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Makin, Alexis David James. "Velocity memory." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/velocity-memory(c5c1c28d-0a23-44a5-93bc-21f993d2e7ad).html.
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It is known that primates are sensitive to the velocity of moving objects. We can also remember velocity information after moving objects disappear. This cognitive faculty has been investigated before, however, the literature on velocity memory to date has been fragmented. For example, velocity memory has been disparately described as a system that controls eye movements and delayed discrimination. Furthermore, velocity memory may have a role in motion extrapolation, i.e. the ability to judge the position of a moving target after it becomes occluded. This thesis provides a unifying account of velocity memory, and uses electroencephalography (EEG) to explore its neural basis. In Chapter 2, the relationship between oculomotor control and motion extrapolation was investigated. Two forms of motion extrapolation task were presented. In the first, participants observed a moving target disappear then reappear further along its path. Reappearance could be at the correct time, too early or too late. Participants discriminated reappearance error with a two-alternative forced choice button press. In the second task, participants saw identical targets travel behind a visible occluder, and they attempted to press a button at the exact time that it reached the other side. Tasks were completed under fixation and free viewing conditions. The accuracy of participant's judgments was reduced by fixation in both tasks. In addition, eye movements were systematically related to behavioural responses, and small eye movements during fixation were affected by occluded motion. These three results imply that common velocity memory and pre-motor systems mediate eye movements and motion extrapolation. In Chapter 3, different types of velocity representation were explored. Another motion extrapolation task was presented, and targets of a particular colour were associated with fast or slow motion. On identical-velocity probe trials, colour still influenced response times. This indicates that long-term colour-velocity associations influence motion extrapolation. In Chapter 4, interference between subsequently encoded velocities was explored. There was robust interference between motion extrapolation and delayed discrimination tasks, suggesting that common processes are involved in both. In Chapter 5, EEG was used to investigate when memory-guided tracking begins during motion extrapolation. This study compared conditions where participants covertly tracked visible and occluded targets. It was found that a specific event related potential (ERP) appeared around 200 ms post occlusion, irrespective of target location or velocity. This component could delineate the onset of memory guided tracking during occlusion. Finally, Chapter 6 presents evidence that a change in alpha band activity is associated with information processing during motion extrapolation tasks. In light of these results, it is concluded that a common velocity memory system is involved a variety of tasks. In the general discussion (Chapter 7), a new account of velocity memory is proposed. It is suggested that a velocity memory reflects persistent synchronization across several velocity sensitive neural populations after stimulus offset. This distributed network is involved in sensory-motor integration, and can remain active without visual input. Theoretical work on eye movements, delayed discrimination and motion extrapolation could benefit from this account of velocity memory.
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Seligman, Joshua R. "Power development through low velocity isotonic, or combined low velocity isotonic-high velocity isokinetic training /." Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/7046.
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Zhu, Weijia. "A new instrumentation for particle velocity and velocity related measurements under water /." View online ; access limited to URI, 2006. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/fullcit/3239913.
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Beg, Sarena. "The determinants of velocity." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq20781.pdf.
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Saeed, Khizer. "Laminar burning velocity measurements." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270733.
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Kopp, Robert William. "Determination of the velocity." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25837.
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Hypervelocity flows for velocities is excess of 1.4 km/sec (Mach 5) require very high stagnation temperature to avoid liquefaction. The arc heater wind tunnel has been designed to provide such flows. The electric-are driven wind tunnel can develop stagnation temperatures up to 13,000 K which will produce hypervelocity flows up to 7 km/sec (earth orbital speed). The nature of the flow, however, is such that the high temperature source flow may cause severe gradients at the nozzle exit. In order to perform aero-thermodynamic tests the characterization of the flow in the test section is required. This paper experimentally determines the stream profiles for an arcjet wind tunnel conical nozzle directly from calorimetry and pitot probe surveys. Keywords: Arcjet flow; Hypervelocity flow; High enthalpy flow; Flow characteristics; Characteristic profile of the flow;
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Teng, Xiaoqing. "High velocity impact fracture." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32118.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Includes bibliographical references (p. 315-330).<br>An in-depth understanding of dynamic ductile fracture is one of the most important steps to improve the survivability of critical structures such as the lost Twin Towers. In the present thesis, the macroscopic fracture modes and the fracture mechanisms of ductile structural components under high velocity impact are investigated numerically and theoretically. Attention is focused on the formation and propagation of through-thickness cracks, which is difficult to experimentally track down using currently available instruments. Studied are three typical and challenging types of impact problems: (i) rigid mass-to beam impact, (ii) the Taylor test, and (iii) dynamic compression tests on an axisymmetric hat specimen. Using an existing finite element code (ABAQUS/Explicit) implemented with the newly developed Bao-Wierzbicki's (BW) fracture criterion, a number of distinct failure modes including fragmentation, shear plugging, tensile tearing in rigid mass-to-beam impact, confined fracture, petalling, and shear cracking in the Taylor test, are successfully recreated for the first time in the open literature. All of the present predictions are in qualitative agreement with experimental observations.<br>(cont.) This investigation convincingly demonstrates the applicability of the BW's fracture criterion to high velocity impact problems and at the same time provides an insight into deficiencies of existing fracture loci. Besides void growth, the adiabatic shear banding is another basic failure mechanism often encountered in high velocity impact. This failure mechanism and subsequent fracture is studied through numerical simulation of a recently conducted compression test on a hat specimen. The periodical occurrence of hot spots in the propagating adiabatic shear bands is successfully captured. The relation between hot spots and crack formation is revealed. The numerical predictions correlate well with experimental results. An explicit expression controlling through-thickness crack growth is proposed and verified by performing an extensive parametric study in a wide range of input variables. Using this expression, a two-stage analytical model is formulated for shear plugging of a beam/plate impacted by a flat-nosed projectile. Obtained theoretical solutions are compared with experimental results published in the literature showing very good agreement.<br>(cont.) Three theoretical models for rigid mass-to-beam impact, the single, double, and multiple impact of beam-to-beam are derived from the momentum conservation principle. The obtained closed-form solutions, which are applicable to the axial stretching dominated case, are validated by finite element analysis.<br>by Xiaoqing Teng.<br>Ph.D.
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Johansson, Torneus Daniel, and Alexander Kotoglou. "Velocity of plasma flow." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-199363.
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Stober, Gunter, and Christoph Jacobi. "Meteor head velocity determination." Universität Leipzig, 2007. https://ul.qucosa.de/id/qucosa%3A15571.
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Meteore, die in die Atmosphäre eindringen, bilden bei hohen Oberflächentemperaturen, die durch Kollisionen mit der umgebenden Luft hervorgerufen werden, einen mehrere Kilometer langen Plasmaschweif aus. An diesem Schweif werden ausgesandte Radarwellen reflektiert und zurückgestreut. Dies führt zu einem charakteristischen Schwingungsverhalten, auch Fresnel Zonen genannt, am Empfänger. Die Überlagerung dieser Wellen ist verantwortlich für die typische Signalform eines Meteors, mit dem abrupten Anstieg und dem exponentiellen Abfall für \'underdense\' Meteore. Mit Hilfe einer Simulation wird der theoretische Zusammenhang zwischen Geschwindigkeit und Signalverlauf demonstriert. Des weiteren wird gezeigt, das die Methode von Baggaley et al. [1997] zur Bestimmung von Meteoreintrittsgeschwindigkeiten auch auf ein Radarinterferometer (SKiYMET) anwendbar ist. Abschliessend werden die gewonnen Ergebnisse mit einem anderen Verfahren sowie der Literatur verglichen.<br>Meteors, penetrating the earths atmosphere, creating at high surface temperatures, which are caused by collisions with the surrounding air molecules, a several kilometer long plasma trail. The ionized plasma backscatters transmitted radar waves. This leads to characteristic oscillations, called Fresnel zones, at the receiver. The interference of these waves entails the typical signal shape of a underdense meteor with the sudden rise of the signal and the exponential decay. By means of a simulation the theoretical connection between velocity and signal shape is demonstrated. Furthermore it is presented, that the method from Baggaley et al. [1997] for determination of meteor entry velocities is applicable for a radar interferometer (SKiYMET). Finally the results are compared to other radar methods on similar equipment and to other experiments.
