• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.485-485
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• 2012

유기발광소자는 고휘도, 넓은 시야각, 빠른 응답속도, 높은 색재현성, 좋은 유연성의 소자특성 때문에 디스플레이 제품에 많이 응용되고 연구가 활발하게 진행되고 있다. 최근에 저소비전력, 고휘도, 소형화 및 장수명의 장점을 가진 유기발광소자의 상용화가 진행되면서 차세대 디스플레이소자로서 관심을 끌게 되었다. 고분자 유기발광소자는 저분자 유기발광소자에 비해 용액 공정법으로 박막을 형성할 수 있어 제조 비용이 적게 들며 대면적 디스플레이를 제작하는데 유리하기 때문에 많은 연구가 진행되고 있다. 고분자 유기발광소자에서 저전력 소자를 위한 저전압 구동 및 전력 효율을 향상시키기 위한 연구는 대단히 중요하다. 본 연구에서는 고분자 유기발광소자의 구동 전압을 낮추기 위해서 그래핀 정공 주입층을 삽입한 고분자 유기발광소자를 화학적 진공 증착법과 용액 공정을 사용하여 제작하였다. 그래핀 정공 주입층을 삽입한 고분자 유기발광소자는 Indium-tin-oxide(ITO) 투명 전극/그래핀 정공주입층/poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT: PSS)/poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-p-phenylenevinylene] (MEH-PPV) 층/lithium quinolate (Liq)/aluminium (Al) 전극의 구조를 가진다. 그래핀 정공주입층을 삽입한 고분자 유기발광소자에서 향상된 정공 주입능력을 통해 구동전압을 낮아지는 현상을 분석하기 위해서 전기적 및 광학적 특성을 조사하였다. 그래핀 정공주입층의 광학적 특성을 분석하기 위해서 빛의 투과도 측정을 한 결과 90% 이상의 값을 얻었다. 그래핀 정공 주입층이 소자에 미치는 영향을 조사하기 위하여 ITO/PEDOT:PSS소자와 ITO/그래핀 층/PEDOT:PSS 소자를 각각 제작하여 원자힘 현미경 측정을 하였다. 그래핀박막층을 삽입할 경우, 그래핀박막층을 삽입하지 않았을 때보다 표면 거칠기가 감소하는 것을 알 수 있었다. 이는 산성을 띠는 PEDOT:PSS 용액이 ITO 투명 전극을 손상시키는 것을 방지하고, 표면 거칠기를 감소시켜 누설 전류를 낮출 수 있다는 사실을 보여준다. 또한, 그래핀 박막은 높은 전기 전도도를 가지기 때문에 그래핀 정공주입층을 삽입하였을 때, 높은 전류 밀도 및 발광 휘도와 더 낮은 구동 전압을 확인할 수 있었다. 이러한 결과는 ITO와 PEDOT:PSS의 계면에서의 전공의 주입 능력을 그래핀박막층이 향상시켜 저전압, 고효율 소자를 제작할 수 있다는 것을 보여준다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.1-9
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• 2015

Recently, with smart device proliferation and providing the various services using this, they have interested in mobile and Smart TV security. Smartphone users are enjoying various service, such as cloud, game, banking. But today's mobile security solutions and Study of Smart TV Security simply stays at the level of malicious code detection, mobile device management, security system itself. Accordingly, there is a need for technology for preventing hacking and leakage of sensitive information, such as certificates, legal documents, individual credit card number. To solve this problem, a variety of security technologies(mobile virtualization, ARM TrustZone, GlobalPlatform, MDM) in mobile devices have been studied. In this paper, we propose an efficient method to implement security technology based on TYPE-I virtualization using ARM TrustZone technology.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.4
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• pp.67-72
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• 1989

Room Temperature Plasma Nitridation of silicon was investigated as a new LOCOS (local oxidation of silicon) process in order to reduce the bird's beak length. In $N_2$ plasma formed by 100kHz, 400W AC power, a thin silicon nitride film (<100${\AA}$) was uniformly grown on a silicon substrate. SEM studies showed that the nitride layer formed by this method can effectively protect the silicon from oxidation and reduce the bird's beak length to $0.2{mu}m$ when 4000${\AA}$ field oxide is grown. This is a considerable improvement comparing with 0.7${mu}m,$ the bird's beak, for the conventional LOCOS process using a thick LPCVD nitride. No appreciable crystalline defect could be found around the bird's beak with SEM cross-section afrer Secco etch. Leakage current tests were carried out on the $N^+/P^-$ well and $P^+/N^-$ well diodes formed by this new LOCOS process. The electrical tests indicate that this new process has electrical properties similar or superior to those of the conventional LOCOS process.

