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A novel robust decentralized adaptive fuzzy control for swarm formation of multiagent systems
, Article IEEE Transactions on Industrial Electronics ; Volume 59, Issue 8 , 2012 , Pages 3124-3134 ; 02780046 (ISSN) ; Shabaninia, F ; Nemati, A ; Stan, S. D ; Sharif University of Technology
IEEE
2012
Abstract
In this paper, a novel decentralized adaptive control scheme for multiagent formation control is proposed based on an integration of artificial potential functions with robust control techniques. Fully actuated mobile agents with partially unknown models are considered, where an adaptive fuzzy logic system is used to approximate the unknown system dynamics. The robust performance criterion is used to attenuate the adaptive fuzzy approximation error and external disturbances to a prescribed level. The advantages of the proposed controller can be listed as robustness to input nonlinearity, external disturbances, and model uncertainties, and applicability on a large diversity of autonomous...
Effect of power randomization on saturation throughput of IEEE 802.11 WLAN
, Article IEEE International Conference on Communications, 23 May 2010 through 27 May 2010, Cape Town ; 2010 ; 05361486 (ISSN) ; 9781424464043 (ISBN) ; Ashtiani, F ; Sharif University of Technology
2010
Abstract
In this paper, we evaluate the saturation throughput for an IEEE 802.11 based wireless network considering capture effect at the receiver, while nodes transmit with random powers. In this respect, we consider a scenario consisting of a specific number of wireless nodes. Then, we derive the transmission as well as collision probabilities with respect to the perfect capture effect. In order to maximize the saturation throughput we set up an optimization problem and obtain how to compute optimum values for the probabilities corresponding to different power levels. By providing the numerical results, we deduce that power randomization may lead to a significant improvement in saturation...
Plant Layout Problem by Considering Aisle Structure
, M.Sc. Thesis Sharif University of Technology ; Eshghi, Kourosh (Supervisor)
Abstract
The layout problem is directly related to the material handling system; therefore, these two concepts are always being considered together. The main criterion for evaluating the layout in the objective function, is the cost of controlling and moving the materials. In order to calculate the material handling cost, it is necessary to provide an accurate information on the distance between departments, number of goods transported, and the cost of moving a unit of goods per unit of distance; therefore, accurate calculation of the distance between departments is an issue of paramount importance. In the literature, the distance between the departments is measured in three ways: Euclidean distance,...
Real-time trajectory generation for mobile robots
, Article 10th Congress of the Italian Association for Artificial Intelligence, AI IA 2007, Rome, 10 September 2007 through 13 September 2007 ; Volume 4733 LNAI , 2007 , Pages 459-470 ; 03029743 (ISSN); 9783540747819 (ISBN) ; Manzuri, M. T ; Razvan, M. R ; Tajfard, M ; Khoshbakht, S ; Sharif University of Technology
Springer Verlag
2007
Abstract
This paper presents a computationally effective trajectory generation algorithm for omni-directional mobile robots. This method uses the Voronoi diagram to find a sketchy path that keeps away from obstacles and then smooths this path with a novel use of Bezier curves. This method determines velocity magnitude of a robot along the curved path to meet optimality conditions and dynamic constrains using Newton method. The proposed algorithm has been implemented on real robots, and experimental results in different environments are presented. © Springer-Verlag Berlin Heidelberg 2007
Idle time and gelation behavior in gelcasting process of PSZ in acrylamide system
, Article Ceramic Transactions, 31 May 2009 through 5 June 2009 ; Volume 212 , JUL , 2010 , Pages 105-113 ; 10421122 (ISSN) ; 9780470876466 (ISBN) ; Faghihi Sani, M. A ; Sharif University of Technology
2010
Abstract
Gelcasting is a novel forming method in fabricating complex three dimensional ceramic parts, and has many parameters and characteristics required to be specified. Up to now, few articles have been published on determination of the idle time of gelation precisely. In this work the chemorheology of gelation in aqueous solution of acrylamide and N, N′ methylenebisacrylamide monomer, and zirconia (PSZ) suspensions of this solution was investigated. As the viscosity of gel system increases abruptly in gelation point, idle time can be determined precisely by measurement of viscosity against time. Idle time can also be determined through temperature measurement against time since the reaction of...
