• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.6
• /
• pp.35-41
• /
• 2006

In this paper, we focus on improving the performance of the piezoelectric diaphragms of valveless micropumps. A circular lightweight piezoelectric composite actuator (LIPCA) with a high level of displacement and output force has been developed for piezoelectrically actuated micropumps. We used numerical and experimental methods to analyze the characteristics of the actuator to select optimal design. With the developed circular LIPCA, we fabricated a valveless micropump by photo-lithography and PDMS molding techniques. The displacement of the diaphragm, the flow rate and the back pressure of the micropump were evaluated and discussed. With a semi-empirical method, the flow rate with respect to driving frequency was predicted and compared with experimental one. The test results confirm that the circular LIPCA is a promising candidate for micropump application and can be used as a substitute for a conventional piezoelectric actuator diaphragm.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2003.07a
• /
• pp.384-389
• /
• 2003

전기가 공급되지 않는 농경지에 물을 공급하기 위해 태양열을 동력원으로 하고 저온에서 비등하는 물질을 작동물질로 하는 물펌프가 연구되어 왔다. 이와 관련하여 김 등(2002, 2003)은 펜탄을 작동물질로 한 태양열 물펌프 연구에서 에너지변환실험, 작동사이클의 열역학적인 해석, 장치의 설계를 수행한 바 있다. 본 연구에서는 펜탄을 작동물질로 한 태양열 물펌프를 실현하기 위하여 기존의 설계를 바탕으로 실험장치를 제작, 실험, 분석하였다. (중략)

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.11a
• /
• pp.3-6
• /
• 2007

In this study, we described the Pyrovalve used in the propulsion system. It is very important to ensure its reliablity of operation because Pyrovalve is a pyrotechnic device for controlling fuel and air line of propulsion system. so we focused on improving operational reliability through several analyses and tests.

• Proceedings of the KAIS Fall Conference
• /
• 2000.10a
• /
• pp.194-198
• /
• 2000

최근 저장 장치로 많이 사용되고 있는 IBM PC의 CD-ROM(Compact Disc Read Only Memory)과 MP3(MPEG-1 Layer Ⅲ Audio) 디코더 칩을 이용하여 PC 작동과 관계없이 독립적으로 작동하는 CD-ROM 기반의 MP3 Player를 구현하였다. 여기서는 CD-ROM의 규격과 CD-ROM에 사용되는 ATAPI(AT Attachment Packet Interface) Format, MPEG-1 Layer Ⅲ의 오디오 부분에 대하여 알아보고 MP3 디코더 칩을 사용하여 CD-ROM에서 읽은 MP3 데이터즐 재생하는 방법을 취하였다. 이리하여 PC 자체로 MP3를 작동시키는 부하를 경감시키는 효과를 얻었다.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.16 no.5
• /
• pp.463-476
• /
• 1987

주기적으로 작동하는 흡수식 장치가 부착된 직접 연소식 고효율 난방기기를 특정 공간 난방 목적으로 설계하여 제작하였다. 작동 유체는 메타놀/물-리치움브로마이드이다. 네개의 구성품으로 된 이 기기에는 동작부품이 없다. 제 1 시제품의 결과와 경험에 기반을 두고 개선형 시제품을 설계, 제작하였다. 현재까지 발생기-응축기 모듈이 설치되어 보일러 운전모드 결과가 확립되어 있다. 또한 난방기기의 경제성과 작동 유체의 안정성 연구가 중요한 부수 조건을 확립하기 위하여 수행되고 있다.

• Proceedings of the Korean Society of Disaster Information Conference
• /
• 2022.10a
• /
• pp.352-354
• /
• 2022

2020년 기준 금정터널 유지관리 계측센서의 정상 작동 실효성 검증 조사결과 정상작동 유효율은 14-2공구 6개 단면의 계측센서 41개중 7.3%, 14-3공구 10개 단면의 계측센서 83개중 24.1%로 편차가 큰 것으로 나타났으며, 전체 16개 단면의 계측센서 124개중 18.5%로 나타났다.

