Two methods for pore network of porous media     

Shengyan Gao  Jay N. Meegoda  Liming Hu 《国际地质力学数值与分析法杂志》2012,36(18):1954-1970

Two approaches of generating pore networks of porous media are presented to capture the pore fabric. The first methodology extracted pore structure from a computer simulated packing of spheres. The modified Delaunay tessellation was used to describe the porous media, and modified Nelder–Mead method in conjunction with three pore‐merging algorithms was used to generate the pore size and coordination number distributions of the randomly packed spheres. The Biconical Abscissa Asymmetric CONcentric bond was used to describe the connection between two adjacent voids. This algorithm was validated by predicting pore structure of a cubic array of spheres of equal radius with known pore sizes, throat sizes and coordination number distributions. The predicted distributions of pore structure agreed well with the measured. Then, the algorithm was used to predict pore structure and permeability of randomly packed spherical particles, and predicted permeability values were compared with published experimental data. The results showed that the predicted permeability values were in good agreement with those measured, confirming the proposed algorithm can capture the main flow paths of packed beds. The second methodology generated an equivalent pore network of porous media, of which the centers of voids were located in a regular lattice with constant pore center distance. However, this network allowed for matching both main geometrical and topological characteristics of the porous media. A comparison of the two approaches suggested that the second approach can also be used as a predictive tool to quantitatively study the microscopic properties of flow through porous media. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Rocking vibrations of a rigid embedded foundation in a poroelastic half‐space     

X. Q. Hu  Y. Q. Cai  G. Y. Ding  J. Wang 《国际地质力学数值与分析法杂志》2010,34(13):1409-1430

This paper presents an analysis of the rocking vibrations of a rigid cylindrical foundation embedded in poroelastic soil. The foundation is subjected to time‐harmonic rocking excitation and is perfectly bonded to the surrounding soil. The soil underlying the foundation base is represented by a homogeneous poroelastic half‐space, whereas the soil along the side of the foundation is modeled as an independent poroelastic stratum composed of a series of infinitesimally thin layers. The behavior of the soil is governed by Biot's poroelastodynamic theory. The contact surface between the foundation base and the poroelastic soil is assumed to be smooth and either fully permeable or impermeable. The dynamic interaction problem is solved by employing a simplified analytical method. Some numerical results for the nondimensional rocking dynamic impedance and nondimensional angular displacement amplitude of the foundation are presented to show the effect of nondimensional frequency of excitation, poroelastic material parameters, hydraulic boundary condition, depth ratio and mass ratio of the foundation. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

无力磁场的稳定性     

胡友秋 《中国天文和天体物理学报》1991,(1)

无力场被广泛用来模拟太阳活动区的强磁场,本文从Bernstein能量原理出发,导出了无力场能量原理的普遍形式,并给出了若干稳定性的充分条件,它们可方便而有效地对无力场进行稳定性判断。  相似文献   

Seawater flux through Taiwan strait     

Fu Zilang  Hu Jianyu  Yu Guoming 《中国海洋湖沼学报》1991,9(3):232-239

After the winter and summer current structures on two or three latitudinal sections in Taiwan Strait were obtained from the measured current data, the seawater fluxs through the sections were calculated. In summer, the currents in the central and northern part of Taiwan Strait normally flow northward at a net flux of 3.32×10⁶m³/s. In winter, the high temperature and salinity Kuroshio and South China Sea water enter Taiwan Strait from the southem section at 1.69×10⁶m³/s and 0.59×10⁶ m³/s respectively, while the East China Sea water enters Taiwan Strait from the northern section at 1.02×10⁶m³/s. About 0.40×10⁶ m³/s of the seawater enters the South China Sea along the coast of Fujian and Guangdong; the other 0.62×10⁶ m³/s of the seawater is mixed with the Kuroshio water and the South China Sea water in the northern sea areas. The net northward flux is 1.74×10⁶m³/s in winter.  相似文献   

