| 1. |
- Andersson Granberg, Tobias, et al.
(author)
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Decision support tools for ambulance dispatch and relocation
- 2007
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In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 58, s. 195-201
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Journal article (peer-reviewed)abstract
- In this paper, the development of decision support tools for dynamic ambulance relocation and automatic ambulance dispatching is described. The ambulance dispatch problem is to choose which ambulance to send to a patient. The dynamic ambulance relocation problem occurs in the operational control of ambulances. The objective is to find new locations for some of the ambulances, to increase the preparedness in the area of responsibility. Preparedness is a way of evaluating the ability to serve potential patients with ambulances now and in the future. Computational tests using a simulation model show that the tools are beneficial in reducing the waiting periods for the patients.
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| 2. |
- Baltz, Andreas, et al.
(author)
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Exact and heuristic algorithms for the Travelling Salesman Problem with Multiple Time Windows and Hotel Selection
- 2015
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In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 66:4, s. 615-626
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Journal article (peer-reviewed)abstract
- We introduce and study the Travelling Salesman Problem with Multiple Time Windows and Hotel Selection (TSP-MTWHS), which generalises the well-known Travelling Salesman Problem with Time Windows and the recently introduced Travelling Salesman Problem with Hotel Selection. The TSP-MTWHS consists in determining a route for a salesman (eg, an employee of a services company) who visits various customers at different locations and different time windows. The salesman may require a several-day tour during which he may need to stay in hotels. The goal is to minimise the tour costs consisting of wage, hotel costs, travelling expenses and penalty fees for possibly omitted customers. We present a mixed integer linear programming (MILP) model for this practical problem and a heuristic combining cheapest insert, 2-OPT and randomised restarting. We show on random instances and on real world instances from industry that the MILP model can be solved to optimality in reasonable time with a standard MILP solver for several small instances. We also show that the heuristic gives the same solutions for most of the small instances, and is also fast, efficient and practical for large instances.
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| 3. |
- Caro, F., et al.
(author)
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School Redistricting : Embedding GISTools with Integer Programming
- 2004
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In: Journal of the Operational Research Society. - : Palgrave Macmillan. - 0160-5682 .- 1476-9360. ; 55:8, s. 836-849
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Journal article (peer-reviewed)abstract
- The paper deals with a school redistricting problem in which blocks of a city must be assigned to schools according to diverse criteria. Previous approaches are reviewed and some desired properties of a good school districting plan are established. An optimization model together with a geographic information system environment are then proposed for finding a solution that satisfies these properties. A prototype of the system is described, some implementation issues are discussed, and two real-life examples from the city of Philadelphia are studied, one corresponding to a relatively easy to solve problem, and the other to a much harder one. The trade-offs in the solutions are analysed and feasibility questions are discussed. The results of the study strongly suggest that ill-defined spatial problems, such as school redistricting, can be addressed effectively by an interaction between objective analysis and subjective judgement.
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| 4. |
- Førsund, F.R., et al.
(author)
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Calculating scale elasticity in DEA models
- 2004
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In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 55:10, s. 1023-1038
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Journal article (peer-reviewed)
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| 5. |
- Gunnarsson (Lidestam), Helene, et al.
(author)
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A combined terminal location and ship routing problem
- 2006
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In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 57:8, s. 928-938
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Journal article (peer-reviewed)abstract
- In this paper, we consider a combined terminal location and ship routing problem at Södra Cell AB. The purpose is to supply the customers' annual demand for pulp products while minimizing the distribution costs. Customers are supplied with various pulp products from pulp mills in Scandinavia by ships, trains, or lorries. The ship routes go from the pulp mills to terminals in Europe. From each terminal, the products are transported to customers by lorry, train, or barge. Some customers can be supplied directly from the pulp mills by trains or lorries. We have developed a mathematical model to select which terminals to use and, at the same time, determine the shipping routes. The mixed integer programming model was solved directly using a commercial solver. When the number of routes generated is large, the time required to obtain an optimal solution is too long. Hence, we have developed heuristics in order to obtain an acceptable solution in reasonable time. In addition to the basic case, five different scenarios were tested. Our heuristics provide solutions that are within 0.12% of the optimal ones.
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| 6. |
- Hartley, Roger, et al.
