Showing papers by "Georgia Institute of Technology published in 1978"

Hints on Test Data Selection: Help for the Practicing Programmer

Abstract: In many cases tests of a program that uncover simple errors are also effective in uncovering much more complex errors. This so-called coupling effect can be used to save work during the testing process.

Methods for Estimating Wind Speed Frequency Distributions.

Abstract: The Weibull function is discussed for representation of the wind speed frequency distribution. Methods are presented for estimating the two Weibull parameters (scale factor c and shape factor k) from simple wind statistics. Comparison is made with a recently proposed method based on the “square-root-normal” distribution with mean wind speed and fastest mile data as input statistics. The Weibull distribution is shown to give smaller root-mean-square errors than the square-root-normal distribution when fitting actual distributions of observed wind speed. Another advantage of the Weibull distribution is the available methodology for projecting to another height the observed Weibull distribution parameters at anemometer height.

A behavioral approach to occupational safety: pinpointing and reinforcing safe performance in a food manufacturing plant.

Abstract: The behavior analysis approach was used to improve worker safety in two departments in a food manufacturing plant. Desired safety practices were identified, permitting construction of observational codes suitable for observing workers' on-the-job performance over a 25-week period of time. The intervention consisted of an explanation and visual presentation of the desired behaviors, as well as frequent, low-cost reinforcement in the form of feedback. A withinsubject (multiple baseline) design was used. Employees in the two departments substantially improved their safety performance from 70% and 78% to 96% and 99%, respectively, after the staggered introduction of the program. During the reversal phase, performance returned to baseline (71% and 72%). It was concluded that the intervention, particularly the frequent feedback, was effective in improving safety performance. Not only did employees react favorably to the program, but the company was later able to maintain the program with a continuing decline in the injury frequency rate. The results suggest that behaviorally denning and positively reinforcing safe practices is a viable approach to occupational accident reduction.

Basic theory of probe-compensated near-field measurements

Abstract: The general problem concerning the interaction of a probe antenna with the near field of an arbitrary antenna is considered. The application of the Lorentz reciprocity theorem to the problem of determining antenna characteristics, including the far-field pattern, is presented. The data required to correct for the directional effects of the probe, the effect of probe correction on the measured data, and the attendant mathematical computations in rectangular systems are described. Extensions to cylindrical and spherical systems are discussed.

What is a "Distributed" Data Processing System?

Abstract: Words have only one purpose in a technical context–the transmission of information. When they fail to do that, they lead to confusion and misunderstanding. "Distributed data processing" and "distributed processing" are two phrases which illustrate that axiom. Like many other words in the lexicon of the computer professional, these have become cliches through over-use, losing much of their original meaning in the process. This paper is an attempt to reverse that trend.

Diffraction efficiencies of thin phase gratings with arbitrary grating shape

Abstract: Diffraction by thin refractive-index gratings of arbitrary periodic shape is treated. Three analytical approaches are indicated and are shown to be equivalent. Resultant expressions for the diffraction efficiencies are given for all diffracted orders.

Two-pupil synthesis of optical transfer functions

Abstract: Incoherent optical spatial filtering systems have a number of advantages over their coherent counterparts; however, they are limited in their conventional form to operating with nonnegative–real input, output, and pointspread distributions. Most serious is the limitation to nonnegative–real impulse responses. A broad class of hybrid methods is investigated that employs two pupils in the synthesis of bipolar–real impulse responses. The mathematical structure of these syntheses is presented along with limitations in the presence of various constraints. Minimization of image plane bias is considered. Methods for implementation are described and categorized.

Applications of probe-compensated near-field measurements

Abstract: The theory of near-field measurements for antenna practitioners is summarized, and the measurement procedures in three coordinate systems, namely rectangular, cylindrical, and spherical are outlined. Specific topics include probe characterization, measurement systems, data reduction, and attendant accuracies. The results of recent studies are also summarized, and some brief remarks on future applications of near-field measurements in the laboratory, the production line, and in field testing and evaluation conclude the paper.

Sex Differences in Job Satisfaction: A Re-examination.

