Showing papers by "Missouri University of Science and Technology published in 1972"
TL;DR: In this article, the two-way array interaction model with one observation per cell is discussed and the model is given by Likelihood ratio tests are presented for two hypotheses: (1) no interaction (λ = 0) and (2) equality of treatments (τ1 = τ2 = … = τt).
Abstract: In this article the two-way array interaction model with one observation per cell is discussed. The model is given by Likelihood ratio tests are presented for two hypotheses: (1) no interaction (λ = 0) and (2) equality of treatments (τ1 = τ2 = … = τt). Also maximum likelihood estimators are given for all parameters including σ2 when λ ≠ 0.
208 citations
01 Nov 1972-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the early stages of cellular precipitation in quenched and aged alloys were investigated using light and electron microscopy observations of the early stage of cellular formation. But the early development of cellular cells was not investigated.
Abstract: The morphology of cellular precipitation in a Cu-9.5 at. pet In alloy has been investigated by light and electron microscopy. Both cellular and general precipitation were observed to occur simultaneously in quenched and aged alloys while only cellular precipitation was observed to occur in isothermally aged alloys. Because of the presence of wide, solute rich, precipitate free zones in the vicinity of grain boundaries in the quenched and aged alloys, the early development of cellular precipitation was found to be identical for both types of heat treatment. From light and electron microscopy observations of the early stages of cellular precipitation a mechanism for the formation of cells was developed. At the start of aging, the unoccupied grain boundary begins to migrate under the influence of grain boundary migration forces as if it were in a single phase alloy. As the boundary migrates, solute segregates along it to form allotriomorphs which pin the boundary. The boundary continues to migrate and bows between the simultaneously forming allotriomorphs. With further aging, the allotriomorphs lengthen following the bowing boundary and the allotriomorphs become the initial precipitate lamellae of the developing cell as a steady-state lamellar structure develops. Assuming that the critical step in the development of a cell is the ability of the boundary to bow between the initial allotriomorphs, a criterion for the occurrence of cellular precipitation was developed.
190 citations
TL;DR: Carbonaceous chondrites contain two isotopically distinct components of trapped xenon which cannot be explained by the occurrence of nuclear or fractionation processes within these meteorites.
Abstract: Carbonaceous chondrites contain two isotopically distinct components of trapped xenon which cannot be explained by the occurrence of nuclear or fractionation processes within these meteorites.
142 citations
TL;DR: In this article, a 16-sublattice model was developed to determine the ordering temperatures and the asymptotic Curie temperature in terms of the exchange integrals.
Abstract: A molecular field treatment of the B-site spinel was used to determine the ordering temperatures and the asymptotic Curie temperature in terms of the exchange integrals. The theory was developed from a 16-sublattice model and took into account interactions between an atom and its nearest to fourth-nearest neighbors. Experimental values of the ordering temperatures and the asymptotic Curie temperature were then used to determine the exchange integrals for the systems Hg1−xCdx Cr2 S4, CdCr2S4(1−y)Se4y, and Zn1−xCdxCr2Se4.
95 citations
TL;DR: In this article, the effect of oxygen activity on the sintering of high-purity Cr2O3 is shown, and the theoretical density is approached at the equilibrium O2 partial pressure needed to maintain the Cr2 O3 phase (Po2=2×10−12 atm).
Abstract: The effect of oxygen activity on the sintering of high-purity Cr2O3 is shown. Theoretical density was approached at the equilibrium O2 partial pressure needed to maintain the Cr2O3 phase (Po2=2×10−12 atm). The presence of N2 in the atmosphere during sintering did not prevent final sintering. The addition of 0.1 wt% MgO at this equilibrium pressure effectively controlled the grain growth and further increased the sintered density to very near the theoretical value. The solute segregation of MgO at the grain boundaries, followed by nucleation of spherulites of magnesium chromite spinel on the boundaries, accounted for the grain-growth control. It is speculated that these isolated spherulites locked the grain boundaries together, changing the fracture mode of the sintered oxide from inter-to intragranular and also that larger MgO additions produced a more continuous spinel formation at the boundaries, resulting in decreased sintered density. Weight loss, which was also monitored as a function of O2 activity, correlated with the changing predominant volatile species in the Cr-O system.
94 citations
TL;DR: In this paper, internal friction and Na and K self-diffusion coefficients for (I-X)Na2OXK2O-3SiO2 glasses were measured and it was concluded that the mechanism of mixed-alkali internal friction is cooperative rearrangement of dissimilar alkali ions.