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Stober, Gunter, and Christoph Jacobi. "Meteor head velocity determination." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-223206.
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Meteore, die in die Atmosphäre eindringen, bilden bei hohen Oberflächentemperaturen, die durch Kollisionen mit der umgebenden Luft hervorgerufen werden, einen mehrere Kilometer langen Plasmaschweif aus. An diesem Schweif werden ausgesandte Radarwellen reflektiert und zurückgestreut. Dies führt zu einem charakteristischen Schwingungsverhalten, auch Fresnel Zonen genannt, am Empfänger. Die Überlagerung dieser Wellen ist verantwortlich für die typische Signalform eines Meteors, mit dem abrupten Anstieg und dem exponentiellen Abfall für \"underdense\" Meteore. Mit Hilfe einer Simulation wird der theoretische Zusammenhang zwischen Geschwindigkeit und Signalverlauf demonstriert. Des weiteren wird gezeigt, das die Methode von Baggaley et al. [1997] zur Bestimmung von Meteoreintrittsgeschwindigkeiten auch auf ein Radarinterferometer (SKiYMET) anwendbar ist. Abschliessend werden die gewonnen Ergebnisse mit einem anderen Verfahren sowie der Literatur verglichen<br>Meteors, penetrating the earths atmosphere, creating at high surface temperatures, which are caused by collisions with the surrounding air molecules, a several kilometer long plasma trail. The ionized plasma backscatters transmitted radar waves. This leads to characteristic oscillations, called Fresnel zones, at the receiver. The interference of these waves entails the typical signal shape of a underdense meteor with the sudden rise of the signal and the exponential decay. By means of a simulation the theoretical connection between velocity and signal shape is demonstrated. Furthermore it is presented, that the method from Baggaley et al. [1997] for determination of meteor entry velocities is applicable for a radar interferometer (SKiYMET). Finally the results are compared to other radar methods on similar equipment and to other experiments
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Hu, Yezheng. "Internal velocity estimation in laterally inhomogeneous areas by deconvolution of stacking velocity profiles." Thesis, University of London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296900.
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The problem of inferring the velocity field is central to exploration seismology. Conventional velocity analysis is based on the hypothesis that reflection traveltime is a hyperbolic function of the distance between the source and the receiver. This is basis upon which interval velocities are obtained using Dix's equation for a horizontally layered model and Shah's equation for a dipping layered structure. However, in laterally inhomogeneous areas, traveltimes do not follow hyperbolae, hence, hyperbola based velocity estimation techniques fail in such areas. Although many sophisticated techniques, such as tomography, migration and model based velocity analysis can be used to obtain accurate velocity fields from seismic data in such areas, these methods are very computationally expensive. In this thesis, a simple, quicker and accurate velocity estimation technique is proposed. This technique does not abandon conventional velocity analysis, but gives further processing to stacking velocity data provided by conventional techniques. The new technique is based on the hypothesis that stacking slowness variations due to lateral interval slowness anomalies can be represented by the outputs of a linear impulse response system. The inputs of the system are the interval slowness anomalies. The system is space invariant for a horizontally layered model, but is space variant for a dipping layered model. A pre-determined background model is required to compute the linear system. Since the linear system is space invariant for a horizontally layered model and space variant for a dipping layered model, there are two schemes for velocity estimation for these two cases. In horizontal geology, the relationship between stacking slowness variations and interval slowness anomalies can be expressed by a set of linear equations in the wavenumber domain. The singular value decomposition method is used to solve the set of linear equations to obtain interval slowness anomalies from stacking slowness variations. In dipping geology, the relationship between stacking slowness variations and interval slowness anomalies cannot be written as a set of linear equations in the wavenumber domain. Interval slownesses must in this case be derived in the least square sense. Basis functions are introduced to construct interval slowness anomalies. Once the interval slowness anomalies have been estimated, interval slownesses (and hence velocities) are obtained by adding these to the background interval slownesses. Finally, the sensitivity of the linear system to data errors and model errors is investigated through a series of synthetic examples, the applications of these velocity estimation techniques and suggestions for further studies of the linear system are discussed
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Håkman, Olof. "Boltzmann Equation and Discrete Velocity Models : A discrete velocity model for polyatomic molecules." Thesis, Karlstads universitet, Institutionen för matematik och datavetenskap (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-76143.
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In the study of kinetic theory and especially in the study of rarefied gas dynamics one often turns to the Boltzmann equation. The mathematical theory developed by Ludwig Boltzmann was at first sight applicable in aerospace engineering and fluid mechanics. As of today, the methods in kinetic theory are extended to other fields, for instance, molecular biology and socioeconomics, which makes the need of finding efficient solution methods still important. In this thesis, we study the underlying theory of the continuous and discrete Boltzmann equation for monatomic gases. We extend the theory where needed, such that, we cover the case of colliding molecules that possess different levels of internal energy. Mainly, we discuss discrete velocity models and present explicit calculations for a model of a gas consisting of polyatomic molecules modelled with two levels of internal energy.<br>I studiet av kinetisk teori och speciellt i studiet av dynamik för tunna gaser vänder man sig ofta till Boltzmannekvationen. Den matematiska teorien utvecklad av Ludwig Boltzmann var vid första anblicken tillämpbar i flyg- och rymdteknik och strömningsmekanik. Idag generaliseras metoder i kinetisk teori till andra områden, till exempel inom molekylärbiologi och socioekonomi, vilket gör att vi har ett fortsatt behov av att finna effektiva lösningsmetoder. Vi studerar i denna uppsats den underliggande teorin av den kontinuerliga och diskreta Boltzmannekvationen för monatomiska gaser. Vi utvidgar teorin där det behövs för att täcka fallet då kolliderande molekyler innehar olika nivåer av intern energi. Vi diskuterar huvudsakligen diskreta hastighetsmodeller och presenterar explicita beräkningar för en modell av en gas bestående av polyatomiska molekyler modellerad med två lägen av intern energi.
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Kotani, Yosuke. "Factors related to creating force-velocity and load-velocity profiles with the squat jump." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2021. https://ro.ecu.edu.au/theses/2487.
