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MOCVD를 이용한 금속 촉매 종류에 따른 β-Ga<sub>2</sub>O<sub>3</sub> 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.
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.
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.
중심장액맥락망막병증의 레이저 치료 후 발생한 맥락막신생혈관 4예
이승현,정혜원,김형찬.Seung Hyen Lee. MD. Hyewon Chung. MD. PhD. Hyung Chan Kim. MD. PhD 대한안과학회 2012 대한안과학회지 Vol.53 No.6
Purpose: To report the choroidal neovascularization of 4 patients in central serous chorioretinopathy treated with laser treatment. Case summary: We reported 4 patients with central serous chorioretinopathy. Three patients were treated with focal laser photocoagulation, and 1 patient with photodynamic treatment. All patients newly developed choroidal neovascularization (CNV) after treatment at the area of laser treatment. Three patients received intravitreal anti-VEGF injection and 1 patient received argon laser photocoagulation for the treatment of CNV. After the treatment, the CNV was resolved with improved visual acuity. Conclusions: Laser treatment may be efficacious tool to achieve rapid resolution in central serous chorioretinopathy until now. However, more caution at the time of treatment and close follow-up after treatment are warranted. J Korean Ophthalmol Soc 2012;53(6):886-894
철도사면파괴 원인 및 대책공법 적용을 위한 강도정수 결정
이승현,김병일,Lee,Seung-Hyun,Kim,Byoung-Il 한국방재학회 2004 한국방재학회논문집 Vol.4 No.3
철도사면은 예상치 못한 연약지반의 존재로 인해 붕괴될 수 있다. 이 연구는 철도사면의 파괴원인을 규명하고 대책공법 적용을 위한 강도정수를 결정하는데 그 목적이 있다. 사면파괴의 원인을 파악하기 위하여 시추조사, 콘관입시험, 현장베인시험 등이 수행되었다. 또한 연약지반의 강도정수를 구하기 위해 불교란상태로 시료를 채취하여 실내시험을 수행하였다. 현장원위치시험 및 실내시험 결과 사면 파괴의 원인은 과압밀점토의 점진적 파괴에 따른 연약지반 강도저하영역의 전파에 기인한 것으로 밝혀졌다. Rail road slope can be fatted because of existence of unexpected soft subsoil. Purpose of this study is verifying the cause of rail road slope failure and determination of soil strength for remedy. Drilling some boreholes, cone penetration test and field vane test were executed in order to find out the cause of slope failure. In addition, laboratory test was conducted in order to determine soil strength of soft soil sampled as undisturbed state. As a result of both the in-situ and the laboratory tests, the cause of slope failure is thought to be propagation of failure zone by progressive rupture of overconsolidated clay Soft soil strength was determined through back analysis of the failed slope.
A New Record of the tribe Atimiini LeConte (Coleoptera: Cerambycidae: Aseminae) in Korea
이승현,유인성,이승환,Lee, Seunghyun,Yoo, In-Seong,Lee, Seunghwan Korean Society of Applied Entomology 2016 한국응용곤충학회지 Vol.55 No.3
하늘소과, 넓적하늘소아과의 무늬넓적하늘소족(Atimiini LeConte)에 속하는 무늬넓적하늘소(Atimia nadezhdae Tsherepanov)의 한국 분포를 최초로 보고한다. 성충의 외부형질, 수컷의 생식기 형질, 생태 정보를 함께 제공한다. Atimia nadezhdae Tsherepanov which belongs to tribe Atimiini LeConte (Coleoptera: Cerambycidae: Aseminae) is recognized in Korea for the first time. Diagnosis and photographs of adult and male genitalia of the species are provided herein.
이기종의 모바일 IP 네트워크에서 끊김없는 프록시 기반의 핸드오프 기법
이승현,신동렬,정종필,Lee, Seung-Hyun,Shin, Dong-Ryeol,Jeong, Jong-Pil 한국정보처리학회 2012 정보처리학회논문지 C : 정보통신,정보보안 Vol.19 No.1
향후의 차세대 무선 네트워크(NGWN) 환경에서는 음성을 비롯한 모든 정보들이 ALL-IP 망에서 동작하게 될 것이며, 현재는 이러한 과도기로서 IP 네트워크에서 사용자로 하여금 끊김없는 서비스를 유지하기 위한 망의 중요성 및 이기종 네트워크 간의 핸드오프에 대한 중요성이 커지고 있다. 이에 본 논문에서는 NGWN에서 여러 기법 중 핸드오프 성능을 높일 수 있는 끊김없는 PMIPv6 기반의 프록시 모델을 이용한 SePH를 제안한다. SePH의 특징으로는 핸드오프 과정 중 탐색 과정을 줄임으로서 끊김없는 IP 기반의 이동성을 효율적으로 지원할 수 있다. 제안한 SePH 기법의 성능 평가는 현재 이동성 관리 프로토콜에 비해 처리량, 핸드오프 지연시간, 패킷손실 및 시그널링 오버헤드 등의 이동성 관리 측면에서 QoS 향상을 보여준다. In Next Generation Wireless Networks (NGWN), lots of information, such as voice and video data, will be used in All-IP networks. It is important note that seamless service for users and handoff between heterogeneous networks must be taken into account in such environments. Therefore, in this paper, we propose a SePH(Seamless Proxy based Handoff) using PMIPv6-based proxy model which is enable to improve the performance of handoff in NGWN. The SePH can efficiently support seamless and IP-based mobility by reducing the search process. The performance results show that our proposed scheme outperforms in terms of QoS (Quality of Service) such as throughput, handoff latency, packet loss, and signaling overhead comparing to the existing schemes.