• Journal of Preventive Medicine and Public Health
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• v.43 no.6
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• pp.543-548
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• 2010

Objectives: The objective of this study was to calculate sample size and power in an ongoing cohort, Korea radiation effect and epidemiology cohort (KREEC). Method: Sample size calculation was performed using PASS 2002 based on Cox regression and Poisson regression models. Person-year was calculated by using data from '1993-1997 Total cancer incidence by sex and age, Seoul' and Korean statistical informative service. Results: With the assumption of relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, sample size calculation was 405 events based on a Cox regression model. When the relative risk was assumed to be 1.5 then number of events was 170. Based on a Poisson regression model, relative risk=1.3, exposure:non-exposure=1:2 and power=0.8 rendered 385 events. Relative risk of 1.5 resulted in a total of 157 events. We calculated person-years (PY) with event numbers and cancer incidence rate in the nonexposure group. Based on a Cox regression model, with relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, 136 245PY was needed to secure the power. In a Poisson regression model, with relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, person-year needed was 129517PY. A total of 1939 cases were identified in KREEC until December 2007. Conclusions: A retrospective power calculation in an ongoing study might be biased by the data. Prospective power calculation should be carried out based on various assumptions prior to the study.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.24
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• pp.10683-10690
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• 2015

The big gap between efficacy of population level prevention and expectations due to heterogeneity and complexity of cancer etiologic factors calls for selective yet personalized interventions based on effective risk assessment. This paper documents our research protocol aimed at refining and validating a two-stage and web-based cancer risk assessment tool, from a tentative one in use by an ongoing project, capable of identifying individuals at elevated risk for one or more types of the 80% leading cancers in rural China with adequate sensitivity and specificity and featuring low cost, easy application and cultural and technical sensitivity for farmers and village doctors. The protocol adopted a modified population-based case control design using 72, 000 non-patients as controls, 2, 200 cancer patients as cases, and another 600 patients as cases for external validation. Factors taken into account comprised 8 domains including diet and nutrition, risk behaviors, family history, precancerous diseases, related medical procedures, exposure to environment hazards, mood and feelings, physical activities and anthropologic and biologic factors. Modeling stresses explored various methodologies like empirical analysis, logistic regression, neuro-network analysis, decision theory and both internal and external validation using concordance statistics, predictive values, etc..

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.2
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• pp.425-433
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• 2016

In smart grid, enhancement of efficiency and interoperability of electric power system is achieved through the connection with outer network, and this induces that power grid system is threatened increasingly, becomes the main target of cyber terrorism, and is sincerely required to design the secure power system. Although SSDLC(Secure System Development Life Cycle) is used for risk management from the design phase, traditional development life cycle is somewhat limited for satisfaction of information security indicator of power control system. Despite that power control system should reflect control entities of information security considering its own characteristics, validation elements are insufficient to apply into real tasks based on existing compliance. To make design of diagnostic model and assessment process for power control system possible and to give a direction for information security and present related indicator, we propose the new risk management framework of power control system which is applied operational security controls and standard architecture presented by IEC 62351 TC 57 with enterprise risk management framework.

• Journal of Korea Trade
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• v.24 no.1
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• pp.1-34
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• 2020

Purpose - In this study, we investigate determinants of hedging with derivatives and its effect on firm value and firm risk for Korean firms. Design/methodology - To avoid the endogeneity problem pointed out in previous studies, we use a two-stage analysis by using gains and losses from derivatives as instrument variable for hedging with derivatives. Findings - Our analysis on the determinants of hedging shows that firms that are more leveraged and less profitable, and with more growth opportunities are likely to hedge through derivatives. Additionally, large firms, firms less diversified into industry, and firms more diversified geographically are likely to use derivatives. Our two-stage analysis shows that indicators of hedging with derivatives have an insignificant effect on firm value, and the indicator of futures/forwards use and of swaps use have significant negative effect on firm value. Whereas, the extent of hedging with derivatives has positive effect on firm value for all types of foreign currency derivatives, which suggests that moderately low hedgers use derivatives inefficiently, but extensive hedgers use derivatives properly. With regard to firm risk, hedging with derivatives increases market-based risk, but decreases accounting-based risk. Thus, we conclude that Korean firms use derivatives to manage operational volatility rather than to manage market risk, and accounting-based risk reduction through hedging is not directly translated into higher firm value. Originality/value - This is not the first study to investigate hedging behavior of Korean firms, but the sample period that that this study analyzed is the longest and various method are used to control the endogeneity problem. We investigate not only total foreign currency derivatives but also by types of derivatives, including futures/forwards, options, and swaps.

• The Research Journal of the Costume Culture
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• v.26 no.6
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• pp.951-965
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• 2018

The purpose of this study was to investigate the effect of perceived risk, community usage motive, and price sensitivity of customers who purchase children's wear directly from overseas on customer satisfaction. Specifically, this study is aimed at verifying the moderating effect of price sensitivity when perceived risk and community usage motive significantly influence customer satisfaction. A survey was conducted among consumers who experienced directly purchasing children's wear from overseas and engaging in communities. A total of 415 questionnaires were distributed, which 41 responses were insincere and excluded; thus, 374 responses were analyzed. Results of this study are as follows. First, the analysis on how perceived risk and community usage motive influence customer satisfaction reveals the significant influence of economic and social psychological risk on customer satisfaction. Moreover, informational, recreational, and social emotional usage motive have a significant influence on customer satisfaction. Second, the effect of perceived risk and community usage motive on customer satisfaction based on different levels of price sensitivity was verified. As a result, delivery and economic risks affect customer satisfaction for consumers with high price sensitivity. Moreover, recreational usage motive has a significant influence on customer satisfaction for high price sensitive consumers. In conclusion, perceived risk negatively impacts customer satisfaction. Therefore, it is essential to provide a system that can reduce the perceived risk of consumers who purchase children's wear directly from overseas.

