Sharif Digital Repository

The increased penetration of cellular networks has made voice channels widely available ubiquitously. On the other hand, mobile voice channels possess properties that make them an ideal choice for high priority, low-rate real-time communications. Mobile voice channel with the mentioned properties, could be utilised in emergency applications in vehicular communications area such as the standardised emergency call system planned to be launched in 2015. This study aims to investigate the challenges of data transmission through these channels and proposes an efficient data transfer structure. To this end, a proper statistical model for the channel distortion is proposed and an optimum detector... 

The objective of this study is to design sub-optimal signature matrices for binary inputs for an overloaded code division multiple access (CDMA) system as developed by this author group. In this study, the authors propose to use the sum capacity, the bit error rate and distance criteria as objective functions for signature matrix optimisation. Three optimisation techniques, the genetic algorithm, the particle swarm optimisation and the conjugate gradient (CG) are exploited in this work. Since the optimisation computational complexity increases by matrix dimensions, it is practically impossible to directly optimise the large signature matrices. In order to address this problem, a method is... 

In this letter, a new approach to perform edge detection is presented using an all-dielectric complimentary metal-oxide-semiconductor-compatible metasurface. Our design is based on the guided-mode resonance, which provides a high quality factor resonance to make the edge detection experimentally realizable. The proposed structure is easy to fabricate, and it can be exploited for detection of edges in two dimensions due to its symmetry. In addition, a tradeoff between gain and the resolution of edge detection is discussed, which can be adjusted using appropriate design parameters. The proposed edge detector potentially can be used in ultrafast analog computing and image processing. ©... 

The everlasting bandwidth limitations in wireless communication networks has directed the researchers' thrust toward analyzing the prospect of overloaded Code Division Multiple Access (CDMA). In this paper, we have proposed a Genetic Algorithm in search of optimum signature matrices for binary-input synchronous CDMA. The main measure of optimality considered in this paper, is the per-user channel capacity of the overall multiple access system. Our resulting matrices differ from the renowned Welch Bound Equality (WBE) codes, regarding the fact that our attention is specifically aimed at binary, rather than Gaussian, input distributions. Since design based on channel capacity is... 

Key performance indicators (KPIs) are the fundamental building blocks in measuring and monitoring processes of safety management. This chapter describes a classification of safety KPIs and a review of literature leads to a new framework. It aims to develop a logical selection and aggregation methodology for generating a single number that reflects safety performance. Determining a mechanism for performance measurement and monitoring is a key part of any management system, and this has a higher importance for total safety management. Personal safety deals with the prevention of occupational accidents that usually have low severities and high frequencies. The measurement of safety has been... 

Key performance indicators (KPIs) are the fundamental building blocks in measuring and monitoring processes of safety management. This chapter describes a classification of safety KPIs and a review of literature leads to a new framework. It aims to develop a logical selection and aggregation methodology for generating a single number that reflects safety performance. Determining a mechanism for performance measurement and monitoring is a key part of any management system, and this has a higher importance for total safety management. Personal safety deals with the prevention of occupational accidents that usually have low severities and high frequencies. The measurement of safety has been... 

We propose a blind image steganalysis method based on the Singular Value Decomposition (SVD) of the Discrete Cosine Transform (DCT) coefficients that are revisited in this work. We compute geometric mean, mean of log values, and statistical moments (mean, variance and skewness) of the SVDs of the DCT sub-blocks that are averaged over the whole image to construct a 480-element feature vector for steganalysis. These features are fed to a Support Vector Machine (SVM) classifier to discriminate between stego and cover images. Experimental results show that the proposed method outperforms most powerful steganalyzers when applied to some well-known steganography algorithms  

Minimization of the number of cluster heads in a wireless sensor network is a very important problem to reduce channel contention and to improve the efficiency of the algorithm when executed at the level of cluster-heads. In this paper, we propose an efficient method based on genetic algorithms (GAs) to solve a sensor network optimization problem. Long communication distances between sensors and a sink in a sensor network can greatly drain the energy of sensors and reduce the lifetime of a network. By clustering a sensor network into a number of independent clusters using a GA, we can greatly minimize the total communication distance, thus prolonging the network lifetime. Simulation results... 

A great amount of effort has been made in order to reach a more precise understanding of the adhesion phenomenon that happens as a vital component of several biological systems. Therefore, a firm understanding of the important factors that influence this phenomenon is of special importance in triggering the adhesive characteristics of different biological, bio-inspired and synthetic materials in fields such as tissue engineering. In this study the adhesive characteristics of a multi-material system consisting of the frequently used synthetic material, graphene, in the form of armchair-configuration sheets, and an important biological filament which is type 1 Collagen consisting of 3 alpha... 

Wet cooling towers are one of the most water-intensive technologies, which are widely used in air conditioning applications, especially in dry regions. Considering the current water crisis around the world, it is essential to improve the design of these cooling towers to reduce their water consumption, while maintaining their cooling performance. Makeup water of cooling tower is usually a constant-temperature water which is cold enough to condensate the moisture content of the cooling tower exhaust air. Therefore, it has great potential to recycle water evaporation of cooling towers, which is not considered so far. This paper investigates a novel design for cooling towers utilising the...