The interstitial concentration and temperature dependence of the diffusion coefficient ratio D12/D11 in ternary austenites containing silicon or manganese has been experimentally determined using diffusion couples based on the concept of "transient equilibrium". The results are compared with values predicted theoretically from statistical and thermodynamic considerations. </p> <p> The kinetics of the growth of proeutectoid ferrite in binary and ternary austenites have been determined, using two-phase diffusion couples. The results are consistent with the premise that carbon diffusion controls the rate of interface migration. It is demonstrated, theoretically and experimentally, that the ternary results fall into two classes - one in which local equilibrium may be assumed, and one in which "constrained local equilibrium" may be postulated. / Thesis / Doctor of Philosophy (PhD)

<p> Rate of adsorption data for gases on molecular sieve·s and coals have been interpreted using equations for unsteady state diffusion derived from Fick's law for spheres usually, ignoring the amount adsorbed and the shape of the adsorption isotherm. These inappropriate equations result in calculated diffusivities that are too low and activation energies that are too large. </p> <p> Numerical. solutions of Fick's law were made for diffusion and adsorption in a porous sphere of radius R by finite difference methods for the following conditions: a. Diffusion is the rate-controlling step, and the diffusivity, D, is constant. b. Within an increment of the particle the total amount of adsorbate per unit volume, T is related to the "effective" concentration, c, by a Langmuir-like isotherm T = abC/(1 + bC). c. At zero tine the particle containing no adsomate is surrounded by adsozbate of concentration, Co, which remains constant throughout the rate process, and d. Equilibrium is established immediately at the periphery of the sphere. </p> <p> The solutions are obtained in terms of Z = Q/Q and T=(DCo/QR^2) t = kt, where t is time, k is a constant equal to the term within the brackets, and Q and Q are the amounts adsorbed per unit volume at time t and at equilibrium. The quantity within brackets is also a valid expression for linear and Freundlich-like adsorption isotherms and probably holds for other isotherms. Plots of z as a function of T shift systematically as the parameter B = bCo increased from 0, corresponding to a linear adsorption isotherm, to large values; the value of Z at a given T increasing with increasing values of B. For B = 0 the numerical solution is identical with analytical solution for the linear adsorption isotherm which for values of z <0.87 is given by kt = (2/π) { (-1 - πZ/6) - (1 ~πZ/3) ^1/2 } where k = DCo/R^2Q. For large values of B the numerical solutions approach as a limit the parabolic law kt = (1/2) {(1- 2Z/3) - (1- Z) } The value of (1/k~) o.zidt~ at short times increases fran 3.385 for B = 0 to 4 .. 243 for very large values of B.. From experimental data the value of k derived using the equation for B = 0 is 1.56 larger than for the parabolic equation. Hence the values of D obtained from the initial linear portions of t.he rate curve change by only a factor of 1.56 when the type of isotherm is changed from linear to rectangular. </p> <p> Rates of adsorption and the adsorption isotherm were determined for N2 , CH4, co2 , and C2H6 on samples of Linde 4A molecular sieve at several temperatures from -78° to +50°C in a manostatic volumetric aborption apparatus. The Langmuir equation satisfactorily approximatedthe isotherms and the values of B were moderately large at the lower temperatures of each series of experiments, eg., for N2 at -78°C, 10.6; for CH4 at -78°C, 7.3; for co2 at 0°C, 64; for Ci!6 at 0° and 30°C, 37 and 10.3. </p> <p> The rate data plotted as Z against t^1/2 were not linear at short times but curved upward initially before becoming linear. The initial (, nonlinear portion persisted significantly longer than the brief uncertain period at the beginning of the experiment. This phenomena could result from the equilibration at the periphecy of the particles requiring a finite time rather than being instantaneous. </p> <p> An equation based on the parabolic law model and a first order equilibration process was derived, which fits. the experimental data for 0.05 < Z < 0.95. This equation is appropriate only to data with a large value of B, but is probably a reasonable approximation for other rate data. </p> <p> The rates of adsorption for different molecules were co2 > N2 > CH4 > c2H6 · The activation energies for the diffusivity were found to be 4.1 and 6.0 kcal./nole for methane and ethane. The _heats of adsorption were found to be 7.2 and 8.3 kcal/mole for methane and ethane. </p> / Thesis / Master of Engineering (MEngr)

