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11.
Jean-Paul Kibambe Lubamba Julien Radoux Pierre Defourny 《International journal of geographical information science》2013,27(5):1005-1022
Accessibility is a key driving factor for economic development, social welfare, resources management, and land use planning. In many studies, modeling accessibility relies on proxy variables such as estimated travel time to selected destinations. In developing countries, estimating the travel time is hindered by scarce information about the transportation network, making it necessary to take into account off-network travel coupled with considerations of multimodal options available within the existing network. This research proposes such a hybrid approach that computes the travel time to selected destinations by optimizing together a fully modeled multimodal network and off-network travel. The model was applied in a region around Kisangani located in northeastern Democratic Republic of the Congo. Travel times to Kisangani from the hybrid approach were found to be in close agreement with field-based information (R 2 = 0.98). The developed approach also proved to better support real-world transportation constraints (such as transfer points between travel modes or barriers) than cost-distance-based travel-time modeling. Demonstration results from the hybrid approach highlight the potential for impact assessment of road construction or rehabilitation, development of secondary towns or markets, and for land use planning in general. 相似文献
12.
Tomas Crols Roger White Inge Uljee Guy Engelen Lien Poelmans Frank Canters 《International journal of geographical information science》2013,27(10):1757-1781
Urban growth and population growth are used in numerous models to determine their potential impacts on both the natural and the socio-economic systems. Cellular automata (CA) land-use models became popular for urban growth modelling since they predict spatial interactions between different land uses in an explicit and straightforward manner. A common deficiency of land-use models is that they only deal with abstract categories, while in reality, several activities are often hosted at one location (e.g. population, employment, agricultural yield, nature…). Recently, a multiple activity-based variable grid CA model was proposed to represent several urban activities (population and economic activities) within single model cells. The distance-decay influence rules of the model included both short- and long-distance interactions, but all distances between cells were simply Euclidean distances. The geometry of the real transportation system, as well as its interrelations with the evolving activities, were therefore not taken into account. To improve this particular model, we make the influence rules functions of time travelled on the transportation system. Specifically, the new algorithm computes and stores all travel times needed for the variable grid CA. This approach provides fast run times, and it has a higher resolution and more easily modified parameters than the alternative approach of coupling the activity-based CA model to an external transportation model. This paper presents results from one Euclidean scenario and four different transport network scenarios to show the effects on land-use and activity change in an application to Belgium. The approach can add value to urban scenario analysis and the development of transport- and activity-related spatial indicators, and constitutes a general improvement of the activity-based CA model. 相似文献
13.
海洋和大气数据多模式动态可视化系统的设计和实现 总被引：1，自引：0，他引：1
为了实现海洋和大气数据多模式动态可视化,本系统使用VC++和CG着色语言进行开发,渲染引擎基于OpenGL三维图形标准。提出了一系列面向海洋和大气数据的模式分析方法,包括:探针功能、线模式、面模式、体模式、矢量模式和动态时间序列分析等,实现了将海量多维海洋大气数据转换为三维空间或动态演变的图像,同时完成用户交互处理操作。并将可视化技术应用于长时间序列的海洋大气数据,通过实时动态的可视化图像来体现海洋大气数据的动态变化过程。结果表明,该系统可实现常见海洋和大气数据的多模式动态可视化。 相似文献
14.
中国北方部分地区黄土、沙漠沙、湖泊、河流细粒沉积物粒度多组分分布特征研究 总被引：12，自引：0，他引：12
通过对我国北方部分地区的黄土、沙漠沙、湖泊、河流细粒沉积物的粒度多组分分布特征系统研究后总结了其粒度分布特征及组分间差异,并提出了风成、水成沉积物成因类型的判别依据。认为:1)细粒沉积物粒度一般由多个组分叠加构成,表现为多组分粒度分布特征。2)黄土粉尘粒径以<70 μm的悬浮颗粒为主,粒度由粗、中、细三个组分构成。粗粒组分含量最高,其中值粒径与源区距离呈负相关,中粒组分百分含量与源区距离呈正相关。3)沙漠沙粒度由一个极其明显的粗粒跳跃组分构成,中值粒径一般位于100~300 μm,分选性极好。4)湖泊沉积物粒度分布最多可有6个组分(中值粒径:<1 μm,2~10 μm,10~70 μm,70~150 μm,150~700 μm,>700 μm),前4个组分属悬浮组分,⑤为跳跃组分,⑥为滚动组分,分选性差。5)河流沉积物粒度分布曲线较复杂,其分布特征蕴含了水动力强弱信息。6)沙漠沙→黄土与河流沙→湖泊沉积物其优势组分的粒径均逐渐变细,但水成相对应组分比风成组分粒径要粗. 相似文献
15.
This work introduces a geometric formalism, based on the use of phasors in the Argand-Gauss plane for the design and sizing of inertial dampers to be applied to multimodal structural oscillators. Their damping effect depends on the fact that the response of the secondary oscillator (the damper) delays the response of the primary mass to be controlled by 90°, so that the elastic force transmitted by the damper becomes a viscous force on the controlled oscillator. When such condition occurs we say that the damper is ‘tuned’ to the main oscillator; the damping induced by the damper is modest and serves only to limit the displacement of main oscillator.Our geometrical approach provides a method whose language is close to that of structural mechanics, thus paving the way to the professional for: (i) sizing the damper parameters; and (ii) evaluating the stability to the damped system and its performance limits. The aim of the development is explore the use of dampers to control the initial response modes of buildings under horizontal seismic and aerodynamic loads. Having introduced the concept of a monomass oscillator equivalent to a given mode of vibration, we develop a multimodal multidamper model which we then use to perform numerical evaluations. Several control strategies (involving changes in number and position of the dampers) are considered in relation to variation in bandwidth and intensity of the external forcing action. We discuss the advantages and limitations of this passive approach to structural control. 相似文献
16.
