• Journal of Institute of Control, Robotics and Systems
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• v.10 no.2
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• pp.192-196
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• 2004

A combined optimal design problem is discussed taking a 3-D truss structure as a design object. We use descriptor forms for a controlled object and a generalized plant because the structural parameters appear naturally in these forms. We consider not only the minimum weight design problem for the structure, but also the suppression problem of the effect of disturbances for the control system as the purpose of the design. A numerical example shows the validity of combined optimal design of the structure and control systems. We also consider the validity of the sensor-actuator collocation for the control system design in this paper.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.153-159
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• 2004

A control-structure combined optimal design problem is discussed taking a 3-D truss structure as a design object. We use descriptor forms for a controlled object and a generalized plant because the structural parameters appear naturally in these forms. We consider not only minimum weight design problem for structure system, but also suppression problem of the effect of disturbances for control system as the purpose of the design. By minimizing the linear sum of the normalized structural objective function and control objective function, it is possible to make optimal design by which the balance of the structural weight and the control performance is taken.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1353-1362
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• 2003

This paper considers a simultaneous optimization problem of structure and control systems. The problem is generally formulated as a non-convex optimization problem for the design parameters of mechanical structure and controller. Therefore, it is not easy to obtain the global solutions for practical problems. In this paper, we parameterize all design parameters of the mechanical structure such that the parameters work in the control system as decentralized static output feedback gains. Using this parameterization, we have formulated a simultaneous optimization problem in which the design specification is defined by the Η$_2$and Η$\_$$\infty$/ norms of the closed loop transfer function. So as to lead to a convex problem we approximate the nonlinear terms of design parameters to the linear terms. Then, we propose a convex optimization method that is based on linear matrix inequality (LMI). Using this method, we can surely obtain suboptimal solution for the design specification. A numerical example is given to illustrate the effectiveness of the proposed method.

• Journal of the Korean Society for Library and Information Science
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• v.28
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• pp.247-266
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• 1995

The purpose of information retrieval is to help users solve their problems. To fulfill the purpose the user's problem needs to be focused on. The purpose of this study is to identify components and the structure of the user's problem in an academic research environment. From this study it was found that the scientific problem dealt within an academic environment is complicate and the problem is composed of 8 topical and 4 non-topical components. And they could be organized into a stucture. This study has three implications for user-oriented information retrieval. (1) The components and the structure of the problem need to be the framework for the effective information retrieval process and for the evaluation of information retrieval. (2) The research methodology used in this study can be applied to other information service situations and this will result in greater practical implication of a study for more effective information retrieval. And (3) for more effective user-oriented information retrieval, the user needs to be observed and studied in the actual' situation. This study showed that the complicate problem of the actual user can be studied in a systematic way and this resulted in important implications for information retrieval.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.1
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• pp.37-43
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• 2015

This paper presents a detailed procedure for a nonlinear soil-structure interaction of a seismically isolated NPP(Nuclear Power Plant) structure using the boundary reaction method (BRM). The BRM offers a two-step method as follows: (1) the calculation of boundary reaction forces in the frequency domain on an interface of linear and nonlinear regions, (2) solving the wave radiation problem subjected to the boundary reaction forces in the time domain. For the purpose of calculating the boundary reaction forces at the base of the isolator, the KIESSI-3D program is employed in this study to solve soil-foundation interaction problem subjected to vertically incident seismic waves. Wave radiation analysis is also employed, in which the nonlinear structure and the linear soil region are modeled by finite elements and energy absorbing elements on the outer model boundary using a general purpose nonlinear FE program. In this study, the MIDAS/Civil program is employed for modeling the wave radiation problem. In order to absorb the outgoing elastic waves to the unbounded soil region, spring and viscous-damper elements are used at the outer FE boundary. The BRM technique utilizing KIESSI-3D and MIDAS/Civil programs is verified using a linear soil-structure analysis problem. Finally the method is applied to nonlinear seismic analysis of a base-isolated NPP structure. The results show that BRM can effectively be applied to nonlinear soil-structure interaction problems.

