Showing papers by "Missouri University of Science and Technology published in 1984"

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

Abstract: Analyse mathematique de l'interaction entre la convection naturelle et le rayonnement thermique dans un ecoulement de couche limite laminaire sur une plaque horizontale isotherme. Presentation de resultats numeriques pour des gaz avec une valeur du nombre de Prandtl de 0,7

Radiative transfer in a two-dimensional rectangular medium exposed to diffuse radiation

Abstract: The integral equation for radiative transfer in a two-dimensional rectangular scattering medium exposed to diffuse radiation is solved numerically by removing the singularity. This method yielded accurate results except at very large optical thicknesses. Graphical and tabular results for the source function, flux, and intensity are presented. The source function is also calculated using the first term of a Taylor series expansion. The Taylor series is fairly accurate for small optical thicknesses and columnar geometries. A method is presented for extending these results to the problem of a strongly anisotropic scattering phase function which is made up of a spike in the forward direction superimposed on an isotropic phase function.

Acoustic nonlinearities and power losses at orifices

Abstract: Acoustic power losses occur when high-amplitude sound waves impinge on an orifice in the absence of mean flow. Described is a simple theoretical model of these losses, in which a harmonic, linear acoustic field is coupled to a nonlinear hydrodynamic flowfield at the orifice. Experimental and theoretical data on power losses at orifices with both pc and flanged acoustic terminations are compared, and fairly good agreement is noted. The structure of the flowfield in the neighborhood of the orifice is broadly described and some quantitative comparisons are made between the measured translational velocity of the ring vortices shed from both sides of the orifice and theoretical predictions. Again, the theory is seen to give generally reasonable results.

Dugdale plastic zone size and CTOD equations for the compact specimen

Abstract: With the aim of applying the Dugdale model to the compact specimen, the equations for stress intensity factor and crack surface displacement are obtained for a pair of pin loads and a uniform stress acting on a segment of the crack surface. The plastic zone size is calculated from the 'finiteness' condition of Dugdale, and the results agree well with collocation results from Terada (1983). The load that causes incipient yielding at the compression point of the compact specimen is calculated from a finite element strip yield analysis for an elastic-perfectly plastic material. The crack tip opening displacement for the compact specimen is calculated by adding the displacement at the tip of the physical crack length due to the pin load and due to the uniform stress. The results are within 1.5 percent of current collocation results.

Resonant Electron Transfer and Excitation in Two-, Three-, and Four- Electron Ca q + 20 and V q + 23 Ions Colliding with Helium

Abstract: Significant new evidence is reported for resonant transfer and excitation in ion-atom collisions. This process, which is analogous to dielectronic recombination, occurs when a target electron is captured simultaneously with the excitation of the projectile followed by photon emission. Strong resonant behavior with structure, in agreement with theoretical calculations, is observed in the cross section for projectile $K$ x rays coincident with single electron capture for 100-360-MeV $_{20}\mathrm{Ca}^{16+,\phantom{\rule{0ex}{0ex}}17+,\phantom{\rule{0ex}{0ex}}18+}$ and 180-460-MeV $_{23}\mathrm{V}^{19+,\phantom{\rule{0ex}{0ex}}20+,\phantom{\rule{0ex}{0ex}}21+}$ ions colliding with helium.

Polymerization of para‐xylylene derivatives (parylene polymerization). I. Deposition kinetics for parylene N and parylene C

Abstract: Kinetic aspects of parylene N [unsubstituted poly(para-xylylene)] and Parylene C [monochlorosubstituted poly(para-xylylene)] were studied. The conversion of starting material (dimer of either p-xylylene or chloro-para-xylylene) to polymer is quantitative (ca. 100%). Consequently, the total polymer formed in a closed system is directly proportional to the amount of dimer charged. However, the percentage of the total amount of polymer formed which deposits on substrate surfaces, placed in the deposition chamber, as well as the polymer film growth rate are dependent on operational factors such as the temperature of the substrate, sublimation of dimer temperature, flow pattern of the reactive species, etc. Parylene C, being a heavier and more polar molecule, has the tendency to deposit easily in the deposition chamber compared to the deposition of Parylene N. Parylene C also has a higher ceiling temperature for deposition than Parylene N. This situation has been investigated from the viewpoint of excess thermal energy which hinders polymer formation (deposition) due to the exceedingly high entropy change necessary for polymer deposition to occur. The addition of a cool (i.e., room temperature) inert gas was shown to increase the deposition of Parylene N on substrate surfaces placed in the deposition chamber. The deposition increase and acceleration of deposition (film growth) rate were found to be related to the size and molecular weight of the inert gas pressure maintained in the system. The accelerating effect is explained by the increase in third-body collisions to dissipate the excess thermal energy of the reactive species.

