Majlesi Journal of Electrical Engineering
Year:2010 | Volume:4 | Issue:1 (12)|Papers Count:8

Deriving a dynamic model based on the coupled-mode and carrier rate equations, the effects of coupling coefficient and corrugation position on all-optical flip-flops (AOFF) we have analyzed in this paper. Also the self phase modulation (SPM) in the distributed coupling coefficient distributed feedback semiconductor optical amplifier (DCCDFB- SOA) has been implemented. Then the effects of SPM on the rise and fall times of the flip-flop DFB-SOA are investigated. It has been shown that the application of the optimized coupling coefficient and corrugation position improves the speed limitation in AOFF significantly. The transfer matrix method (TMM) time domain is utilized for the numerical simulations.

This paper presents a dual-active capacitance in reversed nested Miller compensation (DACRNMC) technique for low-voltage and large capacitive load amplifiers. The frequency bandwidth of the DACRNMC amplifier has been improved due to the usage of active compensation capacitors. The amplifier's die area is reduced in compare to the existing techniques in the RNMC scheme. The architecture also generates two left half plane zeros to increase the phase margin. The simulation for the proposed DACRNMC amplifier with a 0.18μm standard CMOS process reveals a unity gain bandwidth of 17.4MHz and phase margin of 64 degrees , while 500 pF load is driven from a single 1.5 V power supply.

In this paper, a CMOS four quadrant multiplier based on flipped voltage follower and differential squaring circuit is presented. The proposed circuit has a compact architecture which operates at a higher speed and a higher input voltage range compared to the previously presented structures. The transistors operate in both saturation and ohmic regions. The circuit operates with a single supply voltage of 3.3V in a 0.35 μm CMOS technology where the total harmonic distortion (THD) is less than 1.1%, the linearity error is also less than 3%, -3db frequency is more than 180 MHz and the voltage input range is 3 Vp-p− . Simulation results are given to verify the functionality of the proposed multiplier.

The variations of speech parameters due to emotion or stress are noticeable. In the presence of such variations, if a neutral model is used for the system, the speech recognition accuracy deteriorates. The evaluation of how emotion influences speech parameters is the first step towards emotional speech recognition. Pitch frequency is an important parameter in speech processing systems. Therefore in this research the effect of pitch frequency and its slope due to emotion is explored for voiced phonemes. On the other hand, the influence of emotional state on continuous speech recognition performance is evaluated. The results show that the recognition performance of sentences with angry and happy states and also interrogative sentences has the most deterioration. This deterioration is more than 68% when compared to neutral speech recognition accuracy. To improve recognition results, we add the pitch frequency information to the end of speech recognizer feature vector. The amount of improvement depends on the type of emotion and also added pitch information. The results show that, pitch frequency slope has a significant affect on the improvement of speech recognition accuracy even for neutral speech.

In this paper we proposed, a new zero voltage switching isolated buck-boost DC-DC converter with active clamp circuit. The active clamp circuit in this converter not only absorbs voltage spikes across the main switch but also provides soft switching conditions for all switches. All switches are Pulse Width Modulation controlled which simplifies the control implementation. One of the main advantages of this converter is operating at high power levels while soft switching conditions exist in both buck and boost modes of converter operation. Since this converter can operate over a wide input voltage range, it can be employed in power factor correction. The experimental results obtained from a 150W prototype circuit operating at 100 KHz are presented to confirm the integrity of the proposed circuit.

The reports show a rapid growth in the numbers of attacks to the information and communication systems. Also, we witness smarter behaviors from the attackers. Thus, to prevent our systems from these attackers, we need to create smarter intrusion detection systems. In this paper, a new intelligent intrusion detection system has been proposed using genetic algorithms. In this system, at first, the network connection features were ranked according to their importance in detecting attack using information theory measures. Then, the network traffic linear classifiers based on genetic algorithms have been designed. These classifiers were trained and tested using KDD99 data sets. A detection engine based on these classifiers was build and experimented. The experimental results showed a detection rate up to 92.94%. This engine can be used in real-time mode.

One of the challenging problems in machine vision and computer graphic is realistic face modeling and animation. Using markers on the face key points and tracking the movements of the markers is a low cost method to determine these parameters. Since MPEG4 standard has defined parameters for face modeling and animation, we place markers on the key points defined in MPEG-4 standard, and propose a system for accurate tracking of them. We examine the system in real movie capturing conditions. Various distortions such as change of lightening, Gaussian noise, blurring, compression, and temporal filtering are examined, and the system degradation in each case is reported.

The Switched Reluctance (SR) motor is a simple and robust machine, which has found application over a wide range of different power and speed shapes. This paper briefly reviews the different types of SR motors with different geometries and then presents a new configuration for a two phase SR motor with step shaped rotor poles. This motor has the ability to start and run in a specified direction without any difficulties. In other words the motor will always have starting torque no matter where the rotor is positioned. Also centrifugal switch is presented and mounted on the motor shaft for a sudden advancement of current-pulses relative to the rotor position after reaching a preset motor speed in order to develop a higher torque at starting. Then the machine is analyzed in the generator mode. To evaluate the performance of the switched reluctance machine in motoring as well as generating mode, two types of analysis, namely numerical technique and experimental study have been utilized. In the numerical analysis, due to the highly non-linear nature of the motor, a three dimensional finite element analysis is employed, whereas in the experimental study, a proto-type motor has been built and tested.