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systems-analysis
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Efficient symmetry reduction for an actor-based model
, Article 2nd International Conference on Distributed Computing and Internet Technology, ICDCIT 2005, Bhubaneswar, 22 December 2005 through 24 December 2005 ; Volume 3816 LNCS , 2005 , Pages 494-507 ; 03029743 (ISSN); 3540309993 (ISBN); 9783540309994 (ISBN) ; Sirjani, M ; Mousavi, M. R ; Movaghar, A ; Sharif University of Technology
2005
Abstract
Symmetry reduction is a promising technique for combatting state space explosion in model checking. The problem of finding the equivalence classes, i.e., the so-called orbits, of states under symmetry is a difficult problem known to be as hard as graph isomorphism. In this paper, we show how we can automatically find the orbits in an actor-based model, called Rebeca, without enforcing any restriction on the modeler. The proposed algorithm solves the orbit problem for Rebeca models in polynomial time. As a result, the simple actor-based Rebeca language can be utilized efficiently for modeling and verification of systems, without involving the modeler with the details of the verification...
An applied form of Kane's equations of motions of motions
, Article DETC2005: ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Long Beach, CA, 24 September 2005 through 28 September 2005 ; Volume 6 C , 2005 , Pages 2103-2110 ; 0791847438 (ISBN) ; Lotfi Gaskarimahalle, A ; Ghaemi Oskouei, S. B ; Meghdari, A ; Sharif University of Technology
2005
Abstract
In this paper we have presented a new form of Kane's equations. This new form is expressed in the matrix form with the components of partial derivatives of linear and angular velocities relative to the generalized speeds and generalized coordinates. The number of obtained equations is equal to the number of degrees of freedom represented in a closed form. Also the equations can be rearranged to appear only one of the time derivatives of generalized speeds in each equation. This form is appropriate especially when one intends to derive equations recursively. Hence in addition to the simplicity, the amount of calculations is noticeably reduced and also can be used in a control unit. Copyright...
A two-level gradient based approach for intelligent coordination of large-scale systems - Part I
, Article ICTAI 2005: 17th IEEE International Conference on Tools with Artificial Intelligence, ICTAI'05, Hong Kong, 14 November 2005 through 16 November 2005 ; Volume 2005 , 2005 , Pages 470-477 ; 10823409 (ISSN); 0769524885 (ISBN); 9780769524887 (ISBN) ; Sharif University of Technology
IEEE Computer Society
2005
Abstract
In this paper, the concept of coordination is introduced within the framework of two-level large-scale systems and a new approach based on Interaction Prediction Principle is presented. The proposed approach is formulated in an intelligent manner in such a way that it provides a new strategy that can be used to synthesize an on-line supervisory controller for the overall two-level large-scale systems, extendable to multi-level control systems. By using the new methodology which is based on using neural network for modeling each sub-system, typical gradient method for optimization of first-level sub-problems, and the gradient of the interaction prediction errors related to the predicted...
On the performance of optimal flux search controller for DTC based induction motor drives
, Article 2005 IEEE International Conference on Electric Machines and Drives, San Antonio, TX, 15 May 2005 through 15 May 2005 ; 2005 , Pages 1752-1756 ; 0780389875 (ISBN); 9780780389878 (ISBN) ; Vahdati Khajeh, E ; Zolghadri, M. R ; Homaifar, A ; Sharif University of Technology
IEEE Computer Society
2005
Abstract
Application of a flux search controller in direct torque control of induction motor drives produces divergence problem and steady state flux ripple, because of the disturbance in the control loop. In this paper, an investigation about the origin of this noise has been performed. It is shown that the variation of voltage harmonics is the main reason of disturbance in the flux control loop. The minimum allowable value of flux step has been determined based on this analysis to prevent the divergence problem. Feasibility of noise cancellation has been discussed. Experimental results are presented to justify the theoretical analysis. © 2005 IEEE
A fast optimal flux search controller with improved steady state behavior for DTC based induction motor drives
, Article 2005 IEEE International Conference on Electric Machines and Drives, San Antonio, TX, 15 May 2005 through 15 May 2005 ; 2005 , Pages 1732-1736 ; 0780389875 (ISBN); 9780780389878 (ISBN) ; Vahdati Khajeh, E ; Zolghadri, M. R ; Homaifar, A ; Sharif University of Technology
IEEE Computer Society
2005
Abstract
Flux search controllers are proposed to improve the efficiency of electrical motors especially induction motors. In this paper, a flux search controller is proposed to increase the efficiency of a direct torque controlled induction motor with light load. The reference flux value is determined through a two stage minimization algorithm with the amplitude of the stator current as the objective function. In the transient state, a great flux step is used to speed up the convergence. In the steady state, a noise cancellation algorithm is used to let using small flux step and improves the steady state behavior of flux controller. Simulation and experimental confirm the fast dynamics of the...
