• Imaging Science in Dentistry
• /
• 제31권4호
• /
• pp.209-214
• /
• 2001

Purpose: To investigate the ability of double TMJ view by multifunctional panorama to view the bony components and the space of the temporomandibular joint. Materials and Methods: Ten dry skulls fitted with resin shims over the articular surface of the condyle were used to reproduce the temporomandibular joint space. Fine metal wires were attached to the three portions of contours of the condylar head and the articular eminence. With 10 dry skulls and 20 cases having TMJ dysfunction, double TMJ views by multifunctional panorama (Planmeca 2002 Proline CC) and transcranial views were taken, analyzed from the anatomical view point, and compared statistically in view of the widths of the posterior joint space and the condylar head. Results: In double TMJ view, the supero-anterior part of the condyle represented the lateral 1/3, the most superior part represented center portion, and the posterior part medial l/3 of the condyle. In maximum mouth opening, no other structures were superimposed with the condyle in double TMJ view. In double TMJ view, petrous bone was moderately superimposed with the superior part of the condyle and the posterior increment of angle exposure made wider the images of the articular eminence and the condyle. The tendency of reduction in the posterior joint space appeared in the side of TMJ dysfunction compared with the normal side. The posterior joint spaces in double TMJ view were statistically wider (p<0.05) than those in transcranial view. The correlation coefficient was 0.5179 between the widths of the posterior joint spaces in two radiographic views. Conclusions: Double TMJ view can be substituted for transcranial view in evaluating the TMJ dysfunction.

• 대기
• /
• 제25권2호
• /
• pp.271-281
• /
• 2015

The objectives of this study are to develop a hydrological drought outlook system using GloSea5 (Global Seasonal forecasting system 5) which has recently been used by KMA (Korea Meteorological Association) and to evaluate the forecasting capability. For drought analysis, the bilinear interpolation method was applied to spatially downscale the low-resolution outputs of GloSea5 and PR (Predicted Runoff) was produced for different lead times (i.e., 1-, 2-, 3-month) running LSM (Land Surface Model). The behavior of PR anomaly was similar to that of HR (Historical Runoff) and the estimated values were negative up to lead times of 1- and 2-month. For the evaluation of drought outlook, SRI (Standardized Runoff Index) was selected and PR_SRI estimated using PR. ROC score was 0.83, 0.71, 0.60 for 1-, 2- and 3-month lead times, respectively. It also showed the hit rate is high and false alarm rate is low as shorter lead time. The temporal Correlation Coefficient (CC) was 0.82, 0.60, 0.31 and Root Mean Square Error (RMSE) was 0.52, 0.86, 1.20 for 1-, 2-, 3-month lead time, respectively. The accuracy of PR_SRI was high up to 1- and 2-month lead time on local regions except the Gyeonggi and Gangwon province. It can be concluded that GloSea5 has high applicability for hydrological drought outlook.

• 대한의용생체공학회:의공학회지
• /
• 제28권1호
• /
• pp.8-16
• /
• 2007

Finite element analysis (FEA) is an effective means for the analysis of bioelectromagnetism. It has been successfully applied to various problems over conventional methods such as boundary element analysis and finite difference analysis. However, its utilization has been limited due to the overwhelming computational load despite of its analytical power. We have previously developed a novel mesh generation scheme that produces FE meshes that are content-adaptive to given MR images. MRI content-adaptive FE meshes (cMeshes) represent the electrically conducting domain more effectively with far less number of nodes and elements, thus lessen the computational load. In general, the cMesh generation is affected by the quality of feature maps derived from MRI. In this study, we have tested various feature maps created based on the improved differential geometry measures for more effective cMesh head models. As performance indices, correlation coefficient (CC), root mean squared error (RMSE), relative error (RE), and the quality of cMesh triangle elements are used. The results show that there is a significant variation according to the characteristics of specific feature maps on cMesh generation, and offer additional choices of feature maps to yield more effective and efficient generation of cMeshes. We believe that cMeshes with specific and improved feature map generation schemes should be useful in the FEA of bioelectromagnetic problems.

