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efficient-method
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Technical and Economic Modeling Techniques to Improve Efficiency of Gas Turbine Cycle in Different Operational Conditions
, M.Sc. Thesis Sharif University of Technology ; Sattari, Sorena (Supervisor)
Abstract
Gas turbine is one of most widely used in power plants to generate electricity or mechanical power options in the industry , which is having its own advantages and disadvantages . if the turbine use simple , efficiency is generally below 33%. . After installing and employ , these turbines produce efficiency less than their nominal amount . The methods no change in structure exist that increase the efficiency or power of the turbine to acceptable level .In this thesis, gas turbine and to improvement performance methods has been studied . gas turbine with the methods are simulated to obtain the effect of each method in different environmental conditions . Economic sensitivity analysis...
Efficient kernel learning from constraints and unlabeled data
, Article Proceedings - International Conference on Pattern Recognition, 23 August 2010 through 26 August 2010, Istanbul ; 2010 , Pages 3364-3367 ; 10514651 (ISSN) ; 9780769541099 (ISBN) ; Bagheri Shouraki, S ; Sharif University of Technology
2010
Abstract
Recently, distance metric learning has been received an increasing attention and found as a powerful approach for semi-supervised learning tasks. In the last few years, several methods have been proposed for metric learning when must-link and/or cannot-link constraints as supervisory information are available. Although many of these methods learn global Mahalanobis metrics, some recently introduced methods have tried to learn more flexible distance metrics using a kernel-based approach. In this paper, we consider the problem of kernel learning from both pairwise constraints and unlabeled data. We propose a method that adapts a flexible distance metric via learning a nonparametric kernel...
Effect of Electromagnetic Field on Membrane Fouling in Filtration Process
, M.Sc. Thesis Sharif University of Technology ; Kariminia, Hamid Reza (Supervisor) ; Mousavi, Abbas (Supervisor)
Abstract
Current research studies the effect of electromagnetic field on reducing precipitation on membrane surface in reverse osmosis. Reverse osmosis is one of the most widely applied methods for water desalinization. Despite its advantages over other desalinization techniques, suffers from shortcomings such as blockage of membrane surface. Use of magnetic fields for reducing precipitation in process equipment, the so-called magnetic treatment, has been studied and practiced for decades. This research intends to study the effect of electromagnetic field on water and its mineral content, and the possibility of its application as a method for reducing precipitation and blockage in reverse osmosis...
Design and Implementation of a DC/AC Converter with High Step up and High Efficiency in Wide Output Power Range for Photovoltaic Applications
, M.Sc. Thesis Sharif University of Technology ; Zolghardi, Mohammad Reza (Supervisor)
Abstract
Solar power is expensive, so engineers are encouraged to put effort on increasing efficiency of solar power equipments. Since photovoltaic panels usually output a low voltage, variable direct current electricity, a boost converter and a suitable inverter are required to use this energy for ordinary commercial appliances. In this project, high step up, high efficiency converters are investigated, and the best converter with high efficiency and limited switch stress which achieves high voltage gain by capacitor multipliers and coupled inductors is illustrated. Afterwards, methods for improving efficiency such as modifying the converter structure and its control strategy are suggested. The...
Towards an efficient method for spreading information in social network
, Article 2009 3rd Asia International Conference on Modelling and Simulation, AMS 2009, Bandung, Bali, 25 May 2009 through 26 May 2009 ; 2009 , Pages 152-157 ; 9780769536484 (ISBN) ; Mehrbakhsh, A ; Asgarian, E ; Sharif University of Technology
2009
Abstract
Nowadays, content distribution is of high attention in peer to peer information systems. There are two main problems that could be mentioned in this context. The first problem is how to disseminate fragments of information efficiently and the next is to avoid missing same rare fragments towards end of download. For overcoming these problems, a new mechanism is presented in this paper which uses gossip algorithms on basis of social networks. Our mechanism maintains simplicity of gossip and has low overhead. This mechanism includes two phases for managing traffic and solving bottleneck problem: one for spreading rumors inside the social network and finding network of interests and the other...
