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1
Elder, Ian F. "Diode-pumped two micron solid-state lasers." Thesis, University of Strathclyde, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284812.
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Virte, Martin. "Two-mode dynamics and switching in quantum dot lasers." Thesis, Supélec, 2014. http://www.theses.fr/2014SUPL0020/document.
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Dans cette thèse, j'étudie la dynamique non linéaire résultant d’une compétition entre deux modes dans des systèmes lasers à boites quantiques.D’abord, je considère le cas de la compétition entre deux modes de polarisation apparaissant dans les diodes laser nanostructurées à cavité verticale et émettant par la surface (VCSELs). Il est connu que ces composants peuvent avoir une polarisation instable menant à des dynamiques riches. Récemment, un surprenant saut de mode entre deux états polarisés elliptiquement a été récemment découvert dans les VCSELs à boites quantiques. Ce comportement montre des propriétés intrigantes qui nécessitent une interprétation alternative. Dans cette thèse, je montre que ce comportement dynamique peut-être reproduit en utilisant le modèle spin-flip (SFM). En particulier je démontre et confirme expérimentalement que les sauts de modes sont en réalité des fluctuations chaotiques de faible dimension : un chaos en polarisation. Je démontre ensuite la pertinence de la dynamique chaotique observée pour les applications exploitant le chaos optique, en réalisant un générateur de nombres aléatoires à grande vitesse basé sur le chaos en polarisation.Deuxièmement, j'étudie les effet d'une rétroaction optique à délai sur les lasers à boites quantiques émettant simultanément depuis l'état fondamental et le premier état excité. Je clarifie l'impact the cette rétroaction optique ainsi que les mécanismes et bifurcations correspondantes. Je montre théoriquement qu'une rétroaction optique favorise globalement l'émission par l'état fondamental, mais aussi qu'un tel montage peut être utilisé pour commuter entre ces deux modes d'émission lorsque l'on change le taux ou le délai de la rétroaction. Enfin, je confirme ces observations expérimentalement, en rapportant des commutations entre l'état fondamental et l'état excité<br>In this thesis, I study the nonlinear dynamics induced by the competition between two modes in quantum dot laser systems.First, I focus on the competition between polarization modes that takes place in quantum dot vertical-cavity surface-emitting lasers (VCSELs). It is well-known that these devices can exhibit polarization instabilities leading to rich dynamical evolution. Recently, a new peculiar random-like hopping between two non-orthogonal elliptically polarized states has been highlighted in QD VCSELs. This behavior shows intriguing features which clearly call for a different interpretation. In this thesis, I show that the dynamical behavior reported experimentally can accurately be reproduced within the spin-flip model (SFM) framework. In particular, I demonstrate and confirm experimentally that the peculiar random-like hoppings are in fact deterministic low-dimensional chaotic fluctuations, i.e. ``Polarization Chaos''. I then make a proof-of-concept demonstration of a high-speed random bit generator based on polarization chaos, hence demonstrating that the chaotic dynamics uncovered is relevant for optical chaos-based applications.Secondly, I investigate the effects of an external optical feedback on quantum dot lasers emitting simultaneously from the ground and the excited states. I bring new light on the impact of optical feedback and the corresponding mechanisms and bifurcations. I highlight theoretically that optical feedback globally favors the ground state emission, but also that it can be used to switch from one mode to the other when changing the feedback rate and/or the time-delay. In addition, I experimentally report switching between the ground and excited states when varying the external cavity length at the micrometer scale, which supports the theoretical predictions
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Adam, Grain Philip. "Quasi two-level operation of a five-level diode clamped converter." Thesis, University of Strathclyde, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442006.
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Dumond, Julien Xavier Pierre [Verfasser], and A. [Akademischer Betreuer] Class. "Fluidic diode for critical two-phase flows / Julien Xavier Pierre Dumond. Betreuer: A. Class." Karlsruhe : KIT-Bibliothek, 2012. http://d-nb.info/1030315973/34.
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Erchak, Alexei A. (Alexei Andrew) 1976. "Design and fabrication of a light emitting diode using a two-dimensional photonic crystal." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9555.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999.<br>Includes bibliographical references (leaves 51-52).<br>Photonic Crystals are the optical analog of semiconductor crystals. A periodic variation in the dielectric constant may give rise to a photonic bandgap that forbids the propagation of certain frequency light in one, two, and three dimensions. A two dimensional photonic crystal may be used to directly modify the spontaneous emission of a light-emitting diode by eliminating the coupling of light to guided modes. In this work, the design and fabrication of a two-dimensional photonic crystal light-emitting diode with an emission wavelength of 980 nm is discussed. The 980 nm emission wavelength requires the fabrication of l 00 nm feature sizes in a GaAs-based materials system. The nanoscale feature sizes and various III-V materials employed present many fabrication challenges.<br>by Alexei A. Erchak.<br>M.Eng.
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Qiu, Fengjing. "Analog very large scale integrated circuits design of two-phase and multi-phase voltage doublers with frequency regulation." Ohio : Ohio University, 1999. http://www.ohiolink.edu/etd/view.cgi?ohiou1175632756.
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Reiss, Boris. "Development of a two-tone frequency modulation tunable diode laser absorption spectrometer (TTFM-TDLAS) for measuring methane fluxes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0016/MQ56199.pdf.
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Bailey, Hope P. "CHEMOMETRIC ANALYSIS OF COMPREHENSIVE TWO-DIMENSIONAL LIQUID CHROMATOGRAPHIC-DIODE ARRAY DETECTION DATA: PEAK RESOLUTION, QUANTIFICATION AND RAPID SCREENING." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2924.
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This research project sought to explore, compare and develop chemometric methods with the goal of resolving chromatographically overlapped peaks though the use of spectral information gained from the four-way data sets associated with comprehensive two-dimensional liquid chromatography with diode array detection (LC ´ LC-DAD). A chemometric method combining iterative key set factor analysis (IKSFA) and multivariate curve resolution-alternating least squares (MCR-ALS) was developed. In the section of urine data analyzed, over 50 peaks were found, with 18 visually observable and 32 additional compounds found only after application of the chemometric method. Upon successful chemometric resolution of chromatographically overlapped peaks, accurate and precise quantification was then necessary. Of the compared methods for quantification, the manual baseline method was determined to offer the best precisions. Of the 50 found peaks from the urine analysis, 34 were successfully quantified using the manual baseline method with percent relative standard deviations ranging from 0.09 to 16. The accuracy of quantification was then investigated by the analysis of wastewater treatment plant effluent (WWTPE) samples. The chemometrically determined concentration of the unknown phenytoin sample was found to not exhibit a significant difference from the result obtained by the LC-MS/MS reference method, and the precision of the IKSFA-ALS method was better than that of the precision of the LC-MS/MS analysis. Chromatographic factors (data complexity, large dynamic range, retention time shifting, chromatographic and spectral peak overlap and background removal, were all found to affect the quantification results. The last part of this work focused on rapid screening methods that were capable of locating peaks between samples that exhibited significant differences in concentration. The aim here was to reduce the amount of data required to be resolved and quantified to only those peaks that were of interest. This would then reduce the time required to analyze large, complex samples by eliminating the need to first quantify all peaks in a given sample for many different samples. Both the similarity index (SI) method and the Fisher ratio (FR) method were found to fulfill this requirement in a rapid means of screening fifteen wine samples.
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Burns, Iain Stewart. "A sensor for combustion thermometry based on blue diode lasers." Thesis, University of Cambridge, 2006. https://www.repository.cam.ac.uk/handle/1810/244070.
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Spatially-resolved measurements of flame temperature have been demonstrated with diode lasers for the first time. The technique is based on the use of blue diode lasers to perform laser-induced fluorescence on indium atoms seeded to the flame. Temperature measurements have been carried out in laminar flames both by the two-line atomic fluorescence technique, and also by a novel line-shape thermometry method that requires the use of only a single diode laser. The first part of this work involved the development of blue extended cavity diode lasers with favourable tuning properties. Two custom-designed extended cavity diode lasers (ECDL) have been built, emitting at wavelengths of around 410 nm and 451 nm respectively. These devices are capable of mode-hop free tuning over ranges greater than 90 GHz. The performance of these devices exceeds that of commercially available systems and a patent application has been filed. High resolution fluorescence spectroscopy has been performed on both the 52P1/2→62S1/2 and 52P3/2→62S1/2 transitions of indium atoms seeded at trace quantities into atmospheric pressure flames. In both cases, the spectra obtained show excellent agreement with a theoretical fit based on the individual hyperfine components of the transition. The two ECDLs have been used to build a sensor for the measurement of temperature in combustion systems. It is much simpler, more compact, less expensive, and more versatile than any previously existing device. The two lasers were used sequentially to probe indium atoms seeded to the flame. The ratio of the resulting fluorescence signals is related to the relative populations in the two sub-levels of the spin-orbit split ground state of indium, and thus to the temperature. Temperature measurements have been successfully performed in a laminar flame and the data thus obtained do not need to be corrected by any ‘calibration constant’. This novel thermometry technique offers a robust alternative to traditional methods involving bulky high power lasers. A further development has been made by demonstrating a fluorescence line-shape thermometry technique requiring only a single diode laser excitation source. Progress has been made towards the goal of rapid temperature measurements appropriate to the study of turbulent flames. This involved the development of a simple technique for actively locking the wavelength of the blue diode laser to a resonance line of the tellurium molecule. A high-speed thermometry system would work by rapidly switching between the two locked laser beams using an optical modulator.
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Ullah, Md Barkat. "Growth of Zn-polar BeMgZnO/ZnO heterostructure with two dimensional electron gas (2DEG) and fabrication of silver Schottky diode on BeMgZnO/ZnO heterostructure." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4992.
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Title of dissertation: GROWTH OF Zn POLAR BeMgZnO/ZnO HETEROSTRUCTURE WITH TWO DIMENSIONAL ELECTRON GAS (2DEG) AND FABRICATION OF SILVER SCHOTTKY DIODE ON BeMgZnO/ZnO HETEROSTRUCTURE
By Md Barkat Ullah, Ph.D
A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical and Computer Engineering at Virginia Commonwealth University.
Virginia Commonwealth University,2017
Major Director: Dr. Hadis Morkoç, Professor, Electrical and Computer Engineering
This thesis focuses on growth of Zn polar BeMgZnO/ZnO heterostructure on GaN/sapphire template with two dimensional electron gas (2DEG) for the application of UV photodetector/emitter and high speed electronics. The motivation of using BeMgZnO as a barrier layer originates from the need to reach plasmon-LO phonon resonance in order to obtain minimum longitudinal optical (LO) phonon lifetime.
Presence of 2DEG was realized in BeMgZnO/ZnO heterostructure only when the Zn polarity was achieved during the nucleation growth of ZnO on GaN/sapphire template. It was found that, polarity of ZnO on (0001) GaN/sapphire template can be controlled by the oxygen to Zn ratio used during the nucleation growth.
