Thèses : « Applied Physic »

1

PAROZZI, ELISABETTA GIULIA. « Design and optimization of a variable momentum secondary beamline for NP06/ENUBET project ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2023. https://hdl.handle.net/10281/403336.

Texte intégral

Résumé :

La precisione sulla misura della sezione d’urto del neutrino elettronico e muonico è limitata principalmente dalla conoscienza del flusso iniziale. La precisione attuale è dell’ordine del 5 − 10%. Il progetto ENUBET (Enhanced NeUtrino Beam from kaon Tagging) propone una nuova facility in grado di monitorare il fascio di neutrini prodotto da un fascio secondario di mesoni taggando il leptone corrispondente emesso nello stesso decadimento di pro- duzione. Questo tipo di studio pone diverse restrizioni sul fascio secondario, dal quale dipende soprattutto la distribuzione in energia dei neutrini che raggiungono il detector. In questo lavoro di tesi di dottorato si presentano gli studi effettuati per il design e l’ottimizzazione di una beamline a ener- gia modulare (Multi-Momentum Beamline) presso la sezione BE-EA-LE del CERN. Il layout proposto è ottimizzato per il trasporto di mesoni K+ e π+ con momento centrato in 8.5, 6 e 4 GeV/c. Attraverso questa tecnica è possi- bile monitorare l’energia di neutrini nell’area di interesse di esperimenti quali HyperK, T2K e DUNE tramite la stessa configurazione di magneti. Oltre alla modularità, la Multi-Momentum Beamline è caratterizzata da un angolo di produzione che permette un primo filtro dal fondo che raggiungerebbe il tunnel di decadimento. Inoltre, il design è composto da soli elementi già attualmente in uso al CERN. L’impiego di magneti pre-esistenti permette un’analisi quantitativa, oltre che qualitativa delle performance della beam- line oltre a un costo contenuto nell’implementazione.
The precision of the measurement of the cross-section of the electronic and muon neutrino is mainly limited by the knowledge of the initial flux. The cur- rent precision is on the order of 5−10%. The ENUBET (Enhanced NeUtrino Beam from kaon Tagging) project proposes a new facility capable of moni- toring the neutrino beam produced by a secondary meson beam by tagging the corresponding lepton emitted in the same production decay. This type of study places several restrictions on the secondary beam, that essentially de- fines the energy spectrum of the neutrinos reaching the far detector. In this Ph.D. thesis work, we present the studies carried out for the design and op- timization of a modular momentum beamline (Multi-Momentum Beamline) at the BE-EA-LE section of CERN. The proposed layout is optimized for the transport of K+ and π+ mesons with momentum centered around 8.5, 6 and 4 GeV/c. Using this beamline, it is possible to monitor the neutrino en- ergy in the area of interest of experiments such as HyperK, T2K, and DUNE through the same configuration of magnets. In addition to modularity, the developed multi-momentum beamline presents remarkable properties such as a very satisfactory neutrino yield, control of the background, and satisfactory beam properties and performance that are all discussed in detail. A special target optimization procedure for maximizing the hadron yield has also been devised. Furthermore, the design is made up of only elements already in use at CERN. The use of pre-existing magnets allows a quantitative as well as qualitative analysis of the performance of the beamline as well as a low cost in the implementation. Finally, a comparison between Monte-Carlo and data for the ENUBINO prototype, tested at CERN’s EAST area is presented.

Styles APA, Harvard, Vancouver, ISO, etc.

2

Hershberger, Geoffrey D. « APPLIED TEMPERAMENT ». UKnowledge, 2018. https://uknowledge.uky.edu/music_etds/126.

Texte intégral

Résumé :

The following document was created in order to promote intonation consensus in ensembles and to better facilitate learning in educational settings. Non-keyboard instruments provide musicians an opportunity to make nearly infinitesimal adjustments to pitch while performing; this creates difficulties for students and challenges even the most seasoned professionals. Non-keyboard musicians struggle their whole lives to play in tune, and even when one knows exactly where they want to place a pitch, technical difficulties can foul any musician's performance. When performing solo, the musician must choose a tuning system that is suitable for the music being performed, and attempt to realize it. When performing in ensembles, the need for consensus and a systematic approach become more apparent. When performing with keyboards, the difficulties are increased as further compromises are required. This research was conducted with the intention to assist non-keyboard instrumentalists in selecting and recreating an appropriate temperament. Additionally, the author hopes that keyboard instrumentalists will be inclined to make a consideration for the non-keyboard instruments when selecting their temperament. The following document contains information useful to those wishing to employ a consistent approach to tuning. Presented here are the acoustic phenomena that have perplexed scholars around the world for the last 2600 years. The history and science of these acoustic questions will be demonstrated and discussed.

Styles APA, Harvard, Vancouver, ISO, etc.

3

Elf, Patric. « Radiation effects on wide bandgap semiconductor devices ». Thesis, KTH, Tillämpad fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-283320.

Texte intégral

Résumé :

Gallium nitride (GaN) based high-electron-mobility transistors (HEMTs) are used in a wide variety of areas, such as 5G, automotive, aeronautics/astronautics and sensing elds ranging from chemical, mechanical, biological to optical applications. Owing superior material properties, the GaN based HEMTs are especially useful in harsh operation environments e.g. in the combustion engine, exhaust, space, and medical instruments where the reliability and resilience are highly demanded. In this thesis the e ect of proton irradiation on the GaN HEMTs as well as the possible incorporation of them in biomedicine and diagnostics are investigated. The thesis includes mainly two parts: one is on theoretic background of GaN HEMTs, and another presents the experiment/simulation details of the devices before and after proton radiation. In the background section, the HEMTs function, manufacture technique and defect formation mechanism in the device under di erent proton radiation conditions are introduced. Then, the characterizations of the HEMT devices and related test structures before and after the proton radiation with dose range from 1011 to 1015 protons=cm2 are emphasized, as well as the comparison with simulation results obtained using SRIM/TRIM program. In addition, the biocompatibility of GaN devices and their biomedicine applications in proton radiation scenarios are also described and discussed in this thesis.
Gallium Nitrid (GaN) baserade high electron mobility transistors (HEMTs) används inom många olika områden, såsom 5G, bil-industrin, yg/rymd och i sensorer fö kemiska, mekaniska, biologiska och optiska applikationer. Tack vare dess goda materialegenskaper GaN baserade HEMTs särskilt användbara i harda miljöer, som till exempel i förbränningsmotorer, avgaser, i rymden, samt till medicinska instrument där pålitlighet och tålighet är eftersträvat. I det här examensarbetet sa undersöks e ekten av protonbestrålning pa GaN HEMTs samt möjligheten till användning av dem inom biomedicin och diagnostik. Arbetet är uppdelat i två delar: den ena behandlar den teoretiska bakgrunden av GaN HEMTs och den andra presenterar de experiment/simuleringar som utförts för att se efekterna på komponenterna före och efter protonbestrålning. I bakgrunds-sektionen så beskrivs hur HEMTs fungerar, tillverkningstekniker och mekanismerna för hur defekter uppkommer under olika former av protonbestrålning. Därefter sa karaktäriseras HEMT komponenterna och relaterade teststrukturer före och efter protonbestralning, med ett fokus på doser mellan 1011 to 1015 protoner=cm2, samt en jämförelse med resultat som fatts fran simuleringar med SRIM/TRIM-program. Utöver detta sa beskrivs och diskuteras även biokompatibiliteten och applikationer inom biomedicin av GaN komponenter vid protonbestralnings-scenarion i arbetet.

Styles APA, Harvard, Vancouver, ISO, etc.

4

Schneider, Claus M., Daniel E. Bürgler, Peter M. Oppeneer, Vancho Kocevski, Shigeo Arai, Roman Adam, Kazuyoshi Tatsumi, Ján Rusz et Shunsuke Muto. « Quantitative characterization of nanoscale polycrystalline magnets with electron magnetic circular dichroism ». nature publishing group, 2014. http://hdl.handle.net/2237/20835.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

5

Corker, Lloyd A. « Probabilistic methods applied to fluctuating systems ». Doctoral thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10320.

