• Nuclear Engineering and Technology
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• 제50권7호
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• pp.1120-1130
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• 2018

An analysis of a pyroprocessing safeguards methodology employing the Pu-to-$^{244}Cm$ ratio is presented. The analysis includes characterization of representative used nuclear fuel assemblies with respect to computed nuclide composition. The nuclide composition data computationally generated is appropriately reformatted to correspond with the material conditions after each step in the head-end stage of pyroprocessing. Uncertainty in the Pu-to-$^{244}Cm$ ratio is evaluated using the Geary-Hinkley transformation method. This is because the Pu-to-$^{244}Cm$ ratio is a Cauchy distribution since it is the ratio of two normally distributed random variables. The calculated uncertainty of the Pu-to-$^{244}Cm$ ratio is propagated through the mass flow stream in the pyroprocessing steps. Finally, the probability of Type-I error for the plutonium Material Unaccounted For (MUF) is evaluated by the hypothesis testing method as a function of the sizes of powder particles and granules, which are dominant parameters to determine the sample size. The results show the probability of Type-I error is occasionally greater than 5%. However, increasing granule sample sizes could surmount the weakness of material accounting because of the non-uniformity of nuclide composition.

• Journal of Pharmaceutical Investigation
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• 제22권4호
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• pp.267-279
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• 1992

Microencapsulations of amoxicillin and cephalexin, using Eudragit RS, RL, E, S and L were investigated. The microcapsules were prepared by the solvent evaporation process in liquid paraffin phase, which is based on dispersion of acetone/isopropanol containing the drug in liquid paraffin. Aluminium tristearate was used as an additive for the preparation of microcapsules. The size distribution, dissolution test and observation by SEM were examined. Good reproducibility in microcapsule preparation was observed. The microcapsules obtained were spherical and free-flowing particles. The dissolution rates of amoxicillin and cephalexin from the microcapsules were considerably decreased as compared with those from amoxicillin and cephalexin powder, respectively. As the dispersing agents (aluminium tristearate) increased, the particle size of microcapsules decreased and the dissolution rate increased. In order to control the release rate of drugs, microcapsules were prepared by mixing Eudragit RS/RL or Eudragit S/L. As Eudragit RL ratio in microcapsule of Eudragit RS/RL increased, the dissolution rate increased. As Eudragit L ratio in microcapsule of Eudragit S/L increased, the dissolution rate increased. Furthermore, the release rates of drugs from Eudragit RS/L or RS/polyelthylene glycol 1540 (PEG 1540) were examined. The dissolution rate of drugs increased with increasing of Eudragit L or PEG 1540 ratio. In conclusion, the release rates of drugs from Eudragit RS/RL or RS/PEG 1540 microcapsule could be controlled, and these microcapsules will be convenient for reducing frequency of administration.

• 한국세라믹학회지
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• 제39권6호
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• pp.604-609
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• 2002

분자 단위의 균일한 조성을 가지는 $BaCeO_3$ 나노 분말을 Pechini법에 기초한 citrate 공정을 통하여 합성하였다. 금속 이온의 chelating제로서 citric acid를, 반응 촉매로서는 ethylen glycol을 각각 사용하여 고분자 전구체를 형성시켰고, 이를 기반으로 $900^{\circ}C$의 온도에서 4시간동안 열처리하여 약 100nm의 균일한 크기와 형상을 가진, 사방정 구조의 단일상 $BaCeO_3$ 분말을 합성하는데 성공하였다. 잔존하는 미량의 $CO_3^{2-}$는 $1100^{\circ}C$ 이상의 온도에서 완전히 분해되었고, 이 때 평균 입도 는 약 2배 증가하였으나 매우 균일한 분포를 나타내었다.

