Дисертації з теми "FRET experiments"
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Kallis, Eleni [Verfasser]. "Quantitative single-molecule FRET and its application in experiments on DNA damage recognition by PARP-1 / Eleni Kallis." Ulm : Universität Ulm, 2020. http://d-nb.info/1221671170/34.
Повний текст джерела
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Götz, Markus [Verfasser], Thorsten [Akademischer Betreuer] Hugel, Thorsten [Gutachter] Hugel, and Friedrich [Gutachter] Simmel. "Multi-Color Single-Molecule FRET Experiments and Analysis : The Dynamic Protein System Hsp90 / Markus Götz ; Gutachter: Thorsten Hugel, Friedrich Simmel ; Betreuer: Thorsten Hugel." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1172880077/34.
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Koestner, Peter E., Karen Koestner, Daniel G. Neary, and Carl C. Trettin. "An Overview of the Sierra Ancha Experimental Forest's Role in the Free-Air CO₂ Enrichment Large Wood Decomposition Experiment." Arizona-Nevada Academy of Science, 2012. http://hdl.handle.net/10150/301295.
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Minh, David. "Free energy reconstruction from irreversible single-molecule pulling experiments." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3258785.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed June 8, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 69-72).
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D'Agostino, Silvia. "Particle segregation and mixing in a dry free surface granular flow." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/317018.
Повний текст джерелаАнотація:
Geophysical massive flows as snow avalanches and debris flows are characterized by a wide grain size distribution. The interactions between particles among the granulometric classes are a consequent of a such large distribution. However, most of the studies on the geophysical massive flows assume the simplifying hypothesis of a constant granulometry. The aim of this work is studying the coexistence of two granulometric classes in statistically stationary and homogeneous conditions and investigating the physical processes responsible for the particles transfer. Experimental investigations using two different grain size classes were conducted to reproduce the two-phases mixture. The granular material was recirculated in a close system and the experiments were carried out in a laboratory flume having a loose two size
granular bed. A proper optical technique was innovatively improved to obtain the average and instantaneous values of the velocity and concentration from the side-walls. Through these values, the average particle profiles of velocity, concentration and granular temperature of the two solid fractions were computed. Moreover, the instantaneous values provide the average profiles of the second order correlation of the variables, such as the component of the granular temperature and the fluctuating components of the velocity and the concentration. The average distribution profiles in time of velocity and concentration prove the statistically stationary and homogeneous condition in a stretch sufficiently long of the running flow. Moreover, two types of regimes were identified: in case of low and intermediate discharges, the frictional regime nearly prevails at the free surface; for high discharges there is a coexistence across the flow depth of two regimes, the frictional regime in the intermediate flow-depth region and the collisional regime in the free surface. The existence of a vertical velocity component of both phases brings to hypothesize the presence of secondary circulations in the flow.
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D'Agostino, Silvia. "Particle segregation and mixing in a dry free surface granular flow." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/317018.
Повний текст джерелаАнотація:
Geophysical massive flows as snow avalanches and debris flows are characterized by a wide grain size distribution. The interactions between particles among the granulometric classes are a consequent of a such large distribution. However, most of the studies on the geophysical massive flows assume the simplifying hypothesis of a constant granulometry. The aim of this work is studying the coexistence of two granulometric classes in statistically stationary and homogeneous conditions and investigating the physical processes responsible for the particles transfer. Experimental investigations using two different grain size classes were conducted to reproduce the two-phases mixture. The granular material was recirculated in a close system and the experiments were carried out in a laboratory flume having a loose two size
granular bed. A proper optical technique was innovatively improved to obtain the average and instantaneous values of the velocity and concentration from the side-walls. Through these values, the average particle profiles of velocity, concentration and granular temperature of the two solid fractions were computed. Moreover, the instantaneous values provide the average profiles of the second order correlation of the variables, such as the component of the granular temperature and the fluctuating components of the velocity and the concentration. The average distribution profiles in time of velocity and concentration prove the statistically stationary and homogeneous condition in a stretch sufficiently long of the running flow. Moreover, two types of regimes were identified: in case of low and intermediate discharges, the frictional regime nearly prevails at the free surface; for high discharges there is a coexistence across the flow depth of two regimes, the frictional regime in the intermediate flow-depth region and the collisional regime in the free surface. The existence of a vertical velocity component of both phases brings to hypothesize the presence of secondary circulations in the flow.
7
Perreca, Antonio. "Experimental demonstration of displacement noise free interferometry." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/817/.
Повний текст джерелаАнотація:
General relativity describes gravity as the curvature of space-time. The theory predicts the existence of gravitational waves (GWs), which can be described as ripples in space-time propagating at the speed of light. So far no direct detection of GWs has been achieved. The sensitivities of the currently leading laser interferometric GW detectors are limited by various noise sources, i.e. seismic, thermal, shot noises etc. Several conceptual studies are underway investigating new techniques that aim to improve sensitivities enough to fulfil the requirements of the next generation of detectors. One of these new techniques under investigation is displacement and frequency noise free interferometry (DFI). This thesis reports on the experimental demonstration of a new method of partial DFI that is effective in the GW detection frequency band. The isolation of a mimicked GW signal from displacement noise of one mirror is demonstrated for a detuned Fabry-Perot cavity. A significant reduction in the displacement noise of the cavity input mirror was achieved by properly combining the reflected and transmitted signals from the cavity. This result represents the first experimental demonstration of this recently proposed DFI scheme, and lays the foundations for future work aimed at implementing DFI schemes in up-coming laser interferometric GW detectors.
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Anzuola, Valencia Esdras. "Atmospheric compensation experiments on free-space optical coherent communication systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/308498.
Повний текст джерелаАнотація:
In the last years free-space optical communications systems for wireless links have been proposed, studied, and implemented mainly due to the higher bandwidth that this technology is able to provide. Still, radio frequency (RF) systems have been maintained in practical wireless communications systems due to the improvement of the microwave sources and the development of high speed electronics. Nowadays the circumstances are changing as a consequence of the increasing data-rate needed in terrestrial and outer space communications. The shift from RF systems to optical communication systems in the free space applications provide a wide set of advantageous characteristics that are motivating the use of these optical technologies in detriment of the RF systems. One of the key reasons is the advantage of working with optical wavelengths in compare to the RF spectral band. As well as the already mentioned increase in the available bandwidth due to the fact that higher optical frequencies directly mean wider bandwidths, the use of optical frequencies lead to a better performance in terms of the received power: for equal antenna sizes the received signal goes inversely as the square of the wavelength. Of the most interest, recent coherent optical communication systems address modulation and detection techniques for high spectral efficiency and robustness against transmission impairments. Coherent detection is an advanced detection technique for achieving high spectral efficiency and maximizing power or signal-to-noise (SNR) efficiency, as symbol decisions are made using the in-phase and quadrature signals, allowing information to be encoded in all the available degrees of freedom. In this context, the effects of Earth's atmosphere must be taken into account. Turbulenceinduced wavefront distortions affect the transmitted beam responsible for deterioration of the link bit error rate (BER). The use of adaptive optics to mitigate turbulence-induced phase fluctuations in links employing coherent (synchronous) detection is poised to reduce performance penalties enabling a more capable next generation of free-space optical communications. In this work, we describe the implementation of a free space optical coherent communication system using QPSK modulation
and heterodyne downconvertion that uses adaptive optics techniques and digital signal processing to mitigate turbulenceinduced phase fluctuations and channel impairments in coherent receivers. A new method for generating atmospheric turbulence based on binary computer generated holography (BCGH) using binary arrays is presented and its performance is evaluated. The feasibility of FSO coherent systems working with adaptive optics is demonstrated and the system performance in terms of the BER is experimentally evaluated under the influence of atmospheric turbulence. The resulting system performance is compared against the theoretical models. The viability of the approach to improve the system efficiency and sensitivity of coherent receivers is experimentally demonstrated.En los últimos años las comunicaciones ópticas en el espacio libre han sido propuestas, analizadas e implementadas debido, principalmente, al gran ancho de banda disponible mediante esta tecnología. Aún así, en la práctica, los sistemas de radiofrecuencia (RF) han sido mantenidos en las aplicaciones comerciales debido a la mejora de los dispositivos utilizados y al desarrollo de equipos electrónicos con gran velocidad de procesado. Hoy en día la situación está cambiando como consecuencia de un incremento en la tasa de transmisión requerida en sistemas de comunicaciones terrestres y en el espacio exterior. El cambio de sistemas de RF hacia sistemas ópticos en el espacio libre implica una serie de ventajas clave que motiva la transición hacia estas tecnologías. La primera y gran ventaja de trabajar con frecuencias pertenecientes al espectro óptico es el aumento del ancho de banda disponible, ya que trabajar a alta frecuencia implica directamente un incremento en el ancho de banda. Además, la eficiencia en términos de potencia es incrementada, ya que, para un tamaño de antena fijo, la potencia de señal recivida es proporcional al inverso de la longitud de onda al cuadrado. De especial interés es el desarrollo de sistemas de comunicaciones ópticos que utilicen modulaciones complejas, lo que implica una mayor eficiencia espectral y una mayor robustez contra efectos perniciosos introducidos por el canal. La detección coherente es una avanzada técnica que permite un aumento en la eficiencia espectral y maximiza la eficiencia de la potencia recibida. Esto es debido a que los simbolos son demodulados utilizando las señales en fase y cuadratura, aumentando los grados de libertad del sistema. En este contexto, los efectos de la atmósfera sobre las comunicaciones ópticas coherentes deben ser analizadas en detalle. Las turbulencias atmosféricas distorsionan el frente de onda y son responsables del deterioro de la tasa de error en las comunicaciones ópticas en el espacio libre. El uso de óptica adaptativa para mitigar los efectos de turbulencia atmosphérica abre una ventana a la implementación de la próxima generación de sistemas de comunicaciones, basados en tecnologías coherentes. En este trabajo se describe la implementación de un sistema completo de comunicaciones ópticas coherentes utilizando una modulación coherente (QPSK) y detección heterodina. Un sistema de óptica adaptativa y algoritmos de procesado de señal son implementados con el objetivo de mitigar los diferentes efectos introducidos por el canal. Por otro lado, un nuevo método para generar frentes de onda distorsionados por el canal atmosférico es desarrollado y su eficiencia es analizada. Este método se basa en el uso de holografía binaria generada por computador (BCGH) junto con un dispositivo de modulación óptica binaria de bajo coste (DLP). El funcionamiento del sistema completo es verificado y su eficiencia, en términos de tasa de error, son analizados. La eficiencia obtenida experimentalmente es comparada contra los modelos teóricos propuestos en la literatura. La viabilidad del uso de óptica adaptativa para mitigar efectos en sistemas ópticos coherentes es experimentalmente demostrada.
