Solving the waste collection problem from a multiobjective perspective: New methodologies and case studies

Fecha de lectura Tesis Doctoral: 19 de marzo de 2018.Economía Aplicada ( Matemáticas) Resumen tesis: El tratamiento de residuos es un tema de estudio por parte de las administraciones locales a nivel mundial. Distintos factores han de tenerse en cuenta para realizar un servicio eficiente. En este trabajo se desarrolla una herramienta para analizar y resolver el problema de la recogida de residuos sólidos en Málaga. Tras un análisis exhaustivo de los datos, se aborda el problema real como un problema de rutas multiobjetivo con capacidad limitada. Para los problemas multiobjetivo, no suele existir una única solución óptima, sino un conjunto de soluciones eficientes de Pareto. Las características del problema hacen inviable su resolución de forma exacta, por lo que se aplican distintas estrategias metaheurísticas para obtener una buena aproximación. En particular, se combinan las técnicas de GRASP, Path Relinking y Variable Neighborhood Search, que son adaptadas a la perspectiva multicriterio. Se trata de una aproximación en dos fases: una primera aproximación de la frontera eficiente se genera mediante un GRASP multiobjetivo. Tres son los métodos propuestos para la primera aproximación, dos de ellos derivados de la publicación de Martí et al. (2015) y el último se apoya en la función escalarizada de logro de Wierzbicki (Wierzbicki, 1980) para distintas combinaciones de pesos. A continuación, esta aproximación es mejorada con una versión de Path Relinking o Variable Neighborhood Search, con un punto de referencia diseñado para problemas multiobjetivo. Una vez generada la aproximación de la frontera eficiente, el proceso de obtención de la solución que más se adecúa a las preferencias de los gestores se basa en el desarrollo de un método interactivo sin trade – off, derivado de la filosofía NAUTILUS (Miettinen et al. 2010). Para evitar gastos de cómputo extensos, esta metodología se apoya en una pre - computación de los elementos de la frontera eficiente

Decision Support Systems for Scheduling and Routing Problems in a Home Care Business

Programa Oficial de Doutoramento en Estatística e Investigación Operativa. 5017V01[Abstract] Home care services aim to help elderly, sick or dependent people in maintain their quality of life without having to leave their homes. This type of problem is denoted as Home Care Scheduling Problem (HCSP) and the goal is to obtain the routes that the company’s caregivers must follow, as well as the timeframe in which each service should be carried out. That is, a HCSP can be seen as a routing and scheduling problem. This thesis studies a real HCSP presented by a company called Mayores. First, the original problem proposed by the company is presented, which consists in updating the weekly schedules of the caregivers in order to solve a set of possible incidents. This problem is tackled using the Simulated Annealing method embedded inside a custom heuristic algorithm. Second, a more general version of the problem is described, which aims to obtain the best possible schedules of the caregivers from scratch, considering two objectives: the welfare of the users and the cost of the schedule. The problem is solved considering three approaches: two hierarchical ones (prioritizing the welfare or prioritizing the cost) and a biobjective one. Finally, a computational study is presented in order to evaluate the resolution approaches, using instances from the literature and real data from the company[Resumen] Los servicios de atención a domicilio tienen como objetivo ayudar a personas mayores o dependientes a mantener o mejorar su calidad de vida sin necesidad de abandonar sus hogares. Esta clase de problema se denomina Home Care Scheduling Problem (HCSP) y su objetivo es obtener las rutas que deben seguir las auxiliares de la empresa, así como los horarios en los que debe realizarse cada servicio. Es decir, los HCSP pueden ser considerados como problemas de planificación de rutas y horarios. En esta tesis se estudia un HCSP real presentado por una empresa llamada Mayores. En primer lugar, se presenta el problema original propuesto por la empresa, que consiste en actualizar los horarios semanales de las auxiliares con el fin de resolver un conjunto de incidencias. En segundo lugar, se describe una versión más general del problema, cuyo objetivo es obtener, partiendo desde cero, las mejores planificaciones para las auxiliares, considerando dos objetivos: el bienestar de los usuarios y el coste de la planificación. El problema se resuelve considerando tres enfoques: dos jerárquicos (dando prioridad al bienestar o al coste) y uno biobjetivo. Por último, se presenta un estudio computacional para evaluar los enfoques de resolución propuestos, utilizando instancias de la literatura y datos reales proporcionados por la empresa.[Resumo] Os servizos de atención a domicilio teñen como obxectivo axudar a persoas maiores ou dependentes a manter ou mellorar a súa calidade de vida sen necesidade de abandonar os seus fogares. Esta clase de problema denomínase Home Care Scheduling Problem (HCSP) e o seu obxectivo é obter as rutas que deben seguir as auxiliares da empresa, así como os horarios nos que debe realizarse cada servizo. É dicir, os HCSP poden ser considerados como problemas de planificación de rutas e horarios. Nesta tese estúdase un HCSP real presentado por unha empresa chamada Mayores. En primeiro lugar, preséntase o problema orixinal proposto pola empresa, que consiste en actualizar os horarios semanais das auxiliares co fin de resolver un conxunto de incidencias. En segundo lugar, descríbese unha versión máis xeral do problema, cuxo obxectivo é obter, partindo desde cero, as mellores planificacións para as auxiliares, considerando dous obxectivos: o benestar dos usuarios e o custo da planificación. O problema resólvese considerando tres enfoques: dous xerárquicos (dando prioridade ao benestar ou ao custo) e un biobxetivo. Por último, preséntase un estudo computacional para avaliar os enfoques de resolución propostos, empregando instancias da literatura e datos reais proporcionados pola empresa.Xunta de Galicia; ED431C-2020/14Xunta de Galicia; ED431G-2019/01The PhD candidate’s research was sponsored by the Spanish Grant for Predoctoral Research Trainees RD 103/2019. This research was funded by MICINN/AEI/10.13039/501100011033/ and ERDF/EU through R+D+I project grants MTM2017-87197-C3-1-P and PID2021-124030NB-C31 and by Consellería de Cultura, Educación e Universidades, Xunta de Galicia (Grupos de Referencia Competitiva ED431C-2020/14 and Centro de Investigación del Sistema universitario de Galicia ED431G-2019/01)

