• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1602-1610
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• 2005

In this study was investigated and analyzed of damage characteristics for infrastructures by typhoon that have been many occur. The objective Structures were the road and hydraulic structure. The road structure was included the cut-slopes, retaining walls and bridges. The hydraulic structure is divided with the dike, small-scale dam, reservoir and floodgate. The analysis result of the bridge damage cause is river bottom height increase and passage ability decrease. The principal damage reasons of the cut-slope structure are weakening the ground due to the localized torrential downpour and drainage defective. Also, the principal damage reasons of the small-scale dam, reservoir, dike and the floodgate are continuous collapse of dike beside the floodgate.And we divided a typhoon damage occurrence cause with artificial and natural. As the result of analysis, the many damage occurrence cause will be removed by system improvement and technical development.

• 동력기계공학회지
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• 제12권4호
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• pp.57-63
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• 2008

The last stage blade of the low pressure steam turbine remarkably affects turbine plant performance and availability Turbine manufacturers are continuously developing the low pressure last stage blades using the latest technology in order to achieve higher reliability and improved efficiency. They tend to lengthen the last stage blade and apply shrouds at the blades to enhance turbine efficiency. The long blades increase the blade tip circumferential speed and water droplet erosion at shroud is anticipated. Parts of integral shrouds of the last stage 40 inch blades were cracked and liberated recently in a combined cycle power plant. In order to analyze the root cause of the last stage blades shroud cracks, we investigated operational history, heat balance diagram, damaged blades shape, fractured surface of damaged blades, microstructure examination and design data, etc. Root causes were analyzed as the improper material and design of the blade. Notches induced by erosion and blade shroud were failed eventually by high cycle fatigue. This paper describes the root cause analysis and countermeasures for the steam turbine last stage blade shroud cracks of the combined cycle power plant.

• 품질경영학회지
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• 제51권4호
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• pp.735-749
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• 2023

Purpose: The purpose of this study is to derive solutions and prevent similar cases from occurring by analyzing the causes of cracks found in temperature cycling tests of rocket motor. Methods: By combining the results of the current state confirmation test, non-destructive test, domestic and foreign rocket motor comparison test, cutting test, and adhesion test according to the number of times to apply mold release agent, a Cause and Effect Diagram analysis was performed to derive the cause of cracks. Results: Through this study, 26 factors that could cause cracking in rocket motors during temperature cycling tests were identified. Through various additional test results, a total of five causes were identified, including chemical and structural design of the joint between the propellant and stress relief insert, omission of procedure in the manufacturing procedures, natural aging due to temperature, and load accumulation due to temperature changes. The fundamental cause was confirmed to be insufficient consideration of the release properties of the propellant and stress relief insert. Conclusion: During the design process, it was confirmed that this could be solved by structurally or chemically designing the insert so that it does not combine with the propellant, or by applying a mold release agent during the manufacturing process.

• 디지털융복합연구
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• 제12권8호
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• pp.77-84
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• 2014

TRIZ는 원래 러시아인인 알트슐러에 의해 개발되어 기술 분야의 문제 해결에 활용 되어 왔지만, 최근에는 Darrell Mann에 의해 비 기술 영역에도 적용이 되기 시작하였다. 국내에는 1995년 LG전자에서 최초로 도입하여 현재는 삼성, 포스코 등 많은 기업들이 문제 해결도구로 사용하고 있다. TRIZ 문제 해결 방법은 문제를 정의하고, RCA(Root Cause Analysis)를 통해 근본원인을 찾아내어 기술적 모순과 물리적 모순을 정의 하고 있다. TRIZ는 모순을 극복하는 것이 문제를 해결하는 것이다. 본 연구는 문제 해결 방법인 TRIZ 원리를 이용하여 비기술 분야인 물류 영역의 개선에 적용하고자 하였다. 실제 "L" 기업의 물류 재작업이라는 물류 운영 개선을 하기 위해 TRIZ 방법론 중 RCA(Root Cause Analysis)분석, 모순 정의, 40가지 발명원리를 사용하여 문제 해결을 위한 아이디어 도출 및 적용 하였다. 본 연구는 TRIZ를 비기술 분야에 활용하고자 하는 향후 연구자들에게 도움이 되고자 하였다.

