• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.12
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• pp.1129-1134
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• 2007

Payload fairing protects satellites and electrical equipments from the external environment. Payload fairing is jettisoned before satellite separation. Assembly frame for the separation of payload fairing were assembled with shear bolts. The role of shear bolts is to support structural load during flight and they are cut by explosion of pyro. The assembly frame which is connected by shear bolts is separated after the cutting of shear bolts. In this paper, structural tests and analysis were done for the design of the shear bolt. Compression, bending and shear load apply to the hardware including assembly frame. Test results showed that design of the shear bolt satisfied both structural strength for the support of flight load and required low strength for the cutting of shear bolts.

• The Hankook-Saengyark Bo
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• no.234
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• pp.2-2
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• 1999

시호 60t, 산수유 40t 반입결정 생산자단체와 약정서 체결 조건 - '국내산 녹용 안심하고 구입하세요' - 야생삼도 CITES 품목? 정부 대책마련 부심 - 중국 보따리 무역상 농산물 반입 '휴대품 통관 규정' 엄격 적용

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.306-310
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• 2007

Characteristics of GDL (Gas Diffusion Layer) mainly determine the gas diffusion and water removal in a cell, thereby changing the performance and affecting durability of PEFC. To optimize the water management and understand the two phase flow in a GDL, it is important to study the behaviors of GDL micro structure under the real operating condition. In the clamped condition of cell, the GDL beneath the rib is more compressed than beneath the channel. Many researches on physical, electrochemical, mechanical behaviors of gas diffusion layer has been conducted. However, changes in surface properties under clamped condition have rarely studied. In present study, the morphology of broken connections of carbon fibers and detachment of PTFE coatings on the fibers were shown from the microscopic observations. In addition, changes in wetting properties of GDL by compression were investigated by using XPS and liquid uptake methods. The hydrophobic characteristics of GDL surface beneath the rib of the flow field plate are changed due to the deformation of micro structure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1239-1243
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• 2014

This paper presents the application of carbon-fiber-reinforced polymer (CFRP) for the damage absorption and optimal design of portable smart devices to close in life. CFRP specimens are subjected to a tensile test to estimate their mechanical properties in terms of the stacking angles. Further, the screw reverse torque and screw torque at each stacking angle are determined using a torque tester after tapping holes on the CFRP specimens. Two experiments are performed for comparing their results in order to determine optimal conditions. In the tensile test, a woven specimen is found to have the highest strength and stiffness. In the case of the woven specimen, no difference is observed even when it is applied to prevent loosening of the coating. And average result value was excellent.

• Computational Structural Engineering
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• v.7 no.3
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• pp.133-141
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• 1994

When a bolt is tightened up to the range of plastic deformation, yielding may be governed by the combined stresses due to the axial force developed in the bolt and the frictional torque induced on the thread by the contact with the nut. Consideration is taken account of the fact that the unengaged portion of the thread has least sectional area, being subject to initial yielding. Once yielding has taken place some strain hardening effect may result. Incremental stress-strain relations are used to treat the continued yielding, which is equivalent to treat continued yielding as if summing up the effects of thin walled cylinders subject to plastic deformation. M10 bolts of fine threads are used for both computational and experimental purposes. Variation of axial forces and frictional torques vs. the frictional coefficients are presented together with other plots showing some characterist of bolt under plastic deformation. Finally, a design and control aid for the tightening(i.e., kind of nomograph) is presented, showing the relationships among the torque factor and frictional coefficients for that particular bolt used in the experiment.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.31-38
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• 2013

This research analyzed the acoustic emission signals collected from the pin loading tests and investigated the effect of hygrothermal exposure on the fracture behavior of the pin-jointed carbon fiber/epoxy composites. The composite specimens include: the Base specimen that has not been exposed to any environments, the RT specimen that has been immersed in room temperature water, and the HT specimen that has been immersed in high temperature water. According to the pin loading test, the RT and the HT specimens showed 2.2% and 13% decreases in the bearing strength compared to the Base specimen, respectively. The analysis of the acoustic emission signals showed different fracture acceleration points for three types of the specimens. Furthermore, for the RT and the HT specimens, the event from the matrix crack signals in the composites decreased. This shows the effect of the hygrothermal conditions on the acoustic emission signals. Additionally, upon investigating the fracture behaviors of the pin-jointed composites, the exposing specimens to hygrothermal environments decreases the interfacial characteristics of the composites.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.77-86
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• 2011

The advanced geotechnical information has been required to determine the accurate design parameters for complex construction. However, the Standard Penetration Test (SPT), which has low reliability, has been used to estimate the subsurface condition in the field. The objective of this paper is development and application of the Static-Dynamic penetrometer, which detects the resistances in soft clay, sand and rock. The energy losses according to the rod connection methods (perfect or non-perfect connection, and number rods) are experimentally evaluated. The reflection and transmission ratios are used to investigate the energy loss by a simulation. The static-dynamic cone penetrometer, in which the accelerometers and strain gauges are installed on the cone tip and the rod head, is used to estimate the energy loss during penetration by impacts. The experimental and simulation studies show that the transferred energy through rods with non-perfect connection dramatically decreases. Furthermore, the transferred energy on the rod head is not the same as that on the cone tip. This study demonstrates that the energy loss should be evaluated on the cone tip.

• 월간 기계설비
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• s.319
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• pp.86-90
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• 2017

근로계약 체결 시 사용자는 법적 의무를 준수하기 위해 반드시 명시하여야 할 사항은 근로계약서에 기재하고, 기타 개별 근로자와의 특별한 계약내용 및 기업의 인사관리정책상 계약서에 반드시 명시하여야 할 내용이 있다면 계약서에 서면으로 명시하는 것이 계약당사자간 신뢰를 확보하고 분쟁을 예방하는 방안이라 하겠으며 취업규칙에 위임하는 통일적인 근로조건 사항에 대해서는 취업규칙을 열람하게 하는 것이 바람직합니다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1099-1100
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• 2010

• 월간 기계설비
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• s.258
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• pp.74-77
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• 2012

올해부터, 국토해양부 장관이 고시하는 최저가낙찰제 대상공사에 대하여 포괄대금지급보증제도가 시행되며, 건설근로자 노무비 구분관리 및 지급 확인제가 추진된다. 또한 근로계약 체결시 근로조건 일반사항이 명시된 서면을 근로자에게 반드시 교부해야 하며, 장애인 고용부담이 강화된다. 본지는 올해부터 달라지는 건설 중소기업 관련 개편 시행되는 각종 제도를 소개한다.