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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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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.
3
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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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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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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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.
7
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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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).<br>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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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.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>Griffith School of Engineering<br>Science, Environment, Engineering and Technology<br>Full Text
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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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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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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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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.<br>Thesis (Ph.D. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2006.
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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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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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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.<br><p>QC 20140203</p>
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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.<br>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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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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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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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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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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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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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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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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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<br>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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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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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.
Full textAbstract:
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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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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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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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.<br>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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Thomas, Tresa Mary. "An Investigation of the Characteristics of Monsoon Low Pressure Systems in the Present Climate and their Sensitivity to Topography and Climate Change." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5965.
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Monsoon Low-Pressure Systems (LPS) are synoptic-scale tropical disturbances that periodically form over the Indian subcontinent during the summer monsoon season (June-September). Apart from being a lifeline to agriculture, the LPS-triggered precipitation could cause catastrophic floods. This thesis investigates the large-scale factors that influence LPS characteristics under the current and future climate change scenarios. In the early part of the thesis, a new approach is developed to track the formation and propagation of LPS over the Indian subcontinent. A detailed statistical and visual comparison is made between LPS tracks generated using our approach applied to ERA-Interim reanalysis data and tracks obtained in previous studies. Furthermore, extreme rainfall at locations in the vicinity of LPS is analyzed which could be valuable for flood risk assessment during the monsoon season in central India.
In the latter part of the thesis, a fully coupled version of the Community Earth System Model (CESM 1.2.2) is run at 0.9°×1.25° spatial resolution, and 6-hourly output is generated for track analysis. The model’s ability to simulate the characteristics of LPS is first assessed by performing a present-day control simulation. Simulations to study the sensitivity of LPS statistics to topographical features in the south Asian region (presence or absence of southeast Asian mountains and the height of Tibetan and Himalayan Orography (THO)) and the change in LPS characteristics under climate change are also performed. Simulations without the southeast Asian mountains enable determining the influence of these mountains on the downstream amplified systems (remnants of Pacific tropical cyclones) over the Bay of Bengal. The sensitivity analysis on the influence of the height of THO shows an interesting result: while a decrease in monsoon precipitation with a reduction in the height of THO is simulated, the number of LPS increases. A detailed analysis of the dynamic factors leading to this counter-intuitive result is performed. Finally, the change in LPS characteristics and the associated large-scale SST and circulation anomalies in the Indian Ocean and south Asian region are assessed for the RCP8.5 emissions scenario. It is found that the monsoon circulation is weakened, summer monsoon precipitation over India is enhanced, and the number of LPS remains nearly unchanged in a warmer world.
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ChenYen-Te and 陳彥德. "Diamond Synthesis at Low Pressure in Binary Metal Systems." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/06914768343042974744.
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碩士<br>國立臺北科技大學<br>材料及資源工程系碩士班<br>89<br>The idea of low pressure solid state synthetic(LPSSS) diamond was first proposed by professor R.Roy in 1993. It was the technique to precipitate diamond from the saturated carbon melt mixture of the transition metal and graphite powders under pure hydrogen atmosphere. It combines the characteristics of transition metal as “catalyst-solvent” in HPHT and the catalyst effect of atomic hydrogen in CVD , and may become a potential method for diamond synthesis.
The experimental method used in this study is hot filament chemical vapor deposition. The experimental purpose in this study is to understand the following variables that are (a) the eutectic temperature and composition in binary metals, (b) two type reactive atmosphere─pure hydrogen and methane + hydrogen (c) solid state carbon source(graphite) , which influence the size, number and crystalline of diamond in the synthetic progress
Through the analysis of SEM, Raman spectra, and X-ray diffraction, specimens in the methane + hydrogen atmosphere produced diamond crystals on the surface of metal melt which size, number and crystalline were similar to those in ordinary CVD reactor. We found that the catalyst effect of Pd and Ni are better than other metals in the study. Otherwise, specimens in pure hydrogen atmosphere did not produce any diamond crystals on the surface of metal melt, but we found a phenomenon that diamond was covered with metal melt. Sample containing Pd, Ni metal powder would appear this phenomenon.
