MOCVD를 이용한 금속 촉매 종류에 따른 β-Ga₂O₃ 나노 와이어의 제작과 특성

이승현,이서영,정용호,이효종,안형수,양민,Lee, Seunghyun,Lee, Seoyoung,Jeong, Yongho,Lee, Hyojong,Ahn, Hyungsoo,Yang, Min 한국결정성장학회 2017 한국결정성장학회지 Vol.27 No.1

Metal organic chemical vapor deposition(MOCVD) 방법을 이용하여 금속 촉매에 따른 ${\beta}-Ga_2O_3$ 나노 와이어의 제작과 특성에 대해 연구하였다. 본 연구의 성장 조건에서 ${\beta}-Ga_2O_3$ 나노 와이어의 성장이 가능한 금속 촉매는 Au, Cu 그리고 Ni이 있었으며 각 금속 촉매로 성장한 나노 와이어는 성장률과 형상에 많은 차이가 있었다. Ni 촉매 성장의 경우에는 Vapor-Solid(VS) 과정이 ${\beta}-Ga_2O_3$ 나노 와이어 성장의 주된 메커니즘이고 Au, Cu 촉매 성장의 경우에는 Vapor-Liquid-Solid(VLS) 과정이 주된 성장 메커니즘 임을 확인할 수 있었다. 또한, 촉매의 종류에 따라서 ${\beta}-Ga_2O_3$ 나노 와이어의 광학적 특성도 다르게 나타나는 것을 확인할 수 있었다. 반면, 동일한 성장 조건에서 Ti, Ag 그리고 Sn 금속은 나노 와이어 성장을 위한 촉매로 작용하지 못하였다. 본 연구에서는 금속 촉매에 따른 나노 와이어의 성장 가능 여부와 성장한 나노 와이어의 특성 변화가 금속 촉매의 녹는 점, 금속- Ga의 공융 점과 관련이 있음을 상태도와 연관 지어 밝혀내었다. Catalytic synthesis and properties of ${\beta}-Ga_2O_3$ nanowires grown by metal organic chemical vapor deposition are reported. Au, Ni and Cu catalysts were suitable for the growth of $Ga_2O_3$ nanowires under our experimental conditions. The $Ga_2O_3$ nanowires grown by using Au, Ni and Cu catalysts showed different growth rates and morphologies in each case. We found the $Ga_2O_3$ nanowires were grown by the Vapor-Solid (VS) process when Ni was used as a catalyst while the Vapor-Liquid-Solid (VLS) was a dominant process in case of Au and Cu catalysts. Also, we found nanowires showed different optical properties depend on catalytic metals. On the other hand, for the cases of Ti, Sn and Ag catalysts, nanowires could not be obtained under the same condition of Au, Cu and Ni catalytic synthesis. We found that these results are related to the different characteristics of each catalyst, such as, melting points and phase diagrams with gallium metal.

First Record of Subgenus Pronocerodes Plavilstshikov (Coleoptera: Cerambycidae: Ropalopus) from Korea

이승현,오승환,이민혁,승진배,이승환,Lee, Seunghyun,Oh, Seunghwan,Lee, Minhyeuk,Seung, Jinbae,Lee, Seunghwan Korean Society of Applied Entomology 2021 한국응용곤충학회지 Vol.60 No.3

하늘소아과 검정삼나무하늘소속의 미기록아속인 호리검정삼나무하늘소아속(신칭)에 속하는 Ropalopus (Pronocerodes) aurantiicollis Plavilstshikov, 1940의 한반도 분포를 처음으로 보고한다. 형태적 기재와 사진, 국내 검정삼나무하늘소속의 검색표를 함께 제공한다. The subgenus Pronocerodes Plavilstshikov (Coleoptera: Cerambycidae: Cerambycinae) is reported from Korea for the first time with a species of Ropalopus (Pronocerodes) aurantiicollis Plavilstshikov, 1940. The morphological information is provided with a key to the Korean Ropalopus and photographs of an adult specimen.

Data-driven health condition and RUL prognosis for liquid filtration systems

이승현,Seungju Lee,Kwonneung Lee,Sangwon Lee,Jaemin Chung,김창완,윤장혁 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.4

Because the clogging of filters leads to degradation and failure of mechanical systems, it is important to assess the health condition of a filter and predict its remaining useful life (RUL). Despite prior studies of liquid filtration systems, adequate attention has not been paid to data-driven health condition and RUL prognosis. Therefore, this study suggests a datadriven prognosis approach for liquid filtration systems. We define a health index (HI) for the filter under study and then predict HI values from the degradation point to the end-of-life using recurrent neural network algorithms, thereby yielding the filter’s RUL. As a result, the bidirectional LSTM achieved the best performance, and the RUL measured through HI prediction was close to the actual RUL. The proposed approach can be used for the maintenance of liquid filtration systems in various industries.

