이종지질 분포사면에서의 3차원 사면안정해석

서용석 ( Yong Seok Seo ),이경미 ( Kyoung Mi Lee ),김광염 ( Kwang Yeom Kim ) 대한지질공학회 2011 지질공학 Vol.21 No.1

화강암과 안산암질 암맥이 공존하고 있는 붕괴사면을 대상으로 지질에 의한 전단강도의 차이를 반영한 3차원 사면안정해석을 수행하였다. 지질이 서로 다른 두 종류의 파괴면에 대한 전단강도를 파악하기 위하여 흙-암 경계면 직접전단시험을 수행하였고, 또한 상부 풍화토층에 대한 실내토질시험을 실시하였다. 시험결과 풍화토층에 비하여 흙-암 경계면의 전단강도가 낮게 나타났다. 사면내 지질분포의 차이가 안정성해석 결과에 영향을 주는 것을 알아보기 위하여 한계평형법을 이용한 2차원사면안정성 해석을 대표단면에서 실시하였으며, 사면내 분포지질에 따라 입력치를 다르게 할 수 있는 3차원사면안정성해석을 실시하여 2차원안정성해석과 그 결과를 비교하였다. 해석결과에 의하면 안전율이 건기시 0.92와 포화시 0.32로 모두 불안정하게 나타난 2차원해석결과와는 달리 3차원해석결과에서는 건기시에 안전율이 1.26, 포화시에 0.55로 나타났다. 이러한 결과는 사면내 지질분포를 고려할 경우 안정성 해석의 결과가 달라질 수 있음을 보여주고 있으며, 우기 직후 붕괴가 일어났던 점을 고려하면 3차원해석결과가 보다 현실적인 것으로 판단된다. Three-dimensional slope stability analysis was applied to a failed dual-lithology slope containing both granite and an andesitic dyke, taking account of the differences in shear strength of the different lithologies. A direct shear test of the soil-rock boundary was performed to examine the shear strength of two different types of failure surfaces within different lithologies, and a laboratory test was performed on an upper, weathered soil layer. The test results indicate that shear strength was lower at the soil-rock boundary than within the weathered soil layer. A representative geological section was subjected to two-dimensional slope stability analysis using a limit equilibrium method to assess whether the distribution of lithologies upon the slope influences the results of stability analysis. The results were then compared with those of three-dimensional slope stability analysis, for which input parameters can be varied according to the distribution of lithologies upon the slope. The three-dimensional analysis yielded safety factors of 1.26 under dry conditions and 0.55 under wet conditions, whereas the two-dimensional analysis yielded unstable safety factors of 0.92 and 0.32, respectively. These findings show that the results of stability analysis are affected by the distribution of different lithologies upon the slope. Given that the studied slope collapsed immediately after rainfall, it is likely that the results of the three-dimensional analysis are more reliable.

안면 비대칭 환자에서 삼차원 컴퓨터단층촬영 계측법의 신뢰성

김영석,박병윤,유대현,권순만 대한두개안면성형외과학회 2006 Archives of Craniofacial Surgery Vol.7 No.1

3-dimensional computed tomography(3D-CT) imaging has been used in the diagnosis and surgical treatment planning of patients with craniofacial deformities, but its measurements were not commonly accepted contrary to the measurements in cephalometric analysis which was accepted as the best way to evaluate the facial profile on craniofacial & orthognathic fields. The purpose of this study was to compare the measurements from cephalometric analysis and 3D-CT analysis in facial asymmetric patients in order to show the reliability of the latter. 10 facial asymmetry patients had taken both cephalometry x-ray & 3D-CT. The 8 measurements were obtained from cephalometric analysis and 3D-CT analysis on each patient. The cephalometric analysis was based on the manual tracing of PA cephalometry x-ray film and the 3D-CT analysis was performed using the 'measuring tools' of Medical PACS system. The measurements included the maxillar & mandibular height, mandiblular body length, and vertical & horizontal deviation degree of maxilla and mandible. The paired t-test was used to compare differences between measurements from two methods. And also the ratio(affected side/unaffected side) in 3 measurements was calculated and compared using paired t-test to show the reliability. There were no statistically significant differences between measurements from cephalometric analysis and 3D-CT analysis(P>0.05) except mandibular body length. Also no statistically significant differences were noted between the ratio of 3 measurements on cephalometric analysis and 3D-CT analysis(P>0.05). 3D-CT analysis of facial asymmetry presents reliable data as much as cephalometric analysis. Moreover, it is very easy and simple method to use. The 3D-CT analysis as described herein is a practical method of evaluation the morphology of facial asymmetry and can replace the cephalometric analysis.

