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        검색결과 4,563

        2341.
        2008.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The mechanochemical process were employed to prepare the red phosphors (Y,Gd). The main factors affecting particle size, particle distribution, and luminescent properties of the product were investigated in details. Particles sized around 200-600 nm are formed after intensive milling. The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectrum. Results revealed that phosphors with different morphology, small particle size and high luminescence intensity could be obtained by mechanochemical process
        4,000원
        2342.
        2008.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Functional nanomaterial is expected to have improved capacities on various fields. Especially, metal nanoparticles dispersed in polymer matrix and metal nanofiber, one of the functional nanomaterials, are able to achieve improvement of property in the electric and other related fields. In this study, the fabrication of metal (Ag) nanoparticle dispersed nanofibers were attempted. The Ag nanoparticle dispersed polymer nanofiber and Ag nanofiber were fabricated by electrospinning method using electric force. First, PVP/ nanofibers were synthesized by electrospinning in voltage with the starting materials (Ag-nitrate) added polymer (PVP; poly (vinylpyrrolidone)). Then Ag nanoparticle dispersed polymer nanofibers were fabricated to reduce hydrogen reduction at for 3hr. And Ag nanofibers were synthesized by the decomposited of PVP at for 3hr. The nanofibers were analyzed by XRD, TGA, FE-SEM and TEM. The experimental results showed that the Ag nanofibers could be applied in many fields as an advanced material.
        4,000원
        2343.
        2008.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Ultrafine TiC-5%Co powders were synthesized by spray drying of aqueous solution of TiO slurry and cobalt nitrate, followed by calcination and carbothermal reaction. The oxide powders with carbon powder was reduced and carburized at under hydrogen atmosphere. During reduction, CO gas was mainly evolved by reducing reaction of oxides. Ultrafine TiC-5%Co powders were easily formed by carbothermal reaction at due to using ultrafine powders as raw materials. The ultrafine WC-TiC-Co alloy prepared by sintering of mixed powder of ultrafine WC-13%Co powder and ultrafine TiC-5%Co powder has higher sintered density and mechanical properties than WC-TiC-Co alloy prepared by commercial WC, TiC and Co powders
        4,000원
        2344.
        2008.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The objective of the present study is to investigate the increase in the functional characteristics of a substrate by the formation of a thin coating layer. Thin coating layers of have high potential because exhibits high hardness. Shock induced reaction synthesis is an attractive fabrication technique to synthesize uniform coating layer by controlling the shock wave. Ti and Si powders to form using shock induced reaction synthesis, were mixed using high-energy ball mill into small scale. The positive effect of this technique is highly functional coating layer on the substrate due to ultra fine substructure, which improves the bonding strength. These materials are in great demand as heat resisting, structural and corrosion resistant materials. Thin coating layer was successfully recovered and showed high Vickers' hardness (Hv=1183). Characterization studies on microstructure revealed a fairly uniform distribution of powders with good interfacial integrity between the powders and the substrate.
        4,000원
        2345.
        2008.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In order to investigate a nitriding process of spent oxide fuel and the subsequent change in thermal properties after nitriding, simulated spent fuel powder was converted into a nitride pellet with simulated fission product elements through a carbothermic reduction process. Nitriding rate of simulated spent fuel was decreased with increasing of the amount of fission products. Contents of Ba and Sr in simulated spent fuel were decreased after the carbothermic reduction process. The thermal conductivity of the nitride pellet was decreased by an addition of fission product element but was higher than that of the oxide fuel containing fission product elements.
        4,000원
        2346.