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Callas, Eleni. "How Free Am I?: Where Neuroscientific Experiments Can Lead Philosophy." Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:106849.
Повний текст джерелаАнотація:
Thesis advisor: Daniel McKaughanThesis advisor: Liane Young
The first two-thirds of this project is an in-depth analysis of the contemporary Free Will debate as it revolves around the Libet et al, Soon et al, and Wegner et al (“Helper Hands”) experiments. The last section of the thesis illustrates in detail the following suggestions regarding the future of the Free Will debate: that there be a shift in the fundamental question of the debate, a shift in the analysis of famous neuroscientific experiments, and a shift in the formation of future experiments that test potential elements of free will
Thesis (BA) — Boston College, 2016
Submitted to: Boston College. College of Arts and Sciences
Discipline: Scholar of the College
Discipline: Philosophy
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Deutschländer, Robert. "Alltagsintuitionen zur Willensfreiheit." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19245.
Повний текст джерелаАнотація:
Die Willensfreiheit ist ein zentraler Bestandteil des alltäglichen menschlichen Denkens und bildet eine wichtige Grundlage für Mechanismen unserer Gesellschaft. Trotz dieser zentralen Stellung herrscht unter Philosophen und Psychologen Uneinigkeit darüber, was Willensfreiheit eigentlich bedeutet. Dies wird besonders bei Experimenten zur Untersuchung der Willensfreiheit wie das Libet-Experiment deutlich. In dieser Arbeit wird in drei Surveys empirisch untersucht, ob der Freiheitsbegriff, mit dem die Libet-Experimente operieren, von den Freiheitsintuitionen der Laien gestützt wird, oder ob Laien eher den konträren Freiheitsintuitionen der Philosophen zuneigen. Die Ergebnisse der vorgestellten Untersuchungen zeigen, dass Laien eine von den philosophischen Vorstellungen abweichende Vorstellung von Freiheit haben.Free will is one of the most crucial concepts in our daily life. It represents one of the most important aspects of daily human behaviour and has crucial importance in societal mechanism. However, despite its importance and long tradition philosophers still disagree on a definition. At the heart of the problem lie diverging intuitions about what is important for the concept of freedom. This is particular obvious in neuroscientific experiment, like the famous Libet-Experiment. Here I investigate in three empirical surveys whether the lay intuitions about freedom match freedom intuitions on which the Libet-experiment are based or rather the classical philosophical intuitions about freedom. For this purpose I adopt the empirical approach of experimental philosophy. The results demonstrate that lay people’s intuitions are pretty much in line with assumption that are made by the Libet-Experiment and contradict common philosophical intuitions about free will.
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FAINOZZI, DANNY. "Espressione delle potenzialità dei Laser ad elettroni liberi attraverso esperimenti innovativi." Doctoral thesis, Università degli Studi di Trieste, 2021. http://hdl.handle.net/11368/2981745.
Повний текст джерелаАнотація:
The advent of X-Ray Free Electron Lasers (FELs) has opened a new era for exploring the fundamental properties of matter. These machines are the 4th generation light sources and combine the exceptional properties of conventional lasers and synchrotrons, allowing to probe the ultra-fast dynamics of atoms and molecules in simple and complex systems at a nano-scale level. This thesis work is divided in two main branches: at first, it reviews the basic theory behind FELs and points out possible improvement of these sources. Secondly, it presents some results obtained during new and peculiar experiments performed between 2017 and 2020 in different FELs facilities while showing how further improvements are needed in order to accomplish state of art results unreachable with the current state of synchrotrons and FELs. In Chapter 1, the reader is introduced to the charged particle accelerator theory culminating with its application on one of the main component of a FEL: the undulator. In order to provide its special radiation output, a FEL light source makes use of interactions between charged particles and a self-generated electromagnetic radiation inside an undulator. To let the reader easily understand the mechanism behind the radiation generated and its properties, this thesis opens with an approach to the laws of physics that rule the dynamics of the particles. Coupling the Lorentz equation with Maxwell equations we show the collective dynamics of electrons throughout the all FEL structure in Chapter 2. In Chapter 3 we present the two main places where this work of thesis has been built: the FERMI FEL in Italy and the SwissFEL machine based at the Paul Scherrer Institute in Switzerland. Here we explore the secrets of their layouts, beamlines and main experiment performed. Once the reader mastered the fundamental properties of a FEL, we show the main results achieved during this research period at the FERMI FEL and at the SwissFEL. In Chapter 4 we present the very first successfull attempt at X-Ray Transient Grating Spectroscopy on Bismuth Germanate Oxide. In order to confirm some of the results obtained through the X-ray Transient Grating technique, a few satellite measurements and simulations were also performed on the Bismuth Germanate Oxide sample, which are presented in Chapter 5. In Chapter 6 we present what we called a Real-time visualization of ibuprofen dimer vibrations with element- and enantiomeric- selectivity: here we exploit the potential of FELs through an ultrafast soft X-Ray absorption experiment that allows the visualization and disentangling of several low-frequency and near lying vibrational modes, involving specific carbon atoms in a racemic mixture of Ibuprofen. In Chapter 7 we explore the world of soft matter: here we introduce the problematics affecting the protein structure research by showing the main re- results obtained at two synchrotron facilities. Afterward, given the results we obtained, we explore the possibility to overcome such problems by introducing the Coherent and Incoherent Diffraction Imaging techniques at FELs combined to a new approach on protein bidimensional crystallization. Furthermore, we introduce a rather similar approach to a technique aiming at Catching Conical Intersection through Electronic Coherence and Noise Correlation Spectroscopy: we explore the possibility to use the TRUECARS technique to directly visualize the conical intersection dynamics, which regulates the photo-chemestry of most molecules. Chapter 8 opens with an introduction on Resonant Inelastic X-ray Spettroscopy (RIXS). Here we show the results of the application of RIXS exploiting the Ultrafast charge trapping dynamics in Cu2O in-gap states: we investigated the charge trapping dynamics in the defect-related in-gap states of Cu2O, following photoexcitation across the band gap. Finally, the thesis culminates with the Design of a soft X-Rays RIXS spectrometer for the SwissFEL's new beamline FURKA.
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Maddox, Douglas Lamar. "An experimental testbed for a free-floating manipulator." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA277350.
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Zeng, Lingping. "Studying phonon mean free paths at the nanoscale : modeling and experiments." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106784.
Повний текст джерелаАнотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 108-119).
Heat conduction in semiconductors and dielectrics involves cumulative contributions from phonons with different frequencies and mean free paths (MFPs). Knowing the phonon MFP distribution allows us to gain insight into the fundamental microscopic transport physics and has important implications for many energy applications. The key metric that quantifies the relative contributions of different phonon MFPs to thermal conductivity is termed thermal conductivity accumulation function. In this thesis, we advance a thermal conductivity spectroscopy technique based upon experimental observation of non-diffusive thermal transport using wire grid linear polarizer in conjunction with time-domain thermoreflectance (TDTR) pump-and-probe measurement setup. Consistent algorithm based on solution from the phonon Boltzmann transport equation (BTE) is also developed to approximately extract the thermal conductivity accumulation functions in materials studied. The heat flux suppression function appropriate for the experimental sample geometry relates the measured apparent thermal conductivities to the material's phonon MFP distributions. We develop a multi-dimensional thermal transport model based on the gray phonon BTE to find the suppression function relevant to our spectroscopy experiment. The simulation results reveal that the suppression function depends upon both the heater size and the heater array period. We also find that the suppression function depends significantly on the location of the temperature measurement. Residual suppression effect is observed for finite filling fractions (ratio of heater size to heater array period) due to the transport coupling in the underlying substrate induced by the neighboring heaters. Prior phonon MFP spectroscopy techniques suffer from one or several of the following limitations: (1) diffraction limited to micrometer lengthscales by focusing optics, (2) applying only to transparent materials, or (3) involving complex micro-fabrications. We explore an alternate approach here using wire grid linear polarizer in combination with TDTR measurement. The wire grid polarizer is designed with sub-wavelength gaps between neighboring heaters to prevent direct photo-excitation in the substrate while simultaneously functioning as heaters and thermometers during the measurement. The spectroscopy technique is demonstrated in crystalline silicon by studying length-dependent thermal transport across a range of lengthscales and temperatures. We utilize the calculated heat flux suppression functions and the measured size-dependent effective thermal conductivities to reconstruct the phonon MFPs in silicon and achieve reasonably good agreement with calculation results from first principle density function theory. Knowledge of phonon MFP distributions in thermoelectric materials will help design nanostructures to further reduce lattice thermal conductivity to achieve better thermoelectric performance in the next-generation thermoelectric devices. We apply the developed wire grid polarizer spectroscopy technique to study phonon MFP distributions in two thermoelectric materials: Nb0.95 Ti0.05FeSb and boron-doped nanocrystalline Si80Ge20B. We find that the dominant phonon MFPs that contribute to thermal conductivity in those two materials are in the a few tens to a few hundreds of nanometers. The measurement results also shed light on why nanostructuring is an effective approach to scattering phonons and improve the thermoelectric behavior.
by Lingping Zeng.
