Search for: scheduling-problem
Total 55 records
Article Journal of Uncertain Systems ; Vol.4, No.2, pp.123-132, 2010 ; Eshghi, Kourosh ; Eshragh Jahromi, Abdolhamid ; Sharif University of Technology
In this paper, first a fuzzy random resource-constrained project scheduling problem is presented. The object of the problem is to find the optimal scheduling of project activities. In this model, duration of project activities is a fuzzy random variable. Then, the proposed model is formulated by using the expected value of fuzzy random variables as an IP model. An illustrative example is also provided to clarify the concept. © 2010 World Academic Press, UK. All rights reserved
Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) ; Volume 2748 , 2003 , Pages 59-66 ; 03029743 (ISSN); 3540405453 (ISBN) ; Ghodsi, M ; Sharifi, A ; Sharif University of Technology
Springer Verlag 2003
The lazy bureaucrat scheduling is a new class of scheduling problems that was introduced in . In these problems, there is one employee (or more) who should perform the assigned jobs. The objective of the employee is to minimize the amount of work he performs and to be as inefficient as possible. He is subject to a constraint, however, that he should be busy when there is some work to do. In this paper, we focus on the cases of this problem where all jobs have the same common deadline. We show that with this constraint, the problem is still NP-hard, and prove some hardness results. We then present a tight 2-approximation algorithm for this problem under one of the defined objective...
Article Scientia Iranica ; Volume 15, Issue 5 , 2008 , Pages 652-660 ; 10263098 (ISSN) ; Ghandehari, M ; Sharif University of Technology
Sharif University of Technology 2008
In this paper, a new approach to formulate a class of scheduling problems is introduced, which can be applied to many other discrete problems with complicated structures. The concept of graph circular coloring is applied to develop a model for the special case of an open shop scheduling problem. In this problem, there are some independent jobs to be processed in a shop with dedicated renewable resources. Each job consists of several tasks with no precedence restriction. Each task is processed without preemption. The processing time of the tasks is given. Processing each task requires using some multiple specified types of resource, while no more than one task can use each resource,...
Article RAIRO - Operations Research ; Volume 51, Issue 4 , 2017 , Pages 1189-1209 ; 03990559 (ISSN) ; Najafi, A. A ; Akhavan Niaki, S. T ; Sharif University of Technology
Most of the research works conducted on Project Scheduling Problem (PSP) especially Resource Constrain Project Scheduling Problem (RCPSP) either ignore equipment planning or schedule the activities first, and then plan for the required equipment. Moreover, little works that consider simultaneous PSP and Equipment Planning (EP) are based on the assumption that the equipment is continuously available. However, in reality, equipment is subject to either random breakdowns or deterministic maintenance programs that make it not being available all the time. In this paper, the PSP and EP problems are simultaneously considered in closer to reality situations in which the equipment is not always...
Article International Journal of Production Research ; Volume 43, Issue 14 , 2005 , Pages 2895-2929 ; 00207543 (ISSN) ; Saghafian, S ; Sharif University of Technology
This paper is a complete survey of flowshop-scheduling problems and contributions from early works of Johnson of 1954 to recent approaches of metaheuristics of 2004. It mainly considers a flowshop problem with a makespan criterion and it surveys some exact methods (for small size problems), constructive heuristics and developed improving metaheuristic and evolutionary approaches as well as some well-known properties and rules for this problem. Each part has a brief literature review of the contributions and a glimpse of that approach before discussing the implementation for a flowshop problem. Moreover, in the first section, a complete literature review of flowshop-related scheduling...
Nurse Scheduling of an Emergency Department in Order to Decreasing Patients Waiting Time Using Simulation and Genetic Algorithm, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem
This work attempt to analyze the impact of changes in nurse scheduling on quality of services at emergency department of Emam Khomeini Hospital Complex. In nurse scheduling some constraints such as maximum working hours per week and unacceptable working sequences must be considered. A simulation model is developed to cover the complete flow for the patient through the emergency department. Emergency department of Emam Khomeini is simulated in order to obtain the patient average waiting time for each nurse roster. Then a genetic algorithm is integrated with the simulation model. In each iteration genetic algorithm produces many nurse rosters . For each roster the patient average waiting time...
Branch and bound algorithms for resource constrained project scheduling problem subject to nonrenewable resources with prescheduled procurement, Article Mathematical Problems in Engineering ; Vol. 2014, issue , 2014 ; ISSN: 1024123X ; Shadrokh, S ; Fathi, Y ; Sharif University of Technology
A lot of projects in real life are subject to some kinds of nonrenewable resources that are not exactly similar to the type defined in the project scheduling literature. The difference stems from the fact that, in those projects, contrary to the common assumption in the project scheduling literature, nonrenewable resources are not available in full amount at the beginning of the project, but they are procured along the project horizon. In this paper, we study this different type of nonrenewable resources. To that end, we extend the resource constrained project scheduling problem (RCPSP) by this resource type (RCPSP-NR) and customize four basic branch and bound algorithms of RCPSP for it,...
