Gas Pressure Profile Prediction from Variable Strain Rate Deformation Paths in AA5083 Bulge Forming

Two approaches to gas pressure profile prediction for bulge forming of AA5083 sheet under Quick Plastic Forming (QPF) conditions at 450?°C were investigated. The first was based on an algorithm internal to ABAQUS? wherein the gas pressure results from maintaining a constant effective target strain rate at the dome pole. In the second, the nonlinear long wavelength stability analysis was combined with a single creep mechanism material model that accounts for hardening/softening. A series of stability curves, which denote combinations of strain and strain rate for unmitigated thinning and, ultimately, rupture of an AA5083 bar, were computed. These are based on a parameter that characterizes an assumed geometric non-uniformity, ??. The associated uniaxial strains and strain rates were expressed in terms of von Mises effective strains and strains rates, and pressure profiles were computed. An ancillary approach to variable strain rate path prediction based on a thinning factor was used to suggest a suitable value of ?? in the stability analysis for a reasonable thinning level at the end of forming. Key advantages and disadvantages of both approaches to pressure profile prediction are examined relative to bulge forming time and thinning at a 50-mm dome displacement.     

Production of butanol (a biofuel) from agricultural residues: Part II – Use of corn stover and switchgrass hydrolysates

Acetone butanol ethanol (ABE) was produced from hydrolysed corn stover and switchgrass using Clostridium beijerinckii P260. A control experiment using glucose resulted in the production of 21.06 g L^?1 total ABE. In this experiment an ABE yield and productivity of 0.41 and 0.31 g L^?1 h^?1 was achieved, respectively. Fermentation of untreated corn stover hydrolysate (CSH) exhibited no growth and no ABE production; however, upon dilution with water (two fold) and wheat straw hydrolysate (WSH, ratio 1:1), 16.00 and 18.04 g L^?1 ABE was produced, respectively. These experiments resulted in ABE productivity of 0.17–0.21 g L^?1 h^?1. Inhibitors present in CSH were removed by treating the hydrolysate with Ca(OH)₂ (overliming). The culture was able to produce 26.27 g L^?1 ABE after inhibitor removal. Untreated switchgrass hydrolysate (SGH) was poorly fermented and the culture did not produce more than 1.48 g L^?1 ABE which was improved to 14.61 g L^?1. It is suggested that biomass pretreatment methods that do not generate inhibitors be investigated. Alternately, cultures resistant to inhibitors and able to produce butanol at high concentrations may be another approach to improve the current process.     

Not supposed to feel this: Traditional masculinity in psychotherapy with male veterans returning from Afghanistan and Iraq.

Traditional masculine socialization presents challenges in psychotherapy, for example, by decreasing the likelihood of help-seeking and by making emotion-laden content more difficult to address. While this has been established in civilian populations, more intense forms of masculine socialization found in military settings may amplify such issues in male veteran populations. Male veterans returning from and Afghanistan (OEF) and Iraq (OIF) exhibit strong traditional masculine socialization and generally present in a unique manner. It is posited that OEF/OIF male veterans' unique presentation is in large part because of an interaction between high degrees of endorsement of traditional masculine gender role norms, relative youth, recency of distressing events, and recent experience in the social context of the military where traditional masculinity is reinforced. The impact of these variables on the psychotherapeutic process for male OEF/OIF veterans is significant and likely adds to ambivalence about change and increases dropout from psychotherapy. Modifications of traditional psychotherapeutic approaches designed to address traditional masculine gender role norms and their many interactions with other variables are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Hyperbolic Theory for Advection-Diffusion Problems: Mathematical Foundations and Numerical Modeling

Linear parabolic diffusion theories based on Fourier’s or Fick’s laws predict that disturbances can propagate at infinite speed. Although in some applications, the infinite speed paradox may be ignored, there are many other applications in which a theory that predicts propagation at finite speed is mandatory. As a consequence, several alternatives to the linear parabolic diffusion theory, that aim at avoiding the infinite speed paradox, have been proposed over the years. This paper is devoted to the mathematical, physical and numerical analysis of a hyperbolic convection-diffusion theory.     

