• International Journal of Reliability and Applications
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• 제14권2호
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• pp.107-114
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• 2013

Modelling of failures is an important element of reliability modelling. Empirical modelling approach suitable for complex item is explored in this paper. First step of the empirical modelling approach is to plot hazard function, density function, Weibull probability plot as well as cumulative intensity function to see which model fits best for the given data. Next step of the empirical modelling approach is select appropriate model for the data and fit the parametric model accordingly and estimate the parameters.

• 수산해양기술연구
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• 제56권4호
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• pp.374-383
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• 2020

At ship design stage, the maneuverability is generally estimated based on the empirical formula or the computational fluid dynamic (CFD), which is one of the numerical simulation methods. Using the hydrodynamic derivatives derived through these methods can quantitatively estimate the maneuverability of target vessels and evaluate indirect maneuverability. Nevertheless, research on estimating maneuverability is insufficient for ships not subject to IMO maneuverability standard, especially fishing vessels, and even at the design stage, the empirical formula developed for merchant ships is applied without modification. An estimation error may occur due to the empirical formula derived from the regression analysis results of a model test if the empirical formula developed for merchant ships with different hull shapes is applied to fishing vessels without any modification. In this study, the modified empirical formula that can more accurately estimate the fishing vessel's maneuverability was derived by including the hull shape parameter of target fishing trawlers in the regression analysis process that derives Kijima et al. (1990) formula. As a result, the modified empirical formula showed an average estimation error of 6%, and the result improved the average error of 49% of Kijima et al. (1990) formula developed for merchant ships.

• Journal of Positioning, Navigation, and Timing
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• 제10권4호
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• pp.271-278
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• 2021

In this paper, a tropospheric delay error was calculated by using meteorological data collect from weather station and Saastamoinen model, and an empirical variogram of the tropospheric delay in the Korean peninsula was estimated. In order to estimate the empirical variogram of the tropospheric delay according to weather condition, sunny day, rainy day, and typhoon day were selected as analysis days. Analysis results show that a maximum correlation range of the empirical variogram on sunny day was about 560 km because there is overall trend of the tropospheric delay. On the other hand, the maximum correlation range of the empirical variogram on rainy was about 150 km because the regional variation was large. Although there is regional variation when the typhoon exists, there is a trend of the tropospheric delay due to a movement of the typhoon. Therefore, the maximum correlation range of the empirical variogram on typhoon day was about 280 km which is between sunny and rainy day.

• Steel and Composite Structures
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• 제22권3호
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• pp.677-690
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• 2016

In this paper, the effect of damping ratio on nonlinear dynamic analysis response and dynamic increase factor (DIF) in nonlinear static analysis of structures against column removal are investigated and a modified empirical DIF is presented. To this end, series of low and mid-rise moment frame structures with different span lengths and number of storeys are designed and the effect of damping ratio in DIF is investigated, performing several nonlinear static and dynamic analyses. For each damping ratio, a nonlinear dynamic analysis and a step by step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived. The results of the analysis reveal that DIF is decreased with increasing damping ratio. Finally, an empirical formula is recommended that relates to damping ratio. Therefore, the new modified DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of moment frame buildings with different damping ratios.

• 한국산학기술학회논문지
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• 제7권4호
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• pp.665-670
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• 2006

본 연구에서는 교대 및 교각의 측방유동에 대하여, 경험식과 수치해석 결과를 비교, 분석하였다. 연구결과, Tschebotarioff 제안식과 측방유동지수 판정법이 다른 결과를 나타내어 경험식만으로 측방유동 가능성을 판단할 수 없었다. 수치해석결과, 성토사면 선단 하부지반에서의 측방변위는 심도에 따라 감소하였으며, 연약층 상부 1/3위치에서 최대 측방변위가 발생하였다. 최대침하는 사면선단부에서 발생하였으며 선단부에서 13m 떨어진 위치에서 미소한 최대융기가 발생하였다.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.210-212
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• 2015

The growth-share matrix is a portfolio planning tool developed by the Boston Consulting Group (BCG) to assist competitive positioning in the international market including those in the construction industry. This matrix is helpful in balancing the firm's cash-flow, and it can suggest strategic directions for each business unit. However, its effectiveness and applicability have long been debated in the academic field due to the complex and unique industrial context of construction. To solve the dispute, this research clarifies the applicability of theories underlying the growth-share matrix to the construction industry. Empirical research based on actual financial data of Korean construction firms is adopted for the statistical analysis including one-way analysis of variance and correlation analysis. The results of this research show that empirical findings on the relationship between performance variables. In this context, this research can provide important insights on the concept of portfolio management in the construction industry.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3417-3426
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• 2012

