Showing papers by "Missouri University of Science and Technology published in 1982"

When can we introspect accurately about mental processes

Abstract: Some theorists have suggested that the cognitive processes determining a person’s perforance in a given task are unconscious, making introspection a poor research tool for studying these processes. Others have argued that the relevant processes usually are consciously conrolled and can be detailed by asking the person to introspect. Here, a synthesis of these two positions, a dual-factor approach, is proposed. Some of the processes involved in achieving a cognitive goal, such as learning a new concept, are viewed as unconscious and automatic; howver, other processes are intentionally allocated conscious attention, in certain tasks, to accomlish othe goal. To illustrate this dual-factor position, evidence is presented in support of the view that when concept learning occurs solely by automatic frequency processing, introspective reports are inaccurate, but when the nature of the task prompts intentional hypothesis testing, introspective reports are accurate, revealing clues that subjects engage in a conscious hypothesisesting strategy.

Molecular treatment of electron capture by protons from the ground and excited states of alkali-metal atoms

Abstract: Electron-capture cross sections for ${\mathrm{H}}^{+}$ plus alkali-metal atom (Na, K, Rb, and Cs) systems have been computed for projectile energies from 10 eV to 10 keV. An impactparameter perturbed-stationary-state theory using molecular states that incorporate electron translation factors was used to calculate the cross sections. The wave functions were generated by employing the pseudopotential method. These yield equilibrium parameters ${R}_{e}$ and ${D}_{e}$ for the $A^{2}\ensuremath{\Sigma}^{+}$ molecular state that are in good agreement with ab initio results. Interaction energies are also presented for the Li${\mathrm{H}}^{+}$ system. Basis sets of up to eight molecular states were used to calculate the electron-capture cross sections from ground ($\mathrm{ns}$) as well as from the first excited ($\mathrm{np}$) states of the alkali-metal atoms. Results for electron capture from the ground-state alkali-metal atom are in good agreement with the recent experiments of Nagata. Electron capture from excited alkali-metal ($\mathrm{np}$) atoms does not yield enhanced cross sections relative to capture from the ground state and, in fact, shows decreased cross sections for the heavy alkali-metal atoms. Such behavior is contrary to predictions made using arguments based on the magnitude of the energy gap $\ensuremath{\Delta}E$ to the electron-capture product states.

Conversion and Matched Filter Approximations for Serial Minimum-Shift Keyed Modulation

Abstract: Serial minimum-shift keyed (MSK) modulation, a technique for generating and detecting MSK using series filtering, is ideally suited for high data rate applications provided the required conversion and matched filters can be closely approximated. Lowpass implementations of these filters as parallel inphase- and quadrature-mixer structures are characterized in this paper in terms of signal-to-noise ratio (SNR) degradation from ideal and envelope deviation. Several hardware implementation techniques utilizing microwave devices or lumped elements are presented. Optimization of parameter values results in realizations whose SNR degradation is less than 0.5 dB at error probabilities of 10-6.

Exact expressions for radiative transfer in a three-dimensional rectangular geometry☆

Abstract: The equations for the source function, flux, and scattered intensity normal to the surface are formulated in cartesian coordinates for a 3-D rectangular absorbing, emitting, isotropically scattering medium exposed to both diffuse and collimated radiation. Simplifications of these equations for certain important geometries and uniform loading are presented. Also, superposition of these equations and radiative equilibrium are discussed. For pure scattering, the source function at the center of the square and cubic geometries is analytically determined for the diffuse boundary condition. The generalized 3-D equations are shown to reduce to the familiar 1-D results. Also, the equations for a strongly anisotropic phase function which is made up of a spike in the forward direction superimposed on an otherwise isotropic phase function are expressed in terms of the isotropic expressions.

An Analytical Method for Quantifying the Electrical Space Heating Component of a Cold Load Pick Up

Abstract: After an extendfed cold weathler outage on a distribution circuit sumnplying a high satulration o-electrical sn-ace heating, large transient overcurrents persist for several hours because of the undiversified heating load . In this paper, the electrical space heating component of enduring demand is chlaracterized by a smooth curve. Expressions are derived for tlhe parameters of the curve in terms of the outage conditions and a statistical description of the residences. A method is suggested for using this characterization to deternine the effects of a cold load pick-up on the distribution circulit components.

