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Tseitlin, Musii, and Valentina Raiko. "Ratio between heat and mass transfer when concentrating the solution in a cooling tower." Thesis, Lviv Polytechnic National University, 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/42106.
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The ratio between the intensity of the mass transfer in gas and the heat transfer in liquid during the evaporative solution concentration has been studied. It was determined that the share of liquid resistance in the total resistance to enthalpy transfer increases in the temperature range from 30 to 50°C by almost 2 times, and reaches 40 %. The technique has been developed for the separate determination of the mass transfer coefficients in gas and heat transfer in liquid.Досліджено співвідношення між інтенсивністю масопереносу в газі та передачею тепла в рідині під час концентрації випарного розчину. Встановлено, що частка опору рідини в загальному опорі переносу ентальпії зростає в діапазоні температур від 30 до 50 ° С майже в 2 рази, досягає 40%. Розроблена методика для окремого визначення коефіцієнтів масопереносу в газі і теплопередачі в рідині.
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Hopkinson, Jonathan M. "Glass transition, ice and the concentration of the maximally freeze concentrated solution the thermal behavior of sugar solutions /." Ann Arbor, MI : UMI, 1997. http://www.ethbib.ethz.ch/readme/ethz-etext.html.
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Major, Jacqueline. "A solution concentration model for CIP simulation." Thesis, Cape Technikon, 2001. http://hdl.handle.net/20.500.11838/871.
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Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town, 2001.Carbon-in-pulp technology is used extensively in the mining industry to recover metal cyanides from solution. Also this technology has found increasing application in the gold mining sector, replacing the less efficient zinc precipitation procedure. The extensive use of carbon in such processes have prompted many researchers to investigate the mechanism of metal cyanide adsorption. Not only has this provided many viable theories in the understanding of the mechanism, but has also led to an improved understanding of the effects of the various operating conditions on the ClP circuit. Also the modelling of this process has resulted in proposed rate equations of which the famous "kn" model is the most widely used in design. This is a single rate equation that could result in significant errors and hence a dual resistance model was developed. However this model is mathematically complex. Recently in an attempt to overcome the shortcomings of previous models, empirical calculations to accurately describe adsorption kinetics were developed at the Cape Technikon. These correlations were derived using batch experimental data. In this study the focus was on modeling the adsorption process on a continuous scale using a laboratory scale cascade system. This study utilized the fact that solution concentration is the main driving force for aurocyanide adsorption onto activated carbon and that carbon loading has an indirect effect on adsorption kinetics. The metal was ultimately tested against actual plant data and provided very accurate results.
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Lam, Luk Sang. "Flow conductivity of solutions of hyaluronic acid : effects of concentration and molecular weight." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28494.
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Hyaluronic acid plays an important role in regulating the transport of fluid and solutes in the interstitium. The concentration and molecular weight of hyaluronic acid in different connective tissues are different. These factors influence the hydraulic flow conductivity, K', of connective tissues. An experimental study of the effect of concentration and molecular weight of hyaluronic acid on the hydraulic flow conductivity is the subject of this work.
Hyaluronic acid of different molecular weights were obtained by
fractionating commercially available hyaluronic acid using ion-exchange column
chromatography. The results were not reproducible, partly because of the elution
process was not continuous. Nevertheless, three molecular weight fractions
(6.99 to 11.1 X 10⁵ ) were obtained. Hyaluronic acid of lower molecular weights (0.454 to 1.65 X 10⁵) were obtained by acid hydrolysing some of the chromatographed fractions for 15 min., 1 hour and 2 hours. A more homogeneous hyaluronic acid fraction (M.W. = 1.96 X10⁵) was obtained by fractionating hyaluronic acid materials acid hydrolysed for 15 min.
The hydraulic flow conductivity of solutions of hyaluronic acid can be calculated from the sedimentation coefficient of the solutions at 20°C, S₂₀‚ measured by ultracentrifugation. Centrifugation experiments determining the S₂₀ of the molecular weight fractions of hyaluronic acid at various concentrations were therefore undertaken. The results showed that S₂₀ decreased with increased
concentration of hyaluronic acid. Also, the curves of as a function of
hyaluronic acid concentration, c, converged at high concentration, indicating that a three dimensional molecular network is formed at high concentration and the
extent of entanglement between molecules is the same for the high and low
M.W. fractions. At lower concentrations, for the acid hydrolysed fractions, S₂₀
increased with M.W., which is in agreement with past sedimentation data. For
the non-acid hydrolysed fractions, the difference in S₂₀ between two higher M.W.
fractions is small, and the lowest M.W. fraction has consistently higher S₂₀ than
the higher M.W. fractions. This finding does not agree with past literature
results, and the difference in results is most probably due to experimental errors.
However, when the fractionated non-acid hydrolysed fractions are taken as a high M.W. group (M.W. = 6.99 to 11.1X10⁵) and the acid hydrolysed fractions as a low M.W. group (M.W. = 0.454 to 1.96X10⁵), the curves of S₂₀ as a function of c of the low M.W. group fall below those of the high M.W. group, which is in agreement with past sedimentation data.
The hydraulic conductivities (K'), calculated from S₂₀ data, for all the HA fractions varied inversely with concentration. The log-log plots of K' versus c compared well with the results of Ethier (1986). The K' versus c relationships for all the fractions converged at high concentrations. At low concentrations, the HA molecules of the high M.W. group has a higher K' than those of the low M.W. group.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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Chang, Yun Chea. "Concentration dependent diffusion of solid-solute, liquid-solvent systems in the supersautrated region." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/11802.
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Warczok, Justyna. "Concentration of Osmotic Dehydration Solutions using Membrane Separation Processes." Doctoral thesis, Universitat Rovira i Virgili, 2005. http://hdl.handle.net/10803/8534.
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El procesado de alimentos conlleva, en mayoría de los casos, la generación de subproductos o residuos que pueden ser reutilizados o revalorizados mediante la utilización de técnicas de separación por membrana. Estas técnicas ofrecen la posibilidad de tratar las soluciones en condiciones de operación muy suaves, y no comportan en mayoría de las ocasiones, una alteración de los componentes a recuperar. Actualmente, las técnicas de separación por membrana, debido a su alta calidad y relativamente bajos costes, se encuentran completamente integradas en la mayoría de procesos productivos que requieren de una etapa de separación. Sin embargo, la investigación en el área de las técnicas de separación por membrana sigue abriendo nuevos campos de aplicación, que surgen con la mejora de las condiciones tecnológicas de los equipos y la posibilidad de obtener nuevas membranas adaptables a necesidades específicas.En concreto, en este proyecto se utilizaron técnicas de separación por membranas para concentrar soluciones de azúcar procedentes de deshidratación osmótica (en adelante OD). El principal objetivo fue estudiar el potencial de varias técnicas de separación, haciendo hincapié en los flujos obtenidos durante la reconcentración y en la calidad de la solución reconcentrada.
La deshidratación osmótica es un tratamiento que permite una eliminación parcial del agua en un alimento y/o la incorporación de solutos de una manera controlada, respetando la calidad inicial del producto. El proceso consiste en introducir los alimentos en una solución hipertónica, controlando las condiciones de operación para favorecer, en mayor o menor grado la incorporación de solutos y la deshidratación del alimento. La aplicación de OD puede resultar en la mejora de las propiedades nutricionales y funcionales de los alimentos y en la reducción de la energía requerida para la deshidratación. El principal problema de la aplicación industrial de la OD radica en la gestión de la solución procedente del proceso. La reutilización de esta solución plantea una doble ventaja: primero desde el punto de vista ambiental, ya que se elimina un efluente del proceso que a menudo no puede ser vertido directamente, y segundo el ahorro económico que representa la recuperación de las materias primas que muchas veces contienen solutos de importante valor económico.
Los métodos de separación por membrana utilizados para recuperar las soluciones de OD fueron los siguientes: nanofiltración, osmosis directa y destilación osmótica por membranas. La nanofiltración (NF) presenta altos niveles de retención y un menor gasto de energía que la osmosis inversa, y en la industria azucarera se aplica como uno de los pasos en la clarificación y concentración de jarabes. En los procesos de contactores de membranas: osmosis directa (DO) y destilación osmótica por membranas (OMD), a diferencia de los procesos basados en el tamizaje, el flujo depende solamente de la diferencia de potencial osmótico. Las únicas presiones hidráulicas requeridas son las necesarias para bombear la solución de azúcar y la solución osmótica hasta la superficie de la membrana. Estas características hacen que estos procesos presenten como muy prometedores para la reconcentración de soluciones de azúcar de concentraciones elevadas.
Los experimentos de filtración se llevaron a cabo utilizando plantas piloto diseñadas y construidas expresamente para el presente proyecto. Durante todos los procesos de separación por membranas, se empleó como solución modelo una solución de sacarosa a diferentes concentraciones (5-60 ºBrix), debido a que las soluciones aplicadas en la deshidratación osmótica de frutas son habitualmente soluciones de azucares (sacarosa, glucosa o jarabes).
Durante los experimentos de NF se evaluó el funcionamiento de las membranas planas: Desal5 DK (GE- Osmonics), MPF-34 (Koch Membrane), NFT-50 (DSS) y tubulares: MPT-34 (Koch Membrane) y AFC 80 (PCIMembranes). Además de la solución de azúcar de diferentes concentraciones (5-20 ºBrix), se concentraron zumos de pera y manzana.
La reconcentración mediante osmosis directa se realizó utilizando dos modos de operación: off-site e on-site. En el modo off-site, la reconcentración por ósmosis directa se llevó a cabo en una planta de filtración provista de un módulo plano o tubular, dependiendo de la membrana. En el módulo se llevó a cabo la concentración. En el modo on-site, la deshidratación se realizaba conjuntamente con la reconcentración de la solución osmótica. La solución de reconcentración de la osmosis directa en off-site (offsiteDO) fue NaCl, mientras la solución de reconcentración de la osmosis directa on-site (on-site DO) fue una solución de sacarosa más concentrada que la solución osmótica (60 para una solución osmótica de 40 y 68 para una solución de 50 ºBrix). Para garantizar el flujo de agua entre las dos soluciones y altas retenciones de azúcar durante la off-site DO, se utilizaron membranas de NF planas (Desal5-DK y MPF-34) y tubulares (MPT-34 y AFC80). La reconcentración por osmosis directa on-site se levó a cabo empleando una membrana de microfiltración (Durapore, Millipore), ya que la solución de reconcentración (SS) es la misma que la solución osmótica y la alta viscosidad de la SS restringe mucho el flujo de agua si se utiliza una membrana más densa.
En la deshidratación por membranas (OMD) se utilizaron membranas hidrófobas (11806, Sartorius) que presentan una retención teórica del 100 %. Se comparó el rendimiento de dos soluciones de reconcentración: NaCl y CaCl2.
