A general model reduction with primal assembly in structural dynamics

Kim, Jin-Gyun,Park, Young-Jun,Lee, Geun Ho,Kim, Do-Nyun Elsevier 2017 Computer methods in applied mechanics and engineer Vol.324 No.-

<P><B>Abstract</B></P> <P>A new formulation of general model reduction in structural dynamics is presented. The proposed method consists of four attributes: a hybrid method combining dynamic condensation and component mode synthesis that are arguably the most popular model reduction techniques, a precise model reduction taking the inertia effect into consideration, primal assembly at the boundary interface of substructures and general formulations of model reduction with primal assembly. Comparisons of the proposed model reduction method with the conventional methods are provided as well as an efficient model reduction procedure of the proposed method. In particular, its advantages and performance of the proposed method are thoroughly investigated with various numerical examples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We propose a new model reduction method by enhancing dynamic condensation and component mode synthesis. </LI> <LI> The inertia effect is taken into account for precise model reduction. </LI> <LI> We present the excellent performance through various numerical examples. </LI> <LI> This paper offers analytical and numerical investigations based on a comparison of the proposed and conventional methods. </LI> </UL> </P>

지방세 비과세･감면의 경제적 효과 : 문턱모형을 이용한 비선형성 탐색

문광민(Moon, Kwang-Min),윤성일(Yoon, Sung-Il) 한국지방정부학회 2015 지방정부연구 Vol.19 No.1

본 연구는 우리나라의 지방세 비과세･감면이 지역경제성장에 어떠한 영향을 미치는지, 그리고 지방자치단체의 지방세 비과세･감면액의 수준별로 지역경제성장에 미치는 효과가 비단조적(non-monotonic)으로 나타날 가능성은 없는지를 실증적으로 분석하는 것을 목적으로 한다. 이를 위하여 1995년부터 2012년까지 우리나라 15개 광역지방자치단체를 대상으로 분석을 실시하였다. 먼저 고정효과모형에 기반을 둔 일반선형 회귀모형으로 분석을 실시하고, 다음으로 지방자치단체의 지방세 비과세･감면 규모의 이질성(heterogeneity)을 고려하여 지방세 비과세･감면의 지역경제성장에 대한 비단조적 효과를 추정하는 패널문턱회귀모형으로 분석을 실시하였다. 분석결과 감면조례에 따른 지방세 감면의 경우, 감면조례에 따른 지방세 감면의 증가는 선형모형과 문턱모형 모두 지역경제성장과 통계적으로 유의미한 부(-)의 관계를 가지고 있는 것으로 나타났지만, 문턱모형에서는 상위레짐에서 그 효과가 더 큰 것으로 나타났다. 한편 법률에 따른 지방세 비과세･감면의 경우, 법률에 따른 지방세 비과세･감면의 증가는 선형모형과 문턱모형 모두 지역경제성장과 통계적으로 유의미한 정(+)의 관계를 가지는 것으로 나타났지만, 문턱모형에서는 상위레짐에서 그 효과가 더 큰 것으로 나타났다. This study aims to empirically analyze the impacts of South Korea local tax exemption and reduction on regional economic growth and whether it is possible for the effects of the local governments’local tax exemption and reduction on regional economic growth to appear non-monotonically by the level of the amounts. For this purpose, this study conducted analyses of 15 metropolitan municipalities of South Korea from 1995 through 2012. First, it conducted an analysis using a general linear regression model based on a fixed-effects model, and then, it conducted an analysis using a panel threshold regression model which estimates the non-monotonic effect of local tax exemption and reduction on regional economic growth, considering the heterogeneity of the scale of the local governments’ local tax exemption and reduction. As a result of the analyses, regarding local tax reduction by local tax reduction ordinance, it turned out that the increase of the local tax reduction by local tax reduction ordinance had a statistically significant negative (-) correlation with regional economic growth in both linear model and threshold model, but the effect was greater in the upper regime in the threshold model. On the other hand, regarding local tax exemption and reduction by law, it turned out that the increase of the local tax exemption and reduction by the law had a statistically significant positive (+) correlation with regional economic growth in both linear model and threshold model, but the effect was greater in the upper regime in the threshold model.

