• Title/Summary/Keyword: Structure Equation Model

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Free vibration analysis of combined system with variable cross section in tall buildings

  • Jahanshahia, Mohammad Reza;Rahgozar, Reza
    • Structural Engineering and Mechanics
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    • v.42 no.5
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    • pp.715-728
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    • 2012
  • This paper deals with determining the fundamental frequency of tall buildings that consist of framed tube, shear core, belt truss and outrigger systems in which the framed tube and shear core vary in size along the height of the structure. The effect of belt truss and outrigger system is modeled as a concentrated rotational linear spring at the belt truss and outrigger system location. Many cantilevered tall structures can be treated as cantilevered beams with variable cross-section in free vibration analysis. In this paper, the continuous approach, in which a tall building is replaced by an idealized cantilever continuum representing the structural characteristics, is employed and by using energy method and Hamilton's variational principle, the governing equation for free vibration of tall building with variable distributed mass and stiffness is obtained. The general solution of governing equation is obtained by making appropriate selection for mass and stiffness distribution functions. By applying the separation of variables method for time and space, the governing partial differential equation of motion is reduced to an ordinary differential equation with variable coefficients with the assumption that the transverse displacement is harmonic. A power-series solution representing the mode shape function of tall building is used. Applying boundary conditions yields the boundary value problem; the frequency equation is established and solved through a numerical process to determine the natural frequencies. Computer program has been developed in Matlab (R2009b, Version 7.9.0.529, Mathworks Inc., California, USA). A numerical example has been solved to demonstrate the reliability of this method. The results of the proposed mathematical model give a good understanding of the structure's dynamic characteristics; it is easy to use, yet reasonably accurate and suitable for quick evaluations during the preliminary design stages.

A structure-borne noise prediction based on the Boundary Element Method with a Laser Doppler Vibrometer (경계요소법과 레이저 진동센서를 이용한 구조방사소음 예측시스템 구축)

  • Kim, Jung-Seon;Kim, Dae-Sung;Kyong, Yong-Soo;Wang, Se-Myung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.1366-1370
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    • 2007
  • Predicting the noise radiated from vibrating structures is important in the automotive, aerospace, construction equipment, and defense industries. In this paper, a numerical implementation of the boundary element method in solving the Helmholtz integral equation for radiated noise prediction is presented. To predict the noise emitted by vibrating structure, the developed code can use the results from a structure analysis performed by a multi-purpose structural finite element code like ANSYS and directly measured data by non-contact vibration sensor like Laser Doppler Vibrometer. To verify the accuracy of developed code, two kinds of verification are perfomed. Firstly, the computer code used the harmonic analysis results of ANSYS in simple model and try to match with SYSNOISE. After matching with simulation results, the code compared with the result from SYSNOISE which used the velocity data from the LDV measurement with different number of points. The performance of the developed code for vibro-acoustic noise prediction is presented using the experimental results of the non-contact sensor

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A Study on the Signal Distortion Analysis using Full-wave Method at VLSI Interconnection (VLSI 인터커넥션에 대한 풀-웨이브 방법을 이용한 신호 왜곡 해석에 관한 연구)

  • 최익준;원태영
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.41 no.4
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    • pp.101-112
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    • 2004
  • In this paper, we developed a numerical analysis model by using ADI-FDTD method to analyze three-dimensional interconnect structure. We discretized maxwell's curl equation by using ADI-FDTD. Using ADI-FDTD method, a sampler circuit designed from 3.3 V CMOS technology is simplified to 3-metal line structure. Using this simplified structure, the time delay and signal distortion of complex interconnects are investigated. As results of simulation, 5∼10 ps of delay time and 0.1∼0.2 V of signal distortion are measured. As demonstrated in this paper, the full-wave analysis using ADI-FDTD exhibits a promise for accurate modeling of electromagnetic phenomena in high-speed VLSI interconnect.

Vibration Control of Stiffened Hull Structure Using MFC Actuator (MFC 작동기를 이용한 보강 Hull 구조물의 능동 진동 제어)

  • Jeon, Jun-Cheol;Sohn, Jung-Woo;Choi, Seung-Bok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.04a
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    • pp.273-278
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    • 2011
  • This work presents an active vibration control of a stiffened hull structure using a flexible macro fiber composite (MFC) actuator. As first step, the governing equation of the hull structure is derived in a matrix form and its dynamic characteristics such as natural frequency are obtained via a finite element analysis (FEA). The natural frequencies obtained from the FEA are compared with those determined from experimental measurement. After formulating the control model in a state space representation, an optimal controller is designed in order to attenuate the vibration of the stiffened hull structure. The controller is then empirically realized through dSPACE and control responses are evaluated in time domain.

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Vibration Control of Stiffened Hull Structure Using MFC Actuator (MFC 작동기를 이용한 보강 Hull 구조물의 능동 진동 제어)

  • Jeon, Jun-Cheol;Sohn, Jung-Woo;Choi, Seung-Bok
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.7
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    • pp.643-649
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    • 2011
  • This work presents an active vibration control of a stiffened hull structure using a flexible macro fiber composite(MFC) actuator. As first step, the governing equation of the hull structure is derived in a matrix form and its dynamic characteristics such as natural frequency are obtained via a finite element analysis(FEA). The natural frequencies obtained from the FEA are compared with those determined from experimental measurement. After formulating the control model in a state space representation, an optimal controller is designed in order to attenuate the vibration of the stiffened hull structure. The controller is then empirically realized through dSPACE and control responses are evaluated in time domain.

