Sharif Digital Repository

3D Network-on-Chips (3D NoCs) have higher scalability, higher throughput, and lower power consumption over 2D NoCs. However, the reliability of data transfer in 3D NoCs is seriously threatened by thermal problems. This is due to poor heat dissipation, inappropriate traffic distribution, and cooling restriction for layers away of the chip heat-sink in 3D NoCs. To solve this problem, this paper proposes an efficient deadlock-free and traffic-And thermal-Aware routing algorithm, called Floating XY-YX. The main idea behind Floating XY-YX routing algorithm is twofold: 1) to use XY and YX routing algorithms in consecutive layers in dessicate form, and 2) to evenly load the traffic, which is... 

Genetic algorithm for optimization of beam forming in spiral array antenna is used. The goal is to achieve a -20 dB in null over the wide frequency band. Our simulation shows -20 dB over 75 MHz Null Band width, in VHF band. © 2006 IEEE  

We study here the algorithmic analysis of systems modeled in terms of availability languages. Our first main result is a positive answer to the emptiness problem: it is decidable whether a given availability language contains a word. The key idea is an inductive construction that replaces availability languages with Parikh-equivalent regular languages. As a second contribution, we solve the intersection problem modulo bounded languages: given availability languages and a bounded language, it is decidable whether the intersection of the former contains a word from the bounded language. We show that the problem is NP-complete. The idea is to reduce to satisfiability of existential Presburger... 

In1985, Shmuley proposed a theorem about intractability of Composite Diffie-Hellman. The theorem of Shmuley may be paraphrased as saying that if there exist a probabilistic polynomial time oracle machine which solves the Diffie-Hellman modulo an RSA-number with odd-order bases then there exist a probabilistic algorithm which factors the modulo. In the other hand Shmuely proved the theorem only for odd-order bases and left the even-order case as an open problem. In this paper we show that the theorem is also true for even-order bases. Precisely speaking we prove that even if there exist a probabilistic polynomial time oracle machine which can solve the problem only for even-order bases still... 

Modeling and analyzing information system vulnerabilities help predict possible attacks to computer networks using vulnerabilities information and the network configuration. In this paper, we propose a comprehensive approach to analyze network vulnerabilities in order to answer the safety problem focusing on vulnerabilities. The approach which is called Vulnerability Take Grant (VTG) is a graph-based model consists of subject/objects as nodes and rights/relations as edges to represent the system protection state. Each node may have properties including single vulnerabilities such as buffer overflow. We use the new concept of vulnerability rewriting rule to specify the requirements and... 

In future wireless networks, network functions virtualization lays the foundations for establishing a new dynamic resource management framework to efficiently utilize network resources. In this paper, a network service can be viewed as a chain of virtual network functions (VNFs), called a service function chain (SFC), served via placement, admission control (AC), and embedding into network infrastructure, based on the resource management objectives and the state of network. To fully exploit such a potential and reach higher network performance, resource management stages should be jointly performed. To this end, two main challenges are: how to present a system model that formulates the... 

For a set of n disjoint line segments S in R2, the visibility counting problem (VCP) is to preprocess S such that the number of visible segments in S from a query point p can be computed quickly. For this configuration, the visibility testing problem (VTP) is to test whether p sees a fixed segment s. These problems can be solved in logarithmic query time by using O(n4) preprocessing time and space. In this paper, we approximately solve this problem using quadratic preprocessing time and space. Our methods are superior to current approximation algorithms in terms of both approximation factor and preprocessing cost. In this paper, we propose a 2-approximation algorithm for the VCP using at... 

Presented within this paper is the identification of impact force acting on a simply supported beam. The force identification is an inverse problem in which the measured response of the structure is used to determine the applied force. The identification problem is formulated as an optimization problem and genetic algorithm is utilized to solve the optimization problem. The objective function is calculated on the difference between analytical and measured responses and the decision variables are the location and magnitude of the applied force. The results from simulation show the effectiveness of the approach and its robustness to the measurement noise and sensor location  

An adaptive fuzzy sliding mode control scheme is presented in this article. Despite the advantages of sliding mode control design for uncertain dynamic systems, classical sliding mode control has a major problem in the form of chattering, produced by the rapid switching used to conduct the state trajectories toward the sliding surfaces. A variety of methods are used to achieve chattering-free motion by smoothing out the switching functions; a fuzzy method is introduced in this article. In the proposed approach, the switching functions are replaced by adaptive fuzzy control signals such that the Lyapunov stability conditions are satisfied. This adaptive fuzzy controller can improve the... 

