Дисертації: "2- dimensional electron system (2 DES)"

1

Göres, Jörn. "Correlation effects in 2-dimensional electron systems composite fermions and electron liquid crystals /." [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11612017.

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2

Geisler, Martin C. "The Hofstadter butterfly and quantum interferences in modulated 2-dimensional electron systems." [S.l. : s.n.], 2005. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-26027.

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3

Nübler, Johannes [Verfasser], and David [Akademischer Betreuer] Wharam. "Density Dependence of the v=5/2 Fractional Quantum Hall Effect - Compressibility of a Two-dimensional Electron System under Microwave Irradiation / Johannes Nübler ; Betreuer: David Wharam." Tübingen : Universitätsbibliothek Tübingen, 2011. http://d-nb.info/1162699248/34.

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4

Rosner, Helge. "Electronic structure and exchange integrals of low-dimensional cuprates." [S.l. : s.n.], 1999. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9470690.

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5

Magyar, Peter. "Quelques aspects du transport électronique bidimensionnel : études théoriques en champ magnétique faible et fort." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10025.

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Ce travail presente deux etudes de transport des systemes d'electrons bidimensionnels dans les limites du champ magnetique faible et fort. Premierement, nous avons analyse l'utilite d'une nouvelle approche theorique, destinee a calculer la mobilite limitee par (a) des impuretes ionisees ou par (b) des dislocations. Ce traitement a pour but d'ameliorer la description de l'effet d'ecran. Notre etude a revele que la methode ne represente que des avantages tres limites dans le cas (a), tandis que dans le cas (b) les courbes calculees en fonction de la temperature et de la largeur du puits sont en accord avec les mesures. Deuxiemement, l'effet hall quantique entier a ete etudie dans un potentiel de desordre modele. Le systeme a ete couple a un bain thermique. A partir de l'etat stationnaire d'une equation de boltzmann quantique, les conductivites de hall et dissipative ont ete obtenues en fonction de la temperature pour tous les facteurs de remplissage. Nos resultats sont en accord qualitatif avec les experiences. En outre, ils montrent que, du aux phonons, les plateaux quantifies de la conductivite de hall sont sensiblement plus larges a tres basses temperatures que ceux de la conductivite dissipative.

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6

Carter, Paul James Anthony. "Acoustic phonon scattering by a 2 dimensional electron gas." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329844.

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7

Ford, E. M. "Single electron conduction in 2-dimensional arrays of gold nanodots." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599113.

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This dissertation considers single electron conduction through arrays of nanometer-size metallic islands fabricated by Focused Ion Beam (FIB) lithography. Control of the array geometry and the corresponding electrical characteristics were achieved by variation of the FIB deposition conditions. Scanning electron microscopy was used to examine FIB depositions on Si/SiO₂ substrates. For more accurate examination transmission electron microscopy was used to image arrays deposited on carbon membranes. Image analysis software revealed a general increase in island diameter and reduction of island density with increasing FIB dose. The average island size was found to decrease with increasing FIB landing energy, although the uniformity of the deposition was reduced. The process of island formation is discussed in relation to the trends observed. Devices were fabricated with a planar structure, consisting of closely-spaced (~10 nm) source and drain electrodes situated within a large area array of islands. The devices were created on silicon substrates with a top layer of thermally grown silicon dioxide. A chromium oxide film was deposited by R.F. sputtering and the electrodes were then defined by high-resolution electron beam lithography. Electrical measurements were carried out at temperatures between 4.2K and 300K. Characteristics typical of single-electron conduction were observed, including the Coulomb gap and staircase, and the reduction of the Coulomb gap width with increasing temperature. The width of the low-temperature Coulomb gap was found to diminish with increasing dose, while devices fabricated with higher landing energies have lower operating temperatures. A novel device structure was also fabricated, where a small number of gold islands were isolated on the surface of a silicon nanowire. Silicon wires of length ~1μm and width >10nm were fabricated reproducibly using a sacrificial metallic etch mask. The electrical characteristics exhibited Coulomb gaps consistent with single electron transport.

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8

Lee, Sungkoo. "A constraint-based 2-dimensional object display system." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055342896.

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9

McEnaney, Kevin Bernard. "Magneto-absorption of surface acoustic waves by a 2-dimensional electron gas." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293651.

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10

Martin, Theodore Peyton. "Low-dimensional electron transport in mesoscopic semiconductor devices /." view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1280149921&sid=2&Fmt=2&clientId=11238&RQT=309&VName=PQD.

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Thesis (Ph. D.)--University of Oregon, 2006.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 187-196). Also available for download via the World Wide Web; free to University of Oregon users.

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11

Scheid, Matthias. "Tailoring semiconductor spintronics devices : tools for the creation and control of spins in two-dimensional electron gases." Regensburg Univ.-Verl. Regensburg, 2010. http://epub.uni-regensburg.de/14048/.

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12

Salameh, Belal. "Electron spin resonance investigations of organic spin chains and two-dimensional organic conductors." [S.l. : s.n.], 2005. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11947828.

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13

Amriou, Samia. "Synthesis and electrochemical properties of new l,3-dithiol-2-ylidene derivatives." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/4007/.

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The π-electron donor system 9-(l,3-dithiol-2-ylidene)thioxanthene has been synthesised via Homer-Wadsworth-Emmons reactions of l,3-dithioI-2-phosphonate ester reagents with thioxanthen-9-one. The electrochemistry of a range of derivatives shows a single, two-electron oxidation wave, which is quasi-reversible. X-Ray crystal analysis reveals a folded structure. Compound 33c has proved to be a key building block which via lithiation chemistry has provided the hydroxymethyl derivative 37 and hence the synthesis of derivatives with covalently attached fluorenone, dicyanomethylenefluorene and PTM (4-[bis(2,3,4,5,6-pentachlorophenyl)methyl]-2,3,5,6-tetrachlorobenzoyl chloride radical) as electron acceptor substituents has been achieved. Electrochemical, spectroscopic and spectroelectrochemical studies have revealed the presence of intramolecular interactions in these compounds. 9-(4-Iodo-5-methyl-1,3-dithiol-2-ylidene)thioxanthene has been synthesised and shown to undergo clean metal-catalysed cross-coupling reactions under Suzuki and Sonogashira conditions, which is unusual for l,3-dithiol-2-ylidene derivatives. Aldehyde functionality has been attached to the 9-(l,3-dithiol-2-ylidene)thioxanthene core and reacting these aldehyde reagents with C(_60) and sarcosine gave covalent 9-(l,3-dithiol-2-ylidene)thioxanthene- C(_60) 1:1 diad molecules, and the analogous 2:1 adducts. A second series of compounds, with more extension of the π-system, eg compound 66a, has been synthesised and characterised by X-ray crystallography, a range of spectroscopic studies and by epr and electrochemistry.

