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Dissertations / Theses on the topic 'Pulsed pressure'
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1
Bondoc, Bebe N. "Development of a pulsed atmospheric pressure ion source." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30235.
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This thesis describes the development of a high-performance Pulsed High-Voltage Atmospheric Pressure Ion Source for coupling a mass spectrometry system with an HPLC system. This novelty of the design resides in a modified electrospray system, which in addition to its normal DC operation, provides high-voltage of up to 30kV on the capillary by introducing high-voltage pulsing, the Pulsed High-Voltage API is predicted to allow a higher liquid throughput and a reduction in background contamination while maintaining an efficient ionization of the molecules under investigation. The Pulsed High-Voltage API is expected to have possible gains in sensitivity, versatility, and reliability of operation.
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Bondoc, Bebe N. "Development of a pulsed atmospheric pressure ion source." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0034/MQ64211.pdf.
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Rusterholtz, Diane. "Nanosecond Repetitively Pulsed Discharges in Atmospheric Pressure Air." Phd thesis, Ecole Centrale Paris, 2012. http://tel.archives-ouvertes.fr/tel-00997397.
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Nanosecond Repetitively Pulsed (NRP) discharges in atmospheric pressure air have many potential applications. Spark NRP discharges have applications in plasma assisted combustion. These discharges tend to stabilize lean flames which produce less NOx. Furthermore, an increase of several hundreds of Kelvins in less than 20 ns has been observed following NRP spark discharges, which could be used to create nanomaterials. NRP glow discharges, while creating an important number of actives species such as atomic oxygen, do not heat the ambient gas, which allows them to be used in temperature-sensitive applications such as bio-decontamination. In the first part of this thesis, we validate experimentally the mechanism that was proposed to explain the ultrafast heating observed. Time-resolved measurements of the absolute densities of two excited states of nitrogen and of the gas temperature have been performed with calibrated Optical Emission Spectroscopy. The second part of the thesis deals with the NRP glow regime. We have shown that its existence depends on several parameters, gas temperature and pressure, voltage across the electrodes, inter-electrode distance, pulse duration, radius of curvature of the electrodes. This regime had not been observed for temperatures lower than 750 K so far. Thanks to a detailed parametrical experimental study and the analysis of the obtained results, we have succeeded in identifying the NRP glow regime at ambient temperature and we observe a new type of "multi-channel" glow regime.
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Walsh, James L. "Ultra-short pulsed non-equilibrium atmospheric pressure gas discharges." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/15140.
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This thesis presents experimental studies of various non-thermal atmospheric pressure gas discharges generated using short pulsed excitation as an alternative to widely used sinusoidal excitation. Several pulse generators are detailed that provide high voltage pulses ranging from hundreds of microseconds to less than ten nanoseconds in duration. A key enabler to the generation of a stable discharge is a suitably high repetition rate; this prerequisite precludes many conventional pulsed power technologies. Fortunately, recent advances in semiconductor technology have made it possible to construct solid state switches capable of producing high voltage pulses with repetition rates of many kilohertz. Pulsed excitation introduces many opportunities to tailor the applied voltage and consequently enhance the discharge which are not possible with sinusoidal excitation sources. Through detailed electrical and optical analysis it is shown that pulsed excitation is not only more energy efficient than a comparable sinusoidal source but produces a higher flux of excited species that are essential in many applications. When pulse widths are reduced to a sub-microsecond timescale a novel barrier-free mode of operation is observed. It is shown that diffuse large area plasmas are easily produced at kilohertz repetition rates without the usually indispensable dielectric barriers. Experimental results show that a short pulse width prevents the onset of the undesirable glow-to-arc transition thus introducing an added degree of stability. A further benefit of pulsed excitation is the ability to produce gas discharges with a high instantaneous peak power yet low average power consumption, resulting in a high density plasma that exhibits roomtemperature characteristics. Finally, as an acid test to highlight the many benefits of pulsed excitation several real-world applications are considered. It is shown that in all cases pulsed gas discharges provide real benefits compared to their sinusoidal counterparts.
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Zhang, Yiyun S. M. Massachusetts Institute of Technology Department of Aeronautics and Astronautics. "Pulsed nanosecond dielectric barrier discharge in nitrogen at atmospheric pressure." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127118.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 85-87).
Small power devices are of strong interest as many electronics are made more compact. Those portable power sources are widely used in aerospace applications such as small UAVs and satellite thrusters. Typically, these portable devices rely on batteries, but small power generators based on hydrocarbon fuel micro-combustors have much higher energy densities. However, flame instability and extinction are difficult to avoid at small scales. Because of the high surface to volume ratio, significant heat loss and radical quenching at the walls take place. To address this challenge, plasma has shown capabilities in facilitating combustion through thermal, kinetic and transport effects. In this work, a preliminary study of plasma discharge at atmospheric pressure is conducted as the first step to understand Plasma-Assisted Combustion (PAC) at micro scales.
Among various electric discharge mechanisms, Dielectric Barrier Discharge (DBD) is chosen due to its ability to generate non-thermal plasma at atmospheric pressure with a simple geometry and a low power consumption. Repetitive Pulsed Nanosecond Discharge (RPND) technique is also studied. It provides repetitive high voltage pulses on the order of 10 - 20 nanoseconds and is a common technique in non-equilibrium plasma generation. A 1D DBD model is constructed for a volume discharge. It couples particle continuity equations with Poisson's equation, and solves for electric field and charged particle number densities. The numerical model is discretized in space and time to obtain charged particles evolution and electric properties. The model is firstly validated with open literature for both AC and RPND, and is then applied to our DBD setup at atmospheric pressure. In addition, a nitrogen (and air) discharge experiment is designed and operated with RPND.
Preliminary results show the capability to generate sustainable and uniform plasma at atmospheric pressure. The appearance is that of a uniform glow plasma free of micro-discharges. Several experimental findings help to understand the discharge physics and set a foundation for future applications in micro-scale combustion.
by Yiyun Zhang.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics
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Fernelius, Mark H. "Effect of Full-Annular Pressure Pulses on Axial Turbine Performance." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3825.
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Pulse detonation engines show potential to increase the efficiency of conventional gas turbine engines if used in place of the steady combustor. However, since the interaction of pressure pulses with the turbine is not yet well understood, a rig was built to compare steady flow with pulsing flow. Compressed air is used in place of combustion gases and pressure pulses are created by rotating a ball valve with a motor. This work accomplishes two main objectives that are different from previous research in this area. First, steady flow through an axial turbine is compared with full annular pulsed flow closely coupled with the turbine. Second, the error in turbine efficiency is approximately half the error of previous research comparing steady and pulsed flow through an axial turbine. The data shows that a turbine driven by full annular pressure pulses has operation curves that are similar in shape to steady state operation curves, but with a decrease in turbine performance that is dependent on pulsing frequency. It is demonstrated that the turbine pressure ratio increases with pulsed flow through the turbine and that this increase is less for higher pulsing frequencies. For 10 Hz operation the turbine pressure ratio increases by 0.14, for 20 Hz it increases by 0.12, and for 40 Hz it increases by 0.06. It is demonstrated that the peak turbine efficiency is lower for pulsed flow when compared with steady flow. The difference between steady and pulsed flow peak efficiency is less severe at higher pulsing frequencies. For 40 Hz operation the turbine efficiency decreases by 5 efficiency points, for 20 Hz it decreases by 9 points, and for 10 Hz it decreases by 11 points. It is demonstrated that the specific power at a given pressure ratio for pulsed flow is lower than that of steady flow and that the decrease in specific power is lower for higher pulsing frequencies. On average, the difference in specific power between steady and pulsed flow is 0.43 kJ/kg for 40 Hz, 1.40 kJ/kg for 20 Hz, and 1.91 kJ/kg for 10 Hz.
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Tholin, Fabien. "Numerical simulation of nanosecond repetitively pulsed discharges in air at atmospheric pressure : Application to plasma-assisted combustion." Phd thesis, Ecole Centrale Paris, 2012. http://tel.archives-ouvertes.fr/tel-00879856.
