GPS高程转换的神经元网络方法分析   总被引：9，自引：0，他引：9  

鲁铁定  周世键  张立亭  吕开云 《全球定位系统》2004,29(2):24-28

GPS高程转换是GPS高程应用的关键问题之一，试图应用神经元网络方法来进行GPS高程的转换，并在网络的拓扑结构与网络结构的改进等方面作了分析，通过GPS高程转换的二次曲面法和神经元网络法进行了比较试验，结果表明了神经元网络转换GPS高程的可行性和可靠性，对于应用神经网络转换GPS高程具有实际的指导意义。  相似文献   

汾河水库流域人工增雨可行性研究          下载免费PDF全文

孙鸿娉  李培仁  闫世明  孙国德  贺建中 《山西气象》2005,(4):40-43

本文通过对汾河流域40a气象、水文资料的分析,结合现阶段人工增雨技术的研究,以增加水库蓄水量为目的,设计科学可行的人工增雨方案,并对可能的投入和预期产生的效益进行分析研究,为通过人工增雨增加水库蓄水量提供科学依据。  相似文献   

广西南丹地区有色金属尾砂型人工矿床地质特征及其资源化     

陈志强苏亮  杨保疆 《地质找矿论丛》2005,20(8):139-144

广西南丹地区尾矿分布于大厂、车河、芒场等矿区。尾砂来自以锡石为主的多金属矿床，尾砂中除Sn，Pb，Zn，Ag，Sb的质量分数达到工业指标外，Au亦达到综合利用指标。通过试验证明，对尾矿中的细微粒锡石可采用风力分级选矿、磁选和化学选矿等方法回收；尾砂中的非金属资源可作为填充材料、水泥原料利用，使尾砂型人工矿床充分的资源化。  相似文献   

Efficient estimation of flood forecast prediction intervals via single‐ and multi‐objective versions of the LUBE method          下载免费PDF全文

Lei Ye  Jianzhong Zhou  Hoshin V. Gupta  Hairong Zhang  Xiaofan Zeng  Lu Chen 《水文研究》2016,30(15):2703-2716

Prediction intervals (PIs) are commonly used to quantify the accuracy and precision of a forecast. However, traditional ways to construct PIs typically require strong assumptions about data distribution and involve a large computational burden. Here, we improve upon the recent proposed Lower Upper Bound Estimation method and extend it to a multi‐objective framework. The proposed methods are demonstrated using a real‐world flood forecasting case study for the upper Yangtze River Watershed. Results indicate that the proposed methods are able to efficiently construct appropriate PIs, while outperforming other methods including the widely used Generalized Likelihood Uncertainty Estimation approach. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Significance of shallow core transects for reef models and sea‐level curves,Heron Reef,Great Barrier Reef          下载免费PDF全文

Gregory E. Webb  Luke D. Nothdurft  Jian‐Xin Zhao  Bradley Opdyke  Gilbert Price 《Sedimentology》2016,63(6):1396-1424

A sequence of shallow reef cores from Heron Reef, Great Barrier Reef, provides new insights into Holocene reef growth models. Isochron analysis of a leeward core transect suggests that the north‐western end of Heron Reef reached current sea‐level by ca 6·5 kyr bp and then prograded leeward at a rate of ca 19·6 m/kyr between 5·1 kyr and 4·1 kyr bp (pre‐1950) to the present reef margin. A single short core on the opposing margin of the reef is consistent with greater and more recent progradation there. Further to the east, one windward core reached modern sea‐level by ca 6·3 kyr bp , suggesting near ‘keep‐up’ behaviour at that location, but the opposing leeward margin behind the lagoon reached sea‐level much more recently. Hence, Heron Reef exhibited significantly different reef growth behaviour on different parts of the same margin. Mean reef accretion rates calculated from within 20 m of one another in the leeward core transect varied between ca 2·9 m and 4·7 m/kyr depending on relative position in the prograding wedge. These cores serve as a warning regarding the use of isolated cores to inform reef growth rates because apparent aggradation at any given location on a reef varies depending on its location relative to a prograding margin. Only transects of closely spaced cores can document reef behaviour adequately so as to inform reef growth models and sea‐level curves. The cores also emphasize potential problems in U‐series dates for corals within a shallow (ca 1·5 m) zone beneath the reef flat. Apparent age inversions restricted to that active diagenetic zone may reflect remobilization and concentration of Th in irregularly distributed microbialites or biofilms that were missed during sample vetting. Importantly, the Th‐containing contaminant causes ages to appear too old, rather than too young, as would be expected from younger cement.  相似文献   

Stromatoporoid growth forms and Devonian reef fabrics in the Upper Devonian Alexandra Reef System,Canada – Insight on the challenges of applying Devonian reef facies models          下载免费PDF全文

