• 한국세라믹학회지
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• 제26권5호
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• pp.637-644
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• 1989

Beta-sialon powder(Z=1) was synthesized by the simultaeous reduction and nitridation of the mixed powders of Hadong kaolin and silica. Silicon hydroxide was prepared from Si-alkoxide by a hydrolysis method and amorphous silica was obtained from the calcination of the prepared silicon hydroxide. Hadong kaolin was mixed with both the silicon hydroxide and amorphous silica, respectively. The average particle size was 4${\mu}{\textrm}{m}$ and the morphology of particle was rod-like and equiaxed in the case of beta-sialon powder prepared form Hadong kaolin and silicon hydroxide(COMPOSITION A), whereas the average particle size was 3${\mu}{\textrm}{m}$ and the morphology of particle was equiaxed in the case of beta-sialon powder prepared from Hadong kaolin and amorphous silica(COMPOSITION B). The synthesized beta-sialon powders were hot-pressed at 175$0^{\circ}C$ for 2 hours under 30 MPa in a nitrogen atmosphere after YAG composition(8wt%) was added to these powders as a sintering agent. The hot-pressed specimens were annealed a 140$0^{\circ}C$ for 4 hours in a nitrogen atmosphere. The mechanical properties of sintered bodies were investigated in terms of M.O.R., fracture toughness and hardness. The measured values are as follows. COMPOSITION A : M.O.R. 508MPa, KIC 3.5MN/m3/2, hardness 13.6GPa. COMPOSITION B : M.O.R. 653MPa, KIC 5.4MN/m3/2, hardness 13.5GPa.

• 한국잠사곤충학회지
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• 제39권1호
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• pp.44-55
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• 1997

This study was carried out to find out the relationship between qualities and contraction phenomenon of silk fibers by treatment of concentrated neutral salts. The contraction effects of silk fibers showed the critical point on the treatment conditions of concentration, temperature and time, among three kinds of neutral salts such as calcium nitrate, calcium chloride and lithium bromide. But, The silk fibers, pretreated with bromide and/or formaldehyde, did not show the contraction upon treating with calcium nitrate. This indicates that tyrosine and serine can be correlated with the contraction reaction because of coupling these amino acids with bromide and formaldehyde. In conclusion, a mechanism for the contraction of silk fiber with highly concentrated calcium nitrate solution is supposed as follows. At the initial stage of ration, the water was penetrated into the amorphous regions and fibers swollen, therefore, the contraction took place mainly in amorphous regions, which have plenty of functional groups with hydroxyl residues. Then, as the calcium nitrate is penetrated into the microfibril, the gydrogen bonds of tyrosine and serine residues and broken and crystalline regions are more and more influenced by increasing concentration of calcium nitrate solution. Microgibrils of crystalline regions become entangled, contracted to linear direction and rearranged to form new stable hydrogen bonds.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1701-1703
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• 2006

Here we describe a novel driving scheme in the form of negative AC bias stress (NAC) to compensate shift in the threshold voltage for hydrogenated amorphous silicon (${\alpha}$-Si:H) thin film transistor (TFT) for AMOLED applications. This scheme preserves the threshold voltage shift of ${\alpha}$-Si:H TFT for infinitely long duration of time(>30,000 hours) and thereby overall performance, without using any additional TFTs for compensation. We briefly describe about the possible driving schemes in order to implement for real time AMOLED applications. We attribute most of the results based on concept of plugging holes and electrons across the interface of the gate insulator in a controlled manner.

• Bulletin of the Korean Chemical Society
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• 제28권3호
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• pp.457-462
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• 2007

Amorphous calcium carbonate (ACC) can readily be prepared using ethanol as the reaction medium and ammonium carbonate as the source of carbon dioxide. Other additives, or any elaborate pH control are not needed to form the initial calcium carbonate precipitate. Ammonia generated from ammonium carbonate maintains the reaction medium in a neutral or weakly basic condition, retarding the crystallization of ACC, while ethanol itself inhibits the dissolution of ACC. The ACC prepared in this way provides a rare opportunity to fabricate molded biomimetic crystals in vitro, but the ACC is too fragile to be fabricated into proper shapes. The malleability of ACC is, however, greatly enhanced by incorporating poly(ethylenimine) (PEI). The ACC/PEI composite can then be fabricated, using a proper mold or template, into mechanically durable biomimetic crystals of definite shape. The ACC in the ACC/PEI composite can further be transformed into vaterite by heating under N2 atmosphere, while the native ACC simply converts into calcite.

