1996年8月8日闽西地区特大暴雨过程分析

本文研究了9601号热带风暴减弱为低压环流后引起突发性大暴雨的成因。结果表明：9610号热带风暴减弱后的低压环流移支福建省南部地区,造成闽西地区湿斜压锋区和不稳定能量明显增强,在低压西侧辐合线所提供的福合上升运动激发下,中尺度对流云团迅速发展,导致远离低压中心的闽西突发大暴雨。闽西特殊的地形对特大暴雨的产生起了组织和增幅作用。另外,还通过逐时数字红外云团图的分析,揭示中尺度对流云团发展演变特征与突发性大暴雨的关系,供日常短时预报参考。     

若尔盖等地风能资源评价

本文用平均风速和最大风速法对若尔盖等三地的韦伯分布参数k、c进行估算,并用韦伯分布计算风能的指标。计算表明:若尔盖、红原属风能可利用区,用风力发电是有利用价值的;阿坝属风能贫乏地区。     

Mkn501长期光变性质

在R和I波段对Mkn 501进行了测光观测,并结合历史文献得到Mkn 501在近30年间的光学、红外和射电等多个波段的光变曲线;讨论了光变与色指数之间的关系,发现色指数(B—V)与(B—R)之间有强相关,相关系数r=0.73.利用DCF方法分析了多波段光变的相关性,发现B波段与4.8GHz和红外波段的光变存在一定的正相关,利用CLEANest方法对B波段的光变曲线进行频谱分析,结果表明Mkn 501的光变曲线存在2个可能的周期,即(10.06±0.04)年和(21.60±0.17)年.     

Variations of b‐values at the western edge of the Ryukyu Subduction Zone,north‐east Taiwan

Using earthquakes relocated in north‐east Taiwan, we estimated b‐value distribution along a cross‐section located near the Ryukyu slab edge, and four b‐value anomalous areas are evidenced: (1) a high b‐value body lying on top of a low Vp, low Vs and high Vp/Vs sausage‐like body was considered as a region of enhanced partial melt or water supply above which seismicity occurs; (2) beneath the Ilan Plain, an anomalous area characterized by b‐values slightly higher than 1.1 might give evidence to the magma conduits to the Kueishantao Island; (3) above the Ryukyu Wadati‐Benioff zone, at depths ranging from 90 to 110 km, a high b‐value anomaly might correspond to the depth where dehydration occurs in the subducting oceanic plate; and (4) a low b‐value area located within the Ryukyu slab, at depths ranging from 70 to 90 km, might be linked to the compressive mechanisms shown by focal mechanisms and the bending of the subducting plate.     

一种基于小波熵的时间尺度算法

结合小波分析和熵的基本理论,在分析国际原子时TAI的基础上,提出了基于小波熵的时间尺度算法．通过对原子钟信号进行多尺度分解,根据能量划分,综合所有尺度的小波系数得到小波熵,然后利用小波熵对原子钟进行加权．最后,通过某实验室的实测数据对算法进行了检验,结果表明:这种方法能够综合各原子钟信号在不同尺度上的频率波动特征,明显提高了时间尺度的稳定度．     

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。     

基于模糊Hopfield神经网络的大气降水粒子分类

提出基于模糊Hopfield神经网络的大气降水粒子分类,它是通过计算样本间的模糊关系的相似程度,再加上Hopfield网络所特有的高稳定性,对大气降水粒子进行分类.通过对各降水粒子所对应雷达回波数据的分析,验证了方法的可行性.     

The hydrothermal karstification and its effect on Ordovician carbonate reservoir in Tazhong uplift of Tarim Basin,Northwest China

With a detailed study on petrology, mineralogy and geochemistry of some important Ordovician carbonate well core samples in Tazhong uplift of Tarim Basin, the distinguishing symbols of hydrothermal karstification are first put forward as the phenomena of rock hot depigmentation, hot cataclasm and the appearance of typical hydrothermal minerals such as fluorite, barite, pyrite, quartz and sphalerite. The main homogenization temperatures of primary fluid inclusions in fluorite are from 260 to 310°C, indicating the temperature of hydrothermal fluid. The fluid affected the dissolved rocks and showed typical geochemistry features with low contents of Na and Mg, and high contents of Fe, Mn and Si. The ratio of ³He/⁴He is 0.02R _a, indicating the fluid from the typical continental crust. The hydrothermal fluid karstification pattern may be described as follows: the hot fluid is from the Permian magma, containing dissolving ingredients of CO₂ and H₂S, and shifts along fault, ruptures and unconformity, and dissolves the surrounding carbonates while it flows. The mechanism of hydrothermal karstification is that the mixture of two or more fluids, which have different ion intensity and pH values, becomes a new unsaturated fluid to carbonates. The hydrothermal karstification is an important process to form hypo-dissolved pinholes in Ordovician carbonates of Tazhong uplift of Tarim Basin, and the forming of hydrothermal minerals also has favorable influence on carbonate reservoirs.

     

Star formation and figure rotation in the early-type galaxy NGC 2974

We present Galaxy Evolution Explorer ( GALEX ) far-ultraviolet (FUV) and near-ultraviolet (NUV) imaging of the nearby early-type galaxy NGC 2974, along with complementary ground-based optical imaging. In the ultraviolet, the galaxy reveals a central spheroid-like component and a newly discovered complete outer ring of radius 6.2 kpc, with suggestions of another partial ring at an even larger radius. Blue FUV–NUV and UV-optical colours are observed in the centre of the galaxy and from the outer ring outwards, suggesting young stellar populations (≲1 Gyr) and recent star formation in both locations. This is supported by a simple stellar population model which assumes two bursts of star formation, allowing us to constrain the age, mass fraction and surface mass density of the young component pixel by pixel. Overall, the mass fraction of the young component appears to be just under 1 per cent (lower limit, uncorrected for dust extinction). The additional presence of a nuclear and an inner ring (radii 1.4 and 2.9 kpc, respectively), as traced by [O  iii ] emission, suggests ring formation through resonances. All three rings are consistent with a single pattern speed of  78 ± 6  km s⁻¹ kpc⁻¹, typical of S0 galaxies and only marginally slower than expected for a fast bar if traced by a small observed surface brightness plateau. This thus suggests that star formation and morphological evolution in NGC 2974 at the present epoch are primarily driven by a rotating asymmetry (probably a large-scale bar), despite the standard classification of NGC 2974 as an E4 elliptical.