• Structural Engineering and Mechanics
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• 제15권3호
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• pp.345-365
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• 2003

The adoption of fibre reinforced polymer (FRP) rebars (whose behaviour is elastic-brittle) in reinforced concrete (RC) cross sections requires the assessment of the influence of time-dependent behaviour of concrete on the load-carrying capacity of these sections. This paper presents a method of computing the load-carrying capacity of sections that are at first submitted to a constant long-term service load and then overloaded up to ultimate load. The method solves first a non-linear visco-elastic problem, and then a non-linear instantaneous analysis up to ultimate load that takes into account the self-equilibrated stress distribution previously computed. This method is then adopted to perform a parametric analysis that shows that creep and shrinkage of concrete increase the load-carrying capacity of the cross section reinforced with FRP and allows for the suggestion of simple design rules.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.308-314
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• 1997

Shrinkage and creep are the fundamental properties of concrete. These long term deformations can be seen as bothersome(increased deflection) or can be seen as reduction of compressive stress of prestressed concrete. Steel fibers advance the mechanical properties of concrete:tensile strength, ductility, flexural strength, fracture toughness, and post-cracking resistance, etc...Silica fume is pozzolanic material which combines with hydrated lime to generate silicate materials which increase the compressive strength and reduce somewhat the creep of concrete. This paper is the result of the long-term deformation by silica fume and steel fibers with varying percentages.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.1326-1331
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• 2006

The precast concrete deck is one of suitable solutions for replacement and new construction in urban area. However, the precast concrete deck could be a weak point of the steel plate girder bridges structurally due to the connections between precast panels in the longitudinal direction. Thereafter, it is necessary for improvement of durability and load carrying capacity to introduce the prestress force in the longitudinal direction Some cracks of connections at the precast concrete deck may be occurred due to live loads, the difference of temperature and long-term effects. The shrinkage and creep of concrete may significantly affect long-term behaviors which occur tensile stresses at the precast concrete deck of steel plate girder bridges. In this study, the time-dependant analysis program has been developed to determine the initial prestress force in the longitudinal direction considering loss of stress at the precast concrete deck. Also it has been estimated the initial prestress force by construction stages and shapes of girder.

• 한국콘텐츠학회논문지
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• 제21권1호
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• pp.710-721
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• 2021

본 연구의 목적은 요양병원 간호사가 경험하는 임종간호 대처 경험의 구조를 규명하여 경험의 의미를 파악, 기술하고 이해하는 것이다. 현상학적인 연구 방법을 이용하여 요양병원에 근무하는 간호사 16명의 임종간호 대처 경험을 심층적으로 면담하였고, Colaizzi가 제시한 방법으로 분석하였다. 요양병원 간호사의 임종간호 대처 경험은 3개의 범주와 15개의 주제모음으로 구조화하여 규명할 수 있었다. 참여자들의 임종간호 경험의 세 범주는 '임종환자를 돌보는 요양병원 간호사의 태도', '임종간호 스트레스', '임종간호 대처'이었다. 요양병원 간호사의 임종간호 태도를 긍정적으로 변화시키고, 임종간호 스트레스를 줄이기 위한 실제적이고 체계적인 교육이 필요하다. 더불어 대처 능력을 향상할 수 있는 프로그램이나 전문가 상담과 같은 프로그램의 운영을 제언한다.

• 방사성폐기물학회지
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• 제19권2호
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• pp.205-214
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• 2021

Currently, the interim storage pools of spent fuels in South Korea are expected to become saturated from 2024. It is required to prepare an operation plan of a domestic dry storage facility during a long-term period, with the researches on safety evaluation methods. This study modified the FRAPCON code to predict the spent fuel integrity evaluation such as the axial cladding temperature, the hoop stress and hydrogen distribution in dry storage. The cladding temperature in dry storage was calculated using the COBRA-SFS code with the burnup information which was calculated using the FRAPCON code. The hoop stress was calculated using the ideal gas equation with spent fuel information such as rod internal pressure. Numerical analysis method was used to calculate the degree of hydrogen diffusion according to the hydrogen concentration and temperature distribution during a dry storage period. Before 50 years of dry storage, the cladding temperature and hoop stress decreased rapidly. However, after 50 years, they decreased gradually and the cladding temperature was below 400 K. The initial temperature distribution and hydrogen concentration showed a parabolic line, but hydrogen was transferred by the hydrogen concentration and temperature gradient over time.

