Various models and metrics that are based on cognitive theories and assumptions have been proposed in an effort to formalise the concept of programming difficulty. The model and metric proposed here are, instead, based on a problem-space formalisation and an information-theoretic measure (entropy) that provides the complexity of a program specification; this metric can be applied before the specification's implementation is complete. The problem space for a program specification is the set of possible state descriptions that could arise from the execution of the program on that input, as ascertainable from the specification. We show how to define the entropy metric based on the problem space definition, and demonstrate the applicability of this metric to modularity problems.

Thin films of SnO2 prepared by the radio frequency sputtering technique were doped with 1% and 10% Sb2O3,. The films were then tested in a background of synthetic air to understand their response to H2 and CO. For the 1% doped films, the results show the observed sensitivity to be due to a reaction of these trace gases with chemisorbed oxygen ions on the surface of the semiconductor. For the 10% doped SnO2 films, however, the dominant mechanism of sensitivity seems to be the dissociation reaction of these trace gases on the semiconductor surface.

Auger electron spectroscopy (AES) spectra are presented for Cu ternary chalcopyrite compounds. CuInS2, CuInSe2, and CuInTe2 thin films, bulk polycrystalline, and single-crystal samples are examined and their AES spectra are compared. The validity of quantitative analysis methods [(1) calibration with Ag-standard, (2) utilization of sensitivity factors, and (3) calibration with specific ternary standards] is examined and the results are compared. Consistent results are obtained for polycrystalline (bulk and thin film) samples, but not for the single-crystal cases. It is found that peak width variations must be considered in the single-crystal data which vary due to diffraction channeling effects. Calculations, taking these variations into account, yield the expected results.

CdS-CuInSe2thin-film solar cells are examined by Auger electron spectroscopy The effects of device fabrication and post-deposition procedures on the depth-compositional profiles and the performance of these photovoltaic devices are presented. The temperature dependence of the grain boundary diffusion coefficient of Cd from the CdS layer into the CuInSe2film is determined experimentally.

AbstractGreenhouse experiments were conducted to study the influence of K on CO2 assimilation, growth, and morphological characteristics of alfalfa (Medicago sativa L.). Yield increases were consistently obtained with high K. Added K increased plant height. The rate of leaf accumulation, leaf size, and weight per unit area also increased as did stomatal number and aperture. More and larger epidermal cells per leaf were observed with high K nutrition. Net photosynthesis rates of excised leaves increased with K application. Leaves from plants with added K had lower CO2 compensation points, indicating higher efficiency of CO2 assimilation under limiting CO2 conditions.

In experiments with reed canarygrass, white clover, and alfalfa, efficiency of leaves of different ages was measured in terms of growth and CO 2 uptake. Reed canarygrass plants with upper leaves remaining grew more rapidly than those with lower leaves. Plants with only one bottom leaf remaining grew slower than completely defoliated plants. White clover plants with 1‐ or 2‐week old leaves produced more dry matter and absorbed more CO 2 than plants with 3‐ or 4‐week old leaves. Leaves taken from the bottom of alfalfa plants in a 4‐week old stand were about half as efficient in CO 2 uptake as top leaves. Bottom leaves were light saturated at lower intensities than top leaves. Data presented in this paper indicate that leaf age is an important consideration in the manipulation of LAI for increased yields.