Non-adiabatic Electron Pumping through Interacting Quantum Dots

We study non-adiabatic charge pumping through single-level quantum dots taking into account Coulomb interactions. We show how a truncated set of equations of motion can be propagated in time by means of an auxiliary-mode expansion. This formalism is capable of treating the time-dependent electronic transport for arbitrary driving parameters. We verify that the proposed method describes very precisely the well-known limit of adiabatic pumping through quantum dots without Coulomb interactions. As an example we discuss pumping driven by short voltage pulses for various interaction strengths. Such finite pulses are particular suited to investigate transient non-adiabatic effects, which may be also important for periodic drivings, where they are much more difficult to reveal.Comment: 11 pages, 4 figure

Diseño de una secuencia didáctica basada en textos narrativos con temáticas de identidad de género, para el fortalecimiento de la comprensión lectora en estudiantes de grado noveno

La comprensión lectora y la competencia crítica son dos aspectos indispensables en el proceso de aprendizaje, y por tanto, constituyen dos áreas de marcada preocupación para las instituciones educativas colombianas, ya que tanto las pruebas estatales e internacionales que evalúan la recepción del conocimiento y su puesta en práctica, han revelado bajos niveles de comprensión y capacidades críticas en los estudiantes, las cuales son causadas en parte por las problemáticas sociales y por el desinterés de los estudiantes hacia la lectura. El presente trabajo posee como objetivo fundamental, fortalecer la comprensión lectora en los estudiantes de grado noveno a través de textos narrativos cuyas temáticas no son ajenas a sus realidades y por tanto, se espera despierten, susciten y provoquen su interés. Tales temáticas buscan dar a conocer narrativas en torno al desarrollo de la personalidad, y principalmente a la construcción de la identidad de género, siendo éste último, un tópico contemporáneo y de necesaria discusión

Carotid Disease

Atherosclerotic carotid disease causes about 30% of cerebrovascular ischemia transitory or permanent in the world; the severity of symptoms is variable. The clinical manifestations are varied from focal neurological alterations to transient or permanent vascular events. The treatment of the disease will depend on the location, degree, and risk, which can be surgical, endovascular, or medical. Open surgical treatment, endarterectomy, has been preferred as the first option and, however, has been reported to have associated complications like infection, hematoma, stroke, heart attack, restenosis, etc. With the advent of new technologies, endovascular treatment has been described as an option in patients with high risk or restenosis

Thermo-viscoplastic behaviour of 2024-T3 aluminium sheets subjected to low velocity perforation at different temperatures

This paper deals with the mechanical behaviour of the aluminium alloy 2024-T3. This alloy has particular relevance since it is widely used in the aeronautical industry for building aircraft structures. The deformation behaviour of this material has been characterised in tension under wide ranges of strain rate and temperature. Among the aluminium alloys, the AA 2024-T3 highlights due to its high flow stress and strain hardening. Moreover, the material temperature sensitivity has been found dependent on plastic strain. The Modified Rusinek-Klepaczko constitutive description [Rusinek A, Rodriguez-Martinez JA, Arias A. A thermo-viscoplastic constitutive model for FCC metals with application to OFHC copper. Int. J. Mech. Sci. 52 (2010) 120-135], which takes into account such dependence of the temperature sensitivity on plastic strain, has been applied for modelling the thermo-viscoplastic response of the material. Satisfactory agreement between experiments and analytical predictions provided by the Modified Rusinek-Klepaczko model has been found. In order to study the material behaviour under impact loading, low velocity perforation tests on AA 2024-T3 sheets have been performed at different initial temperatures using a drop weight tower. Plastic instabilities formation and progression are identified as the cause behind the target collapse for all the impact tests conducted. The results from these perforation tests are compared with those reported in [Rodriguez-Martinez JA, Pesci R, Rusinek A, Arias A, Zaera R, Pedroche DA. Thermo-mechanical behaviour of TRIP 1000 steel sheets subjected to low velocity perforation by conical projectiles at different temperatures. Int. J. Solids Struct. 47 (2010) 1268-1284.] for TRIP 1000 steel sheets. The comparison reveals that the amount of specific energy absorbed by the aluminium targets is much lower than that corresponding to the steel targets. The role played by inertia on delaying plastic instabilities formation is determined as potential responsible for such behaviour.Publicad

Numerical simulations of impact behaviour of thin steel plates subjected to cylindrical, conical and hemispherical non-deformable projectiles

In this paper, a numerical study of normal perforation of thin steel plates impacted by different projectile shapes is reported. The numerical simulations of this problem have been performed using a finite element code, ABAQUS-Explicit with a fixed and an adaptive mesh for the plate. To define the thermoviscoplastic behaviour of the material constituting the plate, the Johnson-Cook model has been used. This homogeneous behaviour has been coupled with the Johnson-Cook fracture criterion to predict completely the perforation process. Three kinds of projectile shape (blunt, conical and hemispherical) have been simulated with a large range of impact velocities from 190 to 600 m/s. The analysis considers the influence of adiabatic shear bands, plastic work and the gradient of temperature generated in the plate. The numerical results predict correctly the behaviour projectile-plate in agreement with experimental data published by other authors.Publicad

A thermo-viscoplastic constitutive model for FCC metals with application to OFHC copper

In this paper a physical-based constitutive relation for defining the thermo-viscoplastic behaviour of FCC metals with dependence on strain on thermal activation processes is presented. The model, based on previous considerations reported by Rusinek and Klepaczko [Rusinek A, Klepaczko JR. Shear testing of sheet steel at wide range of strain rates and a constitutive relation with strain-rate and temperature dependence of the flow stress. Int J Plasticity 2001;17:87-115], is founded on physical aspects of the material behaviour. The proposed constitutive relation is applied to define the behaviour of oxygen-free high conductivity (OFHC) copper using the experimental data reported in Nemat-Nasser and Li [Nemat-Nasser S, Li Y. Flow stress of FCC polycrystals with application to OFHC copper. Acta Mater 1998;46:565-77]. The description of the material behaviour provided by the model gets satisfactory agreement with the experiments. The analytical predictions of this constitutive description are compared with those obtained from the models due to Voyiadjis and Almasri [Voyiadjis GZ, Almasri AH. A physically based constitutive model for fcc metals with applications to dynamic hardness. Mech Mater 2008;40:549-63], and Nemat-Nasser and Li. This comparison reveals that the original formulation proposed in this paper is a suitable alternative to other physically based relations for modeling OFHC copper.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (ProjectCCG08UC3M/MAT4464) and to the Ministerio de Ciencia e Innovación de España (ProjectDPI/200806408)Publicad