Mg 2+-doped GaN nanoparticles as blue-light emitters: a method to avoid sintering at high temperatures

Bright blue-light emission at 410 nm is observed from Mg(2+)-doped GaN nanoparticles prepared by the nitridation of Ga(2)MgO(4) nanoparticles at 950 degrees C. The sintering of these nanoparticles during high-temperature nitridation was prevented by mixing the Ga(2)MgO(4) precursor nanoparticles with La(2)O(3) as an inert matrix before the nitridation process. The Mg(2+)-doped GaN nanoparticles were isolated from the matrix by etching with 10 % nitric acid. The Mg(2+)-doped GaN nanoparticles were characterized by photoluminescence, atomic force microscopy, X-ray diffraction, and IR analyses.     

Synthesis of crystalline and amorphous,particle-agglomerated 3-D nanostructures of Al and Si oxides by femtosecond laser and the prediction of these particle sizes

We report a single step technique of synthesizing particle-agglomerated, amorphous 3-D nanostructures of Al and Si oxides on powder-fused aluminosilicate ceramic plates and a simple novel method of wafer-foil ablation to fabricate crystalline nanostructures of Al and Si oxides at ambient conditions. We also propose a particle size prediction mechanism to regulate the size of vapor-condensed agglomerated nanoparticles in these structures. Size characterization studies performed on the agglomerated nanoparticles of fabricated 3-D structures showed that the size distributions vary with the fluence-to-threshold ratio. The variation in laser parameters leads to varying plume temperature, pressure, amount of supersaturation, nucleation rate, and the growth rate of particles in the plume. The novel wafer-foil ablation technique could promote the possibilities of fabricating oxide nanostructures with varying Al/Si ratio, and the crystallinity of these structures enhances possible applications. The fabricated nanostructures of Al and Si oxides could have great potentials to be used in the fabrication of low power-consuming complementary metal-oxide-semiconductor circuits and in Mn catalysts to enhance the efficiency of oxidation on ethylbenzene to acetophenone in the super-critical carbon dioxide.     

Effect of hydrogen addition on criteria and greenhouse gas emissions for a marine diesel engine

Hydrogen remains an attractive alternative fuel to petroleum and a number of investigators claim that adding hydrogen to the air intake manifold of a diesel engine will reduce criteria emissions and diesel fuel consumption. Such claims are appealing when trying to simultaneously reduce petroleum consumption, greenhouse gases and criteria pollutants. The goal of this research was to measure the change in criteria emissions (CO, NO_x, and PM_2.5) and greenhouse gases such as carbon dioxide (CO₂), using standard test methods for a wide range of hydrogen addition rates. A two-stroke Detroit Diesel Corporation 12V-71TI marine diesel engine was mounted on an engine dynamometer and tested at three out of the four loads specified in the ISO 8178-4 E3 emission test cycle and at idle. The engine operated on CARB ultra-low sulfur #2 diesel with hydrogen added at flow rates of 0, 22 and 220 SLPM.     

Two dimensional N-doped ZnO-graphitic carbon nitride nanosheets heterojunctions with enhanced photocatalytic hydrogen evolution

The effective separation of photogenerated charge carriers, their transport and interfacial contact is of great significance for excellent performance of semiconductor based photocatalysts. Herein, we report the fabrication of two dimensional (2D) nanosheets heterojunction comprising of N-doped ZnO nanosheets loaded over graphitic carbon nitride (g-C₃N₄) nanosheets for enhanced photocatalytic hydrogen evolution. The prepared 2D-2D heterojunctions with varying amount of g-C₃N₄ nanosheets have been characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) techniques. The optimized heterojunction photocatalyst with 30 wt% of g-C₃N₄ nanosheets (NZCN30) exhibit hydrogen evolution rate of 18836 μmol h^?1 g_cat^?1 in presence of Na₂S and Na₂SO₃ as sacrificial agents under simulated solar light irradiation. The enhanced photocatalytic performance of NZCN30 heterojunction has been supported well by photoluminescence and photoelectrochemical investigations, which shows the minimum recombination rate and high photoinduced current density, respectively. In addition, the existence of 2D-2D interfacial contact plays a major role in enhanced H₂ evolution by high face-to-face contact surface area for separation of photogenerated charge carriers in space which facilitate their transfer for H₂ generation. This work paves way for the development of 2D-2D heterojunctions for diverse applications.     

