• Polymer(Korea)
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• v.38 no.4
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• pp.544-549
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• 2014

Double layered film consisting of polyimide/polysiloxane and interface with nano domain structure was fabricated through stepwise layer formation and subsequent aging steps. During aging of film, nano phase separation occurred between the top layer polysiloxane and the upper layer of polyimide, which was observed by transmission electron microscope (TEM). A stable and uniform polysiloxane layer was obtained, showing the reproducible pressure-sensitive adhesion (PSA) property with the peel strength of 8-13 g/inch at even $300^{\circ}C$. In addition, the resulting polymide/polysiloxane film was thermo-stable up to $435^{\circ}C$, providing the promising properties suitable for application in microelectronics processing.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.479-479
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• 2012

유기발광소자는 낮은 구동전압, 저전력, 높은 명암비, 빠른 응답속도, 넓은 시야각 및 높은 박막의 특성을 가지고 있어서 차세대 평판 패널디스플레이 기술로 각광받고 있다. 하지만 청색 유기발광소자는 적색과 녹색 유기발광소자에 비해 낮은 신뢰성, 발광효율 및 색 순도의 문제점을 가지고 있어, 이를 개선하기 위한 연구가 다양하게 연구되고 있다. 청색 유기발광소자의 경우 발광층 내부로 주입되는 정공과 전자의 균형을 조절하기 위해 p-i-n 구조를 사용하거나 이리듐-유기물 합성물과 같은 인광물질의 적용하여 발광효율을 높이는 청색 유기발광소자에 대한 연구가 진행되고 있다. 하지만 정공 보조층과 청색 형광층의 도핑구조의 청색 유기발광소자에 대한 발광효율 증가 메커니즘에 관한 연구는 비교적 많이 이루어지지 않았다. 본 연구에서는 열 증착 방법을 이용하여 정공 보조층과 청색 형광층으로 구성된 이중 발광층을 사용한 청색유기발광소자의 발광효율 증가 메커니즘에 대해 연구하였다. 10%의 2,9-dimethyl-4,7-diphenyl-1,10-phenanthorlene (BCP)로 도핑된 2-methyl-9,10-bis(naphthalene-2-yl)anthracene (MADN)층을 발광층으로 사용한 유기발광소자, 5% MADN으로 도핑된 1, 3-bis(carbazol-9-yl)benzene (mCP) 층을 발광층으로 사용한 소자 및 10% BCP로 도핑 된 MADN 층과 5% MADN로 도핑 된 mCP층을 혼합하여 발광층으로 사용한 소자의 전류밀도-전압-발광 특성을 비교하여 청색 유기발광소자의 발광효율 증가 메커니즘을 분석하였다. 이중 발광층을 가지는 소자는 두 단일 발광층 중심부의 경계면에서 축적된 정공에 의해 발생한 쿨롱 인력으로 더 많은 전자들을 끌어들이게 되어 엑시톤 형성 및 빛 방출이 증가하였다. 이 실험의 결과는 MADN 형광물질을 가진 청색 유기발광소자의 발광효율 증가 메커니즘에 대한 이해를 높이는데 도움을 줄 수 있다.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.673-679
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• 2011

Bimodal high-density polyethylenes with different comonomer type and content were synthesized by polymerization of ethylene using Ziegler-Natta catalyst. Their structure and properties were studied using GPC, NMR, DSC and tensile test. It was found that ethylene/1-hexene copolymer exhibits higher tensile strength and elongation at break than that of ethylene/1-butylene copolymer with similar comonomer content. The molecular weight decreases as the comonomer content of the polymer increases. Short chain branching affects the crystallinity and thus the morphology and consequently the mechanical properties of the corresponding bimodal high-density polyethylenes. After SSA treated, the multiple endothermic peaks were observed. Multiple endothermic peaks are mainly attributed to the heterogeneity of ethylene sequence length and lamellar thickness. The difference of broadness index indicates that SCB distribution of polyethylene containing higher comonomer content has improved uniformity.

• Composites Research
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• v.33 no.6
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• pp.401-407
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• 2020

At the engineering and industrial areas, the lightweight composite material has been substituted with the metals, such as steel at the structural parts. This composite material has been applied by the adhesive bonding method, as well as the joint methods with rivets, welds or bolts and nuts. The study on the strength characteristics of adhesive interface is necessarily required in order to apply the method to composite materials. CFRP specimens as the fiber reinforced plastic composites were manufactured easily and this study was carried out. The static experiments were performed under the loading conditions of in-plane and out-plane shears with the inhomogeneous composite TDCB specimens with CFRP, aluminum (Al6061), and aluminum foam (Al-foam). Through the result of this study, the durability on the inhomogeneous composite structure with adhesive interface was investigated by examining the fracture characteristic and the point in time.

• Journal of Advanced Navigation Technology
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• v.25 no.6
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• pp.523-529
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• 2021

This paper shows the design and fabrication of antenna embedded in marine buoy for marine IoT service, especially automatic identification system of fishing gears. Frequency band of proposed antenna has dual band of 433 MHz and 920 MHz considering marine IoT extension. Dual pattern monopole type for 920 MHz and meander type for 433 MHz are adopted in the proposed antenna. Voltage standing wave ratio is obtained 1.548 at 433 MHz and obtained 1.5 of mean value at 920 MHz band by measuring the fabricated antenna. The maximum antenna gain of 3.83 dBi is measured at 902 MHz among 920 MHz band, while antenna gain of 433 MHz is obtained 1.18 dBi. Although antenna gain of 433 MHz is low than 920 MHz band, this gain is larger than desired value of -5 dBi. And, it is confirmed that other measured values meet the performance criteria for archiving communication distance of 10 km between marine buoy and fishing ship in automatic identification system of fishing gears.

