The Peierls--Nabarro FE model in two-phase microstructures -- a comparison with atomistics

This paper evaluates qualitatively as well as quantitatively the accuracy of a recently proposed Peierls--Nabarro Finite Element (PN-FE) model for dislocations by a direct comparison with an equivalent molecular statics simulation. To this end, a two-dimensional microstructural specimen subjected to simple shear is considered, consisting of a central soft phase flanked by two hard-phase regions. A hexagonal atomic structure with equal lattice spacing is adopted, the interactions of which are described by the Lennard--Jones potential with phase specific depths of its energy well. During loading, edge dislocation dipoles centred in the soft phase are introduced, which progress towards the phase boundaries, where they pile up. Under a sufficiently high external shear load, the leading dislocation is eventually transmitted into the harder phase. The homogenized PN-FE model is calibrated to an atomistic model in terms of effective elasticity constants and glide plane properties as obtained from simple uniform deformations. To study the influence of different formulations of the glide plane potential, multiple approaches are employed, ranging from a simple sinusoidal function of the tangential disregistry to a complex model that couples the influence of the tangential and the normal disregistries. The obtained results show that, qualitatively, the dislocation structure, displacement, strain fields, and the dislocation evolution are captured adequately. The simplifications of the PN-FE model lead, however, to some discrepancies within the dislocation core. Such discrepancies play a dominant role in the dislocation transmission process, which thus cannot quantitatively be captured properly. Despite its simplicity, the PN-FE model proves to be an elegant tool for a qualitative study of edge dislocation behaviour in two-phase microstructures, although it may not be quantitatively predictive.Comment: 29 pages, 11 figures, 5 tables, abstract shortened to fulfill 1920 character limit, small changes after revie

Resonance-state-induced superconductivity at high Indium contents in In-doped SnTe

We report a reinvestigation of superconducting Sn$_{1-x}$In$_{x}$Te at both low and high In doping levels. Analysis of the superconductivity reveals a fundamental change as a function of \textit{x}: the system evolves from a weakly coupled to a strongly coupled superconductor with increasing indium content. Hall Effect measurements further show that the carrier density does not vary linearly with Indium content; indeed at high Indium content, the samples are overall \textit{n}-type, which is contrary to expectations of the standard picture of In$^{1+}$ replacing Sn$^{2+}$ in this material. Density functional theory calculations probing the electronic state of In in SnTe show that it does not act as a trivial hole dopant, but instead forms a distinct, partly filled In 5\textit{s} - Te 5\textit{p} hybridized state centered around E$_F$, very different from what is seen for other nominal hole dopants such as Na, Ag, and vacant Sn sites. We conclude that superconducting In-doped SnTe therefore cannot be considered as a simple hole doped semiconductor.Comment: 12 pages and 7 figure

Harmonic behavior of metallic glasses up to the metastable melt

In two amorphous alloys ZrTiCuNiBe and ZrAlNiCu coherent neutron scattering has been measured over five decades in energy, including measurements in the metastable melt of a metallic alloy more than 80 K above Tg. In the vibrational spectra a pronounced "boson" peak is found: Even in crystallized samples the density of states exceeds the Debye ω2 model, and in the amorphous state low-frequency vibrations are further enhanced. The peak position shows no dispersion in q, while intensities are strongly correlated with the static structure factor. Over the full energy range the temperature dependence is strictly harmonic. From high-energy resolution measurements we establish lower bounds for the temperatures at which structural α and fast β relaxation become observable

An in-depth look at prior art in fast round-robin arbiter circuits

Arbiters are found where shared resources exist such as busses, switching fabrics, processing elements. Round-robin is a fair arbitration method, where requestors get near-equal shares of a common resource or service. Round-robin arbitration (RRA) finds use in network switches/routers and processor boards/systems as well as many other applications that have concurrency. Today's electronic systems require arbiters with hundreds of ports (e.g., switching fabrics with virtual I/O queues) and clock speeds near the limits of even the latest microelectronics fabrication processes/libraries. Achieving high clock speeds in the presence of large number of ports is only possible with highly parallel arbiter architectures. This paper presents an in-depth literature survey of previous work on this problem. It looks at RRA work in the literature in a bigger context, then defines the typical RRA problem (RRA_typical), and specifically investigates work on fast architectures that solve the RRA_typical problem. There are five such works that are really competitive. This report takes a very in-depth look at these works. It explains each architecture and how/why it works from a unique perspective that cannot be found in the original publication of that architecture. It also proposes improvements to these architectures. We wrote generators for the improved versions of these architectures. We will share a summary of synthesis results in this report – although a detailed account of how these results were obtained and their analysis is the subject of another (upcoming) publicatio

