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Daines, Stuart. "Cooling flows and cold gas in clusters of galaxies." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321020.
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Sebastião, Israel Borges. "Numerical simulation of MEMS-based cold gas micronozzle flows." Instituto Nacional de Pesquisas Espaciais, 2011. http://urlib.net/sid.inpe.br/mtc-m19/2011/08.11.13.08.
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A atual tendência no projeto de sistemas espaciais tem caminhado no sentido de se reduzir o custo do ciclo de vida dos programas através da redução da complexidade das missões dos satélites. Nesse contexto, umas das opções diz respetio à redução da massa total do sistema. Desse modo, conceitos de micropropulsão baseados em microtecnologias têm sido desenvolvidos a fim de se atender as exigências das futuras missões espaciais. O atual estágio da tecnologia de semicondutores à base de silício tem permitido a fabricação de sistemas de pequena escala, denominados por MEMS(MicroElectroMechanical Systems). Dentre as várias aplicações dos MEMS encontram-se os micropropulsores de baixo empuxo, onde os microbocais estão presentes. De acordo com a literatura relevante, a maioria dos estudos investigou o desempenho dos microbocais para diferentes escalas e condições de contorno. Entretanto, essas investigações não focaram na influência da curvatura da superfície na estrutura do escoamento em microbocais. É sabido que, em macrobocais, descontinuidades na curvatura alteram o desempenho dos bocais devido ao surgimento de ondas de choque no interior do dispositivo. Assim, com o intuito de adquirir uma compreensão mais profunda da física presente no escoamento em microbocais, a simulação numérica de um escoamento rarefeito num microbocal do tipo convergente-divergente é realizada através do Método de Simulção Direta de Monte Carlo (DSMC). Tal dispositivo é considerado como parte de uma matriz de microbocais. Considerando ainda uma superfície divergente do tipo convexa-côncava, os impactos de diferentes perfis dessa superfície na estrutura do escoamento, quantidades aerodinâmicas da superfície e desempenho do microbocal são explorados alterando-se a inclinação e o raio de curvatura da superfície no ponto de inflexão. Com o propósito de se desacoplar outros efeitos geométricos, a razão entre as áreas da garganta e de saída assim como o ângulo de divergência na saída são mantidos os mesmos para todos os casos. Além disso, as condições de entrada e saída são baseadas em valores pré-definidos de pressão. Os resultados computacionais apontaram um pequeno impacto nas propriedades macroscópicas devido às variações na inclinação e curvatura da superfície divergente. As hipóteses de simetria adotadas neste trabalho resultaram numa região de recirculação no escoamento externo. As simulações ainda mostraram que o não-equilíbrio termodinâmico ocorre em todo escoamento divergente, em especial, no lábio do bocal. No que diz respeito às quantidades aerodinâmicas, as simulações indicaram que as cargas térmicas e mecânicas que agem ao longo da superfície divergente dependem fortemente da inclinação da superfície próximo ao ponto de inflexão. Finalmente, este estudo ainda revelou que a forma geométrica da superfície divergente não desempenhou uma influência significativa no impulso específico. De qualquer modo, a presença da superfície divergente forneceu um impulso específico que é cerca de duas vezes maior que aquele obtido para um microbocal apenas com a parte convergente operando nas mesmas condições.The recent tendency in the design of space systems has aligned to reduce the life cycle cost of space programs by means of a reduction in the complexity of satellite missions. In this context, one of the possible options is reducing the mass of the whole system. Therefore, concepts of micropropulsion based on microtechnologies have been developed in order to attend the requirements of future space missions. The current state of semiconductor technology based on silicon has allowed the manufacturing process of small scale systems, called as MEMS (MicroElectroMechanical Systems). Among the many MEMS applications are the microunits of low thrust, where micronozzles are present. According to the relevant literature, the most studies investigated the micronozzle performance for different length scales and flow conditions. However, these investigations have not focused on the influence of the surface curvature on the micronozzle flow structure. In macronozzles, it is know that discontinuities on the surface affect the system performance due to the arising of shock waves inside the device. Thus, in order to obtain further insight into the physics of micronozzle flows, a numerical simulation of a rarefied flow in a convergent-divergent micronozzle array with rectangular cross-section is investigated by using the Direct Simulation Monte Carlo~(DSMC) method. By considering a convex-concave divergent surface, the impact of different divergent shapes on the two-dimensional flowfield structure, aerodynamic surface quantities and micronozzle performance are explored by changing the surface slope and radius of curvature at the inflection point. In order to decouple other geometric influences, the ratio between exit and throat areas as well as the divergent exit angle were kept the same for all cases. Moreover, the inlet-outlet boundary conditions are based on pre-defined pressure values. The computational results pointed out a small impact on the macroscopic properties due to variations in the slope and curvature of the divergent surface. The symmetric assumptions employed in this account resulted in a recirculation region in the external flow. The simulations also showed that thermodynamic nonequilibrium takes place in the entire divergent flow, in special, at the nozzle lip. By concerning to the aerodynamic surface quantities, simulations indicated that the thermal and mechanical loads that take place along the divergent surface are highly dependent on the smoothness of the surface along the inflection point. Finally, this study also revealed that the geometric shape of the divergent surface does not perform significant influence on the specific impulse. Anyway, the presence of the divergent surface provided a specific impulse that is almost two times higher than that one obtained by a micronozzle with only the convergent part operating in the same conditions.
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Burns, Paul. "Interactions between downslope flows and a developing cold-air pool." Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/15500.
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Downslope flows and regions of enhanced cooling have important impacts on society and the environment. Parameterisation of these often subgrid-scale phenomena in numerical models requires a sound understanding of the underlying physical processes, which has been the overarching aim of this work. A numerical model has been used to characterise the development of a region of enhanced cooling in an idealised alpine valley with width and depth of order 10 and 1 km, respectively, under stable, decoupled, poorly-drained conditions. A focus of this work has been to remove the uncertainty surrounding the forcing mechanisms behind the development of regions of enhanced cooling. The average valley-atmosphere cooling has been found to be almost equally partitioned between radiative and dynamics effects. Complex interactions between the downslope flows and the region of enhanced cooling have been quantified for the first time. For example, relatively large variations in the downslope flows are generally restricted to the region of enhanced cooling and cannot solely be attributed to the analytical model of [McNider, 1982a]. These flow variations generally coincide with return flows above the downslope flows, where a thin region of unstable air occurs, as well as coinciding with elongated downslope flow structures. The impact of these interactions on the dispersion of passive pollutants has been investigated. For example, pollutants are generally trapped within the region of enhanced cooling. The concentration of pollutants within the region of enhanced cooling, emitted over the lower half of the slopes, increase as the emission source moves away from the ground-based inversion that expands from the bottom of the valley. The concentration of pollutants within the region of enhanced cooling is very similar when varying the location of the emission source over the top half of the valley slopes. This work includes a test of the effects of varying the horizontal numerical grid resolution on average valley-atmosphere temperature changes.
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Bardot, Leon. "Explosive volcanism on Santorini : palaeomagnetic estimation of emplacement temperatures of pyroclastics." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360162.
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Laurantzon, Fredrik. "Flow Measuring Techniques in Steady and Pulsating Compressible Flows." Licentiate thesis, KTH, Mekanik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-26344.
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This thesis deals with flow measuring techniques applied on steady and pulsatingflows. Specifically, it is focused on gas flows where density changes canbe significant, i.e. compressible flows. In such flows only the mass flow ratehas a significance and not the volume flow rate since the latter depends onthe pressure. The motivation for the present study is found in the use of flowmeters for various purposes in the gas exchange system for internal combustionengines. Applications can be found for instance regarding measurements of airflow to the engine, or measurements of the amount of exhaust gas recirculation.However the scope of thesis is wider than this, since the thesis aims toinvestigate the response of flow meters to pulsating flows. The study is mainlyexperimental, but it also includes an introduction and discussion of several inindustry, common flow measuring techniques.The flow meters were studied using a newly developed flow rig, designedfor measurement of steady and pulsating air flow of mass flow rates and pulsefrequencies typically found in the gas exchange system of cars and smallertrucks. Flow rates are up to about 200 g/s and pulsation frequencies from 0 Hz(i.e. steady flow) up to 80 Hz. The study included the following flow meters:hot-film mass flow meter, venturi flowmeter, Pitot tube, vortex flowmeter andturbine flowmeter. The performance of these meters were evaluated at bothsteady and pulsating conditions. Furthermore, the flow under both steady andpulsating conditions were characterized by means of a resistance-wire basedmass flow meter, with the ability to perform time resolved measurements ofboth the mass flux ρu, and the stagnation temperature T0.Experiments shows that, for certain flow meters, a quasi-steady assumptionis fairly well justified at pulsating flow conditions. This means that thefundamental equations describing the steady flow, for each instant of time,is applicable also in the pulsating flow. In the set-up, back-flow occurred atcertain pulse frequencies, which can result in highly inaccurate output fromcertain flow meters, depending on the measurement principle. For the purposeof finding means to determine when back flow prevails, LDV measurementswere also carried out. These measurements were compared with measurementsusing a vortex flow meter together with a new signal processing technique basedon wavelet analysis. The comparison showed that this technique may have apotential to measure pulsating flow rates accurately.Descriptors: Flow measuring, compressible flow, steady flow, pulsating flow,hot-wire anemometry, cold-wire anemometry.QC 20101208
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Nanson, Richard A. "Navier/Stokes/Direct simulation Monte Carlo modeling of small cold gas thruster nozzle and plume flows." Link to electronic thesis, 2002. http://www.wpi.edu/Pubs/ETD/Available/etd-0424102-132343.
