Rozprawy doktorskie na temat „Improved recovery”
Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: Improved recovery.
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „Improved recovery”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
1
Sánchez, Monsalve Diego Alejandro. "Downhole Gasification (DHG) for improved oil recovery". Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642042.
Pełny tekst źródłaStreszczenie:
Gas injection, the fastest growing tertiary oil recovery technique, holds the promise of significant recoveries from those depleted oil reservoirs around the world which fall into a pressure range of (50-200) bar mainly. However, its application with the usual techniques is restricted by the need for various surface facilities such as enormous gas supply and storage. The only surface facility that downhole gasification of hydrocarbons (DHG) requires, on the other hand, is a portable electricity generator. DHG consists in producing inert gases, H2, CO, CO2 and CH4 through the steam reforming reaction of a part of the produced oil in a gasifier-reformer reactor positioned alongside the producer well in the reservoir. The gases, mainly H2 -the most effective displacing gas among produced gases- are injected into a gas cap above the oil formation, to increase oil recovery through a gas displacement drive mechanism. So far, DHG has only been tested under laboratory conditions using methane, pentane/reservoir gas and naphtha/reservoir gas as feedstock at conditions of reservoir pressure up to 130 bar. The studies varied reaction temperature, steam to carbon (S/C) ratio, catalyst types and catalyst loading in the gasifier-reformer reactor of a small pilot scale rig. These experimental studies demonstrated that pressure is one of the main factors influencing the effectiveness of the DHG process. From this starting point, the present investigation was directed at extending the pressure range up to 160 bar in the gasifier-reformer reactor using a naphtha fraction as feedstock in order to investigate whether the conversion and H2 concentration in produced dry gas can be maintained at acceptable levels under conditions of high pressure. To this end, experimental studies were carried out within the laboratory using the existing DHG rig on the small pilot scale, which was successfully commissioned and revamped for the purposes of this study. Initially, the investigation focused on exploring operating conditions, namely, steam to carbon (S/C) ratio, length of the gasifier-reformer reactor tube/ catalyst loading and the relative performance of two different catalysts. Subsequently, experiments on shutdown/start up cycles followed by variation of temperature were performed to simulate the effect of sudden electrical disruptions that usually occur in field operations. Experimental results using naphtha at pressure from 80 to 160 bar at 650 ºC, S/C= 6 achieved total feedstock conversion, no coke deposits and, most importantly, high H2 concentration in the produced dry gas (56-63 vol. % plus other gases). The best result was obtained with a crushed HiFUEL R110 catalyst (40-60 wt. % of NiO/CaO.Al2O3) and a reactor tube length of 72 cm, but the results with a C11-PR catalyst (40 wt. % of NiO/MgO.Al2O3) and a reactor tube length of 30 cm were similarly favourable. These results were supported by results of a numerical DHG model which indicated total feedstock conversion and values of H2 around 67 vol. % (using n-heptane as model surrogate). The results suggest that the DHG process is technically feasible at the pressure values studied, perhaps up to 200 bar where there are many hundreds of depleted, light oil reservoirs, especially in North America and other parts of the world below that pressure value.
2
Essiagne, Franck-Hilaire. "Underground transformation and upgrading for improved oil recovery". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/42888.
Pełny tekst źródłaStreszczenie:
Petroleum refining has entered a significant transition period as the industry moves into the 21st century and the demands for petroleum and petroleum products continue to show a sharp growth in recent years. Refinery operations have evolved to include a range of next-generation processes as the demand for transportation fuels and fuel oil has shown steady growth. The research described in this thesis has been focused on an investigation of hydrothermal processing of hydrocarbons, mainly heavy oils. Experiments were carried out at temperatures from 300 to 380 °C and at a pressure of 220 ± 10 bar in both batch and flow systems separately by using 1/4-inch stainless steel tubing. The experiments were performed by using different reaction systems: toluene/H2O, toluene/H2O2, toluene/H2O/air, and toluene/H2O2/air. A comparative study of these reaction systems spiked with sulphur and metals (nickel, vanadium) were also conducted at the same conditions. Toluene conversion was investigated in a batch reactor at supercritical conditions in the presence of water. The conversion of toluene increases with temperature and steam/carbon (S/C) molar ratio (i.e. H2O to toluene ratio), conditions that provide favourable operating conditions for toluene conversion order to get high content products (gases and liquids). The toluene conversion yields multiple desirable lighter (liquid) hydrocarbons. The major liquid products include benzaldehyde, ethylbenzene, cresols (opm-cresols), styrene, benzyl alcohol and benzoic acid. Progressively larger quantities of these products are possible at higher temperatures and at higher H2O/toluene ratios. The efficiency of toluene conversion into products reaches almost 91% at 380 °C at a H2O/toluene ratio of 3 to 1. The yields improve monotonically as longer reaction times are allowed. Furthermore, when adding H2O2, the yield of the major liquid products benzaldehyde, ethylbenzene, cresols (opm-cresols), styrene, benzyl alcohol, benzoic acid increases with temperature and at higher H2O2/toluene ratios. The efficiency of toluene conversion into products reaches almost 40% at 380 °C at H2O2/toluene ratio equals to 3:1 with 5% H2O2 in 5 min of residence time. The yields improve at longer residence times. In the gas phase, H2 increases with an increasing H2O2 concentration while again, the yield of CH4 is small. The CO content increases up to 40% when between 6% and 8% H2O2 is used at temperatures around 380 °C whereas the CO2 content decreases. The conversion efficiency of toluene converted into liquid and gas products increases with temperature. This increase is accentuated with an increase in the H2O2/toluene ratio. Toluene conversion is slightly higher in the water/toluene mixture (90%) than the H2O2/toluene mixture (just below 90%). This is important, since along with the increased cost associated with the need for H2O2 and hence the increased overall cost of operation, it suggests that the water/toluene system is the more desirable one to consider further. Experimental results also revealed that a maximum of about 90% of the Ni-TPP was converted to intermediate and final Ni-based products at a temperature of 380 °C and after a reaction time of 90 min. Under the same conditions, around 67% of the Ni was removed by the action of supercritical water, proving that supercritical water is capable of removing Ni from Ni-TPP. The same batch reactor system was also used to study vanadium removal. V-TTP (a vanadium-containing compound which was added to the toluene) also reacted with SCW suggestions a pathway for vanadium removal. The effects of reaction time and temperature were investigated, showing that approximately 91% of V-TPP was converted to intermediate and final products at a temperature of 380 °C and reaction time of 100 min. Under the same conditions, approximately 82% of the vanadium was removed. This process was deemed successful since it did not use a catalyst. Finally, the removal of unwanted/undesirable sulphur from the oil was also considered. A gradual increase in the % DBT conversion was found at higher temperatures. The maximum DBT conversion was achieved at the highest investigated temperature, i.e. 380 °C. A maximum DBT conversion of ~ 97% was recorded after 30 min of reaction time. Importantly, and contrary to the findings concerning the conversion of toluene, the introduction of H2O2 lead to a considerable improvement in the metal removal potential.
3
Ramidi, Harika Reddy. "An Improved Crash Recovery Approach for Distributed Systems". OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/218.
Pełny tekst źródłaStreszczenie:
In this paper, we have addressed the complex problem of recovery for concurrent failures in distributed computing environment. We have proposed a new approach in which we have dealt with effectively both orphan and lost messages. The proposed check pointing and recovery approaches enable a process to restart from its recent checkpoint and hence guarantees the least amount of re-computation after recovery. It also means that a process needs to save only its recent local checkpoint. The proposed value of the common check pointing interval enables an initiator process to log the minimum number of messages sent by each application process. The message complexity of the proposed check pointing algorithm as well as the recovery approach is O(n).
4
Henson, Richard M. "Geologically based screening criteria for improved oil recovery projects". Thesis, Heriot-Watt University, 2003. http://hdl.handle.net/10399/307.
Pełny tekst źródła
5
Kim, Jeong-Hee. "Improved recovery of gravity anomalies from dense altimeter data /". The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487862399447755.
Pełny tekst źródła
6
Chewaroungroaj, Jirawat. "Improved procedures for estimating uncertainty in hydrocarbon recovery predictions /". Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992767.
Pełny tekst źródła
7
Lindgård, Ann. "Improved bioenergetic recovery during experimental ischemia and reperfusion by irradiation /". Göteborg : Göteborg University, Bioenergetics Group, Department of Surgery, Wallenberg Laboratory & Lundberg Laboratory for Bioanalysis, Sahlgrenska Academy, Göteborg University, 2007. http://hdl.handle.net/2077/7505.
Pełny tekst źródła
8
Du, Plessis Jan Antonie. "Improved gold recovery by accelerated gravity separation / du Plessis J.A". Thesis, North-West University, 2011. http://hdl.handle.net/10394/7364.
