The effect of sintering dispersed and bulk,low molecular weight(M_n=50,000 Da),nano-emulsionpolytetrafluoroethylene(PTFE)particles near their melting point is described.With the nascent particles consisting of ca.75 n...The effect of sintering dispersed and bulk,low molecular weight(M_n=50,000 Da),nano-emulsionpolytetrafluoroethylene(PTFE)particles near their melting point is described.With the nascent particles consisting of ca.75 nm diameter,hexagonal,single crystals,sintering at,e.g.,350℃,results,initially,in merger of neighboring particles,followed by individual molecular motion on the substrate and the formation of folded chain,lamellar single crystals andspherulites,and on-edge ribbons.It is suggested these structures develop,with time,in the mesomorphic“melt”.Sintering ofthe bulk resin yields extended chain,band structures,as well as folded chain lamellae;end-surface to end-surface merger,possibly by end-to-end polymerization,occurs with increasing time.展开更多
A time-domain method, based on linear velocity potential theory, is presented to study the interaction between narrow-banded random waves and perforated structures. A simple relation is derived to estimate the jet len...A time-domain method, based on linear velocity potential theory, is presented to study the interaction between narrow-banded random waves and perforated structures. A simple relation is derived to estimate the jet length of flows through the perforated wall. The reflection coefficient of narrow banded random waves from perforated structures is calculated by assuming a Rayleigh distribution of the heights of incident random waves. For reflection of narrow-banded waves from a single-chamber perforated breakwater, a comparison of the predicted and measured reflection coefficients shows that the method presented in this paper can provide a prediction better than that of regular waves. Numerical results are also reported on the reflection of narrow-banded waves from multi-chamber perforated breakwaters.展开更多
文摘The effect of sintering dispersed and bulk,low molecular weight(M_n=50,000 Da),nano-emulsionpolytetrafluoroethylene(PTFE)particles near their melting point is described.With the nascent particles consisting of ca.75 nm diameter,hexagonal,single crystals,sintering at,e.g.,350℃,results,initially,in merger of neighboring particles,followed by individual molecular motion on the substrate and the formation of folded chain,lamellar single crystals andspherulites,and on-edge ribbons.It is suggested these structures develop,with time,in the mesomorphic“melt”.Sintering ofthe bulk resin yields extended chain,band structures,as well as folded chain lamellae;end-surface to end-surface merger,possibly by end-to-end polymerization,occurs with increasing time.
基金The project partially supported by the Hong Kong Research Grant Council (DAG03/04.EG39, DAG04/05.EG32)
文摘A time-domain method, based on linear velocity potential theory, is presented to study the interaction between narrow-banded random waves and perforated structures. A simple relation is derived to estimate the jet length of flows through the perforated wall. The reflection coefficient of narrow banded random waves from perforated structures is calculated by assuming a Rayleigh distribution of the heights of incident random waves. For reflection of narrow-banded waves from a single-chamber perforated breakwater, a comparison of the predicted and measured reflection coefficients shows that the method presented in this paper can provide a prediction better than that of regular waves. Numerical results are also reported on the reflection of narrow-banded waves from multi-chamber perforated breakwaters.