홍삼·백년초 복합물이 관절염 개선에 미치는 효과

이승현,이창현,김홍준,김영식,신민지,김지현,마상용,이세연,권진,오찬호,Lee, Seung-Hyeon,Lee, Chang-Hyun,Kim, Hong-Jun,Kim, Young-Sik,Shin, Min-Ji,Kim, Ji-Hyun,Ma, Sang-Yong,Lee, Se-Youn,Kwon, Jin,Oh, Chan-Ho 대한한의학방제학회 2021 大韓韓醫學方劑學會誌 Vol.29 No.2

Objectives : This study was conducted to evaluate the efficacy of a complex mixture of natural substances of ginseng and baeknyeoncho on the arthritic rats. Methods : In vitro experiments were conducted to ensure the stability of the complex. After setting toxicity and concentration by MTT assay, the antioxidant effect was measured through DPPH and ABTS radical scavenging activity. To confirm the anti-inflammatory effects of the complex, levels of nitric oxide (NO) and pro-inflammatory cytokines (IL-1β, TNF-α) were measured in LPS-treated macrophage cell lines (RAW264.7). We injected monosodium iodoacetate (MIA) 50 μl (60 mg/ml) into knee joints of rats to induce osteoarthritis. The rats were divided into three groups (normal (n=5), control (n=5), and OR (n=5) group). The control group consumed 2 mg/kg of physiological saline once a day for 4 weeks, and the OR group was mixed at a concentration of 416.5 mg/kg of Baengnyeoncho (O) and 208.25 mg/kg of red ginseng (R) and ingested 1 mL each 5 days a week. Results : This complex increased the DPPH and ABTS radical scavenging rate. The complex decreased NO production and pro-inflammatory cytokine production of macrophages. In the OR group, the secretion of cytokine in serum was decreased. In histopathological examination, the joint tissue of the composite showed less damage to the synovial membrane, cartilage, and fibrous tissue than the control group. Conclusions : As a result of this study, natural complexes have antioxidant, anti-inflammatory and cartilage protection effects. Therefore, we expect the complex to be effective in treating osteoarthritis.

측두하악관절조영술을 이용한 측두하악관절장애의 임상적 연구

이승현,황의환,이상래,Lee Seung-Hyun,Hwang Eui-Hwan,Lee Sang-Rae 대한영상치의학회 1998 Imaging Science in Dentistry Vol.28 No.1

The purpose of this study was to prove the relationship between arthrographic and clinical features in temporomandibular joint disorders. In order to carry out this study, ninety-eight arthrographic examinations of temporomandibular joints were performed on eighty-two patients who had the temporomandibular joint disorders. As the arthrographic examination, the cases were classified in three groups, disk displacement with reduction, disk displacement without reduction, within normal limit. After this, the cases were clinically examined, and the results were compared and analyzed in each other group. The obtained results were as follows; 1. As the classification by arthrographic examination, three groups (disc displacement with reduction, disc displacement without reduction, within normal limit) were 41 %, 54%, 5% of total cases in this study, respectively. 2. The third decade(65%) was most frequent in this study. The average age of each group (disc displacement with reduction, disc displacement without reduction, within normal limit) was 24, 28, 21, and disc displacement without reduction group was higher than any other group. 3. In the chief complaint, pain was the most frequent in all three groups. Joint sound was also frequent in disc displacement with reduction group, but in disc displacement without reduction group, limitation of mouth opening was more frequent. 4. Of the various pain, the movement pain was most frequent ( 61 %) in this study. In joint sound, click(63%) was the most frequent in disc displacement with reduction group, but sound history(42%) and no sound (31 %) were more frequent in disc displacement without reduction group. 5. The average maximum opening of each group (disc displacement with reduction, disc displacement without reduction, within normal limit) was 44mm, 32.9mm, 44mm, and disc displacement without reduction group was less than any other group. 6. The masticatory disturbance of each group (disc displacement with reduction, disc displacement without reduction, within normal limit) was 53%, 79%, 40%, and the trauma history of each group was 50%, 40%,60%.

Ag층을 이용한 Sn과 In의 무 플럭스 접합

이승현,김영호,Lee Seung-Hyun,Kim Young-Ho 한국마이크로전자및패키징학회 2004 마이크로전자 및 패키징학회지 Vol.11 No.2