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It is well recognized that the ability to rapidly generate high levels of force is an important factor underpinning vertical jump performance. Recently, it has become popular to use forcevelocity (FV) and load-velocity (LV) profiles created from progressively loaded squat jumps (SJs) to guide the resistance training process. By creating FV profiles, the coach can determine if the athlete has a force or velocity deficit and then create an individualized training program based upon the determined deficit. Alternatively, the LV profile can be used to monitor performance and as a method for prescribing training load. While several recent studies have explored the efficacy of the use of training methods based on the FV or LV profile, there is limited research examining the various methodologies and technologies that are commonly used to create these profiles with SJs. Therefore, the primary purpose of this thesis project was to investigate the reliability and validity of various methods for assessing the FV and LV profile during the SJ. In Study 1, progressively loaded SJs were performed on a force plate in order to determine the overall reliability of the FV and LV profiles. After this was completed, Study 2 was used to compare three methods of determining the FV and LV profiles. Specifically, the FV and LV profiles created from data collected with the PUSH BandTM 2.0 (PUSH) and GymAware (GYM) were compared with the profiles created from data collected with a force plate in order to determine if the velocities determined with these methods agreed. In Study 3, the FV and LV profiles created with two accelerometers (Bar Sensei [BS] and Beast Sensor [BEAST]) were compared with a laboratory based four-linear position transducer system (4- LPT) in order to determine if the velocities measured with these devices agreed and were reliable. In Study 4, the mode of exercise (free-weight or Smith Machine) was compared to determine if there was agreement between the FV and LV profiles created with each mode. Finally, in Study 5, SJs that were performed with free-weights and the Smith Machine were compared in order to determine if there was agreement between the FV and LV profiles created with a force plate, the PUSH, and GYM. The primary finding of this thesis was that the FV and LV profiles created from SJs with a force plate were unreliable regardless of which mode of exercise was utilized. Additionally, the PV quantified with the GYM agreed with the PV determined with the force plate regardless of whether the SJ was performed with free-weights or a Smith Machine. Conversely, the PV determined with the PUSH did not agree with the force plate regardless of which mode of exercise was performed. Finally, the PVs determined with the BEAST agreed with the 4-LPT system, whilst the BS did not. Based upon these findings, it is important that coaches are aware that there is a lack of reliability with these profiles and that velocities measured by different devices do not always agree.
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Törnquist, Martin. "Investigation of rotational velocity sensors." Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15904.
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<p><p>To improve the speed measurement of construction equipment, different sensor technologies have been investigated. Many of these sensor technologies are very interesting but to keep the extent of the thesis only two was chosen for testing, magnetic absolute angle sensors using Hall and GMR technology, to investigate if those are a valid replacement for the current measurement system that is using a passive sensor. Tests show that these sensors are capable of speed measurement, but because of noisy angle estimates they need filtering for good speed computation. This filtering introduces a large time delay that is of significance for the quality of the estimate. A Kalman filter has been implemented in an attempt to lower the time delays but since only a very simple model has been used it does not give any improvements over ordinary low pass filtering. For these sensors the mounting tolerance is of great interest. For best performance the offset between the sensor and magnet centres need to be kept small for both sensors. This is due to a non-linearity effect this causes. The distance between the sensors and the magnet is not critical for linearity issues, but only for the quality of the signal, where it might drop out when the distance is too large. This is where the sensor using GMR technology stands out. Compared to the Hall technology sensor, the GMR sensor can handle distances that are more than 10 times larger. The conclusion is that these sensors can be a valid replacement of the current measurement system. They will introduce more functionality with the capability of detecting rotational direction and zero velocity. In an application with more than one sensor they can also be used for more purposes, like detecting slip in clutches etc. Depending on the application, the time delays may not be critical, else more work need to be done to improve the estimate, e.g. with a more advanced model for the Kalman filter.</p></p><p> </p>
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Brown, Ian David. "The velocity of molecular clouds." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293612.
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Kondo, Shinya. "Constant velocity joint fatigue failure." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408722.
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Smith, Warren Robert. "High velocity gas journal bearings." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317910.
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Rhodes, M. J. "High velocity circulating fluidized beds." Thesis, University of Bradford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373219.
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Cleaver, James Arnold Stafford. "Velocity distributions in conical hoppers." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387131.
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Miller, Evan. "Magnetogenesis through Relativistic Velocity Shear." Thesis, Dartmouth College, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10001975.
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<p> Magnetic fields at all scales are prevalent in our universe. However, current cosmological models predict that initially the universe was bereft of large-scale fields. Standard magnetohydrodynamics (MHD) does not permit magnetogenesis; in the MHD Faraday’s law, the change in magnetic field <i> B</i> depends on <i>B</i> itself. Thus if <i> B</i> is initially zero, it will remain zero for all time. A more accurate physical model is needed to explain the origins of the galactic-scale magnetic fields observed today. In this thesis, I explore two velocity-driven mechanisms for magnetogenesis in 2-fluid plasma. The first is a novel kinematic ‘battery’ arising from convection of vorticity. A coupling between thermal and plasma oscillations, this non-relativistic mechanism can operate in flows that are incompressible, quasi-neutral and barotropic. The second mechanism results from inclusion of thermal effects in relativistic shear flow instabilities. In such flows, parallel perturbations are ubiquitously unstable at small scales, with growth rates of order with the plasma frequency over a defined range of parameter-space. Of these two processes, instabilities seem far more likely to account for galactic magnetic fields. Stable kinematic effects will, at best, be comparable to an ideal Biermann battery, which is suspected to be orders of magnitude too weak to produce the observed galactic fields. On the other hand, instabilities grow until saturation is reached, a topic that has yet to be explored in detail on cosmological scales. In addition to investigating these magnetogenesis sources, I derive a general dispersion relation for three dimensional, warm, two species plasma with discontinuous shear flow. The mathematics of relativistic plasma, sheared-flow instability and the Biermann battery are also discussed.</p>
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Bhullar, Anmol. "Velocity Compensation in Shaped Charges." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297800.
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Shaped charges (SC) have been used as a means of explosives in military andcivilian use for decades. Thus, there is a substantial amount of research behindthis area. However, as this is a sensitive subject much of this research is notpublicly available. This thesis will look at how one can use asymmetries in SC’s to velocity compensatethe jet formation. Velocity compensation is required when the SC is perpendicularto the projectile direction, hence, leading to an angled jet which decreases thepenetration potential. The asymmetries that were investigated are• off-center detonation• angled liner• displaced wave shaper• displaced wave shaper & angled liner. The 3D explosive simulation was conducted in IMPETUS AFEA solver and tocompare the performance of these asymmetries the position and velocity of thejet were measured. To create a baseline a simulation without any asymmetrieswas used. The off-center detonation showed some velocity compensating characteristicsat the tip of the jet. However, as the jet progressed it converged towards thereference. Angled liner simulations were conducted with an angle of 0.5 degrees and 1 degreeand these asymmetries behaved vastly differently. Angled Liner 0.5 degrees hada greater jet angle but a greater quantity of the jet particles were concentratedaround one point increasing the penetration potential. A general characteristicthat angled liner displaced was the fact that it had desirable velocity compensatingtraits all through the jet. Displaced Wave Shaper, like off-center detonation, showed promising velocitycompensating attributes at the tip of the jet, however, it too converged towardsthe reference on the later part of the jet. When combining the displaced wave shaper and angled liner asymmetries thedesire was to also combine their velocity compensating traits, i.e achievingthe displaced wave shaper’s tip compensation with the angled liner’s totalcompensation. Unfortunately, this was not achieved. The tip, again, showedpromising velocity compensating attributes but the rest of the jet convergedtowards the reference. Conclusively, angled liner shows the highest potential for compensating thevelocity and allowed the most amount of jet particles to be concentrated aroundone point increasing the penetration potential.
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Trotter, Joshua. "Escape Velocity: A Narrative Short." ScholarWorks@UNO, 2004. http://louisdl.louislibraries.org/u?/NOD,98.
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Thesis (M.F.A.)--University of New Orleans, 2004.<br>Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Master of Fine Arts in the Department of Drama and Communications."--Thesis t.p. Vita. Includes bibliographical references.
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Al, Jailawi Samer Saadi Hussein. "Damage detection using angular velocity." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6539.
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The present work introduces novel methodologies for damage detection and health monitoring of structural and mechanical systems. The new approach uses the angular velocity inside different mathematical forms, via a gyroscope, to detect, locate, and relatively quantify damage. This new approach has been shown to outperform the current state-of-the-art acceleration-based approach in detecting damage on structures. Additionally, the current approach has been shown to be less sensitive to environmental acoustic noises, which present major challenges to the acceleration-based approaches. Furthermore, the current approach has been demonstrated to work effectively on arch structures, which acceleration-based approaches have struggled to deal with. The efficacy of the new approach has been investigated through multiple forms of structural damage indices.
