Effect of orientation stability on recrystallization textures of deformed aluminium single crystals

High purity Al single crystals of the Cube (0 0 1)[1 0 0] and rotated Cube (0 1 1)[0 1 ¯ 1] orientations have been deformed in plane strain compression in a channel die. Deformation was carried out at temperatures between 25 and 600 8C up to strains of 1.2. The as-deformed microstructure has been characterised using electron microscopy and electron backscattered diffraction (EBSD).
Annealing was carried out for various times and temperatures. The recrystallized microstructure has been studied using electron microscopy, and the orientation of recrystallized grains determined using EBSD. After cold deformation and annealing both orientations exhibited a random recrystallization texture component. After hot deformation both orientations retained a similar annealing texture to their starting deformation texture. The annealing texture of deformed single crystals was found to be more sensitive to the temperature of deformation than the stability of the orientation.

Dots versus antidots : computational exploration of structure, magnetism, and half-metallicity in boron-nitride nanostructures

Triangle-shaped nanohole, nanodot, and lattice antidot structures in hexagonal boron-nitride (h-BN) monolayer sheets are characterized with density functional theory calculations utilizing the local spin density approximation. We find that such structures may exhibit very large magnetic moments and associated spin splitting. N-terminated nanodots and antidots show strong spin anisotropy around the Fermi level, that is, half-metallicity. While B-terminated nanodots are shown to lack magnetism due to edge reconstruction, B-terminated nanoholes can retain magnetic character due to the enhanced structural stability of the surrounding two-dimensional matrix. In spite of significant lattice contraction due to the presence of multiple holes, antidot super lattices are predicted to be stable, exhibiting amplified magnetism as well as greatly enhanced half-metallicity. Collectively, the results indicate new opportunities for designing h-BN-based nanoscale devices with potential applications in the areas of spintronics, light emission, and photocatalysis. © 2009 American Chemical Society.

Examination of the stability and consistency of investigative interviewer performance across similar mock interview contexts

Purpose. Three studies examined the degree to which investigative interviewers’ adherence to best-practice guidelines is consistent across similar mock interviews.
Method. In each study, two interviews were administered within a period of several hours. Further, group and individual stability of interviewer performance was analysed, and performance was measured by calculating the proportion of open-ended and leading questions as well as the presence of predetermined problem behaviours. The studies varied depending on the type of interview paradigm employed. Interviewer performance in Study 1was measured in a group context where participants rotated between the role of interviewer, child respondent, and observer. In Study 2, an adult played the role of a child recalling abuse but this occurred in isolation (participants did not observe others or play the child). Study 3 was similar to Study 2 except that in each interview an unfamiliar child aged 5–7 years recalled an innocuous event.
Results. Interviewer performance was relatively stable across tasks, although the strength of the relationship between measures varied across analyses. Improvement in open-ended question usage occurred in Study 1 but not Studies 2 and 3. Irrespective of the assessment context, the dichotomous rating scale yielded greater consistency than when questions were tallied. Further, group stability overestimated individual stability. The practical implications of these findings for trainers and researchers are discussed.

Milk lactate determination with a rotating bioreactor based on an electron transfer mediated by osmium complexes incorporating a continuous-flow/stopped-flow system

The high sensitivity that can be attained using a bienzymatic system and mediated by the redox polymer [Os(bpy)₂ClPyCH₂NHpoly(allylamine)] (Os-PAA), has been verified by on-line interfacing of a rotating bioreactor and continuous-flow/stopped-flow/continuous-flow processing. When the hydrogen peroxide formed by LO_x layer reaches the inner layer, the electronic flow between the immobilized peroxidase and the electrode surface produces a current, proportional to lactate concentration. The determination of lactate was possible with a limit of detection of 5 nmol l⁻¹ in the processing of as many as 30 samples per hour. This arrangement allows working in undiluted milk samples with a good stability and reproducibility. Horseradish peroxidase [EC 1.11.1.7] and Os-PAA were covalently immobilized on the glassy carbon electrode surface (upper cell body), lactate oxidase [EC 1.1.3.x] was immobilized on a disk that can be rotated.

