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Inverse methodology to determine mold set-point temperature in resin transfer molding process

INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2010年第11期49卷 2138-2147页

作者： Sobotka, Vincent Lefevre, Nicolas Jarny, Yvon Delaunay, Didier Nantes Atlantique Univ Ecole Polytech Univ Nantes Lab Thermocinet Nantes UMR CNRS 6607 F-44306 Nantes 03 France

This study consists of determining by inverse method the set-point temperature of the fluid flowing through heating plates in a Resin Transfer Molding (RIM) process tool so as to reach a predetermined thermal history in the composite part. Although the described methodology is applied in a specific mold in this paper, it remains general and may be transposed to a large scale of molding configuration. The considered mold is metallic and composed of several parts. Assembling these parts is not possible without introducing imperfect contacts that perturb heat transfer between them. The heat transfer at the interface is modeled by thermal contact resistances (TCR) whose values are unknown. In the case of metallic molds TCR are of the same order of magnitude than the equivalent thermal resistance of the mold. Therefore they cannot be neglected. The influence of these TCR is then a key-point on heat transfer since a bad knowledge of their values implies a wrong estimation of the temperature field. Then before being able to estimate the set-point of the temperature of the thermoregulated fluid, it is necessary in a first stage to evaluate the most influent TCR that are spatially and time dependent. Their determination is achieved by an optimization approach and carried out on a 2D transverse cut of the mold. Experimental temperature measurements in the mold are matched to the computed responses of the heat conduction model. A least square criterion is minimized by using the conjugate gradient algorithm. The gradient of the criterion is determined by solving a set of adjoint equations. After the identification of these parameters, the same optimization method is used to compute the mold set point temperature. It is notable that the same set of adjoint equations is used to solve both problems. (C) 2010 Elsevier Masson SAS. All rights reserved.

关键词： Resin transfer molding Inverse method Adjoint problem Composite material Two dimensional heat transfer Parameter estimation conjugate gradient algorithm Thermal control

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Estimation of dynamic origin-destination trip tables for a general network

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TRANSPORTATION RESEARCH PART B-METHODOLOGICAL 2001年第3期35卷 217-235页

作者： Sherali, HD Park, T Virginia Polytech Inst & State Univ Dept Ind & Syst Engn 0118 Blacksburg VA 24061 USA

In this paper, we propose a parametric optimization approach to estimate time-dependent path flows, or origin-destination (OD) trip tables, using available data on link traffic volumes for a general road network. Our model assumes knowledge of certain time-dependent link flow contribution factors that are a dynamic generalization of the path-link incidence matrix for the static case. A least squares model is accordingly formulated to determine the time-dependent trip tables. We develop a column generation approach that uses a sequence of dynamic shortest path subproblems in order to solve this problem. Computational results are presented on several variants of two sample test networks from the literature. (C) 2001 Elsevier Science Ltd. All rights reserved.

关键词： dynamic origin-destination trip tables time-dependent flows column generation approach conjugate gradient algorithm

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Mixed L²-Wasserstein optimal mapping between prescribed density functions

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JOURNAL OF OPTIMIZATION THEORY AND APPLICATIONS 2001年第2期111卷 255-271页

作者： Benamou, JD Brenier, Y INRIA Le Chesnay France Univ Paris 06 Anal Numer Lab F-75252 Paris France

A time-dependent minimization problem for the computation of a mixed L-2-Wasserstein distance between two prescribed density functions is introduced in the spirit of Ref. 1 for the classical Wasserstein distance. The optimum of the cost function corresponds to an optimal mapping between prescribed initial and final densities. We enforce the final density conditions through a penalization term added to our cost function. A conjugate gradient method is used to solve this relaxed problem. We obtain an algorithm which computes an interpolated L-2-Wasserstein distance between two densities and the corresponding optimal mapping.

关键词： Monge-Kantorovitch mass transfer problem Wasserstein distance least-square distance optimal control conjugate gradient algorithm

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UNIFIED FORMULATION OF DYNAMICS FOR SERIAL RIGID MULTIBODY SYSTEMS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1991年第3期14卷 531-542页

作者： JAIN, A JPL Pasadena CA

There has been a growing interest in the development of new and efficient algorithms for multibody dynamics in recent years. Serial rigid multibody systems form the basic subcomponents of general multibody systems, and a variety of algorithms to solve the serial chain forward dynamics problem have been proposed. In this paper, the economy of representation and analysis tools provided by the spatial operator algebra are used to clarify the inherent structure of these algorithms, to identify those that are similar, and to study the relationships among the ones that are distinct. For the purposes of this study, the algorithms are categorized into three classes: algorithms that require the explicit computation of the mass matrix, algorithms that are completely recursive in nature, and algorithms of intermediate complexity. In addition, alternative factorizations for the mass matrix and closed form expressions for its inverse are derived. These results provide a unifying perspective, within which these diverse dynamics algorithms arise naturally as a consequence of a progressive exploitation of the structure of the mass matrix.

