O problema de corte de estoque unidimensional multiperíodo

The Multiperiod Cutting Stock Problem arises embedded in the production planning and programming in many industries which have a cutting process as an important stage. Ordered items have different due date over a finite planning horizon. A large scale integer linear optimization model is proposed. The model makes possible to anticipate or not the production of items. Unused objects in inventory in a period become available to the next period, added to new inventory, which are acquired or produced by the own company. The mathematical model's objective considers the waste in the cutting process, and costs for holding objects and final items. The simplex method with column generation was specialized to solve the linear relaxation. Some preliminary computational experiments showed that the multiperiod model could obtain effective gains when compared with the lot-for-lot solution, which is typically used in practice. However, in real world problems, the fractional solution is useless. So, additionally, two rounding procedures are developed to determine integer solutions for multiperiod cutting stock problems. Such procedures are based on a rolling horizon scheme, which roughly means, find an integer solution only for the first period, since this is the solution to be, in fact, carried out. Finally, we conclude that the proposed model for multiperiod cutting stock problems allows flexibility on analyzing a solution to be put in practice. The multiperiod cutting problem can be a tool that provides the decision maker a wide view of the problem and it may help him/her on making decisions.O problema de corte de estoque multiperíodo surge imerso no planejamento e programação da produção em empresas que têm um estágio de produção caracterizado pelo corte de peças. As demandas dos itens ocorrem em períodos diversos de um horizonte de planejamento finito, sendo possível antecipar ou não a produção de itens. Os objetos não utilizados em um período ficam disponíveis no próximo, juntamente com possíveis novos objetos adquiridos ou produzidos pela própria empresa. Um modelo de otimização linear inteira de grande porte é proposto, cujo objetivo pondera as perdas nos cortes, os custos de estocagem de objetos e itens. O método simplex com geração de colunas foi especializado para resolver a relaxação linear. Experiências computacionais preliminares mostram que ganhos efetivos podem ser obtidos, quando comparado com a solução lote-por-lote, tipicamente utilizada na prática. No entanto, em problemas práticos, uma solução fracionária não é aplicável. Então, foram desenvolvidas duas abordagens para o arredondamento da solução para o problema de corte de estoque multiperíodo. Tais procedimentos são baseados em horizonte rolante, que basicamente, consiste em tentar encontrar uma solução inteira apenas para o primeiro período, já que esta será uma solução implementada na prática; para os demais períodos pode haver mudança na demanda, por exemplo, a chegada de novos pedidos ou o cancelamento de pedidos. Finalmente, concluímos que o modelo proposto para o problema de corte de estoque multiperíodo permite flexibilidade na análise da solução a ser posta em prática. O modelo multiperíodo pode ser uma ferramenta que fornece ao tomador de decisões uma ampla visão do problema e pode auxiliá-lo na tomada de decisão.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade Federal de São Paulo (UNIFESP) Departamento de Ciência e TecnologiaUniversidade de São Paulo Inst. de Ciências Matemáticas e de ComputaçãoUNIFESP, Depto. de Ciência e TecnologiaSciEL

The Two-Dimensional, Rectangular, Guillotineable-Layout Cutting Problem with a Single Defect

In this paper, a two-dimensional cutting problem is considered in which a single plate (large object) has to be cut down into a set of small items of maximal value. As opposed to standard cutting problems, the large object contains a defect, which must not be covered by a small item. The problem is represented by means of an AND/OR-graph, and a Branch & Bound procedure (including heuristic modifications for speeding up the search process) is introduced for its exact solution. The proposed method is evaluated in a series of numerical experiments that are run on problem instances taken from the literature, as well as on randomly generated instances.Two-dimensional cutting, defect, AND/OR-graph, Branch & Bound

