1,418 research outputs found
Thermal conductivity of MgO in giant planetary interior conditions predicted by deep potential
Thermal conductivity of MgO plays a fundamental role in
understanding the thermal evolution and mantle convection in the interior of
terrestrial planets. However, previous theoretical calculations deviate from
each other and the of high-pressure B2 phase remains undetermined.
Here, by combining molecular dynamics and deep potential trained with
first-principles data, we systematically investigate the of MgO from
ambient state to the core-mantle boundary (CMB) of super-Earth with
. We point out the significance of 4-phonon scatterings and modify
the conventional thermal conductivity model of MgO by considering the
density-dependent proportion of 3-phonon and 4-phonon scatterings. The
profiles of MgO in Earth and super-Earth are further estimated. For
super-Earth, we predict a significant reduction of at the B1-B2 phase
transition area near the CMB. This work provides new insights into thermal
transport under extreme conditions and an improved thermal model for
terrestrial planets.Comment: 4 figure
An Efficient Multi-solution Solver for the Inverse Kinematics of 3-Section Constant-Curvature Robots
Piecewise constant curvature is a popular kinematics framework for continuum
robots. Computing the model parameters from the desired end pose, known as the
inverse kinematics problem, is fundamental in manipulation, tracking and
planning tasks. In this paper, we propose an efficient multi-solution solver to
address the inverse kinematics problem of 3-section constant-curvature robots
by bridging both the theoretical reduction and numerical correction. We derive
analytical conditions to simplify the original problem into a one-dimensional
problem. Further, the equivalence of the two problems is formalised. In
addition, we introduce an approximation with bounded error so that the one
dimension becomes traversable while the remaining parameters analytically
solvable. With the theoretical results, the global search and numerical
correction are employed to implement the solver. The experiments validate the
better efficiency and higher success rate of our solver than the numerical
methods when one solution is required, and demonstrate the ability of obtaining
multiple solutions with optimal path planning in a space with obstacles.Comment: Robotics: Science and Systems 202
Poly[diaquaÂ(μ2-oxalato-κ4 O 1,O 2:O 1′,O 2′)(μ2-pyrazine-2-carboxylÂato-κ4 N 1,O:O,O′)neodymium(III)]
In the title complex, [Nd(C5H3N2O2)(C2O4)(H2O)2]n, the NdIII atom is ten-coordinated by one N atom and three O atoms from two pyrazine-2-carboxylÂate ligands, four O atoms from two oxalate ligands and two water molÂecules in a distorted bicapped square-antiÂprismatic geometry. The two crystallographically independent oxalate ligands, each lying on an inversion center, act as bridging ligands, linking Nd atoms into an extended zigzag chain. Neighboring chains are linked by the pyrazine-2-carboxylÂate ligands into a two-dimensional layerlike network in the (10) plane. The layers are further connected by O—H⋯O and O—H⋯N hydrogen bonds, forming a three-dimensional supraÂmolecular network
Exchange interactions and temperature dependence of the magnetization in half--metallic Heusler alloys
We study the exchange interactions in half-metallic Heusler alloys using
first-principles calculations in conjunction with the frozen-magnon
approximation. The Curie temperature is estimated within both mean-field (MF)
and random-phase-approximation (RPA) approaches. For the half-Heusler alloys
NiMnSb and CoMnSb the dominant interaction is between the nearest Mn atoms. In
this case the MF and RPA estimations differ strongly. The RPA approach provides
better agreement with experiment. The exchange interactions are more complex in
the case of full-Heusler alloys CoMnSi and CoCrAl where the dominant
effects are the inter-sublattice interactions between the Mn(Cr) and Co atoms
and between Co atoms at different sublattices. For these compounds we find that
both MF and RPA give very close values of the Curie temperature slightly
underestimating experimental quantities. We study the influence of the lattice
compression on the magnetic properties. The temperature dependence of the
magnetization is calculated using the RPA method within both quantum mechanical
and classical approaches.Comment: New figures and discussio
Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IV. H Time Lags and Implications for Super-Eddington Accretion
We have completed two years of photometric and spectroscopic monitoring of a
large number of active galactic nuclei (AGNs) with very high accretion rates.
In this paper, we report on the result of the second phase of the campaign,
during 2013--2014, and the measurements of five new H time lags out of
eight monitored AGNs. All five objects were identified as super-Eddington
accreting massive black holes (SEAMBHs). The highest measured accretion rates
for the objects in this campaign are , where
,
is the mass accretion rates, is the Eddington luminosity and
is the speed of light. We find that the H time lags in SEAMBHs are
significantly shorter than those measured in sub-Eddington AGNs, and the
deviations increase with increasing accretion rates. Thus, the relationship
between broad-line region size () and optical luminosity at
5100\AA, , requires accretion rate as an additional
parameter. We propose that much of the effect may be due to the strong
anisotropy of the emitted slim-disk radiation. Scaling by
the gravitational radius of the black hole, we define a new radius-mass
parameter () and show that it saturates at a critical accretion rate of
, indicating a transition from thin to slim
accretion disk and a saturated luminosity of the slim disks. The parameter
is a very useful probe for understanding the various types of accretion onto
massive black holes. We briefly comment on implications to the general
population of super-Eddington AGNs in the universe and applications to
cosmology.Comment: 53 pages, 12 figures, 7 tables, accepted for publication in The
Astrophysical Journa
The relationship between children’s oral health-related behaviors and their caregiver’s social support
A simulation study on the measurement of D0-D0bar mixing parameter y at BES-III
We established a method on measuring the \dzdzb mixing parameter for
BESIII experiment at the BEPCII collider. In this method, the doubly
tagged events, with one decays to
CP-eigenstates and the other decays semileptonically, are used to
reconstruct the signals. Since this analysis requires good separation,
a likelihood approach, which combines the , time of flight and the
electromagnetic shower detectors information, is used for particle
identification. We estimate the sensitivity of the measurement of to be
0.007 based on a fully simulated MC sample.Comment: 6 pages, 7 figure
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