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The Influence of the Silica Contents for High Temperature Strength for Single Crystal Casting Mold of Superalloys (초합금 단결정 주조용 주형의 실리카 함량에 따른 고온강도 영향)

  • An, Seong-Uk;Larionov, V.;Grafas, I.;Im, Ok-Dong;Jin, Yeong-Hun;Seo, Dong-Lee;Lee, Jae-Hun;Kim, Byeong-Ho;O, Je-Myeong
    • Korean Journal of Materials Research
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    • v.8 no.10
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    • pp.879-883
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    • 1998
  • In the vacuum casting process for superalloys, molten metal are poured into the heated ceramic mold up to $1000^{\circ}C~1700^{\circ}C$. The mold has to have the high temperature strength during casting and made by hlgh purity alumina. In this sturdy, the mold was made by low purity alumina and changed silica contents intended to have high strength The 7.7wt.% SiOz specimens have 10- 55% higher strength than others in room and high temp. Therefore, the cast mold has been developed in this study for single crystal vacuum cast by controlling the ratio of fused alumina and colloidal silica which are used commercially for conventional casting in industries.

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BGA Deveop Process Optimization for the Vertical Wet Equipment Using Taguchi Experiment (다구찌 방법을 이용한 BGA 현상 공정용 수직 습식 장비의 공정 최적화)

  • Ryu, Sun-Joong
    • Journal of the Korean Vacuum Society
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    • v.18 no.4
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    • pp.310-317
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    • 2009
  • Vertical wet equipment for the BGA develop process was newly developed substituted for conventional horizontal wet equipment. The benefits of vertical equipment are that the pattern damages generated by the collision between the patterns and transferring rollers can be eliminated because the direct contact between the equipment's transferring units and the soft dry film patterns does not occurs. Taguchi experiment was conducted to optimize the process characteristics for the vertical equipment. The experiment was organized as the smaller the better problem which includes adequate uncontrollable factor and controllable factors. The uncontrollable factors are the 4 sides of two panels which are loaded to the equipment at the same time. By the analysis of the experiment, temperature of the develop chemicals and develop spraying time are analyzed as the main controllable factors. Finally, line pattern's minimum width which is not damaged for the develop process was improved from $13.8{\mu}m$ for the horizontal equipment to $10.4{\mu}m$ for the vertical equipment. And dot pattern's minimum width is improved from $22.1{\mu}m$ to $16.3{\mu}m$.

Quality Changes of Commercial Kimchi Products by Different Packaging Methods (소포장 김치의 포장방법별 품질특성 변화)

  • Hong, Seok-In;Park, Jin-Sook;Park, Noh-Hyun
    • Korean Journal of Food Science and Technology
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    • v.27 no.1
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    • pp.112-118
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    • 1995
  • The effect of various packaging methods on kimchi quality was investigated in order to develop the packaging techniques for preventing commercial kimchi products from inflation and explosion, due to fermentative gas evolved during storage and distribution. Kimchi was packaged in different methods; 1) atmospheric packaging(AP), 2) check valve packaging(CV), 3) double packaging(DP), and 4) vacuum packaging(VP). The quality of kimchi during storage at $10^{\circ}C$ was evaluated in terms of gas composition, free volume, pH, titratable acidity color index and sensory properties. The gas composition inside packages showed different curves according to the packaging methods. Due to fermentative gas accumulation in both AP and CV, $CO_2$ concentration increased by 2 stepwise pattern, while $O_2$, concentration decreased exponentially. In DP, $O_2$ concentration remained constant, but $CO_2$ concentration increased by 2 stepwise pattern and then decreased. In contrast, VP produced low $O_2$ and high $CO_2$ concentrations only at the end of storage. The free volume in both AP and CV showed typical sigmoidal curves similar to $CO_2$ concentration changes. It remained constant in DP, but started to increase at the late stage of storage in VP. There was no significant effect of packaging methods on pH changes of kimchi. In titratable acidity, DP maintained relatively higher than others. Regarding to the color change of crushed kimchi juice in all packages, L and b values decreased exponentially but a value remained constant during storage. Color index(L b/a) of crushed kimchi juice decreased exponentially and remained constant at the end of storage. The growth of lactic acid bacteria was VP, CV, AP, DP in increasing order. In sensory test, the sourness scores of DP were fairly higher than those of others, but the texture was not significantly affected by the packaging methods. The preference for kimchi showed VP>AP, CV>DP in order of score. In this study, it could be proposed to employ DP and VP method as the effective packaging techniques for preventing commercial kimchi products from inflation.

