准确评估区域植被覆盖度是生态脆弱区生态保护与修复的关键。文中基于FCD(Forest Canopy Density Mapping Model)模型构建综合植被指数,对1991—2022年的鄂尔多斯市植被覆盖度进行估算,运用Theil-Sen趋势分析和Mann-Kendall显著性检验...准确评估区域植被覆盖度是生态脆弱区生态保护与修复的关键。文中基于FCD(Forest Canopy Density Mapping Model)模型构建综合植被指数,对1991—2022年的鄂尔多斯市植被覆盖度进行估算,运用Theil-Sen趋势分析和Mann-Kendall显著性检验探究其时空变化特征,采用多元回归残差分析量化气候变化和人为活动的相对贡献。结果表明:1)研究区植被覆盖度整体提升,中、高覆盖区及极高覆盖区的面积持续扩大,显著提升区面积占比达62.53%。2)气候变化与人类活动共同驱动植被覆盖度变化,其中人为活动是近32年植被覆盖度变化的主导因素。3)两类驱动因素对植被覆盖度变化驱动呈现明显的时空异质性。4)未来应根据植被覆盖度空间分异和时空演变特征,实施差异化的生态保护与修复策略。文中研究可为区域生态保护与修复措施的优化与评估提供科学依据,也可为类似生态脆弱区的植被监测与保护提供参考。展开更多
This study aims to examine the use of Remote Sensing and Geographical Information System (GIS) technology in land use/land cover mapping to aide sustainable planning and development in the Wafi-Golpu project area. At ...This study aims to examine the use of Remote Sensing and Geographical Information System (GIS) technology in land use/land cover mapping to aide sustainable planning and development in the Wafi-Golpu project area. At the same time, this study examines an existing method of Forest Canopy Density (FCD) model to estimate forest canopy density of the proposed deforestation site, which is known as the Advanced Exploration Feasibility Study Activities (AEFSA) area within the Wafi-Golpu Project site. The FCD model calculates the forest canopy density using the three (3) indices of vegetation, soil and shadow from the Landsat-8 Operational Land Imager (OLI) satellite image of year 2013. In this study an attempt has been made to monitor the forest loss or degradation during deforestation in a natural forest stand of the Wafi-Golpu project area using forest FCD mapping and monitoring model and the findings of the study will assist the project planners and developers with their work on forest rehabilitation and reforestation for the purposes of sustainable forest management. The result of the work shows that a considerable amount of forest loss will be undertaken during the AEFSA deforestation exercise and also the findings show that a reliable land use/land cover map will greatly assist sustainable development in a resource project development period.展开更多
城市快速路的车速空间波动常被认为是事故风险的重要因素,但是车速空间波动很难通过传统的固定检测器来提取。为克服传统方法的不足,本文充分利用Floating Car Data(FCD)提取快速路路段的空间车速方差等道路运行指标,并在获取快速路特...城市快速路的车速空间波动常被认为是事故风险的重要因素,但是车速空间波动很难通过传统的固定检测器来提取。为克服传统方法的不足,本文充分利用Floating Car Data(FCD)提取快速路路段的空间车速方差等道路运行指标,并在获取快速路特征指标的基础上,分别以总事故频率、追尾事故频率和侧碰事故频率为因变量建立了负二项模型。模型结果发现空间车速方差、路段行程车速对三类模型的影响呈现一致关系:空间车速方法与三类事故频率呈正相关,说明利用车速空间波动来诊断城市快速路安全风险是可行和有价值的。此外还发现路段行程车速与三类事故频率呈负相关,路段内包含平曲线对事故总频率和追尾事故都有显著正相关,但对侧碰事故的相关性不显著;立交路段与侧碰事故频率相关性显著。展开更多
Based on the mixed pixel model, the vegetation fraction of Kaixian county, China, was extracted with three free CBERS images. VBSI vegetation index suitable for CBERS images constructed with FCD (forest canopy density...Based on the mixed pixel model, the vegetation fraction of Kaixian county, China, was extracted with three free CBERS images. VBSI vegetation index suitable for CBERS images constructed with FCD (forest canopy density) model principle was put forward by ITTO (International Tropical Timber Organization) was used, considering the underestimation of vegetation fraction using NDVI in low mountain-hill region influenced by soils and shadows. And vegetation fraction was divided into five categories from low to high in order to study the special variation of vegetation cover. The results show that the vegetation cover of the region is overall good, with an average of 50%. The area of vegetation fraction below 30% accounts for 11.7% of the entire studied area, mainly concentrates in central eastern Kaixian county, where is the major development zone of cities and towns; that between 30% and 60% accounts for 62%; and that higher than 60% accounts for 26%, and mostly locates in northern middle-mountain area.展开更多
主干道是城市路网的骨架,其复杂的道路交通环境造成事故频发。通过安全建模分析,识别事故的主要影响因素,有利于提出改善措施。基于上海市18条主干道176个路段,选取道路几何特征、用地性质、路段流量和路段平均车速作为影响因素。利用...主干道是城市路网的骨架,其复杂的道路交通环境造成事故频发。通过安全建模分析,识别事故的主要影响因素,有利于提出改善措施。基于上海市18条主干道176个路段,选取道路几何特征、用地性质、路段流量和路段平均车速作为影响因素。利用浮动车数据(floating car data,FCD)计算路段平均车速,克服了定点测速装置断面选取的问题。考虑到同一主干道路段之间的空间相关性,建立分层泊松对数正态模型。采用全贝叶斯方法进行参数估计,并比较不同信息先验对结果的影响。事故特征在高峰时段和平峰时段存在差异,因而分时段研究。结果表明:样本数据呈现分层结构,与极大似然先验(maximum likelihood estimation,MLE)模型相比,分层模型的方差信息标准(deviance information criterion,DIC)值更小。极大似然先验可以提高参数估计可靠性。与无信息先验模型相比,极大似然先验模型估计参数的标准差更小。在主干道层面,路段平均长度越长,事故频率上升。在路段层面,道路几何特征和用地性质对道路安全存在显著影响。事故频率随路段流量增加而上升,尤其在高峰时段,单位流量引起的事故增量更加显著。路段平均车速在高峰时段与事故频率具有正相关关系。展开更多