Pełny tekst źródłaStreszczenie:
This project was specifically aimed at using increased acceleration separation, as a method to optimize the recovery of gold in an ore body mainly consisting of hematite. The specific gravity of gold is much higher in comparison to the carrying material, making it possible to separate gold from other materials such as silica, base metals and their oxides, usually associated with gravitation–gold–recovery processes. The ore body investigated in this project originated from a mined gold reef containing a large proportion of gold locked inside the gold pyrite complexes. In the mine's processing plant a gold pyrite concentrate was produced by means of a flotation process. The roasting process that followed, oxidized the pyrite to iron oxide (hematite) and sulphur dioxide. The gold particles which were locked up inside the pyrite gold complex were exposed or liberated, allowing the chemicals to penetrate the complex and dissolve the gold. After the cyanide gold extraction process, the material was pumped on to a mine reserve dump, referred to as tailings or tailings reserve dump. The tailings usually contain iron oxides, free gold, gold associated with iron oxides and gold associated with silica, and free silica, commonly referred to as calcine. The gold content on the calcine dump was significantly lower than the flotation concentrate before the extraction of the gold and it was no longer viable for the mine to process the tailings further. As the volume of the mine reserve dump increased over the years, it became viable to recover the gold in a high volume low grade plant. Several attempts were made to recover the gold in this dump, but due to the high cost of processing and milling the material, it was not done. The norm in the mining industry is that it is impossible to concentrate the gold by means of gravity separation techniques where the average particle sizes are smaller than 50 um in diameter and upgrading with inexpensive gravity separation techniques was ruled out by the mine, because the average particle sizes were too small.
The dump investigated in this project differed from other reserve dumps in that the main phase of material in this dump was hematite and not silica. A suspension of this material would have different fall–out properties than other mine reserve dumps, because of the hematite's high specific gravity compared to silica. This property of the material birthed the idea that the material will respond positively to high acceleration separation, although the particle sizes were too small for effective upgrading according to the norm in the mining industry. Using acceleration concentration as a first stage in the gold recovery process the production cost per gram of gold produced could be reduced significantly. Firstly, the volume of concentrated material to be treated in the chemical extraction process was reduced ninety percent and secondly, the gold concentration was increased significantly. If the gold could be concentrated to more than twenty grams of gold per ton, it could be extracted economically with an aggressive chemical processes. This was not possible with low grade material contained in the dump. The theoretical principle, on which this project was based, was to make use of high acceleration separation to establish separation between the particles associated with the gold, and the particles not associated with gold. Applying a high gravitational force would have an influence on the velocity by which the particles would fall–out in a suspension. As the acceleration force increased the fall–out velocity would also be increased and the particles with higher specific gravity would be affected more. A factor that was equally important was the particle size and weight distribution. A large hematite particle would compete with a small gold particle due to the similarity in weight. This could cause loss in small gold particles or retention of hematite particles with no gold content.
Very little scientific information was available on the material investigated and in order to assemble a concentration plant setup, the head grade and particle size distribution for both the dump and bulk sample were determined accurately. Thereafter, chemical analyses and mineralogical examination were done on a representative sample of the bulk sample, determining the chemical composition of the material. The results obtained thereof were evaluated and used to configure a pilot plant. A large bulk sample was processed in the pilot plant and from the analytical results the efficiency could be evaluated. The results at optimum acceleration forces applied, resulted in a recovery of 5% of the mass, with a gold concentrate of 90 g/t Au, which represented 58% recovery of the gold. The hematite with high specific gravity as main phase positively influenced the high acceleration separation process. It proved that if the specific gravity of particles in a suspension were increased, high acceleration separation could be applied effectively to separate much smaller particle sizes.Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2012.
9
Taura, Usman Habu. "Improved numerical simulation of non-thermal enhanced heavy oil recovery". Thesis, Heriot-Watt University, 2017. http://hdl.handle.net/10399/3380.
Pełny tekst źródłaStreszczenie:
The dependence on unconventional resources such as heavy oil is on the rise due to geometric increase in demand for energy and the decline of production from mature conventional oil reservoirs. Heavy oil reservoirs contain oil that has some limited mobility under reservoir conditions and only a small fraction of the oil-in-place can be recovered by primary technique which involve harnessing the internal reservoir energy. The remaining oil after the primary depletion is still mostly continuous and present a valuable target for enhanced recovery. However, most of these reservoirs are relatively thin, making them poor candidates for thermal methods, in addition to associated high energy requirement and adverse environmental effects of the heating process. Therefore, any incremental oil recovery must be through non-thermal methods, such as waterflooding, chemical and gas injection. These methods however suffer from adverse mobility ratio which significantly affect the efficiency of the displacement process. The simulation of these processes for the purpose of reservoir prediction and performance is a herculean task due to the complex physics of instability and compositional effect taking place that is not fully understood. In this thesis, the results of improved numerical simulation techniques of non-thermal heavy oil recovery were presented, demonstrating the viability of the techniques as simulation methods heavy oil non-thermal enhanced heavy oil recovery (EHOR). Several displacement mechanisms were identified through the simulation of the secondary and tertiary processes that contributed to significant incremental heavy oil recovery. A systematic lumping scheme of the heavy oil components into pseudo-components based on the behaviour of the produced oil was proposed. A new methodology for the estimation of relative permeability from displacement with instability and compositional effect using a two-dimensional (2D), high-resolution model to effectively capture the finger, and a versatile, three-parameter function (L.E.T correlation) was demonstrated. A semianalytical approach through a combination of theoretical and an empirical prediction method based on the famous works of Koval, and Todd and Longstaff on viscous fingering was employed for the verification of the estimated relative permeability. Lastly, a multiscale approach to history matching, for the estimation of unstable relative permeability that is computationally more efficient, was proposed. It involves the history matching of a set of coarse grid models to predict the fine-scale relative permeability. In this approach, fine-scale information was resolved without direct solution of the global fine-scale problem. The results showed that the time required to estimate relative permeability using the multiscale approach was only about 35% required to estimate the same relative permeability using a single high-resolution model. The memory requirement for the approach was also about 50% required for simulation of the single high-resolution model. Therefore, the lower memory size and computations required in the multiscale approach mean that a less powerful computer can be used to estimate the relative permeability curves for unstable displacements with accuracy similar to that obtained using a high-resolution model approach.
10
Liu, Frances D. (Frances Deen). "Mechanical modulation of indirect repair mechanisms for improved hematopoietic recovery". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119976.
Pełny tekst źródłaStreszczenie:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biological Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 243-264).
Hematopoietic stem cell or bone marrow transplantation is a curative treatment for multiple hematologic malignancies. However, the myeloablative conditioning regimens preceding cell delivery have rendered the rapid and sustained hematopoietic recovery after transplantation an outstanding challenge. Successful long-term engraftment of hematopoietic stem cells is dependent largely on the surrounding stroma components or hematopoietic niche. Cell types within this niche that support hematopoietic recovery include two adherent cell types, mesenchymal stromal cells (MSCs) and vascular endothelial cells (VECs). The niche also contains many biophysical and mechanical cues including cell contractility against other cells or the matrix, pulsatile fluid flow, differences in localized niche stiffness, and occupation of fluid volume by macromolecules. This thesis aims to understand how VECs and MSCs respond to these cues ex vivo, and how these cues can be used to engineer VEC and MSC phenotypes that can predictably support hematopoietic recovery in vivo. VEC-mediated angiogenesis and angiocrine signaling are known to support hematopoietic recovery in vivo. In this thesis, we first explored how the biophysical cue of macromolecular crowding (MMC) and the mechanical cue of strain can regulate angiogenesis. The addition of synthetic MMC to in vitro cultures replicates the endogenous occupation of fluid space due to macromolecules. We explored how MMC affects the basement membrane formation of VECs, and determined that MMC can increase the deposition, areal spread, and alignment of basement membrane proteins. Even with the addition of biochemical signals from pericytes, this biophysical cue of MMC played a dominant role in the organization of the basement membrane. Pericytes that surround blood vessels and the basement membrane have been shown to exert contractile forces, which results in a hoop strain in the blood vessel wall. We translated this strain to in vitro VEC cultures by applying static, uniaxial strain to confluent VEC monolayers using a polydimethyl siloxane (PDMS) substrata, which allowed us to decouple the mechanical cue of pericytes from their chemical signaling. The application of 10% engineering strain was sufficient to induce cell-cycle re-entry in a quiescent monolayer. We then went on to demonstrate in a quasi-3D assay that straining the VECs also produced angiogeniclike sprouts. Together, these results show that biophysical and mechanical cues of the hematopoietic niche alone are sufficient to direct VEC-derived extracellular matrix formation and to induce angiogenic sprouting. Thus, future models of in vitro angiogenesis must include these cues to more comprehensively and accurately replicate the in vivo hematopoietic