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Grewal, Burrinder S. "Mechanisms of chemical and physical transdermal penetration enhancement." Thesis, Aston University, 1999. http://publications.aston.ac.uk/10978/.
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The underlying theme of this thesis is one of exploring the processes involved in the enhancement of percutaneous absorption. The development of an attenuated total reflectance Fourier-Transform infrared (ATR-FTIR) spectroscopic method to analyse diffusion of suitable topically applied compounds in membrane is described. Diffusion coefficients (D/h2) and membrane solubility (AO) for topically applied compounds were determined using a solution to Fick's second law of diffusion. This method was employed to determine the diffusional characteristics of a model permeant, 4-cyanophenol (CP), across silicone membrane as a function of formulation applied and permeant physicochemical properties. The formulations applied were able to either affect CP diffusivity and/or its membrane solubility in the membrane; such parameters partially correlated with permeant physicochemical properties in each formulation. The interplay during the diffusion process between drug, enhancer and vehicle in stratum corneum (SC) was examined. When enhancers were added to the applied formulations, CP diffusivity and solubility were significantly enhanced when compared to the neat propylene glycol (PG) application. Enhancers did not affect PG diffusivity in SC but enhancers did affect PG solubility in SC. PG diffusion closely resembled that of CP, implying that the respective transport processes were inter-related. Additionally, a synergistic effect, which increases CP diffusivity and membrane solubility in SC, was found to occur between PG and water. Using 12-azidooleic acid (AOA) as an IR active probe for oleic acid, the simultaneous penetration of CP, AOA and PG into human stratum corneum was determined. It was found that the diffusion profiles for all three permeants were similar. This indicated that the diffusion of each species through SC was closely related and most likely occurred via the same route or SC microenvironment.
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Veilleux, Jocelyn. "The hydrodynamics of mass diffusion enhancement in nanofluids." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97103.
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In this thesis, mass diffusion processes in nanofluids are investigated by means of total internal reflection fluorescence (TIRF) microscopy and physical modeling. In particular, the design of a novel TIRF microscopy system and image processing algorithms specifically aimed at the measurement of the mass diffusion coefficient of a fluorescent dye in nanofluids are presented.When studying the diffusion of rhodamine 6G (R6G) in deionized water with this TIRF microscopy system, it is found that the mass diffusion coefficient averages to D = 3.3E-10 square meter per second. Both the accuracy and precision of this measurement compare to the best reported values.Numerical simulations are performed to quantify the detrimental effect of solutal buoyancy on mass diffusivity measurements in a confined millichannel geometry. It is shown that the buoyancy-induced fluid motion significantly affects the measurements even at low dye loadings, but that injecting the dyed fluid through a porous hydrophilic membrane hinders the onset of natural convection.The TIRF microscopy method is then applied to the measurement of the mass diffusivity of R6G in water-based alumina nanofluids of various volume fractions (0.1 to 4.0 vol%). A mass diffusion enhancement up to 10-fold is observed in a 2 vol% nanofluid when compared to deionized water.Following this observation, a Brownian motion-induced dispersion model is developed to explain the enhancement of mass diffusion. It appears that the nanoparticle Brownian motion is sufficient to induce velocity disturbances in the surrounding fluid. These velocity disturbances are similar to the velocity profile predicted by the Brinkman equations, which allow to draw an analogy between dispersion in diluted fixed beds and dispersion in nanofluids. It is shown that this model is capable of predicting the order of magnitude of the mass diffusivity enhancement in water-based alumina nanofluids.La diffusion massique dans les nanofluides est étudiée par l'entremise de la microscopie en fluorescence par réflexion totale interne (ci-après nommée microscopie TIRF, pour Total Internal Reflection Fluorescence) et de modélisation physique. En particulier, le design d'un microscope TIRF ainsi que les algorithmes de traitement d'images spécifiquement destinés à la mesure du coefficient de diffusion d'un colorant fluorescent dans les nanofluides sont présentés.La microscopie TIRF et les algorithmes de traitement d'images sont d'abord employés pour déterminer le coefficient de diffusion de la rhodamine 6G (R6G) dans l'eau déminéralisée. Le coefficient moyen obtenu, à savoir D = 3,3E-10 mètre carré par seconde, confirme à la fois la justesse et la précision de la méthode de mesure proposée, comparativement aux techniques établies.L'emploi d'une membrane poreuse hydrophile lors de l'injection de la solution de R6G permet de retarder l'apparition et de réduire les conséquences des effets de la flottabilité solutale sur les mesures de diffusivité dans un canal aux dimensions millimétriques.Ensuite, cette méthode de microscopie TIRF est utilisée pour mesurer le coefficient de diffusion de la R6G dans des suspensions de nanoparticules d'alumine dans l'eau, pour différentes fractions volumiques (0,1 à 4,0%). Les résultats montrent que la diffusion massique est améliorée par un facteur 10 pour un nanofluide contenant 2 vol% de nanoparticules, comparativement à la valeur obtenue dans l'eau déminéralisée.Enfin, un modèle de dispersion induite par mouvement brownien est développé pour expliquer l'amélioration de la diffusion massique. Il s'avère que le mouvement brownien des nanoparticules est suffisant pour induire une perturbation dans le fluide environnant et ainsi créer un profil de vitesse qui sera à l'origine de la dispersion. Ce profil de vitesse s'apparente à la solution aux équations de Brinkman et permet de tirer une analogie entre les nanofluides et les lits de particules fixes pour établir le modèle de dispersion. Les prédictions du modèle concordent avec l'ordre de grandeur du coefficient de diffusion mesuré.
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Johnson, Mark E. "Biophysical aspects of transdermal drug delivery and chemical enhancement." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10912.
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Ling, Juliette Roseanne. "Enhancement of the interfacial transfer of iodine by chemical reaction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ29382.pdf.
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Nadgouda, Sourabh Gangadhar. "Syngas and Hydrogen Production Enhancement Strategies in Chemical Looping Systems." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1564740683265567.
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Pham, Vu Anh. "Surface modifying macromolecules for enhancement of polyethersulfone pervaporation membrane performance." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9817.
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The objective of this work was to modify the surface of polyethersulfone membranes in order to render them more useful in pervaporation for the removal of volatile organic compounds (VOC) from aqueous solutions. Surface Modifying Macromolecules (SMNs) were designed and developed as surface modifiers of asymmetric polyethersulfone (PES) membranes. Eight SMM polymers were synthesized in triplicate using methylene bis-p-phenyl diisocyanate (MDI), polypropylene oxide (PPO) and polyfluoroalcohol (BA-L). They represented a 2$\sp3$ factorial design used to study the effects of reactant stoichiometry, prepolymer reactant concentration and chain length of the polyfluoroalcohol on the SMM properties and reproducibility of the SMM synthesis. The bulk SMM polymers were characterized with differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and elemental analysis. The compatibility between PES and SMM polymers was studied by DSC. The average molecular weight of SMM polymers, determined by GPC, were in the range of $1.0\times10\sp4\rm\ to\ 3.5\times10\sp4$. As predicted by theoretical considerations, SMMs were found to have migrated to the PES surface, rendering it more hydrophobic. This migration effect was confirmed by water droplet contact angle measurements and X-ray photoelectric spectroscopy (XPS). Opaqueness of PES/SMM films and results of DSC showed that SMM was either immiscible or partially miscible with PES. Preliminary pervaporation studies indicated that the addition of SMMs improved the selectivity of PES membranes, used in the separation of chloroform/water mixtures by 150 to 240%, depending on the chemical formulation of the SMM. In several cases, SMMs also improved the permeation rate. From a preliminary assessment of the changes in membrane surface and bulk characteristics, the surface chemistry and energetics were observed to contribute an important role in inducing the membranes' enhanced properties. (Abstract shortened by UMI.)
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McCleave, Robert W. (Robert William). "Impinging jet heat transfer with turbulence enhancement at the nozzle." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68045.
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The effect of turbulence enhancement at the nozzle exit on fluid flow and heat transfer characteristics was investigated for confined jets from sharp-edged nozzles.Average turbulence intensity of the jet flow was characterised by integrating the local turbulence intensity values over the width of the nozzle and at several axial positions from the nozzle exit to the near approach to the impingement surface. Average impingement heat transfer was obtained by integrating the local Nusselt number over an area of the impingement surface relevant to the process engineering application of impingement drying of paper.
Of the several simple methods of turbulence generation examined, the most effective was the simple expedient of placing a bar with a diameter 1/8 that of the nozzle width along the centreline of the slot nozzle. For a heat transfer averaging area equivalent to a nozzle area of 5% of the impingement surface and a nozzle to impingement surface spacing of 1.0 to 1.5 times the nozzle width, this simple method increased average heat transfer rates over those of the plain nozzle by 14%, with only a 7% increase in nozzle operating pressure. The results are presented as enhancement in average heat transfer as a graphical function of mean turbulence intensity, and as an empirical correlation between mean Nusselt number, mean intensity of turbulence and Reynolds number.
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Krishnan, Gayathri. "Skin penetration enhancement techniques." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1471.
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Transdermal drug delivery is an effective alternative to conventional oral and injectable drug delivery routes. It offers painless and convenient once daily or even once weekly dosing for a variety of clinical indications. The major limitation to successful transdermal drug delivery is the efficient barrier properties of the skin. Significant research efforts have been focused on developing strategies to overcome these barrier properties. These strategies include the use of physical and chemical penetration enhancers. Physical skin penetration enhancers use an external energy source to alter the barrier properties of the skin. The current research focuses on some of these physical skin penetration enhancers on a range of drug molecules and peptides.The first technology investigated was Dermaportation that utilised pulsed electromagnetic energy. This technology enhanced the epidermal permeation of naltrexone in vitro as compared to passive diffusion. A 5-fold increase in naltrexone permeation was observed during Dermaportation application when compared to passive administration. Multiphoton tomography-fluorescence life-time imaging microscopy (MPT-FLIM) analysis of the permeation of gold nanoparticles in the presence of Dermaportation revealed increased penetration across ex vivo human skin. These results demonstrated that the channels created by dermaportation must be larger than the 10 nm diameter of the applied nanoparticles.The second technology investigated was an unpowered magnetic film array technology (ETP), which utilised unpowered magnetic energy. Chapter 3 presents enhanced epidermal permeation of urea with ETP. A 4-fold increase in urea penetration was observed across human epidermis in the in vitro permeation study. Optical resonance tomography was used to visualise the changes in epidermal thickness due to urea permeation as an indication of increased hydration. The results revealed an increase in epidermal thickness at 30 min, to 16% for ETP induced urea permeation as compared to 3% with urea from occlusion. These results further substantiated our previous findings that magnetic energy creates hydrophilic diffusion channels or pores in the skin.The third technology investigated was low-frequency sonophoresis that utilises cavitation bubbles as a force to create channels for drug delivery in the skin. Chapter 4 presents enhanced human skin permeation of 5-aminolevuleninic acid in vitro and curcumin dye in vivo with low-frequency sonophoresis. Two different sources of ultrasound devices that generated low-frequency sonophoresis were investigated. MPT-FLIM analysis was utilised to investigate the effects of sonophoresis on human skin in vivo. This revealed that there was substantial disturbance in the epidermal cells due to cavitation by sonophoresis. Permeation of curcumin was found in the deeper layers of the epidermal membrane with 55 kHz sonophoresis and was confined to the more superficial layers of skin with 21 kHz sonophoresis. Permeation of 5-aminolevuleninic acid across human skin increased significantly when compared to passive permeation.The fourth technology investigated in this research was iontophoresis which utilises a small electric current to drive charged and uncharged molecules across the skin. Chapter 5 presents enhanced epidermal permeation of a range of model therapeutic and cosmetic peptides. Various key parameters such as pH, concentration and presence of counterions and co-ions that are essential for effective iontophoretic delivery of these peptides were investigated. The iontophoretic delivery of 5- aminolevulenic acid revealed a 15-fold enhancement when compared to passive diffusion. For dipeptide (Ala-Trp) the mean cumulative amount increased iontophoretic delivery from 0.4±0.4, 0.1μg/cm2 to 16.0±8.8, 3.6μg/cm2 (Mean±SD, SEM) was observed when the donor pH was reduced from 7.4 to 5.5. The corresponding current intensity (0.38mA/cm2) normalised flux was 36.1±19.5, 11.2μg/(mA.h) for iontophoretic Ala-Trp. For the tetrapeptide (Ala-Ala-Pro-Val) the mean cumulative amount that permeation with 2h iontophoresis was 350.4±45.9, 15.3μg/cm2 (Mean±SD, SEM) compared to zero passive permeation. A 4-fold increase in acetyl hexapeptide-3 delivery occurred with iontophoresis compared with passive application. In addition it was observed that lowering of donor solution pH and the presence of counterions and co-ions reduced the iontophoretic delivery of acetylhexapeptide-3. Iontophoresis provided a significant enhancement factor for the decapeptide, triptorelin acetate with a 16-fold increase in epidermal permeation compared with passive permeation. The iontophoretic permeation was concentration dependent with mean cumulative amounts of 48±28, 14 μg/cm2 (Mean±SD, SEM) achieved with 9 mM concentration of triptorelin acetate.Overall the technologies investigated in this research work presented enhanced permeation of drug molecules and peptides. In addition MPT-FLIM was demonstrated to be an efficient visualisation tool for permeation within the skin. This research demonstrates the effectiveness of physical skin permeation enhancement techniques and extends our understanding of these technologies.
