Dissertations / Theses on the topic 'Pressure'
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Lim, C. S. "Plastic limit pressures for pressure vessels with defects at openings." Thesis, Cardiff University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234339.
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Totland, Johan Fredrik Holm. "Fast Pressure Control in Managed Pressure Drilling." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26110.
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In drilling operations, it is of great importance to efficiently and safely control the pressure in the well. To avoid possible damage to the reservoir, equipment, personnel and the environment, the pressure in the well bore must be kept within certain limits, determined by the formations around the well. An emerging drilling technique, intended to increase the efficiency and safety of drilling operations, is known as Managed Pressure Drilling (MPD). MPD differs from conventional drilling by closing the mud system with a controlled choke, often in combination with a backpressure pump to ensure circulation through the choke. The controller objective is to automatically adjust the choke to reach the desired downhole pressure. For optimal control of the downhole pressure, a model describing the flows and pressures in the well is necessary. A modal discretization method is considered and implemented in this thesis, resulting in a rational approximation of a two-dimensional distributed parameter model. The discretized model is used to design a LQG controller, for comparison with a PI controller. Both controllers are implemented in MATLAB to perform computer simulations and experiments in lab. Simulations indicated that the transient response of the LQG stabilized at the desired set-point, more efficiently relative to PI controller. This difference was significantly improved when increasing the length of the simulated well. In experiments performed on a tailor made experimental lab located at NTNU, the performance of the two controllers were about equally great. It is discussed whether the lab is inadequate to demonstrate possible improvements due to the introduction of the two-dimensional model.
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Ng, Wai Nyin. "Pressure changing steps in pressure swing adsorption." Thesis, University of Bath, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296582.
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Brear, Michael John. "Pressure surface separations in low pressure turbines." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620981.
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Holmes, James Wright. "Optical surface pressure measurement using pressure sensitive paint." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/47083/.
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Bowling, Micah. "Intraoral Pressure and Sound Pressure During Woodwind Performance." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849677/.
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For woodwind and brass performers, intraoral pressure is the measure of force exerted on the surface area of the oral cavity by the air transmitted from the lungs. This pressure is the combined effect of the volume of air forced into the oral cavity by the breathing apparatus and the resistance of the embouchure, reed opening, and instrument’s back pressure. Recent research by Michael Adduci shows that intraoral pressures during oboe performance can exceed capabilities for corresponding increases in sound output, suggesting a potentially hazardous situation for the development of soft tissue disorders in the throat and velopharyngeal insufficiencies. However, considering that oboe back pressure is perhaps the highest among the woodwind instruments, this problem may or may not occur in other woodwinds. There has been no research of this type for the other woodwind instruments.
My study was completed to expand the current research by comparing intraoral pressure (IOP) and sound pressure when performing with a characteristic tone on oboe, clarinet, flute, bassoon, and saxophone. The expected results should show that, as sound pressure levels increase, intraoral pressure will also increase. The subjects, undergraduate and graduate music majors at the University of North Texas, performed a series of musical tasks on bassoon, clarinet, flute, oboe, and alto saxophone. The musical tasks cover the standard ranges of each instrument, differences between vibrato and straight-tone, and a variety of musical dynamics. The data was collected and examined for trends. The specific aims of this study are to (1) determine whether there is a correlation between IOP and sound pressure, (2) shed light on how well each instrument responds to rapid fluctuation, and (3) determine which instruments are most efficient when converting air pressure into sound output. Results of this study raised concerns shared by previous studies – that woodwind players are potentially causing harm to their oropharynx by inaccurately perceiving intraoral pressure needed to achieve a characteristic sound. Evidence found by this study suggests that while oboists generate high intraoral pressure for relatively little sound output (a fact corroborated by past studies), the same cannot be said for all of the woodwind instruments, particularly the flute.
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Crescenzo, Domenico. "Pressure measurement in the high pressure fuel system." Thesis, KTH, Förbränningsmotorteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-267549.
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In order to meet the demanding legislations on diesel engines exhaust emissions, an always more accurate control over the amount of fuel injected in the cylinders is required. A comprehensive understanding of the main factors involved in the injection process, therefore, should be achieved. Such factors are the pressure in the common rail, the injection ontime and the temperature at the injector. The rail pressure, in particular, has been the focus of this project: Its accurate acquisition is crucial for the correct determination of the injection duration and, consequently, for an improved control over the amount of fuel injected. The rail pressure, however, is characterized by significant instabilities affecting the measurement. An experimental campaign has been conducted on a Scania D13 engine in order to characterize and understand the rail pressure signature during engine steady operations: The superposition of injections, pump strokes and water-hammer instabilities forms a complex pattern extensively discussed. An attempt to model the pressure fast transients has been made: While the frequency content of the phenomenon investigated is correctly interpreted, the results obtained in the time domain diverge significantly in amplitude and phase from the experimental data collected. Finally, the measurement strategy adopted today at Scania CV AB to acquire the rail pressure has been investigated and its accuracy assessed. On the basis of the knowledge achieved, a new adaptive measurement technique, capable of changing the estimation process accordingly to the engine operating condition detected, is proposed. The potentiality of an increased accuracy in controlling the amount of fuel injected is proved for engine steady operations. Further investigation regarding the method tolerance to engine transients, however, is required.
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Brewin, Ross, and ross brewin@rmit edu au. "Mediating Pressure, Facilitating Exchange: 3 Architectural Projects in Pressured Urban Environments." RMIT University. Architecture and Design, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080215.154127.
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The aim of the research is to demonstrate architectural design strategies and outcomes that provide alternative ways of considering the futures of areas under high developmental pressure. These areas are where the potential detrimental effects of unmediated, rapid change and development are at their most immediate and in need of consideration. Urban environments are complex physical manifestations of economic, environmental, social, cultural and political pressures represented by the often competing desires of public and private interest groups. Given the enormity of scale and complexity of these pressures, it is problematic to think of architecture as something that can design everything (perhaps as seen in traditional master planning) and in doing so, solve the problem. What may be more constructive is the consideration of architecture having the potential to be involved strategically in these issues, over a number of scales to work towards positive outcomes for the public domain. In recent years, both Victorian and Queensland state governments have released policy guiding the future growth of key regions within their borders. Each attempts to address accommodating large population increases over relatively short time periods by proposing consolidation in and around existing urban centres. This consolidation is seen as part of a strategy to limit urban sprawl and curtail its associated negative social, environmental and potential economic impacts. These targeted 'Activity Centres' become places of immanent transformation, points of pressure within the disaggregated field of the contemporary Australian city. Left un-mediated, developmental pressure in locations such as these is likely to create the same detrimental physical and social effects evident in the general prevailing homogeneity, commercialisation and piecemeal nature of current urban development. Through several architectural design projects, the research aims to explore the role of architecture as an urban mediator within these pressured locations. Through bridging scales from the broad metropolitan, to the finer grained specific, this mediation may begin to strategically 'set things up' for the public domain, towards facilitating valuable social exchange.