niche. Paracrine signaling from MSCs is crucial in regulating the self-renewal capacity and differentiation of hematopoietic stem and progenitor cells (HSPCs) that re-populate the bone marrow compartment in vivo. Thus, we then explored if and how to modulate MSC paracrine signaling or the MSC secretome. Like VECs, MSCs are known to respond to microenvironment cues such as substratum stiffness. We developed tissue-culture compatible PDMS-based substrata with tunable viscoelastic properties to assay potential mechanosensitivity. We characterized the bulk and surface properties of this substrata to verify that we could tune stiffness across three orders of magnitude without altering material surface biochemistry. When we expanded the MSCs on compliant substrata (elastic modulus ~I kPa), we found that we could increase the expression of osteopontin as well the expression of at least a dozen other secreted proteins without altering cell capacity for terminal differentiation. We observed changes in the MSC secretome that were significantly correlated to the viscoelastic properties (shear storage and loss moduli G' and G", respectively, and the ratio of G"/G' as tan [delta]) of the substratum material. These results suggested that we could mechanically modulate the MSC secretome using the viscoelastic properties of the extracellular substrata. Finally, we went on to explore how these mechanically modulated changes in MSC phenotype could regulate hematopoiesis in vitro and support hematopoietic recovery in vivo. To do so, we used statistical regression modeling (partial least squares regression or PLSR) to identify the components of the MSC secretome that were significantly correlated with improved radiation rescue and hematopoietic recovery in mouse models of hematopoietic failure. We then characterized the expression of these key secretome components in our mechanoprimed MSCs. The mechanoprimed MSCs expressed equal or higher concentrations of these proteins as a diameter-defined subpopulation of MSCs we previously identified to be therapeutically effective. Using the regression parameters from PLSR and the new expression data from our mechanoprimed MSCs, we then predicted how our mechanoprimed MSCs would elicit radiation recovery of the bone marrow compartment in vivo. From these computational predictions, we found that our mechanoprimed MSCs could potentially improve survival proportion in this in vivo model of hematopoietic failure. Thus, we tested mechanoprimed MSCs by expanding them in co-culture with HSPCs to determine if the MSCs could regulate hematopoiesis in vitro. We found that mechanoprimed MSCs could maximize the proliferation or expansion of HSPCs when co-cultured on top of our most compliant PDMS substrata (~I kPa). When grown on stiffer PDMS substrata (100 kPa), those MSCs could prime differentiation of the HSPCs down myeloid lineages, which include red blood cells. Together, these results demonstrate that these mechanoprimed MSCs can be used to modulate the ex vivo expansion and differentiation of HSPCs. Lastly, we tested these mechanoprimed MSCs in our sub-lethally irradiated mouse models of hematopoietic failure. Our mechanoprimed MSCs significantly increased the survival of the mice. Interestingly, this increased survival and improved hematopoietic recovery outperformed the survival predicted from our regression model. We also observed recovery of red blood cells, white blood cells, and platelets in mice treated with mechanoprimed MSCs, suggesting complete recovery of all hematopoietic lineages. In summary, we have explored how biophysical and mechanical cues can modulate VEC and MSC phenotype in vitro. In the case of VECs, the results presented in this thesis further the development of more accurate in vitro models of angiogenesis. Accurate in vitro models of angiogenesis are necessary to elucidate the mechanisms by which VECs regulate hematopoietic recovery in vivo. We also characterized the components of the MSC secretome correlated with improving hematopoietic recovery and demonstrated that we could engineer the expression of these same MSC secretome components using substratum viscoelastic properties. Lastly, we validated that these mechanically modulated MSCs led to improved survival outcome in vivo. The work presented in this thesis furthers our understanding of how biophysical and mechanical cues regulate hematopoietic niche components that participate in indirect repair of the bone marrow. We also demonstrated how these same cues can be applied in vitro to improve cell-based therapies for hematopoietic recovery in vivo.
by Frances D. Liu.
Ph. D.
11
Elmerhebi, E. "Improved recovery and detection of Salmonella enterica from complex matrices". Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3022749/.
Pełny tekst źródła
12
Daisley, Gavin Rhys. "Membrane Aromatic Recovery System (MARS) : improved membranes and a further application". Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508324.
Pełny tekst źródła
13
FARIAS, MANOEL LEOPOLDINO ROCHA DE. "IMPROVED HEAVY OIL RECOVERY BY INJECTION OF DILUTED OIL-IN-WATER EMULSIONS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23855@1.
Pełny tekst źródłaStreszczenie:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA injeção de água é o método de recuperação secundário mais utilizado no mundo. Mesmo em situações em que esse método não é o mais adequado, a facilidade de implantação e os menores custos comparativos impõem esse método como a opção selecionada. Em campos de óleo pesado, a razão de mobilidade desfavorável e as heterogeneidades de reservatório precipitam a formação de digitações viscosas e altos valores de saturação residual de óleo, levando a baixos fatores finais de recuperação. Os poços produtores desses campos produzem com altas frações de água muito rapidamente. O tratamento da água produzida é o principal custo operacional desses campos. O uso de emulsões diluídas de óleo em água foi avaliado como método de controle de mobilidade. Foi desenvolvido um extenso programa experimental em sandpacks de areia de sílica e plugs de arenito (Berea e Bentheimer) de forma a comparar as recuperações finais de óleo, perfis de pressão de injeção e razões água-óleo acumuladas nos casos de injeção de água, injeção de surfactantes e macroemulsões. Todos os meios porosos ensaiados foram saturados com petróleo cru originário da Bacia de Campos (20 graus API). Um estudo paramétrico foi feito de forma a identificar a influência da vazão de injeção, distribuição de tamanhos de gotas de óleo emulsionadas, concentração de óleo e permeabilidade no desempenho das emulsões injetadas. O programa foi complementado com um ensaio 3D (arenito Castlegate na configuração um quarto de five-spot) onde o fluido injetado foi dopado com Iodeto de Potássio para permitir melhor visualização da modificação de saturações de óleo e água com um tomógrafo de raios X. Os resultados obtidos indicaram ganhos na produção de óleo e redução da razão água-óleo acumulada. A possibilidade de preparar as emulsões óleo-água a serem injetadas a partir da água produzida pelo próprio campo traz um grande ganho ambiental ao se reduzir o descarte superficial de água oleosa. O efluente se transforma em um recurso.
Water injection is the most used secondary recovery method in the world. This option is generally chosen even in situations where it is not the most efficient alternative to recover the oil due to its comparative simple implementation and lower operational costs. In heavy oilfields, the unfavorable mobility ratio between injection and displaced fluids in addition to reservoir heterogeneities cause water fingering phenomenon, high residual oil saturation and consequently poor final oil recoveries. Producer wells start to produce high water cuts very soon. Produced water treatment for surface disposal is the main operational cost in these oilfields. The use of diluted oil-in-water macroemulsions was evaluated as a mobility control method for these cases. An extensive experimental program was performed using silica sandpacks and sandstone plugs (Berea and Bentheimer) in order to evaluate final oil recovery factors, cumulative water-oil ratio and pressure behavior, comparing water injection, surfactant solution injection and oil-in-water injection. All porous media were saturated with crude oil from Campos Basin (20 degrees API). A parametric study was performed to identify the effect of injection rate, oil droplets size distributions, emulsion oil concentration and permeability level in emulsion injection performance. The experimental program was completed by an X-Ray computerized tomography monitored experiment in a Castlegate sandstone block (1/4 five-spot configuration). This block was submitted to an alternate water/emulsion/water injection. All injection fluids were doped with Potassium Iodide in order to better visualize oil and water saturations changes during this experiment. The results obtained have indicated final oil recovery improvement and cumulative water/oil reduction. The possibility, after some treatment, to prepare diluted oil-in-water emulsions using produced water from the oilfield brings the additional environmental benefit to emulsion injection. It would be a way to convert an effluent in a resource with clear environmental advantages.
14
Elizondo, Martinez Jorge. "Microrid operation strategy for improved recovery and inertial response after large disturbances". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105659.
Pełny tekst źródłaStreszczenie:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 177-183).
The electric grid is one of the major achievements of human kind. In the last hundred years it has grown from small clusters of generation and loads, into large networks containing millions of elements and spanning entire continents. Recently, the increasing deployment of distributed generators (DGs) has triggered a grid transformation from a rigid to a flexible and de-centralized structure. Microgrids are an essential element in this transformation because by grouping DGs and loads into controllable units, they can provide a coordinated response to maximize their impact on the grid. Microgrids are inherently different from the larger grid. This thesis shows how by challenging the paradigm of constant frequency and voltage operation, a new strategy can be implemented to achieve an improved response after large disturbances without compromising safety. Large disturbances are commonly encountered in the grid and disrupt the power balance that is required for a reliable operation. If the imbalance is large enough and the proper actions are not taken, then a blackout will occur, affecting millions of people and creating a severe economic impact. To demonstrate the advantages of the proposed operation strategy, two large disturbances are studied: a fault in the distribution network that creates a reactive power imbalance due to induction motor stalling, and a sudden change in generation or consumption that leads to a real power imbalance. In the first part, a framework is created to study fault events and then used to describe a fault recovery strategy that expands the stability region of the system. In the second part, the proposed operation strategy is presented as a new control technique that allows energy to be extracted from the induction motors in the system to achieve an inertial response and provide frequency regulation. All the results are validated using a microgrid experimental set-up that was built as part of this thesis.
by Jorge Elizondo Martinez.
Ph. D.
15
Shang, Kun. "GRACE Time-Variable Gravity Field Recovery Using an Improved Energy Balance Formalism". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437393586.
