• Journal of the Korean Data and Information Science Society
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• v.9 no.1
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• pp.37-45
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• 1998

We consider the problem of obtaining the confidence bands for the survival function with incomplete data. It is a rather simple procedure for constructing confidence bands of survival function. This method uses the weak convergence of normalized cumulative hazard estimator to a mean zero Gaussian process whose distribution can be easily approximated through simulation. Finally, we compare the performance of the proposed confidence bands through Monte Carlo simulation and we applied to construct the proposed bands with the Leukemia patient data.

• Korea journal of population studies
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• v.35 no.2
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• pp.55-72
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• 2012

Few studies have done on the intergenerational relations of married women and their own parents in Japan. This study approaches the topic by examining coresidence and contact frequency between generations. The study expects the likelihood of living together (including living next door) and the extent of contact would differ by the characteristics of woman, her husband, children, her brothers and sisters, her own parents and parents-in-law. From the 2003 Survey for National Family Research in Japan, selected are 853 currently married women in their 30s and 40s whose parent and parents-in-law are alive. The analysis shows that the likelihood of living together with parents decreases as the number of brothers and sisters increases. In particular, the presence of brother substantially decreases the likelihood. Having father only alive (vs. having both parents alive) also increases the likelihood. The frequency of contact with parents is conditioned by the coresidence with parents-in-law. It also differs by the level of education and its gap between spouses. Subjective evaluation of husband's attitude toward her parents is important. As in the case of living together, the number of brothers and sisters and the survival status of parents are significant in explaining the frequency of contact with her parents. The results indicate that number of brothers and sisters as well as widowhood of parents serves as its demographic condition. The findings that the frequency of contact with parent are affected by coresidene with parents-in-law, education gap between spouses and husband's attitude toward her parents suggest that the relationship of married women with her own parents are conditioned by her husband and his parents.

• Journal of Labour Economics
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• v.38 no.4
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• pp.57-81
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• 2015

In this paper we try to explain delays in one's first marriage that are observed in contemporary society by accounting for possible factors that may play a substantial role in delaying marriages. Discrete-time survival analysis with unobserved heterogeneity was employed. The result indicates that the odds of getting married compared to odds of not getting married are 0.91 times, i.e. 8.5% lower for women with bachelor's degree than women with high school diploma or below. The odds of getting married compared to odds of not getting married are 0.4 times, i.e. 59.6% lower in case of women with masters and/or doctorate program degree than women with bachelor's degree. Employed men's odds of getting married to not getting married are increased by a factor of 1.65 compared to the unemployed men. In addition, if one's family circumstances are economically below average at the age of 14, the odds decrease by a multiple of 0.65. With these results, we are able to conclude that not only education level but also one's economic ability play significant roles in determining one's marriage decision.

• Convergence Security Journal
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• v.11 no.6
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• pp.67-72
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• 2011

A system that provides a ubiquitous service is a networked system that has to overcome their circumstances that the service survivability is weak. the survivability of a networked system is defined as an ability of the system that can offer their services without interruption, regardless of whether components comprising the system are under failures, crashes, or physical attacks. This paper presents an approach that end users can obtain a quantitative evaluation of U-service survivability to reflect intended cyber attacks causing the networked system to fall into byzantine failures in addition to the definition of the survivability. In this paper, a Jini system based on wireless local area networks is used as an example for quantitative evaluation of U-service survivability. This paper also presents an continuous time markov chain (CTMC) Model for evaluation of survivability of U-service that a Jini system provides, and an approach to evaluate the survivability of the U-service as a blocking probability that end users can not access U-services.

• Journal of the Korea Society for Simulation
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• v.30 no.1
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• pp.1-9
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• 2021

In actual battlefield environment, the naval ships which have specific missions have to respond to the attack of hostile forces. Especially, in modern warfare, the importance of the survivability of naval ships are increasing due to the high lethality of armaments. Naval ship survivability is generally considered to encompass three constituents, susceptibility, vulnerability and recoverability. Recently, among these three constituents, many researches on vulnerability have been conducted. However, for the vulnerability of naval ships, most of researches are aimed towards the detailed design stages where implementing changes is heavily constrained or even impractical. In this paper, vulnerability assessment model for naval ships on a theater engagement is developed by using M&S technique. By using this model, the characteristics of platform and armaments are reflected on the damage of naval ship. The basic logic of damage assessment is also considered in detail. The damage status of the naval ship is quantified by defining a representative state index of onboard equipment for each system.

• Journal of Korea Water Resources Association
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• v.42 no.6
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• pp.457-464
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• 2009

This paper proposes methodologies for analyzing the accuracy of the proportional hazards model in predicting consecutive break times of water mains and estimating the time interval for economical water main replacement. By using the survival functions that are based on the proportional hazards models a criterion for the prediction of the consecutive pipe breaks is determined so that the prediction errors are minimized. The criterion to predict pipe break times are determined as the survival probability of 0.70 and only the models for the third through the seventh break are analyzed to be reliable for predicting break times for the case study pipes. Subsequently, the criterion and the estimated lower and upper bound survival functions of consecutive breaks are used in predicting the lower and upper bounds of the 95% confidence interval of future break times of an example water main. Two General Pipe Break Prediction Models(GPBMs) are estimated for an example pipe using the two series of recorded and predicted lower and upper bound break times. The threshold break rate is coupled with the two GPBMs and solved for time to obtain the economical replacement time interval.

