Study of Fractal Characteristics of the Cementation Index in Shale Gas     

LIU Hongqi  LIU Shiqiong  LUO Xingping  SUN Yangsh  TIAN Jie  LIANG Lixi  LIU Xiangjun 《《地质学报》英文版》2020,94(2):456-466

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旋翼无人机测算风速风向技术研究   总被引：1，自引：1，他引：0  

何诚  吕振义  李瑾  王越  舒立福 《测绘通报》2019,(12):91-95

目前大部分民用无人机没有准确测量风速、风向和预警风场的功能，然而森林火灾扑救等多种场景需要无人机可以提供准确的风速。本文提出了一种基于旋翼无人机坐标数据测算风速风向的技术，通过无人机主机RTK坐标信息及方位角、倾角数据精准获取螺旋桨点相对坐标信息，选择不同负载条件下无人机以1~16 m/s的不同速度分别飞行30 s以上，根据螺旋桨坐标信息变化数值，结合风洞测试数据及风场动力学原理，研究风速与旋翼无人机倾角关系，并通过风洞试验检验该方法精度；并可根据无人机RTK推算出的螺旋桨坐标变化信息判断风向。结果表明，无人机风速与旋翼无人机倾角呈正相关关系；无人机负载加重时，对应受风速干扰的倾角会相对减小；无人机飞行受阵风干扰出现噪点的概率，高海拔区域大于低海拔区域；并建立六旋翼无人机飞行倾角的风速估算模型y=－1.043 5+1.150 1x，该模型测算风速的中误差值为0.966，绝对值小于1，满足应急指挥现场对无人机测量风速精度要求。该方法得到风速测算精度高，可以为旋翼无人机实时获取风速风向提供一种可行方法，具有一定的实用价值。  相似文献   

不同结构林带防风效能风洞模拟     

李晓烨  王克俭  谷建才  刘启国  崔严 《中国沙漠》2019,39(6):118-125

防风林带结构是影响防风效能的主要因素。建立不同宽度、不同株行距林带防风效能与林带后距离之间的统计模型，可以为防风林建设提供指导性意见。通过风洞实验，在11 m·s^-1风速下，对4种宽度、5种株行距林带的背风面0~10H（H为林带高度）的风速进行测定，采用曲线参数估计法、傅立叶模型、SSF模型（Sum of Sin Functions），构建了不同结构林带防风效能与林带后距离间的统计模型。结果表明：傅立叶模型拟合不同宽度林带的防风效能与林带后距离的关系效果最优，可决系数（R²）均在98%以上；SSF模型拟合不同株行距林带的防风效能与林带后距离的关系效果最优（R²>0.98）。根据构建的统计模型，风速为11 m·s^-1左右时，林带宽度8 m（两行一带）的防风林的防风效能存在明显优势；5种株行距的林带中，株行距为8 m×8 m的防风林带本试验条件下防风效果最好。  相似文献   

湍流度随高度的变化及其对城市宏观地形的依赖     

李大全  孙武  欧阳睿康  黄盛  高梦媛  李庆祥  黄启明 《热带地理》2019,39(3):365-376

分别构建广州主建成区垂直比例尺为1﹕2 000、1﹕1 000和1﹕500的3个建筑物模型，利用大型边界层风洞，在西北和东南两风向下，基于中性流模拟分析了复杂城市地形下湍流度随高度的变化及其对宏观地形的依赖。结果表明：风廓线指数α与不同高度的湍流度之间的关系密切，利用现有模型，根据4类粗糙度边界层和不同垂直比例尺，可确定相应的湍流度随高度变化模型的主要系数，预测精度高。城市地形下最大湍流度面发育在0~0.2 h之间狭窄的范围内。用湍流度形态指数β来表征湍流度随高度的变化，无论城市屋脊还是平坦地形，随着风程区的延伸，廓线的指数α升高，湍流度形态指数β降低。表明同一高度湍流度值具有由迎风区、丘顶区向背风区增高，沿风程逐渐增大的规律，对地形部位和风程的依赖性强，与来流翻越简单地形时的特征一致。  相似文献   

Effects of current climate,paleo-climate,and habitat heterogeneity in determining biogeographical patterns of evergreen broad-leaved woody plants in China   总被引：1，自引：1，他引：0  

Xu  Yue  Shen  Zehao  Ying  Lingxiao  Zang  Runguo  Jiang  Youxu 《地理学报(英文版)》2019,29(7):1142-1158

Journal of Geographical Sciences - Understanding biogeographic patterns and the mechanisms underlying them has been a main issue in macroecology and biogeography, and has implications for...  相似文献   

基于MCR模型和DO指数的九江滨水城市生态安全网络构建   总被引：1，自引：1，他引：0  

戴璐  刘耀彬  黄开忠 《地理学报》2020,75(11):2459-2474

兼顾生态保护和经济增长的生态安全网络对引导滨水城市走可持续发展道路具有重要指导意义。本文以九江市为例,采用景观生态数据集和产业信息数据集,结合最小累积阻力模型（MCR）和连续空间的产业集聚测度指数（DO）构建了综合评价方法,分别对景观生态格局和经济生产空间进行分析,诊断二者的空间冲突确定战略节点并构建生态安全网络。结果表明：① 研究区包含重要生态源地29个,总面积为7323 km²;生态安全阻力高值区面积占39.69%,位于城市中部和东部连片区域,低值区则处于外围,且连通过渡区域较少,呈现空间上两极分化的“中心—外围”景观生态格局;② 经济生产空间临近水资源分布,呈现为小尺度集聚、大尺度分散的空间格局;主要产业集聚区的平均长度和数量均显示出重度污染行业>轻度污染行业>中度污染行业的空间关系;③ 识别出景观生态廊道总长685.57 km,选取了25个生态—经济战略节点,规划了18条总长424.53 km的重要绿带和26条总长662.46 km的一般绿带,共同构成了“蜂巢状”九江市生态安全网络格局。本文采用自然和经济条件相结合的综合分析视角,为生态安全格局的构建提供了多样化的实现途径。  相似文献   