Efficient method for simplifying and approximating the S-boxes based on power functions
, Article IET Information Security ; Volume 3, Issue 3 , 2009 , Pages 114-118 ; 17518709 (ISSN) ; Aref, M. R ; Sharif University of Technology
2009
Abstract
In recently proposed cipher algorithms, power functions over finite fields and specially inversion functions play an important role in the S-box design structure. In this study, a new systematic efficient method is introduced to cryptanalyse (to simplify and approximate) such S-boxes. This method is very simple and does not need any heuristic attempt and can be considered as a quick criterion to find some simple approximations. Using this new method, some approximations can be obtained for advanced encryption standard (AES) like S-boxes, such as AES, Camellia, Shark and so on. Finally as an application of this method, a simple linear approximation for AES S-box is presented. © The...
On Efficiency and Bandwidth Enhancement of Integrated Class-J Power Amplifiers
, Ph.D. Dissertation Sharif University of Technology ; Medi, Ali (Supervisor)
Abstract
Power amplifiers (PAs) are one of the key components in radio-frequency (RF) and microwave systems. In these systems, PAs must be highly efficient to simplify the thermal management and to enhance dc power requirements. Future systems, including WiMax, 4G, 5G, and beyond, will likely require larger bandwidths due to their wider spectral allocations caused by the extended bandwidth of baseband signals. Therefore, highly-efficient and broadband PAs are needed to be employed in these systems. To realize high-efficiencies over wide frequency ranges, class-J mode of operation was introduced by Cripps in 2009. Class-J mode of operation is capable of maintaining a high efficiency (78% in theory)...
Efficient DPCM predictor for hardware implementation of lossless medical brain CT image compression
, Article International Conference on Signals and Electronic Systems, ICSES'10 - Conference Proceeding, 7 September 2010 through 10 September 2010 ; September , 2010 , Pages 123-126 ; 9788390474342 (ISBN) ; Mortazavi, M ; Ghorshi, S ; Sharif University of Technology
2010
Abstract
Computed Tomography (CT) medical images show a specific part of human body and present it in a digital form. Lossless image compression is one of the medical imaging applications. To implement such application on hardware we need a simple and fast algorithm. Differential pulse code modulation (DPCM) is a simple and efficient method for transforming image. In this paper best predictor for DPCM introduce in a manner in which has the best result in compression and also be efficient for hardware implementation. After transforming image by DPCM, Huffman encoding used to compress image. We introduce this method with application to brain CT images
Architecturally modified Al-DRA composites: The effect of size and shape of the DRA rods on fracture behavior
, Article Journal of Materials Science ; Volume 45, Issue 11 , June , 2010 , Pages 2852-2861 ; 00222461 (ISSN) ; Farokhzadeh, K ; Bagheri, R ; Seyed Reihani, S. M ; Sharif University of Technology
2010
Abstract
Architectural modification of aluminum matrix composites is considered as an efficient method to improve fracture toughness. Al-DRA (Al-Al/SiC/20 p) composites were fabricated via "powder extrusion-casting- ingot extrusion" route with structures similar to that of reinforced concrete, so that DRA rods were surrounded by unreinforced aluminum. The effects of variation in shape, size, and number of DRA rods on fracture behavior of Al-DRA composites were investigated. Composites containing DRA rods with hexagonal cross-section exhibited higher resistance to crack initiation and growth, in comparison to those containing circular rods. In the case of hexagonal rods, increasing the number of rods...
Efficient and safe path planning for a mobile robot using genetic algorithm
, Article 2009 IEEE Congress on Evolutionary Computation, CEC 2009, Trondheim, 18 May 2009 through 21 May 2009 ; 2009 , Pages 2091-2097 ; 9781424429592 (ISBN) ; Manzuri Shalmani, T ; Sharif University of Technology
2009
Abstract
In this paper, a new method for path planning is proposed using a genetic algorithm (GA). Our method has two key advantages over existing GA methods. The first is a novel environment representation which allows a more efficient method for obstacles dilation in comparison to current cell based approaches that have a tradeoff between speed and accuracy. The second is the strategy we use to generate the initial population in order to speed up the convergence rate which is completely novel. Simulation results show that our method can find a near optimal path faster than computational geometry approaches and with more accuracy in smaller number of generations than GA methods. © 2009 IEEE
Tolerance–reliability analysis of mechanical assemblies for quality control based on Bayesian modeling
, Article Assembly Automation ; Volume 39, Issue 5 , 2019 , Pages 769-782 ; 01445154 (ISSN) ; Ghaderi, A ; Sharif University of Technology
Emerald Group Publishing Ltd
2019
Abstract
Purpose: The purpose of this paper is to present a new efficient method for the tolerance–reliability analysis and quality control of complex nonlinear assemblies where explicit assembly functions are difficult or impossible to extract based on Bayesian modeling. Design/methodology/approach: In the proposed method, first, tolerances are modelled as the random uncertain variables. Then, based on the assembly data, the explicit assembly function can be expressed by the Bayesian model in terms of manufacturing and assembly tolerances. According to the obtained assembly tolerance, reliability of the mechanical assembly to meet the assembly requirement can be estimated by a proper first-order...
