•We addressed the scheduling and routing of a repair crew after a disaster.•We present a dynamic programming model that solves small/mid-sized problems.•We develop a IGRCP procedure to solve large ...problem instances efficiently.•Our work has societal impact as it helps to efficiently repair a network damaged by a disaster.•Considering the routing of the repair crew makes the problem more realistic.
Every year, hundreds of thousands of people are affected by natural disasters. The number of casualties is usually increased by lack of clean water, food, shelter, and adequate medical care during the aftermath. One of the main problems influencing relief distribution is the state of the post-disaster road network. In this paper, we consider the problem of scheduling the emergency repair of a rural road network that has been damaged by the occurrence of a natural disaster. This problem, which we call the Network Repair Crew Scheduling and Routing Problem addresses the scheduling and routing of a repair crew optimizing accessibility to the towns and villages that demand humanitarian relief by repairing roads. We develop both an exact dynamic programming (DP) algorithm and an iterated greedy-randomized constructive procedure to solve the problem and compare the performance of both approaches on small- to medium-scale instances. Our numerical analysis of the solution structure validates the optimization model and provides managerial insights into the problem and its solutions.
•A model to generate optimized work shifts in a chain of supermarkets in Italy is proposed.•A mathematical formulation of the workforce management problem is defined.•An exact approach to solve the ...problem is described.•An efficient hybrid heuristic is presented and statistically tested.•27 real problem instances faced by the firm within its supermarkets are solved.
This work proposes a scheduling problem for the workforce management in a chain of supermarkets operating in Italy. We focus on determining the ideal mix of full-time and part-time workers which are needed every week to guarantee a satisfactory service level during the check-out operations. The generation of working shifts, to be assigned to retail workers, is subject to several constraints imposed by both labour laws and enterprise bargaining agreements.
We present a mathematical formulation of the problem followed by an exact solution approach which relies on the definition of feasible daily working shifts. The number of feasible daily shifts, that are combined to determine feasible weekly shifts, could drastically increase, depending on the selected planning interval. In addition, there may exist additional constraints, that are difficult to incorporate into the mathematical model. For these reasons, a hybrid heuristic, which does not require the generation of all feasible weekly shifts, is proposed in this paper.
Using appropriate statistical techniques, a sensitivity analysis is performed to test the design of the hybrid heuristic. Computational tests are carried out by solving several real instances provided by the retail firm. The results obtained by the heuristic are compared both with an exact approach and with the solutions adopted by the retail company, which have been determined by using a naïf approach. Our hybrid heuristic exhibits excellent performance finding optimal or near optimal solutions in a very limited CPU time.
A matheuristic approach that combines a reduced variable neighbourhood search (rVNS) algorithm and a mathematical programming (MP) solver to solve a novel model for the districting problem in a ...public bicycle-sharing system is presented. The problem is modelled as an integer programming problem. While the rVNS algorithm aims to find a high-quality set of centres for the repositioning zones, the MP solver computes the optimal allocation network of the stations to the centres of the repositioning zones. We use a predefined grid to reduce the search space the rVNS needs to explore. The proposed approach obtains promising results for small and medium-sized instances, and is also able to handle large-sized models.
The accessibility arc upgrading problem Maya Duque, Pablo A.; Coene, Sofie; Goos, Peter ...
European journal of operational research,
02/2013, Letnik:
224, Številka:
3
Journal Article
Recenzirano
Odprti dostop
► The accessibility arc upgrading problem is a network upgrading problem that arises in real-life decision processes. ► A mathematical formulation for the accessibility arc upgrading problem is ...proposed. ► Two solution approaches for the accessibility arc upgrading problem are described. ► Large improvements in accessibility are obtained by allocating resources properly.
The accessibility arc upgrading problem (AAUP) is a network upgrading problem that arises in real-life decision processes such as rural network planning. In this paper, we propose a linear integer programming formulation and two solution approaches for this problem. The first approach is based on the knapsack problem and uses the knowledge gathered from an analytical study of some special cases of the AAUP. The second approach is a variable neighbourhood search with strategic oscillation. The excellent performance of both approaches is demonstrated using a large set of randomly generated instances. Finally, we stress the importance of a proper allocation of scarce resources in accessibility improvement.