Qualidade de vida do doente após acidente vascular cerebral

Contextualização: Em Portugal, o AVC constitui a principal causa de incapacidade de longa duração e de diminuição da qualidade de vida. A reabilitação funcional do doente é um dos requisitos básicos no tratamento pós-AVC. Neste contexto, o objetivo do presente estudo pretendeu analisar o modo como determinadas variáveis de contexto sociodemográfico, familiar e clínico estão associadas à qualidade de vida destes doentes. Métodos: Realizou-se um estudo transversal, descritivo correlacional, de natureza quantitativa, no qual participaram 75 doentes, maioritariamente do sexo masculino (53,33%), com uma média de idades de 68 anos. Para a mensuração das variáveis utilizaram-se instrumentos de medida, de reconhecida fiabilidade, aferidos e validados para a população portuguesa: Escala de Apgar Familiar, Escala de Barthel e Questionário de avaliação da qualidade de vida (PSN). Foi também utilizada uma ficha sociodemográfica e clínica. Resultados: Analisando as dimensões da qualidade de vida constatamos que os doentes do sexo feminino apresentam scores superiores em todas as dimensões, existindo diferenças estatísticas significativas apenas para o Isolamento Social. Os participantes solteiros revelaram valores médios mais elevados, resultando em diferenças estatisticamente significativas para o Isolamento Social. Os participantes total e severamente dependentes foram os que revelaram médias mais elevadas na maioria das dimensões, com diferenças estatisticamente significativas em todas as dimensões, exceto na Dor. As variáveis idade, influência da residência, habilitações literárias, situação laboral, condições habitacionais, tipo de AVC, tempo de internamento, local da lesão, influência do programa de reabilitação e funcionalidade familiar não revelaram um efeito significativo sobre a qualidade de vida. Conclusão: As evidências encontradas neste estudo fornecem indicadores para uma melhor intervenção junto dos doentes com AVC, de forma a melhorar a sua adaptação e bem-estar, e da sua família, contribuindo para a sua qualidade de vida. Por outro lado, sensibilizou-nos para a importância em ajustar os cuidados específicos de reabilitação às expetativas e necessidades desses indivíduos. Palavras-chave: Acidente Vascular Cerebral, Qualidade de Vida, Reabilitação Funcional.Abstract Background: In Portugal, cerebrovascular accident (CVA) is the leading cause of long-term disability and diminished quality of life. The functional rehabilitation of the patient is one of the basic requirements in the treatment post-CVA. In this context, the objective of the present study is to examine how certain circumstantial, sociodemographic, familiar and clinical variables, the family functionality and functional independence are associated with the quality of life of these patients. Methods: it was made a cross-sectional, descriptive correlacional, quantitative study, in which participated 75 patients, mostly male (53,33%), with a mean age of 68 years old. For the measurement of the variables, were used measuring instruments of acknowledged reliability, measured and validated to the portuguese population: the Familiar Apgar Scale, the Barthel Scale and the Quality of Life Assessment Questionnaire. It was also used a sociodemographic and clinical data sheet. Results: Analyzing the dimensions of quality of life it was found that female patients have higher scores in all dimensions, and there are significant statistical differences only to Social Isolation. Unmarried participants showed higher average values, resulting in significant statistically differences to Social Isolation. The total and severely dependents participants were those who revealed higher average values in most dimensions, with differing slightly significant statistics, very significant and extremely significant in most dimensions, except in Pain. The variables age, influence of residence, qualifications, employment, housing conditions, type of cerebrovascular accident, time of hospitalization, location of the lesion, influence of rehabilitation programme and family functionality did not show a significant effect on the quality of life. Conclusion: The evidence found in this study provide indicators for a better assistance to patients with cerebrovascular accident, in order to improve their well-being and adjustment, and of his family, contributing to their quality of life. On the other hand, moved us to the importance in adjusting the specific rehabilitation cares of these patients’ expectations and needs. Keywords: Cerebrovascular Accident, Quality of Life, Functional Rehabilitation

The Two-Dimensional, Rectangular, Guillotineable-Layout Cutting Problem with a Single Defect

In this paper, a two-dimensional cutting problem is considered in which a single plate (large object) has to be cut down into a set of small items of maximal value. As opposed to standard cutting problems, the large object contains a defect, which must not be covered by a small item. The problem is represented by means of an AND/OR-graph, and a Branch & Bound procedure (including heuristic modifications for speeding up the search process) is introduced for its exact solution. The proposed method is evaluated in a series of numerical experiments that are run on problem instances taken from the literature, as well as on randomly generated instances

Neuromuscular Capabilities in Top-Level Weightlifters and Their Association with Weightlifting Performance

The aim of this study was to determine the associations between the front and back squat, countermovement jump (CMJ) and deep squat jump (DSJ) force–time metrics, and weightlifting performance in top-level weightlifters. Thirteen top-level weightlifters who classified for the World Championship 2023 participated. The heaviest successful snatch and clean and jerk were recorded within a preparation session as performance indicators. The front and back squat one-repetition maximums (1RMs) were evaluated in separate training sessions. The average of three maximum CMJs and DSJs were recorded using a force plate, and jump height, propulsive net impulse, and peak power were calculated for further analysis. Pearson’s correlation coefficients were used to determine the associations between variables. Statistical significance was set at p ≤ 0.05. The front and back squat 1RMs were significant and nearly perfectly associated with weightlifting performance (p < 0.001, r = 0.98–0.99). CMJ and DSJ propulsive net impulse displayed nearly perfect associations with weightlifting performance (p < 0.001, r = 0.96–0.99), while jump height is a less promising metric to assess the weightlifters’ ballistic capabilities. This study reinforces that lower body maximum strength and ballistic capabilities are closely associated with top-level weightlifters’ performance and are of practical importance to monitor their neuromuscular function

Lot sizing and furnace scheduling in small foundries

A lot sizing and scheduling problem prevalent in small market-driven foundries is studied. There are two related decision levels: (1) the furnace scheduling of metal alloy production, and (2) moulding machine planning which specifies the type and size of production lots. A mixed integer programming (MIP) formulation of the problem is proposed, but is impractical to solve in reasonable computing time for non-small instances. As a result, a faster relax-and-fix (RF) approach is developed that can also be used on a rolling horizon basis where only immediate-term schedules are implemented. As well as a MIP method to solve the basic RF approach, three variants of a local search method are also developed and tested using instances based on the literature. Finally, foundry-based tests with a real-order book resulted in a very substantial reduction of delivery delays and finished inventory, better use of capacity, and much faster schedule definition compared to the foundry's own practice. © 2006 Elsevier Ltd. All rights reserved