Search for: generation
Total 1488 records
Article Scientia Iranica ; Volume 7, Issue 3-4 , 2000 , Pages 205-211 ; 10263098 (ISSN) ; Ehsan, M ; Sharif University of Technology
Sharif University of Technology 2000
In this paper, a simple and efficient method for fast dynamic stability assessment of power systems is presented. The proposed approach determines the dynamic stability of a power system without the full dynamic formulation and eigenvalue analysis. This method could be applied as a valuable aid for monitoring dynamic stability in a new system control centers. Application of the singularity of standard load-flow Jacobian has already been presented for evaluation of dynamic stability under certain conditions, but the result is optimistic for any type of dynamic analysis. This deviation is misleading for system control operators and is not recommended. The modification proposed here can...
Article Scientia Iranica ; Volume 7, Issue 3-4 , 2000 , Pages 219-225 ; 10263098 (ISSN) ; Filizadeh, S ; Sharif University of Technology
Sharif University of Technology 2000
To study the dynamic stability of a power system, suitable models of the network and dynamic devices, with different levels of accuracy, are needed. In this paper, a modular method is introduced for modelling power systems. The method is perfectly suited for systems containing FACTS devices. Due to the modularity of the method, which is based on augmentation of state equations of the network and dynamic devices, the introduction of new devices is straightforward. The method presented here can cover both high and low frequency ranges of dynamic phenomena in power systems
M.Sc. Thesis Sharif University of Technology ; Jahangir, Amir Hossein
Generating realistic network traffic serves capacity planning, traffic engineering, understanding internet service performance and anomaly detection. A useful traffic generator must generate characteristics in flows and packets, and add known internet anomalies to legitimate traffic. In this dissertation, we develop a tool for generating realistic and anomalous traffic. This generator can generate traffic in a scalable, reproducible and stochastic manner. Two methods are proposed for this purpose. In the first method, the traffic is generated according to statistical distribution of packets and flow charactristics. In the second method, traffic is generated by modeling the behavior of...
Article Algebra Colloquium ; Volume 9, Issue 1 , 2002 , Pages 1-6 ; 10053867 (ISSN) ; Sharif University of Technology
Let D be an infinite division algebra of finite dimension over its centre Z(D) = F, and n a positive integer. The structure of maximal subgroups of skew linear groups are investigated. In particular, assume N is a normal subgroup of GLn(D) and M is a maximal subgroup of N containing Z(N). It is shown that if M/Z(N) is finite, then N is central. © Inst. Math. CAS 2002
Article Journal of Algebra ; Volume 225, Issue 2 , 2000 , Pages 517-521 ; 00218693 (ISSN) ; Mahmudi, M. G ; Yasamin, S ; Sharif University of Technology
Academic Press Inc 2000
Let D be an infinite division algebra of finite dimension over its center. Assume that N is a subnormal subgroup of GLn(D) with n≥1. It is shown that if N is finitely generated, then N is central. © 2000 Academic Press
Article IEEE Transactions on Power Systems ; Volume 22, Issue 4 , 2007 , Pages 2134-2143 ; 08858950 (ISSN) ; Khodaei, A ; Aminifar, F ; Sharif University of Technology
In this paper, a novel fast straightforward method for thermal generating units scheduling is presented. The new method decomposes the solution of the unit commitment (UC) problem into three subproblems. In the first subproblem, the quadratic cost functions of units are linearized and hourly optimum solution of UC is obtained considering all constraints except the minimum up/down time constraints. In the second subproblem, the minimum up/down times are enforced through a novel optimization process by modifying the schedule obtained in the first step. Finally, in the third subproblem, the extra reserve is minimized using a new decommitment algorithm. For testing the proposed method, the...
Article Thermal Science ; Volume 16, Issue 5 , 2012 , Pages 1289-1295 ; 03549836 (ISSN) ; Ganji, D. D ; Hedayati, F ; Kaffash, M. H ; Jamshidi, M ; Sharif University of Technology
The steady 2-D boundary layer flow over a flat plate is studied analytically by homotopy perturbation method to analyze the entropy generation inside the boundary layer with constant wall temperature. By the transformations of go-verning equations including continuity, momentum, and energy by similarity va-riables, a dimensionless equation for entropy generation inside the boundary layer is obtained. The effects of important parameters such as Reynolds and Eck-ert numbers are investigated and the physical interpretations of the results are explained in details
Generating the Activation Patterns of the Leg Muscles during Human Locomotion Using the Central Pattern Generators as a Control Structure, Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; Volume 40, Issue 2 , 2016 , Pages 87-94 ; 22286187 (ISSN) ; Farahmand, F ; Zohoor, H ; Razeghi, M ; Sharif University of Technology
The central pattern generators have been considered as a method to simplify the control of the complex rhythmic motions, e.g., walking, by the central nervous system. In this study, a control structure was designed to control the soleus and tibialis anterior muscles in a complete gait cycle. The activation patterns of the muscles were measured experimentally and used as the reference signals of a tracking problem. The hip angle and ground reaction force were also used as a feedforward. The feedback from the Golgi tendon acted as a regulator of muscle activity. The controller was applied to two gait trials. The results indicated that the designed controller was capable of tracking the...