We consider the problem of allocating scarce resources to repair a rural road network after it has been damaged by a natural or man-made disaster. We propose a solution approach based on the GRASP ...and VNS metaheuristics that aims to maximize the accessibility of as many people as possible to the main cities or regional centers where the economic and social infrastructure is usually located. The efficiency of our approach is demonstrated by applying it to a set of small and medium size instances and to a large real-life motivated instance. Results point out the importance of OR techniques to support the disaster management decision process operations, particularly during the recovery phase.
Energy is a fundamental tool for human development and this paper presents an approach that seeks to improve its use in Colombian off-grid communities. This approach is based on microgrid concepts ...where generation, storage, and consumption units interact with each other, and these interactions are presented through a linear programming model. In this approach, specific strategies are implemented according to the Colombian context, where some isolated communities already have diesel-based solutions for energy access, and the type of element that is studied, finding that the proposed optimization model is capable of adequately managing the loads of the microgrid,, thus improving the way in which the generated energy is stored and used through said horizon. Finally, different characteristics of the model are evaluated against multiple indicators and it is concluded that there may be much more specific strategies that improve its operation.
This paper deals with the optimal sizing of islanded microgrids (MGs), which use diesel generators to supply energy in off-grid areas. The MG under study integrates photovoltaic (PV) and diesel ...generation, a battery energy storage System (BESS), and an inverter for the connection between AC and DC voltage buses. Levelised cost of energy (LCOE) and annual system cost (ASC) are considered economic indicators, while the loss of power supply probability (LPSP) is used as a reliability indicator. Fiscal incentives such as the tax benefits and accelerated depreciation applied in Colombia are considered for the optimally sizing of each MG element. Solar measurements were taken at a weather station located in the main campus of Universidad de Antioquia in Medellin, Colombia at a latitude of 6.10 and longitude of −75.38. The objective function is the minimization of the total energy delivered from the power sources that successfully meets the load. The model was implemented in Python programming language considering several scenarios. Two cases were evaluated: the first one considered PV panels, a BESS and a diesel generator, while the second one only considered PV panels and a BESS. The option that does not include the diesel generator turned out to be the most expensive, since additional PV and BESS resources are required to meet the load profile. Furthermore, it was found that the LCOE was lower when tax benefits were taken into account.
To make an effective transition towards a circular economy, we must have the responsibility and active participation of all the stakeholders involved, including customers. In this work, we seek to ...develop an agent-based model to describe and analyze an environmental awareness system in a population, whose behavior is based on an indicator that can change by agent’s interaction and modify its consumption habits. The model is described using the ODD + D protocol, and we use Netlogo software for coding. After model validation process, its results are analyzed to understand how can environmental awareness level, consumption habits and social skills of each individual influence on the average environmental awareness level of a heterogeneous population, which makes simple the identification of emerging behaviors and the forecasting of the potentially recyclable waste according to the quality in the separation at source.
El presente trabajo presenta un modelo de programación matemática que permite la obtención de un horario académico en instituciones de educación primaria y secundaria de diferente tamaño, cantidades ...de grupos y materias, considerando restricciones que frecuentemente debe enfrentar quien esta encargado del proceso de planeación. El objetivo del modelo propuesto se diferencia de aquellos encontrados en la literatura referida a este tema, ya que propende la creación de horarios maximizando la cantidad de bloques por materias, es decir asignaciones de dos horas seguidas de la misma clase, lo que favorece el proceso de aprendizaje, beneficia la agenda de los profesores al disminuir tiempos ociosos entre clases, y favorece los costos y acuerdos contractuales con la institución. El modelo es aplicado al caso particular de una institución educativa obteniendo resultados que mejoran considerablemente la calidad de la programación de clases respecto a la que actualmente está en uso. Adicionalmente, se desarrollan experimentos computacionales con instancias de mayor tamaño para validar el comportamiento del modelo, obteniendo resultados promisorios.
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