• 한국전산구조공학회논문집
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• 제15권4호
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• pp.703-713
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• 2002

최근에 불연속 근사변위함수와 보조받침을 이용한 특이기저함수를 도입하여 균열의 불연속성과 특이성을 구현한 개선된 EFG(Element-Free Galerkin) 균열해석기법이 제안되었다. 개선된 EFG 균열해석기법은 균열의 성장에 따른 해석모형의 수정 없이도 높은 정확도로 균열전파해석을 수행할 수 있지만, 다른 무요소법과 마찬가지로 해석결과가 사용되는 해석계수에 의존하게 된다. 본 연구에서는 개선된 EFG 균열해석기법에서 사용하는 해석계수 즉, compact 받침 크기, 팽창계수, 선단주변에서의 형상함수의 평활화, 보조받침을 사용하는 절점개수가 수치해석 결과에 미치는 영향을 분석하였다. 균열문제에 대한 patch 시험을 통해 응력에 대한 L₂오차노름과 응력확대계수를 산정하여 해석계수의 영향을 분석하였으며, 그 결과는 해석계수의 선택에 대한 지침으로 제시된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.697-700
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• 2008

본 논문은 유변학을 이용한 합리적인 크리프 예측 모델의 개발을 목표로 한다. 유변학은 응력에 의해 물질에 변형이 유발되었을 때, 변형과 응력 사이의 관계를 규명하는 학문으로 콘크리트와 같은 다공성의 점탄성 구조체의 변형 규명에 효과적이다. 본 논문에서 제안된 모델은 시간 의존성 여부와 발생 메커니즘에 따라 탄성거동, 장기크리프, 시간 의존적 단기크리프 그리고 시간 독립적 단기크리프로 나뉘며, 이와 같은 현상의 분류는 실제 실험값의 시간 경과에 따른 변형 양상을 근거로 한 것이다. 각 부분의 계수 추정 과정에서는 이론(미세프리스트레스 고체화 이론, Microprestress-solidification theory) 및 설계기준(CEB-FIP MC R99)을 최대한 활용하여 모델의 합리성의 높일 수 있도록 하였으며, 부득이하게 이론적 접근이 어려운 경우에는 제한적으로 수치적 접근을 시도하였다. 끝으로 수립된 모델을 실제 실험 데이터에 적용한 결과를 기존의 기준식 및 이론식의 적용 결과와 비교 평가 하였다.

• 대한기계학회논문집 C: 기술과 교육
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• 제3권1호
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• pp.37-44
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• 2015

본 연구에서는 유한요소해석으로 냉장고 낙하충격에 대한 하힌지의 변형거동을 분석했다. 우선 하힌지 및 하부포장재 동적물성 확보를 위해 각각 속도 별 굽힘시험과 압축시험을 수행했다. 이어 시험에서 얻은 하중-변위곡선과 유사한 거동을 나타내는 하힌지 및 하부 포장재의 유동응력식을 역공학으로 얻었다. 확보한 물성데이터를 이용해 LS-DYNA로 낙하해석을 수행해, 낙하시 냉장고 자체 및 하힌지 변형거동을 분석했다. 최종적으로 3D 측정으로 분석한 실 냉장고 낙하시험으로, 낙하해석 모델의 유효성을 검증했다. 본 연구에서 제시한 해석모델은 추후 하힌지 및 포장재의 내 충격설계 등에 효과적으로 활용될 수 있을 것이다.

• 한국직업건강간호학회지
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• 제14권1호
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• pp.24-33
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• 2005

Purpose: This cross-sectional study was to find out smoking condition, smoking related knowledge and attitudes of white color workers to provide baseline data which were to develope smoking cessation programs. Methods: The subjects were 303 workers in G-city. Data were collected from July 1st to Aug. 31st 2003 by self-reported questionnaire. Data were analyzed by descriptive statistics, t-test, ANOVA, and Duncan's multiple comparison test, using SAS-pc 8.0 version. Results: Average age of the laborers was 32.3 years, and 50.7% of male were smoking currently, and 2.4% of female were so. Starting age of smokers was average 20.1 and smoking period was average 12.4 years. Majority of smokers smoked more than one pack of cigarettes in a day. Average points of nicotine dependency was 3.9 out of 10 and 12.5% were more than 7. Those who wanted to 'quit smoking very soon' and 'decided to quit smoking right now' were 29.1%. But those who got any helps and advices from professional experts in smoking cessation were 6.4%. 83.5% of the smokers had tried to quit smoking but failed due to their stress(44.6%), lack of will(36.6%) etc. Laborers knowledge related smoking score were average 11points out of 15, and attitudes were average 75.7points out of 125. Smokers showed significantly low knowledge(p=.012), and more allowing attitudes(p=.001). Conclusions: The smoking cessation programs for the workers should consist of stress management skills, and strengthened willingness. And should be run the program for those who want to 'quit smoking very soon' and 'decided to quit smoking right now' first of all.

