Cryogenic Stress-Driven Grain Growth Observed via Microcompression with in situ Electron Backscatter Diffraction

The deformation of materials at cryogenic temperature is of interest for space, arctic, and fundamental science applications. In this work, a custom-built cooling system attached to a commercial picoindenter was used for in situ cryogenic microcompression testing of equal-channel angular-pressed copper with real-time electron backscatter diffraction. Stress-driven grain growth at cryogenic temperatures was observed during a series of elastic and plastic deformations. These results provide direct evidence for the previously predicted phenomenon, whereas previous ex situ examinations demonstrated coarsening after cryogenic loading when samples were not maintained at cryogenic temperatures between deformation and characterization

Noncommutative Solitons in Open N=2 String Theory

Coincident D2-branes in open N=2 fermionic string theory with a B-field background yield an integrable modified U(n) sigma model on noncommutative R^{2,1}. This model provides a showcase for an established method (the `dressing approach') to generate solutions for integrable field equations, even in the noncommutative case. We demonstrate the technique by constructing moving U(1) and U(2) solitons and by computing their energies. It is outlined how to derive multi-soliton configurations with arbitrary relative motion; they correspond to D0-branes moving inside the D2-branes.Comment: 1+13 pages, LaTeX; v2: eq.(45) corrected, constructing of multi-solitons enhanced, one reference added; v3: minor corrections but soliton/antisoliton convention interchanged, final JHEP versio

Tunable Hydrogen Storage in Magnesium - Transition Metal Compounds

Magnesium dihydride (\mgh) stores 7.7 weight % hydrogen, but it suffers from a high thermodynamic stability and slow (de)hydrogenation kinetics. Alloying Mg with lightweight transition metals (TM = Sc, Ti, V, Cr) aims at improving the thermodynamic and kinetic properties. We study the structure and stability of Mg$_x$TM$_{1-x}$H$_2$ compounds, $x=[0$-1], by first-principles calculations at the level of density functional theory. We find that the experimentally observed sharp decrease in hydrogenation rates for $x\gtrsim0.8$ correlates with a phase transition of Mg$_x$TM$_{1-x}$H$_2$ from a fluorite to a rutile phase. The stability of these compounds decreases along the series Sc, Ti, V, Cr. Varying the transition metal (TM) and the composition $x$, the formation enthalpy of Mg$_x$TM$_{1-x}$H$_2$ can be tuned over the substantial range 0-2 eV/f.u. Assuming however that the alloy Mg$_x$TM$_{1-x}$ does not decompose upon dehydrogenation, the enthalpy associated with reversible hydrogenation of compounds with a high magnesium content ($x=0.75$) is close to that of pure Mg.Comment: 8 pages, 5 figure

Modeling pedestrian evacuation movement in a swaying ship

With the advance in living standard, cruise travel has been rapidly expanding around the world in recent years. The transportation of passengers in water has also made a rapid development. It is expected that ships will be more and more widely used. Unfortunately, ship disasters occurred in these years caused serious losses. It raised the concern on effectiveness of passenger evacuation on ships. The present study thus focuses on pedestrian evacuation features on ships. On ships, passenger movements are affected by the periodical water motion and thus are quite different from the characteristic when walking on static horizontal floor. Taking into consideration of this special feature, an agent-based pedestrian model is formulized and the effect of ship swaying on pedestrian evacuation efficiency is investigated. Results indicated that the proposed model can be used to quantify the special evacuation process on ships.Comment: Traffic and Granular Flow'15, At Delft, the Netherland

11 x 11 Domineering is Solved: The first player wins

We have developed a program called MUDoS (Maastricht University Domineering Solver) that solves Domineering positions in a very efficient way. This enables the solution of known positions so far (up to the 10 x 10 board) much quicker (measured in number of investigated nodes). More importantly, it enables the solution of the 11 x 11 Domineering board, a board up till now far out of reach of previous Domineering solvers. The solution needed the investigation of 259,689,994,008 nodes, using almost half a year of computation time on a single simple desktop computer. The results show that under optimal play the first player wins the 11 x 11 Domineering game, irrespective if Vertical or Horizontal starts the game. In addition, several other boards hitherto unsolved were solved. Using the convention that Vertical starts, the 8 x 15, 11 x 9, 12 x 8, 12 x 15, 14 x 8, and 17 x 6 boards are all won by Vertical, whereas the 6 x 17, 8 x 12, 9 x 11, and 11 x 10 boards are all won by Horizontal

Decay of Correlations in a Topological Glass

In this paper we continue the study of a topological glassy system. The state space of the model is given by all triangulations of a sphere with $N$ nodes, half of which are red and half are blue. Red nodes want to have 5 neighbors while blue ones want 7. Energies of nodes with other numbers of neighbors are supposed to be positive. The dynamics is that of flipping the diagonal between two adjacent triangles, with a temperature dependent probability. We consider the system at very low temperatures. We concentrate on several new aspects of this model: Starting from a detailed description of the stationary state, we conclude that pairs of defects (nodes with the "wrong" degree) move with very high mobility along 1-dimensional paths. As they wander around, they encounter single defects, which they then move "sideways" with a geometrically defined probability. This induces a diffusive motion of the single defects. If they meet, they annihilate, lowering the energy of the system. We both estimate the decay of energy to equilibrium, as well as the correlations. In particular, we find a decay like $t^{-0.4}$

