• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.658-658
• /
• 2013

Graphene is an attractive material for various device applications due to great electrical properties and chemical properties. However, lack of band gap is significant hurdle of graphene for future electrical device applications. In the past few years, several methods have been attempted to open and tune a band gap of graphene. For example, researchers try to fabricate graphene nanoribbon (GNR) using various templates or unzip the carbon nanotubes itself. However, these methods generate small driving currents or transconductances because of the large amount of scattering source at edge of GNRs. At 2009, Bai et al. introduced graphene nanomesh (GNM) structures which can open the band gap of large area graphene at room temperature with high current. However, this method is complex and only small area is possible. For practical applications, it needs more simple and large scale process. Herein, we introduce a photosensitive graphene device fabrication using CdSe QD coated nano-porous graphene (NPG). In our experiment, NPG was fabricated by thin film anodic aluminum oxide (AAO) film as an etching mask. First of all, we transfer the AAO on the graphene. And then, we etch the graphene using O2 reactive ion etching (RIE). Finally, we fabricate graphene device thorough photolithography process. We can control the length of NPG neckwidth from AAO pore widening time and RIE etching time. And we can increase size of NPG as large as 2 $cm^2$. Thin CdSe QD layer was deposited by spin coatingprocess. We carried out NPG structure by using field emission scanning electron microscopy (FE-SEM). And device measurements were done by Keithley 4200 SCS with 532 nm laser beam (5 mW) irradiation.

• 멤브레인
• /
• 제28권5호
• /
• pp.297-306
• /
• 2018

본 총설은 분리막기술이 적용된 수소생산에 대한 개론으로, 특히, 암모니아를 수소운반체로 이용하는 수소생산에 대한 연구결과를 중점적으로 서술하였다. 암모니아를 수소운반체로 적용한 수소생산은 추가적인 탄소생성이 없다는 점 외에 여러 측면에 있어 이점이 있다. 많은 연구들이 고순도 수소 분리 및 생산을 위한 분리막 개발을 위해 진행되고 있으며, 이들 중 팔라듐을 기본으로 한 분리막(예를 들어, 다공성 세라믹 또는 다공성 금속 지지체와 팔라듐 합금의 얇은 선택층으로 이루어진 분리막)에 대한 연구가 활발하다. 반면에, 효율적인 암모니아 분해를 위해서는 주로 루테늄 촉매가 적용되고 있으며, 루테늄과 지지체 및 촉진제로 이루어진 루테늄에 기반을 둔 촉매에 대한 연구발표가 다수 존재한다. 수소생산을 위한 분리막 반응기 형태로는 충전층, 유동층, 그리고 마이크로반응기 등이 있으며, 이들의 최적화 및 원활한 물질전달 연구는 현재진행형이다. 또한, 높은 암모니아 분해율, 고순도 수소생산 및 높은 수소생산율을 얻기 위해 분리막과 촉매의 다양한 조합에 대한 연구 및 분리막과 촉매의 역할을 동시에 구현할 수 있는 분리막에 대한 연구가 발표되고 있다.

• 한국분말재료학회지
• /
• 제25권1호
• /
• pp.1-6
• /
• 2018

Uniform $TiO_2$ blocking layers (BLs) are fabricated using ultrasonic spray pyrolysis deposition (USPD) method. To improve the photovoltaic performance of dye-sensitized solar cells (DSSCs), the BL thickness is controlled by using USPD times of 0, 20, 60, and 100 min, creating $TiO_2$ BLs of 0, 40, 70, and 100 nm, respectively, in average thickness on fluorine-doped tin oxide (FTO) glass. Compared to the other samples, the DSSC containing the uniform $TiO_2$ BL of 70 nm in thickness shows a superior power conversion efficiency of $7.58{\pm}0.20%$ because of the suppression of electron recombination by the effect of the optimized thickness. The performance improvement is mainly attributed to the increased open-circuit voltage ($0.77{\pm}0.02V$) achieved by the increased Fermi energy levels of the working electrodes and the improved short-circuit current density ($15.67{\pm}0.43mA/cm^2$) by efficient electron transfer pathways. Therefore, optimized $TiO_2$ BLs fabricated by USPD may allow performance improvements in DSSCs.