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Nanson, III Richard A. "Navier/Stokes/Direct Simulation Monte Carlo Modeling of Small Cold Gas Thruster Nozzle and Plume Flows." Digital WPI, 2002. https://digitalcommons.wpi.edu/etd-theses/254.
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This study involves the modeling of small cold-gas (N2) thrusters nozzle and plume flows, their interactions with spacecraft surfaces and the induced pressure environment. These small cold-gas thrusters were used for pitch, yaw and roll control and were mounted on the bottom of the conical Environmental Monitor Payload (EMP) suborbital spacecraft. The pitch and yaw thrusters had 0.906 mm throat diameter and 4.826 mm exit diameter, while the roll thrusters had 1.6 mm throat diameter and 5.882 mm exit diameter. During thruster firing, at altitudes between 670 km and 1200 km, pressure measurements exhibited non-periodic pulses (Gatsonis et al., 1999). The pressure sensor was located inside the EMP and was connected to it's sidewall with a 0.1-m long, 0.022-m diameter tube and the pressure pulses appeared instantaneously with the firings for thrusters without a direct line-of-sight with the sensor entrance. Preliminary analysis showed that the plume of these small EMP thrusters undergoes transition from continuous to rarefied. Therefore, nozzle and plume simulations are performed using a combination of Navier-Stokes and Direct Simulation Monte Carlo codes. This study presents first a validation of the Navier-Stokes code Rampant used for the continuous EMP nozzle and plume simulations. The first Rampant validation example involves a two-dimensional axisymetric freejet expansion and is used to demonstrate the use of Bird's breakdown parameter. Results are compared favorably with those of Bird (1980) obtained through the method of characteristics. The second validation example involves three-dimensional plume simulations of a NASA thruster. This nitrogen nozzle has a throat diameter of 3.18 mm, an exit diameter of 31.8 mm, half-angle of 20 degrees, stagnation temperature of 699 K, stagnation pressure of 6,400 Pa. Simulation results are compared favorably with previous Navier-Stokes and Direct Simulation Monte Carlo numerical work. The third validation example involves three-dimensional simulations of Rothe's (1970) nozzle that has a throat diameter of 2.5 mm, an exit diameter of 20.3 mm, half-angle of 20 degrees, operating at stagnation temperature of 300 K and pressure of 1975 Pa. Numerical results also compared favorably to experimental data. The combined Navier-Stokes/DSMC approach and the EMP simulation results are presented and discussed. The continuous part of the EMP nozzle and plume flow is modeled using the three-dimensional Navier-Stokes Rampant code. The Navier-Stokes domain includes the geometry of the nozzle and the EMP base until transition of the continuous flow established by Bird's breakdown parameter. The rarefied part of the plume flow is modeled using the Direct Simulation Monte Carlo code DAC. Flowfield data obtained inside the breakdown surface from the Navier-Stokes simulation are used as inputs to the DSMC simulations. The DSMC domain includes the input surface and the EMP spacecraft geometry. The combined Navier-Stokes/DSMC simulations show the complex structure of the plume flow as it expands over the EMP surfaces. Plume reflection and backflow are demonstrated. The study also summarizes findings presented by Gatsonis et al. (2000), where the DSMC predictions at the entrance of the pressure sensor are used as inputs to a semi-analytical model to predict the pressure inside the sensor. It is shown that the pressure predictions for the pitch/yaw thrusters are close to the measurements. The plume of a pitch or yaw thruster reaches the pressure sensor after expanding on the EMP base. The pressure predicted for the roll thruster is larger that the measured. This is attributed to the uncertainty in the roll thruster location on the EMP base resulting, in the simulation, in a component of direct flow to the sensor.
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Kalpakli, Athanasia. "Experimental study of turbulent flows through pipe bends." Licentiate thesis, KTH, Linné Flow Center, FLOW, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93316.
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This thesis deals with turbulent flows in 90 degree curved pipes of circular cross-section. The flow cases investigated experimentally are turbulent flow with and without an additional motion, swirling or pulsating, superposed on the primary flow. The aim is to investigate these complex flows in detail both in terms of statistical quantities as well as vortical structures that are apparent when curvature is present. Such a flow field can contain strong secondary flow in a plane normal to the main flow direction as well as reverse flow. The motivation of the study has mainly been the presence of highly pulsating turbulent flow through complex geometries, including sharp bends, in the gas exchange system of Internal Combustion Engines (ICE). On the other hand, the industrial relevance and importance of the other type of flows were not underestimated. The geometry used was curved pipes of different curvature ratios, mounted at the exit of straight pipe sections which constituted the inflow conditions. Two experimental set ups have been used. In the first one, fully developed turbulent flow with a well defined inflow condition was fed into the pipe bend. A swirling motion could be applied in order to study the interaction between the swirl and the secondary flow induced by the bend itself. In the second set up a highly pulsating flow (up to 40 Hz) was achieved by rotating a valve located at a short distance upstream from the measurement site. In this case engine-like conditions were examined, where the turbulent flow into the bend is non-developed and the pipe bend is sharp. In addition to flow measurements, the effect of non-ideal flow conditions on the performance of a turbocharger was investigated. Three different experimental techniques were employed to study the flow field. Time-resolved stereoscopic particle image velocimetry was used in order to visualize but also quantify the secondary motions at different downstream stations from the pipe bend while combined hot-/cold-wire anemometry was used for statistical analysis. Laser Doppler velocimetry was mainly employed for validation of the aforementioned experimental methods. The three-dimensional flow field depicting varying vortical patterns has been captured under turbulent steady, swirling and pulsating flow conditions, for parameter values for which experimental evidence has been missing in literature.QC 20120425
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Örlü, Ramis. "Experimental study of passive scalar mixing in swirling jet flows." Licentiate thesis, KTH, Mechanics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4142.
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Despite its importance in various industrial applications there is still a lack of experimental studies on the dynamic and thermal field of swirling jets in the near-field region. The present study is an attempt to close this lack and provide new insights on the effect of rotation on the turbulent mixing of a passive scalar, on turbulence (joint) statistics as well as the turbulence structure.
Swirl is known to increase the spreading of free turbulent jets and hence to entrain more ambient fluid. Contrary to previous experiments, which leave traces of the swirl generating method especially in the near-field, the swirl was imparted by discharging a slightly heated air flow from an axially rotating and thermally insulated pipe (6 m long, diameter 60 mm). This gives well-defined axisymmetric streamwise and azimuthal velocity distributions as well as a well-defined temperature profile at the jet outlet. The experiments were performed at a Reynolds number of 24000 and a swirl number (ratio between the angular velocity of the pipe wall and the bulk velocity in the pipe) of 0.5.
By means of a specially designed combined X-wire and cold-wire probe it was possible to simultaneously acquire the instantaneous axial and azimuthal velocity components as well as the temperature and compensate the former against temperature variations. The comparison of the swirling and non-swirling cases clearly indicates a modification of the turbulence structure to that effect that the swirling jet spreads and mixes faster than its non-swirling counterpart. It is also shown that the streamwise velocity and temperature fluctuations are highly correlated and that the addition of swirl drastically increases the streamwise passive scalar flux in the near field.
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Ben, Nasr Ouissem. "Numerical simulations of supersonic turbulent wall-bounded flows." Phd thesis, INSA de Rouen, 2012. http://tel.archives-ouvertes.fr/tel-01059805.
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This work deals with spatially-evolving supersonic turbulent boundary layers over adiabatic and cold walls at M∞ = 2 and up to Re0 ≈ 2600 using 3 different SGS models. The numerical methodology is based on high-order split-centered scheme to discretize the convective fluxes of the Navier-Stokes equations . For the adiabatic case, it is demonstrated that all SGS models require a comparable minimum grid-refinement in order to capture accurately the near-wall-turbulence. Overall, the models exhibit correct behavior when predictiong the dynamic properties, but show different performances for the temperature distribution in the near-wall region. For the isothermal case, it is found that the compressibility effects are not enhanced due to the wall cooling. As expected, the total temperature fluctuations are not negligible in the near-wall region. The study shows that the anti-correlation linking both velocity and temperature fields, derived from the Morkovin's hypothesis, is not satisfied.
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Arduini, Gabriele. "Wintertime stable boundary-layer processes in Alpine valleys." Thesis, University of Hertfordshire, 2017. http://hdl.handle.net/2299/19706.
