• 한국안전학회지
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• 제32권3호
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• pp.41-47
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• 2017

Recent studies have shown that there are various systems which can be used to monitor hazardous area in a debris flow location, but lack of methodological research on the exact location where each instrument should be installed has hindered the success of this systems. The objective of this study is to suggest the measurement system for monitoring debris-flow and propose the effective method to determine location of measurement system. Previously studied, from 1991 to 2015, were referred and the applied ratio of every instrument was investigated. The measurement information was divided into 8 categories including rainfall, debris-flow velocity, displacement, fluid pore pressure, ground vibration, image processing, impact force and peak flow depth. The result of this study revealed that the most applied instruments to be rain gauge and geophone for measuring average rainfall and ground vibration respectively. The Analytic Hierarchical Process (AHP) method was selected to determine installation location of instrument and the weighting factors were estimated through fine content, soil thickness, porosity, shear strength, elastic modulus, hydraulic conductivity and saturation. The soil thickness shows highest weights and the fine content relatively demonstrates lowest weights. The score of each position can be calculated through the weighting factors and the lowest score position can be judged as the weak point. The weak point denotes the easily affecting area and thus, the point is suitable for installing the measurement system. This study suggests a better method for safely managing the debris-flow through a precise location for installing measurement system.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1990년도 제12회 학술강연회초록집
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• pp.58-62
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• 1990

The size and concentration of wear debris in lubricating oil often reveal the operating condition of the rotating machinery. To evaluate the possible application of light attenuation measurement for the estimation of wear debris concentration in the lubricating oil, the light transmittance through the lubricating oil cell contaminated with various concentrations of diatomite particles was measured, the attenuation coefficient was estimated from the transmittance measurement and the coefficients were compared with those obtained from the scattering theory. The comparision showed good agreements between them. It is also noted that the experimentally determined attenuation coefficient showed almost linear relation with particle weight concentrations for the concentrations within the range of 2000 ppm. For the case of 0 ppm weight concentration of diatomite particles in the lubricating oil cell, the thickness of the cell required to give $100 \mu W$ light attenuation is 7.75 mm. This result indicates that the light attenuation method will be one of the possible candidates of machine failure diagnostic sensors for the estimation of wear debris concentration in the lubricating oil.

• Tribology and Lubricants
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• 제6권2호
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• pp.94-98
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• 1990

The size and concentration of wear debris in lubricating oil often reveal the operating condition of the rotating machinery. To evaluate the possible application of light attenuation measurement for the estimation of wear debris concentration in the lubricating oil, the light transmittance through the lubricating oil cell contaminated with various concentrations of diatomire particles was measured, the attenuation coefficient was estimated from the transmittance measurement and the coefficients were compared with those obtained from the scattering theory. The comparision showed good agreements between them. It is also noted that the experimentally determined attenuation coefficient showed almost linear relation with particle weight coucentrations for the concentrations within the range of 2000 ppm. For the case of 0 ppm weight concentration of diatomire particles in the lubricating oil cell, the thickness of the cell required to give $100 \muW$ light attenuation is 7.75 mm. This result indicates that the light attenuation method will be one of the possible candidates of machine failure diagnostic sensors for the estimation of wear debris concentration in the lubricating oil.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2016년도 춘계 종합학술대회 논문집
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• pp.241-242
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• 2016

Recent abnormal climate change induces localized heavy rainfall and extreme disasters such as debris flow near urban area. Thus many researches have been conducted to estimate and prevent, especially in focus of physical behavior of debris flow. Even though it is hardly to consider overall related parameters to estimate the extent and degree of directly or indirectly damages due to debris flow. Those analytic restraint would be caused by the diversity and complexity of regional topographic and hydrodynamic characteristics of debris flow inside. We have utilized the Bayesian method to compensate the uncertainty due to the complex characteristics of it after analyzing the numerical results from FLO-2D and field measurement data. Revised values by field measurements will enhance the numerical results and the missing parameters during numerical simulation will be supplemented with this methodology. As a final outcome in this study, the risk index of debris flow damage will be suggested to provide quantitative estimation in terms of hazard protection including the impact on buildings, especially in inner and outer of urban area.

• Tribology and Lubricants
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• 제32권6호
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• pp.189-194
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• 2016

Wear debris in lubricating oil can be indicative of potential damage to mechanical parts in rotating and reciprocating machinery. Therefore, on-line or in-line monitoring of lubricating components in machinery is of great importance. This work presents a device based on inductive measurement of lubricating oil to detect magnetic wear particles in a tested volume. The circuit in the device consists of Maxwell Bridge and LVDT to measure inductance differences between pure and contaminated oil. The device detects the passage of ferrous particles by monitoring inductance change in a coil. The sensing principle is initially demonstrated at the microscale using a solenoid. The device is then tested using iron particles ranging from $50{\mu}m$ to $100{\mu}m$, which are often found in severely worn mechanical components. The test results show that the device is capable of detecting and distinguishing ferrous particles in lubricating oil. The design concept demonstrated here can be extended to an in-line monitoring device for real-time monitoring of ferrous debris particles. A simulation using the CST code is performed to better understand the inductive response in the presence of magnetic bodies in the oil. The CST simulation further verifies the effectiveness of inductance measurement for monitoring magnetic particles within a tube.

