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In Korea, it is difficult to efficiently manage water resources, due to the variability of rainfall in addition to the increasing outflow due to climate change in recent years. Therefore, if the trends and characteristics of rainfall at each station can be identified in advance, the problems caused by the variability of rainfall can be effectively dealt with. In this study, the data on rainfall characteristics of 64 rainfall stations in the Nakdong river basin were collected for the period 2000 to 2019. The data were analyzed according to the elevation of each station using K-means cluster analysis, and the rainfall trends at each station were identified by homogeneity test and modified Mann-Kendall test. The analysis showed an increasing trend in March, April, November, December, spring and autumn, and a decreasing trend in January, May, September, summer and year. Also, based on the cluster analysis, it was confirmed that when the number of clusters was set to three, the rainfall characteristics were different depending on the elevation of each station. It is believed that linking the characteristics of rainfall by cluster and the results of trend analysis by station derived from the study can be used to come up with a water resource management plan that takes into account the variability of rainfall.

In Korea, flood damage occurs every year due to typhoons and heavy rains, resulting in increasing damage to human lives and properties in urban areas. To reduce the scale of flood damage, economic analyses of flood-control work are conducted as part of efficient disaster management in the context of a limited budget. In this study, a quantitative evaluation of flood damage in Ulsan due to Typhoon Chaba was conducted using multi-dimensional flood damage analysis (MD-FDA). However, the land cover map applied to MD-FDA has limited data resolution and update intervals. Examination of domestic and foreign research cases to complement these spatial analysis data showed that grid data were being used in disaster-related fields. This study evaluated whether grid data are suitable for quantitative assessment through economic analyses conducted using new spatial analysis data such as road name address digital maps and 100 × 100 m grid-based spatial analysis data. The results of this study confirm that center-point-method grid data constitute spatial analysis data suitable for economic analysis.

Natural disasters caused by climate change frequently occur around the world. In Korea, flood warnings and storm warnings are used to prepare for flood damage. However, flood warnings are specifically issued for rivers while storm warnings use the same criteria throughout the country. Accordingly, there is a limit to effective flood preparation which reflects the regional characteristics of each administrative district. In this study, the flood risk matrix for each administrative district is developed in order to provide flood risk forecast information that reflects upon local characteristics. Moreover, the applicability is evaluated by using dichotomous forecasting. As a result of the forecast's evaluation, the probability of detection was determined to be over 80%. Therefore, it is possible to prepare for a flood through the forecast information of the administrative district using the flood risk matrix. In the future, it will be necessary to study how to improve the utilization of flood risk forecasting information through the continuous investigation of past damage phenomenon along with a review of flood-influencing factors.

Study region South Korea (KR), Ulsan tidal river. Study focus Climate change and urbanization pose a serious threat to rising water levels and flooding in the estuary region. In particular, tidal river, which is located in the estuary area, is impacted by many hydrological factors such as tide, wave height, and rainfall. This paper develops a new rating curve that can predict the water level of the tidal river. It also assesses the accuracy of the developed rating curve through the verification event. New hydrological insights Tidal rivers show non-linear hydrological characteristics that are influenced by various hydrological factors. Thus, no rating curve has been developed for them. This study proposes a method to develop a rating curve that can estimate the water level by using the runoff from rainfall in a tidal river. To develop the rating curve, the water level at Ulsan station, Korea was decomposed into four components, which are tide, wave, noise and runoff component by using wavelet analysis, curve fitting, and a high pass filter. A distributed grid-based rainfall-runoff model (GRM) was applied to simulate the runoff. The simulated runoff and the water level components influenced by rainfall were used to develop a rating curve and estimate the water level from the simulated runoff. The results were then added to the other three components (tide, wave, noise) to calculate an integrated water level, which was compared with the observed water level at Ulsan station. With less than 10 % error during validation, the results are expected to contribute to the accurate prediction of water level of tidal river during flood season.

