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A simplified method for predicting the penetration distance of cementing slurry in gas hydrate reservoirs around wellbore

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JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING 2018年 52卷 348-355页

作者： Fang, Changliang Zheng, Mingming Lu, Hongzhi Liu, Tianle Jiang, Guosheng Wu, Bisheng China Univ Geosci Fac Engn Wuhan 430074 Hubei Peoples R China Chengdu Univ Technol State Key Lab Geohazard Prevent & Geoenvironm Pro Chengdu 610059 Sichuan Peoples R China CSIRO Energy Melbourne Vic Australia

The permafrost region in the Qinghai-Tibet Plateau of China is abundant in natural gas hydrate (NGH) resources. In this region, there is a great probability of meeting gas hydrate when conducing conventional oil and gas well cementation operations. Because of the relatively developed fractures and not very high pore pressure (usually 3.5-3.6 MPa) in the gas hydrate reservoirs in this area, it is easy for the cementing slurry to penetrate into the gas hydrate reservoirs under the pressure difference during cementing process, undergo hydration and release heat, thus causing hydrate dissociation and cementing quality reduction or even failure. Therefore, it is necessary to first determine the penetration distance of the cementing slurry in the gas hydrate reservoirs to evaluate the effect of hydration of the cementing slurry on the hydrate stability in the reservoirs. In this paper, theoretical and experimental methods for determining the penetration distance value of cementing slurry were established for the first time. The permafrost layer in the Muli area of the Qinghai-Tibet Plateau was selected as the research object and the proposed computational model was verified by using low-density cementing slurry and common cementing process experiments. The results show that the penetration distance calculated by the established computational model is in good agreement with that measured in the experiment, and the computational model can provide technical support for the cementing process design in gas hydrate occurrence area.

关键词： Gas hydrate Cementing Cement hydration Penetration distance computational method Simulation experiment

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A new method for formulation of dynamic responses of shallow foundations in simple general form

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SOIL DYNAMICS AND EARTHQUAKE ENGINEERING 2005年第7-10期25卷 679-688页

作者： Nogami, T Al Mahbub, A Chen, SH Natl Univ Singapore Dept Civil Engn Singapore 117576 Singapore

A single uniform rectangular area, either homogeneous or heterogeneous, is considered in a soil medium (fundamental cell). Two governing ordinary differential equations in special form are developed for the fundamental cell. The ground supporting a partially embedded foundation is divided into a number of coarse rectangular areas (secondary cells). Each secondary cell is treated as either a single fundamental cell for homogeneous ground or a stack of fundamental cells for inhomogeneous ground. Differential equations for the assembly of secondary cells are formed with those for the fundamental cells. These equations lead to the soil responses in each cell expressed in simple closed form. They also lead to the convenient treatment of soil with appropriate Winkler-type models along the foundation faces and concentrated forces acting at the foundation corners. With them, the foundation responses are finally expressed in simple closed form. The approach is demonstrated for various cases and confirmed to produce the results reasonable enough for civil engineering use. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： foundation inhomogeneous soil vibrations computational method

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Bending analysis of simply supported rectangular laminated composite plates using a new computation method based on analytical solution of layerwise theory

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ARCHIVE OF APPLIED MECHANICS 2018年第5期88卷 671-689页

作者： Rakocevic, Marina Popovic, Svetislav Univ Montenegro Fac Civil Engn Cetinjski Put Bb Podgorica 81000 Montenegro Europoles Ingolstadter Str 51 D-92318 Neumarkt In Der Oberpfal Germany

This paper presents the analysis of simply supported rectangular laminated composite plates loaded perpendicularly to the middle plane using a new computational method based on Reddy's layerwise theory. The stress-strain analysis was based on the analytical solution of equations of the layerwise theory, where the plates with an antisymmetric layer arrangement were analysed. Each of the layers contains continuous fibres oriented in one of two mutually orthogonal directions. The results obtained by applying above-mentioned computational procedure have been compared with the results obtained using three different models of finite elements of the ANSYS software package. The quantified limits of the computational method in terms of the impact of plate thickness, the number of layers and the aspect ratio of the plate on the accuracy, convergence and stability of primary variables-components of displacement, and secondary variables-components of stress, have been analysed in the paper.

