• 산업공학
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• 제19권4호
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• pp.316-323
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• 2006

In this study, based on Weibull proportional age reduction model and age replacement policy, we analyze economic life of cutting tool which allows re-grinding. Re-grinding task, usually for high-priced machining tools(e.g., broaching tool), is a kind of preventive maintenance activities to extend tool life at the completion of a lot production. The numerical results are also presented. Among the parameters of Weibull proportional age reduction model, the re-grinding effect parameter and Weibull shape parameter have a strong effect on economic tool life, and in the cost parameters, shortage cost is most sensitive. With further study on the parameter estimation of tool life process and cost function, this study can be expected to give more practical contribution to management of general machining tools.

• 한국융합학회논문지
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• 제6권6호
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• pp.285-291
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• 2015

현재 FTMS(Freeway Traffic Management System: 고속도로 교통관리 시스템), TCS(Toll Collection System: 요금 징수 시스템), 하이패스(Hi-Pass: 통행료 전자 지불 시스템)등의 고속도로 ITS(Intelligent Transportation System) 설비들은 단순한 이력관리 및 수동적인 사후관리가 이루어져 고장관련 DB가 부족하여 시설물의 통합운영관리 활용을 최대화 하지 못하고 있다. 또한, 부품의 교체시기가 없어 고장 발생 시마다 부품을 교체하다 보니 고장건수 증가 및 수리시간이 증가하며, 매번 교체 할 때마다 서비스가 중단되는 문제 점이 발생한다. 본 연구에서는 고속도로 ITS 시설물의 고장이력을 사전에 관리하여 예방적 유지관리를 하려한다. 따라서 하이패스 시설물의 고장이력을 신뢰성 이론에 기반을 두고 체계적인 통계분석을 통해 시스템의 신뢰도인 운용가용도를 산출한다. 교체시기 산정을 통해 고장건수 및 시간이 감소하며 예비품 수량을 확보하여 예산 비용을 줄일 수 있고, 부품의 관리계획을 수립하여 지속적인 예방적 유지관리를 통해 시스템의 품질을 향상시키고, 서비스 품질을 항시 가용한 상태인 무 중단 운용상태를 지향 할 수 있도록 하는 것이 본 연구의 목적이다.

• Safety and Health at Work
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• 제12권4호
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• pp.439-444
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• 2021

Background: In a previous study, we estimated exposure prevalence and the number of workers exposed to carcinogens by industry in Korea. The present study aimed to evaluate the optimal exposure intensity indicators of airborne lead exposure by comparing to blood lead measurements for the future development of the carcinogen exposure intensity database. Methods: Data concerning airborne lead measurements and blood lead levels were collected from nationwide occupational exposure databases, compiled between 2015 and 2016. Summary statistics, including the arithmetic mean (AM), geometric mean (GM), and 95th percentile level (X95) were calculated by industry both for airborne lead and blood lead measurements. Since many measurements were below the limits of detection (LODs), the simple replacement with half of the LOD and maximum likelihood estimation (MLE) methods were used for statistical analysis. For examining the optimal exposure indicator of airborne lead exposure, blood lead levels were used as reference data for subsequent rank correlation analyses. Results: A total of 19,637 airborne lead measurements and 32,848 blood lead measurements were used. In general, simple replacement showed a higher correlation than MLE. The results showed that AM and X95 using simple replacement could be used as optimal exposure intensity indicators, while X95 showed better correlations than AM in industries with 20 or more measurements. Conclusion: Our results showed that AM or X95 could be potential candidates for exposure intensity indicators in the Korean carcinogen exposure database. Especially, X95 is an optimal indicator where there are enough measurements to compute X95 values.

