• Fibers and Polymers
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• 제7권2호
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• pp.129-138
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• 2006

Using a strain-controlled rheometer, the steady shear flow properties of aqueous xanthan gum solutions of different concentrations were measured over a wide range of shear rates. In this article, both the shear rate and concentration dependencies of steady shear flow behavior are reported from the experimentally obtained data. The viscous behavior is quantitatively discussed using a well-known power law type flow equation with a special emphasis on its importance in industrial processing and actual usage. In addition, several inelastic-viscoplastic flow models including a yield stress parameter are employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models is also examined in detail. Finally, the elastic nature is explained with a brief comment on its practical significance. Main results obtained from this study can be summarized as follows: (1) Concentrated xanthan gum solutions exhibit a finite magnitude of yield stress. This may come from the fact that a large number of hydrogen bonds in the helix structure result in a stable configuration that can show a resistance to flow. (2) Concentrated xanthan gum solutions show a marked non-Newtonian shear-thinning behavior which is well described by a power law flow equation and may be interpreted in terms of the conformational status of the polymer molecules under the influence of shear flow. This rheological feature enhances sensory qualities in food, pharmaceutical, and cosmetic products and guarantees a high degree of mix ability, pumpability, and pourability during their processing and/or actual use. (3) The Herschel-Bulkley, Mizrahi-Berk, and Heinz-Casson models are all applicable and have equivalent ability to describe the steady shear flow behavior of concentrated xanthan gum solutions, whereas both the Bingham and Casson models do not give a good applicability. (4) Concentrated xanthan gum solutions exhibit a quite important elastic flow behavior which acts as a significant factor for many industrial applications such as food, pharmaceutical, and cosmetic manufacturing processes.

• 한국가시화정보학회지
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• 제5권1호
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• pp.22-29
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• 2007

In the present study, naturally generated bubbles were investigated to be sure if they could be adopted as the tracer for PIV techniques. The bubble can be grown from the nuclei melted in the water of tunnel and the size of bubbles is changed through the variation of tunnel pressure. Since the trace ability and appropriate size of tracer are so important for PIV techniques, the characteristics of bubbles as tracer are revealed in terms of trace ability and bubble size with the variation of flow speed and tunnel pressure in this study. In addition, PIV measurements of (low behind a rotating propeller are conducted to confirm the trace ability of bubbles even in a highly vortical flow.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.381-383
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• 2002

This paper proposes a MATLAB program for solving security-constrained optimal power flow using linear programming. Security-constrained optimal power flow can find an optimal generation satisfying bus voltage limits, line flow limits, reactive generation limits, even if contingency occurs. Sensitivity matrixes are obtained based on power flow solutions with and without single line contingency. This program is tested for an IEEE 14bus system with 5 generators Results shows good ability of finding optimal solution in case of a single line contingency.

• 대한물리의학회지
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• 제6권4호
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• pp.437-445
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• 2011

Purpose : The purpose of this study was to analysis on diaphragm thickness and lung function of stroke patients by walking ability. Methods : We recruited thirty-five adults after stroke(20 male, 15 female) for our study. The subjects were divided into two groups; independent walking group(11 male, 9 female) and non-independent walking group(9 male, 6 female). Assessment of diaphragm thickness was performed using ultrasound in B-mode with a 7.5 MHz linea probe. During the experiment, the subject was seated in the chair. All subjects performed maximal expiratory flow maneuvers using a spirometer in order to determine the forced expiratory volume in 1 second ($FEV_1$), forced vital capacity(FVC), peak expiratory flow(PEF) and $FEV_1$/FVC. Chest expansion was measured with a tape-measure placed circumferentially around the chest wall at the xiphoid process. The collected data analyzed by independent t-test. Results : The diaphragm thickness were significant differences between the independent walking and nonindependent walking group. Values of forced vital capacity, forced expiratory volume at one second, peak expiratory flow in pulmonary function tests were significant differences between the independent walking and non-independent walking group. However, chest expansion were not significant differences in both of the group. Conclusion : This study showed that walking ability of stroke patients have influenced on diaphragm thickness and pulmonary function.

• 치위생과학회지
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• 제23권4호
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• pp.271-281
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• 2023

Background: This study aims to improve dental hygiene education by investigating the relationship between metacognition, learning flow, and problem-solving abilities in dental hygiene majors. Methods: A survey was conducted on 2nd to 4th-year students from dental hygiene programs, with 132 responses analyzed. Data analysis involved t-tests and ANOVA to examine the differences in metacognition, learning flow, and problem-solving abilities based on the general characteristics. Multiple regression analysis was employed to investigate the factors influencing the dependent variable, which is problem-solving abilities. The collected data were analyzed using SPSS. Results: First, when comparing metacognition, learning flow, and problem-solving abilities based on the general characteristics of the study participants, statistically significant differences were observed in common factors such as major satisfaction, subjective academic performance, GPA (grade point average), and reason for major choice (p<0.05). Second, it was found that there is a significant positive correlation between metacognition, learning flow, and problem-solving abilities in dental hygiene students (r≥0.79, p<0.05). In other words, higher levels of metacognition and learning flow were associated with better problem-solving abilities. Third, factors influencing problem-solving abilities were identified, with both metacognition and learning flow having a statistically significant positive impact. It was also noted that metacognition had a greater influence on problem-solving abilities compared to learning flow (adjusted R²=0.815, p<0.05). Conclusion: To enhance the core competency of problem-solving abilities, it is essential to improve metacognition and learning flow. To enhance metacognition and promote learning flow, strategies such as goal setting, utilizing effective learning methods, boosting self-efficacy, managing the learning environment, choosing activities that foster immersion, stress management, self-assessment and feedback integration, improving focus, and utilization a variety of learning experiences will be necessary.

