城市公共自行车使用与建成环境的关系研究——以南京市桥北片区为例   总被引：4，自引：2，他引：2  

罗桑扎西  甄峰  尹秋怡 《地理科学》2018,38(3):332-341

公共自行车作为一种绿色低碳的交通出行方式,在国内外许多城市得到了快速发展。目前国内公共自行车相关研究多以使用特征分析为主,而与建成环境关系的研究较少。采用运营大数据与网络开放大数据相结合的方法,以南京市桥北区为案例,研究公共自行车站点使用特征及建成环境对其的影响。研究结果表明：① 公共自行车的使用存在明显的时空间差异;② 使用主要受站点300 m范围内日常服务设施网点密度、基础设施及公共交通条件等建成环境因子影响;③ 建成环境对不同时段使用的影响存在较大差异。研究结果可为片区站点的优化布局与管理建设,以及无桩型共享单车的投放与运营管理提供科学的参考依据。  相似文献   

人口密度对居民通勤时耗的影响及条件效应——来自上海证据   总被引：3，自引：1，他引：2  

孙斌栋  尹春 《地理科学》2018,38(1):41-48

基于上海市1 605个居民抽样样本,利用多层次线性回归模型,探讨了街道尺度人口密度对个体居民通勤时耗的影响及条件效应。在控制了个体社会经济属性、通勤方式和其他建成环境要素后发现,高人口密度总体上会增加居民通勤时耗,而且其作用是有条件的,主要受“设计”“地铁站可达性”“到就业中心距离”和“通勤方式”的调节。具体而言,提高街道路网密度和高速路密度,缩短居住地到就业中心距离,提高地铁站密度,鼓励居民采用地铁方式通勤,减少小汽车使用,都可以显著降低人口密度对通勤时耗的增加作用。因而,通过优化城市建成环境和调节人口密度来降低过长的通勤时耗是可行的。  相似文献   

00~h00~m 00°00′天区的类星体物端棱镜光谱巡天(Ⅴ)巡天结果的讨论(英文)     

詹寅  陈建生 《中国天文和天体物理学报》1989,(4)

本文总结巡天的结果并对结果进行讨论,同时发表69个Q=3的紫外超天体的坐标,B_J~*及证认图。  相似文献   

周期和振幅相结合检测地震方法研究     

张念  印苏文  张志俊 《大地测量与地球动力学》2007,27(Z1):133-135

分析了单纯用地震波振幅作为报警阈值的缺点,通过数字地震仪与模拟地震仪报警机制的对比,提出用检测周期和振幅相结合的方法来实现地震报警.  相似文献   

Non‐uniqueness of critical state line in compression and extension conditions     

Zhen‐Yu Yin  Ching S. Chang 《国际地质力学数值与分析法杂志》2009,33(10):1315-1338

Experimental evidence has indicated that the critical state line determined from undrained compression tests is not identical to that determined from undrained extension tests. The purpose of this paper is to investigate a modelling method that accounts for the non‐uniqueness of critical state lines in the compression and the extension testing conditions. Conventional elastic–plastic cap models can predict only a unique critical state line for the compression and the extension tests. A new micromechanical stress–strain model is developed considering explicitly the location of critical state line. The model is then used to simulate undrained triaxial compression and extension tests performed on isotropically consolidated samples with different over‐consolidated ratios. The predictions are compared with experimental results as well as that predicted by models with kinematic hardening of yield surface. All simulations demonstrate that the proposed micromechanical approach is capable of modelling the undrained compression and the undrained extension tests. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Monsoon rivers of Asia   总被引：2，自引：0，他引：2  

Zhongyuan Chen  Avijit Gupta  Hongfu Yin 《Geomorphology》2007,85(3-4):129

  相似文献   

A finite element analysis of tidal deformation of the entire earth with a discontinuous outer layer     

H. L. Xing  J. Zhang  C. Yin 《Geophysical Journal International》2007,170(3):961-970

Tidal deformation of the Earth is normally calculated using the analytical solution with some simplified assumptions, such as the Earth is a perfect sphere of continuous media. This paper proposes an alternative way, in which the Earth crust is discontinuous along its boundaries, to calculate the tidal deformation using a finite element method. An in-house finite element code is firstly introduced in brief and then extended here to calculate the tidal deformation. The tidal deformation of the Earth due to the Moon was calculated for an geophysical earth model with the discontinuous outer layer and compared with the continuous case. The preliminary results indicate that the discontinuity could have different effects on the tidal deformation in the local zone around the fault, but almost no effects on both the locations far from the fault and the global deformation amplitude of the Earth. The localized deformation amplitude seems to depend much on the relative orientation between the fault strike direction and the loading direction (i.e. the location of the Moon) and the physical property of the fault.  相似文献   