Alex J. MacNeil  Brian Jones 《Sedimentology》2016,63(6):1425-1457

Existing facies models for Devonian reef systems can be divided into high‐energy and low‐energy types. A number of assumptions have been made in the development of these models and, in some cases, criteria that distinguish important aspects of the models are poorly defined. The Upper Devonian Alexandra Reef System contains a variety of reef fabrics from different depositional environments and is ideal for studying the range of environments in which stromatoporoids thrived and the facies from these different environments. A wide variety of stromatoporoid growth forms including laminar, tabular, anastamosing laminar and tabular, domal, bulbous, dendroid, expanding conical, concave‐up whorled‐laminar, concave‐up massive tabular and platy‐multicolumnar are present in the Alexandra Reef System. The whorled‐laminar and massive tabular concave‐up growth forms are virtually undocumented from other Devonian reefs but were common in the reef front of the Alexandra, where they thrived in a low‐energy environment around and below fair‐weather wave base. In contrast, high‐energy parts of the reef margin were dominated by bioclastic rubble deposits with narrow ribbon‐like discontinuous bodies of laminar stromatoporoid framestone. In the lagoon, laminar stromatoporoids formed steep‐sided sediment‐dominated bioherms in response to sea‐level rise and flooding. Relying mostly on the different reef facies in the Alexandra system, a new classification scheme for Devonian reef fabrics has been developed. Devonian reef fabrics can be classified as being: (i) sediment‐laden metazoan dominated; (ii) metazoan–microbial dominated (boundstone); (iii) metazoan dominated (framestone); or (iv) metazoan–marine cement dominated. Distinction of these fabrics carries important sedimentary and palaeoecological implications for reconstructing the depositional environment. With examples from the Alexandra Formation, it is demonstrated that reef facies accumulated in a range of depositional environments and that the simple observation of massive stromatoporoids with or without microbial deposits does not automatically imply a high‐energy reef margin, as otherwise portrayed in a number of the existing facies models for these systems.  相似文献   

风暴分类识别技术在人工防雹中的应用   总被引：1，自引：0，他引：1  

方德贤  李红斌  董新宁  丁建芳  濮文耀 《气象》2016,42(9):1124-1134

利用新一代多普勒天气雷达资料,在风暴跟踪识别算法的基础上,发展了风暴分类技术,以提高人工防雹作业指挥的效率。首先以SCIT算法为基础,结合风暴的结构特征,综合利用雷达、探空资料,自动提取风暴结构特征指数;其次采用基于决策树模型的风暴自动分类技术,将风暴按强度分为雷雨云、单体风暴、多单体风暴和强风暴;最后根据风暴强度、高度和位置等属性,对有可能产生冰雹的单体,结合GIS,自动对下游方向或附近作业点进行预警或输出作业参数。通过对2006—2014年期间重庆、辽宁大连和河南三门峡三地发生的较为典型的31次冰雹天气过程、182站次冰雹样本的检验来看:该方法通过对风暴按强度、垂直结构等综合属性进行分类,能有效提高冰雹识别的命中率、降低空报率,其中强风暴的命中率能达到100%,空报率仅为11.4%。能有效提高人工防雹作业的自动化程度,对防雹作业的科学决策有着重要参考作用。  相似文献   

哈密地区空中水汽及增水潜力分析     

卓世新  李如琦  苗运玲  冯桂红 《沙漠与绿洲气象(新疆气象)》2016,10(6):68-72

采用哈密地区6站1975—2014年逐日地面水汽压和降水量资料,计算了哈密各站的大气可降水量、有效空中水资源量、自然降水产出率和人工增水潜力值,并分析了各量的时空分布特征。结果表明:哈密地区年平均整层大气可降水量为2560~4327 mm,年均有效空中水资源量约为232~828 mm,占整层大气可降水量的1/4~1/10;年均自然降水产出率在9%~28%,自然降水产出率与降水量成正比关系。哈密地区的年人工增水潜力理论计算值在844~2399 mm之间,潜力值在夏季最大,巴里坤和伊吾明显多于其它区域。  相似文献   

利用双线偏振雷达分析人工防雹作业效果     

陈羿辰  张龙斌  金永利  马建立  嵇磊  秦睿 《气象科技》2016,44(3):479-488

以北京市平谷区2011年6月11日防雹作业为例,利用双线偏振雷达资料,选取与作业区条件十分接近的云块为对比区,根据回波移动方向和速度,跟踪分析在不同高度上防雹作业前后云体宏观结构特征和粒子相态等微物理变化过程。作业后云体所呈现特征为:1作业区的云顶高度、强回波中心高度迅速下降,对比区变化不明显;2作业区水平反射率Zh减小,差分反射率Zdr、零相关系数ρhv增大,单位差分传播相移Kdp小范围内波动,对比区Zh、Zdr、Kdp变化不明显;ρhv增大;3作业区对流减弱,高层较大冰雹粒子、大雨滴下沉明显,最终以霰粒子为主;而对比区域则对流仍然旺盛,冰雹粒子有增多趋势。以上特征表明防雹作业可有效抑制冰雹胚胎成长为冰雹的过程,通过偏振雷达观测参量可对防雹作业效果进行较好的验证。  相似文献   

一种裸露土壤湿度反演方法   总被引：1，自引：0，他引：1  

张清河  徐飞  朱国强 《测绘科学》2016,41(2):11-14

针对目前土壤湿度反演方法研究较少且缺少实时性的现状,该文提出一种土壤湿度反演方法——最小二乘支持向量机技术。以积分方程模型为正向算法,数值模拟不同雷达参数(频率、入射角及极化)下后向散射系数随土壤含水量和地表粗糙度的变化情况。经过数据敏感性分析,选取C-波段和X-波段、小入射角下的同极化后向散射系数作为支持向量回归的训练样本信息;经过适当的训练,利用支持向量回归技术对土壤含水量进行了反演研究;并考虑通过多频率、多极化、多入射角数据的组合,消除地表粗糙度的影响,提高反演精度。模拟结果表明,该方法反演土壤湿度具有较高的精度和较好的实时性;同时,与人工神经网络方法的结果比较,证明了该方法的有效性,为土壤湿度的反演研究提供了一种方法。  相似文献