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Quin, David John Gilbert. "Bridging the pressure gap : taking surface science to more realistic pressures." Thesis, University of Southampton, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484956.
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Traditional surface science experiments are conducted under ultra high vacuum conditions, this enables surface cleanliness to be strictly controlled and the use of electron based measurements, to determine surface structure and composition. Unfortunately, lftlV conditions are very different from those in real world catalysis (e.g. car exhaust clean-up) and only limited insight can be obtained from such studies. For example, it has been found that certain catalytic species do not exist under UHV conditions. It is an essential step in the progression of surface science to move to more realistic conditions whilst still retaining the simplicity enabled by a UHV cleaned, ideal surface such as a single crystal. this thesis the development of two new pieces of equipment, which bridge this gap, at the SRS at Daresbury Laboratory are presented. The High Pressure Reaction Cell (HPRC), based on the far-IR beamline 13.3 at Daresbury laboratory, enables samples to be cleaned under lJHV conditions before being exposed to pressures, inside the cell, of up to 200 mbar of a chosen gas, without compromising the external vacuum. Far-IR RAIRS, which is useful for adsorbate investigations, is unaffected by the presence of a partial pressure of gas, enabling in-situ measurements as well as postexperiment UHV measurements. Results are presented for investigations into the high pressure oxidation and reduction copper, these are supported by DFT calculations ofthe phonon modes for common copper oxides. The High Ambient Pressure Photoelectron spectroscopY (H.APPY) system is a peripatetic end station designed to allow sample cleaning in UHV, before performing in-situ photoelectron spectroscopy at pressures up to 10-2 mbar. The commissioning experiments in which a commercial supported catalyst was studied are presented. The future of these two newly developed pieces of equipment is discussed alongside the future offar-IR RAIRS as a whole.
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Falkirk, Isabella. "Under Pressure." Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-20701.
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Under pressure is an expression of stress. It is about work becoming everything. It is about not being able to separate your self from your work. It is about carrying the office with you all the time.The result is a well kept together collection of garments ranging from commercial to experimental on the edge of not being wearable.Program: Modedesignutbildningen
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Mynchenberg, JoAnn P. "Under Pressure." Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1216148313.
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Sorvoja, H. (Hannu). "Noninvasive blood pressure pulse detection and blood pressure determination." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514282728.
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This thesis describes the development of pressure sensor arrays and a range of methods suitable for the long-term measurement of heart rate and blood pressure determination using a cuff and a pressure sensor array on the radial artery. This study also reviews the historical background of noninvasive blood pressure measurement methods, summarizes the accuracies achieved and explains the requirements for common national and international standards of accuracy.
Two prototype series of pressure transducer arrays based on electro-mechanical film (EMFi) were designed and tested. By offering high (∼TΩ) resistance, EMFi is an excellent material for low-current long-term measurement applications. About 50 transducer arrays were built using different configurations and electrode materials to sense low-frequency pressure pulsations on the radial artery in the wrist. In addition to uniform quality, essential requirements included an adequate linear response in the desired temperature range. Transducer sensitivity was tested as a function of temperature in the range of 25–45 °C at varying static and alternating pressures. The average sensitivity of the EMFi used in the transducers proved adequate (∼2.2 mV/mmHg and ∼7 mV/mmHg for normal and high sensitive films) for the intended purpose.
The thesis also evaluates blood pressure measurements by the electronic palpation method (EP) and compares the achieved accuracy to that of the oscillometric method (OSC) using average intra-arterial (IA) blood pressure as a reference. All of these three measurements were made simultaneously for each person. In one test group, measurements were conducted on healthy volunteers in sitting and supine position during increasing and decreasing cuff pressure. Another group, comprising elderly cardiac patients, was measured only in the supine position during cuff inflation. The results showed that the EP method was approximately as accurate as the OSC method with the healthy subjects and slightly more accurate with the cardiac patient group. The advantage of the EP method is that also the wave shape and velocity of arterial pressure pulses is available for further analysis, including the assessment of arterial stiffness.
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Frazer, Brittany L. "Approximating Subglottal Pressure from Oral Pressure: A Methodological Study." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1403711283.
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Watts, Travis James. "DIRECT MEASUREMENT OF CROSSTIE-BALLAST INTERFACE PRESSURES USING GRANULAR MATERIAL PRESSURE CELLS." UKnowledge, 2018. https://uknowledge.uky.edu/ce_etds/74.
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The magnitudes and relative pressure distributions transmitted to the crosstie-ballast interface of railroad track significantly influences the subsequent behavior and performance of the overall track structure. If the track structure is not properly designed to distribute the heavy-axle loads of freight cars and locomotives, deficiencies and inherent failures of the crossties, ballast, or underlying support layers can occur, requiring substantial and frequent maintenance activities to achieve requisite track geometrical standards. Incorporating an understanding of the pressure distribution at the crosstie-ballast interface, appropriate designs can be applied to adequately provide a high performing and long-lasting railroad track. Although this can be considered a simple concept, the magnitudes and distributions of pressures at the crosstie-ballast interface have historically proven to be difficult to quantifiably measure and assess over the years.
This document describes the development and application of a method to measure average railroad track crosstie-ballast interfacial pressures using timber crossties and pressure cells specifically designed for granular materials. A procedure was specifically developed for recessing the cells in the bottoms of timber crossties. The validity of the test method was initially verified with a series of laboratory tests. These tests used controlled loads applied to sections of trackbed constructed in specifically designed resilient frames. The prototype trackbed section was intended to simulate typical in-track loading conditions and ballast response.
Cells were subsequently installed at a test site on an NS Railway well-maintained mainline just east of Knoxville, TN. Six successive crossties were fitted with pressure cells at the ballast interface below the rail seat. Pressure cells were also installed at the center of two crossties where the ballast is typically not tamped or consolidated. Trackbed pressures at the crosstie-ballast interface were periodically measured for numerous revenue freight trains during a period of twenty-one months. After raising and surfacing the track, the ballast was permitted to further consolidate under normal train traffic before again measuring pressures. Having the ballast tightly and uniformly compacted under crossties is important to ensuring representative and reproducible pressure measurements.
