• 대한기계학회논문집A
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• 제38권10호
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• pp.1185-1191
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• 2014

가스터빈 블레이드는 증기터빈 블레이드와 달리 냉각홀 및 냉각유로를 포함한 복잡한 형상으로 되어 있으며 복합화력의 운전특성에 따라 반복적이거나 지속적인 열-기계 하중 조건 하에서 운전된다. 따라서 블레이드는 운전시간에 따라 균일하지 못한 온도 분포나 응력 분포를 보이며, 이는 크리프나 열-기계피로 손상을 유발하며, 결국 가스터빈 블레이드의 수명을 단축시킨다. 결국 다양한 운전 조건에 따라 발생하는 응력을 정확하게 계산하는 것은 설비의 신뢰성을 보장하고 나아가 블레이드와 같은 고온 부품의 정확한 수명을 평가하는데 무엇보다 중요하다. 최근 들어 컴퓨터 기능이 좋아지고 상용 소프트웨어의 성능이 향상되어 실증 시험에 대한 대안으로 유동, 열 및 구조해석을 연결하는 전산해석이 많이 사용되고 있다. 본 논문에서는 가스터빈 실 운전조건을 고려하여 유동-열-구조 해석 기법을 연계하는 유체-구조 연성해석을 통해 블레이드 온도 및 응력분포를 계산하였다. 또한 해석 결과를 토대로 대표적인 손상기구인 크리프 및 열-기계 피로 손상 모델을 이용하여 블레이드의 수명을 평가하였다.

• Asian Journal of Atmospheric Environment
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• 제5권2호
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• pp.121-133
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• 2011

This study suggests criteria to conduct a risk assessment of VOCs and formaldehyde in uncontrolled public facilities. Pollutants and facilities were selected based on two years of monitoring data and exposure scenarios in 573 uncontrolled public facilities, composed of 10 types of public institutions. With the exception of social welfare facilities, lifetime ECRs of formaldehyde and benzene in each facility were higher in employees than in users, except in social welfare facilities. In social welfare facilities, the risk of benzene for users ($1{\times}10^{-5}$) was higher than that of workers ($1{\times}10^{-6}$) because facility users live in the facility 24 hours per day, compared to workers who spend an average of 8 hours per day in the facility. The risk of benzene to workers in restaurants, academies, performance halls, internet cafe and pubs were estimated as high as $1{\times}10^{-4}$ and the risk to workers in the theaters and karaoke bars were recorded as $1{\times}10^{-5}$. Because lifetime ECRs of carcinogens exceeded $1{\times}10^{-4}$ for workers and users in most facilities, risk management of formaldehyde and benzene in these facilities is necessary. Although HQs of toluene and xylenes did not exceed 1.0, their HQs did exceed 0.1 in some facilities, so they were evaluated as potentially harmful materials. Additionally, criteria for health protection in IAQ by facility are suggested at $60-100\;{\mu}g/m^3$ for formaldehyde, $400-500\;{\mu}g/m^3$ for TVOCs, $10-20\;{\mu}g/m^3$ for benzene, $150-170\;{\mu}g/m^3$ for toluene and $100\;{\mu}g/m^3$ for xylenes, based on the survey on IAQ and HRA methodology. The excess rates of IAQ to health protection criteria in all facilities were 16% for formaldehyde, 8% for TVOCs and benzene, 9% for toulene, and 5% for xylenes.

• 한국압력기기공학회 논문집
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• 제7권2호
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• pp.14-20
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• 2011

The end of design lifetime for Wolsong unit 1 will be reached on 20th November in 2012. So the license renewal documents for the continuous operation of Wolsong unit 1 is under reviewing now. Major components of primary system such as pressure tubes, feeder pipes including delayed neutron monitoring system tubing are being replaced and many components of secondary system are also being repaired. In this paper, the assessment on the wear degradation of delayed neutron monitoring system tubing(on the other hand, DN tube was called) was performed for the ageing management of the same component. The wear defects of this component was one of causes that resulted in heavy water leakage accidents. Therefore design specifications of Wolsong uint 1 and heavy water leakage accidents of pressurized heavy water reactors were reviewed and causes of wear defect for DN tubes were analyzed. Wear propagation equations based on the heavy water leakage history were made and the proper repairing time was possible to be expected if the continued operation was considered. Finally design change items of DN tubes that were conducted for the long term operation of Wolsong unit 1 are introduced.