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Wagger, David Leonard 1963. "Turbulent flow enhancement by polyelectrolyte additives : mechanistic implications for drag reduction." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13125.
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Anantawaraskul, Siripon. "Heat transfer enhancement under a turbulent impinging slot jet." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33321.
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Heat transfer characteristics under a single turbulent confined slot jet were determined experimentally. New enhancement techniques for the impingement heat transfer rate are proposed and tested experimentally. The results from each enhancement technique are compared with those for a smooth slot nozzle configuration with the same apparatus.The impingement heat transfer rate was observed to increase due to internal finning of the slot nozzles. Both rectangular and triangular fins were tested. The fins acted as roughness elements. Experimental results with the "rough" nozzle show that the stagnation and average heat transfer rates can be enhanced by up to 15% and 10%, respectively. However, an increase in pressure drop across the nozzles is also noted.
Use of inclined confinement surfaces of 10° and 20° angles accelerate the exit flow provides average impingement heat transfer rates comparable with those for parallel wall confinement. Experimental results show no significant change in the heat transfer distribution for the inclination angle of 10°, while the average heat transfer coefficient is in fact decreased slightly for the inclination angle of 20° at high jet Reynolds numbers.
It was found that insertion of a single turbulence generator in the jet flow provides superior impingement heat transfer without any increase in the system pressure drop. Two types of turbulence generators (square rod and thin plate) were investigated. Both turbulence generators provide the same level of average heat transfer enhancement (up to 15%).
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Gullick, Darren R. "The enhancement of percutaneous absorption by chemical modification of therapeutic agents." Thesis, University of Portsmouth, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494435.
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Most drugs are designed primarily for oral administration, but the activity and Stability profiles desirable for this route often make them unsuitable for transdermal delivery. There is current interest in the prodrug approach to enhance percutaneous absorption, and this project investigates the application of QSPRs (quantitative structurepermeability relationships) for prodrug selection by prediction of permeability. Captopril (an ACE-inhibitor) was selected as a model drug with poor percutaneous penetration, for which the sustained steady-state blood plasma level associated with transdermal delivery (and which is unattainable orally) would be particularly beneficial. QSPRs predicted that ester prodrug derivatives of captopril would have higher permeability coefficients (kp) than the parent drug, but lower flux (Jm) values due to the effect of the (predicted) relatively low aqueous solubility. Therefore, the aim of this study was to synthesize a series of prodrugs of captopril and to determine if a QSPR model could be used to design therapeutically viable prodrugs.
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Keller, Klaus 1966. "Chemical enhancement of carbon dioxide transfer across the air-sea interface." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35997.
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Leung, Ricky. "Enhancement of oxygen transfer rate using microencapsulated silicone oils as oxygen carriers." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56795.
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Silicone oils were microencapsulated within polyamide (nylon) membranes cross-linked with polyethylenimine. Solubility of oxygen within the silicone oils, whether encapsulated or not, was approximately 6 mM, representing solubilities 20 fold higher than that of oxygen in water. Assuming that the bioreactor volume consists of 10 to 20% microencapsulated silicone oil, this represents an enhancement of the oxygen reservoir by a factor ranging from 4 to 7. The use of 20%(v/v) microcapsule dispersions also enabled a 4 to 5 times increase of volumetric oxygen transfer coefficient (k$ sb{ rm L}$a), calculated on a per-litre aqueous phase basis, with or without the presence of cells. The improvement in oxygen transfer rates was due to the greatly increased specific surface area in comparison to conventional bubble aeration. These oxygen transfer enhancements were directly translatable into enhancements in overall productivity in a culture of Gluconobacter suboxydans (ATCC 621). The production rate of dihydroxyacetone was increased from 1.5 to 9 mM DHA/hr with the introduction of 20% of microcapsules in a batch fermentation and also from 6 to 8 mM DHA/hr in a fluidized bed fermentation. Thus, the oxygen permeable polymeric membrane coating the silicone oils as oxygen carrier should reduce the toxic or inhibitory effects previously observed in other oxygen carriers during use with live cells while providing an efficient alternative to bioreactor oxygenation with shear sensitive cell systems, or in fermentations with high oxygen requirements.
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Botes, Jacobus Petrus. "Flux enhancement using flow destabilization in capillary membrane ultrafiltration." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51763.
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Thesis (MEng.)--University of Stellenbosch, 2000.ENGLISH ABSTRACT: The aim of the thesis was to investigate the use of flow destabilization methods, combined with permeate backflushing (BIF) or on their own, on flux recovery and maintenance in capillary UF membrane systems under cross-flow (XF) and dead-end (DE) operating conditions. Various hydraulic and mechanical methods have been used to remove the accumulated cake layer and improve steady state process flux. Permeate backflushing (B/F) is the most widely used but the drawbacks are loss of product and extensive down-time. In a pilot plant study for ultrafiltration of surface waters containing high NOM, turbidity and cation loads, the use of flow destabilization, or feed flow reversal (FFR) combined with cross-flow B/F was able to improve the normalised flux by 10.7 ± 3.4 %, compared with 3.2 ± 1.6 % improvement for BIF without FFR. When a second B/F included FFR, the flux improvement was 7.0 ± 2.0 % compared with 4.3 ± 2.5 % for a B/F without FFR. The hypothesis was proposed that the flow destabilization caused slight lifting of the oriented cake layer, while the cross-flow B/F was able to sweep the lifted cake out of the lumen. If the flow destabilization may be effected by a simple but effective and low-cost method, and if this flow destabilization may be combined with reverse flow for short durations, the "lift-and-sweep" approach will be the ideal method of maintaining process flux and increasing membrane life. Such a flow destabilization method, now named "reversepressure pulsing" (RIP), was developed. The method involves circulation of feed water in a recycle loop for 2 s to gain momentum, followed by closure of a fast-action valve upstream of the modules. The momentum of the water in the concentrate loop carries it into an air-filled feed accumulator, while concentrate and reverse-flow permeate (which also lifts the fouling layer) are discharged to the atmosphere using the recycle pump for 15 s. When the valve opens again, the air in the accumulator forces the water under pressure through the membrane lumens, causing a pressure pulse and flow perturbations that lift, shift and break up the fouling layer. During 3 such "lift-and-sweep" events, the cake is lifted and the debris is swept out of the lumen. Experimental results for uninterrupted dead-end filtration at a UF pilot plant using RIP only on a severely fouled membrane, indicated that the RIP increased the flux by 18.4 % and decreased the dP by 8.2 % over a 7.2 h period. The method is effective in removing the cake layer intermittently and no long-term flux decline occurred for a period of 555 h since the previous chemical cleaning.
AFRIKAANSE OPSOMMING: Die doel van die tesis was om die gebruik van vloei-destabiliserings metodes, alleen of gekombineer met permeaat-terugwas, op vloed-herwinning en instandhouding in kapillêre UF membraan-stelsels tydens kruisvloei en doodloop bedryf, te ondersoek. Verskeie meganiese en hidrouliese metodes word gebruik in membraan stelsels om die koeklaag op die membraan se oppervlak te verwyder en die gestadigde-toestand vloed te verbeter. Vanhierdie metodes word permeaat-terugwas die meeste gebruik, maar het sy nadele insluitend verlies van produk en produksietyd. In 'n loodsstudie vir die ultrafiltrasie van oppervlakwaters wat hoë beladings NOM, turbiditeit en katione bevat, is die waarneming gemaak dat kruisvloei terugwas met vloeidestabilisering (voerrigting-verandering) die genormaliseerde vloed met 10.7 ± 3.4 % kon verbeter, vergeleke met 'n 3.2 ± l.6 % verbetering sonder voerrigting-verandering. Vir 'n tweede terugwas was die verbetering 7.0 ± 2.0 % vergeleke met 4.3 ± 2.5 % sonder voerrigtingverandering. Die hipotese was voorgestel dat die vloei-destabilisering die geoiënteerde koeklaag van die oppervlak gelig het, en die kruisvloei terugwas die geligde koeklaag uit die lumen kon vee. Indien hierdie vloei-destabilisering bewerk kan word deur 'n eenvoudige maar effektiewe manier, en indien dit gekombineer kan word met terugvloei van produk vir kort tydperke, sal hierdie "lig-en-vee" benadering die ideale metode wees om die membrane se vloed te verbeter en leeftyd te verleng. So 'n vloei-destabiliseringsmetode, nou genoem "terugdruk-pulsering", is ontwikkel. Die metode behels die sirkuiering van voer-water vir 2 s in 'n hersirkulasielus om momentum op te bou, gevolg deur die toemaak van 'n snel-aksie klep stroom-op van die modules. Die water in die konsentraat-lus se momentum dra dit vorentoe tot in In lug-gevulde voer-akkumulator, terwyl konsentraat en terug-vloei permeaat (wat ook tot 'n mate die koeklaag lig) ook na die atmosfeer gewend word vir 15 s deur die hersirkulasiepomp. As die klep weer oopgaan, ontspan die lug in die akkumulator, en forseer die water daarin onder druk deur die membraan-lumens. Die druk-puls en vloei-perturbasies lig, skuif en breek die koeklaag op. Tydens 3 agtereenvolgende "lig-en-vee" aksies word die koeklaag effektief opgebreek en uit die lumen gevee. Eksperimentele uitslae vir ononderbroke doodloop bedryf op uitermate aangevuilde membrane van 'n ultrafiltrasie loodsaanleg toegerus met terugdruk-pulsering, het getoon dat die vloed met 18.4 % verbeter kon word en die dP met 8.2 % verminder kon word in slegs 7.2 h. Die metode breek die koeklaag effektief op, en geen langtermyn vloed-afname is waargeneem vir meer as 555 h sedert die vorige chemiese was-prosedure nie.
