2,916 research outputs found
Effect of Oil Production and Drilling Operations on the Ecology of Phytoplankton in the OEI Study Area
Paper by Kenneth W. Fucik and Sayed Z. El-Saye
Chaotic behavior of a coupled system of the Riccati map
In this paper, We present the equivalent discrete system of coupled Riccati map. WeĂÂ study some the dynamic behavior such as (xed points and their asymptotic stability,ĂÂ the lyapunov exponents, chaos and bifurcation) of the system. Numerical simulation isĂÂ presented to ensure the analytical results
Modification of Pb-Sb eutectic bearing-solder alloys with bismuth additions rapidly solidified from melt
In this work, various amounts of Bi element have been added to the eutectic Pb-Sb to form bearing- solder materials. The Pb-Sb eutectic has been produced by rapid solidification using melt spinning technique with various amounts of Bi have been added to it, in the ratio 1, 2 , 3, 4, and 5 wt.%. Scanning electron microscopy (SEM), X- ray diffraction (XRD) analysis and differential scanning calorimetry (DSC) have been carried out. Microhardness measurements were also carried out using Vickerâs hardness technique. The results showed that, the ternary alloys up to 4 wt.% Bi have properties superior to binary eutectic material. Bismuth up to 4wt. % increases the Youngâs modulus, Vickerâs hardness and decreases the electrical resistivity, internal friction and melting point. The ternary Pb-13.1Sb-4Bi solder alloy has a lower melting point about 237.87 ?C. Also, the results show that formation of Bi phase developed the mechanical properties and Vickerâs hardness due to addition of Bi element. The addition of Bi refines the crystal size of Sn in case of melt spun alloys as seen in scanning electron micrographs and X-ray diffraction
Monotonic Positive Solutions of Nonlocal Boundary Value Problems for a Second-Order Functional Differential Equation
We study the existence of at least one monotonic positive solution for the nonlocal boundary value problem of the second-order functional differential equation xâ˛â˛(t)=f(t,x(Ď(t))), tâ(0,1), with the nonlocal condition âk=1makx(Ďk)=x0, xâ˛(0)+âj=1nbjxâ˛(Ρj)=x1, where Ďkâ(a,d)â(0,1), Ρjâ(c,e)â(0,1), and x0,x1>0. As an application the integral and the nonlocal conditions âŤadx(t)dt=x0, xâ˛(0)+x(e)-x(c)=x1 will be considered
Validated stability indicating methods for determination of nitazoxanide in presence of its degradation products
AbstractThree sensitive, selective and reproducible stability-indicating methods are presented for determination of nitazoxanide (NTZ), a new anti-protozoal drug, in presence of its degradation products. Method A utilizes the first derivative of ratio spectra spectrophotometry by measurement of the amplitude at 364.4nm using one of the degradation products as a divisor. Method B is a chemometric-assisted spectrophotometry, where principal component regression (PCR) and partial least squares (PLS) were applied. These two approaches were successfully applied to quantify NTZ in presence of degradation products using the information included in the absorption spectra in the range 260â360nm. Method C is based on the separation of NTZ from its degradation products followed by densitometric measurement of the bands at 254nm. The separation was carried out on silica gel 60F254, using chloroformâmethanolâammonia solutionâglacial acetic acid (95:5:1:1 by volume, pH=5.80) as a developing system. These methods are suitable as stability-indicating methods for the determination of NTZ in presence of its degradation products either in bulk powder or in pharmaceutical formulations. Statistical analysis of the results has been carried out revealing high accuracy and good precision
Selective Hydrogenation of Benzofurans Using Ruthenium Nanoparticles in Lewis Acid-Modified Ruthenium-Supported Ionic Liquid Phases
Ruthenium nanoparticles immobilized on a Lewis-acid-functionalized supported ionic liquid phase (Ru@SILP-LA) act as effective catalysts for the selective hydrogenation of benzofuran derivatives to dihydrobenzofurans. The individual components (nanoparticles, chlorozincate-based Lewis-acid, ionic liquid, support) of the catalytic system are assembled using a molecular approach to bring metal and acid sites in close contact on the support material, allowing the hydrogenation of O-containing heteroaromatic rings while keeping the aromaticity of C6-rings intact. The chlorozincate species were identified to be predominantly [ZnCl4]2â anions using X-ray photoelectron spectroscopy and are in close interaction with the metal nanoparticles. The Ru@SILP-[ZnCl4]2â catalyst exhibited high activity, selectivity, and stability for the catalytic hydrogenation of a variety of substituted benzofurans, providing easy access to biologically relevant dihydrobenzofuran motifs under continuous flow conditions