The experimental results show that the diamond nucleation rate in low pressure solid state synthetic(LPSSS) method is much less than in ordinary CVD reactor, and different element and alloy composition will influence the result of diamond nucleation
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Costa, José Miguel Gonçalves Ledo Belo da. "Optimization of filling systems for low pressure by Flow 3D." Master's thesis, 2015. http://hdl.handle.net/1822/40132.
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Dissertação de mestrado integrado em Engenharia Mecânica<br>As part of the dissertation and bearing in mind the parameters in which the possibility
of a choice of tutor and the subject to be addressed is established, the subject for development
’Optimization of filling systems for low pressure by Flow 3D ®’ was chosen. For this it was
necessary to define the objectives to achieve and the methods to attain them.
Despite the wide range of software able to simulate and validate filling systems, Flow
3D® has been shown as one of the best tools in the market, demonstrating its ability to
simulate with distinctive accuracy with respect to the entire process of filling and the
behavioral representation of the fluid obtained. To this end, it is important to explore this tool
for a better understanding of the processes involved and to serve as an exploratory basis for
the simulation of filling systems, simulation being one of the great strengths of the current
industry due to the need to reduce costs and time waste, in practical terms, that lead to the
perfecting of the dimensioning of filling devices, which are reflected in delays and wasted
material.
In this way it is intended to validate the methodology to design a filling system in lowpressure
casting process, exploring their physical models and thus allowing for its
characterization. For this, consider the following main phases: The exploration of the
simulation software Flow 3D®; modeling of filling systems; simulation, validation and
optimization of systems modeled by exploring the parameters of the models. Therefore, it is
intended to validate the pressure curves under study and the eventual mining of the most
relevant information in a casting analysis. The pressure curves that were used were obtained
through the gathered literature and the practical work previously performed. Through the
results it was possible to conclude that the pressure curve with 3 levels meets the intended
purpose of a laminar filling regime and associated speeds never exceeding 0.5 𝑚/𝑠. The
pressure curve with 2 filling levels has a more turbulent system, having filling areas with
velocities above 0.5 𝑚/𝑠. The heat transfer parameter was studied due to the values
previously obtained didn’t corroborate the behavior of dissipation regarding to the casting. In
this way, new values, more in tune with the casting process, were obtained. The achieved
results were compared with those generated by NovaFlow & Solid®, which were shown to be
similar, validating the parameters established in the simulations. Flow 3D® was proven a
powerful tool for the simulation of casting parts.<br>Como parte da dissertação tendo em mente os parâmetros onde está estabelecida e
tendo em conta os moldes estipulados, permitiram a escolha do orientador bem como do tema
a abordar. Optou-se pelo desenvolvimento do tema 'Otimização de sistema de enchimento
para baixa pressão no software Flow 3D®'. Para isso foi necessário definir os objectivos a
atingir e os métodos para alcançá-los.
Apesar da ampla gama de software capazes de simular e validar sistemas de gitagem,
o Flow 3D® tem-se revelado como uma das melhores ferramentas do mercado, evidenciando
a capacidade de simular com maior rigor no que respeita a todo o processo de enchimento de
cavidades. Para tal, torna-se importante a exploração desta ferramenta para uma melhor
compreensão das metodologias envolvidas e como base exploratória para a simulação de
sistemas de enchimento, sendo a simulação um dos grandes trunfos da indústria atual, face à
necessidade de diminuição de custos e de desperdício de tempo no aperfeiçoamento prático
do dimensionamento dos sistemas de enchimento, que se refletem em atrasos e em
desperdício de material.
