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Total 129 records

    Modeling performance of distributed programs by stochastic decision free petri nets

    , Article Scientia Iranica ; Volume 8, Issue 4 , 2001 , Pages 287-296 ; 10263098 (ISSN) Ghodsi, M ; Sharif University of Technology
    Sharif University of Technology  2001
    Abstract
    In this paper, performance modeling of synchronization delays is considered in a distributed program which consists of a number of processes that interact via message passing only. A class of timed Petri nets called Stochastic Decision Free Petri Nets (SDFPNs) is used to model such distributed programs with deterministic control flow. An exact solution technique is proposed for this model which does not follow the usual approach of reachability analysis for Petri nets and solving global balance equations for a Markovian system. Therefore, it does not require exponential distributions and does not suffer from state space explosion. The complexity of exact solution is still exponential in... 

    High radix signed digit number systems: Representation paradigms

    , Article Scientia Iranica ; Volume 10, Issue 4 , 2003 , Pages 383-391 ; 10263098 (ISSN) Jaberipur, G ; Ghodsi, M ; Sharif University of Technology
    Sharif University of Technology  2003
    Abstract
    Redundant signed digit number systems are popular in computationally intensive environments, particularly because of their carry-free property, which allows for digit-parallel addition. The time required for addition is particularly important because other arithmetic operations heavily depend on it. Signed digit number systems with high radices are of particular interest because of less memory requirement to represent a given number. But, the time required to perform digit-parallel addition is, by a relatively large coefficient, logarithmically proportional to the radix. Reduction of this coefficient is the prime goal of the study in this paper, where least cost implementations are... 

    Fundamentals of Java programming

    , Book Ogihara, Mitsunori
    Springer International Publishing AG  2018

    A survey of syntax and semantics frameworks of modeling languages

    , Article Proceedings of the 2009 2nd International Conference on Computer Science and Its Applications, CSA 2009 ; 2009 ; 9781424449460 (ISBN) Kamandi, A ; Habibi, J ; Sharif University of Technology
    Abstract
    Modeling languages as programming languages need precise and unambiguous semantics to be used appropriately, the formal semantics is significant for designing CASE tools and model verification. Several approaches have been used throughout these years to describe the semantics of modeling languages, but in spite of programming languages, these semantics frameworks are not used in large scale for modeling languages. This paper reviews the history of developments on semantics frameworks for modeling languages. © 2009 IEEE  

    Optimal installation capacity of medium hydro-power plants considering technical, economic and reliability indices

    , Article International Journal of Power and Energy Systems ; Volume 28, Issue 1 , 2008 , Pages 15-22 ; 10783466 (ISSN) Hosseini, S. M. H ; Forouzbakhsh, F ; Fotuhi Firuzabad, M ; Sharif University of Technology
    Acta Press  2008
    Abstract
    One of the most important issues in planning the reservoir type of Medium Hydro-Power Plants (MHPP) is to determine the optimal installation capacity of the MHPP and estimate its optimal annual energy value. In this paper, a method is presented to calculate the annual energy. A computer program has been developed to analyse energy calculation and estimation of the most important economic indices of an MHPP using the sensitivity analysis method. Another program, developed by Matlab software, calculates the reliability indices for a number of units of an MHPP with a specified load duration curve using the Monte Carlo method. Ultimately, comparing the technical, economic and reliability indices... 

    Utility constrained energy minimization in aloha networks

    , Article 2007 4th Annual IEEE Consumer Communications and Networking Conference, CCNC 2007, Las Vegas, NV, 11 January 2007 through 13 January 2007 ; January , 2007 , Pages 665-669 ; 1424406668 (ISBN); 9781424406661 (ISBN) Khodaian, A ; Hossein Khalaj, B ; Talebi, M. S ; Sharif University of Technology
    2007
    Abstract
    In this paper we consider the issue of energy efficiency in random access networks and show that optimizing transmission probabilities of nodes can enhance network performance in terms of energy consumption and fairness. First, we propose a heuristic power control method that improves throughput, and then we model the Utility Constrained Energy Minimization (UCEM) problem in which the utility constraint takes into account single and multi node performance. UCEM is modeled as a convex optimization problem and Sequential Quadratic Programming (SQP) is used to find optimal transmission probabilities. Numerical results show that our method can achieve fairness, reduce energy consumption and... 