• Journal of Preventive Medicine and Public Health
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• 제36권3호
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• pp.279-288
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• 2003

Objectives : Evidence for an effect of rerroductive factors on colorectal carcinogenesis is not yet consistent. Little research has been conducted to investigate whether reproductive factors were associated with colorectal adenomas that are the precursors of colorecta1 cancer, We evaluated the relationships between reproductive factors and the degree of dysplasia of the colorectal adenoma and cancer as colorectal adenoma-carcinoma sequence. Methods : For this study, 241 adenoma cases with histopathologically confirmed incident colorectal adenoma, 76 cancer cases with colorectal cancer and 1677 controls were collected from Our Lady of Mercy Hospital, The Catholic University of Korea, during 1994-1999. Before colonoscopy, information on demographic characteristics, reproductive factors, life style habits and dietary intake were obtained by interviewed questionnaire. Adjusted OR and 95% CI were estimated by using polytomous logistic regression model, Potential confounders that were selected based on the goodness of fit Statistics and interaction between risk factors were considered in this adjustment. The Wald statistic was calculated to test the heterogeneity of the odds ratios for each case. Results .: Postmenopausal women with natural menopause were found to be positively associated with the risk of mild dysplasia adenoma (multivariate-adjusted OR : 2.59, 95% CI=1.1-0.2). Parity was found to be negatively associated with the risk of colorectal lancer (age-adjusted OR : 0.40, 95% CI=0.2-0.9), but did not significantly decrease the risk of colorectal cancer (multivariate-adjusted OR : 0.95, 95% CI=0.3-2.9). Me associations were seen between a9e at menarche, breast feeding, induced abortion, oral contraceptive use, menopausal types, menopausal age or hormone replacement therapy (HRT and the degree of dysplasia of the colorectal adenoma and cancer. However, none of these associations differed' significantly between the degree of dysplasia of the colorectal adenoma and cancer. Conclusions : These findings suggest that postmenopausal women with natural menopause may experience increased risk of mild dysplasia adenorna among colorectal adenoma-carcinoma sequence.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권2호
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• pp.159-167
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• 2017

Purpose: The purpose of this research is to study research trend in the field of warranty and maintenance policy of second-hand products. Methods: To this end, we consider research articles, which deal with warranty and maintenance of the second-hand products, published on journals during the past 20 years and classify them by taxonomy scheme proposed by Shafiee and Chukova (2013). The taxonomy scheme consists of three maintenance models in warranty for second-hand product. In each models, we analyze proposed maintenance and warranty policies with respect to types of upgrade models, types of preventive maintenances, decision variables and decision criteria model. Results: We obtain the scheme of maintenance and warranty of the second-hand products and define cost related to warranty and maintenance of the second-hand item. Also, we summarize the characteristics of maintenance and warranty policies in each classified model. Conclusion: There have been several research reviews on maintenance and warranty polity of new products. This research surveys researches of authors during the past 20 years and classifies, summarizes and compares proposed maintenance and warranty policies of the second-hand products. This research provides useful information to researchers who are interested in maintenance and warranty of the second-hand products.

• 한국재료학회지
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• 제29권11호
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• pp.670-676
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• 2019

We study substrate support structures and materials to improve uptime and shorten preventive maintenance cycles for chemical vapor deposition equipment. In order to improve the rolling of the substrate support, the bushing device adopts a ball transfer method in which a large ball and a small ball are mixed. When the main transfer ball of the bushing part of the substrate support contacts the substrate support, the small ball also rotates simultaneously with the rotation of the main ball, minimizing the resistance that can be generated during the vertical movement of the substrate support. As a result of the improvement, the glass substrate breakage rate is reduced by more than 90 ~ 95 %, and the equipment preventive maintenance and board support replacement cycles are extended four times or more, from once a month to more than four months, and the equipment uptime is at least 15 % improved. This study proposes an optimization method for substrate support structure and material improvement of chemical vapor deposition equipment.

• 한국병원경영학회지
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• 제14권1호
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• pp.23-35
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• 2009

The objectives of the present study is to examine the validity of Charlson Comorbidity Index(CCI) based on medical record data; to utilize the index to determine outcome indexes such as mortality, length of stay and cost for the domestic patients whose have received total hip arthroplasty. Based on medical record date, 1-year Mortality was analyzed to be 0.664 of C statistic. The $R^2$ for the predictability for length of stay and the cost was about 0.0181, 0.1842. Fee of national health insurance and total cost including the cost not covered by insurance, also had statistically significance above 3 points of Charlson point score(p=0.0290, 0.0472; $p.{\le}0.05$). The 1-year mortality index, length of stay and cost of the total hip arthroplasty patients which was obtained utilizing CCI have a limitative prediction power and therefore should be carefully analyzed for use.

