• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.65-65
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• 2012

Copper zinc tin sulfide ($Cu_2ZnSnS_4$, CZTS) is a very promising material as a low cost absorber alternative to other chalcopyrite-type semiconductors based on Ga or In because of the abundant and economical elements. In addition, CZTS has a band-gap energy of 1.4~1.5eV and large absorption coefficient over ${\sim}10^4cm^{-1}$, which is similar to those of $Cu(In,Ga)Se_2$(CIGS) regarded as one of the most successful absorber materials for high efficient solar cell. Most previous works on the fabrication of CZTS thin films were based on the vacuum deposition such as thermal evaporation and RF magnetron sputtering. Although the vacuum deposition has been widely adopted, it is quite expensive and complicated. In this regard, the solution processes such as sol-gel method, nanocrystal dispersion and hybrid slurry method have been developed for easy and cost-effective fabrication of CZTS film. Among these methods, the hybrid slurry method is favorable to make high crystalline and dense absorber layer. However, this method has the demerit using the toxic and explosive hydrazine solvent, which has severe limitation for common use. With these considerations, it is highly desirable to develop a robust, easily scalable and relatively safe solution-based process for the fabrication of a high quality CZTS absorber layer. Here, we demonstrate the fabrication of a high quality CZTS absorber layer with a thickness of 1.5~2.0 ${\mu}m$ and micrometer-scaled grains using two different non-vacuum approaches. The first solution-processing approach includes air-stable non-toxic solvent-based inks in which the commercially available precursor nanoparticles are dispersed in ethanol. Our readily achievable air-stable precursor ink, without the involvement of complex particle synthesis, high toxic solvents, or organic additives, facilitates a convenient method to fabricate a high quality CZTS absorber layer with uniform surface composition and across the film depth when annealed at $530^{\circ}C$. The conversion efficiency and fill factor for the non-toxic ink based solar cells are 5.14% and 52.8%, respectively. The other method is based on the nanocrystal dispersions that are a key ingredient in the deposition of thermally annealed absorber layers. We report a facile synthetic method to produce phase-pure CZTS nanocrystals capped with less toxic and more easily removable ligands. The resulting CZTS nanoparticle dispersion enables us to fabricate uniform, crack-free absorber layer onto Mo-coated soda-lime glass at $500^{\circ}C$, which exhibits a robust and reproducible photovoltaic response. Our simple and less-toxic approach for the fabrication of CZTS layer, reported here, will be the first step in realizing the low-cost solution-processed CZTS solar cell with high efficiency.

• Composites Research
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• 제19권1호
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• pp.29-35
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• 2006

첨단 전자무기체계의 지속적인 발전으로 인하여 현대전의 승패는 적 레이더 탐지의 회피에 크게 좌우된다고 할 수 있다. 반사되는 레이더의 탐지신호를 최소화시키기 위한 다양한 연구가 수행되어 왔는데, 본 연구에서는 뛰어난 기계적, 전자기적 물성으로 응용분야가 지속적으로 확대되고 있는 섬유강화 복합재료를 이용하여 레이더 전자파 흡수체(Radar absorbing structure, RAS)를 제작하고 레이더 단면적(Radar cross section, RCS)을 평가하였다 유리섬유 복합재에 뛰어난 유전적 특성을 지닌 나노 크기의 카본블랙(Carbon-black)을 첨가하여 흡수층을 구성하고, 반사특성이 탁월한 탄소섬유 복합재를 후면의 반사층으로 배치하여 "C" 및 "U" 형상의 하이브리드 복합재 RAS 겔을 제작하였다. RAS 쉘의 제작간 서로 다른 두 재료의 열적물성치 차이로 스프링 백이라 불리는 변형이 발생하였는데, 금형의 굽힘각도 제어를 통하여 효과적으로 보정할 수 있었다. 또한 상용 유한요소해석 프로그램인 ANSYS를 이용하여 스프링 백 보정 결과를 예측하고 실험결과와 비교하였다. 제작된 RAS쉘의 RCS는 근사적 계산기법인 물리광학법을 이용하여 예측하고 컴팩트 레인지(Compact range)를 이용하여 측정한 실힘결과와 비교하였다 두가지 형상의 RCS 모두 측정결과와 예측된 RCS 값이 일치하며 우수한 레이더 전자파 흡수 특성을 지닌 것을 확인하였다.

