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    Bus maintenance systems and maintenance scheduling: Model formulations and solutions

    , Article Transportation Research Part A: Policy and Practice ; Volume 36, Issue 5 , 2002 , Pages 453-482 ; 09658564 (ISSN) Haghani, A ; Shafahi, Y ; Sharif University of Technology
    Elsevier Ltd  2002
    This paper deals with the problem of scheduling bus maintenance activities. The scheduling of maintenance activities is an important component in bus transit operations planning process. The other components include network route design, setting timetables, scheduling vehicles, and assignment of drivers. This paper presents a mathematical programming approach to the problem. This approach takes as input a given daily operating schedule for all buses assigned to a depot along with available maintenance resources. It, then, attempts to design daily inspection and maintenance schedules for the buses that are due for inspection so as to minimize the interruptions in the daily bus operating... 

    Modeling and technical-economic optimization of electricity supply network by three photovoltaic systems

    , Article Journal of Solar Energy Engineering, Transactions of the ASME ; Vol. 136, issue. 2 , 2014 ; ISSN: 0199-6231 Safarian, S ; Khodaparast, P ; Kateb, M ; Sharif University of Technology
    To attain an ongoing electricity economy, developing novel widespread electricity supply systems based on diverse energy resources are critically important. Several photovoltaic (PV) technologies exist, which cause various pathways to produce electricity from solar energy. This paper evaluates the competition between three influential solar technologies based on photovoltaic technique to find the optimal pathways for satisfying the electricity demand: (1) multicrystalline silicon; (2) copper, indium, gallium, and selenium (CIGS); and (3) multijunction. Besides the technical factors, there are other effective parameters such as cost, operability, feasibility, and capacity that should be... 

    Optimization Models for Financial Portfolio Problem

    , M.Sc. Thesis Sharif University of Technology Hayati, Nahid (Author) ; Mahdavi Amiri, Nezameddin (Supervisor)
    In financial portfolio problem, optimization models with uncertainty has been considered. The multi-stage stochastic programming methodology has been used as a solution method for these problems. In this study, we use multi-stage programming with uncertainity to evaluate the asset allocation problem. Some general models have been introduced for problem solving. Non-anticipativity and parent-child models are implemented and solved by both simplex and interior-point methods and the results are compared. The results show the parent-child model to have a better performance. Also, the interior-point method appears to need less computing time than the simplex method  

    New approach for strategic bidding of gencos in energy and spinning reserve markets

    , Article Energy Conversion and Management ; Volume 48, Issue 7 , 2007 , Pages 2044-2052 ; 01968904 (ISSN) Soleymani, S ; Ranjbar, A. M ; Shirani, A. R ; Sharif University of Technology
    In restructured and de-regulated power systems, generating companies (Gencos) are responsible for supplying electricity for both energy and reserve markets, which usually operate simultaneously. In this condition, the question is how much and for what price must each Genco generate for each market to maximize its profit, so this paper intends to answer to this question. In this paper, first, the combined energy and reserve markets are considered, and the Nash equilibrium points are determined. Then, the bidding strategies for each Genco at these points will be presented. The bids for the energy and 10 min spinning reserve (TMSR) markets are separated in the second stage, and again, the... 

    Using Water Trading to Address Water Supply Challenges in the Face of Climate Change

    , M.Sc. Thesis Sharif University of Technology Ansari, Meysam (Author) ; Abrishamchi, Ahmad (Supervisor)
    There is increasing demand for water due to rising world population. In addition, lower supplies of water under varying hydrological condition because of changing climate, renders further stress on an already over-allocated water resource. Thus, this condition would exacerbate water supply-demand conflicts resulting in penalties on local economy. On the other hand fresh water as a scarce resource requires comprehensive management. To maintain fresh water resources, systems need principles of ecologically sustainable development that keeps environmental uses as legal. Hence, in this situation there is a need to develop appropriate methods to minimize the climate change consequences and... 

