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기계화학적 고상반응에 의한 YAG 분말의 합성 및 상 형성 거동에 관한 연구
정현기,황길호,임광영,이영훈,강성군,Jung Hyun-Gi,Hwang Gil-Ho,Lim Kwang-Young,Lee Young-Hun,Kang Sung-Goon 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.4
Yttrium aluminum garnet (YAG) powders were synthesized via mechanochemical solid reaction using $Y_2O_3$ with three types of aluminum compounds. $Y_2O_3$ reacted mechanochemically with all A1 compounds and formed YAM (yttrium aluminum monoclinic), YAG and YAP (yttrium aluminum perovskite) phases depending on the starting materials. The ground samples containing ${\gamma}-A1_2O_3$ showed the best reactivity, whereas the ground sample containing A100H, which had the largest surface area, exhibited pure YAG after calcination at $1200^{\circ}C$. The sample containing Al had the least reactivity, producing YAP along with YAG at $1200^{\circ}C$. The types and grinding characteristics of the starting materials and grinding time are believed to be important factors in the mechanochemical synthesis of YAG.
플라즈마 표면처리를 이용한 YBCO Coated Conductor의 Ag 박막층 증착에 관한 연구
정현기,양성채,최병정,두호익,Jeong, Hyun-Gi,Yang, Sung-Chae,Choi, Byoung-Jung,Du, Ho-Ik 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.1
The Ag thin film of YBCO (yttrium barium copper oxide) CC (coated conductor) protect the YBCO layer and, at the same time, affects the electrical characteristics of the YBCO CC. Therefore, YBCO CC with the commercialization of the Ag thin film layers makes it easy to establish a process, it can lead to a variety of characteristic changes in YBCO CC. In this paper, plasma surface treatment was carried out to facilitate the deposition of the Ag thin film and the deposition process of YBCO CC. Surface roughness from the test results was increased as the time of the plasma surface treatment increased from 5 to 20 minutes. On the other hand, the surface roughness was decreased for the time of the plasma surface treatment over 20 minutes. Furthermore, after depositing, the increasing of deposit amount and reduced lifting phenomenon showed a similar tendency with the rise time of surface roughness.
마음알아차리기 기록이 공상자각, 탈중심화, 양육스트레스 및주관적 안녕감에 미치는 영향: 청소년기 자녀를 둔 부모를 중심으로
정현기 ( Hyun Gi Jung ),성승연 ( Seoung Yun Sung ) 한국가족관계학회 2016 한국가족관계학회지 Vol.20 No.4
Objectives: The purpose of this study is to examine the effects of reading mind recording on awareness of imaginations, Method: Decentering, parenting stress and subjective well-being through comparing expressive writing. random assignment was performed on each 13 persons of a recording group (experimental group) and an expressive writing group (comparison group) for reading mind from 26 parents having adolescents. The experimental group conducted the reading of reading mind and the comparison group performed expressive writing twice a week for eight weeks, twenty minutes per time, and responded to four questions on thought arrangement after writing. The researcher participated in the groups once per week and an assignment was suggested once per week. Repeated Measurement Two-way Repeated Measures ANOVA was conducted to confirm the differences according to periods and groups for the data analysis method. In order to examine the changes according to periods, t-test was conducted on the pre- and post-test. Results: The findings are as follows: First, regarding awareness of imaginations and decentering, the reading mind recording group showed a significant result in repeated measurement. Second, the reading mind recording group showed a significant decrease in the pre- and post-t-test about parenting stress. Third, all the reading mind recording group and expressive writing group showed significant results about subjective well-being. Conclusions: This study is significant in that it verified the effectiveness of reading mind recording on awareness of imaginations, decentering and parenting stress, and proved the possibility as an oriental counseling model that considers the characteristics of our culture.
수중 원통형 쉘 구조물의 고주파 진동 전달특성에 대한 실험적 연구
정현기(Hyun-Gi Jung),민천홍(Cheon-Hong Min),박한일(Han-Il Park) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
Underwater vehicles such as a UUV(Unmanned Underwater Vehicle) and a ROV(Remotely Operated Vehicle) use the sonar in order to detect underwater environment or other underwater vehicles. The underwater vehicles designed recently have a high rotation and power electric propulsion system. This system can generate high frequency vibrations above 10kHz and these vibrations have bad effects on the performance of the sonar. In many previous investigations, numerical analyses for high frequency vibration problem have been used. In this study, an experimental analysis is carried out and a circular cylindrical shell is considered as a hull structure of underwater vehicle. Frequency transfer functions for the circular cylindrical shell are identified by experimental vibration analysis in the air and in fully-submerged condition. We compare frequency transfer functions in the air and water to obtain hydro-elastic effects. It is found that dynamic characteristics of the circular cylindrical shell are changed by the variation of response position.
