• Title/Summary/Keyword: Large-scale nonlinear analysis

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Inelastic Analysis of Steel-Concrete Composite Column with Non-Compact Steel Section (비조밀단면을 가진 SC 합성 기둥의 비선형 해석)

  • Oh, Myoung Ho;Jang, Tae Young;Kim, Myeong Han;Kim, Dae Joong;Kim, Sang Dae
    • Journal of Korean Society of Steel Construction
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    • v.17 no.1 s.74
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    • pp.63-71
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    • 2005
  • There were already several studies conducted on the steel-concrete (SC) composite column, which was developedcomplement the weaknesses and maintain the advantages of previous composite columns. The axial compressive capacity of the SC composite column was estimated by the tests in previous studies, but the experiments for the large-scale column could not be performed because of the limitation with the laboratory's capacity. In this study, the analytical study was performed using the general finite element analysis program to reflect the interaction of concrete and steel and the local buckling of steel flange composed of the non-compact section. The appropriateness of the analytical model was verified by the comparison between experimental and analytical results. The nonlinear behavior of full-scale SC composite column was analyzed using the verified analytical model. From these analytical studies, it was concluded that the width-to-thickness ratio of the steel cross-section of the SC composite column should not exceed 25:0. The section area of the link is best when it is over 0.025 dt, and the link distance is to be less than D/2 or 300mm.

Seismic Response Control of Structures Using Decentralized Response-Dependent MR Dampers (분산제어식 응답의존형 MR 감쇠기를 이용한 구조물의 지진응답제어)

  • Youn, Kyung-Jo;Min, Kyung-Won;Lee, Sang-Hyun
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.6
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    • pp.761-767
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    • 2007
  • In centralized control system, complicated control systems including sensors, power supply and dampers should be required to satisfy the target response of large-scale structures. The practical applications of the centralized control system, however, is very difficult due to high order finite element model of structures, uncertainty of models, and limitations of the excitation system. In this study, the decentralized response-dependent MR damper of which magnetic field is automatically modulated according to the displacement or velocity transferred to the damper without any sensing and computing systems. this decentralized response-dependent MR damper are investigated according to the ranges of relative magnitude between the control force of MR damper and the story shear force of structures by nonlinear time history analysis. Finally, its performance is compared with centralized LQR algorithm which is used in general centralized control theory for a three story building structure.

Development a Downscaling Method of Remotely-Sensed Soil Moisture Data Using Neural Networks and Ancillary Data (신경망기법과 보조 자료를 사용한 원격측정 토양수분자료의 Downscaling기법 개발)

  • Kim, Gwang-Seob;Lee, Eul-Rae
    • Journal of Korea Water Resources Association
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    • v.37 no.1
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    • pp.21-29
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    • 2004
  • The growth of water resources engineering associated with stable supply, management, development is essential to overcome the coming water deficit of our country. Large scale remote sensing and the analysis of sub-pixel variability of soil moisture fields are necessary in order to understand water cycle and to develop appropriate hydrologic model. The target resolution of coming Global monitoring of soil moisture field is about 10km which is not appropriate for the regional scale hydrologic model. Therefore, we need a downscaling scheme to generate hydrologic variables which are suitable for the regional hydrologic model. The results of the analysis of sub-pixel soil moisture variability show that the relationship between ancillary data and soil moisture fields shows there is very weak linear relationship. A downscaling scheme was developed using physically-based classification scheme and Neural Networks which are able to link the nonlinear relationship between ancillary data and soil moisture fields. The model is demonstrated by downscaling soil moisture fields from 4km to 0.2km resolution using remotely-sensed data from the Washita'92 experiment.

Evaluation of Reinforced Concrete Beam's Inelastic Behavior Characteristics using Beam-column Fiber Finite Element considering Shear Deformation Effect (전단변형 효과가 고려된 보-기둥 섬유유한요소를 이용한 철근콘크리트 보의 비탄성 거동특성 평가)

  • Cheon, Ju-Hyun;Hwang, Cheol-Seong;Park, Kwang-Min;Shin, Hyun-Mock
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.3
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    • pp.130-137
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    • 2017
  • The purpose of this study is to provide a reasonable analytical method for the reinforced concrete beams which shows failure mode of shear and flexure-shear by proposing a modified formulation to consider the effect of shear deformation on the beam-column fiber element based on the flexibility method and a new constitutive law of inelastic shear response history for the section. A total of 6 specimens of reinforced concrete beams which is designed to cause shear failure before yielding longitudinal reinforcement to investigate the influence of the main experimental variables on the shear behavior characteristics and the analysis was performed by using a non-linear finite element analysis program (RCAHEST) applying the newly modified constitutive equation by the authors. The failure mode and the overall behavior characteristics until fracture are predicted appropriately for all specimens and the results are expected to be useful enough for the 3 - D analysis to carry out reliable results of large-scale and complicated structures in the future.

