Search for: analytical-modelling
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    Analysis of a dynamic assignment of impatient customers to parallel queues

    , Article Queueing Systems ; Volume 67, Issue 3 , 2011 , Pages 251-273 ; 02570130 (ISSN) Movaghar, A ; Sharif University of Technology
    Consider a number of parallel queues, each with an arbitrary capacity and multiple identical exponential servers. The service discipline in each queue is first-come-first-served (FCFS). Customers arrive according to a state-dependent Poisson process. Upon arrival, a customer joins a queue according to a state-dependent policy or leaves the system immediately if it is full. No jockeying among queues is allowed. An incoming customer to a parallel queue has a general patience time dependent on that queue after which he/she must depart from the system immediately. Parallel queues are of two types: type 1, wherein the impatience mechanism acts on the waiting time; or type 2, a single server queue... 

    Analytical model based on cohesive energy to indicate the edge and corner effects on melting temperature of metallic nanoparticles

    , Article Chemical Physics ; Volume 378, Issue 1-3 , 2010 , Pages 14-18 ; 03010104 (ISSN) Shidpour, R ; Delavari H. H ; Vossoughi, M ; Sharif University of Technology
    An analytical model based on cohesive energy has been conducted to study the effects of edge, corner, and inward surface relaxation as varying parameters on melting temperature of nanoparticles. It is shown that taking into account the edge and corner (EC) atoms of nanoparticle, causes to drop melting temperature more, when compared to consider them the same as only surface atoms. This reduction is significant especially when the size of nanoparticle is below 10 nm. The results are supported by available experimental results of tin, lead and gold melting temperature (Tm). Finally, it is shown that inward relaxation increases melting temperature slightly  

    A New Analytical Simulator for the Provisioning Stage of IoT-based WSNs

    , Article 3rd CSI/CPSSI International Symposium on Real-Time and Embedded Systems and Technologies, RTEST 2020, 10 June 2020 through 11 June 2020 ; 2020 Sadeghi, P ; Ejlali, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    With IoT devices becoming abundant and WSN applications becoming evermore present, the once dream of ubiquitous connectivity is closer to realization than ever before. but this realization is hindered by many technical problems and lengthy time to markets. Currently, our best practice of feasibility analysis relies in the same simulators used to model and develop the network applications. Because of their broad range and immense usability challenges, these jack-of-all-trades simulators tend to be computation-intensive and hard to work with.Here, we propose a relatively light-weight simulator based on the analytical models of different parts of the network to aid in rapid development and ease... 

    Computing accurate performance bounds for best effort networks-on-chip

    , Article IEEE Transactions on Computers ; Volume 62, Issue 3 , 2013 , Pages 452-467 ; 00189340 (ISSN) Rahmati, D ; Murali, S ; Benini, L ; Angiolini, F ; De Micheli, G ; Sarbazi Azad, H ; Sharif University of Technology
    Real-time (RT) communication support is a critical requirement for many complex embedded applications which are currently targeted to Network-on-chip (NoC) platforms. In this paper, we present novel methods to efficiently calculate worst case bandwidth and latency bounds for RT traffic streams on wormhole-switched NoCs with arbitrary topology. The proposed methods apply to best-effort NoC architectures, with no extra hardware dedicated to RT traffic support. By applying our methods to several realistic NoC designs, we show substantial improvements (more than 30 percent in bandwidth and 50 percent in latency, on average) in bound tightness with respect to existing approaches  

    Analysis of gossip-based information propagation in wireless mesh networks

    , Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 12 October 2011 through 13 October 2011, Borrowdale ; Volume 6977 LNCS , 2011 , Pages 174-188 ; 03029743 (ISSN) ; 9783642247484 (ISBN) Shamsaie, A ; Fokkink, W ; Habibi, J ; Sharif University of Technology
    Analytical models exist for evaluating gossip-based information propagation. Up to now these models were developed only for fully connected networks. We provide analytical models for information propagation of a push-pull gossiping protocol in a wireless mesh network. The underlying topology is abstracted away by assuming that the wireless nodes are uniformly deployed. We compare our models with simulation results for different topologies  

    Analytical modeling of phosphorene-based NO2 gas sensor

    , Article International Journal of Modern Physics B ; Volume 33, Issue 14 , 2019 ; 02179792 (ISSN) Mansouri, E ; Karamdel, J ; Ahmadi, M. T ; Berahman, M ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2019
    Phosphorene is a new two-dimensional material that has great potentials in Nano electronic application, so it has attracted more researchers' attention nowadays. Indeed, phosphorene is an interesting material in gas sensing, due to its high surface-to-volume ratio and its carrier mobility. Many studies have been reported on phosphorene gas sensing, but there is not enough study on analytical modeling of phosphorene gas sensing properties. In this research, by adopting data from experimental NO2-based gas sensor, an analytical model of the phosphorene gas sensing behavior is presented. Then, the experimental results of NO2 gas sensing are compared with the proposed model and acceptable... 

