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Total 77 records

    Optimal distribution network automation considering earth fault events

    , Article IEEE Transactions on Smart Grid ; Vol. 6, issue. 2 , 2015 , p. 1010-1018 ; ISSN: 19493053 Siirto, O. K ; Safdarian, A ; Lehtonen, M ; Fotuhi-Firuzabad, M ; Sharif University of Technology
    Abstract
    In the past decade, distribution network operators have been broadly engrossed toward automated distribution networks. The operators acknowledge network automation as an efficient investment toward a better service reliability. This paper aims to provide a new long-term cost/benefit analysis for an optimal level of distribution network automation. In the analysis, reduction in customer outage cost is considered as the benefit of implementing automation systems with capital investment, and annual operation and maintenance costs. In the Finnish regulation model, there is a special incentive based on customer outage cost reduction. As the main contribution of this paper, the impact of earth... 

    Aging aircraft cost analysis using system dynamics modeling

    , Article 29th Congress of the International Council of the Aeronautical Sciences, ICAS 2014 ; 7-12 September , 2014 ; ISBN: 3932182804 Fouladi, E ; Shadaab, N ; Abedian, A ; Tanara, A. K ; Sharif University of Technology
    Abstract
    Ways to reduce an airline's cost has been studied for years. In fact, in order to achieve this goal, ones need to know different types of airline's costs including; fuel and oil, maintenance, Ticketing, passenger services, etc. and their impact on the total cost of an airline. According to announcement of ICAO [1], "maintenance cost (about 11% of total cost) is the second major cost after fuel and oil". Therefore, this may attract airline owners' attention to find ways to control maintenance cost and eventually the total cost of an airline. Though, there are many systematic approaches to analyze cost reduction and making policies, in this article, SD modeling is applied to develop a... 

    Feasibility of using laser bit beside of common bits to drilling slim holes

    , Article Society of Petroleum Engineers - International Petroleum Technology Conference 2013, IPTC 2013: Challenging Technology and Economic Limits to Meet the Global Energy Demand ; Volume 1 , 2013 , Pages 422-433 ; 9781627481762 (ISBN) Bazargan, M ; Jalalyfar, H ; Koohian, A ; Habibpour, M ; Sharif University of Technology
    2013
    Abstract
    The capability level of rotary as well as first generation drilling operation could not be matched for deeply drilling programs. To reach that deep, the increasing in drill string length could also cause an additional constraint on hydraulic performance. The operation of slim hole drilling has significant potential to reduce well costs. This cost might be savings are especially important with increased demand for reduced capital finance under current economic conditions in the Iranian oil and gas industry. This savings achievement could be caused by use of smaller drilling rigs, work over rigs, reduced casing size, reducing requirement for drilling consumables and other costs associated with... 

    An integrated vendor-buyer inventory model with partial backordering

    , Article Journal of Manufacturing Technology Management ; Volume 23, Issue 7 , 2012 , Pages 869-884 ; 1741038X (ISSN) Moshrefi, F ; Jokar, M. R. A ; Sharif University of Technology
    2012
    Abstract
    Purpose - The purpose of this paper is to analyze the effects of supply chain coordination on inventory management while the retailer inventory cycle consists of a shortage period and the backorder rate linearly decreases as a function of shortage duration. It is intended to consider how on-hand inventory and shortage durations are altered when the decisions are centralized. Design/methodology/approach - Mathematical modelling of inventory costs for the retailer and the vendor is used to formulate objective functions. The vendor sets his inventory period as an integer multiple (n) of the retailer inventory cycle in which the integer multiple is a decision variable. Solution spaces of models... 

    Mining distributed frequent itemsets using a gossip based protocol

    , Article Proceedings - IEEE 9th International Conference on Ubiquitous Intelligence and Computing and IEEE 9th International Conference on Autonomic and Trusted Computing, UIC-ATC 2012 ; 2012 , Pages 780-785 Bagheri, M ; Mirian Hosseinabadi, S. H ; Mashayekhi, H ; Habibi, J ; Sharif University of Technology
    2012
    Abstract
    Recently, there has been a growing attention in frequent itemset mining in distributed systems. In this paper, we present an algorithm to extract frequent itemsets from large distributed datasets. Our algorithm uses gossip as the communication mechanism and does not rely on any central node. In gossip based communication, nodes repeatedly select other random nodes in the system, and exchange information with them. Our algorithm proceeds in rounds and provides all nodes with the required support counts of itemsets, such that each node is able to extract the global frequent itemsets. For local iteration and generation of candidate itemsets, a trie data structure is used, which facilitates the... 