Measured maximum pressures under the rail at the crosstie-ballast interface ranged from 20 to 30 psi (140 to 210 kPa) for locomotives and loaded freight cars with smooth wheels producing negligible wheel/rail impacts. Crosstie-ballast interface pressures were typically 3 psi (20 kPa) maximum for empty freight cars with smooth wheels. Heavily loaded articulated intermodal car pressures for shared trucks tended to reach nearly 40 psi (280 kPa), actually higher than locomotive-produced pressures. The recorded pressures under the center of the ties were normally negligible, less than 1 psi (7 kPa) for locomotives and loaded freight cars.
Wheel-Rail force parameters measured by nearby wheel-impact load detectors (WILD) were compared to crosstie-ballast pressure data for the same trains traversing the test site. Increases in peak WILD forces, either due to heavier wheel loads or increased impacts, were determined to relate favorably to increases in recorded trackbed pressures with a power relationship. The ratios between the peak and nominal wheel forces and trackbed pressures also have strong relationships.
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Citty, Sandra Wolfe. "Ambulatory blood pressure biosituational feedback and systolic blood pressure estimation." [Gainesville, Fla.]: University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000663.
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Ng, Kok Chian. "Numerical investigation of pressure gradient effect on wall-pressure fluctuations." Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/6829.
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This research investigates the effect of pressure gradient on wall-pressure fluctuations in turbulent boundary layers using a delayed detached eddy simulation (DDES) turbulence scheme. The results are compared to Goody's and Efimtsov's empirical single-point wall-pressure spectrum models. Three different types of pressure gradient conditions were investigated numerically: zero pressure gradient (Flat Plate as a baseline model), favorable pressure gradient (Convex 10 , 20 , and 40 Plates), and adverse pressure gradient (Concave 10 , 20 , and 40 Plates). The numerical results were subsequently compared with each other. For the zero pressure gradient case, results compared well with empirical solutions. It was observed that, for cases with adverse pressure gradients, the pressure fluctuations were more chaotic than for the favorable pressure gradient models. In contrast, the favorable pressure gradient models induced lower frequency noise relative to adverse pressure gradient models.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering
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Carstairs, Rachael Caroline. "Human cardiovascular responses to positive pressure breathing with counter pressure." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322225.
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Tuinea-Bobe, Cristina L. "A stretchable pressure sensor for early detection of pressure ulcers." Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.528378.
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Ogden, Sam. "High-Pressure Microfluidics." Doctoral thesis, Uppsala universitet, Mikrosystemteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-208915.
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In this thesis, some fundamentals and possible applications of high-pressure microfluidics have been explored. Furthermore, handling fluids at high pressures has been addressed, specifically by creating and characterizing strong microvalves and pumps. A variety of microstructuring techniques was used to realize these microfluidic devices, e.g., etching, lithography, and bonding. To be able to handle high pressures, the valves and pumps need to be strong. This necessitates a strong actuator material. In this thesis, the material of choice is paraffin wax. A new way of latching paraffin-actuated microvalves into either closed or open position has been developed, using the low thermal conductivity of paraffin to create large thermal gradients within a microactuator. This allows for long open and closed times without power consumption. In addition, three types of paraffin-actuated pumps are presented: A peristaltic high-pressure pump with integrated temperature control, a microdispensing pump with high repeatability, and a pump system with two pumps working with an offset to reduce flow irregularities. Furthermore, the fundamental behavior of paraffin as a microactuator material has been explored by finite element modeling. One possibility that arises with high-pressure microfluidics, is the utilization of supercritical fluids for different applications. The unique combination of material properties found in supercritical fluids yields them interesting applications in, e.g., extraction and cleaning. In an attempt to understand the microfluidic behavior of supercritical carbon dioxide, the two-phase flow, with liquid water as the second phase, in a microchannel has been studied and mapped with respect to both flow regime and droplet behavior at a bi-furcating outlet.
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Guilcher, Antoine. "Central blood pressure." Thesis, King's College London (University of London), 2012. https://kclpure.kcl.ac.uk/portal/en/theses/central-blood-pressure(cfe1a0fc-56e8-4338-a6aa-462c6d6de0bb).html.
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Central aortic systolic blood pressure (cSBP) differs from peripheral systolic blood pressure (pSBP) measured in the arm. cSBP may be estimated non-invasively by application of a generalised transfer function (GIF) to a high fidelity peripheral arterial waveform or from the late systolic shoulder (SBP2) of such a waveform. The relative accuracy of these estimates and the degree to which they depend on the accuracy of peripheral blood pressure is unknown. The interest in estimates of central blood pressure is driven in large part by the fact that aortic pulse pressure (cPP) is thought to be a better predictor of cardiovascular risk and response to antihypertensive treatment than peripheral BP. However, little is known concerning the mechanism by which drugs may reduce cPP independently of effects on peripheral BP. Objectives of this thesis were to: 1. Examine the relative accuracy of different methods (GTF and SBP2) for estimating cSBP and cPP from a high fidelity peripheral arterial waveform. 2. Determine errors introduced by non-invasive calibration of this waveform (as would be the case when such methods are used in practice), 3. Explore the use of a simplified method for estimating cSBP based upon pressure oscillations within an arm cuff. 4. Determine the mechanism by which nitroglycerin (NTG, a drug that has relatively selective actions to lower cSBP) lowers cPP. Pressure and in some cases combined pressure and flow velocity were acquired at the aortic root during cardiac catheterisation. Peripheral blood pressure was measured by oscillometry and peripheral blood pressure waveforms were obtained from blood pressure cuffs, radial tonometry and a servo-controlled finger cuff. To address objective 4 additional measurements of ventricular and arterial mechanics where made using ultrasound and magnetic resonance imaging.
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Setlock, Robert J. Jr. "Hydrostatic Pressure Retainment." Ohio University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1091108803.
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Setlock, Robert J. "Hydrostatic pressure retainment." Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1091108803.
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Trolliet, Alexia. "Pressure Sensor Miniaturization." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175784.
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As far as the Printed Circuit Boards (PCB) manufacture industry is concerned, for high production volumes, solder paste is applied on the connection pads through customized stencils. This is a very productive method, yet if the design has to be updated, cost is increasing as the stencil should be changed. For higher exibility, such as in rapid prototyping, jet-printing machines similar to Mycronic MY500 are used. In these equipments, solder paste is jet-printed on the circuit board. The shooting is done by a piston moving on the vertical axis at high speed, hence projecting solder paste onto the connection pads of the PCB. In order to improve the understanding of the jetting process, it is important to collect data on pressure uctuations in the jetting head. To do so, this project is using a strain gauge to sense the strain applied by the piston on the nozzle. The gauge is connected in a Wheatstone bridge, and the differential signal is extracted and amplified a first time with an instrumentation amplifier. The remaining amplification is then performed with the help of an operational amplifier so that the signal matches the Analog to Digital Converter (ADC) levels. Finally, the converted results are transmitted to a personal computer for further analysis.