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14

Zakaria, Marwan F. "An automated vision system using a fast 2-dimensional moment invariants algorithm /." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66244.

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15

Digby, Julian Edward. "Phonon absorption by a 2-dimensional carrier system in the quantised Hall regime." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363907.

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16

Ong, Seow Meng. "A Mission Planning Expert System with Three-Dimensional Path Optimization for the NPS Model 2 Autonomous Underwater Vehicle." Thesis, Monterey, California. Naval Postgraduate School, 1990. http://hdl.handle.net/10945/23457.

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Approved for public release; distribution is unlimited
Unmanned vehicle technology has matured significantly over the last two decades. This is evidenced by its widespread use in industrial and military applications ranging from deep-ocean exploration to anti-submarine warefare. Indeed, the feasiblity of short-range, special-purpose vehicles (whether aunonomous or remotely operated) is no longer in question. The research efforts have now begun to shift their focus on development of reliable, longer-range, high-endurance and fully autonomous systems. One of the major underlying technologies required to realize this goal is Artificial Intelligence (AI). The latter offers great potential to endow vehicles with the intelligence needed for full autonomy and extended range capability; this involves the increased application of AI technologies to support mission planning and execution, navigation and contingency planning. This thesis addresses two issues associated with the above goal for Autonomous Underwater Vehicles (AUV's). Firstly, a new approach is proposed for path planning in underwater environments that is capable of dealing with uncharted obstacles and which requires significantly less planning time and computer memory. Secondly, it explores the use of expert system technology in the planning of AUV missions.

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17

Huang, Ran. "Thermodynamics and Ideal Glass Transition on the Surface of a Monatomic System Modeled as Quasi "2-Dimensional" Recursive Lattices." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1342379960.

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18

Moji, Kabelo McDonald. "Comparison of measured photon and electron beam dose distributions between 3D water phanton and profiler 2 scanning system, South Africa." Thesis, University of Limpopo (Medunsa Campus), 2013. http://hdl.handle.net/10386/1086.

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Thesis ( MSc ( Physics) ) -- University of Limpopo, 2013.
Background and Objectives: To establish whether the profiler 2 scanning system can be used as a substitute for the 3D-water phantom, by comparing the percentage depth doses and beam profiles for both the photons and electron beams, and validating the results using CMS XiO treatment planning system. Methods: Beam data (profiles, percentage depth doses and absolute dosimetry) were acquired for the two systems: (3D-water phantom and profiler 2 scanning system) for beam energies 6 MV and 15 MV photon beams, and 4, 6, 8, 10, 12 and 15 MeV electron beams generated by the Elekta Synergy linear accelerator (linac) for the field sizes of 6 × 6 cm2, 10 × 10 cm2, 14 × 14 cm2, 20 × 20 cm2, and 25 × 25 cm2 at depths of 0.5 cm, 1.0 cm, 2.0 cm, and 5.0 cm respectively. These measurements were acquired using ionization chambers in water and diode detectors in Perspex. The acquired data was sent to CMS XiO treatment planning system for validation. Results: In general, the dose distributions for both systems compared very well with uncertainties within recommended limits. The largest maximum difference in symmetry was 1.6 % for a 6 MV photon beam defined at 25 × 25 cm2 field size. The largest maximum difference in flatness was 2.77 % for a 4 MeV electron beam defined at 10 × 10 cm2 applicator size. The penumbra largest maximum difference was 1.708 cm for 8 MeV electron beam defined at 25 × 25 cm2 applicator size, which was outside the recommended limit of 1.2 cm. The largest maximum difference in field size was 2.388 cm for a 6 MeV electron beam defined at 20 × 20 cm2 applicator size, which was outside the recommended limit of 0.4 cm. The largest maximum difference in percentage depth dose at 10 cm depth was 1.69 % for the 6 MV photon beam. The absolute dose output measurements showed a very good agreement between the two systems to a maximum percentage difference and highest standard deviation of -0.99 % and 0.69 % respectively for the 6 MV photon beam. Validation measurements showed an agreement to less than 1 % and 2 mm for percentage depth doses and beam profiles respectively. Conclusion and recommendation: From the results obtained, it is evident that the profiler 2 scanning system can be used as a substitute for the 3D-water phantom beam data acquisitions during linear accelerator commissioning. The future work based on this study could be to study the limitations involved with the profiler 2 scanning system when used during measurements for commissioning of a linear accelerator. Limitations like field size (maximum field size of 20 × 30 cm2 at SSD = 100 cm), number of Perspex slabs to be used on top of the profiler 2 scanning system and diagonal profile measurements.

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19

PETIT, PIERRE. "Magnetisme et proprietes de conduction des derives cristallins et liquides cristallins de la bisphtalocyanine de lutecium : effet de dimensionnalite." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13163.

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Etude parrpe et par des mesures de la conductivite dc et de la reponse dielectrique ac hyperfrequence. Mise en evidence de la nature radicalaire de type pi du systeme, a l'etat cristallin comme en solution; effet du solvant et de la temperature; observation de sauts de l'electron non apparie d'un macrocycle a l'autre a une frequence voisine de 1 mhz. Mise en evidence de la possibilite de formation de deux systemes cristallins (empilement de chaines ou de plans paralleles) et de leur caractere 1d ou 2d au moyen du modele de richards. La susceptibilite du systeme mesomorphe indique un desordre magnetique comparable a celui de la phase liquide; la conductivite est celle des systemes desordonnes. Les cristaux solvates sont des semiconducteurs moleculaires intrinseques

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20

Lee, Paul Chong Chan. "A QUALITATIVE AND QUANTITATIVE ANALYSIS OF SOFT TISSUE CHANGE EVALUATION BY ORTHODONTISTS IN CLASS II NON EXTRACTION ORTHODONTIC TREATMENT USING THE 3dMD SYSTEM." Master's thesis, Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/217032.