Article Journal of Scheduling ; Volume 16, Issue 2 , April , 2013 , Pages 151-160 ; 10946136 (ISSN) ; Ghodsi, M ; Hajiaghayi, M ; Sayedi Roshkhar, A. S ; Zadimoghaddam, M ; Sharif University of Technology
This paper considers scheduling tasks while minimizing the power consumption of one or more processors, each of which can go to sleep at a fixed cost α. There are two natural versions of this problem, both considered extensively in recent work: minimize the total power consumption (including computation time), or minimize the number of "gaps" in execution. For both versions in a multiprocessor system, we develop a polynomial-time algorithm based on sophisticated dynamic programming. In a generalization of the power-saving problem, where each task can execute in any of a specified set of time intervals, we develop a (1+23α) -approximation, and show that dependence on α is necessary. In...
Article IEEE Transactions on Wireless Communications ; Volume 14, Issue 6 , 2015 , Pages 3402-3414 ; 15361276 (ISSN) ; Malekimajd, M ; Ashouri, M ; Movaghar, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2015
Data aggregation is a key, yet time-consuming functionality introduced to conserve energy in wireless sensor networks (WSNs). In this paper, to minimize time latency, we focus on aggregation scheduling problem and propose an efficient distributed algorithm that generates a collision-free schedule with the least number of time slots. In contrast to others, our approach named FAST mainly contributes to both tree construction, where the former studies employ Connected 2-hop Dominating Sets, and aggregation scheduling that was previously addressed through the Competitor Sets computation. We prove that the latency of FAST under the protocol interference model is upper-bounded by 12R+Δ-2, where R...
Article European Journal of Industrial Engineering ; Volume 13, Issue 1 , 2019 , Pages 54-80 ; 17515254 (ISSN) ; Salmasi, N ; Varmazyar, M ; Sharif University of Technology
Inderscience Enterprises Ltd 2019
In this research, we approach the flowshop sequence-dependent group scheduling problem with minimisation of total weighted earliness and tardiness as the objective for the first time. A mixed integer linear programming model is developed to solve the problem optimally. Since the proposed research problem is proven to be NP-hard, a hybrid meta-heuristic algorithm based on the particle swarm optimisation (PSO) algorithm, enhanced with neighbourhood search is developed to heuristically solve the problem. Since the objective is a non-regular, a timing algorithm is developed to find the best schedule for each sequence provided by the metaheuristic algorithm. A lower bounding method is also...
Article Journal of Applied Sciences ; Volume 8, Issue 9 , 2008 , Pages 1651-1659 ; 18125654 (ISSN) ; Shadrokh, S ; Sharif University of Technology
This research considers a project scheduling problem with the object of minimizing weighted earliness-tardiness penalty costs, taking into account a deadline for the project and precedence relations among the activities. An exact recursive method has been proposed for solving the basic form of this problem. We present a new depth-first branch and bound algorithm for extended form of the problem, which time value of money is taken into account by discounting the cash flows. The algorithm is extended with two bounding rules in order to reduce the size of the branch and bound tree. Finally, some test problems are solved and computational results are reported. © 2008 Asian Network for Scientific...
Article Energy Systems ; Volume 12, Issue 2 , 2021 , Pages 431-458 ; 18683967 (ISSN) ; Afshar Nadjafi, B ; Akhavan Niaki, S. T ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH 2021
The growing importance of energy consumption has become an integral part of many decision-making processes in various organizations. In this paper, a framework is proposed for an organization where the undertaken project is implemented by multi-skilled workforce and energy tariffs depending on the time-of-use. This is a real-life situation where energy tariffs are significantly high during the peak demand compared to the one in off peak demand in order to control overloaded consumption of energy. A formulation is developed for the problem to minimize the total cost of consuming required energy. The proposed formulation is validated using several small-scale instances solved by GAMS software....
An efficient hybrid genetic algorithm to solve assembly line balancing problem with sequence-dependent setup times, Article Computers and Industrial Engineering ; Volume 62, Issue 4 , 2012 , Pages 936-945 ; 03608352 (ISSN) ; Kianfar, F ; Sharif University of Technology
In this paper the setup assembly line balancing and scheduling problem (SUALBSP) is considered. Since this problem is NP-hard, a hybrid genetic algorithm (GA) is proposed to solve the problem. This problem involves assigning the tasks to the stations and scheduling them inside each station. A simple permutation is used to determine the sequence of tasks. To determine the assignment of tasks to stations, the algorithm is hybridized using a dynamic programming procedure. Using dynamic programming, at any time a chromosome can be converted to an optimal solution (subject to the chromosome sequence). Since population diversity is very important to prevent from being trapped in local optimum...
