1,936 research outputs found
Analysis of X-ray spectra emitted from laser-produced plasmas of uranium
In this paper, we used the multiconfiguration Dirac-Fock method to generate
theoretical X-ray spectra for Co-, Ni-, Cu-, Zn-, Ga-, Ge-, As-, Se-, Br-, Kr-,
and Rb-like uranium ions. Using the distribution of these ions in a
laser-produced plasma, for different plasma temperatures, we generate
theoretical spectra, which are compared to experimental data
K X-Ray Energies and Transition Probabilities for He-, Li- and Be-like Praseodymium ions
Theoretical transition energies and probabilities for He-, Li- and Be-like
Praseodymium ions are calculated in the framework of the multi-configuration
Dirac-Fock method (MCDF), including QED corrections. These calculated values
are compared to recent experimental data obtained in the Livermore SuperEBIT
electron beam ion trap facility
Relativistic correlation correction to the binding energies of the ground configuration of Beryllium-like, Neon-like, Magnesium-like and Argon-like ions
Total electronic correlation correction to the binding energies of the
isoelectronic series of Beryllium, Neon, Magnesium and Argon, are calculated in
the framework of relativistic multiconfiguration Dirac-Fock method. Convergence
of the correlation energies is studied as the active set of orbitals is
increased. The Breit interaction is treated fully self-consistently. The final
results can be used in the accurately determination of atomic masses from
highly charged ions data obtained in Penning-trap experiments.Comment: version soumise 3/08/200
Relativistic calculation of L satellite spectra of W and Au
L X-ray satellite spectra of tungsten and gold are calculated using
the Multi-Configuration Dirac-Fock energies and compared with recent
experimental data. New calculations of L-LM Coster-Kronig
transition energies for tungsten are presented, confirming the origin of the
L visible satellites reported by two experimental groups. We found
the value 5.09 eV for the average energy of the L-LM
Coster-Kronig transition in tungsten. A detailed calculation of the L
and L satellite spectra was performed for gold.Comment: version soumise \`{a} EPJ
Laser microtextured surfaces for friction reduction: Does the pattern matter?
Frictional performances of different textures, including axisymmetric and directional patterns, have been tested in the mixed and the hydrodynamic lubrication regimes. Experimental results, corroborated by numerical simulations, show that the leading parameter is the geometrical pattern void ratio since a large number of dimples offers, at low speed, a trap for debris whereas, at high speed, due to the flow expansion in each micro-hole, fosters a fluid pressure drop, the consequent insurgence of micro-cavitation and, ultimately, the reductions of the shear stresses. Furthermore, in this paper, it is shown that, by means of directional textures, equivalent hydrodynamic wedges can be built up, thus establishing different friction performances depending on the flow direction
Prediction, validation, and uncertainties of a nationâwide postâfire soil erosion risk assessment in Portugal
Wildfires are a recurrent and increasing threat in mainland Portugal, where over 4.5 million hectares of forests and scrublands have burned over the last 38 years. These fire-affected landscapes have suffered an intensification of soil erosion processes, which can negatively affect soil carbon storage, reduce fertility and forest productivity, and can become a source of pollutants. The main objective of the present study is to produce a post-fire soil erosion risk map for the forest and shrubland areas in mainland Portugal and assess its reliability. To this end, the semi-empirical MorganâMorganâFinney erosion model was used to assess the potential post-fire soil erosion according to distinct burn severity and climate scenarios, and the accuracy of the predictions was verified by an uncertainty analysis and validated against independent field datasets. The proposed approach successfully allowed mapping post-fire soil erosion in Portugal and identified the areas with higher post-fire erosion risk for past and future climate extremes. The outcomes of this study comprise a set of tools to help forest managers in their decision-making for post-fire emergency stabilization, ensuring the adequate selection of areas for mitigation to minimize the economic and environmental losses caused by fire-enhanced soil erosion.publishe
A Cryogenic Test Set-Up for the Qualification of Pre-Series Test Cells for the LHC Cryogenic Distribution Line
Three pre-series Test Cells of the LHC Cryogenic Distribution Line (QRL) [1], manufactured by three European industrial companies, will be tested in the year 2000 to qualify the design chosen and verify the thermal and mechanical performances. A dedicated test stand (170 m x 13 m) has been built for extensive testing and performance assessment of the pre-series units in parallel. They will be fed with saturated liquid helium at 4.2 K supplied by a mobile helium dewar. In addition, LN2 cooled helium will be used for cool-down and thermal shielding. For each of the three pre-series units, a set of end boxes has been designed and manufactured at CERN. This paper presents the layout of the cryogenic system for the pre-series units, the calorimetric methods as well as the results of the thermal calculation of the end box test
Study of the middle ear behavior considering the presence of fluid
O objetivo deste trabalho foi estudar a influĂȘncia de diferentes fluidos dentro e fora da cavidade timpĂąnica no comportamento biomecĂąnico do ouvido mĂ©dio. O modelo computacional 3 D da cadeia tĂmpanoâossicular foi construĂdo atravĂ©s de imagens de tomografia axial computorizada (TAC). ApĂłs a construção do modelo da cadeia tĂmpanoâossicular, para a parte interna da membrana timpĂąnica foi criada a caixa timpĂąnica, que inclui toda a cadeia ossicular, e para a parte externa da membrana foi criada uma passagem, simulando o canal auditivo externo.
A discretização do modelo foi feita utilizando o mĂ©todo dos elementos finitos, com base no software ABAQUS. As propriedades mecĂąnicas foram extraĂdas de trabalhos anteriores. Foram obtidos os deslocamentos do umbo e de um ponto central da platina do estribo, para um nĂvel de pressĂŁo sonora de 105 dB aplicada na membrana timpĂąnica, comparando a cadeia tĂmpanoâossicular e os diferentes nĂveis de pressĂŁo externa e interna do ouvido mĂ©dio (fluido lĂquido e fluido gasoso). Os resultados demonstram que o comportamento biomecĂąnico do ouvido mĂ©dio Ă© diferente para os diferentes nĂveis de pressĂ”es testadas neste modelo. Quando utilizada uma pressĂŁo de fluido lĂquido, os deslocamentos sĂŁo de amplitude inferior quando comparados com os resultados obtidos com pressĂŁo de ar.The objective of this work is to study the influence of different fluids of the tympanic cavity into the biomechanical behavior of the middle ear. The 3 D computer model of the tympanic ossicular chain was built using images from computed tomography (CT). After construction of the tympanic ossicular chain model, it was adapted the simulation by placing the passage to the external auditory canal and to the tympanic cavity.
The discretization of the model was made using the finite element method based on ABAQUS software. The mechanical properties were extracted from previous works. The umbo and the stapes footplate displacements, for a sound pressure level of 105 dB applied in tympanic membrane were obtained, comparing the tympanic ossicular chain and the different levels of external and internal pressure in the middle ear (liquid and air). The results demonstrate that the biomechanical behavior of the middle ear is different for different levels of pressure tested in this model. When using liquid, displacements are of lower amplitude when compared with the results obtained with air.Peer Reviewe
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