• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.6
• /
• pp.512-518
• /
• 2006

In this paper, we investigated the deposition of pentacene thin film on a large area substrate by Organic Vapor Phase Deposition(OVPD) and applied it to fabrication of Organic Thin Film Transistor(OTFT). We extracted the optimum deposition conditions such as evaporation temperature of $260^{\circ}C$, carrier gas flow rate of 10 sccm and chamber vacuum pressure of 0.1 torr. We fabricated 72 OTFTs on the 4 inch size Si Wafer, Which produced the average mobility of $0.1{\pm}0.021cm^2/V{\cdot}s$, average subthreshold slope of 1.04 dec/V, average threshold voltage of -6.55 V, and off-state current is $0.973pA/{\mu}m$. The overall performance of pentacene TFTs over 4 ' wafer exhibited the uniformity with the variation less than 20 %. This proves that OVPD is a suitable methode for the deposition of organic thin film over a large area substrate.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.4
• /
• pp.17-31
• /
• 2016

Many researchers have evaluated the influence of vegetation cover on slope stability. However, due to the extensive variety of site conditions and vegetation types, different studies have often provided inconsistent results, especially when evaluating in different regions. Therefore, additional studies need to be conducted to identify the positive impacts of vegetation cover for slope stabilization. This study used the Transient Rainfall Infiltration and Grid-based Regional Slope-stability Model (TRIGRS) to predict the occurrence of landslides in a watershed in Jinbu-Myeon, Pyeongchang-gun, Korea. The influence of vegetation cover was assessed by spatially and temporally comparing the predicted landslides corresponding to multiple trials of cohesion values (which include the role of root cohesion) and real observed landslide scars to back-calculate the contribution of vegetation cover to slope stabilization. The lower bound of cohesion was defined based on the fact that there are no unstable cells in the raster stability map at initial conditions, and the modified success rate was used to evaluate the model performance. In the next step, the most reliable value representing the contribution of vegetation cover in the study area was applied for landslide assessment. The analyzed results showed that the role of vegetation cover could be replaced by increasing the soil cohesion by 3.8 kPa. Without considering the influence of vegetation cover, a large area of the studied watershed is unconditionally unstable in the initial condition. However, when tree root cohesion is taken into account, the model produces more realistic results with about 76.7% of observed unstable cells and 78.6% of observed stable cells being well predicted.

• Journal of the Korean GEO-environmental Society
• /
• v.8 no.3
• /
• pp.51-57
• /
• 2007

In the design of slopes during rainfall, the groundwater level is assumed to be located at the ground surface, based on the change in characteristics of rainfall. In addition, stability investigations are performed for large cut slopes in the design of slopes while standard inclinations specified in the design criteria are applied for the slopes that stability investigations are not performed. In spite of the strengthened criteria of groundwater location, slope failures continuously occur during heavy rainfall, regardless of magnitude of slopes. In order to investigate the cause of the failures, stability investigations have been performed on standard inclination of slopes suggested in the design criteria for both dry and rainfall cases by ground condition in this research. Despite that standard inclination of slopes specified in the design criteria should be stable for both dry and rainfall cases, the results show that standard factor of safety has not been obtained in many cases; more than 50% of total cases for dry cases and more than 65% of total cases for rainfall case. Based on the results, this paper indicates the problems in the current design criteria and proposes the plans for establishment of countermeasure.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.26 no.2
• /
• pp.117-127
• /
• 2008

Korea has a large number of landslides due to localized torrential downpours and typhoons in summer, causing great human damage and economic losses. In particular, most roads in the Gangwon area are located in mountains, making them expose to a great risk of landslide. Therefore, it is urgent to prepare countermeasures to prevent these landslides. Necessary for that are various slope investigation and high-tech observation techniques for slope maintenance. Recently there have been slope observation techniques using optical fiber sensors, GPS, CCD cameras, Total Station and satellite images; however, these are not used much due to poor economic feasibility, low accuracy and efficiency. This study evaluated accuracy of displacement extraction of model slopes using terrestrial LiDAR to determine its application to landslide monitoring. As a result, it can measure several mm of minute displacement with high accuracy and help to rapidly obtain geographical features of slope.

• Journal of Korea Water Resources Association
• /
• v.40 no.4
• /
• pp.287-297
• /
• 2007

The procedures for identifying channel network are suggested by exploring the scaling property between the local slope and the contributing area, given that the area threshold criterion is an indispensable complement to the slope-area threshold criterion. Through the use of the above procedures and the field data, the basin slopes illustrate the trends of large scatters in space for the geomorphologic/topographic factors. According to the scaling regimes of them both the forms of landscape can be classified as topographic divergence and convergence. The presentation of the procedures proposed in this study is implemented in the case study on Seolma experimental catchment in Korea. As a result the dynamic behaviors of basin are confirmed, and thus the dynamics of channel head advance and channel network are shown to represent better than the method using the topographic chart manually.