Analysis and interaction of exergy, environmental and economic in multi-objective optimization of BTX process based on evolutionary algorithm
, Article Energy ; Volume 59 , 2013 , Pages 147-156 ; 03605442 (ISSN) ; Farhadi, F ; Boozarjomehry, R. B ; Sharif University of Technology
2013
Abstract
In this paper sustainability analysis (exergy, environmental and economic) and multi-objective optimization for an aromatic plant are provided and interactions between decision variables are discussed. Environmental evaluation shows that the cancer human toxicity and global warming are the most important environmental concerns and the weight of EIs (environmental impacts) are mainly due to process wastes. The optimizations results demonstrate parameters like reactor temperature have a wide range in the optimizations while some variables, such as extraction unit variables have the same value. Utility EI reduction occurred in economic and exergy optimizations rather than environmental...
Real-time parameter identification for highly coupled nonlinear systems using Adaptive Particle Swarm Optimization
, Article Mechanika ; Volume 86, Issue 6 , 2010 , Pages 43-49 ; 13921207 (ISSN) ; Nemati, A ; Safavi, A. A ; Sharif University of Technology
2010
Abstract
The In this paper, an Adaptive Particle Swarm Optimization (APSO) method is proposed for parameter identification of highly coupled electromechanical systems. Using some modifications on the APSO, better computational efficiency is achieved. In this way, the speed of real-time identification procedure is improved. In addition, to show the effectiveness of the proposed method, it is implemented on a real ball on plate setup and its dynamic model is achieved. Both the simulation and the experimental results show that parameter identification of the proposed algorithm is significantly improved when compared with other existing identification methods based on the traditional PSO and Genetic...
Adaptive fuzzy sliding mode control approach for swarm formation control of multi-agent systems
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 5 , 2010 , Pages 485-490 ; 9780791849194 (ISBN) ; Nemati, A ; Farshchi, M ; Meghdari, A ; Sharif University of Technology
2010
Abstract
In this paper, an adaptive control scheme for multi-agent formation control is proposed. This control method is based on artificial potential functions integrated with adaptive fuzzy sliding mode control technique. We consider fully actuated mobile agents with completely unknown dynamics. An adaptive fuzzy logic system is used to approximate the unknown system dynamics. Sliding Mode Control (SMC) theory is used to force agents' motion to obey the dynamics defined by the simple inter-agent artificial potential functions. Stability proof is given using Lyapunov functions, which shows the robustness of controller with respect to disturbances and system uncertainties. Simulation results are...
Reducing occupant injury in frontal crashes for a low-floor city bus
, Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005, Orlando, FL, 5 November 2005 through 11 November 2005 ; Volume 2006 , 2006 , Pages 113-120 ; Darvish, K ; Parnianpour, M ; Bateni, A ; Sharif University of Technology
2006
Abstract
In this research, the effect of beam buckling in a predefined direction is used to reduce occupant injuries in frontal crashes of an ultra-low-floor (ULF) city bus. In ULF buses, the floor structure consists of several longitudinal long beams, which in case of a frontal crash may buckle due to the axial impact. The direction of rotational acceleration of the driver seat due to buckling is highly affected by the position of the driver seat. A finite element model of an ULF bus was developed using LS-Dyna. The driver model, a Hybrid III 50 th male dummy with deformable jacket and abdomen, was restrained to the seat with a 3-point belt. An Elastic-Plastic material model was used for the bus...
Experimental Study and Modeling of Saturation Molality of Inorganic Salts in formation water
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Ghotbi, Sirous (Supervisor) ; Yousefi, Leyla (Co-Advisor)
Abstract
Saturation molality for a number of single and mixed aqueous electrolyte solutions containing NaCl, Na2CO3, and K2SO4, was measured at atmospheric pressure over a wide range of temperature. In order to check the repeatability of the experimental data, the experiments were replicated three times and average of the results was considered as final saturation molality. Experimental data of saturation molality for single electrolyte solutions were correlated using the modified UNIFAC–Dortmund model to account for the shortrange interaction. Binary interaction parameters, between water molecules and ionic species were also reported. For the long-range interactions between the ionic species in...