• 한국재료학회지
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• 제25권2호
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• pp.95-99
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• 2015

$NiAl_2O_4$ nanoparticle was synthesized by a reverse micelle processing for inorganic pigment. $Ni(NO_3)_2{\cdot}6H_2O$ and $Al(NO_3)_3{\cdot}9H_2O$ were used for the precursor in order to synthesize $NiAl_2O_4$ nanoparticles. The aqueous solution, which consisted of a mixing molar ratio of Ni/Al, was 1:2 and heat treated at $800{\sim}1100^{\circ}C$ for 2h. The average size and distribution of synthesized $NiAl_2O_4$ powders are in the range of 10-20 nm and narrow, respectively. The average size of the synthesized $NiAl_2O_4$ powders increased with an increasing water-to-surfactant molar ratio and heating temperature. The crystallinity of synthesized $NiAl_2O_4$ powder increased with an increasing heating temperature. The synthesized $NiAl_2O_4$ powders were characterized by X-ray diffraction analysis(XRD), a field emission scanning electron microscopy(FE-SEM), and a color spectrophotometer. The properties of synthesized powders were affected as a function such as a molar ratio and heating temperature. Results indicate that synthesis using a reverse miclle processing is a favorable process to obtain $NiAl_2O_4$ spinels at low temperatures. The procedure performed suggests that this new synthesis route for producing these oxides has the advantage of being fast and simple. Colorimetric coordinates indicate that the pigments obtained exhibit blue colors.

• 대한토목학회논문집
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• 제31권5C호
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• pp.171-185
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• 2011

레디믹스트(Ready-mixed) 숏크리트는 전문공장에서 원재료를 건조배합 형태로 생산하여 시공현장으로 운반 및 타설되는 재료로서, 확실한 골재 품질관리가 가능하며 규격화된 재료 사용으로 시공 품질 개선이 가능하다. 특히, 현장 배치플랜트의 축소 혹은 생략이 가능하기 때문에, 설치비용 절감 및 부지확보로 인한 민원과 환경문제를 해결할 수 있는 추가적인 장점이 있다. 본 연구에서는 숏크리트 성능 향상을 위한 방법으로 혼화재 및 급결제에만 국한되어 있던 기존 연구방향을 벗어나, 골재 자체의 품질 개선을 통해 숏크리트 성능을 향상시키고자 하였다. 기초 연구에서는 국내 숏크리트 시공실태 및 공급골재의 품질파악을 실시하였고, 현장실험을 통해 레디믹스트 숏크리트의 굵은 골재 최대치수를 8mm로 결정하였다. 또한, Pilot Plant Test를 실시하여 공장생산 공정의 재료분리 현상을 최소화 하고자 하였고, 현장실험을 통해 강섬유와 동일 수준의 휨인성을 발휘할 수 있는 합성섬유의 최적 혼입량과 고로슬래그 미분말의 최적 치환율을 도출하였다.

• 공업화학
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• 제18권4호
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• pp.320-325
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• 2007

본 연구에서는 재래식 및 마이크로파 합성법을 통하여 비수계 유기용매인 diethanolamine을 용매로 하여 초산니켈 수용액과 히드라진 수화물로부터 니켈 분말을 합성하였다. X선 회절분석, 주사 전자현미경 분석, 열분석 및 X선 광전자 분광기 분석등을 통하여 마이크로파의 비열적 효과 및 반응 조건이 니켈분말의 합성에 미치는 영향을 조사하였다. 재래식 합성과 비교해보면, 마이크로파를 이용한 합성에서 마이크로파의 비열적 효과에 기인하여 상대적으로 응집이 적게 일어나고, 입자 크기는 작고, 입도 분포는 균일하였다.

• 한국재료학회지
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• 제21권10호
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• pp.568-572
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• 2011

