• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.401-407
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• 2004

This study is on the constant-current stress corrosion test related to the load stress in welded zone and non-welded zone of high tensile strength steel for natural gas transmission. The surface corrosion pattern of the welded zone of API 5L-X65 specimens for natural gas transmission showed global corrosion and narrow pitting, and the pitting was increased by increasing the load stress. Initially, the average relative electrode potential and the average relative current of the high tensile strength steel for natural gas transmission specimens was decreased suddenly, and the average relative electrode potential was higher and the average relative current was lower in welded zone than base metal. and the average relative electrode potential was decreased by increasing the load stress, and the average relative current was somewhat increased by increasing the load stress. The corrosion rate was less in welded zone than base metal, and the corrosion rate was decreased by increasing the load stress.

• 한국정밀공학회지
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• 제27권8호
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• pp.70-75
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• 2010

The aim of this study is to evaluate the axial residual stress in multi-pass drawn high carbon steel wire by using FE analysis and XRD. When FE analysis is applied to evaluate the residual stress in drawn wire of multi-pass drawing process, obtaining the reliable effective stress-strain curve at high strain is very important. In this study, a model, which can express the reliable effective stress-strain curve at high strain, is introduced based on the Bridgman correction and tensile test for multi-pass drawn high carbon steel wires. By using the introduced model, FE analysis was carried out to evaluate the axial residual stress in the drawn wires. Finally, the effectiveness of the FE analysis with the introduced stress-strain relation was verified by the measurement of residual stress in the drawn wires through XRD. As a result, the evaluated residual stress of FE analysis shows good agreement with the measured residual stress.

• 한국화재소방학회논문지
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• 제31권4호
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• pp.80-85
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• 2017

최근 우리나라에서는 초고층 건축물의 신축이 급증하고 있어 화재 발생 시 인명 및 재산피해를 최소화하기 위해 현행 법규와 동등 이상의 성능을 요구하는 '성능위주설계'를 의무적으로 시행하고 있다. 그러나 성능위주설계에서 큰 비중을 차지하고 있는 화재 및 피난 시뮬레이션 분야는 아직 세부적인 기술적 가이드라인이 제정되지 않아 설계자들이 앞서 수행했던 여러 설계도서들을 참고하여 그와 유사하게 진행하고 있는 실정이다. 그 중에서도 화재시뮬레이션의 경우에는 설계자의 판단에 따라 시나리오 유형을 선정하고 임의로 입력값을 설정하고 있어 같은 용도의 건축물이라 하더라도 누가 어떻게 설계했느냐에 따라 다른 결과가 도출되고 있는 것도 사실이다. 이에 본 논문에서는 실제 B도시지역에 접수된 성능위주설계(건축심의 전 단계) 도서 7건을 무작위로 조사하여 화재시나리오 유형과 시나리오별 입력조건 현황을 파악하고 합리적인 화재시뮬레이션의 수행을 위한 개선방안을 제시하여 기술적 가이드라인 제정에 대한 초석을 다지고자 한다.

• International Journal of Precision Engineering and Manufacturing
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• 제4권1호
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• pp.30-36
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• 2003

Brittle materials such as glasses and ceramics, which are very weak under impact loading, show fragile failure mode due to their low fracture toughness and crack sensitivity. When brittle materials are subjected to impact by small spheres, high contact pressure occurs at the impacted surface causing local damage on the specimen. This damage is a dangerous factor in causing the final fracture of structures. In this research, the crack propagation process of soda-lime glass by the impact of small spheres is explained and the effects of several constraint conditions for impact damage were studied by using soda-lime glass; that is, the effects for the materials and sizes of impact ball, thickness of specimen and residual strength were evaluated. Especially, this research has focused on the damage behavior of ring cracks, cone cracks and several other kinds of cracks.

• 한국생산제조학회지
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• 제26권2호
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• pp.230-237
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• 2017

Various drones have extended application area very fast. In this paper, we define two contradictions in designing a portable-size drone by using TRIZ technique. The first is a physical contradiction between high rigidity and good portability, and the second is a technical contradiction between high stability and good portability. Through TRIZ technique, six design principles, which guide direction for optimal design, were driven. Consequently, an umbrella mechanism and design criteria were proposed for a portable-size drone. Detail design is verified through finite element method. Test results for the portable-size prototype drone show good performance, and prove its usefulness to be equivalent to a general full-size drone.

