Дисертації: "Low Pressure Systeams"

1

Pickering, Paul Frederick. "Instabilities in low pressure boiling systems." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/7784.

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2

Goparaju, Sravanthi. "Low Power Tire Pressure Monitoring System." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1220637163.

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3

Ding, Bowen. "Aerodynamics of low pressure steam turbine exhaust systems." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290137.

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The low pressure (LP) exhaust system presents a promising avenue for improving the performance of large steam turbines. For this reason, LP exhaust systems have attracted the attention of the research community for decades. Nevertheless, we still lack understanding of the flow physics and loss mechanisms in the exhaust system, especially at part-load conditions. It is also unclear how the exhaust system should be designed when its required operating range widens. This thesis provides solutions to these aerodynamic issues through experimental and numerical investigations, and provides tools that could contribute to better designs of LP exhaust systems. Firstly, the Computational Fluid Dynamics (CFD) solver ANSYS CFX was validated against experiments performed on a scaled test rig under representative part-load flow conditions. This validation exposed the weakness of Reynolds-averaged Navier-Stokes (RANS) CFD when there is a highly swirling flow and large separation regions in the exhaust diffuser. To facilitate the numerical studies, a series of tools were also developed. A design suite, ExhaustGen, was used to automate the pre- and post-processing of CFD calculations. The exhaust diffuser was parametrised using "Minimum Energy Curves", which reduce the dimension of parameter space. Further, a suitable stage-hood interface treatment (Multiple Mixing Planes) was chosen to predict the circumferentially non-uniform flow in the exhaust hood at low computational cost. Numerical investigation of the baseline geometry provided insights into the key flow features and loss mechanisms in the exhaust system, over a wide range of operating conditions. In particular, the bearing cone separation was identified as a key source of loss at part-load conditions. The effect of stage-hood interaction on the performance and design of the exhaust system was studied by varying the rotor blade design, which can positively influence system performance. Finally, a global sensitivity study was performed to identify the most influential design parameters of the exhaust hood. These findings allow, for the first time, LP exhaust hood performance maps to be constructed, so that the benefits of choosing a suitable hood geometry and blade design can be revealed. The thesis also offers contribution towards formulating LP exhaust system design guidance for a wide operating range.

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4

Degen, Marcia J. "Denitrification in low pressure distribution onsite wastewater disposal systems." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/29272.

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5

Rattner, Alexander S. "Single-pressure absorption refrigeration systems for low-source-temperature applications." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53912.

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The diffusion absorption refrigeration (DAR) cycle is a promising technology for fully thermally driven cooling. It is well suited to applications in medicine refrigeration and air-conditioning in off-grid settings. However, design and engineering knowhow for the technology is limited; therefore, system development has historically been an iterative and expensive process. Additionally, conventional system designs require high-grade energy input for operation, and are unsuitable for low-temperature solar- or waste-heat activated applications. In the present effort, component- and system-level DAR engineering analyses are performed. Detailed bubble-pump generator (BPG) component models are developed, and are validated experimentally and with direct simulations. Investigations into the BPG focus on the Taylor flow pattern in the intermediate Bond number regime, which has not yet been thoroughly characterized in the literature, and has numerous industry applications, including nuclear fuel processing and well dewatering. A coupling-fluid heated BPG design is also investigated experimentally for low-source-temperature operation. Phase-change simulation methodologies are developed to rigorously study the continuously developing flow pattern in this BPG configuration. Detailed component-level models are also formulated for all of the other DAR heat and mass exchangers, and are integrated to yield a complete system-level model. Results from these modeling studies are applied to develop a novel fully passive low-source-temperature (110 - 130°C) DAR system that delivers refrigeration grade cooling. This design achieves operation at target conditions through the use of alternate working fluids (NH3-NaSCN-He), the coupling-fluid heated BPG, and a novel absorber configuration. The complete DAR system is demonstrated experimentally, and evaluated over a range of operating conditions. Experimental results are applied to assess and refine component- and system- level models.

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6

Parkinson, J. S. "Control system design for low pressure gas distribution networks." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378367.

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7

Rouse, Anna Jane. "Fast cycle low pressure drop systems for the separation of COâ‚‚." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406861.

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8

Cameron, Christopher Alistair. "High-pressure studies on molecular systems at ambient and low temperatures." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/9952.

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Pressure and temperature are two environmental variables that are increasingly being exploited by solid-state researchers probing structure-property relationships in the crystalline state. Modern high-pressure apparatus is capable of generating many billions of Pascals in the laboratory, and therefore can produce significantly greater alterations to crystalline materials than changes in temperature, which can typically be varied by only a few thousand Kelvin. Many systems such as single-molecule magnets exhibit interesting properties under low-temperature regimes that can be substantially altered with pressure. The desire by investigators to perform analogous single-crystal X-ray diffraction studies has driven the development of new high-pressure apparatus and techniques designed to accommodate low-temperature environments. [Ni(en)3][NO3]2 undergoes a displacive phase transition from P6322 at ambient pressure to a lower symmetry P6122/P6522 structure between 0.82 and 0.87 GPa, which is characterized by a tripling of the unit cell c axis and the number of molecules per unit cell. The same transition has been previously observed at 108 K. The application of pressure leads to a general shortening of O···H hydrogen bonding interactions in the structure, with the greatest contraction (24%) occurring diagonally between stacks of Ni cation moieties and nitrate anions. A novel Turnbuckle Diamond Anvil Cell designed for high-pressure low-temperature single-crystal X-ray experiments on an open-flow cryostat has been calibrated using the previously reported phase transitions of five compounds: NH4H2PO4 (148 K), ferrocene (164 K), barbituric acid dihydrate (216 K), ammonium bromide (235 K), and potassium nitrite (264 K). From the observed thermal differentials between the reported and observed transition temperatures a linear calibration curve has been constructed that is applicable between ambient-temperature and 148 K. Low-temperature measurements using a thermocouple have been shown to vary significantly depending on the experimental setup for the insertion wire, whilst also adding undesirable thermal energy into the sample chamber which was largely independent of attachment configuration. High-pressure low-temperature single-crystal X-ray diffraction data of [Mn12O12(O2CMe)16(H2O)4] (known as Mn12OAc) reveals a pressure-induced expulsion of the crystallized acetic acid from the crystal structure and resolution of the Jahn-Teller axes disorder between ambient pressure and 0.87 GPa. These structural changes have been correlated with high-pressure magnetic data indicating the elimination of a slow-relaxing isomer over this pressure range. Further application of pressure to 2.02 GPa leads to the expansion of these Jahn-Teller axes, resulting in an enhancement of the slow-relaxing magnetic anisotropy as observed in the literature. Relaxation of pressure leads to a resolvation of the crystal structure and re-disordering of the Jahn-Teller axes, demonstrating that this structural-magnetic phenomenon is fully reversible with respect to pressure. The space group of the Prussian blue analogue Mn3[Cr(CN)6].15H2O has been re-evaluated as R-3m between ambient pressure and 2.07 GPa using high-pressure single-crystal X-ray and high-pressure neutron powder data. Reductions in metal-metal distances and gradual distortions of the Mn octahedral geometry have been correlated with previously reported increases in Tc and declines in ferrimagnetic moment in the same pressure range. Increasing the applied pressure to 2.97 GPa leads to partial amorphization and results in a loss of long-range magnetic order as shown by the literature. The application of pressure (1.8 GPa) to the structure of K2[Pt(CN)4]Br0.24.3.24H2O (KCP(Br)) causes a reduction in the Pt intra-chain and inter-chain distances, and results in an enhancement of the overall conductivity under these conditions as demonstrated in the literature. Almost no changes occur to the high-pressure crystal structure upon cooling to 4 K, except in the Pt-Pt intra-chain distances which converge and suppress the Peierls distortion known to occur at 4 K, resulting in a comparatively greater electrical conductivity under these conditions.

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9

Burton, Zoe. "Analysis of low pressure steam turbine diffuser and exhaust hood systems." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10531/.