Structure effect on the oxygen permeation properties of barium bismuth iron oxide membranes

In this work, we investigated the oxygen permeation properties of barium bismuth iron oxide within the family of [Ba_2−3xBi_3x−1][Fe_2xBi_1−2x]O_2+3x/2 for x = 0.17–0.60. The structure changed progressively from cubic to tetragonal and then to hexagonal as function of x in accordance with the different relative amounts of bismuth on A-site and B-site of ABO_3−δ perovskite lattices. We found that the oxygen flux and electrical conductivity correlated strongly, and it was prevalent for the cubic structure (x = 0.33–0.40) which conferred the highest oxygen flux of 0.59 ml min⁻¹ cm⁻² at 950 °C for a disk membrane x = 0.33 with a thickness of 1.2 mm. By reducing the thickness of the disk membrane to 0.8 mm, the oxygen flux increased to 0.77 ml min⁻¹ cm⁻², suggesting both surface kinetics and ion diffusion controlled oxygen flux, though the former was more prominent at higher temperatures. For disk membranes x = 0.45–0.60, the perovskite structure changed to tetragonal and hexagonal, and the oxygen flux was insignificant below 900 °C, clearly indicating electron conduction properties only. However, for two compositions with relatively high bismuth content, e.g. x = 0.55 and 0.60, there was a sudden and significant rise of oxygen permeability above 900 °C, by more than one order of magnitude. These materials changed conduction behavior from metallic to semiconductor at around 900 °C. These results suggest the advent of mixed ionic electronic conducting properties caused by the structure transition as bismuth ions changed their valence states to compensate for the oxygen vacancies formed within the perovskite lattices.

One image reduction algorithm for RGB color images

We investigate the problem of combining or aggregating several color values given in coding scheme RGB. For this reason, we study the problem of averaging values on lattices, and in particular on discrete product lattices. We study the arithemtic mean and the median on product lattices. We apply these aggregation functions in image reduction and we present a new algorithm based on the minimization of penalty functions on discrete product lattices.

Aggregation for Atanassov's intuitionistic and interval valued fuzzy sets: the median operator

Atanassov's intuitionistic fuzzy sets (AIFS) and interval valued fuzzy sets (IVFS) are two generalizations of a fuzzy set, which are equivalent mathematically although different semantically. We analyze the median aggregation operator for AIFS and IVFS. Different mathematical theories have lead to different definitions of the median operator. We look at the median from various perspectives: as an instance of the intuitionistic ordered weighted averaging operator, as a Fermat point in a plane, as a minimizer of input disagreement, and as an operation on distributive lattices. We underline several connections between these approaches and summarize essential properties of the median in different representations.

Color image reduction by minimizing penalty functions

In image processing, particularly in image reduction, averaging aggregation functions play an important role. In this work we study the aggregation of color values (RGB) and we present an image reduction algorithm for RGB color images. For this purpose, we define and study aggregation functions and penalty functions in product lattices. We show how the arithmetic mean and the median can be obtained by minimizing specific penalty functions. Moreover, we study other penalty functions and we show that, in general, aggregation functions on product lattices do not coincide with the cartesian product of the corresponding aggregation functions. Finally, we make an experimental study where we test our reduction algorithm and we analyze the stability of the penalty functions in images affected by noise.

