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성찬용,윤준노,김영익,임상혁,정덕현 충남대학교 농업과학연구소 2003 농업과학연구 Vol.30 No.2
이 연구는 플라이 애시를 결합재 중량의 20%, 재생굵은골재를 천연쇄석굵은 골재의 0%, 25%, 50%, 75%, 100%를 치환하여 압축강도와 동결융해 특성을 구명하였으며, 이 연구를 통해 얻어진 결과를 요약하면 다음과 같다. 1. 재령 28일의 압축강도는 모든 배합비와 W/B 35%에서 400㎏f/㎠이상으로 나타나 고강도콘크리트에 이용될 수 있을 것으로 생각된다. 2. 중량감소율은 동결융해 300사이클에서 1%미만으로 나타났고, 표면박리와 같은 현상은 나타나지 않았으며, 재생골재의 대체율이 증가할수록 감소율은 증가하였다. 3. 초음파진동속도는 동결융해 300사이클에서 19~24%정도의 감소율을 나타내었으며, 재생골재의 대체율이 증가할수록 감소율은 증가하는 경향을 나타내었다. 4. 상대동탄성계슈는 재생골재의 대체율에 따라 60~72%의 범위로 나타내었으며, 재생골재 대체율이 증가할수록 감소하는 경향을 나타내었다. 5. 내구성지수는 모든 배합에서 60이상을 나타내었으나, 재생골재 대체율이 100%일때는 급격히 떨어지는 경향을 나타내었다. 6. 재생굵은골재를 사용한 콘크리트의 압축강도, 중량감소율, 초음파진동속도, 상대동탄성계수, 내구성지수 시험결과를 볼 때, 시험에 사용한 재생굵은 골재는 고강도콘크리트에 사용이 가능할 것으로 판단된다. This study was performed to examine the freezing and thawing properties of the high strength concrete using recycled coarse aggregate. The recycled coarse aggregate was replaced by 0%, 25%, 50%, 75% and 100% of natural crushed aggregate. The compressive strength of the concrete used recycled coarse aggregate was shown in more than 400kgf/㎤ at the curing age 28 days. The weight loss ratio by freezing and thawing was shown in less than 1% at all mix type. The pulse velocity and relative dynamic modulus were decreased with increasing the freezing and thawing cycles. Also, durability factor for the freezing and thawing were decreased with increasing the content of recycled coarse aggregate. But, recycled concrete replaced with recycled coarse aggregate 100% was shown in more than 60 by durability factor in freezing and thawing of 300cycles Accordingly, these recycled coarse aggregate can be used for high strength concrete.
성찬용,류능환,윤준노,김영익,임상혁 강원대학교 부설 석재복합신소재 제품연구센터 2003 석재연 논문집 Vol.8 No.-
본 연구는 석분과 황토를 사용한 건자재 제품을 개발하기 위하여 황토의 첨가량를 5종류, 석분의 첨가량을 3종류로 하여 총 16종류의 모르타르에 대하여 단위중량, 흡수율, 압축강도, 휨강도, 동탄성계수, 초음파진동속도, 중성화 깊이에 대하여 구명하였다. 단위중량, 압축강도, 휨강도, 동탄성계수 및 초음파진동속도는 황토와 석분의 사용량이 증가할수록 감소하는 경향을 나타내었고, 흡수율과 중성화 깊이는 증가하는 경향을 나타내었다. 주사전자현미경에 의한 관찰에서는 비활성황토의 사용량이 증가할수록 결정이 증가한 것으로 나타났다. 황토의 사용량은 강도적인 측면에서는 결합재량의 40%까지 사용이 가능하고, 흡수율 측면에서는 10%까지 사용이 가능하며, 건자재의 사용목적에 따라 황토의 사용량을 조절하는 것이 필요할 것으로 생각된다. The purpose of this study is to obtain the basic data for the development of construction materialproducts using stone dust and non-active Hwangto. The results of physical and mechanical properties were as follows. The unit weight, compressive and flexural strengths, dynamic modulus and ultrasonic pulse velocity are decreased with increase of the stone dust and Hwangto. The absorption ratio and neutralization depth are increased with increase of the stone dust and Hwangto. In the results of SEM analysis, the crystals are increased with increase of the non-active Hwangto. Accordingly, the Hwangto may be suitably used as a cement replacement material in the construction material products.
이정동,유진혁,임채윤,박성배 한국생산성학회 2001 生産性論集 Vol.15 No.2
Learning effect has implication for the performance analysis for the LCD industry which is highly process oriented and capital intensive industry. In this study, we estimate the learning parameter in that industry and investigate the difference in learning across generations. Based on the estimated learning effect, we provide some implication for the question whether the leadership in the industry is sustainable or not.