• 정보교육학회논문지
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• 제15권1호
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• pp.1-10
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• 2011

교육 현장에서 프로그래밍 교육은 고등 사고력 향상을 위한 학습보다는 프로그래밍의 개념이나 기초 문법의 주입 및 단순 반복으로 진행되고 있다. 따라서 학습자들이 프로그래밍 교육에 대해 긍정적인 흥미를 가지고 적극 참여하여 교육적인 효과를 거둘 수 있는 새로운 프로그래밍 교육 방안에 대한 모색이 필요하다. 스크래치 EPL(Educational Programming Languages)은 블록 쌓기를 통해 프로그래밍이 가능한 직관적인 언어로 초등학생들도 보다 쉽게 프로그래밍을 이해할 수 있다. 스크래치의 이런 특징은 프로그래밍 교육에 대한 학습자의 학습 몰입(Flow)에 긍정적인 영향을 미칠 수 있다. 따라서 본 연구에서는 프로그래밍 교육의 새로운 방안으로 스크래치 프로그래밍 교육을 진행하고 초등학생의 학습 몰입과 프로그래밍 능력에 미치는 영향에 대해 검증하고자 한다. 본 연구의 결과 스크래치 프로그래밍 교육이 학습자의 전반적인 학습 몰입 수준 향상에 긍정적인 효과가 있음을 알 수 있다.

• Restorative Dentistry and Endodontics
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• 제29권4호
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• pp.365-369
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• 2004

The purpose of this study was to evaluate the apical sealing ability of Super-EBA, MTA and Dyract-flow as retrofilling materials. Forty-eight extracted human teeth with straight and single root canal were used in this study. The root canals were prepared to a #40 apical canal size and obturated with gutter-percha. Apicoectomies were performed and root end cavities were prepared to a depth of 3mm using an ultrasonic device. The root end cavities were filled with Super-EBA, MTA or Dyract-flow. Leakage was measured using an electrochemical technique for 4 weeks. According to this study, the results were as follows. 1. Increasing leakage with time was observed in all groups. 2. No significant difference was noted among the 3 groups with time (p =0.216). 3. No significant difference was noted among the 3 groups when measured within the same time interval (p =0.814). The results of this study suggest that the sealing ability of Dyract-flow is equal to that of Super-EBA and MTA, and Dyract-flow may be an alternative to other materials for root-end filling.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 추계 학술대회논문집
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• pp.91-97
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• 2001

The thin-layer Navier-Stokes equations are solved for the hypersonic flow over blunt cone configurations with applications to laminar as well as turbulent flows. The equations are expressed in the forms of flux-vector splitting and explicit algorithm. The upwind schemes of Steger-Warming and van Leer are investigated in their ability to accurately predict the heating loads along the surface of the body. A comparison with the second order extensions of these schemes is made and a hybrid scheme incorporating a combination of central differencing and flux-vector-splitting is presented. This scheme is also investigated in its ability to accurately predict heat transfer distributions.

• 정보처리학회논문지D
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• 제13D권1호
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• pp.117-124
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• 2006

UML(Unified Modeling Language)은 객체지향 모델링을 위한 언어이다 UML에 포함되어 있는 AD(Activity Diagram; 활동 다이어그램)는 워크플로우 시스템의 모델링에 적합하지만 수행 과정의 평가가 수학적이지 못하므로 수행 과정을 직관적으로 파악해야 하는 단점이 있다. 그러나 EMFG(Extended Mark Flow Graph)는 이산적인 시스템의 모델링에 적합할 뿐 아니라 수행 과정을 수학적으로 평가할 수 있다. 따라서 본 연구에서는 EMFG를 사용하여 모델링된 AD의 수행 동작을 평가하려고 한다. 우선 AD를 EMFG로 변환하는 방법에 대하여 제안하고, 변환된 EMFG의 수행을 평가함으로써 모델링된 AD의 수행완료 가능성을 평가한다. 그리고 컴퓨터 시뮬레이션을 통하여 이를 입증한다. 제안한 알고리듬은 대규모 워크플로우 시스템을 모델링한 AD의 수행완료 가능성도 쉽게 평가할 수 있는 장점이 있다.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2214-2221
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• 2011

본 연구는 수상인명구조원 교육 참여 대학생들의 목표지향, 몰입경험 및 자아성취감에 관계된 요인을 파악하기 위해 시도하였다. 첫째, 수상인명구조원 교육 참여 대학생들의 목표지향 중 과제관여는 인지몰입과 행동몰입에 자아관여는 인지몰입에 영향을 미쳤다. 둘째, 수상인명구조원 교육 참여 대학생들의 목표지향의 하위변인인 과제관여는 자아성취감의 자아실현, 능력발휘, 능력개발에 영향을 미쳤다. 또한 자아관여는 자아실현에 영향을 미친다. 셋째, 수상인명구조원 교육 참여 대학생들의 몰입경험의 하위변인인 인지몰입과 행위몰입은 자아성취감의 자아실현, 능력발휘, 능력개발에 영향을 미쳤다. 넷째, 수상인명구조원 교육 참여 대학생들의 목표지향은 몰입경험과 자아성취감에는 직접적인 관계, 몰입경험을 매개로 자아성취감에 간접적인 인과적 관계가 있다. 이러한 결과들로 보아 수상인명구조원 교육을 주관하는 단체에서는 프로그램 개발을 통하여 자발적으로 교육에 참여하는 교육생들에게 양질의 체계적인 실무 훈련 교육을 통해 인명구조에 대한 자신감 및 교육의 효과를 얻을 것으로 사료된다.