• Korean Journal of Radiology
• /
• 제24권4호
• /
• pp.284-293
• /
• 2023

Objective: To validate a simplified ordinal scoring method, referred to as modified length-based grading, for assessing coronary artery calcium (CAC) severity on non-electrocardiogram (ECG)-gated chest computed tomography (CT). Materials and Methods: This retrospective study enrolled 120 patients (mean age ± standard deviation [SD], 63.1 ± 14.5 years; male, 64) who underwent both non-ECG-gated chest CT and ECG-gated cardiac CT between January 2011 and December 2021. Six radiologists independently assessed CAC severity on chest CT using two scoring methods (visual assessment and modified length-based grading) and categorized the results as none, mild, moderate, or severe. The CAC category on cardiac CT assessed using the Agatston score was used as the reference standard. Agreement among the six observers for CAC category classification was assessed using Fleiss kappa statistics. Agreement between CAC categories on chest CT obtained using either method and the Agatston score categories on cardiac CT was assessed using Cohen's kappa. The time taken to evaluate CAC grading was compared between the observers and two grading methods. Results: For differentiation of the four CAC categories, interobserver agreement was moderate for visual assessment (Fleiss kappa, 0.553 [95% confidence interval {CI}: 0.496-0.610]) and good for modified length-based grading (Fleiss kappa, 0.695 [95% CI: 0.636-0.754]). The modified length-based grading demonstrated better agreement with the reference standard categorization with cardiac CT than visual assessment (Cohen's kappa, 0.565 [95% CI: 0.511-0.619 for visual assessment vs. 0.695 [95% CI: 0.638-0.752] for modified length-based grading). The overall time for evaluating CAC grading was slightly shorter in visual assessment (mean ± SD, 41.8 ± 38.9 s) than in modified length-based grading (43.5 ± 33.2 s) (P < 0.001). Conclusion: The modified length-based grading worked well for evaluating CAC on non-ECG-gated chest CT with better interobserver agreement and agreement with cardiac CT than visual assessment.

• 해양환경안전학회지
• /
• 제19권3호
• /
• pp.290-301
• /
• 2013

The docking analysis of a global ship structure is requested to evaluate its structural safety against the reaction forces at supports during docking works inside a dry dock. That problem becomes more important recently as the size of ships is getting larger and larger. The docking supports are appropriately arranged in a dock to avoid their excessive reaction forces which primarily cause the structural damages in docking a ship and, up to now, the structural safety has been assessed against the support arrangement by the finite element analysis (FEA) of a global ship structure. However, it is complicated to establish the finite element model of the ship in the current structural design environment of a shipyard and it takes over a month to finish the work. This paper investigates a simple and fast approach to carry out a ship docking analysis by a simplified grillage model and to assign the docking supports position on the model. The grillage analysis was considered from the motivation that only the reaction forces at supports are sufficient to assess their arrangement. Since the simplified grillage model of the ship cannot guarantee its accuracy quantitatively, modeling strategies are proposed to improve the accuracy. In this paper, comparisons between the proposed approach and three-dimensional FEA for typical types of ships show that the results from the present grillage model have reasonably good agreement with the FEA model. Finally, an integrated program developed for docking supports planning and its evaluation by the proposed approach is briefly described.

• Structural Engineering and Mechanics
• /
• 제74권6호
• /
• pp.821-832
• /
• 2020

The fundamental period is an important parameter for seismic design and seismic risk assessment of building structures. In this paper, a simplified theoretical method to predict the fundamental period of masonry infilled reinforced concrete (RC) frame is developed based on the basic theory of engineering mechanics. The different configurations of the RC frame as well as masonry walls were taken into account in the developed method. The fundamental period of the infilled structure is calculated according to the integration of the lateral stiffness of the RC frame and masonry walls along the height. A correction coefficient is considered to control the error for the period estimation, and it is determined according to the multiple linear regression analysis. The corrected formula is verified by shaking table tests on two masonry infilled RC frame models, and the errors between the estimated and test period are 2.3% and 23.2%. Finally, a probability-based method is proposed for the corrected formula, and it allows the structural engineers to select an appropriate fundamental period with a certain safety redundancy. The proposed method can be quickly and flexibly used for prediction, and it can be hand-calculated and easily understood. Thus it would be a good choice in determining the fundamental period of RC frames infilled with masonry wall structures in engineering practice instead of the existing methods.

