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1
Ozfidan, Asli Isil. "Electron-Electron Interactions in Optical Properties of Graphene Quantum Dots." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32857.
Testo completoAbstract (sommario):
In this thesis, I present a theory of electron-electron interactions in optical properties of graphene and transition metal dichalcogenides (TMDCs), two dimensional nanostructures with a hexagonal lattice.
We start our discussion with electron-electron interactions in artificial rings for which the strength of interactions can be varied and exact results can be obtained. The artificial rings are described by the extended Hubbard model and solved using an exact diagonalization method in real and Fourier space of configurations. Exact and analytical results for charged rings are obtained in the limit of very strong interactions. For the quadruple quantum dot ring and the artificial benzene ring, we find that chirality leads to the appearance of a topological phase and an effective gauge field that determines the ground state character with varied interaction strength. For the charged artificial benzene ring, our numerical results show a transition from a degenerate to a non-degenerate ground state with increasing strength of Coulomb interactions. We show that the artificial gauge and the transition in the ground state can be detected as changes in the optical absorption spectrum.
In the second part of the thesis, the electronic and optical properties of colloidal graphene quantum dots (CGQD) consisting of many benzene rings are determined. The CGQDs are described by the combination of tight binding, mean field Hartree Fock (HF) and Configuration Interaction methods. The single particle properties are described through the tight binding method based on the pz carbon orbitals. Screened Coulomb interactions between electrons, including direct, exchange, and scattering matrix elements, are calculated using Slater pz orbitals. HF ground states corresponding to semiconductor, Mott-insulator, and spin-polarized phases are obtained as a function of the strength of the screened interaction versus the tunnelling matrix element. The many-body ground and excited states in the semiconducting phase are constructed as a linear combination of a finite number of electron-hole pair excitations from the HF ground state (GS). The Hamiltonian is constructed in the subspace of multi-pair HF excitations to obtain the low energy, many body states by exact diagonalization using the Lanczos method.
The degeneracy of the valence- and conduction-band edges of 3-fold rotationally symmetric CGQDs is shown to lead to a characteristic exciton and bi-exciton spectrum. The low-energy exciton spectrum is predicted to consist of two bright-singlet exciton states corresponding to two circular polarizations of light and a lower-energy band of dark singlets and dark triplets. The robustness of the bright degenerate singlet pair against correlations in the many-body state is demonstrated as well as the breaking of the degeneracy by the lowering of symmetry of the CGQD.
Band edge biexciton energies and binding energies are predicted, and two degenerate exciton (X) states and a corresponding biexciton (XX) state are identified for the generation of an XX-X cascade. The Auger coupling of XX and excited X states is determined and our theoretical results are compared with experimental absorption and non-linear transient absorption spectra.
In the third and final part of the thesis, we replace the two non-equivalent carbon atoms of the graphene hexagonal lattice with a heavy transition-metal atom M, (e.g. Mo or W) and a dimer X2 (e.g. S). The bandstructure of a monolayer MX2 is calculated using density functional theory (DFT). It is shown that a direct gap opens up at all K points of the Brillouin zone and strong spin orbit coupling leads to spin splitting of the valence and conduction bands and emergence of valley dependent optical selection rules. Finally, the magnetoluminescence experiments on a monolayer WS2 emitting circularly polarized light upon its excitation by unpolarized light are described. The emission of polarized light in zero magnetic field is explained by the possibility of formation of a valley polarized 2D electron gas in unintentionally doped WS2.
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Kimani, Peter Borgia Ndungu. "Electronic structure and electron correlation in weakly confining spherical quantum dot potentials." abstract and full text PDF (free order & download UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3307466.
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Reyes, Vasquez David Fernando. "Magnetic configurations in Co-based nanowires explored by electron holography and micromagnetic calculations." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30356/document.
Testo completoAbstract (sommario):
Les nanofils magnétiques suscitent un intérêt considérable depuis une quinzaine d'années en raison de leur utilisation potentielle pour la spintronique. Leur utilisation potentielle dans des dispositifs exige une description détaillée des états magnétiques locaux des nanofils. Dans cette thèse, j'ai étudié qualitativement et quantitativement les états magnétiques à l'état rémanent de nanofils magnétiques par holographie électronique (EH) et simulations micromagnétiques. Une analyse détaillée a été réalisée sur deux types de nanofils : multicouches Co/Cu et nanofils FeCoCu à diamètre modulé. Les deux systèmes ont été synthétisés par électrodéposition dans des membranes. La combinaison des caractérisations magnétiques, structurales et chimiques locales obtenues dans un TEM avec des simulations micromagnétiques ont permis une description complète de ces systèmes. Pour les nanofils multicouches Co / Cu, j'ai analysé l'influence des épaisseurs de cobalt et de cuivre ou de la structure cristalline de Co sur la configuration magnétique de nanofils isolés. Après l'application d'un champs de saturation dans des directions parallèle et perpendiculaire à l'axe des nanofils, j'ai étudié les configurations magnétiques pour les épaisseurs de Co / Cu suivantes : 25nm / 15nm, 25nm / 45nm, 50nm / 50nm et 100nm / 100nm. Trois configurations principales à la rémanence ont été trouvées : (i) un couplage antiparallèle entre les couches Co, (ii) une structure mono-domaine et (iii) un état vortex. Dans les nanofils Co (25 nm) / Cu (15 nm), en fonction de la direction du champ de saturation, les couches de Co peuvent présenter soit un couplage antiparallèle (champ de saturation perpendiculaire) ou un couplage de type vortex (champ de saturation en parallèle) avec un coeur aligné parallèlement à l'axe du fil. Cependant, 10% des nanofils étudié présente un état mono-domaine quel que soit le champ de saturation parallèle et perpendiculaire. Dans le cas Co (50 nm) / Cu (50 nm) et Co (25 nm) / Cu (45 nm), l'épaisseur plus grande de Cu séparant les couches ferromagnétiques réduit l'interaction magnétique entre des couches de Co voisines. L'état rémanent est donc formé de la combinaison de couches de Co monodomaines orientés perpendiculairement à l'axe du fil et de certains états vortex. Enfin pour la configuration Co (100 nm) / Cu (100 nm), un état monodomaine est observé quel que soit la direction du champ appliqué lors de la saturation. Toutes ces configurations magnétiques ont été déterminées et simulées à l'aide des calculs micromagnétiques jusqu'à ce qu'un accord quantitatif avec les résultats expérimentaux aient été obtenus. J'ai ainsi pu expliquer l'apparition et la stabilité de ces configurations en fonction des principaux paramètres magnétiques tels que l'échange, la valeur et la direction de l'anisotropie et l'aimantation. La comparaison entre les simulations et les résultats expérimentaux ont ainsi servi à déterminer précisément la valeur de ces paramètres. Dans les nanofils FeCoCu à diamètre modulé, une description détaillée de l'influence de la géométrie sur la configuration locale de spins a été réalisée. Les expériences d'holographie électronique montrent une structure magnétique monodomaines avec l'aimantation alignée longitudinalement. Cependant, nous avons trouvé grâce à des simulations micromagnétiques que cette configuration monodomaine est fortement affectée par la variation locale du diamètre. L'étude en particulier du champ de fuite mais aussi du champ démagnétisant à l'intérieur des nanofils a mis en évidence le rôle prépondérant des charges magnétiques aux zones de variation de diamètre. De plus l'aimantation présente une structure plus compliquée qu'un simple alignement le long de l'axe du fil. Enfin les résultats que j'ai obtenus ont abouti à une interprétation différente d'expériences précédentes en MFM<br>Magnetic nanowires have raised significant interest in the last 15 years due to their potential use for spintronics. Technical achievements require a detailed description of the local magnetic states inside the nanowires at the remnant state. In this thesis, I performed quantitative and qualitative studies of the remnant magnetic states on magnetic nanowires by Electron Holography (EH) experiments and micromagnetic simulations. A detailed investigation was carried out on two types of nanowires: multilayered Co/Cu and diameter-modulated FeCoCu nanowires. Both systems were grown by template-based synthesis using electrodeposition process. The combination of local magnetic, structural and chemical characterizations obtained in a TEM with micromagnetic simulations brought a complete description of the