Con el fin de obtener información referente a la influencia de las propiedades de las membranas sobre el desarrollo del proceso de concentración de las soluciones procedentes de la deshidratación osmótica, se realizó un estudio detallado de las propiedades de las membranas aplicadas mediante AFM, SEM, FTIR, ángulo de contacto y medidas de potencial zeta. Con la finalidad de generar soluciones osmóticas para someterlas a reconcentración, y también para disponer de productos procedentes de deshidratación osmótica con soluciones frescas que pudieran compararse con aquellas procedentes de OD con solución reconcentrada, se deshidrataron diferentes lotes de manzana (Granny Smith) con soluciones de sacarosa de 40, 50 y 60 ºBrix. Estas pruebas permitieron determinar también el tímelo de operación para una máxima pérdida de agua con relativamente poca impregnación de las manzanas. Después de cada experimento se analizaron los siguientes parámetros: concentración de azúcar, pH, absorbancia a 420 nm de las soluciones y humedad de las manzanas.
La nanofiltración, aplicada en la primera fase del presente estudio, resultó ser viable solamente para la reconcentración de soluciones de concentraciones hasta 24 ºBrix. El aumento de la temperatura de 25 hasta 35 ºC para las dos membranas tubulares ocasionó un incremento del flujo de permeado, y el mismo efecto tuvo el aumento de presión transmembranaria de 8 a 12 bar.
Se comprobó que el factor más importante para la eficacia del proceso es disponer de una membrana que combine altos flujos y retenciones durante el proceso. La deposición de las partículas de sacarosa y/o los zumos se caracterizó mediante SEM y la topología de la capa filtrante de la membrana se identificó usando AFM. La topología de la capa filtrante de las membranas era diferente para cada una de ellas, a pesar de que todas estaban preparadas con el mismo material (poliamida). En las imágenes de los cortes transversales de las membranas realizados con SEM, se observaron los cambios en la estructura de las membranas producidos por la aplicación de presión durante los experimentos y las altas temperaturas empleadas durante su acondicionamiento. Gracias a las imágenes de SEM se pudo verificar también la eficacia del proceso de acondicionamiento de membranas.
A diferencia de NF, tanto la ósmosis directa como la destilación osmótica por membrana permiten la reconcentración de soluciones concentradas de sacarosa (hasta60 ºBrix). La eficacia de estas dos últimas técnicas se evaluó en unción de los flujos de agua obtenidos.
El sistema de ósmosis directa on-site propuesto para la reconcentración de las soluciones de OD permitió reutilizar las soluciones osmóticas como mínimo cuatro veces. Para la solución osmótica de 40 ºBrix la humedad de las manzanas fue similar utilizando solución fresca o reconcentrada. En cambio, una solución osmótica de 50 ºBrix, la pérdida de agua de las manzanas fue mayor cuando la deshidratación osmótica se llevó a cabo con reconcentración on-site de la solución osmótica. Los análisis de concentración de azúcar de las soluciones osmóticas y de la solución de reconcentración indican que la membrana elegida para los experimentos facilita el transporte óptimo de solutos y agua entre las dos soluciones. Además, el sistema de reconcentración por membrana propuesto es muy sencillo y de bajo coste porque no requiere presurización.
La osmosis directa en off-site proporcionó flujos mucho mayores que los obtenidos con el sistema on-site (1.3 kg/m2h para la solución osmótica de 50 ºBrix respecto a 0.0023 kg/m2h durante on-site DO para la misma solución). Sin embargo, el transporte de solutos de la solución de reconcentración hacía la solución osmótica puede ser considerado un obstáculo para su aplicación a escala industrial.
Los flujos de agua más elevados fueron obtenidos utilizando la OMD (2.01 kg/m2h para la solución osmótica de 50 ºBrix y con CaCl2 con la solución de reconcentración). Otra gran ventaja de este proceso es la retención de solutos que proporciona, hecho confirmado por los análisis realizados.
El estudio sobre el transporte durante los procesos de contactores de membranas indicó que la viscosidad es la propiedad limitante para la solución osmótica y la actividad de agua/alta presión osmótica como la propiedad más importante a la hora de elegir una solución de reconcentración. Para todos los procesos de separación aplicados, el aumento de la concentración de azúcar de la solución osmótica comporta una disminución notable del flujo de agua.
El desarrollo de un posible proceso de deshidratación osmótica con una etapa de reconcentración de la solución osmótica mediante procesos con contactores de membrana ha permitido calcular el área requerida para realizar la reconcentración: 3.6,9.7, 1608 m2 para OMD, off-site DO e on-site DO, respectivamente.
Las conclusiones del trabajo confirman la posibilidad de utilizar procesos por membrana para realizar la reconcentración de soluciones osmóticas. No obstante se ha constatado que técnicas más tradicionales basadas en diferencias de presión (NF) no son
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Bailey, Adelaide Fiona Grace. "The Concentration of Aqueous Solutions By Osmotic Distillation (OD)." Queensland University of Technology, 2005. http://eprints.qut.edu.au/16006/.
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This study was to investigate theory and application of Osmotic Distillation (OD). OD is a new novel membrane separation process used for the concentration of aqueous solutions such as fruit juices without the application of heat. The present work was undertaken to investigate flux limitations focusing on feedside, membrane and stripper side characteristics of OD. Once the limiting areas were identified, further studies were undertaken to determine methods of minimizing those limitations without losing the quality and integrity of the liquid feed. A laboratory scale OD system was used to simulate the industrial process which takes place during the production of grape juice concentrate for the fruit juice industry. Results of a UF pretreatment study showed that the use of UF membranes with pore diameters of 0.1 fÝm or less as a pretreatment for the subsequent OD of grape juice resulted in significant increases in OD flux over that observed for juice not subjected to UF. The study of the physical properties of the feed played an important role in the explanation of the OD process. The increase in OD flux was attributed to a reduction in juice viscosity as the result of the removal of protein and other high molecular weight components. Apart from an increase in OD flux, UF pretreatment of the grape juice proved to be beneficial in other areas of the OD process. HPLC measurements showed that the normal concentration of fermentable sugars in standard 68 oBrix concentrate can be achieved at a lower Brix value in feed subjected to UF pretreatment, further reducing the need to handle highly viscous feeds. UF pretreatment also resulted in an increase in juice surface tension consequently reducing the tendency for membrane wet-out to occur. The study of the deoxygenation of the feed solution shows that the removal of dissolved gases by the pre boiling method and the perstraction with chemical reaction (PCR) method both had a positive affect on OD flux. Pre boiling the brine resulted in an indirect reduction in dissolved oxygen in the feed. Pre boiling both the feed and brine, further increased the flux. Throughout the PCR study, it was evident that stripper side mass transfer of O2 was not limited by flowrate but was limited by higher stripper concentration. However, the latter had an insignificant effect when the sulfite-oxygen reaction was catalysed. The use of a catalyst and increase in temperature gave a significant improvement in overall mass transfer coefficient. Ten types of hydrophobic microporous membranes were tested for their influence on OD flux. While the pore diameter is a considerable factor in mass transport of gases through the membrane, it was also noted that the type of membrane material used had an affect on the overall mass transfer. All top three performing membranes had pore diameters of 0.2 x 10-6 m and were made from polytetrafluoroethylene (PTFE). The choice of brine to use as the stripper was based on criteria that were confirmed by the brine studies performed here. The best performing stripper solutions demonstrating the greatest improvement in OD flux over the most commonly used brines, NaCl, CaCl2 and CH3COOK were aqueous solutions of potassium salts of phosphoric acid, pyrophosphoric acid and blends thereof. These salts agreed with all the required characteristics of a suitable brine, demonstrating high solubility rates, supporting the ability to lower water vapour pressure. The study of the corrosion effects of brine salts confirmed the phosphate salts are superior demonstrating some of the lowest corrosion rates and highest pH.
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Tao, Jing. "Effects of Molecular Weight and Solution Concentration on Electrospinning of PVA." Digital WPI, 2003. https://digitalcommons.wpi.edu/etd-theses/889.
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"The effects of molecular weight (Mw) and concentration (c) on the structure of electrospun PVA have been studied. Experiments have been conducted for Mw values ranging from 9000 g/mol to 124,000 g/mol. The concentration was varied from 5 to 35 wt %. Data were acquired for several solvents including water, Dimethyl Sulfoxide, Ethylene Glycol and N-Methyl Pyrrolidone. The transient phenomena occurring during jet breakdown were examined by high speed digital photography. The structure in the electrospun polymer was analyzed by scanning electron microscopy. The fiber diameter distribution for various conditions was characterized by optical image analysis. The effects of additives such as NaCl and Poly Ethylene Glycol on the structure have been studied. The results indicate that a minimum Mw and c corresponding to [h]c ~ 5 or Capillary number, Ca ~ 0.5 is necessary for forming a fibrous structure. As Mw or c increase, the fiber diameter becomes larger and a broader distribution of fibers may be obtained. The average diameter of the fiber, D, follows a Power law relationship: D (nm) = 18.6([h]c)1.11. Round fibers may be obtained at low Mw and c, while flat fibers are observed at high Mw and c. The transition from round to flat fibers appears to begin at [h]c ~ 12. At any [h]c, there is a minimum Capillary and Ohnesorge numbers at which fibers are stabilized and a maximum at which viscous effects become dominant. The addition of NaCl lowers the average fiber diameter in PVA samples with a high molecular weight. Electrospinning can be used to produce nanofibers of PVA with various architectures. "
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Gilley, Andrew. "Amorphous solid dispersion effects on in vitro solution concentrations of quercetin." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/72864.
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Quercetin is a flavonol with potential health benefits including activities against cardiovascular disease, obesity, and oxidative stress. However, the benefits of quercetin are likely limited by poor bioavailability, primarily attributed to its poor aqueous solubility (due to its hydrophobicity and crystallinity) and extensive phase-II metabolism. Improving the apparent solubility of quercetin has the potential to improve its in vivo bioavailability. Strategies to increase solution concentrations in the small intestinal lumen have the potential to substantially increase quercetin bioavailability, and efficacy. We aimed to achieve this by incorporating quercetin into amorphous solid dispersions (ASDs) with cellulose derivatives, eliminating crystallinity, and selectively releasing amorphous quercetin under simulated intestinal conditions (pH 6.8, 37C). Amorphous quercetin was dispersed in cellulose esters including 6-carboxycellulose acetate butyrate (CCAB), hydroxypropylmethylcellulose acetate succinate (HPMCAS) and cellulose acetate suberate (CASub) to achieve stability and provide pH-triggered release. In addition, polyvinylpyrrolidone (PVP) containing CASub and CCAB blends were prepared to further promote enhanced dissolution. The ASD employing 10% quercetin in 20% PVP:70% CASub was most successful at enhancing the solution concentration of quercetin, providing an 18-fold increase in the area under the concentration/time curve (AUC) compared to quercetin alone. These results warrant in vivo assessment of quercetin-loaded ASDs formulated with CASub and its blend with PVP towards improving the bioavailability of quercetin.Master of Science in Life Sciences
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Проценко, Сергій Іванович, Сергей Иванович Проценко, Serhii Ivanovych Protsenko, Оксана Анатоліївна Гричановська, Оксана Анатольевна Гричановская, Oksana Anatoliivna Hrychanovska, Лариса Валентинівна Однодворець, et al. "Тemperature and Concentration Dependences of Anisotropic Magnetoresistance Film Materials." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42726.