(author)
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On the design of lottery games
- 2003
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In: Journal of the Operational Research Society. - : Palgrave Macmillan. - 0160-5682 .- 1476-9360. ; 54:1, s. 89-100
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Journal article (peer-reviewed)abstract
- We describe a model of participation in lottery games designed to address the optimisation of tax revenue in state-sponsored lotteries. The model treats participants dynamically and examines a long-run equilibrium. A novel high frequency approximation is used to turn the problem into a static, state-contingent deterministic programming problem. We demonstrate that the solution of this problem has qualitatively plausible properties and then calibrate the model against the United Kingdom National Lottery (UKNL). The results suggest that the current design of the UKNL may not be maximising tax revenue.
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| 7. |
- Holmberg, Kaj
(author)
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Formation of student groups with the help of optimisation
- 2019
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In: Journal of the Operational Research Society. - : TAYLOR & FRANCIS LTD. - 0160-5682 .- 1476-9360. ; 70:9, s. 1538-1553
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Journal article (peer-reviewed)abstract
- We study the problem of forming groups of students so that the groups are as even as possible with respect to certain aspects and group members are changed as much as possible compared to previous groups, and formulate it as a mixed integer programming problem. We find that standard software cannot solve real life sized instances, so we develop several heuristics and metaheuristics for the problem. Computational tests are made on randomly generated instances as well as real life instances. Some of the heuristics give good solutions in short time, and tests on real life problems indicate that satisfactory solutions can be found within 60 seconds.
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| 8. |
- Javed, Farrukh, et al.
(author)
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Tangency portfolio weights under a skew-normal model in small and large dimensions
- 2024
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In: Journal of the Operational Research Society. - : Taylor & Francis Group. - 0160-5682 .- 1476-9360. ; 75:7, s. 1395-1406
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Journal article (peer-reviewed)abstract
- In this paper, we investigate the distributional properties of the estimated tangency portfolio (TP) weights assuming that the asset returns follow a matrix variate closed skew-normal distribution. We establish a stochastic representation of the linear combination of the estimated TP weights that fully characterizes its distribution. Using the stochastic representation we derive the mean and variance of the estimated weights of TP which are of key importance in portfolio analysis. Furthermore, we provide the asymptotic distribution of the linear combination of the estimated TP weights under the high-dimensional asymptotic regime, i.e., the dimension of the portfolio p and the sample size n tend to infinity such that p/n & RARR;c & ISIN;(0,1). A good performance of the theoretical findings is documented in the simulation study. In an empirical study, we apply the theoretical results to real data of the stocks included in the S & P 500 index.
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| 9. |
- Lind, Mikael, et al.
(author)
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Team-based reconstruction for expanding organisational ability
- 2003
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In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 54:2, s. 119-129
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Journal article (peer-reviewed)abstract
- Organisations can be interpreted as a collection of actors who produce value for clients. In order for organisations to stay competitive there is a need for organisations to continuously develop their ability. An organisation’s ability is determined by its ability to effectively apply existing knowledge to create new knowledge and to take action that forms the basis for achieving competitive advantage from knowledge-based assets. One means for developing the organisational ability is to establish a mutually accepted understanding of the context in which the actors are acting. One important part of the organisation’s knowledge creation processes is to facilitate the sharing of personal knowledge. A condition for developing the organisational ability is to expand the amount of shared knowledge to an appropriate level. One type of knowledge that needs to be shared among different actors within the organisation is the knowledge about how and in which order actions are performed (contextual knowledge) in order to satisfy client needs. In this paper an approach for team-based reconstruction, used for moving from personal to shared contextual knowledge, is presented. The approach bears on the foundation of theories about knowledge management for understanding the process of externalisation and theories about language action for understanding organisations. Experiences from three case studies are presented. Team-based reconstruction can be used for (1) moving from personal knowledge to shared contextual knowledge in an efficient way, (2) arriving at a foundation for efficient organisational coordination, (3) arriving at a base for development work, and (4) organisational learning.
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| 10. |
- Nilsson, Andreas, et al.