• 한국화재소방학회논문지
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• 제30권4호
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• pp.73-81
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• 2016

정온전선은 평형 도체 사이에 반도전성 폴리머를 연속 압출 방식으로 충전시킨 후 양 도체 사이에 전기를 흐르게 함으로써 고분자에 의한 전열을 이용한 전기 발열체이다. 정온전선은 가격이 저렴하고 시공이 편리하기 때문에 겨울철 수배관의 동파방지용 열선으로 주로 사용되고 있다. 하지만 이러한 유용함에도 불구하고 구조적인 문제로 인하여 두 평형 도체의 절연이 파괴되는 경우에는 화재로 이어질 수도 있는 위험성이 존재하고 있다. 본 논문은 정온전선에 의한 화재현장을 조사하여 원인을 도출하는 방식으로 직접적인 원인을 추론하고자 하였으며, 결함수 분석을 통해 근본적인 문제를 파악해 보고자 하였다. 실제 냉동창고 화재현장을 조사하여 정온전선에 의한 화재원인을 추론한 결과 전선 말단 절연처리 결함에 의한 절연파괴인 것으로 판단되었다. 향후 이 결과는 안전활동 및 유사 화재원인조사 시에도 활용될 수 있을 것이다

• 한국화재소방학회논문지
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• 제31권4호
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• pp.111-118
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• 2017

본 논문은 반단선과 트래킹에 의한 복합적 전기화재의 위험성분석에 관한 연구이다. 먼저, 단일원인인 반단선에 의한 전기화재 위험성을 분석하기 위해 전선의 소선 수 및 정격전류의 변화에 따른 열적특성을 측정하였다. 또한, 그 후 복합적 원인에 의한 전기화재 위험성을 분석하기 위해 반단선 상태에서 추가적으로 가속트래킹 실험을 실시하여 반단선과 트래킹의 화재연관성을 확인하였다. 실험결과 반단선이 단일원인으로 작용할 때의 전류에 의해 발생된 기존 열적특성과 트래킹이 복합적으로 작용함으로써 전류가 크게 증가되어 열적특성이 더욱 뚜렷이 나타나 단일원인에서 발생되지 않았던 급격한 온도상승으로 인한 소선의 단선이 복합적 원인에서 나타났다. 즉, 기존의 반단선에 의한 전기화재 위험성보다 반단선과 트래킹이 복합적으로 작용될 경우 상대적으로 그 위험성이 크게 증가되는 것을 확인할 수 있었다.

• 한국안전학회지
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• 제37권3호
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• pp.9-15
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• 2022

The analysis of the causes of accidents in workplaces where machines and tools are used is essential to improve the effectiveness and efficiency of safety prevention policies in places of employment in Korea. The causes of workplace accidents are not fully understood mainly due to difficulties in analyzing available descriptive information. This study focuses on the automated accident cause analysis in workplaces based on the accident abstracts found in industrial accident reports written in an unstructured descriptive format. The method proposed in this paper is based on text data mining and uses the keyword search function of Excel software to automate the analysis. The analysis results indicate that the primary reason for the frequency of accidents is related to technical aspects at a stage in which dangerous situations occur in the workplace. Accidents due to managerial causes are typically observed when danger exists in the workplace; however, managerial actions play a more important role in reducing accident severity. A small company tends to use unsafe machines and devices, leading to further accidents due to technical causes, whereas managerial causes are more conspicuous as the company grows. To preclude the occurrence of accidents due to inadequate knowledge, the implementation of safety management and the provision of safety education to elderly workers at the early stage of their employment are particularly important for small companies with less than 100 workers.

