分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the discovery and characterisation of the transiting mini-Neptune HD~207496~b (TOI-1099) as part of a large programme that aims to characterise naked core planets. We obtained HARPS spectroscopic observations, one ground-based transit, and high-resolution imaging which we combined with the TESS photometry to confirm and characterise the TESS candidate and its host star. The host star is an active early K dwarf with a mass of $0.80 \pm 0.04\,$M$_\odot$, a radius of $0.769 \pm 0.026\,$R$_\odot$, and a G magnitude of 8. We found that the host star is young, $\sim 0.52\,$ Myr, allowing us to gain insight into planetary evolution. We derived a planetary mass of $6.1 \pm 1.6\,\mathrm{M}_E$,\, a planetary radius of $2.25 \pm 0.12\,\mathrm{R}_E$,\ and a planetary density of $\rho_p = 3.27_{-0.91}^{+0.97}\,\mathrm{g.cm^{-3}}$. From internal structure modelling of the planet, we conclude that the planet has either a water-rich envelope, a gas-rich envelope, or a mixture of both. We have performed evaporation modelling of the planet. If we assume the planet has a gas-rich envelope, we find that the planet has lost a significant fraction of its envelope and its radius has shrunk. Furthermore, we estimate it will lose all its remaining gaseous envelope in $\sim 0.52\,$ Gyr. Otherwise, the planet could have already lost all its primordial gas and is now a bare ocean planet. Further observations of its possible atmosphere and/or mass-loss rate would allow us to distinguish between these two hypotheses. Such observations would determine if the planet remains above the radius gap or if it will shrink and be below the gap.
分类: 材料科学 >> 材料科学(综合) 提交时间: 2016-11-15 合作期刊: 《金属学报》
摘要: 本工作研究了基体材料的机械性能对冷喷涂316L不锈钢单颗粒沉积行为的影响. 研究结果表明, 除硬度之外, 弹性模量和Poisson比也会影响颗粒的沉积行为. 这是由于基体性质对颗粒/基体的能量分配和结合机制造成了影响. 其中, 沉积颗粒的变形行为与颗粒吸收的能量有关, 而沉积效率与基体吸收的能量及结合机制有关. 根据沉积颗粒的变形行为, 将基体分为2类: 颗粒几乎不变形, 此时基体的硬度和弹性模量皆低于颗粒材料, 颗粒与基体的结合主要是机械咬合, 推导出可用于推断相同颗粒在基体上沉积趋势的参数Epara, 并以AZ91镁合金为基体进行验证; 颗粒发生强烈变形, 此时基体的硬度或弹性模量高于颗粒材料, 结合机制更为复杂, 此时增加颗粒/基体新鲜表面接触面积有利于沉积效率提高.