957 resultados para 2D cutting and packing
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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In this paper a mathematical model that combines lot-sizing and cutting-stock problems applied to the furniture industry is presented. The model considers the usual decisions of the lot sizing problems, as well as operational decisions related to the cutting machine programming. Two sets of a priori generated cutting patterns are used, industry cutting patterns and a class of n-group cutting patterns. A strategy to improve the utilization of the cutting machine is also tested. An optimization package was used to solve the model and the computational results, using real data from a furniture factory, show that a small subset of n-group cutting patterns provides good results and that the cutting machine utilization can be improved by the proposed strategy.
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Nickel-titanium rotatory systems should remove dentin during the root canal preparation to promote the enlargement and tapered shape with continuously narrowing towards the apex. Objective: The aim of this study was to analyze the cutting ability of three NiTi rotatory systems (n = 12): ProTaper (group 1), Mtwo (group 2), and K3 (group 3). Material and methods: Thirty six maxillary molar teeth were weighted on an analytical balance before and after the rotatory preparation of the mesio-buccal root canal. Data was statistically analyzed by ANOVA and Tukey s test with a significance level of 5%. Results: The results revealed the following mass differences (g) before and after the root canal preparation: ProTaper (group 1 – 0.0159 ± 0.004), Mtwo (group 2 – 0.0125 ± 0.002), and K3 (group 3 – 0.007 ± 0.003). Conclusion: ProTaper showed the highest cutting ability among the three tested nickel-titanium rotatory systems followed by Mtwo and K3.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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1. 1. The oxygen consumption in workers of two simpatric leaf cutting ants, Atta laevigata and Atta sexdens rubropilosa was measured at different temperatures. 2. 2. In the temperature range between 5-35°C, with 5°C increments, the respiratory rates increased with temperature, but the R-T curves of both ants showed neither a marked drop at the low end nor a break at the high end; except between 30 and 35°C. 3. 3. The respiratory rates of A. s. rubropilosa were higher than those of A. laevigata and in the midrange of temperatures, the rates of A. laevigata increased faster than those of A. s. rubropilosa. 4. 4. Q10 values did not indicate regions of compensation for temperature in both ants, but suggested that adjustments may occur at high temperatures (25-35°C), as expected for tropical ants. 5. 5. Temperature variations did not alter significantly the slope of the curve relating oxygen consumption and body weight in both species. © 1982.
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1. 1. The respiration of the different castes of two species of leaf-cutting ants, Atta laevigata and Atta sexdens rubropilosa was measured in both workers and sexed forms. 2. 2. The respiratory rates (μl O2/mg(live)/hr) were, in A. laevigata, 0.644 (gardeners), 0.594 (cutters), 0.354 (soldiers), 0.233 (males) and 0.085 (females); in A. s. rubropilosa, 0.803 (gardeners), 0.748 (cutters), 0.510 (soldiers), 0.375 (males) and 0.274 (females), significantly higher than A. laevigata. 3. 3. All castes considered, the b-values of the equation relating oxygen consumption and weight in A. laevigata (0.53) were significantly different from that in A. s. rubropilosa (0.73). © 1981.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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It is marvelously fitting that we gather here in Nebraska City on this lovely fall afternoon to officially celebrate this wonderful new center. Fall is a traditional-time of harvest in Nebraska, and for many of us there is a deep and abiding satisfaction in bringing a good crop to fruition. Apple harvests at Nebraska City orchards long have brought visitors here each year for fresh fruit and cider.
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The irregular shape packing problem is approached. The container has a fixed width and an open dimension to be minimized. The proposed algorithm constructively creates the solution using an ordered list of items and a placement heuristic. Simulated annealing is the adopted metaheuristic to solve the optimization problem. A two-level algorithm is used to minimize the open dimension of the container. To ensure feasible layouts, the concept of collision free region is used. A collision free region represents all possible translations for an item to be placed and may be degenerated. For a moving item, the proposed placement heuristic detects the presence of exact fits (when the item is fully constrained by its surroundings) and exact slides (when the item position is constrained in all but one direction). The relevance of these positions is analyzed and a new placement heuristic is proposed. Computational comparisons on benchmark problems show that the proposed algorithm generated highly competitive solutions. Moreover, our algorithm updated some best known results. (C) 2012 Elsevier Ltd. All rights reserved.
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Fluorene-based systems have shown great potential as components in organic electronics and optoelectronics (organic photovoltaics, OPVs, organic light emitting diodes, OLEDs, and organic transistors, OTFTs). These systems have drawn attention primarily because they exhibit strong blue emission associated with relatively good thermal stability. It is well-known that the electronic properties of polymers are directly related to the molecular conformations and chain packing of polymers. Here, we used three oligofluorenes (trimer, pentamer, and heptamer) as model systems to theoretically investigate the conformational properties of fluorene molecules, starting with the identification of preferred conformations. The hybrid exchange correlation functional, OPBE, and ZINDO/S-CI showed that each oligomer exhibits a tendency to adopt a specific chain arrangement, which could be distinguished by comparing their UV/vis electronic absorption and C-13 NMR spectra. This feature was used to identify the preferred conformation of the oligomer chains in chloroform-cast films by comparing experimental and theoretical UV/vis and C-13 NMR spectra. Moreover, the oligomer chain packing and dynamics in the films were studied by DSC and several solid state NMR techniques, which indicated that the phase behavior of the films may be influenced by the tendency that each oligomeric chain has to adopt a given conformation.