• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 2차
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• pp.200-211
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• 2010

Tunnel Mapper, which is tunnel face survey system was used to conduct Face Mapping on the face of the tunnel that is under construction. Then, accuracy and utility value on the forecast of discontinuity were verified to verify the field application in order to present the measures for the use of the system for conducting research on the discontinuity. As result of the directivity verification following discontinuity‘s project, forecasted measurement and actually researched measurement error for the Dip direction and Dip angle was less than ${\pm}10$. Accuracy was 82.6% for Dip direction and 90.7% for Dip angle, which are high. Accordingly, face research discontinuity forecasting system's reliability level towards directivity is high. Tunnel Mapper, a tunnel face survey system can be leveraged to replace face's visual survey and to obtain objective information, enabling execution of the survey system that can automate face survey going beyond time and space related limitations.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.438-442
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• 2003

For an efficient sliding mode control system stability and chattering avoidance should be guaranteed. A continuation method using boundary layer is well known as one solution for this. However since not only model uncertainties and disturbances but also control task itself is variable. it is practically impossible to set controller parameters - control discontinuity, control bandwidth, boundary layer thickness - in advance. In this paper first an adaptation law of control discontinuity is introduced to assure system stability and then fuzzy logic based tuning algorithm of design parameters is applied based on monitored performance indices of tracking error, control chattering, and model precision. In the end maximum control bandwidth not exciting unmodeled dynamics and minimum control discontinuity, boundary layer thickness making system stable and free of chattering are found respectively. This eliminates control chattering and enhances control accuracy as much as possible under given control situation. In order to demonstrate the validity of the proposed algorithm safe headway maintenance control for autonomous transportation system is simulated. The control results show that the proposed algorithm guarantees system stability all the time and tunes control parameters consistently and in consequence implements an efficient control in terms of both accuracy and actuator chattering.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.5-10
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• 2003

In order to reduce the excessive numerical dissipation, the new spatial discretization scheme is introduced. The present method in this paper has the formula that has an additional procedure of defining transferred properties at a cell-interface, based on AUSMPW+. The newly defined transferred property could eliminate numerical dissipation effectively in non-flow aligned grid system. In addition, the present method guarantees the monotonic characteristic in capturing a discontinuity. Through a stationary or moving contact discontinuity and a stationary or moving shock discontinuity, a vortex discontinuity and shock wave/ boundary layer interaction, it is verified that the accuracy of the present method is improved.

• 보존과학회지
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• 제19권
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• pp.85-98
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• 2006

서산 마애삼존불상을 구성하는 암석은 중립질 흑운모 화강암이다. 이 삼존불은 전면에 걸쳐 절리 및 균열과 탈락, 박리박락, 표면의 결로현상 및 이차적 오염물에 의한 변색 등으로 심하게 손상된 상태이다. 이 삼존불이 조각된 암반은 다양한 형태를 갖는 수십 개의 암괴로 분리되어 있으며, 불규칙한 불연속면이 발달되어 있다. 또한 주변의 암반에는 식생이 밀집되어 습도가 높고 미생물의 오염이 가중된 상태이다. 이 암반의 구조적 안정성 검토결과, 암반에 발달한 불연속면들은 불안정한 사면 환경에 노출된 상태로서 삼존불의 구조적 안정성을 위협하고 있는 것으로 해석되었다. 따라서 암반을 포함한 주변의 식생환경에 관한 정비가 필요하며 지속적인 모니터링을 통해 보다 정밀한 암반의 거동특성을 규명해야 할 것이다.

• Structural Engineering and Mechanics
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• 제17권3_4호
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• pp.409-428
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• 2004

In this paper, a Holder exponent, a measure of the degree to which a signal is differentiable, is presented to detect the presence of a discontinuity and when the discontinuity occurs in a dynamic signal. This discontinuity detection has potential applications to structural health monitoring because discontinuities are often introduced into dynamic response data as a result of certain types of damage. Wavelet transforms are incorporated with the Holder exponent to capture the time varying nature of discontinuities, and a classification procedure is developed to quantify when changes in the Holder exponent are significant. The proposed Holder exponent analysis is applied to various experimental signals to reveal underlying damage causing events from the signals. Signals being analyzed include acceleration response of a mechanical system with a rattling internal part, acceleration signals of a three-story building model with a loosing bolt, and strain records of an in-situ bridge during construction. The experimental results presented in this paper demonstrate that the Holder exponent can be an effective tool for identifying certain types of events that introduce discontinuities into the measured dynamic response data.