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This thesis concerns the computational modelling of low pressure (LP) steam turbine exhaust hood flows. A test case for LP last stage blades (LSBs) with a full aerodynamic definition and an accompanying exhaust hood was developed which is representative of current industrial practice. The test case geometry is freely available allowing other researchers to build on this work and is the first of its kind. Studies on this Durham Stage and Exhaust Hood Test Case showed the geometry produces a representative flow pattern and performance metrics comparable to other published research. Using the test case, the effect of condenser cooling water pressure gradient on the hood flow was computed for the first time. A generic boundary condition was developed to represent the transverse condenser cooling water flow and, when applied to the test case, was shown to have a larger influence on the flow asymmetry within the hood than the tip leakage jet. This thesis describes the first application of the non-linear harmonic (NLH) method to couple the LSBs to the exhaust hood. This method enabled the circumferential non-uniformity which develops in the exhaust hood to be transferred across the interface to the stage, in half the computational demand of the full annulus frozen rotor approach. The first review of the influence of inlet circumferential asymmetry on the hood flow field highlighted that modelling its effect is not as crucial as indicated in the literature, unless the diffuser axial length is very compact or if off-design flows are to be studied. A series of recommendations and guidelines for the CFD modelling of steam turbine exhaust hood flows based on this work are supplied. Experimental validation of the Durham Stage and Exhaust Hood Test Case and a comparison of full unsteady studies with the NLH method should be the next steps in this research.

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10

Singleton, Andrew Thomas. "Cut-off low pressure systems and extreme rainfall over South Africa." Doctoral thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/6504.

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Includes bibliographical references (p. 257-271).
This thesis is an investigation of cut-off low pressure systems over South Africa. These weather systems have been responsible for many of the flooding disasters that have affected South Africa, particularly the coastal regions, over recent decades. The thesis has two main objectives, namely, to construct a 30-year climatology of cut-off lows over South Africa, and to further understanding of the evolution of the low-level flow that leads to these systems producing extreme quantities of rainfall.

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11

Kumar, Shivendra. "An Analytical Index for Evaluating Low-Pressure Hollow-Fibre Membrane Systems." Thesis, Griffith University, 2015. http://hdl.handle.net/10072/366948.

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Water and wastewater treatment through the use of membrane filtration technology is one of the processes utilised currently to meet the growing demand for water. While new technologies can harness water from various non-traditional sources such as oceans, there remains the possibility of making drinking water more expensive through the use of costly treatment equipment. To prevent this and ensuing catastrophes around the world, the water industry needs a strategy that keeps the price of water and price of products aiding in the treatment of water controlled into the future. The overall aim of this study is to develop an analytical index that could be used by the water industry to measure, monitor, and control the price of water. A structured method to evaluate membrane manufacturing costs against the lifetime performance of membranes was developed. The method was then extended and a costing model for the application of membrane in water and wastewater treatment plants was established. Thereafter, a software application was developed to aid in the implementation of the analytical index. The results indicate that, with a measurable index in place, the evaluation of technologies with respect to the cost of water production can be effectively carried out.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

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12

Grant, Elizabeth J. "Design and Implementation of a Pressure-Equalizing Vent System for Low-Slope Roofs." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/34928.

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Winds create forces on buildings, sometimes with disastrous results. Low-slope roofs are subjected to potentially high levels of suction pressure, especially when winds strike the corner of a building, creating vortices. Traditional methods of attaching roof membranes to substrates are prone to failure when the low pressure on the roof surface instigates a transfer of forces to the roof membrane. Existing pressure-equalized roof systems use the power of the wind to transmit low pressure to the space immediately beneath the roof membrane, pulling the membrane down to the roof surface. The object of this study is the design of a wind vent which, when coupled with a single-ply roof membrane in a complete roof assembly, will successfully equalize low pressure throughout the entire field of the roof. The proposed wind vent differs from existing equalizer valves in its use of the Bernoulli effect to create low pressure. Optimized for ease of manufacturing and installation, the vent is omni-directional and contains no moving parts. After the wind vent prototype is developed, future study will be required to determine the tributary area of each vent, the interaction with the insulation beneath the membrane, the response time of the system when subjected to dynamic wind loading, the effect on the vent of various weather conditions, and the permissible amount of infiltration into the roof system. Associated research will also investigate the benefits of incorporating the heat evacuating capacity of the pressure-equalizing roof vent system into a roof membrane containing an amorphous photovoltaic array.
Master of Science

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13

Mu, Yang. "A distributed control system for low pressure plant growth chambers." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0009183.

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14

Lee, Sung-Mo. "A performance evaluation of low pressure carbon dioxide discharge test." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0430104-041342/.

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Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: Deap-seated fire; flow calculation; maximum percent of agent in pipe; free efflux; carbon dioxide extinguishing system; low pressure; no efflux; surface fire; NFPA 12. Includes bibliographical references (p. 69-70).

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15

Kela, L. (Lari). "Attenuating amplitude of pulsating pressure in a low-pressure hydraulic system by an adaptive Helmholtz resonator." Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514261602.

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Abstract The adaptive Helmholtz resonator for decreasing harmonic pulsating pressure in a low-pressure hydraulic system is presented in this study. Adaptivity is executed by both open loop and closed loop controls so that continuous -20dB attenuation of the peak-to-peak value of the amplitude of pressure is reached. The study begins by a theory review including the theory of effective bulk modulus, sound velocity measurements, adjustable dynamic vibration absorbers and control methods of dynamic vibration absorbers. The main target of the paper, the Helmholtz resonator, is presented in its own chapter, albeit it is noted to be one application of the dynamic vibration absorber. The review is completed by the analytical model of the hydraulic pipe with a T-filter or Helmholtz resonator. After the theory review, the test equipment and its characteristics are presented. The main parts of the test equipment were a main pipe and an adjustable Helmholtz resonator, which were both developed for this study. Certain properties of the hydraulic oils used were determined experimentally to increase understanding of the system. The experimental section includes sound velocity measurements, sonic bulk modulus definitions, measurements of the resonant frequencies of the adaptive Helmholtz resonator in the test equipment, and tests of the open loop and closed loop control of the resonator. Control is verified to maintain -20dB attenuating of pressure pulsations in the system. The presented Helmholtz resonator and controls are available for installation into a hydraulic system to damp out harmonic vibrations at low frequency. For example, the roll in the size press of a paper machine might become excited to vibrate at its resonance frequency after the paper wad has washed through the nip. In that case, tuned Helmholtz resonators in the hydraulic cylinders of the size press would damp out the pulsating pressures, and if the resonators are adaptive, as presented in this study, they can operate in a wider frequency range.

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16

Thompson, Evan J. "Hydraulics of IDEal Drip Irrigation Systems." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/296.

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The hydraulics of IDEal drip irrigation system components were analyzed under controlled laboratory conditions and the results can be applied to the design of IDEal systems. The hydraulic loss coefficient for the lateral-submain connector valves was determined based on laboratory measurements. It was found that the hydraulic loss due to friction in the lay-flat laterals can be accurately estimated with standard friction loss equations using a smaller effective diameter based on the wall thickness and inlet pressure head. The equivalent length barb loss, expressed as an equivalent length of lateral, was calculated for button emitters, as well as for micro-tubes inserted to lengths of 5 and 10 cm. It was concluded that the barb loss is essentially constant over the micro-tube insertion range of 5-10 cm. The head-discharge relationship and coefficient of manufacturer's variation of pre-punched lateral holes (without emitters), button emitters, and micro-tubes were characterized. Finally, several IDEal drip irrigation systems in the Central Rift Valley of Ethiopia were evaluated in the field. Recommendations were given for future research and improvements in the manufacturing, installation, operation, and maintenance of IDEal drip irrigation equipment.

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17

Fangmeier, D. D., and S. H. Husman. "Evaluation of a Low Pressure, Linear Move Irrigation System for Cotton." College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/204072.

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18

Krepak, Dariia Ihorivna. "Decision making in emergency situation of air navigation system’s operator: low oil pressure." Thesis, Національний авіаційний університет, 2020. http://er.nau.edu.ua/handle/NAU/41873.

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Робота публікується згідно наказу ректора від 21.01.2020 р. №008/од "Про перевірку кваліфікаційних робіт на академічний плагіат 2019-2020р.р. навчальному році" . Керівник проекту: професор, д.т.н. Шмельова Тетяна Федорівна
Air navigation system can be considered as a complex system with multiple composite parts or subsystems that constantly interact with each other, e.g.: – Airspace users (AU); – Air navigation service providers (ANSP); – Airports; – Network Manager (NM). Due to growing demand in air transportation, the complexity of the systems and load on it increases constantly. However, at the same time, the requirements for the level of safety, security remains the same. In order to meet the required levels of safety, there is a need for supporting systems that would support operators (e.g. flight crew, air traffic controller, etc.) of air navigation systems in making decision in day-to-day operations. That’s why the decision support systems became widely used in the air navigation systems to support the human operators. They are aimed at helping and supporting decision making processes or human operators in air transportation sphere and allow them to select the best decision in conditions of limited time or uncertainty. The wide introduction of decision support systems in air navigation will contribute to the optimisation of human operator work which will lead to an increase in operational efficiency and safety. One of the components that negatively contribute to the safety of flights are human errors that could lead to emergency situations and later on to incidents or accidents. The emergency situation of low oil pressure is a serious issue for both flight crew and air traffic controller and possess a threat to the flight safety due to its nature. It can lead to serious incidents and accidents and due to the type of the issue it is close to impossible to eliminate it. However, it is possible to provide all necessary means to support decision making of a human operator (e.g. air traffic controller) to ensure that correct and safe decisions are taken by the operator to resolve an emergency situation.

