城市大比例尺航测成图质量评定     

胡景海  钟生伟 《地理空间信息》2008,6(1):121-123

主要从大比例尺航测成图质量评定角度出发,提出了既要满足相应规范和用户要求,又要最大限度的发挥航测成图的优势,对产品质量做出公正、客观、正确的质量评价方法。  相似文献   

连作马铃薯根系分泌物鉴定及其对尖孢镰孢菌（Fusariumoxysporum）的作用     

谢奎忠  邱慧珍  胡新元  罗爱花 《中国沙漠》2021,41(3):7-15

为了揭示马铃薯连作化感物质与枯萎病之间的关系,通过水培和田间长期定位试验相结合方法,收集不同连作年限马铃薯根系分泌物,采用GC-TOF-MS进行分离鉴定。结果表明：在检测到的马铃薯根系分泌的48种物质中有机酸占30种。比较轮作、连作5年和连作10年马铃薯根系分泌物中有机酸的相对含量,发现苹果酸和棕榈酸的差异比较大。马铃薯连作条件下根系分泌物能显著增强尖孢镰孢菌（Fusariumoxysporum）的发育并加重枯萎病发生。通过外源添加法研究苹果酸和棕榈酸对尖孢镰孢菌的化感作用,苹果酸和棕榈酸浓度分别在0.10—0.50 mmol·L^-1和0.05—0.10 mmol·L^-1对尖孢镰孢菌生长起到显著的促进作用。盆栽试验表明,浓度0.05—0.50 mmol·L^-1苹果酸和棕榈酸对马铃薯枯萎病有显著的促进作用。这说明苹果酸和棕榈酸是马铃薯根系分泌的化感自毒物质,对尖孢镰孢菌生长起促进作用是连作马铃薯枯萎病发病主要原因。  相似文献   

华南桉树人工林芒萁层片的生态筛效应     

刘美洁  孙中宇  耿守保  温美丽  戴佳玲  杨龙 《热带地理》2021,41(6):1338-1346

芒萁是华南退化坡地上最具代表性的先锋种、优势种和关键种,能够快速形成密集的单优种层片结构。与传统阻碍更新的观点不同,野外观察发现芒萁层片内仍有少数物种能够成功定居,被认为具有生态筛效应。文章通过设置4种芒萁层片处理（芒萁层片完全剔除-UR;仅保留地上层-AF;仅保留根毯层-AR;芒萁层片全部保留-CK）,分别在不同处理下移植目标种幼苗并结合土壤性状,探究芒萁层片生态筛效应及其潜在机理。结果发现：1）桉林芒萁根毯层中土壤有机质、全氮、碱解氮、有效磷、速效钾、交换性钠、交换性钙、交换性镁和阳离子交换量均显著高于芒萁红壤层和裸地红壤;2）多数乔木种和草本种在芒萁根毯层保留时无法存活,仅荷木、桃金娘、梅叶冬青和野牡丹等目标种幼苗在保留芒萁根毯层处理（AR和CK）下能够存活与生长。这表明芒萁层片确实具有生态筛效应,且其关键在于根毯层的作用而并非土壤养分改善作用。理论上,芒萁层片（尤其是根毯层）与生态恢复的生物阈值突破密切相关,未来需要进一步解析芒萁根毯层的结构与功能。应用上,华南地区存在大量以芒萁为单优林下植物的人工林类型（如桉林等）,在进行结构优化与林分改造时需注意芒萁的生态筛效应。  相似文献   

一种新型非线性滤波理论及其应用     

吴江飞  雷辉  王世忠 《测绘工程》2008,17(6):16-19

研究一种新型的非线性滤波理论,即Unscented卡尔曼滤波（UKF）,同时为了获得更高的计算效率和确保协方差阵的非负定性,研究了平方根UKF。将UKF和平方根UKF应用到星载GPS卫星定轨中,实际算例表明UKF和平方根UKF的性能要优于常用的推广卡尔曼滤波的性能。  相似文献   

利用三山岛金矿尾矿制备塑料母料          下载免费PDF全文

渠美云  王志明  董延钰 《山东国土资源》2020,36(12)

经磨矿作业后,金矿选别过程通常会产生大量细粒尾矿,三山岛金矿尾矿堆存量较大,尾矿资源丰富。尾矿中有价元素含量不高,尾矿中丰富的非金属矿资源尚未得到有效回收利用。本文以三山岛金矿尾矿为主要原料,进行了有价元素回收探索研究、分级提纯研究、表面改性研究以及制备PP,PE母料添料的试验研究。将分级提纯后的尾矿作为碳酸钙替代料制备的PP,PE母料添料具有良好的性能指标,实现节能减排,减轻环境负担的同时,减少橡胶原料的消耗。  相似文献   

Performance of the CMA-GD Model in Predicting Wind Speed at Wind Farms in Hubei, China     

许沛华  成驰  王文  陈正洪  钟水新  张艳霞 《热带气象学报(英文版)》2023,29(4):473-481

This study assesses the predictive capabilities of the CMA-GD model for wind speed prediction in two wind farms located in Hubei Province, China. The observed wind speeds at the height of 70m in wind turbines of two wind farms in Suizhou serve as the actual observation data for comparison and testing. At the same time, the wind speed predicted by the EC model is also included for comparative analysis. The results indicate that the CMA-GD model performs better than the EC model in Wind Farm A. Th...  相似文献   

The alluvial architecture of a suspended sediment dominated meandering river: the Río Bermejo,Argentina          下载免费PDF全文

Gregory H. Sambrook Smith  James L. Best  Jessica Z. Leroy  Oscar Orfeo 《Sedimentology》2016,63(5):1187-1208

