• 한국세라믹학회지
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• 제53권3호
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• pp.325-331
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• 2016

Anatase particles of titanium dioxide were prepared from $TiCl_4$ aqueous solution by using an electro-dialysis [ED] process. For the preparation of an aqueous solution of $TiCl_4$ precipitates, $TiCl_4$ liquid frozen in ice was transferred to a neck flask and then hydrolyzed using deionized [DI] $H_2O$. During the hydrolysis of the $TiCl_4$ solution at $0^{\circ}C$, a slurry solution of $TiOCl_2$ was obtained and the color changed from red to orange. The ED process was applied for the removal of chlorine content in the slurry solution. Two kinds of hydrolyzed slurry solution with lower [$Ti^{4+}$] and higher [$Ti^{4+}$] were sampled and the ED process was applied for the samples according to the removal time of [$Cl^-$]. With de-chlorination, the solution status changed from sol to gel and the color quickly changed to blue. Finally, white crystalline powders were formed and the phase was confirmed by XRD to be anatase crystallites. The morphology of the hydrous titania particles in the solution was observed by FE-SEM. The hydrous titania particles were nano-crystalline, and easily coagulated with drying.

• 한국세라믹학회지
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• 제55권6호
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• pp.562-569
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• 2018

We propose an economic and facile method for the preparation of silica nanoparticles through a two-step process utilizing chlorosilane residues. Mixed chlorosilane residue was alcoholized with absolute ethanol as a first step to form tetraethoxysilane (TEOS). The TEOS was then utilized as a silicon source to synthesize silica nanoparticles in a sol-gel method. The alcoholysis process was designed and optimized utilizing the Taguchi experimental design method and the yield of TEOS was as high as 82.2% under optimal synthetic conditions. Similarly, the Taguchi method was also utilized to study the effects of synthesis factors on the particle size of silica nanoparticles. The results of statistical analysis indicate that the concentration of ammonia has a greater influence on particle size compared to the mass fractions of TEOS and polyethylene glycol (4.6% and 9.7%). The purity of the silica particles synthesized in our experiments is high, but the specific surface area and pore volume are small.

• 대한전자공학회논문지
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• 제19권6호
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• pp.9-16
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• 1982

이 설계 과정은 보통의 더지탈 하아드웨어 담계에 복합 기계 개념을 응용한 일설계 기법을 소개한 것이다. 이 과정은 계산기용 소프트웨어 설계의 경우와 마찬가지로 새 시스템을 흐름도에 의해 표현시키는 것으로 부터 시작되며, 이어서 흐름도를 분해하여 발산형 요소를 얻고, 이 발산형 요소를 근거로 소기계를 작성하게 되는데, 이렇게 소기계의 작성이 끝나게 되면. 이번에는 통합 과정을 통해서 복합체와 지시기를 만들고, 논리자로를 완척함으로써 전휴의 설계 과정을 완료하게 된다. This is an introduction to an art of digital hardware design using polymachine image as a target structure of the product. As in the case of software design of a computer, the design process begins with a sketch of planned system in flow chart description and the flow charts is partitioned into divergent elements. Each of the element machine is derived from those divergent elements. We can build a complete digital system with the preparation of an index, and a polymer of these element machines.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.443-446
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• 2006

Carbon-supported Platinum (Pt) is the potential electro-catalyst material for anodic and cathodic reactions in fuel cell. Catalytic activity of the metal strongly depends on the particle shape, size and distribution of the metal in the porous supportive network. Conventional preparation techniques based on wet impregnation and chemical reduction of the metal precursors often do not provide adequate control of particle size and shape. We have proposed a novel route for preparing nano sized Pt colloidal particles in solution by oxidation of ethylene glycol. These Pt nano particles were deposited on large surface area carbon support. The process of nano Pt colloid formation involves the oxidation of solvent ethylene glycol to mainly glycolic acid and the presence of its anion glycolate depends on the solution pH. In the process of colloidal Pt formation glycolate actsas stabilizer for the Pt colloidal particle and prevents the agglomeration of colloidal Pt particles. These mono disperse Pt particles in carbon support are found uniformly distributed in nearly spherical shape and the size distribution was narrow for both supported and unsupported metals. The average diameter of the Pt nano particle was controlled in the range off to 3 nm by optimizing reaction parameters. Transmission electron microscopy, CV and RRDE experiments were used to compliment the results.

• 한국세라믹학회지
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• 제49권1호
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• pp.95-99
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• 2012

Silicon carbide ceramics are used for oxidation resistive coating films due to their excellent properties like high strength, good oxidation resistance, and good abrasion resistance, but they have poor formability and are prepared by vapor process which is complicated, costly, and sometimes hazardous. In this study, preparation of silicon carbide coating film by liquid process using polymer precursor was attempted. Coating film was prepared by dip coating on substrate followed by heat treatment in argon at $1200^{\circ}C$. By changing the dipping speed, the thickness was controlled. The effects of plasticizer, binder, or fiber addition on suppression of crack generation in the polymer and ceramic films were examined. It was found that fiber additives was effective for suppressing crack generation.

