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        검색결과 550

        281.
        2009.09 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The silver nanofluids were synthesized by the pulsed wire evaporation (PWE) method in a liquid-gas mixture. The size and microstructure of nanoparticles in the deionized water were investigated by a particle size analyzer (PSA), transmission electron microscope (TEM), and scanning electron microscope (SEM). Also, the synthesized nanofluids were investigated in order to assess the stability of dispersion of nanofluid by the zetapotential analyzer and dispersion stability analyzer. The results showed that the spherical silver nanoparticle formed in the deionized water and mean particle size was about 50 nm. Also, when explosion times were in the range of 20~200 times, the absolute value of zeta potential was less than -27 mV and the dispersion stability characteristic of low concentration silver nanofluid was better than the high concentration silver nanofluid by turbiscan.
        4,000원
        282.
        2009.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        3-D shape soft magnetic composite parts can be formed by general compaction method of powder metallurgy. In this study, the results on the high density nanostructured Fe-Si/Fe composite prepared by a warm compaction method were presented. Ball-milled Fe-25 wt.%Si powder, pure Fe powder and Si-polymer were mixed and then the powder mixture was compacted at various temperatures and pressures. Pore free density of samples up to 95% theoretical value has been obtained. The warm compacted sample prepared at 650 MPa and 240℃ had highest compaction properties in comparison with other compacts prepared at 300, 400 MPa and room temperature and 120℃. The magnetic properties such as core loss, magnetization saturation and coercivity were measured by B-H curve analyzer and vibration sample magnetometer.
        4,000원
        284.
        2009.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was performed to investigate the effect of extract mixture(IPGE) drink from Inonotus Obliquus, Phellinus Linteus and Ganoderma Lucidum on hematopoietic stem cells and lymphocyte subset[lymphocyte, CD4+ T cell, CD8+ T cell, Natural Killer(NK) cells] of blood in 37 participants who were healthy and about 40~70 years old. They were divided into two groups; extract mixture drink administration group(n=27) and placebo administration group(n=12). They were given the test drink daily for 4 weeks. Blood was obtained from the subjects every two week in the beginning of administration day to evaluate the CD34+ hematopoietic stem cells and immune cells. As results, CD34+ hematopoietic stem cells were significanly increased after taking IPGE drink for 4 weeks compared to that before taking the drink (p < 0.001). There was no significant changes in number of lymphocytes, CD4+ T cells, CD8+ T cells, NK cells and in the ratio of CD4+/CD8+ cell after taking the test drink. From these results, it was suggested that IPGE have a good health effect by promoting the proliferation of the hematopoietic stem cells.
        4,000원
        285.
        2009.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 마샬 시험기를 이용하여 아스팔트 혼합물의 균열저항성을 평가할 수 있는 보다 간편하고 합리적인 측정시스템을 개발하는데 목적이 있다. 균열저항성 평가를 위한 파라메타로서 파괴에너지를 이용하였다. 마샬 시험기는 기본적으로 공시체 외부에 거치한 LVDT를 이용하여 수직변형률을 측정하는 시스템이며, 이 같은 외부 수직변형률 측정방식은 하중 스트랩 부분에서 발생하는 국부적인 변형으로 인해 측정오차를 야기할 가능성이 있다. 따라서 추가적인 계측 시스템을 설치하지 않고 기본적인 마샬 시험기를 이용하여 혼합물의 파괴에너지를 측정하기 위해서는 공시체 외부에 거치한 LVDT를 이용한 수직변형률 측정값이 파괴에너지 산정에 적용가능한지 여부를 검증하여야 한다. 이를 위해 본 연구에서는 공시체 중앙부분에서의 수평변형률과 외부에 거치한 LVDT를 이용한 수직변형률을 측정하는 두 가지 방식의 간접인장강도실험을 수행하여 그 차이를 비교 분석하였다. 실험결과, 외부 수직변형률 측정의 문제점으로 지적되었던 하중 스트랩 부분에서 발생하는 국부적인 변형은 파괴시점 이전에는 극히 적은 것으로 나타나 파괴에너지 계산에 오차를 유발하지 않음을 보여주었다. 또한 외부 수직변형률 측정의 실험변동성을 확인한 결과, 변동계수가 15% 이하로 마샬시험기를 이용한 균열저항성 평가시스템에 이용 가능함을 알 수 있었다.
