• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.437-447
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• 2009

It is easily found by several references of NATM that the cracks on the lining concrete of NATM are more developed than those of the conventional tunnel methods. Based on the results of research, the new method is proposed to control and protect the axial cracks on the tunnel linings. Also, the efficiency of proposed method is evaluated using the Distinct Element Method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.10a
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• pp.21-27
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• 1993

매개변수가진에 종속되는 현의 횡방향진동을 시간영역에서 필터작업, 힐버트 변환과 순간주파수 개념을 도입하여 해석함으로서 종방향의 순간진동변위를 추정하는 방법이 제시되었다. 그리고, 실험을 통하여 이론의 타당성을 검증 하였다. 또한, 모의 실험의 결과 일반적인 현구동계에 있어서는 넓은 적용변 수의 선\ulcorner영역에서 종변위가 횡변위와 분리(decoupling) 되어서 공간적으로 길이에 따르는 선형적인 증가성과 시간적으로 조화적인 주기성을 가진다는 것을 확인함으로서 임의의 위치에서의 종변위를 파악함이 가능하였다.

• Journal of the Korean Society of Hazard Mitigation
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• v.2 no.3 s.6
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• pp.119-125
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• 2002

The objective of this study is to evaluate elastic modulus of bridge-axis direction for optimum structure system in the cable-stayed bridge design. In numerical example of this study, a slight change in axis direction elastic modulus causes major modifications of the bridge characteristics when it is $1\times10^4$ tonf/m/bearing or less. Therefore, the elastic modulus was set at this lower limit of $1\times10^4$ tonf/m/bearing where the strength of the entire bridge system is still determined by girder strength and the entire system is insensitive to variations in elastic modulus. Besides, cable-stayed bridge with freely supported girders have slightly longer vibration periods in the horizontal direction for earthquake forces.

• Journal of the Korean GEO-environmental Society
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• v.20 no.10
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• pp.15-27
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• 2019

In this study, in order to analyze the effect of cylindrical baffles on the debris flow energy, small-scale tests were conducted using a flume with cylindrical baffles. Various row numbers of installed baffles were considered as a test condition. To investigate the scale effect of debris flow and cylindrical baffles on flow characteristics, large-scale tests were also performed according to varying row numbers of baffle for same baffle configuration with small-scale tests. Both small- and large-scale test results showed that the increase of row number of baffle increase the energy dissipation effect due to reduction of the velocity and flow depth of debris flow.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.931-940
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• 2017

This paper describes a predictive fault diagnosis algorithm for autonomous vehicles based on a kinematic model that uses a sliding mode observer. To ensure the safety of autonomous vehicles, reliable information about the environment and vehicle dynamic states is required. A predictive algorithm that can interactively diagnose longitudinal environment and vehicle acceleration information is proposed in this paper to evaluate the reliability of sensors. To design the diagnosis algorithm, a longitudinal kinematic model is used based on a sliding mode observer. The reliability of the fault diagnosis algorithm can be ensured because the sliding mode observer utilized can reconstruct the relative acceleration despite faulty signals in the longitudinal environment information. Actual data based performance evaluations are conducted with various fault conditions for a reasonable performance evaluation of the predictive fault diagnosis algorithm presented in this paper. The evaluation results show that the proposed diagnosis algorithm can reasonably diagnose the faults in the longitudinal environment and acceleration information for all fault conditions.

• Journal of Korean Society of Steel Construction
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• v.22 no.3
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• pp.219-228
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• 2010

This paper describes an experimental research on the structural behavior and the ultimate strength of longitudinally stiffened plates subjected to local, distortional, or mixed-mode buckling under compression. The stiffened plate undergoes local, distortional, or interactive local-distortional buckling according to the flexural rigidity of the plate's longitudinal stiffeners and the width-thickness ratios of the sub-panels of the stiffened plate. A significant post-buckling strength in the local and distortional modes affects the ultimate strength of the longitudinally stiffened plate. Compression tests were conducted on stiffened plates that were fabricated from 4mm-thick SM400 steel plates with a nominal yield stress of 235MPa. A simple strength formula for the Direct Strength Method based on the test results was proposed. This paper proves that the Direct Strength Method can properly predict the ultimate strength of stiffened plates when the local buckling and distortional buckling occur simultaneously or nearly simultaneously.