• Geomechanics and Engineering
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• 제34권1호
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• pp.43-49
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• 2023

Knowledge of minimum horizontal stress (S_hmin) is a significant step in determining full stress tensor. It provides crucial information for the production of sand, hydraulic fracturing, determination of safe mud weight window, reservoir production behavior, and wellbore stability. Calculating the S_hmin using indirect methods has been proved to be awkward because a lot of data are required in all of these models. Also, direct techniques such as hydraulic fracturing are costly and time-consuming. To figure these problems out, this work aims to apply the long-short-term memory (LSTM) algorithm to S_hmin time-series prediction. 13956 datasets obtained from an oil well logging operation were applied in the models. 80% of the data were used for training, and 20% of the data were used for testing. In order to achieve the maximum accuracy of the LSTM model, its hyper-parameters were optimized significantly. Through different statistical indices, the LSTM model's performance was compared with with other machine learning methods. Finally, the optimized LSTM model was recommended for S_hmin prediction in the well logging operation.

• 한국노년학
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• 제31권2호
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• pp.277-290
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• 2011

이 연구는 노인장기요양 인력의 직무 스트레스와 직무 만족이 이직 의도에 미치는 영향을 살펴보고, 이들의 이직 의도를 감소시키기 위한 제언을 하고 있다. 장기요양서비스를 제공하는 인력의 높은 이직률이 노인들에 대한 서비스 연속성과 서비스 질을 방해하고 있기 때문에 이직에 대한 해결책이 필요하다. 연구 대상은 전남지역 노인장기요양기관에 근무하는 사회복지사, 간호사, 요양보호사를 포함하는 직원 235명이다. 조사 기간은 2009년 7월 1일부터 10일까지 진행하였고, 자료수집은 자기기입식 방법의 설문지를 활용하여 수집하였으며, 분석방법으로 SPSS 12.0을 이용하여 회귀분석을 실시하였다. 이 연구에서 사용한 직무스트레스 척도는 MBI의 정서적 탈진 척도롤 활용하였고, 직무 만족은 한국노동패널의 전반적 직무만족도 척도를 활용하였으며, 이직 의도는 조직구성원의 자발적 이직 의도를 측정하는 척도를 활용하였다. 분석 결과에 의하면, 사회인구학적 특성으로 연령, 교육수준, 직위, 기관위치 등의 변수가 유의미한 영향을 미쳤고, 직무 스트레스와 직무 만족 변수도 이직 의도에 유의미한 영향을 끼쳤다. 연구 결과를 통해 이직 의도를 예방하기 위하여 직무 스트레스를 줄이고, 직무 만족을 높이는 전략이 필요함을 확인하였다. 결론으로 장기요양 인력의 이직 의도를 예방하기 위한 제도적 실천적 함의를 제언하였다.

• 대한조선학회논문집
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• 제34권2호
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• pp.75-84
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• 1997

본 연구에서는 스펙트럼 해석법에 기초한 새로운 개념의 정밀한 선체구조 피로강도평가 시스템을 개발하였으며 membrane 방식 LNG 운반선을 대상으로 하여 수치계산을 수행함으로써 그 효용성을 검증하였다. 선체에 작용하는 파랑하중을 스트립 이론으로 직접계산하고 3차원 정밀 구조해석과 영향계수 개념을 바탕으로 Miner 법칙에 의한 누적손상도를 계산하여 설계기준과 비교, 검토하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.29-33
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• 2002

A procedure of free span and fatigue analysis of offshore pipelines was made per DNV-RP-F105, 2002. The new method includes the axial force and deflection load in pipelines. The screening criteria were used to calculate the allowable span lengths. The screening criteria allow small amplitudes of vortex-induced vibration due to wave and current loading. However, the induced pipe stress is very small and usually below the limit stress of a typical S-N curve. A simplified method was established to calculate the fatigue damage due to long-term current distribution. The long-term current statistics was assumed with a 3-parameter Weibull distribution. The fatigue damage was estimated for the span lengths obtained from the screening criteria for various conditions. Sample calculations show the effect of axial force for various boundary conditions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.562-563
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• 2005

In case of aged porcelain, the failure in basic performance tests happened in cool-heat tests. Based on this characteristic, we studied the method predicting failure phenomena through more severe accelerated cool-heat ageing and accelerating thermal mechanical performance tests. Test results indicated that the thermal stress by temperature gradient was more severe parameter than thermal stress by quenching cycles within a category of standard or accelerating methods. And there is no the deterioration of statistic strength, but the deterioration of strength according to accelerating tests is serious.