원자력 계통 열수력 해석코드의 3차원 모듈을 이용한 LOFT L2-5 실험 분석

김준혁,정재준,정법동 대한기계학회 2019 大韓機械學會論文集B Vol.43 No.8

A multi-dimensional approach is necessary for a better understanding of complex thermal-hydraulic phenomena in a reactor pressure vessel (RPV) during a large-break loss of coolant accident (LBLOCA). LBLOCA is one of the design basis accidents in a pressurized water reactor. The thermal-hydraulic system analysis code, MARS-KS, has a multi-dimensional module which enables both one-dimensional and three-dimensional analyses. However, the multi-dimensional module has not been studied extensively. In this study, the result of a LOFT L2-5 LBLOCA experiment was analyzed using the MARS-KS code. The multi-dimensional and one-dimensional modules were respectively used for the multi-dimensional phenomena in RPV and for the remaining regions. The results of the three-dimensional analysis for the RPV thermalhydraulics were compared with the experimental data for the assessment of the multi-dimensional module. 가압경수형 원자력발전소의 설계기준사고 중 하나인 대형냉각재상실사고(LBLOCA: Large-Break Loss of Coolant Accident) 발생 시 원자로 압력용기 내에서 발생하는 복잡한 열수력 현상을 보다 잘 이해하기 위해 다차원 해석이 필요하다. 열수력계통해석 코드인 MARS-KS는 다차원(multi-d) 모듈을 포함하고 있어 1차원 해석뿐만 아니라 3차원 해석도 가능하지만, 다차원 모듈에 대한 평가 계산이 부족한 실정이다. 본 연구에서는 대표적인 LBLOCA 실험인 LOFT L2-5 실험의 원자로 압력용기(RPV: Reactor Pressure Vessel)에서 발생하는 다차원 열수력 현상을 3차원 모듈로 분석하였다. 원자로 압력용기를 제외한 나머지 부분은 1차원으로 해석하였다. RPV 내의 온도 분포 3차원 해석 결과를 실험 결과와 비교함으로써 MARS-KS 코드의 다차원 모듈을 이용해 RPV를 모델링 하였을 때 LBLOCA 동안 RPV 내의 열수력학적 거동을 더욱 정확하게 분석할 수 있다는 것을 확인하였다.

두부 방사선 규격사진을 이용한 3차원 계측 시스템의 개발

이상한(Sang Han Lee),권대근(Tae Geon Kwon),김종배(Jong Bae Kim) 대한구강악안면외과학회 1999 대한구강악안면외과학회지 Vol.25 No.2

