Thèses sur le sujet « ELECTRIC RESONANCE »
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Neff, Joseph Daniel. « Controlled stochastic resonance and nonlinear electronic circuits ». Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/30476.
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ARDUINO, ALESSANDRO. « Mathematical methods for magnetic resonance based electric properties tomography ». Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2698325.
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Magnetic resonance-based electric properties tomography (MREPT) is a recent quantitative imaging technique that could provide useful additional information to the results of magnetic resonance imaging (MRI) examinations. Precisely, MREPT is a collective name that gathers all the techniques that elaborate the radiofrequency (RF) magnetic field B1 generated and measured by a MRI scanner in order to map the electric properties inside a human body. The range of uses of MREPT in clinical oncology, patient-specific treatment planning and MRI safety motivates the increasing scientific interest in its development. The main advantage of MREPT with respect to other techniques for electric properties imaging is the knowledge of the input field inside the examined body, which guarantees the possibility of achieving high-resolution. On the other hand, MREPT techniques rely on just the incomplete information that MRI scanners can measure of the RF magnetic field, typically limited to the transmit sensitivity B1+.
In this thesis, the state of art is described in detail by analysing the whole bibliography of MREPT, started few years ago but already rich of contents. With reference to the advantages and drawbacks of each technique proposed for MREPT, the particular implementation based on the contrast source inversion method is selected as the most promising approach for MRI safety applications and is denoted by the symbol csiEPT. Motivated by this observation, a substantial part of the thesis is devoted to a thoroughly study of csiEPT. Precisely, a generalised framework based on a functional point of view is proposed for its implementation. In this way, it is possible to adapt csiEPT to various physical situations. In particular, an original formulation, specifically developed to take into account the effects of the conductive shield always employed in RF coils, shows how an accurate modelling of the measurement system leads to more precise estimations of the electric properties. In addition, a preliminary study for the uncertainty assessment of csiEPT, an imperative requirement in order to make the method reliable for in vivo applications, is performed. The uncertainty propagation through csiEPT is studied using the Monte Carlo method as prescribed by the Supplement 1 to GUM (Guide to the expression of Uncertainty in Measurement). The robustness of the method when measurements are performed by multi-channel TEM coils for parallel transmission confirms the eligibility of csiEPT for MRI safety applications.
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Aydin, Ahmet. « Application of electric potential sensors in nuclear Magnetic resonance signal acquisition ». Thesis, University of Sussex, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536554.
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Hsu, Fang-Chi. « Electric field effect in "metallic" polymers ». Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127229727.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xxi, 177 p.; also includes graphics (some col.). Includes bibliographical references (p. 167-177). Available online via OhioLINK's ETD Center
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Cheng, Mao-Sen. « Molecular beam electric resonance spectroscopy of CO-SO₂ and Kr-SO₂ complexes / ». view abstract or download file of text, 2000. http://wwwlib.umi.com/cr/uoregon/fullcit?p9998027.
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Thesis (Ph. D.)--University of Oregon, 2000.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 110-113). Also available for download via the World Wide Web; free to University of Oregon users.
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Bolton, David Robert. « Circuits and systems for CW and pulsed high-field electron spin resonance ». Thesis, University of St Andrews, 2006. http://hdl.handle.net/10023/7104.
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This thesis is concerned with the design and realisation of components for a new state of the art 94GHz Electron Spin Resonance (ESR) spectrometer capable of operating in both pulsed and CW modes. The complete spectrometer is designed to provide phase coherent 1kW peak power sub-nanosecond π/2 pulses having variable duration and repetition rate. The mm-wave response of a paramagnetic sample to these pulses is detected with a superheterodyne detector. Such a system would offer a step change in performance, promising unprecedented resolution and sensitivity. These aims should be compared with the performance of commercial (Bruker) instruments capable of delivering 200mW 30ns π/2 pulses. For this type of system, both the long term (thermal) and short term (phase) stability of oscillators and sources employed are extremely important. Consideration of phase noise, frequency, tunability and power output shows that multiplied sources offer substantial benefits compared to fundamental sources. A delay line discriminator method of phase noise measurement, suitable for use with the low frequency oscillators is described and implemented. This is extended to 94GHz using a down convertor with a quasi-optically stabilised Gunn oscillator. These tools are used to select an optimum oscillator-multiplier combination to produce a low noise 94GHz source. Anew method of pulse generation, which has produced +23dBm peak power 250ps rectangular and 115ps Gaussian envelope phase coherent pulses, is described. These are believed to be the shortest phase coherent pulses at 94GHz available. This system will be used to provide ns pulses suitable for amplification to 1kW using a Klystron amplifier. A heterodyne detector has been constructed which employs the same oscillator/multiplier techniques identified above to produce the required local oscillator signal. It is demonstrated that by careful consideration of multiplication factors a system employing one variable and one fixed oscillator allows all the signals required in the spectrometer to maintain phase coherence. It is demonstrated that the complete demodulator responds to pulses on a ns time scale and has a noise temperature of 737K.
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Goulding, Philip. « The use of electric potential sensors in nuclear magnetic resonance and particle detection applications ». Thesis, University of Sussex, 2015. http://sro.sussex.ac.uk/id/eprint/57919/.
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The work in this thesis extends the applications of the Electric Potential Sensor (EPS) designed by the Sensor Research Technology Centre. Combined is work undertaken in two areas related by their application in security systems: low-field nuclear magnetic resonance with electric-field acquisition, and particle detection for alpha, beta and neutron radiation. In both these areas the EPS is used as to acquire signals. The first half of the thesis consists of the work undertaken to design a low-field Nuclear Magnetic Resonance spectrometer to detect drugs and explosives. In doing so, the use of the electric field detection technique - patented by Sussex University - is extended to low-field NMR work. The eventual negative results in this field lead first to the design of a simpler proton magnetometer apparatus, a design which would confirm the use of the EPS at low frequencies, and eventually to a change in direction of the research: particle detection. Detailed in this first section are a theoretical explanation of NMR in chapter 2, and a chapter covering the design and testing of the equipment in chapter 3. The particle detection part of the thesis covers modifications made to the EPS in order to detect particles and experiments conducted to confirm their operation. As in the NMR section, the work is split into a theory chapter which underpins the work, providing context for the experiments chapter. Chapter 5 covers the detection of alpha, beta and neutron radiation and the use of feedback to control the RC time constant of the front end of the sensor. The work in this thesis concludes negative results in the NMR area, but proves the EPS particle detector as a viable, cost effective alternative to conventional detectors.
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Mukherjee, Shrijit. « Broadband electric field sensing and its application to material characterisation and nuclear quadrupole resonance ». Thesis, University of Sussex, 2012. http://sro.sussex.ac.uk/id/eprint/7666/.
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The aim of this project is to address the challenges associated with extending the radio frequency capability of Electric Potential Sensors to greater than 10 MHz. This has culminated in a single broadband sensor, with a frequency range of 200 Hz to greater than 200 MHz. The use of Electric Potential Sensors for the measurement of electric field with minimal perturbation has already been demonstrated at Sussex. These high impedance sensors have been successfully employed in measuring signals with frequencies in the range 1 mHz to 2 MHz. Many different versions of these sensors have been produced to cater for specific measurement requirements in a wide variety of experimental situations. From the point of view of this project, the relevant prior work is the acquisition of a 2 MHz electric field nuclear magnetic resonance signal, and the non-destructive testing of composite materials at audio frequency. Two very distinct electric field measurement scenarios are described which illustrate the diverse capabilities of the broadband sensor. Firstly, an electric field readout system for nuclear quadrupole resonance is demonstrated for the first time, with a sodium chlorate sample at a frequency of 30 MHz. Nuclear quadrupole resonance is an important technique with applications in the detection of explosives and narcotics. Unlike nuclear magnetic resonance a large magnet is not required, opening up the possibility of portable equipment. The electric field readout system is shown to be simpler than the conventional magnetic readout and may therefore contribute to the development of portable devices. Secondly, a broadband, high spatial resolution microscope system for materials characterisation with four different imaging modes is described. This includes; the surface topography of a conducting sample; the dielectric constant variation in glass/epoxy composite; the conductivity variation in a carbon fibre composite; and the electrode pixels inside a solid state CMOS fingerprint sensor.