Thermodynamics and Kinetics Study of Gas Hydrates in Presence of Ionic Liquids
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Cyrus (Supervisor) ; Taghikhani, Vahid (Supervisor) ; Nazari, Khodadad (Supervisor)
Abstract
Gas hydrates are ice-like clathrate compounds. Methane, carbon dioxie and natural gas compounds can form gas hydrate and plug pipelines, in order to preventing of gas hydrate formation, inhibitors like electrolytes are added to the natural gas pipelines. In this work a model proposed to predict the hydrate formation conditions in presence of some inhibitors such as NaCl, KCl, NaBr, KBr, [BMIM][BF4] and [BMIM][Br]. So a new equation of state that can be applied to both electrolyte and associating solutions called GV-SAFT-MSA is developed. Two dialkylimidazolium ionic liquids [BMIM][BF4] and [BMIM][MS] have been investigated for their potential application as novel gas hydrate inhibitors. The...
The relationship between an EFL teacher's gender and students' willingness to communicate
, Article International Journal of Communication and Linguistic Studies ; Volume 10, Issue 4 , 2013 , Pages 17-29 ; 23277882 (ISSN) ; Pakzadian, S. S
Common Ground Publishing
2013
Abstract
Learning a foreign language encompasses a process of trial and error that can lead to the progression of the learner's interlanguage, meaning that the learners make use of their language knowledge that receives feedback and brings about progress through diagnosis of the problems and being corrected by the teacher. Therefore, there exists a need to analyze the underlying reasons causing the students to remain taciturn with a low willingness to communicate (WTC) during a language class. There has been much work done investigating the role of the learner's stable personal characteristics (traits) along with their situational changes at a specific time (states) that influence the student's...
An automated simple algorithm for realistic pore network extraction from micro-tomography images
, Article Journal of Petroleum Science and Engineering ; Vol. 123, issue , 2014 , pp. 164-171 ; ISSN: 09204105 ; Jamshidi, S ; Salehi, S
2014
Abstract
Using 3-D scanned data to analyze and extract pore network plays a vital role in investigation of porous media's characteristics. In this paper, a new simple method is developed to detect pores and throats for analyzing the connectivity and permeability of the network. This automated method utilizes some of the common and well-known image processing functions which are widely accessible by researchers and this has led to an easy algorithm implementation. In this method, after polishing and quality control of images, using city-block distance function and watershed segmentation algorithm, pores and throats are detected and 3-D network is produced. This method can also be applied on 2-D images...
Discrimination of heart arrhythmias using novel features in heart rate phase space
, Article Computing in Cardiology ; Volume 40 , Sept , 2013 , Pages 1035-1038 ; 23258861 (ISSN); 9781479908844 (ISBN) ; Rezaei, S ; Salavatian, S
2013
Abstract
In this paper, we try to recognize and distinguish different groups of arrhythmia using novel features which have been obtained from the heart rate's phase space in recent years. For this purpose, we used Triangular Phase Space Mapping (TPSM) and Parabolic Phase Space Mapping (PPSM). For recognition, we used three groups of 15 subjects using the Physionet database (Arrhythmia, Congestive Heart Failure (CHF), and Atrial Fibrillation (AF)) with Normal Sinus Rhythm (NSR). The obtained features discriminate arrhythmia from NSR by p
An intelligent hybrid classification algorithm integrating fuzzy rule-based extraction and harmony search optimization: Medical diagnosis applications
, Article Knowledge-Based Systems ; Volume 220 , 2021 ; 09507051 (ISSN) ; Abdullah, S ; Akhavan Niaki, S. T ; Banihashemi, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Uncertainty is a critical factor in medical datasets needed to be overcome for increasing diagnosis efficiency. This paper proposes an intelligent classification algorithm comprising a fuzzy rule-based approach, a harmony search (HS) algorithm, and a heuristic algorithm to classify medical datasets intelligently. Two fuzzy approaches, as well as orthogonal and triangular fuzzy sets, are first utilized to define the attributes of data. Then, an HS algorithm is integrated with a heuristic to generate fuzzy rules to select the best rules in the fuzzy rule-based systems. Moreover, to improve the performance of the proposed classification approach, a three-phase parameter tuning approach is...