The first methodology proposed a damage index that is based on the changes in the second spatial derivative (curvature) of the power spectral density (PSD) of the angular velocity during vibration. The proposed method is based on the output motion only and does not require information about the input forces/motions. The PSD of the angular velocity signal at different locations on structural beams was used to identify the frequencies where the beams show large magnitude of angular velocity. The curvature of the PSD of the angular velocity at these peak frequencies was then calculated. A damage index is presented that measures the differences between the PSD curvature of the angular velocity of a damaged structure and an artificial healthy baseline structure.
The second methodology proposed a damage index that is used to detect and locate damage on straight and curved beams. The approach introduces the transmissibility and coherence functions of the output angular velocity between two points on a structure where damage may occur to calculate a damage index as a metric of the changes in the dynamic integrity of the structure. The damage index considers limited-frequency bands of the transmissibility function at frequencies where the coherence is high. The efficacy of the proposed angular-velocity damage-detection approach as compared to the traditional linear-acceleration damage-detection approach was tested on straight and curved beams with different chord heights. Numerical results showed the effectiveness of the angular-velocity approach in detecting damage of multiple levels. It was observed that the magnitude of the damage index increased with the magnitude of damage, indicating the sensitivity of the proposed method to damage intensity. The results on straight and curved beams showed that the proposed approach is superior to the linear-acceleration-based approach, especially when dealing with curved beams with increasing chord heights. The experimental results showed that the damage index of the angular-velocity approach outweighed that of the acceleration approach by multiple levels in terms of detecting damage.
A third methodology for health-monitoring and updating of structure supports, which resemble bridges’ bearings, is introduced in this work. The proposed method models the resistance of the supports as rotational springs and uses the transmissibility and coherence functions of the output response of the angular velocity in the neighborhood of the bearings to detect changes in the support conditions. The proposed methodology generates a health-monitoring index that evaluates the level of deterioration in the support and a support-updating scheme to update the stiffness resistance of the supports. Numerical and experimental examples using beams with different support conditions are introduced to demonstrate the effectiveness of the proposed method. The results show that the proposed method detected changes in the state of the bearings and successfully updated the changes in the stiffness of the supports.
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Hartman, Chase. "Development of a Velocity Controller for Following a Human Using Target Velocity in GPS-Denied Environments." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin154409977396946.
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Ma, Yu-Bin. "Velocity compensation in stepped frequency rada." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA305583.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, December 1995.<br>Thesis advisor(s): G.S. Gill, David C. Jenn. "December 1995." Includes bibliographical references. Also available online.
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Patton, Jesse Earl. "Empirical velocity predictions at culvert inlets." Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/patton/PattonJ0506.pdf.
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Grytten, Frode. "Low-Velocity Penetration of Aluminium Plates." Doctoral thesis, Norwegian University of Science and Technology, Department of Structural Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2123.
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<p>The present thesis describes research on quasi-static and low velocity perforation of rolled aluminium plates, where the main objective has been to gain a better knowledge of the physical processes taking place during this type of structural problem. The objective has been met by a combination of laboratory tests, material modelling and non-linear finite element simulations.</p><p>The thesis is organized in a synopsis, giving a brief introduction to the problem and summarising the main findings and conclusions, in addition to four independent papers. </p><p>Paper I presents an experimental technique for measuring the deformations the plate undergoes during impact and perforation. This information can be used to validate numerical models and to increase the understanding of how energy is absorbed by the plate.</p><p>Paper II presents an experimental and numerical investigation on the quasi-static perforation of AA5083-H116 aluminium plates. In the tests, square plates were mounted in a circular frame and penetrated by a cylindrical punch. A full factorial design was used to investigate the effects of varying plate thickness, boundary conditions, punch diameter and nose shape. Based on the obtained results, both the main and interaction effects on the maximum force, displacement at fracture and energy absorption until perforation were determined. The perforation process was then computer analysed using the nonlinear finite element code LS-DYNA. Simulations with axisymmetric elements, brick elements and shell elements were conducted. Slightly modified versions of the Johnson-Cook constitutive relation and fracture criterion were used to model the material behaviour. It was shown that the FEM models were able to predict the trends observed in experiments.</p><p>Paper III evaluates methods for determination of the anisotropic properties of polycrystalline metallic materials. Four calibration methods were evaluated for the linear transformation-based anisotropic yield function YLD2004-18p (Barlat et al., 2005) and the aluminium alloy AA5083-H116. The different parameter identifications are based on least squares fits to combinations of uniaxial tensile tests in seven directions with respect to the rolling direction, compression (upsetting) tests in the normal direction and stress states found using the full-constraint (FC) Taylor model for 690 evenly distributed strain paths. An elastic-plastic constitutive model based on YLD2004-18p has been implemented in a non-linear finite element code and used in finite element simulations of plane-strain tension tests, shear tests and upsetting tests. The experimental results as well as the Taylor model predictions can be satisfactorily reproduced by the considered yield function. However, the lacking ability of the Taylor model to quantitatively reproduce the experiments calls for more advanced texture models.</p><p>Paper IV presents an experimental and numerical investigation on low velocity perforation of AA5083-H116 aluminium plates. In the tests, square plates were mounted in a circular frame and penetrated by a cylindrical blunt-nosed projectile. The perforation process was then computer analysed using the nonlinear finite element code LS-DYNA, in order to investigate the effects of anisotropy, dynamic strain aging and thermal softening in low velocity impacts on the present aluminium alloy. Dynamic strain aging has been shown to influence both the predicted force level and fracture, while thermal softening only influences the fracture prediction. No effect of plastic anisotropy was observed.</p>
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Järhult, Susann J. "Hyperemic Brachial Artery Blood Flow Velocity." Doctoral thesis, Uppsala universitet, Medicin, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132918.
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This thesis aims to evaluate the blood flow velocity in the Brachial artery during reactive hyperemia. Primarily to appraise the information it might contain regarding cardiovascular function and cardiovascular risk. Ultrasonographic doppler measurements of the Brachial artery were made on the 1016 men and women aged 70 included in the prospective investigation of the vasculature in Uppsala seniors (PIVUS) study. Analysis of the blood flow velocity in the forearm was made in comparison to established methods of estimating endothelial function, clinical markers of cardiovascular risk, the Framingham risk score and global atherosclerosis determined by whole body magnetic resonance angiography. Systolic blood flow velocity was positively related to cardiovascular risk whereas the diastolic velocity was inversely correlated. However, the systolic to diastolic blood flow velocity (SDFV) ratio was more closely associated with cardiovascular risk than its components apart. Ultrasonographic markers of Carotid atherosclerosis were related to the SDFV ratio. Concentric left ventricular remodeling and left ventricular mass index were also associated with the SDFV ratio, but not to its numerator or denominator separately. A similar pattern was found when assessing SDFV ratio in relation to global atherosclerosis, as well as to established markers of arterial compliance and vasodilation. In conclusion, during reactive hyperemia of the Brachial artery, the systolic to diastolic blood flow velocity ratio appears to contain information of additional value than its components separately, independently of established cardiovascular risk factors. Possibly, the SDFV ratio could offer a promising means to estimate cardiovascular risk in aging populations.<br>PIVUS
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Khoo, Stephen W. "Low velocity impact of composite structures." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/7388.
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Li, Jinxia. "µPIV Measurement of Grease Velocity Profiles." Licentiate thesis, Luleå tekniska universitet, Maskinelement, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17504.
