• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.347.1-347.1
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• 2016

Screen printing is commonly used to form the electrode for crystalline silicon solar cells. However, it has caused high resistance and low aspect ratio, resulting in decrease of conversion efficiency. Accordingly, Ni/Cu/Ag plating method could be applied for crystalline silicon solar cells to reduce contact resistance. For Ni/Cu/Ag plating, laser ablation process is required to remove anti-reflection layers prior to the plating process, but laser ablation results in surface damage and then decrease of open-circuit voltage and cell efficiency. Another issue with plating process is ghost plating. Ghost plating occurred in the non-metallized region, resulting from pin-hole in anti-reflection layer. In this paper, we investigated the effect of Ni/Cu/Ag plating on the electrical properties, compared to screen printing method. In addition, phosphoric acid layer was spin-coated prior to laser ablation to minimize emitter damage by the laser. Phosphorous elements in phosphoric acid generated selective emitter throughout emitter layer during laser process. Then, KOH treatment was applied to remove surface damage by laser. At this step, amorphous silicon formed by laser ablation was recrystallized during firing process and remaining of amorphous silicon was removed by KOH treatment. As a result, electrical properties as Jsc, FF and efficiency were improved, but Voc was lower than screen printed solar cells because Voc was decreased due to surface damage by laser process. Accordingly, we expect that efficiency of solar cells could be improved by optimization of the process to remove surface damage.

• 복식
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• 제65권6호
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• pp.1-14
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• 2015

This study is aims to study the background of how the shape of the wooden shoes developed and worn by Koreans and Japanese in the ancient times by sorting and examining the types and shapes. Relevant bibliography, which are mainly related to the excavated wooden shoes from 3 B.C.E to C.E. 8., were used as research materials. The formation of wooden shoes required easy access to raw materials -which is trees- for production. According to the analysis, both Korea and Japan made the flat wooden shoes using cuboid wood. Both countries bore a hole on a specific location to distinguish the right foot and left foot, however the style of the heel was different in the two countries. The slip-on(Undu-hyeong) wooden shoes were also common in both countries. The slip-on had no-heels and was made by digging-out a piece of the cuboid wood. Some slip-ons made by the Japanese had furrows on the bottom, and they were known to make different types of the slip-on wooden shoes depending on the purpose. Observation of the wearing methods show that commonality can be found between the wooden shoes of Korea and Japan, and this indicates that cultural exchanges between the Silla/Baekje and Japan took place from the 4th to the 6th century. Also, the flat wooden shoes in Japan developed rapidly, as the shoes became an integral part of its life and culture, which was closely tied to agriculture. Eventually, due to the difference in climate and life-style, the slip-ons became the primary type of wooden shoes in Korea, while the flats became the main type of wooden shoes in Japan. It is, however, clear that as the relationship between the two countries became closer, the cultural exchanges regarding the wooden shoes were considerable.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.27-28
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• 2008

We have studied an organic layer-thickness dependent electrical and optical properties of organic light-emitting diodes in a device structure of ITO/TPD/$Alq_3$/LiF/Al. While a hole-transport layer thickness of TPD was varied from 35 to 65nm, an emissive layer thickness of $Alq_3$ was varied from 50 to 100nm. A ratio of those two layers was kept to about 2:3. Variation of the layer thickness changes a traverse time of injected carriers across the organic layer, so that it may affect on the chance of probability of exciton formation. Current-voltage-luminance characteristics of the devices show that there are typical rectifying behaviors, and the luminance reaches about $30,000cd/m^2$. Thickness-dependent current efficiency shows that there is a gradual increase of the efficiency as the total layer thickness increases. The efficiency becomes saturated to be about 10cd/A when the total thickness is above 140nm. They show that emission was from the $Alq_3$ layer, because the peak wavelength is about 525nm. View angle-dependent emission spectra show that the emission intensity decreases as the angle increases.