• 한국측량학회지
• /
• 제34권4호
• /
• pp.413-423
• /
• 2016

Worldview-3 satellite sensor provides panchromatic image with high-spatial resolution and 8-band multispectral images. Therefore, an image-sharpening technique, which sharpens the spatial resolution of multispectral images by using high-spatial resolution panchromatic images, is essential for various applications of Worldview-3 images based on image interpretation and processing. The existing pansharpening algorithms tend to tradeoff between spectral distortion and spatial enhancement. In this study, we applied six pansharpening algorithms to Worldview-3 satellite imagery and assessed the quality of pansharpened images qualitatively and quantitatively. We also analyzed the effects of time lag for each multispectral band during the pansharpening process. Quantitative assessment of pansharpened images was performed by comparing ERGAS (Erreur Relative Globale Adimensionnelle de Synthèse), SAM (Spectral Angle Mapper), Q-index and sCC (spatial Correlation Coefficient) based on real data set. In experiment, quantitative results obtained by MRA (Multi-Resolution Analysis)-based algorithm were better than those by the CS (Component Substitution)-based algorithm. Nevertheless, qualitative quality of spectral information was similar to each other. In addition, images obtained by the CS-based algorithm and by division of two multispectral sensors were shaper in terms of spatial quality than those obtained by the other pansharpening algorithm. Therefore, there is a need to determine a pansharpening method for Worldview-3 images for application to remote sensing data, such as spectral and spatial information-based applications.

• 대한원격탐사학회지
• /
• 제36권4호
• /
• pp.573-586
• /
• 2020

PM (particulate matter) is of interest to everyone because it can have adverse effects on human health by the infiltration from respiratory to internal organs. To date, many studies have made efforts for the prediction of PM10 and PM2.5 concentrations. Unlike previous studies, we conducted the prediction of tomorrow's PM10 concentration for the Air Korea stations using Chinese PM10 data in addition to the satellite AOD and weather variables. We constructed 230,639 matchups from the raw data over 3 million and built an RF (random forest) model from the matchups to cope with the complexity and nonlinearity. The validation statistics from the blind test showed excellent accuracy with the RMSE (root mean square error) of 9.905 ㎍/㎥ and the CC (correlation coefficient) of 0.918. Moreover, our prediction model showed a stable performance without the dependency on seasons or the degree of PM10 concentration. However, part of coastal areas had a relatively low accuracy, which implies that a dedicated model for coastal areas will be necessary. Additional input variables such as wind direction, precipitation, and air stability should also be incorporated into the prediction model as future work.

• 대한원격탐사학회지
• /
• 제37권5_1호
• /
• pp.1187-1198
• /
• 2021

해상풍 데이터는 최근 들어서 신재생 에너지 개발의 일환으로 해상 풍력발전 단지가 각광받으면서 더욱 중요성을 더하고 있다. 본 연구에서는 2015~2020년 부울경(부산, 울산, 경남) 연안해역을 촬영한 Sentinel-1 영상 368장과 저해상도 수치모델의 UV 컴포넌트를 이용한 DNN (Deep Neural Network) 모델을 개발하여 해상풍 데이터를 공간해상도 10 m 수준으로 정밀하게 생산하는 방법을 제시하였다. 이를 통해 기존의 CMOD (C-band Model) 함수에 비해 40% 정도 오차가 감소하였으며, U 컴포넌트와 V 컴포넌트는 각각 상관계수 0.901, 0.826의 비교적 높은 정확도를 나타냈다. 본 연구에서 부울경 해역(해안선으로부터 3 km 버퍼 영역)에 대해 산출한 10 m 해상도의 바람장 지도를 작성해 보면, 내륙에서 외해로 갈수록 풍속이 강해지는 일반적인 경향을 따르면서도 공간적으로 상세화된 바람 패턴을 잘 나타낼 수 있었다. 이러한 고해상도 해상풍 지도는 해상 풍력발전을 위한 상세조사뿐 아니라, SAR를 활용한 전천후 연안 방재 및 연안레저 정보 제공을 지원할 수 있을 것으로 기대한다.

