Instituto Superior Técnico

About: Instituto Superior Técnico is a based out in . It is known for research contribution in the topics: Catalysis & Finite element method. The organization has 10085 authors who have published 30226 publications receiving 667524 citations. The organization is also known as: IST & Instituto Superior Tecnico.

A Brief History of Fluorescence and Phosphorescence before the Emergence of Quantum Theory

Abstract: Fluorescence and phosphorescence are two forms of photoluminescence used in modern research and in practical applications The early observations of these phenomena, before the emergence of quantum theory, highlight the investigation into the mechanism of light emission In contrast to incandescence, photoluminescence does not require high temperatures and does not usually produce noticeable heat Such a “cold light” was the object of an interesting controversy in the 19th century: does it fit into thermodynamics? The early applications, such as the fluorescent tube, fluorescence analysis, and fluorescent tracers, are described

High mobility indium free amorphous oxide thin film transistors

Abstract: High mobility bottom gate thin film transistors (TFTs) with an amorphous gallium tin zinc oxide (a-GSZO) channel layer have been produced by rf magnetron cosputtering using a gallium zinc oxide (GZO) and tin (Sn) targets. The effect of postannealing temperatures (200, 250, and 300°C) was evaluated and compared with two series of TFTs produced at room temperature (S1) and 150°C (S2) during the channel deposition. From the results, it was observed that the effect of postannealing is crucial for both series of TFTs either for stability as well as for improving the electrical characteristics. The a-GSZO TFTs (W∕L=50∕50μm) operate in the enhancement mode (n-type), present a high saturation mobility of 24.6cm2∕Vs, a subthreshold gate swing voltage of 0.38V/decade, a turn-on voltage of −0.5V, a threshold voltage of 4.6V, and an Ion∕Ioff ratio of 8×107, satisfying all the requirements to be used as active-matrix backplane.

Influence of silicon powder-mixed dielectric on conventional electrical discharge machining

Abstract: Electrical discharge machining (EDM) is a technological process with a large industrial implementation. Its use is particularly intense when very complex shapes on hard materials with a high geometrical and dimensional accuracy are required. However, the technological capability of the process has limited its application when the specification of the part surface quality imposes polished and mirror-like characteristics. The addition of powder particles in suspension in the dielectric modifies some process variables and creates the conditions to achieve a high surface quality in large areas. This paper presents a new research work aiming to study the performance improvement of conventional EDM when used with a powder-mixed dielectric. A silicon powder was used and the improvement is assessed through quality surface indicators and process time measurements, over a set of different processing areas. The results show the positive influence of the silicon powder in the reduction of the operating time, required to achieve a specific surface quality, and in the decrease of the surface roughness, allowing the generation of mirror-like surfaces.

3D deflagration simulations leaving bound remnants: a model for 2002cx-like Type Ia supernovae

Abstract: cx-like supernovae are a sub-class of sub-luminous Type Ia supernovae. Their light curves and spectra are characterized by distinct features that indicate strong mixing of the explosion ejecta. Pure turbulent deagrations have been shown to produce such mixed ejecta. Here, we present hydrodynamics, nucleosynthesis and radiative transfer calculations for a 3D full-star deagration of a Chandrasekhar-mass white dwarf. Our model is able to reproduce the characteristic observational features of SN 2005hk (a proto-typical 2002cx-like supernova), not only in the optical, but also in the near- infrared. For that purpose we present, for the rst time, ve near-infrared spectra of SN 2005hk from 0:2 to 26:6 days with respect to B-band maximum. Since our model burns only small parts of the initial white dwarf, it fails to completely unbind the white dwarf and leaves behind a bound remnant of 1.03 M { consisting mainly of unburned carbon and oxygen, but also enriched by some amount of intermediate-mass and iron-group elements from the explosion products that fall back on the remnant. We discuss possibilities for detecting this bound remnant and how it might inuence the late-time observables of 2002cx-like SNe.