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WO<sub>3</sub>-TiH<sub>2</sub> 혼합분말의 동결건조 및 수소환원에 의한 W-Ti 다공체 제조
강현지,박성현,오승탁,Kang, Hyunji,Park, Sung Hyun,Oh, Sung-Tag 한국분말야금학회 2017 한국분말재료학회지 (KPMI) Vol.24 No.6
Porous W-10 wt% Ti alloys are prepared by freeze-drying a $WO_3-TiH_2$/camphene slurry, using a sintering process. X-ray diffraction analysis of the heat-treated powder in an argon atmosphere shows the $WO_3$ peak of the starting powder and reaction-phase peaks such as $WO_{2.9}$, $WO_2$, and $TiO_2$ peaks. In contrast, a powder mixture heated in a hydrogen atmosphere is composed of the W and TiW phases. The formation of reaction phases that are dependent on the atmosphere is explained by a thermodynamic consideration of the reduction behavior of $WO_3$ and the dehydrogenation reaction of $TiH_2$. To fabricate a porous W-Ti alloy, the camphene slurry is frozen at $-30^{\circ}C$, and pores are generated in the frozen specimens by the sublimation of camphene while drying in air. The green body is hydrogen-reduced and sintered at $1000^{\circ}C$ for 1 h. The sintered sample prepared by freeze-drying the camphene slurry shows large and aligned parallel pores in the camphene growth direction, and small pores in the internal walls of the large pores. The strut between large pores consists of very fine particles with partial necking between them.
MoO<sub>3</sub>-CuO 혼합분말의 볼 밀링 및 수소분위기 열처리에 의한 Mo-Cu 복합분말 제조
강현지,오승탁,Kang, Hyunji,Oh, Sung-Tag 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.4
The hydrogen reduction behavior of $MoO_3-CuO$ powder mixture for the synthesis of homogeneous Mo-20 wt% Cu composite powder is investigated. The reduction behavior of ball-milled powder mixture is analyzed by XRD and temperature programmed reduction method at various heating rates in Ar-10% $H_2$ atmosphere. The XRD analysis of the heat-treated powder at $300^{\circ}C$ shows Cu, $MoO_3$, and $Cu_2MoO_5$ phases. In contrast, the powder mixture heated at $400^{\circ}C$ is composed of Cu and $MoO_2$ phases. The hydrogen reduction kinetic is evaluated by the amount of peak shift with heating rates. The activation energies for the reduction, estimated by the slope of the Kissinger plot, are measured as 112.2 kJ/mol and 65.2 kJ/mol, depending on the reduction steps from CuO to Cu and from $MoO_3$ to $MoO_2$, respectively. The measured activation energy for the reduction of $MoO_3$ is explained by the effect of pre-reduced Cu particles. The powder mixture, hydrogen-reduced at $700^{\circ}C$, shows the dispersion of nano-sized Cu agglomerates on the surface of Mo powders.
WO<sub>3</sub>-TiH<sub>2</sub> 혼합분말의 반응처리 및 방전 플라스마 소결에 의한 W-Ti 치밀체 제조
강현지,김헌주,한주연,이윤주,정영근,오승탁,Kang, Hyunji,Kim, Heun Joo,Han, Ju-Yeon,Lee, Yunju,Jeong, Young-Keun,Oh, Sung-Tag 한국재료학회 2018 한국재료학회지 Vol.28 No.9
W-10 wt% Ti alloys that have a homogeneous microstructure are prepared by thermal decomposition of $WO_3-TiH_2$ powder mixtures and spark plasma sintering. The reduction and dehydrogenation behavior of $WO_3$ and $TiH_2$ are analyzed by temperature programmed reduction and a thermogravimetric method, respectively. The X-ray diffraction analysis of the powder mixture, heat-treated in an argon atmosphere, shows W- oxides and $TiO_2$ peaks. Conversely, the powder mixtures heated in a hydrogen atmosphere are composed of W, $WO_2$ and $TiO_2$ phases at $600^{\circ}C$ and W and W-rich ${\beta}$ phases at $800^{\circ}C$. The densified specimen by spark plasma sintering at $1500^{\circ}C$ in a vacuum using hydrogen-reduced $WO_3-TiH_2$ powder mixtures shows a Vickers hardness value of 4.6 GPa and a homogeneous microstructure with pure W, ${\beta}$ and Ti phases. The phase evolution dependent on the atmosphere and temperature is explained by the thermal decomposition and reaction behavior of $WO_3$ and $TiH_2$.
금속산화물 분말의 동결건조 및 수소환원에 의한 Mo-Cu 다공체 제조
강현지,한주연,오승탁,Kang, Hyunji,Han, Ju-Yeon,Oh, Sung-Tag 한국분말재료학회 (*구 분말야금학회) 2019 한국분말재료학회지 (KPMI) Vol.26 No.1
In this study, porous Mo-5 wt% Cu with unidirectionally aligned pores is prepared by freeze drying of camphene slurry with $MoO_3-CuO$ powders. Unidirectional freezing of camphene slurry with dispersion stability is conducted at $-25^{\circ}C$, and pores in the frozen specimens are generated by sublimation of the camphene crystals. The green bodies are hydrogen-reduced at $750^{\circ}C$ and sintered at $1000^{\circ}C$ for 1 h. X-ray diffraction analysis reveals that $MoO_3-CuO$ composite powders are completely converted to a Mo-and-Cu phase without any reaction phases by hydrogen reduction. The sintered bodies with the Mo-Cu phase show large and aligned parallel pores to the camphene growth direction as well as small pores in the internal walls of large pores. The pore size and porosity decrease with increasing composite powder content from 5 to 10 vol%. The change of pore characteristics is explained by the degree of powder rearrangement in slurry and the accumulation behavior of powders in the interdendritic spaces of solidified camphene.