• Advances in environmental research
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• 제6권4호
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• pp.241-254
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• 2017

This study was conducted to investigate the levels of heavy metals in twelve species of vegetables and assessment of health risk. Samples were analyzed using inductively coupled plasma mass spectrometer (ICP-MS). The ranges of Cr, Ni, Cu, As, Cd and Pb in vegetables species were 0.37-5.4, 0.03-17, 0.35-45, 0.01-2.6, 0.001-2.2, and 0.04-8.8 [mg/kg, fresh weight (fw)], respectively. The concentrations of As, Cd and Pb in most vegetable species exceeded the maximum permissible levels, indicating unsafe for human consumption. Health risks associated with the intake of these metals were evaluated in terms of estimated daily intake (EDI), and carcinogenic and non-carcinogenic risks by target hazard quotient (THQ). Total THQ of the studied metals from most of the vegetables species were higher than 1, indicated that these types of vegetables might pose health risk due to metal exposure. The target carcinogenic risk (TR) for As ranged from 0.03 to 0.48 and 0.0004 to 0.025 for Pb which were higher than the USEPA acceptable risk limit (0.000001) indicating that the inhabitants consuming these vegetables are exposed to As and Pb with a lifetime cancer risk. The findings of this study reveal the health risks associated with the consumption of heavy metals through the intake of selected vegetables in adult population of Bangladesh.

• 대한기계학회논문집A
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• 제41권9호
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• pp.887-895
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• 2017

본 논문에서는 일반적으로 문틀과 문짝을 연결하여 개폐시 작동하는 부품인 힌지의 가속수명시험법에 대한 연구이다. 힌지는 사용하는 용도에 따라 구조와 고장모드가 상이하며 본 연구에서는 전자파 차폐시설에 사용되는 개폐장치 구성품 중 하나인 힌지에 대해서 고장모드를 분석하고 현장작동조건에서의 이론적 검증과 시험장비에 대한 타당성을 분석하였다. 그리고 형상모수와 가속지수의 추정을 통한 특성수명 예측을 위한 가속수명시험법을 설계하였다.

• Smart Structures and Systems
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• 제5권4호
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• pp.415-426
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• 2009

This study focuses on the concept of multi-scale wireless sensor networks for damage detection in civil infrastructure systems by first over viewing the general network philosophy and attributes in the areas of data acquisition, data reduction, assessment and decision making. The data acquisition aspect includes a scalable wireless sensor network acquiring acceleration and strain data, triggered using a Restricted Input Network Activation scheme (RINAS) that extends network lifetime and reduces the size of the requisite undamaged reference pool. Major emphasis is given in this study to data reduction and assessment aspects that enable a decentralized approach operating within the hardware and power constraints of wireless sensor networks to avoid issues associated with packet loss, synchronization and latency. After over viewing various models for data reduction, the concept of a data-driven Bivariate Regressive Adaptive INdex (BRAIN) for damage detection is presented. Subsequent examples using experimental and simulated data verify two major hypotheses related to the BRAIN concept: (i) data-driven damage metrics are more robust and reliable than their counterparts and (ii) the use of heterogeneous sensing enhances overall detection capability of such data-driven damage metrics.

• Structural Engineering and Mechanics
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• 제91권2호
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• pp.123-133
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• 2024

The assessment of seismic behavior and seismic performance of ageing Sarıyar concrete gravity dam constructed on Sakarya River in Türkiye is the main focus of this paper. For this purpose, the impact of sediment domain, ageing of concrete material under the impact of chemical and mechanical actions, and dam-water-sediment interaction are included in the two-dimensional (2D) finite element (FE) model developed in FORTRAN 90 environment. In the FE model, the dam and age dependent sediment domains are modeled by solid elements, while reservoir domain is modeled by Lagrangian fluid elements. The radiation of reflected waves to the unbounded water domain is modeled by infinite Lagrangian fluid elements, while unbounded sediment domain is modeled by infinite solid elements. The coupled system was assumed to be under the simultaneous impact of Vertical (V) and Horizontal (H) ingredients of 1976 Koyna earthquake and the coupled system was analyzed in Laplace domain by direct method. Due to the deterioration of the concrete, the H and V displacement responses together with the fundamental period of the body, elongate throughout the lifetime and this reduce the seismic safety of the dam. It was deduced that the ageing dam body will not experience major damages under the Koyna earthquake both at the earlier and later ages. Furthermore, at the heel of the dam, the hydrodynamic pressure responses are decreased by rising the sediment domain depth.