Ph. D.
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PeÌrez, Navarro J. M. "Develping a 'recipe' for success in free-response Ganzfeld ESP experimental research." Thesis, Coventry University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289245.
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Stögbauer, Tobias Roland. "Experiment and quantitative modeling of cell-free gene expression dynamics." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-151600.
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Li, Jinxia. "Lubricating grease Experiments and modeling of wall-bounded- and free-surface flows." Doctoral thesis, Luleå tekniska universitet, Maskinelement, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26489.
Повний текст джерелаАнотація:
Lubricating grease is commonly applied to lubricate e.g. rolling bearings, sealsand gears. Grease has some clear advantages over lubricating oil: it is a semisolidmaterial, which prevents it from flowing/ leaking out from the bearingsystem and gives it sealing properties, and it also protects the system fromcontaminants and corrosion. Due to its consistency, lubricating grease has manyadditional advantages over lubricating oil: it does not require pumps, filters andsumps. However, the rheology of grease makes it more difficult to measure andstudy its flow dynamics. This study focuses on the influence of rheology ongrease flow in different geometries involving a straight channel with restrictions,concentric cylinder geometry, and free-surface flow on a rotating disc.To better understand grease flow in bearings and seals, two types of flowrestrictions were applied into the straight channel in order to simulate the flowof grease near a seal pocket. In the case of a single restriction, the horizontaldistance required for the velocity profile to fully develop is approximately thesame as the height of the channel. In the corner before and after the restriction,the velocities are very low and part of the grease is stationary. For the channelwith two flow restrictions, this effect is even more pronounced in the narrowspace between the restrictions. Clearly, a large part of the grease is not moving.This condition particularly applies in the case of a low-pressure gradient andwhere high-consistency grease is used. In practice this means that grease may belocally trapped and consequently old/contaminated grease will remain in theseal pockets.A configuration comprising a rotating shaft and two narrow gap sealing-likerestrictions (also called Double Restriction Seal, DRS) was designed to simulatea sealing contact. Two different gap heights in the DRS have been used tocompare the grease flow. It is shown that partially yielded grease flow isdetected in the large gap geometry and fully yielded grease flow in the small gapgeometry. For the small gap geometry, it is shown that three distinct grease flowregions are present: a slip layer close to the stationary wall, a bulk flow layer,and a slip layer near the rotating shaft. The shear thinning behaviour of thegrease and its wall slip effects have been determined and discussed.Free-surface flow of grease occurs in a variety of situations such as during relubrication and inside a rolling element bearing which is filled to about 30%with grease in order to prevent heavy churning. Here the reflow of lubricant tothe bearing races is a key point in the lubricant film build-up, and centrifugalforces have a direct impact on the amount of available grease. Understanding ofthe free-surface flow behaviour of grease is hence important for theunderstanding of the lubrication mechanism. Adhesion and mass loss aremeasured for greases with different rheology on different surfaces andtemperatures. It is shown that the critical speed at which the grease starts tomove is mostly determined by grease type, yield stress and temperature ratherthan surface material. A developed analytical model covers a stationary analysisof the flow resulting in solutions for the velocity profile of the grease as well as asolution for the thickness of the viscous layer remaining on the disc.Godkänd; 2014; 20141017 (jinlit); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Jinxia Li Ämne: Maskinelement/Machine Elements Avhandling: Lubricating Grease Experiments and Modellingo f Wall-Bounded and Free-Surface Flours Opponent: Professor Arto Lehtovaara, University of Technology, Tampere, Finland Ordförande: Professor Erik Höglund, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Fredag den 19 december 2014, kl 09.00 Plats: E632, Luleå tekniska universitet
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Thomson, Robert W. "Experimental damage studies for a free electron laser weapon." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA366836.
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Jones, Ryan Edward 1974. "Design and testing of experimental free-piston cryogenic expander." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80237.
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Chiu, Yuen-Yuen. "Experimental and theoretical analysis of free radical crosslinking polymerizations /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu148785841798507.
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Latham, Andrew James. "Indirect Compatibilism." Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/20440.
Повний текст джерелаАнотація:
In this thesis, I will defend a new kind of compatibilist account of free action, indirect conscious control compatibilism (or indirect compatibilism for short), and argue that some of our actions are free according to it. My argument has three components, and involves the development of a brand new tool for experimental philosophy, and the use of cognitive neuroscience. The first component of the argument shows that compatibilism (of some kind) is a conceptual truth. Contrary to the current orthodoxy in the free will literature, which is that our concept of free will is an incompatibilist concept - a concept according to which we have free will only if determinism is false - I will show that our concept of free will is in fact a compatibilist concept - a concept according to which we can have free will even if determinism is true - and I do so using a new experimental philosophy methodology inspired by two-dimensional semantics. Of course, even if our concept of free will is a compatibilist concept, this does not mean that there are any free actions in the world: the current empirical evidence from the brain sciences appears to show that there might be no, or very few, free actions in the world, even on many compatibilist understandings of what it would take for there to be free will. The second component of the argument addresses this concern by extending our understanding of compatibilism. Agents act freely either when their actions are caused by compatibilistically acceptable psychological processes, or are indirectly caused by those same processes. Hence the name of my account: indirect compatibilism. The final component of the argument defends my new account against some interesting objections and provides evidence from cognitive neuroscience that some of our actions count as free by the lights of indirect compatibilism.
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Maroju, Praveen Kumar [Verfasser], and Giuseppe [Akademischer Betreuer] Sansone. "Attosecond pulse shaping at a seeded free-electron laser : : towards attosecond time-resolved experiments at the free-electron lasers." Freiburg : Universität, 2021. http://d-nb.info/1239556527/34.
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Sumantran, V. "The effect of free stream disturbances and control surface deflections on the performance of the Wortmann airfoil at low Reynolds numbers." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/49921.
Повний текст джерелаАнотація:
A wing with a Wortmann FX-63-137-ESM airfoil section has been used to study some unique problems encountered in wing aerodynamics in the range of Reynolds numbers between 50,000 and 500,000. The wind-tunnel testing conducted in the 6'x 6' Stability tunnel included strain-gauge data, pressure data, and flow-visualization studies. The laminar separation bubble which frequently occurs on the upper surface of the wing is found to dominate its performance and gives rise to a hysteresis loop for lift and drag. Changes in airfoil performance due to positive flap or control surface deflections resemble changes witnessed at higher Reynolds numbers. Negative deflections are seen to considerably change the stall behavior and the flow over the airfoil. This is due to the considerably greater effect on the separation bubble for negative flap deflections.
The structure and mechanism of the laminar separation bubble can also be altered by the introduction of selected acoustic disturbance and increased free-stream turbulence. The wind-tunnel test-section environment is, therefore, capable of considerably altering wing performance in this regime.Ph. D.
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González, Guerrero Ana Belén. "Bimodal waveguide interferometer device based on silicon photonics technology for label-free and high sensitive biosensing." Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/107886.
Повний текст джерелаАнотація:
Els dispositius òptics biosensors basats en la detecció d’ona evanescent podrien superar les limitacions dels tests de diagnòstic actuals (que són lents i cars) degut a la possibilitat de realitzar les deteccions a temps reals i fent servir un esquema sense la necessitat de marcatges. Entre els diferents transductors òptics, els interferomètrics són els que posseeixen els millors límits de detecció (LOD) deguts a canvis en el índex de refracció de dissolucions (10-7-10-8 Unitats d’Índex de Refracció, RIU) així com per sensibilitat superficial (en el rang dels pg/ml) i un rang lineal més gran. No obstant, les configuracions interferomètriques (l’interferòmetre Mach-Zehnder o el Young) més usuals fan servir un divisor amb forma de Y, que és essencial per dividir o recombinar la llum, lo qual, degut a les toleràncies de les actuals tècniques de fabricació es una gran desavantatge per la reproduibilitat d’aquests dispositius.
Per evitar aquests problemes, hem desenvolupat una configuració interferomètrica més simple basada en un guia de ones recte on dos modes de llum de la mateixa polarització interfereixen entre si. Aquesta configuració elimina la complexitat dels interferòmetres més utilitzats i conseqüentment, el biosensors que s’obtenen són més fiables i reproduïbles.
Aquesta tesis esta dirigida al desenvolupament i la caracterització d’un nou transductor fotònic per biosensat d’alta sensibilitat i sense marcatges, el dispositiu de guia d’ona bimodal (BiMW). Amb aquest propòsit, els següents punts han estat plantejats:
1. Disseny, fabricació i caracterització òptica del transductor que opera segons el principi de la interferència de dos modes de llum.
2. Desenvolupament i optimització de les estratègies de funcionalització de la superfície transductora fent servir processos de silanització.
3. Estudi de l’aplicabilitat del biosensor amb la demostració del diagnosis analític de problemes clínics rellevants.
El transductor es fabrica a nivell d’oblea a la Sala Blanca, lo qual garanteix la producció en massa del dispositiu així com un preu baix del mateix. El dispositiu és molt sensible a variacions en l’índex de refracció de dissolucions, obtenint un límit de detecció de 2×10-7 RIU. La biofuncionalització de l’àrea sensora es un dels aspectes més importants d’aquest treball. Diferents protocols per immobilitzar els diferents bioreceptor en la superfície del dispositiu (cadenes d’ADN, proteïnes i anticossos) han estat desenvolupats. Aquests protocols s’han fet servir per la demostració de diferents bioaplicacions; la detecció d’hormones, bactèries o seqüències d´ADN complementàries.