Kamut (Triticum turgidum spp.) 식빵 급여가 고지방식이 유도 비만 C57BL/6 마우스에 미치는 효과
정현기(Hyun Gi Jung),백지윤(Ji Yun Baek),최예정(Ye Jung Choi),강기성(Ki Sung Kang),김현영(Hyun Young Kim),김지현(Ji Hyun Kim),최진상(Jine Shang Choi) 한방비만학회 2021 한방비만학회지 Vol.21 No.2
Objectives: The purpose of this study was to investigate the effect of white pan bread added with Kamut (Triticum turgidum spp.) on high fat diet (HFD)-induced obese C57BL/6 mice. Methods: The white pan bread or white pan bread with Kamut (BK) were administered for 8 weeks in HFD-induced obese C57BL/6 mice. To evaluate the effect and its mechanisms of BK on obese mice, we measured body weight change, serum lipid profiles, histopathological analysis, and protein expression of CCAAT/enhancer binding protein-α (C/EBPα) in the liver. Results: Administration of BK significantly decreased body weight in HFD-induced obese mice. In addition, BK-administered group significantly reduced serum total cholesterol, glucose, and high-density lipoprotein cholesterol levels compared with the HFD-induced control group. The HFD-induced mice had damaged liver tissue and increased the size of adipose tissue, but BK-administered group attenuated liver damage and decreased the size of adipocyte. Furthermore, administration of BK significantly down-regulated C/EBPα in the liver compared with HFD-fed mice. In particular, BK-administered group has higher inhibited body weight, serum lipid profiles, and C/EBPα expressions than white pan bread-administered group. Conclusions: This study demonstrated that administration of BK attenuated HFD-induced obesity by regulation of C/EBPα than consumption of white pan bread. Therefore, BK could be developed as a bread for prevention of obesity.
여름철 얕은 저수지의 중앙과 연안에서 동물플랑크톤 군집의 서식지 선택
정현기 ( Hyun Gi Jeong ),서정관 ( Jung Kwan Seo ),이혜진 ( Hae Jin Lee ),이원철 ( Won Choel Lee ),이재관 ( Jaek Wan Lee ) 한국환경생물학회 2010 환경생물 : 환경생물학회지 Vol.28 No.4
The Abundance of zooplankton was studied in the pelagic and the littoral zone in four shallow reservoirs along with the Nakdong river basin of S. Korea. In the pelagic zone, there was a higher zooplankton density (477.5±312.4 ind. L-1) than in the littoral zone during our study period (t=2.337, p?0.05). Overall, Rotifers were the most abundant group in the studied reservoirs. However, there are no significant correlations between the pelagic and the littoral zone in physical and chemical parameters. In the pelagic and the littoral zone, zooplankton density usually increased with increasing density of aquatic plants in the littoral zone. However, this study showed different trends. Although macrophyte abundance was higher in the littoral zone than in the pelagic zone, zooplankton abundance was higher in pelagic zone. Moreover, when macrophytes (Trapa japonica and Spirodela plyrhiza) covered the complete water surface of the reservoir, zooplankton abundance was higher. It appears that comparisons between the pelagic and the littoral zone give important cues on the selection of habitats by zooplankton. It is assumed that a higher density of aquatic plants does not always imply a higher density of zooplankton in the littoral zone. Furthermore, when the water surface was covered with aquatic plants, the zooplankton communities showed the highest density in the pelagic zone. These results imply that habitat selection of the zooplankton community (Rotifers) is influenced by aquatic plant density with an associated decrease in predation pressure during summer.
연구논문 : 농업용저수지인 오태지의 수생태계구조와 수질과의 관련성
서정관 ( Jung Kwan Seo ),이혜진 ( Hae Jin Lee ),정현기 ( Hyun Gi Jeong ),탁보미 ( Bo Mi Tak ),이재관 ( Jae Kwan Lee ),김인택 ( In Taek Kim ),이종은 ( Jong Eun Lee ),황의욱 ( Ui Wook Hwang ) 한국환경과학회 2010 한국환경과학회지 Vol.19 No.11
This study was carried out to elucidate the relation between water quality and structure of the aquatic ecosystem in the agriculture reservoir Otae-ji from January to December in 2009. The proportion of forest was 46.98%, which means that non-point sources are major contributor of water pollution in this area. The annual mean COD(Chemical Oxygen Demand) in Otae-ji was 3.6 mg L-1, indicating, level II of environmental standards and the trophic state was mesotrophic. Although total phosporus concentration in the reservoir was high in August due to large inflow of nutrients from outside the reservoir during monsoon season, there was no break out of significant algal bloom in the summer. The seasonal succession of phytoplankton showed that the dinophyta dominated in the the spring, chlorophyta in the summer, chrysophyta and chlorophyta in the autumn and chrysophyta in the winter. In case of zooplankton, rotifers dominated in the most seasons, but cladoceran(Bosmina longirostris) dominated in June and copepod(Nauplii) in August. The macrophyte plants showed diverse species composition consisted of 3 varieties, 24 species, 23 genera, 15 families and 14 orders. The macroinvertebrates also showed various FFG(Functional Feeding Groups) such as GC(Gathering-Collector), P(Predator), SH(Shedder), FC(Filter-Collector) and PP(Plant-Piercer). Ecosystem stability analysis using aquatic insects was classified as Group I, which has high resilience and resistance indices. A total of 14 species of fish was collected but exotic species such as Lepomis macrochirus and Micropterus salmoides were not found in Otae-ji. In conclusion, the preservation of healthy food wed in the reservoir ecosystem is closely related to water quality management as well as effective prevention of algal bloom by helping good material circulation in aquatic ecosystems.