A hybrid fault injection approach based on simulation and emulation CO-operation
, Article 2003 International Conference on Dependable Systems and Networks, San Francisco, CA, 22 June 2003 through 25 June 2003 ; 2003 , Pages 479-488 ; Miremadi, S. G ; Zarandi, H ; Asadi, G ; Sarmadi, S. B ; Sharif University of Technology
2003
Abstract
This paper presents a new fault injection approach, which is based on a co-operation between a simulator and an emulator. This hybrid approach utilizes the advantages of both simulation-based fault injection as well as physical fault injection to provide a good controllability, observability and also a high speed in the fault injection experiments. To do this, parts of a circuit are simulated while the rest pans of the circuit are emulated. A fault injection tool called FITSEC (Fault Injection Tool based on Simulation and Emulation Co-operation) is developed, which supports the entire process of a system design. This is based on both Verilog and VHDL languages and can be used to inject...
Modeling the Operation of a General Insurance Company with System Dynamics Approach
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Farhad (Supervisor)
Abstract
Market share of some private insurance companies in Iran has demonstrated upward and then downward trends over the years . Due to the similarity of conditions among all companies, the internal structure of companies is the main reason for the creation such trends. The operation of insurance companies has a lot of feedback mechanisms and delay relationships. In this research for purpose of modeling a holistic and comprehensive view and understanding the structure of private insurance companies in Iran, feedbacks and delay relations System dynamics approach is used. The developed model structure consists of five interconnected modules, each representing a relatively detached sphere of...
Modeling and Design Analysis of an Aircraft Longitudinal Reversible Flight Control System and its Enhancement to Irreversible One
, M.Sc. Thesis Sharif University of Technology ; Pourtakdoust, Hossien (Supervisor) ; Raeesi Charmkani, Kamran (Supervisor)
Abstract
Flight control system (FCS) design, analysis and modeling has an important role in aircraft design and development process. However, FCS analysis and studies are rarely focused at university levels and its know-how and technical issues are almost proprietary to various aircraft industries. One of the key goals of this thesis is to express, introduce and implement the processes that need to be followed for a sample longitudinal reversible FCS design (RFCS), where the modelling aspects are described for an existing aircraft. The latter is achieved using existing drawings, system and aerodynamic data of an existing aircraft utilizing commercial tools such as CATIA for initial design and ADAMS...
Digital Marketing Management in Businesses and Startups Using Dynamic Systems Modeling
, M.Sc. Thesis Sharif University of Technology ; Shadrokh, Shahram (Supervisor)
Abstract
As today's world becomes more digital in every way, digital marketing has become a thriving industry, and digital marketing has become an important part of the world of digital business. Given the importance of this issue and the prominent role of startups in the today’s business world, in this project we discuss about digital marketing in start-ups business with a view to health sector using dynamic systems modeling. First, the effective variables are determined, then the relationships between them are determined and the model is designed. Finally, after analyzing the model factors and determining the extent and type of its impact on the main factors and variables, smooth the way to create...
A decomposed solution to multiple-energy carriers optimal power flow
, Article IEEE Transactions on Power Systems ; Vol. 29, issue. 2 , March , 2014 , p. 707-716 ; ISSN: 8858950 ; Abbaspour, A ; Fotuhi-Firuzabad, M ; Hajipour, E ; Sharif University of Technology
Abstract
Presence of energy hubs in the future vision of energy networks creates a great opportunity for system planners and operators to move towards more efficient systems. The role of energy hubs as the intermediate in multi-carrier energy (MCE) systems calls for a generic framework to study the new upcoming technical as well as economical effects on the system performance. In response, this paper attempts to develop a general optimization and modeling framework for coupled power flow studies on different energy infrastructures. This, as a large-scale nonlinear problem, is approached through a robust optimization technique, i.e., multi-agent genetic algorithm (MAGA). The proposed procedure...