Els resultats presentats en aquesta tesis han destacat pel superior funcionament d’aquest dispositiu en comparació amb els tests de diagnosis convencionals degut a: i) la possibilitat de monitoritzar les interaccions biomoleculars en temps real i fent servir un esquema sense marcadors reduint el temps i el cost de l’assaig, ii) la fabricació del dispositiu fent servir microtecnologia de silici, possibilitant la producció en massa, iii) l’alta sensibilitat (pg/ml, femtomolar) demostrada per les diferents bioaplicacions avaluades i iv) el dispositiu reuneix els requeriments específics per ser miniaturitzat e integrat en una plataforma de sensat multiplexada.
Aquest treball obre la porta a la integració d’aquest transductor en un dispositiu lab-on-a -chip, una feina que inclou l’acoblament/detecció de la llum, un sistema capaç de modular la senyal interferomètrica i la incorporació de canals microfluídics per anàlisis multiplexats. Cadascun d’aquests temes afegeix molta complexitat al dispositiu final, han de ser individualment desenvolupades i optimitzades per ser integrades en un biosensor lab-on-a-chip. Finalment, la possibilitat de detectar simultàniament múltiples analits involucra el desenvolupament de noves tècniques per recollir les múltiples senyals així com desenvolupar noves estratègies de biofuncionalització.Optical biosensor devices based on evanescent wave detection could overcome the limitations of conventional diagnostic tests (expensive and time-consuming) due to the possibility of carrying out the detection in real-time and using a label-free scheme. Among the different optical transducers, interferometric devices have evidenced the best limit of detection (LOD) for refractive index changes of bulk solutions (10-7-10-8 Refractive Index Units, RIU) and for surface sensing (in the pg/ml range) and a wider linear range. However, usual interferometric transducers (Mach-Zehnder or Young interferometers) employ the Y-junction to split or recombine light, a drawback for the coherence and performance of the device due to standard tolerances of microfabrication techniques. To overcome these problems, we have developed a simple configuration based on a single straight waveguide where two modes of the light of the same polarization are interfering between them. This simple approach avoids the complexity of the usual interferometric transducers and as a consequence, more reliable and reproducible biosensors can be obtained. This thesis is focused on the development and characterization of a new photonic transducer, the Bimodal Waveguide device (BiMW), for label- free and high sensitive biosensing. To achieve this, the following steps have been pursued: 1. Design, fabrication, and optical characterization of an optical transducer operating by two-mode interference principle. 2. Development and optimization of biofunctionalization strategies on the transducer surface using silanization techniques. 3. Study of the applicability of the biosensor with the demonstration of bioanalytical diagnosis of relevant problems. The transducers are fabricated at wafer level in Clean Room facilities, which warrants a cost-effective and mass-production of the sensor chips. The device is highly sensitive to small changes in the refractive index occurring on the sensor area, leading to a detection limit of 2.5×10-7 RIU for bulk changes in refractive index solutions. The biofunctionalization of the sensor area is one of the most crucial aspects of this work. Optimized functionalization procedures have been achieved, which has been employed to immobilize different types of bioreceptors (DNA strands, proteins, and antibodies) on the surface. The optimized protocols have been used for the demonstration of different bioapplications such as the detection of hormones, bacteria, or complementary DNA sequences. The results presented in this work have highlighted the superior performance of this device in comparison with conventional diagnostics tests due to: i) the possibility of monitoring biomolecular interactions in real-time and by using a label-free scheme which reduce the time and cost of the assay , ii) the fabrication of the device using standard silicon microelectronics technology opening the possibility for mass-production, iii) the high sensitivity demonstrated for the different bioapplications assessed achieving detection limits in the pg/ml range (femtomolar), and iv) the device meets the specific requirements to be miniaturized and integrated in a multiplexed platform. This work opens the door for the integration of this transducer in a lab-on-a-chip device, including the in-coupling/out-coupling of light, a system able to modulate the interferometric signal, and the incorporation of microfluidics channels for multiplexing. Each of these subjects adds a great complexity to the final device, and must be independently developed and optimized in order to be successfully integrated at the final lab-on-a-chip biosensor. Finally, the possibility to detect simultaneously multiple analytes will involve further efforts in developing new optical in and outcoupling as well as new biofunctionalization strategies.
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Heintze, Olaf. "A Computationally Efficient Free Energy Model for Shape Memory Alloys - Experiments and Theory." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-12172004-221828/.
Повний текст джерелаАнотація:
Shape memory alloys (SMA) belong to the class of active materials and have recently been considered as novel actuation and damping mechanisms in micro- and macro-scale applications. Combined with their advantageous lightweight and high work output characteristics is a complex, highly non-linear and hysteretic material behavior, which is also thermo-mechanically coupled. Due to this complexity, model development for SMA material behavior is a challenging task, and experimental data in particular about the inner hysteresis loops is necessary to gain further understanding and successfully design applications. In this thesis, a single crystal material model is presented and subsequently extended to the more realistic polycrystalline case considering material inhomogeneities, grain impurities and lattice imperfections. A first implementation, based on a stochastic homogenization procedure, provides a very accurate description of the observed phenomena, but also requires very high computation times. A reformulation of the underlying concept leads to a parameterization method, which preserves the advantages of the original method, but dramatically reduces the computation times. It is shown that the material behavior prediction of both models are identical, and the parameterization method is compared extensively to data from tensile experiments with a pseudoelastic SMA wire. Remarkably, the model is able to capture all facets of the material behavior including rate-dependence and minor loops. The versatility of the model also allows for the simulation of SMA actuator behavior including the electrical resistance. Finally, a MEMS device using polycrystalline SMA thin film actuators is experimentally investigated. As a first step, the material behavior of the SMA thin films is presented using strain-temperature and resistance-temperature measurements. Secondly, the performance of the MEMS device was determined for different driving frequencies.
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Doshi, Urmi R. "One-dimensional free energy surface models of protein folding: connecting theory and experiments." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6875.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Melendez, Ramirez Antonio Jose Beckermann Christoph. "Experimental investigation of free dendritic growth of succinonitrile-acetone alloys." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/407.
Повний текст джерела
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Pedley, Tony J. "An experimental investigation into coherent structures in free shear flows." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277480.
Повний текст джерела
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Allison, Mark. "An experimental and computational investigation of transition metal-free reactions." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30916.
Повний текст джерелаАнотація:
Over recent decades transition metal-catalysed cross-coupling has been developed significantly, opening up new areas of reactivity in both an academic and industrial environment. However, over recent years transition metal-free coupling reactions of haloarenes to arenes, proceeding by the Base-promoted Homolytic Aromatic Substitution (BHAS) mechanism have been widely reported in the literature. These reactions work well when initiated by organic electron donors that are formed in situ from organic additives of various types. The work in this thesis builds on previous work carried out within the Murphy group and other groups working in this field. Scheme 1 - BHAS mechanism proposed by Studer and Curran as responsible for transition metal-free cross coupling reactions. The work in this thesis looks at transition metal-free reactions in two forms; firstly looking at new additives that could form electron donors to initiate the BHAS mechanism and secondly, looking at where coupling reactions are occurring when there is no electron donor present. The final aspect of this thesis looks at exploring observations seen in experiments with haloarenes and potassium hydride. The first set of work was looking at a series of additives that were designed to form electron-rich alkenes, a common feature of electron donors, under basic conditions. These were studied both computationally and experimentally and this work showed these can work together effectively in studying electron donors. Scheme 2 - Additives used in Chapter 4 produced high yields of coupled products. While these reactions proceed in good yield when there is an electron donor present in the reaction, when there is no electron donor a measurable amount of cross coupling still occurs. A plausible mechanism, shown in scheme 3, has been proposed for the initiation of the BHAS pathway. This thesis shows that biradicals, generated in Bergman cyclisations and hexadehydro-Diels-Alder reactions, can indeed act as a source of initiation for this pathway. This thesis now shows that additives that afford arenediyls, provide independent initiation of the coupling reactions for this substrate in the absence of electron donors, supporting a similar capability for benzyne generated by base-dependent means. Scheme 3 - Proposed benzyne initiation of the BHAS cycle. In reactions performed by other members of the Murphy group involving haloarenes and KH, some interesting reaction products were observed. In this thesis these have been rationalised using computational studies. Scheme 4 - This thesis proposes formation of 7.7 proceeds via the four-memberedtransition state calculated.
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Zeng, Lingping. "Experimental and numerical investigation of phonon mean free path distribution." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79267.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 99-107).
Knowledge of phonon mean free path (MFP) distribution is critically important to engineering size effects. Phenomenological models of phonon relaxation times can give us some sense about the mean free path distribution, but they are not accurate. Further improvement of thermoelectric performance requires the phonon MFP to be known. In this thesis, we improve recently developed thermal conductivity spectroscopy technique to experimentally measure MFPs using ultrafast transient thermoreflectance method. By optically heating lithographically patterned metallic nanodot arrays, we are able to probe heat transfer at length scales down to 100 nm, far below the diffraction limit for visible light. We demonstrate the new implementation by measuring MFPs in sapphire at room temperature. A multidimensional transport model based on the grey phonon Boltzmann equation is developed and solved to study the quasi-ballistic transport occurring in the spectroscopy experiments. To account for the nonlinear dispersion relation, we present a variance reduced Monte Carlo scheme to solve the full Boltzmann transport equation and compare the simulation results with experimental data on silicon.
by Lingping Zeng.
