Crystallographic Orientation Effect On Hole Polar Optical Phonon Scattering Rates in Thin Gaas/Alxga1-Xas Quantum Wells

We report on hole polar optical phonon scattering processes in thin GaAs/AlxGa1-xAs quantum wells grown in various crystallographic directions, such as [001], [110]. Using the dielectric continuum model we focus on how the different scattering processes of holes with interface phonon modes depend on the initial hole energy. In our work, we use the Luttinger-Kohn (LK) 6×6 k.p Hamiltonian with the envelope function approximation, from which we compute numerically the electronic structure of holes for a thin quantum well sustaining only one bound state for each type of hole. Due to mixing between the heavy, light, and split off bands, hole subbands exhibit strong nonparabolicity and important warping that have their word to say on physical properties. Detailed and extensive calculations that the rates for intra-subband scattering processes differ significantly from those of bulk GaAs because of quantization and reduced dimensionality. Moreover, the study of scattering as a function of hole energy shows that the trend of the scattering rates is governed mostly by i) overlap integrals and ii) the density of the final states to which the hole scatters. The influence of warping, in the hole energy dispersion, on the phonon scattering rates is also explored and found to be important when the initial hole energy is high. Our calculations show evidence of strong anisotropy in the scattering rates especially for processes involving the heavy hole subband, which anisotropy is in fact quite important and far from being negligible. However, strain effect can reduce scattering rates.

Solar Photovoltaic Emulation under Uniform Irradiance and Partial Shading Conditions using Sliding Mode Control

For the purpose of minimizing greenhouse gas emissions and contributing strongly to the climate change mitigation, many researchers and scientists are making tremendous efforts in order to boost the research and development in renewable energies as an important solution to reduce the use of conventional power generation resources. Solar photovoltaic (PV) energy is widely used and has known a significant interest in last years. However, its dependence on the atmospheric conditions does not allow researchers to perform their experiences at the desired atmospheric parameters especially temperature (T) and irradiance (G). Furthermore, using real PV modules with controllable light source to carry out measurements and tests on PV applications such as Maximum Power Point Tracking (MPPT) and solar connected inverters is considerably inefficient and less flexible. Therefore, PV array emulator were appeared to deal with those limitations and to replace efficiently the use of real PV modules in laboratory tests by delivering similar PV characteristics and mimicking the electrical behavior of PV panels. In addition to the emulation of PV modules under varying environmental conditions, the emulation of PV array under partial shading conditions is an interesting topic especially for the aim of using PV array emulators in testing Global Maximum Power Point Tracking (GMPPT) techniques, which constitute nowadays a huge challenge for PV researchers. This paper presents the design of PV array emulator based on robust sliding mode controller, which is able to emulate accurately the PV array under both uniform solar insolation and partial shading conditions. Simulation results using Matlab Simulink software are presented and discussed so as to investigate the static and dynamic performances of the developed power device.

Determination Of Proximate Composition And Crude Yeild Of Shrimp Shells(Peneaus Semisulcatus)

The present study was carried out to determine the proximate composition of green tiger prawn and to select the suitable solvent system for carotenoid extraction. Samples (P. semisulcatus) were purchased from the landsites and transported to the laboratory in an ice box. The whole shrimp were peeled manually, and the residues, consisting head, tail and shells are separated. The moisture content, total lipid, protein, and ash content were quantified using standard methods. Weight of extracted crude of shrimp shells and retention factor (Rf) for the shrimp shell powder were determined using different pure and mixed organic solvents. Moisture content of the fresh shrimp shells was found to be 76.40 ± 0.92 %. In the present study, quantification showed that the shrimp shells are significantly rich in ash content (25.52 ± 0.06 % in dry weight). Significantly (p < 0.05) the highest crude yield of 10.24 ± 0.02 % was obtained from shrimp shells, when the dried shrimp shells powder was dissolved with the mixture of acetone and ethanol (1:1) than the other solvents. The lowest crude yield (2.32 ± 0.01 %) was extracted with ether. The highest Rf was obtained when the shrimp shell crude was dissolved with the mixture of acetone and ethanol (1:1). It can be recommended from our findings that the dried shrimp shells of Peneaus semisulcatus would be directly utilized for formulations of poultry animal feeds and sea cucumber juvenile feeds due to its high ash content. The mixture of the acetone and ethanol (1:1) would be the better choice for obtaining the highest crude yield from the shrimp shells.

