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The 3-D non-axisymmetrical Lamb's problem in transversely isotropic saturated poroelastic media

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Science China(Technological Sciences) 2004年第5期47卷 526-549页

作者： HUANG Yi1 & WANG Xiaogang1,2 1. School of Civil Engineering, Xian University of Architecture & Technology, Xian 710055, China 2. Department of Civil Engineering, Qinghai University, Xining 810016, China Correspondence should be addressed to Huang Yi (email: huangyih@***) Received April 15, 2004 revised July 12, 2004 School of Civil Engineering Xi’an University of Architecture & Technology Xi’an China Department of Civil Engineering Qinghai University Xining China

Based on Biots theory on fluid-saturated porous media, the displacement functions are adopted to convert the 3-D Biots wave equations in the cylindrical coordinate for transversely isotropic saturated poroelastic media into two棗one 6-order and one 2-order棗uncoupling differential governing equations. Then, the differential equations are solved by the Fourier expanding and Hankel integral transform method. Integral solutions of soil skeleton displacements and pore pressure as well as the total stresses for poroelastic media are obtained. Furthermore, the systematic study on Lambs problems for the transversely isotropic saturated poroelastic media is performed. Integral solutions for surface radial, vertical and circumferential displacements are obtained in both cases of drained surface and undrained surface under the vertical and horizontal harmonic excitation force. In the end of this paper, the numerical examples are presented. The calculation results indicate that the difference between the model of isotropic saturated poroelastic media and that of transversely isotropic saturated poroelastic media is obvious.

关键词： transversely isotropic saturated poroelastic media, Biot's wave equations, Lamb's problems.

Fundamental solutions for transversely isotropic magneto-electro-elastic media and boundary integral formulation

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Science China(Technological Sciences) 2003年第6期46卷 607-619页

作者：丁皓江江爱民 Department of Civil Engineering Zhejiang University Hangzhou 310027 China West Branch of Zhejiang University of Technology Quzhou 324006 China

To obtain the fundamental solutions for computation of magneto-electro-elastic media by the boundary element method, the general solutions in the case of distinct eigenvalues are de-rived and expressed in five harmonic functions from the governing equations and the strict differ-ential operator theorem. On the basis of these general solutions, the fundamental solution of infi-nite magneto-electro-elastic solid are obtained with the method of trial-and-error. Finally, the boundary integral formulation is derived and the corresponding boundary element method program is implemented to perform two numerical calculations(a column under uni-axial tension, uniform electric displacement or uniform magnetic induction, an annular plate simply-supported on outer and inner surfaces under axial loads). The numerical results agree well with the analytical ones.

关键词： transversely isotropic magneto-electro-elastic media, fundamental solution, boundary integral formulation.

BulkTree: an overlay network architecture for live media streaming

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第Z1期7卷 125-130页

作者： GONG An DING Gui-guang DAI Qiong-hai LIN Chuang Department of Computer Science & Technology Tsinghua University Beijing 100084 China Broadband Networks & Digital Media Laboratory Department of Automation Tsinghua University Beijing 100084 China Broadband Networks & Digital Media Laboratory Department of Automation Tsinghua University Beijing 100084 China Department of Computer Science & Technology Tsinghua University Beijing 100084 China

Peer-to-peer (P2P) systems are now very popular. Current P2P systems are broadly of two kinds, structured and unstructured. The tree structured P2P systems used technologies such as distributed hash tables (DHT) and hierarchical clustering can search the required target quickly, however, in a tree, the internal node has a higher load and its leave or crash often causes a large population of its offspring's problems, so that in the highly dynamic Internet environment the tree structure may still suffer frequent breaks. On the other hand, most widely used unstructured P2P networks rely on central directory servers or massive message flooding, clearly not scalable. So, we consider both of the above systems' advantages and disadvantages and realize that in the P2P systems one node may fail easily, but that when a number of nodes organized as a set, which we call "super node", the set is robust. Super nodes can be created and updated aware of topology-aware, and used with simple protocol such as flooding or "servers" to exchange information. Furthermore the entire robust super node can be organized into exquisite tree structure. By using this overlay network architecture, P2P systems are robust, efficient, scalable and secure. The simulation results demonstrated that our architecture greatly reduces the alteration time of the structure while decreasing the average delay time, compared to the common tree structure.