Pełny tekst źródła
16
Brown, Ashlie M. "Improved thermal energy utilization through coupled and cascaded cooling cycles". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31645.
Pełny tekst źródłaStreszczenie:
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Dr. Srinivas Garimella; Committee Member: Dr. Samuel Graham; Committee Member: Dr. Sheldon Jeter. Part of the SMARTech Electronic Thesis and Dissertation Collection.
17
Loahardjo, Nina. "Improved oil recovery by sequential waterflooding and by injection of low salinity brine". Laramie, Wyo. : University of Wyoming, 2009. http://proquest.umi.com/pqdweb?did=1960194421&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Pełny tekst źródła
18
Chouinard, Allison M. "Evaluation of heat recovery options for improved energy efficiency of a manufacturing facility". Thesis, Marquette University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1569971.
Pełny tekst źródłaStreszczenie:
Nationwide process heating in the manufacturing sector accounts for 7,815 trillion BTU of energy use annually; this is roughly one-third of the sector's total energy consumption [Energetics Incorporated, 2014]. The U.S. Department of Energy estimates that seventy percent of process heating is fueled by the onsite burning of fossil fuels [Energetics Incorporated, 2014]. These fuel-fired process heating applications are prime opportunities for heat recovery projects capable of saving energy and, consequently, reducing operating costs. This thesis evaluates different methods for heat recovery in the Milwaukee manufacturing facility of STRATTEC Security Corporation. As a basis for this work, the overall energy usage of the facility is evaluated and the largest process heating and cooling loads are identified. Systems that will be evaluated include the zinc melt furnace, the low pressure steam system and the chilled water system. The energy recovered can be used to improve the efficiency of the source piece of equipment, to meet other process heating needs in the facility, or to generate electricity. These systems also can benefit from receiving energy recovered from a power generating process. Models of the energy and exergy balances in these systems are developed to predict the potential reduction in operating costs when heat recovery is implemented in the STRATTEC facility. In addition, the models and energy use information are used to identify inefficiencies in the systems that should be addressed before heat recovery is applied. Finally, a thermo-economic analysis is used to compare the various heat recovery options and select the most cost effective plan for implementing heat recovery. This analysis found that, for the existing equipment, heat recovery could not be implemented economically. However, opportunities for cost savings exist in the selection of new equipment to replace aging systems. Specifically, it was found that heat recovery could be implemented economically by replacing the existing chiller with an absorption chiller system that used waste heat from a power generation system.
19
Mas, Hernandez Elizabeth. "Modelling foam displacement during improved oil recovery with the pressure-driven growth model". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/modelling-foam-displacement-during-improved-oil-recovery-with-the-pressuredriven-growth-model(03d99c27-dd40-4f9d-9ca2-cb581f8e6f6d).html.
Pełny tekst źródłaStreszczenie:
During oil production several processes are used for extracting oil from underground reservoirs at different stages of the production process. After exploiting so called primary recovery, that depends on the “natural” depletion of the reservoir, other techniques are applied in subsequent stages. In tertiary recovery, foam can be injected and used as the displacing fluid. Foams have the capacity to provide a better percentage of recovery compared to other fluids because foams lower gas mobility, permitting a more uniform and efficient sweep of oil in the formation. However foams are complex fluids and the study of their flow within porous systems, like oil reservoirs, is challenging. Therefore the aim of this work is to study the propagation of a foam front within reservoirs in the context of improved oil recovery. The perspective that is adopted here is to use a simple model for foam rheology known as pressure-driven growth, to describe the foam displacement process using numerical simulations and (in some cases) solving the system analytically. The pressure-driven growth model is a limiting case of the viscous froth model, where terms for surface tension and curvature are removed. Taking this particular limiting case has consequences for the numerical solution of the system as the governing equations become far less stable both physically and numerically. An injection strategy called surfactant alternating gas is described by pressure-driven growth, where all resistance to motion in the advance of the foam is assumed to be focused on a region of wet small bubbles (the foam front) forming the interface of the water and gas phases. This front can be considered to be a one-dimensional curve. We then follow the propagation of the foam front over time, obtaining the front location and its shape. For the case of a homogeneous reservoir with constant driving pressure, the foam front is expected to have a convex shape. However, the numerical solution of pressure-driven growth can admit the formation of concavities in the front shape. These prove to be difficult to handle numerically since they focus down into sharp concave corners. As a consequence, robust numerical schemes are needed, and such schemes can be derived informed by the analysis of asymptotic solutions for the process. In order to deal with concavities, a modification is applied to the velocity of concave corners, which is used to recover the expected convex shape for the entire foam front. Other cases of interest arise in the scope of this study, where the development of concavities are expected due to the nature of the processes themselves, rather than being a mere numerical artifact. These are the case when there is surfactant slumping (i.e. downward migration of surfactant), the case when driving pressure is increased part-way through the process, and the case when the reservoir itself is heterogeneous. The pressure-driven growth model can be used in all these cases with the appropriate modifications to front velocities that each case requires within concavities, and spurious behaviour that would otherwise affect numerical results is thereby prevented.
20
Cheng, Liang. "Modeling and simulation studies of foam processes in improved oil recovery and acid-diversions". Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2002. http://wwwlib.umi.com/cr/utexas/fullcit?p3077619.
Pełny tekst źródła
21
Francis, Breeson. "Enhancing TCP Congestion Control for Improved Performance in Wireless Networks". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23254.
Pełny tekst źródłaStreszczenie:
Transmission Control Protocol (TCP) designed to deliver seamless and reliable end-to-end data transfer across unreliable networks works impeccably well in wired environment. In fact, TCP carries the around 90% of Internet traffic, so performance of Internet is largely based on the performance of TCP. However, end-to-end throughput in TCP degrades notably when operated in wireless networks. In wireless networks, due to high bit error rate and changing level of congestion, retransmission timeouts for packets lost in transmission is unavoidable. TCP misinterprets these random packet losses, due to the unpredictable nature of wireless environment, and the subsequent packet reordering as congestion and invokes congestion control by triggering fast retransmission and fast recovery, leading to underutilization of the network resources and affecting TCP performance critically. This thesis reviews existing approaches, details two proposed systems for better handling in networks with random loss and delay. Evaluation of the proposed systems is conducted using OPNET simulator by comparing against standard TCP variants and with varying number of hops.
22
Lienhard, Jasper Z. (Jasper Zebulon). "What is measured is managed : statistical analysis of compositional data towards improved materials recovery". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98661.
Pełny tekst źródłaStreszczenie:
Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 35-36).
As materials consumption increases globally, minimizing the end-of-life impact of solid waste has become a critical challenge. Cost-effective methods of quantifying and tracking municipal solid waste contents and disposal processes are necessary to drive and track increases in material recovery and recycling. This work presents an algorithm for estimating the average quantity and composition of municipal waste produced by individual locations. Mass fraction confidence intervals for different types of waste were calculated from data collected by sorting and weighing waste samples from municipal sites. This algorithm recognizes the compositional nature of mass fraction waste data. The algorithm developed in this work also evaluated the value of additional waste samples in refining mass fraction confidence intervals. Additionally, a greenhouse gas emissions model compared carbon dioxide emissions for different disposal methods of waste, in particular landfilling and recycling, based on the waste stream. This allowed for identification of recycling opportunities based on carbon dioxide emission savings from offsetting the need for primary materials extraction. Casework was conduced with this methodology using site-specific waste audit data from industry. The waste streams and carbon dioxide emissions of three categories of municipal waste producers, retail, commercial, and industrial, were compared. Paper and plastic products, whose mass fraction averages ranged from 40% to 52% and 26% to 29%, respectively, dominated the waste streams of these three industries. Average carbon dioxide emissions in each of these three industries ranged from 2.18 kg of CO₂ to 2.5 kg of CO₂ per kilogram of waste thrown away. On average, Americans throw away about 2 kilograms per person per day of solid waste.
by Jasper Z. Lienhard.
S.B.
23
Ahmed, Elfeel Mohamed. "Improved upscaling and reservoir simulation of enhanced oil recovery processes in naturally fractured reservoirs". Thesis, Heriot-Watt University, 2014. http://hdl.handle.net/10399/2755.
Pełny tekst źródłaStreszczenie:
Naturally fractured reservoirs (NFR) contain a significant amount of remaining petroleum reserves and are now considered for Enhanced Oil Recovery (EOR) schemes that involve three-phase flow such as water-alternating-gas (WAG) injection. Accurate numerical simulation of flow in NFR is essential for sound reservoir management decisions to maximise oil recovery and minimise the cost of field development. In this thesis, two important issues related to flow simulation in NFR are investigated. First, a step-wise upscaling approach is developed to evaluate the accuracy of dual porosity models in estimating matrix-fracture transfer duringWAG injection. It was found that the classical dual porosity models generally overestimate recovery from matrix blocks. Hence, a double block model was developed and extended to a multi-rate dual porosity (MRDP). The multi-rate double block model showed significant improvements in matching detailed fine grid simulations of three-phase matrix-fracture transfer. Second, the accuracy of upscaling discrete fracture networks (DFN) is assessed and its impact on history matching was investigated on a real fractured reservoir. A new method to upscale the shape factors needed for MRDP models from DFN is presented. This method is a notable step towards more accurate but still efficient reservoir simulation in NFR.