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Alpine valleys are rarely closed systems, implying that the atmospheric boundary layer of a particular valley section is influenced by the surrounding terrain and large-scale flows. A detailed characterisation and quantification of these effects is required in order to design appropriate parameterisation schemes for complex terrains. The focus of this work is to improve the understanding of the effects of surrounding terrain (plains, valleys or tributaries) on the heat and mass budgets of the stable boundary layer of a valley section, under dry and weak large-scale wind conditions. Numerical simulations using idealised and real frameworks are performed to meet this goal. Several idealised terrains (configurations) were considered: an infinitely long valley (i.e. two-dimensional), and upstream valleys opening either on a plain (valley-plain), on a wider valley (draining) or on a narrower valley (pooling). In three-dimensional valleys, two main regimes can be identified for all configurations: a transient regime, before the down-valley flow develops, followed by a quasi-steady regime, when the down-valley flow is fully developed. The presence of a downstream valley reduces the along-valley temperature difference, therefore leading to weaker down-valley flows. As a result, the duration of the transient regime increases compared to the respective valley-plain configuration. Its duration is longest for the pooling configuration. For strong pooling the along-valley temperature difference can reverse, forcing up-valley flows from the narrower towards the wider valley. In this regime, the average cooling rate at the valley-scale is found to be a maximum and its magnitude is dependent on the configuration considered. Therefore pooling and draining induce colder and deeper boundary layers than the respective valley-plain configurations. In the quasisteady regime the cooling rate is smaller than during the transient regime, and almost independent of the configuration considered. Indeed, as the pooling character is more pronounced, the warming contribution from advection to the heat budget decreases because of weaker down-valley flows, and so does the cooling contribution from the surface sensible heat flux. The mass budget of the valley boundary layer was found to be controlled by a balance between the convergence of downslope flows at the top of the boundary layer and the divergence of the down-valley flow along the valley axis, with negligible contributions of subsidence far from the valley sidewalls. The mass budget highlighted the importance of the return current above the down-valley flow, which may contribute significantly to the inflow of air at the top of the boundary layer. A case-study of a persistent cold-air pool event which occurred in February 2015 in the Arve River Valley during the intensive observation period 1 (IOP1) of the PASSY- 2015 field campaign, allowed us to quantify the effects of neighbouring valleys on the heat and mass budgets of a real valley atmosphere. The cold-air pool persisted as a result of warm air advection at the valley top, associated with the passage of an upper-level ridge over Europe. The contributions from each tributary valley to the mass and heat budgets of the valley atmosphere were found to vary from day to day within the persistent stage of the cold-air pool, depending on the large-scale flow. Tributary flows had significant impact on the height of the inversion layer and the strength of the cold-air pool, transporting a significant amount of mass within the valley atmosphere throughout the night. The strong stratification of the near-surface atmosphere prevented the tributary flows from penetrating down to the valley floor. The evolution of the large-scale flow during the episode had a profound impact on the near-surface circulation of the valley. The channelling of the large-scale flow at night, can lead to the decrease of the horizontal temperature difference driving the near-surface down-valley flow, favouring the stagnation of the air close to the ground.
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Trachte, Katja [Verfasser], and Jörg [Akademischer Betreuer] Bendix. "Cold Air Drainage Flows and their Relation to the Formation of Nocturnal Convective Clouds at the Eastern Andes of South Ecuador / Katja Trachte. Betreuer: Jörg Bendix." Marburg : Philipps-Universität Marburg, 2011. http://d-nb.info/1013255658/34.
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Sykes, Harrison G. "COLD FLOW PERFORMANCE OF A RAMJET ENGINE." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1334.
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The design process and construction of the initial modular ramjet attachment to the Cal Poly supersonic wind tunnel is presented. The design of a modular inlet, combustor, and nozzle are studied in depth with the intentions of testing in the modular ramjet. The efforts undertaken to characterize the Cal Poly supersonic wind tunnel and the individual component testing of this attachment are also discussed. The data gathered will be used as a base model for future expansion of the ramjet facility and eventual hot fire testing of the initial components. Modularity of the inlet, combustion chamber, and nozzle will allow for easier modification of the initial design and the designs ability to incorporate clear walls will allow for flow and combustion visualization once the performance of the hot flow ramjet is determined. The testing of the blank ramjet duct resulted in an error of less than 10% from predicted results. The duct was also tested with the modular inlet installed and resulted in between a 13-30% error based on the predicted results. Hot flow characteristics of the ramjet were not achieved, and the final cold flow test with the nozzle installed was a failure due to improper configuration of the nozzle. The errors associated with this testing can largely be placed on the poor performance of the Cal Poly supersonic wind tunnel and the alterations made to the testing in an attempt to accommodate these flaws. The final tests were halted for safety concerns and could continue after a thorough safety review.
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Chiu, Chuang-Wei. "Biodiesel synthesis and impact of cold flow additives /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1421124.
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Azarinezhad-Mohammadi, Roghieh. "A chemical based wet cold flow approach for addressing hydrate flow assurance problems." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2414.
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Current gas hydrate flow assurance methods are becoming less economical and/or practical for deepwater operations, long tiebacks and ageing reservoirs. The industry thus needs novel flow assurance techniques to address these challenging conditions. An alternative approach called HYDRAFLOW, a chemical based wet Cold Flow method, has been presented in this thesis in which gas hydrate management, rather than prevention, is the aim. The idea is to convert most of the gas phase into hydrates and transfer it in the form of hydrate-slurry in the pipeline. This study investigates the concept, i.e. the transportability of hydrate slurries, for different systems (low and high GOR oil systems in the presence and absence of AAs) in different operating conditions, especially in conditions where the other flow assurance solutions either cannot be applied or are not economically viable, e.g. at high watercuts or under very high degree of subcoolings. The experiments involve investigating the rheological behaviour and flow properties of hydrate slurries using the HTI-set up (Helical Tube Impeller, an apparatus designed and build in-house for measuring viscosity of hydrate slurries at high pressures). Additionally, the rate of hydrate formation in low and high oil systems and also at subzero conditions has been measured. Furthermore, the effect of key variables, (e.g. heat transfer, mass transfer, degree of subcooling, salt, anti-agglomerants (AAs) and thermodynamic inhibitors) on the rate of hydrate formation and also on the rheology of hydrate suspensions have been studied in this work. The partitioning of a commercial AA between hydrate, oil and aqueous phases and its performances in each phase have also been determined which can help for decision making about recovering and/or recycling all or part of AAs. And finally, it has been shown that hydrate flow can potentially reducing wax deposition problems in pipeline by abrasion of the deposited wax.
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Baudet, Alvaro. "Optimize cold sector material flow of a steel rolling mill." Thesis, KTH, Industriell produktion, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50380.
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The steel production is a highly capital and energy intensive industry that due to recent raw materials’ price increase and lowered demand, it has been squeezed and forced to look more deeply on how to add value to the customer at lower operative costs. The project was carried out on site at the ArcelorMittal’s millin Esch-Belval, Luxembourg which comprises an integrated melt shop, continuous casting plant and the rolling mill with the objectives of proposing optimization rules for the cold sector of the rolling mill and to analyze the impact of the future truckbay shipment area. The course of action followed was to draw a Value Stream Map (VSM) in order to understand the plants’ current status and serve as a roadmap to build a discrete event simulation model that after its validation, served as a support tool to analyze what-if scenarios. Similarly, a current status analysis of the shipment/stock area was conducted collecting statistics about potential truckshipments and finally proposing a series of recommendations for its operation. The main proposed solutions to optimize the rolling mill’s cold sector were:(a) Integer programming model to globally optimize the scrap level when cutting the mother beams to customer size beams. (b) Updating pacemaker parameters and (c) Local process time improvements. Concerning the future truck loading, the simulation model was used as a support tool to dimension the transition area between the cranes’ and forklift operations resulting in a 6-9 bundles buffer capacity. Additionally, the current length-based storage policy was found to have competitive objectives so a turnover class-based storage policy is proposed with A, B, C classes which should provide an improved organization of the stock and travel distance of the cranes. The evaluation of the cranes’ performance remains an issue since there are currently no objective measures like, for instance, travelled distance. Optical measuring devices are suggested as one option to have a performance indicator that would help further investigate root cause problems in the shipping/stock area.
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Tjøstheim, Sindre. "Chemical Looping Combustion Cold Flow Model commissioning and performance evaluation." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11059.