    LAYMOD: A layered and modular platform for CAx product data integration based on the modular architecture of the standard for exchange of product data

    , Article International Journal of Computer Integrated Manufacturing ; Volume 25, Issue 6 , 2012 , Pages 473-487 ; 0951192X (ISSN) Houshmand, M ; Valilai, O. F ; Sharif University of Technology
    2012
    Abstract
    Nowadays, companies strive to survive in a competitive global environment. Reduction of product development cycle plays a major role in market penetration and cost reduction. To speed up product development/modifications, it is suggested to adopt a collaborative product development approach. Collaborative design and manufacture requires an integrated platform to support related CAx product data models. To integrate CAx product data, a number of solutions are proposed. The most successful solution is adopting the STandard for Exchange of Product Data (STEP). In the course of the STEP standard structure and procedure development, two approaches can be recognised: classical and modular. The... 

    Cost and inventory benefits of cooperation in multi-period and multi-product supply

    , Article Scientia Iranica ; Volume 18, Issue 3 E , 2011 , Pages 731-741 ; 10263098 (ISSN) Sepehri, M ; Sharif University of Technology
    2011
    Abstract
    Cooperation among supply chain members, both horizontally and vertically, has become the norm in practice. Unlike traditional supply chains with members competing to reduce their individual costs, the overall cost of the entire supply chain is minimized in a cooperative supply chain. The savings from cooperation may be shared among the members, while a lower average cost and a lower cost variation is materialized for individual members. The problem is formulated as an integrated flow network and expanded to multi-period and multi-product, with the possibility of holding inventories in a multi-stage, multi-member cooperative supply chain. Simulation results indicate an approximately 26%... 

    Recent progress in inorganic and composite coatings with bactericidal capability for orthopaedic applications

    , Article Nanomedicine: Nanotechnology, Biology, and Medicine ; Volume 7, Issue 1 , Feb , 2011 , Pages 22-39 ; 15499634 (ISSN) Simchi, A ; Tamjid, E ; Pishbin, F ; Boccaccini, A. R ; Sharif University of Technology
    Abstract
    This review covers the most recent developments of inorganic and organic-inorganic composite coatings for orthopedic implants, providing the interface with living tissue and with potential for drug delivery to combat infections. Conventional systemic delivery of drugs is an inefficient procedure that may cause toxicity and may require a patient's hospitalization for monitoring. Local delivery of antibiotics and other bioactive molecules maximizes their effect where they are required, reduces potential systemic toxicity and increases timeliness and cost efficiency. In addition, local delivery has broad applications in combating infection-related diseases. Polymeric coatings may present some... 

    Weak visibility counting in simple polygons

    , Article Journal of Computational and Applied Mathematics ; Volume 288 , November , 2015 , Pages 215-222 ; 03770427 (ISSN) Nouri Bygi, M ; Daneshpajouh, S ; Alipour, S ; Ghodsi, M ; Sharif University of Technology
    Elsevier  2015
    Abstract
    For a simple polygon P of size n, we define weak visibility counting problem (WVCP) as finding the number of visible segments of P from a query line segment pq. We present different algorithms to compute WVCP in sub-linear time. In our first algorithm, we spend O(n7) time to preprocess the polygon and build a data structure of size O(n6), so that we can optimally answer WVCP in O(logn) time. Then, we reduce the preprocessing costs to O(n4+ε) time and space at the expense of more query time of O(log5n). We also obtain a trade-off between preprocessing and query time costs. Finally, we propose an approximation method to reduce the preprocessing costs to O(n2) time and space and O(n1/2+ε) query... 

    Project Scheduling Subject to Non-Renewable Perishable Resources

    , M.Sc. Thesis Sharif University of Technology Najafi Farashah, Mohammad Hadi (Author) ; Shadrokh, Shahram (Supervisor)
    Abstract
    In this research a mathematical formulation is presented for project scheduling problem subject to non-renewable perishable resources where the objective is minimize the cost of ordering and maintenance of resources. We use the framework of a resource constrained project scheduling problem (RCPSP) with finish-start precedence relations between activities and resources will be perished after a determined duration and must be procured. Resource procurement have ordering and purchasing costs and excess resources must be stored and have maintenance cost. There is a unique way to perform the activities and preemption is not allowed.
    This work employs Genetics Algorithms to solve the problem... 

