空间集聚与外商直接投资的区位选择——基于珠江三角洲地区的实证分析   总被引：7，自引：0，他引：7  

李郇  DING Xin-Zheng  丁行政 《地理科学》2007,27(5):636-641

在揭示改革开放以来外商直接投资在珠江三角洲空间分布呈现向珠江三角洲集聚的基础上,采用动态局部调整模型对1992～2003年外商直接投资在珠江三角洲9个地级城市中的区位选择影响因素进行了实证分析,结果表明外商直接投资在广东省的区位选择,除受到城市区位特性因素的影响外,更为主要的影响因素是外商直接投资的集聚效应,即与城市已有的外商直接投资数量呈正相关,存在外商直接投资的空间集聚效应,进一步的提出了通过产业集群培育和升级促进珠江三角洲城市外商直接投资持续集聚的策略.  相似文献   

A simple approach for determining particle size enlargement mechanisms in nickel reduction     

V.C. Taty Costodes  C.F. MausseK. Molala  A.E. Lewis 《International Journal of Mineral Processing》2006

This paper examines the active mechanisms responsible for the size enlargement of nickel metal particles during reduction by hydrogen gas. The population balance, related to particle size distribution, is discretized and solved with the method of moments to model the experimental data. This data was generated in a solution of intermittently constant supersaturation during the batch reduction in an 11,000 l of autoclave. PSD and mass distributions were determined by periodically removing suspension samples. In the proposed model, only the growth mechanism is taken into account and aggregation is ignored. Comparison of simulated and experimental PSD and mass distributions show that growth was not the only active mechanisms. Results from the plant indicate that there is an increase in particle size as the cycle progresses. The model generally underpredicts the growth shift in the PSDs' for the early and the larger densifications although it correctly predicts the growth shift in the middle densifications. Constant growth is therefore not the exclusive controlling mechanism. The findings have been confirmed by the trend of the zeroth moment as a function of time.  相似文献   

Heterogeneous growth of cordierite in low P/T Tsukuba metamorphic rocks from central Japan     

K. Miyazaki 《Journal of Metamorphic Geology》2001,19(2):155-164

This paper examines the spatial statistics of matrix minerals and complex patterned cordierite porphyroblasts in the low‐pressure, high‐temperature (low P/T) Tsukuba metamorphic rocks from central Japan, using a density correlation function. The cordierite‐producing reaction is sillimanite + biotite + quartz = K‐feldspar + cordierite + water. The density correlation function shows that quartz is distributed randomly. However, the density correlation functions of biotite, plagioclase and K‐feldspar show that their spatial distributions are clearly affected by the formation of cordierite porphyroblasts. These observations suggest that cordierite growth occurred through a selective growth mechanism: quartz adjacent to cordierite has a tendency to prevent the growth of cordierite, whereas other matrix minerals adjacent to cordierite have a tendency to enhance the growth of cordierite. The density correlation functions of complex patterned cordierite porphyroblasts show power‐law behaviour. A selective growth mechanism alone cannot explain the origin of the power‐law behaviour. Comparison of the morphology and fractal dimension of cordierite with two‐dimensional sections from a three‐dimensional diffusion‐limited aggregation (DLA) suggests that the formation of cordierite porphyroblasts can be modelled as a DLA process. DLA is the simple statistical model for the universal fractal pattern developed in a macroscopic diffusion field. Diffusion‐controlled growth interacting with a random field is essential to the formation of a DLA‐like pattern. The selective growth mechanism will provide a random noise for the growth of cordierite due to random distribution of quartz. Therefore, a selective growth mechanism coupled with diffusion‐controlled growth is proposed to explain the power‐law behaviour of the density correlation function of complex patterned cordierite. The results in this paper suggest that not only the growth kinetics but also the spatial distribution of matrix minerals affect the progress of the metamorphic reaction and pattern formation of metamorphic rocks.  相似文献   

青海湖底沉积物中球状白云石集合体的发现及其地质意义   总被引：10，自引：0，他引：10  

于炳松  董海良  蒋宏忱  李善营  刘英超 《现代地质》2007,21(1):66-70

青海湖为盐度低于海水的微咸水湖。为了探索白云石的成因,在青海湖二浪尖以北约15 km的湖底采集了长25 cm的沉积物柱状样品。对样品所做的X-衍射矿物物相定量分析表明其中含有2.2％的白云石。文献中也曾报道青海湖底沉积物中含有高达10％的白云石矿物。对这些含白云石矿物的湖底沉积物所进行的扫描电镜研究发现了其中呈球状、椭球状,大小1~2 μm的白云石集合体及其伴生的草莓状黄铁矿的存在。其特征与文献中报道的现代近海高盐度泻湖和萨勃哈中发现的微生物成因的白云石极为相似。这是内陆低盐度环境中此类白云石的首次发现,对于探讨不同盐度环境中白云石的形成机理,促进“白云石问题”的深入研究具有重要的理论意义。  相似文献   

In situ acoustic target strength measurements of tuna associated with a fish aggregating device     

Josse  Erwan; Bertrand  Arnaud 《ICES Journal of Marine Science》2000,57(4):911-918

