Dissertations / Theses on the topic 'Controlled and field conditions'
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Al, Masri Ali [Verfasser]. "Application of proximal sensing techniques for epidemiological investigations of Fusarium head blight in wheat under field and controlled conditions / Ali Al Masri." Bonn : Universitäts- und Landesbibliothek Bonn, 2018. http://d-nb.info/1155922778/34.
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Beckers, Felix [Verfasser]. "Mobilization, Methylation, and Ethylation of Mercury in Contaminated Floodplain Soils under Controlled Laboratory Redox Conditions as Influenced by Potential Immobilizing Agents as well as Mobilization of Mercury under Field Conditions / Felix Beckers." Wuppertal : Universitätsbibliothek Wuppertal, 2019. http://d-nb.info/1206122870/34.
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Bredemeier, Christian [Verfasser]. "Laser-induced chlorophyll fluorescence sensing as a tool for site-specific nitrogen fertilization – evaluation under controlled environmental and field conditions in wheat and maize / Christian Bredemeier." Aachen : Shaker, 2005. http://d-nb.info/1181614112/34.
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Neu, Silke [Verfasser], E. Gert [Gutachter] Dudel, Karl-Heinz [Gutachter] Feger, and Hermann [Gutachter] Heilmeier. "Assessment of gentle remediation options for trace element-contaminated agricultural land under semi-controlled and field conditions / Silke Neu ; Gutachter: E. Gert Dudel, Karl-Heinz Feger, Hermann Heilmeier." Dresden : Technische Universität Dresden, 2020. http://d-nb.info/1231917504/34.
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Danielsen, Lara [Verfasser], Andrea [Akademischer Betreuer] Polle, and Stefan [Akademischer Betreuer] Scheu. "Fungal diversity in a transgenic poplar plantation and the role of ectomycorrhizal fungi for tree performance under field and controlled drought stress conditions / Lara Danielsen. Gutachter: Andrea Polle ; Stefan Scheu. Betreuer: Andrea Polle." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044361697/34.
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Lopisso, Daniel Teshome Verfasser], Andreas von [Akademischer Betreuer] Tiedemann, Petr [Gutachter] Karlovsky, and Heiko [Gutachter] [Becker. "Studies on Resistance of Oilseed Rape (Brassica napus) to Verticillium longisporum – Interaction with Drought Stress, Role of Xylem Sap Modulations and Phenotyping Under Controlled and Field Conditions / Daniel Teshome Lopisso ; Gutachter: Petr Karlovsky, Heiko C. Becker ; Betreuer: Andreas von Tiedemann." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://d-nb.info/1120701996/34.
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Song, Haiwen. "Diesel soot oxidation under controlled conditions." Thesis, Brunel University, 2003. http://bura.brunel.ac.uk/handle/2438/4814.
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In order to improve understanding of diesel soot oxidation, an experimental rig was designed and set up, in which the soot oxidation conditions, such as temperature, oxygen partial pressure, and CO2 partial pressure, could be varied independently of each other. The oxidizing gas flow in the oxidizer was under laminar condition. This test rig comprised a naturally-aspirated single cylinder engine which acted as the soot generator, and a separate premixed oxidation burner system in which soot extracted from the engine was oxidized under controlled conditions. Diesel soot was extracted from the engine exhaust pipe and from the engine pre-combustion chamber, and the soot-laden gas was then conveyed to the burner where it was oxidized. The burner was positioned vertically and it had a flat flame whose thickness was only a few millimetres. The hot gases from the flame flew upwards through a quartz transparent tube which acted as the soot oxidation duct. The soot-laden gas from the engine was premixed with the feedgas (itself a premixed mixture of methane, air, oxygen, and nitrogen) to the burner. The soot particles passed vertically through the flame front and continued burning in the post-flame gas flowing through the quartz tube oxidation duct. The oxygen concentration and temperature of the post-flame soot oxidation gas were controllable by adjusting the flowrate and composition of the burner feedgas. Diesel soot particles were sampled at different heights along the centreline of the quartz tube above the burner. Profiles of oxygen concentration, temperature, and soot particle velocity in the oxidation zone were thus measured. Morphology and size distributions of the sampled diesel soot particles were analyzed by means of Transmission Electron Microscopy (TEM) and a computer software called ImagePro Plus. Subsequently, the specific surface oxidation rates of the soot particles were worked out based on soot particle size distributions. The TEM micrographs obtained in this study showed that the diesel soot agglomerates existed in forms of clusters and chains, each containing between a small number and thousands of individual, mostly spherical tiny particles. Of order 97% of the individual spherical particles (spherules) had a size range from 10 to 80 nm. Occasionally, individual spherules of about 150 nm in diameter could be observed. The diesel soot particles sampled from the pre-chamber of the engine had different size distributions from those sampled from the exhaust of the engine, indicating that the soot underwent an oxidation process in the combustion chamber. Soot oxidation experiments were performed in the burner post-flame gas under oxygen partial pressures ranging from 0.010 to 0.050 atm and temperatures from 1520 to 1820 K. The test results showed that the oxidation rates of the diesel soot extracted from the diesel engine were generally lower than those predicted by the well-known Nagle and Strickland-Constable formula; however, the measured oxidation rates were higher than the predictions made with another well-known formula - the Lee formula. The soot extracted from the engine pre-chamber appeared not to oxidize as fast as the soot extracted from the exhaust of the engine. CO2 gas injection to the post-flame oxidation gas at constant oxygen partial pressure and oxidation temperature seemed to have accelerated the diesel soot oxidation rate. Based on the experimental results of this study and the results of other researchers, modifications to the Nagle and Strickland-Constable formula and to the Lee formula were accomplished. Also, an empirical expression, as an alternative to semi-empirical formulae, was worked out and presented in the thesis.
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Thomas, Sophie. "Pressions de sélection exercées par les résistances génétiques du melon sur les populations d’Aphis gossypii." Thesis, Avignon, 2011. http://www.theses.fr/2011AVIG0637/document.
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La réponse adaptative de populations de bioagresseurs aux pressions de sélection exercées par les activités agricoles détermine la durabilité des moyens de lutte. Chez le melon, le gène Vat qui confère la résistance à Aphis gossypii étant déployé depuis plus de 10 ans, on craint son contournement. L’enjeu est de proposer des éléments stratégiques aux semenciers sur le risque d’évolution des pucerons vers la virulence, pour développer de nouvelles variétés avec des résistances durables. Dans le cadre de cette thèse, nous avons : i) Estimé la diversité génétique disponible dans des populations d’A. gossypii de différentes régions de production de melon. Elle est structurée géographiquement. La grande diversité observée en France aurait en partie pour origine des évènements de reproduction sexuée suggérant un potentiel évolutif élevé d’A. gossypii. ii) Estimé la pression de sélection exercée par différentes combinaisons de résistance (gène Vat et QTL) sur ces populations. Les densités de population sont plus faibles sur les plantes Vat que sur les plantes non Vat et la structure génétique des populations est modifiée dans certaines régions de production quand le gène Vat est présent. Les clones se multipliant sur les plantes Vat ont une forte fitness et le risque de leurs extensions est grand. Aucun effet de QTL de résistance n’a été mis en évidence en plein champ. iii) Caractérisé les clones contournant le gène Vat. Nos résultats suggèrent que l’adaptation des clones s’effectue soit par modification du gène d’avirulence du puceron soit par l’adaptation du puceron aux effecteurs de la résistance. De nouvelles stratégies de gestion de la résistance Vat sont proposéesThe adaptive response of pest populations to selection pressures exerted by agricultural activities determines the sustainability of control methods. In melon, the Vat gene that confers resistance to Aphis gossypii has been deployed for over 10 years, so there are fears it will be overcome. The challenge is to provide strategic elements to plant breeders, concerning the risk of development of virulent aphids, in order to develop new varieties with durable resistances. In the context of this PhD, we have : i) Estimated the available genetic diversity in populations of A. gossypii from different melongrowing areas. The diversity is structured geographically. The great diversity observed in France would have its origine in part from the events of sexual reproduction, suggesting a high evolutionary potential of A. gossypii. ii) Estimated the selection pressure exerted by different resistance combinations (Vat gene and QTLs) on these populations. Population densities are lower on VatR plants than VatS plants and population genetic structure is altered in certain growing areas when the VatR gene is present. The clones multiplying on VatR plants have good fitness and the risk of their spreading is great. No effect of QTLs has been identified in the field. iii) Characterized the clones overcoming the VatR gene. Our results suggest that the adaptation of clones made either by alteration of the avirulence gene of aphids or by adaptation of aphids toresistance effectors. New strategies for Vat resistance management are proposed
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Hackston, Abigail Jane. "Activation of faulting under controlled stress conditions." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/activation-of-faulting-under-controlled-stress-conditions(2eb0b3f9-33c4-43d3-bbf2-490744f94d23).html.
