• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.83-83
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• 2017

생체재료의 표면은 이식과 동시에 생체계면의 역할을 하게 되어, 일련의 생물학적 반응이 시작되고 진행되는 중요한 장소가 된다. 초기에 생체계면에서 일어나는 단백질 흡착이나 염증반응을 비롯한 생물학적 반응들은 궁극적으로 임플란트의 성패를 좌우할 만큼 중요하다. 골융합을 개선하기 위한 다른 방법으로 생체불활성의 타이타늄 (Ti)과 골조직의 능동적인 반응을 이루기 위해 생체활성 표면을 부여함으로서 계면에서의 골형성 반응을 증진시키는 방법이 이용된다. 생체불활성의 Ti과 Ti합금은 골조직과 직접적인 결합을 이루지 못하므로, 골조직과의 반응을 향상하기 위해 여러 종류의 생체활성 재료를 코팅하는 방법이 연구되어 왔고, 이 중 생체의 변화와 가장 유사한 하이드록시아파타이트 코팅이 가장 대중적인 방법으로 사용되었으며 이는 초기 골형성을 촉진하는 것으로 알려졌다. 치과용 임플란트의 표면형상과 화학조성이 골 융합에 영향을 미치는 가장 중요한 인자이므로 최근의 연구동향은 이들 두 가지 표면특성을 결합함으로서 결과적으로 최적의 골세포반응을 유도하고, 골융합 후 골조직과의 micromechanical interlocking에 의해 임플란트의 안정성에 중요한 역할을 하는 마이크론 단위의 표면조도와 표면 구조를 유지하면서, 부가적으로 골 조직 반응을 능동적으로 개선할 수 있는 생체활성 성분을 부여하여 골 융합에 상승효과를 이루기 위한 표면처리법에 관해 많은 연구가 요구되어지고 있다. 따라서 골을 구하는 원소인 망간과 실리콘으로 치환된 하이드록시아파타이트를 플라즈마 전해 산화법으로 코팅하여 세포와 잘 결합할 수 있는 표면을 제공함으로써 골 융합과 치유기간을 단축시킬 수 있을 것으로 사료된다. 실험방법은 시편은 치과 임플란트 제작 합금인 Ti-6Al-4V ELI disk (grade 5, Timet Co., USA; diameter, 10 mm, thickness, 3 mm)이며, calcium acetate monohydrate, calcium glycerophosphate, manganese(II) acetate tetrahydrate, sodium metasilicate을 설계조건에 따라 혼합 제조된 전해질 용액을 이용하여 플라즈마 전해 산화법으로 표면 코팅을 실시하였다. 각 시편의 플라즈마 전해시 전압은 280V로 인가하였고, 전류밀도는 70mA로 정전류를 공급하여 해당 인가전압 도달 후 3분 동안 정전압 방식을 유지하였다. 코팅된 피막 표면을 주사전자현미경과 X-선 회절분석을 통하여 미세구조 및 결정상을 관찰하였다. 또한 코팅된 표면의 생체활성 평가는 정량적으로 평가하기 위해 동전위시험과 AC 임피던스를 통하여 시행하였다. 분극거동을 확인하기 위해 potentiostat (Model PARSTAT 2273, EG&G, USA)을 이용하여 구강 내 환경과 유사한 $36.5{\pm}1^{\circ}C$의 0.9 wt.% NaCl에서 실시하였다. 전기화학적 부식 거동은 potentiodynamic 방법으로 조사하였고 인가전위는 -1500 mV에서 2000 mV까지 분당 1.67 mV/min 의 주사속도로 인가하여 시험을 수행하였다. 임피던스 측정은 potentiostat (Model PARSTAT 2273, EG&G, USA)을 이용하였으며, 측정에 사용한 주파수 영역은 10mHz ~ 100kHz 까지의 범위로 하여 조사하였고 ZSimWin(Princeton applied Research, USA) 소프트웨어를 사용하여 용액의 저항, 분극 저항 값을 산출하였다. 망간의 함량이 증가할수록 불규칙한 기공을 보였으며, 실리콘은 $TiO_2$ 산화막 형성을 저해하는 경향을 확인할 수 있었다. 단독으로 표면을 처리한 경우보다 두 가지 원소를 이용해 복합 표면처리를 시행한 경우가 내식성이 좋아 임플란트과의 골 유착에 긍정적인 영향을 미칠 것으로 사료된다.

