77 research outputs found
Optimization model to assess electric vehicles as an alternative for fleet composition in station-based car sharing systems
No full textElectromobility can be one of many solutions to the environmental challenge facing society nowadays, and the dissemination of policies towards the adoption of electric vehicles (EVs) urges the development of studies to assess their actual benefits in contrast to both conventional and other alternative technologies. This work proposes an optimization model to evaluate the influence of the selected parameters in the economic and environmental dimensions of different vehicle technologies and the optimal fleet composition for small-scale car sharing. The model is applied to car sharing system VAMO, located in Fortaleza (Brazil), and the decision variables comprise pure electric (BEV), plug-in hybrid (PHEV) and internal combustion engine (ICEV) vehicles. Baseline results are strongly influenced by the economic dimension, showing that existing infrastructure and well-established technology are great advantages for ICEVs and major barriers for EVs. In that sense, ethanol arises as a balanced alternative between costs and emissions. However, EVs represent a strong environmental appeal considering global emissions and local pollutants and even with economic losses in the short-term, investments in electromobility could come out as a positioning strategy in a future business with strong perspectives of growth, be it technological or in market share. The results suggest that all vehicle technologies will play an important role during this transition period to a desired sustainable mobility.</p
Integrating berth allocation decisions in a fleet composition and periodic routing problem of platform supply vessels
No full textThe aim of this work is to present mathematical models and a heuristic solution strategy to solve the heterogeneous fleet-sizing problem of platform supply vessels (PSVs) that support the offshore oil and gas exploration and production (E&P) activities. The problem considered in this research takes into account a novel characteristic related to the berth allocation problem of the supply base, which must be considered together with the decisions of selecting the departure days and the routes. The adopted solution strategy consists of sequentially solving models that capture different aspects of the problem, by starting with models that are simpler to solve. The solution found in one step provides a lower bound to the next step. This procedure was devised in order to reduce the search space and to speed up convergence. The proposed solution strategy was applied to real instances in Brazil, which has up to 79 offshore units grouped into clusters, with fair/acceptable results. The procedure allowed for assessing the impact of the number of berths on the fleet composition
Long-term integrated surgery room optimization and recovery ward planning, with a case study in the Brazilian National Institute of Traumatology and Orthopedics (INTO)
No full textThis paper proposes an integrated approach for the long-term planning and surgery allocation problem with downstream constraints. It is motivated by a case study in the Brazilian National Institute of Traumatology and Orthopedics, which provides elective high complexity surgeries for patients from the Brazilian public health system. We introduce an optimization problem that designs a periodic surgery allocation schedule as well as a recovery ward utilization plan, with a view at balancing patient arrivals and releases in the long term, in such a way that all surgeries are performed in a timely manner.</p
Integrated surgery planning and bed allocation with multiple routes of post-surgical care, with application to a military hospital’s orthopaedic department
No full textThis paper presents an integrated surgery scheduling and post-surgical bed planning problem for a standard hospital setting. The setting gives rise to a general healthcare modelling problem with a number of innovations with respect to the literature. The model includes multiple post-surgical recovery trajectories involving possible stays at the intensive (ICU) or semi-intensive care unit (SICU) and allows the decision maker to assign a bed allocation plan that considers the maximum length of stays at both SICU and ICU. The approach is designed to ensure a seamless patient flow, avoiding surgery cancellations due to insufficient downstream resources, and enables tactical planning that considers the long-term balance between demand and surgery provision across all specialities. To validate the model and investigate the sensitivity with respect to model parameters and the availability of resources, we use a series of experiments that were based on the actual operation of a military hospital’s orthopaedic department. The results illustrate the demand pressures, as an optimised allocation with the current demand and resources results in an occupation of 96.5%. We also show that increases in demand should be matched by a similar percentage increase in operating theatre capacity in order to keep the occupation below 100%.</p
Dimensionality reduction for multi-criteria problems: An application to the decommissioning of oil and gas installations
Get PDFThis paper is motivated by decommissioning studies in the field of oil and gas, which comprise a very large number of installations and are of interest to a large number of stakeholders. Generally, the problem gives rise to complicated multi-criteria decision aid tools that rely upon the costly evaluation of multiple criteria for every piece of equipment. We propose the use of machine learning techniques to reduce the number of criteria by feature selection, thereby reducing the number of required evaluations and producing a simplified decision aid tool with no sacrifice in performance. In addition, we also propose the use of machine learning to explore the patterns of the multi-criteria decision aid tool in a training set. Hence, we predict the outcome of the analysis for the remaining pieces of equipment, effectively replacing the multi-criteria analysis by the computational intelligence acquired from running it in the training set. Computational experiments illustrate the effectiveness of the proposed approach.</p