The evolution of microbands and their interaction with NbC precipitates during hot deformation of a Fe-30Ni-Nb model austenitic steel

The present work has investigated the evolution of microbands (MBs) and their interaction with strain-induced NbC precipitates during uniaxial compression of a model austenitic Fe-30Ni-Nb steel at 925 °C. The (1 1 0) fibre grains, both without and with copious amounts of precipitates, contained up to large strains crystallographic MBs aligned close to the highly stressed {1 1 1} slip planes having large Schmid factors. The MBs thus maintained their crystallographic character during straining, through continuously rearranging themselves, and did not follow the macroscopically imposed rigid body rotation. During double-pass deformation, fine NbC particles formed at short inter-pass holding remained strongly pinned at small reloading strains and appeared to be dragged by rearranging MB walls. With increasing reloading strain, the fine precipitates became progressively released from the above walls. During reloading after increased holding time, the coarsened particles tended with their increased size to become increasingly detached from the MB walls already at a small strain. The precipitate-free MB wall segments rearranged during straining to maintain their crystallographic alignment, while the detached precipitates followed the sample shape change and rotated towards the compression plane. The MB wall rearrangement generally occurred through cooperative migration of the corresponding dislocation networks.

Ultra-wideline 14N solid-state NMR as a method for differentiating polymorphs: glycine as a case study

Nitrogen-14 solid-state NMR (SSNMR) is utilized to differentiate three polymorphic forms and a hydrochloride (HCl) salt of the amino acid glycine. Frequency-swept Wideband, Uniform Rate, Smooth Truncated (WURST) pulses were used in conjunction with Carr-Purcell Meiboom-Gill refocusing, in the form of the WURST-CPMG pulse sequence, for all spectral acquisitions. The ¹⁴N quadrupolar interaction is shown to be very sensitive to variations in the local electric field gradients (EFGs) about the ¹⁴N nucleus; hence, differentiation of the samples is accomplished through determination of the quadrupolar parameters CQ and ηQ, which are obtained from analytical simulations of the ¹⁴N SSNMR powder patterns of stationary samples (i.e., static NMR spectra). Additionally, differentiation of the polymorphs is also possible via the measurement of ¹⁴N effective transverse relaxation time constants, T^eff2(¹⁴N). Plane-wave density functional theory (DFT) calculations, which exploit the periodicity of crystal lattices, are utilized to confirm the experimentally determined quadrupolar parameters as well as to determine the orientation of the ¹⁴N EFG tensors in the molecular frames. Several signal-enhancement techniques are also discussed to help improve the sensitivity of the ¹⁴N SSNMR acquisition method, including the use of selective deuteration, the application of the BRoadband Adiabatic INversion Cross-Polarization (BRAIN-CP) technique, and the use of variable-temperature (VT) experiments. Finally, we examine several cases where ¹⁴N VT experiments employing Carr-Purcell-Meiboom-Gill (CPMG) refocusing are used to approximate the rotational energy barriers for RNH3⁺ groups.

Orientation dependence of the deformation microstructure in a Fe-30Ni-Nb model austenitic steel subjected to hot uniaxial compression

The present work was aimed at a detailed investigation of the orientation dependence of the microstructure characteristics in a Fe-30Ni-Nb austenitic model steel subjected to hot uniaxial compression at 1198 K (925 °C) at a strain rate of 1 s−1 to several strain levels up to 1.0. The quantification of the substructure evolution as a function of strain was performed for the stable 〈011〉 oriented grains. Other grain orientations were also investigated in detail at a strain of 0.2. The 〈110〉 oriented grains contained self-screening arrays of “microbands” (MBs) aligned with high Schmid factor {111} slip planes. The MB crystallographic alignment was largely maintained up to a strain of 1.0, which suggests that the corresponding boundaries kept continuously rearranging themselves during straining and did not follow the sample shape change. The mean MB spacing decreased and misorientation angle increased with strain towards saturation, indicating the operation of the “repolygonization” dynamic recovery mechanism. The non-〈011〉 oriented grains displayed a strong tendency to split during deformation into deformation bands having alternating orientations and being mutually rotated by large angles. The bands were separated by transition regions comprising arrays of closely spaced, extended sub-boundaries collectively accommodating large misorientations across very small distances.