• Elastomers and Composites
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• 제51권3호
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• pp.195-205
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• 2016

A series of aromatic poly(hydroxyamide)s (PHAs) containing varying oligo(oxyethylene) substituents and 1,3-phenylene imide ring unit in the main chain were synthesized by the direct polycondensation reaction. The inherent viscosities of the PHAs exhibited in the range of 0.89~1.12 dL/g in DMAc or DMAc/LiCl solution. The PH-2~5 copolymers were easily soluble in strong aprotic solvents: DMAc, NMP, DMSO etc. and the PH-5 copolymer was soluble in less polar solvents such as m-creasol and pyridine with LiCl salt on heating. However, all PBOs were quite insoluble in other solvents, but only partially soluble in sulfuric acid. All copolymers (PH-2~5) could afford the flexible and tough films by solution casting. We identified that the PHAs were converted to the PBOs by the thermal cyclization reaction in the range of $200{\sim}380^{\circ}C$. The 10% weight loss temperatures and char yields of the PBOs were recorded in the range of $382{\sim}647^{\circ}C$ and 38.7~73.1% values at $900^{\circ}C$. The tensile strength and initial modulus of the PH-5 in the copolmers showed the highest values of 2.46 GPa and 49.55 MPa, respectively. The LOI values of the PHAs were in the range 26.6~29.0%, and increased with increasing 1,3-phenylene imide ring unit.

• 한국재료학회지
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• 제28권7호
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• pp.423-427
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• 2018

For diamond/metal composites it is better to use diamond particles coated with metal carbide because of improved wettability between the diamond particles and the matrix. In this study, the coating of diamond particles with a chromium carbide layer is investigated. On heating diamond and chromium powders at $800{\sim}900^{\circ}C$ in molten salts of LiCl, KCl, $CaCl_2$, the diamond particles are coated with $Cr_7C_3$. The surfaces of the diamond powders are analyzed using X-ray diffraction and scanning electron microscopy. The average thickness of the $Cr_7C_3$ coating layers is calculated from the result of the particle size analysis. By using the molten salt method, the $Cr_7C_3$ coating layer is uniformly formed on the diamond particles at a relatively low temperature at which the graphitization of the diamond particles is avoided. Treatment temperatures are lower than those in the previously proposed methods. The coated layer is thickened with an increase in heating temperature up to $900^{\circ}C$. The coating reaction of the diamond particles with chromium carbide is much more rapid in $LiCl-KCl-CaCl_2$ molten salts than with the molten salts of $KCl-CaCl_2$.

• 폴리머
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• 제33권6호
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• pp.544-550
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• 2009

본 연구에서는 $LiPF_6$ 하에서의 에폭시, 폴리에틸렌글리콜, 이미다졸 촉매, ethylene carbonate와 propylene carbonate 1:1 가소제 혼합물을 열 경화하여 [Epoxy/PEG] 고분자겔 전해질 시스템을 고안하였다. 얻어진 [Epoxy/PEG] 고분자겔 전해질의 기계적 물성을 보완하기 위해서 PVdF-HFP를 복합화하였다. [Epoxy/PEG/PVdF-HFP] 복합체 고분자겔 전해질은 기계적 안정성 및 치수 안정성이 우수하였으며, 복합체의 이온전도도는 복합체의 액체 전해질의 양뿐만 아니라 PVdF-HFP 양에 크게 의존하는 결과를 얻었다. 최적화된 고분자겔 시스템의 상온 이온전도도는 $2.56\times10^{-3}S/cm$를 나타내었다.

• Journal of Applied Biological Chemistry
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• 제57권2호
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• pp.123-129
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• 2014

