• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.39-40
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• 2006

The relationship between the powder particle size change and a mechanical property of the Metal Injection Molding (MIM) product was examined in detail. The XRD results indicate that the diffraction peaks of BCC appeared in compacts of powder particle size of 4 to $10{\mu}m$ as well as the bulk SUS630. However, the diffraction peaks from both BCC and FCC were observed in the compact with powder size less than $3{\mu}m$. TEM observation revealed that the powder with those BCC/FCC two phase structure have a finely dispersed $SiO_2$ precipitates. Because the Si is ferrite stabilizing element, decrease of Si composition in the matrix phase by the $SiO_2$ precipitation resulted in formation of the retained austenite. Therefore, controlling the elements such as Si as well as oxygen decrease is very important to obtain a normal microstructure in ultra-fine powder $(<3{\mu}m)$ injection molding.

• Applied Microscopy
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• 제5권1호
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• pp.1-8
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• 1975

These studies were carried out the observation of polymorphonuclear leukocyte phagocytosis of Candida albicans in vitro and also detected to the cytoplasmic changes of polymorphonuclear leukocyte during phagocytosis by the method of electron microscopy. The results were summarized as follows: 1. In normal polymorphonuclear leukocyte, nuclear lobes showed a preponderance of dense, granular chromatin located peripherally. The cytoplasm of polymorphonuclear leukocyte was not extensive; the cytoplasmic matrix was moderate dense and of a granular appearance. Golgi complex and rough endoplasmic reticulum system was poorly developed. But a various type of granules were seen abundantly. 2. After 30 minutes of incubation, Candida albicans was completely engulfed. These had come to lie in the vacuole which was limited by the membrane. 3. After 90 minutes of incubation, the phagocytic vacuoles were larger, and many granules devoid of membranes were seen within them. Though the granules has lost their membrane after entering the vacuoles. 4. After 2 hours of incubation, the cytoplamsic components of polymorphonuclear leuko cytes were changed their original morphology.

• 한국주조공학회지
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• 제12권6호
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• pp.464-470
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• 1992

In the present study, the effects of Al/SiC interface reaction and the formation of $Al_4C_3$ compounds on the mechanical properties of the Al/SiC composites prepared by squeeze casting were investigated. After squeeze casting, the size of dendrites in Al without whiskers were larger than those with whiskers. The hardness of composite materials (about 72 Hv) was found to be approximating 40% higher than that of matrix metal (29Hv), which gradually increases which heat treatment Time showing maximum hardness at 12hr. The observation of increasing number of compounds in 12hrs heat treatment suggests that these compounds are responsible for the increase of hardness. By X-ray diffraction studies, those compounds were identified as $Al_4C_3$, (Al, Si). And intensity of Si peak increased. The tensile strengh of composite materials was gradually decresed by heat tretment, which was in contrast to the behavior of hardeness. With incresing heat tretment time, the fracture mode of composite materials was changed from large dimples and pull-out form of fiber to the fracture and rupture foum of fiber.

• Composites Research
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• 제34권2호
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• pp.123-128
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• 2021

본 논문은 Mori-Tanaka법, 혼합법칙 및 Halpin-Tsai 이론식을 적용하여 굴곡진 탄소나노튜브(CNT)로 보강된 복합재의 멀티스케일 고유진동 특성을 규명하였다. Eshelby 텐서를 이용하여 곡률을 갖는 CNT가 함유된 폴리머의 하중 전달 특성값이론을 유도하였다. 도출된 수치해석 결과는 기존의 연구결과와 잘 일치하였다. 본 연구에서 제시한 새로운 결과는 적층 복합재의 CNT 함유량, 굴곡성 및 적층배열의 상호작용 특성을 규명하였다. 주요 결과에 대하여 분석하였으며, CNT 보강 복합재의 실용적 설계를 위한 중요 고려사항을 제시하였다.

• Smart Structures and Systems
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• 제24권2호
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• pp.209-221
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• 2019

The classical Kalman filter (KF) provides a practical and efficient way for state estimation. It is, however, not applicable when the external excitations applied to the structures are unknown. Moreover, it is known the classical KF is only suitable for linear systems and can't handle the nonlinear cases. The aim of this paper is to extend the classical KF approach to circumvent the aforementioned limitations for the joint estimation of structural states and the unknown inputs. On the basis of the scheme of the classical KF, analytical recursive solution of an improved KF approach is derived and presented. A revised form of observation equation is obtained basing on a projection matrix. The structural states and the unknown inputs are then simultaneously estimated with limited measurements in linear or nonlinear systems. The efficiency and accuracy of the proposed approach is verified via a five-story shear building, a simply supported beam, and three sorts of nonlinear hysteretic structures. The shaking table tests of a five-story building structure are also employed for the validation of the robustness of the proposed approach. Numerical and experimental results show that the proposed approach can not only satisfactorily estimate structural states, but also identify unknown loadings with acceptable accuracy for both linear and nonlinear systems.