Iterative implicit integration procedure for hybrid simulation of large nonlinear structures
, Article Earthquake Engineering and Structural Dynamics ; Volume 40, Issue 9 , October , 2011 , Pages 945-960 ; 00988847 (ISSN) ; Ahmadizadeh, M ; Sharif University of Technology
2011
Abstract
A fully implicit iterative integration procedure is presented for local and geographically distributed hybrid simulation of the seismic response of complex structural systems with distributed nonlinear behavior. The purpose of this procedure is to seamlessly incorporate experimental elements in simulations using existing fully implicit integration algorithms designed for pure numerical simulations. The difficulties of implementing implicit integrators in a hybrid simulation are addressed at the element level by introducing a safe iteration strategy and using an efficient procedure for online estimation of the experimental tangent stiffness matrix. In order to avoid physical application of...
An efficient method to reliable data transmission in Network-on-Chips
, 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 467-474 ; 9780769541716 (ISBN) ; Tabkhi, H ; Miremadi, S. G ; Sharif University of Technology
2010
Abstract
Data transmission in Network-on-Chips (NoCs) is a serious problem due to crosstalk faults happening in adjacent communication links. This paper proposes an efficient flow-control method to enhance the reliability of packet transmission in Network-on-Chips. The method investigates the opposite direction transitions appearing between flits of a packet to reorder the flits in the packet. Flits are reordered in a fixed-size window to reduce: 1) the probability of crosstalk occurrence, and 2) the total power consumed for packet delivery. The proposed flow-control method is evaluated by a VHDL-based simulator under different window sizes and various channel widths. Simulation results enable NoC...
An efficient lossless medical image transformation method by improving prediction model
, Article International Conference on Signal Processing Proceedings, ICSP, 24 October 2010 through 28 October 2010 ; 2010 , Pages 728-731 ; 9781424458981 (ISBN) ; Mortazavi, M ; Ghorshi, S ; IEEE Beijing Section; The Chinese Institute of Electronics (CIE); The Institution of Engineering and Technology (IET); Union Radio Scientifique Internationale (URSI); National Natural Science Foundation of China ; Sharif University of Technology
Abstract
Medical images include human body picture and it is used in diagnosis purpose [1]. Lossless compression of medical image is an application of medical imaging. During lossless compression task, transformation algorithm can be used to increase compression ratio. In Real time applications such as telemedicine and online diagnosis, hardware implementation accelerates the process. Hence, for such purposes medical compression is better to be simple. Lossless JPEG and JPEG2000 are some compression method. JPEG2000 gives better compression ratio. However, it is complex. In this paper an efficient method of lossless image transformation has been introduced by improving prediction model. Simulation...
A novel approach for secure and fast generation of RSA public and private keys on SmartCard
, Article Proceedings of the 8th IEEE International NEWCAS Conference, NEWCAS2010, 20 June 2010 through 23 June 2010 ; June , 2010 , Pages 265-268 ; 9781424468058 (ISBN) ; Mali, M. R ; Sarbishei, O ; Atarodi, M ; Sharifkhani, M ; IEEE CAS Society ; Sharif University of Technology
2010
Abstract
RSA based SmartCards have been widely used in security services such as secure data transmission in many applications over the past few years. Generation of a secure key pair which is based on finding a pair of large prime numbers is an indispensable part of creating a secure channel. This paper describes a novel approach for secure and fast key generation of the public key cryptographic algorithm of RSA. This method has been implemented on a typical SmartCard equipped with a crypto-coprocessor and a true random number generator. An efficient method for generating the large random prime numbers is proposed that considerably reduces the total time required for generating a key pair. The key...