systems. In the multilayered Co/Cu nanowires, I analysed how different factors such as the Co and Cu thicknesses or the Co crystal structure define the remnant magnetic configuration into isolated nanowires. After applying saturation fields along directions either parallel or perpendicular to the NW axis, I studied multilayered Co/Cu nanowires with the following relative Co/Cu thickness layers: 25nm/15nm, 25nm/45nm, 50nm/50nm, and 100nm/100nm. Three main remnant configurations were found: (i) antiparallel coupling between Co layers, (ii) mono-domain-like state and (iii) vortex state. In the Co(25 nm)/Cu(15 nm) nanowires, depending on the direction of the saturation field, the Co layers can present either an antiparallel coupling (perpendicular saturation field) or vortex coupling (parallel saturation field) with their core aligned parallel to the wire axis. However, 10% of the nanowires studied present a mono-domain-like state that remains for both parallel and perpendicular saturation fields. In the Co(50 nm)/Cu(50 nm) and Co(25 nm)/Cu(45 nm) nanowires, a larger Cu thickness separating the ferromagnetic layers reduces the magnetic interaction between neighbouring Co layers. The remnant state is hence formed by the combination of monodomain Co layers oriented perpendicularly to the wire axis and some tilted vortex states. Finally for the Co(100 nm)/Cu(100 nm) nanowires a monodomain-like state is found no matters the direction of the saturation field. All these magnetic configurations were determined and simulated using micromagnetic calculations until a quantitative agreement with experimental results has been obtained. I was able to explain the appearance and stability of these configurations according to the main magnetic parameters such as exchange, value and direction of the anisotropy and magnetization. The comparison between simulations and experimental results were used to precisely determine the value of these parameters. In the diameter-modulated cylindrical FeCoCu nanowires, a detailed description of the geometry-induced effect on the local spin configuration was performed. EH experiments seem to reveal that the wires present a remnant single-domain magnetic state with the spins longitudinally aligned. However, we found through micromagnetic simulations that such apparent single-domain state is strongly affected by the local variation of the diameter. The study of the leakage field and the demagnetizing field inside the nanowire highlighted the leading role of magnetic charges in modulated areas. The magnetization presents a more complicated structure than a simple alignment along the wire axis. Finally my results have led to a new interpretation of previous MFM experiments
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Bridges, Craig Allan Greedan John E. "Structural and electronic properties of BaV10O15, BaV10-xTixO15, and BaVO3-x /." *McMaster only, 2002.
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5
Sans, Aguilar Juan R. "Four dimensional analysis of free electron lasers in the amplifier configuration." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Dec%5FSans%5FAguilar.pdf.
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Thesis (M.S. in Applied Science)--Naval Postgraduate School, December 2007.<br>Thesis Advisor(s): Colson, William B. "December 2007." Description based on title screen as viewed on January 18, 2008. Includes bibliographical references (p. 63). Also available in print.
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Napier, Stuart A. "Electron correlation and spin-dependent effects in the electron impact excitation of zinc atoms." University of Western Australia. School of Physics, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0098.
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[Truncated abstract] This work investigated electron correlation and spin-dependent effects in electron scattering from zinc for incident electron energies from the lowest excitation threshold at 4.003 eV to 50 eV. Experiments were performed using a crossed-beams electron impact spectrometer, which included an unpolarised electron gun, and also a spin-polarised electron gun. The apparatus was tested, and shown to be operating well, by repeating past studies of electron scattering from helium and argon. Emission cross sections for the 4s4p 3P1, 4s4p 1P1, 4s5s 3S1, 4s4d; 5d; 6d 3D1;2;3 and 4s4d; 5d 1D2 states were measured from the respective thresholds to 50 eV. These were compared with Convergent Close-Coupling (CCC) and B-spline R-matrix (BSRM) calculations of the 4s4p 3P1, 4s4p 1P1, 4s5s 3S1, 4s4d 1D2 and 4s4d 3D1;2;3 emission cross sections. There are serious discrepancies between the theories, and between the theories and experiment, which indicates strong continuum coupling and innershell excitation effects in the electron excitation of zinc. The differential elastic scattering signal at scattering angles of 30 , 54 , 90 and 110 was measured for incident electron energies from just below the lowest excitation threshold at 4.003 eV, to the ionisation threshold at 9.394 eV. Some assignments given by Sullivan et al [1] and Zatsarinny and Bartschat [2] were confirmed by the present experiment. An area of disagreement in the literature concerning the nature of a feature observed at the 4s4p 1P1 threshold at 5.796 eV was resolved in favour of Zatsarinny and Bartschat, who assign the feature as a cusp. ... Below the ionisation threshold, the 4s4p 3P1 photon excitation function supports the assignment of the near-4s4p 1P1 threshold feature as a cusp. Some of the overlapping negative-ion resonances which were observed near 7.5 eV in the 4s4p 3P1, 4s4p 1P1 and 4s5s 3S1 photon excitation functions were assigned with the assistance of the BSRM calculations of Zatsarinny and Bartschat. However, continuum coupling effects above 8 eV seem to cause the theoretical negative-ion resonance predictions to break down. Above the ionisation threshold, the near-11 eV negative-ion resonance effects depend on the configuration n, L and S of the neutral state excitation observed. This may be due to the properties of the mixed negative ion component states. Postcollision interaction (PCI) effects the 4s5s 3S1, 4s4d; 5d; 6d 3D1;2;3 and 4s4d; 5d 1D2 photon excitation functions. The PCI mechanism can populate the 4s4d; 5d; 6d 3D1;2;3 and 4s4d; 5d 1D2 states because the scattered and ejected electrons have a similar energy, and can thus exchange a large amount of orbital angular momentum. The present work demonstrates that electron correlation effects, especially those associated with innershell excitation, are very significant in electron scattering from zinc. Existing theoretical models of electron scattering from zinc inadequately treat electron correlations, and as a result of this are inaccurate, as shown here. The studies presented here should guide the development of models that accurately describe the innershell excitation effects, which are important for zinc and a great many other atoms.
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Sloggett, Clare Physics Faculty of Science UNSW. "Electron correlations in mesoscopic systems." Awarded by:University of New South Wales. School of Physics, 2007. http://handle.unsw.edu.au/1959.4/31875.
Testo completoAbstract (sommario):
This thesis deals with electron correlation effects within low-dimensional, mesoscopic systems. We study phenomena within two different types of system in which correlations play an important role. The first involves the spectra and spin structure of small symmetric quantum dots, or "eartificial atoms"e. The second is the "e0.7 structure"e, a well-known but mysterious anomalous conductance plateau which occurs in the conductance profile of a quantum point contact. Artificial atoms are manufactured mesoscopic devices: quantum dots which resemble real atoms in that their symmetry gives them a "eshell structure"e. We examine two-dimensional circular artificial atoms numerically, using restricted and unrestricted Hartree-Fock simulation. We go beyond the mean-field approximation by direct calculation of second-order correlation terms; a method which works well for real atoms but to our knowledge has not been used before for quantum dots. We examine the spectra and spin structure of such dots and find, contrary to previous theoretical mean-field studies, that Hund's rule is not followed. We also find, in agreement with previous numerical studies, that the shell structure is fragile with respect to a simple elliptical deformation. The 0.7 structure appears in the conductance of a quantum point contact. The conductance through a ballistic quantum point contact is quantised in units of 2e^2/h. On the lowest conductance step, an anomalous narrow conductance plateau at about G = 0.7 x 2e^2/h is known to exist, which cannot be explained in the non-interacting picture. Based on suggestive numerical results, we model conductance through the lowest channel of a quantum point contact analytically. The model is based on the screening of the electron-electron interaction outside the QPC, and our observation that the wavefunctions at the Fermi level are peaked within the QPC. We use a kinetic equation approach, with perturbative account of electron-electron backscattering, to demonstrate that these simple features lead to the existence of a 0.7-like structure in the conductance. The behaviour of this structure reproduces experimentally observed features of the 0.7 structure, including the temperature dependence and the behaviour under applied in-plane magnetic fields.
