• Polymer(Korea)
• /
• v.38 no.1
• /
• pp.98-102
• /
• 2014

Nowadays, silk fibroin receives a lot of attention as novel natural biomaterials due to its excellent biocompatibility and biodegradability. Electrohydrodynamic spraying (EHDS) is one of the method for the preparation of micro or nanoparticles by applying high voltage to the polymer solution. In this research, we fabricated silk fibroin porous microparticles by electrohydrodynamic spraying. Poly(ethylene glycol) (PEG) was added to the fibroin solution to give pores to silk fibroin microparticles. By the addition of PEG, the microparticle size was decreased despite of the decrease in conductivity and the increase of viscosity of the spraying solution. It seems that the immiscibility of silk fibroin and PEG affected much more to the microparticle size than the conductivity and viscosity. Immersing the as-sprayed microparticles into the water removed the phase-separated PEG, and finally, porous silk fibroin microparticles were prepared. The porous silk fibroin microparticles are expected to be applied as drug carriers in drug delivery or cell carriers in tissue engineering.

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.1
• /
• pp.23-28
• /
• 2019

The Titanium oxide ($TiO_2$) is an attractive ceramic material which shows non-toxic, high refractive index, catalytic activity and biocompatibility, and can be fabricated at a low cost due to its high chemical stability and large anisotropy. $TiO_2$ nanoparticles have been prepared by sol-gel method. The pH of solution can affect the $TiO_2$ crystallinity during the formation of nanoparticles. The prepared nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy in order to investigate their structural and photoluminescence properties. Through these analysis, the size of $TiO_2$ nanoparticles were found to be smaller than 5 nm. As the crystallinity of the nanoparticles increased, the emission of PL in the 550 nm region increased. Therefore, luminescence characteristics can be improved by controlling the crystallinity of the $TiO_2$ nanoparticles.

• Proceedings of the KAIS Fall Conference
• /
• 2011.12b
• /
• pp.646-648
• /
• 2011

본 논문에서는 쌍롤 박판주조(Twin Roll Casting, TRC)법을 이용하여 AA4343 합금을 제작하였다. 주조시 롤 간격을 조절하여 냉각속도를 달리하였으며 인고트 주조(Ingot Casting, IC)법을 이용하여 제조된 합금과의 미세조직학적 차이와 이에 따른 물성 변화를 고찰하였다. TRC 및 IC로 제조된 합금을 냉간압연하였으며 압연 건전성을 평가하였다. 한편, 냉각속도별로 상이한 미세조직을 구현할 수 있는 스텝몰드(Step Mold Casting, SMC)법을 이용하여 제조된 합금의 냉각속도에 따른 미세조직 및 경도 차이를 조사하여 상대 비교하였다. 냉각속도가 빠를수록 주조 셀조직의 크기 및 공정 Si 입자의 크기가 감소하였으며 이로 인하여 경도가 증가되는 효과를 나타내었다. 주조시 생성된 공정 Si 입자의 크기는 압연에 의하여 그 크기의 변화가 거의 없었으며 열분석 결과 액상선 온도의 변화가 일부 발생하나 큰 차이가 없었다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.4
• /
• pp.24-31
• /
• 2005

A plused laser ablation deposition(PLAD) technique has been used for producing fine particle as well as thin film at relatively low substrate temperatures. However, in order to manufacture and evaluate such materials in detail, motions of plume particles generated by laser ablation have to be understood and interactions between the particles by ablation and gas plasma have to be clarified. Therefore this paper was focused on the understanding of plume motion in laser ablation assisted by hi plasmas at 100[mTorr]. One-dimensional hybrid model consisting of fluid and particle models was developed and three kinds of plume particles which are carbon atom(C), $ion(C^+)$ and electron were considered in the calculation of particle method. It was obtained that ablated $C^+$ was electrically captured in Ar plasmas by strong electric field(E). The difference between motions of the ablated electrons and $C^+$ made E strong and the collisional processes active. The energies of plume particles were investigated on a substrate surface. In addition the plume motion in Ar gas was also calculated and discussed.

