基于高分辨率遥感影像的林地变化检测方法研究     

刘自远  陈飞  宋康明 《测绘与空间地理信息》2021,44(12):153-155

本文采用2013年QuickBird和2017年GF-1卫星遥感影像,以黑龙江省五常市为研究区,利用遥感影像的光谱特征提取纯净森林像元,构建整合森林指数(Integrated Forest Z-Score,IFZ)对影像的森林和非森林区域进行区分,叠加对比分析两期影像提取结果,得到研究区内林地的变化区域.再将自动提取结果与人工判读图斑进行精度验证,面积误差为4.2％,图斑重叠率为85％.从精度结果可知,高分辨遥感影像可以准确地监测林地变化,对研究环境变化和森林经营管理具有决策性作用.  相似文献   

中国南北带地壳上地幔三维面波速度结构和各向异性   总被引：6，自引：1，他引：5       下载免费PDF全文

陈立华  庄真 《地球物理学报》1992,35(5):574-583

本文用长周期763地震仪面波群速度资料反演了中国南北带及邻区的三维速度结构.其中采集238条瑞利波和358条勒夫波混合频散曲线,使用均等显示滤波方法,并以4°×4°为一格将我国境内分为147格.用随机逆反演方法得到了研究区16格的纯路径频散.面波速度结构及演结果表明:1.莫霍界面深度一般在40-50km之间,最深达65km.总趋势是从东到西加深,且在南北带西侧南北两端向中部明显加深,东侧变化小.2.地幔顶部普遍出现很厚的低速层,上界面一般埋深60-80km.上地幔顶盖厚度一般为20-60km,速度为4.30-4.50km/s.3.研究区普遍存在各向异性,而且勒夫波和瑞利波速度的差值(V_SV-V_SH)的绝对值随深度有增大的特点,在南北带南部和西北部V_SV-V_SH各向异性现象更为明显.  相似文献   

荒漠植被红砂（Reaumurta soongorica）水热响应的年轮学研究     

肖生春  肖洪浪  宋耀选  段争虎  陆明峰 《中国沙漠》2006,26(4):548-552

 红砂是黄土高原荒漠植被带主要建群植物种之一，在植被恢复重建和生态建设中具有重要意义。本文以皋兰县40 a天然植被封育区为例，运用树木年轮学方法，对不同坡向红砂与当地水热条件变化的时空响应及分布格局进行了研究。研究结果表明，红砂具有明显的年轮特征，可以进行树木年轮方面的研究。虽然不同坡向水分条件和植被状况有很大差异，但红砂径向生长对区域水热变化具有非常一致的响应模式：同生长季降水呈正相关关系，尤以7月降水量最为显著；同生长季气温呈负相关关系，以6月最为显著。根据不同坡向红砂年龄分布格局分析结果，并考虑到水土流失的防治效果，黄土高原西部荒漠植被带的封育期限不宜少于10 a。  相似文献   

1980²000北京市农业土地生产性的变动分析   总被引：1，自引：0，他引：1  

王鹏飞  鲁奇  傅桦  李娟 《地理研究》2006,25(4):719-729

根据1980、1990、2000年的统计资料和实地走访观察,本文分析了北京市乡镇一级的粮食作物、蔬菜作物和果品作物的分布格局及农业土地生产性近20年的变化。研究认为:1980年北京农业生产分布格局与土地生产性为比较典型的杜能模式;随着农业经营的多样化,1990年和2000年北京农业土地生产性呈现出多样的分布格局;北京粮食作物、蔬菜作物、果品作物的分布格局及农业土地生产性近20年的变化与此阶段的农业生产政策、农业以外的社会经济活动变化有较强的关联性;对北京以上问题的研究为验证杜能、辛克利亚、布莱昂特城市周边农业地域研究经典理论的演变提供了实证案例。  相似文献   

纳滤膜分离技术及其在盐湖卤水资源开发中的应用          下载免费PDF全文

宋卫得  王海增  邢坤  郭鲁钢  李冬梅 《盐湖研究》2006,14(4):56-60

介绍了纳滤膜分离技术原理及其主要应用领域,结合我国盐湖卤水资源的特点与开发利用现状,提出了将纳滤膜分离技术应用于卤水资源综合利用的设想。  相似文献   

Modeling the seismic response of basin-edge structure by a sequential waveform method     

Lian-Feng Zhao  Wei-Min Wang  Juan Li  Zhen-Xing Yao 《Tectonophysics》2006,420(3-4):493-507