• Water for future
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• v.29 no.4
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• pp.187-198
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• 1996

A numerical model for unsteady dispersion of horizontal line source in turbulent shear flow is developed. A fractional step finite difference method is used which splits the unsteady two-dimensional advective diffusion equation into the longitudinal advection and the vertical diffusion equations, and solves them alternately for half time intervals by the Holly-Preissmann scheme and the Crank-Nicholson scheme, respectively. The developed numerical model is verified using a semi-analytic solution for steady dispersion in turbulent shear flow. Dispersion of an instantaneous plane source in turbulent shear flow is analyzed using the model. The degree of mixing at the same dimensionless time is almost the same regardless of the friction factor, and the travel distance required to reach a certain degree of mixing is inversely proportional to the square root of the friction factor.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.897-900
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• 2000

본 논문에서는 종방향 충돌경보 및 회피시스템(FCWA ; forward collision warning and avoidance)의 일환으로 가변적인 경사도를 가지는 고속도로상의 차선, 차량, 그리고 도로의 곡률을 효과적으로 검출할 수 있는 알고리듬을 제안하였다. 먼저 2D 영상좌표계에 나타나는 투영효과를 제거하기 위한 역투영(IPM; inverse perspective mapping)기법을 소개하였다. 또한 IPM과 필터로부터 차선과 차량을 효과적으로 검출할 수 있는 알고리듬을 소개하였다. 마지막으로 경사가 있는 실제도로영상에 대한 IMP의 수정된 파라미터 보정에 대한 개념 및 실제도로의 곡률 검출을 위한 기하학적 함수 추정기법을 설명하였다 실험결과 제안한 알고리듬이 실제도로영상에서 차선, 차량, 그리고 곡률의 검출에 효과적임을 확인할 수 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.498-500
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• 2015

본 논문에서는 검사 시간과 비용이 적게 드는 초음파 영상에서 결절종을 추출하는 방법을 제안한다. 제안된 방법은 초음파의 영상에서 퍼지 Stretching기법을 적용하여 명암 대비를 증가시킨 후, 8방향 윤곽선 추적 방법을 적용하여 결절종 후보 영역을 추출한다. 결절종이 형태학적으로 타원 형태를 가지는 정보를 이용하여 추출된 결절종 후보 영역에 침식과 팽창 기법을 적용하여 최종적으로 결절종 영역을 추출한다. 제안된 방법을 결절종 초음파 영상을 대상으로 실험한 결과, 결절종 영상에서 결절종 영역이 비교적 정확히 추출되었고 전문의가 결절종의 수술 여부를 분석할 수 있는 정보를 제공할 수 있는 가능성을 확인하였다.

• Journal of the Korean GEO-environmental Society
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• v.16 no.9
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• pp.43-51
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• 2015

In this paper, a 3D shell-spring model that can perform time history analysis of buried pipelines is used to evaluate the effect of the incident direction of the earthquake motion. When applying harmonic motions, it is shown that the period of vibration has pronounced influence on the response of buried pipelines. With decrease in the period, the curvature of the pipeline and corresponding response are shown to increase. To evaluate the effect of the incident angle, the motions are applied in the direction of the pipleline, horizontal, and vertical planes. When the motion is applied parallel to the direction of the pipeline, it only induces bending strains and therefore, the response is the lowest. Under motions subjected in horizontal and vertical planes at an angle of $45^{\circ}$ from the longitudinal axis of the buried pipeline, the axial deformation is shown to contribute greatly to the response of the pipelines. When imposing two-components simultaneously, the calculated response is similar to the case where only single-component is imposed. It is because one component only induces bending strain, resulting in very small increase in the response. The trend of the response is shown to be quite similar for recorded motions. Therefore, it is concluded that use of a single-component is sufficient for estimation of the longitudinal response of buried pipelines.