The antioxidant and antimicrobial activities of Camellia oleifera seed oil were studied. Four kinds of seed oil samples were prepared, crude oil and refined oil, extracted by cold pressing method (CPC, CPR), and organic solvent extraction (OSC, OSR). Antioxidant activity analysis was measured in 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)-diammonium salt, ferric reducing Ability of Plasma, and 2,2-diphenyl-1-picrylhydrazyl assays. Besides, the percentage of inhibition of red blood cells hemolysis induced by 2,2'-azobis(2-amidnopropane) dihydrochlorid, the lag time of LDL conjugated dienes formation in vitro, and the inhibitors of loss in tryptophan fluorescence were all used to estimate the antioxidant activity of the samples. The total phenolic contents (TPC) were detemined by Folin-Ciocalteu method. The TPC of the C. oleifera seed oils can be arranged in descending order: CPC ($1.9172{\mu}g/mL$) > OSC ($1.5218{\mu}g/mL$) > CPR ($1.0611{\mu}g/mL$) > OSR ($0.6782{\mu}g/mL$). And the oils were investigated for activity against Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae and Aspergillus niger. The results showed the antioxidant activity of crude oil by cold pressing method was stronger than others, and all oils did inhibit activity of the top three bacteria expert A. niger. The further significance of the study contributes to measure the antioxidant and antimicrobial activity of the potential health benefits by the different methods of preparation and the oil of C. oleifera seeds acting as free radical scavenger, pharmaceuticals and preservatives may offer some information in medicine and cosmetic not just in food field.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.490-494
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• 2019

Experimental studies to investigate the behaviors of hydrogen in molten FLiNaK (LiF-NaF-KF) have been conducted at $500-700^{\circ}C$. On the basis of previous studies, the diffusivity and solubility of hydrogen in FLiNaK have been revised, and the expressions can be correlated to the following Arrhenius equations: $D_{H2}=1.62{\times}10^{-5}{\exp}(-48.20{\times}10^3/Rg{\cdot}T) m^2/s]$ and $S_{H2}=1.03{\times}10^{-4}{\exp}(-14.96{\times}10^3/Rg{\cdot}T) [mol-H_2/m^3/Pa]$, respectively. The behavior characteristics of deuterium in FLiNaK were studied and compared with the hydrogen behaviors in FLiNaK. The results showed the behaviors of deuterium were consistence with the behaviors of hydrogen in FLiNaK. The difference between hydrogen and deuterium has not been observed upon the experimental research of the behavior characteristics of hydrogen and deuterium in FLiNaK, which suggested the results obtained here might apply equally to the behavior characteristics of tritium in FLiNaK.

• 멤브레인
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• 제31권5호
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• pp.333-342
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• 2021

유연한 전기변색 소자(electrochromic device, ECD)는 스마트 윈도우 등 다양한 분야에서 응용이 기대되는 유망한 기술이다. 고분자 전해질은 유연한 ECD의 탈-변색 성능 및 물리적 안정성을 결정하는 중요한 구성요소이다. 본 연구에서는 효과적인 유연한 ECD 제조 및 내구성 향상을 위해 치수안정성이 우수한 세공충진 고분자 전해질 멤브레인(PFPEM)을 개발하였다. 저렴하며 물리적 및 화학적 안정성이 우수한 폴리에틸렌 재질의 다공성 지지체의 세공에 접착력이 우수한 polyvinyl acetate와 이온전도도를 향상시킬 수 있는 polyethylene glycol을 사용하여 제조한 고분자 전해질을 충진하였다. 제조된 PFPEM의 최적 리튬 염(LiTFSI) 함량은 약 27 wt%에서 결정되었으며 우수한 치수안정성와 접착 강도 그리고 종래의 고분자 전해질에 근접하는 이온전도 특성을 가지고 있음을 확인하였다. 다공성 지지체의 사용으로 가시광 투과율이 저하되었으나 변색 상태에서는 오히려 장점으로 작용할 것으로 전망되었다.

• 한국식품저장유통학회지
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• 제14권4호
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• pp.431-437
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• 2007

