• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.1
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• pp.108-120
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• 1998

많은 주거용 및 상업용 건물에서 콘크리트 구조물이 사용되고 있는데 콘크리트 슬래브 아래의 기초부분에 공동이 생기는 경우가 종종 발견되었다. 이 현상은 진동하중, 반복되는 충격, 흙의 유실, 혹은 불량시공 등 여러가지 이유에 의해 발생할 수 있다. 이러한 현상은 구조물의 지지력을 저하시키고 결국 수명을 단축시키는 원인이 되므로 이러한 문제는 일찍 발견되고 조치가 취해질수록 구조물의 수명을 연장시킬 수 있을 것이다. 이러한 공동이 슬래브 아래에서 형성되고 커져가는 과정을 모니터할 수 있으면 현재 상태에서 지지력을 결정하고 또한 앞으로 남은 수명을 예측함으로써 적절한 유지보수계획을 세우는 데에 큰 도움이 될 것이다. 이 연구에서는 음파와 응력파, 특히 표면파가 슬래브 아래의 공동을 찾아내는데 이용되었고 두 가지 방법의 효과가 상호 비교되었다. 두개의 콘크리트 슬래브를 만들어 이용했는데 하나는 미리 공동이 만들어져 있었고 다른 하나에는 공동이 없었다. 공동이 없던 슬래브는 처음 손상안된 상태에서 실험을 한 후 나중에 하부에 공동을 만들어 다시 실험하였다. 실험결과와 실제 공동의 위치가 잘 일치되는 것으로 나타났다. 응력파를 이용하는 방법과 음파를 이용하는 방법사이의 장단점이 비교검토되었고 실험의 표준방법과 결과에 대한 일반적인 기준이 확립되어야 하는 필요성에 대해서도 설명되었다.

• Tunnel and Underground Space
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• v.14 no.1
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• pp.35-42
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• 2004

Impact-echo is a method for non-destructive testing of concrete structure. This method is based on the use of impact-generated stress wave which is propagated and reflected from internal flaws within concrete structure and external surface. In this study, we performed non-destructive testing using impact-echo methods for safety diagnosis of civil engineering and building structures. There are testing cases for the three models having one-dimensional form ; The first case is the measurement of thickness change of the model, the second is the detection of cavity in the model, and the third is the predictions of the lining thickness and the position of the cavity under tunnel lining condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.307-311
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• 2008

Ground test of model Scramjet engine was performed with T4 free-piston shock tunnel at University of Queensland, Australia. Test condition of free stream was Mach 7.6 at 31 km altitude. With this condition, variation effects of fuel equivalence ratio, cavity, cowl setting were investigated. In the results, supersonic combustion or thermal choking was observed depending on the amount of fuel. Cavity and W-shape cowl showed early ignition and enhanced mixing respectively.

• The Journal of Engineering Geology
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• v.18 no.1
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• pp.7-16
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• 2008

Limestone area have mostly certain geological defects such as the internal cavities due to melting and fractured zone by external pressures. Especially, in case of constructing grand bridge, the treatment of the limestone cavities area having the geological defects is inevitable. In order to reduce foundation settlement and to reinforce the ground in the limestone cavities area, high pressure jet grouting has been carried out as a countermeasure method. Despite the fact that high pressure jet grouting method has already adopted at a lot of limestone cavities area, but the amount of research and technical data on the high pressure jet grouting have not been accumulated properly so for. Therefore this paper intends to investigate the strength characteristics and deformation characteristics for reinforced limestone cavities area by high pressure jet grouting method. In addition, load carrying capacity obtained by static pile load test with load transfer measuring system is analyzed.

• Tunnel and Underground Space
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• v.17 no.5
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• pp.389-410
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• 2007

For moderately jointed to massive rock masses, the failure and deformation behaviors around an excavated opening are absolutely influenced by the initial rock stress and strength of in-situ rock mass. The localized and progressive brittle failure around an opening does not mean whole collapse of an excavated opening. But, for many cases, it may induce temporary stopping of excavation works and reexamination of the current supporting system, which can result in delay of the entire construction works and additional construction cost. In this paper, the characteristics of the brittle failure around an opening with stress level and tunnel shape was studied by the biaxial compressive test using scaled specimen and by the numerical simulation with $PFC^{2D}$. The biaxial test results were well coincided with the stress induced failure patterns around the excavated openings observed and monitored in the in-situ condition. For the circular part of the opening wall, the stress induced cracks initially occurred at the wall surface in the direction of the minimum principal stress and contributed to the localized notch shaped failure region having a certain range of angle. But for the corner and straight part of the opening wall, the cracks initiated at sharp corners were connected and coalesced each other and with existing micro cracks. Further they resulted in a big notch shaped failure region connecting two sharp corners.