Abstract: This study was designed to test the hypothesis that observed sex differences in job satisfaction are due not to the influence of sex per se, but rather to the effects of several variables which covary with sex. Biographical and job satisfaction (Job Descriptive Index) data were obtained from 154 male and 326 female state government employees. Significant observed differences (male greater than female) in satisfactions with promotions and work “washed out” when the effects of age, education, tenure in organization, tenure in present position, and four cross-product variables were held constant through analysis of covariance. However, a nonsignificant observed difference (female greater than male) in satisfaction with pay was greatly magnified (to significance) through analysis of covariance. The hypothesis received only partial support, since a significant difference in overall job satisfaction remained after the effects of the covariate variables were partialled out. Alternative explanations for the reversal in the direction of the difference in overall job satisfaction are discussed.

Glass Transitions in Lubricants: Its Relation to Elastohydrodynamic Lubrication (EHD)

Abstract: A preliminary investigation into the possible role of glass transition and glassy state behavior of lubricants in EHD contacts is reported. Measurements of the glass transition of lubricants as a function of pressure by two methods are presented along with a discussion indicating possible implications of the results to EHD lubrication.

An evaluation of pore structure by mercury penetration

Abstract: The pore structure of graded series of controlled pore glasses and Nuclepore membranes—both materials having pores with right-cylinder characteristics—were assessed by electron microscopy and mercury penetration. From comparisons of results, parameters in mercury penetration theory were evaluated, the correction for compressibility was examined, the cause of hysteresis was explored, and the general accuracy of the technique was appraised.

Interlaminar Stresses in Symmetric Composite Laminates

Abstract: Interlaminar stresses and displacements of each layer satisfying geo metrical boundary conditions are represented in series of Legendre poly nomials The extended Galerkin procedure is used for each layer, and the final solutions are obtained by requiring the satisfaction of continuity conditions at each interface and the stress boundary conditions at exterior planes A computer program has been prepared, and numerical results are presented and compared with existing data

Probabilistic formulation of the emergency service location problem.

Abstract: The problem of locating emergency service facilities is studied under the assumption that the locations of incidents (accidents, fires, or customers) are random variables. The probability distribution for rectilinear travel time between a new facility location and the random location of the incident Pi is developed for the case of Pi being uniformly distributed over a rectangular region. The location problem is considered in a discrete space. A deterministic formulation is obtained and recognized to be a set cover problem. Probabilistic variation of the central facility location problem is also presented.

Separation of Hydrodynamic, Entropy, and Combustion Noise in a Gas Turbine Combustor

Abstract: This paper deals with noise sources which are centra! to the problem of core engine noise in turbopropulsion systems. The sources dealt with are entropy noise and direct combustion noise, as well as a nonpropagating psuedosound which is hydrodynaniic noise. It is shown analytically and experimentally that a transition can occur from a combustion noise-dominant situation to an entropy noise-dominant case if the contraction of a terminating nozzle to the combustor is high enough. In the conibustor tested, entropy noise is the dominant source for propagationai noise if the combustor is choked at the exit. It is also speculated that there might be another unexplored noise source interior of the combustor. Analysis techniques include spectral, cross spectral, correlation, and ordinary and partial coherence analysis. Measurements include exterior and interior fluctuating and mean pressures and temperatures. T has been known for some time that there are at least two probable causes for core noise—entropy or indirect noise and direct combustion noise.! Direct combustion noise is caused by a fluid dilatation caused by a fluctuating heat release. Entropy noise is caused by hot (or cold) spots passing through the pressure gradients of. the turbine assembly. Both noise sources have the same fundamental cause—heat release fluctuations—but they are formed in a different manner. Entropy noise depends upon the heat release history following a fluid element through the combustor, whereas combustion noise depends on the instantaneous aggregate heat release rate fluctuation. The purpose of this program was to isolate the two suspected causes of core noise and determine their relative importance to the core noise problem. It is clear that core noise presents a noise floor in current turbopropulsion systems, but there is controversy concerning the strength of core noise relative to other sources.2'4 It is sufficient to remark here that core noise exists and is measurable. Entropy and combustion noise are not the only possibilities for core noise. Another possibility is vorticity- nozzle interaction nose,5 which is essentially a resistance of a nozzle to pass an axial velocity fluctuation. While sources other than entropy and combustion noise are not directly investigated here, the analysis techniques do reveal whether or not entropy and combustion noise are dominant over other sources. The analysis techniques presented essentially try to relate processes taking place inside a combustor to the noise radiated to the surroundings. One troublesome problem encountered in a prior program6 was the contamination of interior pressure fluctuation measurements by non- propagating psuedosound (hydrodynamic noise). Another purpose of this paper was to eliminate this contaminant as much as possible in order to concentrate on propagationai sound and its causes.