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SINTEF and NTNU are planning to build a 150 kWth Chemical Looping Combustion (CLC) reactor system. This is new technology and the CLC reactor system is going to be one of the largest of its kind in the world. The technology is promising for CO2 capture in terms of energy efficiency and economics. To verify the design a Cold Flow Model, CFM, has been built. In the CFM no reactions take place, but it simulates the hydrodynamics of the 150 kWth CLC reactor system. The reactor system consists of two reactors exchanging solids in a loop. The two reactors are one air reactor, AR, and one fuel reactor, FR. Air is injected at different locations in the CFM to fluidize the solids and achieve the proper mass flows. The Cold Flow Model has been commissioned and an experimental campaign was executed. A series of experiments running each reactor singularly were performed. The rig seems to be functioning satisfactory and a minimum of plugging in the pipes were observed. The Cold Flow model has two cyclones that showed collection efficiencies at approximately 99 %. This is important to avoid emissions of solids from the future CLC reactor system, both for economic and environmental reasons. An investigation and mapping of the operating area of the reactors singularly and coupled was the target of the experiments. Correlations between operating velocity, total solid inventory, air distribution and flux were found. Appropriate flow regimes, meant to give good gas solid contact efficiency, and mass flow’s entrainments were achieved. The targets of a solid circulation rate of 2 kg/s in the AR and 1 kg/s in the FR were also achieved. Air is injected in the bottom of the reactors to fluidize the particles. This air is distributed through primary and secondary nozzles. The highest primary air percentage tested in the FR, 75%, gave the highest flux. In the AR 100% was tested, but 70% gave the highest flux. The last result is in contradiction with other experimental work in the area which says that 100% primary air should give the highest flux. After the mapping of the operating area of the single reactors it was possible to try to run the two reactors coupled. The divided loop seal was tested but led to a pressure short circuit and a large amount of the total solid inventory was lost out of the cyclones in a short time. The operation of a divided loop seal is probably possible, but seems difficult. The internal part of the loop seals were sealed to make the operation easier. The loop seals could then be operated as traditional loop seals. A challenge was the mass balance between the fuel reactor and air reactor. The mass flows of particles from both reactors must be equal to have a mass balance. Otherwise all the particles eventually ends up in one reactor. Results from the single reactor experiments were used to know approximately which operating conditions gave a mass balance between the reactors. The Cold Flow Model seemed to a certain degree be self regulating for achieving a mass balance if initial operating conditions were reasonable. Two experiments with coupled reactors and mass exchange only through the loop seals were done. A global solid circulation rate of 0.7 kg/s and 1 kg/s was achieved. Both AR and FR had the proper flow regimes. Proper flow regimes in the reactors are turbulent or fast fluidization. A third experiment utilized a lifter to enhance the solid transport between the reactors. A lifter is a additional transporter of solids from one reactor to another. The lifter worked successfully. The experiment had a global solid circulation rate of 1.4 kg/s. The mass flows were 1.4 kg/s from the AR loop seal and 1 kg/s from the FR loop seal. The remaining part 0.4 kg/s from the FR to the AR was transported with the lifter. Both reactors had proper flow regimes. A fourth experiment trying to achieve a global solid circulation rate of 2 kg/s failed. The bottleneck seems to be the AR loop seal. Solids accumulated and the loop seal was not able to handle this rate of solid flow. A new operation philosophy and design of the loop seal has been proposed. The new design of the loop seal and operation philosophy reduces the air flow needed in the loop seal, but it may not necessarily solve the solid circulation limit in the AR loop seal. Further investigation is needed. Manipulating the pressure in the AR may contribute to enhance the rate of solid flow through the loop seal. The successful experiments were presented at the 1st International Conference on Chemical Looping, IFP-Lyon, France, 17 - 19 March 2010. After the experimental campaign was finished the experiments were simulated with the fluidization software ERGUN developed by Compiegne University of Technology. ERGUN applies different mathematical models. For the simulations performed Horio’s and Berruti’s model were applied. The evaluation of the ERGUN simulations by means of the experiments shows that Horio’s and Berruti’s model should not be used for a detailed investigation of the flow structure in the CFM’s risers. However, despite its strongly empirical nature, a preliminary investigation of the riser’s behavior with Berruti’s model may be useful. Berruti’s model is a reasonable tool for modeling the upper part of the pressure profile in the AR and FR at the operating conditions tested. The operating conditions tested in the AR are total solid inventories of 35 and 45 kg, and superficial gas velocities from 0.9-1.9 m/s. The operating conditions tested in the FR are total solid inventories of 35 and 50 kg, and superficial gas velocities from 1.5-2.0 m/s. Berruti’s model is not capable of accounting for the dense bed in the lower part of the reactor as Horio’s model does. However, Horio’s model mismatched the experimental results too much. Horio’s model seems to be a provide a better match at larger total solid inventory and smaller operating velocities, hence flow regimes not relevant for the CLC reactor system.
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Larsson, Sofia. "Analysis of the cold flow field in a rotary kiln." Licentiate thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18444.
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The pelletizing process where the crude ore from the mine is upgraded to pellets is a process which includes several stages involving complex fluid dynamics. In this thesis, focus is on the grate-kiln pelletizing process and especially on the rotary kiln, with the objective to get a deeper understanding of the aerodynamics and its influence on the combustion process. The aim is to discover flow features taking place in the kiln, and the kiln hood, by using Computational Fluid Dynamics (CFD) on simplified models of the real kiln, and to validate the set-ups of the numerical model with physical experiments using Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV). By starting as simple as possible, studying only the cold flow field without combustion and validating the simulations, a foundation for future geometrical optimizations can be achieved. Later on more realistic geometries may be studied with the validated simulations as a base. In Paper A the initial down-scaled, simplified model of the real kiln is studied, and both numerical and experimental analyses of the flow field are performed. Paper B focuses on the turbulent secondary flow that arises in ducts with non-circular cross-section. One of the inlet ducts to the kiln of interest here is close to semi-circular in cross section, hence the focus of this work. Numerical and experimental results are reported. Paper C is a development of the model, where instead of parallel inlet ducts as in Paper A, the top one has an inclination angle to the kiln axis. A thorough experimental analysis of the flow field is performed in this case. Conclusions are that steady state simulations can be used to get an overview over the main features of the flow field. Precautions should though be taken when analyzing the recirculation zone which is important for the flame stabilization. A stable flame is safe and crucial for efficient combustion. Steady state simulations do not capture the transient, oscillating behavior of the flow seen in the physical experiment. These oscillations will under certain conditions considerably affect the size of the recirculation zone. Another parameter affecting the size of the recirculation zone is the inclination of the upper inlet duct, where a decrease in recirculation length is seen although the actual inclination of the incoming jet is only about 3-4º. The choice of turbulence model affects the prediction of turbulent secondary flow. If this flow feature needs to be revealed, a more advanced turbulence model should be used.Godkänd; 2011; 20110826 (soflar); LICENTIATSEMINARIUM Ämnesområde: Strömningslära/Fluid Mechanics Examinator: Professor Staffan Lundström, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: PhD / Forskarassistent Lisa Prahl Wittberg, Kungliga Tekniska Högskolan, Stockholm Tid: Fredag den 30 september 2011 kl 10.00 Plats: E231, Luleå tekniska universitet
Fastelaboratoriet - VINNEXC
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Nilsson, Mikael. "Ribosomes and subunits from Escherichia coli studied by asymmetrical flow field-flow fractionation." Lund : Technical Analytical Chemistry, Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/39761331.html.
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Kuppa, Subrahmanyam. "Visualization and velocity measurement of unsteady flow in a gas generator using cold-flow technique." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54226.
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Modeling of internal flow fields with hot, compressible fluids and sometimes combustion using cold flow techniques is discussed. The flow in a gas generator has been modeled using cold air. Experimental set up was designed and fabricated to simulate the unsteady flow with different configurations of inlet tubes. Tests were run for flow visualization and measurement of axial velocity at different frequencies ranging from 4 Hz to 12 Hz. Flow visualization showed that the incoming flow was a complex jet flow conformed to a cylindrical enclosure, while the outgoing flow resembled the venting of a pressurized vessel. The pictures show a complex flow pattern due to the angling of the jet towards the wall for the bent tube configurations and straightened flows with straight tube and other configurations with straighteners. Velocity measurements were made at an inlet Re of 8.1 x 10⁴ based on maximum velocity and inlet diameter using a single sensor hot wire anemometer at several locations in the plane of the inlet tube at 4 Hz, 8 Hz and 12 Hz for the straight tube and bent tube inlet configurations. The axial velocity near the entrance showed a strong component of the forcing frequency. Phase averaged mean velocities were observed to be well defined during charging and diminished during venting inside the cylinder. The jet flow penetrated most for the 4 Hz and least for the 12 Hz case. For the straight tube inlet comparison with a steady flow measurement of sudden expansion flow showed a qualitative similarity of the mean axial velocity distribution and centerline velocity decay during the charging phases. For the bent tube inlet case the contour plots showed the flow tendency towards the wall. Two cells were seen in the contours for the 8 Hz and 12 Hz cases. The deviation of the point of occurrence of maximum velocity in a radial profile was found to be about 6.5°. Entrance velocity profiles showed symmetry for the straight tube inlet while were skewed for the bent tube inlet. Contour plots of the phase averaged axial turbulence intensity for bent tube cases showed higher values in the core and near the wall in the region of impingement. Axial turbulence intensity measured for the straight tube case showed features as observed in an axisymmetric sudden expansion flow.Ph. D.
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Huber, Michael R. "A boundary-layer model of thermocapillary flow in a cold corner." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA379665.
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Dissertation (Ph.D. in Applied Mathematics)--Naval Postgraduate School, June 2000.Dissertation supervisor(s): Canright, David. "June 2000." Includes bibliographical references (p. 113-115). Also available online.