        2008.04 구독 인증기관 무료, 개인회원 유료
        <그림 1>과 <그림 2>, <그림 3>은 통계 패키지(Econometric Views)를 사용하여 제조업용 로봇의 수출입을 2007년부터 2008년까지 추정한 값이며, 자료는 2001년도 이후의 관세청 수출입 실적자료를 활용하였다. <그림 1>은 SAENGF는 제조업용 로봇 국내생산의 추정치이며, 점선은 95% 신뢰구간을 의미한다. <그림 2>는 통계 패키지(Econometric Views)를 사용하여 제조업용 로봇의 수출을 2007년부터 2008년까지 추정한 값이며, EXPORTF는 제조업용 로봇 수출의 추정치이며, 점선은 95% 신뢰구간을 의미한다. <그림 3>은 통계 패키지(Econometric Views)를 사용하여 제조업용 로봇의 수입을 2007년부터 2008년까지 추정한 값이며, IMPORTF는 제조업용 로봇 수출의 추정치이며, 점선은 95% 신뢰구간을 의미한다. <표 1>은 국내 제조업용 로봇의 국내생산, 수출과 수입의 추정치이며, ARIMA모형을 사용하였으며, 자료는 2001년도 이후의 데이터로 관세청 수출입 실적자료를 활용하였다.
        4,000원
        2348.
        2008.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The morphology of three-dimensional (3D) cross-linked electrodeposits of copper and tin was investigated as a function of the content of metal sulfate and acetic acid in a deposition bath. The composition of copper sulfate had little effect on the overall copper network structure, whereas that of tin sulfate produced significant differences in the tin network structure. The effect of the metal sulfate content on the copper and tin network is discussed in terms of whether or not hydrogen evolution occurs on electrodeposits. In addition, the hydrophobic additive, i.e., acetic acid, which suppresses the coalescence of evolved hydrogen bubbles and thereby makes the pore size controllable, proved to be detrimental to the formation of a well-defined network structure. This led to a non-uniform or discontinuous copper network. This implies that acetic acid critically retards the electrodeposition of copper.
        4,000원
        2349.
        2008.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Fe-aluminides have the potential to replace many types of stainless steels that are currently used in structural applications. Once commercialized, it is expected that they will be twice as strong as stainless steels with higher corrosion resistance at high temperatures, while their average production cost will be approximately 10% of that of stainless steels. Self-propagating, high-temperature Synthesis (SHS) has been used to produce intermetallic and ceramic compounds from reactions between elemental constituents. The driving force for the SHS is the high thermodynamic stability during the formation of the intermetallic compound. Therefore, the advantages of the SHS method include a higher purity of the products, low energy requirements and the relative simplicity of the process. In this work, a Fe-aluminide intermetallic compound was formed from high-purity elemental Fe and Al foils via a SHS reaction in a hot press. The formation of iron aluminides at the interface between the Fe and Al foil was observed to be controlled by the temperature, pressure and heating rate. Particularly, the heating rate plays the most important role in the formation of the intermetallic compound during the SHS reaction. According to a DSC analysis, a SHS reaction appeared at two different temperatures below and above the metaling point of Al. It was also observed that the SHS reaction temperatures increased as the heating rate increased. A fully dense, well-bonded intermetallic composite sheet with a thickness of 700 μm was formed by a heat treatment at 665˚C for 15 hours after a SHS reaction of alternatively layered 10 Fe and 9 Al foils. The phases and microstructures of the intermetallic composite sheets were confirmed by EPMA and XRD analyses.
        4,000원
        2350.
        2008.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        분리막 공정은 에너지 절약형 분리공정으로 전통적인 증류 분리공정과 비교하여 높은 선택도를 나타내기 때문에 액상 혼합물 분리의 대체 공정으로서 주목받고 있다. 제올라이트 막을 비롯한 무기분리막은 유기분리막의 단점을 보완하고 혹독한 조업조건에서도 운전이 가능한 장점을 지니고 있다. 최근 기존의 제올라이트 분리막의 단점을 보완하고 더욱 향상된 분리성능을 위한 새로운 무기분리막 재료들이 연구되어지고 있다. Kalsilite는 Si/Al 비율이 1로써 기존의 4A 제올라이트와 같이 친수성을 나타낼 것으로 예상되며 세공의 크기가 4A보다 더 작은 0.36 nm로 분리막으로 제조 시 가스분리, 물/유기물 혼합물에서 물의 선택적 분리가 가능할 것이다. 본 연구에서는 Si : Al : K : H2O = 1 : 1 : 8 : 60의 원료 포성 비율을 사용하여 kalsilite 분말을 경제적으로 수열합성 할 수 있는 새로운 공정을 개발하였으며. 최적의 합성조건인 합성온도 300℃, 합성시간 6시간으로 kalsilite를 합성할 수 있었다. XRD 분석을 통하여 kalsilite임을 확인하였으며 입도 분석 결과 평균입도는 2.73 μm이었다. 증기흡착 결과 kalsilite는 유기물보다 물에 대한 흡착능력이 큰 친수성 알루미노실리케이트임을 알 수 있었다.
