Papers

2023

1. Adherence to standard operating procedures for improving data quality: An empirical analysis in the postal service industry

   Eskandarzadeh, Saman, Fahimnia, Behnam, and Hoberg, Kai

   Transportation Research Part E: Logistics and Transportation Review 2023

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2022

1. TRE

   Rest break policy comparison for heavy vehicle drivers in Australia

   Eskandarzadeh, Saman, and Fahimnia, Behnam

   Transportation Research Part E: Logistics and Transportation Review 2022

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   Carriers and postal companies are under increasing pressure to reduce their operating costs and increase efficiency. One way to reduce costs is to improve the utilisation of drivers’ working hours by employing more efficient rest break policies. A rest break policy is a restrictive set of rules consistent with national regulations for hours of service. We develop and validate a novel framework to model and analyse a class of these policies that concern the location of the rest breaks. In particular, we compare two representative rest break policies using data from a major Australian postal carrier. The first policy imposes no restriction on the location of a rest break. The second policy requires the driver to return to a depot for rest taking allowing time for socialising and making use of full amenities. Using postal transport data from Sydney metropolitan area, we find that the difference between the two polices in terms of tour length is just over 1%. We further apply the proposed framework to assess the impact of increasing the minimum break time on the two representative policies.

2019

1. arXiv

   Maintenance scheduling in a railway corricdor

   Eskandarzadeh, Saman, Kalinowski, Thomas, and Waterer, Hamish

   2019

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   We investigate a novel scheduling problem which is motivated by an application in the Australian railway industry. Given a set of maintenance jobs and a set of train paths over a railway corridor with bidirectional traffic, we seek a schedule of jobs such that a minimum number of train paths are cancelled due to conflict with the job schedule. We show that the problem is NP-complete in general. In a special case of the problem when every job under any schedule just affects one train path, and the speed of trains is bounded from above and below, we show that the problem can be solved in polynomial time. Moreover, in another special case of the problem where the traffic is unidirectional, we show that the problem can be solved in time O(n^ 4).

2017

1. MODSIM

   Maintenance scheduling in a railway corridor

   Eskandarzadeh, Saman, Kalinowski, Thomas, and Waterer, Hamish

   In MODSIM2017 22nd International Congress on Modelling and Simulation, Hobart, TAS 2017

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   Australia has a large operational heavy railway network which is approximately 33,355 routekilometres. This network accounted for approximately 55 percent of all freight transport activity in Australia in the financial year 2013-14, almost 367 billion tonne-kilometres which was up 50 percent from 2011-12 (BITRE (2016)). To provide a safe and reliable railway network to customers, an effective maintenance regime is a key requirement. Planned maintenance and asset renewal in capital intensive industries such as the railway industry, which has expensive infrastructure, is a common and effective maintenance practice. Infrastructure is of essential importance to maintain a reliable customer service. To prevent long unplanned interruptions in the service to customers, a proper maintenance and renewal program is required. The objective is to schedule planned maintenance and asset renewal jobs in such a way that their impact on the capacity that will be provided to customers is minimised while at the same time keeping the infrastructure in good working condition. A proper maintenance and renewal schedule limits the frequency with which disruptive emergency maintenance is needed. We investigate a planned maintenance and asset renewal scheduling problem on a railway corridor with train traffic in both directions. Potential train journeys are represented by train paths, where a train path is specified by a sequence of (location,time)-pairs, and we distinguish between up- and down paths, depending on the direction of travel. Necessary maintenance and renewal activities, or work, are specified by a release time, a deadline, a processing time and a location. Scheduling work at a particular time has the consequence that the train paths passing through the corresponding location while the work is carried out have to be cancelled. An instance of the problem is given by a set of train paths and a set of work activities, and the task is to schedule all the work such that the total number of cancelled paths is minimised. There is a vast literature on scheduling problems and on transportation network problems. However, the interaction of these problems in contexts such as the railway industry have not been studied thoroughly. Boland et al. (2014) study the problem of scheduling maintenance jobs in a network. Each maintenance job causes a loss in the capacity of network while it is being done. The objective is to minimize this loss or equivalently maximize the capacity over time horizon in such a way that all jobs are scheduled. They model the problem as a network flow problem over t ime. This problem and its variants are investigated in Boland et al. (2013), Boland et al. (2014), Boland et al. (2015), Boland et al. (2016) and Abed et al. (2017). Our work is different from the previous works. The main difference is that we model the capacity by train paths whereas in a network flow model over time the capacity is modelled approximately by flows over time. The primary purpose of this study is to provide further insight into this problem, to characterize the structural properties of optimal solutions, and to use these properties to develop efficient c ombinatorial a nd integer programming based solution algorithms. We present theoretical and computational results on the performance of the developed solution approaches.

