• Journal of the Korean Data and Information Science Society
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• 제16권4호
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• pp.791-799
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• 2005

We consider two components parallel system in which the lifetimes have the bivariate Pareto model with bivariate random censored data. We assume that bivariate Pareto model is affected by common stress which is independent of the lifetimes of the components. We obtain estimators for the system reliability based on likelihood function and relative frequency. Also we construct approximated confidence intervals for the reliability based on maximum likelihood estimator and relative frequency estimator, respectively. Finally we present a numerical study.

• Journal of the Korean Data and Information Science Society
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• 제15권3호
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• pp.655-662
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• 2004

In this paper, we assume that strengths of two components system follow a type II bivariate Pareto model with bivariate type I censored data. And these two components are subjected to a common stress which is independent of the strengths of the components. We obtain estimators for the system reliability based on likelihood function and relative frequency, respectively. Also we construct approximated confidence intervals for the reliability based on maximum likelihood estimator and relative frequency estimator, respectively. Finally we present a numerical study.

• Journal of the Korean Data and Information Science Society
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• 제5권2호
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• pp.11-18
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• 1994

Sample sizes for experiments concerned with inference on R=Pr(X

• 시큐리티연구
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• 제12호
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• pp.177-200
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• 2006

본 연구는 민간경비원의 직무스트레스가 이직의사에 미치는 영향을 규명하는데 연구의 목적이 있으며, 2005년 현재 경찰청에 등록된 서울 및 수도권 소재 민간경비업체 중, 50명 이상 근무하고 있는 업체를 모집단으로 설정하였다. 선정된 경비업체의 민간경비원을 표집대상으로 설정한 후 유층집락무선표집법(stratified cluster random sampling)과 할당표집방법(quota sampling)을 병행 사용하여 표본을 추출하였다. 조사도구는 설문지를 사용하였으며, 타당도와 신뢰도 분석을 통해 검증을 실시한 후 사용하였다. 데이터는 각 목적에 맞게 부호화하여 입력시킨 후 사회과학통계 프로그램인 SPSS 12.0 version을 이용하여 전산처리 하였다. 이와 같은 방법과 절차에 따른 자료 분석을 통하여 본 연구에서 얻은 결론은 다음과 같다. 첫째, 민간경비원의 사회인구학적 특성에 따라 직무스트레스 및 이직의사의 차이를 검증한 결과 부분적으로 유의한 차이가 있는 것으로 나타났다. 둘째, 직무스트레스와 이직의사의 상관과계 분석 결과 직무환경과 이직의사에서 정적인 관계를 나타내었다. 셋째, 민간경비원의 직무스트레스가 이직의사에 미치는 영향을 검증한 결과 통계적으로 유의한 차이가 있는 것으로 나타났다.

• 한국농공학회논문집
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• 제46권1호
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• pp.41-51
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• 2004

FRP re-bar in concrete structures could be used as a substitute of steel re-bars for that cases in which aggressive environment produce high steel corrosion, or lightweight is an important design factor, or transportation cost increase significantly with the weight of the materials. But FRP fibers have only linearly elastic stress-strain behavior; whereas, steel re-bar has linear elastic behavior up to the yield point followed by large plastic deformation and strain hardening. Thus, the current FRP re-bars are not suitable concrete reinforcement where a large amount of plastic deformation prior to collapse is required. The main objectives of this study in to evaluate the tensile behavior and the fracture mode of hybrid FRP re-bar. Fracture mode of hybrid FRP re-bar is unique. The only feature common to the failure of the hybrid FRP re-bars and the composite is the random fiber fracture and multilevel fracture of sleeve fibers, and the resin laceration behavior in both the sleeve and the core areas. Also, the result of the tensile and interlaminar shear stress test results of hybrid FRP re-bar can provide its excellent tensile strength-strain and interlaminar stress-strain behavior.

• Safety and Health at Work
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• 제14권3호
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• pp.325-331
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• 2023

Background: Heat stress is a harmful physical hazard in many occupational settings. However, consequences of occupational heat exposure among workers in a sugarcane factory in Ethiopia are not well characterized. This study aimed to assess the level of occupational heat exposure-related symptoms and contributing factors. Methods: In this cross-sectional study, five workstations were selected for temperature measurement. Heat stress levels were measured using a wet-bulb globe temperature index meter. A stratified random sampling technique was used to select 1,524 participants. Heat-related symptoms were assessed using validated questionnaires. Results: The level of occupational heat exposure was 72.4% (95% CI: 70.2%-74.8%), while 71.6% (95% CI: 69.3%-74.9%) of participants experienced at least one symptom related to heat stress. The most common heat-related symptoms were swelling of hands and feet (78%), severe thirst (77.8%) and dry mouth (77.4%). The identified risk factors were a lack of reflective shields (AOR: 2.20, 95% CI: 1.53, 3.17), not-enclosed extreme heat sources (AOR: 1.76, 95% CI: 1.23, 2.51), a lack of access to shade (AOR: 9.62, 95% CI: 6.20, 14.92), and inappropriate protective clothing provision (AOR: 1.58, 95% CI: 1.27, 2.71). Conclusions: The burden of occupational heat exposure and heat-induced symptoms was high. Lack of reflective shields, the absence of enclosed extreme heat sources, a lack of access to shade, and inappropriate protective clothing provision were considerable attributes of heat stress. Therefore, the use of mechanical solutions to stop heat emissions at their sources and the key factors identified were areas for future intervention.