(author)
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A simple improvement on Silver's heuristic for the joint replenishment problem
- 2008
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In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 59:10, s. 1415-1421
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Journal article (peer-reviewed)abstract
- In this paper, we revisit the well-known joint replenishment problem. There is a family of items with a major fixed cost associated with any replenishment of the family and a minor, (item-dependent) setup cost for each item that is included in the replenishment. In contrast with optimization methods and sophisticated (iterative) heuristics that have been presented in the literature, we present a simple (including ease of understanding) improvement routine to be used in conjunction with the original, simple approach advocated by one of the authors 30 years ago. Tests on 48,000 examples reveal that the improvement routine does, indeed, substantially improve performance and with relatively little extra computational effort. Thus, it should be of particular interest to practitioners and for teaching materials.
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| 11. |
- Norin, Anna, et al.
(author)
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Scheduling de-icing vehicles within airport logistics: a heuristic algorithm and performance evaluation
- 2012
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In: Journal of the Operational Research Society. - : Palgrave Macmillan. - 0160-5682 .- 1476-9360. ; 63:8, s. 1116-1125
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Journal article (peer-reviewed)abstract
- Most delays in the air transport occur at the airport. A particular reason is the complexity of managing the large number of supporting flows in airport logistics. We consider the optimisation problem of scheduling de-icing vehicles that is one of the key supporting logistic flows in the turn-around process of aircraft. The objective is to minimise the delay of flights due to de-icing, and the travel distance of the de-icing vehicles. We study the complexity of the problem, and develop a solution algorithm using greedy randomised adaptive search. A case study of real-life data from Stockholm Arlanda Airport shows that optimised schedule leads to significantly better performance in comparison to intuitive and simple scheduling strategies. The benefit of optimisation in reducing the waiting time for de-icing is further demonstrated via dynamic simulations.
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| 12. |
- Nyström, Kaj, 1969-, et al.
(author)
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Hawkes-Based Models for High Frequency Financial Data
- 2022
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In: Journal of the Operational Research Society. - : Taylor & Francis. - 0160-5682 .- 1476-9360. ; 73:10, s. 2168-2185
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Journal article (peer-reviewed)abstract
- Compared with low frequency data, high frequency data exhibit distinct empirical properties,including, for instance, essentially discontinuous evolution paths, time-varying intensities, and self-exciting features. All these make it more challenging to model appropriately the dynamics associatedwith high frequency data such as order arrival and price formation. To capture more accuratelythe microscopic structures and properties pertaining to the limit order books, this paper focuses onmodeling high frequency data using Hawkes processes. Two models, one with exponential kernels andthe other with power-law kernels, are introduced systematically, algorithmized precisely, and comparedwith each other extensively from various perspectives, including the goodness of fit to the original dataand the computational time in searching for the maximum likelihood estimator, with search algorithmbeing taken into consideration as well. To measure the goodness of fit, a number of quantities areproposed. Studies based on both multiple-trading-day data of one stock and multiple-stock data onone trading day indicate that Hawkes processes with slowly-decaying kernels are able to reproduce theintensity of jumps in the price processes more accurately. The results suggest that Hawkes processeswith power-law kernels and their implied long memory nature of self-excitation phenomena could, onthe level of microstructure, serve as a realistic model for high frequency data.
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| 13. |
- Papahristodoulou, Christos, et al.
(author)
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Optimal portfolios using Linear Programming Models
- 2004
-
In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 55:11, s. 1169-1177
-
Journal article (peer-reviewed)abstract
- The classical Quadratic Programming (QP) formulation of the well-known portfolio selection problem has traditionally been regarded as cumbersome and time consuming. This paper formulates two additional models, (i) maximin, and (ii) minimization of mean absolute deviation. Data from 67 securities over 48 months are used to examine to what extent all three formulations provide similar portfolios. As expected, the maximin formulation yields the highest return and risk, while the QP formulation provides the lowest risk and return, which also creates the efficient frontier. The minimization of mean absolute deviation is close to the QP formulation. When the expected returns are confronted with the true ones at the end of a six months period, the maximin portfolios seem to be the most robust of all.
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| 14. |
- Pazirandeh, Ala, 1983, et al.