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吳潔貞 and Kit-ching Betty Ng. "Correlation effects in crystal field splitting." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31230714.
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Ng, Kit-ching Betty. "Correlation effects in crystal field splitting /." [Hong Kong : University of Hong Kong], 1986. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12323342.
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Temperley, J. "Electron spin resonance studies of early d-transition metal compounds with a d#1#-configuration." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382736.
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Baǧcı, V. M. Kemal Krokhin Arkadii. "Anderson localization in two-channel wires with correlated disorder DNA as an application /." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5204.
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Olguin, Marco Augusto. "The isotopological homodesmotic reaction a further refinement to the quantification of aromaticity /." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Bagci, V. M. Kemal. "Anderson Localization in Two-Channel Wires with Correlated Disorder: DNA as an Application." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc5204/.
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This research studied the Anderson localization of electrons in two-channel wires with correlated disorder and in DNA molecules. It involved an analytical calculation part where the formula for the inverse localization length for electron states in a two-channel wire is derived. It also involved a computational part where the localization length is calculated for some DNA molecules. Electron localization in two-channel wires with correlated disorder was studied using a single-electron tight-binding model. Calculations were within second-order Born-approximation to second-order in disorder parameters. An analytical expression for localization length as a functional of correlations in potentials was found. Anderson localization in DNA molecules were studied in single-channel wire and two-channel models for electron transport in DNA. In both of the models, some DNA sequences exhibited delocalized electron states in their energy spectrum. Studies with two-channel wire model for DNA yielded important link between electron localization properties and genetic information.
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Bezugly, Viktor. "Wavefunction-based method for excited-state electron correlations in periodic systems - application to polymers." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1081263150312-71894.
Testo completoAbstract (sommario):
In this work a systematic method for determining correlated wavefunctions of extended systems in the ground state as well as in excited states is presented. It allows to fully exploit the power of quantum-chemical programs designed for correlation calculations of finite molecules. Using localized Hartree-Fock (HF) orbitals (both occupied and virtual ones), an effective Hamiltonian which can easily be transferred from finite to infinite systems is built up. Correlation corrections to the matrix elements of the effective Hamiltonian are derived from clusters using an incremental scheme. To treat the correlation effects, multireference configuration interaction (MRCI) calculations with singly and doubly excited configurations (SD) are performed. This way one is able to generate both valence and conduction bands where all correlation effects in the excited states as well as in the ground state of the system are taken into account. An appropriate size-extensivity correction to the MRCI(SD) correlation energies is developed which takes into account the open-shell character of the excited states. This approach is applicable to a wide range of polymers and crystals. In the present work trans-polyacetylene is chosen as a test system. The corresponding band structure is obtained with the correlation of all electrons in the system being included on a very high level of sophistication. The account of correlation effects leads to substantial shifts of the &quot;center-of-mass&quot; positions of the bands (valence bands are shifted upwards and conduction bands downwards) and a flattening of all bands compared to the corresponding HF band structure. The method reaches the quantum-chemical level of accuracy. Further an extention of the above approach to excitons (optical excitations) in crystals is developed which allows to use standard quantum-chemical methods to describe the electron-hole pairs and to finally obtain excitonic bands.
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Bezugly, Viktor. "Wavefunction-based method for excited-state electron correlations in periodic systems - application to polymers." Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A24323.
Testo completoAbstract (sommario):
In this work a systematic method for determining correlated wavefunctions of extended systems in the ground state as well as in excited states is presented. It allows to fully exploit the power of quantum-chemical programs designed for correlation calculations of finite molecules. Using localized Hartree-Fock (HF) orbitals (both occupied and virtual ones), an effective Hamiltonian which can easily be transferred from finite to infinite systems is built up. Correlation corrections to the matrix elements of the effective Hamiltonian are derived from clusters using an incremental scheme. To treat the correlation effects, multireference configuration interaction (MRCI) calculations with singly and doubly excited configurations (SD) are performed. This way one is able to generate both valence and conduction bands where all correlation effects in the excited states as well as in the ground state of the system are taken into account. An appropriate size-extensivity correction to the MRCI(SD) correlation energies is developed which takes into account the open-shell character of the excited states. This approach is applicable to a wide range of polymers and crystals. In the present work trans-polyacetylene is chosen as a test system. The corresponding band structure is obtained with the correlation of all electrons in the system being included on a very high level of sophistication. The account of correlation effects leads to substantial shifts of the &quot;center-of-mass&quot; positions of the bands (valence bands are shifted upwards and conduction bands downwards) and a flattening of all bands compared to the corresponding HF band structure. The method reaches the quantum-chemical level of accuracy. Further an extention of the above approach to excitons (optical excitations) in crystals is developed which allows to use standard quantum-chemical methods to describe the electron-hole pairs and to finally obtain excitonic bands.
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Kenmochi, Naoki. "Study of magnetic field configuration effects on internal transport barrier formation in Heliotron J." Kyoto University, 2016. http://hdl.handle.net/2433/215652.
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Dobrautz, Werner [Verfasser], and Ali [Akademischer Betreuer] Alavi. "Development of full configuration interaction quantum Monte Carlo methods for strongly correlated electron systems / Werner Dobrautz ; Betreuer: Ali Alavi." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2019. http://d-nb.info/1197056459/34.
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Amow, Gisele. "Structural and physical properties of the vacancy doped systems R(1-x)TiO3 (R = Nd for 0.00< x < 0.33 and Sm for 0.00< x < 0.17) : an investigation of metal-insulator transitions /." *McMaster only, 1999.
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Sohier, Thibault. "Electrons et phonons dans le graphène : couplage électron-phonon, écrantage et transport dans une configuration type transistor à effet de champ." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066393/document.
