• 대한기계학회논문집B
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• 제23권10호
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• pp.1229-1239
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• 1999

A computational study on unsteady compressible flows has been performed by adopting a low Reynolds number $k-{\omega}$ turbulence model in conjunction with dual time stepping scheme. An explicit four-stage Runge-Kutta scheme for the Navier-Stokes equations and an approximate factorization scheme for the $k-{\omega}$ turbulence model equations are used. Computational results obtained for blade surface pressure distributions in the process of rotor-stator interaction in a turbine stage are in good agreement with extant experimental data. The effects of the wake from the stator on the boundary-layer transition over the rotor blade surface are discussed by showing that high intensity turbulence of the stator wake induces an early transition.

• Nuclear Engineering and Technology
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• 제27권4호
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• pp.503-517
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• 1995

강제대류 천이비등 열유속을 보다 실제 적으로 예측하기 위한 역학적 모델을 개발하였다. 이 모델은 가열된 벽면 근처를 어떤 기포기둥(Vapor Blanket)이 통과할 때 일어나는 다단계 비등과정 즉, 임계 기포기둥의 형성, 기포기둥밑의 미소액막(Macrolayer)의 기화 및 고갈, 그리고 얇은 기체막에서 일어나는 불안정한 막비등과정에 기초하였다. 핵비등이탈점 (DNB )과 막비등이탈점 (DFB)사이의 천이비등 곡선상의 열유속은 임계 기포기둥이 주어진 벽면을 통과할 동안 상기한 각 비등과정의 지속 시간비(Time Fraction)를 각 비등열유속에 곱한 후 그것을 합하여 정량화하였다. 이 모델의 예측치를 현재까지 발표된 문헌들에 나타난 실험치와 비교한 결과, 본 모델은 저건도 및 10 bar 근처의 고압조건의 실험치를 잘예측하는 것으로 나타났다.

• 대한산업공학회지
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• 제11권2호
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• pp.1-9
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• 1985

In this study, two stage transfer line with limited repair capability is modeled to formulate optimal dynamic repair priority policy. The method of Markov Chains is used to analyze the analytical model of this line. An efficient algorithm is developed, utilizing the block tridiagonal structure of the transition probability matrix, to obtain the steady state probabilities and system performance measures, such as the steady state production rate of the line and the average in-process inventory in the interstage buffer.

• Advances in concrete construction
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• 제1권3호
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• pp.239-252
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• 2013

Mortar microstructure is considered as a three-phase composite material, which is cement paste, fine aggregate and interfacial transition zone. Interfacial transition zone is the weakest link between the cement paste and fine aggregate, so it has a significant role to determine the properties of cementitious composites. In this study, specimens (w/c = 0.35, 0.45, 0.55) with various volume fractions of fine aggregate ($V_f$ = 0, 0.1, 0.2, 0.3 and 0.4) were cast and tested. To predict the equivalent migration coefficient ($M_e$) and migration coefficient of interfacial transition zone ($M_{itz}$), double-inclusion method and Mori-Tanaka theory were used to estimate. There are two stages to estimate and calculate the thickness of interfacial transition zone (h) and migration coefficient of interfacial transition zone ($M_{itz}$). The first stage, the data of experimental chloride ion migration coefficient ($M_s$) was used to calculate the equivalent migration coefficient of fine aggregate with interfacial transition zone ($M_e$) by Mori-Tanaka theory. The second stage, the thickness of interfacial transition zone (h) and migration coefficient of interfacial transition zone ($M_{itz}$) was calculated by Hori and Nemat-Nasser's double inclusion model. Between the theoretical and experimental data a comparison was conducted to investigate the behavior of interfacial transition zone in mortar and the effect of interfacial transition zone on the chloride migration coefficient, the results indicated that the numerical simulations is derived to the $M_{itz}/M_m$ ratio is 2.11~8.28. Additionally, thickness of interfacial transition zone is predicted from $10{\mu}m$, 60 to $80{\mu}m$, 70 to $100{\mu}m$ and 90 to $130{\mu}m$ for SM30, M35, M45 and M55, respectively.

• 응용통계연구
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• 제24권4호
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• pp.709-719
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• 2011

We investigate the latent stage-sequential patterns of drinking behaviors of U.S. adolescents who have started to drink by age 14 years (seven years before the legal drinking age). A multiple-group latent transition analysis(LTA) with logistic regression is employed to identify the subsequent patterns of drinking behaviors among early-onset drinkers. A sample of 1407 early-onset adolescents from the National Longitudinal Survey of Youth(NLSY97) is analyzed using maximum-likelihood estimation. The analysis demonstrates that early-onset adolescents' drinking behaviors can be represented by four latent classes and their prevalence and transition are influenced by demographic factors of gender, age, and race.