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In this Ph.D. thesis, we have carried out numerical simulations to study nanosecond repetitively pulsed discharges (NRPD) in a point-to-point geometry at atmospheric pressure in air and in H2-air mixtures. Experimentally, three discharge regimes have been observed for NRPD in air at atmospheric pressure for the temperature range Tg = 300 to 1000 K: corona, glow and spark. To study these regimes, first, we have considered a discharge occurring during one of the nanosecond voltage pulses. We have shown that a key parameter for the transition between the discharge regimes is the ratio between the connection-time of positive and negative discharges initiated at point electrodes and the pulse duration. In a second step, we have studied the dynamics of charged species during the interpulse at Tg = 300 and 1000 K and we have shown that the discharge characteristics during a given voltage pulse remain rather close whatever the preionization level (in the range 109-1011 cm��3) left by previous discharges. Then, we have simulated several consecutive nanosecond voltage pulses at Tg = 1000 K at a repetition frequency of 10 kHz. We have shown that in a few voltage pulses, the discharge reaches a stable quasi-periodic glow regime observed in the experiments. We have studied the nanosecond spark discharge regime. We have shown that the fraction of the discharge energy going to fast heating is in the range 20%- 30%. Due to this fast heating, we have observed the propagation of a cylindrical shockwave followed by the formation of a hot channel in the path of the discharge that expands radially on short timescales (t < 1 _s), as observed in experiments. Then we have taken into account an external circuit model to limit the current and then, we have simulated several consecutive pulses to study the transition from multipulse nanosecond glow to spark discharges. Finally the results of this Ph.D. have been used to find conditions to obtain a stable glow regime in air at 300 K and atmospheric pressure. Second we have studied on short time-scales (t_ 100_s) the ignition by a nanosecond spark discharge of a lean H2-air mixture at 1000 K and atmospheric pressure with an equivalence ratio of _ = 0:3. We have compared the relative importance for ignition of the fast-heating of the discharge and of the production of atomic oxygen. We have shown that the ignition with atomic oxygen seems to be slightly more efficient and has a completely different dynamics.
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Cave, Hadley Mervyn. "Development of Modelling Techniques for Pulsed Pressure Chemical Vapour Deposition (PP-CVD)." Thesis, University of Canterbury. Mechanical Engineering, 2008. http://hdl.handle.net/10092/1572.
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In this thesis, a numerical and theoretical investigation of the Pulsed Pressure Chemical
Vapour Deposition (PP-CVD) progress is presented. This process is a novel method for the
deposition of thin films of materials from either liquid or gaseous precursors. PP-CVD
operates in an unsteady manner whereby timed pulsed of the precursor are injected into a
continuously evacuated reactor volume.
A non-dimensional parameter indicating the extent of continuum breakdown under strong
temporal gradients is developed. Experimental measurements, supplemented by basic
continuum simulations, reveal that spatio-temporal breakdown of the continuum condition
occurs within the reactor volume. This means that the use of continuum equation based
solvers for modelling the flow field is inappropriate. In this thesis, appropriate methods are
developed for modelling unsteady non-continuum flows, centred on the particle-based Direct
Simulation Monte Carlo (DSMC) method.
As a first step, a basic particle tracking method and single processor DSMC code are used to
investigate the physical mechanisms for the high precursor conversion efficiency and
deposition uniformity observed in experimental reactors. This investigation reveals that at
soon after the completion of the PP-CVD injection phase, the precursor particles have an
approximately uniform distribution within the reactor volume. The particles then simply
diffuse to the substrate during the pump-down phase, during which the rate of diffusion
greatly exceeds the rate at which particles can be removed from the reactor. Higher precursor
conversion efficiency was found to correlate with smaller size carrier gas molecules and
moderate reactor peak pressure.
An unsteady sampling routine for a general parallel DSMC method called PDSC, allowing the
simulation of time-dependent flow problems in the near continuum range, is then developed
in detail. Nearest neighbour collision routines are also implemented and verified for this code.
A post-processing procedure called DSMC Rapid Ensemble Averaging Method (DREAM) is
developed to improve the statistical scatter in the results while minimising both memory and
simulation time. This method builds an ensemble average of repeated runs over small number
of sampling intervals prior to the sampling point of interest by restarting the flow using either
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a Maxwellian distribution based on macroscopic properties for near equilibrium flows
(DREAM-I) or output instantaneous particle data obtained by the original unsteady sampling
of PDSC for strongly non-equilibrium flows (DREAM-II). The method is validated by
simulating shock tube flow and the development of simple Couette flow. Unsteady PDSC is
found to accurately predict the flow field in both cases with significantly reduced run-times
over single processor code and DREAM greatly reduces the statistical scatter in the results
while maintaining accurate particle velocity distributions. Verification simulations are
conducted involving the interaction of shocks over wedges and a benchmark study against
other DSMC code is conducted.
The unsteady PDSC routines are then used to simulate the PP-CVD injection phase. These
simulations reveal the complex flow phenomena present during this stage. The initial
expansion is highly unsteady; however a quasi-steady jet structure forms within the reactor
after this initial stage. The simulations give additional evidence that the collapse of the jet at
the end of the injection phase results in an approximately uniform distribution of precursor
throughout the reactor volume.
Advanced modelling methods and the future work required for development of the PP-CVD
method are then proposed. These methods will allow all configurations of reactor to be
modelled while reducing the computational expense of the simulations.
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Buzrul, Sencer. "High Hydrostatic Pressure (hhp) Applications In Food Science: A Study On Compression Heating, Microbial Inactivation Kinetics, Pulsed Pressure And High Pressure Carbon Dioxide Treatments." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609466/index.pdf.
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In this study the action of high hydrostatic pressure (HHP) on compression heating of liquid foods and pressure transmitting fluids, inactivation of Escherichia coli and Listeria innocua in different food media (milk and fruit juices), pulsed pressure and high pressure carbon dioxide treatments was investigated.
The experimental results in this study allowed pointing out some important results:
(i) The thermal effects of compression should be taken into account when HHP pasteurization processes are developed. Initial temperature of the food product and compression rate should carefully be selected in order to compensate the compression heating(ii) The HHP inactivation kinetics need not follow traditional first-order kinetics, hence alternative inactivation models are ought to be found. Weibull model can be used for HHP inactivation kinetics of microorganisms
(iii) The pulsed pressure treatment could be an alternative to continuous HHP, but optimization should be done between the pulse holding time, the number of pulses and the pressure level to reach the desirable number of log-reduction of microorganisms (E. coli and L. innocua) compatible with an industrial application
(iv) The storage duration and storage temperature after HHP treatment should carefully be optimized to increase the safety of HHP treated fruit juices since the growth of injured microorganisms can be avoided during storage
(v) The high pressure carbon dioxide (HPCD) treatment in combination with pulsed pressure can be an efficient way to inactivate the microorganisms in skim milk and to reduce the maximum pressure level for the desired log-reduction.
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Tadic, Dihon Misha. "Investigation of cavitating and pulsed high-pressure water jet devices for process scale removal /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17660.pdf.
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Aval, Sattar Motedayen. "A study of pulsed sprays in a high pressure and temperature gas cross flow." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333238.
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Lim, Chin Wai. "Numerical Modelling of Transient and Droplet Transport for Pulsed Pressure - Chemical Vapour Deposition (PP-CVD) Process." Thesis, University of Canterbury. Mechanical Engineering, 2012. http://hdl.handle.net/10092/6829.
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The objective of this thesis is to develop an easy-to-use and computationally economical numerical tool to investigate the flow field in the Pulsed Pressure Chemical Vapour Deposition (PP-CVD) reactor. The PP-CVD process is a novel thin film deposition technique with some advantages over traditional CVD methods. The numerical modelling of the PP-CVD flow field is carried out using the Quiet Direct Simulation (QDS) method, which is a flux-based kinetic-theory approach. Two approaches are considered for the flux reconstruction, which are the true directional manner and the directional splitting method. Both the true directional and the directional decoupled QDS codes are validated against various numerical methods which include EFM, direct simulation, Riemann solver and the Godunov method. Both two dimensional and axisymmetric test problems are considered. Simulations are conducted to investigate the PP-CVD reactor flow field at 1 Pa and 1 kPa reactor base pressures. A droplet flash evaporation model is presented to model the evaporation and transport of the liquid droplets injected. The solution of the droplet flash evaporation model is used as the inlet conditions for the QDS gas phase solver. The droplet model is found to be able to provide pressure rise in the reactor at the predicted rate. A series of parametric studies are conducted for the PP-CVD process. The numerical study confirms the hypothesis that the flow field uniformity is insensitive to the reactor geometry. However, a sufficient distance from the injection inlet is required to allow the injected precursor solution to diffuse uniformly before reaching the substrate. It is also recommended that placement of the substrate at the reactor’s centre axis should be avoided.
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Donovan, Molly Hope. "Unsteady Effects of a Pulsed Blowing System on an Endwall Vortex." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1559398697459176.
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Buntat, Zolkafle. "Ozone generation using electrical discharges : a comparative study between pulsed streamer discharge and atmospheric pressure glow discharge." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/14556.