Texte intégral

Résumé :

In this work the hierarchical structure of three diverse stochastic systems is studied by investigating the probability densities of their scale-dependent measures across various scales. In the first system studied, velocity increments are used to investigate the order of complexity and disorder of wind turbulence. The second system investigates the disorders of skeletal muscles and the nervous system by considering the fluctuation of electric potentials of skeletal muscles. The last system studied is a non-physical system where price increments are used to classify the financial markets in terms of predictability of price changes and market efficiency. In all three stochastic systems a Fokker-Planck equation is used to describe how the scale-dependent measure is correlated across nested scales.

Styles APA, Harvard, Vancouver, ISO, etc.

6

Sugden, Kate E. P. « Nonequilibrium statistical physics applied to biophysical cellular processes ». Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4339.

Texte intégral

Résumé :

The methods of statistical physics are increasingly being employed in a range of interdisciplinary areas. In particular, aspects of complex biological processes have been elucidated by bringing the problems down to the level of simple interactions studied in a statistical sense. In nonequilibrium statistical physics, a one dimensional lattice model known as the totally asymmetric simple exclusion processes (TASEP) has become prominent as a tool for modelling various cellular transport processes. Indeed the context in which the TASEP was first introduced (MacDonald et. al., 1968) was to model ribosome motion along mRNA during protein synthesis. In this work I study a variation of the TASEP in which particles hop along a one dimensional lattice which extends as they reach the end. We introduce this model to describe the unique growth dynamics of filamentous fungi, whereby a narrow fungal filament extends purely from its tip region while being supplied with growth materials from behind the tip. We find that the steady state behaviour of our model reflects that of the TASEP, however there is an additional phase where a dynamic shock is present in the system. I show through Monte Carlo simulation and theoretical analysis that the qualitative behaviour of this model can be predicted with a simple mean-field approximation, while the details of the phase behaviour are accurate only in a refined approximation which takes into account some correlations. I also discuss a further refined mean-field approximation and give a heuristic argument for our results. Next I present an extension of the model which allows the particles to interact with a second lattice, on which they diffuse in either direction. A first order meanfield continuum approximation suggests that the steady states of this system will exhibit some novel behaviour. Through Monte Carlo simulation I discuss the qualitative changes that arise due to the on-off dynamics. Finally I study a model for a second biological phenomenon: the length fluctuations of microtubules. The model describes stochastic polymerisation events at the tip of a microtubule. Using a mean-field theory, we find a transition between regimes where the microtubule grows on average, and where the length remains finite. For low rates of polymerisation and depolymerisation, the transition is in good agreement with Monte Carlo simulation.

Styles APA, Harvard, Vancouver, ISO, etc.

7

Ariane, Mostapha. « The discrete multi-physics method applied to biomechanics ». Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8048/.

Texte intégral

Résumé :

In this thesis, a fully Lagrangian approach called the Discrete Multi-Physics is adopted and applied to biomechanics. The Discrete Multi-Physics combines the Smoothed Particle Hydrodynamics, the Mass and Spring Model and the Discrete Element Method in a common particle-based framework. In the Discrete Multi-Physics, high deformations and contact of solid structures (e.g. valve’s leaflets during closing phase or colloid contact) can be easily modelled. In biological valve simulations, for instance, we were able to account for repeated opening-closing cycles and to introduce an agglomeration algorithm to model clotting. Besides cardiovascular and venous flows, we also applied the Discrete Multi-Physics to respiratory tracts for modelling (i) cilia motion and drug diffusion in the periciliary layer (ciliated epithelium) and (ii) the release of active ingredients in powder inhalers for drug delivery in the lungs.

Styles APA, Harvard, Vancouver, ISO, etc.

8

Blickenstaff, Jacob Arin. « A framework for effective physics education applied to secondary and university physics courses / ». For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

9

Wierst, Pauline Manninne Anna van. « Paradoxes of the applied infinite : infinite idealizations in Physics ». Doctoral thesis, Scuola Normale Superiore, 2018. http://hdl.handle.net/11384/86153.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

10

Anderson, Jesse Charles. « The Intrinsic Variability in the Water Vapor Saturation Ratio Due to Turbulence ». Thesis, Michigan Technological University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10684480.

Texte intégral

Résumé :

The water vapor concentration plays an important role for many atmospheric processes. The mean concentration is key to understand water vapor's effect on the climate as a greenhouse gas. The fluctuations about the mean are important to understand heat fluxes between Earth's surface and the boundary layer. These fluctuations are linked to turbulence that is present in the boundary layer. Turbulent conditions are simulated in Michigan Tech’s multiphase, turbulent reaction chamber, the Π chamber. Measurements for temperature and water vapor concentration were recorded under forced Rayleigh- Bénard convection at several turbulent intensities. These were used to calculate the saturation ratio, often referred to as the relative humidity. The fluctuations in the water vapor concentration were found to be the more important than the temperature for the variability of the saturation ratio. The fluctuations in the saturation ratio result in some cloud droplets experiencing a higher supersaturation than other cloud droplets, causing those "lucky" droplets to grow at a faster rate than other droplets. This difference in growth rates could contribute to a broadening of the size distribution of cloud droplets, resulting in the enhancement of collision-coalescence. These fluctuations become more pronounced with more intense turbulence.

Styles APA, Harvard, Vancouver, ISO, etc.

11

Jimenez, Nicholas M. « Implementation of Magneto Optical Kerr Effect Microscopy for the Observation of Magnetic Domain Structure in Thin Films ». Thesis, California State University, Long Beach, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13425872.

Texte intégral

Résumé :

The home built Magneto-Optical Kerr Effect (MOKE) microscope was implemented to probe the magnetic domain patterns of thin film samples. A CCD camera is introduced to the existing MOKE rotation measurement setup. The images captured by the camera are used to analyze the change in the magnetic domain patterns by the Kerr effect. Using 6.5× zoom lens and 1.33× extension tube attached to the CCD camera, the size of the sample down to a 1.02mm by 0.75 mm area can be viewed in the image capture. Magnetic hysteresis loop is first measured to investigate the magnetic switching behavior and measure the coercivity. Domain images that exhibited the most significant change were mostly captured between magnetic remanence and near coercivity. The images of samarium cobalt thin film at or near magnetic coercivity showed the changes in shape and light intensity of the magnetic domain light patterns due to the Kerr rotation.

Styles APA, Harvard, Vancouver, ISO, etc.

12

Baker, Terence Lee. « Magnetic Force Microscopy of Permalloy Thin Films on Nanosphere Templates ». Thesis, California State University, Long Beach, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13426819.

Texte intégral

Résumé :

Magnetic Force Microscopy (MFM) is a viable method of analyzing magnetic characteristics of ferromagnetic nanostructure materials. The nanosphere template produces a variety of magnetic domains for the endeavor of advancing technological applications such as nanomagnetic logic and magnetoplasmonic nanoparticles. These nanomagnetic applications demand very specific magnetic characteristics, so the profiling of different magnetic domains using magnetic force microscopy is essential. During this work, we studied the magnetic domains that came from permalloy material on nanosphere templates. We investigated the most optimal MFM scan parameters that could produce a viable and trustworthy magnetic domain image. After analyzing two types of samples with different nanosphere template arrangements scanned at two scan angles, 0° and 90°, relative to the cantilever, it was concluded that both scan angles produced optimal images. The optimal lift scan height, relative to the sample surface, was determined to be 65 nm away, where the magnetic domain is most accurately observed. When the tip magnetization was reversed, the MFM images show a corresponding flipping of the magnetic domain characteristics, but maintained the domain size and pattern. Further research is needed to determine the cause of magnetic domain ripples that appear in images.

Styles APA, Harvard, Vancouver, ISO, etc.

13

Platt, John Daniel. « Dynamics and Materials Physics of Fault Rupture and Glacial Processes ». Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:14226054.

