A Dual-Stage Attention-Based Recurrent Neural Network for Time Series Prediction

The Nonlinear autoregressive exogenous (NARX) model, which predicts the current value of a time series based upon its previous values as well as the current and past values of multiple driving (exogenous) series, has been studied for decades. Despite the fact that various NARX models have been developed, few of them can capture the long-term temporal dependencies appropriately and select the relevant driving series to make predictions. In this paper, we propose a dual-stage attention-based recurrent neural network (DA-RNN) to address these two issues. In the first stage, we introduce an input attention mechanism to adaptively extract relevant driving series (a.k.a., input features) at each time step by referring to the previous encoder hidden state. In the second stage, we use a temporal attention mechanism to select relevant encoder hidden states across all time steps. With this dual-stage attention scheme, our model can not only make predictions effectively, but can also be easily interpreted. Thorough empirical studies based upon the SML 2010 dataset and the NASDAQ 100 Stock dataset demonstrate that the DA-RNN can outperform state-of-the-art methods for time series prediction.Comment: International Joint Conference on Artificial Intelligence (IJCAI), 201

Superconducting proximity effect to the block antiferromagnetism in Ky_{y}Fe2−x_{2-x}Se2_{2}

Recent discovery of superconducting (SC) ternary iron selenides has block antiferromagentic (AFM) long range order. Many experiments show possible mesoscopic phase separation of the superconductivity and antiferromagnetism, while the neutron experiment reveals a sizable suppression of magnetic moment due to the superconductivity indicating a possible phase coexistence. Here we propose that the observed suppression of the magnetic moment may be explained due to the proximity effect within a phase separation scenario. We use a two-orbital model to study the proximity effect on a layer of block AFM state induced by neighboring SC layers via an interlayer tunneling mechanism. We argue that the proximity effect in ternary Fe-selenides should be large because of the large interlayer coupling and weak electron correlation. The result of our mean field theory is compared with the neutron experiments semi-quantitatively. The suppression of the magnetic moment due to the SC proximity effect is found to be more pronounced in the d-wave superconductivity and may be enhanced by the frustrated structure of the block AFM state.Comment: 6 pages, 6 figure

CEN34 -- High-Mass YSO in M17 or Background Post-AGB Star?

We investigate the proposed high-mass young stellar object (YSO) candidate CEN34, thought to be associated with the star forming region M17. Its optical to near-infrared (550-2500 nm) spectrum reveals several photospheric absorption features, such as H{\alpha}, Ca triplet and CO bandheads but lacks any emission lines. The spectral features in the range 8375-8770{\AA} are used to constrain an effective temperature of 5250\pm250 (early-/mid-G) and a surface gravity of 2.0\pm0.3 (supergiant). The spectral energy distribution of CEN34 resembles the SED of a high-mass YSO or an evolved star. Moreover, the observed temperature and surface gravity are identical for high-mass YSOs and evolved stars. The radial velocity relative to LSR (V_LSR) of CEN34 as obtained from various photospheric lines is of the order of -60 km/s and thus distinct from the +25 km/s found for several OB stars in the cluster and for the associated molecular cloud. The SED modeling yields ~ 10^{-4} M_sun of circumstellar material which contributes only a tiny fraction to the total visual extinction (11 mag). In the case of a YSO, a dynamical ejection process is proposed to explain the V_LSR difference between CEN34 and M17. Additionally, to match the temperature and luminosity, we speculate that CEN34 had accumulated the bulk of its mass with accretion rate > 4x10^{-3} M_sun/yr in a very short time span (~ 10^3 yrs), and currently undergoes a phase of gravitational contraction without any further mass gain. However, all the aforementioned characteristics of CEN34 are compatible with an evolved star of 5-7 M_sun and an age of 50-100 Myrs, most likely a background post-AGB star with a distance between 2.0 kpc and 4.5 kpc. We consider the latter classification as the more likely interpretation. Further discrimination between the two possible scenarios should come from the more strict confinement of CEN34's distance.Comment: 8 pages, 8 figures, 2 tables; accepted by A&