두부방사선 규격사진을 이용한 3차원 계측시스템을 자체 개발하여 3차원적인 상하악골의 형태를 동일 좌표계로 비교하여 임상적으로 만족스러운 정도를 얻을 수 있도록 다섯 개의 건조두개골에 직경 약 0.38±0.05㎜의 금속구를 접착시키고 건조두개골의 자세를 변화시켜 정모 및 측모 두부방사선사진을 촬영한 후 자체 오차분석과 각각 촬영된 한쌍의 정모 및 측모두부방사선사진을 한개의 삼차원적 영상으로 구축된 3차원 계측치와 두부방사선사진상의 계측치 및 실계측치를 각각 비교하여 다음과 같은 결과를 얻었다. 1. 방사선 촬영시의 두부 위치의 변화에 따른 오차의 개입없이 순수한 오차를 측정한 결과 정모와 측모 두부방사선사진에서 모두 1㎜ 이하의 오차를 보였으며, 오차의 범위는 정모 및 측모 두부방사선 사진의 경우 각각 0.11 - 0.73㎜, 0.12 - 0.57㎜ 였다(p<0.05). 2. 측모 및 정모 두부방사선사진에서 얻어진 좌표값으로 산출한 3차원 계측치에서는 실험자의 오류(intra-examiner vias)가 90개 계측요소중 7개(7.8%)에서만 유의한 오차가 나타났으며, x, y, z 좌표간의 평균적인 편차(error of single measurements)는 각각 0.04±0.21㎜, 0.01±0.01㎜, 0.08±0.08㎜로 나타났다. 3. 동일 건조두개골상에서 14가지 계측거리를 실측한 결과 통계적으로 유의한 차이가 없었으며 (p>0.01), 평균 0.16±0.22 ㎜의 차이를 가지고 있었다. 가장 큰 편차를 나타낸 L-UMC, L-UIC간의 거리의 경우 0.43±0.54㎜의 차이를 보였다. 4. 3차원 계측치와 실계측치와의 차이에서 14개 항목중 6개 항목은 축소되었고 8개 항목은 확대되어 나타났으며(평균차이 0.13 ± 1.54㎜의 차이), 이중 L-Co, R-Co가 2.59±3.00㎜의 차이로 가장 크게 확대되어 나타났다. 백분율로 계산한 결과 100.74±3.92% 확대율을 보였으며 실측보다 가장 축소되어 나타난 항목은 ANS, R-Or간의 거리(97.75±3.11%)였으며, 가장 확대되어 나타난 항목은 L-UMC, L-UIC 간 거리(106.59±20.33%)였다. 5. 실측치와 2차원적 두부방사선 계측치 사이에는 다양한 정도의 차이가 있었으며 필름면과 평행하지 않는 시상면에 놓인 계측거리 측정에서 축소가 두드러 졌다. 필름과 건조두개골 각 계측점간의 거리는 항목에 따라 달랐으며 이를 3차원적 계측치와 비교하였을 때 훨씬 그 오차가 큰 것을 알 수 있었다. 이를 종합할 때 3차원계측치의 정확도는 방사선사진의 재현성이 보장되어질 경우 정모, 측모두부방사선 사진중의 좌표점을 인식하는 정확도에 좌우된다고 할 수 있다. 측모 및 정모두부방사선사진에서 판독이 어려운 좌표점의 선택은 3차원적인 좌표값의 오류로 나타나게 되기 때문에 충분한 해부학적인 지식으로 2차원적인 두부방사선 사진을 트레이싱한다면 구강악안면영역에서 이용될 수 있는 정도의 정확도 즉, 술전술후 비교평가등의 경우에 충분히 이용되어 질 수 있을것으로 사료된다. Diagnosis of dentofacial deformity needs three dimensional comprehensive understanding of craniofacial skeleton. Eventhough three dimensional computerized tomogram has been developed, the quantified measurement analysis is merely depend on cephalomeric analysis. In our pilot study using the ordinary cephalometric radiogram which is commonly used in clinical basis, we tried to reconstruct three dimensional coordinates from frontal and lateral cephalogram taken from five dry skulls attached with small metal ball. To evaluate the reproducibility of the cephalogram, intra-examiner error was measured and compared with the three dimensional coordinates. Fourteen linear measurement of dry skull and three dimensional value has been compared. The results were as follows ; 1. The intia-examiner error of the two dimensional cephalogram showed a similar variation below 1 ㎜ in frontal and lateral cephalogram. The error ranged from 0.11 - 0.13㎜ in the case of frontal cephalometrics and 0.12 - 0.57㎜ for lateral cephalometrics Three dimensional coordinates showed relatively high reproducibility except 7 coordinates out of 90 (7.8%). The average error of the single measurement of x,y,z point shown to be 0.04±0.21㎜, 0.01±0.01㎜, 0.08±0.08㎜. 2. Compare the 14 linear measurement of dry skull and three dimensional measurement, the mean difference was 0.13±1.54㎜, ranging from 2.59±3.00㎜ (L-Co, R-Co) to 0.01±0.38 (ANS, L-Or). From the result by taking real value percentage rate by 3 dimensional measuring value, the mean value was 100.74±3.92% and the measurement which showed the most shortening compared with the real value was the distance between R-Or and ANS (97.75±3.11%) and the most enlarged measurement was the distance between L-VMC, L-VIC (106.59±20.33%) 3. However, compare the real value and two dimensional cephalometric radiograph, difference between the two is significant degree which hinder the use of two dimensional measurement in clinical situation. This potential pitfall of the cephalogram might be overcome by using our three dimensional coordinate system. If the reproducibility of the frontal and lateral cephalogram is achieved, maior concern related to the accuracy of three dimensional measurement is correct detection of anatomical landmark. Further investigation of anatomical investigation of facial skeleton will make this system more accurate and popular in clinical field.

