• The Journal of Engineering Geology
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• v.32 no.1
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• pp.13-26
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• 2022

Calcite twins were analyzed in six oriented samples of the Pungchon limestone, Joseon Supergroup, to reconstruct the paleostress field. The orientations of c-axis of calcite and e twin plane were measured along with the average thickness and numbers of twins, and the widths of calcite grains. Twin strain, mean width, and intensity of twinning, and the relative magnitude and orientations of principal stresses were calculated using Calcite Strain Gauge program. Twin strain, mean width, and intensity of twinning showed ranges of 1.09-15.36%, 0.53-3.72 ㎛ and 21.0-53.1 twim/mm, respectively. Metamorphic temperatures calculated from the twins were 170-200℃, indicating that the twins developed after the Pungchon limestone was uplifted to at least half of the maximum burial depth. Results for five of the samples indicate that the calcite twins formed during two events with principal stress axes of different orientations, while the remaining sample recorded only one event that produced calcite twins. The axis of maximum compressive stress was oriented mainly WNW-ESE to ENE-WSW, and to a lesser degree NW-SE and NE-SW. Comparison of paleostress orientations measured here and in other studies indicates that most twins were produced during the Songrim orogeny. However, the Daebo orogeny and the Bulguksa orogeny also produced calcite twins in the Punchon limestone.

• Journal of the Korean Geophysical Society
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• v.2 no.2
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• pp.135-142
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• 1999

Interpretations of 3-component magnetic logging data obtained for a reinforced bar as a model of the line of the magnetic dipoles are conducted using a least squared inversion technique. The length of the bar is 1.12 m, sampling interval is 0.05 m, the distance between the bar and the borehole is 0.3 m, and the top of the bar is fixed at 0 m of depth. The bar is set to be approximately vertical. Magnetic anomalies smoothed with FFT are used as input data for the inversion. For the interpretation of magnetic logging data the depth to the top, the length, the magnetic moment per unit length, the direction of the magnetization (declination and inclination), and the bearing and plunge of the line of magnetic dipoles are left as unknown parameters. The comparison of the results obtained from the individual inversion of the horizontal component or the vertical component of the magnetic anomalies, and those from the simultaneous inversion of horizontal and vertical component of the magnetic anomalies shows that there exist some disagreements between each inversion result. The depth to the bottom of the bar, which is actually 1.12 m, is estimated as 1.18 m, and the inclination of the magnetization is estimated as -76°by simultaneous inversion. The negative value of the inclination indicates that the strength of the remnant magnetization is much greater than that of the induced magnetization, so that the direction of the resultant magnetization points to the top of the bar.

• Journal of the Korean Society of Radiology
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• v.85 no.3
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• pp.607-617
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• 2024

Purpose Recent studies have demonstrated the usefulness of diffusion-weighted MR neurography (DW MRN) for assessing nerve roots. This study aimed to evaluate the utility of DW MRN with a unidirectional motion-probing gradient (MPG) for the lumbar nerve roots at 1.5T MR. Materials and Methods Sixty-four lumbar spine MRI scans with DW MRN using anteroposterior unidirectional MPG were retrospectively analyzed. Any changes in the 512 lumbar spinal nerve roots from L3 to S1 were evaluated using T2-weighted imaging (T2WI), contrast-enhanced T1-weighted imaging (CE T1WI), and DW MRN, with agreement and correlation analysis. Results T2WI revealed compression of 78 nerve roots, and CE T1WI revealed 52 instances of nerve root enhancement. Sixty-seven nerve roots showed swelling and hyperintensity on DW MRN. A total of 42 nerve roots showed changes in the CE T1WI and DW MRN sequences. Moderate to substantial agreement and moderate positive correlation were observed between DW MRN and CE T1WI, as well as DW MRN and T2WI (κ = 0.59-0.65, ρ = 0.600-0.653). Conclusion DW MRN with unidirectional anteroposterior MPG can help evaluate neuritisrelated changes in spinal nerve roots and could serve as a sequence capable of complementing or substituting gadolinium CE imaging.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.3
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• pp.273-281
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• 2001

The landslide occurrence in Sam-Chuck area was analyzed through Geo-Spatial Information System and AHP(Analytic Hierarchy Process). Among many factors which causes landslide, terrain slope, terrain aspect, lithology, soil texture and vegetation arc taken as input data from existing maps and constructed as a database. These factors are determined by each environmental factor by environmental and geological characters in the study area, and the rating and weight about factor are input using AHP. Possible areas for landslide have been extracted by overlaying each layers. Finally, the estimated results are compared with real landslide sites to know which factor is the most effective for landslide. The results showed that lithology and soil factor have high susceptibility in Sam-Chuck area.