Power-efficient prefetching on GPGPUs
, Article Journal of Supercomputing ; Volume 71, Issue 8 , August , 2015 , pp. 2808-2829 ; ISSN: 09208542 ; Hessabi, S ; Abdi, M ; Baniasadi, A ; Sharif University of Technology
Abstract
The graphics processing unit (GPU) is the most promising candidate platform for achieving faster improvements in peak processing speed, low latency and high performance. The highly programmable and multithreaded nature of GPUs makes them a remarkable candidate for general purpose computing. However, supporting non-graphics computing on graphics processors requires addressing several architectural challenges. In this paper, we focus on improving performance by better hiding long waiting time for transferring data from the slow global memory. Furthermore, we show that the proposed method can reduce power and energy. Reduction in access time to off-chip data has a noticeable role in reducing...
ONC3: All-optical NoC based on cube-connected cycles with quasi-DOR algorithm
, Article Proceedings - 15th Euromicro Conference on Digital System Design, DSD 2012 ; 2012 , Pages 296-303 ; 9780769547985 (ISBN) ; Tavana, M. K ; Koohi, S ; Hessabi, S ; Sharif University of Technology
2012
Abstract
This paper proposes a nanophotonic Network-on-Chip architecture based on the traditional Cube-Connected Cycles topology (CCC), which is named as ONC3. We also suggest a contention-free quasi-Dimension-Order-Routing algorithm for the proposed structure. Compared to the previous 2D layouts, our novel scheme lessens the crosstalk parameter of the insertion loss and consequently, the power consumption. Besides, the router structure is area-efficient. On the other hand, optical destination checking supersedes electrical resource reservation, with utilizing passive wavelength routing method and Wavelength Division Multiplexing scheme, simultaneously. The efficiency of the proposed architecture, in...
Using genetic algorithm to identify soft-error derating blocks of an application program
, Article Proceedings - 15th Euromicro Conference on Digital System Design, DSD 2012, 5 September 2012 through 8 September 2012 ; September , 2012 , Pages 359-367 ; 9780769547985 (ISBN) ; Rahmani, A. M ; Mansoor, A ; Miremadi, S. G ; Sharif University of Technology
2012
Abstract
Soft-errors are increasingly considered as a major cause for computer system failures. Software techniques are used as cost-effective and flexible techniques to tolerate soft-errors but the introduced overhead is not acceptable in some safety-critical real-time systems. The identification of the program blocks and protecting only vulnerable blocks against soft-errors reduces the performance overhead. In this paper, we present a genetic algorithm to identify the vulnerable program blocks as well as the derating program blocks against soft-errors. Then, only vulnerable blocks are protected by some software-based soft-error tolerance techniques to achieve a lower performance and space overhead....
A comparative study on single-channel noise estimation methods for speech enhancement
, Article International Conference on Intelligent Systems Design and Applications, ISDA ; 2012 , Pages 645-650 ; 21647143 (ISSN) ; 9781467351188 (ISBN) ; Sameti, H ; Sharif University of Technology
2012
Abstract
This paper studies a number of well-known noise estimation techniques and provides a comparative performance analysis of them in speech enhancement platform. Two types of evaluation data that simulate consistent and inconsistent noisy conditions are prepared in the presence of six noise types at different SNR levels. The performance of speech enhancement systems and the spectrum distance of the estimated and original noise spectrums are used as evaluation criteria. The evaluations indicate that a simple VAD method outperforms noise estimation methods in most of the consistent noisy conditions
From traditional to fractional PI control: A key for generalization
, Article IEEE Industrial Electronics Magazine ; Volume 6, Issue 3 , 2012 , Pages 41-51 ; 19324529 (ISSN) ; Sharif University of Technology
IEEE
2012
Abstract
Proportional-integral (PI) controllers are the most common form of feedback used in industrial applications today [1][3]. The use of proportional and integral feedback also has a long history of practical applications [4]. For example, in the middle of the 18th century, centrifugal governors as the proportional feedback were applied to regulate the speed of windmills [5]. By the 19th century, it was known that using integral feedback could remove the offsets appearing in working with governors [6]. At present, PI control, still a very basic form of feedback, is also one of the first solutions often considered in the control of industrial systems [7]. On the other hand, in some applications,...