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Misner, Scottie. "High Blood Pressure." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2010. http://hdl.handle.net/10150/146443.
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Tissot, Héloïse. "Beyond the gap of pressure : XPS studies of interfaces at near ambient pressures." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066615/document.
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Dans de nombreux procédés technologiques, tels que la fabrication de matériaux pour la microélectronique, l’étude des réactions chimiques à une électrode, ou encore la catalyse… L’interface entre la surface d’un solide ou d’un liquide avec un liquide ou une phase gaz joue un rôle fondamental. De façon analogue, les sciences de l’environnement ainsi que celles du vivant intègrent dans leurs modèles la réactivité aux interfaces solide/ liquide ou liquide/ gaz.L’XPS est une technique parfaitement adaptée à l’étude des interfaces et a été largement utilisée pour l’analyse des surfaces de solides. Le principal avantage de l’XPS est sa grande sensibilité aux surfaces. En effet, en raison du faible libre parcours moyen des électrons dans un solide, uniquement les photoélectrons provenant de l’extrême surface (1 – 10 nm) peuvent échapper à celle-ci. Cependant, l’XPS est traditionnellement utilisée dans des conditions d’ultravide (UHV) et cela pour deux raisons. La première est que les analyseurs d’électrons sont construits pour fonctionner en UHV. La seconde est que les électrons doivent pouvoir atteindre l’analyseur, or leur libre parcours moyen est faible dans un gaz à haute pression. Par exemple, à une pression de 1 mbar, des électrons possédant une énergie de 100 eV vont parcourir 1 mm alors qu’ en UHV ils pourront atteindre jusqu’ à 105 m.Dans le but de rendre possible l’utilisation de l’XPS à des pressions plus élevées, quelques groupes autour du monde, dont le groupe de Berkeley (sous la direction de M. Salmeron at de H. Bluhm) et celui du Fritz Haber Institute à Berlin, ont élaborés un équipement permettant d’atteindre des pressions proche de l’ambiant (5 mbar). La construction d’un analyseur d’électron capable de fonctionner à des pressions de l’ordre du mbar, c’est-à-dire à des pressions 7 ordres de grandeur supérieures à l’UHV, a été une avancée à la fois conceptuelle et technologique. Un système de pompage différentiel permet de maintenir l’échantillon dans des conditions dites environnementales tout en maximisant le libre parcours moyen des électrons de façon à ce qu’ils atteignent l’analyseur. De plus, des tensions sont appliquées à des lentilles électrostatiques dans le but d’accélérer et de focaliser ces électrons.Un système similaire (Near Ambient Pressure XPS, NAP-XPS) a été installé sur la ligne TEMPO du synchrotron Soleil en février 2013, le premier temps de faisceau ayant eu lieu au mois de mai suivant. Durant ma thèse, deux projets différents ont été développés, tous les deux liés à l’étude d’interfaces avec l’utilisation de la NAP-XPS.Le premier projet traite des procédés utilisés en micro-electronique pour déposer de fines couches d’oxydes : le dépôt chimique en phase vapeur (CVD) et la déposition de couches atomiques (ALD). En particulier, des molécules de la famille des silanes sont utilisées pour fonctionnaliser des surfaces d’oxyde de silicium ou comme précurseur, combiné à un agent oxydant comme l’eau pour le dépôt de films mince d’oxyde de silicium. Cependant, les mécanismes réactionnels des silanes sur les surfaces de silicium n’ont jamais été étudiés par des techniques telles que la microscopie a effet tunnel (STM) ou l’XPS et l’on sait peu de choses concernant leur mécanisme de dissociation et l’adsorption des divers fragments sur la surfaceIn many processes or technological objects, such as coating deposition, advanced material processing for electronics, magnetic or optical devices, electrochemical processes at an electrode, sensors and catalysis, etc. the interface between a surface of a solid and a liquid or a gas phase, plays a prominent role. Analogously, environmental sciences and sciences of the Living integrate into their models chemical reactions taking place at solid/liquid or liquid/gas interfaces.XPS is a powerful technique for interface analysis and has been widely use in the case of solid surface. The main advantage of XPS is its sensitivity to the material surface. Indeed, due to the low electron mean free path of electrons in a solid, only the photoelectrons at the extreme outer surface (1-10 nm) can escape the sample. However, XPS has traditionally been conducted under ultra-high vacuum (UHV) conditions. UHV conditions are utilized for two reasons. First, the analyzers are designed to work under UHV conditions. Second, the electrons must reach the detector and their mean free path is short at high pressures. For example at a pressure of 1 mbar, 100 eV electrons will travel 1 mm while under UHV conditions, the mean free path increases to 105 m. UHV chambers (10-10 mbar) help maximize the mean free path so that a high number of electrons will reach the detector/analyzer and the signal/noise ratio will increase making it possible to analyze the spectrum produced. This constraint makes UHV the standard environment of X-ray Photoelectron Spectroscopy (XPS) experiments.In order to make possible the use of XPS on a larger pressure range, a few groups around the world have designed photoemission equipment that can be operated under ambient pressure (up to 5 mbar). The Berkeley group (M. Salmeron LBNL-Materials Sciences Division, H. Bluhm LBNL-Chemical Sciences Division), who pioneered this field, has two such setups installed at the Advanced Light Source. The Fritz Haber Institute has built a high pressure XPS based on the Berkeley prototype, installed at BESSY synchrotron (Berlin), since 2002. The building of Ambient Pressure XPS (APXPS) analyzers of the Berkeley type, able to be operated at pressures in the range of 1 mbar, about 7 orders of magnitude higher than the pressure limit of conventional UHV equipment is both a technological and conceptual breakthrough. Differential pumping stages allow the sample to remain at environmental pressures, while maximizing the mean free path of emitted electrons, so they can reach the detector. Additionally, voltages are applied to electrostatic lenses in the unit to accelerate and focus the electrons onto the focal plane of the electron energy analyzer. A similar system Near-Ambient Pressure XPS, NAP-XPS), described in details in chapter 1, was delivered in December 2012 and installed at TEMPO beamline in February 2013. The first beamtime occurred in May 2013. During my thesis that started in October 2011 two different projects were developed, both related to interface analysis using the NAP-XPS instrument
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Gilmore, Tim. "Evaluation of Various Inspiratory Times and Inflation Pressures During Airway Pressure Release Ventilation." Diss., NSUWorks, 2017. https://nsuworks.nova.edu/hpd_hs_stuetd/5.