A Study on Foreign Exchange Rate Prediction Based on KTB, IRS and CCS Rates: Empirical Evidence from the Use of Artificial Intelligence (국고채, 금리 스왑 그리고 통화 스왑 가격에 기반한 외환시장 환율예측 연구: 인공지능 활용의 실증적 증거)

  • Lim, Hyun Wook;Jeong, Seung Hwan;Lee, Hee Soo;Oh, Kyong Joo
    • Knowledge Management Research
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    • v.22 no.4
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    • pp.71-85
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    • 2021
  • The purpose of this study is to find out which artificial intelligence methodology is most suitable for creating a foreign exchange rate prediction model using the indicators of bond market and interest rate market. KTBs and MSBs, which are representative products of the Korea bond market, are sold on a large scale when a risk aversion occurs, and in such cases, the USD/KRW exchange rate often rises. When USD liquidity problems occur in the onshore Korean market, the KRW Cross-Currency Swap price in the interest rate market falls, then it plays as a signal to buy USD/KRW in the foreign exchange market. Considering that the price and movement of products traded in the bond market and interest rate market directly or indirectly affect the foreign exchange market, it may be regarded that there is a close and complementary relationship among the three markets. There have been studies that reveal the relationship and correlation between the bond market, interest rate market, and foreign exchange market, but many exchange rate prediction studies in the past have mainly focused on studies based on macroeconomic indicators such as GDP, current account surplus/deficit, and inflation while active research to predict the exchange rate of the foreign exchange market using artificial intelligence based on the bond market and interest rate market indicators has not been conducted yet. This study uses the bond market and interest rate market indicator, runs artificial neural network suitable for nonlinear data analysis, logistic regression suitable for linear data analysis, and decision tree suitable for nonlinear & linear data analysis, and proves that the artificial neural network is the most suitable methodology for predicting the foreign exchange rates which are nonlinear and times series data. Beyond revealing the simple correlation between the bond market, interest rate market, and foreign exchange market, capturing the trading signals between the three markets to reveal the active correlation and prove the mutual organic movement is not only to provide foreign exchange market traders with a new trading model but also to be expected to contribute to increasing the efficiency and the knowledge management of the entire financial market.

Optimal Active-Control & Development of Optimization Algorithm for Reduction of Drag in Flow Problems(1) - Development of Optimization Algorithm and Techniques for Large-Scale and Highly Nonlinear Flow Problem (드래그 감소를 위한 유체의 최적 엑티브 제어 및 최적화 알고리즘의 개발(1) - 대용량, 비선헝 유체의 최적화를 위한 알고리즘 및 테크닉의 개발)

  • Bark, Jai-Hyeong
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.5
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    • pp.661-669
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    • 2007
  • Eyer since the Prandtl's experiment in 1934 and X-21 airjet test in 1950 both attempting to reduce drag, it was found that controlling the velocities of surface for extremely fast-moving object in the air through suction or injection was highly effective and active method. To obtain the right amount of suction or injection, however, repetitive trial-and error parameter test has been still used up to now. This study started from an attempt to decide optimal amount of suction and injection of incompressible Navier-Stokes by employing optimization techniques. However, optimization with traditional methods are very limited, especially when Reynolds number gets high and many unexpected variables emerges. In earlier study, we have proposed an algorithm to solve this problem by using step by step method in analysis and introducing SQP method in optimization. In this study, we propose more effective and robust algorithm and techniques in solving flow optimization problem.

