• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1998년도 가을 학술발표회 논문집
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• pp.121-128
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• 1998

• 한국도로학회논문집
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• 제18권6호
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• pp.61-67
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• 2016

OBJECTIVES : The objective of this study is to detect road cavities using multi-channel 3D ground penetrating radar (GPR) tests owned by the Seoul Metropolitan Government. METHODS : Ground-penetrating radar tests were conducted on 204 road-cavity test sections, and the GPR signal patterns were analyzed to classify signal shape, amplitude, and phase change. RESULTS : The shapes of the GPR signals of road-cavity sections were circular or ellipsoidal in the plane image of the 3D GPR results. However, in the longitudinal or transverse direction, the signals showed mostly unsymmetrical (or symmetrical in some cases) parabolic shapes. The amplitude of the GPR signals reflected from road cavities was stronger than that from other media. No particular pattern of the amplitude was found because of nonuniform medium and utilities nearby. In many cases where road cavities extended to the bottom of the asphalt concrete layer, the signal phase was reversed. However, no reversed signal was found in subbase, subgrade, or deeper locations. CONCLUSIONS : For detecting road cavities, the results of the GPR signal-pattern analysis can be applied. In general, GPR signals on road cavity-sections had unsymmetrical hyperbolic shape, relatively stronger amplitude, and reversed phase. Owing to the uncertainties of underground materials, utilities, and road cavities, GPR signal interpretation was difficult. To perform quantitative analysis for road cavity detection, additional GPR tests and signal pattern analysis need to be conducted.

• 지질공학
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• 제25권2호
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• pp.251-263
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• 2015

본 연구에서는 석회암 공동이 분포하는 지역에서 발생한 지반침하 현상의 원인을 파악하고 공동의 분포 위치 및 규모를 분석하기 위하여 지표지질조사, 시추조사, 전기비저항, 토모그래피 탐사 등을 실시하였다. 지표지질조사 및 시추조사 결과에 의하면 연구지역에서 석회암은 방해석의 함량에 따라 고함유대와 저함유대가 교호하며 분포한다. 시추조사 결과를 중심으로 전기비저항 및 탄성파 토모그래피 탐사 결과와 비교분석한 결과에 의하면 대부분의 공동은 지반침하가 발생한 지점을 중심으로 심도 7~14 m의 토사층과 암반의 경계부 주변에 집중되어 분포하고 있다. 또한 공동의 규모는 558~835 ㎥로 소규모이며, 침하의 형태는 사질토 지반에서 흔히 발생하는 Suffosion sinkhole에 속한다.

• Imaging Science in Dentistry
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• 제42권1호
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• pp.19-24
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• 2012

Purpose : Field of view and voxel resolution of cone beam computed tomography (CBCT) might affect the diagnostic capability. This study was performed to compare between the standard and HiRes zoom modes in the diagnosis of external root resorption (ERR) using CBCT. Materials and Methods : Sixty three small cavities (0.25 mm depth and 0.5 mm diameter) were simulated on the buccal, lingual, and proximal surfaces at three different levels of 16 roots of teeth. After covering the root with nail varnish, the roots were inserted in the sockets and the model was placed in a water-containing lacuna. CBCT scans were taken in both standard and HiRes zoom modes using NewTom VG (QR srl Company, Verona, Italy). Then, an observer assessed the images to determine the presence or absence of the cavities. This process was repeated by increasing the size and depth of cavities to 0.5 mm depth and 1 mm diameter. Data were analyzed by McNemar test. The sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio in evaluation of the simulated cavities were calculated. Results : There was a significant difference between the two imaging modes in diagnosing the shallow cavities (p=0.02).The sensitivity of the standard zoom in detecting the shallow cavities was lower than that of the HiRes zoom. The likelihood ratio of the HiRes zoom was higher in the diagnosis of both cavity types. Conclusion : This study suggested that a smaller voxel size in the HiRes zoom mode of CBCT is preferred for diagnosis of ERR.

• Restorative Dentistry and Endodontics
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• 제19권2호
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• pp.384-408
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• 1994