A Study on Multi-layer Fuzzy Inference System based on a Modified GMDH Algorithm (수정된 GMDH 알고리즘 기반 다층 퍼지 추론 시스템에 관한 연구)

  • Park, Byoung-Jun;Park, Chun-Seong;Oh, Sung-Kwun
    • Proceedings of the KIEE Conference
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    • 1998.11b
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    • pp.675-677
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    • 1998
  • In this paper, we propose the fuzzy inference algorithm with multi-layer structure. MFIS(Multi-layer Fuzzy Inference System) uses PNN(Polynomial Neural networks) structure and the fuzzy inference method. The PNN is the extended structure of the GMDH(Group Method of Data Hendling), and uses several types of polynomials such as linear, quadratic and cubic, as well as the biquadratic polynomial used in the GMDH. In the fuzzy inference method, the simplified and regression polynomial inference methods are used. Here, the regression polynomial inference is based on consequence of fuzzy rules with the polynomial equations such as linear, quadratic and cubic equation. Each node of the MFIS is defined as fuzzy rules and its structure is a kind of neuro-fuzzy structure. We use the training and testing data set to obtain a balance between the approximation and the generalization of process model. Several numerical examples are used to evaluate the performance of the our proposed model.

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The FPNN Algorithm combined with fuzzy inference rules and PNN structure (퍼지추론규칙과 PNN 구조를 융합한 FPNN 알고리즘)

  • Park, Ho-Sung;Park, Byoung-Jun;Ahn, Tae-Chon;Oh, Sung-Kwun
    • Proceedings of the KIEE Conference
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    • 1999.07g
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    • pp.2856-2858
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    • 1999
  • In this paper, the FPNN(Fuzzy Polynomial Neural Networks) algorithm with multi-layer fuzzy inference structure is proposed for the model identification of a complex nonlinear system. The FPNN structure is generated from the mutual combination of PNN (Polynomial Neural Network) structure and fuzzy inference method. The PNN extended from the GMDH(Group Method of Data Handling) uses several types of polynomials such as linear, quadratic and modifled quadratic besides the biquadratic polynomial used in the GMDH. In the fuzzy inference method, simplified and regression polynomial inference method which is based on the consequence of fuzzy rule expressed with a polynomial such as linear, quadratic and modified quadratic equation are used Each node of the FPNN is defined as a fuzzy rule and its structure is a kind of fuzzy-neural networks. Gas furnace data used to evaluate the performance of our proposed model.

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A Methodological Quality Assessment of South Korean Nursing Research using Structural Equation Modeling in South Korea (국내 간호학 학회지에 출판된 구조방정식모형 연구의 방법론적 질 평가)

  • Kim, Jung-Hee;Shin, Sujin;Park, Jin-Hwa
    • Journal of Korean Academy of Nursing
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    • v.45 no.2
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    • pp.159-168
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    • 2015
  • Purpose: The purpose of this study was to evaluate the methodological quality of nursing studies using structural equation modeling in Korea. Methods: Databases of KISS, DBPIA, and National Assembly Library up to March 2014 were searched using the MeSH terms 'nursing', 'structure', 'model'. A total of 152 studies were screened. After removal of duplicates and non-relevant titles, 61 papers were read in full. Results: Of the sixty-one articles retrieved, 14 studies were published between 1992 and 2000, 27, between 2001 and 2010, and 20, between 2011 and March 2014. The methodological quality of the review examined varied considerably. Conclusion: The findings of this study suggest that more rigorous research is necessary to address theoretical identification, two indicator rule, distribution of sample, treatment of missing values, mediator effect, discriminant validity, convergent validity, post hoc model modification, equivalent models issues, and alternative models issues should be undergone. Further research with robust consistent methodological study designs from model identification to model respecification is needed to improve the validity of the research.

The Impact of Climate Change on the Dynamics of Soil Water and Plant Water Stress (토양수분과 식생 스트레스 동역학에 기후변화가 미치는 영향)

  • Han, Su-Hee;Kim, Sang-Dan
    • Proceedings of the Korea Water Resources Association Conference
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    • 2009.05a
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    • pp.52-56
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    • 2009
  • In this study a dynamic modeling scheme is presented to derive the probabilistic structure of soil water and plant water stress when subject to stochastic precipitation conditions. The newly developed model has the form of the Fokker-Planck equation, and its applicability as a model for the probabilistic evolution of the soil water and plant water stress is investigated under climate change scenarios. This model is based on the cumulant expansion theory, and has the advantage of providing the probabilistic solution in the form of probability distribution function (PDF), from which one can obtain the ensemble average behavior of the dynamics. The simulation result of soil water confirms that the proposed soil water model can properly reproduce the results obtained from observations, and it also proves that the soil water behaves with consistent cycle based on the precipitation pattern. The plant water stress simulation, also, shows two different PDF patterns according to the precipitation. Moreover, with all the simulation results with climate change scenarios, it can be concluded that the future soil water and plant water stress dynamics will differently behave with different climate change scenarios.

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Stochastic Behavior of Plant Water Stress Index and the Impact of Climate Change (식생 물 부족 지수의 추계학적 거동과 기후변화가 그에 미치는 영향)

  • Han, Suhee;Yoo, Gayoung;Kim, Sangdan
    • Journal of Korean Society on Water Environment
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    • v.25 no.4
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    • pp.507-514
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    • 2009
  • In this study, a dynamic modeling scheme is presented to describe the probabilistic structure of soil water and plant water stress index under stochastic precipitation conditions. The proposed model has the form of the Fokker-Planck equation, and its applicability as a model for the probabilistic evolution of the soil water and plant water stress index is investigated under a climate change scenario. The simulation results of soil water confirm that the proposed soil water model can properly reproduce the observations and show that the soil water behaves with consistent cycle based on the precipitation pattern. The simulation results of plant water stress index show two different PDF patterns according to the precipitation. The simple impact assessment of climate change to soil water and plant water stress is discussed with Korean Meteorological Administration regional climate model.