• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.55-55
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• 2008

압전폴리머 PVDF(polyvinylidene difluoride)의 기판소재를 기반으로 한 디스플레이 소자를 연구하였다. 압전 폴리머 PVDF의 양면은 두께 300nm정도의 ITO(Indium Tin Oxide)를 TCO(Transparent conducting oxide)로 R2R(roll to roll)증착하였으며, 이를 적외선 계열 Pulsed Laser로 상온 건식 에칭을 통해 패턴해내고, 이후 고진공 환경에서 Alq3 를 기반의 유기발광소자를 제작하였다. 전기적 신호에 대해서 기계적인 작동이 가능한 투명 압전 폴리머 재료를 디스플레이 발광소자의 기판 소재로 사용함으로써, 궁극적으로 발광기능과 더불어 압전효과에 의한 스피커 기능이 한 개의 개체내에서 독립적으로 구현될 수 있도록 설계하고, 기술적으로 실현시켰다는 점이 본 연구의 의의라고 할 수 있다. 이를 위해서, 섭씨 80도 이상의 온도에서 압전 성질을 상실하는 것으로 알려진 PVDF에 대해서 투명산화전극을 레이져를 이용한 비가열식 승화방법을 통해 패턴화하는 것을 사용했으며, 밀리미터 단위에서 수십 마이크로미터 수준까지 패턴화할 수 있었다. 제작된 복합형 유연 OLED소자는 기계적으로 휘어진 상태에서도 발광 성능과 스피커 성능을 각각 독립적으로 보였으며, Alq3에 의한 녹색발광을 보임을 확인하였고, 이 경우 양자효율은 약 3%이하의 값을 보였다. 또한 각주파수별 음압(SPL: Sound Pressure Level)측정 결과는 압번폴리머가 가청주파수 영역에서 작동함을 보였으며, 고주파영역에서의 SPL값이 증가하는 전형적인 PVDF사용 필름 스피커의 특성을 보였다. 이로부터 제작된 복합형 소자는 본 연구에서 제안된 목적에서 보인 것과 같이, 두 개의 기능이 서로간의 간섭없이 독립적으로 한 개의 개체 내에서 작동함을 확인할 수 있었다. 본 연구 결과로부터 새로운 유연 전자 소자에 대한 디자인 개념을 제시하고, 기타 다른 기능이 접합된 형태의 신개념 전자 소자를 제안하는 것도 가능할 것으로 기대된다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.10
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• pp.699-705
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• 2001

Six types of planar thermal converters from TC 1 to TC 6 were designed and fabricated for the purpose of being used as practical standards to alternating current. The respective voltage responses in air and in a vacuum of TC 6, which has the smallest thermal loss, were about 4.03mV/mW and about 6.38 mV/mW. Thermal time constant of TC 6, which has also the smallest heater thermal inertia, was about 8 ms. The respective variations of AC-DC voltage and current transfer errors from sample to sample, which were measured by FRDC(fast reversed DC) method, were about $\pm$0.41 ~$\pm$0.85 ppm and about $\pm$0.15~$\pm$1.16 ppm in the frequent range of 40 Hz~10 KHz with appling 1 V and 5 mA rms sine waves to the converters. All converters investigated exhibited sufficiently low AC-DC transfer errors to be used as practical standards.

• Composites Research
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• v.24 no.5
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• pp.23-28
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• 2011

In this paper, the bonding strengths of co-cured T800 carbon/epoxy composite-aluminum single lap joints with and without additional pressures were investigated using the pressure information induced by the fiber tension during a filament winding process. The specimens of all the tests were fabricated by an autoclave vacuum bag de-gassing molding being controlled forming pressures (absolute pressures of 0.1MPa, 0.3MPa and 0.7MPa including vacuum). A special device which can act uniform additional pressures on the joining part of the single lap joint specimen was designed to measure the bonding strengths of composite-aluminum liners of type III hydrogen pressure vessel fabricated by a filament winding process. After the three different additional pressures (absolute pressures of 0.1MPa, 0.3MPa and 0.7MPa) were applied to the specimens the effect of the additional pressures on the bonding strengths of the co-cured single-lap joints were evaluated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.9
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• pp.122-129
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• 2004

An accurate thrust measurement is one of the critical paths to the successful test and evaluation program of small liquid propulsion engines. This study describes the design factors for the development of thrust measurement system (TMS) as well as manufacturing practice of TMS hardware. We investigate characteristics of the TMS and its performance through hot-firing test of small liquid engine in a vacuum test cell which is capable of simulating 100,000 ft of altitude or higher. For performance test of TMS, we measure thrusts by changing propellant injection pressure at steady state firing mode as well as at pulse firing mode. Measured eigen frequency of the TMS is 67 Hz. Linearity test of the TMS shows good performance with less than 0.5% of linearity error.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.3
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• pp.258-263
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• 2012