S.M.
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Melendez, Ramirez Antonio Jose. "Experimental investigation of free dendritic growth of succinonitrile-acetone alloys." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/407.
Повний текст джерелаАнотація:
Measurements are carried out for dendrite tip growth of succinonitrile-acetone alloys solidifying freely in an undercooled melt. The current experimental investigation is conducted using the equiaxed dendritic solidification experiment (EDSE). This setup allows for precise measurements of the dendrite tip velocity, radius and shape for a range of undercoolings and solute concentrations. The collected data are compared to available theories of free dendritic growth, such as the Lipton-Glicksman-Kurz and Li-Beckermann models. It is found that for dilute succinonitrile-acetone alloys, the measured dendrite tip Péclet numbers agree well with previous theories of free dendritic growth, if the effects of melt convection are taken into account. The tip selection parameter deviates significantly from the pure succinonitrile value and is inversely related to the applied undercooling. Besides, the selection parameter shows no dependence on the solute concentration. These results are consistent with phase-field simulations and preceding experimental investigations. In addition, scaling relationships for the sidebranching shape were obtained in terms of the dendritic envelope, projection area and contour length. These new scaling relations agree well with previous measurements in pure succinonitrile dendrites by Li and Beckermann.
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Flores, Michel Luz. "Rationalisation and design of molecular recognition : computational and experimental approaches." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/rationalisation-and-design-of-molecular-recognition-computational-and-experimental-approaches(0bcfe73a-bee9-45db-aa43-90b742ccb9fd).html.
Повний текст джерелаАнотація:
Molecular recognition is essential to all biological interactions and processes. Knowledge of the structural basis of recognition offers a powerful mechanism for understanding, predicting and controlling the behaviour of biological systems. In this thesis, we present, firstly a computational and crystallographic analysis of molecular recognition in protein-ligand systems; and secondly, progress towards the synthesis of a fluorescent probe for calcium ion recognition. Class I phosphoinositide 3-kinases (PI3Ks), in particular PI3Kγ, have long been considered promising drug targets for the treatment of inflammatory and autoimmune disorders. As a step towards improved understanding of PI3K binding preferences, we examine the basis on which PI3Kγ distinguishes γ-selective inhibitors AS-605240 and AS-604850, with a ~30-fold preference for the former. Interestingly, despite the chemical similarity of the two ligands, the X-ray structures for their PI3Kγ complexes exhibit the molecules in different conformers, s-cis for AS-604850 and s-trans for AS-605240. Here, we re-examine the PI3Kγ/AS-605240 crystallographic data and find that not only is a s-cis conformation possible but in fact it has a much higher occupancy (87%) than the originally modelled s-trans isomer (13%). Subsequently, to account for the isomeric complexities presented by the ligands, we perform 140 ns MD simulations of the four PI3Kγ complexes in explicit solvent: this reveals similar conformational flexibility at the active site for all systems. Yet, the conformations sampled by the s-cis isomers are more consistent with the conformations reported by the X-ray crystal structures. Subsequent energetic analysis was performed incorporating ensemble-averaging and desolvation effects via the Poisson-Boltzmann continuum solvent model. For both inhibitors the s-cis isomers are predicted to be the most favourable conformations. Additionally, the results indicate a preference for AS-605240, as observed experimentally. The molecular basis for this preference is discussed, together with a comparison of molecular mechanical and quantum chemical treatments of the key ligand-Val882 interaction. This study provides structural, dynamical and energetic insights into the subtle basis of molecular recognition by PI3Kγ.Fluorescent probes have evolved into an extremely useful tool for the detection of calcium in biological systems. Benzothiazole derivatives BTC, and its iminocoumarin analogue BTIC, are two low affinity calcium indicators featuring many desirable properties for cellular calcium measurement. In an effort to produce fluorophores that can be chemically conjugated with a screening protein, such as Green Fluorescent Protein (GFP), we aimed to derivatise BTC and BTIC. Two synthetic approaches towards the synthesis of these potential fluorescent probes are outlined.
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Lamounier, Lucia. "Between slavery and free labour : experiments with free labour and patterns of slave emancipation in Brazil and Cuba c.1830-1888." Thesis, London School of Economics and Political Science (University of London), 1993. http://etheses.lse.ac.uk/108/.
Повний текст джерелаАнотація:
This thesis is divided in two main parts. The first part compares and contrasts early experiments with non-slave labour in Cuba and Sao Paulo. The second part considers projects for the gradual abolition of slavery and the transition to free labour. The objective is to examine how Cuban and Brazilian planters solved the problem of labour supply triggered by a rapid growth of plantation exports during the nineteenth century. At this time sugar and coffee plantations came to characterize economic development in the two areas. Continued expansion was threatened by international pressures to end the trans- Atlantic slave trade. Challenged by international demands to terminate the "African trade" Cuba and Brazil sought to solve the labour problem by means of immigration. From the mid-century until the end of slavery in the 1880s, planters would experiment with several labour systems, involving a variety of labour relations. Besides slaves, Europeans, Chinese, Mexican Indians, Canary Islanders, and free domestic workers (white and coloured) would be employed on the plantations. Substituting "free" labour for slave labour was not simply a matter of labour supply. For Cuba there was the question of the relationship with Spain and its consequences for the defense of slavery and the impact on immigration. For Brazil there was the question of forging a national identity. What would be the place of slaves, freedmen and immigrants in the new nation. In both regions these considerations had a racial dimension. Also planters were anxious to secure a cheap disciplined workforce. What labour system would best meet these requirements? As this thesis demonstrates this was a time of experimentation. From the first, in Brazil alternative supplies of labour were regarded as a means of transition to free labour. In Cuba new supplies of workers were viewed as complementing slavery. But the first experiments with non-slave labour affected the processes of the abolition of slavery and the transition to free labour while the meaning of "free labour” and “transition” also changed over time.
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Umirova, Arailym. "Experimental Design for Ceramic Panel Production." Thesis, Luleå tekniska universitet, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85954.
Повний текст джерелаАнотація:
This thesis work is a continuation of a project aimed at the consolidation of insulation material (IM) to produce porous ceramics with sufficient porosity and compression strength for post-insulation of buildings. The porous structure and contact points are tailored to produce IM with ultra-low thermal conductivity. One of the main goals is to introduce expandable microspheres, that are perfect lightweight fillers and blowing agents into production. They are relatively new materials in the market which are used to manufacture products with low weight and controlled foam structure. Therefore, it is of interest to be integrated into the construction field as a component for insulating materials. The project is built on the advanced structuring of porous materials with tailored porosity to offer 5-10 times lower thermal conductivity value providing adequate insulation with an insulation cover of 2-10 mm in thickness. Enhancing the insulating capacity allows to limit the use of energy to improve energy efficiency. Thus, less energy is required to heat or cool the indoor climate. The success in achieving such thin effective IM will eliminate the need for any modification of existing window frames, electrical and heating installations. In the first stage, it is necessary to confirm the entire concept of creating a thermal IM with a controlled porous structure using various compositions of materials and an assessment of the structure, porosity, and functional properties. This project focuses on developing a composition of ceramic panels. The various components of the ceramic panels including the type of ceramic are adjusted and their effects on the composition are described. Pure alumina, activated alumina and silica have been investigated to find the optimized quality and price. In addition, various methods and conditions have been implemented for panel fabrication. Prototypes of ceramic panels are prepared for demonstration, followed by upscaling at the facilities of industrial partners. The project has been performed in collaboration with companies i.e., Nouryon, HIPOR Materials AB, and LindePac AB as the industrial partner.
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Wünscher, Michael [Verfasser], and Eckehard [Akademischer Betreuer] Schöll. "Crucible-free Crystal Growth of Germanium - Experiments and Simulations / Michael Wünscher. Betreuer: Eckehard Schöll." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2011. http://d-nb.info/1017154147/34.
Повний текст джерела
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Bateman, Brett E. "Experiments on laser beam jitter control with applications to a shipboard free electron laser." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Dec%5FBateman.pdf.
Повний текст джерелаАнотація:
Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2007.Thesis Advisor(s): Baker, Steven R. ; Agrawal, Brij N. "December 2007." Description based on title screen as viewed on January 18, 2008. Includes bibliographical references (p. 81-82). Also available in print.
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Djouadi, Manil. "Wire Boom Deployment and Attitude of Spinning Free Falling Units in Sounding Rocket Experiments." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235747.
