• Composites Research
• /
• 제14권5호
• /
• pp.1-11
• /
• 2001

본 논문은 금속복합재료를 반용융상태로 재가열하여 Thixoforming을 하는데 필요한 소재를 제공하기 위한 장비 설계와 제조방법 등에 관한 내용을 소개하고 있다. 장비 설계에서 기지재내에 강화재가 균일하게 분산되도록 하기 위하여 강화재의 연속주입 방법과 강화재의 온도를 제어하는 방법을 소개하고 있다. 일정한 양의 강화재를 기지재료 내에 분산시키는 것은 균일 혼합을 위하여 필요한 기술이다. 또한 분산시 강화재의 수분제거를 위하여 강화재의 온도를 제어하면서 연속적으로 강제분산시키는 것은 균일분산을 위하여 필요하다. 기지재의 초정 $\alpha$의 크기가 강화재의 분산성에 크게 영향을 미치기 때문에 기지재의 초기 온도가 초정$\alpha$의 크기에 미치는 영향 등을 검토하여 복합재료 빌렛트의 제조조건에 이용하였다.

• Composites Research
• /
• 제31권5호
• /
• pp.251-259
• /
• 2018

본 논문에서는 섬유강화복합재의 멀티스케일 해석을 위해 필요한 대규모/소규모 통계적 체적요소 모델을 개발하였다. 미시영역모델의 크기효과를 최소화하기 위해서 섬유를 최대한 포함한 거대모델을 구성하였다. 이를 위해 국부 영역의 요소 절단법을 이용하여 전체 유한요소 크기에 상관없이 신속한 격자 섬유/기지의 모델링이 가능한 요소생성기를 구성하였다. 이를 통해 대규모 통계 체적 모델을 도출하여 체적모델의 크기에 따른 국부하중 공유의 차이를 고찰하고, 섬유방향의 연속체손상역학모델을 BSVEs 모델 해석으로부터 도출 하였다. BSVEs 모델을 보편적인 RVE모델과 비교 검증하였다.

• 대한방사선치료학회지
• /
• 제31권1호
• /
• pp.25-32
• /
• 2019

목 적: 두경부 방사선 치료 시 Dental Implant에 의한 Metal Artifact로 인해 보철물의 크기, 모양 및 Volume이 달라지고 이로 인해 타겟 및 주변 정상조직에 대한 방사선치료계획의 정확성이 떨어진다. 본 연구는 치아크기를 재현한 Metal을 KVCT, SMART-MAR CT, MVCT를 통해 영상을 획득 하여 Volume을 평가하고 양성자 치료계획에 적용시켜 선량분포의 차이를 분석해 보고자 한다. 대상 및 방법: 치과에서 치료하는 방법을 고려하여 인레이, 크라운, 브릿지와 비슷한 크기의 A보철물($0.5{\times}0.5{\times}0.5cm$), B보철물($1{\times}1{\times}1cm$), C보철물($1{\times}2{\times}1cm$)을 저용융점납합금(Cerrobend, $9.64g/cm^3$) 사용하여 제작하였다. In House Head & Neck Phantom 안에 보철물를 위치시키고 CT Simulator(Discovery CT 590RT, GE, USA)를 이용해 Slice thickness 1.25 mm로 KVCT 영상과 SMART-MAR 영상을 획득하였다. MVCT 영상은 $RADIXACT^{(R)}$ Series(Accuray $Pricision^{(R)}$, USA)을 이용해 동일한 방법으로 획득하였다. MVCT, SMART-MAR CT, KVCT를 통해 획득한 보철물의 형상을 전산화 치료계획장비 Pinnacle(Ver 9.10, Philips, Palo Alto, USA)의 Autocontour Thresholds Raw Values를 통해 X, Y, Z축의 크기 및 Volume을 비교하였다. 양성자 치료계획은 위의 실험에서 얻은 보철물B($1{\times}1{\times}1cm$)의 각 CT별 치아 Contour를 KVCT 상에 fusion하여 양성자 치료계획(Ray station 5.1, RaySearch, USA)을 세우고 선량의 차이를 비교 평가하였다. 결 과: 실측 사이즈 대비 A보철물(MVCT : 1.0배, SMART-MAR CT : 1.84배, KVCT : 1.92배), B보철물(MVCT : 1.02배, SMART-MAR CT : 1.47배, KVCT : 1.82배), C보철물(MVCT : 1.0배, SMART-MAR CT : 1.46배, KVCT : 1.66배)로 각 크기의 보철물에서 MVCT가 가장 실제 Volume과 유사하게 측정되었다. 양성자 치료계획에서 B보철물의 Volume을 각각 적용하여 측정한 결과 $D_{99\%}$ volume의 선량이 기준 3082 CcGE 대비 MVCT:3094 CcGE, SMART-MAR CT:2902 CcGE, KVCT:2880 CcGE로 측정되었다. 결 론: 전체적인 Volume과 X축 Z축의 크기는 MVCT에서 실제 크기와 가장 일치했고 superior-Inferior방향인 Y축은 CT에 따라 차이 없이 길이가 일정했다. 두경부 양성자 치료 시 보철물의 크기, 모양 및 Volume이 비슷한 MVCT에서 가장 실제 값과 비슷한 선량분포를 보였고 MVCT를 이용한 보철물의 contour를 KVCT에 fusion하여 양성자치료계획에 적용 시 매우 유용할 것으로 사료된다.