    Brace-frame interaction in tension braced MRFs

    , Article International Conference on Numerical Analysis and Applied Mathematics, ICNAAM 2008, Psalidi, Kos, 16 September 2008 through 20 September 2008 ; Volume 1048 , 2008 , Pages 364-367 ; 0094243X (ISSN); 9780735405769 (ISBN) Lotfollahi, M ; Mofid, M ; Alinia, M. M ; Greek Ministry of Education and Religious Affairs; European Soc. Computational Methods in Sci. Eng. (ESCMSE) ; Sharif University of Technology
    This study investigates the possibility of sequential failure analysis of Tension Braced Moment Resisting Frames (TBMRFs) by examining its performance in the linear and nonlinear stages under idealized seismic loading conditions. The results obtained from rigorous analyses by means of numerical methods are utilized to set up and calibrate an analytical model which would appropriately differentiate the contribution shares of the frame and the bracing elements. The paper provides information on key response parameters, including interaction value between frame and brace elements, as well as tensile strength capacity and ductility capability of such systems. © 2008 American Institute of Physics... 

    Analytical leakage-aware thermal modeling of a real-time system

    , Article IEEE Transactions on Computers ; Vol. 63, issue. 6 , 2014 , pp. 1377-1391 ; ISSN: 00189340 Mohaqeqi, M ; Kargahi, M ; Movaghar, A ; Sharif University of Technology
    We consider a firm real-time system with a single processor working in two power modes depending on whether it is idle or executing a job. The system is equipped with dynamic thermal management through a cooling subsystem which can switch between two cooling modes. Real-time jobs which arrive to the system have stochastic properties and are prone to soft errors. A successful job is one that enters the system and completes its execution with no timing or soft error. Appropriateness of the system is evaluated based on its performance, temperature behavior, reliability, and energy consumption. It is noteworthy that these criteria have mutual interactions to each other: the stochastic nature of... 

    Locomotion modes of a novel piezo-driven microrobot: Analytical modeling and performance evaluation

    , Article Mechanism and Machine Theory ; Volume 52 , 2012 , Pages 248-266 ; 0094114X (ISSN) Eigoli, A. K ; Vossoughi, G. R ; Sharif University of Technology
    This paper presents a novel, sliding, A-shaped microrobot with nanometric resolution for precision positioning applications. The microrobot is actuated near its natural frequency using a piezoelectric stack actuator to produce translational motion. The dynamic modeling of the mechanism is based on the assumptions of the linear piezoelectric behavior and the Coulomb friction model. Using this model the required condition for generating net motion is found. The suitability of three simple, friction-based locomotion modes for implementation on the proposed device is addressed. Influences of some important configuration parameters on the behavior of the microrobot, based on defined criteria, are... 

    Analytical prediction of the temperature field in laser assisted machining

    , Article Procedia CIRP, 31 May 2016 through 2 June 2016 ; Volume 46 , 2016 , Pages 575-578 ; 22128271 (ISSN) Kashani, M. M ; Movahhedy, M. R ; Ahmadian, M. T ; Razavi, R. S ; Sharif University of Technology
    Elsevier  2016
    Laser assisted machining (LAM) is a promising technology for machining hard to cut materials. In most experimental cases, LAM is undergone in two stages; first, the temperature at the material removal point (Tmr) is tuned by adjusting laser parameters and next, the cutting tool is engaged. Introduction of highly localized heat energy to the workpiece makes the modeling of this process very complicated. Hence, an analytical model for the first stage of the process - rather than multiple experiments or FE modelling - would be beneficial. This article presents an analytical solution to the transient, temperature field in a rotating cylinder subject to a localized laser heat source. The... 