    A new acceptance sampling policy based on number of successive conforming items

    , Article Communications in Statistics - Theory and Methods ; Volume 42, Issue 8 , Apr , 2013 , Pages 1542-1552 ; 03610926 (ISSN) Nezhad, M. S. F ; Niaki, S. T. A ; Sharif University of Technology
    In an acceptance-sampling plan, where items of an incoming batch of products are inspected one by one, if the number of conforming items between successive non conforming items falls below a lower control threshold, the batch is rejected. If it falls above an upper control threshold, the batch is accepted, and if it lies within the thresholds then the process of inspecting the items continues. The purpose of this article is to develop an optimization model to determine the optimum values of the thresholds such that constraints on the probability of Type I and Type II errors are satisfied. This article starts by developing a Markovian model to derive the expected total cost of the inspection... 

    Optimal capacity planning of substation transformers by demand response combined with network automation

    , Article Electric Power Systems Research ; Volume 134 , 2016 , Pages 176-185 ; 03787796 (ISSN) Humayun, M ; Safdarian, A ; Mubbashir, A ; Degefa, M. Z ; Lehtonen, M ; Sharif University of Technology
    Elsevier Ltd 
    The inclusion of smart grid features such as demand response (DR) and network automation for capacity planning of substation transformers may provide substantial monetary savings. This paper proposes an optimization model for quantification of the savings in capacity management of substation transformers over long-run. The proposed model incorporates the DR as a resource to decrease the outage cost during contingencies while considering existing switching types for load transfer between substations. The model provides optimal selection and scheduling of multistage transformer installations and their refurbishments by considering all the costs associated with them including investment,... 

    Modeling and optimizing recovery strategies for power distribution system resilience

    , Article IEEE Systems Journal ; Volume 15, Issue 4 , 2021 , Pages 4725-4734 ; 19328184 (ISSN) Arjomandi Nezhad, A ; Fotuhi Firuzabad, M ; Moeini Aghtaie, M ; Safdarian, A ; Dehghanian, P ; Wang, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Both frequency and intensity of natural disasters have intensified in recent years. It is, therefore, essential to design effective strategies to minimize their catastrophic consequences. Optimizing recovery tasks, including distribution system reconfiguration (DSR) and repair sequence optimization (RSO), are the key to enhance the agility of disaster recovery. This article aims to develop a resilience-oriented DSR and RSO optimization model and a mechanism to quantify the recovery agility. In doing so, a new metric is developed to quantify the recovery agility and to identify the optimal resilience enhancement strategies. The metric is defined as 'the number of recovered customers divided... 

    Phase identification of singlephase customers and PV panels via smart Meter data

    , Article IEEE Transactions on Smart Grid ; Volume 12, Issue 5 , 2021 , Pages 4543-4552 ; 19493053 (ISSN) Heidari-Akhijahani, A ; Safdarian, A ; Aminifar, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    With proliferation of single-phase rooftop photovoltaic (PV) panels, phase balancing in low voltage (LV) distribution feeders becomes the point of concern. In this way, identification of the hosting phase of connected single-phase customers and PV panels is a prerequisite. This paper proposes an optimization model for the phase identification problem. The objective is to minimize the summation of the absolute error between estimated and measured variables. Smart meters (SMs) data including active and reactive power absorptions/injections, nodal voltage magnitudes, and network configuration data form the input of the model. Potential errors in the input data are captured in the model while... 

    Development of a multi-reservoir flood control optimization model; Application to the Karkheh River Basin, Iran

    , Article World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress, 22 May 2011 through 26 May 2011 ; May , 2011 , Pages 3048-3057 ; 9780784411735 (ISBN) Abrishamchi, A ; Dashti, M ; Tajrishy, M ; Sharif University of Technology
    Flood control as an important purpose of reservoir systems faces a wide range of natural, social and political challenges, mainly due to different uncertainties. Over the time, these uncertainties call for necessary changes in the original plan of the systems. Therefore, construction of new flood control systems as well as the storage reallocation and reservoir reoperation of existing ones are essential for adapting the systems to new information, conditions and policies. Furthermore, multipurpose nature of the multi-reservoir systems requires considering conflicts among various purposes. In this paper, a multiobjective optimization model is developed for analyzing such conflicts in a... 