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In framework the phenomenological approach the question of the temperature dependence of anisotropic magnetoresistance (AMR) at the fixed value inducing an external magnetic field (B) and the concentration dependence of AMR at the fixed B and T were analyzes. The obtained ratio to assess and predict the magnitude of thermal and concentration coefficients of AMR, virtually can not be done in the classical model, since it allows complex ratio with many uncertain parameters.
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Edali, Mohamed. "Rheological study of solutions of high concentrations of carboxymethyl cellulose." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0003/MQ43657.pdf.
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MERMA, ANTONIO GUTIERREZ. "ELETROCOAGULATION APPLIED TO TREAT SOLUTIONS WITH HIGH CONCENTRATION OF OIL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=12209@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOREfluentes oleosos são gerados de muitas fontes, tais como: indústrias petroquímicas, refinarias, plataformas de petróleo, fabricação de maquinarias, e até mesmo, no transporte, distribuição e armazenagem de óleo. O óleo presente na forma de emulsão é difícil de separar. Para quebrar essas emulsões, geralmente, são usados tratamentos químicos, biológicos, eletroquímicos, ultrafiltração. O processo de eletrocoagulação-flotação se inicia com a dissolução do anodo produzindo espécies aquosas (monoméricas, poliméricas) e precipitadas, espécies que funcionam como coagulantes e floculantes. As mesmas causam a desestabilização das emulsões através de mecanismos como a neutralização de carga superficial, ponte interparticular e coagulação por varredura, formando flocos de gotículas de óleo. A dissolução do metal no anodo é acompanhada da geração do gás hidrogênio no catodo. As bolhas são aderidas aos flocos, carregando-os até a superfície, onde são separados do reator, porém, dependendo da densidade deles, poderiam sedimentar-se. Neste trabalho, é avaliada a remoção de óleo de uma emulsão sintético pelo processo de eletrocoagulação-flotação. Avaliou-se a influência dos principais parâmetros de operação na taxa de redução da demanda química de oxigênio (DQO): concentração inicial do óleo; densidade de corrente; separação entre eletrodos; pH da solução; concentração de eletrólito. O efluente sintético foi preparado a partir de óleo Shell Talpa 30 e Oleáto de sódio como surfatante. Foi adicionado NaCl para aumentar a condutividade da solução. O pH inicial da emulsão foi de 8,70. O potencial zeta nessas condições teve um valor médio de -75mV, valor este que indicou a estabilidade da emulsão.
The separation of emulsions or colloidal particles from wastewater is a major concern for the petroleum, metal manufacturing, food, textile, paper and hydrometallurgy industries. The emulsion present is very stable due to the presence of surfactants, so conventional methods can not be applied and it is necessary to combine one or two treatment processes for highly effective purification. Several techniques have been applied to treat these types of oily wastewater, e.g.: chemical, biological and electrochemical destabilization, ultrafiltration. Electrocoagulation is initiated by the oxidation of sacrificial anodes. The metal ions released combine to the hydroxyl ions produced at the cathode to form the corresponding metal hydroxides and others species, which cause the destabilization of the contaminants or particulate suspensions and form flocs. The bubbles hydrogen gas capturing and floating the flocs formed and separating from the liquid surface by scraping or settling depending on density of the flocs. In this work, the electrocoagulation technique was studied in order to treat concentrated oil-water emulsions chemically stabilized. This study was mainly focused on the effects of operating parameters such as: initial pH, current density, reaction time, NaCl concentration, electrode distance and inlet concentration on the abatement rate of chemical oxygen demand (COD). The synthetic emulsion was prepared from Shell - Talpa 30 oil (3g.L-1) and sodium dodecyl sulfate (1.0 g.L-1), also was added NaCl (3g L-1) for increasing the conductivity of the emulsion. Under those conditions we had a pH value around 8.70 and a zeta potential around -70mV, showing a good stability of the emulsion.
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Wu, Min. "Effect of Nutrient Solution Electrical Conductivity Levels on Lycopene Concentration, Sugar Composition and Concentration of Tomato (Lycopersicon esculentum Mill.)." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195203.
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Tomato is an important commodity in fresh vegetable market. Recently, there is great interest for North American hydroponic growers to improve the fruit quality by introducing better cultivation methods. Manipulation of electrical conductivity (EC) of nutrient solution is a well-known technique to increase sugar concentrations of tomato; however, the potential risk of lower yield is the drawback of introducing this technique. Therefore to find a range of EC that can enhance the fruit quality while maintaining overall yield was the goal of this research. For this purpose, plant physiological responses such as transpirational and photosynthetic characteristics and fruit quality attributes including sugars and lycopene were investigated for selected cultivars under different EC. Regardless of cultivar, tomato plants showed a greater net photosynthetic rate at the reproductive growth stage compared to the vegetative growth stage. An increase of EC of influx nutrient solution up to 4.8 dS m-1 did not reduce the leaf photosynthesis, which supported a hypothesis that there is an optimum EC range for enhancing fruit quality without significant yield loss. A following experiment showed that the tomato fruit quality could be significantly enhanced when plants were grown under around 4.5 dS m-1 EC, in terms of total soluble solids (TSS) and lycopene concentration with no significant yield loss. Last experiment was conducted to quantitatively understand the accumulation of lycopene and sugars in fruits as affected by EC and its application timing relative to the fruit ripeness stages. High EC treatment of 4.5 dS m-1, regardless of its application timing, enhanced TSS and sugar concentration in the juice and lycopene concentrations of the fruit. However, the delayed high EC treatment (application of high EC after 4 weeks of anthesis) showed less enhancement for TSS and sugar concentration. Lycopene concentration of the fruit in the delayed EC treatment reached the same level as that in the standard high EC treatment (application since anthesis), which suggests that enhanced lycopene development under high EC is more related to an abiotic stress response during the fruit maturation, rather than fruit mass balance altered by the limited water flux to the fruit.
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Pape, Alicia Richelle. "Influence of Solvent Removal Rate and Polymer Concentration on Ordering Kinetics of Block Copolymers in Solution." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/85438.
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An examination of the ordering process of block copolymer microstructure with respect to concentration was performed. Specifically, the process of solution casting block copolymer films was studied using small-angle X-ray scattering (SAXS). A method for determining the volume fraction of ordered phase in solution as the system dried was developed and used to analyze the solution casting process in several different block copolymer films in the neutral solvent toluene; these polymers include poly(styrene-b-butadiene), poly(styrene-b-isoprene-b-styrene), poly(styrene-b-butadiene-b-styrene), and several poly(methyl methacrylate-b-butyl acrylate-b-methyl methacrylate) polymers with different block fractions. A method was also developed for studying different drying rates of these films at a constant temperature. Temperature quenches of poly(styrene-b-isoprene-b-styrene) were performed to evaluate the effect of concentration on ordering rate.
In all cases studied, an ordering layer was observed where self-assembly was thermodynamically favorable. This layer steadily grew until it reached the bottom substrate, resulting in a two-step ordering process. In the case of the styrene/diene copolymers, a constant polymer concentration was observed in the ordering layer as it grew to encompass the entire film. Kinetic entrapment was observed in the case of the diblock copolymer, as the system with a medium drying rate with respect to the other two experienced faster kinetics than the other two systems. For the two triblock copolymers, it was found that similar kinetics were observed with respect to the ordering layer concentration, largely due to skinning on the surface allowing time for lower sections of the film to order more completely.
In the acrylate copolymers studied, the kinetics were not able to be evaluated with respect to drying rate. This was due to domain compression that cause a disordering of ordered microstructure as solvent was removed. This disordering was attributed to interfacial disruption caused by the compression in the film. In addition, a significant decrease in domain spacing was observed to occur in the vertical direction as a result of compression in that direction and pinning of the film to the substrate in the horizontal direction.
Finally, the Avrami kinetic model was fit to several concentration of styrene/isoprene triblock copolymers as they ordered after a temperature quench. A U-shaped curve was observed in the system, as a result of competition between chain mobility effects and thermodynamic effects that occur as polymer concentration increases away from the CODT. It was found that the Avrami exponent remained constant over all concentrations, and an empirical model was fit to find the various rate constants at each polymer concentration.Ph. D.
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Aidibi, Ali. "Stress Concentration Factor and Fatigue Life Evaluation in offshore tubular KT-Joints." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Find full textAbstract:
In the last few decades, offshore field has grown fast especially after the notable development of technologies, explorations of oil and gas in deep water and the high concern of offshore companies in renewable energy mainly Wind Energy. Fatigue damage was noticed as one of the main problems causing failure of offshore structures. The purpose of this research is to focus on the evaluation of Stress Concentration Factor and its influence on Fatigue Life for 2 tubular KT-Joints in offshore Jacket structure using different calculation methods. The work is done by using analytical calculations, mainly Efthymiou’s formulations, and numerical solutions, FEM analysis, using ABAQUS software. As for the analytical formulations, the calculations were done according to the geometrical parameters of each method using excel sheets. As for the numerical model, 2 different types of tubular KT-Joints are present where for each model 5 shell element type, 3 solid element type and 3 solid-with-weld element type models were built on ABAQUS. Meshing was assigned according to International Institute of Welding (IIW) recommendations, 5 types of mesh element, to evaluate the Hot-spot stresses. 23 different types of unitary loading conditions were assigned, 9 axial, 7 in-plane bending moment and 7 out-plane bending moment loads. The extraction of Hot-spot stresses and the evaluation of the Stress Concentration Factor were done using PYTHON scripting and MATLAB. Then, the fatigue damage evaluation for a critical KT tubular joint based on Simplified Fatigue Damage Rule and Local Approaches (Strain Damage Parameter and Stress Damage Parameter) methods were calculated according to the maximum Stress Concentration Factor conducted from DNV and FEA methods. In conclusion, this research helped us to compare different results of Stress Concentration Factor and Fatigue Life using different methods and provided us with a general overview about what to study next in the future.
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Grisel, Michel. "Système schizophyllane/borax. Interactions en milieu dilué et semi-dilué. Rhéologie et morphologie des gels." Rouen, 1996. http://www.theses.fr/1996ROUES057.