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In 1951, it was first suggested by E.M. Anderson that faults in nature will form at specific angles to the maximum principal stress. For most cases, this concept agrees with observations. However, in nature there are some notable exceptions to this rule, with some faults becoming activated in unfavourable orientations. This project was designed to examine conditions that might affect the angle of faulting and the friction coefficient for sliding. Faults that do not conform to generally accepted ‘Andersonian’ theory include low-angle detachment faults (e.g. Basin and Range Province (USA)), the San Andreas Fault (USA) the Nordfjord Sojn Detachment (Norway), high angle (steeply dipping) normal faults (Britain) and the Zuccale Fault, Italy. Various explanations have been given for sliding on these unfavourably-oriented faults, including high pressure CO2 or water infiltration (Zuccale Fault), low-friction minerals growing in fault gouge (Zuccale fault, San Andreas Fault), stress refraction (San Andreas Fault), reactivation of thrust faults (Nordfjord Sojn Detachment) and fracture under a combination of compression and tension (UK).Experiments were performed in compression and extension using a triaxial deformation rig. Darley Dale sandstone and Pennant sandstone blocks were cut into cores and tested under the following conditions: (a) intact rock failure (dry); (b) sawcut at 35°, 45° and 55° (dry) to the core axis using (i) constant confining pressure, (ii) constant normal stress (iii) constant mean stress; (c) with pore pressure in all three sawcut angles; and (d) with a gouge layer of 70% quartz to 30% kaolinite mixed with 0, 2, 5, 10, 20, 50 and 100% wt of either graphite or talc. Microstructural studies were carried out on deformed samples. These experiments showed that: The angle of failure in extension was 16-20° to the maximum principal stress for Darley Dale sandstone, and 18-21° for Pennant sandstone whereas in compression it was >30°. This angle in extension is lower than expected, but microstructural analysis indicated occurrence of stress refraction, which may help explain this result. The friction coefficient does not appear to change with pre-cut fault angle in dry samples. Pore pressure tests confirmed the general applicability of the law of effective stress, but anomalous apparent reduction of friction coefficient and production of an apparent cohesive strength in pore pressure tests suggested tests should be run slower to avoid disparity between applied pore pressure and true pore pressure in the sample. Attempts to induce hydraulic fractures showed that high overpressures may often be required to do this. Addition of a low-friction phase (talc or graphite) to fault gouge reduced friction by a disproportionately large amount for very planar faults. This was shown to be due to mechanical smearing of the weak phase over the fault plane, increasing its apparent area of coverage. It was concluded that commonly some combination of high fluid pressure in fault planes coupled with low-friction fault gouges may be required to explain slip on natural, unfavourably –oriented faults.
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Cumbria, Neil M. "Robust controlled flux estimation for indirect field-oriented controlled induction motor drives." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0023/MQ31386.pdf.
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Jordan, Marie-Odile. "Mise en place du systeme racinaire du mais : definition et caracterisation au champ et en conditions controlees des parametres descriptifs du systeme racinaire, construction de l'organigramme d'un modele cinetique." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13329.
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Une analyse bibliographique montre que si l'architecture des parties aeriennes est bien connue chez le mais, il n'en est pas de meme du systeme racinaire. Nous avons donc entrepris un travail de synthese a ce sujet. Dans la premiere partie de cette etude, les parametres descriptifs de la structure racinaire sont definis. Leur evolution au cours du cycle est ensuite caracterisee en conditions habituelles de culture, et, en rhizotrons. Quatre categories de racines primaires ont pu etre mises en evidence
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Smith, C. J. "Energy conditions in quantum field theory." Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434155.
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Westmoreland, Shawn. "Energy conditions and scalar field cosmology." Kansas State University, 2013. http://hdl.handle.net/2097/15811.
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Master of ScienceDepartment of Physics
Bharat Ratra
In this report, we discuss the four standard energy conditions of General Relativity (null, weak, dominant, and strong) and investigate their cosmological consequences. We note that these energy conditions can be compatible with cosmic acceleration provided that a repulsive cosmological constant exists and the acceleration stays within certain bounds. Scalar fields and dark energy, and their relationships to the energy conditions, are also discussed. Special attention is paid to the 1988 Ratra-Peebles scalar field model, which is notable in that it provides a physical self-consistent framework for the phenomenology of dark energy. Appendix B, which is part of joint-research with Anatoly Pavlov, Khaled Saaidi, and Bharat Ratra, reports on the existence of the Ratra-Peebles scalar field tracker solution in a curvature-dominated universe, and discusses the problem of investigating the evolution of long-wavelength inhomogeneities in this solution while taking into account the gravitational back-reaction (in the linear perturbative approximation).
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Loginova, Irina. "Phase-field modeling of diffusion controlled phase transformations." Doctoral thesis, KTH, Mechanics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3626.
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Diffusion controlled phase transformations are studied bymeans of the phase-field method. Morphological evolution ofdendrites, grains and Widmanst\"atten plates is modeled andsimulated.
Growth of dendrites into highly supersaturated liquids ismodeled for binary alloy solidification. Phase-field equationsthat involve both temperature and solute redistribution areformulated. It is demonstrated that while at low undercoolingheat diffusion does not affect the growth of dendrites, i.e.solidification is nearly isothermal, at high cooling rates thesupersaturation is replaced by the thermal undercooling as thedriving force for growth.
In experiments many crystals with different orientationsnucleate. The growth of randomly oriented dendrites, theirsubsequent impingement ant formation of grain boundaries arestudied in two dimensions using the FEM on adaptive grids.
The structure of dendrites is determined by growthconditions and physical parameters of the solidifying material.Effects of the undercooling and anisotropic surface energy onthe crystal morphology are investigated. Transition betweenseaweeds, doublons and dendrites solidifying out of puresubstance is studied and compared to experimental data. Two-and three-dimensional simulations are performed in parallel onadaptive and uniform meshes.
A phase-field method based on the Gibbs energy functional isformulated for ferrite to austenite phase transformation inFe-C. In combination with the solute drag model, transitionbetween diffusion controlled and massive transformations as afunction of C concentration and temperature is established byperforming a large number of one dimensional calculations withreal physical parameters. In two dimensions, growth ofWidmanstaetten plates is governed by the highly anisotropicsurface energy. It is found that the plate tip can beapproximated as sharp, in agreement with experiments.
Keywords:heat and solute diffusion, solidification,solid-solid phase transformation, microstructure, crystalgrowth, dendrite, grain boundary, Widmanstaetten plate,phase-field, adaptive mesh generation, FEM.
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Ciccarelli, Chiara. "Magnetically controlled chemical potential in field effect devices." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/265543.