• 한국태양에너지학회 논문집
• /
• 제32권2호
• /
• pp.19-27
• /
• 2012

This paper describes an experimental study on efficiency of solar collector in solar water heating system connected to hourly water heating load. In general, the functional form of solar efficiency is expressed as a function of fluid temperature entering solar collector, ambient temperature, and solar irradiance. When energy saving from solar heating of water heating system is analyzed on along-term basis such as one year with given solar irradiance data, simplified analysis is more convenient han detailed system simulation for quick assessment. However, the functional form of the efficiency is not convenient for approximately simplified energy analysis because the inlet temperature can be obtained through a detailed system simulation. In the study, solar collector efficiency is obtained with various daily water heating load sand daily solar irradiance using experimental tests. The study also considers large residential buildings such as apartment buildings for application of solar water heating systems. From test results, it is found that daily solar collector efficiency is proportional to daily water heating loads and daily solar irradiance. The data obtained from the study can be utilized to find a functional relation between daily solar irradiance and daily heating load in stead of collector inlet temperature for application of solar collector efficiency to long-term approximated energy analysis of solar heating system.

• 대한토목학회논문집
• /
• 제31권2B호
• /
• pp.147-154
• /
• 2011

유량증분방법론에 근거한 물리서식처 평가 모형은 생태유량 산정과 하천의 이수 및 환경 기능과 관련한 유량 산정을 지원하기 위한 의사결정수단으로 개발되었다. 물리서식처 평가 모형은 다양한 관련 학문의 이해, 복잡한 입력자료, 그리고 경험을 필요로 한다. 본 연구에서는 계획 단계에서 물리서식처 구조와 생태유량 규모를 개략적으로 추정할 수 있는 간편 물리서식처 모의 모형(SIMHAB)을 제시하였다. SIMHAB을 물리 및 생태자료가 있는 하천에 적용하고 모형의 적정성을 검토하였다. 제시된 모형은 현장자료와 PHABSIM 및 River2D와 같은 기존의 물리서식처 모형의 결과와 유사하나, 적은 입력자료를 필요로 한다. 따라서 SIMHAB은 물리서식처, 생태유량, 수자원 관리 등을 포함하는 하천복원 사업에 손쉽게 활용될 수 있을 것이다.

• Ocean and Polar Research
• /
• 제29권4호
• /
• pp.391-400
• /
• 2007

To identify the spatial distribution pattern of water quality in Masan Bay, Pearson's correlation as a common statistic method and Moran's I as a spatial autocorrelation statistics were applied to the hydrological data seasonally collected from Masan Bay for two years ($2004{\sim}2005$). Spatial distribution of salinity, DO and silicate among the hydrological parameters clustered strongly while chlorophyll a distribution displayed a weak clustering. When the similarity matrix of Moran's I was compared with correlation matrix of Pearson's r, only the relationships of temperature vs. salinity, temperature vs. silicate and silicate vs. total inorganic nitrogen showed significant correlation and similarity of spatial clustered pattern. Considering Pearson's correlation and the spatial autocorrelation results, water quality distribution patterns of Masan Bay were conceptually simplified into four types. Based on the simplified types, Moran's I and Pearson's r were compared respectively with spatial distribution maps on salinity and silicate with a strong clustered pattern, and with chlorophyll a having no clustered pattern. According to these test results, spatial distribution of the water quality in Masan Bay could be summed up in four patterns. This summation should be developed as spatial index to be linked with pollutant and ecological indicators for coastal health assessment.

• Acute and Critical Care
• /
• 제33권4호
• /
• pp.216-221
• /
• 2018

Background: In this study, we analyze the performance of the Acute Physiology and Chronic Health Evaluation (APACHE) II, APACHE IV, Simplified Acute Physiology Score (SAPS) 3, and Mortality Probability Model $(MPM)_0$ III in order to determine which system best implements data related to the severity of medical intensive care unit (ICU) patients. Methods: The present study was a retrospective investigation analyzing the discrimination and calibration of APACHE II, APACHE IV, SAPS 3, and $MPM_0$ III when used to evaluate medical ICU patients. Data were collected for 788 patients admitted to the ICU from January 1, 2015 to December 31, 2015. All patients were aged 18 years or older with ICU stays of at least 24 hours. The discrimination abilities of the three systems were evaluated using c-statistics, while calibration was evaluated by the Hosmer-Lemeshow test. A severity correction model was created using logistics regression analysis. Results: For the APACHE IV, SAPS 3, $MPM_0$ III, and APACHE II systems, the area under the receiver operating characteristic curves was 0.745 for APACHE IV, resulting in the highest discrimination among all four scoring systems. The value was 0.729 for APACHE II, 0.700 for SAP 3, and 0.670 for $MPM_0$ III. All severity scoring systems showed good calibrations: APACHE II (chi-square, 12.540; P=0.129), APACHE IV (chi-square, 6.959; P=0.541), SAPS 3 (chi-square, 9.290; P=0.318), and $MPM_0$ III (chi-square, 11.128; P=0.133). Conclusions: APACHE IV provided the best discrimination and calibration abilities and was useful for quality assessment and predicting mortality in medical ICU patients.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2022년도 춘계학술대회
• /
• pp.270-272
• /
• 2022