Testo completoAbstract (sommario):
Comprendre le transport électronique dans les cristaux bidimensionnels est un enjeu conceptuel majeur pour la nanoélectornique de demain. Dans cette thèse, on dévelloppe des méthodes ab initio pour étudier l'interaction électron-phonon, l'écrantage et le transport dans le graphène. Pour surpasser les limites des méthodes ab initio en ondes planes, à l'origine destinées aux matériaux périodiques en trois dimensions, on tronque l'interaction coulombienne dans la troisième dimension, isolant ainsi le système bidimensionnel de ses images périodiques. Ceci est réalisé au sein de la théorie de la fonctionnelle de la densité en perturbation, afin de calculer la réponse de la densité de charge et le spectre des phonons dans un cadre bidimensionnel. On utilise ces méthodes pour obtenir un modèle quantitatif du couplage électron-phonon dans le graphène pour une configuration de type transistor à effet de champ. Le couplage aux phonons acoustiques est dominé par le champ de jauge non-écranté, que nous calculons en incluant l'effet des interactions électron-électron au niveau GW. Nos simulations des propriétés d'écrantage statiques du graphene valident les modèles analytiques et montrent que le potentiel de déformation est fortement écranté, de sorte que sa contribution à la diffusion des électrons par les phonons acoustiques est négligeable. On montre également que le couplage avec les phonons hors-plan est faible mais fini. On obtient la contribution de la diffusion par les phonons à la résistivité en résolvant l'équation de Boltzmann pour le transport. En dessous de la température ambiante, nos résultats confirment le rôle des phonons acoustiques et une augmentation de 15% du paramètre de jauge it ab initio permet un excellent accord avec l'expérience. Au dessus de la température ambiante, on dénote l'importance des phonons optiques intrinsèques<br>Understanding the transport properties of two-dimensional crystals doped by field effect is a conceptual milestone for tomorrow's nanoelectronics. In this thesis we develop first-principles methods to investigate electron-phonon interactions, screening and phonon-limited transport in graphene. To overcome the limitations of existing plane-wave ab initio packages, originally devised for three-dimensional periodic solids, we truncate the Coulomb interaction in the third direction and isolate the 2D system from its periodic images. This is implemented in density-functional perturbation theory to calculate charge density responses and phonon spectra in a two-dimensional framework. We use those methods to develop a quantitative model of electron-phonon coupling for graphene in the field effect transistor configuration. We find that the coupling of electrons to acoustic phonons is dominated by the unscreened gauge field, which we compute with full inclusion of electron-electron interactions at the GW level. Our simulations of the static screening properties of graphene validate analytical models and reveal that the deformation potential is strongly screened, such that its contribution to acoustic phonon scattering is negligible. We find a small but finite linear coupling with out-of-plane phonons. By solving the Boltzmann transport equation we obtain the phonon-limited resistivity. Below room temperature, our results confirm the role of acoustic phonons and a 15% increase of the ab initio gauge field parameter leads to an excellent quantitative agreement with experiment. Above room-temperature, we point to the importance of the coupling with intrinsic optical phonons
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Okubo, Hitoshi, Katsumi Kato, Keiya Suzuki, and Kojima Hiroki. "ELECTRIC FIELD OPTIMIZATION OF FLOATING ELECTRODE CONFIGURATION IN VACUUM INTERRUPTER." IEEE, 2010. http://hdl.handle.net/2237/14457.
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Ait, Saadi Bachir. "Configuration des dislocations dans l'acier z3 cnd 17-12 apres fatigue : correlation au comportement mecanique." Poitiers, 1988. http://www.theses.fr/1988POIT2259.
Testo completoAbstract (sommario):
Etude du comportement en fatigue plastique de l'acier inoxydable austenitique 316l fatigue sous vide a 20, 300 et 600c dans une gamme de deformations plastiques imposees. Analyse par microscopie electronique en transmission des sous-structures a20 et 600c, les microstructures sont constituees de bandes de glissement persistantes, de murs-canaux des labyrinthes et des structures en echelle evoluant vers la structure cellulaire. A300c, une structure de contraste en cotes de velours est observee. Cette structure est fonction de la deformation plastique et provoque un durcissement cyclique secondaire. Presentation de modeles de formation et d'evolution de microstructures de fatigue
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Boniface, Claude. "Modélisation et diagnostics d'un propulseur à effet Hall pour satellites : configuration magnétique et nouveaux concepts." Toulouse 3, 2006. http://www.theses.fr/2006TOU30016.
Testo completoAbstract (sommario):
Le Propulseur à Effet Hall est un moteur sans grille, dans lequel un champ magnétique radial confine les électrons d'un plasma formé entre deux cylindres coaxiaux diélectriques. La chute de la conductivité électronique qui en résulte permet l'établissement d'un champ électrique axial pour extraire les ions. La relativement faible poussée (100 mN) et la forte impulsion spécifique (vitesse des ions éjectés de 20 km/s) rendent le propulseur bien adapté aux tâches de maintien sur orbite des satellites ou de petits transferts d'orbite. L'étude porte sur la modélisation des phénomènes physiques dans le propulseur associée à une étude expérimentale, plus limitée, et destinée à valider ou compléter les modèles. La modélisation est basée sur une description des phénomènes de transport des particules (électrons, ions, neutres) en champs électrique et magnétique croisés. Un modèle développé au CPAT a été complété et utilisé pour chercher les conditions optimales de fonctionnement, en particulier l'étude de la configuration magnétique des moteurs à Effet Hall existants. De plus, nous avons développé un modèle pour étudier de nouveaux concepts de moteurs à Effet Hall, en particulier un moteur à Effet Hall à Double Etage, dans lequel on cherche à contrôler séparément la génération du plasma et l'accélération des ions. La partie expérimentale a consisté à utiliser des techniques de diagnostics plasma (interférométrie de Fabry-Pérot) permettant de mesurer la distribution du champ électrique dans le système, résultant de la présence du plasma et des tensions appliquées aux électrodes. Les mesures ont été effectuées sur le moyen d'essai PIVOINE installé à Orléans. La confrontation systématique des résultats expérimentaux et de simulation a permis de mieux définir les possibilités et les limites du modèle et d'en améliorer ses capacités prédictives<br>Hall Effect Thrusters (HETs) are gridless ion engines where a magnetic field barrier is used to impede the electron motion toward the anode and generate a large electric field that provides collisionless ion acceleration. The thrust is about 100 mN and the specific impulse of HETs is in the range 1600-2000 s (i. E. The velocity of ejected xenon ions is on the order of 16-20 km/s). The thrust and the specific impulse of standard Single Stage HETs are well adapted to the missions of orbit correction and station keeping. The goal here is to model the physical phenomena occurring in such a thruster, and, in correlation with experimental studies, to validate and/or improve the assumptions of the model. The model describes the transport of the electrons, ions, and neutrals in crossed electric and magnetic fields. The model developed at CPAT was extended and used to identify conditions for optimal operation of the thruster, with particular attention to the influence of the magnetic field distribution on the thruster operation. In addition, we developed a model to study new thuster concepts such as a Double Stage Hall Effect Thruster, where ionization and acceleration are accomplished in two stages. The experimental study involved using specific plasma diagnostics (Fabry-Perot Interferometry) in order to measure the electric field distribution in the thruster. Measurements were made at the PIVOINE test facility in Orléans. Systematic comparisons between experimental results and simulations allowed us to define more clearly the limits of the model and to improve its predictive ability
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Mahmoud, Salman. "Étude théorique des molécules diatomiques BN, SiN et LaH, structure électronique et spectroscopie." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20080/document.
