• Plant Journal
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• v.15 no.4
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• pp.43-51
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• 2019

The stress concentration of the integral welded attachments (IWA) often used to support piping system has been a big issue because it induces local stresses in piping. The method to evaluate local stresses associated with attachments on elbows has been suggested in EPRI TR-107453. However, there are limitations regarding specific parameters range in order to use correlation equation. In this paper, parametric study based on piping elbow size and attachment dimension was performed utilizing finite element analysis (FEA) to evaluate the secondary stress indices of hollow circular cross section welded attachments on piping elbows with the extended parameters range. The results of the FEA were used to develop correlation formulas for calculating secondary stress indices. The empirical equations in this study are suggested as an alternative evaluation method of EPRI TR-107453 by extending parameters range.

• The Journal of the Korea Contents Association
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• v.16 no.2
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• pp.666-672
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• 2016

We extracted 50 LVH patients out of 30'~80's who performing ECG and echocardiography examination. We used Devereux's theory to examinate LVH with echocardiography and used Sokolow-Lyon's theory to examinate LVH with ECG. We used regression and correlation analysis by SPSS, used ROC curve analysis to decide predominance of two ways of .Age, BMI, SBP and DBP whice are the danger factors of LVH and standard value of LVH diagnosis examination seems correlated. Out of 50 LVH patients, 50 patients were diagnosed LVH by echcardiography examination and only 21 patients were diagnosed LVH by ECG examination. Also echocardiography was AUC 99%, sensitivity 96%, singularity 95%, accuracy 95.5%. And ECG was AUC 76%, sensitivity 62%, singularity 76%, accuracy 68%.By comparing accuracy between echocardiography and ECG in diagnosing LVH, we could tell echocardiography was examination with higher accuracy. Therefore, if one was diagnosed with summit on 1st examination with ECG, considering age, body mass index, systolic blood pressure and dilator blood pressure, should offer echocardiography examination.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.898-900
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• 2005

모듈러 멱승은 양수 x, E, N에 대하여 $x^Emod$ N로 정의된다. 모듈러 멱승 연산은 대부분의 공개키 암호화 알고리즘과 전자서명 프로토콜에서 핵심적인 연산으로 사용되고 있으므로, 그 효율성은 암호 프로토콜의 성능에 직접적인 영향을 미친다. 따라서 모듈러 멱승 연산에 필요한 곱셈 수를 감소시키기 위하여, 슬라이딩 윈도우를 적용한 CLNW 방법이나 VLNW 방법이 가장 널리 사용되고 있다. 본 논문에서는 조합론(combinatorics)에서 많이 응용되는 그래프 모델을 모듈러 멱승 연산에 적용할 수 있음을 보이고, 일반화된 그래프 모델을 통하여 VLNW 방법보다 더 적은 곱셈 수로 모듈러 멱승을 수행하는 방법을 설명한다. 본 논문이 제안하는 방법은 전체 곱셈 수를 감소시키는 새로운 블록들을 일반화된 그래프 모델의 초기 블록 테이블에 추가할 수 있는 초기 블록 테이블의 두 가지 확장 방법들로써, 접두사 블록의 확장과 덧셈 사슬 블록의 확장이다. 이 방법들은 새로운 블록을 초기 블록 테이블에 추가하기 위해 필요한 곱셈의 수와 추가한 뒤의 전체 곱셈 수를 비교하면서 초기 블록 테이블을 제한적으로 확장하므로, 지수 E에 non-zero bit가 많이 나타날수록 VLNW 방법에 비해 좋은 성능을 보이며 이는 실험을 통하여 검증하였다.

• The Korean Journal of Applied Statistics
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• v.26 no.6
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• pp.1019-1032
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• 2013

The accurate prediction of future mortality is an important issue due to recent rapid increases in life expectancy. An accurate estimation and prediction of mortality is important to future welfare policies. The optimal selection of a mortality model is important to estimate and predict mortality; however, the period of time series data used is also an important issue. It is essential to understand that the time series data for mortality is short in Korea and the data before 1982 is incomplete. This paper divides the time series of Korean mortality into two sets to compare the parameter estimates of the LC model and LC model with a cohort effect by the period of data used. A modeling and prediction of the mortality index and cohort effect index as well as the evaluation of future life expectancy is conducted. Finally, some suggestions are proposed for the future prediction of mortality.