In this paper the Chemical Propulsion Subsystem of COMS is briefly explained and some telemetries acquired by a series operations of CPS during the Launch and Early Operation Phase of COMS are presented. The pressure and temperature of pressurant tank telemetries are compared with the results of the developed computer program. The changes in pressure are due to the two major phases. The first one is the initialization phases of CPS composed of the venting phase to vent the helium gas in the pipe network from the downstream of the propellant tanks to the thrusters for safety, the priming phase to fill the vented pipe network with oxidizer and fuel respectively and then the pressurization phase to pressurize the ullage of propellant tank to regulated pressure. And the other is the apogee engine firings in which COMS CPS is in the orbit raising phase to use helium as a pressurant to keep the pressure of propellant tank as the liquid apogee engine get fired until COMS reached to the target orbit. This program can be applicable to prepare basis design data of the next Geostationary Satellite CPS.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.54-59
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• 2017

A study for process design to curtail the utility consumption during residual styrene monomer recovery in an ABS polymerization process was carried out. Among different techniques for residual monomer recovery, the steam stripping is dominantly employed in industries. The existing process, however, consumes a large amount of utility (steam and cooling water), and this study focused on the design of a new process that can substantially spare the utility consumption. A new process was configured to utilize the latent heat of the stripping steam, which is condensed with the monomer using cooling water after exiting the stripper. The condenser was modified to use vacuum state water as coolant and to generate vacuum state steam using the latent heat of the stripping steam. The steam is injected to the stripper as the stripping steam after upgrading using a compressor. Through this modification, consumption of steam and also cooling water could be significantly reduced at some expense of electricity for compressor operation.

• Korean Journal of Optics and Photonics
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• v.22 no.2
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• pp.77-82
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• 2011

Reproducibility obtained by a minimum-volume cell for photoacoustic (PA) signals is strongly dependent upon the sealing materials and sealing efficiency. Therefore, we have proposed, designed, and constructed an apparatus to enhance the sealing efficiency, and we have examined the reproducibility of amplitude and phase of PA signals with a minimum-volume cell. In particular, we have measured the PA signal as a function of modulation frequency for various rubber O-rings by using our apparatus. The results show that a silicon rubber O-ring can improve the reproducibility of the PA signal and phase by up to 53.4% and 80.4%, respectively, compared to that obtained by using the conventional sealing material, vacuum grease.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.47.4-47.4
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• 2009

초소형전기기계시스템(MEMS: Micro-Electro-Mechanical Systems) 기술로 제작된 마이크로미러 어레이를 장착한 MEMS 우주망원경은 특유의 광시야각 감시, 목표 확인, 확대 및 고속 추적 기능을 가지며 고층대기에서의 초대형 방전현상과 같이 넓은 영역에서 드물게 임의로 일어나는 섬광현상을 관측하기에 최적이다. 러시아 과학위성 Tatiana-2의 주 탑재체로 선정된 극소형 MEMS 우주망원경 MTEL(MEMS Telescope for Extreme Lightning)은 광시야각 감시와 목표 확인을 위한 트리거망원경, 목표 확대와 고속추적을 위한 확대망원경 및 섬광현상의 분광측정을 위한 분광계로 구성되어 있다. 1년간의 개발 및 성능 검증 후 MTEL은 위성탑재를 위한 모든 우주인증 시험을 성공적으로 마쳤다. 현재 MTEL은 Tatiana-2 위성에 탑재되어 있으며, 9월 18일에 우주로 발사되어 1-3년간 800km 궤도를 비행하며 지구 대기에서 발생하는 섬광현상을 관측할 예정이다. 이 발표에서는 MTEL 탑재체의 설계, 제작, 성능 측정 및 calibration 결과를 보고하고, 위성탑재를 위한 진동 및 충격, 열, 진공 및 전자기파 적합성 등의 우주인증 시험 결과 또한 보고한다. 또한 발사 후 과학위성 및 MTEL의 이 발표 때까지의 우주에서의 상황을 보고한다.

• Composites Research
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• v.23 no.6
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• pp.61-66
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• 2010

In this paper, the variation of mechanical properties of T800 carbon/epoxy composites according to the forming pressure, which was referred to previous studies on a filament winding process, were investigated. The specimens of all the tests were fabricated by an autoclave de-gassing molding process controlling forming pressure (absolute pressures of 0.1MPa, 0.3MPa, 0.7MPa including vacuum) and water jet cutting after fabricating composite laminates. Various tensile tests were performed for in-plane properties and interlaminar properties were also measured by using Iosipescu test jig. Fiber volume fraction was measured to correlate the property variation and the forming pressure. This properties are expected to be utilized in the design of Type III pressure vessel for hydrogen vehicles which uses the same carbon fiber (T800 carbon fiber) for the filament winding process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.489-494
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• 2004

Long Period Gratings (LPG) is currently receiving considerable attention because of their consistent measuring results fur pressure, temperature, strain and flow. LPG is easier to prepare and has a high sensitivity compared with Fiber Bragg Gratings (FBG). In addition, this kind of optical fiber sensors could be used for implementations in various structures. In this paper, LPG was used to monitor in situ the resin flow and the curing process in VARTM (Vacuum Assisted Resin Transfer. Molding). In order to demonstrate the effectiveness of the method, FBG is inserted into the glass mat to monitor the resin flow using optical spectrum analyzer (OSA). The curing reactions in VARTM are also observed using the same method. From the results, the attenuation wavelength shift and the loss change of attenuation band can be obtained from the status of the RTM (Resin Transfer Molding) sample owing to the internal variations of the .effective index, temperature, and pressure. It is shown that the proposed LPG is more effective in monitoring the curing reaction than FBG.