OPTIMIZATION OF RAILWAY TRANSPORTATION HAZMATS AND REGULAR COMMODITIES

Transportation of dangerous goods has been receiving more attention in the realm of academic and scientific research during the last few decades as countries have been increasingly becoming industrialized throughout the world, thereby making Hazmats an integral part of our life style. However, the number of scholarly articles in this field is not as many as those of other areas in SCM. Considering the low-probability-and-high-consequence (LPHC) essence of transportation of Hazmats, on the one hand, and immense volume of shipments accounting for more than hundred tons in North America and Europe, on the other, we can safely state that the number of scholarly articles and dissertations have not been proportional to the significance of the subject of interest. On this ground, we conducted our research to contribute towards further developing the domain of Hazmats transportation, and sustainable supply chain management (SSCM), in general terms. Transportation of Hazmats, from logistical standpoint, may include all modes of transport via air, marine, road and rail, as well as intermodal transportation systems. Although road shipment is predominant in most of the literature, railway transportation of Hazmats has proven to be a potentially significant means of transporting dangerous goods with respect to both economies of scale and risk of transportation; these factors, have not just given rise to more thoroughly investigation of intermodal transportation of Hazmats using road and rail networks, but has encouraged the competition between rail and road companies which may indeed have some inherent advantages compared to the other medium due to their infrastructural and technological backgrounds. Truck shipment has ostensibly proven to be providing more flexibility; trains, per contra, provide more reliability in terms of transport risk for conveying Hazmats in bulks. In this thesis, in consonance with the aforementioned motivation, we provide an introduction into the hazardous commodities shipment through rail network in the first chapter of the thesis. Providing relevant statistics on the volume of Hazmat goods, number of accidents, rate of incidents, and rate of fatalities and injuries due to the incidents involving Hazmats, will shed light onto the significance of the topic under study. As well, we review the most pertinent articles while putting more emphasis on the state-of-the-art papers, in chapter two. Following the discussion in chapter 3 and looking at the problem from carrier company’s perspective, a mixed integer quadratically constraint problem (MIQCP) is developed which seeks for the minimization of transportation cost under a set of constraints including those associating with Hazmats. Due to the complexity of the problem, the risk function has been piecewise linearized using a set of auxiliary variables, thereby resulting in an MIP problem. Further, considering the interests of both carrier companies and regulatory agencies, which are minimization of cost and risk, respectively, a multiobjective MINLP model is developed, which has been reduced to an MILP through piecewise linearization of the risk term in the objective function. For both single-objective and multiobjective formulations, model variants with bifurcated and nonbifurcated flows have been presented. Then, in chapter 4, we carry out experiments considering two main cases where the first case presents smaller instances of the problem and the second case focuses on a larger instance of the problem. Eventually, in chapter five, we conclude the dissertation with a summary of the overall discussion as well as presenting some comments on avenues of future work

Multi-objective optimization of a two-echelon vehicle routing problem with vehicle synchronization and "grey Zone" customers arising in urban logistics

We present a multi-objective two-echelon vehicle routing problem with vehicle synchronization and "grey zone" customers arising in the context of urban freight deliveries. Inner-city center deliveries are performed by small vehicles due to access restrictions, while deliveries outside this area are carried out by conventional vehicles for economic reasons. Goods are transferred from the first to the second echelon by synchronized meetings between vehicles of the respective echelons. We investigate the assignment of customers to vehicles, i.e., to the first or second echelon, within a so-called "grey Zone" on the border of the inner city and the area around it. While doing this, the economic objective as well as negative external effects of transport, such as emissions and disturbance (negative impact on citizens due to noise and congestion), are taken into account to include objectives of companies as well as of citizens and municipal authorities. Our metaheuristic - a large neighborhood search embedded in a heuristic rectangle/cuboid splitting - addresses this problem efficiently. We investigate the impact of the free assignment of part of the customers ("grey Zone") to echelons and of three different city layouts on the solution. Computational results show that the impact of a "grey Zone" and thus the assignment of these customers to echelons depend significantly on the layout of a city. Potentially pareto-optimal solutions for two and three objectives are illustrated to efficiently support decision makers in sustainable city logistics planning processes

