Anti-Dissipative Schemes for Advection and Application to Hamilton–Jacobi–Bellmann Equations

We propose two new antidiffusive schemes for advection (or linear transport), one of them being a mixture of Roe’s Super-Bee scheme and of the “Ultra-Bee” scheme. We show how to apply these schemes to treat time-dependent first order Hamilton–Jacobi–Bellman equations with discontinuous initial data, possibly infinitely-valued. Numerical tests are proposed, in one and two space dimensions, in order to validate the methods AMS subject classifications. Primary 65M12, Secondary 58J47     

Determination of nanotubes properties by Raman spectroscopy

The basic concepts and characteristics of Raman spectra from single-wall carbon nanotubes (SWNTs, both isolated and bundled) are presented. The physical properties of the SWNTs are introduced, followed by the conceptual framework and characteristics of their Raman spectra. Each Raman feature, namely the radial breathing mode, the tangential G band, combination modes and disorder-induced bands are discussed, addressing their physical origin, as well as their capability for characterizing SWNT properties.     

Mathematical modeling of gas‐phase biofilter performance

In the present paper, a new mathematical model describing the physical, chemical and biological phenomena involved in the process of contaminant removal in biofilters is developed. In addition to the contaminant, the key components of the present theoretical model are carbon dioxide and oxygen. The model predicts the concentration profile of the key components in the gas phase, the biofilm and the sorption liquid retained in the solid particles composing the filter bed at both steady and transient regimes. The model equations were solved numerically and comparison between theory and experiment showed that the model results for styrene and carbon dioxide concentration profiles were in very good agreement with experimental data for the biofiltration of styrene vapors at steady state. The analysis of oxygen concentration profile in the biofilm predicted by the theoretical model revealed that oxygen limitation does not occur under the operating styrene biodegradation rate in the biofilter. Copyright © 2003 Society of Chemical Industry     

Radiation induced carbon complexes in gallium arsenide

Gallium arsenide grown by the metallorganic chemical vapour deposition method and n-doped to various silicon concentrations was irradiated with reactor neutrons (1 MeV equivalent damage in silicon) in the fluence range 0 to 3 × 10¹⁵ cm⁻². Native defects, including carbon which is a residual impurity of the growth method, and those introduced by irradiation, were characterized by photoluminescence (PL) and deep level transient spectroscopy (DLTS). In some samples with fixed doping value, the PL intensity of all the transitions, including that to the carbon impurity increases at low fluence levels before decreasing at high fluence. At higher fluences, the transition to the carbon impurity goes through other maxima. The carbon PL intensity versus fluence curve depends on initial doping. DLTS results reveal the removal of a trap EL12 at low fluences, but the introduction of other traps at higher fluences. The defect introduction rates depend on fluence. We attribute the variation in the carbon PL intensity to an interaction between the defects introduced by the irradiation and the carbon impurity.     

Value of the Di Maria leads in the electrocardiographic diagnosis of posterior myocardial infarct

Authors retain, on the basis of their experiences, that right chest leads proposed by Di Maria for the infer-posterior and postero-basic myocardium wall study can overall be useful in those cases which had posterior myocardial infarction and where standard leads did not show variations or showed untrustworthy variations. Therefore Authors also supported by vectorcardiographic findings, recommend the routine use of Di Maria leads.     

Biodiesel compatibility with carbon steel and HDPE parts

Compatibility of the new environmentally-friendly alternative of diesel engine fuels, biodiesel, with storage and engine part materials, is still an open issue. In this work, the interaction between three fuels (petroleum diesel and two types of biodiesel — soybean and sunflower) and two materials (carbon steel and high density polyethylene) used in storage and automotive tanks, is analyzed in detail. A wide set of characterization techniques was used to evaluate the changes in both solid and fluid materials, as weight change measurement, optical, scanning electron and atomic force (AFM) microscopies, Raman and FTIR spectroscopies, and differential scanning calorimetry. The AFM technique allowed detecting surface roughness and morphology changes in the metallic material following the trends in the weight losses. In the case of polymeric material, weight gain by fluid absorption occurred, being detected by the spectroscopic techniques. The biodiesel fuels underwent some ageing however this phenomenon did not affect the interaction between the biodiesel fuels and the substrates. The petrodiesel, which did not age, caused more significant degradation of the substrates.     

