Sharif Digital Repository

Ultrasound waves have been used in these days for most surgeries. They are applied to remove body tissues through surgery, for example in removing eye lens in cataract surgery. In a nutshell, a 3mm incision near cornea has been created and then after, a folded lens will be implanted and the patient can be released soon after the operation. The process is done by a vibrating metal tip in order to emulsify the lenses and the small particles will aspirate the debris through the hollow center of the tip. The problem of this procedure in some cases is thermal damage. This research addresses the aforementioned problem through an important parameter, different operating modes of the system. The... 

This paper presents a kinematics and workspace analysis of cable-suspended manipulators with elastic cable. The mechanics of extensible cable with a deflection to its selfweight are studied. The problem of evaluating the workspace is approached by using a modified formulation for a deformable cable. The proposed algorithm for testing whether a given configuration lies within the reachable workspace is applied. Starting with a general statement of the kinetic equations of the elastic cable and incorporate cable flexibility into workspace generation. This algorithm is verified through simulation results of various cable-suspended robots. © 2008 IEEE  

One of the most important parameters in evaluating a watermarking algorithm is its capacity. Of course capacity has a paradoxical relation with two other important parameters: image quality and robustness. Generally, watermarking capacity is expressed by bit per pixel (bpp) unit measure. This measure does not show what the side effects would be on image quality and capacity. Therefore, we proposed a two dimensional measure named capacity curve which shows the effects of capacity on visual quality. In this measure we can find the amount of degradation by a numerical value for each modification in pixels. Our experimental results are compatible with previous works in this field. © 2008... 

Recently, the trade-off between power consumption and fault tolerance in embedded processors has been highlighted. This paper proposes an approach to reduce dynamic power of conventional high-level fault-tolerant techniques used in the register file of processors, without affecting the effectiveness of the fault-tolerant techniques. The power reduction is based on the reduction of dynamic power of the unaccessed parts of the register file. This approach is applied to three transient fault-tolerant techniques: Single Error Correction (SEC) hamming code, duplication with parity, and Triple Modular Redundancy (TMR). As a case study, this approach is implemented on the register file of an... 

Watermarking is the process of hiding information in a media and usually used to for copyright protection. In software watermarking, the information is added to the source code of program and can be extracted from compiled executable code. In this paper, a new software watermarking algorithm is proposed by equation reordering. In this method, the order of operands in an equation is changed according to the information we want to hide in a way that the result of the equation is unchanged. One of the main advantages of this method is that no code added to the program, so the size and speed of the program not changed  

This paper presents a novel and fast homography-based tracking method to segment and track the instructor placed in front of a class board using two synchronized views. In the proposed method we estimate the instructor as a planar object and track its planar parameters. At first, the homography of board and fundamental geometry of two views are extracted using six point correspondences. The homography transformation matrix of object is calculated by obtaining three point correspondences in parallax region introduced with homography of the board. The parameters to be tracked by Kalman filter are obtained frame by frame by object's homography decomposition. Our proposed method is robust... 

In the image segmentation field, traditional techniques do not completely meet the segmentation challenges mostly posed by inherently fuzzy images. Fuzzy connectedness and fuzzy clustering are considered as two well-known techniques for introducing fuzzy concepts to the problem of image segmentation. Fuzzy connectedness-based Segmentation methods consider spatial relation of image pixels by "hanging togetherness" a notion based on intensity homogeneity. But, they do not inherently utilize feature information of image pixels. On the other hand, as the segmentation domain of fuzzy clustering-based methods is the feature space they do not consider spatial relations among image pixels. Recently,... 

A routing algorithm defines a route which packet traverses to get to destination. In this research we study some kind of routing algorithms that are used in internal connections networks of multi-processor and multi-computers systems. Then we discuss about some routing algorithms which have been implemented network on chip architecture. First, we present a group of routing algorithms based on various criterions, and review so-called category. Afterwards, we study adaptive and deterministic routing algorithms and express circular model applying in internal connections networks and its governing rules in order to prevent dead lock. Then we survey adaptive algorithms such as Deflection routing,... 

This paper presents an analysis of the effects and propagation of faults in the open-core 32-bit OpenRISC 1200 microprocessor. The analysis is based on a total of 13,000 transient faults injected into 65 parts of the CPU module in the OpenRISC 1200 core described at the RTL model. A comparison of the effects of faults on the various parts of the CPU including the pipeline's registers, the CPU component such as the register file, the control unit, and the ALU, and the data and address buses is done. It is shown that about 30%, 40% and 27% of injected faults terminated in address, data, and control errors respectively. About 28% of all injected faults resulted in failures. © 2008 IEEE  

This paper investigates fault effects and error propagation in a FlexRay-based network with hybrid topology that includes a bus subnetwork and a star subnetwork "The investigation is based on about 43500 bit-flip fault injection inside different parts of the FlexRay communication controller. To do this, a FlexRay communication controller is modeled by Verilog HDL at the behavioral level. Then, this controller is exploited to setup a FlexRay-based network composed of eight nodes (four nodes in the bus subnetwork and four nodes in the star subnetwork). The faults are injected in a node of the bus subnetwork and a node of the star subnetwork of the hybrid network. Then, the faults resulting in... 