    Optimal distribution network automation considering earth fault events

    , Article IEEE Transactions on Smart Grid ; Volume 6, Issue 2 , 2015 , Pages 1010-1018 ; 19493053 (ISSN) Siirto, O. K ; Safdarian, A ; Lehtonen, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
    Abstract
    In the past decade, distribution network operators have been broadly engrossed toward automated distribution networks. The operators acknowledge network automation as an efficient investment toward a better service reliability. This paper aims to provide a new long-term cost/benefit analysis for an optimal level of distribution network automation. In the analysis, reduction in customer outage cost is considered as the benefit of implementing automation systems with capital investment, and annual operation and maintenance costs. In the Finnish regulation model, there is a special incentive based on customer outage cost reduction. As the main contribution of this paper, the impact of earth... 

    Electrolytic capacitor-less AC-DC LED driver with constant output current and PFC

    , Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; 2015 , Pages 107-112 ; 9781479976539 (ISBN) Valipour, H ; Rezazadeh, G ; Zolghadri, M. R ; Noroozi, N ; Sharif University of Technology
    Abstract
    Recent developments in improving lighting efficiency and cost reduction of LED's have caused them to be a suitable alternative for the current lighting systems. In this paper a novel off-line structure is proposed to drive LED's. The proposed circuit has a high power factor and high efficiency and a long lifetime. To increase the life time of the converter, the proposed circuit doesn't use any electrolytic capacitors in the power stage. The proposed circuit consists of a transition mode (TM) Flyback converter in order to have power factor correction (PFC). A Buck converter is added to the third winding of the Flyback transformer in order to create two paths for the electrical power. DC power... 

    Conceptual design and techno-economic assessment of integrated solar combined cycle system with DSG technology

    , Article Solar Energy ; Volume 84, Issue 9 , September , 2010 , Pages 1696-1705 ; 0038092X (ISSN) Nezammahalleh, H ; Farhadi, F ; Tanhaemami, M ; Sharif University of Technology
    2010
    Abstract
    Direct steam generation (DSG) in parabolic trough collectors causes an increase to competitiveness of solar thermal power plants (STPP) by substitution of oil with direct steam generation that results in lower investment and operating costs. In this study the integrated solar combined cycle system with DSG technology is introduced and techno-economic assessment of this plant is reported compared with two conventional cases. Three considered cases are: an integrated solar combined cycle system with DSG technology (ISCCS-DSG), a solar electric generating system (SEGS), and an integrated solar combined cycle system with HTF (heat transfer fluid) technology (ISCCS-HTF).This study shows that... 

    Toward a business model for software product line architecture

    , Article 8th ACIS International Conference on Software Engineering Research, Management and Applications, SERA 2010, 24 May 2010 through 26 May 2010, Montreal, QC ; 2010 , Pages 50-56 ; 9780769540757 (ISBN) Tanhaei, M ; Moaven, S ; Habibi, J ; Ahmadi, H ; Sharif University of Technology
    2010
    Abstract
    Nowadays, software product line is an approach to reduce costs of software development, decrease time to market, and increase capabilities of reuse in designing and exploiting software development processes. Moreover, other quality attributes of the project domain should be considered to enhance quality of the product. Meanwhile, taking advantage of software product line makes developers capable of estimating development costs and time to market in a more realistic way. However, old approaches to estimate cost of development and foresee time to market are not suitable enough for software product line. In this paper, some important business parameters and a way to calculate cost and time to... 

    Toward an architecture-based method for selecting composer components to make software product line

    , Article ITNG2010 - 7th International Conference on Information Technology: New Generations, 12 April 2010 through 14 April 2010 ; April , 2010 , Pages 1233-1236 ; 9780769539843 (ISBN) Tanhaei, M ; Moaven, S ; Habibi, J ; Sharif University of Technology
    2010
    Abstract
    Nowadays, product line, as an important topic in software development domain, has been paid attention by software engineering practitioners. Finding suitable components to construct an efficient and comprehensive product line with low costs is one of the critical problems in this domain which demands to be satisfied. In this paper a method is presented which can manage and control complexities of component selection problem, an NP problem, and result in creation of declared product line. By making use of this method, a product line will be constructed with suitably-adopted components to cover up requirements based on architecture; that's why software product line development process will... 