大气污染物浓度全方位动态监测是进行区域大气污染精细化防控的重要前提。为开展长三角地区小时分辨率PM2.5浓度无缝制图,本研究通过耦合AOD缺失信息重建与多模数据融合技术,建立了一套能够有效集成卫星遥感、地面观测、数值模拟等多源异构数据资料的近地面PM2.5浓度无缝制图方案,并据此生产了2015年—2020年长三角地区小时分辨率无缝PM2.5浓度格点数据产品。结果表明：本研究生产的PM2.5浓度无缝格点产品与国控站点观测数据的交叉验证相关系数达0.9,平均偏差不超过10 μg·m-3。较于空间分布不均且相对稀疏的站点观测PM2.5浓度资料,面域无缝PM2.5浓度格点数据更能有效揭示长三角地区PM2.5污染的时空变化特征;在2015年—2020年研究期内,其平均下降速率超过3 μg·m-3·a-1。本研究发展的PM2.5浓度无缝制图方法和生产的相关数据产品有望为区域灰霾污染防控和PM2.5暴露健康风险评估研究提供方法参考和基础数据支撑。 相似文献
17.
The problem of finding the least-cost path from a source point to a destination point can be dealt with by routing across a continuous surface or routing along a discrete network. The solutions within these two contexts are linked to the use of a raster- or a vector-based least-cost path algorithm. This study presents a technique which integrates raster- and vector-based least-cost path algorithms for determining the least-cost path across a continuous raster surface with discrete vector networks. The technique incorporates ancillary vector data sets that are required to examine the travel cost at each link, connections between nodes, and the representation of intersecting links in the discrete vector network into raster-based least-cost path analysis. The integrated technique presented here is applicable to all-terrain vehicle navigation where a continuous raster surface and discrete vector networks need to be considered simultaneously in order to find least-cost paths. This paper describes the concept behind, and details of, the integrated technique. Applications of the technique with synthetic and real-world data sets are also presented. They provide proof that the technique is effective in finding least-cost paths across a continuous raster surface with discrete vector networks. 相似文献
18.
源区距离对黄土粒度多组分分布特征的影响 总被引：4，自引：2，他引：2
利用高分辨率激光粒度仪MS2000对陕西渭南、北京灵山、河南邙山等地大量黄土样品的粒度多组分分布特征进行了系统研究,总结了其多组分粒度分布及组分间差异特征并讨论了源区距离对黄土粒度多组分分布特征的影响。取得了以下认识：（1）黄土粉尘粒径以〈70μm的悬浮组分为主,其粒度由细、中、粗3个组分（中值粒径范围分别为〈1μm、1～10μm、10～70μm）构成,表现为多组分粒度特征。粗粒组分含量最高,峰形最明显。粗粒与中粒组分粒径与百分含量变化很大程度受控于源区距离变化。（2）不同地区黄土粉尘粒度差异明显,粗粒组分中值粒径随源区距离增加而减小,二者负相关;中粒组分百分含量随源区距离增加而增加,二者正相关。（3）粒度组分分离方法能够反映同一源区粒度的细微差异,显示其粒度组分分离的优越性。（4）理论推导了黄土粗粒组分的中值粒径与源区距离的关系并用实际拟合函数验证了其正确性。 相似文献
19.
利用高分辨率激光粒度仪MS2000对安固里淖、三台河以及长江等多个地点湖泊和河流沉积物样品细粒部分的粒度多组分分布特征进行了系统、深入研究。总结了其粒度分布特征及组分间差异并讨论了其成因机制。研究认为:1)湖泊沉积物粒度一般由多个组分叠加构成,表现为多组分粒度分布特征,其受控于水动力强度和搬运方式等因素。2)粒度分布最多可有6个组分（中值粒径范围分别为①<1μm,②2～10μm,③10～70μm,④70～>150μm,⑤150～700μm,⑥>700μm）,其中前4个组分属悬浮组分（③组分是流域内风成作用强弱的判别标志）,⑤为跳跃组分,⑥为滚动组分,整体分选性差。3)据粒度分布特征可分为湖滨、过渡和湖心三相,三相间粒度分布特征有明显差异,同时又存在此消彼长的良好过渡关系。湖滨相以④组分为优势组分,该组分含量越高,指示沉积物越靠近湖滨;过渡相④组分含量随距湖心距离靠近而减小,但②组分含量却在逐渐增加;湖心相以②组分占主导优势,该组分含量越高,指示沉积物越靠近湖心。4)湖相沉积物受湖滨拍岸浪和湖心波浪的影响而产生了明显的粒度分异规律。 相似文献
20.
对于弯梁桥支座病害中普遍存在的刚度不足,甚至脱空现象,提出利用平面多阶模态及高斯曲率模态相关系数来识别弯梁桥支座的损伤情况。在理论推导的基础上,以某小半径弯梁桥为研究对象,建立了相关分析模型。分析结果表明:无论单支座损伤,还是多支座损伤,相应支座处的高斯曲率模态相关系数与其它支座位置处的差异明显,可实现支座损伤的准确定位;且支座损伤越严重,相关系数下降越多;支点预偏心和抗扭支承等因素对损伤定位没有影响,相邻控制点处相关系数有所降低,但不会影响支座损伤识别的有效性。 相似文献