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Oral Biology
M.S.
With the advent of cephalometrics in the 1930s, numerous studies have focused on the profile of a face to achieve a more esthetic orthodontic treatment outcome. With such heavy emphasis on facial esthetics, a shift in focus from the profile view to the oblique view has become necessary as the smile in the oblique view is what the general public evaluates. The purpose of this pilot study was to determine whether the current tools for diagnosis and treatment evaluation are sufficient. Currently, 2-dimensional composite photographs are utilized in evaluating the soft tissue. At Temple University, 3-dimensional images, which show all sides of the patient's face, are used adjunctively to 2-dimensional composite photographs. In this study, faculty members at the Temple University Department of Orthodontics were asked to complete surveys after viewing two different image modalities, 2-dimensional images and a 3-dimensional video of the same patient. They were asked to fill out the soft tissue goals for specific facial landmarks. Patient photos were in the smiling view as current literature lacks studies on this view. Faculty members' responses from analyzing the 2-dimensional images and 3-dimensional video for each patient were compared to determine which areas had frequent discrepancies from using two different image modalities. During the survey, a voice recorder captured any comments regarding the images. The ultimate goal of this qualitative pilot study was to identify when 3-dimensional imaging is necessary in treatment planning and evaluation, with an added hope to further advance research in 3-dimensional imaging and its vast possibilities to advance the field of orthodontics. Based on the data collected, the following conclusions were made: 1. The qualitative data highlighted that 3-dimensional imaging would be necessary in cases with skeletal deformities. 2. In the oblique view, 3-dimensional imaging is superior than 2-dimensional imaging by showing more accurate shadow, contour, and depth of the soft tissue. 3. Further improvement is necessary to create a virtual patient with treatment simulation abilities. 4. The comfort level among orthodontists of 2-dimensional imaging was higher than 3-dimensional imaging. With more widespread use of 3-dimensional imaging, more orthodontists may gradually reach a higher comfort level in using this relatively new technology. 5. Faculty members expressed high willingness to use 3-dimensional imaging if improvement in new technology could allow for more manipulation and accurate soft tissue prediction. 6. 3-dimensional imaging is superior in its efficiency, quick capture time, and lack of need for multiple images. Implementation of 3-dimensional imaging could streamline the records process and help with practice efficiency without compromising the image quality. 7. Both patients and orthodontists may benefit from using 3-dimensional imaging. Patients can see an accurate representation of themselves and possibly view their own treatment simulation upon further improvement in current technology. Orthodontists would benefit with much more accurate images that may serve as the virtual patient. 8. Besides the exorbitantly high cost, faculty members thought that more advances were needed and the current benefit was not great enough to justify the investment. The results were consistent with other studies that used the oblique view in that the 2-dimensional oblique view lacks depth and does not provide adequate information. With further improvement in current 3-dimensional imaging, this technology can benefit orthodontists in visualizing their patients. In addition, patients can benefit by hopefully seeing a live and accurate simulation of themselves instantly as a virtual patient. With these benefits of 3-dimensional imaging, it may one day be the new standard in patient records in the field of orthodontics.
Temple University--Theses

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21

Wang, Yin-Yu. "Réseaux supraconducteurs : température critique et états mixtes." Grenoble 1, 1987. http://www.theses.fr/1987GRE10060.

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Les effets de quantification du flux magnetique sur des reseaux supraconducteurs bidimensionnels sont etudies dans ce memoire. Du point de vue theorique, la temperature de transition supraconductrice en fonction du champ magnetique applique est determinee en resolvant les equations d'alexander pour divers reseaux : periodiques, quasiperiodiques et fractals. Quelques un de ces reseaux submicroniques ont ete realises par lithographie electronique. Leurs temperatures critiques sont mesurees et l'accord entre la theorie et l'experience est discute. A l'interieur de la phase supraconductrice, les vortex entrent dans le reseau et induisent des supercourants diamagnetiques. L'etat d'equilibre est traite d'une maniere analogue au traitement de l'etat mixte d'un supraconducteur massif d'abrikosov : on determine l'amplitude du parametre d'ordre en tenant compte du terme non-lineaire de l'equation de ginzburg-landau par une methode de perturbation. On en deduit les quantites thermodynamiques, en particulier l'energie libre et l'aimantation du reseau, qui sont des fonctions de la difference entre la temperature et la temperature critique t - t::(c), ainsi que du parametre d'abrikosov beta ::(a). Ce formalisme a ete applique au reseau carre pour lequel les configurations du parametre d'ordre et les distributions du courant diamagnetique ont ete determinees pour quelques valeurs simples du champ magnetique. D'autre part, la derivee de la ligne critique par rapport au champ magnetique, qui s'identifie a la derivee du bord du spectre d'hofstadter a ete calculee a l'aide d'une approximation continue. Cette derivee contient un terme anormal que l'on peut relier a la phase de berry. Elle donne directement la derivee de l'aimantation par rapport a la temperature d rond m/d rond t. Nous donnons egalement quelques resultats preliminaires sur l'etat mixte du reseau supraconducteur en presence d'un courant exterieur. Le courant critique au-dessus duquel cet etat n'existe plus est obtenu pour quelques cas simples (boucles, reseau carre). Quelques mesures preliminaires de ce courant ont ete effectuees sur un reseau carre

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22

Negri, Carlotta. "Controlling electron transport : quantum pumping and single-electron tunneling oscillations." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14670/document.

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Exploiter des effets dépendants du temps pour induire et contrôler des courants à travers des conducteurs mésoscopiques et nanoscopiques est un enjeu majeur dans le domaine du transport quantique. Dans cette thèse, nous considérons deux systèmes de taille nanométrique pour lesquels un courant est induit grâce au couplage entre champs extérieurs dépendants du temps et le transport d'électrons. Nous étudions d'abord un problème de pompage quantique au sein d'un système à trois sites en configuration d'anneau, en considérant la possibilité d'induire un courant continu par modulation temporelle des paramètres de contrôle. Nous nous intéressons en particulier à la transition entre régime adiabatique et antiadiabatique en présence d'un mécanisme de dissipation modélisé par un couplage entre le système et un bain extérieur.Nous montrons que le modèle dissipatif admet une solution analytique complète valable pour la composante DC du courant à fréquence arbitraire. Ceci nous permet de bien comprendre comment le courant induit dépend de la fréquence de pompage. Nous nous concentrons ensuite sur un autre système de contrôle du courant exploitant le phénomène des oscillations tunnel à un électron (SETOs). Contrairement au cas précédent, ici la circulation d'un courant continu à travers un circuit comportant une jonction tunnel produit, pour le régime approprié, un courant quasi-périodique d'électrons. On étudie le spectre de bruit à température nulle d'une jonction tunnel dans différents environnements résistifs dans le but de déterminer les limites du régime des SETOs et de quantifier leur degré de périodicité. Nous généralisons par la suite les résultats à température finie et discutons des effets des fluctuations quantiques
Exploiting time-dependent effects to induce and control currents through mesoscopic and nano\-scopic conductors is a major challenge in the field of quantum transport. In this dissertation we consider two nanoscale systems in which a current can be induced through intriguing mechanisms of coupling between excitations by external fields and electron transport.We first study a quantum pumping problem, analyzing the possibility to induce a DC response to an AC parametric driving through a three-site system in a ring configuration. We are interested in particular in the crossover between adiabatic and antiadiabatic driving regimes and in the presence of dissipation, which is accounted for by coupling with an external bath. We show that for a clever choice of this coupling the dissipative model admits a full analytical solution for the steady state current valid at arbitrary frequency, which allows us to fully understand the pumping-frequency dependence of the induced current. We then focus on a different current-controlling scheme exploiting the phenomenon of single-electron tunneling oscillations (SETOs). In this case, opposite to what happens for pumping, an AC effect, an almost periodic current of single electrons, arises through a tunnel junction circuit as a consequence of a DC bias. We study the zero-temperature noise spectrum of a tunnel junction in different resistive environments with the aim to determine the boundaries of the SETOs regime and quantify their quality in terms of periodicity. We then discuss the finite-temperature generalization and the possibility to account for the effects of quantum fluctuations

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Blauch, David N. Anson Fred C. Anson Fred C. "Part I. Improvements in the rotation-rate step experiment for the evaluation of diffusion coefficients at rotating disk electrodes. : Part II. Ion-pairing and electric field effects on electron hopping in the Nafion-tris(2,2'-bipyridine)osmium(3+/2+) system /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06152007-081035.