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19

Peng, Xiong. "Aircraft environmental control systems modeling for configuration selection." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8471.

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According to the statistics about civil transportation aircraft Environmental Control system (ECS), the three-wheel high pressure water separation system (HPWS) and low pressure water separation system (LPWS) are the most common choices for the 150-seat airliners. Although the former has become the mainstream configuration for air conditioning pack, the latter is still used on Boeing 737-600/700. In order to compare the two configurations and choose the better one for a specific aircraft, simulation and analysis are done. The cabin heat load is calculated at first in order to calculate required engine bleed air mass flow. Then a specific aircraft is defined so that required structural dimensions and cabin comfort indexes can be obtained based on Airbus 320. Thirdly, the component models are built by Matlab/Simulink according to the fundamental knowledge of heat transfer and aerodynamics, the working principles and mechanical dimensions of the components, the ambient environmental parameters and some data from Airbus 320. Consequently, the complete system model can be assembled. After confirming the validity of the model by checking the required ram air mass flow and temperature deviation of the state points referred to Airbus 320, the simulation model is used to do analyze the specific aircraft. Finally, through comparing the different values of ram air mass flow and turbine expansion ratio, as well as the system mass, economic cost and reliability, the better configuration is selected. It can be summarized that the three-wheel LPWS requires less ram air mass flow (0.012kg/s) and a little lower expansion ratio (0.02) than the HPWS, and it also has lower weight (63% of HPWS), lower (83% of HPWS) cost and higher reliability (140% of HPWS), thus it is the suitable configuration for the specific aircraft.

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20

Miclea, Corneliu Florin. "Investigation of superconducting order parameters in heavy-fermion and low-dimensional metallic systems under pressure." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1153315149468-90260.

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The understanding of new emerging unconventional ground states is a great challenge for experimental and theoretical solid-state physicists. New ground states are developing, where different energy scales compete, leading to a high sensitivity of the system to external tuning parameters like doping, pressure or magnetic field. The exploration of superconductivity proved to be a fascinating and challenging scientific undertaking. Discovered by H. Kammerlingh Onnes in 1911, prior to the development of the quantum theory of matter, superconductivity was defying a microscopic theory for more than four decades until the BCS theory was formulated in 1957 by J. Bardeen, L. N. Cooper and J. R. Schrieffer. Superconductivity of most of the simple metals or metallic alloys is well described within the frame of the BCS scenario, however, in the last thirty years numerous new superconducting materials were found to exhibit exotic properties not accounted for by the BCS theory. Among them are included the high-Tc compounds, the heavy-fermion superconductors and as well the organic superconductors. It was the purpose of this work to probe different facets of superconductivity in heavy-fermion and in low-dimensional metallic compounds. This dissertation is divided into six chapters. After this introduction, in Chapter 1 we will outline the basic theoretical concepts later needed for the analysis of the experimental results. In Chapter 2 we briefly introduce the experimental techniques with a special focus on the new pressure cells developed during this thesis and used for the measurements presented in Chapters 3 to 5. In Chapter 3 the possible realization of the inhomogeneous superconducting FFLO state in CeCoIn5 is studied by specific heat measurements under hydrostatic pressure, while in Chapter 4 the results of AC specific heat experiments on UBe13 under uniaxial pressure are presented. The ambient pressure properties as well as results obtained by resistivity measurements under hydrostatic pressure on the one-dimensional metallic compounds TlxV6S8 are discussed in Chapter 5. At the end, Chapter 6 summarizes and concludes this thesis.

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21

Campbell, Quentin Peter. "Dewatering of fine coal with flowing air using low pressure drop systems / Quentin Peter Campbell." Thesis, North-West University, 2006. http://hdl.handle.net/10394/1075.

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Successful dewatering and filtration of coal fines remain the major obstacles in preventing the extensive re-use of large reserves of high calorific quality coal fines as an additional energy source in South Africa. The high levels of final moisture in coal fines make it uneconomical to transport, handle and use. The industry is rapidly reaching the limit of current technology of mechanical dewatering; this limit is defined by fundamental coal properties, like amongst others, particle size, porosity and mineral content. This thesis describes research investigating a shift in approach from high vacuum or pressure systems, to high air flow systems. Results from various projects at laboratory scale showed that it was possible to decrease the fine coal filter cake moisture to as low as 15%. This was obtained by allowing air to flow freely through a filter cake, even at ambient temperatures, and replacing the necessity for high applied vacuum levels. There was also an increase in the dewatering rate, as well as a lower breakthrough pressure. Such an approach can utilise existing equipment with minor modifications. Other investigations showed that forced air-drying, both at ambient and elevated temperatures, could be used to overcome this mechanical limit. Again, an increased air flow rate at ambient pressure was used. Using air drying, moisture levels down to zero were possible. These investigations led to the conclusion that increased air flow through a fine coal cake was more advantageous than an increase in the applied vacuum, or a longer dewatering time. This new approach to lowering the final moisture content in coal fines is crucial in any advancement of the use of this largely untapped energy source.
Thesis (Ph.D. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2006.

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22

Miclea, Corneliu Florin. "Investigation of superconducting order parameters in heavy fermion and low dimensional metallic systems under pressure." Doctoral thesis, Göttingen Cuvillier, 2005. http://d-nb.info/990426440/04.

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23

Ghavam-Nasiri, Ali. "Thermo-Hydro-Mechanical Behaviour of Composite Geosynthetic Lining Systems under High Temperature and Low Pressure." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17782.

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Aim. Composite geosynthetic clay lining systems (CGCLS), a combination of high density polyethylene geomembranes and geosynthetic clay liners (GCLs), have been used in brine ponds to manage the large amount of waste water produced by coal seam gas extraction. Exposure to sunlight combined with the thermal properties of brine water can lead to temperatures of up to 85-95°C at the liner. The goal of the thesis is to investigate whether GCLs may desiccate in engineering applications with high temperatures and low overburden loads. Methodology. A multi-phase, thermo-hydro-elastic theory of soil behaviour is first adopted to the study of desiccation of GCLs. The theory has been implemented in a computer simulation environment (CODE_BRIGHT). Next, the dependence of the GCL’s soil-water chararcteristic curve (SWCC) on temperature and overburden load are characterised experimentally and new forms of the SWCC equations are developed. A set of column studies are conducted. The aims of the column studies are to assess whether desiccation of bentonite occurs and to generate experimental data that can be used to validate the above-mentioned theory. Findings. The new developed SWCCs perform well in predicting the effects of void ratio on SWCC based on the available data. A non-linear thermo-hydro-elastic theory is found to be capable of replicating the observed change in time of temperature and water contents in the subsoil with reasonable accuracy, even with minimal back-fitting of data and independent determination of material properties of both GCLs and subsoil. The thesis has established experimentally, for the first time, that GCLs in composite liners, subject to surface temperatures of 78°C and overburden loads of 20kPa, may experience high levels of desiccation cracking. The findings of this thesis call for caution in using the type of GCL studied here in applications in which they are exposed to temperatures higher than 60°C.

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24

Reifarth, Simon. "Efficiency and Mixing Analysis of EGR-Systems for Diesel Engines." Doctoral thesis, KTH, Förbränningsmotorteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-140850.

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The reduction of fuel consumption and the reduction of toxic emissions are the main goals of research and development in the area of internal combustion engines. The use of exhaust gas recirculation (EGR) to come further in that direction is today an established method for diesel engines. EGR reduces the emissions of nitrogen oxides with a low penalty in fuel consumption. The increasingly hard regulations on emissions put high pressure on the manufacturers to improve these systems. The present work aims at increasing the knowledge in the area of EGR. Two of the main challenges when applying EGR are addressed, efficiency and mixing. The efficiency of the EGR-system is analyzed, focusing on keeping the fuel penalty low for a given EGR-rate. Different layouts of the EGR system are studied and compared regarding their stationary and transient properties. Exergy analysis is used to show the potential for improvement in different system components. In the same time, exergy analysis as a tool is introduced and compared to energy analysis of a system. The usefulness of exergy analysis of the entire gas exchange is shown by the example of a heavy-duty diesel engine. The problem of EGR and air mixing is approached by a detailed study of the mixing process in a heavy-duty diesel engine. Different methods for the measurement of EGR distribution are presented and compared. Additionally, the possibility to predict the mixing effects by 1-D and 3-D simulation is assessed. It is shown that the mixing between air and EGR is highly dependent on the pulsating nature of the flow. The EGR is shown to be transported in packets in the air flow. This leads to the conclusion that mixing not only at the mixing point, but also mixing in flow direction needs to be optimized, as the distribution of EGR between the cylinders is dependent on the timing between the passage of the EGR packets and the valve opening time.

