提高自然伽马测井曲线分辨率的正则化方法   总被引：4，自引：2，他引：4       下载免费PDF全文

汪宏年  李舟波 《地球物理学报》1997,40(6):847-856

应用正则化反演理论研究了提高自然伽马测井曲线纵向分辨率的正则反褶积处理技术，通过正则化因子对噪音和信号影响的分析和研究，给出了估计反褶积结果与地层真值偏差大小的新公式，提出了直接根据信噪比大小选择正则化因子的新方法．由于正则化因子保证使反褶积结果与地层真值偏差为最小，使计算结果的稳定性和精度均得到明显提高．此外，大部分测井记录的信噪比均可以很容易估计，从而大大提高了正则反褶积的适用性．最后通过理论模型实验和井场数据处理证明了正则反褶积技术是十分有效的．  相似文献   

花岗岩崩岗侵蚀劣地的生态恢复试验研究   总被引：2，自引：0，他引：2  

李先琨  叶惊春 《热带地理》1997,17(4):405-411

花岗岩崩岗侵蚀是红壤区最严重的侵蚀方式，本研究根据生态学的原理和方法，探索了花岗岩崩岗区水土流失治理和生态恢复的途径，提出了植被重建的模式。  相似文献   

极端干旱地区清绿线K170段铁路沙害机械措施治理     

刘阳宣  张民力 《中国沙漠》1997,17(3):280-285

清绿线Ｋ１７０段铁路地处极端干旱区，植物固沙难度大，铁路沙害的治理宜采用机械措施综合防治体系。２年的防护效益观测证实，用草方格沙障固沙，２０ｃｍ高度风速可比流沙区降低７６．３％，层内输沙率仅为流沙区的０．２８％；用砾石覆盖措施固沙，相应防护效果依次为１９．０９％和０．９１％；各防护措施下的风沙流特征值Ｑ６～２０／Ｑ０～６，都达到了＞１的有效防护指标。  相似文献   

近20年来黄河流域植被覆盖变化分析   总被引：50，自引：2，他引：50  

杨胜天  刘昌明  孙睿 《地理学报》2002,57(6):679-684

利用1982～1999年AVHRR-NDVI数据和对应年份黄河流域气象观测数据，通过计算、分析春季、夏汛及伏秋黄河流域NDVI距平值和湿润指数距平值的年际变化，得出了20世纪80年代至90年代初黄河流域气候相对湿润，90年代中后期相对干旱，植被覆盖状况总体一直处于上升趋势的结论，并评估了黄河流域近20年来生态保护和建设工作成效。  相似文献   

An investigation of the relationship between uniaxial compressive strength and degradation for selected rock types     

Margaret Kasim  Abdul Shakoor 《Engineering Geology》1996,44(1-4):213-227

The relationship between uniaxial compressive strength and degradation was investigated for selected rock types, by using regression analyses to determine whether degradation was a useful predictor of compressive strength. In addition, the effects of aggregate particle size, number of hammer blows during the degradation test, engineering index properties, petrographic characteristics, and water saturation on the compressive strength-degradation relationship were evaluated. The results show that strong inverse relationships exist between compressive strength and degradation (measured on a 9.5-4.75-mm size aggregate) for sandstones and igneous/metamorphic rocks, but that no significant relationship exists for limestones/dolomites. The results also indicate a strong positive correlation between degradation and L.A. abrasion loss and can be used to establish a limit of allowable degradation for practical applications. Engineering index properties do not significantly affect the relationship between compressive strength and degradation but petrographic characteristics are important in explaining the strength and degradation behavior of the rocks studied. Water saturation decreases compressive strength and increases degradation to varying degrees.  相似文献   

珠海荷包岛植被资源及其开发利用   总被引：6，自引：0，他引：6  

曹洪麟  陈树培 《热带地理》1996,16(3):258-264

本文在多次实地调查基础上，对珠海荷包岛的自然环境条件、植被类型和资源植物等作了较详细的阐述，并根据本岛旅游资源丰富，自然林面积在等特性，提出建立海岛森林公园，达到保护和发展植被资源的目的。  相似文献   

The three screen doors: can marine "protected" areas be effective?     