Prediction of vegetation anomalies over an inland river basin in north‐western China          下载免费PDF全文

Jing Fu  Jun Niu  Bellie Sivakumar 《水文研究》2018,32(12):1814-1827

Vegetation cover plays an important role in linking the atmosphere, water, and land and is deemed as a key indicator in the terrestrial ecological system. Therefore, it is of great importance to monitor vegetation dynamics and understand the mechanisms of vegetation change, including that driven by climate change. This study examines (a) the evolution of vegetation dynamics over the Heihe River Basin in the typical arid zone in north‐western China using nonparametric Mann–Kendall test and Thiel Sen's slope; (b) the relationships between remotely sensed vegetation indices (normalized difference vegetation index [NDVI] and enhanced vegetation index [EVI]) and hydroclimatic variables based on correlation analysis; and (c) the prediction of vegetation anomalies using a multiple linear regression model. For the analysis, the Moderate Resolution Imaging Spectroradiometer NDVI/EVI product and the gridded daily meteorological data at a spatial resolution of 0.125° over the period 2001–2010 are considered. The results indicate that vegetation cover improved over a large proportion during 2001–2010, with a significant trend towards warm and wet, characterized by an increase in average annual temperature and precipitation by 0.042 °C/year and 5.8 mm/year, respectively. We test the feasibility of NDVI and EVI in quantifying the responses of vegetation anomaly to climate change and develop a statistical model to predict vegetation dynamics in the basin. The NDVI‐based model is found to be more reliable than the EVI‐based model, partly due to the vegetation characteristics and geomorphologic properties of the study region. The proposed model performs well when there is no lag time between meteorological factors and vegetation indices for grassland and cropland, whereas 1‐month lead time prediction is found to be best for forest. The soil water content is introduced as an extra explanatory variable, which effectively improves the prediction accuracy for different land use types. In general, the predictive ability of the proposed model is stable and satisfactory, and the model can provide useful early warning information for regional water resources management under changing climate.  相似文献   

海气动量通量研究综述   总被引：1，自引：0，他引：1  

冯兴如  李水清  尹宝树 《海洋科学》2018,42(10):103-109

海气界面动量通量也称为风应力,是海流和表面海浪的主要驱动力,是海洋从大气获得动量的重要途径。因此,合理可靠的海洋表面风应力的参数化对于海洋、大气和波浪以及气候模式的准确预报都具有非常重要的科学意义和实用价值。对风应力拖曳系数的参数化是风应力参数化的主要内容。近来的观测发现,风应力拖曳系数随着风速的增加出现了先增后减的趋势,同时还与海面的波浪状态以及海流有关。基于观测或理论分析,目前已经得到了一系列的风应力拖曳系数计算方法或公式,有的考虑了海浪的作用,有的没有,但这些方案大都是适合中低风速,在高风速下的适用性还有待检验。本文回顾了目前在海气动量通量观测和参数化方面的研究进展,并建议应增加高风速下风速、海流以及海浪等的同步观测,以进一步完善风应力参数化方案。  相似文献   

Tropical Cyclone Genesis Potential Index for Bay of Bengal During Peak Post-Monsoon (October-November) Season Including Atmosphere-Ocean Parameters     

P. Suneeta 《Marine Geodesy》2018,41(1):86-97

Several studies on tropical cyclone genesis potential index (GPI) mainly using atmospheric parameters (relative/absolute vorticity, relative humidity, vertical wind shear, potential instability, vertical velocity etc.) have been reported earlier. Though the ocean plays a vital role in the genesis and intensification of cyclones, no ocean parameter has been included in most of the studies. In this study, we have made an attempt to develop a new GPI for Bay of Bengal during peak post-monsoon (October-November) season including upper ocean heat content (UOHC) using the data for the period 1995–2015. It is found that the new GPI is better correlated with the total number of depressions, cyclones and severe cyclones (TNDC) compared with the existing GPI which was developed for the north Indian Ocean and presently used by India Meteorological Department (IMD), New Delhi. The correlation has significantly enhanced (r=0.86:significant at >99% level) by using the first differences [year(0) –year(?1)] of the time series data. Since, the new GPI which considers atmosphere and ocean (UOHC) parameters, it appears to be more suitable for Bay of Bengal during the peak post-monsoon season.  相似文献   

In situ measurements of wind‐driven salt fluxes through constructed channels in a coastal wetland ecosystem          下载免费PDF全文

Alex K. Manda  Enrique Reyes  James M. Pitt 《水文研究》2018,32(5):636-643

A suite of instruments was deployed in a coastal wetland ecosystem in the Albemarle estuarine system, North Carolina (USA), to characterize wind‐driven transport of saltwater through a constructed (man‐made) channel. Flow velocity, electrical conductivity, and stage were measured in a representative channel over a 2‐month period from May to July 2014, during which 4 wind tides were observed. Collected data show that thousands of metric tons of salt were advected through the channel into coastal wetlands during each event, which lasted up to 4 days. The results reveal that as much as 36% of advected salts accumulated in the wetlands, suggesting that the cumulative effects of these events on the health of coastal wetlands in the Albemarle system may be substantial due to the abundance of constructed channels and the frequency of wind‐driven tidal events. This study is the first to quantify wind‐driven salt fluxes through constructed channels in coastal wetland settings.  相似文献