To obtain high structural and optical quality of BeMgZnO quaternary alloy, growth kinetics of BeMgZnO layer has been studied at the temperature range from 450°C-500°C. We have achieved the growth of single crystal Be.03Mg00.15ZnO alloy at 500 °C, more than 100°C higher compared to what reported in literature, on the (0001) GaN/sapphire template through the control of Zn/(Be+Mg) flux ratio. We have also observed a thermodynamic limitation of Mg incorporation into the wurtzite BeMgZnO alloy where the excess Mg adatom accumulated in the growing surface as a MgO rich cluster.
Two dimensional electron gas with high (1.2×1013cm-2) sheet carrier density was achieved at the Be0.03Mg0.41ZnO/ZnO interface through strain engineering by incorporating Be into MgZnO ternary alloy. To obtain the similar sheet carrier density it would require above 60% of Mg in MgZnO/ZnO heterostructure with reduced structural quality. A systematic comparison of sheet carrier density has been made with the already reported results from Zn polar MgZnO/ZnO heterostructure as well as with the theoretical calculation.
Silver Schottky diode on Be0.02Mg0.26ZnO/ZnO heterostructure with barrier height 1.07 eV and ideality factor 1.22 was obtained with 8 order of rectification ratio. The temperature-dependent electrical characteristics were studied by using temperature dependent current-voltage (I-V) measurements. Richardson constant value of 34.8 Acm-2K-2 was found experimentally which was close to the theoretical value of 36 Acm-2K-2 known for Be0.02Mg0.26ZnO alloy.
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Allen, Robert. "Investigations into Background Correction and Retention Time Alignment to Enhance Quantitative Chemometric Analysis of Comprehensive Two-Dimensional Liquid Chromatography-Diode Array Detection Data." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2912.
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The focus of the projects presented here was to develop possible solutions to three issues commonly encountered during chemometric analysis of comprehensive two-dimensional liquid chromatography diode array detector (LCxLC-DAD) data. The focus of the first project was to determine a means of performing background correction that removed two background ridges. The methods of simply subtracting out a mean blank sample, singular value decomposition based background correction (SVD-BC) and asymmetrically weighted least squares (AWLS) were compared. AWLS was found to be the only background correction technique to fully remove the ridges. However, AWLS was also found to attenuate the peak intensity by approximately 25% due to over fitting of the background at the lower wavelengths. The focus of the second project was the investigation of five common interpolation strategies for the reconstruction of the sampled first dimension peak. The interpolation strategy that best reproduced the original first dimension retention time was Gaussian fitting. This was expected given that the simulated data set was generated using a Gaussian model for the peak shape. An algorithm, semi-automated alignment method (SAAM), was then developed that allowed for each peak to be aligned independently of the other peaks in the data set. SAAM was validated using both simulated and experimental data. The simulated results indicated that SAAM produced percent recoveries close to 100%. SAAM was also compared to iterative key set factor analysis-alternating least squares (IKSFA-ALS) for the analysis of phenytoin in a waste water treatment plant effluent. SAAM produced a concentration of 26±3 ppb compared to 39±9 ppb from IKSFA-ALS. While these results are very different, the result produced by SAAM is still within the experimental error of the reference 2D-LC/MS/MS method, 42±19. Finally, SAAM was compared to two existing literature methods. A mixture of simulated and experimental data sets was used to measure the accuracy and precision of the results. SAAM was found to be impacted less by intra- and inter-sample retention time shifting then PARAFAC2. SAAM and shifted candecomp/PARAFAC were found to produce very similar results. However, SAAM was found to experience some difficulty producing accurate and precise results with some of the experimental data sets.
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Mbaye, Nogaye. "Contribution à l’étude de la fiabilité des technologies avancées en environnement radiatif atmosphérique et spatial par des méthodes optiques." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR15009/document.
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Ce travail présente la mise en œuvre du test par faisceau laser TPA pour l’étude de la sensibilité au phénomène SEB dans les diodes schottky en carbure de silicium. Le contexte de l’étude est décrit par un état de l’art du SEB sur les MOSFETs et Diodes en Silicium et en carbure de silicium. Une étude technologique et structurelle des composants en SiC a permis de dégager les avantages du SiC par rapport au Si conventionnel et a permis d’analyser les dégâts causés par le faisceau TPA. L’utilisation du montage expérimental sur la plateforme ATLAS dédié spécifiquement au test de matériaux à grand gap a permis de mettre en place une méthodologie de test sur des diodes schottky en SiC. L’efficacité de cette méthodologie est prouvée par l’obtention de résultats expérimentaux très originaux. La susceptibilité au SEB induit par la technique laser TPA a été démontrée. Les mesures SOA ont permis d’évaluer la robustesse des diodes schottky SiC face aux événements singuliers. Une modélisation analytique a été menée afin de comprendre la cause du mécanisme du SEB et la localisation des défauts induits par le faisceau TPA<br>This work presents the implementation of the TPA laser beam testing to study the SEB phenomenon in silicon carbide Schottky diodes. The context of the study is described by a state of the art of SEB on Si and SiC MOSFETs and Diodes. Technological and structural study of SiC components has identified the benefits of SiC compared to conventional Si and permits to analyze the damage caused by the TPA beam. Using the experimental setup of the ATLAS platform dedicated specifically to test large gap materials has set up a test methodology on SiC Schottky diodes. The effectiveness of this methodology is demonstrated by obtaining original experimental results. Susceptibility to SEB induced by TPA laser technique has been demonstrated. SOA measurements were used to assess the robustness of SiC Schottky diodes to single event effects.An analytical modeling was conducted to understand the cause of the SEB mechanism and the location of defects induced by the TPA beam
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Cook, Daniel W. "Chemometric Curve Resolution for Quantitative Liquid Chromatographic Analysis." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4362.
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In chemical analyses, it is crucial to distinguish between chemical species. This is often accomplished via chromatographic separations. These separations are often pushed to their limits in terms of the number of analytes that can be sufficiently resolved from one another, particularly when a quantitative analysis of these compounds is needed. Very often, complicated methods or new technology is required to provide adequate separation of samples arising from a variety of fields such as metabolomics, environmental science, food analysis, etc.
An often overlooked means for improving analysis is the use of chemometric data analysis techniques. Particularly, the use of chemometric curve resolution techniques can mathematically resolve analyte signals that may be overlapped in the instrumental data. The use of chemometric techniques facilitates quantitation, pattern recognition, or any other desired analyses. Unfortunately, these methods have seen little use outside of traditionally chemometrics focused research groups. In this dissertation, we attempt to show the utility of one of these methods, multivariate curve resolution-alternating least squares (MCR-ALS), to liquid chromatography as well as its application to more advanced separation techniques.
First, a general characterization of the performance of MCR-ALS for the analysis of liquid chromatography-diode array detection (LC-DAD) data is accomplished. It is shown that under a wide range of conditions (low chromatographic resolution, low signal-to-noise, and high similarity between analyte spectra), MCR-ALS is able to increase the number of quantitatively analyzable peaks. This increase is up to five-fold in many cases.
Second, a novel methodology for MCR-ALS analysis of comprehensive two-dimensional liquid chromatography (LC x LC) is described. This method, called two dimensional assisted liquid chromatography (2DALC), aims to improve quantitation in LC x LC by combining the advantages of both one-dimensional and two dimensional chromatographic data. We show that 2DALC can provide superior quantitation to both LC x LC and one dimensional LC under certain conditions.
Finally, we apply MCR-ALS to an LC x LC analysis of fourteen furanocoumarins in three apiaceous vegetables. The optimal implementation of MCR-ALS and subsequent integration was determined. For these data, simply performing MCR-ALS on the two dimensional chromatogram and manually integrating the results proved to be the superior method. These results demonstrate the usefulness of these curve resolution techniques as a compliment to advanced chromatographic techniques.
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Pasquali, Valerio. "Fabrication and measurement of strain-free GaAs/AlAs quantum dot devices." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066631.
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Dans cette thèse, nous nous intéressons à la croissance de boîtes quantiques par formation de nano-trous in-situ par « droplet-etching » ainsi qu’à la fabrication et caractérisation de dispositifs basés sur ces nanostructures. La thèse comporte sept chapitres. Le premier chapitre est une introduction au sujet et les méthodes expérimentales sont présentées dans le second chapitre. Les méthodes de fabrication ainsi que les résultats expérimentaux obtenus sont discutés dans le troisième chapitre.Nous montrons que l’utilisation in-situ de la méthode de droplet-etching permet de modifier localement l’épaisseur d’un puits quantique à modulation de dopage et créer des boîtes quantiques dans le puits où existe un gaz bidimensionnel d’électrons. Ces nanostructures constituent des diodes n-i Schottky que nous avons étudié. Les effets de ces boîtes quantiques non-contraintes et les fluctuations d’épaisseur à l’échelle nanométrique du puits quantique sur la mobilité du gaz bidimensionnel d’électrons sont discutés dans le quatrième chapitre et cinquième. Le sixième chapitre présente la fabrication d’une jonction p-n latérale basée sur l’échantillon de puits quantique avec des boîtes. Nous discutons les différentes étapes de fabrication et analysons leur influence sur le dispositif, ainsi que leurs propriétés optiques. En particulier, nous démontrons l’électroluminescence d’une boîte unique localisée dans une jonction p-n latérale. Finalement, le dernier chapitre conclue ce travail et en présente les perspectives<br>In this thesis the formation of quantum dots (QD) via in-situ droplet nanohole etching, the fabrication and characterization of devices based on these nanostructures is described. The thesis consists of seven chapters. In the first chapter an introduction is given to present the topic to the reader. In the second chapter the experimental methods are presented. In the third chapter, the fabrication method is described and the experimental results obtained in this project are discussed. It will be shown the use of in-situ droplet etching to locally modify the thickness of a modulation doped quantum well, to create QDs embedded in a quantum well(QW) where a two dimensional electorn gas (2DEG) is confined by modulation doping and the embedding of these nanostructures in a n-i-Schottky diode. The effect of these strain-free dots, and the related nanoscale thickness fluctuations of the quantum well, on the 2DEG mobility are discussed in the fourth and in particular in the fifth chapter. In the sixth chapter, the fabrication of a lateral p-n junction based on the QW sample with embedded QD is presented. Following describing the fabrication stages and analysing the influence of each stage on the device, the optical properties of the junction will be discussed. In particular, it will be shown the electroluminescence of a single dot located at lateral the p-n junction. Finally, in the last chapter the conclusion of this work and the future projects are presented
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Peck, Andrew John. "Lateral tunnelling in two-dimensional electron systems." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385345.
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Yildirim, Dogan. "Field Oriented Control Of A Permanent Magnet Synchronous Motor Using Space Vector Modulated Direct Ac-ac Matrix Converter." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614302/index.pdf.