This paper presents an algorithm that can efficiently simulate a grid-based one-dimensional distributed rainfall-runoff model by performing parallel computations using flow accumulation values for individual grid cells, which are calculated through an eight flow direction method. This parallel computation algorithm uses information about flow accumulation to automatically find parallel computation target grid cells within the overall area and perform parallel computation on the grid by unit. The Microsoft.NET Parallel class was used to apply and evaluate the parallel computation algorithm independently on two machines. The results showed that the time reduction effect of parallel computation differed for each target domain, because flow accumulation values varied depending on the domain. Parallel computation reduced computation time by around 40% to 78% in virtual domains and around 63% in the real domain compared to sequential computation. The results of this study can be utilized to reduce the computation time of distributed models.

The choice of the computational time step (dt) value and the method for setting dt can have a bearing on the accuracy and performance of a simulation, and this effect has not been comprehensively researched across different simulation conditions. In this study, the effects of the fixed time step (FTS) method and the automatic time step (ATS) method on the simulated runoff of a distributed rainfall&ndash, runoff model were compared. The results revealed that the ATS method had less peak flow variability than the FTS method for the virtual catchment. In the FTS method, the difference in time step had more impact on the runoff simulation results than the other factors such as differences in the amount of rainfall, the density of the stream network, or the spatial resolution of the input data. Different optimal parameter values according to the computational time step were found when FTS and ATS were used in a real catchment, and the changes in the optimal parameter values were smaller in ATS than in FTS. The results of our analyses can help to yield reliable runoff simulation results.

The objective of this study is to estimate the flood flow of inaccessible regions using satellite-derived rainfall and global geographic data. This study focuses on Dongsingun, an area located upstream of the Cheongcheon River in North Korea. The IFAS model was used to estimate flood flow. The model was calibrated in the Gap Stream watershed in South Korea and verified for the Byeongsung Stream watershed in the Nakdong River basin. Satellite-derived rainfalls for North Korea was revised using ground gauge data. Analysis results using CMORPH and GSMaP_NRT showed and respectively. In future studies, hydrological analysis in unmeasured and inaccessible regions will be carried out by applying more rainfall events.

Most runoff analyses using a grid-based distributed model use one parameter group calibrated at the outlet of a watershed, instead of dividing the watershed into subwatersheds. Significant differences between the observed value and the simulation result of the subwatersheds can occur if just one parameter group is used in all subwatersheds that have different hydrological characteristics from each other. Therefore, to improve the simulation results of the subwatersheds within a watershed, a model calibrated at every subwatershed needs to be used to reflect the characteristics of each subwatershed. In this study, different parameter groups were set up for one or two sites using a distributed model, the GRM (Grid based Rainfall-runoff Model), and the evaluations were based on the results of rainfall–runoff analysis, which uses a multi-site calibration (MSC) technique to calibrate the model at the outlet of each site. The Hyangseok watershed in Naeseong River, which is a tributary of Nakdong River in Korea, was chosen as the study area. The watershed was divided into five subwatersheds each with a subwatershed outlet that was applied to the calibration sites. The MSC was applied for five cases. When a site was added for calibration in a watershed, the runoff simulation showed better results than the calibration of only one site at the most downstream area of the watershed. The MSC approach could improve the simulation results on the calibrated sites and even on the non-calibrated sites, and the effect of MSC was improved when the calibrated site was closer to the runoff site. Copyright © 2014 John Wiley & Sons, Ltd.