Model Order Reduction of Nonlinear Models based on Decoupled Multi-model via Trajectory Piecewise Linearization

Seyed Saleh Mohseni,Mohamad Javad Yazdanpanah,Abolfazl Ranjbar Noei 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.5

In this paper a novel model order reduction method for nonlinear models, based on decoupled multimodel,via trajectory piecewise-linearization is proposed. Through different strategies in trajectory piecewiselinearmodel reduction, model order reduction of a trajectory piecewise-linear model based on output weighting(TPWLOW), has been developed by authors of current work. The structure of mentioned work was founded basedon Krylov subspace method, which is appropriate for high order models. Indeed the size of the Krylov subspacesmay increase with the number of inputs of the system. As a result, the use of Krylov subspace method may becomedeficient the case for multi-input systems of order few decades. This paper aims to generalize the idea of modelreduction of TPWLOW model by concentrating on balanced truncation technique which is appropriate for mediumsize systems. In addition, the proposed method either guarantees or provides guaranteed stability in some mentionedconditions. Finally, applicability of the reduced model, instead of high-order decoupled multi-model in weightingmulti-model controllers, is investigated through the control of a nonlinear Alstom gasifier benchmark.

A Large Scale System Model-Order Reduction Method Based on SVD-Krylov

Zhe Yan,Fangming Lu,lin Zhou 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.10

A SVD-Krylov method for large scale MIMO(multi-input multi-output) system model-order reduction is proposed in this paper. Its aim is to combined the singular value decomposition(SVD)and Krylov methods by retaining the best feature that can be applied for solving some problems for the large scale system model-order reduction. The method matches the first r Markov parameters and minimizes the error in the remaining ones in the least-squares sense. The reduced model is asymptotically stable, matches a certain number of moments, and minimizes a weighted error in the discrete time case. The effectiveness of the proposed approaches is tested by the Iss (international space station)model that in the SLICOT library, getting the frequency-response, the error and the error bounds of different order reduced model. The result shows that the proposed method is efficiently.

Scale-model method for measuring noise reduction in residential buildings by vegetation

Jang, Hyung Suk,Kim, Ho Jun,Jeon, Jin Yong Elsevier 2015 Building and environment Vol.86 No.-

<P><B>Abstract</B></P> <P>This paper proposes an evaluation procedure using a scale model to assess the noise reduction effects of vegetated façades for sustainable urban building designs. The absorption coefficients of the scale-model materials were measured to fit the absorption characteristics of real vegetation. The ground impedance of asphalt was also measured to deduce the acoustical properties of ground surfaces and to select the ground material. To assess the reduction of road traffic noise, a line source for a 1:10 scale model was modelled using ribbon tweeters that generated high frequencies ranging from 1 kHz to 40 kHz. Accordingly, the effects of adding vegetated façades were evaluated in the scale model of a street canyon. The noise reduction due to the vegetated façades was less than 2 dB at pedestrian level in a two-lane street canyon. The scale model results were compared with geometric computer simulation results, and both evaluation methods showed similar results. The suggested modelling method can be useful for evaluating the noise reduction in street canyons by vegetation considering realistic features such as the absorption, scattering, and diffraction associated with the materials and sound sources according to the shape of the vegetation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Scale-model vegetation materials with realistic absorption coefficients were used. </LI> <LI> The ground impedance was measured to select the asphalt scale model. </LI> <LI> A line source was constructed using a ribbon tweeter array. </LI> <LI> The insertion loss of vegetated façades in a two-lane street canyon was <2 dB. </LI> </UL> </P>

Model reduction techniques for high-rise buildings and its reduced-order controller with an improved BT method

Chao-Jun Chen,Jun Teng,Zuo-Hua Li,Qing-Gui Wu,Bei-Chun Lin 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.3

An AMD control system is usually built based on the original model of a target building. As a result, the fact leads a large calculation workload exists. Therefore, the orders of a structural model should be reduced appropriately. Among various model-reduction methods, a suitable reduced-order model is important to high-rise buildings. Meanwhile, a partial structural information is discarded directly in the model-reduction process, which leads to the accuracy reduction of its controller design. In this paper, an optimal technique is selected through comparing several common model-reduction methods. Then, considering the dynamic characteristics of a high-rise building, an improved balanced truncation (BT) method is proposed for establishing its reduced-order model. The abandoned structural information, including natural frequencies, damping ratios and modal information of the original model, is reconsidered. Based on the improved reduced-order model, a new reduced-order controller is designed by a regional pole-placement method. A high-rise building with an AMD system is regarded as an example, in which the energy distribution, the control effects and the control parameters are used as the indexes to analyze the performance of the improved reduced-order controller. To verify its effectiveness, the proposed methodology is also applied to a four-storey experimental frame. The results demonstrate that the new controller has a stable control performance and a relatively short calculation time, which provides good potential for structural vibration control of high-rise buildings.

