Grain Boundary Responses to Heterogeneous Deformation in Tantalum Polycrystals

The evolution of heterogeneous deformation in a tantalum polycrystal was examined during a three-point bending experiment using electron backscatter pattern mapping. Slip bands formed at strains as low as 1%, and they became more intense with strain. Heterogeneous deformation was evident as intragranular orientation gradients as large as 30° were observed after a strain of about 8%. Nonmonotonic changes in the local average misorientation distribution were observed, implying that dislocation substructure developed in a complex manner. Slip bands were analyzed using plane traces computed from local orientation information. With the assumption of uniaxial stress, Schmid factors for favorable slip systems were identified for each grain and compared with observations, showing evidence for macroscopic activity on both {110} and {112} slip systems. Reconstructed boundary data were used to estimate the geometric potential for slip transfer at grain boundaries. The correlations indicated that when active slip systems were favorably oriented for slip transfer across the boundary, it was often observed in the form of continuous slip bands aligned across the boundary. In boundaries where geometrical alignment and Schmid factors were not favorable for slip transfer, there was a higher likelihood to form ledges (topographic discontinuities) along the grain boundaries. Dislocation pileups at grain boundaries were also correlated with a low potential for slip transfer.     

Investigation of NCN and prompt-NO formation in low-pressure C1–C4 alkane flames

Temperature, CH, NCN, and NO profiles were measured for eight low-pressure hydrocarbon flames fueled by methane, ethane, propane, and butane using laser-induced fluorescence (LIF) diagnostics. These measurements were used (1) to assess NCN and prompt-NO formation chemistry across a series of fuels of increasing number of carbons at different equivalence ratios (? = 1.07 and 1.28); (2) to examine the predictive capabilities of current C1–C4 hydrocarbon and NCN formation/consumption combustion mechanisms on properly capturing prompt-NO formation and (3) to examine the postulation that additional prompt-NO precursors (other than CH) exist for fuels larger than methane. For a given equivalence ratio, the measured peak CH concentration is fairly constant across all four fuels, while both the peak NCN and post-flame NO concentrations steadily increase. Furthermore, it is found that as the fuels increase in number of carbons, i.e., methane to butane, the correlation between the peak NCN and post-flame NO remains high, while the correlation between peak CH and peak NCN and peak CH and post-flame NO becomes increasingly lower. This is especially evident for rich flame cases. The experimental profiles are compared to numerical calculations using two comprehensive kinetic mechanisms suitable for C4 chemistry, where the CH + N₂ → NCN + H reaction is assumed as the only prompt-NO initiation reaction. For the ? = 1.28 flame cases, CH is over-predicted using both mechanisms for all four fuels and by as much as 60%, while for the ? = 1.07 cases, CH is predicted to within 15% of the experimentally-derived results, although there is some discrepancy concerning the spatial locations of the CH profiles. For both NCN and NO, there is an increasing under-prediction for the ? = 1.28 cases as the fuel increases in number of carbons, while for the ? = 1.07 cases there is a systematic under-prediction of NCN and NO with a weaker (although evident) fuel dependence. From the experimental results and the comparison to modeling predictions, it is apparent that additional work concerning CH formation and consumption kinetics is necessary to accurately capture the CH concentration profiles across a broad range of conditions. Furthermore the comparisons to the modeling predictions using only a single prompt-NO precursor, CH, indicate a reasonable plausibility that (an) additional prompt-NO precursor (s) exist and become important when considering fuels larger than methane, especially under rich flame conditions. Possible precursors in addition to CH are discussed.     

Modeling of mixed-mode crack growth in ductile thin sheets under combined in-plane and out-of-plane loading

This paper describes a modeling approach for analyzing mixed-mode crack growth events in ductile thin-sheet materials under large deformation and combined in-plane and out-of-plane loading conditions. The remote mixed-mode I/III loading leads to local mixed-mode I/II/III fields near the crack front. Making use of full-field surface deformation measurements, finite element models of mixed-mode I/III stable tearing events in thin-sheet specimens have been developed. Model predictions have been compared with experimental measurements (a) just prior to initial crack growth and (b) during stable tearing crack growth. Analyses of curvilinear crack growth events are carried out using a nodal release option or a local re-meshing option and using a generalized CTOD parameter with experimentally measured critical CTOD values. Results of this study suggest that the modeling approach can be employed to numerically re-construct experimental crack growth events in thin plate specimens. This offers a viable means of analyzing and understanding the mixed-mode crack growth events and provides a tool for further investigations of 3D crack front fields (which are otherwise unavailable experimentally) and for the study of fracture criteria for stable tearing events.     