• Composites Research
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• v.13 no.2
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• pp.40-50
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• 2000

In an effort to construct a structure under the design principle of minimal use of materials for maximum performances, a discrete gradient structure has been introduced in laminate composite systems. Using a sequential linear programming method, the gradient structure of composites to maximize the buckling load was optimized in terms of fiber volume fraction and thickness of each layer. The buckling load showed maximum value with the outmost [$0^{\circ}$] layer concentrated by almost all the fibers when the ratio of length to width(aspect ratio) was less than 1.0. But when the aspect ratio was 2.0, the optimum was determined in a structure where the thickness and fiber volume fraction were well-balanced in each layer. From the optimization of gradient structure, the optimal fiber volume fraction and thickness of each layer were proposed. Gradient structures have also shown an advantage in the weight reduction of composites compared with the conventional homogeneous structures.

• The Journal of the Korea Contents Association
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• v.9 no.3
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• pp.296-304
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• 2009

The purpose of this study were to examine the effect of two different pelvic alignments and the back belt on electromyographic(EMG) activity of the erector spinae during lifting. The results were as follows: 1) EMG activity of erector spinae was greater when the pelvis was tilted anteriorly than when the pelvis was tilted posteriorly during lifting. 2) EMG activity of erector spinae was greater when the back belt than when without the back belt during lifting. These results suggest that the greater EMG activity of erector spinae with an anterior pelvic tilt position and with back belt during lifting may ensure optimal muscular support for the spine while handling loads.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.5
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• pp.389-397
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• 2006

The purpose of the present paper is to offer an analysis of LiDAR data processing and three dimensional terrain for Geographic Information System (CIS) applications. Generally, LiDAR survey is the method which obtains quantitative and qualitative information of the terrain using airborne laser scanning (ALS). We will get a most topographic data at a Triangular Irregular Network (TIN), Digital Surface Model (DSM) and Digital Elevation Model (DEM) using LiDAR data. We examined many factors such as visibility, hillshade, aspect and slope using DEM and DSM. The analyzing results obtained from each item are thought to be regarded as leading factors in the terrain analysis. It is to be hoped that LiDAR survey will contribute a new approach to the terrain analysis.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.5-5
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• 2022

하천의 서식처 특성 즉, 수리, 하도 및 하안 특성 평가의 목적은 하천기본계획 수립과 하천복원사업의 실행과정에 있어 기본방향의 설정 및 통합적 평가기준으로서 사업의 성공여부를 평가하고, 또한 하천 이용과 보전, 나아가 복원계획에 대한 잠재적인 적합성의 근거를 파악하고 이에 가치를 부여하기 위함이다. 본 연구에서는 하천 실무자가 적용할 수 있는 물리 서식처의 수리 및 하도 특성 평가를 위한 지표와 정량적 평가기준을 마련함에 있어 선진국 하천의 분류체계 및 물리 서식처 평가기준을 검토하였다. 또한, 검토 결과를 토대로 우리나라 하천의 물리적 특성을 반영할 수 있는 하천의 유형을 분류하고 각 유형의 특성을 반영할 수 있는 정량적 평가기준을 제시하고자 하였다. 평가체계의 가장 중요한 특징 중 하나는 개발 목적에 따라 하천의 물리, 생태, 경관, 이용 상황 등을 고려하여 하천환경의 다양성과 고유성을 제대로 반영한 평가시스템으로 구축하였다. 하도특성을 지배하는 주요 인자로 하상경사와 하상재료를 조합하여 급경사, 중경사, 완경사로 하천유형을 분류하고 하도 및 수리, 하안 및 식생, 하천교란 등의 3개 영역으로 하천을 세분화하여 평가 시스템을 구축하였으며, 또한 하천환경의 수리 및 하도특성의 정도는 두 가지로 첫째는 하천의 자연적인 모습인 참조하천의 관련된 것이고 나머지는 인간에 의해 교란된 비교하천으로 보았으며, 인간에 의해 교란된 정도와 서식처 기반 수준에 따라 1등급에서 5등급으로 등급화하여 평가체계를 구성하였다.

