• Structural Engineering and Mechanics
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• 제46권1호
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• pp.39-51
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• 2013

An extremum method is presented to predict the wrinkling characteristics of the inflated cone in bending. The wrinkling factor is firstly defined so as to obtain the wrinkling condition. The initial wrinkling location is then determined by searching the maximum of the wrinkling factor. The critical wrinkling load is finally obtained by determining the ratio of the wrinkling moment versus the initial wrinkling location. The extremum method is proposed based on the assumption of membrane material of beam wall, and it is extended to consider beam wall with thin-shell material in the end. The nondimensional analyses show that the initial wrinkling location is closely related to the taper ratio. When the taper ratio is higher than the critical value, the initial wrinkles will be initiated at a different location. The nondimensional critical wrinkling load nonlinearly increases as the taper ratio increases firstly, and then linearly increases after the critical taper ratio. The critical taper ratio reflects the highest load-carrying efficiency of the inflated cone in bending, and it can be regarded as a measure to optimize the geometry of the inflated cone. The comparative analysis shows fairly good agreement between analytical and numerical results. Over the whole range of the comparison, the mean differences are lower than 3%. This gives confidence to use extremum method for bending-wrinkling analysis of inflated conical cantilever beam.

• 한국가정과교육학회지
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• 제33권2호
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• pp.57-80
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• 2021

본 연구는 시민성 교육의 일환으로서 비판적 리터러시 역량을 향상시킬 수 있는 주생활 교육과정을 개발하는 것을 목적으로 한다. 이를 위해 비판적 리터러시 관점에서 현행 2015 개정 가정과 교육과정 주생활 영역의 내용 체계와 성취기준 및 교과서를 분석하였고, Laster(1986)의 비판과학 관점의 교육과정 개발 과정을 적용, 미국 위스콘신 주의 식생활 교사용 지도서 "A Teacher's guide : Family, Food and Society"(Staaland & Storm, 1996)을 참고하여 주생활 교수·학습지도안을 개발하였다. 본 연구의 결과를 요약하면 다음과 같다. 첫째, 교과 목표 및 주생활 영역 성취기준, 학습요소, 평가방법에서는 비판적 리터러시 내용이 포함될 수 있는 실천적 문제해결 교육과정으로 구성되어 있으나, 교수학습방법에서는 실천적 추론과 비판적 사고 기술이 포함되어 있지 않았다. 또한, 3개의 교과서 주생활 영역의 텍스트를 분석한 결과, 대부분 현재 문화에 적응, 대처하는 내용으로 기술되었고 비판적 해석과 사회행동에까지 이를 수 있는 문제 제기나 사회적 이슈가 거의 없었다. 둘째, 현행 교육과정과 교과서를 분석한 결과를 바탕으로 주생활 교육과정을 개발한 결과, 주생활의 지속적인 관심사, 가치를 둔 목표, 학습내용선정 및 조직, 그리고 총 7개 모듈로 된 13차시 교수·학습지도안과 읽기 자료, 학습지, 영상자료 등 총 학습자료 26개를 개발하였다. 본 연구결과를 토대로, 차기교육과정과 교과서에서 비판적 리터러시를 활용할 수 있는 주생활 관련 사회적 이슈와 다양한 계층의 주생활 모습을 다루어야 하며, 학생들이 실천적 추론과 비판적 사고 등의 모범이 되는 교사를 지원하는 교사공동체 및 연수가 운영되어야 할 것이다.

• 한국세라믹학회지
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• 제43권2호
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• pp.98-105
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• 2006

YBCO film was synthesized by using a new approach to the TFA-MOD method. In the fabrication process, $Y_2Ba_1Cu_1O_x\;and\;Ba_3Cu_5O_8$ powders were used as precursors (the so called '211 process'), instead of Y-, Ba-, and Cu-based acetates, and dissolved in trifluoroacetic acid followed by calcining and firing heat treatment. Consequently, we successfully fabricated YBCO film and evaluated the phase formation, texture evolution, and critical properties as a function of the calcining and firing temperature and humidity, in order to explore its possible application in coated conductor fabrication. The films were calcined at $430-460^{\circ}C$ and then fired at $750-800^{\circ}C\;in\;a\;0-20\%$ humidified $Ar-O_2$ atmosphere. We observed that $BaF_2$ phase was effectively reduced and that a sharp and strong biaxial texture formed under humidified atmosphere leading to increased critical properties. In addition, we found that the microstructure varied significantly with the firing temperature: the grain grew further, the film became denser, and the degree of texture and phase purity varied as the firing temperature increased. For the film fired at $775^{\circ}C$ after calcining at $460^{\circ}C$, the critical current was obtained to be 39 A/cm-width (corresponding critical current density is $2.0\;MA/cm^2$ which was probably attributed to such factors as the enhanced phase purity and out-of-plane texture, the moderate film density and grain size, and crack-free surface.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2008년도 High Temperature Superconductivity Vol.XVIII
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• pp.69-69
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• 2008