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Adamov, Minja Gemisic. « Measurements of local electric fields by doppler-free laser spectroscopy of hydrogen resonance lines ». Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15576.
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In dieser Arbeit wurde eine einfache laserspektroskopische Messmethode für lokale elektrische Feldstärken im Hinblick auf ihre Messmöglichkeiten und -grenzen untersucht. Als empfindliche optische Feldsensoren dienen dabei Wasserstoffatome, für die die Stark-Aufspaltung der Spektrallinien im elektrischen Feld wohl bekannt und exakt berechenbar ist. Die experimentellen Untersuchungen wurden an einer Niederdruck-Gaszelle durchgeführt, in der ein elektrisch geheizter Wolframdraht für thermische Dissoziation von Wasserstoffmolekülen sorgte. Die Wasserstoffatome wurden durch zwei gegenläufige Laserstrahlen Doppler-frei angeregt. Die Durchstimmung der schmalbandigen Laserstrahlung über den Wellenlängenbereich der Zwei-Photonen-Resonanz lieferte direkt das vom elektrischen Feld hervorgerufene Stark-Spektrum des angeregten Zustands. Weil die Methode im Gegensatz zu ähnlichen, erheblich aufwendigeren Verfahren nur die niedrigsten Wasserstoff-Energieniveaus benutzt, die mit Zwei-Photonen-Anregung direkt aus dem Grundzustand erreichbar sind, kommt sie mit einem einzigen Laser aus. Für das erste angeregte Niveau mit n = 2 wird Strahlung bei 243 nm benötigt, das nächsthöhere Niveau mit n = 3 erfordert 205 nm. Für n = 2 wurden Untersuchungen an Wasserstoff und Deuterium durchgeführt und Stark-Spektren mittels optogalvanischer Detektion gemessen. Schwerpunkt der Arbeit waren aber die Messungen an Wasserstoff für n = 3, bei denen zusätzlich Balmer-alpha-Fluoreszenz im Sichtbaren zur Detektion eingesetzt werden konnte. Bei elektrischen Feldern bis 200 V/cm wurden Stark-Spektren für drei verschiedene Polarisationszustände der Laserstrahlung aufgenommen. Als Ergebnis konnte jeweils ein Paar isolierter Stark-Komponenten in den Spektren identifiziert werden, dessen gut messbarer Frequenzabstand durch Vergleich mit theoretischen Werten die Bestimmung der elektrischen Feldstärke ermöglicht.A method for electric field measurements that observes the Stark spectra of the low excited levels n = 2 and n = 3 of atomic hydrogen has been explored in this work. As advantage these levels can be excited Doppler-free from the ground state by a single laser and the highly resolved Stark spectra are easy to understand and to be calculated. Good sensitivity of electric field measurements is achieved with specially designed solid state laser systems, which provide tuneable pulsed UV radiation with a high pulse peak-power and a narrow bandwidth needed for Doppler-free two-photon excitation. Using hydrogen and deuterium the Stark spectra of the n = 2 level are detected as optogalvanic signal. For three different cases of laser polarization the n = 3 spectra of hydrogen are measured simultaneously with optogalvanic and laser induced Balmer alpha fluorescence detection. Electric fields down to 200 V/cm can be determined from the Stark spectra of n = 2 level, while the spectra of n = 3 level enable measurements of electric fields as small as 50 V/cm in each of the three cases of laser polarization.
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Kurimura, Tomo. « Driving micro-scale object by a dc electric field ». 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215288.
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Stefan, Anca Irina. « Modeling and design of resonators for electron paramagnetic resonance imaging and ultra high field magnetic resonance imaging ». Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1133293403.
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SWANSON, DALE DORSETT. « ELECTROCHEMICAL AND SPECTROSCOPIC STUDIES OF THIOETHER COORDINATION COMPLEXES (CYCLIC VOLTAMMETRY, OCTAHEDRAL LOW-SPIN METALS, BLUE COPPER PROTEINS, ELECTRON PARAMAGNETIC RESONANCE) ». Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188102.
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The bis 1,4,7-trithiacyclononane (1,4,7-TTCN) complexes of iron, cobalt, nickel and copper are reported in this work. Their properties have been examined using computer-controlled electrochemical and spectroscopic techniques. These TTCN complexes form readily, are unusually symmetrical and support electron transfer reactions at the metal center. The cobalt(II) complex is octahedral, low spin and symmetrical. Four oxidation states of cobalt-TTCN complex are observed; two one-electron transfer processes are reversible. Copper (II) bis 1,4,7-TTCN is unusually symmetrical evidenced by both solid phase and ambient temperature aqueous phase electron paramagnetic resonance spectra. An unusually high redox potential for the copper complex indicates extraordinary stability of the Cu(I) oxidation state but evidently not at the expense of Cu(II) stability. The complex also has a high formation constant compared to other copper-thioether complexes. This unusual strength of thioether donor is attributed to ligand geometry. The 1,4,7-TTCN molecule is the only known cyclic polythioether to have all sulfur atoms endodentate. This structure contributes to thermodynamic stability of complexes as the ground state configuration of the free ligand is maintained in the complex.
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Yigitler, Huseyin. « Permanent Magnet Design And Image Reconstruction Algorithm For Magnetic Resonance Imaging In Inhomogeneous Magnetic Fields ». Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607627/index.pdf.
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Recently, the use of permanent magnets as magnetic field sources in biomedical applications has become widespread. However, usage of permanent magnets in magnetic resonance imaging (MRI) is limited due to their inhomogeneous magnetic field distributions. In this thesis, shape and geometry optimization of a magnet is performed. Moreover, placement of more than one magnet is optimized to obtain desired magnetic field distribution in specific region of space. However, obtained magnetic field distribution can not be used in the conventional MRI image reconstruction techniques. Consequently, an image reconstruction technique for MRI in inhomogeneous magnetic fields is developed. Apart from these, since any reconstruction technique requires signal data, an MRI simulator in inhomogeneous magnetic fields is constructed as a part of this thesis. Obtained results show that the theory developed in this thesis is valid. Consequently, new MRI devices that have permanent magnets as magnetic field sources can be constructed in the future.
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Zheng, Shengmei. « Circular microresonator cross-connect filters and hexagonal microresonator add-drop filters in silicon nitride / ». View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20ZHENG.
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Xu, Fang. « Silicon cross-connect filters and switches using microring resonator coupled multimode-interference-based waveguide crossings / ». View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20XU.
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Egidi, Franco. « Theoretical models for the calculation of electric properties and raman spectra of molecules in solution ». Doctoral thesis, Scuola Normale Superiore, 2014. http://hdl.handle.net/11384/85800.
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Gölén, Jakob, et Simon Persson. « "Resonance frequency, Q-factor, coupling of a cylindrical cavity and the effect on graphite from an alternating electric field" ». Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444033.
