• 한국항공우주학회지
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• 제47권10호
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• pp.712-719
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• 2019

본 연구에서는 최근 다양한 큐브위성 임무에 사용되는 테이프 스프링 힌지의 거동 해석을 수행하였다. 테이프 스프링은 곡선 단면을 갖는 직선형의 얇은 스트립이며 곡률에 따라 달라지는 강성변화로 인해 비선형성이 강하게 발생한다. 이전 연구에서 제시된 회전-모멘트 선도 모델을 바탕으로 테이프 스프링의 거동 특성을 분석하였으며, 시중에 판매되는 상용 테이프 스프링 형상을 정확하게 모사하여 ABAQUS 수치 해석을 진행하였다. 테이프 스프링을 굽히는데 소요되는 최대 모멘트를 예측하였으며 단면의 원호각이나 두께 등의 변화에 따른 파라미터 스터디를 수행하였다. 또한 간략한 실험을 통해 수치해석 결과를 비교 검증하여 보다 정밀한 큐브위성 동적 거동 해석을 위한 향후 연구 방향을 제시한다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.169-172
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• 2002

This study demonstrated the feasibility of using tape-casting followed by sintering as a low-cost alternative for coating glass-ceramic or glass film on a metal substrate. The process has been successfully used to fabricate a glass-on-stainless steel and a glass-ceramic-on-molybdenum electrostatic chuck(ESC) with the insulating layer thickness about $150{\mu}{\textrm}{m}$. Electrical resistivity data of the coaling were obtained between room temperature and 55$0^{\circ}C$; although the resistivity values dropped rapidly with increasing temperature in both coatings, the glass-ceramic still retained a high value of $10^{10}$ ohm-cm at $500^{\circ}C$. Clamping pressure measurements were done using a mechanical apparatus equipped with a load-cell at temperatures up to $350^{\circ}C$ and applied voltages up to 600V; the clamping behavior of all ESCs generally followed the voltage-squared curve as predicted by theory. Based on these results, we believe that we have a viable technology for manufacturing ESCs for use in reactive-ion etch systems.

• 한국초전도ㆍ저온공학회논문지
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• 제5권3호
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• pp.15-19
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• 2003

For the purpose of standardization of the critical current measurement, it is meaningful to describe how $I_{c}$ will behave as the stress/strain level changes. In this study, strain dependencies of the critical current $I_{c}$ in Ag-alloy sheathed multifilamentary Bi(2212) and Bi(2223) superconducting tapes were evaluated at 77K, 0T. The external reinforcement was accomplished by soldering AgMgNi alloy tapes onto single or both sides of the sample. With the external reinforcement to the Bi(2212) tape, the strength of the tapes increased but the critical current at the strain free state, $I_{c0}$ decreased in some cases. The strain for onset of the $I_{c}$ degradation, $\varepsilon$$_{\irr}$, increased with an increase of the reinforcing volume and then saturated to a certain value. The effect of external reinforcement on the degradation of $I_{c}$ due to the bending strain in the Bi(2223) tape was also examined. Contrary to the expectation, it showed a significant $I_{c}$ degradation even at a small strain of 0.4 %. The observations of damage morphologies gave a good explanation to the $I_{c}$ behavior.c/ behavior.r.

• 한국세라믹학회지
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• 제47권6호
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• pp.566-571
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• 2010

Dispersion behavior of the slurries consisted of bimodal-type AlN powders was examined in non-aqueous solvent system. Azotropic solvent system and copolymer acidic dispersant were applied to the slurries. Measurements of the sedimentation height and the viscosity of the each slurry, and the test of particle size distribution of the each powder sample were conducted as examinations for the dispersion behavior at the various dispersant contents. The bimodal-type particle size distribution was continued after addition of the dispersant and small particle portions were increased as the dispersant content increases. The density of the green sheet was also increased as the dispersant content increases and a green density of $2.114\;g/cm^3$ was obtained at the sample prepared from 2.4 wt% dispersant content. The increase of large particle portions resulted in the surface defects of the green sheets.

• 한국전기전자재료학회논문지
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• 제20권6호
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• pp.541-545
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• 2007

The critical current degradation behaviors of multifilamentary Bi-2223 superconducting tapes under pressurized liquid nitrogen were investigated using a r-shaped sample holder which gives a series of bending strains to tape. Three kinds of externally-reinforced Bi-2223 tapes with different hermeticity were used as samples. The tape with the thicker reinforcement layer had a better bending strain tolerance of $I_c$, but when the bending strain was calculated at the outermost filament, the $I_c$ degradation behavior became identical. For all samples, $I_{c0}$ decreased with the increase of applied pressure, but the $I_c$ degradation behavior with bending strain at each pressure level was similar. Furthermore, after depressurization from 1 MPa to atmospheric pressure, $I_c$ was completely recovered to its initial values. When the samples were warmed up to room temperature after pressurization tests, the ballooning damage occurred at lower bending strain regions. The region where ballooning was observed was identical to the one where the significant $I_c$ degradation occurred.