• 한국재료학회지
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• 제26권7호
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• pp.370-375
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• 2016

Tensile tests and creep tests were carried out at high temperatures on an Al-$Al_4C_3$ alloy prepared by mechanical alloying technique. The material contains about 2.0% carbon and 0.9% oxygen in mass percent, and the volume fractions of $Al_4C_3$ and $Al_2O_3$ particles are estimated at 7.4 and 1.4%, respectively, from the chemical composition. Minimum creep rate decreased steeply near two critical stresses, ${\sigma}_{cl}$ (the lower critical stress) and ${\sigma}_{cu}$ (the upper critical stress), with decreasing applied stress at temperatures below 723 K. Instantaneous plastic strain was observed in creep tests above a critical stress, ${\sigma}_{ci}$, at each test temperature. ${\sigma}_{cu}$ and ${\sigma}_{ci}$ were fairly close to the 0.2% proof stress obtained by tensile tests at each test temperature. It is thought that ${\sigma}_{cl}$ and ${\sigma}_{cu}$ correspond to the microscopic yield stress and the macroscopic yield stress, respectively. The lower critical stress corresponds to the local yield stress needed for dislocations to move in the soft region within subgrains. The creep strain in the low stress range below 723 K arises mainly from the local deformation of the soft region. The upper critical stress is equivalent to the macroscopic yield stress necessary for dislocations within subgrains or in subboundaries; this stress can extensively move beyond subboundaries under a stress above the critical point to yield a macroscopic deformation. At higher temperatures above 773 K, the influence of the diffusional creep increases and the stress exponent of the creep rate decreases.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.76-76
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• 2002

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.77-77
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• 2002

• 한국의상디자인학회지
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• 제22권2호
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• pp.87-103
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• 2020

This study investigates critical fashion and discusses its critical messages, as it challenges the existing system of the fashion industry. This study reviews the literature on critical art and critical design and analyzes exhibition catalogs, magazines, and websites related to critical fashion practices. Thereupon, this study assumes the two distinctive messages of critical fashion design: materiality and experience, and the redefinition of the ideal body. First, materiality and experience pursues a change in perceptions of clothing materials by way of deconstructing clothes and exposing the process of production. This type of critical fashion breaks away from the traditional sartorial conventions and articulates new structures and experiences through dematerialization. Second, the redefinition of the ideal human body attempts to subvert the stereotypes of ideal beauty and introduce a variety of beauty in the human body. This type of critical design reconstructs the human body through transformation, expansion, and deconstruction and is often liberated from the dichotomy of gender norms.

• Progress in Superconductivity
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• 제4권2호
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• pp.162-167
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• 2003

The critical current value of Bi-2223/Ag tape can be influenced by various factors. In particular, it was known that properties of precursor powders could affect the formation of Bi -2223 and grain growth rate of the same. Since, moistures and organic matters can easily contaminate the precursor powders of Bi-2223 tapes and degrade properties of superconductors, the precursor powders should be kept in optimal conditions to minimize contamination. In this study, the effect of moisture and organic matters has been investigated. A Bi-2223/Ag tape contaminated with a large amount of moisture and organic matter has been characterized by low critical current values and bubbling. It has been found that as the quantity of moisture increases, the Bi-2223 phases are formed at lower temperature and the amount of non-superconducting phase increases.

• Progress in Superconductivity
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• 제1권1호
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• pp.56-60
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• 1999

Ultra fine MgO particles added BSCCO tapes were fabricated by tape casting using Doctor Blade Method and enclosed by silver foil for different starting compositions (that is, 2223 major, 2212 major). In order to obtain optimum microstructure, thermomechanical treatment was done. Microstructure and phase were analyzed by XRD, SEM and DTA. The critical current density was measured under magnetic field at 77K. The tapes fabricated from the precursor powder with BSCCO-2223 phase (>90%) result in a microstructure with a larger grain size and higher transport critical current density value under magnetic field at given thermomechanical treatment conditions.