        4,000원
        286.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Demineralized Freeze Dried Bone(DFDB) graft material have been used for reconstruction of large bony defects or augmentation of thin alveolar ridge during implantation of titanium fixtures. But at present osteogenic effect of DFDB do not overcome the capacity of autogenic bone graft. Thus many investigators had applicated various bioactive substance to DFDB to enhance the ability of osteogenesis of DFDB. In this study, mixture of grafting material was made from fibrin glue(F) and DFDB(D)(group 1: F+D), fibrin glue, DFDB and rhBMP-2(B) (group 2: F+D+B), fibrin glue, DFDB, polylactic- co-glycolic acid(PLGA)(P) and rhBMP-2(goup 3: F+D+B+P), fibrin glue, DFDB, PLGA, rhBMP-2 and autogenic osteoblasts( O)(group 4: F+D+B+P+O), and fibrin glue, DFDB, autogenic osteoblasts (group 5: F+D+O). During first surgical procedure, extraction of molar teeth was performed at male Biggle dog's mandible, and collected bone marrow tissue from tibia at same Biggle dog. Collected bone marrow tissue was cultured and differentiated into osteoblasts in vitro, and stored in nitrogen bottle. After four months, titanium fixture was implanted with prepared graft material to Biggle dog's mandible. After four and eight weeks respectively, experimental dog was sacrificed. Obtained tissues were prepared for examination by using resin embedded ground section method. Prepared sections were evaluated with transmitted and polarized microscope, and areas of osteoid and cacified bone were calculated with IPTK 5.0( image processing tool kit version 5.0). Resultant data was statistically analyzed by SPSS 13.0 software. Results of this study showed that autogenic osteoblats had more enhancing capacity of bone formation than rhBMP-2, but PLGA inhibited bone forming potential of bony tissue.
        4,300원
        287.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        To investigate the synergy effect on the pyrolysis of mixture of polyethylene(PE) and polystyrene(PS), the pyrolysis of PE, PS and the mixture of PE-PS was carried out in a batch reactor at the atmospheric pressure and 450℃. The pyrolysis time was from 20 to 80 mins. The liquid products formed during pyrolysis were classified into gas, gasoline, kerosene, gas oil and heavy oil according to the distillation temperatures based on the petroleum product quality standard of Korea Institute of Petroleum Quality. The analysis of the product oils by GC/MS showed that the new components produced by mixing were not detected. The synergy effect according to mixing of PE and PS did not also appear. The conversion and yield of mixtures were in proportion to the mixing ratio of sample.
        4,000원
        288.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 논문은 유색아스팔트 혼합물에 사용된 안료가 유색아스팔트 혼합물 성능에 미치는 영향에 대한 시험 및 분석결과이다. 안료 입자 크기는 필러의 입자에 비하여 매우 미세하기 때문에 배합설계시 필러 량의 조절이 필요하다. 현행의 배합설계를 조사한 결과 필러의 투입량에 관계없이 배합설계시 골재중량의 약 2%를 투입하고 있는 것으로 조사되었다. 안료의 투입은 필러의 양을 증가시키는 것으로 아스팔트 혼합물의 공극관련 인자(공극률 및 VMA)에 영향을 주어 매우 불안정한 혼합물을 구성하게 된다. 이러한 영향은 포장의 공용성과 파손에 밀접한 관련이 있으며 역학 성능(간접인장강도, 회복탄성계수, 수분 민감도 및 크리프) 저하를 초래하는 것으로 시험결과 발견되었다.
        4,000원
        289.
        2008.11 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this study, the additivity factors of compositions to density and glass transition point (Tg) in a xLi2O-(1-x)[(1-y)TeO2-yZnO] (0<x<20, 0<y<20) glass system were analyzed by using mixture design, and the change of ionic conductivity with density and Tg was discussed. As a method for predicting the relation between glass structure and ionic conductivity, density was measured by the Archimedes method. The glass transition point was analyzed to predict the relation between ionic conductivity and the bonding energy between alkali ions and non-bridge oxygen (NBO). The relation equations showing the additivity factor of each composition to the two properties are as follows: Density(g/cm3) = 2.441x1 + 5.559x2 + 4.863x3 Tg(˚C) = 319x1 + 247x2 + 609x3 - 1950x1x3 (x1 : fraction of Li2O, x2 : fraction of TeO2, x3 : fraction of ZnO) The density decreased as Li2O content increased. This was attributed to change of the TeO2 structure. From this structural result, the electric conductivity of the glass samples was predicted following the ionic conduction mechanism. Finally, it is expected that electric conductivity will increase as the activation energy for ion movement decreases.
        4,000원
        293.