• 한국응용과학기술학회지
• /
• 제30권4호
• /
• pp.602-611
• /
• 2013

We have investigated the influence of system composition and preparation conditions on the particle size of vitamin E acetate (VE)-loaded nanoemulsions prepared by PIC(phase inversion composition) emulsification. This method relies on the formation of very fine oil droplets when water is added to oil/surfactant mixture. The oil-to-emulsion ratio content was kept constant (5 wt.%) while the surfactant-to-oil ratio (%SOR) was varied from 50 to 200 %. Oil phase composition (vitamin E to medium chain ester ratio, %VOR) had an effect on particle size, with the smallest droplets being formed below 60 % of VOR. Food-grade non-ionic surfactants (Tween 80 and Span 80) were used as an emulsifier. The effect of f on the droplet size distribution has been studied. In our system, the droplet volume fraction, given by the oil volume fraction plus the surfactant volume fraction, was varied from 0.1 to 0.3. The droplet diameter remains less than 350 nm when O/S is fixed at 1:1. The droplet size increases gradually as the increasing the volume fraction. Particle size could also be reduced by increasing the temperature when water was added to oil/surfactant mixture. By optimizing system composition and homogenization conditions we were able to form VE-loaded nanoemulsions with small mean droplet diameters (d < 50 nm). The PIC emulsification method therefore has great potential for forming nanoemulsion-based delivery systems for food, personal care, and pharmaceutical applications.

• 환경위생공학
• /
• 제13권3호
• /
• pp.19-29
• /
• 1998

The calcination reactivity of limestone and physical property changes of calcined lime were investigated with a temperature($720~1000^{\circ}C$ under atmospheric gas($N_2$, $CO_2$) conditions. The mechanisms of mass transport in a lime matrix were represented by the evaporation and condensation (${\gamma}=1.7$) at $1000^{\circ}C$ and the volume diffusion (${\gamma}=2.7$) at $800^{\circ}C$, which was obtained by the specific surface area of calcined lime with sintering conditions. Also, the effect of physical property on the reactivity of sulfation reaction was determined by the changes of pore size with $lime-SO_2$ reaction in this work. The initial sulfation rate of calcined lime increased with increasing temperature, whereas the capture capacity of $SO_2$ exhibited a maximum value at $900^{\circ}C$. The pore volume of sulfated lime was decreased with increasing sulfation time, but the major pores shifted to the distribution of larger size at a temperature of $850{\;}~{\;}1000^{\circ}C$. The mean pore size of sulfated lime based on pore volume decreased gradually at $1000^{\circ}C$; however, it increased with sulfation time up to 40 min and rapidly decreased thereafter.