(author)
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Improved coordination during disaster relief operations through sharing of resources
- 2018
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In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 69:8, s. 1227-1241
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Journal article (peer-reviewed)abstract
- Abstract In this paper, we focus on coordination dynamics between nonprofit organizations in the short-term, nonprofit, and competitive settings in disaster relief operations. Sharing resources across organizations can be a key to better coordination. Thus, we tested the link between resource sharing, aspects impacting resource sharing, and operational performance of the organizations using 101 data points. Data was collected through a survey from HOs within the Southeast Asian region and was analyzed using the Structural Equation Modeling-Partial Least Square (SEM-PLS) approach. The results show that resource sharing can improve organizational performance in this horizontal and competitive context, and that complementarity of resources between organizations increases their willingness to share resources. Complementarity of resources can also improve the interdependencies between organizations, which is not perceived very highly in the current highly competitive settings.
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| 15. |
- Petropoulos, Fotios, et al.
(author)
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Forecast combinations for intermittent demand
- 2015
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In: Journal of the Operational Research Society. - : Taylor & Francis. - 0160-5682 .- 1476-9360. ; 66:6, s. 914-924
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Journal article (peer-reviewed)abstract
- Intermittent demand is characterised by infrequent demand arrivals, where many periods have zero demand, coupled with varied demand sizes. The dual source of variation renders forecasting for intermittent demand a very challenging task. Many researchers have focused on the development of specialised methods for intermittent demand. However, apart from a case study on hierarchical forecasting, the effects of combining, which is a standard practice for regular demand, have not been investigated. This paper empirically explores the efficiency of forecast combinations in the intermittent demand context. We examine both method and temporal combinations of forecasts. The first are based on combinations of different methods on the same time series, while the latter use combinations of forecasts produced on different views of the time series, based on temporal aggregation. Temporal combinations of single or multiple methods are investigated, leading to a new time-series classification, which leads to model selection and combination. Results suggest that appropriate combinations lead to improved forecasting performance over single methods, as well as simplifying the forecasting process by limiting the need for manual selection of methods or hyper-parameters of good performing benchmarks. This has direct implications for intermittent demand forecasting in practice.
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| 16. |
- Petropoulos, F., et al.
(author)
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Operational Research : methods and applications
- 2024
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In: Journal of the Operational Research Society. - : Taylor and Francis Ltd.. - 0160-5682 .- 1476-9360.
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Research review (peer-reviewed)abstract
- Throughout its history, Operational Research has evolved to include methods, models and algorithms that have been applied to a wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first summarises the up-to-date knowledge and provides an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion and used as a point of reference by a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order. The authors dedicate this paper to the 2023 Turkey/Syria earthquake victims. We sincerely hope that advances in OR will play a role towards minimising the pain and suffering caused by this and future catastrophes.
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| 17. |
- Petropoulos, Fotios, et al.
(author)
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Operational Research : methods and applications
- 2024
-
In: Journal of the Operational Research Society. - : Taylor & Francis Group. - 0160-5682 .- 1476-9360. ; 75:3, s. 423-617
-
Research review (peer-reviewed)abstract
- Throughout its history, Operational Research has evolved to include methods, models and algorithms that have been applied to a wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first summarises the up-to-date knowledge and provides an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion and used as a point of reference by a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order. The authors dedicate this paper to the 2023 Turkey/Syria earthquake victims. We sincerely hope that advances in OR will play a role towards minimising the pain and suffering caused by this and future catastrophes.
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| 18. |
- Sahamkhadam, Maziar, et al.
(author)
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Socially responsible multiobjective optimal portfolios
- 2024
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In: Journal of the Operational Research Society. - : Taylor & Francis Group. - 0160-5682 .- 1476-9360. ; , s. 1-12
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Journal article (peer-reviewed)abstract
- This article extends the socially responsible multiobjective problem to (i) estimating optimal portfolios via reward/risk maximization, (ii) including dependence structure between asset returns using vine copulas, and (iii) incorporating enhanced indexation utilizing cumulative zero-order stochastic dominance (CZϵSD). Applying the multiobjective optimal portfolio (MOOP) approach to a sample of EuroStoxx 50 constituents, the results show that the MOOPs provide investors with the flexibility to incorporate different objectives while investing in optimal portfolios. Including social responsibility results in lower portfolio return and economic performance, but at the same time portfolio risk, expected shortfall of portfolio returns below the benchmark, and turnover are reduced. The copula-based predictive models lead to MOOPs with higher returns and reward/risk ratios. Moreover, optimizing environmental scores leads to less risky MOOPs, while optimizing social scores results in higher average return and better risk-adjusted performance.
