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Publications

Publications by CEGI

2022

On-line three-dimensional packing problems: A review of off-line and on-line solution approaches

Authors
Ali, S; Ramos, AG; Carravilla, MA; Oliveira, JF;

Publication
COMPUTERS & INDUSTRIAL ENGINEERING

Abstract
Three-Dimensional Packing Problems (3D-PPs) can be applied to effectively reduce logistics costs in various areas, such as airline cargo management and warehouse management. In general, 3D-PP studies can be divided into two different streams: those tackling the off-line problem, where full knowledge about items is available beforehand; and those tackling the on-line (real-time) problem, where items arrive one by one and should be packed immediately without having full prior knowledge about them. During the past decades, off-line and online 3D-PPs have been studied in the literature with various constraints and solution approaches. However, and despite the numerous practical applications of on-line problems in real-world situations, most of the literature to date has focused on off-line problems and is quite sparse when it comes to on-line solution methods. In this regard, and despite the different nature of on-line and off-line problems, some approaches can be applied in both environments. Hence, we conducted an in-depth and updated literature review to identify and structure various constraints and solution methods employed by researchers in off-line and on-line 3D-PPs. Building on this, by bringing together the two separate streams of the literature, we identified several off-line approaches that can be adopted in on-line environments. Additionally, we addressed relevant research gaps and ways to bridge them in the future, which can help to develop this research field.

2022

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

Authors
Gimenez Palacios, I; Parreno, F; Alvarez Valdes, R; Paquay, C; Oliveira, BB; Carravilla, MA; Olivera, JF;

Publication
TRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANSPORTATION REVIEW

Abstract
First-mile logistics tackles the movement of products from retailers to a warehouse or distri-bution 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 hetero-geneous 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.

2022

The two-dimensional cutting stock problem with usable leftovers: mathematical modelling and heuristic approaches

Authors
do Nascimento, DN; Cherri, AC; Oliveira, JF;

Publication
OPERATIONAL RESEARCH

Abstract
Different variations of the classic cutting stock problem (CSP) have emerged and presented increasingly complex challenges for scientists and researchers. One of these variations, which is the central subject of this work, is the two-dimensional cutting stock problem with usable leftovers (2D-CSPUL). In these problems, leftovers can be generated to reduce waste. This technique has great practical importance for many companies, with a strong economic and environmental impact. In this paper, a non-linear mathematical model and its linearization are proposed to represent the 2D-CSPUL. Due to the complexity of the model, a heuristic procedure was also proposed. Computational tests were performed with instances from the literature and randomly generated instances. The results demonstrate that the proposed model and the heuristic procedure satisfactorily solve the problem, proving to be adequate and beneficial tools when applied to real situations.

2022

The Probabilistic Travelling Salesman Problem with Crowdsourcing

Authors
Santini, A; Viana, A; Klimentova, X; Pedroso, JP;

Publication
COMPUTERS & OPERATIONS RESEARCH

Abstract
We study a variant of the Probabilistic Travelling Salesman Problem arising when retailers crowdsource last-mile deliveries to their own customers, who can refuse or accept in exchange for a reward. A planner must identify which deliveries to offer, knowing that all deliveries need fulfilment, either via crowdsourcing or using the retailer's own vehicle. We formalise the problem and position it in both the literature about crowdsourcing and among routing problems in which not all customers need a visit. We show that to evaluate the objective function of this stochastic problem for even one solution, one needs to solve an exponential number of Travelling Salesman Problems. To address this complexity, we propose Machine Learning and Monte Carlo simulation methods to approximate the objective function, and both a branch-and-bound algorithm and heuristics to reduce the number of evaluations. We show that these approaches work well on small size instances and derive managerial insights on the economic and environmental benefits of crowdsourcing to customers.

2022

2-echelon lastmile delivery with lockers and occasional couriers

Authors
Dos Santos, AG; Viana, A; Pedroso, JP;

Publication
TRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANSPORTATION REVIEW

Abstract
We propose a new approach for the lastmile delivery problem where, besides serving as collecting points of orders for customers, parcel lockers are also used as transshipment nodes in a 2-echelon delivery system. Moreover, we consider that a customer (occasional courier) visiting a locker may accept a compensation to make a delivery to another customer on their regular traveling path. The proposed shared use of the locker facilities - by customers that prefer to self-pick up their orders, and also as a transfer deposit for customers that prefer home delivery - will contribute to better usage of an already available storage capacity. Furthermore, the use of occasional couriers (OCs) brings an extra layer of flexibility to the delivery process and may positively contribute to achieving some environmental goals: although non-consolidation of deliveries may, at first sight, seem negative, by only considering OCs that would go to the locker independently of making or not a delivery on their way home, and their selection being constrained by a maximum detour, the carbon footprint can be potentially reduced when compared to that of dedicated vehicles. We present a mixed-integer linear programming formulation for the problem that integrates three delivery options - depot to locker, depot to locker followed by final delivery by a professional fleet, and depot to locker followed by final delivery by an OC. Furthermore, to assess the impact of OCs' no show on the delivery process, we extend the formulation to re-schedule the delivery of previous undelivered parcels, and analyze the impact of different no-show rates. Thorough computational experiments show that the use of OCs has a positive impact both on the delivery cost and on the total distance traveled by the dedicated fleets. Experiments also show that the negative impact of no-shows may be reduced by using lockers with higher capacities.

2022

Mitigating rural fires through transformative service research: value cocreation with forest-related rural communities

Authors
Souza, MEB; Teixeira, JG; Pacheco, AP;

Publication
Advances in Forest Fire Research 2022

Abstract
Socioeconomic changes have caused profound transformations in forest landscapes and increased abandonment of rural areas, leading to fuel accumulation and higher landscape homogeneity, and consequently, raising the rural fires risk. Rural fires risk is also fueled by climate change, due to heat waves and lack of precipitation. In this context, rural communities inhabiting forest areas are those who suffer the most, because rural fires, land degradation and climate change can disturb their food and economic strategy. These communities already suffer from underdeveloped rural infrastructure, and services, lack of labor and education opportunities, that trigger poverty and migration. Given this accelerating pace of change and increasing uncertainty, many fields of knowledge have been dedicated to contributing towards a more sustainable and inclusive future. In service research, transformative service research (TSR) literature plays a central role on understanding problems and finding solutions that improve well-being and create uplifting change through services. Similarly, the fire research field highlights the need for an integrated perspective to analyze all the aspects involved in rural fires occurrence, whether they are of an environmental or economic nature, or a sociological or demographic nature. This study aims to explore new services to cocreate value with forest-related rural communities, thus helping to manage forest areas and mitigate rural fires risks. A qualitative methodology was employed involving 28 participants related to fire management and forest areas and communities, including actors from industries, public entities, academics, the third sector. The data collected through individual interviews were transcribed, coded, and analyzed following a thematic analysis approach, with NVivo software support. Overall, the study emphasizes the need for an endogenous and adapted set of services to cocreate value with vulnerable communities in forest areas, which consequently enable rural fires mitigation. Given the high level of land abandonment and accumulation of residual materials that increases the risk of rural fires, the development of valuing and recovery solutions is a priority. Finally, this research can also help decision-makers and stakeholders to generate and support services that cocreate value with rural communities to a sustainable, safe and inclusive future.

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