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The purpose of this project was to investigate a cylindrical cavity resonator and use microwaves to heat up a material in the cavity. This was done by measuring the Q-factor and the resonance frequency of the cavity, both with and without material inside. The chosen material was graphite, and more accurate measurements were done with that specific material. A program called QZero was used to export the Q-factor and the resonance frequency from the measurement data received from a VNA and the program also gave error estimations. Then electromagnetic simulations were done using Comsol. Both an empty cavity and a cavity where graphite has been inserted were simulated and the results were compared to the actual measurements. To measure temperatures inside the cavity, a pyrometer was to be used. The cavity resonator has small circular holes through the side, and a frame was designed and produced using a 3D-printer in order to lock the pyrometer in place in front of one of the holes. A power supply was also installed to the pyrometer. In order to send microwaves into the cavity, a signal generator was used. It was connected to an amplifier and the amplification as well as the efficiency was noted. The pyrometer could only measure temperatures above 490 $\degree$C. This was not achieved, so a handheld electrical thermometer was used. The temperature of the graphite was measured and then compared to how hot the graphite would be without heat loss. For the empty cavity, a Q-factor of 3200 for the resonance frequency of around 2.4 GHz was measured, which matched the simulated measurements in Comsol. When graphite was inserted to the cavity, the Q-factor lowered to 300 in the real experiment. A discrepancy was found between the actual measurements, and the Comsol simulations in which the graphite only lowered the Q-factor to 2570. The reason for this is believed to be either with an error to how the material was chosen in Comsol, since there were many types of graphite to select with many settings to change. Another reason could be an error with the setup itself due to the sheer complexity of the program.Syftet med detta projekt är att undersöka en cylindrisk kavitet samt att använda mikrovågor för att värma upp ett material i kaviteten. Detta gjordes genom att mäta kavitetens Q-faktor och resonansfrekvens med och utan material. Sedan valdes grafit ut som det materialet som skulle testas och mer noggranna mätningar gjordes på just det materialet, och programmet QZero användes för att få ut mer noggrann data samt gav en felmarginal på Q-faktorn. Efter det gjordes simuleringar i programmet Comsol av kaviteten med och utan grafit och jämfördes med de faktiska värdena. För att mäta temperatur av materialet i kaviteten designades en hållare som en pyrometer skulle fästas vid och riktas mot materialet i kaviteten. Även en strömförsörjning till pyrometern installerades. För att skicka in mikrovågor i kaviteten användes en signalgenerator som var kopplad till en förstärkare. Förstärkningen mättes och förstärkarens effekt noterades. I slutändan nåddes inte de temperaturer som krävdes för pyrometern, så en elektrisk termometer användes för att mäta temperaturen på grafiten och detta jämfördes sedan mot den energin som absorberades av grafiten, då energin tillförd till grafiten och grafitens specifika värmekapacitet var känt. Prestandan av experimentuppställningen undersöktes också. For den tomma kaviteten mättes en Q-faktor på 3200 och resonansfrekvensen var 2.4 GHz. Detta stämde bra överens med simuleringarna i Comsol. När grafit fördes in i kaviteten sänktes Q-faktorn till 300. En avvikelse upptäcktes mellan de faktiska mätningarna och simuleringarna. I simuleringen sänktes Q-faktorn bara till 2570, en andledning till detta tros vara antingen vara hur materialet valdes, då det fanns olika typer av grafit med olika inställningar att välja mellan i Comsol. En annan felkälla kan vara något fel med uppställningen på grund af hur avancerat Comsol var. I värmeexperimentet hade förstärkaren en låg verkningsgrad vilket ledde till överhettning om för stor effekt användes. Experimentet begränsades därför till att använda upp till två watt. Vid exponerig under 30 sekunder värmdes grafiten upp till 100-150$\degree$C, vilket var avsevärt lägre än den teoretiska uppvärmingen till 1700$\degree$ beräknad från energin tillförd till grafiten. Antagandet är att temperaturen hamnade i ett jämnviktsläge kring 100-200$\degree$C eller att resonansfrekvensen ändrades vilket ledde till en minskning av energi tillförd till grafiten.
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Foster, David H. « Fabry-Perot and Whispering Gallery Modes In Realistic Resonator Models ». Thesis, view abstract or download file of text, 2006. http://wwwlib.umi.com/cr/uoregon/fullcit?p3211216.
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Thesis (Ph. D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 204-213). Also available for download via the World Wide Web; free to University of Oregon users.
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Hon, Kam Yan. « Surface plasmon resonance-assisted coupling to whispering-gallery modes in micropillar resonators and silicon microdisk-based depletion-type modulators using integrated schottky diodes / ». View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20HON.
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Ferdoush, Md Asif. « System Stability of the Overhead Power Supply System used in the Electric Road System ». Thesis, Scania CV AB, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-399815.
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This thesis presents the stability analysis of an Electric Road System (ERS), which is often abbreviated as eHighway, used for the electrification of the hybrid vehicle. The overall system modelling of the ERS, starting from the sub-station to the critical part of the Scania hybrid truck is performed in the MATLAB Simulink environment. The ERS consists of an overhead catenary line (OCL), where vehicles are electrified by using a pantograph mounted over the vehicle. The stability analysis of the power supply of the overhead line is done by taking into account several aspects of the system. The simulation results are validated with the real test track measurements and the deviations are shown. The frequency response of the system is considered to measure the stability margin. The resonance conditions are clarified and essential variable choke is proposed to damp them out. Also the harmonic components injected from the vehicle side, that are in the closer range of the resonance, are figured out and filtered. When multiple vehicles are electrified from the same catenary line, then there are interferences in between the vehicles. These disturbances both to the vehicles and the overhead power supply system are presented in the time domain. Finally, the results are shown to demonstrate the effectiveness of the variable choke to increase the stability margin in the overhead supply system. In the frequency domain results, it has shown that the resonance is shifted out of the system operating frequency. In the time domain results, it has shown that the high amplitude of the current and voltage signals are sufficiently damped out by variable choke implementation.
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Otto, E., S. Rubbert et J. Borrmeister. « Thermodynamics and charge exchange of the new BMW six-cylinder engine ». Sage, 2000. https://publish.fid-move.qucosa.de/id/qucosa%3A38437.
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The BMW in-line six-cylinder engine has been modified and introduced to production in the new BMW 3 Series model. Its major features include variable intake and exhaust camshaft timing, a new induction system with resonance charging, a turbulence-generating system in the intake ports and a new exhaust system with two closed-loop, coupled catalysts integrated into the exhaust manifold. The cam timing of both camshafts can be adjusted continuously within a range of 40° crank angle (CA) for the inlet cams and 25° CA for the exhaust cams. The turbulence-generating system supplies combustion air to the engine during part load operation and produces the necessary charge motion to run the engine with greater valve overlap at low loads and speeds. Its combination with variable camshaft timing results in lower fuel consumption and exhaust emissions that meet the LEV emission standard. In addition, the variable cam timing raises the torque curve of the unthrottled engine, particularly at low engine speed. The maximum values for torque and power output are unchanged, but maximum torque is reached 500 r/min earlier than with the previous engine.
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Tobgay, Sonam. « Novel concepts for RF surface coils with integrated receivers ». Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0419104-141545.
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Herwald, Marc A. « Control Design and Analysis of an Advanced Induction Motor Electric Vehicle Drive ». Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/32934.
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This thesis is about the development and performance enhancement of an induction motor electric vehicle drive system. The fundamental operation of the induction motor drive hardware and control software are introduced, and the different modulation techniques tested are described. A software simulation package is developed to assist in the control design and analysis of the drive system. Next, to establish the efficiency gains obtained by using space vector modulation in the improved drive system, an inverter with hysteresis current control is compared to the same inverter with space vector modulation in steady state and on separate driving profiles. A method for determining induction motor harmonic losses is introduced and is based on obtaining the phase current harmonics from sampled induction motor stator phase currents obtained. Using a semi-empirical loss model, the induction motor losses are compared between different pulse width modulation control strategies throughout the torque versus speed operating region. Next, several issues related to the robustness of the control design are addressed. To obtain good performance in the actual vehicle, a new method for driveline resonance compensation is developed and proven to work well through simulation and experiment. Lastly, this thesis discusses the development of a new method to compensate for the gain and phase error obtained in the feedback of the d-axis and q-axis stator flux linkages. Improved accuracy of the measured stator flux linkages will be shown to improve the field oriented controller by obtaining a more accurate measurement of the feedback electromagnetic torque.Master of Science
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Zamodzki, Rafael. « Investigação da estabilidade e da qualidade de energia no ponto de conexão de um inversor trifásico com filtro LCL operando de forma conectada ou ilhada sujeito a variações de carga ». Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2356.