위성패널 열전도모델 축소 및 상세모델 온도 역계산

김정훈(J.H. Kim),전형열(H.Y. Jun),김병수(B. Kim) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.3

The conductive thermal model reduction method is introduced to condense a satellite panel thermal model into a simplified model to make efficient calculations in the thermal analysis of a satellite in orbit. The static condensation algorithm with a substitution matrix manipulation is employed to handle the large matrices without any numerical restriction. On the conductive thermal model reduction in the steady state and transient, the reduced thermal model analysis is performed to compare with the results of the detailed model. The temperature difference between the reduced model and the detailed model is not affected by condensed node selection. By using the reduced model temperatures, the eliminated node temperatures in the detailed model are able to be recovered without differences by the substitution matrix.

Study on the reduction method of the satellite thermal mathematical model

Kim, Jung Hoon,Kim, Byoungsoo Elsevier 2017 Advances in engineering software Vol.108 No.-

<P><B>Abstract</B></P> <P>The thermal model reduction method is introduced to condense a huge satellite panel thermal model into a simplified model in order to make efficient calculations in the thermal analysis of a satellite in orbit. The static condensation algorithm with a substitution matrix manipulation is employed to handle the huge matrices without any numerical restriction. The relevant mathematical procedures of reduction are described step-by-step. The thermal model example of a satellite panel is illustrated to demonstrate the developed reduction method and its results are discussed. The influence of generated meshes for the reduced thermal model is reviewed. The calculation times are assessed and comparison between the developed method and the classical block-form LU decomposition method is also performed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Proposing a thermal model reduction algorithm for non-symmetric full matrices manipulation. </LI> <LI> Performance of the multi-thread computing architecture for model reduction. </LI> <LI> Evaluating the quality of the reduced model with isothermal meshing tolerances. </LI> </UL> </P>

Numerical study on turbulent blood flow in a stenosed artery bifurcation under periodic body acceleration using a modified k-ε model

Kyoung Chul Ro,유홍선 한국유변학회 2010 Korea-Australia rheology journal Vol.22 No.2

This article describes the numerical investigation of turbulent blood flow in the stenosed artery bifurcation under periodic acceleration of the human body. Numerical analyses for turbulent blood flow were performed for six simulation cases with different magnitude of periodic accelerations using a modified k-e turbulence model which is considering drag reduction of non-Newtonian fluid. The blood was considered to be a non-Newtonian fluid which is based on the power-law viscosity model. In order to validate the modified k-e model, numerical simulations were compared with laminar flow, the standard k-e model and the Malin's turbulence model for power-law fluid. As results, laminar flow showed under predictions of blood velocity and wall shear stress, on the other hand, standard k-e model over estimates. The modified k-e model represents intermediate characteristics between laminar and standard k-e model, and the modified k-e model show good agreements with Malin's verified power law model. Moreover, the computing time and computer resource of the modified k-e model are reduced about one third than low Reynolds number model including Malin's model.

Calculation of design sensitivity for large-size transient dynamic problems using Krylov subspace-based model order reduction

한정삼 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.9

Nowadays, transient dynamic responses of a large-size finite element (FE) model can be solved within a reasonable computation time owing to rapid improvement in both numerical schemes and computing resources. However, increasing demands for accurate simulation and complicated modeling have led to larger and more complex finite element models, which consequently result in considerably high computational cost. In addition, when structural optimizations include transient responses such as displacement, velocity, and acceleration,the optimizations often do not end within a reasonable process time because the large-size simulation must be repeated many times. In order to reduce the computational cost in this respect, model order reduction (MOR) for the original full-order model (FOM) can be used for the transient response simulation. In this paper, a transient dynamic response analysis using Krylov subspace-based MOR and its design sensitivity analysis with respect to sizing design variables is suggested as an approach to the handling of large-size finite element models. Large-size finite element models can incur the problem of a long computation time in gradient-based optimization iterations because of the need for repeated simulation of transient responses. In the suggested method, the reduced order models (ROMs) generated from the original FOMs using implicit moment-matching via the Arnoldi process are used to calculate the transient response and its design sensitivity. As a result, the speed of numerical computation for the transient response and its design sensitivity is maximized. Newmark’s time integration method is employed to calculate transient responses and their design sensitivities. In the case of the transient sensitivity analysis, we apply a temporal discretization scheme to the design sensitivity equation derived by directly differentiating the governing equation with respect to design variables. This methodology has been programmed on the MATLAB with the FE information extracted from the FE package ANSYS. Two application examples are provided to demonstrate the numerical accuracy and efficiency of the suggested approach. The relative errors of transient response and design sensitivity between the FOMs and ROMs are also compared according to the orders of the reduced model. Calculation of transient dynamic responses and their sensitivities using Krylov subspacebased MOR shows a sizeable reduction in computation time and a good agreement with those provided by the FOM.