    A linear programming optimization model for optimal operation strategy design and sizing of the CCHP systems

    , Article Energy Efficiency ; Volume 11, Issue 1 , 2018 , Pages 225-238 ; 1570646X (ISSN) Kialashaki, Y ; Sharif University of Technology
    Springer Netherlands  2018
    Combined cooling, heat, and power (CCHP) system offers numerous potential advantages for the supply of energy to residential buildings in the sense of improved energy efficiency and reduced environmental burdens. To realize the potential for being more beneficial, however, such systems must reduce total costs relative to conventional systems. In this study, a linear programming optimization model was presented for optimum planning and sizing of CCHP systems. The purpose of the model is to give the design of the CCHP system by considering electrical chiller and absorption chiller simultaneously in economic viewpoint. A numerical study was conducted in Tehran to evaluate the CCHP system model.... 

    Multi-Depot Periodic Routing of Service Vessels with Time Windows (Case study: Oil Industry)

    , Ph.D. Dissertation Sharif University of Technology Ighani Yazdeley, Roohollah (Author) ; Eshraghniaye Jahromi, Abdolhamid (Supervisor)
    For offshore oil production, oil facilities should be continuously provided. The focus of this research is on the problems associated with a fleet of vessels from central depot(s) that are periodically utilized to serve wells and wellhead platforms with different demands and time limits. Iranian Offshore Oil Company, the largest offshore oil producer in Iran, was selected as a case study in this thesis. The main objectives is twofold. The first objective in the current study is to plan periodic routing of mobile wellhead servants and supporter vessels, as providers of general and technical services for the equipment on wellhead platforms. In some periods, the mobile wellhead servants require... 

    Observability of hybrid AC/DC power systems with variable-cost PMUs

    , Article IEEE Transactions on Power Delivery ; Vol. 29, issue. 1 , February , 2014 , p. 345-352 ; ISSN: 8858977 Aminifar, F ; Fotuhi-Firuzabad, M ; Safdarian, A ; Shahidehpour, M ; Sharif University of Technology
    The integration of high-voltage direct-current (dc) transmission lines in conventional alternating-current (ac) systems would affect the indirect measurement of phasor measurement unit (PMU) devices since the concept of phasors would not correspond to dc transmission circuits. The optimal PMU placement problem in ac/dc systems subjected to the system observability is presented in this paper by applying a mixed-integer programming model. In practice, the cost of each PMU is variable as a function of PMU measurement channels. This attribute is incorporated in the proposed model as well. In addition, the number of PMU measurement channels is deemed to be technically limited; thus, the common... 

    Modelling and analysis of the effect of angular velocity and acceleration on brain strain field in traumatic brain injury

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 3 A , 2013 ; 9780791856215 (ISBN) Hoursan, H ; Ahmadian, M. T ; Barari, A ; Beidokhti, H. N ; Sharif University of Technology
    Traumatic brain injury (TBI) has long been known as one of the most anonymous reasons for death around the world. A presentation of a model of what happens in the process has been under study for many years; and yet it remains a question due to physiological, geometrical and computational complications. Although the facilities for soft tissue modeling have improved and the precise CT-imaging of human head has revealed novel details of brain, skull and the interface (the meninges), a comprehensive FEM model of TBI is still being studied. This study aims to present an optimized model of human head including the brain, skull, and the meninges after a comprehensive study of the previous models.... 

    Trust-based coordination mechanism in a divergent supply Chain

    , Article 62nd IIE Annual Conference and Expo 2012, 19 May 2012 through 23 May 2012 ; May , 2012 , Pages 3268-3277 Pezeshki, Y ; Baboli, A ; Cheikhrouhou, N ; Modarres, M ; Jokar, M. R. A ; Campagne, J. P ; Sharif University of Technology
    Institute of Industrial Engineers  2012
    We consider coordination by contract in a divergent supply chain including one manufacturer and several retailers which produces fashion products with short sale seasons. The retailers cooperate with the manufacturer as sales agents; i.e., they work in the framework of revenue sharing contracts. Because of their proximity to the market, retailers can provide more accurate demand forecast for the manufacturer when he wants to decide on his capacity building (expansion), product assignment decision and market prices with regard to retailers stiff due date, different lead times and different price-dependent demand functions. To ensure abundant supply and increase their sales, the retailers have... 

