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Estimation of Hydrate Inhibitor Loss in Hydrocarbon Liquid Phase

PETROLEUM SCIENCE AND TECHNOLOGY 2009年第9期27卷 943-951页

作者： Bahadori, A. Curtin Univ Technol Dept Chem Engn Perth WA 6845 Australia

The amount of hydrate inhibitor to be injected in the gas processing and transmission system to avoid hydrate formation not only must be sufficient to prevent freezing of the inhibitor in the water phase but also must be sufficient to provide for the equilibrium vapor phase content of the inhibitor and the loss of the inhibitor in any liquid hydrocarbon. In this article, a new numerical algorithm is developed for estimation of loss of methanol in paraffinic hydrocarbons at various temperatures and methanol concentrations in the water phase The predicted values showed good agreement with the reported data. The solubility of methanol in paraffin hydrocarbons is calculated for temperatures in the range of 240 to 320K and methanol concentrations up to 70% in the water phase, where the average absolute deviation is around 4%.

关键词： correlation gas hydrate hydrate inhibitor methanol natural gas numerical algorithm

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On the plastic flow rule formulation in anisotropic yielding aluminium alloys

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INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2018年第1-4期99卷 255-274页

作者： Mendiguren, Joseba Galdos, Lander Saenz de Argandona, Eneko Mondragon Unibertsitatea Dept Mech & Ind Prod Loramendi 4 Arrasate Mondragon 20500 Gipuzkoa Spain

In the last decade, an increasing trend has been observed in the use of advanced anisotropic material models to improve the numerical predictions about sheet metal-forming processes. Among the actions following this trend, the use of non-associated flow rule (NAFR) models has been presented as an alternative to the classic associated flow rule (AFR) models. In this work, the influence of the flow rule in advanced anisotropic models has been analysed, following a systematic methodology. To evaluate both advantages and disadvantages of the flow rule, models with similar flexibility (i.e. with 8 and 16 parameters) have been compared by performing a finite element (FE) simulation of a cup-drawing process to study earing phenomena regarding accuracy, computational time and complexity. From the present study, it has been concluded that the main drivers on the final cup-drawing profile prediction are the model flexibility and the coefficient selection rather than the flow rule. Even though the NAFR formulation is complex when compared to the AFR regarding numerical implementation, this study shows that the total simulation time in a cup-drawing process while using explicit FE solvers is reduced in some cases, this one being strongly dependent on the material parameter definition.

关键词： Yield condition Anisotropic material Constitutive behaviour Metallic material numerical algorithm Non-associated flow rule

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An Adjoint-Based Hybrid Computational Method for Crosswell Seismic Inversion

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COMPUTING IN SCIENCE & ENGINEERING 2014年第6期16卷 60-67页

作者： Cao, Danping Liao, Wenyuan China Univ Petr Sch Geosci Huadong Peoples R China Univ Calgary Calgary AB T2N 1N4 Canada

Here, a cascade-like hybrid tomography technology is proposed to solve the crosswell seismic inversion problem. This new method combines several widely used tomography technologies, implemented in a sequence starting with the Radon-transform-based back-projection method, then the Linear Iterative Reconstruction method, next the nonlinear Gradient-based Eikonal Equation Tomography method, and finally full waveform inversion.

关键词： Radon transforms conjugate gradient methods geophysical techniques geophysics computing nonlinear equations seismology FWI Radon-transform-based back-projection method adjoint-based hybrid computational method cascade-like hybrid tomography technology crosswell seismic inversion problem full-waveform inversion linear iterative reconstruction method nonlinear-gradient-based Eikonal equation tomography method ray tomography methods selective internal radiation therapy velocity model reconstruction waveform tomography Computational modeling Iterative methods Mathematical model numerical models Seismic measurements Subspace constraints Tomography FWI GEET LIR algorithm design back projection inverse problem numerical algorithm ray tomography scientific computing waveform tomography

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A new interpolative homogenization model for evaluation of the effective elasto-plastic responses of two-phase composites

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COMPOSITE STRUCTURES 2019年 210卷 810-821页

