• 한국해안·해양공학회논문집
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• 제21권3호
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• pp.254-265
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• 2009

해양 및 해안의 구조물 설계 시 극치해면 연구가 필수적이다. 본 논문에서는 한반도 주변의 무역항과 연안항 총 52개 항에서 수치모의 된 폭풍해일 자료를 연최대치 시계열 방법, 부분 시계열 방법, 경험모의기법을 이용하여 빈도분석을 수행한 후 비교하였다. 연최대치 시계열 방법과 부분 시계열 방법에서 매개변수 추정을 위해 최우도법을 사용하였다. 분포는 Generalized Pareto 분포를 사용하였고 적합성은 5% 유의수준으로 $\chi^2$ 및 K-S 검정을 수행하였다. 또한, 경험모의기법에 조석을 추가하여 극치해면을 산정하였으며 정 등(2008)이 제시한 극치 해면과 비슷한 값을 나타내었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제44권1호
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• pp.25-28
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• 2018

Objectives: This study aimed to describe recent patterns in the types of statistical test used in original articles that were published in Journal of the Korean Association of Oral and Maxillofacial Surgeons. Materials and Methods: Thirty-six original articles published in the Journal in 2015 and 2016 were ascertained. The type of statistical test was identified by one researcher. Descriptive statistics, such as frequency, rank, and proportion, were calculated. Graphical statistics, such as a histogram, were constructed to reveal the overall utilization pattern of statistical test types. Results: Twenty-two types of statistical test were used. Statistical test type was not reported in four original articles and classified as unclear in 5%. The four most frequently used statistical tests constituted 47% of the total tests and these were the chi-square test, Student's t-test, Fisher's exact test, and Mann-Whitney test in descending order. Regression models, such as the Cox proportional hazard model and multiple logistic regression to adjust for potential confounding variables, were used in only 6% of the studies. Normality tests, including the Kolmogorov-Smirnov test, Levene test, Shapiro-Wilk test, and $Scheff{\acute{e}}^{\prime}s$ test, were used diversely but in only 10% of the studies. Conclusion: A total of 22 statistical tests were identified, with four tests occupying almost half of the results. Adoption of a nonparametric test is recommended when the status of normality is vague. Adjustment for confounding variables should be pursued using a multiple regression model when the number of potential confounding variables is numerous.

• Safety and Health at Work
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• 제10권1호
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• pp.54-60
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• 2019

Background: Increasing the establishment of integrated management systems (IMSs) is done with the purpose of leaving traditional management methods and replacing them with modern management methods. Thus, the present study sought to analyze the events and investigate the impact of IMS on health and safety performance indices in an Iranian combined cycle power plants. Methods: This case study was conducted in 2012 in all units of the Yazd Combined Cycle Power Plant on accident victims before and after the implementation of IMS. For data analysis and prediction of indices after the implementation of IMS, descriptive statistics and Kolmogorov-Smirnov test, Chi-square, linear regression, and Cubic tests were conducted using SPSS software. Results: The number of people employed in the power plant in an 8-year period (2004-2011) was 1,189, and 287 cases of work-related accidents were recorded. The highest accident frequency rate and accident severity rate were in 2004 (32.65) and 2008 (209), respectively. Safe T-score reached to below -3 during 2010-2011. In addition, given the regression results, the relation between all predictor variables with outcomes was significant (p < 0.05), except for the variable $X^1$ belonging to the accident severity rate index. Conclusion: The implementation of safety programs especially that of IMS and its annual audits has had a significant impact on reducing accident indices and improving safety within the study period. Accordingly, health and safety management systems are appropriate tools for reducing accident rate, and the use of regression models and accident indices is also a suitable way for monitoring safety performance.

• 한국표면공학회지
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• 제53권6호
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• pp.330-342
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• 2020

Since the original report on ferroelectricity in Si-doped HfO2 in 2011, fluorite-structured ferroelectrics have attracted increasing interest due to their scalability, established deposition techniques including atomic layer deposition, and compatibility with the complementary-metal-oxide-semiconductor technology. Especially, the emerging fluorite-structured ferroelectrics are considered promising for the next-generation semiconductor devices such as storage class memories, memory-logic hybrid devices, and neuromorphic computing devices. For achieving the practical semiconductor devices, understanding polarization switching kinetics in fluorite-structured ferroelectrics is an urgent task. To understand the polarization switching kinetics and domain dynamics in this emerging ferroelectric materials, various classical models such as Kolmogorov-Avrami-Ishibashi model, nucleation limited switching model, inhomogeneous field mechanism model, and Du-Chen model have been applied to the fluorite-structured ferroelectrics. However, the polarization switching kinetics of fluorite-structured ferroelectrics are reported to be strongly affected by various nonideal factors such as nanoscale polymorphism, strong effect of defects such as oxygen vacancies and residual impurities, and polycrystallinity with a weak texture. Moreover, some important parameters for polarization switching kinetics and domain dynamics including activation field, domain wall velocity, and switching time distribution have been reported quantitatively different from conventional ferroelectrics such as perovskite-structured ferroelectrics. In this focused review, therefore, the polarization switching kinetics of fluorite-structured ferroelectrics are comprehensively reviewed based on the available literature.