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The study designs and constructs a three-phase to three-phase direct AC&ndash<br>AC matrix converter based surface mounted permanent magnet synchronous motor (PMSM) drive system. First, the matrix converter topologies are analyzed and the state-space equations describing the system have been derived in terms of the input and output variables. After that, matrix converter commutation and modulation methods are investigated. A four-step commutation technique based on output current direction provides safe commutation between the matrix converter switches. Then, the matrix converter is simulated for both the open-loop and the closed-loop control. For the closed-loop control, a current regulator (PI controller) controls the output currents and their phase angles. Advanced pulse width modulation and control techniques, such as space vector pulse width modulation and field oriented control, have been used for the closed-loop control of the system. Next, a model of diode-rectified two-level voltage source inverter is developed for simulations. A comparative study of indirect space vector modulated direct matrix converter and space vector modulated diode-rectified two-level voltage source inverter is given in terms of input/output waveforms to verify that the matrix converter fulfills the two-level voltage source inverter operation. Following the verification of matrix converter operation comparing with the diode-rectified two-level voltage source inverter, the simulation model of permanent magnet motor drive system is implemented. Also, a direct matrix converter prototype is constructed for experimental verifications of the results. As a first step in experimental works, filter types are investigated and a three-phase input filter is constructed to reduce the harmonic pollution. Then, direct matrix converter power circuitry and gate-driver circuitry are designed and constructed. To control the matrix switches, the control algorithm is implemented using a DSP and a FPGA. This digital control system measures the output currents and the input voltages with the aid of sensors and controls the matrix converter switches to produce the required PWM pattern to synthesize the reference input current and output voltage vectors, as well. Finally, the simulation results are tested and supported by laboratory experiments involving both an R-L load and a permanent magnet synchronous motor load. During the tests, the line-to-line supply voltage is set to 26 V peak value and a 400 V/3.5 kW surface mounted permanent magnet motor is used.
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Pasquali, Valerio. "Fabrication and measurement of strain-free GaAs/AlAs quantum dot devices." Electronic Thesis or Diss., Paris 6, 2017. http://www.theses.fr/2017PA066631.
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Dans cette thèse, nous nous intéressons à la croissance de boîtes quantiques par formation de nano-trous in-situ par « droplet-etching » ainsi qu’à la fabrication et caractérisation de dispositifs basés sur ces nanostructures. La thèse comporte sept chapitres. Le premier chapitre est une introduction au sujet et les méthodes expérimentales sont présentées dans le second chapitre. Les méthodes de fabrication ainsi que les résultats expérimentaux obtenus sont discutés dans le troisième chapitre.Nous montrons que l’utilisation in-situ de la méthode de droplet-etching permet de modifier localement l’épaisseur d’un puits quantique à modulation de dopage et créer des boîtes quantiques dans le puits où existe un gaz bidimensionnel d’électrons. Ces nanostructures constituent des diodes n-i Schottky que nous avons étudié. Les effets de ces boîtes quantiques non-contraintes et les fluctuations d’épaisseur à l’échelle nanométrique du puits quantique sur la mobilité du gaz bidimensionnel d’électrons sont discutés dans le quatrième chapitre et cinquième. Le sixième chapitre présente la fabrication d’une jonction p-n latérale basée sur l’échantillon de puits quantique avec des boîtes. Nous discutons les différentes étapes de fabrication et analysons leur influence sur le dispositif, ainsi que leurs propriétés optiques. En particulier, nous démontrons l’électroluminescence d’une boîte unique localisée dans une jonction p-n latérale. Finalement, le dernier chapitre conclue ce travail et en présente les perspectives<br>In this thesis the formation of quantum dots (QD) via in-situ droplet nanohole etching, the fabrication and characterization of devices based on these nanostructures is described. The thesis consists of seven chapters. In the first chapter an introduction is given to present the topic to the reader. In the second chapter the experimental methods are presented. In the third chapter, the fabrication method is described and the experimental results obtained in this project are discussed. It will be shown the use of in-situ droplet etching to locally modify the thickness of a modulation doped quantum well, to create QDs embedded in a quantum well(QW) where a two dimensional electorn gas (2DEG) is confined by modulation doping and the embedding of these nanostructures in a n-i-Schottky diode. The effect of these strain-free dots, and the related nanoscale thickness fluctuations of the quantum well, on the 2DEG mobility are discussed in the fourth and in particular in the fifth chapter. In the sixth chapter, the fabrication of a lateral p-n junction based on the QW sample with embedded QD is presented. Following describing the fabrication stages and analysing the influence of each stage on the device, the optical properties of the junction will be discussed. In particular, it will be shown the electroluminescence of a single dot located at lateral the p-n junction. Finally, in the last chapter the conclusion of this work and the future projects are presented
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Larroque, Joël. "Etude, conception et realisation d'un demodulateur a remodulation quadriphase : application a la regeneration du signal dans les satellites de telecommunications ou de relais de donnees." Toulouse 3, 1988. http://www.theses.fr/1988TOU30087.
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Ce memoire presente l'etude d'un demolutateur a remodulation quadriphase a la frequence de b, 87 ghz permettant la regeneration des signaux hyperfrequence a bord des satellites de telecommunications (a acces multiples commutes a bord) ou de relais de donnees (pour les liaisons avec des satellites ou des navettes en orbite basse ainsi qu'avec des mobiles terrestres. Le demodulateur a remodulation quadriphase est compose de sous-equipements dont une simulation permet de connaitre leurs influences sur les performances du systeme complet
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Remella, Siva Rama Karthik. "Operation and Heuristic Design of Closed Loop Two-Phase Wicked Thermosyphons (CLTPWT) for Cooling Light Emitting Diodes (LEDs)." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522314073895889.
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Tomita, Yuto. "Alternative transparent electrodes for organic light emitting diodes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1236711483222-35217.
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Solid state lighting is a new environmentally friendly light source. So far, light emitting diodes (LEDs) and organic LEDs (OLEDs) have been presented as candidates with potentially high efficiency. Recent advances of OLEDs in device architecture, light-out coupling, and materials have ensured high efficiency, exceeding that of incandescent light bulbs. In contrast to conventional point source LEDs, OLEDs distribute light throughout the surface area and are not restricted by their size. Additionally, OLEDs are expected to reach sufficient stability in the near future. The remaining challenge for OLEDs is their cost. New OLED technologies provide cost effective manufacturing methods which could be presented for transparent electrode materials because indium tin oxide (ITO), a widely used material as a transparent electrode for OLEDs, is less than optimal due to its high element price. In this work, alternative transparent electrodes for OLEDs as a replacement of ITO were studied. First, Al doped ZnO (ZnO:Al) which is composed of abundant materials was investigated with DC magnetron sputtering under a wide range of experimental conditions. The optimised ZnO:Al received comparable performance with conventional ITO films, low sheet resistance of 22.8 Ω/sq as well as a high transparency of 93.1 % (average value in the visible range). Various type of p-i-n OLEDs were employed on the structured ZnO:Al using photolithography. Green OLEDs with double emission layers have been archived stable efficiencies even at higher luminance. Also, OLEDs using two fluorescent colour system on ZnO:Al anode showed a purely white emission. It has been found that the OLEDs on ZnO:Al anode has comparable or better device efficiencies and operational lifetime compared to OLEDs on conventional ITO anode. As another alternative electrode, the conductive polymer Baytron®PH510 (PEDOT:PSS) was investigated. Due to a relatively high sheet resistance of PEDOT:PSS, metal grid was designed for large size OLEDs. White OLEDs on PEDOT anode with a size of 5 × 5 cm2 have achieved more than 10 lm/W of power efficiency using a scattering foil. Furthermore, up-scaled devices on 10 × 10 cm2 were also demonstrated. These results showed ZnO:Al and PEDOT are suitable for OLEDs as anode and have high potential as alternative transparent electrode materials.
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Tomita, Yuto. "Alternative transparent electrodes for organic light emitting diodes." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23806.
Full textAbstract:
Solid state lighting is a new environmentally friendly light source. So far, light emitting diodes (LEDs) and organic LEDs (OLEDs) have been presented as candidates with potentially high efficiency. Recent advances of OLEDs in device architecture, light-out coupling, and materials have ensured high efficiency, exceeding that of incandescent light bulbs. In contrast to conventional point source LEDs, OLEDs distribute light throughout the surface area and are not restricted by their size. Additionally, OLEDs are expected to reach sufficient stability in the near future. The remaining challenge for OLEDs is their cost. New OLED technologies provide cost effective manufacturing methods which could be presented for transparent electrode materials because indium tin oxide (ITO), a widely used material as a transparent electrode for OLEDs, is less than optimal due to its high element price. In this work, alternative transparent electrodes for OLEDs as a replacement of ITO were studied. First, Al doped ZnO (ZnO:Al) which is composed of abundant materials was investigated with DC magnetron sputtering under a wide range of experimental conditions. The optimised ZnO:Al received comparable performance with conventional ITO films, low sheet resistance of 22.8 Ω/sq as well as a high transparency of 93.1 % (average value in the visible range). Various type of p-i-n OLEDs were employed on the structured ZnO:Al using photolithography. Green OLEDs with double emission layers have been archived stable efficiencies even at higher luminance. Also, OLEDs using two fluorescent colour system on ZnO:Al anode showed a purely white emission. It has been found that the OLEDs on ZnO:Al anode has comparable or better device efficiencies and operational lifetime compared to OLEDs on conventional ITO anode. As another alternative electrode, the conductive polymer Baytron®PH510 (PEDOT:PSS) was investigated. Due to a relatively high sheet resistance of PEDOT:PSS, metal grid was designed for large size OLEDs. White OLEDs on PEDOT anode with a size of 5 × 5 cm2 have achieved more than 10 lm/W of power efficiency using a scattering foil. Furthermore, up-scaled devices on 10 × 10 cm2 were also demonstrated. These results showed ZnO:Al and PEDOT are suitable for OLEDs as anode and have high potential as alternative transparent electrode materials.
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LÓPEZ, Jesús Pavón. "Emissão coerente no azul induzida por lasers de diodo e de femtosegundos em vapor de rubído." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17697.
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Previous issue date: 2015-09-03<br>CNPq<br>Neste trabalho apresentamos um estudo da geração de luz no azul, em vapor de rubídio,
devido à ação combinada de um trem de pulsos ultracurtos (fs) e um laser contínuo (diodo).
Os dois feixes com polarizações paralelas e lineares, operando em 780 nm (diodo) e 776 nm
(fs), são focalizados no centro da célula de Rb, e são responsáveis por cada etapa da transição
de dois fótons 5S1/2 - 5P3/2 - 5D. Na configuração de feixes co-propagantes, uma coerência
entre as transições 5S1/2 - 5P3/2 - 5D - 6P é induzida e, na condição de casamento de fase, um
feixe azul, coerente, é gerado em 420 nm, através de um processo de mistura de quarto ondas.