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In this thesis I describe a sensitive technique for quantifying the chemical potential anisotropy of magnetically ordered and spin-orbit coupled materials. An aluminium single electron transistor (SET) lithographically fabricated on top of a magnetic gate is used to characterise the chemical potential anisotropy of Ga0 .97Mno. 03As and Gao.941\1no.o6As. The conductance variation of the SET provides a direct probe of the magnetisation-dependent change in the chemical potential of the magnetic gate with ?eV resolution. The control of the SET conductance by the magnetisation direction of the gate opens the way to a new recording mechanism. Achieving the same control in a semiconductor device represents a first step towards possible applications in computer memories. In the second part of my work I present the measurements on a CoPt gated metal-oxide-semiconductor� field effect transistor. In the last part of my thesis, I present a study of the response of a metal SET to a radio-frequency perturbation, which showed the conditions of maximum sensitivity and set a lower limit to the detection bandwidth of the SET. This study is important for assessing the performance of a prototypical device for detecting fast magnetisation switching or for quantifying the chemical potential anisotropy of magnetic nano-structures that cannot be electrically connected to an electrode, but that are still expected to have interesting anisotropic properties.
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Bas, Gokcen. "Electric Field Analysis In Stress Controlled High Voltage Cables." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605778/index.pdf.
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The terminations and the joints are the basic accessories of the power cables. Power cables require electrical stress control when terminated.
Since there are different types of terminations, the analysis should be done to choose the proper method for electric field control problem at the terminations.
Throughout this study two different types of termination methods are investigated by using the finite element analysis program (ANSYS): Stress Controlled Termination Model with Deflector and Stress Control Tube (SCT). The results are compared with those obtained for a cable without stress control model termination.
The numerical calculations are also compared with the measurements obtained by an experimental model: the electrolytic tank model.
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Gomm, James Barry. "On-line detection of fault conditions in controlled industrial processes." Thesis, Liverpool John Moores University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304482.
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Tecle, Aregai, Peter Kitanidis, and Martin Reinhard. "Biodegradability of BTEX Contaminants Under Natural Field Conditions." Arizona-Nevada Academy of Science, 1997. http://hdl.handle.net/10150/296486.
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Korbman, Michael. "Modeling light-field-controlled electron motion in atoms and solids." Diss., Ludwig-Maximilians-Universität München, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-159586.
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Recent advancements in laser technology are quickly moving the frontiers of research: quantum
dynamics can now be investigated in more detail, on new timescales, with an unprecedented
level of control. These new possibilities offer a new ground for the theoretical study of fundamental processes; at the same time, a proper understanding of phenomena involved is necessary
to explain measurements, and to indicate directions for further experiments. This Thesis deals with the theoretical investigation of particular cases of light-matter interaction, in atoms and in dielectrics. Regimes considered here have just become a subject of intensive investigation: they are acquiring more and more relevance as technological advancements make them experimentally accessible.
In the first part of the Thesis I consider a process as fundamental as the single-photon
ionization of atoms: my modeling will include an ultrashort pulse (full width half maximum
~ 100 as = 10^-16 s) exciting an electron to the continuum, and a strong few-cycle near-infrared
laser field. This configuration is suitable to reproduce recent streaking experiments on atoms. I
developed a numerical tool to simulate these dynamics in three dimensions: the process is quite
elaborate and requires an adequate description of multi-electron atoms. With proper approximations
I was able to calculate photoelectron spectra using just a few dipole matrix elements,
which were obtained with the aid of our external collaborators, from refined atomic structure
calculations. The results of our relatively simple tool are in very good agreement with more
sophisticated numerical calculations. In addition to that, I discuss my contribution to the theoretical support of a fundamental experiment [I]: both simulations and measurements indicate a
delay between two different channel of photoemission in neon. A careful investigation of the limit of validity of approximations employed reveals that the Coulomb-Volkov approximation is
not suitable to describe fine details of the interaction with the laser pulse. I also report on our
analysis of experimental data from angle-resolved attosecond streaking.
The second part of the Thesis is devoted to the investigation of inter-band excitations in
dielectrics; driving this process with a high degree of control is on the edge of current technology.
The ultrafast creation of charge carriers in an insulator is intriguing: dielectric properties of
the medium change drastically, revealing features of the peculiar electron dynamics in such a
situation. I have simulated this process solving the time dependent Schroedinger equation for
a single electron in a one-dimensional lattice and analyzed how the charge Q displaced during
the interaction with the pulse depends on laser parameters. These calculations reproduce to a
good extent the behavior observed in the experiment. Both the theory and the experiment
point out a strong dependence of Q on laser parameters: this promises a high degree of control, and at the same time suggests the possibility of a solid-state device to characterize an optical pulse. I also study in detail the modification occurring in the electric response of the sample to the electric field. The purpose of this analysis is to identify some features directly related to dynamics of newly created charge carriers.
During my investigation of electron dynamics during an excitation process, I have often
faced the difficulty to identify quantities which might resemble eigenstates of the time-dependent
Hamiltonian. Similar field-dressed states would describe the distortion due to the field, of eigenstates of the field-free Hamiltonian. A proper definition of field-dressed states would allow a correct interpretation of the wavefunction in terms of instantaneous excited population, which is otherwise impossible to define.Neueste Fortschritte im Bereich der Lasertechnologie erweitern schnell die Grenzen der Forschung. Quantendynamiken koennen genauer den je untersucht werden, aus kuerzeren Zeitskalen und mit einer hoeheren Kontrollebene. Diese Entwicklung bietet neue Moeglichkeiten, fundamentale Prozesse theoretisch zu untersuchen; darueber hinaus ist ein Verstaendnis der zu Grunde liegenden physikalischen Vorgaenge erforderlich, um Messresultate zu erklaeren und moegliche Richtungen fuer kuenftige Experimente aufzuzeigen. Diese Doktorarbeit befasst sich mit der theoretischen Analyse bestimmter Licht-Materie-Wechselwirkungen in Atomen und Dielektrika. Die im Rahmen dieser Thesis untersuchten Bereiche sind aktuell Thema intensiver Forschung. Dank weiterer technologischer Entwicklungen, die Experimente in diesen Bereichen ausfuehrbar machen, gewinnen sie immer weiter an Relevanz.Neueste Fortschritte im Bereich der Lasertechnologie erweitern schnell die Grenzen der Forschung. Quantendynamiken koennen genauer den je untersucht werden, aus kuerzeren Zeitskalen und mit einer hoeheren Kontrollebene. Diese Entwicklung bietet neue Moeglichkeiten, fundamentale Prozesse theoretisch zu untersuchen; darueber hinaus ist ein Verstaendnis der zu Grunde liegenden physikalischen Vorgaenge erforderlich, um Messresultate zu erklaeren und moegliche Richtungen fuer kuenftige Experimente aufzuzeigen. Diese Doktorarbeit befasst sich mit der theoretischen Analyse bestimmter Licht-Materie-Wechselwirkungen in Atomen und Dielektrika. Die im Rahmen dieser Thesis untersuchten Bereiche sind aktuell Thema intensiver Forschung. Dank weiterer technologischer Entwicklungen, die Experimente in diesen Bereichen ausfuehrbar machen, gewinnen sie immer weiter an Relevanz. Im ersten Teil der Arbeit beschreibe ich den fundamentalen Prozess der atomaren Ionisation durch ein einzelnes Photon. Mein Model enthaelt einen ultrakurzen Lichtpuls mit einer Halbwertsbreite von ~ 100 as = 10^-16 s, der ein Elektron in das Kontinuum anregt, sowie einen starkes Laserfeld im nahen infraroten Spektralbereich mit wenigen Zyklen. Diese Konfiguration erlaubt die Nachbildung von neuesten Streaking Experimenten an Atomen. Ich habe ein numerisches Werkzeug entwickelt, um diese Dynamiken in drei Dimensionen zu simulieren. Der Prozess ist sehr komplex und bedarf einer hinreichenden Beschreibung von Atomen mit mehreren Elektronen. Unter Beruecksichtigung geeigneter Naeherungen war es mir moeglich, Photoelektronenspektren mit Hilfe nur