        4,000원
        2351.
        2008.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구에서는 기존의 이차전지의 분리막보다 좋은 성능으로 각광받고 있는 PVdF (poly(vinylidene fluoride))에 공극률을 높여 전지의 성능을 향상시켜주는 수용성 고분자인 PEG (Poly(ethylene glycol))를 첨가하여 충전용 리튬 이차전지의 분리막을 상전이 방법으로 제조하였다. 용매인 DMF (N,N-dimethylformamide)에 PVdF-PEG를 단일상으로 녹인 후 깨끗한 유리판에 캐스팅하여 막을 얻었다. 기공은 증류수로 채워진 응고조에서 용매-빈용매 교환으로 형성되어진다. 주사전자현미경(scanning electron microscopy, SEM)을 이용하여 분리막의 단면 관찰을 통해 다공성을 확인하였고 UTM (universal testing machine)을 이용하여 기계적 물성을 확인하였다. PEG-10의 정체시간 30 s에서 균일한 스폰지 구조를 확인할 수 있었으며, 이는 87%의 뛰어난 공극률을 가지며 인장강도의 경우 PEG-10에서 3.72 MPa로 가장 크게 나타났고, 신장률과 모듈러스 부분에서도 역시 75.45%와 275.27 MPa로 뛰어난 성능을 나타냈다.
        4,000원
        2352.
        2008.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
          It is important to manage quality and safety of a product for coping with fast-paced world effectively. This paper demonstrates an integrated model between ISO 9001 Quality Management System and Product Safety Management System. And the paper presents a
        4,000원
        2353.
        2008.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        엽연의 모양이 다른 4종류의 잎을 식물재료로 사용 하고, 망사잎 제작을 위한 엽육제거시 sodium hydroxide( NaOH)의 농도와 처리시간의 최적 조건을 찾고자 하였다. 중국단풍(장상열)은 NaOH 60% 용액에서 50 분간, 호랑가시나무(예거치)는 NaOH 20% 용액에서 50분간, 신갈나무(천열)는 NaOH 20-60% 용액에서 70분간, 대왕참나무(전열)는 NaOH 20-40% 용액에서 70분간 열탕 처리하다 엽육제거율도 높고 관상가치가 높은 망사잎을 만들 수 있었다.
        4,000원
        2354.
        2008.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The ferroelectric properties of UV irradiated and non-irradiated PZT films prepared via photochemical metal-organic deposition using photosensitive precursors were characterized. Fourier transform infrared spectroscopy showed that complete removal of organic groups was possible through UV exposure of the spin-coated PZT precursor films at room temperature. The measured remnant polarization values of UV-irradiated and non-irradiated PZT films after annealing at 650˚C were 29 and 23 μC/cm2, respectively. The UV irradiation was found to be effective for the enhancement of the<111> growth orientation and ferroelectric property of PZT film and in the direct patterning in the fabrication of micro-patterned systems without dry etching.
        4,000원
        2355.
        2008.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In spray pyrolysis, the effects of the preparation temperature, flow rate of the carrier gas and concentration of the spray solution on characteristics such as the morphology, size, and emission intensity of Ca8Mg(SiO4)4Cl2:Eu2+ phosphor powders under long-wavelength ultraviolet light were investigated. The phosphor powders obtained post-treatment had a range of micron sizes with regular morphologies. However, the composition, crystal structure and photoluminescence intensity of the phosphor powders were affected by the preparation conditions of the precursor powders. The Ca8Mg(SiO4)4Cl2:Eu2+ phosphor powders prepared at temperatures that were lower and higher than 700˚C had low photoluminescence intensities due to deficiencies related to the of Cl component. The phosphor powders with the deficient Cl component had impurity peaks of Ca2SiO4. The optimum flow rates of the carrier gas in the preparation of the Ca8Mg(SiO4)4Cl2:Eu2+ phosphor powders with high photoluminescence intensities and regular morphologies were between 40 and 60 l/minute. Phosphor powders prepared from a spray solution above 0.5 M had regular morphologies and high photoluminescence intensities.