• Journal of the Korean Institute of Gas
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• v.8 no.4 s.25
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• pp.55-61
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• 2004

This paper provided a counter measures against the troubles and accidents that are likely to take place in the power plant using hydrogen gas as a coolant for the cooling system of the generator. Because of the extremely wide flammability limits of hydrogen in comparison to the other flammable gases, the safety measures against the hydrogen accidents is very important to ensure the normal operation of electric-power facility. This study's purpose was a presentation of standard model of safety management of hydrogen equipments in the coal firing power plant such as following items: 1) providing the technical prevention manual of the hydrogen explosions and hydrogen fires occurring in the cooling system of power generator; 2) the selection of explosion-proof equipments in terms of the risk level of operating environment; 3) the establishment of regulations and counter measures, such as the incorporation of gas leakage alarm device, for preventing the accidents from arising, 4) the establishment of safety management system to ensure the normal operation of the power plant.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.1
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• pp.17-24
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• 2003

In this paper, a high efficiency leakage transformer for neon tube is developed to improve its power factor, to reduce its core loss and weight by using a technique of shape optimization and grain direction of non-oriented silicon steel strip. A protection circuit is designed for all types of neon transformer loaded with one or more neon tubes. Whenever the neon tube fails to be started up or comes to the life end, or encounters faults with open-circuits at the output terminals of the neon transformer, the electronic type protection circuit will be initiated to avoid more critical hazards. These neon transformers need a electronic type protection circuit to prevent from current stresses on circuit components by neon tube fail. The input of the transformer is automatically cut on when the abnormal condition occurs, preventing waste of no-load power.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.187-193
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• 2018

There has been a gradual increase in the demand for the electric power in Korea. In order to meet the demand, power station should have technical functions with increased effectiveness. When accident happens in electric machinery at power stations, huge amount of economic losses and mulfunction of equipments occur. One of the accidents is a deteriorated cables operating power stations. In order to prevent cable accident in advance, we should monitor the insulation status of the cable. Cable accidents are resulting from the junctions. We have developed and installed a device in order to identify the status of junction part of power cable at Korea Western Power Co., Ltd.. We performed an accurate diagnosis for the stable utilization of junctions where the accidents occurs most frequently, and to increase the reliability. In this paper, we present the concepts of our device and the method of monitoring diagnosis for the stable use of junctions at cables predicting the life time of cables by analyzing the data obtained by the device. We also present the hardware aspect of the device we have developed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.875-882
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• 2011

In the present study, the imbalance in the axial-thrust and variation in the volumetric efficiency that occurred during the trimming of impeller diameter were investigated. The present study was focused on low-specific-speed multistage centrifugal pumps with a balancing piston as the balancing mechanism. The effects of impeller trimming on the axial-thrust balance in multistage pumps with horizontal and vertical axes were compared. The results showed that impeller trimming resulted in an additional axial-thrust acting in direction of pump inlet. The axial-thrust imbalance due to impeller trimming was more severe in the vertical-axis pumps than in the horizontal-axis pumps. The rate of increase in the diameter of the balancing piston, which was proportional to the rate of impeller trimming, was evaluated to maintain the axial-thrust balance. Furthermore, a simultaneous increase in the piston length and piston diameter was more effective for reducing the axial-thrust imbalance along with the volumetric efficiency drop.

• Fire Science and Engineering
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• v.31 no.3
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• pp.63-72
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• 2017

This study fabricated a low-voltage 10 circuit distribution board based on the KEMC (Korea Electrical Manufacturers Cooperative) 2102-610 standard and performed a characteristics assessment of the developed 10 circuit distribution board to secure product stability. The developed 10 circuit distribution board is designed to have the characteristics of insulation materials, as well as resistance to corrosion ultraviolet radiation and mechanical impact. The developed distribution board is fabricated to have an appropriate protection class of enclosure, electric shock prevention and protection circuits, switchgear and its components, internal electrical circuits and connectors, external conduct terminal, insulation characteristics, temperature rise test, heat resistance, etc. The developed 10 circuit distribution board consists of a single phase circuit and 3-phase circuits. It is possible to measure in real time the leakage current generated from the load distribution line by installing a sensor module at the load side of each of the branched switchgears. In addition, it is possible to increase a circuit according to the use and purpose of the load and to also manage and check the load in real time. Temperature rise tests were performed on the developed 10 circuit distribution board at 18 places including the inlet connection, main circuit and distribution circuit bus bars and bus bar supports, etc. The highest temperature of $65.3^{\circ}C$ was measured at the R-Phase of the connection of the MCCB power supply for the branch circuit bus bar and a temperature rise of $61.6^{\circ}C$ was measured at the T-Phase of the load side. When applying thermal stress to an MCCB for 6 hours at $180^{\circ}C$ using a heat resistant experimental device, it was found that the actuator lever was transformed and moved in the tripped state.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.170.1-170.1
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• 2015

