No description available.

Three key questions are identified and answered in this paper. Firstly, have the average annual temperatures in the Prince George Region changed in recent years? Secondly, have the seasonal flow rates changed for local waterways? Lastly, have the timing of the annual flood cycles in the Prince George, British Columbia changed? By reviewing data from local weather and hydrological monitoring stations, this paper identifies that the average annual temperature in Prince George, British Columbia has not only increased but also shifted to a pattern of warmer winters and cooler summers. The flow rates for the region were seen to have been altered as well, indicating increased flow rates in the winter and early spring and decreased flow rates in the summer and early fall. The magnitude of flood frequency events such as the 10, 25 and 100 year flood occurrence does not seem to have the increased in recent years.

This research examines different techniques and proposes a Computational Fluid Dynamics (CFD) model as a robust tool for flow characterization of load leveling valves. The load leveling valve is a critical component of an air suspension system since it manages air spring pressure, a key function that directly impacts vehicle dynamic performance in addition to maintaining a static ride height. Efficiency of operation of a load leveling valve is established by its flow characteristics, a metric useful in determining suitability of the valve for application in a truck-suspension configuration and for comparison among similar products. The disk-slot type load leveling valve was chosen as the subject of this study due to its popularity in the heavy truck industry. Three distinct methods are presented to model and evaluate flow characteristics of a disk-slot valve. First is a theoretical formulation based on gas dynamic behavior through an orifice; second is an experimental technique in which a full pneumatic apparatus is used to collect instantaneous pressure data to estimate air discharge; and third is a CFD approach. Significant discrepancies observed between theoretically estimated results and experimental data suggest that the theoretical model is incapable of accurately capturing losses that occur during air flow. These variations diminish as the magnitude of discharge coefficient is altered. A detailed CFD model is submitted as an effective tool for load leveling valve flow characterization/analysis. This model overcomes the deficiencies of the theoretical model and improves the accuracy of simulations. A 2-D axisymmetric approximation of the real fluid domain is analyzed for flow characteristics using a Realizable k-ϵ turbulence model, scalable wall functions, and a pressure-based coupled algorithm with a second order discretization function. The CFD-generated results were observed to be in agreement with the experimental findings. CFD is found to be advantageous in the evaluation of flow characteristics as it furnishes precise data without the need to experimentally evaluate a physical model/prototype of the valve, thereby benefitting suspension engineers involved in the development and testing of load leveling valve designs. This document concludes with a sample case study which uses CFD to characterize flow in a modified disk-slot load leveling valve, and discusses the results in light of application on a heavy truck. / MS / A majority of heavy trucks in North America equipped with air suspensions use a device known as a load leveling valve. This is a mechanical control system which manages pressure in air springs to maintain a preset/constant static ride height irrespective of the payload, doing so by sensing the distance between the truck frame and the axle. The rate of airflow to/from air springs in response to a road disturbance or load shift is critical to the stability of the truck when on the road. This rate of airflow for a given set of conditions constitutes flow characteristics of a load leveling valve. Accurate measurement of flow characteristics is necessary to understand the actual effect of the use of a particular valve on a truck-suspension configuration. This research addresses that requirement by presenting three distinct methods to model and evaluate flow characteristics of a load leveling valve, conducted on the disk-slot valve for its popularity in the heavy truck industry. First is a theoretical formulation based on flow of gas through an orifice; second is an experimental technique in which a full pneumatic apparatus is used to collect