利用主成分背景抑制的红外目标检测     

陈炳文  王文伟  秦前清 《武汉大学学报(信息科学版)》2012,37(8):925-928

提出了一种基于主成分背景抑制的红外目标检测算法。首先分析了红外成像的时空相关性,采用主成分分析技术分解时域关联信息抑制背景杂波;接着采用空间关联模糊自适应共振神经网络建立时空背景模型检测目标。实验结果显示,该算法能有效地抑制背景突显目标和检测出复杂场景下的红外目标,其F1指标值高达94.2%。  相似文献   

白云鄂博铁、铌、稀土矿床:研究进展、存在问题和新认识   总被引：2，自引：1，他引：1  

谢玉玲  曲云伟  杨占峰  梁培  钟日晨  王其伟  夏加明  李必成 《矿床地质》2019,38(5):983-1003

白云鄂博是世界第一大稀土元素矿床,其稀土元素资源量占世界目前已知稀土元素资源总量的三分之二以上,具有重要的经济和战略地位。白云鄂博自1927年发现至今已有92年,对其的开发和研究历史悠久,在赋矿碳酸岩的成因、成矿年代、稀土矿物学等方面取得了一系列重要进展,为碳酸岩型稀土元素成矿理论发展做出了突出贡献。由于矿床经历了成矿后复杂的构造变形和热液蚀变,致使其地质、地球化学特征复杂,学界对其成因和成矿过程一直存在不同认识,对成矿碳酸岩的岩浆演化、稀土元素迁移与富集机理等方面的研究也相对薄弱。笔者最新研究表明,矿区过去被认为是下白云鄂博群的H1、H2、H9岩石单元并非沉积变质岩或变质火山岩,而应为岩浆侵入成因,矿区其他岩石单元(H3～H7)的成因也值得商榷。H9岩石单元中的黑云母岩(前人称为黑云母板岩)和富含黑云母的碳酸岩(前人称为暗色板岩)为成矿碳酸岩的一部分,是碳酸岩不同岩相带的表现。黑云母岩和富黑云母碳酸岩相对于含矿碳酸岩具有相对低的稀土元素含量和轻、重稀土元素比值,表明岩浆演化可能对稀土元素的富集和分异具有重要贡献。矿区主要岩石单元成因的新认识不仅为矿床成因、成矿背景研究提供了新的依据,同时也为研究区域构造演化、正确厘定矿区构造式样和指导矿区深部和外围找矿提供了新的思路。  相似文献   

Transformation,partitioning and flow–deposit interactions during the run‐out of megaflows          下载免费PDF全文

Claus Fallgatter  Ben Kneller  Paulo S. G. Paim  Juan P. Milana 《Sedimentology》2017,64(2):359-387

Four megabeds (I to IV) were recognized throughout the Cerro Bola inlier, a glacially influenced depositional area of the Carboniferous Paganzo Basin, south‐western La Rioja Province, Argentina. Such anomalous thick beds are associated with the collapse of an unstable basin margin after periods of large meltwater discharge and sediment accumulation. Failure of these previously deposited sediments triggered mass flows and associated turbidity currents into the basin. Megabed I is up to 188 m thick and was deposited during a transgressive stage by re‐sedimentation of ice‐rafted debris. Also part of the transgressive stage, Megabeds II, III and IV are up to 9 m thick and are associated with a dropstone‐free period of flooding. Megabeds were subdivided into three divisions (1 to 3) that represent a spectrum of flow properties and rheologies, indicative of a wide range of grain support mechanisms. These divisions are proposed as an idealized deposit that may or may not be completely present; the Cerro Bola megabeds thus display bipartite or tripartite organization, each division inferred to reflect a rheologically distinct phase of flow. Division 1 is a basal layer that consists of clast‐supported and matrix‐supported, pebble conglomerate, rarely followed by weak normally graded to ungraded, very coarse‐ to coarse‐grained sandstone. This lower interval is interpreted to be the deposit of a concentrated density flow and is absent in bipartite megabeds. Division 2 is represented by a mud‐rich sandstone matrix with dispersed granule to pebble‐size crystalline and mudstone clasts. It also includes fragments of sandstone up to boulder size, as well as rafts of cohesive muddy material and wood fragments. Division 2 is interpreted to be a result of debris‐flow deposition. A debrite‐related topography, resulting from the freezing of high yield strength material, captures and partially confines the succeeding upper division 3, which fills the topographic lows and pinches out against topographic highs. Division 3 is rich in mudstone chips and consists of very coarse‐grained, dirty sandstones grading upward to siltstones and mudstones. It is interpreted to be a deposit of a co‐genetic turbidity current. Spectral gamma ray and petrographic analyses indicate that both debrite and co‐genetic turbidite have high depositional mud content and are of similar composition. One of the megabeds is correlated with an initial slump‐derived debris flow, which suggests that the mass flow becomes partitioned both at the top, generating a co‐genetic turbidity current and, at the base, segregating into a concentrated density flow that seems to behave as a gravelly traction carpet.  相似文献   