• Korean Journal of Construction Engineering and Management
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• v.23 no.3
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• pp.25-35
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• 2022

The purpose of this study is to derive risk events that occurred during aircraft runway construction and analyze loss costs for project participants. For this purpose, design change data, contracted statement and completed statement were investigated. The results of this study are as follows: There were 12 risk events in the process of construction, 5 design errors and 7 construction errors. The increased construction costs due to such risk events were calculated as KRW 726 million. Of the KRW 726 million that was increased due to risk events, about 52.57% was spent by the ordering agency, and about 47.43% contractors. The increased construction costs due to such risk events are about 4.86% of the direct construction costs of KRW 14.9 billion. Based on the results derived from these case studies, a method for estimating reserve costs and construction costs considering risk events is presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.8
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• pp.3804-3814
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• 2013

This study examined the fitness of a structural model on the relationship among biological risk disposition, sociocultural risk factors, self-control, social support, and suicidal ideation for woman adolescents. Data were collected from December 3, 2012 to March 28, 2013 by questionnaires from 343 middle and high school students in the D metropolitan city. The data was analyzed by the SPSS and AMOS programs. Biological risk disposition, sociocultural risk factors, self-control, and social support showed a direct effect on suicidal ideation for woman adolescents, while biological risk disposition and sociocultural risk factors showed an indirect effect on suicidal ideation for woman adolescents. Biological risk disposition and sociocultural risk factors showed a direct effect on self-control and social support for woman adolescents. Based on the outcomes of this study, it is necessary to design an intervention program that emphasizes the reducement of biological risk disposition, sociocultural risk factors and enhancement self-control and social support in order to prevention woman adolescents' suicidal ideation.

• Earthquakes and Structures
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• v.24 no.4
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• pp.275-288
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• 2023

Based on the crucial role of high-speed railway bridges (HSRBs) in the safety of high-speed railway operations, it is an important approach to mitigate earthquake hazards by proceeding with seismic risk assessments in their whole life. Bridge seismic risk assessment, which usually evaluates the seismic performance of bridges from a probabilistic perspective, provides technical support for bridge risk management. The seismic performance of bridges is greatly affected by the degradation of material properties, therefore, material damage plays a nonnegligible role in the seismic risk assessment of the bridge. The effect of material damage is not considered in most current studies on seismic risk analysis of bridges, nevertheless. To fill the gap in this area, in this paper, a nonlinear dynamic time-history analysis has been carried out by establishing OpenSees finite element model, and a seismic vulnerability analysis is carried out based on the incremental dynamic analysis (IDA) method. On this basis, combined with the site risk analysis, the time-dependent seismic risk analysis of an offshore three-span HSRB in the whole life cycle has been conducted. The results showed that the seismic risk probabilities of both components and system of the bridge increase with the service time, and their seismic risk probabilities increase significantly in the last service period due to the degradation of the material strength, which demonstrates that the impact of durability damage should be considered when evaluating the seismic performance of bridges in the design and service period.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.135-140
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• 2002

Bridge columns in strong earthquake area are to be designed and constructed so that enough ductility should be guaranteed. Therefore, large amount of transverse reinforcement is required to confine core concrete of the bridge column by design specifications. In moderate seismicity regions, however, adopting the full ductility design concept sometimes results in construction problems due to reinforcement congestion. For the moderate seismicity regions, a design based on required ductility and required transverse reinforcement might be a reasonable approach. Ductility demand design or performance-based design might be an appropriate approach especially for regions of moderate seismic risk. The procedure and application of this design approach are presented in this paper.

• Earthquakes and Structures
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• v.11 no.4
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• pp.583-607
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• 2016

One of the main applications of seismic risk assessment is that an specific design could be selected for a bridge from different alternatives by considering damage losses alongside primary construction costs. Therefore, in this paper, the focus is on selecting the shape of pylon, which is a changeable component in the design of a cable-stayed bridge, as a double criterion decision-making problem. Different shapes of pylons include H, A, Y, and diamond shape, and the two criterion are construction costs and probable earthquake losses. In this research, decision-making is performed by using developed seismic risk assessment process as a powerful method. Considering the existing uncertainties in seismic risk assessment process, the combined incremental dynamic analysis (IDA) and uniform design (UD) based fragility assessment method is proposed, in which the UD method is utilized to provide the logical capacity models of the structure, and the IDA method is employed to give the probabilistic seismic demand model of structure. Using the aforementioned models and by defining damage states, the fragility curves of the bridge system are obtained for the different pylon shapes usage. Finally, by combining the fragility curves with damage losses and implementing the proposed cost-loss-benefit (CLB) method, the seismic risk assessment process is developed with financial-comparative approach. Thus, the optimal shape of the pylon can be determined using double criterion decision-making. The final results of decision-making study indicate that the optimal pylon shapes for the studied span of cable-stayed bridge are, respectively, H shape, diamond shape, Y shape, and A shape.