차원축소를 통한 결측자료의 군집분석

송주원(Juwon Song) 한국자료분석학회 2020 Journal of the Korean Data Analysis Society Vol.22 No.2

군집분석은 유사한 특성들을 지닌 관측값들을 같은 군집으로, 다른 특성들을 지닌 관측값들은 서로 다른 군집으로 분류하는 분석 기법이다. 많은 변수를 포함한 고차원 자료에서는 일반적인 군집분석 대신 차원축소를 통하여 군집분석을 실시하는 방법들이 제안되어 왔다. 주성분 분석을 통해 차원을 축소한 후 축소된 차원에서 군집분석을 실시하는 직렬분석 방법보다 차원축소와 군집분석을 결합하여 동시에 실시하는 방법들이 더 우수한 성능을 보인다는 것이 알려져 있다. 한편, 대부분의 자료는 결측값을 포함하고 있는데 결측값이 포함된 자료에 대하여 군집분석을 실시하는 경우 불완전하게 관측된 자료들은 어느 군집으로도 분류되지 않는 문제가 발생한다. 따라서 군집분석을 실시하기 전에 먼저 결측값 대체를 실시하는 것이 일반적이다. 본 연구에서는 고차원 결측자료에 대하여 차원축소를 통한 k-평균 군집분석을 실시할 때 결측값 대체를 결합하여 실시하는 방법을 제안한다. 이 방법은 군집 정보를 이용한 결측값 대체를 통해 정확한 차원축소를 통한 군집분석이 가능하게 하는 장점을 지닌다. 제안된 방법은 모의실험을 통해 성능을 평가하였고 결측값을 대체한 후 대체된 자료에 대하여 차원축소를 통한 군집분석을 실시하는 직렬식 분석방법과 비교하였다. 제안된 방법은 적절한 차원축소를 통한 k-평균 군집분석을 실시한다면 직렬식 분석보다 오분류율이 낮게 나타났다. Cluster analysis classify similar observations into the same cluster and different observations into different clusters. When data include many variables, reduced dimension clustering methods have been suggested instead of the standard clustering methods. The joint analysis of dimension reduction and clustering is known to perform better than tandem analysis that sequentially conducts dimension reduction and clustering. On the other hand, most data include missing values. When cluster analysis is conducted with incomplete data, incomplete observations can not be classified into any group. To avoid this problem, it is common to impute missing values before conducting cluster analysis. In this study, we suggest a method for combining dimension reduction k-means clustering and missing data imputation. The suggested method has an advantage to accurate classify observations through imputation using cluster information. A simulation is conducted to evaluate performance of the suggested method and compare the result with the one based on tandem analysis. The suggested method using an appropriate dimension reduction k-means clustering showed lower misclassification rates than tandem analysis.

