沙坡头地区人工植被油蒿种群结构与更新的研究   总被引：7，自引：7，他引：7  

马凤云  李新荣  龙利群  张景光 《中国沙漠》2002,22(6):571-575

采用野外调查和比较分析的方法,对沙坡头地区人工植被油蒿种群的结构和更新进行了研究.通过对不同固沙起始年代油蒿种群大小结构的分析发现,幼树个体的数量较多,中等大小的成年个体数量少,老龄个体的数量极少.年限较短的人工植被区油蒿幼树个体的数量多于年限较长的人工植被区,而油蒿幼苗的数量则呈相反的趋势.油蒿幼苗在不同的地形中分布数量也不同,丘间地有较多的幼苗,背风坡幼苗特别少.油蒿成年个体在人工植被区中呈均匀分布,油蒿幼苗则呈聚集分布.  相似文献   

Sentinel-1卫星TOPS模式影像增强谱分集配准优化     

吴文豪  张磊  张腾旭  王明洲  龙四春  段梦  周志伟  祝传广 《测绘学报》1957,49(11):1451-1462

Sentinel-1卫星TOPS模式影像通常在几何配准的基础上,再次利用Burst重叠区域进行增强谱分集处理以实现高精度配准。几何配准主要依赖卫星轨道参数,难以进一步提高其配准精度,因此Sentinel-1影像配准的关键则是通过增强谱分集准确估计出几何配准后的残余偏移量。然而,增强谱分集易受失相干噪声等因素的影响,低相干条件下难以满足0.001像素的配准精度要求。因此本文首先针对单基线条件下的增强谱分集配准处理进行以下改进：①完善增强谱分集多视理论,采用前置多视处理,优化增强谱分集处理流程;②基于增强谱分集相位的残余偏移量等权估计升级为加权估计,改善参数估计方法;③完善距离向增强谱分集加权估计理论,实施距离向增强谱分集配准,增加增强谱分集的观测量。然后在单基线配准的基础上,针对时序影像处理提出优化方案：①根据影像干涉对组合所形成的增强谱分集冗余观测量进行多基线配准;②采用分布式目标技术提高增强谱分集干涉图相位质量。上述改进方案互相补充,不但能独立实施,而且可以联合使用。研究结果表明,以上改进方法能够在一定程度上提高配准精度。  相似文献   

STUDY ON SOURCE PARAMETERS OF THE 8 AUGUST 2017 M7.0 JIUZHAIGOU EARTHQUAKE AND ITS AFTERSHOCKS,NORTHERN SICHUAN          下载免费PDF全文

WU Wei-wei  WEI Ya-ling  LONG Feng  LIANG Ming-jian  CHEN Xue-fen  SUN Wei  ZHAO Jing 《地震地质》1979,42(2):492-512