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Panday, Rupendranath. "Modeling, identification and control of a cold flow circulating fluidized bed." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5833.
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Thesis (M.S.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains xiii, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 94-99).
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Ovaici, Hooman. "The cold extrusion processing of chocolate during stable and unstable flow." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428800.
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Ferguson, Kevin M. "Design and cold flow evaluation of a miniature Mach 4 Ramjet." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FFerguson.pdf.
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Thesis (M.S. in Aeronauticl Engineering)--Naval Postgraduate School, June 2003.Thesis advisor(s): Garth V. Hobson, Raymond P. Shreeve. Includes bibliographical references (p. 67). Also available online.
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Larsson, Sofia. "The Fluid Dynamics of the Cold Flow in a Rotary Kiln." Doctoral thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25940.
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Godkänd; 2014; 20140307 (soflar); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Sofia Larsson Ämne: Strömningslära/Fluid Mechanics Avhandling: The Fluid Dynamics of the Cold Flow in a Rotary Kiln Opponent: Forskningsassistent Lisa Prahl Wittberg, Skolan för teknikvetenskap, Mekanik, KTH, Stockholm Ordförande: Professor Staffan Lundström, Avd för strömningslära och experimentell mekanik, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Fredag den 11 april 2014, kl 10.00 Plats: E231, Luleå tekniska universitetFastelaboratoriet - VINNEXC
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Fox, Karen Elizabeth. "Contrast therapy and post injury lower leg blood flow." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 44 p, 2008. http://proquest.umi.com/pqdweb?did=1459905891&sid=14&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Huber, Michael R. "An investigation of low Marangoni number fluid flow in a cold corner." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from the National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA271317.
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Rubenstein, Samuel. "Cold Flow Heat Transfer of Group D Particles in a Fluidized Bed." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1592717365378709.
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Goulet, Richard Roger. "Mechanisms affecting metal retention by surface-flow wetlands in cold temperate climates." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9210.
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The mechanisms affecting metal retention by surface-flow wetlands were investigated by relating variations in metal retention to variables such as hydraulic residence time, temperature (i.e. seasonal effects), phytoplankton biomass, photosynthesis and the presence of emergent vegetation. The importance of hydraulic residence time was investigated at the Monahan surface-flow wetland in Kanata, Ontario. This wetland retained metals best during summer and fall whereas during winter, the metal retention was significantly lower. The first-order removal model predicted Fe and Mn retention in the spring and Zn retention from spring to fall in both years of the study. Hydraulic residence times, greater than 7 days, provided the maximum retention of Fe, Mn, and Zn. However, first-order removal models failed to fit summer, fall and winter data for almost every metal under investigation (Fe, Mn, Cu, As) suggesting that hydraulic residence time (<1--25 days) do not regulate metal retention during these seasons. The Monahan wetland also affected the partitioning of metals between particulate and dissolved phases thus potentially affecting the bioavailability of metals to downstream systems. On a yearly basis, the wetland showed significant retention of the dissolved phase, but the retention of total Fe and Mn was poor. The wetland transformed dissolved into particulate metals from spring to fall whereas during the winter, dissolved metals were released. Changes in pH, alkalinity and temperature could explain 11% and 40% of the variation in the ratio of dissolved to total Fe and Mn respectively. Furthermore, from spring to late summer, planktonic algal biomass was negatively related to the ratio of dissolved to total Fe and Mn, which suggests the importance of phytoplankton in affecting the partitioning of metal in young plankton-dominated wetlands. In the Monahan wetland and in an acid mine drainage wetland (Falconbridge) near Sudbury, Ontario, diel changes in metal concentrations followed diel changes in pH and oxygen induced by photosynthesis. During the day, metal concentrations in the water column were low because high pH and oxygen favored the precipitation of Fe and Mn oxides at the sediment-water interface. At night, Fe and Mn oxides were reduced and released to the water column because intense biological respiration decreased oxygen and pH. Diel changes in metal concentrations have to be considered when evaluating the retention performance by surface-flow wetlands. Finally, the effect of emergent vegetation on the concentration and partitioning of metals in surface sediments of four wetlands was investigated. (Abstract shortened by UMI.)
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El, Siblani Ali. "Tool condition analysis and monitoring in cold rolling process." Thesis, KTH, Industriell produktion, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-41318.
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This research is about a costly problem in the automotive industry due to tool fracture during the splines cold rolling of steel shafts. The objective is to study the cause of this failure and propose solutions that can be implemented in the workshop.The writing starts with a brief introduction of the companies involved in shafts production and problem solving. It introduces the cold rolling process and its advantages on splines manufacturing, and it goes through relevant material and process characteristics that help to determine the cause of tool fracture.In order to understand the process failure and production flow, it has been necessary to build up an Ishikawa diagram with possible tool fracture causes. After collecting and analysing the data about the machine tool, cold rolling process and work-piece and rolling tool materials, tests and experiments have been done.It has been considered that there is a rolling tool fatigue that causes tool fracture. Beside tool fracture, two more problems with production flow instability and the right side rolling tool have been detected. Testing the material hardness of the work-piece has shown continuous hardness fluctuations from the supplier. Rolling tool misalignment has been measured by using a vernier caliper measurement device. Rolling tools material hardness analysis shows that tool is very hard and it is possible to use a tougher material which responds better to cyclic loads.Leax has tried to solve the problem by testing another lubrication and tool coatings. A modal analysis test has been performed in order to find the natural frequency of the work-piece which possibly may lead to vibration and over loading one of the rolling tools.The conclusion that has been reached is that main cause of fracture is rolling tool fatigue due to cyclic loads and it is important to use other rolling tool material. The other two detected problems, production flow instability and rigth side rolling tool fracture, should be considered as a part of the problem in order to significantly increase tools life and stabilize production flow rate.
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Smith, Carole-Anne. "The synthesis of some new polymeric materials as potential additives for diesel fuel." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/2214/.
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Wax crystal formation in diesel and related hydrocarbon fuels during cold weather is a long standing problem. Current polymeric additives to diesel fuel modify the crystal habit of the wax, in a variety of ways, to improve its performance at low temperature. These wax crystal modifiers (WCM) have to operate at low concentrations (0.01-0.1%) to make their use economical, so it is critical that their structures are optimised for the application. The objectives of this work was to synthesise, characterise and test some new polymeric additives which are anticipated to effect the crystallisation of the wax from the fuel and to prepare a model ethylene vinyl acetate (EVA) polymer to gain insights into the mode of action of the EVA co-polymers which are currently in use as WCM. Ring opening metathesis polymerisation was chosen as the method of preparation for these new polymeric additives. An introduction to wax crystallisation in diesel fuel and some proposals for the preparation of these new polymeric additives are given in Chapter 1. Chapter 2 discusses olefin metathesis and ring opening metathesis polymerisation reactions. The synthesis and characterisation of monomers and polymers are given in Chapters 3 and 4 respectively. Results from fuel tests are described in Chapter 5.
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Tayal, Sumit. "Detection of cold flow properties of diesel and biodiesel fuel using optical sensor." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4508.
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Thesis (M.S.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 23, 2007) Includes bibliographical references.
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Hussain, Qassim. "Crystallisation of long chain methyl esters in relation to their cold flow behaviour." Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590479.
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A detailed examination of the solution behaviour and crystallisation kinetics of fatty acid methyl esters (FAME) is presented. The systems studied are: methyl palmitate, methyl stearate and their binary mixtures in dodecane and methyl oleate solvents. Fractionation behaviour in palm methyl ester, soybean methyl ester and rapeseed methyl ester fuel is also studied. Two principal techniques are employed in this work, i.e. turbidometric analysis of solutions during polythermal cycles and the gas chromatography analysis of solution supernatants as a function of temperature. The foundations of these two studied have been laid via the x-ray diffraction (XRD) analysis of the solid-state forms of methyl palmitate and methyl stearate crystallised from solution. No evidence is found to suggest that the methyl stearate and methyl palmitate binary mixtures crystallise from methyl oleate solvent as a solid solution and no shift in the XRD patterns generated, i.e. no transition in solid state form crystallised is observed for the conditions under which solutions are crystallised. It is found that solution behaviour for methyl palmitate, methyl stearate and their binary mixtures in both solvents is in negative deviation to ideality, with the pure solutes being the more deviated in comparison to the binary mixtures. Eutectic points are discovered at a composition of 75 mol% C16:0 in the C16:0 I C18:0 binary mixture crystallisation from both solvents. Metastable zone widths (MSZW) are larger for both solutes in the methyl oleate solvent (6-9.50C) as compared to dodecane (3-6.5oC) and MSZWs are significantly smaller at the 100mI scale, being about half those at the 1ml scale. Nucleation rates for both solutes and their binary mixtures are about 2-13 k gilimin over a 100-250 g/l concentration range in both solvents. From the palm methyl ester and its blends with soy methyl ester and rapeseed methyl ester only C16:0 is found to crystallise at the cloud points. A thermodynamic model for methyl palmitate and methyl stearate solubilities in methyl oleate solvent predicts the fractionation behaviour in the blended fuels satisfactorily but less well in the pure palm methyl ester.