• Communications for Statistical Applications and Methods
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• v.16 no.3
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• pp.449-461
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• 2009

Higher sigma quality level is generally perceived by customers as improved performance by assigning a correspondingly higher satisfaction score. The process capability indices and the sigma level $Z_{st}$ ave been widely used in six sigma industries to assess process performance. Most evaluations on process capability indices focus on statistical estimation under normal process which may result in unreliable assessments of process performance. In this paper, we consider statistical estimation for bivariate VPCI(Vector-valued Process Capability Index) $C_{pkl}=(C_{pklx},\;C_{pklx})$ under Marshall and Olkin (1967)'s bivariate exponential process. First, we derive some limiting distribution for statistical inference of bivariate VPCI $C_{pkl}$. And we propose two asymptotic normal confidence regions for bivariate VPCI $C_{pkl}$. The proposed method may be very useful under bivariate exponential process. A numerical result based on our proposed method shows to be more reliable.

• Korean Journal of Construction Engineering and Management
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• v.10 no.1
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• pp.69-77
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• 2009

Recently, a research of the urban regeneration has been performed very actively. This is one of the efforts to resolve various social and economic problems coming from the existing deteriorated building and facilities by new urban development or redevelopment. However, an urban regeneration has a characteristic to be unable to ensure the project performance due to the exposed numerous risks coming from the various and complex stake-holders, and its mega sizes. This paper proposes the method of risk performance index in order to improve an efficiency of performance measurement expanding to the risk view point from the existing integrated cost/schedule performance measurement. A risk performance index is compatible with the existing EVMS, and can make the performance measurement in 3 dimensions of the integrated cost/schedule/risk with 18 sub-indexes and variables.

• Sleep Medicine and Psychophysiology
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• v.12 no.1
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• pp.39-44
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• 2005

Objectives: Much attention has been paid to sleep apnea syndrome (SAS) in the elderly because of its high prevalence. It is expected that SAS in the elderly has both similarities and differences compared to SAS in the young or middle-aged populations. The aim of this study was to elucidate the characteristics and consequences of SAS in the elderly. Methods: In this study we included 210 young or middle-aged adults between 23 and 59 years (20 women and 190 men) and 65 older adults between 60 and 83 years of age (16 women and 49 men). Respiratory disturbance indices (RDIs) of the study subjects were more than 5 in an overnight polysomnography. They completed the Epworth Sleepiness Scale (ESS) and Pittsburgh Sleep Quality Index (PSQI). Informations about body mass index (BMI), neck, waist, and hip measurements, and blood pressure were obtained. Results: No difference was observed between older adults with SAS (older SAS) and adults aged under 60 with SAS (SAS aged under 60) in RDI, apnea index, % time of oxygen saturation less than 90%, and PSQI. Obstructive apnea index and oxygen desaturation index (ODI) were lower in older SAS. Compared to SAS aged under 60, lowest oxygen saturation and central apnea index were higher in older SAS, but they were statistically not significant. BMI and neck circumference were significantly lower in older SAS compared to SAS aged under 60. Diastolic blood pressure was lower in older SAS compared to SAS aged under 60 with no difference in systolic blood pressure. Older SAS showed lower scores in ESS than SAS aged under 60. Significant correlation was observed between RDI and BMI in SAS aged under 60, but not in the case of older SAS. The relationships between RDI and neck circumference, systolic and diastolic pressure, and ESS were similar. Conclusions: The elderly with SAS were not over-weight and there was no relationship between body weight and the severity of SAS. Also, the behavioral and cardiovascular effects of SAS were not marked in the elderly, which might be partly explained by decreased ODI and relatively higher lowest oxygen saturation in older SAS. The normal aging process, aside from increased body weight, might contribute to the development of SAS in the elderly with modest complications.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.6
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• pp.499-506
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• 2019

NDSM (Normalized Digital Surface Model) is key information for the detailed analysis of remote sensing data. Although NDSM can be simply obtained by subtracting a DTM (Digital Terrain Model) from a DSM (Digital Surface Model), in case of UAV (Unmanned Aerial Vehicle) data, it is difficult to get an accurate DTM due to high resolution characteristics of UAV data containing a large number of complex objects on the ground such as vegetation and urban structures. In this study, RGB-based UAV vegetation index, ExG (Excess Green) was used to extract initial seed points having low ExG values for region growing such that a DTM can be generated cost-effectively based on high resolution UAV data. For this process, local window analysis was applied to resolve the problem of erroneous seed point extraction from local low ExG points. Using the DSM values of seed points, region growing was applied to merge neighboring terrain pixels. Slope criteria were adopted for the region growing process and the seed points were determined as terrain points in case the size of segments is larger than 0.25 ㎡. Various slope criteria were tested to derive the optimized value for UAV data-based NDSM generation. Finally, the extracted terrain points were evaluated and interpolation was performed using the terrain points to generate an NDSM. The proposed method was applied to agricultural area in order to extract the above ground heights of crops and check feasibility of agricultural monitoring.