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This thesis deals with an investigation into atmospheric pressure glow discharge and pulsed streamer discharge techniques of ozone generation, in an attempt to compare their performances in the generation of a high concentration and high yield of ozone. It is motivated by the desire to exploit further the ability and potential possessed by both techniques for ozone generation and to provide support to the increased demand for ozone in many areas of application. Chapter 1 of the thesis provides a brief history into the application of ozone. In Chapter 2, a basic understanding of the gas discharge is given for both thermal and non-thermal plasm as, and the theory 0 f non-thermal plasma is presented. The different types of electric discharges commonly used for ozone generation are explained. A review of the effect of both the physical configuration and the electrical parameters on the ozone yield and concentration is presented in Chapter 3, with the three main parameters that limit the efficiency of the production being highlighted. The second part of the thesis describes a thorough experimental investigation. In Chapter 4, a study is made of the stability of the atmospheric pressure glow discharge (APGD) which is found to be more stable when perforated electrodes are used rather than a fine steel wire mesh. Following this, a comparative study between APGD and pulsed streamer discharge (PSD) is presented in Chapter 5. A detailed investigation into both APGD and PSD in air is described. The effects of varying the input voltage, gap distance, chamber length, air flow rate and gas residence time are all used to evaluate the performance of both techniques. The PSD is found to generate a higher concentration but with a lower ozone yield. On the other hand, the APGD generates a lower concentration but with a higher yield. Chapter 6 presents the effect of a cross magnetic field on an AC corona and the PSD techniques and its influence on ozone generation. Results show no apparent effect of the magnetic field in either technique. Chapter 7 describes the use of dimensional analysis in investigating the effect of the electrical and the discharge configuration parameters on ozone production in oxygen by means of a PSD. Ozone destruction factors are taken into account in the model, and predicted results are shown to be in good agreement with experimental findings.
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Li, Ting. "Experimental Study of the Effects of Nanosecond-Pulsed Non-equilibrium Plasmas on Low-Pressure, Laminar, Premixed Flames." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417632325.
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Brisson, Élodie. "Étude expérimentale et numérique du frittage-assemblage d’un composite conducteur l’Ag-SnO2 par courants pulsés." Thesis, Lorient, 2014. http://www.theses.fr/2014LORIS339.
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Ces travaux de thèse s’inscrivent dans le cadre du projet "IMPULSE" qui traite du développement d’un procédé innovant d’élaboration de multi-matériaux par courant pulsé et est financé par l’Agence National de la Recherche. Ils ont pour objectif d’étudier et de mettre en évidence la faisabilité, du frittage-assemblage sous charge par courants pulsés, d’un composite conducteur l’AgSn-O2 sur un support en cuivre. Cette problématique, en lien avec les applications industrielles de Schneider Electric Industries, a été abordée au travers de simulations numériques du procédé de frittage-assemblage et d’essais expérimentaux. Les travaux sur les étapes de frittage et d’assemblage ont pu être traités séparément. Les phénomènes qui interviennent lors du frittage par effet Joule et les effets spécifiques liés à l’utilisation de certaines formes ou fréquences de courant, divisent encore la communauté scientifique. Des essais de frittage et frittage-assemblage par chauffage résistif avec différents types de courant (pulsé, continu, 50 Hz) ont été réalisés et ont permis de mettre en évidence l’absence d’effets spécifiques associés aux courants pulsés dans le cas de l’Ag-SnO2. Par conséquence, un modèle électrocinétique classique stationnaire a été retenu concernant les aspects électriques du modèle macroscopique de frittage. Ces essais ont également révélé l’importance des résistances de contact électrique, présentes entre les outillages (poinçons) et l’échantillon, et de la résistance de contact thermique qui existe entre l’échantillon et la matrice. Le modèle thermique instationnaire choisi est couplé fortement au modèle électrocinétique. Les lois de comportement utilisées pour la masse volumique et les conductivités (électrique et thermique), qui interviennent dans le modèle Electro-Thermique (ET), tiennent compte des changements de microstructure grâce à l’utilisation de variables internes de « densification » et de « cohésion ». Les évolutions des résistances de contact électrique et thermique, mesurées sur un dispositif ex-situ, sont aussi implémentées dans le modèle ET.D’un point de vue mécanique, un modèle de Norton associé au critère de Green a été choisi pour modéliser le comportement viscoplastique de la matière et la compressibilité irréversible du matériau lors du frittage sous charge de l’Ag-SnO2. Les fonctions intervenant dans le critère dépendent de la densité relative, dont la cinétique de densification est calculée à partir de la trace du tenseur des vitesses de déformation irréversible. Les paramètres de la loi de comportement mécanique ont été identifiés par méthodes inverses, à l’aide des logiciels SiDoLo et Abaqus, à partir d’essais thermomécaniques spécifiques réalisés sur la machine Gleeble du LIMatB. La loi de comportement mécanique a été implémentée dans une bibliothèque spécifique du code de calcul par éléments finis Sysweld qui est utilisé pour la simulation numérique d’essais de frittage instrumentés. La concordance entre les résultats numériques et expérimentaux (tensions, températures, mesure extensométrique), est satisfaisante et les écarts restent inférieurs aux erreurs expérimentales. Concernant l’étape d’assemblage, une campagne de caractérisation de la tenue de l’assemblage Ag-SnO2/Cu, a été menée sur la machine Gleeble grâce à des essais de frittage-assemblage anisothermes. Différentes cinétiques thermiques et différentes températures maximales, ont été testées afin de mettre en évidence l’effet du temps et de la température. Des tests de cisaillement de l’assemblage, ont permis le calcul d’un observable afin de juger de la qualité de la liaison. Au vu des résultats, un modèle dépendant uniquement de la température atteinte dans l’échantillon a été développé afin d’estimer la tenue de l’assemblage Ag-SnO2/CuThis thesis is part of the "IMPULSE" project, which is financed by the NationalAgency of Research. This project concerns the development of innovative process to produce multimaterials by pulsed currents. The ability of sintering and joining Ag-SnO2 powder on a copper support in the same process under pressure by pulsed currents is investigated. This problematic, linked to industrial applications of Schneider Electric Industries SEI), has been approached through numerical simulations and experimental tests of sintering-joining. Sintering and joining steps have been dealt separately in this works. Sintering phenomena and specific effects of pulsed currents still divide the scientific community. Sintering and sintering-joining test by resistive heating thanks different kinds of current (pulsed, DC, AC) have been realized. They have enabled to highlight that there are not specific effects of pulsed currents in the Ag-SnO2 case. Consequently, a classical stationary electrokinetic model has been used for electrical aspects in the macroscopic sintering model. These tests have also revealed the importance of the contact resistance (CR) present between tools and sample, and more particularly the electrical CR between punches and sample and the thermal CR between die and sample. The non-stationary thermal model chose is strongly coupled with the electrokinetic model. Characterization tests have shown that electrical and thermal conductivities increase with inter-granular contact rate improvement, which is caused by strain during densification and by diffusion ("cohesion" mechanisms). The behavior laws used to calculate the density and the conductivities (electrical and thermal) of the Electrokinetic-Thermal model (ET), take into account these microstructural evolutions by mean of internal variables of "densification" and "cohesion". Electrical and thermal contact resistances, measured in LIMatB’s device versus pressure and temperature, are implemented in the ET model. From a mechanical point of view, a Norton model combined with a Green criterion has been chosen to modeling the viscoplastic behavior of matter and the irreversible compressibility of Ag-SnO2 material during sintering under pressure. The criterion functions depend on the relative density. The densification kinetic is calculated from the trace of the irreversible deformation kinetics. The properties (viscoplastic parameters, elasticity limit,...) of mechanical behavior law have been identified by inverse methods using SiDoLo and Abaqus software from thermo-mechanical tests achieved on LIMatB’s Gleeble machine. The mechanical properties don’t depend of cohesion mechanisms. The mechanical behavior law has been implemented in the finite element code Sysweld to simulate sintering tests. The agreement between numerical and experimental results (tensions, temperatures, extensometric measurements) is correct and the differences remain inferior to the experimental errors. Tests of joining of Ag-SnO2 on a copper support, non isothermal under low pressure, have been achieved on Gleeble machine. Different thermal kinetics and different maximal temperatures have been explored to highlight time and temperature effects on diffusion mechanisms at the interface. Shear tests of the joining have enabled the calculation of an observable to estimate the bonding quality. From these results, a model which only depends of temperature reached in the sample has been developed to estimate the Ag-SnO2/Cu joining resistance. This joining model could be easily integrated in the more complex sintering model
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Scharlemann, Carsten A. "Investigation of thrust mechanisms in a water fed pulsed plasma thruster." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1070354149.
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Bolduc, Mathieu. "Deposition of Commercially Pure Titanium Powder Using Low Pressure Cold Spray and Pulsed Gas Dynamic Spray for Aerospace Repairs." Thesis, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24249.
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The objective of this study is to investigate the feasibility of depositing 1.5 mm thick titanium coatings, as a repair method for aerospace Ti-6Al-4V substrates, using two new commercially available processes: Low Pressure Cold Spray (LPCS) and Pulsed Gas Dynamic Spray (PGDS). The coatings produced were examined and characterized by their porosity level, microhardness, adhesion strength, particle flattening ratio, wipe tests, fracture surface type and wear tests. Phases and chemical composition were determined using X-Ray diffraction analysis and energy dispersive spectroscopy, respectively. It was found that both spraying processes are capable of producing dense, hard and oxide-free coatings using specific parameters. Finally, as a first step towards repair implementation of these processes, damages were simulated on Ti-6Al-4V samples, which were successfully repaired with low porosity and high hardness levels. The feasibility of repairs was confirmed, the next step will consist in qualification testing to assess coating performances under real life application.