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CAPES; CNPq; Fundação AraucáriaA operação de unidades de geração distribuída (UGDs) é um assunto relativamente novo no cenário energético brasileiro. A conexão destas unidades à rede, bem como sua desconexão vêm sendo abordadas em pesquisas recentes em todo o mundo. É necessário que a energia elétrica entregue à rede e à carga tenha certos níveis de qualidade para que o consumidor seja devidamente atendido até mesmo em situações de contingência. Outro cuidado necessário é com relação aos sistemas de controle envolvidos, para que operem sem degradar a qualidade de energia. Neste sentido, este trabalho propõe a análise da estabilidade e da qualidade de energia no ponto de conexão de uma unidade de geração distribuída à rede e a carga ou apenas à carga, sendo ambas situações através de filtro LCL (indutivo-capacitivo-indutivo). Este tipo de filtro possui uma impedância caracterizada por um pico de ressonância próximo a sua frequência de corte. É necessário que este pico seja amortecido para que o sistema não seja levado à instabilidade. Nesta dissertação são propostos alguns casos para análise. Estes casos se diferem pela variável controlada, pela forma de operação do sistema e pela técnica não amortecimento utilizada. No caso do inversor conectado à rede e à carga, são analisados os casos em que a corrente do primeiro ou do segundo indutor de filtro é a variável controlada. Já para o caso em que o inversor está apenas alimentando a carga local, a variável controlada é a tensão no capacitor do filtro LCL. Todos estes casos são avaliados operando sem amortecimento nenhum da ressonância, com amortecimento passivo ou com amortecimento ativo. Além disso, para estes cenários há ainda a variação nos parâmetros da carga RL(resistiva-indutiva) a fim de verificar qual é a influência da variação da carga na estabilidade do sistema e na qualidade de energia no ponto de conexão. As análises de estabilidade são realizadas através de diagramas de Bode e mapas de polos e zeros do sistema. A análise da qualidade da energia realiza-se por meio de resultados experimentais obtidos em uma bancada experimental. Verifica-se através dos resultados que em termos de qualidade de energia não existem alterações significativas controlando-se diferentes variáveis no modo conectado. Além disso, constata-se também que outros fatores, além da variável controlada, do tipo de técnica utilizada para amortecimento e da frequência crítica influenciam na instabilidade ou não do sistema devido à ressonância. Através das análises, observa-se também que um controlador PI (proporcional-integral) bem ajustado pode oferecer robustez ao sistema frente às variações de parâmetros da carga e consequentes variações nas variáveis controladas. Nota-se também que para o caso ilhado, as DHTi e DHTv (Distorções Harmônicas Totais de Corrente e de Tensão) são baixas, fornecendo energia com boa qualidade para a carga local alimentada pelo sistema.
The operation of distributed generation units (DGUs) is a relatively recent issue in the Brazilian energetic scenario. The connection of these units to the grid, as their disconnection are being approached in recent researches worldwide. It is necessary that the electrial power delivered to the grid and to the power has some levels of quality so the consumer may be well attended even in contingence situations. Another necessary caution is related to the control systems involved, so they operate without degrade the power quality. At this point, this work proposes the stability and power quality analysis in the point connection of a distributed generation unit to the grid and to the load or just to the load, both situations through LCL (inductive-capacitive-inductive) filter. This kind of filter has an impedance that is characterized by resonance peak near to its cut-off frequency. It is necessary to damp this peak in order that the sytem is not lead to instability. In this Master Thesis, some cases are proposed to be analyzed. These cases differ one from another because of the controlled variable, by the kind of operation of the system and by the damping technique that is used. In the case of the grid and load-tied inverter, the analyzed cases are those in which the first or second filter inductor current is the controlled variable. For the case in which the inverter is just feeding the local load, the controlled variable is the LCL filter capacitor voltage. All of these cases are evaluated by operating with none resonace damping, passive damping or active damping. Beyond this, for these scenarios, there is the parameters variation of the RL (resistive-inductive) load in order to check which is the influence of the load variations in the system stability and in the power quality at the connection point. The stability analysis are performed through Bode diagrams and pole-zero maps of the system. The power quality analysis is carried out by means of experimental results obtained in an experimental bench. It is verified through the results that in terms of power quality, there is not significantly changes by controlling different variables in the grid-tied mode. Furthermore, other factors, beyond the controlled variable, the kind of damping technique and the criticak frequency influence in the instability of the system due to the resonance. Through the analysis, it is oberserved that a well-adjusted PI (proporcional-integral) controller may offer robustness to the system under load parameter variations and consquent controlled variable variations. It is also noted that for the stand-alone case, the THDi and the THDv (Total Harmonic Distortions of Current and Voltage) are low, providing good power to the local load fed by the system.
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Davids, Mathias [Verfasser], et Lothar R. [Akademischer Betreuer] Schad. « Minimizing the Adverse Effects of Electric Fields in Magnetic Resonance Imaging using Optimized Gradient Encoding and Peripheral Nerve Models / Mathias Davids ; Betreuer : Lothar R. Schad ». Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/1177251698/34.
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Attrell, Robert J. « A Solid-State 35Cl and 81Br NMR and Computational Study of Chlorine and Bromine Electric Field Gradient and Chemical Shift Tensors in Haloanilinium Halides ». Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20546.
Texte intégralRésumé :
The results of a systematic 35Cl, 81Br, and 127I SSNMR spectroscopic study of a series of halogen-substituted anilinium halide salts are presented. Solid-state NMR of these nuclides, bromine-/81 and iodine-127 in particular, is not well established. Twenty-one compounds thought to exhibit halogen bonding were prepared based on modified literature procedures, and two crystal structures were solved. Experiments show that collection of SSNMR spectra of the anions is feasible, though ultrahigh magnetic fields (21.1 T) and variable offset data acquisition were found to be essential. Electric field gradient and chemical shift tensors are measured experimentally for all 21 compounds, significantly expanding the body of data for the quadrupolar halogen nuclei. Quadrupolar coupling constants for chlorine-35 ranged from 2.12 to 6.04 MHz, for bromine-81 from 12.3 to 45.3 MHz, and for iodine-127 from 57.50 to 152.50 MHz. Gauge-including projector-augmented wave density functional theory (GIPAW-DFT) calculations were used to provide insight as to how the NMR parameters vary with local environment and long-range crystal packing. Overall, calculations reproduced the experimental trends in quadrupolar coupling constants and chemical shift tensor span (Ω) but failed to provide quantitative agreement within experimental error. Experimental and computational data were analyzed in order to provide insight into how halogen bonding influences NMR parameters. Several trends were elucidated from this study, including an inverse correlation between Ω and the length of the shortest halogen-halide contact (d). In selected bromine compounds, for example, Ω (81Br) was measured to increase from 120 to 240 ppm as d decreased from 3.838 to 3.443 Å. In summary, this study has demonstrated the feasibility and utility of quadrupolar halogen SSNMR, and that these techniques may prove useful in characterizing halogen bonding interactions in solids.
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Verhaven, Alexandra. « Fluorescent detection of DNA single nucleotide polymorphism by electric field assisted hybridization/melting of surface-immobilized oligonucleotides ». Doctoral thesis, Universite Libre de Bruxelles, 2020. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/314944.