Повний текст джерелаАнотація:
The SPIDER experiment conducted in February 2016 made it possible togather measurements in an aurora and is likely to bring a better understandingof instabilities occurring in it, especially of the Farley-Buneman instability.To exploit properly these measurements, the attitude of the Free-Falling Units(FFUs) that gather the measurements must be well known. However the attitudereconstruction process is made harder as the camera included in the FFUfor that purpose failed to provide usable data. Using raw GPS data and datafrom the Inertial Measurement Unit, and knowing the magnetic field’s behavioroutside of the electrojet, the attitude of one FFU can be determined with anacceptable level of precision. This could extend to other scientific projects andprovide an inexpensive alternative to the use of star trackers.A re-flight by 2019 is scheduled for the SPIDER experiment. Improvementson the Boom Deployment Unit (BDU) are being investigated so their mechanismis more robust, as well as easier and faster to assemble. Getting a betterunderstanding of it through functional analysis helped finding directionsfor improvement on the pin release mechanism, on the solutions to ensure therotational guiding, on making the hardware resistant to vibrations during thelaunch, and on the connections between the measurement probes and the electronicsto process the measurements acquisition. A BDU including the modificationsproposed should be assembled and tested in the perspective of includingthe new design in the re-flight.Uppskjutningen för SPIDER experimentet skedde i februari 2016. Mätningar från en Aurora/Norrsken/Polarsken samlades. Det är troligt att få en bättre förståelse för instabiliteter som förekommer i den, särskilt av Farley-Buneman instabilitet. För att kunna utnyttja denna mätning korrekt måste inställningen hos de frit-fallande detektorer kallades FFU -Free-Falling Units på engelska- som samlar mätningarna vara välkända. Men återställningsprocessen görs svårare genom en extra wobblingrörelse som gäller för enheterna. Genom att använda rå data från GPS-satelliter och data från tröghetsmätaren och genom att känna till magnetfältets beteende utanför elektrojet kan inställningen hos ett FFU avgöras med en acceptabel nivå av precision. Detta kan sträcka sig till andra veten- skapliga projekt och erbjuda ett billigt alternativ till användningen av stjärn- spårare. Ett nytt flyg till 2019 är planerat för SPIDER-experimentet. Förbättringar av boom-implementeringsenhet -Boom Deployment Unit (BDU) på engelska- un- dersöks så att dess mekanism är robustare, så väl som enklare och snabbare att montera. Att få en bättre förståelse av den genom funktionell analys har hjälpt till att hitta riktningar för förbättringar på pinfrigörningsmekanismen, på lös- ningarna för att säkerställa rotationsstyrningen, avskärmning från vibrationer under uppskjutningen och på anslutningarna mellan mätproberna och elektron- iken för att bearbeta mätförvärv. Ett BDU inklusive de föreslagna ändringarna bör monteras och testas med tanke på att den nya designen ingår i omflyttningen
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Allen, Lucy Ruth. "Free energy landscapes of proteins : combining experimental data with numerical simulation." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507863.
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Ng, Edwin S. B. Massachusetts Institute of Technology. "Experimental designs for efficient free-space multi-spatial-mode optical communication." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83831.
Повний текст джерелаАнотація:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (page 77).
In optical communications, two measures of efficiency are commonly at odds. The first is the photon information efficiency (in bits/photon) which measures the information that each detected photon conveys; the second is the spectral efficiency (in bits/s/Hz) which measures the bit rate achieved under limited bandwidth. One interesting communication protocol which can simultaneously obtain high information efficiency without sacrificing spectral efficiency, however, is spatial pulse-position- modulation (spatial-PPM), in which information is encoded into the spatial modes of light and sent through free space between transmitter and receiver. This thesis aims to lay the groundwork for an experimental design to achieve efficient spatial-PPM free-space optical communication using 1550 nm light at the single photon level. We focus on presenting and evaluating a transmitter-receiver design by giving a precise characterization of its operation, properties, and limitations.
by Edwin Ng.
S.B.
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Wen, Yang. "Experimental and numerical investigations of rotating flows with deformable free surface." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS455.
Повний текст джерелаАнотація:
Ce travail est une contribution à la compréhension des instabilités dans les écoulements tournants à surface libre déformable. La configuration étudiée est un récipient cylindrique partiellement rempli d'eau ou d'un mélange eau-glycérine, et la rotation est créée par un disque tournant situé au fond du récipient. Ce type d'écoulements est le siège de plusieurs familles d'instabilités en fonction des paramètres (nombres de Froude et de Reynolds, rapport de forme). Ces investigations utilisent des simulations stationnaires et instationnaires à l'aide des deux codes maison ROSE et Sunfluidh en conjonction avec des expériences. L'originalité du travail réside dans la simulation numérique d'écoulements diphasiques avec forte déformation de l'interface et grand rapport de densité, dans l'utilisation de mesures d'élévation de la surface et de vitesse par vélocimétrie Laser-Doppler, et dans la validation croisée entre techniques numériques et expérimentales. L'écoulement de base est tout d'abord décrit en détail. Les solutions stationnaires axisymétriques révèlent la structure de l'écoulement tournant: une région centrale en rotation solide et une cellule toroïdale à sa périphérie, cellule dont l'intensité et la géométries sont caractérisées. Quand on considère des nombres de Reynolds suffisamment grands pour que des couches limites se forment aux parois solides, deux couches supplémentaires apparaissent: une couche interne située au bord de la région centrale, et une couche sous la surface libre qui n'a jamais été décrite auparavant. Cette structuration de l'écoulement s'avère robuste vis-à-vis des changements du nombre de Froude. Des simulations tri-dimensionnelles instationnaires révèlent que l'écoulement moyenné en temps et en espace présente de nombreuses similarités avec les solutions stationnaires axisymétriques, et que la surface reste pratiquement plate alors même que de grosses structures issues d'instabilités tridimensionnelles se sont développées au sein du fluide. Cette approche numérique complète corroborée par des mesures expérimentales de la vitesse apporte des clarifications sur la structure de l'écoulement, qui est comparée aux modèles simplifiés de la littérature. La dynamique de spin-up qui résulte de la mise en rotation d’un fluide à partir du repos est étudiée pour deux configurations, le seau de Newton (Newton's bucket) et l'écoulement à fond tournant. L'élévation de la surface et l'évolution de la vitesse déterminées expérimentalement sont en très bon accord avec les simulations instationnaires axisymétriques. Ces résultats pourront servir de référence (benchmark) pour les simulations instationnaires d'écoulements diphasiques en rotation. Finalement, les ondes de surface tri-dimensionnelles de grande amplitude connues sous le nom de polygônes tournants sont étudiées expérimentalement. Ces ondes sont habituellement observées à grand nombre de Reynolds. En les étudiant en régime plus visqueux, on tente d'élucider le lien entre instabilités de volume et de surface. Par analyse spectrale de la déformation de la surface et par des mesures de vitesses, on montre que la vitesse de phase rapportée à la vitesse du disque est proche de 1/3 pour les polygônes tournants, alors qu'elle est proche de 2/3 pour l'instabilité de volumeThis work is a contribution to the understanding of instabilities in rotating flows with deformable free surface. The configuration under study is a cylindrical container partially filled with water or water-glycerin mixture and the rotation is driven by a disk located at the bottom. In such flow, several families of instability patterns can be triggered depending on the flow parameters (Froude and Reynolds numbers and aspect ratio). As a mean of investigation, steady and unsteady simulations are conducted using the two in-house codes ROSE and Sunfluidh, in conjunction with experiments. The novelty lies in two-phase numerical simulations with strongly deformed interface and large density ratio between the phases, in accurate surface height and Laser-Doppler Velocimetry measurements, and in cross validations between numerical and experimental techniques. The base flow is first carefully described. Axisymmetric steady solutions show the structure of the rotating flow: a central solid body rotation and a toroidal flow cell located at the periphery, the intensity and geometry of which are characterized. Focusing on Reynolds numbers large enough so that boundary layers form at solid walls, two additional layers are described: an internal layer at the edge of the central region and a layer under the free surface never reported before. This flow structure is shown to be robust as Froude number is varied. Three-dimensional unsteady simulations reveal that the time and space averaged flow shows many similarities with steady axisymmetric solutions and that the surface remains almost flat even though three-dimensional large structure instabilities have developed in the bulk. Through this full numerical approach corroborated by velocity measurements, the flow structure is thus clarified and compared to the simplified models used in the literature. The transient spin-up dynamics of a fluid from rest are also investigated for two configurations, namely Newton's bucket and the bottom-driven flow. Experimental surface height and velocity evolution are found in very good agreement with axisymmetric unsteady simulations. These results are meant to serve as a benchmark for unsteady rotating two-phase flow simulations. Large amplitude three-dimensional surface deformation waves known as rotating polygons are eventually studied experimentally. These patterns are usually observed at very large Reynolds number. Conducting investigations in more viscous flow regimes, the link between bulk and surface polygon instabilities is tentatively elucidated. Through a spectral analysis of surface deformation and velocity measurements, the phase-velocity to disk speed ratio is found to be close to 1/3 for rotating polygons whereas it is 2/3 for the bulk instability
40
Garcia, de la Cruz Lopez Juan Marcos. "Experimental study of free surface mixing in vortical and chaotic flows." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9007.
Повний текст джерелаАнотація:
The free surface mixing properties of a scalar advected by a quasi-steady or unsteady electromagnetically forced flow are investigated. The scalar statistics are related with the topology of the velocity fields stirring them. The benefits and consequences of topologically folding a scalar to enhance homogenization are discussed, identifying how this process may lead to the attenuation of diffusion in vortical and chaotic flows. A pair of magnets, whose attitude is controlled during the experiment, is employed to generate a wide range of velocity fields in a shallow layer of conductive stratified brine. The simplicity of the system makes it possible to analyze the basic properties of the flows generated, relating them with more complex geometries found in literature. The concentration measurements characterizing the scalar field are based on LIF, for which a novel experimental procedure (including calibration, error management and statistical estimators) is presented. Special attention is paid to the relation between the variance decay rate and the mean gradient square, identifying several mechanisms that reduce the fidelity of Q2D experiments in reproducing some features of the transport equation. Evidence of the scalar spiral range is presented in the wavenumber and physical spaces for particular quasi-steady samples. When required, the system unsteadiness is generated by modifying the body forcing geometry throughout the experiment, producing chaotic advection regardless of the flow Re. The periodic nature of the forcing oscillations leads to an exponential variance decay dominated by a strange eigenmode. It is shown that such a system contains recurring temporal patterns and becomes independent of the scalar initial condition.
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Barbosa, Michele. "Uma abordagem para análise de dados com medidas repetidas utilizando modelos lineares mistos." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/11/11134/tde-14102009-084734/.