关键词： Laminated plates Layerwise theory Analytical solution computational method

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Nonlinear micromechanical formulation of the high fidelity generalized method of cells

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INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES 2009年第13期46卷 2577-2592页

作者： Haj-Ali, Rami Aboudi, Jacob Tel Aviv Univ Fac Engn Sch Mech Engn IL-69978 Ramat Aviv Israel

The recent High Fidelity Generalized method of Cells (HFGMC) micromechnical modeling framework of multiphase composites is formulated in a new form which facilitates its computational efficiency that allows an effective multiscale material-structural analysis. Towards this goal, incremental and total formulations of the governing equations are derived. A new stress update computational method is established to solve for the nonlinear material constituents along with the micromechanical equations. The method is well-suited for multiaxial finite increments of applied average stress or strain fields. Explicit matrix form of the HFGMC model is presented which allows an immediate and convenient computer implementation of the offered method. In particular, the offered derivations provide for the residual field vector (error) in its incremental and total forms along with an explicit expression for the Jacobian matrix. This enables the efficient iterative computational implementation of the HFGMC as a stand alone. Furthermore, the new formulation of the HFGMC is used to generate a nested local-global nonlinear finite element analysis of composite materials and structures. Applications are presented to demonstrate the efficiency of the proposed approach. These include the behavior of multiphase composites with nonlinearly elastic, elastoplastic and viscoplastic constituents. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Micromechanical analysis computational method Nonlinear multiphase composites High fidelity generalized method of cells

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Drug-motif-based diverse monomer selection: method and application in combinatorial chemistry

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JOURNAL OF MOLECULAR GRAPHICS & MODELLING 1997年第1期15卷 43-&页

作者： Lewell, XQ Smith, R Glaxo Wellcome Research and Development Stevenage Herts U.K.

This article describes a strategy to explore monomer diversity while incorporating drug motif knowledge into the design and selection of monomers for combinatorial chemistry. The process involves collecting from available electronic databases all those molecules that potentially could be monomers. In this manner we have assembled five DAYLIGHT databases, each containing one of the common functional groups: carboxylic acids, aldehydes, nitriles, pri mary amines, and secondary amines. The molecules in the databases are then subjected to fingerprint and cluster analysis using the Jarvis-Patrick algorithm and profiles of the compounds are calculated relating to molecular weight, H-bond counts, and rotatable bond flexibility. The cluster information and profiles of the molecules are stored back into the databases for similarity and diversity searches, and for profile prescreening of monomers. To apply drug motif knowledge to a selection an application to an aldehyde set is discussed, in which representatives of each cluster in the aldehyde database are compared with drug molecules in the Standard Derwent File (SDF) in one of three ways to select drug motif-based monomers for purchase or synthesis. (C) 1997 by Elsevier Science Inc.

关键词： drug motif monomer selection combinatorial chemistry computational method database

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Explicit versus implicit method for radiative heat transfer in gray and diffuse enclosures

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2012年第13-14期55卷 3829-3833页

作者： Dama, Alessandro Lastaria, Federico Politecn Milan Dept Energy I-20156 Milan Italy Politecn Milan Dept Math I-20133 Milan Italy

The paper presents an explicit formulation of the radiative problem in gray enclosures. The method is based on a series expansion that derives the mutual radiation factors by means of summation of the contributions to the radiative thermal exchange given by the multi-reflection process. A mathematical proof that the infinite expansion converges to the well known solution, given by the implicit formulation and based on radiosities balance, is provided. Moreover a parametric analysis of the approximation induced by the explicit algorithm, as a result of the truncation order in the calculation of the series expansion, is carried out. The analysis shows how the precision of every approximation order is mainly related to the surface averaged infrared reflectance and is weakly dependent on the reflectance distribution. For high emissive and low reflecting surfaces, very few summations are required to meet high precision;the same level of precision is achievable also with medium and high reflecting surfaces, by increasing the truncation order of the series. More generally, the explicit formulation provides an alternative approach to problems involving multi-reflecting cavities in different engineering applications, from heat transfer to optics. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： computational method Radiative heat transfer Reflective enclosures

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Lattice Boltzmann method for compressible Euler equations based on exact kinetic system

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INTERNATIONAL JOURNAL FOR NUMERICAL methodS IN FLUIDS 2021年第8期93卷 2554-2569页