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Ahmadouche, Ahmed Abdelkader. "Modélisation électrique des interconnexions multiniveaux en présence de diélectriques stratifiés." Grenoble INPG, 1987. http://www.theses.fr/1987INPG0140.

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Modelisation des lignes d'interconnexions dans un circuit logique a partir de matrices capacite, inductance resistance et conductance. Le probleme est traite en deux ou trois dimensions suivant la configuration envisagee. Presentation des resultats theoriques obtenus sur des dispositifs realises en technologie silicium et arseniure de gallium et en technologie hybride et comparaison a ceux issus du test

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25

Le, Touze Christophe. "Etude des propriétés associées aux ondes de densité de charge dans les bronzes oxygénés quasi-bidimensionnels (PO2)4(WO3)2m." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10183.

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Nous avons etudie les proprietes associees aux ondes de densite de charge dans les bronzes quasi-bidimensionnels (po#2)#4(wo#3)#2#m (m=4, 5, 6, 7, 10, 11 et 12). Ces composes subissent des transitions de peierls a des temperatures t#p vers un etat d'onde de densite de charge caracterise par une distorsion periodique de reseau couplee a une modulation de la densite electronique. La chaleur specifique a ete mesuree pour les composes 4m entre 1,7k et 300k. Nous avons obtenu des termes lineaires en temperature anormalement eleves et qui augmentent avec m. Les temperatures de debye se situent autour de 250k et diminuent lorsque m augmente. Ce comportement pourrait etre du a la diminution de la liaison metallique ou (et) a l'augmentation du caractere bidimensionnel quand le parametre m croit. Des oscillations quantiques shubnikov-de haas et de haas-van alphen ont ete observees dans les composes m=4 et m=6 lors de mesures de magnetoresistance (m=4 et m=6) et de couple magnetique (m=6) effectuees a tres basse temperature et sous fort champ magnetique. Nous avons attribue ces phenomenes a l'existence de petites poches cylindriques subsistant sur la surface de fermi dans l'etat onde de densite de charge, plus petites pour le compose m=6 que pour le compose m=4: la surface de fermi est plus detruite dans le compose m=6 que dans le compose m=4. Le caractere de basse dimensionnalite pourrait donc augmenter avec m. Enfin, nous avons mesure la resistivite electrique des composes 10m2 en fonction de la temperature entre 4k et 800k. Cette etude nous a permis de differencier les composes a petit m des composes a grand m: contrairement aux premiers, dans le domaine des basses temperatures, les seconds ont une resistivite qui decroit a temperature croissante. Nous avons attribue l'augmentation en fonction de m de la resistivite a 300k (p(300k)) et du rapport de resistivite p(300k)/p(4k) a l'augmentation des interactions electrons-electrons via la diminution du nombre moyen d'electrons de conduction par atome de tungstene. D'autre part, nous pensons que l'absence d'anomalie tres marquee, caracteristique d'une transition de peierls, pour la plupart des composes a grand m, est due a des phenomenes de desordre empechant l'apparition d'un ordre a grande distance dans l'etat onde de densite de charge

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Utard, Christian. "Les oscillateurs microondes faible bruit de fond a base de mesfet gaas, tegfet gaalas et transistor bipolaire silicium : modelisation, caracterisation et comparaison." Toulouse 3, 1988. http://www.theses.fr/1988TOU30078.

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On presente une methode simplifiee de modelisation fort signal des mesfet et tegfet et transistors bipolaires. Ces trois types de transistors sont utilises dans un montage oscillateur dont les caracteristiques ont ete determines de trois facons differentes, analytique par simulation electrique temporelle et par mesures experimentales. On presente enfin une etude en bruit bf et bruit mf des transistors et des oscillateurs afin de determiner le composant le plus performant. Nous proposons trois facons de determiner le coefficient de conversion bruit bf - bruit mf, par des mesures directes; indirectes et par simulation temporelle

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27

Lovisa, Stephane. "Propriétés optiques de puits quantiques de CdTe contenant un gaz d'électrons bidimensionnel." Université Joseph Fourier (Grenoble ; 1971-2015), 1998. http://www.theses.fr/1998GRE10099.

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Les proprietes optiques et magneto-optiques de puits quantiques de cdte contenant un gaz d'electrons bidimensionnel ont ete etudiees par spectroscopie d'absorption et d'emission, en fonction de la concentration des electrons. Une premiere etude par spectroscopie d'emission, effectuee sur une serie d'echantillons a densite electronique fixe, a montre que la masse effective des electrons depend fortement de leur concentration. Des calculs tenant compte des effets a n corps expliquent bien cette renormalisation de masse. Par ailleurs, des dispositifs schottky ont ete realises qui permettent de varier continument la densite du gaz d'electrons dans un puits quantique de cdte a l'aide d'une tension inverse appliquee. L'etude des proprietes de magneto-absorption en fonction de la densite a mene a une modelisation de la force d'oscillateur de l'exciton charge negativement ou trion. Les spectres d'absorption obtenus en champ nul sur des echantillons possedant des desordres electrostatiques differents ont montre l'apparition de zones isolantes pour une valeur du rapport de la densite d'electrons et du parametre de desordre exactement egale a celle prevue par la theorie recente d'efros. La transition optique temoignant de l'apparition de ces zones est attribuee a un trion a n corps.

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28

Dulieu, Olivier. "Etude des systemes atomiques a deux electrons externes par la methode de fonction d'onde correlee de pluvinage : application a l'etude des ions alcalins negatifs." Paris 6, 1987. http://www.theses.fr/1987PA066350.

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Анотація:

Par cette methode, etude detaillee des etats excites et autoionisants de l'atome me; comparaison aux donnees experimentales et a des calculs par d'autres methodes. Extension de la methode de l'analyse a des systemes a deux electrons externes : li**(-), na**(-), k**(-)

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29

Driss, Khodja Kouider. "Etude expérimentale et modélisation de la fonction diélectrique des milieux inhomogènes 2D et 3D." Rouen, 1989. http://www.theses.fr/1989ROUES018.