Повний текст джерелаАнотація:
No presente trabalho propôs-se uma abordagem simples visando à escolha de um modelo linear misto a ser ajustado a dados com medidas repetidas. A construção do modelo envolveu a escolha dos efeitos aleatórios, dos efeitos fixos e da estrutura de covariâncias utilizando técnicas gráficas e analíticas. O uso do Teste da Razão de Verossimilhança e dos Critérios de Informação de Akaike - AIC e de Schwarz - BIC pode levar a escolhas diferentes da estrutura de covariâncias, o que pode influenciar os resultados das inferências feitas sobre os parâmetros de efeitos fixos. A abordagem foi aplicada a conjuntos de dados resultantes de estudos agropecuários utilizando o software livre R. Foram feitas comparações dos resultados obtidos de modelos implementados com o proc mixed do SAS e com a função lme() do R, observando as vantagens e restrições destes dois softwares.In this present work was proposed a simple approach to know how to choose a linear mixed model that can be adjustable to data with repeated measures. The construction of the model involved the choice of random effects, the fixed effects and covariance structure, using graphical and analytical techniques. The use of the Likelihood Ratio Test and the Akaike Information Criteria - AIC and Schwarz - BIC can lead to different choices of the structure of covariance, which may influence the results of inferences made about the parameters of fixed effects. The approach was applied to data sets that was resulted from farming studies using the software R. Comparisons of the results of models implemented were made with the proc mixed of SAS and with the function lme() of R, noting the advantages and limitations of these two softwares.
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Mahé, Jérôme. "Far infrared/Tera-Hertz spectroscopy in the gas phase : experiments and theory." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLE043/document.
Повний текст джерелаАнотація:
La spectroscopie infrarouge permet d’identifier la structure 3D de systèmes moléculaires, par comparaison des spectres mesurés et simulés. Nous travaillons en phase gazeuse, où les molécules et clusters sont libres d’interactions intermoléculaires. Notre travail combine les expériences IR-UV ion-dip et le calcul de spectres IR anharmoniques par la méthode DFT-MD. Le spectre IR est calculé pour les structures 3D de plus basses énergies,le meilleur accord donnant la connaissance de la structure présente dans les conditions expérimentales.Nous démontrons que le domaine de l’IR lointain/THz (<800 cm-1, <24 THz) permet d’identifier sans ambiguïté la structure 3D de molécules et clusters en phase gazeuse, là ou les signatures du domaine 1000-4000 cm-1 peuvent être limitées. Les systèmes considérés sont des dipeptides, un modèle de feuillet β, dérivés du phénol (et complexés à l’eau) des paires de bases de l’ADN, dont les structures sont bâties sur des liaisons hydrogène intra/intermoléculairesInfrared spectroscopy allows the assignment of three dimensional structures of molecular systems, by comparing experimental and theoretical spectra. Our investigations take place in the gas phase, where molecules and clusters are free of intermolecular interactions.Our work combines experimental IR-UV ion dip spectroscopy and theoretical DFT-MD anharmonic spectroscopy. The infrared spectrum is calculated for low energy 3Dstructures and the best match between theory and experiment provides the information about the structure present in the experimental conditions.We demonstrate for several systems that far infrared/THz spectroscopy (<800 cm-1, <24THz) allows conformational assignment without ambiguities, contrary to the more traditional 1000-4000 cm-1 range. Systems investigated here are dipeptides, a β-sheet model, phenol derivatives (also complexe dwith water molecules), DNA base pairs, all these structures being built on intra-/intermolecular hydrogen bonds
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Seggebrock, Thorben. "Conceptual design of a laser-plasma accelerator driven free-electron laser demonstration experiment." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-184314.
Повний текст джерелаАнотація:
Up to now, short-wavelength free-electron lasers (FEL) have been systems on the scale of hundreds of meters up to multiple kilometers. Due to the advancements in laser-plasma acceleration in the recent years, these accelerators have become a promising candidate for driving a fifth-generation synchrotron light source – a lab-scale free-electron laser.
So far, demonstration experiments have been hindered by the broad energy spread typical for this type of accelerator. This thesis addresses the most important challenges of the conceptual design for a first lab-scale FEL demonstration experiment using analytical considerations as well as simulations.
The broad energy spread reduces the FEL performance directly by weakening the microbunching and indirectly via chromatic emittance growth, caused by the focusing system. Both issues can be mitigated by decompressing the electron bunch in a magnetic chicane, resulting in a sorting by energies. This reduces the local energy spread as well as the local chromatic emittance growth and also lowers performance degradations caused by the short bunch length. Moreover, the energy dependent focus position leads to a focus motion within the bunch, which can be synchronized with the radiation pulse, maximizing the current density in the interaction region. This concept is termed chromatic focus matching. A comparison shows the advantages of the longitudinal decompression concept compared to the alternative approach of transverse dispersion.
When using typical laser-plasma based electron bunches, coherent synchrotron radiation and space-charge contribute in equal measure to the emittance growth during decompression. It is shown that a chicane for this purpose must not be as weak and long as affordable to reduce coherent synchrotron radiation, but that an intermediate length is required.
Furthermore, the interplay of the individual concepts and components is assessed in a start-to-end simulation, confirming the feasibility of the envisioned experiment. Moreover, the setup tolerances for a first demonstration experiment are determined, confirming the general practicability. The revealed challenges, besides the energy spread, especially concern the source stability and the precision of the beam optics setup.
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Bharathula, Ashwini. "Experimental and Computational Investigations of Strain Localization in Metallic Glasses." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282158393.
Повний текст джерела
45
Wohaieb, Saleh A. "Oxygen free radical scavenging systems in clinical and experimental (chemical and spontaneous) diabetes mellitus." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27567.
Повний текст джерелаАнотація:
The extent to which endogenous free radical-scavenging defense mechanisms
are involved in experimental and human diabetes was investigated in various tissues of animals with chemically-induced or spontaneous diabetes (BB Wistar rats) and in erythrocytes of patients with either Type I or Type II diabetes. Diabetes was induced in female Wistar rats using alloxan (ALX) or streptozotocin (STZ), each administered in a dose of 50 mg/kg body wt., intravenously. The present study also included a group -of animals in which body wt. loss was induced by food-deprivation for 72 h. The effects of pharmacological interventions (insulin or allopurinol (ALP)), on these processes were also investigated in chemically-induced diabetes., The activities
of catalase (CAT), CuZn-superoxide dismutase (CuZn-SOD), glutathione peroxidase (GSH-PX) and glutathione reductase (GSSG-RD) as well as levels of reduced glutathione (GSH) were examined in heart, pancreas, liver and kidney as well as in erythrocytes. Erythrocytes were also examined for their susceptibility
to in vitro oxidative stress induced by hydrogen peroxide (H₂0₂). Criteria studied in this regard were GSH-depletion and malondi-aldehyde (MDA) production (an index of lipid peroxidation).
The results obtained showed that tissue antioxidant systems are altered in experimental diabetes and that the magnitude of the alterations increased with the degree of body weight loss. Furthermore, the duration of hypoinsulinemia might contribute to the nature of alterations in antioxidant mechanisms. The complex patterns of the alterations observed varied from one tissue to another and may be the result of compensatory increases, usually involving enzymes whose activity in the particular tissue may be limiting, and direct inhibitory effects of endogenous oxidants on the enzymatic
components of tissue antioxidant systems.
The ability of insulin (9-12 U/kg body wt., subcutaneously) to reverse the many similar alterations of tissue antioxidant enzymes in diabetes induced by either STZ or ALX suggests that these changes are more likely attributable to hypoinsulinemia rather than to direct effects of either diabetogenic drug. The above-mentioned effects indicate that insulin can markedly influence tissue antioxidant status. However, the reason for the persistence of decreased CuZn-SOD activity in both liver and kidney of ALX-diabetic rats after 12 wk of treatment with insulin is not clear at present, and requires further investigation to determine whether this reflects the presence of a residual deficit in tissue antioxidant processes in liver and kidney despite insulin treatment, or whether it is the result of a direct effect exerted by ALX. Acute ALP administration (50 mg/kg body wt., intraperitoneally) was associated with reductions in ketonuria and early mortality among ALX-diabetic rats, and long-term ALP treatment (1.9 mg/day in drinking water) resulted in a normalization of renal CuZn-SOD activity in these animals.
Comparable (although not identical) changes in tissue antioxidant status are present in insulin-dependent spontaneously diabetic BB (ISDBB) rats and in animals made diabetic by STZ or ALX administration. Our data also demonstate that the alterations in tissue GSH levels characterizing ALX-diabetes more closely paralleled changes seen in the ISDBB rat than did those in the diabetic state induced by STZ. If the alterations in antioxidant
status in uncontrolled chemically-induced diabetes are attributable to a lack of insulin, the observed changes in ISDBB rats are suggestive of sub-optimal insulin therapy in these animals.
The results obtained from BB rats demonstrate two types of alterations in antioxidant status: strain-related differences (increased CAT activity in pancreas and decreased GSH levels in pancreas and liver of both ISDBB and their non-diabetic littermates (NDLM)) and diabetes-related changes (mani- fested by an increase in cardiac GSH content and increases in activities of cardiac CAT and GSSG-RD, pancreatic CuZn-SOD and GSSG-RD, and renal GSH-PX). Whether or not these "strain-related" alterations in antioxidant status increase the susceptibility of these animals to developing diabetes remains unknown.
