• 한국정밀공학회지
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• 제33권6호
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• pp.453-458
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• 2016

CFRP (Carbon Fiber Reinforced Plastic) and CFRP-metal stacks have recently been widely used in the aerospace and automobile industries. When CFRP is machined by a brittle fracture mechanism, defect generation behaviors are different from those associated with metal cutting. The machining quality is strongly dependent on the properties of CFRP materials. Therefore, process control for CFRP machining is necessary to minimize the defects of differently manufactured CFRPs. In this study, defects in drilling of CFRP substrates with a variety of fiber directions and resin types are compared with respect to thrust force. An experimental study on material interface detection is carried out to investigate its benefits in process control.

• 지질공학
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• 제22권1호
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• pp.27-37
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• 2012

미고결대수층에서 우물 굴착 시 대수층 교란이 수리특성에 미치는 영향을 파악하기 위하여 우물굴착 이후의 우물개량 공법인 서지블록과 에어서징을 실시하였다. 그리고 우물 굴착 및 개량의 대수층 변화를 비교 분석하기, 위하여 단계 및 장기 양수시험을 수행하였다. 그 결과 우물 굴착 및 개량 이후의 단계양수시험에서 동일 양수율 $700m^3/day$에 대한 수위강하와 비교하였을 때 수위강하는 각각 26.01 m, 21.62 m로 4.39 m정도 감소되었다. 이때 우물특성을 파악하기 위한 우물 굴착 및 개량 이후의 스킨계수는 7.92에서 5.04로 감소되어 우물상태가 개선된 것으로 나타났다. 우물 굴착 및 개량 이후의 장기양수시험에서 양수정을 중심으로 주변 MW-2, 3, 4호정의 투수량계수 범위는 각각 $1.684{\times}10^{-3}{\sim}4.490{\times}10^{-3}m^2/sec$, $4.002{\times}10^{-3}{\sim}4.939{\times}10^{-3}m^2/sec$ 범위로 우물개량 이후의 수리전도도 값이 조금 증가되었으며, MW-1호정은 $1.018{\times}10^{-2}m^2/sec$에서 $6.988{\times}10^{-3}m^2/sec$로 감소되었다. 이는 서징하는 동안 대수층의 공기 차단 및 폐색의 잠재적인 요인으로 인하여 MW-1호정 주변 대수층의 투수성이 미세하게 감소되는 효과로 나타났다. 따라서 미고결대수층에서 우물 굴착 시 미세입자가 양수정 주변의 수리특성에 영향을 미칠 수 있음을 반드시 유의해야 한다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.259-264
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• 2009

Most of the fossil power plants firing lower grade coals are challenged with maintaining good combustion conditions while maximizing generation and minimizing emissions. In many cases significant derate, availability losses and increase in unburned carbon levels can be attributed to poor combustion conditions as a result of poorly controlled local fuel and air distribution within the boiler furnace. The poor combustion conditions are directly related to the gas flow deviation in upper furnace and convection tube-bank but a less reported issue related to in large-scale oppose wall fired boilers. In order to develop a on-line combustion monitoring system and suggest an alternative heat flux estimation method at tube bank, which is very useful information for boiler design tool and blower optimizing system, field test was conducted at operating power boiler. During the field test the exhaust gases' temperature and tube metal temperature were monitored by using a spatially distributed sensors grid which located in the boiler's high temperature vestibule region. At these locations. the flue gas flow is still significantly stratified, and air in-leakage is minimal which enables tracing of poor combustion zones to specific burners and over-fire air ports. Test results showed that the flue gas monitoring method is more proper than metal temperature distribution monitoring for real time combustion monitoring because tube metal temp. distribution monitoring method is related to so many variables such as flue gas, internal flow unbalance, spray etc., Heat flux estimation at the tube bank with flue gas temp. and metal temp. data can be alternative method when tube drilling type sensor can't able to use.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2004년도 Proceedings of the 4th Korea-China Joint Workshop on Nuclear Waste Management
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• pp.51-59
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• 2004

The geological research as a part of HLW disposal program in Korea is carried out to provide necessary data for the establishment of the reference repository system in term of design and safety assessment in the crystalline rock terrains. Six deep boreholes were drilled to obtain hydrogeological and hydrochemical data from Jurassic granites in the Yuseong area, Korea. The core observation, televiewer logging and hydraulic testing were carried out during and after drilling and multi-packer system were installed in the boreholes of 500m depth for hydraulic and hydrochemical monitoring including environmental isotopes. The integration of hydrogeochemical and hydrodynamic data would be built greater confidence for the understanding of groundwater system in fractured rock mass. This geoscientific program could be possible to suggest a general guideline to develop the reference disposal concept of high-level radioactive waste in Korea.

