• 전기전자학회논문지
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• 제24권1호
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• pp.216-224
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• 2020

본 논문은 계통 연계 기준인 Low Voltage Ride Through(LVRT) 및 High Voltage Ride Through(HVRT) 기능을 평가하기 위한 시험 장비의 임피던스 설계 방법을 제안한다. LVRT/HVRT 시험 장비는 계통 연계 규정에 명시되어 있는 계통 사고 전압을 일정시간 동안 발생시킬 수 있어야 하며 설계 사양에 맞게 사고전류의 크기를 제한해야 한다. 본 논문에서는 LVRT/HVRT 동작 시 탭 변환 단권변압기 시험 장비의 등가 모델을 기반으로 계통 연계 규정을 만족하기 위한 단권변압기의 임피던스를 설계한다. 제안하는 설계 방법을 이용하여 LVRT/HVRT 시험 시 요구되는 다양한 사고전압을 출력할 수 있는 시험장비의 설계를 위한 탭 간의 임피던스 설계 과정을 설명한다. 제안하는 설계 방법의 타당성을 검증하기 위하여, 10MVA급 LVRT/HVRT 시험 장비의 설계 과정을 설명하고 시뮬레이션을 통하여 확인하였다.

• 한국산학기술학회논문지
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• 제22권4호
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• pp.255-262
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• 2021

본 연구는 숲체험 놀이에서 밧줄 놀이가 유아 자신감에 미치는 효과를 분석하는 데 있다. 이를 위해 실험집단 15명(남아7명, 여아8명)과 비실험집단 15명(남아9명, 여아6명)을 대상으로 실험설계를 통한 실증분석하였다. 실험처치를 하고 실험집단 및 통제집단 간 효과를 검정하기 위해 공분산분석(ANCOVA)을 실시한 결과, 실험집단의 평균이 통제집단의 평균보다 통계적으로 의미있게 높은 것으로 나타났다(F=357.350, p<.001). 이같은 결과는 숲체험 밧줄 놀이를 통해 유아의 자신감에 미치는 효과가 통계적으로 의미 있는 효과를 나타낸 것으로 평가할 수 있다. 이는 또래 간 숲체험 밧줄 놀이가 유아의 자신감 향상에 보다 긍정적인 효과를 나타내주는 유익한 놀이로 유아들의 숲체험 놀이를 통해 또래 간 협력을 통한 상호작용 속에 감정과 충동조절로 소극적 성격의 유아의 자신감을 높여주는 긍정적인 놀이활동임을 확인시켜준 것으로 판단할 수 있다.

• Journal of Korean Biological Nursing Science
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• 제22권2호
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• pp.90-101
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• 2020

Purpose: The purpose of this study was to build and verify a structural model that could predict the severity of irritable bowel syndrome in university students. Methods: Participants were 205 students enrolled in college with irritable bowel syndrome using the irritable bowel syndrome module of the ROME IV Adult Questionnaire. The data were collected using online questionnaires in AprilMay 2019. The data were analyzed using the SPSS WIN 25.0 and AMOS 20.0 programs. Results: 1) The symptom severity that participants experienced were mild (14.6%), moderate (45.4%), and severe (40%). 2) Fit indices of the model were x²= 79.66 (df = 52, p= .009), CFI= .94, TLI= .96, RMSEA= .05, RMR= 1.59, GFI= .94, and TLI= .96.3). The severity of irritable bowel syndrome was influenced directly by anxiety and sleep, and indirectly by family history, perfectionism, social support, coping, and stress. The severity of irritable bowel syndrome was indirectly affected by the following: family history through anxiety; perfectionism through stress, anxiety, and sleep; social support through coping, stress, anxiety, and sleep; coping through stress and anxiety; and stress through anxiety and sleep. Conclusion: Based on the results of this study, a nursing intervention is needed to reduce the anxiety and stress and improve the quality of sleep to improve the health of the college students and manage the symptoms of patients with irritable bowel syndrome.

• Earthquakes and Structures
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• 제16권6호
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• pp.727-741
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• 2019

A reinforced concrete water tank is a typical functional liquid storage structure and cracks are the greatest threat to the liquid storage structure. Tanks are readily cracked due to seismic activity, thereby leading to the leakage of the stored liquid and a loss of function. In order to study the effect of cracks on liquid storage tanks, self-healing and leakage tests for bending cracks and through cracks in the walls of a reinforced concrete water tank were conducted. Material performance tests were also performed. The self-healing performance of bending cracks in a lentic environment and through cracks in a lotic environment were tested, thereby the self-healing width of bending micro-cracks in the lentic environment in the short term were determined. The through cracks had the capacity for self-healing in the lotic environment was found. The leakage characteristics of the bending cracks and through cracks were tested with the actual water head on the crack. The effects on liquid leakage of the width of bending cracks, the depth of the compression zone, and the acting head were determined. The relationships between the leakage rate and time with the height of the water head were analyzed. Based on the tests, the relationships between the crack characteristics and self-healing as well as the leakage were obtained. Thereby the references for water tank structure design and grading earthquake damage were provided.

• Steel and Composite Structures
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• 제46권3호
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• pp.353-366
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• 2023

This paper presents a finite-element analysis (FEA) of aluminum alloy rectangular hollow sections (RHSs) and square hollow sections (SHSs) with circular through-openings under three-point and four-point bending. First, a finite-element model (FEM) was developed and validated against the corresponding test results available in the literature. Next, using the validated FE models, a parametric study comprising 180 FE models was conducted. The cross-section width-to-thickness ratio (b/t) ranged from 2 to 5, the hole size ratio (d/h) ranged from 0.2 to 0.8 and the quantity of holes (n) ranged from 2 to 6, respectively. Third, results obtained from laboratory test and FEA were compared with current design strengths calculated in accordance with the North American Specifications (NAS), the modified direct strength method (DSM) and the modified Continuous strength method (CSM). The comparison shows that the modified CSM are conservative by 15% on average for aluminum alloy RHSs and SHSs with circular through-openings subject to bending. Finally, a new design equation is proposed based on the modified CSM after being validated with results obtained from laboratory test and FEA. The proposed design equation can provide accurate predictions of flexural capacities for aluminum alloy RHSs and SHSs with circular through-openings.

