ANALYSES OF THE ANNUAL FREQUENCY ANOMALIES OF TYPHOONS AND HURRICANES IN 1998     

李曾中  程明虎  杨振斌  孙除荣  薛建军 《热带气象学报(英文版)》2004,10(2):144-149

In 1998, the annual frequency of typhoon (including tropical storms) genesis created a minimum value — 14, far lower than the minimum of 20 in 1950 over North-West Pacific, while in the Atlantic Ocean, the annual frequency of hurricanes (including the …  相似文献   

相同强度双台风相互作用的物理机制   总被引：2，自引：1，他引：1  

田永祥  江燕如 《南京气象学院学报》1998,21(2):215-222

在无基本气流的假定下,应用无辐数正压模式研究双台风相互作用的物理机制。台风Ａ位于观风Ｂ以西,两台风相距６０ｋｍ,且具有相同的强度。在台风Ａ（台风Ｂ）的非对称流场中,由台风Ａ（台风Ｂ）的线性β效应产生的非对称涡旋的方位相位与由台风Ｂ（台风Ａ）形成的非对称涡旋方位相位相反（相同）。因此,台风Ａ（台风Ｂ）的大尺度非对称涡旋较弱（较强）。小尺度涡旋逆时针旋转导致台风Ａ逆时将打转。稳定的偏南非对称气流使台风  相似文献   

数学形态学及其在二值影象分析中的应用     

李德仁  陈晓勇 《武汉大学学报(信息科学版)》1989,(3)

本文介绍了数学形态学的基本概念,利用一些简单例子叙述其定义、逻辑变换和形态变换的基本算子及其作用。文中对数学形态学在二值影象如汉字和栅格扫描的地图的数据分析中的应用可能性也进行了探讨。这些讨论对于建立地理信息系统的测量数据库是有益的。  相似文献   

中国跨省流动人口回流意愿的空间差异及影响因素   总被引：1，自引：0，他引：1  

张华  刘哲达  殷小冰 《地理科学进展》2021,40(1):73-84

在中国城市产业结构升级和乡村经济发展的宏观背景下,乡城流动人口的返乡回流现象逐渐显现,流动人口呈现外出与回流并存的趋势,大量的流动人口回流对中国的新型城镇化和城乡发展产生了重要影响,是探索中国城乡关系变化的重要视角。论文采用2016年全国流动人口卫生计生动态监测调查数据,建立二分类Logistic模型,对全国跨省流动人口回流意愿的空间差异和影响因素进行分析。研究结果表明：① 具有回流意愿的流动人口具有相似的人口学特征,包括年龄较大、受教育水平较低、没有稳定的婚姻状态等;② 跨省流动人口的回流意愿具有明显的空间差异,从流入地来看,东南沿海地区和西部地区的流动人口回流意愿较高,从流出地来看,中部地区的流动人口回流意愿较高;③ 流动人口的回流意愿受到个人因素、流动因素、家庭因素、制度因素多个方面的影响,其中年龄、婚姻状况、受教育程度、进城务工时间、是否为独自流动、家庭月收入、现住房性质、社会保障制度对流动人口回流意愿具有显著影响。  相似文献   

二值马尔科夫模型和多波段遥感影像的多尺度纹理分割     

龚龑  舒宁 《武汉大学学报(信息科学版)》2008,33(1):21-24

提出一种二值马尔科夫纹理分割模型,用于多波段遥感影像的纹理分割.将一次性多类纹理分割问题转化为多次的二类纹理分割,综合考虑影像二维空间尺度和光谱空间尺度,采取多级二值分割的方式,得到多尺度纹理分割结果.  相似文献   

Local integrals and the plane motion of a point in rotating systems     

Vadim A. Antonov  Faziliddin T. Shamshiev 《Celestial Mechanics and Dynamical Astronomy》1993,56(3):451-469