<p> The analysis, construction and performance of a new type of evaporated thin-film filter is described. It has the capability of frequency tuning by means of a single bias voltage.</p> <p> The device is basically a uniformly distributed resistance-capacitance network (URC) with a thin semiconductor film incorporated in the structure. The resistive film, insulator and semiconductor films constitute a metal-insulator-semiconductor system (MIS) whose capacitance is bias dependent. The device differs from other proposed tunable thin-film filters in the fact that the capacitance can be altered independently of the distributed resistance.</p> <p> A theory is developed to account for the effects of MIS-losses and parasitic inductance on the performance of URC-null networks. These parasitic effects manifest themselves in four different ways: (i) A shift of the null from the position predicted by the ideal theory. (ii) A change in the notch parameter α for an optimum null. (iii) A detuning effect in the case of tunable notch filters. (iv) A reduction in the available tuning range; the so-called "tuning range compression".</p> <p> Experimental units were made by vacuum evaporation of Nichrome, Y2O3, CdS and Al onto alumina substrates. An attempt is made to relate the device characteristics to the material properties. In this respect, the relative dielectric permittivity and thickness of the insulator, the doping density of the semiconductor, the semiconductor-insulator interface states and the bulk states in the semiconductor are found to be the most important parameters.</p> <p> Filters were built which operated in the frequency range 600 kHz to 6 MHz. The best notch filter has a tuning capability of 30% with a ±15V bias voltage. The notch depth is over 60 dB in most cases. A tunable bandpass amplifier which was constructed, has a centre frequency which can be shifted between 6 MHz and 7 MHz with a ±3.5V bias voltage. The Q of this particular device was measured to be 742.</p> / Thesis / Doctor of Philosophy (PhD)

Acid rock drainage (ARD), caused by the oxidation of sulphide bearing minerals, continues to be an environmental impact of both closed and operational mines, leading to waters with low pH values and high metal concentrations (Park et al., 2019). A potential treatment method for ARD is controlled eutrophication, where algae growth is stimulated in the water and metals are accumulated within the algae cells or sorbed to the outside of the cell walls (Samal et al., 2020). The aim of this study is to determine if the addition of wood ash to acidic mine waters can increase the pH, stimulate algal growth, and lower metal concentrations in the water. Two types of wood ash, as well as KNO3 and KH2PO4 were utilized for this study, along with three water sample types: neutral (pH of 7.0) water from Åkerberg pit lake, acidic (pH of 5.7) water from Maurliden mine site (Maurliden East), and very acidic (pH of 2.3) water from Maurliden mine site (Maurliden West). Two experiments were performed, Experiment I (Exp. I) involved a one-time addition of wood ash and KNO3 to samples from each of the three sites, and Experiment II (Exp. II) involved a feeding style ash addition where ash was added every five days to samples from Åkerberg and Maurliden East. Exp. II also included one sample set where artificial nutrients only (KNO3 and KH2PO4) were added to Maurliden East samples. Samples were placed inside of a climate chamber to provide daily irradiation and pH, electrical conductivity (EC), and fluorescence signal measurements were taken daily. Additionally, absorbance samples and O2 saturation measurements were taken daily for Exp. II. At the end of each experiment, samples were sent to an accredited laboratory for elemental analysis and chl-a analysis.  Algal growth was observed in Exp. I in Åkerberg samples only, and in Exp. II in Åkerberg samples and in Maurliden East samples with artificial nutrient additions only. The algal growth rate was similar in both experiments; however, Exp. II yielded a higher concentration of chl-a than Exp. I. Precipitates were observed in all samples in both experiments, including in control samples. pH results cannot confirm the ability of the wood ash to increase the pH in the samples from Maurliden East or West, and metal concentration decreases in these samples are most likely due to precipitation reactions. Metal concentration decreases in Åkerberg samples could be due to precipitation reactions and/or algal uptake.

With the increased application of large eddy simulations and hybrid Reynolds-averaged Navier-Stokes techniques, the generation of realistic turbulence at inflow boundaries is crucial for the accuracy of numerical results. In this dissertation research, two novel turbulence inflow generation methods are derived and validated. The first method, the Triple Hill's Vortex Synthetic Eddy Method, is a new type of synthetic eddy method, where the fundamental eddy is constructed through a superposition of three orthogonal Hill's vortices. The amplitudes of the three vortices that form the fundamental eddy are calculated from known Reynolds stress profiles through a transformation from the physical reference frame to the principal-axis reference frame. In this way, divergenceree anisotropic turbulent velocity fields are obtained that can reproduce a given Reynolds stress tensor. The model was tested on isotropic turbulence decay, turbulent channel flow, and a spatially developing turbulent mixing layer. The Triple Hill's Vortex Synthetic Eddy Method exhibited a quicker recovery of the desired turbulent flow conditions when compared with other current synthetic turbulence methods. The second method is the Control Forced Concurrent Precursor Method which combines an existing concurrent precursor method and a mean flow forcing method with a new extension of the controlled forcing method. Turbulent inflow boundary conditions are imposed through a region of body forces added as source terms to the momentum equations of the main simulation which transfer flow variables from the precursor simulation. Controlled forcing planes imposed in the precursor simulation, allow for specific Reynolds stress tensors and mean velocities to be imposed. A unique feature of the approach is that the proposed fluctuating flow controlled forcing method can be applied to multiple fluctuating velocity components and couple their calculation to amplify the existing fluctuations present in the precursor flow field so that prescribed anisotropic Reynolds stress tensors can be reproduced. The new method was tested on high and low Reynolds number turbulent boundary layer flows, where the proposed fluctuating flow controlled forcing method greatly accelerated the development of the turbulent boundary layers when compared with cases without controlled forcing and with only the original controlled forcing.

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