嘉陵江中下游地区近30年土地利用与 覆被变化过程研究   总被引：12，自引：3，他引：12  

仙巍  邵怀勇  周万村 《地理科学进展》2005,24(2):114-121

应用遥感和GIS技术及数理统计学的方法，利用1972年MSS遥感影像、1986年和2000年的TM遥感影像，在总结了目前使用较广泛的土地利用类型动态度模型的基础上，提出了转出速度、转入速度、综合动态度、状态指数等模型，并指出唯有将这些模型综合运用，才能更好地理解土地利用类型的动态变化。利用上述模型以及LUCC的幅度、区域差异模型，深入而全面的研究了自上世纪70年代初期以来嘉陵江中下游地区14个县市区LUCC的过程。  相似文献   

"04.8"山西中部短时大暴雨天气的多普勒雷达资料分析          下载免费PDF全文

赵桂香  杨世刚  乔丽霞  臧曦 《山西气象》2005,(3):5-7

利用山西省新一代多普勒天气雷达资料,对2004年8月13日02时～08时发生在山西省中部的短时大暴雨天气过程进行了简要分析。结果表明:此次降水是在深厚的暖平流条件下产生的大范围降水,低空急流为此次降水提供了水汽来源;而雷达回波上表现出中尺度弥合回波,说明在局地动力和热力条件下加强发展的中小尺度系统是造成此次暴雨的主要原因。  相似文献   

Middle Yangtze sea-basin over Paleozoic-Mesozoic transition     

Dinghua Huang  Yichun Duan  Bin Li  Lingqing Yao  Heng Zhang  Fan Zhang  Junhui Wang  Hao Guo  Hongfu Yin 《中国科学D辑(英文版)》2002,45(8):730-740

On the centimeter scale of lithologic change, we conduct poly-statistic analysis on the sedimentary behavior and dynamic features of the stratigraphic sequence from upper Dalong formation to lower Daye formation, which across the Permian-Triassic boundary in East Hubei. From the perspective of stochastically dynamic system, the depositional process of upper Dalong formation can be regarded as a stable Markovian process with weakly stratigraphie correlation and randomly lithologic alteration. Compared to it, the depositional process of lower Daye formation was unstable Markovian process with much closer stratigraphic correlation and ordered lithologic change. As for the replacement style of the sedimental cycle, the former was chaotic, while the latter was periodical. Otherwise, although the overall depositional process of the two formations was continuous, their dynamic characteristics were obviously different. So this P-T sedimental boundary can also be regarded as a dynamic limit. It was a kind of depositional reaction in response to a catastrophic alteration when the geological environment was in continuous change but came over a certain threshold state.  相似文献   

Middle Yangtze sea-basin over Paleozoic-Mesozoic transition--Sedimental continuity and environmental catastrophe     

黄定华  段怡春  李斌  姚凌青  张恒  张凡  王君慧  郭浩  殷鸿福 《中国科学D辑(英文版)》2002,45(8)

On the centimeter scale of lithologic change,we conduct poly-statistic analysis on the sedimentary behavior and dynamic features of the stratigraphic sequence from upper Dalong formation to lower Daye formation,which across the Permian-Triassic boundary in East Hubei.From the perspective of stochastically dynamic system,the depositional process of upper Dalong formation can be regarded as a stable Markovian process with weakly stratigraphic correlation and randomly lithologic alteration.Compared to it,the depositional process of lower Daye formation was unstable Markovian process with much closer stratigraphic correlation and ordered lithologic change.As for the replacement style of the sedimental cycle,the former was chaotic,while the latter was periodical.Otherwise,although the overall depositional process of the two formations was continuous,their dynamic characteristics were obviously different.So this P-T sedimental boundary can also be regarded as a dynamic limit.It was a kind of depositional reaction in response to a catastrophic alteration when the geological environment was in continuous change but came over a certain threshold state.  相似文献   

