Sharif Digital Repository

Optical coherence tomography (OCT) is a noninvasive imaging modality that provides cross-sectional images from microstructures of tissues. This optical imaging system works based on Michelson interferometry principle and has intermediate resolution and penetration depth which makes it appropriate for imaging thin tissues such as skin and eye. OCT images suffer from three main artifacts that make images difficult to be analyzed. The first one is small grainy structures called speckle which degrade image quality and decreases axial and lateral resolution. The second one is light intensity attenuation which is a function of depth. It happens because of absorbing and scattering nature of tissue... 

Almost all existing multi-description coding (MDC) schemes are designed for media streaming over Internet. In this work, a wavelet-based video MDC technique is introduced that fits the criteria of media streaming over peer-to-peer networks. Our proposed method assigns descriptions to the senders due to their characteristic (i.e. bandwidth and availability). In contrast to traditional MDC, different descriptions in the proposed method have different importance in remaking the original media. Our simulation results show considerable improvement of video quality at the receiver (up to 10 dB) as compared to the state-of-the-art. ©2007 IEEE  

The important problem of content location in an unstructured distributed network (such as P2P, with no central searching system, graph construction control or file placement regulation) is addressed. The existing methods that are based on either flooding or random walk impose a large traffic load on the network or require a long time to search. In this work, we propose a method that outperforms the existing methods in both of these measures. These advantages are achieved by publishing traces of the contents of each node in its nearby nodes, so that the closer nodes to the target have a stronger trace of it. Such traces are used to rapidly locate the desired content. The superb performance of... 

Due to the constraints of P2P networks (such as bandwidth limitation) multiple senders should be employed for reliable multimedia streaming. This paper introduces a mathematic approach to select a set of senders among all available senders to provide the most reliable stream for the receiver. This selection is based on upload bandwidths and availability of peers as well as bandwidth of links connecting the senders and the receiver. Our method is called IPROMISE as it is an improved version of the PROMISE algorithm. Simulation results demonstrate improved media quality delivered to the receiver, while the complexity of sender selection remains the same. © 2007 IEEE  

Unlike those on Internet, the media providers on P2P networks are ordinary nodes with limited shared resources such as bandwidth. Multi-sender methods are the best existing solutions to video streaming on P2P networks. In this paper, we propose use of a multicast method on the top of an arbitrary multi-sender method so that all requesting peers receive almost the same expected bit-rate. Experimental results, derived from implementation of the proposed algorithm on Pastry P2P network confirm our claim. Another advantage of our method over the existing methods is its scalability with the number of receivers. © 2007 Elsevier B.V. All rights reserved  

Unlike those on Internet, the media providers on P2P networks are ordinary nodes with limited shared resources such as bandwidth. Multi-sender methods are the best existing solutions to video streaming on P2P networks. In this paper, we propose use of a multicast method on the top of an arbitrary multi-sender method so that all requesting peers receive almost the same expected bit-rate. Experimental results, derived from implementation of the proposed algorithm on Pastry P2P network confirm our claim. Another advantage of our method over the existing methods is its scalability with the number of receivers  

In this research, we present results of simulated annealing (SA), a heuristic optimization algorithm, for focusing light through a turbid medium. Performance of the algorithm on phase and amplitude modulations has been evaluated. A number of tips to tune the optimization parameters are provided. The effect of measurement noise on the performance of the SA algorithm is explored. Additionally, SA performance is compared with continuous sequential and briefly with other optimization algorithms. © 2018 Optical Society of America  

Light propagation in turbid media, such as biological tissues, experience scattering due to inhomogeneous distribution of refractive indices. Control of light scattering is important for focusing the light or imaging through scattering medium. By spatially shaping the wave-front of the incident beam, using spatial light modulator (SLM), the scattered light can be focused to a point. Iterative optimization is a popular way of obtaining the most optimum phase map on the SLM. In this study, we implement six optimization algorithms including continuous sequential, partitioning algorithm, transmission matrix estimation method, genetic algorithms, particle swarm optimization, and simulated... 

Infill walls are realized to affect the nonlinear response of infilled frames. Yet, due to modeling and analysis complexities, infill walls are usually neglected in the modeling and analysis phase. In this paper, the nonlinear behavior of infilled steel braced frames is investigated using the Endurance Time (ET) method. The ET method is a novel and straightforward approach for the nonlinear analysis of structures under dynamic excitations. Two 2D braced frames, one concentrically braced frame and one eccentrically braced frame, with unreinforced masonry clay brick walls as infills, are considered. The infill panels are macro-modeled using equivalent compressive struts, with appropriate... 

In this research, we present the results of applying simulated annealing (SA) which is a heuristic optimization algorithm for focusing light through a turbid media. The performance of this algorithm on both phase optimization and amplitude optimization has been demonstrated. A guideline to set up the SA parameters is also suggested. The performance of SA algorithm in different levels of measurement noise has been also explored. The results showed that the SA algorithm performs effectively in measurement noises as high as 0.3(I0). © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only  

Peer to Peer networks have received considerable attention during the past decade and have been the focus of many research and development activities. New applications such as video streaming or gaming would benefit from multicast topologies and creating such trees in peer to peer networks is a challenging task. Proper multicast trees should minimize the traffic delay and bandwidth consumption. At the same time, construction of these trees should not be very complicated in terms of the required processing power so they can be implemented easily. The required time for construction of multicast trees should also be minimized and that helps with their adaptation to the dynamics of the network.... 

Unlike those on Internet, the media providers on P2P networks are ordinary nodes whose contribution bandwidth is limited. Multi-sender methods are the best solutions known to video streaming on P2P networks. In this paper, we propose use of a multi-cast method on the top of an arbitrary multi-sender method so that all requesting peers receive almost the same expected bit-rate. That is while the existing multi-sender methods maximize the bit-rate delivered to the first receiver and cannot provide acceptable bit-rates to the next requesting nodes. © 2006 IEEE  

Due to special constraints in peer-to-peer (P2P) networks (such as bandwidth limitation) and because of their highly dynamic characteristics, a single node cannot provide a reliable multimedia stream to the receivers. Several multi-sender algorithms are proposed to reliably deliver a media stream to the receiver through the intrinsically unreliable P2P networks. Based on upload bandwidths and availability of peers as well as the bandwidths of the links connecting the senders and the receiver, PROMISE selects a set of active senders to maximize the expected bit-rate delivered to the receiver. By careful investigation of PROMISE, in this paper, we present why and how it deviates from finding...