Leandro C Coelho

Université Laval | ULAVAL · Department of Operations and Decision Systems

The distribution of products using compartmentalized vehicles involves many decisions such as the allocation of products to vehicle compartments, vehicle routing and inventory control. These decisions often span several periods, yielding a difficult optimization problem. In this paper we define and compare four main categories of the Multi-Compartm...

The combination of inventory management and vehicle routing decisions yields a difficult combinatorial optimization problem called the Inventory-Routing Problem (IRP). This problem arises when both types of decisions must be made jointly, which is the case in vendor-managed inventory systems. The IRP has received significant attention in recent yea...

Inventory-routing problems (IRP) combine inventory control and vehicle routing, effectively optimizing inventory and replenishment decisions over several periods at a centralized level. In this paper we provide an exact formulation which includes several well-known valid inequalities for some classes of IRPs. We then propose three new valid inequal...

Inventory-routing problems (IRPs) arise in vendor-managed inventory systems. They require jointly solving a vehicle routing problem and an inventory management problem. Whereas the solutions they yield tend to benefit the vendor and customers, solving IRPs solely based on cost considerations may lead to inconveniences to both parties. These are rel...

This paper introduces the Inventory-Routing Problem with Transshipment (IRPT). This problem arises when vehicle routing and inventory decisions must be made simultaneously, which is typically the case in vendor-managed inventory systems. Heuristics and exact algorithms have already been proposed for the Inventory-Routing Problem (IRP), but these al...

For several decades, researchers have developed optimization techniques for warehouse operations. These techniques are related in particular to the material handling, the order picking and storage assignment strategies for a myriad of warehouse configurations. It is often neglected that these strategies need to be regularly adjusted in order to ada...

The Quadratic Knapsack Problem (QKP) is a challenging combinatorial optimization problem that has attracted significant attention due to its complexity and practical applications. In recent years, Binary Decision Diagrams (BDDs) have emerged as a powerful tool in combinatorial optimization, providing efficient bounds. In the literature of the QKP,...

We present new formulations for the robust vehicle routing problem with time windows (RVRPTW) under cardinality- and knapsack-constrained demand and travel time uncertainty. They are the first compact models to address the RVRPTW under travel time uncertainty while considering the knapsack uncertainty set. Moreover, our models employ different type...

Dial-a-ride operations consist of door-to-door transportation systems designed for users with specific needs. Governments and companies offer such services, and due to the flexibility and service level required by the users, it is considerably more costly than public transportation, besides emitting higher levels of CO\(_2\). Hence, it is crucial t...

The Quadratic Knapsack Problem (QKP) is a well-studied combinatorial optimization problem with practical applications in various fields such as finance, logistics, and telecommunications. Despite its longstanding interest, the QKP remains challenging due to its strong NP hardness. Moreover, recent studies have introduced new instances where all exi...

The preprint can be downloaded in the following link: https://cirrelt.ca/?Page=DocumentsRecherche4

The demand for efficient last-mile delivery systems in large cities creates an opportunity to develop innovative logistics schemes. In this paper, we study a problem in which each vehicle may travel with more than one deliveryman to serve multiple customers with a single stop of the vehicle, increasing the delivery efficiency. We extend the vehicle...

A crescente demanda por entregas rápidas em áreas densamente povoadas cria novos desafios na literatura e prática envolvendo o roteamento de veículos. Nesse trabalho, são introduzidas duas variantes do problema de roteamento de veículos em que mais de um entregador pode viajar com os veículos de forma a reduzir o tempo de serviço ao longo da rota,...

Transporting patients between different healthcare units in large hospitals is indispensable. Beds and wheelchairs are usually used to transport patients in one-building hospitals; however, campus-based ambulances and mini-vehicles are needed in many-building hospitals to perform patient transportation activities. In many cases, this service is man...

Production and inventory routing problems consider a single-product supply chain operating under a vendor-managed inventory system. A plant creates a production plan and vehicle routes over a planning horizon to replenish its customers at minimum cost. In this paper, we present two- and three-index formulations, implement a branch-and-cut algorithm...

