非匀一冠层热辐射方向性3维模型构建——以玉米冠层为例     

马红章  刘素美  孙根云  杜永明  孙林  柳钦火 《遥感学报》2016,20(3):374-381

建立适用于多类型植被场景的热辐射方向性模型是进行地表热辐射方向性研究的一种手段。利用真实植株几何及生理参数的统计平均值来刻画理念植株,并给定其空间分布特征,进行不同生长期植被冠层的描述。基于冠层双向孔隙率思想构建了冠层热辐射方向性3维模型,模型继承了孔隙率模型在计算冠层热辐射方向性上的简洁优势同时以几何光学的思想考虑了冠层空间异质性对冠层热辐射方向性的影响。以玉米冠层为例,进行了不同生长期玉米冠层热辐射方向亮温的模拟,通过与实地测量数据的比对表明,本文发展的模型能够较准确地模拟不同生长期玉米植被场景的方向亮温变化规律,模拟误差主要来自理念株的刻画误差、玉米叶片形状的近似以及忽略了多次散射贡献等3个方面。模型的构建方法对稀疏植被场景、浓密植被场景、多类型植被的混合场景均可适用,不同观测几何下的植被场景4组份面积比计算结果有望应用于复杂地表条件下地表返照率的研究。  相似文献   

混凝土灌注桩桩头渗水的处理及预防措施          下载免费PDF全文

孙立宝 《探矿工程》2016,43(5):86-88

混凝土灌注桩桩头渗水对桩体混凝土受力和基底防水产生影响,对混凝土结构中的钢筋造成腐蚀。结合工程实例,对桩头渗水产生的原因进行分析,主要有操作经验不足、责任心不强,灌注器具不合格,混凝土质量指标不符合要求,灌注接近结束时拔管速度过快、灌注终了超灌高度测量不准,基土含水量高、水压大等;出现桩头渗水可采用人工剔除或注浆封堵处理;介绍了预防措施,包括加强作业人员培训,强化灌注器具检查,严控混凝土质量,重点监管终灌时的状态,做好基坑内降水工作等。  相似文献   

Ontogenic variation and effect of collection procedure on leaf biomechanical properties of Mediterranean seagrass Posidonia oceanica (L.) Delile          下载免费PDF全文

Carmen B. de los Santos  Bárbara Vicencio‐Rammsy  Gilles Lepoint  François Remy  Tjeerd J. Bouma  Sylvie Gobert 《Marine Ecology》2016,37(4):750-759

Leaf mechanical traits are important to understand how aquatic plants fracture and deform when subjected to abiotic (currents or waves) or biotic (herbivory attack) mechanical forces. The likely occurrence of variation during leaf ontogeny in these traits may thus have implications for hydrodynamic performance and vulnerability to herbivory damage, and may be associated with changes in morphologic and chemical traits. Seagrasses, marine flowering plants, consist of shoot bundles holding several leaves with different developmental stages, in which outer older leaves protect inner younger leaves. In this study we examined the long‐lived seagrass Posidonia oceanica to determine ontogenic variation in mechanical traits across leaf position within a shoot, representing different developmental stages. Moreover, we investigated whether or not the collection procedure (classical uprooted shoot versus non‐destructive shoot method: cutting the shoot without a portion of rhizome) and time span after collection influence mechanical measurements. Neither collection procedure nor time elapsed within 48 h of collection affected measurements of leaf biomechanical traits when seagrass shoots were kept moist in dark cool conditions. Ontogenic variation in mechanical traits in P. oceanica leaves over intermediate and adult developmental stages was observed: leaves weakened and lost stiffness with aging, while mid‐aged leaves (the longest and thickest ones) were able to withstand higher breaking forces. In addition, younger leaves had higher nitrogen content and lower fiber content than older leaves. The observed patterns may explain fine‐scale within‐shoot ecological processes of leaves at different developmental stages, such as leaf shedding and herbivory consumption in P. oceanica.  相似文献   

