Anisotropic flow of Pb+Pb sNN\sqrt{s_{\rm NN}} = 5.02 TeV from A Multi-Phase Transport Model

Anisotropic flow is an important observable in the study of the Quark-Gluon Plasma that is expected to be formed in heavy-ion collisions. With a multiphase transport (AMPT) model we investigate the elliptic(\emph{v}_{2}), triangular(\emph{v}_{3}), and quadrangular(\emph{v}_{4}) flow of charged particles in Pb+Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. Then We compare our flow results with the published ALICE flow results. We found our AMPT simulated results are consistent with ALICE experimental data

Quantum Size Effect on Dielectric Properties of Ultrathin Metallic Film: A First-Principles Study of Al(111)

Quantum manifestations of various properties of metallic thin films by quantum size effect (QSE) have been studied intensively. Here, using first-principles calculations, we show quantum manifestation in dielectric properties of Al(111) ultrathin films. The QSE on the dielectric function is revealed, which arises from size dependent contributions from both intraband and interband electronic transitions. More importantly, the in-plane interband transitions in the films thinner than 15 monolayers are found to be smaller than the bulk counterpart in the energy range from 1.5~eV to 2.5~eV. This indicates less energy loss with plasmonic material of Al in the form of ultrathin film. Our findings may shed light on searching for low-loss plasmonic materials via quantum size effect

Heavy quark correlations and the effective volume for quarkonia production

Using the Boltzmann transport approach, we study the effective volume of a correlated heavy quark pair in a partonic medium based on their collision rate. We find that the effective volume is finite and depends sensitively on the momentum of the heavy quark and the temperature of the medium. Generally, it increases linearly with time $t$ at the very beginning and the increase then becomes slower due to multiple scattering, and finally it increases linearly with respect to $t^{3/2}$. We further find that the colliding heavy quark pair has an effective temperature similar to that of the medium even though their initial transverse momentum spectra are far from thermal equilibrium.Comment: 7 pages, 7 figure

Effects of Li doping on H-diffusion in MgH2_2: a first-principles study

The effects of Li doping in MgH$_2$ on H-diffusion process are investigated, using first-principles calculations. We have identified two key effects: (1) The concentration of H vacancy in the $+1$ charge state (V$_H^{+1}$) can increase by several orders of magnitude upon Li doping, which significantly increases the vacancy mediated H diffusion rate. It is caused by the preferred charge states of substitutional Li in the $-1$ state (Li$_{Mg}^{-1}$) and of interstitial Li in the $+1$ state (Li$_i^{+1}$), which indirectly reduce the formation energy of V$_H^{+1}$ by up to 0.39 eV depending on the position of Fermi energy. (2) The interaction between V$_H^{+1}$ and Li$_{Mg}^{-1}$ is found to be attractive with a binding energy of 0.55 eV, which immobilizes the V$_H^{+1}$ next to Li$_{Mg}^{-1}$ at high Li doping concentration. As a result, the competition between these two effects leads to large enhancement of H diffusion at low Li doping concentration due to the increased H-vacancy concentration, but only limited enhancement at high Li concentration due to the immobilization of H vacancies by too many Li

Giant Rashba-Spin Splitting of Bi(111) Bilayer on Large Band Gap β−\beta-In2_2Se3_3

Experimentally it is still challenging to epitaxially grow Bi(111) bilayer (BL) on conventional semiconductor substrate. Here, we propose a substrate of $\beta-$In$_2$Se$_3$(0001) with van der Waals like cleavage and large band gap of 1.2~eV. We have investigated the electronic structure of BL on one quintuple-layer (QL) $\beta-$In$_2$Se$_3$(0001) using density functional theory calculation. It is found that the intermediate hybridization between BL and one QL $\beta-$In$_2$Se$_3$(0001) results in the formation of bands with giant Rashba spin splitting in the large band gap of the substrate. Furthermore the Rashba parameter $\alpha_R$ can be increased significantly by tensile strain of substrate. Our findings provide a good candidate substrate for BL growth to experimentally realize spin splitting Rashba states with insignificant effect of spin degenerate states from the substrate

