The spectral variations of the O-type runaway supergiant HD 188209

We report spectral time series of the late O-type runaway supergiant HD 188209. Radial velocity variations of photospheric absorption lines with a possible quasi-period of ∼6.4 d have been detected in high-resolution echelle spectra. Night-to-night variations in the position and strength of the central emission reversal of the H α profile occurring over ill-defined time-scales have been observed. The fundamental parameters of the star are derived using state-of-the-art plane-parallel and unified non-LTE model atmospheres, the latter including the mass-loss rate. The derived helium abundance is moderately enhanced with respect to solar, and the stellar masses are lower than those predicted by the evolutionary models. The binary nature of this star is not suggested either from Hipparcos photometry or from radial velocity curves.     

Magnetic confinement, magnetohydrodynamic waves and smooth line profiles in active galactic nuclei

In this paper, we show that if the broad-line region clouds are in approximate energy equipartition between the magnetic field and gravity, as hypothesized by Rees, there will be a significant effect on the shape and smoothness of broad emission-line profiles in active galactic nuclei. Linewidths of contributing clouds or flow elements are much wider than their thermal widths, because of the presence of non-dissipative magnetohydrodynamic waves and their collective contribution produce emission-line profiles broader and smoother than would be expected if a magnetic field were not present. As an illustration, a simple model of isotropically emitting clouds, normally distributed in velocity, is used to show that smoothness can be achieved for less than ∼8×10⁴ clouds and may even be as low as a few hundred. We conclude that magnetic confinement has far-reaching consequences for observing and modelling active galactic nuclei.     

Neon abundances in normal late-B and mercury–manganese stars

We make new non-local thermodynamic equilibrium calculations to deduce the abundances of neon from visible-region echelle spectra of selected Ne  i lines in seven normal stars and 20 HgMn stars. We find that the best strong blend-free Ne line that can be used at the lower end of the effective temperature T _eff range is λ 6402, although several other potentially useful Ne  i lines are found in the red region of the spectra of these stars. The mean neon abundance in the normal stars (log  A =8.10) is in excellent agreement with the standard abundance of neon (8.08). However, in HgMn stars neon is almost universally underabundant, ranging from marginal deficits of 0.1–0.3 dex to underabundances of an order of magnitude or more. In many cases, the lines are so weak that only upper limits can be established. The most extreme example found is υ Her with an underabundance of at least 1.5 dex. These underabundances are qualitatively expected from radiative acceleration calculations, which show that Ne has a very small radiative acceleration in the photosphere, and that it is expected to undergo gravitational settling if the mixing processes are sufficiently weak and there is no strong stellar wind. According to theoretical predictions , the low Ne abundances place an important constraint on the intensity of such stellar winds, which must be less than 10⁻¹⁴ M_⊙ yr⁻¹ if they are non-turbulent.     

两种结构延绳钓渔具使用效果的比较研究--以金枪鱼(Thunnus)为例

分析比较两种不同结构的延绳钓渔具 1998年 2～ 9月期间在印度洋东部作业的生产效果。结果显示 ,钓具 A(平均放钓水深 90 .8m)与钓具 B(平均放钓水深 72 .7m)相比 ,钓捕效果差异显著 ,在渔获尾数、渔获重量、上钓率三个指标上 ,A钓具分别高于后者 2 9.52 %、30 .2 1%和9.80 %。提出了符合印度洋生产需要的钓具优化设计方案。     

Rotational contours of CH2X chain species compared with several diffuse interstellar bands

We have calculated synthetic spectra of perpendicular and parallel rovibronic bands of cumulene carbene molecules of the form C _n H₂. The perpendicular bands are consistent with a regularly spaced group of diffuse interstellar bands (DIBs) near 6850 Å. Parallel bands calculated for these molecular structures are consistent with the intrinsic profile of the associated 6614-Å DIB. Both types of bands are expected for an electronic transition that these species should have at those energies. We could not determine if the molecule was charged or if an atom other than carbon terminated the chain-end. Constraints due to molecular geometry and temperature place the chain length at 7–15 carbons to fit the 6850-Å group and 9–13 carbons to fit the 6614-Å DIB.     

K-shell photoionization cross-sections of N v and O vi

An 11-state R -matrix calculation is performed to obtain cross-sections for the photoionization of the 1s²2s ²S ground states of N  v and O  vi . For both ions at low photon energies, corresponding solely to the 2s photoionization cross-section, excellent agreement is found with previous calculations. For higher photon energies, permitting inner-shell photoionization of the 1s electron, excellent accord is found with the recent calculation of Nahar for O  vi , whilst for N  v resonance structure is found which previous calculations omitted.     

导管架海洋平台优化设计中约束的有效处理

对导管架海洋平台优化设计中的应力约束、桩基横向承载力约束和构件长细比约束进行了分析,论证了应力约束取构件截机最大Ｍｉｓｅｓ应力、桩基横向承载力约束取桩顶侧位移或最大抗力比和构件长细约束取受压构件长细比许用值作为约束的合理性。提出了精细一维搜索算法,并用此法求我件截面Ｍｉｓｅｓ应力最大值。     

基于GIS规划道路红线的设计与实现

规划道路红线是规划、布局整个城市的基本骨架, 是规划部门非常重要的数据信息.但目前规划道路红线还停留在传统手工设计和管理上, 已经跟不上城市的快速发展.只有将规划道路数字化, 才能解决这种矛盾.分析了规划道路红线在城市规划行业中的重要性, 以及GIS技术在规划道路红线中的地位, 并针对规划道路红线的特点, 设计出规划道路红线地理信息数据并对红线的录入操作, 比如说道路中线、边线、拐角处理, 交叉口处理, 以及喇叭口处理都做了详细的介绍, 旨在能够利用计算机技术和GIS技术实现规划道路红线的数字化, 以满足城市规划领域的需求      

局部加载条件下二维土质边坡稳定性的数值分析

借助Hill的材料应变局部化原理和土的弹塑性本构模型,应用声学张量示踪边坡失稳滑移线发生和发展,提出了局部加载条件下的确定边坡失稳滑移线的方法。在弹塑性有限元分析过程中,应用边坡材料的塑性一致性条件或滑移线两侧的应力连续条件,即应变局部化条件,检测每一个高斯点的声学张量行列式的值,当其等于或接近0时,标出滑移萌生的位置、方向,模拟边坡滑移线萌生和发展过程。