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Tensile Strength of Composite Laminate Repaired Using Heat-blanket and a Novel Pressurization System (히트블랑켓과 새롭게 개발된 가압장치를 이용해 수리한 복합재 적층판의 인장강도 연구)

  • Chae, Song-Su;Lee, Gwang-Eun;Ahn, Hyonsu;Choi, Jin-Ho;Kweon, Jin-Hwe
    • Composites Research
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    • v.31 no.1
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    • pp.1-7
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    • 2018
  • In the case of a conventional composite patch repair using a heat blanket, the adhesive is pressurized using only a vacuum bag. In this study, however, a pressurization system has been developed to apply additional air pressure on the vacuum bag. In order to verify the performance of the developed system, the composite laminates were repaired with scarf patches and then tested under tensile load to be compared with the strength of the defect-free laminate. Tensile tests were also conducted on specimens with the same configuration but bonded in an autoclave. As a result of the test, the tensile strengths of the specimens repaired using the heat blanket with vacuum only without external pressure, the specimens repaired with additional pressure by the developed system, and the specimens repaired with the same external pressure in an autoclave, showed the strength recovery ratios of 74.9, 81.0, and 78.2%, respectively. The results of the tensile test after moisture saturation and the dried fatigue test also showed that the strength recovery ratios of the specimens repaired under the external pressure of 1 atm using the developed system are slightly higher than that of specimens bonded in autoclave.

Vacuum Assisted Auto-Lancing Technique for Capillary Blood Sampling on the Forearm with Minimized Pain (전완부위 최소통증 채혈을 위한 진공 자동 채혈기법)

  • Park Mi Sook;Park Kyung Soon;Kim Kyung Ah;Jun Myung Hee;Kim Tae Im;Lee Tae Soo;Cha Eun Jong
    • Journal of Biomedical Engineering Research
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    • v.25 no.6
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    • pp.557-563
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    • 2004
  • A new vacuum assisted auto-lancing technique is proposed to minimize pain. Specially designed lancing device was introduced, which applied -100mmHg right after skin puncture on the forearm. Sampled blood volumes were measured in 58 normal females. Mean volume of 464 samples was approximately 2.6$\muL$ and the frequency of more than 0.5$\muL$ was 86%. Thus the success rate of blood sugar test should also be the same when using modern glucose meters capable of testing with only 0.3~0.5$\muL$ of capillary blood. When pain scores were quantitatively evaluated by the visual pain measure, only 23% pain of the traditional finger sampling was experienced, demonstrating that capillary blood sampling was performed on the forearm with almost no pain. The present technique reduced pain to a great degree, though resampling might be unavoidable due to 14% of test failure rate estimated for modern glucose meters. However, minimized pain makes the present technique of great convenience for diabetic patients who need blood sampling a few times a day.

Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.302-303
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    • 2010
  • Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

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Effect of Vapor-Cooled Heat Stations in a Cryogenic Vessel (극저온액체 저장용기에서 열전도 차폐단의 영향)

  • Kim, S.Y.;Kang, B.H.;Choi, H.J.
    • Journal of Hydrogen and New Energy
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    • v.9 no.4
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    • pp.169-176
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    • 1998
  • An experimental study on effect of vapor-cooled heat stations in a 5.5 liter cryogenic vessel has been performed. The cryogenic vessel is made of stainless steel of thickness of 1mm and insulated by the combined insulation of vacuum, MLI(multi-layer insulation) and vapor-cooled radiation shield. Vapor-cooled heat stations are also constructed based on the 1-dimensional thermal analysis to reduce the heat inleak through a filling tube. Thermal analysis indicates that the vapor-cooled heat stations can substantially enhance the performance of vessel for cryogenic fluids with high $C_p/h_{fg}$ where $C_p$ the specific heat and $h_{fg}$ the heat of vaporization, such as $LH_2$ and LHe. The experimental results for $LN_2$ shows that the total heat inleak into inner vessel consists of 14% radiation and 86% conduction through the filling tube. Therefore, it is expected that the conduction heat in leak of the vessel for high $C_p/h_{fg}$ cryogenic fluids can be significantly reduced. powders. The amount of copper coating was 20wt%. In order to examine corrosion behavior of the electrodes, the corrosion current and the current density, in 6M KOH aqueous solution after removal of oxygen in the solution, were measured by potentiodynamic and cyclic voltamo methods. The results showed that Co in the alloy increased corrosion resistance of the electrode whereas Ni decreased the stability of the electrode during the charge-discharge cycles. The electrode used Si sealant as a binder showed a lower corrosion current density than the electrode used PTFE and the electrode used Cu-coated alloy powders showed the best corrosion resistance.

