北京城市休闲商务区的时空分布特征与成因   总被引：12，自引：1，他引：11  

朱鹤  刘家明  陶慧  李玏  王润 《地理学报》2015,70(8):1215-1228

城市休闲商务区（Recreational Business District, RBD）作为城市重要的游憩空间,为外来游客和城市居民提供休闲消费的场所,逐渐受到学界和业界重视。目前大多数研究还停留在概念层面,在分类、空间结构、分布规律、分异成因等方面上还缺乏一定的实证和定量研究。结合前人研究经验,重新定义RBD,并依据城市RBD的特征和属性将其分为大型购物中心、休闲商业街、城市休闲区三类。选取1990年、2000年、2014年三个时间截面对北京各类城市RBD点进行统计,采用基尼系数、空间插值、核密度分析、地理探测器等方法,结合ArcGIS软件,对北京城市RBD的时空分布特征和成因进行分析,得出以下结论：① 时序上看,北京城市RBD的数量和规模不断增加,增速变快,不同类型的RBD出现不同幅度的空间扩张;② 北京城市RBD的空间集聚程度不断加强,不同类型的RBD,存在一定的增幅和增速差异;③ 北京城市RBD的整体空间结构呈“单核聚集—双核发展—网状扩散”的发展模式;④ 城市RBD多选址在交通便利、临近旅游景区、居民和游客密度较高、地价相对较高的地区。⑤ 游客密度对各类型的城市RBD规模均有较大影响;对于不同类型的城市RBD,各因素对其规模的影响也有所不同。  相似文献   

WEPP模型(坡面版)在贵州石漠化地区土壤侵蚀模拟的适用性评价   总被引：6，自引：2，他引：4  

龙明忠  吴克华  熊康宁 《中国岩溶》2014,33(2):201-207

文章以贵州花江喀斯特石漠化地区为研究区域,利用WEPP模型(坡面版)分别模拟2006年、2010年土壤侵蚀模数,并将实测数据与WEPP模型模拟值作比较,探讨WEPP软件在喀斯特石漠化地区的适用性。研究表明:WEPP模型对于模拟喀斯特石漠化地区土壤侵蚀有较大误差,对土壤侵蚀模数模拟的有效性系数均为负值,不适用于直接计算该区域土壤侵蚀模数。WEPP模型对微度侵蚀模拟精度不够,但能大体反映不同径流小区之间土壤侵蚀强弱的关系和生态修复过程土壤侵蚀的变化趋势。若要应用WEPP模型对喀斯特地区土壤侵蚀模数模拟计算,必须考虑水土的地下漏失、地表裸岩率、地形高度破碎等环境条件。裸岩率、土壤漏失、地形条件等都是WEPP模型修正所必须注意的内容。   相似文献   

Sedimentary Environment and Mineralization of the Black Shale Polymetallic Layer in the Early Cambrian, SW China: Constraints from in situ LA-ICP-MS Analysis of Pyrite     

YANG Zhen  FU Yong  LI Chao  CAI Xi  GUO Chuan 《《地质学报》英文版》2024,98(2):416-429

A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province. The mineral that makes up the polymetallic layer is related to the sedimentary facies. To analyze the differentiation mechanism between polymetallic deposits (Ni-Mo and V), the Zhijin Gezhongwu profile located in the outer shelf and the Sansui Haishan V deposit located in the lower slope are selected to study the in situ sulfur isotopes and trace elements of pyrite. The results show that δ34S values of pyrite vary widely from ?7.8 ‰ to 28 ‰ in the Gezhongwu profile, while the δ34S values are relatively uniform (from 27.8 ‰ to 38.4 ‰) in the Haishan profile. The isotopic S composition is consistent with the transition that occurs in the sedimentary phase from the shelf to the deep sea on the transgressive Yangtze platform; this indicates that the δ34SO42? values in seawater must be differently distributed in depositional environments. The sulfur in the Ni-Mo layer is produced after the mixing of seawater and hydrothermal fluid, while the V layer mainly originates from seawater. Overall, the Ni-Mo and V deposits have been differentiated primarily on the basis of the combined effect of continental weathering and hydrothermal fluid.  相似文献   