Abstract: Internal friction and Na and K self-diffusion coefficients for (I–X)Na2OXK2O-3SiO2 glasses were measured. Alkali diffusion was measured between 300° and 500°C using radioactive isotopes and a thin-sectioning technique; internal friction was determined at room temperature to 500°C at 0.1 to 2000 Hz. Comparison of the data for alkali diffusion and internal friction in Na-K glasses with those for other mixed-alkali glasses shows that the mixed-alkali peak is related to alkali mobility. It is concluded that the mechanism of mixed-alkali internal friction is cooperative rearrangement of dissimilar alkali ions, with the slower-moving ion controlling the rate of reorientation.
74 citations
TL;DR: In this paper, a study was made on the plasma polymerization of styrene monomer in a cold, low-power, inductively coupled RF plasma, and it was found that the initiation step was the rate controlling step and that the reaction followed a cationic polymerization scheme.
Abstract: A study has been made on the plasma polymerization of styrene monomer in a cold, low-power, inductively coupled RF plasma. Styrene monomer yielded an insoluble, crosslinked film which was slightly colored. A kinetic study is reported for styrene. The effects of power level, bleed rate of monomer, pressure, and reactor geometry on the rate of polymer formation are reported. A mechanism is postulated for plasma polymerization. It was found that the initiation step was the rate controlling step and that the reaction followed a cationic polymerization scheme. Both crosslinking and discoloration of the polymers occur at the time of polymerization and are not a result of exposure of the reacted polymer to the plasma. The polymerization was shown to take place in the bulk phase as well as on the reaction wall surfaces.
65 citations
TL;DR: In this article, an induction-coupled RF field was used to allow vinyl-type monomers to polymerize at ambient temperatures in the presence of an inductively coupled RF field.
Abstract: An apparatus was constructed which would allow vinyl-type monomers (and others) to polymerize at ambient temperatures in the presence of an inductively coupled RF field. The details of the construction of the system are reported along with preliminary results obtained from nine monomers: styrene, methylvinyldichlorosilane, vinyl acetate, acrylonitrile, vinyl fluoride, 1,1-difluoroethylene, vinyl chloride, ethylene, and 1,3-butadiene.
58 citations
TL;DR: In this article, the lattice parameters, thermal expansion coefficients and Gruneisen parameters of silicon are determined by an X-Ray diffraction method in the temperature range of 180-40 K without the use of liquid gases.
53 citations
01 Jan 1972
48 citations
TL;DR: The isotopic composition of xenon in four different samples of tellurobismuthite, Boliden, Sweden, of varying tellurium content was reported in this paper.
01 Apr 1972
TL;DR: In this paper, a molecular model for the prenucleation water clusters is proposed with a view toward resolving some of the difficulties caused by statistical mechanical correction factors to a basically thermodynamic theory, which destroy much of the agreement with experiment in the case of water vapor.
Abstract: The tranquility of classical homogeneous nucleation theory has been disturbed by the introduction of statistical mechanical correction factors to a basically thermodynamic theory. These factors, which appear to be essential, destroy much of the agreement with experiment in the case of water vapor. A molecular model for the prenucleation water clusters is proposed with a view toward resolving some of these difficulties. As a first step, the properties of a few specific cluster configurations have, been examined. Clathrate-like structures containing 16 to 57 water molecules are discussed. The hydrogen bonds were treated as simple harmonic oscillators for the purpose of calculating normal mode frequencies. The Helmholtz free energy of formation of the cluster is calculated from the appropriate partition functions. For these clathrate-like structures the free energy of formation was not found to be a smoothly increasing function of the number of molecules but showed minima corresponding to closed cages.
TL;DR: The results indicated that noise-intensity and display-difficulty level were significantly interrelated with respect to detection speed but not to detection error.
Abstract: The purpose of the present study was to determine the effects of continuous white noise on visual target-detection performance. The variables manipulated were noise-intensity level, display-difficulty level, and target location. Four noise levels were utilized: 0, 80, 90, and 100 db. The 0-db. level served as the control condition. Display difficulty was defined in terms of the number of nontarget, or background, display elements. Three levels of difficulty were used: 8, 16, and 32 background letter characters. The target locations examined were the central and peripheral regions of the visual display. Twenty subjects were tested under all conditions. Both detection time and detection error were recorded. The results indicated that noise-intensity and display-difficulty level were significantly interrelated with respect to detection speed but not to detection error.
TL;DR: In this paper, a computer simulation of the ordered Fe3Al lattice was devised to simulate radiation damage, a selected atom was given a known kinetic energy in a predetermined direction.
