6 research outputs found
Mathematical Optimization Approach for Facility Layout on Several Rows
The facility layout problem is concerned with finding an arrangement of non-overlapping indivisible departments within a facility so as to minimize the total expected flow cost. In this paper we consider the special case of multi-row layout in which all the departments are to be placed in three or more rows, and our focus is on, for the first time, solutions for large instances. We first propose a new mixed integer linear programming formulation that uses continuous variables to represent the departmentsâ location in both x and y coordinates, where x represents the position of a department within a row and y represents the row assigned to the department. We prove that this formulation always achieves an optimal solution with integer values of y, but it is limited to solving instances with up to 13 departments. This limitation motivates the application of a two-stage optimization algorithm that combines two mathematical optimization models by taking the output of the first-stage model as the input of the second-stage model. This algorithm is, to the best of our knowledge, the first one in the literature reporting solutions for instances with up to 100 departments.publishersversionpublishe
Mathematical optimization approaches for facility layout problems: The state-of-the-art and future research directions
Sem PDF conforme despacho. Fundacao para a Ciencia e a Tecnologia - PEstOE/MAT/UI0297/2014.Facility layout problems are an important class of operations research problems that has been studied for several decades. Most variants of facility layout are NP-hard, therefore global optimal solutions are difficult or impossible to compute in reasonable time. Mathematical optimization approaches that guarantee global optimality of solutions or tight bounds on the global optimal value have nevertheless been successfully applied to several variants of facility layout. This review covers three classes of layout problems, namely row layout, unequal-areas layout, and multifloor layout. We summarize the main contributions to the area made using mathematical optimization, mostly mixed integer linear optimization and conic optimization. For each class of problems, we also briefly discuss directions that remain open for future research.publishe
Time Reduction of the Packing Process
Savana is a company in the footwear sector which is over 27 years old and has more than 150 employees. This company specializes in childrenâs footwear of sizes ranging from 18 to 40. Each pair is individually packed in a box which is customized for each client. The ideal size of each box depends on the model of the footwear and the position in which it is placed inside the box. These boxes are ordered from an external supplier that has only certain measures available, so boxes of the same size have to be used for footwear of various sizes and models.
Due to a frequent introduction of new models in the production environ- ment, the box sizes are initially set manually in an experimental procedure (testing), which is often time consuming. Savana challenged ESGIâs par- ticipants to study their packing process, in order to reduce the variety of box sizes, the empty space inside the boxes and to eliminate the need to perform testing, thereby reducing the time and increasing the eïżœciency of the packing process.
Furthermore, the footwear ordered by each customer is packed into large boxes, which will henceforth be referred to as containers. With regard to these large boxes, various designs and sizes can be delivered to a single client. The dimensions, weight and forms of these are subject to the customerâs specifications. In this context, Savana intends to determine automatically the sizes of the containers to be sent to each customer and how to arrange the individual boxes for each clientâs order.
This report tells how to automatize and speed up the overall process. It describes how to automatically assign shoes to boxes, and gives a manner to pack the shoe boxes, in such way that permit to reduce the size of the card box.
Savana should be aware that this is not yet a ready to use solution, because more data analysis need to be done, in order to improve and make the method reliable. Furthermore, during implementation it may appear new important challenges
Animal infections by vaccinia-like viruses in the state of Rio de Janeiro: an expanding disease InfecçÔes animais por vĂrus semelhantes ao vaccĂnia no estado do Rio de Janeiro: uma doença em expansĂŁo
In the present study we investigated the presence of infections by vaccinia-like viruses in dairy cattle from 12 counties in the state of Rio de Janeiro in the last 9 years. Clinical specimens were collected from adult animals with vesicular/pustular lesions mainly in the udder and teats, and from calves with lesions around the nose and mouth. A plaque reduction neutralization test (PRNT) was applied to search for antibodies to Orthopoxvirus; the vesicular/pustular fluids and scabs were examined by PCR, electron microscopy (EM) and by inoculation in VERO cells for virus isolation. Antibodies to Orthopoxvirus were detected in most cases. The PCR test indicated a high nucleotide homology among the isolates and the vaccinia viruses (VACV) used as controls. By EM, typical orthopoxvirus particles were observed in some specimens. The agents isolated in tissue culture were confirmed as vaccinia-like viruses by EM and PCR. The HA gene of the vaccinia-like Cantagalo/IOC virus isolated in our laboratory was sequenced and compared with other vaccinia-like isolates, showing high homology with the original Cantagalo strain, both strains isolated in 1999 from dairy cattle. Antibodies to Orthopoxvirus were detected in one wild rodent (genus Akodon sp.) collected in the northwestern region of the state, indicating the circulation of poxvirus in this area. Nonetheless, PCR applied to tissue samples collected from the wild rodents were negative. Vesicular/pustular lesions in people in close contact with animals have been also recorded. Thus, the vaccinia-like virus infections in cattle and humans in the state seem to be an expanding condition, resulting in economic losses to dairy herds and leading to transient incapacitating human disease. Therefore, a possible immunization of the dairy cattle in the state should be carefully evaluated.<br>Neste estudo avaliou-se a presença de infecçÔes por vĂrus semelhantes ao vĂrus vaccĂnia (VACV) em gado leiteiro em 12 municĂpios no estado do Rio de Janeiro, ao longo dos Ășltimos nove anos. Amostras clĂnicas foram coletadas de animais com vesĂculas, pĂșstulas e crostas no Ășbere e tetas, e da regiĂŁo do nariz e da cavidade oral de bezerros. Um teste de neutralização viral por redução de placas foi desenvolvido para investigar a presença de anticorpos contra Orthopoxvirus. Os fluidos de vesĂculas / pĂșstulas e as crostas foram testadas por PCR, microscopia eletrĂŽnica (ME) e por inoculação em cĂ©lulas VERO para isolamento viral. Anticorpos contra Orthopoxvirus foram detectados na grande maioria dos animais. O teste de PCR demonstrou homologia entre os vĂrus isolados e amostras de vĂrus vaccĂnia usados como controles. Na ME, partĂculas tĂpicas de Orthopoxvirus foram observadas em vĂĄrios espĂ©cimes analisados. Os vĂrus isolados em cultivo celular foram confirmados como Orthopoxvirus por PCR e ME. O gene HA da amostra Cantagalo/IOC isolada em nosso laboratĂłrio foi seqĂŒenciado e comparado com outras amostras semelhantes ao vaccĂnia, mostrando uma alta homologia com a amostra original Cantagalo, tendo sido as duas amostras isoladas em 1999 de gado leiteiro. Anticorpos para Orthopoxvirus foram detectados em um roedor silvestre do gĂȘnero Akodon sp. coletado na regiĂŁo noroeste do estado, sugerindo uma circulação de poxvĂrus na natureza. No entanto, os testes de PCR aplicados a tecidos de roedores silvestres foram negativos. InfecçÔes vesiculares / pustulares em humanos que mantinham contato com os animais afetados tambĂ©m foram relatadas. Assim, infecçÔes por amostras semelhantes ao vĂrus VACV em bovinos e em humanos parecem em expansĂŁo no estado, gerando perdas econĂŽmicas em animais e quadros de doença incapacitante temporĂĄria em pacientes humanos. Dessa forma, a possibilidade da imunização do gado leiteiro no estado deve ser devidamente avaliada