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Анотація:

Pour prendre en compte la structure réelle des milieux inhomogènes, nous avons proposé une théorie de milieu effectif à 2D et 3D basée sur une procédure de renormalisation dans l'espace réel. Ces modèles utilisent la technique des blocs de Kadanoff. Dans un premier temps cette approche a été appliquée à des réseaux carrés générés par ordinateur dont les sites sont occupés aléatoirement pour une concentration donnée. Dans une deuxième étape nous avons appliqué cette procédure à des images réelles constituées de micrographies de microscopie électronique par transmission digitalisées puis binarisées de systèmes 2D et 3D. On présente également une interprétation des similarités et des différences entre la théorie et l'expérience. Les résultats obtenus sur des réseaux simulés rendent compte à la fois de l'anomalie diélectrique et de la percolation optique. Notre approche est ainsi l'une des rares théories à modéliser la transition métal-non métal. Nous avons montré que la fonction diélectrique effective obéit à des lois d'échelle avec des exposants critiques S3D et S2D pour la polarisation et T3D et T2D pour la conduction, valeurs proches des estimations théoriques. Les fonctions diélectriques obtenues par l'application de ces modèles à des micrographies de microscopie électronique par transmission digitalisées puis binarisées sont en bon accord avec la plupart des résultats expérimentaux

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30

Pesquet-Popescu, Béatrice. "Modélisation bidimensionnelle de processus non stationnaires et application à l'étude du fond sous-marin." Cachan, Ecole normale supérieure, 1998. http://www.theses.fr/1998DENS0021.

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Dans cette thèse, nous proposons des généralisations anisotropes des champs 2D de type fractal. Tout d'abord, nous introduisons les champs 2D à accroissements stationnaires fractionnaires et nous montrons que le mouvement brownien fractionnaire appartient à cette classe de processus. L'intérêt d'une analyse multi résolution de ces champs est démontré théoriquement et sur un exemple d'application à la localisation sous-marine. Pour la modélisation de données, un moyen efficace pour caractériser les textures à accroissements stationnaires est fourni par la fonction de structure. Nous soulignons la possibilité de contrôler l'anisotropie de ces champs par le biais de cette fonction, dont nous proposons également plusieurs modèles. La fonction de structure est aussi employée pour l'interpolation des champs non stationnaires à accroissements stationnaires. Un autre aspect de ce travail concerne les extensions bidimensionnelles des processus ARIMA fractionnaires et leurs liens avec les champs continus présentés. Finalement, nous considérons des processus auto-similaires non-gaussiens et étudions les statistiques de leurs coefficients d'ondelettes.

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31

Pignol, Valérie. "Évolution et caractérisation de structures cellulaires bidimensionnelles expérimentales, en particulier les mousses de savon, et simulées." Phd thesis, Institut National Polytechnique de Lorraine - INPL, 1996. http://tel.archives-ouvertes.fr/tel-00717860.

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Ce travail est consacré à l'étude de structures cellulaires bidimensionnelles et notamment à leur évolution au cours du temps. Après une phase transitoire (dont la durée dépend de l'ordre initial de la structure) l'évolution atteint généralement un régime stationnaire (où l'aire moyenne des cellules varie linéairement avec le temps et où les propriétés sans dimension, telles que le désordre topologique et la distribution des nombres de côtés des cellules, sont invariantes). Une méthodologie d'analyse d'images a été mise au point pour caractériser les structures à un instant donné. Leurs propriétés métriques et topologiques sont déterminées en tenant compte d'une correction de biais statistique. Nous avons réalisé des expériences portant sur des mousses de savon bidimensionnelles (réalisées entre deux plaques). Un système de drainage a également été mis en place dans le but de conserver l'épaisseur des arêtes constante au cours de l'évolution. Lorsque l'état initial de la structure est très ordonné, le stade transitoire est très long, ce qui limite notre étude à cette seule phase de l'évolution. En revanche, nous avons pû étudier le régime stationnaire en partant de structures initiales désordonnées et en particulier déterminer la valeur du désordre topologique dans cette phase. Cette valeur semble dépendre de la composition du liquide moussant, de la taille de la boîte contenant la mousse, mais apparemment pas du drainage. Des simulations ont été effectuées à l'aide d'un programme développé par H. Telley à l'EPFL. Ce programme est fondé sur l'utilisation des complexes de Laguerre bidimensionnels et périodiques. Ces simulations ont fourni des résultats comparables à ceux observés pour les mousses, mais également pour les polycristaux, grâce à l'ajustement d'un paramètre distributif. Celui-ci est relié de façon simple aux transformations topologiques élémentaires intervenant au cours de l'évolution. La validation du programme a été effectuée non seulement pour le régime stationnaire mais aussi pour le régime transitoire (pour les mousses de savon)

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32

Chickering, William Elbridge. "Thermopower in Two-Dimensional Electron Systems." Thesis, 2016. https://thesis.library.caltech.edu/9320/2/thesis.pdf.

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The subject of this thesis is the measurement and interpretation of thermopower in high-mobility two-dimensional electron systems (2DESs). These 2DESs are realized within state-of-the-art GaAs/AlGaAs heterostructures that are cooled to temperatures as low as T = 20 mK. Much of this work takes place within strong magnetic fields where the single-particle density of states quantizes into discrete Landau levels (LLs), a regime best known for the quantum Hall effect (QHE). In addition, we review a novel hot-electron technique for measuring thermopower of 2DESs that dramatically reduces the influence of phonon drag.

Early chapters concentrate on experimental materials and methods. A brief overview of GaAs/AlGaAs heterostructures and device fabrication is followed by details of our cryogenic setup. Next, we provide a primer on thermopower that focuses on 2DESs at low temperatures. We then review our experimental devices, temperature calibration methods, as well as measurement circuits and protocols.

Latter chapters focus on the physics and thermopower results in the QHE regime. After reviewing the basic phenomena associated with the QHE, we discuss thermopower in this regime. Emphasis is given to the relationship between diffusion thermopower and entropy. Experimental results demonstrate this relationship persists well into the fractional quantum Hall (FQH) regime.

Several experimental results are reviewed. Unprecedented observations of the diffusion thermopower of a high-mobility 2DES at temperatures as high as T = 2 K are achieved using our hot-electron technique. The composite fermion (CF) effective mass is extracted from measurements of thermopower at LL filling factor ν = 3/2. The thermopower versus magnetic field in the FQH regime is shown to be qualitatively consistent with a simple entropic model of CFs. The thermopower at ν = 5/2 is shown to be quantitatively consistent with the presence of non-Abelian anyons. An abrupt collapse of thermopower is observed at the onset of the reentrant integer quantum Hall effect (RIQHE). And the thermopower at temperatures just above the RIQHE transition suggests the existence of an unconventional conducting phase.

