• Journal of the Korean Data and Information Science Society
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• 제5권2호
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• pp.59-74
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• 1994

The hazard ratio may be useful as a descriptive measure to compare the hazard experience of a treatment group with that of a control group. In this paper, we propose a kernel estimator of hazard ratio with censored survival data. The uniform consistency and asymptotic normality of the proposed estimator are proved by using counting process approach. In order to assess the performance of the proposed estimator, we compare the kernel estimator with Cox estimator and the generalized rank estimators of hazard ratio in terms of MSE by Monte Carlo simulation.

• Journal of the Korean Data and Information Science Society
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• 제3권1호
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• pp.79-90
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• 1992

We consider hazard ratio as a descriptive measure to compare the hazard experience of a treatment group with that of a control group with censored survival data. In this paper, we propose a kernel estimator of hazard ratio. The uniform consistency and asymptotic normality of a kernel estimator are proved by using counting process approach via martingale theory and stochastic integrals.

• Journal of the Korean Data and Information Science Society
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• 제12권2호
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• pp.125-143
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• 2001

We, in this paper, propose a kernel estimator of hazard ratio with censored survival data. The uniform consistency and asymptotic normality of the proposed estimator are proved by using counting process approach. In order to assess the performance of the proposed estimator, we compare the kernel estimator with Cox estimator and the generalized rank estimators of hazard ratio in terms of MSE by Monte Carlo simulation. Two examples are illustrated for our results.

• 한국산학기술학회논문지
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• 제13권5호
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• pp.2219-2231
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• 2012

본 연구에서는 우리나라 30세 이상 성인들의 허혈성심장질환(ischemic heart disease, IHD) 발생률을 계산하고, 지질지표(콜레스테롤, 중성지방, 고밀도지단백콜레스테롤, 저밀도지단백콜레스테롤)가 허혈성심장질환 발생에 미치는 위험도를 파악하고자 19개 대학 및 종합병원의 건강검진센터에서 검진을 받은 417,642명을 대상으로 1993년 9월부터 2009년 6월까지 평균 8.5년동안 허혈성심장질환의 발생을 추적관찰하였다. 자료수집은 검진자들에 대한 설문조사지를 이용하였고, 허혈성심장질환의 발생여부는 국민건강보험공단의 데이터베이스에서 확인하였다. 발생률은 발생밀도로 계산하였고, 혈청지질 지표에 따른 허혈성심장질환의 발생 위험도는 콕스의 비례위험 회귀모형을 이용하여 연령, BMI, 생활양식을 보정한 상태에서 성별에 따른 위험요인별 위험비와 95% 신뢰구간을 계산하였다. 연구결과 TC/HDL 비의 증가에 따라 IHD의 발생 위험비는 남자에서 1.21배에서 1.84배까지, 여자는 1.26배에서 1.86배까지 증가하였으며, TG/HDL 비의 증가에 따른 IHD의 발생 위험비는 남자에서 1.17배에서 1.49배까지, 여자는 1.42배에서 1.97배까지, LDL/HDL 비에 따라 IHD의 발생 위험비는 남자에서 1.26배에서 1.82배까지, 여자는 1.26배에서 1.68배까지 증가하였다. 결론적으로 혈청지질지표는 심혈관질환의 중요한 위험요인으로 총콜레스테롤, 저밀도지단백콜레스테롤, 중성지방은 혈중 농도가 높을수록, 고밀도지단백콜레스테롤은 낮을수록 IHD의 위험이 높아지는 것으로 나타났고, TC/HDL 비, TG/HDL 비, LDL/HDL 비에서 단독의 지질지표보다 위험도가 더 높게 나타나는 경향이 있었다. 따라서 추후 허혈성 심장질환의 예방 및 관리에는 혈청지질지표의 비도 감안하여야 한다.