24
Hwessa, Mahmod Mjahead. "Numerical Simulation Study: Air Injection Technique for Improved Oil Recovery (IOR) from Light Oil Reservoirs". Thesis, University of Bath, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508714.
Pełny tekst źródła
25
Shnaib, Fathi Younis. "Air injection technique for improved oil recovery from light oil reservoirs : accelerating rate calorimetry studies". Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250839.
Pełny tekst źródła
26
Bailey, Neil A. "An investigation and modelling of thermal agglomeration of poly-#beta#-hydroxybutyric acid for improved downstream recovery". Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363814.
Pełny tekst źródła
27
Bali, Amol Bhagwan. "Design and real-time process optimisation of steam assisted gravity drainage for improved heavy oil recovery". Thesis, Robert Gordon University, 2013. http://hdl.handle.net/10059/2107.
Pełny tekst źródłaStreszczenie:
“Introduction to the Canadian Oil Sands”, “Canada’s Oil Sand Industry: An Overview”, “Heavy Oil Technologies”, and so many other topics about heavy oil have become the hotcakes in the oil industry. A number of new projects are in Execute phase for the development of heavy oil assets. This clearly shows the increasing demand for heavy oil. An oil industry is working hard to meet the world oil demand by developing deep water, HPHT, heavy oil, shale sands and all other non-conventional reservoirs but the main challenge is to develop and operate them in a risk free environment. Understanding the reservoir and fluid properties and developing new technologies help the industry to reduce the risk in developing non-conventional fields. A major problem in heavy oil field is to understand the behaviour of heavy oil. The viscous oil flows sluggishly in the formations and hence it is difficult to transport through unconsolidated formations and is very difficult to produce by conventional methods. Viscous oil recovery entails neatly designed enhanced oil recovery processes like Steam Assisted Gravity Drainage and the success of such technologies are critically dependent on accurate knowledge of reservoir, well and fluid properties of oil under variety of pressure and temperature conditions. This research project has provided some solutions to the challenges in heavy oil field development and can help the oil industry to optimise heavy oil production. Detailed experimental understanding of PVT properties has allowed this project to contribute to the knowledge. Reservoir, well and fluid properties were studied thoroughly and demonstrated the criticality of each parameter on the efficiency of Steam Assisted Gravity Drainage. An user friendly SAGD simulator is a big output of this research which allows the user to optimise the heavy oil recovery and enables to do risk assessments quickly during design phase of SAGD. A SAGD simulator is developed.
28
Osindero, Adeyemi O. "Exothermicity and oxidative kinetics of light crude oils for air injection improved oil recovery (IOR) processes". Thesis, University of Bath, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340994.
Pełny tekst źródła
29
Mogla, Sankalp. "Telecommunication Network Survivability for Improved Reliability in Smart power Grids". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5380.
Pełny tekst źródłaStreszczenie:
Power transmission grid infrastructures deliver electricity across large distance and are vital to the functioning of modern society. Increasingly these setups embody highly-coupled cyber-physical systems where advanced telecommunications networks are used to send status and control information to operate power transmission grid components, i.e., "smart grids". However, due to the high inter-dependency between the communication and power grid network layers, failure events can lead to further loss of control of key grid components, i.e., even if they are undamaged. In turn, such dependencies can exacerbate cascading failures and lead to larger electricity blackouts, particularly under disaster conditions. As a result, a range of studies have looked at modelling failures in interdependent smart grids. However most of these designs have not considered the use of proactive network-level survivability schemes. Indeed, these strategies can help maintain vital control connectivity during failures and potentially lead to reduced outages. Hence this thesis addresses this critical area and applies connection protection methodologies to reduce communication/control disruption in transmission grids. The performance of these schemes is then analyzed using detailed simulation for a sample IEEE transmission grid. Overall findings show a good reduction in the number of overloaded transmission lines when applying network-level recovery schemes.
30
Hall, Jennifer M. "Manipulation of N mineralisation/immobilisation dynamics to investigate poor fertiliser recovery in improved grass pasture on ombrotrophic peat". Thesis, University of Aberdeen, 1995. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU068793.
Pełny tekst źródłaStreszczenie:
The spring application of fertiliser N often fails to stimulate grass growth in improved grass pastures on peaty soils. Fertiliser utilisation efficiencies under these conditions have been found to be low, suggesting that available N is not taken up by the plant. Previous work has suggested that in this type of system, the soil microbial biomass may function as a strong sink for fertiliser N and therefore limit plant growth in the Spring. A series of laboratory based experiments utilising reconstituted and intact cores, and homogenised peat, was set up to identify the factors controlling the competition between N uptake by plants and N immobilisation by soil microorganisms following the addition of fertiliser N to peat. Microbial biomass N concentrations were determined in order to quantify the amount of N present in the microbial pool. The use of 15N labelled fertilisers and selective biocides provides a powerful tool with which to characterise the microbial population responsible for the immobilisation of N under these conditions. Improvement of a grass pasture at Sletill Hill has resulted in the formation of a distinct layer comprised of partially decomposed roots, underneath the surface vegetation and it was within this layer, that microbial immobilisation of fertiliser N was found to occur. Approximately 30% of applied N (equivalent to ca 50 kgN ha-1) was found within the microbial biomass in this layer, 30 days after the addition of fertiliser N. Intact cores were removed from Sletill Hill and maintained under controlled abiotic conditions. Water table level and temperature were found to be important in controlling the extent of microbial immobilisation of applied N. Lowering the water table level increased the quantity of N present in plant and microbial N pools, particularly at lower temperatures (8°C). At higher temperatures (20°C), plant uptake of N tended to be less due to a restriction on plant growth caused by 'droughty' soil conditions.
31
Leporini, Mariella. "Design and Optimisation of a Steam Assisted Gravity Drainage (SAGD) Facility for Improved Recovery from Canadian Oil Sands". Doctoral thesis, Università Politecnica delle Marche, 2014. http://hdl.handle.net/11566/242874.
Pełny tekst źródłaStreszczenie:
La sempre più limitata disponibilità di olio prodotto da fonti convenzionali sta
valorizzando la produzione di combustibili da fonti non convenzionali quali le
sabbie bituminose. Le sabbie bituminose sono una combinazione di sabbia, argilla,
acqua e bitume, ovvero petrolio. Il più grande accumulo conosciuto si trova nella
regione dell’Alberta (Canada). Numerose tecniche di estrazione di olio da sabbie
bituminose sono state sviluppate negli ultimi decenni. La tecnica “Steam Assisted
Gravity Drainage” è la più promettente tra quelle utilizzate per la produzione di oli
viscosi. La tecnologia SAGD si basa sulla riduzione della viscosità delle sabbie
bituminose operata attraverso la diluizione con vapor d’acqua in combinazione con
il drenaggio per gravità che utilizza una coppia di lunghi pozzi orizzontali,
configurata in modo che dal pozzo superiore si possa iniettare il vapore e da quello
inferiore produrre l’olio diluito. L’obiettivo generale di questo lavoro di Tesi è di
presentare un dettagliato studio di ottimizzazione di un ipotetico impianto, di scala
industriale, di recupero di bitume da oil sands canadesi tramite SAGD, chiamato
ipoteticamente LINK. Tutti i dati relativi all’impianto LINK sono stati ricavati da
un’attenta analisi della letteratura relativa ad impianti SAGD esistenti oppure
coerentemente ipotizzati. L’impianto LINK permette di estrarre una miscela
multifase di bitume, acqua, vapore e gas e di recuperarne il bitume in un CPF
(Central Processing Facility). Scopo principale di questo lavoro di Tesi è una
dettagliata ottimizzazione tecnica del sistema di pipeline dell’impianto ipotizzato
basata sulla disciplina della Flow Assurance. Lo studio di “Flow Assurance” è stato
condotto tramite l’utilizzo del software OLGA (SPT) for quattro sistemi principali: il
sistema emulsione, quello vapore, quello gas naturale ed il sistema acqua. Una
linea aggiuntiva è stata considerata per il trasporto del gas naturale da una
stazione erogatrice (considerata privata e chiamata NGS) all’impianto LINK. Sulla
base dei dati raccolti e delle assunzioni fatte e dopo una corretta caratterizzazione
termodinamica dei fluidi studiati tramite l’utilizzo del software PVTsim (Calsep), lo
studio di Flow Assurance è stato condotto per mezzo di simulazioni in condizioni
stazionarie e transitorie. Dall’analisi svolta, sono stati ottenuti i seguenti risultati:
configurazione dei sistemi, diametri delle pipeline, comportamento termico,
idraulico e chimico dei sistemi, integrità meccanica, performance del sistema e
possibili problematiche relative ad alcune operazioni transitorie. Secondo obiettivo
della presente Tesi è la valutazione economica del sistema studiato secondo il
metodo dei Flussi di Cassa Attualizzati, condotto su un foglio Excel
opportunamente sviluppato. I costi (di investimento e operativi) di impianti basati
sulla tecnologia SAGD già esistenti sono stati trovati in letteratura. Gli indici di
valutazione della redditività degli investimenti calcolati mostrano che l’investimento
relativo all’impianto LINK è economicamente conveniente. Terzo ed ultimo
obiettivo della presente Tesi è un’analisi di tipo ambientale dell’impianto studiato.
