The effects of pH upon methane production from anaerobic digestion of dairy cattle manure were investigated. One liter digesters were maintained by daily adjustment at the following pH levels: 7.6, 7.0, 6.0, 5.5, and 5.0. After 33 weeks of incubation the working volume of the digesters was increased to 3 liters. Digesters were incubated on a rotary shaker at 37°C. Digesters were loaded at the desired volatile solids concentrations, without an inoculum, and maintained from day one by daily additions and withdrawals to achieve a 3 day retention time. After 50 weeks of operation the manure from a second dairy was utilized as substrate. Active digestion was achieved at all pH levels except pH 5.0. Biogas production was evident in 4 to 6 days after incubation. Biogas production was highest at pH 7.0 with manure from both dairies (3.047 ± 0.403 liters per liter of digester per day with Dairy II manure and 1.43 ± 0.09 liters per liter per day with Dairy I manure). Methane production was also highest at pH 7.0 (1.43 ± 0.292 liters per liter of digester per day with Dairy II manure and 0.611 ± 0.057 liters per liter per day with Dairy I manure although the highest percentages of methane in the biogas occurred at pH 7.6 (65.9 ± 5.2 from Dairy I manure and 50.4 ± 4.6 from Dairy II manure). Dairy II manure produced significantly more biogas and methane at all pH levels. This increased production could not be attributed solely to differences in volatile solids concentrations of the two substrates. Total volatile acid concentrations were highest at the highest pH levels and were higher with Dairy II manure as a substrate. Digesters at all pH levels had volatile acid concentrations above 2000 mg/liter normally considered inhibitory for methane bacteria (2314-2890 mg/liter with Dairy I manure and 5.708-7.434 mg/liter with Dairy II manure). The results reported here indicate that stable methane digestion of dairy cattle manure can be established maintained at 37°C with a 3 day retention time. Digestion at pH levels as low as 5.5 continued for periods up to 24 months without a failure. High levels of volatile acids did not cause digester failure. Characteristics of the manure have significant effects on biogas and methane production.

The purpose of this investigation is the application of the penetration model for gas absorption with chemical reaction in a stirred reactor and the evaluation of the parameters of the penetration model, viz. the gas-liquid interfacial area and gas-liquid particle contact time, for the different agitation intensities and gas rates. The values of these parameters for the model were determined by measuring the rates of absorption of carbon dioxide into caustic solutions and then forcing the model to give values of the parameter consistent with observed rates of absorption. The contact times and interfacial areas were determined for five agitation rates ranging from 150 revolutions of the agitator to 350 and for five gas input rates ranging from superficial gas velocities of 0.29 centimeter per second to about 1.2 centimeters per second. These parameters were evaluated for three different caustic strengths. The interfacial areas show discrepancies in values for the three different caustic strengths. These results, together with the work of an earlier investigator, seem to suggest that, for design and scale-up purposes for gas absorption in solutions, experiments be set up with the solutions of actual interest. The interfacial areas obtained correlate well] with the correlations given by Calderbank, which is based on the work of Hinze on bubble sizes in turbulent regimes. The gas-liquid particle contact times are again found to be dependent on the intensity of agitation and the gas rates. A correlation based on the theory of isotropic turbulence has been proposed and found to correlate the data well. / Ph. D.

En los últimos años, los esfuerzos para desarrollar una fuente de energía limpia y econó³micamente viable se han incrementado. Estos esfuerzos surgen como respuesta al creciente consumo de combustibles y al alto impacto ambiental y socio-político de la exploración y el uso de hidrocarburos o energía nuclear. Una de las alternativas más prometedoras exploradas hoy en díaa es el uso de H2 como vector energético. Sin embargo, existen algunas limitaciones relacionadas con la producciónn y almacenamiento que deben ser superadas. Centrados en el problema del almacenamiento de H2 , en esta investigación se ha estudiado, empleando técnicas químico-computacionales, las propiedades físico-quí�micas que promueven la adsorción de hidrógeno en sólidos cristalinos microporosos metal-orgánicos (MOFs). A partir del análisis de los resultados, se han identificado algunos parámetros que pueden ser utilizados como referencia para orientar el diseño y la síntesis de nuevos MOFs con mejores propiedades para la adsorción de H2 . A lo largo del estudio, los siguientes aspectos han sido evaluadas en detalle: I. la naturaleza de las interacciones moleculares entre el adsorbato y los diferentes componentes del material y II. las características estructurales que promueven o limitar la adsorción. Estos aspectos fueron estudiados con técnicas de químico-computacionales, tales como cálculos de química cuántica (con métodos los semi-empíricos PM6, HF y MP2) y simulaciones de dinámica molecular y Monte Carlo. Los resultados se analizaron en una función de las propiedades fÃ�sicas de los ma- teriales seleccionados para el estudio. En una primera fase, la interacción de las moléculas de H2 con el MOF-5 se evaluaron a través de cálculos de química cuántica. En vista de que los sitios de adsorciónn más fuertes fueron localizados en posiciones cercanas a los Átomos del metal (Zn (II)), se realiza un estudio adicional con cuatro tipos de centros metálicos...... / Gómez Hernández, DA. (2012). Caracterización de la Adsorción de Hidrógeno en MOFs por Métodos Químico-Computacionales [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17462