The alluvial architecture of fine‐grained (silt‐bed) meandering rivers remains poorly understood in comparison to the extensive study given to sand‐bed and gravel‐bed channels. This paucity of knowledge stems, in part, from the difficulty of studying such modern rivers and deriving analogue information from which to inform facies models for ancient sediments. This paper employs a new technique, the parametric echosounder, to quantify the subsurface structure of the Río Bermejo, Argentina, which is a predominantly silt‐bed river with a large suspended sediment load. These results show that the parametric echosounder can provide high‐resolution (decimetre) subsurface imaging from fine‐grained rivers that is equivalent to the more commonly used ground‐penetrating radar that has been shown to work well in coarser‐grained rivers. Analysis of the data reveals that the alluvial architecture of the Río Bermejo is characterized by large‐scale inclined heterolithic stratification generated by point‐bar evolution, and associated large‐scale scour surfaces that result from channel migration. The small‐scale and medium‐scale structure of the sedimentary architecture is generated by vertical accretion deposits, bed sets associated with small bars, dunes and climbing ripples and the cut and fill from small cross‐bar channels. This style of alluvial architecture is very different from other modern fine‐grained rivers reported in the literature that emphasize the presence of oblique accretion. The Río Bermejo differs from these other rivers because it is much more active, with very high rates of bank erosion and channel migration. Modern examples of this type of highly active fine‐grained river have been reported rarely in the literature, although ancient examples are more prevalent and show similarities with the alluvial architecture of the Río Bermejo, which thus represents a useful analogue for their identification and interpretation. Although the full spectrum of the sedimentology of fine‐grained rivers has yet to be revealed, meandering rivers dominated by lateral or oblique accretion probably represent end members of such channels, with the specific style of sedimentation being controlled by grain size and sediment load characteristics.  相似文献   

利用Abel-Poisson径向基函数模型化局部重力场     

马志伟  陆洋  涂弋  朱传东  郗慧 《测绘学报》2016,45(9):1019-1027

多种类型高分辨率重力场数据的不断增加,使得在局部范围内精化重力场模型成为了可能。本文采用Abel-Poisson核将重力场量表示成有限个径向基函数线性求和的形式,对局部区域的多种重力场数据进行联合建模。为了提高运算速度,运用了基于自适应精化格网算法的最小均方根误差准则(RMS)来求解径向基函数平均带宽。以南海核心地区为例,联合两种不同类型、不同分辨率的重力场资料(大地水准面起伏6'×6'、重力异常2'×2'),构建了局部区域高分辨率的重力场模型。所建模型表示的重力场参量达到了2'×2'的分辨率,对原始的重力异常数据(2'×2')拟合的符合程度达到±0.8×10-5m/s2。结果表明,利用径向基函数方法进行局部重力场建模,避免了球谐函数建模收敛慢的问题,有效提高了模型表示重力场的分辨率。  相似文献   

Incorporation of a dynamic root distribution into CLM4.5: Evaluation of carbon and water fluxes over the Amazon     

Yuanyuan Wang  Zhenghui Xie  Binghao Jia 《大气科学进展》2016,33(9):1047-1060

Roots are responsible for the uptake of water and nutrients by plants and have the plasticity to dynamically respond to different environmental conditions. However, most land surface models currently prescribe rooting profiles as a function only of vegetation type, with no consideration of the surroundings. In this study, a dynamic rooting scheme, which describes root growth as a compromise between water and nitrogen availability, was incorporated into CLM4.5 with carbon–nitrogen(CN) interactions(CLM4.5-CN) to investigate the effects of a dynamic root distribution on eco-hydrological modeling. Two paired numerical simulations were conducted for the Tapajos National Forest km83(BRSa3) site and the Amazon, one using CLM4.5-CN without the dynamic rooting scheme and the other including the proposed scheme. Simulations for the BRSa3 site showed that inclusion of the dynamic rooting scheme increased the amplitudes and peak values of diurnal gross primary production(GPP) and latent heat flux(LE) for the dry season, and improved the carbon(C) and water cycle modeling by reducing the RMSE of GPP by 0.4 g C m~(-2)d~(-1), net ecosystem exchange by 1.96 g C m~(-2)d~(-1), LE by 5.0 W m~(-2), and soil moisture by 0.03 m~3m~(-3), at the seasonal scale, compared with eddy flux measurements, while having little impact during the wet season. For the Amazon, regional analysis also revealed that vegetation responses(including GPP and LE) to seasonal drought and the severe drought of 2005 were better captured with the dynamic rooting scheme incorporated.  相似文献   

Revisiting Sustainable Development of Dry Valleys in Hengduan Mountains Region   总被引：5，自引：1，他引：4  

TANGYa XIEJiasui SUNHui 《山地科学学报》2004,1(1):38-45

Dry valleys are a striking geographic landscape in Hengduan Mountains Region and are characterized by low rainfall, desert type of vegetation and fragile environment. Past efforts and resources have been concentrated mainly on rehabilitation of degraded ecosystem and fragile environment, particularly reforestation, while socio-economic development has been largely overlooked. Despite successes in pocket areas, the overall trend of unsustainability and environmental deterioration are continuing. It is important to understand that uplift of the Tibetan Plateau is the root cause of development of dry valleys, and development and formation of dry valleys is a natural process. Human intervention has played a secondary role in development of dry valleys and degradation of dry valleys though human intervention in many cases has speeded up environmental degradation of the dry valleys. It is important to understand that dry valleys are climatic enclaves and an integrated approach that combines rehabilitation of degraded ecosystems and socio-economic development should be adopted if the overall goal of sustainable development of dry valleys is to be achieved. Promotion of niche-based cash crops, rural energy including hydropower, solar energy, biogas and fuelwood plantation is recommended as the priority activities.  相似文献