MODARES TECHNICAL AND ENGINEERING
Year:2007 | Volume:- | Issue:26 (SPECIAL ISSUE ON ELECTRICAL ENGINEERING)|Papers Count:10

Transfer matrix method (TMM) has been applied to analyze characteristics of semiconductor laser optical amplifiers. The input signal is sinusoidal modulating wave and we do not assume the modulating bias signal as well. We have shown that the distortion arises from gain modulation at low modulation frequencies, but in microwave modulation frequencies, the gain takes an average value and the response becomes linear.

To be sure, that a program behaves correctly at runtime; the behavior of the program should be verified. Where the program source code is available, it is possible to extract the operational logic (i.e., behavior) of the program. But in this paper, programs are considered as black boxes, so no information is available about the operational logic of programs. However, some efforts are spent to learn inductively the operational logic of programs by executing them successfully (i.e., correctly) for many (i.e., > 1000) times and logging their system calls implicitly. Therefore, in the first phase, few mechanisms are developed to discover inductively the loops and branching points of a program using its log system calls. Then, the operational logic of the program is constructed in system call level abstraction by applying a novel method. In the second phase, any deviation of the program execution (in system call level abstraction) from its operational logic (in system call level abstraction) is detected, just like white box approaches. Two major applications for the proposed approach are suggested: (1) to make critical programs somehow, detect their misuses (i.e., buffer overflow attack) by themselves, and (2) to protect programs against their runtime faults. The effectiveness of the proposed approach is demonstrated by some experiments.

In this paper a new algorithm is presented for coherent radar detection of targets, when distribution of the interference (clutter and noise) is non-Gaussian. The Neyman-Pearson criterion is used for optimal detection and several successive received samples from a radar range cell are used for detection in the same cell. On the basis of recent empirical evidences, the interference distribution is described statistically by the correlated pseudo-Gaussian distribution which is also called SIRP. The joint pdf of the pseudo-Gaussian interference distribution is too complicated to lead to the optimum detector (or ALR detector). Therefore, a convenient approximation of its analytical solution is utilized. The obtained AALR detector outperforms the GLR detector. Moreover, the proposed algorithm is similar to the GLR detector. Since, the AALR detector-has been derived from the analytical solution of the ALR detector, its similarity to the GLR algorithm confirms the proper performance of the GLR detector. The performance of the proposed detector is also compared to the OLD and ECD detectors.Computer simulations confirm superiority of the ALR detector to the GLR detector while both are significantly better than the OLD and ECD detectors. The proposed detector completely prefers to the other detectors when the deviation of the interference distribution from Gaussian assumption is considerably high.

Voltage stability may be improved by various control functions. In this paper, it is shown that how High Side Voltage Control (HIVC) may be employed for this purpose. Two test systems, namely a 22- bus and IEEE U8-bus systems are used to demonstrate the proposed tuning strategy for HSVC control parameters.

This paper presents a framework for long term transmission expansion planning in competitive, electricity markets. Transmission lines and phase shifters are taken into account as expansion options. Maximization of the network users' benefits, with satisfying security constraints are considered as the criterion for transmission expansion planning. The elements of the objective function are the benefits of each network. The proposed model is as a non-linear mixed-integer programming (NLMIP) optimization problem. A GA (Genetic Algorithm) based method and quadratic programming (QP) approach is used to solve the problem. The discrete decision-making variables of the expansion plan are optimized by genetic algorithm, while QP optimizes the continuous variables.

Many of the video processing algorithms cannot be implemented in real time on general computers, due to their computational complexity. For an efficient implementation, a custom hardware that can be reconfigured for the algorithm, is used. In this paper a new acceleration hardware based on FPGA elements is proposed. This hardware can be adapted with the processing algorithm through FPGA design reconfiguration. Using a PCI slot, this hardware communicates with a Pc. The FPGAs are programmed through the PCI slot. The video frames are supplied to this hardware for processing. The performance of this hardware is evaluated using warping algorithms. The first and second order warping for a 512*512 frame can be done in 7.9 ms.

Home Uterine Activity Monitoring (HUAM) has demonstrated to be of great value for preventing preterm labor in recent years. In this research, a low cost monitoring device for non-invasive monitoring of the uterine activity in pregnant women is presented. The new device has been designed based on an inductive Colpitz oscillator and vertical displacement of a ferrite core in a coil. The resulting frequency of the oscillator is proportional to the pressure in the external surface of the abdomen. This frequency is measured by the portable monitor. A low-power static random access memory (SRAM) provides long-term data storage. The proposed sensor for detecting uterine contractions has light weight, high stability and low cost. This sensor is very simple to manufacture and use for long-term ambulatory monitoring of the uterine activity. Furthermore, this sensor can be calibrated using software. Other features of the sensor are, resolution of 0.13 mmHg, repeatability close to 96% and input range from 0 to 95.32 mmHg.

In this paper the reflection coefficient of electromagnetic wave incidence on the walls of the buildings and obstacles that occurs in mobile communication path was modified by solving the Riccati nonlinear equations. For this purpose, the building walls are assumed inhomogeneous layers where their permittivity changes as function of the wall thickness. Using this reflection coefficient, a new propagation model based on urn and GID (uniform geometrical theory of diffraction and geometrical theory of diffraction) for multiple diffraction paths is proposed. Using this model, the diffraction loss as well as the path loss for a row of buildings with two in homogeneous faces is calculated and compared with measured data. Comparison of theoretical and measured results reveals that the modified reflection coefficient can adequately predict the reflective properties of the building walls. Moreover, results obtained with the proposed UID model are in good agreement with the measurement data. Therefore, the modified reflection coefficients well as the new UID model can be used for estimation of multipath signals strength, diffraction loss and also path delay in ray tracing algorithms used in mobile communication, radar and radio links.