    Kinetic parameters estimation of MgO-C refractory by shrinking core model

    , Article Journal of Materials Science and Technology ; Volume 22, Issue 6 , 2006 , Pages 826-832 ; 10050302 (ISSN) Hashemi, B ; Nemati, Z. A ; Sadrnezhaad, S. K ; Moghimi, Z. A ; Sharif University of Technology
    2006
    Abstract
    Kinetics of oxidation of MgO-C refractories was investigated by shrinking core modeling of the gas-solid reactions taking place during heating the porous materials to the high temperatures. Samples containing 4.5-17 wt pct graphite were isothermally oxidized at 1000-1350°C. Weight loss data was compared with predictions of the model. A mixed 2-stage mechanism comprised of pore diffusion plus boundary layer gas transfer was shown to generally control the oxidation rate. Pore diffusion was however more effective, especially at graphite contents lower than 10 wt pct under forced convection blowing of the air. Model calculations showed that effective gas diffusion coefficients were in the range... 

    A procedure for obtaining a behavioral description for the control logic of a non-linear pipeline

    , Article Proceedings of the ASP - DAC 2004 Asia and South Pacific Design Automation Conference - 2004, Yokohama, 27 January 2004 through 30 January 2004 ; 2004 , Pages 86-91 Najaf Abadi, H. H ; Sharif University of Technology
    2004
    Abstract
    Much attention has been directed to different aspects of the design of pipelines. Design of the control logic of non-linear pipelines has however, been considered as a subsidiary issue in that an RTL description for such logic can easily be obtained from a behavioral description, with the use of widely available synthesis tools. But, as the complexity of a non-linear pipeline increases, so does the complexity of the control logic. The complexity may be to an extent that obtaining even a behavioral description for the control logic is rendered difficult. This paper focuses on further automating the development of systems consisting of non-linear or multi-function pipelines by proposing an... 

    Syllable duration prediction for Farsi text-to-speech systems

    , Article Scientia Iranica ; Volume 11, Issue 3 , 2004 , Pages 225-233 ; 10263098 (ISSN) Nazari, B ; Nayebi, K ; Sheikhzadeh, H ; Sharif University of Technology
    Sharif University of Technology  2004
    Abstract
    In this paper, two different statistical approaches are used for duration prediction of the Farsi language. These two statistical models are Neural Networks (NN) and Classification And Regression Trees (CART). The first step in this work was to create a database and develop a flexible feature extraction and selection module. In the next step, the output of the feature selection module was used to train both models. The results of the trained models are further studied to determine the most important parameters affecting the syllable duration in Farsi, The model accuracy is evaluated by using separate training and test data. In the third step of this work, ah automatic rule generator module... 

    Toward an intelligent approach for determination of saturation pressure of crude oil

    , Article Fuel Processing Technology ; Volume 115 , 2013 , Pages 201-214 ; 03783820 (ISSN) Farasat, A ; Shokrollahi, A ; Arabloo, M ; Gharagheizi, F ; Mohammadi, A. H ; Sharif University of Technology
    2013
    Abstract
    Bubble point pressure is a crucial PVT parameter of reservoir fluids, which has a significant effect on oil field development strategies, reservoir evaluation and production calculations. This communication presents a new mathematical model to calculate the saturation pressures of crude oils as a function of temperature, hydrocarbon and non-hydrocarbon reservoir fluid compositions, and characteristics of the heptane-plus fraction. The model was developed and tested using a total set of 130 experimentally measured compositions and saturation pressures of crude oil samples from different geographical locations covering wide ranges of crude oil properties and reservoir temperatures. In-depth... 