• 성인간호학회지
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• 제21권4호
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• pp.391-402
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• 2009

Purpose: This study was conducted to identify predictors of the stage of change for smoking cessation of male university students on the basis of the Transtheoretical model (TTM). Methods: The 388 current smokers or exsmokers who agreed to participate were recruited from three areas in Korea from August 2 to September 5, 2006. Data was analyzed using a SPSS program for descriptive statistics, ANOVA, and multiple logistic regression. Results: Most subjects (76.8%) were current smokers. According to stages of change, there were statistically significant differences in self efficacy, smoking temptation, decisional balance (cons, pros), and processes of change. The predictors of transition from contemplation to preparation were behavioral and experiential processes. The predictors of transition from preparation to action were pros of smoking and experiential process. The predictors of transition from action to maintenance were cons of smoking and behavioral process. Conclusion: Specific nursing interventions based on stages of change need to be developed for smoking cessation of male university students.

• 대한간호학회지
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• 제39권4호
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• pp.469-479
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• 2009

Purpose: The purpose of this study was to identify the effectiveness of public health center smoking cessation counseling program using the transtheoretical model on the process of change, smoking temptation, decisional balance and stage change transition. Methods: A nonequivalent control group non-synchronized design was used for this study. The study population was 115 adult smokers. The counseling program was administered to the experimental group and a smoking cessation program from the Korean Ministry of Health & Welfare was administered to the control group. Descriptive analysis, $\chi^2-test$, t-test, and ANCOVA were used with the SPSS 12.0 program to analyze the data. Results: After treatment with this program, the experimental group showed significantly higher scores for process of change (t=4.148, p<.001), smoking temptation (t=-2.988, p=.003), and stage change transition ($\chi^2=5.871$, p=.031) compared to the control group. Experimental group members also showed significantly lower score for Pros of smoking (t=-3.151, p=.002). Conclusion: The findings indicate that this program could have positive effect on process of change, smoking temptation, decisional balance and stage transition for adult smokers. Based on these findings, the authors suggest additional counseling program focusing on smokers in specific stages.

• 성인간호학회지
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• 제16권3호
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• pp.421-431
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• 2004

Purpose: The study was performed to investigate the predictors associated transition with each stage of exercise behavior based to the Transtheoretical Model, and to provide basic data for exercise behavior programs for middle aged women. Methods: The subjects consisted of 434 women residing in B city by convenience sampling. The collected data were analyzed with multiple logistic regression using SPSS/WIN program. Results: The predictors of transition from precontemplation to contemplation were consciousness raising(OR=2.095, 95% CI: 1.305-3.363), Reinforcement management(OR= 1.903, 95% CI: 1.107-3.271), Stimulus control (OR=2.176, 95% CI:1.239-3.820), Menstrual status (OR=5.327, 95% CI: 1.110-25.562). The predictors of transition from contemplation to preparation were Helping relationship(OR= 1.671, 95% CI: 1.065-2.662), Pros(OR=2.500, 95% CI: 1.254-4.982), Perceived Health status (OR=.178, 95% CI: .041-.770). The predictor of transition from preparation to action was Stimulus control(OR=1.918, 95% CI: 1.103- 3.336). The predictors of transition from action to maintenance were Consciousness raising(OR= 1.939, 95% CI: 1.031-3.647), Dramatic relief (OR=2.249, 95% CI: 1.025-4.931). Conclusions: Adequate examination on the factors, which can predict the transitional stages of change exercise behaviors among middle aged women, which is presented in this study. The results of this study will become the pillar of exercise intervention program planning and application.

• 대기
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• 제15권1호
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• pp.17-25
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• 2005

A significant number of tropical cyclones move into the midlatitudes and go through transformation procedure into extratropical cyclones. This process is generally referred to as extratropical transition of the tropical cyclone. In this study, MIDULLE(0407) case is selected. A thorough analysis is made using the GDAPS analysis data and MTM (Moving-nest Typhoon Model) model output. It is found that during the extratropical transition an important dynamics in the environmetal flow field occurs in which colder, drier (warm, moist) air penetrates in the western (eastern) quadrant of MINDULLE's outer circulation, which in turn initiates an asymmetry in the distribution of wind and temperature of the tropical cyclone. Simulated MTM result also reveals similar properties as in GDAPS analysis data. MTM result shows the gradual transition to the asymmetric distribution of wind and thickness as the extratropical transition proceeds. It is also found that the warm core disappears during the extratropical transition stage. Also, vortex tube is shown tilting towards the west during the transition. And the precipitation expands poleward of the center and the maximum precipitation appears to the left of MINDULLE which is consistent to the observations.

• 한국수학교육학회지시리즈A:수학교육
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• 제42권3호
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• pp.303-325
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• 2003

This study sought to provide an explanation of university students' concept understanding on the infinity and infinite process and utilized a psychological constructivist perspective to examine the differences in transitions that students make from static concept of limit to actualized infinity stage in context of problems. Open-ended questions were used to gather data that were used to develop an explanation concerning student understanding. 47 university students answered individually and were asked to solve 16 tasks developed by Petty(1996). Microgenetic method with two cases from the expert-novice perspective were used to develop and substantiate an explanation regarding students' transitions from static concept of limit to actualized infinity stage. The protocols were analyzed to document student conceptions. Cifarelli(1988)'s levels of reflective abstraction and Robert(1982) and Sierpinska(1985)'s three-stage concept development model of infinity and infinite process provided a framework for this explanation. Students who completed a transition to actualized infinity operated higher levels of reflective abstraction than students who was unable to complete such a transition. Developing this ability was found to be critical in achieving about understanding the concept of infinity and infinite process.