The purpose of this study was to evaluate the fracture resistance of tooth restored with gold inlay. A profound understanding of the isthmus width factor, which is one of the several parameters of cavity designs, would facilitate the appropriate cavity preparation in a specific clinical situation. In this study, the cavities for gold inlay were prepared in maxillary left first premolar. A three-dimensional model was designed using I-DEAS program. The model was composed of 2515- nodes and 2172 isoparametric brick elements. In the model isthmus width was varied into 1/4, 1/3 and 1/2 of intercuspal width respectively, and numeric values of the material properties of enamel, dentin and gold was set. Three types of load : concentrated load, divided load and distributed load was 500N. The empty cavities in the model were also examined using divided load and distributed load. The three - dimensional Finite Element Method was used to analysis the displacement and stress distribution. The results were as follows : 1. All of the experimental models which were filled with gold inlay revealed similar direction of displacement to that of the natural tooth model under the same load type. But in the models with empty cavities, as the isthmus width increased, the degree of displacement increased in the case of divided load type. 2. All experimental models which were filled with gold inlay showed stress concentration at load points, but in the models with empty cavities at divided load type, as isthmus width increased, stress was concentrated at the comer of the pulpal floor. 3. In the models with empty cavities at divided load type, tooth fracture was expected regardless of isthmus width, but all experimental models which were filled with gold inlay after cavity preparation were not susceptible to fracture. 4. In all experimental models which were filled with gold inlay after cavity preparation, displacement patterns were similar under both concentrated and divided load types. In the models with empty cavities, a divided load resulted in a bucco-lingual cuspal displacemenat in both sides, but a distributed load resulted in a lingual displacement of the tooth.

• 지구물리와물리탐사
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• 제7권1호
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• pp.80-87
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• 2004

During excavation work for the construction of a highway bridge in a limestone area in Korea, several cavities were found, and construction work was stopped temporarily. Cavities under the bridge piers might seriously threaten the safety of the planned bridge, because they could lead to excessive subsidence and differential settlement of the pier foundations. In order to establish a method for reinforcement of the pier foundations, borehole radar reflection and tomography surveys were carried out, to locate cavities under the planned pier locations and to determine their sizes where they exist. Since travel time data from the crosshole radar survey showed anisotropy, we applied an anisotropic tomography inversion algorithm assuming heterogeneous elliptic anisotropy, in order to reconstruct three kinds of tomograms: tomograms of maximum and minimum velocities, and of the direction of the symmetry axis. The distribution of maximum velocity matched core logging results better than that of the minimum velocity. The degree of anisotropy, defined by the normalized difference between maximum and minimum velocities, was helpful in deciding whether an anomalous zone in a tomogram was a cavity or not. By careful examination of borehole radar reflection and tomography images, the spatial distributions of cavities were delineated, and most of them were interpreted as being filled with clay and/or water. All the interpretation results implied that two faults imaged clearly by a DC resistivity survey were among the most important factors controlling the groundwater movement in the survey area, and therefore were closely related to the development of cavities. The method of reinforcement of the pier foundations was based on the interpretation results, and the results were confirmed when construction work was resumed.

• 지구물리와물리탐사
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• 제12권1호
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• pp.27-32
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• 2009

이 연구는 한국 남서쪽에 위치한 무안군 용월리의 카르스트 지역에서 지하 공동 탐지를 위하여 3차원 전기비저항탐사의 적용성을 시험한 것이다. 현장 조사지역은 과거에 지반침하가 발생하였으며, 지하 공동은 충적층 하부에 분포하고 있는 석회암내에서 발견된다. 석회암 공동은 대부분 지하수와 점성토로 충진 되어 있기 때문에 주변의 기반암에 비하여 전기비저항이 상대적으로 낮게 나타난다. 이 연구 결과에 의하면 시추공에서 인식되고 있는 공동 분포대가 저비저항대와 일치하고 있으며, 이로부터 3차원 전기비저항탐사가 카르스트 지역에서의 지하 공동을 탐지하고 영상화 하는데 매우 유용함을 입증했다.

• Restorative Dentistry and Endodontics
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• 제18권1호
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• pp.103-113
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• 1993

The purpose of this study was to evaluate the tensile bond strength of composite resin inlays according to the their internal surface treatment and types of luting cement and compared them with the conventional direct resin filling thchnique. Class II cavities were prepared in 50 extracted human molar teeth, and then equally divided into five groups. Group 1 : Cavities of control group were directly filled with P-50. Group 2 : Cavities of resin inlay group were luted with resin cement. Group 3 : Cavities of resin inlay group were luted with luting G-I cement. Group 4 : Cavities of resin inlay group were luted with resin cement after sandblasting. Group 5 : Cavities of resin inlay group were luted with luting G-I cement after sandblasting. All specimens were polished with same method and stored in normal saline for 24 hours before testing. An Universal Testing machine(Model No. AGS-100A, Shimadzu, Japan) was used to apply tensile loads in the vertical direction, and the force required for separation was recorded with a cross-head speed of 5mm/min and 100kg in full scale. The results were as follows : 1. The mean tensile bond strength was lowest in group luted with luting G-I cement, with measurements of $14.45{\pm}0.78(kg/cm^2)$ and highest in group luted with resin cement after sandblasting, with measurements of $49.6{\pm}2.74(kg/cm^2)$. 2. The tensile bond strength was greater in resin inlay groups luted with resin cement than in control group and resin inlay groups luted with luting G-I cement(P<0.05). 3. The tensile bond strength was lower in resin inlay groups luted with luting G-I cement than in control group(P<0.05). 4. The tensile bond strength was greater in resin inlay groups luted with resin cement or luting G-I cement after sandblasting than without that(P<0.05).