    Impacts of relays coordination and alternate supply availability on radial sub-transmission networks reliability assessment

    , Article 2005 IEEE/PES Transmission and DistributionConference and Exhibition - Asia and Pacific, Dalian, 15 August 2005 through 18 August 2005 ; Volume 2005 , 2005 , Pages 1-5 ; 0780391144 (ISBN); 9780780391147 (ISBN) Ahmadi, I ; Barforoushi, T ; Fotuhi Firuzabad, M ; Yazdian Variani, A ; Sharif University of Technology
    2005
    Abstract
    Protection systems play a major role in the performance of electric power systems. There are a number of techniques such as redundancy within the relay system or local and remote backup methods to improve protection system reliability to remove faults as fast as possible, coordination of protective relays is very important. Also availability to neighboring systems affects significantly on repair time after occurring an event. An approach is presented in this paper to incorporate relay coordination and alternative supply availability on radial sub-transmission system reliability. For this purpose, a computer program has been developed. As a case study, a practical 63 KV sub-transmission... 

    A new human interactive proofs system for deaf persons

    , Article International Conference on Information Technology: New Generations, ITNG 2008, Las Vegas, NV, 7 April 2008 through 9 April 2008 ; 2008 , Pages 807-810 ; 0769530990 (ISBN); 9780769530994 (ISBN) Shirali Shahreza, S ; Shirali Shahreza, M ; Sharif University of Technology
    2008
    Abstract
    Nowadays the Internet users are from different ages and groups. Disabled people are a group of the Internet users. Some websites are especially created for disabled people and public access to them is undesirable. In this paper, for the first time, a method is introduced for distinguishing between deaf persons and other users using a new HIP (Human Interactive Proofs) system. In this method, the sign language is used. A word is shown as a movie using a sign language. The user should recognize the word and select it from a list. Only deaf persons can understand sign language and recognize the word, therefore other persons and also computer programs cannot enter the website. This project has... 

    A new approach in object-oriented methodology for creating event-based simulator

    , Article 2006 Canadian Conference on Electrical and Computer Engineering, CCECE'06, Ottawa, ON, 7 May 2006 through 10 May 2006 ; 2006 , Pages 2424-2427 ; 08407789 (ISSN); 1424400384 (ISBN); 9781424400386 (ISBN) Aliakbarian, S ; Abdollahzadeh, A ; Jalali, L ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Abstract
    This paper explores software design methodologies in the context of creating a simulator and proposes a methodology to design and implement an event-based simulator namely Sim Met. SimMet is explored in the context of the development of a complex simulator for simulating real world conditions to use in science, technology and medicine and other simulations. In this paper we interested in event-based approach to create a real world with variety range of event possibilities. The paper first discusses the role of time concept as the cornerstone of a methodical analysis and design phase. In Sim Met we use an adaptation of object-oriented methodology to meet time and event concepts in creating a... 

    On validity assurance of dynamic reconfiguration for component-based programs

    , Article Electronic Notes in Theoretical Computer Science ; Volume 159, Issue 1 , 2006 , Pages 227-239 ; 15710661 (ISSN) Niamanesh, M ; Fekrazad Nobakht, N ; Jalili, R ; Heydarian Dehkordi, F ; Sharif University of Technology
    2006
    Abstract
    Growing the need for long-life and high-available programs, dynamic reconfiguration is going to be an important research issue. Dynamic reconfiguration enables the software systems to change at runtime to decrease their down-time in case of any updating, upgrading or in any changes. Any invalid reconfiguration at runtime may lead programs into invalid states. In this paper, we investigate on validity of dynamic reconfiguration for component-based programs and propose validity conditions for it. We show that the problem of validity assurance in general is undecidable and there is no general-purpose algorithm to verify dynamic reconfiguration validity. To have a computable algorithm for... 

    Integrating model checking and deduction for Rebeca

    , Article Scientia Iranica ; Volume 12, Issue 1 , 2005 , Pages 55-65 ; 10263098 (ISSN) Sirjani, M ; Movaghar, A ; Sharif University of Technology
    Sharif University of Technology  2005
    Abstract
    Rebeca is an actor-based language for modeling concurrent and distributed systems. Its Java-like syntax makes it easy-to-use for practitioners and its formal foundation is a basis to make different formal verification approaches applicable. Compositional verification and abstraction techniques are used in formal verification of Rebeca models to overcome state explosion problems. The main contribution of this paper is to show how model checking and deduction are integrated for verifying certain properties of these models. Deduction is used to prove that abstraction techniques preserve a set of behavioral specifications in temporal logic and is also used in applying the compositional... 

