Adopting a Bi-level Optimization Method for the Freight Transportation Problem: A Multi-objective Programming Approach
Transportation Research Record: Journal of the Transportation Research Board
Nowadays, various companies find it a crucial task to elevate their distribution system efficienc... more Nowadays, various companies find it a crucial task to elevate their distribution system efficiency to survive in what is an intensely competitive environment. Freight transportation via road systems may not always be a practical option for the shipper because of financial, social, and environmental aspects. So, in addition to the road system, the shipper can benefit greatly from the rail system. Thus, taking advantage of different transportation modes can help shippers to tackle, to some extent, arising issues. In this paper, we aim at investigating a freight transportation network including rail and road transportation modes in which the shipper’s choice affects the decisions deeply. Given that this problem as a bi-level programming model, the rail operator acts as a leader and the shipper is treated as a follower. Once the rail operator reveals the rail transportation price, an appropriate response is received from the shipper and this pattern is repeated until an equilibrium is a...
Proposing a New Train Rescheduling Approach with Simultaneous Consideration of Cancelling, Delaying and Re-Ordering Policies
This paper presents a novel approach to solve the double-track railway rescheduling problem, when... more This paper presents a novel approach to solve the double-track railway rescheduling problem, when an incident occurs into one of the block sections of the railway. The approach restricts the effects of an incident to a specific time, based on which the trains are divided into rescheduled and unchanged ones, so that the latter retain their original time-table after the incident. The main contribution of this approach is the simultaneous consideration of three rescheduling policies: cancelling, delaying and re-ordering. A mixed integer optimization model is developed to find optimal conflict-free time-table compatible with the proposed approach. The objective function minimizes two cost parts: the cost of deviation from the primary time-table and the cost of train cancellation. The model is implemented in JAVA software and is solved by CPLEX 11 software which automatically generates the optimal solution of a problem. An experimental analysis with two incident scenarios on a double-tra...
This paper investigates optimal multi discount price and order quantity for deteriorating product... more This paper investigates optimal multi discount price and order quantity for deteriorating product. We initially consider a time dependent demand function with two scenarios including positive exponential for the rst interval and negative exponential for the second one, due to the obsolescent characteristic, without any exogenous factor. Then, we study the e ect of changing selling price as an exogenous factor causing increase in demand. Finally, optimization model is formulated and the closed form solutions of the optimal prices are gained.
Nowadays, the majority of international trade in goods is carried by sea, and especially by ships... more Nowadays, the majority of international trade in goods is carried by sea, and especially by ships deployed in the industrial and tramp segments. This paper addresses routing the tramp ships and determining the schedules including the arrival times to the ports, berthing times at the ports, and the departure times in an operational planning level. In the operational planning level, the weather can be almost exactly forecasted, however in some routes some uncertainties may remain. In this paper, the voyaging times between some of the ports are considered to be uncertain. To that end, a two stage stochastic mathematical model is proposed. In order to find near to optimum solutions in a limited amount of time, a new hybrid heuristic algorithm is proposed to solve large-size examples. Moreover, a case study is defined and tested with the presented model. The computational results show that this mathematical model is promising and can represent acceptable solutions. Specifically, the valu...
One of the key factors for successiveness of a company is to share the finance, facilities and hu... more One of the key factors for successiveness of a company is to share the finance, facilities and human resources to the most profit-making projects, this factor can be much more affecting to those kinds of companies conducting overseas projects. In competition environment, projects are putting out to tenders. A successive company is that participate to money-making low risk tenders considering all resources of its company. In this paper after a brief introduction of this problem, a multi objective binary model and a mixed integer linear model will be introduced. The latter one addresses the situation where the decision makers have different approaches to different tenders considering the rate of return as well as the probability of winning the tenders. As all the parameters of these models are uncertain, two different fuzzy approaches are applied to these problems. Finally, to illustrate the application of the proposed models some examples are presented. The results show that by the f...