CuO-Al<sub>2</sub>O<sub>3</sub>/camphene 슬러리의 동결건조 공정에 의한 Al<sub>2</sub>O<sub>3</sub> 입자분산 Cu 다공체 제조
강현지,류도형,오승탁,Kang, Hyunji,Riu, Doh-Hyung,Oh, Sung-Tag 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.1
Porous Cu with a dispersion of nanoscale $Al_2O_3$ particles is fabricated by freeze-drying $CuO-Al_2O_3$/camphene slurry and sintering. Camphene slurries with $CuO-Al_2O_3$ contents of 5 and 10 vol% are unidirectionally frozen at $-30^{\circ}C$, and pores are generated in the frozen specimens by camphene sublimation during air drying. The green bodies are sintered for 1 h at $700^{\circ}C$ and $800^{\circ}C$ in $H_2$ atmosphere. The sintered samples show large pores of $100{\mu}m$ in average size aligned parallel to the camphene growth direction. The internal walls of the large pores feature relatively small pores of ${\sim}10{\mu}m$ in size. The size of the large pores decreases with increasing $CuO-Al_2O_3$ content by the changing degree of powder rearrangement in the slurry. The size of the small pores decreases with increasing sintering temperature. Microstructural analysis reveals that 100-nm $Al_2O_3$ particles are homogeneously dispersed in the Cu matrix. These results suggest that a porous composite body with aligned large pores could be fabricated by a freeze-drying and $H_2$ reducing process.
The Interpretation of Linguistic Sarcasm
강현지(Kang Hyun-jee) 한국사회언어학회 2013 사회언어학 Vol.21 No.2
If politeness principles aim at maintaining a harmonious relationship among interlocutors, sarcasm targets the opposite end; it is designed to throw sarcastic accusation. Quite often, sarcasm is originated from Speaker. On occasions Hearer infers sarcasm out of Speaker's well-wishing utterances. In other times, Speaker's sarcasm is so blurry that Hearer cannot judge whether Speaker's utterance is sarcastic or not. This writer attempts to interpret linguistic sarcasm by illustrating different cases in which sarcasm is generated, transferred and interpreted. The first kind is Speaker-originated sarcasm. Speaker generates sarcasm and delivers it. Hearer interprets Speaker's sarcastic message as sarcasm. The second case refers to Hearer-originated sarcasm. Because of his or her own person hood or viewpoints of the world, Hearer infers sarcasm out of Speaker's innocuous utterances. The final case is the exploitation of ambiguity. Taking advantage of the linguistic ambiguity between sarcastic irony and banter, Speaker throws a punch of acerbic sarcasm. (165)
강현지 ( Hyeonji Kang ),고란희 ( Ranhee Ko ),이소연 ( Soyeon Lee ),강신혜 ( Sinhye Kang ),권상철 ( Sangcheol Kwon ),조정원 ( Jungwon Cho ) 한국컴퓨터교육학회 2017 한국컴퓨터교육학회 학술발표대회논문집 Vol.21 No.2
전 세계적으로 과학, 기술, 공학, 예술, 수학이 융합된 STEAM교육이 강조되고 있는 가운데 우리나라도 STEAM교육의 효율성을 높여줄 수 있는 콘텐츠에 대한 관심과 적용이 늘어가고 있다. 본 논문은 "공업입지론“ 내용을 바탕으로 개발된 에듀테인먼트 콘텐츠의 교육적 효과를 향상시키고자 분석 피드백 기능을 강화 하였다. 강화된 분석 피드백 기능은 첫째, 학습자가 공장 선택 조건과 각 공장의 장점 확인, 둘째, 상품의 운송조건 제시, 셋째, 학습 결과에 대한 분석이다. 이에 학습자가 콘텐츠를 통해 학습하는 과정에서 분석 피드백을 제공 받아 학습에 대한 이해도 등 교육적 효과를 향상 시키고자 한다.
피지컬 컴퓨팅을 적용한 가상현실 기반 학교안전교육 어플리케이션
강현지(HyeonJi Kang),강소희(Sohee Kang),고란희(RanHee Ko),이경희(KyungHee Lee),조정원(JungWon Cho) 한국컴퓨터교육학회 2018 한국컴퓨터교육학회 학술발표대회논문집 Vol.22 No.2
학교에서 자연재난으로 인해 학생들의 인명피해가 발생하는 사례가 빈번하게 발생하고 있다. 이에 학생들에게 발생하는 각 재난상황들에 대하여 학생들 스스로 재난상황에 대응할 수 있는 안전능력배양 중요성이 부각되어지고 학교의 안전교육을 강화해야 한다는 지적이 제기되고 있다. 하지만, 현재 학교에서 학생들에게 실시하는 안전교육은 주로 강의식이고, 안전교육을 위한 시설과 장비, 담당하는 인력의 전문성과 안전교육의 체계가 부족하다는 문제점들이 제기되고 있다. 본 논문은 가상현실과 피지컬컴퓨팅 기반의 안전교육 프로그램을 통해 학생들은 동작인식컨트롤러를 이용하여 가상현실 속 재난상황을 체험하고 행동요령과 사용법 등을 학습하여 위기대응능력을 배양 하고자 한다.