• Journal of the Korean Magnetics Society
• /
• v.15 no.3
• /
• pp.172-176
• /
• 2005

Four nano-sized Fe-nano particle samples synthesized by Chemical Vapor Condensation (CVC) were analyzed using $M\ddot{o}ssbauer$ spectroscopy, XRD, BET and TEM. The samples were consisted as functions of carrier gas and decomposition temperature. The synthesized nanoparticles consisted of two- or three-layers with the circular shape. The average particle size was increased with increasing the decomposition temperature. At $500^{\circ}C$ for the decomposition temperature, $Fe_3C$ was formed more under the environment of CO carrier gas than that of $CH_4$. However, at $1,100^{\circ}C$, almost of Fe-nano particles were transformed into $Fe_3C$ with using both carrier gas.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.4
• /
• pp.363-370
• /
• 2017

This paper is concerned with the evaluation of mixing performance of a particle mixer, which consists of a vertical cylindrical vessel and a rotating impeller with several blades. We consider four design variables for the mixer blades, such as the angle, length, and number of blades, and the gap between the blades and the vessel bottom. The particle mixing process due to the impeller rotation is simulated using the discrete element method, and the mixing performance is quantitatively evaluated by introducing a mixing index. Analyzing the main effects and interactions of the four design variables through the design-of-experiments approach, it is concluded that the blade angle has the most dominant influence on the mixing performance whereas the gap has no significant influence. In addition, we determine the best combination of design parameters to maximize the mixing performance.

• Journal of the Korean Applied Science and Technology
• /
• v.39 no.5
• /
• pp.623-631
• /
• 2022

Using the design of experiment (DOE), factors affecting the particle size of hydrated liquid crystalline vesicles containing a high content of ceramide were analyzed and the mixture composition was optimized. Manufacturing temperature, amount of ethanol, and ultrasonic time were selected as the main variables affecting the droplet size of the vesicles, and the effect of these variables on the droplet size was examined through the signal to noise (S/N) ratios of Taguchi method and ANOVA analysis. In addition, mixture composition experiments of three lipid components constituting the vesicle membrane, hydrogenated phosphatidyl choline (HPC), cholesterol (Chol), and ceramide (Cer), were performed according to the simplex central design matrix of the mixture. Regression analysis was conducted with the experimental data to obtain a model equation, and the optimal mixing composition of the three lipid components to minimize the vesicle droplet size was determined as HPC (0.6), Chol (0.1), and Cer (0.3).

• Journal of the Korea Institute of Military Science and Technology
• /
• v.6 no.4
• /
• pp.89-99
• /
• 2003

Smoothed particle hydrodynamics, SPH, is a gridless Lagrangian technique which is a useful alternative numerical analysis method to simulate high velocity deformation problems as well as astrophysical and cosmological problems. The SPH method brings about some difficulties such as tensile Instability and stress oscillation. A new SPH method, so called normalized algorithm, was introduced to overcome these difficulties. In this paper we aimed to estimate this method and have developed an one-dimensional normalized SPH program. The high velocity impact model of an aluminum bar has been analysed by using the developed program and a commercial hydrocode, LS-DYNA. The obtained numerical results showed good agreement with the results of the same model in reference. The program also showed more stable results than those of LS-DYNA in stress oscillation. We hopefully expect that the developed one-dimensional normalized SPH program can be used to solve hydrodynamic problems especially for explosive detonation analysis.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1599_1600
• /
• 2009

ZnS:Mn 나노입자가 포함된 PVP 고분자 하이브리드 나노사를 전기방사법으로 제작하였다. 하이브리드 나노사의 표면 특성은 주사 전자 현미경으로 관측하였으며, 형광분광광도계와 공초점 주사현미경 (CLSM)을 이용하여 하이브리드 나노사의 발광특성을 조사하였다. 순수한 PVP 나노사와 하이브리드 나노사의 photoluminescence (PL) 스펙트럼 비교를 통하여, 586 nm에서 관찰된 PL 피크는 ZnS:Mn 나노입자에서 기인되었음을 알 수 있었으며, CLSM을 이용하여 ZnS:Mn 나노입자의 발광을 이미지화 하였다.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.11 no.6
• /
• pp.164-171
• /
• 2008

A modified generalized particle algorithm, MGPA, was suggested to improve the computational efficiency of standard SPH method in numerical analysis of high speed impact behavior. This method uses a numerical failure mechanism than material failure models to describe the target penetration. MGPA algorithm was more effective to describe the impact phenomena and new boundaries produced during the calculation process were well recognized and treated in the target penetration problem of a bullet. When bullet perforation problems were analyzed by this method, MGPA algorithm calculation gives the stable numerical solution and stress oscillation or particle penetration phenomena were not shown. The error range in ballistic velocity limit is less than $2{\sim}13%$ for various target thickness.