The necessary electricity of the workshops and buildings (W&Bs) located at the metro depot are pr... more The necessary electricity of the workshops and buildings (W&Bs) located at the metro depot are provided by lighting power substation (LPS). To transmit electricity between LPS and W&Bs, some trenches should be dig and the requisite cables should be located in the trenches. This paper presents a new mixed integer linear programming (MILP) long-term decision model to find the best cable trench route between LPS and W&Bs and also the location of all W&Bs and LPS are fixed. In this problem, the objective is to minimize (1) used cables cost, and (2) trench digging cost. It should be considered that there exist many cases in which the minimum either used cables or trench digging does not result in minimum total cost. Therefore, in optimum solution, a tradeoff between these objectives should be achieved. Finally, the proposed model is applied to a real case study at the metro depot in Iran and the optimum solution is analyzed.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 2017
A train makeup problem specifies the frequency of freight trains and allocates the shipment to tr... more A train makeup problem specifies the frequency of freight trains and allocates the shipment to trains based on the desired shipment-to-train allocation scheme. In this study, a multi-objective model is presented for train makeup, taking into account the locomotive limitations on a railway network. The objective functions include maximization of the total profit and the customers' satisfaction level as well as minimization of the total number of shunting operations in yards, the unused capacity of trains, the total lost demand, the transfer time of trains and the total fuel consumed. The main constraints of the model are the establishment of flow balance for each yard and each demand, the upper and lower limits of the train length, and the upper limit of the following: train makeup in each yard, shunting operations in each yard, capacity of each train and locomotive utilization in each period. Goal programming and Lp metric methods are used for the multi-objective problem conside...
Journal of Rail Transport Planning & Management, 2018
Buffer times are essential for preventing delay propagation and ensuring robustness in railway ti... more Buffer times are essential for preventing delay propagation and ensuring robustness in railway timetabling. While robustness analysis deals with ensuring the effectiveness of allocated buffer times in schedules, the number of trains is generally assumed to be fixed. The feasibility of the train operation concept needs to be checked by strategic long-term capacity planning beforehand. Capacity analysis methods depend on buffer times and involve some sort of delay prognosis. The goal of the present paper is to analyse the effects of buffer time distributions on nominal capacity obtained with stochastic (analytic) capacity analysis approaches. Complementing previous work where Monte-Carlo simulation had been applied, it is shown how convolution integrals arising in analytic delay propagation models can be explicitly calculated using moment generating functions. Based on this approach, a generalisation of the STRELE framework, which is the standard methodology of German infrastructure manager DB Netz AG for capacity analysis of railway lines, is derived and the effects of different buffer time distributions on nominal capacity are studied.
This paper presents a new bi-objective multi-modal hub location problem with multiple assignment ... more This paper presents a new bi-objective multi-modal hub location problem with multiple assignment and capacity considerations for the design of an urban public transportation network under uncertainty. Because of the high construction costs of hub links in an urban public transportation network, it is not economic to create a complete hub network. Moreover, the demand is assumed to be dependent on the utility proposed by each hub. Thus, the elasticity of the demand is considered in this paper. The presented model also has the ability to compute the number of each type of transportation vehicles between every two hubs. The objectives of this model are to maximize the benefits of transportation by establishing hub facilities and to minimize the total transportation time. Since exact values of some parameters are not known in advance, a fuzzy multi-objective programming based approach is proposed to optimally solve small-sized problems. For medium and large-sized problems, a meta-heuris...
IEEE Intelligent Transportation Systems Magazine, 2018
This study proposes a multi-objective simulation-based optimization framework to effectively mana... more This study proposes a multi-objective simulation-based optimization framework to effectively manage the train traffic after the occurrences of a disturbance caused by a partial/full blockage. In such conditions, the train orders and the corresponding priorities can be changed to effectively manage the disturbed situation. At this point, a multi-objective version of the variable neighborhood search metaheuristic is proposed to solve the real-time traffic rescheduling problem and generate Pareto frontiers. The obtained Pareto optimal solutions for disturbance management model supports the decisions made by the rail controllers to find a trade-off between both user and operator viewpoints. We evaluate the proposed approach on a set of disturbance scenarios covering a large part of the Iranian rail network. The computational results demonstrate that the proposed model can generate good-quality disposition timetables with the minimum total average delay of trains at destinations and deviation from the initial timetable. The results indicate that the disturbance management methodology has important advantages in producing practical solution quickly when compared to existing solutions.