안티모니 (Sb)를 기반으로 한 제2형 초격자 (Type II superlattice, T2SL)구조 적외선 검출기 연구는 2000년대 들어 Sb 계열의 화합물 반도체 성장 기술이 발전함에 따라 HgCdTe (MCT), InSb, 양자우물 적외선 검출기 (QWIP)를 대체할 수 있는 고성능의 양자형 적외선 검출 소재로 부상하였으며, 현재 전 세계적으로 활발한 연구가 진행되고 있다. 특히, 기존의 양자형 적외선 검출소자에 비해 전자의 유효질량이 상대적으로 커서 밴드 간의 투과전류가 줄어들 뿐만 아니라, 전자와 정공이 서로 다른 물질 영역에 분포하여 Auger 재결합률을 효과적으로 줄일 수 있어 상온 동작이 가능한 소재로 주목을 받고 있다. 또한, T2SL 구조는 초격자를 구성하는 물질의 두께나 조성 변화를 통한 밴드갭 변조가 용이하여 단파장에서 장파장 적외선에 이르는 광범위한 파장 대역에서 동작이 가능할 뿐만 아니라 구조적 변화를 통해 이중 대역을 동시에 검출 할 수 있는 차세대 적외선 열영상 소자로 알려져 있다. 본 연구에서는 분자선 에피택시(MBE)법을 이용하여 300 주기의 InAs/GaSb (10/10 ML) 제2형 초격자 구조를 성장하여 적외선 검출소자를 제작하였다. 제2형 초격자 구조를 구성하는 물질계에 p-type dopant인 Be을 이용하여 각각 도핑 농도가 다른 시료를 성장하였다. 이때 p-type 도핑 농도는 각각 $1/5/10{\times}10^{15}cm^{-3}$로 변화를 주었다. 성장된 시료의 구조적 특성 분석을 위해 고분해능 X선 회절 (High resolution X-ray diffraction, HRXRD)법을 이용하였으며, 초격자 한 주기의 두께가 6.2~6.4 nm 로 설계된 구조와 동일하게 성장됨을 확인 하였으며, 1차 위성피크의 반치폭은 30~80 arcsec로 우수한 결정성을 가짐을 확인하였다. 적외선 검출을 위한 $410{\times}410{\mu}m^2$ 크기의 단위 소자 공정을 진행하였으며 이때 적외선의 전면 입사를 위해 소자 위에 $300{\mu}m$의 윈도우 창을 제작하였다. 단위 소자의 측벽에는 표면 누설 전류가 흐르는데 이를 방지하기 위해서 표면보호막을 증착하였다. 적외선 검출 소자의 전기적 특성 평가를 위해 각각의 시료의 암전류 (dark current)와 파장별 반응 (spectral response)을 온도별로 측정하여 비교 및 분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.85-91
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• 2018

Recently, there have been a lot of casualties due to fires in high-rise buildings. The toxic gases and smokes generated by fires in high-rise buildings spread rapidly through the elevator shaft and stairwell, due to the stack effect, and can cause critical casualties. To reduce the number of casualties, smoke control systems have been introduced. Smoke control systems play an essential role in preventing the spread of smoke in high-rise buildings and securing the evacuation route. Also, in high-rise buildings, evacuation by an elevator is considered to be indispensable. However, the pressure field in the shaft is strongly disturbed when the elevator is moving and this can affect the performance of the smoke control system. Therefore, in this study, we experimentally and numerically analyzed the effect of elevator movement on the pressure difference between the vestibule and living room by building a model using the sandwich pressurization method based on the performance based design. To consider the leakage areas in high-rise buildings, e.g. the windows, fire door and elevator, the National Fire Safety Codes and area ratio were used. The elevator speed in the model building was varied between 20 m/s and 100 m/s corresponding to a real elevator speed of 7 m/s~17 m/s. As a result, the relationship between the pressure difference and elevator speed was found to be ${\Delta}P=40{\cdot}{\exp}$(-Ves /-104.7)-23.735. This result can be used to take into consideration the effect of elevator movement when designing smoke control systems.