기존 3차원 인터랙션 동작인식 기술 현황 파악을 위한 메타분석

김용우(YongWoo Kim),황민철(Min Cheol Whang),김종화(Jong Hwa Kim),우진철(Jin Cheol Woo),김치중(ChiJung Kim),김지혜(Ji Hye Kim) 대한인간공학회 2010 大韓人間工學會誌 Vol.29 No.6

Most of the research on three-dimensional interaction field have showed different accuracy in terms of sensing, mode and method. Furthermore, implementation of interaction has been a lack of consistency in application field. Therefore, this study is to suggest research trends of three-dimensional interaction using meta-analysis. Searching relative keyword in database provided with 153 domestic papers and 188 international papers covering three-dimensional interaction. Analytical coding tables determined 18 domestic papers and 28 international papers for analysis. Frequency analysis was carried out on method of action, element, number, accuracy and then verified accuracy by effect size of the meta-analysis. As the results, the effect size of sensor-based was higher than vision-based, but the effect size was extracted to small as 0.02. The effect size of vision-based using hand motion was higher than sensor-based using band motion. Therefore, implementation of three-dimensional sensor-based interaction and vision-based using hand motions more efficient. This study was significant to comprehensive analysis of three-dimensional motion recognition for interaction and suggest to application directions of three-dimensional interaction.

GGobi를 이용한 한중일 청소년의 가치관에 관한 요인분석

오정아,이은경 한국자료분석학회 2013 Journal of the Korean Data Analysis Society Vol.15 No.2

Factor analysis is a widely used multi-variate data analysis method in sociology and psychology area. However the result of exploratory factor analysis depends on the initial factor extract method, number of factors, and method of rotation. It is not easy to choose the right options for the factor analysis in specific data set and we need to be careful to choose these options. In this paper, we use dynamic graphical methods to explore the result from factor analysis for the right options of the factor analysis. We explore and compare the results from the factor analysis with various options. Also we analyze the results from different population. We apply 2008 survey on the value of teenagers in three countries to our methods, find the optimal factor analysis model, and compare the result from three countries using dynamic graphical method. In the importance in life part, the result of the exploratory factor analysis on Korea is a little bit different from the results of the other two countries. On the other hands, the results of Japan in the reliability in family, society, and nation are quite different from the results of Korea and China. This result is verified from the result of the confirmatory factor analysis. 요인분석은 사회학, 심리학 관련분야에서 활발하게 사용하고 있는 다변량 통계 분석 방법이다. 그러나 요인분석 중 탐색적 요인분석은 초기 요인추출방법, 공통요인의 수, 회전 방법 등을 분석자가 주관적으로 결정하는 경향이 있으나 이들의 선택에 따라 결과가 크게 달라질 수 있다. 그러므로 최종 요인모형을 선택하기 위해 요인분석의 결과를 면밀히 살펴보아야 할 필요가 있다. 본 연구에서는 요인분석에서 최적의 요인 수, 초기 추출방법, 회전 방법 등을 선택하기 위하여 각 조건 하에서의 요인분석결과를 동적그래프 방법을 이용하여 살펴보고 이를 비교, 분석하는 방안을 제시하였다. 또한 실제 자료인 한, 중, 일 청소년 가치관에 대한 설문조사자료 중 인생에서의 중요도와 가족, 사회, 그리고 국가에 대한 신뢰도에 관한 항목들을 이용하여 요인분석을 실시하고 본 논문에서 제안한 방법을 이용하여 최적의 요인수와 초기추출방법, 그리고 회전 방법을 찾고 요인분석을 실시한 후 각 나라마다의 결과를 비교, 분석하였다. 인생에서의 중요도의 경우 중국과 일본이 한국과는 다른 요인분석 결과를 나타내고 있으나 차이가 크지는 않았다. 반면 가족, 사회, 그리고 국가에 대한 신뢰도의 경우 일본이 한국과 중국의 결과와 차이를 보이고 있으며 이 차이는 다소 크게 나타나고 있다. 이 결과는 확증적 요인분석을 통하여서도 확인할 수 있었다.

