新型全防护拉索在管道跨越中的应用     

江焕宏  赵军  宁世伟  程梦鹏 《油气储运》2002,21(10):28-31

介绍了新型全防护拉索在管道跨越中的应用，以往管道跨越采用不同规格钢丝绳作为承重索，抗风索，但由于钢丝绳本身的结构特点，给管道跨越设计施工带来了很多困难，苏州华能热网工程首次采用高强钢丝新型全防护拉索作为管道跨越的承重索及抗风索，效果很好，就这种新型全防护拉索的帛作技术及其特点进行了详细描述。  相似文献   

Changes in landscape patterns in Georgia,USA   总被引：39，自引：0，他引：39  

Monica Goigel Turner  C. Lynn Ruscher 《Landscape Ecology》1988,1(4):241-251

The objectives of this study were to determine how landscape patterns in Georgia, USA have changed through time and whether the spatial patterns varied by physiographic region. Historical aerial photography was used to analyze spatial patterns of land use from the 1930's to the 1980's. Land use patterns were quantified by: (1) mean number and size of patches; (2) fractal dimension of patches; (3) amount of edge between land uses; and (4) indices of diversity, dominance, and contagion. Forest cover increased in aerial extent and in mean patch size. The mean size of agricultural patches increased in the coastal plain and decreased in the mountains and piedmont. Edges between land uses decreased through time, indicating less dissection of the landscape. Fractal dimensions also decreased, indicating simpler patch shapes. Indices of diversity and dominance differed through time but not among regions; the contagion index differed among regions but not through time. A geographic trend of decreasing diversity and increasing dominance and contagion was observed from the mountains to the lower coastal plain. Landscape patterns exhibited the greatest changes in the piedmont region. Overall, the Georgia landscape has become less fragmented and more connected during the past 50 years. Changing patterns in the landscape may have implications for many ecological processes and resources.  相似文献   

Drought damage in the park forests of the city of Helsinki   总被引：1，自引：0，他引：1  

Markus Holopainen  Olli Leino  Hannu Kmri  Mervi Talvitie 《Urban Forestry & Urban Greening》2006,4(2):75-83

During spring and summer 2003 severe drought-caused damage was observed in the park forests of the city of Helsinki; especially in barren site pine and spruce stands. The objectives of this study were to map and document the extent of the damage through the use of existing geographical information, digital aerial photography and field surveys and to examine the feasibility of assessing drought damage by visual interpretation of digital aerial photography. Our aim was also to assess the reasons for drought damage in Helsinki city park forests using geographic information system (GIS) analyses of existing interpretative and geographical data, i.e. digital aerial photographs, rainfall statistics and the compartmentwise GIS database of the park forest site and soil types.The total amount of area falling into serious damage classes represented approximately 25 ha (the total forested area in Helsinki is about 3700 ha). A majority of these areas were located on rocky sites having low stem volumes. The total proportion of damaged stock volume was estimated as 17 300 m³, which is 3.3% of the total stock volume in the study area. An accuracy assessment showed that visual interpretation of digital aerial photos is an excellent tool for assessing drought damage. The mean estimation error was 0.7 classes, and errors comprising 2 classes were found in all test grids. The overall correct percentage of photointerpretation was 46%, and estimation was unbiased (kappa 0.264). The forest site and soil type together with the tree species on site showed the greatest correlation with drought damage. The drier and more barren the site, the more likely that damage will occur. Roadside forests were in better condition than areas located further off the roads. Hills clearly impacted the condition of the trees through soil type and flow.  相似文献   

玉米高产创建栽培技术研究进展   总被引：17，自引：3，他引：14  

冯国良  刘福虎 《山西农业科学》2012,40(12)

玉米高产创建栽培技术一直是国内外玉米专家研究的热点。通过汇总国内外专家在玉米高产创建方面取得的成绩,得出高产玉米需要关注的2大主要生理指标——不同生育期地上部干物质的变化和不同生育期叶面积指数(LAI);最后总结出玉米高产体系栽培技术:选择合适的品种;选择播种期及播种密度,构建适宜的植株群体结构;培肥土壤和充足的水肥供应;精细播种,加强田间管理,适期收获。  相似文献   

航空静电喷雾与非静电喷雾沉积效果的比较   总被引：3，自引：0，他引：3  

舒朝然  潘宏阳  周宏平  詹敏  梅爱华  茹煜  贾志成  陈国发 《林业科学》2012,48(4):75-80

利用直升机R44和固定翼飞机Y5B挂载自主研制的航空静电喷雾系统设备进行机场和野外航空静电喷雾与非静电喷雾的比较试验.结果表明:静电喷雾存地面和空中靶标表面、树冠中上部叶片正面的沉积效果明显优于非静电喷雾:雾粒细小、分布均匀、沉积密度提高1倍以上,最高达1.75倍;直升机静电喷雾在叶片背面的沉积率为非静电喷雾的2.15倍,是常规航空喷雾的3.31倍.Y5B静电喷雾在叶片背面的沉积率为非静电喷雾的2.38倍,是常规航空喷雾的3.44倍.  相似文献   