Performance evaluation of shared hosting security methods
, Article Proc. of the 11th IEEE Int. Conference on Trust, Security and Privacy in Computing and Communications, TrustCom-2012 - 11th IEEE Int. Conference on Ubiquitous Computing and Communications ; 2012 , Pages 1310-1315 ; 9780769547459 (ISBN) ; Arshad, S ; Khoshkdahan, S ; Sharif University of Technology
2012
Abstract
Shared hosting is a kind of web hosting in which multiple websites reside on one webserver. It is cost-effective and makes the administration easier for websites' owners. However, shared hosting has some performance and security issues. In default shared hosting configuration, all websites' scripts are executed under the webserver's user account regardless of their owners. Therefore, a website is able to access other websites' resources. This security problem arises from lack of proper isolation between different websites hosted on the same webserver. In this survey, we have examined different methods for handling mentioned security issue. Also we evaluated the performance of mentioned...
The behaviour of an artificially cemented sandy gravel
, Article Geotechnical and Geological Engineering ; Volume 23, Issue 5 , 2005 , Pages 537-560 ; 09603182 (ISSN) ; Hosseini, S. M ; Toll, D. G ; Yasrebi, S. S ; Sharif University of Technology
2005
Abstract
The major section of the city of Tehran, Iran has been developed on cemented coarse-grained alluvium. This deposit consists of gravely sand to sandy gravel with some cobbles and is dominantly cemented by carbonaceous materials. In order to understand the mechanical behaviour of this soil, a series of undrained triaxial compression tests and unconfined compression tests were performed on uncemented and artificially cemented samples. Portland cement type I was used as the cementation agent for preparing artificially cemented samples. Uncemented samples and lightly cemented samples (1.5% cement) tested at high confining pressure showed contractive behaviour accompanied with positive excess pore...
An imperialist competitive algorithm approach for multi-objective optimization of direct coupling photovoltaic-electrolyzer systems
, Article International Journal of Hydrogen Energy ; Vol. 39, Issue 33 , 11 November , 2014 , pp. 18743-18757 ; ISSN: 03603199 ; Sayedin, F ; Khavas, S. S
2014
Abstract
In the context of sustainable clean hydrogen production pathways, photovoltaic-electrolyzer systems are one of the most promising alternatives for acquiring hydrogen from renewable energy sources. In fact, determining the optimal set of design and operating variables are always a key issue while coupling directly renewable electricity sources to PEM electrolyzers. Few previous studies have attempted to find the optimal size and operational condition of directly coupled photovoltaic-electrolyzer (PV/El) systems in order to maximize the hydrogen production or to minimize energy transfer loss between photovoltaic devices and the electrolyzer. Nevertheless an easy and efficient approach still...
Kalman filter based packet loss replacement in presence of additive noise
, Article 2012 25th IEEE Canadian Conference on Electrical and Computer Engineering: Vision for a Greener Future, CCECE 2012 ; 2012 ; 9781467314336 (ISBN) ; Ghorshi, S ; Tahaei, A
2012
Abstract
A major problem in real-time packet-based communication systems, is misrouted or delayed packets which results in degraded perceived voice quality. If packets are not available on time, the packets are considered as lost. The easiest solution in a network terminal receiver is to replace silence for the duration of lost speech segments. In a high quality communication system, to avoid degradation in speech quality due to packet loss, a suitable method or algorithm is needed to replace the missing segments of speech. In this paper, we introduce an adaptive filter for replacement of lost speech segment. In this method Kalman filter as a state-space based method will be used to predict the...
Investigation of Mesh Sensitivity Influence to Determine Crack Characteristic by Finite Element Methods
, Article Journal of Failure Analysis and Prevention ; Volume 16, Issue 3 , 2016 , Pages 506-512 ; 15477029 (ISSN) ; Mirjavadi, S. S ; Asli, S. A ; Sharif University of Technology
Springer New York LLC
2016
Abstract
In this research, an extended finite element model has been investigated. Investigation of opening and closure stress always has been one of the difficult parameters to analysis of results; therefore, the utilization of finite element methods would be a good and logical alternative for this purpose. In addition, linear elastic fracture criteria are used for validation of numerical results from the simulation. In this work, a detailed analysis of the influence of different parameters in the results of a specific specimen with a semi-elliptical tooling groove in terms of closure and opening stress is presented, and the impact of optimum element size in fracture characteristic in various load...