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Magenetic Properties of Nd-Fe-B-Co-based Melt-spun Ribbons an dTheir Bonded Magents (Nd-Fe-B-Co계 급냉리본과 Bond 자석의 자기적 성질)

  • Gang, Gye-Myeong;Gang, Gi-Won;O, Yeong-Min;Song, Jin-Tae
    • Korean Journal of Materials Research
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    • v.3 no.2
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    • pp.175-184
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    • 1993
  • Abstract Co-and/or AI-added Nd-Fe-B-based magnetic alloys were fabricated by using vacuum induction melting frunace, and melt-spun ribbons were made of the magnetic alloys with single roll rapid quenching method. The variation of magnetic properties of the melt-spun ribbons as a function of Cuwheel velocity (Vs) were investigated. Bonded magnets were made of the optimally quenched ribbon fragments, and the magnetic properties of the melt-spun ribbons and the bonded magnets were studied, relating to the microstructure and crystalline structure. Cu-wheel surface velocity had a strong effect on the magnetic properties of the melt-spun ribbons, and the maximum properties were obtained around Vs =20m/sec. The optimally quenched ribbon had a cellura-type microstructure, in which fine N$d_2$F$e_14$B grains were surrounded by thin Nd-rich phase. In case of a 2.1at% AI-added melt-spun ribbon, the magnetic properties were as follows: iHc, Br, and (BH)max were 15.5KOe, 7.8KG and 8.5MGOe respectively. And resin bonded magnets were fabricated by mixing optimally quenched ribbon fragments with 2.5wt % polyamide resin, compacting and binding at room temperature. The iHc, Br and (BH)max of bonded magnet were lO.2KOe, 4.4KG and 3.3MGOe respectively. And hot-pressed magnets were made by pressing the overquenched ribbons at high temperature. The magnetic properties of hot-pressed magnets were better than those of bonded magnets, and when the holding time was 8 minutes, the iHc, Br, and (BH)max of the hot-pressed magnet were 1O.8KOe, 7.3KG and 8.0MGOe respectively. Domain structure was mainly maze pattern, which means that the easy magnetization axis could be aligned, and the domain width of the hot-pressed magnets was smaller than that of bonded magnets.

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Characteristics of Soil Stress using Expansion Liquid Sheet (팽창약액시트를 이용한 지중응력 특성에 관한 연구)

  • Kang, Hyounhoi;Kim, Juho;Chung, Yoonseok;Park, Jeongjun
    • Journal of the Society of Disaster Information
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    • v.13 no.1
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    • pp.43-50
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    • 2017
  • In this study, to investigate the strength enhancement and stress transfer effect of the inflatable chemicals used in the recovery of soft ground or partial settlement, the dilatant solution was prepared and classified by measuring the density and the earth pressure in the sand ground. The inflation reinforcing agent was prepared by injecting into a separate impervious vacuum sheet by dividing into a relatively high expansion group and a low expansion group, and a cementation experiment was performed in the lower part of the homogeneously formed model ground. As a result, reinforcing effect was shown up to about 15cm above the expansion reinforcement, and the soil pressure showed a compaction tendency similar to the concentrated load of $1.150{\sim}11.298t/m^2$.

Life Prediction of Failure Mechanisms of the CubeSat Mission Board using Sherlock of Reliability and Life Prediction Tools (신뢰성 수명예측 도구 Sherlock을 이용한 큐브위성용 임무보드의 고장 메커니즘별 수명예측)

  • Jeon, Su-Hyeon;Kwon, Yae-Ha;Kwon, Hyeong-Ahn;Lee, Yong-Geun;Lim, In-OK;Oh, Hyun-Ung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.44 no.2
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    • pp.172-180
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    • 2016
  • A cubesat classified as a pico-satellite typically uses commercial-grade components that satisfy the vibration and thermal environmental specifications and goes into mission orbit even after undergoing minimum environment tests due to their lower cost and short development period. However, its reliability exposed to the physical environment such as on-orbit thermal vacuum for long periods cannot be assured under minimum tests criterion. In this paper, we have analysed the reliability and life prediction of the failure mechanisms of the cubesat mission board during its service life under the launch and on-orbit environment by using the sherlock software which has been widely used in automobile fields to predict the reliability of electronic devices.