The application of preprocessing and cutting plane techniques for a class of production planning problems

This paper investigates properties of integer programming models for a class of production planning problems. The models are developed within a decision support system to advise a sales team of the products on which to focus their efforts in gaining new orders in the short term. The products generally require processing on several manufacturing cells and involve precedence relationships. The cells are already (partially) committed with products for stock and to satisfy existing orders and therefore only the residual capacities of each cell in each time period of the planning horizon are considered. The determination of production recommendations to the sales team that make use of residual capacities is a nontrivial optimization problem. Solving such models is computationally demanding and techniques for speeding up solution times are highly desirable. An integer programming model is developed and various preprocessing techniques are investigated and evaluated. In addition, a number of cutting plane approaches have been applied. The performance of these approaches which are both general and application specific is examined.

Combinatorial and geometrical properties of a class of tilings

In this paper, we consider a tiling generated by a Pisot unit number of degree d >= 3 which has a finite expansible property. We compute the states of a finite automaton which recognizes the boundary of the central tile. We also prove in the case d = 3 that the interior of each tile is simply connected.

High-speed cavity preparation techniques with different water flows

Statement of problem. Cavity and tooth preparations generate heat because the use of rotary cutting instruments on dental tissues creates friction. Dental pulps cannot survive temperature increases greater than 5.5degreesC.Purpose. This study evaluated the efficiency of 3 different water flows for 2 different tooth preparation techniques to determine which are safe for use.Material and methods. Thermocouples were placed in the pulpal chambers of 30 bovine teeth, and 1 of 2 tooth preparation techniques was used: a low-load intermittent tooth preparation technique or a high-load tooth preparation technique without intervals. Water flows of 0, 30, and 45 mL/min were associated with each technique, for a total of 6 different groups. The results were analyzed with a 2-factor analysis of variance (P<.05).Results. Temperature increases with the high-load technique were 16.40&DEG;C without cooling (group 1), 11.68&DEG;C with 30 mL/min air-water spray cooling (group III), and 9.96&DEG;C with 45 mL/min cooling (group V). With the low-load tooth preparation technique, a 9.54&DEG;C increase resulted with no cooling (group II), a 1.56&DEG;C increase with 30 mL/min air-water spray cooling (group TV), and a 0.04&DEG;C decrease with 45 mL/min cooling (group VI). The low-load technique was associated with more ideal temperature changes.Conclusion. The results of this study confirm the necessity of using a low-load technique and water coolants during cavity and tooth preparation procedures.

Anatomy of the oral cavity of hylid larvae from the genera Aplastodiscus, Bokermannohyla, and Hypsiboas (Amphibia, anura): Description and systematic implications

Internal larval oral anatomy was used to explore morphological diversity and its contribution to the systematics of the genera Aplastodiscus, Bokerinannohyla, and Hypsiboas, belonging to the tribe Cophomantini. Internal oral morphology was examined for tadpoles of 12 species. All species have a large pair of infralabial papillae on the buccal floor and other papillae on the prelingual region. In Aplastodiscus and Bokerinannohyla, the large infralabial papillae have digitiform secondary projections. The number and arrangement of the buccal floor papillae varies among species, but they are more numerous in Aplastodiscus and Bokerinannohyla. The arrangement of the postnarial papillae is variable, but in Aplastodiscus and Bokerinannohyla, they show a definite, inverted V-shape pattern. The lateral ridge papillae are more complex in larvae of Bokertnannohyla with long digitiform secondary projections. Tadpoles of only Aplastodiscus albofrenatus, Aplastodiscus eugenioi, and Bokerinannohyla luctuosa have papillae on the buccal roof arena and larvae of all species have lateral roof papillae except Hypsiboas albomarginatus and Hypsiboas cinerascens. Larvae of Aplastodiscus, Bokermannohyla, and Hypsiboas presumably share the presence of vacuities anterior to the internal nares; although this character state is clearly synapomorphic within hylids, it is still uncertain whether it is exclusive of these three genera or whether it is present in the other genera of the tribe Cophomantini (Hyloscirtus and Myersiohyla). The inclusion of internal oral anatomy characters, such as the narial vacuities, in systematic studies is certainly valuable because it will provide additional information toward the understanding of phylogenetic relationships.

Bound states of the Dirac equation for a class of effective quadratic plus inversely quadratic potentials

The Dirac equation is exactly solved for a pseudoscalar linear plus Coulomb-like potential in a two-dimensional world. This sort of potential gives rise to an effective quadratic plus inversely quadratic potential in a Sturm-Liouville problem, regardless the sign of the parameter of the linear potential, in sharp contrast with the Schrodinger case. The generalized Dirac oscillator already analyzed in a previous work is obtained as a particular case. (C) 2004 Elsevier B.V. All rights reserved.