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        검색결과 5

        1.
        2015.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Impedancemetric NOx (NO and NO2) gas sensors were designed with a stacked-layer structure and fabricated using LaCrxCo1-xO3 (x = 0, 0.2, 0.5, 0.8 and 1) as the receptor material and Li1.3Al0.3Ti1.7(PO4)3 plates as the solid-electrolyte transducer material. The LaCrxCo1-xO3 layers were prepared with a polymeric precursor method that used ethylene glycol as the solvent, acetyl acetone as the chelating agent, and polyvinylpyrrolidone as the polymer additive. The effects of the Co concentration on the structural, morphological, and NOx sensing properties of the LaCrxCo1-xO3 powders were investigated with powder Xray diffraction, field emission scanning electron microscopy, and its response to 20~250 ppm of NOx at 400 oC (for 1 kHz and 0.5 V), respectively. When the as-prepared precursors were calcined at 700 oC, only a single phase was detected, which corresponded to a perovskite-type structure. The XRD results showed that as the Co concentration of the LaCrxCo1-xO3 powders increased, the crystal structure was transformed from an orthorhombic phase to a rhombohedral phase. Moreover, the LaCrxCo1-xO3 powders with 0 ≤ x < 0.8 had a rhombohedral symmetry. The size of the particles in the LaCrxCo1-xO3 powders increased from 0.1 to 0.5 μm as the Co concentration increased. The sensing performance of the stack-structured LaCrxCo1-xO3/Li1.3Al0.3Ti1.7(PO4)3 sensors was found to divide the impedance component between the resistance and capacitance. The response of these sensors to NO gas was more sensitive than that to NO2 gas. Compared to other impedancemetric sensors, the LaCr0.8Co0.2O3/Li1.3Al0.3Ti1.7(PO4)3 sensor exhibited good reversibility and reliable sensingresponse properties for NOx gases.
        4,000원
        2.
        2011.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        [ LaMeO3 ](Me = Cr, Co) powders were prepared using the polymeric precursor method. The effects of the chelating agent and the polymeric additive on the synthesis of the LaMeO3 perovskite were studied. The samples were synthesized using ethylene glycol (EG) as the solvent, acetyl acetone (AcAc) as the chelating agent, and polyvinylpyrrolidone (PVP) as the polymer additive. The thermal decomposition behavior of the precursor powder was characterized using a thermal analysis (TG-DTA). The crystallization and particle sizes of the LaMeO3 powders were investigated via powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and particle size analyzer, respectively. The as-prepared precursor primarily has LaMeO3 at the optimum condition, i.e. for a molar ratio of both metal-source (a : a) : EG (80a : 80a) : AcAc (8a) inclusive of 1 wt% PVP. When the as-prepared precursor was calcined at 700˚C, only a single phase was observed to correspond with the orthorhombic structure of LaCrO3 and the rhombohedral structure of LaCoO3. A solid-electrolyte impedance-metric sensor device composed of Li1.5Al0.5Ti1.5(PO4)3 as a transducer and LaMeO3 as a receptor has been systematically investigated for the detection of NOx in the range of 20 to 250 ppm at 400˚C. The sensor responses were able to divide the component between resistance and capacitance. The impedance-metric sensor for the NO showed higher sensitivity compared with NO2. The responses of the impedance-metric sensor device showed dependence on each value of the NOx concentration.
        4,000원
        3.
        2005.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In order to investigate the formation of AlN, mechanical alloying was carried out in and atmosphere. Differential thermal analysis (DTA), x-ray diffraction (XRD) and chemical analysis were carried out to examine the formation behavior of aluminum nitrides. No diffraction pattern of AlN was observed in XRD analysis of the as-milled powders in atmosphere. However, DTA and chemical analysis indicated that the precursors for AlN were formed in the Al powders milled in atmosphere. The AlN precursors transformed to AlN after heat treatment at and above . It was considered that the reaction between Al and was possible by the formation of fresh Al surface during mechanical alloying of Al powders.
        4,000원
        4.
        2018.12 KCI 등재 서비스 종료(열람 제한)
        The purpose of this study at water quality pollutants to propose proper management method for the Osu-A unit watershed which is the influent tributary located upstream of the Sumjin -river among the 13 unit watersheds in the Sumjin-river water system. Analyzed the correlation between flow-pollution loading and the correlation between land use type, BOD and TP items, and analyzed 8-day intervals Cumulative Flow Duration Curve (CFDC) and Load Duration Curve (LDC) to evaluate water quality damage. As a result, both BOD and TP were larger than 1 and the concentration of water pollutants increased with increasing flow. BOD was positively correlated with Urban and Field, and TP was positively correlated with Field with 0.710. As a result of the LDC, BOD was analyzed that the target water quality was achieved with the excess rate of less than 50%, and TP exceeded the target water quality by 50.1%. BOD usually exceeded the standard value (exceedance probability 50%) at low flow zone and On the other hand, TP usually exceeded the standard value at high flow zone. Monthly BOD (April to June) and TP (May to August) exceeded the standard. Sewage Wastewater treatment and non-point pollution control is Osu-A unit watersheds are effective in improving BOD and TP.
        5.
        2015.10 KCI 등재 서비스 종료(열람 제한)
        Nonalcoholic fatty liver disease (NAFLD) is a kind of liver inflammation caused by an accumulation of fat in the liver. Patients with NAFLD have an increased risk to develop liver fibrosis, which leads to cirrhosis. To investigate hepatoprotective effects of Agrimonia eupatoria L (A. eupatoria), oleic acid-induced NAFLD in HepG2 cells was used and A. eupatoria was fractionated with ethanol (EtOH), n-hexane, dichloromethane (CH2Cl2), ethyl acetate (EtOAc), n-butanol (BuOH), and H2O. Cells treated with the EtOAc fraction showed the highest lipid accumulation inhibiting effect. A. eupatoria also suppressed triglyceride accumulation and inhibited expression of lipid marker gene, such as a peroxisome proliferator activated receptor γ (PPAR-γ). Moreover, another marker, mRNA expression level of peroxisome proliferator activated receptor α (PPAR-α) was significantly increased by in a dose-dependent manner. These results suggest that A. eupatoria is a potent agent for the treatment of NAFLD.