On August 8, 2017, a strong earthquake of M7.0 occurred in Jiuzhaigou County, Aba Prefecture, northern Sichuan. The earthquake occurred on a branch fault at the southern end of the eastern section of the East Kunlun fault zone. In the northwest of the aftershock area is the Maqu-Maqin seismic gap, which is in a locking state under high stress. Destructive earthquakes are frequent along the southeast direction of the aftershocks area. In Songpan-Pingwu area, only 50~80km away from the Jiuzhaigou earthquake, two M7.2 earthquakes and one M6.7 earthquake occurred from August 16 to 23, 1976. Therefore, the Jiuzhaigou earthquake was an earthquake that occurred at the transition part between the historical earthquake fracture gap and the neotectonic active area. Compared with other M7.0 earthquakes, there are few moderate-strong aftershocks following this Jiuzhaigou earthquake, and the maximum magnitude of aftershocks is much smaller than the main shock. There is no surface rupture zone discovered corresponding to the M7.0 earthquake. In order to understand the feature of source structure and the tectonic environment of the source region, we calculate the parameters of the initial earthquake catalogue by Loc3D based on the digital waveform data recorded by Sichuan seismic network and seismic phase data collected by the China Earthquake Networks Center. Smaller events in the sequence are relocated using double-difference algorithm; source mechanism solutions and centroid depths of 29 earthquakes with M_L≥3.4 are obtained by CAP method. Moreover, the source spectrum of 186 earthquakes with 2.0≤M_L≤5.5 is restored and the spatial distribution of source stress drop along faults is obtained. According to the relocations and focal mechanism results, the Jiuzhaigou M7.0 earthquake is a high-angle left-lateral strike-slip event. The earthquake sequence mainly extends along the NW-SE direction, with the dominant focal depth of 4~18km. There are few shallow earthquakes and few earthquakes with depth greater than 20km. The relocation results show that the distribution of aftershocks is bounded by the M7.0 main shock, which shows obvious segmental characteristics in space, and the aftershock area is divided into NW segment and SE segment. The NW segment is about 16km long and 12km wide, with scattered and less earthquakes, the dominant focal depth is 4~12km, the source stress drop is large, and the type of focal mechanism is complicated. The SE segment is about 20km long and 8km wide, with concentrated earthquakes, the dominant depth is 4~12km, most moderate-strong earthquakes occurred in the depth between 11~14km. Aftershock activity extends eastward from the start point of the M7.0 main earthquake. The middle-late-stage aftershocks are released intensively on this segment, most of them are strike-slip earthquakes. The stress drop of the aftershock sequence gradually decreases with time. Principal stress axis distribution also shows segmentation characteristics. On the NW segment, the dominant azimuth of P axis is about 91.39°, the average elevation angle is about 20.80°, the dominant azimuth of T axis is NE-SW, and the average elevation angle is about 58.44°. On the SE segment, the dominant azimuth of P axis is about 103.66°, the average elevation angle is about 19.03°, the dominant azimuth of T axis is NNE-SSW, and the average elevation angle is about 15.44°. According to the fault profile inferred from the focal mechanism solution, the main controlling structure in the source area is in NW-SE direction, which may be a concealed fault or the north extension of Huya Fault. The northwest end of the fault is limited to the horsetail structure at the east end of the East Kunlun Fault, and the SE extension requires clear seismic geological evidence. The dip angle of the NW segment of the seismogenic fault is about 65°, which may be a reverse fault striking NNW and dipping NE. According to the basic characteristics of inverse fault ruptures, the rupture often extends short along the strike, the rupture length is often disproportionate to the magnitude of the earthquake, and it is not easy to form a rupture zone on the surface. The dip angle of the SE segment of the seismogenic fault is about 82°, which may be a strike-slip fault that strikes NW and dips SW. The fault plane solution shows significant change on the north and south sides of the main earthquake, and turns gradually from compressional thrust to strike-slip movement, with a certain degree of rotation.  相似文献   

基于波段组合的高光谱数据湿地分类研究     

乔雯钰  龙亦凡  付杰 《北京测绘》2020,(5):651-656

对高光谱数据进行波段组合,可以减少信息量的冗余,提高数据的处理速度。对黄河口入海口湿地进行分类,对合理利用、开发保护该地区湿地资源具有重要意义。本文首先分析了“珠海一号”高光谱数据各个波段的信息量及波段之间的相关系数,然后利用最佳波段指数(OIF)方法选出波段组合B7-B8-B32,进一步在OIF基础上设置信息量与相关系数阈值,选出波段组合B7-B18-B32,实验结果证明分类精度提高了5.4%。最后,根据地物的光谱特征分析,选择光谱差异较大的波段进行组合B6-B13-B18,分类后精度比OIF筛选出的波段组合精度高12.6694%。经实验验证,结合地物光谱特征的波段组合可以大大提高分类精度。  相似文献   

Quantitative Electron-probe Microanalysis of Rock-forming Minerals   总被引：1，自引：0，他引：1  