Texte intégral

Résumé :

This thesis focuses on two main topics, the physics governing how faults rapidly weaken during an earthquake and the thermal and mechanical structure of ice stream shear margins. The common theme linking these two projects is the desire to understand how the complicated interactions between stress and temperature control deformation and failure. All of the problems in this thesis are attacked using a combination of analytic and numerical methods, and the interplay between these two approaches provides a powerful way to understand the different physical balances that dominate in different regimes. We also use aspects of materials science to understand how the often complicated rheologies are controlled by underlying physical phenomena such as melting, phase transitions, diffusion, and dislocation motion. With regards to fault mechanics, we begin by showing how co-seismic weakening mechanisms driven by elevated pore fluid pressures lead to micron-scale strain localization during an earthquake. We solve for the localized zone thickness for a range of fault temperatures, test these predictions using numerical simulations, and show how the onset of localization accelerates fault weakening. Next we present the first solutions to account for thermal decomposition reactions during a dynamic rupture, showing that the activation of thermal decomposition may lead to a larger slip duration and total slip. Finally we present a new set of experiments studying flash heating of serpentinite, highlighting the dependence of friction on normal stress and the presence of gouge, and producing the first model to explain the hysteresis commonly observed in flash heating experiments. With regards to ice stream shear margins, we begin by extending the work of Perol and Rice [2011] to study the formation of temperate ice in shear margins, and quantify the total melt that may be generated within the shear margins. We conclude by investigating how the presence of such a channel alters the stress on and strength of the undeforming bed in the shear margin, showing that the transition from a deforming to an undeforming bed across a channel is stable when the water flux in the channel exceeds a critical value.

Styles APA, Harvard, Vancouver, ISO, etc.

14

Gleason, Russell. « Nanosphere lithography applied to magnetic thin films ». Thesis, California State University, Long Beach, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1524199.

Texte intégral

Résumé :

Magnetic nanostructures have widespread applications in many areas of physics and engineering, and nanosphere lithography has recently emerged as promising tool for the fabrication of such nanostructures. The goal of this research is to explore the magnetic properties of a thin film of ferromagnetic material deposited onto a hexagonally close-packed monolayer array of polystyrene nanospheres, and how they differ from the magnetic properties of a typical flat thin film. The first portion of this research focuses on determining the optimum conditions for depositing a monolayer of nanospheres onto chemically pretreated silicon substrates (via drop-coating) and the subsequent characterization of the deposited nanosphere layer with scanning electron microscopy. Single layers of permalloy (Ni80Fe20) are then deposited on top of the nanosphere array via DC magnetron sputtering, resulting in a thin film array of magnetic nanocaps. The coercivities of the thin films are measured using a home-built magneto-optical Kerr effect (MOKE) system in longitudinal arrangement. MOKE measurements show that for a single layer of permalloy (Py), the coercivity of a thin film deposited onto an array of nanospheres increases compared to that of a flat thin film. In addition, the coercivity increases as the nanosphere size decreases for the same deposited layer. It is postulated that magnetic exchange decoupling between neighboring nanocaps suppresses the propagation of magnetic domain walls, and this pinning of the domain walls is thought to be the primary source of the increase in coercivity.

Styles APA, Harvard, Vancouver, ISO, etc.

15

Stevenson, Samual Wilfred. « Hartree-Fock peturbation theory applied to lithium ». Thesis, Queen's University Belfast, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235825.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

16

Gullman-Strand, Johan. « Turbulence and scalar flux modelling applied to separated flows ». Doctoral thesis, Stockholm : Department of Mechanics, Royal Institute of Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

17

Gonoskov, Arkady. « Ultra-intense laser-plasma interaction for applied and fundamental physics ». Doctoral thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-84245.

Texte intégral

Résumé :

Rapid progress in ultra-intense laser technology has resulted in intensity levels surpassing 1022 W/cm2, reaching the highest possible density of electromagnetic energy amongst all controlled sources available in the laboratory. During recent decades, fast growth in available intensity has stimulated numerous studies based on the use of high intensity lasers as a unique tool for the initiation of nonlinear behavior in various basic systems: first molecules and atoms, then plasma resulting from the ionization of gases and solids, and, finally, pure vacuum. Apart from their fundamental importance, these studies reveal various mechanisms for the conversion of a laser pulse's energy into other forms, opening up new possibilities for generating beams of energetic particles and radiation with tailored properties. In particular, the cheapness and compactness of laser based sources of energetic protons are expected to make a revolution in medicine and industry. In this thesis we study nonlinear phenomena in the process of laser radiation interacting with plasmas of ionized targets. We develop advanced numerical tools and use them for the simulation of laser-plasma interactions in various configurations relating to both current and proposed experiments. Phenomenological analysis of numerical results helps us to reveal several new effects, understand the physics behind them and develop related theoretical models capable of making general conclusions and predictions. We develop target designs to use studied effects for charged particle acceleration and for the generation of attosecond pulses of unprecedented intensity. Finally, we analyze prospects for experimental activity at the upcoming international high intensity laser facilities and uncover a basic effect of anomalous radiative trapping, which opens up new possibilities for fundamental science.

Styles APA, Harvard, Vancouver, ISO, etc.

18

Keating, Christopher M. « Using Strong Laser Fields to Produce Antihydrogen Ions ». Thesis, Portland State University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10846288.

Texte intégral

Résumé :

We provide estimates of both cross section and rate for the stimulated attachment of a second positron into the (1s² ¹S^e) state of the H¯ ⁺ ion using Ohmura and Ohmura’s (1960 Phys. Rev. 118 154) effective range theory, Reiss’s strong field approximation (1980 Phys. Rev. A 22, 1786), and the principle of detailed balancing. Our motivation for producing H¯⁺ ion include its potential to be used as an intermediate state in bringing antihydrogen to ultra-cold (sub-mK) temperatures required for a variety of studies, which include both spectroscopy and the probing of the gravitational interaction of the anti-atom. We show that both cross section and rate are increased with the use of a resonant laser field.

Styles APA, Harvard, Vancouver, ISO, etc.

19

Piedra, Patricio G. « Radiative Transfer and Spectrophotometric Characterization of Mineral Dust Optics on Photovoltaic Cells ». Thesis, University of Nevada, Reno, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10681519.

Texte intégral

Résumé :

Efficiency of solar cells is degraded by deposition of mineral dust as well as other particles, and experiments reveal that losses can be significant (up to ~85%) depending on various factors. However, little is known about the role of light scattering and absorption in reducing optical transmission to the solar cell semiconductor. This dissertation first develops a fundamental model of optical losses due to particle-on-substrate scattering for light propagating into the forward direction. We use discrete dipole approximation with surface interaction (DDA-SI), which is a numerical solution of light scattering for an arbitrarily shaped particle-on-substrate. Using DDA-SI, we studied transmission losses due to hemispheric backward scattering (HBS) and absorption. A parameter called the fraction of power lost, defined as the ratio of HBS efficiency plus absorption efficiency to extinction efficiency, was found appropriate to describe optical losses into the forward direction. We found that fine particles lead to higher losses (per optical depth or layer optical thickness) than coarser ones. Losses into the forward direction are maximized when the ratio of skin depth to particles diameter approaches unity.

In addition, we conducted a resuspension-deposition experiment with two types of mineral dust, optically absorbing and non-absorbing dust. The dust samples were suspended and deposited onto glass slides, acting as surrogates for solar cells. Dust-deposited glass slides with increasing amounts of mass per area were spectroscopically characterized using a spectrophotometer with an integrating sphere (SIS) detector system. The SIS device allowed us to measure forward-hemisphere scattering, HBS, and direct beam transmission. Transmission into the forward direction was found to decrease as function of optical depth, depending on the absorptivity of the dust. Multiple-scattering radiative transfer theory, specifically the two-stream model as well as Monte Carlo stochastic calculations, were used to describe transmission as function of optical depth for both absorbing and nonabsorbing dust, yielding good agreement with experimental results within ~5%. Two-stream model and Monte Carlo techniques yield a multiple-scattering transmission calculation that depends on the single-scattering parameters of albedo and asymmetry parameter.