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Schröder, Hendrik. "Metal-Catalyzed Radical Polymerization up to High Pressure." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://hdl.handle.net/11858/00-1735-0000-0023-962F-C.
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Woods, Nathan Michael. "PHASE-LOCKED PIV INVESTIGATION OF THE EFFECTS OF THE BLOWING RATIO OF A PULSED VORTEX GENERATOR JET IN A LOW-PRESSURE TURBINE." Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1190066085.
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Bogdanov, Bogdan. "Structures, thermochemistry, and dynamics of negative gas phase cluster ions studied by pulsed-ionization high pressure mass spectrometry and computational quantum chemistry techniques." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ65224.pdf.
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Siriwongrungson, Vilailuck. "Characterisation of Step Coverage by Pulsed-Pressure Metalorganic Chemical Vapour Deposition: Titanium Dioxide Thin Films on 3-D Micro- and Nano-Scale Structures." Thesis, University of Canterbury. Mechanical Engineering, 2010. http://hdl.handle.net/10092/3615.
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An examination of the possibility of applying pulse pressure metalorganic chemical vapour deposition (PP-MOCVD) to conformal coating and an investigation of PP-MOCVD processing parameters were undertaken using the deposition of thin, conformal titanium dioxide (TiO₂) on 3-D featured and non-featured substrates. The characterisation of the conformality and wettability analysis of thin TiO₂ was carried out using titanium tetraisopropoxide (TTIP) dissolved in toluene as a precursor and featured silicon (Si) and silicon nitride (Si₃N₄) as substrates. The features on the substrates were in micro- and nano-scale with the aspect ratio up to 2:1.
The processing parameters investigated were temperatures between 400 and 600°C, reactor base pressures from 50 to 200 Pa, injection volumes between 50 and 250 µl, precursor concentrations in the range of 0.15 to 0.50 mol% and pulsing times from 10 to 20 sec. The surface morphology and thickness were examined using a scanning electron microscope (SEM). The composition of the films was qualitatively identified by energy dispersive X-ray spectroscopy (EDS). X-ray diffraction (XRD) and Raman spectroscopy were used to analyse the phase and grain size. The surface roughness and grain size were evaluated using atomic force microscopy (AFM). The optical properties were characterised using UV-VIS light spectroscopy. The anti-sticking characteristic was examined by wettability analysis, measuring the contact angle of the film with water. The research examined the relationships between processing parameters and growth rate, conformality, surface roughness, grain size, phase and water contact angle.
A new measurement for thin film conformality was derived based on a statistical analysis of a large number of film thickness measurements on a fracture surface over the lithographed features. The best conformality of 0.95 was obtained for micro-scale features at the lowest temperature in the range of investigation, 400℃, with pulse exposure characterised by a base pressure of 100 Pa, TTIP concentration of 0.50 mol%, injection volume of 50 µl and pulsing time of 10 sec. Conformality for micro-scale features was in the range of 0.82 to 0.97 over a wide range of deposition temperatures. Conformality was as low as 0.45 over nano-scale structures at the higher exposure rate. The conformality decreased as the temperature and precursor concentration increased. The precursor injection volume was found to have minor influences on conformality.
The growth rate increased as the temperature increased and reached the maximum at the deposition temperature of 450℃ with the precursor concentration of 0.50 mol% and injection volume of 100 µl. The base pressure and relaxation time had slight influences on the growth rate over the deposition temperature range of 400 to 500℃. The growth rate was increased as the precursor concentration and precursor injection volume increased.
The deposited TiO₂ films exhibited columnar growth and anatase phase. The base pressure and pulsing time had no obvious effects on grain size and surface roughness. The grain size decreased as the deposition temperature increased. The surface roughness increased as the deposition temperature increased.
Contact angles of over 100° were found with conformality of over 0.80. The variation in contact angle was related to the surface morphology of the deposited films. The contact angle increased as the grain size decreased. High wettability was found for films in the mid-range of pulse exposure, in this study at pulse exposure of 53, or at high deposition temperature, in this case at 600°C. The as-deposited TiO₂ thin films were hydrophobic depending on the surface morphology, surface roughness and grain size.
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Schmidt, Jacob Brian. "Ultrashort Two-Photon-Absorption Laser-Induced Fluorescence in Nanosecond-Duration, Repetitively Pulsed Discharges." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437694779.
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Memory, Curtis L. "Turbulent Transition Behavior in a Low Pressure Turbine Subjected to Separated and Attached-Flow Conditions." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1290996104.
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Meyer, Tricia Lynn. "Structure, magnetism and transport properties of CaxSr1-xMn0.5Ru0.5O3 bulk and thin film materials." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386001173.
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Schregel, Christian-Georg [Verfasser], Uwe [Gutachter] Czarnetzki, and Achim von [Gutachter] Keudell. "Thomson scattering on a nanosecond pulsed atmospheric pressure helium micro-discharge / Christian-Georg Schregel ; Gutachter: Uwe Czarnetzki, Achim von Keudell ; Fakultät für Physik und Astronomie." Bochum : Ruhr-Universität Bochum, 2018. http://d-nb.info/1152077856/34.
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Fernelius, Mark H. "Experimental and Computational Analysis of an Axial Turbine Driven by Pulsing Flow." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6548.
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Pressure gain combustion is a form of combustion that uses pressure waves to transfer energy and generate a rise in total pressure during the combustion process. Pressure gain combustion shows potential to increase the cycle efficiency of conventional gas turbine engines if used in place of the steady combustor. However, one of the challenges of integrating pressure gain combustion into a gas turbine engine is that a turbine driven by pulsing flow experiences a decrease in efficiency. The interaction of pressure pulses with a turbine was investigated to gain physical insights and to provide guidelines for designing turbines to be driven by pulsing flow. An experimental rig was built to compare steady flow with pulsing flow. Compressed air was used in place of combustion gases; pressure pulses were created by rotating a ball valve with a motor. The data showed that a turbine driven by full annular pressure pulses has a decrease in turbine efficiency and pressure ratio. The average decrease in turbine efficiency was 0.12 for 10 Hz, 0.08 for 20 Hz, and 0.04 for 40 Hz. The turbine pressure ratio, defined as the turbine exit total pressure divided by the turbine inlet total pressure, ranged from 0.55 to 0.76. The average decrease in turbine pressure ratio was 0.082 for 10 Hz, 0.053 for 20 Hz, and 0.064 for 40 Hz. The turbine temperature ratio and specific turbine work were constant. Pressure pulse amplitude, not frequency, was shown to be the main cause for the decrease in turbine efficiency. Computational fluid dynamics simulations were created and were validated with the experimental results. Simulations run at the same conditions as the experiments showed a decrease in turbine efficiency of 0.24 for 10 Hz, 0.12 for 20 Hz, and 0.05 for 40 Hz. In agreement with the experimental results, the simulations also showed that pressure pulse amplitude is the driving factor for decreased turbine efficiency and not the pulsing frequency. For a pulsing amplitude of 86.5 kPa, the efficiency difference between a 10 Hz and a 40 Hz simulation was only 0.005. A quadratic correlation between turbine efficiency and corrected pulse amplitude was presented with an R-squared value of 0.99. Incidence variation was shown to cause the change in turbine efficiency and a correlation between corrected incidence and corrected amplitude was established. The turbine geometry was then optimized for pulsing flow conditions. Based on the optimization results and observations, design recommendations were made for designing turbines for pulsing flow. The first design recommendation was to weight the design of the turbine toward the peak of the pressure pulse. The second design recommendation was to consider the range of inlet angles and reduce the camber near the leading edge of the blade. The third design recommendation was to reduce the blade turning to reduce the wake caused by pulsing flow. A new turbine design was created and tested following these design recommendations. The time-accurate validation simulation for a 10 Hz pressure pulse showed that the new turbine decreased the entropy generation by 35% and increased the efficiency by 0.04 (5.4%).
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Lögdberg, Ola. "Turbulent Boundary Layer Separation and Control." Doctoral thesis, KTH, Linné Flow Center, FLOW, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9821.