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33

Lee, Ming-Tang, and 李明堂. "Study of a 2+1 dimensional electron-monopole system via supersymmetry." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/36198875235707486035.

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34

Höpfner, Philipp Alexander. "Two-Dimensional Electron Systems at Surfaces — Spin-Orbit Interaction and Electronic Correlations." Doctoral thesis, 2012. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-78876.

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This thesis addresses three different realizations of a truly two-dimensional electron system (2DES), established at the surface of elemental semiconductors, i.e., Pt/Si(111), Au/Ge(111), and Sn/Si(111). Characteristic features of atomic structures at surfaces have been studied using scanning tunneling microscopy and low energy electron diffraction with special emphasis on Pt deposition onto Si(111). Topographic inspection reveals that Pt atoms agglomerate as trimers, which represent the structural building block of phase-slip domains. Surprisingly, each trimer is rotated by 30° with respect to the substrate, which results in an unexpected symmetry breaking. In turn, this represents a unique example of a chiral structure at a semiconductor surface, and marks Pt/Si(111) as a promising candidate for catalytic processes at the atomic scale. Spin-orbit interactions (SOIs) play a significant role at surfaces involving heavy adatoms. As a result, a lift of the spin degeneracy in the electronic states, termed as Rashba effect, may be observed. A candidate system to exhibit such physics is Au/Ge(111). Its large hexagonal Fermi sheet is suggested to be spin-split by calculations within the density functional theory. Experimental clarification is obtained by exploiting the unique capabilities of three-dimensional spin detection in spin- and angle-resolved photoelectron spectroscopy. Besides verification of the spin splitting, the in-plane components of the spin are shown to possess helical character, while also a prominent rotation out of this plane is observed along straight sections of the Fermi surface. Surprisingly and for the first time in a 2DES, additional in-plane rotations of the spin are revealed close to high symmetry directions. This complex spin pattern must originate from crystalline anisotropies, and it is best described by augmenting the original Rashba model with higher order Dresselhaus-like SOI terms. The alternative use of group-IV adatoms at a significantly reduced coverage drastically changes the basic properties of a 2DES. Electron localization is strongly enhanced, and the ground state characteristics will be dominated by correlation effects then. Sn/Si(111) is scrutinized with this regard. It serves as an ideal realization of a triangular lattice, that inherently suffers from spin frustration. Consequently, long-range magnetic order is prohibited, and the ground state is assumed to be either a spiral antiferromagnetic (AFM) insulator or a spin liquid. Here, the single-particle spectral function is utilized as a fundamental quantity to address the complex interplay of geometric frustration and electronic correlations. In particular, this is achieved by combining the complementary strengths of ab initio local density approximation (LDA) calculations, state-of-the-art angle-resolved photoelectron spectroscopy, and the sophisticated many-body LDA+DCA. In this way, the evolution of a shadow band and a band backfolding incompatible with a spiral AFM order are unveiled. Moreover, beyond nearest-neighbor hopping processes are crucial here, and the spectral features must be attributed to a collinear AFM ground state, contrary to common expectation for a frustrated spin lattice
In der vorliegenden Arbeit werden drei unterschiedliche Beispiele für ein zweidimensionales Elektronensystem (2DES) auf der Oberfläche von Elementhalbleitern behandelt: Pt/Si(111), Au/Ge(111) und Sn/Si(111). Atomare Strukturen und deren spezielle Merkmale wurden mit Rastertunnelmikroskopie (STM) und Elektronenbeugung (LEED) untersucht, wobei ein Schwerpunkt die Abscheidung von Pt auf Si(111) war. Hervorzuheben ist hier die Anordnung von Pt Atomen als Trimere, die das Grundgerüst phasenverschobener Domänen bilden. Interessanterweise sind die Trimere um 30° gegenüber dem Substrat verdreht, was einen unerwarteten Symmetriebruch bedeutet. Daher stellt Pt/Si(111) ein einzigartiges Beispiel einer chiralen Struktur auf Halbleitern dar und könnte außerdem für katalytische Prozesse im atomaren Bereich interessant sein. Die Spin-Bahn Wechselwirkung ist auf Oberflächen, die schwere Elemente enthalten, von großer Bedeutung. Hier kann die Spin-Entartung in den elektronischen Zuständen aufgehoben sein, was als Rashba-Effekt bekannt ist. Rechnungen mittels Dichtefunktionaltheorie (DFT) zeigen, dass eine solche Aufspaltung in der hexagonalen Fermi-Fläche von Au/Ge(111) existiert. Experimentell wurde dies mit dreidimensionaler spin- und winkelaufgelöster Photoelektronenspektroskopie bestätigt. Dabei folgt die planare Spin-Komponente einem kreisförmigen Umlaufsinn, während zudem eine starke Aufrichtung des Spins aus der Ebene hinaus entlang gerader Abschnitte der Fermi-Fläche auftritt. Hierbei wurden zum ersten Mal in einem 2DES zusätzliche Rotationen des planaren Spinanteils in der Oberflächenebene nahe von Hochsymmetrierichtungen nachgewiesen. Dieses komplexe Spin-Muster resultiert aus den kristallinen Anisotropien und kann exzellent modelliert werden, indem das Rashba-Modell um Dresselhaus-artige Spin-Bahn Terme höherer Ordnung erweitert wird. Die alternative Verwendung von Gruppe-IV Adatomen bei einer geringeren Bedeckung ändert die Eigenschaften eines 2DES deutlich. Kennzeichnend sind eine verstärkte Ladungsträger-Lokalisierung und ein von Korrelationen bestimmter Grundzustand. Dabei stellt Sn/Si(111) ein Modell-System dar, das zudem ein spin-frustriertes Dreiecksgitter bildet. In einem solchen fehlt üblicherweise die langreichweitige magnetische Ordnung und der Grundzustand ist entweder ein isolierender spiralförmiger Antiferromagnet (AF) oder eine Spin-Flüssigkeit. Zur Analyse des Wechselspiels von geometrischer Frustration und elektronischen Korrelationen dient die Ein-Teilchen Spektralfunktion als Basisgröße. Dazu wurden die sich ergänzenden Stärken von Bandstruktur-Rechnungen in der lokalen Dichtenäherung (LDA), winkelaufgelöster Photoelektronenspektroskopie und Viel-Teilchen Modellen (hier LDA+DCA) kombiniert. Dabei wurde die Existenz eines Schattenbandes und einer Bandrückfaltung nachgewiesen, wobei letztere einen spiralförmigen AF als Grundzustand ausschließt. Vielmehr sind Hüpfprozesse über den nächsten Nachbarn im Gitter hinaus relevant und die spektralen Merkmale sind, trotz der Spin-Frustration, durch einen langreichweitigen kollinearen AF als Grundzustand erklärbar

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35

Hsieh, Li-Ching, and 謝立青. "2-DIMENSION ELECTRON SYSTEM IN CROSSING STATIC ELECTRIC AND MAGNETIC FIELDS." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/65835364848147057334.