This study has the potential to help with solar energy forecasting, aiding smart power grids in predicting and adapting to variations in solar cell energy output due to aerosol deposition. In addition, this study can help optimize cleaning procedures and schedules to save water in desert and semi-arid regions by describing transmission losses as function of dust type.

Styles APA, Harvard, Vancouver, ISO, etc.

20

Yamamoto, Kiyoshi. « Optical theory applied to thin films ». Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1061392348.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

21

Ammon, Martin Matthias. « Gauge/Gravity Duality applied to Condensed Matter Systems ». Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-117739.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

22

Doost, Mark. « Resonant state expansion applied to open optical systems ». Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/61445/.

Texte intégral

Résumé :

This thesis presents work that I have done with Egor Muljarov and Wolfgang Langbein in order to extend an existing perturbation theory for open systems describable by a scalar equation to 3D systems which cannot be reduced to effectively lower dimensions. This perturbation theory is called the resonant-state expansion (RSE). The RSE is derived from properties of the dyadic tensor Green’s function (GF) of the unperturbed system written in terms of resonant states (RSs). Hence to extend the RSE it was necessary for us to derive this spectral form of the GF in terms of normalised RSs for arbitrary 3D systems. To process the numerical output of the RSE, we develop and evaluated algorithms for error estimation and their reduction by extrapolation. In the case of planar systems the RSE can be compared with other methods such as the scattering matrix or transfer matrix methods. It is also possible to solve the boundary conditions analytically to provide transcendental equations that can be solved by the Newton-Raphson method. We study these systems for that reason since we can validate the numerical calculations of the RSE by showing the convergence of perturbed solutions to the exact result found from these other methods. We study the planar systems both zero and non-zero in-plane wavevector. As an intermediate step to a fully 3D perturbation theory for open systems we make an implementation of the RSE in 2D. We use as a basis the analytically known RSs of the infinitely extended homogeneous dielectric cylinder. We find that the unperturbed GF contains a cut in the complex frequency plane, which must be included in the RSE basis for the accuracy of the perturbation theory. Zero frequency longitudinal modes are found to be formal solutions of Maxwell’s wave equation which also must be included in the basis for the accuracy of the method. Zero frequency modes occur for systems of all dimensionality when considering the TM modes, modes with electric field component normal to the interfaces. In the penultimate chapter of this thesis we apply the RSE to fully 3D open systems. We use as a basis the analytically known RSs of the homogeneous dielectric sphere. This advance was non-trivial due to a general mixing of transversal and longitudinal electro-magnetic modes. We compare the performance of the RSE with available commercial electromagnetic solvers. In the case of 3D perturbations, we find that the RSE provides a higher accuracy than the finite element method (FEM) and finite difference in time domain (FDTD) for a given computational effort, demonstrating its potential to supersede presently used methods. At the end of the penultimate chapter we introduce a local perturbation method for RSE, which is a unique capability of the RSE compared to FEM or FDTD, and allows to calculate small perturbations of a system with a small computational effort.

Styles APA, Harvard, Vancouver, ISO, etc.

23

Lloyd, Christopher James. « Diffusing wave spectroscopy applied to material analysis and process control ». Thesis, Open University, 1997. http://oro.open.ac.uk/54375/.

Texte intégral

Résumé :

Diffusing Wave Spectroscopy (DWS) was studied as a method of laboratory analysis of submicron particles, and developed as a prospective in-line, industrial, process control sensor, capable of near real-time feedback. No sample pre-treatment was required and measurement was via a noninvasive, flexible, dip in probe. DWS relies on the concept of the diffusive migration of light, as opposed to the ballistic scatter model used in conventional dynamic light scattering. The specific requirements of the optoelectronic hardware, data analysis methods and light scattering model were studied experimentally and, where practical, theoretically resulting in a novel technique of analysis of particle suspensions and emulsions of volume fractions between 0.01 and 0.4. Operation at high concentrations made the technique oblivious to dust and contamination. A pure homodyne (autodyne) experimental arrangement described was resilient to environmental disturbances, unlike many other systems which utilise optical fibres or heterodyne operation. Pilot and subsequent prototype development led to a highly accurate method of size ranking, suitable for analysis of a wide range of suspensions and emulsions. The technique was shown to operate on real industrial samples with statistical variance as low as 0.3% with minimal software processing. Whilst the application studied was the analysis of Ti02 suspensions, a diverse range of materials including polystyrene beads, cell pastes and industrial cutting fluid emulsions were tested. Results suggest that, whilst all sizing should be comparative to suitable standards, concentration effects may be minimised and even completely modelled-out in many applications. Adhesion to the optical probe was initially a significant problem but was minimised after the evaluation and use of suitable non stick coating materials. Unexpected behaviour in the correlation in the region of short decay times led to consideration of the effects of rotational diffusion coefficient. The inherent instability of high density suspensions instigated high speed analysis techniques capable of monitoring suspensions that were undergoing rapid change as well as suggesting novel methods for the evaluation of the state of sample dispersion.

Styles APA, Harvard, Vancouver, ISO, etc.

24

Adams, Rory Montague. « Flux corrected transport applied to hydrodynamics for heavy ion collisions ». Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/6521.

Texte intégral

Résumé :

Includes abstract.
Includes bibliographical references (p.145-154).
This thesis presents FCTHydro, a ROOT package, and its application to hydrodynamic simulations through the packages RelHydro and Nonideal xy. These packages aim to provide the broader heavy ion collision community with access to hydrodynamic simulation software which is now accessible from within the primary analysis framework, ROOT. Tests are performed and show how well the high-order, monotone, conservative, positivity preserving routines within FCTHydro simulate hydrodynamic systems with harsh initial conditions. RelHydro illustrates the application of FCTHydro to relativistic systems and Nonideal xy the application to causal non-ideal hydrodynamic systems. Nonideal xy is also used to obtain a first order understanding of the effects of the relaxation times in causal non-ideal hydrodynamics. In addition, a semi-analytic solution for the particle rapidity spectra obtained by combining Landau hydrodynamics and the Cooper-Frye freezeout formalism is given. The results are compared with the Landau Gaussian and a known approximation for midrapidies. The Landau Gaussian provides the best approximation to experimental data. Furthermore, the chemical freezeout results for preliminary data from AGS for central Au-Au collisions at nominal beam energies 2, 4, 6 and 8 AGeV are shown to agree with the E/N = 1 GeV freezeout criteria. These data allow access to a previously unexplored region in the T-μB phase space.

Styles APA, Harvard, Vancouver, ISO, etc.

25

Smith, Lorcan Stuart Peter Stillwell. « Bond graph modelling of physical systems ». Thesis, University of Glasgow, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337440.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

26

Numanovic, Kerim. « Advanced Clinical Data Processing : A Predictive Maintenance Model for Anesthesia Machines ». Thesis, KTH, Tillämpad fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-283323.

Texte intégral

Résumé :