        4,000원
        2356.
        2008.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Ni-20Cr-20Fe-5Nb alloy with or without was manufactured by mechanical alloying process and consolidated by spark plasma sintering (SPS). The grain size of the alloy with was smaller than that of alloy without which results from the effect of suppressing grain growth. The tensile strength at room temperature was increased by the addition of but decreased abruptly at temperature above . It seems to result from the change of deformation mechanism due to fine grain size, that is, grain boundary sliding is predominant at above while internal dislocation movement is predominant at below . After conventional heat treatment process of solution treatment and aging, a small amount of phase was formed in Ni-20Cr-20Fe-5Nb alloy while a large amount of was formed in Inconel 718 in the previous report. This is due to exhaustion of Nb content by the formation of NbC during consolidation.
        4,000원
        2358.
        2008.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        ZnS- composite is normally used for sputtering target. In recent years, high sputtering power for higher deposition rate often causes crack formation of the target. Therefore the target material is required that the sintered target material should have high crack resistance, excellent strength and a homogeneous microstructure with high sintered density. In this study, raw ZnS and ZnS- powders prepared by a 3-D mixer or high energy ball-milling were successfully densified by spark plasma sintering, the effective densification method of hard-to-sinter materials in a short time. After sintering, the fracture toughness was measured by the indentation fracture (IF) method. Due to the effect of crack deflection by the residual stress occurred by the second phase of fine , the hardness and fracture toughness reached to 3.031 GPa and , respectively
        4,000원
        2359.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was carried out to develop and characterize a drinking extract of disk abalone to keep the price level and to raise a added value of disk abalone. Fresh raw disk abalone was composed of 29.3% of the shell part, 17.7% of the intestinal part, and 43.9% of the flesh part. and the amount of nutritive substances in the intestinal part were higher those in the flesh part. Arginine was the most abundant amino acid both in raw and drinking extract of disk abalone. Drinking extract prepared with 250 g of the flesh of disk abalone at 100℃ for 2 hours was better in color and overall taste than those made with 150 g or 200 g of the flesh. As the extracting temperature was gradually increased or the extracting period was gradually extended, the extracting effect was slightly improved but the color of the extract turned out to undesirable one. The desirable sea tangle extract could be made when 15 g of sea tangle was extracted in 1 l of water at 100℃ for 2 hours, and which was accorded well with the color of drinking abalone extract. From these results the best drinking extract of disk abalone can be manufactured with 250 g of the abalone flesh extracted in 1 l of water at 100℃ for 2 hours.
        4,000원
        2360.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Physicochemical and sensory properties of sponge cakes using 2 kinds of domestic wheat flour(white flour, whole wheat flour) and imported cake flour were investigated. In the proximate analysis, white flour had higher contents of water and protein compared with those of imported flour. Whole wheat flour had the highest contents of protein, lipid and ash. Regarding the batter, imported flour sample showed lower specific gravity and higher viscosity than those of domestic flour sample, implying that there was more air incorporation and higher batter stability. As a result, imported flour batter produced larger cake compared to that of domestic flour batter. But indexes of symmetry and uniformity showed no significant difference among the samples. In textural analysis using rheometer, cakes with imported flour were softer compared with that with domestic flour. In gumminess and brittleness, cakes with domestic white flour showed the highest value while that with the imported flour showed the lowest value. For the color measurements of cake crumb, no significant difference in DE was found among the samples. Regarding the cross-sections of the cake observed using SEM, imported flour produced cake with smaller and more even air cells compared to that with the domestic flour cake. In sensory evaluation, cakes with the domestic white flour showed the highest moistness value. But there was no significant difference in springiness, firmness, adhesiveness and ease of swallow among the samples. In conclusion, cakes with domestic white flour and whole wheat flour were as good as that with imported cake flour for the sponge cake preparation.
        4,000원