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36

Zou, Yue. "Quantum Phases and Phase Transitions in Disordered Low-Dimensional Systems: Thin Film Superconductors, Bilayer Two-Dimensional Electron Systems, and One-Dimensional Optical Lattices." Thesis, 2011. https://thesis.library.caltech.edu/6024/2/thesis_v5.pdf.

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The study of various quantum phases and the phase transitions between them in low-dimensional disordered systems has been a central theme of recent developments of condensed matter physics. Examples include disordered thin film superconductors, whose critical temperature and density of states can be affected by a normal metallic layer deposited on top of them; amorphous thin films exhibiting superconductor-insulator transitions (SIT) tuned by disorder or magnetic field; and bilayer two-dimensional electron systems at total filling factor ν=1, which exhibit interlayer coherent quantum Hall state at small layer separation and have a phase transition tuned by layer separation, parallel magnetic field, density imbalance, or temperature. Although a lot of theoretical and experimental investigations have been done, many properties of these phases and natures of the phase transitions in these systems are still being debated. Here in this thesis, we report our progress towards a better understanding of these systems. For disordered thin film superconductors, we first propose that the experimentally observed lower-than-theory gap-T_c ratio in bilayer superconducting-normal-metal films is due to inhomogeneous couplings. Next, for films demonstrating superconductor-insulator transitions, we propose a new type of experiment, namely the drag resistance measurement, as a method capable of pointing to the correct theory among major candidates such as the quantum vortex picture and the percolation picture. For bilayer two-dimensional electron systems, we propose that a first-order phase transition scenario and the resulting Clausius-Clapeyron equations can describe various transitions observed in experiments quite well. Finally, in one-dimensional optical lattices, we show that one can engineer the long-sought-after random hopping model with only off-diagonal disorder by fast-modulating an Anderson insulator.

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37

Göres, Jörn [Verfasser]. "Correlation effects in 2-dimensional electron systems : composite fermions and electron liquid crystals / vorgelegt von Jörn Göres." 2005. http://d-nb.info/973886056/34.

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38

Geisler, Martin C. [Verfasser]. "The Hofstadter butterfly and quantum interferences in modulated 2-dimensional electron systems / Martin C. Geisler." 2006. http://d-nb.info/980568595/34.

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39

Huang, Chun-Wei, and 黃俊瑋. "Image-Based measuring system and it applications in 2-dimensional localization." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/85454170831358116390.

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Анотація:

碩士
淡江大學
電機工程學系碩士班
96
Localization is an important topic in Robotics. It is essential to have accurate position information of the robot so that the robot can be moved to any desired location. Although various Many localization methods have been proposed, those methods, however, usually use sensor fusion techniques to calculate the location of the robot. As a result, excessively calculation time might be required. In this thesis, we present a distance measurement method by using a single CCD camera and two parallel laser projectors beside the camera to measure the distance between the CCD camera and a target object. The proposed measuring system can measure the distance between arbitrarily points on an oblique surface and the angle between the oblique surface and the horizon. We also apply the proposed image-based measurement system to determine the position of the robot in 2-dimensional plane. Furthermore, this thesis also establishes a parameter identification system to make the proposed measuring system suitable for all kinds of CCD cameras. Thus, measurement accuracy of the proposed system can be significantly improved. Finally, practical experiments are conducted in the thesis to validate the effectiveness and viability of the proposed method. Simulation results also demonstrate the measurement system has a satisfactory accuracy in 2-dimensional localization.

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40

Tchaplyguine, Igor [Verfasser]. "Electronic structure of strongly correlated low-dimensional spin 1/2 systems : cuprates and vanadates / von Igor Tchaplyguine." 2002. http://d-nb.info/967614309/34.

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41

Yan, Jaw-Jenq, and 顏召政. "The Study of 2 Dimensional Vision Servo Tracking System on Robot Positioning." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/83184499690617632419.

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Анотація:

碩士
華梵大學
機電工程研究所
93
Robots are now in widespread use on automatic engineering﹐which has the advantage of high speed﹐high accuracy﹐and stably performance﹒It doesn’t have the disadvantage of human easy feel boring on repeating works﹒On traditionally robot use the method of teaching or teaching box guiding the route and recording in memory﹐then repeat again﹒Otherwise it can control the robot with programming the moving procedure﹒So it always plans the moving route beforehand﹒ Robot control system needs a on-time tracking ability for tracking moving object﹒Machine vision bases on image processing﹐it can recognize the grabbing image information﹐then output the result to control robot﹒Machine vision likes the human see a object then have a reactive﹐it is a method of realizing control robot on time﹒This dissertation uses machine vision﹐and set the CCD on robot arm﹐grabbing and analyzing the image information﹒So it can flexible change the route doesn’t plan the way previously﹐and achieve the goal of tracking on time﹒

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42

Chen, A., Soo-Jin Chua, Clifton G. Jr Fonstad, B. Wang, and O. Wilhelmi. "Two-dimensional Photonic Crystals Fabricated by Nanoimprint Lithography." 2004. http://hdl.handle.net/1721.1/7374.

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Анотація:

We report on the process parameters of nanoimprint lithography (NIL) for the fabrication of two-dimensional (2-D) photonic crystals. The nickel mould with 2-D photonic crystal patterns covering the area up to 20mm² is produced by electron-beam lithography (EBL) and electroplating. Periodic pillars as high as 200nm to 250nm are produced on the mould with the diameters ranging from 180nm to 400nm. The mould is employed for nanoimprinting on the poly-methyl-methacrylate (PMMA) layer spin-coated on the silicon substrate. Periodic air holes are formed in PMMA above its glass-transition temperature and the patterns on the mould are well transferred. This nanometer-size structure provided by NIL is subjective to further pattern transfer.
Singapore-MIT Alliance (SMA)

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43

Wu, Chun-Te, and 吳俊德. "The Characteristic study of 2-D electron gas induced in AlN/GaN heterojunction using Helicon Sputtering system." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/77945262056671636616.