• Applied Biological Chemistry
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• 제49권3호
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• pp.186-191
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• 2006

본 연구는 전기적 세포융합방법인 electrofusion을 이용하여 우량균주의 육성을 목적으로 S. cerevisiae KCTC7904와 Z. rouxii KCTC7966 간의 전기융합을 실시하였고, 융합주의 내당성과 내염성을 확인하였으며, 융합주의 선별방법을 연구하였다. 또한 융합주의 유전안정성과 RAPD-PCR 분석을 통한 융합여부의 직접적인 증거를 확인하고자 실험하였다. S. cerevisiae KCTC7904와 Z. rouxii KCTC 7966를 각각 $12{\sim}36$시간 배양하여 분리 세척한 다음 1.5% 2-mercaptoethanol로 20분간 전 처리하여 lyticase(200 U/ml)로 $30^{\circ}C$에서 최종적으로 $60{\sim}90$분간 처리했을 때, 91% 이상의 원형질체를 얻을 수 있었다. 얻어진 원형질체를 $1.0{\sim}1.2\;M$ sorbitol 용액으로 세척 한 다음 각각 1 : 1의 비율로 혼합하여 1.5 MHz/50 pV의 고주파를 가하였을때 paired protoplast가 형성되었으며, 615 $V/256\;{\mu}sec$의 고전압을 가한 결과 약 25% 정도의 융합체를 얻을 수 있었다. 선별된 융합주의 내당성과 내염성을 각각의 모균주와 비교하여 실험한 결과 50%의 glucose와 15%의 NaCl을 함유한 배지에서 모두 생육이 가능하여 각각의 균주 특성을 가지고 있음을 확인하였고, 또한 융합주를 $4^{\circ}C$에서 5개월간 보관했을 때 약 28%정도가 모균주로 복귀되었지만, 72%의 융합안정성을 나타내므로 비교적 안정한 상태를 확인할 수 있었다. 융합의 진위 여부를 증명하기 위해 유전적인 분석방법인 RAPD-PCR 법을 사용하여 실험한 결과 각각의 균주가 agarose gel 상에서 보인 band의 패턴이 융합주에서도 모두 보여짐을 확인하였다.

• Korea-Australia Rheology Journal
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• 제19권4호
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• pp.191-199
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• 2007

Precision injection molding process is of great importance since precision optical products such as CD, DVD and various lens are manufactured by those process. In such products, birefringence affects the optical performance while residual stress that determines the geometric precision level. Therefore, it is needed to study residual stress and birefringence that affect deformation and optical quality, respectively in precision optical product. In the present study, we tried to predict residual stress, final shrinkage and birefringence in injection molded parts in a systematic way, and compared numerical results with the corresponding experimental data. Residual stress and birefringence can be divided into two parts, namely flow induced and thermally induced portions. Flow induced birefringence is dominant during the flow, whereas thermally induced stress is much higher than flow induced one when amorphous polymer undergoes rapid cooling across the glass transition region. A numerical system that is able to predict birefringence, residual stress and final shrinkage in injection molding process has been developed using hybrid finite element-difference method for a general three dimensional thin part geometry. The present modeling attempts to integrate the analysis of the entire process consistently by assuming polymeric materials as nonlinear viscoelastic fluids above a no-flow temperature and as linear viscoelastic solids below the no-flow temperature, while calculating residual stress, shrinkage and birefringence accordingly. Thus, for flow induced ones, the Leonov model and stress-optical law are adopted, while the linear viscoelastic model, photoviscoelastic model and free volume theory taking into account the density relaxation phenomena are employed to predict thermally induced ones. Special cares are taken of the modeling of the lateral boundary condition which can consider product geometry, histories of pressure and residual stress. Deformations at and after ejection have been considered using thin shell viscoelastic finite element method. There were good correspondences between numerical results and experimental data if final shrinkage, residual stress and birefringence were compared.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.657-662
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• 2005

