北极航道的贸易替代效应与贸易互补效应分析          下载免费PDF全文

刘权  胡麦秀 《海洋开发与管理》2021,38(11):3-10

随着北极冰雪加速消融,北极航道在国际贸易运输中的关注度日益提升。文章采用理论模型进行分析,认为北极航道通过贸易替代效应与贸易互补效应对世界贸易格局产生影响。研究发现北极航道开通将：提升航道沿线各国间的贸易潜力,改变沿线国与非沿线国间部分贸易活动的流向;催生北极航道沿线国之间部分贸易活动的产生,改变北极航道沿线国之间部分贸易活动的流量。  相似文献   

城市化进程中工业用地置换的生态环境影响探讨   总被引：6，自引：0，他引：6  

范群杰  徐启新  张明成  赵沁娜 《世界地理研究》2005,14(4):86-91

城市工业用地置换是城市化发展的必然要求,本文对城市开发过程中工业用地置换产生的生态环境影响进行了理论探讨,并以上海某工业区的工业用地置换过程为例进行了实证分析,认为原生产遗留的土壤污染以及置换过程的搬迁、施工对区域的生态环境产生影响,应通过实施环境影响评价及建立全过程的生态环境管理体系予以控制。  相似文献   

An interface-condition substitution strategy for theoretical study of dissolution-timescale reactive infiltration instability in fluid-saturated porous rocks     

Chongbin Zhao  Bruce E. Hobbs  Alison Ord 《国际地质力学数值与分析法杂志》2019,43(8):1576-1593

A theoretical study of reactive infiltration instability is conducted on the dissolution timescale. In the present theoretical study, the transient behavior of a dissolution-timescale reactive infiltration system needs to be considered, so that the upstream region of the chemical dissolution front should be finite. In addition, the chemical dissolution front of finite thickness should be considered on the dissolution timescale. Owing to these different considerations, it is very difficult, even in some special cases, to derive the first-order perturbation solutions of the reactive infiltration system on the dissolution timescale. To overcome this difficulty, an interface-condition substitution strategy is proposed in this paper. The basic idea behind the proposed strategy is that although the first-order perturbation equations in the downstream region cannot be directly solved in a purely mathematical manner, they should hold at the planar reference front, which is the interface between the upstream region and the downstream region. This can lead to two new equations at the interface. The main advantage of using the proposed interface-condition substitution strategy is that through using the original interface conditions as a bridge, the perturbation solutions for the dimensionless acid concentration, dimensionless Darcy velocity, and their derivatives involved in the two new equations at the interface can be evaluated just by using the obtained analytical solutions in the upstream region. The proposed strategy has been successfully used to derive the dimensionless growth rate, which is the key issue associated with the theoretical study of dissolution-timescale reactive infiltration instability in fluid-saturated porous rocks.  相似文献   

城市空间形态的最低成本-周期扩张规律——以昆明为例   总被引：2，自引：0，他引：2  

吴启焰  陈辉  Belinda Wu  曾文 《地理研究》2012,31(3):484-794

城市形态演化反演城市土地利用模式的转变,是内部最低成本土地利用模式驱动力的外部表达。这一城市空间格局演变遵循本文提出的"外部扩张,内部填充"相互交替总体规律。它既是集聚与扩散驱动因子作用的结果,也是植入与再植入的"扬弃"选择过程的交互作用产物。基于最低成本—周期扩张模型的假设,本文选取昆明建成区近现代的影像资料,运用形态学的视角分析城市空间结构的变迁,探寻城市形态演化规律。结果表明:(1)从城市形态演变的一般理性微观、宏观过程来看,城市形态变迁在统计学上遵循最低成本—周期扩张规律假设;(2)在最低成本—周期扩张模型内,公共投资与基层设施建设变动及其要素替代效应对形态的周期性扰动响应是其核心作用机制。  相似文献   

铀矿成矿过程的耗散结构分析   总被引：1，自引：0，他引：1  

王京贵 《华东地质学院学报》1993,16(1):1-6

  相似文献   

Fe-Li云母化学成分的解释和分类   总被引：3，自引：0，他引：3       下载免费PDF全文

孙世华 《地质科学》1988,(3):213-228

用置换矢量概念解释了115个天然 Fe-Li 云母化学成分的变化。Fe-Li 云母是三八面体 Li-Fe-Al 云母,其基本置换是四锂云母置换。由于 Al-Li 白云母置换和白云母置换的影响,其化学组成变化的基本趋势呈明显的非线性,因而 Fe-Li 云母不是真正的二元系。作为 Fe-Li 云母,富铁黑云母和铁叶云母都是最富铁的成员,因而建议称 Fe-Li 云母为黑云母-锂云母系列。根据化学成分,晶胞参数和折光率的异常变化还提出了该系列自然分类的方案。  相似文献   