Simulation model to determine ratios between quay, yard and intra-terminal transfer equipment in an integrated container handling system

This paper presents a generic simulation model to determine the equipment mix (quay, yard and intra-terminal transfer) for a Container Terminal Logistics Operations System (CTLOS). The simulation model for the CTLOS, a typical type of discrete event dynamic system (DEDS), consists of three sub-models: ship queue, loading-unloading operations and yard-gate operations. The simulation model is empirically applied to phase 1 of the Yangshan Deep Water Port in Shanghai. This study considers different scenarios in terms of container throughput levels, equipment utilization rates, and operational bottle-necks, and presents a sensitivity analysis to evaluate and choose reasonable equipment ratio ranges under different operational conditions

AIRO 2016. 46th Annual Conference of the Italian Operational Research Society. Emerging Advances in Logistics Systems Trieste, September 6-9, 2016 - Abstracts Book

The AIRO 2016 book of abstract collects the contributions from the conference participants. The AIRO 2016 Conference is a special occasion for the Italian Operations Research community, as AIRO annual conferences turn 46th edition in 2016. To reflect this special occasion, the Programme and Organizing Committee, chaired by Walter Ukovich, prepared a high quality Scientific Programme including the first initiative of AIRO Young, the new AIRO poster section that aims to promote the work of students, PhD students, and Postdocs with an interest in Operations Research. The Scientific Programme of the Conference offers a broad spectrum of contributions covering the variety of OR topics and research areas with an emphasis on “Emerging Advances in Logistics Systems”. The event aims at stimulating integration of existing methods and systems, fostering communication amongst different research groups, and laying the foundations for OR integrated research projects in the next decade. Distinct thematic sections follow the AIRO 2016 days starting by initial presentation of the objectives and features of the Conference. In addition three invited internationally known speakers will present Plenary Lectures, by Gianni Di Pillo, Frédéric Semet e Stefan Nickel, gathering AIRO 2016 participants together to offer key presentations on the latest advances and developments in OR’s research

How to locate services optimizing redundancy: A comparative analysis of K-Covering Facility Location models

Redundancy aspects related to covering facility location problems are of extreme importance for many applications, in particular those regarding critical services. For example, in the healthcare sector, facilities such as ambulances or first -aid centers must be located robustly against unpredictable events causing disruption or congestion. In this paper, we propose different modeling tools that explicitly address coverage redundancy for the underlying service. We also evaluate, both theoretically and experimentally, the properties and behavior of the models, and compare them from a computational and managerial point of view. More precisely, by starting from three classical double -covering models from the literature (BACOP1, BACOP2, and DSM), we define three parametric families of models (namely, K-BACOP1, K-BACOP2, and K-DSM) which generalize the former to any possible Kth coverage level of interest. The study of such generalizations allows us to derive interesting managerial insights on location decisions at the strategic level. The CPU performance and the quality of the solutions returned are assessed through ad -hoc KPIs collected over many representative instances with different sizes and topological characteristics, and also by dynamically simulating scenarios involving possible disruption for the located facilities. Finally, a real case study concerning ambulance service in Morocco is analyzed. The results show that, in general, K-BACOP1 performs very well, even if intrinsic feasibility issues limit its broad applicability. Instead, K-DSM achieves the best coverage and equity performances for lower levels of redundancy, while K-BACOP2 seems the most robust choice when high redundancy is required, showing smoother and more predictable trends

A Polyhedral Study of Mixed 0-1 Set

We consider a variant of the well-known single node fixed charge network flow set with constant capacities. This set arises from the relaxation of more general mixed integer sets such as lot-sizing problems with multiple suppliers. We provide a complete polyhedral characterization of the convex hull of the given set

Arc routing problems: A review of the past, present, and future

[EN] Arc routing problems (ARPs) are defined and introduced. Following a brief history of developments in this area of research, different types of ARPs are described that are currently relevant for study. In addition, particular features of ARPs that are important from a theoretical or practical point of view are discussed. A section on applications describes some of the changes that have occurred from early applications of ARP models to the present day and points the way to emerging topics for study. A final section provides information on libraries and instance repositories for ARPs. The review concludes with some perspectives on future research developments and opportunities for emerging applicationsThis research was supported by the Ministerio de Economia y Competitividad and Fondo Europeo de Desarrollo Regional, Grant/Award Number: PGC2018-099428-B-I00. The Research Council of Norway, Grant/Award Numbers: 246825/O70 (DynamITe), 263031/O70 (AXIOM).Corberán, Á.; Eglese, R.; Hasle, G.; Plana, I.; Sanchís Llopis, JM. (2021). Arc routing problems: A review of the past, present, and future. Networks. 77(1):88-115. https://doi.org/10.1002/net.21965S8811577