• 한국초전도ㆍ저온공학회논문지
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• 제11권4호
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• pp.12-15
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• 2009

The $I_c$ degradation behavior of critical current in differently processed YBCO and SmBCO CC tapes with IBAD template has been investigated. It has been known that the residual strain in the CC tape will influence the shape of the $I_c$-strain window; $I_c$ may show a peak value if there exist a residual strain induced in the tape during manufacturing. The difference of residual strain may be resulted from the adopted different deposition techniques. In this study, bending test of CC tapes has been done using the Goldacker bending test rig which can produce both compressive and tensile bending strain continuously or alternately to the sample. For SmBCO CC tapes, in continuous compressive bending test, $I_c$ showed a minimal increase and did not degrade up to the largest strain that can be applied using the bending rig equivalent to 1.15% based on the sample thickness. However, in the case of alternate application of compressive and tensile bending strain, $I_c$ showed a larger degradation and a lower reversible limit when compared with the case of continuous application of the bending strain. When $I_c$ started to degrade significantly at the tension side, the reversibility ended, also at the compression side which is resulted from the permanent deformation like delamination or cracks that was induced due to tensile bending strain.

• 한국지반환경공학회 논문집
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• 제12권9호
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• pp.35-45
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• 2011

본 연구에서는 터널 지보재의 거동을 전기펄스를 이용한 계측 시스템인 TDR센서를 이용하여 파악하고자 하였다. 터널 지보재의 거동을 파악하기 위해 먼저 구리테이프를 TDR센서의 계측재료로 이용하여 터널 지보재에 설치하기 위한 제작기법에 대해 연구하였다. 그 결과 구리테이프의 상부에 유리테이프, 하부에 스티로폼+전자파 차단시트를 설치했을 때 TDR센서의 민감도가 적절했고 노이즈 발생량도 적었다. PVC파이프 터널모형단면을 통해 단면의 강성과 지점 조건에 따라 데이터의 형태가 어떠한 경향을 나타내는 지 확인할 수 있었다. 이는 실제 현장에 구리테이프를 이용하여 터널 지보재의 거동을 정확히 파악하기 위해서는 지보재의 강성과 지점 조건을 현장과 동일하게 하여야 함을 알 수 있었다. TDR데이터와 유한요소해석과의 비교를 통해 TDR센서를 이용하여 터널의 거동을 파악할 수 있음을 알 수 있다. TDR데이터를 통해 지보재의 변형을 정성적으로 파악할 수 있고, 응력과 변형률 관계를 통해 지보재의 부재력까지 파악할 수 있을 것으로 기대된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.76-78
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• 1994

Owing to the discover of oxide superconducting over critical temperature100K, it is being made experimentally somewhere under the possibility that there is superconducting magnet by cooling liquid nitrogen. The issues of thermal stability and quench process of Low-Tc superconductor has been studied and used application of oxide superconducting magnets. However the quench propagation property of oxide superconductor, especially experimental data about thermal behavior has not been reported yet. Therefore we measured the effect of temperature dependance of quench propagation velocity, Vq, by using the short samples made up of silver sheathed Bismuth-family (2223phase) superconducting oxide tape.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.17-20
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• 2001

Stress/strain dependencies of the critical current I$_{c}$ in AgMgNi sheathed multifilamentary Bi(2212) superconducting tapes were evaluated at 77K. The external reinforcement was accomplished by soldering Ag-Mg tapes to single side or both sides of the sample. With the external reinforcement, the strength of tapes increased but I$_{c}$ decreased. The I$_{c}$ degradation characteristic according to the external reinforcement was improved markedly in terms of the stress although it appeared less remarkable on the basis of the strain. Effects of external reinforcement were discussed in a viewpoint of monitoring sensitivity of cracking in superconducting filaments by considering n-value representing the transport behavior of the current, which is closely associated with the location of them relative to the voltage-monitoring region in the tape. tape.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.72-75
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• 2001

The persistent current mode operation of HTS coils is one of the key technologies required for very high-field MRI magnets composed of LTS and HTS coils. But to date, the fabrication of persistent current mode system using HTS is not investigated well. In this paper, we fabricated the magnet and PCS using by BSCCO-2223 tape and jointed them with solder. The current decay behavior of the circuit was measured in liquid nitrogen by monitoring the magnetic field in the centre of magnet with a Hall sensor. To enhance the characteristic of persistent current mode system, superconducting joint method should be investigated.