• The Mathematical Education
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• v.26 no.2
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• pp.9-13
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• 1988

Mathematics education is generally to cultivate mathematical thought. Most meaningful thought is to solve a certain given situation, that is, a problem. The aim of mathematies education could be identified with the cultivation of mathematical problem-solving ability. To cultivate mathematical problem-solving ability, it is necessary to study the nature of mathematical ability and its aspects pertaining to problem-solving ability. The purpose of this study is to investigate the relation between problem-solving ability and classficational viewpoint of mathematical verbal problems, and bet ween the detailed abilities of problem-solving procedure and classificational viewpoint of mathematical verbal problems. With the intention of doing this work, two tests were given to the third-year students of middle school, one is problem-solving test and the other classificational viewpoint test. The results of these two tests are follow ing. 1. The detailed abilities of problem-solving procedure are correlated with each other: such as ability of understanding, execution and looking-back. 2. From the viewpoint of structure and context, students classified mathematical verbal problems. 3. The students who are proficient at problem-solving, understanding, execution, and looking-back have a tendency to classify mathematical verbal problems from a structural viewpoint, while the students who are not proficient at the above four abilities have a tendency to classify mathematical verbal problems from a contextual viewpoint. As the above results, following conclusions can be made. 1. The students have recognized at least two fundamental dimensions of structure and context when they classified mathematical verbal problems. 2. The abilities of understanding, execution, and looking- back effect problem-solving ability correlating with each other. 3. The instruction emphasizing the importance of the structure of mathematical problems could be one of the methods cultivating student's problem-solving ability.

• Korean System Dynamics Review
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• v.15 no.1
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• pp.29-50
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• 2014

This study aims to comprehensively understand the dynamics of the dementia as a social problem and to find out its causes and solutions, using the systems thinking approach. The contents of the study are as follows. Firstly, it examines the existing studies on the dementia, draws their limitations and further presents the major variables to understand the dementia as a social problem. Second, it analyzes the structure of the causation in order to find out the dynamics of the problem. Lastly, it concludes with the suggestions to solve the problem based on its feedback structure presented in the causal loop diagrams. This study is expected to make a useful and basic material to grope for the solutions, as the first research to dynamically understand the dementia as a social problem.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.49-58
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• 2019

Efficient evidential reasoning is an important issue in the development of advanced knowledge based systems. Efficiency is closely related to the design of problems solving methods adopted in the system. The explicit modeling of problem-solving structures is suggested for efficient and effective reasoning. It is pointed out that the problem-solving method framework is often too coarse-grained and too abstract to specify the detailed design and implementation of a reasoning system. Therefore, as a key step in developing a new reasoning scheme based on properties of the problem, the problem-solving method framework is expanded by introducing finer grained problem-solving primitives and defining an overall control structure in terms of these primitives. Once the individual components of the control structure are defined in terms of problem solving primitives, the overall control algorithm for the reasoning system can be represented in terms of a finite state diagram.

• Computational Structural Engineering : An International Journal
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• v.2 no.1
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• pp.33-42
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• 2002

A computationally efficient stiffness design method for building structures is proposed in which dynamic soil-structure interaction based on the wave-propagation theory is taken into account. A sway-rocking shear building model with appropriate ground impedances derived from the cone models due to Meek and Wolf (1994) is used as a simplified design model. Two representative models, i.e. a structure on a homogeneous half-space ground and a structure on a soil layer on rigid rock, are considered. Super-structure stiffness satisfying a desired stiffness performance condition are determined via an inverse problem formulation for a prescribed ground-surface response spectrum. It is shown through a simple yet reasonably accurate model that the ground conditions, e.g. homogeneous half-space or soil layer on rigid rock (frequency-dependence of impedance functions), ground properties (shear wave velocity), depth of surface ground, have extensive influence on the super-structure design.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.260-267
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• 1999

In this paper, We propose the initial shape finding and dynamic analysis of cable dome structure are presented. Cable dome that is consist of three component such as cable, strut and fabric membrane have complex structural characteristics. Main structural system of cable dome is cable-strut tensegric system, and fabric membrane element Is conceived as cladding roof material. One of the important problem of cable dome is shape finding of those subjected to cable and membrane forces, which stabilize the structures. And the other is structural response from external load effect such as snow and wind When cable dome are subjected to dynamic load such as wind load each structural component has many important problem because of their special structural characteristics. One problem is that geometrical nonlinearity should be considered in the dynamic analysis because large deformation is occurred from their flexible characteristic. The other problem is that wrinkling occurs occasionally because cable and membrane elements can not transmit compressive forces. So this paper describe the physical structural response of cable dome structure.