Texte intégralRésumé :
RésuméLes monocouches auto-assemblées d'ADN immobilisées sur électrodes d'or sont à la base de nombreux biocapteurs électrochimiques. Le contrôle du comportement interfacial de l'ADN par le biais d'un champ électrique est intéressant pour la détection de polymorphisme nucléotidique simple (PNS). La caractérisation in situ de monocouches d'ADN à l'échelle moléculaire est importante pour la fabrication de biocapteurs robustes, fiables et sensibles.La thèse porte sur la détection du PNS dans l'ADN par le biais d'hybridation/dénaturation induite par le champ électrique. La microscopie de fluorescence sous conditions électrochimiques est utilisée comme méthodologie de détection et outil de caractérisation de l'interface d'ADN. À cette fin, des séquences d'ADN marquées par des sondes fluorescentes sont immobilisées sur des électrodes d'or sous forme de monocouches auto-assemblées (SAM) thiolées.Premièrement, les SAMs sont composées de séquences cibles présentant ou non une mutation ponctuelle. La relation entre le potentiel appliqué et la dénaturation du double brin est étudiée. La dénaturation électrochimique est observée à -0,25 V vs AgDeoxyribonucleic acid (DNA) self-assembled monolayers (SAMs) immobilized on gold electrodes are the basis of many electrochemical biosensors. Control of the interfacial behavior of DNA by means of an electric field is of interest for sensing applications such as the detection of single nucleotide polymorphisms (SNPs). Moreover, the in situ characterization of immobilized DNA monolayers at a molecular level is important for the fabrication of robust, reliable and sensitive sensors.The thesis aims at studying the discrimination between DNA strands containing SNPs on the basis of electric-field assisted hybridization/denaturation of DNA. In situ electrochemical fluorescence microscopy is used as a detection methodology and characterization tool for DNA interfaces. For this purpose, fluorescently labeled DNA sequences are immobilized at gold electrodes as thiol SAMs.First, the SAMs under investigation were composed of perfect match or SNP-containing target sequences. The relationship between the applied potential and the denaturation of DNA duplexes was investigated. Electrochemical melting was observed at -0.25 V vs. Ag
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Šulgas, Arvydas. « Geodezinių prietaisų kalibravimo stendo pozicionavimo staliuko pjezopavaros tyrimas ». Master's thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090701_154044-80163.
Texte intégralRésumé :
Nagrinėjama pjezoelektrinės pavaros pozicionavimo tikslumas ir pjezoelemento suveikimo laikas. Aprašomas tiriamas objektas, jo valdymo įrenginiai ir bandymams naudojama aparatūra. Aptariami atliktų bandymų rezultatai. Pateikiamos išvados ir rekomendacijos.The piezoelectric drive positioning accuracy and the piezo element play time are analyzed in the paper. The investigated object, its control and equipment for testing are described. Experimentation results are analyzed. Conclusion and recommendations are given.
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Suever, Jonathan D. « MRI methods for predicting response to cardiac resynchronization therapy ». Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50224.
Texte intégralRésumé :
Cardiac Resynchronization Therapy (CRT) is a treatment option for heart failure patients with ventricular dyssynchrony. CRT corrects for dyssynchrony by electrically stimulating the septal and lateral walls of the left ventricle (LV), forcing synchronous con- traction and improving cardiac output. Current selection criteria for CRT rely upon the QRS duration, measured from a surface electrocardiogram, as a marker of electrical dyssynchrony. Unfortunately, 30-40% of patients undergoing CRT fail to benefit from the treatment. A multitude of studies have shown that presence of mechanical dyssynchrony in the LV is an important factor in determining if a patient will benefit from CRT. Furthermore, recent evidence suggests that patient response can be improved by placing the LV pacing lead in the most dyssynchronous or latest contracting segment. The overall goal of this project was to develop methods that allow for accurate assessment and display of regional mechanical dyssynchrony throughout the LV and at the site of the LV pacing lead. To accomplish this goal, we developed a method for quantifying regional dyssynchrony from standard short-axis cine magnetic resonance (MR) images. To assess the effects of LV lead placement, we developed a registration method that allows us to project the LV lead location from dual-plane fluoroscopy onto MR measurements of cardiac function. By applying these techniques in patients undergoing CRT, we were able to investigate the relationship between regional dyssynchrony, LV pacing lead location, and CRT response.
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Ersoy, Mehmet Okan. « Application Of A Natural-resonance Based Feature Extraction Technique To Small-scale Aircraft Modeled By Conducting Wires For Electromagnetic Target Classification ». Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12605522/index.pdf.
Texte intégralRésumé :
The problem studied in this thesis, is the classification of the small-scale
aircraft targets by using a natural resonance based electromagnetic feature extraction
technique. The aircraft targets are modeled by perfectly conducting, thin wire
structures. The electromagnetic back-scattered data used in the classification process,
are numerically generated for five aircraft models.
A contemporary signal processing tool, the Wigner-Ville distribution is
employed in this study in addition to using the principal components analysis
technique to extract target features mainly from late-time target responses. The
Wigner-Ville distribution (WD) is applied to the electromagnetic back-scattered
responses from different aspects. Then, feature vectors are extracted from suitably
chosen late-time portions of the WD outputs, which include natural resonance related
v
information, for every target and aspect to decrease aspect dependency. The database
of the classifier is constructed by the feature vectors extracted at only a few reference
aspects. Principal components analysis is also used to fuse the feature vectors and/or
late-time aircraft responses extracted from reference aspects of a given target into a
single characteristic feature vector of that target to further reduce aspect dependency.
Consequently, an almost aspect independent classifier is designed for small-scale
aircraft targets reaching high correct classification rate.
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Johansson, Nicklas. « Aspects on Dynamic Power Flow Controllers and Related Devices for Increased Flexibility in Electric Power Systems ». Doctoral thesis, KTH, Elektriska maskiner och effektelektronik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-37823.
Texte intégralRésumé :
This thesis studies different aspects of Flexible AC Transmission System (FACTS) devices which are used to improve the power transfer capability and increase the controllability in electric power systems. In the thesis, different aspects on the usage and control of Dynamic Power Flow Controllers (DPFC) and related FACTS devices are studied. The DPFC is a combination of a Phase Shifting Transformer (PST) and a Thyristor Switched Series Capacitor (TSSC)/Thyristor Switched Series Reactor (TSSR). The thesis proposes and studies a new method, the Ideal Phase-Shifter (IPS) method, for selection and rating of Power Flow Controllers (PFC) in a power grid. The IPS method, which is based on steady-state calculations, is proposed as a first step in the design process for a PFC. The method uses the Power controller plane, introduced by Brochu et al in 1999. The IPS method extends the usage of decoupling methods in the Power controller plane to a power system of arbitrary size. The IPS method was in the thesis used to compare the ratings of different PFC:s required to improve the power transfer capability in two test systems. The studied devices were here the PST, the TSSC/TSSR and the DPFC. The thesis treats control of ideal Controlled Series Capacitors (CSC), TCSC, TSSC/TSSR, and DPFC. The goals of the FACTS controllers which are developed are Power Oscillation Damping (POD), fast power flow control, and transient stability improvement in the power system. New adaptive control strategies for POD and power flow control are proposed and studied in different models of power systems by time-domain simulations. A strategy for transient stability improvement is also proposed and studied. Additionally, different methods for study of Subsynchronous Resonance (SSR), which is associated with series compensation in power systems, are investigated. Here, four of the most common methods for frequency scanning to determine the electrical damping of subsynchronous oscillations in a power grid are studied. The study reveals significant differences of the electrical damping estimates of the studied standard methods when applied to a four-machine test system.QC 20110819
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Brenneman, Keith Richard. « Heteroatom-containing organic electronic oligomers and polymers : electron paramagnetic resonance studies / ». The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu148820315882799.
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Widdifield, Cory. « Multinuclear Solid-State Magnetic Resonance Studies on ‘Exotic’ Quadrupolar Nuclei : Acquisition Methods, High-Order Effects, Quantum Chemical Computations, and NMR Crystallography ». Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20722.