SWEATMAN  T. R.; LONG  J. V. P. 《Journal of Petrology》1969,10(2):332-379

A number of well-characterized silicate minerals and metal oxideshave been analysed by the electron-probe technique in two differentinstruments with a range of accelerating potentials. Simpleoxides and minerals have been used as standards for the elementsNa to Ca and pure metals for the elements Ti to Ni. Factors affecting the accuracy of analysis are discussed indetail. The effect of wavelengthshift errors is treated in ageneral manner and curves enabling the magnitude of the effectto be determined in any instrument are given. Corrections associatedwith X-ray generation (the atomic number correction), absorptionand secondary excitation by characteristic and continuous radiationare examined separately. It is shown that analyses with an accuracyof 1 per cent or better can be obtained with recently developedcorrection methods and it is suggested that this approach isnow a workable and possibly a preferable alternative to methodsemploying empirical calibration.  相似文献   

加强矿产资源管理 促进工业化进程     

龙服忠  余少华  杨利民 《湖南地质》2002,21(3):161-167

新中国成立后,经过50余年的地质勘查和矿山建设,奠定了湖南作为我国矿产资源大省的地位,赢得了“有色金属之乡”和“非金属之乡”的美誉．在经历了计划经济和过渡时期的管理模式之后,湖南省的矿产资源管理正逐步由行政手段为主转为以法律手段为主,由直接组织或干预地勘单位的勘查和矿山企业的开采活动转为以矿业权管理为核心的新型管理模式．湖南省矿产资源面临看自然禀赋存在缺陷,开发成本高、难度大,保有储量消耗过快,接替资源不足,地勘投入短缺,矿业结构失调,经营方式粗放,资源利用率低,环境污染和破坏严重等一系列严峻问题．为此,应采取逐步建立和完善矿业市场,实现地勘业和矿业开发管理体制创新,加强处质勘查,提高矿产资源开发利用的集约化程度,加强矿山环境保护等措施,保证矿业可持续发展,促进全省工业化进程。  相似文献   

应用GIS技术恢复蛤蟆洞哺乳动物化石群古生态环境     

高杨  龙昱 《地质科技情报》2003,22(4):33-36

以湖北省房县桥上乡蛤蟆洞新发现的哺乳动物化石产地的自然地理特征和动物化石所反映的动物种群的生活习性为基础，通过GIS的三维成图技术和化石产地自中更新世—晚更新世以来地表抬升的负变换，恢复了哺乳动物群生存时代的古环境。根据古今地貌类型的定量对比得出了研究区自中更新世—晚更新世以来的古环境，地表的起伏程度总体上逐渐增大，但基本形态变化不大；在中更新世—晚更新世哺乳动物生存的区域是一个三面环山—面峡谷的相对封闭的自然环境；适合该区森林草原型哺乳动物生存的平缓地带不断遭到河流的侵蚀破坏，因而面积逐渐减少；河谷平地的不断破坏和台地、山前缓坡带的减少是适合森林草原型动物生存环境逐渐减少的主要原因。  相似文献   

沿层地震属性分析在川东北储层研究中的应用   总被引：6，自引：0，他引：6  

巫盛洪  李志荣  龙资强  姚付生 《物探化探计算技术》2003,25(3):201-206

提取相关的地震属性，对这些地震属性进行聚类研究及分析归纳，找出针对储集体的敏感属性，建立起储集层的地震响应模式。这里对几种重要参数的计算原理、物理特性进行了分析，并做了正演模型研究，对川东北部地区飞仙关组鲕滩储层进行了参数提取与过井参数聚类。结果表明，对高品质的地震资料，使用属性分析进行储层的模式建立以及储层的横向变化研究是可行的。  相似文献   

水资源(环境)承载力的研究进展   总被引：46，自引：0，他引：46       下载免费PDF全文

龙腾锐  姜文超 《水科学进展》2003,14(2):249-253

概述了水资源(环境)承载力的概念、特征、量化评价方法及其总体研究的进展。强调了系统研究水资源(环境)承载力的重要现实意义。指出了当前研究中的不足,以及有待进一步研究的问题。  相似文献   

"土地整理理论"初探   总被引：17，自引：2，他引：17  

罗明  龙花楼 《地理与地理信息科学》2003,19(6):60-64

土地整理已成为土地科学的一个新的学科“生长点”，该文借鉴土地科学的相关理论基础，结合目前我国土地整理工作的任务与实践，探讨土地整理的理论：阶段理论、市场理论、广域理论、区域差异理论、效益统一理论、人居环境理论。  相似文献