• Journal of Conservation Science
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• v.33 no.3
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• pp.203-214
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• 2017

This study evaluated the degradation characteristics of FRP by ultraviolet (UV) rays and applied a UV-resistant coating to prevent the degradation of the surface of these sculptures. As a result of the degradation caused by UV rays, there were slight changes in the FRP surface and contact angle. The chromaticity sharply increased in the early phase of degradation. After applying the coating to the FRP, no significant surface changes were observed. However, it had lower changes in color as compared to the uncoated specimen, so it was verified that the control of discoloration could be possible. Some changes in the gloss and contact angle were observed depending on the extent of degradation, but the UV coating agent remained relatively stable. Analysis of the infrared light spectrum showed that there were almost no chemical changes, and it could be concluded that the coating treatment prevented degradation for a certain period. This study investigated the degradation of FRP used as materials in artwork exposed to UV rays, and it was found that there was a delay in the onset of degradation in the FRP with the UV-resistant coating when compared to the uncoated FRP.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.6
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• pp.325-331
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• 2017

Adsorption experiments of carbon dioxide were performed on ZSM5 and Molecular Sieve 13X (MS13X) impregnated with Monoethanol Amine (MEA). Adsorption efficiency of $CO_2$ was investigated in a U type packed column with GC/TCD. The adsorption capacities of adsorbents are estimated in the temperature range of $30-80^{\circ}C$. The modified adsorbents was characterized by BET surface area, $N_2$ adsorption/desorption isotherms, X-ray diffraction and FT-IR. Surface analysis results showed that the impregnation method did not affect the crystallinity of any adsorbents. BET surface area of the MS13X impregnated amine decreased to $19.945m^2/g$ from $718.335m^2/g$. These reults showed that amine molecules were filled with the pore volume in MS13X, as a results restricting access of nitrogen into the pores. The MEA modified MS13X showed improvement in $CO_2$ adsorption capacity over the ZSM5 impregnated with MEA. The MS13X-MEA showed the highest adsorption capacity due to physical adsorption and chemical adsorption by amino-group content. This results also showed that adsorption capacity of MS13X-MEA increases with the temperature range of $60-80^{\circ}C$ compared with pristine MS13X.

• Korean journal of food and cookery science
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• v.27 no.4
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• pp.35-46
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• 2011

We developed hasuo jeungpyun with added polygonum multiflorum Thunb powder to increase the functional value and flavor of traditional jeungpyun. Hasuo jeungpyun containing 0, 2, 4, 6 and 8% polygonum multiflorum Thunb powder was prepared and the moisture contents, pH, color, texture and sensory analysis of the samples were measured. With increasing polygonum multiflorum Thunb powder content, the moisture content of hasuo jeungpyun decreased, and pH increased significantly. Hasuo jeungpyun prepared with 2-4% polygonum multiflorum Thunb powder displayed significantly higher swelling power. As the level of polygonum multiflorum Thunb powder increased, the L-value decreased, whereas the a- and, b-values increased. A textural profile analysis showed that the hardness increased but cohesiveness decreased with increasing polygonum multiflorum Thunb powder content. A sensory evaluation showed the highest value for air cell uniformity, flavor, and overall acceptability of 4% hasuo jeungpyun, which suggests hasuo jeungpyun with improved sensory characteristics. In the analysis of the correlation between sensory characteristics and mechanical properties of hasuo jeungpyun, hardness and brittleness were negatively correlated with after swallow, appearance, flavor, texture, taste, and overall acceptability.

• Korean Journal of Plant Tissue Culture
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• v.26 no.3
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• pp.197-203
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• 1999

The albino plants of tobacco (Nicotiana tobacum L. cv. BY-4) were isolated from seed populations that were induced by heavy-ion ($^{14}N$) beam irradiation to proembryo and the in vitro growth and differentiation have been characterized. The in vitro cultured albino plants showed significant reduction of chlorophyll content and possessed larger number of stomata on both upper and lower epidermis than that of wild-type plants. Stem growth of the mutants remained dwarfed, however, the internode recovered its normal length after GA$_3$ treatment (10.0mg/L) on the MS medium containing sucrose under continuous light. When explants of leaf blades of albino plants were cultured, multiple shoots formed directly on MS medium containing 1.0mg/L of BAP or kinetin and a large number of calli were induced on the MS medium containing 1.0mg/L NAA or 1.0 mg/L 2,4-D. The albino calli regenerated multiple albino plantlets in the MS medium containing 0.1mg/L NAA + 1.0 mg/L BAP. No significant differences between the wild-type and albino plants were detected in the multiple shoot induction, callus formation from the explants and the plantlets regeneration from calli. In addition, albino plants have a similar organogenesis Pattern to that of the wild-type in the media with different combinations of NAA (0 to 5.0mg/L) and BAP (0 to 5.0mg/L) treatment. These results indicate that the albino mutant has the same normal regeneration ability as that of wild-type, although the mutant has lost functions in photosynthesis, such as pigmentation.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.381-391
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• 2011

Weathering can reduce rock strength and eventually affect the structural stability of a rock mass, which is important in the field of engineering geology. Several methods have been developed to evaluate the degree of weathering, including the chemical weathering index. In this study, we analyzed the weathering degree and characteristics of microtextures and pores in crystalline rocks (gneiss and granites) based on petrographic observations, the chemical weathering index, mineralogy by XRD, microtextural analysis by SEM/EDS, measurements of pore size and surface area by the BET method, and microporosity by X-ray CT. The formation of secondary minerals and microtexture in gneiss and granitic rocks are assumed to be affected by complex processes such as dissolution, precipitation, and fracturing. Hence, it is clear that some chemical weathering indices that are based solely on whole-rock chemistry (e.g., CIA and CWI) are unable to provide reliable assessments of the degree of weathering. Great care is needed to evaluate the degree of chemical weathering, including an understanding of the mineralogy and microtexture of the rock mass, as well as the characteristics of micropores.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.994-999
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• 1997