Texte intégralRésumé :
This dissertation attempts to extend the classes of halogen-containing systems which may be studied using solid-state nuclear magnetic resonance (SSNMR). As line shape broadening due to the quadrupolar interaction (QI) scales inversely with the applied field, high-field magnet technology is indispensable for this research. Combining advanced radiofrequency pulse sequences with high-field wideline data acquisition allowed for the collection of very broad SSNMR signals of all quadrupolar halogen nuclei (i.e., 35/37Cl, 79/81Br and 127I) within a reasonable amount of experimental time. The initial systems for study were of the MX2 variety (M = Mg, Ca, Sr, Ba; X = Cl, Br, I). In total, 9 anhydrous compounds were tested. The effects of hydrate formation were tested on 7 additional compounds. Systematic trends in the observed δiso values (and to a lesser extent, Ω and CQ) were found to be diagnostic of the extent of hydration in these materials. Resolving power was successfully tested using SrBr2, which possesses 4 magnetically unique sites. The composition of CaBr2•xH2O was convincingly determined using SSNMR data and the hydration trends noted above. The sensitivity of the QI to the local bonding environment (e.g., bond distance changes of less than 0.05 Å) was used to refine (when coupled with gauge-including projector augmented-wave density functional theory (GIPAW DFT) quantum chemical computations) the structure of MgBr2, and was used to correct prior NMR data for CaCl2 (earlier accounts had been performed upon a CaCl2 hydrate). During NMR data analysis of certain iodine-containing materials, it was found that standard fitting software (which uses perturbation theory) could not reproduce the observations. Proper analysis required the use of exact simulation software and allowed for the observation of high-order quadrupole-induced effects (HOQIE). This motivated further studies using rhenium-185/187 nuclei, where it was expected that HOQIE would be more dramatic. The observed rhenium SSNMR spectra possessed additional fine structure that had never been observed before experimentally, nor would be expected from currently-available perturbation theory analysis software. Lastly, preliminary results are shown where 127I SSNMR is used to study important supramolecular systems, and the composition of the popular synthetic reagent ‘GaI’ is elucidated.
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Chapman, Rebecca. « Development and Application of Chlorine Solid-State Nuclear Magnetic Resonance and Quantum Chemical Calculations to the Study of Organic and Inorganic Systems ». Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20555.
Texte intégralRésumé :
Chlorine solid-state nuclear magnetic resonance (SSNMR) is an ideal site specific probe of chloride-containing solids as SSNMR tensor properties are sensitive to the local chlorine environment. In this thesis, the development and use of chlorine SSNMR as a method to characterize a wide variety of chemical environments was explored. Ultrahigh field, and multi-field studies were essential to overcome the difficulties associated with the collection of chlorine SSNMR spectra.
Benchmark chemical shift (CS) and electric field gradient (EFG) tensor data were collected for organic chloride systems, including several amino acid hydrochlorides. These experiments demonstrated the sensitivity of chlorine SSNMR to slight changes in chemical environment. Quantum chemical calculations were used to complement experimental data, with the gauge-including projector augmented wave DFT (GIPAW-DFT) method shown to yield better agreement than B3LYP or RHF methods. The GIPAW-DFT method was found to slightly, but systematically, overestimate the chlorine quadrupolar coupling constant and the CS tensor span. Other organic chlorides examined by chlorine SSMR included a known ion receptor, meso-octamethylcalix[4]pyrrole. This compound was found to have a very small quadrupole interaction (QI), but significant chemical shift anisotropy (CSA). GIPAW-DFT calculations were also utilized and, in combination with the experimental results, used to identify the solvate structure of the material analyzed by NMR.
Chlorine SSNMR was further used to study different solvate structures and polymorphism. The technique was an effective means to distinguish different room temperature polymorphs of benzidine hydrochloride, despite the similarities of the chloride environments. In the case of magnesium chloride, chlorine SSNMR was sensitive to the level of hydration and through the use of GIPAW-DFT calculations, the identity of an unknown hydrate was determined.
An analysis of several group thirteen chlorides demonstrated that chlorine SSNMR was also capable of characterizing the chlorine environment in cases where the QI is large, despite the resulting broad line widths. In these systems GIPAW-DFT calculations also yielded excellent agreement with experimental values.
Throughout this research, chlorine SSNMR has been shown to be a useful and effective means to study both organic and inorganic chlorides, with computational methods proving to be an important complement to experimental data.
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Berry, Paul A. D. « The interaction of atomic systems with coherent and stochastic fields ». Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343098.
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Evans, Jesse. « Synthesis of Rhenium and Manganese Pyridazoal Complexes ». TopSCHOLAR®, 2013. http://digitalcommons.wku.edu/theses/1239.
Texte intégralRésumé :
Pyridazines are a heterocyclic aromatic compound containing a characteristic N-N bond that are utilized in many fields, including medicine and electronics. It is this latter field that Dr. Snyder's research group is focused upon. Organometallic compounds are a better conducting material than the current inorganic compounds used in electronics due to better conductance of electricity, lower production cost, and the ability to be formed into thin films. With this in mind, Dr. Snyder's research group has set out to synthesize organometallic compounds for this purpose. Following procedures set forth by Snyder etc, and altered to form an off-metal route, we have successfully synthesized a library of fulvenes, Thalium Cp salts, 5,6 fused pyridazines, and pyridazial complexes. Thalium Cp salts were converted to Rhenium and Magnenese complexes through transmetalation. We have had success with the off-metal route at both higher yields and greater purity than the previous published on-metal route. These compounds have been fully characterized by 1H NMR, 13C NMR, IR, and Elemental Analysis. In addition, progress has been initiated to form Bromo Thiophene complexes following procedures set forth in Snyder, etc and modified for the off-metal route. However only fulvenes, pyridazine, and Thalium Cp salts have been synthesized and characterized by 1H NMR and 13C NMR.
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Alfonsov, Alexey. « High-field electron spin resonance study of electronic inhomogeneities in correlated transition metal compounds ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-74492.
Texte intégralRésumé :
Electronic inhomogeneities play an important role in the definition of physical properties of correlated systems. To study these inhomogeneities one has to use local probe techniques which can distinguish electronic, magnetic and structural variations at the nanoscale. In the present work the high-field electron spin resonance technique (HF-ESR) is used to probe electronic and magnetic inhomogeneities in two transition-metal element based systems with very different properties. The first system is an iron based hightemperature superconductor, namely a member of a so called 1111-family, the (La,Gd)O1−xFxFeAs compound. Our HF-ESR spectroscopy study on Gd3+ ion has revealed that this material exhibits anisotropic interaction between Gd and Fe layers, which is frustrated in the absence of an external magnetic field. Moreover, the study of the superconducting samples has shown a coexistence of a static short range magnetic order with superconductivity up to high doping levels. The second system is a lightly hole doped cubic perovskite LaCoO3. Here, our HF-ESR investigation, complemented with static magnetometry and nuclear magnetic resonance techniques, has established that the hole doping induces a strong interaction between electrons on neighboring Co ions which leads to a collective high-spin state, called a spin-state polaron. These polarons are inhomogeneously distributed in the nonmagnetic matrix.
This thesis is organized in three chapters. The first chapter gives basic ideas of magnetism in solids, focusing on the localized picture. The aim of the second chapter is to introduce the method of ESR. The third chapter is dedicated to the study of 1111-type iron arsenide superconductors. In the first part X-band (9.5 GHz) ESR measurements on 2% and 5% Gd-doped LaO1−xFxFeAs are presented. In the second part a combined investigation of the properties of GdO1−xFxFeAs samples by means of thermodynamic, transport and high-field electron spin resonance methods is presented. The last, fourth chapter presents the investigation of the unexpected magnetic properties of lightly hole-doped LaCoO3 cobaltite by means of the electron spin resonance technique complemented by magnetization and nuclear magnetic resonance measurements.
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Zhang, Xingguang. « Plasmonic photocatalysts of supported gold nanoparticles for organic conversions ». Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/67714/4/Xingguang_Zhang_Thesis.pdf.
Texte intégralRésumé :
This thesis is a comprehensive study of plasmonic gold photocatalysts for organic conversions. It presents the advantages of plasmonic gold photocatalysts in the selective oxidation, reduction, and acetalisation. It is discovered that plasmonic gold photocatalysts exhibit better catalytic performance (higher selectivity or activity) in these organic conversions. The study in this thesis highlights the capacity of plasmonic gold photocatalysts in harvesting solar energy for converting organic raw materials to value-added chemicals, and the great potential of gold photocatalysts in chemical production.
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PEREIRA, CLOTILDE C. « Desenvolvimento de membranas aniônicas obtidas por enxertia via irradiação para aplicação em células a combustível alcalinas ». reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27979.
