• Proceedings of the Materials Research Society of Korea Conference
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• 2000.11a
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• pp.54-54
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• 2000

• Carbon letters
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• v.13 no.4
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• pp.254-259
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• 2012

Nanoporous non-woven carbon fibers for a gas sensor were prepared from a pitch/polyacrylonitrile (PAN) mixed solution through an electrospinning process and their gas-sensing properties were investigated. In order to create nanoscale pores, magnesium oxide (MgO) powders were added as a pore-forming agent during the mixing of these carbon precursors. The prepared nanoporous carbon fibers derived from the MgO pore-forming agent were characterized by scanning electron microscopy (SEM), $N_2$-adsorption isotherms, and a gas-sensing analysis. The SEM images showed that the MgO powders affected the viscosity of the pitch/PAN solution, which led to the production of beaded fibers. The specific surface area of carbon fibers increased from 2.0 to $763.2m^2/g$ when using this method. The template method therefore improved the porous structure, which allows for more efficient gas adsorption. The sensing ability and the response time for the NO gas adsorption were improved by the increased surface area and micropore fraction. In conclusion, the carbon fibers with high micropore fractions created through the use of MgO as a pore-forming agent exhibited improved NO gas sensitivity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.925-931
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• 2007

We successively fabricated the Ni metal mask by additive method and evaluated the effects of wetting agents addition on the microstructure, hardness, and friction coefficient. In the process, the additive patterns with fine hole and pitch were made by photolithography technique and subsequently Ni plate was electroformed on the patterns. We found that the microstructure and mechanical properties were significantly varied when the different combinations of the wetting agents were used. When the wetting agents of both SF-1 and SF-2 were added, the microstructure consisted of crystal and amorphous phases, the grain size reduced to 5-40 nm, the RMS value decreased to 11.4 nm and the wear resistance improved. In addition, the hardness was as high as 638 Hv which is higher than that of commercial stainless steel mask and this improvement is probably due to the presence of amorphous Phase and fine grain size. The improvement of the wear resistance can provide a higher reliability and a longer service life.

• Speech Sciences
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• v.7 no.2
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• pp.139-155
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• 2000

The aim of this research is to investigate acoustic characteristics of three different types of Korean Stops-plain, tensed, and aspirated-, and employ these as a base to determine which one(s) can be used as perceptual cues. In this paper, we have examined acoustic characteristics of Korean Stops, especially voice onset time(VOT), closure duration(CD), degree of pitch of following vowels and differences in the intensity of the Stops build-up after the onset of voicing. From the above characteristics, differences can be made between word-initial and word-medial positions. That is to say, in word-initial position, the three Korean Stops are distinguished by VOT and pitch, whereas in word-medial by CD, VOT and pitch. However, the acoustic characteristics do not have the same value as perceptual cues. In both word-initial, and medial positions, the immediately following vowels play the most important role in perceiving Korean Stops. And in case of word'-medial positions,. CD and VOT also play important perceptual roles. In order to have a more fine-grained distinction among Korean Stops, we think future research should be done to investigate which factor(s) of the following vowels is/are the most determinative perceptual cue(s). However, based on our investigation, we may conclude that it is highly plausible that pitch can be one of the most important perceptual cues when distinguishing the three Korean Stops.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2006.10a
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• pp.179-212
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• 2006

1. $Welco^{(R)}$ Ultra fine solder powders are suitable for wafer bumping applications; mass production of ultra fine powders with high quality and high yield. - UFP based pastes for wafer bumping by stencil printing ($60-80{\mu}m$ pitch) are now available - Residue free solder flux was developed; meets voids specification of 20%. - F645 type 5 paste is suitable for components 01005

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.177-177
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• 2010

본 연구에서는 반도체용 Si wafer에 마스크 공정 및 slit etching 공정을 적용하여 목표인 30um 이하의 Probe unit을 개발하기 위해 Deep Si Etching(DRIE) 장비를 이용하여 식각 공정에 따른 특성을 평가하였다. 마스크는 Probe block 조립에 적합한 패턴으로 설계 하였으며, slit의 에칭된 지점에 pin이 삽입될 수 있도록 그 폭을 최소한으로 설계하였다. 30um pitch와 20um pitch의 마스크를 각각 설계하여 포토공정에 의해 마스크패턴을 제작하였으며, 식각공정 결과 식각율 5um/min, profile angle $89^{\circ}{\pm}1^{\circ}$로 400um wafer의 양면관통 식각을 확인하였으며, 표면 및 단면 식각특성을 조사하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.1008-1011
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• 2005

It is necessary for the design of lead frame punches in blanking to consider buckling because inner lead pitch of lead frame has been narrowed by miniaturization and high accumulation of semiconductor. In addition, if process variables change in press stamping process, the lift of punches is no longer influenced in wear and punches can be broken suddenly. To prevent the fracture of fine pitch lead frame punches, having considered applying reinforcement to it, this paper verified the design with buckling analysis. This study presents the optimal position and number of reinforcement to be attached to punches. Finally this study presents design rules of attaching reinforcement.

• Journal of Plant Biology
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• v.37 no.3
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• pp.309-316
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• 1994

To make regional comparisons of water status of pitch pine, the temporal changes of water status in pitch pine were investigated at different areas; urban Seoul (heavily polluted area), surburb of Seoul (lightly polluted area), and rural area (control). The effects of air pollutants, acid rain and chemical properties of soil on water deficit in pitch pine were also investiaged. Water content of needles growing at polluted areas were usually lower than that at unpolluted area. Water saturation deficit of needles growing at polluted areas were usually higher than that at unpolluted area especially in dry season. These results indicated that water in needles growing at polluted areas were usually more deficient than that at unpolluted area, and were more deficient in April than other months. At polluted areas, the older the needles were, the more quickly transpirated the water in the needle was. At unpolluted areas, however, water in old needles was not so quickly transpirated as those at polluted areas. Water potential of needles of pitch pine seedlings treated with simulated acid rain (SAR) of pH 3.5 decreased more quickly than that of needles treated with SAR of pH 5.6. Loss of water through epicuticular layer was greater in the following order: magnesium deficiency＋100 $\mu$M aluminium>100$\mu$M aluminium>magnesium deficiency>control. In addition to Mg deficiency and Al toxicity, growth decline of pitch pine widely occurring in polluated Seoul could to a large extent be due to cuticle degredation and abnormal vertical distribution of fine roots, which lead to water stress, particularly in dry seasons.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.09a
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• pp.87-119
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• 2001

Fine Pitch Technology will be accelerated among next decade. Buildup Technology is Key Technology for High Density Interconnection. Novel Base Material is critical for High Speed, Area Array Flip Chip Application. Japanese PWB Technology Roadmap will be Published soon.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.657-658
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• 2007