应力作用下煤层气非稳定耦合渗流模型及数值模拟     

狄军贞殷志祥  刘建军 《中国煤田地质》2007,19(4):36-38

基于多孔介质渗流力学和流固耦合理论,建立了应力作用下煤储层中煤层气流固耦合数学模型,并根据数学模型的非线性特性,采用多重物理量耦合软件COMSOL Multiphysic进行数值模拟分析,通过模拟结果研究了煤岩体中压力和浓度的分布特性,并且研究了耦合与非耦合情况下压力动态曲线,为模拟煤层气产量预测和预防矿井瓦斯突出提供了理论依据。  相似文献   

A comparative study of nutrient transfer via surface runoff from two small agricultural catchments in north China   总被引：1，自引：0，他引：1  

Haiming Lu  Chengqing Yin  Weidong Wang  Baoqing Shan 《Environmental Geology》2007,52(8):1549-1558

A field study was conducted to determine the effect of landscape spatial pattern and micro-topography on nutrient transfer via runoff from two catchments into Yuqiao Reservoir in north China. The surface runoff discharge was measured during rainfall events and water samples were analyzed in 2004 and 2005. The mean annual total nitrogen (TN) and total phosphorus (TP) exports per unit area from Caogezhuang catchment (C catchment) were 1.048 and 0.561 kg ha⁻¹ year⁻¹, respectively, while the TN and TP exports from Taohuasi catchment (T catchment) were 0.158 and 0.027 kg ha⁻¹ year⁻¹. In both catchments, village and vineyard shared the highest nutrient export ability due to the accumulated animal waste and heavy application of fertilizer and manure. In T catchment, the distance of village and vineyard was about 1,500 m away from the receiving water and in between were woodland and cropland. In the hydrological pathway, there were sink landscape structures of small stone dams, roadside swale, vegetated filter strip and dry ponds, which could detain water and nutrients. In C catchment, the distance between the village and the receiving water was about 200 m, and the hydrological pathway was compacted roads and ditches with no sink structures. It is suggested that the distance between the pollution source area and the receiving water and the micro-topographical features were the main factors to control the great difference in nutrient export rates.  相似文献   

Timing and duration of supergene mineralization at the Xinrong manganese deposit,western Guangdong Province,South China: cryptomelane <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar dating     

Jian-Wei Li  Paulo Vasconcelos  Wei Zhang  Xiao-Dong Deng  Nurdan Duzgoren-Aydin  Dai-Rong Yan  Jian-Qiang Zhang  Ming-An Hu 《Mineralium Deposita》2007,42(4):361-383

Supergene Mn-oxide deposits are widely distributed in Guangxi, Guangdong, Yunnan, and Hunan Provinces, South China, accounting for 18% of the total Mn reserves in the country. Direct dating of supergene Mn enrichment, however, is lacking. In this paper, we present high-resolution ⁴⁰Ar/³⁹Ar ages of Mn oxides from the Xinrong Mn deposit, western Guangdong, to place numerical constraints on the timing and duration of supergene Mn enrichment. A total of ten cryptomelane samples, spanning a vertical extent of 67 m, were dated using the ⁴⁰Ar/³⁹Ar laser incremental heating technique, with seven samples yielding well-defined plateau or pseudo-plateau ages ranging from 23.48 ± 0.91 to 2.06 ± 0.05 Ma (2σ). One sample yields a staircase spectrum that does not reach a plateau; the spectrum, however, indicates the presence of two or more generations of Mn oxides in the sample, whose ages are best estimated at 22.34 ± 0.31 and 10.2 ± 0.86 Ma, respectively. The remaining two samples gave meaningless or uninterpretable results due to significant ³⁹Ar recoil and contamination by old phases. The ⁴⁰Ar/³⁹Ar data thus reveal a protracted history of weathering and supergene Mn enrichment that started at least in the end of the Oligocene or beginning of Miocene and extending into the latest Pliocene. Staircase-apparent age spectra, resulting from banded or botryoidal samples, yield an average growth rate of Mn oxides at 0.6–0.7 × 10⁻³ mm kyr⁻¹. The values indicate that a 1-mm grain of Mn oxides may host minerals precipitated during a time span of ca. 1.5 m.y., and accumulation of Mn oxides to form economic deposits under weathering environments may take millions of years. The distribution of weathering ages shows that the oldest Mn oxides occur on the top of the profile, whereas the youngest minerals are found at the bottom, suggesting downward propagation of weathering fronts. However, two samples located at the intermediate depths of the profile yield ages comparable with those occurring at the highest elevations. Such a complexity of age distribution is interpreted in terms of preferential penetration of Mn-rich weathering solutions along more permeable fault zones, or as a result of multi stages of dissolution and re-precipitation of Mn oxides. A synthesis of geochronological and geological data suggests that formation of the Xinrong deposit was a consequence of a combination of favorable lithological, climatic, and structural conditions. Because the climatic and structural conditions are similar among the provinces of South China during the Cenozoic, the geochronological results obtained at Xinrong may also have implications for the timing of supergene Mn enrichment throughout South China.  相似文献