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RISS 인기검색어
- 검색키워드
- 저자 : S. H. Chew (검색결과 5 건)
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Geotextile Bags and Tubes for Beach and Riverbank Restoration
S. H. Chew,C. Y. Tan,K. E. Chua,W. H. Ho 한국토목섬유학회 2011 한국토목섬유학회 학술발표회 Vol.2011 No.11
There is an increasing popularity on the use of geotextile tubes and bags for different sizes and shapes for coastal, beach and river bank application in this region over the last 10 years. These geotextile bags, tubes, and containers are basically functioned as either a gravity mass as part of containment bunds; or massive surface protection for beach stabilization and restoration, or vegetated erosion control slope protection for river bank and riverfront; or a mean of dewatering of soft sediments contained inside. This paper summarizes the two recent projects in Singapore and Malaysia: (a) Beach restoration using specially designed geotextiles bags, and (b) Riverfront restoration using combination of geotextiles tubes and bags. It highlights the innovative and cost effective solution in these applications. For the beach restoration project in Singapore, stacked geotextile bags have been used to reconstruct the eroded shoreline due to the wave action on the beaches along the east coast of Singapore. For the riverfront project that involved reclamation and slope protection in Malaysia, geotextile tubes and bags are used as an alternative design to the conventional armor rock system and anchored bulkhead.
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S.M. Kwa,S. Ramesh,L.T. Bang,Y.H. Wong,W.J. Kelvin Chew,C.Y. Tan,J. Purbolaksono,H. Misran,W.D. Teng 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.2
The sintering of yttria-tetragonal zirconia polycrystals (Y-TZP) is commonly carried at a predefined temperature using a long holding time of 2 hours. This often has resulted in grain coarsening which affects the mechanical properties of the sintered body and low temperature degradation (LTD) behaviour of the ceramic when exposed to moist environment. In this research, the effect of using a short holding time of 1 min. during sintering coupled with small amounts (0.5 and 1 wt%) of manganese oxide, MnO2 as dopant on the mechanical properties and LTD behaviour of 3 mol% Y-TZP were investigated. The results showed that the mechanical properties improved significantly with the addition of 0.5 wt% MnO2 for the 1-min. and 12-min. holding time samples when compared to 2 hours holding time sintered at the same temperature of 1350 ℃. Nevertheless, regardless of the holding time employed, the 1 wt% MnO2 addition was not effective in improving the mechanical properties and ageing resistance of Y-TZP ceramic.
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Compressive dynamic scission of carbon nanotubes under sonication: fracture by atomic ejection
Chew, H. B.,Moon, M.-W.,Lee, K. R.,Kim, K.-S. The Royal Society 2011 Proceedings, Mathematical, physical, and engineeri Vol.467 No.2129
<P>We report that a graphene sheet has an unusual mode of atomic-scale fracture owing to its structural peculiarity, i.e. single sheet of atoms. Unlike conventional bond-breaking tensile fracture, a graphene sheet can be cut by in-plane compression, which is able to eject a row of atoms out-of-plane. Our scale-bridging molecular dynamics simulations and experiments reveal that this compressive atomic-sheet fracture is the critical precursor mechanism of cutting single-walled carbon nanotubes (SWCNTs) by sonication. The atomic-sheet fracture typically occurs within 200 fs during the dynamic axial buckling of a SWCNT; the nanotube is loaded by local nanoscale flow drag of water molecules caused by the collapse of a microbubble during sonication. This is on the contrary to common speculations that the nanotubes would be cut in tension, or by high-temperature chemical reactions in ultrasonication processes. The compressive fracture mechanism clarifies previously unexplainable diameter-dependent cutting of the SWCNTs under sonication.</P>
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E.S. Goh,L.-H. Ong,T.L. Yoon,K.-H. Chew 한국물리학회 2016 Current Applied Physics Vol.16 No.11
Symmetric BaTiO3 slabs of different thickness (6, 8 and 10-unit-cell thick) with BaO (100) surface terminations in tetragonal phase were computed by first-principles. The effects of surface termination on the structural parameters were studied. In contrast to previous literature findings, all interlayer spacings were subjected to expansions except for the outmost interlayer spacing. A comparison among three slabs with varying thickness revealed that the expansion in interlayer spacings in the 8-unit-cell thick slab is smaller than the other two slabs. The surface relaxation effects penetrated into five layers from BaO (100) surface, beyond which a trailing effect in form of small expansion of interlayer spacing was noticed and there is zero rumpling. The computed in-plane ferroelectric displacements of each layer were relatively independent of the slab thickness. In agreement of previous works, symmetric tetragonal BaTiO3 slab with BaO (100) surface terminations was predicted to possess a much smaller value of in-plane spontaneous polarization than that in the bulk case. This is due to the computed polarization value using Berry phase formalism is too small with regard to ferroelectric displacements in the TiO2 layers.
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