Search for: cost-reduction
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    The impact of demand response programs on UPFC placement

    , Article Turkish Journal of Electrical Engineering and Computer Sciences ; Volume 27, Issue 6 , 2019 , Pages 4624-4639 ; 13000632 (ISSN) Sharifi Nasab Anari, A ; Ehsan, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
    Turkiye Klinikleri  2019
    Demand response (DR) and flexible AC transmission system (FACTS) devices can be effectively used for congestion management in power transmission systems. However, demand response program (DRP) implementation can itself affect the optimum location of FACTS devices, which is one of the main issues in power system planning. This paper investigates the impact of DRPs on unified power flow controller (UPFC) placement. The harmony search algorithm is employed to determine the optimum locations and parameter setting of UPFC in a long-term framework. The optimization problem is solved with different objectives including generation and congestion cost reduction, as well as loss reduction. In this... 

    Network and application-aware cloud service selection in peer-assisted environments

    , Article IEEE Transactions on Cloud Computing ; Volume 9, Issue 1 , 2021 , Pages 258-271 ; 21687161 (ISSN) Askarnejad, S ; Malekimajd, M ; Movaghar, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    There are a vast number of cloud service providers, which offer virtual machines (VMs) with different configurations. From the companies perspective, an appropriate selection of VMs is an important issue, as the proper service selection leads to improved productivity, higher efficiency, and lower cost. An effective service selection cannot be done without a systematic approach due to the modularity of requests, the conflicts between requirements, and the impact of network parameters. In this paper, we introduce an innovative framework, called PCA, to solve service selection problem in the hybrid environment of peer-assisted, public, and private clouds. PCA detects the conflicts between the... 

    3RSeT: Read disturbance rate reduction in STT-mram caches by selective tag comparison

    , Article IEEE Transactions on Computers ; 2021 ; 00189340 (ISSN) Cheshmikhani, E ; Farbeh, H ; Asadi, H ; Sharif University of Technology
    IEEE Computer Society  2021
    Recent development in memory technologies has introduced Spin-Transfer Torque Magnetic RAM (STT-MRAM) as the most promising replacement for SRAMs in on-chip cache memories. Besides its lower leakage power, higher density, immunity to radiation-induced particles, and non-volatility, an unintentional bit flip during read operation, referred to as read disturbance error, is a severe reliability challenge in STT-MRAM caches. One major source of read disturbance error in STT-MRAM caches is simultaneous accesses to all tags for parallel comparison operation in a cache set, which has not been addressed in previous work. This paper first demonstrates that high read accesses to tag arrays extremely... 

    A new designed linear Fresnel lens solar concentrator based on spectral splitting for passive cooling of solar cells

    , Article Energy Conversion and Management ; Volume 230 , 2021 ; 01968904 (ISSN) Kiyaee, S ; Saboohi, Y ; Moshfegh, A. Z ; Sharif University of Technology
    Elsevier Ltd  2021
    The use of solar concentrators can be an alternative for initial cost reduction in the PV systems. However, they suffer from high cell temperature that can be overcome by different active or passive cooling approaches. Spectral splitting and the elimination of high-energy solar photons are effective solutions for cell temperature reduction. In this study, we developed a Polymethyl methacrylate Spectral Splitting Fresnel Lens (SSFL) for linear concentration using a new design, which directs the desired portion of the spectrum towards the cell and diffracts the rest to eliminate the use of beam splitters or nanofluids in the spectral splitting system. Different SSFLs were considered for... 

    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
    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... 

    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
    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... 

    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
    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
    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%... 

    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
    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
    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... 

    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
    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... 

    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
    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
    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... 

    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
    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
    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  

    A novel BEM- based channel estimation algorithm for time variant uplink OFDMA system

    , Article International Conference on Advanced Communication Technology, ICACT, 7 February 2010 through 10 February 2010 ; Volume 2 , Feb , 2010 , Pages 1289-1293 ; 17389445 (ISSN) ; 9788955191455 (ISBN) Ganji, F ; Tabatabavakili, V ; Samsami Khodadad, F ; Hosseinnezhad, M ; Safaei, A ; Sharif University of Technology
    IN this paper the effect of different channel estimation approaches in OFDMA uplink system which are based on Basis Expansion Model (BEM) and widely used to consider time varying channels are discussed. It has been shown in previous works that modeling error will be reduced by applying oversampled BEM with cost of increasing sensitivity to noise. This problem will be solved by combining oversampled BEM and MMSE channel estimator with cost of increasing computational complexity. In this paper a novel channel estimation approach is represented in which by combining oversampled BEM and low rank MMSE in frequency domain, almost the same performance as the full rank MMSE has been achieved while... 

    Flicker-free electrolytic capacitor-less universal input offline LED driver with PFC

    , Article IEEE Transactions on Power Electronics ; Volume 31, Issue 9 , 2016 , Pages 6553-6561 ; 08858993 (ISSN) Valipour, H ; Rezazadeh, G ; Zolghadri, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Recent developments in improving lighting efficiency and cost reduction of LEDs have made them suitable alternatives to the current lighting systems. In this paper, a novel offline structure is proposed to drive LEDs. The proposed circuit has a high-input power factor, high efficiency, a long lifetime, and it produces no flicker. To increase the lifetime of the converter, the proposed circuit does not include any electrolytic capacitors in the power stage. The proposed circuit consists of a transition mode flyback converter in order to improve power factor. Additionally, a buck converter is added to the third winding of the flyback transformer in order to create two parallel paths for the... 

    A novel PSO (Particle Swarm Optimization)-based approach for optimal schedule of refrigerators using experimental models

    , Article Energy ; Volume 107 , 2016 , Pages 707-715 ; 03605442 (ISSN) Farzamkia, S ; Ranjbar, H ; Hatami, A ; Iman Eini, H ; Sharif University of Technology
    Elsevier Ltd  2016
    Refrigerators have considerable share of residential consumption. They can be, however, flexible loads because their operating time and consumption patterns can be changed to some extent. Accordingly, they can be selected as a target for the study of Demand Side Management plans. In this paper, two experimental models for a refrigerator are derived. In obtaining the first model, following assumptions are made: the ambient temperature of refrigerator is assumed to be constant and the refrigerator door is remained closed. However, in the second model the variation of ambient temperature and door-opening effects are considered according to some general patterns. Further, two strategies are... 

    An overview to applicability of multilateral drilling in the Middle East Fields

    , Article Society of Petroleum Engineers - Offshore Europe Oil and Gas Conference and Exhibition 2009, OE 2009, 8 September 2009 through 11 September 2009, Aberdeen ; Volume 1 , 2009 , Pages 567-577 ; 9781615675821 (ISBN) Mirzaei Paiaman, A ; Moghadasi, J ; Sharif University of Technology
    There are several types of drilling methods to increase the productivity of a well, such as horizontal drilling, extended reach horizontal drilling and Multilateral (ML) drilling. It is thought that ML wells could be more economic with higher productivities than horizontal or extended reach horizontal wells. Advances in ML drilling promise reduced costs, greater flexibility and increased profit potential. In the last 20 years, thousands of ML wells have been drilled worldwide, but only a small percentage of the total number of wells is multilateral. The probable reason may be lack of concise information and misconceptions surrounding the costs and perceived risks. However, recent advances in... 

    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) Kuchaki Rafsanjani, M ; Khavasi, A. A ; Movaghar, A ; Sharif University of Technology
    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