Showing papers by "Missouri University of Science and Technology published in 1983"

Optical properties of the metals Al, Co, Cu, Au, Fe, Pb, Ni, Pd, Pt, Ag, Ti, and W in the infrared and far infrared

Abstract: Infrared optical constants collected from the literature are tabulated. The data for the noble metals and Al, Pb, and W can be reasonably fit using the Drude model. It is shown that -epsilon1(omega) = epsilon2(omega) approximately omega(2)(p)/(2omega(2)(tau)) at the damping frequency omega = omega(tau). Also -epsilon1(omega(tau)) approximately - (1/2) epsilon1(0), where the plasma frequency is omega(p).

Analysis of the Isolated Induction Generator

Abstract: The increasing rate of depletion of conventional energy resources and the ability of induction generators to convert mechanical power over a wide range of rotor speeds have given rise to an interest in the possible contribution of wind energy to provide fuel displacement.

Mechanisms for alkali leaching in mized-NaK silicate glasses

Abstract: The kinetics of alkali removal from (1-X) Na2O·XK2O·3SiO2 glasses were studied using pH stat titration techniques, solution analyses, and elemental depth profiling by Rutherford backscattering spectrometry and elastic recoil detection. In the first stage of leaching ( t 1 2 kinetics), the interdiffusion coefficients measured for the exchange of alkali cations by H3O+ are orders of magnitude greater than the alkali diffusion coefficients in bulk glass and show no evidence of the mixed-alkali effect. At longer times, the rate of alkali removal becomes constant with time, but selective alkali leaching is still observed rather than uniform dissolution. These results support a model where the rate determining step for alkali leaching is the rate at which molecular water diffuses into the glass.

Homogeneous nucleation rate measurements for water over a wide range of temperature and nucleation rate

Abstract: An expansion cloud chamber was used to measure the homogeneous nucleation rate for water over a wide range of temperature from 230–290 K and nucleation rates of 1–106 drops cm−3 s−1. The comprehensive and extensive nature of this data allows a much more detailed comparison between theory and experiment than has previously been possible. The expansion chamber technique employs continuous pressure measurement and an adiabatic pulse of supersaturation to give the time history of supersaturation and temperature during the nucleation. The resulting drop concentration is determined using photographic techniques. The experimental observations are presented in tabular form and from them an empirical nucleation rate formula is determined: J=S2 exp[328.124−5.582 43T+0.030 365T2−5.0319E−5T3 −(999.814−4.100 87 T+3.010 84E−3 T2)ln−2S], where J is the nucleation rate in units of drops cm−3 s−1. S is the supersaturation ratio and T is the temperature in K.

Linear inversion method to obtain aerosol size distributions from measurements with a differential mobility analyzer

Abstract: The use of a differential mobility analyzer to perform aerosol size spectrum measurements requires an inversion method to go from the measured sensor responses to the desired size spectrum information. Here we present a linear inversion method that can be run on a microcomputer or a small minicomputer. It does not use some of the approximations made in the techniques currently available and hence gives better inversion accuracy. The method shows good immunity to both random and systematic experimental error. It is applied to numerous test case aerosols.

Uniqueness of locally optimal quantizer for log-concave density and convex error weighting function

Abstract: It is desired to encode a random variable X using an N -level quantizer Q to minimize the expected distortion E \rho(|X-Q(X))I) , where the error weighting function \rho is convex, strictly increasing and continuously differentiable. It is shown that if X has a log-concave density, then there exists a unique locally optimal quantizer Q \ast and Lloyd's Method I may be used to find Q \ast . Trushkin had earlier shown this result for the error weighting functions \rho (t) \equiv t and \rho(t) \euiv t^{2} .