        2008.10 구독 인증기관·개인회원 무료
        In soil ecosystems, chemicals are often found as mixtures. Therefore, the toxicity data generated by single toxicity tests are inadequate for assessing the potential risk of complex mixtures of chemicals for soil ecosystems. In the present study, the mixture toxicity of copper and manganese on the reproduction of Paronychiurus kimi were assessed using a Toxic Unit approach (1TU=EC50). The concentrations of each metal in the mixture were summed as follows: TUmixture = CCu/EC50 of Cu + CMn/EC50 of Mn, where CMetal are the concentrations of copper and manganese in the mixture. From the Sum TU based dose-response relationships, sum of a toxicunit (TU50) at 50% reduction for the mixture (EC50mix) was calculated. The binary mixture toxicity was defined as being concentration additiv (EC50mix=1TU) or as being more or less than additive (EC50mix<1TU or 1>TU, respectively). Also, values of the mixture (TUi) at i% reduction found were predicted to get more insight regarding the relationship between mixture toxicity and various effect levels (ranging from EC10 to EC90). The toxicities of copper and manganese mixtures were less than additive at the EC10 level, whereas more than additive at the EC90 level. These findings imply that the effect levels are important for determining the toxicity of metal mixtures.
        294.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was conducted to develop an organic control method of two spotted spider mite (Tetranychus urticae) by using cooking oil and yolk mixture (COY) through evaluating its acaricidal activity in laboratory and green house. In laboratory, there is no significant difference in acaricidal activity against T. urticae within the COY including soybean, canola (rape seed), sunflower and olive oil. The acaricidal activity against T. urticae. increased from 17.6% to 94.1% as the COY became concentrated between 0.1% to 1%. The COY acricidal activity was effected by the quantity of treatment according to application methods. The COY dealt with T. urticae eggs presented 95% of the ovicidal activity. In rose greenhouse damaged by T. urticae, the COY (0.3%) was sprayed three times and resulted in the high control value of mites between 69.0% to 89.6%.
        4,000원
        295.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 사료작물 작부체계에 따른 액상분뇨 시용수준이 호밀과 호밀-레드 클로버의 생산성 및 지력증진에 미치는 영향을 조사하기 위한 것으로, 경기도 광주시 곤지암에서 2년간 수행 되었다. 작부체계(호밀단작, 호밀-레드 클로버 혼작)를 주구, 우분액비의 시용수준(0,150, 300 kg/N/ha)를 세 구로 하여 분할구 배치법 3반복으로 실험하였다. 파종량은 호밀-레드 클로버 혼작시 호밀 130 kg/ha, 레드 클로버 20 kg/ha을 매년 파종했으며,
        4,000원
        296.
        2008.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        고준위폐기물 처분장의 완충재 및 뒷채움재 후보물질로 고려되고 있는 경주벤토나이트를 대상으로 압축 벤토나이트 및 벤토나이트-모래 혼합물의 열전도도가 측정되었다. 압축벤토나이트는 건조밀도가 에서 범위에 대해, 압축 벤토나이트-모래 혼합물은 건조밀도가 에서 사이이고, 모래의 함량이 중량비로 10 wt%에서 30 wt%인 범위의 혼합물에 대해 측정하였다. 측정시료의 수분 함량은 중량비로 10 wt%에서 20 wt% 까지 변화시켰다. 압축 벤토나이트 및 벤토나이트-모래 혼합물의 열전도도는 수분함량이 일정할 때, 건조밀도가 증가할수록, 모래 함량이 많을수록 증가하였으며, 건조밀도가 일정한 경우에는 수분 함량과 모래 함량이 증가할수록 증가하였다. 각 건조밀도에서의 수분함량의 증가에 따른 열전도도 변화를 나타낼 수 있는 실험적 관계식들이 제시되었다. 이 관계식들은 10% 오차 범위에서 압축벤토나이트 및 벤토나이트-모래 혼합물의 열전도도 값을 예측할 수 있다.
        4,000원
        297.
        2008.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Separation of naphthalene from naphthalene and 2-methylnaphthalene mixture has been studied by layered melt and solution crystallization using ethylalcohol. Purity and yield of naphthalene depended mainly on the cooling rate: The effective distribution coefficient (Keff) as the degree of impurity removal was observed to decrease with the decreasing in cooling rate. Purity of naphthalene can be enhanced to 5~7% by melt crystallization using 90% naphthalene and the purity of naphthalene can be obtained to be 99% up by solution crystallization.
        4,000원
        298.
        2008.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 poly(vinyl alcohol) (PVA)와 가교제 poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA)을 이용하여 제조된 막에 tetraethylorthosilicate (TEOS)를 도입하여 물-에탄올 계에 대한 투과증발 실험을 다양한 가교온도별(120~140℃), 조업온도별(25~70℃)로 수행하였다. TEOS의 함량은 PVA 대비 3, 5, 7 wt%를 사용하였으며, 원액의 조성은 무게비로 물 10, 20, 30 및 50%에 대하여 조사하였다. 물 에탄올 = 10 : 90 조성, 조업온도 50℃에서 선택도 1730과 투과도 16.3g/m2·hr를 PVA/7 wt% PSSA_MA/5 wt% TEOS 막이 보여 주었다.
        4,000원