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Al-Atta, Ammar Jaber. "Supercritical water oxidation of hazardous waste : process enhancement and reactor design." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/53356/.
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The work presented in this thesis is focused on two specific areas of supercritical water oxidation (SCWO). Firstly, the design and testing of an innovative anticorrosive reactor design that can be used for the SCWO of hazardous organic waste. Secondly, exploiting the merits of counter current mixing reactor in combining two processes; Supercritical water oxidation (SCWO) and supercritical water hydrothermal synthesis (SCWHS) in one reactor. In Chapter 1, an introduction to supercritical fluid and supercritical water oxidation is given, followed by a brief account of the main problems associated with SCWO. This includes a review of the experience to date, with different reactor designs for corrosion control. This Chapter also provide an introduction to hydrothermal methodology and continuous flow reactor design for nanoparticle production, along with the aims and objective of this PhD. Chapter 2 details the components and construction of the experimental rigs used in this thesis. Additionally, this Chapter presents the principles behind the main analytical techniques used throughout this work, along with the definition of some important parameters. Chapter 3 reports the use of a physical modelling approach to assess mixingdynamics inside three different types of reactor where supercritical water is mixed with a second colder, waste containing, effluent flow. Physical or `pseudo'modelling was used to simulate the general flow patterns and mixing regimes in transparent pseudo reactors (to allow visualization). Towns water was used to simulate the supercritical water flow and 40% w/w aqueous sucrose solution to simulate the cold aqueous effluent flow. This visual technique allowed the quantification of mixing efficiency, as well as identification of issues such as flow recycling, stagnant zones, and other inconsistencies in the mixing dynamics. An upwards co-current protected wall reactor arrangement provided the `best' mixing i.e. with minimal wall contact during the downstream oxidation process. A combined process of SCWO and SCWHS in a continuous counter current reactor is the focus of Chapter 4. Acrylic acid was chosen as a model compound to represent an organic wastewater and the effects of the reaction temperature, residence time, oxidant ratio and acrylic acid concentration on chemical oxygen demand (COD) were all investigated. Two different experimental configurations for oxidant delivery were carried out in `pre-heated' and `non-preheated' oxidant configurations. With a stoichiometric excess of 100% oxygen, COD reduction levels of 80% (non-preheated) and 15% (preheated) were achieved with very short residence times. SCWHS was achieved through the addition of small amounts of various soluble metal salts in the cold up flow resulted in nanoparticles forming which increased the reaction rate and hydrothermal oxidation efficiency. The addition of small amounts of chromium nitrate (>5mM) results in nearly 100% COD reduction at 380C and residence times of 0.75 seconds. The potential economic benefits of combining the two processes together, in the different configurations, were also evaluated. In Chapter 5, The results of the catalytic oxidation in supercritical water of a non-biodegradable and highly toxic organic compound (phenol) are presented. The reactions were studied in a continuous counter current reactor through the in-situ formation of Fe2O3 catalyst. The preliminary results showed that catalytic non-preheated oxidant configuration resulted in increased COD removal when compared to other oxidant delivery methods. It was shown that temperatures below 400C could be used to decompose these compounds into final product and that complete conversion of COD could likely be expected within less than 1 second. It was demonstrated that SCWO combined with SCWHS is a feasible and cost-effective alternative for the destruction of contaminants in water. In Chapter 6, A laboratory-scale protected wall reactor rig was designed, constructed, tested, and operated to validate the pseudo modelling for application to SCWO. SEM, SEM/EDS, and XRD results showed that 1 meter long protected wall reactor was divided into two regions. 25% of the reactor length was protected by the flow of clean supercritical water. Near complete removal of the organic content of 2,4-DCP was obtained at mild operating conditions. To conclude, a summary of the work detailed in this thesis is delivered in Chapter 7. The most pertinent findings from this work are put forward, followed by a discussion of future work which could lead on from this thesis.
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Waletzko, Ryan Scott. "Determining soft segment structure-property effects in the enhancement of segmented polyurethane performance." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/46671.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.Includes bibliographical references.
Liquid Crystalline Elastomer (LCE)-inspired segmented polyurethane elastomers possessing widely different extents of ordering were created to mimic the hierarchical structure of the continuous matrix and superior mechanical performance of spider silk fibers. The silk's remarkable toughness originates from a fiber morphology that possesses [beta]-pleated crystalline sheets within an amorphous matrix. In the polyurethane materials, various extents of poly(ethylene oxide) (PEO) soft segment ordering were implemented within continuous soft domains that were connected by hexamethylene diisocyanate-butanediol (HDI-BDO) hard segments. Soft segment crystallinity studies revealed the need to optimize the extent of continuous soft domain ordering. Highly crystalline PEO soft segments, while they display good microphase segregation properties, sacrifice extensibility due to their high melting transition temperature. Moderately crystalline PEO soft segments, meanwhile, possess less defined phase segregation but enhanced mechanical properties from their reversible dispersed crystalline soft segment domains. Non-crystalline Pluronic copolymer systems had good mechanical properties that resulted from both a strong hard segment incompatibility and a highly mobile soft segment matrix. Hydrogen-bonded hard domain shearing during in-situ tensile deformation yields oriented hard blocks that align at a preferred tilt angle of ±60° from the strain direction. Extensive alignment and orientation of the moderately-ordered PEO soft segments occurred during deformation, which was consistent with its observed mechanical behavior. Pluronic-containing segmented polyurethanes formed an ordered mesophase in the continuous soft matrix during deformation. A series of cyclic, aliphatic polyurethanes with dicyclohexyl methane diisocyanate (HMDI) hard segments and poly(tetramethylene oxide) (PTMO) soft segments was synthesized to study compositional effects on the extent of soft segment mixing, and how these effects translated to both mechanical and barrier performance. Shorter soft segment chain systems displayed a greater hard segment compatibility, which resulted in materials that were both more rigid mechanically and provided better barrier characteristics.
(cont.) Longer soft segments in the continuous polymer matrix displayed a more phase segregated structure, which enhanced their mechanical properties but sacrificed barrier effectiveness. Incorporation of dimethyl propane diol (DMPD), a branched chain extender, created a completely amorphous polyurethane matrix. Polyurethane/Laponite nanocomposites were also created using particles that were capable of preferentially associating with hard or soft segments. HMDI-BDO-PTMO polyurethane/Laponite nanocomposites demonstrated drastically reduced mechanical performance (~13-fold decrease in toughness and ~10-fold decrease in extensibility). The deteriorated mechanical performance was attributed to the formation of an interconnected hard segment continuous morphology that significantly reduced matrix extensibility. HMDI-DMPDPTMO polyurethane/Laponite composites, on the other hand, only experienced modest reductions in extensibility (-70% of total initial extensibility) while maintaining toughess and increasing initial modulus 10-fold. Mechanical behavior resulted from well-dispersed Laponite clay platelets that reinforced the amorphous polymer matrix while imposing modest chain segmental mobility restrictions.
by Ryan Scott Waletzko.
Ph.D.
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Valentine, Mark Edward. "Fundamental flux enhancement modelling of membrane microfiltration." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:f1b0388e-25b9-4038-be04-360b1414d172.
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Membrane filtration is used in a variety of industries, including water treatment and the food industry. Membrane systems include microfiltration and reverse osmosis processes. Membranes used in reverse osmosis are nonporous or pores at 0.2-2 A. This work will focus on mechanical microfiltration. These filtration systems suffer from an accumulation of the rejected material near the membrane surface. This causes additional resistance to the flow through the membrane (flux), resulting in a decline in the performance of the system. Sparging gas bubbles into the mixture has been shown to improve performance. The flow field promotes the transport of material away from the membrane surface and into the bulk. The goal is to predict the sparging that will achieve the maximum flux. Existing flux prediction models often assume steady shear at the membrane surface but in bubbling regimes the shear stresses are unsteady. In this thesis a model is developed to calculate the flux based not solely on shear but on the behaviour and resistance of suspended particles in a gas-liquid flow field. The bubble shape and flow field is calculated using computation fluid dynamics (CFD). The flow around a bubble in gap between two parallel flat sheet membranes is investigated. The calculated bubble shape correlates well with the results seen in experiments. The bubble rise velocity with respect to gap width is shown to transition between that expected in the literature for extended flow for large gap widths and that for a two dimensional case for smaller gap widths. The transitional region however, does not behave as may be expected. The rise velocity does not monotonically decrease as the gap width is reduced. The particle concentration is found by the solution of the convection-diffusion equation, where the convection velocity terms are given by the results of the CFD calculation. The permeate flux is then calculated using a resistance model giving the enhancement due to the bubble. The model is also applied to single phase crossflow. As the shear stresses are steady in this single-phase flow regime, established membrane shear linked mass-transfer coefficient methods can be employed. Good agreement is found between the model and theory. The flux results obtained when the model is applied to the flow around the bubble show a peak in performance with respect to the gap between the membranes for a given bubble volume. The optimal flux enhancement is found to correlate well with the bubble size compared to the flow area. The results show a bubble width of around 60% of the flow width provides the best flux performance.
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Peng, Xiaodong. "Liquid air energy storage : process optimization and performance enhancement." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8615/.
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Liquid Air Energy Storage (LAES) aims to large scale operations a~d-:_has caught the attention due to the advantages of high energy density, a highly competitive capital cost, no geographical constraints and environmental friendliness. However, the situation is getting more challenging due to its disappointed performance in the current configuration. This thesis focuses increase the system performance of the LAES technology, particularly through developing novel thermodynamic cycles for an increased use of the thermal energy and system optimization strategies. The improvements to the LAES mainly aim at two points: increasing power output by using compression heat and rising the liquification rate through external cold sources. To effectively use the heat, three integrated LAES systems with the Organic Rankine Cycle (ORC) are proposed, termed LAES-ORC-VCRC system, LAES-ORC-ARC system and LAES-ORC system respectively according to different cooling methods. External cold sources, such as Liquefied Natural Gas (LNG), can be used to enhance air liquefication, and hence two integrated LAES systems, termed the LAES-LNG and the LAES-LNG-CS, are investigated and optimized.
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Ibrahim, Sarah A. "A Structure-Enhancement Relationship and Mechanistic Study of Chemical Enhancers on Human Epidermal Membrane based on Maximum Enhancement Effect (Emax)." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1266598335.
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Maxson, Andrew. "Heat Transfer Enhancement in Turbulent Drag Reducing Surfactant Solutions." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500419520976994.
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Hassan, Faiza. "Heterogeneous catalysis in supercritical fluids : the enhancement of catalytic stability to coking." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3166/.
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Catalytic deactivation caused by coking was studied in ZSM5 and zeolite Y catalysts during the isomerisation of 1-hexene under sub and supercritical conditions. The effects of varying temperature and pressure, from 220–250 °C and 10-70 bar respectively, on conversion and coke deposition were studied in both zeolites. TGA, DRIFTS, nitrogen sorption isotherms for fresh and coked catalysts and catalyst acidity measurements were compared. In ZSM5 the catalyst was stable for 96 hours. TGA and DRIFTS results show coke deposits were mainly polyolefinic and the amount decreases considerably from 18.8 wt% in the subcritical region to 10 wt% in the supercritical region. In zeolite Y, decay in conversion was observed with the rate of deactivation being slower at supercritical conditions at 235 °C and 40 bar. Naphthalene hydrogenation on NiMo/γ-Al2O3 catalyst was also studied. The effect of temperature, pressure, varying naphthalene feed concentration and operating in sub and supercritical conditions were studied. Coke deposit decreased by 38 wt% in the supercritical region. SC CO2 (Tc 31.04 °C, Pc 73.8 bar) was also used to re-activate the coked catalysts. This resulted in recovering 93% of the catalytic activity and 37% of the coke was effectively extracted by SC CO2.