Oxidation-reduction behaviour of La-doped SrTiO3

Abstract: Thermogravimetric measurements as a function of oxygen activity were performed in the temperature range of 1200 to 1400° C on a series of lanthanum SrTiO3 compounds. A model which assumes the absorption of excess oxygen in the structure which compensates the donors by formation of cationic defects is postulated. Comparison of this model with the experimental results show reasonable agreement.

Glass formation and properties in the gallia-calcia system

Abstract: The critical cooling rate for glass formation was measured for five compositions in the Ga2O3-CaO system and varied from a low of (315 + or - 85) C/s for a eutectic melt containing 37.5 mol pct Ga2O3 to a high of (840 + or - 60) C/s for a melt containing 52 mol pct Ga2O3. The density and refractive index both increased with increasing Ga2O3 content, but the crystallization temperature and microhardness varied only slightly. The IR spectra of these glasses suggest that both GaO4 tetrahedra and GaO6 octahedra are present.

Removal of naturally occurring compounds by coagulation and sedimentation

Abstract: Naturally occurring compounds are defined as all nonsynthetic materials of constant composition. The emphasis in this review is placed on the removal of humic materials, other organic compounds, trace metals, and certain inorganic ligands. Removal of the alkaline earths is not reviewed. Associations between different compounds, or between compounds of interest and naturally occurring particulates, are important and complex. In this context, the formation and removal of such aggregates is reviewed. As a result, the removal of particles by coagulation and settling is briefly discussed. The removal of certain synthetic compounds is also reviewed, to the extent that removal of such compounds is dependent on the removal of naturally occurring compounds. Both inorganic and organic coagulants are considered.

Concurrent Evaluation of Career Indecision and Indecisiveness

Abstract: Career indecision is reconceptualized as a complex, multidimensional problem composed of an undecided state and an indecisive trait.

The application of spline functions to trajectory generation for computer-controlled manipulators

Abstract: This paper describes how cubic spline functions may represent both the trajectory of the tool tip of the manipulator hand in three space and the trajectories of the manipulator joints in time. Mathematically, the curve is continuous through the second derivative providing continuous velocity and acceleration functions for the tool tip moving along its trajectory. The boundary conditions for liftoff and setdown of tool tip are also accommodated. This approach offers flexibility, computational efficiency, and a compact representation

Evaporite diapirs in the La Popa basin, Nuevo León, Mexico

Abstract: Reconnaissance mapping and stratigraphic work in the La Popa basin of Nuevo Leon, northern Mexico, has revealed two large structural features with cores of gypsum and anhydrite at the surface. These features are interpreted to be the surface expression of evaporite diapirs. They are exposed in folded sedimentary rocks belonging to the Potrerillos Formation of the Difunta Group of Maastrichtian age (Late Cretaceous). Sandstone units within the Potrerillos Formation pinch out toward the piercement features. Carbonate lentils composed of rudistid reefs and associated carbonate clastics flank the features and pinch out away from the features into marine shale members of the Potrerillos Formation. Most carbonate lentils occur in the immediate vicinity of the evaporite features and are interpreted to be genetically related to the diapirs. Syndiapiric sedimentary-facies patterns can be documented over 4,000 vertical feet (1,200 m) of section within the Potrerillos Formation. The large vertical extent of facies peculiarities near the piercement features indicates that the features were active for an extended period corresponding to at least two regressive-transgressive cycles during Maastrichtian time. A radial drainage pattern away from the northern feature indicates that the features are probably active today. A limestone inclusion from within one of the features has been dated as Kimmeridgian in age (Zuloaga or Smackover equivalent) and suggests that the evaporites are probably derived from the Jurassic Minas Viejas Formation. It is not known at present whether salt underlies the surface crust of gypsum and anhydrite. At the time that the first syndiapiric sediments of the Potrerillos Formation were deposited, the Minas Viejas Formation was buried at an estimated depth of 17,000 ft (5,200 m). The thick pre-Laramide cover, the pre-Laramide age of at least some of the syndiapiric sedimentary features, and the location of stocks away from major anticlines indicate that the emplacement of the diapirs is not related to Laramide compression. Geostatic loading is considered to be the most important mechanism for emplacement of the domes.