• Safety and Health at Work
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• 제13권4호
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• pp.469-474
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• 2022

Background: Nowadays, counter-productive work behaviors (CWBs) have turned into a common and costly position for many organizations and especially health centers. Therefore, the study was carried out to examine and compare the demand-control-support (DCS) and effort-reward imbalance (ERI) models as predictors of CWBs. Methods: The study was cross-sectional. The population was all nurses working in public hospitals in Hamadan, Iran of whom 320 were selected as the sample based on simple random sampling method. The instruments used were Job Content Questionnaire, Effort-Reward Imbalance Questionnaire, and Counterproductivity Work Behavior Questionnaire. Data were analyzed using correlation and regression analysis in SPSS18. Results: The findings indicated that both ERI and DCS models could predict CWB (p ≤ 0.05); however, the DCS model variables can explain the variance of CWB-I and CWB-O approximately 8% more than the ERI model variables and have more power in predicting these behaviors in the nursing community. Conclusion: According to the results, job stress is a key factor in the incidence of CWBs among nurses. Considering the importance and impact of each component of ERI and DCS models in the occurrence of CWBs, corrective actions can be taken to reduce their incidence in nurses.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.137-143
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• 2008

For most bearings, it is a common requirement to have long durability. Especially wheel bearing fatigue life is the most important in automotive quality. The contact fatigue life analysis of automotive wheel bearing considering real raceway rough surface is presented in this paper. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions; the subsurface stress field is obtained using rectangular patch solutions. Mesoscopic multiaxial fatigue criterion which can yield satisfactory results for non-proportional loading is then applied to predict fatigue damage. Suitable counting method and damage rule were used to calculate the fatigue life of random loading caused by rough surface. The life analysis considering real rough surface of wheel bearing raceway is in good agreement with the experimental results.

• 응용통계연구
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• 제9권2호
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• pp.119-134
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• 1996

가속수명검사는 시간과 경비를 현실적인 여건에 맞추기 위하여 정상조건보다 열악한(강도가 높은) 조건에서 검사를 수행하여 그 결과를 정상조건에서의 수명분포와 관련된 관심사(기대수명, 신뢰도) 등을 추정하는 것을 목적으로 하는 검사 방법이다. 이 연구에서는 고장률이 다른 두 개의 부품이 직렬형으로 구성된 시스템의 가속수명검사 자료를 분석할 때 사용되는 하나의 모형을 제안하고 분석 과정 및 기존의 두 개의 부품이 서로 독립이라고 가정한 모형과 비교하는 것을 주요 내용으로 하였다. 시스템이 작동될 때 받는 관찰이 가능하지 않은 총체적인 환경의 효과를 동일 시스템내의 두 개의 부품이 공유하게 됨으로써 발생되는 두 부품의 수명의 의존성을 frailty 모형을 이용하여 모형화하였고, 분석 과정에서는 Profile 우도함수를 사용하여 최대 우도 추정 과정에서의 초기치 문제를 해결하는 방법을 제시하고 모의실험을 통하여 독립성의 가정을 검토하여 보았다.

• 농촌지도와개발
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• 제11권1호
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• pp.95-110
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• 2004

The purposes of this study were to analyze rural youth's leisure activity and to suggest measures for activation. This study was conducted by review of literature and questionnaire, The data was collected from 1,209 stratified cluster random sampled rural youth who are in middle school and high school. To analyze the data, SPSS/WIN program was employed. The major finding of the study were as follows: 1) About 30% of rural youths had less than 1-2 hours for leisure activity in daily life and more than 8 hours for leisure activity during the weekend, and over 40% of rural youths had no plan for leisure activity. 1) They recognized that leisure activity made them enjoy common life, decrease their stress, and get new experience far self-development, 3) participation in sports, organized-activity and self-directed activity of the middle schools youths were higher compare to youths in high schools, 4) to activate leisure life, rural youths expected to get a) direct support for participating leisure activity expenses(27%), b) develop and diffusion of diverse and interesting leisure programs(23%), and c) securing appropriate leisure facilities(22%).