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Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2017-11-09T12:16:30Z
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As membranas de troca aniônica são uma alternativa promissora para o desenvolvimento de eletrólitos mais eficientes para células a combustível alcalinas. Em geral, as membranas de troca aniônica são ionômeros capazes de conduzir íons hidroxila devido aos grupos quaternário de amônio e têm como característica elevado pH equivalente. Com o objetivo de desenvolver membranas aniônicas química e termicamente estáveis, com satisfatória condutividade iônica para aplicação em células a combustível alcalinas, as membranas aniônicas foram sintetizadas a partir de polímeros base de polietileno de baixa densidade (LDPE), polietileno de ultra alto peso molecular (PEUHMW), poli(etileno-co-tetrafluoroetileno) (PETFE) e poli(tetrafluoroetilleno-co-hexafluoroetileno) (PFEP) previamente irradiados nas fontes de radiação gama de 60Co ou com feixe de elétrons, para enxertia do monômero de estireno e funcionalizados com trimetilamina para incorporação dos grupos quaternário de amônio. As membranas resultantes foram caracterizadas por espectroscopia de ressonância paramagnética eletrônica (EPR), espectroscopia Raman, termogravimetria (TG), espectroscopia de impedância eletroquímica (EIS), além da determinação do grau de enxertia, capacidade de absorção de água por gravimetria e capacidade de troca iônica, por titulação. As membranas sintetizadas com os polímeros LDPE e UHMWPE pré-irradiados a 70 kGy com feixe de elétrons e armazenadas a baixa temperatura (-70 °C) por até 10 meses, mostraram resultados de condutividade iônica, quando na forma (OH-), de 29 mS.cm-1 e 14 mS.cm-1 a 65 °C, respectivamente. Os filmes de PFEP irradiados no processo simultâneo mostram níveis de enxertia insuficientes para a síntese de membranas aniônicas, necessitando maiores estudos para aperfeiçoar os processos de irradiação e enxertia. As membranas baseadas em PETFE, pré-irradiadas a 70 kGy com feixe de elétrons e armazenadas a baixa temperatura (-70 °C) por até 10 meses, mostraram maior condutividade iônica, quando na forma hidroxila (OH-), com valores de condutividade iônica entre 90 mS.cm-1 e 165 mS.cm-1 na faixa de temperatura entre 30 e 60 °C. Estes resultados mostraram que membranas de LDPE, UHMWPE e PETFE são eletrólitos promissores para a aplicação em células a combustível alcalinas.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Smith, Paul David. « Flash photolysis electron spin resonance ». Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316901.
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Wain, Andrew John. « Electron spin resonance in electrochemistry ». Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432259.
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Lea-Wilson, M. A. « Electron spin resonance studies of electron irradiated diamond ». Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381911.
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Dorin, Catalina I. « Electron paramagnetic resonance and electron nuclear double resonance study of Nb⁵⁺ hole center in CdWO₄ ». Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=745.
Texte intégralRésumé :
Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains ix, 72 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 40).
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Wan, Xiaoming. « Electron spin resonance imaging and in-vivo electron spin resonance studies of biological and nonbiological systems / ». The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487599963591964.
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Souza, Jean Carlo 1993. « Estudos de ressonância de spin eletrônico (RSE) em isolantes topológicos dopados com terras-rara ». [s.n.], 2017. http://repositorio.unicamp.br/jspui/handle/REPOSIP/326704.
Texte intégralRésumé :
Orientador: Pascoal José Giglio PagliusoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: A ideia de topologia na Física da Matéria da Condensada, apesar de ter surgido com o efeito Hall quântico inteiro, só voltou a ser explorada recentemente na busca de novas fases da matéria depois do surgimento dos Isolantes Topológicos (ITs) 2D. Após a previsão teórica, e a descoberta experimental, foi proposto que esta nova fase poderia ser generalizada para sistemas 3D, em que o volume do material seria isolante com estados metálicos de superfície que possuiriam canais de spin polarizados. Apesar de diversos experimentos e o surgimento de outras fases topológicas da matéria subsequentes, ainda há dúvidas sobre a natureza dos ITs 3D. Os efeitos topológicos mais claros ainda não foram observados de forma inequívoca e reprodutível experimentalmente e ainda seria de extrema valia encontrar técnicas experimentais que possam complementar os mais discutidos experimentos de ARPES. Nesta dissertação foram estudadas duas famílias distintas de materiais propostas como possíveis ITs 3D: os binários Bi2Se3 e Sb2Te3 e o half-Heusler YPdBi. Utilizando a técnica de auto-fluxo e a fusão estequiométrica, os sistemas foram sintetizados dopados com os terras-rara Gd3+, Nd3+ e Er3+ para realizar estudos de ressonância de spin eletrônico (RSE) e do papel dos efeitos de campo cristalino (CEF) - no caso do half-Heusler. Para o ternário YPdBi foram feitos dois estudos. Na família dos half-Heuslers, a ordem topológica surge da relação entre o acoplamento spin-órbita e a hibridização, que está ligada com a mudança do parâmetro de rede, então os efeitos de CEF poderiam estar refletindo a transição entre a trivialidade e a não-trivialidade. A partir das medidas de susceptibilidade magnética em função da temperatura das amostras dopadas com Nd3+ e Er3+ combinadas com os estudos de RSE, foi possível extrair os parâmetros de campo cristalino (CFP) de quarta e sexta ordem. Comparando esses dados com resultados anteriores para o material, supostamente, não-trivial YPtBi, observou-se uma mudança sistemática no sinal dos CFP. Resultados prévios para as amostras de YPtBi dopadas com Nd3+ mostram uma evolução não usual para uma forma de linha difusiva com a potência de micro-onda. Neste trabalho também foi realizado um estudo da forma de linha em função da potência. Apenas a ressonância do Nd3+ para os monocristais de 10% de Nd em YPdBi mostrou uma forma de linha difusiva que evolui com a potência da micro-onda. No caso dos binários Bi2Se3 e Sb2Te3, o objetivo era otimizar a rampa de tratamento térmico para obter monocristais melhores que poderiam permitir a observação de um espectro totalmente resolvido do Gd3+. Após mudanças no crescimento dos monocristais, o espectro totalmente resolvido foi obtido para as amostras de Bi2Se3. No caso do Sb2Te3 apenas uma linha central com a estrutura fina colapsada foi observada. Acompanhando o deslocamento g e a evolução da largura de linha dH da RSE do Gd3+ com a temperatura, o comportamento negativo do deslocamento g para toda a faixa de temperatura indica que elétrons do tipo p são os grandes responsáveis pela formação da superfície de Fermi residual destes sistemas. Um aumento no coeficiente angular de dH em função da temperatura, a taxa Korringa b, foi observado em baixas temperaturas, logo diferentes concentrações de Gd3+ foram utilizadas para estudar este comportamento. Novamente observou-se um comportamento anômalo em baixas temperaturas, o que poderia estar relacionado com a evolução dos CFP com a temperatura. Todos esses resultados foram discutidos levando-se em conta a possibilidade de existência de topologia não-trivial na estrutura eletrônica desses materiais, com foco particular na relação da interação spin-órbita e os efeitos de campo cristalino com a manifestação da topologia não trivial nesses sistemas
Abstract: The idea of topological systems in Condensed Matter Physics, although already explored in the Quantum Hall Effect, has recently become a topic of intense scientific investigation. In particular, great efforts have been dedicated to the search for new quantum phases since the proposal of the Topological Insulators (TIs) in 2D. After the theoretical prediction and the experimental discovery of the TIs in the 2D case, the existence of the Quantum Hall Spin Effect in 3D, 3D TIs, was proposed, where an insulator bulk and metallic surface states with spin polarized channels could be experimentally realized. Although many experiments have been performed, and some groups claimed the direct observation of such new topological phases, there is still a lot of controversy about the nature of the 3D TIs and about the actual microscopic origin of the metallic states on the surface of the studied materials. Other signatures of the topological phases have not been unambiguously and repeatedly measured yet and there is an obvious lack of a supplementary lab technique to be compared to the most used technique to probe these states, which is ARPES. In this work we have studied two different classes of 3D TIs: the binaries Bi2Se3 and Sb2Te3 and the half-Heusler YPdBi. We have been able to grow single crystals of these materials pure and rare-earth doped with Gd3+, Nd3+ and Er3+ using the self-flux technique and the stoichiometric melting. The aim was to use these crystals to study Electron Spin Resonance (ESR) as a potential probe to investigate the existence of the metallic surface states and to explore the possible of the crystalline electrical field (CEF) effects on the formation of the non-trivial electronic structure of these materials. Regarding the YPdBi, our ESR and magnetization studies have revealed that, in the half-Heusler family, the topological order emerges