QC 20140203

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25

DiPaola, Tracey Stickley. "Biological and Chemical Renovation of Wastewater with a Soil Infiltrator Low-Pressure Distribution System." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36809.

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An alternative on-site wastewater treatment and disposal system (OSWTDS) consisting of a soil infiltrator with low pressure distribution was evaluated in a soil that was unsuitable for a conventional OSWTDS under current Commonwealth of Virginia Sewage Handling and Disposal Regulations, due to a shallow seasonally perched water table and low hydraulic conductivity. The absorption field consisted of two subsystems numbered as 1 and 2 with effluent design loading rates of 5.1 and 10.2 Lpd/m2, respectively (actual loading rates of 2.4 and 4.9 Lpd/m2, respectively). Soil matric potentials compared seasonally for each subsystem and indicated that both provided similar hydraulic performance. Background water quality was generally improved by subsurface movement through the absorption fields. A bacterial tracer was found in shallow (45.7 cm) and deep (213.4 cm) sampling wells within 24 h in the two subsystems (but in low numbers) over both summer and winter sampling periods. A viral tracer was detected within 48 h in both shallow and deep wells, but only in subsystem 2 in the winter. In evaluating denitrification potential, the addition of glucose to soil core samples did increase quantitatively, although not significantly, nitrous oxide production in each subsystem, at each depth, during each season. Overall, the performance of both subsystems was very similar. The soil infiltrator functioned very well, as designed for the site and soil limitations. It appears to be a potential alternative OSWTDS for use in problem soils.
Master of Science

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26

Weller, Matthias. "NMR NQR studies at very low temperatures and high pressures in strongly correlated electron systems." kostenfrei, 2007. http://e-collection.ethbib.ethz.ch/view/eth:30167.

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27

Ijzerman, M. Marian. "Evaluation of shallow-placed low pressure distribution systems in soils marginally suited for on-site waste treatment." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03242009-040620/.

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28

Starbuck, J. M. "Tribological evaluation of dual lubricant condition-bearing materials for use in low pressure aerospace fuel pump systems." Thesis, University of Portsmouth, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271449.

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29

Lui, Samson Sze-Sang. "A Data Acquisition System Experiment for Gas Temperature and Pressure Measurements on a Liquid-Nitrogen-Powered Vehicle." Thesis, University of North Texas, 1998. https://digital.library.unt.edu/ark:/67531/metadc278790/.

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A data acquisition system was set up to measure gas temperatures and pressures at various points on a liquid-nitrogen-powered vehicle. The experiment was attempted to develop a data acquisition method for applications on engines that use liquid air as the fuel. Two thermocouples and a pressure transducer were connected using data acquisition instruments interfaced to a laptop computer to acquire data.

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30

Liu, Congrui. "Wearable Fall Detection using Barometric Pressure Sensor." Thesis, Mittuniversitetet, Avdelningen för elektronikkonstruktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-29968.

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Wearable wireless sensor devices, which are implemented by deploying sensor nodes on objects, are widely utilized in a broad field of applica-tions, especially in the healthcare system for improving the quality of life or monitoring different types of physical data from the observed objects. The aim of this study is to design an in-home, small-size and long-term wearable fall detection system in wireless network by using barometric pressure sensing for elderly or patient who needs healthcare monitoring. This threshold-based fall detection system is to measure the altitude of different positions on the human body, and detect the fall event from that altitude information. As a surveillance system, it would trigger an alert when the fall event occurs so that to protect people from the potential life risk by immediate rescue and treatment. After all the performances evaluation, the measurement result shows that standing, sitting and fall state was detected with 100% accuracy and lying on bed state was detected with 93.3% accuracy by using this wireless fall detection system. Furthermore, this system with low power consumption on battery-node can operate continuously up to 150 days.

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31

Volkert, Marcus [Verfasser], and Dietrich [Akademischer Betreuer] Knorr. "High pressure-low temperature induced structures in dairy foams and protein model systems / Marcus Volkert. Betreuer: Dietrich Knorr." Berlin : Technische Universität Berlin, 2009. http://d-nb.info/1066160333/34.

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32

Bykov, Maxim [Verfasser], and Sander van [Akademischer Betreuer] Smaalen. "Structural aspects of pressure- and temperature-induced phase transitions in low-dimensional systems / Maxim Bykov. Betreuer: Sander van Smaalen." Bayreuth : Universität Bayreuth, 2015. http://d-nb.info/1073201945/34.

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33

Schneider, Marius [Verfasser]. "Robust aero-thermal design of high pressure turbines at uncertain exit conditions of low-emission combustion systems / Marius Schneider." Düren : Shaker, 2019. http://d-nb.info/119859974X/34.

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34

Caudill, Landon S. "PRESSURE-DRIVEN STABILIZATION OF CAPACITIVE DEIONIZATION." UKnowledge, 2018. https://uknowledge.uky.edu/me_etds/113.

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The effects of system pressure on the performance stability of flow-through capacitive deionization (CDI) cells was investigated. Initial data showed that the highly porous carbon electrodes possessed air/oxygen in the micropores, and the increased system pressure boosts the gases solubility in saline solution and carries them out of the cell in the effluent. Upon applying a potential difference to the electrodes, capacitive-based ion adsorption occurs in competition with faradaic reactions that consume oxygen. Through the addition of backpressure, the rate of degradation decreases, allowing the cell to maintain its salt adsorption capacity (SAC) longer. The removal of oxygen from the pore space of the electrodes makes it no longer immediately accessible to faradaic reactions, thus hindering the rate of reactions and giving the competing ion adsorption an advantage that is progressively seen throughout the life of the cell. A quick calculation shows that the energy penalty to power the pump is fairly insignificant, especially in comparison to the cost of replacing the electrodes in the cell. Thus, operating at elevated pressures is shown to be cost effective for continuous operation through the reduced electrode replenishment costs.

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35

Svindland, Richard C. "PREDICTING THE LOCATION AND DURATION OF TRANSIENT INDUCED LOW OR NEGATIVE PRESSURES WITHIN A LARGE WATER DISTRIBUTION SYSTEM." UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_theses/214.

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Surge modeling is a tool used by engineers and utility owners in determining the surge pressures or transients that may result from routine pump and valve operations. Recent surge modeling work has focused on low and/or negative pressures within water distribution systems and how those occurrences could lead to intrusions. Effective surge modeling is needed in order to determine if the intrusion potential exists and what mitigation is needed to prevent intrusions. This work focuses on the generally unexplored area of using surge models to predict the location and duration of transient induced low and/or negative pressures within large complex water distribution systems. The studied system serves 350,000 people in the southeast United States, has 65 MGD of pumping capacity at two treatment plants, over 1500 miles of main and 12 storage tanks. This work focuses on the correlation between field data and the surge model using the author's extensive operational knowledge of the system, access to real-time SCADA data, and different celerity or wave speed values. This work also traces the steps taken by the author to locate areas within the system that experienced transient induced low and / or negative pressure.

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36

Christou, Ilias. "Optimisation of high voltage electrical systems for aerospace applications." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/optimisation-of-high-voltage-electrical-systems-for-aerospace-applications(9b8c70c0-7c82-4191-9199-bb05360f1b40).html.

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Increased electrical power demands are being experienced on the new generation of aircraft due to an increased reliance on electrical technology of systems such as air conditioning, de-icing systems and electrical flight control actuation. Distribution of power at higher AC and DC voltages is therefore now being seen in modern aircraft to avoid the penalties incurred due to high cable weights. Voltages have increased past the minimum of Paschen's law resulting in a risk that life limiting partial discharge (PD) damage can occur in the insulation systems. This thesis uses a theoretical analysis backed by PD experimental results to investigate the optimal operating voltage of a cabling system. In addition, it proposes a methodology for optimizing the operating voltage level based on an analysis of the power carrying capability of cabling within a fixed and a non-fixed volume system and the derivation of the cable weight as a function of voltage. Furthermore the power carrying capability of a certain round cable system is compared with an insulated flat conductor system as in a printed circuit board (PCB). An initial assessment has been carried out to determine whether more power can be delivered via insulated flat solid conductors as in a PCB, instead of using round cables. The reason why there is a need to investigate this aspect, is because using new PCB technology can offer several advantages over traditional cabling harnesses. The work done has shown that the optimal operating point (e.g. maximum power to weight ratio) for an aircraft power system, does not improve after certain voltage levels. A tradeoff between cable weight and power transfer is required and furthermore the use of DC systems can result in higher power transfers than conventional three phase/400Hz AC systems. The PCB maximum power transfer assessment has also shown that insulated flat conductor systems can offer higher power transfer efficiencies. In addition, experimental AC and DC PD tests on certain unscreened aerospace cables (laid out in different configurations), have shown that the theoretical analysis employed to determine cable safe operating voltages gives conservative results.

