Showing papers by "University of Houston published in 1977"

The search for organic substances and inorganic volatile compounds in the surface of Mars

Abstract: A total of four Martian samples, one surface and one subsurface sample at each of the two Viking landing sites, Chryse Planitia and Utopia Planitia, have been analyzed for organic compounds by a gas chromatograph-mass spectrometer. In none of these experiments could organic material of Martian origin be detected at detection limits generally of the order of parts per billion and for a few substances closer to parts per million. The evolution of water and carbon dioxide, but not of other inorganic gases, was observed upon heating the sample to temperatures of up to 500 C. The absence of organic compounds seems to preclude their production on the planet at rates that exceed the rate of their destruction. It also makes it unlikely that living systems that behave in a manner similar to terrestrial biota exist, at least at the two Viking landing sites.

Adaptive noise canceling applied to sinusoidal interferences

Abstract: This paper investigates a new method for eliminating sinusoidal or other periodic interference corrupting a signal. This task is typically accomplished by explicitly measuring the frequency of the interference and implementing a notch filter at that frequency. The method proposed herein uses an adaptive filter to eliminate the interference. The procedure is called adaptive noise canceling and is applicable when an auxiliary reference input is available containing the interference alone. The reference input is filtered in such a way that it closely matches the interfering sinusoid, and is then subtracted from the primary input leaving the signal alone. The results of this research show that when a sum of sinusoids is applied to an adaptive filter, the filter converges to a dynamic solution in which the weights of the filter are time varying. This time-varying solution implements a tunable notch filter, with a notch located at each of the reference frequencies. When used in noise-canceling applications, this adaptive notch filter provides a simple alternative to other methods of tracking and eliminating sinusoidal interferences.

Resonant frequency of a circular disc, printed-circuit antenna

Abstract: The resonant frequency is obtained in analytical form for a planar, circular disc antenna which is etched on a printed-circuit board so that the low-profile antenna is separated from the ground plane only by a thin layer of dielectric material. The formula is found to have an error of less than 2.5 percent when compared with experimental data.

Walsh operational matrices for fractional calculus and their application to distributed systems

Abstract: The Walsh operational matrix for performing integration and solving state equations is generalized to fractional calculus for investigating distributed systems. A new set of orthogonal functions is derived from Walsh functions. By using the new functions, the generalized Walsh operational matrices corresponding to √s, √(s2 + 1), e-s and e-√s etc. are established. Several distributed parameter problems are solved by the new approach.

On the factorization and fitting of molecular scattering information

Abstract: The reported analysis is based on the factored IOS T-matrix. It is shown that line shape measurements may be used over a range of temperatures to evaluate inelastic scattering cross sections. Basic factorization or parameterization relations are derived by considering the wavefunction equations. The parameterization of cross sections is considered, taking into account the differential scattering amplitude and cross section, integral cross sections, phenomenological cross sections for general relaxation processes, and viscosity and diffusion cross sections. Thermal averages and rates are discussed, giving attention to integral cross sections and rates, and general phenomenological cross sections. The results of computational studies are also presented.

Upstream influence on the near field of a plane turbulent jet

Abstract: The effects of the mean and turbulence characteristics of the upstream (initial) boundary layer on the evolution of the flow in the near field of a plane jet have been experimentally investigated for four initial conditions. Rates of jet widening and centerline mean velocity decay as well as the kinematic and geometric virtual origins show evidence of systematic dependence on initial conditions. The growth rate of longitudinal turbulence intensity, and the mass flux are higher when the initial boundary layer is laminar than when turbulent. Immediately downstream of the exit, the nondimensional entrainment rates for the laminar initial boundary layer cases reach peak values which are about twice the delayed peak values for the fully turbulent initial boundary layer cases. Within the first 40 slit widths, increases in total average streamwise momentum flux range from 20% to 56%, the larger increases occurring for the laminar initial boundary layers; about 10% of each increase is due to the turbulence field. While such increases violate the traditionally accepted momentum flux invariance, they are consistent with the negative mean static pressure data.

How to Ask Questions about Drinking and Sex: Response Effects in Measuring Consumer Behavior:

Abstract: This article reports a nationwide study of response effects based on answers from almost 1,200 respondents to threatening behavioral questions presented in various formats. Results indicate that th...

A Unified Analysis of Pseudonoise Synchronization by Envelope Correlation

Abstract: The problem of acquiring and maintaining synchronization of a pseudonoise code, particularly at low signal-to-noise ratios, is analyzed to determine the mean time to acquisition and the mean time to lose lock. An analysis procedure is developed which explicitly considers the search/lock strategy and the transition from search to lock. A practical example is included to demonstrate the technique.