weniger Dipolmatrixelemente zu berechnen, welche in Zusammenarbeit mit unseren externen Kollaborationspartner durch verfeinerte Atomstruktur-Berechnungen bestimmt wurden. Die Ergebnisse unseres verhaeltnismaeßig einfachen Vorgehens stimmen in einem hohen Grad mit fortgeschritteneren numerischen Methoden ueberein. Darueber hinaus diskutiere ich meinen Beitrag zur theoretischen Unterstuetzung eines grundlegenden Experiments. Sowohl Simulationen als auch Messungen weisen auf eine Verzoegerung zwischen zwei Photoemissionskanaelen in Neon hin. Eine sorgfaeltige Pruefung der Gueltigkeit der verwendeten Naeherungen verraet, dass die Coulomb-Volkov Naeherung nicht geeignet ist, um feine Einzelheiten in der Wechselwirkung mit dem Laserpuls zu beschreiben. Außerdem berichte ich ueber unsere Analyse der Messdaten der winkelaufgeloesten Attosekunden Streaking Experimente. Der zweite Teil der Thesis widmet sich der Untersuchung von Interband-Anregungen in Dielektrika. Die kontrollierte Lenkung dieser Ue bergaenge wurde erst mit aktuellster Technologie ermeoglicht. Die ultraschnelle Erzeugung von Ladungstraegern in einem Isolator ist bemerkenswert. Die dielektrischen Eigenschaften aendern sich dramatisch, was Rueckschluesse auf die Elektronendynamik waehrend dieser Anregung zulaesst. Ich habe diesen Prozess durch Loesung der zeitabhaengigen Schroedingergleichung fuer ein einzelnes Elektron in einem eindimensionalen Gitter simuliert und untersucht, wie sich die waehrend des Lichtpulses verlagerte Ladung mit den Laserparametern aendert. Diese Berechnungen reproduzieren in hohem Maße das im Experiment beobachtete Verhalten. Sowohl Theorie als auch Experiment weisen auf eine starke Abhaengigkeit der Ladung von den Laserparametern hin. Dies verspricht ein hohes Maß an Kontrolle und deutet auf eine moegliche Anwendung eines Festkoerperbauelements fuer die Charakterisierung eines optischen Pulses hin. Außerdem untersuche ich detailliert die Modifikationen der elektrischen Antwort des Samples auf ein externes elektrisches Feld. Das Ziel dieser Analyse ist die Identifikation einiger Eigenschaften die direkt mit der Dynamik der erzeugten Ladungstraeger zusammenhaengen. Waehrend der Untersuchung der Elektronendynamiken in einem Anregungsprozeß, stieß ich oft auf die Problematik, Groeßen zu ermitteln, die Eigenzustaenden des zeitabhaengigen Hamilton- Operators aehneln koennten. Aehnliche “Field-dressed States” wuerden die Verzerrung der Eigenzusteande des feldfreien Hamiltonoperators aufgrund des Felds beschreiben. Eine geeignete Definition der Field-dressed States wuerde eine korrekte Interpretation der Wellenfunktion in Abhaengigkeit der instantanen angeregten Besetzung ermoeglichen, welche sich auf anderem Wege nicht bestimmen laesst.
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Sandoval, Aleida J. "Studies of wheat starch transformations in a controlled shear field." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311378.
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Tu, Ryan H. "Germanium nanowire controlled synthesis, alignment, and field-effect-transistor characteristics /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Sebastian, Dalys. "Development of a field-deployable voice-controlled ultrasound scanner system." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0625104-170951/.
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McAlister, Darrell Scott. "Analysis of energy flow in controlled structures subject to initial conditions." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-02132009-172708/.
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Kopec, D. M., R. Scott, B. D. Munda, M. J. Pater, C. F. Mancino, and A. E. Ralowicz. "Germination of Lehman Lovegrass and Black Grama Under Controlled Environment Conditions." College of Agriculture, University of Arizona (Tucson, AZ), 1989. http://hdl.handle.net/10150/216078.
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Mechanical scarification greatly improved the germination of Lehmann Lovegrass seed. Depending on the type and duration of scarification, seed gemzination can be improved from 10 %-12% germination (untreated seed) to over 90% (60-second scarification in a commercial seed scarifier). Black grama is sensitive to both dehulling and dehulling followed by scarification. Unhulled black grama seed should be used for field plantings.
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Baserinia, Reza. "Flow of fine and cohesive powders under controlled air pressure conditions." Thesis, University of Leicester, 2017. http://hdl.handle.net/2381/39826.
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Powder flow appears in many industrial processes, including pharmaceuticals, food, detergents etc. Understanding the parameters affecting powder flow is necessary for rational product and process design. This research examines powder-air interactions for three powder handling systems: bin discharge, linear shoe-die system and rotary paddle feeder. As a starting point the flow behaviour of powders was characterised using established procedures to provide basic set of properties for assessing flowability. Powder permeability and the influence of small levels of compaction on permeability were determined. The influence of differential pressure on flow initiation from arching state was examined for powders discharging from bins. A dimensional model was developed to predict the differential pressure required to initiate powder flow as a function of orifice diameter and height of the powder above the exit. The mass flow rate of the powders were measured under a range of differential pressures. A dimensional model was developed to predict the mass flow rate as a function of differential pressure and exit diameter. The effect of processing parameters on the mass of the powder delivered into the die in linear shoe-die systems under the gravity and suction fill mechanism were investigated. The system was accommodated with differential pressure transducers and the evolution of the pressure inside during the process was monitored. Dimensional models were developed to predict the mass delivered into the die as a function of powder differential pressure developed during gravity and suction fill, shoe velocity and the velocity of the punch in the die. The influence of paddle rotational speed, exit diameter and differential pressure on the mass flow rate of powders in rotary feeding system was examined. This research identified the dimensionless groups relevant for the understanding of the flow of fine and cohesive powders under differential air pressure conditions. The dimensional models developed account for air pressure effects for 1) flow initiation and 2) flow rate during bin discharge, 3) gravity and 4) suction fill mechanisms in linear shoe-die filling systems. These models can be used to aid the design of powder flow processes where air pressure effects are influential.
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Aramrun, P. "Measuring terrestrial wildlife external radiation exposure under field conditions." Thesis, University of Salford, 2018. http://usir.salford.ac.uk/47703/.
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This thesis presents the results of a 3-year project to develop methods for measuring external radiation exposure of free-ranging terrestrial animals under field conditions. An evaluation of available passive dosimeter technologies was undertaken and guidance developed on the selection of dosimeters for different sizes of terrestrial animals. To test dosimeters under field conditions, a field study using reindeer in an area of Norway with elevated 137Cs was initiated. The dosimeter selection guidance was used to identify four passive dosimeters (i.e. TLD, OSLD, RPLD and DIS), which should be suitable for reindeer. To protect these dosimeters during use, they were housed in an aluminium box that could be attached to a collar around the reindeer’s neck. The performance of dosimeters within the box was tested in a laboratory. This testing confirmed dose linearity, angular linearity for the angles tested (45 ̊ – 135 ̊) and energy linearity for radionuclides tested (137Cs, 60Co, 226Ra). The dosimeter box did not respond to beta exposure. The external absorbed doses of a reindeer herd (Vågå, Norway) were measured over 11 months using the dosimeter box developed. Dosimeter results were then compared with model predictions. There was a significant difference between the estimates of dosimeters, but the difference of the mean doses between maximum and minimum values was <14 %. Reindeer external doses were modelled based on GPS tracking data and data on radiation in their environment. The mean predicted doses using the GPS tracking data were not significantly different to RPLD and DIS. However, the TLD and OSLD results were 18% higher than the mean dose estimated using the reindeer GPS tracking data. Average external doses predicted across the herd area (without using GPS data) were significantly lower than doses from all dosimeter types and predicted using the GPS data because the animals favoured the more contaminated areas of the study site which were good grazing in several seasons for those reindeer. A deer dosimetry phantom was created from red deer CT images and a human adult dosimetry phantom to estimate a whole-body dose and organ doses from external radiation exposure. The data of whole-body and organ doses from x-ray and 137Cs were used to calculate conversion factors that can be used to convert from external whole-organism doses of deer species to individual organ doses from external exposure.
