• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제6권1호
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• pp.60-68
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• 2003

This paper proposes an optimum design method of structural and control systems, using a 2-D truss structure as an example. The structure is subjected to initial static loads and disturbances. For the structure, a FEM model is formed. Using modal transformation, the equation of motion is transformed into modal coordinates, in order to decrease D.O.F. of the FEM model. To suppress the effect of the disturbances, the structure is controlled by an output feedback $H_{\infty}$ controller. The design variables of the combined optimal design of the control-structure systems are the cross sectional areas of truss members. The structural objective function is the structural weight. The control objective function is the $H_{\infty}$ norm, the performance index of control. The second structural objective function is the energy of the response related to the initial state, which is derived from the time integration of the quadratic form of the state in the closed-loop system. In a numerical example, simulations have been perform. Through the consideration of structural weight and $H_{\infty}$ norm, an advantage of the combined optimum design of structural and control systems is shown. Moreover, since the performance index of control is almost nearly optimiz, we can acquire better design of structural strength.

• Nuclear Engineering and Technology
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• 제41권5호
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• pp.649-654
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• 2009

The finite element based lattice Boltzmann method (FELBM) has been developed to model complex fluid domain shapes, which is essential for studying fluid-structure interaction problems in commercial nuclear power systems, for example. The present study addresses a new finite element formulation of the lattice Boltzmann equation using a general weighted residual technique. Among the weighted residual formulations, the collocation method, Galerkin method, and method of moments are used for finite element based Lattice Boltzmann solutions. Different finite element geometries, such as triangular, quadrilateral, and general six-sided solids, were used in this work. Some examples using the FELBM are studied. The results were compared with both analytical and computational fluid dynamics solutions.

• 전자공학회논문지B
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• 제30B권10호
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• pp.77-85
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• 1993

In this paper, we present a method to solve a convexly combined fuzzy relational equation with generalized connectives. For this, we propose a neural network whose structure represents the fuzzy relational equation. Then we derive a learning algorithm by using the concept of back-propagation learning. Since the proposed method can be used for a general form of fuzzy relational equations, such fuzzy max-min or min-max relational equations can be treated as its special cases. Moreover, the relational structure adopted in the proposed neurocomputational approach can work in a highly parallel manner so that real-time applications of fuzzy sets are possibles as in fuzzy logic controllers, knowledge-based systems, and pattern recognition systems.

• 전기의세계
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• 제30권12호
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• pp.822-831
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• 1981

Many different schemes of the adaptive observer and controller have been developed for both continuous and discrete systems. In this paper we have presented a new scheme of the reduced order adaptive observer for the single input discrete linear time invariant plant. The output equation of the plant, is transformed into the bilinear form in terms of system parameters and the states of the state variable filters. Using the plant output equation the discrete implicit adaptive observer based on the similar philosophy to Nuyan and Carroll is derived and the parameter adaptation algorithm is derived based on the exponentially weighted least square method. The adaptive model following control system is also constructed according to the proposed observer scheme. The proposed observer and controller are rather than simple structure and have a fast adaptive algorithm, so it may be expected that the scheme is suitable to the practical application of control system design. The effectiveness of the algorithm and structure is illustrated by the computer simulation of a third order system. The simulation results show that the convergence speed is proportinal to the increasing of weighting factor alpha, and that the full order and reduced order observer have similar convergence characteristics.

• Coupled systems mechanics
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• 제12권4호
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• pp.337-364
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• 2023

The Rayleigh wave propagation is considered in the structure of the functionally graded piezoelectric material (FGPM) layer over the elastic substrate. The elastic substrate loosely bonds the layer through a corrugated interface, whereas its upper boundary is also corrugated but stress-free. Additionally, the solutions for the FGPM layer and substrate are derived using the fundamental variable separable approach to convert the partial differential equation to an ordinary differential equation. The results with boundary conditions lead to dispersion relations for the electrically open and electrically short cases in the determinant form. The outcomes have been numerically analyzed using a specific model. The findings were presented in the form of graphs, which were created using Mathematica 7. Graphs are plotted for variations in wavenumber and phase velocity. The outcomes may help measure interface defects and design Surface Acoustic Wave (SAW) devices.

• Structural Engineering and Mechanics
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• 제85권1호
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• pp.119-133
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• 2023

Impact event is the key factor influencing the operational state of the mechanical equipment. Additionally, nonlinear factors existing in the complex mechanical equipment which are currently attracting more and more attention. Therefore, this paper proposes a novel hybrid-separate identification strategy to solve the force identification problem of the nonlinear structure under impact excitation. The 'hybrid' means that the identification strategy contains both l1-norm (sparse) and l2-norm regularization methods. The 'separate' means that the nonlinear response part only generated by nonlinear force needs to be separated from measured response. First, the state-of-the-art two-step iterative shrinkage/thresholding (TwIST) algorithm and sparse representation with the cubic B-spline function are developed to solve established normalized sparse regularization model to identify the accurate impact force and accurate peak value of the nonlinear force. Then, the identified impact force is substituted into the nonlinear response separation equation to obtain the nonlinear response part. Finally, a reduced transfer equation is established and solved by the classical Tikhonove regularization method to obtain the wave profile (variation trend) of the nonlinear force. Numerical and experimental identification results demonstrate that the novel hybrid-separate strategy can accurately and efficiently obtain the nonlinear force and impact force for the nonlinear structure.

