Carbon nanotube(CNT) plays an essential role in various fields of nano based science and technology. Recently, silica coated CNT composites are interested because they are useful for the optical, magnetical, and catalytic applications. In this report, carboxyl groups were introduced on the MWCNT using nitric acid. In order to maximize the silica encapsulation efficiency, carboxyl groups of MWCNT reacted with a silane coupling agent were used to prepare silica coated MWCNT. Due to their strong interaction between modified MWCNT and TEOS. Silica layer with a controllable thickness was achieved. Silica coated MWCNT were further utilized as the template for the synthesis of hollow silica nanotubes after 800℃ calcination.
With the foundation of the WTO in 1995, the era of boundless and unlimited competition between many of the countries around the world has begun. In order to elevate the competitiveness in the international market, we have incorporated the QMS and the EMS system, establish by the International Standardization Organization, and the process has been operated under the authorization. However, many Korea companies' separate enforcement of the QMS and the EMS system is causing the dissipation of the labor force and the invested capital. As we can see through studying the contents on this paper, the number of documents has been reduced down to 54% (From 139 of them to 64 of them), and the conflict and the chaos that could have happened between the documents has been prevented. Its' outcome is attributed to the foundation and the embarkation on the Integrated Management Systems of the KS, QMS, and EMS. Not only that, it has also reduced the waste elements up to greater than 40%.
A series of molecular dynamic (MD), finite element (FE) and ab initio simulations are carried out to establish suitable modeling schemes for the continuum-based analysis of aluminum matrix nanocomposites reinforced with carbon nanotubes (CNTs). From a comparison of the MD with FE models and inferences based on bond structures and electron distributions, we propose that the effective thickness of a CNT wall for its continuum representation should be related to the graphitic inter-planar spacing of 3.4Å. We also show that shell element representation of a CNT structure in the FE models properly simulated the carbon-carbon covalent bonding and long-range interactions in terms of the load-displacement behaviors. Estimation of the effective interfacial elastic properties by ab initio simulations showed that the in-plane interfacial bond strength is negligibly weaker than the normal counterpart due to the nature of the weak secondary bonding at the CNT-Al interface. Therefore, we suggest that a third-phase solid element representation of the CNT-Al interface in nanocomposites is not physically meaningful and that spring or bar element representation of the weak interfacial bonding would be more appropriate as in the cases of polymer matrix counterparts. The possibility of treating the interface as a simply contacted phase boundary is also discussed.
Many contemporary architectural avant gardes tend to use painting as a medium to create architecture which goes beyond the rationalized spatial conception of modem architecture represented by perspectivism. They produce non perspective drawings to represent spatial Ideas, and expand it through poetic imagination to create an unexpected architectural form and space. This paper attempts to analyze the historical origin and background of dominance of drawing in the production of architecture. It was with the invention of perspective that architectural representation became important tool for architectural production. Thereafter, drawing was considered prior to actual building and architecture was considered a three dimensional realization of two dimensional drawing. Modernist avant gardes such as Cubism shattered the rationalized pictorial space of perspective and found a new pictorial space. They tried to extend it to three dimensional space through parallel projection largely based on the Hildebrand's theory of pure visibility. However, due to the ambiguity of the position of the viewing subject, their attempts could not succeed in creating a new architecture. The new architectural avant garde of the 70's rediscovered the early 20th century avant gardes in their attempt to create a new architecture which can register the fragmented spatial condition of contemporary society, and used painting as a medium to create architecture. Their difference from the early avant gardes was that they used poetic imagination rather than parallel projection in the process of projecting three dimensional space and form from the painting. However, their architecture cannot escape the scopic field of perspectivism in that they rely on the picture plane and the distance between object and viewing subject. Therefore, I conclude that in order to create architecture which goes beyond the rationalized space of modern architecture, it is necessary to resort to other tradition of modern architecture than visual one.
질화규소 요업체에서 입계상의 변화가 파괴인성에 미치는 영향에 대해 살펴보았다 실험에는 Si3N4-Y2O3-SiO2(YS)계와 Si3N4-Y2O3-A12O3(YA) 계를 사용하였으며, 1750˚C에서 Can/HIP 처리한 후 1800~2000˚C 온도구간에서 열처리시키면서 입계상의 변화에 따른 파괴인성의 변화를 조사하였다. 열처리 온도구간에서 입계상이 비정질상만으로 존재하였던 YA계의 경우는 열처리 온도가 증가되어 입성장됨에 따라 파괴인성 값이 증가되었으나, 1900˚C 이상에서 열처리될 때 입계상이 결정상에서 비정질상으로 변화하였던 YS계의 경우는 오히려 파괴인성 값이 급격히 감소되었다. YS계에서 파괴인성의 급격한 저하는 열처리 온도 증가에 따라 입계상이 결정상과 비정질상의 공존 상태에서 비정질상만의 상태로 전이하며 파괴거동에 영향을 미쳤기 때문이라고 생각된다.