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Zak, Andrew Joseph. "Determining the Transport Enhancement of Sodium Fluorescein in Mechanically-Loaded Canine Tibia." Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1449314893.
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Alsoqyani, Faihan Saleh. "Supercritical water oxidation of nitrogen-containing organic compounds : process enhancement using isopropyl alcohol." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7296/.
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The research in this thesis aimed to study efficiency and viability of supercritical water oxidation (SCWO) technology in treating diluted N,N-dimethylformamide (DMF), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and ammonia containing model wastewaters that were selected due to their hazard, wide usage in industry and having different degrees of refractoriness. A lab-scale SCWO tubular reactor was operated to obtain necessary data to investigate the destruction of selected compounds at certain operating conditions in addition to studying the oxidation kinetics of DMF and DBU. Also, Isopropyl Alcohol was used to enhance the destruction of treating DMF, DBU and ammonia. Results showed that temperature was the most influential variable where near complete TOC removal was obtained during DMF and DBU oxidation at 525oC and 250 bars. Temperatures of 400-550oC were not enough to achieve a significant destruction for ammonia. Organic concentrations and oxidant ratios also showed positive effects on the destruction of DMF, DBU and ammonia. IPA showed an essential role to destroy DMF, DBU and ammonia when used where a TOC removal of 99.4% and 99.2% was achieved for DMF and DBU respectively at 525oC and 250 bars and maximum TN removal of 97% was obtained at 550oC and 250 bars during ammonia oxidation. Also the presence of IPA reduced the activation energy of treated compounds where the values were 21.9 and 25.7 kJ/mol for DMF and DBU, respectively. Also it was found that oxygen has an influence and with oxygen order of 0.38 and 0.32 for DMF and DBU respectively.
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Shi, Haifeng. "Surfactant Drag Reduction and Heat Transfer Enhancement." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343664380.
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Muniz, Maisonet Maritza. "Topographical Enhancement of Cell Adhesion on Poorly Adhesive Materials." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5748.
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The overall thrust of this dissertation is to gain a fundamental understanding of the synergistic effects between surface topography and chemical functionality of poorly adhesive materials on enhancing the adhesion of mouse embryonic fibroblasts. Cellular response to surface topography and chemical functionality have been extensively studied on their own providing valuable information that helps in the design of new and improved biomaterials for tissue engineering applications. However, there is a lack of understanding of the synergistic effect of microscale and nanoscale topography with chemical functionality and the relative impact and contribution of each in modulating cellular behavior. By understanding the relationship between these cues, in particular using materials that are poorly adhesive, this study will provide new clues as to how cells adapt to their environment and also suggest new dimensions of biomaterial design for fine-tuning cellular control.
A microstructure that combined non adhesive materials with defined surface topography and surface chemistry is presented, to assess and correlate the enhancement of mouse embryonic fibroblasts cell adhesion and spreading. Poly (N-isopropylacrylamide) or PNIPAAm electrospun fibers were overlaid on PNIPAAm thin films (100 nm) at various time points to investigate the role of topography on such coatings by keeping the chemical functionality the same. After doing this, several topographical patterns were developed, spanning from sparse to dense fiber mats, and cell adhesion strongly depended on the relative available areas for attachment on either the fibers or the supporting surface. To gain a better understanding of this finding, two surface chemistries, non-adhesive (self-assembled monolayer of polyethylene glycol (PEGSAM) alkanethiol on gold) or an adhesive coating (3-aminopropyltriethoxysilane (APTES) on glass) with well characterized adhesive properties were included in this study to assess the effect of topographical cues provided by the PNIPAAm electrospun fibers on cellular responses. With the deposition of the PNIPAAm fibers onto a PEGSAM surface, cell adhesion increased to almost 100%, and unlike the PNIPAAm surface, cell spreading was significantly enhanced. With the deposition of PNIPAAm fibers onto APTES, both cell adhesion and spreading were unaffected up to 60% fiber coverage. For both surfaces, PNIPAAm fiber densities above 60% coverage lead to adhesion and spreading independent of the underlying surface. These findings indicate the presence of a sparse topographical feature can stimulate cell adhesion on a typically non-adhesive material, and that a chemical dissimilarity between the topographic features and the background enhances this effect through greater cell-surface interaction.
In addition to the aforementioned studies, cell response was also assessed on PNIPAAm thin films coatings with thicknesses ranging from 100 nm to 7 nm. Cell adhesion and spreading was enhanced as the thickness of the thin film decreased. This change was more noticeable below 30 nm, wherein 7 nm shows the highest cell adhesion and spreading enhancement. The results reported are preliminary results and further experiments will be conducted, to support the data. It is believed that cellular response was enhanced due to a change in surface topography at the nanoscale level.
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Sumair, Faisal Ahmed. "Preparation and characterisation of eutectic nanofluids for heat transfer enhancement in flat plate solar collectors." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/48390/.
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Use of thermal energy storage (TES) materials in solar collectors is known to be the most effective way of storing thermal energy. The most conventional and traditional heat storage element is water. However, due to low thermal conductivity (TC) in vapor state its applications as a heat storage medium are limited. An alternative option is to utilize organic and inorganic TES materials as they both operate at low and medium temperature ranges. Organic TES materials such as paraffins are non-corrosive and possess high latent heat capacity. On the contrary, inorganic TES materials possess high density and appreciable specific heat capacity (SHC). Due to rapid progress and advancement in nanotechnology, varieties of nanomaterials were dispersed in various base fluid(s) to enhance thermo-physical properties. Here the current status and future development trends of TES materials has been presented. Furthermore, an extensive research on enhancement of TC and SHC of various TES material doped with nanomaterials has been discussed. Enhancement in heat capacity (HC) and thermal conductivity (TC) with dispersion of graphene (GE) nanoparticles in low temperature molten salt was investigated. Three different nanoparticle concentrations (0.01, 0.05 and 0.1 wt. %) were dispersed in molten salt composed of 5.76% NaNO3, 21.36% KNO3, 24.84% Ca(NO3)2, 41.08% CsNO3 and LiNO3 7.44% by weight. Doping of GE resulted in enhanced HC ranging from 5-13%, whereas, TC showed enhancement up to 2.44%, with respect to GE concentration. Various theoretical models were tested to predict TC and HC of GE doped molten salt. Maxwell and Hamilton-Crosser TC models show good agreement with experimental results with deviation of ±3% while Nan’s TC model over predicted TC value. Conventional HC equation fits well with the experimental data with deviation < 14%. Thus, the results obtained show the potential of GE doped molten salt as thermal energy storage (TES) medium in various heat transfer applications. This work also investigates the rheological and corrosion properties of graphene (GE) dispersed in eutectic salts. It was observed that doping of GE has significantly enhanced the viscosity of base salt. This enhancement in GE dispersed eutectic salt is mainly due to the presence of solid GE sheets and its coagulation in eutectic salts. Various concentrations of GE and temperature ranges were studied here. Eutectic salt dispersed GE behaved as non-Newtonian fluid at 70, 80 and 90 oC except at 200 oC, where it behaved as a Newtonian fluid. Viscosity of nanosuspension was predicted using Einstein’s equation. Furthermore, corrosion studies using ASTM D130 method were performed to analyse the effects of base fluid on copper and stainless steel (SS304) at elevated temperatures. Fourier transform infrared spectrometer (FTIR) result shows that the presence of all nitrate bonds in synthesized base salt and GE dispersed base salt. X-ray diffraction depicts that the doping of GE in eutectic salt does not alter the crystal structure of nitrate molecules. EDX results confirm that both Cu and SS304 material were corroded. SS304 exhibited constant corrosion with an increase in GE concentration dispersed in eutectic salt, whereas copper exhibited an increase in corrosion rate with an increase in GE concentration. Kinetic studies have been carried out for molten salt and GE dispersed molten salt. It was concluded that dispersion of GE has not altered decomposition rate of nitrate of ions. In application, we have fabricated and tested two types of solar collectors, i.e., solar thermal collector and photo-voltaic/thermal collector for TES material. Test was carried out to confirm the thermal performance of both solar collectors under water, base salt and GE dispersed base salt as TES. Results proved that in both types of solar collectors, all three concentrations of GE (0.01, 0.05 and 0.1 wt. %) dispersed base salt were having high thermal performance than water and base salt. Thus, it was concluded that GE dispersed molten salt can be successfully used as TES material in both solar collectors.
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Latorre, Federico [Verfasser], Leticia Gutachter] Gonzales, and Volker [Gutachter] [Deckert. "Quantum chemical investigation towards Raman enhancement effects / Federico Latorre ; Gutachter: Leticia Gonzales, Volker Deckert." Jena : Friedrich-Schiller-Universität Jena, 2017. http://d-nb.info/1177599740/34.
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Matthews, Ben J. H. "The rate of air-sea COâ‚‚ exchange : chemical enhancement and catalysis by marine microalgae." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323350.
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Marr, Kevin M. "Transport Enhancement of Rate-Limited Chemical Reactions via Pt-Decorated, Carbon Nanotube Microarray Membranes." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5537.
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Rate limited chemical reactions can be enhanced by improving the mass transport of the suspended analyte to the catalytic (or electrocatalytic) surface. While many attempts have been made to enhance this mass transport, these approaches are limited to utilizing only two enhancement methods – increasing available catalytic surface area, and increasing the flow of analyte in solution. Flow through high aspect ratio microstructures, however, would provide additional mass transport enhancement via boundary layer confinement. Platinum functionalized carbon nanotube microarray membranes (Pt-CNT-MMs) offer enhanced mass transport via all three methods, and were fabricated for demonstration in a H2O2 sample system, for which propulsion and chemical sensing applications were investigated. Propulsion testing of Pt-CNT-MM samples demonstrated thrust typically required for MUV propulsion, while achieving high H2O2 fuel utilization. Also, the proposed approach minimizes component exposure to the environment and is comprised of a simple, static architecture relative to other micro-propulsion systems. Moreover, it was shown that additional thrust is attainable by further enhancing the introductory rate of the H2O2 fuel to the Pt-CNT-MMs, which would effectively increase the locomotive capability of this propulsion system. Pt-CNT-MMs used for chemical sensing of H2O2 likewise demonstrated favorable performance. Initial studies revealed that the molar flux achieved for a Pt-CNT-MM sample in a through-flow environment (50 [µL s-1]) was approximately a ten-fold increase over that achieved in a stirred environment (150 [rpm]). This ten-fold increase in molar flux can be attributed to both an increase in exposed electrocatalytic surface area, as well as increase in boundary layer confinement. Furthermore, comparison of sensed molar flux to calculated molar flux for through-flow conditions revealed that Pt-CNT-MMs can achieve near-complete H2O2 oxidation within the flowrate range studied. Additionally, chronoamperometric testing of a Pt-CNT-MM sample demonstrated a sensitivity toward H2O2 of 9.18 [mA mM-1 cm-2], over one hundred times that of the GluOx/Pt-SWCNT/PAA structures referenced herein (0.0724 [mA mM-1 cm-2]).1 These findings suggest that mass transport enhancement, achieved by Pt-CNT-MMs applied in through-flow environments, heightens the performance achieved in rate-limited chemical reactions. Specifically, Pt-CNT-MMs demonstrate high fuel utilization in H2O2 based propulsion applications, as well as offer a highly sensitive preliminary structures for non-invasive glucose sensing.