中国荔波锥状喀斯特世界自然遗产价值全球对比分析   总被引：1，自引：0，他引：1  

陈品冬  熊康宁  肖时珍 《地理研究》2013,32(8):1517-1527

研究世界自然遗产地价值,对遗产地本身以及其他类似区域的可持续发展有重要意义。基于系统论思想,将"中国南方喀斯特"第一批三处遗产地中的荔波锥状喀斯特置于全球视角,选取相似的、具有代表性的区域,结合世界遗产第八条有关地质地貌特征与演化历史等方面的评价标准,进行全球对比分析,揭示其全球显著价值。研究表明:荔波锥状喀斯特具有更为独特的演化环境与更为复杂的地质演化过程;更有典型的锥状喀斯特单体形态与较为齐全的地貌组合类型,更有罕见的锥状喀斯特森林生态系统和生命记录。荔波锥状喀斯特是反映地球热带-亚热带锥状喀斯特演化历史主要阶段的典型范例,极具代表中国南方喀斯特的世界遗产价值。  相似文献   

Multi-directional modeling for prediction of fabric anisotropy in sand liquefaction     

《Computers and Geotechnics》2017

Anisotropy in the onset of liquefaction and post liquefaction under cyclic loading condition causes the change in response behavior of the soil. The proposed model operates within the integration of sliding/opening/closing framework of 17 predefined planes as local deformation. This leads to the use of better stress/strain multilaminate histories with many directional effects on soil behavior specifically internal mechanism during pre and post-liquefaction. The ability of multilaminate model for fabric anisotropy has been proven by comparison with the experimental results under drain and undrained conditions and monotonic and cyclic loading. The effects of induced anisotropy was also investigated.  相似文献   

Temporal–spatial variability of atmospheric and hydrological natural disasters during recent 500 years in Inner Mongolia,China     

Peng  Yu  Song  Jingyi  Cui  Tiantian  Cheng  Xiang 《Natural Hazards》2017,89(1):441-456

Natural Hazards - Inner Mongolia, located in the northern China, is a natural disaster-prone region. This study is dedicated to making a comprehensive and quantitative analysis of the...  相似文献   

突发水污染事故中污染物输移主导水动力识别——以深圳湾为例          下载免费PDF全文

陶亚  雷坤  夏建新 《水科学进展》2017,28(6):888-897

河口地区感潮河段水动力过程复杂,为在突发水污染事故中合理制定精细化应急方案,基于环境流体水动力模型（EFDC）从水动力学角度对不同水文条件下深圳河口水域突发水污染事故的影响范围、时间及程度进行了数值模拟分析,提出了一种判断河口海湾地区主导水动力因素的分析方法。采用基于傅里叶变换的频谱分析法对事故中污染物输移扩散的主要影响因子进行了准确识别,并采用单因变量多因素方差分析法进行了印证。结果表明,潮流是感潮河段水动力过程的主要驱动因素,但在突发水污染事故中,深圳河各断面特征污染物浓度变化与陆地径流关系密切,径流是感潮河段内突发事故中特征污染物输移的主导动力因素。  相似文献   

不同粒度颗粒在非恒定管流中跟随性试验          下载免费PDF全文

曹斌  邹燚  夏建新 《水科学进展》2017,28(3):356-363

管道中固液两相流水击对管道和输送系统可能产生严重的破坏,而固液两相在这种非恒定流中的运动特性是计算最大水击压力变化的重要依据。采用粒子图像测速技术（Particle Image Velocimetry,PIV）,通过试验研究水击发生时,水平圆管中不同平均流速、颗粒粒径条件下,流体介质和粗颗粒在管道断面的速度分布以及粗颗粒跟随性的变化规律。研究结果表明:①在水击发生的不同时刻,圆管流中粗颗粒的流速在管道断面分布呈不规则的抛物线型分布,主要表现为靠近管道壁面底部的颗粒流速略小于靠近管道顶部流速,当颗粒粒径大于1.5 mm,平均流速小于2.5 m/s时,粗颗粒表现出明显的沉降特性;②粗颗粒的跟随性与颗粒受力有密切关系,其中颗粒速度与流体速度的变化量是影响颗粒受力的重要参数;③基于试验数据拟合得到了水击条件下粗颗粒跟随性系数k的经验公式,并分析了颗粒粒径、管道直径、两相流平均流速以及水击发生时间等不同参数对粗颗粒跟随性系数的影响,公式计算值与实测值之间的误差在5%以内。  相似文献   

