Sharif Digital Repository

This paper presents a solution to the boundary stabilization of a FGM plate in free transverse vibration. The composite laminated plate dynamics is presented by a linear forth order partial differential equation (PDE). A linear control law is constructed to stabilize the plate. The control force consists of feedback of the velocity at the boundaries of plate. The novelty of this article is that it is possible to stabilize asymptotically a free transversely vibrating composite plate with simply supported or clamped boundary condition via boundary control without resorting to truncation of the model. © 2008 IEEE  

In this study, silicon microchannel heat sink (MCHS) performance using nanofluids as coolants was analyzed. The nanofluid was a mixture of nanoscale Cu particles and pure water with various volume fractions. Based on theoretical models and experimental correlations, the heat transfer and friction coefficients required in the analysis were used. In the theoretical model, nanofluid was treated as a single-phase fluid. In the experimental correlation, thermal dispersion due to particle random motion was included. The microchannel heat sink performances for a specific geometries with Wch = W fin = 100 μm and Lch =300 μm is examined. In this study, flow in laminar and turbulent regimes using the... 

Dealing with crosscutting requirements in software development usually makes the process more complex. Modeling and analyzing of these requirements in the software architecture facilitate detecting architectural risks early. Distributed systems have more complexity and so these facilities are much useful in development of such systems. Aspect oriented Architectural Description Languages(ADL) have emerged to represent solutions for discussed problems; nevertheless, imposing radical changes to existing architectural modeling methods is not easily acceptable by architects. Software architecture analysis methods, furthermore, intend to verify that the quality requirements have been addressed... 

Because of several vulnerabilities in software products and high amount of damage caused by them, software developers are enforced to produce more secure systems. Software grows up through its life cycle, so software development methodologies should pay special attention to security aspects of the product. This paper focuses on agile methodologies in order to equip them with security activities. We can restrain reduction of agile nature of organization's current process by means of agility measurement and applying an efficient activity integration algorithm with a tunable parameter named agility reduction tolerance (ART). Using this approach, method engineer of the project can enhance his... 

In this paper, a novel clustering algorithm using an agent-based architecture along with a force-based clustering algorithm is proposed. To this end, a set of simple mobile agents thai have limited processing power is used. These agents communicate in a pairwise manner to exchange their position information. As opposed to the bio-inspired clustering algorithms that need a set of local rules to specify the agent movements, in this paper the agent motions are driven from attractive and repulsive potential fields that are created by the data points and the other agents respectively. Each agent moves according to the resulted force from applying the potential fields and announces its next... 

This paper proposes a Distant Speech Recognition system based on a novel speaker Localization and Beamforming (SRLB) algorithm. To localize the speaker an algorithm based on Steered Response Power by utilizing harmonic structures of speech signal is proposed. This new scheme has the ability of speaker verification by fundamental frequency variation: therefore it can be utilized in the design of a speech recognition system for verified speakers. Then the performance of the Farsi speech recognition engine is evaluated under notorious conditions of noise and reverberation. Simulation results and tests on real data shows that by utilizing proposed localization scheme, recognition accuracy... 

VoIP over WLAN is a promising technology as a powerful replacement for current local wireless telephony systems. Packet timing Jitter is a constant issue in QoS of IEEE802.11 networks and exploiting an optimum jitter handling algorithm is an essential part of any VoIP over WLAN (VoWiFi) devices especially for the low cost devices with limited resources. In this paper two common algorithms using buffer as a method for Jitter handling are analyzed with relation to different traffic patterns. The effect of different buffer sizes on the quality of voice will be assessed for these patterns. Various traffic patterns were generated using OPNET and Quality of output voice was evaluated based on ITU... 

In this paper, advantages of energy-efficient motors over standard-motors in terms of electrical energy saving and demand reduction in a tire-rubber factory are thoroughly evaluated. Energy-efficient motors reduce losses because of their better design, materials, and manufacturing. These motors are 2 to 8% more efficient than standard ones. Lengthening the core and using lower-electrical-loss steel, thinner stator laminations, and more copper in the windings reduce electrical losses. Because a motor consumes energy worth 4 to 10 times its own cost each year, energy-efficient motors often make economic sense in a wide variety of applications. At the end of this study, the amount of energy... 

Fractional order PID controllers are suitable for almost all types of dynamic models. In this paper, a new adaptive fractional order PID controller using neural networks is introduced.The overall performance using the proposed adaptive fractional order PID controller is demonstrated through some examples. It is shown that the new controller scheme can give excellent performance and more robustness in comparison with the conventional controllers like GPC  

Carbon nanotubes are widely used in the design of nanosensors and actuators. Any defect in the manufactured nanotube plays an important role in the natural frequencies of these structures. In this paper, the effect of vacancy defects on the vibration of carbon nanotubes is investigated by using an atomistic modeling technique, called the molecular structural mechanics method. Vibration analysis is performed for armchair and zigzag nanotubes with cantilever boundary condition. The shift of the principal frequency of the nanotube with vacancy defect at different locations on the length is plotted. The results indicate that the frequency of the defective nanotube can be larger or smaller or... 

