Showing papers by "Michigan Technological University published in 1970"

Mass Transfer Limitations in Substrate Removal

Abstract: The existence of an intraparticle diffusional resistance in the uptake of organic substrate by particles of zoogloeal floc is established by comparing the glucose and oxygen uptake rates for large floc particles with those exhibited by the same particles after blending. A zero order effectiveness factor model predicting the magnitude of this diffusional limitation in terms of the particle size distribution, particle shape, uptake rate, substrate concentration, and effective diffusivity of the substance within the particle is developed by considering a particle of biological floc to be analogous to a porous catalyst particle. Mean values for the effective diffusivity of glucose in the zoogloeal floc material ranged from about 7% to 9% of the corresponding values for glucose in water. Subjecting activated sludge floc particles to high turbulence in a laboratory blender caused a marked increase in the oxygen uptake rate. This phenomenon was apparently due to the solubilization of some sludge components.

Solid solution strengthening in Nb-Ta and Nb-Mo alloy single crystals

Abstract: The strength of Nb, Nb-Ta, and Nb-Mo alloys was investigated in tension and compression as a function of composition, temperature, and strain rate. The room-temperature properties show molybdenum to have a significant effect on the strength of niobium while the effects of tantalum are nearly zero. The room-temperature strength is shown to be well correlated with the atomic misfit parameter. Analysis of the low-temperature behavior of Nb-Ta alloys indicates that they behave similarly to the pure metal while Nb-Mo alloys show a marked deviation from this behavior. The strengthening phenomena occurring in the Nb-Mo alloys at low temperature is interpreted as being an impurity interaction. A transition between the mechanism operating in the pure metal and the impurity interaction occurs at low solute contents.

Wave propagation in thermoelastic solids at very low temperature

Abstract: The one-dimensional problem of an elastic half-space subjected to thermal and mechanical disturbances at its free surface is considered, using a generalized theory of the thermoelasticity which takes into account a finite velocity of propagation of thermal disturbances. An approximation of the general solution is obtained in closed form valid at temperatures near absolute zero, resulting in expresssions for temperature and strain response due to arbitrary inputs at the free boundary. These general expressions are applied to the particular problem of a step-strain input at the boundary and the results compared with previous work. The problem of a half-sine temperature pulse input is also treated.

Transpiration resistance in vaccinium myrtillus

Abstract: A B S T R A C T Measurements of transpiration resistance of Vaccinium myrtillus at various wind speeds indicate that this quantity is relatively insensitive to variations in wind speed in the range normally experienced under field conditions. The resistance is relatively low when compared with values reported in the literature for other plants. Placed in an identical environment, V. myrtillus plants from sunny sites were found to have measurably lower resistance and lower leaf temperatures than those from shady sites. Transpiration resistance appears to be inversely related to stomatal density. THIS INVESTIGATION of the transpiration resistance of the mountain blueberry Vaccinium myrtillus L. was made in connection with an ecological study of this plant in the Front Range of Colorado (Janke, 1968). One phase of the investigation was to determine how constant the transpiration resistance remains under the changing wind conditions which the plant normally experiences in the field. Another was to compare the transpiration resistance of plants found in the forest (shade plants) with those in the open (sun plants) under equivalent environmental conditions. Vaccinium myrtillus is a low shrub varying in height from 3-35 cm and spreading by horizontal rhizomes to form extensive clones. The leaves are small and elliptical, with an average length of 1.5 cm. In the Front Range of Colorado this species of blueberry comprises more than 95 % of the vascular plant ground cover in the sub

Feeder for high pressure autoclave

Abstract: A material handler for a high pressure autoclave includes a combination of a body and a dished in cross section material carrier relatively arranged in a telescoping manner. The material carrier can be withdrawn from the body to a carrying position or telescoped into the body to eliminate the volume of the carrier. The body and carrier move in a passage to alternately position the carrier at a material transfer opening or in the autoclave. The carrier is telescoped into the body after material is removed therefrom, and while still in the autoclave, to eliminate its volume and avoid transferring atmosphere from one position to the other. The body and carrier combination has a sealed engagement in the passage.