• 한국기후변화학회지
• /
• 제6권4호
• /
• pp.331-344
• /
• 2015

A long-term gridded historical data at 3 km spatial resolution has been generated for practical regional applications such as hydrologic modelling. However, overly high or low values have been found at some grid points where complex topography or sparse observational network exist. In this study, the Inverse Distance Weighting (IDW) method was applied to properly smooth the overly predicted values of Improved GIS-based Regression Model (IGISRM), called the IDW-IGISRM grid data, at the same resolution for daily precipitation, maximum temperature and minimum temperature from 2001 to 2010 over South Korea. We tested various effective distances in the IDW method to detect an optimal distance that provides the highest performance. IDW-IGISRM was compared with IGISRM to evaluate the effectiveness of IDW-IGISRM with regard to spatial patterns, and quantitative performance metrics over 243 AWS observational points and four selected stations showing the largest biases. Regarding the spatial pattern, IDW-IGISRM reduced irrational overly predicted values, i. e. producing smoother spatial maps that IGISRM for all variables. In addition, all quantitative performance metrics were improved by IDW-IGISRM; correlation coefficient (CC), Index Of Agreement (IOA) increase up to 11.2% and 2.0%, respectively. Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were also reduced up to 5.4% and 15.2% respectively. At the selected four stations, this study demonstrated that the improvement was more considerable. These results indicate that IDW-IGISRM can improve the predictive performance of IGISRM, consequently providing more reliable high-resolution gridded data for assessment, adaptation, and vulnerability studies of climate change impacts.

• Composite Materials and Engineering
• /
• 제3권3호
• /
• pp.201-220
• /
• 2021

In this study, potential of three machine learning techniques i.e., M5P, Support vector machines and Gaussian processes were evaluated to find the best algorithm for the prediction of flexural strength of concrete mix with steel fibre. The study comprises the comparison of results obtained from above-said techniques for given dataset. The dataset consists of 124 observations from past research studies and this dataset is randomly divided into two subsets namely training and testing datasets with (70-30)% proportion by weight. Cement, fine aggregates, coarse aggregates, water, super plasticizer/ high-range water reducer, steel fibre, fibre length and curing days were taken as input parameters whereas flexural strength of the concrete mix was taken as the output parameter. Performance of the techniques was checked by statistic evaluation parameters. Results show that the Gaussian process technique works better than other techniques with its minimum error bandwidth. Statistical analysis shows that the Gaussian process predicts better results with higher coefficient of correlation value (0.9138) and minimum mean absolute error (1.2954) and Root mean square error value (1.9672). Sensitivity analysis proves that steel fibre is the significant parameter among other parameters to predict the flexural strength of concrete mix. According to the shape of the fibre, the mixed type performs better for this data than the hooked shape of the steel fibre, which has a higher CC of 0.9649, which shows that the shape of fibers do effect the flexural strength of the concrete. However, the intricacy of the mixed fibres needs further investigations. For future mixes, the most favorable range for the increase in flexural strength of concrete mix found to be (1-3)%.

