117 research outputs found
Enseñanza de química a alumnos con discapacidad visual
La educación formal en Brasil tiene como primer principio la “igualdad de condiciones de acceso y permanencia en la escuela” (Brasil, 1996). En este contexto, el proyecto “Enseñanza de Química a Alumnos con Discapacidad Visual” busca desarrollar recursos y metodologías para una enseñanza de Química que atienda alumnos con ceguera o baja visión. En este proyecto, con el objetivo de atender alumnos y profesores de la enseñanza secundaria, iniciamos la adaptación del libro “Química e Sociedade” (Santos, Mol y colaboradores, 2005). El trabajo consiste de varias etapas: transcripción de los textos del libro; descripción de imágenes; construcción de modelos didácticos; adaptación de actividades experimentales
Low Bias Negative Differential Resistance in Graphene Nanoribbon Superlattices
We theoretically investigate negative differential resistance (NDR) for
ballistic transport in semiconducting armchair graphene nanoribbon (aGNR)
superlattices (5 to 20 barriers) at low bias voltages V_SD < 500 mV. We combine
the graphene Dirac Hamiltonian with the Landauer-B\"uttiker formalism to
calculate the current I_SD through the system. We find three distinct transport
regimes in which NDR occurs: (i) a "classical" regime for wide layers, through
which the transport across band gaps is strongly suppressed, leading to
alternating regions of nearly unity and zero transmission probabilities as a
function of V_SD due to crossing of band gaps from different layers; (ii) a
quantum regime dominated by superlattice miniband conduction, with current
suppression arising from the misalignment of miniband states with increasing
V_SD; and (iii) a Wannier-Stark ladder regime with current peaks occurring at
the crossings of Wannier-Stark rungs from distinct ladders. We observe NDR at
voltage biases as low as 10 mV with a high current density, making the aGNR
superlattices attractive for device applications.Comment: 6 pages, 4 figure
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