奇异的波至现象   总被引：1，自引：0，他引：1  

於文辉  周玉琦等 《地球科学》2002,27(5):651-658

1997年，笔者在水力压裂后砂岩产油井中进行高分辨率VSP工作时，除观测到常规纵波及转换波,还观测到来自产油层的几种奇异的慢速波至。由于该慢速波至的性质不明，按视速度从高到低分别命名为W1，W2，W3，…（W为wave的第1个字母），在顺5井裂隙优势方向，1210m深度上观测到5种反射波；反射纵波，反射转换波，W1，W2，W3波，在裂隙非优势方向上，W2，W3波没有出现，在顺4井1532m深度上观测到4种反射波；反射纵波，反射转换波，还有2种慢速波至，为了区别于顺5井中观测到的慢速波至，将其命名为W4，W5波。结合该区钻井，测井，地面地震，井间地震等资料对观测到的慢速波至进行了详细分析，分析结果表明：该慢速波至既不属于不均匀介质产生的绕射波，侧界面产生的反射波，槽波，管波，斯通利波，也与Biot慢纵波动力学特征相悖，现有波动理论不能解释这种慢速波至现象，这意味着地球内部介质中存在人类还未认识的弹性波传播规律。  相似文献   

河道开挖效果预测方法初步研究          下载免费PDF全文

杨国录  吴虹娟  余明辉  李纪泽  王昌慈 《水科学进展》2002,13(3):345-350

针对河道开挖后挖河效果预测的重要性,初步提出了预测挖河效果的三个评判标准:挖沙减淤比、复原率和稳定坡.引用黄河山东河段“挖河固堤工程”资料,通过数学模型计算结果对挖河效果预测的三个评判标准进行了说明,并展示使用三个评判因子分析挖河效果的有效性和应用潜力.  相似文献   

低爆速细长型震源药柱提高地震勘探分辨率     

陈双华  崔若飞 《中国煤田地质》2002,14(4):59-61

提高地震勘探分辨率是一个系统工程，必须在野外采集，资料处理等方面采取各种不同手段，达到提高分辨率的目的。采用低爆速细长型药柱震源，在提高地震勘探分辨率方面具有特殊的效果，在研究中发现，同时接收纵波和转换横波，与高爆速炸药相比，低爆速细长型震源药柱可以有效地拓宽频带（纵波频带达220Hz以上），提高目的层反射波的主频（纵波主频达120Hz以上），低爆速细长型震源药柱在地震勘探中的推广应用。必将有效地提地震勘探的分辨率。  相似文献   

苍山5.2级地震前后沂沭断裂带地壳垂直形变时空动态演化特征     

李杰  赵金花 《地震研究》2001,24(4):307-314

对苍山5．2级地震前后出现的跨断层形态异常特征进行了分析，并系统地分析了由跨断层形变测量资料提取无量纲年速率比γh的时空分布和动态演化特征。  相似文献   

The Statistical Prediction Of Offshore Winds From Land-Based Data For Wind-Energy Applications   总被引：3，自引：0，他引：3  

John L. Walmsley  Rebecca J. Barthelmie  William R. Burrows 《Boundary-Layer Meteorology》2001,101(3):409-433

Land-based meteorological measurements at two locations on the Danish coast are used to predict offshore wind speeds. Offshore wind-speed data are used only for developing the statistical prediction algorithms and forverification. As a first step, the two datasets were separated into ninepercentile-based bins, with a minimum of 30 data records in each bin. Next, the records were randomly selected with approximately 70% of the data in each bin being used as a training set for development of the prediction algorithms, and the remaining 30% being reserved as a test set for evaluation purposes. The binning procedure ensured that both training and test sets fairly represented the overall data distribution.To base the conclusions on firmer ground, five permutations of these training and test sets were created. Thus, all calculations were based on five cases, each one representing a different random selection from the same data, but maintaining the (approximate) 70-30 split in each bin. This procedure served to ensure that conclusions were not based on a single randomly-selected case. Two statistical methods are employed:multiple linear regression (MLR), and Classification and Regression Trees(CART). MLR produces excellent results using only land-based predictors.The CART results are similar to those from MLR, and tend to be slightly better.Retired  相似文献   

一种全局优化算法:遗传算法-单纯形法   总被引：20，自引：0，他引：20  

韩炜  廖振鹏 《地震工程与工程振动》2001,21(2):6-12

针对遗传算法搜索效不高和早熟的缺点，本文提出了将遗传算法和单纯形法组合的一种全局优化算法，并用七个典型检验函数验证了此方法的有效性。  相似文献