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Photosensors-based on cadmium sulfide (CdS) nanostructures: a review
An Byung-Gi,김홍래,Chang Young Wook,Park Jae-Gwan,Pyun Jae-Chul 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.6
Cadmium sulfi de (CdS) is an II – VI semiconductor with a direct bandgap of 2.4 eV; it has been used for various applications, such as nonlinear optical devices, fl at-panel displays, light-emitting diodes, lasers, logic gates, transistors, photoresistors, solar cells, infrared waveguides, and splitters. CdS nanostructures have been synthesized through two diff erent routes: (1) vapor-phase growth and (2) liquid-phase growth. The vapor-phase growth system can yield highly pure single-crystal nano- structures, and liquid-phase growth has been carried out through chemical or electrochemical reactions in solution with templates. The fabricated nanostructures of CdS showed a relatively low work function, high refractive index, excellent transport properties, good chemical capability, thermal stability, high electronic mobility, and piezoelectric properties. For these reasons, CdS photosensors have been produced using various nanostructures of CdS, such as nanorods, nanoribbons, and nanowires. For the fabrication of CdS nanowire photosensors, many diff erent approaches have been demonstrated to connect nanostructures in devices and circuits using various techniques, such as dry transfer, wet transfer, and contact print- ing. Each method has practical advantages and drawbacks in the implementation of nanostructures in devices. In this article, the synthesis of CdS nanostructures and the fabrication of photosensors based on the CdS nanostructures are reviewed.
Selective Laser Ablation of Metal Thin Films Using Ultrashort Pulses
Byunggi Kim,Han Ku Nam,Shotaro Watanabe,Sanguk Park,Yunseok Kim,Young Jin Kim,Kazuyoshi Fushinobu,김승우 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.3
Selective thin-film removal is needed in many microfabrication processes such as 3-D patterning of optoelectronic devices and localized repairing of integrated circuits. Various wet or dry etching methods are available, but laser machining is a tool of green manufacturing as it can remove thin films by ablation without use of toxic chemicals. However, laser ablation causes thermal damage on neighboring patterns and underneath substrates, hindering its extensive use with high precision and integrity. Here, using ultrashort laser pulses of sub-picosecond duration, we demonstrate an ultrafast mechanism of laser ablation that leads to selective removal of a thin metal film with minimal damage on the substrate. The ultrafast laser ablation is accomplished with the insertion of a transition metal interlayer that offers high electron–phonon coupling to trigger vaporization in a picosecond timescale. This contained form of heat transfer permits lifting off the metal thin-film layer while blocking heat conduction to the substrate. Our ultrafast scheme of selective thin film removal is analytically validated using a two-temperature model of heat transfer between electrons and phonons in material. Further, experimental verification is made using 0.2 ps laser pulses by micropatterning metal films for various applications.
분산 화일 시스템의 확장성을 위한 대리인-시작 캐쉬 일관성 유지 방식
홍병기(ByungGi Hong),장태무(TaeMu Chang) 한국정보과학회 1996 정보과학회논문지 : 시스템 및 이론 Vol.23 No.2
분산 화일 시스템의 확장성은 화일 서버의 작업 부하를 감소시킴으로써 향상될 수 있다. 화일 서버에서 유지되는 상태 정보의 양이 화일 서버의 작업 부담에 비례한다는 가정 하에 본 논문에서는 화일 서버의 작업 부담을 클라이언트들에게 이양시킬 수 있는 대리인에 의한 캐쉬 일관성 유지(Agent-Initiated Cache Consistency) 방식을 제안하였다. 기존의 방식에서 화일 서버가 사용되는 화일의 개수에 평균 공유 정도를 곱한 것만큼의 상태 정보를 유지하지만 대리인 방식의 경우 공유 정도에 관계없이 화일 서버가 유지하는 상태 정보의 양은 사용되는 화일의 개수와 같음을 보여준다. 본 논문에서 제안하는 방식의 유효성을 시뮬레이션을 통하여 검증하였으며, 그 결과 공유 확률이 0.1일 경우에는 화일 서버의 사용들이 기존의 방식에 비해 약 1-2% 낮게 나타났고, 공유 확률이 0.2일 경우에는 약 8-10%를 줄일 수 있는 것으로 나타났다. The scalability of a distributed file system can be enhanced by reducing the server CPU load. In this paper, under the assumption that the amount of the state information maintained in the file server is proportional to that of its load, we propose the agent-initiated cache consistency model which can shift the work for servicing the client requests from a file server to several clients. In this model, the state information in the file server can be reduced as much as the number of active files regardless of the degree of sharing We verified the effectiveness of our model using event-driven simulation method. As the simulation results, the file server utilization reduced about 1-2% and 8-10% in the case that the probability of shared accesses was fixed at 0.1 and 0.2, respectively.