본 실험에서는 Ag 층을 이용한 무 플럭스 접합 공정을 개발하였으며 Ag의 유무에 따른 효과를 관찰하기 위해 In ($10{\mu}m$)과 Sn ($10{\mu}m$)솔더 및 Ag (100 nm)/In과 Ag/Sn 솔더를 thermal evaporation 방법으로 하부 금속층 위에 형성하였다. 접합부의 접촉저항과 전단 하중을 측정하기 위해 쿠폰시편을 제조하였으며 이리한 쿠폰시편은 $130^{\circ}C$에서 0.8, 1.6, 3.2 MPa의 접합압력을 가하여 30초간 접합을 실시하였다. 전단하중과 4단자 저항측정법을 이용하여 접합부의 특성을 분석하였으며 주사전자현미경(Scanning Electron Microscope), EDS (Energy Dispersive Spectrometry)과 X-ray mapping을 통해 접합부를 관찰하였다. 전단하중 측정 결과 0.8 MPa에서는 In-Sn 솔더의 접합이 이루어지지 않았으며 접합압력이 증가해도 Ag/In-Ag/Sn 시편의 전단하중 측정값이 In-Sn 시편에 비해 높게 나타났다. 접합부의 저항감은 $2-4\;m{\Omega}$을 나타내었으며 접합압력이 증가할수록 In-Sn 혼합층이 더 많이 관찰되었다. We utilized Ag capping layer for fluxless bonding. To investigate the effect of Ag capping layer, two sets of sample were used. One set was bare In and Sn solders. The other set was In and Sn solders with Ag capping layer. In ($10{\mu}m$) and Sn ($10{\mu}m$) solders were deposited on Cu/Ti/Si substrate using thermal-evaporation, and Ag ($0.1{\mu}m$) capping layers were deposited on In and Sn solders. Solder joints were made by joining two In and Sn deposited specimens at $130^{\circ}C$ for 30 s under 0.8, 1.6, 3.2 MPa using thermal compression bonder. The contact resistance was measured using four-point probe method. The shear strength of the solder joints was measured by the shear test of cross-bar sample in the direction. The microstructure of the solder joints was characterized with SEM and EDS. In and Sn solders without Ag capping layers were only bonded at $130^{\circ}C$ under high bonding pressure. Also the shear strength of the In-Sn solder joints under was lower than that of the Ag/In-Ag/Sn solder joints. The resistance of the solder joints was $2-4\;m{\Omega}$ The solder joints consisted of In-rich phase and Sn-rich phase and the intermixed compounds were found at the interface. As bonding pressure increased, the intermixed compounds formed more.

불활성 증발 응축방법으로 제조된 금과 은 나노입자의 소결특성

이승현,민동열,이광민,Lee, Seung-Hyun,Min, Dong-Ryoul,Lee, Kwang-Min 한국분말야금학회 2007 한국분말재료학회지 (KPMI) Vol.14 No.3

The purpose of this study was to analyze the sintering characteristics of gold and silver nanoparticles. In this study, gold and silver nanoparticles were prepared by using Inert Gas Cndensation (IGC). The sintering temperatures for gold and silver nanoparticles were $100{\sim}1000^{\circ}C\;and\'100{\sim}500^{\circ}C$, respectively. The sintering characteristics of gold and silver nanoparticles prepared by IGC were evaluated by X-ray diffraction(XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Gold and silver nanoparticles with the size of $1{\sim}100\;nm\;and\;10{\sim}100\;nm$, respectively, were obtained. The size of sintered gold and silver nanoparticles increased with an increase in the sintering temperature. XRD data showed that silver nanoparticles were similar with polycrystal single-phase.

주의력결핍 과잉행동 장애의 원인(原因) 및 병기(病機)에 따른 한방음악치료의 기법(機法)에 관한 연구

이승현,김여진,Lee, Seung-Hyun,Kim, Yeo-Jin 대한한방소아과학회 2009 대한한방소아과학회지 Vol.23 No.1

Objectives The purpose of this study is to introduce oriental medicine music therapy related to the treatment of ADHD. Methods This study observed ADHD from the oriental medical point of view and tried to treat this disease with the oriental medicine music therapy. Results ADHD is caused by excess of Yang energy, flaming-up of fire, blood deficiency of the heart and the spleen, deficiency of the kidney essence, and instability of emotions. The ADHD patients with the case of excess of Yang energy and flaming-up of fire, patients were played Fire-Gi rhythm as a treatment, and they listened to Metal-Gi music. Whereas, the ADHD patient with blood deficiency of the heart and the spleen, invigoration of vital energy music therapy can be used. Another case of ADHD patients with deficiency of the kidney, Water-Gi rhythm and replenishing vital essence music therapy can be used. According to the patients' seven modes of emotions, the proper music should be chosen. Conclusions Oriental medicine music therapy can be a new type of treatment for ADHD patients.

[초청논문] Track 2-1 : CEM 이론과 기술 CEM Academic Session

이승현,Lee, Seung-Hyeon 한국건설관리학회 2009 한국건설관리학회 논문집 Vol.10 No.6

패럴랙스배리어와 렌티큘러 스크린 방식의 3D 디스플레이

이승현,Lee, Seung-Hyeon 한국정보디스플레이학회 2007 인포메이션 디스플레이 Vol.8 No.4