• 보건교육건강증진학회지
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• 제28권3호
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• pp.67-82
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• 2011

Objectives: The purpose of this study was to identify the factors influencing the stages of exercise behavior change after adjusting for related covariates. Methods: Participants included 362 of fourth to sixth graders in 3 elementary schools in a metropolitan city in Korea. The data were collected using structured questionnaire included Korean Stages of Change Scale for Exercise. Results: Logistic regression results showed that the motivational factors associated with transition from precontemplation to contemplation were cognitive process of change, self-reevaluation, conscious raising; regarding that from contemplation to preparation, cons of the decisional balance; regarding those from preparation to action, behavioral process, counter-conditioning, stimulus control, which were very similar to the results of previous researches subjected other age groups. But, there was no motivational factors associated with from action to maintenance, and self-efficacy had no influence on forwarding stages of change. Conclusions: TTM would be applicable to explain the exercise behavior of some children in Korea, which suggested that it be useful in developing the programs to improve physical activities of Korean school children.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1996년도 재료학회 추계학술발표회
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• pp.174-176
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• 1996

In the YBCO matrix, 10wt.% Y$_2$BaCuO$\_$5/ (211 phase) was added, the final 211 content of YBCO made by MTG process could reach about 20wt.% which was the optimum value for the critical current density. And also 10wt.% Ag was added in the matrix of YBCO, which was nearly about the saturate solubility of silver in textured YBCO. SmBaCuO crystal was grown by the melted-condensed process. A 5${\times}$5${\times}$2㎣ single crystal of SmBaCuO was used to be the seed in the preparation of YBCO. It was proved the orientation of YBCO was the same as the orientation of the SmBaCuO seed. The oxygen absorption of bulk oriented YBCO was studied and the heat treatment of oxygen absorption would be in flowing oxygen, at 400$^{\circ}C$ for about 24 hours. the magnetic hysteresis loops were measured by Vibrating Smaple Magnetometer and the J$\_$c/ was calcuated by means of Bean's model.

• 한국식품과학회지
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• 제2권2호
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• pp.49-55
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• 1970

대두단백육(textured soybean protein food)의 제조 과정에서 분리한 대두단백의 건조공정은 단백 gel의 성질과 보수력, 점성도 같은 단백질 특성에 영향을 미쳤다. 모델시스템의 실험에서 질소용해계수로 표시한 대두단백의 변성도는 분리대두단백 gel의 강도의 중요한 변수로 나타났다. gel strength는 질소용해계수가 43이었을 때 최대가 되었고 질소 용해계수가 그보다 증가할 때나 감소할 때는 gel strength가 감소되었다. 이러한 사실은 분리대두단백의 건조공정 중 적당한 단백의 변성은 단백육제조에 필요하며 그 이상의 높은 질소용해계수를 갖도록 할 필요는 없다.

• 공업화학
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• 제7권3호
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• pp.511-517
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• 1996

본 논문에서는 속경화 SMC와 저비중 SMC를 제조하기 위한 경화시스템과 배합시스템을 연구하였다. 속경화 SMC를 제조하기 위한 경화시스템으로는 혼합개시제를 사용한 시스템과 촉진제를 사용한 시스템으로 나누어 실험하였고, 저비중용 SMC는 glass micro-baloon(GMB)을 충진제로 사용하여 실험하였다. 본실험에서는 두시스템으로 제조된 시편으로 경화 거동, 기계적 성질, 물리적 성질 등을 측정하였다. 속경화용 SMC 시편의 경우는 혼합개시제의 양 및 촉진제의 양이 증가할수록 경화 속도는 증가하였으나 SMC 성형 시편의 물성은 큰 변화를 보이지 않았다. 저비중용 SMC에서는 GMB의 양이 증가함에 따라 비중이 감소하였으며, 물성치에서도 약간의 감소를 보였다.

• 한국표면공학회지
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• 제32권6호
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• pp.709-716
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• 1999

Ceramic is select for an alternative substrate material for high-speed circuits due to its low-thermal expansion. As, in this study, ceramic was prepared by ISG (interlayer sol-gel) process using metal salts and a metal alkoxide as the starting materials. Generally ceramic substrate is used electroless copper plating for the metallization. But it has been indicate weakely the adhesion strength between the substrate and copper layer. Therefore, this research, using the ISG process on the preparation of homogeneous and possible preparation at law temperature fabricated sol solution. Using of the dip coating method was coated for the purpose of giving the anchoring effect on the coating layer and enhancing the adhesion strength between the $Al_2$O$_3$ substrate and copper layer. This study examined primary the characteristic of the sol making condition and differential thermal analysis (DTA) X-ray diffraction (XRD) were mearsured to identify the crystal phase of heat treatment specimens. The morphology of the coated films were studied by scanning electron microscopy(SEM). As a resurt, XRD analysis was obtained patterns of $\alpha$-cordierite after heat-treatment about 2 hours at $1000^{\circ}C$. SEM analysis could have seen a large number of voids on coated film. The more contants of$ Al_2$$O_3$ Wt% was increased the more voids was advanced. Peel adhesion strength has a maximum in the contants of the TEOS:ANE of 1:0.7 mole%. In this case, adhesion strength has been measured 1150gf, peel adhesion strength were about 10 times more than uncoated of the ceramics film.