2016

1. EJOR

   Risk shaping in production planning problem with pricing under random yield

   Eskandarzadeh, Saman, Eshghi, Kourosh, and Bahramgiri, Mohsen

   European Journal of Operational Research 2016

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   In this paper, we address a basic production planning problem with price dependent demand and stochastic yield of production. We use price and target quantity as decision variables to control the risk of low production yield. The value of risk control becomes more important especially for products with short life cycle where high losses are unbearable in the short run. In this cases, optimization of a solely scalar function of profit is not sufficient to control the risk. We apply Conditional Value at Risk (CVaR) measure to model the risk preferences of the producer. The producer is interested in shaping the risk by bounding from below the means of α-tail distributions of profit for different values of α. The resulting model is nonconvex. We propose an efficient solution algorithm and present a sufficient optimality condition.

2014

1. JSSSE

   Production planning problem with pricing under random yield: CVaR criterion

   Eskandarzadeh, Saman, Eshghi, Kourosh, Yazdi, Mohammad Modarres, and Bahramgiri, Mohsen

   Journal of Systems Science and Systems Engineering 2014

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   In this paper, we address a basic production planning problem with price dependent demand and stochastic yield of production. We use price and target quantity as decision variables to lower the risk of low yield. The value of risk control becomes more important especially for products with short life cycle. This is because, the profit implications of low yield might be unbearable in the short run. We apply Conditional Value at Risk (CVaR) to model the risk. CVaR measure is a coherent risk measure and thereby having nice conceptual and mathematical underpinnings. It is also widely used in practice. We consider the problem under general demand function and general distribution function of yield and find sufficient conditions under which the problem has a unique local maximum. We also both analytically and numerically analyze the impact of parameter change on the optimal solution. Among our results, we analytically show that with increasing risk aversion, the optimal price increases. This relation is opposite to that of in Newsvendor problem where the uncertainty lies in demand side.

2013

1. EJOR

   Decision tree analysis for a risk averse decision maker: CVaR Criterion

   Eskandarzadeh, Saman, and Eshghi, Kourosh

   European Journal of Operational Research 2013

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   Risk aversion is a prevalent phenomenon when sufficiently large amounts are at risk. In this paper, we introduce a new prescriptive approach for coping with risk in sequential decision problems with discrete scenario space. We use Conditional Value-at-Risk (CVaR) risk measure as optimization criterion and prove that there is an explicit linear representation of the proposed model for the problem.

2. JBASR

   A demand model of influenza vaccine in a heterogeneous population

   Bahramgiri, Mohsen, and Eskandarzadeh, Saman

   Journal of Basic and Applied Scientific Research 2013

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   In this paper, we develop a demand model for influenza vaccine. When the vaccination is not compulsory, exploration of demand mechanism and total demand anticipation, help the governments better organize their efforts and adopt more effective measures to contain influenza outbreak in advance of influenza season. In this research, the population is divided into two classes. Pre 65 years old class and over 65-year-old class. Current influenza vaccines have different effectiveness on each age class. We build a game theoretic demand model for each age class based on utilities of individuals. Utilities of individuals is a function of the vaccine effectiveness, price, chance of getting infected, estimated cost of infection and a random element specific to each individual. Since getting vaccinated for an individual exerts positive externalities on the others, the decision of individuals is not independent of each other.

2009

1. JCO

   An extension of the relaxation algorithm for solving a special case of capacitated arc routing problems

   Eskandarzadeh, Saman, Tavakkoli-Moghaddam, Reza, and Azaron, Amir

   Journal of Combinatorial Optimization 2009

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   In this paper, we propose an exact method for solving a special integer program associated with the classical capacitated arc routing problems (CARPs) called split demand arc routing problems (SDARP). This method is developed in the context of monotropic programming theory and bases a promising foundation for developing specialized algorithms in order to solve general integer programming problems. In particular, the proposed algorithm generalizes the relaxation algorithm developed by Tseng and Bertsekas (Math. Oper. Res. 12(4):569–596, 1987) for solving linear programming problems. This method can also be viewed as an alternative for the subgradient method for solving Lagrangian relaxed problems. Computational experiments show its high potential in terms of efficiency and goodness of solutions on standard test problems.

2005

1. IIEC

   A modified model in evaluation of an investment project in a widget factory

   Eskandarzadeh, Saman, and Rabbani, Masoud

   In 5th International Industrial Engineering Conference, Tehran, Iran 2005

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   This paper presents a dynamic asset pricing method to evaluate an investment project of a factory construction considering timing of investment and option to abandon production simultaneously when the investor is risk neutral. The factory produces a widget after construction with the market price governed by Geometric Brownian motion. There is a fixed cost of constructing and while building factory or producing the widget regarding the changes in the selling price of the widget, we have the option to abandon the course of current work to avoid further losses. These options are valuable in evaluating investment projects. The researchers showed how these options interact to affect investment decisions and obtained optimal decision rules for this case under the assumption that there exists a complete market.