본 연구는 기본적으로 소유구조(내부 외국인 지분율)가 대리인 비용(자산효율성 비중 영업외비용 비중)에 어떠한 영향을 미치는 가에 대한 실증연구이다. 그러나 소유구조와 대리인 비용의 상관성에 대한 기존연구들이 단순히 Pooled OLS Model을 사용하고 있기에 본 연구에서는 단순 Pooled OLS Model이 방대한 양의 패널형 자료의 검증에는 통계적 신뢰성이 부족하다는 전제하에, Pooled-OLS Model의 적합성 검증 결과를 토대로, 자료형성의 시점 및 기업의 효과를 반영하는 Fixed Effect Model과 Random Effect Model을 추가적인 연구모형으로 형성하고 이를 비교분석함으로써 실증분석 결과의 신뢰성 및 통계적 타당성을 높이고자 하였다. 연구 자료는 IMF 경제 위기 이후인 1998~2007년까지 10년간이며 금융업을 제외한 331개 기업을 대상으로 하였다. 주요 결과로는 모델의 적합성 검증결과 대리인 비용 항목 중 자산효율성 비중은 Random Effect Model을 사용하는 것이 적절하였으나 이에 반하여 영업외비용 비중은 Fixed Effect Model의 사용이 적합하였다. 이에 따른 실증분석결과는 Pooled OLS Model에서 채택되었던 가설이 대부분 기각되는 결과가 나왔다. 이는 실증분석에 있어서 사용하는 모형에 따라 다른 분석결과의 도출이 가능하다는 점을 보여주어 연구 자료에 따른 적합한 연구모형의 형성이 통계적으로 유의한 실증결과의 도출을 위해 무엇보다 중요하다는 점을 시사하고 있다.

• 한국IT서비스학회지
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• 제18권4호
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• pp.151-170
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• 2019

This study conducted an empirical analysis through the Kaplan-Meier method, which is mainly used for clinical experiment analysis, on the survival rate and the survival duration of small and medium-sized enterprises using B2B e-commerce guarantee provided by credit guarantee institutions for activating B2B e-commerce transactions. The variables presented in this study are analyzed by the subdivision of the survival characteristics of enterprises using B2B e-commerce guaranteee by year, enterprises attribute, representative attribute, and guarantee use amount based on the variables tested through previous studies. According to the empirical analysis, SMEs using B2B e-commerce guarantees have a higher survival rate compared to general enterprises Simply by year and have a variety of survival characteristics, and most of the variables have a significant effect except for some variables. The implication of this study is that the researches conducted on enterprises participating in B2B e-commerce for a long period of time to support the establishment of stable business environment of SMEs and the results of empirical analysis on the survival characteristics are useful information to the stakeholders of B2B e-commerce And it can contribute to enhance the survival rate of related enterprises.

• Geomechanics and Engineering
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• 제3권3호
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• pp.189-206
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• 2011

Amplification based on empirical relations is widely used for seismic microzonation of urban centers. Amplifications are used to represent the site effects of a particular soil column. Many empirical correlations are available to estimate the amplification of seismic waves. These correlations are based on the ratio of shear wave velocity of foundation/rock to soil velocity or 30 m equivalent shear wave velocity ($Vs^{30}$) and are developed considering deep soil data. The aim of this work is to examine the applicability of available amplification relations in the literature for shallow engineering bedrock sites by carrying out site response studies. Shear wave velocity of thirteen sites having shallow engineering bedrock have been selected for the study. In these locations, the depth of engineering bedrock (> 760 ${\pm}$ 60 m/s) is matched with the drilled bore hole. Shear wave velocity (SWV) has been measured using Multichannel Analysis of Surface Wave survey. These sites are classified according to the National Earthquake Hazards Reduction Program (NEHRP) classification system. Amplifications for an earthquake are arrived for these sites using empirical relations and measured SWV data. Site response analysis has been carried out in SHAKE using SWV and using synthetic and real earthquake data. Amplification from site response analysis and empirical relations are compared. Study shows that the amplification arrived using empirical relations does not match with the site response amplification. Site response amplification is much more than empirical values for same shear wave velocity.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제3권8호
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• pp.271-276
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• 2014

본 연구는 취약점 분석 평가 수행 시 N/A 점검항목이 보안 수준 결과에 미치는 영향 정도를 분석하였다. 이를 위하여, 본 논문에서는 취약점 분석 평가 범위 및 점검항목과 정량적 산출 방식을 이용하였으며, 항목의 중요성에 따른 등급과 가중치를 부여하였다. 또한, 주위 환경과 IT 기술 발달로 기관은 항상 위험에 노출되어 있으므로 위험 허용 수준을 적용하여 실증적 분석을 수행하였다. 분석한 결과, N/A 점검항목이 보안 수준에 영향을 미치는 요인으로 증명되었다. 즉, 취약점 분석 평가 수행 시 기관 특성상 연계성이 없는 점검항목은 제외시켜야 하는 것을 알 수 있었다. 본 연구에서는 실증검증을 토대로 기관 특성과 연계성을 갖지 않는 항목을 제외한 후 보안 수준 평가를 수행해야 함을 시사 하였으며, 기관 특성을 고려한 취약점 분석 평가 점검항목 정립 모델 연구가 필요함을 제시하였다.