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Boundary layer separation is an unwanted phenomenon in most technical applications, as for instance on airplane wings, ground vehicles and in internal flow systems. If separation occurs, it causes loss of lift, higher drag and energy losses. It is thus essential to develop methods to eliminate or delay separation.In the present experimental work streamwise vortices are introduced in turbulent boundary layers to transport higher momentum fluid towards the wall. This enables the boundary layer to stay attached at larger pressure gradients. First the adverse pressure gradient (APG) separation bubbles that are to be eliminated are studied. It is shown that, independent of pressure gradient, the mean velocity defect profiles are self-similar when the scaling proposed by Zagarola and Smits is applied to the data. Then vortex pairs and arrays of vortices of different initial strength are studied in zero pressure gradient (ZPG). Vane-type vortex generators (VGs) are used to generate counter-rotating vortex pairs, and it is shown that the vortex core trajectories scale with the VG height h and the spanwise spacing of the blades. Also the streamwise evolution of the turbulent quantities scale with h. As the vortices are convected downstream they seem to move towards a equidistant state, where the distance from the vortex centres to the wall is half the spanwise distance between two vortices. Yawing the VGs up to 20° do not change the generated circulation of a VG pair. After the ZPG measurements, the VGs where applied in the APG mentioned above. It is shown that that the circulation needed to eliminate separation is nearly independent of the pressure gradient and that the streamwise position of the VG array relative to the separated region is not critical to the control effect. In a similar APG jet vortex generators (VGJs) are shown to as effective as the passive VGs. The ratio VR of jet velocity and test section inlet velocity is varied and a control effectiveness optimum is found for VR=5. At 40° yaw the VGJs have only lost approximately 20% of the control effect. For pulsed VGJs the pulsing frequency, the duty cycle and VR were varied. It was shown that to achieve maximum control effect the injected mass flow rate should be as large as possible, within an optimal range of jet VRs. For a given injected mass flow rate, the important parameter was shown to be the injection time t1. A non-dimensional injection time is defined as t1+ = t1Ujet/d, where d is the jet orifice diameter. Here, the optimal t1+ was 100-200.QC 20100825
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Saroya, Harlin Kaur. "Innovative Non-Thermal Food Processing Technologies Used By The Food Industry In The United States." TopSCHOLAR®, 2017. https://digitalcommons.wku.edu/theses/2028.
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This thesis discussed the non-thermal food processing technologies being used within the United States of America. The technologies discussed in this thesis are High- Pressure Processing (HHP), Pulsed Electric Field, Pulsed Light, Irradiation, Ultra Sound, Oscillating Magnetic Fields, and Cold Atmospheric Plasma. A survey was designed and conducted to study the major reasons behind a preference for a particular technology by the organization, and the limitations for not implementing specific technologies. The survey participants were management level, food scientists and, food technologists employed by food processing companies. The questionnaire consisted of ten questions related to demographics, current technology, barriers from other technologies, and research and development of new technologies.
There were a total 223 respondents from various regions of the United States. The respondents had a wide array of industry experience. Of the respondents, 91% of the respondents had either a Bachelor’s Degree, Master’s Degree or Ph D. Thirty-six percent of the participants chose high pressure processing and 20 % chose pulsed electric as the most commonly used non-thermal food processing technologies. Rapidly increasing technologies included cold atmospheric plasma and oscillating magnetic fields. Seventyone percent mentioned the main driver for them to choose non-thermal food processing was better nutrient and sensory properties. As per the results, 41% of respondents believed the major limitations in implementing non-thermal food processing technologies was high investment. The results indicated the main drivers for innovation were equipment manufacturers and research. These researches were either academic or government funded.
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Zocher, Maria Katja Verfasser], Michael [Akademischer Betreuer] Lalk, Jürgen F. [Akademischer Betreuer] Kolb, Michael [Gutachter] Lalk, Jürgen F. [Gutachter] Kolb, and Timo H. J. [Gutachter] [Niedermeyer. "Extraction of bioactive primary and secondary Metabolites from Microalgae by atmospheric pressure Plasmas and pulsed Discharges in Water / Maria Katja Zocher ; Gutachter: Michael Lalk, Jürgen F. Kolb, Timo Niedermeyer ; Michael Lalk, Jürgen F. Kolb." Greifswald : Universität Greifswald, 2019. http://d-nb.info/1202111319/34.
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Zocher, Maria Katja [Verfasser], Michael Akademischer Betreuer] Lalk, Jürgen F. [Akademischer Betreuer] Kolb, Michael [Gutachter] Lalk, Jürgen F. [Gutachter] Kolb, and Timo H. J. [Gutachter] [Niedermeyer. "Extraction of bioactive primary and secondary Metabolites from Microalgae by atmospheric pressure Plasmas and pulsed Discharges in Water / Maria Katja Zocher ; Gutachter: Michael Lalk, Jürgen F. Kolb, Timo Niedermeyer ; Michael Lalk, Jürgen F. Kolb." Greifswald : Universität Greifswald, 2019. http://d-nb.info/1202111319/34.
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Zocher, Maria Katja [Verfasser], Michael [Akademischer Betreuer] Lalk, Jürgen F. Akademischer Betreuer] Kolb, Michael [Gutachter] Lalk, Jürgen F. [Gutachter] Kolb, and Timo H. J. [Gutachter] [Niedermeyer. "Extraction of bioactive primary and secondary Metabolites from Microalgae by atmospheric pressure Plasmas and pulsed Discharges in Water / Maria Katja Zocher ; Gutachter: Michael Lalk, Jürgen F. Kolb, Timo Niedermeyer ; Michael Lalk, Jürgen F. Kolb." Greifswald : Universität Greifswald, 2019. http://nbn-resolving.de/urn:nbn:de:gbv:9-opus-34358.
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Söderström, Daniel. "Modelling and Applications of the Hollow Cathode Plasma." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8747.
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This thesis presents experimental and modelling research on atmospheric pressure hollow cathodes and hollow electrodes. Experiments with the hybrid hollow electrode activated discharge (H-HEAD), which is a combination of a hollow cathode and a microwave plasma source, is presented. The experiments show that this source is able to produce long plasma columns in air and nitrogen at atmospheric pressure and at very low gas flow rates. Measurements of the vibrational temperature of the nitrogen molecules are also presented in this thesis. The vibrational temperature is an indication of the electron temperature in the plasma, an important characteristic of the plasma. Modelling work on the hollow cathode at atmospheric pressure with fluid equations is also presented. It is shown that the inclusion of fast and secondary electrons, characteristic of the hollow cathode plasmas, increases the sheath width. The sheath width was found to be of the order of 100 μm. By modelling the plasma as highly collisional by using the drift-diffusion approximation, it was shown that the increase in sheath thickness was larger at lower pressures than at higher pressures. Still, the sheath width can be of the order of 100 μm. A pulsed atmospheric plasma in a hollow electrode geometry was also modelled by the drift-diffusion fluid equations, with the addition of the energy equation for electrons. Rate and transport coefficients for the electrons were calculated from the solution to the Boltzmann equation as functions of mean electron energy. The dynamics of the plasma at pulse rise time showed large electron density and mean energy peaks at the cathode ends, but also that these quantities were enhanced at the centre of the discharge, between the cathode plates.
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Lee, Darryl Liang Wee. "Development of a PP-MOCVD System and its Design and Operational Parameters for Uniform Industrial Coatings on 3D Objects." Thesis, University of Canterbury. Dept. of Mechanical Engineering, 2014. http://hdl.handle.net/10092/9644.
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Increase in demand for uniform ceramic coatings on larger industrial components have led to a need for a PP-MOCVD coating system scale up. The objective of this thesis is to develop a fully functional coating system operating in the PP-MOCVD regime that is able to deposit thin film ceramic coatings on commercial or industrial components with complex 3D geometries.
This can be achieved by applying engineering and vacuum science theories, coupled with the established fundamentals of PP-MOCVD. A larger system was designed and assembled around the boundaries set by the dimensions and geometry of a stainless steel water pump impellor acting as the base substrate. Most of the components were sourced off the shelf from vacuum and fluid specialists. Components which were unavailable for various reasons were designed, and machined in-house by the departmental workshop.
Initial test depositions were conducted using small stainless steel disk substrates, heated using a resistive heater similar to the one utilised on the research scale system. The test depositions were performed with the heater and substrate combination placed in strategic locations. This is to test the overall uniformity of precursor flux in the chamber volume. The resulting coating uniformity on the disk surfaces were fair but problems such as the large collection of unreacted precursor on the chamber viewport and valve timing issues had to be addressed.
Before making any improvements to the system, each of the process areas leading to a successful deposition needed to be understood. Five process areas were developed: ‘Liquid Delivery’, ‘Atomization’, ‘Evaporation’, ‘Transport and Reactor Geometry’, and ‘Droplet Management’. Each of the process areas were analysed individually and changes were made to push for a maximum evaporation efficiency.
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The improved system provided opportunities to perform depositions that were once not possible for PP-MOCVD. Two sets of deposition tests were designed and conducted. Firstly, the improvements were justified with a series of depositions using flat stainless steel plates with dimensions 65x65x5mm. The other set of 3D case study depositions involve observing the effects of the operational parameters of PP-MOCVD on the uniformity and penetration depths of the coatings into different sized macro blind trenches.
