A stepwise method for determining the number of component distributions in a mixture     

Yu-Sheng Hsu  Joseph J. Walker  David E. Ogren 《Mathematical Geology》1986,18(2):153-160

This paper considers the problem of estimatingm, the number of components in a finite mixture of distributions from a parametric family. A step-up procedure using the bootstrap method is proposed. Some properties of the procedure are illustrated with simulation studies. An example of the method, applied to orientation of beach clasts, is given.  相似文献   

MERLIN Images of Five Compact Symmetric Object Candidates at 1.6 GHz     

Hai－YanZhang  XiangLiu 《中国天文和天体物理学报》2001,1(2):129-132

1 INTRODUCTIONCompact Symmetric Objects (CSOs) are powerful and compact sources (overall size <1 bpc) with lobe emission on both sides of the central engine. The small size of these sourcesis almost certainly to be attributed to the youth of the sources themselves (ages < 104 yr) andnot due to a dense coallning medium (Readhead 1996). The unification scenario assumes thatCSOs evolve into compact steep spectrum (CSS) sotirces and then into Fanaroff-Riley type 11objects (Fanti 1995). …  相似文献   

Apsidal corotation in mean motion resonance: the 55 Cancri system as an example   总被引：2，自引：0，他引：2  

Li-Yong Zhou  Harry J. Lehto  Yi-Sui Sun  Jia-Qing Zheng 《Monthly notices of the Royal Astronomical Society》2004,350(4):1495-1502

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The apparent copper complexing capacity of seawater and the interaction of copper with humic matter     

Mingyi  Sun 《中国海洋湖沼学报》1985,3(2):224-234

The anodic stripping voltammetry with physically-coating mercury film electrode was used to investigate the complexing action of trace heavy metals in seawater with organic ligands. The apparent copper complexing capacity of seawater was determined by titrating the organic ligands in natural seawater with standard ionic copper solution. The complexing actions of copper in seawater with humic acid (HA) or fulvic acid (FA) were investigated by titrating copper in seawater with HA or FA solution. The equilibrium time, electrodeposition potential, and effect of pH etc. were investigated respectively. The results show that the interaction of copper in seawater with organic matter is a fast process. At natural pH, HA or FA tend to act with copper in seawater to form nonlabile complexes. During experimental electrode process, these complexes did not significantly dissociate. The experimental results were calculated according to 1∶1 complex formation.  相似文献   

On the microwave millisecond spike emission and its associated phenomena during the impulsive phase of large solar flare     

Chun-sheng Li  Qi-jun Fu  Yu-hua Yan  Shu-ying Jiang  Hong-wei Li 《Chinese Astronomy and Astrophysics》1985,9(2):128-133

We propose a model of two acceleration regions, which can explain, on the basis of microwave maser caused by a “hollow-beam” distribution of electrons, the presence of millisecond spikes in the event of 1981 May 16 and their absence in the event of 1981 October 12, and the enhanced continuous emission in the latter. We have also uncovered relations among the features, e.g. the Type III_G, Type IV_DCIM and hard x-ray bursts, that accompany the microwave millisecond spikes during the impulsive phase of a large flare.  相似文献   

The elastodynamic near field     

Ru-Shan Wu  Ari Ben-Menahem† 《Geophysical Journal International》1985,81(3):609-621

Summary. The elastodynamic fields of point forces and shear dislocations of finite source duration are analysed with the aim of establishing the frequency and time-domain characteristics of the field in the near-source region. Criteria are obtained for amplitude dominance in regions where the source–sensor distance is much smaller than the wavelength.
It is shown that in the frequency domain , the Green's tensor (and hence the displacement field of a single point force) attenuates like R ⁻¹ in the near-source region and there exists no region in which the 'near-field' term becomes dominant such that the 'far-field' term can be neglected. Hence, there is no real 'near-field' term for the elastodynamic Green's tensor. The near-field terms of the displacements, velocities and accelerations excited by a shear dislocation attenuate like R ⁻², since the R ⁻³ and R ⁻⁴ terms tend to be eliminated due to mutual cancellation of P and S motions in the near-source region.
In the time domain , the corresponding near field of the displacement field is defined for the steady amplitude interval (away from transients) R /β < t < R /α+ T by the condition R ≤βT where β is the shear velocity and T is the source's duration. The relative strengths of all other arrivals will depend on the particular time window under consideration.
The particle motion patterns due to a single force in the near-source region are shown to be similar to rotating hyperbolas with an axis along the force direction, which are quite different from the 'smoke ring' motion patterns of the so-called 'near-field' term itself.  相似文献   

Study on numerical simulation to water lowering in an open coal mine digging     

Yanjun ZHANG Fenglong ZHANG Full QI Fuquan NI 《东北亚地学研究》2006,9(2):199-203

In view of the situation of excavation of open coal mine for the underground water disaster,we should carry out simulation studies for the numerical value of the water lowering project and improve the accuracy and the level of the water lowering project.On the basis of the hydrological geological conditions of certain open mine digging,a more reasonable seepage numerical model was built according to MODFLOW.It was simulated in advance that the process of the confined water level descending with the time,and combining with the actual observations to test the correctness of the model.The calculation showed that the results coincided well with the results of actual measurement.Based on this,different water lowering numerical simulations were built for the open coal mine digging.It could be simulated and forecast that the changes of the groundwater level in drainage process within and outside the mine pit,and it was quantitatively assessed that the possible water lowering result of the opencast water drainage process,which provide an important basis for the actual water lowering project and the possible project disposal.  相似文献   

The global joule heat production rate and the AE index     

Sun Wei  B.-H. Ahn  S.-I. Akasofu 《Planetary and Space Science》1985,33(3):279-281

The accuracy of the AE index as a measure of the joule heat production rate is examined for a typical substorm event on 18 March 1978 by estimating the global joule heat production rate, as a function of time, using data obtained from the IMS six meridian chains. In spite of the fact that the AE index had had an initial slow growth which was followed by a rapid growth, the joule heat production rate attained a high level during the slow growth and thus their variations were considerably different from those of the AE index. Therefore, although the AE index is statistically linearly related to the global joule heat production rate, one should be cautious in assuming that details of time variations of the AE index during individual events represent those of the joule heat production rate.  相似文献   

石英砂扫描电镜在漓江“泥砾”成因中的应用     

吴枝坦  王壬林  姚若飞 《南方国土资源》1992,(4)

本文根据扫描电镜对从漓江河谷钻孔中的泥砾层取得的481粒石英砂表面形态特证研究结果:石英砂多数颗粒保持棱角状外形并遭受不同程度的磨蚀,具阶状贝壳断口,平直或弧形刮削面和多向擦痕,沿解理面破碎呈“V”字形沟和撞击碟形坑,以及微溶蚀孔、隙、蜂窝状溶孔群和SiO_2再沉积等表面形态结构特征。认为它是在第四纪古地理湿热气候条件下泥石流沉积的产物,物源可能来自境内或周边的泥盆系砂岩和境外的花岗岩。  相似文献   

差分观测与伪距观测的定位精度     

孙宏伟  李玉莉 《时间频率学报》1993,(2)

严格论证了在对空间或地面目标的定位中,利用伪距测量观测模型的几何因子大于用台站间一次差分观测模型的几何因子.此外,台站间完全差分测量观测的定位精度优于不完全测量情形的定位精度.这些结果给人们在实际工作中采取何种定位方式提供了可靠的理论依据.  相似文献