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There are few recommendations on how best to apply certain modes of mechanical ventilation. The application of Airway Pressure Release Ventilation (APRV) includes strategic implementation of specific inspiratory times (I-times) and particular mean airway pressures (MAWP) neither of which is standardized. This study utilized a retrospective analysis of archived electronic health record data to evaluate the clinical outcomes of adult patients that had been placed on APRV for at least 8 hours. 68 adult subjects were evaluated as part of a convenient purposive sample. All outcomes of interest (surrogates) for short-term clinical outcomes to include the PaO2/FiO2 (P/F) ratio, Oxygen Index and Oxygen Saturation Index (OI; OSI), and Modified Sequential Organ Failure Assessment (MSOFA) scores showed improvement after at least 8 hours on APRV. Most notably, there was significant improvement in P/F ratio (p = .012) and OSI (p = .000). Results of regression analysis showed P low as a statistically significant negative predictor of pre-APRV P/F ratio with a higher initial P low coinciding with a lower P/F ratio. The regression analysis also showed MAWP as a significant positive predictor of post-APRV OSI and P high and P low as significant negative predictors of post-APRV MSOFA scores. In summary, it was found that settings for P high, Plow, and T low in addition to overall MAWP and Body Mass Index (BMI) had significant correlation to impact at least one of the short-term clinical outcomes measured.
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Baumann, Peter D. "Investigation of pressure and temperature sensitivities of a pressure sensitive paint." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA356858.
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Thesis (M.S. in Aeronautical Engineering) Naval Postgraduate School, September 1998."September 1998." Thesis advisor(s): Raymond P. Shreeve. Includes bibliographical references (p. 79-81). Also avaliable online.
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Wolf, Erich N. "Pressure broadening and pressure shift of diatomic iodine at 675 nm." Thesis, Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2009. http://hdl.handle.net/1794/10267.
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Little, Andrew P. F. "The performance of corrugated carbon fibre pressure vessels under external pressure." Thesis, University of Portsmouth, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323284.
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Blacknell, Hannah Irene. "Modification of PTFE using low-pressure and atmospheric-pressure plasma methods." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12759/.
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As an inherently chemically inert and physically stable polymer, PTFE has the potential to be used in medical applications as replacement ligaments or vascular stents. In the work presented in this thesis, atmospheric and low-pressure plasma processes were used to modify PTFE surfaces without altering the bulk properties of the substrate. The coupling of two low-pressure gas plasma treatments together into a two-step process was investigated as a method of producing a stable hydrophilic PTFE surface. A roughening oxygen plasma treatment was used to create a high water contact angle (WCA) Cassie-Baxter surface, before an ammonia plasma treatment transformed it into a hydrophilic Wenzel state. Although these surfaces initially exhibited a WCA of < 10°, solvent washing caused significant hydrophobic recovery which was attributed to the washing off of low molecular weight oxidised species (LMWOS). Economically, an atmospheric-pressure plasma process is industrially favourable to low-pressure methods. The simple equipment required for a dielectric barrier discharge (DBD) process means that PTFE modification could be carried out in situ to prevent contamination or hydrophobic recovery being an issue in surgeries. The work presented here produced surfaces with a stable surface potential, the polarity of which was determined by the feed gas. Doping in water and/or ammonia molecules into inert feed gases was found to change the polarity of the surface potential. The use of the theory of electrowetting to decrease the WCA of DBD plasma-treated surfaces was successful, although only a small decrease in WCA was observed on the charged surfaces. However, the surface potential of the substrates was used to initialise the grafting and subsequent polymerization of a number of monomers, as well as deposition of a sulfobetaine zwitterionic layer. The lowest WCA was produced by the dipping of DBD-charged PTFE substrates into an aqueous sulfobetaine solution which produced a WCA of < 10° recovering to 39° after solvent washing. The methods described in this thesis present a number of ways in which stable hydrophilic PTFE surfaces can be produced: an effective low-pressure treatment altered the wetting state of the surface using roughening effect, and DBD plasma-treated surfaces used the surface potential imparted by the plasma to initialise further grafting processes to achieve stable hydrophilicity.
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Svalling, Erik. "TO PERFORM UNDER PRESSURE : BASKETBALL PLAYERS FREE THROW SHOOTING UNDER PRESSURE." Thesis, Uppsala universitet, Nationalekonomiska institutionen, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414926.
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How people perform tasks and under what circumstances they perform them optimally has been a fascination for humanity for a long time and more particularly whether people perform better or worse under pressure. In this paper, I try to find out whether people perform better or worse when there is pressure. The data used is the free throw percentages for teams of the Swedish basketball leagues “Svenska basketligan” and “Svenska Superettan” for both men and women 2003-2019. I then investigate if the teams perform worse or better when games have a lot of pressure. I use definitions of pressure such as the size of the audience, if the game was close in terms of points and whether it was a playoff game. The findings are that for certain definitions of pressure, such as if the game was close and the size of the audience, players performed worse.
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Muller, Judith A. "Calibration to determine pressure and temperature sensitivities of a pressure-sensitive paint." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA380715.
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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, June 2000.Thesis advisor: Shreeve, Raymond P. "June 2000." Includes bibliographical references (p. 71). Also available in print.
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Ercan, Can. "Phpa As A Frictional Pressure Loss Reducer And Its Pressure Loss Estimation." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608451/index.pdf.
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As the demand of oil and gas is increasing, using the existing reservoirs more efficiently as well as searching for new reservoirs is mandatory. Most undiscovered reservoirs are in deep or ultra-deep offshore locations, where drilling to such targets are very difficult with the available fluid circulation technology, since there exists a significant frictional pressure loss due to extreme long wellbores. In order to reduce the frictional pressure losses inside the drillstring, frictional drag reducers are used. Frictional drag reducers are mostly high molecular weight linear polymer molecules and can be used with water or hydrocarbon based solvents. The system used in this study is Baroid EZ-Mud water solutions. Baroid EZ-Mud is a liquid polymer emulsion containing partially hydrolyzed polyacrylamide / polyacrylate (PHPA) co-polymer.
