• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.703-713
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• 2002

Recently, an improved EFG(Element-Free Galerkin) crack analysis technique, which includes a discontinuous approximation and a singular basis function on the auxiliary supports, was developed. The technique is able to accurately analyze the crack propagation problem without any modification of the analysis model; however, it shows some dependency on the analysis parameters used. In this study, the effect of analysis parameters such as the size of compact support, dilation parameter, the smoothness of shape function around the crack tip, and the number of node using auxiliary supports on the accuracy of solution has been investigated. Through a patch test with a crack, relative L₂ error norm of stresses and the stress intensity factor were computed and compared for various analysis parameters and the results were presented as guidelines for adequate choice of analysis parameters.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.697-700
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• 2008

The object of this paper is to propose a logical prediction model of a concrete creep using rheology. Rheology is the study on the flow and stress relationship of matter under the influence of an applied stress. It is also estimated as an effective theory to describe concrete long-term deformations. According to a time dependency and a mechanism of occurrence, the proposed creep model was divided into four components, such as an elastic deformation, a long-term creep, a time dependent short-term creep and a time independent short-term creep. Evaluation on an actual creep deformation pattern by time passage confirmed these classification. In order to approve a rationality of the proposed model, most coefficients of each components were derived by the microprestresssolidification theory and design codes. Numerical approaches were also used when it was restricted within narrow limits. Finally, the proposed rheolgical model was verified by actual creep test results and compared with common methods.

• Transactions of the KSME C: Technology and Education
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• v.3 no.1
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• pp.37-44
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• 2015

In this paper dynamic deformation of lower hinge of refrigerator is simulated using dynamic finite element analysis while refrigerator is being dropped. The flow stress curves considering velocity dependency of hinge and lower packing material are determined through bending test and compression test at several dropping speeds. The determined material properties and flow stress from reverse engineering were used as input data for refrigerator's drop test using a dynamic finite element analysis software LS-DYNA. Additionally the result between CAE and 3D deformation measurement from real refrigerator drop test are compared and the result shows that the proposed analysis model is very useful to design lower hinge and lower packing endurable to the impulsive drop impact.

• Korean Journal of Occupational Health Nursing
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• v.14 no.1
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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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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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.

• The KSFM Journal of Fluid Machinery
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• v.19 no.1
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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.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.1
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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.

• Journal of Korean Academy of Nursing
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• v.46 no.5
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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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• v.4 no.1
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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.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.3
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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.