This study is motivated by a major fast-moving consumer goods company. It considers a 3-echelon supply chain made of one plant, one distribution center and several shops. A flexible planning (FLEXP) approach is proposed to reduce the supply chain nervosity (e.g., bullwhip effect, peaks of production, peaks of inventories, shortages). FLEXP tries to...

Inventory-routing problems (IRPs) define a class of combinatorial optimization problems, encompassing inventory management and vehicle routing decisions into the same framework. In this article, we propose a new modular mechanism capable of recovering feasibility and improving even partial solutions by reorganizing delivery routes and optimizing in...

This paper considers an extension of classical distribution problems and introduces the time-dependent fleet size and mix multi-depot vehicle routing problem. This important class of problems finds applications in urban logistics and service design. The solution to this problem impacts the performance of distribution companies and can help design p...

We address a new variant of the Bid Construction Problem (BCP) with stochastic clearing prices in combinatorial auctions for the procurement of truckload transportation service that tackles uncertainty on bids success and auctioned contracts materialization. We propose the first exact method to generate multiple non-overlapping bids while ensuring...

Dial-a-ride problems aim to design the least-costly door-to-door vehicle routes for transporting individual users, subject to several service constraints like time windows, service and route durations, and ride-time. In some cases, providers cannot meet the demand and may outsource some requests. In this paper, we introduce, model, and solve the di...

The scheduling and location (ScheLoc) problem is a new and important research topic with a wide range of practical applications. It jointly optimizes machine locations, job assignments, and sequence decisions to yield a globally optimal solution. Current studies on the ScheLoc problem are limited, and most have focused on makespan minimization. Thi...

Commercial waste collection is an essential service requiring efficient and reliable provision for customers. At the operational level, one of the most challenging problems is to design a set of refuse vehicle routes to collect waste from a set of bins. To be used multiple times, these vehicles must be emptied regularly throughout the day. This pap...

Signal priority is a strategy to handle traffic that adjusts the timing of a traffic signal phases to achieve a mobility goal, typically to reduce congestion or waiting time. This strategy enables increased mobility and is usually used in public transport operations; it works by making small modifications to the phases of a cycle in order to delay...

The ABC storage is the most popular class-based policy for the storage location assignment in warehouses. It divides a storage area into three zones and assigns the most demanded products to the best-located zone. Despite the policy’s popularity, arbitrary zone sizes are commonly used, which can lead to major efficiency losses. We investigate how s...

Bio-based waste valorization is one of the current trends in municipal waste management. It decreases the amount of waste to be disposed of, reduces the sourcing of limited chemical compounds used in fertilizer production, and promotes a circular economy perspective vital in big cities. However, modeling and optimizing a biorefinery plant’s operati...

This paper proposes techniques to improve the efficiency of transportation activities within hospitals. Transportation is a major activity in hospitals which requires management efforts to improve its efficiency and increase the quality of patient services. One of the most powerful ways of achieving more efficiency of transportation systems in hosp...

In response to increasingly fierce competition and highly customized demands, many companies adopt a distributed production model but manage their orders in a centralized manner. Coordination between multiple factories requires unified information and resources to provide a close match between supply and demand. One of the crucial tasks is to solve...

We consider a generalization of the selective traveling salesman problem (STSP) in which the benefit of visiting a location changes over time. This new problem, called the selective travelling salesman problem with time-dependent profits (STSP-TDP), is defined on a graph with time-dependent profits associated with the vertices, and consists of dete...

The robotic mobile fulfillment system (RMFS) allows easy inventory repositioning by returning pods to different locations after their use. A better inventory arrangement leads to an energy-efficient picking process since pods can be parked closer to where they will be requested next. After an order arrives, we have to decide which picking station w...

Efficient Water Distribution Systems (WDSs) are crucial for modern society. Their operation requires large amounts of energy with significant financial impact for the utility providers. Existing solution methods are often oversimplified and can only solve the problem for very small, schematic networks. This article studies a pumping scheduling prob...

