GRASP with path relinking for the selective pickup and delivery problem

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Multi-echelon distribution systems in city logistics

In the last decades , the increasing quality of services requested by the cust omer, yields to the necessity of optimizing the whole distribution process. This goal may be achieved through a smart exploitation of existing resources other than a clever planning of the whole distribution process. For doing that, it is necessary to enha nce goods consolidation. One of the most efficient way to implement it is to adopt Multi - Echelon distribution systems which are very common in City Logistic context, in which they allow to keep large trucks from the city center, with strong environmental a dvantages . The aim of the paper is to review routing problems arising in City Logistics , in which multi - e chelon distribution systems are involved: the Two Echelon Location Routing Problem ( 2E - LRP) , the Two Echelon Vehicle Routing Problem (2E - VRP) and Truck and Trailer Routing Problem (TTRP), and to discuss literature on optimization methods, both exact and heuristic, developed to address these problems

A review of the Tabu Search Literature on Traveling Salesman Problems

The Traveling Salesman Problem (TSP) is one of the most widely studied problems inrncombinatorial optimization. It has long been known to be NP-hard and hence research onrndeveloping algorithms for the TSP has focused on approximate methods in addition to exactrnmethods. Tabu search is one of the most widely applied metaheuristic for solving the TSP. Inrnthis paper, we review the tabu search literature on the TSP, point out trends in it, and bringrnout some interesting research gaps in this literature.

A multiple type bike repositioning problem

This paper investigates a new static bicycle repositioning problem in which multiple types of bikes are considered. Some types of bikes that are in short supply at a station can be substituted by other types, whereas some types of bikes can occupy the spaces of other types in the vehicle during repositioning. These activities provide two new strategies, substitution and occupancy, which are examined in this paper. The problem is formulated as a mixed-integer linear programming problem to minimize the total cost, which consists of the route travel cost, penalties due to unmet demand, and penalties associated with the substitution and occupancy strategies. A combined hybrid genetic algorithm is proposed to solve this problem. This solution algorithm consists of (i) a modified version of a hybrid genetic search with adaptive diversity control to determine routing decisions and (ii) a proposed greedy heuristic to determine the loading and unloading instructions at each visited station and the substitution and occupancy strategies. The results show that the proposed method can provide high-quality solutions with short computing times. Using small examples, this paper also reveals problem properties and repositioning strategies in bike sharing systems with multiple types of bikes.published_or_final_versio

Analysis of the characteristics and applications of vehicle routing systems

El ruteo de vehículos, permite establecer una estrategia para realizar la distribución adecuada de las mercancías, en los diferentes puntos en los cuales lo desee una organización. Esto se logra, a través del diseño de rutas para una flota de vehículos determinada; ya sea homogénea o heterogénea. El estudio de este problema de ruteo, como ha sido considerado, se ha clasificado en diferentes sistemas, de acuerdo a las condiciones del entorno en el cual se desean aplicar. Sin embargo, no todas las tipologías son conocidas a cabalidad por las organizaciones o investigadores, debido a su reciente desarrollo o su poco nivel de aplicación. Es por ello, que en la presente investigación, se plantea realizar un análisis de las características y aplicaciones de los tipos de sistemas de ruteo de vehículos, a través de una revisión bibliográfica de trabajos previos, con el propósito de brindar información sólida y concisa a futuros investigadores. La metodología empleada, conlleva principalmente a una investigación de tipo cualitativa, en la cual se realizó una búsqueda sistemática en bases de datos del problema planteado de los últimos cinco años. A partir de esto, fue posible establecer que durante este período de tiempo, las publicaciones en este campo, presentaron un incremento de aproximadamente el doble, evidenciando el aumento en el interés por el tema objetivo.The vehicle routing allows to establish a strategy for the proper distribution of goods in different points at which you want an organization. This is achieved through the design of routes to a particular fleet vehicle; either homogeneous or heterogeneous. Studying this routing problem, as has been seen, has been classified into different systems, according to the environmental conditions in which is applied. However, not all types are known at all by the organizations or researchers, due to its recent development or some application level. That is why, in this research, we propose an analysis of the characteristics and applications of the types of systems vehicle routing through a literature review of previous works, in order to provide solid and concise information to future researchers. The methodology used primarily involves qualitative research type, in which a systematic search was performed in databases of the problem of the past five years. From this, it was possible to establish that during this period, the publications in this field, showed an increase of about twice, showing increased interest in the subject target