• 대한수학회지
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• 제48권4호
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• pp.669-689
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• 2011

The notion of quasi-Einstein manifolds arose during the study of exact solutions of the Einstein field equations as well as during considerations of quasi-umbilical hypersurfaces. For instance, the Robertson-Walker spacetimes are quasi-Einstein manifolds. The object of the present paper is to study Lorentzian quasi-Einstein manifolds. Some basic geometric properties of such a manifold are obtained. The applications of Lorentzian quasi-Einstein manifolds to the general relativity and cosmology are investigated. Theories of gravitational collapse and models of Supernova explosions [5] are based on a relativistic fluid model for the star. In the theories of galaxy formation, relativistic fluid models have been used in order to describe the evolution of perturbations of the baryon and radiation components of the cosmic medium [32]. Theories of the structure and stability of neutron stars assume that the medium can be treated as a relativistic perfectly conducting magneto fluid. Theories of relativistic stars (which would be models for supermassive stars) are also based on relativistic fluid models. The problem of accretion onto a neutron star or a black hole is usually set in the framework of relativistic fluid models. Among others it is shown that a quasi-Einstein spacetime represents perfect fluid spacetime model in cosmology and consequently such a spacetime determines the final phase in the evolution of the universe. Finally the existence of such manifolds is ensured by several examples constructed from various well known geometric structures.

• 마이크로전자및패키징학회지
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• 제19권4호
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• pp.51-56
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• 2012

습식공정으로 thermal via용 SI 관통 via를 형성하기 위해 TMAH 용액의 농도와 온도에 따른 Si 기판의 이방성 습식식각 거동을 분석하였다. TMAH 용액의 온도를 $80^{\circ}C$로 유지한 경우, 5 wt%, 10 wt% 및 25 wt% 농도의 TMAH 용액은 각기 $0.76{\mu}m/min$, $0.75{\mu}m/min$ 및 $0.30{\mu}m/min$의 Si 식각속도를 나타내었다. 10 wt% TMAH 용액의 온도를 $20^{\circ}C$와 $50^{\circ}C$로 유지시에는 각기 $0.07{\mu}m/min$와 $0.23{\mu}m/min$으로 식각속도가 저하하였다. Si 기판의 양면에 동일한 형태의 식각 패턴을 형성하여 $80^{\circ}C$의 10 wt% TMAH 용액에 장입하고 5시간 식각하여 깊이 $500{\mu}m$의 관통 via hole을 형성하였다.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.913-918
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• 2014

Five mol % tungsten-doped tin oxide ($W_{0.05}Sn_{0.95}O_2$, TTO5) was prepared by co-precipitation of $SnCl_4{\cdot}5H_2O$ and $WCl_4$, followed by calcination at $1000^{\circ}C$. The as-prepared TTO5 was in the pure cassiterite phase with a particle size of ~50 nm and optical bandgap of 2.51 eV. Herein it was applied for the formation of TTO5/$TiO_2$ heterojunctions by covering the TTO5 surface with $TiO_2$ by sol-gel method. Under visible-light irradiation (${\lambda}{\geq}420$ nm), TTO5/$TiO_2$ showed a significantly high photocatalytic activity in removing gaseous 2-propanol (IP) and evolving $CO_2$. It is deduced that its high visible-light activity is caused by inter-semiconductor holetransfer between the valence band (VB) of TTO5 and $TiO_2$, since the TTO5 nanoparticle (NP) exhibits the absorption edge at ~450 nm and its VB level is located more positive side than that of $TiO_2$. The evidence for the hole-transport mechanism between TTO5 and $TiO_2$ was also investigated by monitoring the holescavenging reaction with 1,4-terephthalic acid (TA).

• 한국분무공학회지
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• 제3권3호
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• pp.33-41
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• 1998

In recently, a study on the lean combustion is investigated intensively, because it is expected that this method may decrease the harmful exhaust gas and improve fuel economy in gasoline engine. The problems of lean combustion system in gasoline engine are ignition difficulty, misfire and instability of combustion. The investigation on the optimization of fuel metering and the control of mixing gas flow may be critical to improve the performance of lean combustion. In the fuel injection gasoline engine, the formation of mixture influences strongly on the engine performance such that the importance of fuel metering system becomes apparent. First of all, a study on the fuel breakup characteristics of gasoline fuel injector was carried out in this paper. Fuel injectors are pintle and 4hole-2spray type. The purpose of this study is to clarify the atomization mechanism of spray injected into atomosphere field through electronic controlled-fuel injectors, and to analyze spray characteristics such as drop size distribution and mean drop diameter produced at fuel injector. In this paper, the spray development is observed by taking photograps using 80mm still-camera system, and drop sizes are measured by PMAS. From these experiment, spray pattern injected from gasoline fuel injectors was investigated clearly. Also, it was found that SMD and drop size distribution of injected fuel spray from gasoline fuel injectors.