A sequential waveform method is developed to simulate the seismic response of basin-edge structure excited by a plane incident P-wave. The full procedure involves: (a) a previous parameterization of the investigated model using the seismic wave velocities and depths of the sedimentary stratifications; (b) an input motion determined from the records at stations installed on hard rock; (c) forward computation of the P-SV elastic wave field by means of a two-dimensional finite difference (FD) method; (d) the optimization of the model vector using simulated annealing technique and comparing the simulated seismic response of the tested structure with the observed wave field; (e) the correction of the initial model by trial-and-error by testing the differences between synthetics and observed data, and (f) the final solution obtained by iteration using the conjugate gradient algorithm. The search of an optimal basin-edge model has been parallel processed by varying the shapes and velocities of strata on the basis of the fitting of relative timing, amplitude and phase between the output and the observed data. The input motion and sensitivity have been checked and the validity of the method has been demonstrated by numeric analysis. Using the teleseismic records generated by 7 earthquakes recorded at 26 broadband seismic stations, we have studied the seismic velocity structure of the southern edge of the Jiyang depression located in the Bohai Bay basin, northern China. Two cross sections show an agreement between the velocity results and the geological sections available in the region. In addition, we obtain evidence of three hidden faults under the sections and features that suggest major extensions at the Paleogene.  相似文献   

加固含水平软弱层高陡边坡预应力锚索倾角的取值范围     

宋书志孔纪名  杨宗佶刘正梁 《山地学报》2006,24(B10):217-221

用直线和曲线滑面两种模型，模拟预应力锚索加固含有水平软弱层的高陡边坡的潜在滑动面，通过对锚索加固的力学机理分析来阐述预应力在滑动面主滑方向上产生分力的原因。从锚索受力角度上对锚索倾角的取值范围进行探讨，结合实际造孔过程有不同程度的孔斜或弯曲以及获取较好的锚固灌浆效果，就仰角锚固和俯角锚固两种锚固条件分别得出锚索倾角的取值范围，并以此来判定锚索的预应力是否会在滑动面走向方向上产生不利于坡体稳定的下滑力。  相似文献   

Climatic characteristics of summer high temperature and assessment methods in the large cities of North China     

ZHANG Shangyin  ZHANG Dekuan  WANG Shourong  SONG Yanling 《地理学报》2006,16(1):13-22

Based on the high temperature data of June to August in 1961-2000 in North China, the high temperature weather processes are investigated, and a more complete data set for severe high temperature processes is created. The climatic characteristics of adverse high temperature weather in Beijing, Tianjin, Shijiazhuang, Jinan and Taiyuan are analyzed respectively. The major features of the East-Asia Subtropical High and Transformed Continental High are discussed. The outcomes indicate that the influence of both East Asia Subtropical High and Transformed Continental High on these weather events varies, by a larger margin, from one city to another over North China and they are also closely related to the relative humidity. It is found that the behaviours of East-Asia Subtropical High and Transformed Continental High are the major important systems that give rise to the summer high temperature weather over the region. Based on these findings, the 5-day, 10-day and monthly assessment models for such high impact events have been developed. The assessment outcomes prove to be useful in assessing severe high-temperature events in major cities of North China.  相似文献   

Geothermal evidence for fluid flow through the gas hydrate stability field off Central Chile—transient flow related to large subduction zone earthquakes?     

Ingo Grevemeyer  Norbert Kaul  Juan L. Diaz-Naveas 《Geophysical Journal International》2006,166(1):461-468

  相似文献   

Evolution from Oceanic Subduction to Continental Collision: a Case Study from the Northern Tibetan Plateau Based on Geochemical and Geochronological Data   总被引：41，自引：0，他引：41  

SONG  SHUGUANG; ZHANG  LIFEI; NIU  YAOLING; SU  LI; SONG  BIAO; LIU  DUNYI 《Journal of Petrology》2006,47(3):435-455

Two apparently distinct, sub-parallel, paleo-subduction zonescan be recognized along the northern margin of the Tibetan Plateau:the North Qilian Suture Zone (oceanic-type) with ophioliticmélanges and high-pressure eclogites and blueschistsin the north, and the North Qaidam Belt (continental-type) inthe south, an ultrahigh-pressure (UHP) metamorphic terrane comprisingpelitic and granitic gneisses, eclogites and garnet peridotites.Eclogites from both belts have protoliths broadly similar tomid-ocean ridge basalts (MORB) or oceanic island basalts (OIB)in composition with overlapping metamorphic ages (480–440Ma, with weighted mean ages of 464 ± 6 Ma for North Qilianand 457 ± 7 Ma for North Qaidam), determined by zirconU–Pb sensitive high-resolution ion microprobe dating.Coesite-bearing zircon grains in pelitic gneisses from the NorthQaidam UHP Belt yield a peak metamorphic age of 423 ±6 Ma, 40 Myr younger than the age of eclogite formation, anda retrograde age of 403 ± 9 Ma. These data, combinedwith regional relationships, allow us to infer that these twoparallel belts may represent an evolutionary sequence from oceanicsubduction to continental collision, and continental underthrusting,to final exhumation. The Qilian–Qaidam Craton was probablya fragment of the Rodinia supercontinent with a passive marginand extended oceanic lithosphere in the north, which was subductedbeneath the North China Craton to depths >100 km at c. 423Ma and exhumed at c. 403 Ma (zircon rim ages in pelitic gneiss). KEY WORDS: HP and UHP rocks; subduction belts; zircon SHRIMP ages; Northern Tibetan Plateau  相似文献