• Macromolecular Research
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• 제16권5호
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• pp.411-417
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• 2008

The surfaces of henequen fibers, which can be obtained from the leaves of agave plants, were treated with two different media, tap water and sodium hydroxide, that underwent both soaking and ultrasonic methods for the fiber surface treatment. Various biocomposites were fabricated with untreated and treated, chopped henequen fibers and polypropylene using a compression molding method. The result is discussed in terms of interfacial shear strength, flexural properties, dynamic mechanical properties, and fracture surface observations of the biocomposites. The soaking (static method) and ultrasonic (dynamic method) treatments with tap water and sodium hydroxide at different concentrations and treatment times significantly influenced the interfacial, flexural and dynamic mechanical properties of henequen/polypropylene biocomposites. The alkali treatment was more effective than the water treatment in improving the interfacial and mechanical properties of randomly oriented, chopped henequen/PP bio-composites. In addition, the application of the ultrasonic method to each treatment was relatively more effective in increasing the properties than the soaking method, depending on the treatment medium and condition. The greatest improvement in the properties studied was achieved by ultrasonic alkalization of natural fibers, which was in agreement with the other results of interfacial shear strength, flexural strength and modulus, storage modulus, and fracture surfaces.

• 한국식품과학회지
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• 제26권3호
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• pp.300-304
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• 1994

고추장의 유통기간 중 품질변화를 예측하기 위하여 숙성 완료된 고추장을 $13^{\circ}C$, $27^{\circ}C$ and $37^{\circ}C$ 에 저장하면서 품질의 변화를 측정하였다. 수분, 조단백질, 캡사이신함량은 저장 중 거의 변화하지 않았으나, 아미노태질소, 표면색도, pH는 감소하는 경향을 나타내었으며 암모니아태질소, 산도는 증가하였다. 이러한 증감현상은 저장온도가 높을수록 더욱 뚜렷하여 저장 온도가 고추장의 품질변화에 밀접한 관련이 있음을 알 수 있었다. 총균수는 저장온도 및 기간의 증가에 따라 큰 변화는 보이지 않았으며, 진균류는 검출되지 않았다. 이화학적 품질 특성과 관능검사와의 상관관계를 구한 결과 아미노태질소의 변화가 가장 높은 상관관계를 보였다. 저장기간에 따른 아미노태 질소값의 변화율은 1차 반응식으로 해석되었음, 반응상수로부터 계산된 $Q_{10}$값은 2.98이었다. 또한, Arrhenius equation을 이용하여 활성화에너지를 구한 결과 15.84 Kcal/mole인 것으로 나타났다.

• 대한금속재료학회지
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• 제50권3호
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• pp.256-262
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• 2012

This study investigated the hydrogen storage properties of Zr-Based $AB_{2-x}M_x$ metal hybride made by HCS (Hydriding Combustion Synthesis). The materials were prepared by HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm, HCS 80 wt% $AB_2$-20 wt% Mg and pure Zr-Based $AB_2$, These materials were activated at 298 K under 20 bar. Both HCS 80 wt% $AB_2$-20 wt% Mg and HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm were absorbed within 1 minute. In the case of the $AB_2$, it was perfectly absorbed within 6 minutes. Then, the materials were evaluated to obtain P-C-T (Pressure-Composition-Temperature) curves at 298K. As a result, the hydrogen storage capacity of HCS 80 wt% $AB_2$-20 wt% Mg, HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm and pure Zr-Based $AB_2$ were determined to be 1.2, 1.6 and 1.74 wt%, respectively. The activation energy and rate controlling step were calculated by the Johnson-Mehl Avrami equation. The activation energies of HCS 80 wt% $AB_2$-20 wt% Mg, HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm and pure Zr-Based $AB_2$ were 26.91, 20.45, and 60.41 kJ/mol, respectively. Also, the values of ${\eta}$ in the Johnson-Mehl Avrami equation for HCS 80 wt% $AB_2$-20 wt% Mg, HCS 80 wt% $AB_2$-15 wt% Mg-5 wt% Mm and pure Zr-Based $AB_2$ are 0.60, 0.51, and 0.44. So, the rate controlling steps which indicate hydrogen storage mechanism are an one dimensional diffusion process.

• Korean Chemical Engineering Research
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• 제52권2호
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• pp.166-174
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• 2014

본 연구에서는 점화제로 사용되는 $B-KNO_3$의 가속노화 실험에 따른 특성변화를 고찰하였다. 점화제는 보관 방법이나 보관기간에 따라 점화 효율이 저하되는 경향이 있으며 안정된 사용을 위해서는 이에 대한 명확한 이해가 필요하다. 따라서 노화에 대한 원인 규명을 위해 가속화 시험 시편의 미세구조와 결정구조 및 열분석을 수행하였으며 점화 특성에 끼치는 영향성을 규명하고자 하였다. 산화제로 첨가된 $KNO_3$의 결정구조를 분석함으로써 노화에 끼치는 산화제 영향을 해석하였다. 결론적으로 산화제의 결정구조가 안정한 구조로 변화되었으며 활성화 에너지변화에 영향을 끼쳤다.