Traditionally, to handle security for stand-alone computers and small networks, user authentication and access control mechanisms would be almost enough. However, considering distributed networks such as the Internet and pervasive environments, these kinds of approaches are confronted with flexibility challenges and scalability problems. This is mainly because open environments lack a central control, and users in them are not predetermined. In such ubiquitous computing environments, issues concerning security and trust become crucial. Adding trust to the existing security infrastructures would enhance the security of these environments. Although many trust models are proposed to deal with... 

High availability of software systems is an essential requirement for pervasive computing environments. In such systems self-adaptation, using dynamic reconfiguration is also a key feature. However, dynamic reconfiguration potentially decreases the system availability by making parts of the system temporary frozen, especially during incomplete or faulty execution of the reconfiguration process. In this paper, we propose Assured Dynamic Reconfiguration Framework (ADRF), consisting of run-time analysis phases, assuring the desired correctness and completeness of dynamic reconfiguration process. We also specify factors that affect availability of reconfigurable software in pervasive computing... 

This paper proposes a decentralized algorithm to organize an ad-hoc sensor network into clusters. Each sensor operates independently, monitoring communication among others. Those sensors which have many neighbors that are not already part of a cluster are likely candidates to creating a new cluster by declaring themselves to be a new cluster-head. The Clustering Algorithm via Deadline Timer (CADT) provides a protocol whereby this can be achieved and the process continues until all sensors are part of a cluster. Because of the difficulty of analyses simplified models are used to study and abstract its performance. A simple formula to estimate the number of clusters which will be formed in an... 

This paper proposes a new technique called CFEDC to detect and correct control flow errors (CFEs) without program interruption. The proposed technique is based on the modification of application software and minor changes in the underlying hardware. To demonstrate the effectiveness of CFEDC, it has been implemented on an OpenRISC 1200 as a case study. Analytical results for three workload programs show that this technique detects all CFEs and corrects on average about 81.6% of CFEs. These figures are achieved with zero error detection /correction latency. According to the experimental results, the overheads are generally low as compared to other techniques; the performance overhead and the... 

In this paper a new method for automatic word clustering is presented. We used this method for building n-gram language models for Persian continuous speech recognition (CSR) systems. In this method, each word is specified by a feature vector that represents the statistics of parts of speech (POS) of that word. The feature vectors are clustered by k-means algorithm. Using this method causes a reduction in time complexity which is a defect in other automatic clustering methods. Also, the problem of high perplexity in manual clustering methods is abated. The experimental results are based on "Persian Text Corpus" which contains about 9 million words. The extracted language models are evaluated... 

An stochastic version of the classical shortest path problem whereby for each node of a graph, a probability distribution over the set of successor nodes must be chosen so as to reach a certain destination node with minimum expected cost. In this paper, we propose a new algorithm based on Particle Swarm Optimization (PSO) for solving Stochastic Shortest Path Problem (SSPP). The comparison of our algorithm with other algorithms indicates that its performance is suitable even by the less number of iterations. © 2008 Springer-Verlag Berlin Heidelberg  

Applications in pervasive computing environment exploit information about the context of use, such as the location, tasks and preferences of the user, in order to adapt their behavior in response to changing operating environments and user requirements. Utilizing context with aid of ontology in data and model, decision support systems can provide better and more desirable support to their users. The effects and advantages of exploiting ontology in user modeling and DSS is discussed. We propose a framework of a Ontology-based Decision Support System (O2DSS), including ontology in model base, database and their advantages. © 2008 IEEE  

In this paper, dynamic programming alignment is replaced by a particle swarm optimization (PSO) procedure in time warping problem. The basic PSO is a very slow process to be applied to speech recognition application. In order to achieve a higher performance, by inspiring of PSO optimization methodology, we introduced a PSO Inspired Time warping Algorithm (PTW) that significantly increase the computational performance of time warping in alignments of long length massive data sets. As a main enhancement, a pruning strategy with an add-in controlling threshold is defined in PTW that causes a considerable reduction in recognition time, while maintaining the system accuracy comparing to DTW. ©... 

The rule based scheduling algorithms are a new trend in grid scheduling algorithms; the combination of rule based algorithms for resource selection with various dispatching rules for queuing of jobs can improve or deteriorate their performance. Thus, choosing a proper queuing strategy for each algorithm is a prominent issue in scheduling. In this paper, we introduce two new dispatching rules for resource selection and three new dispatching rules for queuing of jobs; we evaluate the performance of various combinations of these new rule based scheduling algorithms and queuing strategies. Also, we use some major combination of rule based scheduling algorithms with some important queuing... 

The IP Lookup Process is a key bottleneck in routing due to the increase in routing table size, increasing traffic and migration to IPv6 addresses. The IP routing lookup involves computation of the Longest Prefix Matching for which existing solutions, such as BSD Radix Tries, scale poorly when traffic in the router increases or when employed for IPv6 address lookups. In this paper, we describe a CREW PRAM multiprocessor organization lookup that uses P processor for solving LPM problem. By this technique P-1 IP addresses can be looked up simultaneously thus the performance of processors increase in linear manner. First we categorize all prefixes in some groups based on their first two bytes...