The maintenance of medical devices is of great importance to ensure that the devices are stable, well-functioning, and safe to use. The current method of maintenance, which is called preventive maintenance, has its advantages but can be problematic both from an operators’ and a manufacturers’ side. Developing a model that will predict failure in anesthesia machines can be of great use for the manufacturer, the customers, and the patients. This thesis sets to examine the possibility of creating a predictive maintenance model for anesthesia machines by utilizing device data and machine learning. This thesis also investigates the influence of the data on the model performance and compare different lag sizes and future horizons to model performance. The time-series data collected came from 87 unique devices and a specific test was chosen to be the output variable of the model. A whole pipeline was created, which included pre-processing of the data, feature engineering, and model development. Feature extraction was done on the time series data, with the help of a library called tsfresh, which transformed time series characteristics into features that would enable supervised learning. Two models were developed: logistic regression and XGBoost. The logistic regression model acted as a baseline model and the result of its performance was as expected, quite poor. The XGBoost yielded an AUCPR score of 0.21 on the full dataset and 0.32 on a downsampled dataset. Although a quite low score, it was surprisingly high considering the extreme class imbalance that existed in the dataset. No clear pattern was found between the lag sizes and future horizons with the model performance. Something that could be seen was that the data imbalance had a great impact on the model performance, which was discovered when the downsampled dataset with less class imbalance yielded a higher AUCPR score.
Underhållet av medicintekniska produkter är mycket viktigt för att säkerställa att enheterna är stabila, välfungerande och säkra att använda. Den nuvarande underhållsmetoden, som kallas förebyggande underhåll, har sina fördelar men kan vara problematisk både från operatörens och tillverkarsidan. Att utveckla en modell som förutsäger fel i anestesimaskiner kan vara till stor nytta för tillverkaren, kunderna och patienterna. Denna avhandling syftar till att undersöka möjligheten att skapa en förutsägbar underhållsmodell för anestesimaskiner genom att använda enhetsdata och maskininlärning. Denna avhandling undersöker också påverkan av data på modellprestanda och jämför olika fördröjningsstorlekar och framtida horisonter med modellprestanda. Tidsseriedata som samlats in kom från 87 unika enheter och ett specifikt test valdes för att vara modellens outputvariabel. En hel pipeline skapades, som inkluderade förbehandling av data, funktionsteknik och modellutveckling. Funktionsextraktion gjordes på tidsseriedata med hjälp av ett bibliotek som heter tsfresh, som förvandlade tidsserieegenskaper till funktioner som skulle möjliggöra övervakat lärande. Två modeller utvecklades: logistisk regression och XGBoost. Den logistiska regressionsmodellen fungerade som en basmodell och resultatet av dess prestanda var som förväntat ganska dåligt. XGBoost gav en AUCPR-poäng på 0,21 på hela datamängden och 0,32 på en nedmonterad datamängd. Även om det var en ganska låg poäng, var det överraskande högt med tanke på den extrema klassobalansen som fanns i datasetet. Inget tydligt mönster hittades mellan fördröjningsstorlekarna och framtida horisonter med modellprestanda. Något som kunde ses var att dataobalansen hade stor inverkan på modellens prestanda, vilket upptäcktes när den nedprovade datamängden med mindre obalans i klassen gav en högre AUCPR-poäng.

Styles APA, Harvard, Vancouver, ISO, etc.

27

Westacott, Robin E. « Direct free energy calculations applied to clathrate hydrates ». Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283787.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

28

Zimmermann, Julia. « Dissociation properties of biomolecules under an externally applied force ». Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-91986.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

29

Shinn, Mannix A. « Development of Magneto-Optic Sensors with Gallium in Bismuth Doped Rare-Earth Iron-Garnet Thick Films ». Thesis, Temple University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10639984.

Texte intégral

Résumé :

We have investigated the Faraday effect of bismuth-doped rare-earth iron-garnets with varying doping levels of gallium from z = 1.0 to 1.35. We used lutetium to control the film's in-plane magnetic properties and found that gallium doping levels above the compensation point caused a loss of anisotropy control, a canted out-of-plane magnetization in the film, and an extremely weak but linear coercivity above 10 micro-Tesla fields. Using these results we focused on in-plane films to create 8 layer stacks of 500 um thick films to achieve a minimum detectable field of 50 pT at 1 kHz. Unlike previous Magneto-Optic (MO) studies that typically used thin films of approximately 1um thickness, we used approximately 400um thick films to allow experimentation with the final, robust, ideal form the MO sensor would take. We measured what most other MO studies with garnets neglected: the magnetic anisotropy axis or structure within the film. Knowledge of this structure is essential in improving the sensitivity of a stacked MO probe. Studying thick films proved to be key to understanding the magnetic anisotropy and domain properties that can degrade or enhance the sensitivity of the Faraday rotation in bismuth doped rare-earth iron-garnets to an applied magnetic field and to pointing the direction of future research to develop the conditions for rugged magnetometer sensors.

Styles APA, Harvard, Vancouver, ISO, etc.

30

Grover, Tarun Ph D. Massachusetts Institute of Technology. « Applied fractionalization : quantum phases and phase transitions of strongly interacting systems ». Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/68973.

Texte intégral

Résumé :

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 131-136).
Strongly correlated systems present interesting challenges in condensed matter physics. On the one hand, the theoretical work in the last two decades suggests that strong interactions may lead to new phases and phase transitions of matter that don't fit paradigms such as Fermi liquid theory or Landau's theory of phase transitions. On the other hand, there are actual materials which are undoubtedly governed by strong interactions and indeed do not fit the conventional paradigms but whose behavior often doesn't quite match our theoretical expectations. This gap between theory and experiments is slowly narrowing owing to the discovery of new materials and recent advances in numerical simulations. As an example, the material K - (ET)2Cu 2(CN) 3 exhibits metallic specific heat in its insulating phase. This is indicative of the theoretically proposed phenomena of 'fractionalization' where elementary excitations in a phase carry quantum numbers that are fractions of that corresponding to an electron. Similarly, there is growing numerical evidence of the theoretical phenomena of 'deconfined quantum criticality', where quantum Berry phases lead to emergence of fractionalized particles right at the phase transition. In this thesis we study phenomena where the concept of fractionalization is a useful tool to explore new phases and phase transitions. Most of our examples are in the context of frustrated quantum magnets. Along the way, we also explore topics such as quantum numbers of topological defects and non-abelian phases of matter. Whenever possible, we compare theoretical predictions with experimental and numerical data. We also discuss deconfined quantum criticality in the context of metallic systems where it opens the route to phase transitions very different from the conventional spin-density wave instability of Fermi surface.
by Tarun Grover.
Ph.D.

Styles APA, Harvard, Vancouver, ISO, etc.

31

Walker, Edwin Parker. « Superresolution applied to optical data storage systems ». Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/289046.

Texte intégral

Résumé :

This dissertation investigates superresolution applications in optical data storage systems. The performance of standard and superresolving magneto-optic data storage system are quantified by scalar diffraction modeling and experiments. Classical resolution measures are reviewed. Background on superresolution definitions and their conceptual development in scanning optical microscopes, optical data storage, and image processing is presented. Figures of merit for quantifying the performance of the systems are reviewed, such as system transfer function, two-point response, focused spot size, and signal-to-noise ratio. The description of the scalar diffraction modeling used to simulate an optical data storage system is reviewed. Operation of the magneto-optic data storage system and tradeoffs of superresolving techniques are discussed. The signal and noise spatial distribution in the pupil of an optical data storage system are shown to be different. For a particular spatial frequency bandwidth, the signal and noise are concentrated in different regions of the pupil. This understanding allows the use of optical filters that partially equalize the system transfer function and increase the signal-to-noise ratio. The main superresolution techniques investigated are those that increase the transmission of the higher spatial frequencies, or equalize the system transfer function, without changing the system cutoff frequency. The optical methods used to achieve superresolution are amplitude and phase filters placed in strategic system locations. One location influences the properties of the focused spot such as the irradiance distribution and width of the central core. Another location does not change the focused spot at all, but does change the signal and noise properties of the system. Electronic filtering techniques are also used to increase the transmission of the high spatial frequencies. The amplitude and phase filter sensitivities to aberration are also investigated. Optical properties of a new laser diode are investigated. The new laser diode has potential superresolving properties that are inherent to the device. Potential application of this device in an optical data storage device is presented. Another method of increasing the transmission of higher spatial frequencies within the system bandwidth and beyond the system cutoff frequency is to use adaptive optical systems. Adaptive systems for optical data storage are also discussed.

Styles APA, Harvard, Vancouver, ISO, etc.

32

Ellison, Charles Leland. « Development of Multistep and Degenerate Variational Integrators for Applications in Plasma Physics ». Thesis, Princeton University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10090246.

Texte intégral

Résumé :

Geometric integrators yield high-fidelity numerical results by retaining conservation laws in the time advance. A particularly powerful class of geometric integrators is symplectic integrators, which are widely used in orbital mechanics and accelerator physics. An important application presently lacking symplectic integrators is the guiding center motion of magnetized particles represented by non-canonical coordinates. Because guiding center trajectories are foundational to many simulations of magnetically confined plasmas, geometric guiding center algorithms have high potential for impact. The motivation is compounded by the need to simulate long-pulse fusion devices, including ITER, and opportunities in high performance computing, including the use of petascale resources and beyond.