Medidas do espectro de excitação em função da frequência do laseres de diodo, para
diferentes temperaturas da amostra e intensidades dos laseres incidentes, indicam uma forte
competição entre os efeitos de saturação, ganho e absorção. Estudos de polarização e uma
comparação com os recentes resultados de fluorescência permitem caracterizar para que
parâmetros o mecanismo de mistura de ondas é responsável pelo sinal observado. Utilizando
um laser de femtosegundos com uma taxa de repetição da ordem de 76 MHz, é possível
observar, dentro do perfil Doppler, a contribuição dos diferentes modos do pente de
frequência na geração do feixe coerente.<br>We present a study of blue light generation, in rubidium vapor, due to the combined action of
a train of ultrashort pulses (fs) and a continuous laser (diode). The two beams with parallel
and linear polarizations, operating at 780 nm (diode) and 776 nm (fs) are focused on the
center of the Rb cell and are responsible for each step of the two photon transition from 55S1/2
- 5P3/2 - 5D. In the configuration of the co-propagating beams, a coherence between the
5S1/2 - 5P3/2 - 5D - 6P transitions is induced and, in phase matching condition, a blue coherent
beam is generated at 420 nm through a process of four wave mixing. The measurements of
excitation spectrum as a function of the frequency of the diode laser, for different
temperatures of the sample and intensities of the incident laseres, indicate a strong
competition among saturation, gain and absorption effects. The polarization studies and a
comparison with recent results of fluorescence are used to characterize the parameters for
which the wave mixing mechanism is responsible for the observed signal. Using a
femtosecond laser with a repetition rate of about 76 MHz, it is possible observe, within the
Doppler profile, the contribution of the different modes of the frequency comb in the
generation of the coherent beam.
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Zarghami, Majid. "Characterization, calibration, and optimization of time-resolved CMOS single-photon avalanche diode image sensor." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/273463.
Full textAbstract:
Vision has always been one of the most important cognitive tools of human beings. In this regard, the development of image sensors opens up the potential to view objects that our eyes cannot see. One of the most promising capability in some image sensors is their single-photon sensitivity that provides information at the ultimate fundamental limit of light. Time-resolved single-photon avalanche diode (SPAD) image sensors bring a new dimension as they measure the arrival time of incident photons with a precision in the order of hundred picoseconds. In addition to this characteristic, they can be fabricated in complementary metal-oxide-semiconductor (CMOS) technology enabling the integration of complex signal processing blocks at the pixel level. These unique features made CMOS SPAD sensors a prime candidate for a broad spectrum of applications. This thesis is dedicated to the optimization and characterization of quantum imagers based on the SPADs as part of the E.U. funded SUPERTWIN project to surpass the fundamental diffraction limit known as the Rayleigh limit by exploiting the spatio-temporal correlation of entangled photons.
The first characterized sensor is a 32×32-pixel SPAD array, named “SuperEllen”, with in-pixel time-to-digital converters (TDC) that measure the spatial cross-correlation functions of a flux of entangled photons. Each pixel features 19.48% fill-factor (FF) in 44.64-μm pitch fabricated in a 150-nm CMOS standard technology. The sensor is fully characterized in several electro-optical experiments, in order to be used in quantum imaging measurements. Moreover, the chip is calibrated in terms of coincidence detection achieving the minimal coincidence window determined by the SPAD jitter. The second developed sensor in the context of SUPERTWIN project is a 224×272-pixel SPAD-based array called “SuperAlice”, a multi-functional image sensor fabricated in a 110-nm CMOS image sensor technology. SuperAlice can operate in multiple modes (time-resolving or photon counting or binary imaging mode).
Thanks to the digital intrinsic nature of SPAD imagers, they have an inherent capability to achieve a high frame rate. However, running at high frame rate means high I/O power consumption and thus inefficient handling of the generated data, as SPAD arrays are employed for low light applications in which data are very sparse over time and space. Here, we present three zero-suppression mechanisms to increase the frame rate without adversely affecting power consumption. A row-skipping mechanism that is implemented in both SuperEllen and SuperAlice detects the absence of SPAD activity in a row to increase the duty cycle. A current-based mechanism implemented in SuperEllen ignores reading out a full frame when the number of triggered pixels is less than a user-defined value. A different zero-suppression technique is developed in the SuperAlice chip that is based on jumping through the non-zero pixels within one row.
The acquisition of TDC-based SPAD imagers can be speeded up further by storing and processing events inside the chip without the need to read out all data. An on-chip histogramming architecture based on analog counters is developed in a 150-nm CMOS standard technology. The test structure is a 16-bin histogram with 9 bit depth for each bin.
SPAD technology demonstrates its capability in other applications such as automotive that demands high dynamic range (HDR) imaging. We proposed two methods based on processing photon arrival times to create HDR images. The proposed methods are validated experimentally with SuperEllen obtaining >130 dB dynamic range within 30 ms of integration time and can be further extended by using a timestamping mechanism with a higher resolution.
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Zarghami, Majid. "Characterization, calibration, and optimization of time-resolved CMOS single-photon avalanche diode image sensor." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/273463.
Full textAbstract:
Vision has always been one of the most important cognitive tools of human beings. In this regard, the development of image sensors opens up the potential to view objects that our eyes cannot see. One of the most promising capability in some image sensors is their single-photon sensitivity that provides information at the ultimate fundamental limit of light. Time-resolved single-photon avalanche diode (SPAD) image sensors bring a new dimension as they measure the arrival time of incident photons with a precision in the order of hundred picoseconds. In addition to this characteristic, they can be fabricated in complementary metal-oxide-semiconductor (CMOS) technology enabling the integration of complex signal processing blocks at the pixel level. These unique features made CMOS SPAD sensors a prime candidate for a broad spectrum of applications. This thesis is dedicated to the optimization and characterization of quantum imagers based on the SPADs as part of the E.U. funded SUPERTWIN project to surpass the fundamental diffraction limit known as the Rayleigh limit by exploiting the spatio-temporal correlation of entangled photons.
The first characterized sensor is a 32×32-pixel SPAD array, named “SuperEllen”, with in-pixel time-to-digital converters (TDC) that measure the spatial cross-correlation functions of a flux of entangled photons. Each pixel features 19.48% fill-factor (FF) in 44.64-μm pitch fabricated in a 150-nm CMOS standard technology. The sensor is fully characterized in several electro-optical experiments, in order to be used in quantum imaging measurements. Moreover, the chip is calibrated in terms of coincidence detection achieving the minimal coincidence window determined by the SPAD jitter. The second developed sensor in the context of SUPERTWIN project is a 224×272-pixel SPAD-based array called “SuperAlice”, a multi-functional image sensor fabricated in a 110-nm CMOS image sensor technology. SuperAlice can operate in multiple modes (time-resolving or photon counting or binary imaging mode).
Thanks to the digital intrinsic nature of SPAD imagers, they have an inherent capability to achieve a high frame rate. However, running at high frame rate means high I/O power consumption and thus inefficient handling of the generated data, as SPAD arrays are employed for low light applications in which data are very sparse over time and space. Here, we present three zero-suppression mechanisms to increase the frame rate without adversely affecting power consumption. A row-skipping mechanism that is implemented in both SuperEllen and SuperAlice detects the absence of SPAD activity in a row to increase the duty cycle. A current-based mechanism implemented in SuperEllen ignores reading out a full frame when the number of triggered pixels is less than a user-defined value. A different zero-suppression technique is developed in the SuperAlice chip that is based on jumping through the non-zero pixels within one row.
The acquisition of TDC-based SPAD imagers can be speeded up further by storing and processing events inside the chip without the need to read out all data. An on-chip histogramming architecture based on analog counters is developed in a 150-nm CMOS standard technology. The test structure is a 16-bin histogram with 9 bit depth for each bin.
SPAD technology demonstrates its capability in other applications such as automotive that demands high dynamic range (HDR) imaging. We proposed two methods based on processing photon arrival times to create HDR images. The proposed methods are validated experimentally with SuperEllen obtaining >130 dB dynamic range within 30 ms of integration time and can be further extended by using a timestamping mechanism with a higher resolution.
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Bartzsch, Matthias. "Herstellung von Schottky-Dioden mittels Rolle-zu-Rolle-Verfahren." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-78462.
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Im Rahmen der vorliegenden Arbeit wurden Schottky-Dioden mittels Rolle-zu-Rolle-Verfahren hergestellt und charakterisiert. Die Dioden bestanden dabei aus einer Kathode (Aluminium oder Kupfer), die durch Sputtern aufgebracht wurde, einer Halbleiterschicht aus Polytriphenylaminen (PTPA3), die mittels Tiefdruck aufgebracht wurde und einer im Flexodruck hergestellten Anode (PEDOT:PSS, Pani oder Carbon Black). Aus elektrischer Sicht wiesen dabei Dioden mit Kupfer und Carbon Black die besten Eigenschaften auf. Mit Hilfe dieser Elektrodenmaterialien und bei Halbleiterschichtdicken von ca. 200 nm konnten Grenzfrequenzen der Dioden von über 1 MHz realisiert werden. Weiterhin wiesen diese Dioden eine gute Langzeitstabilität sowie eine gute Stabilität gegenüber UV-Licht, Feuchtigkeit und Temperatur auf<br>Aim of this work was to demonstrate that Schottky-Diodes can be fabricated by means of Roll-to-Roll-Methods and to characterize these diodes. The diodes consists of a sputtered cathode (Aluminum or Copper), a gravure printed semiconducting layer of Polytriphenylamine (PTPA3) and a flexo printed anode (PEDOT:PSS, Pani, Carbon Black). Best electrical characteristics were obtained with diodes consisting Copper and Carbon Black as electrodes. With a thickness of the semiconducting layer of ~200 nm diodes with a cut-off frequency above 1 MHz could be demonstrated. These diodes showed also a good stability when exposed to UV-light, moisture and temperature
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Vallurupalli, Subhash C. C. "Fabrication and characterization of Schottky diode and heterojunction solar cells based on Copper Phthalocyanine (CuPc), Buckminster Fullerene (C₆₀) and titanium dioxide (TiO₂)." Lexington, Ky. : [University of Kentucky Libraries], 2005. http://lib.uky.edu/ETD/ukyelen2005t00340/Subhash.pdf.
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Thesis (M.S.)--University of Kentucky, 2005.<br>Title from document title page (viewed on November 18, 2005). Document formatted into pages; contains xiv, 101 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 99-100).
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Kulisek, Jonathan Andrew. "The Effects of Nuclear Radiation on Schottky Power Diodes and Power MOSFETs." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1267502877.
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Parmesan, Luca. "Photon efficient, high resolution, time resolved SPAD image sensors for fluorescence lifetime imaging microscopy." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33171.