• 한국기계가공학회지
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• 제17권5호
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• pp.64-69
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• 2018

Clear aligners are popular in the field of dental orthodontic treatment because they offer a discreet alternative to braces due to their use of transparent materials. They are formed from flat transparent polymer materials by hot pressed molding. It is necessary to know the mechanical properties of the polymer materials to be able to form the exact shapes of the clear aligners. However, this information is not publicly available. In this study, we present a method to reliably measure the mechanical properties of clear aligner polymer materials and analyze the factors effecting these mechanical properties. First, we surveyed standards related to the mechanical properties of polymer materials to obtain reliable data. Consequently, ISO 527 was selected for use in this study because of the size and thickness of the flat transparent polymer material. The uniaxial tensile tester was constructed and it was verified whether displacement of a crosshead could be regarded as a displacement of gauge-length by optical analysis. Uniaxial tensile tests of three thicknesses from three different companies were performed and each engineering stress-strain curve was measured. Tensile strengths and elastic moduli were obtained by analysis of the stress-strain curves. The tensile strength and elastic modulus of ISO 527 was found to be approximately 50MPa and 2.3GPa, respectively. Both values showed material and thickness dependency.

• 한국유체기계학회 논문집
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• 제19권1호
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• pp.37-44
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• 2016

In this study, a parametric study of a centrifugal pump with double volute has been performed numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport model was selected as turbulence closure through turbulence model test. The finite volume method and unstructured grid system were used for the numerical analysis. The optimal grid system in the computational domain was determined through a grid dependency test. The expansion coefficient, circumferential and radial starting positions and length of divider were selected as the geometric parameters to be tested. And, the hydraulic efficiency and the radial thrust coefficient were considered as performance parameters. It was found that the radial thrust and hydrualic efficiency are more sensitive to the expansion angle and circumferential starting position of the divider than the other geometrical parameters.

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.151-159
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• 2020

This study aimed to investigate the performance characteristics of vertical axis turbine of tidal energy convertor. Three-dimensional Reynolds-averaged Navier-Stokes equation with shear stress transport turbulence model has been solved to analyze the fluid flow of the vertical axis turbine. The hexahedral grids have been used to construct the computational domain and the grid dependency test has been performed to find the optimum grid system. Four steps have been carried out to design the vertical axis turbine of the 100 kW class tidal energy convertor.

• 대한간호학회지
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• 제46권5호
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• pp.663-674
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• 2016

Purpose: The purposes of this study were to develop and test a prediction model for caregiving experiences including caregiving satisfaction and burden in dementia family caregivers. Methods: The stress process model and a two factor model were used as the conceptual frameworks. Secondary data analysis was done with 320 family caregivers who were selected from the Seoul Dementia Management Survey (2014) data set. In the hypothesis model, the exogenous variable was patient symptomatology which included cognitive impairment, behavioral problems, dependency in activity of daily living and in instrumental activity of daily living. Endogenous variables were caregiver's perception of dementia patient's unmet needs, caregiving satisfaction and caregiving burden. Data were analysed using SPSS/WINdows and AMOS program. Results: Caregiving burden was explained by patient symptomatology and caregiving satisfaction indicating significant direct effects and significant indirect effect from unmet needs. The proposed model explained 37.8% of the variance. Caregiving satisfaction was explained by patient symptomatology and unmet needs. Mediating effect of unmet needs was significant in the relationship between patient symptomatology and caregiving satisfaction. Conclusion: Results indicate that interventions focusing on relieving caregiving burden and enhancing caregiver satisfaction should be provided to caregivers with high levels of dementia patients' unmet needs and low level of caregiving satisfaction.

• Child Health Nursing Research
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• 제4권1호
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• pp.128-149
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• 1998

Cigarette smoking has been identified as the single most important source of preventable morbidity and mortality. Smoking behavior varies each individual, so individuality & subjectivity of smoking behavior must be specially focused upon to understand smoking behavior. The purpose of this study was to find attitudes of university students in the prediction of smoking behavior. Q-Methodological method was used as a research design and data were collected during the period from Jan.1, 1997 to Feb. 28, 1998. As the research method, Q-statements were collected through in- depth interviews and a literature review. For the study 33 Q-statements were selected. There were 45 university students as subjects for the research. The 45 university students sorted the 33 statements using the principle of Forced Normal Distribution. The principle of Forced Normal Distribution, which has nine scales to measure the individual opinions, Pc Quanl program was used for analysis and Q-factors were analyzed by using principal component analysis. According to the results of this study, there were four categories of opinion about the smoking behavior in university students. The first type is seeking the habitual dependency. The second type is seeking the stress relief : The third type is seeking the active disapproval : The fourth type is seeking the self control. As a result, The meaning of the smoking behavior is affected by perceived subjective experience, so we need to understand each persons meaning of the smoking behavior and to develop appropriate nursing interventions based on the typology of smoking behavior. Finally, The result of the study will provide basic data for smoking prevention and cessation program.

• 한국수소및신에너지학회논문집
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• 제31권3호
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• pp.314-321
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• 2020

In this work, a preliminary design of an inlet guide vane and runner for developing a 2.5 kW hydraulic turbine was conducted by using computational fluid dynamic analysis. Three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used to analyze the fluid flow in the hydraulic turbine. The hexahedral grid system was used to construct computational domain, and the grid dependency test was performed to obtain the optimal grid system. Velocity triangle diagram considering the flow angles of the inlet guide vane and runner was analyzed to obtain a basic geometry of the inlet guide vane and runner. Through modification of the preliminary design, the hydraulic performances of the turbine have improved under overall drop conditions. Especially, the efficiency and power of the turbine increased by 0.95% and 1.45%, respectively, compared to those of the reference model.