A microfluidic concentration gradient generator for simultaneous delivery of two reagents on a millimeter-sized sample, Article Journal of Flow Chemistry ; Volume 10, Issue 4 , 2020 , Pages 615-625 ; Saidi, M. S ; Kashaninejad, N ; Sharif University of Technology
Springer International Publishing 2020
Microfluidic concentration gradient generators (μCGGs) are indispensable parts of many emerging lab-on-a-chip platforms for biological studies and drug delivery applications. Most of the μCGGs reported in the literature can only generate the desired concentration gradients in a micron-sized sample (e.g., cells). As such, there is an unmet need to design a μCGG that can generate continuous concentration gradients of multi reagents (e.g., drugs) in a millimeter-sized sample (e.g., tissue). Herein, we report the proof-of-concept of this class of μCGG by combining a modified tree-like CGG with a micromixer. By conducting both experimental investigation and numerical analysis, we show that the...
Article TENCON 2005 - 2005 IEEE Region 10 Conference, Melbourne, 21 November 2005 through 24 November 2005 ; Volume 2007 , 2005 ; 21593442 (ISSN); 0780393112 (ISBN); 9780780393110 (ISBN) ; Fotuhi, M ; Abbaspour, A ; Ranjbar, A. M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2005
Wind generation is one of the most successful sources of renewable energy for the production of electrical energy. The technical characteristics of wind generation make existing conventional generation models not directly applicable. This paper presents an analytical method for the reliability assessment of the flat-rated wind turbine generation systems. An example of flat rating is that of the MOD-2, a second-generation class of wind turbines. The power-velocity characteristic of the flat-rated wind turbines is employed in this paper to model the operating behavior of the installed wind turbine generators. For wind-power potential estimation, the Weibull distribution model is used. The...
Article 2004 International Conference on Power System Technology, POWERCON 2004, 21 November 2004 through 24 November 2004 ; Volume 2 , 2004 , Pages 1067-1071 ; 0780386108 (ISBN) ; Parniani, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
Distributed generation (DG) portion of power production is increasing more and more. DG poses different benefits and difficulties in a power system. Inadvertent islanding is a problem with DG which may cause health danger to line crew and can damage both DG and power system equipments. This paper investigates the effect of reactive power on ROCOF islanding detection method. Impacts of load power factor and load combination are studied using a sample test system. The paper offers a corrective method to cope with impacts of load reactive power. A way is suggested to locate DG such that the role of reactive power becomes a positive factor in islanding detection. © 2004 IEEE
Article 2004 International Conference on Power System Technology, POWERCON 2004, 21 November 2004 through 24 November 2004 ; Volume 1 , 2004 , Pages 856-861 ; 0780386108 (ISBN) ; Fotuhi Firuzabad, M ; Parniani, M ; Sharif University of Technology
The electric power industry around the world is presently undergoing considerable changes with respect to structure, operation and regulation. Distributed generation is expected to play a major role in this new environment One the main benefits of DG is to enhance system reliability as it can restore power to the separated or bottle-necked part of distribution system in case of a contingency occurs. This paper presents an approach to examine and evaluates the applicability and customer interruption cost analysis in DG-connected distribution system in a specified planning horizon. The impacts on customer interruption cost reduction of different load growth rate, DG location and different...
Article International Communications in Heat and Mass Transfer ; Volume 30, Issue 4 , 2003 , Pages 565-576 ; 07351933 (ISSN) ; Saidi, M. H ; Mozaffari, A. A ; Sharif University of Technology
Falling film heat and mass transfer analysis of a horizontal tube bundle in a generator of absorption chillers have been studied. The film Reynolds number is limited to the laminar flow and the effect of ripple on the free surface has been ignored. Thermal boundary conditions are considered to be constant wall temperature and desorption is considered to be free surface evaporation. Analysis is based on a single column of horizontal tubes, arranged in a vertically spaced configuration. A comprehensive numerical code has been developed to solved the governing equations. The functional relationship of average heat transfer coefficient of tube bundle has been analytically correlated to the first...