关键词： Peer-to-peer (P2P), Overlay networks, Scalability, Live media, Distributed hash tables (DHT), Hierarchical clustering

The upwind finite difference fractional steps method for combinatorial system of dynamics of fluids in porous media and its application

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Science China Mathematics 2002年第5期45卷 578-593页

作者：袁益让 Institute of Mathematics Shandong University Jinan 250100 China

For combinatorial system of multilayer dynamics of fluids in porous media, the second order and first order upwind finite difference fractional steps schemes applicable to parallel arithmetic are put forward and two-dimensional and three-dimensional schemes are used to form a complete set. Some techniques,such as implicit-explicit difference scheme, calculus of variations, multiplicative commutation rule of difference operators, decomposition of high order difference operators and prior estimates, are adopted. Optimal order estimates in L2 norm are derived to determine the error in the second order approximate solution. This method has already been applied to the numerical simulation of migration-accumulation of oil resources.

关键词： combinatorial system, multilayer dynamics of fluids in porous media, twoclass upwind finite difference fractional steps method, convergence, numerical simulation of energy sources.

How Netanyahu＇s New media Policy is Influencing Israeli,American and Global Politics

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International Relations and Diplomacy 2017年第8期5卷 501-510页

作者： Yaron Katz Holon Institute of Technology Holon Israel

This paper analyzes how the Prime Minister of Israel, Binyamin Netanyalau, uses Israel＇s technological superiorityand innovative use of digital diplomacy to maintain a leading role in social media and an active and on-goingimpact on American politics. His global policy approach is based on the realization that we live in a world oftechnology, and since technology improves at a rapid rate, Israel should stand in the front of global change. Hispolitical and social media reign is unquestionable. He was elected the 10th most admired person in the United States,according to the ＂World＇s Most Admired 2016＂ YouGov poll that gauged the popularity of famous people in 30different countries. His personal Facebook page reached two million followers worldwide, more than half of themfrom the United States. As the research demonstrates, his popularity is the result of the ability to mobilize politicalskills with an effective media campaign. He derives his power directly from the public and engages that public indirect dialogue, bypassing the traditional media. This demonstrates a calculated and savvy use of new mediaplatforms, as his accounts are able to motivate high rates of interaction and interest among followers and others whocan view the posts.

关键词： social media, Israel, American politics, digital diplomacy

Synchronized Firing in Coupled Inhomogeneous Excitable Neurons

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Communications in Theoretical Physics 2002年第10期38卷 415-420页

作者： ZHENG Zhi-Gang WANG Fu-Zhong Department of Physics Beijing Normal University Beijing 100875 China Department of Physics Jinzhou Teachers College Jinzhou 121003 Liaoning Province China Department of Physics Jinzhou Teachers College Jinzhou 121003 Liaoning Province China

We study the firing synchronization behavior of the inhomogeneous excitable media. Phase synchronizationof neuron firings is observed with increasing the coupling, while the phases of neurons are different (out-of-phase synchronization). We found the synchronization of bursts can be greatly enhanced by applying an external forcing (in-phasesynchronization). The external forcing can be either a periodic or just homogeneous thermal noise. The mechanismresponsible for this enhancement is *** numbers: 05.45.-a, 87.10.