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Le schizophyllane est un polysaccharide neutre d'origine fongique soluble dans l'eau ; il existe sous deux conformations distinctes selon les conditions de solvant : une conformation de triple-hélice ordonnée rigide et une conformation de pelote isolée. Nous avons étudié, principalement par rhéologie, la complexation du polysaccharide par les ions borate qui peut conduire, dans des conditions appropriées de salinité, à la formation de gels physiques lorsque le polysaccharide est sous forme de triple-hélice. Les mélanges schizophyllane/ions borate ont un comportement viscoélastique caractéristique de solutions visqueuses ou de gels selon la concentration en ions borate. Nous présentons l'influence des différents paramètres (concentrations, salinité, température. . . ) Sur le comportement des mélanges en régimes dilué et semi-dilué. La cinétique de formation des gels a également été étudiée, et leur morphologie a été examinée par microscopie électronique à balayage.
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Jiang, Bin. "Separation of water out of highly concentrated electrolyte solutions using multistage vacuum membrane distillation." Thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-129358.
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Absorption dehumidification requires regeneration system to regenerate diluted desiccant solutions, which are still highly concentrated. A novel multi-stage vacuum membrane distillation system was applied for separating water out of the highly concentrated solution. The performance of this novel membrane distillation system with high concentration solution is studied, as well as the effect of solution concentration, heating temperature and feed flow rate on concentration increase, permeate flux and specific energy consumption was studied. Feed solutions are LiCl solution (22-30 wt%) and CH3COOK solution (50-60 wt%).Other experimental parameters studied were: heating temperature, 70-80 °C, feed flow rate, 1.2-2.0 l/min. Response surface method is applied for model building, in order to provide a better understanding of the interactions between different parameters. Compared with pure water, high concentration solution has lower vapor pressure, which leads to lower permeate flux. The highest concentration the system can reach is 36.5 wt% for LiCl solution and over 70 wt% for CH3COOK solution, when the heating temperature is 80 °C. Lower concentration and higher heating temperature will result in larger increase in concentration, higher permeate flux and also lower specific energy consumption. But due to the configuration of the system, optimal flow rates can be found under different conditions. Within the testing region, the permeate flux ranges between 0.147-1.802 l/(m2h) for LiCl solution and 0.189-1.263 l/(m2h) for CH3COOK solution. With low concentration, high heating temperature and low feed flow rate, low specific energy consumptions, 0.85 kWh/l and 0.94 kWh/l for LiCl and CH3COOK solutions are observed respectively. With external heating recovery system, this value can be further reduced.
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Frayer, Daniel Keith. "Measurement of surface concentration of aqueous copper sulfate solutions: An optical technique." Thesis, The University of Arizona, 2000. http://hdl.handle.net/10150/278740.
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An integrated optical waveguide is described that can measure surface concentrations of ions while immersed in an ionic solution, especially the commercially interesting case of ionic copper. Several such sensors were manufactured and tested. The theory behind this measurement technology is described. Techniques for the manufacture and experimental measurement are described. The devices made were able to measure surface concentrations on the order of 10 12 atoms per square centimeter. Several potential methods for improving the performance are given.
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Lim, ChangHoon Ph D. Massachusetts Institute of Technology. "Prediction of concentrations of reactive nitrogen species in aqueous solutions and cells." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/70400.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 194-208).
Reactive nitrogen species (RNS) derived from nitric oxide (NO) have been implicated in cancer and other diseases, but their intracellular concentrations are largely unknown. To estimate them under steady-state conditions representative of inflamed tissues, a kinetic model was developed that included the effects of cellular antioxidants, amino acids, proteins, and lipids. For an NO concentration of 1 [mu]M, total peroxynitrite (Per, the sum of ONOO- and ONOOH), nitrogen dioxide (NO2), and nitrous anhydride (N20 3) were calculated to have concentrations in the nM, pM, and fM ranges, respectively. The concentrations of NO2 and N20 3 were predicted to decrease markedly with increases in glutathione (GSH) levels, due to the scavenging of each by GSH. Although lipids accelerate the oxidation of NO by 02 (because of the high solubility of each in hydrophobic media), lipid-phase reactions were calculated to have little effect on NO2 or N20 3 concentrations. The major sources of intracellular NO2 were found to be the reaction of Per with metals and with CO 2, whereas the major sinks were its reactions with GSH and ascorbate (AH-). The radical-scavenging ability of GSH and AH- caused 3-nitrotyrosine to be the only tyrosine derivative predicted to be formed at a significant rate. The major GSH reaction product was S-nitrosoglutathione. Analytical (algebraic) expressions were derived for the concentrations of the key reactive intermediates, allowing the calculations to be extended readily. To investigate the mutagenic and toxic effects of NO on cells, methods are needed to expose them to constant, physiological levels of NO for hours to days. One way to do this is to co-culture target cells with activated macrophages, which can synthesize NO at constant rates for long periods. A novel method, developed in the laboratory of Professor G. N. Wogan at MIT, involves the use of TranswellTM permeable supports (Coming), in which a porous membrane separates two chambers in a culture dish. Target cells and macrophages are placed on the top and bottom of the insert, respectively. Although the two cell types are in close diffusional contact, the target cells can be recovered separately for viability and mutation assays. To infer the NO concentration at the level of the cells from measured rates of formation of nitrite (N02-), a reaction-diffusion model was developed to calculate NO and 02 concentrations as a function of height in the medium. In this system the oxidation of NO to NO2 competes with the diffusional loss of NO to the incubator gas. It was shown that a one-dimensional, steady-state formulation is justified. The key factors affecting NO and 02 concentrations are the total rate of respiratory 02 consumption by the cells and their net rate of NO generation. Because the overall rate of the multi-step NO oxidation is second order in NO, the fractional loss of NO from the system by diffusion increases as the NO concentration is reduced. Also, the fractional loss of NO is increased if cellular 02 consumption is elevated. The cellular NO concentration was predicted to be nearly proportional to the square root of the NO2 formation rate. Thus, in experiments in the Wogan laboratory in which NMA (an inhibitor of NO synthase) was added to the culture medium, reducing NO2 formation by 90%, the cellular NO concentration was calculated to decrease only by about two-thirds (from 1.1 [mu]M to 0.36 [mu]M). To facilitate the use of the reaction-diffusion model by other laboratories, a graphical method was developed to allow cellular NO concentrations to be estimated from measured rates of NO2 accumulation. The controlled delivery of NO2 into aqueous solutions, in the absence of NO, would be useful in investigating its rates of reaction with biological molecules and in isolating its effects on cells from those of other RNS. Two possible NO2 delivery methods were investigated theoretically. One was the direct contact of NO2 gas mixtures with stirred aqueous solutions, and the other was diffusion of NO2 through gas-permeable tubing (such as polydimethylsiloxane, PDMS) into such solutions. In gases and in water, NO2 dimerizes reversibly to form dinitrogen tetroxide (N204), which reacts rapidly with water to produce nitrite and nitrate. Thus, it was necessary to describe the coupled reaction and diffusion of NO2 and N20 4 in each kind of system. Microscopic models were developed to describe spatial variations in concentrations near the gasliquid interface, or within the tubing wall and immediately adjacent liquid. These were used to predict parameter values (such as mass transfer coefficients) in macroscopic models designed to describe bulk aqueous concentrations. Because the direct measurement of NO2 and N20 4 concentrations at the low levels desired for biological experiments is impractical, the combined models are needed to estimate bulk NO2 and N20 4 concentrations from measurable quantities such as rates of N0 2- accumulation. For direct gas-liquid contacting, the utility of a quasiequilibrium approximation (QEA) was examined. This assumes that the NO2 and N20 4 concentrations are related as for dimerization equilibrium. At relatively high NO2 concentrations in the delivery gas, the results from the QEA and exact equations were in excellent agreement. As the NO2 level was reduced, the QEA eventually fails, because NO2 increasingly resembles an unreactive species as its concentration approaches zero. However, the QEA was found to be quite accurate throughout the practical range of concentrations (0.001% to 1% NO2 gas), the relative error in total fluxes not exceeding 6%. The results show that it is desirable to use as low an NO2 concentration as is analytically feasible (such as 0.001% NO2 gas). This minimizes both the concentration of N20 4 and the effects of concentration nonuniformities in the aqueous boundary layer. For NO2 delivery through gas-permeable tubing such as PDMS, the modeling was more complicated and the results more uncertain. The main complication was due to the presence of a concentration boundary layer within the membrane next to the liquid, which required that the governing equations be rescaled for that region. The major source of uncertainty is the unknown solubility of N20 4 in PDMS. However, as the gas concentration was lowered, the results became insensitive to this parameter. For 1% NO2 gas, the estimated bulk NO2 concentrations were 7.1 pM for the direct gas contact and 0.35 pM for the gas-permeable tubing. For 0.001% NO2 gas, the estimated NO2 concentrations were 0.45 [mu]M for the direct gas contact and 0.14 [mu]M for the gas-permeable tubing. For both methods, the times to reach steady state were predicted to be quite fast, at most 10 seconds.
by ChangHoon Lim.
Ph.D.
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Zanain, Mabrouk Ali Masaud. "Removal of low concentrations of silver from aqueous solutions using adsorption methods." Thesis, Swansea University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678471.
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Cornu, Jean-Yves. "Evolution temporelle de la concentration de Cd²⁺ en solution de sol au cours d'une culture végétale : impact sur l'exposition racinaire." Bordeaux 1, 2007. http://www.theses.fr/2007BOR13516.
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La contamination des sols par les éléments traces métalliques constitue un danger pour la santé humaine, notamment /via/ la contamination de la chaîne alimentaire. Le cadmium (Cd) présente un danger particulièrement important en raison de sa forte toxicité à long terme pour l’homme (source INRS) et de sa capacité élevée de transfert du sol vers les parties consommées des végétaux. Le développement d’outils prédictifs du transfert sol-plante de Cd est de ce fait à favoriser. Il passe par la compréhension et la modélisation du transfert de Cd du sol vers la racine végétale. Dans ce contexte, l'objectif général de cette étude était d'identifier et de hiérarchiser les paramètres physicochimiques, et les processus associés, affectant la concentration de Cd2+ en solution de sol au cours d'une culture végétale. Ce travail a confirmé la difficulté d’évaluer la spéciation de Cd en solutions naturelles. Il a mis en évidence de fortes variations de la concentration de Cd2+ en solution de sol au cours du temps de culture, en lien avec l'établissement localisé de conditions anaérobies. L'activité dénitrifiante de la microflore s'est avérée être un processus majeur de contrôle de la concentration de Cd2+ en solution de sol au cours du temps, son impact sur le bilan ionique de la solution de sol conditionnant la désorption de Cd depuis la phase solide. Un mode de calcul de l'exposition racinaire tenant compte de ces variations temporelles de concentration de Cd2+ en solution a permis de mieux prédire le prélèvement de Cd par les racines végétalesThe contamination of soils by trace elements constitutes a danger for human health, notably through the contamination of the food chain. Cadmium (Cd) is particularly dangerous because of its high toxicity to man for the long term (source INRS) and its high transfer capacity from the soil to the edible parts of plants. Thus, the development of tools which are able to predict the soil-plant transfer of Cd is desirable. It requires the understanding and the modelling of the transfer of Cd from the soil to the plant root. In this context, the aim of this study was to identify and to prioritize the physico-chemical parameters, and the related processes, that affect the Cd2+ concentration in soil solution over a culture period. This work confirmed the difficulties in evaluating the speciation of Cd in natural solutions. It put into evidence strong temporal changes in solution Cd2+ concentration, in relation with the localized establishment of anaerobic conditions in soil. Microbial denitrification emerged as a major process in controlling the concentration of Cd2+ in soil solution over time, its impact on the solution ionic strength conditioning the desorption of Cd from the solid phase. The integration of the temporal variations in Cd2+ concentration through the calculation of the root exposure to solution Cd improved the prediction of the uptake of Cd by plant roots
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Merlin, Aurore. "Cinétiques de concentration de suspensions colloïdales par évaporation microfluidique : de la solution diluée aux cristaux colloïdaux." Phd thesis, Bordeaux 1, 2010. http://tel.archives-ouvertes.fr/tel-00564692.
