service security, since firewall and intrusion detection system work on network layer while these attacks are launched on application layer. In contrast to prior work focusing on detection of high-rate DDoS attacks at static web sites, we propose a novel approach to detect low-rate application-layer DDoS attacks at dynamic web sites. A feature matrix is introduced to characterize user browsing behavior. Principal component analysis (PCA) is applied to profile the user browsing behavior pattern. Outliers from this pattern are used to identify anomaly users. Experiments are conducted to validate our approach. Experimental results show that our approach is accurate to detect low-rate application-layer DDoS attacks.

Abstract: Trust mechanism has been identified as one of key areas in the field of Internet security. Our objective in this paper is to develop a dynamic trust evaluation model for Internet computing. The proposed scheme divides the recommendation trust into the direct recommendation trust and the indirect recommendation trust, and considers variety of factors to calculate the two types of recommendation trust degree. Simulation results show that, compared to the existing trust model, the model can effectively improve the accuracy of trust evaluation, and provide a better capacity of resisting malicious entities.

Abstract: Deploying Pico cell Base Station (PBS) throughout a Macro cell layout is a promising solution to enhance system capacity and users throughput. However, the strong received power from Macro cell Base Station (MBS) makes the Pico cell areas narrow and limits cell splitting gain. Range Expansion (RE) is desirable to balance the network load between MBS and PBS by expanding the coverage, which subsequently increases cell splitting gains. However, more interference may be introduced if the bias value of RE is not set properly. In this paper, we propose a Dynamic Cell Range Expansion (DCRE) strategy that the bias value of RE is set dynamically according to the change of network environment. The proposed scheme aims to fulfill the resources utilization by RE scheme, and meanwhile improve the users performance of cell edge through cell load balancing method. Simulation results show that DCRE scheme can improve the network performance of cell edge, and increase the cell capacity and users throughput compared with the existing methods.

Abstract: This paper was concerned with the dynamic output feedback H_∞ controller design for Networked Control Systems. Data transmission in multiple-packet was adopted due to the limited communication. The random communication delays existing both from the sensor to the controller and from the controller to the actuator were considered simultaneously. The dynamic output feedback H_∞ controller design was given. The result shows that a numerical example presented here illustrates the effectiveness of the proposed method.

Abstract: This paper studies the stabilization problems of networked control systems (NCSs) with dynamical quantizers. A new model is proposed that takes into consideration the effect of the network induced delay, the quantization levels, and based on this model, dynamical quantization scheme is introduced. The relationship between the delay bound，the quantization range and stability is given by using Lyapunov stability theory and linear matrix inequalities (LMIs) approach, and convex condition of the stabilization controller is presented. A simulation example shows the effectiveness of the proposed method.