• Communications for Statistical Applications and Methods
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• 제27권6호
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• pp.675-688
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• 2020

In survival analysis of observational data, the inverse probability weighting method and the Cox proportional hazards model are widely used when estimating the causal effects of multiple-valued treatment. In this paper, the two kinds of weights have been examined in the inverse probability weighting method. We explain the reason why the stabilized weight is more appropriate when an inverse probability weighting method using the generalized propensity score is applied. We also emphasize that a marginal hazard ratio and the conditional hazard ratio should be distinguished when defining the hazard ratio as a treatment effect under the Cox proportional hazards model. A simulation study based on real data is conducted to provide concrete numerical evidence.

• 한국지진공학회논문집
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• 제26권4호
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• pp.173-180
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• 2022

Most of the drinking water dams managed by the local governments in Korea are earthfill dams, and these dams have almost no geotechnical property information necessary for seismic performance evaluation. Nevertheless, in the rough planning stage for improving seismic safety for these dams, it is necessary to classify their relative seismic hazard against earthquakes and conduct an additional ground investigation. The zero seismic failure probability curve is a curve suggested in this study in which the probability of failure due to an earthquake becomes '0' regardless of the geotechnical properties of the earthfill dam. By examining the method and procedure for calculating failure probability due to an earthquake suggested in previous researches, the zero seismic failure probability curves for an earthquake in 1,000-year and 2,400-year return periods in Korea were presented in the form of a hyperbola on the plane of the dam height versus freeboard ratio (ratio of freeboard to dam height), respectively. The distribution characteristics of the dam height and the freeboard ratio of 81 Korean earthfill dams were presented. The two proposed zero seismic failure probability curves are shown on the plane of the dam height versus freeboard ratio, and the relative seismic hazard of 81 dams can be classified into three groups using these curves as boundaries. This study presented the method of classifying the relative seismic hazard and the classification result.

• 대한원격탐사학회지
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• 제34권1호
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• pp.75-87
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• 2018

The Baekdu volcano (2,750 m a.s.l.) is located on the border between Yanggando Province in North Korea and Jilin Province in China. Its eruption in 946 A.D. was among the largest and most violent eruptions in the past 5,000 years, with a volcanic explosivity index (VEI) of 7. In this study, we processed and analyzed lahar-inundation hazard zone data, applying a geographic information system program with menu-driven software (LAHARZ)to a shuttle radar topography mission 30 m digital elevation model. LAHARZ can simulate inundation hazard zones created by large lahar flows that originate on volcano flanks using simple input parameters. The LAHARZ is useful both for mapping hazard zones and estimating the extent of damage due to active volcanic eruption. These results can be used to establish evacuation plans for nearby residents without field survey data. We applied two different simulation methods in LAHARZ to examine six water systems near Baekdu volcano, selecting weighting factors by varying the ratio of height and distance. There was a slight difference between uniform and non-uniform ratio changes in the lahar-inundation hazard zone maps, particularly as slopes changed on the east and west sides of the Baekdu volcano. This result can be used to improve monitoring of volcanic eruption hazard zones and prevent disasters due to large lahar flows.

• Earthquakes and Structures
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• 제19권5호
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• pp.379-393
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• 2020

The purpose of this study is to first evaluate the seismic behavior of ageing arch bridges by using the Intensity Measure - based demand and DCFD format, which is referred to as the fragility-hazard format. Then, an investigation is performed for their seismic vulnerability. Analytical models are created for bridges concerning different features and these models are subjected to Incremental Dynamic Analysis (IDA) analysis using a set of 22 earthquake records. The hazard curve and results of IDA analysis are employed to evaluate the return period of exceeding the limit states in the IM-based probabilistic performance-based context. Subsequently, the fragility-hazard format is used to assess factored demand, factored capacity, and the ratio of the factored demand to the factored capacity of the models with respect to different performance objectives. Finally, the vulnerability curves are obtained for the investigated bridges in terms of the loss ratio. The results revealed that decreasing the span length of the unreinforced arch bridges leads to the increase in the return period of exceeding various limit states and factored capacity and decrease in the displacement demand, the probability of failure, the factored demand, as well as the factored demand to factored capacity ratios, loss ratio, and seismic vulnerability. Finally, it is derived that the probability of the need for rehabilitation increases by an increase in the span length of the models.