Full textAbstract:
FLIM is branch of microscopy mainly used in biology which is quickly improving thanks to a rapid enhancement of instrumentation and techniques enabled by new sensors. In FLIM, the most precise method of measuring fluorescent decays is called TCSPC. High voltage PMT detection devices together with costly and bulky optical setups which scan the sample are usually required in TCSPC instrumentation. SPADs have enabled a big improvement in TCSPC measurement setup, providing a CMOS compatible device which can be designed in wide arrays format. However, sensors providing in-pixel TCSPC do not scale in size and in large array like the time-gated SPAD pixel sensors do. Time-gated pixels offer a less precise lifetime estimation, discarding any photon information outside a given time window, but this loss in photon-efficiency is offset by gains in pixel size. This work is aimed at the development of a wide field TCSPC sensor with a pixel size and fill factor able to reduce the cost of such devices and to obtain a high resolution time-resolved fluorescence image in the shortest time possible. The study focuses on SPAD and pixel design required to maximise the fill factor in sub 10 μm pixel pitch. Multiple pixel designs are proposed in order to reduce pixel area and so enable affordable wide array TCSPC systems. The first proposed pixel performs the CMM lifetime estimation in order to reduce the frame rate needed to stream the data out of the SPAD array. This pixel is designed in a 10 μm pitch and attains with the most aggressive design a fill factor of 10:17 %. A second design proposes an analogue TCSPC which consists in a S/H TAC circuitry. This simpler pixel can achieve a higher fill factor of 19:63% as well as smaller pitch of 8 μm thanks to the adoption of SPAD n-well and electronics area sharing. This last design is implemented in a 320 x 256 SPAD array in which is included part of a novel ADC aimed at reduction of the processing time required to build a TCSPC histogram. A more conventional analogue readout is used to evaluate the pixel performance as well as a more fine TCSPC histogram. The device was used to measure the fluorescence lifetime of green micro-spheres while the 2b flash ADC is used to demonstrate rapid resolution and separation of two different fluorescence decays.
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Gur, Sourav, and Sourav Gur. "Atomistic to Continuum Multiscale and Multiphysics Simulation of NiTi Shape Memory Alloy." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625589.
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Shape memory alloys (SMAs) are materials that show reversible, thermo-elastic, diffusionless, displacive (solid to solid) phase transformation, due to the application of temperature and/ or stress (/strain). Among different SMAs, NiTi is a popular one. NiTi shows reversible phase transformation, the shape memory effect (SME), where irreversible deformations are recovered upon heating, and superelasticity (SE), where large strains imposed at high enough temperatures are fully recovered. Phase transformation process in NiTi SMA is a very complex process that involves the competition between developed internal strain and phonon dispersion instability. In NiTi SMA, phase transformation occurs over a wide range of temperature and/ or stress (strain) which involves, evolution of different crystalline phases (cubic austenite i.e. B2, different monoclinic variant of martensite i.e. B19', and orthorhombic B19 or BCO structures). Further, it is observed from experimental and computational studies that the evolution kinetics and growth rate of different phases in NiTi SMA vary significantly over a wide spectrum of spatio-temporal scales, especially with length scales. At nano-meter length scale, phase transformation temperatures, critical transformation stress (or strain) and phase fraction evolution change significantly with sample or simulation cell size and grain size. Even, below a critical length scale, the phase transformation process stops. All these aspects make NiTi SMA very interesting to the science and engineering research community and in this context, the present focuses on the following aspects.
At first this study address the stability, evolution and growth kinetics of different phases (B2 and variants of B19'), at different length scales, starting from the atomic level and ending at the continuum macroscopic level. The effects of simulation cell size, grain size, and presence of free surface and grain boundary on the phase transformation process (transformation temperature, phase fraction evolution kinetics due to temperature) are also demonstrated herein. Next, to couple and transfer the statistical information of length scale dependent phase transformation process, multiscale/ multiphysics methods are used. Here, the computational difficulty from the fact that the representative governing equations (i.e. different sub-methods such as molecular dynamics simulations, phase field simulations and continuum level constitutive/ material models) are only valid or can be implemented over a range of spatiotemporal scales. Therefore, in the present study, a wavelet based multiscale coupling method is used, where simulation results (phase fraction evolution kinetics) from different sub-methods are linked via concurrent multiscale coupling fashion. Finally, these multiscale/ multiphysics simulation results are used to develop/ modify the macro/ continuum scale thermo-mechanical constitutive relations for NiTi SMA. Finally, the improved material model is used to model new devices, such as thermal diodes and smart dampers.
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Zolfaghari, Zahra. "Study of the Effect of Light Emitting Diode (LED) on the Optimum Window-to-Wall Ratio and Whole-Building Energy Consumption in Open Offices." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/100642.
Full textAbstract:
Daylight harvesting is an essential strategy that is often used to enhance both the design and performance of an architectural project. Windows, as crucial architectural elements, not only admit natural light into spaces but also provide the occupants with visual connections. However, the excessive usage of windows brings an uncontrolled amount of solar energy to the spaces and negatively affect the building's energy performance.
When utilizing passive design strategies such as daylight harvesting, several parameters, including the electrical lighting system, can impact the outcome. The current study investigates the role of lighting systems on daylight harvesting's effectiveness and their impact on window dimension and total energy consumption. In this study, the optimum window-to-wall ratio of an open office in the presence of two different light sources (LED and fluorescent) is explored through a computer simulation method. A combination of tools including AGi32, ElumTools, OpenStudio, EnergyPlus, Radiance, and MATLAB helps to conduct the simulation and deliver optimal results.
In the results and conclusion chapter, the study provides guidelines to specify optimal window percentages considering two lighting systems in each cardinal direction. Importantly, the guideline focuses only on energy performance and not on the spatial quality of the design.<br>Master of Architecture<br>Harnessing daylight with the use of windows helps to offset parts of the electric lighting needs, and decrease the total building energy consumption. This is accomplished by using glazed materials to admit daylight and lighting control systems, which can respond to the dynamic light level. However, improper implementation of a passive daylighting strategy may cause increased energy consumption. Sunlight is accompanied by solar heat radiation which can increase the HVAC load of a space and compromise the energy savings achieved by daylighting. Therefore, a balance between solar heat and light gain is required to fully take advantage of solar energy without reverse impacts.
Concerning the mentioned balance, recent advancements in lighting technology question the effectiveness of natural light in reducing whole-building energy consumption. Due to the high energy efficiency of LED luminaires, lighting power consumption is rather low, even when the lighting system operates at full capacity. Therefore, it is unclear whether the solar energy coming through glazed materials works to the advantage or disadvantage of total building energy consumption. This study hypothesized that the total energy consumption of an open office with LED luminaires would be less in absence of solar energy compared to a scenario which utilizes the solar energy. A simulation-based methodology, using a combination of photometric computation and building energy simulation tools, was utilized to examine the hypothesis and explore the impacts of lighting systems on the optimum window-to-wall ratio.
The results provide a helpful guideline which highlights the impact of lighting systems on window dimensions and their mutual effect on whole-building energy consumption. Although the optimum window-to-wall ratios suggested by this study only concern energy consumption, integration of them with occupants' preferences can propose an acceptable window-to-wall ratio that satisfies both design quality and performance of a building.
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Urig, Christina S. "EVALUATION OF SINGLE MOLECULE DIODES FABRICATED VIA ELECTRON-BEAM LITHOGRAPHY AND METAL-ORGANIC FRAMEWORKS INCORPORATING TWO NOVEL LIGANDS, A TRIGONAL PLANAR CARBOXYLATE LIGAND AND A TETRAHEDRAL TETRAZOLATE-BASED LIGAND." Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1176829199.
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Della, Casa Pietro [Verfasser], Markus [Akademischer Betreuer] Weyers, Michael [Gutachter] Kneissl, Michael [Gutachter] Jetter, and Markus [Gutachter] Weyers. "Two-step MOVPE, in-situ etching and buried implantation: applications to the realization of GaAs laser diodes / Pietro Della Casa ; Gutachter: Michael Kneissl, Michael Jetter, Markus Weyers ; Betreuer: Markus Weyers." Berlin : Technische Universität Berlin, 2021. http://d-nb.info/1230468420/34.
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Abdulahi, Mohamed Abdirahman, and Wännström Aksel. "Quality Control of Light Emitting Diodes : Using power factor, harmonic distortion and light to power ratios." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301196.
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This study addresses quality control for Light Emitting Diodes (LED) according to fouraspects, the power factor of LED lamps, their harmonics and total harmonic distortion (THD), the luminosity for total power to radiated power ratio. It focuses on four brands and six different LED lamps, and concludes that IKEA's LED lamps pertain as the quality lamp, with a power factor over 0.9, THD less than 4% and a power to radiated light of over 4%.
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Cunin, Bernard. "Etude et realisation d'un modulateur parametrique a double bande laterale fonctionnant a 10 ghz : application a la detection d'impulsions lumineuses breves." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13127.
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Les proprietes d'un modulateur parametrique sont analysees. On montre que ce dispositif, constitue par la capacite variable d'une jonction pn pompee a 10 ghz, est caracterise par un gain de conversion, une impedance d'entree capacitive et un bruit interne tres reduit et qu'en consequence un systeme de detection optique, forme par une diode pin rapide couplee au convertisseur parametrique, presente un rapport signal a bruit superieur a celui des dispositifs de detection sans amplification interne habituellement utilises, au moins tant que la bande passante video est inferieure a 4 ghz. Enfin, on decrit une realisation pratique pour laquelle on a mesure un gain de conversion de 7db et une largeur a mi-hauteur de la reponse percussionnelle du modulateur seul voisine de 500 ps
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Angelini, Marina Robles. "Efeito de genótipos de maracujazeiro sobre Dione juno juno (Cramer, 1779) (Lepidoptera: Nymphalidae) e associação ao predador Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae) /." Jaboticabal : [s.n.], 2007. http://hdl.handle.net/11449/102303.