instantaneous pressure data to estimate air discharge; and third is a Computational Fluid Dynamics (CFD) approach. Significant discrepancies observed between theoretically estimated results and experimental data suggest that the theoretical model is incapable of accurately capturing losses that occur during air flow. The disparities also justify the adoption of CFD as an alternate method. A comprehensive CFD model is proposed as a capable tool for load leveling valve flow analysis/characterization. This model overcomes the deficiencies of the theoretical model and improves the accuracy of simulations. CFD-generated results are found to be in agreement with the experimental findings, highlighting its effectiveness at flow characterization. The ability of a CFD model to furnish precise data without the need to experimentally evaluate a physical model/prototype of the valve promises to benefit suspension engineers involved in the development and testing of load leveling valve designs. This document concludes with a sample case study which uses CFD to characterize flow in a modified disk-slot valve, and discusses the results in light of application on a heavy truck.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Distillation column design and operation require understanding of both the hydrodynamic and thermodynamic behaviour and limitations. One of the hydrodynamic aspects that negatively influence separation efficiency in the distillation column is entrainment of the liquid with the rising vapour or gas. Inaccurate entrainment predictions will lead to poor separation efficiencies in the column and consequently over design of the column diameter and/or height has to be incorporated. This has a significant impact on the capital cost due to the size and scale of industrial columns. Therefore, small improvements in entrainment prediction will lead to large savings in capital investment. Previous research published in the open literature focused primarily on the influence of gas and liquid flow rates and, tray geometry on entrainment for the air/water system. Consequently the non-air/water database is small and consists of data obtained from various tray and column geometries. As a result the accuracy of current entrainment prediction models is questionable for systems other than air/water. Therefore, the first objective of this work was to investigate whether current prediction models perform well for systems other than air/water. To prove this air/water, air/ethylene glycol and air/silicon oil data were measured and compared with current prediction correlations. It was found that current prediction models perform poorly for the air/ethylene glycol and air/silicone oil systems. At the same time a new observation was made with regard to froth development and behaviour inside the column. The observation shows that liquid flow rate has a nonmonotonic influence on entrainment, caused by the short (475mm) tray flow path. The second objective was to examine the influence of gas physical properties on entrainment. New entrainment data were measured by individually contacting air, CO2 and SF6 with water and ethylene glycol, while n-butanol was contacted with CO2 and SF6. The data was compared with current prediction models which performed poorly for SF6 results. This shows the inability of these models to predict entrainment for gas systems with high densities. Modified Reynolds and Froude numbers were developed to show the influence of gas physical properties on entrainment. Low modified Reynolds numbers and large modified Froude numbers resulted in high entrainment. The third objective was to determine the influence of liquid physical properties on entrainment. New entrainment data were measured using CO2 with Isopar G, n-butanol, water, silicone oil and ethylene glycol. Current prediction models compared poorly to the data and did not include the influence of liquid viscosity on entrainment. It was found that viscosity had an intricate non-monotonic influence on entrainment. The fourth and final objective was to correlate the influence of gas and liquid properties on entrainment as determined by the previous two objectives. To make the dataset more complete, entrainment was measured for four tray spacings using CO2/Isopar, CO2/nbutanol, air/ethylene glycol, CO2/ethylene glycol, air/silicone oil and CO2/silicone oil (over 1700 data points). Two new correlations are presented to predict the fraction of liquid entraining with the rising gas (L’/G with R2 = 85%) and the fraction of liquid entering