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基于顶点线性插值的建筑物群聚合的简易方法     

黄玉兰  郭庆胜  王慧慧  王勇 《地理空间信息》2022,20(2):15-21

提出了基于顶点线性插值的建筑物群聚合的简易方法:首先通过插值加密建筑物轮廓线顶点,以最短邻近连线互不相交为原则,构建相邻建筑物轮廓线顶点之间的最短邻近连线;其次依据这些最短邻近连线自动确定相邻建筑物之间的聚合区域;最后按照渐进式方法聚合建筑物群,获取聚合后的新建筑物轮廓线,该方法还可以处理建筑物群的多边形存在相交和重叠...  相似文献   

冠瘤海鞘同种群聚的化学诱因初步研究   总被引：2，自引：0，他引：2  

黄英  柯才焕  冯丹青  周时强  张朝霞  李复雪 《海洋学报》2005,27(3):104-109

研究了不同浓度的冠瘤海鞘成体被囊萃取物和幼体萃取物及不同的幼体密度对冠瘤海鞘(Styela canopus)幼体附着和变态的影响.结果表明,冠瘤海鞘被囊萃取物和幼体萃取物在5%和10%的浓度下均促进冠瘤海鞘幼体的附着和变态,但被囊萃取物的诱导效果明显强于幼体萃取物;幼体密度高于25只/cm3时,促进冠瘤海鞘幼体的附着和变态;幼体密度低于10只/cm3时,幼体的附着和变态不受密度影响.这些结果提示海区中冠瘤海鞘的同种群聚可能与其被囊或幼体内含诱导幼体附着和变态的化学因子有关.  相似文献   

水化学性质对蒙脱石悬浮液膨胀性的影响     

马蕾  彭昌盛  范超  徐兴永  于洪军 《中国海洋大学学报(自然科学版)》2011,(Z1):379-385

实验研究了NaOH、HCl、NaCl和CaCl2等电解质加入量对蒙脱石悬浮液膨胀性的影响,并通过离子色谱、体视显微镜和激光粒度分析技术,研究了蒙脱石粒度变化与体积膨胀之间的关系。实验结果表明,NaOH、HCl对蒙脱石悬浮液膨胀性影响不明显,而NaCl和CaCl2对蒙脱石悬浮液的膨胀有明显的抑制作用;而且CaCl2对蒙脱石膨胀的抑制作用明显强于NaCl,CaCl2浓度比NaCl少了1个数量级时即可达到相同的膨胀抑制效果。离子色谱分析显示,CaCl2溶液与蒙脱石混合后,悬浮液上清液中的Ca2+浓度减少,而Na+浓度增加,分析存在离子交换过程。经激光粒度分析仪和体视显微镜观察,电解质的加入使颗粒之间产生了团聚作用,改变了颗粒的粒径,从而在宏观上表现为蒙脱石悬浮液体积的减少。  相似文献   

Magnetic aggregation: II. Laboratory and microgravity experiments     

Henrik Nübold  Torsten Poppe  Carsten Dominik 《Icarus》2003,165(1):195-214

In a previous publication (Dominik and Nübold, 2002, Icarus 157, 173-186), we presented analytical expressions and theoretical considerations concerning preplanetary dust aggregation with magnetized grains in the solar nebula. The present work is dedicated to the experimental study of magnetic aggregation in a ground-based laboratory as well as under microgravity conditions on parabolic flights. We conducted aggregation experiments with dust analogues in order to study the temporal evolution and the structural outcome of grain growth processes dominated by or comprising exclusively magnetic grains. Within aggregation times ranging from a couple of seconds to a few minutes only, formation of huge chain-like and/or web-like dust aggregates was observed. After aggregate retrieval we were able to study the sizes and structures of the aggregates in great detail. We established the fractal dimension of the aggregates as D_fs=1.20±0.05 for single chains and D_fc=1.50±0.21 for inter-connected web-like structures. This is considerably lower than for non-magnetic grain growth. The dynamic exponent z for the mass increase with time according to t^z was found to be z=2.7 from in-situ video images of the microgravity aggregation runs. The results are compared with the theoretical considerations presented earlier as well as with previous experimental work on the same and on related topics, respectively.  相似文献   

泰森多边形和狄洛尼三角网的林木空间格局分析   总被引：1，自引：0，他引：1  

赵春燕  李际平  袁晓红  封尧 《测绘科学》2014,39(10)

Voronoi图依据地物之间邻近关系对空间进行剖分,Delaunay三角网是Voronoi图的对偶图.文章以单株木为平面点构建Voronoi图和Delaunay三角网,Voronoi图多边形面积表示林木影响范围,Delaunay三角网中每个三角形边长表示对应林木之间距离.在岳阳平江福寿林场设置12块标准地进行试验,计算基于Voronoi图的角尺度、传统的角尺度、基于Delaunay三角网的集聚指数和Voronoi图多边形面积的变异系数,结果表明:这4个指数均能反映样地林木之间的空间分布,变异系数对空间均匀分布和聚集分布有较好的区分度.  相似文献