The sintering properties of hydroxyapatite isolated from tuna bone and hydroxyapatite-containing wollastonite sintered by solid-state reaction was investigated. As the sinterability of hydroxyapatite dependent upon the particle size by dry milling, it showed a sintering. But the hydroxyapatite-containing wollastonite was appeared good sinterability. On X-ray measurements, the major phases of hydroxyapatite-containing wollastonite by solid state reaction at $1250^{\circ}C$ were identified as hydroxyapatite and pseudowollastonite(${\alpha}-CaSiO_3$). And the phases appeared as whitlockite [$Ca_3(PO_4)_2$] by decomposition of hydroxyapatite at higher temperature above $1250^{\circ}C$. The shapes of microstructure on SEM images changed from porous to dense bulk by elevating temperature. The mean bending strength of hydroxyapatite-containing wollastonite sintered by solid-state reaction at $1300^{\circ}C$ was about 18 MPa, it was close to the cancellous bone's maximum strength, 20 MPa.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.7
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• pp.1055-1061
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• 2014

Innovative freezing technology is currently applied to preserve foodstuffs for long-term storage. Generally, the quality of frozen food is closely related to the types of freezing and thawing processes. In this study, we characterized the physicochemical properties of onions depending on freezing rate. When onions were frozen at $-40^{\circ}C$, freezing rates were 0.1, 0.5, and $0.7^{\circ}C/min$ depending on air-blast quick freezer mode. Onions were thawed by microwave irradiation at 400 W. Hardness of onion dramatically decreased after freezing and thawing compared with blanched onion. However, the fastest freezing rate did not affect hardness. Thawing loss of onion decreased with a faster freezing rate. For morphological observation, onion frozen at a faster rate showed a smaller ice-crystal size. Vitamin C content decreased upon blanching or freezing, but there was no significant difference according to freezing rate. Although free sugar content also decreased upon blanching and freezing, its highest content was at $0.7^{\circ}C/min$ freezing. Among organic acids, malic acid content was highest at $0.7^{\circ}C/min$ freezing. Based on this study, it could be suggested that a faster freezing rate is effective to improve frozen food quality in accordance with preventing tissue damage or minimizing destruction of nutrients.

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.799-805
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• 2001

Two commercial alumina powders having different particle size of $0.5{\mu}m$ and 3${\mu}$m were presintered at 1120$^{\circ}$C for 2h and then lanthanum aluminosilicate glass was infiltrated at 1100$^{\circ}$C for up to 4h to obtain the densified glass-alumina composites. The effect of alumina particle size on packing factor, microstructure, wetting, porosity and pore size, and mechanical properties of the composite was investigated. The optimum mechanical properties and compaction behavior were observed for the 3${\mu}$m alumina particle dispersed composite. The 3${\mu}$m alumina particle size and distribution for he preform were within 0.1 to 48${\mu}$m and bimodal and random orientation. The strength and the fracture toughness of the composite having 3${\mu}$m alumina particles were 519MPa and $4.5MPa{\cdot}m^{1/2}$, respectively.

• Clean Technology
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• v.24 no.3
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• pp.239-248
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• 2018

In this study, pervaporation experiments of water, ethanol and IPA (Isopropyl alcohol) single components and water/ethanol, water/IPA mixtures were carried out using zeolite 4A membranes developed by Fine Tech Co. Ltd. Those membranes were fabricated by hydrothermal synthesis (growth in hydrothermal condition) after uniformly dispersing the zeolite seeds on the tubular alumina supports. They have a pore size of about $4{\AA}$ by ion exchange of $Na^+$ to the LTA structure with Si/Al ratio of 1.0, and shows strong hydrophilic property. Physical characteristics of prepared membranes were evaluated by using SEM (surface morphology), porosimetry (macro- or meso- pore analysis), BET (micropore analysis), and load tester (compressive strength). Pervaporation experiments with various temperature and concentration conditions confirmed that the zeolite 4A membrane can selectively separate water from ethanol and IPA. Water/ethanol separation factor was over 3,000 and water/IPA separation factor was over 1,500 (50 : 50 wt%, initial feed concentration). Pervaporation behaviors of single components and binary mixtures were predicted using ACM (activity coefficient model), GMS (generalized Maxwell Stefan) model and DGM (Dusty Gas Model). The adsorption and diffusion coefficients of the zeolite top layer were obtained by parameter estimation using GA (Genetic Algorithm, stochastic optimization method). All the calculations were carried out using MATLAB 2018a version.