Drag reduction features in the transition regime of channel flow with fibre suspension were analyzed in terms of the linear stability theory. The modified stability equation was obtained based on the slender-body theo...Drag reduction features in the transition regime of channel flow with fibre suspension were analyzed in terms of the linear stability theory. The modified stability equation was obtained based on the slender-body theory and natural closure approximation. Results of the stability analysis show attenuating effects of fibre additives to the flow instability. For the cases leading to transition, drag reduction rate increases with the characteristic parameter H of fibres. The mechanism of drag reduction by fibres is revealed through the variation of velocity profile and the decrease of wall shear stress. The theoretical results are qualitatively consistent with some typical experiments.展开更多
Molecularly imprinted polymers are generated by curing a cross-linked polymer in the presence of a template. During the curing process, noncovalent bonds form between the polymer and the template. The interaction site...Molecularly imprinted polymers are generated by curing a cross-linked polymer in the presence of a template. During the curing process, noncovalent bonds form between the polymer and the template. The interaction sites for the noncovalent bonds become "frozen" in the cross-linking polymer and maintain their shape even after the template is removed. The resulting cavities reproduce the size and shape of the template and can selectively reincorporate the template when a mixture containing it flows over the imprinted surface. In the last few decades the field of molecular imprinting has evolved from being able to selectively capture only small molecules to dealing with all kinds of samples. Molecularly imprinted polymers (MIPs) have been generated for analytes as diverse as metal ions, drug molecules, environmental pollutants, proteins and viruses to entire cells. We review here the relatively new field of surface imprinting, which creates imprints of large, biologically relevant templates. The traditional bulk imprinting, where a template is simply added to a prepolymer before curing, cannot be applied if the analyte is too large to diffuse from the cured polymer. Special methods must be used to generate binding sites only on a surface. Those techniques have solved crucial problems in separation science as well as chemical and biochemical sensing. The implementation of imprinted polymers into microfluidic chips has greatly improved the applicability of microfluidics. We present the latest advances and different approaches of surface imprinting and their applications for microfluidic devices.展开更多
The conventional charge transport models based on density- and field-dependent mobility, only having a non-Arrhenius tem- perature dependence, cannot give good current-voltage characteristics of poly （2-methoxy-5-（2...The conventional charge transport models based on density- and field-dependent mobility, only having a non-Arrhenius tem- perature dependence, cannot give good current-voltage characteristics of poly （2-methoxy-5-（2＇-ethylhexyloxy）-p-phenylene vinylene） （MEH-PPV） hole-only devices. In this paper, we demonstrate that the current-voltage characteristics can give a good unified description of the temperature, carrier density mad electric field dependence of mobility based on both the Arrhenius temperature dependence and the non-Arrhenius temperature dependence. Fu^hermore, we perform a systematic study of charge transport and electrical properties for MEH-PPV. It is shown that the boundary carrier density has an important effect on the current-voltage characteristics. Too large or too small values of boundary carrier density will lead to incorrect cur- rent-voltage characteristics. The numerically calculated carrier density is a decreasing function of the distance to the interface, and the numerically calculated electric field is an increasing function of the distance. Both the maximum of carrier density and the minimum of electric field appear near the interface.展开更多
基金the National Natural Science Foundation of China (No. 10372090 and No. 10102017).
文摘Drag reduction features in the transition regime of channel flow with fibre suspension were analyzed in terms of the linear stability theory. The modified stability equation was obtained based on the slender-body theory and natural closure approximation. Results of the stability analysis show attenuating effects of fibre additives to the flow instability. For the cases leading to transition, drag reduction rate increases with the characteristic parameter H of fibres. The mechanism of drag reduction by fibres is revealed through the variation of velocity profile and the decrease of wall shear stress. The theoretical results are qualitatively consistent with some typical experiments.
文摘Molecularly imprinted polymers are generated by curing a cross-linked polymer in the presence of a template. During the curing process, noncovalent bonds form between the polymer and the template. The interaction sites for the noncovalent bonds become "frozen" in the cross-linking polymer and maintain their shape even after the template is removed. The resulting cavities reproduce the size and shape of the template and can selectively reincorporate the template when a mixture containing it flows over the imprinted surface. In the last few decades the field of molecular imprinting has evolved from being able to selectively capture only small molecules to dealing with all kinds of samples. Molecularly imprinted polymers (MIPs) have been generated for analytes as diverse as metal ions, drug molecules, environmental pollutants, proteins and viruses to entire cells. We review here the relatively new field of surface imprinting, which creates imprints of large, biologically relevant templates. The traditional bulk imprinting, where a template is simply added to a prepolymer before curing, cannot be applied if the analyte is too large to diffuse from the cured polymer. Special methods must be used to generate binding sites only on a surface. Those techniques have solved crucial problems in separation science as well as chemical and biochemical sensing. The implementation of imprinted polymers into microfluidic chips has greatly improved the applicability of microfluidics. We present the latest advances and different approaches of surface imprinting and their applications for microfluidic devices.
基金supported by the National Basic Research Program of China (Grant No.2007CB310407)Foundation for Innovative Research Groups of the NSFC (Grant No.61021061)+1 种基金the National Natural Science Foundation of China (Grant Nos.50972023 and 61071028)the International S&T Cooperation Program of China (Grant No.2006DFA53410)
文摘The conventional charge transport models based on density- and field-dependent mobility, only having a non-Arrhenius tem- perature dependence, cannot give good current-voltage characteristics of poly （2-methoxy-5-（2＇-ethylhexyloxy）-p-phenylene vinylene） （MEH-PPV） hole-only devices. In this paper, we demonstrate that the current-voltage characteristics can give a good unified description of the temperature, carrier density mad electric field dependence of mobility based on both the Arrhenius temperature dependence and the non-Arrhenius temperature dependence. Fu^hermore, we perform a systematic study of charge transport and electrical properties for MEH-PPV. It is shown that the boundary carrier density has an important effect on the current-voltage characteristics. Too large or too small values of boundary carrier density will lead to incorrect cur- rent-voltage characteristics. The numerically calculated carrier density is a decreasing function of the distance to the interface, and the numerically calculated electric field is an increasing function of the distance. Both the maximum of carrier density and the minimum of electric field appear near the interface.
