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F tests with random sample sizes. Theory and applications
Publication . Moreira, Elsa E.; Mexia, João T.; Minder, Christoph E.; DM - Departamento de Matemática; CMA - Centro de Matemática e Aplicações; Elsevier Science B.V., Inc
Given a fixed time span for collecting observations in a study comparing, for example, the pathologies of patients entering a hospital sequentially, it is advisable to consider the sample sizes of the ANOVA levels as random variables. Using this approach, more powerful tests are developed, leading to lower critical values. The approach is used to obtain the minimum duration of data collection to ensure a pre-fixed power for the F test.
Assessing and improving management practices when planning packaging waste collection systems
Publication . Ramos, Tânia Rodrigues Pereira; Gomes, Maria Isabel Azevedo Rodrigues; Barbosa-povoa, Ana Paula; DM - Departamento de Matemática; CMA - Centro de Matemática e Aplicações; Elsevier
Packaging waste collection systems are responsible to collect, within a geographic area, threetypes of packaging materials (paper, glass and plastic/metal) that are disposed by the finalconsumer into special bins. Those systems are often characterized by having a network withmultiple depots that act as transfer and sorting stations, and where the vehicle fleet is based.However, each depot is often managed independently and not as a part of a unique system. Inthis work, four current tactical/operational practices that contribute to the independentmanagement of each depot are analysed. The change of such practices is investigated andtheir impact assessed on the total collection cost. A solution methodology based onmathematical formulations is developed to plan service areas, vehicle routes and vehicleschedules taken into account new alternative solutions in managing the system as a whole.Such methodology is applied to a real case study of a company responsible for the collection ofthe packaging waste in 7 municipalities in mainland Portugal. New service areas, collectionroutes and vehicle schedules are defined and significant savings are obtained in terms of thetotal distance travelled as well as in terms of the number of vehicles required, resulting in adecreasing of the total system cost.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
Concurso para Financiamento de Projectos de IC&DT Estratégicos e de Interesse Público promovidos por Laboratórios Associados e Unidades de I&D - 2011 - OE
Número da atribuição
PEst-OE/MAT/UI0297/2011