Advanced Materials Research Vols. 403-408

Abstract: In this paper, a digitally programmable AC current source is introduced. The proposed scheme provides the ability of digitally setting the output current frequency and amplitude. The realization method, based on commercially available devices, employs digital-to-analog converter (DAC), and voltage controlled current source (VCCS). The proposed circuit offering high accuracy and linearity is suitable for measuring soil conductivity. Experimental results showing the circuit performances are also included. The developed source provides acceptable precision i.e. absolute percentage error of 3%. The covered conductivity range indicates the importance of such a low cost and reliable source.

Abstract: A GPS tracking system utilizing the license-free RF communication is proposed as viable alternative to using the available GSM network for low-cost maintenance. The proposed system is designed based on the popular 8-bit embedded system. It consists of a monitoring unit and a remote unit. Each unit is equipped with, among others, a GPS receiver and an RF transceiver as main components. While there is a need for the remote unit to be small and compact, the monitoring unit is also designed as a portable device. Prototypes are built for design verification. Initial functionality test shows that the system is capable of tracking mobile object not only in outdoor but also in indoor environment.

Abstract: Network on Chip (NoC) has been proposed as a new paradigm for designing System on Chip which supports high degree of scalability and reusability. Mapping the IP cores onto a given platform is an important phase of NoC design which can greatly affect the performance and energy consumption of the chip. Mapping which is an instance of the constrained quadratic assignment problem (QAP) belongs to the class of NP-hard problems. Due to the complexity of many of these problems, particularly those of large sizes encountered in most practical settings, meta heuristic algorithms are conspicuously preferable. These algorithms help us achieve optimal or near optimal solutions in large size applications with reasonable time. In this paper eight types of Genetic Algorithms (GA), Particle Swarm Optimization(PSO), Simulated Annealing(SA), Differential Evolution(DE) and Imperialist Competitive Algorithm (ICA) are applied in their basic frameworks for solving the mapping problem on two real core graphs Video Objective Plan Decoder and MPEG-4. The experimental results show the comparisons of these different meta heuristic algorithms with each other.

Abstract: In this paper, we implement and analyze different Network-on-Chip (NoC) designs with Static Random Access Memory (SRAM) Last Level Cache (LLC) and Dynamic Random Access Memory (DRAM) LLC. Different 2D/3D NoCs with SRAM/DRAM are modeled based on state-of-the-art chips. The impact of integrating DRAM cache into a NoC platform is discussed. We explore the advantages and disadvantages of DRAM cache for NoC in terms of access latency, cache size, area and power consumption. We present benchmark results using a cycle accurate full system simulator based on realistic workloads. Experiments show that under different workloads, the average cache hit latencies in two DRAM based designs are increased by 12.53% (2D) and reduced by 27.97% (3D) respectively compared with the SRAM. It is also shown that the power consumption is a tradeoff consideration in improving the cache hit latency of DRAM LLC. Overall, the power consumption of 3D NoC design with DRAM LLC has reduced 25.78% compared with the SRAM design. Our analysis and experimental results provide a guideline to design efficient 3D NoCs with DRAM LLC.

Abstract: Excited capacitor of power winding has much influence on the capacity of excited converter of dual-winding induction generator. The capacity of excited converter can be optimized by changing the excited capacitor. The influence law of the capacity of excited converter by variable excited capacitor are compared under variable speed and variable load recured to simulation methods.

Abstract: Doubly fed induction generator use a back-to-back dual PWM converters that it can decouple of active power and reactive power, leading to reduce the system's frequency response. If it does not take additional control strategy, when the wind turbine capacity increases to a certain extent, frequency stability of the grid will have a significant hazard. On the one hand, when the frequency control loop responding the diversification of the system frequency is installed in the rotor of the doubly-fed variable speed wind turbines, the frequency can be regulated by controlling the rotor’s kinetic energy. On the other hand, by additional frequency control loop is installed in pitch angle control system, the wind turbine can also contribute to frequency control. In this paper by synthesizing the above two methods, wind farms can be participate in a better performance in frequency regulation. The results of the simulation show that the above-mentioned method is correct.

Abstract: It is necessary to built an accurate model of direct methanol fuel cell (DMFC) as a complex nonlinear multi-input multi-output system .In this paper .the methanol concentrations, temperature and current were considered as inputs, the cell voltage was taken as output, and the performance of a direct methanol fuel cell was modeled by neural network model. This model is based on Matlab / Simulink software .The simulation shows that the neural network model has better accuracy than the physical model, while analyzing the performance of the DMFC in different temperatures and concentrations.

Abstract: This paper considers the mean square consensus problems for second order multi-agent systems with fixed topologies and measurement noises. Two cases were analyzed: 1) undirected networks with fixed topologies; 2) undirected networks with fixed topologies and measurement noises. In order to attenuate the measurement noises, a time-varying consensus gain was introduced in the consensus protocol. Sufficient conditions were derived for all agents to reach consensus in mean square via algebraic graph theory, matrix theory and stochastic analysis approach, by constructing an appropriate Lyapunov function. A numerical example was given to verify our theoretical analysis.

Abstract: Motors of electric automobile with low noise characteristics are increasingly in demand due to environmental considerations. The primary source of noise is attributed to electromagnetic noise, mainly affected by electromagnetic radial force. To obtain a better understanding of origination and components of radial force, in this paper, theoretically, calculate and analyze electromagnetic radial force principles; and establish 2-dimension CAE model of PMSM subsequently. After simulation and data analysis, in terms of time and frequency domain, respectively, calculate the numerical radial air-gap flux and radial force. Compare the theory with numerical results. To some extent, ratify the radial force theory of PMSM in electric vehicles.

Abstract: This paper aims to develop a small permanent magnet (PM) synchronous generator for direct-coupled, low-speed wind turbine applications. The generator, rated 3-phase 110 V and 1 kW is designed as an outer rotor structure. The design and optimization of the generator is done with the aid of the electromagnetic field analysis based on the finite element method.