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Naseer, Zarga. "Chemical and physical changes associated with maturity of different plants and enhancement of nutritional value by chemical treatment of crop residues." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07122007-103928/.
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Bryden, Michelle D. (Michelle Denise). "Transport in Lagrangian-unsteady flows : dipersion in diverging or converging ducts, and transport rate enhancement accompanying laminar chaos." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46053.
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Hozhabr, Sassan. "Enhancement of interfacial adhesion in polymer blends of polypropylene and poly (ethylene vinyl alcohol copolymer)." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60598.
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In the present study a blend system containing polypropylene (PP) and ethylene vinyl alcohol copolymer (EVOH) was considered. Maleic anhydride grafted polypropylene (MAH-g-PP) was used to improve adhesion at the interface. The preliminary work was conducted in a batch mixer and then extended to a single and a twin screw extruders.The results in the batch mixer demonstrated that blends containing high levels of MAH have well bonded morphology and impact strengths comparable to pure materials. Statistical analysis of the results showed that at processing temperature of 200$ sp circ$C and mixing time of 13 minutes, the highest impact strength and largest elongation at break were obtained.
In the extruder the morphological studies revealed the presence of a layered structure in the core region of the samples when a slit die was employed. The oxygen permeability of extruded samples with EVOH content higher than 20vol% resembled multi-layer systems.
Impact strength of extruded ribbons drastically improved by increasing the maleation level to 0.2wt% and precompounding the virgin resins in a twin screw extruder. Morphological observations however, revealed some disruption in the layered structure and consequently decline of oxygen barrier properties.
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Dadafarin, Hesam. "Electrochemically-assisted functionalization of a 316L stainless steel surface with fibronectin: towards the enhancement of biocompatibility of coronary stents." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114476.
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Cardiovascular disease (CVD) is reported to be the single largest cause of death in developed countries. Among different types of CVD, a common and prevalent disorder is atherosclerosis, which is characterized mostly by the formation of a plaque resulting in considerable narrowing (stenosis) and hardening of the arteries. Approximately one third of atherosclerosis patients are treated by angioplasty and stenting. However, all current stents offer low biocompatibility, which results in occurrence of in-stent thrombosis and restenosis in up to ca. 30% patients, and the need for further medical treatment. Various stent-surface modification approaches have been employed in order to minimize in-stent restenosis, but none of them has proven to give long-term satisfactory benefits. The aim of this work was to develop a new method for the stent surface modification, in an attempt to decrease the in-stent restenosis rate. The ultimate aim of the project was to functionalize 316L stainless steel, CoCr and NiTi surfaces with a chemically-bound extracellular matrix protein fibronectin (Fn), in order to control and mediate endothelial cell (EC) and smooth muscle cell (SMC) / surface (Fn) interactions. In this PhD project, a novel electrochemistry-based method for the immobilization of Fn on 316L stainless steel, CoCr and NiTi surface was developed. The method is based on the formation of a stable alkanethiol monolayer ("linker") on the alloy surface, which was further chemically modified to allow covalent attachment of Fn. Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) revealed that the formed alkanethiol monolayer is relatively ordered and well-packed. X-ray photoelectron spectroscopy (XPS) demonstrated that monolayer is attached to the 316L stainless steel surface through the sulfur atom. It was further confirmed that the monolayer remained stable over a period of seven days of constant immersion in a corrosive phosphate buffered saline solution. Long-term electrochemical impedance spectroscopy experiments demonstrated that the formed monolayer also provided a diffusion barrier for aggressive / corrosive ions, yielding a high (ca. 94%) corrosion protection efficiency for 316L stainless steel. It was determined that the covalent attachment of Fn to the alkanethiol monolayer pre-formed on 316L stainless steel, CoCr and NiTi surfaces resulted in the formation of a very stable protein layer. PM-IRRAS indicated that the covalent attachment of Fn resulted in a change of the protein's secondary structure. Scanning electron microscopy (SEM) and energy dispersive X-Ray (EDX) analysis of Fn molecules immobilized on a surface of a commercial 316L stainless steel cardiovascular stent revealed that a relative homogenous spatial distribution of Fn was achieved and the molecule spacing was appropriate for cell adhesion.The effect of Fn immobilization on a 316L stainless steel surface on cell/surface behavior was further investigated by examining the interaction with platelets, ECs and SMCs. Lower platelet adhesion and aggregation was observed on Fn-modified surfaces, in comparison to the naked (unmodified) surface, which implies a lower thrombogenicity of the Fn-modified surface. It was shown that the presence of Fn on the surface significantly enhanced EC attachment, while no detectable improvement in SMC attachment was observed. Higher proliferation rate of both ECs and SMCs was achieved on the Fn-modified surface. The comparative study of EC and SMC attachment revealed that Fn-modified surfaces can selectively attract more ECs than SMCs. This indicates a higher biocompatibility of the Fn-modified surface for coronary stent applications.Les maladies cardiovasculaires (MCV) sont la primaire cause de décès dans les pays développés. Parmi les différents types de maladies cardiovasculaires, l'athérosclérose est une maladie fréquente et répandue. Il est caractérisé principalement par la formation d'une plaque, ce qui entraîne un rétrécissement considérable (sténose) et le durcissement des artères. Cependant, toutes les endoprothèses vasculaires actuelles offrent une biocompatibilité faible ce qui résulte en la présence d'intra- endoprothèse vasculaire thrombose et une resténose chez environ 30 % des patients et la nécessité de traitement médical supplémentaire. Des approches diverses qui consistenten la modification de la surface des endoprothèses vasculaires ont été utilisées afin de minimiser la resténose intra-endoprothèse vasculaire, mais aucune d'entre elles n'a prouvé être satisfaisante à long terme. Le but de ce travail a été de développer une nouvelle méthode pour la modification de la surface de l'endoprothèse vasculaire, dans le but de réduire le taux de resténose intra-endoprothèse vasculaire. Le but ultime du projet était de rendre fonctionnant làcier inoxydable 316L, CoCr et les surfaces NiTi avec une matrice chimiquement liée et extracellulaire de la protéine fibronectine (Fn) avec le but de contrôler et de se faire le médiateur de l`interaction entre les cellules endothéliales (CE) et des cellules musculaires (CML). Dans ce projet, une nouvelle méthode basée sur l'électrochimie pour immobiliser le Fn sur l'acier inoxydable 316L, CoCr et les surfaces NiTi a été développé. La méthode est basé sur la formation d'une monocouche stable d'alcanethiol sur la surface de l'alliage, qui a été plus modifiée chimiquement pour permettre la fixation covalente de Fn. La Spectroscopie InfraRouge de Réflexion Absorption Modulation Polarisation (PM-IRRAS) a révélé que la monocouche d'alcanethiol formée est relativement ordonnée. La spectroscopie des photélectrons X-ray (XPS) a démontré que la monocouche est fixée sur la surface ende làcier inoxydable par l'atome de soufre. À long terme, des expériences de spectroscopie d'impédance électrochimique ont démontré que la monocouche formée a également fourni une barrière de diffusion pour les ions agressifs/corrosifs, ce qui donne un taux élevé (env. 94 %) d'efficacité en ce qui concerne la protection contre la corrosion de l'acier inoxydable 316L.Il a été déterminé que la liaison covalente entre Fn et la monocouche d'alcanethiol préformée sur l'acier inoxydable 316L, CoCr et les surfaces en NiTi, a résulté à la formation d'une couche de protéine très stable. PM-IRRAS indique que la fixation covalente du Fn a entraîné un changement dans la structure secondaire de la protéine. Microscopie électronique à balayage (MEB) et de dispersion d'énergie X-Ray (EDX) des molécules Fn immobilisées sur une stent commerciale en acier inoxydable 316L cardiovasculaire a révélé une distribution spatiale homogène de Fn et l'espacement moléculaire était approprié pour l'adhérence des cellules. L'effet de l'immobilisation de Fn sur une surface dàcier inoxydable 316L, sur le comportement entre la surface et la cellule a été plus abondamment étudié en examinant l'interaction entre les plaquettes, les CPP et les CML. Un taux inférieur d'adhérence et d'agrégation plaquettaire a été observé sur les surfaces modifiées avec Fn, ce qu'implique une thrombogénicité de la surface. Il a été démontré que la présence de Fn sur la surface a amélioré considérablement la fixation CE et aucune amélioration dans l'adhérence SMC n'a été observée. Une augmentation des taux de prolifération des ECs et SMCs a été réalisé sur les surfaces modifiées avec Fn. L'étude comparative de l'attachement EC et SMC a révélé que les surfaces Fn modifiées attirent sélectivement plus les ECs que les SMCs. Ca indique une meilleure biocompatibilité des surfaces modifiées avec Fn pour des applications coronaires endoprothèse vasculaire.
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Rodriguez-Chiang, Lourdes. "Enhancement of methane production from the anaerobic digestion of chemical pulp and paper mill effluents." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/669251.
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Sustainability of resources such as energy, water and waste have become important drivers in our current economy. For large industries that are water and energy intensive like pulp and paper (P&P) mills, this is a specifically relevant issue. The large and heterogenous volumes of effluents in P&P mills make it a difficult task to properly treat before discharge. Anaerobic digestion is an efficient wastewater technology that cleans the effluent, reduces wasted sludge and simultaneously produces methane that can be further used as energy. The research work described in this thesis aims to enhance the methane production from the anaerobic digestion of different chemical P&P mill effluents. Through effluent characterization, variability of process parameters, promoting agents and the assessment of biochemical methane potential (BMP) tests, the benefits of three potential methods to enhance methane yields of wastewaters were evaluated. In addition, the conversion of chemical pulp fibers directly to methane was explored. The attained results described the different improvements that can be made to enhance methane production.
