• Title/Summary/Keyword: Integration scheme

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Finite Element Analysis of Auto-body Panel Stamping (리어 힌지 패널 스템핑의 유한요소해석)

  • 정동원;이장희;양동열
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1996.06a
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    • pp.97-109
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    • 1996
  • In the present work computations are carried out for analysis of complicated sheet metal forming process such as forming of a rear hinge. Finite element formulation using dynamic explicit time integration scheme and step-wise combined Implicit/Explicit scheme are introduced for numerical analysis of sheet metal forming process. The rigid-plastic finite element method based on membrane elements has long been employed as a useful numerical technique for the analysis of sheet metal forming because of its time effectiveness. The explicit scheme in general use is based on the elastic-plastic modelling of material requiring large computation time. In finite element simulation of sheet metal forming processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. The implicit scheme employs a more reliable and rigorous scheme in considering the equilibrium at each step of deformation, while in the explicit scheme the problem of convergency is eliminated at the cost of solution accuracy. The explicit approach and the implicit approach have merits and demerits, respectively. In order to combine the merits of these two methods a step-wise combined implicit/explicit scheme has been developed.

A Storage Scheme for Logging and Indexing B2Bi XML Messages (기업간통합 XML 메시지의 기록과 색인을 위한 저장 방식)

  • Song Ha-Joo;Kim Chang-Su;Kwon Oh-Heum
    • Journal of KIISE:Computing Practices and Letters
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    • v.11 no.5
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    • pp.416-426
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    • 2005
  • A B2Bi system needs a message storage subsystem that efficiently logs and searches XML messages which have been sent from orreceived by it. XML database systems and XML enabled relational databases systems are not adequate as a message storage system because of their expensiveness and excessiveness in functionality. Storage schemes that split XML messages into database records are also unacceptable because of either low performance or implementation hardness. In this paper, we propose a storage scheme that can be applied to implement a message storage system based on a relational database system. In this scheme, messages are examined only through the index fields that have been registered for each message types. Therefore, the proposed storage scheme cannot support such a powerful search facility like XQL, but it provides high performance message legging and restricted search facility. There are three alternative database schemas to store the index fields. This paper compares the advantages and disadvantages of the three schemas through experimental tests.

Numerical assessment of step-by-step integration methods in the paradigm of real-time hybrid testing

  • Verma, Mohit;Rajasankar, J.;Iyer, Nagesh R.
    • Earthquakes and Structures
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    • v.8 no.6
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    • pp.1325-1348
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    • 2015
  • Real-time hybrid testing (RTHT) involves virtual splitting of the structure into two parts: physical substructure that contains the key region of interest which is tested in a laboratory and numerical substructure that contains the remaining part of the structure in the form of a numerical model. This paper numerically assesses four step-by-step integration methods (Central difference method (CDM), Operator splitting method (OSM), Rosenbrock based method (RBM) and CR-integration method (CR)) which are widely used in RTHT. The methods have been assessed in terms of stability and accuracy for various realistic damping ratios of the physical substructure. The stability is assessed in terms of the spectral radii of the amplification matrix while the accuracy in terms of numerical damping and period distortion. In order to evaluate the performance of the methods, five carefully chosen examples have been studied - undamped SDOF, damped SDOF, instantaneous softening, instantaneous hardening and hysteretic system. The performance of the methods is measured in terms of a non-dimensional error index for displacement and velocity. Based on the error indices, it is observed that OSM and RBM are robust and performs fairly well in all the cases. CDM performed well for undamped SDOF system. CR method can be used for the system showing softening behaviour. The error indices indicate that accuracy of OSM is more than other method in case of hysteretic system. The accuracy of the results obtained through time integration methods for different damping ratios of the physical substructure is addressed in the present study. In the presence of a number of integration methods, it is preferable to have criteria for the selection of the time integration scheme. As such criteria are not available presently, this paper attempts to fill this gap by numerically assessing the four commonly used step-by-step methods.

Integrating Forestry Offsets into a Domestic Emission Trading Scheme in Korea (해외 배출권 시장 사례 분석과 국내 배출권 시장 도입에 있어서 산림분야 참여에 관한 고찰)

  • Han, Ki-Joo;Youn, Yeo-Chang
    • Journal of Environmental Policy
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    • v.8 no.1
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    • pp.1-30
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    • 2009
  • Emission trading schemes, exemplified by the EU Emission Trading Scheme, have been playing active roles in mitigating greenhouse gas emissions since the Kyoto Protocol employed an emission trading as one of the cost-effective mechanisms. The objective of this study is to investigate potential integration of forestry offsets in designing an emission trading scheme in South Korea. First, the study found feasible scopes in which forestry sectors can take part by analyzing five emission trading schemes: EU Emission Trading Scheme, Chicago Climate Exchange, New South Wales Greenhouse Gas Abatement Scheme, New Zealand Emission Trading Scheme, and Regional Greenhouse Gas Initiative. The rationale of including forestry offsets in a domestic emission trading scheme was derived from the fact that forestry offset credits can provide cost-effective ways for market participants to commit their emission targets and expand abatement activities through reducing greenhouse gases in other geographical locations as well as other industrial sectors. Even though forestry offset credits have risks induced by their technical complexities in terms of accounting, additionality, and leakage, the integration of forestry offset credits into an emission trading scheme would be able to provide positive opportunities both to forestry sectors and other industrial sectors. In addition, there are technical questions which need to be answered in order to maintain these opportunities.