A hybrid genetic algorithm and variable neighborhood search for task scheduling problem in grid environment, Article Procedia Engineering ; Volume 29 , 2012 , Pages 3808-3814 ; 18777058 (ISSN) ; Khodadadi, F ; Entezari Maleki, R ; Movaghar, A ; Sharif University of Technology
This paper addresses scheduling problem of independent tasks in the market-based grid environment. In market-based grids, resource providers can charge users based on the amount of resource requested by them. In this case, scheduling algorithms should consider users' willingness to execute their applications in most economical manner. As a solution to this problem, a hybrid genetic algorithm and variable neighborhood search is presented to reduce overall cost of task executions without noticeable increment in system makespan. Simulation results show that our algorithm performs much better than other algorithms in terms of cost of task executions. Considering the negative correlation between...
Article International Journal of Advanced Manufacturing Technology ; Volume 56, Issue 1-4 , 2011 , Pages 261-272 ; 02683768 (ISSN) ; Aliahmadi, A ; Sefidkoohi, H. M ; Omran, M. M ; Sharif University of Technology
Queuing networks present as beneficial models for a category of problems emerging in modern manufacturing systems. As the optimal control problem for queuing networks in familiar to be difficult, an important topic of research during the last two decades has been the growth of difficult estimations, and the use of these estimations to control optimal controls. Flexible moderations are an important class of such estimations that have received much consideration in recent years. The central objective of this paper is to determine the utilization of flexible moderations in solving a diversity of scheduling problems. In this paper, we investigate the role of flexible moderations in solving...
Article International Journal of Advanced Manufacturing Technology ; Volume 40, Issue 11-12 , 2009 , Pages 1216-1226 ; 02683768 (ISSN) ; Hendizadeh, S. H ; Salmasi, N ; Sharif University of Technology
A two-machine flowshop scheduling problem is addressed to minimize setups and makespan where each job is characterized by a pair of attributes that entail setups on each machine. The setup times are sequence-dependent on both machines. It is shown that these objectives conflict, so the Pareto optimization approach is considered. The scheduling problems considering either of these objectives are N p - hard, so exact optimization techniques are impractical for large-sized problems. We propose two multi-objective metaheurisctics based on genetic algorithms (MOGA) and simulated annealing (MOSA) to find approximations of Pareto-optimal sets. The performances of these approaches are compared with...
A hybrid genetic and Lagrangian relaxation algorithm for resource-constrained project scheduling under nonrenewable resources, Article Applied Soft Computing Journal ; Volume 94 , 2020 ; Shadrokh, S ; Khakifirooz, M ; Fathi, M ; Pardalos, P. M ; Sharif University of Technology
Elsevier Ltd 2020
Scheduling under nonrenewable resources is one of the challenging issues in project scheduling problems. There are many cases where the projects are subject to some nonrenewable resources. In most of the literature, nonrenewable resources are assumed to be available in full amount at the beginning of the project. However, in practice, it is prevalent that these resources are procured along the project horizon. This paper studies the generalized resource-constrained project scheduling problem (RCPSP) where, in addition to renewable resources, nonrenewable resources are considered, such as budget or consuming materials by the project activities. As the problem is NP-hard, some sub-algorithm...
M.Sc. Thesis Sharif University of Technology ; Salmasi, Naser
Nurse scheduling problem has received a great amount of attention during recent years. In this problem number of needed nurses from different skill levels is given for each Location-shift during planning horizon, and the goal is to allocate each nurse to shifts, such that the demand of each location-shift is satisfied. Many researches have been done with the aim of minimizing the number of needed nurses to satisfy the demand of locationshifts or maximizing nurses preferences to work in desired shifts. In this research an integer programming model is proposed to minimize the number of needed nurses and maximize nurses preferences simultaneously. The proposed mathematical model is appropriate...
M.Sc. Thesis Sharif University of Technology ; Kianfar, Freydoon
Train timetabling is one of the most important problems in the railway scheduling field. It concerns with determining the trians’ arrival and departure times to/from each station so that some constraints are satisfied and some objectives are met. The objective in this thesis is to minimize the summation of dwell times of all trains. The timetables which are offered in this thesis are periodic. It means that each event repeats after a period time. The events are arrivals and departures of trains to/ from stations. In this timetable, the praying constraint is considered as wellso that after Azan time, the train has to dwell in the first station which has enough place for praying. So an integer...
M.Sc. Thesis Sharif University of Technology ; Najafi, Mehdi
The nurse scheduling problem is an inevitable issue in managing of hospital wards. Maintaining high quality of working in hospitals is too difficult in tense and high-pressure work environment. Manually solving the scheduling problem is time-consuming. It can pose problems to considering individual excellence, personnel requests and distributing shifts in a fair and desirable manner. These problems and the impossibility of considering all conditions together made the nurse scheduling as an important scheduling problem. In this research we propose a model to assign nurses to shifts considering regulations and hospital’s policies. Unlike nurse scheduling literature we consider nurses...