Role of various water clusters in IR absorption in the 8–14-μm window region

Abstract: A controversy exists over the cause of the IR absorption in the 8–14-μm wavelength window region. One explanation for the continuum absorption is to consider the accumulation of the far wings of strong water monomer absorption lines. On the other hand, other researchers believe that the IR absorption originates from the water dimer complex. Some other researchers claim that either water clusters of larger size or hydrated aerosols are responsible for the continuum absorption. Here we explore the hitherto less-understood systems of water clusters, both homomolecular and heteromolecular, including the water dimer, to enhance our knowledge of the cause of the IR absorption. The present study indicates that homomolecular water clusters larger than the dimer are not responsible for the continuum absorption.

A Monte Carlo Method for Approximating Critical Cluster Size in the Nucleation of Model Systems

Abstract: A formalism is presented for estimating critical cluster size as defined in classical models for nucleation phenomena. The method combines Bennett's Monte Carlo technique for determining free-energy differences for clusters containingn andn- 1 atoms with the steady state nucleation rate formalism. A simple form for the free energy of formation of then cluster [including a termA (n)n2/3] is used to predict critical cluster size and critical supersaturation ratio, S*. This approach is applied to Lennard-Jones vapor clusters at 60 K. Results for free-energy differences for the 13, 18, 24, and 43 clusters predict a critical cluster size of 70 ± 5 atoms at a critical supersaturation ratio given bylnS*=2,45 0.15. This method is intended to provide estimates of critical cluster size for more ambitious attempts to calculate cluster free energies or for initializing conditions in microscopic simulations of nucleating systems.

Thermally Stimulated Currents and Alkali-Ion Motion in Silicate Glasses

Abstract: The thermally stimulated polarizatioddepolarization (TSPC/TSDC) current technique is used to investigate alkali-ion motion in silicate glasses. lbo TSDC peaks are observed in all these glasses along with the dc conduction current at high temperatures. The low-temperature TSDC peak magnitude is essentially constant, but the second TSDC peak magnitude varies with the type of alkali ion present in these glasses. Based on a proposed model, the two TSDC peaks are interpreted in terms of the localized alkali-ion motion around the nonbridging oxygen ion and through the limited conduction pathways, respectively.

Atomic Interfacial Mixing to Create Water Insensitive Adhesion

Abstract: The concept of Atomic Interfacial Mixing (AIM) is suggested to account for the enhanced water-resistant adhesion of plasma-deposited polymer to various substrate materials. The interfacial interactions were achieved using several techniques involving two basic methods. One method involves using ion implantation to modify the interface. The second method involves manipulation of the plasma discharge conditions to control plasma/substrate interactions. A variety of experimental techniques yields results which provide strong support for the concept of AIM.

Production of highly charged rare-gas recoil ions by 1.4-MeV/amu U 4 4 +

Abstract: Recoil-ion-production cross sections in rare gases are measured for 1.4-MeV/amu ${\mathrm{U}}^{44+}$ ions and are calculated for 1-5-MeV/amu projectiles in charge state 44 + with the use of the classical-trajectory Monte Carlo method and the independent-electron model. The calculations reasonably predict the net-charge-production cross sections, which exceed ${10}^{\ensuremath{-}13}$ ${\mathrm{cm}}^{2}$ for the heavy rare gases; the calculations are found to underestimate the cross sections for low-charge-state recoil ions and to overestimate the cross sections for high-charge-state recoil ions. The experimental cross sections for production of highly charged recoil ions are found to be large, e.g., greater than 1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$ for production of ${\mathrm{Ne}}^{8+}$, ${\mathrm{Ar}}^{10+}$, ${\mathrm{Kr}}^{12+}$, and ${\mathrm{Xe}}^{18+}$.