    Optimal DR through HVAC loads in distribution systems hosting large wind generation

    , Article IEEE Innovative Smart Grid Technologies, 3 November 2015 through 6 November 2015 ; 2015 ; 9781509012381 (ISBN) Ali, M ; Humayun, M ; Degefa, M ; Lehtonen, M ; Safdarain, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    The penetration of wind generation in distribution networks is steadily increasing and may provide ample business opportunities for aggregators. While, residential demand response (DR) has proven to be a feasible economic tool in smart grids, the quantitative evaluation of various aggregator-based DR services is required to tap the maximum benefits from the DR flexibility. This paper provides an overview of benefits of different DR aggregator services such as minimization of energy cost and wind curtailment given the scenario of large wind generation hosted by distribution network. An optimization model is formulated from aggregator perspective to manage the population of heating,... 

    A framework for activating residential HVAC demand response for wind generation balancing

    , Article IEEE Innovative Smart Grid Technologies, 3 November 2015 through 6 November 2015 ; 2015 ; 9781509012381 (ISBN) Ali, M ; Humayun, M ; Degefa, M ; Alahaivala, A ; Lehtonen, M ; Safdarian, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    The integration of a great deal of intermittent renewable generation in future grids will require more operational flexibility. Residential demand response can provide the load shaping potentials thereby alleviating the need for operational flexibility. This paper intends to develop a centralized framework focusing on realization of domestic heating, ventilation, and air conditioning (HVAC) demand response capability for wind power balancing. In the proposed optimization model, energy consumption of HVAC loads is optimized to tackle the variability of wind power. The thermal comfort penalty is explicitly integrated in the objective function in order to oblige different customers' thermal... 

    Optimal capacity management of substation transformers over long-run

    , Article IEEE Transactions on Power Systems ; Volume 31, Issue 1 , 2016 , Pages 632-641 ; 08858950 (ISSN) Humayun, M ; Sousa, B. J. O ; Safdarian, A ; Ali, M ; Degefa, M. Z ; Lehtonen, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    The management of transformers' capacity is a vital task for planners and asset managers due to their high cost. This paper proposes an optimization model for capacity management of transformers in a substation over long-run. The model considers the present worth costs of investment, losses, maintenance, reliability, and the salvage value of transformers for providing the optimal selection and scheduling of multistage transformer installations and their refurbishments. In the optimization model, growing failure rate of transformers along with their age is incorporated and the cumulative loss-of-life (LOL) of transformers is also used in determining their salvage value. The developed model is... 

    Deployment of fault indicator in distribution networks: a MIP-based approach

    , Article IEEE Transactions on Smart Grid ; Volume 9, Issue 3 , May , 2018 , Pages 2259-2267 ; 19493053 (ISSN) Farajollahi, M ; Fotuhi Firuzabad, M ; Safdarian, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Fault indicator (FI) plays a crucial rule in enhancing service reliability in distribution systems. This device brings substantial benefits for fault management procedure by speeding up fault location procedure. This paper intends to develop a new optimization model to optimally deploy FI in distribution systems. The proposed model aims to consider a tradeoff between the total customer interruption cost and FI relevant costs, including capital investment, installation, and maintenance costs. As the main contribution of this paper, the problem is formulated in mixed integer programing, which guarantees global optimum solution achieved in an effective runtime. Moreover, the model takes... 

    Optimal scheduling of renewable-based energy hubs considering time-of-use pricing scheme

    , Article 2017 IEEE Smart Grid Conference, SGC 2017, 20 December 2017 through 21 December 2017 ; Volume 2018-January , March , 2018 , Pages 1-6 ; 9781538642795 (ISBN) Pasban Gajan, A ; Moeini Aghtaie, M ; Parvini, Z ; Fotuhi Firuzabad, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    To more clearly show the abilities of multi-energy carrier systems in managing different energy demands, this paper investigates optimal scheduling of an energy hub in presence of price-based demand response (DR) programs. In this regard, the mathematical model of different energy converters and storage units including combined heat and power (CHP), electrical storage, heat storage and ice storage are extracted. Then, time-of-use (TOU) electrical energy price is set in such a way to reach lower demand in peak hours. Extracting the optimization model of energy scheduling for an energy hub in presence of TOU DR program, the proposed algorithm is implemented on a typical energy hub and the...