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- Meng, Zhou, et al.
(författare)
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Observation of the lower hybrid waves near the three-dimensional null pair
- 2009
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Ingår i: Science in China Series G. - : Science Press. - 1672-1799 .- 1862-2844. ; 52:4, s. 626-630
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic reconnection is a fundamental process in plasma, which is thought to play important roles both in laboratory and natural plasmas through affecting magnetic topology, heating and accelerating particles. During an event on Oct. 1st, 2001, the Cluster tetrahedron circled around the magnetic reconnection region several times, and Xiao et al. first identified the null pair and found that the spectrum of the null-point oscillation shows the maximum power near the lower-hybrid frequency. In this paper we report the observation of electromagnetic and electrostatic wave enhancements near lower hybrid frequency associated with the reconnection process near the null pair. The lower hybrid waves (LHWs) with quasi-perpendicular propagation were identified and also confirmed by the power law of the spectrum of electric and magnetic fields.
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| 2. |
- Xu, Qiang, et al.
(författare)
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Theoretical prediction, synthesis, and crystal structure determination of new MAX phase compound V2SnC
- 2020
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Ingår i: JOURNAL OF ADVANCED CERAMICS. - : SPRINGER. - 2226-4108 .- 2227-8508. ; 9:4, s. 481-492
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Tidskriftsartikel (refereegranskat)abstract
- Guided by the theoretical prediction, a new MAX phase V2SnC was synthesized experimentally for the first time by reaction of V, Sn, and C mixtures at 1000 degrees C. The chemical composition and crystal structure of this new compound were identified by the cross-check combination of first-principles calculations, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and high resolution scanning transmission electron microscopy (HR-STEM). The stacking sequence of V2C and Sn layers results in a crystal structure of space group P6(3)/mmc. Thea- andc-lattice parameters, which were determined by the Rietveld analysis of powder XRD pattern, are 0.2981(0) nm and 1.3470(6) nm, respectively. The atomic positions are V at 4f (1/3, 2/3, 0.0776(5)), Sn at 2d (2/3, 1/3, 1/4), and C at 2a (0, 0, 0). A new set of XRD data of V2SnC was also obtained. Theoretical calculations suggest that this new compound is stable with negative formation energy and formation enthalpy, satisfied Born-Huang criteria of mechanical stability, and positive phonon branches over the Brillouin zone. It also has low shear deformation resistancec(44)(second-order elastic constant,c(ij)) and shear modulus (G), positive Cauchy pressure, and low Pughs ratio (G/B= 0.500 < 0.571), which is regarded as a quasi-ductile MAX phase. The mechanism underpinning the quasi-ductility is associated with the presence of a metallic bond.
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