Clear-cut Detection in Boreal Forest Aided by Remote Sensing     

《Scandinavian Journal of Forest Research》2012,27(6):537-546

The study compares the applicability of different remote sensing data and digital change detection methods in detecting clear-cut areas in boreal forest. The methods selected for comparisons are simple and straightforward and thus applicable in practical forestry. The data tested were from Landsat satellite imagery and high-altitude panchromatic aerial orthophotographs. The change detection was based on image differencing. Three different approaches were tested: (1) pixel-by-pixel differencing and segmentation; (2) pixel block-level differencing and thresholding; and (3) presegmentation and unsupervised classification. The study shows that the methods and data sources used are accurate enough for operational detection of clear-cut areas. The study suggests that predelineated segments or pixel blocks should be used for image differencing to decrease the number of misinterpreted small areas. For the same reason the use of a digital forest mask is crucial in operational applications.  相似文献   

植保无人机施药技术研究进展     

宋雷洁  李建平 《现代农业科技》2019,(11)

农用植保无人作业机是农业生产中防治病虫害的新兴植保装备之一。通过分析、总结近几年植保无人机在田间病虫害防治、智能调控、作业航路规划等方面的施药技术研究与应用,分析植保无人机作业模式与作业特点,明确了现阶段利用植保无人机进行病虫害防控的发展趋势,以期为植保无人机的推广应用提供参考。  相似文献   

无人机森林航摄影像三维点云估测林分蓄积量研究     

李亚东  曹明兰  李长青  明海军 《中南林业科技大学学报(自然科学版)》2019,(3):56-60

森林蓄积量能够评估林地生产力的高低及经营措施的效果,为森林经营与采伐提供重要依据。目前,大多基于无人机影像的蓄积量估算,均建立在测绘标准所生成的DOM、DSM、DEM等测绘成果基础上,而未充分利用原始影像数据上的林业特征,无法从点云层面上加入林业业务逻辑产生成果数据。获取无人机影像后,利用特征点提取与匹配方法自动相对定向,结合控制点和光束法平差的迭代求解,解算出精确的相机姿态数据,并沿核线方向一维搜索特征点进行影像密集匹配生成密集点云。对原始三维点云过滤后进行树冠分割,在聚类后的林冠点云中提取了树顶点和树高因子估测了森林蓄积量。研究结果表明,冠幅的提取精度85.15%,树高的提取精度83.69%,林分蓄积量估算的精度达到了82.46%。  相似文献   

无人机摄影获取单木三维信息方法研究   总被引：1，自引：0，他引：1  

李涛  冯仲科  于东海  程文生 《中南林业科技大学学报(自然科学版)》2019,(3):61-68

随着无人机航空摄影测量技术的成熟和发展,改变了传统森林调查的手段,加快了森林调查的数字化、智能化发展。为提高单木因子的采集效率和精度,降低外业的工作强度,基于倾斜摄影测量技术,以多旋翼无人机为数据采集平台,实现了孤立单木的三维点云模型重建。在此基础上,建立了单木三维信息量测算法,提出切割法和投影法两种提取树冠投影面积的方法,并提取树高、树干任意处直径、树冠投影面积、冠幅、树冠表面积、树冠体积6项测树因子参数。结果表明:1)树木的总高度和第一枝下高的提取精度分别为96.28%和95.61%,胸径和上部直径的提取精度分别为96.24%和93.78%;2)利用切割法和投影法提取树冠投影面积的精度分别为96.28%和98.24%,提取冠幅的精度分别为89.65%和91.50%,提取树冠表面积的精度分别为96.78%和97.58%,提取树冠体积的精度分别为94.29%和96.14%;3)实践证明,该技术可很好地应用到古树名木的保护工作中,并可对森林调查的方式提供新的技术参考,具有较高的现实意义和实际应用价值。  相似文献   

基于无线传感网络的农业无人机航线控制系统     

赵峰  姜攀 《农机化研究》2019,(1):226-229

无人机是一个由飞行器、控制站、通讯设备和其它部件形成的系统,在农业领域主要应用于农药喷洒、信息监测和农业保险勘察。农业无人机在飞行过程中的实际航线与规划航路之间会存在偏差,不仅降低了作业质量,还会影响作业效率。无线传感网络是一种与无人机紧密结合的技术,可以用于对无人机的航线进行控制。为此,基于无线传感网络,设计了无人机的航线控制系统。该系统由无人机平台、传感节点、汇聚节点和控制中心4部分组成,对航线的控制通过二维坐标系跟随算法完成。试验结果表明:无线传感网络对直线和曲线航线的跟踪更加稳定,具有较高的航线控制精确度。  相似文献