• Investigative Magnetic Resonance Imaging
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• v.16 no.1
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• pp.6-15
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• 2012

Purpose : The objective of this study was to develop background gradient correction method using excitation pulse profile compensation for accurate fat and $T_2{^*}$ quantification in the liver. Materials and Methods: In liver imaging using gradient echo, signal decay induced by linear background gradient is weighted by an excitation pulse profile and therefore hinders accurate quantification of $T_2{^*}$and fat. To correct this, a linear background gradient in the slice-selection direction was estimated from a $B_0$ field map and signal decays were corrected using the excitation pulse profile. Improved estimation of fat fraction and $T_2{^*}$ from the corrected data were demonstrated by phantom and in vivo experiments at 3 Tesla magnetic field. Results: After correction, in the phantom experiments, the estimated $T_2{^*}$ and fat fractions were changed close to that of a well-shimmed condition while, for in vivo experiments, the background gradients were estimated to be up to approximately 120 ${\mu}T/m$ with increased homogeneity in $T_2{^*}$ and fat fractions obtained. Conclusion: The background gradient correction method using excitation pulse profile can reduce the effect of macroscopic field inhomogeneity in signal decay and can be applied for simultaneous fat and iron quantification in 2D gradient echo liver imaging.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.242-242
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• 2020

도시화와 산업화에 따른 유출환경의 변화로 인해 도심지에서 발생하는 대부분의 유출은 도로표면을 따라 이동하고 도로변에 설치된 빗물받이에 의해 배수된다. 이 때 빗물이 원활하게 배수되지 않아 노면수가 정체되고, 이 노면수가 인근 주택지로 유입되어 침수 피해가 발생한다. 이러한 현상은 유출량이 집중되는 도심지 저지대에서 주로 발생하며 설계 한도를 초과하지 않는 정상적인 강우 조건에서도 빈번히 나타나고 있다. 이는 최근의 기후 변화로 인한 집중 호우 등을 고려하여 설계 기준이 지속적으로 조정되어야 함과 동시에 도로 노면수의 배수 능력 평가를 위한 실제적인 연구가 이루어져야 한다는 필요성을 나타내고 있다. 특히 도로 빗물받이의 효율은 주로 종경사 및 횡경사 등의 도로 조건, 표면 유출 우수량, 빗물받이의 형상 등에 의존한다. 그러므로 상향된 설계빈도 및 도로 조건을 고려한 도로 표면 유출에 대한 흐름 분석과 빗물받이 특성을 고려한 실증연구의 분석 및 설계 해석 알고리즘의 개발이 시급한 실정이다. 본 연구에서는 도로 노면수의 배수 능력 증대를 위해 연속 설치된 빗물받이 조건 및 도로 경사조건을 고려하여 도로 배수시설의 표면 유출 모델 설계 알고리즘을 개발하였다. 표면 유출 유량은 도로의 차선(2~4차선), 경사(종경사 2~10% 및 횡경사 2~10%) 및 설계빈도(최대 30년)를 고려하였으며 유량이 노면 진행방향을 따라 연속적으로 증가하는 부등류 흐름 해석 방법을 채택하였다. 또한, 빗물받이 설치간격(L)과 도로의 폭(W)의 곱으로 계산되는 단순 직사각형 형태의 노면 형상이 아닌 도로 종경사 및 횡경사에 따른 유달거리를 산정하여 평행사변형 형태의 노면 형상을 계산하고 이에 따른 면적(A), 도달시간(tc) 및 강우강도(I)를 산정하였다. 이와 같은 1차원 흐름분석을 통해 도로 표면흐름 및 빗물받이 설치 간격을 제시하고 기존의 제시된 빗물받이 설치 간격과 비교하여 본 연구에서 제시한 설계 알고리즘을 검증하였다. 또한, 수리 실험을 통해 측정된 빗물받이 차집효율을 이용하여 연속 구간에서의 도로 표면 유출 모델의 적용성을 제시하였다. 이는 빗물받이 유입구를 통해 모든 유량이 유출된다고 가정하고 단독 구간에서의 수리분석 결과만을 고려하여 이를 확장시켜 개발된 기존의 도로 표면 유출 모델을 보완할 수 있을 것으로 기대된다. 본 연구에서 제시하고 있는 설계 알고리즘을 적용한다면 도로 전체 구간에서의 흐름 변화 분석과 배수효율의 정량적인 분석이 가능하므로 향후 도로 표면 침수 피해 저감 및 배수능력 증대를 위한 실증적이고 정량적인 분석 방법이 될 것으로 판단된다.