• Asian Pacific Journal of Cancer Prevention
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• 제14권4호
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• pp.2259-2263
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• 2013

Background: Public use National Health and Nutrition Examination Survey (NHANES III) and NHANES III linked mortality data were here applied to investigate the association between health insurance coverage and all cause and all cancer mortality in adults. Patients and Methods: NHANES III household adult, laboratory and mortality data were merged. Only patients examined in the mobile examination center (MEC) were included in this study. The sampling weight employed was WTPFEX6, SDPPSU6 being used for the probability sampling unit and SDPSTRA6 to designate the strata for the survey analysis. All cause and all cancer mortalities were used as binary outcomes. The effect of health insurance coverage status on all cause and all cancer mortalities were analyzed with potential socioeconomic, behavioral and health status confounders. Results: There were 2398 sample persons included in this study. The mean age was 40 years and the mean (S.E.) follow up was 171.85 (3.12) person months from the MEC examination. For all cause mortality, the odds ratios (significant p-values) of the covariates were: age, 1.0095 (0.000); no health insurance coverage (using subjects with health insurance), 1.71 (0.092); black race (using non-Hispanic white subjects as the reference group) 1.43, (0.083); Mexican-Americans, 0.60 (0.089); DMPPIR, 0.82, (0.000); and drinking hard liquor, 1.014 (0.007). For all cancer mortality, the odds ratio (significant p-values) of the covariates were: age, 1.0072 (0.00); no health insurance coverage, using with health coverage as the reference group, 2.91 (0.002); black race, using non-Hispanic whites as the reference group, 1.64 (0.047); Mexican Americans, 0.33 (0.008) and smoking, 1.017 (0.118). Conclusion: There was a 70% increase in risk of all cause death and almost 300% of all cancer death for people without any health insurance coverage.

• Korean Journal of Radiology
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• 제23권10호
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• pp.998-1008
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• 2022

Objective: The present study aimed to assess the relationship between incidental abnormalities on thoracic computed tomography (CT) and mortality in a general screening population using a long-term follow-up analysis. Materials and Methods: We retrospectively collected the medical records and CT images of 840 participants (mean age ± standard deviation [SD], 58.5 ± 6.7 years; 564 male) who underwent thoracic CT at a single health promotion center between 2007 and 2010. Two thoracic radiologists independently reviewed all CT images and evaluated any incidental abnormalities (interstitial lung abnormality [ILA], emphysema, coronary artery calcification [CAC], aortic valve [AV] calcification, and pulmonary nodules). Kaplan-Meier analysis with log-rank and z-tests was performed to assess the relationship between incidental CT abnormalities and all-cause mortality in the subsequent follow-up. Cox proportional hazards regression was performed to further identify risk factors of all-cause mortality among the incidental CT abnormalities and clinical factors. Results: Among the 840 participants, 55 (6%), 171 (20%), 288 (34%), 396 (47%), and 97 (11%) had findings of ILA, emphysema, CAC, pulmonary nodule, and AV calcification, respectively, on initial CT. The participants were followed up for a mean period ± SD of 10.9 ± 1.4 years. All incidental CT abnormalities were associated with all-cause mortality in univariable analysis (p < 0.05). However, multivariable analysis further revealed fibrotic ILA as an independent risk factor for all-cause mortality (hazard ratio, 2.52 [95% confidence interval, 1.02-6.22], p = 0.046). ILA were also identified as an independent risk factor for lung cancer or respiratory disease-related deaths. Conclusion: Incidental abnormalities on screening thoracic CT were associated with increased mortality during the long-term follow-up. Among incidental CT abnormalities, fibrotic ILA were independently associated with increased mortality. Appropriate management and surveillance may be required for patients with fibrotic ILA on thoracic CT obtained for general screening purposes.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.718-723
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• 2003

The acceptance test of KTX has been performed in Korea. During the test lateral vibration of carbody over the accepted value called sway was found. Many activities have been taken to find the cause of the vibration and the counter-measure. KTX has 20 car trainset formation whose trailer cars are linked by articulate bogies. So this study is performed to see the effects of long trainset formation on vehicle dynamics and the train stability by 16 car vehicle model. Firstly the reliable vehicle model which shows well the tendencies appeared in the tests on the high speed test line is required to find the cause of lateral vibration and the countermeasure. Vehicle model was made for the analysis with VAMPIRE. The analysis results show that secondary air spring lateral stiffness is the most significant parameter to cause carbody lateral vibration. Mode analysis results show that the least damped mode shape is similar to the vibration pattern shown in the tests that the amplitude of the motion increases along the train set and decreases in the tail part. The lateral vibration was appeared at the speed range between 100km/h and 200km/h and disappeared at the low speed and the high speed.