数据自相关多次波偏移成像   总被引：1，自引：1，他引：0       下载免费PDF全文

郑忆康  王一博  徐嘉亮  常旭  姚振兴 《地球物理学报》2015,58(3):993-1001

在常规偏移方法中一般都需要压制地震数据中的多次波,仅利用一次波信息成像,把自由表面反射的多次波视为噪声,但是在多次波中也包含着地下结构信息,应该将其充分利用到成像中来.事实上,已经有不少成像方法试图利用多次波信息,但是大部分方法都需要对多次波进行预测.本文提出了基于傅里叶有限差分偏移算子的数据自相关偏移方法.在这种偏移方法中,对含有一次波和多次波的地震数据,分别进行下行和上行延拓,然后直接利用常规的互相关成像条件成像.由于波场延拓采用了傅里叶有限差分算子,其计算效率高,能够很好地对复杂介质中的地震数据进行延拓.在数值试验中,使用了一个含散射点的三层模型和Marmousi模型.合成数据测试结果表明,这种方法可以对更大范围的地下构造成像,比常规的只利用一次波的傅里叶有限差分法照明度更好,并且在浅层可以提供更高的分辨率.我们提出的数据自相关策略易于实现且避免了繁杂的多次波预测,这对于复杂地下构造成像可能有着重大意义.  相似文献   

一阶多次波聚焦变换成像   总被引：2，自引：2，他引：0       下载免费PDF全文

刘学建  刘伊克  胡昊  谢宋雷 《地球物理学报》2015,58(6):1985-1997

将多次波转换成反射波并按传统反射波偏移算法成像,是多次波成像的一种方法.聚焦变换能准确的将多次波转换为纵向分辨率更高的新波场记录,其中一阶多次波转换为反射波.本文对聚焦变换提出了两点改进:1)提出局部聚焦变换,以减小存储量和计算量,增强该方法对检波点随炮点移动的采集数据的适应性;2)引入加权矩阵,理论上证明原始记录的炮点比检波点稀疏时,共检波点道集域的局部聚焦变换可以将多次波准确转换成炮点与检波点有相同采样频率的新波场记录.本文在第一个数值实验中对比了对包含反射波与多次波的原始记录做局部聚焦变换和直接对预测的多次波做局部聚焦变换两种方案,验证了第二种方案转换得到的波场记录信噪比更高且避免了第一个方案中切聚焦点这项比较繁杂的工作.第二个数值实验表明:在炮点采样较为稀疏时,该方法能有效的将一阶多次波转换成反射波;转换的反射波能提供更丰富的波场信息,成像结果更均衡、在局部有更高的信噪比,以及较高的纵向分辨率.  相似文献   

青海木里地区天然气水合物形成条件分析   总被引：3，自引：0，他引：3  

曹代勇  ;刘天绩  ;王丹  ;王佟  ;文怀军  ;潘语录 《中国煤炭地质》2009,(9):3-6

我国的青藏高原地区有大面积的多年冻土分布,其适宜的温压条件为天然气水合物的形成创造了有利的环境。在青藏高原北部祁连山区木里煤田多年冻土层煤炭地质勘查施工中,发现天然气水合物存在的证据。通过分析木里地区多年冻土带天然气水合物的形成条件,对天然气水合物烃类气体的来源进行了探讨,提出煤层和煤系分散有机质热演化过程中形成的烃类气体是木里煤田天然气水合物主要来源的观点,将并其称之为“煤型气源”天然气水合物。  相似文献   

2007年7月16日日本新潟地震对柏崎刈羽核电站的影响     

潘华  李金臣  吴迪忠 《国际地震动态》2007,(11)

