• Korean Journal of Computational Design and Engineering
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• v.7 no.3
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• pp.190-201
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• 2002

Surfaces of many engineering structures, specially, those of ships and airplanes are commonly fabricated as doubly curved shapes as well as singly curved surfaces to fulfill functional requirements. Given a three dimensional design surface, the first step in the fabrication process is unfolding or planar development of this surfaces into a planar shape so that the manufacturer can determine the initial shape of the flat plate. Also a good planar development enables the manufacturer to estimate the strain distribution required to form the design shape. In this paper, an algorithm for optimal approximated development of a general curved surface, including both singly and doubly curved surface is developed in the sense that the strain energy from its planar development to the design surface is minimized, subjected to some constraints. The development process is formulated into a constrained nonlinear programming problem, which is on basis of deformation theory and finite element. Constraints are subjected to characteristics of the fabrication method. Some examples on typical surfaces and the practical ship surfaces show the effectiveness of this algorithm.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1112-1115
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• 2004

Recently, KTX start service 2004 and speed up the Chung-ang line and Ho-nam line using tilting train. When the train speed up at curve the vibration environment are changed. It is the reason of the wave propagation problem in the curved source. In this research, using SSI Program SASSI, Predict the vibration propagation around the curved source of vibration. The curved source of vibration propagation is different from straight source of vibration propagation. In this study, made a curved vibration source model and compared with straight model.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1118-1124
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• 2023

Experimental study on the fluidelastic instability (FEI) of a curved tube bundle in single phase downward cross flow is investigated for the design qualification and analysis input preparation of helical coiled steam generator tubing. A 6×9 normal square curved tube array with equal and different vertical/horizontal pitch-to-diameter ratio was under-tested up to 6 m/s in term of gap flow velocity to measure the critical velocity for FEI. The critical velocity for FEI was measured at the turning point from the vibration amplitude plot along the gap flow velocity. Our test results were compared with straight tube results and published data in the design guideline. The applicability of the current design guidelines to a curved tube bundle is also assessed. We found that introducing frequency difference in a curved tube array increases the critical velocity for fluidelastic instability.

• Structural Engineering and Mechanics
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• v.87 no.1
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• pp.85-94
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• 2023

In the present work, thermal buckling and post-buckling behaviors of imperfect graphene platelet reinforced metal foams (GPRMFs) doubly curved shells are examined. Material properties of GPRMFs doubly curved shells are presumed to be the function of the thickness. Reddy' shell theory incorporating geometric nonlinearity is utilized to derive the governing equations. Various types of the graphene platelets (GPLs) distribution patterns and doubly curved shell types are taken into account. The nonlinear equations are discretized for the case of simply supported boundary conditions. The thermal post-buckling response are presented to analyze the effects of GPLs distribution patterns, initial geometric imperfection, GPLs weight fraction, porosity coefficient, porosity distribution forms, doubly curved shell types. The results show that these factors have significant effects on the thermal post-buckling problems.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.793-802
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• 2002

This study presented a finite element formulation for the dynamic analysis of horizontally curved I-girder bridges. The stiffness and mass matrices of the curved and the straight beam elements are formulated. Each node of both elements has seven degrees of freedom, including the warping degree of freedom. The curved beam element is derived from Kang and Yoo's theory of thin-walled curved beams. The computer program EQCVB has been developed to perform dynamic analyses of various horizontally curved I-girder bridges. The Gupta method is used to solve the eigenvalue problem efficiently, while the Wilson-${\theta}$ method is used for the seismic analysis. The efficiency of EQCVB is demonstrated by comparing solution time with ABAQUS. Using EQCVB, the study is applied to investigate the dynamic behavior of horizontally curved I-girder bridges under seismic loading.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.4
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• pp.342-348
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• 2014

In general, the forming process of the curved hull plates consists of sub tasks, such as roll bending, line heating, and triangle heating. In order to complement the automated curved hull forming system, it is necessary to develop an algorithm to classify the curved hull plates of a ship into standard shapes with respect to the techniques of forming task, such as the roll bending, the line heating, and the triangle heating. In the previous research, the classification algorithm of curved hull plates was studied only about rectangle shaped plates, and other limitations were notified. In this paper, the classification algorithm is extended to classify not only rectangle shaped plates but also arbitrary polygon hull plates. The discrete curvature can be computed by using arbitrary polygon mesh which is represented by half-edge data structure and discrete differential geometry. The algorithm tests to verify the developed algorithm with sample plates of a real ship data have been performed.