The preparation of $Y_2O_3$-doped $ZrO_2$ nanoparticles in Igepal CO-520/cyclohexane reverse micelle solutions is studied here. In this work, we synthesized nanosized $Y_2O_3$-doped $ZrO_2$ powders in a reverse micelle process using aqueous ammonia as the precipitant. In this way, a hydroxide precursor was obtained from nitrate solutions dispersed in the nanosized aqueous domains of a microemulsion consisting of cyclohexane as the oil phase, with poly (oxyethylene) nonylphenylether (Igepal CO-520) as the non-ionic surfactant. The synthesized and calcined powders were characterized by thermogravimetrydifferential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The crystallite size was found to nearly identical with an increase in the water-to-surfactant (R) molar ratio. A FTIR analysis was carried to monitor the elimination of residual oil and surfactant phases from the microemulsion-derived precursor and the calcined powder. The average particle size and distribution of the synthesized $Y_2O_3$-doped $ZrO_2$ were below 5 nm and narrow, respectively. The TG-DTA analysis showed that the phase of the $Y_2O_3$-doped $ZrO_2$ nanoparticles changes from the monoclinic phase to the tetragonal phase at temperatures close to $530^{\circ}C$. The phase of the synthesized $Y_2O_3$-doped $ZrO_2$ when heated to $600^{\circ}C$ was tetragonal $ZrO_2$.

• 한국재료학회지
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• 제24권2호
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• pp.98-104
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• 2014

Vacuum kinetic spray(VKS) is a relatively advanced process for fabricating thin/thick and dense ceramic coatings via submicron-sized particle impact at room temperature. However, unfortunately, the particle velocity, which is an important value for investigating the deposition mechanism, has not been clarified yet. Thus, in this research, VKS average particle velocities were derived by numerical analysis method(CFD: computational fluid dynamics) connected with an experimental approach(SCM: slit cell method). When the process gas or powder particles are accelerated by a compressive force generated by gas pressure in kinetic spraying, a tensile force generated by the vacuum in the VKS system accelerates the process gas. As a result, the gas is able to reach supersonic speed even though only 0.6MPa gas pressure is used in VKS. In addition, small size powders can be accelerated up to supersonic velocity by means of the drag-force of the low pressure process gas flow. Furthermore, in this process, the increase of gas flow makes the drag-force stronger and gas distribution more homogenized in the pipe, by which the total particle average velocity becomes higher and the difference between max. and min. particle velocity decreases. Consequently, the control of particle size and gas flow rate are important factors in making the velocity of particles high enough for successful deposition in the VKS system.

• 한국수소및신에너지학회논문집
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• 제25권4호
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• pp.436-442
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• 2014

$LaCoO_3$ powders synthesized by Pechini process were pulverized by planetary ball-milling to decrease particle size and characterized as a catalyst in alkaline solution for oxygen reduction and evolution reaction (ORR & OER). The changes of physical properties, such as particle size distribution, surface area and electric conductivity, were analyzed as a function of ball-milling time. Also, the variations of the crystal structure and surface morphology of ball-milled powders were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The electrochemically catalytic activities of the intrinsic $LaCoO_3$ powders decreased with increasing ball-milling time, but their electrochemical performance as an electrode improved by the increase of the surface area of the powder.

• 한국실내디자인학회논문집
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• 제16권6호
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• pp.116-124
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• 2007

The purpose of this study is to find out the spatial characteristics of the multi-housing units in Seoul and Kyung-gi area since 2006. Literature review and content analysis were used for this study and 82units of the big size over $165m^2$ were analyzed to review such design characteristics as spatial composition, layout and linkage. Through this study, the following conclusions have been reached; 1) Most unit plans had 4LDK and 3bath types including family room as a public space. This results shows that family-room and bathroom has recently become more important than number of rooms in multi-housing units planning. 2) Diversity of plan figures such as mass-mixing, mass-separation and polygons(L, V-type)was showed in most unit plan, breaking from the standardized forms of box types. 3) Intermediated spaces such as foyers and halls in entrance zone were planned and sub-entrance into kitchen were planned for the various types of circulation and work-efficiency. Cases had private space separated from public space, the dispersion of rooms with the increase of connection by corridors, L-DK meaning the living room isolated from the dining and kitchen, partially located living room for a view in area distribution. The spatial planning of master-zone mostly consists of the types of two-rooms and an entry into a foyer(library, dress-powder room, bathroom and master bedroom). This study has a significant meaning on grasping current trend in Korean multi-housing and to provide information for future direction on housing-unit design.