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Cette thèse est consacrée à l'étude de processus de concentration de solutions colloïdales par voie microfluidique, pour former des matériaux denses et structurés. A partir d'un outil basé sur la perméation de l'eau à travers le PDMS : le microévaporateur, nous proposons de contrôler le séchage de solution pour maîtriser la concentration de solutés afin de former des états denses organisés au choix, alternant cristaux et états amorphes de colloïdes. En adaptant les outils de microévaporation à différentes techniques d'observations, la nucléation et la croissance d'états denses ont été finement étudiées et correlées à un modèle simple de la microévaporation. Ces études expérimentales ont montré le contrôle précis qu'apporte le microévaporateur sur les cinétiques de concentration d'espèces chimiques pour la formation d'états denses de particules. Des études complémentaires ont aussi mis en évidence l'existence d'une dynamique de construction de cristaux colloïdaux avec des réorganisations au niveau du front ainsi qu'un effet de compaction présents lors de la croissance de l'état dense.
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Wang, Hui. "Interfacial and Solution Characterization of Rhamnolipid Biosurfactants and their Synthetic Analogues." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/217062.
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Rhamnolipid (RL) biosurfactants have been considered "green" alternatives to synthetic surfactants. Here, systematic studies of monorhamnolipids (mRLs) and their synthetic analogues are performed to characterize their interfacial and solution behaviors as surfactants. Chemical structure-surface activity relationships of rhamnolipids were probed using surface tension measurements on RLs and a series of their synthetic analogues designed by "truncation modification." Based on our study on RLs and the rationally-designed RL analogues, the key structural factor responsible for the excellent surface activity performance of rhamnolipids is the presence of the rhamnose moiety in the headgroup. As a result, rhamnopyranosides (RhEs), the simplest surfactants with a rhamnose moiety in the headgroup, show surface activity comparable to the bioproduced mRLs. The purified mixture of mRLs harvested from Pseudomonas aeruginosa ATCC 9027 was mixed with a nonionic surfactant Tween-20 (TW) and studied by surface tension measurements at pH 8. The experimental values of CMC show deviation from the theoretical values predicted by ideal solution theory, which is hypothesized to be due to a shape change from rod-shaped to spherical as the mole fraction of TW is increased. The hypothesis about the shape change is supported by dynamic light scattering results, regular solution theory, and packing parameter theory. Polarization modulated-infrared reflection-absorption spectroscopy (PM-IRRAS) has been used to characterize the orientation of the synthetic rhamnolipid Rha-C18-C18 at the air-water interface. Although rhamnolipids exhibit pH-dependent micellization, their orientation at the air-water interface is not affected by pH. The average tilt angle of their alkyl chains is determined to be ~45° at a surface pressure π = 40 mN/m which decreases to 36° when Pb²⁺ is present in the subphase. Assisted by molecular modeling, the packing of mRLs at the air-water interface is believed to be dominated by the packing of their large hydrophilic headgroups. Finally, the adsorption isotherm of mRLs on hydrophobic polyethylene surfaces was generated by ATR-FTIR from solutions of different pH, which were then fit to a Frumkin adsorption model to yield the thermodynamic adsorption parameters, the adsorption equilibrium constant and the interaction parameter. mRLs strongly adsorb to d-PE, and the adsorption is pH dependent.
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Papadopoulos, Dimitrios [Verfasser]. "Quantification of concentration measurements in multicomponent systems through inverse problem solutions / Dimitrios Papadopoulos." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2011. http://d-nb.info/1018186948/34.
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Li, Melissa. "A microscale molecular weight analysis method for characterizing polymers solutions of unknown concentrations." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31673.
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Thesis (M. S.)--Biomedical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Hang Lu; Committee Co-Chair: Rachel Chen; Committee Member: Johnna Temenoff; Committee Member: Yonathan Thio. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Meets, Michiel. "The determination of the concentration of aqueous smoke solutions used in restoration projects." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51955.
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Thesis (M.Sc.)--Stellenbosch University, 2000.ENGLISH ABSTRACT: It is well known that smoke and aqueous smoke solutions promote the germination of certain seeds. This has considerable practical implications for restoration in fire prone areas like the Cape fynbos. The aqueous smoke solution (more commonly known as smoke water) can be used in restoration projects to stimulate seeds to germinate faster so that a wide diversity of plants can be established rapidly. Smoke water is made using different methods and different plant materials. This inevitably results in different concentrations of smoke water. Although made in different ways, different smoke waters may all have an enhancing effect on seed germination. In this study, the germination of Grand Rapids lettuce seed was used to determine the differences between five different types of smoke water. Germination was done in a controlled environment, using through-flow germination boxes (patent no. ZA2000/1832, registered 1114/2000) instead of traditional petri dishes. The differences in the concentrations were determined using bioassays. A very strong concentration of smoke water damaged the seed and a very weak concentration did not have any enhancing effect on germination. The concentrations of the different smoke waters were compared to a standard smoke solution (the first smoke solution ever made, that of De Lange & Boucher (1990». The different concentrations of the smoke solutions were determined by comparing them to the standard, using a best fit line on the germination graphs. Each of the smoke solutions tested is given a "delb" rating (after De Lange & Boucher), with the standard smoke water being 1 delb. The delb value is used to determine the dilution factor for each smoke solution. It is concluded that the five smoke solutions tested all differed from each other emphasizing the need for quality control in commercial and experimental applications.
AFRIKAANSE OPSOMMING: Dit is wel bekend dat rook en vloeibare rook oplossings (rookwater) die ontkieming van sekere sade bespoedig. Dit het groot praktiese implikasies vir hervestiging in gebiede met gereelde vuur, soos die Kaapse fynbos. Die rookwater kan in hervestiginsprojekte gebruik word om sade te stimuleer om vinniger te ontkiem om sodoende 'n groot diversiteit van plante vinnig te vestig. Rookwater word op verskillende maniere en met verskillende materiaal vervaardig. Dit kan lei tot verskillende konsentrasies rookwater, alhoewel al die verskillende rookwaters 'n stimulerende effek op saadontkieming kan bewerkstellig. In hierdei studie is Grand Rapids slaai saad gebruik om die verskille tussen vyf verskillende rookwaters te ondersoek. Ontkieming was in 'n beheerde atmosfeer gedoen en deurvloei ontkiemingsbakke (patent nr. ZA2000/1832, geregistreer 11/4/2000) is gebruik, i. p. v. traditionele petri bakkies. Die verskille in konsentrasies is gemeet m. b. v. biotoetse. 'n Baie serk konsentrasie het die sade beskadig en 'n baie flou konsentrasie het geen stimulerende effek op ontkieming gehad nie. Die konsentrasie van die verskillende rookwaters is vergelyk teenoor 'n standaard rookwater (die eerste rookwater ooit gemaak, die van De Lange en Boucher (1990». Die verskillende rookwater konsentrasies is bepaal deur dit met die standaard te vergelyk m. b. v. 'n regressie lyn op die ontkiemingsgrafieke. Elke rookwater getoets kry dan 'n "delb" waarde (n. a. v. De Lange & Boucher), met die standard gelyk aan 1 delb. Die delb waarde word gebruik om die optimale verdunning van elke rookwater te bepaal. Daar word opgesom dat al die rookwaters getoets wel van mekaar verskil en dit beklemtoon die waarde van kwaliteits beheer in kommersiële en eksperimentele toepassings.
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Garlock, Lori A. "The effect of various acidic solutions on the concentration of genistein in tempeh." Online version, 2000. http://www.uwstout.edu/lib/thesis/2000/2000garlockl.pdf.
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Awobusuyi, Tolulope David. "Concentration of Ammonium from Dilute Aqueous Solutions using Commercially Available Reverse Osmosis Membranes." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34642.
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Several commercially available reverse osmosis (RO) membranes were characterized with aqueous solutions of ammonium sulfate, potassium triphosphate, and mixtures of these two salts at different feed concentrations, compositions and pressures. The objective of this study was to investigate the rejection of these solutes, in particular the ammonium ion (NH4+), by different RO membranes. The aqueous solutions were assumed to come from an anaerobic digester via a process, currently under investigation by CHFour Biogas Inc., to maintain low concentrations of ammonia in the digester in order to maximize the biogas production. The ammonium ions present in the liquid produced from the process are then concentrated using membrane separation. The concentrated ammonium solution would be a valuable fertilizer that could be used by agriculture.
The membranes were characterized with three models: the solution-diffusion model, the Kedem-Katchalsky model, also known as the irreversible thermodynamics model, and the Donnan Steric Pore Model (DSPM). The solution-diffusion and irreversible thermodynamics models were found to be inadequate for proper membrane characterization and the use of the DSPM model yielded membrane properties in good agreement with those found in already existing literature. The pore radius of investigated membranes ranged from 0.39 to 0.51 nm. The effect of pH on membrane surface charge was also studied, with the conclusion that increases in pH led to increasingly negative surface charges. This affected the transport of individual ions through the membrane due to preferential passage of the counter-ions. The effects of applied pressure on the stoichiometric nature of salt rejections were also studied.
The minimal observed rejection from the range of experiments carried out using ammonium sulfate was 93%Non-stoichiometric rejections of ions were also observed in the experiments with single and multiple solutes. Furthermore, the rejection of ammonium ions in the presence of other ions (K+, SO42-, PO43-) increased as feed concentration increased, which was a result of the synergistic effects of feed pH and ionic interactions. The minimum NH4+ rejection in the presence of other ions was 95.4%, which suitability using RO membranes for concentration of ammonium from dilute aqueous solutions.