• Journal of Korea Water Resources Association
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• v.49 no.5
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• pp.439-450
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• 2016

For the design of infrastructures controlling the flood events at ungauged basins, this study tries to find the regional flood frequencies using peak flow data generated by the spatial extension of flood records. The Chungju Dam watershed is selected to validate the possibility of regional flood frequency analysis using the spatially extended flood data. Firstly, based on the index flood method, the flood event data from the spatial extension method is evaluated for 22 mid/smaller sub-basins at the Chungju Dam watershed. The homogeneity of the Chungju dam watershed was assessed in terms of the different size of watershed conditions such as accumulated and individual sub-basins. Based on the result of homogeneity analysis, this watershed is heterogeneous with respect to individual sub-basins because of the heterogeneity of rainfall distribution. To decide the regional probability distribution, goodness-of fit measure and weighted moving averages method from flood frequency analysis were adopted. Finally, GEV distribution was selected as a representative distribution and regional quantile were estimated. This research is one step further method to estimate regional flood frequency for ungauged basins.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.105.2-105.2
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• 2011

화비정질 실리콘의 빛에 의한 노화현상 (light-induced degradation; LID)은 이미 1977년 보고된 Staebler-Wronski 효과에 의해서 확인된 바 있다. 이는 비정질 실리콘이 빛에 노출될 때, 이미 포함되어 있는 수소원자가 빛 에너지에 의해서 이동하게 되고, 이로 인해서 생성 또는 소멸되는 댕글링 본드 때문에 일어난다. 특히, 일상적인 태양광의 노출 하에서 태양전지의 장시간 성능을 예측하는데 물리적인 이해의 부족 및 기술 환경적인 어려움이 있고, 이러한 요인들은 안정된 태양전지를 개발하는데 장해요인으로 나타난다. 그러므로 비정질 실리콘 태양전지가 장시간 태양광에 노출되어 시간이 지남에 따라서 "성능이 어떻게 변하는지?" 그리고 "이에 대한 원인은 무엇인지?" 등은 여전히 과학적으로 풀어야할 숙제로 남아있다. 본 논문에서는 비정질 실리콘으로 구성된 태양전지가 태양광에 노출될 때 시간이 지남에 따라서 (1) 성능이 어떻게 변하는지, (2) LID의 변화는 언제 안정화되는지, 그리고 (3) 성능변화에 대한 원인은 무엇인지에 대해서 논의한다. 본 논문은 장시간 빛에 노출되는 비정질 실리콘 태양전지의 성능예측에 관해서 연구하였다. 결함밀도의 운동학적 모형을 통해서 태양광 노출에 대한 태양전지 성능변화를 예측하는데 초점을 맞추었고, 이를 위해서 태양전지에 조사되는 태양광 세기, 주변온도, 등이 고려되었다. 특히, 전하운반자의 수명이 결함밀도에 의해서 결정되기 때문에 비정질 실리콘 태양전지의 빛에 대한 노화현상 (LID)이 확장지수함수 (stretched-exponential) 완화법칙을 따르는 결함밀도에 의해서 물리적으로 설명된다. 한편 이와 같은 물리적 계산의 유용성을 확인하기 위해서 동일한 태양전지에 대해서 AMPS-1D 컴퓨터 프로그램을 사용하였고, 이를 통해서 비정질 실리콘 태양전지의 빛에 대한 노화현상을 물리적 및 정량적으로 이해하였다. 본 연구에 적용되는 태양전지는 비정질 실리콘으로 구성된 pin 구조 (glass/$SnO_2$/a-SiC:H:B/a-Si:H/a-Si:H:P/ITO)로서 다음과 같은 특성을 갖는다: 에너지 띠간격~1.72 eV, 두께~400 nm, 내부전위~1.05 V, 초기 fill factor~0.71, 초기 단락전류~16.4 mA/$cm^2$, 초기 개방전압 0.90 V, 초기 변환효율 10.6 %. 우리는 이와 같은 연구를 통해서 과학적으로 비정질 실리콘의 빛에 의한 노화현상을 이해하고, 기술적으로 효율 및 경제성이 높은 태양전지의 개발에 도전한다.