Certain alterations were observed in red cells from diabetic patients and from animals with experimental diabetes suggesting that these alterations
are more likely to be diabetes-related than species-dependent. Red cells in chemically-induced and clinical diabetes showed an increased resistance
to peroxide-induced depletion of GSH, an effect attributed to hyperglycemia,
which results in an increased supply of NADPH through the hexose monophosphate shunt for regeneration of GSH from GSSG via the GSSG-RD system. However, the susceptibility of red cells from diabetic patients and animals to lipid peroxidative damage was increased as reflected in augmented MDA production. In addition, insulin treatment did not normalize MDA production in red cells subjected to oxidative challenge and vigorous insulin treatment in both ALX- and STZ-diabetic rats resulted in a markedly decreased MDA production in response to H₂0₂. Moreover, GSSG-RD activity
of red cells was increased in both uncontrolled and insulin-treated diabetic animals as well as in diabetic patients.
However, some differences in erythrocyte antioxidant enzymes were also observed in erythrocytes from diabetic subjects and animals. For example, diabetic patients showed an increased activity of CuZn-SOD, while erythrocytes
from diabetic animals showed no alterations in the activity of this enzyme. Erythrocyte membrane NADH-dehydrogenase activity was increased only in diabetic patients with Type I diabetes, but not in Type II diabetes or in diabetic animals. Erythrocytes from ALX- and STZ-diabetic animals showed an increase in the activity of GSH-PX and those from NDLM BB rats showed a decrease in CAT activity, alterations that were not observed in human diabetes.
Finally, as far as antioxidant defense mechanisms are concerned, our results suggest that diabetes is associated with some common alterations in these mechanisms regardless of the model (chemically-induced versus the spontaneous type of diabetes) or the species used (animal versus human diabetes). Some of these alterations seem to be influenced by the degree of diabetic control, while others are apparently independent of it. Future studies will focus on the extent to which alterations in red cells of human diabetics can be used to predict the development of long-term sequelae of the disease.Medicine, Faculty of
Anesthesiology, Pharmacology and Therapeutics, Department of
Graduate
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Zambrano, Cruzatty Luis Eduardo. "Advancements for the Numerical Simulation of Free Fall Penetrometers and the Analysis of Wind Erosion of Sands." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/104861.
Повний текст джерелаАнотація:
The coastal population is growing, putting extra stress on coastal sediments and protection features, such as beach dunes. Moreover, global warming will increase the frequency of storms, and coastal dunes and other defense infrastructure will be subjected to increased erosion and scouring, endangering the people they are meant to protect. Understanding soil dynamics and fluid interaction is crucial to predict the effects of sand erosion. In particular, the study of wind erosion of sands in coastal dunes is essential due to the protective role these earthen structures have during storm events.
One of the challenges about predicting wind erosion in coastal dunes is its extended spatial scale and the associated economic and logistics costs of sampling and characterizing the sediments. Because of this, in-situ testing for sediment characterization is essential. In particular, the usage of free-fall penetrometers (FFP) is appealing due to their portability and robustness. The sediment properties obtained with this type of testing can later be used to assess wind erosion susceptibility by determining, for example, the wind velocity to initiate the erosion process.
FFP testing involves dropping an instrumented probe that impacts the soil and measures the kinematics or kinetics during the penetration process. For example, deceleration measurements are used to compute an equivalent quasi-static failure, which is not in line with the dynamic process characteristic of FFP testing. This preassumed failure mechanism is used to back-calculate the sand's geomechanical properties. However, soil behavior is highly complex under rapid loading, and incorporating this behavior into FFP sediment characterization models is challenging. Advanced numerical modeling can improve the understanding of the physics behind FFP testing.
This thesis presents various advancements in numerical modeling and erosion models to bridge FFP in-situ testing with predicting the initiation of wind erosion of sands. First, improvements oriented to the Material Point Method (MPM) for modeling in-situ FFP testing are proposed. The numerical results show that the simulation of FFP deployment in sands is affected by strain localization and highlight the importance of considering constitutive models sensitive to different loading rates. Because of the importance of rate effects in soil behavior, the second aspect of this thesis proposes a novel consistency framework. Two constitutive models are adapted to study strain-rate sensitive non-cohesive materials: i) a strain-softening Mohr-Coulomb, and ii) a NorSand model. In addition to increased strength, the proposed framework captures increased dilatation, an early peak deviatoric stress, and relaxation.
Finally, a novel sand erosion model is derived using a continuum approximation and limit equilibrium analysis. The erosion law considers geotechnical parameters, the effects of slope, and moisture suction, in a combined manner. The proposed model is theoretically consistent with existing expressions in the literature. It covers a wide range of environmental and geometrical conditions and helps to reconcile the results from FFP testing with the prediction of the initiation of wind erosion. The model was validated in a wind tunnel and is demonstrated to be a viable alternative for predicting sand erosion initiation.
This thesis opens up new research prospects, such as improving the soil characterization models or the direct prediction of sand erosion using rapid, reliable, and efficient in-situ testing methods.Doctor of Philosophy
With global warming and climate change, it is expected that the frequency and intensity of storms will increase. This increment will put extra stress on coastal sediments such as beach sand and coastal dunes, making them prone to erosion. Coastal dunes lose their ability to withstand storms as they erode, potentially making coastal flooding more frequent. In light of this, all stakeholders involved in the protection against coastal disasters must have the tools to predict, prepare for, and mitigate for situations like the ones stated above. An essential aspect of the prediction component is dependent on a successful sediment characterization, for example, determining how much wind the sand can withstand before it erodes. Free-fall penetrometers (FFP) are devices designed to conduct the characterization mentioned above. However, the procedures used to perform this characterization are mainly based on empirical or semi-empirical expressions. Computer models, capable of simulating the physics behind FFP testing, can bring more insight into the process of interaction between FFP devices, sands, and water and can be the basis to improve the characterization methods. The latter results can be utilized for instance to predict wind erosion, including several properties of the sand, such as its mineralogy and shape. This study contributes to developing the computer simulations of FFP deployment and the wind erosion prediction models. Eventually, these developments can help engineers and coastal managers to anticipate and prepare for more frequent coastal hazards.
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Badam, Vijay Kumar. "Experimental and theoretical investigations of the evaporation of fluids from free surfaces." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=984903402.
Повний текст джерела
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Rana, Md Ruhul Amin. "Numerical and experimental study of orientation dependency of free convection heat sinks." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52716.
Повний текст джерелаАнотація:
The flow momentum in free convection heat transfer is generally lower than forced convection, and the flow direction is determined by the gravitational direction. Hence, the thermal performance of heat sinks relying on free convection could vary significantly depending on the mounting orientation. This is confirmed by the present work, a computational fluid dynamics and heat transfer study with focus on the relation between the design of heat sinks and their thermal performance under varied mounting orientations. A heat sink with rectangular straight fins, a very commonly used type of heat sink, is first studied. The results show poor thermal performance when the heat sink is placed vertically and fin length horizontally to the ground. The fluid dynamics analysis indicates interruption of buoyancy flow by the horizontally placed fins, which in turn impedes heat transfer. An experimental work on straight fin heat sink is also performed, and with the help of infrared camera and thermocouples the orientation dependencies are observed for a wide range of orientation angles. In order to minimize the negative effect of mounting orientations, two other types of heat sinks are studied. One is angled-fin heat sink, which has plate fins parallel to the diagonal rather than the side of the heat sink base. The other type is pin-fin heat sinks. The two types of heat sinks are shown to provide similar thermal performances for both horizontal and vertical orientations, and the low orientation dependency is attributed to the low orientation effect on the buoyancy flow. The fin thickness, fin spacing and number of fins are varied for both the heat sinks. The purpose is to study the effect of these changes on thermal performance for different mounting orientations. For angled-fin, the effects of fin interruptions are also studied, where horizontal orientation shows better cooling performance than the vertical. In case of pin fin heat sink, the temperature differences between the vertical and horizontal orientations show that, the fin spacing plays an important role in the selection of mounting orientation. This study is useful for designing free convection heat sinks for orientation-independent cooling performance.Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate
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Donnelly, Martin John. "An Experimental Investigation of Spanwise Vortices Interacting with Solid and Free Surfaces." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28130.
Повний текст джерелаАнотація:
Coherent vortices are generated in flow fields due to flow interaction with sharp solid surfaces. Such vortices generate significant disturbances in the flow and affect its further development. In this dissertation attention is focused on the interaction of vortices with solid or free liquid/air surfaces. We examine vortices with their axis parallel or normal to the surface. Three main cases were examined: the interaction of a vortex pair propagating towards a solid boundary, the interaction of spanwise vortices in a turbulent boundary layer, and finally the interaction of spanwise vortices with a flat-plate wake and a free liquid surface. These problems hold significance in several engineering applications, including investigations into trailing wing tip vortices and their interaction with the ground, vortical effects on the development of turbulent boundary layers and free surface signatures and their detection in ship/submarine wakes. Data are acquired with a laser Doppler velocimetry system (LDV) and with Particle-Image Velocimetry (PIV), using a high-speed digital video camera. The LDV system measures two components of velocity along appropriately chosen planes. Grids of data were acquired for different pitch rates of a disturbing flap that generates vortices. Phase-averaged vorticity and turbulence level contours are estimated and presented. It is found that vortices with diameter the order of the boundary layer quickly diffuse and disappear while their turbulent kinetic energy spreads uniformly across the entire boundary layer. Larger vortices have a considerably longer life span and in turn feed more vorticity into the boundary layer. Trailing edge vortices are generated in a water tunnel by sharp hinged motions of a flap. These vortices are allowed to reconnect with the free surface and mix with a turbulent free shear layer. The flow is conditionally sampled via frame grabbing of free surface shadowgraphs. It is found that the vortex core bends away from the plane of the shear layer. Moreover, contrary to earlier findings, organized velocity fluctuations decrease as the free surface is approached.Ph. D.
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Leonard, James W. Jr. "Replacing indirect manual assistive solutions with hands-free, direct selection." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1309282777.
Повний текст джерела