作者： Tian, Wenlong Qi, Lehua Chao, Xujiang Liang, Junhao Fu, M. W. Northwestern Polytech Univ Sch Mech Engn Xian 710072 Shaanxi Peoples R China Hong Kong Polytech Univ Dept Mech Engn Hung Hom Kowloon Hong Kong Peoples R China Northwestern Polytech Univ Sch Mat Sci & Engn Xian 710072 Shaanxi Peoples R China

To accurately predict the effective elasto-plastic responses of two-phase composites, an interpolative M-T/D-I mean-field homogenization model with the tangent formulation is proposed, and the numerical implementation algorithm of the proposed M-T/D-I model with the tangent formulation is presented. The comparisons between the effective elastic properties and elasto-plastic responses of two-phase composites predicted by the M-T/D-I model with the tangent formulation and the RVE based FE homogenization method show that the M-T/D-I model with the tangent formulations can accurately evaluate the effective mechanical properties of two-phase composites. The simulation results demonstrate that the elastic properties of two-phase composites predicted by the M-T/D-I model are more accurate than those predicted by the D-I and M-T models, and the effective elastoplastic responses of two-phase composites predicted by the M-T/D-I model vary in the range of those predicted by the D-I and M-T models. It is revealed that the M-T/D-I model with the tangent formulation allows to simulate the tensile/compression and biaxial tensile/shear elasto-plastic responses of two-phase composites. Lastly, the effects of the inclusion volume fraction and elastic properties on the effective elasto-plastic responses of two-phase composites are discussed for showing the capability of the proposed interpolative M-T/D-I model with the tangent formulation.

关键词： Elasto-plastic response FE homogenization Interpolative M-T/D-I model Micro-mechanics numerical algorithm Tangent formulation

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Sparse representation via optimal matching convolution framelets

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IET SIGNAL PROCESSING 2018年第9期12卷 1082-1090页

作者： Wang, Zelong Zhu, Jubo Natl Univ Def Technol Coll Liberal Arts & Sci Changsha 410073 Hunan Peoples R China

Recently, a tight frame, called convolution framelets (CFs) and constructed by convolving local and non-local bases, is proposed to provide valuable insights in understanding the patch-based processing approaches in the viewpoint of sparse representation (SR). However, it is still unclear how to represent signals with energy concentration guarantee in its lifted space and how to optimise the local base for a given non-local base. To address these issues, the equivalence between the signal space and its lifted space is established by the Hankel operator. In the lifted space, the energy concentration property of signals is measured by the sparsity instead of the Euclidean norm and the rank. With the new objective function, an optimisation model is built to train the optimal local base for a given nonlocal base from the training samples, motivating us to propose the optimal matching convolution framelets (OMCFs). In addition, a numerical algorithm is also designed to solve the proposed model using alternating optimisation strategy. The OMCF for SR is tested on the speech signals, and the comparisons with traditional popular SR tools, such as discrete cosine transform (DCT) and Haar wavelets, demonstrate its better performance.

关键词： speech processing signal representation convolution optimisation Hankel matrices sparse representation optimal matching convolution framelets local basis nonlocal basis patch-based processing approaches signal representation energy concentration Hankel operator signal space energy concentration property objective function optimisation model OMCF numerical algorithm alternating optimisation strategy speech signals

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Computing the stationary distribution of an SRBM in an orthant with applications to queueing networks

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QUEUEING SYSTEMS 2003年第1期45卷 27-45页

作者： Chen, H Shen, XY Cheung Kong Grad Sch Business Beijing 100738 Peoples R China MarketRx Bridgewater NJ 07060 USA Univ British Columbia Fac Commerce & Business Adm Vancouver BC V5Z 1M9 Canada Chinese Univ Hong Kong Dept Syst Engn & Engn Management Hong Kong Hong Kong Peoples R China

In [15], a BNAfm (Brownian network analyzer with finite element method) algorithm was developed for computing the stationary distribution of a semimartingale reflecting Brownian motion (SRBM) in a hypercube. In this companion paper, that BNAfm algorithm is extended to computing the stationary distribution of an SRBM in an orthant, which is achieved by constructing a converging sequence of SRBMs in hypercubes. The SRBM in the orthant serves as an approximation model of queueing networks with infinite buffers. We show that the constructed sequence of SRBMs in the hypercubes converges weakly to the SRBM in the orthant as the hypercubes approach the orthant. Under the conjecture that the set of the stationary distributions of the SRBMs in the hypercubes is relatively compact, we prove that the sequence of the stationary distributions of the SRBMs in the hypercubes converges weakly to the stationary distribution of the SRBM in the orthant. A three-machine job shop example is presented to illustrate the effectiveness of the SRBM approximation model and our BNAfm algorithm. The BNAfm algorithm is shown to produce good estimates for stationary probabilities of queueing networks.