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Reaume, Stephen John. "Cold flow improvements to biodiesel through the use of heterogeneous catalytic skeletal isomerization." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45336.
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Biodiesel is a promising alternative to petroleum diesel with the potential to reduce overall net CO₂ emissions. However, the high cloud point of biodiesel must be reduced when used in cold climates. Cloud point is the temperature at which solid crystals first start to appear. Skeletal isomerization of biodiesel and/or its feedstocks was investigated to reduce the high cloud point. Catalytic isomerization and hydroisomerization reactions were carried out on pure unsaturated fatty acid (UFA) and saturated fatty acid (SFA) samples, respectively. The catalyst used for the experiments was a beta zeolite and 0.5 wt% Pt-doped beta zeolite for the isomerization and hydroisomerization reactions, respectively. Reaction conditions of temperature, pressure, co-catalyst and time were varied to find an optimal reduction in the cloud point of the products. It was concluded that isomerization was unsuccessful at reducing the cloud point; in contrast, hydroisomerization was successful at reducing cloud point. A 10 degree Celsius reduction was achieved at 285 degrees Celsius and 4.0 MPa H₂ pressure. The next stage of the research studied the combined effects of isomerization and hydroisomerization on a mixture of UFAs and SFAs, namely oleic and palmitic acids. It was shown that the combination of the reaction gave a cloud point reduction of 7.5 degrees Celsius on a 55/45 mass ratio of oleic to palmitic acids. These results led to the conclusion that SFAs and UFAs through skeletal isomerization can reduce the cloud point of a mixture of fatty acids. Thus, vegetable oil feedstocks can be improved for their biodiesel cloud point. A study of ten different oils was conducted with varying contents of fatty acids. Results have shown that high unsaturated fatty acid biodiesels increased in cloud point, due to the hydrogenation side reaction. In contrast, low unsaturated fatty acid biodiesels yielded cloud point reductions, and overall improvement in the flow properties. A maximum cloud point reduction of 16.5 degrees Celsius was observed with coconut oil as the starting material. These results led to the design of an optimal cloud point improvement process of for vegetable oil biodiesel of: hydrolysis (of vegetable oil → hydroisomerization (300 degrees Celsius, 4.0 MPa H₂ pressure → and esterification.
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Gautam, Dibash. "Use of Dean flow Ultraviolet Reactors For Cold Pasteurization of Tender Coconut Water." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2002.
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The natural water inside green coconuts is regarded as a healthy drink due to the elements of nutritional and therapeutic value. Since there is chance of contamination of tender coconut water (TCW) with psychrophilic microbes during extraction from its hard shell if stored at 4 ºC, thermal pasteurization is currently practiced. However, the thermal treatment of TCW causes a rise in off flavors and loss of the vital nutrients. To solve this problem, a non-thermal pasteurization technology is desirable. The goal of this research was to assess the antimicrobial effectiveness of ultraviolet light C (UVC) as non-thermal pasteurization of TCW and evaluation of physico-chemical and sensory quality of the treated TCW in comparison to the fresh TCW. A dean flow ultraviolet reactor was used with wavelength of 254 nm at the residence time of 14.0 seconds. The independent variables were three Reynold numbers (Re1 = 198.8, Re2 = 397.7 and Re3 =596.4) and two different diameters of transparent PFA tubes (3.2 mm and 1.6 mm). TCW was inoculated with cultures of Escherichia coli and Listeria monocytogenes separately up to 8 log10 CFU/mL and inactivation by cold pasteurization was evaluated with number of log reduction of each bacteria. Physico-chemical properties like total solid content (TSS) and pH were analyzed throughout the storage period of four weeks. The sensorial quality, flavor and color of the coconut water was also evaluated by a panel of 30 people to compare the organoleptic characteristics of UVC treated samples with untreated fresh coconut water. In case of Escherichia coli W1485, UVC treatment gave the log reduction of 5.27 and 4.74 log10 CFU/mL in coconut water for 1.6 mm and 3.2 mm ID reactors, respectively. Whereas the reduction of Listeria monocytogenes were 4.18 and 2.96 log10 CFU/mL for 1.6 mm and 3.2 mm ID reactors, respectively. In case of both the bacteria, as the tube size increased, microbial reduction decreased; and as the Reynold number increased, microbial reduction also increased except where there was an interaction effect. The change of tube diameters gave significantly different inactivation for both test bacteria at all Reynolds number except at Re2 and Re3 in case of Escherichia coli. The different levels of Reynolds number were not significantly variant when compared with consecutive levels, but Re1 to Re3 were significantly different for both test bacteria. The physico-chemical and sensorial changes of cold pasteurized TCW weres not significantly different compared to the fresh TCW, providing the conformity of retention of natural and organoleptic characteristics of TCW.
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Dupuis, Philippe. "Flow Structure Characterization and Performance Evaluation of Pin Fins Produced Using Cold Spray." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35496.
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Energy efficiency has become a growing concern in a world driven by a fossil fuel economy. Recuperated micro-gas-turbine systems offer the possibility of high efficiency power generation for low output power systems. To this end, increasing the performance while decreasing the cost, the weight and the volume of heat exchangers such as recuperators has become a critical research focus. Recent work done by Brayton Energy Canada (BEC) has renewed interest in Wire Mesh Heat Exchangers (WMHE) by introducing a new production method that uses cells of stacked wire mesh sheets that have a thick external shell deposited by cold spray. Fins are then machined in this external shell, creating a heat exchanger.
Net shaped pin fins were successfully deposited using Cold Gas Dynamic Spraying (CGDS or simply cold spray) as an additive manufacturing technique to replace the plate fin arrays currently used. This new development is envisioned to save costs while providing higher heat transfer efficiency than traditional fin arrays. Increasing the performance of such fin arrays would yield higher heat exchanger efficiencies and increase the total efficiency of the gas turbine system.
The present thesis provides a description of the research performed, as well as the results thereof, with regards to the performance of pin fin arrays produced using cold spray. A review of the relevant literature is performed to establish the motivation of this study and to describe the relevant work that has been performed by other authors in this respect. The research objectives are to evaluate the thermal and hydrodynamic performance of these fin arrays and relate those to the flow structures arising from fluid motion between these extended surfaces. Furthermore, the proposed approach and the experimental equipment that will be used are described in this work. The research objectives were successfully met, with the results obtained from this work presented in the form of peer-reviewed publications.
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Rubinstein, Abraham B. "An experimental investigation of spinal cord blood flow, it's autoregulation, and the effects of cerebral compression on spinal cord blood flow /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66220.
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Bucknor, Matthew David. "Study of In-Core Flow Blockage by Insulation Debris." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236382376.
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Pugalia, Neeraj. "Numerical modeling of cold flow and hot gas desulfurization in a circulating fluidized bed." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2056.
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Thesis (M.S.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains xvi, 119 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 103-106).
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Nastic, Aleksandra. "Repair of Aluminum Alloy Aerospace Components and Cold Gas Dynamic Spray Flow Distribution Study." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32998.
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Aluminum alloys have been used for decades in aircraft as they offer a wide range of properties explicitly developed to provide a set of characteristics adapted to structural and non-structural components. However, aircraft components inevitably undergo degradation during service due to their extensive use and exposure to harsh environments. Typical repair methods are either not efficient for large scale repairs due to their low material growth rate, not suitable for field repair or involve the use of high process temperatures. The present research aims at evaluating the cold gas dynamic spray (CGDS) as a potential repair technology to restore Al7075-T6 nose landing gear steering actuator threads found on the Boeing 757 aircraft. Moreover, it studies the suitability of using cold spray to deposit Al2024 material. The influence of process parameters and substrate surface preparation on the material deposition efficiency and resulting microstructural and mechanical repair properties is also evaluated.
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Lim, Bryan Neo Beng. "Computational simulations of fuel/air mixture flow in the intake port of a SI engine." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310769.
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Redmond, Eric. "Nitrogen removal from wastewater by an aerated subsurface flow constructed wetland." Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/2971.
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The purpose of this research was to assess the ability of subsurface flow wetlands, with aeration and vegetation, to remove nitrogen in cold weather climates. Aeration was shown to enhance the wetland cell's ability to remove not only nitrogen but also CBOD, COD, and phosphorus (retention) more effectively. There was a significant difference (p< 0.05) in both total nitrogen and ammonia effluent concentrations comparing aerated to unaerated wetland cells, while no significance was found comparing planted and unplanted wetland cells. The effluent ammonia concentrations from the aerated wetland cells ranged from 2.7 to 5.7 mg N/L, while for unaerated cells effluent concentration ranged from 22 to 23 mg N/L. The effluent total nitrogen concentrations from the aerated wetland cells ranged from 9.0 to 12 mg N/L, while those from unaerated cells ranged from 23 to 24 mg N/L. The effluent concentrations showed no significant difference (p < 0.05) when comparing results of three temperature ranges. There is a correlation when comparing ammonia mass removal rates to mass loading rates. Ammonia removal in the aerated wetland cells ranged from 82 to 95%, while unaerated cells ranged from 39 to 45%. The hydraulic retention times ranged from 3.13 to 4.33 days and the tanks-in-series ranged from 1.46 to 2.84. Using this information the wetland cells were modeled using both the TIS and the PkC* models. The k values (PkC* model) of the aerated wetlands for ammonia ranged from 131 to 221 m/d, while the unaerated wetland cells had values ranging from 20.4 to 36.7 m/d. The models appear to show a good prediction of the effluent ammonia concentration for the unaerated cells but the aerated cells show the model does not effectively capture the effects of aeration.