We study a two-dimensional packing problem where rectangular items are placed into a circular container to maximize either the number or the total area of items packed. We adapt a mixed-integer linear programming model from the case with a rectangular container and design a cutting plane method to solve this problem by adding linear cuts to forbid...

This work investigates a new multi-period vaccination planning problem that simultaneously optimizes the total travel distance of vaccination recipients (service level) and the operational cost. An optimal plan determines, for each period, which vaccination sites to open, how many vaccination stations to launch at each site, how to assign recipient...

We address a new variant of the Bid Construction Problem (BCP) with stochastic clearing prices in combinatorial auctions for the procurement of truckload transportation service that tackles uncertainty on bids success and auctioned contracts materialization. We propose the first exact method to generate multiple non-overlapping OR bids while ensuri...

The Inventory-Routing Problem (IRP) deals with the joint optimisation of inventory and the associated routing decisions. The IRP with time windows (IRPTW) considers time windows for the deliveries to the customers. Due to its importance and several real-world applications, in this paper, we develop an intricate solution algorithm for this problem....

We introduce the time-dependent shortest path and vehicle routing problem. In this problem, a set of homogeneous vehicles is used to visit a set of customer locations dispersed over a very large network where the travel times are time-dependent and therefore the shortest path between two locations may change over time. The aim of the problem is to...

This study investigates the unrelated parallel machine scheduling problem with release dates to minimise the makespan. The solution to this problem finds wide applications in manufacturing and logistics systems. Due to the strong NP-hardness of the problem, most researchers develop heuristics, and the largest instances they consider are limited to...

We study a two-dimensional packing problem where rectangular items are placed into a circular container to maximize either the number or the total area of items packed. We adapt a mixed integer linear programming model from the case with a rectangular container and design a branch-and-cut algorithm to solve this problem by adding linear cuts to for...

In this paper, we propose and assess the accuracy of new fuel consumption estimation models for vehicle routing. Based on real-world data consisting of instantaneous fuel consumption, time-varying speeds observations, and high-frequency traffic, we propose effective methods to estimate fuel consumption. By carrying out nonlinear regression analysis...

We investigate the discrete parallel machine scheduling and location (ScheLoc) problem, which consists of locating multiple machines to a set of candidate locations, assigning jobs from different locations to the located machines, and sequencing the assigned jobs. The objective is to minimize the maximum completion time of all jobs, i.e., the makes...

In combinatorial auctions for the procurement of transportation services, each carrier has to determine the set of profitable contracts to bid on and the associated ask prices. This is known as the Bid Construction Problem (BCP). Our paper addresses a BCP with stochastic clearing prices taking into account uncertainty on other competing carriers’ o...

The ABC storage policy is the most popular method used to determine storage location assignment in warehouses. It consists of dividing the storage area into three zones, and the products to be stored into three classes, such that the most demanded class of products is assigned to the best-located storage zone. Despite the method’s popularity, zone...

During the last two decades, integrated production-distribution problems have attracted a great deal of attention in the operations research literature. Within a short period, a large number of papers have been published and the field has expanded dramatically. The purpose of this paper is to provide a comprehensive review of the existing literatur...

We present a generic branch-and-cut framework for solving routing problems with multiple depots and asymmetric cost structures, which determines a set of cost-minimizing (capacitated) vehicle tours that fulfill a set of customer demands. The backbone of the framework is a series of valid inequalities with corresponding separation algorithms that ex...

We propose an optimal actuation of operational commands for regularizing bus headways. Assuming that a transit headway control system manages the bus operation by issuing reference arrival times at the next station for a bus, the problem is how to implement the control decisions for the bus in terms of three nonexclusive alternative actions: holdin...

Meta-analysis, a systematic statistical examination that combines the results of several independent studies, has the potential of obtaining problem- and implementation-independent knowledge and understanding of metaheuristic algorithms, but has not yet been applied in the domain of operations research. To illustrate the procedure, we carried out a...