• 한국염색가공학회지
• /
• 제12권6호
• /
• pp.380-388
• /
• 2000

The porosity of polyester fibers treated with sodium hydroxide aqueous solution was investigated using a nitrogen porosimeter, and the dyeability of the treated fibers was discussed in terms of the porosity. In pore distribution, the polyester fibers treated with sodium hydroxide aqueous solution were characterized by higher amount of pores below $10\AA$ than those of the untreated fibers, and by shift of the pore size having maximum accumulated volume from $10\AA$ for the untreated fibers to $5~6\AA$. As the weight loss of the polyester fibers treated with sodium hydroxide aqueous solution increased, BET surface area and total pore volume increased linearly, but average pore size, showing some different aspect, increased steeply at earlier stage and then approached the maximum value. The dye uptakes of the polyester fibers treated with sodium hydroxide aqueous solution increased with the BET surface area, the total pore volume and the average pore size. The alkali treatment increased the surface area of polyester fibers, so that the chance of contact between the fiber and dye molecules increased. In addition, the pores created on the surface of polyester fibers by alkali treatment might act as pathways for dye molecules into the polyester fibers.

• Ocean and Polar Research
• /
• 제36권4호
• /
• pp.319-326
• /
• 2014

Mineral dust in the polar snow plays an important role both in the climate system of the Earth and in global biogeochemical cycles. Analysis of the concentration and the particle size distribution of mineral dust has been carried out in the snow from the Antarctic surface snow and the Greenland snowpit. Among the various particle size determination techniques, a Multisizer 3 Coulter Counter in a class 100 clean bench counted all particles between 1.1 and $30.0{\mu}m$ with a $50{\mu}m$ aperture tube. The aperture tube size, the concentration of electrolytes and the accuracy of the particle size distribution were determined in this study. The number concentrations from the Antarctic surface snow were 81,843 particles $mL^{-1}$, but those from the Greenland snowpit were 10,666 particles $mL^{-1}$. In the volume distribution, the distributions of mineral dust in both the Antarctic surface snow and the Greenland snowpit showed lognormal distribution in the size interval 1.1 to $6.0{\mu}m$ with the mode, 3.562 and $3.836{\mu}m$, respectively. The analysis technique using a coulter counter for mineral dust could be used for reconstructing paleoclimates from polar ice cores.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제4C권2호
• /
• pp.68-72
• /
• 2004

The performance of copper-tungsten for electrodes used in an ultra high voltage interruption system was evaluated by means of an interruption test, which requires a large-scale apparatus and high cost. In this study, prior to the interruption test, the characteristics of a Cu-W electrode were estimated through the DC arc test, which is a simple, low cost procedure. The DC arc characteristics of a 20wt%Cu-80wt%W electrode were investigated with the change of tungsten powder size distribution and the addition of nickel. In specimens containing a high volume fraction of large sized tungsten particles, the relative density and hardness of sintered Cu-W electrodes increased while the electrical conductivity and the DC arc resistance decreased. Furthermore, the relative density became enhanced with the increase of the amount of nickel while the hardness and electrical conductivity diminished and the DC arc resistance worsened.

• Korean Chemical Engineering Research
• /
• 제44권3호
• /
• pp.289-293
• /
• 2006

탄산칼슘을 제조하는 연속식 결정화 공정에서 결정의 입도분포에 대한 온도와 교반속도 영향을 연구하였다. 연속식조업에서 용액의 산도 변화는 적었다. 교반속도가 300 RPM 이하, 용액의 온도가 낮으면 탄산칼슘 결정의 부피 평균크기는 안정하였고, 전자현미경 사진 관찰에서 calcite와 aragonite가 만들어졌음을 알 수 있었다

• 한국의류학회지
• /
• 제26권7호
• /
• pp.1078-1084
• /
• 2002

Cotton fabrics were treated with 1,2,3,4-butanetetracarboxylic acid(BTCA) to impart durable press performance, which is formaldehyde-free DP finishing reagent. The pore structures of BTCA treated cottons were compared using a reverse gel permeation chromatographic technique(reverse GPC). A series consisting 4 kinds of water soluble sugars was used to study the elution characteristics of columns prepared from cotton fibers. From these data, differences in pore size distribution in the control and BTCA treated cottons were distinguished. BTCA crosslinks cellulose molecules provided wrinkle resistance to the treated cotton fabrics through ester linkages. Although crosslinking of cotton with BTCA reduced accessible internal volume across the entire range of pore size, differences in line pores were larger than in small pores. BTCA treated cotton exhibited reductions over 40% in large pore sizes.