文摘准确评估区域植被覆盖度是生态脆弱区生态保护与修复的关键。文中基于FCD(Forest Canopy Density Mapping Model)模型构建综合植被指数,对1991—2022年的鄂尔多斯市植被覆盖度进行估算,运用Theil-Sen趋势分析和Mann-Kendall显著性检验探究其时空变化特征,采用多元回归残差分析量化气候变化和人为活动的相对贡献。结果表明:1)研究区植被覆盖度整体提升,中、高覆盖区及极高覆盖区的面积持续扩大,显著提升区面积占比达62.53%。2)气候变化与人类活动共同驱动植被覆盖度变化,其中人为活动是近32年植被覆盖度变化的主导因素。3)两类驱动因素对植被覆盖度变化驱动呈现明显的时空异质性。4)未来应根据植被覆盖度空间分异和时空演变特征,实施差异化的生态保护与修复策略。文中研究可为区域生态保护与修复措施的优化与评估提供科学依据,也可为类似生态脆弱区的植被监测与保护提供参考。
文摘This study aims to examine the use of Remote Sensing and Geographical Information System (GIS) technology in land use/land cover mapping to aide sustainable planning and development in the Wafi-Golpu project area. At the same time, this study examines an existing method of Forest Canopy Density (FCD) model to estimate forest canopy density of the proposed deforestation site, which is known as the Advanced Exploration Feasibility Study Activities (AEFSA) area within the Wafi-Golpu Project site. The FCD model calculates the forest canopy density using the three (3) indices of vegetation, soil and shadow from the Landsat-8 Operational Land Imager (OLI) satellite image of year 2013. In this study an attempt has been made to monitor the forest loss or degradation during deforestation in a natural forest stand of the Wafi-Golpu project area using forest FCD mapping and monitoring model and the findings of the study will assist the project planners and developers with their work on forest rehabilitation and reforestation for the purposes of sustainable forest management. The result of the work shows that a considerable amount of forest loss will be undertaken during the AEFSA deforestation exercise and also the findings show that a reliable land use/land cover map will greatly assist sustainable development in a resource project development period.
文摘城市快速路的车速空间波动常被认为是事故风险的重要因素,但是车速空间波动很难通过传统的固定检测器来提取。为克服传统方法的不足,本文充分利用Floating Car Data(FCD)提取快速路路段的空间车速方差等道路运行指标,并在获取快速路特征指标的基础上,分别以总事故频率、追尾事故频率和侧碰事故频率为因变量建立了负二项模型。模型结果发现空间车速方差、路段行程车速对三类模型的影响呈现一致关系:空间车速方法与三类事故频率呈正相关,说明利用车速空间波动来诊断城市快速路安全风险是可行和有价值的。此外还发现路段行程车速与三类事故频率呈负相关,路段内包含平曲线对事故总频率和追尾事故都有显著正相关,但对侧碰事故的相关性不显著;立交路段与侧碰事故频率相关性显著。
基金Project(11YJC790139)supported by Humanities and Social Sciences Program of MOE(Ministry of Education in China)Project(2011GGJS-053)supported by the Foundation for University Young Key Teacher by Henan Province of ChinaProject(B2011-045)supported by the Foundation of Henan Polytechnic University for the Doctor,China
文摘Based on the mixed pixel model, the vegetation fraction of Kaixian county, China, was extracted with three free CBERS images. VBSI vegetation index suitable for CBERS images constructed with FCD (forest canopy density) model principle was put forward by ITTO (International Tropical Timber Organization) was used, considering the underestimation of vegetation fraction using NDVI in low mountain-hill region influenced by soils and shadows. And vegetation fraction was divided into five categories from low to high in order to study the special variation of vegetation cover. The results show that the vegetation cover of the region is overall good, with an average of 50%. The area of vegetation fraction below 30% accounts for 11.7% of the entire studied area, mainly concentrates in central eastern Kaixian county, where is the major development zone of cities and towns; that between 30% and 60% accounts for 62%; and that higher than 60% accounts for 26%, and mostly locates in northern middle-mountain area.
文摘主干道是城市路网的骨架,其复杂的道路交通环境造成事故频发。通过安全建模分析,识别事故的主要影响因素,有利于提出改善措施。基于上海市18条主干道176个路段,选取道路几何特征、用地性质、路段流量和路段平均车速作为影响因素。利用浮动车数据(floating car data,FCD)计算路段平均车速,克服了定点测速装置断面选取的问题。考虑到同一主干道路段之间的空间相关性,建立分层泊松对数正态模型。采用全贝叶斯方法进行参数估计,并比较不同信息先验对结果的影响。事故特征在高峰时段和平峰时段存在差异,因而分时段研究。结果表明:样本数据呈现分层结构,与极大似然先验(maximum likelihood estimation,MLE)模型相比,分层模型的方差信息标准(deviance information criterion,DIC)值更小。极大似然先验可以提高参数估计可靠性。与无信息先验模型相比,极大似然先验模型估计参数的标准差更小。在主干道层面,路段平均长度越长,事故频率上升。在路段层面,道路几何特征和用地性质对道路安全存在显著影响。事故频率随路段流量增加而上升,尤其在高峰时段,单位流量引起的事故增量更加显著。路段平均车速在高峰时段与事故频率具有正相关关系。