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Lubricating grease is commonly applied to lubricate e.g. rolling bearings, seals and gears. Grease has some clear advantages over lubricating oil. It is a semi-solid material, which prevents it from flowing/leaking out from the lubricated system and gives it sealing properties, protecting the system against contaminants. Unlike oil, grease has a much more complicated rheology, which makes it more difficult to model and understand grease flow. Grease acts as a lubricant reservoir, and understanding grease flow is essential in order to model and predict how grease is transported within e.g., a rolling element bearing housing, a sealing arrangement or replenishment of a gear mesh. Three greases with different rheological behaviors (NLGI 2 grease, NLGI1 grease and NLGI00 grease) have been used in two kinds of test rigs: a straight channel with different restrictions and a rotating shaft with two narrow gap sealing-like restrictions.In the first test rig two types of flow restrictions were applied into a straight channel in order to simulate flow of grease near a sealing pocket. In the case of a single restriction, the distance required for the velocity profile to fully develop when going from a wide to a narrow gap is approximately the same as the initial height of the channel. In the corner pocket before and after the restriction, the velocity is very low and part of the grease is stationary. For the channel with two flow restrictions, this effect is even more pronounced in the “pocket” between the restrictions. Clearly, a large part of the grease is not moving since the yield stress of the grease is not exceeded. This condition particularly applies to the cases with a low-pressure gradient and where high consistency grease is used. In practice this means that grease is not replaced in such “pockets” and that some aged/contaminated grease will remain there. A test rig comprising of a rotating shaft with two narrow gap sealing-like restrictions (a so called Double Restriction Seal, DRS) was designed to simulate the a labyrinth type of seal. Two different gap heights in the DRS have been designed to compare grease flow. It is shown that partially yielded grease is detected in the large gap geometry and fully yielded grease in the small gap geometry. Grease shear thinning behavior and wall slip effects have been detected and discussed. For the small gap geometry, it is shown that three distinct grease flow regions are present: a slip layer close to the stationary wall, a bulk flow layer, and a slip layer near the rotating shaft.<br>Godkänd; 2013; 20130219 (jinlit); Tillkännagivande licentiatseminarium 2013-03-08 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Jinxia Li Ämne: Maskinelement/Machine Elements Uppsats: µPIV Measurement of Grease Velocity Profiles Examinator: Professor Erik Höglund, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Teknologie doktor Henrik Åström, SCANIA, Södertälje Tid: Måndag den 25 mars 2013 kl 10.00 Plats: E231, Luleå tekniska universitet
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Valentine, Helen Elizabeth Mary. "Reconstructing cosmological density and velocity fields." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/27570.
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I present a new quasi-linear method for reconstructing cosmological density and velocity fields from all-sky redshift surveys. The method is used to reconstruct the velocity field, dipole, bulk flows and distortion parameter <i>b</i> = Ω<sup>0.6</sup>/<i>b </i>from the PSCz survey. Analytic expressions for the cosmic variance and shot noise uncertainties on the reconstructed velocity field are presented. It is found that the uncertainties are reduced if reconstruction is carried out in the Local Group frame. The uncertainty on the dipole is also found. A generalised version of the Path Interchange Zel'dovich Approximation (PIZA) is presented. PIZA is a simple Lagrangian reconstruction method based on the Zel'dovich Approximation and the Least Action Principle, which reconstructs cosmological fields given the present day real space positions of galaxies. The generalizations take account of redshift space distortions, incomplete sky coverage, and the selection function. The method can be used to estimate <i>b</i> from radial velocities, bulk flows and the dipole. Generalised PIZA has been tested using a set of PSCz-like simulations. The reconstructed radial peculiar velocity field is compared with that of the simulation and that reconstructed by linear theory. The generalized PIZA is applied to the <i>IRAS </i>PSCz Survey. The dipole, bulk velocities and peculiar velocity field, and the derived value of <i>b</i> are presented. The Local Group is found to have an average displacement of 1225<i>kms</i><sup>-1</sup> in the direction of (1.b)=(264°, 42°). From this it is found that <i>b</i> = 0.512 ± 0.141.
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Dolbec, Michael R. "Velocity estimation using forward looking sonar." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion.exe/07Mar%5FDolbec.pdf.
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Thesis (M.S. in Engineering Science)--Naval Postgraduate School, March 2007.<br>Thesis Advisor(s): Doug Horner, Mathias Kölsch. "March 2007." Includes bibliographical references (p. 113). Also available in print.
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Archer, Grant R. "Seismic velocity analysis using dynamic programming /." Title page, contents and abstract only, 1987. http://web4.library.adelaide.edu.au/theses/09S.B/09s.ba671.pdf.
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Clark, Andrew P. "Velocity mapping of elementary photodissociation reactions." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433316.
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Bass, Mark James. "Velocity mapping of elementary bimolecular reactions." Thesis, University of Oxford, 2004. http://ora.ox.ac.uk/objects/uuid:ea381f05-6a68-435f-91d6-30d14a8c8dc4.
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A new and flexible velocity-map ion imaging apparatus, designed for the study of photodissociation processes and photon-initiated bimolecular reactions in a single molecular beam, has been constructed, developed and characterised. An image Legendre moment fitting analysis was developed to allow recovery of centre-of-mass (CM) angular scattering and kinetic energy release distributions from velocity-map ion images of the products of photon-initiated bimolecular reactions. The Legendre moment analysis methodology has been applied to images of the HCl(v' = 0,j' = 0-6) products of the reactions of Cl(²P<sub>3/2</sub>) atoms with ethane and n-butane at collision energies of 0.24 eV and 0.32 eV respectively. The Cl(²P<sub>3/2</sub>) reactants were generated by polarised laser photodissociation of Cl₂ at 355 nm. For reaction with ethane, the CM angular scattering distributions show a steady trend from forward scattering at low j' to more isotropic, but backward peaking, scattering at high j'. An impact parameter-based mechanism is proposed to account for the observed dynamics. Abstraction of a hydrogen atom from a primary carbon site in n-butane is seen to produce rotationally very cold HCl products that are forward scattered, whereas H atom abstraction from a secondary carbon site in n-butane yields more isotropically scattered HCl products formed with higher rotational excitation. A peripheral mechanism is proposed to operate for the primary abstraction channel, whilst a more rebound type mechanism is seen to account for the dynamics of the secondary abstraction channel. Around 22% and 30% of the available energy is found in internal modes of the alkyl radical co-products of the Cl + C₂H₆ and Cl + n-C₄H₁₀ reactions respectively. Possible sources of alkyl co-product excitation are discussed in each case. The hydrogen or deuterium atom abstraction reactions of Cl(²P<sub>3/2</sub>) with CH₄, CD₄ and CH₃D, have been studied at mean collision energies around 0.3 eV. Chlorine atom reactants were generated by polarised laser photodissociation of Cl₂ at 308 nm. The methyl radical products were detected using (2+1) resonance-enhanced multi-photon ionisation, coupled with velocity-map ion imaging. The laboratory frame speed distributions obtained from the images are in excellent agreement with previous work. The interpretation of the experiments is shown to be very sensitive to assumptions made about the reactant velocity distributions. If these are assumed to be narrow, the data are seen to suggest that a significant fraction of the product signal must arise from the reaction of Cl with vibrationally excited methane reactants. This conclusion is in agreement with previous photon-initiated reaction studies. However, by allowing for the spread in collision energies in the molecular beam, it is shown that it is possible to fit the data sensibly assuming reaction with vibrational ground state methane alone. CM angular scattering distributions thereby derived are presented for all three reactions.
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Engels, Wouter Peter. "Decentralised velocity feedback control of structures." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427705.
