• 한국지반공학회논문집
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• 제20권7호
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• pp.207-215
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• 2004

본 연구는 보강사면에 상계이론를 적용하여 실제 한계상태에 가까운 신뢰성이 높은 해석방법을 개발하는데 목적이 있으며 상계해석의 유한요소공식화를 전개하는데 있어 거시적인 관점으로부터 비등방성이면서 균질한 재료에 대한 수치해석의 기본 개념은 얻을 수 있다. 보강토는 뒷채움한 성토와 보강재 경계면의 상호작용으로 보강토의 강도가 보강재의 재료적 특성에 의존하고 있기 때문에 흙의 역학적 특성과 보강토의 전체 거동은 보강재의 기하학적인 배열과 상대적인 면적에 의해서 조절할 수 있다. 따라서, 상계이론은 보강사면의 한계상태 거동을 효과적으로 산정할 수 있어 국부적으로 발생하는 소성파괴를 예측할 수 있다.

• 한국수자원학회논문집
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• 제40권4호
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• pp.287-297
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• 2007

DEM을 이용하여 국부경사와 기여면적 사이의 규모에 따른 거동특성을 조사하여 면적한계기준과 경사-면적한계 기준이 상호보완적인 형태의 수로망 추적절차를 제시하였다. 상기방법과 현장자료에 대한 적용을 통하여 유역의 경사는 공간적으로 대규모의 산포경향을 갖는 지형인자임을 확인할 수 있었다. 양자의 규모에 따른 거동특성권역에 따라 지면의 형상은 발산지형과 수렴지형으로 분류될 수 있었다. 본 연구에서 제시한 수로망 동정 절차를 설마천 시험 유역에 대하여 수행한 결과 유역의 동적 거동을 확인할 수 있었다. 또한 이로부터 지형도를 이용한 수작업에 기초한 방법에 비하여 하천두부의 거동과 수로망의 동적특성을 잘 표현하고 있음을 볼 수 있었다.

• Wind and Structures
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• 제22권4호
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• pp.477-501
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• 2016

Though hilly topography influences both wind speeds and directions aloft, only the influence on wind speeds, i.e. the speed-up effect, has been thoroughly investigated. Due to the importance of a model showing the spatial variations of wind directions above hilly terrains, it is worthwhile to systematically assess the applicability and limitations of the model describing the influence of hilly topographies on wind directions. Based on wind-tunnel test results, a model, which describes the horizontal and vertical variations of the wind directions separately, has been proposed in a companion paper. CFD (Computational Fluid Dynamics) techniques were employed in the present paper to evaluate the applicability of the proposed model. From the investigation, it has been found that the model is acceptable for describing the vertical variation of wind directions by a shallow hill whose primary-to-secondary axis ratio (aspect ratio) is larger than 1. When the overall hill slope exceeds $20^{\circ}$, the proposed model should be used with caution. When the aspect ratio is less than 1, the proposed model is less accurate in predicting the spatial variation of wind directions in the wake zone in a separated flow. In addition, it has been found that local slope of a hill has significant impact on the applicability of the proposed model. Specifically, the proposed model is only applicable when local slope of a hill varies gradually from 0 (at the hill foot) to the maximum value (at the mid-slope point) and then to 0 (at the hill top).

• 지질공학
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• 제24권3호
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• pp.333-341
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• 2014

The construction of roads, tunnels, and bridges results in changes to the local terrain that may influence the ground safety factor, which represents the stability of geotechnical structures. In this study, we assessed construction sites that had collapsed as a result of terrain change, and then simulated variation in the ground safety factor with respect to terrain change caused by road construction. We assumed steep slopes to simulate changes in terrain in a mountainous area and assumed that earthworks took place for road construction by cutting a platform into the slope and altering the slope angle of the terrain both above and below the road. We calculated values of the ground safety factor through a stability analysis of the slope both above and below the road, and examined the variation in the safety factor of the above- and below-road slopes with respect to changes in road width. We found that if the slope angle was the same above and below the road, then the change in the ground safety factor during/after road construction occurred in the slope below the road, and if the slope angle above the road differed from that below, then the change occurred in both the above- and below-road slopes. Furthermore, the ground safety factor was essentially constant for road widths exceeding 2-6 m, depending on both above- and below-road slope angle. The findings of this study can be used to guide the management of construction sites and to assess changes in ground stability during road construction work, particularly in the early stages of earthworks, when the road width is narrow.

• 한국지형학회지
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• 제18권4호
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• pp.247-259
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• 2011

본 연구는 중요한 문화역사와 다양한 생태환경을 갖추고 있는 팔공산(주로 화강암 구역)을 대상으로 지형자원을 분석하여 다음과 같은 결과를 얻었다. 1) 남사면(화강암)은 북사면(화강암과 변성퇴적암)에 비해 지질적 경계가 뚜렷하게 나타난다. 특히 단층선(남사면의 화강암 지대와 변성퇴적암 지대 사이)으로 인한 차별침식 결과 소규모 분지가 발달한다. 2) 국지적인 기후, 지형 및 지질적 차이로 인해 남사면보다 북사면의 계곡이 비교적 크게 발달한 것으로 판단된다. 3) 토르, 판상절리지형, 거터, 등은 남·북사면 모두에서 잘 발달한다. 그러나 다각형균열바위와 암괴류 등은 남사면상에서, 계곡 발달이 현저한 북사면상에서는 하식애, 소, 폭포 등의 지형발달이 상대적으로 우세하다. 4) 비교적 수려한 지형경관은 팔공산 남사면에 위치하는 동산계곡과 치산계곡에 주로 발달한다. 5) 팔공산지에 발달하는 지형자원 중에는 스토리텔링에 활용할만한 자원이 많아 활용을 위한 계획이 필요하다.