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Wee, Teik Khoo. "Cold flow drag measurement and numerical performance prediction of a miniature ramjet at Mach 4." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FWee.pdf.
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Thesis (M.S. in Engineering Science (Mechanical Engineering))--Naval Postgraduate School, December 2003.Thesis advisor(s): Garth V. Hobson, Rayomnd P. Shreeve. Includes bibliographical references (p. 67). Also available online.
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Wopat, Kathryn K. "Development of a to-scale fluid mixing visualization process for analysis of cold-flow mixing." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98752.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (page 34).
Torrefaction is a process by which low energy density biomass is converted to a higher energy density biofuel, called char. Small-scale torrefaction systems are a promising technology for developing countries where large amounts of biomass go underutilized due to inaccessibility and transportation costs. A by-product of torrefaction is volatile gas, thus, a system may be built to harness this otherwise wasted energy and use it to power the treatment of biomass. An efficient fuel-mixer and combustor system which recycles this volatile gas is central to the overall torrefaction system efficiency. In order to analyze the mixing efficiency in a swirl-type mixer such as the design proposed for the small-scale torrefaction system, a project was designed to visualize mixing in an annular mixer. A to-scale cold-mixing system was constructed from two cylinders, three pump systems, as well as an imaging system using a retrofitted green laser. The final model is a tested and proven system for flow imaging of two cold flows within a to-scale fuel-mixer.
by Kathryn K. Wopat.
S.B.
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Mawhinney, C. "The influence of cold-water immersion on limb blood flow and thermoregulatory responses to exercise." Thesis, Liverpool John Moores University, 2016. http://researchonline.ljmu.ac.uk/4709/.
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The accumulated stresses of training and competition may temporarily cause impairments in an athlete’s physiological and muscular function, leading to suboptimal performance levels. Cold-water immersion (CWI) has become a widely used post-exercise recovery method to accelerate the recovery process by purportedly reducing the symptoms associated with exercise-induced muscle damage (EIMD). However, the underlying physiological mechanisms, which mediate the effects of CWI, are not well understood. Therefore, the aim of this thesis was to investigate the influence of cold-water immersion (CWI) on limb blood flow and thermoregulatory responses following different modes of exercise. In study 1 (Chapter 4), the reliability of Doppler ultrasound in the assessment of superficial femoral artery blood flow (FABF) was examined under resting conditions. A Doppler ultrasound scan of the superficial femoral artery was measured on eight recreationally active male participants; twice on the same day separated by 5-min (within-day), and on a separate day (between-days). The coefficient of variation (CV) for mean blood flow (MBF) was ~16 % and ~20 % for within and between-days, respectively. A relatively small standard error of measurement (SEM) was found both within day, 13.30 mL·min-1 (95% CI, -14.79 to 38.40 mL·min-1) and between-day, 17.75 mL·min-1 (95% CI, -40.12 to 30.88 mL·min-1) for MBF differences. These findings suggest duplex Doppler ultrasound is a reliable method to collect measurements of FABF under resting conditions. The purpose of study 2 and 3 was to determine the influence of different degrees of water immersion cooling on FABF and cutaneous blood flow (CBF) and thermoregulatory responses after endurance (Chapter 5) and resistance (Chapter 6) exercise, respectively. Participants completed a prescribed endurance of resistance exercise protocol prior to immersion into 8 ºC (cold) or 22 ºC (cool) water to the iliac crest or rested non-immersion (CON) in a randomized order. Limb blood flow and thermoregulatory responses were measured before and up to 30-min after immersion. In both studies, thigh skin temperature (Tskthigh) (P < 0.001) and muscle temperature (Tmuscle) (P < 0.01) were lowest in the 8 ºC trial compared with 22 ºC and control trials. However, femoral artery conductance (FVC) was similar after immersion in both cooling conditions and was reduced (~50-55 %) compared with the CON condition 30-min after immersion (P < 0.01). Similarly, there was a greater thigh (P < 0.01) and calf (P < 0.05) cutaneous vasoconstriction during and after immersion in both cooling conditions relative to CON with no differences noted between 8 and 22 ºC immersion. Together, these findings suggest that colder water temperatures may be more effective in the treatment of EIMD and injury after both endurance and resistance exercise, respectively, due to greater reductions in Tmuscle and not limb blood flow per se. The aim of study 4 (Chapter 7) was to compare the influence of CWI and whole body cryotherapy (WBC) on FABF and CBF and thermoregulatory responses after endurance exercise. On separate days, participants completed a continuous cycle ergometer protocol before being immersed semi-reclined into 8 ºC water to the iliac crest for 10 min (CWI), or exposed to 2.5 min (30 s -60 ºC, 2 min -110 ºC) WBC in a specialized cryotherapy chamber, in a randomized order. Limb blood flow and thermoregulatory responses were measured before and up to 40-min after immersion Reductions in Tskthigh (P < 0.001) and Tmuscle (P < 0.001) were larger in CWI during recovery. Similarly, decreases in FVC were greater (~45-50 %) in the CWI condition throughout the recovery period (P < 0.05). There was also a greater skin vasoconstriction observed in CWI at the thigh (P < 0.001) and calf (P < 0.001) throughout the post-cooling recovery period. These results demonstrate that CWI may be a better recovery strategy compared with WBC due greater reductions in both Tmuscle and limb blood flow. This thesis provides a novel insight into the influence of different degrees of water immersion cooling, as well as WBC, on limb blood flow and thermoregulatory responses after different modes of exercise. These findings provide practical application for athletes and an important insight into the possible mechanisms responsible for CWI in alleviating inflammation in sport and athletic contexts.
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Dethloff, Frederik. "In vivo 13C stable isotope tracing of single leaf development in the cold." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/7048/.
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Measuring the metabolite profile of plants can be a strong phenotyping tool, but the changes of metabolite pool sizes are often difficult to interpret, not least because metabolite pool sizes may stay constant while carbon flows are altered and vice versa. Hence, measuring the carbon allocation of metabolites enables a better understanding of the metabolic phenotype. The main challenge of such measurements is the in vivo integration of a stable or radioactive label into a plant without perturbation of the system.
To follow the carbon flow of a precursor metabolite, a method is developed in this work that is based on metabolite profiling of primary metabolites measured with a mass spectrometer preceded by a gas chromatograph (Wagner et al. 2003; Erban et al. 2007; Dethloff et al. submitted). This method generates stable isotope profiling data, besides conventional metabolite profiling data. In order to allow the feeding of a 13C sucrose solution into the plant, a petiole and a hypocotyl feeding assay are developed. To enable the processing of large numbers of single leaf samples, their preparation and extraction are simplified and optimised. The metabolite profiles of primary metabolites are measured, and a simple relative calculation is done to gain information on carbon allocation from 13C sucrose.