Keluarga sebagai Titik Awal Perkembangan Sosial Anak Usia Dini ( sebuah Kajian Sosiologis )

Setiap orang tua menaruh harapan agar putra-putrinya berhasil dalam perkembangan sosialnya, yakni mampu menjadi sosok manusia sosial yang dapat diterima oleh lingkungan sosialnya dan menjadi anggota masyarakat yang bermanfaat bagi kehidupan sesamanya. Orang tua akan merasa gagal manakala putra-putrinya berkembang sebagai manusia yang a-sosial (tidak lumrah/wajar secara sosial ) apalagi sampai menjadi manusia anti - sosial (membuat resah bahkan membahayakan bagi kehidupan masyarakatnya ). Anak usia dini berada pada masa usia paling peka dan adaptif terhadap berbagai stimulus yang datang dari lingkungannya, juga berada pada masa-masa kritis bagi pertumbuhan dan perkembangannya yang akan mempengaruhi tahap perkembangan selanjutnya. Disadari bahwa upaya optimalisasi perkembangan anak usia dini membutuhkan dukungan lingkungan yang kondusif untuk pengasuhan dan pengembangannya. The Consultative Group on Early Chidlhood Care and Development mendefinisikan “Pengasuhan dan Pengembangan Anak Usia Dini “ sebagai suatu kegiatan yang ditujukan bagi orang tua dan anggota keluarga lainnya untuk membina tumbuh kembang anak usia 0-8 tahun secara menyeluruh dengan memberikan rangsangan bagi pengembangan mental, intelektual, emosional, moral dan sosial yang tepat dan benar, agar anak dapat tumbuh dan berkembang secara optimal. Usaha yang dapat dilakukan mencakup pemeliharaan aspek kesehatan, pemberian nutrisi, stimulasi intelektual, penyediaan kesempatan yang luas untuk mengeksplorasi dan belajar secara aktif, pengembangan sosial dan emosional, pengasuhan dan bimbingan anak untuk memahami potensi diri yang dimilikinya serta berperan aktif dalam keluarga dan masyarakat. Oleh sebab itu keluarga diharapkan mampu menjadi lingkungan pendidik pertama dan utama dalam proses pengasuhan dan pengembangan anak usia dini, serta menjadi wahana awal bagi perkembangan sosialnya melalui pengembangan “social skills – socialization” yang berlangsung dalam kehidupan keluarga. Tujuan utama pengembangan sosial pada anak usia dini adalah agar anak dapat mengembangkan pola-pola interaksi sosial secara sukses, terjadi keselarasan antara nilai-nilai social control dan internal control, sehingga mampu berkembang sebagai manusia sosial. Berhasil tidaknya perkembangan sosial anak usia dini akan ditentukan oleh kualitas proses sosialisasinya dalam keluarga, yang menjadi awal penentu keberhasilan perkembangan sosialnya

A Sparse Stress Model

Force-directed layout methods constitute the most common approach to draw general graphs. Among them, stress minimization produces layouts of comparatively high quality but also imposes comparatively high computational demands. We propose a speed-up method based on the aggregation of terms in the objective function. It is akin to aggregate repulsion from far-away nodes during spring embedding but transfers the idea from the layout space into a preprocessing phase. An initial experimental study informs a method to select representatives, and subsequent more extensive experiments indicate that our method yields better approximations of minimum-stress layouts in less time than related methods.Comment: Appears in the Proceedings of the 24th International Symposium on Graph Drawing and Network Visualization (GD 2016

Towards a Timbral Classification System for Musical Excerpts

Searching for audio samples within a library can be a tedious and time-consuming task. In this paper, we report on the design of a pilot automatic classification system that utilises timbral properties to automatically classify audio samples. At this stage of the study, we have decided to work only with orchestral audio samples. In addition, we conducted a perceptual experiment to evaluate the performance of the system across five timbral attributes: breathiness, brightness, dullness, roughness and warmth. Promising classification results indicate that this approach may be suitable for further work that could also benefit some music production tasks

Feynman Rules in the Type III Natural Flavour-Conserving Two-Higgs Doublet Model

We consider a two Higgs-doublet model with $S_3$ symmetry, which implies a $\pi \over 2$ rather than 0 relative phase between the vacuum expectation values $$and$$. The corresponding Feynman rules are derived accordingly and the transformation of the Higgs fields from the weak to the mass eigenstates includes not only an angle rotation but also a phase transformation. In this model, both doublets couple to the same type of fermions and the flavour-changing neutral currents are naturally suppressed. We also demonstrate that the Type III natural flavour-conserving model is valid at tree-level even when an explicit $S_3$ symmetry breaking perturbation is introduced to get a reasonable CKM matrix. In the special case $\beta = \alpha$, as the ratio $\tan\beta = {v_2 \over v_1}$ runs from 0 to $\infty$, the dominant Yukawa coupling will change from the first two generations to the third generation. In the Feynman rules, we also find that the charged Higgs currents are explicitly left-right asymmetric. The ratios between the left- and right-handed currents for the quarks in the same generations are estimated.Comment: 16 pages (figures not included), NCKU-HEP/93-1