XUV spectroscopic characterization of warm dense aluminum plasmas generated by the free-electron-laser FLASH

We report on experiments aimed at the generation and characterization of solid density plasmas at the free-electron laser FLASH in Hamburg. Aluminum samples were irradiated with XUV pulses at 13.5 nm wavelength (92 eV photon energy). The pulses with duration of a few tens of femtoseconds and pulse energy up to 100 mu J are focused to intensities ranging between 10(13) and 10(17) W/cm(2). We investigate the absorption and temporal evolution of the sample under irradiation by use of XUV and optical spectroscopy. We discuss the origin of saturable absorption, radiative decay, bremsstrahlung and atomic and ionic line emission. Our experimental results are in good agreement with simulations.

Photo-ionized neon plasmas induced by radiation pulses of a laser-plasma EUV source and a free electron laser FLASH

In this work, a laser-produced plasma extreme ultraviolet source and a free electron laser were used to create Ne photo-ionized plasmas. In both cases, a radiation beam was focused onto a gas stream injected into a vacuum chamber synchronously with the radiation pulse. Extreme ultraviolet radiation from the plasma spanned a wide spectral range with pronounced maximum centered at lambda = 11 +/- 1 nm while the free electron laser pulses were emitted at a wavelength of 32 nm. The power density of the focused plasma radiation was approximately 2 x 10(7) W/cm(2) and was seven orders of magnitude lower compared with the focused free electron laser beam. Radiation fluences in both experimental conditions were comparable. Despite quite different spectral characteristics and extremely different power densities, emission spectra of both photo-ionized plasmas consist of the same spectral lines within a wavelength range of 20 to 50 nm, however, with different relative intensities of the corresponding lines. The dominating spectral lines originated from singly charged ions (Ne II); however, Ne III lines were also detected. Additionally, computer simulations of the emission spectra, obtained for photo-ionized plasmas, driven by the plasma extreme ultraviolet source, were performed. The corresponding measured and calculated spectra are presented. An electron temperature and ionic composition were estimated. Differences between the experimental spectra, obtained for both irradiation conditions, were analyzed. The differences were attributed mainly to different energies of driving photons.

Warm Dense Aluminum Plasma generated by the Free-Electron-Laser FLASH

We report on experiments aimed at the generation and characterization of solid density plasmas at the free-electron laser FLASH in Hamburg. Aluminum samples were irradiated with XUV pulses at 13.5 nm wavelength (92 eV photon energy). The pulses with duration of a few tens of femtoseconds and pulse energy up to 100 mu J are focused to intensities ranging from 10(13) to 10(17) W/cm(2). We investigate the absorption and temporal evolution of the sample under irradiation by use of XUV spectroscopy. We discuss the origin of saturable absorption, radiative decay, bremsstrahlung and ionic line emission. Our experimental results are in good agreement with hydrodynamic simulations.

Understanding the Flash Sintering of Rare-Earth-Doped Ceria for Solid Oxide Fuel Cell

A novel electrical current applied technique known as flash sintering has been applied to rapidly (within 10 min) densify electrolytes including Ce_0.8Gd_0.2O_1.9 (GDC20), Ce_0.9Gd_0.1O_1.95 (GDC10), and Ce_0.8Sm_0.2O_1.9 (SDC20) for application in Solid Oxide Fuel Cells (SOFCs). The densification temperature for the three electrolytes was 554°C, 635°C, and 667°C, respectively, which is far below conventional sintering temperatures. All specimens after flash sintering maintained the pure fluorite structure and exhibited a well-densified microstructure. To investigate the flash-sintering mechanism, we have applied Joule heating effect with blackbody radiation theory, and found that this theory could reasonably interpret the flash-sintering phenomenon by matching theoretically calculated temperature with the real temperature. More importantly, one of the materials inherent properties, the electronic conductivity, has been found correlated with the onset of flash sintering, which indicates that the electrons and holes are the primary current carriers during the start of flash-sintering process. As a result, potential densification mechanisms have been discussed in terms of spark plasma discharge.

The Day Roads Became Rivers: A GIS-Based Assessment of Flash Floods in Worcester

In the last 4 years Worcester, UK has been hit by several intense convective rainstorms, which caused flash floods outside of existing surface drainage networks. This paper addresses two questions related to such events: Firstly to what extent can the occurrence of flash flood flow accumulation can be determined using only commonly available data and tools, assuming the rainfall events caused mainly surface runoff due to their tropical intensity and the relatively impermeable urban catchment surface? Secondly, are the flood in-cidents in Worcester aggravated by roads serving as preferential flow paths under these conditions? The as-sessment results indicated that roads do not have an influence on the flow path of flash flood rainfall in Worcester. Flow accumulation calculated with a 10m DEM, corresponds well with reported flood incidents. This basic assessment method can be used to inform the implementation of non structural flood mitigation and public awareness.

Análise dos modos de falha e seus efeitos (FMEA) aplicada a um secador industrial

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

Estudo de caso do programa Flash! Vidas : informação ou entretenimento?

O presente estudo de caso resulta de três meses de estágio no Grupo Cofina Media, onde foram desempenhadas funções jornalísticas na secção Vidas, do jornal Correio da Manhã (CM) e no programa televisivo Flash!Vidas, do canal Correio da Manhã TV (CMTV), desde o dia 2 de fevereiro até ao dia 2 de maio de 2015. Foi elaborado no âmbito do Mestrado em Jornalismo, no Instituto Politécnico de Lisboa, Escola Superior de Comunicação Social, e por objetivo a obtenção do grau de mestre no curso anteriormente referido. A análise tem como propósito perceber se as alegadas peças noticiosas transmitidas pelo programa televisivo Flash!Vidas, no canal Correio da Manhã TV, podem ser consideradas informação, entretenimento ou os dois géneros. É importante referir que o presente trabalho terá como base fundamental os valores-notícias estudados pelo teórico Nelson Traquina e o conceito de infotainment.