• Journal of Gastric Cancer
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• 제12권4호
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• pp.210-216
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• 2012

Purpose: To assess independent prognostic factors for lymph node-negative metastatic gastric cancer patients following curative resection is valuable for more effective follow-up strategies. Materials and Methods: Among 1,874 gastric cancer patients who received curative resection, 967 patients were lymph node-negative. Independent prognostic factors for overall survival in lymph node-negative gastric cancer patients grouped by tumor invasion depth (early gastric cancer versus advanced gastric cancer) were explored with univariate and multivariate analyses. Results: There was a significant difference in the distribution of recurrence pattern between lymph node-negative and lymph nodepositive group. In the lymph node-negative group, the recurrence pattern differed by the depth of tumor invasion. In univariate analysis for overall survival of the early gastric cancer group, age, macroscopic appearance, histologic type, venous invasion, lymphatic invasion, and carcinoembryonic antigen level were significant prognostic factors. Multivariate analysis for these factors showed that venous invasion (hazard ratio, 6.695), age (${\geq}59$, hazard ratio, 2.882), and carcinoembryonic antigen level (${\geq}5$ ng/dl, hazard ratio, 3.938) were significant prognostic factors. Multivariate analysis of advanced gastric cancer group showed that depth of tumor invasion (T2 versus T3, hazard ratio, 2.809), and age (hazard ratio, 2.319) were prognostic factors on overall survival. Conclusions: Based on our results, independent prognostic factors such as venous permeation, carcinoembryonic antigen level, and age, depth of tumor invasion on overall survival were different between early gastric cancer and advanced gastric cancer group in lymph node-negative gastric cancer patients. Therefore, we are confident that our results will contribute to planning follow-up strategies.

• Asian Pacific Journal of Cancer Prevention
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• 제15권5호
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• pp.2369-2374
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• 2014

Background and Aim: Selumetinib is a promising and interesting targeted therapy agent as it may reverse radioiodine uptake in patients with radioiodine-refractory differentiated thyroid cancer. We conduct this metaanalysis to compare the efficacy and safety of selumetinib with current therapies in patients with advanced cancer. Methods: An electronic search was conducted using PubMed/ Medicine, EMBASE and Cochrane library databases. Statistical analyses were carried out using either random-effects or fixed-effects models according to the heterogeneity of eligible studies. Results: Six eligible trials involved 601 patients were identified. Compared with current therapies, treatment schedules with selumetinib did not improve progression free survival (hazard ratio, 0.91; 95%CI 0.70-1.17, P= 0.448), but did identify better clinical benefits (odds ratio, 1.24; 95%CI 0.69-2.24, P = 0.472) and less disease progression (hazard ratio, 0.72; 95%CI 0.51-1.00, P = 0.052) though its impact was not statistically significant. Sub-group analysis resulted in significantly improved progression free survival (hazard ratio, 0.61; 95%CI 0.49-0.57, P = 0.00), clinical benefits (odds ratio, 3.04; 95%CI 1.60-5.77, P = 0.001) and reduced disease progression (hazard ratio, 0.35; 95%CI 0.18-0.67, P = 0.001) in patients administrated selumetinib. Dermatitis acneiform (risk ratio, 9.775; 95%CI 3.143-30.395, P = 0.00) and peripheral edema (risk ratio, 2.371; 95%CI 1.690-3.327, P = 0.00) are the most frequently observed adverse effects associated with selumetinib. Conclusions: Compared with current chemotherapy, selumetinib has modest clinical activity as monotherapy in patients with advanced cancer, but combinations of selumetinib with cytotoxic agents in patients with BRAF or KRAS mutations hold great promise for cancer treatment. Dermatitis acneiform and peripheral edema are the most frequently observed adverse effects in patients with selumetinib.