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Analysis of Coplanar Waveguide Discontinuities Using Accurate Closed-Form Green's function (정확한 Closed-Form 그린함수를 이용한 코플래너 도파로 불연속 해석)

  • Kang, Yeon-Duk;Song, Sung-Chan;Lee, Taek-Kyung
    • Journal of Advanced Navigation Technology
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    • v.7 no.2
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    • pp.180-190
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    • 2003
  • By using accurate closed-form Green's functions obtained from real-axis integration method, the full-wave analysis of CPW discontinuities are performed in space domain. In solving MPIE(Mixed Potential Integral Equation), Galerkin's scheme is employed with the linear basis functions on the triangular elements in air-dielectric boundary. In the singular integral arising when the observation point and source point coincides, the surface integral is transformed into the line integral and the integral is evaluated by regular integration. By using the Green's function from the real-axis integration method, the discontinuities are characterized accurately.

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Hourglass Control in Rigid-Plastic Finite Element Analysis (강소성 유한요소해석에서 Hourglass Control)

  • Gang, Jeong-Jin;O, Su-Ik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.4
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    • pp.1290-1300
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    • 1996
  • The finite element method, based on rigid-plastic formulation, is widely used to simulate metal forming processes. In order to improve the computational efficiency of the rigid-plastic FEM, one-point integration is used to evaluate the stiffness matrix with four-node rectangular elements and eight-node brick elements. In order to control the hourglass modes, hourglass strain rate components were introduced and included in the effective strain rate definition, Numerical tests have shown that the proposed one-point integration scheme reduces the stiffness matrix evaluation time without deteriorating the convergence behavior of Newton-Raphson method. Simulations of a ring compression, a plane-strain closed-die forging and the three-dimensional spike forging processes were carried out by using the proposed integration method. The simulation results are compared to those obtained by applying the conventional integraiton method in terms of the solution accuracy and computational efficiency.

An Integration Type Adaptive Compensator for a Class of Linearly Parameterized Systems (선형 파라미터화된 시스템에 대한 적분형 적응보상기)

  • Yoo Byung-Kook;Yang Keun-Ho
    • Journal of the Institute of Convergence Signal Processing
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    • v.6 no.2
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    • pp.82-88
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    • 2005
  • A compensation scheme for a class of linearly parameterized systems is presented. The compensator consists of a typical linearizing control and an adaptive observer with integration type update law, which is based on Speed Gradient (SG) algorithm.. Instead of the intermediate functions of the compensation schemes suggested by other researchers, the proposed compensator is designed with some design functions which guarantee the growth, convexity, attainability, and pseudo gradient conditions in the update law. The scheme achieves the asymptotic stability of the tracking error and the boundedness of the estimation errors. A numerical example is given to demonstrate the validity of the proposed design.

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Modeling & Simulation Software Design for Coverage Analysis of Multiple Radio Positioning Integration System

  • Koo, Moonsuk;Kim, YoungJoon;So, Hyoungmin;Oh, Sang Heon;Kim, Seong-Cheol;Hwang, Dong-Hwan
    • Journal of Positioning, Navigation, and Timing
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    • v.5 no.2
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    • pp.47-57
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    • 2016
  • Since the Global Navigation Satellite System (GNSS) may not provide navigation information due to external interferences, many countries have plans to prepare a backup system for this situation. One of the possible GNSS backup systems is a multiple radio positioning integration system in combination with the terrestrial radio navigation system. Before constructing such a GNSS backup system, M&S software is needed to analyze if the system satisfies the performance the required navigation performance. This study presents requirements of M&S software for coverage analysis of the navigation system, and proposes an M&S software design scheme on the basis of the requirements. The M&S software is implemented, and coverage analysis is performed to verify the validity of the proposed design scheme.

As-Rigid-As-Possible Dynamic Deformation with Oriented Particles (방향성 입자를 이용한 ARAP 동적 변형)

  • Choi, Min Gyu
    • Journal of Korea Game Society
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    • v.17 no.1
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    • pp.89-98
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    • 2017
  • This paper presents a novel ARAP (as-rigid-as-possible) approach to real-time simulation of physics-based deformation. To cope with one, two and three dimensional deformable bodies in an efficient, robust and uniform manner, we introduce a deformation graph of oriented particles and formulate the corresponding ARAP deformation energy. For stable time integration of the oriented particles, we develop an implicit integration scheme formulated in a variational form. Our method seeks the optimal positions and rotations of the oriented particles by iteratively applying an alternating local/global optimization scheme. The proposed method is easy to implement and computationally efficient to simulate complex deformable models in real time.

Finite Element Analysis of Multi-Stage Deep Drawing Process for High Precision Rectangular Case with Extreme Aspect Ratio (세장비가 큰 사각컵 디프 드로잉의 유한요소 해석)

  • Ku T.W.;Ha B.K.;Song W.J.;Kang B.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2002.02a
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    • pp.274-284
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    • 2002
  • Deep drawing process for rectangular drawn section is different with that for axisymmetric circular one. Therefore deep drawing process for rectangular drawn section requires several intermediate steps to generate the final configuration without any significant defect. In this study, finite element analysis for multi-stage deep drawing process for high precision rectangular cases is carried out especially for an extreme aspect ratio. The analysis is performed using rigid-plastic finite element method with an explicit time integration scheme of the commercial program, LS-DYNA3D. The sheet blank is modeled using eight-node continuum brick elements. The results of analysis show that the irregular contact condition between blank and die affects the occurrence of failure, and the difference of aspect ratio in the drawn section leads to non-uniform metal flow, which may cause failure. A series of experiments for multi-stage deep drawing process for the rectangular cases are conducted, and the deformation configuration and the thickness distribution of the drawn rectangular cases are investigated by comparing with the results of the numerical analysis. The numerical analysis with an explicit time integration scheme shows good agreement with the experimental observation.

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