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Michael, Joseph R. Jr. "Field conditions : the stadium, the city, and the masses." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57527.
Full textAbstract:
Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 136-137).
The past 30 years has seen the emergence of two seemingly unrelated problems: The first problem is the underperformance and looming demolition of Boston City Hall and the unavoidable commercial development of its plaza. The problems of City Hall and its plaza, however, are part of a larger misguided notion of public space for the masses--how, when, and by whom it is occupied. The masses, however, have always and will continue to gather regularly for the ritual of sport. This raises the second problem--the continued suburbanization of the stadium has taken the most dynamic urban spectacle out of the city. To compound this problem, sports franchises use competing cities' desire to host one of a limited set of professional teams as leverage for stadium building. If a city refuses to finance new facilities, a franchise will find another more desperate city willing to put up the funding. Stadia, costly and iconic structures, have an extremely brief shelf life, and though heavily publically funded are almost entirely private. Boston is a self-proclaimed "Titletown." In celebration of sports is the only time that citizens gather en masse in Boston City Hall's public plaza. The iconic Boston City Hall, unlike stadiums, is stubbornly permanent and universally despised. The convergence of these two problems results in a proposal for a new kind of urban form and public space in the heart of Boston. This thesis proposes a new kind of stadium for the City Hall site, one that is not hermetically sealed for only sporting events, but one that engages the city with a high degree of porosity.
(cont.) The inevitable obsolescence of stadia will not be ignored; therefore, this proposal aims to create an urban form which is highly activated independently of sporting events. This proposal also seeks to insert a new kind of public space within a city: one that is of the highly organized and functioning spectacle of a sporting event, and one that is of the modern flâneur.
by Joseph R. Michael, Jr.
M.Arch.
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Hills, Daniel. "Generating boundary conditions for integrable field theories using defects." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/16379/.
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In this thesis, we examine the construction and characteristics of generalised reflection matrices, within the a_1^(1), a_2^(1) and a_2^(2) integrable affine Toda field theories. In doing so, we generalise the existing finite-dimensional reflection matrices because our construction involves the dressing of an integrable boundary with a defect. Within this framework, an integrable defect's ability to store an unlimited amount of topological charge is exploited, therefore all generalised solutions are intrinsically infinite-dimensional and exhibit interesting features. Overall, further evidence of the rich interplay between integrable defects and boundaries is provided. It is hoped that the generalised solutions presented in this thesis are potential quantum analogues of more general classical integrable boundary conditions.
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Jouan, Alexis. "DC and AC transport in field-effect controlled LaAlO3/SrTiO3 interface." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066073/document.
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Cette thèse est consacrée à l'étude des propriétés de transport statique et dynamique du gaz d'électrons bidimensionnel supraconducteur à l'interface LaAlO3/SrTiO3. Dans un premier temps, nous étudions l'effet du désordre microscopique induit par le dopage en Chrome, sur la supraconductivité et le couplage spin-orbite en fonction de la densité de porteur modulée par effet de champ. Dans une géométrie de grille locale au-dessus du gaz, nous montrons le contrôle électrostatique de la transition supraconducteur-isolant. De même, nous analysons l'ajustement du couplage spin-orbite contrôlé par effet de champ. A l'aide de méthodes de nanofabrication par lithographie électronique, nous démontrons la première réalisation d'un point critique quantique dans LaAlO3/SrTiO3. En changeant le confinement latéral et le niveau de Fermi par effet de champ, nous sommes capables de régler le nombre de canaux conducteurs dans l'état normal et de mesurer la quantification de la conductance. Enfin, nous présentons des mesures radio-fréquence qui donnent accès aux propriétés dynamiques du gaz supraconducteur. L'évolution de la conductivité en fonction de la densité de porteurs et de la température est comparée avec la théorie standard BCS/Mattis-Bardeen d'une part, et avec la théorie BKT d'autre partThis thesis is devoted to the study of static and dynamical transport properties of the superconducting two-dimensional electron gas at the LaAlO3/SrTiO3 interface. Under strong 2D confinement, the degeneracy of the t$_{2g}$ bands of SrTiO$_3$ is lifted at the interface, generating a rich and complex band structure. Starting from a free electron model, we derive numerically a self-consistent calculation of the potential well and the band structure (chapter 1). These simulations highlight the presence of two types of bands d$_{xy}$ and d$_{xz/yz}$ with very different transport properties. We investigate first the effect of microscopic disorder introduced by Cr doping, on superconductivity and spin-orbit coupling over a wide range of back-gate doping (chapter 3). We also describe the first implementation of a field-effect device where the superconductor-insulator transition could be continuously tuned with a top-gate. The presence of a strong spin-orbit coupling that could be controlled with the top-gate voltage is also demonstrated by analyzing the magneto-transport measurements. The gate dependence of the spin-splitting energy, of the order of a few meV, is found to be consistent with Rashba spin-orbit coupling. Going one step further in nanofabrication, we report on the first realization of a quantum point contact in LaAlO$_3$/SrTiO$_3$ using split gates (chapter 6). To go further in the understanding of the LaAlO$_3$/SrTiO$_3$ interface, we present high frequency measurements of the conductivity $\sigma$ (chapter 5). This measurement gives us access to the superfluid stiffness and to the gap energy via the BCS theory. We show that the competition between these two energy scales controls the superconducting Tc in the phase diagram
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Legesse, Michael. "Coupled simulation of an indirect field oriented controlled induction motor drive." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116014.
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Conventionally, system simulations of induction motor drives use lumped parameters model of the motor. This approach assumes motor parameters to be constant during the entire operation of the drive. Unfortunately, these are known to vary significantly over the operating range of the motor due to factors such as magnetic saturation, skin effects, and operating temperature. The variations in motor parameters affect motor output and control parameters resulting in degraded drive performance. One way of overcoming this problem is by coupling the field model of the induction motor with the drive simulation. By replacing the lumped parameters model with the field model, the influence of different operating conditions on motor parameters can be taken into account dynamically. In this thesis such an approach is investigated by coupling the finite element analysis of an induction motor with the system simulation of the field oriented controlled drive. The results obtained for the coupled simulation are promising and possible future works to make this method of simulation more accurate and reliable are recommended.
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Bal, Gungor. "Performance analysis of field-orientation controlled induction motor with parameter adaptation." Thesis, University of Strathclyde, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392468.
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Antunes, Fernando Luiz Marcelo. "A microprocessor-controlled DC servo-drive with spill-over field weakening." Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/33224.
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The thesis presents a speed-control scheme for a separately-excited DC motor using a microprocessor. The control strategy incorporates both armature-voltage control and spill-over field weakening. The armature voltage is controlled in closed loop using a lead term in series with an integral term. The analogue Lead-Integral (LI) controller parameters were obtained and optimised by observing the system time response in successive digital simulations. The parameters determined provide the motor with a fast response and minimum speed overshoot during transient operations. The analogue LI controller was emulated to form a digital filter using the bilinear transformation and implemented in a 16-bit microprocessor using floating point arithmetic.
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Wissman, James P. "Selected Methods for Field-Controlled Reconfiguration of Soft-Matter Electrical Contacts." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/920.
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Just as conventional mechatronic systems rely on switches and relays, machines that are soft and elastically deformable will require compliant materials that can support field-controlled reconfiguration. In this dissertation, I present several novel approaches to shape programmability that primarily rely on condensed soft matter and are stimulated by electric or magnetic fields. I begin with electric-field-driven methods for achieving shape programmability of elastomer-based systems. These include dielectric elastomer actuators and electrostatic beams that undergo extreme stretch. Classical theories in elasticity and electrostatics are used to examine the mechanical responses and instabilities of these soft, hyperelastic systems. Such modeling techniques are also used to examine another switching mode based on the snap through behavior of a buckled ferromagnetic beam under magnetic load. I will then discuss a unique approach to shape programmability that is based on electrochemistry and exploits the coalescence and separation of anchored liquid metal drops. In this case, electrical signals under 10V are utilized to manipulate surface energies and transition between bi-stable states. Experiments and Surface Evolver simulations show that oxidation and reduction on opposing poles of the coalesced drops create an interfacial tension gradient that eventually leads to limit-point instability. Theory derived from bipolar electrochemistry and vertical electrical sounding predicts droplet motion and separation based on geometry and bath conductivity, facilitating the optimization of reconfigurable devices using this phenomenon. I conclude with the application of the bi-stable droplets to a simple toggle switch capable of changing circuit conductivity by over three orders of magnitude.
