多源地理空间数据同化的主动更新与应用分析

为提高数据更新过程中多源数据整合利用的效率和更新的自动化程度,将"数据同化"和主动数据库的思想与方法引入空间数据的更新。论述了"多源地理空间数据同化"和"主动更新"的概念、内涵和关键技术,提出了"地理事件-条件-动作"规则驱动下数据同化的地理空间数据主动更新机制。最后,将数据同化中常用的最优插值方法,应用于多源地理空间数据的合并,该方法与其他合并方法相比,能提高数据的精度;将主动更新机制应用于数据更新实践,结果表明,该机制可以提高更新的自动化程度。     

中国各省市区开放型经济水平比较研究

改革开放以来,中国不断深化发展开放型经济。十七大报告明确提出"拓展对外开放广度和深度,提高开放型经济水平"。由于受地缘、人缘、政府宏观调控、跨国公司产业配置、国际分工、生产要素全球流动等因素影响,各省市区开放型经济水平存在差异。在前人研究的基础上设计了评价国内各省市区开放型经济水平的指标体系,并采用2004—2008年连续5年的相关数据,用主成分分析法测算出我国各省市区开放型经济水平。最后,对计算结果进行综合评价和分类比较得出若干结论。     

沉井侧壁摩阻力室内试验研究

沉井侧壁摩阻力的大小和分布是沉井结构设计以及助沉方法选择的依据。目前,其计算方法带有较强的经验性,计算结果与实际情况往往存在较大差异。为了进一步认识和掌握其分布规律,研制了能够直接测量沉井侧壁阻力的微型摩阻力仪,并对其准确性、稳定性和可靠性进行了验证;然后,利用该仪器以及静态应变测试系统等电测设备开展沉井下沉阻力的模型试验。试验表明：随着入土深度的增加,沉井侧壁摩阻力的变化特征可分为3个阶段,在第1阶段,侧壁摩阻力随深度的增加接近线性增加;在第2阶段,随着深度的增加,侧壁摩阻力总体仍是上升的,但其上升速率则有所降低,在下沉一定深度后,摩阻力达到峰值;在第3阶段,侧壁摩阻力随入土深度的增加而逐渐减小。运用极限分析理论,对上述变化规律的原因进行了分析。上述试验及分析成果可作为现场原位测试数据的补充,两者共同为沉井下沉阶段的侧壁摩阻力计算研究提供基础数据支持。     

厦门高集海堤开口改造工程潮流泥沙物理模型试验研究

通过潮汐水流和悬沙淤积物理模型试验,研究厦门高集海堤开口改造工程潮流泥沙问题,研究表明,高集海堤开口后,东、西海域两股水流的汇流区和分流区在高集海堤附近,东海域涨潮流速有所增大,落潮流速有所减小,西海域则相反;随着开口宽度增大,流速变幅增大,开口大于800 m后流速变幅趋缓;海堤开口后净输水方向为自东海域向西海域,有利于厦门湾内水体与外海的交换;高集海堤开口对东渡港区泥沙淤积影响不大.综合分析认为高集海堤开口宽度800～1 000 m较为合适,开口800 m时大潮条件下1d的净输水量约0.91×108m3,东渡北港区港池年平均回淤强度增大0.18 m/a左右,航道淤强增大0.05 m/a左右.     

The massive star binary fraction in young open clusters – I. NGC 6231 revisited

We present the results of a long-term high-resolution spectroscopy campaign on the O-type stars in NGC 6231. We revise the spectral classification and multiplicity of these objects and we constrain the fundamental properties of the O-star population. Almost three quarters of the O-type stars in the cluster are members of a binary system. The minimum binary fraction is 0.63, with half the O-type binaries having an orbital period of the order of a few days. The eccentricities of all the short-period binaries are revised downward, and henceforth match a normal period–eccentricity distribution. The mass ratio distribution shows a large preference for O + OB binaries, ruling out the possibility that, in NGC 6231, the companion of an O-type star is randomly drawn from a standard initial mass function. Obtained from a complete and homogeneous population of O-type stars, our conclusions provide interesting observational constraints to be confronted with the formation and early evolution theories of O-stars.     

A robust statistical estimation of the basic parameters of single stellar populations – I. Method

The colour–magnitude diagrams of resolved single stellar populations, such as open and globular clusters, have provided the best natural laboratories to test stellar evolution theory. Whilst a variety of techniques have been used to infer the basic properties of these simple populations, systematic uncertainties arise from the purely geometrical degeneracy produced by the similar shape of isochrones of different ages and metallicities. Here we present an objective and robust statistical technique which lifts this degeneracy to a great extent through the use of a key observable: the number of stars along the isochrone. Through extensive Monte Carlo simulations we show that, for instance, we can infer the four main parameters (age, metallicity, distance and reddening) in an objective way, along with robust confidence intervals and their full covariance matrix. We show that systematic uncertainties due to field contamination, unresolved binaries, initial or present-day stellar mass function are either negligible or well under control. This technique provides, for the first time, a proper way to infer with unprecedented accuracy the fundamental properties of simple stellar populations, in an easy-to-implement algorithm.     

Stellar contents and star formation in the young star cluster Be 59

We present   UBV  I _c   CCD photometry of the young open cluster Be 59 with the aim to study the star formation scenario in the cluster. The radial extent of the cluster is found to be ∼10 arcmin (2.9 pc). The interstellar extinction in the cluster region varies between   E ( B − V ) ≃ 1.4  to 1.8 mag. The ratio of total-to-selective extinction in the cluster region is estimated as  3.7 ± 0.3  . The distance of the cluster is found to be  1.00 ± 0.05 kpc  . Using near-infrared (NIR) colours and slitless spectroscopy, we have identified young stellar objects (YSOs) in the open cluster Be 59 region. The ages of these YSOs range between <1 and ∼2 Myr, whereas the mean age of the massive stars in the cluster region is found to be ∼2 Myr. There is evidence for second-generation star formation outside the boundary of the cluster, which may be triggered by massive stars in the cluster. The slope of the initial mass function, Γ, in the mass range  2.5 < M /M_⊙≤ 28  is found to be  −1.01 ± 0.11  which is shallower than the Salpeter value (−1.35), whereas in the mass range  1.5 < M /M_⊙≤ 2.5  the slope is almost flat. The slope of the K -band luminosity function is estimated as  0.27 ± 0.02  , which is smaller than the average value (∼0.4) reported for young embedded clusters. Approximately 32 per cent of Hα emission stars of Be 59 exhibit NIR excess indicating that inner discs of the T Tauri star (TTS) population have not dissipated. The Midcourse Space Experiment (MSX) and IRAS-HIRES images around the cluster region are also used to study the emission from unidentified infrared bands and to estimate the spatial distribution of optical depth of warm and cold interstellar dust.     

L dwarfs in the Hyades

We present the results of a proper motion survey of the Hyades to search for brown dwarfs, based on UKIRT Deep Sky Survey (UKIDSS) and Two-Micron All Sky Survey (2MASS) data. This survey covers  ∼275 deg²  to a depth of   K ∼ 15  mag, equivalent to a mass of  ∼0.05 M_⊙  assuming a cluster age of 625 Myr. The discovery of 12 L dwarf Hyades members is reported. These members are also brown dwarfs, with masses between  0.05 < M < 0.075 M_⊙  . A high proportion of these L dwarfs appear to be photometric binaries.