Evaluation of three-dimensional stresses in shrink-fit problems by scattered-light photoelasticity

Abstract: Stresses caused by shrink fits are commonly evaluated by using Lame's solution or by other analytical methods in which it is assumed that the radial stresses on the surface of contact are distributed uniformly, or in some stepwise manner, and that friction forces between the bodies are zero. These assumptions were not necessary in the experimental problem solved. Heretofore, no experimental techniques have been available to check the existing theories on a three-dimensional basis. The stresses which result when a short, hollow, thick-walled cylinder is shrunk over a shaft which is a solid shaft or a thick-walled, hollow shaft were determined. Equipment and techniques using scattered-light three-dimensional photoelasticity with a laser light source were developed and applied.

Apparatus for measuring angular rotation

Abstract: Relative angular rotation between two spaced areas on a rotatable member is converted to linear motion by providing a threaded engagement between two tubes each of which is connected to a respective one of said areas for rotational movement therewith. Relative rotation between the spaced areas causes relative rotation between the tubes and this is converted by the threaded engagement into axial or linear movement. This linear movement can then be converted into an electrical signal which can be registered or recorded by an electronic device. To increase the range of angular rotation which can be effectively measured, a third member is interposed between those already discussed. A threaded connection is provided between this third member and one of the first mentioned members and a pin and slot connection is provided between the third member and the other of the two first mentioned members. The pin and slot connection accommodates linear movement so that axial movement of the connections of the tubes at the spaced areas does not occur.

The Decay of 144Ce

Abstract: The energies and relative intensities of the gamma rays of 144 Ce have been determined with use of a Ge(Li) detector. The quantum energies are 33.7, 40.8, 53.4, 80.1, 99.8, and 133.5 keV, the associated relative intensities being 2.3±0.2, 5±4, 1.1±0.1, 16±1, 0.39±0.04, and 100±6. These data have been interpreted to indicate excited nuclear energy states in 144 Pr at 59.03, 80.1, 99.8 and 133.5 keV.

Mechanical Behavior of a Carbide Reinforced Co-Cr Eutectic Alloy

Abstract: The tensile and creep behavior of a unidirectionally solidified (Co, Cr)−(Cr, Co)7C3 monovariant eutectic alloy have been examined. The effect of fiber orientation on the tensile strength has been studied at temperatures to 2200°F. The composite was found to be anisotropic with considerable strengthening in the longitudinal direction and with the transverse and 45 deg ultimate strengths being limited by cracks initiating in the carbide phase. At room temperature, prestressing due to thermal expansion mismatch results in a large difference between the longitudinal compressive and tensile yield stresses. Longitudinal creep data for the 1800° to 2200°F temperature range are presented and examined in terms of the directional structure. The activation energy for creep is observed to be much higher than that for chromium diffusion in a Co−Cr alloy. These analyses suggest that the creep of the eutectic composite is controlled by the creep and fracture of the reinforcing carbides.

Minimizing Some Of The Mesh Errors InBoundary Element Method

Abstract: The discretization of the boundary in Boundary Element Method (BEM) requires several decisions that affect the accuracy of the BEM solution. These decisions include: the order of polynomial in each element, the continuity requirement at the element end, the location of the nodes inside the element, the size of the element, the location of the element end nodes, and the location of collocation points where the boundary conditions are imposed. The errors that are generated from these decisions are referred to as the mesh errors in this paper. In Ammons and Vable* the errors from continuity and collocation were discussed in detail and will not be considered here. But how to numerically determine an interpolation functions of a given order to satisfy a given continuity requirement will be discussed. The presentation will briefly describe three algorithms that minimize the LI norm of the mesh error from the remaining sources. These algorithms are applicable two-dimensional problems of Poisson's equation, Plate-Bending, Elastostatic, and Fracture mechanics formulated using direct or indirect BEM. Numerical examples will be presented showing the validity of these algorithms.