Convexity cuts for multiple choice problems

The purpose of this note is to show that the convexity (or intensection) cut ideas can be exploited to special advantage for integer programs with certain structures. In particular, we show how to obtain now cuts for “multiple choice” and other related “combinatorial” problems. Our approach can usefully be applied to problems involving logical alternatives without having to reformulate (and enlarge) such problems by the addition of 0–1 variables and associated linear constraints.     

One-Dimensional Poisson Growth Models With Random and Asymmetric Growth

Suppose there is a Poisson process of points X _i on the line. Starting at time zero, a grain begins to grow from each point X _i , growing at rate A _i to the left and rate B _i to the right, with the pairs (A _i , B _i ) being i.i.d. A grain stops growing as soon as it touches another grain. When all growth stops, the line consists of covered intervals (made up of contiguous grains) separated by gaps. We show (i) a fraction 1/e of the line remains uncovered, (ii) the fraction of covered intervals which contain exactly k grains is (k–1)/k!, (iii) the length of a covered interval containing k grains has a gamma(k–1) distribution, (iv) the distribution of the grain sizes depends only on the distribution of the total growth rate A _i +B _i , and other results. Similar theorems are obtained for growth processes on a circle; in this case we need only assume the pairs (A _i , B _i ) are exchangeable. These results extend those of Daley, et al. (2000) who studied the case where A _i =B _i =1. Simulation results are given to illustrate the various theorems.     

An optoelectronic recirculating sorter based on CMOS/vertical cavity surface emitting laser smart pixel arrays; architecture and system demonstration

The architecture of an optoelectronic recirculating sorter based on the hybrid integration of CMOS logic circuitry, silicon detector/receivers and vertical cavity surface emitting lasers is presented along with the demonstration of the system.     

Ab initio calculations on Pro-Ala and Pro-Gly dipeptides

The geometries of the dipeptides -Pro- -Ala, -Pro- -Ala and -Pro-Gly were investigated by a grid scan ab initio calculation. The 6-31G basis set was used to estimate the effect of the alanyl side-chain on the conformation of the peptide backbone and to provide a computational basis for the interpretation of known physical-chemical properties of larger peptides that contain these dipeptides. These calculations furnish a direct quantum mechanical assessment of the energetic consequences of a methyl side-chain in the i + 2 position of a turn. The results of the calculation support the current view that the presence of a -Ala residue in the i + 2 position favors a type II β-turn over a type I β-turn conformation, while -Ala has the opposite effect. Total and relative energies for all the optimized conformations identified by the grid search are given and geometric parameters (bond lengths, bond angles and dihedral angles) and net atomic charges have been calculated.     

Tandem mass spectrometry: From infancy to maturity in twenty-five years

When this journal was initiated in 1968, there were only hints of the important applications of tandem mass spectrometry that are so well recognized today. It appears particularly appropriate to review briefly this development when celebrating the silver anniversary of the first mass spectrometry journal.     

Survey of Literature on Continuously Deteriorating Inventory Models

This paper presents a complete and up-to-date survey of published inventory literature for the deteriorating (decaying) inventory models. More specifically, those papers are addressed that consider the effect of deterioration as a function of the on-hand level of inventory. The basic features, extensions and generalization of various models are discussed. A classification scheme is presented along with suggestions for future research.     

Tabu search for graph partitioning

In this paper, we develop a tabu search procedure for solving the uniform graph partitioning problem. Tabu search, an abstract heuristic search method, has been shown to have promise in solving several NP-hard problems, such as job shop and flow shop scheduling, vehicle routing, quadratic assignment, and maximum satisfiability. We compare tabu search to other heuristic procedures for graph partitioning, and demonstrate that tabu search is superior to other solution approaches for the uniform graph partitioning problem both with respect to solution quality and computational requirements.     

The potential of pyrolysis/gas chromatography/mass spectrometry for determining the progress of lignification: An investigation of maturing asparagus sclerenchyma tissue

Sclerenchyma tissues from semi-mature and mature asparagus spears were analysed by pyrolysis/gas chromatography/mass spectrometry and by conventional chemical methods in order to determine the degree of lignification and compare analytical techniques. The pyrolysis data are similar to those obtained by a chemical method involving alkaline extraction at 70°C followed by spectrophotometric determination of phenolic content. The pyrolysis method was more rapid, sensitive and informative than the chemical technique and shows considerable potential for studying the chemical basis of the textural development of plant foods.