Modelling the intermixing effects in highly strained asymmetric InGaAs/GaAs quantum well

In this work, we have theoretically investigated the intermixing effect in highly strained In$_{0.3}$Ga$_{0.7}$As/GaAs quantum well (QW) taking into consideration the composition profile change resulting from in-situ indium surface segregation. To study the impact of the segregation effects on the postgrowth intermixing, one dimensional steady state Schrodinger equation and Fick's second law of diffusion have been numerically solved by using the finite difference methods. The impact of the In/Ga interdiffusion on the QW emission energy is considered for different In segregation coefficients. Our results show that the intermixed QW emission energy is strongly dependent on the segregation effects. The interdiffusion enhanced energy shift is found to be considerably reduced for higher segregation coefficients. This work adds a considerable insight into the understanding and modelling of the effects of interdiffusion in semiconductor nanostructures.Comment: 6 pages, 4 figure

Base pressure control by supersonic micro jets in a suddenly expanded nozzle

Experimental studies were conducted in sudden expansion axi-symmetric passage for controlling base pressure and their outputs were showcased in current paper. Micro jet active control techniques are used for controlling base pressure. These controls constitute four spaces around base and symmetric to nozzle axis. Mach numbers of the abruptly expanded flows studied for base pressure range from 1.1 to 2.8 and the obtained wall pressure distribution is depicted for Mach number 1.1, 1.5, 2.1, and 2.8 respectively. In this paper the area ratio of the study was 2.56 and the L/D ratios were up to 1 from 10 respectively. Nozzles working on the concerned inertia level were performed with NPR from 3 to 11. It is found that the active controls through the micro jets are capable of regulating the pressure in the recirculation zone. In the presence of favourable pressure gradient the control becomes effective. An appreciable 65% hike in the pressure at the base was accomplished for the above discussed parameters of the current research

Experimental investigation on the effectiveness of active control mechanism on base pressure at low supersonic mach numbers

In the current investigation, the experiments were carried out to evaluate the effectiveness of microjets in controlling the base pressure from a convergentdivergent nozzle at low supersonic Mach at different expansion level. Tests were carried out for low supersonic Mach numbers 1.25, 1.3, 1.48, and 1.6 while nozzle pressure ratio ranges from 3 to 11. The jets are augmented abruptly into an axisymmetric circular channel with different cross-sectional areas as that of nozzle exit area. The results show that the proficiency of the microjets is only marginal in controlling the base pressure even under the influence of favorable pressure gradient at lower NPRs namely 3 and 5. It was also observed that for higher values of the NPRs such as 7, 9, and 11, the dynamic control by very small jets results in rise of base pressure for the different values of the L/D ratios of these investigations. For NPRs 5 and 7, the trend differs due to the level of expansion, nature of waves present in the base region, relief available to the flow, length to diameter ratio of the enlarged duct, and the Mach numbers. It is seen that most of the cases exhibit similar behavior for higher as well as the lower length to diameter ratios, which means; that the back pressure has not adversely influenced the flow field in the base region as well as in the duct. With this it can be stated that the microjets can be an alternative for the experimentalist for base pressure control in the form of microjets

RETRATO SIN IDENTIFICAR [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201