Sensitivity Sⁱ_p is defined as the ratio of the fractional change of gas ionization current to the fractional change of gas pressure. A maximum obtainable sensitivity was calculated, Sⁱ_p]_max = -0.309 A/B V, where A, B are constants for a given gas within a particular range of field-to-pressure ratio. Experiments were conducted to investigate the sensitivity of air and krypton under different combinations of voltage, electrode separation and primary electron source strength. A curie of tritium placed on the central portion of either electrode produced a constant initial emission current and a high sensitivity. Sensitivity could be increased by using a stronger current source, higher voltage and a larger electrode separation. Observed values of Sⁱ_p for high voltage at larger separation are greater than those expected even when breakdown occurs at a (pd) quite larger than the one for Sⁱ_p]_max. The fractional pressure change, Δp/p, is independent of the initial pressure, p, and is greater for a heavier gas subject to the same acceleration, a fact which suggests the use of a heavier gas to obtain a higher fractional current change for the same sensitivity. Krypton behaves in a similar way as air in the system. Operating current level may be higher than 10⁻⁵ ampere if stronger source is used. There is a limit in the separation for a given source configuration. Further increase in Sⁱ_p and current level may be achieved through better design of the configuration and location of the current source between the electrodes. The fractional current change, Δi/i, depends more on Δp rather than on the initial operating pressure, p. From the experiment performed, it appears that a gas system will perform satisfactorily as a transient velocity gauge. / M.S.

The problem of determining thermodynamic properties of gaseous systems in which real-gas effects must be considered can be greatly simplified through use of existing ideal-gas theories for the processes of dissociation and ionization. Since, however, the ideal dissociating gas theory neglects ionization effects and the ideal ionizing gas theory does not take into account dissociation, an additional assumption must be made in order to use these two theories within a single system experiencing both effects. The added assumption which is made is that the processes of dissociation, single ionization, and higher levels of ionization all occur independently of one another though in a definite order within the system. With this linearizing assumption of independent gas processes the ideal gas theories then can be applied within their respective ranges of application in order to calculate the thermodynamic properties of any system under equilibrium conditions, provided the ranges of application can be determined. Neither the ideal dissociating gas theory nor the ideal ionizing gas theory explicitly defines the pressure-temperature region throughout which the theory is applicable. In the present work an analytic expression is developed which gives the limiting temperature as a function of pressure for the ideal dissociating gas theory. The method is then generalized in the ionization range so as to provide pressure-temperature boundaries for all levels of ionization within the assumption of independent first-level, second-level, and higher-level ionization processes. / Master of Science

In this work, we investigate numerically the evolution of perturbed Vlasov equilibria. according to the full nonlinear system with particular emphasis on analyzing the asymptotic states towards which the system evolves. The simulations are carried out with the numerical code that we have implemented on the Cray X-MP of the Pittsburgh Supercomputing Center and which is based on the splitting scheme algorithm. Maxwellian symmetric and one-sided bump-on-tail and two-stream type of equilibrium distributions are considered: the only distribution which seems to evolve towards a BGK equilibrium is the two-stream while the asymptotic states for the other distributions are better described by superpositions of possible BGK modes. Perturbations with wave-like dependence in space and both symmetric and non-symmetric dependence on velocity are considered. For weakly unstable modes, the problem of the discrepancy between different theoretical models about the scaling of the saturation amplitude with the growth rate is addressed for the first time with the splitting scheme algorithm. The results are in agreement with the ones obtained in the past with less accurate algorithms and do not exhibit spurious numerical effects present in those. Finally, collisions are included in the splitting scheme in the form of the Krook model and some simulations are performed whose results are in agreement with existing theoretical models. / Ph. D.