Population growth in Bejing: trends and countermeasures     

Zhaoliang Hu  Francis Yee  George Chusheng Lin 《中国地理科学(英文版)》1991,1(3):212-220

Beijing’ population has experienced a dramatic increase eversince the founding of the People’s Republic of China. Population growthin Beijing can be broadly broken down into three major components:natural increase, immigration, and the growth of floating population. Thecontinuous growth of Beijing’s population is closely linked with its centralized multi-function. The comprehensive countermeasures to control Beijing’s population growth are proposed, for example, decentralizing economicfunctions, including developing the suburbs, developing the metropolitan areaand creating counter-magnetic centers, reforming the administrative and economic systems.  相似文献   

140OΜα前的后生动物实体化石?     

胡健民  孟庆任  李文厚 《地球科学与环境学报》1991,(2)

本文首次报道了在我国豫西晚前寒武系白草坪组中发现的一种可能的蠕虫状后生动物实体化石:Ruyangia Cylindrica Hu et Meng,1989。化石产于砂岩表面浪成波痕之波谷中,圆筒状,已压扁,中空,可见长度4.5～9.5cm,直径4mm左右,虫体外壁具体环,环背间距1.5～2mm,虫体一端较大,具平行纵向边缘的纵纹,可能为头部;另一端渐尖,可能为尾部。与该实体化石伴生的有大量遗迹化石。已知白草坪组的时代超过1400Ma,因此,该实体化石的发现对研究地球上后生动物起源与早期演化等具重要意义。  相似文献   

元素的环境化学与地球的温室效应          下载免费PDF全文

胡诗林 《山东国土资源》1991,(1)

本文讨论了一些重要元素的环境化学特征和一些重要金属和痕量元素对人类健康的影响。在地球温室效应一节中重点叙述了本世纪初以来CO_2浓度剧烈的增加,使地球的气候变暖,海洋表面的温度也上升了0.6±0.3℃。因此,必须严格限制CO_2排放。还讨论了对流层中的臭氧是一种对植物有害和对人体不利的污染物,然而平流层中的臭氧却是地球表面免受紫外线辐射的重要屏障。因此,应防止CFCl_3和CF_2Cl_2的一组化学剂,以便保护臭氧。  相似文献   

用向量作图法解等角应变花     

胡庆陪 《广东海洋大学学报》1991,(1)

本文提出用向量作图法解等角应变花的问题,这是一种比较完整的图解法,只需利用比例尺、三角板和量角器,就可用作图法简捷地得到所求的结果。本文还举了两个数值例题,与数解法作了比较,说明图解法的精确性相当好。  相似文献   

第一代北斗星座卫星对GALILEO卫星导航定位系统增强性能仿真     

蒋虎  余金培  李国通 《天文研究与技术》2006,3(3):264-270

第一代北斗星座已经于2003年布置完毕，基本实现了中国本土及周边的导航定位功能。中国作为GALILEO卫星导航定位系统开发的重要参与者，研究北斗系统和GALILEO卫星导航定位系统的集成问题十分必要和迫切。本文，就第一代北斗星座对GALILEO卫星导航定位系统的增强性能进行分析，主要对PDOP指标进行了仿真。给出了国内典型城市的PDOP及其一天内的变化曲线。  相似文献   

非对称四极无力场的磁能释放     

李醒  胡友秋 《天文学报》1995,36(4):350-358

本文采用二维三分量耗散ＭＨＤ模型，对带高电流层的局地非对称的四极无力场的磁能释放过程进行数值模拟，结果表明，磁能释放过程大体可以分为两个阶段：高电流层引起的异常电阻耗散使该层等离子体加热至３×１０６Ｋ的高温，形成一高温环；在高电流层耗散的触发下，磁分隔面的电流急剧增长并爆发异常电阻耗散和磁场重联，导致耀斑发生，主要的能量释放发生在磁分隔线和高剪切无力场中的磁分隔面上，等离子体温度可以达到１．９×１０７Ｋ。上述无力场的触发释能过程可能是太阳耀斑的一种重要的释能机制。  相似文献