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37

Prenzlow, Bjorn. "Design of a low pressure system to determine the acoustic nonlinearity parameter B/A for small volumes of sample liquids." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/5122.

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Includes bibliographical references.
This thesis aimed to design a measurement system to obtain B/A readings for different liquids using the isentropic phase method. The resulting system uses a sinusoidal wave source that operates on less than 20kPa to pressurize a sample liquid of less than 0.2 ml. The advantage of the system is that it can obtain measurements using relatively few parameters of the liquid, requiring only density and sound speed, and that it can obtain a result in a relatively short amount of time (less than 15 minutes after system has reached thermal equilibrium).

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38

Sauer, Patrick. "Liberation of low molecular weight organic acids from sedimentary organic matter and their role on microbial activity." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2013/6883/.

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Low molecular weight organic acids (LMWOAs) are important nutrients for microbes. However, most LMWOAs do not exist freely in the environment but are bound to macromolecular organic matter, e.g. kerogen, lignite and coal. During burial and geological maturation of sedimentary macromolecular organic matter biological and abiological processes promote the liberation of LMWOAs into the surrounding sediment. Through this process, microbes in sedimentary subsurface environments are supplied with essential nutrients. To estimate the feedstock potential of buried macromolecular organic matter to many environments it is important to determine the amount of LMWOAs that are bound to such a matrix. However, high-pressure and high temperature are a key feature of deep subsurface environments, and these physical parameters have a profound influence on chemical reaction kinetics. Therefore it is essential for the estimation of the feedstock potential to generate high-pressure and high temperature for the liberation of LMWOAs to recreate true in-situ conditions. This work presents a newly developed, inexpensive incubation system for biological and geological samples. It allows the application of high-pressure and high temperature as well as a subsampling of the liquid phase without loss of pressure, thereby not disturbing the on-going processes. When simulating the liberation of LMWOAs from sedimentary organic matter, the newly developed incubation system produces more realistic results than other extraction systems like Soxhlet. The extraction products remain in the extraction medium throughout the extraction, influencing the chemical conditions of the extraction medium. Sub-bituminous coal samples from New Zealand as well as lignite samples from Germany were extracted at elevated temperature (90˚C) and pressure (5 MPa). The main LMWOAs released from these low rank coals were formate, acetate and oxalate. Extraction efficiency was increased by two to four times for formate, acetate and oxalate in comparison to existing extraction methods without pressurisation and with demineralised water. This shows the importance of pressure for the simulation of true in-situ conditions and suggests that the amount of bioavailable LMWOAs is higher than previously thought. With the increase in carbon capture and storage (CCS) and the enhanced recovery of oil and gas (EOR/EGR), more and more CO2 becomes injected into the underground. However, the effects of elevated concentrations of carbon dioxide on sedimentary organic matter are rarely investigated. As the incuabtion system allows the manipulation of the composition and partial pressure of dissolved gasses, the effect of highly gas-enriched (CO2, CO2/SO2, CO2/NO2; to simulate flue gas conditions) waters on the extraction yield of LMWOAs from macromolecular organic matter was evaluated. For sub-bituminous coal the concentrations of all LMWAOs decreased upon the addition of gas, irrespective of its composition, whereas for lignite formate always and acetate mostly increased, while oxalate decreased. This suggests an positive effect on the nutrient supply for the subsurface microbiota of lignite layers, as formate and acetate are the most common LMWOAs used for microbial metabolism. In terrestrial mud volcanoes (TMVs), sedimentary material is rapidly ascending from great depth to the surface. Therefore LMWOAs that were produced from buried macromolecular organic matter at depth are also brought up to the surface, and fuel heterotrophic microbial ecosystems at the surface. TMVs represent geochemically and microbiologically diverse habitats, which are supplied with organic substrates and electron acceptors from deep-seated hydrocarbon-generating systems and intersected shallow aquifers, respectively. The main electron donor in TMVs in Azerbaijan is sulphate, and microbial sulphate reduction leads to the production of a wide range of reduced sulphur species that are key players in several biological processes. In our study we estimated the effect of LMWOAs on the sulphur metabolising activity of microorganims in TMVs from Azerbaijan. The addition of a mixture of volatile fatty acids containing acetate and other LMWOAs showed significant positive response to the sulphate reduction rate (SRR) of samples of several mud volcanoes. Further investigations on the temperature dependency of the SRR and the characterisation of thermophilic sulphate-reducing bacteria (SRB) showed a connection between the deep hot subsurface and the surface.
Niedermolekulare organische Säuren (nachfolgend als LMWOAs - low molecular weight organic acids - bezeichnet) stellen wichtige mikrobielle Substrate dar. Jedoch liegen die meisten LMWOAs nicht in freier, bioverfügbarer Form vor, sondern sind vielmehr an hochmolekulare organische Substanzen gebunden, z.B. Kerogen, Lignit und Kohle. Während der geologischen Verbringung in tiefe Erdschichten und der geologischen Reifung von sedimentären hochmolekularen organischen Substanzen, führen biologische und abiologische Prozesse zu einer Freisetzung von LMWOAs in die umgebenden Sedimente. Durch diesen Prozess werden Mikroorganismen in unterirdischen sedimentären Ökosystemen mit essentiellen Nährstoffen versorgt. Um das Nährstoffpotential tief liegender hochmolekularer organischer Substanzen für diverse Ökosystemen abschätzen zu können, ist es notwendig, die Menge an LMWOAs, die an solch eine hochmolekulare Matrix gebunden ist, zu bestimmen. Dabei stellen hoher Druck sowie hohe Temperatur entscheidende Faktoren in tiefen unterirdischen Ökosystemen dar, welche einen signifikanten Einfluss auf chemische Reaktionen haben. Daher ist es für die Abschätzung des Nährstoffpotentials entscheidend, hohen Druck und hohe Temperatur bei der Freisetzung von LMWOAs zu erzeugen, um wahre in situ Bedingungen zu schaffen. In der vorliegenden Arbeit wird ein neu entwickeltes, preiswertes Inkubationssystem für biologische und geologische Proben präsentiert. Es erlaubt die Verwendung von hohem Druck als auch hoher Temperatur sowie eine Unterprobennahme der flüssigen Phase ohne Druckverlust, um den fortlaufende Prozess nicht zu unterbrechen. Bei der Simulierung der Freisetzung von LMWOAs aus sedimentären organischen Substanzen erhält man mit dem neu entwickelten Inkubationssystem realistischere Resultate als mit anderen Extraktionssystemen, wie z.B. eine Soxhlet-Apparatur. Die Extraktionsprodukte verbleiben während der Extraktion im Extraktionsmedium, wodurch die chemischen Bedingungen verändert werden. Kohleproben aus Neuseeland sowie aus Deutschland wurden mittels erhöhter Temperatur (90°C) und Druck (5 MPa) extrahiert. Die wichtigsten LMWOAs, die aus diesen Kohlen freigesetzt wurden, waren Formiat, Acetat und Oxalat. Die Extraktionseffizienz für diese LMWOAs konnte im Vergleich zu existierenden Extraktionsmethoden ohne Druck um den Faktor 2 bis 4 gesteigert werden. Dies zeigt die Bedeutung von Druck bei der Simulation von in situ Bedingungen und legt nahe, dass die Menge an bioverfügbaren LMWOAs größer ist als bisher angenommen. Durch die Zunahme der CO2-Speicherung im Untergrund (carbon capture and storage, CCS) sowie der erweiterten Förderung von Öl und Gas (enhanced recovery of oil and gas, EOR/EGR) wird immer mehr CO2 in den Untergrund gepresst. Jedoch sind die Auswirkungen von erhöhten CO2-Konzentrationen auf sedimentäre organische Materie noch unerforscht. Da mit dem Inkubationssystem die Veränderung der Zusammensetzung und des Partialdruckes von gelösten Gasen möglich ist, wurde der Effekt von hoch mit Gasen (CO2, CO2/SO2, CO2/NO2; um Kraftwerksabgase zu simulieren) angereicherten Wässern auf die Extraktionsausbeute von LMWOAs untersucht. Bei der subbituminösen Kohle zeigte sich eine Abnahme aller LMWOAs-Konzentrationen durch die Lösung von Gas im Extraktionsmedium, wobei die Art des Gases keine Rolle spielte. Bei Lignit konnte hingegen festgestellt werden, dass die Extraktionsausbeute an Formiat immer und an Acetat meistens erhöht wurde, während sie sich bei Oxalat verringerte. Dies deutet auf einen positiven Effekt für die Nährstoffversorgung von Mikroorganismen um Lignit-Lagerstätten an, da Formiat und Acetat die am häufigsten verwendeten LMWOAs im mikrobiellen Stoffwechsel darstellen. In terrestrischen Schlammvulkanen (terrestrial mud volcanoes, TMVs) steigt sedimentäres Material aus großen Tiefen an die Erdoberfläche. Somit werden auch LMWOAs, welche aus hochmolekularen organischen Substanzen freigesetzt werden, an die Oberfläche verbracht, und ermöglichen dort heterotrophe Ökosysteme. TMVs stellen dabei geochemisch und mikrobiell unterschiedliche Habitate dar, welche mit organischen Substraten und Elektronenakzeptoren aus tief liegenden, Kohlenwasserstoffe erzeugenden Systemen versorgt werden. In TMVs in Aserbaidschan stellt Sulfat den Hauptelektronenakzeptor dar, wobei mikrobielle Sulfatreduktion zu einer Vielzahl an reduzierten Schwefelspezies führt. In der vorliegenden Arbeit wurde der Effekt von LMWOAs auf die Aktivität von Mikroorganismen bei der Umsetzung von Schwefel in TMVs in Aserbaidschan untersucht. Die Zugabe einer Mischung verschiedener kurzkettiger Fettsäuren zu Schlammproben verschiedener TMVs erzeugte eine signifikant positive Reaktion in Bezug auf die Sulfat-Reduktionsraten. Weiterführende Untersuchungen zur Temperaturabhängigkeit der Sulfat-Reduktionsraten und die Charakterisierung thermophiler, Sulfat-Reduzierender Bakterien zeigte eine Verbindung zwischen der tiefen, heißen Biosphäre und der Erdoberfläche auf.