임상을 거친 약물이 시중에 유통되지 못하는 요인 중 하나는 안전성이다. 약물 부작용으로 인해 발생하는 안전성 문제의 주된 원인인 신경독성의 경우, 사전에 약물이나 화합물에 대한 위험 평가가 필요하다. 현재 약물의 안전성 검사를 위한 실험들은 동물 실험을 기반으로 하고 있으며, 이는 시간과 비용이 많이 든다는 단점을 갖는다. 따라서 위 문제를 해결하기 위해 in silico 실험을 통한 신경독성 예측모델을 제안하고자 한다. 본 연구에서는 의학 언어 시스템 (Unified Medical Language System)을 이용해 신경독성의 범주를 확대하고, 통합 데이터베이스를 기반으로 다양한 관련 화합물 데이터를 얻었다. 얻은 화합물들의 SMILES (Simplified Molecular Input Line Entry System)를 fingerprint로 변환시키고 이를 사용한 기계학습 기반의 모델을 만들었다. 모델은 최종적으로 신경독성의 유무를 예측한다. 해당 연구에서 제안된 실험은 in vivo 실험에 소요되는 시간 및 비용을 줄일 수 있다. 더 나아가 신약 개발 연구 기간을 단축하고 개발 중지 등의 부담을 줄일 수 있을 것으로 기대된다.

• 콘크리트학회논문집
• /
• 제26권3호
• /
• pp.351-360
• /
• 2014

이 연구의 목적은 감쇠시스템 설계 시 ASCE7-10의 등가선형해석과 응답스펙트럼해석의 설계절차 및 비선형해석에 간략화된 등가프레임모델을 제안하여, 선형 및 비선형 해석 시 소모되는 시간을 줄이고 해석 조건 및 변수조건을 다양화함으로 감쇠시스템 적용 시 효과를 합리적으로 검토하는데 있다. 이 연구에서는 최근에 이슈화 되고 있는 공동주택의 감쇠시스템 도입과 관련하여 ASCE7-10의 성능기반 내진설계를 근간으로 내진성능평가 및 감쇠시스템 설계를 비선형응답이력 해석을 통하여 수행하였다. 특히 공동주택 대상건물을 건축구조기준의 75% 지진력 수준으로 최적화 설계 시 내진성능평가를 수행하여 안전성을 검토하는 한편, 기준에 제시된 지진력 수준으로 내진설계 시 골조물량을 비교 하여 경제성을 검토하였다. 또한, 대상건물에 외부제어 이력형 감쇠장치를 적용 시 제안한 프레임 등가모델을 이용하여 ASCE7-10 감쇠시스템 설계를 수행하였으며 Full Scale Model에서 그 제어효과를 검증하였다.

• 한국수자원학회논문집
• /
• 제56권10호
• /
• pp.667-678
• /
• 2023

본 연구에서는 단순한 형상의 지하역사를 대상으로 준3차원 침수 흐름 시뮬레이션을 수행하였으며, 우수유입지점 수와 우수 유입량 변화에 따른 침수 흐름 특성 및 침수 위험도를 분석했다. 침수 해석 결과로부터 보행 안정성 평가를 위한 한계유속을 계산하여 미끄러짐 및 전도 사고 발생 가능 영역을 분석했다. 그 결과, 미끄러짐 사고는 침수계단에서 발생할 가능성이 있고 전도 사고는 침수계단과 지하2층 계단 주변에서 발생할 우려가 있었다. 침수 위험도에 대한 세부적 판단을 위해 4단계로 침수 위험도를 평가하는 Flood Hazard Degree (FD)와 3단계로 평가하는 Flood Intensity Factor (FIF)를 적용했다. 그 결과, FD가 FIF에 비해 더 넓은 영역에서 침수 흐름에 의한 위험이 있는 것으로 판단했다. 한계비력, 미끄러짐 및 전도 사고 발생 한계유속, FD, FIF 방법으로 평가한 침수 위험 발생 영역을 비교했을 때 한계비력은 다른 평가 방법에 비해 침수 위험 영역을 과대 산정했고, FIF는 과소산정하는 결과를 나타냈다. 또한 모든 평가 방법을 고려했을 때 우수 유입량이 우수유입지점 수보다 침수 위험도 평가 결과에 지배적 영향을 미쳤다. 또한 동일한 방향으로 침수 흐름을 일으키는 우수 유입 조건 보다 서로 충돌하는 침수 흐름을 일으키는 조건에서 침수 위험도가 증가했다.