• Journal of Preventive Medicine and Public Health
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• 제55권4호
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• pp.313-320
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• 2022

The KoreaN Cohort Study for Outcomes in Patients With Chronic Kidney Disease (KNOW-CKD) was launched in 2011 with the support of the Korea Disease Control and Prevention Agency. The study was designed with the aim of exploring the various clinical features and characteristics of chronic kidney disease (CKD) in Koreans, and elucidating the risk factors for CKD progression and adverse outcomes of CKD. For the cohort study, nephrologists at 9 tertiary university-affiliated hospitals participated in patient recruitment and follow-up. Biostatisticians and epidemiologists also participated in the basic design and structuring of the study. From 2011 until 2016, the KNOW-CKD Phase I recruited 2238 adult patients with CKD from stages G1 to G5, who were not receiving renal replacement therapy. The KNOW-CKD Phase II recruitment was started in 2019, with an enrollment target of 1500 subjects, focused on diabetic nephropathy and hypertensive kidney diseases in patients with reduced kidney function who are presumed to be at a higher risk of adverse outcomes. As of 2021, the KNOW-CKD investigators have published articles in the fields of socioeconomics, quality of life, nutrition, physical activity, renal progression, cardiovascular disease and outcomes, anemia, mineral bone disease, serum and urine biomarkers, and international and inter-ethnic comparisons. The KNOW-CKD researchers will elaborate a prediction model for various outcomes of CKD such as the development of end-stage kidney disease, major adverse cardiovascular events, and death.

• Journal of Preventive Medicine and Public Health
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• 제38권1호
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• pp.82-92
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• 2005

Objective : To evaluate the relationships among sociodemographic characteristics, health behaviors, levels of pros and cons and stages of change in Pap testing for uterine cervical cancer. Methods : A questionnaire survey was performed on 560 randomly sampled people who were assigned to participate in a Pap testing program by the National Cancer Screening Project in 2003' between 25 September and 10 October in Gyeonggi, Korea. Data about the behaviors and intentions of Pap testing, sociodemographic characteristics, health behaviors, and levels of acknowledged benefit (pros) and barrier (cons) for Pap testing was collected. The stages of change were grouped according to behaviors and intentions of Pap testing as passive, active, and relapse. Results : Logistic analysis between the passive and active groups showed that city dwellers, 'high' and 'middle' groups in terms of the individual s health belief, those who had undergone a health examination within the past 2 years, and those who had undergone hormone replacement therapy had a higher odds ratios to be in the active group. As the 'benefit' scores increased and the 'Unnecessity' scores decreased, the probabilities to be in the active group increased. According to the logistic analysis results between the active and relapse groups, those who were 60 years or older, members of the National Heath Insurance, and those who had not undergone a health examination within the past 2 years had a higher odds ratio to be in the relapse group. The 'Benefit' scores were not significant in this relationship. The probabilities of being in the relapse group increased as the Unnecessity and 'Shamefulness' scores increased. Conclusions : In conclusion, health planners should inform women in the passive group of the benefits and necessity of Pap testing. It would be better to reduce the barriers to the active group of undergoing Pap smear. This study might be a useful guide for future planning of Pap testing program.

• Preventive Nutrition and Food Science
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• 제20권3호
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• pp.204-209
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• 2015

To develop new type of sponge cake, the effects of partial (0~40%) replacement with Rubus coreanus powder (RCP) on the quality characteristics of sponge cakes were investigated. The pH level and moisture content ranged from 4.05~8.23 and 28.49~36.59, respectively, and significantly decreased upon addition of RCP (P<0.05). Baking loss rate and cake firmness significantly increased with higher RCP content in the formulation, whereas morphological characteristics of cakes such as height, volume, and symmetry indices significantly decreased (P<0.05). For crumb color values, $L^*$-and $b^*$-values significantly decreased while $a^*$-value significantly increased as a result of RCP substitution (P<0.05). Hedonic sensory results indicated that sponge cakes supplemented with 30~40% RCP showed the most favorable acceptance scores for most of the sensory attributes evaluated. Overall, Rubus coreanus sponge cake could be developed with comparable physicochemical qualities without sacrificing consumer acceptability.