青藏高原东缘休瓦促钨钼矿区复式岩体时空分布及演化意义          下载免费PDF全文

张向飞  李文昌  杨镇  王裕琴  严桃桃  张军军 《沉积与特提斯地质》2022,42(1):105-121

休瓦促钨钼矿区位于义敦地体南段,是该区域唯一存在晚三叠世、晚白垩世和新生代酸性侵入体直接接触形成复式岩体的矿区.目前尚未对该复式岩体的岩浆演化过程开展过系统深入研究,限制了对该矿区及区域构造事件和岩浆演化的认识.本文通过系统梳理前人研究成果,开展东矿段黑云母花岗岩,西矿段二长花岗岩、花岗斑岩地质年代学和地球化学分析,探...  相似文献   

Fluid evolution of the Yuchiling porphyry Mo deposit,East Qinling,China     

《Ore Geology Reviews》2012

The Yuchiling Mo deposit, East Qinling, China, belongs to a typical porphyry Mo system associated with high-K calc-alkaline intrusions. The pure CO₂ (PC), CO₂-bearing (C), aqueous H₂O-NaCl (W), and daughter mineral-bearing (S) fluid inclusions were observed in the hydrothermal quartz. Based on field investigations, petrographic, microthermometric and LA-ICP-MS studies of fluid inclusions, we develop a five-stage fluid evolution model to understand the ore-forming processes of the Yuchiling deposit. The earliest barren quartz ± potassic feldspar veins, developed in intensively potassic alteration, were crystallized from carbonic-dominant fluids at high temperature (> 416 °C) and high pressure (> 133 MPa). Following the barren quartz ± potassic feldspar veins are quartz-pyrite veins occasionally containing minor K-feldspar and molybdenite, which were formed by immiscible fluids at pressures of 47–159 MPa and temperatures of 360–400 °C. The fluids were characterized by high CO₂ contents (approximately 8 mol%) and variable salinities, as well as the highest Mo contents that resulted in the development of quartz-molybdenite veins. The quartz-molybdenite veins, accounting for > 90% Mo in the orebody, were also formed by immiscible fluids with lower salinity and lower CO₂ content of 7 mol%, at temperatures of 340–380 °C and pressures of 39–137 MPa, as constrained by fluid inclusion assemblages. After the main Mo-mineralization, the uneconomic Cu-Pb-Zn mineralization occurred, as represented by quartz-polymetallic sulfides veins consisting of pyrite, molybdenite, chalcopyrite, digenite, galena, sphalerite and quartz. The quartz-polymetallic sulfide veins were formed by fluids containing 5 mol% CO₂, with minimum pressures of 32–110 MPa and temperatures of 260–300 °C. Finally, the fluids became dilute (5 wt.% NaCl equiv) and CO₂-poor, which caused the formation of late barren quartz ± carbonate ± fluorite veins at 140–180 °C and 18–82 MPa.It is clear that the fluids became more dilute, CO₂-poor, and less fertile, with decreasing temperature and pressure from quartz-pyrite to late barren veins. Molybdenite and other sulfides can only be observed in the middle three stages, i.e., quartz-pyrite, quartz-molybdenite and quartz-polymetallic sulfide veins. These three kinds of veins are generally hosted in potassic altered rocks with remarkable K-feldspathization, but always partly overprinted by phyllic alteration. The traditional porphyry-style potassic–phyllic–propylitic alteration zoning is not conspicuous at Yuchiling, which may be related to, and characteristic of, the CO₂-rich fluids derived from the magmas generated in intercontinental collision orogens.Among the fluid inclusions at Yuchiling, only the C-type contains maximum detectable Mo that gradationally decreases from 73 ppm in quartz-pyrite veins, through 19 ppm in quartz-molybdenite veins, and to 13 ppm in quartz-polymetallic sulfide veins, coinciding well with the decreasing CO₂ contents from 8 mol%, through 7 mol%, to 5 mol%, respectively. Hence it is suggested that decreasing CO₂ possibly results in decreasing Mo concentration in the fluids, as well as the precipitation of molybdenite from the fluids. This direct relationship might be a common characteristic for other porphyry Mo systems in the world.The Yuchiling Mo deposit represents a new type Mo mineralization, with features of collision-related setting, high-K calc-alkaline intrusion, CO₂-rich fluid, and unique wall-rock alterations characterized by strong K-feldspathization and fluoritization.  相似文献