• 한국표면공학회지
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• 제54권5호
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• pp.248-259
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• 2021

This study examined the influence of post weld heat treatment (PWHT) conditions on corrosion behaviors of laser-welded super duplex stainless steel tube. Due to the high cooling rate of laser welding, the phase fraction of ferrite and austenite in the weld metal became unbalanced significantly. In addition, the Cr₂N particles were precipitated adjacent to the fusion line, which can be susceptible to the localized corrosion. On the other hand, the phase fraction in the weld metal was restored at a ratio of 5:5 when exposed to temperatures above 1060 ℃ during the post weld heat treatment. Nevertheless, the high beltline speed during the PWHT, leading to the insufficient cooling rate, caused a precipitation of σ phase at the interface between ferrite/austenite in both weld metal and base metal. This resulted in the severe corrosion damages and significant decrease in critical pitting temperature (CPT), which was even lower than that measured in as-welded condition. Moreover, the fraction of σ phase in the center region of post weld heat treated steel tube was obtained to be higher than in the surface region. These results suggest that the PWHT conditions for the steel tube should be optimized to ensure the high corrosion resistance by excluding the precipitation of σ phase even in center region.

• 한국과학예술포럼
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• 제37권3호
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• pp.113-123
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• 2019

본 연구는 영상콘텐츠 산업과 과학문화 산업의 지형 변화에서 시작되었다. 모바일 과학기술 영상 콘텐츠는 수요와 정책적 지원에 따라 성장 가능성이 예견된다. 본 연구의 목적은 과학기술 관련 모바일 영상콘텐츠 활성화를 위해 현황을 분석하여 기획 및 제작시의 시사점을 제시하는 것이다. 따라서 본 논문은 모바일 영상 중 영향력이 가장 큰 유튜브의 과학기술 채널의 영상을 사례로 하여 유형 및 스토리텔링 분석을 시도하는 융복합적 연구를 진행하였다. 연구결과 및 내용은 다음과 같다. 첫째, 과학기술 유튜브 채널 글로벌 선도그룹의 영상 콘텐츠는 과학기술의 맥락과 활동에 따라 활동형, 해설형, 비평형의 세 유형으로 범주화된다. 둘째, 언어의존성이 낮고 재매개 가능성이 높은 활동형 채널은 다시 라이프 해킹형, 소품 제작형, 파괴형, 탐구형으로 분류된다. 셋째, 활동형 채널들의 핵심 스토리텔링 전략은 일상적 소재를 전문과학기술적 방법을 통해 다루는 익숙함과 낯섦의 조화이다. 이러한 연구결과를 바탕으로 국제적 경쟁력을 가질 수 있는 킬러 콘텐츠 기획 및 제작을 기대한다.

• Imaging Science in Dentistry
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• 제49권2호
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• pp.139-151
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• 2019

Purpose: This study was performed to investigate the effect of exposure parameters on image quality obtained using a cone-beam computed tomography (CBCT) scanner and the relationship between physical factors and clinical image quality depending on the diagnostic task. Materials and Methods: CBCT images of a SedentexCT IQ phantom and a real skull phantom were obtained under different combinations of tube voltage and tube current (Alphard 3030 CBCT scanner, 78-90 kVp and 2-8 mA). The images obtained using a SedentexCT IQ phantom were analyzed technically, and the physical factors of image noise, contrast resolution, spatial resolution, and metal artifacts were measured. The images obtained using a real skull phantom were evaluated for each diagnostic task by 6 oral and maxillofacial radiologists, and each setting was classified as acceptable or unacceptable based on those evaluations. A statistical analysis of the relationships of exposure parameters and physical factors with observer scores was conducted. Results: For periapical diagnosis and implant planning, the tube current of the acceptable images was significantly higher than that of the unacceptable images. Image noise, the contrast-to-noise ratio (CNR), the line pair chart on the Z axis, and modulation transfer function (MTF) values showed statistically significant differences between the acceptable and unacceptable image groups. The cut-off values obtained using receiver operating characteristic curves for CNR and MTF 10 were useful for determining acceptability. Conclusion: Tube current had a major influence on clinical image quality. CNR and MTF 10 were useful physical factors that showed significantly associations with clinical image quality.