• 한국보육지원학회지
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• 제16권5호
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• pp.105-126
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• 2020

Objective: This study aimed to reveal pre-service early childhood teachers' perception of children's environmental education using concept mapping and demonstrating its importance. Methods: Based on Kane and Trochim's(2007) procedure, 33 pre-service early childhood teachers conducted brainstorming and statement writing, and then the importance of selected statements were rated by 202 pre-service early childhood teachers. Selected statements were analyzed through multidimensional scaling and hierarchical cluster analysis. Results: Pre-service early childhood teachers perceived children's environmental education as concept mapping with 2-dimensions and eight clusters. The following eight clusters were established (1) daily practice through hands on experience, (2) nature environment, (3) recognizing and coping with environmental issues, (4) environmental preservation practices, (5) environmental sensitivity and consideration, (6) purpose of children's environmental education, (7) necessity for children's environmental education (8) Practice through connection with child's home and community. And then among the eight clusters, the most important was recognized as 'daily practice through hands on experience', and among the statements 'young children learn through the method of playing in nature and experience nature' was considered the most important. Conclusion/Implications: Based on these results, we discuss the importance of children's environmental education of pre-service early childhood teachers and how to support to develop teacher's training program.

• 한국의류산업학회지
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• 제3권3호
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• pp.219-226
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• 2001

This study analyzed the works, introduced in the collections of Thierry Mugler in an aim to identify formative aesthetic and design concepts. As the data to study the creative concepts and expressions of the designer, fashion photographs were gathered in a focus on collections. The formative aesthetic expressed in the works of Thierry Mugler were characterized by the eroticism and the futurism. The formative aesthetic of eroticism were specified into the sexualism, primitivism and fetishism, and those of futurism were divided into the cosmocorps and the grotesque. The eroticism was based on the design concept on the body of woman. The sexuality was expressed through the design concept of opposing, extreme and conversion method. The primitivism was presented through the design concept of extreme method to express a returning to nature and a nostalgia and an adoration for the past. The pieces, expressed the fetishism, was presented through opposing concepts, such as a bondage and an extreme expose. It was indicated that the design concept of futurism was based on the future. The cosmocorps was expressed through the extreme method by using geometrical formative aesthetic and contrast color combination. The grotesque represented the mysterious and abhorrent futurism through the design concept of depaysment conversion and analogy.

• Advances in concrete construction
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• 제11권4호
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• pp.307-314
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• 2021

Activated hwangtoh (ACT) is a natural resource abundant in South Korea, approximately 15.0% of soil. It is an efficient mineral admixture that has activated pozzolanic properties through high-temperature heating and rapid cooling. The purpose of this study is to improve a curb mixture that can reduce NOx outside and investigate durability performance. To this end, mortar curb specimens were manufactured by replacing OPC with ACT. The ACT substitution ratios of 0.0, 10.0, and 25.0% were considered, and mechanical and durability tests on the curb specimens were conducted at 28 and 91 days of age. Steam curing was carried out for three days for the production of curbs, which was very effective to strength development at early ages. The reduction in strength at early ages could be compensated through this process, and no significant performance degradation was evaluated in the tests on chloride attack, carbonation, and freezing and thawing. The mortar curb with an ACT of 10.0~25.0% replacement ratio exhibited clear NOx reduction through photocatalytic (TiO2) treatment. This is due to the increase in physical absorption through surface absorption and the photocatalyst-containing TiO2 coating. In this study, the reasonable range of the ACT replacement ratio for NOx reduction was quantitatively evaluated through a comprehensive analysis of each test.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제25권3호
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• pp.201-225
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• 2022

This paper details case study vignettes that focus on enhancing the teaching and learning of geometry and measurement in the elementary grades with attention to pedagogical practices for teaching through problem solving with rigor and centering equitable teaching practices. Rigor is a matter of equity and opportunity (Dana Center, 2019). Rigor matters for each and every student and yet research indicates historically disadvantaged and underserved groups have more of an opportunity gap when it comes to rigorous mathematics instruction (NCTM, 2020). Along with providing a conceptual framework that focuses on the importance of equitable instruction, our study unpacks ways teachers can leverage their deep understanding of geometry and measurement learning trajectories to amplify the mathematics through rigorous problems using multiple approaches including learning by doing, challenged-based and mathematical modeling instruction. Through these vignettes, we provide examples of tasks taught through rigorous problem solving approaches that support conceptual teaching and learning of geometry and measurement. Specifically, each of the three vignettes presented includes a task that was implemented in an elementary classroom and a vertically articulated task that engaged teachers in a professional learning workshop. By beginning with elementary tasks to more sophisticated concepts in higher grades, we demonstrate how vertically articulating a deeper understanding of the learning trajectory in geometric thinking can add to the rigor of the mathematics.

• 한국주거학회논문집
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• 제12권1호
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• pp.67-75
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• 2001

There were the rites and customs in building of the traditional houses. The purpose of this study is to search the meaning of the building rites, and to search the spatial structure and meaning of the traditional houses through the rites as establishing the true dwelling. The traditional houses show the oppositional structure of the sacred and profane through the rites and customs of the building as the communication with the gods and men. The traditional houses are the center of which the gods of four sides defined and have the cardinal points and vertical axis which has the mythical and symbolic meaning.