• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1209-1212
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• 1999

The entropies and chemical potentials of hard-sphere solutes solvated in hard-sphere solids were calculated by Monte Carlo method using the radial free-space distribution function. This method is based on calculating the entropy by comparing the free volume of a molecule with that of an ideal gas, and is applicable even when the size of solute is very large and the solvent is a solid. When the diameter of hard-sphere solute is small the solute molecule behaves as like as a fluid in solid structures, but when the diameter of solute becomes large, a fluid-to-solid phase transition takes place. The fluid-to-solid phase transition occurs at the region of the smaller size of solute with the more increase of solvent density. The least square fit values of analytical form of the radial free-space distribution functions of solute molecules are presented for future uses.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.4
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• pp.572-578
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• 2008

We analyze the search space considered by the previously proposed R-CORE method for learning Bayesian network structures of large scale. Experimental analysis on the search space of the method is also shown. The R-CORE method reduces the search space considered for Bayesian network structures by recursively clustering the random variables and restricting the orders between clusters. We show the R-CORE method has a similar search space with the previous method in the worst case but has a much less search space in the average case. By considering much less search space in the average case, the R-CORE method shows less tendency of overfitting in learning Bayesian network structures compared to the previous method.

• Steel and Composite Structures
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• v.46 no.2
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• pp.211-220
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• 2023

Welded hollow spherical joints are commonly used joints in space grid structures. An internal stiffener is generally adopted to strengthen the joints when large hollow spheres are used. To further strengthen it, external stiffeners can be used at the same time. In this study, axial compression tests are conducted on four full-scale 550 mm spherical joints. The failure modes and strengths of the tested joints are investigated. It shows that the external stiffeners are able to increase the strength of the joint up to 25%. A numerical model for large spherical joints with stiffeners is established and verified against the experimental results. Parametric studies are executed considering six main design factors using the verified model. It is found that the strength of the spherical joint increases as the thickness, height and number of the external stiffeners increase, and the hollow sphere's diameter has a neglectable effect on the enhancement caused by the external stiffeners. Based on the experimental and numerical results, a practical formula for the compressive bearing capacity of large welded hollow spherical joints with both internal and external stiffeners is proposed. The proposed formula gives a conservative prediction on the compressive capacity of large welded hollow spherical joints with both internal and external stiffeners.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.3
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• pp.17-21
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• 2004

Tape-wrapped structures have been generally used in nozzle parts of guided missiles. A continuous band of woven composite material is wrapped around a mandrel that is designed to produce real products. After going through a vacuum bagging process, this woven composite material is cured in a high-pressure autoclave or hydroclave. However, tape-wrapped structures are difficult to analyze because of its large thickness and inclined lay-up. The present study investigates the method of analysis and failure prediction of tape-wrapped structures. The four-point bending test and its finite element analysis were performed to study how to model tape-wrapped structures and investigate their failure characteristics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2502-2512
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• 2000

Truss structures are widely used in many space structures, such as large antenna systems, space stations, precision segmented telescopes because they are light in weight and amenable in assembly or deployment. But, due to the low damping capacity, they remain excited for a long time once disturbed. These structural vibrations can reduce life of the structures and cause unstable dynamic characteristics. In this research, vibration suppression experiment has carried out with a three-dimensional 15-member truss structure using two piezoelectric actuators. Piezoelectric actuators which consist of stacks of thin piezoelectric material disks are directly inserted to the truss structure collocated with the strain sensors. Each actuator is controlled digitally in decentralized manner, based on local integral and proportional feedback. The optimal positions of the actuators are determined by the modal damping ratio and the control force. Numerical simulation has carried out to determine optimal position of each actuator.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.129-136
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• 1999

This research proposes an effective analytical methodology for vertical vibration of three dimensional frame structures including slabs. The consideration of slabs, although allows more precise results, requires large amount of computer time and memory space due to the use of plane stress elements. In consideration of these problems, a method to properly manage nodal points and degrees of freedom is proposed based on matrix condensation technique. Also studied is the use of substructure method to obtain fast and reliable results with simple input data when they are applied to conventional building structures.

• Journal of Korean Association for Spatial Structures
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• v.4 no.4 s.14
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• pp.77-84
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• 2004

Researches on spherical shell which is most usually applied have been completed by many investigators already and generalized numerical formula was derived. But the existent researches are limited to those on spherical shell with isotropic or orthotropic roof stiffness, periodic distribution of roof stiffness that can be caused by spherical and latticed roof system is not considered. Therefore, the object of this study is to develop a structural analysis program to analyze spherical shells that have periodicity of roof stiffness distribution caused by latticed roof of large space structure, grasp buckling characteristics and behavior of structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.225-233
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• 2004

Deployable structures are space frames consisting of straight bars that are linked together into bundle and can be deployed large, load bearing structures. Deployable structures are easy to set up, to assemble, to disassemble, to transport and to keep for the use. Also, reusability and flexibility are another important advantages for environmental matter. Since deployable structures have various advantages, they offer viable alternatives for a wide range of potential applications in the temporary construction industry as well as in the aerospace industry, The purpose of this thesis is to decide on geometrical parameters of the design through the numerical analysis and create a final configuration of deployable structures using the geometrical parameters. The Multibody Dynamic Analysis that is dealt with mechanics and aeronautics is used for the method of analysis.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.176-183
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• 2004

Deployable structures are space frames consisting of straight bars that are linked together into bundle and can be deployed large, load bearing structures. Deployable structures are easy to set up, to assemble, to disassemble, to transport and to keep for the use. Also, reusability and flexibility are another important advantages for environmental matter. Since deployable structures have various advantages, they offer viable alternatives for a wide range of potential applications in the temporary construction industry as well as in the aerospace industry. The purpose of this thesis is to decide on geometrical parameters of the design through the numerical analysis and create a final configuration of deployable structures using the geometrical parameters. The Multibody Dynamic Analysis that is dealt with mechanics and aeronautics is used for the method of analysis.

• Journal of Korean Association for Spatial Structures
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• v.5 no.2 s.16
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• pp.81-87
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• 2005

The Space structures may have large freedom in scale and form. And especially Hybrid structures are received much attention from the view points of their light weight and aesthetics. Hybrid systems are stable structures which are reticulated spatial structures composed of compressive straight members, struts and cables and Membranes. In this paper, The Hybrid Unit System are suggested using the Membrane and Cable elements based on the Tensegrity Unit system. Also, The Hybrid System of double-layered single curvature is presented. We analyze the force density method allowing form-finding for Tensegrity systems. And We analyze the shape analysis by the LARSH which is the program for nonlinear analysis.