• 대한전자공학회논문지SD
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• 제48권7호
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• pp.76-81
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• 2011

본 논문에서는 비아 절단 구조를 제안하고 2층 구조의 DRAM 패키지 기판 설계에 적용하여 낮은 임피던스를 가지는 파워 분배망(Power Distribution Network)을 구현하였다. 제안한 신규 비아 구조는 비아의 일부가 절단된 형태이고 본딩 패드와 결합하여 넓은 배선 면적을 필요로 하지 않는 장점을 가진다. 또한 비아 절단 구조를 적용한 설계에서는 본딩 패드에서 VSSQ까지의 배선 경로를 효과적으로 단축시킴으로써 PDN 임피던스를 개선시킬 수 있다. DRAM 패키지 기판 상의 윈도우 영역 형성과 동시에 비아의 일부 영역이 제거되므로 비아 절단 구조 제작을 위한 추가적인 공정은 없다. 또한 비아 홀 내부를 솔더 레지스트로 채움으로써 버(Burr) 발생을 최소화하였으며, 이를 패키지 기판 단면 촬영을 통해 검증하였다. 비아 절단 구조의 적용 및 VDDQ/VSSQ 배치에 의한 PDN 임피던스 변화를 검증하기 위해서 3차원 전자장 시뮬레이션 및 네트워크 분석기 측정을 통해 기존 방식을 적용한 패키지 기판과 비교 검증을 진행하였다. 신규 DRAM 패키지 기판은 대부분의 주파수 범위에서 보다 우수한 PDN 임피던스를 가졌으며, 이는 제안한 비아 절단 구조와 파워/그라운드 설계 배치가 PDN 임피던스 감소에 효과적임을 증명한다.

• Journal of Welding and Joining
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• 제12권4호
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• pp.85-101
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• 1994

Effect of Cr, Cu and Ni metal powders addition on the alloyed layer of aluminum alloy (AC2B) has been investigated with the plasma transferred arc (PTA) overlaying process. The overlaying conditions were 125-200A in plasma arc current, 150mm/min in process speed and 5-20g/min in powder feeding rate. Main results obtained are summarized as follows: 1) It was made clear that formation of thick surface alloyed layer on aluminum alloy is possible by PTA overlaying process. 2) The range of optimum alloying conditions were much wider in case of Cu and Ni powder additions than the case of Cr powder addition judging from the surface appearance and the bead macrostructure. 3) Alloyed layer with Cu showed almost the homogeneous microstructure through the whole layer by eutectic reaction. alloyed layers with Cr and Ni showed needle-like and agglomerated microstructures, the structure of which has compound layer in upper zone of bead by peritectic and eutectic-peritectic reactions, respectively. 4) Microconstituents of the alloyed layer were analyzed as A1+CrA $l_{7}$ eutectics, C $r_{2}$al sub 11/, CrA $l_{4}$, C $r_{4}$A $l_{9}$ and C $r_{5}$A $l_{*}$ 8/ for Cr addition, Al+CuA $l_{2}$(.theta.) eutectics and .theta. for Cu addition, and Al+NiA $l_{3}$ eutectics. NiA $l_{3}$, N $i_{2}$A $l_{3}$ and NiAl for Ni addition. 5) Concerning defect of the alloyed layer, many blow holes were seen in Cr and Ni additions although there was lesser in Cu addition. Residual gas contents in blow hole for Cu and Ni alloyed layer were confirmed as mainly $H_{2}$ and a littie of $N_{2}$ Cracking was observed in compound zone of the alloyed layer in case of Cr and Ni addition but not in Cu alloyed layer.r.r.

• 멤브레인
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• 제29권6호
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• pp.299-307
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• 2019

광촉매는 물에서 유기 염료를 분해하는 친환경적 기술이다. 산화 텅스텐은 이산화 티타늄에 비해 더 작은 밴드갭을 지니고 있어 광촉매 나노물질로서 활발히 연구되고 있다. 계층적 구조의 합성, 백금 도핑, 나노 복합물 또는 다른 반도체와의 결합 등이 광촉매 분해 효율을 향상시키는 방법들로 연구되고 있다. 이들 방법들은 광 파장의 적색편이를 유도하여 전자 이동, 전자-정공 쌍의 형성과 재결합에 영향을 미친다. 산화 텅스텐의 형태 개질을 통해 앞서 언급한 광촉매 분해 효율을 향상시키는 방법들과 합성에 대해 분석하였으며 금속 산화물과 탄소 복합재를 결합하는 방법이 새로운 물질의 합성이 필요없으며 가장 효율적인 방법으로 조사되었다. 이러한 광촉매 기술은 수처리 분리막기술과 모듈화하여 정수처리 목적으로 사용될 수 있다.