• Journal of Korean Association for Spatial Structures
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• v.5 no.2 s.16
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• pp.47-55
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• 2005

The method to form the space of the pneumatic structures by internal pressure is classified greatly as the dual type with the nlty type. The shape of the pneumatic structures consists of the curved surface under uniform tension not greatly to be deformed by the design load and stress must not be concentrated also. Therefore, In this study, we have done the structural analysis of the unity typed pneumatic structures by the NASS which is the program for nonlinear analysis. The analytic model is a rectangular pneumatic membrane structures which have four side fixed edges. And we have done the nonlinear incremental analysis considering the orthotropic material.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.51-57
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• 2013

This study aims to experimentally investigate the combustion characteristics of a lean premixed swirl-stabilized burner with dual-stage fuel injection arrays. The results show that a variation in the fuel distribution to fuel stages 1 (upstream) and 2 (downstream) produces a noticeable change in the NOx and CO emissions. Reducing the confined ratio, defined as the ratio of the nozzle exit diameter to the liner diameter, may reduce NOx and CO emissions owing to reduced combustion loading and longer residence time, respectively. A nozzle exit velocity of 30 m/s shows the optimum characteristics in terms of NOx and CO emissions and flame stability: increasing or decreasing the nozzle exit velocity leads to a degradation in emissions or flame stability, respectively.

• The KIPS Transactions:PartA
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• v.15A no.6
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• pp.309-316
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• 2008

The mission-critical engagement control computer for air defense has to maintain its operation without any fault for a long mission time. The mission performed by large-scale and complex embedded software is extremely critical in terms of dependability and safety of computer system, and it is very important that engagement control computer has high reliability. The engagement control computer was implemented using four processors. The distributed computer composed of four processors quarantees the dependability and safety, and ASR fault-tolerant technique applied to each processor guarantees the reliability. In this paper, the mechanism and performance of ASR fault-tolerant technique are analysed. And MTBF, reliability, availability, and cost-effectiveness for ASR, DMR and TMR techniques applied to the engagement control computer are analysed. The mission-critical engagement control computer using software-based ASR fault-tolerant technique provides high reliability and fast recovery time at a low cost. The mission reliability of the engagement control computer using ASR technique in 4 processors board is almost same the reliability of the computer using TMR technique in 6 processors board. ASR technique is most suitable to the mission-critical engagement control computer.

• Journal of Digital Contents Society
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• v.19 no.4
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• pp.693-700
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• 2018

Virtual router redundancy protocol (VRRP) was designed as a solution to support fast fail-over in case of network failure. There exists virtual router which acts as default gateway in LAN, and the virtual router is dynamically elected between master and backup router. Through this protocol, end-hosts can be provided seamless network service. However, it needs expensive license fees and maintenance costs to adopt current commercial network operating systems. Furthermore, they are commonly enterprise proprietary software and inherently closed source. In order to tackle these problem, Open N2OS which is open source based open network software platform was developed. It has no dependency on hardware equipment, and provides high availability, scalability, various networking functions. In this paper, we handle VRRP operation and mechanism with related command line interface (CLI).

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.201.2-201.2
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• 2015

현대 디지털 사회에서 고효율 에너지와 파워소스에 관한 요구가 커짐에 따라 차세대 에너지 저장 소자에 대한 연구가 계속되고 있다. 그 중 리튬이온 배터리, 슈퍼커패시터, 그리고 연료 전지들이 우리의 일상생활에서 점점 더 중요하게 자리잡아가고 있는데 이런 다양한 에너지 저장소자 중 슈퍼커패시터가 많은 관심을 받고 있다. 이는 긴 수명, 빠른 충-방전 속도, 높은 에너지 밀도, 그리고 안전함 때문이다. 슈퍼커패시터는 에너지 저장 메커니즘에 따라 두 가지로 분류될 수 있는데 전기이중층 커패시터(EDLC)와 슈도커패시터(pseudocapacitor)로 나누어질 수 있다. 슈도커패시터는 active 물질과 전해질 이온 간의 전기화학적 반응으로 인해 EDLC보다 더 많은 에너지를 저장할 수 있다. 그러므로 지금까지 새로운 형태의 슈도용량성 물질을 만들기 위한 노력이 집중되고 있다. 본 연구에서는 전기화학적증착 방법을 통해 graphene-like ${\beta}$-nickel hydroxide (${\beta}-Ni(OH)_2$) 나노판 구조를 전도성 직물에 합성하였다. ${\beta}-Ni(OH)_2$ 슈도커패시터의 유연하고 효율적인 비용의 전극으로서 높은 비정전용량, 우수한 전기화학 가역성, 그리고 뛰어난 사이클 안정성을 보였다. 이런 쉬운 방법으로 유연한 전도성 직물에 합성된 metal hydroxide/oxide 나노구조는 웨어러블 에너지 저장소자와 변환소자 분야에 사용될 것으로 기대된다.