作者： Hanada, Takaya Kataoka, Takeshi Kobe Univ Rokkodai Grad Sch Engn Kobe Hyogo Japan

We have developed a new type of simple lattice Boltzmann (LB) model for the compressible Euler equations based on the collisionless kinetic-equation approach proposed by Sone. The model uses the collisionless kinetic equation in the streaming process, and modifies the distribution function to its Chapman-Enskog type at each time step. Compared with the current LB models which solve the kinetic equation of the BGK type, the proposed model is superior in the following two points: (i) Inviscid flows can be computed stably while there is no such model in the current LBM;(ii) The velocity distribution function does not need to be memorized in computation. We calculate various inviscid compressible flows described by the compressible Euler equations using our new one-, two-, and three-dimensional models. Numerical results show the capability of our scheme to simulate high-speed supersonic flows with shock waves.

关键词： compressible flow computational method Euler flow lattice Boltzmann shock wave supersonic

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Numerical split-shift potential method for relativistic quantum systems with radial symmetry

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JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 2016年第6期49卷 1-9页

作者： Lv, Q. Z. Norris, S. Su, Q. Grobe, R. Chinese Acad Sci Beijing Natl Lab Condensed Matter Phys Inst Phys Beijing 100190 Peoples R China Illinois State Univ Intense Laser Phys Theory Unit Normal IL 61790 USA Illinois State Univ Dept Phys Normal IL 61790 USA

We show how the spectrum of a radially symmetric Dirac Hamiltonian can be computed rather accurately on a spatial grid using a split-shift potential method. This method is sufficiently accurate such that the fine structure splittings of hydrogen-like relativistic ions with nuclear charge Z can be reproduced for a relatively small number of spatial radial grid points. We use this analytically known spectrum to examine the error scaling of this method. The method is then applied to examine the impact of a spatial confinement on the fine structure splittings and the bound states for hydrogen.

关键词： computational method Dirac equation atoms in strong fields

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Three dimensional thermal diffusion in anisotropic heterogeneous structures simulated by a non-dimensional lattice Boltzmann method with a controllable structure generation scheme based on discrete Gaussian quadrature space and velocity

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2017年第PartA期108卷 386-401页

作者： Su, Yan Ng, Tiniao Zhang, Yinping Davidson, Jane H. Univ Macau FST Dept Elect Engn Taipa Macau Peoples R China Tsinghua Univ Dept Bldg Sci Beijing 100084 Peoples R China Univ Minnesota Dept Mech Engn Minneapolis MN 55455 USA

A new Controllable Structure Generation Scheme (CSGS) based on discrete Gaussian quadrature space and velocity is presented and used to generate multiple-phase random isotropic homogenous and shape-constrained anisotropic heterogeneous structures. The primary advantage of the new CSGS over the existing random structure generation growth method is the ability to model a wide variety of structures by controlling the shape through relatively simple constraint indexes. The growth speed probability function is introduced to control the mesoscopic porosities and mixture/separation of material phases. The model is applied to generate four packed structure types (shapeless random, separated solid shapes, separated random-filled shapes, and random-mixture-filled shapes). Three-dimensional steady and transient thermal diffusion are simulated by Non-Dimensional Lattice Boltzmann method (NDLBM). The steady state results are compared to measured data available in the published literature. The transient results reveal how the mesoscopic shape of a structure impacts thermal diffusion. With equivalent macroscopic volume fractions, structures with higher mesoscopic volume fractions of high conductivity phases possess higher effective thermal conductivity/diffusivity because there is greater connectivity of the higher conductive material at mesoscopic scale. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： computational method Multi-phase Porous medium Thermal diffusion

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method for building databases of electro-optical parameters for calculating the spectral properties of nano-objects

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JOURNAL OF APPLIED SPECTROSCOPY 2013年第6期79卷 955-961页

作者： Gribov, L. A. Dementiev, V. A. Russian Acad Sci VI Vernadsky Inst Geochem & Analyt Chem Moscow 119991 Russia

This is a discussion of the theoretical basis for the optimum number and values of electro-optical parameters for inclusion in databases for calculating the spectral properties of nano-objects with specified microstru... 详细信息

关键词： spectrum nano-object computational method spectral analysis

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