Al fine di valutare le emissioni di gas serra (GHG) dell’impianto LINK, un ulteriore
file Excel è stato sviluppato basandosi su dati di letteratura. Dalla comparazione
dei risultati ottenuti con i valori di emissioni di olio prodotto da fonti convenzionali e
tramite tecnologia in situ è evidente che la tecnologia SAGD è molto promettente
anche dal punto di vista ambientaleAs conventional oil production becomes limited, transportation fuels are being produced from other unconventional fossil resources such as oil sands. Oil sands are a combination of clay, sand, water and bitumen. Vast quantities of oil sands resources have been found worldwide. The largest known reservoir of oil sands in the world is located in the province of Alberta (Canada). Several techniques for the extraction of the oil from oil sands have been developed in recent decades. Steam- Assisted Gravity Drainage (SAGD) is the most promising approach for recovering heavy and viscous oil resources. In SAGD, two closely-spaced horizontal wells, one above the other, form a steam-injector and producer pair. The reservoir oil is heated by the injected steam and drains to the producer under the effect of gravity. The general aim of this dissertation is a detailed study of optimisation of an hypothetical industrial scale facility (named LINK), located in Alberta. All data relating to LINK plant have been obtained from a review of the existing literature references or have been assumed. The facility employs Steam Assisted Gravity Drainage (SAGD) technology to recover bitumen and deliver a multiphase mixture of bitumen, water, steam and gas to the CPF (Central Processing Facility). The main purpose of this work is to present a detailed technical optimisation of the pipeline system based on the Flow Assurance discipline. Flow Assurance analysis has been carried out through the use of the multiphase flow simulation tool OLGA (SPT) for four systems: emulsion, steam, natural gas and source water pipeline systems. An additional underground pipeline has been considered to connect the CPF to a private station (called NGS Metering Station) in order to supply natural gas tor the facility. On the basis of the collected data and assumptions, the Flow Assurance study has been carried out by performing simulations in steady state and transient conditions. They have been performed after a detailed thermodynamic characterization of the different fluids, carried out by the software PVTsim (Calsep). Results have been obtained in terms of systems configurations and selected diameters, thermal, chemical and hydraulic behaviors, operability characteristics, design and operating parameters, mechanical integrity, system deliverability, systems performance, possible uncertainties and criticalities that can occur. The second aim of this Thesis is an economic optimisation and evaluation of the hypothetical system studied. Discounted Cash Flow Analysis (DCFA) of LINK Facility has been performed in a MS Excel spreadsheet. Cost (capital and operating) of existing projects have been found in literature. The results show that the hypothetical plant LINK is a good investment. Third and last purpose of the present work is an environmental analysis of the LINK plant: in order to evaluate GHG emissions from LINK plant, an Excel spreadsheet has been developed for the LCA analysis. The calculated emissions from oil sand production by SAGD technology have been compared with values relating to conventional crude oil pathways and to recovery and extraction of bitumen through surface mining from literature. The comparison demonstrated that SAGD is a promising technology also from an environmental point of view.
32
Kobayashi, Kazuya. "Molecular simulations of mineral-solution interfaces for improved description of crude oil-brine-mineral interactions". 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225615.
Pełny tekst źródła
33
Aspinwall, Jacob Raleigh. "Design of an Improved Moisture Separator in a Turbocharger System for Fuel Cells". Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4976.
Pełny tekst źródłaStreszczenie:
Moisture recovery is important in the operation of many fuel cell systems, especially proton exchange membrane (PEM) fuel cells. The exhaust of a PEM fuel cell is a moderate temperature, pressurized humid air stream. A system that recovers liquid water condensate from the pressurized humid exhaust stream of a PEM fuel cell would markedly increase the effectiveness of such a system. The recovered water could be used to hydrate the fuel cell membrane, and it could supply a hydrocarbon reformer used for generating hydrogen.
This project investigated and documented moisture recovery from the simulated humid exhaust stream of a 25 kW fuel cell with an improved axial flow separator. An axial flow centrifugal separator design was chosen as the best candidate due to its high efficiency and low pressure drop and a prototype was designed and constructed. The separator was then integrated into an experimental test system. First, the stream was simulated by heating compressed air and then humidifying it with superheated steam. Then, after expanding through the turbine section of an automotive turbocharger, the humid stream was passed through the moisture separator where liquid water condensate was removed from the flow. Results are presented for varying turbine inlet conditions at three separate separation lengths. It is shown that the separation efficiency for the improved design was 40% higher and the pressure drop was only 1/3 that of the conventional separator.
34
Murgham, Haithem Abualasaad. "Enhancing and Expanding Conventional Simulation Models of Refrigeration Systems for Improved Correlations". University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1544524232130074.
Pełny tekst źródła
35
Marappan, Saravanan. "A study of the current best practice in the Scottish electroplating industry and improved metal recovery technique for waste water streams". Thesis, Robert Gordon University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425379.
Pełny tekst źródła
36
Nyarko, Esmond Boafo. "Improved Recovery And Rapid Identification Of Strains, Mixed Strains, Mixed Species, And Various Physiological States Of Foodborne Pathogens Using Infrared Spectroscopy". ScholarWorks @ UVM, 2014. http://scholarworks.uvm.edu/graddis/276.
Pełny tekst źródłaStreszczenie:
Challenges encountered in pathogen identification and detection include the genetic heterogeneity of strains within species of some foodborne pathogens, isolation of injured cells, mixed strains or mixed species contamination of foods, and differentiation between viable and dead cells. The first objective of this research was to evaluate an isolation medium that was based on time-delayed release (5 to 6 h) of selective agents in tablet format to a modified Listeria recovery enrichment broth (mLRB) medium for enhanced and rapid recovery of injured Listeria. The second objective involved the use of Fourier transform infrared (FT-IR) spectroscopy and chemometric analysis for the differentiation of: Listeria monocytogenes epidemic clones (ECs); viable versus heat-killed populations; different mixed strains and mixed species of Listeria; and different injury treatments and repair in Listeria populations. Nitrite- or acid-injured Listeria at approximately 10 CFU/ml were recovered in mLRB medium, and cell populations enumerated at various times (12 to 48 h) of incubation at 37oC. Analysis of variance revealed that acid-injured Listeria populations in mLRBS6 (mLRB plus the selective agents at 6 h) were significantly higher (P < 0.05) than those in mLRBS0 (mLRB plus the selective agents at 0 h) at 24 h; however, the differences in populations on these two media were not significant for nitrite-injured Listeria. Cell populations of four strains of Listeria recovered in mLRBTD (mLRB plus the time-delayed release tablets of the selective agents) were significantly higher than when those strains were enriched in the U.S. Food and Drug Administration (FDA), International Organization for Standardization (ISO), and U.S. Department of Agriculture (USDA) broths at 24 h. Comparison between artificially contaminated milk and meat samples with a four-strain cocktail of Listeria resulted in cell populations that were significantly higher (P < 0.05) on mLRBTD for contaminated meat than on mLRBTD for contaminated milk at 24 h. FT-IR spectroscopy in the mid-infrared region (4000 to 600 cm-1) and chemometrics was successfully applied to discriminate L. monocytogenes strains belonging to the same EC (ECII or ECIV) (100% accurate spectral classification), intact and heat-killed populations of each EC strain (100% accurate spectral classification), and spectral wavenumbers 1650 to 1390 cm-1 were used to differentiate heat-killed from intact populations. FT-IR spectroscopy and chemometrics in the wavelength region 1800 to 900 cm-1 could successfully discriminate different mixed strains of L. monocytogenes (98.15% accurate spectral classification) and different mixed species of L. monocytogenes and L. innocua (92.06% accurate spectral classification) from individual strains; Wavelength range 1800 to 900 cm-1 was successfully used to discriminate between intact, acid-injured, and heat-injured Listeria, with repaired cells from acid and heat treatments clustering closer to intact cells (93.33% of spectra accurately classified). Delayed-addition of selective agents to broth medium improves recovery of injured Listeria by allowing repair time, could minimize contamination through manual addition of selective agents, and saves analyst time; FT-IR spectroscopy is a highly discriminatory and reproducible technique that can be used for the differentiation of strains and various physiological states of Listeria.
37
Green, Jeffrey Andrew. "IMPROVING THE ENERGY EFFICIENCY OF A MID-SIZE POWER PLANT BY REDUCTION IN AUXILIARY POWER AND IMPROVED HEAT TRANSFER". OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1502.
