André Gustavo dos Santos’s research while affiliated with Universidade Federal de Viçosa (UFV) and other places

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Publications (64)


Optimizing a Car Patrolling Application by Iterated Local Search
  • Conference Paper

July 2024

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12 Reads

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Thiago Alves de Queiroz

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An iterated local search for a multi‐period orienteering problem arising in a car patrolling application
  • Article
  • Full-text available

September 2023

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130 Reads

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3 Citations

Networks

This paper addresses a real‐world multi‐period orienteering problem arising in a large Italian company that needs to patrol an area in order to provide security services to a set of customers. Each customer requires different services on a weekly basis. Some services are mandatory, while others are optional. It might be impossible to perform all optional services, and each of them is assigned a score when performed. The challenge is to determine a set of routes, one per day, that maximizes a weighted sum of the total collected score and total working time, while meeting several operational constraints, including hard time windows, maximum riding time, minimum number of services performed, and minimum time between two consecutive visits for the same service at the same customer. To solve the problem, we propose an iterated local search that invokes at each iteration an inner variable neighborhood descent procedure. Computational tests performed on a large number of real‐world instances prove that the developed algorithm is very efficient, and finds in a short time solutions that are consistently better than those produced by a mathematical model, and those in use at the company.

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Designing an optimized landscape restoration with spatially interdependent non-linear models

February 2023

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79 Reads

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2 Citations

The Science of The Total Environment

Brazilian Atlantic Forest is a biodiversity hotspot drastically fragmented due to different land use practices. Our understanding on the impacts of fragmentation and restoration practices on ecosystem functionality significantly increased during the last decades. However, it is unknown to our knowledge how a precision restoration approach, integrated with landscape metrics, will affect the decision-making process of forest restoration. Here, we applied Landscape Shape Index and Contagion metrics in a genetic algorithm for planning forest restoration in watersheds at the pixel level. We evaluated how such integration may configure the precision of restoration with scenarios related to landscape ecology metrics. The genetic algorithm worked toward optimizing the site, shape, and size of forest patches across the landscape according to the results obtained in applying the metrics. Our results, obtained by simulations of scenarios, support aggregation of forest restoration zones as expected, with priority restoration areas indicated where most of the aggregation of forest patches occurs. Our optimized solutions for the study area (Santa Maria do Rio Doce Watershed) predicted an important improvement of landscape metrics (LSI = 44 %; Contagion/LSI = 73 %). Largest shifts are suggested based on LSI (i.e., three larger fragments) and Contagion/LSI (i.e., only one well-connected fragment) optimizations. Our findings indicate that restoration in an extremely fragmented landscape will promote a shift toward more connected patches and with reduction of the surface:volume ratio. Our work explores the use of genetic algorithms to propose forest restoration based on landscape ecology metrics in a spatially explicit innovative approach. Our results indicate that LSI and Contagion:LSI ratio may affect the choice concerning precise location of restoration sites based on forest fragments scattered in the landscape and reinforce the usefulness of genetic algorithms to yield an optimized-driven solution for restoration initiatives.


Industrial Waste Collection Optimization: A Real-World Case Study in Northern Italy

September 2022

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46 Reads

In this work, we present a real case application of a Rollon-Rolloff Vehicle Routing Problem (RRVRP) that arises at a waste collection company in Northern Italy. Compared to other RRVRP applications, where large containers are emptied and moved, our problem presents two additional types of services regarding the collection of bulk waste materials. Moreover, the problem deals with customer selection based on an objective function with two components: outsourcing costs incurred when customers are given to a third-party logistic operator, and internal routing costs. We model the RRVRP as a Mixed Integer Program and we solve it through a commercial solver and a simple but effective Iterated Greedy algorithm. Computational results are provided on 30 real case instances. Solutions provided by the Iterated Greedy are constantly better than the ones implemented by the company, showing that relevant cost reduction can be obtained with a limited computational effort.KeywordsRollon-Rolloff Vehicle Routing ProblemIndustrial waste collectionIterated greedy


2-echelon lastmile delivery with lockers and occasional couriers

June 2022

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51 Reads

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22 Citations

Transportation Research Part E Logistics and Transportation Review

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.