Simulation of mixed-mode I/III stable tearing crack growth events using the cohesive zone model approach

A cohesive zone model (CZM) approach is applied to simulate mixed-mode I/III stable tearing crack growth events in specimens made of 6061-T6 aluminum alloy and GM 6208 steel. The materials are treated as elastic–plastic following the \(J_{2}\) flow theory of plasticity, and the triangular cohesive law is employed to describe the traction-separation relation in the cohesive zone ahead of crack front. A hybrid numerical/experimental approach is employed in simulations using 3D finite element method. For each material, CZM parameter values are chosen by matching simulation prediction with experimental measurement (Yan et al. in Int J Fract 144:297–321, 2009), of the crack extension-time curve for the \(30^{\circ }\) mixed-mode I/III stable tearing crack growth test. With the same sets of CZM parameter values, simulations are performed for the \(60^{\circ }\) loading cases. Good agreements are reached between simulation predictions of the crack extension-time curve and experimental results. The variations of CTOD with crack extension are calculated from CZM simulations under both \(30^{\circ }\) and \(60^{\circ }\) mixed-mode I/III conditions for the aluminum alloy and steel respectively. The predictions agree well with experimental measurements (Yan et al. in Int J Fract 144:297–321, 2009). The findings of the current study demonstrate the applicability of the CZM approach in mixed-mode I/III stable tearing simulations and reaffirm the connection between CTOD and CZM based simulation approaches shown previously for mixed-mode I/II crack growth events.     

Interlinking Music-Related Data on the Web

This article describes how Semantic Web technologies can be used to interlink musical data sources that have traditionally been isolated and difficult to integrate.     

Measuring people intensively.

An overview is provided of measures that are administered repeatedly in daily life. Variations of this methodology have been referred to as ecological momentary assessment, diary methods, daily process measures, and most broadly as intensive repeated measures in naturalistic settings (IRM-NS). Contrasts are drawn between IRM-NS methods on the basis of different sampling strategies, such as time-contingent recording, signal-contingent recording, and event-contingent recording. Common threats to the internal validity, construct validity, and external validity of IRM-NS measures are reviewed, along with ways to reduce these threats. The statistical analysis of IRM-NS data is considered, with a particular focus on the investigation of intraindividual variability. An extended example is provided of an IRM-NS measure, an event-contingent recording method for the assessment of interpersonal behaviour. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anodic Films on Aluminium and its Alloys for Protection against Corrosion

The effect of periodic reversal of current upon concentration over-potential and current efficiencies in electrolysis has been investigated for a metal depositon reaction which is purely diffusion-controlled. In the cathodic part of the cycle the onset of limiting diffusion conditions is deferred, and the current efficiency and average rate of metal deposition are increased. The magnitude of the effect depends upon the ratio of the quantities of electricity passed in anodic and cathodic pulses, and it is greatest under conditions such that diffusion away from the electrode of anodically-formed ions is minimised. Quantitative theoretical treatment is possible in a limiting case to which actual experimental results approximate. Supplementary experiments have been carried out in more complex cases of metal deposition.     

Sequential analysis of the effects of naltrexone on the environmental meditation of self-injurious behavior.

Accumulated evidence shows that biology and the environment can mediate self-injurious behavior (SIB) in persons with mental retardation. Whether pharmacological treatment alters the environmental mediation of self-injury is unclear. Opioid antagonist effects on sequential dependencies for self-injury were studied in the context of experimental single-subject double-blind placebo-controlled designs. Direct observational data were collected for 4 adult subjects in real time on daily rate of SIB and staff interactions. Clinically significant reductions (i.e., ≥ 33%) in SIB rate were observed for 3 of the 4 subjects. For all subjects, the magnitude of the sequential dependency between staff behavior and self-injury was significantly greater during treatment with naltrexone than during treatment with a placebo. Results are discussed in relation to behavioral mechanisms of action regulating medication effects for self-injury. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Microbial Transglutaminase on the Wheat Proteins of Bread and Croissant Dough

ABSTRACT: Transglutaminase is a crosslinking enzyme that is finding increasing use in foods, yet the molecular changes responsible for its effects are not fully understood. Proteins were extracted from bread and croissant doughs that had been treated with transglutaminase and compared to those from control doughs by size exclusion high performance liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. Transglutaminase increased the amount of protein extracted in the gliadin fraction in both bread and croissant doughs. In croissant doughs, a corresponding decrease in the protein extracted in the albumin to globulin fraction was seen. In each case, crosslinking of the high molecular weight glutenins was observed. The possible role of each of these changes on the functional properties of baked products is discussed.