Abstract: A computer simulation of the ordered Fe3Al lattice was devised. This lattice array consisted of 559 atoms interacting with two-body forces. To simulate radiation damage, a selected atom was given a known kinetic energy in a predetermined direction. The damage threshold in the [100] direction was found to be 22 eV while in the [110] direction the threshold was 44 eV. Vacancies and interstitials were found to be the normal stable defects, the interstitial residing in the split configuration oriented in the [110] direction. Replacement chains were prevalent in the [100] and [110] directions. Focusons served as the primary mechanism for dissipating energy from the collision chains in the [110] and [111] directions. Along a defocusing chain the energy dissipation appears to resemble a thermal spike, while near the end of the chain, especially in the [111] direction, there is an extensive lattice expansion due to energy dissipation which appears to give a plasticity spike. Disordering in the ordered al...
TL;DR: The addition of small amounts of certain materials to fluids undergoing turbulent flow causes a reduction on pressure drop called drag reduction as mentioned in this paper, which has been shown to be beneficial in many applications.
Abstract: THE addition of small amounts of certain materials to fluids undergoing turbulent flow causes a reduction on pressure drop called drag reduction. Polymer solutions, soap solutions and solid suspensions in liquids and gases have all demonstrated this phenomenon1.
TL;DR: In this paper, the authors quantitatively predict increased work function changes for adsorption of silicon and boron on tungsten substrates using a resonance-tunneling model.
TL;DR: In this article, the abundance of iodine and uranium in sedimentary rocks was determined by neutron activation analyses, showing that the iodine content is higher in the sediments than in igneous rocks and the iodine concentrations follow the same general pattern as chlorine and bromine.
01 Jun 1972
TL;DR: In this paper, a model based on the dynamics of a dislocation stacking fault configuration (DSFC) was proposed to describe previous data as well as their own observations of a sharp decrease of the elastic constants of a Fe-28 wt pct Ni alloy just prior to the onset of the transformation.
Abstract: The martensitic transformation involves, at least partly, a shear deformation of the parent lattice. Because the assumption that the martensitic transformation represents a macroscopic shear instability of the parent solid is at variance with experimental observations, the shear instabilities must be microscopic in nature. A model based on the dynamics of a dislocation stacking fault configuration (DSFC) adequately describes previous data as well as our own observations of a sharp decrease of the elastic constants of a Fe-28 wt pct Ni alloy just prior to the onset of the transformation. In terms of this model, theMs temperature represents the temperature at which the dislocation stacking fault configuration becomes thermodynamically unstable. In terms of the present harmonic approximation, the unhindered expansion of the DSFC will therefore trigger the martensitic transformation.
TL;DR: In this paper, the wave-induced movement of oil lenses and other floats was studied by using mechanically generated gravity waves in a water tank, and the measured surface drift velocities were in all cases higher than those predicted by the Stokes theory of deep water waves.
Abstract: The wave-induced movement of oil lenses and other floats was studied by using mechanically generated gravity waves in a water tank. The measured surface drift velocities were in all cases higher than those predicted by the Stokes theory of deep water waves. For wave conditions at which the Stokes velocity is higher than 2 cm sec−1, the measured surface velocities were 35–150% higher than the Stokes velocity. The drift velocity was insensitive to float size when the float length was larger than one wavelength. Thin, flexible, plastic floats were found to have the same drift speed as similarly sized oil lenses. A discussion of the movement of oil spills on the open ocean is included.
TL;DR: In this article, the authors introduced protons into the surface of an Li2O·Al2O3·2SiO2 glass fiber (0.5 mm in diameter) by ion exchange in NH4HSO4 at 366°C for 21 hours.
Abstract: Protons were introduced into the surface of an Li2O·Al2O3·2SiO2 glass fiber (0.5 mm in diameter) by ion exchange in NH4HSO4 at 366°C for 21 h. Infrared absorption measurements established that the protons were associated with bridging oxygen ions. After ion exchange, the magnitude of the alkali internal friction peak decreased and a new peak appeared at ∼220°C. This new peak is attributed to the interaction of alkali and hydrogen ions, independent of the presence of nonbridging oxygen ions.
TL;DR: In this paper, the local radiative flux in an isothermal spherical layer is systematically investigated and the functions h 1 (τ; τ 1 ) τ 2 and h 2 (τ, τ, τ 1, τ 2 ) τ2, analogous to the planar functions E3(τ−τ1) and E3 (τ2−τ), are studied and tabulated.
Abstract: The local radiative flux in an isothermal spherical layer is systematically investigated. The functions h 1 (τ; τ 1 ) τ 2 and h 2 (τ; τ 1 , τ 2 ) τ 2 , analogous to the planar functions E3(τ−τ1) and E3(τ2−τ), are studied and tabulated. Limiting solutions are presented and evaluated. The radiative flux from an isothermal spherical layer is presented in graphical and tabular form. A comprehensive review of radiative transfer in a spherical geometry is performed.