This dissertation uses a systematic procedure for constructing geometric integrators — known as variational integration — to deliver new algorithms for guiding center trajectories and other plasma-relevant dynamical systems. These variational integrators are non-trivial because the Lagrangians of interest are degenerate - the Euler-Lagrange equations are first-order differential equations and the Legendre transform is not invertible. The first contribution of this dissertation is that variational integrators for degenerate Lagrangian systems are typically multistep methods. Multistep methods admit parasitic mode instabilities that can ruin the numerical results. These instabilities motivate the second major contribution: degenerate variational integrators. By replicating the degeneracy of the continuous system, degenerate variational integrators avoid parasitic mode instabilities. The new methods are therefore robust geometric integrators for degenerate Lagrangian systems.

These developments in variational integration theory culminate in one-step degenerate variational integrators for non-canonical magnetic field line flow and guiding center dynamics. The guiding center integrator assumes coordinates such that one component of the magnetic field is zero; it is shown how to construct such coordinates for nested magnetic surface configurations. Additionally, collisional drag effects are incorporated in the variational guiding center algorithm for the first time, allowing simulation of energetic particle thermalization. Advantages relative to existing canonical-symplectic and non-geometric algorithms are numerically demonstrated. All algorithms have been implemented as part of a modern, parallel, ODE-solving library, suitable for use in high-performance simulations.

Styles APA, Harvard, Vancouver, ISO, etc.

33

Rhoades, Matthew W. « Pulsed Laser Deposition and Electrical Properties of Zinc Selenide Based Thin Film Structures for Integration with Mid-infrared Applications ». Thesis, The University of Alabama at Birmingham, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10787536.

Texte intégral

Résumé :

Thin films of chlorine (Cl) and copper (Cu) doped zinc selenide (Cl:ZnSe and Cu:ZnSe) were fabricated by pulsed laser deposition (PLD) with the goal of enabling a multilayered semiconductor structure for a mid-infrared (mid-IR) electrically excited laser. Doping of ZnSe is achieved by varying the mass ratio of zinc chloride (ZnCl₂) or copper selenide (Cu₂Se) to ZnSe precursors in starting pressed powder targets. Appropriate adjustment of the fraction of dopant precursor in the mixtures allows for the control of the dopant concentration, N_D–N_A for N_D >> N_A (or N_A-N_D for N_A >> N_D) in the thin films, where N_D is the donor concentration and N_A is the acceptor concentration. PLD is used to ablate the Cl:ZnSe or Cu:ZnSe targets, to produce thin films on gallium arsenide (GaAs) substrates. Impedance spectroscopy allows current-voltage and capacitance-voltage (C-V) characterization. Specifically Mott-Schottky measurements determine N_D-N_A (or N_A-N_D) of the fabricated thin film samples with comparisons to the nominal dopant concentration of the targets. The Mott-Schottky, 1/C² vs. V, measurements for determining N_D-N_A were calibrated against well-characterized silicon wafers with known values of N_D. The goal of this project was to demonstrate a reliable method for controlling the dopant concentration in PLD-deposited Cl:ZnSe and Cu:ZnSe thin films. The results obtained allows for the fabrication of Cl:ZnSe and Cu:ZnSe thin films with known N_D-N_A for use in a mid-IR electrically-excited laser devices under development in our research group.

Styles APA, Harvard, Vancouver, ISO, etc.

34

Beach, Alexander R. « Fabrication of Self-Assembled Nanosphere Templates to Investigate the Magnetic Behavior of Permalloy Cap Layers ». Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10841251.

Texte intégral

Résumé :

The Langmuir-Blodgett deposition process is investigated for creating polystyrene nanosphere monolayers on a hydrophilic silicon substrate. The monolayers are fabricated over areas ~1 cm² and sputter coated with 100Å of permalloy. The quality of the monolayers is analyzed with optical microscope image processing, and 2D Fourier transforms of electron microscope images. The magnetic switching behavior of the sputtered samples is measured using an alternating gradient magnetometer, and compared to completely flat permalloy. The magnetic hysteresis measurements are done at different angle between the easy and hard axis of the flat permalloy films. The measurements show different hysteresis shapes for nanosphere patterned permalloy and flat permalloy, with the difference becoming greater nearer the hard axis of the flat permalloy samples. The ambiguity of an easy or hard axis on a curved surface is likely to contribute to the difference in magnetic switching behavior between the two sample types.

Styles APA, Harvard, Vancouver, ISO, etc.

35

Pyper, Graham. « Aspects of laser tissue interaction in photodynamic therapy ». Thesis, University of Hull, 1997. http://hydra.hull.ac.uk/resources/hull:11088.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

36

Key, Philip Henry. « Excimer laser micromachining of inorganic materials ». Thesis, University of Hull, 1989. http://hydra.hull.ac.uk/resources/hull:11090.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

37

Khosroshahi, Mohammed Etrati. « Ablation of ophthalmic tissues with fibre delivered UV and IR lasers ». Thesis, University of Hull, 1993. http://hydra.hull.ac.uk/resources/hull:16870.

Texte intégral

Résumé :

In this thesis investigations of short pulse XeCl, KrF and ArF excimer lasers and HF laser transmission in fused silica and fluoride glass fibres respectively are reported, together with studies of polymer and soft tissue ablation in air and saline. Etch rate and photoacoustic measurements have been used to study the ablation process for the tissue and polymer samples with excimer lasers. The main emphasis is on the HF laser where a UV preionized transverse discharge in SF6 - C3H8 mixtures was used to generate ≃400ns (FWHM) pulses of energy up to 380mJ. Transmission measurements made on a 500μm core diameter fluoride glass fibre gave a distributed loss coefficient of −3 1.5x10 cm−1, and a maximum useful input fluence of ≃15Jcm−2 set by non-linear loss at the fibre input surface. For bovine cornea in air the onset of ablation occured at a fluence of ≃0.5Jcm−2, removal rates increased slowly up to ≃3Jcm−2 but above this increased sharply, reaching ≃17μm per pulse at 8Jcm−2. In saline the interaction becomes considerably more complicated because strong-heating of water at the fibre tip leads to the formation of a hot, high pressure vapour cavity (optical cavitation). Under these conditions the damage range may extend well beyond the beam penetration depth as a result of flow effects (eg. jetting) and intense acoustic emission associated with the 'bubble' growth and collapse. The dynamics of cavitation 'bubbles' have been investigated using pulsed dye laser shadowgraphy for various fibre-tissue geometries and results in free liquid modelled using the Rayleigh-Plesset theory. Time resolved photoacoustic measurements have also been made and revealed that very large transient pressures are generated in tissue near the fibre tip when ablation occurs in liquid; for example, at 8Jcm−2, B peak pressures reached about 1.5x108Pa. When the fibre-to- sample spacing was varied physical surface damage was evident out to distances of ≃250μm for cornea and ≃2mm for retina. As these are much greater than the characteristic beam absorption length in water (≃1.6μn), the main damage mechanism is then not through photoablation but jetting or acoustic emission associated with optical cavitation.

Styles APA, Harvard, Vancouver, ISO, etc.

38

Witwit, Mohammed R. M. « Perburbation and non-perburbation numerical calculations to compute energy eigenvalues for the Schrödinger equation with various types of potential ». Thesis, University of Hull, 1989. http://hydra.hull.ac.uk/resources/hull:12766.