• International Journal of Heart Failure
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• 제6권3호
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• pp.93-106
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• 2024

Being commonly diagnosed in elderly women and associated with comorbidities as well as ageing-related cardio-vascular changes, heart failure with preserved ejection fraction (HFpEF) has been recently considered as a distinct cardiogeriatric syndrome. Frailty is another frequent geriatric syndrome. HFpEF and frailty share common underlying mechanisms, often co-exist, and represent each other's risk factors. A threshold of 65 years old is usually used to screen patients for both frailty and HFpEF in research and clinical settings. However, both HFpEF and frailty are very heterogenous conditions that may develop at younger ages. In this review we aim to provide a broader overview on the coexistence of HFpEF and frailty throughout the lifetime. We hypothesize that HFpEF and frailty patients' profiles (young, elderly, superaged) represent a continuum of the common ageing process modified by cumulative exposure to risk factors resulting to a presentation of HFpEF and frailty at different ages. We believe, that suggested approach might stimulate assessment of frailty in HFpEF assessment and vice versa regardless of age and early implementation of targeted interventions. Future studies of pathophysiology, clinical features, and outcomes of frailty in HFpEF by age are needed.

• 한국지하수토양환경학회지:지하수토양환경
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• 제12권1호
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• pp.64-72
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• 2007

토양매체중의 오염물질들은 다양한 경로를 통해 인체나 생태계에 노출되어 위해성 문제를 유발하고 있다. 토양위해성평가(Soil Risk Assessment)는 토양오염물질로 인한 악영향의 개연성을 정량적으로 평가하는 과정으로, 유해성 확인(Hazard Identification), 용량-반응평가(Dose-Response Assessment), 노출평가(Exposure Assessment), 그리고 위해도 결정(Risk Characterization)의 4가지 단계적 과정으로 이루어진다. 이중 노출평가과정에서 매우 중요하게 작용하는 노출인자(Exposure Factor)는 토양오염물질의 인체노출량을 산정하는데 필수적인 요소로, 미국, 유럽국가 등 선진국에서는 나라별 상황에 적절한 노출인자를 사용하고 있으나, 우리나라는 아직 국내에 적용하기 적합한 노출 인자에 대한 연구가 매우 부족한 실정이다. 본 연구에서는 토양오염 위해성평가를 위한 국가별 노출인자를 비교분석하고, 이를 토대로 국내상황에 적용가능한 노출인자를 제시하였다. 국가별 노출인자 연구는 미국 Environmental Protection Agency, 영국 Environmental Agency, 네덜란드 RIVM, 호주, 그리고 독일에서 적용되고 있는 노출인자값에 대해 노출인자별로 총괄적인 비교분석을 수행하였다. 또한 국가별 비교분석연구와 국내에서 제시된 노출인자 자료를 종합하여, 국내자료가 없는 경우 외국에서 보편적으로 적용하고 있는 인자값을 국내 적용 타당성을 고려하여 제시하였다. 본 연구에서 고려된 노출인자 조사항목은 평균수명, 노출기간, 노출빈도, 체중, 체표면적(또는 노출체표면적), 피부흡수계수(Skin Absorption Factor), 토양-피부간 흡착계수(Soil-Skin Adherence Factor), 음용수 섭취량, 호흡률, 토양 섭취량 그리고 농작물 섭취량 등이다. 본 연구는 오염토양의 위해성평가를 수행할 때 국내 상황을 고려한 노출평가에 필요한 기반연구가 될 것이다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.184.1-184.1
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• 2010

In order to research the way to evaluate wind resource without actual Met Mast data, this paper has been carried out on the southeastern region of Jeju island, Korea. Although wind turbine has been an economical alternative energy resource, misjudging the prediction of lifetime or payback period occurs because of the inaccurate assessment of wind resource and the location of wind turbine. Using WindPRO(Ver. 2.7), a software for wind farm design developed by EMD from Denmark, wind resources for the southeastern region of Jeju island was analyzed, and the performance of WindPRO prediction was evaluated in detail. Met Mast data in Su-san 5.5Km far from Samdal wind farm, AWS in Sung-san 4.5km far from Samdal wind farm, and Korea Wind Map data had been collected for this work.