TL;DR: In this article, the authors report experimental results for channel multipliers in magnetic fields of up to 300 G and find that the applied voltage must be increased to about 4000 V to maintain a sufficiently high gain.
Abstract: The gain and total count rate of electron channel multipliers depend strongly on applied magnetic fields. We report experimental results for Channeltrons operated in magnetic fields of up to 300 G, and find that the applied voltage must be increased to about 4000 V to maintain a sufficiently high gain. Slightly higher count rates are observed if the magnetic field is parallel to the plane of the Channeltron, as compared to perpendicular to that plane.
TL;DR: In this article, a curve fitting technique has been applied to extract relative singlet-triplet cross sections for levels within the (2p 5 )3s configuration of Neon, and the results are compared with previous optical measurements of the emissian cross sections of lines from these levels as ex+ + cited by H and He impact.
Abstract: The technique of heavy-ion energy-loss spectrometry has been used to measure excitation cross sections for the 5 5 . (2p )3s and (2p )3p electron1c configurations of Neon. + + + The incident particles used were H , H2 and He at impact energies from 20-180 keV. The results are compared with previous optical measurements of the emissian cross sections of lines from these levels as ex+ + cited by H and He impact. Agreement is not good, either in shape or in absolute magnitude for excitation of the (2p 5 )3s configuration. However, agreement is surprisingly good for excitation of the (2p 5 )3p configuration. A curve fitting technique has been applied to extract relative singlet-triplet cross sections for levels within the (2p 5 )3s configuration. Almost no trip+ + let excitation is observed for H and H2 impact. The former is expected while the latter is somewhat surprising. Significant triplet excitation is observed only for He+
TL;DR: In this paper, the radiative lifetime of the A2Π state of CO+ for the vibrational levels υ′ = 1, 2, 3, 4, 5, and 6 have been measured at six pressures.
Abstract: The radiative lifetime of the A2Π state of CO+ for the vibrational levels υ′ = 1, 2, 3, 4, 5, and 6 have been measured at six pressures. The lifetimes extrapolated to zero pressure were 3.97±0.12, 4.11±0.27, 3.16±0.57, 3.95±0.09, 4.11±0.27, and 3.98±0.12 μs, respectively. The corresponding oscillator strengths for the (1,0), (2,0), (3,0), (4,0), (5,0), and (6,0) transitions were 0.458 × 10−3, 0.659 × 10−3, 0.682 × 10−3, 0.571 × 10−3, 0.409 × 10−3, and 0.259 × 10−3, respectively.
TL;DR: In this paper, the use of the epsilon method is demonstrated and a method of solution using the Rayleigh-Ritz representation and a modified Newton-Raphson minimization is described.
Abstract: The use of Balakrishnan's epsilon method is demonstrated. Whereas most optimization schemes are based upon exact satisfaction of the system dynamics and penalty for terminal error, the epsilon method is based upon exact satisfaction of the terminal conditions and penalty for erroneous dynamics. Thus theoretical aspects of the epsilon method are discussed, a method of solution using the Rayleigh-Ritz representation and a modified Newton-Raphson minimization is described, and an optimization problem is solved. Finally, advantages and disadvantages of the epsilon method are discussed.
TL;DR: In this article, the internal friction and the Li and Na concentration profiles were measured in an ion-exchanged glass for 1 to 300 min in an NaNO3 bath at 366°C.
Abstract: Fibers of Li2O.Al2O3.2SiO2 glass were ion-exchanged for 1 to 300 min in an NaNO3 bath at 366°C. The internal friction and the Li and Na concentration profiles were measured. As Na progressively replaced Li, the alkali internal friction peak became smaller while a new peak (mixed-alkali peak) appeared and increased in magnitude. These changes in internal friction are similar to those that occur when a second alkali is added to glasses prepared by conventional melting. The magnitudes of both internal friction peaks in the ion-exchanged glass depended on the overall composition of the glass; that of the alkali peak depended on the composition of the unexchanged glass core, whereas that of the mixed-alkali peak depended on the composition of the exchanged layer on the glass surface. When the exchanged surface layer was dissolved, the original alkali peak was restored, and the mixed-alkali peak disappeared. Changing the alkali distribution did not affect the mixed-alkali peak much; however, it caused the alkali peak to shift to higher temperatures and become smaller. The height of the alkali peak can be used to determine the maximum depth of penetration of the second alkali.
TL;DR: In this paper, low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) methods were used to characterize the (111) surface of Si wafers before and after the deposition of P2 molecules.