Texte intégral

Résumé :

The present work is concerned with methods of finding the energy eigenvalues of the one-particle Schrödinger equation for various model potentials in one, two, three and N-dimensional space. One major theme of this thesis is the study of diverent Rayleigh-Schrödinger perturbation series which are encountered in non-relativistic quantum mechanics and on the behaviour of the series coefficients E(n) in the energy expansion E(λ):E(O)+∑ E(n)λⁿ. Several perturbative techniques are used. Hypervirial and Hellmann-Feynman theorems with renormalised constants are used to obtain perturbation series for large numbers of potentials. Pade approximant methods are applied to various problems and also an inner product method with a renormalised constant is used to calculate energy eigenvalues with very high accuracy. The non-perturbative methods which are used to calculate energy eigenvalues include finite difference and power series methods. Expectation values are determined by an approach based on eigenvalue calculations, without the explicit use of wave functions. The first chapter provides a glance back into history and a preview of the problems and ideas to be investigated. Chapter two deals with one dimensional problems, including the calculation of the energy eigenvalues for quasi-bound states for some types of perturbation (λx²ⁿ⁺¹). Chapter three is concerned with two, three and N-dimensional problems. Chapter four deals with non-polynomial potentials in one and three dimensions. The final chapter is devoted to a variety of eigenvalue problems. Most of the energy eigenvalues are computed by more than one method with double precision accuracy, and the agreement between the results serves to illustrate the accuracy of the methods.

Styles APA, Harvard, Vancouver, ISO, etc.

39

Layfield, Andrew. « An evaluation of selected estimation methods for the processing of differential absorption lidar data ». Thesis, University of Hull, 1987. http://hydra.hull.ac.uk/resources/hull:16436.

Texte intégral

Résumé :

This work examines the application of selected estimation methods to path integrated direct detection CO2 lidar data, with the objective of improving the precision in the estimates of the log power, and log power ratios. Particular emphasis is given to the optimal estimation techniques of Kalman filtering theory, and to the consequent requirements for system and measurement model identification. A dual wavelength system was designed and constructed, employing two hybridised TEA lasers, a co-axial transceiver, and direct detection. Over a period of several months, a database of differential absorption measurements was accumulated, each consisting of 10,000 dual wavelength lidar returns. Various wavelength pairs were used, including those recommended for the monitoring of H2O, CO2, NH3 and C2H4. A subset of this database is used to evaluate the above mentioned estimation methods. The results are compared with simulated data files in which it was possible to control precisely process models which are believed to form an approximation to the real processes latent in the actual lidar data.

Styles APA, Harvard, Vancouver, ISO, etc.

40

O'Neal, Jared. « A Numerical Study of a Disorder-driven 2D Mott Insulator-to-Metal Quantum Phase Transition ». The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492701913534985.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

41

Novick, Jaison Allen. « Chaotic scattering in an open vase-shaped cavity : Topological, numerical, and experimental results ». W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539623550.

Texte intégral

Résumé :

We present a study of trajectories in a two-dimensional, open, vase-shaped cavity in the absence of forces The classical trajectories freely propagate between elastic collisions. Bound trajectories, regular scattering trajectories, and chaotic scattering trajectories are present in the vase. Most importantly, we find that classical trajectories passing through the vase's mouth escape without return. In our simulations, we propagate bursts of trajectories from point sources located along the vase walls. We record the time for escaping trajectories to pass through the vase's neck. Constructing a plot of escape time versus the initial launch angle for the chaotic trajectories reveals a vastly complicated recursive structure or a fractal. This fractal structure can be understood by a suitable coordinate transform. Reducing the dynamics to two dimensions reveals that the chaotic dynamics are organized by a homoclinic tangle, which is formed by the union of infinitely long, intersecting stable and unstable manifolds.;This study is broken down into three major components. We first present a topological theory that extracts the essential topological information from a finite subset of the tangle and encodes this information in a set of symbolic dynamical equations. These equations can be used to predict a topologically forced minimal subset of the recursive structure seen in numerically computed escape time plots. We present three applications of the theory and compare these predictions to our simulations. The second component is a presentation of an experiment in which the vase was constructed from Teflon walls using an ultrasound transducer as a point source. We compare the escaping signal to a classical simulation and find agreement between the two. Finally, we present an approximate solution to the time independent Schrodinger Equation for escaping waves. We choose a set of points at which to evaluate the wave function and interpolate trajectories connecting the source point to each "detector point". We then construct the wave function directly from these classical trajectories using the two-dimensional WKB approximation. The wave function is Fourier Transformed using a Fast Fourier Transform algorithm resulting in a spectrum in which each peak corresponds to an interpolated trajectory. Our predictions are based on an imagined experiment that uses microwave propagation within an electromagnetic waveguide. Such an experiment exploits the fact that under suitable conditions both Maxwell's Equations and the Schrodinger Equation can be reduced to the Helmholtz Equation. Therefore, our predictions, while compared to the electromagnetic experiment, contain information about the quantum system. Identifying peaks in the transmission spectrum with chaotic trajectories will allow for an additional experimental verification of the intermediate recursive structure. Finally, we summarize our results and discuss possible extensions of this project.

Styles APA, Harvard, Vancouver, ISO, etc.

42

Miller, Corey Alexander. « Intelligent Feature Selection Techniques for Pattern Classification of Time-Domain Signals ». W&M ScholarWorks, 2013. https://scholarworks.wm.edu/etd/1539623620.

Texte intégral

Résumé :

Time-domain signals form the basis of analysis for a variety of applications, including those involving variable conditions or physical changes that result in degraded signal quality. Typical approaches to signal analysis fail under these conditions, as these types of changes often lie outside the scope of the domain's basic analytic theory and are too complex for modeling. Sophisticated signal processing techniques are required as a result. In this work, we develop a robust signal analysis technique that is suitable for a wide variety of time-domain signal analysis applications. Statistical pattern classification routines are applied to problems of interest involving a physical change in the domain of the problem that translate into changes in the signal characteristics. The basis of this technique involves a signal transformation known as the Dynamic Wavelet Fingerprint, used to generate a feature space in addition to features related to the physical domain of the individual application. Feature selection techniques are explored that incorporate the context of the problem into the feature space reduction in an attempt to identify optimal representations of these data sets.

Styles APA, Harvard, Vancouver, ISO, etc.

43

Keller, Steven Ede. « Flux-limited Diffusion Coefficient Applied to Reactor Analysis ». Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16126.

Texte intégral

Résumé :

A new definition of the diffusion coefficient for use in reactor physics calculations is evaluated in this thesis. It is based on naturally flux-limited diffusion theory (FDT), sometimes referred to as Levermore-Pomraning diffusion theory. Another diffusion coefficient more loosely based on FDT is also evaluated in this thesis. Flux-limited diffusion theory adheres to the physical principle of flux-limiting, which is that the magnitude of neutron current is not allowed to exceed the scalar flux. Because the diffusion coefficients currently used in the nuclear industry are not flux-limited they may violate this principle in regions of large spatial gradients, and because they encompass other assumptions, they are only accurate when used in the types of calculations for which they were intended. The evaluations were performed using fine-mesh diffusion theory. They are in one spatial dimension and in 47, 4, and 2 energy groups, and were compared against a transport theory benchmark using equivalent energy structures and spatial discretization. The results show that the flux-limited diffusion coefficient (FD) outperforms the standard diffusion coefficient in calculations of single assemblies with vacuum boundaries, according to flux- and eigenvalue-errors. In single assemblies with reflective boundary conditions, the FD yielded smaller improvements, and tended to improve only the fast-group results. The results also computationally confirm that the FD adheres to flux-limiting, while the standard diffusion coefficient does not.

Styles APA, Harvard, Vancouver, ISO, etc.

44

Adianto. « Plasma polymerized organic thin films applied to electronic devices ». Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386600.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

45

Halstead, David Michael. « Time dependent quantum methods applied to molecule-surface interactions ». Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303642.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

46

Nieuwenhoven, Michiel Adrianus van. « Gastrointestinal function during physical exercise basic and applied research / ». [Maastricht : Maastricht : Universiteit Maastricht] ; University Library, Maastricht University [Host], 1999. http://arno.unimaas.nl/show.cgi?fid=6880.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

47

Dieste, Martina. « Random-vortex-particle methods applied to broadband fan interaction noise ». Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/192591/.