Pełny tekst źródłaStreszczenie:
This study incorporates the potential use of Variable Frequency Drives on various motors as well as areas of improved heat transfer in an older, mid-sized coal fired power plant. In power plants, fluid flow rates are often controlled using dampers or valves while the motors that power the pumps stay at full speed resulting in a significant amount of wasted electrical power; energy is also lost due to poor heat recovery prior to gases leaving the system. By examining pump usage as well as additional heat available for recovery, potential energy savings will be determined. Preliminary results of five motors suggested for variable frequency drive application show annual savings that total 31.1 GWh, resulting in a 1.66% increase in overall plant efficiency. Total project costs are near $2 million resulting in a simple payback period of less than two years assuming 0.04 $/kWh. For every degree reduction of the flue gas temperature by means of heat recovery that is reused elsewhere in the cycle, 2 Billion BTU of coal would be saved annually. One realistic scenario suggested heat recovery resulting in a 120°F degree reduction of flue gas temperature amounting to a 2.54% increase in cycle efficiency.
38
Ferguson, Chad D. "Conservation genetics of a near threatened freshwater mussel species (Lampsilis cardium) and improved prospects for recovery: how nuclear and mitochondrial DNA analyses inform natural history and conservation". Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1244144062.
Pełny tekst źródła
39
Romuli, Sebastian [Verfasser]. "Process optimisation of oil and protein recovery from Jatropha curcas L. seeds in terms of hulling, shelling and mechanical extraction for improved efficiency and product quality / Sebastian Romuli". Aachen : Shaker, 2017. http://d-nb.info/1149278633/34.
Pełny tekst źródła
40
Duboué, Jennifer. "Émulsification spontanée de l’eau dans les pétroles bruts". Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS599.
Pełny tekst źródłaStreszczenie:
Depuis 5 ans, l’autoémulsification de l’eau dans les bruts a été reportée sur plusieurs systèmes, et associée une récupération améliorée du pétrole. Nous avons tenté de comprendre quelle était son origine physico-chimique. Nous avons constaté que lorsqu’on mettait en contact du pétrole brut avec de l’eau, il se formait alors des micro-gouttes d’eau dans l’huile pour toutes les huiles lourdes étudiées. Nous avons montré que le phénomène d’émulsification spontanée observé lors du contact de pétrole brut avec de l’eau de faible salinité est un mécanisme doublement osmotique, régit par la double pénétration d’eau et des espèces « osmogènes » (ie espèces générant de la pression osmotique) dans les gouttelettes d’eau. Puis nous avons montré que le phénomène limitant est celui de la diffusion de l’eau dans l’huile et nous proposons une expression pour sa cinétique. En outre, nous avons observé deux phénomènes concomitants lors de l’étude de la récupération en huile à l’échelle microfluidique : récupération additionnelle d’huile et présence de micro-gouttes d’eau. Nous proposons d’expliquer cela par le gonflement des poches d’eau par le phénomène d’émulsification spontanéeSince 5 years, the autoemulsification of water in crude oils has been reported on several systems, and associated with improved oil recovery. We tried to understand what was its physicochemical origin. We found that when we put crude oil in contact with water, micro-droplets of water were formed in the oil for all the crude oils studied. We have shown that the phenomenon of spontaneous emulsification observed during the contact of crude oil with low salinity water is a double osmotic mechanism, governed by the double penetration of water and "osmogeneous" species (ie species generating osmotic pressure) in the water droplets. Then, we showed that the limiting phenomenon is the diffusion of water in the oil and we propose an expression for its kinetics. In addition, we observed two concomitant phenomena during the study of microfluidic scale oil recovery: additional oil recovery and the presence of micro-droplets of water. We propose to explain this by the swelling of the water pockets due to the phenomenon of spontaneous emulsification
41
Yazdanpanah, Mehrdad. "Pyruvate improves myocardial functional recovery after ischemia and reperfusion". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0028/MQ34078.pdf.
Pełny tekst źródła
42
Kozinn, Rachel. "Adductor Canal Nerve Block to Improve Total Knee Arthroplasty Recovery". Thesis, The University of Arizona, 2018. http://hdl.handle.net/10150/626858.
Pełny tekst źródła
43
Veselkov, Kirill. "Computational approaches to improve information recovery from biological NMR spectra". Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502905.
Pełny tekst źródła
44
Alia, Claudia. "Studying and modulating post-stroke neuroplasticity to improve motor recovery". Doctoral thesis, Scuola Normale Superiore, 2016. http://hdl.handle.net/11384/86002.
Pełny tekst źródłaStreszczenie:
Limited restoration of motor function occurs spontaneously during a plastic time window after stroke. A deeper understanding of post-stroke plasticity is critical to devise more effective pharmacological and rehabilitative treatments.
Here, I have characterized the spontaneous evolution after a photothrombotic lesion in mice, both in terms of motor deficit and plasticity in the perilesional cortex. In generalized motor tasks such as the Gridwalk and Schallert Cylinder test, motor deficits were stable for at least 30 days after photothrombotic stroke in the Caudal Forelimb Area (CFA). The skilled reaching test, performed once a week, showed a trend for spontaneous improvement over time in the number of correct graspings. However, kinematic analysis, evaluated by means of an innovative semi-automated tool, revealed a persistent alterations in grasping movements, pointing to the development of compensatory strategies.
The perilesional cortex has been proposed as the area mediating functional recovery. I found a reorganization of the motor maps in sensorimotor cortex around to the lesion. Particularly, I observed a significant shrinkage of the forelimb area, in favour of hindlimb representation using Intracortical Microstimulation (ICMS). Moreover, neuroanatomical markers, previously characterized in the literature as “neuroplasticity brakes” (i.e. Perineuronal nets, Parvalbumin- and Somatostatin-positive cells) spontaneously decrease after stroke, suggesting an enhancement of the potential for plastic rearrangements. Altogether these results, suggest a spontaneous attempt to reopen a critical period characterized by sprouting and plasticity phenomena, that needs to be amplified and properly guided for maximizing recovery.
The GABAergic system is one of the key modulators of plasticity in the brain, and its role has been amply studied in relation to opening and closure of the “critical period” in sensory cortices during development. To test whether reductions in GABAergic signalling were causally involved in motor improvements, we treated animals during an early post-stroke period with a benzodiazepine inverse agonist, which impairs GABAA receptor function. We found that hampering GABAA signalling led to significant restoration of function in general motor tests such as the gridwalk and the pellet reaching tasks, with no significant impact on the kinematics of reaching movements. Improvements were persistent as they remained detectable about three weeks after treatment.
Using electrophysiological recordings I found an electrical imbalance between the two hemispheres. In particular, contralesional motor cortex was found to exert an enhanced transcallosal inhibition over the spared, perilesional tissue. Silencing the healthy hemisphere using cortical infusion of Botulinum Neurotoxin E, partially improved motor recovery in the gridwalk test.
We then established a rehabilitation protocol that combined intensive and highly repeatable exercise of the mouse forelimb with a robotic platform with reversible inactivation of the healthy, contralesional motor cortex. We found that such treatment promoted recovery in both Gridwalk and Schallert Cylinder tests and in end point measures during Skilled reaching test. Remarkably, the combined therapy also restores pre-lesion movement patterns during reaching movement, as evaluated by kinematic analysis. Furthermore, such rehabilitated animals showed a more plastic perilesional cortex, with an additional significant decrease in plasticity brakes.
45
Ackerley, Suzanne Jennifer. "Promoting use-dependent plasticity to improve upper limb recovery after stroke". Thesis, University of Auckland, 2011. http://hdl.handle.net/2292/9899.
Pełny tekst źródłaStreszczenie:
Motor recovery is a major factor influencing independence in everyday living after stroke. The objective of this dissertation was to explore two ways to promote use-dependent plasticity (UDP) to improve upper limb recovery after stroke. One approach was to adapt the delivery of training by incorporating auditory pacing. The specific aim was to augment UDP within the primary motor cortex (M1) by increasing synaptic efficacy through the synchronous arrival of auditory and sensorimotor input. Two cross-over, repeated-measures, studies were conducted in healthy adults. Training protocols consisted of simple, repetitive, upper limb movements that were either metronome-paced in synchrony or syncopation, selfpaced, or paced at a fast rate. Neurophysiological measures obtained with transcranial magnetic stimulation (TMS), and behavioural measures, were collected before and after training to evaluate UDP. The second approach was to prime M1 with theta burst stimulation (TBS) prior to training. The aim was to facilitate ipsilesional M1 excitability, and lower the threshold for UDP during subsequent training. TBS primed training was evaluated in two blinded, sham-controlled, repeated-measures studies in chronic subcortical stroke patients with upper limb impairment. In separate sessions, neurophysiological, behavioural, and clinical assessments were performed before and after precision grip training primed by one of three different TBS protocols (intermittent TBS, continuous TBS and sham TBS). A preliminary technical study was conducted to ensure the validity of the measure of sensorimotor integration used for the final study. Metronome-paced training at a comfortable speed improved synaptic efficacy within M1, as shown by selective facilitation of corticomotor excitability and altered kinematics of TMS-evoked movement that reflected the trained movement. Priming with intermittent TBS increased the receptiveness of ipsilesional M1 to afferent input and enabled stroke patients to engage in better quality motor training. Overall, this dissertation presents two clinically feasible approaches, “auditory-paced training” and “TBS primed training” to enhance UDP within a given therapy dose. Further clinical research is warranted to translate these promising novel approaches into rehabilitation practice.
