基于DOA估计的阵列式探地雷达逆向投影目标成像方法     

曾昭发  李文奔  习建军  黄玲  王者江 《吉林大学学报(地球科学版)》2017,47(4)

本文针对阵列式天线探地雷达系统的目标成像问题,理论模拟分析了最小二乘(LS)估计、Capon估计、幅度相位估计(APES)三种波束形成算法在目标回波到达角(direction of arrival,DOA)估计上的效果和精度,提出了基于DOA估计的阵列式探地雷达逆向投影目标成像方法。该方法综合利用多输入多输出(MIMO)阵列信号估计得到的目标回波信号DOA和阵列空间观测信息对目标体进行成像,通过成像点空间扫描对各测点估计DOA幅度值在成像点的加权积分进行目标定位及反射强度估计。该方法实现简单高效,可以广泛应用于地下简单目标体的快速成像。  相似文献   

Correlation of the largest craters,stratigraphic impact signatures,and extinction events over the past 250 Myr     

Michael R. Rampino  Ken Caldeira 《地学前缘(英文版)》2017,8(6):1241-1245

The six largest known impact craters of the last 250 Myr(≥70 km in diameter),which are capable of causing significant environmental damage,coincide with four times of recognized extinction events at 36(with 2 craters),66,and 145 Myr ago,and possibly with two provisional extinction events at 168 and215 Myr ago.These impact cratering events are accompanied by layers in the geologic record interpreted as impact ejecta.Chance occurrences of impacts and extinctions can be rejected at confidence levels of99.96%(for 4 impact/extinctions)to 99.99%(for 6 impact/extinctions).These results argue that several extinction events over the last 250 Myr may be related to the effects of large-body impacts.  相似文献   

Defining and selecting characteristic values of geotechnical parameters for designs to Eurocode 7     

Trevor L. L. Orr 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2017,11(1):103-115

ABSTRACT

Recent geotechnical design codes (such as Eurocode 7) aim to achieve geotechnical designs with an appropriate target reliability by applying partial factors to characteristic parameter values. Development in Eurocode 7 of the definition and selection of the characteristic values is traced. A significant development occurred with the definition of the characteristic value as a cautious estimate of the value affecting the occurrence of the limit state. Statistical equations to select characteristic values are presented, including one proposed for the revised of Eurocode 7.An alternative equation reduces the amount of subjective judgement and is more likely to achieve the target reliability.  相似文献   

Changes of Extreme Indices over China in Response to 1.5 ℃ Global Warming Projected by a Regional Climate Model     

Li Donghuan  Zou Liwei  Zhou Tianjun 《地球科学进展》2017,32(4):446-457

The possible changes of extreme climates over China under 1.5 ℃ global warming scenario were investigated by using the output of CORDEX (COordinated Regional Downscaling Experiment) experiments with a regional air-sea coupled model FROALS over East Asia domain. Results indicated that compared to the baseline period of 1986-2005, warm events would significantly increase while cold events would significantly decrease over China in a 1.5 ℃ warmer world. The risks of extreme and moderate warm events would be 2.14 and 1.93 times of that in the baseline period, respectively. The risks of extreme and moderate cold events would be 0.58 and 0.63 times of that in the baseline period, respectively. Compared to other sub-regions, the increasing amplitude of extreme warm events would be higher in North China, while the decreasing amplitude of extreme cold events would be higher in Northeast China. Risks of extreme dry events would increase in Northwest China, Tibetan Plateau and Northeast China (1.13, 1.02 and 1.22 times of that in baseline period). Precipitation intensity and extreme wet events would increase significantly over most parts of China, and the increasing amplitudes extreme wet events will be higher in North China and South China (1.88 and 1.85 times of that in the baseline period). Days when people may feel uncomfortable would increase significantly in eastern China, and compared to simple extreme warm events, the increasing amplitude of extreme uncomfortable days would be larger. The absolute changes of heating degree-days would be larger than that of cooling degree-days (-258℃·d and 72℃·d, respectively) in eastern China, but the relative change of heating degree-days would be smaller than cooling degree-days (-10% and 82%, respectively).  相似文献   

河南省崤山地区综合信息找矿模型及靶区预测     

常云真  李永超  徐文超  贾慧敏  李森林 《世界地质》2017,36(2):530-540

通过2010—2014年在崤山地区开展的1∶5万区域矿产调查工作,系统总结了该区成矿地质条件、矿床地质特征,结合取得的区域地质、地球物探、地球化探和遥感解译等成果,运用相似类比理论、综合成矿信息及成矿模型理论,建立综合信息找矿模型,并根据找矿模型对该成矿远景区进行了预测,圈定了6个有利找矿靶区,其中A级靶区2个,B级靶区2个,C级靶区2个。  相似文献   