In the Quadratic Assignment Problem (QAP), facilities are assigned to sites in order to minimize interactions between pairs of facilities. Although easy to define, it is among the hardest problems in combina-torial optimization, due to its non-linear nature. After decades of research on the QAP, many variants of this problem arose to deal with diff...

The Team Orienteering Problem (TOP) is a well-known NP-Hard vehicle routing problem in which one maximizes the collected profits for visiting some nodes. In this paper, we propose a Hybrid Adaptive Large Neighborhood Search (HALNS) to solve this problem. Our algorithm combines the exploration power of ALNS with local search procedures and an optimi...

In this paper we study a Multi-Attribute Inventory Routing Problem (MAIRP). A mathematical formulation and exact solution algorithms are introduced for this problem. More precisely, we extend the Multi-Depot Inventory Routing Problem (MDIRP) in order to consider the multi-product case with a heterogeneous fleet of vehicles and explicit constraints...

This paper introduces the Two-Echelon Inventory-Routing Problem with Fleet Management. This problem arises under a two-echelon vendor-managed inventory system when a company must make vehicle routing and inventory management decisions, while renting a fleet subject to short- and mid-term agreements. Different chemical products are transported conta...

This paper proposes a variant of the vehicle routing problem with time windows (VRPTW) in which one disposes of two heterogeneous fleets to serve the customers; the first fleet is in charge of deliveries with the possibility to install products while the second one only performs installations. Customers receive some furniture, electronics and home...

Storage location and order picking are two interdependent problems arising in warehouse planning traditionally solved independently. We introduce and model the integrated storage location and order picking problem and four special cases with imposed routing policies (return, S-shape, midpoint and largest gap). Experiments show that these models are...

This paper studies the Dynamic Facility Location Problem with Modular Capacities (DFLPM). It generalizes several facility location problems and consists in determining locations and sizes of facilities to minimize location and demand allocation costs with decisions taken periodically over a planning horizon. The DFLPM is solved using heuristics tai...

Motivated by the problem faced by a company that provides installation and maintenance services of electrical infrastructures, we study the Multi-Period Workforce Scheduling and Routing Problem (MPWSRP). A set of jobs requiring a service is given. A given set of workers, each proficient in a number of skills, is available to serve the jobs. Each jo...

This paper introduces the Two-Echelon Production-Routing Problem. This problem is motivated from the petrochemical industry, enlarging the supply chain integration by taking into account production, inventory, and routing decisions in a two-echelon vendor-managed inventory system. We describe, model, and design a branch-and-cut (B&C) to solve the p...

In this paper we introduce the vehicle routing problem with simultaneous pickup and delivery and handling costs (VRPSPD-H). In the VRPSPD-H, a fleet of vehicles operates from a single depot to service all customers, which have both a delivery and a pickup demand such that all delivery items originate from and all pickup items go to the depot. The i...

In combinatorial auctions for the procurement of transportation services, each carrier has to determine the set of profitable contracts to bid on and the associated ask prices. This is known as the Bid Construction Problem (BCP). Our paper adresses a BCP with stochastic clearing prices taking into account uncertainty on other competing carriers' of...

In the multi-pickup and delivery problem with time windows (MPDPTW) a set of vehicles must be routed to satisfy a set of client requests between given origins and destinations. A request is composed of several pickups of different items, followed by a single delivery at the client location. This paper introduces two new formulations for the MPDPTW,...

In this paper, we address multiple container loading problems, consisting of placing rectangular boxes, orthogonally and without overlapping, inside containers in order to optimize a given objective function, generally maximizing the value of the packed boxes or minimizing the number of containers required to pack all available boxes. Four techniqu...

In the Quadratic Assignment Problem (QAP), facilities are assigned to sites in order to minimize interactions between pairs of facilities. Although easy to define, it is considered as one of the hardest problems in combinatorial optimization, due to its non-linear nature. After decades of research on the QAP, many variations of this problem arose t...

