• 한국콘텐츠학회논문지
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• 제9권9호
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• pp.191-198
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• 2009

21세기는 기술 발달로 인해 소재의 다양화와 학문적 연계를 통한 디자인 결합은 우리의 삶에 있어 다양한 욕구의 변화를 가져왔으며, 그로인해 시각적인 관심과 함께 기능적 역할의 조화로 자기 개성에 맞는 디자인 개발이 관심의 대상이 되고 있다. 최근 다양한 소재를 이용한 디자인 개발이 추세이고 이러한 디자인 경향은 개인의 감성과 취향을 존중하고 있으며, 이에 따라 다변화 되고 있다. 생활수준의 향상으로 건강과 개성에 대한 관심과 향기에 대한 관심이 높아지고 향(香)은 기억이나 감성 등 개인의 취향과 개성에 맞게 다양한 형태로 개발되고 있다. 이에 본 연구자는 향기 나는 소재를 사용하여 기계적인 특성과 미적 요소를 가미한 소재를 가지고 소비자의 감성적 욕구에 맞게 장신구 분야에 적용하고 시각적 디자인에 후각을 접목하면서 여성의 보조적 디자인에서 벗어나 남성만의 개성과 감성을 표현 할 수 있는 남성 신변장신구에 대한 활용 방안을 제시 하고자 한다.

• Advances in materials Research
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• 제13권3호
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• pp.243-251
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• 2024

The asymmetric polylactic acid (PLA) membrane was prepared via phase inversion method using non-solvent induced separation (NIPS) technique. This study aims to synthesized as well as to characterize the PLA membrane and evaluating the membrane performance on water flux and permeability. In addition, this research also studied the removal performance of methylene blue dye. The polymer solution has been prepared using 12 wt.% of PLA and dissolved in 88 wt.% of Dimethylacetamide (DMAc) as a solvent. Then, the cast film was immersed in different ratio of coagulant bath medium (distilled water: methanol: ethanol) ranging from 100:0:0, 75:25:0, 75:0:25 and 75:12.5:12.5, respectively). Several characterizations were performed which include, membrane contact angle and membrane porosity. Performance PLA membranes were determined in terms of water flux and permeability at 1 bar transmembrane pressure using dead-end permeation cell. Finally, methylene blue (MB) removal efficiency was tested at the same transmembrane pressure. The findings revealed that the increase of alcohol concentration in coagulant bath resulted in higher porosity and lower contact angle. In short, MB dye rejection efficiency is also closely related to the amount of alcohol ratio used in coagulant baths. Increases in concentration of methanol and ethanol in coagulant bath medium increases the membrane porosity thus increased in efficiency of methylene blue rejection.

• KSBB Journal
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• 제26권4호
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• pp.333-340
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• 2011

In this study, gemcitabine-loaded methoxy poly(ethylene glycol)-b-poly(L-lactide) (MPEG-PLLA) microparticles with different PEG block lengths were prepared by a W/O/W double emulsion technique. The present study focuses on the investigation of the influence of various preparative parameters such as the ratio of internal water phase and oil phase, polymer concentration, solvent composition of organic phase and salt concentration of external water phase on the morphology and encapsulation efficiency of the microparticles. The microparticles fabricated at high volume ratios of internal water phase to oil phase and at high polymer concentrations showed a relatively high encapsulation efficiency and low porosity. When a dichloromethane/ethyl acetate mixture was used as solvent, both the encapsulation efficiency and drug loading of the microparticles decreased as the level of ethyl acetate increased. The addition of a salt (NaCl) to the external water phase significantly improved the encapsulation efficiency up to 40%, and the microparticles became more spherical with their size and porosity decreased.

• 한국세라믹학회지
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• 제34권9호
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• pp.969-978
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• 1997

The properties of microstructure, hydrophobicity/hydrophilicity, mechanical strength, and thermal conduction of pure/opacified silica aerogels synthesized by the sol-gel supercritical drying technique were investigated. The hydrophobic surface of opacified silica aerogels doped with carbon (0.13 g/cm3 density, 94% porosity, 580 m2/g specific surface area) transformed to hydrophilic surface after heat-treated above 30$0^{\circ}C$. The values of compressive modulus (1.85 MPa) and strength (0.5 MPa) of opacfied silica aerogels were about 20 times higher than those of pure silica aerogels. The mechanical properties of pure silica aerogels heat-treated at $700^{\circ}C$ were also considerably improved without changing their porosity and density. Particularly, compressive modulus and compressive strength of pure silica aerogels GPSed under 100$0^{\circ}C$ and 80 bar were improved 140 and 37 times, respectively. Thermal conductivities of pure/opacified silica aerogels measured at room temperature and 227$^{\circ}C$ were about 0.013 and 0.019 W/m.K, respectively, and were to be found very low value of 0.004 W/m.K below 10 torr pressure at room temperature.

• 품질경영학회지
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• 제42권4호
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• pp.579-590
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• 2014

Purpose: Ball milling is a popular process for obtaining fine powders in the part and material industry. One of important issues in the ball milling is to produce particles with a uniform size. Although many factors affect uniformity of particles, this paper focuses on the choice of ball diameter. Consider a ball milling where balls can be taken with three different diameters. The purpose of this paper is to find a ball mix which minimizes the average particle size. Methods: Ball diameters are selected as 10mm, 3mm, and 0.5mm. In order to find an optimum mixing ratio, the method of mixture experiments is employed in this paper. Taguchi's signal-to-noise ratio (SNR) for smaller-the-better type is also used to analyze experimental data. Results: According to the experimental result, SNR is maximized when the ball mix is taken as either 7:3:0 or 6:4:0. Such mixing ratios can be technically validated in terms of porosity reduction. Conclusion: The ball mixing technique presented in this paper provides a useful way to improve the production efficiency with a low cost.