• 한국수소및신에너지학회논문집
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• 제14권4호
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• pp.321-326
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• 2003

We tried to improve the $H_2$-sorption properties of Mg by mechanical grinding under $H_2$ (reactive grinding) with CoO. The sample Mg+10wt.%CoO as prepared absorbs 1.25wt.% hydrogen and the activated sample absorbs 2.39wt.% hydrogen for 60min at 598K, $11.2barH_2$. The reactive grinding of Mg with CoO increases the $H_2$-sorption rates by facilitating nueleation(by creating defects on the surface of the Mg particles and by the additive), by making cracks on the surface of Mg particles and reducing the particle size of Mg and thus by shortening the diffusion distances of hydrogen atoms. Hydriding-dehydriding cycling increases the $H_2$-sorption rates by making cracks on the surface of Mg particles and reducing the particle size of Mg.

• Macromolecular Research
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• 제16권3호
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• pp.253-260
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• 2008

Environmentally friendly biocomposites were made using plant-based natural fibers, such as henequen and kenaf. The natural fiber reinforced polypropylene (PP) and unsaturated polyester (UP) biocomposites were examined in terms of the reinforcing effect of natural fibers on thermoplastic and thermosetting polymers. Kenaf (KE) and henequen (HQ) fibers were treated with an electron beam (EB) of 10 and 200 kGy doses, respectively, or with a 5 wt% NaOH solution. Four types of biocomposites (KE/PP, HQ/PP, KE/UP and HQ/UP) were fabricated by compression molding and each biocomposite was characterized by dynamic mechanical analysis and thermogravimetric analysis. The kenaf fiber had the larger reinforcing effect on the dynamic mechanical properties of both PP and UP biocomposites than the henequen fiber. The highest storage modulus was obtained from the biocomposite with the combination of UP matrix and 200 kGy EB treated kenaf fibers.

• Elastomers and Composites
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• 제54권1호
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• pp.22-29
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• 2019

Chitosan-polyvinyl alcohol (PVA) -bamboo charcoal/silica (CS-PVA-BC/SI) hybrid fillers with compatibilized styrene-butadiene rubber (SBR) composites were fabricated by the interpenetrating polymer network (IPN) method. The structure and composition of the composite samples were characterized by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). The viscoelastic behaviors of the rubber composites and their vulcanizates were explored using a rubber processing analyzer (RPA) in the rheometer, strain sweep and temperature sweep modes. The storage and loss moduli of SBR increased significantly with the incorporation of different hybrid fillers, which was attributed to the formation of an interphase between the hybrid fillers and rubber matrix, and the effective dispersion of the hybrid fillers. The mechanical properties (hardness, tensile strength, oxygen transmission rate, and swelling rate) of the composite samples were characterized in detail. From the results of the mechanical test, it was found that BC-CS-PVA0SBR had the best mechanical properties. Therefore, the BC-CS-PVA hybrid filler provided the best reinforcement effects for the SBR latex in this research.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1311_1312
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• 2009

In this article, current state of development of energy storage system using superconductor was summarized. As a result of continuous efforts, high critical current density exceeding $10^4\;A/cm^3$ at 77K and strong levitation capacity have been achieved in Y-Ba-Cu-O superconductor which is fabricated by melting technique. Various applications using the levitation properties of high-Tc superconductor is expected to come true in near future.

• 태양에너지
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• 제17권2호
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• pp.43-53
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• 1997

Characteristics and properties of batteries applicable to the photovoltaic system are described in this paper. The use of a number of different types of batteries and designs depends on the many and varied requirements for battery power and the different environmental and electrical conditions under which they must operate. Most of the batteries used in PV systems are lead/acid batteries, though nickel/cadmium batteries are used for small applications in locations with extreme climates or where high reliability is essential such as spacecraft. The vanadium redox battery has been acknowledged as a promising energy storage system for a wide range of applications.

• 한국전기전자재료학회논문지
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• 제27권6호
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• pp.399-406
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• 2014

Thermal batteries are used for military power sources that require robustness and long storage life such as missiles and torpedoes. $FeS_2$ powder is currently used for cathode materials because of its high specific energy density, environmental non-toxicity and low cost. However, large particle size of conventional $FeS_2$ has been deterred its possible application for higher power thermal batteries. In order to improve the power density, high energy ball milling of $FeS_2$ has been introduced to crush the micron-sized $FeS_2$. Discharge characteristics of the single cells fabricated with nano-materials and conventional $FeS_2$ powder were evaluated.