Forming-Limit Diagrams for Magnesium AZ31B and ZEK100 Alloy Sheets at Elevated Temperatures

Modern design and manufacturing methodologies for magnesium (Mg) sheet panels require formability data for use in computer-aided design and computer-aided engineering tools. To meet this need, forming-limit diagrams (FLDs) for AZ31B and ZEK100 wrought Mg alloy sheets were developed at elevated temperatures for strain rates of 10^?3 and 10^?2 s^?1. The elevated temperatures investigated range from 250 to 450 °C for AZ31B and 300 to 450 °C for ZEK100. The FLDs were generated using data from uniaxial tension, biaxial bulge, and plane-strain bulge tests, all carried out until specimen rupture. The unique aspect of this study is that data from materials with consistent processing histories were produced using consistent testing techniques across all test conditions. The ZEK100 alloy reaches greater major true strains at rupture, by up to 60%, than the AZ31B alloy for all strain paths at all temperatures and strain rates examined. Formability limits decrease only slightly with a decrease in temperature, less than 30% decrease for AZ31B and less than 35% decrease for ZEK100 as the temperature decreases from 450 to 300 °C. This suggests that forming processes at 250-300 °C are potentially viable for manufacturing complex Mg components.     

Modelling of the radiative properties of an opaque porous ceramic layer

Solid Oxide Fuel Cells (SOFCs) operate at temperatures above 1,100 K where radiation effects can be significant. Therefore, an accurate thermal model of an SOFC requires the inclusion of the contribution of thermal radiation. This implies that the thermal radiative properties of the oxide ceramics used in the design of SOFCs must be known. However, little information can be found in the literature concerning their operating temperatures. On the other hand, several types of ceramics with different chemical compositions and microstructures for designing efficient cells are now being tested. This is a situation where the use of a numerical tool making possible the prediction of the thermal radiative properties of SOFC materials, whatever their chemical composition and microstructure are, may be a decisive help. Using this method, first attempts to predict the radiative properties of a lanthanum nickelate porous layer deposited onto an yttria stabilized zirconium substrate can be reported.     

Photocatalytic degradation of organic dyes by mesoporous nanocrystalline anatase

Mesoporous nanocrystalline anatase was prepared via EISA employing P123 and CTAB as structure directing agents. The resultant mesoporous crystalline phases exhibited specific surface areas as high as ∼150 m² g⁻¹, average unimodal pore sizes of ∼3 nm and ∼6 nm, and average crystallite size of ∼10 nm; and were used as photocatalysts for the UV degradation of methylene blue, methyl orange, methyl red and rhodamine 6G. The mesoporous anatase phases photodegraded MB, MO and MR ∼2–3 times faster than conventional nanocrystalline anatase and showed limited photocatalytic activity for rhodamine 6G.     

Lattice dynamics,thermodynamics and elastic properties of monoclinic Li2CO3 from density functional theory

Monoclinic Li₂CO₃ has been identified as a critical component of the solid electrolyte interphase (SEI), a passivating film that forms on Li-ion battery anode surfaces. Here, lattice dynamics, finite temperature thermodynamics and the elastic properties of monoclinic Li₂CO₃ are examined with density functional theory (DFT) and various exchange–correlation functionals. To account for LO-TO splittings in phonon dispersion relations of Li₂CO₃, which is a polar compound, a mixed-space phonon approach is employed. Bond strengths between atoms are quantitatively explored with phonon force constants. Temperature variations of the entropy, enthalpy, isobaric heat capacity and linear (average) thermal expansion are computed using the quasiharmonic approach. The single-crystal elasticity tensor components along with polycrystalline bulk, shear and Young’s moduli are computed with a least-squares approach based upon the stress tensor computed from DFT. Computed thermodynamic properties as well as structural and elastic properties of the monoclinic Li₂CO₃ are in close accord with available theoretical and experimental data. In contrast to a recent DFT study, however, computed vibrational spectra suggest that neither the monoclinic Li₂CO₃ nor its high-temperature hexagonal phase exhibits either elastic or vibrational instabilities.     

WebBase: a repository of Web pages

In this paper, we study the problem of constructing and maintaining a large shared repository of Web pages. We discuss the unique characteristics of such a repository, propose an architecture, and identify its functional modules. We focus on the storage manager module, and illustrate how traditional techniques for storage and indexing can be tailored to meet the requirements of a Web repository. To evaluate design alternatives, we also present experimental results from a prototype repository called WebBase, that is currently being developed at Stanford University.     

Temperature response to reactant concentration perturbations in a packed‐bed reactor

Unsteady‐state operations are known to enhance the performance of some packed‐bed reactor systems. However, negative effects of this type of operation should not be neglected. Temperature excursions developed during transients may accelerate some deactivation mechanisms, reducing catalyst lifetime and selectivity. Temperature response to perturbations in reactant concentration was studied for CO oxidation over Pt/Al₂O₃ in a packed‐bed reactor. Experiments were conducted in the CO concentration range for which multiple steady states are observed. Temperature and concentration profiles in the packed‐bed reactor at steady state were found to depend on the dynamic history of the reactor prior to the steady‐state condition.