四川盆地干旱动态评估指标的研究

在仔细分析干旱灾害物理成因基础上,围绕定量化和实时化这一核心,根据土壤水分盈亏原理,建立了具有清晰的物理意义的干旱动态评估指标。经检验,该方法符合实际,简便可行。     

A direct comparison of C and Th ages at Searles Lake, California

Thorium-230 dating on saline of the Lower Salt unit in pluvial Searles Lake, California, shows that this unit was formed between 24,500 and 32,000 years ago. The initial apparent ¹⁴C age of the lake is estimated to be about 900 years. After correcting for nonradiogenic ²³⁰Th and for the initial ¹⁴C age, excellent agreement between ²³⁰Th and ¹⁴C ages is obtained. The reliability of ²³⁰Th dating on salt deposit opens a new way for continuation of absolute chronology below the Lower Salt in Searles Lake.     

Correlations among color,morphology, and luminosity for the luminous red galaxy (LRG) sample of the SDSS data release 5

We have investigated the correlations among color, morphology and luminosity for all LRGs, cut I LRGs, cut II LRGs, and Main galaxies that are also classified as LRGs. It is found that the morphology of LRGs is tightly correlated with luminosity. The rest-frame u-g color of cut I LRGs and cut II LRGs is nearly independent of luminosity, but the color of Main galaxies is correlated with luminosity. For cut I LRGs and Main galaxies, the early type proportion apparently changes with color: at the rest-frame u-g < 1.3 it increases strongly with increasing color, while at the rest-frame u-g > 1.3 it decreases with increasing color. We also notice that the morphology of cut II LRGs is only a weak function of color. Published in Astrofizika, Vol. 50, No. 3, pp. 335–345 (August 2007).     

Eclipses and Occultations of Galilean Satellites Observed at Yunnan Observatory in 2003

We describe and analyze observations of mutual events of Galilean satellites made at the Yunnan Observatory in February 2003 from CCD imaging for the first time in China. Astrometric positions were deduced from these photometric observations by modelling the relative motion and the photometry of the involved satellites during each event.     

Quantitative determination of the salinity of seawater droplet in 10−6 to 10−10 gram

The rate of evaporation of seawater droplets in the air-sea boundary layer can be estimated by its salinity change compared to the sea surface salinity. A micro-chemical method based on Farlow (1954) is developed for quantitative determination of the salinity of an individual droplet without the error due to further evaporation after sampling. A halide ion-sensitive sampling surface is prepared by colloidally dispersing brown silver dichromate into the gelatin layer of a commercially available film. The reaction of soluble chlorides with the silver salt leaves a clear white halo with diametera on the brown film to reveal the volume of the droplet. After the film is developed in a water vapor saturated atmosphere, the halo grows to diameterd with the original as the embryo to indicate the quantity of chloride ion involved in the action. The ratio ofd/(a^1.5) is a function of the salinity of the droplet. The method can be used to determine the salinity of seawater droplet of 10⁻⁶ to 10⁻¹⁰ gram. Details of the principle and preparation, and calibration of the reagent film, are presented. Contribution No. 1708 from the Institute of Oceanology, Academia Sinica. The research was supported by the Chinese National Natural Science Foundation. The paper was prepared while the author was a visiting scholar at the Department of Atmospheric Sciences, AK-40, University of Washington, Seattle, Washington 98195, USA (from May to July, 1989), and Scripps Institution of Oceanography, A-030, University of California, La Jolla, California 92093, USA (from September, 1989 to February, 1990).     

GAIM电离层同化方法进展

电离层是复杂的空间层结,其变化受太阳活动强度、地球磁场等因素影响。随着空间技术发展的需求,电离层天气变化成为目前空间天气预报最重要的内容之一。最近10年,人们利用卫星在电离层观测方面取得了重大进展,尤其引人注意的是:无线电掩星观测技术正走向应用的新阶段,加上已经建立的全球大量的地基GPS观测网,它们不仅为电离层动力学模式研究提供了丰富的电离层资料,而且为电离层预报提供了很好基础。因此,电离层天气预报成为当前重要的、前瞻性的研究方向,电离层资料同化是电离层预报最重要的研究内容之一。该文系统介绍这方面国际动态,重点是美国的USC/JPL和犹他州大学开展全球电离层同化模型研究、全球电离层同化研究的进展,以及在电离层天气预报中应用的初步成果。     

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Disk Thicknesses and Some Parameters of 108 Non-Edge-On Spiral Galaxies

We present disk thicknesses, some other parameters and their statistics of 108 non-edge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson's equation for a disturbance of matter density in three-dimensional spiral galaxies. From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point (the forbidden region with radius r 0 to the galactic center) of the spiral arm, and finally the thickness.     

一种新的超声波心动图像分割算法

针对超声心动图像噪声大,边界模糊,灰度分布不均匀等特点,提出了一种新的图像分割算法.首先对超声图像进行滤波和边缘锐化等预处理,然后再使用GVFSnake模型对预处理后的图像进行分割,从而提取出心室的边界.经试验证明,这种新的超声心动图像分割算法,比传统的超声图像分割算法在图像分割精度上有显著的提高.     

50个发射线天体的物端稜镜光谱

从1981年开始,北京天文台开展了发射线星系的物端稜镜巡天。用60/90cm Schmidt望远镜加5.°3的物端稜镜在敏化的ⅢaJ底片上可以得到亮于16~m的星系光谱像。本文公布了第一批巡天结果:在覆盖天区约220平方度的12张底片上证认出50个发射线天体,47个河外星系(其中3个可能是新的Seyfert星系),3个行星状星云(其中一个N2242以前被当作河外星系)。文中给出了这些天体的名称、坐标、星等及光谱结构分类等资料,并比较系统地讨论了发射线星系的证认及光谱结构分类。我们还将本巡天的结果与其他天文台的结果作了比较。这些天体的证认图见图版Ⅰ—Ⅱ。