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Benhabiles, Ali. "Étude d'un nouveau procédé de concentration de solutions thermosensibles : l'évaporation osmotique : optimisation et application à la concentration de jus de pomme." Compiègne, 1998. http://www.theses.fr/1998COMP1135.
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L'évaporation osmotique est une nouvelle opération membranaire dont le but est la concentration de solutions aqueuses à température ambiante et à pression atmosphérique. Le liquide à concentrer (phase d'alimentation) est séparé d'une solution salée très concentrée (phase réceptrice) par l'intermédiaire d'une fine membrane microporeuse hydrophobe. Le moteur du transfert de vapeur d'eau de la phase d'alimentation vers la phase réceptrice est un gradient de pression de vapeur d'eau dû à la différence de pression osmotique entre les deux liquides de part et d'autre de la membrane. Une synthèse bibliographique permet de situer l'évaporation osmotique par rapport aux autres contacteurs à membrane et notamment, par rapport à la distillation membranaire. L'étude théorique montre que dans des conditions normales d'utilisation, le flux de vapeur s'exprimera de façon différente selon la valeur du rapport du libre parcours moyen des molécules à la dimension de pore : selon les cas, la dimension de pore influera ou non sur le flux de vapeur transférée. Par la suite, une étude du procédé en cellule de diffusion a été menée. Les influences sur le flux de la pression osmotique de la phase réceptrice, des vitesses d'agitation des solutions, de la température ainsi que celles de l'épaisseur et de la dimension des pores de la membrane ont été évaluées. Les résultats de cette étude paramétrique ont ensuite été utilisés pour vérifier la validité du modèle de transport, évaluer les résistances au transport dues à la membrane et à la couche limite de concentration dans la phase réceptrice et enfin pour modéliser le procédé en cellule agitée (régime non laminaire) par l'établissement d'une expression reliant les trois nombres adimensionnels Reynolds, Schmidt et Sherwood. L'étude en cellule agitée a été complétée par une évaluation du rôle joué par la présence d'air dans les pores et par une application à la concentration de solutions à fortes teneurs en glucose. La dernière partie du travail concerne des essais pilotes sur du jus de pomme. Elle a montré la possibilité de concentrer ce jus de fruit jusqu'à 630 g/I. Dans la perspective d'une application industrielle, un schéma type d'installation combinant osmose inverse et évaporation osmotique a été proposé et les consommations énergétiques estimées.
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Shukla, Sushumna. "Membrane distillation with porous metal hollow fibers for the concentration of thermo-sensitive solutions." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20215/document.
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Cette thèse présente une approche originale du procédé de distillation membranaire avec balayage gazeux pour la concentration des solutions thermosensibles (SGMD). Pour ce faire, un nouveau contacteur membranaire avec des fibres creuses métalliques a été conçu afin réaliser le procédé de distillation à basse température. La chaleur nécessaire au procédé est produite au niveau des fibres par effet Joule, plutôt qu'à partir de chaleur latente de la phase aqueuse. La génération localisée de la chaleur a comme conséquence une réduction du phénomène de polarisation de la température. Des fibres creuses en acier inoxydable ont été synthétisées avec les propriétés structurales appropriées et une bonne résistance mécanique. La surface des pores des fibres a été rendue hydrophobe par le dépôt d'une fine couche d'un élastomère. En outre, une nouvelle méthode « verte » a été développée pour fabriquer des fibres creuses en alumine et acier inoxydable. Cette méthode est basée sur la gélification ionique des bio-polymères et ne n'utilise pas des solvants nocifs. L'étude expérimentale détaillée du SGMD a permis de déterminer l'influence de différents paramètres opérationnels sur les performances du procédé. Il a été démontré que l'effet Joule permet d'améliorer le flux et l'efficacité de la séparation non seulement pour le SGMD mais aussi pour la pervaporationThis thesis presents an original approach for the concentration of thermo-sensitive solutions: the Sweep Gas Membrane Distillation (SGMD) process. A new membrane contactor with metallic hollow fibers has been designed and allows the distillation process to be operational at low temperature. Heat is generated in the fibers by the Joule effect, rather than being supplied as latent heat in the liquid bulk. The localized generation of heat results in a reduction of temperature polarization phenomena. The stainless-steel hollow fiber membranes have been synthetized with appropriate structural properties and sufficient mechanical strength. The pore surface of the fibers has been made hydrophobic by the deposition of a thin layer of an elastomer. Moreover, a novel and green method is presented to fabricate alumina and stainless-steel hollow fibers. This method is based on ionic gelation of a biopolymer and completely avoids the use of harmful solvents. By a detailed experimental study of the SGMD the influence of different operational parameters on the process performance has been investigated. The improvements in the flux and the separation efficiency using Joule effect have been successfully demonstrated, even in the case of pervaporation
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Berriaud, Jouon Nadine. "Contribution à l'étude des propriétés du hyaluronane : comportement rhéologique, hydratation." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10164.
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Au cours de ce travail, nous avons caracterise les echantillons de hyaluronane et tente d'obtenir des hyaluronanes de differentes masses molaires par hydrolyse acide ou reticulation menagee. Nous avons montre que le hyaluronane se compose comme une chaine simple semi-rigide et que les echantillons utilises sont tres purs avec un indice de polymolecularite faible. Nous avons egalement etudie les proprietes rheologiques et viscoelastiques des solutions de hyaluronate de sodium dans les regimes semi-dilue et concentre en fonction de differents parametres. Nous montrons en presence de sel que le comportement en fonction de la concentration en polymere et du gradient de cisaillement est tres semblable a celui des polymeres flexibles. Par contre, une difference est obtenue en fonction de la masse molaire. L'etude viscosimetrique des melanges de hyaluronate de differentes masses molaires a permis de montrer que les regles classiques d'additivite permettaient de determiner les masses molaires moyennes et les viscosites intrinseques des melanges. Nous montrons aussi que la viscosite des solutions suit une loi identique a celle des constituants seuls en fonction du parametre de recouvrement. L'etude de l'hydratation du hyaluronane a l'aide de la technique de calorimetrie differentielle a balayage nous a permis de montrer l'influence importante de la nature des ions compensateurs et du ph de precipitation du polymere sur la quantite et la nature de l'eau absorbee
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Chintala, Rajesh. "Lime induced changes in the surface and soil solution chemistry of variable charge soils." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5552.
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Thesis (Ph. D.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains ix, 128 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
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Hamzah, Khaidzir. "A study on the effects of solution concentration, surface finish and corrosion processes on electrochemical noise." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515142.
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The aims of this research were to study the effects of electrolyte concentration, surface finish of samples and different types of corrosion on electrochemical noise. Basically, electrochemical noise is a term used to describe the spontaneous fluctuations of potential or current at electrode surfaces in electrochemical processes. In order to achieve the research aims, several experiments involving different corrosion systems were carried out. The corrosion systems were chosen to produce known types of corrosion. For the effects of varying electrolyte concentration on uniform corrosion, two systems were chosen; mild steel in hydrochloric acid, HCI and in sulfuric acid, H2S04 solutions. As for pitting corrosion, four systems were chosen, namely mild steel in a mixture of calcium hydroxide, Ca(OH)2 and sodium chloride, NaCI, mild steel in a mixture of sodium nitrite, NaN02 and NaCI, stainless steel 303 and stainless steel 304 in NaCI solution. Electrolyte concentration was varied in experiments involving the two former systems in order to see the effect of concentration on pitting corrosion. For the other two systems, the surface of the electrodes was varied to three finishes. 320. 600 and 1200 grit. This was to see the effect of surface finish on pitting corrosion. Analysis of the data obtained was carried out by examining the time records, the power spectra (including the impedance spectra). corrosion parameters (noise resistance, Rpo characteristic charge, q and characteristic frequency,ln, which were derived from simple statistical parameters). Maps of pairs of the corrosion parameters and the cumulative probability of each parameter occurring were plotted. Evolvement of corrosion parameters with time was also investigated. Analysis of the time record showed that they could distinguish uniform corrosion from pitting corrosion. From power spectra analysis, it was found that the technique could not be used to see the effects of changes in concentration and surfaces finish nor could it be used to distinguish uniform corrosion from pitting corrosion. It was found that parameter maps were not able to distinguish the changes in solution concentrations and surface fInish. Parameter maps were not able to distinguish between uniform and pitting corrosion of similar type of samples from different systems but were able to distinguish uniform corrosion from pitting corrosion. Cumulative probability method was not able to differentiate the variation in solution concentrations and in surface finish. It was also not able to distinguish between uniform and pitting corrosion. Impedance spectra analysis was not suitable to indicate the types of corrosion occurring. It was also unable to distinguish the variations in the solution concentrations and surface finishes used. Finally, it was found that, evolvement of corrosion parameters is independent of time.
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Kłos, J. S., and J. U. Sommer. "Dendrimer solutions: a Monte Carlo study." Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A36416.
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We study the conformational properties of dendrimers with flexible spacers in solutions over a wide range of concentrations from dilute solutions to melts. By combining large scale computer simulations using the bond fluctuation model with scaling arguments we identify the semi-dilute regime of dendrimers which is controlled by the concentration behavior of the linear spacers. Associated with this observation we find that the decrease in the size of flexible dendrimers is accompanied by increasing interpenetration between the molecules with increasing concentration of the solution. In the melt state we show that the size of individual dendrimers follows the scaling prediction for isolated dendrimers at the θ-point rather than that of collapsed dendrimers. The pair correlation functions between the centers of dendrimers indicate that for short spacers dendrimer solutions retain the morphological characteristics of simple liquids. For long spacers the functions reveal high penetration of neighboring dendrimers in the melt state. Our studies show that flexible dendrimers in solution can be understood with arguments similar to those of linear polymers. The role of generation is to influence the particular form of the crossover-function.
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Spelling, Victor, Mathias Axelsson, Lovisa Ringström, af Rosenschöld Johanna Munck, and Anton Lindblad. "Mapping the intrinsic viscosityof hyaluronic acid at high concentrations of OH-." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325348.
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Hyaluronic acid is commonly used in dermatological fillers in the form of gels. It is established how these gels' firmness is affected by the amount of cross linker and hyaluronic acid respectively. However, the effect of hydroxide ions in solution is rather unknown. This thesis examines how the alkalinity of the solvent affects the intrinsic viscosity of 3 MDa hyaluronic acid by using the method of Ubbelohde capillary viscometry. Sodium hydroxide solutions between 2 and 10 wt% were prepared to study the variation in intrinsic viscosity at concentrations relevant for cross linking (1<wt%). From these respective solutions, four solutions of different mass concentrations of hyaluronic acid were made. The flow time of respective samples were measured between two points in the capillary viscometer in a controlled temperature of 25 °C with an SI Viscoclock to ensure a high accuracy.From the resulting flow times, the intrinsic viscosity was calculated. The intrinsic viscosity varied between 0,55 and 0,70. The relation between intrinsic viscosity and hydroxide ion concentration had a correlation coefficient r < 0,001. No trend could be ensured as the confidence interval for the intrinsic viscosity at the different concentrations was too large.