• TTA Journal
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• s.51
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• pp.94-96
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• 1997

일본의 주요 연구소들은 디지털 지상방송 시스템의 개발을 위하여 변조방식을 중점으로 기본적인 현장시험을 공동으로 시작할 예정이다. 이 현장시험은 디지털 지상 TV방송의 조기도입을 촉진하도록 1998년까지 잠정적인 방송시스템의 설정을 목표로 진행되고 있다.

• Communications for Statistical Applications and Methods
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• v.2 no.1
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• pp.229-247
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• 1995

신뢰할만한 임상시험연구결과를 얻기 위해서는 통계학자가 임상시험연구의 준비단계에서부터 실험계획 및 연구의 운용, 분석은 물론 결과의 보고에 이르기까지 총체적으로 관여해야 한다. 의학전문가들과의 원활한 공동연구를 위해서는 통계학자들이 의학분야에서의 용어나 관례, 임상시험이 이루어지는 절차등에 대한 명확한 이해가 필요하게 된다. 이 논문에서는 임상시험에서 진행되는 제반문제에 대해 통계학자가 숙지해야 할 사항들에 대해 논의 하였다.

• Annual Conference on Human and Language Technology
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• 1994.11a
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• pp.378-385
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• 1994

정보검색분야의 여러 기술들을 연구하고 이 결과들을 실험 평가하기 위해서는 모든 연구자들이 공동으로 사용할 수 있는 시험용 데이터 모음(Test Data Collection)이 필요하다. 외국에서는 이미 오래전부터 각 분야별 시험용 데이터 모음들을 준비하여 검색시스팀의 개발 및 객관적인 성능평가에 이용하여 왔는데 국내에서는 아직까지 이러한 시험용 데이터 모음이 개발되지 못한 실정이다. 본 연구는 한국어 정보검색 기술연구 활성화에 기여하기 위하여 한국어정보검색 기술 연구결과의 성능평가에 공동으로 활용할 수 있는 국내 최초의 시험용 데이터 모음인 KTSET을 개발하였다. KTSET은 정보과학회와 정보관리학회지의 논문지 및 학술대회 논문집으로부터 추출된 1,053개의 논문과 이를 검색대상으로 한 50개의 자연어질의어로 구성되었으며 대상문서들과 질의어 각각에 대한 색인결과와 질의어와 대상문서들간의 적합도 정보를 제공한다.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.41-46
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• 2008

After choosing twenty sluice culverts located at national rivers by detailed appearance evaluation, hydraulic response test and acoustic televiewer in addition to surface geophysical explorations were carried out to investigate the cavities which exist at the boundary of sluice culvert and ground. Tapping, GPR, 3-D resistivity surveys and acoustic televiewer imagery obtained successful results in limited conditions according to characteristics of the sites. On the other hand, hydraulic response test successfully detected cavity existing at the lower part of sluice culvert and its continuity. However, hydraulic response test can not supply the quantitative informations on the scale and the shape of cavity. Thus it is very important for accurate investigation to make comprehensive interpretation after supplying various surveys proper to site characteristics.

• Journal of the Korean Geotechnical Society
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• v.37 no.10
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• pp.65-76
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• 2021

There is a possibility of cavities occurring inside and behind the lining of an aged tunnel structure. In most cases, it is not easy to check the cavity because it exists in a place where visual inspection is impossible. Recently, attempts have been made to evaluate the condition of the tunnel lining and the backfill materials using non-destructive tests such as Ground Penetrating Radar, and various related model tests and numerical analysis studies have been conducted. In this study, the GPR signal characteristics for tunnel lining model testing were analyzed using gprMax software, which was compared with model test results. The numerical model applied to the model test reasonably simulated the electromagnetic wave signal according to the change of the material such as tunnel lining and internal cavity. Using the verified GPR model, B-scan data for the development of the GPR signal analysis technique were obtained, which can evaluate the thickness of the tunnel lining, the presence of the cavity, the effect of the waterproof membrane, and the frequency band.