CT 유도하의 경피적 폐생검 : 임상적 의의 및 합병증에 관한 연구 A Study of Clinical Significance and Complication
박재성,백상현,차장규,홍현숙,김대호,박성진,조준희,임한혁,이혜경 순천향의학연구소 2003 Journal of Soonchunhyang Medical Science Vol.9 No.2
Purpose : To determine the diagnostic accuracy and predicting factor of pneumothorax on CT-guided percutaneous transthoracic needle biopsy. Materials and Methods : Using automated biopsy devices, 107 CT-guided percutaneous needle biopsies of pulmonary lesions were performed. Final diagnosis was made with operation or other methods. We retrospectively analyzed the frequency of complications and diagnostic yields of 107 biopsies. The clinical features, treatment, and courses of complications were reviewed, and risk factors of pneumothorax such as depth and size of lesion, CT emphysema score of whole lung and pathway of needle, and the result of pulmonary function test were analyzed. Result : 96 biopsies(89.7%) yielded sufficient tissue for pathologic evaluation. For cases of malignant and benign disease, sensitivity was 91.5% and 87.5% respectively; the corresponding figures for diagnostic accuracy were 88.1% and 77.1%. So, sensitivity and diagnostic accuracy of percutaneous transthoracic needle biopsy was 89.7% and 83.2%. Eighteen(16.8%) of 107 patients developed pneumothorax and 3 of these required application of chest tube or percutaneous catheter drainage. In the group with pneumonthorax, the lesion was significantly smaller(p=0.029) and higher CT emphysema score of pathway of needle(p=0.032). But there were no significant difference between two groups(with or without pneumothorax) for depth of lesion, pulmonary function test(% predictive value of FEV1 and FEV1/FVC) and CT emphysema score of whole lung. Conclusion : CT-guided transthoracic needle biopsy of the pulmonary lesions is safe and easy method of obtaining specimens of good quality and quantity. It may be an useful procedure in the diagnosis of localized pulmonary lesions. For the prediction of pneumothorax, size of lesion and CT emphysema score of pathway of a needle are significant risk factors.
Reorientation of Colloidal Crystalline Domains by a Thinning Meniscus
Im, Sang-Hyuk,Park, O-Ok The Polymer Society of Korea 2004 Macromolecular Research Vol.12 No.2
When water is evaporated quickly from a water-based colloidal suspension, colloidal particles protrude from the water surface, distorting it and generating lateral capillary forces between the colloidal particles. The protruded colloidal particles are then assembled into ordered colloidal crystalline domains that float on the water surface on account of their having a lower effective density than water. These colloidal crystal domains then assemble together by lateral capillary force and convective flow; the generated colloidal crystal has grain boundaries. The single domain size of the colloidal crystal could be controlled, to some extent, by changing the rate of water evaporation, but it seems very difficult to fabricate a single crystal over a large area of the water's surface without reorienting each colloidal crystal domain. To reorient such colloidal crystal domains, a glass plate was dipped into the colloidal suspension at a tilted angle because the meniscus (airwaterglass plate interface) is pinned and thinned by further water evaporation. The thinning meniscus generated a shear force and reoriented the colloidal crystalline domains into a single domain.
Im, Sang-Hyuk,Lee, Yong-Hui,Kim, Hi-Jung,Lim, Choong-Sun,Kang, Yong-Ku,Seok, Sang-Il The Korean Electrochemical Society 2011 Journal of electrochemical science and technology Vol.2 No.3
The mesoscopic $Sb_2S_3$-sensitized photoelectrochemical solar cells using cobalt redox electrolyte exhibit nonlinear behavior of power conversion efficiency with illuminated sun intensity. From the measurement of bulk diffusion and electrochemical impedance spectroscopy studies, we suggest that the nonlinearity of device performance with illuminated sun intensity is attributed not to the slow bulk diffusion problem of cobalt electrolyte but to the limited mass transport in narrowed pore volume in mesoscopic $TiO_2$ electrode.
All solid state multiply layered PbS colloidal quantum-dot-sensitized photovoltaic cells
Im, Sang Hyuk,Kim, Hi-jung,Kim, Sung Woo,Kim, Sang-Wook,Seok, Sang Il Royal Society of Chemistry 2011 ENERGY AND ENVIRONMENTAL SCIENCE Vol.4 No.10
<P>The combination of solution processable colloidal quantum dots (CQDs) and organic conjugated polymers has attracted growing interest in the past few years, because devices fabricated using this combination can have potentially low cost and high efficiency. In this paper, we propose a new device architecture of multiply layered PbS CQD-sensitized photovoltaic cells. The multiple layers of PbS CQDs were formed by the repeated spin-coating of oleic-acid-capped PbS CQD solution and 1 wt% 1,2-ethanedithiol (EDT) solution onto mesoporous (mp)-TiO<SUB>2</SUB> as photoanode. Through the structural advantage of a sensitized type device and post-treatment in 10 wt% EDT solution for 16 h, we could fabricate efficient photovoltaic cells having an overall energy conversion efficiency of 2.9% under 1 sun illumination, and an external quantum efficiency of over 15% at zero bias with a signal attenuation to frequency of 10 kHz levels in the near-infrared (NIR) range.</P> <P>Graphic Abstract</P><P>We demonstrate the successful fabrication of multiply layered PbS CQD-sensitized PV cells. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1ee01774h'> </P>