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Анотація:

碩士
中原大學
電子工程研究所
92
AlGaN/GaN heterostructure field-effect transistors (HFETs) have been a subject of intensive investigation recently and have emerged as attractive candidates for high voltage, high-power operation at microwave frequencies such as low noise microwave amplifier, power microwave amplifier, high temperature devices and power suppliers. However, there exist some problems. One of those is large lattice mismatch as increasing the Al content, which increases the defects of interface and decreases the sheet carrier concentration as well as the carrier mobility. Therefore some research groups suggested to use the AlN/GaN heterostructure. AlN/GaN heterostructure would have much higher sheet carrier concentration, if the difficulties of deposition can be overcome. The aims of this study are to deposit epitaxial AlN films on GaN/Sapphire substrates at low growth temperature, and investigate the presence of large polarization field in the AlN barrier layer which results in high values of the 2DEG sheet density. Epitaxial AlN films have been successfully deposited on GaN/Sapphire substrates at low-temperature (300℃) using Helicon sputtering system. The FWHM of XRD rocking curve for (002) peak of AlN film is 0.125 and the �� scan confirms the epitaxial orientation relationship between the three layers of AlN/GaN/Sapphire. The two dimensional electron gas induced by AlN/GaN heterojunction has been measured to achieve -1.24×1013cm-2. The fruitful results will have contributions for fabricating high-power devices based on AlN/GaN heterojunction.

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44

Liu, Weihao, and 劉韋豪. "Detection of the Pathological Changes of Superficial Tissues and Development of a 2-Dimensional Image Measurement System Based on Bioimpedance Technique." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/65041250604292427448.

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Анотація:

碩士
國立暨南國際大學
生物醫學科技研究所
99
In Taiwan, 35.9 out of 100,000 people diagnosed with oral cancer, just second to New Guinea and Solomon. According to the statistics reported by the Department of Health, oral and skin cancer ranked sixth and twenty-first positions respectively in major cause of cancer death for four consecutive years in Taiwan. Currently non-invasive oral and skin cancer diagnostic products are very scarce, and the equipment is very expensive and heavy. Therefore, the purpose of this study is to develop a 2-dimensional image measurement system based on bioimpedance technique. The system has been evaluated with the averaged percentage error of about 5.2% ± 2.8%. Finally, we can use this system to distinguish normal and morbid tissues by the 2-dimensional image.

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45

Huang, Yu Shiang, and 黃鈺翔. "Establish a beam characteristic analysis system for the Chang Gung Memorial Hospital (CGMH) proton pencil beam scanning technique using a 2-dimensional ionization chamber array." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/76823621396314962858.

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Анотація:

碩士
長庚大學
醫學影像暨放射科學系
103
Quality assurance is an important procedure in radiation therapy. The purpose of this investigation was to establish a beam characteristic analysis system for Chang Gung Memorial Hospital (CGMH) proton pencil beam scanning technique using a 2-dimensional ionization chamber array and to evaluate the effect of clinical instruments set up error affecting the analyzed results. The following beam properties of the proton pencil beam scanning technique were analyzed: beam position, beam size, beam intensity, scanning velocity of beams, and beam energy. The detector distribution of 2D-arrays and a pre-designed scanning pattern were simulated using in-house program. Because 2D ion-chamber arrays challenge with coarse resolution, we applied mathematical methods such as 2D Gaussian fitting function to post-processing the signals. To compare the signals in ideal spatial resolution and discrete distribution, the differences were analyzed quantitatively. The differences for position and spot size analysis were within 0.3 mm and 0.6 mm, respectively , but intensity difference is larger than 10% at small spot situation. However, energy verification behaved good agreement in R80 value. The analysis results from the 2D ion-chamber arrays detected signals by pre-designed scanning pattern can be used to confirm the beam properties. The most obviously difference between the 2D arrays and high resolution dosimeters was their ability to test intensity stability for small spot size. And we suggested that the clinical set up error could not exceed 1˚ rotation and 1 mm position shift.

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46

Yuan, Judy Chia-Chun. "Defining a natural tooth color space based on a three-dimensional shade system." 2007. http://proquest.umi.com/pqdweb?did=1320964491&sid=20&Fmt=2&clientId=39334&RQT=309&VName=PQD.

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Анотація:

Thesis (M.S.)--State University of New York at Buffalo, 2007.
Title from PDF title page (viewed on Nov. 28, 2007) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Brewer, Jane D. Includes bibliographical references.

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Blauch, David N. "Part I. Improvements in the rotation-rate step experiment for the evaluation of diffusion coefficients at rotating disk electrodes. Part II. Ion-pairing and electric field effects on electron hopping in the Nafion-tris(2,2'-bipyridine)osmium(3+/2+) system." Thesis, 1991. https://thesis.library.caltech.edu/2613/1/Blauch_dn_1991.pdf.

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Part I: An improved description of the current transient produced by an abrupt change in the rate of rotation of a rotating disk electrode has been obtained by the method of orthogonal collocation. The procedure provides a formula that accurately describes the expected current transient for at least 90% of its duration. If the final rotation rate is chosen to be ca. 58% of the initial rotation rate, the resulting current transient exhibits simple exponential decay, thereby facilitating data analysis. A simple offset in the time scale of the experiment proves effective in compensating for the effects of both hydrodynamic relaxation and imperfections in the response of the electrode rotator. Part II: The high ionic content and low dielectric constant that prevail in the interior of many redox polymers are expected to promote ionic association between the polyelectrolyte and counterions. The present study is an attempt to evaluate the influence of ion-pairing interactions on charge propagation within polyelectrolyte films. The system under investigation consists of the Os(bpy)3(3+/2+) redox couple incorporated into Nafion, where ion-pairing between the osmium complex and pendant sulfonate groups is argued to be responsible for the irreversible retention of the complex within the film. The apparent diffusion coefficient characterizing the dynamics of electron propagation through the redox polymer exhibits a remarkably sudden increase as the film approaches electrostatic saturation with the Os(bpy)3(3+) complex. Existing models, even those taking into account the presence of electric fields within the film, do not account satisfactorily for the observed behavior of the apparent diffusion coefficients. The introduction of ion-pairing into the model for charge transport leads to predictions that are consistent with the observed behavior. Key ingredients in the successful model are the assumptions that the predominant forms of the Os(bpy)3(3+/2+) complex incorporated in Nafion are neutral aggregates resulting from the formation of triple or double ion-pairs and that the triply ion-paired Os(bpy)3(3+) species dissociates into a singly charged species containing the same number of sulfonate groups as the predominant form of the Os(bpy)3(2+) complex, thereby providing a low-energy pathway for electron self-exchange. The dissociation of the triply ion-paired Os(bpy)3(3+) complex provides a natural explanation for the steep increase in the apparent diffusion coefficient, i.e., the rate of electron propagation, as the concentration of the osmium complex comes close to saturation, because as saturation is approached the ion-pairing equilibrium shifts to favor the formation of the doubly ion-paired form of Os(bpy)3(3+) that is the best partner for accepting an electron from the doubly ion-paired Os(bpy)3(2+) complex. The inevitable presence of electric fields within the polyelectrolyte films also affects the observed behavior, especially as the concentration of the incorporated cation is increased.

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Дисертації з теми "2- dimensional electron system (2 DES)"

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