Discussion of “Wave setup and setdown generated by obliquely incident waves” by T.-W. Hsu et al., Coastal Engineering, 53, 865–877, 2006     

Fengyan Shi  James T. Kirby 《Coastal Engineering》2008,55(12):1247-1249

In the recent paper by Tai-Wen Hsu, John R.-C. Hsu, Wen-Kai Weng, Swun-Kwang Wang, and Shan-Hwei Ou (Coastal Engineering, 53, 865–877, 2006), the authors derived theoretical formulations for calculating the wave setup and setdown induced by obliquely incident waves on a beach. The derivation of an expression for setdown contains errors which would lead to an imbalance in longshore momentum flux outside the surfzone. We correct their derivation and give results in terms of the radiation stress concept in a general case including an oblique wave incidence. We also point out that the correct form of wave setdown is important to describe the zero-net force in the momentum balance outside the surfzone.  相似文献   

国土资源数据管理初探   总被引：2，自引：0，他引：2  

史辉  李军  冯永玉 《山东国土资源》2008,24(3):45-50

在分析国土资源数据及其管理特点的基础上，基于国土资源信息化和数据资源保护，将国土资源数据整体上分为资料数据、基础数据、业务数据、管理数据和元数据5类，提出了各类数据进行计算机管理的组织方法和采用的相关技术。  相似文献   

"珍珠"台风强度及路径异常的分析   总被引：2，自引：1，他引：1  

姜丽萍  夏冠聪  尤红  黄静  马慧 《台湾海峡》2008,27(1):124-128

利用常规观测资料和NCEP 1°×1°格点资料,从能量场、湿度场、辐散场以及西南季风和越赤道气流等多方面对"珍珠"的强度及路径进行分析,发现副高前期在南海的维持以及副高后期环流形势的调整是"珍珠"强度维持和路径突变的关键;南海海域维持高能区、弱水平风垂直切变、对流层上层强大的辐散场、以及充沛的水汽供应、风场动力非对称结构等是"珍珠"强度能维持的重要原因;西南季风、越赤道气流和副高南落而引发的东南风急流形成的季风汇合线是"珍珠"北翘的直接原因.台风风场结构中不对称强风速区的转移对台风路径改变有预示作用.  相似文献   

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赵建虎  刘辉  王胜平 《大地测量与地球动力学》2009,29(2):82-87

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a′Trous小波变换与PCA变换相结合的遥感影像融合分析     

林卉  景海涛  张连蓬 《地球信息科学学报》2008,10(2):269-272

随着高分辨率遥感卫星的产生,传统的融合技术难以达到较好的融合效果,如主成分分析(PrincipalComponents Analysis)变换融合受到融合区域的限制,而传统的小波融合(Wavelet Transformation)算法由于高频直接替换,导致了一定程度的光谱失真,由此本文在分析主成分分析变换和a′Trous小波变换(WT)的基础上,以QuickBird全色和多光谱数据为实验数据,提出了一种将两者相结合的遥感影像融合方法,通过与其他融合方法的定量和视觉比较,结果表明该方法能得到更好的融合效果。  相似文献   

A Statistical Study of Rapid Sunspot Structure Change Associated with Flares     

Wei-Zhong Chen Chang Liu Hui Song Na Deng Chang-Yi Tan Hai-Min Wang 《中国天文和天体物理学报》2007,7(5):733-742

We reported recently some rapid changes of sunspot structure in white-light(WL) associated with major flares.We extend the study to smaller events and present here results of a statistical study of this phenomenon.In total,we investigate 403 events from 1998 May 9 to 2004 July 17,including 40 X-class,174 M-class,and 189 C-class flares.By monitoring the structure of the flaring active regions using the WL observations from the Transition Region and Coronal Explorer(TRACE),we find that segments in the outer sunspot structure decayed rapidly right after many flares;and that,on the other hand,the central part of sunspots near the flare-associated magnetic neutral line became darkened.These rapid and permanent changes are evidenced in the time profiles of WL mean intensity and are not likely resulted from the flare emissions.Our study further shows that the outer sunspot structure decay as well as the central structure darkening are more likely to be detected in larger solar flares.For X-class flares,over 40% events show distinct sunspot structure change.For M-and C-class flares,this percentage drops to 17% and 10%,respectively.The results of this statistical study support our previously proposed reconnection picture,i.e.,the flare-related magnetic fields evolve from a highly inclined to a more vertical configuration.  相似文献   