贵阳新一代天气雷达(CINRAD/CD)交流伺服系统的故障分析与处理          下载免费PDF全文

雷登林  钟健  田程 《中低纬山地气象》2018,42(6):67-69

CINRAD/CD伺服系统在升级改造后,大部分都由直流伺服改为交流伺服,该文从介绍新一代天气雷达(CINRAD/CD)交流伺服系统的工作原理入手,通过维修处理伺服系统的3个故障事例,逐一剖析伺服系统出现故障的原因,并针对伺服系统方位与俯仰结构相同的特点,用组件替代的方法查找故障,节省维修时间,快速处理故障。  相似文献   

南海西部晚渐新世主要断裂活动特征及与红河断裂之关系   总被引：2，自引：2，他引：0  

蔡周荣  夏斌  万志峰  刘维亮  张毅 《大地构造与成矿学》2008,32(4)

南海的形成演化是众多被动型边缘海中最复杂的,而南海西部的断裂带构造活动特征又是南海中最复杂的构造之一。本文针对前人提出的红河断裂带出莺歌海盆地后的东延、南延以及东南延问题,通过晚渐新世-早中新世琼东南盆地受到南北向挤压的区域应力场分析,认为这期的应力主要来自南海西部近南北向断裂带的右旋剪切活动,结合红河断裂带的构造运动特征,提出晚渐新世末南海西部发生断裂构造置换,红河断裂带17°30′N以南近SN走向部分被南海西缘断裂带所置换,并且构造活动特征与北部红河断裂带明显不同,南海西部晚渐新世前后两个时期不同的断裂构造活动特征反映了印度板块与欧亚板块碰撞造成的两种不同影响效应。  相似文献   

地貌发育演化研究的空代时理论与方法   总被引：2，自引：0，他引：2  

黄骁力  丁浒  那嘉明  汤国安 《地理学报》2017,72(1):94-104

地貌的发育在特定的条件下往往呈现空间分布上由“新”至“老”的过渡,据此,对地貌类型与特征在空间上的序列采样,即可为研究某种地貌的个体发育提供基本依据。该方法即为地貌学研究中的空代时。本文首先介绍了空代时方法产生的背景与基本概念。分析了近年来空代时方法应用于河流地貌、构造地貌、河口海岸地貌等不同地貌类型演化过程的研究进展。在此基础上,明确了空代时方法在地貌学研究中的适用条件、影响因素及分类体系,并提出了地貌学空代时的研究范式。本文认为今后的研究工作一方面应充分利用海量的地理空间数据,运用空代时方法研究多种空间尺度下的地貌演化的问题;另一方面,应结合现有的物理机制和统计规律,构建集形、数、理一体化的地貌演化模型。  相似文献   

Effective bulk modulus of the pore fluid at patchy saturation          下载免费PDF全文

Uri Wollner  Jack Dvorkin 《Geophysical Prospecting》2018,66(7):1372-1383

We explore a package of parallel porous layers, each filled with a different fluid. Assume that this package is sampled by an elastic wave with the wavelength much larger than the thickness of an individual layer. Also assume that the layers are hydraulically isolated from each other, meaning that the diffusion length is smaller than that of the individual layer. This assumption is relevant to a patchy saturation scenario. Suppose that we wish to conduct the fluid substitution operation on this package treated as a single porous elastic body. What is the effective bulk modulus of the pore fluid to be used in this operation that will result in the same elastic modulus as computed by Backus averaging the individual moduli of the layers? We address this question analytically by assuming that the porosity, dry frame, and the mineral matrix properties of the individual layers are the same for all layers. The only difference between the layers is the pore fluid. We find that the resulting effective bulk modulus of the fluid thus derived falls between the arithmetic and harmonic averages of the fluid bulk moduli in the layers. It can be approximated by a linear combination of these two bounds where the weights are 0.50 and 0.50 or 0.75 for the arithmetic average and 0.25 for the harmonic average, depending on the elastic moduli of the dry frame, the mineral, and the pore fluids. This solution also provides a relation between the effective bulk modulus of the pore fluid in the system under examination and water saturation to be used in the fluid substitution operation at a coarse spatial scale.  相似文献