Different Goal Setting Treatments and Their Effects On Performance and Job Satisfaction

Abstract: A field experiment was conducted to compare three goal setting treatments. Measures of four hard performance criteria and two job satisfaction indices were collected. The participation and assigned...

Saint-Venant’s Principle and End Effects in Anisotropic Elasticity

Abstract: The purpose of this paper is to draw attention to the fact that the routine application of Saint-Venant’s principle in the solution of elasticity problems involving highly anisotropic or composite materials is not justified in general. This is illustrated in the context of the plane problem of elasticity for an anisotropic rectangular strip loaded only on the short ends. For highly anisotropic transversely isotropic materials, the slow decay of end effects is demonstrated using a method involving self-equilibrating eigenfunctions. For a graphite/epoxy composite, for example, the characteristic decay length is shown to be approximately four times that for an isotropic material. The results have implications in the accurate measurement of mechanical properties of anisotropic materials.

Morphometric adaptation of the housefly, musca domestica l., in the united states.

Abstract: It has long been recognized that morphometric difference among geographic populations of a species can reveal modes of adaptation to environment and of eventual speciation. Most early studies of such variation were limited to few characters (e.g., Alpatov, 1929; Dobzhansky, 1933), and not until the advent of computers could large suites of characters be analyzed by appropriate techniques of covariation, such as principal component or factor analysis, to isolate and identify underlying patterns of morphogenesis (Blackith, 1960). The statistical revolution in geographic variation analysis, however, has not generated a similar revolution of insight into population dynamics, and for the most part, morphometric approaches have been abandoned by population biologists uninterested in systematics. A part of this problem is that few modern studies attempt to separate spatial from temporal aspects of variability or genetic causation from environmental induction of phenotype, typically present in early work (e.g., Goldschmidt, 1934; Stalker and Carson, 1947, 1948, 1949). This paper attempts to partition morphometric variation in the housefly, Musca domestica L., in the United States into temporal, spatial, and genetic components, and thereby elucidate the dynamics of adaptation to differing environments in this species. The lack of systematically recognized variatioi of the housefly in the United States offers reasonable assurance of common niche and habitat requirements of flies from widespread populations, so that sample partitions of variation can be compared to reveal trends of populational adaptation to changing environments. The essence of the methodology utilized here, paralleling an analysis of variance, was to collect flies from numerous localities throughout the United States, return to selected localities at the same times in subsequent years to assess year-to-year variation within sites, and then to follow at least one population throughout the year to determine a seasonal component of morphometric change. Thus variance components can be estimated at these various levels of potential variation, to discern underlying causes of morphometric adaptation. Comparisons among repeated collections within localities and between wild and laboratory reared flies were used to determine repeatability and consistency in patterns of covariation and to ascertain the extent of genetic commitment to morphometric response.

Shear requirements for load reversals on rc members

Abstract: Considerable experimental research on the influence of shear on the performance of flexural hinges under reversed loadings has been reported in the literature Using existing data, a means of making comparisons between test results is devised and design requirements for shear in members under reversed loading are suggested Results of 65 tests from six investigations are compared on the basis of modified work index, a measure of the hysteresis exhibited by the test specimens under load reversals Factors that significantly influenced the work index were level of axial force, shear span to depth ratio, and maximum applied shear stress Design recommendations for maximum shear stress and minimum transverse reinforcement are developed for satisfactory performance of hinging regions

An Empirical Test of Causal Inference Between Role Perceptions, Satisfaction with Work, Performance and Organizational Level.

Abstract: Previous research has suggested that organizational level may explain to a significant extent the differential impact of role perceptions (i.e., role ambiguity and role conflict) on employee satisfaction and performance. Causal inferences could not be drawn from these studies because of the predominant use of static correlational methods. In this study, in a hospital setting, a six-month time-lag between data collection periods was used to develop causal inferences. The results supported the hypothesis that role ambiguity was a source of causal inference with satisfaction with work at the higher organizational level, while role conflict was a source of causal inference with satisfaction with work at the lower organizational level. The source and direction of causal influence with respect to role perceptions and performance was supported only at the higher organizational level.

Characterization of bacterial growth by means of flow microfluorometry

Abstract: By means of flow microfluorometry, the protein and nucleic acid contents of individual bacterial cells may be measured at the rate of several thousand cells per second. Accumulation of such information over a few minutes yields the composition distribution of the microbial population. These distributions have been determined at different times during batch growth of Bactillus subtilis, and the results indicate that the variance of cell composition decreases as the population passes through the exponential into the stationary phase. The relative abundance of endospores and vegetative cells as well as the protein distributions of these subpopulations may be readily determined from flow microfluorometry data. Experimental access to such details of microbial population dynamics should foster improved understanding of cell growth, spore germination, and spore formation kinetics.