• 현장농수산연구지
• /
• 제23권2호
• /
• pp.71-86
• /
• 2021

빅데이터 분석기술인 웹 크롤링 기술을 이용하여 네이버 뉴스 데이터 내에 담겨 있는 '한농대' 에 대한 이미지 단어를 추출하였다. 뉴스 기사에서 언급된 빈도에 따라 중요한 단어로 평가는 단어빈도 분석에서는 청년농업인을 육성하는 한농대의 특성을 잘 설명하는 '농업', '교육', '지원', '농업인', '청년', '대학', '사업', '농촌', '대표' 등의 단어가 자주 사용되는 것으로 나타났다. 또한 '디지털', '스마트', '드론', '졸업생', '창업', '새만금', '교육과정' 등 디지털 농업 전문 인재를 육성하기 위한 학교의 교육, 지원, 비전 등과 관련한 단어들이 추출되었다. 모든 기사 데이터의 단어 빈도(TF) 및 역 문서 빈도(IDF)를 이용한 TF-IDF 가중치의 전체 순위는 '농업인', '드론', '농림축산식품부', '전북', '청년농업인', '농업', '전주', '대학', '장치', '파종' 등의 단어가 한농대와 관련된 뉴스 기사에서 중요한 핵심어 역할을 하는 것으로 나타났다. 단어 빈도에서 '드론', '농림축산식품부', '전북', '청년농업인', '전주', '장치, '파종' 등은 순위가 매우 낮았으나 TF-IDF 가중치 순위에서는 한농대를 표현하는 핵심어로 나타났다. TF-IDF 평가에서 '교육', '지원', '청년', '사업', '농촌' 등의 키워드는 단어빈도가 높으면서 많은 문서에서 자주 등장하는 키워드로서 핵심어 역할은 크지 않은 것으로 나타났다. 단어 간 연계성을 파악하기 위한 의미연결망 분석에서 추출한 바이그램은 '청년'-'농업인', '디지털'-'농업', '영농'-'정착', '농업'-'농촌', '디지털'-'전환' 등의 순으로 빈도가 높게 나타났다. 중심성 지표로 키워드의 영향력을 평가한 결과 모든 지표에서 '농업'이 1위로 나타났으며, 2위에는 '농업인'(근접 중심성, 매개 중심성), '교육'(연결 중심성, 페이지랭크 중심성) 및 '미래'(고유벡터 중심성)으로 나타났다. 스피어먼 순위 상관계수에 의한 중심성 지표별 키워드의 순위의 유사성은 연결 중심성과 페이지랭크 중심성이 0.89 전후의 가장 높은 상관관계를 보였다. 이상으로 네이버 뉴스의 한농대 관련 기사에서 단어 빈도로 보면 '농업', '교육', '지원', '농업인', '청년', '대학', '사업', '농촌', '대표' 등이 중요한 단어로 평가되었으나, 문서빈도를 함께 고려한 평가에서는 '농업인', '드론', '농림축산식품부', '전북', '청년농업인', '농업', '전주', '대학', '장치', '파종' 등의 단어가 핵심어 역할을 하는 것으로 나타났다. 한편 단어나 문서의 빈도가 아니라 단어 간 네트워크 연계성을 고려한 중심성 분석에서는 연결 중심성과 페이지랭크 중심성에 의한 평가가 적합한 것으로 나타났으며, '농업', '교육', '미래', '농업인', '디지털', '지원', '활용' 등이 중심성이 강한 단어로 나타났다.

• 한국수자원학회논문집
• /
• 제48권7호
• /
• pp.581-593
• /
• 2015

본 연구에서는 ESP (Ensemble Streamflow Prediction)기법을 활용한 가뭄전망 체계를 구축하고 가뭄예보에 있어 활용성을 평가하였다. 과거 관측 수문기상 및 지형정보를 이용하여 우리나라 전역에 지면모델(Land Surface Model, LSM)을 구축하고 유출량(Historical Runoff, HR)을 생산하였다. 또한, 모의기간 동안 과거 30개 기상자료와 초기 토양수분량을 이용하여 선행시간별(1, 2, 3개월) 전망된 유출량(Predicted Runoff, PR)을 생산하였다. 평가결과 여름 및 가을철 보다 봄철 및 겨울철에 정확도가 높았으며, 1개월 전망 이후로는 정확도가 낮게 나타났다. 가뭄지수는 국내 가뭄해석에 있어 검증된 표준유출지수(Standardized Runoff Index, SRI)를 활용하였으며, PR_SRI을 산정 및 평가하였다. 1, 2개월 전망에서는 과거 HR이 고려되어 ESP HR에 비해 정확도가 크게 개선됨을 알 수 있었다. 선행시간별 상관계수는 평균 0.71, 0.48, 0.00, 평균제곱근오차는 0.46, 0.76, 1.01로 나타났으며, 건조기에 정확도가 높게 나타나 1, 2개월 전망까지는 ESP를 활용한 국내 가뭄예보의 활용성이 높다고 판단된다.