Modeling of Ga1−xInxAs1−y−zNySbz/GaAs quantum well properties for near-infrared lasers

The aim of this work is to model the properties of GaInAsNSb/GaAs compressively strained structures. Indeed, Ga_1?xIn_xAs_1?y?zN_ySb_z has been found to be a potentially superior material to GaInAsN for long wavelength laser dedicated to optical fiber communications. Furthermore, this material can be grown on GaAs substrate while having a bandgap smaller than that of GaInNAs. The influence of nitrogen and antimony on the bandgap and the transition energy is explored. Also, the effect of these two elements on the optical gain and threshold current density is investigated. For example, a structure composed of one 7.5 nm thick quantum well of material with In=30%, N=3.5%, Sb=1% composition exhibits a threshold current density of 339.8 A/cm² and an emission wavelength of 1.5365 μm (at T=300 K). It can be shown that increasing the concentration of indium to 35% with a concentration of nitrogen and antimony, of 2.5% and 1%, respectively, results in a decrease of the threshold current density down to 253.7 A/cm² for a two well structure. Same structure incorporating five wells shows a threshold current density as low as 221.4 A/cm² for T=300 K, which agrees well with the reported experimental results.     

Sliding mode audio class-D amplifier for portable devices

Audio class-D amplifiers are widely used in industrial and consumer portable electronic devices, such as mobile phones, thanks to their high efficiency. However, these amplifiers have a limited linearity due to their switching behavior and also a limited control bandwidth. To overcome these major drawbacks, this paper introduces a self-oscillating control technique based on the sliding mode theory which combines a large control bandwidth and a spread spectrum technique. A high power supply rejection, which is a crucial parameter in modules directly connected to a noisy battery, has also been achieved by introducing a variable hysteresis window. Theoretical analysis, behavioral and electrical simulations are discussed in detail in this paper. An integrated circuit using 0.13 μm CMOS process has been realized focused on mobile phone applications (0.8 W, 3.6 V and 8 Ω). The audio amplifier achieves 97 dB(A) signal-to-noise ratio, 0.02 % harmonic distortion and up to 80 dB of power supply rejection. The die area is smaller than 0.4 mm² while keeping more than 90 % efficiency at 1 W.     

Gamma irradiation-aided chitin/chitosan extraction from prawn shells

Chitin and chitosan were extracted from prawn shells. The influence of a 25 kGy irradiation dose on the deproteination process was investigated. The deproteination degree was followed by Lowry-Folin method. The demineralisation degree versus reaction time with 1 N hydrochloric acid solution was followed by atomic absorption spectrometry.Chitin and chitosan obtained were characterised by FTIR spectrometry. The influence of some parameters, such as reaction time, alkaline concentration and temperature on the deacetylation degree was also investigated. The deacetylation degree was evaluated by FTIR spectrometry using the bands at 1320 cm⁻¹ and 1420 cm⁻¹.It was found that the irradiation of the shells at a dose of 25 kGy reduces the time of the deproteination reaction by a factor of three, comparatively to the non-irradiated samples.     

Sulfuric Containing Sugar Bath and Permanent Weak Magnetic Field Effect during Anodizing AlCu<Subscript>6</Subscript>Si Alloy Sheet Surfaces

Rolling and perpendicular to rolling surfaces of AlCu₆Si aluminum sheet have been anodized at 27 ± 1°C in 20 wt % sulfuric acid containing an additive of white sugar powder with and without permanent weak magnetic field. After one hour of anodizing, some hillocks-shaped micropores are developed and craters are formed in the oxide layers. The micropores obtained in rolling faces are often smaller than those obtained on other faces. Sulfuric anodizing at 21 V causes the formation of combined micropore-nanopore structures in rolling surface. It demonstrated that sugar additive increases the density of micropores in spherical shape in rolling surface and the increasing of sugar concentration changes the pores to hillocks form. In addition, the application of weak magnetic field induces homogeneous repartition of micropores.     

Illustrative Discussion of MC-Dropout in General Dataset: Uncertainty Estimation in Bitcoin

Neural Processing Letters - The past few years have witnessed the resurgence of uncertainty estimation generally in neural networks. Providing uncertainty quantification besides the predictive...     

Corrosion behavior on the different zones of AA2014 welded aluminum alloy by AA5554 filler aluminum alloy with TIG process: Before and after solution heat treatments followed by ageing

In this work, we have studied the effects of solution heat treatment followed by ageing on the corrosion behavior of AA2014 aluminum alloy welded by AA5554 aluminum alloy. Two samples are then analyzed, in the first case the solution heat treatment is followed by quenching and natural ageing of 90 days (sample 1), and in the second one, the solution heat treatment is followed by quenching and artificial ageing of twelve hours at 190°C (sample 2). The principal observations can be summarized as: evaporation of magnesium in fusion zone, and diffusion of magnesium and copper from the heat affected zone to the fusion zone were identified. Solution heat treatment, quenching and 90 days of natural ageing leads to a uniform corrosion in the heat affected zone and in the fusion one, when the material is immersed for ten seconds in Keller reagent solution. After immersion in 0.3% NaCl chloride solution, and after solution treatment and quenching, we observed that applied artificial ageing at 190°C causes localized corrosion surrounding precipitates and then develops uniform corrosion in all zones, particularly in the fusion one. Finally, it is noted that the surface of different zones became nobler after applying solution heat treatment followed by natural ageing.     

Immobilization of Rhodococcus erythropolis B4 on radiation crosslinked poly(vinylpyrrolidone) hydrogel: Application to the degradation of polycyclic aromatic hydrocarbons

A poly(vinylpyrrolidone) (PVP) hydrogel crosslinked by gamma radiation was used to immobilize, by adsorption, Rhodococcus erythropolis B4 strain. Immobilized cells were tested for their capacity to degrade naphthalene and anthracene, under aerobic conditions.The results showed that, the strain fixed is capable of growing in the presence of naphthalene or anthracene as a unique source of carbon. It was also shown that, the fixed strain can be preserved by freeze-drying for further use. The biodegradation capacity was improved during the second use.