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Ou X.,Fudan University | Ou X.,Beijing Institute of Spacecraft Environment Engineering | Wang H.,Fudan University | Fan F.,Fudan University | And 2 more authors.
Physical Review Letters | Year: 2015

Large magnetic anisotropy energy (MAE) is desirable and critical for nanoscale magnetic devices. Here, using ligand-field level diagrams and density functional calculations, we well explain the very recent discovery [I. G. Rau et al., Science 344, 988 (2014)] that an individual Co adatom on a MgO (001) surface has a large MAE of more than 60 meV. More importantly, we predict that a giant MAE up to 110 meV could be realized for Ru adatoms on MgO (001), and even more for the Os adatoms (208 meV). This is a joint effect of the special ligand field, orbital multiplet, and significant spin-orbit interaction, in the intermediate-spin state of the Ru or Os adatoms on top of the surface oxygens. The giant MAE could provide a route to atomic scale memory. © 2015 American Physical Society. Source

Yan R.,Beijing Institute of Spacecraft Environment Engineering
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2015

The gas transport, viathe fairly long sampling pipeline in its partial pressure measurement, was empirically approximated, mathematically modeled on the basis of the previous studies on adsorption of unsteady-state gas, and analytically calculated and experimentally evaluated. The impact of the transport conditions, including but not limited to the pipeline length, position and pressure at the pipeline inlet, pressure and pumping speed of the analysis chamber, gas properties, stabilization and analysis times, on the partial pressure measurement was theoretically investigated. The gas transportation equation and pumping equation in the analysis chamber were formulated with the appropriate initial and boundary conditions, so the transient gas partial pressure distribution could be obtained. The spacecraft gas propellants were exemplified to test the calculated results. The experimental and calculated results were found to be in good agreement. ©, 2015, Science Press. All right reserved. Source

Liu Y.,Dalian Maritime University | Li G.-H.,Dalian Jiaotong University | Jiang L.-X.,Beijing Institute of Spacecraft Environment Engineering
Acta Astronautica | Year: 2010

An Euler-Euler two-fluid model incorporating with the influence of gravity to describe the hydrodynamic behavior of dense gas-particle flows in gas-fluidization reactor is presented and simulated numerically. It based on the dense gases of kinetic theory and the kinetic theory of granular media for considering the interactions between particleparticle and gas-particles. Gas turbulent flow is solved by large eddy simulation. Results showed that the mean value and the variance of vertical particle velocity are greater than those of horizontal velocity under both lunar-reduced and earth gravity conditions. Comparison of the earth gravity, reduced condition is easier to produce the bigger volume bubble and the more heterogeneous flow structure, as well as the greater the variance of vertical and horizontal particle velocity and the higher particle fluctuation intensity. © 2010 Elsevier Ltd. All rights reserved. Source

Deng L.,Carnegie Institution of Washington | Deng L.,Peking University | Fei Y.,Carnegie Institution of Washington | Liu X.,Peking University | And 2 more authors.
Geochimica et Cosmochimica Acta | Year: 2013

High-pressure melting experiments in the Fe-S-C ternary and Fe-S-Si-C quaternary systems have been conducted in the range of 3.5-20GPa and 920-1700°C in the multi-anvil press. The mutual solubility, melting relations, and crystallization sequences were systematically investigated with changes of pressure, temperature and bulk composition. Five starting materials of Fe(84.69wt%)-C(4.35wt%)-S(7.85wt%), Fe(84.87wt%)-C(2.08wt%)-S(11.41wt%), Fe(86.36wt%)-C(0.96wt%)-S(10.31wt%), Fe(85.71wt%)-C(0.33wt%)-S(11.86wt%) and Fe(82.95wt%)-C(0.66wt%)-S(13.7wt%)-Si(2.89wt%) were employed. For Fe(84.69wt%)-C(4.35wt%)-S(7.85wt%), the first crystallized phase is Fe3C at 5GPa and Fe7C3 at 10-20GPa. For Fe(84.87wt%)-C(2.08wt%)-S(11.41wt%), Fe3C is the stable carbide at subsolidus temperature at 5-15GPa. For Fe(86.36wt%)-C(0.96wt%)-S(10.31wt%) and Fe(85.71wt%)-C(0.33wt%)-S(11.86wt%), the first crystallized phase is metallic Fe instead of iron carbide at 5-10GPa. The cotectic curves in Fe-S-C ternary system indicate only a small amount of C is needed to form an iron carbide solid inner core with the presence of S. Experiments on Fe(82.95wt%)-C(0.66wt%)-S(13.7wt%)-Si(2.89wt%) showed that a small amount of C does not significantly change the closure pressure of miscibility gap compared with that in Fe-S-Si system. It is observed that S preferentially partitions into molten iron while a significant amount of Si enters the solid phase with temperature decrease. Meanwhile, the C concentration in the liquid and solid iron metal changes little with temperature variations. If S, C and Si partitioning behavior between molten iron and solid iron metal with temperature remains the same under Earth's present core pressure conditions, the solid inner core should be iron dominated with dissolved Si. On the other hand, the liquid outer core will be S rich and Si poor. Moderate carbon will be evenly present in both solid and liquid cores. Based on our melting data in a multi-component system, no layered liquid core should exist in the Earth, Mars and Mercury. © 2013. Source

Beijing Institute of Spacecraft Environment Engineering | Date: 2013-05-07

A chemical-electromagnetic hybrid propeller with variable specific impulse. Fuel gas ejected out from a spraying tube of the chemical propeller through chemical propulsion enters an ionization chamber through a first magnetic mirror tube for ionization. The fuel gas after ionization is heated up by radio-frequency ion cyclotron waves in an ion cyclotron wave heating chamber so as to improve the kinetic energy. Then a second magnetic mirror tube is used, so that ions in the fuel gas after the ionization are heated up many times in a reciprocating manner between the magnetic mirror tubes, and ejected to generate forward propulsion force. By means of the propeller, the propulsion force and the specific impulse are greatly increased.

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