In this study, we assess impact of spatial resolution of radar rainfall and a distributed hydrologic model on parameter estimat ion and rainfall-runoff response. Radar data measured by S-band polarimetric radar located at Mt. Bisl in the year of 2012 are used for the comparative study. As different rainfall estimates such as R-KDP, R-Z, and R-ZDR show good agreement with ground rainfall, R-KDP are applied for rainfall-runoff modeling due to relatively high accuracy in terms of catchment averaged and gauging point rainfall. GRM (grid based rainfall-runoff model) is implemented for flood simulations at the Geumho River catchment with spatial resolutions of 200m, 500m, and 1000m. Automatic calibration is performed by PEST (model independent parameter estimation tool) to find suitable parameters for each spatial resolution. For 200m resolution, multipliers of overlandflow and soil hydraulic co nductivity are estimated within stable ranges, while high variations are found from results for 500m and 1000m resolution. No tendency is found in the estimated initial soil moisture. When parameters estimated for d ifferent spatial resolution are applied for other resolutions, 200m resolution model shows higher sensitivity compared to 1000m resolution model.Key words : Distributed hydrologic model, Radar rainfall estimates, Spatial resolution, PEST, Parameter estimation, Uncertainty assessment초 록본 연구는 레이더 강우와 분포형 수문모형의 공간해상도가 매개변수 추정 및 강우 -유출 모의에 미치는 영향을 분석하였다. 레이더 강우는 비슬산 S밴드 이중편파 강우레이더에서 2012년 관측된 강우사상을 대상으로, R-KDP, R-Z, R-ZDR의 관계식에 의해 추정된 레이더 강우를 지상 관측 강우와 비교하였다. 세 가지 강우 추정식에 의한 레이더 강우를 지상 관측 강우와 비교 시 유역 평균에 대해서는 모두 높은 일치도를 보였으며, 이는 지상 관측 강우에 대한 레이더 강우 보정의 영향으로 판단되었다. 그 중에서도 R-KDP에 의한 추정 강우가 비교적 높은 정확도를 보였으며, 이를 강우-유출 모형의 입력자료로 적용하였다. 강우-유출 모형으로는 GRM (grid based rainfall-runoff model) 모형을 이용하여, 낙동Water Engineering

The purpose of this study is to simulate inundation and evaluate the applicability of LISFLOOD model to the streams in South Korea by comparing with the inundation map using FLUMEN. The suggested levee breaching scenarios were applied to the LISFLOOD model, and the results obtained from scenarios were evaluated. The modeling results using LISFLOOD by appling the levee breaching scenarios showed 0.2% ~ 42% relative error with FLUMEN model in inundation area. But the relative error of maximum inundation area by overlapping all the flood analysis results from levee breaching scenarios such as the way making flood risk map was approximately 1.2% between two models. Meanwhile, LISFLOOD model was easy to construct input data, DEM as topographic data and discharge hydrograph as upper boundary conditions. And computing time of LISFLOOD was shorter than FLUMEN. Therefore LISFLOOD model can be applied usefully in the region that needs immediate inundation modeling.

The objective of this study is to suggest a method for estimating rainfall-runoff relationship using runoff analysis with satellite rainfall and global geographic data for the region due to lack of observed data. This study uses CMORPH and GSMaP_NRT as satellite rainfall data, and GTOPO30 and GLCC as global geographic data. IFAS is used for runoff modeling. In the evaluation of rainfall data, the correlation coefficients of CMORPH and GSMaP_NRT with observed data are 0.37 and 0.30 respectively. Calculated peak runoffs using IFAS show small relative errors with observed data in case of parameters are not calibrated with satellite rainfall data. Therefore, the 2013년 12월 27일 접수 Received on December 27, 2013 / 2014년 3월 5일 수정 Revised on March 5, 2014 / 2014년 3월 7일 심사완료 Accepted on March 7, 2013 1 한국건설기술연구원 수자원연구실 Water Resources Research Division, Korea Institute of Construction Technology ※ Corresponding Author E-mail : ktkim1@kict.re.kr Runoff Estimation Using Rainfalls Derived from Multi-Satellite Images 108 methods suggested in this study could be applied to ungauged watershed. In the future, this study will analyze runoff for North Korea, a representative inaccessible region, using satellite rainfall and global geographic data.