Testo completoAbstract (sommario):
Une étude théorique ab initio des structures électroniques des molécules Diatomiques polaires BN, SiN et LaH dans la représentation 2s+1Λ(+/-)Ont été effectués par la méthode du champ auto-cohérent de l'espace Actif complet (CASSCF), suivie par l'interaction de la configuration multiréférence (MRSDCI). La correction de Davidson, notée (MRSDCI+ Q), a ensuite été appliquée pour rendre compte de clusters ou agrégats quadruples non liés. L'ensemble de l'espace de configuration de CASSCF a été utilisé comme référence dans le calcul MRCI, qui a été effectués en utilisant le programme de calcul de chimie physique MOLPRO et en tirant parti de l'interface graphique Gabedit. Quarante-deux de plus bas états électroniques dans la représentation 2s+1Λ(+/-)au-dessous de 95000 cm-1 ont été étudiés de la molécule BN. Alors que vingt-huit états électroniques dans les représentations 2s+1Λ(+/-) jusqu'à 70000 cm-1 de la molécule de SiN ont été étudiés. D'autre part, les vingt-quatre bas états électroniques de LaH dans les représentations 2s+1Λ(+/-) au-dessous de 70000 cm-1 ont été étudiées par deux méthodes différentes et en prenant en considération l'effet des spin-orbite de la molécule LaH et nous avons observé la division énergétique des huit états électroniques. Les courbes d'énergie potentielle ont été construites avec la fréquence co-harmonique ωe, la distance internucléaire de l'équilibre re, les constantes de rotation Be. L'énergie électronique par rapport à l'état fondamentale Te a été calculé pour les états électroniques considérés comme des BN, SiN et la molécule LaH respectivement. En utilisant l'approche des fonctions canoniques, les valeurs propres Ev, les constantes rotationnelles Bv, la constante de distorsion centrifuge Dv et les abscisses des points de retournement Rmin and Rmax ont été calculés pour les états électroniques au niveau de vibration v=51 pour LaH molécule. Dix-huit et neuf états électroniques ont été étudiées pour la molécule BN et SiN respectivement. Pour LaH, vingt-trois états électroniques de la molécule LaH et l'effet de spin-orbite de molécule LaH sont donnés ici pour la première fois. La comparaison avec les données expérimentales et théoriques pour la plupart des constantes calculées démontre une très bonne précision. Enfin, ces résultats devraient ainsi mener à des études expérimentales plus poussées pour ces molécules. Nos résultats ont été publiés dans le Canadian Journal of Chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer, nous avons deux autres articles en préparation à soumettre<br>In the present work a theoretical investigation of the lowest molecular states of BN, SiN and LaH molecule, in the representation 2s+1Λ(+/-), has been performed via complete active space self-consistent field method (CASSCF) followed by multireference single and double configuration interaction method (MRSDCI). The Davidson correction noted as (MRSDCI+Q) was then invoked in order to account for unlinked quadruple clusters. The entire CASSCF configuration space was used as a reference in the MRCI calculation which has been performed via the computational chemistry program MOLPRO and by taking advantage of the graphical user interface Gabedit. Forty-two singlet, triplet, and quintet lowest electronic states in the 2s+1Λ(+/-) representation below 95000 cm-1 have been investigated of the molecule BN. While twenty-eight electronic states in the representation2s+1Λ(+/-)up to 70000 cm-1 of the SiN molecule have been investigated.On the other hand the Twenty four low-lying electronic states of LaH in the representation 2s+1Λ(+/-) below 35000 cm-1 have been studied by two different methods and by taking into consideration the spin orbit effect of the molecule LaH we give in the energy splitting of the eight electronic states. The potential energy curves (PECs) together with the harmonic frequency ωe, the equilibrium internuclear distance re, the rotational constants Be and the electronic energy with respect to the ground state Te have been calculated for the considered electronic states of BN, SiN and LaH molecule respectively. Using the canonical functions approach, the eigenvalues Ev, the rotational constants Bv ,the centrifugal distortion constants Dv and the abscissas of the turning points Rmin and Rmax have been calculated for electronic states up to the vibrational level v =51 for LaH molecule.Eighteen and Nine electronic states have been investigated here for the first time for the molecules of BN and SiN respectively, while for LaH, news results are performed for twenty three electronic states of LaH molecule and the spin-orbit effect of LaH molecule is given here for the first time. A comparison with experimental and theoretical data for most of the calculated constants demonstrated a very good accuracy. Finally, we expect that the results of our work should invoke further experimental investigations for these molecules. Our results have been published in Canadian journal of chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer and we have two other papers in preparation to submit
24
Verdebout, Simon. "On the use of non-orthogonal partition correlation functions in atomic physics: theory and applications." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209620.
Testo completoAbstract (sommario):
Our thesis tackles the many-electronic problem considering a non-relativistic and a relativistic orbital approach. Using the suites of programs ATSP and GRASP, we are able to approximate many-electron wave functions beyond the independent particle model by considering a superposition of CSFs. The optimization process, based on the variational principle, provides the best possible mixing coefficients fixing the linear combination of CSFs and spin-orbital basis on which we impose the orthonormality condition between functions of the same l or kappa subspace. Using this conventional approach within the relativistic framework, we estimate different properties of the triply ionized antimony atom (Sb IV), namely transition energies, transition probabilities, isotope shifts and a hyperfine-induced transition.<p><p>In the aim of partially relaxing the orthogonality constraints between correlation orbitals, we use the variational principle for targeting specific correlation effects by tailoring the configuration space. Independent sets of correlation orbitals, embedded in PCF, are produced from MCHF calculations. These non-orthogonal functions span CSF spaces that are coupled to each other by solving the associated generalized eigenvalue problem. The Hamiltonian and overlap matrix elements are evaluated using the biorthonormal orbital transformations and the efficient counter-transformations of the configuration interaction eigenvectors. This original method is successfully applied for describing different light atomic systems such as Li I, Be I, B I, C II and Ne I. An unwanted effect, called the ``constraint effect', is described and studied for these particular atomic systems. Even if this constraint can be completely relaxed through the DPCFI method, the computational resources required by such an approach lead us to study some simple strategies relaxing partially this constraint. This study takes it place in the context of neutral beryllium for which we test two particular strategies: one based on a weight criterion and one based on the type of excitations. Before concluding, we expose some developments combining the SCF process and the biorthonormal condition to relax the orthogonality constraints that are presently applied to the optimization process of the spin-orbital basis.<p>/<p>Dans notre thèse, nous abordons le problème polyélectronique dans un contexte non-relativiste et relativiste en adoptant une approche orbitalaire. En utilisant les suites de programmes reconnues ATSP et GRASP, nous sommes aptes à approcher des fonctions d'ondes polyélectroniques au-delà du modèle des particules indépendantes en utilisant une superposition de CSFs. Le processus d'optimisation, basé sur le principe des variations, fournit la meilleure estimation possible des coefficients de mélange, fixant la combinaison linéaire de CSFs et la meilleure base de spin-orbitales sur laquelle on impose la condition d'orthonormalité entre les fonctions appartenant au même sous-espace l ou kappa. En adoptant cette approche dans un cadre relativiste, nous évaluons des énergies de transition, des probabilités de transition, des déplacements isotopiques ainsi qu'une transition induite par mélange hyperfin pour l'atome d'antimoine trois fois ionisé (Sb IV).<p><p>Dans le but de relâcher partiellement les contraintes d'orthogonalité entre les orbitales de corrélation, nous utilisons le principe des variations afin de cibler des effets précis de la corrélation en taillant l'espace des configurations. Les ensembles indépendants d'orbitales de corrélation sont obtenus via la méthode MCHF. Les espaces de CSFs, exprimés sur ces fonctions mono-électronique non-orthogonales, sont couplés en résolvant le problème aux valeurs propres généralisé associé. Les matrices Hamiltonienne et de recouvrement sont déterminées au moyen de la technique des transformations biorthonormales et de la contre-transformation des vecteurs propres associés. Cette méthode originale est utilisée avec succès pour décrire des systèmes atomiques légers comme Li I, Be I, B I, C II et Ne I. Un effet indésirable, appelé ``effet de contrainte', est déecrit et étudié pour ces derniers systèmes atomiques. Même si ces contraintes peuvent-être en principe totalement levées au travers de la méthode DPCFI, les ressources nécessaires à l'application de cette dernière approche nous ont conduit à la recherche de stratégies simples et efficaces autorisant leur levée partielle. Pour ce faire, dans le cadre de nos calculs réalisés sur l'atome de béryllium, nous avons envisagé deux stratégies particulières: l'une basée sur les coefficients de mélange et l'autre basée sur le type d'excitation. Avant de conclure, nous proposons quelques développements combinant le processus auto-cohérent et la condition de biorthonormalité dans le but de relâcher les contraintes d'orthogonalité appliquées lors du processus d'optimisation de la base de spin-orbitales.<br>Doctorat en Sciences de l'ingénieur<br>info:eu-repo/semantics/nonPublished
25
Haidara, Modibo. "Impulsions de Trichel dans le cyclohexane liquide et les gaz comprimés." Grenoble 1, 1988. http://www.theses.fr/1988GRE10160.
