NONSPECIFICITY IN Rn

Open problems posed by Klir and Wierman (1998) for a nonspecificity measure are solved; the measure is proven additive, and its extension to nonconvex sets given. Several different proofs of additivity are given, to suggest certain techniques of wider applicability in system problems and to motivate further research possibihties. A study is initiated to refine nonspecificity separately to each dimension k≤n for the bodies residing in Rⁿ.     

UNCERTAINTY IN THE DEMPSTER-SHAFER THEORY: A CRITICAL RE-EXAMINATION

Measures of two types of uncertainty that coexist in the Dempster-Shafer theory are overviewed. A measure of one type of uncertainty, which expresses nonspecificity of evidential claims, is well justified on both intuitive and mathematical grounds. Proposed measures of the other types of uncertainty, which atlempt to capture conflicts among evidential claims, are shown to have some deficiencies. To alleviate these deficiencies, a new measure is proposed. This measure, which is called a measure of discord, is not only satisfactory on intuitive grounds, but has also desirable mathematical properties. A measure of total uncertainty, which is defined as the sum of nonspecificity and discord, is also discussed. The paper focuses on conceptual issues. Mathematical properties of the measure of discord are only slated; their proofs are given in a companion paper.¹⁵     

The control of radiation resistance in space solar cells

Solar cells, powering satellites and other space vehicles, can suffer substantial degradation in performance by electron and proton irradiation experienced in orbit. These effects are first described, and the behaviour of silicon solar cells compared with cells of gallium arsenide and indium phosphide, and the more recent thin film type cells. In particular, the paper will discuss the phenomenon of ‘photon degradation’ in silicon cells, and recent progress in understanding the defect mechanisms responsible for this effect occurring after illumination of irradiated cells. Strategies for improving the radiation resistance of silicon solar cells, including the use of ‘defect gettering’ will be discussed, while the effects of annealing radiation damage will be outlined. Finally, the paper will seek to identify areas where an improved understanding of defect behaviour is necessary to produce further improvements in performance. In particular, it highlights the need for fundamental studies of advanced solar cell structures and materials, including CIS cells, where significant improvement in radiation tolerance has been found.     

Modelling planting configuration and canopy architecture effects on diurnal light absorption changes in cotton

Abstract

A simplified model that accounts for diurnal solar zenith and azimuth angle illumination changes and plant geometry effects on photosynthetically active radiation (PAR) was developed, h was tested using diurnal absorbed PAR (APAR) measurements acquired for cotton (Gossvpium hirsuium L.) grown at Weslaco, Texas, during the 1984 and 1986 growing seasons. Diurnal canopy reflectance and transmittance measurements were automatically collected at 3-minute intervals from about 9.00 to 14.50 local standard time (LST) using radiometers mounted 3·7m above the soil surface and PAR light bar sensors located beneath the crop canopy perpendicular to the crop rows. Plant growth measurements estimated by the model were significantly correlated with observed measurements during crop development. Model-estimated heliotropic leaf elevation trends agreed with published results for cotton canopies. APAR, relative to incident PAR, was generally lower for east-west rows than for north-south rows during crop development. The APAR response of cotton canopies for both east-west and north-south rows were found to be essentially flat when solar azimuth was between 90° and 270° so one observation close to noon would probably be representative of the diurnal APAR measurements.     

SEGMENTED SECONDARY LINEAR RELUCTANCE MOTOR: ANALYTICAL AND EXPERIMENTAL RESULTS

ABSTRACT

The segmented secondary linear reluctance motor is analyzed using a permeance function approach. The basic assumptions are iron linearity and current excitation. The resulting analytical equations are implemented for numerical computation. The numerical results are compared with experimental results which are obtained from a 2 pole, 37 m/s laboratory model linear reluctance motor.     

Prediction Equations for Gases in Flexible Modified-Atmosphere Packages of Respiring Produce are Different Than Those for Rigid Packages

Total pressure generally decreases in a sealed rigid package containing respiring produce, whereas total pressure is essentially constant and free volume decreases in a flexible package. We found that predicted O₂, CO₂, and N₂ partial pressures were different for similarly designed (same surface area, thickness, film permeabilities and produce mass) flexible and rigid packages at “quasi steady state” and steady state, respectively. Predicted O₂ and CO₂ partial pressures were slightly higher in a flexible package than in a rigid package and were a function of the film permeability ratio of N₂ to O₂ and of CO₂ to O₂. They also related to the ratio of product CO₂ production rate to O₂ uptake rate, target steady-state O₂ partial pressure, and respiration characteristics. Differences were slight for films such as low-density polyethylene.     

ANALYSIS OF GASES DISSOLVED IN GLASS AND GASES PRESENT IN SEEDS*

A method of analysis for gases dissolved in glass has been developed which gives more reproducible results than those previously reported. The problem of the volatilization of alkali from the sample during the course of analysis appears to have been satisfactorily solved through the use of an auxiliary furnace. A number of commercial glasses have been analyzed for dissolved gases. Water vapor, sulfur dioxide, and oxygen are the principal gases found in flint glass. Water vapor seems to be the principal constituent of the gases found in amber glass. A method for the analysis of gases present in seeds in glass has been developed which gives fairly satisfactory quantitative results on samples containing more than 1 cu. mm. of gas. The results obtained on samples containing less than 1 cu. mm. of gas are qualitative only. The procedure consists (1) in the determination of the temperatures at which gases present in the seeds undergo a change of state and (2) in the microchemical analysis of these same gases. Seeds have been found that contained entrapped air, sulfur dioxide, and also carbon dioxide. Some seeds, especially those in amber glass, appear to be vacuum seeds, and these frequently contain a deposit on the inside which has been identified as a sulfite or a sulfate.