Sharif Digital Repository

InAlAs/InGaAs/InP high electron mobility transistors have higher mobility comparing to structures without indium. But existence of indium causes smaller Eg and as a result smaller breakdown voltage. However, increasing percentage of indium results in higher mobility and as a result higher current and transconductance. Therefore decreasing percentage of indium causes higher breakdown voltage at the sometime lower transconductance. One of the most important parameters that limit maximum output power of transistor is breakdown voltage. In this paper, InAIAs/InGaAs/InP HEMTs with different structures are simulated and a structure with a good transconductance and breakdown voltage is introduced  

Based on the closed-form solution of a one-dimensional wave equation, the primary, secondary and acoustic feedback paths for the active control of sound in an acoustic duct have been investigated. Accurate models for the condenser microphone and loudspeaker, which include both the electro-mechanical and mechano-acoustical couplings as well as acoustical damping, have been considered. A generalized form of the filtered-x least mean square (FXLMS) algorithm that uses a more general recursive adaptive weight update equation to improve the performance of the FXLMS algorithm has been developed. Computer simulations were carried out to investigate the performance of acoustical feedback and... 

The exact closed-form solution of a one-dimensional wave equation including the viscous damping effect has been obtained from the Green's function. Accurate models for the error sensor and secondary loudspeaker, which includes the electro-mechanical and mechano-acoustical couplings, have been used and the transfer function of the primary, secondary and acoustic feedback paths of the active noise control system have been obtained. The generalized form of the classical FXLMS algorithm, referred to G-FXLMS algorithm, has been developed. In contrast to the FXLMS algorithm, G-FXLMS algorithm does not neglect the time shift of the filter coefficients and employs a more general recursive adaptive... 

The single-reference/multi-output active noise control (ANC) of an accurate physical model of an acoustic duct system has been investigated. Computer model of a multi-channel ANC system with tonal and sweep sine input signals, and an adaptive feedforward algorithm that minimizes the generic cost function are developed. Results obtained for various single-input/single-output (SISO) configurations of ANC systems were compared. The dynamic response of a single-reference/multi-output ANC system, using Minimax and MEFXLMS algorithms, is studied and the effect of acoustical feedback neutralization in a multi-channel ANC system is studied. Simulation results demonstrate that the multi-channel... 

The use of adaptive feedforward controllers has proven to be a very successful strategy for controlling noise and vibration in a variety of applications. One reason is that the feedforward controller is an open loop controller, which can be designed to cancel the undesired noise in one position with any accuracy. However, the feedforward controller requires an input signal, called a reference signal, correlated to the noise source. As a consequence, a single reference controller can only reduce noise radiated from a single noise source. In many applications, there is a need to attenuate noise produced by several noise sources. In this paper, three different structures, single, modulating and... 

Dynamic and stability analysis of non-uniform Timoshenko beam under axial loads is carried out. In the first case of study, the axial force is assumed to be perpendicular to the shear force, while for the second case the axial force is tangent to the axis of the beam column. For each case, a pair of differential equations coupled in terms of the flexural displacement and the angle of rotation due to bending was obtained. The parameters of the frequency equation were determined for various boundary conditions. Several illustrative examples of uniform and non-uniform beams with different boundary conditions such as clamped supported, elastically supported, and free end mass have been... 

Learning a foreign language encompasses a process of trial and error that can lead to the progression of the learner's interlanguage, meaning that the learners make use of their language knowledge that receives feedback and brings about progress through diagnosis of the problems and being corrected by the teacher. Therefore, there exists a need to analyze the underlying reasons causing the students to remain taciturn with a low willingness to communicate (WTC) during a language class. There has been much work done investigating the role of the learner's stable personal characteristics (traits) along with their situational changes at a specific time (states) that influence the student's... 

Using 3-D scanned data to analyze and extract pore network plays a vital role in investigation of porous media's characteristics. In this paper, a new simple method is developed to detect pores and throats for analyzing the connectivity and permeability of the network. This automated method utilizes some of the common and well-known image processing functions which are widely accessible by researchers and this has led to an easy algorithm implementation. In this method, after polishing and quality control of images, using city-block distance function and watershed segmentation algorithm, pores and throats are detected and 3-D network is produced. This method can also be applied on 2-D images... 

In this paper, we try to recognize and distinguish different groups of arrhythmia using novel features which have been obtained from the heart rate's phase space in recent years. For this purpose, we used Triangular Phase Space Mapping (TPSM) and Parabolic Phase Space Mapping (PPSM). For recognition, we used three groups of 15 subjects using the Physionet database (Arrhythmia, Congestive Heart Failure (CHF), and Atrial Fibrillation (AF)) with Normal Sinus Rhythm (NSR). The obtained features discriminate arrhythmia from NSR by p