In this study, the deposition of micrometer-scale metallic interconnects on LCD glass for the repair of open-circuit type defects is investigated. Although there had been a few studies Since 1980 s for the deposition of metallic interconnects by laser-induced chemical vapor deposition, those studies mostly used continuous wave lasers. In this work, a third harmonic Nd:YLF laser (351nm) of high repetition rates, up to 10 KHz, was used as the illumination source and $W(CO)_6$ was selected as the precursor. General characteristics of the metal deposit (tungsten) such as height, width, morphology as well as electrical properties were examined for various process conditions. Height of the deposited tungsten lines ranged from 35 to 500 nm depending on laser power and scan speed while the width was controlled between $3\~50{\mu}$ using a slit placed in the beam path. The resistivity of the deposited tungsten lines was measured to be below 1 $O\cdot{\mu}m$, which is an acceptable value according to the manufacturing standard. The tungsten lines produced at high scan speed had good surface morphology with little particles around the patterns. Experimental results demonstrated that it is likely that the deposit forms through a hybrid process, namely through the combination of photolytic and pyrolytic mechanisms.

• 복식문화연구
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• 제19권3호
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• pp.473-487
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• 2011

The purpose of this study is to analyze the body type and fashion of posthuman in SF movies. The method of this study was to analyze documentaries, internet web site, fashion books and so forth. The results were as follows: The body types of posthuman were expressed as mutation type, prosthetic type, clone type by biological hybrid or renovation and digital type by computer simulation. The mutation type was expressed as reinforcement of masculinity or feminity and reinforcement of body functions. The fashion item was expressed as a black tailored suit, leather jacket, cat suit, whip, black sunglass, garter belt, high heel shoes, short pants, black one piece dress and functional body suit. The prosthetic type was expressed as reinforcement of body functions and reinforcement of masculinity or feminity. The fashion item was expressed as a military item, high-tech power suit and ergonomic armor suit. The clone type was expressed as the plural ego with reinforcement of body functions. The fashion item was expressed as a power shoulder jacket, fake fur coat, vinyl, black see-through look and functional suit. The digital type was expressed as reinforcement of masculinity or feminity and the plural ego with reinforcement of body functions. The fashion item was expressed as a data suit, leather jacket, black over coat, boots, black sun glass, ethnic items and military items. The meanings of posthuman fashion in SF movies were impurity of posthuman, display of superhuman's power by sexuality, metaphor of power and fantasy of superhero in opposition futuristic dystopia. As mentioned above, posthuman body type and fashion in SF movies become the conversational topic in the real world. The fact that we think about utopia and identity of posthuman in the future is of great significance.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.314-314
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• 2013

Recently, flexibility is one of the hottest issues in the field of electronic devices. For flexible displays or solar cells, a development of transparent conductive electrodes (TCEs) with flexibility, bendability and foldability is an essential element. Hundreds of nanometers indium-tin-oxide (ITO) films have been widely used and commercialized as a transparent electrode, but their brittleness make them difficulty to apply flexible electronics. Many researchers have been studying for flexible TCEs such as a few layers of graphene sheets, carbon nanotube networks, conductive polymer films and combinations among them. Although gained flexibility, their transmittance and resistivity have not reached those of commercialized ITO films. Metal grids electrode cannot act as TCEs only, but they can be used to lower the resistance of TCEs with few losses of transmittance. However, the possibility of device shortage will be rise at the devices with metal grids because a surface flatness of TCEs may be deteriorated when metal grids are introduced using conventional methods. In our research, we have developed hybrid TCEs, which combined tens of nanometers ITO film and metal grids which are embedded in flexible substrate. They show $13{\Omega}$/${\Box}f$ sheet resistance with 94% of transmittance. Moreover, the sheet resistance was maintained up to 1 mm of bending radius. Also, we have verified that flexible organic light emitting diodes and organic solar cells with the TCEs showed similar performances compared to commercial ITO (on glass substrate) devices.