HMIPv6의 중첩된 이동 네트워크에서 MAP의 캐시 정보를 이용한 명시적 경로 지정(Explicit Path Assignment) 알고리즘
송지영(Jiyoung Song),김병기(Byunggi Kim) 한국정보과학회 2006 정보과학회논문지 : 정보통신 Vol.33 No.6
HMIPv6는 노드와 라우터의 이동성으로 중첩된 형태의 이동 네트워크가 형성될 수 있다. 중첩된 이동 네트워크에서는 여러 개의 서브넷이 존재하고 또 여러 개의 이동 라우터(MR)와 이동 노드(MN)가 활동한다. 중첩의 깊이가 커지면 패킷이 경유하는 이동 라우터의 수가 증가하고, 이로 인해 데이타의 전송지연이 커질 수 있다. 본 논문에서는 Mobility Anchor Point(MAP)의 바인딩 캐시 정보를 활용하여 MAP에서 목적지 이동 노드까지의 경로를 구하고, 그 경로 정보를 패킷의 헤더에 포함하여 처리하는 EPA 알고리즘을 제안한다. EPA 알고리즘을 적용하면 MAP 도메인내의 불필요한 패킷의 양을 줄일 수 있다. 또 중간 이동 라우터에서는 간단한 패킷 치환 작업만으로 패킷의 재전송을 지원할 수 있어 전송지연을 줄일 수 있다. In HMIPv6, the nested mobile network because of the mobility of node and router can be constituted. Many subnets exist and many mobile router(MR)s and mobile node(MN)s activate in the nested mobile network. If the nested depth is deeper, the number of mobile router that packet goes through, increases and data transmission delay owing to this might be larger. This paper proposes EPA algorithm which finds out the path from Mobility Anchor Point(MAP) to a destination mobile node using the binding cache information of MAP and processes the path information by adding it to packet header. If we apply EAP algorithm, the quantity of unnecessary packet within MAP domain can be decreased. Also, the transmission delay can be decreased in a intermediate mobile router because it supports packet re-transmission just by simple packet substitution.
Seungjin Seo,Hwajeong Han,Byunggi Park,Sungyeol Choi 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
Corrosion products generated from the oxidation of structure materials are deposited on the surface of coolant systems, forming CRUD (Corrosion Related Unidentified Deposits). The CRUD deposition on the fuel surface has influenced the heat transfer through the fuel rod. When CRUD was deposited on a fuel surface, heat resistance may increase, and this increase in heat resistance leads to the increase in temperature distribution from cladding to coolant. Also, the temperature distribution is related to the radiolytic and chemical reactions within the CRUD deposits. This influence may be enough to change the pH distribution within the CRUD deposits. To estimate the influence of thermal resistance, the composition, microstructure, and vapor fraction within the CRUD should be considered, by investigating the thermal conductivity model of CRUD deposits. Therefore, in this study, the CRUD thermal conductivity was studied through the literature study, by considering composition, capillary flow characteristics, and vapor fraction. For the uncertainty parameters, a sensitivity study was conducted to check the degree of influence on thermal conductivity. The effective thermal conductivity was applied to the radiochemistry model within the CRUD deposits and an analysis of the influence in radiolysis reaction within the CRUD deposits with a fixed thickness.