In this paper, we use simulated annealing heuristics for constructing an intrusion detection system (IDS). The proposed IDS combines the learning ability of simulated annealing heuristics with the approximate reasoning method of fuzzy systems. The use of simulated annealing is an effort to effectively explore the large search space related to intrusion detection problems, and find the optimum set of fuzzy if-then rules. The aim of this paper is to present the capability of simulated annealing based fuzzy system to deal with intrusion detection classification problem as a new real-world application area. Experiments were performed with KDD-Cup99 intrusion detection benchmark data set. © 2008... 

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 confront with flexibility challenges and scalability problems. This is mainly because of that 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 have been proposed to... 

k-Neigh is a basic neighbor-based topology control protocol based on the construction of k-neighbor graph as logical communication graph. Although k-Neigh is based on a connectivity theory, several topological aspects of the constructed topology are not yet analytically investigated. In this paper, several topological properties of the constructed topology after execution of the protocol, including probability density function of the distance between each node to its ith neighbor, probability of unidirectional links after execution of the first phase of the protocol, average logical degree, and average final transmission range, are investigated analytically. Moreover, an extensive simulation... 

Modeling languages are needed to describe the conceptual construct underlying software. Several modeling languages have been proposed during the last decades. In order to properly understand and assess software modeling languages, we believe that a set of techniques is needed. In this paper, we describe several techniques that can be applied for studying and evaluating cognitive complexity (comprehensibility) of software modeling languages. These techniques have been applied to human-computer interaction, human languages, programming languages and cognitive science before. © 2008 IEEE  

Peer-to-peer networks have gained a tremendous popularity in sharing huge volumes of data. Success of such networks highly depends on the performance of their search algorithm. We propose a semantic based search algorithm for unstructured peer-to-peer networks. In the proposed method we establish ontology based indexes for outgoing links of each node, which are utilized in routing the query through the network. In contrast to available approaches, we maintain limited size indexes and also consider number of documents accessible via each link and the distance between source and destination nodes, to improve the accuracy and efficiency of our algorithm. Our design is scalable and adaptable, to... 

OMG's Model Driven Architecture (MDA) has deeply influenced modern-day software development, not only by providing promising means for automating the software process, but also through revitalizing the role of modeling in software development, the importance of which had been neglected during the recent euphoria over lightweight development methods. However, MDA's need to remain reasonably abstract means that it is more a software development approach rather than a standalone methodology, and therefore needs methodology support to be practically useful. Several MDA-based methodologies exist today, yet the need remains for the definition of an instantiable MDA-based development process. We... 

Several e-business frameworks are developed to define standards for information sharing within and between companies. These frameworks only standardize structure of messages and aren't able to define semantics. It leads to slow and costly dynamic Business-to-Business (B2B) integration. The use of Semantic Web Senice (SWS) technologies has been suggested to enable more dynamic B2B integration of heterogeneous systems and partners. We present a semantic B2B mediator based on the WSMX -a SWS execution environment, to tackle heterogeneities in B2B services. We particularly show how WSMX can be made to support the RosettaNet e-business framework and how it can add dynamics to B2B interactions by... 

This article proposes a new architecture for distributed data management and update massage exchange in massively multiuser virtual environments. The key points in the design of such environments are scalability and QoS-aware message delivery. Therefore it requires robust distributed algorithms in a dynamic peer-to-peer system with frequent node arrivals and departures. Our proposed approach is mainly based on distributed hash tables (DHTs) in order to achieve a decentralized system where any participating node can efficiently retrieve the updates associated with a given object. Therefore, the responsibility of maintaining the mapping from names to values is distributed among the nodes in a... 

Massively multi user virtual environment (MMVE) applications must deal with the challenge of update message exchange among a large set of nodes distributed over the Internet. Therefore design of scalable network protocols is a major concern in such large scale distributed architectures. Several approaches have been proposed to aid update exchange in MMVEs. Message localization has always been a key point in the design of such distributed network protocols. Area of Interest Management (AoIM) mainly deals with the issues related to the update message localization with respect to the user's interest. As the number of users in the virtual environment increases, update message localization... 

Low scalability and power efficiency of the shared bus in SoCs is a motivation to use on chip networks instead of traditional buses. In this paper we have modified the Orion power model to reach an analytical model to estimate the average message energy in K-Ary n-Cubes with focus on the number of virtual channels. Afterward by using the power model and also the performance model proposed in [11] the effect of number of virtual channels on Energy-Delay product have been analyzed. In addition a cycle accurate power and performance simulator have been implemented in VHDL to verify the results. ©2008 IEEE