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Berg, Peter. "Optimal-velocity models of motorway traffic." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367664.
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Dodd, P. W. "Measurement of velocity profiles in ultrafiltration." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37995.
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Weber, Charles M. (Charles Maria) 1955. "Rapid learning in high velocity environments." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/8003.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Sloan School of Management, 2003.<br>Includes bibliographical references (p. 524-569).<br>This dissertation investigates how rapid learning occurs in high technology industries, many of which operate in what Bourgeois and Eisenhardt (1988) term "high velocity environments." The dissertation consists of three empirical studies, which follow the method of extended case study research (e.g. Yin, 1981; Eisenhardt, 1989a). Semiconductor manufacturing and process development are chosen as settings for this dissertation because they exemplify some of the attributes of high velocity environments. The first study looks into how firms organize for learning. Existing definitions of modularity (McClelland & Rumelhart, 1995; Ulrich, 1995b; Baldwin & Clark, 1997) are expanded to provide a theoretical framework for differentiation and integration of organizations (Lawrence & Lorsch, 1967, 1967a, 1969), technology (Iansiti & West, 1997; Iansiti, 1998), learning activity, accumulated knowledge and performance metrics in high velocity environments. The results of the study imply that differentiation in high velocity environments occurs with a high degree of modularity (the individual modules exhibit little interdependence), which fosters learning efficiency. The results also indicate that integrating technological subsystems in is significantly more complicated than integrating organizational subsystems. The second study explores the inner mechanisms of rapid learning by building a model of the lifecycle of a semiconductor manufacturing process. The output of the model suggests that the performance of a system is proportional to the performance of its most limiting subsystem. Learning in an organization occurs by paying attention to the weakest mechanism within that organization until that mechanism is no longer the weakest one, and shifting attention to the mechanism that replaces it as the weakest one.<br>(cont.) Learning in high velocity environments is likely to be highly punctuated and to include substantial engineering efforts, which may occur prior to the release of a product. The third study investigates the effects of rapid learning on a firm's profitability, suggesting that the ability to conduct and accelerate punctuated learning serves as the primary source of competitive advantage in high velocity environments. In conjunction, these studies lay the foundation for a normative, metrics-driven, pragmatic theory of learning. The theory recommends that firms should 1) Define the global objective of a venture and select the global metrics that best measure whether the venture is making progress towards its stated objective; 2) Build a learning architecture that supports the global objective of the venture, i.e. define a hierarchy the metrics that allow the firm to achieve the objective in the most effective manner; 3) Organize for learning by defining a hierarchy of activities that are aligned with the metrics of the learning architecture; 4) Manage bottlenecks; and 5) Prepare for change before change occurs, by spreading knowledge as rapidly as possible throughout the organization.<br>by Charles M. Weber.<br>Ph.D.
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Schneider, Eduardo da Silva. "Exact Calculations for the Lagrangian Velocity." Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1555086598198833.
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Barbu, Ioana. "Tridimensional Estimation of Turbulent Fluid Velocity." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S115/document.
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L'analyse du mouvement en 3 dimensions (3D) des fluides turbulents à évoluée vers un cadre nécessitant (i). un système de capteurs puissants (ii). le développement d'outils d'estimation de basse complexité (iii). des connaissances a priori issues de la physique du fluide. Des nouvelles techniques formulées dans ce contexte et s'appuyant sur le traitement d'images ont été proposées. Leur méthodologie repose sur la conjugaison du savoir propre à la communauté Vision par Ordinateur avec des modèles physiques de la dynamiques du fluide. Mais voilà, la plupart de ces procédures sont exprimées dans un cadre bidimensionnel (2D), dans le sens où elles reconstruisent un champ 2D à partir des deux images consécutives 2D ; dès lors, ces-dernières ne sont pas adaptées pour certains régimes du fluide. Récemment, des nouvelles contributions ont proposé l'estimation du champ 3D des fluides à partir des densités volumiques préalablement reconstruites. De plus, une amélioration de ces schémas classiques suggère un apport signifiant en netteté de la reconstruction dans un cadre joint d'estimation volume-mouvement. Motivés par ces développements, nous proposons dans cette étude une alternative au schéma joint déjà présent dans la littérature afin d'estimer la vitesse 3D des fluides à partir de plusieurs séquences synchronisées d'images 2D. Le cadre théorique de cette thèse a été présenté en connexion avec les communautés de la Vision par Ordinateur, du Traitement du Signal et de la Tomographie PIV. Notre travail peut être divisé en trois tâches majeures : (i). la formulation d'un modèle proche de la physique du système observé (ii). la conception des algorithmes de reconstruction volumique de basse complexité qui prennent en compte des particularités notables sur le système (iii). l'élaboration d'un schéma de reconstruction des champs de vitesse qui considère des scénarios bruités et la structure cohérente volumique entre deux instants. Nous évaluons les performances de nos méthodes sur des scènes réalistes représentant le signal de Tomographie PIV<br>The challenge of the modern understanding of the 3D turbulent flows involves the need for (i). a reliable sensing technology (ii). the design of low-complexity estimation tools (iii). Physically-sound priors. Novel techniques relying on processing image sequences have been advanced. Their methodology relies on conjugating approaches issued from the computer vision community with physical knowledge on fluid dynamics with the intent of designing an accurate motion estimator.Most of these procedures are formalized within a bidimensional framework, i.e., they reconstruct a 2D motion field out of two consecutive 2D images, making them unsuitable for several fluid regimes with high 3D structures. Estimating the fluid motion within a 3D framework seems more pertinent. In related work, the velocity fields are most often retrieved from previously estimated volumetric densities. Recent contributions estimating the volumetric distribution with regard to the motion field that links them suggest a joint optimization approach as the appropriate modus operandi towards rigorous retrieval of turbulent fluid flow. In this thesis, we have proposed a novel joint solution to address the task of 3D fluid motion estimation out of multiple sequences of synchronized 2D images. The theoretical frame has been presented with connections to the computer vision and signal processing fields, as well as to the Tomographic PIV (tomoPIV) community. Our work can be divided into three main tasks: (i). the design of a physically sound model with respect to the nature of the visualized scene (ii). the devise of volume reconstruction algorithmic schemes with low complexity that take into account known priors on the physical signal and output a satisfying estimation within a few iterations (iii). the formalization of a velocity reconstruction scheme that accounts for noisy settings and for the linked structure between two instantaneous volume reconstructions. We evaluate the agility of our methods and highlight their performance throughout realistic numerical experiments mimicking the real-world tomoPIV signal
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Zhang, Peihui. "Joining enabled by high velocity deformation." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1061233577.
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Thesis (Ph. D.)--Ohio State University, 2003.<br>Title from first page of PDF file. Document formatted into pages; contains xvi, 255 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Glenn S. Daehn, Dept. of Materials Science and Engineering. Includes bibliographical references (p. 201-202).
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Chumacero, Polanco Erik. "Velocity sensorless control switched reluctance motors." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112062/document.
