Guy L. Curry

Distribution model of organism development times.

Abstract It is shown in this analysis that the distribution of organism development times for constant and variable temperatures can be described based upon one simple assumption. This assumption is that the concentration of enzymes which are rate controlling for development are symmetrically distributed about some genetically determined mean concentration. It then follows mathematically that the skew in the distribution in development times, observed by Stinner, Butler, Bacheler & Tuttle (1975) and others, results naturally from the transformation from development rates to emergence times. The distribution model is shown to agree with observed data for (i) boll weevil, Anthonomus grandis Boheman, and (ii) cotton fleahopper, Pseudatomoscelis seriatus Reuter, reared under both constant and variable temperature regimes. The resulting model enables predictions of the distribution of emergence times for organisms reared under any set of variable temperature field conditions.

Foundations of stochastic development

Abstract A consistent mathematical theory of stochastic poikilotherm development has been derived based upon a minimum set of biological assumptions obtained from the literature. In the subsequent analysis, the resulting developmental rate can be justifiably represented as a random variable. Three cases are considered: (1) developmental rates dependent only on temperature, (2) rates dependent on both temperature and age, and (3) rates dependent on a general function of temperature and time. The analysis provides a mathematical foundation for the current practice of superimposing a probability distribution function on a biological time scale to describe the development of individuals from a population.

A stochastic model of a temperature-dependent population☆

Abstract The theoretical basis is developed for a population model which allows the use of constant temperature experimental data in predicting the size of an insect population for any variable temperature environment. The model is based on a stochastic analysis of an insects mortality, development, and reproduction response to temperature. The key concept in the model is the utilization of a physiological time scale. Different temperatures affect the population by increasing an individuals physiological age by differing rates. Conditions for the temperature response properties are given which establish the validity of the model for variable temperature regimes. These conditions refer to the relationship between chronological and physiological age. Reasonable agreement between the model and field populations demonstrates the practicality of this approach.

Towards the real time solution of strike force asset allocation problems

The strike force asset allocation problem consists of grouping strike force assets into packages and assigning these packages to targets and defensive assets in a way that maximizes the strike force potential. Integer programming formulations are developed, semi-real and random problems are built up, and computational results via the CPLEX MIP Solver are presented.

A general law for direct sunlight penetration

Abstract Under the assumption that foliage area distributions may be adequately approximated by probability distributions, a general law for the prediction of direct sunlight penetration of crop canopies is derived. It is shown that the Poisson (Beers) law is a special case of this more general law. Area and transect problems are treated, and stochastic variation in leaf sizes is considered. Numerical studies are presented which indicate that the Poisson law is not adequate in all cases for the prediction of sunlight penetration and that stochastic variation in leaf sizes is of less consequence than average leaf size and/or leaf-area index.

Solving multidimensional knapsack problems with generalized upper bound constraints using critical event tabu search

A critical event tabu search method which navigates both sides of the feasibility boundary has been shown effective for solving the multidimensional knapsack problem. In this paper, we apply the method to the multidimensional knapsack problem with generalized upper bound constraints. This paper also demonstrates the merits of using surrogate constraint information vs. a Lagrangian relaxation scheme as choice rules for the problem class. A constraint normalization method is presented to strengthen the surrogate constraint information and improve the computational results. The advantages of intensifying the search at critical solutions are also demonstrated.

Light interception by isolated plants

Abstract Foliage of single plants invariably appears to be nonuniformly distributed when viewed from the direction of the sun. The nonuniformity of foliage in space and its constraint within an envelope should both be considered when analyzing light interception. This study uses a generalized treatment of the distribution of foliage and its projection onto a plane within or below the canopy. Given this projected foliage distribution, the general light penetration law of Mann et al. (1977) can be applied to calculate either the light interception or penetration. The analysis is illustrated by calculation of the sunlight interception of model plants in the shape of ellipsoids. Different distributions of foliage density with height and radial distance give different light interceptions. Comparison of light interceptions by uniform and nonuniform foliage structures show differences as high as 43%.

A Dynamic Programming Algorithm for Facility Location and Allocation

Abstract This article considers the problem of facility location-allocation. The problem is to allocate K facilities in M facility locations and assign N demands such that the total cost is minimized. The model is formulated as a mathematical programming problem and decomposed into the recursive equations of dynamic programming. A sample problem is presented and analyzed in detail in order to demonstrate an application of the model. The procedure was coded in Fortran IV and used to obtain the sample problem results.

Queueing network model for a class of material-handling systems

A queueing network-based approximation model was developed to evaluate the performance of a fixed-route material-handling system supporting a multiple-workcentre manufacturing facility. The closest transporter allocation scheme was used to assign empty transporters to jobs needing to be moved between various workcentres. This control methodology creates two interesting difficulties that require solving for an accurate approximation model. A model of the distributions of the location of an assigned transporter as a function of the number of available transporters is developed. In addition, it is shown that owing to the strong dependent service time aspect of this situation, the standard queueing network decomposition approach of treating the material-handling systems as a GI/G/c queue can be highly inaccurate. Thus, it is necessary to develop a dependent service-time model for approximating the queueing delay encountered while waiting for an empty transporter assignment.

Optimization of MOX enrichment distributions in typical LWR assemblies using a simplex method-based algorithm

Abstract The enrichment distributions within light water reactor (LWR) fuel assemblies are optimized using a modified linear programming (SIMPLEX Method) technique initiated from a flat enrichment distribution until a target, maximum local power peaking factor is achieved. The optimum rod enrichment distribution when each rod is allowed to have its own individual enrichment (for this case the target, maximum local power peaking factor is 1.0) is obtained at an intermediate point of the optimization procedure. Later, the optimal locations and values for a reduced number of rod enrichments (groups) are obtained for an input target maximum local power peaking factor by applying sensitivity to change techniques. After an initial set of enrichment groups have been defined, interchanges of rods among neighboring groups are carried out to obtain the final assembly enrichment distribution. The optimization procedure is demonstrated by presenting results for both boiling water reactor (BWR) and pressurized water reactor (PWR) fuel assembly designs. Reactor-grade plutonium (with a fissile Pu fraction of 59.6%) and weapons-grade plutonium (with a fissile Pu fraction of 94.0%) were assumed to be the feed Pu material for the MOX fuel rods in the BWR and PWR examples, respectively. Hot-full-power-temperature and beginning-of-life conditions were also assumed in the example problems.