Great loss of life and property has been occurred by the severe flood globally. In Korea, a flood inundation map is used as one of the non-structural measures for reducing flood damage, and various inundation models have been studied for flood inundation analysis. This study applies LiDAR data and LISFLOOD model for flood inundation analysis and discusses the the modeling results from levee breaching 2013년 8월 14일 접수 Received on August 14, 2013 / 2013년 9월 16일 수정 Revised on September 16, 2013 / 2013년 10월 7일 심사완료 Accepted on October 7, 2013 * 본 연구는 한국건설기술연구원 13주요-시드사업(과제명-지방하천 홍수위험지도 제작기술 개발)의 연구비지원에 의해 수행되었음. 1 한국건설기술연구원 수자원연구실 Water Resources Research Division, Korea Institute of Construction Technology ※ Corresponding Author E-mail : ckchoi@kict.re.kr Analysis of Flood Inundation Using LiDAR and LISFLOOD Model 2 scenarios for evaluating the applicability of the model to stream inundation modeling. In the results of LISFLOOD modeling, maximum inundation area was similar to the inundation map by HEC-RAS model just less than 4%. The inundation area by each levee breaching scenario showed the difference from 0.2% to 6.5%. Inundation processes were different each other according to the position of levee breach point, and maximum inundation area and depth were changed by the flow direction of stream and flood plain. This study shows that LISFLOOD model can be applied properly to stream inundation analysis using various inundation scenarios.

In this study, we estimate parameters of a distributed hydrologic model, GRM (grid based rainfall-runoff model), using a model-independent parameter estimation tool, PEST. We implement auto calibration of model parameters such as initial soil moisture, multipliers of overland roughness and soil hydraulic conductivity in the Geumho River Catchment and the Gamcheon Catchment using radar rainfall estimates and ground-observed rainfall represented by Thiessen interpolation. Automatic calibration is performed by GRM-MP (multiple projects), a modified version of GRM without GUI (graphic user interface) implementation, and "Parallel PEST" to improve estimation efficiency. Although ground rainfall shows similar or higher cumulative amount compared to radar rainfall in the areal average, high spatial variation is found only in radar rainfall. In terms of accuracy of hydrologic simulations, radar rainfall is equivalent or superior to ground rainfall. In the case of radar rainfall, the estimated multiplier of soil hydraulic conductivity is lower than 1, which may be affected by high rainfall intensity of radar rainfall. Other parameters such as initial soil moisture and the multiplier of overland roughness do not show consistent trends in the calibration results. Overall, calibrated parameters show different patterns in radar and ground rainfall, which should be carefully considered in the rainfall-runoff modelling applications using radar rainfall.

This study analyzes the application possibilities of the satellite-derived precipitation to water resources field. Precipitation observed by ground gauges and climate prediction center morphing method (CMORPH) which is global scale precipitation estimated by National Oceanic and Atmospheric Administration Climate Prediction Center (NOAA CPC) using satellite images are compared to evaluate the quality of precipitation estimated from satellite images. Precipitation data from 10-years (2002 to 2011) is applied. The correlation coefficient of 1-day cumulative precipitation is 0.87, but the 1-year precipitation is 4 to 5 times different. The variability of root mean square error (RMSE) become smaller as temporal resolution lower. On the results for the watershed scale, the precipitation from gauges and CMORPH shows better agreement as the watershed become larger.

A distributed model can easily obtain discharge at any grids spatially distributed in a watershed. But if there are subwatersheds which have various characteristics in a watershed, it is needed to apply a model calibrated at each subwatershed to obtain reliable simulation results for each subwatershed. In this study, a multi-site calibration module that can calibrate a distributed model at each subwatershed using observed flow data was developed. Methods to select multi-site calibration parameters, to apply subwatershed parameters, and to set subwatershed network information are suggested. Classes to implement multi-site calibration technique are designed and a GUI was developed, and procedures for runoff modelling using subwatershed parameters were established. Multi-site calibration module was applied to Sunsan watershed() of Nakdong river basin. Application results showed that the multi-site calibration technique could be applied effectively to model the calibration for each subwatershed, and the simulation results of subwatershed were improved by the application of multi-site calibration.