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39

Alge, Daniele. "Pressures to plead guilty or playing the system? : an exploration of the causes of cracked trials." Thesis, University of Manchester, 2009. http://repository.uwl.ac.uk/id/eprint/2367/.

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This thesis is an empirical exploration of cracked trials at Manchester Minshull Street Crown Court. Cracked trials are cases which are listed for trial but on the day they are due to be tried are disposed of in some other way. The thesis presents quantitative and qualitative data extracted from prosecution case files, as well as interviews with legal professionals, to examine the reasons for cracked trials, focusing on those trials which crack as a result of a late guilty plea. The data are analysed in order to explore the features of cracked trials, and the defence lawyer’s role in late guilty pleas (identified as significant by previous studies) is also examined. The existing literature has identified plea bargaining as a significant cause of late guilty pleas; the extent to which this was a feature within the sampled cases is assessed, and the nature of the plea bargains which were present in the data is explored. It is argued that the data demonstrate that plea bargaining played a key role in those cases which cracked as a result of a late guilty plea and that several types of plea bargain were prevalent within the sample. In light of these findings, the thesis analyses the reasons for the criminal justice system’s reluctance to acknowledge the role of plea bargaining in cracked trials (despite some recent formalisation of plea bargaining itself), and examines the extent to which grounds for policy and academic objections to plea bargaining and cracked trials were evidenced in the data collected. The thesis then considers whether either policy objections (that cracked trials represent defendants ‘playing the system’) or academic objections, (that plea bargains create pressure on defendants to plead guilty, and cracked trials are a manifestation of that pressure) are necessarily true, and whether plea bargaining could alternatively be viewed as a legitimate consensual or contractual exchange of concessions. The thesis concludes with the argument that a contradictory and hypocritical approach to plea bargaining has created a situation whereby the significance of plea bargaining is often ignored by a criminal justice system which has come to rely upon it. It is argued that the policies pursued in an attempt to reduce cracked trials are therefore flawed in their failure to acknowledge that cracked trials are inextricably bound together with plea bargaining.

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40

Omara, Abdelaziz Ibrahim Abdelaziz Aly [Mitwirkender]. "Further development of a mobile wind energy plant for a low pressure irrigation system / FAL, Bundesforschungsanstalt für Landwirtschaft. Abdelaziz Ibrahim Abdelaziz Aly Omara." Braunschweig : FAL, 2004. http://d-nb.info/98179582X/34.

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41

Donovan, Molly Hope. "Unsteady Effects of a Pulsed Blowing System on an Endwall Vortex." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1559398697459176.

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42

Abadie, Cédric. "On-line non-intrusive partial discharges detection in aeronautical systems." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30041/document.

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L'évolution de l'électronique de puissance ces dernières années a entraîné une augmentation de la densité de puissance et une diminution du coût des onduleurs de tension à modulation de largeur d'impulsion (MLI). Ces évolutions ont répandu l'utilisation de convertisseurs de puissance pour les applications de variateurs de vitesse ce qui a permis le développement du concept d' " avion plus électrique ". Ce concept consiste à remplacer un des vecteurs énergétiques (pneumatique ou hydraulique) par l'énergie électrique. Cependant, le développement du réseau électrique a entraîné une augmentation de la tension embarquée, ce qui a conduit à un vieillissement prématuré des équipements électriques embarqués. La forme de tension appliquée, appelée "modulation de largeur d'impulsion" (MLI), est constituée de trains d'impulsions. Avec l'application de ces impulsions, la tension n'est plus distribuée de manière homogène le long du bobinage. Dans ce cas, on pourra observer d'importantes différences de potentiel entre les spires d'une même phase voire entre deux phases du bobinage. En outre, un autre paramètre important provient du type d'enroulement des moteurs utilisés par l'industrie. L'enroulement aléatoire est la technique de bobinage la plus courante pour les moteurs basses tensions car cette méthode présente un faible coût. Le risque induit par ce type d'enroulement est que la première et une des dernières spires de la première bobine peuvent être proches l'une de l'autre. Dans ce cas, jusqu'à 80% de la tension sera supportée par quelques dizaines de microns d'émail, et les systèmes d'isolation existants ne sont pas dimensionnés pour résister à de telles contraintes. L'utilisation de longs câbles reliant l'onduleur au moteur peut aussi provoquer des surtensions importantes aux bornes du moteur. Ce phénomène s'explique par le fait que le câble se comporte comme une ligne de transmission qui n'est pas adaptée en termes d'impédance au bobinage du moteur. De plus, ces importantes différences de potentiel associées à de faibles pressions, présentes dans les zones dépressurisées de l'aéronef, peuvent entraîner l'apparition de décharges partielles. Les décharges partielles sont des décharges électriques qui court-circuitent partiellement l'intervalle entre deux conducteurs. Il existe de nombreuses méthodes de détection bien connues pour les tensions AC et DC, cependant, la détection sous tension de type MLI dans des moteurs basse tension est beaucoup plus complexe. Les signaux de décharge partielle sont en effet intégrés dans le bruit électromagnétique généré par la commutation. Le but de cette thèse est donc de développer un procédé de détection et un procédé de filtrage permettant une détection non intrusive et en fonctionnement (on-line) des décharges partielles dans le domaine aéronautique afin de qualifier les systèmes d'isolation électrique utilisés dans les aéronefs
The development of power electronics in recent years has led to increase power density and to decrease pulse width modulation (PWM) voltage inverter cost. These developments have expanded the use of power converters for variable speed drive applications which enabled the development of the concept of "more electric aircraft". This concept consists in replacing one of energy carriers (pneumatic or hydraulic) with electrical energy. However, the deployment of electrical energy has increased the onboard voltage, which leads to premature aging of onboard electrical equipment. The shape of the PWM voltage consists of pulse trains. With the application of these pulses, the voltage is no longer homogeneously distributed along the coil. In this case, large differences in potential between the strands are present. In addition, another important parameter derived from the winding type motor used in industry. The random winding is the most common technique for low voltage motors due to its lower cost. The risk generated by this type of winding is that the first and the last turns of the first coil can be facing one another. In this case, up to 80% of the voltage will be supported by a few tens of microns of enamel, and existing insulation systems are not designed to withstand such severe constraints. The use of long cable connecting the inverter to the motor can also cause significant overvoltage at the motor terminals. This phenomenon is explained by the fact that the cable behaves as a transmission line to which the motor coils is not adapted in terms of impedance. In addition, these large potential differences associated with low pressures in the depressurized areas of the aircraft, may cause the occurrence of partial discharge. Partial discharges are electrical discharges that short-circuited partially the gap between two conductors. There are many detection methods well known under AC and DC voltage, however, in the case of the detection under PWM like voltage in low-voltage motors, the detection is much more complex. Partial discharge signals are embedded in the electromagnetic noise generated by the switching. The aim of this thesis is to develop a detection method and filtering method enabling a non-intrusive and an "on-line" partial discharges detection in the aeronautical field in order to qualify the electrical insulation systems used in aircraft

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43

Zea, Luis. "EXPERIMENTAL ANALYSIS OF THE HYDROGEN SULFIDE ABSORTION PHENOMENA IN BRINE/OIL MIXTURES AS A FUNCTION OF SYSTEM PRESSURE AND H2S." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3053.