Finite plane strain deformations of nonlinear viscoelastic rubber-covered rolls

Abstract: SUMMARY ~ Finite deformations of a nonlinear viscoelastic rubber layer bonded to a uniformly rotating rigid cylinder and indented by anoth~r rigid cylinder are studied by the finite element method. The problem formulation includes both material and geometric nonlinearities. The effect of the change in the thickness of the layer, its speed of rotation and its material properties on the pressure distribution at the contact surface, and other aspects of the deformation of the layer, are studied. ( I q l' INTRODUCTION I Rubber-covered roll covers similar~o}he,set-up shown in Figure I are used in the paper-mill industry and the textile industry. In these and other applications of the roll covers, a relatively thin rubberlike layer bonded to a cylindrical. core made of a consiqerably harder material is indented by another cylinder also made ofa hard material. Typically, the iridentot and the core are made of steel or granite. The maximum principal strain induced in the rubberlike layer in these applications seems to exceed 20 per cent. Also, depending upon how the rubber was cured and other factors (such as the environmental temperature), the rubberlike layer may behave viscoelastically. Earlier, Batra2 studied the deformations of these roll covers wherein the rubber has been modelled as a nonlinear elastic material. Herein we assume that the rubberlike layer can be modelled as a nonlinear viscoelastic material and study its finite deformations. We assume that sufficient time has e1apsed since the start-up of the operation for the transient effects to die down and consequently we study the steady-state problem wherein the rubberlike layer has a constant angular velocity of.o rad/sec. We briefly review some of the previous work done on this and other related problems. For the case of infinitesimal deformations of the rubberlike layer presumed to be made of a Hookean material, Hahn and Levinson2 used the Airy stress function to solve the problem. They also showed that the effect of Coulomb friction at the contact surface on the deformations of the layer was negligible for moderate values of the coefficient of friction. Soong and Li3 used the same Airy stress function, but used the point-matching method rather than the Gralil-Schmidt . orthonormalization method used by Hahn and Levinson. In a later paper,4 Soong and Li

Crystallization of calcia-gallia-silica glasses

Abstract: A thermal image furance is presently used to study the critical cooling rate for glass formation, and the kinetics of crystallization, of the compositions 18.4CaO-(81.6-X)Ga2O3-XSiO2, where X = 3, 6, 9, and 13.8. Crystallization was studied nonisothermally, and the data were analyzed in light of the Avrami (1939) equation. Critical cooling rate and crystallization activation energy are both found to decrease with increasing silica content, and the results obtained by the present technique are noted to agree with those obtained on the basis of differential thermal analysis measurements.

Exact Formulation of Multiple Scattering in a Three-Dimensional Cylindrical Geometry

Abstract: Exact expressions for the source function, flux, and scattered intensity normal to the surface are developed in cylindrical coordinates for a three-dimensional, absorbing, emitting, isotropically scattering medium exposed to both diffuse and collimated radiation. Simplifications of these expressions for certain important geometries and uniform loading are presented. Also, superposition of these equations and radiative equilibrium are discussed. The generalized three-dimensional equations are shown to reduce to the familiar one-dimensional 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.

Thermal Impact of Residential Ground‐Water Heat Pumps

Abstract: A computer simulation study was conducted to quantify the potential thermal impact of residential water-source heat pump usage on ground-water aquifers. In a first phase of the study, weather data for nine locations throughout the country were used to estimate the energy requirements for heating and air conditioning a typical residence. These energy requirements were then translated into the volumetric water demands for a selected heat pump at each location. A representative model aquifer was then defined and its characteristics used, along with the heat pump water requirements and design ΔT's (difference between inlet and outlet water temperature) to identify the important parameters that contribute to heat transfer and to model the movement of the thermal front resulting from injection of heat pump discharge water at the nine locations. The major factor that determines the heat pump thermal impact was found to be the net amount of heat injected into, or removed from an aquifer. Other significant factors included well design, heat pump design ΔT, and physical properties of the aquifer such as thickness, porosity and dispersivity. The study showed that, in climates where winter heating demand is very nearly equal to summer cooling demands, the injection of heat pump discharge water did not cause any significant modification of the ambient model aquifer temperature. However, in hot or cold climates where air conditioning or heating demand dominates, measurable thermal changes occurred in the model aquifer. In most cases, the maximum temperature