<p> A method of modelling the mixing phenomenon in natural streams is presented. A wide range of mixing situations can be characterized using a lumped parameter model consisting of a network of ideally mixed components. The components represent two ideal states of mixing: complete mixing of the total component volume, and the other extreme where no mixing occurs in the direction of flow through the component volume. The use of frequency response techniques to match the mathematical model to the real situation is also discussed.</p> <p> Experimental work was carried out on a small natural stream to illustrate how the method is to be applied. The frequency response was obtained using sinusoidal, pulse, and impulse inputs and fluorometric dye tracing techniques. The non-linear model parameters were evaluated using the principles of least squares. The mathematical model chosen for this particular stream illustrates how the phenomenon of stagnant or slow moving regions can be included. The necessary data was collected on several days under different flow conditions to show how the model can be made a function of stream flow.</p> / Thesis / Master of Engineering (MEngr)

No description available.

No description available.

<p> The static electrical characteristics of dual-gate silicon n-channel insulated-gate field-effect trapsistors are investigated experimentally. A mathematical model based on theoretical expressions and containing twelve parameters adjusted for. best fit was developed. </p> <p> The mathematical model was used to calculate the low frequency conversion transconductance as a function of operating conditions. </p> / Thesis / Master of Engineering (MEngr)

Solvent-free extrusion emulsification (SFEE) is new top-down technique specially suited to high viscosity polymers (100-1000 Pa.s) for producing sub-micron (100-500 nm) particles inside a twin screw extruder (TSE) without the use of hazardous solvents. SFEE has been difficult to implement in industry due to process sensitivities and a lack of mechanistic knowledge on how the polymer-water morphology must develop prior to inversion. To devise a mechanistic explanation of the critical stages of the process, an inline orifice-plate type viscometer was developed to monitor rheological changes previously witnessed in early batch studies. The general variables of study throughout the thesis included the manner by which sodium hydroxide (NaOH) can be added as well as the NaOH content necessary, resin-to-water (R/W) ratio, and surfactant content. The last study in the thesis explores the influence of matrix viscosity, which was accomplished by crosslinking the polyester. The striated lamellae morphology of the polyester-water system, critically controlling the final particle size, depended on two factors, specifically surface energy (determined by endgroup conversion and added surfactant) and matrix viscosity. Analysis of the rheological response indicated that a higher polar surface energy contribution had the greatest influence on the morphological state, demonstrating a steeper viscosity transition due to more favourable and more rapid incorporation of water within the polyester matrix. A strong correlation was repeatedly found between particle size and this viscosity transition, which has been related to the thickness of striated lamellae through a theory of lamellae coarsening (or thinning as is more relevant to the current process). The reported lamellae coarsening model in the literature, which shows the predominant effects of interfacial energy and viscosity on lamellae thickness in a mixed phase system showed excellent correspondence to the results in this thesis. Among the variables of study in this thesis, the dissolution of the sodium hydroxide species (when added as a solid particle) and the kinetics of end-groups conversion proved to be rate-limiting phenomena to generating thinner striated lamellae. The ionic strength of the system was notably important to the viscosity change occurring in the process as water was added for the first time and subsequently influenced the particle size produced, particularly when additional surfactant was not added and the system relied exclusively on the carboxylate endgroups present. Finally, with mounting evidence that SFEE showed significant sensitivity to the matrix viscosity, a final study examined the effectiveness of SFEE in the face of ever increasing viscous force by blending a crosslinked polyester into the neat resin at different weight fractions. With higher viscosity there was a corresponding decrease in interfacial area growth between the polyester and water, resulting in increased particle size but even with a viscosity near 800 Pa.s, far above a traditional oil-in-water system, it was still found possible in this study to create nano-sized particles by SFEE. / Thesis / Doctor of Philosophy (PhD)

We consider a modified non-relativistic quantum mechanics where the position and momentum operators satisfy a non-standard commutation relation of the form [X_i, P_j] = 𝑖ℏ({1 + βP²) + β′P_iP_j}. Such a theory incorporates an absolute minimal length, UV/IR mixing and non-commutative position space. The possible representations in terms of differential operators are analyzed and their equivalence to first order is established. Simple quantum systems, namely the harmonic oscillator, the Coulomb potential and the gravitational well are studied in one of these representations, the pseudo-position one, and results are compared to previously published results. The Coulomb potential is also analyzed by an alternative analytical/numerical method. A constraint of ~ 3 GeV on the scale of the parameters β, β′ is obtained from precision experimental data on the atomic hydrogen energy levels. / Ph. D.

Using data recorded by the CLEO II detector operating at the Upsilon(4S) resonance at the Cornell Electron Storage Ring, several properties of B mesons are measured using a partially reconstructed tag of the decay mode bar{B0} -> D*+ l- bar{nu}. Using 2.38 fb**{-1} of on-resonance data and the averaged B meson semileptonic branching fraction through inclusive lepton momentum spectrum obtained by previous CLEO analysis, we measure the B0 and B- semileptonic branching fraction to be (10.78 +/- 0.60 +/- 0.69)% and (10.25 +/- 0.57 +/- 0.65)% respectively, which yields the lifetime ratio tau_+/tau_0 = 0.950 +0.117-0.080 +0.091-0.068, assuming the equality of semileptonic partial branching width for bar{B0} and B-. With a larger dataset of 3.1 fb**{-1}, we measured the B0-bar{B0} mixing parameter chi_d to be 0.189 +/- 0.019 +/- 0.006. / Ph. D.