Testo completoAbstract (sommario):
Resultats d'etude de la conduction electrique de liquides non polaires tres purs (cyclohexane, n-propane) en geometrie pointe-plan, en fonction du rayon de courbure de la pointe et de la pression hydrostatique (p<->10**(7)pa)
26
Rusz, Ján, Ikuo Nishida, Shunsuke Muto, and Kazuyoshi Tatsumi. "Site-specific electronic configurations of Fe 3d states by energy loss by channeled electrons." AIP publishing, 2010. http://hdl.handle.net/2237/20791.
Testo completo
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Allatt, Roger Giles. "Fine structure in the alpha decay of '1'9'2Po : shape coexistence in '1'8'8Pb." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367136.
Testo completo
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Hasaani, A. S. "Pulsed electron cyclotron maser experiments with different configurations." Thesis, University of Strathclyde, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381323.
Testo completo
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Kumar, Santhosh Tekke Athayil, and santhosh kumar@anu edu au. "Experimental Studies of Magnetic Islands, Configurations and Plasma Confinement in the H-1NF Heliac." The Australian National University. Research School of Physical Sciences and Engineering, 2008. http://thesis.anu.edu.au./public/adt-ANU20080611.171513.
Testo completoAbstract (sommario):
Rational magnetic flux surfaces in fusion (toroidal plasma confinement) devices can break the magnetic field lines and reconnect
them in the form of magnetic islands. Formation of these magnetic islands can have a serious impact on the plasma confinement properties of the device. Islands can in general degrade the confinement by
mixing up different regions of the plasma. However there has been experimental evidence of confinement improvement by island induced transport barriers, under certain conditions. Even though there are a
large number of theoretical and experimental works on magnetic islands to date, there is clearly a paucity of convincing experimental
understanding on the nature of behaviour of islands in plasma. This thesis reports detailed experimental studies conducted on the H-1NF heliac stellarator, to gain an in-depth understanding of magnetic islands and their influence in plasma confinement.¶
Work reported in this thesis can be mainly divided into three parts: (a) high resolution imaging of vacuum magnetic islands and flux surfaces of H-1NF, (b) accurate computer modeling of H-1NF magnetic
geometry and (c) detailed experiments on magnetic islands in plasma configurations.¶
Electron-beam wire-tomography in the H-1NF has been used for the high resolution mapping of vacuum magnetic flux surfaces and islands. Point-to-point comparison of the mapping results with
computer tracing, in conjunction with an image warping technique, has enabled systematic exploration of magnetic islands and surfaces of interest. A fast mapping technique has been developed, which
significantly reduced the mapping time and made this technique suitable for mapping at higher magnetic fields.¶
Flux surface mapping has been carried out at various magnetic configurations and field strengths. The extreme accuracy of this technique has been exploited to understand the nature of error fields,
by point-by-point matching with computer tracing results. This has helped in developing a best-fit computer model for H-1NF magnetic configurations, which can predict rotational transform correct to
three decimal places. Results from plasma experiments on magnetic configuration studies are best explained by the new model.¶
Experiments with low order magnetic islands in plasma configurations yielded some new results. It has been observed that the low order magnetic islands (m = 2) near the core of the plasma serve as pockets of improved confinement region under favourable conditions. This results in significant profile modifications including enhancement of the radial electric field near the core to a large positive value. The characteristics of islands are found to be
dependent on the plasma collisionality and the island width.¶
Experiments with a magnetic configuration which exhibits no vacuum islands, but the core rotational transform very close to
low order rational value, show a spontaneous transition of the radial electric field near the core to a large positive value (nearly 5
kV/m), with a strong electric field shear (nearly 700 kV/m2) and localised improvement in confinement, during the discharge. Evidence indicates that the transition is driven by the excitation of low order magnetic islands near the axis during the plasma discharge, due to the modification of rotational transform profile by toroidal plasma currents. The situation is similar to the Core Electron-Root Confinement (CERC) observed during high temperature ECH
plasma discharges on other helical devices. This result provides an experimental evidence for the hypothesis that the threshold conditions for observing CERC can be reduced by exciting magnetic islands near
the core of the plasma.
30
Carrere, Marcel Henri Michel. "Etude expérimentale d'un plasma de décharge à confinement multipolaire." Grenoble 1, 1994. http://www.theses.fr/1994GRE10039.
Testo completoAbstract (sommario):
Les decharges a confinement magnetique multipolaire excitees par des filaments emissifs sont largement utilisees pour des etudes fondamentales dans les plasmas. Le but de cette these est de comprendre leur fonctionnement et notamment comment l'energie est distribuee entre les electrons en l'absence de collisions. Apres la description d'un modele simple de bilan entre creation et pertes dans le plasma et le rappel de quelques instabilites, nous presentons une analyse detaillee de l'interaction filament-plasma et une etude de la correlation turbulence-temperature. L'equilibre thermique du filament est fortement couple a l'emission des electrons: il existe un profil de temperature le long du filament et l'emission d'electrons du filament vers le plasma presente deux etats stables. La transition du courant de decharge entre ces deux etats presente parfois un saut et un hysteresis lorsqu'on varie continument un parametre de controle de la decharge. Nous attribuons ce saut a un ecrasement de la gaine emissive. En l'absence de champ magnetique, la largeur de l'hysteresis est principalement regie par les profils de temperature et de potentiel le long du filament. Le champ magnetique local a la gaine introduit une brisure de symetrie supplementaire dans la dynamique des porteurs de charge. En l'absence de champ magnetique multipolaire nous avons trouve une correlation turbulence-temperature. Avec le champ magnetique multipolaire, pour des pressions superieures a 10##4 mb, nous observons la pression electronique est constante. En dessous de cette pression, le comportement du plasma est plus complexe. L'ensemble de ces resultats experimentaux ouvre des perspectives pour l'etude theorique et la modelisation numerique de ces decharges
31
Voughs, Tyrone Y. "High-power amplifier free electron lasers." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FVoughs.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2006.<br>Thesis Advisor(s): William B. Colson, Robert L. Armstead. "June 2006." Includes bibliographical references (p. 57). Also available in print.
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Rinskopf, Nathalie. "Etude ab initio des effets de corrélation et des effets relativistes dans les halogénures diatomiques de métaux de transition." Doctoral thesis, Universite Libre de Bruxelles, 2007. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210678.