• The Journal of Engineering Geology
• /
• v.21 no.3
• /
• pp.247-257
• /
• 2011

In this study the infinite slope model, one of the physical landslide models has been suggested to evaluate the susceptibility of the landslide. However, applying the infinite slope model in regional study area can be difficult or impossible because of the difficulties in obtaining and processing of large spatial data sets. With limited site investigation data, uncertainties were inevitably involved with. Therefore, the probabilistic analysis method such as Monte Carlo simulation and the GIS based infinite slope stability model have been used to evaluate the probability of failure. The proposed approach has been applied to practical example. The study area in Boeun area been selected since the area has been experienced tremendous amount of landslide occurrence. The geometric characteristics of the slope and the mechanical properties of soils like to friction angle and cohesion were obtained. In addition, coefficient of variation (COV) values in the uncertain parameters were varied from 10% to 30% in order to evaluate the effect of the uncertainty. The analysis results showed that the probabilistic analysis method can reduce the effect of uncertainty involved in input parameters.

• The Journal of Engineering Geology
• /
• v.27 no.3
• /
• pp.275-292
• /
• 2017

Large landslides have occurred more than 100 times each year by the influence of cyclones and torrential rain each year in Vietnam. Nevertheless, they $don^{\circ}$Øt have a scientific management system to prevent the landslide disaster in advance. In this study, we acquisited the risk factor and damage factor about each slope throughout basic survey at Hoang Sa Costal Road, Danang and at Ho Chi Minh Road, Quangnam. The priority of investigation technique considering of the exposure characteristics of the road slope in Vietnam developed by the empirical analysis with the acquired data. As a result, we can set the foundation of scientific management for the road slope management system in Vietnam.

• Journal of Environmental Science International
• /
• v.11 no.9
• /
• pp.865-880
• /
• 2002

As prevailing synoptic scale westerly wind blowing over high steep Mt. Taegulyang in the west of Kangnung coastal city toward the Sea of Japan became downslope wind and easterly upslope wind combined with both valley wind and sea breeze(valley-sea breeze) also blew from the sea toward the top of the mountain, two different kinds of wind regimes confronted each other in the mid of eastern slope of the mountain and further downward motion of downlsope wind along the eastern slope of the mountain should be prohibited by the upslope wind. Then, the upslope wind away from the eastern slope of the mountain went up to 1700m height over the ground, becoming an easterly return flow in the upper level of the sea. Two kinds of circulations were detected with a small one in the coastal sea and a large one from the coast toward the open sea. Convective boundary layer was developed with a thickness of about 1km over the ground in the upwind side of the mountain in the west, while a thickness of thermal internal boundary layer(TIBL) form the coast along the eastern slope of the mountain was only confined to less than 200m. After sunset, under no prohibition of upslope wind, westerly downslope wind blew from the top of the mountain toward the coastal basin and the downslope wind should be intensified by both mountain wind and land breeze(mountain-land breeze) induced by nighttime radiative cooling of the ground surfaces, resulting in the formation of downslope wind storm. The wind storm caused the development of internal gravity waves with hydraulic jump motion bounding up toward the upper level of the sea in the coastal plain and relatively moderate wind on the sea.

• Tunnel and Underground Space
• /
• v.17 no.5
• /
• pp.360-371
• /
• 2007

This paper presents an application of drainage control and slope stability by GIS-based hydrological modeling to control the surface water from an operational point of view. This study was carried out on a region of Pasir open-pit coal mine, Indonesia. A detailed topographical survey was performed at the study area to generate a reliable DEM (Digital Elevation Model). Hydrology tools implemented in ArcGIS 9.1 were used to extract the characteristics of drainage system such as flow direction, flow accumulation and catchment area from DEM. The results of hydrological modeling and spatial analysis showed that current arrangement of pumping facility is not suitable and some vulnerable places to erosion exist on the bench face due to concentrated surface runoff. Finally, some practical measures were suggested to optimize the design of drainage system and to monitor the slope stability by the surface water management at the study region during heavy rainfall.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.4
• /
• pp.33-41
• /
• 2003

The large planar failure has occurred in a rock cut slope of highway construction site in Boeun. This area is considered to be unstable since the discontinuity, whose orientation is similar to the orientation of the failure plane, is observed in many areas. Therefore, several analysis techniques such as SMR, stereographic analysis, limit equilibrium, numerical analysis, which are commonly used in rock slope stability analysis, are adopted in this area. In order to analyze the stress redistribution and nonlinear displacement caused by cut, which are not able to be obtained in limit equilibrium method, DEM and shear strength reduction technique were used in this study. Then the factors of safety evaluated by shear strength reduction technique and limit equilibrium were compared. In addition, the factor of safety under fully saturated slope condition was calculated and subsequently, the effect of the reinforcement was evaluated.