Impurity-induced polaritons in a one-dimensional chain

A detailed analytical study of an impurity induced polariton band arising inside a spectral gap between lower and upper polariton branches is presented. Using the microcanonical method, we calculate the density of states and localization length of the impurity polaritons. Analytical results are compared with numerical simulations and excellent agreement is found.Comment: 10 pages, 3 figures, RevTe

Resonant states in GaAs/Ga1-xAlxAs Multi-Quantum-Wells

The effect of buffer layers on resonant states in a Multi-Quantum-Well (MQW) sandwiched between two substrates is investigated here theoretically. These resonances appear as well-defined peaks in the density of states (DOS). The local and total densities of states are obtained from an analytical determination of the Green functions. Due to the substrate/buffer layer/ MQW /substrate interaction, different kinds of resonant states are found and their properties are investigated. We show in particular that an incident electron in the left-hand side substrate is transmitted in the right hand side substrate of the structure with large time delays in the phase time. The peaks in the phase time associated with the transmission coefficient are found to be similar to those corresponding to the DOS. The intensity of these peaks associated with extended states in MQW’s and Tamm like states lying at the MQW/buffer layer interface, strongly depends on the width of the buffer layer.The effect of buffer layers on resonant states in a Multi-Quantum-Well (MQW) sandwiched between two substrates is investigated here theoretically. These resonances appear as well-defined peaks in the density of states (DOS). The local and total densities of states are obtained from an analytical determination of the Green functions. Due to the substrate/buffer layer/ MQW /substrate interaction, different kinds of resonant states are found and their properties are investigated. We show in particular that an incident electron in the left-hand side substrate is transmitted in the right hand side substrate of the structure with large time delays in the phase time. The peaks in the phase time associated with the transmission coefficient are found to be similar to those corresponding to the DOS. The intensity of these peaks associated with extended states in MQW’s and Tamm like states lying at the MQW/buffer layer interface, strongly depends on the width of the buffer layer

Coal and Biomass Co-Combustion: CFD Prediction of Velocity Field for Multi-Channel Burner in Cement Rotary Kiln

This paper represents the medialization of alternative fuels co-combustion, in a cement rotary kiln, established on the commercial computational fluid dynamic (CFD) software ANSYS FLUENT. The focus is placed on the key issues in the flow field, mainly on how they are affected by turbulence models and co-processing conditions. Real data, from a Moroccan cement plant, are used for model input. The simulation results have shown a potential effect of the physics model on turbulent and gas-solid flow prediction. The CFD results can be taken as a guideline for improved co-processing burner design and reduce the effect of using alternative fuels

CFD-simulation of gas-solid flow in bubbling fluidized bed reactor

The hydrodynamic behaviour of gas-solid flow has been studied in a two-dimensional bubbling fluidized bed reactor filled with particles of 275 µm in size, using computational fluid dynamics (CFD). The two-fluid model (TFM) approach based on the concept of Eulerian–Eulerian in combination with Kinetic Theory of Granular Flow (KTGF) is used to represent the fluid mechanics involved in the flow. The computational implementation was realized by the commercial software ANSYS FLUENT. Interphase momentum exchange between gas and solid phases were calculated using the modified Syamlal O’Brien drag force function. The simulation predictions have been comprehensively validated with experimental data measurements of bed expansion rate, pressure drops and average gas volume fraction profiles. The pressure drops predicted by the simulations were in comparatively strong agreement with the experimental data at higher superficial gas velocities. The bed expansion ratio of the simulation results is closer to that of the experimental data. This work provides a scalable means to assist in the design and operation of fluidised bed reactors and fluidisation processes

Étude des phases solides et vitreuses de l’hydrazine et des mélanges hydrazine – eau

Entrant dans le cadre plus large d’une étude, menée dans notre Laboratoire et en collaboration, sur les propriétés physiques des systèmes eau-hydrazine(1, 2) et eau-alkylhydrazines asymétriques(2, 3, 4), le travail présenté ici résume l’étude des phases hors d’équilibre et des transformations des systèmes eau-hydrazine de compositions comprises entre 0,2 et 0,5.Mettant en jeu des phases solides non connues jusqu’alors, l’étude de ces mélanges est particulièrement intéressante même si elle est complexe, car les transformations sont nombreuses et bien reproductibles

Electron channel drop tunnelling

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