Standard Biological Part Automatic Modeling Database Language (MoDeL)

This BioBricks Foundation Request for Comments (BBF RFC) describes the Standard Biological Part Automatic Modeling Database Language (MoDeL). MoDeL provides a language and syntax standard for automatic modeling databases used by synthetic biology software. Meanwhile, MoDeL allows detailed description of biological complex, and presents the concept of Chain-Node Model

Commanding Wheelchair in Virtual Reality with Thoughts by Multiclass BCI based on Movement-related Cortical Potentials

Brain-driven wheelchair control is an attractive application in theBrain-Computer Interface (BCI) field. In this research, wedesigned and validated a virtual wheelchair navigation systemcontrolled by our latest multiclass BCI Menu interface based on afast brain switch, which provides five commands: move forward,turn left, turn right, move backward, and stop. Preliminary resultshave shown that subjects can successfully control the wheelchairto hit all targets in the immersive virtual reality (VR)environment. This system proves an avenue to bridge the gapbetween simulation control in VR environments and real-lifewheelchair applications for mobility impairment

Spin Liquid Ground State of the Spin-1/2 Square J1J_1-J2J_2 Heisenberg Model

We perform highly accurate density matrix renormalization group (DMRG) simulations to investigate the ground state properties of the spin-1/2 antiferromagnetic square lattice Heisenberg $J_1$-$J_2$ model. Based on studies of numerous long cylinders with circumferences of up to 14 lattice spacings, we obtain strong evidence for a topological quantum spin liquid state in the region $0.41\leq J_2/J_1\leq 0.62$, separating conventional N\'eel and striped antiferromagnetic states for smaller and larger $J_2/J_1$, respectively. The quantum spin liquid is characterized numerically by the absence of magnetic or valence bond solid order, and non-zero singlet and triplet energy gaps. Furthermore, we positively identify its topological nature by measuring a non-zero topological entanglement entropy $\gamma=0.70\pm 0.02$, extremely close to $\gamma=\ln(2) \approx 0.69$ (expected for a $Z_2$ quantum spin liquid) and a non-trivial finite size dimerization effect depending upon the parity of the circumference of the cylinder. We also point out that a valence bond solid, and indeed any discrete symmetry breaking state, would be expected to show a constant correction to the entanglement entropy of {\sl opposite} sign to the topological entanglement entropy.Comment: 14 pages, 6 figures in the main text. Accuracy improved and missing references adde

Theory for charge and orbital density-wave states in manganite La0.5_{0.5}Sr1.5_{1.5}MnO4_4

We investigate the high temperature phase of layered manganites, and demonstrate that the charge-orbital phase transition without magnetic order in La$_{0.5}$Sr$_{1.5}$MnO$_4$ can be understood in terms of the density wave instability. The orbital ordering is found to be induced by the nesting between segments of Fermi surface with different orbital characters. The simultaneous charge and orbital orderings are elaborated with a mean field theory. The ordered orbitals are shown to be $d_{x^2-y^2} \pm d_{3z^2-r^2}$.Comment: published versio

A Chemical Study of Nine Star-forming Regions with Evidence of Infall Motion

The study of the physical and chemical properties of gas infall motion in the molecular clumps helps us understand the initial stages of star formation. We used the FTS wide-sideband mode of the IRAM 30-m telescope to observe nine infall sources with significant double peaked blue line profile. The observation frequency range are 83.7 - 91.5 GHz and 99.4 - 107.2 GHz. We have obtained numbers of molecular line data. Using XCLASS, a total of 7 to 27 different molecules and isotopic transition lines have been identified in these nine sources, including carbon chain molecules such as CCH, c-C3H2 and HC3N. According to the radiation transfer model, we estimated the rotation temperatures and column densities of these sources. Chemical simulations adopting a physical model of HMSFRs are used to fit the observed molecular abundances. The comparison shows that most sources are in the early HMPO stage, with the inner temperature around several ten K