基于SPOT6遥感影像的滩涂湿地入侵种互花米草植株高度的反演研究   总被引：1，自引：0，他引：1  

周在明  杨燕明  陈本清 《海洋学报》2016,38(6):1-7

本文以SPOT6 高空间分辨率遥感影像为数据源,通过植被覆盖度和地上生物量两个参数进行滩涂湿地入侵种互花米草植株高度的估算研究。结果表明,三沙湾滩涂湿地互花米草植株高度平均值为2.04 m,以1~2 m和2~3 m植株为主要分布高度,分布面积分别为6.83 km2和10.31 km2,占研究区互花米草总面积的33.83%和51.06%,小于1 m和大于3 m的互花米草仅占9.26%和5.84%。估算值与真实值之间的均方根误差为0.204,绝对误差为0.04~0.37 m。该方法是对高空间分辨率光学影像应用研究的重要尝试,其反演方法具有较好的可行性,可较为准确的获取滩涂湿地植株高度信息。  相似文献   

台山核电邻近海域春秋季浮游植物群落结构特征     

粟丽  黄梓荣  徐珊楠  陈作志 《海洋科学》2016,40(9):61-68

根据2013年4月(春季)和9月(秋季)2个航次调查数据,对台山核电邻近海域浮游植物种类组成、时空分布及多样性指数等群落特征进行了分析。共鉴定浮游植物3门61种,其中硅藻类48种,占78.69%;甲藻类11种,占18.03%;金藻类2种,占3.28%。种类组成以暖水种和广温种为主。浮游植物丰度均值春季(11.78×107个/m3)与秋季(29.37×107个/m3)无明显差异;然而丰度水平变化较大,整体表现为春秋两季核电站温排水口附近站位均低于远离站位。春秋两季浮游植物优势种共出现了7种,春季仅出现了中肋骨条藻Skeletonema costatum1种,优势度高达0.996;秋季出现了7种,包括中肋骨条藻(0.291)、柔弱拟菱形藻Pseudo-nitzschia delicatissima(0.222)、拟弯角毛藻Chaetoceros pseudocurvisetus(0.214)和并基角毛藻Chaetoceros decipiens(0.056)等。海域春季Shannon-Wiener多样性指数H′、Pielou均匀度指数J′和Margalef物种丰富度指数D均值分别为0.55、0.18和0.50;秋季分别为2.80、0.62和0.80。多样性指数显示台山核电附近海域水质状态受到了一定程度的污染。  相似文献   

全珊瑚骨料海水混凝土力学性能试验研究   总被引：3，自引：1，他引：2  

糜人杰  余红发  麻海燕  达波  袁银峰  张小平  朱海威  窦雪梅 《海洋工程》2016,34(4):47-54

为了探讨全珊瑚骨料海水混凝土的基本力学性能,并比较其与普通混凝土和轻集料混凝土的差异,通过实验系统测定了珊瑚混凝土的基本力学性能,建立了其轴心抗压强度(f_(c,m))、劈裂抗拉强度(f_(sp,m))、抗折强度(f_(t,m))与立方体抗压强度(f_(cu,m))之间的线性关系与计算公式。结果表明:在强度等级C20~C50的范围内,珊瑚混凝土的f_(c,m)和f_(sp,m)分别比普通混凝土的f_(c,m)和f_(sp,m)高出10%~48%和9%~33%,随着强度等级的提高,两种混凝土之间的差距在减小。珊瑚混凝土的f_(t,m)与普通混凝土的ft,m之间的差异规律与强度等级有关,较低强度等级的C30珊瑚混凝土ft,m比普通混凝土的f_(t,m)要高4%,而较高强度等级的C55珊瑚混凝土f_(t,m)比普通混凝土的f_(t,m)低13%。较高强度等级的C50珊瑚混凝土f_(c,m)、f_(sp,m)和f_(t,m)分别比页岩陶粒轻集料混凝土的f_(c,m)、f_(sp,m)和f_(t,m)低11%、0.9%和4%。  相似文献   

Representation and discovery of building patterns: a three-level relational approach     

Shihong Du  Mi Shu  Chen-Chieh Feng 《International journal of geographical information science》2016,30(6):1161-1186

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The Effect of Concrete Deformation on Displacement of an Axially Loaded Drilled Shaft     

