10,215 research outputs found
Tetraaquabis[2-(2,4-dichlorophenoxy)acetato]nickel(II)
In the title complex, [Ni(C8H5Cl2O3)2(H2O)4], the NiII atom (site symmetry ) adopts a slightly distorted NiO6 octahedral coordination. An intramolecular O—H⋯O hydrogen bond helps to establish the conformation. In the crystal, further O—H⋯O hydrogen bonds link the molecules
Efficient parallel solver for high-speed rarefied gas flow using GSIS
Recently, the general synthetic iterative scheme (GSIS) has been proposed to
find the steady-state solution of the Boltzmann equation in the whole range of
gas rarefaction, where its fast-converging and asymptotic-preserving properties
lead to the significant reduction of iteration numbers and spatial cells in the
near-continuum flow regime. However, the efficiency and accuracy of GSIS has
only been demonstrated in two-dimensional problems with small numbers of
spatial cell and discrete velocities. Here, a large-scale parallel computing
strategy is designed to extend the GSIS to three-dimensional high-speed flow
problems. Since the GSIS involves the calculation of the mesoscopic kinetic
equation which is defined in six-dimensional phase-space, and the macroscopic
high-temperature Navier-Stokes-Fourier equations in three-dimensional physical
space, the proper partition of the spatial and velocity spaces, and the
allocation of CPU cores to the mesoscopic and macroscopic solvers, are the keys
to improving the overall computational efficiency. These factors are
systematically tested to achieve optimal performance, up to 100 billion spatial
and velocity grids. For hypersonic flows around the Apollo reentry capsule, the
X38-like vehicle, and the space station, our parallel solver can get the
converged solution within one hour
Optimized synthesis of ultrahigh-surface-area and oxygen-doped carbon nanobelts for high cycle-stability lithium-sulfur batteries
Hierarchical clews of carbon nanobelts (CsCNBs) with ultrahigh specific surface area (2300 m2 g−1) and large pore volume (up to 1.29 cm3 g−1) has been successfully fabricated through carbonization and KOH activation of phenolic resin based nanobelts. The product possesses hierarchically porous structure, three-dimensional conductive network framework, and polar oxygen-rich groups, which are very befitting to load sulfur leading to excellent cycling stability of lithium-sulfur batteries. The composites of CsCNBs/sulfur exhibit an ultrahigh initial discharge capacity of 1245 mA h g−1 and ultralow capacity decay rate as low as 0.162% per cycle after 200 cycles at 0.1 C. Even at high current rate of 4 C, the cells still display a high initial discharge capacity (621 mA h g−1) and ultralow capacity decay rate (only 0.039% per cycle) after 1000 cycles. These encouraging results indicate that polar oxygen-containing functional groups are important for improving the electrochemical performance of carbons. The oxygen-doped carbon nanobelts have excellent energy storage potential in the field of energy storage
High-mass Starless Clumps in the inner Galactic Plane: the Sample and Dust Properties
We report a sample of 463 high-mass starless clump (HMSC) candidates within
and . This sample has been singled out from
10861 ATLASGAL clumps. All of these sources are not associated with any known
star-forming activities collected in SIMBAD and young stellar objects
identified using color-based criteria. We also make sure that the HMSC
candidates have neither point sources at 24 and 70 \micron~nor strong extended
emission at 24 m. Most of the identified HMSCs are infrared (
m) dark and some are even dark at 70 m. Their distribution shows
crowding in Galactic spiral arms and toward the Galactic center and some
well-known star-forming complexes. Many HMSCs are associated with large-scale
filaments. Some basic parameters were attained from column density and dust
temperature maps constructed via fitting far-infrared and submillimeter
continuum data to modified blackbodies. The HMSC candidates have sizes, masses,
and densities similar to clumps associated with Class II methanol masers and
HII regions, suggesting they will evolve into star-forming clumps. More than
90% of the HMSC candidates have densities above some proposed thresholds for
forming high-mass stars. With dust temperatures and luminosity-to-mass ratios
significantly lower than that for star-forming sources, the HMSC candidates are
externally heated and genuinely at very early stages of high-mass star
formation. Twenty sources with equivalent radius pc and
mass surface density g cm could be possible high-mass
starless cores. Further investigations toward these HMSCs would undoubtedly
shed light on comprehensively understanding the birth of high-mass stars.Comment: 16 pages, 15 figures, and 5 tables. Accepted for publication in ApJS.
FITS images for the far-IR to sub-mm data, H2 column density and dust
temperature maps of all the HMSC candidates are available at https:
//yuanjinghua.github.io/hmscs.html. Codes used for this work are publicly
available from https://github.com/yuanjinghua/HMSCs_ca
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