Diffraction regimes of transmission gratings

Abstract: The diffraction characteristics of phase, absorption, and mixed transmission gratings of arbitrary thickness, modulation, and shape are treated. Single-wave, two-wave, and multiwave diffraction regimes are quantified and discussed. Boundaries between these regimes and their relationships to elementary “thin” and “thick” grating theories are presented.

A kinetics study of the reactions of OH with several aromatic and olefinic compounds

Abstract: The reactions of hydroxyl radicals with eight substituted aromatic hydrocarbons and four olefins were studied utilizing the flash photolysis–resonance fluorescence technique. The rate constants were measured at 298°K using either Ar or He as the diluent gas. The values of the rate constants (k × 1012) in the units of cm3/molec. sec are (a) OH + o-xylene products: (12.9±3.8), 20 torr He; (13.0±0.3), 20 torr Ar; (12.4±0.1), 200 torr He; (b) OH + m-xylene products: (15.6±1.4), 3 torr Ar; (19.4±0.8), 20 torr Ar; (21.4±0.2), 20 torr He; (20.3±1.9), 200 torr Ar; (20.6±1.3), 200 Torr He; (c) OH + p-xylene products: (8.8±1.2), 3 torr Ar; (10.1±1.0), 20 torr He; (10.5±0.6), 200 torr He; (d) OH + ethyl benzene products: (7.50±0.38), 3 torr He; (7.06±0.26), 20 torr He; (7.95±0.28), 200 torr He; (e) OH + n-propylbenzene products: (6.40±0.36), 20 torr He; (5.86±0.16), 200 torr He; (f) OH + isopropylbenzene products: (7.79±0.40), 200 torr He; (g) OH + hexafluorobenzene products: (0.221±0.020), 20 torr He; (0.219±0.016) 200 torr He; (h) OH + n-propyl pentafluorobenzene products: (2.52±0.54), 3 torr He; (3.01±0.76), 20 torr He; (3.06±0.24), 200 torr He; (i) OH + propylene products: (25.6±1.2), 20 torr He; (26.3±1.2), 200 torr He; (j) OH + 1-butene products: (29.6±1.9), 3 torr He; (29.4±1.4), 20 torr He; (k) OH + cis-2-butene products: (43.2±4.1), 3 torr He; (42.6±2.5), 20 torr He; (l) OH + tetramethylethylene products: (56.9±1.3), 20 torr He.

The effect of additional variables on factor indeterminacy in models with a single common factor

Abstract: “Determinate” solutions for the indeterminate common factor ofp variables satisfying the single common factor model are not unique. Therefore an infinite sequence of additional variables that conform jointly with the originalp variables to the original single common factor model does not determine a unique solution for the indeterminate factor of thep variables (although the solution is unique for the factor of the infinite sequence). Other infinite sequences may be found to determine different solutions for the factor of the originalp variables. The paper discusses a number of theorems about the effects of additional variables on factor indeterminacy in a model with a single common factor and draws conclusions from them for factor theory in general.

Lectures on algebraic system theory: Linear systems over rings

Abstract: The presentation centers on four classes of systems that can be treated as linear systems over a ring. These are: (1) discrete-time systems over a ring of scalars such as the integers; (2) continuous-time systems containing time delays; (3) large-scale discrete-time systems; and (4) time-varying discrete-time systems.

Improving the Performance Effectiveness of Groups Through a Task-Contingent Selection of Intervention Strategies

Abstract: A framework is presented for selecting general intervention strategies based on an analysis of the group task. Using this framework, studies which have tried to assess the effects of various intervention strategies on group performance are reviewed and findings shown to be consistent with predictions made by the framework; seemingly contradictory findings are shown to be reconcilable.