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| 19. |
- Tanaka, Makoto, et al.
(author)
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Regulatory jurisdiction and policy coordination : A bi-level modeling approach for performance-based environmental policy
- 2022
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In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 73:3, s. 509-524
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Journal article (peer-reviewed)abstract
- This study discusses important aspects of policy modeling based on a leader-follower game of policymakers. We specifically investigate non-cooperation between policymakers and the jurisdictional scope of regulation via bi-level programming. Performance-based environmental policy under the Clean Power Plan in the United States is chosen for our analysis. We argue that the cooperation of policymakers is welfare enhancing. Somewhat counterintuitively, full coordination among policymakers renders performance-based environmental policy redundant. We also find that distinct state-by-state regulation yields higher social welfare than broader regional regulation. This is because power producers can participate in a single power market even under state-by-state environmental regulation and arbitrage away the CO2 price differences by adjusting their generation across states. Numerical examples implemented for a stylized test network illustrate the theoretical findings.
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| 20. |
- Tansini, Libertad, 1973, et al.
(author)
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New measures of proximity for the assignment algorithms in the MDVRPTW
- 2006
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In: Journal of the Operational Research Society. - : Informa UK Limited. - 0160-5682 .- 1476-9360. ; 57:3, s. 241-249
-
Journal article (peer-reviewed)abstract
- This paper proposes new proximity measures for assignment algorithms for the Multi-Depot Vehicle Routing Problem with Time Windows (MDVRPTW). Given the intrinsic difficulty of this problem class, two-step approximation methods of the type 'cluster first, route second' seem to be the most promising for practical size problems. The focus is on the clustering phase, the assignment of customers to depots. Our approach is to extend the existing metrics with time windows. New measures that include time windows and distances are added to two assignment heuristics, that previously only used distance to evaluate proximity between customers and depots. A computational study of their performance is presented, which shows that the inclusion of time windows in the measures of proximity gives better results, in terms of routing, than only using the distance.
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| 21. |
- Trapero, Juan R., et al.
(author)
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On the identification of sales forecasting models in the presence of promotions
- 2015
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In: Journal of the Operational Research Society. - : Taylor & Francis. - 0160-5682 .- 1476-9360. ; 66:2, s. 299-307
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Journal article (peer-reviewed)abstract
- Shorter product life cycles and aggressive marketing, among other factors, have increased the complexity of sales forecasting. Forecasts are often produced using a Forecasting Support System that integrates univariate statistical forecasting with managerial judgment. Forecasting sales under promotional activity is one of the main reasons to use expert judgment. Alternatively, one can replace expert adjustments by regression models whose exogenous inputs are promotion features (price, display, etc). However, these regression models may have large dimensionality as well as multicollinearity issues. We propose a novel promotional model that overcomes these limitations. It combines Principal Component Analysis to reduce the dimensionality of the problem and automatically identifies the demand dynamics. For items with limited history, the proposed model is capable of providing promotional forecasts by selectively pooling information across established products. The performance of the model is compared against forecasts provided by experts and statistical benchmarks, on weekly data; outperforming both substantially.
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| 22. |
- Zhang, Changyong
(author)
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An Origin-Based Model for Unique Shortest Path Routing
- 2016
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In: Journal of the Operational Research Society. - : Springer. - 0160-5682 .- 1476-9360. ; 68
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Journal article (peer-reviewed)abstract
- Link weights are the main parameters of shortest path routing protocols, the most commonly used protocols for IP networks. The problem of optimally setting link weights for unique shortest path routing is addressed. Due to the complexity of the constraints involved, there exist challenges to formulate the problem in such a way based on which a more efficient solution algorithm than the existing ones may be developed. In this paper, an exact formulation is first introduced and then mathematically proved correct. It is further illustrated that the formulation has advantages over a prior one in terms of both constraint structure and model size for a proposed decomposition method to solve the problem.
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| 23. |
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| 24. |
- Axsäter, Sven
(author)
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Hierarchical Allocation
- 1982
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In: Journal of the Operational Research Society. - 0160-5682. ; 33:No 8, s. 751-756
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Journal article (peer-reviewed)
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