    Experimental and analytical study of thermohydraulic performance of a novel loop heat pipe with an innovative active temperature control method

    , Article Applied Thermal Engineering ; Volume 143 , 2018 , Pages 964-976 ; 13594311 (ISSN) Khalili, M ; Mostafazade Abolmaali, A ; Shafii, M. B ; Sharif University of Technology
    In this study, a novel type of LHP is innovated, fabricated, and its performance is assessed by numerous experiments. Compared to conventional LHPs, this novel design has some modifications in its evaporator and reservoir configuration. This particular type has a simpler and less costly fabrication procedure compared to other LHPs and it yields acceptable performance. Additionally, a novel method is introduced to control the temperature distribution in the system. A steel ball is placed in the evaporator to actively control the operating temperature. The ball is moved by two magnets installed outside of the evaporator. Moreover, a steady-state one-dimensional mathematical model of the... 

    Effect of initial surface treatment on shot peening residual stress field: analytical approach with experimental verification

    , Article International Journal of Mechanical Sciences ; Volume 137 , 2018 , Pages 171-181 ; 00207403 (ISSN) Sherafatnia, K ; Farrahi, G. H ; Mahmoudi, A. H ; Sharif University of Technology
    Elsevier Ltd  2018
    Shot peening is the most common surface treatment employed to enhance the fatigue performance of structural metallic materials and often carried out after other surface treatments. This paper mainly focuses on the effects of initial conditions of surface such as initial stress filed and hardness profile on shot peening residual stress field. The residual stress distribution induced by shot peening is obtained using Hertzian contact theory and elastic–plastic evaluation after yielding occurred during impingement and rebound of shots. Elastic plastic calculations are performed using different hardening models considering Bauschinger effect. The present model is able to predict redistribution... 

    A general mathematical performance model for wormhole-switched irregular networks

    , Article Cluster Computing ; Volume 12, Issue 3 , 2009 , Pages 285-297 ; 13867857 (ISSN) Moraveji, R ; Moinzadeh, P ; Sarbazi Azad, H ; Sharif University of Technology
    Irregular topologies are desirable network structures for building scalable cluster systems and very recently they have also been employed in SoC (system-on-chip) design. Many analytical models have been proposed in the literature to evaluate the performance of networks with different topologies such as hypercube, torus, mesh, hypermesh, Cartesian product networks, star graph, and k-ary n-cube; however, to the best of our knowledge, no mathematical model has been presented for irregular networks. Therefore, as an effort to fill this gap, this paper presents a comprehensive mathematical model for fully adaptive routing in wormhole-switched irregular networks. Moreover, since our approach... 

    An analytical model for performance and lifetime estimation of hybrid DRAM-NVM main memories

    , Article IEEE Transactions on Computers ; Volume 68, Issue 8 , 2019 , Pages 1114-1130 ; 00189340 (ISSN) Salkhordeh, R ; Mutlu, O ; Asadi, H ; Sharif University of Technology
    IEEE Computer Society  2019
    Emerging Non-Volatile Memories (NVMs) have promising advantages (e.g., lower idle power, higher density, and non-volatility) over the existing predominant main memory technology, DRAM. Yet, NVMs also have disadvantages (e.g., longer latencies, higher active power, and limited endurance). System architects are therefore examining hybrid DRAM-NVM main memories to enable the advantages of NVMs while avoiding the disadvantages as much as possible. Unfortunately, the hybrid memory design space is very large and complex due to the existence of very different types of NVMs and their rapidly-changing characteristics. Therefore, optimization of performance and lifetime of hybrid memory based... 

    Analytical model of the electro-mechanical impedance response of frame structures with L-shaped beams

    , Article Research in Nondestructive Evaluation ; Volume 31, Issue 3 , 2 January , 2020 , Pages 187-202 Mohsenzadeh, M ; Hamzeloo, S. R ; Barzegar, M ; Pourkamali Anaraki, A ; Sharif University of Technology
    Taylor and Francis Inc  2020
    The electro-mechanical impedance (EMI) method has been accepted as an effective technique for detecting damages in the Structural health monitoring (SHM). EMI at any point of the structure depends on material properties, geometry and boundary conditions that all appears in dynamic stiffness of the structure. In spite of the expensive experimental methods for measuring the mechanical impedance, or the cheaper one electromechanical impedance, of structures, various analytical methods could be substitutions for them. In this paper, an analytical method is developed to obtain the EMI response of L-shaped beams through calculating the dynamic stiffness of the structure. To verify the model, an... 