sd2 Graphene: Kagome Band in Hexagonal lattice

Graphene, made of sp2 hybridized carbon, is characterized with a Dirac band, representative of its underlying 2D hexagonal lattice. Fundamental understanding of graphene has recently spurred a surge of searching for 2D topological quantum phases in solid-state materials. Here, we propose a new form of 2D material, consisting of sd2 hybridized transition metal atoms in hexagonal lattice, called sd2 graphene. The sd2 graphene is characterized with bond-centered electronic hopping, which transforms the apparent atomic hexagonal lattice into the physics of kagome lattice that may exhibit a wide range of topological quantum phases. Based on first-principles calculations, room temperature quantum anomalous Hall states with an energy gap of 0.1 eV are demonstrated for one such lattice made of W, which can be epitaxially grown on a semiconductor surface of 1/3 monolayer Cl-covered Si(111), with high thermodynamic and kinetic stability.Comment: Phys. Rev. Lett.(2014), In press. It includes main text and 5 figures. Supplemental material is available upon reques

Implicit Distortion and Fertility Models for Attention-based Encoder-Decoder NMT Model

Neural machine translation has shown very promising results lately. Most NMT models follow the encoder-decoder framework. To make encoder-decoder models more flexible, attention mechanism was introduced to machine translation and also other tasks like speech recognition and image captioning. We observe that the quality of translation by attention-based encoder-decoder can be significantly damaged when the alignment is incorrect. We attribute these problems to the lack of distortion and fertility models. Aiming to resolve these problems, we propose new variations of attention-based encoder-decoder and compare them with other models on machine translation. Our proposed method achieved an improvement of 2 BLEU points over the original attention-based encoder-decoder.Comment: 11 pages, updated detail

A Simple Pooling-Based Design for Real-Time Salient Object Detection

We solve the problem of salient object detection by investigating how to expand the role of pooling in convolutional neural networks. Based on the U-shape architecture, we first build a global guidance module (GGM) upon the bottom-up pathway, aiming at providing layers at different feature levels the location information of potential salient objects. We further design a feature aggregation module (FAM) to make the coarse-level semantic information well fused with the fine-level features from the top-down pathway. By adding FAMs after the fusion operations in the top-down pathway, coarse-level features from the GGM can be seamlessly merged with features at various scales. These two pooling-based modules allow the high-level semantic features to be progressively refined, yielding detail enriched saliency maps. Experiment results show that our proposed approach can more accurately locate the salient objects with sharpened details and hence substantially improve the performance compared to the previous state-of-the-arts. Our approach is fast as well and can run at a speed of more than 30 FPS when processing a $300 \times 400$ image. Code can be found at http://mmcheng.net/poolnet/.Comment: Accepted by CVPR201

Thermodynamics of the α\alpha-γ\gamma transition in cerium studied by an LDA + Gutzwiller method

The $\alpha$-$\gamma$ transition in cerium has been studied in both zero and finite temperature by Gutzwiller density functional theory. We find that the first order transition between $\alpha$ and $\gamma$ phases persists to the zero temperature with negative pressure. By further including the entropy contributed by both electronic quasi-particles and lattice vibration, we obtain the total free energy at given volume and temperature, from which we obtain the $\alpha$-$\gamma$ transition from the first principle calculation. We also computed the phase diagram and pressure versus volume isotherms of cerium at finite temperature and pressure, finding excellent agreement with the experiments. Our calculation indicate that both the electronic entropy and lattice vibration entropy plays important role in the $\alpha$-$\gamma$ transition.Comment: 5 pages, 4 figure

Learning Pixel-wise Labeling from the Internet without Human Interaction

Deep learning stands at the forefront in many computer vision tasks. However, deep neural networks are usually data-hungry and require a huge amount of well-annotated training samples. Collecting sufficient annotated data is very expensive in many applications, especially for pixel-level prediction tasks such as semantic segmentation. To solve this fundamental issue, we consider a new challenging vision task, Internetly supervised semantic segmentation, which only uses Internet data with noisy image-level supervision of corresponding query keywords for segmentation model training. We address this task by proposing the following solution. A class-specific attention model unifying multiscale forward and backward convolutional features is proposed to provide initial segmentation "ground truth". The model trained with such noisy annotations is then improved by an online fine-tuning procedure. It achieves state-of-the-art performance under the weakly-supervised setting on PASCAL VOC2012 dataset. The proposed framework also paves a new way towards learning from the Internet without human interaction and could serve as a strong baseline therein. Code and data will be released upon the paper acceptance