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In underground oil reservoirs, Hydrogen sulfide is usually found coexisting with the oil due to bacteria reduction over a long period of time. The amount of H2S in the oil varies from place to place around the globe. When the oil extraction process begins, the presence of Hydrogen sulfide becomes noticeable as drilling tools, piping and other equipment suffer from sulfide stress cracking, electrochemical corrosion and corrosion fatigue. For this reason, the oil industry invests millions of dollars per year trying to find better ways to reduce the amount of H2S in oil. An important part of the current investigations deals with brine (sea water)/oil mixtures. The reasons are two-fold: 1) one way of extracting the petroleum from the reservoir is by injecting brine into it and since it has a higher density than oil, the latter will be ejected up to the surface. Taking into account the complex fluid flow occurring within the reservoir it is easy to understand that some brine will also be present as part of the ejected fluid; 2) brine is already present in the reservoir, so independent of the extraction method used, there will be a brine/oil mixture in the ejected flow. When brine and oil have absorbed H2S under pressure in the reservoir and then suffer a decompression during the extraction process, a certain amount of H2S is released from the liquid phase. In order to have a better prediction of how much Hydrogen sulfide can be liberated a good understanding of H2S absorption by these liquids is necessary. The amount of gas a solvent absorbs is a function of pressure, original gas concentration and temperature as described by Henry's Law. The purpose of this thesis is to experimentally analyze how much of the corrosive gas is absorbed into different brine/oil mixtures, and brine and oil, separately. In order to find sufficient data for a thorough analysis, different reservoir simulation scenarios were created. The liquids were mixed from pure brine to pure oil, resulting in 33% and 66% water cuts. Data were obtained at 2 pressures of 20atm and 70atm at room temperature. H2S concentration was also a variable, changing the original gas concentration through different values: 50, 100, and 300ppm. These experiments were conducted in an autoclave system and will better explain the hydrostatic process that occurs inside the reservoir. It was found that throughout all the water cuts, the role that total pressure plays in the absorption phenomena is of less importance as the original H2S concentration is increased. In the same manner it was observed that the highest mass-absorption ratios are always found between 50 and 100ppm and the lowest at 300ppm, this is observed for all water cuts and total pressures. Another important finding was that the ability to absorb the corrosive gas decreases as the original H2S concentration increases and this proves to be true for all water cuts and system pressures. After conducting these different reservoir scenarios, tests were conducted to simulate 300m of the horizontal section of the pipe that connects the head of the well with the platform. This was done with a high pressure 300-meter long loop. It was found that the corrosive gas is absorbed at a higher rate when there is a flow, opposite to a hydrostatic case. Henry's Law constant was identified for each water cut and each pressure, however, the test procedure could not be validated since the gas being studied was not in its pure form. Understanding the absorption phenomena of Hydrogen sulfide in different water cuts will definitely be of great help to the oil industry to make better forecasts of H2S concentrations being ejected from each well.
M.S.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Aerospace Engineering MSAE

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44

Maier, Maximilian Bernhard [Verfasser], Rudi F. [Akademischer Betreuer] Vogel, Horst-Christian [Gutachter] Langowski, and Rudi F. [Gutachter] Vogel. "High pressure temperature inactivation of Clostridium botulinum endospores in low-acid foods and food model systems / Maximilian Bernhard Maier ; Gutachter: Horst-Christian Langowski, Rudi F. Vogel ; Betreuer: Rudi F. Vogel." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1185637850/34.

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45

VITOLO, ROBERTO. "Reduction of fuel consumption and pollutant emissions from vehicles: implementation of low-temperature diesel combustion and development of an advanced central tire inflation system." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2755753.

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46

Simiema, de Freitas Barbosa Gustavo [Verfasser], Bernd [Akademischer Betreuer] Mayer, Bernd [Gutachter] Mayer, and Jürgen [Gutachter] Meichsner. "Construction and Evaluation of Gas Feed-in System, Electrodes and Gas Exhaustion System applied to Low Pressure Plasma Coating Processes / Gustavo Simiema de Freitas Barbosa ; Gutachter: Bernd Mayer, Jürgen Meichsner ; Betreuer: Bernd Mayer." Bremen : Staats- und Universitätsbibliothek Bremen, 2018. http://d-nb.info/1165772302/34.

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47

Jazzar, Jacques. "Methods of post-treatment of aerodynamic tests of engine boosters." Thesis, KTH, Kraft- och värmeteknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-260474.

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Анотація:

Aerodynamics studies in a booster such as analysis of the flow through the whole component or study of local turbulent phenomenon constitute a crucial part of its development in order to get better overall performances, like efficiency of the compressor and compression ratio. In order to put in perspective the computational predictions, it is critical to obtain sets of data from tests to caliber numerical analyses and to assure the booster respects design specifications. Aerodynamics testing is then an important part of the development of a compressor. However, it is complicated to obtain such values for many reasons: time constraints, problems regarding support, important costs etc. Thus, it is important to get as much information as possible from these tests data in a limited period in order to spend more time in results interpretation and less in treating raw data. Thus, an optimized tool of treatment to first deduce results from test data; and then to compare different engines or different sets of tests data, to get a wider state of the art and to avoid time-consuming analyses was needed. In order to do so, the first part of the development consists in investigating the existing methods to extract and analyze data from tests already used, and then deducing a general methodology to obtain from raw measures the performances of the studied booster compared to other available data. Once the methods have been set up and validated, the tool in itself was implemented in a practical way. Then, it was important to validate it on real tests values and to observe if it was adjustable for all kind of aerodynamics tests.
Aerodynamikstudier i en booster som analys av flödet genom hela komponenten eller studie av lokal turbulens fenomen utgör en avgörande del av dess utveckling för att få bättre generella prestanda, som kompressorns verkningsgrad och kompressionsförhållandet. För att sätta beräkningsresultat i perspektiv är det kritisk att få datauppsättningar från tester för att kalibrera de numeriska analyser och för att säkerställa att booster uppfyller konstruktionsspecifikationer. Aerodynamisk provning är då en viktig del av utvecklingen av en kompressor. Det är dock komplicerat att få sådana värden av många skäl: tidsbegränsningar, problem angående support, viktiga kostnader osv. Därför är det viktigt att få så mycket information som möjligt från provdata under en begränsad period för att tillbringa mer tid i resultat tolkning och mindre tid på att behandla rådata. Således ett optimerat behandlingsverktyg för att först dra resultat från provdata; och sedan att jämföra olika motorer eller olika uppsättningar av provdata, för att få en bredare databank och att undvika tidskrävande analyser behövdes. För att göra det består den första delen av utvecklingen i att undersöka de befintliga metoderna för att extrahera och analysera data från tester som redan använts, och sedan dra ut en allmän metod för att från råa mått erhålla prestandan hos den studerade boosteren jämfört med andra tillgängliga data. När metoderna har installerats och validerats implementerades verktyget i sig på ett praktiskt sätt. Då var det viktigt att validera det på verkliga testvärden och att se om det var justerbart för alla typer av aerodynamiska test.

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48

Alayoubi, Mzayan. "Risk Analysis for Intermittent Water Supply Systems." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-234554.

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Intermitted Water Supply strategy is implemented commonly in some developing countries nowadays in order to minimize the water scarcity problems. Unstable hydraulic conditions in the distribution system, low pressure, high risk of water contamination, wasting water, rising costs paid by consumers and water providers, failures and problems with consumption metering and inconvenience to consumers are some of the consequences. Risk Analysis Methodology is developed to handle with intermittent water supply systems in developing countries conditions that include undesired events identification; risk estimation and risk evaluation and reduction plan, the catalogue list of potential undesired events (UE) which may occur in these types of systems have been also developed using the HAZard and OPerability technique (HAZOP). The developed methodology is implemented and tested in this research on one of the potential undesired events UE _ Low operational pressure

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49

Al-Zaidi, Ebraheam Saheb Azeaz. "Experimental studies on displacements of CO₂ in sandstone core samples." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33183.