New Statistical Method to Analyze Three-Dimensional Landmark Configurations Obtained with Cone-Beam CT: Basic Features and Clinical Application for Rapid Maxillary Expansion

Jennifer Gamble,Manuel O. Lagravère,Paul W. Major,Giseon Heo 대한영상의학회 2012 Korean Journal of Radiology Vol.13 No.2

Objective: To describe a statistical method of three-dimensional landmark configuration data and apply it to an orthodontic data set comparing two types of rapid maxillary expansion (RME) treatments. Materials and Methods: Landmark configurations obtained from cone beam CT scans were used to represent patients in two types (please describe what were two types) of RME groups and a control group over four time points. A method using tools from persistent homology and dimensionality reduction is presented and used to identify variability between the subjects. Results: The analysis was in agreement with previous results using conventional methods, which found significant differences between treatment groups and the control, but no distinction between the types of treatment. Additionally, it was found that second molar eruption varied considerably between the subjects, and this has not been evaluated in previous analyses. Conclusion: This method of analysis allows entire configurations to be considered as a whole, and does not require specific inter-landmark distances or angles to be selected. Sources of variability present themselves, without having to be individually sought after. This method is suggested as an additional tool for the analysis of landmark configuration data. Objective: To describe a statistical method of three-dimensional landmark configuration data and apply it to an orthodontic data set comparing two types of rapid maxillary expansion (RME) treatments. Materials and Methods: Landmark configurations obtained from cone beam CT scans were used to represent patients in two types (please describe what were two types) of RME groups and a control group over four time points. A method using tools from persistent homology and dimensionality reduction is presented and used to identify variability between the subjects. Results: The analysis was in agreement with previous results using conventional methods, which found significant differences between treatment groups and the control, but no distinction between the types of treatment. Additionally, it was found that second molar eruption varied considerably between the subjects, and this has not been evaluated in previous analyses. Conclusion: This method of analysis allows entire configurations to be considered as a whole, and does not require specific inter-landmark distances or angles to be selected. Sources of variability present themselves, without having to be individually sought after. This method is suggested as an additional tool for the analysis of landmark configuration data.

APPLICATION OF PSEUDO-THREE-DIMENSIONAL HEAT EXCHANGER MODEL IN THE ONE-DIMENSIONAL SIMULATION OF THE VEHICLE COOLING SYSTEM UNDER THE FTP-72 DRIVING SCHEDULE

구자군,양휘주,차용길,유상석 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.6

In designing the heat exchanger model, the existing epsilon-number of transfer units (NTU) method cannot reflect factors inside the heat exchanger, such as the local flow rate changes. Furthermore, it is difficult to apply a three-dimensional model to a one-dimensional analysis since high computational power is required. In contrast, a pseudo-three-dimensional heat exchanger model which has higher accuracy than the existing epsilon-NTU method and has faster speed for application in one-dimensional analysis. However, pseudo-three-dimensional model has still improvements in the simulation time as the mesh counts increase. In this study, the improved pseudo-three-dimensional heat exchanger model was developed and integrated within a one-dimensional analysis loop capable of simulating vehicle driving and the cooling system. The integrated model calculated the change in the energy consumption of the entire cooling system with the change in the aspect ratio of the heat exchanger. Also, the optimal operation strategy of the cooling system, which incorporated a proportional integral derivative controller of the three-way valve, was determined to reduce the parasitic losses. As a result, parasitic loss of the cooling system decreased by 14.1 % as aspect ratio increased by 46 % under FTP-72 (UDDS) driving schedule and simulation time was reduced 90.1 % while accuracy degrades only 2.7 %.

Structural Dynamic Analysis of a Space Launch Vehicle using an Axisymmetric Two-dimensional Shell Element

JiSoo Sim,SangGu Lee,JunBeom Kim,SangJoon Shin,SeungSoo Park,WonSuk Ohm 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.3

The pogo phenomenon refers to a type of multidiscipline-related instability found in space launch vehicles. It is caused by coupling between the fuselage structure and other structural propulsion components. To predict the pogo phenomenon, it is essential to undertake adequate structural modeling and to understand the characteristics of the feedlines and the propulsion system. To do this, a modal analysis is conducted using axisymmetric two-dimensional shell elements. The analysis is validated using examples of existing launch vehicles. Other applications and further plans for pogo analyses are suggested. In addition, research on the pogo phenomenon of Saturn V and the space shuttle is conducted in order to constitute a pogo stability analysis using the results of the present modal analysis.