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Djolov, George Georgiev. "The Herfindahl-Hirschman Index as an official statistic of business concentration : challenges and solutions." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71678.
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Thesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: This dissertation examines the measurement of business concentration by the Herfindahl- Hirschman Index (HHI). In the course of the examination, a modification to this method of measurement of business concentration is proposed, in terms of which the accuracy of the conventional depiction of the HHI can be enhanced by a formulation involving the Gini index. Computational advantages in the use of this new method are identified, which reveal the Ginibased HHI to be an effective substitute for its regular counterpart. It is found that theoretically and in practice, the proposed new method has strengths that favour its usage. The practical advantages of employing this method are considered with a view to encouraging the measurement of business concentration using the Gini-based index of the HHI.
AFRIKAANSE OPSOMMING: Hierdie verhandeling ondersoek die meting van sakekonsentrasie deur middel van die Herfindahl- Hirschman-indeks (HHI). ‘n Wysiging aan hierdie metode word voorgestel, deur middel waarvan die akkuraatheid van die konvensionele voorstelling van die HHI verhoog word, deur ‘n formulering wat die Gini-indeks betrek. Die berekeningsvoordele van hierdie nuwe metode word geïdentifiseer en dit word aangetoon dat die Gini-gebaseerde HHI ’n doeltreffende plaasvervanger vir sy meer bekende teenvoeter is. Daar word bevind dat die voorgestelde nuwe metode teoretiese en praktiese sterkpunte het wat die gebruik daarvan ondersteun. Die praktiese voordele van die voorgestelde metode word oorweeg met die oog op die aanmoediging van die gebruik van die Gini-gebaseerde HHI-indeks as maatstaf van sakekonsentrasie.
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McNulty, Christopher S. (Christopher Sean) 1976. "Spectral processing algorithms for predicting glucose concentration of various solutions from NIR absorbance spectroscopy." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80611.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 83-84).
by Christopher S. McNulty.
M.Eng.
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Kuhn, Jeff. "Parameters influencing the concentration of aqueous tin in acidic sulphate solutions containing Fe(III." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5302.
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Includes abstract.Includes bibliographical references (leaves 118-123).
This thesis investigates parameters influencing the concentration of aqueous tin in acidic sulphate solutions containing Fe(III/II) as they arise in the Reduction Releach process at Teck Cominco Trail Operations (TCML). This study documents the impact of initial sulphuric acid and As(V) concentrations, temperature, and lead concentrate reductant amount on tin solubility in acidic Fe(III/II) sulphate solutions as they arise in an intermediate leaching step at TCML. Supporting test work examined the speciation of commercial tin bearing residues involved in the processing of indium and germanium. Analysis of these residues determined the oxidation state of crystalline tin in ZnO fume, Ge Preconcentrate, and Releach residue to be primarily Sn(IV), and associated with zinc, lead, and iron oxides; in addition to lead, iron, and aluminum silicates, and minor amounts of Sn(II) as SnO or SnSO₄. Experimental validation of Sn(II) solubility values in 100 g/L H2SO4, between 30 to 90 °C, compared well with literature and theoretical tin solubility values. Measured tin solubility values ranged between 95 g/L Sn and 99 g/L Sn concentration. The aqueous tin concentration decreased slightly (4 g/L Sn) when the temperature was increased from 30 to 90°C. Measured aqueous tin values for both thesis benchscale test work and commercial Reduction Releach process were all less than 1 g/L Sn. The oxidation rate of Sn(II) between 300 mg/L and 700 mg/L in 100 g/L H₂SO₄ at 20 °C, was first order kinetics with a rate constant ranging between 0.0002 and 0.0003 mg Sn/L∙s, and the REDOX potential (Eh) varied between 550 and 650 mV. The low rate constants may have been due to poor mass transfer. Iodometry could not be used for aqueous tin analysis with other divalent and trivalent cations present in solution and, therefore, inductive coupled plasma analysis was used.
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Malpas, David George. "The mass transport properties of selected membranes in potassium hydroxide solutions of various concentrations." Thesis, Middlesex University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.568381.
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Aspects of the mass transport processes occurring in the ion-exchange membranes, PUDO 193, a Cellophane membrane derived from regenerated cellulose and Permion 2291 40/30, a grafted co-polymer of polyethylene and methacrylic acid, were studied while the membranes were swollen in solutions of KOH of a wide range of concentrations. Measurement of the dimensional changes (length, width and thickness) of as received Cellophane films, after immersion in solutions of KOH, revealed a complex swelling behaviour with the majority of swelling resulting in changes in thickness. Unlike Cellophane, and as a consequence of their different structure, the swelling behaviour of Permion films were found to be less complex. The swelling behaviour was used to determine the porosity of the swollen membranes. The ion-exchange capacity of the mono-functional Permion was obtained by pH titration, a method unsuitable for use with Cellophane since it is not fully exchanged at low external electrolyte concentrations. The ion-exchange properties of Cellophane were determined using atomic absorption techniques and a crion tracer method which was deemed suitable since similar results were obtained for Permion by this method and by pH titration. Transport numbers of potassium ions and transference numbers of water through Cellophane and Permion as single membrane types were obtained using a meticulous technique, which minimised the unwanted effects of diffusion and osmosis. The method obtained transport numbers relevant to a specific concentration by holding solution composition constant and equal on either side of the membrane. The confidence gained in the technique, enhanced by careful cell testing and the application of correction factors, provided a sound basis for the measurement and subsequent understanding of transport behaviour in the less obvious situation, namely in assemblies of membranes. Measurements of the resistance of Cellophane and Permion ftlms equilibrated in solutions of KOH were made. Membrane resistance vs. membrane thickness plots were curved due to current refraction into the region where the membrane was clamped between the two halves of the conductivity cell. The data was linearised using a nonempirical correction factor and hence the accuracy of the measured membrane conductivity was improved. From the primary resistance data, electrolyte conductivity and the mobilities of the potassium and hydroxyl ions in free solution were calculated. The ratio of potassium to hydroxyl ion mobility in free solution formed a basis for a comparison with a similar mobility ratio in the membrane phase. This method allowed a comparison of mobilities in free solution and the membrane phase without the necessity of estimating a suitable tortuosity factor. Models of tortuosity were then introduced to assess the blocking characteristics of the two membranes. The transport properties of assemblies of Cellophane and Perm ion were investigated. Transport numbers entering and leaving the assembly were found to be different and depended on the orientation of the assembly. For the situation where transport numbers were greater leaving the assembly and at low current densities a steady state was reached and the depletion of electrolyte at the interface was replaced by diffusion, osmosis and hydraulic flow. At high current densities depletion of electrolyte at the interface was rapid causing the decomposition of the Cellophane. For the situation where transport numbers were greater entering the assembly, the assembly separated at the Permion/Cellophane interface due to the accumulation of electrolyte, the difference between measured and predicted transport numbers was accounted for by the effects of diffusion and osmosis which occurred mainly in the Cellophane.
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Lopes, Gustavo Henndel. "On the coupling of membrane transport to hydrodynamics and bulk mass transfer in reverse osmosis : numerical modeling and experimental studies." Thesis, Ecole centrale de Marseille, 2014. http://www.theses.fr/2014ECDM0013/document.
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La prédiction des performances des séparations membranaires barométriques, fortement affectées par la polarisation de concentration, serait une avancée importante pour le dimensionnement et l’optimisation des procédés. Dans ce contexte, les équations couplées de Navier-Stokes et de conservation du soluté adimensionnées sont résolues numériquement dans le cas d’un écoulement stationnaire laminaire en filtration tangentielle. Le canal plan bidimensionnel comporte des parois perméables soumises à des conditions aux limites du type solubilisation-diffusion. Le flux de perméat, le taux de rétention et le débit, la concentration et la chute de pression du rétentat sont déterminés localement. Les simulations soulignent l’influence des perméabilités membranaires au soluté et au solvant sur la polarisation de concentration et la dépendance non-asymptotique du taux de rétention avec la pression appliquée. Le modèle est validé pour des modules plans et spiralés d’osmose inverse et de nanofiltration dense en comparant les calculs à des résultats expérimentaux tirés de la littérature et de nos propres essais pilotes de dessalement. Aussi, une méthode à l’échelle de la paillasse permettant de déterminer les perméabilités au soluté et au solvant par des expériences d’osmose et diffusion est développée et appliquée à des membranes d’osmose inverse et de nanofiltration. La divergence des mécanismes de transfert engendrés sous l’influence de la pression ou sous l’influence d’un gradient osmotique est mise en évidence. Le modèle numérique et la méthode expérimentale sont des outils prometteurs d’applicabilité immédiate dans le domaine des membranesThe prediction of the performance of pressure-driven membrane separations, deeply affected by concentration polarization, would be an important advance for process design and optimization. In this context, the dimensionless coupled Navier-Stokes and solute conservation equations are solved numerically for a steady laminar cross-flow filtration. The two-dimensional flat channel consists of permeable walls subject to solution-diffusion boundary conditions. The permeate flux, the rejection rate and the retentate’s flow rate, concentration and pressure drop are determined locally. The simulations highlight the influence of the membrane solute and solvent permeabilities on concentration polarization and the non-asymptotic dependence of the rejection rate on the applied pressure. The model is validated for reverse osmosis and tight-nanofiltration plate-and-frame and spiral-wound modules by comparison to experimental results from the literature and from our own pilot desalination tests. Furthermore, a bench-scale method enabling the determination of solute and solvent permeabilities from osmotic-diffusive experiments is developed and applied to reverse osmosis and nanofiltration membranes. The divergence between the transport mechanisms engendered by pressure and by an osmotic gradient is evidenced. The numerical model and the experimental method are new promising tools with immediate applicability in the membrane field
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Pisarenko, Aleksey N. "Analytical Measurements and Predictions of Perchlorate Ion Concentration in Sodium Hypochlorite Solutions and Drinking Water: Kinetics of Perchlorate Ion Formation and Effects of Associated Contaminants." Oxford, Ohio : Miami University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1258154594.
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Conza, Adelaida Otazu. "Modelagem matemática do espalhamento do poluente mercúrio na água." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/169289.