Article Proceedings of the International Conference on Telecommunications 2002, Beijing, 23 June 2002 through 26 June 2002 ; Volume 1 , 2002 , Pages 383-387 ; 7505377027 (ISBN) ; Kenari, M. N ; Ahmadian, M ; Sharif University of Technology
UMTS is the European standard of third generation of mobile communications and its air interface is called WCDMA. In this paper a simple WCDMA system in downlink and in FDD mode is simulated and results is presented. The simulation that is an execution of apart of physical layer functions as layer 1, is including data modulation, spreading multipath channel, AWGN noise, data demodulation, despreading and Rake receiver. It is obvious that transmission methods of data correspond with WCDMA standard. In the other word, frames and slots structure, data symbols setting and requiring parameters follow the defined standards
Article 1st IEEE International Conference on Circuits and Systems for Communications, ICCSC 2002, 26 June 2002 through 28 June 2002 ; Volume 2002-June , 2002 , Pages 254-257 ; 5742202601 (ISBN); 9785742202608 (ISBN) ; Kenari, M. N ; Ahmadian, M ; Salahi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2002
UMTS is the European standard of the third generation of mobile communications and its air interface is called WCDMA. In this paper a simple WCDMA system in downlink and FDD mode is simulated and results are presented. The simulation that is an execution, apart from physical layer functions as layer 1, includes data modulation, spreading multipath channel, AWGN noise, data demodulation, despreading and Rake receiver. It is obvious that transmission methods of data correspond to WCDMA standards. In other words, frames and slots structure, data symbols setting and required parameters follow the defined standards. © 2002 St. Petersburg State Poly Univ
Article Proceedings of the American Mathematical Society ; Volume 128, Issue 6 , 2000 , Pages 1627-1632 ; 00029939 (ISSN) ; Mahdavi Hezavehi, M ; Sharif University of Technology
American Mathematical Society 2000
As a generalization of Wedderburn's classic theorem, it is shown that the multiplicative group of a noncommutative finite dimensional division algebra cannot be finitely generated. Also, the following conjecture is investigated: An infinite non-central normal subgroup of GLn(D) cannot be finitely generated. © 2000 American Mathematical Society
Article Pattern Recognition ; Volume 48, Issue 1 , January , 2015 , Pages 174-188 ; 00313203 (ISSN) ; Jamzad, M ; Sharif University of Technology
Elsevier Ltd 2015
Image annotation approaches need an annotated dataset to learn a model for the relation between images and words. Unfortunately, preparing a labeled dataset is highly time consuming and expensive. In this work, we describe the development of an annotation system in semi-supervised learning framework which by incorporating unlabeled images into training phase reduces the system demand to labeled images. Our approach constructs a generative model for each semantic class in two main steps. First, based on Gamma distribution, a generative model is constructed for each semantic class using labeled images in that class. The second step incorporates the unlabeled images by using a modified EM...
Implementing an automated feedback program for a foreign language writing course: A learner-centric study, Article Journal of Computer Assisted Learning ; Volume 37, Issue 5 , 2021 , Pages 1494-1507 ; 02664909 (ISSN) ; Fotoohnejad, S ; Sharif University of Technology
John Wiley and Sons Inc 2021
Considering the prominence attached to written corrective feedback (WCF) within the domain of second/foreign language (L2) acquisition, automated writing evaluation (AWE) tools have steadily gained ground over the last two decades. The current study was an attempt to investigate the extent incorporating an AWE program, known as Criterion®, within a process writing framework would affect learners' writing quality in an English as a foreign language context. Moreover, we drew a comparison between the overall effects of computer- versus teacher-generated WCF. Participants consisted of 53 tertiary level students from two intact essay-writing classes. The within-group findings revealed that the...
Microwave-promoted pseudo-thia-Fries rearrangement of aryl benzylsulfonates; highly reactive benzyl cation generation, Article Journal of Sulfur Chemistry ; Volume 25, Issue 2-3 , 2004 , Pages 125-130 ; 17415993 (ISSN) ; Hoor, A. A ; Dekamin, M. G ; Sharif University of Technology
Aryl benzylsulfonates undergo so-called pseudo-thia-Fries rearrangement under microwave irradiation. Benzylated phenolic compounds have been obtained with the loss of 'SO2' from the starting materials
Article IEEE Transactions on Plasma Science ; Volume 46, Issue 6 , 2018 , Pages 2059-2063 ; 00933813 (ISSN) ; Hashemi, M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2018
A megawatt-range short pulse generator based on the diode step recovery phenomenon and the Marx generator idea is presented. This generator utilizes both opening and closing switches in one circuit. The proposed circuit is compact, light, and low cost and is driven by a low-power source. By using a three-stage Marx generator, the output peak power of 0.6 MW was obtained. The dimensions of the generator are 8 cm $ imes8$ cm. Experimental measurements of the output pulse characteristics showed a rise time of 100 ns for a 16- $Omega $ load. The input peak power was 4 W which showed more than 105 times increase in the pulse peak power. © 1973-2012 IEEE