• Journal of Positioning, Navigation, and Timing
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• 제8권4호
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• pp.175-181
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• 2019

This paper suggests a velocity integration algorithm for Synthetic Aperture Radar (SAR) motion measurement to reduce discontinuity of range error. When using position data from Embedded GPS/INS (EGI) to form SAR image, the discontinuity of the data degrades SAR image quality. In this paper, to reduce the discontinuity of EGI position data, EGI velocity integration is suggested which obtains navigation solution by integrating velocity data from EGI. Simulation shows that the method improves SAR image quality by reducing the discontinuity of range error. INS is a similar algorithm to EGI velocity integration in the way that it also obtains navigation solution by integrating velocity measured by IMU. Comparing INS and EGI velocity integration according to grades of IMU and GPS, EGI velocity integration is more suitable for the real system. Through this, EGI velocity integration is suggested, which improves SAR image quality more than existing algorithms.

• 터널과지하공간
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• 제5권2호
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• pp.104-113
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• 1995

Shear strength of the discontinuity on which the pre-failure of rock slope was occurred during surface excavation was measured through the direct shear test using core samples obtained in-situ. Internal friction angle was increased as the roughness of discontinuity surface(JRC) was increased. Results of the tilt test using core samples of higher JRC also showed very similar trend as those of the direct shear test. When the samples replicated from natural cores were used int he tilt test, results of friction angles showed almost perfect continuation of the residual friction angles from the direct shear test. However, when the gouge material existed in the discontinuity the internal friction angle strongly depended upon the rate of filling thickness to the height of asperity irrespective of the JRC. Based on the results of both direct shear test and tilt test internal friction angle and cohesion of discontinuity, which reflect the in-situ conditions fo pre-sliding failure and also can be used for the optimum design of support system, were assessed. Two kinds of support measures which were expected to increase the stability of rock slope were considered; lowering of slope face angle and installation of rock cable. But, it was found that the first method might lead to more unstable conditions of rock slope when the cohesion of discontinuity plane was negligibly low and in that case the support systems of any kind which could exert actual resisting force were needed to ensure the permanent stability of rock slope.

• Advances in biomechanics and applications
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• 제1권2호
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• pp.85-93
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• 2014

In this paper, two procedures of enumerating the axial rotation are proposed using the unit sphere of the spherical rotation coordinate system specifying 3D rotation. If the trajectory of the movement is known, the integration of the axial component of the angular velocity plus the geometric effect equal to the enclosed area subtended by the geodesic path on the surface of the unit sphere. If the postures of the initial and final positions are known, the axial rotation is determined by the angular difference from the parallel transport along the geodesic path. The path dependency of the axial rotation of the three dimensional rigid body motion is due to the geometric effect corresponding to the closed loop discontinuity. Firstly, the closed loop discontinuity is examined for the infinitesimal region. The general closed loop discontinuity can be evaluated by the summation of those discontinuities of the infinitesimal regions forming the whole loop. This general loop discontinuity is equal to the surface area enclosed by the closed loop on the surface of the unit sphere. Using this quantification of the closed loop discontinuity of the axial rotation, the geometric effect is determined in enumerating the axial rotation. As an example, the axial rotation of the arm by the Codman's movement is evaluated, which other methods of enumerating the axial rotations failed.

• Architectural research
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• 제24권2호
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• pp.53-61
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• 2022

Irregularities in the structure are crucial factors in screening structural vulnerability under extreme loadings. Numerical analyses were carried out considering wind and seismic loadings for four structures with discrete irregularity: continuous and discontinuous beams with varied story levels, and L-shaped irregular buildings. Structural responses such as maximum displacements, bending moments, axial forces, torsions, and story drifts are evaluated as per the criteria and limits defined by ACI 318. The outcomes indicate that the frame system with beam discontinuity on the upper half of the height exhibits the best structural performance. The results also indicate that the asymmetrical design of the L-shaped model makes it more susceptible to damage when subjected to strong lateral loading conditions.

• 한국지반공학회논문집
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• 제23권1호
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• pp.51-65
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• 2007

본 논문의 목적은 초음파 탐사 방법을 이용하여 지반내의 불연속 물질을 탐측할 수 있는 고해상도의 시스템을 개발하고 실내에서 적용하는 것이다. 초음파 탐측 방법은 불연속면의 경계면에서 반사되어온 반사파를 탐측하고, 이를 배열하여 불연속면의 존재를 찾는 방법이다. 본 논문은 암반내 초음파의 전달 양상, 최적화된 트랜스듀서의 선택, 데이터 획득, 신호처리 방법, 영상화 기법, 그리고 실내 적용실험을 포함하고 있다. 실내실험은 수평이동장치와 회전이동장치를 이용하여 수행된다. 수중에서 수평이동 및 회전실험 결과, 불연속면의 위치와 크기가 정확하게 평가 되었다. 또한 석고시료에서 회전실험결과 석고 내에 존재하는 균열과 공동이 비교적 정확하게 영상화됨을 알 수 있다. 본 논문은 새롭게 제시된 방법이 암반 불연속면 탐측에 매우 경제적이고 효과적인 방법이 될 수 있음을 보여준다.