• 한국산학기술학회논문지
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• 제22권5호
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• pp.180-187
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• 2021

TV 오디션 프로그램과 K-POP 열풍에 가장 큰 영향을 받는 많은 청소년들은 자신들의 진로를 음악으로 정하기 시작하였다. 그들은 학원이나 개인레슨을 통해 음악수업을 받았고, 이후 대학의 실용음악과에 진학하게 된다. 지원생들이 많아지면서 대학교 실용음악과의 경쟁률이 기형적으로 높아지는 현상도 발생하였다. 그에 따라 많은 학생들은 어린 나이부터 음악을 시작하였고, 학원 등 사교육 기관을 통해 음악을 배우게 되었다. 이후 실용음악 관련 고등학교가 생기기 시작하면서 고등학교를 실용음악 전문학교에 입학하는 학생들이 늘어나게 되었다. 하지만 실용음악 고등학교에도 큰 문제가 있었다. 바로 해당 음악을 전공한 전문교사를 찾기 힘들다는 점이었다. 이는 실용음악 전공자가 정교사 자격증을 취득하기가 매우 어려운 구조에서 비롯되었다. 교원 자격증을 취득 할 수 있는 방법은 여러 가지 방법이 있지만, 실용음악 전공자가 선택 가능한 방법은 교육대학원을 졸업하는 방법뿐이다. 그런데 교육대학원은 클래식과 국악에 한정되어 있어 입학 자체도 어려운 상황이다. 입학을 하여도 교육대학원 교과목의 대부분이 클래식과 국악교육에 관련된 수업으로 구성되어 실용음악전공자들에겐 매우 어려운 상황이다. 이에 본 논문에서는 실용음악 고등학교의 현재 상황과 정교사 2급 자격증이 왜 필요한지, 자격증을 취득하기 위해서는 어떻게 해야 하는지 등에 대해 연구하였다.

• 한국기계가공학회지
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• 제10권3호
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• pp.28-32
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• 2011

The safety of transporting equipment in a cryogenic condition is one of important problems under the circumstances that the application weight of natural gas is gradually increasing. As a larger disaster may be generated by leakage of oil or gas from valves in case of fire occurrence of a ship, the present research applied a numerical analysis method on thermal stress distribution and deformation, etc. to the design of ball valves satisfying fire safety test's specification(API607) to prevent this. In addition, the present research progressed fire safety tests and compared the test result with numerical analysis results. The Max stress by parts was confirmed through thermal analysis of major parts to evaluate safety. The fire safety test was progressed according to the regulation of API607.

• 한국안전학회지
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• 제25권5호
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• pp.22-26
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• 2010

The ignitability(minimum ignition energy, MIE) of a suspended dust clouds is very important aspect of technical safety indices. This paper reported the experimental results dealing with the influence of discharge circuit on the MIE of a suspended dust clouds. The movement of a suspended dust clouds was also observed with the high speed camera. The Hartmann vertical-tube apparatus(MIKE-3) described in the international standard of IEC and Polypropylene (PP, 50% volume-average, D50: $761{\mu}m$) resin powders were used in this experiment. The following results were obtained: (1) the MIE of a suspended PP powder depended markedly on the discharge circuit; in other words, when a resistor was connected in series with the discharge sparking circuit(RC), the lowest value(31mJ) of MIE was obtained for a suspended PP powder comparison with the other circuits(C circuit; 370mJ or LC circuit; 71mJ). (2) the discharge duration time is more important than other factors with regard to MIE of a suspended PP powder.

• Molecules and Cells
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• 제41권10호
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• pp.881-888
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• 2018

During the cortical development, cells in the brain acquire somatic mutations that can be implicated in various neurodevelopmental disorders. There is increasing evidence that brain somatic mutations lead to sporadic form of epileptic disorders with previously unknown etiology. In particular, malformation of cortical developments (MCD), ganglioglioma (GG) associated with intractable epilepsy and non-lesional focal epilepsy (NLFE) are known to be attributable to brain somatic mutations in mTOR pathway genes and others. In order to identify such somatic mutations presenting as low-level in epileptic brain tissues, the mutated cells should be enriched and sequenced with high-depth coverage. Nevertheless, there are a lot of technical limitations to accurately detect low-level of somatic mutations. Also, it is important to validate whether identified somatic mutations are truly causative for epileptic seizures or not. Furthermore, it will be necessary to understand the molecular mechanism of how brain somatic mutations disturb neuronal circuitry since epilepsy is a typical example of neural network disorder. In this review, we overview current genetic techniques and experimental tools in neuroscience that can address the existence and significance of brain somatic mutations in epileptic disorders as well as their effect on neuronal circuitry.

• 한국전기전자재료학회논문지
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• 제29권8호
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• pp.455-460
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• 2016

A textured front surface is required in high efficiency silicon solar cells to reduce reflectance and to improve light trapping. Wet etching with alkaline solution is usually applied for mono crystalline silicon solar cells. However, alkali texturing method is not appropriate for multi-crystalline silicon wafers due to grain boundary of random crystallographic orientation. Accordingly, acid texturing method is generally used for multi-crystalline silicon wafers to reduce the surface reflectance. To reduce reflectivity of multi-crystalline silicon wafers, double texturing method with combination of acid and reactive ion etching is an attractive technical solution. In this paper, we have studied to optimize RIE condition by different RF power condition (100, 150, 200, 250, 300 W).