Modeling of the R CrB star chromosphere

A model of the R CrB star chromosphere is calculated on the basis of the observed profiles of the Ca II H and K lines and IR triplet and D lines of Na I and H-alpha. The calculated profiles of Ca II H and K lines and IR triplet and H-alpha are in good agreement with the observed ones both for an undisturbed state and for the light minimum. The line profiles for the light minimum are calculated under the assumption that the minimum is attributed to obscuring of the star disc with a dust cloud. In this case, the chromosphere is not hydrostatic since the column density at the chromosphere base is two orders of magnitude higher as compared to that in a hydrostatic model. The model proposed is more extended, less dense at the chromosphere base, and denser in the upper chromosphere. The extension of the calculated chromosphere is about 3 star radii. The density in the chromosphere is 108–1010 atoms per 1 cm³ and the temperature is 5000–7000 K. Agreement of the calculated and observed profiles of Na I D absorption lines is possible if we assume that, around the star, there is a cold envelope containing Na I atoms which expands with a velocity of about 30 km/s. This envelope is beyond the chromosphere, but near enough for the star and the envelope to be observed as a single whole. The optical thickness of the envelope in the Na I D2 line is 1.8. At the brightness minimum, this envelope illuminated with the star light yields additional emission attributed to resonant scattering in the Na I D lines.     

An atlas of predicted exotic gravitational lenses

We present an investigation of the relationships between the radio properties of a giant radio galaxy MRC B0319−454 and the surrounding galaxy distribution with the aim of examining the influence of intergalactic gas and gravity associated with the large-scale structure on the evolution in the radio morphology. Our new radio continuum observations of the radio source, with high surface brightness sensitivity, images the asymmetries in the megaparsec-scale radio structure in total intensity and polarization. We compare these with the three-dimensional galaxy distribution derived from galaxy redshift surveys. Galaxy density gradients are observed along and perpendicular to the radio axis: the large-scale structure is consistent with a model wherein the galaxies trace the ambient intergalactic gas and the evolution of the radio structures are ram-pressure limited by this associated gas. Additionally, we have modelled the off-axis evolution of the south-west radio lobe as deflection of a buoyant jet backflow by a transverse gravitational field: the model is plausible if entrainment is small. The case study presented here is a demonstration that giant radio galaxies may be useful probes of the warm-hot intergalactic medium believed to be associated with moderately over dense galaxy distributions.     

利用声卡为计算机提供标准时间

根据时统IRIG B(简称“B码”)的码形特点和编码原理 ,介绍利用计算机普通声卡接收标准化时统设备B码信号的硬件工作机理 ,着重阐述了软件解码的实现过程和为计算机提供标准时间的方法。     

基于HJ-1B卫星数据的积雪面积制图算法研究

积雪是影响气候变化的重要因子, 采用更高时空分辨率的环境减灾卫星遥感数据进行积雪制图算法的研究, 对推进我国自主遥感卫星在积雪监测领域的应用具有重要意义. 采用环境减灾HJ-1B卫星数据, 以青海省果洛藏族自治州达日县为研究区, 应用归一化差值积雪指数(NDSI)法建立了基于HJ-1B卫星数据的积雪面积制图算法, 并比较MODIS与HJ-1B积雪图精度. 结果表明: 研究区HJ-1B积雪制图合理的NDSI阈值为0.37, 总分类精度达到97.97%; 与"真值"影像比较, HJ-1B积雪图K_hat系数为0.911, 高于MODIS的0.817. 说明该研究建立的基于HJ-1B积雪制图算法精度可靠, 适合对研究区积雪进行实时动态监测. HJ-1B更高的空间分辨率对提高研究区积雪覆盖面积监测精度具有重要的使用价值, 但是地形因素是影响HJ-1B数据积雪分类精度的一个重要原因, 随着坡度的增加, 分类误差也随之增大, 尤其是多测误差增加比较显著.     

Timing models for the long orbital period binary pulsar PSR B1259–63

The pulsar PSR B1259–63 is in a highly eccentric 3.4-yr orbit with the Be star SS 2883. Timing observations of this pulsar, made over a 7-yr period using the Parkes 64-m radio telescope, cover two periastron passages, in 1990 August and 1994 January. The timing data cannot be fitted by the normal pulsar and Keplerian binary parameters. A timing solution including a (non-precessing) Keplerian orbit and timing noise (represented as a polynomial of fifth order in time) provides a satisfactory fit to the data. However, because the Be star probably has a significant quadrupole moment, we prefer to interpret the data by a combination of timing noise, dominated by a cubic phase term, and ω^. and x ^. terms. We show that the ω^. and x ^. terms are likely to be a result of a precessing orbit caused by the quadrupole moment of the tilted companion star. We further rule out a number of possible physical effects which could contribute to the timing data of PSR B1259–63 on a measurable level.     

基于浏览器的气象再分析平台通用架构及组件设计

气象再分析在互联网中的应用还处于起步阶段,缺乏成熟的系统体系及开发标准。为降低开发人员开发气象再分析产品的难度,提升开发效率,同时避免开发人员误解气象用户需求,论文总结国家科技基础条件平台运行服务主系统功能完善项目的开发过程,基于经典的MVC三层模模型,提出面向气象领域的在线再分析平台通用架构,并将架构中数据过滤和数据显示封装为组件。工作以专业气象用户需求设计效果及习惯,以开发人员的开发模式开放配置接口,建立在线平台的开发基础。该成果用于洪水监测预警系统项目的需求分析,开发人员使用通用架构,再通过三步操作:匹配数据源、设计页面布局、配置组件,完成原型开发。以此优化系统架构过程,复用已有组件。     

Slow glitches in the pulsar B1822-09

The pulsar B1822-09 (J1825-0935) experienced a series of five unusual, slow glitches over the 1995–2004 interval. The results of further study of this unusual glitch phenomenon are presented. It is also reported the detection a new glitch of typical signature that occurred in the pulsar period in 2006 January.      

Radio Phase-Resolved Spectra of the Conal-Double Pulsar B1133 16

Based on dividing the profile into a number of absolute phase intervals,the phase-resolved spectra (PHRS) are derived from published time-aligned average profiles at radio frequencies over two decades for the classic conal-double pulsar B1133 16. The relative spectral index,defined as the difference between the spectral indices of a reference and the given arbitrary phase interval,is obtained by power-law fit at each phase interval. The derived phase-resolved spectra show an "M-like" shape,of which the leading part and trailing part are approximately symmetrical. The basic feature of the PHRS is that the spectrum first flat-tens then steepens as the pulse phase sweeps from the profile center to the profile edges. The PHRS provide a coherent explanation of the major features of profile evolution of B1133 16,namely,the pulse width shrinkage with increasing frequency and the frequency evolution of the relative intensity between the leading and trailing conal components,and the bridge emission. The PHRS may be an indicator for emission spectral variation across the pulsar magnetosphere. Possible mapping from PHRS to emission-location-dependent spectral vari-ation is presented,and some intrinsic mechanisms are discussed.