关键词： Multibody Dynamics conjugate gradient algorithm Computing Kalman Filter conjugate gradient Method D'Alembert's Principle Euler Equations Boundary Value Problems Gaussian Elimination Lyapunov Equation

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An adaptive nonmonotone active set - weight constrained - neural network training algorithm

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NEUROCOMPUTING 2019年 360卷 294-303页

作者： Livieris, Ioannis E. Pintelas, Panagiotis Univ Patras Dept Math GR-26500 Patras Greece

In this work, a new direction for improving the classification accuracy of artificial neural networks is proposed by bounding the weights of the network, during the training process. Furthermore, a new adaptive nonmonotone active set - weight constrained - neural network training algorithm is proposed in order to demonstrate the efficacy and efficiency of our approach. The proposed training algorithm consists of two phases: a gradient projection phase which utilizes an adaptive nonmonotone line search and an unconstrained optimization phase which exploits the box structure of the bounds. Also, a set of switching criteria is defined for efficiently switching between the two phases. Our preliminary numerical experiments illustrate that the classification efficiency of the proposed algorithm outperforms classical neural network training algorithms, providing empirical evidence that it provides more stable, efficient and reliable learning. (C) 2019 Elsevier B.V. All rights reserved.

关键词： Artificial neural networks Constrained optimization Weight bounds ASA method conjugate gradient algorithm Accuracy

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Neural Volterra filter for chaotic time series prediction

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CHINESE PHYSICS 2005年第11期14卷 2181-2188页

作者： Li, HC Zhang, JS Xiao, XC SW Jiaotong Univ Sichuan Prov Key Lab Signal & Informat Proc Chengdu 610031 Peoples R China Univ Elect Sci & Technol China Dept Elect Engn Chengdu 610054 Peoples R China

A new second-order neural Volterra filter (SONVF) with conjugate gradient (CG) algorithm is proposed to predict chaotic time series based on phase space delay-coordinate reconstruction of chaotic dynamics system in this paper, where the neuron activation functions are introduced to constraint Volterra series terms for improving the nonlinear approximation of second-order Volterra filter (SOVF). The SONVF with CG algorithm improves the accuracy of prediction without increasing the computation complexity. Meanwhile, the difficulty of neuron number determination does not exist here. Experimental results show that the proposed filter can predict chaotic time series effectively, and one-step and multi-step prediction performances are obviously superior to those of SOVF, which demonstrate that the proposed SONVF is feasible and effective.

关键词： chaotic time series adaptive neural Volterra filter conjugate gradient algorithm

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Estimation of boundary condition of two-dimensional nonlinear PDE with application to continuous casting

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COMPUTERS & MATHEMATICS WITH APPLICATIONS 2020年第12期80卷 3082-3097页

作者： Yu, Yang Luo, Xiaochuan Wang, Yuan (Yulin) Zhang, Huaxi Shenyang Aerosp Univ Sch Automat Shenyang 110136 Peoples R China Shanghai Univ Sch Mech Engn & Automat Shanghai 200072 Peoples R China Northeastern Univ Coll Informat Sci & Engn Shenyang 110819 Peoples R China Northeastern Univ State Key Lab Synthet Automat Proc Ind Shenyang 110819 Peoples R China Chinese Univ Hong Kong Sch Sci & Engn Shenzhen 518172 Peoples R China Univ Picardie Jules Verne LTI Lab F-80025 St Quentin en Yvelines France

Solidification heat transfer process of billet is described by nonlinear partial differential equation (PDE). Due to the poor productive environment, the boundary condition of this nonlinear PDE is difficult to be fixed. Therefore, the identification of boundary condition of two-dimensional nonlinear PDE is considered. This paper transforms the identification of boundary condition into a PDE optimization problem. The Lipchitz continuous of the gradient of cost function is proved based on the dual equation. In order to solve this optimization problem, this paper presents a modified conjugate gradient algorithm, and the global convergence of which is analyzed. The results of the simulation experiment show that the modified conjugate gradient algorithm obviously reduces the iterative number and running time. Due to the ill-posedness of the identification of boundary condition, this paper combines regularization method with the modified conjugate gradient algorithm. The simulation experiment illustrates that regularization method can eliminate the ill-posedness of this problem. Finally, the experimental data of a steel plant illustrate the validity of this paper's method. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： PDE optimization problem Ill-posedness Lipchitz continuous conjugate gradient algorithm Regularization method