Five geometric setup conditions were used to justify the improvements made to the system. These are: ‘Substrate positioned in the direct line of spray’, ‘Use of an unheated receptor’, ‘Use of a heated receptor’, ‘Use of an unheated receptor with a non-axial substrate setup’, and “Choked Flow’. As expected, the uniformity of the coatings on both sides of the plate varied significantly when the substrate is placed over the line of sight of the precursor spray. Similarly, the coating produced under the induced choked flow condition resulted in low conformality. The introduction of an unheated receptor plate resulted in an increase in uniformity on both sides of the plate. Further prove that PP-MOCVD is geometry independent is provided by the deposition made with the non-axial substrate placement resulting in a coating of similar result to the unheated receptor. The use of a heated receptor provided a source for a secondary evaporation of the larger precursor droplets collected resulting in an increase in coating thickness while maintaining good conformality.
The effects of temperature, pressure, injection volume, and concentration were explored in the final case study. With maximum depths of 50mm, the macro blind trenches has an aspect ratio of 1:1 and cross-sectional areas of 3x3mm, 9x9mm, and 15x15mm. The final results show that as the temperature rises, the depth penetrated into the trench decreases. This could be due to the change in rate limiting steps as homogeneous reactions begin to increase at higher temperatures. Similar trends were observed with increasing pressure. As the pressure difference between the volume of the trenches and the rest of the chamber decreases, the push needed to
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force the precursor down the trench also decreases, resulting in less depth penetration. The effects of injection volume and concentration observed, can be explained by how much precursor molecules are present during one pulse cycle. The more that is available at any given time, the more likely a reaction will occur and deeper the penetration will get. Of course a ceiling or a limit exists where the molecules in the chamber will get evacuated without being reacted.
The future work made possible as a result of the scaled up system are proposed. These include a scale up of the operational parameters to suit any given substrate geometry, improvements to the heating source to achieve greater thermal uniformity, further improvements to the overall system accessibility, and performing other depositions using different substrate materials and precursor types.
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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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Iqbal, Hena. "Diastolic echocardiographic parameters in patients with atrial fibrillation." Thesis, Malmö högskola, Fakulteten för hälsa och samhälle (HS), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-26051.
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Vid flertalet hjärtsjukdomar kan det förekomma störningar i den diastoliska funktionen, detta tillstånd benämns diastolisk dysfunktion. Detta innebär att fyllnadstrycken i vänsterkammare ökar på grund av nedsatt eftergivlighet i kammaren. Bedömning av diastolisk funktion, hos patienter som utvecklat förmaksflimmer, är en utmaning inom ekokardiografi. Detta beror på att förmaksflimmer innebär utebliven förmakskontraktion, oregelbunden längd av hjärtcykeln och förmaksdilatation, vilket försvårar bedömningen. Syftet med studien var att med ekokardiografi studera diastoliska parametrar hos patienter med förmaksflimmer för att studera om dessa kan användas vid bedömning av den diastoliska vänsterkammarfunktionen hos denna patientgrupp. I studien inkluderades 37 deltagare med förmaksflimmer som var remitterade för en ekokardiografisk undersökning med olika frågeställningar. Pulsad doppler teknik och vävnads doppler teknik användes för att registrera följande diastoliska parametrar: förmaksvolym, mitralisinflöde (E-vågshastigheten) och myokardiets diastoliska hastigheter (e´). Utöver dessa uppskattades även ejektionsfraktion, hjärtfrekvens, hypertrofi och trycket i lilla kretsloppet, som togs med vid bedömningen. Mann-Whitneys test visade att det förelåg ett starkt statistiskt samband mellan fyllnadstrycket (E/e´) och E-vågen, e ´samt förmaksvolym (p = <0,05). Signifikant resultat erhölls även för sambandet mellan PA-tryck och fyllnadstryck (p = 0,014) genom ett chitvå-test. Vidare gav multipel linjär regression utslag på E-vågen och e´. Analysen visade att det förelåg en hög förklaringsgrad för E-vågen (p = <0,001) och e´ (p = 0,008). Sammanfattningsvis visade resultaten att ekokardiografi kan användas för diagnostik av förmaksflimmerpatienter avseende fyllnadstryck där förmaksvolym, E-vågshastigheten och e´ anses vara bästa parametrarna.In the majority of heart diseases disturbances in the diastolic function may occur, this condition is called diastolic dysfunction. This means that the left ventricular filling pressure increases due to reduced compliance in the chamber. The assessment of diastolic function in patients who have developed atrial fibrillation (AF), is a challenge in echocardiography. This is a result of AF which involves absence of atrial contraction, irregular length of the cardiac cycle and left atrium dilatation that complicates the assessment. The aim of this study was to observe the diastolic echocardiographic parameters in patients with AF to examine if these can be used in the assessment of diastolic left ventricular function in this population. The study included 37 participants with AF who were remitted for an echocardiographic examination due to various concerns. Pulsed Doppler technique and tissue Doppler technique was used to record the following diastolic parameters: atrial volume, mitral inflow velocity (E) and the myocardial diastolic velocity (e'). Ejection fraction, heart-rate, hypertrophy and pulmonary artery pressure were also estimated and included in the assessment. Mann-Whitneys test showed that there was a strong statistical correlation between the filling pressure (E/e') and E, e' and atrial volume (p = <0.05). Significant results were also obtained for the relation between pulmonary artery pressure and the filling pressure (p = 0.014) by a chi-square test. A multiple linear regression showed association between E and e'. The analysis showed that there was a significant value of coefficient of determination for E (p = <0.001) and e' (p = 0.008). In conclusion, the results showed that echocardiography can be used for diagnosis of AF patients regarding filling pressures, where atrial volume, E velocity and e' are considered to be the best parameters.
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Morgan, Andrew J. "Analysis of the intraocular pressure pulse." Thesis, Aston University, 2003. http://publications.aston.ac.uk/14542/.
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This thesis was concerned with investigating methods of improving the IOP pulse’s potential as a measure of clinical utility. There were three principal sections to the work. 1. Optimisation of measurement and analysis of the IOP pulse. A literature review, covering the years 1960 – 2002 and other relevant scientific publications, provided a knowledge base on the IOP pulse. Initial studies investigated suitable instrumentation and measurement techniques. Fourier transformation was identified as a promising method of analysing the IOP pulse and this technique was developed. 2. Investigation of ocular and systemic variables that affect IOP pulse measurements In order to recognise clinically important changes in IOP pulse measurement, studies were performed to identify influencing factors. Fourier analysis was tested against traditional parameters in order to assess its ability to detect differences in IOP pulse. In addition, it had been speculated that the waveform components of the IOP pulse contained vascular characteristic analogous to those components found in arterial pulse waves. Validation studies to test this hypothesis were attempted. 3. The nature of the intraocular pressure pulse in health and disease and its relation to systemic cardiovascular variables. Fourier analysis and traditional parameters were applied to the IOP pulse measurements taken on diseased and healthy eyes. Only the derived parameter, pulsatile ocular blood flow (POBF) detected differences in diseased groups. The use of an ocular pressure-volume relationship may have improved the POBF measure’s variance in comparison to the measurement of the pulse’s amplitude or Fourier components. Finally, the importance of the driving force of pulsatile blood flow, the arterial pressure pulse, is highlighted. A method of combining the measurements of pulsatile blood flow and pulsatile blood pressure to create a measure of ocular vascular impedance is described along with its advantages for future studies.
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Rotthäuser, Siegfried, Wilhelm Hagemeister, and Harald Pott. "Pressure Pulse Generation with Energy Recovery." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200010.
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The Pressure Impulse test-rig uses the principal energetic advantages of displacementcontrolled systems versus valve-controlled systems. The use of digital-control technology enables a high dynamic in the pressure curve, according to the requirements of ISO6605. Accumulators, along with inertia, make energy recovery possible, as well as, enabling the compression energy to be re-used. As a result of this, there is a drastic reduction in operating costs. A simulation of the system before starting the project allows the development risks to be calculated and the physically achievable performance limits to be shown.
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Baier, Anne Kathrin [Verfasser], Dietrich [Akademischer Betreuer] Knorr, Dietrich [Gutachter] Knorr, and Sascha [Gutachter] Rohn. "Potential of high isostatic pressure and pulsed electric fields for the processing of potato and pea proteins : structural and techno-functional characterization in model solutions and plant tissue / Anne Kathrin Baier ; Gutachter: Dietrich Knorr, Sascha Rohn ; Betreuer: Dietrich Knorr." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156186315/34.
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Archer, Martin. "Dynamic pressure pulses in Earth's dayside magnetosheath." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24743.