    Extended Rebeca: A component-based actor language with synchronous message passing

    , Article 5th International Conference on Application of Concurrency to System Design, ACSD 2005, St. Malo, 7 June 2005 through 9 June 2005 ; Volume 2005 , 2005 , Pages 212-220 ; 15504808 (ISSN); 0769523633 (ISBN); 9780769523637 (ISBN) Sirjani, M ; De Boer, F ; Movaghar, A ; Shali, A ; Sharif University of Technology
    2005
    Abstract
    In this paper, we propose extended Rebeca as a tool-supported actor-based language for modeling and verifying concurrent and distributed systems. We enrich Rebeca with a formal concept of components which integrates the message-driven computational model of actor-based languages with synchronous message passing. Components are used to encapsulate a set of internal active objects which react asynchronously to messages by means of methods and which additionally interact via a synchronous message passing mechanism. Components themselves interact only via asynchronous and anonymous messages. We present our compositional verification approach and abstraction techniques, and the theory... 

    Efficient polynomial root finding using SIMD extensions

    , Article 11th International Conference on Parallel and Distributed Systems Workshops, ICPADS 2005, Fukuoka, 20 July 2005 through 22 July 2005 ; Volume 2 , 2005 , Pages 529-533 ; 15219097 (ISSN); 0769522815 (ISBN) Moslemi, M ; Ahmadi, H ; Sarbazi Azad, H ; Ma J ; Yang L. T ; Sharif University of Technology
    2005
    Abstract
    In this paper, the parallel implementations of different iterative polynomial root finding methods on a processor with SIMD processing capability are reported. These methods are based on the construction of a sequence of approximations that converge to the set of roots. We have chosen four widely used methods namely Newton's, Durand-Kerner's, Aberth-Ehrlich's, and QD and implemented them using the SIMD instruction set of the Pentium processor with C++ and assembly language. Experiments show that a speedup of 3 or higher can be achieved, depending on the order of polynomial, required accuracy, and the method employed. © 2005 IEEE  

    Risk assessment of vapor cloud explosions in a hydrogen production facility with consequence modeling

    , Article Journal of Research in Health Sciences ; Volume 13, Issue 2 , 2013 , Pages 181-187 ; 16822765 (ISSN) Zarei, E ; Jafari, M. J ; Badri, N ; Sharif University of Technology
    2013
    Abstract
    Background: New technologies using hazardous materials usually have certain risks. It is more serious when the technology is supposed to be applied in a large scale and become widely used by many people. The objective of this paper was to evaluate the risk of vapor cloud explosion in a hydrogen production process. Methods: Potential hazards were identified using the conventional hazard identification method (HAZID). The frequency of the proposed scenarios was estimated from statistical data and existing records. The PHAST professional software was applied for consequence modeling. Both individual and societal risks were evaluated. This cross-sectional study was conducted from June 2010 to... 

    NETAL: A new graph-based method for global alignment of protein-protein interaction networks

    , Article Bioinformatics ; Volume 29, Issue 13 , 2013 , Pages 1654-1662 ; 13674803 (ISSN) Neyshabur, B ; Khadem, A ; Hashemifar, S ; Arab, S. S ; Sharif University of Technology
    2013
    Abstract
    Motivation: The interactions among proteins and the resulting networks of such interactions have a central role in cell biology. Aligning these networks gives us important information, such as conserved complexes and evolutionary relationships. Although there have been several publications on the global alignment of protein networks; however, none of proposed methods are able to produce a highly conserved and meaningful alignment. Moreover, time complexity of current algorithms makes them impossible to use for multiple alignment of several large networks together.Results: We present a novel algorithm for the global alignment of protein-protein interaction networks. It uses a greedy method,...