This paper presents a reactive power valuation method with regard to its effect on realization of MW transactions. The security constraint optimization model in which the objective function is maximization of transactions is solved by the genetic algorithm approach. The proposed scheme allocates a specific amount of MW transactions to each dynamic reactive power source. An index is introduced to derive VAr value from the calculated optimal parameters of power network. This index represents the system-wide effect of MVAr sources on MW transactions implementations. Application of proposed method has been illustrated using IEEE 30 and 14 bus test systems. Results are discussed and compared in... 

In this paper, we first introduce a network of learning automata, which we call it as distributed learning automata and then propose some iterative algorithms for solving stochastic shortest path problem. These algorithms use distributed learning automata to find a policy that determines a path from a source node to a destination node with minimal expected cost (length). In these algorithms, at each stage distributed learning automata determines which edges to be sampled. This sampling method may result in decreasing unnecessary samples and hence decreasing the running time of algorithms. It is shown that the shortest path is found with a probability as close as to unity by proper choice of... 

In this study, two methods for solving economic dispatch problems, namely Hopfield neural network and X iteration method are compared. Three sample of power system with 3, 6 and 20 units have been considered. The time required for CPU, for solving economic dispatch of these two systems has been calculated. It has been shown that for on-line economic dispatch, Hopfield neural network is more efficient and the time required for convergence is considerably smaller compared to classical methods. © 2006 IEEE  

Fuzzy logic is a powerful problem-solving methodology that provides a remarkably simple way to draw definite conclusions from vague, ambiguous or imprecise information. This study is a review on the possibility of developing a tool to help site managers and planners in selecting the most suitable actions for construction productivity improvement in a complex construction site, using fuzzy logic theory. Improving productivity can have a large impact on the overall construction process and consequently result in significant time and cost savings, i.e. minimizing capital cost on the construction projects. Problems associated with productivity measurement such as "lack of a standard productivity... 

The distributed nature and complexity of computer networks and various services provided via them, makes the networks vulnerable to numerous attacks. The TCP/IP presumptions which are based on using this protocol to provide a simple, open communication infrastructure in an academic and collaborative environment, causes this protocol lack of built-in mechanisms for authentication, integrity and privacy. Even though in the last few years a more systematic approach to TCP/IP network security problem has been followed, a formal approach to this problem is lacking. In this paper, we propose using Description Logics as a formal model which could be used to analyze TCP/IP networks against attacks.... 

Grammar induction, also known as grammar inference, is one of the most important research areas in the domain of natural language processing. Availability of large corpora has encouraged many researchers to use statistical methods for grammar induction. This problem can be divided into three different categories of supervised, semi-supervised, and unsupervised, based on type of the required data set for the training phase. Most current inductive methods are supervised, which need a bracketed data set for their training phase; but the lack of this kind of data set in many languages, encouraged us to focus on unsupervised approaches. Here, we introduce a novel approach, which we call... 

In this paper, a new approach based on hybrid Particle Swarm-Based- Simulated Annealing Optimization (PSO-B-SA) for solving thermal unit commitment (UC) problems is proposed. The PSO-B-SA presented in this paper solves the two sub-problems simultaneously and independently; unit-scheduled problem that determines on/off status of units and the economic dispatch problem for production amount of generating units. Problem formulation of UC is defined as minimization of total objective function while satisfying all the associated constraints such as minimum up and down time, production limits and the required demand and spinning reserve. Simulation results show that the proposed approach can... 

This paper presents a bi-objective vendor managed inventory (BOVMI) model for a supply chain problem with a single vendor and multiple retailers, in which the demand is fuzzy and the vendor manages the retailers' inventory in a central warehouse. The vendor confronts two constraints: number of orders and available budget. In this model, the fuzzy demand is formulated using trapezoidal fuzzy number (TrFN) where the centroid defuzzification method is employed to defuzzify fuzzy output functions. Minimizing both the total inventory cost and the warehouse space are the two objectives of the model. Since the proposed model is formulated into a bi-objective integer nonlinear programming (INLP)... 

This paper presents optimal scheduling in a two-machine flow shop, in which the objective function is to minimize the sum of maximum earliness and tardiness (n/2/P/ETmax). Since this problem tries to minimize earliness and tardiness, the results can be useful for different production systems such as just in time (JIT). This objective function has already been considered for n jobs and m machines, but the proposed algorithms are not efficient to solve large scale problems. In this paper, neighborhood conditions are developed and the dominant set for any optimal solution is determined. The branch-and-bound (B&B) method is used to solve the problem and the proper upper and lower bounds are also...