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Solar wind mass, energy and momentum can be transferred to Earth's magnetosphere at the magnetopause with the shocked magnetosheath acting as an interface between the two regions. In particular the magnetosheath pressure is important in terms of the position and motion of the magnetopause, which in turn can have effects throughout the dayside magnetosphere. A variety of transient phenomena often occur in the magnetosheath and in this thesis one example is studied, namely pulses in the magnetosheath dynamic pressure, using multipoint spacecraft observations to investigate their origins and magnetospheric impacts and illuminate dayside magnetospheric dynamics. Simultaneous observations in the solar wind, foreshock and magnetosheath reveal an interval of dynamic pressure pulses that did not exist upstream of the bow shock in the pristine solar wind or foreshock and appear consistent with previous simulations of solar wind discontinuities interacting with the bow shock, which predict large amplitude pulses when the local geometry of the shock changes. A statistical study of these structures, however, reveals their predominant origin near the quasi-parallel shock, typically under steady interplanetary magnetic fields, suggestive that the foreshock is important in their generation. The enhanced pressure on the magnetopause due to these pulses can perturb the boundary, exciting ultra-low frequency waves in the magnetosphere and travelling convection vortices in the ionosphere, similar to the response to pressure variations of solar wind origin. However, in this case the response is smoother and on longer timescales than the sharp, impulsive pressure variations and often a collective effect of numerous pulses. Conditions at the magnetopause are often inferred from suitably time lagged measurements of the pristine solar wind taken far upstream of Earth at the L1 Lagrangian point. However, such methods cannot predict the precise locations and times of dynamic pressure pulses in the magnetosheath, which directly drive magnetospheric dynamics.
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Mafi, Majid. "Blood Pressure Estimation Using Oscillometric Pulse Morphology." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20630.
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This thesis work presents the analysis of Oscillometric blood pressure pulse waveform under different pressure points (Systolic, Mean Arterial, and Diastolic Pressures). Pulse waveforms' characteristics were determined from the waveforms at three different pressures and are compared for subjects at three different age groups. Estimation of blood pressure using a morphology based approach was done by using the change of pulse waveform characteristics at different pressure points. Pulse waveforms' characteristics that were obtained from pulse waveforms are utilized to estimate SBP, MAP, and DBP. The estimates obtained with pulse morphology based technique are compared with a BP measurement device and Maximum Amplitude Algorithm. Maximum slope of the pulse was also used for blood pressure estimation. The effect of movement and breathing on proposed method and MAA were compared and it was observed that breathing artifacts affect less the proposed method.
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Zienkiewicz, A. (Aleksandra). "Blood pressure estimation using pulse transit time models." Master's thesis, University of Oulu, 2017. http://jultika.oulu.fi/Record/nbnfioulu-201712063289.
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Abstract. Blood pressure (BP) is an important indicator of human health. Common methods for measuring BP continuously are either invasive, intermittent or they require using a cumbersome cuff. Pulse Transmit Time (PTT) -based measurement can be an alternative for such methods, as it ensures continue and non-invasive monitoring. However, since the method is indirect, it requires careful modelling of PTT-BP relation. In this thesis, three approaches of BP estimation from PTT are tested: linear regression, nonlinear Moens and Korteweg model and nonlinear model developed by Gesche. In the experiments, cardiovascular pulses for PTT were sensed using two fiber optics based accelerometers developed at the University of Oulu.
To evaluate feasibility of presented models, the results were compared with reference BP values, measured using methods accepted for the commercial use. There were two groups of data. One was compared with BP measured using invasive catheter. Second group was compared with BP measured using volume clamp method. Obtained results suggest, that the presented calculation methods in present state still require further development in order to provide accurate BP values, however, they can be potentially used for observation of BP changes.
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Fok, Henry Wing Hang. "Ventricular-vascular coupling and central arterial pulse pressure." Thesis, King's College London (University of London), 2015. http://kclpure.kcl.ac.uk/portal/en/theses/ventricularvascular-coupling-and-central-arterial-pulse-pressure(c9b79392-15e3-4c43-b940-10bb9cbe35f7).html.
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Central pulse pressure (cPP), a product of ventricular-arterial interaction, is an important determinant of cardiovascular outcomes in hypertension. The aim of this thesis is to advance the understanding of pulsatile haemodynamics and to explore mechanisms that may selectively reduce cPP. The conventional view is that cPP comprises a component determined by the direct interaction of myocardial contraction with the impedance of the proximal arterial tree (closely related to pulse wave velocity, PWV) and a component ‘augmentation pressure’ generated by pressure wave reflections from muscular conduit arteries. Surprisingly little is known regarding regulation of conduit artery tone despite its potential influence on cPP. In the first part of this thesis, muscular large arterial tone was examined using a human forearm blood flow model. Vasoactive substances were infused locally into the brachial artery and vasodilator responses of the radial artery, as a muscular conduit artery, and forearm resistance microvasculature were examined. Nitric oxide donors, in particular, glyceryl trinitrate (GTN) were found to have the most selective action on conduit arteries compared to other vasodilators. In the second part of the thesis, I examined whether the action of GTN to reduce augmentation pressure could be accounted for by this selective dilation of muscular arteries. GTN was given systemically and by intra-coronary infusion in patients undergoing cardiac catheterisation. Invasive aortic blood pressure and flow velocity were analysed in the time domain by wave intensity analysis. This allows separation of pressure into a forward component generated by myocardial contraction and a backward component generated by ‘reflection’ from the peripheral arterial tree. A surprising finding was that changes induced by GTN were mainly attributable to a reduction in forward rather than backward pressure waves. That this resulted from a change in myocardial contractility was confirmed by local intracoronary injection of GTN. The final part of the thesis examines the relative contribution of forward and backward pressure waves in hypertension. An elevated cPP in hypertensive compared to normotensive subjects was accounted for primarily by an increased forward pressure wave. That this was due to increased myocardial contractility was confirmed by examining whether the pattern of wave intensity seen in hypertension could be reproduced, in normotensive subjects, by the inotrope dobutamine (when compared to the vasoconstrictor norepinephrine used as a control). This thesis thus provides novel insight into a) regulation of conduit artery tone, and b) pulsatile haemodynamics, highlighting the contribution of left ventricular ejection characteristics in determining pressure augmentation and cPP.
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Maines, Geoffrey C. "Underwater Pressure Pulses Generated by Mechanically Alloyed Intermolecular Composites." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30708.
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Recently, the use of thermite-based pressure waves for applications in cellular transfection and drug delivery have shown significant improvements over previous technologies. In the present study, a new technique for producing thermite-generated pressure pulses using fully-dense nano-scale thermite mixtures was evaluated. This was accomplished by evaluation of a stoichiometric mixture of aluminium (Al) and copper(II)-oxide (CuO) prepared by mechanical alloying. Flame propagation speeds, constant-volume pressure characteristics and underwater pressure characteristics of both a micron-scale and mechanically alloyed mixture were measured experimentally and compared with conventional nano-scale thermites. It was determined that mechanically alloyed mixtures are capable of attaining flame propagation speeds on the same order as nano-scale mixtures, with flame speeds reaching as high as approximately 100 m/s. Constant-volume pressure experiments indicated that mechanically alloyed mixtures result in lower pressurization rates compared with conventional nano-scale mixtures, however, an improvement by as much as an order of magnitude was achieved compared with micron-scale mixtures. Thermochemical equilibrium predictions for pressures observed in constant-volume reactions were found to capture relatively well the equilibrium pressure for both low and high values of relative density. Generally, the predictions over-estimated the measured pressures by approximately 60%.
Results from underwater experiments indicated that the mechanically alloyed samples produced peak shock pressures and waveforms similar to those for a nano-scale Al-Bi2O3 mixture reported by Apperson et al. (2008). In an effort to model the pressure signal obtained from the underwater reaction, calculations were performed based on the rate of expansion of the high pressure gas sphere. Predicted pressures were found to agree fairly well in terms of both the peak pressure and pressurization rate.
The present study has thus identified the ability for mechanically alloyed thermite mixtures to produce underwater pressure profiles that may be conducive for applications in cellular transfection and drug delivery.
Récemment, l'utilisation d'ondes de pression produite par des mélanges de thermite pour des applications dans la transfection cellulaire et l'administration de médicaments ont démontré des améliorations importantes par rapport aux technologies précédentes. Dans l'étude ci jointe, une nouvelle technique pour produire des impulsions de pression générée par un mélange thermite, soumit a de l'alliage mécanique, a été évaluée. Ceci a été accompli par l'évaluation d'un mélange stoechiométrique d' aluminium (Al) et de l'oxyde de cuivre(II) (CuO), préparé par mécanosynthèse. Les vitesses de propagation de la flamme, les caractéristiques de pression pour la combustion à volume constant et les caractéristiques de pression pour la combustion sous l'eau ont été mesurées expérimentalement et comparés avec les thermites conventionnel à l'échelle nano. Nous avons déterminé que les mélanges alliés mécaniquement sont capables d'atteindre des vitesses de propagation de flamme du même ordre que les mélanges à l'échelle nanométrique, atteignant jusqu'à environ 100 m/s. Les expériences de combusition à volume constant, indique que les mélanges alliés mécaniquement induit des taux de pressurisation inférieures à celles des mélanges de nano-échelle conventionnel, cependant, une amélioration de près d'un ordre de grandeur a été atteint par rapport aux mélanges d'échelle micronique. Prédictions thermochimiques des pression de compbustion se sont révélés capable de relativement bien saisir les valeurs observées dans les expériences à volume constant. En règle générale, les prévisions sur-estimé les pressions mesurées par environ 60%.