Jameson SC  Tupper MH  Ridley JM 《Marine pollution bulletin》2002,44(11):1177-1183

The great majority of marine protected areas (MPAs) fail to meet their management objectives. So MPAs can be effective conservation tools, we recommend two paradigm shifts, the first related to how they are located and the second related to how they are managed. MPAs are unlikely to be effective if they are located in areas that are subject to numerous, and often uncontrollable, external stressors from atmospheric, terrestrial, and oceanic sources, all of which can degrade the environment and compromise protection. MPA effectiveness is also limited by low institutional and community capacity for management and inappropriate size with respect to ecological needs. In particular, the check list approach to management does not ensure that key threats are dealt with, or that management expenditures provide a quantifiable return. We recommend a business planning approach to MPA management, in which managers focus on the viability of the management system, i.e., the ability of the MPA to provide ecological goods and services to its target users over the long term.  相似文献   

Integrated Spatio‐temporal Data Mining for Forest Fire Prediction     

Tao Cheng  Jiaqiu Wang 《Transactions in GIS》2008,12(5):591-611

Forests play a critical role in sustaining the human environment. Most forest fires not only destroy the natural environment and ecological balance, but also seriously threaten the security of life and property. The early discovery and forecasting of forest fires are both urgent and necessary for forest fire control. This article explores the possible applications of Spatio‐temporal Data Mining for forest fire prevention. The research pays special attention to the spatio‐temporal forecasting of forest fire areas based upon historic observations. An integrated spatio‐temporal forecasting framework – ISTFF – is proposed: it uses a dynamic recurrent neural network for spatial forecasting. The principle and algorithm of ISTFF are presented, and are then illustrated by a case study of forest fire area prediction in Canada. Comparative analysis of ISTFF with other methods shows its high accuracy in short‐term prediction. The effect of spatial correlations on the prediction accuracy of spatial forecasting is also explored.  相似文献   

Applying time series Landsat data for vegetation change analysis in the Florida Everglades Water Conservation Area 2A during 1996–2016     

《International Journal of Applied Earth Observation and Geoinformation》2017

Mapping plant communities and documenting their changes is critical to the on-going Florida Everglades restoration project. In this study, a framework was designed to map dominant vegetation communities and inventory their changes in the Florida Everglades Water Conservation Area 2A (WCA-2A) using time series Landsat images spanning 1996–2016. The object-based change analysis technique was combined in the framework. A hybrid pixel/object-based change detection approach was developed to effectively collect training samples for historical images with sparse reference data. An object-based quantification approach was also developed to assess the expansion/reduction of a specific class such as cattail (an invasive species in the Everglades) from the object-based classifications of two dates of imagery. The study confirmed the results in the literature that cattail was largely expanded during 1996–2007. It also revealed that cattail expansion was constrained after 2007. Application of time series Landsat data is valuable to document vegetation changes for the WCA-2A impoundment. The digital techniques developed will benefit global wetland mapping and change analysis in general, and the Florida Everglades WCA-2A in particular.  相似文献   

Estimating fractional vegetation cover and the vegetation index of bare soil and highly dense vegetation with a physically based method     

《International Journal of Applied Earth Observation and Geoinformation》2017

Normalized difference vegetation index (NDVI) of highly dense vegetation (NDVI_v) and bare soil (NDVI_s), identified as the key parameters for Fractional Vegetation Cover (FVC) estimation, are usually obtained with empirical statistical methods However, it is often difficult to obtain reasonable values of NDVI_v and NDVI_s at a coarse resolution (e.g., 1 km), or in arid, semiarid, and evergreen areas. The uncertainty of estimated NDVI_s and NDVI_v can cause substantial errors in FVC estimations when a simple linear mixture model is used. To address this problem, this paper proposes a physically based method. The leaf area index (LAI) and directional NDVI are introduced in a gap fraction model and a linear mixture model for FVC estimation to calculate NDVI_v and NDVI_s. The model incorporates the Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) model parameters product (MCD43B1) and LAI product, which are convenient to acquire. Two types of evaluation experiments are designed 1) with data simulated by a canopy radiative transfer model and 2) with satellite observations. The root-mean-square deviation (RMSD) for simulated data is less than 0.117, depending on the type of noise added on the data. In the real data experiment, the RMSD for cropland is 0.127, for grassland is 0.075, and for forest is 0.107. The experimental areas respectively lack fully vegetated and non-vegetated pixels at 1 km resolution. Consequently, a relatively large uncertainty is found while using the statistical methods and the RMSD ranges from 0.110 to 0.363 based on the real data. The proposed method is convenient to produce NDVI_v and NDVI_s maps for FVC estimation on regional and global scales.  相似文献