Characterization of electroplated FeSe thin films

Thin films of iron selenide (FeSe) were electrodeposited on tin oxide coated conducting glass substrates at various bath temperatures, deposition potential and solution pH values. The deposited films were characterized by X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy and optical absorption techniques, respectively. The structure was found to be hexagonal with preferential orientation along {002} plane. X-ray line profile analysis technique by the method of variance has been used to evaluate the microstructural parameters. The variation of microstructural parameters with bath temperature, deposition potential and solution pH values were studied. The observed results are discussed in detail.     

Effect of nanoparticle on emission and performance characteristics of a diesel engine fueled with cashew nut shell biodiesel

High-rise in the air pollution levels due to combustion of the fossil fuel gives us the opportunity to discover environmentally friendly and clean fuels for the engines. Biodiesel originated from cashew nut shell oil through transesterification process can be blended or used as a neat fuel in unmodified engines. This work investigates the effect of alumina nanoparticles on emission and performance characteristics of cashew nut shell biodiesel. Neat cashew nut shell biodiesel prepared by conventional transesterification is termed as BD100 and biodiesel prepared by modified transesterification with the addition of alumina nanoparticles is termed as BD100A. Experimental results on unmodified diesel engine revealed that emission parameters such as CO, HC, NOx, and smoke were decreased by 5.3%, 7.4%, 10.23%, and 16.1% for BD100% and 8.8%, 10.1%, 12.4%, and 18.4% for B100A, respectively, compared to diesel fuel. At full load conditions, compared to diesel fuel, the BTE dropped by 1.1% and 2.3%, whereas the BSFC increased by 3.8% and 5.1% for B100A and B100 correspondingly.     

A Fuzzy Optimization Approach for Variation Aware Power Minimization During Gate Sizing

Technology scaling in the nanometer era has increased the transistor's susceptibility to process variations. The effects of such variations are having a huge impact on the yield of the integrated circuits and need to be considered early in the design flow. Traditional corner based deterministic methods are no longer effective and circuit optimization methods require reinvention with a statistical perspective. In this paper, we propose a new gate sizing algorithm using fuzzy linear programming in which the uncertainty due to process variations is modeled using fuzzy numbers. The variations in gate delay which is a function of the gate sizes and the fan-outs of the gates are represented using triangular fuzzy numbers with linear membership functions. Initially, as a preprocessing step for fuzzy optimization, we perform deterministic optimizations by fixing the fuzzy parameters to the worst and the average case values, the results of which are used to convert the fuzzy optimization problem into a crisp nonlinear problem. The crisp problem with delay and power as constraints is then formulated to maximize the robustness, i.e., the variation resistance of the circuit. The fuzzy optimization approach was tested on ITC'99 benchmark circuits and the results were validated for timing yield using Monte Carlo simulations. The proposed approach is shown to achieve better power reduction than the worst case deterministic optimization as well as the stochastic programming based gate sizing methods, while having comparable runtimes.     

InAs/InGaSb photodetectors grown on GaAs bonded substrates

The results of wafer fusion between GaAs and InP followed by transfer of an InGaAs film from the InP to GaAs substrate are presented in this paper. This technique of film transfer allowed the subsequent growth of epitaxial materials with approximately 7% lattice mismatch. Type-II InAs/GaInSb superlattices photodetectors of different designs have been grown by molecular beam epitaxy (MBE) on the alternative InGaAs/GaAs substrate and on standard GaSb substrates. Comparison between photodetectors grown on the two different substrates with nearly identical superlattice periods showed a shift in the cut-off wavelength. The superlattices grown on the alternative substrates were found to have uniform layers, with broader x-ray linewidths than superlattices grown on GaSb substrates.