Ion-atom differential cross sections at intermediate energies

Abstract: The classical-trajectory Monte Carlo method has been used to calculate ${\mathrm{H}}^{+}+\mathrm{H}(1s)$ electron-capture and ionization differential cross sections in the range 25-200 keV. The results indicate the importance of including excited product states to describe the small-angle electron-capture scattering. Angular scattering of the electron removed by the ionization process has been studied as a function of ejected-electron velocity ${v}_{e}$. The classical calculations are in reasonable agreement with coupled-channel results of Shakeshaft [Phys. Rev. A 18, 1930 (1978)] as to the "electron capture to the continuum" (ECC) component of the ionization process where this term is defined as the ejected electron being more closely centered to the projectile than the target nucleus after the collision. The ECC cross section ${\ensuremath{\sigma}}_{\mathrm{ECC}}$ was studied as a function of collision energy (50-500 keV/amu) and projectile charge state ($q=1\ensuremath{-}10$). At high energies, ${\ensuremath{\sigma}}_{\mathrm{ECC}}$ scales as $\frac{{q}^{2.3}}{{E}^{2.5}}$. The maximum value for ${\ensuremath{\sigma}}_{\mathrm{ECC}}$ was determined to be an energy ${E}_{max}\ensuremath{\cong}(56 \frac{\mathrm{keV}}{\mathrm{amu}}){q}^{0.4}$. Restricting the ECC component to small electron-scattering angles, ${\ensuremath{\theta}}_{\mathrm{lab}}\ensuremath{\le}5\ifmmode^\circ\else\textdegree\fi{}$, and electron-ejection velocities ${v}_{e}={v}_{p}(1.0\ifmmode\pm\else\textpm\fi{}0.1)$, where ${v}_{p}$ is the projectile velocity, indicates this process is a minor component of the total ionization cross section at intermediate energies.

A Numerical Procedure for Predicting Creep and Delayed Failures in Laminated Composites

Abstract: A numerical procedure is described for predicting the viscoelastic response of general laminates. A nonlinear compliance model is used to predict the creep response of the individual laminae. A biaxial delayed failure model predicts ply failure. The numerical procedure, based on lamination theory, increases by increments through time to predict creep compliance and delayed failures in laminates. Numerical stability problems and experimental verification are discussed. Although the program has been quite successful in predicting creep of general laminates, the assumptions associated with lamination theory have resulted in erroneous bounds on the predicted material response. Delayed failure predictions have been conservative. Several improvements are suggested to increase the accuracy of the procedure.

Thermochemical excess properties of multicomponent systems: Representation and estimation from binary mixing data

Abstract: A general equation for the estimation of thermodynamic excess properties of multicomponent systems from observed excess properties of the various binary combinations of the components has been developed, based on a simple model of the multicomponent system. This estimation takes the form $$\Delta \bar Z_{12...N}^{ex} = \sum\limits_{i = 1}^N {\sum\limits_{j > i}^N {(X_i + X_j )(f_i + f_j )(\Delta \bar Z_{ij}^{ex} )^* } } $$

Solar abundances of the elements

Abstract: The isotopic compositions of noble gases in the solar wind show high enrichments of light isotopes. When corrected for mass fractionation all five noble gases there can be resolved in terms of the two primitive noble gas components that have been identified in planetary solids. Reasons are presented for assigning the fractionation to a solar process that selectively enriches lighter nuclei at the surface of the Sun. When abundances of the elements at the Sun's surface are corrected for this fractionation, it is shown that atomic abundances for major elements in the bulk Sun are (in decreasing order): Fe, Ni, O, Si, S and Mg. Solar elements at about the 1% atomic abundance level include He, C, Ne, Ca and Cr. These results suggest that fusion of hydrogen is probably not the Sun's primary energy source.

Helical shear of an elastic, circular tube with a non-convex stored energy

Abstract: In 1949, in one of his pioneering studies on large elastic deformations, Rivlin [1] applied the general theory of non-linear elasticity for an incompressible, isotropic, homogeneous body to study the helical shearing of a circular tube for a Mooney material. Approximately 25 years later, Ogden, Chadwick & Haddon [2] reconsidered this problem in some detail for more general materials, but in neither of these works was there an emphasis placed upon the structure of the stored energy function and, in particular, on its convexity. In the present work, we wish to emphasize the case of a non-convex stored energy function and the related emergence of equilibrium states with discontinuous deformation gradients. It is most convenient to consider the problem as one of minimization, and we shall seek to characterize the uniqueness, existence, and detailed structural properties of an absolute minimizer.