• 한국지반신소재학회논문집
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• 제17권4호
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• pp.267-275
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• 2018

사방댐 배면의 준설퇴적물에 대한 준설시기를 객관적, 정량적, 과학적으로 결정할 수 있도록 준설퇴적물 측정장치를 개발하고 실제 현장에 시범 구축하였다. 사방댐 배면의 준설퇴적물 하중을 측정하기 위하여 준설퇴적물 관리시스템을 설계 및 개발하였다. 본 관리시스템은 Data Acquisition System (DAS), Solar System 및 준설퇴적물 하중변화 측정유닛으로 구성되어 있다. 또한 사방댐 배면의 준설퇴적물 하중, 수위 및 강우량을 실시간으로 측정하고 무선통신을 통하여 자료를 전송할 수 있다. 준설퇴적물 하중변화 측정유닛은 강우를 측정하기 위한 강우계, 사방댐 배면의 준설퇴적물 하중을 측정하기 위한 하중측정계, 사방댐 배면 수위를 측정하기 위한 수위계로 구성되어 있다. 사방댐 배면의 준설퇴적물 관리기준은 준설퇴적물의 하중을 기준으로 제안하였다. 사방댐 배면에 퇴적될 수 있는 최대 준설퇴적물의 양을 산정하고, 최대 준설퇴적물의 50%, 70% 및 90%가 쌓인 경우 관심, 주의 및 경보의 단계로 구분하여 관리기준을 마련하였다. 사방댐 배면의 준설퇴적물 관리시스템을 활용하여 현재 준설퇴적물의 하중을 실시간으로 측정할 수 있으며, 이를 토대로 사방댐의 상태와 준설퇴적물의 준설시기를 결정할 수 있을 것으로 판단된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.855-859
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• 2005

Carbon fiber polymeric composites have been widely used in bearing materials under high pressure without oil-lubrication due to their self-lubricating characteristics. However, the severe wear of carbon composite surface occurs due to the generation of wear debris when the pressure applied on the composite surface is higher than the critical value of composite surface. In this work, in order to remove wear debris continuously during sliding operation, composite specimens with many micro-grooves on their sliding surfaces were devised. To investigate the effect of wear debris on the tribological behavior of carbon/epoxy composites, dry sliding tests were performed with respect to applied pressure using the composite specimens with and without micro-grooves. From the measurement of friction coefficients and wear rates, a model for the effect of wear debris on the friction and wear of composites was proposed.

• 대한기계학회논문집A
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• 제41권2호
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• pp.149-156
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• 2017

핵연료는 고도의 신뢰성과 안전성이 요구되는 구조물로서 손상유발 이물질이 유입되지 않도록 이물질여과 기구를 포함하고 있다. 핵연료의 이물질여과 성능은 건전성에 가장 중요한 영향 인자로 합리적이고 객관적으로 평가되어야 하는 지표이다. 본 연구에서는 표준 여과효율 성능지수를 수립하고자 가중평균을 이용하여 종합 이물질여과 효율 계산 방법을 제시하였다. 제안된 방법의 적합성을 확인하기 위해 대표 이물질 시편을 선정하고 이물질여과 실험을 통해 가중평균 여과 효율을 산술평균 여과 효율과 비교하였다. 가중평균법은 성능의 변별력을 강화하고자 이물질의 통과 가능 정도를 가중인자로 사용하였다. 부가적으로 이물질 시편의 크기와 여과 기구의 주요 치수에 따른 상용 핵연료의 여과 거동 분석을 수행하였다.

• 한국방재안전학회논문집
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• 제12권4호
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• pp.53-61
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• 2019

토석류의 발생은 산악지역에 위치한 도로나 주택가에 심각한 위험을 초래하며 많은 재산의 손실을 발생시킨다. 본 연구에서는 산악지역에서 발생한 토석류를 모의하기 위해 2개의 유역을 선정하고 공간자료를 구축하였다. 첫 번째 유역의 경우 지상 LiDAR를 활용하여 토석류 발생 구간을 스캔하고 지형 자료를 구축하였으며 두 번째 유역의 경우는 드론을 활용하여 유역의 퇴적부를 촬영하고 DSM(Digital surface model)을 생성하였다. 그리고 토석류 발생이 하류부에 미치는 영향을 분석하기 위해 2차원 상용 모델인 FLO-2D를 사용하여 토석류의 흐름 영역을 시뮬레이션하고 지상 LiDAR 및 드론 측정데이터의 퇴적부와 비교분석하였다.

• 한국지리정보학회지
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• 제13권2호
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• pp.54-63
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• 2010

2009년 7월 9일부터 14일까지 누적강우 455mm의 집중호우에 의해 제천시 일대에 다수의 토석류 사태가 발생하였다. 토석류 발생에 따른 지형변화를 분석하기 위하여 수치지도와 라이다(LiDAR) 자료를 이용하여 고해상도의 수치고도모델(DEM)을 생성하였다. 라이다측량을 위해서 고해상도의 디지털 카메라와 GPS가 탑재된 3차원 스캐너 시스템 (RIEGLE LMS-Z390i)을 이용하였다. 라이다 스캐닝에 의해 생성된 포인트 자료는 클리핑과 필터링 작업을 거친 후 수치지도에 중첩시켜 토석류 발생 후의 지형의 DEM을 생성한다. 이렇게 토석류 발생 전후의 DEM 비교결과, 토석류 발생에 의한 침식과 퇴적량은 각각 $17,586m^3$, $7,520m^3$으로 평가되었다. 이러한 고해상도 지상라이다시스템을 이용하여 지형변화 관측을 통해 장래 토석류 모델 연구에 기여할 수 있을 것으로 판단되었다.