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O objetivo deste trabalho e a modelagem matem atica da propagaçãao do poluente mercúrio na agua. O modelo bidimensional consiste na drenagem da agua atrav es de um canal, onde o poluente (mercúrio) entra. O modelo consiste em um conjunto de equaçõoes diferenciais parciais: as equações para a conservação da massa, a quantidade de movimento, e a concentração das espécies, sujeitas a condições iniciais e de contorno apropriadas. Estas equações foram discretizadas pelo método de diferenças finitas centrais, gerando sistemas lineares que foram resolvidos pelo método de Gauss-Seidel e a convergência foi acelerada usando a técnica de sobre-relaxações SOR. A an alise da consistência e estabilidade da equação de concentração foi feita. Além disso, a solução analítica da equação de concentração, que e uma equação diferencial parcial bidimensional não homogênea com uma condição de contorno não homogênea, foi obtida com a transformada de Laplace. Os resultados obtidos a partir do modelo numérico e da solução analítica foram comparados e apresentam concordância razoável.The goal of this work is the mathematical modeling of the spreading of the polluting mercury in the water. The two-dimensional model consists of water drainage through a canal, where the pollutant (mercury) enters. The model consists of a set of partial di erential equations: the equations for the conservation of the mass, the momentum, and the concentration of the species, subject to appropriate initial and boundary conditions. These equations were discretized by the method of central nite di erences, generating linear systems, which were solved by the Gauss-Seidel method and convergence was accelerated using the over-relaxation SOR technique. The analysis of the consistency and stability of the concentration equation was made. Furthermore, the analytical solution of the concentration equation, which is a two-dimensional non-homogeneous partial di erential equation with one nonhomogeneous contour condition, was obtained using Laplace transform. The results obtained from the numerical model and the analytical solution were compared and presented reasonable agreement.
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Won, Jooyoung [Verfasser], and Gerald [Akademischer Betreuer] Brezesinski. "Dynamic and equilibrium adsorption behaviour of ß-lactoglobulin at the solution/tetradecane interface: Effect of solution concentration, pH and ionic strength / Jooyoung Won ; Betreuer: Gerald Brezesinski." Potsdam : Universität Potsdam, 2016. http://d-nb.info/1218792973/34.
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Dindar, Cigdem. "High-pressure viscosity and density of polymer solutions at the critical polymer concentration in near-critical and supercritical fluids." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35720.
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The motivation for the determination of the viscosity of polymer solutions in dense fluids at the critical polymer concentration stems from the need to understand the factors that influence the time scale of phase separation in systems that undergo spinodal decomposition upon a pressure quench. In a recent investigation of PDMS + CO2 and PE + n-pentane where molecular weights of the polymers and the critical polymer concentrations were comparable, significant differences were observed in the time evolution of new phase growth. Among the reasons that contribute to the difference in phase separation kinetics is the viscosity of the solutions.
This thesis has been carried out to experimentally demonstrate the differences in viscosities of solutions at their critical polymer concentration. Specifically, the thesis focused on the high-pressure density and viscosity of solutions of poly(dimethylsiloxane) (Mw = 93,700, Mw/Mn = 2.99) in supercritical carbon dioxide and of polyethylene (Mw = 121,000, Mw/Mn = 4.3) in near-critical n-pentane. The measurements have been carried out at the critical polymer concentrations, which is 5.5 wt % for solution of PDMS in CO2 and 5.75 wt % for solution of PE in n-pentane. For PDMS + CO2 system, the measurements were conducted at 55, 70, 85 and 100 oC and pressures up to 50 MPa. For PE + n-pentane system, the measurements were conducted at 140 and 150 oC and again up to 50 MPa. All measurements were conducted in the one-phase homogenous regions. At these temperatures and pressures, the viscosities were observed to be in the range from 0.14 mPa.s to 0.22 mPa.s for PDMS + CO2, and from 2.3 mPa.s to 4.6 mPa.s for PE + n-pentane systems. In both systems the viscosities increase with pressure and decrease with temperature. The temperature and pressure dependence could be described by Arrhenius type relationships in terms of flow activation energy (E#) and flow activation volume (V#) parameters. The flow activation energies in PDMS + CO2 system were about 7 kJ/mol compared to about 18 kJ/mol for the PE + n-pentane system. The activation volumes were in the range 40-64 cm3/mol for PDMS + CO2 system and 65-75 cm3/mol for the PE + n-pentane solution. The higher values of E# and V# represent the higher sensitivity of viscosity to temperature and pressure changes in the PE + n-pentane system. The viscosity data could also be correlated in terms of density using free-volume based Doolittle type equations. Density is shown to be an effective scaling parameter to describe T/P dependency of viscosity. The closed packed volumes suggested from density correlations were found to be around 0.33 cm3/g for the PDMS and 0.48 cm3/g for the PE systems. Comparison of the viscosity data in these systems with the data on the kinetics of pressure-induced phase separation confirms that the slower kinetics in the PE + n-pentane stems from the higher viscosity in this solution compared to the PDMS + CO2 system, despite the similarity in the molecular weight of the polymer and the critical polymer concentrations.
These viscosity and density measurements were conducted in a special falling-body type viscometer. In the course of this thesis a more reliable procedure for determining the terminal velocity of the falling sinker was implemented. This is based on the precise and more complete description of the position of the sinker with time with the aid of a set of linear variable differential transformers (LVDTs). The design of the new arrangement and procedure for terminal velocity determination and calibration procedures for the viscometer are also presented. The densities and viscosities are determined with an accuracy of ± 1 % and ± 5 % or better, respectively.Master of Science
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Essi, Marc. "Elaboration et caractérisation de membranes chalcogénures ionosensibles : réalisation d'un module de pré-concentration d'ions lourds en solution." Montpellier 2, 2006. http://www.theses.fr/2006MON20058.
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Sandhi, Arifin. "ARSENIC REMOVAL BY PHYTOFILTRATION AND SILICON TREATMENT : A POTENTIAL SOLUTION FOR LOWERING ARSENIC CONCENTRATIONS IN FOOD CROPS." Doctoral thesis, KTH, Mark- och vattenteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-203995.
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Use of arsenic-rich groundwater for crop irrigation can increase the arsenic (As) content in food crops and act as a carcinogen, compromising human health. Using aquatic plant based phytofiltration is a potential eco-technique for removing arsenic from water. The aquatic moss species Warnstorfia fluitans grows naturally in mining areas in northern Sweden, where high concentrations of arsenic occur in lakes and rivers. This species was selected as a model for field, climate chamber and greenhouse studies on factors governing arsenic removal and arsenic phytofiltration of irrigation water. The arsenic and silicon (Si) concentrations in soil, water and plant samples were measured by AAS (atomic absorption spectrophotometry), while arsenite and arsenate species were determined using AAS combined with high pressure liquid chromatography (HPLC) with an anion exchange column. The arsenic content in grains of hybrid and local aromatic rice (Oryza sativa) cultivars with differing arsenic accumulation factor (AF) values was investigated in an arsenic hotspot in Bangladesh. The results showed that arsenic AF was important in identifying arsenic-safer rice cultivars for growing in an arsenic hotspot. The study based on silicon effect on arsenic uptake in lettuce showed that arsenic accumulation in lettuce (Lactuca sativa) could be reduced by silicon addition. The aquatic moss had good phytofiltration capacity, with fast arsenic removal of up to 82% from a medium with low arsenic concentration (1 µM). Extraction analysis showed that inorganic arsenic species were firmly bound inside moss tissue. Absorption of arsenic was relatively higher than adsorption in the moss. Regarding effects of different abiotic factors, plants were stressed at low pH (pH 2.5) and arsenic removal rate was lower from the medium, while arsenic efflux occurred in arsenate-treated medium at low (12°C) and high (30°C) temperature regimes. Besides these factors, low oxygenation increased the efficiency of arsenic removal from the medium. Finally, combining W. fluitans as a phytofilter with a lettuce crop on a constructed wetland significantly reduced the arsenic content in edible parts (leaves) of lettuce. Thus W. fluitans has great potential for use as an arsenic phytofilter in temperate regions.QC 20170323
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Kriaa, Abdelkader. "Mécanismes de corrosion du fer en solutions acqueuses et hydro-organiques à fortes concentrations d'acide." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37614800r.
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Bassani-Linck, Valquiria. "Valorisation de formes galéniques végétales : désalcoolisation et concentration de solutions extractives sur membrane d'osmose inverse." Montpellier 1, 1990. http://www.theses.fr/1990MON13514.
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Sinquin, Anne. "Alginates associatifs : synthèse et étude physico-chimique en milieu aqueux." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL035N.
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La synthèse de polymères hydrosolubles présentant un caractère associatif a été effectuée, par réaction de diverses alkylamines à chaine longue (Cn-NH2, 8≤n≤16) sur l'alginate de propylène glycol (PGA), un dérivé partiellement estérifié d'un polysaccharide extrait des algues. Les propriétés physico-chimiques des dérivés hydrophobisés résultants ont été étudiées, comparativement à celles des polymères parents, en rhéologie, en spectrophotométrie de fluorescence et par des mesures de tension superficielle, dans l'eau pure ou en présence de sels. De façon générale, on observe que le caractère associatif des dérivés synthétisés augmente avec le taux et la longueur des segments hydrophobes immobilisés sur le PGA. Ainsi, si les effets d'interactions hydrophobes ne sont pas mis en évidence pour le dérivé en C8, les dérivés hydrophobisés par des chaines alkyles longues (C12 et C14) présentent, quant à eux, d'importantes variations de comportement par rapport aux polymères parents. Celles-ci résultent de la mise en place d'interactions hydrophobes entre les chaines alkyles immobilisées sur le squelette polysaccharidique. Ces interactions sont essentiellement de nature intramoléculaire en solution diluée tandis que les associations intermoléculaires deviennent prépondérantes en régime semi-dilué. Des entités de volume hydrodynamique élevé apparaissent alors et conduisent à une augmentation spectaculaire de la viscosité, pouvant aller jusqu'à la formation d'un réseau tridimensionnel ayant une structure de gel physique
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Huraux, Karine. "Morphologies et gradients de concentration induits par le séchage dans des solutions polymères et des gels." Paris 6, 2008. http://www.theses.fr/2008PA066457.
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Cette thèse présente l’étude de morphologies de surface induites, à la surface de films polymères et de gels, par le séchage. La première partie porte sur la séparation de phases induite par évaporation du solvant dans des films réalisés à partir d’un mélange de deux polymères immiscibles, l’un vitreux, l’autre cristallin à température ambiante, en solvant commun. La morphologie obtenue dépend des conditions de séchage et des propriétés physicochimiques du système. Nous avons mis en évidence, en fonction de la composition du mélange, une inversion de morphologie. L’étude d’une composition donnée permet de distinguer, en fonction de la vitesse de séchage, différents régimes. La seconde partie traite de la formation, à la surface de gels chimiques de polyalcool vinylique, d’instabilités de plissement dépendant des conditions de séchage et de synthèse. Cette morphologie est attribuée à la formation d’une peau vitreuse qui subit, lors de la contraction du gel, une force de compression relaxée par la formation de plis. Nos travaux confirment expérimentalement l’existence de cette peau vitreuse (microscopie à force atomique) et estiment son épaisseur par simulation.