高频地波雷达海上目标航迹跟踪新思路   总被引：1，自引：1，他引：0  

孙伟峰  戴永寿  纪永刚  周鹏  万勇 《海洋科学》2017,41(6):144-149

高频地波雷达是对海上运动目标进行监视监测的一种重要手段,为了提高地波雷达对海上特定目标独立跟踪探测时的性能,本文对高频地波雷达海上目标跟踪技术的研究现状进行了综述,分析总结了目前航迹跟踪方法存在的主要问题。结合海上目标跟踪的实际应用需求,借助目前流行的深度学习方法充分挖掘其他同步探测手段获取的目标信息,提出了基于知识辅助的特定目标跟踪方法,改善后续地波雷达对特定目标独立跟踪时的航迹质量,初步的航迹跟踪结果验证了提出方法的有效性。提出的地波雷达特定目标跟踪方法对目标跟踪方法的理论研究及地波雷达目标跟踪系统的业务化应用均具有重要意义及参考价值。  相似文献   

一类三阶微分方程组边值问题特殊正解的存在性     

唐玉莲  夏大峰 《南京气象学院学报》2012,4(1):87-91

采用地面降水资料、多普勒雷达数据、探空资料等,利用自主开发的系统软件对实测资料进行增雨效果统计检验,通过目标区作业前后雷达参量的演变或目标区与对比区的回波参量的差异,来完整的分析2010年8月11日海南西部多点作业情况的催化效果。物理统计分析结果显示,催化一般在作业后半小时内起到效果并达到最强,目标区的最大强度、强回波区面积、液态水含量、回波顶高的增大率大于对比区的值,催化作业确实延长了目标云的寿命。  相似文献   

浅析黔西北水东—五指山地区铅锌矿控矿因素、成矿规律及找矿方向   总被引：1，自引：0，他引：1  

黄林  张坤 《贵州地质》2010,27(3):202-207

黔西北水东—五指山地区铅锌矿位于扬子陆块西南缘,紫云—垭都北西向构造旁侧,是黔西北铅锌成矿带的一个组成部份,通过该地区矿产资源远景调查及矿产评价成果展现了较好的找矿前景,发现了中型矿床5个,并在攻深找盲取得了突破性进展。笔者通过区域控矿因素、成矿地质背景分析,结合工作成果及认识,模拟类比在相似地质条件,指出找矿方向,认为区内成矿地质条件优越,找矿前景好,具备寻找大型、超大型矿床的潜力。  相似文献   

Differences of Hydrocarbon Enrichment between the Upper and the Lower Structural Layers in the Tazhong Paleouplift     

JIANG Zhenxue  YANG Haijun  LI Zhuo  PANG Xiongqi  HAN Jianf  LI Dongxu  HUANG Yuyan 《《地质学报》英文版》2010,84(5):1116-1127

<正>The Tazhong paleouplift is divided into the upper and the lower structural layers,bounded by the unconformity surface at the top of the Ordovician carbonate rock.The reservoirs in the two layers from different parts vary in number,type and reserves,but the mechanism was rarely researched before.Therefore,an explanation of the mechanism will promote petroleum exploration in Tazhong paleouplift.After studying the evolution and reservoir distribution of the Tazhong paleouplift,it is concluded that the evolution hi late Caledonian,late Hercynian and Himalayan periods resulted in the upper and the lower structural layers.It is also defined that in the upper structural layer,structural and stratigraphic overlap reservoirs are developed at the top and the upper part of the paleouplift,which are dominated by oil reservoirs,while for the lower structural layer,lithological reservoirs are developed in the lower part of the paleouplift,which are dominated by gas reservoirs,and more reserves are discovered in the lower structural layer than the upper. Through a comparative analysis of accumulation conditions of the upper and the lower structural layers,the mechanism of enrichment differences is clearly explained.The reservoir and seal conditions of the lower structural layer are better than those of the upper layer,which is the reason why more reservoirs have been found in the former.The differences in the carrier system types,trap types and charging periods between the upper and the lower structural layers lead to differences in the reservoir types and distribution.An accumulation model is established for the Tazhong paleouplift.For the upper structural layer,the structural reservoirs and the stratigraphic overlap reservoirs are formed at the upper part of the paleouplift,while for the lower structural layer,the weathering crust reservoirs are formed at the top,the reef-flat reservoirs are formed on the lateral margin,the karst and inside reservoirs are formed in the lower part of the paleouplift.  相似文献   

新疆西天山玉希莫勒盖达坂一带铜金矿地质特征及找矿思路探讨     

赵春雷  吴玉诗  张海洋 《吉林地质》2010,29(3):24-28

玉希莫勒盖达坂一带是新疆重要的铜金及多金属成矿区,通过前期的中小比例尺地质矿产调查和化探工作,已初步摸清该区的成矿机理、矿床类型及元素富集规律,在此基础上划分出玉希莫勒盖达坂铜金和旺江德克银铜两个找矿靶区,为该地区今后开展矿产普查指明了方向。  相似文献