The primary objective of this study was to determine the effects of abalone in reducing blood pressure and increasing anti-coagulant capacity. The serum angiotensin-converting-enzyme (ACE) activities of rats on an abalone-supplemented diet did not significantly differ from the ACE levels of rats on a normal diet, at any time (before the experiment, or 1 week, 2 weeks, 3 weeks, and 4 weeks, after commencement of the abalone diet) during the experiment. This result showed that abalone-supplemented diets had no effect on the activity of ACE, which controls blood pressure. To determine if an abalone-containing diet might increase anti-coagulant capacity, both prothrombin (PT) and activated partial thromboplastin time (APTT) levels were measured. The PT levels of control rats remained constant throughout the experiment. In rats fed the abalone-containing diet, PT levels increased with time, and the increase became statistically significant after 2 weeks, when compared to pre-trial PT levels. Control rats showed no significant change in APTT levels over time. The rats fed abalone, however, showed significant differences in APTT levels. Specifically, when pre-trial APTT levels were compared with 4-week levels, and when 1-week levels were compared with 4-week levels, the differences attained statistical significance. These results indicate that an abalone-supplemented diet may inhibit blood coagulation in normal rats. The results of this study prove the inherent health value of abalone, and may encourage investment in the seafood industry. Future studies will explore other possible beneficial effects of abalone, apart from the anti-hypertension and anti-coagulant effects examined above.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권1호
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• pp.132-148
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• 2013

Via the Internet, the information infrastructure of modern health care has already established medical information systems to share electronic health records among patients and health care providers. Data hiding plays an important role to protect medical images. Because modern medical devices have improved, high resolutions of medical images are provided to detect early diseases. The high quality medical images are used to recognize complicated anatomical structures such as soft tissues, muscles, and internal organs to support diagnosis of diseases. For instance, 16-bit depth medical images will provide 65,536 discrete levels to show more details of anatomical structures. In general, the feature of low utilization rate of intensity in 16-bit depth will be utilized to handle overflow/underflow problem. Nowadays, most of data hiding algorithms are still experimenting on 8-bit depth medical images. We proposed a novel reversible data hiding scheme testing on 16-bit depth CT and MRI medical image. And the peak point and zero point of a histogram are applied to embed secret message k bits without salt-and-pepper.

• Korean Chemical Engineering Research
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• 제54권1호
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• pp.36-43
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• 2016

Hydrosilylation reactions of 2.4.6.8-tetrahydro-2.4.6.8-tetramethylcyclotetrasiloxane with allyl butyrate catalyzed by Karstedt's, $H_2PtCl_6$ and Pt/C catalyst were studied and 2.4.6.8-tetra (propyl butyrate)-2.4.6.8-tetramethylcyclotetrasiloxane was obtained. The reaction order, activation energies and rate constants were determined. Ringopening polymerization of 2.4.6.8-tetra (propyl butyrate)-2.4.6.8-tetramethylcyclotetrasiloxane in the presence of $CaF_2$, LiF, KF and anhydrous potassium hydroxide in $60-70^{\circ}C$ temperature range was carried out and methylsiloxane oligomers with regular arrangement of propyl butyrate pendant groups were obtained. The synthesized products were studied by FTIR and NMR spectroscopy. The polysiloxanes were characterized by wide-angle X-ray, gel-permeation chromatography and DSC analyses. Via sol-gel processes of oligomers doped with lithium trifluoromethylsulfonate or lithium bis (trifluoromethylsulfonyl)imide, solid polymer electrolyte membranes were obtained. The dependences of ionic conductivity of obtained polyelectrolytes on temperature and salt concentration were investigated, and it was shown that electric conductivity of the polymer electrolyte membranes at room temperature changed in the range $3.5{\times}10^{-4}{\sim}6.4{\times}10^{-7}S/cm$.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2004년도 학술논문집
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• pp.337-337
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• 2004

As one of researches for the P ＆ T purposes, a basic experiment on the recovery of actinide elements from the mixture with rare earth elements by means of electrorefining using a liquid cadmium cathode in the LiCl-KC1 eutectic melt was carried out. In order to examine the behaviors of electrodeposition of metal ions on a liquid electrode, recovery experiments of rare earth metals resulting from forming electrodeposits were performed by a galvanostatic electrolysis method at various current densities. A cyclic voltammetric technique was applied to determine reduction-oxidation potential of each metal element in the melt and to detect the changes of the multi component melt composition for on-line monitoring. Also, a collaboration study with RIAR was completed to test the preliminary feasibility on a recovery of actinide elements from the mixture with rare earth elements using a liquid cadmium cathode and actinide metals. Experimental results showed that the ratio of actinides to rare earths, 9: 0.5∼1 led to the rare earth content of about 5∼10 wt% in the deposit.