    Fast spectral solutions of the double-gyre problem in a turbulent flow regime

    , Article Applied Mathematical Modelling ; Volume 66 , 2019 , Pages 745-767 ; 0307904X (ISSN) Naghibi, S. E ; Karabasov, S. A ; Jalali, M. A ; Sadati, S. M. H ; Sharif University of Technology
    Elsevier Inc  2019
    Several semi-analytical models are considered for a double-gyre problem in a turbulent flow regime for which a reference fully numerical eddy-resolving solution is obtained. The semi-analytical models correspond to solving the depth-averaged Navier–Stokes equations using the spectral Galerkin approach. The robustness of the linear and Smagorinsky eddy-viscosity models for turbulent diffusion approximation is investigated. To capture essential properties of the double-gyre configuration, such as the integral kinetic energy, the integral angular momentum, and the jet mean-flow distribution, an improved semi-analytical model is suggested that is inspired by the idea of scale decomposition... 

    Dependability and Performability Modeling and Evaluation in Cloud Computing

    , M.Sc. Thesis Sharif University of Technology Faraji Shoyari, Mahsa (Author) ; Movaghar, Ali (Supervisor)
    In cloud computing services, high availability is one of the most quality requirements that it is necessary to maintain customer confidence. This requires various fault tolerance mechanisms for coping with software and hardware failures.In this thesis, after reviewing previous research, eight different scenarios was designed for availability evaluation of redundant openstack private clouds, represented by RBDs and Markov chains, hierarchically assembled.Based on the availability and downtime results obtained from the scenarios and cost consideration of company, best architecture for openstack is implemented.For real world modeling, we tried to collect and analyze the hardware and... 

    Mathematical performance modelling of stretched hypercubes

    , Article 9th International Conference on Distributed Computing and Networking, ICDCN 2008, Kolkata, 5 January 2008 through 8 January 2008 ; Volume 4904 LNCS , 2008 , Pages 375-386 ; 03029743 (ISSN); 3540774432 (ISBN); 9783540774433 (ISBN) Meraji, S ; Sarbazi Azad, H ; Sharif University of Technology
    Springer Verlag  2008
    The stretched hypercube has recently been introduced as an attractive alternative to the well-known hypercube. Previous research on this network topology has mainly focused on topological properties, VLSI and algorithmic aspects of this network. Several analytical models have been proposed in the literature for different interconnection networks, as the most cost-effective tools to evaluate the performance merits of such systems. This paper proposes an analytical performance model to predict message latency in wormhole-switched stretched hypercube interconnection networks with fully adaptive routing. The analysis focuses on a fully adaptive routing algorithm which has been shown to be the... 

    Basic modifications in 3D micromechanical modeling of short fiber composites with bonded and debonded fiber end

    , Article Computational Materials Science ; Volume 40, Issue 3 , 2007 , Pages 421-433 ; 09270256 (ISSN) Abedian, A ; Mondali, M ; Pahlavanpour, M ; Sharif University of Technology
    A modified analytical model is developed for analysis of 3D elastic stress fields in short fiber composites subjected to an applied axial load. Two sets of exact displacement solutions for the matrix and fiber are derived based on the theory of elasticity. The superposition state of these solutions are then used to obtain the analytical expressions for the 3D stress field components over the entire composite system including the fiber end region, which is modeled by the use of imaginary fiber technique. The main difference with the previous works here is that the stress field is considered to be a function of both radial and axial directions. Such an assumption made it possible to calculate... 

    Performance modeling of wormhole hypermeshes under hotspot traffic

    , Article 2nd International Symposium on Computer Science in Russia, CSR 2007, Ekaterinburg, 3 September 2007 through 7 September 2007 ; Volume 4649 LNCS , 2007 , Pages 290-302 ; 03029743 (ISSN); 9783540745099 (ISBN) Moraveji, R ; Sarbazi Azad, H ; Nayebi, A ; Navi, K ; Sharif University of Technology
    Springer Verlag  2007
    Traffic pattern is a point of concern in today's modeling approach of network-based computing systems including NoCs and Clusters. Hypermesh is a promising network topology suitable for a range of networks. Although there are few models reported for hypermeshes with uniform traffic pattern, no analytical model has been reported yet that deal with hotspot traffic load. Since uniform traffic assumption is not always justifiable in practice as there are many parallel applications that exhibit non-uniform traffic patterns, which can produce hotspots in the network, in this study we propose a novel analytical model to analyze the mean message latency in wormhole-switched hypermesh in the presence...