the tray that entrains (L’/L with R2 = 92%). The performance of the L’/G correlation (R2 = 85%) is vastly superior to two other prominent correlations (R2 = 61% and 23%). This correlation can be implemented to predict entrainment successfully for different tray geometries by combining the predicted influence of tray geometry, by Kister and Haas (1988), with results from the newly developed correlation. All four objectives are presented as manuscripts for journal publication and serve as alone standing documents. / AFRIKAANSE OPSOMMING: Distillasie kolom ontwerp en bedryf vereis begrip van beide die hidrodinamiese en termodinamiese gedrag en beperkings. Een van die hidrodinamiese aspekte wat skeiding doeltreffendheid negatief beïnvloed in die distillasie kolom is meesleuring van die vloeistof met die stygende dampe of gas. Onakkurate meesleuring voorspellings sal lei tot swak skeiding doeltreffendheid in die kolom en gevolglik word die ontwerp van die kolom deursnee en / of hoogte beinvloed. Dit het 'n beduidende impak op die kapitale koste as gevolg van die grootte en skaal van industriële kolomme. Klein verbeterings in meesleuring voorspelling sal dus lei tot groot besparings in kapitaal belegging. Vorige navorsing gepubliseer in die oop literatuur het hoofsaaklik gefokus op die invloed van gas- en vloeistof vloeitempos en plaat geometrie op meesleuring vir die lug/water sisteem. Gevolglik is die nie-lug/water databasis klein en bestaan van die data wat verkry is uit verskeie plaat en kolom-geometrieë. As gevolg is die akkuraatheid van die huidige meesleuring voorspelling modelle vir stelsels anders as lug/water te betwyfel. Daarom is die eerste doel van hierdie werk om ondersoek in te stel of die huidige voorspelling modelle goed presteer vir stelsels anders as lug/water. Om dit te bewys was lug/water, lug/etileenglikol en lug/silikon olie data gemeet en vergelyk met die huidige voorspelling korrelasies. Daar is bevind dat die huidige voorspellings modelle swak presteer vir die lug/etileenglikol en lug/silikon olie. Op dieselfde tyd was 'n nuwe waarneming gemaak met betrekking tot dispersie ontwikkeling en gedrag binne die kolom. Die waarneming toon dat vloeistof vloeitempo 'n nie-monotoniese invloed op meesleuring het, veroorsaak deur die kort (475mm) plaat vloei pad lengte. Die tweede doelwit was om die invloed van gas fisiese eienskappe op meesleuring te ondersoek. Nuwe meesleuring data was gemeet deur individuele kontak van lug, CO2 en SF6 met water en etileenglikol, terwyl n-butanol slegs met CO2 en SF6 inkontak gebring was. Die eksperimentele resultate word vergelyk met die huidige voorspellings modelle wat swak presteer invergelyking met SF6 resultate. Dit toon die onvermoë van hierdie modelle om meesleuring vir gas stelsels met hoë digthede te voorspel. Gemodifiseerde Reynolds en Froude getalle was ontwikkel om die invloed van gas fisiese eienskappe op meesleuring aan te toon. Lae gemodifiseerde Reynolds getalle en groot gemodifiseerde Froude getalle lei na hoë meesleuring. Die derde doelwit was om die invloed van vloeistof fisiese eienskappe op meesleuring te bepaal. Nuwe meesleuring data is gemeet deur gebruik te maak van CO2 met Isopar G, nbutanol, water, silikon olie en etileenglikol. Huidige voorspellings modelle vergelyk swak met die data en sluit nie die invloed van vloeistof viskositeit op meesleuring in nie. Daar is gevind dat viskositeit 'n ingewikkelde nie-monotoniese invloed op meesleuring het. Die vierde en finale doelwit was om die invloed van die gas en vloeistof eienskappe op meesleuring soos bepaal deur die vorige twee doelwitte te korreleer. Om die datastel meer volledig te maak, is meesleuring vir vier plaat spasiërings met CO2/Isopar, CO2/n-butanol, lug/etileenglikol, CO2/ethylene glycol, lug/silikon olie en CO2/silikon olie (meer as 1700 data punte gemeet). Twee nuwe korrelasies word aangebied om die fraksie vloeistof wat meegesleur word met die stygende gas (L’/G met R2 = 85%) en die fraksie vloeistof wat die plaat binnetree wat meegesleur word (L’/L met R2 = 92%) te voorspel. Die prestasie van die L’/G korrelasie (R2 = 85%) is aansienlik beter as twee ander prominente korrelasies (R2 = 61% en 23%). Hierdie korrelasie kan suksesvol geïmplementeer word om meesleuring vir verskillende plaat geometrieë te voorspel deur die voorspelde invloed van plaat geometrie deur Kister en Haas (1988), met die resultate van die nuut ontwikkelde korrelasie te kombineer. Al vier doelwitte word as manuskripte vir joernaal publikasie aangebied en dien as alleenstaande dokumente.