• Composites Research
• /
• v.26 no.1
• /
• pp.14-20
• /
• 2013

The electrospun PVDF containing CNT was made for fabricating materials of the actuator. The electrochemical and their actuating movement were evaluated for the actuator performance in the electrochemical environment. The actuator (which was fabricated by electrospinning) had some advantages, i.e., good dispersion and flexible properties. In the electrospinning process, the final product would have different forms based on different essential factors. In this work, electrospun nanofibers were aligned by using the drum-type collector, and the morphology was identified via the field emission-scanning electron microscope (FE-SEM). The uniform dispersion of CNT in PVDF nanofiber was observed by electron probe X-ray micro-analysis (EPMA) test. The results of tensile strength and electrical resistivity provided the aligned state. The electrospun CNT/PVDF nanofiber sheet on the aligned direction showed better mechanical and electrical properties than the case of the vertically-aligned direction. The efficiency and electrical capacities of electrospun CNT/PVDF nanofiber sheets were compared with the cast PVDF sheet for actuator application. Electrospun CNT/PVDF nanofiber sheet exhibited much better the case of actuator performance than cast neat PVDF actuator, due to the excellent electrical connecting areas.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.6
• /
• pp.110-117
• /
• 2003

The operational characteristics of the landing gear retraction/extension depend on the complexity of design variables operational/environmental conditions. In order to meet the requirements of minimum stow area and performance, the integration of the landing gear system requires operational kinematic and dynamic analysis considering an effect of its related system. This study investigates operational dynamic behaviors of the T-50 landing gear system using ADAMS. Taking into account for various operational/environmental conditions, an analysis of dynamic behavior on the landing gear operational characteristics is performed with experience derived from a wide range of proprietary designs. Analytical results are presented for discussing the effects of temperature, aerodynamic and maneuver load on normal/emergency operation of the landing gears and doors. This analysis leads us to the conclusion that the proposed program is shown to be a better quantitative one that apply to a new development and troubleshooting of the landing gear system.

• Composites Research
• /
• v.23 no.2
• /
• pp.24-30
• /
• 2010

Interfacial evaluation and hydrophobicity of Ni-nanopowder/epoxy composites were investigated for self-sensing and actuation. Contact resistance and resistivity were measured using gradient micro-specimens. The actuation of the composites in the electromagnetic field was studied with three wave functions, i.e., sine, triangle and square functions. Due tothe presence of hydrophobic domains on the heterogeneous surface, the static contact angle of Ni-nanopowder/epoxy nanocomposite wasabout $100^{\circ}$, which was rather lower than that for super-hydrophobicity. The dynamic contact angle showed the similar trend of static contact angle. Ni-nanopowder/epoxy composite was responded wellfor both self-sensing and actuation in electromagnetic field due to the intrinsic metal property of Ni-nanopowder. Displacement of the actuator of Ni-nanopowder/epoxy composite was evaluated to obtain the maximum and the optimum performance using laser displacement sensor as functions of the wave type, frequency, and voltage. Actuation of Ni-nanopowder/epoxy composites also increased as functions of applied frequency and voltage. Actuated strain increased more rapidly at sine wave with increasing voltage compared to those of triangle or rectangular waves.

• Fire Science and Engineering
• /
• v.22 no.2
• /
• pp.116-120
• /
• 2008

According to the Fire Services Act revised in 2005, it has been required to set up sprinkler systems to all floors to the newly builded apartments having above 11 floors. But, according to the Fire Services Act before 2005, it had been required to set up sprinkler systems from 16 floors to the top floors to the apartments having above 16 floors. This case is the accident that a victim was dead by the fire which is inferred as an accidental fire by a cigarette butt in a 17th floor apartment unit in an apartment having 17th floors and that the bereaved family called in question why the sprinklers non worked at the fire. Through the field investigation, we checked that the sprinklers worked well when the fire detectors at the 16th floor of the apartment were operated and that the sprinklers non worked when the fire detectors at the 17th floor of the apartment were operated. We made clear that the cause of the sprinkler non-working at the 17th floor is the programming error of the sprinkler controller.