폐주물사를 혼입한 콘크리트의 최적배합설계를 위한 기초적 연구

박제선,김태경 江原大學校 産業技術硏究所 1996 産業技術硏究 Vol.16 No.-

The waste foundry sand might be recycled in concrete, resulting in energy saving and enviromental protection. An half Factorial Experiments were performed with the variables of W/C ratio, S/A, Sand/Waste foundry sand ratio and Slump as a preliminary study for optimum mis design of concrete. The resutls show that then W/C ratio is the most important factor to the concrete strength. The substitute fo waste foundry sand uo to 305 has little influence, saying that it can substitute the fine aggregate without damaging the concrete properties.

熟地黃의 抱製에 따른 5-hydroxymethyl-2-furaldehyde 함량 연구

이제현,고정아,황은영,홍선표 대한본초학회 2002 大韓本草學會誌 Vol.17 No.2

Objectives : Rehmanniae Radix Preparata has been used to enrich blood and supply yin for a several thousand years. We have studied on the quantity of 5-hydroxymethyl-2-furaldehyde (5-HMF) from Rehmanniae Radix Preparata at various processings and tried to develop the making method. Methods : The Rehmanniae Radix Preparata was prepared from the steaming process with rice wine, sterilized rice wine, diluted ethanol and water each other. And the change of 5-HMF was determinated. The analysis of 5-HMF was conducted by HPLC with reversed-phase C18 column and a UV detector at 280 nm. Elution was carried out at 1.0 ml/min with 5% acetonitrile. Results and Conclusions : From this analysis, we found out that the content of 5-HMF was increased with the number of processing times and the content of 5-HMF from Rehmanniae Radix Preparata steamed for 4 times was the same as that of Korea pharmacopoeia.

불소화합물의 골육종 및 구강암 세포주에 대한 독성의 비교분석

송제선,이백수,김정희 한국환경독성학회 1999 환경독성보건학회지 Vol.14 No.3

Fluorination of drinking water has been used world widely to reduce the incidence of caries. Recently, contradictory results on the cytotoxicity of fluoride compounds are reported. In addition, there are attempts to use fluorosilicate for fuorination of drinking water in Korea, therefore, we tried to analyze the cytotoxicity of fluoride compounds on oral epidermoid carcinoma (KB and A253) and osteosarcoma (HOS and MG-63) cells in this study. We treated cells with 0, 10, 50 and 250 ppm of fluorosilicic acid (domestic or from Fluka, F_(6)H₂Si), sodium fluorosilicate (F_(5)Na₂Si), sodium fluoroacetate (FCH2CO2Na), sodium fluoride (NaF) or potassium fluoride (KF) and measured the relative cell survival by Mn' assay. At the concentration of C 10 ppm, no significant cytotoxicity was observed. At 50 ppm, each cells revealed different response to fluoride treatment. Among cells used in this study, MG-63 was the most resistant to fluoride treatment. Comparable toxicity data from domestic and imported fluorosilicic acids were obtained. When we compared the relative cytotoxicity of fluoride compounds against their fluoride contents, the differences in relative cell survival were smaller. Most of cells showed C 20% of survival at 250 ppm. In order to analyze the pH dependence of the cytotoxicity of fluorosilicates, the pH of cell culture media containing fluorosilicate was adjusted to 7.4 or 6.5 and the relative cytotoxicity was measured. At lower pH, about 10% higher cytotoxicity was obtained. Thus, our data suggested that the toxicity of domestic fluorosilicic acid was sirnilar to that of fluorosilicic acid from Fluka, and the cytotoxicity of fluoride compounds was dependent an the relative content of fluoride and pH.

액상 실리카륨을 혼입한 콘크리트의 파괴특성

박제선,민창동,김태경,이주형 江原大學校 産業技術硏究所 1995 産業技術硏究 Vol.15 No.-

The experimental study is conducted to analyze the characteristics of concrete included silica fume. The workability of concrete is controled by the ratio of mixture, such as superplastcizer, based on the constant rates of sand and cement. It is concluded that the strength and the frectu Toughness of concrete with silica fume are very improved.

