Dust-to-gas ratio, XCOX_{\rm CO} factor and CO-dark gas in the Galactic anticentre: an observational study

We investigate the correlation between extinction and H~{\sc i} and CO emission at intermediate and high Galactic latitudes (|b|>10\degr) within the footprint of the Xuyi Schmidt Telescope Photometric Survey of the Galactic anticentre (XSTPS-GAC) on small and large scales. In Paper I (Chen et al. 2014), we present a three-dimensional dust extinction map within the footprint of XSTPS-GAC, covering a sky area of over 6,000\,deg$^2$ at a spatial angular resolution of 6\,arcmin. In the current work, the map is combined with data from gas tracers, including H~{\sc i} data from the Galactic Arecibo L-band Feed Array H~{\sc i} survey and CO data from the Planck mission, to constrain the values of dust-to-gas ratio $DGR=A_V/N({\rm H})$ and CO-to-$\rm H_2$ conversion factor $X_{\rm CO}=N({\rm H_2})/W_{\rm CO}$ for the entire GAC footprint excluding the Galactic plane, as well as for selected star-forming regions (such as the Orion, Taurus and Perseus clouds) and a region of diffuse gas in the northern Galactic hemisphere. For the whole GAC footprint, we find $DGR=(4.15\pm0.01) \times 10^{-22}$\,$\rm mag\,cm^{2}$ and $X_{\rm CO}=(1.72 \pm 0.03) \times 10^{20}$\,$\rm cm^{-2}\,(K\,km\,s^{-1})^{-1}$. We have also investigated the distribution of "CO-dark" gas (DG) within the footprint of GAC and found a linear correlation between the DG column density and the $V$-band extinction: $N({\rm DG}) \simeq 2.2 \times 10^{21} (A_V - A^{c}_{V})\,\rm cm^{-2}$. The mass fraction of DG is found to be $f_{\rm DG}\sim 0.55$ toward the Galactic anticentre, which is respectively about 23 and 124 per cent of the atomic and CO-traced molecular gas in the same region. This result is consistent with the theoretical work of Papadopoulos et al. but much larger than that expected in the $\rm H_2$ cloud models by Wolfire et al.Comment: 11 pages, 7 figures, accepted for publication in MNRA

Numerical investigation of added mass coefficient of a subsea manifold in the accelerating flow and oscillating flow

The hydrodynamic forces and dynamic responses of subsea equipment, like manifolds, are significantly affected by the motions of the mothership or the unexpected incoming underwater flows like current or internal wave. In this paper, the hydrodynamic coefficients of a simplified subsea manifold, a submerged 3D prism are predicted through the constant acceleration method and forced oscillating method, which are both implemented by the CFD simulation approach. The three directional added mass coefficients of the prism in accelerating flow with different accelerations are obtained. But the value of constant acceleration is found not significantly influencing the added mass coefficient of the rectangular prism. The added mass coefficient of the rectangular prism studied in the paper is 0.233, 0.395, and 2.191 in X, Y and Z direction, respectively. In order to predict the added mass coefficient of the 3D rectangular prism in oscillating flow, the forced oscillating method is used to simulate the rectangular prism oscillating in three directions (X, Y, Z) under different oscillating amplitude and frequency

Bulk Rotational Symmetry Breaking in Kondo Insulator SmB6

Kondo insulator samarium hexaboride (SmB6) has been intensely studied in recent years as a potential candidate of a strongly correlated topological insulator. One of the most exciting phenomena observed in SmB6 is the clear quantum oscillations appearing in magnetic torque at a low temperature despite the insulating behavior in resistance. These quantum oscillations show multiple frequencies and varied effective masses. The origin of quantum oscillation is, however, still under debate with evidence of both two-dimensional Fermi surfaces and three-dimensional Fermi surfaces. Here, we carry out angle-resolved torque magnetometry measurements in a magnetic field up to 45 T and a temperature range down to 40 mK. With the magnetic field rotated in the (010) plane, the quantum oscillation frequency of the strongest oscillation branch shows a four-fold rotational symmetry. However, in the angular dependence of the amplitude of the same branch, this four-fold symmetry is broken and, instead, a twofold symmetry shows up, which is consistent with the prediction of a two-dimensional Lifshitz-Kosevich model. No deviation of Lifshitz-Kosevich behavior is observed down to 40 mK. Our results suggest the existence of multiple light-mass surface states in SmB6, with their mobility significantly depending on the surface disorder level.Comment: 15 pages, 9 figure

Numerical investigation of added mass coefficient of a subsea manifold in the accelerating flow and oscillating flow

944-953The hydrodynamic forces and dynamic responses of subsea equipment, like manifolds, are significantly affected by the motions of the mothership or the unexpected incoming underwater flows like current or internal wave. In this paper, the hydrodynamic coefficients of a simplified subsea manifold, a submerged 3D prism are predicted through the constant acceleration method and forced oscillating method, which are both implemented by the CFD simulation approach. The three directional added mass coefficients of the prism in accelerating flow with different accelerations are obtained. But the value of constant acceleration is found not significantly influencing the added mass coefficient of the rectangular prism. The added mass coefficient of the rectangular prism studied in the paper is 0.233, 0.395, and 2.191 in X, Y and Z direction, respectively. In order to predict the added mass coefficient of the 3D rectangular prism in oscillating flow, the forced oscillating method is used to simulate the rectangular prism oscillating in three directions (X, Y, Z) under different oscillating amplitude and frequency