• 한국광물학회지
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• 제24권2호
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• pp.111-118
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• 2011

울릉도의 조면암질 응회암의 저온변질작용으로 할로이사이트가 생성되었다. 할로이사이트는 자연 상태에서 수화된 상태로 발견되었으며, 양파구조의 구상 또는 가장자리가 휘어진 판상 입자로 산출된다. 할로이사이트는 Si의 함량이 고령토 광물의 이상값보다 높아서 약간의 비정질이 혼재한 것으로 해석되었다. 또한 할로이사이트의 높은 Fe 함량은 판상 할로이사이트 생성의 원인이다. 조면암질 유리가 변질되면서 용탈된 원소들이 주로 화산유리의 입간 공극에 할로이사이트로 침전되었으며, 유리를 교대한 Si가 풍부한 반구상 비정질 집합체도 부분적으로 구상할로이사이트로 변질된 것으로 보인다. 할로이사이트는 조면암질 화산활동이 활발했던 울릉도에서 화산재의 주요 변질물 중의 하나이다.

• Current Photovoltaic Research
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• 제5권4호
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• pp.113-121
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• 2017

The researches on the silicon-based thin films are being actively carried out. The silicon-based thin films can be made as amorphous, microcrystalline and mixed phase and it is known that the optical bandgap can be controlled accordingly. They are suitable materials for the fabrication of single junction, tandem and triple junction solar cells. It can be used as a doping layer through the bonding of boron and phosphorus. The carbon and oxygen can bond with silicon to form a wide range of optical gap. Also, The optical gap of hydrogenated amorphous silicon germanium can be lower than that of silicon. By controlling the optical gaps, it is possible to fabricate multi-junction thin film silicon solar cells with high efficiencies which can be promising photovoltaic devices.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.363-370
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• 2003

Shrinkage of injection molded parts is different form operational conditions of injection molding such as injection temperature, injection pressure and mold temperature, and mold design such as gate size. It is also various for different resins which have crystalline structure or not. In this study part shrinkage was investigated for various operational condition and resins; PBT for crystalline polymer, and PC and PMMA for amorphous polymer was used in experiment. Crystalline polymer shows higher part shrinkage by about three times than amorphous polymer. Part shrinkage increased as injection temperature and mold temperature increased and injection pressure decreased. Part shrinkage decreased as gate size increased since the pressure delivery is mush easier for large gate size. Part shrinkage according to the gate location was that the position in the part with close to the gate showed large shrinkage and this phenomenon might be occurred by residual stress.

• 한국가축번식학회지
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• 제11권3호
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• pp.206-217
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• 1987

Testes from the drake and the gander have been examined by the electron microscopy in thin sections in order to examine the spermiogenesis and the structure of spermatozoa. The spermiogenesis can be divided into three stages: early spermatid, nuclear elongation, and matured spermatid. In the early spermatid of the drake, there are thread-like material in the nucleus, a prominent nuclear envelope around the nucleus, and big lumens in the cytoplasm. The shape of the gander's mitochondria in the early spermatid is slender compared to that of the drake, and the inner membrane of the mitochondria is thicker than the outer membrane. The distal centriole of the drake and the gander in the early spermatid is a long hollow cylinder form. In the nuclear elongation stage, elongated nucleus forms two or three cross sections in one spermatid cell and it is surrounded by the amorphous sheath. The nucleus of the matured spermatid is compact and its apical end is covered with acrosome cap and acrosome spine. The axoneme is surrounded by the amorphous material.

• 대한전기학회논문지
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• 제41권2호
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• pp.163-169
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• 1992

A new analytical expression for the temperature variation characteristics of hydrogenerated amorphous silicon thin film transistors(a-si:H TFT), between 223K and 433K, is presented and experimentally verified. The results show that the experimental transfer and output characteristics at several temperatures are easily modeled between -5$0^{\circ}C$ and 9$0^{\circ}C$. The model is based on three functions obtained from the experimental data of IS1DT versus VS1GT. Theoretical results confirm the simple form of the model in terms of the device geometry. It was determined that as the temperature increased, the saturated drain current increased and, at a fixed gate voltage, the device saturated at increasingly larger drain voltages while the threshold voltages decreased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1992년도 추계학술대회 논문집
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• pp.3-6
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• 1992

A new analytical expression for the saturated I-V characteristics of hydrogenerated amorphous silicon thin film transistors(a-si:H TFT) is presented and experimentally verified. The results show that the experimental transfer and output characteristics at several temperatures are easily modeled. The model is based on three functions obtained from the experimental data of $I_D$ versus $V_G$. Theoretical results confirm the simple form of the model in terms of the device geometry. It was determined that the saturated drain current increased at a fixed gate voltage and the device saturated at increasingly larger drain voltages while the threshold voltages decreased.