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Dans ce mémoire de thèse, nous présentons la conception, l'analyse de la stabilité, les simulations numériques et aussi les résultats des expérimentes concernant différents contrôleurs de vitesse mécanique du moteur à réluctance variable (MRV).Dans les deux premiers chapitres une brève description de la physique et de la construction du MRV est présenté ainsi que le problème du contrôle d'être abordé, c'est la commande de vitesse sans capteur. Il est aussi présenté l'état de l'art de ce problème et certains des solutions proposées dans d'autres travaux. On propose notre solution et on présente un petit résumé des articles scientifiques qui ont été publiés dans des magazines et des conférences.Dans le chapitre numéro trois est présenté le design du contrôleur adaptatif et sans capteur du MRV. On suppose, dans une première étape que seule la vitesse mécanique est inconnue et la stabilité exponentielle uniforme des erreurs de suivement est obtenue. Dans une deuxième étape, les conditions d'opération sont aggravées et, en plus de la vitesse, les paramètres physiques sont également supposées inconnues, la stabilité asymptotique uniforme est obtenue dans ce cas. L'estimation des paramètres du MRV est garantie grâce à la condition de persistance d'excitation. Cette commande se compose de deux boucles, une boucle interne basée sur un contrôleur de type PI2D qui est particulièrement intéressant parce qu'il est libre de modèle; cette boucle entraîne les variables mécaniques -la position et la vitesse- vers une référence désirée. Une deuxième boucle de contrôle externe prend le courant électrique vers un ' "courant de référence virtuelle" qui est généré sur la base d'une approche de partage de couple. Le contrôleur propose est testé au niveau de simulations numériques qui sont également présentés.Dans le quatrième chapitre, une nouvelle approche de modélisation du MRV est utilisée pour concevoir le contrôleur. Dans ce scénario, on suppose que l'ensemble de l'état et tous les paramètres physiques sont disponibles, cette approche est pensée pour être adapté au contrôleur basé sur observateur, recherche qui est en cours de développement. Le contrôleur est composé de deux boucles, également que celui qui a été mentionné précédemment. Ce contrôleur est sélectionné parce qu'il est approprié pour le contrôle d'équivalence vraie, qui il s'agit de remplacer les «mesures physiques» provenant d'un capteur par les «observations» provenant d'un observateur. La mise en oeuvre numérique est effectuée sur Simulink de Matlab.Enfin, dans le chapitre cinq, les résultats expérimentaux qui ont été effectués pour évaluer la performance des contrôleurs proposés -ce sont les PI2D et adaptatif PI2D pour le modèle simplifie ainsi que le PID pour le nouveau approche de modélisation- sont présentés. Dans la première partie, une brève description de la construction du banc de tests utilisé est présenté ainsi que quelques-unes caractéristiques techniques. Trois différentes profils de vitesse sont imposées à chacun des contrôleurs proposés -ce sont la tangente hyperbolique, la rampe saturée et la référence sinusoïdal- et de bonnes résultats sont obtenus en considérant que la variable contrôlée est la vitesse. Le dernier chapitre correspond aux conclusions de la recherche effectuée ainsi qu'aux travaux futurs<br>In this thesis dissertation we present the design, stability analysis, numerical simulations and physical experiments of different controllers designed to drive the mechanical velocity of the switched reluctance motor (SRM). In the First and Second Chapters a brief description of the physics and construction of the SRM is presented, as well as the problem of control to be aboard, that is the velocity sensorless control of motors and the state of the art of this problem. The proposed solution is introduced and a summary of the published papers as well as the contribution are also presented.In the Chapter number three is presented the velocity sensorless and adaptive control of the SRM. It is assumed, in a first stage, that only mechanical velocity is unknown, uniform exponential stability of the errors is achieved in this scenario. In a second stage, conditions are stressed and in addition to the velocity, physical parameters are also assumed unknown, uniform asymptotical stability is achieved in this case and parameters estimation is guaranteed under a persistence of excitation condition. This controller consists of two loops, an internal loop based on a PI2D–type controller which is of particular interest given it is free-model; this loop drives the mechanical variables –that is position and velocity- towards a desired reference. An external control loop takes the electrical current towards a ‘’virtual” current reference which is generated based on a torque share approach. The controller is tested on numerical simulations, which are also presented.In the fourth chapter, a new approach on the modeling of the SRM is utilized to design the controller, in this scenario is assumed that the whole state and all the physical parameters are available, however this approach is thought to be suitable to observer based controller, whose ongoing research is being performed. The controller is composed by two loops, similarly to the one mentioned previously. This controller is selected because it is suitable for certainty equivalence control, that is, to substitute the “measurements” by the “observations” coming from a virtual sensor. Numerical implementation is performed on Simulink of Matlab.Finally, in the Chapter five, the experimental results carried out to evaluate the performance of the proposed controllers are presented, these are the PI2D and the adaptive PI2D controllers for the simplified model and the $PID$ controller for the novel modeling approach. In the first part, a brief description of the construction of the utilized bench is presented as well as the some technical characteristics. Three different velocity profiles were imposed to each of the overmentioned controllers –these are the so called smooth step, the saturated ramp and the sinusoidal reference- and good results, considering that the controlled variable is the velocity, were obtained. The last chapter corresponds to the conclusions of the performed research as well as to the future work
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Bezerra, Rufino Ferreira Paiva Eduardo. "Wind Velocity Estimation for Wind Farms." Electronic Thesis or Diss., Université Paris sciences et lettres, 2023. http://www.theses.fr/2023UPSLM046.
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Cette thèse propose des algorithmes pour estimer la vitesse et la direction du vent pour des éoliennes et des parcs éoliens.Tout d'abord, nous proposons des méthodes basées sur les données pour estimer la vitesse effective du rotor (REWS) sans nécessiter la connaissance de certains paramètres physiques de l'éolienne, qui pourraient être inconnus de l'opérateur. Nous fournissons deux méthodes basées sur les données, l'une basée sur la régression par processus gaussien et l'autre combinant la régression par processus gaussien avec un observateur grand gain.Ensuite, en nous basant sur cette estimation locale de la REWS, au niveau d'une éolinenne, nous abordons la question de l'estimation du vent en écoulement libre au niveau du parc éolien.Nous commençons par nous concentrer sur l'estimation de la vitesse du vent, pour une direction du vent connue. Pour un parc éolien de géométrie simple, nous démontrons qu'une mesure locale de la vitesse perturbée par la présence des éoliennes peut être utilisée pour estimer la vitesse du vent en écoulement libre. Nous fondons notre méthodologie d'estimation sur une modélisation simplifiée de l'effet de sillage qui consiste en des équations aux dérivées partielles hyperboliques du premier ordre en cascade, et dont la vitesse de transport est la vitesse du vent en écoulement libre. Nous proposons d'utiliser une solution analytique de ces équations, impliquant des retards de transport, pour effectuer une estimation de la mesure locale et mettre à jour l'estimation de la vitesse du vent en écoulement libre. Nous démontrons formellement la convergence de cette estimation et illustrons numériquement l'efficacité de cette méthode.Enfin, nous passons à une configuration plus générale où à la fois la vitesse et la direction du vent en écoulement libre sont inconnues. Nous proposons d'utiliser une modélisation bidimensionelle du sillage et de nous appuyer sur une méthode basée sur l'optimisation. Le problème d'identification que nous formulons se révèle être particulièrement difficile en raison de l'apparition de retards de transport, mais nous montrons comment contourner cette difficulté en considérant une valeur moyenne de l'historique de la vitesse du vent en écoulement libre. Des résultats de simulation obtenus avec le simulateur FAST.Farm illustrent l'intérêt de la méthode proposée<br>This thesis designs algorithms to estimate the wind speed and direction for wind turbines and wind farms.First, we propose data-based methods to estimate the Rotor Effective Wind Speed (REWS) for a single turbine without prior knowledge of certain physical parameters of the turbine that might be unknown to an operator.We provide two data-based methods, based respectively on Gaussian Process Regression (GPR) and on an combination of GPR with high-gain observers.Second, grounding on this REWS estimation at the local level of one turbine, we address the question of estimating the free-flow wind at the level of a wind farm.We start by focusing on wind speed estimation, for a given known wind direction. For a wind farm with a simple geometry, we prove that a local speed measurement disturbed by the presence of the turbines can be used to estimate the free-flow wind speed. We ground our estimation methodology on a simplified wake model, which consists of first-order hyperbolic partial differential equations, the transport speed of which is the free-flow wind speed. We propose to use an analytical solution of these equations, involving transport delays, to perform an estimate of the local measurement and to update the free-flow wind speed estimate. We formally prove the convergence of this estimate and numerically illustrate the efficiency of this method.Finally, we move to a more general setup where both the free-flow wind speed and direction are unknown. We propose to use a two-dimensional wake model and to rely on an optimization-based method. This identification problem reveals to be particularly challenging due to the appearance of transport delays, but we illustrate how to circumvent this issue by considering an average value of the free flow wind speed history. Simulation results obtained with the simulator FAST.Farm illustrate the interest of the proposed method
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Jonathan, Bremer Lin Weili. "Single scan MR velocity quantification in ROI by alternating velocity encoding gradient pulse polarity between phase encoding steps." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2008. http://dc.lib.unc.edu/u?/etd,2046.