Desta forma pretende-se validar uma metodologia de projeto dum sistema de
enchimento através do processo de fundição de baixa pressão, explorando as capacidades e
modelos matemáticos do Flow 3D®. Para isso, consideraram-se as seguintes fases principais:
modelação, discretização do modelo; simulação, validação e otimização de sistemas
modelados explorando os parâmetros dos mesmos. De forma a simular o enchimento da
cavidade moldante, utilizaram-se curvas de pressão obtidas através da bibliografia e de
trabalhos práticos previamente realizados. Pelos resultados obtidos foi possível concluir que
uma curva de pressão com 3 patamares se encontra em regime de enchimento laminar, com
velocidades associadas nunca superiores a 0.5𝑚⁄𝑠 .Na curva de pressão com 2 patamares o
regime de enchimento é mais turbulento, havendo zonas de enchimento com velocidades
acima dos 0.5𝑚⁄𝑠. O parâmetro de transferência de calor, full energy, foi estudado devido
aos valores obtidos inicialmente não corroborarem com comportamento da dissipação face à
fundição. Assim, foram obtidos valores consensuais com a prática de fundição. Compararamse
os resultados obtidos com resultados gerados pelo NovaFlow & Solid®, que se mostraram
idênticos, validando deste modo os parâmetros relativos às simulações. O Flow 3D® revelouse
uma ferramenta poderosa face à simulação de elementos de fundição.
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Ndlovu, Mkhokheli. "Development of a dynamic still for measuring low pressure vapour-liquid-liquid equilibria : systems of partial liquid miscibility." Thesis, 2005. http://hdl.handle.net/10413/2775.
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The dynamic still originally designed by Raal (Raal and Muhlbauer [1998]) has been transformed into a valuable still that can now be used for measuring both low pressure vapour-liquid equilibria (VLE) for systems that are completely miscible and vapour-liquid-liquid equilibria (VLLE) for systems that are partially miscible. The resultant equilibrium data are important in the design and analysis of distillation and allied separation process equipment, with VLLE data, in particular, being useful in the design of heterogeneous azeotropic distillation columns. The original Raal still was based on the designs of Heertjies [1960] and Yerazunis [1964], who successfully used a packed equilibrium chamber where the liquid and vapour phases are forced downward co-currently to achieve rapid and dynamic equilibrium (Joseph et al [2001]). Direct analysis of the vapour composition prior to condensation through a new heated valving system with superheated sample conveyance to a gas chromatograph, a modification incorporated into the Raal still, ensured that accurate and reproducible equilibrium data were obtained. This new arrangement dispenses with the impossible task of getting the actual vapour composition that would result were the vapours allowed to condense and form two liquid phases. The initial testing of the still which established the operating procedures was conducted on two previously measured systems - the first which was homogeneous and the second heterogeneous. For the homogeneous system the new vapour sampling system was tested by comparing the measured composition to that of a condensed sample sent manually to the GC using a gas-tight syringe. In order to completely describe the VLLE for the systems studied, the liquid-liquid equilibrium (LLE) data for these systems were also measured. The LLE measurements were conducted in a newly-developed small jacketed glass cell with temperatures maintained constant by circulating water from a bath maintained at the desired temperatures. The main focus of this project was thus the development of an apparatus and procedures for measuring low pressure vapour-liquid-liquid equilibria. The project also went on to measuring and modeling VLE, VLLE and LLE data for selected binary and ternary systems. Both the Gamma-Phi and the Phi-Phi methods of VLE analysis were carried out on the measured data. The NRTL, Wilson, TK-Wi1son and UNIQUAC activity coefficient models were used in the Gamma- Phi method together with the Virial equation of state for vapour phase non-idealities. In the Phi-Phi method, The Peng and Robinson Equation of State (EOS), the Soave Redlich-Kwong EOS and the Stryjek and Vera modified Peng and Robinson EOS were all used, first with the classical mixing rules and then with the theoretically correct Wong and Sandler [1992] mixing rules. Ternary LLE binodal curves were correlated to the Hlavaty correlation, the beta function and the log gamma function while the corresponding tie-lines were fitted to the NRTL model.<br>Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.