Analysis of The Use of Phase Change For The Safe Operation of Electrical Equipment

Cooling is currently a serious issue for any manufacturing company, no matter what it is dealing with. Cooling affects all areas of production and relates directly to primary production or to the completion of final products. The ability to accurately manage large-scale electrical voltages has enabled many effective and significant innovations. These devices require high-efficiency electronics cooling. Dielectric fluids are also safe in contact with electronics. They can be used to cool various devices. They work without compromising the health of workers or harming the environment. Special devices called heat pipes are used more and more widely to transfer the excessive heat to a colder environment. The mechanical moving parts are removed. Pulsating (or oscillating) heat pipe present promising alternatives for the removal of high localized heat fluxes to provide a necessary level of temperature uniformity across the components that need to be cooled. PHP is a capillary tube (with no wick structure) bent into many turns and partially filled with a working fluid. Because the tube is thin, the liquid plugs and vapor bubbles are formed inside it. This article presents the results of experiments using heat pipes for cooling.

Application of Optimization Based Finite Element Model Updating Method On 3d Printed Model Structures

Nowadays it becomes trend in studying of dynamic behavior on complex structure. Model updating is one of the tools developed for verifying accuracy of finite element models. In this paper, method for computing model updating on finite element model and effective the experimental modal analysis of structural systems is developed. The identification method developed in this study is based on time-domain system identification numerical techniques. The case study considered in this work is a 3D printed structure that be modeled as a two-story shear building system with irregular torsion. A preliminary numerical model of the two-story shear building system is developed by using SAP2000 and the experimental modal parameters data are collected in the laboratory buy some test then are modeled by Artemis modal pro. After obtaining the results from numerical modal and experimental modal, it was brought to FEMtools software to improve the match between the dynamic properties of an initial structure and the experimentally estimated modal data for updating. After updating, it’s shown that optimization was done, that some unknown material parameters (such as mass density and young modulus) of materials and/or boundary conditions were optimized by FEMtools Optimization that provides the possibility to perform design optimization on updated finite element models.

Quantitative Analysis Of Trace Metal In Water And Soft Tissues Of Balanus Amphitrite In Nandikadal Lagoon, Sri Lanka

Due to long–term military activities carried out in Nandikadal lagoon situated at Mullaitivu, Sri Lanka, there are high possibilities to impact water and biota with heavy metals. Balanus amphitrite (Barnacles) has been found as a strong candidate for biomonitoring of trace metals. Therefore, the present study describes the impacts of trace metal pollution on water and the soft tissues of Balanus amphitrite. Water samples and barnacles were collected from two locations of the lagoon for four months during the dry and wet seasons. Quantitative analysis of trace metals (Cd, Cu, Cr, Pb and Zn) were detected in the water and tissue samples using flame atomic absorption spectrometry. Cd, Cr, Pb and Cu found in tissues of barnacles were several times higher than the International recommended level except for Zn. The concentration of Pb in tissues of barnacles showed a significant (p < 0.05) spatial variation. The Cd and Cu concentrations obtained in soft tissues showed significant (p < 0.05) seasonal variations. The concentration of Cr in water showed a significant (p < 0.05) spatial variation and other trace metals (Pb,Cd) except Zn, showed significant (p < 0.05) seasonal variations. There were significant positive correlations between water and soft tissues with respect to Cd (p=0.000 & r = 0.893) and Pb (p=0.002 & r=0.435). Zn found in samples showed negative correlation between water and soft tissues. According to this results Balanus amphitrite has an ability to accumulate trace metals several times greater than in the lagoon water. Therefore, Balanus amphitrite is a strong net–accumulator of Cd, Pb, Zn, Cu, Cr. Hence, it is a good choice to be used as a bioindicator organism to find the level impact of trace metal contamination.