Optimization of a recyclabe waste collection system: The Valorsul case study

This paper studies alternative scenarios for a recyclable waste collection system in order to increase efficiency in their operations. Three alternative scenarios are proposed where two different locations for one or two additional depots are studied. The problem is considered as a multi-depot vehicle routing problem and a solution approach is developed. The three scenarios are compared with the current solution regarding distance travelled, working hours, amount of waste collected and vehicle usage. Significant gains are obtained when depots are added to the current logistics system.info:eu-repo/semantics/acceptedVersio

Ventilator-associated pneumonia prevention: one good turn does not always deserve another

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Short-Term scheduling of a polymer compounding plant

This paper addresses the optimal short-term scheduling of a three parallel production line plymer compounding plant, whose equipments require cleaning between product changeovers. A very effective user-friendly software tool was developed, which consists of a general scheduling model coupled with capabilities of Microsoft Excel for data handling and analysis. The scheduling model is based on a Resource Task Network discrete time formulation and leads to Mixed Integer Linear Programming problems. As outputs the user can access the optimal schedules for a number of different objectives

Planning a sustainable reverse logistics system: balancing costs with environmental and social concerns

The present work aims to support tactical and operational planning decisions of reverse logistics systems while considering economical, environmental and social objectives. In the literature, when addressing such systems economical aspects have been often used, while environmental concerns have been only recently emerging. The social component is the one less studied, and rarely the combination of the three concerns has been analyzed. This work address the three objectives and was motivated by the challenge of supporting decisions makers when managing a real case study of a recyclable waste collection system, where strategic decisions on the number and location of depots, vehicles and containers were taken beforehand. Tactical and operational decisions are studied involving the establishment of service areas for each depot and the definition and scheduling of collection routes for each vehicle. Such decisions should represent a compromise solution between the three objectives considered and support a sustainable reverse logistics plan. A multi-objective solution approach based on mixed-integer linear programming models is developed. Trade-offs between the objectives are discussed. Moreover the solutions obtained when each objective is tackled individually are compared between themselves and with the balanced solution.info:eu-repo/semantics/publishedVersio

Economic and environmental concerns in planning recyclable waste collection systems

This paper addresses the planning of recyclable waste collection systems while accounting for economic and environmental concerns. Service areas and vehicle routes are defined for multiple-depot logistics networks where different products have to be collected. The problem is modeled as a multi-product, multi-depot vehicle routing problem with two objective functions: distance and CO2 emissions minimization. A decomposition solution method is developed and applied to a real case-study. Six scenarios are studied regarding different service areas configuration and different objective functions. Savings up to 22% in distance and 27% in CO2 emissions are achieved, excelling economical and environmental goals.info:eu-repo/semantics/publishedVersio

The effect of inventory record inaccuracy in information exchange supply chains

The goal of this paper is to quantify the impact of Inventory Record Inaccuracy on the dynamics of collaborative supply chains, both in terms of operational performance (i.e. order and inventory stability), and customer service level. To do so, we model an Information Exchange Supply Chain under shrinkage errors in the inventory item recording activity of their nodes, present the mathematical formulation of such supply chain model, and conduct a numerical simulation assuming different levels of errors. Results clearly show that Inventory Record Inaccuracy strongly compromises supply chain stability, particularly when moving upwards in the supply chain. Important managerial insights can be extracted from this analysis, such as the role of 'benefit-sharing' strategies in order to guarantee the advantage of investments in connectivity technologies

The smart waste collection routing problem: alternative operational management approaches

Waste collection is nowadays an increasingly important business. However, it is often an inefficient op- eration due to the high uncertainty associated with the real waste bins’ fill-levels. To deal with such uncertainty the use of sensors to transmit real time information is seen as possible solution. But, in order to improve operations’ efficiency, the sensors’ usage must be combined with optimization procedures that inform on the optimal collection routes to operationalize, so as to guarantee a maximization of the waste collected while also minimizing transportation costs. The present work explores this challenge and studies three operational management approaches to define dynamic optimal routes, considering the access to real-time information on the bins’ fill-levels. A real case study is solved and important results were found where significant profit improvements are observed when compared to the real operation. This shows the potential of the proposed approaches to build an expert system, which can support the operations manager’s decisions.info:eu-repo/semantics/acceptedVersio

Cost-effectiveness analysis for sustainable wastewater engineering : a case study at Minho-Lima’s rivers basins (Portugal)

The present work was focused on a methodological assessment for defining cost-effective measures regarding to wastewater sanitation in rural areas and was carried out within the project AQUA Project – Preliminary Studies for the Water Framework Directive Implementation at the Minho and Lima’s Rivers Basins. In order to assure a good ecological and chemical status in water bodies according to Water Framework Directive, a set of priority and complementary actions combined with a cost-effectiveness analysis was used to select a wastewater treatment strategy to increase public attendance. Using geoprocessing methodologies and geographic information multicriteria analysis (e.g.: soil, land use, topography), locations with high potential for implementation of low-energy wastewater treatment systems were identified and worked out with cost-functions. The results show that a combination of centralized and decentralized plants allow a cost-effectiveness attendance of 1,51 k¤/equivalent inhabitant in Minho and Lima’s river basins. The approach indicates that low-energy wastewater treatment plants are interesting options with a promising cost-effectiveness potential in rural areas

From problem structuring to optimization: a multi-methodological framework to assist the planning of medical training

Medical training is an intricate and long process, which is compulsory to medical practice and often lasts up to twelve years for some specialties. Health stakeholders recognise that an adequate planning is crucial for health systems to deliver necessary care services. However, proper planning needs to account for complexity related with the setting of medical school vacancies and of residency programs, which are highly influenced by multiple stakeholders with diverse perspectives and views, as well as by the specificities of medical training. Aiming at building comprehensive models with a potential to assist health decision-makers, this article develops a multi-methodological framework to assist the planning of medical training under such a complex environment. It combines the structuring of the objectives and specificities of the medical training problem with a Soft Systems Methodology through the CATWOE (Customer, Actor, Transformation, Weltanschauung, Owner, Environment) approach, and the formulation of a Mixed Integer Linear Programming model that considers all relevant aspects. Considering the specificities of countries based on a National Health Service structure, a multi-objective planning model emerges, informing on how many vacancies should be opened/closed per year in medical schools and in each specialty. This model aims at (i) minimizing imbalances between medical demand and supply; (ii) minimizing costs; and (iii) maximizing equity across medical specialties. A case study in Portugal is explored so as to illustrate the applicability of the proposed multi-methodology, showing the relevance of proper structuring for planning models having the potential to inform health decision-makers and planners in practice.info:eu-repo/semantics/acceptedVersio

Cost-effectiveness analysis for sustainable wastewater engineering and water resources management : a case study at Minho–Lima river basins (Portugal)

A cost-effectiveness integrated methodology applied in a water resources management and sanitation project in Minho and Lima’s region (Portugal) is presented. First, environmental objectives and programmes of measures (PM) are established and priorities are identified using a cause–effect assessment matrix and a global effectiveness index. Aiming to achieve more demanding goals, some complementary actions are considered, including “decentralized low-energy wastewater treatment plants construction”. A geographic information system was used to select potential implementation sites, and suitable treatment processes for each location are identified. The centralized and decentralized wastewater treatment plants combination is promising, achieving a cost-effectiveness attendance of €1510/equivalent-inhabitant in Minho–Lima river basins