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Luscher, Cornelius Martin [Verfasser]. "Effect of high pressure - low temperature phase transitions on model systems, foods and microorganisms / vorgelegt von Cornelius Martin Luscher." 2008. http://d-nb.info/988780593/34.
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Miclea, Corneliu Florin [Verfasser]. "Investigation of superconducting order parameters in heavy fermion and low dimensional metallic systems under pressure / von Corneliu Florin Miclea." 2006. http://d-nb.info/981340512/34.
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Lo, Kuo-Cheng, and 羅國誠. "Applying WRF-Chem model to analyze the changes in ambient air quality of southern Taiwan caused by the approach of high/low pressure systems." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/40821133132013578778.
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博士<br>國立高雄第一科技大學<br>工學院工程科技博士班<br>103<br>This study aims at exploring the pollution cases featuring high and fine particulate matters in the air quality region of West Taiwan in winter (January 17-19, 2013) and the Tropical depression cases including Typhoon Nanmadol (August 24-28, 2011) and Typhoon Usagi (September 16-20, 2013) in summer by referring to the measuring results obtained at the air quality monitoring stations and WRF-Chem model simulation and analysis. The study further discussed correlations between the effects of locations, tracks and wind fields of high and low pressure and the variation of ambient pollutant concentrations (e.g. O3) in Southern Taiwan. Four major tasks were conducted in this study, which include to simulate and analyze the effects of West Pacific Subtropical High (WPSH) on ambient O3 concentration in the air quality monitoring regions of Kaohsiung and Pingtung in summer; to find out the effects of Tropical Depression (Typhoons) formed in the Pacific on ambient O3 concentration in the air quality monitoring regions of Kaohsiung and Pingtung in summer; to explore the effects of long-range transport of air pollutants on fine particulate matter (PM2.5) pollution in East Asia and Taiwan under high pressure in winter; and to analyze the general trends of the effects of high and low pressure systems on air quality in Taiwan.
Several important results are achieved in the study. First, being influenced by the high pressure system in winter/summer, the atmospheric environment features downdraft. However, the geophysical properties of this system make some differences. The high pressure system in winter forces the low-temperature and dry middle and high layers to go down, which forms a condition allowing long-range transport of air pollutants to flow with the high pressure system and then affect West Taiwan. The effect of low inversion layer is not favorable to parallel diffusion of air pollutants, which leads to greater accumulation of particulate matter. Second, the high pressure system in summer cam be characterized to be high-temperature, dry and downward with low relative humidity so there are scarce clouds and strong photochemical reaction within the range of the West Pacific High. The downward inversion at the low layer further leads to the accumulation of high O3 concentration. Apart from the above, the synergy between the West Pacific High system and the approaching low pressure system (typhoon) contributes to the accumulation of air pollutant concentration at a higher degree.
In this study, WRF-Chem was applied and the simulation results via this model proved the following facts. First, O3 concentration was 2-3 times higher than that in an ordinary summer when the air quality in Kaohsiung and Pingtung, southwest of Taiwan, was affected by WPSH. Moreover, before low pressure system (typhoon) hit Taiwan and around the typhoon sea warning issuance, the variations of O3 spatial distribution can serve as a reference for predicting the tracks of a typhoon coming at Taiwan. Higher O3 concentration was measured 2.0 to 2.5 days before a typhoon hitting Taiwan. Finally, by applying the model simulation and analysis, long-range transport of air pollutants was also estimated. The air pollutants coming from afar contributed to 26.7-47.3% of the concentration of PM 2.5 in winter. The high pressure system (Polar Continent Air Mass) in winter formed an environment favorable to long-range transport of air pollutants and further caused pollution at an obvious level.