Train formation planning faces two types of challenges; namely, the determination of the quantity... more Train formation planning faces two types of challenges; namely, the determination of the quantity of cargo trains run known as the frequency of cargo trains and the formation of desired allocations of demands to a freight train. To investigate the issues of train makeup and train routing simultaneously, this multiobjective model optimizes the total profit, satisfaction level of customers, yard activities in terms of the total size of a shunting operation, and underutilized train capacity. It also considers the guarantee for the yard-demand balance of flow, maximum and minimum limitations for the length of trains, maximum yard limitation for train formation, maximum yard limitation for operations related to shunting, maximum limitation for the train capacity, and upper limit of the capacity of each arc in passing trains. In this paper, a goal programming approach and an Lp norm method are applied to the problem. Furthermore, a simulated annealing (SA) algorithm is designed. Some test problems are also carried out via simulation and solved using the SA algorithm. Furthermore, a sample investigation is carried out in a railway company in Iran. The findings show the capability and performance of the proposed approach to solve the problems in a real rail network.
The present paper extends the idea of job shop scheduling problem with resting constraints to the... more The present paper extends the idea of job shop scheduling problem with resting constraints to the train scheduling problem with the Muslim praying considerations. For this purpose, after proposing the new mathematical model, a heuristic algorithm based on the Electromagnetism-Like algorithm (EM) which is well adjusted to scheduling problems is employed to solve the large-size practical cases. The effectiveness of the proposed algorithm is then validated by comparing with optimum solution using small-size instances and simulated annealing algorithm, and Particle swarm Optimization (PSO) using medium and large-size instances. At the end, a practical case from Iranian railway network is studied and the results are reported. The results indicate that in the case of considering the Muslim praying constraint, the ratios of total tardiness of trains, and the total praying times are 14.5%, and 3.5%, respectively, while in the case of relaxing this constraint; the first ratio reduces to 12.3%. This result demonstrates that the proposed algorithm is able to schedule the praying times so that in many cases the trains with different directions meet each other during the praying times.
A robust periodic train-scheduling problem under perturbation is discussed in this paper. The int... more A robust periodic train-scheduling problem under perturbation is discussed in this paper. The intention is to develop a robustness index and to propose a mathematical model which is robust against perturbations. Some practical assumptions as well as the acceleration and deceleration times along with periodic scheduling in addition to a practical new robustness index are considered. The aim is to obtain timetables with minimum traveling time that are robust against minor perturbations, while the unnecessary stops are minimized. In general, the spread of delays in the railway system is called delay propagation. We show that in addition to this phenomenon, there exists a more complicated case in periodic type of scheduling that is the fact of delay propagation from one period to the next. In fact, if the delays of a period are not absorbed by the next one, the size of delays may converge to infinity. We name this as delay intensification. Furthermore, we develop a hybrid heuristic algorithm which is able to find near-optimal schedules in a limited amount of time and can absorb perturbations. To validate the algorithm, a new lower bound is introduced.
In this article, a new approach is presented to solve the double-track railway rescheduling probl... more In this article, a new approach is presented to solve the double-track railway rescheduling problem, when an incident occurs into one of the block sections of the railway. The approach simultaneously considers three rescheduling policies: cancelling, delaying, and reordering. To nd the optimal con ict-free timetables compatible with the approach, a mathematical model and an exact three-phase solution method are proposed. The method is based on Branch-and-Bound (B&B) algorithm. The lower bound consists of two cost parts: the cost of deviation from the primary timetable and the cost of train cancellation. To generate an appropriate upper bound, the method exploits an innovative algorithm called \Local Left Shifting". A heuristic beam search technique is also developed for tackling the large-scale problems. An experimental analysis on two double-track railways of the Iranian network indicates that the proposed solution method provides the optimal solution in much shorter time, compared with the time taken to solve the mathematical model by CPLEX software. Based on the ndings of this research, it is possible to optimally retrieve the primary timetable after incident occurrence during a pre-determined time horizon.