This paper deals with the plane motion of a star in the gravitational field of a system which is in a steady state and rotates with a constant angular velocity. For these systems a class of potentials permitting a local integral, linear with respect to the velocity components, has been found. The concept of the local integral itself was introduced by one of the authors of the present paper (Antonov, 1981). A detailed model has been constructed. The corresponding domain of the particle motion and the form of the trajectory coils have been determined. The result is compared with the motion in a more realistic potential.  相似文献   

基于休憩行为的"东道主/游客"二元关系研究——以黄山市屯溪区为例     

徐工作  苏勤  李慧 《亚热带资源与环境学报》2007,2(3):76-80

基于游客与居民休憩的态度和行为,以黄山市屯溪区为例,通过实地的问卷和访谈调查,对当地的游客与居民休憩行为进行了实证研究.在此基础之上,对当地的休憩行为做了"东道主/游客"二元关系的探讨,经比较研究发现:居民在主客交往中具有很强的主动性,交往的意愿非常强烈,而游客却略显被动,交往的意愿不太强烈,并且有所顾虑.  相似文献   

A white dwarf in the state of an ejector     

N. R. Ikhsanov  V. V. Neustroev  N. G. Beskrovnaya 《Astronomy Letters》2004,30(10):675-684

We analyze the possibility of observational identification of white dwarfs in the state of an ejector. Among the distinctive features of this class of objects are a high rate of rotational energy loss comparable to or higher than the observed luminosity of the object and nonthermal gamma-ray and/or radio spectra. The manifestations of the white dwarf in the close binary system AE Aquarii closely match these criteria. We show that most of the peculiar manifestations of this object in the hard spectral range and the observed pattern of mass transfer in the system can be explained in terms of a model in which the state of the white dwarf is classified as an ejector.  相似文献   

Teacher''s Aide: Geologic Characteristics of Hole-Effect Variograms Calculated from Lithology-Indicator Variables     

Thomas A. Jones  Yuan Z. Ma 《Mathematical Geology》2001,33(5):615-629

Variograms calculated from binary variables, such as from two lithologies, tend to show sinusoidal forms with decreasing amplitudes for increasing lag distances. This cyclicity is observed often when analyzing drill-hole data for rock sequences with alternating lithologies, and the variograms are thus labeled hole-effect variograms. Such variograms show a variety of forms: (1) Low to moderate variation in lithologic-body dimensions causes variograms to have strong cyclicity with decaying amplitude. (2) Variograms with one or more peaks and troughs usually result from a binary variable for which lithologies are about equally abundant but possibly large variations exist in the size of lithologic bodies. (3) Variograms show poor cyclicity if one lithology has highly variable body sizes and the other has moderately variable body dimensions. (4) Variograms that attain a plateau at short lag distances represent extremely high or low sandstone fraction, high variability in size of the most abundant lithology, and low variability in the other. Information about the dimensions of lithologic bodies makes it possible to approximate characteristics of the variogram of the lithology variable without numerous wells. Conversely, a hole-effect variogram of lithology may be used to estimate lithologic dimensions.  相似文献   

Non-LTE effects for Na I lines in X-ray illuminated stellar atmospheres     

N. A. Sakhibullin  V. V. Shimansky 《Astronomy Letters》2000,26(5):309-318

The formation of Na I lines in X-ray illuminated atmospheres is investigated by abandoning the assumption of local thermodynamic equilibrium (LTE). Calculations are performed on the basis of a 21-level Na I model atom for the LTE model atmospheres of irradiated F-G stars obtained with allowance for a reflection effect in the first approximation. The state of extreme “overrecombination” is shown to exist for the populations of all Na I levels in the case of external illumination. Absorption features in the profiles of “cool” and “normal” Na I lines have been found to be enhanced compared to the LTE approximation. Effects of the angle of incidence and intensity of the external radiation on the formation of level populations and line profiles when abandoning LTE are analyzed. The existence of overrecombination for Na I is explained by the small X-ray heating function and the large optical cooling function. Na I level populations are shown to depend weakly on the presence of “overionization” for Na II in the atmospheres of irradiated stars.  相似文献