Creating mixing at low Reynolds numbers is a non-trivial challenge that has been approached from many different perspectives, using passive or active methods. This challenge been further highlighted with the rise of microfluidics. Based on the diminutive size of these devices, the Reynolds numbers are often less than 10, but have high Peclet numbers. Therefore, creating effective mixing is non-trivial and is a topic of active research, and is of paramount importance in order to improve performance of microfluidic devices in a wide range of applications. The objective of this research was to develop a novel active device for laminar mixing. The mixing device developed herein capitalized on Nafion ionic polymers, which are a class of active materials that are thin, flexible, inexpensive, and readily deployable in an aqueous medium and offer strains up to 5% under a small (<2V) applied voltage. The effect of these deflections on an incident flow is the mixing mechanism in a laminar channel flow explored in this effort. To the author's knowledge, the high-risk effort presented herein is the first attempt to exploit ionic polymers as an active mixing device. Several different configurations of ionic polymers were tested and Digital Particle Image Velocimetry (DPIV) measurements were obtained. Resulting analysis using a quantitative mixing metric shows that using cantilevered polymers create increases mixing potential in the flow for some actuation cases. Although these differences are present, they do not appear consistently in the results. However, only a partial set of flow information was obtained from DPIV, and an improved understanding of the effect of these polymers could be developed from additional experiments. Using cantilevered ionic polymers for laminar mixing could foster the development of a new generation of efficient micromixing devices, which will improve the capabilities and effectiveness of numerous microfluidic technologies that range across biomedical, lab-on-a-chip, separation and sorting technologies and many more. / Master of Science

Several flow control schemes were designed and tested to determine the most suitable method for reducing the momentum deficit in a rotor wake and thus attenuate rotor-stator interaction noise. A secondary concern of the project was to reduce the amount of blowing required air for wake filling and thus limit the efficiency penalty in an aircraft engine environment. Testing was performed in a linear blow down cascade wind tunnel, which produced an inlet Mach number of 0.345. The cascade consisted of five blades with the stagger angle, pitch, and airfoil cross-section representative of 90% span of the rotor geometry for NASA's Active Noise Control Fan (ANCF) test rig. The Reynolds number for the tests was based on inlet conditions and a chord length of 4 inches. Trailing edge jets, trailing edge slots, ejector pumps, and pressure/suction side jets were among the configurations tested for wake filling. A range of mass flow percentages were applied to each configuration and a pressure loss coefficient was determined for each. Considerable reduction in wake losses took place for discrete jet blowing techniques as well as pressure side and suction side jets. In the case of the pressure and suction side jets, near full wake filling occurred at 0.75% of the total mass flow. In terms of loss coefficients and calculated momentum coefficients, the suction/pressure surface jets were the most successful. Jets located upstream of the trailing edge helped to re-energize the momentum deficits in the wake region by using a flow pattern capable of mixing the region while also adding momentum to the wake. The slotted configuration was modeled after NASA's current blowing scheme and served as a baseline for comparison for all data. Digital particle image velocimetry was performed for flow visualizations as well as velocity analysis in the wake region. / Master of Science

This thesis presents numerical investigations of two-dimensional single-phase turbulent jets and bubbly mixing layers using Reynolds-Averaged Navier-Stokes (RANS) equations. The behavior of a turbulent jet confined in a channel depends on the Reynolds number and geometry of the channel which is given by the expansion ratio (channel width to jet thickness) and offset ratio (eccentricity of the jet entrance). Steady solutions to the RANS equations for a two-dimensional turbulent jet injected in the middle of a channel have been obtained. When no entrainment from the channel base is allowed, the flow is asymmetric for a wide range of expansion ratio at high Reynolds number. The jet attaches to one of the channel side walls. The attachment length increases linearly with the channel width for fixed value of Reynolds number. The attachment length is also found to be independent of the (turbulent) jet Reynolds number for fixed expansion ratio. By simulating half of the channel and imposing symmetry, we can construct a steady symmetric solution to the RANS equations. This implies that there are possibly two solutions to the steady RANS equations, one is symmetric but unstable, and the other solution is asymmetric (the jet attaches to one of the side walls) but stable. A symmetric solution is also obtained if entrainment from jet exit plane is permitted. Fearn et al. (Journal of Fluid Mechanics, vol. 121, 1990) studied the laminar problem, and showed that the flow asymmetry of a symmetric expansion arises at a symmetry-breaking bifurcation as the jet Reynolds number is increased from zero. In the present study the Reynolds number is high and the jet is turbulent. Therefore, a symmetry-breaking bifurcation parameter might be the level of entrainment or expansion ratio. The two-dimensional turbulent bubbly mixing layer, which is a multiphase problem, is investigated using RANS based models. Available experimental data show that the spreading rate of turbulent bubbly mixing layers is greater than that of the corresponding single phase flow. The presence of bubbles also increases the turbulence level. The global structure of the flow proved to be sensitive to the void fraction. The present RANS simulations predict this behavior, but different turbulence models give different spreading rates. There is a significant difference in turbulence kinetic energy between numerical predictions and experimental data. The models tested include 𝘬—𝜖, shear-stress transport (SST), and Reynolds stress transport (SSG) models. All tested turbulence models under predict the spreading rate of the bubbly mixing layer, even though they accurately predict the spreading rate for single phase flow. The best predictions are obtained by using SST model. / Master of Science