Recently, forest soil sediment disasters resulting from locally concentrated heavy rainfall have been occurring frequently in steep slope areas. The importance of landslide hazard map is emerging to analyze landslide vulnerable areas. This study was carried out to develop HyGIS-Landslide based on Hydro Geographic Information System in order to analyze forest soil sediment disaster in the mountainous river basin. HyGIS-Landslide is one of HyGIS components designed by considering the landslide hazard criteria of Korea Forest Service. It could show the distribution of landslide hazard areas after calculating the spatial data. In this system, the user could reset the weight of hazard criteria to reflect the regional characteristics of the landslide area. This component provided user interface that could make the latest spatial data available in the area of interest. HyGIS-Landslide could be applied to the surveyor`s compensation score and it was possible to reflect the landslide risk exactly through it. Also, it could be used in topographic analysis techniques providing spatial analysis and making topographical parameters in HyGIS. Finally the accuracy could be acquired by calculating the landslide hazard grade map and landslide mapping data. This study applied HyGIS-Landslide at the Gangwon-do province sample site. As a result, HyGIS-Landslide could be applied to a decision support system searching for mountainous disaster risk region; it could be classified more effectively by re-weighting the landslide hazard criteria.

This study purposes to develop a model to analyze soil loss in estimating prior disaster influence. The model of analyzing soil loss develops the soil loss analysis system on the basis of Internet by introducing cloud computing system, and also develops a standalone type in connection with HyGIS. The soil loss analysis system is developed to draw a distribution chart without requiring a S/W license as well as without preparing basic data such as DEM, soil map and land cover map. Besides, it can help users to draw a soil loss distribution chart by applying various factors like direct 2011년 9월 5일 접수 Received on September 5, 2011 / 2011년 10월 7일 수정 Revised on October 7, 2011 / 2011년 10월 11일 심사완료 Accepted on October 11, 2011 1 한국건설기술연구원 수자원연구실 Water Resources Research Div., KICT 2 한국건설기술연구원 하천해안항만연구실 River·Coastal and Harbor Research Div., KICT ※ 연락저자 E-mail : jh-kim@kict.re.kr Development of Soil Erosion Analysis Systems Based on Cloud and HyGIS 64 rain factors. The tools of Soil Loss Anaysis Model in connection with HyGiS are developed as add-on type of GMMap2009 in GEOMania, and also are developed to draw Soil Loss Hazard Map suggested by OECD. As a result of using both models, they are developed very conveniently to analyze soil loss. Hereafter, these models will be able to be improved continuously through researches to analyze sediment a watershed outlet and to calculate R value using data of many rain stations.

The temperature of power transformers is very important factor for power system operation in substation because load capacity and limited lifetime of power transformers are determined by winding temperature. Also, The temperature of power transformers varies with the structure, capacity, operation condition and manufacturers. Thus, it is necessary for temperature distribution to be exactly investigated because of efficient load management and prediction of limited lifetime. Nevertheless, there was no case of analysis as well as measurement of the temperature of power transformers. In this paper, we manufactured the 154kV standard power transformer for the test. And we measured the temperature by the heat run test and analyzed the temperature distribution of transformer.

Ship are a box-shaped structure. It is used often fore and aft parts, bilge strake, deck with camber of ship structures. When this structure is compared with flat plate structure, it different to behaviour. Generally, if it subjected to axial compressive load, ultimate strength depend on the change of curvature. Also, In this paper, stiffened curved plate with 1/2+1+1/2 bay model subjected to compressive load carried out the elasto-plastic large deflection series analysis. and parameter effect considered slender ratio, web height/thickness as well as change of curvature and investigated collapse mode for analysis model.

The water-level time series of a tidal river is influenced by various factors and has a complex structure, which limits its use as hydrological forecast data. This study proposes a methodology for decomposing the water-level time series of a tidal river into various components that influence the water level. To this end, the tide, wave, rainfall-induced runoff and noise components were selected as the main components that affect the water-level time series. The tide component and the wave component were first separated through wavelet analysis and curve fitting and then they were removed from the water-level data. A high-pass filter was then applied to the resulting time series to separate the rainfall-induced runoff component and the noise component. These methods made it possible to determine the rate of influence that each component has on the water level of a tidal river. The results could be used as a basis for calibrating a rainfall-runoff model and issuing flood forecasts and warnings for a tidal river.

