Roles of horizontal and vertical tree canopy structure in mitigating daytime and nighttime urban heat island effects

The urban heat island (UHI) is increasingly recognized as a serious, worldwide problem because of urbanization and climate change. Urban vegetation is capable of alleviating UHI and improving urban environment by shading together with evapotranspiration. While the impacts of abundance and spatial configuration of vegetation on land surface temperature (LST) have been widely examined, very little attention has been paid to the role of vertical structure of vegetation in regulating LST. In this study, we investigated the relationships between horizontal/vertical structure characteristics of urban tree canopy and LST as well as diurnal divergence in Nanjing City, China, with the help of high resolution vegetation map, Light Detection and Ranging (LiDAR) data and various statistical analysis methods. The results indicated that composition, configuration and vertical structure of tree canopy were all significantly related to both daytime LST and nighttime LST. Tree canopy showed stronger influence on LST during the day than at night. Note that the contribution of composition of tree canopy to explaining spatial heterogeneity of LST, regardless of day and night, was the highest, followed by vertical structure and configuration. Combining composition, configuration and vertical structure of tree canopy can take advantage of their respective advantages, and best explain variation in both daytime LST and nighttime LST. As for the independent importance of factors affecting spatial variation of LST, percent cover of tree canopy (PLAND), mean tree canopy height (TH_Mean), amplitude of tree canopy height (TA) and patch cohesion index (COHESION) were the most influential during the day, while the most important variables were PLAND, maximum height of tree canopy (TH_Max), variance of tree canopy height (TH_SD) and COHESION at night. This research extends our understanding of the impacts of urban trees on the UHI effect from the horizontal to three-dimensional space. In addition, it may offer sustainable and effective strategies for urban designers and planners to cope with increasing temperature.     

反应谱的数值计算及其应用中的误差问题

本文将湖北省丹江坝强震记录作反应谱计算,通过计算和对比,说明目前常用的几种反应谱数值计算法的一般误差状况。得出的结果表明:自振周期低于10倍采样间隔时,数值法将产生较大的(甚至可达一倍以上)误差。这也表明这种数值计算法仅适用于柔性的高层建筑或低振型建筑的抗震计算上。     

半重叠总方差法在惯性传感器随机误差分析中的应用

针对总方差法在分析随机误差时计算时间较长的问题,从Allan方差和完全重叠Allan方差入手,提出3种数据采样方式,并在此基础上构造了半重叠总方差法。通过光纤陀螺惯组的静态实验验证算法的有效性,结果表明,半重叠总方差法与总方差法分析精度一致,而运算时间大为缩短。     

钻孔体应变仪高采样对比观测实验研究

为分析提高应变观测采样率及拓展观测频带对低频观测的影响,在张家口地震台、怀来地震台选择TJ-2型体应变仪进行台站对比观测实验,并在时域和频域分别对实验数据进行分析,总结体应变与测震观测频带的特性.     

浅谈我国某金红石矿采样设计

选矿试验采样设计是一项复杂而又重要的工作,确保试样的代表性是采样设计工作的关键。本文以我国某金红石矿为例,根据矿床地质特征和矿石的性质,综合考虑影响矿石代表性的各种因素,对其进行了采样设计,以确保能够采出满足试验要求、且具有带表性的试验样品。对类似项目具有一定的指导和借鉴意义。     

超像素与主动学习相结合的遥感影像变化检测方法

针对高分辨率遥感影像变化检测结果较破碎,易产生椒盐噪声、监督训练过程中人工标注成本较高、训练样本冗余以及大量未标注样本信息未有效利用等问题,提出一种超像素与主动学习相结合的高分辨率遥感影像变化检测方法。利用超像素分割算法得到超像素对象,提取其光谱和纹理特征;引入并借助主动学习样本选择策略充分利用未标注样本信息,挖掘不确定性最大、最易错分的样本交由用户人工标注;为保证所选样本的多样性,加入基于余弦角距离的样本相似性度量,以减少样本间信息冗余,在减轻人工标注负担的同时获得良好的分类性能。通过对2组不同场景的遥感影像的实验,表明本文提出的2种方法能够在标注少量训练样本的情况下获得较好的变化检测结果,且加入样本相似性度量的变化检测方法在有效减少人工标注成本和训练样本冗余的同时,能够更快地达到收敛、提升检测质量。     

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地质数据的抽样检查方法研究

地质数据内容复杂,数据量大,抽样是检查地质数据质量不可缺少的方法。但到目前为止,地质数据的抽样检查基本上采用百分比抽样方案及简单随机和分层抽样方法。本文是在制定地质数据质量检查评价规范过程中进行有关研究的基础上写成的。首先阐述国内外用于数据,特别是空间数据抽样检查的标准及相关研究的现状,并结合地质数据的特点,分析适用于地质数据质量检查的抽样技术,探讨解决不同类型地质数据的抽样方案和抽样方法。     

取样电阻对功耗分析攻击的影响

针对目前针功耗分析攻击的影响因素研究偏少的情况,讨论和分析了取样电阻对功耗分析攻击的影响.功耗分析攻击的研究对象是功耗曲线,现有常见实验平台采集的通常是包括各种噪声的功耗综合.取样电阻作为功耗分析平台中的一部分,会在电阻噪声和功耗区分度两方面造成影响,进而影响到功耗分析攻击的正确率.因此为了提高攻击正确率,在不影响区分度的前提下可选用相对小的电阻.     

地质岩心钻探技术及其在资源勘探中的应用

简要回顾了地质岩心钻探技术的发展历程,介绍了进入21世纪地质岩心钻探设备与技术的发展现状;举例说明了地质岩心钻探技术在资源勘探开发中的应用,并对地质岩心钻探技术在科学钻探和环境保护中的应用情况进行了概括性描述。