Intersubband optical absorption in (In,Ga)N/GaN double quantum wells considering applied electric field effects

Journal of Computational Electronics - In the present paper, we theoretically examine the total absorption coefficient related to inter-conduction subband 1S–2P transitions in symmetric...     

Evaluation of the two‐parameter fracture criterion for various crack configurations made of 7075‐T6 aluminium alloy using finite‐element fracture simulations

For many years, a two‐parameter fracture criterion (TPFC) has been used to correlate and predict failure loads on cracked metallic fracture specimens. The current study was conducted to evaluate the use of the TPFC on a high‐strength aluminium alloy, using elastic‐plastic finite‐element (FE) analyses with the critical crack‐tip‐opening angle (CTOA) fracture criterion. In 1966, Forman generated fracture data on middle‐crack tension, M(T), specimens made of thin‐sheet 7075‐T6 aluminium alloy, which is a quasi‐brittle material. The fracture data included a wide range of specimen half‐widths (w) ranging from 38 to 305 mm. A two‐dimensional FE analysis code (ZIP2D) with a “plane‐strain core” option was used to model the fracture process with a critical CTOA chosen to fit the M(T) test data. Fracture simulations were then conducted on other M(T), single‐edge‐crack tension, SE(T), and bend, SE(B), specimens over a wide range in widths (w = 19‐610 mm). No test data were available on the SE‐type specimens. The results supported the TPFC equation for net‐section stresses less than the material proportional limit. However, some discrepancies in the FE fracture simulations results were observed among the numerical analyses made on the three specimen types. Thus, more research is needed to improve the transferability of the TPFC from the M(T) specimen to both the SE(T) and SE(B) specimens for quasi‐brittle materials.     

Ion beam nanopatterning and micro-Raman spectroscopy analysis on HOPG for testing FIB performances

This work reports Ga⁺ focused ion beam nanopatterning to create amorphous defects with periodic square arrays in highly oriented pyrolytic graphite and the use of Raman spectroscopy as a new protocol to test and compare progresses in ion beam optics, for low fluence bombardment or fast writing speed. This can be ultimately used as a metrological tool for comparing different FIB machines and can contribute to Focused Ion Beam (FIB) development in general for tailoring nanostructures with higher precision. In order to do that, the amount of ion at each spot was varied from about 10⁶ down to roughly 1 ion per dot. These defects were also analyzed by using high resolution scanning electron microscopy and atomic force microscopy. The sensitivities of these techniques were compared and a geometrical model is proposed for micro-Raman spectroscopy in which the intensity of the defect induced D band, for a fixed ion dose, is associated with the diameter of the ion beam. In addition, the lateral increase in the bombarded spot due to the cascade effect of the ions on graphite surface was extracted from this model. A semi-quantitative analysis of the distribution of ions at low doses per dot or high writing speed for soft modification of materials is discussed.     

A novel procedure for the measurement of the kinetics of styrene biodegradation in a biofilter

A novel procedure for the study of the biodegradation kinetics of styrene is proposed in this paper. Microbial growth tests in the presence of styrene were performed using suspensions of microorganisms prepared from samples of filter bed material. This material had been directly withdrawn previously from an operating biofilter employed for the removal of styrene vapours from air. The kinetics tests were initiated immediately after transfer of filter bed samples from the active styrene filter bed to sealed flasks containing a mineral‐based medium, and were performed in such a manner that no enrichment technique or lag phase treatment was necessary to activate the desired biodegradation of styrene. The complete biodegradation of freshly introduced styrene was observed within a few hours of the filter bed's initial contact with the active microbial suspension. A novel theoretical development, as proposed in this study, has provided us with the means for estimating the yield coefficient of the biomass with respect to the styrene consumed and the kinetic coefficients of the growth rate without having to perform any analyses of the liquid phase after start‐up of the growth tests. Only monitoring of the styrene and carbon dioxide concentrations in the liquid and gas phases in the test flasks was necessary. The Haldane model, with inhibition expected at high styrene concentrations, was found to be the best to represent the biodegradation kinetics of styrene in this environment. Copyright © 2005 Society of Chemical Industry