The effects of certain impurities and their interactions on zinc electrowinning

Abstract: The effects of germanium, antimony, arsenic, cobalt, glue, and free acid concentration were studied on both commercial and synthetic electrolytes. The effects of a single factor and the combined effects of multiple factors were elucidated. The temperature, zinc concentration, and current density were varied for some of the tests. It was found that the acid content was the most critical factor when impurity levels were at normal plant solution concentrations. The ranges where the effect of the impurity became apparent were: greater than 20 ppb (parts per billion) for antimony; 40 ppb for germanium; 120 ppb for arsenic; and 7 to 8 mg/1 for cobalt for a solution containing 65 g/1 zinc and 100 g/1 free sulfuric acid. At higher levels of acid, the acceptable level of impurity declined markedly. Glue additions were found to counteract the effects of antimony and germanium, but did little to counteract the effects of cobalt and arsenic. The level of acid was found to be especially critical when cobalt and arsenic were in the electrolyte. Cobalt and arsenic exhibited synergism, and lower current efficiencies were obtained for arsenic-cobalt combinations than expected. A factorially designed experiment was conducted to quantify the effects observed by one-factor-at-a-time testing. The structures and morphologies of the deposits were examined using X-ray diffraction and scanning electron microscopy.

Anomalous diffusion of vapors through solid polymers. Part I: Irreversible thermodynamics of diffusion and solution processes

Abstract: The solubility and diffusivity of vapors in polymers below and in the vicinity of glass transition temperature are known to be explicitly time-dependent. It is assumed here that the polymers are in nonequilibrium states, characterized by an internal order. The latter relaxes with time and moves towards equilibrium. The changes in the internal order bring about changes in the properties of the polymer-solute system. The time dependence of diffusivity and solubility has been derived for isothermal processes not far from equilibrium. Well-known procedures for analyzing relaxing systems are used to obtain the above results, and the knowledge of how the internal order is related to the molecular properties is not required.

Electrical properties of plasma-polymerized thin organic films

Abstract: The electrical properties of plasma-polymerized films are summarized and compared to those of conventional polymers. Particular attention is devoted to the dielectric relaxation, dielectric breakdown, electric conductivity and photoconductivity, and their control via control of the plasma parameters.

Study of the iron-phosphorus-oxygen system by Moessbauer effect, neutron diffraction, magnetic susceptibility, and analytical electron microscopy: some pitfalls and solutions in the analysis of a complex mixture

Abstract: Caracterisation de FePO 4 par diffraction de rayons X et de neutrons (coordonnees atomiques). Mise en evidence d'un melange de FePO 4 cristallin, d'une phase amorphe de composition approchee Fe 3 P 5 O 17 et du compose a valence mixte Fe 7 (PO 4 ) 6 , dont les proportions respectives sont determinees par effet Mossbauer. Mise en ordre magnetique de FePO 4 a 23,8 K, de la phase amorphe a 7 K, la 3eme phase restant paramagnetique jusqu'a 10 K d'apres les spectres Mossbauer; confirmation par mesures de susceptibilites magnetiques

Thermochemical investigations of nearly idial binary solvents. 6. Solubilities of iodine and benzil in systems of nonspecific interactions

Abstract: Solubilities have been determined at 25°C for iodine in binary mixtures of carbon tetrachloride with cyclohexane, n-hexane, n-heptane, and octamethylcyclotetrasiloxane (OMCTS) and in mixtures of cyclohexane with n-hexane and OMCTS; and for benzil in binary mixtures of carbon tetrachloride with cyclohexane, n-hexane, and n-heptane, mixtures of n-hexane with cyclohexane and n-heptane, and mixtures of benzene with cyclohexane and toluene. With the exception of the benzene+cyclohexane system, the nearly ideal binary solvent model predicts these solubilities with a maximum deviation of 6% and an overall standard deviation of 2.4%. The model correctly predicts minima for solubility (mole fraction) of iodine in the OMCTS systems, and predicts solubilities within 4% for benzil in the carbon tetrachloride+n-hexane system, in which the solubility changes by a factor of 14. The failure of the model for predicting solubilities of benzil in mixtures of benzene and cyclohexane (maximum error of 25% for and 18-fold range of solubilities) is possibly due to specific interactions between benzil and benzene.