Using partial tag comparison in low-power snoop-based chip multiprocessors
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 19 June 2010 through 23 June 2010 ; Volume 6161 LNCS , June , 2012 , Pages 211-221 ; 03029743 (ISSN) ; 9783642243219 (ISBN) ; Shahidi, N ; Baniasadi, A ; Sharif University of Technology
Abstract
In this work we introduce power optimizations relying on partial tag comparison (PTC) in snoop-based chip multiprocessors. Our optimizations rely on the observation that detecting tag mismatches in a snoop-based chip multiprocessor does not require aggressively processing the entire tag. In fact, a high percentage of cache mismatches could be detected by utilizing a small subset but highly informative portion of the tag bits. Based on this, we introduce a source-based snoop filtering mechanism referred to as S-PTC. In S-PTC possible remote tag mismatches are detected prior to sending the request. We reduce power as S-PTC prevents sending unnecessary snoops and avoids unessential tag lookups...
Performance investigation of a four stroke diesel engine, using water-based ferrofluid as an additive
, Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011, 11 November 2011 through 17 November 2011 ; Volume 4, Issue PARTS A AND B , November , 2011 , Pages 1339-1343 ; 9780791854907 (ISBN) ; Jahani, N ; Shafii, M. B ; ASME ; Sharif University of Technology
Abstract
In this experimental study, a four stroke diesel engine was conducted to investigate the effect of adding water-based ferrofluid to diesel fuel on engine performance. To our knowledge, Magnetic nanoparticles had not been used before. To this end, emulsified diesel fuels of 0, 0.4, and 0.8 water-based ferrofluid/Diesel ratios by volume were used as fuel. The ferrofluid used in this study was a handmade water-based ferrofluid prepared by the authors. The results show that adding water-based ferrofluid to diesel fuel has a perceptible effect on engine performance, increasing the brake thermal efficiency relatively up to 12%, and decreasing the brake specific fuel consumption relatively up to...
Dynamic assessment of capacity investment in electricity market considering complementary capacity mechanisms
, Article Energy ; Volume 36, Issue 1 , January , 2011 , Pages 277-293 ; 03605442 (ISSN) ; Hosseini, S. H ; Sharif University of Technology
2011
Abstract
This paper proposes a decentralized market-based model for long-term capacity investment decisions in a liberalized electricity market. Investment decisions are fundamentally based on total revenues gained by investors. In most electricity markets, the complementary mechanisms are designed to ensure a desired level of reliability while covering investment costs of the suppliers. In such an environment, investment decisions are highly sensitive to expectation of price signals in both of energy market and capacity mechanisms. In this work, the system dynamics concepts are used to model the structural characteristics of electricity market such as, long-term firms' behavior and relationships...
A fast analytical approach to multi-cycle soft error rate estimation of sequential circuits
, Article Proceedings - 13th Euromicro Conference on Digital System Design: Architectures, Methods and Tools, DSD 2010, 1 September 2010 through 3 September 2010, Lille ; 2010 , Pages 797-800 ; 9780769541716 (ISBN) ; Miremadi, S. G ; Asadi, H ; Baradaran Tahoori, M ; Sharif University of Technology
2010
Abstract
In this paper, we propose a very fast analytical approach to measure the overall circuit Soft Error Rate (SER) and to identify the most vulnerable gates and flip-flops. In the proposed approach, we first compute the error propagation probability from an error site to primary outputs as well as system bistables. Then, we perform a multi-cycle error propagation analysis in the sequential circuit. The results show that the proposed approach is four to five orders of magnitude faster than the Monte Carlo (MC) simulation-based fault injection approach with 92% accuracy. This makes the proposed approach applicable to industrial-scale circuits
Investigating optimum procedures needed to maintain a model satellite's CG stable about design point, under subsystem configuration changes
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 4 , 2010 , Pages 585-588 ; 9780791849187 (ISBN) ; Abedian, A ; Teimouri, H ; Sharif University of Technology
2010
Abstract
During design, microsatellites are subject to different changes like the changes in weight, location and dimension of parts and elements of subsystems and the payload. These changes should be accumulated by the structure subsystem in a way that some key structural parameters like the center of gravity (CG) and inertia moments remain unchanged. This subject is also important regarding the design of a modular structure of a satellite. In the present study it is tried to accommodate any changes in weight and location of any part(s) and element(s) of a microsatellite by optimum (minimum) rearrangement of other parts on their plane of rest in order to keep the CG and inertia moments unchanged....