    A practical approach for coherent signal surveillance and blind parameter assessment in asynchoronous DS-CDMA systems in multipath channel

    , Article Proceedings - 2010 18th Iranian Conference on Electrical Engineering, ICEE 2010, 11 May 2010 through 13 May 2010 ; 2010 , Pages 305-310 ; 9781424467600 (ISBN) Samsami Khodadad, F ; Ganji, F ; Aref, M. R ; Sharif University of Technology
    Abstract
    A novel, robust and practical method for active user enumeration in asynchronous CDMA in multipath channel condition is proposed in this paper. Most of the previous works do not consider the fact that in practical case, user's signals with the help of receiver arrive asynchronously. The proposed method can be used practically in blind multi-user detection such as eavesdropping; moreover, the method is based on information theory criteria which outperform other methods. Minimum description length (MDL) has better performance than all other information criteria used in such scenarios. Unlike most of the pervious works, we do not exploit array antenna to gather necessary data of the users.... 

    A graph weighting method for reducing consensus time in random geographical networks

    , Article 24th IEEE International Conference on Advanced Information Networking and Applications Workshops, WAINA 2010, 20 April 2010 through 23 April 2010, Perth ; 2010 , Pages 317-322 ; 9780769540191 (ISBN) Jalili, M ; Sharif University of Technology
    2010
    Abstract
    Sensor networks are increasingly employed in many applications ranging from environmental to military cases. The network topology used in many sensor network applications has a kind of geographical structure. A graph weighting method for reducing consensus time in random geographical networks is proposed in this paper. We consider a method based on the mutually coupled oscillators for providing general consensus in the network. In this way, one can relate the consensus time to the properties of the Laplacian matrix of the connection graph, i.e. to the second smallest eigenvalue (algebraic connectivity). Our weighting algorithm is based on the node and edge between centrality measures. The... 

    A novel optimal distribution system planning framework implementing distributed generation in a deregulated electricity market

    , Article Electric Power Systems Research ; Volume 80, Issue 7 , July , 2010 , Pages 828-837 ; 03787796 (ISSN) Porkar, S ; Poure, P ; Abbaspour Tehrani fard, A ; Saadate, S ; Sharif University of Technology
    2010
    Abstract
    This paper introduces a new framework included mathematical model and a new software package interfacing two powerful softwares (MATLAB and GAMS) for obtaining the optimal distributed generation (DG) capacity sizing and sitting investments with capability to simulate large distribution system planning. The proposed optimization model allows minimizing total system planning costs for DG investment, DG operation and maintenance, purchase of power by the distribution companies (DISCOs) from transmission companies (TRANSCOs) and system power losses. The proposed model provides not only the DG size and site but also the new market price as well. Three different cases depending on system... 

    An investigation of vendor-managed inventory application in supply chain: The EOQ model with shortage

    , Article International Journal of Advanced Manufacturing Technology ; Volume 49, Issue 1-4 , July , 2010 , Pages 329-339 ; 02683768 (ISSN) Pasandideh, S. H. R ; Akhavan Niaki, S. T ; Roozbeh Nia, A ; Sharif University of Technology
    2010
    Abstract
    Recent researches have shown the importance of improving the supply chain competitiveness by means of strategic alliances. This study considers the retailer-supplier partnership through a vendor-managed inventory (VMI) system and develops an analytical model to explore the effect of important supply chain parameters on the cost savings realized from collaborative initiatives. This model is developed for a two-level supply chain consisting of a single supplier and a single retailer and examines the inventory management practices before and after implementation of VMI. The results of analytical examination show that VMI implementation in economic order quantity model when shortage is... 

    Locating and parameters setting of unified power flow controller for congestion management and improving the voltage profile

    , Article Asia-Pacific Power and Energy Engineering Conference, APPEEC, 28 March 2010 through 31 March 2010 ; March , 2010 ; 21574839 (ISSN) ; 9781424448135 (ISBN) Hashemzadeh, H ; Ehsan, M ; Sharif University of Technology
    2010
    Abstract
    This paper propose a particle swarm optimization based algorithm for locating Unified power flow controller (UPFC), as well as set its parameters, with static point of view in deregulated electricity markets in order to reduce generation cost, voltage violation and manage congestion. The modeling of UPFC has been adapted based on power injection method. In order to verify and validate the effectiveness of the proposed method, it was applied to 24-bus Reliability Test System (RTS) and the results have been discussed