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Thesis (M.S.)--University of North Carolina at Chapel Hill, 2008.<br>Title from electronic title page (viewed Feb. 17, 2009). "... in partial fulfillment of the requirement for the degree of Master in the Department of Biomedical Engineering." Discipline: Biomedical Engineering; Department/School: Medicine.
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Lindgren, Harri. "Radial velocity measurements of late-type stars." Lund : Institutionen för astronomi, Lunds universitet, 1994. http://catalog.hathitrust.org/api/volumes/oclc/40300933.html.
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Dehra, Mala Seth. "High velocity formability and factors affecting it." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1143214139.
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Nerbråten, Stian. "Vehicle velocity estimation on non-flat roads." Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9521.
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<p>The main purpose of this report, is to evaluate feasibility of using The Global Positioning System as an aiding tool for vehicle state estimation based on nonlinear techniques, and to develop a potential solution to the road bank angle problem. Previous work within the CEmACS project, includes development of a general nonlinear observer for lateral and longitudinal velocity, and an augmentation in the form of road-tire friction adaptation. Because the existing solutions have been shown to lack robustness with regards to certain disturbances, such as road grade and road bank angle, it has been stated that the estimation scheme should be upgraded, so that these disturbances can be accounted for. By including GPS velocity or a or a roll rate gyro measurement in the observer feedback loop, the possibility of detecting previously inobservable quantities is gained. In simple terms, evaluation of feasibility corresponds to demonstrating improvements and limitations of new solutions, using relatively crude methods in the test procedures. Problems related to the above mentioned task, are approached by means of signal processing and control theory. Following an intuitive sequence of operations, the report presents GPS theory and results first, as this lays the foundation for all subsequent results. Methods used comprise simple differentiaton, rotational kinematics and discrete filtering. Secondly, theory and results related to nonlinear observers, with focus on GPS aiding, are examined thoroughly. Lyapunov theory, known from control engineering, is used to evaluate stability, while data from simulations and actual vehicle tests is used to show how a new observer scheme can improve existing solutions. Before the most important results are presented, something should be said about their accuracy and significance. It has already been pointed out that the methods used are not based on optimality requirements, and consequently the results are best viewed as indicators of potential, rather than absolute solutions. This is especially true for the GPS velocity calculations, which are based on differentiation of position measurements; generally not a desired approach. In this report, it is firstly shown that GPS position measurements can be used to compute receiver velocity in the body-fixed coordinate frame. While this is a crude approach, resulting in relatively poor signal to noise ratio, it is easily implemented on low-level equipment. It is also shown that it is possible to use these velocities as measurements in a nonlinear observer structure, slightly modified from previous solutions within the CEmACS project. By doing this, accurate estimates of road grade and bank v angle are achieved, so long as these vary slowly enough. Stability of the observer is not proven in the general sense, but it is shown that it can be made stable through realistic assumptions and gain selection. Stability is further demonstrated through the use of data sets from actual vehicle tests. Secondly, a mathematical model of roll dynamics is combined with a roll rate measurement to create the possibility of detecting road bank angle. This is done by the now familiar nonlinear observer approach. Usefulness is demonstrated by simulations, but no stability proof is presented. The main conclusion is that it is feasible to use GPS aiding to account for robustness problems in a vehicle state estimation scheme, and that the inclusion of a roll rate measurement opens up possibilities for cheap bank angle detection. A direct implementation of results presented in the report may not be ideal, but the fact that the system works for a large set of conditions, suggests that it is worthwhile to develop it further. This is especially true when it is assumed that GPS receivers will become an integral part of new vehicles in the near future. Refinements and upgrades can be made in the form of more advanced GPS technology, new parameter estimation techniques and integration with the road-tire friction adaptation scheme.</p>
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Dahl, Trond-Olav. "Velocity Estimation in muscular Tissue by Ultrasound." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9598.
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<p>When estimating tissue velocities, the conventional autocorrelation method (AM) is only biased if the demodulation frequency is correctly estimated. While AM assumes the received centre frequency to be constant, the modified autocorrelation method (MAM) estimates the received centre frequency continuously from pulse to pulse. Although MAM has shown superior performance in simulation environments, it fails to show consistently better performance compared to AM when applied to experimental data. In order to investigate this lack of consistency, a model for simulation of signal from moving tissue was developed, including realistic aspects such as thermal noise, signal from clutter and aliasing. The simulation model was adapted using experimental tissue data and parameters from a true acquisition system. A 1st order FIR filter was applied for clutter rejection prior to velocity estimation. The investigations using simulation data shown faster performance degradation of MAM compared to AM when the amount of signal from clutter or thermal noise were increased independently. For clutter signal mimicking acoustic noise from reverberations, MAM went from significantly better under low-noise conditions to approaching AM performance when the signal-to-clutter ratio became lower than 10 dB. Analogously, MAM approached AM performance when the signal-to-noise ratio was lower than 15 dB. Velocity estimation of experimental data shown MAM's robustness to frequency dependent attenuation by means of frequency compensation, while AM suffered from bias effects due to erroneously estimated demodulation frequency. The frequency compensation did, however, not succeed to approve lower estimation variance in MAM compared to AM. Statistical analysis based on expected values from simulations, demonstrated correlation between the estimation error in AM and MAM.</p>
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Josefsson, Mattias. "3D camera with built-in velocity measurement." Thesis, Linköpings universitet, Datorseende, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-68632.
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In today's industry 3D cameras are often used to inspect products. The camera produces both a 3D model and an intensity image by capturing a series of profiles of the object using laser triangulation. In many of these setups a physical encoder is attached to, for example, the conveyor belt that the product is travelling on. The encoder is used to get an accurate reading of the speed that the product has when it passes through the laser. Without this, the output image from the camera can be distorted due to a variation in velocity. In this master thesis a method for integrating the functionality of this physical encoder into the software of the camera is proposed. The object is scanned together with a pattern, with the help of this pattern the object can be restored to its original proportions.<br>I dagens industri används ofta 3D-kameror för att inspektera produkter. Kameran producerar en 3D-modell samt en intensitetsbild genom att sätta ihop en serie av profilbilder av objektet som erhålls genom lasertriangulering. I många av dessa uppställningar används en fysisk encoder som återspeglar hastigheten på till exempel transportbandet som produkten ligger på. Utan den här encodern kan bilden som kameran fångar bli förvrängd på grund av hastighetsvariationer. I det här examensarbetet presenteras en metod för att integrera funktionaliteten av encodern in i kamerans mjukvara. För att göra detta krävs att ett mönster placeras längs med objektet som ska bli skannat. Mönstret återfinns i bilden fångad av kameran och med hjälp av detta mönster kan hastigheten bestämmas och objektets korrekta proportioner återställas.