Computational assessment of ballistic impact on a high strength structural steel/polyurea composite plate
Ballistic impact on a polyurea retroďŹtted high strength structural steel plate is simulated and validated. A soft material model for polyurea, which is capable of capturing complex mechanical behavior characterized by large strains, hysteresis, rate sensitivity, stress softening (Mullins effect), and deviatoric and volumetric plasticity, is calibrated against several uniaxial tension experiments and a threedimensional release wave experiment to capture both the material point and bulk behaviors. A porous plasticity model is employed to model the high strength structural steel and localization elements are included to capture adiabatic shear bands and strain localization. The computational capabilities
of these models are demonstrated by the prediction of the
target plate displacement, which shows excellent agreement
with experiments
Role of hydrogen in volatile behaviour of defects in SiO2-based electronic devices
Charge capture and emission by point defects in gate oxides of metalâoxideâsemiconductor field-effect transistors (MOSFETs) strongly affect reliability and performance of electronic devices. Recent advances in experimental techniques used for probing defect properties have led to new insights into their characteristics. In particular, these experimental data show a repeated dis- and reappearance (the so-called volatility) of the defect-related signals. We use multiscale modelling to explain the charge capture and emission as well as defect volatility in amorphous SiO2 gate dielectrics. We first briefly discuss the recent experimental results and use a multiphonon charge capture model to describe the charge-trapping behaviour of defects in silicon-based MOSFETs. We then link this model to ab initio calculations that investigate the three most promising defect candidates. Statistical distributions of defect characteristics obtained from ab initio calculations in amorphous SiO2 are compared with the experimentally measured statistical properties of charge traps. This allows us to suggest an atomistic mechanism to explain the experimentally observed volatile behaviour of defects. We conclude that the hydroxyl-EⲠcentre is a promising candidate to explain all the observed features, including defect volatility
Time-resolved protein fluorescence studies of intermediates in the photochemical cycle of bacteriorhodopsin.
The Effect of EMI Generated from Spread-Spectrum-Modulated SiC-Based Buck Converter on the G3-PLC Channel
6siPower line communication (PLC) is increasingly emerging as an important communication technology for the smart-grid environment. As PLC systems use the existing infrastructure, they are always exposed to conducted electromagnetic interference (EMI) from switching mode power converters, which need to be tightly controlled to meet EMC regulations and to ensure the proper operation of the PLC system. For this purpose, spread-spectrum modulation (SSM) techniques are widely adopted to decrease the amplitude of the generated EMI from the power converters so as to comply with EMC regulations. In this paper, the influence of a spread-spectrum-modulated SiC-based buck converter on the G3-PLC channel performance is described in terms of channel capacity reduction using the ShannonâHartley equation. The experimental setup was implemented to emulate a specific coupling path between the power and communication circuits and the channel capacity reduction was evaluated by the ShannonâHartley equation in several operating scenarios and compared with the measured frame error rate. Based on the obtained results, SSM provides the EMI spectral peak amplitude reduction required to pass the electromagnetic compatibility (EMC) tests, but results in increased EMI-induced channel capacity degradation and increased transmission error rate in PLC systems.openopenWaseem El Sayed; Piotr Lezynski; Robert Smolenski; Niek Moonen; Paolo Crovetti; Dave W. P. ThomasEl Sayed, Waseem; Lezynski, Piotr; Smolenski, Robert; Moonen, Niek; Crovetti, PAOLO STEFANO; Thomas, Dave W. P
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