Within-herd effects of age at test day and lactation stage on test-day yields

Variance ratios were estimated for random within-herd effects of age at test day and lactation stage, on test-day yield and somatic cell score to determine whether including these effects would improve the accuracy of estimation. Test-day data starting with 1990 calvings for the entire US Jersey population and Holsteins from California, Pennsylvania, Wisconsin, and Texas were analyzed. Test-day yields were adjusted for across-herd effects using solutions from a regional analysis. Estimates of the relative variance ( fraction of total variance) due to within-herd age effects were small, indicating that regional adjustments for age were adequate. The relative variances for within-herd lactation stage were large enough to indicate that accuracy of genetic evaluations could be improved by including herd stage effects in the model for milk, fat, and protein, but not for somatic cell score. Because the within-herd lactation stage effect is assumed to be random, the effect is regressed toward the regional effects for small herds, but in large herds, lactation curves become herd specific. Model comparisons demonstrated the greater explanatory power of the model with a within-herd-stage effect as prediction error standard deviations were greater for the model without this effect. The benefit of the within-herd-stage effects was confirmed in a random regression model by comparing variance components from models with and without random within-herd regressions and through log-likelihood ratio tests

Effects of Forage Maturity on Phosphorus Digestion in Beef Cows

For environmental reasons, minimizing phosphorus excretion from cattle is of great interest. Current estimates of forage phosphorus digestibility by cattle consider that phosphorus digestibility does not change with composition of the pasture. To better estimate phosphorus (P) excretion, estimates of P digestibility for forages of different compositions are needed. Four crossbred cow/calf pairs were stocked on four pastures managed with grazing (G) or grazing with hay removal (G/H). Forage was maintained in paddocks at 50% removal. Collected pasture samples and fecal samples from cows administered chromic oxide were analyzed for P, NDF, and ADL contents. Rumen evacuations of steers were conducted to evaluate composition of consumed forage for each treatment. Forage analyzed from paddocks where steers grazed demonstrated no grazing management effects on composition, which was evidenced by no differences in composition of rumen contents of the steers. Analysis of the 13th rib bone concludes the cattle were not deficient in phosphorus. Year 1 results suggest that pastures managed under a combination of grazing and initial hay removal resulted in greater P content of the forage and concomitant increased P excretion by cows consuming that forage. There was no treatment effect for P retention, however a there was a date effect with the G treatment having higher P retention in July and September. These results verify that grazing management practices can have a substantial effect on water pollution potential

Das falsch vermessene Kunstwerk:zur kunstgeographischen Bestimmung stilistischer Stetigkeit im zeitlichen Wandel, wissenschaftsgeschichtlich nach den Quellen dargestellt

Die Kunstgeographie hat derzeit in der deutschen Kunsthistoriographie einen schweren Stand. Ihre methodologische Annahme eines Raumstiles machte sie vordergründig mit den nationalsozialistischen Raumphantasien gemein. Diese bis in die Gegenwart anhaltende Perhorreszenz freilich verkennt, daß die Vorstellung eines Zusammenspiels landschaftlichen Wesens und eines daraus emergierenden sittlichen wie künstlerischen Geschehens, die Vorstellung mithin einer „Daseinsursprünglichkeit überindividueller Zusammenhänge“ (Thomas Mann) auf die Antike zurückgeht und sich bis in die Moderne durchgehalten hat. Vor allem die Fundamentalontologie Martin Heideggers erweist die deutsche kunstgeographische Forschung der 1920er und 30er Jahre (Dagobert Frey, Paul Pieper, Hans Erich Kubach u.v.m.) als eine phänomenologisch-hermeneutische Wissenschaft, der es um die Aufzeigung einer sich in den Kunstwerken aussprechenden „Gleichzeitigkeit des Ungleichzeitigen“ (Wilhelm Pinder) im Kunstgeschehen angelegen ist