• 한국음향학회지
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• 제29권2호
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• pp.118-124
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• 2010

본 논문에서는 차량 구동라인의 굽힘 진동을 저감시키기 위해 사용되는 동흡진기의 설계 파라미터에 대한 최적설계를 수행하였다. 정확한 동적 응답특성을 얻기 위해 구동라인을 구성하는 추진축의 진동해석으로부터 추출된 유연성 데이터를 구동라인 동역학 모델에 적용하여 유연체 구동라인을 만들었다. 동흡진기의 내부 튜브 질량, 고무 강성계수 및 고무 감쇠계수를 최적화를 위한 설계 파라미터로 선택하였다. 구동라인의 수직 가속도를 최소화시키기 위해 중심합성 실험계획법의 3-요인, 2-수준 실험을 15회 수행하여 목적함수에 대한 2차 회귀방정식을 만들었으며, 최적화 프로그램을 이용하여 동흡진기 설계 파라미터들을 결정하였다. 최적화된 동흡진기를 장착한 차량 모델은 초기 모델에 비해 구동라인의 수직 가속도 피크값을 17.1% 감소시켰다.

• 대한전자공학회논문지
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• 제9권4호
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• pp.1-6
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• 1972

본초광대역AMqus조기는 회로구성요소에 초광대역 AM변조작용을 제한하는 동조회로를 사용하지 않고 전송선의 임피단스변환성을 이용하여, 인가한 변조신호의 진폭에 비례되게 반송파의 진폭이 변하도록 하는 변조원리를 이용한 것이다. 본논문에서는 이 AM변조기를 해석연구 하였으며 또 본변조기의 Active 소자로서 VHF 진실관, FET, VVC 다이오우드를 각각 사용하여 실험하여 얻은 AM변조파형의 사진도 첨가하였다.

• 품질경영학회지
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• 제29권3호
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• pp.124-137
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• 2001

In general, it is very efficient and effective to use screening variables that are correlated with the performance variable in case that measuring the performance variable is impossible (destructive) or expensive. The general methodology for searching surrogate variables is regression analysis. This paper considers the inspection problem in CRT (Cathode Ray Tube) production line, in which the performance variable (dependent variable) is binary type and screening variables are continuous. The general regression with dummy variable, discriminant analysis and binary logistic regression are considered. The cost model is also formulated to determine economically inspection procedure with screening variables.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.102-109
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• 1997

The surface deformation of shadow mask was studied by the experiments and numerical analysis for process improvement and delet of the stabilizing process in the shadow mask manufaturing line. To inverigate the thermal deformation of shadow mask with and without stabilizing process mask, data of spring strength, frame flatness, frame magnetic force and a mask surface curvature were measured. The tube characteristics of two kind of shadow masks were also investigated.

• 한국자원식물학회지
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• 제3권1호
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• pp.1-30
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• 1990

The traditional plant imprownent methods consisted of pure line selection, cross breeding, heterosis breeding, polyploid breeding, mutati-onbreeding, ect.Biotechmoiogy is divided into gene spliclng , monocle-nal antibodies , protein engineering , agricultural research, and microbiological engineering. Of these , high plants deal with agricultural research, and the importent part of which is tissue culture and celLculture , Tissue .culture and cell culture are again divided into embryoculture, test tube fertilization, anther and pollen culture, somatichybridization , transformation, recombination, recombinant DNA moleculehybrid plasmid, ect For these haploid production, protoplast culture,protoplast fusion, selection and propagation, ect. , the technical sett-lement is needed.

• 반도체디스플레이기술학회지
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• 제14권1호
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• pp.45-49
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• 2015

Process gases with vapor or liquid phase as well as gas phase may experience alteration in itself or be contaminated in the fluid pipe to the process chamber. And thus it result in as particles or defects on the substrates in semiconductor, LCD, LED manufacturing. Purifiers and filters are used for control of contamination. However, none of detection device is available in the delivery line. In this paper, we propose simple device with lighting and sensing in order to predict contamination of the fluid or the tube wall. For some general purpose gases, it showed constant voltage output regardless of the flow rates. But, the smoke and the moisture in the air lowered the figure due to its concentration. Numerical values for several solid and liquid media were obtained. And, the operating temperature tendency was investigated.

• Journal of Welding and Joining
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• 제11권1호
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• pp.21-32
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• 1993

A cracking failure of a austenitic stainless steel elbow in a naphtha cracking line in a petrochenmical plant occurred, resulting in leakage of organic compound flowing inside the elbow. Due to the failure, emergency shutdown of the plant was enforced to repair the troubled part of the line. The repair cost as well as production loss during the unscheduled plant shutdown has cost the company a great amount of financial loss. In this studies, a failure analysis of the cracked elbow was performed using NDT, chemical analysis, microstructural analysis including optical microscopy as well as scanning electron microscopy with EPMA, mechanical testings such as tensile testing, hardness testing and Charphy impact test fractography. The results indicated that several problems such as a welding defect and presence of a detrimental phase which was found to be relate to improper postforming heat treatment process was identified and the failure was concluded to be due to a low temperature embrittlement of the defect-containing elbows.