This study aims to observe the performance of EZ-Mud as a frictional drag reducer. For this purpose, a flow loop that consisted of a circular pipe where the frictional pressure losses can be observed under various flow rates and concentrations is developed.
Pipe flow experiments were performed using water-based mud generated using different concentrations of Baroid EZ-Mud at different flow rates. Differential pressure values were recorded for each run. Rheological properties of each mud sample were determined using Fann (Couette) viscometer in order to determine the theoretical frictional pressure losses. Theoretical and measured frictional pressure losses were compared. Results showed that, as the concentration of EZ-Mud was increased, considerable frictional drag reduction as high as 60% was observed.
Based on the experimental data obtained from the flow loop using EZ-Mud with different concentrations, a friction factor correlation as a function of Reynolds Number and EZ-Mud concentration is developed. The proposed correlation performance was also compared with the existing correlations from the literature. It has been observed that, frictional pressure losses using the developed friction factor could be estimated within an error range of maximum 15 %, whereas, the existing models could not predict frictional pressure losses as accurate as the proposed model.
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Løvik, Pål Skønberg. "Estimation of Bottomhole Pressure for Managed Pressure Drilling : Comparison of Nonlinear Estimators." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13309.
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To avoid hole stability problems in an increasingly fierce drilling environment, the demand for accurate control of the pressure profile during drilling operations is rising. As standard instrumentation of drilling rigs have poor measurement of the bottom hole pressure, there is a need for estimation. However, a precise model of a drilling process is difficult to obtain, so a competent observer, using a simpler, lower order model, should be satisfactory.In this master thesis several approaches on estimation are discussed together with a suggested improvement in the annular friction model. The estimators tested are: First, the moving horizon observer, which is presented together with prior work by the author and Marcel Paasche; Second, the unscented Kalman filter, which is a new estimation candidate introduced together with regularization to compensate for the slow update and lack of availability in bottom hole pressure measurements. Last, different combinations of the two observers are proposed.All observers are tested in simulations and good performance is found for both the MHE and UKF. Parameter adaptation is found to be effective for both observers, but the UKF encounters some minor observability issues when the system is not sufficiently exciting. Different combinations of the two observers increase computational complexity, unfortunately without achieving better accuracy in estimates. The estimates are deteriorated when the alternative friction model is tested, and it is thus considered a failed attempt to improve the simple third order Kaasa model.
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Soueidan, Karen. "Augmented blood pressure measurement through the estimation of physiological blood pressure variability." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28828.
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Current noninvasive blood pressure (BP) measurement methods estimate the systolic and diastolic blood pressure (SBP and DBP) at two random instants in time. The BP variability and its serious consequences on the measurement are not recognized by most physicians. The standard for automated BP devices sets a maximum allowable system error of +/- 5 mmHg, even though natural BP variability often exceeds these limits. This thesis characterizes the variability of SBP and DBP and proposes a new approach to augment the conventional noninvasive measurement using simultaneous recordings of the oscillometric and continuous arterial pulse waveforms by providing: 1) The mean SBP (or DBP) over the measurement interval, 2) Their respective standard deviations, and 3) An indicator as to whether or not the oscillometric reading is an outlier. Recordings with healthy subjects showed that the approach has prominent potential and does not suffer from bias relative to the conventional method.
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Mallon, Kelsey N. "Altering the Gag Reflex via a Hand Pressure Device: Perceptions of Pressure." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1398622026.
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Branner, James Lester. "Noise due to pressure pulsations in a pressure-balanced sliding vane pump." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/101167.
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An experimental investigation of noise in a pressure-balanced sliding vane pump was conducted. The test pump for this research was used in an automobile's hydraulic power steering system. As currently designed, a small portion of the manufactured pumps generate excessive noise during operation.
An experimental test stand facility was used to represent a power steering system for analysis of the excessive noise problem with the objective of determining ways to reduce the noise. Through signature analysis techniques, the sliding vane pump noise was related to the pump's pressure pulsations. The pulsations consisted of three types of pressure oscillations: the pressure ripple with a fundamental component at the vane passage frequency together with harmonics; the low-frequency pressure oscillation with a fundamental component at the rotational frequency together with harmonics; and the high-frequency pressure oscillation. The fundamental vane passage frequency and its harmonics dominated the noise signal frequency spectrum. The pump's internal leakage, which was a function of three clearances in the pumping chamber, determined the magnitude of the pressure pulsations. If the pumping chamber components had inadequate clearances, the pump produced excessive pressure pulsations for a given discharge pressure and, consequently, excessive fluid-borne noise generation. Thus, this study indicated increasing the pump's clearances would minimize the pump's noise generation.M.S.
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Nesson, Silas. "Miniature fiber optic pressure sensors for intervertebral disc pressure measurements in rodents." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7394.
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Thesis (M.S.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept.of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Yehdego, Daniel T. "Pressure induced phase transformation of SNO₂ an AB initio constant pressure study /." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Holt, Øystein. "Pressure Tolerant Power Electronics." Thesis, Norwegian University of Science and Technology, Department of Electrical Power Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9844.
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The thermal behaviour of an IGBT module was investigated, especially with respect to the module being immersed in dielectric oil. An equivalent thermal model was built using thermal transients and network synthesis. The thermal behaviour was further investigated using thermocamera measurements and simple finite element models. Passive pressure testing of electronic components relevant for the test setup was performed. The testing showed no significant influence on the electrical behaviour of the components. An IGBT module without gel covering the chips was switched while immersed in dielectric oil. The switching transients were compared to the case of a normal module switching in air. Only minor differences were found between the switching waveforms from the two cases. A test was performed where water was added to the dielectric oil in order to reduce the breakdown voltage of the oil. No breakdown phenomena were observed for the voltages that were tested. A brief litterature study regarding stray inductance considerations in the test setup was performed.
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Pogson, Mark. "High pressure vibrational spectroscopy." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/33858.