• 한국수자원학회논문집
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• 제42권10호
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• pp.857-866
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• 2009

본 연구에서는 전국의 30년 이상의 강우관측기록을 보유하고 있는 기상청 산하 56개 강우관측소의 연 최대치 강우자료들로부터 확률분포형에 대하여 모멘트법, 최우추정법, 확률가중모멘트법을 이용하여 모수를 추정하고, 그 모수의 범위와 확률변수의 범위에 대한 적정성을 알아보았다. 적정성이 있는 모수를 대상으로 적합도 검정법인 x$^2$-검정, K-S검정, Cramer von Mises (CVM)검정, Probability Plot Correlation Coefficient (PPCC) 검정을 실시한 결과 중, 최근 연구에서 많이 이용되고 있고 표본자료의 크기가 작거나 왜곡된 자료일 경우에도 비교적 안정적인 결과를 얻을 수 있는 확률가중모멘트법과 상관계수에 의한 검정인 PPCC검정을 통과한 분포형을 우선적으로 적합도 평가 대상 분포형으로 선정하였다. 선정된 분포형을 대상으로 적합도 평가기준인 SLSC, MLL, AIC를 적용하여 적합도 평가를 실시하여 대표확률분포형 후보군을 추출하였다. 대표확률분포형 후보군으로 선정된 확률분포형에 대하여 resampling방법인 Jackknife기법을 적용하여 변동성을 파악하고, 변동성이 가장 작게 나타난 분포형을 그 지점의 대표확률분포형으로 결정하였다. 본 논문에서는 분석 결과의 분량을 감안하여 대표적으로 서울, 강릉, 대구, 전주, 부산 지점에 대해 작성하였으며, 확률강우량의 변동성이 가장 작은 확률분포형을 56개 지점의 각 지점 대표확률분포형으로 제시하였으며, Gumbel 분포(GUM)의 선정 비율이 지속기간 12시간, 24시간에 대해 각각 41 %, 32 %로 가장 높게 나타났다. 본 연구에서는 적합도 평가를 함에 있어서 객관적 정량화가 가능한 세 가지 기준과 Jackknife기법을 이용한 새로운 확률분포형 선정의 가능성을 제시하였다.

• Journal of Preventive Medicine and Public Health
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• 제23권1호
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• pp.11-21
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• 1990

This study refers to the problem of long-term inpatient flow in a general hospital. In this study, a queueing simulation model was developed for the two departments in the hospital with a homogeneous case mix and relatively many long-term inpatients in order to increase the turnover rate and hospital charges. Before the simulation n, the model was verified by the Kolmogorov-Smirnov test. The following results were generated by three alternative models of the special bed policies. 1. Alternative I : When long term inpatients were admitted to the wards belonging to departments A and B without transfer to other departments and special beds, the average turn-over rate decreased by 2-4% and the average hospital charges decreased by 70 million won. 2. Alternative II : When long-term inpatients were transferred to department C but the transfer of wards was determined by department C in order of clinical need, the average turnover rate increased by 4-13% but the average hospital charges decreased by 30 million won. This result was not greatly different from the present state. 3. Alternative III : When long-term inpatients were transferred to the special wards and department C simultaneously, the increase in the average turnover rate and hospital charges was equivalent to the increase of two beds in the special wards. When the special wards were allocated 16 beds, the average turnover rate of departments A and B increased by about 55% and 20% respectively. Also, the hospital charges increased by about 0.44 billion won. As a result, transfer to department C and the use of 16 beds in the special wards for long-term inpatients of departments A and B is expected to maximize the hospital revenue. However, as the above special bed policy can not increase the turnover rate above 60%, there is a need for a more comprehensive policy to further increase the rate. The development of an elaborate model should include the number of long-term inpatients in all clinical departments, the special wards system or an increase of hospital beds to handle admission needs, and the resources of the hospital by department. When the alternatives are evaluated, a cost-benefit analysis in addition to the turnover rate and the hospital charges should be considered.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제12권6호
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• pp.259-266
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• 2023

기계학습을 통해 학습된 모델은 업무 활용 시 그 성능을 실측하기 매우 어렵다. 때문에 운영 부서에서는 모델의 성능을 효과적으로 관리하지 못한다. 이로 인해 모델의 상태를 판단하기 위한 Concept drift 탐지 방법이 다양하게 연구되고 있다. 운영 부서에서는 운영 중인 모델의 성능을 정량적으로 관리하려고 한다. 그러나 Concept drift는 모델 상태를 데이터 관계적으로 판단 할 뿐, 모델의 정량적 성능 수치를 추정하지는 못한다. 본 연구에서는 Concept drift의 통계량을 통해 정량적으로 precision 값을 추정하는 성능 예측 모델(PPM, Performance prediction model)을 제안한다. 제안 모델의 Algorithm 1에서는, 학습데이터에서 복원 추출한 샘플링 데이터에 인위적인 drift를 유도하고 이때의 precision을 측정하여 drift와 precision의 데이터 셋을 만들어 학습한다. Algorithm 2에서는 테스트 데이터를 통해 실제 precision과 예측 precision의 차이를 측정하여 성능 예측 모델의 오차를 보정 한다. 현실 비즈니스에서 사용될 수 있는 대출 심사 모델과 신용카드 오사용 탐지 모델에 PPM을 적용하여 성능 예측의 유효성을 확인했다.