from the interplay between spin-orbit coupling and the hybridization, which is connected with the changes on the lattice parameter. Thus, the CEF effects could reflect the transition from trivial to nontrivial topology. From the magnetic susceptibility data as a function of temperature from the Nd3+ and Er3+ doped samples combined with the ESR studies, it was possible to extract the fourth and sixth order crystal field parameters (CFP). Comparing our data with the previous results from YPtBi, which is a putative non-trivial material, a systematic change in the sign of the CFP was observed. Previous results with the YPtBi Nd-doped samples show an unusual evolution of the Nd3+ ESR line to a diusive-like line shape as a function of the microwave power. In this work we have performed a similar study of the Nd3+ ESR line shape as a function of the microwave power. Only for the single crystal of 10% Nd in YPdBi resonance shows a diffusive-like line shape that evolves with the microwave power. In the case of the binaries Bi2Se3 e Sb2Te3, the aim of this work was to optimize the heat treatment used in previous works of our group to obtain better single crystals that could allow the observation of the full resolved spectra from Gd3+. After many changes in the single crystal growth method, we were able to observe fully resolved Gd3+ ESR spectra in the Bi2Se3 samples. Regarding the Sb2Te3 single crystals, only a single Gd3+ Dysonian ESR line was observed. Following the Gd3+ ESR dg and dH as a function of temperature, the observed negative behavior of dg, in the whole temperature range studied, indicates that p-type electrons are the main source for the formation of the small the Fermi surface of these materials. An increase of the angular coefficient of dH as a function of temperature, the Korringa rate b, at low temperatures was observed and different concentrations of Gd3+ were required to investigate this anomaly. Again this anomalous behavior at low temperatures was observed for the all Gd-doped samples, which could be related to an evolution of CFP with temperature. We discuss our results taking into account the existence of non-trivial topological states in our samples and the role of spin-orbit and CEF effects might have in the formation of such states
Mestrado
Física
Mestre em Física
132653/2015-0
CNPQ
CAPES
FAPESP
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Radebe, Kelvin G. « Ore sorting using microwave resonant cavities ». Master's thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/8362.
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Felizari, Alessandra. « Caracterização e monitoramento remoto aplicado a um sensor magnetoelástico ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/149791.
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Uma vasta gama de sensores são aplicados no mercado atual na busca pela melhoria de processos e produtos. Há um grande crescimento em novos sistemas que possam apresentar recursos que técnicas convencionais não apresentam. A busca por uma nova plataforma de sensoriamento surge a partir do interesse em identificar e controlar parâmetros ambientais isolados. Esta pesquisa em área incipiente no Brasil mostra o desenvolvimento de um sensor a partir de um material inteligente (smart material), que por definição, possui uma ou mais propriedades que podem sofrer mudanças significativas a partir de um estímulo externo. O presente trabalho é baseado na investigação de uma fita de material magnético amorfo, que ao exibir propriedades magnéticas e elásticas pelo efeito da magnetostricção, permite o monitoramento remoto de fenômenos físico-químicos do ambiente em que estiver exposta. O desenvolvimento deste sensor tem finalidade no monitoramento sem fio de solicitação mecânica, e alteração do tipo de fluido presente em um dado ambiente. O estudo e avaliação do sensor contou com técnicas de caracterização experimentais e de simulação. São apresentados sistemas e ensaios capazes verificar as ressonâncias do modo de vibração puro da amostra a partir de medidas ópticas e elétricas, quando submetidos a variação de fenômenos físicos. Os resultados indicam a dependência do efeito direto ao estímulo na ação externa do campo magnético em decorrências das características do material. Os resultados quantificados e qualificados na correlação entre os métodos utilizados, justificam a aplicação do smart material no sensoriamento de viscosidade e carregamento aplicado em ambientes isolados. Em consequência das discussões apresentadas para as curvas comportamentais na variação dos parâmetros físico-químico a plataforma de sensoriamento é validada.New amorphous magnetic materials have magnetic and elastic properties which allows the identification and control of environmental parameters remotely. This work was based in the investigation of a magnetoelastic thin strip, widely used as anti-theft device. In this study it was discussed the employment of this material as a sensor capable identify an environmental change through magnetoelasticity. In order to characterize the strips it was employed several techniques, namely: finite element modeling of the vibrational modes, electromagnetic impedance and laser interferometry. It was presented an analysis of the displacement of the longitudinal modes. The knowledge of the vibration mode allowed the sensor electric characterization when subjected to environmental changes. According to the sample dimensions under magnetic field, test systems were developed in order to perform optic and electric measurements. A proper parameter adjustment of the power supply allowed the determination of the fundamental and higher order resonance frequencies. The magnetostrictive behaviour of the anti-theft strips is related to the Young modulus where the vibration frequency is inversely proportional to the length of the strip. Studies showed that the strip performance is also related to many other parameters, such as the mechanical and electromagnetic properties and the environment to which it is exposed. The strips here presented are largely employed as sensor for temperature, pressure, density, mas variation, viscosity and flux velocity mainly because their wireless capabilities. The data from the polarization field are a section of the knowledge required to better investigate the best performance of the sensor. The sensor characterization through several techniques applied in viscous media and under pressure raise some issues. However, the construction of some devices allowed the application of different values of viscosity and pressure upon the magnetized strip. This made the results interpretation less complex. The resonances were observed in the experimental data and mathematical modellin. Calibration curves were defined to make the results interpretation easier.Previously applied and studied techniques which cover the characterization and behaviour of the material provide valid justifications for the implementation of remote sensors made of amorphous metallic strips. The results presented here justify the application of the analysed amorphous strip as a viscosity and pressure sensor in isolated enviroments.
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Rodas, Elvis. « Ion Cyclotron Resonance Heating in WEST ». Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254260.
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In a fusion power plant the plasma must be confined to prevent instabilities and energy loss. The confinement machine studied is a tokamak. The focus of the project is to optimize ion resonance heating in WEST. The code called FEMIC was used to simulate different scenarios where parameters such as ion concentrations, antenna frequency are analysed for the case of minority hydrogen in deuterium plasma. The optimal Hconcentration in D-plasma was found to be 10 5%, which allows for a wide concentration interval. However, the strongest coupled power was found to be at the H-concentration of 6%. Thus, the optimal concentration for strongest coupled power and H-minority absorption is 6% in WEST for the case of Hydrogen minority in Deuterium plasma.
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Arshak, K. I. « A study of electron paramagnetic resonance and some optical and electrical properties in thin dielectric oxide films ». Thesis, Brunel University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356687.
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Powley, Nicholas R. (Nicholas Ransom) 1982. « A device for testing the electronic and mechanical properties of conducting polymers with electron paramagnetic resonance spectroscopy ». Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32776.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaf 35).
Conducting polymers have the potential to serve the technical and commercial communities with novel actuators, sensors, and biomimetic devices. The conjugated structures of these polymers and the addition of dopants enable conduction. [1] One current goal in the conducting polymer field is to observe and understand the events by which these polymers carryout their active mechanical functions (contraction and expansion) upon the application of a potential. This thesis presents the design and a prototype of a new device for investigating the relationship between the mechanical and electronic properties of conducting polymers with EPR Spectroscopy. The performance of the testing device was explored with a controlled experiment. The results of this experiment suggest that the response of conducting polymer actuators to mechanical inputs can be examined with EPR Spectroscopy.
by Nicholas R. Powley.
S.B.