One of the most important airline's products is to determine the aircraft routing and scheduling ... more One of the most important airline's products is to determine the aircraft routing and scheduling and fleet assignment. The key input data of this problem is the traffic forecasting and allocation that forecasts traffic on each flight leg. The complexity of this problem is to define the connecting flights when passengers should change the aircraft to reach the final destination. Moreover, as there exists various types of uncertainties during the flights, finding a solution which is able to absorb these uncertainties is invaluable. In this paper, a new robust mixed integer mathematical model for the integrated aircraft routing and scheduling, with consideration of fleet assignment problem is proposed. Then to find good solutions for large-scale problems in a rational amount of time, a heuristic algorithm based on the Simulated Annealing (SA) is introduced. In addition, some examples are randomly generated and the proposed heuristic algorithm is validated by comparing the results with the optimum solutions. The effects of robust vs non-robust solutions are examined, and finally, a hybrid algorithm is generated which results in more effective solution in comparison with SA, and Particle Swarm Optimization (PSO).
Resource Constraint Project Scheduling to meet Net Present Value and quality objectives of the program
2016 12th International Conference on Industrial Engineering (ICIE), 2016
Resource Constraint Project Scheduling Problem (RCPSP) is one of the most important problems in p... more Resource Constraint Project Scheduling Problem (RCPSP) is one of the most important problems in project scheduling and operation research and has attracted an ever growing attention. In the real world, most of the strategic goals of organizations are reached with different programs which are consisting a set of interrelated projects. Regarding to what has been said, in this paper, a model for programs scheduling with considering the constraint of resources is provided. In this model, two objective functions including Net Present Value (NPV) and quality of the program have been considered. The purpose of this model is to maximize net present value of program's benefits and minimize the time and cost non-conformities which are related to activities' quality deficiencies. Finally a numerical example has been provided and solved by GAMS 23.5 version in order to show how the proposed mathematical model is working.
This paper presents a novel approach to solve the double-track railway rescheduling problem, when... more This paper presents a novel approach to solve the double-track railway rescheduling problem, when an incident occurs into one of the block sections of the railway. The approach restricts the effects of an incident to a specific time, based on which the trains are divided into rescheduled and unchanged ones, so that the latter retain their original time-table after the incident. The main contribution of this approach is the simultaneous consideration of three rescheduling policies: cancelling, delaying and reordering. A mixed-integer optimization model is developed to find optimal conflict-free time-table compatible with the proposed approach. The objective function minimizes two cost parts: the cost of deviation from the primary timetable and the cost of train cancellation. The model is solved by CPLEX 11 software which automatically generates the optimal solution of a problem. Also, a meta-heuristic solution method based on simulated annealing algorithm is proposed for tackling the large-scale problems. The results of an experimental analysis on two double-track railways of the Iranian network show an appropriate capability of the model and solution method for handling the simultaneous train rescheduling. The results indicate that the proposed solution method can provide good solutions in much shorter time, compared with the time taken to solve the mathematical model by CPLEX software.
International Journal of Operational Research, 2016
This paper studies a double-track train rescheduling problem, when an un-foreseen incident over a... more This paper studies a double-track train rescheduling problem, when an un-foreseen incident over a specific time horizon occurs. We solve the problem by utilising a rescheduling technique named bi-operational approach. An incident-based mixed-integer rescheduling model is proposed which is solved using CPLEX software which automatically generates optimal solutions. To reduce the computation time, an innovative method is proposed which decomposes the main problem to five smaller sub-problems, each of which is solved by branch-and-bound algorithm. Moreover, a novel heuristic is proposed which divides the available computation time between sub-problems proportionately depending on their sizes. An experimental analysis, on two double-track railways of Iranian network, indicates that the decomposition method provides near-optimal solutions with much shorter computation times compared with CPLEX. The analysis also provides evidence for effectiveness of the proposed heuristic in tackling large-scale problems; so that good feasible solutions are achievable in limited times compatible with real-time use.
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