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Bawana, Niyem Mawenbe. "Thermal Response in a Field Oriented Controlled Three-phase Induction Motor." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7740.
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The research conducted at the department of Electrical Engineering of the University of South Florida campus in Tampa only covers the electrical aspect of electric drives. However, the performance of electric machinery is significantly impacted by temperature variation. The
literature review shows three main control techniques in use today in electric drives namely, Scalar control, Direct Torque control and Field Oriented control.
This thesis presents a temperature rise of rotor bars, stator winding, stator core and stator frame in a running three phase field-oriented controlled induction machine. A literature search shows that none of research has been carried out to investigate a thermal response of a field-oriented controlled induction motor. With this motivation, we were able to implement a lumped parameters thermal model of a three-phase field-oriented IM in MATLAB Simulink, which allows us to determine that rotor bars have the highest temperatures rising to 84 degrees Celsius. This confirms that rotors bars are the hottest part of a running IM as stipulated in literature.
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Nowakowska, Anna Maria. "Visual search strategies under normal viewing conditions, and under conditions that simulate visual field deficit." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=239258.
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A cardinal role of selective visual attention is to serve our action by selecting all the relevant information. One task that has been applied extensively to explore attention is visual search for a target among distractors. Given the extensive practice of human observers with visual search, and its ecological relevance, one could expect a high level of efficiency when performing visual search tasks. Indeed, a prominent in the literature Ideal Observer model (Najemnik & Geisler, 2005, 2008) suggests, that human visual system is extremely efficient, in that every eye movement during visual search is executed to the locations that could be expected to yield maximum information; similarly to the Ideal Observer, humans require the minimum number of eye moments possible to find the target (Najemnik & Geisler, 2005, 2008). The present programme of research tests the prediction of the Ideal Observer model (Najemnik & Geisler, 2005, 2008) against a simpler, but similarly effective stochastic selection model (Clarke, Green, Chantler, & Hunt, 2016), by examining human visual search strategies under normal viewing conditions, and conditions that simulate visual field deficit. Across nine experiments, I observed strikingly inefficient search behaviour that speaks against the assumptions of the Ideal Observer model. Although on the surface these cumulative results appear to be in line with the random process of fixation selection (Clarke et al., 2016), such conclusion appears to be valid only for the observed group results. The individual observer's data that was carefully documented in each of the experiments did not allow such a conclusion. The individual observers' data showed full spectrum of search strategies, with some observers being extremely efficient, some being average searchers, and others applying a very inefficient strategy. The large individual differences between participants suggest that the fixation selection process is neither optimal nor random, but rather idiosyncratic.
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Kabadshow, Ivo [Verfasser]. "Periodic Boundary Conditions and the Error-Controlled Fast Multipole Method / Ivo Kabadshow." Wuppertal : Universitätsbibliothek Wuppertal, 2012. http://d-nb.info/1020476176/34.
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Tuffrey, Nigel Edwin. "Pyrometry studies of the combustion of lead concentrate particles under controlled conditions." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/29309.
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An investigation of the combustion of lead sulphide .concentrates under controlled conditions has been carried out. A fast response, two-wavelength radiation pyrometer and a "laminar flow" furnace were constructed to facilitate the measurement of the temperature of individual particles during combustion. Chemical analysis and electron microscopy studies of the reaction products were also performed.
The combustion of galena, pyrite, pyrrhotite, sphalerite and two commercial concentrates (Brunswick and Sullivan) at 1130K was investigated. The effects of particle size between 63-125μm and gaseous oxygen concentration between 10 and 100% were examined.
For combustion in both air and oxygen a number of different combustion pulses were identified which corresponded to the combustion of different mineral species or to different physical phenomena. An analogous series of pulse classifications was identified for combustion in oxygen however they reflected the greater intensity and temperature of the reactions. The form of combustion was strongly dependent on oxygen concentration. From the results it was not possible to identify the effect of particle size on combustion behaviour.
The vaporisation of lead sulphide appears important to the mechanism of galena combustion. In air the temperature of combustion appears limited to 1500-1700K (of boiling point PbS of 1609K); whereas in oxygen, massive vaporisation results in a heating arrest at 1700-2000K and disintegration into droplets which combust at 2000-2400K. Transition from air-type to oxygen-type combustion occurs at oxygen concentrations between 40 and 65% and is thought to be due to the transition from a liquid to gaseous phase PbO reaction product.
The initial stage of pyrite reaction is thermal decomposition to porous pyrrhotite. The ignition of this porous pyrrhotite was more rapid than dense pyrrhotite, but once molten, the combustion of the two was indistinguishable and the peak temperature observed was very reproducible. In air the peak combustion temperatures of 2400-2600K appeared to coincide with a sudden expansion of the particle, possibly due to the inflation of thin-walled iron oxide cenospheres. In oxygen the reactions are more intense and disintegration typically occurs on reaching a peak temperature of 3000-3400K, Between ~10 and 35% oxygen the maximum combustion temperature increased linearly, but at higher concentrations remained constant at 3000-3400K. The results suggest the maximum temperature reached is limited by the occurrence of a physical phenomenum possibly associated with the vaporisation of iron.
Sphalerite did not ignite at the temperatures considered, but shells of zinc oxide were observed in the reaction products.
For the commercial concentrates pulses of intermediate combustion characteristics and a wide range of combustion temperatures (typically intermediate to those of PbS and FeS) were observed, as well as many pulses similar to those of the constituent minerals. The former were considered to be due to the combustion of agglomerations of many smaller individual particles. The effect of the mineral composition was evident in the combustion results, with increased quantities of iron sulphide tending to result in more intense reactions. The results suggest that metallic lead formation occurs during the initial stages of reaction, probably after melting as the result of reaction between the surface oxides/sulphates and unreacted PbS.
A simple reaction model for iron sulphide combustion suggests that the reaction of the molten drop is controlled by gas-phase oxygen mass transfer with the measured heating rates consistent with the formation of wustite and sulphur dioxide.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Gorkowski, Kyle J. "The Morphology and Equilibration of Levitated Secondary Organic Particles Under Controlled Conditions." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1067.
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I advanced the understanding of particle morphology and its implications for the behavior and effects of atmospheric aerosol particles. I have developed new experimental methods for the Aerosol Optical Tweezers (AOT) system and expanded the AOT’s application into studying realistic secondary organic aerosol (SOA) particle phases. The AOT is a highly accurate system developed to study individual particles in real-time for prolonged periods of time. While previous AOT studies have focused on binary or ternary chemical systems, I have investigated complex SOA, and how they interact with other chemical phases, and the surrounding gas-phase. This work has led to new insights into liquid-liquid phase separation and the resulting particle morphology, the surface tension, solubility, and volatility of SOA, and diffusion coefficients of SOA phases. I designed a new aerosol optical tweezers chamber for delivering a uniformly mixed aerosol flow to the trapped droplet’s position. I used this chamber to determine the phase-separation morphology and resulting properties of complex mixed droplets. A series of experiments using simple compounds are presented to establish my ability to use the cavity enhanced Raman spectra to distinguish between homogenous single-phase, and phase-separated core-shell or partially-engulfed morphologies. I have developed a new algorithm for the analysis of whispering gallery modes (WGMs) present in the cavity enhanced Raman spectra retrieved from droplets trapped in the AOT. My algorithm improves the computational scaling when analyzing core-shell droplets (i.e. phase-separated or biphasic droplets) in the AOT, making it computationally practical to analyze spectra collected over many hours at a few Hz. I then demonstrate for the first time the capture and analysis of SOA on a droplet suspended in an AOT. I examined three initial chemical systems of aqueous NaCl, aqueous glycerol, and squalane at ~ 75% relative humidity. For each system I added α-pinene SOA – generated directly in the AOT chamber – to the trapped droplet. The resulting morphology was always observed to be a core of the initial droplet surrounded by a shell of the added SOA. By combining my AOT observations of particle morphology with results from SOA smog chamber experiments, I conclude that the α-pinene SOA shell creates no major diffusion limitations for water, glycerol, and squalane under humid conditions. My AOT experiments highlight the prominence of phase-separated core-shell morphologies for secondary organic aerosols interacting with a range of other chemical phases. The unique analytical capabilities of the aerosol optical tweezers provide a new approach for advancing the understanding of the chemical and physical evolution of complex atmospheric particulate matter, and the important environmental impacts of aerosols on atmospheric chemistry, air quality, human health, and climate change.