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The study of solids at high pressure and variable temperature enables development of accurate interatomic potential functions over wide ranges of interatomic distances. A review of the main models used in the determination of these potentials is given in Chapter one. A discussion of phonon frequency as a variable physical parameter reflecting the interatomic potential is given. A high pressure Raman study of inorganic salts of the types MSCN, (M = K,Rb,Cs & NH4+) and MNO2, (M = K,Na) has been completed. The studies have revealed two new phases in KNO2 and one new phase in NaNO2 at high pressure. The accurate phonon shift data have enabled the determination of the pure and biphasic stability regions of the phases of KNO2. A discussion of the B1, B2 relationship of univalent nitrites is also given. In the series of thiocyanates studied new phases have been found in all four materials. In both the potassium and rubidium salts two new phases have been detected, and in the ceasium salt one new phase has been detected, all at high pressure, from accurate phonon shift data. These transitions are discussed in terms of second-order mechanisms with space groups suggested for all phases, based on Landau's theory of second-order phase transitions. In the ammonium salt one new phase has been detected. This new phase transition has been interpreted as a second-order transition. The series of molecular crystals CH3HgX, (X = Cl,Br & I) has been studied at high pressure and at variable temperature. In Chapter five, their phase behaviour at high pressure is detailed along with the pressure dependencies of their phonon frequencies. In the chloride and the bromide two new phases have been detected. In the bromide one has been detected at high temperature and one at high pressure, the latter being interpreted as the stopping of the methyl rotation. In the chloride one phase has been found at both low temperature as well as high pressure, and the other only at high pressure, the latter again associated with the stopping of methyl rotation. The iodide displays two high pressure transitions. A Raman-active soft-mode has been observed in all three analogues, at both high pressure and variable temperature. For the chloride and bromide analogues there is a discussion of the nature of the soft-mode along with the mechanism associated with the I/II transition. The results of the X-ray crystal structure determination of CH3HgBr at ambient temperature and pressure are given.
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Safaricz, Markus. "Pressure solution in chalk." Thesis, Royal Holloway, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404924.
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Abel, Evan Dale. "Insulin and blood pressure." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257939.
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SILVEIRA, BRUNA TEIXEIRA. "3D PORE PRESSURE ESTIMATION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31857@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
Nos projetos de engenharia de poço, o conhecimento das pressões é fundamental para o planejamento do poço e otimização do processo construtivo. Em geral, as estimativas de pressão de poros são feitas baseadas em análises unidimensionais de poços de correlação e dependem da experiência do analista responsável. Tais estimativas não contemplam todos os dados de uma região e muitas vezes dados não são bem aproveitados. Neste trabalho, é apresentada uma metodologia para estimativa de pressão de poros tridimensional, onde as propriedades dos poços da mesma região foram extrapoladas para toda área através da ferramenta geoestatística. A partir desta extrapolação, foi possível obter-se perfis sintéticos em qualquer locação dentro da região delimitada com maior confiabilidade, enriquecer a compreensão global da região modelada e finalmente construir um cubo tridimensional de pressão de poros utilizando os modelos de Eaton e Bowers, baseando-se no critério que a região apresenta a mesma tendência de compactação.
The knowledge of pore pressures of rocks is critical to several aspects of petroleum the well design and planning. Usually, in the petroleum industry, estimations are based on 1D analyses of the analogues wells and depend on the professional experience. Moreover, estimations do not consider the whole base data of the field. In this dissertation, is presented a methodology for 3D pore pressure estimation, where well data is calculated for the whole area applying a geostatistical tool to build the 3D properties model. From that, it was possible to make more credible synthetics well logs at any location, enrich the whole area comprehension, and also, to build the pore pressure cube based on Eaton and Bowers pore pressure estimations models.
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Hric, George Richard III. "Contact Pressure Distribution Optimization." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71645.
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A novel design technique that is used to optimize contact pressure distribution was introduced and investigated. The primary objective of this design tool, called the Predicted Displacement Method, was to provide a calculated contact surface shape alteration of a contact body that induces a uniform contact pressure across its entire nominal contact surface when pressed against its destination contact boundary at a specified magnitude. This technique was developed so it could be applied to any contact surface to spread out a once poorly distributed and localized contact pressure distribution. The methodology was detailed in this work and a proof of concept was conducted to test the idea's feasibility. The proof of concept supported the methodology's ability to shape a cantilevered beam so that it pressed against a semi-infinite space uniformly. This methodology was then applied to two relevant contact assemblies and resulted in uniform contact across each contact interface. The results also illustrated the ability to control contact magnitude and demonstrated improved contact distribution at magnitudes beyond the design value. The methodology presented in this work provides engineers with a analytical and numerical tool to improve contact pressure distribution between any contact surfaces. Possible future use of this methodology includes incorporation into engineering software packages for contact surface design.Master of Science
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Winroth, Marcus. "Pressure measurements in pulsatingflows." Thesis, KTH, Mekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-204013.
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Due to confidentiality several axis in the figures and large parts of the specifics of the resultsand of the experimental setups have been replaced by symbols. Also one section of the report,concerning a prototype sensor, has been removed completely due to the sensitive nature of theresults.Measuring the exhaust gas pressure and the boost pressure at the air intake manifold isconsidered a standard procedure in modern cars and trucks. Although how to measure thepressure accurately for steady flows is well known, the pressure measurements in pulsatingflows is not a trivial task. This theses shows, experimentally, how well the characteristics of apressure measurement systems, using different dimensions of straight pneumatic tubing, canbe predicted using the Helmholtz resonator model. Also how much this resonance influencethe pressure measurements for different pressure transducers used in trucks today. This thesisalso demonstrates the effects that the sampling frequency and the averaging time has on theaccuracy of measuring an average pressure in pulsating gas flows and how clogging of thepneumatic tubes influence the measurements. This was done using two types of experiments;a step response experiment to properly show the characteristics of the measuring system and apulse rig experiment that shows the impact, of the tubing, on the measurements for typicalfrequencies found in medium sized trucks. The experiments shows that the response time andresonance frequency of a measurement system can be predicted with an accuracy of 𝜇! % fortubes longer than 725 mm. It also that the average absolute pressure measurement keeps anaccuracy of 𝜇! % for all tube dimensions, including clogging of the tube with a decrease ofdiameter up to 𝜇! %. It does however show that if the sensor has some internal resonance that4matches the Helmholtz resonance the measurement can be overestimated by over 𝜇! %. Testsof the sampling frequency shows that if the sampling frequency is chosen as a divisor or amultiple of the pulse frequency the error due to averaging is increased by one order ofmagnitude. Using the information given in this thesis it is possible to avoid unnecessary errorswhen performing pressure measurements in a pulsating flow.Då stora delar av resultaten är hemlighetsstämplade har dessa siffror ersatts av symboler ochaxlarna i vissa figurer har tagits bort helt. Utöver detta så har ett delkapitel, rörande enprototypgivare, tagits bort i sin helhet då det avslöjade känslig information.Det är, i moderna bilar och lastbilar, standard att mäta både laddtrycket i luftintaget tillmotorn och avgasmottrycket efter förbränningen. Att mäta tryck i stationära flöden är någotsom har gjorts länge och är väl utforskat, men hur man skall mäta ett korrekt tryck ipulserande flöden är inte banalt. Denna rapport visar, experimentellt, hur noggrant man kan,med hjälp av en Helmholtz-resonatormodell, förutspå karaktäristiken för ett mätsystem därpneumatiska tryckrör av olika dimensioner används. Den visar även hur mycket resonans idessa system påverkar tryckmätningarna för olika tryckgivare som används i lastbilar idag.Detta examensarbete visar också samplingsfrekvensens och medelvärdesbildningstidenseffekter när ett medeltryck mäts i ett pulserande flöde och hur igensättning av de pneumatiskarören påverkar mätningarna. Detta har genomförts genom två olika typer av experiment; ettstegsvarsexperiment, för att visa på mätsystemens karaktäristik, och ett pulsriggsexperimentsom visar på hur stor inverkan de pneumatiska rören har på mätningar i flöden typiska förmellanstora lastbilar. Experimenten visar att responstiden och resonansfrekvensen för ettmätsystem kan förutspås teoretiskt med en noggrannhet av 𝜇! % för tryckrör längre än 725mm. De visar även att medelvärdet av absoluttrycket kan mätas med en noggrannhet av 𝜇! %för alla rördimensioner, detta inkluderar igensättning av rören upp till en förminskning avdiametern med 𝜇! %. Däremot har det visats att ifall givaren har någon sorts intern resonanssom sammanfaller med Helmholtz-resonansen kan mätningarna överskatta trycket med över𝜇! %. Undersökningen av samplingsfrekvensen visar att om samplingsfrekvensen väljs som2en divisor eller en multipel av pulsfrekvensen ökar felet, på grund av medelvärdesbildning,med en storleksordning. Genom att använda den information som ges i denna rapport är detmöjligt att undvika onödiga fel när tryck mäts i pulserande flöden.
