Sharif Digital Repository

Motivated by the bus escape routing problem in printed circuit boards (PCBs), we study the following optimization problem: given a set of rectangles attached to the boundary of a rectangular region, find a subset of nonoverlapping rectangles with maximum total weight. We present an efficient algorithm that solves this problem optimally in O(n4) time, where n is the number of rectangles in the input instance. This improves over the best previous O(n6) -time algorithm available for the problem. We also present two efficient approximation algorithms for the problem that find near-optimal solutions with guaranteed approximation factors. The first algorithm finds a 2-approximate solution in O(n2)... 

People make decisions and express their opinions according to their communities. A natural idea for controlling the diffusion of a behavior is to find influential people, and employ them to spread a desired behavior. We investigate an influencing problem when individuals' behaviors are affected by their friends in an opinion formation process. Our goal is to design efficient algorithms for finding opinion leaders such that changing their opinions has a great impact on the overall external behaviors in the society. We study directed social networks and define a set of problems like maximizing the sum of individuals' behaviors or maximizing the number of individuals whose external behaviors... 

Motivated by the bus escape routing problem in printed circuit boards, we study the following rectangle escape problem: given a set S of n axis-aligned rectangles inside an axis-aligned rectangular region R, extend each rectangle in S toward one of the four borders of R so that the maximum density over the region R is minimized. The density of each point p∈R is defined as the number of extended rectangles containing p. We show that the problem is hard to approximate to within a factor better than 3/2 in general. When the optimal density is sufficiently large, we provide a randomized algorithm that achieves an approximation factor of 1+ε with high probability improving over the current best... 

Although an early and influential review led to the often-cited conclusion that color vision is rare among mammals, more recent findings suggest that it is actually widespread. According to Jacobs (1993, 2004), all non-nocturnal mammalian species that have been adequately examined show some color vision capacity, although the degree varies enormously. Data on the presence and characteristics of color vision in the horse, however, remain sparse (and almost none in the case of ponies). Eight Caspian pony (four mares and four stallions) were presented with a series of two-choice color vs. grey discrimination problems. Experiments were performed in a box of 3×3 meter containing a wall with two... 

Energy storage and supply in solar thermal collector systems rely heavily on phase change materials (PCM). It is vital to establish the appropriate values for energy discharge time (tPCM) and net amount of stored energy (Qnet) within the PCMs in order to increase the efficiency of solar thermal collectors. For this study, we implemented a multi-objective evolutionary algorithm based on decomposition (MOEA/D) for the optimization process using the MATLAB simulator software. The simulation findings show that, under ideal circumstances where tPCM is large and Qnet is low, these two goal functions are inversely connected to one another. According to an analysis of how input parameters affect the... 

During recording lung sounds over the chest, heart sounds (HS) are also recorded and interferes with the inteipretation of lung sounds especially at low frequencies. Hence, several methods have been proposed to remove or reduce HS from lung sounds. The first step in most of the methods developed for HS reduction is to localize the segments of lung sounds including HS. In this study a method based on multi-resolution product of lung sounds wavelet coefficients was implemented for HS localization and its performance was compared to that of three methods developed for HS localization. The methods were tested on data from 6 healthy subjects recorded at low (7.5ml/s/kg) and medium (15ml/s/kg)...