• 대한전자공학회논문지SD
• /
• 제40권5호
• /
• pp.369-378
• /
• 2003

본논문은 ATM/AAL 처리를 위한 재조립 처리기으 설계 및 VLSI 구현에 대하여 기술한다. ATM/AAL 재조립 처리기는 물리계층으로부터 수신된 ATM셀을 처리하는 장치로서 AAL5 패킷의 유료부하를 호스트의 메모리에 정렬하고 이를 전송하며 망 관련 정보와 패킷의 오류 사항을 점검한다. ATM 셀매칭 알고리즘과 지능형 분산 방식의 개념을 적용하여 여러 개의 채널을 동시에 운영할 때 시간 지연 없이 처리할 수 있도록 설계하였다. 셀매칭 알고리즘은 ATM의 헤더로부터 해당정보의 위치를 신속하게 찾을 수 있도록 해쉬함수를 이용하여 구현되었고 이로써 VCI/VPI 값의 할당에 있어서 시간상의 제약을 완화하였으며 지능형 분산 방식과 DMA를 이용하여 메모리의 낭비를 최소화하면서 데이터를 호스트 쪽으로 25Mbps의 속도로 전송이 가능하도록 하였다. 상용시스템과 통신을 수행하여 칩의 정확한 동작과 CRC, 오류 점검 등의 동작을 점검하였다. 본 재조립 처릭는 0.6㎛ CMOS 공정을 통하여 제작되었다.

• 대한두개안면성형외과학회지
• /
• 제13권1호
• /
• pp.46-49
• /
• 2012

Purpose: The forehead flap is the workhorse in nasal reconstruction, which provides a similar skin color, texture, structure, and reliability. There are some disadvantages, including donor site morbidities, 2- or 3-stage operations, and postoperative management after initial flap transfer. Furthermore, there has been little attention to the exposed raw surface wound, after the first stage of an operation. This article describes the authors' modification to overcome this problem, using artificial collagen membrane. Methods: An Artificial collagen membrane is composed of an outer silicone membrane and an inner collagen layer. After a forehead flap elevation, the expected raw surface was covered by an artificial collagen membrane with 5-0 nylon suture. A simple dressing, which had been applied to the site, was changed every 2 or 3 days in an outpatient unit. At 3 weeks postprocedure, a second stage operation was performed. Results: With biosynthetic protection of the raw surface, there were no wound problems, such as infection or flap loss. Thus, the patient was satisfied due to an effortless management of the wound and a reduction in pain. Conclusion: The application of an artificial collagen membrane to the raw under-surface of the flap could be a comfortable and a protective choice for this procedure.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
• /
• pp.545-553
• /
• 2009

A lot of long-span marine bridge, which connects land to island or island to island, are being designed and constructed lately in south-west coast in South Korea. In the past, caisson foundations in marine were mainly adopted in construction and stability aspect, however, nowadays with development of pile construction technology, drilled shaft foundations are mainly adopted. As the long span cable stayed bridge and suspension bridge applied with lots of loads are being designed, the scale of pile foundations are getting larger. As the construction cost of substructure including foundation in marine bridges is too high, the appropriate evaluation of the axial bearing capacity of pile becomes a core factor to decide the construction cost of foundation if the drilled shaft is adopted as foundation type of bridge. The evaluation values of skin friction and end bearing capacity of drilled shaft in weathered rock suggested in south Korea are only to introduce the foreign specifications, and most of them are designed in a kind of hard soil layer. Also the allowable load of pile section is less than the expected bearing capacity of pile in the soil condition since the allowable capacity of pile is undervalued. Recently in order to improve this factor the bi-axial hydraulic load test of pile was taken, the data of load transfer analysis of pile, unit of skin friction and end bearing capacity are accumulated. In our country, the design of piles are made with ASD, however, LRFD considering service, strength and extreme state was adopted in Incheon Grand Bridge implemented with BTL, and the research to systematize the resistance coefficient appropriate at home country are being progressed.

