Majlesi Journal of Electrical Engineering
Year:2008 | Volume:1 | Issue:3 (3)|Papers Count:8

Although voice is a mandatory service in the wireless telecommunication networks, most of new data services are based on Internet. These services include http, telnet, SMTP, etc. In addition, mobile channel is a multipath fading channel. TCP/IP performance in the wired systems depends on the link congestion and packet loss. In this paper we study how TCP/P protocol is used in UMTS and survey its performance reduction in a multipath fading channel alone and with an ARQ protocol.

In this paper we propose a good way to decrease the effects of noisy channels on the JPEG images using multiple description coding. In this way we can compress the data of image with a better signal to noise ratio. first, we use over sampling to increase the redundant of the data, then we divide the image into sub-images that each can be passed through several channels (Multiple Description Channel), the ways that are simulated are passing the image in noisy channel: without adding zero and without blocky, without adding zero and with blocky, with adding zero and with blocky, in the first method the affection of noise is clearly, the 2nd method shows that with dividing data into 2 channels, when one of the channels becomes noisy, we can reconstruct the image from the other channel, with good quality.the last method shows that with the proposed way, we can repair the noisy image and obtain high PSNR.

In this paper a new sliding mode controller based on predictive control is used for the first order system, which is a good model for the industrial process. In this method a developed predictive control is used to optimize the sliding mode control including sliding surface and switching function coefficient at every moment. A new smooth function is used to reduce the chattering problems. Simulation results show the high effectiveness of the proposed controller.

Permanent magnet synchronous motors attract more attentions in motion control application in recent years. In this paper a novel stator flux oriented vector control scheme with maximum power factor to current trajectory is presented for a permanent magnet synchronous motor. This system is then implemented in Matlab/Simulink and the motor performance under this control method is investigated via excessive simulation results. Finally, the effect of stator resistance on the power factor of motor is shown.

Location awareness is an important capability for a series of enhanced wireless businesses. sensor networks are dense wireless networks of small low cost sensors, which collect and disseminate environmental data, for monitoring, military application and so on. Localization is an unconstrained optimization problem. position estimation is based on various, distance / path measures, which include anchor and non-anchor nodes. Anchor positions, have been predetermined to help us localize other nodes. This study proposes using a combination of fuzzy techniques, and advanced APS method, to estimate unknown nodes. In a network with twenty hundred nodes of which twenty percent operates as anchors. These nodes localize the other one hundred and sixties. It is necessary to select the best four anchors for localizing. We suppose that the anchors neighbor to unknown nodes are the best. It is time consuming to find the distance of unknown anchors in such a widespread network. Using the fuzzy logic, putting the limitation of distance, and selecting the nearest anchor to the unknown node, the nearest four anchoress can be selected. In this case the rate of localization error will be decreased due to selecting neighbor anchors. Therefore, we can localize nodes by using ad-hoc positioning system.Fuzzy rules help us to estimate position in less than 2.4 seconds with mean normal positioning deviation of z=0.4597.

For accessing to higher speed and more densities in packaging, FET structures have become small increasing from day to day. Devices as small as 18nm can still exhibit acceptable transistor characteristics but At such small sizes, the nature of carrier transport in the device begins to change. In such MOSFETs that the device size becomes smaller than the carrier scattering length, it is statistically very probable for carriers to traverse the channel from the source to drain electrodes without encountering a scattering event. Such transport is called ballistic transport technically. In this article, we have conducted a survey on the electron transport in nanotransistor and using the semi-classical approach based on Boltzmann Equations for ballistic regimes, the electrical currents for a two dimensional structure as well as a quantum wire have been calculated that this calculations are based on model that is indicated by A. Rahman, J. Guo, S. Datta.

Software testing is one of the most important phases in the software development procedure which ensures the accordance of the software and its description. Testing is mainly a manual task accomplished by the human operators. This results in increasing the cost and time of the software development process. Also, due to the uncertain nature of the human activities, software reliability will be under threat and the probability of having some aspects and parts of the software untested always would be high. Therefore, the more automatic, the more intelligent, and the more reliable testing procedure always would be of interest. In this paper we introduce a new approach to the software testing automation in web based applications, using Artificial Neural Network (ANN). The applied ANN will be trained by diverse pairs of input/output data provided according to the software functionality, then it attempts to model a testing tool for the software. Next we can use this ANN-based testing tool to evaluate and test the software. We apply the proposed testing scheme on a modified version of a web based university course registration software and show its performance on both error free and faulty cases.

In this paper, a non-linear carrier controller with an exponential carrier generator is designed and simulated for power factor correction (pfc). then, this controller is applied to single phase and three phase rectifier using a boost regulator for PFC. the power factor and its variations are measured by computer simulation against the changes in various loads and switching frequencies and the results are discussed. In order to produce voltages lower than the input voltage, a PFC using a buck regulator is used in rectifiers. However, the buck type PFC produces lower power factor then the boost type. For this reson, a flyback regulator is used as a PFC to produce lower voltage then input voltage. Power factor obtained by computer simulation of Fly back pfc are acceptable and are above 95%.