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Orientador: Arlindo Leal Boiça Junior<br>Banca: José Djair Vendramin<br>Banca: João Carlos de Oliveira<br>Banca: Carlos Amadeu Leite de Oliveira<br>Banca: Teresinha Monteiro dos Santos<br>Resumo: O presente trabalho teve como objetivos estudar o comportamento de genótipos de maracujazeiro em relação à infestação de Dione juno juno (Cramer, 1779) (Lepidoptera: Nymphalidae), bem como verificar a influência desses genótipos sobre o predador Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae). Verificou-se a influência de genótipos de maracujazeiro sobre a preferência alimentar e os aspectos biológicos de D. juno juno. Em testes posteriores avaliou-se a atratividade e capacidade predatória de P. nigrispinus por lagartas de D. juno juno, e os aspectos biológicos do predador quando alimentado com presas, criadas em diferentes genótipos de maracujazeiro. Os experimentos foram conduzidos no Departamento de Fitossanidade da Faculdade de Ciências Agrárias e Veterinárias, Câmpus de Jaboticabal/SP, sendo os testes de laboratório realizados no Laboratório de Resistência de Plantas a Insetos deste mesmo local, sob condições ambientais controladas (temperatura: 26 l 1°C, U. R. de 60 l 10% e fotofase de 14 horas). Foram utilizados os genótipos de maracujazeiro Passiflora edulis Sims., P. alata Dryand, P. serrato-digitata L., P. edulis f. flavicarpa Deg. (cv. Sul Brasil), P. edulis f. flavicarpa (cv. IAC-275), P. edulis f. flavicarpa (cv. Flora FB 300), P. gibertii N. E. Br, P. edulis f. flavicarpa, P. edulis f. flavicarpa (cv. Maguary FB-100) e P. foetida L., os quais foram obtidos junto aos Bancos de Germoplasma da FCAV, do Instituto Agronômico de Campinas e na Associação de Fruticultores de Vera Cruz/SP (AFRUVEC). O genótipo menos atrativo às lagartas recém-eclodidas e de 10 dias de idade foi P. alata em testes com e sem chance de escolha...(Resumo completo, clicar acesso eletrõnico abaixo)<br>Abstract: This work was carried out to study the behavior of passion fruit genotypes under the attack of Dione juno juno (Cramer, 1779) (Lepidoptera: Nymphalidae), as well as observe the influence of genotypes on the predator Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae). The influence of passion fruit genotypes on the feeding preference and biology aspects of D. juno juno were studied. Further experiments evaluated the attractivity and predatory capacity of P. nigrispinus on D. juno juno, as well as biological aspects of the predator when fed with preys reared in different passion fruit genotypes. Experiments were conducted at the Department of Fitossanidade - Faculdade de Ciências Agrárias e Veterinárias (FCAV/UNESP), Jaboticabal/SP, and lab trials were performed at the Laboratory of Plant Resistance to Insects under controlled conditions (temperature: 26 l 1°C, RH = 60 l 10% and photophase of 14 hours). The genotypes used in this study: Passiflora edulis Sims, P. alata Dryand, P. serrato-digitata L., P. edulis f. flavicarpa Deg (cv. Sul Brasil), P. edulis f. flavicarpa (cv. IAC-275), P. edulis f. flavicarpa (cv. Flora FB 300), P. gibertii N. E. Br, P. edulis f. flavicarpa, P. edulis f. flavicarpa (cv. Maguary FB-100) and P. foetida L. were obtained from the germplasm banks of FCAV-UNESP, Instituto Agronômico de Campinas and Vera Cruz Fruit Growers Association (AFRUVEC). P. alata was the least attractive genotype to just-hatched larvae in free and no-choice tests. In terms of leaf consumption, P. alata was the least preferred in the free-choice test, while in the no-choice test both P. alata and P. foetida were the least consumed by just-hatched and 10-day-old larvae...(Complete abstract, click electronic address below)<br>Doutor
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Angelini, Marina Robles [UNESP]. "Efeito de genótipos de maracujazeiro sobre Dione juno juno (Cramer, 1779) (Lepidoptera: Nymphalidae) e associação ao predador Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae)." Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/102303.
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angelini_mr_dr_jabo.pdf: 469730 bytes, checksum: cef2daa5a3247bc3ede3d4385bd2681e (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>O presente trabalho teve como objetivos estudar o comportamento de genótipos de maracujazeiro em relação à infestação de Dione juno juno (Cramer, 1779) (Lepidoptera: Nymphalidae), bem como verificar a influência desses genótipos sobre o predador Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae). Verificou-se a influência de genótipos de maracujazeiro sobre a preferência alimentar e os aspectos biológicos de D. juno juno. Em testes posteriores avaliou-se a atratividade e capacidade predatória de P. nigrispinus por lagartas de D. juno juno, e os aspectos biológicos do predador quando alimentado com presas, criadas em diferentes genótipos de maracujazeiro. Os experimentos foram conduzidos no Departamento de Fitossanidade da Faculdade de Ciências Agrárias e Veterinárias, Câmpus de Jaboticabal/SP, sendo os testes de laboratório realizados no Laboratório de Resistência de Plantas a Insetos deste mesmo local, sob condições ambientais controladas (temperatura: 26 l 1°C, U. R. de 60 l 10% e fotofase de 14 horas). Foram utilizados os genótipos de maracujazeiro Passiflora edulis Sims., P. alata Dryand, P. serrato-digitata L., P. edulis f. flavicarpa Deg. (cv. Sul Brasil), P. edulis f. flavicarpa (cv. IAC-275), P. edulis f. flavicarpa (cv. Flora FB 300), P. gibertii N. E. Br, P. edulis f. flavicarpa, P. edulis f. flavicarpa (cv. Maguary FB-100) e P. foetida L., os quais foram obtidos junto aos Bancos de Germoplasma da FCAV, do Instituto Agronômico de Campinas e na Associação de Fruticultores de Vera Cruz/SP (AFRUVEC). O genótipo menos atrativo às lagartas recém-eclodidas e de 10 dias de idade foi P. alata em testes com e sem chance de escolha...<br>This work was carried out to study the behavior of passion fruit genotypes under the attack of Dione juno juno (Cramer, 1779) (Lepidoptera: Nymphalidae), as well as observe the influence of genotypes on the predator Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae). The influence of passion fruit genotypes on the feeding preference and biology aspects of D. juno juno were studied. Further experiments evaluated the attractivity and predatory capacity of P. nigrispinus on D. juno juno, as well as biological aspects of the predator when fed with preys reared in different passion fruit genotypes. Experiments were conducted at the Department of Fitossanidade - Faculdade de Ciências Agrárias e Veterinárias (FCAV/UNESP), Jaboticabal/SP, and lab trials were performed at the Laboratory of Plant Resistance to Insects under controlled conditions (temperature: 26 l 1°C, RH = 60 l 10% and photophase of 14 hours). The genotypes used in this study: Passiflora edulis Sims, P. alata Dryand, P. serrato-digitata L., P. edulis f. flavicarpa Deg (cv. Sul Brasil), P. edulis f. flavicarpa (cv. IAC-275), P. edulis f. flavicarpa (cv. Flora FB 300), P. gibertii N. E. Br, P. edulis f. flavicarpa, P. edulis f. flavicarpa (cv. Maguary FB-100) and P. foetida L. were obtained from the germplasm banks of FCAV-UNESP, Instituto Agronômico de Campinas and Vera Cruz Fruit Growers Association (AFRUVEC). P. alata was the least attractive genotype to just-hatched larvae in free and no-choice tests. In terms of leaf consumption, P. alata was the least preferred in the free-choice test, while in the no-choice test both P. alata and P. foetida were the least consumed by just-hatched and 10-day-old larvae...(Complete abstract, click electronic address below)
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Kratochvíl, Robert. "Návrh zařízení pro analýzu povrchových vlastností materiálů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219038.
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The thesis deals with the application of laser beams for examination of material properties. The properties being examined are quality of surface finish and transmissivity of materials in the optical portion of the electromagnetic spectrum. A measuring device containing laser diodes as a source of laser beam and photodiodes for evaluation of examined phenomena serves for examination of both properties. Conversion of the signal to digital quantity and its further processing take place in a microcontroller. The data is then sent via a serial bus and a converter to a computer, where it may be saved in a user program and where the user can work with them later. The thesis contains results of reflectivity measurement of a set of metal samples with different surface finish. Transmissivity measurement was applied on a set of optical filters.
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Semeniuk, Konstantin. "Correlated low temperature states of YFe2Ge2 and pressure metallised NiS2." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274346.
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While the free electron model can often be surprisingly successful in describing properties of solids, there are plenty of materials in which interactions between electrons are too significant to be neglected. These strongly correlated systems sometimes exhibit rather unexpected, unusual and useful phenomena, understanding of which is one of the aims of condensed matter physics. Heat capacity measurements of paramagnetic YFe$_{2}$Ge$_{2}$ give a Sommerfeld coefficient of about 100 mJ mol$^{−1}$ K$^{−2}$, which is about an order of magnitude higher than the value predicted by band structure calculations. This suggests the existence of strong electronic correlations in the compound, potentially due to proximity to an antiferromagnetic quantum critical point (QCP). Existence of the latter is also indicated by the non-Fermi liquid T$^{3/2}$ behaviour of the low temperature resistivity. Below 1.8 K a superconducting phase develops in the material, making it a rare case of a non-pnictide and non-chalcogenide iron based superconductor with the 1-2-2 structure. This thesis describes growth and study of a new generation of high quality YFe$_{2}$Ge$_{2}$ samples with residual resistance ratios reaching 200. Measurements of resistivity, heat capacity and magnetic susceptibility confirm the intrinsic and bulk character of the superconductivity, which is also argued to be of an unconventional nature. In order to test the hypothesis of the nearby QCP, resistance measurements under high pressure of up to 35 kbar have been conducted. Pressure dependence of the critical temperature of the superconductivity has been found to be rather weak. μSR measurements have been performed, but provided limited information due to sample inhomogeneity resulting in a broad distribution of the critical temperature. While the superconductivity is the result of an effective attraction between electrons, under different circumstances the electronic properties of a system can instead be dictated by the Coulomb repulsion. This is the case for another transition metal based compound NiS$_{2}$, which is a Mott insulator. Applying hydrostatic pressure of about 30 kbar brings the material across the Mott metal-insulator transition (MIT) into the metallic phase. We have used the tunnel diode oscillator (TDO) technique to measure quantum oscillations in the metallised state of NiS$_{2}$, making it possible to track the evolution of the principal Fermi surface and the associated effective mass as a function of pressure. New results are presented which access a wider pressure range than previous studies and provide strong evidence that the effective carrier mass diverges close to the Mott MIT, as expected within the Brinkman-Rice scenario and predicted in dynamical mean field theory calculations. Quantum oscillations have been measured at pressures as close to the insulating phase as 33 kbar and as high as 97 kbar. In addition to providing a valuable insight into the mechanism of the Mott MIT, this study has also demonstrated the potential of the TDO technique for studying materials at high pressures.
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Kaňa, Leoš. "Návrh vnitřního optického spoje." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219165.
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In last years phenomena of wireless communication technologies became a primary interest of big development laboratories whole world. Domain of point to point links which are realized by laser technology with narrow beam divergence and very sensitive photo-detectors is ordinarily used these days. This trend of using light waves as carrier medium turned interests of scientist to the sphere of wide area networks which is domain of wi-fi radio technologies. One of new trends in this sphere is also in-door free space optics. With expansion which leads to using LED's in everyday applications and with technological progress of last years, also grows tendency of most effective utilization of LED systems. The result of this effort is thought which considerate LED as source of artificial lighting and source of carrier medium for modulated signal. This kind of device must fulfill hygienic standards for illumination and also must be able to work with high frequency by which is signal modulated. These systems can provide links with sufficient capacity in order of hundred megabits.
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Daubriac, Richard. "Caractérisation de techniques d'implantations ioniques alternatives pour l'optimisation du module source-drain de la technologie FDSOI 28nm." Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0031/document.
