Sharif Digital Repository

In this paper, we analyze and obtain performance of a multilevel Optical Code Division Multiple Access (OCDMA) system with Variable-Weight Optical Orthogonal Codes (VW-OOCs) under the same-bit-energy assumption. The exact error-probability of this system is derived for the Generalized VW-OOCs (codes with arbitrary cross-correlation) which is necessary for the optimum design of multilevel OCDMA systems. We show that the bit power has an important role on determining the performance of codes with different weights. Furthermore, the results reveal that the performance of low-weight codes depends on the weight of the low-weight codes and the code-weight ratio of two classes. Moreover, our exact... 

An important issue for efficient execution of MapReduce jobs on a cloud platform is selecting the best fitting virtual machine (VM) configuration(s) among the miscellany of choices that cloud providers offer. Wise selection of VM configurations can lead to better performance, cost and energy consumption. Therefore, it is crucial to explore the available configurations and choose the best one for each given MapReduce application. Executing the given application on all the configurations for comparison is a costly, time and energy consuming process. An alternative is to run the application on a subset of configurations (sample configurations) and estimate its performance on other... 

This paper addresses a nonlinear model predictive controller design for a single-phase PFC rectifier exploiting the Sheppard-Taylor converter. After approximation of the tracking error in the receding horizon by its Taylor-series expansion to any specified order, an analytic solution to the MPC is developed and a closed-form nonlinear predictive controller is introduced. The proposed nonlinear model predictive control (NMPC) derived using approximation can stabilize the original nonlinear systems if certain conditions, which can be met by properly choosing predictive times and the order for Taylor expansion, are satisfied. The main advantage of this digital control method is that unity power... 

The track fusion combines individual tracks formed by different sensors. Tracks are usually obtained by Kalman Filter (KF), since it is suitable for real-time application. The KF is an optimal linear estimator when the measurement noise has a Gaussian distribution with known covariance. However, in practice, some of the sensors do not have these properties, and the traditional KF is not an optimal estimator. In this paper, a novel adaptive Kalman filter (NAKF) is proposed. In this approach, the measurement noise covariance is adjusted by using an introduced simple mathematical function of one variable, called the degree of matching (DoM), where it is defined on the basis of covariance... 

Single-phase ac-dc Power Factor Correction (PFC) rectifiers have attracted considerable attention in recent years due to the adoption of increasingly stringent power quality regulations. In this paper a nonlinear model predictive controller design for a single-phase Flyback PFC rectifier is presented. After approximation of the tracking error in the receding horizon by its Taylor-series expansion to a specified order, an analytic solution to the model predictive control (MPC) is developed and a closed-loop nonlinear predictive controller is introduced. The main advantage of this digital control method is that unity power factor can be achieved over wide input voltage, load current range and...