There are several overvoltages by abnormal conditions in power system. We need to calculate these ovevoltages for the insulation design and the fault analysis. For these calculations, we used EMTP(Electro-magnetic Transients Program). During EMTP calculations, the accurate modelling of the equipments is very important for analysis results. In this paper, we considered the effects of the modelling condition`s changes for transmission line within EMTP modelling cases of overvoltage analysis. Specially, we considered CB closing cases of 765[kV] system. So, we had changed the calculation frequencies of Line Constants, which is used for CB closing cases. In addition, we compared the calculation result and the measured result.

This paper describes a study that is to redesign insulation of transmission lines and determine required the numbers of insulators in order to enhance the insulation performance of existing transmission lines which were constructed with standard insulation design, considering overvoltage analysis results, probabilities and characteristics of faults. To ensure proper insulation distance without deteriorating the required performance, EMTP model is established to calculate maximum overvoltage in the line. The fault records and predicted outage rates due to lightning and contamination in the line were investigated and analyzed respectively. It presents a method to determine the numbers of insulators considering the probability and the characteristic of fault.

It needs to conceptualize watershed with triangular or rectangular elements and to analyze the changes in hydrological components of each element for distributed modeling of rainfall-runoff process. This study is the network analysis of watershed grid for flow routing occurred in each element when analyzing rainfall-runoff process by one-dimensional kinematic wave equation. Single flow direction from D8-method(deterministic eight-neighbors method) is used, and the information of flow direction and flow accumulation are used to determine the computation order of each element. The application theory of finite volume method is suggested for each flow direction pattern between elements, and it is applied it to calculate the flow of each grid. Network analysis method from this study is applied to GRM(Grid based Rainfall-runoff Model) which is physically based distributed rainfall-runoff model, and the results from simplified hypothetical watersheds are compared with to examine the reasonability of the method. It is applied to Jungrangcheon watershed in Han river for verification, and examination of the applicability to real site. The results from Jungrangcheon watershed show good agreement with measured hydrographs, and the application of the network analysis method to real site is proper.

This work develops a grid based rainfall-runoff model (GRM), which is a physically based and spatially distributed model. Surface flow was analyzed using a kinematic wave model with the governing equations discretized using the finite volume method (FVM). This paper suggests a grid network flow analysis technique using variable rainfall intensity according to the flow directions to analyze one-dimensional flows between the grids. The model was evaluated by applying it to the Wuicheon watershed, a tributary of the Nakdonggang (Riv.), in Korea. The results showed that the grid-based, one-dimensional kinematic wave model adopted the FVM and the grid network flow analysis technique well. The simulation results showed good agreement with the observed hydrographs and the initial soil saturation ratio was most sensitive to the modeling results.

The aim of this animal study was to evaluate, through immunochemical analysis, new bone formation in rabbit maxillary sinuses with and without bone grafts.Bilateral sinus augmentation procedures were performed in rabbits. Bony windows were created with a piezoelectric surgical device with a saw insert. In the first group, the bony window was repositioned after careful elevation of the sinus mucosa without bone grafting. A miniscrew was inserted into the bony window to support the elevated sinus membrane. In the second group, anorganic bovine graft (Bio-Oss) was grafted after very careful elevation of the sinus membrane. Collagen membrane was placed over the bone graft. Rabbits were sacrificed after 1, 2, 4, 6, and 8 weeks. The augmented sinuses were evaluated by immunochemical analysis of proliferating cell nuclear antigen (PCNA), type I collagen, and osteocalcin content.Immunochemically positive cells for PCNA were present along the floor of the replaced bony window and the elevated sinus membrane from 1 to 4 weeks in the graftless group. In the grafted group, immunochemically positive cells for PCNA were not present after 1 week. In the ungrafted group, the expression of type I collagen was present from week 1. However, the expression of type I collagen was present after 2 weeks in the grafted group. Osteocalcin was observed in both groups after 1 week. Osteocalcin was observed along the floor of the replaced bony window in the graftless group but was not observed along the collagen membrane in the grafted group.According to this immunochemical study, faster and greater new bone formation was observed in sites that received no grafting material. The repositioned bony window may accelerate new bone formation earlier during healing versus the placement of a collagen membrane grafting material in the sinus.