Easily degradable effluents such as hydrolyzed filtrates and evaporator condensates contain high concentrations of sugars and acetic acid respectively, which could encourage an oversaturation of acids during acidogenesis. An inoculum to substrate ratio (ISR) of 2 proved to be the optimal in order to add the required buffering capacity to neutralize the pH and produce significantly high methane yields of up to 333 mLCH4/gVS. The high productivity of these effluents can be then considered for co-digestion with harder to treat effluents such as lignin-rich streams. Lignin clearly hinders methane production indicated by the negative linear correlation found between lignin content and methane yield. The co-digestion of lignin-rich effluent with evaporator condensates from neutral sulfite semi-chemical (NSSC) pulping proved to enhance the overall methane productivity of the mill´s wastewater treatment. Furthermore, the assessment of hydrotalcites (HT) addition indicated a contribution towards an increase in methane yield, faster production rates and a greater lignin removal. The poor performance of calcined HT suggests that the advantages of HT addition came from the layered sheet structure. Finally, besides establishing the methane potential in various P&P effluents, the examination of methane productivity of different pulp fibers and its products proved to be a promising new energy alternative to explore. Brown, oxygen delignified and bleached pulp gathered biodegradabilities of up to 90% and methane yields as high as 380 mLCH4/gVS. With the current changing bio-economy this last approach paves the way in exploring alternative and novel uses for chemical pulp mill products.La sostenibilidad en la gestión de recursos como la energía, el agua y los residuos se ha convertido en un aspecto clave en nuestra economía actual. Para grandes industrias que consumen mucha agua y energía, como la industria de pulpa y papel (P&P) este es un tema especialmente relevante. Los grandes y heterogéneos volúmenes de efluentes que producen las fábricas de P&P hacen que su adecuado tratamiento sea una tarea difícil. La digestión anaerobia es una tecnología eficiente para el tratamiento de aguas residuales; que limpia el efluente, reduce el lodo producido y simultáneamente produce metano que puede usarse como fuente de energía. El objetivo del trabajo de investigación descrito en esta tesis es aumentar la producción de metano a partir de la digestión anaerobia de diferentes efluentes producidos en fábricas de pulpa. A través de la caracterización del efluente, determinación de parámetros del proceso, agentes promotores y la evaluación de pruebas de producción de metano bioquímico se evaluaron los beneficios de tres métodos potenciales para mejorar los rendimientos de metano de los efluentes. Asimismo, se exploró la conversión directa de fibras de pulpa química a metano. Los efluentes fácilmente degradables, como los filtrados hidrolizados y los condensados del evaporador, contienen altas concentraciones de azúcares y ácido acético, respectivamente, lo que podría provocar una sobresaturación de ácidos durante la acidogénesis. Se ha demostrado que una relación de inóculo a sustrato de 2 resulta óptima para aumentar la capacidad tampón del sistema y neutralizar el pH y producir rendimientos de metano significativamente altos, de hasta 333 mLCH4/gVS. La alta productividad de estos efluentes hace que se puedan considerar para la co-digestión con efluentes más difíciles de tratar, como las aguas ricas en lignina. Claramente la lignina obstaculiza la producción de metano, tal y como indica la correlación lineal negativa encontrada entre el contenido de lignina y el rendimiento de metano. La co-digestión del efluente rico en lignina con el condensado de evaporadores de pulpa semi-química de sulfito ha demostrado mejorar la productividad de metano en el tratamiento de aguas residuales de la planta. Además, la adición de hidrotalcitas (HT) como catatlizadores contribuye hacia un aumento en la producción de metano, tasas de producción más rápidas y una mayor eliminación de lignina. Con HT calcinadas se han obtenido rendimientos bajos, lo que sugiere que las ventajas de la adición de HT provienen de su estructura laminar. Finalmente, además de establecer el potencial de metano que existen en los efluentes de P&P, la evaluación de la productividad de metano de diferentes fibras de pulpa y sus productos ha demostrado ser una nueva alternativa energética para explorar. El uso de pulpa blanqueada, sin blanquear y deslignificada con oxígeno muestran biodegradabilidades de hasta 90% y rendimientos de metano de hasta 380 mLCH4/gVS. Con la cambiante bioeconomía actual, este último enfoque estimula la exploración de usos alternativos y novedosos para productos de plantas de pulpa química.
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Chui, Yiu Loon. "Mechanisms of long term rat kidney allograft survival induced by chemical immunosuppression or immunological enhancement." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37975.
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Pap, Ilona. "Productivity enhancement in optical semiconductor manufacturing: Early warning of failures in BHet laser fabrication." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26736.
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There are unique challenges in the fabrication and testing of optical semiconductor devices because, unlike typical silicon semiconductor devices, which can be tested cost-effectively on the wafer, many optical devices can only be 'fully' tested once the individual die is bonded to a heat sink. As a result, both the manufacturing process and test strategy need to be capable of predicting yields and product quality attributes based on limited sampling from a batch of the product. The large number of product quality and process variables that are measured for each device when it is manufactured makes it almost impractical to manually analyze them for valuable decision-making information. There is a need for understanding the complex, interactive effects of process variables on the product quality variables as well as automated analysis and discovery tools for extracting useful knowledge from the raw data. Such knowledge could have a significant impact on productivity and quality improvement. The objective of the present study is to identify useful correlations amongst the numerous process variables and to develop simple empirical models to predict important process quality indicators.
Quality is assessed using statistical data analysis, focusing on the primary functions of major failures. Validation of the data set also demonstrated that linear models were accurate in predicting new data points for some of the output variables, whereas the variation of some output variables could not be explained using the available industrial data bank. Some models were powerful in making predictions and to provide a clearer insight in determining the key factors in manufacturing of BHet. BHet is a directly modulated laser operating at 2.5 Gb/s and reaches up to 360 km. Application of this research for failure prediction at an early stage of the manufacturing line could result in a dramatic reduction in the number of defective wafers that are completely processed and thereby lowering the overall manufacturing cost.
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Hagelin, Johnny. "Enhancement of hydrolysis from co-fermentation of food waste and primary sludge." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299643.
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Research about resource recovery from complex waste streams is getting an increased scientific attention since valuable resources can be produced by sustainable biological means. In anaerobic degradation processes, resources such as volatile fatty acids (VFAs) and biogas are highly coveted. One of the key parameters affecting the yield of resources is the hydrolytic efficiency in the waste stream by hydrolytic bacteria. The aim of this study was to examine how bioaugmentation can be implemented as a strategy to enhance hydrolysis in complex waste streams. In pursuit of this aim, three selected species of hydrolytic bacteria, Bacteroides thetaiotaomicron, Bacteroides amylophilus and Bacteroides ruminicola were inoculated both in pure culture combinations and bioaugmented with granular sludge as mixed culture in reactors. The studied waste stream was food waste mixed with primary sludge collected from Henriksdals wastewater treatment plant at Stockholm, Sweden. The highest hydrolytic efficiency (90%) was reached by the pure culture fermented reactor inoculated with Bacteroides thetaiotaomicron and Bacteroides ruminicola. This efficiency was measured at day 10 after reactor set-up. Among the bioaugmented reactors, highest hydrolytic activity (66%) was achieved by the reactor inoculated with Bacteroides thetaiotaomicron and it was measured at day 10. The increase in hydrolytic efficiency for bioaugmented reactors was slower compared to pure culture fermented reactors and the most probable reason to that is due to competition amongst introduced species and pre-existing mixed culture in granular seed sludge.Mer uppmärksamhet riktas till forskning kring resursåtervinning från komplexa avfallsströmmar eftersom värdefulla resurser kan produceras genom mer hållbara biologiska tillvägagångssätt. I anaeroba nedbrytningsprocesser är produkter såsom flyktiga fettsyror (VFAs) och biogas mycket eftertraktade. En av huvudparametrarna som påverkar utbytet av återvunna resurser är den hydrolytiska effektiviteten i avfallsströmmen av hydrolytiska bakterier. Syftet med studien var att undersöka hur bioaugmentering kan implementeras som strategi för att förstärka hydrolys i komplexa avfallsströmmar. Därav utfördes fermentering med tre valda hydrolytiska bakterier, Bacteroides thetaiotaomicron, Bacteroides amylophilus och Bacteroides ruminicola både i renkultur och bioaugmenterat med granulärt slam som mixad kultur i reaktorer. Avfallsströmmen som studerades var matavfall mixat med primärt slam hämtat från Henriksdals vattenreningsverk i Stockholm, Sverige. Högsta hydrolytiska effektivitet (90%) uppnåddes för reaktorn inokulerat med Bacteroides thetaiotaomicron och Bacteroides ruminicola i renkultur. Denna effektivitet uppmättes dag 10 efter reaktorerna sattes upp. För de bioaugmenterade reaktorerna så uppnåddes högsta hydrolytiska effektivitet (66%) dag 10 av reaktorn inokulerat med Bacteroides thetaiotaomicron. Ökningen i hydrolytisk effektivitet var långsammare för de bioaugmenterade reaktorerna jämfört med reaktorerna med renkultur. Den mest sannolika förklaringen till det är tävling om näringsämnen och vitaminer mellan introducerade bakterier och de bakterier som redan existerar i det granulära slammet.
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Kashfipour, Marjan Alsadat. "Thermal Conductivity Enhancement Of Polymer Based Materials." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron156415885613422.
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Boss, Michael. "The Role of Diffusion in NMR Proton Relaxation Enhancement by Ferritin." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275484465.
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Habibzadeh, Sajjad. "Employment of Ir/Ti-oxide coatings and electrochemical polishing of a 316L stainless steel surface for the enhancement of biocompatibility of coronary stents." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121444.
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Metallic cardiovascular stents are medical devices (implants) that can provide endovascular scaffolding in order to relieve a vascular obstruction and minimize the risk of myocardial infarction (heart attack). However, current stents are considered to offer poor bio/hemocompatibility, since their surface provokes undesirable tissue reaction upon implantation. In most cases, this results in in-stent restenosis (re-blocking of the blood vessel at the implantation site). Thus, various surface characteristics of stents play a determinant role in their bio/hemocompatibility, and hence their functionality and safety. Therefore, in order to increase the bio/hemocompatibility of stents, an appropriate surface-modification method can be employed to tune the stent's surface texture and physico-chemical properties in a way to promote desirable cell/platelet-surface interactions and render the stent surface more electrochemically stable (corrosion resistant). The aim of this work was to investigate a possibility of increasing a bio/hemocompatibility of a metal surface by employing two surface-modification approaches: (i) formation of IrxTi1-x-oxide coatings (x=0, 0.2, 0.4, 0.6, 0.8 and 1) on a Ti substrate and on a commercial 316L stainless steel (316L-SS) coronary stent and (ii) electrochemical polishing of a 316L-SS surface. The former approach was also employed with the aim of increasing the stent's radiopacity (visibility). Electrochemical and surface-characterization results showed that the physic-chemical properties were highly depended on the coating composition. All the coatings were found to be electrochemically stable (corrosion resistant) under experimental conditions employed in the research. 316L-SS coronary stents modified by Ir/Ti-oxide coatings were found to be more radiopaque than the bare (naked) 316L-SS stent. The Ir0.4Ti0.6-oxide coating showed to be the most uniform, corrosion resistant and radiopaque. Electrochemical polishing (EP) of a 316L-SS surface in an electrolyte of a new chemical composition was investigated at different cell voltages. The influence of the EP cell voltage on the topographical/morphological and physico-chemical properties of resulting passive oxide films formed on the surface was studied. A particularly high enrichment with Cr species was recorded at the outermost layer of the EP oxide films. As a result of the increase in the oxide film thickness and relative Cr enrichment, the EP-treated 316L-SS surfaces offered a notable improvement in general and pitting corrosion resistance. The influence of the employed surface-modification methods on the resulting bio/hemocompatibility was further investigated. This was implemented by examining the interaction of platelets, endothelial cells (ECs) and smooth muscle cells (SMCs) with the modified surfaces. A significant decrease in platelet adhesion and activation was obtained on Ir0.2Ti0.8-oxide and Ir0.4Ti0.6-oxide coatings (among Ir/Ti-oxide surfaces) and on the surfaces electrochemically polished at the cell voltages of 4 and 10 V (among electropolished surfaces), rendering the surfaces more blood compatible, in comparison to the control (316L-SS). Moreover, ECs and SMCs showed a desirable response to the modified surfaces (the Ir/Ti-oxide coated and the electropolished surfaces). The cell/surface interaction experiments revealed a a higher affinity of ECs towards attachment to the modified surfaces, relative to the attachment of SMCs. Hence, the modified surfaces would enable faster endothelialization, rendering them potentially superior for coronary stenting applications.Endoprothèses vasculaires métalliques sont des dispositifs médicaux (implantes) qui peuvent fournir des échafaudages endovasculaire afin de soulager une obstruction vasculaire et minimiser le risque d'infarctus du myocarde (crise cardiaque). Cependant, les prothèses actuels sont considérés d'offrir mauvais bio/hémocompatibilité, car leur surface provoque une réaction tissulaire indésirable lors de l'implantation.Dans la plupart des cas, cela se traduit par une resténose intra-prothèses (re-blocage des vaisseaux sanguins au niveau du site d'implantation). Alors, diverses caractéristiques de surface des prothèses jouent un rôle déterminant dans leur biocompatibilité et subséquemment leur fonctionnalité et sécurité. Par conséquent, afin d'augmenter la bio/hémocompatibilité de prothèses s, une méthode de modification de surface appropriée peut être utilisée pour ajuster la texture de la surface du stprothèses et les propriétés physico-chimiques de manière à favoriser les interactions cellulaires/surface souhaitables et rendre la surface des prothèses plus électrochimique stable (résistant à la corrosion).Le but de ce travail était d'étudier la possibilité d'augmenter un bio/hémocompatibilité d'une surface métallique en utilisant deux approches de modification de surface: (i) la formation de revêtements IrxTi1-x-oxyde (x = 0, 0,2, 0,4, 0,6, 0.8 et 1) sur un substrat de Ti et sur une base commerciale acier inoxydable 316L (316L-SS) prothèses coronariens et (ii) le polissage électrochimique d'une surface 316L-SS. La première approche a également été utilisée dans le but d'augmenter la radio-opacité des prothèses (visibilité). Des techniques électrochimiques et surface-caractérisation ont été utilisées pour étudier la topographie/morphologie de la surface, la structure et la composition chimique des revêtements Ir/Ti-oxyde, ainsi que leurs propriétés électrochimiques et des radio-opacité. Ces propriétés ont été trouvés fortement dépendent de la composition de revêtement. Tous les revêtements ont été jugées électrochimiquement stables dans les conditions expérimentales utilisées dans la recherche. 316L-SS prothèses coronaires modifiés par des revêtements Ir/Ti-oxyde ont été trouvés à être plus radio-opaque que celui sans revêtements 316L-SS prothèses. Le revêtement Ir0.4Ti0.6-oxyde a été montré pour être le plus uniforme, résistant à la corrosion et radio-opaque. Spectrométrie photoélectron du rayon-X résultats de spectroscopie de photoélectrons ont révélé que les films d'oxyde du EP ont été caractérisées par une proportion beaucoup plus élevé atomique Cr/Fe et d'épaisseur de film, par rapport au film d'oxyde passif naturellement développée formée sur la surface non traitée 316L-SS. Un particulièrement enrichissement élevé avec des espèces Cr a été enregistré à la couche la plus externe des films d'oxyde EP. En raison de l'augmentation de l'épaisseur du film d'oxyde et enrichissement relatif Cr, les surfaces 316-SS EP-traités offert une amélioration notable de la résistance à la corrosion générale et piqûres. L'influence des méthodes de modification de surface utilisés sur la bio/hémocompatibilité a été étudiée. Ceci a été implémenté en examinant l'interaction des plaquettes, des cellules endothéliales (EC) et les cellules musculaires lisses (SMC) avec les surfaces modifiées. Les expériences sur l'interaction entre la cellule et la surface ont révélé un plus grand ratio de fixation EC/SMC pour Ir0.2Ti0.8-oxyde, Ir0.4Ti0.6-oxyde et les trois surfaces du EP, lorsque en comparant avec la contrôle 316L-SS. Ceci. Ainsi, les surfaces modifiées permettront une endothélialisation plus rapide, ce qui les rend potentiellement supérieure pour les applications de prothèses coronaire.