关键词： excitable media, phase synchronization, FitzHugh-Nagumo model

Effect and mechanism of stresses on rock permeability at different scales

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Science China Earth Sciences 2006年第7期49卷 714-723页

作者： YIN Shangxian1 & WANG Shangxu2 1. Safety Engineering College, North China Institute of Science and Technology, Yanjiao, Beijing 101601, China 2. Key Laboratory of Geophysics Exploration, China University of Petroleum, Beijing 100083, China Safety Engineering College North China Institute of Science and Technology Yanjiao Beijing China Key Laboratory of Geophysics Exploration China University of Petroleum Beijing China

The effect of geo-stress fields on macroscopic hydro-geological conditions or micro-cosmic permeability of water-bearing media should follow some laws or principles. Cases study and tests show that: (1) At macro-geologic large scale, deformed and crashed rocks which were induced by geo-stress fields changing provided space for groundwater storage and flow. Groundwater adjusts water-bearing space and dilatants fractures by flowing and press transferring. Coupling of liquid and solid can be implemented for rocks and groundwater. Although tectonic fields witness several times of change and build-up in geological time, stress fields forming regional tectonic framework are coherent with seepage fields, orientation of the maximum horizontal stress demonstrates main seepage direc-tions. (2) At macro-geologic middle scale, zones of stresses changing sharply, quite low stresses, stress or shear concentration can be used to show locations and types of main fractures, zones of geo-stresses changing equably can be acted as normal base media zones of tri-porosity media. (3) At micro-geologic small scale, tri-porosity media include fractured rocks, porous rocks and capillary rocks. Investigations indicate that porosity or permeability is functions of effective stresses, and po-rosity or permeability changing rules of porous rocks with variation of effective stresses can be de-scribed as the index model, the model of power exponent functions is suitable for those of fractured rocks, the model of the second power parabola for capillary rocks. The porosity and permeability loss in fractured rocks, which are greater than that in porous rocks, are shown by calculation of effective compressive coefficient and closing pressure in cracks. The calculations can also explain the mecha-nism why porosity changes are always larger than permeability changes. It is proved by the thick wall cylinder theory that the second power parabola relation between porosity or permeability loss and effective

关键词： geo-stress fields, seepage fields, tri-porosity media, effective stresses, permeability, porosity,scale.

Study on two-phase countercurrent flow and transport phenomenon in PEM of a direct methanol fuel cell

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Science China(Technological Sciences) 2006年第1期49卷 102-114页

作者： WANG Jiang SHI Mingheng Department of Power Engineering Southeast University Nanjing 210096 China Department of Power Engineering Southeast University Nanjing 210096 China

Based on the requirement of water management for a direct methanol fuel cell, this paper analyzes qualitatively the mechanism of occurrence and development of a two-phase countercurrent flow with corresponding transport phenomenon in the PEM. A one-dimensional, steady state quantitative model of heat and mass transfer in internal volumetric ohmic heating porous media saturated by liquid and vapor phases is developed. The effects of capillarity, electro-osmotic drag and phase change are included. Two im-portant formulas to calculate the theoretical length of two-phase zone δ t and determine the critical criterion |?ω /γ |cr for dryout in PEM are deduced. By use of these two dimen-sionless parameters, dryout of PEM can be easily predicted. Theoretical temperature, pressure and saturation profiles within the two-phase region are obtained numerically, which can help to explore the performance of a DMFC operating in its ohmic polarization region. The simulation results can be used to determine the catalyst content of cathode catalyst layer and the corresponding optimal thickness of PEM.

关键词： direct methanol fuel cell, porous media, two-phase countercurrent flow, dryout.

Determination of effective thermal conductivity for polyurethane foam by use of fractal method

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Science China(Technological Sciences) 2006年第4期49卷 468-475页

作者： SHI Mingheng LI Xiaochuan CHEN Yongping Department of Power Engineering Southeast University Nanjing 210096 China Department of Power Engineering Southeast University Nanjing 210096 China Department of Power Engineering Southeast University Nanjing 210096 China

The microstructure of polyurethane foam is disordered, which influences the foam heat conduction process significantly. In this paper foam structure is described by using the local area fractal dimension in a certain small range of length scales. An equivalent element cell is constructed based on the local fractal dimensions along the directions parallel and transverse to the heat flux. By use of fractal void fraction a simpli- fied heat conduction model is proposed to calculate the effective thermal conductivity of polyurethane foam. The predicted effective thermal conductivity agrees well with the ex- perimental data.

关键词： polyurethane foam, porous media, thermal conductivity, fractal.