• Journal of Ecology and Environment
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• 제43권2호
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• pp.161-182
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• 2019

Quantifying the amount of carbon pools in forest ecosystems enables to understand about various carbon pools in the forest ecosystem. Therefore, this study was conducted in the Chilimo dry afromontane forest to estimate the amount of carbon stored. The natural forest was stratified into three forest patches based on species composition, diversity, and structure. A total of 50 permanent sample plots of 20 m × 20 m (400 ㎡ ) each were established, laid out on transects of altitudinal gradients with a distance of 100 m between plots. The plots were measured twice in 2012 and 2017. Tree, deadwood, mineral soil, forest floor, and stump data were collected in the main plots, while shrubs, saplings, herbaceous plants, and seedling data were sampled inside subplots. Soil organic carbon (SOC %) was analyzed following Walkely, while Black's procedure and bulk density were estimated following the procedure of Blake (Methods of soil analysis, 1965). Aboveground biomass was calculated using the equation of Chave et al. (Glob Chang Biol_20:3177-3190, 2014). Data analysis was made using RStudio software. To analyze equality of means, we used ANOVA for multiple comparisons among elevation classes at α = 0.05. The aboveground carbon of the natural forest ranged from 148.30 ± 115.02 for high altitude to 100.14 ± 39.93 for middle altitude, was highest at 151.35 ± 108.98 t C ha^-1 for gentle slope, and was lowest at 88.01 ± 49.72 t C ha^-1 for middle slope. The mean stump carbon density 2.33 ± 1.64 t C ha^-1 was the highest for the middle slope, and 1.68 ± 1.21 t C ha^-1 was the lowest for the steep slope range. The highest 1.44 ± 2.21 t C ha^-1 deadwood carbon density was found under the middle slope range, and the lowest 0.21 ± 0.20 t C ha^-1 was found under the lowest slope range. The SOCD up to 1 m depth was highest at 295.96 ± 80.45 t C ha^-1 under the middle altitudinal gradient; however, it was lowest at 206.40 ± 65.59 t C ha^-1 under the lower altitudinal gradient. The mean ecosystem carbon stock density of the sampled plots in natural forests ranged from 221.89 to 819.44 t C ha^-1. There was a temporal variation in carbon pools along environmental and social factors. The highest carbon pool was contributed by SOC. We recommend forest carbon-related awareness creation for local people, and promotion of the local knowledge can be regarded as a possible option for sustainable forest management.

• 터널과지하공간
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• 제8권1호
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• pp.37-45
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• 1998

In this study, two dimensional and three dimensional numerical analysis were performed with a finite difference code for the safe maintenance of the spillway slope of the Boryeong dam. Results of the geological survey and the stereographic projection analysis on the discontinuities were used as input data for the numerical analysis. As a result, several suggestions were given such as the reinforcement of the local tension zone, the decrease in the angle of the slope, the drawdown of the pore pressure in the slope and the removal of the upper benches. A systematic and long-term monitoring system was also suggested.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.253-262
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• 2010

In this study, localized heavy rainfall occurred during the collapse of steep slopes adjacent to the construction site and to ensure the safety of residents to build an early warning system was performed. Forecast/Alert range was estimated based on vulnerability landslide map and past disaster history. And established a critical line in consideration of the characteristics of local rainfall and operating a snake line, the study calculated causing and non-causing points. Also, be measured in real-time analysis of rainfall data in conjunction with the system before the steep slope failure occurred forecast/Alert System is presented.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.504-507
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• 2006

Airborn Lidar technology has been applied to diverse applications with the advantages of accurate 3D information. Further, Lidar intensity, backscattered signal power, can provid us additional information regarding target's characteristics. Lidar intensity varies by the target reflectance, moisture condition, range, and viewing geometry. This study purposes to generate normalized airborne LiDAR intensity image considering those influential factors such as reflectance, range and geometric/topographic factors (scan angle, ground height, aspect, slope, local incidence angle: LIA). Laser points from one flight line were extracted to simplify the geometric conditions. Laser intensities of sample plots, selected by using a set of reference data and ground survey, werethen statistically analyzed with independent variables. Target reflectance, range between sensor and target, and surface slope were main factors to influence the laser intensity. Intensity of laser points was initially normalized by removing range effect only. However, microsite topographic factor, such as slope angle, was not normalized due to difficulty of automatic calculation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.711-714
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• 2003

In this presentation, we investigated the abnormal subthreshold slope of the FD SOI MOSFETs upon the rapid thermal annealing. Based on subthreshold technique and C-V measurement, we deduced that the hump of the subthreshold slope comes from the abnormal D$_{it}$ distribution after RTA. The local kink in the interface trap density distribution by RTA drastically degrades the subthreshold characteristics and mini hump can be eliminated by S-PGA.A.