Predicting Viscoelastic Response and Delayed Failures in General Laminated Composites

Abstract: Although graphite fibers behave in an essentially elastic manner, the polymeric matrix of graphite/epoxy composites is a viscoelastic material which exhibits creep and delayed failures. The creep process is quite slow at room temperature, but may be accelerated by higher temperatures, moisture absorption, and other factors. Techniques are being studied to predict long-term behavior of general laminates based on short-term observations of the unidirectional material at elevated temperatures. A preliminary numerical procedure based on lamination theory is developed for predicting creep and delayed failures in laminated composites. A modification of the Findley nonlinear power law is used to model the constitutive behavior of a lamina. An adaptation of the Tsai-Hill failure criterion is used to predict the time-dependent strength of a lamina. Predicted creep and delayed failure results are compared with typical experimental data.

Effect of Surface Energetics of Substrates on Adhesion Characteristics of Poly (p-xylylenes)

Abstract: In investigating the effect of the surface energetics of substrate materials on the adhesion characteristics of poly(p-xylylene) and poly(chloro-p-xylylene) by the “Scotch Tape” method, it was found that if the substrates had not been preconditioned (treated with argon or a methane plasma), the adhesion was poor. The characteristics of water resistant adhesion that were observed when coated substrates were boiled in 0.9% sodium chloride solution were found to vary from excellent (when the polymer did not peel from the substrate after three cycles of 8 hours of boiling and 16 hours at room temperature) to poor (when the polymer peeled off almost immediately). It was noticed that water resistant adhesion depends on the hydrophobicity of the substrate material (the greater the hydrophobicity, the greater the adhesion) and is not related to the dry adhesive strength of poly(p-xylylene). The oxygen glow discharge treatment of the substrates decreased both the dry and wet adhesive strength of the polym...

Plasma polymerization of hexafluoroethane

Abstract: It was found that when hydrogen is mixed in a plasma, hexafluoroethane polymerization is accelerated. ESCA and IR spectroscopy were used to characterize the resulting polymers and to reveal the reaction mechanism. At relatively low hydrogen/hexafluoroethane ratios and radio-frequency powers of 30 and 100 W (13.56 MHz), no hydrogen could be detected in the polymers with IR spectroscopy. However, after the ratio had increased above one, the hydrogen content increased abruptly. Thus, hydrogen might be looked upon as a sort of scavenger for active fluorine species. ESCA deconvolution analysis of the C1s peaks of the polymers indicated that the polymer structures were uniform throughout the reactor in the hydrogen/hexafluoroethane system at 30 W, even though the distribution of the deposition rate could still be observed. By examining sodium chloride powder exposed to the plasma with IR spectroscopy, it was possible to detect various fluorosilicates, which indicated ablation of the reactor's glass wall by the plasma.

On Prediction Limits for Samples From a Weibull or Extreme-Value Distribution

Abstract: A new, simplified approximation for lower prediction limits is derived for the smallest of a set of future observations from a Weibull or extreme-value distribution. The proposed limit can be expressed explicitly in terms of estimates of the location and scale parameters of the extremevalue distribution and the variances and covariance of the estimates.

Two-dimensional isotropic scattering in a finite thick cylindrical medium exposed to a laser beam

Abstract: Graphical and tabular results are presented for the back-scattered intensity from a finite two-dimensional cylindrical medium exposed to a Gaussian beam of radiation. Also, results for the source function and flux at the boundaries are presented. The influence of optical thickness and albedo are most pronounced at large optical radii. The semi-infinite results can be used to approximate the finite case for small optical radii. Ranges for single, double, and multiple scattering are discussed. For locations far from the incident beam, the results can be expressed in terms of universal functions independent of beam size. A method is presented for extending the isotropic results to the anisotropic case where the phase function is made up of a spike superimposed on an otherwise isotropic phase function.

Natural convection - Radiation interaction in boundary layer flow over horizontal surfaces

Abstract: A numerical model is developed for natural convection-radiation interaction in the boundary layer over a semi-infinite horizontal flat plate with one hot and one cold surface. The fluid is assumed to be gray, to emit, absorb, be nonscattering, and constant with a density variation in the vertical direction, which induces a buoyancy force. Two-dimensional, boundary-layer equations are defined, and the radiative heat flux is simplified using a Rosseland approximation. Conservation equations are transformed into a system of nonlinear ordinary differential equations which can be solved simultaneously with a Runge-Kutta integration scheme, along with the Newton-Raphson shooting technique. The thermal radiation is found to enhance the wall shear stress and the surface heat transfer rate on both the hot and cold sides