In many irrigation systems and networks, there are multiple water users and shareholders who take their water from different locations along a single canal or pipeline. Often, irrigation splitter boxes are used to divert water to multiple shareholders from a single location. The splitter boxes, which can be small and compact, are generally installed at different locations along a piped irrigation supply line. The purpose of a splitter box is to split a specific amount of water so that each user receives their allotted portion, regardless of the flow rate in the system. Each splitter box usually includes two compartments, separated by a wall that acts as a weir for the water to flow over. The water in the supply pipe enters the box and fills the upstream compartment until it spills over the weir. As water flows over the weir, it is separated by vertical dividers. Each divider is positioned to split a certain percentage of the total flow to one of the outlet pipes, which carry the water to various destinations. In general, splitter boxes perform very well at lower flow rates. However, if high flow rates are present in the box, due to under-design of the box or for any reason, the water surface becomes turbulent and the flow profile over the weir becomes disturbed and nonuniform. Because of these conditions, the flow becomes unevenly distributed and an accurate flow split cannot be achieved. This study focuses on developing a solution that can be installed in flow splitter boxes to effectively dissipate energy and uniformly distribute the flow across the length of the weir during times of high flow rates.

abstract: Developing countries suffer from various health challenges due to inaccessible medical diagnostic laboratories and lack of resources to establish new laboratories. One way to address these issues is to develop diagnostic systems that are suitable for the low-resource setting. In addition to this, applications requiring rapid analyses further motivates the development of portable, easy-to-use, and accurate Point of Care (POC) diagnostics. Lateral Flow Immunoassays (LFIAs) are among the most successful POC tests as they satisfy most of the ASSURED criteria. However, factors like reagent stability, reaction rates limit the performance and robustness of LFIAs. The fluid flow rate in LFIA significantly affect the factors mentioned above, and hence, it is desirable to maintain an optimal fluid velocity in porous media. The main objective of this study is to build a statistical model that enables us to determine the optimal design parameters and ambient conditions for achieving a desired fluid velocity in porous media. This study mainly focuses on the effects of relative humidity and temperature on evaporation in porous media and the impact of geometry on fluid velocity in LFIAs. A set of finite element analyses were performed, and the obtained simulation results were then experimentally verified using Whatman filter paper with different geometry under varying ambient conditions. Design of experiments was conducted to estimate the significant factors affecting the fluid flow rate. Literature suggests that liquid evaporation is one of the major factors that inhibit fluid penetration and capillary flow in lateral flow Immunoassays. The obtained results closely align with the existing literature and conclude that a desired fluid flow rate can be achieved by tuning the geometry of the porous media. The derived statistical model suggests that a dry and warm atmosphere is expected to inhibit the fluid flow rate the most and vice-versa. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

No description available.

No description available.

Made available in DSpace on 2014-06-11T19:28:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-02-12Bitstream added on 2014-06-13T18:07:23Z : No. of bitstreams: 1 pires_jr_dr_arafo.pdf: 422001 bytes, checksum: 5fdba3ee936d59216f9c3b7bd4ad41a3 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O objetivo deste estudo foi avaliar os efeitos do tratamento periodontal em pacientes diabéticos do tipo 2 sobre alterações de fluxo salivar, xerostomia, Candida spp. na saliva e candidose bucal clínica. Foram selecionados 20 pacientes diabéticos tipo 2 e 17 pacientes não-diabéticos de ambos os gêneros, com idade média entre 37 e 55 anos, portadores de doença periodontal crônica. Após exame clínico para avaliação das condições clínicas periodontais, presença de xerostomia e presença clínica de candidose bucal, amostras de saliva foram coletadas para mensuração do fluxo salivar (mL/min), contagem das colônias de Candida spp. (UFC/mL) e identificação das espécies. Esse procedimento foi realizado antes da terapia periodontal (baseline), que consistiu em raspagem e alisamento radicular, instrução de higiene bucal e motivação do paciente, aos 30 e 90 dias após a mesma. Os resultados demonstraram