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Van, den Berg Jacobus A. "The utilisation of the ash disposal system as a salt sink : enhancement and optimisation of chemical interactions." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16450.
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Thesis (MScIng)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: The fine ash produced at the Sasol Secunda Petrochemical Plant is disposed of through a wet ash disposal system. Other process waste streams with high salt concentrations are co-disposed of in the Sasol Secunda ash disposal system. This has led to a steady rise in the salt concentrations of the recycled clear ash effluent (CAE) over the past 17 years. To combat this increase in salt concentrations, the capability of the Sasol Secunda ash disposal system to act as a salt sink, needs to be enhanced. This investigation focussed on ways to enhance the salt removal/retention capabilities of the Sasol Secunda ash disposal system and consisted of the following: • A literature survey of relevant information. • The mixing of different combinations of fine ash, brine and CAE. • Adding CO2 to the fine ash and CAE mixtures. • Investigation to enhance salt precipitation in the CAE and Evaporation dams. • Salt balances and a residence time calculation over the CAE and Evaporation dams. From these investigations it were concluded that the Sasol Secunda ash disposal system could be used as a salt sink for SO4 ions. Up to 43% of the SO4 is removed from the brines after the initial ash/water contact. It was also found that the tubular reverse osmosis (TRO) brine could be used as a carrier medium for the ash. The large amounts of Ca that is leached into the ash water during the mixing of the CAE and fine ash can be prevented by the addition of CO2 to the mixing point. There is usually an increase of 240% in the Ca concentration and this is reduced to only an 8% increase with the CO2 addition. The most feasible precipitation enhancement for the CAE and Evaporation dams is an increase in evaporation. This enhances CaCO3 precipitation, which is the main mechanism for salt removal in the CAE and Evaporation dams. Ca, Na and Cl are retained in the evaporation and CAE dams. SO4 is leached from solid phases in the dams. There is however an overall decrease in the total dissolved solids (TDS) of the ash water. The salt removal of the CAE and Evaporation dams is approximately 57 tons per day. The capability of the Sasol Secunda ash disposal system to act as a salt sink can be enhanced by the addition of CO2 at the mixing point and by increasing the evaporation rate in the CAE and Evaporation dams. Using the TRO brine as carrier medium may also increase the SO4 precipitation capabilities of the Sasol Secunda ash disposal system.
AFRIKAANSE OPSOMMING: Die fynas wat by die Sasol Secunda Petrochemiese Aanleg geproduseer word, word verwyder deur ‘n geslote nat asstelsel. Ander afvalstrome wat hoë konsentrasies soute bevat word ook in die Sasol Secunda asstelsel gestort. Dit het tot gevolg dat daar oor die afgelope 17 jaar ‘n volgehoue styging in die sout konsentrasies van die hergebruikte aswater (genoem CAE – “clear ash effluent”) was. ‘n Manier om hierdie styging in die sout konsentrasies teen te werk, is om die sout verwyderingsvermoë van die Sasol Secunda asstelsel te verbeter. Hierdie ondersoek het gefokus op maniere om die sout verwyderings- /terughoudingsvermoë van die Sasol Secunda asstelsel te verbeter en het die volgende ingesluit: • ‘n Literatuur oorsig van toepaslike inligting. • Die meng van verskillende kombinasies van fynas, soutstrome en CAE. • Toediening van CO2 by die fynas en CAE mengsels. • ‘n Ondersoek na metodes om die soutverwydering in die CAE en Verdampingsdamme te verbeter. • Soutbalanse en ‘n residensie tyd berekening vir die CAE en Verdampingsdamme. Na hierdie ondersoeke kon die gevolgtrekking gemaak word dat die Sasol Secunda asstelsel ‘n sout sink vir SO4 ione is. Tot 43% van die SO4 word verwyder na die aanvanklike as/water kontak. Daar is ook gevind dat die TRO (“tubular reverse osmosis”) soutstroom gebruik kan word as ‘n draer vir die fynas. Die groot hoeveelhede Ca wat in die aswater in loog, kan voorkom word deur die toediening van CO2 by die mengpunt van die fynas en aswater. Daar is normaalweg ‘n verhoging van 240% in die Ca konsentrasie van die aswater en dit word verminder na ‘n skrale 8% met die toediening van CO2. Die mees praktiese metode om die soutverwydering in die CAE en Verdampingsdamme te verbeter, is met die verhoging van die verdamping. Dit sal die neerslag van CaCO3, wat die meeste soutverwydering tot gevolg het, verhoog. Ca, Na en Cl word teruggehou in die Verdampings en CAE damme. SO4 loog uit soliede fases in die damme. Daar is wel ‘n afname in die algehele opgeloste spesies (“TDS”) van die aswater. Die soutverwydering van die Verdampings en CAE damme is ongeveer 57 ton per dag. Die vermoë van die Sasol Secunda asstelsel om as ‘n sout sink gebruik te word, kan verbeter word deur CO2 by die mengpunt by te voeg en die verdampingstempo in die Verdampings en CAE damme te verhoog. Die gebruik van die TRO pekelstroom as draer van die as kan die SO4 neerslag in die Sasol Secunda asstelsel ook verhoog.
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Olsson, Kevin. "Optimization of gas flow uniformity in enhancement of Metal Organic Chemical Vapor Deposition growth for III-nitrides." Thesis, Linköpings universitet, Halvledarmaterial, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-157378.
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The thesis focuses on the gas flow profile optimization of a non-conventional injector in a hot-wall MOCVD system. The injector’s gas flow profile is simulated with CFD and demonstrates awell-behaved laminar flow with a parabolic profile. To ensure the theory is in coherence with the reality, a qualitative study with five thermocouples in a test graphite piece of the was performed. First the thesis will take you through an introduction of the semiconductor field to arrive in a problem formulation. Then you will read about the principles of MOCVD systems, fluid dynamics principles and thermocouple theory. The experiment’s way of approach is thendescribed through all steps from blue print to results. A discussion about the result and the conclusion will be read before the proposals of future work based on the thesis work. The laminar flow is confirmed according to the resulting data and the limitations of the system is set to two different cases depending on background temperature. At 1000 °C a laminar flow is strongly indicated to be obtained at position 3A, closest to the growth area, within the gas flow range of 25 SLM regardless of background pressure, except for 700 mBar indicating turbulent flow for 15 SLM an up. At 20 and 200 mBar the laminar flow limit is suggested by data to be even higher and reaching a value of 35 SLM. At 450 °C the data indicate a laminar flow up to 20 SLM at position 3A regardless of background pressure condition, except for 700 mBar where the data indicate a laminar flow at 35 and 40 SLM. 50 mBar strongly indicates a laminar flow profile up to a gas flow of 35 SLM. With a background pressure of 20 mBar, the data suggests a laminar flow profile up to at least 25 SLM. At 100 mBar the data indicates a laminar flow within the range of 30 SLM.
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Dickerson, Matthew Thomas. "PROTEIN BASED BIOMIMETIC APPROACHS TO SURFACE HEMOCOMPATIBILITY AND BIOCOMPATIBILITY ENHANCEMENT." UKnowledge, 2012. http://uknowledge.uky.edu/cme_etds/6.
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T. pallidum can survive a primary immune response and continue growing in the host for an extended period of time. T. pallidum is thought to bind serum fibronectin (FN) through Tp0483 on the surface to obscure antigens. A Tp0483 fragment (rTp0483) was adsorbed onto functionalized self-assembled monolayers (SAMs) with FN. FN capture by adsorbed rTp0483 depended greatly on surface chemistry with COO- groups being best for FN binding. Hemocompatibility was determined by analysis of plasma protein adsorption, intrinsic pathway activation, and platelet activation. rTp0483+FN bound an equal or lesser amount of fibrinogen (Fg), human serum albumin (HSA), and factor XII (FXII) compared to rTp0483 or FN alone and adsorption of rTp0483 prior to FN greatly decreased platelet activation. Inhibition of protein binding and platelet activation suggested an attenuated hematological response. Biocompatibility of rTp0483 and FN coated surfaces was characterized by macrophage uptake of protein coated polystyrene microspheres (PSMs), macrophage adsorption onto protein coated surfaces, cytotoxic effects of adsorbed rTp0483 and FN, and TNF-α and NO2- release in macrophages stimulated with rTp0483 and FN adsorbed and in solution. Addition of FN to rTp0483 on plain and COO- PSMs reduced phagocytosis compared to rTp0483 alone and on plain PSMs compared to FN alone. On plain PSMs addition of FN to adsorbed rTp0483 decreased TNF-α generation. Adsorption of rTp0483 before FN on large, flat COO- surfaces decreased macrophage adsorption and TNF-α and NO2- generation. High concentrations of rTp0483 were mildly cytotoxic to macrophages. FN binding by Tp0483 on T. pallidum likely plays a role in antigenic disguise and rTp0483+FN coatings may potentially inhibit FN and rTp0483 specific interactions with macrophages. Molecularly imprinted polymer coatings were also examined for biomaterial development. Fouling resistant 2-methacryloyloxyethyl phosphorylcholine (MPC) was imprinted with bovine serum albumin (BSA) protein templates to facilitate BSA specific binding. The BSA template was constructed and verified and BSA specific binding quantified using quartz crystal microbalance (QCM) and enzyme linked immunosorbent assay (ELISA). BSA imprinted coatings were determined to bind significantly more BSA than nonfouling MPC controls demonstrating the feasibility of targeted protein capture.