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Bent, Denzil. "A comparison of Brine evaporation rates under controlled conditions in a laboratory." University of the Western Cape, 2018. http://hdl.handle.net/11394/6443.
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Magister Scientiae - MSc (Environ & Water Science)There are growing concerns around the environmental issues related to processed water as the demand for potable water is on the increase in South Africa. Effluents discharged from various sectors such as water treatment facilities pose a constant threat to the environment and natural water resources, including rivers and groundwater due to their poor chemical and physical composition. As a result, the demand for predicting the elevated concentrations of salts in a spatial and temporal dimension is constantly growing. The effluent at the eMalahleni water reclamation plant in Mpumalanga, South Africa, is being processed through a triple reverse osmosis that improves the water quality of the mine water to potable standards. Two water quality streams emerge from this process, i.e. a potable standard and the other a brine concentrate which is stored in ponds. Brine ponds are used for inland brine disposal in the eMalahleni water reclamation plant. The large volumes and limited capacity to store brines has placed great emphasis on enhanced evaporation rates to increase the efficiency of the ponds. In order to improve the rate of brine evaporation in the pond, an understanding of the effect of brine salt content and other parameters affecting the rate of evaporation is required. This study aimed at establishing the physical and chemical behaviour of the brine from the eMalahleni plant in a controlled environment. The investigation incorporated actual brine from the eMalahleni plant as well as synthetic salts typical of the major components of the eMalahleni brine.
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Razavi, Seyed Esmail. "Far field boundary conditions for computation of compressible aerodynamic flows." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28896.
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The formulation and implementation of a far field boundary condition (FFBC) model for compressible flows is reported in this thesis. This FFBC model, developed for quasi-one-dimensional and two-dimensional flows, aims to permit a substantial reduction of the computational domain, leading to a considerable improvement in the computational efficiency. The present FFBC approach uses asymptotic expansions of the Riemann variables, which are truncated up to the required degree of accuracy. Then, the far field perturbation equations are integrated in time and applied in conjunction with the solution calculated within the computational domain. The propagating information from the computational domain is determined along the outgoing characteristic fronts, based on the estimation of the wave front orientation.The proposed FFBC model is implemented in conjunction with an implicit finite-difference flow field solver using an alternating direction implicit (ADI) scheme for solving the Euler equations. The discretized form of the governing equations are solved using a time-marching technique until the steady-state solution is reached. An accurate procedure for the solid boundary treatment was also used.
The proposed FFBC model was used for solving typical problems of confined and external compressible flows in subsonic and transonic regimes. For the transonic regime, the proposed FFBC model has been extended for the case of non-isentrophic outgoing flows, which appear behind the shock waves. The solutions obtained are compared with previous theoretical and numerical results. This comparison shows that the proposed FFBC model can generate accurate solutions using a substantially reduced computational domain, which reduces by an order of magnitude the size of the block tridiagonal matrices to be inverted. This leads to a corresponding improvement in the overall computational efficiency.
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Potgieter, Carl Edzard. "Evaluation of resin-based fissure sealants placed under field conditions." Thesis, University of the Western Cape, 2015. http://hdl.handle.net/11394/5030.
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Magister Scientiae Dentium - MSc(Dent)BACKGROUND: The application of dental sealants is a recommended procedure to prevent and control dental caries. However, despite strong evidence for the safety and effectiveness of dental sealants, their use still remains low, especially among children from lower socioeconomic communities. The World Health Organization (WHO), Centres for Disease Control and Prevention (CDC) and the Association of State and Territorial Dental Directors (ASTDD) strongly endorse the implementation of school based dental sealant programmes as a community-based preventive strategy to increase sealant use and reduce dental caries. However, in the WHO African Region, oral health is seen as a very low priority and this is compounded by limited technical and managerial resources. The availability of human resources and equipment are crucial for the successful placement of dental sealants. A gap in the research literature was identified for determining the effectiveness of fissure sealants placed under field conditions. AIM: To evaluate the caries preventive effect as well as retention status of a resin-based fissure sealant that was placed under field conditions as part of a school based sealant programme. METHODOLOGY: A cross-sectional comparative study was conducted at two primary schools in close proximity of each other in the same low socio-economic area in Beaufort West, South Africa. The study population consisted of grade two children between the ages of 7-9 years who had fully erupted first permanent molar teeth. The case group consisted of 100 learners who received dental sealants on caries-free first permanent molar teeth 12 months earlier. The control group consisted of a random selection of the same number of learners from the adjacent school. Dental caries on the occlusal surfaces of the first permanent molar teeth was detected by making use of the decayed (D) portion of the decayed, missing and filled tooth (DMFT) score, while a separate diagnosis distinguished between cavitated and non-cavitated lesions. Sealant retention was determined by a calibrated examiner who was not involved in the placement of the sealants. RESULTS: The response rate of the study was 80.0% (n=100) and 78.9% (n=356) of the fissure sealants that were originally placed were evaluated. When the sealants were placed in 2013, 52.0% of the children were female and at the 12 month follow-up, 51.3% were female. The average age of the female children at follow-up was 8 years and 4 months (99.9 months) and 8 years and 5 months (101.8 months) for the males. The standard deviation of the gender profiles differed by 1 month only and implies an equal distribution of age between female and male children throughout the study. Just less than ten per cent (7.8%) of the sealants were fully intact at the 12 month follow-up examination and 91% were totally lost, which is a higher sealant loss rate than what is generally reported on in the literature. Of the 7.8% fully retained sealants, a statistically significant proportion (p=0.044) were found on the mandibular molar teeth. The caries incidence rate in the sealed group was 7.1% versus 9.1% in the control group. Relative risk (RR) calculations was slightly lower for the sealed (RR=0.79) than the unsealed (RR=1.02) teeth. CONCLUSION: The study showed a 2% lower caries prevalence rate on the occlusal surfaces of the sealed versus the unsealed teeth. However, this does not represent a statistically significant finding (P=0.39). The study also showed a low retention rate for the resin-based sealants placed under field conditions (12 month retention rate of 7.8%). The results from this study has therefore shown that resin-based fissure sealants placed on grade 1 learners under field conditions appear to be not ideal in preventing the onset of dental caries on the occlusal surfaces of the first permanent molar teeth.
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Coons, J., J. McGrady, and N. Simons. "Thermodormancy of Several Lettuce Cultivars in Laboratory vs. Field Conditions." College of Agriculture, University of Arizona (Tucson, AZ), 1988. http://hdl.handle.net/10150/214151.
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Gebreselassie, Hailemichael. "Iron supplementation and malaria infection, results of a randomized controlled field trial." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ29944.pdf.
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Gebreselassie, Hailemichael. "Iron supplementation and malaria infection : results of a randomized controlled field trial." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42040.
