복합레진 수복시 상아질 표면처리가 미세 변연 누출에 미치는 영향에 관한 연구

학위논문(석사)--서울대학교 대학원 :치의학과 치과보존학전공,1996.Maste

Effect of pH and storage time on the elution of residual monomers from polymerized composite resins

학위논문(박사)--서울대학교 대학원 :치의학과 치과보존학 전공,2004.Docto

Suitability of four Korean coal ashes as an aluminosilicate source for production of geopolymers

Briquette ash and three coal ashes collected from power stations in Korea were examined. The contenr of glass and crystalline phases present in each ash was determined by XRF. Briquette ash showed a wide range from 3.39 to 15.35 of reactive Si:Al ratio due to the crystallite-size parameter dependence of dehydroxylated miscovite and dehydroxylated pyrophyllite on the refinement results.tive Si:Al ratio due to the crystallite-size parameter dependence of dehydroxylated miscovite and dehydroxylated pyrophyllite on the refinement results.1

Grinding Effects of Coal-Fired Pond Ash on Compressive Strength of Geopolymers

화력발전소 바닥재는 입자크기의 범위가 넓고 미연탄소 함량이 높아 지오폴리머의 원료로 잘 사용되지 않는다. 지오폴리머의 원료로서 바닥재가 대부분인 매립 석탄재를 대량 재활용하기 위한 가공공정을 평가하기 위하여 로드밀과 유성볼밀로 분쇄하여 지오폴리머의 강도에 미치는 영향을 알아보았다. 기계적 분쇄가 바닥재의 비정질 함량 변화에 미치는 영향은 거의 없었다. 이는 석탄재의 주요 결정질 상인 뮬라이트가 침상으로 존재하는데, 침상의 뮬라이트는 높은 강도와 인성을 갖기 때문에 비정질화되기 어렵기 때문으로 판단된다. 그러나 분쇄 효과는 입자크기를 감소시켰으며 매립 석탄재 입자의 크기 분포를 보다 균일하게 하여 알칼리와의 반응성을 증가시켰다. 로드밀은 상대적으로 입자크기의 범위를 좁게 만들었지만 입자크기 감소효과는 적었다. 그럼에도 불구하고 로드밀의 분쇄는 최대 약 37%의 압축강도를 증가시켰으며, 이는 유성볼밀의 효과와 동일하였다. 로드밀 분쇄는 매립 석탄재의 반응성을 증가시켜 지오폴리머의 원료로 대량 재활용하기에 적합한 공정이다. Bottom ash from coal fired power plants is not widely used due to a broad range of particle sizes and a high carbon content for producing geopolymers. The effect of mechanical activation on compressive strength of bottom ash- based geopolymers was examined by rod and planetary-ball milling to encourage full-fledged recycling of bottom ash, the main component of pond ash. The amount of amorphous component in the milled ash samples did not change significantly after the mechanical activation. It is presumably because needle-shaped mullite crystals, which is a major crystalline phase and grown in a glassy matrix, possess high strength and toughness, and therefore, they could endure external shocks and remain almost intact. Milling operation, however, decreased the particle size and improved the homogeneity of ash, thereby leading to increase reactivity of milled ash with alkali activators. Rod milling produced a relatively narrow particle size distribution of the milled ash particles; however, it was less effective in reducing the particle size. Nevertheless, it was interesting to observe that rod milling had equal effect on improving the compressive strength of geopolymers up to about 37%, as that of planetary ball milling. Rod milling is believed to be suitable process for enhancing the reactivity of bottom ash for large-scale recycling of bottom ash and producing geopolymers.22Nkc

Geopolymer mix design by determination of the reactive component of coal ash and its compressive strength

지오폴리머 합성을 위해 원료물질외에 사욛되는 여러가지 용매의 배합에 있어 지오폴리머의 강도를 최대화 할 수 있는 화학조성비를 만들기 위한 용매의 선택, 비울 등에 관해 고찰하였다.2

South Korea Coal Ashes as Source Materials for manufacturing Geopolymers

The coal ashes were selected for promoting mass consumption of untapped coal ash dumpedin landfills. The bulk chemical composition of coal ashes was determined using XRF. The sum of silica, alumina and iron oxide was around 90% for all coal ashes, which corresponds to Class F fly ash designated in ASTM C 618. The crystalline phases were determined as quartz, mullite, hematite, magnetite, rutile, dehydroxylated pyrophyllite, dehydroxylated muscovite and corundum. Briquette ash showed a wide range from 3.39 to 15.35 of reactive Si:Al ratio due to the crystallite-size parameter dependence of dehydroxylated muscovite and pyrophyllite on the refinement results. The alkali activators were selected on the basis of the reactive Si:Al ratio of each ashes in order to produce geopolymers having Si:Al atomic ratio 2.0 and Na:Al atomic ratio 1.20.coal ashes, which corresponds to Class F fly ash designated in ASTM C 618. The crystalline phases were determined as quartz, mullite, hematite, magnetite, rutile, dehydroxylated pyrophyllite, dehydroxylated muscovite and corundum. Briquette ash showed a wide range from 3.39 to 15.35 of reactive Si:Al ratio due to the crystallite-size parameter dependence of dehydroxylated muscovite and pyrophyllite on the refinement results. The alkali activators were selected on the basis of the reactive Si:Al ratio of each ashes in order to produce geopolymers having Si:Al atomic ratio 2.0 and Na:Al atomic ratio 1.20.1

Nanoscale enzyme reactors of organophosphorous hydrolase in mesoporous carbons for reliable and sensitive detection of organophosphate nerve agents

2

Linear Planning and Simulation for Allocation of Ambulances in a Twotiered Emergency Medical Service System

Purpose: Shorter response time is very important for critically-ill patients. The study utilized a linear planning and simulation technique to design a two-tiered system with advanced life support (ALS) ambulances. Methods: We collected the ambulance run-sheet data from a fire department from January, 2006 to December, 2007 to determine emergency medical service (EMS) demands. The location of patient ambulance stations were mapped by geocoding and the most appropriate number and location of ambulances was calculated with the linear planning method. The planning result was validated with a discrete simulation. Results: The initial enrollment was 227,377 cases of 119 calls. After geocoding, 170,472 (74.9%) cases were directly matched, 56,899 (25.0%) were indirectly matched, and (0.1%) were not matched. The latter were excluded. Using the linear planning method, the number of additional ambulances was calculated for a new two-tiered ambulance system that could achieve a 90% service level. From the current single-tiered system with 112 ambulances to a twotiered system of 211 basic life support (BLS) units and 40 ALS units, the BLS service level for minor patients could be raised to 90%. For severely-ill patients , a BLS and ALS service level of up to 82% and 89%, respectively, service level could be achieved. The new two-tiered system was validated with the discrete simulation. After the simulation, the BLS and ALS service level for severely-ill patients reached 85% and 93%, respectively. As well, a 100% BLS service level for minor patients was achieved. Conclusion: Linear planning and discrete simulation with GIS data enabled the simulation of a two-tiered ambulance system that can shorten the response time of the current single-tiered system

A study on the 3-D pore structures of geopolymer by electron tomography

시멘트의 대체 재료로 사용되고 있는 지오폴리머 재료에 대해 전자토모그래피를 수행하여 지오폴리머내에 존재하는 기공구조를 구명하고자 하였다. 전자토모그래피의 결과로 얻어진 z-slice 단면 및 3-D redering 이미지로 부터 다양한 크기의 기공들의 분포를 관찰할 수 있었으며, 크기에 대한 정량적인 분석을 시도하였다.분포를 관찰할 수 있었으며, 크기에 대한 정량적인 분석을 시도하였다.2