• Journal of the Ergonomics Society of Korea
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• v.33 no.3
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• pp.191-202
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• 2014

Objective: This study is conducted on the differences between flat and curved displays with respect to location of focused points, posture and satisfaction as well as preferred tilt angles. Background: In order to avoid physical and eye fatigue caused by misplayed sitting posture, many studies have asserted that the display requires appropriate location, size and tilt angle as well as curvature. However, most studies have focused on the work environment and the results are varied in the extent. Method: Eye height data in sitting posture were collected from 30 participants. Participants selected the most comfortable viewing angle within the range from $0^{\circ}$ to $12^{\circ}$ while watching videos for both curved and flat display. Then, physical and eye fatigue and overall satisfaction were subjectively evaluated. Lateral diagram describing viewing display condition was set and used to develop linear models for expecting the preferred tilt angle. Results: Due to sitting in the natural viewing posture rather than upright, the eye height is lowered to about 4.6 centimeters, on average, for both displays showing no significant differences. In contrast, preferred angles for the two displays are significantly different and this can be interpreted that curvature vary the points focused. Two linear models as functions of sitting eye height are developed to expect preferred tilt angle for each display. Based on the result of overall satisfaction evaluation, curved display is statistically better than flat display. Conclusion: The results show that flat and curved displays are significantly different expect for the viewing posture. However, reasons for preferring curved display are not accurately factorized and the linear models are limited in the experiment condition such as size of display, distance between display and viewer and other physical environmental factors. Further studies on curved displays under more various conditions are required. Application: This study can contribute to use of the curved display in various way.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.3 s.18
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• pp.11-21
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• 2005

This study is performed to understand complex behavior and to investigate the rational analysis methods for seismic design of the curved bridges. To analyze the curved bridges for the seismic loadings, it is used that the finite element analysis program has the 7-dof curved beam and straight beam element. The free vibration characteristics of the curved bridges are compared with the straight bridges that have span length same as the average arc length of inside and outside girder of those. For the same case, the dynamic behavior is compared under seismic loadings. It is found that regular bridges classified by AASHTO are analyzed as if those were straight. To investigate the dynamic behavior of general curved bridges under seismic loading, the seismic loading directions and the subtended angle of curved bridges are varied.

• Korean Institute of Interior Design Journal
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• v.26 no.6
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• pp.163-171
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• 2017

Brick is not only aesthetically beautiful and emotional material, but also eco-friendly and good building commodity for human health. Nonetheless, the use of brick has declined, due to the difficulty of building high-rise buildings and the limitation of the free form implementation. However, modern society is increasingly interested in environmentally friendly finishing materials for solving environmental problems. From this point of view, the brick architecture is being reexamined as a material to improve the living environment and to provide comfort without destroying nature. In addition, the development of digital technology enables the implementation of various types of masonry method and curved forms. Parametric design is one of the ways to realize the curved forms and various architectural expressions for brick architecture. In this background, the purpose of this study is to develop algorithms that can easily generate curved brick walls through parametric design, enable various pattern designs, and respond to real-time feedback. The details of the study are as follows. First of all, we examine organic architecture, the trend of brick architecture, and the concept of parametric design. Secondly, In order to generate curved surface with complex curvature, major planning factors affecting form generation are examined. Finally, we develop a parametric design method that consists of generating a curved surface for brick arrangement, implementing a parametric algorithm, and generating a curved form using bricks. Consequentially, we propose an algorithm that can maximize the use of ready-made bricks without using cut bricks to design curved walls and present efficient and economical design alternatives.

• Journal of the Korean Institute of Gas
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• v.6 no.1 s.17
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• pp.1-9
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• 2002

This paper presents simple models for flow and the PIG dynamics when it passes through a $90^{\circ}$ curved section of pipeline. The simulation has been done with two different operational boundary conditions. The solution fur non-linear hyperbolic partial equations for flow is given by using MOC. The Runge-Kuta method is used to solve the initial condition equation fur flow and the PIG dynamics equation. The simulation results show that the proposed model and solution can be used fur estimating the PIG dynamics when the pig runs in the pipeline including curved section. In this paper, dynamic modeling and its analysis for the PIG flow through $90^{\circ}$ curved pipe with compressible and unsteady flow are studied. The PIG dynamics model is derived by using Lagrange equation under assumption that it passes through 3 different sections in the curved pipeline such that it moves into, inside and out of the curved section. The downstream and up stream flow dynamics including the curved sections are solved using MOC. The effectiveness of the derived mathematical models is estimated by simulation results fur a low pressure natural gas pipeline including downward and upward curved sections. The simulation results show that the proposed model and solution can be used for estimating the PIG dynamics when we pig the pipeline including curved section.