電子商去來의 擴散과 價格構造, 企業戰略

崔善奎,李明豪,趙伯濟 서울大學校經濟硏究所 2001 經濟論集 Vol.40 No.4

이 글에서는 최근 전자상거래의 비중이 높아짐에 따라 경제학의 주요 연구대상인 가격구조, 시장의 효율성, 기업의 전략 측면에서는 어떤 이슈가 생성·연구되고 있는지 살펴보고 있다. 이 논문에서 다루고 있는 주요 내용은 다음과 같다. 소비자의 탐색비용이 낮아짐에 따라 전자상거래에서 팔리고 있는 제품의 전반적인 가격수준은 오프라인에 비해선 낮아지고 있다. 전자상거래가 소비자 수요의 가격탄력성에 미치는 영향은 양면적으로 보인다. 전자상거래의 가격구조에서 흥미로운 사실은 오프라인에 비해서 동일 제품에 대한 가격분산의 폭이 크다는 것이다. 전자상거래가 확산되면서 가격경쟁이 벌어질 경우 디지털 정보재화시장에서의 가격은 한계비용인 영에 근접하기 쉽다. 기업들은 가격경쟁을 회피하는 방안으로 여러 가지 차별화전략을 구사하게 되고, 새로운 중계기관이 생겨나고 있다. 또 기존의 예상과는 구매자-판매자 관계는 시장 지향적이라기 보다는 위계 지향적인 관계가 주류를 이루고 있는 것으로 나타난다. 인터넷의 등장과 전자상거래의 확산으로 기업전략 측면에서 제품의 효과적인 개인화 방법, 브랜드 관리기법, 인터넷 광고의 효과성, 전자상거래 하에서의 여러 혁신적인 가격차별전략(경매가격, 실시간 동적 가격차별), 기존의 유통채널과 온라인 유통채널 간의 갈등(channel conflict) 등의 문제가 나타나고 있다.

첨가질량이 존재하는 변단면 4변고정 적층복합판으 진동해석

박제선,김경진,원치문,심도식 江原大學校 産業技術硏究所 1995 産業技術硏究 Vol.15 No.-

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross-sections and with arbitrary boundary conditions was developed and reported by D. H. Kim in 1974. This method has been developed for two-dimensional problems including the laminated composite plates and was proved to be very effective for the plates with arbitrary boundary conditions and irregular sections. In this paper, the result of application of this method to the clamped composite plates with non-uniform cross-section and with attached point mass/masses is presented.

양생온도변화에 따른 콘크리트의 강도 예측

박제선,김태경,이주형,윤청호 江原大學校 産業技術硏究所 1997 産業技術硏究 Vol.17 No.-

The maturity concept was adopted to predict the strength of concrete, which was subjected to several temperature levels and variable curing conditions. Penetration test and compressive test were conducted to measure the initial and final setting time and the compressible strength of concrete specimen, respectively. Also, the temperature and time were measured at some time intervals for calculating the maturity. The initial and final setting were delayed as the w/c ration increased and curing temperature decreased. The relationships at the relative strength and the equivalent age were proposed at different w/c ratio for the several temperature curing conditions, and these were applied for the variable curing conditions.

폐주물사를 혼입한 콘크리트의 내구특성에 관한 연구

박제선,윤경구,이주형,용석응 江原大學校 産業技術硏究所 1997 産業技術硏究 Vol.17 No.-

This study was conducted to evaluate durability of concrete which are increasingly demanded recently. Concrete durability properties incorporating waste foundry sand was performed with the variable of W/C ratio, Sand/Waste foundry sand ratio and Air entrainment-Non air entrainment. Cylinder specimens were made and subjected to freezing and thawing cycle at -18℃ and 4℃. Dynamic modulus of elasticity were as F/T cycle increase. The results show that decreasing W/C ratio and AE concrete makes improved resistance of freezing and thawing improved. Especially, resistance for freezing and thawing is improved by Fine aggregate/Waste foundry sand ratio which is 50%, 25%, 0% in a row.

