• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.6
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• pp.689-693
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• 2023

Domestic bridges with a service life of more than 30 years are expected to account for approximately 54% of all bridges within the next 10 years. As bridges rapidly deteriorate, it is necessary to establish an appropriate maintenance plan. Recent domestic and international research have focused on the integration of BIM to digitize bridge maintenance information and then enhance accessibility and usability of the information. Accordingly, this study developed a BIM-FEM interoperability algorithm for bridge decks to convert maintenance information into data and efficiently manage the history of maintenance. After creating an initial crack BIM based on an exterior damage map, bridge specification and damage information were linked to a numerical analysis that performs damage analysis considering damage scenarios and design loads. The spread of cracks obtained from the analysis results were updated into the BIM. Based on the damage spread information on the BIM, an automated technology was also developed to assess both the current and future condition ratings of the bridge deck. This approach can enable an efficient maintenance of the deck using the history data from bridge inspection and diagnosis as well as future information on cracks and defects. The expected early detection and prevention would ultimately improve the lifespan and safety of bridges.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.1
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• pp.57-63
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• 2007

The systematic method to construct equivalent static load from a given dynamic load is proposed in the present study. Previously reported works to construct equivalent static load were based on ad hoc methods. Due to improper selection of loading position, they may results in unreliable structural design. The present study proposes the employment of primary degrees of freedom for imposing the equivalent static loads. The degrees of freedom are selected by two-level condensation scheme with reliability and efficiency. In several numerical examples, the efficiency and reliability of the proposed scheme is verified by comparison displacement for equivalent static loading and dynamic loading at the critical time.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.746-752
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• 2009

In this paper, we deal with the development of an optimal design program for a triple-band PTFA(Planar Inverted-F Antenna) of 433 MHz, 912 MHz and 2.45 GHz by using evolution strategy. Generally, the resonance frequency of the PIFA is determined by the width and length of a U-type slot used. However the resonance frequencies of the multiple U slots are varied by the mutual effect of the slots. Thus the optimal width and length of U-type slots are determined by using an optimal design program based on the evolution strategy. To achieve this, an interface program between a commercial EM analysis tool and the optimal design program is constructed for implementing the evolution strategy technique that seeks a global optimum of the objective function through the iterative design process consisting of variation and reproduction. The resonance frequencies of the triple-band PIFA yielded by the optimal design program are 430 MHz, 910.5 MHz and 2.458 GHz that show a good agreement to the design target values.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.176-182
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• 1997

A simulation model for the analysis of the transmissivity of direct and diffuse solar radiation In glasshouse was developed. This model would be applicable to investigate the influences of time of year, orientation and slope of glasshouse, dimensions of the frames used, and latitude of the site on the transmissivity of direct and diffuse solar radiation in single-span or multispan glasshouse. The transmissivity of diffuse solar radiation was 60.4％ for the single-span glass-house. It was independent of both orientation and time of year, During the winter season, the transmissivity of direct solar radiation was 67~69％ for the E-W orientation single-span glasshouse, which was 14~16％ higher than that for the S-N orientation. Oppositely the transmissivity of direct solar radiation for the S-N orientation was higher than that for the E-W orientation. during the autumn season. There was no influence of the latitude In the country on the transmissivity of direct solar radiation.

• The KIPS Transactions:PartA
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• v.14A no.2
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• pp.125-132
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• 2007

Recently, in the engineering area, there is an increasing need for researchers at a distance to share the result of the experiment, without having to visit the experiment facilities. Especially in the civil engineering, researchers feel the need for participating in a experiment conducted at a distant location. In addition, it is suggested that high-cost facilities should be used by remote researchers thereby increasing the utilization rate. This paper proposes a remote experiment environment in civil engineering that are being developed in a project called Korea Construction Engineering Development(KOCED), which connects major civil engineering experiment facilities using grid technology, allows researchers to participate in a remote experiment, and has the experiment results shared by remote researchers automatically. Then, based on the suggested environment, we designed a hybrid test facility that involves two physical experiment facility sites and one numerical simulation site that are geographically apart. Then, we implemented its prototype and ran some tests, which showed a possibility of grid-based civil engineering experiment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.4
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• pp.326-333
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• 2015

A turbo fan engine performance analysis program combined with a particle swarm optimization(PSO) has been developed to optimize the major design parameters of the combat aircraft gas turbine engine. The optimized parameters includes bypass ratio, fan pressure ratio, high pressure compression ratio and burner exit temperature. The objective parameters have been determined using a multi-objective function consisting of the net thrust and specific fuel consumption along a weight function. The basic model for the combat aircraft gas turbine engine has been selected as the F404 turbofan engine which is widely used in the combat aircraft, F-18 and Korean high level training aircraft, T-50. The optimal conditions of four parameters have been obtained for various design conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.138-146
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• 2010

DC railway power supply system generally uses the running rails as negative-polarity return conductor for traction load current, and the induced rail potential and stay current cause serious problems to any electrified matter in the underground and also safety problems to human body. This paper presents a new algorithm for the analysis of the rail potential and the stray current in DC railway power system operated under independent/parallel power feeding mode. The effect of load current fluctuation during train operation is also calculated by using TPS(Train Performance Simulation) program to analysis the variation of the railway potential and stray current along railway track. Simulation program is developed based on the proposed algorithm and case studies are provided.

• Journal of Korean Society of Steel Construction
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• v.12 no.1 s.44
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• pp.45-54
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• 2000

Design-oriented approximate structural reanalysis models are compared and assessed, particularly with focus on the case of large changes of design variables. The effectiveness and reliability are demonstrated by means of numerical examples. The results of the study suggest the following conclusions relative to the potential of the procedures. (A) local approximation is only appropriate for the case of small changes in design : (B) global approximation is exact for the case of large changes in a small number of design variables, but inefficient : (C) local-global approximation is most effective and reliable for the case of large changes with a large number of design variables. These methods can improve the total efficiency when they are appropriately used to the design information for the redesign process of large scale structures.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.3
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• pp.237-242
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• 2014

Surge phenomenon can be occurred in a compressor when the performance of turbofan engine for an aircraft is changed considerably such as take-off phase. This study is aimed to avoid surge phenomenon. This paper propose the PID and Fuzzy control System for the turbofan engine with control inputs, the VIGV(Variable Inlet Guide Vane) in closed loop, and the fuel mass flow in open loop. We design the Dynamic modeling, NPSS S-function, which is connection block of simulink between NPSS(Engine analysis program) and Simulink. Finally, we certify the performance to prevent a serge phenomenon in the VIGV control system using the both methods, PID and fuzzy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.67-75
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• 2011

This paper investigates the radiated emission from the enclosure aperture, when the enclosure contains a 4-layer PCB and the PCB is driven by a pulse train additive with the switching noise from an active device. Radiated emission characteristics with and without switch noise cases, respectively, are analyzed by changing the PCB location and the slot direction. The equivalent circuit of a DC-DC converter is used to simulate the switching noise of active device. Also, MWS simulation results are directly connected to the ADS simulator as a 2-port block. The simulated results are compared with the measured ones.