Testo completoAbstract (sommario):
Ce travail est une contribution ab initio à la caractérisation d'halogénures diatomiques de métaux de transition. Nous avons choisi de caractériser la structure électronique des chlorures de métaux de transition du groupe Vb (NbCl et TaCl) et du fluorure de nickel car une série de spectres les concernant ont été enregistrés mais aucune donnée théorique fiable n'était disponible dans la littérature.<p><p>Pour étudier ces molécules, nous avons appliqué une procédure de calcul à deux étapes qui permet de tenir compte des effets de corrélation électronique et des effets relativistes. Dans la première étape, nous avons réalisé des calculs CASSCF/ICMRCI+Q de grande taille qui tiennent compte de l'énergie de corrélation et introduisent des effets relativistes scalaires. Dans la deuxième étape, le couplage spin-orbite est traité par la "state interacting method" implémentée dans le logiciel MOLPRO. Nous avons développé des stratégies de calcul basées sur ces méthodes de calcul et adaptées aux différentes molécules ciblées. Ainsi, pour les molécules NbCl et TaCl, nous avons utilisé des pseudopotentiels relativistes scalaires et spin-orbite, tandis que pour la molécule NiF, nous avons réalisé des calculs tous électrons.<p><p>Nous avons d'abord testé la stratégie de calcul sur les cations Nb+ et Ta+. Ensuite, nous avons calculé pour la première fois les structures électroniques relativiste scalaire et spin-orbite des molécules NbCl (de 0 à 17000 cm-1) et TaCl (de 0 à 23000 cm-1). A l'aide de ces données théoriques, nous avons interprété les spectres expérimentaux en collaboration avec Bernath et al. Nous avons proposé plusieurs attributions de transitions électroniques en accord avec l'expérience mais nos résultats théoriques ne nous ont pas permis de les attribuer toutes. Néanmoins, nous avons mis en évidence une série d'autres transitions électroniques probables qui pourraient, à l'avenir, servir à l'interprétation de nouveaux spectres mieux résolus. <p><p>Outre son intérêt expérimental, cette étude a permis de comparer les structures électroniques des molécules isovalencielles VCl, NbCl et TaCl, mettant en évidence des différences importantes.<p>L'élaboration d'une nouvelle stratégie de calcul pour décrire les systèmes contenant l'atome de nickel représentait un véritable défi en raison de la complexité des effets de corrélation électronique. Notre stratégie de calcul a consisté à introduire ces effets en veillant à réduire au maximum la taille des calculs qui devenait considérable.<p>Nous l'avons testée sur l'atome Ni et appliquée ensuite au calcul des structures électroniques relativiste scalaire et spin-orbite de la molécule NiF entre 0 à 2500 cm-1. Nous avons obtenus des résultats qui corroborent l'expérience. <p><br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
33
Mirzaei, Shokoufeh. "Supply chain network configuration: dynamicity and sustainability." Diss., Wichita State University, 2012. http://hdl.handle.net/10057/5362.
Testo completoAbstract (sommario):
This dissertation consists of five submission-ready accepted/submitted papers that address some of the key supply chain problems. Supply chain problems, in terms of the area that they address, can be classified into four major groups: location-allocation problem, transportation problem, manufacturing problem, and inventory problem. In this dissertation, location-allocation and location-routing problems, also called LRPs, are studied using two approaches. In the first approach, presented in Chapters 2 and 3, it is assumed that the value of some parameters of the network are dynamically changing. The objective here is to minimize the total system cost by finding the best location-allocation and routing plan when demand and travel times are dynamic. The dynamic nature of demand/travel time is presented by functions obtained from historical data. In the second approach, the sustainability perspective of the LRP is considered. The objective here is also to minimize the total network cost. However, the total cost is presented in terms of energy cost because of the lack of literature investigating the energy effectiveness of a location-routing plan. Traditionally, the objective function of the LRP is expressed in terms of distance minimization, although distance is not the only factor that contributes to energy consumption in an LRP. This perspective is thoroughly discussed in chapters 4 and 5.
Due to the rising price of fuel, industries are concerned more than ever about their transportation costs and modes. In the current economic atmosphere, railway transportation is extremely in demand. Hence, to continue the sustainability part of this dissertation, a rail freight transportation system is investigated. The objective here is to develop a heuristic algorithm that can provide a cost-effective train scheduling plan in a matter of seconds. The main contribution in this section is the integration of a pool of business cost elements and constraints existing in practical train-scheduling problems for obtaining results.<br>Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering
34
Jacob, Aju. "Distributed configuration management for reconfigurable cluster computing." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0007181.
Testo completo
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Ogunjobi, Taiwo A. "Computational Study of Ring-Cusp Magnet Configurations that Provide Maximum Electron Confinement." Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1166226698.
Testo completo
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Zhao, Qinliang. "Conformation and electronic configuration of complexes with multiple dimetal units." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1441.
Testo completo
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Spencer, Robert. "Managing configuration history in domestic networks." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52115/.
Testo completoAbstract (sommario):
Domestic Networks are gaining in complexity, with an increasing number and variety of devices. Increasing complexity results in greater difficulty managing configuration and troubleshooting when problems occur. This thesis presents strategies to assist users in managing the complexity of their networks. The work is split into several parts. First, configuration changes are tracked and users are presented with a timeline of changes to their network. Provision of a selective undo system is the second feature. The undo facility is designed to allow any change to be undone independently of any other. Users are also given the option of reverting to an earlier point, either before a specific change, or to a specific timestamp. The next feature is use of notifications. Any changes that require further actions can be broadcast to users directly. Changing Wi-Fi configuration is one example. The range of devices in use makes changing Wi-Fi configuration (and the subsequent reconfiguration of devices) a challenge, because the devices affected may be part of the infrastructure of a home (lights or thermostat for example). Because these devices have unique methods of network setup, restoring connectivity to every device can be challenging. This thesis also presents a method of changing Wi-Fi configuration which allows users a grace period to reconnect all their devices. Each of these features was assessed by a user study, the results of which are also discussed.
38
Shi, Yinghui. "Acoustical Performance of Lined Induction Furnace in Electric Field Configuration." University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1627658524197215.
Testo completo
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Schinner, Charles Edward 1957. "Electronic manufacturing test cell automation and configuration using AI techniques." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278327.
Testo completoAbstract (sommario):
This thesis utilizes artificial intelligence techniques and problem specific knowledge to assist in the design of an manufacturing test cell for electronic products. The electronic printed circuit board (PCB) is subjected to one or more functional evaluation(s) during the manufacturing process. The purpose of these evaluations is to assure product quality. This thesis is focused on, with historical knowledge, the configuration of this testing environment and associated fault isolation processes. By using such knowledge, an improvement in the testing efficiency will be realized which will allow the overall product cost to be minimized.
40
Lee, Seung Jae. "Configuration control of distribution feeders in normal and emergency states /." Thesis, Connect to this title online; UW restricted, 1988. http://hdl.handle.net/1773/5923.
Testo completo
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Smith, Jonathan Burke. "Optimum hybrid vehicle configurations for heavy duty applications." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1985.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2001.<br>Title from document title page. Document formatted into pages; contains viii, 109 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 71-72).
42
Pontara, Davide <1986>. "Multi-Drive Powertrain Configurations for Electric and Hybrid Vehicles." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/7824/1/z_Tesi_Pontara_v01.pdf.
Testo completoAbstract (sommario):
Over the last fifteen years, the automotive market experienced a renewed interest towards electric and hybrid cars which, in turn, pushed the mayor manufacturers to increase investments in this sector, while also allowing new players to enter the market with innovative solutions.
This gave rise to traction systems significantly different from the traditional ones, also from the conceptual point of view. An example is the powertrain “splitting”, namely the subdivision of the propulsive power between several subsystems more or less independent from each other.
Literature shows that this solution can bring significant benefits, both under the powertrain point of view and the vehicle as a whole.
Since the tractive effort is divided among several sub-components, these can be sized to a lower rated power, be more compact and easier to accommodate in the vehicle.
Furthermore, the power splitting brings to higher reliability and enhanced vehicle dynamic performance.
Eventually, for selected power ranges, it has been found possible to supply the traction drives at ultra-low voltage, i.e. 48 V, still achieving interesting performances, with clear benefits in terms of safety and simplicity.
The research activity found practical application in the “AMBER-ULV” FP7 European project, for which a two-motor, two-axle, two-batteries traction system with a centralized control unit was developed.
A model of the high-level control algorithm was conceived and run on the ECU thanks to model-based automatic code generation with integration of a stability control algorithm externally provided.
The research activity also included the design of the traction drives, the low-level software and their integration on the vehicle.
The prototype was also widely tested in several conditions in order to demonstrate the validity of the design process and choices.
43
Chang, Kai-Han. "Achromatic Liquid Crystal Electro-Optical Devices Based On a Twisted Vertical Alignment Configuration." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1523807996464507.