Recognizing combinations of facial action units with different intensity using a mixture of hidden Markov models and neural network
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 7 April 2010 through 9 April 2010 ; Volume 5997 LNCS , April , 2010 , Pages 304-313 ; 03029743 (ISSN) ; 9783642121265 (ISBN) ; Manzuri Shalmani, M. T ; Kiapour, M. H ; Kiaei, A. A ; Sharif University of Technology
2010
Abstract
Facial Action Coding System consists of 44 action units (AUs) and more than 7000 combinations. Hidden Markov models (HMMs) classifier has been used successfully to recognize facial action units (AUs) and expressions due to its ability to deal with AU dynamics. However, a separate HMM is necessary for each single AU and each AU combination. Since combinations of AU numbering in thousands, a more efficient method will be needed. In this paper an accurate real-time sequence-based system for representation and recognition of facial AUs is presented. Our system has the following characteristics: 1) employing a mixture of HMMs and neural network, we develop a novel accurate classifier, which can...
A novel approach for avoiding wormhole attacks in VANET
, Article 1st South Central Asian Himalayas Regional IEEE/IFIP International Conference on Internet, AH-ICI 2009, 3 November 2009 through 5 November 2009, Kathmundu ; 2009 ; 9781424445707 (ISBN) ; Movaghar, A ; Mohammadizadeh, M ; Sharif University of Technology
Abstract
Different attacks on routing protocols in ad hoc networks occur that one of the most dangerous types is called wormhole attack. This attack happens with the assistance of at least two or more malicious nodes. In this attack nodes create a private tunnel which if a packet comes to one of them, it will be guided to other pair of these malicious nodes by this tunnel and that node broadcasts it into network. This action provides a short connection in the network that is controlled by these malicious nodes. Hence they control all Packets that come to them and threaten the security of data within packets or delete them. Totally, what a wormhole does is an incorrect understanding of network...
Intelligent clustering in wireless sensor networks
, Article 1st International Conference on Networks and Communications, NetCoM 2009, 27 December 2009 through 29 December 2009, Chennai ; 2009 , Pages 12-17 ; 9780769539249 (ISBN) ; Movaghar, A ; Sharif University of Technology
Abstract
Minimization of the number of cluster heads in a wireless sensor network is a very important problem to reduce channel contention and to improve the efficiency of the algorithm when executed at the level of cluster-heads. In this paper, we propose an efficient method based on genetic algorithms (GAs) to solve a sensor network optimization problem. Long communication distances between sensors and a sink in a sensor network can greatly drain the energy of sensors and reduce the lifetime of a network. By clustering a sensor network into a number of independent clusters using a GA, we can greatly minimize the total communication distance, thus prolonging the network lifetime. Simulation results...
A novel approach for avoiding wormhole attacks in VANET
, Article 2nd International Workshop on Computer Science and Engineering, WCSE 2009, 28 October 2009 through 30 October 2009 ; Volume 2 , 2009 , Pages 160-165 ; 9780769538815 (ISBN) ; Movaghar, A ; Mohammadizadeh, M ; Sharif University of Technology
Abstract
Different attacks on routing protocols in ad hoc networks occur that one of the most dangerous types is called wormhole attack. This attack happens with the assistance of at least two or more malicious nodes. In this attack nodes create a private tunnel which if a packet comes to one of them, it will be guided to other pair of these malicious nodes by this tunnel and that node broadcasts it into network. This action provides a short connection in the network that is controlled by these malicious nodes. Hence they control all Packets that come to them and threaten the security of data within packets or delete them. Totally, what a wormhole does is an incorrect understanding of network...
An efficient method for identifying IDS agent nodes by discovering compromised nodes in MANET
, Article 2009 International Conference on Computer and Electrical Engineering, ICCEE 2009, 28 December 2009 through 30 December 2009, Dubai ; Volume 1 , 2009 , Pages 625-629 ; 9780769539256 (ISBN) ; Khavasi, A. A ; Movaghar, A ; Sharif University of Technology
Abstract
Intrusion Detection Systems (IDS) for Mobile Ad hoc NETworks (MANETs) are necessary when they are deployed in reality. In This paper, we have presented a combined method of selecting IDS agent nodes in mobile ad hoc networks. Since, the IDS agents in MANET due to more activities need to more battery power. In our method, first, compromised nodes are detected and then the nodes with the highest energy power from among valid nodes as IDS agent nodes are considered. So, with this method, some valid nodes contribute in intrusion detection activities and costs of the network monitoring will be reduced and the network lifetime will be increased. © 2009 IEEE