First-mile logistics parcel pickup: Vehicle routing with packing constraints under disruption

peer reviewedFirst-mile logistics tackles the movement of products from retailers to a warehouse or distribution centre. This first step towards the end customer has been pushed by large e-commerce platforms forming extensive networks of partners and is critical for fast deliveries. First-mile pickup requires efficient methods different from those developed for last-mile delivery, among other reasons due to the complexity of cargo features and volume — increasing the relevance of advanced packing methods. More importantly, the problem is essentially dynamic and the pickup process, in which the vehicle is initially empty, is much more flexible to react to disruptions arising when the vehicles are en route. We model the static first-mile pickup problem as a vehicle routing problem for a heterogeneous fleet, with time windows and three-dimensional packing constraints. Moreover, we propose an approach to tackle the dynamic problem, in which the routes can be modified to accommodate disruptions — new customers’ demands and modified requests of known customers that are arriving while the initially established routes are being covered. We propose three reactive strategies for addressing the disruptions depending on the number of vehicles available, and study their results on a newly generated benchmark for dynamic problems. The results allow quantifying the impact of disruptions depending on the strategy used and can help the logistics companies to define their own strategy, considering the characteristics of their customers and products and the available fleet

GRASP: uma aplicação ao problema de recolha e distribuição de produtos agrícolas em circuitos de proximidade

Trabalho de projeto de mestrado, Matemática Aplicada à Economia e Gestão, Universidade de Lisboa, Faculdade de Ciências, 2019A maioria dos produtos agrícolas que são consumidos passam por centros de logística de grande distribuição. Um dos grandes problemas destes centros é o elevado número de quilómetros que os produtos percorrem e o elevado intervalo de tempo entre colheita e consumo. Vários fatores, por parte do consumidor, tais como, a necessidade de consumir alimentos frescos, de conhecer as suas origens e a forma como são produzidos e de ajudar os agricultores e o ambiente, conduziu a um crescimento do comércio local. Esta mudança de atitude levou à implementação de circuitos curtos e de proximidade. Nos circuitos curtos existem apenas um ou nenhum intermediário. Nos circuitos de proximidade define-se uma distância máxima entre o local de produção e venda. Pretende-se obter circuitos que sejam uma combinação entre ambos, ou seja, rotas de recolha e distribuição de produtos agrícolas, tal que, o número de intermediários e a distância entre produção e venda seja mínimo. Este trabalho de projeto tem como base o desenvolvimento de rotas, para vários veículos, que incluem pontos de recolha e distribuição, que respeitam os princípios dos circuitos curtos e de proximidade. Os pontos de recolha são os agricultores e os mercados onde os agricultores fazem a venda direta dos seus produtos, enquanto que a distribuição é efectuada nos clientes. Os clientes podem ser: vendas online, restaurantes, escolas, mercearias, lojas de organização de produtores, cabazes, entre outros. Estas rotas contribuem para o desenvolvimento de sistemas locais e regionais de produção de alimentos. O desenvolvimento de um sistema local é um processo difícil, sendo importante a participação dos agricultores e dos consumidores. O método utilizado neste trabalho de projeto, de forma a obter soluções admissíveis para este problema, é a heurística GRASP (Greedy Randomized Adaptive Search Procedure). A heurística GRASP será implementada em linguagem de programação MATLAB e testada com exemplos gerados aleatoriamente. A geração dos dados, considera diferentes valores para vários parâmetros, de maneira a obter diferentes cenários como objectivo de simular a realidade