• 대한간호학회지
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• 제39권3호
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• pp.446-457
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• 2009

Purpose: The aim of this study was to construct a structural equation model that would further explain the continuously increasing substance use disorder in Korean adolescents. Methods: Survey visits using a structured questionnaire were conducted with 3,885 students in 2 middle schools and 2 high schools in Busan. A total of 13 instruments were used in this model. The analysis of data was done with both SPSS 14.0 for descriptive statistics and AMOS 5.0 for covariance structure analysis. Results: Based on the constructed model, belief on substance use was found to have a significantly direct effect in influencing adolescent substance use. In addition, other factors such as family environment, satisfaction with school life, self-concept, social support, and personality vulnerability indirectly affected substance use. The final modified model yielded Chi-square=2,987(p<.001), df=121, ${\chi}^2$/df=22.1, GFI=.96, AGFI=.93, NFI=.91, PNFI=.72, PGFI=.72, RMSEA=.07 and exhibited fit indices. Conclusion: This study constructed a model that addresses the factors related to adolescent substance use and explains the relationship of these factors in influencing substance use among Korean adolescents. Findings from this study can contribute to designing appropriate prevention strategies to reduce substance related disorders in adolescents.

• Nutrition Research and Practice
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• 제6권4호
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• pp.357-365
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• 2012

This study was conducted to develop a construct model regarding the daily activities, emotional security provided by food, enjoyment of food, level of satisfaction with delivered food, and the quality of life of homebound seniors who benefitted from meal delivery programs. The data were analyzed by SAS 9.2 and the Structural Equation Model (SEM), which was created by Analysis of Moment Structure (AMOS) 5.0 packages. The reliability of the data was confirmed by an exploratory factor analysis and through a Cronbach's alpha coefficient, and the measurement model proved to be appropriate by a confirmatory factor analysis of the measurement model in conjunction with AMOS. The results of the correlations between all the variables showed significant positive correlations (P < 0.05). The path analysis demonstrated that the daily activities (P < 0.01) and the emotional security created by food (P < 0.05) had positive correlations with the foodservice satisfaction (P < 0.05), while the daily activities (P < 0.05), the sense of emotional security made by food (P < 0.05), and food enjoyment (P < 0.05) also presented significant positive correlations with the quality of life. However, the food service satisfaction was shown to directly, but not significantly, affect the quality of life. This revealed that the current meal delivery programs needed to be improved in several directions.

• 한국정보전자통신기술학회논문지
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• 제11권4호
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• pp.340-345
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• 2018

수식은 일반 문장에 비해 복잡한 구조와 다양한 문자와 기호가 사용되어 단순한 키보드 입력만으로는 모든 문자 집합을 입력할 수 없어 한글이나 워드 같은 문서편집기 내에서도 자체적으로 구현된 수식 편집기를 사용하고 있다. 수식을 올바르게 표현하기 위해 구문을 해석할 수 있는 의미가 될 수 있는 사전 학습 정보가 필요하다. 문자가 입력되더라도 크기와 위치 서로간의 관계에 따라 다른 수식으로 표현될 수 있기 때문이다. 즉 표현될 위치와 크기 등 문자와 기호들 간의 상호관계를 고려하여 수식의 형태를 트리 모델로 표현한다. 문자인식 응용의 한 분야로 문자나 기호(부호)를 인식하는 기술을 이미 널리 알려졌지만, 수식을 입력과 해석하는 방법은 일반적인 텍스트에 비해 복잡한 분석 과정이 필요하다. 본 논문에서는 수식의 문자를 인식하고 표현되는 위치와 크기의 결정을 빠르게 해석하는 수식 인식기를 구현하였다.

• 한국포장학회지
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• 제12권1호
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• pp.45-53
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• 2006

Thermal insulation is used in a variety of applications to protect temperature sensitive products from thermal damage. Several factors affect the performance of insulation packages. Among these factors, the thermal resistance of the insulating wall is the most important factor to determine the performance of the insulating package. In many cases, insulating wall consists of multi-layered structure and the heat transfer through this structure is a very complex process. In this study, an one-dimensional mathematical model, which includes all of the heat transfer principles covering conduction, convection and radiation in multi-layered structure, were developed. Based on this model, several heat transfer phenomena occurred in the air space between the layer of the insulating wall were investigated. From the simulation results, it was observed that the heat transfer through the air space between the layer were dominated by conduction and radiation and the low emissivity of the surface of each solid layer of the wall can dramatically increase the thermal resistance of the wall. For practical use, an equation was derived for the calculation of the thermal resistance of a multi-layered wall.