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Durant ces dernières années, l’apparition de nouvelles architectures (FDSOI, FinFETs ou NW-FETs) et l’utilisation de nouveaux matériaux (notamment SiGe) ont permis de repousser les limites des performances des dispositifs MOS et de contourner l’effet canal court inhérent à la miniaturisation des composants. Cependant, pour toutes ces nouvelles architectures, la résistance de contact se dégrade au fil des nœuds technologiques. Celle-ci dépend fortement de deux paramètres physiques : la concentration de dopants actifs proches de la surface du semi-conducteur et de la hauteur de barrière Schottky du contact siliciuré. De multiples procédés avancés ont été proposé pour améliorer ces deux paramètres physiques (pré-amorphisation, recuit laser, ségrégation de dopants, etc…). Afin d’optimiser les conditions expérimentales de ces nouvelles techniques de fabrication, il est primordial de pouvoir caractériser avec fiabilité leur impact sur les deux grandeurs physiques citées. Dans le cadre de cette thèse, deux thématiques dédiées à l’étude de chacun des paramètres sont abordées, explicitant les méthodes de caractérisation développées ainsi que des exemples concrets d’applications. La première partie concerne l’étude de la concentration de dopants actifs proches de la surface du semi-conducteur. Dans cet axe, nous avons mis en place une méthode d’Effet Hall Différentiel (DHE). Cette technique combine gravures successives et mesures par effet Hall conventionnel afin d’obtenir le profil de concentration de dopants actifs en fonction de la profondeur. Nous avons développé et validé une méthode de gravure chimique et de mesure électrique pour des couches ultra-minces de SiGe et de Si dopées. Les profils de concentration générés ont une résolution en profondeur inférieure à 1 nm et ont permis d’étudier de façon approfondie dans les premiers nanomètres proches de la surface de couches fabriquées grâce à des techniques d’implantation et de recuit avancées comme par exemple, la croissance en phase solide activée par recuit laser. La deuxième partie porte sur la mesure de hauteurs de barrière Schottky pour des contacts siliciurés. Durant cette étude, nous avons transféré une technique se basant sur des diodes en tête bêche pour caractériser l’impact de la ségrégation de différentes espèces à l’interface siliciure/semi-conducteur sur la hauteur de barrière Schottky d’un contact en siliciure de platine. Cette méthode de mesure associée à des simulations physiques a permis d’une part, d’extrairer avec fiabilité des hauteurs de barrières avec une précision de 10meV et d’autre part, d’effectuer une sélection des meilleures conditions de ségrégation de dopants pour la réduction de la hauteur de barrière Schottky. Pour conclure, ce projet a rendu possible le développement de méthodes de caractérisation pour l’étude de matériaux utilisés en nanoélectronique. De plus, nous avons pu apporter des éclaircissements concernant l’impact de techniques d’implantation ionique alternatives sur des couches de Si et SiGe ultrafines, et ce, dans le but de réduire la résistance de contact entre siliciure et semi-conducteur dans le module source-drain de transistors ultimes<br>During the past few decades, the emergence of new architectures (FDSOI, FinFETs or NW-FETs) and the use of new materials (like silicon/germanium alloys) allowed to go further in MOS devices scaling by solving short channel effect issues. However, new architectures suffer from contact resistance degradation with size reduction. This resistance strongly depends on two parameters: the active dopant concentration close to the semi-conductor surface and the Schottky barrier height of the silicide contact. Many solutions have been proposed to improve both of these physical parameters: pre-amorphisation, laser annealing, dopant segregation and others. In order to optimize the experimental conditions of these fabrication techniques, it is mandatory to measure precisely and reliably their impact on cited parameters.Within the scope of this thesis, two parts are dedicated to each lever of the contact resistance, each time precising the developed characterization method and concrete application studies. The first part concerns the study of the active dopant concentration close to the semi-conductor surface. In this axis, we developed a Differential Hall Effet method (DHE) which can provide accurate depth profiles of active dopant concentration combining successive etching processes and conventional Hall Effect measurements. To do so, we validated layer chemical etching and precise electrical characterization method for doped Si and SiGe. Obtained generated profiles have a sub-1nm resolution and allowed to scan the first few nanometers of layers fabricated by advanced ion implantation and annealing techniques, like solid-phase epitaxy regrowth activated by laser annealing. In the second part, we focused on the measurement of Schottky barrier height of platinum silicide contact. We transferred a characterization method based on back-to-back diodes structure to measure platinum silicide contacts with different dopant segregation conditions. The electrical measurements were then fitted with physical models to extract Schottky barrier height with a precision of about 10meV. This combination between measurements and simulations allowed to point out the best ion implantation and annealing conditions for Schottky barrier height reduction.To conclude, thanks to this project, we developed highly sensitive characterization methods for nanoelectronics application. Moreover, we brought several clarifications on the impact of alternative ion implantation and annealing processes on Si and SiGe ultra-thin layers in the perspective of contact resistance reduction in FDSOI source-drain module
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Tan, Jiak-San. "Flexibility in MLVR-VSC back-to-back link." Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1119.
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This thesis describes the flexible voltage control of a multi-level-voltage-reinjection voltage source converter. The main purposes are to achieve reactive power generation flexibility when applied for HVdc transmission systems, reduce dynamic voltage balancing for direct series connected switches and an improvement of high power converter efficiency and reliability. Waveform shapes and the impact on ac harmonics caused by the modulation process are studied in detail. A configuration is proposed embracing concepts of multi level, soft-switching and harmonic cancellation. For the configuration, the firing sequence, waveform analysis, steady-state and dynamic performances and close-loop control strategies are presented. In order not to severely compromise the original advantages of the converter, the modulated waveforms are proposed based on the restrictions imposed mathematically by the harmonic cancellation concept and practically by the synthesis circuit complexity and high switching losses. The harmonic impact on the ac power system prompted by the modulation process is studied from idealistic and practical aspects. The circuit topology being proposed in this thesis is developed from a 12-pulse bridge and a converter used classically for inverting power from separated dc sources. Switching functions are deduced and current paths through the converter are analysed. Safe and steady-state operating regions of the converter are studied in phasor diagrams to facilitate the design of simple controllers for active power transfer and reactive power generations. An investigation into the application of this topology to the back-to-back VSC HVdc interconnection is preformed via EMTDC simulations.
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Adabi, Firouzjaee Jafar. "Remediation strategies of shaft and common mode voltages in adjustable speed drive systems." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/39293/1/Jafar_Adabi_Firouzjaeel_Thesis.pdf.
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AC motors are largely used in a wide range of modern systems, from household appliances to automated industry applications such as: ventilations systems, fans, pumps, conveyors and machine tool drives. Inverters are widely used in industrial and commercial applications due to the growing need for speed control in ASD systems. Fast switching transients and the common mode voltage, in interaction with parasitic capacitive couplings, may cause many unwanted problems in the ASD applications. These include shaft voltage and leakage currents.
One of the inherent characteristics of Pulse Width Modulation (PWM) techniques is the generation of the common mode voltage, which is defined as the voltage between the electrical neutral of the inverter output and the ground. Shaft voltage can cause bearing currents when it exceeds the amount of breakdown voltage level of the thin lubricant film between the inner and outer rings of the bearing. This phenomenon is the main reason for early bearing failures.
A rapid development in power switches technology has lead to a drastic decrement of switching rise and fall times. Because there is considerable capacitance between the stator windings and the frame, there can be a significant capacitive current (ground current escaping to earth through stray capacitors inside a motor) if the common mode voltage has high frequency components. This current leads to noises and Electromagnetic Interferences (EMI) issues in motor drive systems.
These problems have been dealt with using a variety of methods which have been reported in the literature. However, cost and maintenance issues have prevented these methods from being widely accepted. Extra cost or rating of the inverter switches is usually the price to pay for such approaches. Thus, the determination of cost-effective techniques for shaft and common mode voltage reduction in ASD systems, with the focus on the first step of the design process, is the targeted scope of this thesis. An introduction to this research – including a description of the research problem, the literature review and an account of the research progress linking the research papers – is presented in Chapter 1.
Electrical power generation from renewable energy sources, such as wind energy systems, has become a crucial issue because of environmental problems and a predicted future shortage of traditional energy sources. Thus, Chapter 2 focuses on the shaft voltage analysis of stator-fed induction generators (IG) and Doubly Fed Induction Generators DFIGs in wind turbine applications. This shaft voltage analysis includes: topologies, high frequency modelling, calculation and mitigation techniques. A back-to-back AC-DC-AC converter is investigated in terms of shaft voltage generation in a DFIG. Different topologies of LC filter placement are analysed in an effort to eliminate the shaft voltage.
Different capacitive couplings exist in the motor/generator structure and any change in design parameters affects the capacitive couplings. Thus, an appropriate design for AC motors should lead to the smallest possible shaft voltage. Calculation of the shaft voltage based on different capacitive couplings, and an investigation of the effects of different design parameters are discussed in Chapter 3. This is achieved through 2-D and 3-D finite element simulation and experimental analysis.
End-winding parameters of the motor are also effective factors in the calculation of the shaft voltage and have not been taken into account in previous reported studies. Calculation of the end-winding capacitances is rather complex because of the diversity of end winding shapes and the complexity of their geometry. A comprehensive analysis of these capacitances has been carried out with 3-D finite element simulations and experimental studies to determine their effective design parameters. These are documented in Chapter 4. Results of this analysis show that, by choosing appropriate design parameters, it is possible to decrease the shaft voltage and resultant bearing current in the primary stage of generator/motor design without using any additional active and passive filter-based techniques.
The common mode voltage is defined by a switching pattern and, by using the appropriate pattern; the common mode voltage level can be controlled. Therefore, any PWM pattern which eliminates or minimizes the common mode voltage will be an effective shaft voltage reduction technique. Thus, common mode voltage reduction of a three-phase AC motor supplied with a single-phase diode rectifier is the focus of Chapter 5. The proposed strategy is mainly based on proper utilization of the zero vectors.
Multilevel inverters are also used in ASD systems which have more voltage levels and switching states, and can provide more possibilities to reduce common mode voltage. A description of common mode voltage of multilevel inverters is investigated in Chapter 6.
Chapter 7 investigates the elimination techniques of the shaft voltage in a DFIG based on the methods presented in the literature by the use of simulation results. However, it could be shown that every solution to reduce the shaft voltage in DFIG systems has its own characteristics, and these have to be taken into account in determining the most effective strategy.
Calculation of the capacitive coupling and electric fields between the outer and inner races and the balls at different motor speeds in symmetrical and asymmetrical shaft and balls positions is discussed in Chapter 8. The analysis is carried out using finite element simulations to determine the conditions which will increase the probability of high rates of bearing failure due to current discharges through the balls and races.
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Harouni, Zied. "Conception et caractérisation d’une Rectenna à double polarisation circulaire à 2.45 GHz." Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST1026/document.