A flood resulting from climate changes recently has brought about tremendous damage to the people and property. For restoration and to establish the countermeasure, various investigations into the flood-inundated area have been underway. Among the investigation measures commonly adopted in South Korea are on-site survey and indirect investigation using flood outflow model. However, with such methods, it's difficult to obtain a quick outcome as well as require verification for reliability. SAR that provides data irrespective of weather conditions and enables to perform rapid and precise investigation has been used since 1990s for flood monitoring. This study as basic research in preparation for launching KOMPSAT-5 in 2010 to use SAR sensor for water resources development is intended to compare the existing method to identify flood inundated area with that using SAR image, and measures to make use of SAR image.

연구목적: 임플란트 경부 디자인의 차이가 경부 치밀골의 응력분포에 미치는 영향을 유한요소법을 이용하여 분석하고자 한다. 연구재료 및 방법: 몸체 형상은 유사 (직경 4.3 mm, 길이 10 mm)하나 경부 디자인이 internal형, external형, 및 submerged형으로 다른 3종의 임플란트 시스템 ((주)덴티스, 대구, 대한민국)에 대하여 축대칭 유한요소모델을 사용하여 해석하였다. 악골 폭경은 7 mm로 동일하게 모델링하였고 하중 조건으로는 임플란트 장축에 평행한 수직하중 50 N, 임플란트 장축에 $45^{\circ}$ 방향으로 작용하는 경사력 50N을 설정하였다. 결과: 해석한 3종의 임플란트 모두 경부 피질골에 응력집중을 발생시켰으며 디자인 차이에 따른 응력 수준의 차이가 관찰되었다. 경부 피질골의 최대 응력은 수직력 조건에서 internal형, submerged형, external형의 순으로 컸으며, 그 값은 각각 2.71, 2.60, 2.48 MPa였다. 경사력 조건에서는 internal형, external형, submerged형의 순으로 컸으며 그 값은 각각 9.30, 9.14, 8.97 MPa였다. 결론: 임플란트 경부 디자인이 주위 치밀골의 응력 분포에 영향을 미칠 수 있지만 그 차이는 크지 않은 것으로 분석되었다. 【Statement of problem: High stress concentration on the crestal cortical bone has been regraded as a major etiologic factor jeopardizing long term stability of endosseous implants. Purpose: To investigate if the design characteristics of crestal module, i.e. internal type, external type, and submerged type, affect stress distribution on the crestal cortical bone. Material and methods: A cylindrical shaped implant, 4.3 mm in diameter and 10 mm in length, with 3 different crestal modules, i.e. internal type, external type, and submerged type, were analysed. An axisymmetric scheme was used for finite elment formulation. A vertical load of 50 N and an oblique load of 50N acting at $45^{\circ}$ with the implant's long axis was applied. The peak crestal bone stress acting at the intersection of implant and crestal bone was compared. Results: Under vertical load, the crestal bone stress was high in the order of internal, external, and submerged types. Under the oblique loading condition, it was in the order of internal, submerged, and external types. Conclusion: Crestal module design was found to affect the level of the crestal bone stresses although the actual amount was not significant.】

Using facing target sputtering (FTS) with a mixture of Ar and Kr, direct Al cathode sputtering on LiF∕Alq3 layers was accomplished without the need for a protective layer against plasma damage. Organic light emitting diodes (OLEDs) with a directly sputtered Al cathode in a mixture of Ar and Kr showed a much lower leakage current density (∼1×10−5mA∕cm2 at −6V) than those (∼1×10−1mA∕cm2 at −6V) of OLEDs with an Al cathode prepared by FTS or dc sputtering in a pure Ar ambient. This indicates that the bombardment of energetic particles is effectively restricted by mixing a heavy noble gas. Based on the current-voltage curve for the OLED, a possible mechanism is proposed to explain the effect of a heavy noble gas mixture on electrical properties of OLEDs for direct Al cathode sputtering by FTS.