The use of wood stoves for residential heating has been increasing over the past several years. This increased use of wood stoves has caused significant concern about increased air pollution. Development of improved emissions and efficiency measurement methods will allow the development of improved stoves. Room calorimetry is used as the standard for measuring the energy efficiency of stoves. Unfortunately, this method is expensive and few wood stove manufacturers can afford it. For this reason, flue loss methods which are generally less expensive are attractive. Flue loss methods measure either directly or indirectly the following instantaneous losses: 1. Sensible energy loss due to the flue gases being at a higher temperature than the ambient. 2. Chemical energy loss from incomplete combustion. 3. Latent energy loss due to water existing as a vapor in the flue gas. This loss is included since the higher heating value of wood is used. The instantaneous efficiency of the stove can then be determined from measurement of these three losses and the instantaneous energy input. This project is part of a larger project which has an overall objective to develop an accurate flue loss method. An accurate flue loss method is needed since many of the traditional flue loss methods have unknown accuracies. / Master of Science

Yes / This study aims to address a critical gap in the literature by examining the incorporation of uncertainty in measuring carbon emissions using the greenhouse gas (GHG) Protocol methodology across all three scopes. By comprehensively considering the various dimensions of CO2 emissions within the context of organizational activities, our research contributes significantly to the existing body of knowledge. We address challenges such as data quality issues and a high prevalence of missing values by using information entropy, techniques for order preference by similarity to ideal solution (TOPSIS), and an artificial neural network (ANN) to analyze the contextual variables. Our findings, derived from the data sample of 56 companies across 18 sectors and 13 Brazilian states between 2017 and 2019, reveal that Scope 3 emissions exhibit the highest levels of information entropy. Additionally, we highlight the pivotal role of public policies in enhancing the availability of GHG emissions data, which, in turn, positively impacts policy-making practices. By demonstrating the potential for a virtuous cycle between improved information availability and enhanced policy outcomes, our research underscores the importance of addressing uncertainty in carbon emissions measurement for advancing effective climate change mitigation strategies. / The full-text of this article will be released for public view at the end of the publisher embargo on 3 Aug 2025.

The work presented in this dissertation provides the groundwork for characterizing multi-scale gaseous media, the interstellar medium (ISM) to the circumgalactic medium (CGM) in a data driven approach. Both the ISM and CGM play fundamental roles in galaxy evolution, yet their relation remains poorly understood due to the vast differences in spatial and temporal scales between them. Bridging the gap between these gaseous media at different scales requires more than observational evidence or theoretical insights in isolation. Instead, it demands a combined effort that integrates both approaches, along with the development of advanced analysis tools capable of capturing and connecting the underlying physical processes. The results of this dissertation demonstrate the power of combining diverse observational features and probes with cutting-edge data analysis techniques. These findings enhance our understanding of structures at the interface between the ISM and CGM, and provides robust methodologies for connecting theoretical models with observations, contributing to a deeper understanding of the multi-scale gas media that impact galaxy evolution.

A high-order macroscopic model for the accurate description of rarefied polyatomic gas flows is introduced based on a simplified kinetic equation. The different energy exchange processes are accounted for with a two term collision model. The order of magnitude method is applied to the primary moment equations to acquire the optimized moment definitions and the final scaled set of Grad's 36 moment equations for polyatomic gases. The proposed kinetic model, which is an extension of the S-model, predicts correct relaxation of higher moments and delivers the accurate Prandtl (Pr) number. Also, the model has a proven H-theorem. At the first order, a modification of the Navier-Stokes-Fourier (NSF) equations is obtained, which shows considerable extended range of validity in comparison to the classical NSF equations in modeling sound waves. At third order of accuracy, a set of 19 regularized PDEs (R19) is obtained. Furthermore, the terms associated with the internal degrees of freedom yield various intermediate orders of accuracy, a total of 13 different orders. Attenuation and speed of linear waves are studied as the first application of the many sets of equations. For frequencies were the internal degrees of freedom are effectively frozen, the equations reproduce the behavior of monatomic gases. Thereafter, boundary conditions for the proposed macroscopic model are introduced. The unsteady heat conduction of a gas at rest and steady Couette flow are studied numerically and analytically as examples of boundary value problems. The results for different gases are given and effects of Knudsen numbers, degrees of freedom, accommodation coefficients and temperature dependent properties are investigated. For some cases, the higher order effects are very dominant and the widely used first order set of the Navier Stokes Fourier equations fails to accurately capture the gas behavior and should be replaced by a higher order set of equations. / Graduate / 0346, 0791, 0548, 0759 / behnamr@uvic.ca