• 한국수소및신에너지학회논문집
• /
• 제25권1호
• /
• pp.28-38
• /
• 2014

The organic-inorganic composite membrane in polymer exchange membrane fuel cells (PEMFCs) have several fascinating technological advantages such as a proton conductivity, thermal stability and mechanical properties. As the inorganic filler, silicon carbide (SiC) fiber have been used in various fields due to its unique properties such as thermal stability, conductivity, and tensile strength. In this study, composite membrane was successfully fabricated by modified-silicon carbide fiber. Modified process, as a novel process in SiC, takes reaction by phosphoric acid after oxidation process (generated homogeniusly $SiO_2$ layer on SiC fiber). The mechanical property which was conducted by tensile test of the 5wt% modified-$SiO_2@SiCf$ composite membrane was better than that of Aquivion casting membrane as well as ion cxchange capacity(IEC) and proton conductivity. In addition, the single cell performance was observed that the 5wt% modified-$SiO_2@SiCf$ composite membrane was approximately $0.2A/cm^2$ higher than that of a Aquivion casting electrolyte membrane and electrochemical impedance was improved with the charge transfer resistance and membrane resistance.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2017년도 춘계학술대회
• /
• pp.77-80
• /
• 2017

저전력 블루투스 통신의 가장 큰 한계점은 데이터 전송이 두 노드 사이의 싱글 홉 통신에서만 이루어질 수 있다는 것이다. 본 연구에서는 스타 토폴로지를 고려하여 설계된 블루투스 통신의 한계를 보완하기 위해, 안정적인 멀티홉 데이터 전송을 보장하는 방법을 제안하였다. 싱글 홉 형태의 통신이 연속적으로 맺고 끊어져야 하는 멀티홉 환경에서의 안정성을 보장하기 위해, 본 연구에서는 GATT 계층에 정보를 저장하고 이를 동적으로 전달하는 방식을 시도하였다. 여러 노드들에 대한 통신 안정성을 보장하기 위해 전체 과정을 4개의 State로 나누어 해당 과정에서 전송 프로세스의 주요과정을 수행할 수 있도록 하였다. 또한 각 State에 대한 체류 시간 및 이동 루틴을 설정하여 강건한 통신 체제를 설정하였고, 성능을 실제 실험을 통해 평가하였다. 실제 실험 환경을 통해 해당 방법이 3개 이상의 노드로 이루어진 네트워크에서 각각 높은 품질의 패킷 전송률을 보여주는 것을 확인하였다.

• 전력전자학회논문지
• /
• 제20권5호
• /
• pp.410-420
• /
• 2015

This paper provides a comparison of power converter loss and thermal description for voltage source and current source type 5 MW-class medium-voltage topologies of wind turbines. Neutral-point clamped three-level converter is adopted for a voltage source type topology, whereas a two-level converter is employed for current source type topology, considering the popularity in the industry. To match the required voltage level of 4160 V with the same switching device of IGCT as in the voltage source converter, two active switches are connected in series for the case of current source converter. Transient thermal modeling of a four-layer Foster network for heat transfer is done to better estimate the transient junction and case temperature of power semiconductors during various operating conditions in wind turbines. The loss analysis is confirmed through PLECS simulations. Comparison result shows that the VSC-based wind turbine system has higher efficiency than the CSC under the rated operating conditions.

• Composites Research
• /
• 제33권2호
• /
• pp.61-67
• /
• 2020

프리폼 성형은 섬유 직조물을 이용한 RTM 성형에 있어서 매우 중요한 부분을 차지하고 있다. 탄소 섬유 직조물의 프리폼의 변형은 소재의 강도에 영향을 미치며, 그 중 전단 잠김 각도를 넘어서는 힘이 작용하게 되면 제품에 주름이 발생되어 RTM공정 시 불량발생의 원인이 된다. 그러므로 본 연구에서는 탄소섬유직조물의 전단변형 허용치를 정량화하고 실제 직조물의 성형과 수치모사를 이용하여 성형 특성을 검증하고자 한다. 그 결과 섬유 방향의 설정에 따른 주름의 특성을 확인하고 그 결과를 평가하였다. 앞에 언급한 물성 측정 결과들을 이용하여 수치해석을 수행하였고, 이 결과를 실험 결과와 비교 분석하였다.