• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.54-64
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• 1998

This study was initiated to examine the stress and deformation characteristics of the pipelines which were subjected to various environmental conditions in order to confirm their integrity. As the part of them, this paper presents the analysis results for the effect of ground subsidence combined with main loads on buried natural gas pipelines. The ground subsidence which can occur for buried gas pipeline has been classified to the three cases. Finite element method was used to analyze the effect of ground subsidences on pipeline of 26 inch(0.660 m) and 30 inch(0.762 m) diameter used as high pressure ($70 kg_f/cm^2(6.86 MPa)$) main pipelines of KOGAS. This paper shows the result of stress analysis for the pipelines subjected to those three case ground subsidence. Comparing these results with safety criterion of KOGAS(0.9 $\sigma_y$), maximum allowable settlement and loads have been calculated.

• Advances in Computational Design
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• v.2 no.4
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• pp.273-281
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• 2017

In this work, a comparative study of multi-objective meta-heuristics (MOMHs) for optimum design of a walking tractor handlebar is conducted in order to reduce the structural mass and increase structural static and dynamic stiffness. The design problem has objective functions as maximising structural natural frequencies, minimising structural mass, bending deflection and torsional deflection with stress constraints. The problem is classified as a many-objective optimisation since there are more than three objectives. Design variables are structural shape and size. Several well established multi-objective optimisers are employed to solve the proposed many-objective optimisation problems of the walking tractor handlebar. The results are compared whereas optimum design solutions of the walking tractor handlebar are illustrated.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.86-93
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• 1999

Turbocharger has been used to increase the performance of diesel engine, especially ship engine , for years. Recently, the turbocharger is being adopted not only for an agricultural engine but also for an automobile engine. To improve the performance of diesel engine , the problem of the reduction of A/F ratio in high speed should be solved. Turbocharger is well known for its cost effectiveness, reliability and duration . In this study, an experiment was conducted to verify simulation program . The results for natural aspiration engine and turbocharged engine were compared. In order to estimate the characteristics of exhaust gas, D-13 mode was selected. Power, torque and BSFC of turbocharged engine were increased than those of natural aspiration engine by about 48%, 46% and 5%, respectively . The components in exhaust gas except NOx from turbocharger engine were less than the amount set up for 2000-year regulation.

• Coupled systems mechanics
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• v.5 no.1
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• pp.59-86
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• 2016

This paper deals with the free vibration analysis of a dynamical coupled system: flexible gravity dam- compressible rectangular reservoir. The finite element method is used to compute the natural frequencies and modal shapes of the system. Firstly, the reservoir and subsequently the dam is modeled by classical 8-node elements and the natural frequencies plus modal shapes are calculated. Afterwards, a new 21-node element is introduced and the same procedure is conducted in which an efficient method is employed to carry out the integration operations. Finally, the coupled dam-reservoir system is modeled by solely one 21-node element and the free vibration of dam-reservoir interaction system is investigated. As an important result, it is clearly concluded that the one high-order element treats more precisely than the eight-node elements, since the first one utilizes fifth-degree polynomials to construct the shape functions and the second implements polynomials of degree two.

• Structural Monitoring and Maintenance
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• v.7 no.1
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• pp.59-67
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• 2020

This study aims to develop the fuzzy risk assessment model of the debris flow to verify the accuracy of risk assessment in order to help related organizations reduce losses caused by landslides. In this study, actual cases of landslides that occurred are utilized as the database. The established models help us assess the occurrence of debris flows using computed indicators, and to verify the model errors. In addition, comparisons are made between the models to determine the best one to use in practical applications. The results prove that the risk assessment model systems are quite suitable for debris flow risk assessment. The reproduction consequences of highlight point discovery are shown in highlight guide coordinating toward discover steady and coordinating component focuses and effectively identified utilizing these two systems, by examining the variety in the distinguished highlights and the element coordinating.

• Architectural research
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• v.15 no.1
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• pp.35-42
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• 2013

A study on the free vibration and linear buckling analyses of thick plates is described in this article. In order to determine the natural frequencies and buckling loads of plates, a plate element is developed by using isogeometric approach. The Non-uniform B-spline surface (NURBS) is used to represent both plate geometry and the unknown displacement field of plate. All terms required in isogeometric formulation are consistently derived by NURBS definition. The capability of the present plate element is demonstrated by using several numerical examples. From numerical results, it is found to be that the present isogeometric element can predict accurate natural frequencies and buckling loads of plates.

• Journal of Korea Multimedia Society
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• v.18 no.10
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• pp.1231-1240
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• 2015

Nowadays, in islands where electricity should be provided autonomously, stand-alone microgrid technologies using renewable energy such as sunlight generation and wind power generation come into wide use. The microgrid electricity generation using renewable energy is greatly affected by the natural environment of a site. In order to maintain stable electricity supply for fluctuating electricity generation due to natural environment, the energy management via EMS is positively necessary. In existing stand-alone microgrid EMS, system operation logic is not changeable flexibly because compiled or builded codes are released into the EMS of a site, respectively. In this paper, we designed a flexible operating script-based microgrid EMS Framework for various sites and applied it to some island sites. We could confirm its usability.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.33-35
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• 2005

We propose an eye gaze tracking system under natural head movements. The system consists of one CCD camera and two front-surface mirrors. The mirrors rotate to follow head movements in order to keep the eye within the view of the camera. However, the mirror controller cannot guarantee the fast head movements, because the frame rate is generally 30Hz. To overcome this problem, we applied Kalman predictor to estimate next eye position from the current eye image. In the results, our system allows the subjects head to move 50cm horizontally and 40cm vertically, with the speed about 10cm/sec and 6cm/sec, respectively. And spatial gaze resolutions are about 4.5 degree and 4.5 degree, respectively, and the gaze estimation accuracy is 92% under natural head movements.

• YAKHAK HOEJI
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• v.54 no.4
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• pp.232-239
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• 2010

Stems and roots of Acanthopanax koreanum Nakai were extracted with water and treated on immune cells in order to determine their immunomodulatory activites. Various Th-1 type cytokines were measured using ELISA including interleukin (IL)-2, IL-12, interferon-gamma (IFN-$gamma$), and tumor necrosis factor-alpha (TNF-$\alpha$) secreted by dendritic cells, T-cells, intestinal epithelial cells, natural killer cells, and macrophages. As a result, there was a significant increase in IL-12 and IFN-$\gamma$, secretion, but there was no change in the secretion of TNF-$alpha$. Additionally T-cells slightly increased the secretion of IL-2, but there was a significant increase of IL-2 in intestinal epithelial cells. Therefore, our results suggest that A. koreanum Nakai may act as an immunomodulator by stimulating the cell-mediated immunity which can help the immune system defend against infections or cancer cells.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.4
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• pp.265-277
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• 1993

Recently, underground transmission system is growing continuously according to the electric power demand increase in the downtown area. Even if domestic cable makers are manufacturing 154kV oil filled cable and joint, the design technology of cable-joint has not been fully self-reliance. This study is aimed at the detail heat transfer analysis of 154kV cable-joint. So, that is cut into the five sections in order to analyze a conjugate natural convection in two dimensional $r-{\theta}$ coordinate. The streamline and temperature distributions are obtained for each sections. Also the changes of those are analyzed with respect to the variation of transmission currents and cable-joint surface heat transfer coefficients. The same analyses are also shown in view point of the maximum temperature of conductor and local equivalent conductivity.