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Upamali, Karasinghe A. Nadeeka. "Carbazole-Based, Self-Assembled, Π-Conjugated Systems As Fluorescent Micro And Nanomaterials - Synthesis, Photophysical Properties, Emission Enhancement And Chemical Sensing." Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1323099511.
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Myers, Philip D. Jr. "Additives for Heat Transfer Enhancement in High Temperature Thermal Energy Storage Media: Selection and Characterization." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5749.
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Inorganic salts are very promising as high-temperature heat transfer fluids and thermal storage media in solar thermal power production. The dual-tank molten salt storage system, for example, has been demonstrated to be effective for continuous operation in solar power tower plants. In this particular storage regime, however, much of the thermal storage potential of the salts is ignored. Most inorganic salts are characterized by high heats of fusion, so their use as phase-change materials (PCMs) allows for substantially higher energy storage density than their use as sensible heat storage alone. For instance, use of molten sodium-potassium eutectic salt over a temperature range of 260 to 560°C (the approximate operating parameters of a proposed utility-scale storage system) allows for a volumetric energy storage density of 212 kWhth/m3, whereas the use of pure sodium nitrate (T_m = 307°C) over the same temperature range (utilizing both sensible and latent heat) yields a storage density of 347 kWhth/m3.
The main downside to these media is their relatively low thermal conductivity (typically on the order of 1 W/m-K). While low conductivity is not as much an issue with heat transfer fluids, which, owing to convective heat transfer, are not as reliant on conduction as a heat transfer mode, it can become important for PCM storage strategies, in which transient charging behavior will necessarily involve heating the solid-phase material up to and through the process of melting. This investigation seeks to develop new methods of improving heat transfer in inorganic salt latent heat thermal energy storage (TES) media, such as sodium / potassium nitrates and chlorides. These methods include two basic strategies: first, inclusion of conductivity-enhancing additives, and second, incorporation of infrared absorptive additives in otherwise transparent media. Also, in the process, a group of chloride based salts for use as sensible storage media and/or heat transfer fluids has been developed, based on relevant cost and thermophysical properties data.
For direct conductivity enhancement, the idea is simple: a PCM with low conductivity can be enhanced by incorporation of nanoparticulate additives at low concentration (~5 wt %). This concept has been explored extensively with lower temperature heat transfer fluids such as water, ethylene glycol, etc. (e.g., nanofluids), as well as with many lower temperature PCMs, such as paraffin wax. Extension of the concept to high temperature inorganic salt thermal storage media brings new challenges—most importantly, material compatibility. Also, maintenance of the additive distribution can be more difficult. Promising results were obtained in both these regards with nitrate salt systems.
The second heat transfer enhancement strategy examined here is more novel in principle: increasing the infrared absorption of a semitransparent salt PCM (e.g., NaCl) with a suitable additive can theoretically enhance radiative heat transfer (for sufficiently high temperatures), thereby compensating for low thermal conductivity. Here again, material compatibility and maintenance of additive dispersion become the focus, but in very different ways, owing to the higher temperatures of application (>600°C) and the much lower concentration of additives required (~0.5 wt %). Promising results have been obtained in this case, as well, in terms of demonstrably greater infrared absorptance with inclusion of additives.
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Shapero-Holder, Barbara C. "Contributory role status and the development and treatment of chemical dependence a contextual enhancement of current recovery models /." View full text, 2003.
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Kuhlman, Andrew. "An Ab-Initio Study on the Chemical Modification of Raman Spectra of Organic Adsorbates on Semiconductor Surfaces." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1402334244.
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Orgill, James J. "Enhancement of Mass Transfer and Electron Usage for Syngas Fermentation." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4029.
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Biofuel production via fermentation is produced primarily by fermentation of simple sugars. Besides the sugar fermentation route, there exists a promising alternative process that uses syngas (CO, H2, CO2) produced from biomass as building blocks for biofuels. Although syngas fermentation has many benefits, there are several challenges that still need to be addressed in order for syngas fermentation to become a viable process for producing biofuels on a large scale. One challenge is mass transfer limitations due to low solubilities of syngas species. The hollow fiber reactor (HFR) is one type of reactor that has the potential for achieving high mass transfer rates for biofuels production. However, a better understanding of mass transfer limitations in HFRs is still needed. In addition there have been relatively few studies performing actual fermentations in an HFR to assess whether high mass transfer rates equate to better fermentation results. Besides mass transfer, one other difficulty with syngas fermentation is understanding the role that CO and H2 play as electron donors and how different CO and H2 ratios effect syngas fermentation. In addition to electrons from CO and H2, electrodes can also be used to augment the supply of electrons or provide the only source of electrons for syngas fermentation. This work performed an in depth reactor comparison that compared mass transfer rates and fermentation abilities. The HFR achieved the highest oxygen mass transfer coefficient (1062 h-1) compared to other reactors. In fermentations, the HFR showed very high production rates (5.3 mMc/hr) and ethanol to acetic acid ratios (13) compared to other common reactors. This work also analyzed the use of electrons from H2 and CO by C. ragsdalei and to study the effects of these two different electron sources on product formation and cell growth. This study showed that cell growth is not largely effected by CO composition although there must be at least some minimum amount of CO present (between 5-20%). Interestingly, H2 composition has no effect on cell growth. Also, more electron equivalents will lead to higher product formation rates. Following Acetyl-CoA formation, H2 is only used for product formation but not cell growth. In addition to these studies on electrons from H2 and CO, this work also assessed the redox states of methyl viologen (MV) for use as an artificial electron carrier in applications such as syngas fermentation. A validated thermodynamic model was presented in order to illustrate the most likely redox state of MV depending on the system setup. Variable MV extinction coefficients and standard redox potentials reported in literature were assessed to provide recommended values for modeling and analysis. Model results showed that there are narrow potential ranges in which MV can change from one redox state to another, thus affecting the potential use as an artificial electron carrier.
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Giberti, Sara. "Surface Area enhancement of biochar and forestry biomass through activation by means of chemical impregnation with ZnCl2 and H3PO4." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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This dissertation is dedicated to the research of methods for the production of activated carbon by means of chemical impregnation from renewable resources such as waste biochar and forestry biomass.
The goal of the research is to find a method that generates high performances activated carbon which can be scaled up and added to the supply chain of an already existing gasification concept located in Innsbruck, Austria.
Biochar has been impregnated with ZnCl2 in ratios of 1:1 and 5:1 and activated in a mixed bed reactor in presence of H2O steam in a temperatures range of 500 and 700 °C for 30 and 60 minutes.
Forestry biomass and biochar have been impregnated with ZnCl2 and H33PO4 in ratios of 1:1, 3:1, 5:1 then pyrolyzed at 500 °C for 1 hour.
The activated carbon has been characterized through N2 adsorption at 77 K, total carbon content and scanning electron microscopy. The best results were obtained with the ZnCl2 5:1 impregnated biomass pyrolyzed at 500 °C for 1 hour, with a specific surface area of 1626 m2/g, a total pore volume of 0,79 cm3/g with a microporous percentage of the 75%, and a total carbon content of 84%.
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Johnsen, Kim. "Sorption-enhanced steam methane reforming in fluidized bed reactors." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-994.
Full textAbstract:
Hydrogen is considered to be an important potential energy carrier; however, its advantages are unlikely to be realized unless efficient means can be found to produce it without generation of CO2. Sorption-enhanced steam methane reforming (SE-SMR) represent a novel, energy-efficient hydrogen production route with in situ CO2 capture, shifting the reforming and water gas shift reactions beyond their conventional thermodynamic limits.
The use of fluidized bed reactors for SE-SMR has been investigated. Arctic dolomite, a calcium-based natural sorbent, was chosen as the primary CO2-acceptor in this study due to high absorption capacity, relatively high reaction rate and low cost. An experimental investigation was conducted in a bubbling fluidized bed reactor of diameter 0.1 m, which was operated cyclically and batchwise, alternating between reforming/carbonation conditions and higher-temperature calcination conditions. Hydrogen concentrations of >98 mole% on a dry basis were reached at 600°C and 1 atm, for superficial gas velocities in the range of ~0.03-0.1 m/s. Multiple reforming-regeneration cycles showed that the hydrogen concentration remained at ~98 mole% after four cycles. The total production time was reduced with an increasing number of cycles due to loss of CO2 -uptake capacity of the dolomite, but the reaction rates of steam reforming and carbonation seemed to be unaffected for the conditions investigated.
A modified shrinking core model was applied for deriving carbonation kinetics of Arctic dolomite, using experimental data from a novel thermo gravimetric reactor. An apparent activation energy of 32.6 kJ/mole was found from parameter fitting, which is in good agreement with previous reported results. The derived rate expression was able to predict experimental conversion up to ~30% very well, whereas the prediction of higher conversion levels was poorer. However, the residence time of sorbent in a continuous reformer-calciner system is likely to be rather low, so that only a fraction of the sorbent is utilized, highlighting the importance of the carbonation model at lower conversions.
A dual fluidized bed reactor for the SE-SMR system was modeled by using a simple two-phase hydrodynamic model, the experimentally derived carbonation kinetics and literature values for the kinetics of steam reforming and water gas shift reactions. The model delineates important features of the process. Hydrogen concentrations of >98 mole% were predicted for temperatures ~600°C and a superficial gas velocity of 0.1 m/s. The reformer temperature should not be lower than 540°C or greater than 630°C for carbon capture efficiencies to exceed 90%. Operating at relatively high solid circulation rates to reduce the need for fresh sorbent, is predicted to give higher system efficiencies than for the case where fresh solid is added. This finding is attributed to the additional energy required to decompose both CaCO3 and MgCO3 in fresh dolomite. Moreover, adding fresh sorbent is likely to result in catalyst loss in the purge stream, requiring sorbents with lifetimes comparable to those of the catalyst.
Thermo gravimetric analysis (TGA) was used to study the reversible CO2-uptake of sorbents. In general, the multi-cycle capacity of the dolomite was found rather poor. Therefore, synthetic sorbents that maintain their capacities upon multiple reforming-calcination cycles were investigated. A low-temperature liquid phase co-precipitation method was used for synthesis of Li2ZrO3 and Na2ZrO3. Li2ZrO3 showed a superior multi-cycle capacity compared to Arctic dolomite in TGA, but the rate of reaction in diluted CO2 atmospheres was very slow. The synthesized Na2ZrO3 proved to have both fast carbonation kinetics and stable multi-cycle performance. However, regeneration in the presence of carbon dioxide was not easily accomplished.
The findings of this thesis suggest that the bubbling fluidized bed reactor is an attractive reactor configuration for SE-SMR. Low gas throughput is the major disadvantage for this configuration, and operation in the fast fluidization regime is most likely to be preferred on an industrial scale of the process. Future work should focus on developing sorbents and catalysts that are suited for high velocity operation, with respect to reactivity and mechanical strength.