2007年7月16日日本新潟县柏崎市附近海域发生MW6.6地震(日本气象局震级MJMA6.8)。该地震引发世界最大核电厂——柏崎刈羽核电站多起核安全事件,是世界范围内有记载的对核电站影响最为严重的一次地震。本文根据收集到的资料,详细介绍了该地震对柏崎刈羽核电站造成的影响,文章最后概述了日本、国际原子能机构对该地震的反思以及我们应该从中吸取的经验教训。  相似文献   

Understanding finite-frequency wave phenomena: phase-ray formulation and inhomogeneity scattering   总被引：1，自引：0，他引：1  

Tianfei Zhu  Kin-Yip Chun 《Geophysical Journal International》1994,119(1):78-90

  相似文献   

贸易壁垒、市场相关多样化与城市出口韧性     

王文宇  任卓然  李伟  贺灿飞 《地理研究》2021,40(12):3287-3301

近年来,逆全球化趋势上升,许多国家对中国竖起贸易壁垒,在此背景下,如何提升城市的出口韧性已成为重要研究议题。现有文献普遍关注本地产业结构与区域韧性的关系,发现多样化产业结构有助于缓解贸易壁垒造成的外部冲击,但是较少探讨外部市场结构的作用。本文使用2001—2016年中国海关数据库贸易数据,引入市场关联概念,首次构建市场相关多样化指标,研究在贸易壁垒冲击下,中国城市出口市场相关多样化对城市出口韧性的影响。研究发现：① 市场相关多样化程度较高的城市,表现出更高的城市出口韧性,其可借助互补性的出口经验和风险分散的市场结构,减小贸易壁垒产生的直接和间接影响。② 外资比例较高、具有国家级经济开发区的城市,由于城市内部企业集聚程度高和信息交流频繁,更容易发挥市场相关多样化的作用。③ 城市相关多样化的市场结构很难抵抗发达国家（地区）贸易壁垒带来的冲击。本文认为地方政府应高度重视城市出口韧性,积极招商引资、申请经济开发区、保持对外联系,推动企业集聚、多举办展会以促进企业间贸易经验交流,尤其是要促进发展中国家的出口信息扩散,要积极引导本地企业利用本地已有贸易市场信息,拓展新市场。  相似文献   

Geology, Fluid Inclusion and Isotopic Study of the Neoproterozoic Suoi Thau Copper Deposit, Northwest Vietnam     

TRAN Mydung  LIU Junlai  LI Xiaochun  DANG Mycung 《《地质学报》英文版》2016,90(3):913-927

The Sin Quyen-Lung Po district is an important Cu metallogenic province in Vietnam, but there are few temporal and genetic constraints on deposits from this belt. Suoi Thau is one of the representative Cu deposits associated with granitic intrusion. The deposit consists of ore bodies in altered granite or along the contact zone between granite and Proterozoic meta-sedimentary rocks. The Cu-bearing intrusion is sub-alkaline I-type granite. It has a zircon U-Pb age of ~776 Ma, and has subduction-related geochemical signatures. Geochemical analysis reveals that the intrusion may be formed by melting of mafic lower crust in a subduction regime. Three stages of alteration and mineralization are identified in the Suoi Thau deposit, i.e., potassic alteration; silicification and Cu mineralization; and phyllic alteration. Two-phase aqueous fluid inclusions in quartz from silicification stage show wide ranges of homogenization temperatures(140–383℃) and salinities(4.18wt%–19.13wt%). The high temperature and high salinity natures of some inclusions are consistent with a magmatic derivation of the fluids, which is also supported by the H-O-S isotopes. Fluids in quartz have δD values of –41.9‰ to –68.8‰. The fluids in isotopic equilibrium with quartz have δ~(18)O values ranging from 7.9‰ to 9.2‰. These values are just plotted in the compositional field of magmatichydrothermal fluids in the δD_(water) versus δ~(18)O_(water) diagram. Sulfide minerals have relatively uniform δ~(34)S values from 1.84‰ to 3.57‰, which is supportive of a magmatic derivation of sulfur. The fluid inclusions with relatively low temperatures and salinities most probably represent variably cooled magmatic-hydrothermal fluids. The magmatic derivation of fluids and the close spatial relationship between Cu ore bodies and intrusion suggest that the Cu mineralization most likely had a genetic association with granite. The Suoi Thau deposit, together with other deposits in the region, may define a Neoproterozoic subduction-related ore-forming belt.  相似文献