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Rai, Gurjeet Kaur. "Accommodation and intraocular pressure." Thesis, Aston University, 2007. http://publications.aston.ac.uk/14645/.
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The relationship between accommodation and intraocular pressure (IOP) has not been addressed as a research question for over 20 years, when measurement of both of these parameters was less advanced than today. Hence the central aim of this thesis was to evaluate the effects of accommodation on lOP. The instrument of choice throughout this thesis was the Pulsair EasyEye non-contact tonometer (NCT) due principally to its slim-line design which allowed the measurement of lOP in one eye and simultaneous stimulation of accommodation in the other eye. A second reason for using the Pulsair EasyEye NCT was that through collaboration with the manufacturers (Keeler, UK) the instrument's operational technology was made accessible. Hence, the principle components underpinning non-contact lOP measures of 0.1mmHg resolution (an order of magnitude greater than other methods) were made available. The relationship between the pressure-output and corneal response has been termed the pressure-response relationship, aspects of which have been shown to be related to ocular biometric parameters. Further, analysis of the components of the pressure-response relationship together with high-speed photography of the cornea during tonometry has enhanced our understanding of the derivation of an IOP measure with the Pulsair EasyEye NCT. The NCT samples the corneal response to the pressure pulse over a 19 ms cycle photoelectronically, but computes the subject's lOP using the data collected in the first 2.34 ms. The relatively instantaneous nature of the lOP measurement renders the measures susceptible to variations in the steady-state lOP caused by the respiratory and cardiac cycles. As such, the variance associated with these cycles was minimised by synchronising the lOP measures with the cardiac trace and maintaining a constant pace respiratory cycle at 15 breathes/minute. It is apparent that synchronising the lOP measures with the peak, middle or trough of the cardiac trace significantly reduced the spread of consecutive measures. Of the 3 locations investigated, synchronisation with the middle location demonstrated the least variance (coeflicient of variation = 9.1%) and a strong correlation (r = 0.90, p = <0.001) with lOP values obtained with Goldmann contact tonometry (n = 50). Accordingly IOP measures synchronised with the middle location of the cardiac cycle were taken in the RE while the LE fixated low (L; zero D), intermediate (I; 1.50 D) and high (H; 4 D) accommodation targets, Quasi-continuous measures of accommodation responses were obtained during the lOP measurement period using the portable infrared Grand Seiko FR-5000 autorefractor. The lOP reduced between L and I accommodative levels by approximately 0.61 mmHg (p <0.00 I). No significant reduction in IOP between L and H accommodation levels was elicited (p = 0.65) (n = 40). The relationship between accommodation and lOP was characterised by substantial inter-subject variations. Myopes demonstrated a tendency to show a reduction in IOP with accommodation which was significant only with I accommodation levels when measured with the NCT (r = 0.50, p = 0.01). However, the relationship between myopia and lOP change with accommodation reached significance for both I (r = 0.61, p= 0.003) and H (r = 0.531, p= 0.0 1) accommodation levels when measured with the Ocular blood Flow Analyser (OBFA). Investigation of the effects of accommodation on the parameters measured by the OBFA demonstrated that with H accommodation levels the pulse amplitude (PA) and pulse rate (PR) responses differed between myopes and emmetropes (PA: p = 0.03; PR: p = 0.004). As thc axial length increased there was a tendency for the pulsatile ocular blood flow (POBF) to reduce with accommodation, which was significant only with H accommodation levels (r = 0.38, p = 0.02). It is proposed that emmetropes arc able to regulate the POBF responses to changes in ocular perfusion pressure caused by changes in lOP with I (r = 0.77, p <0.001) and H (r = 0.73, p = 0.001) accommodation levels. However, thc relationship between lOP and POBF changes in the myopes was not correlated for both I (r = 0.33, p = 0.20) and H (r = 0.05, p = 0.85) accommodation levels. The thesis presents new data on the relationships between accommodation, lOP and parameters of the OBFA,: and provides evidence for possible lOP and choroidal blood flow regulatory mechanisms. Further the data highlight possible deficits in the vascular regulation of the myopic eye during accommodation, which may play a putative role in the aetiology of myopia development.
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Wang, Fa-Liang. "Blood pressure monitoring system /." Online version of thesis, 1992. http://hdl.handle.net/1850/11172.
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Barkley, Clayde Betts Mikel Olay Anthony. "Indirect pipe pressure measurement /." Click here to view, 2009. http://digitalcommons.calpoly.edu/mesp/12.
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Thesis (B.S.)--California Polytechnic State University, 2009.Project advisor: Jim Meagher. Title from PDF title page; viewed on Jan. 20, 2010. Includes bibliographical references. Also available on microfiche.
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Summonte, Luca. "High pressure fog system." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5685/.
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