长江沿江地区化工产业空间格局演化及影响因素   总被引：1，自引：1，他引：1  

邹辉  段学军 《地理研究》2019,38(4):884-897

基于企业数据和空间计量方法,探讨了长江沿江地区2000—2013年化工产业空间格局演化及影响因素。结果表明：化工产业主要分布在上海市和江苏沿江地区;中上游部分地区化工产业呈现明显的增长势头,由3个主要热点区发展到20余个不同规模大小的分布热点,成为化工产业新兴“增长极”;城市主城区化工产业减少而远郊区县增加,分布热点变化也反映了化工产业“郊区化”“园区化”的过程;相对低端基础的行业呈现集聚趋势,其中肥料业集聚明显;相对高端精细的行业呈现扩散趋势,其中合成材料业分散化明显;地区化工产业增长受到环境规制、外商投资、交通区位等因素显著影响,外商投资和交通区位具有显著的促进作用,而环境规制呈现显著的抑制效果。  相似文献   

Examining the sensitivity of spatial scale in cellular automata Markov chain simulation of land use change   总被引：2，自引：0，他引：2  

Hao Wu  Zhen Li  Keith C. Clarke  Wenzhong Shi  Anqi Lin 《International journal of geographical information science》2019,33(5):1040-1061

Understanding the spatial scale sensitivity of cellular automata is crucial for improving the accuracy of land use change simulation. We propose a framework based on a response surface method to comprehensively explore spatial scale sensitivity of the cellular automata Markov chain (CA-Markov) model, and present a hybrid evaluation model for expressing simulation accuracy that merges the strengths of the Kappa coefficient and of Contagion index. Three Landsat-Thematic Mapper remote sensing images of Wuhan in 1987, 1996, and 2005 were used to extract land use information. The results demonstrate that the spatial scale sensitivity of the CA-Markov model resulting from individual components and their combinations are both worthy of attention. The utility of our proposed hybrid evaluation model and response surface method to investigate the sensitivity has proven to be more accurate than the single Kappa coefficient method and more efficient than traditional methods. The findings also show that the CA-Markov model is more sensitive to neighborhood size than to cell size or neighborhood type considering individual component effects. Particularly, the bilateral and trilateral interactions between neighborhood and cell size result in a more remarkable scale effect than that of a single cell size.  相似文献   

基于DEM数据的巴丹吉林沙漠沙丘分布规律及其形态参数     

汪克奇  赵晖  王兴繁  杨宏宇  晁倩 《中国沙漠》2020,40(4):81-94

沙丘形态特征是风沙地貌研究的重要内容。数字高程模型（DEM）因卓越的三维地形表达能力被广泛应用于沙丘形态研究中。长期以来，受交通条件和研究方法的制约以及高大沙山分布位置的限定，对巴丹吉林沙漠沙丘形态的研究主要集中在沙漠东南部，缺乏对整个沙漠沙丘分布规律及其形态参数特征的系统认知。而对整个沙漠沙丘形态特征的研究，是区域风沙地貌形成与演化研究的重要组成部分。以巴丹吉林沙漠内所有独立沙丘为研究对象，利用研究区DEM数据和一种新的算法，研究了沙漠内两种主要类型沙丘（横向沙丘、星状沙丘）的分布规律及其形态参数特征。结果表明：沙漠内独立沙丘大约有6 033座，高度9~433 m，高度超过350 m的巨型沙山共有53座，其中星状沙山7座，最大高度383 m；横向沙山46座，最大高度433 m。横向沙丘高度与等效沙丘厚度呈正相关的线性函数关系，星状沙丘高度与等效沙丘厚度呈正相关的对数函数关系，表明在现代气候和环境条件下，横向沙丘高度仍在增加，而星状沙丘高度增长已经趋缓。两类沙丘的主轴向大都垂直于研究区主风向NW-SE。横向沙丘起沙风风向单一，沙丘轴向集中在NE-SW和NNE-SSW方向；星状沙丘起沙风风向略为复杂，沙丘存在多个次级轴向。  相似文献   

Application of Astronomic Time-latitude Residuals in Earthquake Prediction   总被引：1，自引：0，他引：1  

Han Yanben  Ma Lihua  Hu Hui  Wang Rui  Su Youjin 《Earth, Moon, and Planets》2007,100(1-2):125-135

After the earthquake (Ms = 6.1) occurred in Luquan county of Yunnan province on April 18, 1985, the relationship between major earthquakes and astronomical time-latitude residuals (ATLR) of a photoelectric astrolabe in Yunnan Observatory was analyzed. ATLR are the rest after deducting the effects of Earth’s whole motion from the observations of time and latitude. It was found that there appeared the anomalies of the ATLR before earthquakes which happened in and around Yunnan, a seismic active region. The reason of the anomalies is possibly from change of the plumb line due to the motion of the groundmass before earthquakes. Afterwards, using studies of the anomalous characters and laws of ATLR, we tried to provide the warning information prior to the occurrence of a few major earthquakes in the region. The significant synchronous anomalies of ATLR of the observatory appeared before the earthquake of magnitude 6.2 in Dayao county of Yunnan province, on July 21, 2003. It has been again verified that the anomalies possibly provide the prediction information for strong earthquakes around the observatory.  相似文献