This method is tested examining single leaves of one rosette in different developmental stages, both metabolically and regarding carbon allocation from 13C sucrose. It is revealed that some metabolite pool sizes and 13C pools are tightly associated to relative leaf growth, i.e. to the developmental stage of the leaf. Fumaric acid turns out to be the most interesting candidate for further studies because pool size and 13C pool diverge considerably. In addition, the analyses are also performed on plants grown in the cold, and the initial results show a different metabolite pool size pattern across single leaves of one Arabidopsis rosette, compared to the plants grown under normal temperatures. Lastly, in situ expression of REIL genes in the cold is examined using promotor-GUS plants. Initial results suggest that single leaf metabolite profiles of reil2 differ from those of the WT.Messungen des pflanzlichen Metaboloms können ein hilfreiches Werkzeug sein, um Pflanzen zu phänotypisieren. Jedoch sind die Änderungen der Poolgrößen teilweise schwer zu interpretieren, weil sich nicht nur die Poolgrößen sondern auch die Kohlenstoffflüsse unabhängig voneinander ändern können. Werden nun zusätzlich Informationen über die Flüsse ermittelt, kann der pflanzliche Phänotyp deutlich genauer beschrieben werden. Die größte Herausforderung für diese Messungen ist die In-vivo-Integration einer stabilen oder radioaktiven Markierung in einer Pflanze, ohne das System dabei zu stören. In dieser Arbeit wird ein Verfahren entwickelt, um die Verteilung von Kohlenstoffen aus einer gefütterten Vorstufe zu messen. Die Messung basiert dabei auf einem Primärmetabolitenprofil, das mit Hilfe eines Massenspektrometers mit vorgeschaltetem Gaschromatographen erstellt wird (Wagner et al. 2003; Erban et al. 2007; Dethloff et al. eingereicht). Mit dieser Methode ist es einfach möglich, stabile Isotopenprofildaten neben herkömmlichen Metabolitprofildaten zu erzeugen. Die Vorstufe, in diesem Fall 13C Saccharose, wird dazu mit Hilfe eines neuen Petiolen- und Hypokotyl-Fütterungs-Assay in die Pflanze gefüttert. Um die große Menge an Einzelblattproben aufzuarbeiten, die dabei anfallen, wird eine vereinfachte und optimierte Extraktion angewendet. Mit Hilfe einer einfachen Berechnung kann aus den Messdaten eine relative Verteilung des Kohlenstoffs aus 13C Saccharose bestimmt werden. Die Funktionalität dieses Verfahrens wird an Einzelblättern von Arabidopsis-Rosetten gezeigt, wobei sowohl Primärmetabolitenprofile als auch stabile Isotopenprofile erzeugt und untersucht werden. Es kann hierbei gezeigt werden, dass konventionelle Poolgrößen und 13C Poolgrößen einiger Metaboliten eng mit dem relativen Wachstum einzelner Blattpositionen bzw. mit dem jeweiligen Entwicklungsstadium der Blätter zusammenhängen. Anders als bei den meisten anderen Metaboliten zeigen die konventionellen Poolgrößen und 13C Poolgrößen von Fumarsäure ein unterschiedliches Verhalten in den einzelnen Blättern, was Fumarsäure zum interessantesten Kandidaten für weitere Studien macht. Die beschriebenen Untersuchungen werden weiterhin an in Kälte gewachsenen Pflanzen durchgeführt, wobei erste Ergebnisse ein verändertes Metabolitenprofil in den einzelnen Blättern zeigen. Des Weiteren wird die In-situ-Expression von REIL-Genen mit Hilfe von Promotor-GUS-Reportern untersucht. Erste Ergebnisse von Einzelblatt-Metabolitenprofilen der reil2 zeigen einen deutlichen Unterschied zum WT.
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Rapaka, Srikanth. "Reduction and Speciation of Monoglycerides to Produce High Quality Biodiesel." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23104.
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Biodiesel is rapidly growing as a fuel of interest due to the various advantages it has over conventional diesel fuel. While the pros – non-toxic, biodegradable, low green house gas emissions seem advantageous, the major issue that plagues the use of biodiesel is its cold weather operability. Biodiesel can present challenges in cold-weather operation, because certain of its constituent compounds can form precipitates in the fuel. These precipitates can cause undesired effects like plugging of fuel filters and deposits. This issue has been attributed to the presence of impurities (mostly saturated monoglycerides, di-glycerides, soap etc) in biodiesel and has been discussed in the literature. There is a move by users and standards associations to implement more stringent norms and quality control to avoid problems in the widespread use of biodiesel. This study involves ways to reduce MG’s in biodiesel by mitigating to a greater extent the possibility of side reactions (formation of soap). The effect of selective transesterification of oil as a function of alcohol, temperature and catalyst concentration was also studied. Although saturated MG’s with high melting points are a greater source of deposits, it can be hypothesized that the polymorphic nature of unsaturated Monoglycerides could also be contributing to cold flow issues. It is hence vital to make sure the biodiesel is free from all forms of monoglycerides. It was also seen that there is very little specificity of selection of fatty acid types in the transesterification reaction and that the amount and type of MGs present in the biodiesel is reflected by the relative amount of fatty acids types present in the oil. In biodiesel derived from Canola oil, a preponderance of monoolein was found for all runs. The initial runs carried out as a two stage process using the membrane followed by batch reactor gave very low MG concentrations, well below ASTM standards.
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Anwar, Adeel. "Enhancing properties of biodiesel via heterogeneous catalysis." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/enhancing-properties-of-biodiesel-via-heterogeneous-catalysis(7e52f44f-4c50-4cd3-b5a8-cf6ce714b7d6).html.
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Biodiesel is a re-emerging biofuel as an alternative to the traditional petroleum derived diesel. There are however, several factors that currently hinder the widespread uptake. Majority of the biodiesel are currently produced from edible oils thereby sparking the food versus fuel debate, the cost of feedstock is significantly high, there are problems experienced in the traditional production process and the resulting fuel is of inadequate quality. This work focused on addressing the issue of poor cold flow properties to improve the overall quality of biodiesel. The skeletal isomerisation of linear fatty acid methyl esters (FAMEs) into branched chain isomers, using solid acid catalysts, appears to be the most comprehensive solution in enhancing the cold flow properties of biodiesel. However, obtaining high branched chain yields, mitigation of undesired side reactions, achieving shorter reaction times, using fewer processing steps and lower operating conditions have still not been achieved to a large extent. Moreover, no studies were found to date investigating isomerisation of FAMEs as a continuous process. A trickle bed reactor (TBR) system has been identified to be an effective continuous reactor. Its key features of being a three phase system and allowing a high degree of contact between the reactant and the catalyst offering a high conversion per unit volume provides an encouraging opportunity to lower reaction times, reaction steps and conditions whilst increasing branched chain yields. This thesis explores the use of the TBR system, for the first time, to enhance the cold flow properties of biodiesel through molecular modification using zeolite beta catalyst with Si/Al ratios of 180 and 12.5. A range of reactions have been investigated including isomerisation, dewaxing (hydroisomerisation and hydrocracking) and decarboxylation on biodiesels derived from camelina, palm and coconut oils. Significant progress has been made in this research area with a 7 °C drop in MP being achieved upon the dewaxing of the coconut biodiesel at 250 °C, 1.01 bar pressure, 0.2 ml/min LF and 37.5 ml/min GF. To achieve greater drops in melting points it has been suggested to investigate mesoporous catalysts as they will ensure greater facilitated molecular access to the active sites, resulting in a higher conversion by preventing pore blockages. All in all, a series of key findings and serendipitous discoveries have brought to surface an array of new challenges as well as paving the way for a host of exciting opportunities for future research. The ability to continuously produce high quality renewable fuel offers a fascinating prospective for various industrial associates such as Argent Energy, Olleco, Neste Oil and ConocoPhillips.
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Bayliss, Danny. "Understanding the inactivation mechanism of foodborne pathogens using cold atmospheric plasma." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/12844.
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Experimental studies into the use of cold atmospheric plasmas for inactivating foodborne pathogens are presented in this thesis. Eliminating the possibility that treatment delivered by a plasma to a population or assemblage of micro-organisms is unevenly distributed is an essential pre-requisite to attempting to interpret inactivation kinetics with a view to elucidating mechanisms of inactivation. A filtration method of depositing cells evenly on the surface of a membrane without cell stacking was developed and used throughout the work described here. Two atmospheric plasma systems were evaluated and each brought about microbial inactivation in a distinct way. A pulsed radio frequency plasma jet operated at 3.47 MHz caused gross morphological changes to L. innocua whereas a low frequency air mesh plasma system operated at a frequency of 24 kHz led to the inactivation of these bacteria without inducing observable structural changes. Changing the operating parameters of the plasma jet system had a significant effect on the composition of the reactive plasma species generated as revealed by changes to the mode of inactivation of bacteria. In addition to inactivating bacteria, the pulsed plasma jet was shown to be highly effective in degrading and removing amyloid aggregates from the surface of mica coupons. Amyloids have widely been used as a non-infectious model for prions, and the results obtained here show potential for the application of gas plasma technology for removing prions from abiotic surfaces in medical and other applications. It has widely been assumed that bacterial envelopes are the principal sites at which reactive plasma species bring about damage to cells. However, changing the composition of the bacterial membranes of E. coli and Listeria innocua by cultivating them at widely different temperatures to induce changes proved not to result in enhanced inactivation. Flow cytometry was also used to provide additional insights into possible mechanisms of inactivation. The following fluorescent dyes were used either singly or in combination; SYTO 13, DiBAC4(3), cFDA and PI. The results obtained with the dyes DiBAC4(3) and PI showed that Gram positive bacteria became depolarised prior to the bacterial membrane becoming compromised, possibly suggesting that the inactivating plasma species are affecting membrane proteins responsible for maintaining the bacterial charge. Differences between the fluorescent dye staining of Gram negative and Gram positive species were obtained using SYTO13 and PI demonstrating that the different membrane structures affect their interaction with the plasma. In additional studies, the air mesh plasma was used to treat multi-drug resistant strains of Methicillin resistant Staphylococcus aureus (MRSA) in an attempt to reverse antibiotic resistance. MRSA PM 64 was shown to reverse its antibiotic resistance to Oxacillin, Kanamycin and Trimethoprim. Culturing the bacteria in a nutrient limited media led to increased resistance towards plasma treatment and maintenance of their high levels of antibiotic resistance.
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Schima, Francis Joseph. "Groundwater transport of Escherichia coli bacteria to open surface waters on Virginia's Coastal Plain : a GIS approach /." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-12162009-020249/.
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