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Les travaux présentés dans ce mémoire s'inscrivent dans la thématique de la transmission d'énergie sans fil, appliquée à l'alimentation à distance de capteurs, de réseaux de capteurs et d'actionneurs à faible consommation. Cette étude porte sur la conception, la caractérisation, et la mesure d'un circuit Rectenna (Rectifying antenna) à double polarisation circulaire à 2.45 GHz, compact et à rendement de conversion RF-DC optimisé. Un outil d'analyse globale basé sur la méthode itérative a été développé et exploité pour valider la faisabilité de cette analyse. La diode Schottky a été modélisée en utilisant une impédance de surface. La rectenna à double polarisation circulaire, réalisée en technologie micro-ruban, a été validée expérimentalement. Elle est caractérisée par la rejection de la 2ème harmonique et une possibilité de recevoir les deux sens de polarisation LHCP et RHCP par l'intermédiaire de 2 accès. Le rendement mesuré avec une densité de puissance de 0.525 mW/cm² est de l'ordre de 63%, tandis que la tension DC obtenue aux bornes d'une charge optimale de 1.6 kohm est de 2.82 V<br>The work presented in this thesis is within the subject of wireless power transmission, power applied to the remote sensors, networks of sensors and actuators with low power consumption. This study focuses on the design, characterization, and measurement of a rectenna circuit (rectifying antenna) with dual circular polarization at 2.45 GHz, and optimisation of the conversion efficiency. A global analysis tool, based on the iterative method was developed and used to validate the feasibility of this concept by this method. The Schottky diode was modeled using surface impedance. The dual circular polarization rectenna with microstrip technology has been optimized and characterized experimentally operating at 2.45 GHz. It includes the property of harmonic rejections. Two accesses can receive either direction LHCP or RHCP sense. The conversion efficiency of 63% has been measured with a power density of 0.525 mW/cm². A DC voltage of 2.82V was measured across an optimum load of 1.6 kohm
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Takhedmit, Hakim. "Modélisation et conception de circuits de réception complexes pour la transmission d'énergie sans fil à 2.45 GHz." Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00564596.
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Les travaux présentés dans ce mémoire s'inscrivent dans la thématique de la transmission d'énergie sans fil, appliquée à l'alimentation à distance de capteurs, de réseaux de capteurs et d'actionneurs à faible consommation. Cette étude porte sur la conception,l'optimisation, la réalisation et la mesure de circuits Rectennas (Rectifying antennas)compacts, à faible coût et à haut rendement de conversion RF-DC.Un outil d'analyse globale, basé sur la méthode des Différences Finies dans le Domaine Temporel (FDTD), a été développé et utilisé pour prédire avec précision la sortie DC des rectennas étudiées. Les résultats numériques obtenus se sont avérés plus précis et plus complets que ceux de simulations à base d'outils commerciaux. La diode Schottky a été rigoureusement modélisée, en tenant compte de ses éléments parasites et de son boîtier SOT23, et introduite dans le calcul itératif FDTD.Trois rectennas innovantes, en technologie micro-ruban, ont été développées,optimisées et caractérisées expérimentalement. Elles fonctionnent à 2.45 GHz et elles ne contiennent ni filtre d'entrée HF ni vias de retour à la masse. Des rendements supérieurs à 80% ont pu être mesurés avec une densité surfacique de puissance de l'ordre de 0.21 mW/cm²(E = 28 V/m). Une tension DC de 3.1 V a été mesurée aux bornes d'une charge optimale de1.05 k_, lorsque le niveau du champ électrique est égal à 34 V/m (0.31 mW/cm²).Des réseaux de rectennas connectées en série et en parallèle ont été développés. Les tensions et les puissances DC ont été doublées et quadruplées à l'aide de deux et de quatre éléments, respectivement.
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Chang, Chen-Ching, and 張振清. "Diode-Laser Frequency Stabilization by Two-Frequency Doppler-Broadened Absorption Spectroscopy." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/13086883631272788560.
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碩士<br>國立東華大學<br>應用物理研究所<br>93<br>In this paper we used a robust method for frequency stabilization of a diode laser by two Doppler-broadened absorption spectra of the cesium D2 line. We used an acousto-optical modulator(AOM) to generate two frequencies from a diode laser to perform the spectroscopy. We generate two Doppler-broadened absorption spectra by passing two laser beams through an atomic vapor cell while the laser frequency is scanned across the atomic transition. The difference between the two spectra shows an error signal passing the zero point. This error signal can be control a piezoelectric transducer(PZT) or the injection current of an external-cavity diode laser to stabilize the laser’s frequency to the zero crossing of the error signal.
As the usual Doppler-broadened spectrum has a linewidth of about some hundred megahertz, the locking range can be lager than twice the linewidth when the spectra are shifted by a Doppler linewidth. This wide locking range can prevent the diode laser from becoming unlocked as a result of environmental perturbations.
To characterize the stability of the frequency-stabilized diode laser we compared this laser with a frequency-stabilized femtosecond(fs) mode-locked laser.
We measured beat frequency between the frequency-stabilized diode laser and the frequency-stabilized fs laser comb. The peak-to-peak frequency fluctuation is about 5MHz. The frequency stability(Allan variance) was obtained at the averaging time .
The Two-Frequency Doppler-Broadened Absorption Spectroscopy method for diode laser frequency stabilization is robust against environmental perturbation and free of modulation. It is suitable for use in building commercial equipment.
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Chang, Ruei-nan, and 張瑞男. "Parameter Extraction of Impact Ionization Rate in Two-Dimensional PIN Diode Simulation." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/41369995462989339529.
Full textAbstract:
碩士<br>國立中央大學<br>電機工程研究所<br>99<br>In this thesis, we design a 2-D device simulator which includes the impact ionization model to simulate the avalanche breakdown. At first, we discuss two device structures. One is simple p-n junction diode. We use it to discuss the transmission of carriers for different doping concentration, and to proceed a series of simulation for p-n junction diodes. Another is p-i-n diode with an undoped intrinsic semiconductor layer in the middle, and we use this structure to extract the electron and hole impact-ionization rate for Si in high electric field. Then we compare it with the original theoretical value to analyze and find out the reasons which make different results. Finally, we extract the hole impact ionization rate based on the electron impact ionization rate obtained in the previous simulation.
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Wang, Szu-Chieh, and 王思婕. "Two-Dimensional photonic crystals for improving GaN-based Light Emitting Diode efficiency." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/86351210618497554383.
Full textAbstract:
碩士<br>國立臺灣大學<br>光電工程學研究所<br>99<br>In the recent years, PhCs as diffraction grating have been widely explored to improve light extraction and to modify radiation profiles of LEDs. But most reports in the related field utilized shallow PhC structure on the device surface in order not to damage the multiple quantum wells (MQWs). As a result, the shallow patterns are only effective on higher order modes while a large portion of the optical energy of low order modes is poorly extracted due to less overlap with the PhCs. Therefore, this kind of structure limits the potential of light extraction efficiency by utilizing PhC structure.
In this thesis, we define two dimensional PhC pattern by e-beam lithography at the periphery of the light-emitting mesa area and etch them through MQWs as nanohole array. The structure can effectively diffract out the low order modes of laterally propagated light by interacting with PhCs and thus reaches high output power. With larger width of nanohole arrays, the light output power enhancement is enlarger due to the better coupling effect between PhCs and guided modes, then saturate till the width of 40 μm. The different extraction efficiency and the emission pattern can be achieved by designing parameters of photonic crystal (pitch and diameter). The light intensity enhancement factor of the device with a/d=400/320 and a/d=400/280 are 31.5% at the vertical direction (90°) and 21.7% at the 75°, respectively.
Continuing from the previous experiment, we not only fabricate the nanohole reflectors surrounding the light emitting mesa but also the PhC structure on the mesa surface to diminish the total internal reflection. In that way, all the guided modes in the material can be effectively diffracted by PhCs of this structure. We compare the novel structure with the general PhCLED(LED only with surface PhC), and the light intensity enhancement factor are 56% and 40%, respectively. The measurement and the simulation results consist with our idea. With the nanohole arrays applied at the periphery of the mesa, a higher output power can be achieved due to the enhanced collection and diffraction of low order modes of laterally propagated light interacted with nanoholes. The interaction of in-plane optical wave with the nanoholes is much stronger than that with surface PhC, suggesting an efficient light diffraction to the surface normal by nanoholes.
keywords：photonic crystal、GaN、nanohole array、light-emitting diode
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Tseng, Kuo-Yen, and 曾國晏. "High-Efficiency Deep-Blue Organic Light-Emitting Diode with Two Carrier Modulation Layers." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/15671546381500346003.
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Guey, Chiou Yueh, and 邱岳貴. "Two-dimensional numerical simulation of Si Schottky-2DEG diode using boundary element method." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/52554595513162258030.
Full textAbstract:
碩士<br>國立成功大學<br>電機工程研究所<br>82<br>A new two-dimensional numerical method, namely, the boundary
element method (BEM) is proposed to investigate the electrical
characteristics of Si Schottky-two dimensional electron gas
(2DEG ) diode. for the one-dimensional charge distribution in
the cal- culation of two-dimensional Poisson's equation, the
finite ele- ment method (FEM) is unreasonable and nonsensical.
Therefore, the BEM is the only way to simulate the two-
dimensional character- istics of the Schottky-2DEG diode. the
BEM, which is similar to the boundary technique but is improved
in its feasibility, is em- ployed to solve Poisson's equation.
Since only discretized equations on the boundary of solved
domain need to be solved, the BEM is powerful over the finite
difference method (FDM) and the FEM. An efficient and reliable
program has been implemented and quite satisfied results have
been obtained. Using the present numerical simulation work
consisting of solving Schrodinger's and Poisson's equations
iteratively, the differences between the Fermi level (Ef) and
the conduction band edge (Ec) in the δ-doped channel have been
extracted for the following calculations. A new algorithm is
proposed to determine the depletion layer width along the δ-
doped channel. The calcu- lation of potential and electric
field distributions is based on the BEM. The dependence of the
electrical properties of the Schottky-2DEG diode on the
semiconductor parameters, such as the depletion layer width, δ-
doping level, surface charge density, the applied voltage, etc.
are analyzed and discussed. It is ex- pected that the
preliminary simulation results obtained in this work may give
aids in understanding the behaviors of Schottky- 2DEG diode and
the conceptions of BEM.
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LIN, YOU-ZU, and 林佑儒. "Isolated Multi Level DC-DC Power Converters Based on Connection of two Diode Rectifiers." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6e4u65.
Full textAbstract:
碩士<br>國立高雄應用科技大學<br>電機工程系博碩士班<br>106<br>This paper proposes two multi-level isolated DC-DC power converters based on two bridge rectifiers, which consists of a half-bridge DC-AC inverter, a high frequency transformer, two bridge rectifiers, a switching selection circuit, an output L-C filter and a digital signal processor(DSP) controller. Compared with the conventional isolated multi-level DC-DC power converters, the proposed power converters can reduce switching losses and output voltage ripple, and it can also reduce the capacity of output filter. Both symmetrical and asymmetrical high-frequency transformers are used in this paper, and it shows the topology using asymmetrical transformer can further reduce the output voltage ripple and the voltage stress in switches. The half-bridge rectifier are adopted in this paper, and it has the function of a voltage doubler. For the same output voltage, one of two output winding of three-winding transformer is half that of the other winding. It has advantage of reducing cost of winding cost of three-winding transformer. Both simulation and hardware tested of a 3.2kW prototype are used to verify that the performance of the proposed multi-level isolated DC-DC power converter based on two bridge rectifiers, Finally, the power devices of different materials were used for testing to understand which material had better efficiency in the circuit topology of this paper.