Citations (33)


... Concerning future works, it would be interesting to add new micro-services in the DSS to, e.g., handle other logistic problems faced by the company in activities such as pick-up and delivery and car patrolling (see, e.g., [34]). Another interesting direction would be to investigate the impact of new constraints on the problem, e.g., labor constraints or maximum CO 2 emissions. ...

Reference:

An Optimization-Based Decision Support System for Multi-trip Vehicle Routing Problems
An iterated local search for a multi‐period orienteering problem arising in a car patrolling application

Networks

Designing an optimized landscape restoration with spatially interdependent non-linear models
  • Citing Article
  • February 2023

The Science of The Total Environment

... Although researches about couriers are plenty, most of them are about courier related information system [7], courier's traffic accident compensation [8], courier service design [9], financial benefits [10], courier employment protection [11] and courier work efficiency improvement design [12][13][14]. Research on protecting couriers with WAI is still in the blank globally. While wearables can bring benefits such as workforce optimization and cost-cutting to couriers, there are barriers to adoption by couriers. ...

2-echelon lastmile delivery with lockers and occasional couriers
  • Citing Article
  • June 2022

Transportation Research Part E Logistics and Transportation Review

... ThOP was first formulated in 2018 by Santos and Chagas [12] and several heuristics have since been designed for it [4,5,8]. In 2023, Bloch-Hansen et al. [2] proved that there exists no approximation algorithm for the thief orienteering problem with constant approximation ratio unless P = N P , and they presented a polynomial-time approximation scheme (PTAS) for ThOP when the input graph G is directed and acyclic (DAG). ...

A Genetic Algorithm for the Thief Orienteering Problem
  • Citing Conference Paper
  • July 2020

... These results highlighted the difference in soil erosion due to anthropogenic disturbance in mountainous catchments. Human expansion into mountainous regions is raising concerns among researchers and policymakers regarding erosion and sedimentation issues (Domingues et al., 2020;Li et al., 2021;Wang et al., 2020). The local government has integrated the restoration of areas affected by human activities into its agenda and stressed the importance of promptly evaluating and addressing water and soil erosion risks in the region. ...

Optimized allocation of forest restoration zones to minimize soil losses in watersheds
  • Citing Article
  • October 2020

Journal of Environmental Management

... They created an integer linear programming model to minimize the cost objective and applied an Xpress solver to conduct numerical experiments on a case study. Nogueira et al. [18] investigated an IPDS problem with parallel batching machines, aiming to gain an effective integration between production and delivery activities for maximizing profits. To achieve this goal, two fast polynomial algorithms were improved, namely RKP and CMFFDA. ...

Problem on the integration between production and delivery with parallel batching machines of generic job sizes and processing times
  • Citing Article
  • June 2020

Computers & Industrial Engineering

... A few studies have examined empty truck behavior. Rodrigues and Santos [3] developed a combinatorial optimization problem to reduce the number of empty trucks in Brazil, and the results revealed a decrease in empty trucks and environmental emissions. Samchuk et al. [4] developed a regression model to determine the empty truck rate based on trip distance, truck size, and freight volume. ...

Reducing Empty Truck Trips in Long Distance Network by Combining Trips
  • Citing Conference Paper
  • January 2018

... If we specify the number of squares of each size that must tile a given rectangle (or even square), then the problem is NP-complete [LTW + 90]. If we allow arbitrary squares but instead require the fewest possible squares, Kenyon [Ken96] proved upper and lower bounds that match up to constant factors, which Walters [Wal09] generalized to higher dimensions, while other work considers computational heuristics [MdS18]. Heubach [Heu99] studied counting the number of different rectangle tilings when limiting the square sizes. ...

Minimum tiling of a rectangle by squares

Annals of Operations Research

... As a result, an improved, elitist-NSGA (NSGA-II) was proposed and shown to perform better than other elitist MOEAs (e.g., pareto archive evolution strategy (PAES) and strength pareto evolution algorithm (SPEA)) in finding diverse solutions and in converging close to the true (actual) pareto-optimal set. These results encourage the application of NSGA-II to more complex real-life MO problems [29,30]. Irrespective of the numerous applications of NSGA-II, it had the issue of premature convergence to a suboptimal solution set, and as such, the proposal of the controlled-NSGA-II comes with controlled elitism for better convergence performance. ...

Application of NSGA-II Framework to the Travel Planning Problem Using Real-World Travel Data
  • Citing Conference Paper
  • July 2016