• 천문학회보
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• 제43권2호
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• pp.57.2-57.2
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• 2018

In astronomical observation, sequential device control and real-time data processing are important to maximize observing efficiency. We have developed series of automatic observing software (KAOS, KHU Automatic Observing Software), e.g. KAOS30 for the 30 inch telescope in the McDonald Observatory and KAOS76 for the 76 cm telescope in the KHAO. The series consist of four packages: the DAP (Data Acquisition Package) for CCD Camera control, the TCP (Telescope Control Package) for telescope control, the AFP (Auto Focus Package) for focusing, and the SMP (Script Mode Package) for automation of sequences. In this poster, we introduce KAOS10 which is being developed for controlling a small telescope such as aperture size of 10 cm. The hardware components are the QHY8pro CCD, the QHY5-II CMOS, the iOptron CEM 25 mount, and the Stellarvue SV102ED telescope. The devices are controlled on ASCOM Platform. In addition to the previous packages (DAP, SMP, TCP), KAOS10 has QLP (Quick Look Package) and astrometry function in the TCP. QHY8pro CCD has RGB Bayer matrix and the QLP transforms RGB images into BVR images in real-time. The TCP includes astrometry function which adjusts the telescope position by comparing the image with a star catalog. In the future, We expect KAOS10 be used on the research of transient objects such as a variable star.

• 한국재료학회지
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• 제29권4호
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• pp.252-257
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• 2019

Fabrication of soft magnetic composite powders for the $Fe_2O_3-Ca$ system by mechanical alloying(MA) has been investigated at room temperature. It is found that soft magnetic composite powders in which CaO is dispersed in ${\alpha}-Fe$ matrix are obtained by MA of $Fe_2O_3$ with Ca for 5 hours. Changes in magnetization and coercivity also reflect the details of the solidstate reduction process of hematite by pure metal of Ca during MA. The saturation magnetization of MA powders increases with increasing MA time and reaches a maximum value of 65 emu/g after 7 hours of MA. The average grain size of ${\alpha}-Fe$ in MA powders, estimated by diffraction line-width, gradually decreases with increasing MA time and reaches 52 nm after 5 hours of MA. It can also be seen that the coercivity of the 5-hour MA sample is fairly high at 190 Oe, suggesting that the grain refinement of already-produced ${\alpha}-Fe$ tends to clearly occur during MA.

• 아태비즈니스연구
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• 제11권1호
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• pp.1-16
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• 2020

Purpose - The purpose of this research is to investigate the determinants of bakery revisit intention. This research selects Paris Baguette as the research context because the market share of Paris Baguette was the highest in Korean bakery market. Design/methodology/approach -This research employed revisit intention as the dependent variable, while this research chooses six attributes to account for revisit intention. Six attributes are price fairness, taste, product variety, accessibility, display, and membership. This research uses survey as the main instrument. For the data collection, online survey using Google survey form was implemented. The survey participants are domestic consumers of Paris Baguette. The number of observation is 245. For the data analysis, this study used frequency analysis, correlation matrix, exploratory factor analysis, reliability analysis, and multiple regression model. There are four control variables, which contains age, gender, visiting frequency, and monthly income. Findings - The results shows that price fairness, taste, product diversity, and accessibility are significant attributes with the positive effect. Among the significant attributes, taste presented the highest magnitude to explain the revisit intention. However, membership and display appeared as non-significant attributes to account for bakery revisit intention. Research implications or Originality - This study provides the bakery managers with the information to design their service and product. This study also contributes to the literature by understanding the consumer behavior more in the domain of bakery service.

• International Journal of Internet, Broadcasting and Communication
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• 제14권4호
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• pp.173-180
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• 2022

In the naked eye observation, the health of livestock can be controlled by the range of activity, temperature, pulse, cough, snot, eye excrement, ears and feces. In order to confirm the health of livestock, this paper uses calf face image data to classify the health status by image shape, color and texture. A series of images that have been processed in advance and can judge the health status of calves were used in the study, including 177 images of normal calves and 130 images of abnormal calves. We used GLCM calculation and Convolutional Neural Networks to extract 6 texture attributes of GLCM from the dataset containing the health status of calves by detecting the image of calves and learning the composite image of Convolutional Neural Networks. In the research, the classification ability of GLCM-CNN shows a classification rate of 91.3%, and the subsequent research will be further applied to the texture attributes of GLCM. It is hoped that this study can help us master the health status of livestock that cannot be observed by the naked eye.

• Educational Technology International
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• 제19권1호
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• pp.35-60
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• 2018

The purpose of this study was to analyze the types of lesson and its effectiveness with digital textbook. To address those goals, we had observed five classes of the primary school, which designated as a research pilot school for digital textbook. Based on the result of observation, 3 types of lesson with digital textbook were categorized: Teacher-directed lecture (type 1), Blended learning (type 2), and Flipped learning (type 3). Depending on the type of lesson was analyzed the positive and negative effectiveness by means of matrix analysis method. As a result, in Teacher-directed lecture (type 1), there was found out the participation of the lesson in atmosphere of stable and comfortable as positive experience, also digital textbook operating immature and boring as negative experience. In Blended learning (type 2), there was found out the fun by sharing the product and peer feedback, and flow by learning transfer as positive experience, also digital textbook operating immature and understanding the difference between assignments as negative experience. In Flipped learning (type 3), there was shown the positive attitude and ownership in the lesson as positive experience, also distracting and boring in the lesson when learner was excluded in participation as negative experience. Based on the results, we suggested some strategies for improving positive experience and protecting negative experience in the lesson with using digital textbook.