• The Korean Journal of Applied Statistics
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• v.34 no.6
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• pp.957-968
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• 2021

Inverse censoring probability weighting (ICPW) is a popular technique in survival data analysis. In applications of the ICPW technique such as the censored regression, it is crucial to accurately estimate the censoring probability. A simulation study is undertaken in this article to see how censoring probability estimate influences model performance in censored regression using the ICPW scheme. We compare three censoring probability estimators, including Kaplan-Meier (KM) estimator, Cox proportional hazard model estimator, and local KM estimator. For the local KM estimator, we propose to reduce the predictor dimension to avoid the curse of dimensionality and consider two popular dimension reduction tools: principal component analysis and sliced inverse regression. Finally, we found that the Cox proportional hazard model estimator shows the best performance as a censoring probability estimator in both mean and median censored regressions.

• 한국벤처창업학회:학술대회논문집
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• 2020.06a
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• pp.113-121
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• 2020

최근 정부가 창업기업에게 3년간 공공금융기관 등을 통해 약 100조원 투입하였으며, 금융위원회가 신용보증기관과 산업은행 등 정책금융 등의 많은 창업지원 자금을 통해 약 35조원을 지원하는 등 최근 3년간(2015년~2018년) 창업기업에 약 100조원 이상을 지원하였다. 실제로 중소기업청의 지원예산 중 스타트업 지원 비중은 85%에 달한 반면 스케일업(성장·성숙기)지원은 15%에 불과하다. 그러나 국내 창업기업의 생존율은 선진국에 비해 턱없이 낮은 것으로 조사되었다. 창업 후 3년간 생존율은 39.1%로 10곳 중 4곳 정도만 살아남는 것으로 조사되었고, 5년간 살아남을 확률은 27.5% 10곳 중 3곳 정도만 살아남는다. 반면 해외 창업기업들은 5년간 창업기업 생존율은 우리나라의 2배에 달한다. 이에 따라 본 연구는 최근 정부의 적극적인 지원이 이루어지고 있는 초기창업자에 대한 연구의 필요성과 함께 창업동기와 창업준비가 사업계속의도에 미치는 영향관계에서 창업만족도의 매개역할에 관한 영향을 실증적으로 분석하고 살펴보고자 한다. 또한, 초기창업자의 창업동기와 창업준비에 기초하여 창업을 한 후에 창업에 대한 만족도를 높일 수 있는 방법보다는 창업 전 부터 사전 준비의 필요성을 고찰하고자 한다. 이러한 관점에서 실무적 시사점을 도출하고, 초기창업자들의 창업만족도를 높이고 계속 가능한 창업수행을 할 수 있도록 유용한 정책적 시사점을 제시하고자 한다.

• The KSFM Journal of Fluid Machinery
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• v.16 no.2
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• pp.42-47
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• 2013

Ship stability prediction is very complex in reality. In this paper, risk based approach is applied to predict the probability of a certified ship, which is effected by the forces of sea especially the wave loading. Safety assessment and risk analysis process are also applied for the probabilistic prediction of ship stability. The survival probability of ships encountering with different waves at sea is calculated by the existed statistics data and risk based models. Finally, ship capsizing probability is calculated according to single degree of freedom(SDF) rolling differential equation and basin erosion theory of nonlinear dynamics. Calculation results show that the survival probabilities of ship excited by the forces of the seas, especially in the beam seas status, can be predicted by the risk based method.

• The Korean Journal of Applied Statistics
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• v.29 no.7
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• pp.1459-1473
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• 2016

Both longitudinal data and survival data are collected simultaneously in longitudinal data which are observed throughout the passage of time. In this case, the effect of the independent variable becomes biased (provided that sole use of longitudinal data analysis does not consider the relation between both data used) if the missing that occurred in the longitudinal data is non-ignorable because it is caused by a correlation with the survival data. A joint model of longitudinal data and survival data was studied as a solution for such problem in order to obtain an unbiased result by considering the survival model for the cause of missing. In this paper, a joint model of the longitudinal zero-inflated count data and survival data is studied by replacing the longitudinal part with zero-inflated count data. A hurdle model and proportional hazards model were used for each longitudinal zero inflated count data and survival data; in addition, both sub-models were linked based on the assumption that the random effect of sub-models follow the multivariate normal distribution. We used the EM algorithm for the maximum likelihood estimator of parameters and estimated standard errors of parameters were calculated using the profile likelihood method. In simulation, we observed a better performance of the joint model in bias and coverage probability compared to the separate model.