关键词： Brownian approximation heavy traffic semimartingale reflecting Brownian motion stationary distribution performance analysis queueing networks finite buffer infinite buffer finite element method BNAfm BNAsm basic adjoint relationship numerical algorithm

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A NOVEL METHOD FOR NONLINEAR IMPULSIVE DIFFERENTIAL EQUATIONS IN BROKEN REPRODUCING KERNEL SPACE

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Acta Mathematica Scientia 2020年第3期40卷 723-733页

作者： Liangcai MEI Zhuhai Campus Beijing Institute of TechnologyZhuhai 519088China

In this article,a new algorithm is presented to solve the nonlinear impulsive differential *** the first time,this article combines the reproducing kernel method with the least squares method to solve the second-order nonlinear impulsive differential ***,the uniform convergence of the numerical solution is proved,and the time consuming Schmidt orthogonalization process is *** algorithm is employed successfully on some numerical examples.

关键词： Nonlinear impulsive differential equations Broken reproducing kernel space numerical algorithm

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Non-symbolic algorithms for the inversion of tridiagonal matrices

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JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS 2013年 252卷 3-11页

作者： Abderraman Marrero, J. Rachidi, M. Tomeo, V. Tech Univ Madrid ETSIT UPM Telecommun Engn Sch Dept Math Appl Informat Technol Madrid 28040 Spain Univ Moulay Ismail Fac Sci Dept Math & Informat Grp DEFA Beni Mhamed Meknes Morocco Univ Complutense EUE UCM Sch Stat Dept Algebra E-28040 Madrid Spain

A representation for the entries of the inverse of general tridiagonal matrices is based on the determinants of their principal submatrices. It enables us to introduce, through the linear recurrence relations satisfied by such determinants, a simple algorithm for the entries of the inverse of any tridiagonal nonsingular matrix, reduced as well as unreduced. The numerical approach is preserved here, without invoking the symbolic computation. For tridiagonal diagonally dominant matrices, a scaling transformation on the recurrences allows us to give another algorithm to avoid overflow and underflow. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Computational complexity Difference equation Inverse matrix numerical algorithm Tridiagonal matrix

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Simplified reproducing kernel method and convergence order for linear Volterra integral equations with variable coefficients

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JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS 2019年 346卷 390-398页

作者： Mei, Liangcai Lin, Yingzhen Beijing Inst Technol Zhuhai Campus Zhuhai 519088 Peoples R China

This paper proposes a simplified reproducing kernel method to solve the linear Volterra integral equations with variable coefficients. The main idea of the method is to establish a reproducing kernel direct space that can be used in Volterra integral equations. And in the first time, this paper analyzes the convergence order and stability of the approximate solution. Then the uniform convergence of the numerical solution is proved, and the time consuming Schmidt orthogonalization process is avoided. The proposed method is proved to be stable and is not less than the second order convergence. The algorithm is proved to be feasible and stable through some numerical examples. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Volterra integral equations Reproducing kernel direct space Convergence order Stability analysis numerical algorithm

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Reconstructing discontinuities using complex geometrical optics solutions

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SIAM JOURNAL ON APPLIED MATHEMATICS 2008年第4期68卷 1026-1044页

作者： Uhlmann, Gunther Wang, Jenn-Nan Univ Washington Dept Math Seattle WA 98195 USA Natl Taiwan Univ Dept Math Taida Inst Math Sci Taipei 106 Taiwan NCTS Taipei 106 Taiwan

In this paper we provide a framework for constructing general complex geometrical optics solutions for several systems of two variables that can be reduced to a system with the Laplacian as the leading order term. We apply these special solutions to the problem of reconstructing inclusions inside a domain filled with known conductivity from local boundary measurements. Computational results demonstrate the versatility of these solutions to determine electrical inclusions.

关键词： geometrical optics inclusions numerical algorithm

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