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CO2 sequestration is a promising strategy to reduce the emissions of CO2 concentration in the atmosphere, to enhance hydrocarbon production, and/or to extract geothermal heat. The target formations can be deep saline aquifers, abandoned or depleted hydrocarbon reservoirs, and/or coal bed seams or even deep oceanic waters. Thus, the potential formations for CO2 sequestration and EOR (enhanced oil recovery) projects can vary broadly in pressure and temperature conditions from deep and cold where CO2 can exist in a liquid state to shallow and warm where CO2 can exist in a gaseous state, and to deep and hot where CO2 can exist in a supercritical state. The injection, transport and displacement of CO2 in these formations involves the flow of CO2 in subsurface rocks which already contain water and/or oil, i.e. multiphase flow occurs. Deepening our understanding about multiphase flow characteristics will help us building models that can predict multiphase flow behaviour, designing sequestration and EOR programmes, and selecting appropriate formations for CO2 sequestration more accurately. However, multiphase flow in porous media is a complex process and mainly governed by the interfacial interactions between the injected CO2, formation water, and formation rock in host formation (e.g. interfacial tension, wettability, capillarity, and mass transfer across the interface), and by the capillary , viscous, buoyant, gravity, diffusive, and inertial forces; some of these forces can be neglected based on the rock-fluid properties and the configuration of the model investigated. The most influential forces are the capillary ones as they are responsible for the entrapment of about 70% of the total oil in place, which is left behind primary and secondary production processes. During CO2 injection in subsurface formations, at early stages, most of the injected CO2 (as a non-wetting phase) will displace the formation water/oil (as a wetting phase) in a drainage immiscible displacement. Later, the formation water/oil will push back the injected CO2 in an imbibition displacement. Generally, the main concern for most of the CO2 sequestration projects is the storage capacity and the security of the target formations, which directly influenced by the dynamic of CO2 flow within these formations. Any change in the state of the injected CO2 as well as the subsurface conditions (e.g. pressure, temperature, injection rate and its duration), properties of the injected and present fluids (e.g. brine composition and concentration, and viscosity and density), and properties of the rock formation (e.g. mineral composition, pore size distribution, porosity, permeability, and wettability) will have a direct impact on the interfacial interactions, capillary forces and viscous forces, which, in turn, will have a direct influence on the injection, displacement, migration, storage capacity and integrity of CO2. Nevertheless, despite their high importance, investigations have widely overlooked the impact of CO2 the phase as well as the operational conditions on multiphase characteristics during CO2 geo-sequestration and CO2 enhanced oil recovery processes. In this PhD project, unsteady-state drainage and imbibition investigations have been performed under a gaseous, liquid, or supercritical CO2 condition to evaluate the significance of the effects that a number of important parameters (namely CO2 phase, fluid pressure, temperature, salinity, and CO2 injection rate) can have on the multiphase flow characteristics (such as differential pressure profile, production profile, displacement efficiency, and endpoint CO2 effective (relative) permeability). The study sheds more light on the impact of capillary and viscous forces on multiphase flow characteristics and shows the conditions when capillary or viscous forces dominate the flow. Up to date, there has been no such experimental data presented in the literature on the potential effects of these parameters on the multiphase flow characteristics when CO2 is injected into a gaseous, liquid, or supercritical state. The first main part of this research deals with gaseous, liquid, and supercritical CO2- water/brine drainage displacements. These displacements have been conducted by injecting CO2 into a water or brine-saturated sandstone core sample under either a gaseous, liquid or supercritical state. The results reveal a moderate to considerable impact of the fluid pressure, temperature, salinity and injection rate on the differential pressure profile, production profile, displacement efficiency, and endpoint CO2 effective (relative) permeability). The results show that the extent and the trend of the impact depend significantly on the state of the injected CO2. For gaseous CO2-water drainage displacements, the results showed that the extent of the impact of the experimental temperature and CO2 injection rate on multiphase flow characteristics, i.e. the differential pressure profile, production profile (i.e. cumulative produced volumes), endpoint relative permeability of CO2 (KrCO2) and residual water saturation (Swr) is a function of the associated fluid pressure. This indicates that for formations where CO2 can exist in a gaseous state, fluid pressure has more influence on multiphase flow characteristics in comparison to other parameters investigated. Overall, the increase in fluid pressure (40-70 bar), temperature (29-45 °C), and CO2 injection rate (0.1-2 ml/min) caused an increase in the differential pressure. The increase in differential pressure with increasing fluid pressure and injection rate indicate that viscous forces dominate the multi-phase flow. Nevertheless, increasing the differential pressure with temperature indicates that capillary forces dominate the multi-phase flow as viscous forces are expected to decrease with this increasing temperature. Capillary forces have a direct impact on the entry pressure and capillary number. Therefore, reducing the impact of capillary forces with increasing pressure and injection rate can ease the upward migration of CO2 (thereby, affecting the storage capacity and integrity of the sequestered CO2) and enhance displacement efficiency. On the other hand, increasing the impact of the capillary force with increasing temperature can result in a more secure storage of CO2 and a reduction in the displacement efficiency. Nevertheless, the change in pressure and temperature can also have a direct impact on storage capacity and security of CO2 due to their impact on density and hence on buoyancy forces. Thus, in order to decide the extent of change in storage capacity and security of CO2 with the change in the above-investigated parameters, a qualitative study is required to determine the size of the change in both capillary forces and buoyancy forces. The data showed a significant influence of the capillary forces on the pressure and production profiles. The capillary forces produced high oscillations in the pressure and production profiles while the increase in viscous forces impeded the appearance of these oscillations. The appearance and frequency of these oscillations depend on the fluid pressure, temperature, and CO2 injection rate but to different extents. The appearance of the oscillations can increase CO2 residual saturation due to the re-imbibition process accompanied with these oscillations, thereby increasing storage capacity and integrity of the injected CO2. The differential pressure required to open the blocked flow channels during these oscillations can be useful in calculating the largest effective pore diameters and hence the sealing efficiency of the rock. Swr was in ranges of 0.38-0.42 while KrCO2 was found to be less than 0.25 under our experimental conditions. Increasing fluid pressure, temperature, and CO2 injection rate resulted in an increase in the KrCO2, displacement efficiency (i.e. a reduction in the Swr), and cumulative produced volumes. For liquid CO2-water drainage displacements, the increase in fluid pressure (60-70 bar), CO2 injection rate (0.4-1ml/min) and salinity (1% NaCl, 5% NaCl, and 1% CaCl2) generated an increase in the differential pressure; the highest increase occurred with increasing the injection rate and the lowest with increasing the salinity. On the other hand, on the whole, increasing temperature (20-29 °C) led to a reduction in the differential pressure apart from the gradual increase occurred at the end of flooding.

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50

Asghari, Mooneghi Maryam. "Experimental and Analytical Methodologies for Predicting Peak Loads on Building Envelopes and Roofing Systems." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1846.

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The performance of building envelopes and roofing systems significantly depends on accurate knowledge of wind loads and the response of envelope components under realistic wind conditions. Wind tunnel testing is a well-established practice to determine wind loads on structures. For small structures much larger model scales are needed than for large structures, to maintain modeling accuracy and minimize Reynolds number effects. In these circumstances the ability to obtain a large enough turbulence integral scale is usually compromised by the limited dimensions of the wind tunnel meaning that it is not possible to simulate the low frequency end of the turbulence spectrum. Such flows are called flows with Partial Turbulence Simulation. In this dissertation, the test procedure and scaling requirements for tests in partial turbulence simulation are discussed. A theoretical method is proposed for including the effects of low-frequency turbulences in the post-test analysis. In this theory the turbulence spectrum is divided into two distinct statistical processes, one at high frequencies which can be simulated in the wind tunnel, and one at low frequencies which can be treated in a quasi-steady manner. The joint probability of load resulting from the two processes is derived from which full-scale equivalent peak pressure coefficients can be obtained. The efficacy of the method is proved by comparing predicted data derived from tests on large-scale models of the Silsoe Cube and Texas-Tech University buildings in Wall of Wind facility at Florida International University with the available full-scale data. For multi-layer building envelopes such as rain-screen walls, roof pavers, and vented energy efficient walls not only peak wind loads but also their spatial gradients are important. Wind permeable roof claddings like roof pavers are not well dealt with in many existing building codes and standards. Large-scale experiments were carried out to investigate the wind loading on concrete pavers including wind blow-off tests and pressure measurements. Simplified guidelines were developed for design of loose-laid roof pavers against wind uplift. The guidelines are formatted so that use can be made of the existing information in codes and standards such as ASCE 7-10 on pressure coefficients on components and cladding.

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Дисертації з теми "Low Pressure Systeams"

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