• 한국추진공학회지
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• 제12권6호
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• pp.12-20
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• 2008

강내탄도 전산해석 코드 개발을 위한 효율적인 방안과 수치 기법에 관해 연구하였다. 탄자이동에 의한 이동경계면에 대한 수치 해석 기법은 자유 피스톤 운동 문제를 통해서 비교 검증하였다. 강내탄도의 초기 연소를 수치적으로 계산하여 고체추진제의 연소와 기공률 효과에 의한 압력구배를 예측할 수 있었다. 본 연구를 통해서 강내탄도 전산 해석 코드 개발에 관한 방안과 기초 기법에 대한 전산화 기술을 확보하였다.

• 한국분말재료학회지
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• 제19권4호
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• pp.278-284
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• 2012

$Al_2O_3$ foam is an important engineering material because of its exceptional high-temperature stability, low thermal conductivity, good wear resistance, and stability in hostile chemical environment. In this work, $Al_2O_3$ foams were designed to control the microstructure, porosity, and cell size by varying different parameters such as the amount of amphiphile, solid loading, and stirring speed. Particle stabilized direct foaming technique was used and the $Al_2O_3$ particles were partially hydrophobized upon the adsorption of valeric acid on particles surface. The foam stability was drastically improved when these particles were irreversibly adsorbed at the air/water interface. However, there is still considerable ambiguity with regard to the effect of process parameters on the microstructure of particle-stabilized foam. In this study, the $Al_2O_3$ foam with open and closed-cell structure, cell size ranging from $20{\mu}m$ to $300{\mu}m$ having single strut wall and porosity from 75% to 93% were successfully fabricated by sintering at $1600^{\circ}C$ for 2 h in air.

• Corrosion Science and Technology
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• 제9권6호
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• pp.325-330
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• 2010

Many surface protection methods have been developed to apply for constructional steels used under severe corrosive environment. Thermal spray coating has been known to be an attractive technique due to its relatively high coating speed. Furthermore high corrosion resistance of coated film with thermal spray is required to expand its application. Four types of coated films(DFT:300 um) such as pure zinc, pure aluminum and two Al-Zn alloy (Al:Zn=85:15 and Al:Zn=95:5) onto the carbon steel (SS401) were prepared with arc spray, and the corrosion behavior of their samples were evaluated by electrochemical method in this study. Pure aluminum sample showed high corrosion resistance behavior exposed to sea water solution and pure zinc and alloy (Al:Zn=95:5) samples followed pure aluminum sample. The other alloy(Al:Zn=85:15) so called galvalume coated onto the carbon steel ranks the 4th corrosion resistance in this study. The results of porosity ratio of those samples by observation are well matched with the electrochemical data.

• Journal of the Korean Wood Science and Technology
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• 제45권2호
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• pp.232-242
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• 2017

The objective of this study was to examine changes in the porosity and internal structure of wood as it goes through the process of saccharification (extraction of fermentable sugars). This study also examined the use of different drying methods to prepare samples for characterization of internal pores, with particular emphasis on the partially disrupted cell wall. Aspen wood flour samples after dilute acid pretreatment followed by enzymatic hydrolysis were examined for nitrogen adsorption. The resulting isotherms were analyzed for surface area, pore size distribution, and total pore volume. Results showed that freeze drying (with sample pre-freezing) maintains the cell wall structure, allowing for examination of saccharification effects. Acid pretreatment (hemicellulose removal) doubled the surface area and tripled the total volume of pores, which were mostly 10-20 nm wide. Subsequent enzymatic hydrolysis (cellulose removal) caused a 5-fold increase in the surface area and a ~ 11-fold increase in the total volume of pores, which ranged from 5 to 100 nm in width. These results indicate that nitrogen adsorption analysis is a feasible technique to examine the internal pore structure of lignocellulosic residues after saccharification. The information on the pore structure will be useful when considering value-adding options for utilizing the solid waste for biofuel production.

• Wind and Structures
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• 제19권4호
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• pp.389-404
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• 2014

The flow characteristics of a circular cylinder surrounded by an outer permeable cylinder were experimentally investigated using Particle Image Velocimetry Technique in deep water flow. In order to consider the effects of diameter and porosity of the outer cylinder on flow structures of the inner cylinder, five different outer cylinder diameters (D=37.5, 52.5, 60, 75 and 90 mm) and eight different porosities (${\beta}$=0.4, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8 and 0.85) were selected. During the experiments, the diameter of inner cylinder was kept constant as d=30 mm. The depth-averaged free-stream velocity was adjusted as U=0.156 m/s, which corresponds to the Reynolds number of Re=5000 based on the inner cylinder diameter. It has been concluded that both the outer permeable cylinder diameter and the porosity have important influences on the attenuation of vortex shedding in the wake region. The presence of outer permeable cylinder decreases the magnitude of Reynolds shear stress and turbulent kinetic energy compared to the bare cylinder case. Moreover, the spectral analysis of vortex shedding frequency has revealed that the dominant frequency of vortex shedding downstream of the cylinder arrangement also reduces substantially due to the weakened Karman shear layer instability.