46
Rinaldi, Claudia. "Link-Layer Error Recovery Techniques to improve TCP Performance over Wireless Links". Thesis, KTH, Reglerteknik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-109460.
Pełny tekst źródłaStreszczenie:
Recent technology has involved TCP in wireless applications even if it was originally designed to work over wired links. It is well known that wireless links are usually characterized by phenomena like shadowing, multipath propagation and path loss that cause an increase in the bit error rate. Moreover,TCP protocol was supposed to interpret all the losses as due to congestion because of it was designed to work over wired networks. All these problems caused by the wireless application of TCP usually degrade TCP performances. In order to improve TCP behavior over wireless links several solutions have been proposed in literature as: the split connection approach, the end-to-end approach and the link-layer approach. Starting from the link-layer solution that have been studied by Barman and Matta, the main contribution of this thesis is the study of the effects of different modulation formats on the maximum achievable value of an objective function, defined as the ratio between the TCP throughput and a cost function. Appropriate power management and error correction techniques are assumed to improve the link reliability observed by TCP and increase the objective function performance accordingly.
47
van, Wyk David. "A survey to determine the recovery strategies that medical support staff of rugby teams use to improve recovery of the players". Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/2997.
Pełny tekst źródłaStreszczenie:
Includes abstract.Includes bibliographical references (leaves 66-73).
In an attempt to facilitate the recovery of th eplayers, the support staff associated with teams have used a variety of techniques with the goal of ensuring that the muscles of players have the best opportunity to repair before the next training session/match. Several different strategies are used by support staff. These include cryotherapy, contraxt baths, nutrional intervention, compression garments, massage, active recovery and non-steroidal anti-inflammatories. Ice/cold water immersion is a relatively new and popular recovery strategy derived from cryotherapy.
48
Arbat, i. Plana Ariadna. "Modulation of the stretch reflex arc to improve functional recovery after peripheral nerve injury". Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/394061.
Pełny tekst źródłaStreszczenie:
Després d’una lesió del sistema nerviós perifèric, aquest té la capacitat de regenerar però la seva recuperació funcional sol ser limitada, principalment degut a la inespecificitat de la reinnervació dels òrgans perifèrics i als canvis plàstics maladaptatius de la circuiteria espinal. En aquesta tesi hem volgut modular els canvis a la circuiteria espinal del reflex d’estirament per poder millorar la recuperació funcional després de lesions del nervi perifèric en un model animal.
En primer lloc, es va dur a terme una caracterització immunohistoquímica dels canvis que patien les motoneurones espinals després d'una lesió del nervi ciàtic; aquests canvis es van estudiar en animal postnatal i en l’adult. En els animals postnatals, també es va estudiar la composició sinàptica de l’arbre dendrític de les neurones, i es va observar una elevada pèrdua de sinapsis excitatòries que no s’arriben a recuperar després de 2 mesos. Pel que fa als canvis produïts en l’adult, vam observar que la màxima pèrdua de sinapsis glutamatèrgiques i de xarxes perineurals (PNN) es produïa dues setmanes després de la lesió, amb una progressiva recuperació a partir de la quarta setmana.
Per intentar atenuar aquesta pèrdua sinàptica i de PNN, vam estudiar l’efecte de l’estimulació elèctrica i de la capacitat de diferents factors tròfics (aplicats a la zona de lesió mitjançant una matriu de col·lagen en un tub de silicona). No es van obtenir diferències significatives en cap de les dues teràpies. També vam avaluar diferents protocols d'exercici físic, concretament l’exercici forçat, voluntari i passiu. Si es feia servir un protocol d’alta intensitat, la pèrdua sinàptica i de PNN que patien les motoneurones era menor que la pèrdua observada en les motoneurones d'animals que no havien estat sotmesos a exercici, mentre que en aquells que corrien menys no presentaven millores respecte als animals no exercitats A més, en els animals exercitats també vam observar un augment de l’astrogliosis al voltant de les motoneurones axotomitzades i una disminució de l’activació de la microglia, excepte en l’exercici voluntari i passiu a baixa intensitat, on vam observar un augment de l’activació de microglia.
Degut als efectes positius induïts per l’exercici físic sobre els canvis plàstics en el nostre model, vam valorar potencials mecanismes implicats en aquestes efectes. Tot i que se sap que l’exercici incrementa l’expressió de neurotrofines, es desconeix com l'exercici modula aquestes neurotrofines i quines són les seves accions específiques. Per valorar el paper del BDNF en els efectes de l'exercici observats en el nostre model, vam administrar sistèmicament un agonista i un antagonista del TrkB. Vam observar que el manteniment de les sinapsis mediat per l'exercici físic depenia parcialment de l’activació del TrkB, però l'activació farmacològica d'aquest receptor no mimetitzava els efectes de l'exercici.
Com que l'exercici físic provoca un augment de l'activitat neural, també vam valorar el paper de les projeccions descendents noradrenèrgiques del tronc de l'encèfal en els efectes moduladors de l'exercici sobre les motoneurones. Aquestes vies descendents modulen l'excitabilitat de les motoneurones espinals i s'activen en situació d’estrès, com l'exercici forçat. Mitjançant l’administració de DSP-4, que destrueix el locus coeruleus i per tan, provoca la pèrdua de les projeccions noradrenergiques descendents, vam veure una reducció de PNN i una marcada reactivitat de la microglia. En els animals sotmesos a exercici, la pèrdua d'aquestes projeccions impedia la preservació de sinapsis i de PNN al voltant de les motoneurones lesionades, si bé la reactivitat microglial es veia igualment disminuïda. Aquestes troballes suggereixen que la modulació dels canvis espinals induïts per l'exercici físic seria parcialment dependent de l'activació d'aquestes projeccions noradrenèrgiques, mentre que la modulació de la micròglia per l'exercici en seria independentAfter a peripheral nerve injury, axons are able to regenerate but functional recovery is usually limited, mainly due to unspecific reinnervation of target organs and also to maladaptive plastic changes in the spinal circuitry. In this thesis we wanted to modulate the stretch reflex arc to improve functional recovery after peripheral nerve lesions in animal model. Firstly, we carried out an immunohistochemical characterization of the changes surrounding spinal motoneurons after sciatic nerve injury; these changes were studied in postnatal and adult animals. In postnatal animals, we also studied VGlut1 contacts along dendrites, observing a high loss of excitatory synapses that were not recovered at 2 months. Regarding adult motoneurons, we found that the maximum loss of glutamatergic synapses and perineuronal nets (PNN) took place two weeks after injury, with a progressive recovery at 4 weeks. To try to ameliorate this loss of synapses and PNN, we studied the effect of electrical stimulation and different trophic factors (applied directly to the injury with a collagen matrix in a silicone tube). No significant differences were observed in none of them. We also evaluated different exercise protocols, specifically forced, voluntary and passive exercise. A high intensity protocol was able to partially prevent the synaptic and PNN loss that suffer axotomized motoneurons, whereas low intensity programs did not show significant differences compared to untrained ones. We also observed an increase of astrogliosis surrounding axotomized motoneurons and a decrease of microglia activation in exercised animals, except for those receiving low intensity voluntary and passive exercise, where there was a significant increase of microglia. Due to the positive effects induced by physical exercise on central plastic changes, we evaluate potential mechanisms involved in these effects. Although it is known that exercise increase neurotrophins, it is unknown how exercise modulates these neurotrophins and their specific actions. To evaluate the role of BDNF in the effects of exercise on axotomized motoneurons, we systemically administered a TrkB agonist and antagonist. We observed that the maintenance of synapses mediated by exercise was partially dependent of TrkB activation, but pharmacological activation of this receptor did not mimic exercise effects. As after physical exercise there was an increase of neural activity, we studied the role of noradrenergic descending projections from brainstem in spinal cord motoneurons after exercise. These descending pathways modulate excitability of the spinal motoneurons and are activated by stress situations, such as forced exercise. By DSP-4 administration, we provoked the desestructuration of the Locus Coeruleus and thus, loss of noradrenergic descending projections, observing a reduction of PNN and a marked reactivity of microglia. In animals submitted to exercise, the loss of these projections prevented the preservation of synapses and PNN around injured motoneurons, although microglial reactivity was also decreased. These findings suggest that modulation of spinal changes induced by physical exercise would be partially dependent on the activation of noradrenergic projections, whereas the modulation of microglia is independent of the exercise.
49
Fan, Man-hin Michael, i 范文軒. "Endotoxin from porphyromonas gingivalis improves recovery of the electrically induced Ca2+ transient following ischemia andreperfusion". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B45011205.
Pełny tekst źródła
50
Gill, Bradley Cameron. "Neurotrophin Therapy Improves Recovery from Postpartum Stress Urinary Incontinence Following Simulated Childbirth Injury in Rats". Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1336054611.
Pełny tekst źródła