The Team Orienteering Problem (TOP) is a well-known NP-Hard problem in which one maximizes the collected profits for visiting some nodes. In this paper, we propose a new Hybrid Adaptive Large Neighborhood Search (HALNS) to solve this problem. Our algorithm combines the exploration power of ALNS with local search procedures and an optimization stage...

The Inventory Routing Problem with Logistic Ratio (IRPLR) is a variant of the classical IRP where, instead of the total distribution cost, the ratio between the total distribution cost and the total delivered quantity is minimized, giving rise to a fractional objective function. An exact algorithm is known, solving instances with up to 15 customers...

We address an inventory routing problem (IRP) in which routing and inventory decisions are dictated by supply rather than demand. Moreover, inventory is held in containers that act as both a storage container and a movable transport unit. This problem emanates from logistics related to biogas transportation in which biogas is transported in contain...

In the inventory management of automated teller machines (ATMs) many activities affect the total costs, such as forecasting, replenishments and the denomination mix used. The denomination mix is the combination of bills used to fulfill a customer’s demand. We investigate whether allowing the denomination mix to vary over time based on the forecast...

We investigate a perishable food production routing problem with multiple plants and packaging considerations. The study is inspired by the fact that perishable food products usually have a short shelf life and are frequently sold with discounts. In particular, package selection is for the first time integrated into a supply chain planning problem....

This paper proposes a variant of the vehicle routing problem with time windows (VRPTW) in which one disposes of two heterogeneous fleets to serve the customers; the first fleet is in charge of deliveries and the second one performs the installations. The customers receive some furniture, electronics and home appliances, and may require an installat...

The European Union aims for a 40% reduction in greenhouse gas emissions by 2030, compared to 1990 levels, and recognizes the opportunities of Liquefied Natural Gas (LNG) as an alternative fuel for transportation to reach this goal. The lack of a mature supply chain for LNG as a fuel results in a need to invest in new (satellite) terminals, bunker b...

The operation of Water Distribution Systems (WDS) is often complex, especially when considering the changes in tariffs throughout the day. The cost of energy in these systems can reach 30% of total operating costs and its careful management can represent increased efficiency. The optimization of WDS scheduling operation appears as an effective meth...

This paper solves the bid construction problem (BCP) for heterogeneous truckload operations. Exact and heuristic solution methods are proposed to solve the BCP. The heuristic framework is based on a destroy-repair principle coupled with local search procedures. A heuristic variant integrating a post-optimization method considering solutions obtaine...

Hashiwokakero, or simply Hashi, is a Japanese single-player puzzle played on a rectangular grid with no standard size. Some cells of the grid contain a circle, called island, with a number inside it ranging from one to eight. The remaining positions of the grid are empty. The player must connect all of the islands by drawing a series of horizontal...

As the largest contributor to greenhouse gas (GHG) emissions in the transportation sector, road freight transportation is the focus of numerous strategies to tackle increased pollution. One way to reduce emissions is to consider congestion and being able to route traffic around it. In this paper we study time-dependent minimum cost paths under seve...

In this paper we study the multi-period vehicle routing problem with due dates. A supplier has to determine a distribution plan to visit a set of customers over a given planning horizon. Each customer is associated with a release date and a due date, that is, the date at which the goods required by the customer become available at the supplier’s de...

This paper deals with an integrated routing problem in which a supplier delivers a commodity to its customers through a two-echelon supply network. Over a planning horizon, the commodity is first sent from a single depot to a set of Distribution Centers (DCs). Then, from the DCs, it is delivered to customers. Two sources of flexibility are analyzed...

Dans cet article, nous présentons une analyse spatiotemporelle des tournées de livraison à domicile d’une entreprise d’électroménagers qui détient sa propre flotte de véhicules. Plusieurs millions d’observations de géolocalisation GPS issues de ces tournées de livraison sont collectées, traitées et assignées au réseau routier. À la suite de ces ana...