• 한국생산제조학회지
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• 제8권3호
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• pp.42-51
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• 1999

An experimental modeling of cutting and structural dynamics and the on-line detection of malfunction process is substantial not only for the investigation of the static and dynamic characteristics of cutting process but also for the analytic realization of diagnostic systems. In this regard, We have discussed on the comparative assessment of two recursive time series modeling algorithms that can represent the machining process and detect the abnormal machining behaviors in precision round shape machining such as turning, drilling and boring in mold and die making. In this study, simulation and experimental work were performed to show the malfunctioned behaviors. For this purpose, two new recursive approach (REIVM, RLSM) were adopted fur the on-line system identification and monitoring of a machining process, we can apply these new algorithm in real process for the detection of abnormal machining behaviors such as chipping, chatter, wear and round shape lobe waviness.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.435-440
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• 2000

In this study, we aims to develop the machining technology for the ultra precision surface and profile accuracy. For this purpose, we construct the electrolytic in process grinding system (ELID grinding) and apply to the cylindrical and internal grinding. Through the various machining experiments such as SCM steel., ceramics, tungsten carbide etc., we have obtained nanometer surface roughness. And we have applied this mirror grinding technique to hydraulic manual valve and mold core of mini disk optical pick-up base. For the development of fine mechanical part machining technology, e have made multi fiber optical connector using fine grinding technology. And constructed micro drilling system with process monitoring system which is possible to drill 50${\mu}{\textrm}{m}$ diameter hole.

• 한국기계가공학회지
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• 제9권5호
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• pp.1-6
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• 2010

The wavelet transform is a popular tool for studying intermittent and localized phenomena in signals. In this study the wavelet transform of cutting force signals was conducted for the detection of a tool failure in turning process. We used the Daubechies wavelet analyzing function to detect a sudden change in cutting signal level. A preliminary stepped workpiece which had intentionally a hard condition was cut by the inserted cermet tool and a tool dynamometer obtained cutting force signals. From the results of the wavelet transform, the obtained signals were divided into approximation terms and detailed terms. At tool failure, the approximation signals were suddenly increased and the detailed signals were extremely oscillated just before tool failure.

• 한국산업융합학회 논문집
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• 제23권3호
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• pp.411-417
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• 2020

Therefore, it was agreed that an earthquake monitoring station should be set up within the site of Handong University by analyzing drilling data and Disaster such as earthquakes is urgently needed to prepare for earthquakes in that people's lives and national development depend on the nation's ability to manage disasters. Many experts say that the Korean Peninsula is also under the influence of earthquakes and is not a safe zone for earthquakes. A seismological observatory will be established in Pohang to monitor ground sensors and study seismic characteristics through the task of "Development of Smart Sensor-based Intelligent Information Platform in Earthquake Region." Therefore, it was agreed to set up a seismological observatory within the site of Handong University by analyzing drilling data and conducting on-site surveys in northern Pohang, which were heavily damaged by liquefaction and earthquakes. In this study, it was decided to make a comprehensive judgment by considering the geological characteristics of the site, whether it can perform functions, and the convenience of construction and maintenance for the final site of the seismological observatory discussed with Handong University. After completing a feasibility review on selecting a site for Handong University, we will establish a seismological observatory and actively utilize it for seismic research using data from alarm issuance and seismic data in the event of a future earthquake.

• 기술사
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• 제17권3호
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• pp.32-49
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• 1984

The East gate station area is 205M long and 24m deep which is located 13 meter in front of cultural treasure east gate. The area to be excavated by blasting is composed of granite rocks from 10M depth to 25M. Surface earth extends to up 10M depth. This job site has in involves heavy traffic congestion such as over 10,000 cars passing in rush hour where clossing No 1 lint of subway running 3 minitues head way. This east gate station construction is to be executed for the provent of the setting down of underground level and blasting vibration effects to cultural treasure east gate. Therefore, the caltural treasure committee approved this execution subject to the following condition. 1. Subway gelogical foundation and measured natural frequency 2. Execution of water tight wall 3. Sellection and test of damping material for wall and under rail 4. Measurement of monitoring system during the execution 5. Measurement of histogram system The above two projects was carried out by Dr. Kwang team in KAIST and prof, Han in Hanyang University under accadamic study contract. In the blasting work, for the pourpose of reduced vibration and low explosion velocity such as CCR, Kovex slurry. The 2nd, used electrical caps shall be delay cap and M/S caps in multi delay. The 3rd, drilling pattern is bench cut in open cut and applied control blasting in tunnelling and also shall drill anti-vibration holes as line drilling.

• 터널과지하공간
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• 제16권6호
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• pp.451-466
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• 2006

DOM 시추코어에서 측정된 불연속면의 위치 및 방향성 자료를 이용하여 현장암반의 구조적 특성을 고려한 사면거동 해석이 가능하였다. 3차원 공간에서 설정된 절리들의 위치에 의거하여 붕락 현상이 발생된 개착사면의 추가적인 파괴양상을 예측하였으며, 개별 절리면의 붕락위해 가능성과 개착면 상에서의 trace 위치를 파악하여 세부적인 사면거동 양상을 파악하였다. 개착사면 횡단면에서 개별절리들의 파괴거동 양상과 사면체 블록형성을 대수학적으로 산출하여 사면 붕락심도를 규명하였다. 현장사면에 자동화 계측시스템을 설치하여 사면 거동에 대한 계측자료를 수집하였으며, DOM 시추공 내에 지중경사계를 설치하여 사면거동 양상을 횡단면 해석 결과와 대비시켜 분석하였다. 지중경사계를 이용하여 측정된 개착면의 표면변위 자료에 의거하여 사면 파괴시기를 예측할 수 있는 방법론을 고찰하였으며, 강우가 사면거동에 끼치는 영향성을 분석하였다.