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Iron deficiency anaemia is associated with several ill-health effects. Its treatment and/or control with iron preparations in malaria endemic areas has, however, been implicated to increase host susceptibility to malaria infection. Scientific evidence accumulated to date remains equivocal about the presence of this increased susceptibility. The present work was planned to address the existing controversy by assessing the effect of oral iron supplementation on host susceptibility to malaria infection.A randomized, double-blind, placebo-controlled field trial of oral ferrous sulphate supplementation in schoolchildren 5 to 14 years of age was carried out in northwest Ethiopia where transmission of malaria is high. A total of 500 school children, all with mild-to-moderate iron deficiency, were randomly assigned to receive either ferrous sulphate (60 mg elemental iron per day) or a look-alike placebo, over a period of 12 weeks. Follow-up continued for 24 weeks post-randomization.
Children who received iron supplementation tended to develop more clinical attacks of malaria than those children who received placebo, although the difference between the groups was not statistically significant, either during the initial 12 week supplementation period (RR = 1.59; 95% CI: 0.92-2.75) or during the 24 weeks of follow-up (RR = 1.45; 95% CI: 0.95-2.20). Similarly, a trend of increased risk of malaria infection (parasitemia) was noted in the iron-supplemented group over the 24 week follow-up period (RR = 1.22; 95% CI: 0.98-1.52). No difference in any other outcome measure (spleen rate, average enlarged spleen index, and parasite density index) was observed between the groups either during the 12 weeks of supplementation or the 24 weeks of follow-up.
This study suggests that iron supplementation, in areas where iron deficiency and malaria co-occur, may enhance host susceptibility to malaria infection. Thus, approaches to control or prevent iron deficiency anaemia in malaria endemic areas should be integrated with malaria control activities in order to minimize the unintended effects of malaria infection while providing the greatest benefit.
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Wan, Junjun. "Towards the realization of an all electrically controlled Spin Field Effect Transistor." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1292519781.
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Gao, Wenzhu. "Hierarchically Controlled Helical Polyacetylenes Synthesized in Advanced Asymmetric Liquid Crystal Reaction Field." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124552.
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Li, Melissa M. EngMassachusetts Institute of Technology. "Photoluminescent quantum-dot light emitting devices controlled by electric field induced quenching." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123210.
Full textAbstract:
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 61-63).
Colloidal quantum dots (QDs) have been promising luminophores due to their bright, pure, and tunable colors. The ability to control the emission properties of QDs has far-reaching potential applications for a new generation of display and lighting technologies. The emission control of QDs in a QD light-emitting device (LED) is usually achieved by changing the injection current density. However, these devices face issues with lifetime and stability as well as low external quantum efficiency (EQE) at high biases. In this thesis, we demonstrate a unique approach in operating a QD device that avoids these limitations. The device is a photoluminescent LED (PL-LED) where the emission from the LED is from optical excitation. To tune the emission, we apply a bias to intentionally dim or turn off the QD PL, using the PL quenching at high biases to our advantage. We also study the field-induced quenching mechanisms using capacitor structured PL-LEDs and QD-LEDs. Traditional electroluminescent QD-LEDs can be used as a PL-LED when operated under reverse bias. We propose that the electric-field induced quenching in our devices is due to exciton dissociation and reduced band-edge exciton formation at high field strengths. The resulting QD PL device exhibits voltage-controlled PL quenching up to 99.5%, corresponding to a high contrast ratio of 200:1, and a sub-microsecond response time. Our demonstration of PL tunability can lead to a new class of devices for fluorescent displays and voltage-controlled devices.
by Melissa Li.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Svanholm, Ulrika. "Evaluation of measurements of pulsating flow under controlled conditions using phase contrast MRI." Thesis, Stockholm University, Medical Radiation Physics (together with KI), 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7222.
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The accuracy and precision of measurements of pulsating flow obtained with phase contrast magnetic resonance imaging (PC MRI) was studied. Measurements were carried out using known flow rates through a phantom connected to a pump that created pulsation in the flow. Repeated measurements were made in both the negative and positive encoding direction, using both breath-hold and non breath hold sequences. The obtained data was analyzed using code written in MATLAB and also using the FLOW software that is offered by the manufacturer of the MRI system.
A range of different flow velocities was scanned, and results show that the overall accuracy of the measurements is relatively good, with an average error of between 1.2% to 5.7% using the clinically employed flow calculation software. There is however indication of a systematic phase offset in the data that influences the measurements. The effect of the offset on the results depends on the direction of flow and the sequence used. The results also show the importance of properly selecting the area over which the flow rate is calculated.
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Gulzar, Muhammad. "Dry heating of whey proteins under controlled physiocochdemical conditions : structures, inteactions and functionalities." Rennes, Agrocampus Ouest, 2011. http://www.theses.fr/2011NSARB220.
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L’étuvage est utilisé comme procédé de pré-texturation des ingrédients protéiques alimentaires dans le but d’améliorer leurs fonctionnalités technologiques (gélifiant, moussant, émulsifiant). L’objectif de cette thèse était d’identifier les caractéristiques physicochimiques des poudres de lactosérum qui modulent les changements structuraux des protéines lors de l’étuvage et de leurs propriétés gélifiantes. Pour cela, des poudres de lactosérum possédant des caractéristiques physicochimiques variées en terme de pH, d’activité d’eau, et de composition (ratios protéiques, trace de calcium et de lactose) ont été étuvées sous différentes intensités thermiques (température/temps). L'activité d'eau de la poudre et la température d’étuvage accélèrent la cinétique de dénaturation/agrégation des protéines de lactosérum. Le pH et des traces de lactose dans les poudres affectent aussi la structure des protéines étuvées. A pH 2,5 les protéines s’associent par des ponts disulfures intermoléculaires ; En revanche, à pH 6,5 des liaisons covalentes autres que les ponts disulfures sont aussi impliquées dans la formation des agrégats. Le lactose affecte différemment la dénaturation/agrégation des protéines de lactosérum selon pH de la poudre et selon sa nature (libre ou fixé aux protéines). En outre, des monomères protéiques non-natifs (perte de masse de 18 Da) sont générées. Les propriétés gélifiantes évoluent en fonction des quantités d’agrégats protéiques solubles et insolubles dans les poudres étuvées. Ces résultats montrent la prépondérance de certaines caractéristiques physicochimiques de la poudre sur les modifications des protéines et leurs propriétés gélifiantes. De ce fait, ils fournissent des indications pour améliorer la reproductibilité de la fonctionnalité des ingrédients protéiques pré-texturés par étuvage en industrieDry heating is a pre-texturization process for food protein ingredients to improve their techno-functional properties (gelling, foaming, and emulsifying). The aim of this thesis was to identify the physicochemical characteristics of whey powders that modulate the structural changes of proteins during dry heating and the gelling properties of dry heated proteins. For this purpose, whey powders with various physicochemical characteristics in terms of pH, water activity, and composition (protein ratio, trace of calcium and lactose) were dry heated under different heat intensities (temperature/times). The water activity of the powder and dry heat intensity (temperature/times) accelerate the kinetic of denaturation/aggregation of whey proteins. Trace of lactose and pH also affect the structure of dry heated proteins. At pH 2. 5 the protein molecules were mainly linked together by intermolecular disulfide bonds, while at pH 6. 5, covalent cross-links other than disulfide bonds were also involved in formed aggregates. Depending upon its nature (free or fixed to proteins) and pH of powder, the lactose affects differently the denaturation/aggregation of whey proteins. In addition, non-native protein monomers having mass loss of 18 Da were also generated. Depending upon the quantity of soluble and insoluble aggregates of proteins, the gelling properties were changed. These results show the dominance of certain physicochemical characteristics of powder on protein structure modifications and their gelling properties, thus giving indications for improving the reproducibility of the functionality of dry heated protein ingredients at the industry
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Ieamsupapong, Supat. "Mechanisms of Iron Carbonate Formation on Mild Steel in Controlled Water Chemistry Conditions." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1473264400862079.
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