Dongwook Kim  Hobi Kim  Kyung Joon Shin 《Marine Georesources & Geotechnology》2016,34(2):116-126

This article presents the settlement of drilled shafts resulting from their structural deformations. Although drilled shafts are widely used as foundations for settlement-sensitive structures such as bridges and high-rise buildings, the structural deformations of drilled shafts are not typically taken into account in the design process. However, if unexpected structural deformations of drilled shafts cause additional settlement to the foundation, the serviceability of the superstructure can be jeopardized. Unfortunately, very few research efforts have been made to quantify the structural deformation of drilled shafts; this needs to be addressed to accurately predict the settlement of drilled shafts. In this study, we investigate the effect of structural deformation on displacement of axially loaded drilled shafts. Finite element analyses were performed to quantify the structural deformation of drilled shafts. The analysis results indicated that the structural deformation of drilled shafts could be quite significant for long drilled shafts. The main factors that affected the structural deformation of drilled shafts were found to be pile length, the material properties of drilled shafts, and the relative humidity of surrounding soil. An approximate equation is proposed to estimate the long-term deformation of drilled shafts.  相似文献   

Evaluation of effectiveness of three fuzzy systems and three texture extraction methods for building damage detection from post-event LiDAR data     

Milad Janalipour 《International Journal of Digital Earth》2018,11(12):1241-1268

Building damage maps after disasters can help us to better manage the rescue operations. Researchers have used Light Detection and Ranging (LiDAR) data for extracting the building damage maps. For producing building damage maps from LiDAR data in a rapid manner, it is necessary to understand the effectiveness of features and classifiers. However, there is no comprehensive study on the performance of features and classifiers in identifying damaged areas. In this study, the effectiveness of three texture extraction methods and three fuzzy systems for producing the building damage maps was investigated. In the proposed method, at first, a pre-processing stage was utilized to apply essential processes on post-event LiDAR data. Second, textural features were extracted from the pre-processed LiDAR data. Third, fuzzy inference systems were generated to make a relation between the extracted textural features of buildings and their damage extents. The proposed method was tested across three areas over the 2010 Haiti earthquake. Three building damage maps with overall accuracies of 75.0%, 78.1% and 61.4% were achieved. Based on outcomes, the fuzzy inference systems were stronger than random forest, bagging, boosting and support vector machine classifiers for detecting damaged buildings.  相似文献   

基于逻辑回归的四川青川县区域滑坡灾害预警模型          下载免费PDF全文

方然可  刘艳辉  苏永超  黄志全 《水文地质工程地质》2021,48(1):181-187

四川省青川县滑坡灾害群发,点多面广,区域滑坡灾害预警是有效防灾减灾的重要手段,预警模型是成功预警的核心。由于研究区滑坡诱发机理复杂、调查监测大数据及分析方法不足等原因,传统区域地质灾害预警模型存在预警精度有限、精细化不足等问题。文章在青川县地质灾害调查监测和降水监测成果集成整理与数据清洗基础上,构建了青川县区域滑坡灾害训练样本集,样本集包括地质环境、降雨等27个输入特征属性和1个输出特征属性,涵盖了青川县近9年（2010—2018年）全部样本,数量达1 826个（其中,正样本613个,负样本1 213个）。基于逻辑回归算法,对样本集进行5折交叉验证学习训练,采用贝叶斯优化算法进行模型优化,采用精确度、ROC曲线和AUC值等指标校验模型准确度和模型泛化能力。其中,ROC曲线也称为“受试者工作特征”曲线;AUC值表示ROC曲线下的面积。校验结果显示,基于逻辑回归算法的模型训练结果准确率和泛化能力均较好（准确率94.3%,AUC为0.980）。开展区域滑坡实际预警时,按训练样本特征属性格式,输入研究区各预警单元27个特征属性,调用预先学习训练好的模型,输出滑坡灾害发生概率,根据输出概率分段确定滑坡灾害预警等级。当输出概率P≥40%且P<60%时,发布黄色预警;当输出概率P≥60%且P<80%时,发布橙色预警;当输出概率P≥80%时,发布红色预警。  相似文献