que os pacientes diabéticos apresentaram maior ocorrência de xerostomia e de candidose bucal, sendo estes colonizados por várias espécies de Candida spp. com predominância de C. albicans, sem no entanto, implicar no desenvolvimento da candidose clinicamente. A terapia periodontal, a motivação do paciente e a instrução de higiene bucal foram importantes para melhorar as condições clínicas periodontais e evitar a formação de reservatórios intrabucais de infecção. / In order to investigate the effect of periodontal therapy, in type 2 diabetes mellitus subjects about salivar flow rates, presence of xerostomia, presence of Candida species in the saliva and presence of buccal candidose, twenty type 2 diabetes mellitus subjects and seventeen no-diabetes mellitus subjects, with medium age among 33 to 55 years, presenting generalized chronic periodontal disease were selected. After initial clinical exam to analyze periodontal parameters, xerostomia and buccal candidose presence, saliva samples were assessed to quantify as millimeters of saliva generated per minute (mL/min), account yeasts by colony forming units per mL (CFU/mL) and identificated species. That procedure was accomplished before periodontal therapy (baseline) that it consisted in scaling and root planning, oral hygiene instructions and patient's motivation to the thirty and ninety days after these. Diabetics subjects showed to having hyposalivation in similar levels in no-diabetics groups and in all the analyzed periods, higher prevalence of xerostomia and higher occurrence of buccal candidose. Candida albicans were the prevalent yeast at all periods in both groups, but the presence of yeasts in saliva not implied in the development of buccal candidose. Concluded that the periodontal therapy, the patients' motivation and the buccal hygiene instructions improve periodontal conditions and avoid the formation of microbial reservoirs in mouth.

Orientador: Denise Madalena Palomari Spolidorio / Banca: Elaine Maria Sgavioli Massucato / Banca: Antonio Olavo Cardoso Jorge / Resumo: O objetivo deste estudo foi avaliar os efeitos do tratamento periodontal em pacientes diabéticos do tipo 2 sobre alterações de fluxo salivar, xerostomia, Candida spp. na saliva e candidose bucal clínica. Foram selecionados 20 pacientes diabéticos tipo 2 e 17 pacientes não-diabéticos de ambos os gêneros, com idade média entre 37 e 55 anos, portadores de doença periodontal crônica. Após exame clínico para avaliação das condições clínicas periodontais, presença de xerostomia e presença clínica de candidose bucal, amostras de saliva foram coletadas para mensuração do fluxo salivar (mL/min), contagem das colônias de Candida spp. (UFC/mL) e identificação das espécies. Esse procedimento foi realizado antes da terapia periodontal (baseline), que consistiu em raspagem e alisamento radicular, instrução de higiene bucal e motivação do paciente, aos 30 e 90 dias após a mesma. Os resultados demonstraram que os pacientes diabéticos apresentaram maior ocorrência de xerostomia e de candidose bucal, sendo estes colonizados por várias espécies de Candida spp. com predominância de C. albicans, sem no entanto, implicar no desenvolvimento da candidose clinicamente. A terapia periodontal, a motivação do paciente e a instrução de higiene bucal foram importantes para melhorar as condições clínicas periodontais e evitar a formação de reservatórios intrabucais de infecção. / Abstract: In order to investigate the effect of periodontal therapy, in type 2 diabetes mellitus subjects about salivar flow rates, presence of xerostomia, presence of Candida species in the saliva and presence of buccal candidose, twenty type 2 diabetes mellitus subjects and seventeen no-diabetes mellitus subjects, with medium age among 33 to 55 years, presenting generalized chronic periodontal disease were selected. After initial clinical exam to analyze periodontal parameters, xerostomia and buccal candidose presence, saliva samples were assessed to quantify as millimeters of saliva generated per minute (mL/min), account yeasts by colony forming units per mL (CFU/mL) and identificated species. That procedure was accomplished before periodontal therapy (baseline) that it consisted in scaling and root planning, oral hygiene instructions and patient's motivation to the thirty and ninety days after these. Diabetics subjects showed to having hyposalivation in similar levels in no-diabetics groups and in all the analyzed periods, higher prevalence of xerostomia and higher occurrence of buccal candidose. Candida albicans were the prevalent yeast at all periods in both groups, but the presence of yeasts in saliva not implied in the development of buccal candidose. Concluded that the periodontal therapy, the patients' motivation and the buccal hygiene instructions improve periodontal conditions and avoid the formation of microbial reservoirs in mouth. / Mestre