• 자원환경지질
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• 제39권5호
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• pp.597-605
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• 2006

본 연구는 석회규산염암 공동에 의한 지반침하 지역에 3차원 전기비저항탐사를 실시하여 그 결과로부터 지하공동의 영상화를 시도했다. 조사지역은 무안군 용월리에 위치하고 있으며, 충적층 하부에 석회규산염암이 분포하고 있는 곳이다. 이 지역의 지질특성은 충적층 하부 석회규산염암의 용식작용에 의한 돌리네와 파쇄대를 따라 공동이 발달되어 있으며 과거 여러 차례 돌리네의 함몰에 의한 지반침하가 발생하였다. 조사지에 실시한 2차원 전기비저항탐사 결과로부터 지하공동이 분포하고 있는 곳은 주변의 기반암에 비하여 전기비저항이 낮게 나타나고 있는데 그 이유는 대부분의 석회규산염암 공동에 지하수와 점토로 충전되어 있기 때문임을 알았다. 2차원 전기비저항탐사 결과로부터 저비저항 분포 영역을 중심으로 3차원 전기비저항탐사를 실시하고, 전기비저항이 50ohm-m 이하를 지하공동으로 가정하여 3차원 전기비저항탐사 결과로부터 석회규산염암 공동을 영상화 하였다. 이것을 시추조사에서 공동이 발견된 위치와 비교한 결과 양자가 일치하고 있음을 알 수 있었으며, 석회규산염암에 발달되어 있는 지하공동 탐지에 3차원 전기비저항탐사가 유용함을 알 수 있었다.

• Tuberculosis and Respiratory Diseases
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• 제62권5호
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• pp.374-381
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• 2007

배 경: 여러 개의 공동이 있는 활동성 폐결핵환자에서 객담도말 음성과 관련된 CT소견을 알아보고 진단 및 치료에 도움을 주고자 하였다. 방 법: CT에서 여러 개의 공동이 있는 38명의 활동성 폐결핵환자를 대상으로 하였다. 객담도말검사의 결과에 따라 객담도말검사 양성(n=30)과 음성(n=8)인 두 군으로 나누었다. CT 소견을 후향적으로 분석하였다. CT 소견은 공동의 크기와 수, 공동이 있는 폐엽의 수 그리고 동반된 소견들을 분석하였다. 공동의 크기는 최대내경으로 하였다. 공동의 최대내경이 20 mm 이하인 경우와 20 mm보다 큰 경우로 나누어 두 군의 빈도를 조사하였다. 동반된 소견은 간유리음영, 폐경결 미세결절과 결절로 나누어 분석하였다. 각 소견의 유무와 소견이 보이는 폐엽의 수를 기록하였다. 또한 폐경결 속에 동반된 공동이 있어 괴사성 폐렴의 양상을 보이는 빈도를 조사하였다. 두 군 간에 CT소견에 어떤 차이가 있는지 알아보았다. 결 과: 공동의 평균 최대내경은 1군은 $32.23{\pm}17.66mm$, 그리고 2군은 $15.50{\pm}11.12mm$로 두 군 간에 유의한 차이가 있었다(p=0.0042). 공동의 수도 1군은 $5.53{\pm}3.17$, 2군은 $2.43{\pm}1.13$로 의미 있는 차이가 있었다(p=0.0002). 공동의 개수가 3개 이상인 경우는 1군은 23예(23/30, 76.7%)가 있었고 2군은 1예(1/8, 12.5%)가 있었다(p<0.005). 간유리음영과 폐경결이 보이는 폐엽의 수는 1군과 2군에서 각각 $1.5{\pm}1.50$, $0.38{\pm}0.52$(p=0.0016) 그리고 $2.00{\pm}1.34$, $0.25{\pm}0.46$으로 유의한 차이가 있었다(p=0.001). 괴사성 폐렴과 유사한 양상을 보인 예는 1군에서 43.3%(13/30)가 있었고 2군에서는 없었다. 다른 소견들은 두 군 간에 차이가 없었다(p>0.05). 폐경결이 보이거나 3개 이상의 공동이 있거나 공동의 최대내경이 20 mm 보다 큰 경우에 객담도말검사에 대한 민감도, 특이도, 양성예측도, 그리고 음성 예측도는 각각 100%(30/30), 62.5%(5/8), 90.9%(30/33), 100%(5/5)이었다. 결 론: CT에서 폐경결이 없고 공동이 2개이면서 공동의 최대내경이 2 cm 이하인 다발성 공동 폐결핵은 객담도말 음성과 관련이 있다.