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Publications

Publications by Ana Viana

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.

2021

Positive and Negative Social-Cultural, Economic and Environmental Impacts of Tourism on Residents

Authors
Ferreira, FA; Castro, C; Gomes, AS;

Publication
ADVANCES IN TOURISM, TECHNOLOGY AND SYSTEMS, VOL 1

Abstract
Tourism is a socio-cultural phenomenon that has intensified with technological development and with the advancement of communication and transport systems. However, the increase in the number of people moving around the world does not necessarily represent success or tourist access, but it can mostly serve more immediate marketing interests. Since tourism is considered a phenomenon, the sociological interest to study it arises. Tourist practice is an educational process, a learning process, which is established through the relationship between visitors and residents and their cultural backgrounds. Several authors dedicate their studies to this field, and several are also those who try to understand the relations between tourists and the residents in the host region. The purpose of this work is to review the scientific literature that is focused on the sociology of tourism as a subject to study the economic, social, and environmental impacts of tourism on societies and residents and how residents perceived the benefits and costs of tourism developments in the local community. Review of literature suggests that interactions between visitors and the host community can lead to short and long term positive and negative social-cultural, economic and environmental impacts on destinations.

2023

Stochastic crowd shipping last-mile delivery with correlated marginals and probabilistic constraints

Authors
Silva, M; Pedroso, JP; Viana, A;

Publication
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
In this work, we study last-mile delivery with the option of crowd shipping. A company uses occasional drivers to complement its fleet in the activity of delivering products to its customers. We model it as a variant of the stochastic capacitated vehicle routing problem. Our approach is data-driven, where not only customer orders but also the availability of occasional drivers are uncertain. It is assumed that marginal distributions of the uncertainty vector are known, but the joint distribution is difficult to estimate. We optimize considering a worst-case joint distribution and model with a strategic planning perspective, where we calculate an optimal a priori solution before the uncertainty is revealed. A limit on the infea-sibility of the routes due to the capacity is imposed using probabilistic constraints. We propose an extended formulation for the problem using column-dependent rows and implement a branch-price-and-cut algorithm to solve it. We also develop a heuristic approximation to cope with larger instances of the problem. Through computational experiments, we analyze the solution and performance of the implemented algorithms.

2021

A comparison of matching algorithms for kidney exchange programs addressing waiting time

Authors
Monteiro, T; Klimentova, X; Pedroso, JP; Viana, A;

Publication
CENTRAL EUROPEAN JOURNAL OF OPERATIONS RESEARCH

Abstract
Kidney exchange programs (KEP) allow an incompatible patient-donor pair, whose donor cannot provide a kidney to the respective patient, to have a transplant exchange with another in a similar situation if there is compatibility. Exchanges can be performed via cycles or chains initiated by non-directed donors (NDD), i.e., donors that do not have an associated patient. The objective for optimization in KEP is generally to maximize the number of possible transplants. Following the course of recent approaches that consider a dynamic matching (exchanges are decided every time a pair or a NDD joins the pool), in this paper we explore two matching policies to find feasible exchanges: periodic, where the algorithm runs within some period (e.g each 3 month); and greedy, in which a matching run is done as soon as the pool is updated with a new pair or NDD. For each policy, we propose a matching algorithm that addresses the waiting times of pairs in a pool. We conduct computational experiments with the proposed algorithms and compare the results with those obtained when periodic and greedy matching aim at maximizing the number of transplants.

2023

Preface to the Special Issue on Operations Research in Healthcare

Authors
Viana, A; Marques, I; Dias, JM;

Publication
INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH

Abstract

2023

A data-driven compensation scheme for last-mile delivery with crowdsourcing

Authors
Barbosa, M; Pedroso, JP; Viana, A;

Publication
COMPUTERS & OPERATIONS RESEARCH

Abstract
A recent relevant innovation in last-mile delivery is to consider the possibility of goods being delivered by couriers appointed through crowdsourcing. In this paper we focus on the setting of in-store customers delivering goods, ordered by online customers, on their way home. We assume that not all the proposed delivery tasks will necessarily be accepted, and use logistic regression to model the crowd agents' willingness to undertake a delivery. This model is then used to build a novel compensation scheme that determines reward values, based on the current plan for the professional fleet's routes and on the couriers' probabilities of acceptance, by employing a direct search algorithm that seeks to minimise the expected cost.

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