Texte intégral

Résumé :

The general aim of this thesis is to investigate the suitability of a stochastic method for computational aeroacoustics, the specific objective being to devise a stochastic method to generate synthetic turbulence and combine it with the linearised Euler equations to predict broadband fan interaction noise. In modern turbofan designs broadband fan noise is a dominant source of aircraft noise, the most efficient source being the interaction between upstream turbulence and the stator vanes. The stochastic method developed to generate synthetic turbulence reproduces twodimensional isotropic turbulent flows by filtering a random field. The fillter is expressed in terms of the energy spectrum and controls the spatial properties of the synthetic turbulence. In contrast with previous work, non-Gaussian filters are developed to model more realistic energy spectra such as Liepmann and von Karman spectra. The temporal decorrelation present in turbulent flows is modelled using Langevin Equations. A standard Langevin equation and a second-order Langevin model are derived in details and validated for fan interaction noise. In contrast with classical methods to generate synthetic turbulence, random-vortex-particle methods can be extended to cope with inhomogeneous non-stationary turbulence with little modification from the formulation for homogeneous turbulence. The stochastic method is applied for first time to broadband fan interaction noise. The method is firstly validated for frozen turbulence interacting with an airfoil. The temporal decorrelation is then included in the method to assess the influence of the integral time scale on the radiated acoustic sound field. The method is also combined with an existing wake model to represent the inhomogeneous non-stationary turbulent flow found downstream of a fan. Finally, comparison with existing experimental data for an isolated airfoil in a turbulent jet demonstrates the benefits of using more realistic energy spectra

Styles APA, Harvard, Vancouver, ISO, etc.

48

Marshall, Mark. « Physical interface design for digital musical instruments ». Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40788.

Texte intégral

Résumé :

This thesis deals with the study of performer-instrument interaction during the performance of novel digital musical instruments (DMIs). Unlike acoustic instruments, digital musical instruments have no coupling between the sound generation system and the physical interface with which the performer interacts. As a result of this, such instruments also lack the direct physical feedback to the performer which is present in an acoustic instrument. In fact in contrast to acoustic musical instruments, haptic and vibrotactile feedback is generally not present in a DMI contributing to a poor feel for the instrument. The main goal of this thesis is to propose ways to improve the overall feel of digital musical instruments through the study and design of its physical interface: the instrument body, sensors and feedback actuators. It includes a detailed study of the existing theory and practice of the design on physical interfaces for digital musical instruments, including a survey of 266 existing DMIs presented since the inception of the NIME conference. From this, a number of differences become apparent between the existing theory and practice, particularly in the areas of sensors and feedback. The research in this thesis then addresses these differences. It includes a series of experiments on the optimal choice of sensors for a digital musical instrument. This is followed by research into the provision of vibrotactile feedback in a digital musical instrument, including the choice of actuator, modification of actuator frequency response, and the effects of response modification on human vibrotactile frequency discrimination. Following this, a number of new digital musical instruments are presented, which were created during the course of this work. This includes an instrument designed specifically to follow the results of research in this thesis and also instruments designed as part of larger collaborative projects involving engineers, composers and performers. Fro
Cette thèse porte sur l'étude de l'interaction ayant lieu, en situation de jeu,entre un(e) instrumentiste et un instrument musical numérique (IMN).A l'inverse des instruments acoustiques traditionnels, il n'existe aucun couplageentre le dispositif de production du son et l'interface sur laquelle agit l'instrumentistedans le cas des IMN. L'une des implications de cette observation est que cesinstruments ne procurent pas la rétroaction tactile normalement présente dans lesinstruments de musique traditionels. Par conséquent, les IMN sont souvent perçuspar leurs interprètes comme manquant d'âme, de personnalité.Le but de ce travail de thèse est d'avancer quelques solutions permettant d'insuer un peu plus âme à un instrument musical numérique. Le point focal de larecherche étant l'étude et la conception de l'interface physique (corps de l'instrument,capteurs et dispositifs de rétroaction utilisés) d'un tel instrument.Ce mémoire présente, en premier lieu, une étude détaillée de la théorie et de lapratique actuelles dans le domaine de la conception d'interfaces physiques pour lesIMN. L'inventaire des 266 instruments recensés depuis la création de la conférenceNIME constitue l'un des points majeurs de cette partie du travail. En effet, ce tour d'horizon permet de faire ressortir les incohérences entre théorie et pratique. Cesdifférences sont particulièrement frappantes en ce qui concerne les capteurs et lesdispositifs de rétroaction.Le travail de recherche de cette thèse a donc pour objectif de mieux comprendrecomment réduire ces incohérences. Des expériences portant sur le choix optimaldes capteurs à utiliser dans un IMN ont donc été menées. Différents dispositifs derétroaction vibrotactile ont aussi été étudiés en regardant d'abord quels actuateursutiliser, et en évaluant les effets de la modication de leur réponse en fréquencesur la discrimination fréquentielle de stimuli vibrotactiles chez des sujets humains.Des exemp

Styles APA, Harvard, Vancouver, ISO, etc.

49

Clifford, Ivor David. « Object-oriented multi-physics applied to spatial reactor dynamics / Ivor David Clifford ». Thesis, North-West University, 2007. http://hdl.handle.net/10394/1656.

Texte intégral

Résumé :

Traditionally coupled field reactor analysis has been carried out using several loosely coupled solvers, each having been developed independently from the others. In the field of multi-physics, the current generation of object-oriented toolkits provides robust close coupling of multiple fields on a single framework. This research investigates the suitability of such frameworks, in particular the Open-source Field Operation and Manipulation (OpenFOAM) framework, for the solution of spatial reactor dynamics problems. For this a subset of the theory of the Time-dependent Neutronics and Temperatures (TINTE) code, a time-dependent two-group diffusion solver, was implemented in the OpenFOAM framework. This newly created code, called diffusionFOAM, was tested for a number of steady-state and transient cases. The solver was found to perform satisfactorily, despite a number of numerical issues. The object-oriented structure of the framework allowed for rapid and efficient development of the solver. Further investigations suggest that more advanced transport methods and higher order spatial discretization schemes can potentially be implemented using such a framework as well.
Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2008.

Styles APA, Harvard, Vancouver, ISO, etc.

50

Claus, Daniel. « Resolution improvement methods applied to digital holography ». Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/47211/.

Texte intégral

Résumé :

This thesis discusses the creation, acquisition and processing of digital holograms. Several techniques to improve the optical resolution have been investigated and developed. The optical resolution of numerically reconstructed digital holograms is restricted by both the sampling frequency and the overall sensor-size of the digital camera chip used. This thesis explores the limitations on the optical resolution of the holograms obtained. A typical sensor-size and sampling frequency for digital holograms is 10 mm and 100 lp/mm, respectively, whereas holographic plates used for optical holography can be more than a meter in size and have a sampling frequency of 3000 lp/mm. In order to take full advantage of the benefits digital holography offers, such as fast image acquisition and direct phase accessibility, the problem of reduced resolution needs to be overcome. Three resolution improvement methods have been developed in the scope of this PhD thesis. Prior to implementing the resolution improvement methods, different holographic setups have been analyzed, using the Space-bandwidth product (SBP) to calculate the information distribution both in the recording and reconstruction process. The first resolution improvement method is based on the synthetic aperture method. In this manner an increased sensor area can be obtained resulting in a larger numerical aperture (NA). A larger NA enables a more detailed reconstruction. The problem encountered in doing this is that an increased optical resolution results in a smaller depth of field. This has been overcome in this thesis by applying the extended depth of field method. As a result a high resolution in focus reconstruction of all longitudinal object regions is obtained. Moreover, the extended depth of field method allows a topological mapping of the object. The second resolution improvement method is based on sampling the interference pattern with sub-pixel accuracy. This was carried out on a CMOS-sensor and implemented by moving the light sensitive pixel-area into the dead zone in a 4x4 grid to cover whole the pixel-area. As a result the sensor's sampling frequency is doubled. The increased sampling frequency permits a reduction of the recording distance which results in an increased optical resolution of the reconstructed hologram. The third and novel approach described in this thesis has been to increase the optical resolution stored in a digital hologram by the combination of the synthetic aperture and the sub-pixel sampling methodBy analogy with the Fresnel-. The resolution improvement methods have been demonstrated both for lens-less digital holography and digital holographic microscopy.

Styles APA, Harvard, Vancouver, ISO, etc.

Thèses sur le sujet « Applied Physic »

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres