Search results for "NOE"
showing 10 items of 825 documents
Simulations of Piezoelectric, Electronic and Optical Properties of Nanowires
2016
Los nanohilos semiconductores han atraido un interés creciente debido a sus potenciales aplicaciones en electrónica, óptica y fotónica. Un amplio rango de dispositivos fotónicos y electrónicos basados en nanohilos han sido ya demostrados, incluyendo células solares, fotodetectores, diodos emisores de luz, y láseres. Para comprender las propiedades de los nanohilos es necesario conocer su estructura electrónica. Además, es importante conocer cómo estas propiedades dependen del tamaño, estructura cristalina y orientación, y cómo se ven afectadas por las deformaciones. El objetivo de esta tesis es desarrollar modelos teóricos realistas, pero manejables desde un punto de vista computacional, pa…
Análisis de los antecedentes histórico-filosóficos de la "paradoja cognitiva de Duval"
2015
In a famous article published in 1993, Raymond Duval highlighted a simple fact: the student may confuse the mathematical object O he is trying to build cognitively with one of its semiotic representations R(O). Duval explained that this confusion was due to a sort of inevitable paradox: only someone who has already built O, can recognize R(O) as a representation of O and not as an object in itself. Thereafter, this thought has been extremely influential for researchers. However, even if in different terms, many scholars of semiotics have emphasized the same phenomenon. In this paper we propose to remind some of them. En un famoso artículo publicado en 1993, Raymond Duval evidenciaba el sigu…
Highmann's Theorem on Discrete Sets
2006
In this paper we investigate properties of different classes of discrete sets with respect to the partial-order of subpicture. In particular we take in consideration the classes of convex polyominoes and L-convex polyominoes. In the first part of the paper we study closure properties of these classes with respect the order and we give a new characterization of L-convex polyominoes. In the second part we pose the question to extend Higman’s theoremto discrete sets. We give a negative answer in the general case and we prove that the set of L-convex polyominoes is well-partially-ordered by using a representation of L-convex polyominoes in terms of words of a regular language.
Image formation with plasmonic nanostructures
2015
En 1873, Ernst Abbe concluyó que debido a la difracción de la luz el límite de resolución de un sistema óptico es aproximadamente la mitad de la longitud de onda de trabajo. Este límite, llamado el límite de difracción produce porque las ondas evanescentes no contribuyen a la formación de la imagen. En cualquier sistema óptico formado por materiales presentes en la naturaleza los detalles espaciales del objeto que sean más pequeños que el límite de resolución son transportados por ondas evanescentes. Normalmente estas ondas se pierden debido a la fuerte atenuación que experimentan viajando del objeto a la imagen. // En 1968, Veselago mostró que un material con permitividad y permeabilidad n…
Superconducting tunnel junctions and nanorefrigeration using InAs nanowires
2017
Työssä selvitettiin menetelmää suprajohtavien kontaktien liittämiseksi ohuen eristekerroksen avulla vahvasti n-seostettuun puolijohtavaan InAs-nanolankaan. Lisäksi tutkittiin näin luotujen tunneliliitosten soveltamista nanolankojen elektronisen lämpötilan mittaukseen ja sen jäähdyttämiseen. Nanolangat oli kasvatettu epitaksiaalisesti kultananopartikkeleiden katalysoimina, ja suprajohtavat kontaktit valmistettiin niiden päälle käyttäen tavanomaisia mikrovalmistusmenetelmiä, elektronisuihkulitografiaa ja -höyrystystystä. Aluksi langan päälle höyrystettiin ohut kerros titaania ja paksumpi kerros alumiinimangaania, joka oksidoitiin in situ eristekerroksen luomiseksi, ja lopuksi lisättiin supraj…
Topological polarization, dual invariants, and surface flat band in crystalline insulators
2020
We describe a three-dimensional crystalline topological insulator (TI) phase of matter that exhibits spontaneous polarization. This polarization results from the presence of (approximately) flat bands on the surface of such TIs. These flat bands are a consequence of the bulk-boundary correspondence of polarized topological media, and contrary to related nodal line semimetal phases also containing surface flat bands, they span the entire surface Brillouin zone. We also present an example Hamiltonian exhibiting a Lifshitz transition from the nodal line phase to the TI phase with polarization. Utilizing elasticity tetrads, we show a complete classification of 3D crystalline TI phases and invar…
Time-dependent quantum transport in nanosystems : a nonequilibrium Green's function approach
2016
A time-dependent extension to the Landauer–Büttiker approach to study transient quantum transport in arbitrary junctions composed of leads and conducting devices is developed. The nonequilibrium Green’s function approach is employed for describing the charge and heat transport dynamics. The importance of the developed method is that it provides a closed formula for the time-dependent density matrix in both electronic and phononic systems. In the electronic case the nonequilibrium conditions are due to a switch-on of a bias voltage in the leads or a perturbation in the junction whereas in the phononic case the central region of interest is coupled to reservoirs of di erent temperatures. In b…
Emmy Noether in Bryn Mawr
2020
In the annals of higher education for women, two elite colleges were particularly important for mathematics: Girton College, in Cambridge, England and Bryn Mawr College, near Philadelphia, Pennsylvania.
Max and Emmy Noether: Mathematics in Erlangen
2020
Until 1933, most of Emmy Noether’s life was spent in two middle-sized cities: Erlangen, her birthplace, and Gottingen, where she began her mathematical career.
Memories and Legacies of Emmy Noether
2021
Those who knew Emmy Noether best were her fellow Germans in exile, in particular her former colleague in Gottingen, Hermann Weyl.