Modeling the integrated mine-to-client supply chain: a survey
Get PDFMining is an important economic activity and a highly complex industry. As such, it demands a complex supply chain to connect mines to clients, often involving railways, ports and long-distance maritime shipping. State-of-the-art optimization tools are an invaluable asset to help manage such a complex environment, which makes mining industry a very fertile ground for operational research applications. This paper aims to present a bibliographical review of published works involving operational research applications in the mining industry. We start by mapping applications within each isolated link of the chain. Then, we make inroads into the researches involving and connecting multiple links of the mining chain. Finally, we present summaries of our finding and pinpoint some directions for research opportunities in the mining industry.</p
Optimisation and control of the supply of blood bags in hemotherapic centres via Markov decision process with discounted arrival rate
Get PDFRunning a cost-effective human blood transfusion supply chain challenges decision makers in blood services world-wide. In this paper, we develop a Markov decision process with the objective of minimising the overall costs of internal and external collections, storing, producing and disposing of blood bags, whilst explicitly considering the probability that a donated blog bag will perish before demanded. The model finds an optimal policy to collect additional bags based on the number of bags in stock rather than using information about the age of the oldest item. Using data from the literature, we validate our model and carry out a case study based on data from a large blood supplier in South America. The study helped achieve an overall increase of 4.5% in blood donations in one year.</p
Modelagem e otimização aplicadas no agendamento de cirurgias ortopédicas
No full textThe work addressed to the planning of orthopedic surgeries using mathematical programming. It aims to portray the importance of the different sectors involved in surgical management in a weekly surgery allocation plan, calculating the weekly times used to perform surgeries and the number of procedures performed throughout the week and balancing the vacancies in beds for recovery of patients in the postoperative period. Firstly, the mathematical modeling was presented to solve the problem, followed by the computational experiments containing all the scenarios used by programming. The total amount of time of use of the operating room for surgeries throughout the week, the total number of surgeries performed in the period, and the division of beds allocated by the model implemented for each orthopedic subspecialty under study were presented. Based on works in the literature that corroborate the planning proposed in this study, the importance of employing mathematical programming in research that addresses the use of the operating room was reinforced based on modeling that aims to maximize the time of operating rooms to perform surgeries, and that contemplates the balance in the use of this space. It is concluded that in order to reduce the waiting time in queues, the structuring of the planning elaborated by the mathematicalmodeling must contemplate the fl ow of patients in and out of the operating rooms, keeping balance at all stages of the process, and aiming to overcome the number minimum of surgical procedures to meet the stipulated demand
Mine-to-client planning with Markov Decision Process
No full textThis works presents an innovative application of Markov Decision Process (MDP) to a medium-term mining logistics planning problem considering the mine-to-client supply chain. We implemented three distinct algorithms based on state-of-the-art approaches to solve large-scale problems, and compared their results. Furthermore, we combined all three variants in a single novel algorithm that attained fast convergence and may be an alternative to circumvent the curse of dimensionality underlying large scale problems
Formas de escritas de si em Annie Ernaux
No full textO objetivo deste trabalho é apresentar um estudo dos textos literários de Annie Ernaux, tendo como fio condutor seu projeto de escrita, que se revelou, ao longo desta pesquisa, ser não só de caráter literário, mas também social, político, feminista. Para a autora, a escrita literária está ligada a ideias como verdade e realidade, palavras tão difíceis de definir quanto a literatura. Na busca por um estilo próprio, Ernaux decidiu-se, então, por aproximar-se o máximo possível do real, relatando exclusivamente acontecimentos verídicos, usando uma linguagem desprovida de qualquer ornamento que afastasse sua escrita da bruta realidade social de seus pais, pequenos comerciantes, integrantes da classe popular. Este trabalho apresenta, então, um estudo do gênero autobiográfico, no qual se insere a maior parte dos escritos de Annie Ernaux; além de uma análise de alguns de seus textos literários, selecionados de forma a dar uma visão global de sua trajetória como escritora e de sua contribuição para o enriquecimento das formas de escritas de siThe objective of this work is to present a study of the literary texts of Annie Ernaux, having as a guiding thread her project of writing; which, during this research, revealed itself not only being of a literary nature, but also being social, political and feminist. According to the author, literary writing is linked to ideas such as truth and reality, words that are as difficult to define as literature itself. While searching for her own writing style, Ernaux decided to be as close to reality as possible, reporting only actual events, using a language deprived of any decoration that could affect her writing about the brutal social reality of her parents, small merchants, members of the lower class. Therefore, this work presents a autobiographical gender study, in which almost all writings of Annie Ernaux could be included, as well as an analysis of her literary texts, selected in such a way as to offer a global view of her trajectory as a female writer, in addition to her contributions to the enrichment of the forms of writing about one’s own self167 f
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