Les résultats des expériences sous-marines ont indiqué que les échantillons alliés mécaniquement ont produit des pressions et des profils d'onde similaires à celles produit par un mélange de Al-Bi2O3 de nano-échelle, comme indiqué par Apperson et al. (2008). Pour modéliser les pressions obtenues dans les expériences sous-marines, des calculs basés sur le taux d'expansion de la bulle de gaz à haute pression ont été obtenus. Les pressions prédites ont été trouvés d'être relativement en accord avec la pression maximale et le taux de pressurisation observé.
Cette étude a ainsi identifié la possibilité pour l'utilisation des mélanges de thermites alliés mécaniquement pour produire des profils de pression sous l'eau propices pour des applications de transfection cellulaire et l'administration de médicaments.
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Smithers, Breana Gray. "Evaluating the Pulse Sensor as a Low-Cost and Portable Measurement of Blood Pulse Waveform." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849682/.
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This study was aimed at determining whether the digital volume pulse waveform using the Pulse Sensor can be used to extract features related to arterial compliance. The Pulse Sensor, a low-cost photoplethysmograph, measures green light reflection in the finger and generates output, which is indicative of blood flow and can be read by the low-cost Arduino UNO™. The Pulse Sensor code was modified to increase the sampling frequency and to capture the data in a file, which is subsequently used for waveform analysis using programs written in the R system. Waveforms were obtained using the Pulse Sensor during two 30-s periods of seated rest, in each of 44 participants, who were between the ages of 20 and 80 years. For each cardiac cycle, the first four derivatives of the waveform were calculated and low-pass filtered by convolution before every differentiation step. The program was written to extract 19 features from the pulse waveform and its derivatives. These features were selected from those that have been reported to relate to the physiopathology of hemodynamics. Results indicate that subtle features of the pulse waveform can be calculated from the fourth derivative. Feature misidentification occurred in cases of saturation or low voltage and resulted in outliers; therefore, trimmed means of the features were calculated by automatically discarding the outliers. There was a high efficiency of extraction for most features. Significant relationships were found between several of the features and age, and systolic, diastolic, and mean arterial blood pressure, suggesting that these features might be employed to predict arterial compliance. Further improvements in experimental design could lead to a more detailed evaluation of the Pulse Sensor with respect to its capability to predict factors related to arterial compliance.
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Åkesson, Krister. "Floc behaviour in a twin-wire blade pressure pulse /." Stockholm, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-386.
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Wikström, Magnus. "Influence of temperature and pressure pulses on the calendering result /." Stockholm, 1999. http://www.lib.kth.se/abs99/wiks0528.pdf.
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JAIN, ALOK. "A BIOPARTICLE SEPARATION TECHNIQUE THROUGH MICROCHANNELS USING SEQUENTIAL PRESSURE PULSES." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1085759166.
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Payne, Rupert Alistair. "Pulse transit time and the pulse wave contour as measured by photoplethysmography : the effect of drugs and exercise." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/5950.
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Photoplethysmography (PPG) is a simple means of measuring the pulse wave in humans, exploitable for the purposes of timing the arrival of the pulse at a particular point in the arterial tree, and for pulse contour analysis. This thesis describes a methodology for measuring arterial pulse transit time (PTT) from cardiac ejection to pulse arrival at the finger. It describes the effect on PTT of drug and exercise induced changes in BP. The nature of the relationship between the PPG and arterial pressure is also examined, and the PTT technique extended to assessment of conduit vessel pulse wave velocity (PWV) during exercise. PTT measured from ECG R-wave to PPG finger wave (rPTT) had a negative correlation (R2=0.39) with systolic BP (SBP), unaffected by vasoactive drugs in some but not all persons. rPTT showed similar beat-to-beat variability to SBP, unaffected by drugs. rPTT correlated weakly with diastolic (DBP) and mean (MAP) pressure. Cardiac pre-ejection period (PEP) formed a substantial and variable part of rPTT (12% to 35%). Transit time adjusted for PEP (pPTT) correlated better with DBP (R2=0.41) and MAP (R2=0.45), than with SBP. The PPG wave tracked changes in the peripheral pressure wave. Drugs had little effect on the generalised transfer function (GTF) describing the association between arterial and PPG waves. Strenuous exercise induced a large decrease in rPTT, mainly accounted for by decreases in PEP (53% of the total change in rPTT) and in transit time from aorta to distal brachial artery (33%). In contrast, minimal change in transit time from wrist to finger tip occurred with exercise. Simultaneous ear-finger PPG signals were used to measure conduit artery PWV during exercise. Ear-finger PWV (PWVef) overestimated carotid-radial PWV throughout exertion (overall bias 0.81±1.05ms-1, p<0.001), but the degree of difference remained constant. The increase in PWVef with exercise, was greater (1.18±0.54ms-1, p=0.035) in healthy subjects with a positive cardiovascular family history compared to those without. PPG enables analysis of the pulse contour during exercise, but estimation of the radial pressure wave from finger PPG by use of a GTF derived at rest, resulted in inaccuracy following exertion. These effects were variable and relatively short-lived. Furthermore, a resting GTF used to determine central pressure from the peripheral wave, resulted in underestimation of SBP (-5.9±2.1mmHg) and central pressure augmentation index (-8.3±2.9%), which persisted for 10 minutes post-exercise. rPTT had a negative linear association with SBP (R2=0.94) during strenuous exercise, slightly stronger than during recovery (R2=0.85). Differences existed in area-undercurve of the rPTT/SBP relationship between exercise and recovery, due to discrepancies in rate and degree of recovery of SBP and PEP. The linear relationship between the rPTT/SBP during exercise was affected by aerobic capacity, and the regression slope was less in the anaerobic compared to aerobic phase of exercise due to minimal change in PEP during anaerobic exertion. The correlation between rPTT/SBP did not change with prolonged aerobic exercise. Finally, measures of baroreflex sensitivity during exercise, were not significantly different between actual beat-to-beat SBP and SBP estimated using rPTT. In conclusion, absolute BP cannot be reliably estimated by measurement of rPTT following administration of drugs and during exercise. However, rPTT may have a role in measuring BP variability and in the assessing exercise capacity. PPG may also be useful in determining the effects of exercise on arterial stiffness, and for estimating the pressure wave contour, although its use during exercise for the latter purpose must be treated with caution.
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Janka, Adam Martin. "Methods of Diffusing Pulse Detonation Combustion." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/49152.
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Pulse detonation combustion has been of interest for many years since it offers several advantages over standard deflagrative combustion. In theory, detonative combustion is a better use of fuel compared to deflagrative combustion since less entropy is generated during a detonation. As a result, detonation offers higher pressure and temperature gain across the wave front compared to the comparable deflagration. Since a detonation is a supersonic event which uses a shock to compress and dissociate reactants, a Pulse Detonation Combustor (PDC) is a relatively simple device that does not necessarily require a large compressor section at the inlet. Despite these benefits, using a turbine to extract work from a PDC is a problem littered with technical challenges. A PDC necessarily operates cyclically, producing highly transient pressure and temperature fields. This cyclic operation presents concerns with regards to turbine reliability and effective work extraction.
The research presented here investigated the implementation of a pulse detonation diffuser, a device intended to temporally and spatially distribute the energy produced during a detonation pulse. This device would be an inert extension from a baseline PDC, manipulating the decaying detonation front while minimizing entropy production. A diffuser will seek to elongate, steady, attenuate, and maintain the quality of energy contained in the exhaust of a detonation pulse. These functions intend to reduce stresses introduced to a turbine and aid in effective work extraction. The goal of this research was to design, implement, and evaluate such a diffuser using the using conventional analysis and simulated and physical experimentation.
Diffuser concepts using various wave dynamic mechanisms were generated. Analytical models were developed to estimate basic timing and wave attenuation parameters for a given design. These models served to inform the detail design process, providing an idea for geometric scale for a diffuser. Designs were simulated in ANSYS Fluent. The simulated performance of each diffuser was measured using metrics quantifying the wave attenuation, pulse elongation, pulse steadying, and entropy generation for each design. The most promising diffuser was fabricated and tested using a detonation tube. Diffuser performance was compared against analytical and computational models using dynamic pressure transducer diagnostics.Master of Science