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Deformable Overset Grid for Multibody Unsteady Flow Simulation

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AIAA JOURNAL 2016年第8期54卷 2392-2406页

作者： Xiao, Tianhang Qin, Ning Luo, Dongming Deng, Shuanghou Nanjing Univ Aeronaut & Astronaut Coll Aeronaut & Astronaut 29 Yudao St Nanjing 210016 Jiangsu Peoples R China Univ Sheffield Dept Mech Engn Mappin St Sheffield S1 3JD S Yorkshire England Delft Univ Technol Fac Aerosp Engn Kluyverweg 1 NL-2629 HS Delft Netherlands

A deformable overset grid method is proposed to simulate the unsteady aerodynamic problems with multiple flexible moving bodies. This method uses an unstructured overset grid coupled with local mesh deformation to achieve both robustness and efficiency. The overset grid hierarchically organizes the subgrids into clusters and layers, allowing for overlapping/embedding of different type meshes, in which the mesh quality and resolution can be independently controlled. At each time step, mesh deformation is locally applied to the subgrids associated with deforming bodies by an improved Delaunay graph mapping method that uses a very coarse Delaunay mesh as the background graph. The graph is moved and deformed by the spring analogy method according to the specified motion, and then the computational meshes are relocated by a simple one-to-one mapping. An efficient implicit hole-cutting and intergrid boundary definition procedure is implemented fully automatically for both cell-centered and cell-vertex schemes based on the wall distance and an alternative digital tree data search algorithm. This method is successfully applied to several complex multibody unsteady aerodynamic simulations, and the results demonstrate the robustness and efficiency of the proposed method for complex unsteady flow problems, particularly for those involving simultaneous large relative motion and self-deformation.

关键词： Compressible Flow Aerodynamic Simulation Search algorithm Reynolds Averaged Navier Stokes Flexible Wings Wingtip Vortices conjugate gradient algorithm Rigid Wings Unstructured Grid Camber

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Grating profile reconstruction based on finite elements and optimization techniques

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SIAM JOURNAL ON APPLIED MATHEMATICS 2003年第2期64卷 525-545页

作者： Elschner, J Hsiao, GC Rathsfeld, A Weierstr Inst Angew Anal & Stochast D-10117 Berlin Germany Univ Delaware Dept Math Sci Newark DE 19716 USA

We consider the inverse diffraction problem to recover a two-dimensional periodic structure from scattered waves measured above and beneath the structure. The task is reformulated in the form of an optimization problem including special regularization terms. The solvability and the dependence on the parameter of regularization is analyzed. Numerical results for synthetic data demonstrate the practicability of the inversion algorithm.

关键词： difraction grating profile reconstruction optimization method conjugate gradient algorithm

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An Efficient Broadband Adaptive Beamforming algorithm Based on Frequency-Space Cascade Processing

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CIRCUITS SYSTEMS AND SIGNAL PROCESSING 2018年第1期37卷 432-443页

作者： Hu, Pei Shen, Mingwei Liang, Chao Wu, Di Zhu, Daiyin Hohai Univ Coll Comp & Informat Engn 8Focheng Xi Rd Nanjing Jiangsu Peoples R China Sci & Technol Elect Informat Control Lab 493Yingkang Xi Rd Chengdu Sichuan Peoples R China Nanjing Univ Aeronaut & Astronaut Key Lab Radar Imaging & Microwave Photon 29Jiangning Dist Nanjing Jiangsu Peoples R China

In this paper, the performance loss caused by the aperture fill phenomena and heavy computational burden in broadband adaptive beamforming (ADBF) is analyzed, and an efficient approach based on frequency-space cascade processing is presented. First, a digital compensation method is applied to compensate for the aperture fill time of the broadband phased array in the range-frequency domain, removing the dependence of the wideband array steering vector on the instantaneous frequency. Second, a subband adaptive beamforming scheme using range-compressed data is implemented, reducing the degrees of freedom of wideband jamming and avoiding signal cancelation in the ADBF covariance matrix estimation. Moreover, the conjugate gradient algorithm is used to iteratively calculate the ADBF weight vector to reduce the computational complexity. Finally, wideband ADBF can be achieved by subband synthesis. Theoretical analysis and simulation results are provided to demonstrate that the proposed approach can suppress jamming sufficiently with a rapid convergence rate, making this approach feasible for engineering implementation.

关键词： Broadband adaptive beamforming Aperture fill time conjugate gradient algorithm Interference suppression

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