Optimal Active-Control & Development of Optimization Algorithm for Reduction of Drag in Flow Problems(3) -Construction of the Formulation for True Newton Method and Application to Viscous Drag Reduction of Three-Dimensional Flow (드래그 감소를 위한 유체의 최적 엑티브 제어 및 최적화 알고리즘의 개발(3) - 트루 뉴턴법을 위한 정식화 개발 및 유체의 3차원 최적 엑티브 제어)

  • Bark, Jai-Hyeong
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.6
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    • pp.751-759
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    • 2007
  • We have developed several methods for the optimization problem having large-scale and highly nonlinear system. First, step by step method in optimization process was employed to improve the convergence. In addition, techniques of furnishing good initial guesses for analysis using sensitivity information acquired from optimization iteration, and of manipulating analysis/optimization convergency criterion motivated from simultaneous technique were used. We applied them to flow control problem and verified their efficiency and robustness. However, they are based on quasi-Newton method that approximate the Hessian matrix using exact first derivatives. However solution of the Navier-Stokes equations are very cost, so we want to improve the efficiency of the optimization algorithm as much as possible. Thus we develop a true Newton method that uses exact Hessian matrix. And we apply that to the three-dimensional problem of flow around a sphere. This problem is certainly intractable with existing methods for optimal flow control. However, we can attack such problems with the methods that we developed previously and true Newton method.

Object Tracking Based on Exactly Reweighted Online Total-Error-Rate Minimization (정확히 재가중되는 온라인 전체 에러율 최소화 기반의 객체 추적)

  • JANG, Se-In;PARK, Choong-Shik
    • Journal of Intelligence and Information Systems
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    • v.25 no.4
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    • pp.53-65
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    • 2019
  • Object tracking is one of important steps to achieve video-based surveillance systems. Object tracking is considered as an essential task similar to object detection and recognition. In order to perform object tracking, various machine learning methods (e.g., least-squares, perceptron and support vector machine) can be applied for different designs of tracking systems. In general, generative methods (e.g., principal component analysis) were utilized due to its simplicity and effectiveness. However, the generative methods were only focused on modeling the target object. Due to this limitation, discriminative methods (e.g., binary classification) were adopted to distinguish the target object and the background. Among the machine learning methods for binary classification, total error rate minimization can be used as one of successful machine learning methods for binary classification. The total error rate minimization can achieve a global minimum due to a quadratic approximation to a step function while other methods (e.g., support vector machine) seek local minima using nonlinear functions (e.g., hinge loss function). Due to this quadratic approximation, the total error rate minimization could obtain appropriate properties in solving optimization problems for binary classification. However, this total error rate minimization was based on a batch mode setting. The batch mode setting can be limited to several applications under offline learning. Due to limited computing resources, offline learning could not handle large scale data sets. Compared to offline learning, online learning can update its solution without storing all training samples in learning process. Due to increment of large scale data sets, online learning becomes one of essential properties for various applications. Since object tracking needs to handle data samples in real time, online learning based total error rate minimization methods are necessary to efficiently address object tracking problems. Due to the need of the online learning, an online learning based total error rate minimization method was developed. However, an approximately reweighted technique was developed. Although the approximation technique is utilized, this online version of the total error rate minimization could achieve good performances in biometric applications. However, this method is assumed that the total error rate minimization can be asymptotically achieved when only the number of training samples is infinite. Although there is the assumption to achieve the total error rate minimization, the approximation issue can continuously accumulate learning errors according to increment of training samples. Due to this reason, the approximated online learning solution can then lead a wrong solution. The wrong solution can make significant errors when it is applied to surveillance systems. In this paper, we propose an exactly reweighted technique to recursively update the solution of the total error rate minimization in online learning manner. Compared to the approximately reweighted online total error rate minimization, an exactly reweighted online total error rate minimization is achieved. The proposed exact online learning method based on the total error rate minimization is then applied to object tracking problems. In our object tracking system, particle filtering is adopted. In particle filtering, our observation model is consisted of both generative and discriminative methods to leverage the advantages between generative and discriminative properties. In our experiments, our proposed object tracking system achieves promising performances on 8 public video sequences over competing object tracking systems. The paired t-test is also reported to evaluate its quality of the results. Our proposed online learning method can be extended under the deep learning architecture which can cover the shallow and deep networks. Moreover, online learning methods, that need the exact reweighting process, can use our proposed reweighting technique. In addition to object tracking, the proposed online learning method can be easily applied to object detection and recognition. Therefore, our proposed methods can contribute to online learning community and object tracking, detection and recognition communities.