• Korean Chemical Engineering Research
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• 제48권3호
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• pp.350-354
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• 2010

자연계에는 유/무기 복합막 형성시 크기와 배열이 정교하게 제어되면서 여러 무기물 결정들이 성장한다. 이와 같은 자연계의 유/무기 복합막을 인공적으로 재현하기 위한 시도가 다각적으로 이루어지고 있다. 유/무기 계면에서 생체모방 결정화의 대표적인 물질 중의 하나가 바로 탄산칼슘 결정이다. 탄산칼슘은 생체 내의 골격을 이루는 주성분이고 성장방법이 비교적 간단하여 많은 연구가 수행되어 왔다. 분자수준에서의 우수한 정돈 상태들을 지니고 있는 폴리다이아세틸렌(polydiacetylene: PDA)은 무기결정성장에 관하여 효과적인 template를 제공할 수 있다. 본 실험에서는 폴리다이아세틸렌의 패턴들을 고체기판에 동시에 증착시키기 위하여, 신규로 고안한 mini arrayer의 air/water의 계면을 이용하여 소수성 유리기판위에 PDA를 전이시켰다. 이 방법을 이용한 결정화 과정의 제어는 생체유도결정화의 매커니즘을 이해하는데 기여할 수 있을 것이다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.620-621
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• 2008

Transparent electronics has been one of the key terminologies forecasting the ubiquitous technology era. Several researchers have thus extensively developed transparent oxide-based thin-film transistors (TFTs) on glass and plastic substrates although in general high voltage operating devices have been mainly studied considering transparent display drivers. However, low voltage operating oxide TFTs with transparent electrodes are very necessary if we are aiming at logic circuit applications, for which transparent complementary or one-type channel inverters are required. The most effective and low power consuming inverter should be a form of complementary p-channel and n-channel transistors but real application of those complementary TFT inverters also requires electrical- and even photo-stabilities. Since p-type oxide TFTs have not been developed yet, we previously adopted organic pentacene TFTs for the p-channel while ZnO TFTs were chosen for n-channel on sputter-deposited $AlO_x$ film. As a result, decent inverting behavior was achieved but some electrical gate instability was unavoidable at the ZnO/$AlO_x$ channel interface. Here, considering such gate instability issues we have designed a unique transparent complementary TFT (CTFTs) inverter structure with top n-ZnO channel and bottom p-pentacene channel based on 12 nm-thin nano-oxide/self assembled monolayer laminated dielectric, which has a large dielectric strength comparable to that of thin film amorphous $Al_2O_3$. Our transparent CTFT inverter well operate under 3 V, demonstrating a maximum voltage gain of ~20, good electrical and even photoelectric stabilities. The device transmittance was over 60 % and this type of transparent inverter has never been reported, to the best of our limited knowledge.

• The Journal of Advanced Prosthodontics
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• 제10권2호
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• pp.101-112
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• 2018

PURPOSE. The purpose of this study was to investigate the effect of various surface treatments (ST) on the shear bond strength of resin composite to three bilayer dental ceramics made by CAD/CAM and two veneering ceramics. MATERIALS AND METHODS. Three different bilayer dental ceramics and two different veneering ceramics were used (Group A: IPS e.max CAD+IPS e.max Ceram; Group B: IPS e.max ZirCAD+IPS e.max Ceram, Group C: Vita Suprinity+Vita VM11; Group D: IPS e.max Ceram; Group E: Vita VM11). All groups were divided into eight subgroups according to the ST. Then, all test specimens were repaired with a nano hybrid resin composite. Half of the test specimens were subjected to thermocycling procedure and the other half was stored in distilled water at $37^{\circ}C$. Shear bond strength tests for all test specimens were carried out with a universal testing machine. RESULTS. There were statistically significant differences among the tested surface treatments within the all tested fracture types (P<.005). HF etching showed higher bond strength values in Groups A, C, D, and E than the other tested ST. However, bonding durability of all the surface-treated groups were similar after thermocycling (P>.00125). CONCLUSION. This study revealed that HF etching for glass ceramics and sandblasting for zirconia ceramics were adequate for repair of all ceramic restorations. The effect of ceramic type exposed on the fracture area was not significant on the repair bond strength of resin composites to different ceramic types.