The influences of density and dimension of carbon nanotubes on their electron emission from arrays are studied. The tip electric field of nanotubes, electric field enhancement factor, and optimum nanotube density are ...The influences of density and dimension of carbon nanotubes on their electron emission from arrays are studied. The tip electric field of nanotubes, electric field enhancement factor, and optimum nanotube density are expressed by analytic equations. The theoretical analyses show that the field enhancement factor is sensitive to nanotube density, and can be sharply improved at a specific and optimum density. Some experiments have demonstrated these. Owning to electrostatic screening effect, the length of carbon nanotubes has little effect on their emission. A uniformly-distributed carbon nanotube array model is set up, and applied to analysis of carbon nanotube arrays. The results obtained here are in good agreement with the experimental data.展开更多
The hydrodynamic performance of a bottom-hinged flap wave energy converter （WEC） is investigated through a frequency domain numerical model. The numerical model is verified through a two-dimensional analytic solutio...The hydrodynamic performance of a bottom-hinged flap wave energy converter （WEC） is investigated through a frequency domain numerical model. The numerical model is verified through a two-dimensional analytic solution, as well as the qualitative analysis on the dynamic response of avibrating system. The concept of ＂optimum density＂ of the bottom-hinged flap is proposed, and its analytic expression is derived as well. The frequency interval in which the optimum density exists is also obtained. The analytic expression of the optimum linear damping coefficient is obtained by a bottom-hinged WEC. Some basic dynamic properties involving natural period, excitation moment, pitch amplitude, and optimum damping coefficient are analyzed and discussed in detail. In addition, this paper highlights the analysis of effects on the conversion performance of the device exerted by some important parameters. The results indicate that ＂the optimum linear damping period of 5.0 s＂ is the most ideal option in the short wave sea states with the wave period below 6.0 s. Shallow water depth, large flap thickness and low flap density are advised in the practical design of the device in short wave sea states in order to maximize power capture. In the sea state with water depth of 5.0 m and wave period of 5.0 s, the results of parametric optimization suggest a flap with the width of 8.0 m, thickness of 1.6 m, and with the density as little as possible when the optimum power take-off （PTO） damping coefficient is adopted.展开更多
文摘The influences of density and dimension of carbon nanotubes on their electron emission from arrays are studied. The tip electric field of nanotubes, electric field enhancement factor, and optimum nanotube density are expressed by analytic equations. The theoretical analyses show that the field enhancement factor is sensitive to nanotube density, and can be sharply improved at a specific and optimum density. Some experiments have demonstrated these. Owning to electrostatic screening effect, the length of carbon nanotubes has little effect on their emission. A uniformly-distributed carbon nanotube array model is set up, and applied to analysis of carbon nanotube arrays. The results obtained here are in good agreement with the experimental data.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41206074 and 51205346)the Special Fund for Marine Renewable Energy (Grant Nos. GHME2011CX01 and GHME2011ZC05)
文摘The hydrodynamic performance of a bottom-hinged flap wave energy converter （WEC） is investigated through a frequency domain numerical model. The numerical model is verified through a two-dimensional analytic solution, as well as the qualitative analysis on the dynamic response of avibrating system. The concept of ＂optimum density＂ of the bottom-hinged flap is proposed, and its analytic expression is derived as well. The frequency interval in which the optimum density exists is also obtained. The analytic expression of the optimum linear damping coefficient is obtained by a bottom-hinged WEC. Some basic dynamic properties involving natural period, excitation moment, pitch amplitude, and optimum damping coefficient are analyzed and discussed in detail. In addition, this paper highlights the analysis of effects on the conversion performance of the device exerted by some important parameters. The results indicate that ＂the optimum linear damping period of 5.0 s＂ is the most ideal option in the short wave sea states with the wave period below 6.0 s. Shallow water depth, large flap thickness and low flap density are advised in the practical design of the device in short wave sea states in order to maximize power capture. In the sea state with water depth of 5.0 m and wave period of 5.0 s, the results of parametric optimization suggest a flap with the width of 8.0 m, thickness of 1.6 m, and with the density as little as possible when the optimum power take-off （PTO） damping coefficient is adopted.