천연 Zeolite를 이용한 매립지 침출수의 고농도 암모니아성 질소 제거에 관한 연구

오재일,홍성효,이선구,최영화,안봉규 중앙대학교 기술과학연구소 2002 기술과학연구소 논문집 Vol.32 No.-

천연 제올라이트의 일종인 Clinoptilolite를 이용하여 매립지 침출수내의 암모니아성 질소를 제거하는 실험을 수행하였다. 고정상 칼럼을 이용한 인공 침출수와 실제 침출수 조건의 실험에서 배출농도가 유입농도의 5%인 시점을 파과점으로 상정할 때, 인공 침출수 조건에서의 파괴시간은 53hr, 실제 침출수 조건에서의 파과시간은 32.5hr으로 나타났다. 또한, 허용 파과점 및 소모점에서의 제올라이트 100g(건조중량)당 제거된 암모늄 이온 성분량은 인공 침출수의 경우 각각 79.30meq/100g, 93.34meq/100g이었으며, 실제 침출수의 경우 각각 48.60meq/100g, 57.60meq/100g으로 나타났다. 침출수 조건의 경우 인공 침출수에 비해 약 39% 가량의 제거 효율 저하를 보이고 있으며, 이는 실제 침출수에 존재하고 있는 공존 양이온의 영향으로 사료된다. 실제 침출수 내에서 공존 양이온의 용출 특성을 보면, Na, Ca, Mg의 용출량은 증가하나 K는 용출량이 감소하는 것으로 나타났다. This experiment was conducted to remove the ammonia nitrogen in the landfill leachate by Clinoptilolite which is a sort of the natural zeolite. In fixed-bed column test driven in the artificial and actual condition of the leachate, when the ejection concentration was supposed the point of 5% of the initial concentration as the breakthrough point, the breakthrough time was 53hr in the artificial condition of the leachate and was 32.5hr in the actual condition of the leachate. The ingredient volume of the removed ammonium ion per 100g(based upon the dry weight) of the zeolite in the allowed breakthrough point and exhaustion point were individually 79.30meq/100g, 93.34meq/100g in the artificial leachate and 48.60meq/100g, 57.60meq/100g in the actual leachate. In case of the actual condition of the leachate, the removal efficiency was decreased by 39% than the artificial condition of the leachate, and it seems to be caused by the coexist cation in the actual leachate. The ejection characteristics of the coexist cation in the actual leachate was observed that Na, Ca, Mg was increased and K was decreased.

합성섬유보강 콘크리트의 구속수축균열 제어특성연구

박제선,윤경구,이주형,최성용,김태환 강원대학교 부설 석재복합신소재 제품연구센터 1999 석재연 논문집 Vol.4 No.-

최근에 폴리프로필렌 섬유를 첨가하여 콘크리트의 인성을 증가시키고, 균열에 대한 저항성을 향상시키고자 하는 노력이 계속되어 왔다. 그러나 첨가된 섬유의 구조에 대한 이해부족으로 인하여 연구자들간에 실험결과에 대한 해석이 상이한 경우가 많았다. 이러한 연구의 일환으로 섬유의 첨가에 따른 건조수축 균열의 조절 가능성을 분석하기 위하여 섬유의 첨가에 따른 유동성과 건조수축의 변화를 조사하였다. 섬유의 첨가에 따른 유동성의 변화와 건조수축을 측정하기 위한 강제링 시편을 제작하였다. 본 연구에서는 섬유를 첨가한 콘크리트의 역학적 거동특성인 압축강도, 휨강도, 인성, 그리고 균열특성을 실험적으로 규명하고자 하였다. 본 연구는 강도 및 건조수축특성을 규명하기 위하여 수행되었고 섬유의 영향으로 인한 건조수축특성을 예견할 수 있다. Polypropylene Fibers have been used to increase the toughness of concrete and to increase the resistance to crack formation. However, there are many contradictory argument about the effectiveness of the fiber due to the lack of knowledge about the mechanism of fiber in concrete. In order to study the effect of fibers on possible crack control, the effects of fibers on workability and drying shrinkage have been studied. The workability change due to the addition of fibers has been studied, and full size concrete steel ring specimen have been cast at field to investigate the effect of fibers on the shrinkage properties. This laboratory have been performed to obtain the properties of pp fiber reinforced concrete such as compressive, flexural strength, toughness, slump, drying shrinkage crack and drying shrinkage characteristics. The present study was performed clarify the strength and drying shrinkage properties. From these results, we can expect the effect of the admixtures of polypropylene fiber for concrete and mortar about strength and drying shrinkage properties.