Kalman filter formulation of low-Level television image motion estimation

Abstract: The problem of television image motion estimation is formulated as an application of Kalman filter theory. The nonuniform image motion present in a television scene is represented as the state variable of a randomly driven difference equation. A new approach is then introduced for linearizing measurement equations that arise in low-level image velocity estimation. Kalman filter theory is applied to the problem of optimally solving the nonuniform motion estimation problem based upon the image motion model and the linearized measurement equations.

Ion scattering from state-selected Rydberg atoms

Abstract: Classical-trajectory Monte Carlo calculations have been performed for collisions of protons with state-selected hydrogenic Rydberg atoms. The examples investigated were Rydberg atoms in the $n=10$, $l=9$ level with ${m}_{l}=0 \mathrm{and} 9$. The collision velocity range was 0.1 to 1.0 a.u. (2.2\ifmmode\times\else\texttimes\fi{}${10}^{7}$ to 2.2\ifmmode\times\else\texttimes\fi{}${10}^{8}$ cm/s). The ionization cross sections were found to be relatively insensitive to changes in the ${m}_{l}$ levels. However, the charge-transfer cross sections showed considerable enhancement if the Rydberg electron is orientated in a plane which is parallel to the direction of the incident projectile.

Anomalous diffusion of vapors through solid polymers. Part II: Anomalous sorption

Abstract: Sorption of vapors in polymer membranes in the vicinity of and below the glass transition temperatures do not follow the Fickian (classical) diffusion. The reasons have been attributed to the molecular relaxation which affects both diffusivities and solubilities. A time- and memory-dependent diffusion coefficient has been evaluated in Part I, in a form which is analogous to the treatment in the rheology of such materials. Together with a time-dependent solubility, the conservation equation for the sorption process has been solved. Two special cases are considered, where the relaxation times are short and where they are long. The results explain the anomalous behavior observed in the experiments. Comparison with the experiments has been made.

Molecular treatment of charge transfer in Li + +Ca collisions

Abstract: The perturbed-stationary-state method, appended with electron translation factors, has been applied to charge transfer in ${\mathrm{Li}}^{+}$ +Ca collisions for energies from 0.1 to 20 keV/amu. The Born-Oppenheimer wave functions and eigenvalues were generated using the pseudopotential technique, which reduced the many-electron system to a simpler two-electron problem. The molecular ground-state $X^{1}\ensuremath{\Sigma}^{+}$ is calculated to be bound and has the potential-well parameters ${R}_{e}=6.20{a}_{0}$, ${D}_{e}=1.11$ eV, ${\ensuremath{\omega}}_{e}=235$ ${\mathrm{cm}}^{\ensuremath{-}1}$, and ${B}_{e}=0.263$ ${\mathrm{cm}}^{\ensuremath{-}1}$. From the scattering computations, a representative value for the charge-transfer cross section is 4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}15}$ ${\mathrm{cm}}^{2}$ at 5 keV/amu. The cross section decreases rapidly as the energy is reduced below 1 keV/amu. At all energies studied, the dominant electron-capture reaction product is the ground-state Li atom.

Interactions of Simple Ion-Atom Systems

Abstract: Publisher Summary This chapter discusses the interactions of simple ion–atom systems. The interactions of ion–atom systems provide a unique opportunity for experimental tests of the foundations of quantum scattering theory. In the collisions of simple ion–atom systems, comparison of the experimental and theoretical results tests the quantum mechanical model of the process in situations where the fundamental interaction forces are known. The simplest three-body collision system, which consists of a proton incident on a hydrogen atom, holds the key for understanding three-body collision physics. The experimental methods employed in the study of ion–atom collisions can be divided into two classes. The classes are distinguished by the particle detected after the collision process. In one case, the primary particle is detected. In the other case, a secondary particle is detected. The secondary particle may be a photon or an electron ejected from the target or the projectile, or the nucleus of the target.