Testo completo
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Daraio, Chiara. "Design of materials Configurations for enhanced phononic and electronic properties." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3211373.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, San Diego, 2006.<br>Title from first page of PDF file (viewed June 5, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 252-265).
45
Escudero, Adán Eduardo Carmelo. "High resolution X-ray single crystal diffraction." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/586278.
Testo completoAbstract (sommario):
Aquesta tesi doctoral descriu l'ús de dades d'alta resolució de difracció de raigs X de monocristall per a la
obtenció de mapes experimentals detallats de distribució de densitat de càrrega. Aquests mapes serveixen per
evidenciar experimentalment l'existència d'interaccions intra- i inter-moleculars febles dins de l'estructura
del vidre. Els mapes de densitat de càrrega s'obtenen mitjançant un refinament multipolar de l'estructura
cristal·lina. En concret, aquest treball se centra en evidenciar experimentalment les interaccions atractives no
covalent recentment descrites teòricament i que donen lloc a la formació d'enllaços de tipus "sigma i pi hole".
Els termes enllaços de Triel, tetrel, pnictogen i chalcogen van ser recentment introduïts per referir-se a aquestes
interaccions en funció del grup (14, 15 i 16) al qual pertany l'àtom implicat com a centre electrofílic. el
fet que aquestes interaccions siguin molt febles fa necessari l'obtenció de mapes de densitat electrònica
molt precisos. També s'han utilitzat aquests mapes de densitat electrònica per determinar experimental el
moment quadrupolar i el potencial electrostàtic molecular d'una sèrie d'anells de fenil amb diferents
substituents. Les dades experimentals obtingudes d'aquesta manera han servit per validar els resultats de càlculs
teòrics.<br>Esta tesis doctoral describe el uso de datos de alta resolución de difracción de rayos X de monocristal para la
obtención de mapas experimentales detallados de distribución de densidad de carga. Estos mapas sirven para
evidenciar experimentalmente la existencia de interacciones intra- e inter-moleculares débiles dentro de la estructura
del cristal. Los mapas de densidad de carga se obtienen mediante un refinamiento multipolar de la estructura
cristalina. En concreto, este trabajo se centra en evidenciar experimentalmente las interacciones atractivas no
covalente recientemente descritas teóricamente y que dan lugar a la formación de enlaces de tipo "sigma y pi hole".
Los términos enlaces de Triel, tetrel, pnictogen y chalcogen fueron recientemente introducidos para referirse a estas
interacciones en función del grupo (14, 15 y 16) al que pertenece el átomo implicado como centro electrofílico. El
hecho de que estas interacciones sean muy débiles hace necesario la obtención de mapas de densidad electrónica
muy precisos. También se han utilizado estos mapas de densidad electrónica para determinar experimental el
momento cuadrupolar y el potencial electrostático molecular de una serie de anillos de fenilo con diferentes
sustituyentes. Los datos experimentales obtenidos de esta forma han servido para validar los resultados de cálculos
teóricos.<br>radiación de molibdeno para asignar la configuración absoluta de una serie de moléculas orgánicas. Las moléculas
medidas fueron seleccionadas teniendo en cuenta que el elemento más pesado de su composición química fuera el
oxígeno. Es bien conocido que la dispersión anómala de este tipo de compuestos es muy débil y dificulta la
asignación de configuración absoluta mediante esta técnica. El resultados de este trabajo demuestran que la
metodología empleada es muy efectivo para poder asignar inequívocamente la configuración absoluta correcta en
este tipo de moléculas.
This thesis uses high resolution single crystal X-ray diffraction data in order to obtain experimental detailed charge
density distribution maps that can exhibit intra and intermolecular interactions. The charge density maps are obtained
through the multipolar refinement. Particularly, this work focuses in lasts classified non-covalent attractive interactions
due to sigma and pi holes, triel, tetrel, pnictogen and chalcogen bonds. The weakness of these interactions make
necessary very accurate and precise maps.
In the same manner, in this works they have been determined the quadrupolar moment and the molecular electrostatic
potential of a series of phenyl rings substituted with different chemical groups. The experimental data obtained in this
way have been used to validate theoretical predictions.
Eventually in this work, high resolution single crystal X-ray diffraction data using molybdenum radiation has been
employed to assign the absolute configuration of a series of organic molecules. The measured molecules were
selected containing oxygen as heaviest atom since the anomalous dispersion of these kind of compounds is very
weak. The use of high resolution data has been proved to be effective in order to unequivocally assign the correct
absolute configuration in this kind of molecules.
46
Warren, Ian. "A model for dynamic configuration which preserves application integrity." Thesis, Lancaster University, 2001. http://eprints.lancs.ac.uk/11980/.
Testo completo
47
Weiner, Christian. "High performance switched reluctance drives for electric vehicle application." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324930.
Testo completo
48
Maughan, Bret, Percy Zahl, Peter Sutter, and Oliver L. A. Monti. "Configuration-specific electronic structure of strongly interacting interfaces: TiOPc on Cu(110)." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/626466.
Testo completoAbstract (sommario):
We use low-temperature scanning tunneling microscopy in combination with angle-resolved ultraviolet and two-photon photoemission spectroscopy to investigate the interfacial electronic structure of titanyl phthalocyanine (TiOPc) on Cu(110). We show that the presence of two unique molecular adsorption configurations is crucial for a molecular-level analysis of the hybridized interfacial electronic structure. Specifically, thermally induced self-assembly exposes marked adsorbate-configuration-specific contributions to the interfacial electronic structure. The results of this work demonstrate an avenue towards understanding and controlling interfacial electronic structure in chemisorbed films even for the case of complex film structure.
49
Chakraborty, Debanond. "Configuration interaction (singles) study of geometric and electronic properties of conducting polymers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ54869.pdf.
Testo completo
50
Beck, Jennifer 1968. "Effects of chest wall configuration and electrode positioning on human diaphragmatic EMG." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22536.
Testo completoAbstract (sommario):
The measurement and analysis of the human diaphragm electromyogram (EMGdi), as obtained with an esophageal electrode, requires objective control of the disturbances and filtering effects which can influence the signal. One issue of importance is that an increase in the muscle-to-electrode distance (MEdist) acts as a low-pass filter, filtering out the high frequency components of the EMG power spectrum (the MEdist filter). Due to the numerous factors which can influence the EMGdi, control of signal quality is also of utmost importance. The aims of this study were: (1) to evaluate the effect of the MEdist filter on EMGdi, as measured with a multiple array esophageal electrode, (2) to take advantage of the MEdist filter in order to locate the position of the diaphragm with respect to the electrodes, and (3) to evaluate the influence of changes in chest wall configuration on EMGdi center frequency (CF) values, while controlling for both signal quality and the MEdist filter.<br>Five normal male subjects performed static contractions of the diaphragm at seven predetermined chest wall configurations. The EMGdi was measured with an array of eight steel rings mounted on a catheter, forming seven sequential pairs of electrodes, with an interelectrode distance of 10 mm. EMGdi signal quality was evaluated by computer algorithms. The pair of electrodes whose EMGdi signals (and power spectrums) were the least influenced by the MEdist filter was assumed to be closest to the diaphragm.<br>The results of the study indicated (1) EMGdi power spectrums and their associated CF values were strongly affected by the position of the diaphragm with respect to the multiple array esophageal electrode. CF decreased by approximately 1 Hz per mm displacement away from the diaphragm. (2) By controlling for the MEdist filter, there was no relationship found between changes in chest wall configuration and CF values. These data demonstrate that changes in chest wall configuration, and hence diaphragm length, do not influence the CF values of the EMGdi, if the distance between the electrodes and the diaphragm and signal quality are controlled for.