为扩大射频识别系统中阅读器天线的有效识别范围,设计了一款宽波束圆极化微带天线。天线采用输出相位差为90°的功分器正交馈电激励起圆极化波,并结合圆形金属电容片耦合馈电技术、贴片表面开槽技术以及使用折叠导体墙结构。整体尺...为扩大射频识别系统中阅读器天线的有效识别范围,设计了一款宽波束圆极化微带天线。天线采用输出相位差为90°的功分器正交馈电激励起圆极化波,并结合圆形金属电容片耦合馈电技术、贴片表面开槽技术以及使用折叠导体墙结构。整体尺寸为113 mm×113 mm×13.27 mm,圆极化轴比带宽以及阻抗带宽均覆盖840~960 MHz,天线3 d B波瓣宽度为104°,增益值为4.8 d Bi。展开更多
For MHD flows in a rectangular duct with unsymmetrical walls, two analytical solutions have been obtained by solving the gov- erning equations in the liquid and in the walls coupled with the boundary conditions at flu...For MHD flows in a rectangular duct with unsymmetrical walls, two analytical solutions have been obtained by solving the gov- erning equations in the liquid and in the walls coupled with the boundary conditions at fluid-wall interface. One solution of ＇Case I＇ is for MHD flows in a duct with side walls insulated and unsymmetrical Hartmann walls of arbitrary conductivity, and another one of ＇Case II＇ is for the flows with unsymmetrical side walls of arbitrary conductivity and Hartmann walls perfectly conductive. The walls are unsymmetrical with either the conductivity or the thickness different from each other. The solutions, which include three parts, well reveal the wall effects on MHD. The first part represents the contribution from insulated walls, the second part represents the contribution from the conductivity of the walls and the third part represents the contribution from the unsymmetri- cal walls. The solution is reduced to the Hunt＇s analytical solutions when the walls are symmetrical and thin enough. With wall thickness runs from 0 to co, there exist many solutions for a fixed conductance ratio. The unsymmetrical walls have great effects on velocity distribution. Unsymmetrical jets may form with a stronger one near the low conductive wall, which may introduce stronger MHD instability. The pressure gradient distributions as a function of Hartmann number are given, in which the wall effects on the distributions are well illustrated.展开更多
文摘为扩大射频识别系统中阅读器天线的有效识别范围,设计了一款宽波束圆极化微带天线。天线采用输出相位差为90°的功分器正交馈电激励起圆极化波,并结合圆形金属电容片耦合馈电技术、贴片表面开槽技术以及使用折叠导体墙结构。整体尺寸为113 mm×113 mm×13.27 mm,圆极化轴比带宽以及阻抗带宽均覆盖840~960 MHz,天线3 d B波瓣宽度为104°,增益值为4.8 d Bi。
基金supported by the National Natural Science Foundation of China(Grant Nos.11125212 and 50936066)the International Thermonuclear Experimental Reactor Project in China(Grant No.2013GB11400)
文摘For MHD flows in a rectangular duct with unsymmetrical walls, two analytical solutions have been obtained by solving the gov- erning equations in the liquid and in the walls coupled with the boundary conditions at fluid-wall interface. One solution of ＇Case I＇ is for MHD flows in a duct with side walls insulated and unsymmetrical Hartmann walls of arbitrary conductivity, and another one of ＇Case II＇ is for the flows with unsymmetrical side walls of arbitrary conductivity and Hartmann walls perfectly conductive. The walls are unsymmetrical with either the conductivity or the thickness different from each other. The solutions, which include three parts, well reveal the wall effects on MHD. The first part represents the contribution from insulated walls, the second part represents the contribution from the conductivity of the walls and the third part represents the contribution from the unsymmetri- cal walls. The solution is reduced to the Hunt＇s analytical solutions when the walls are symmetrical and thin enough. With wall thickness runs from 0 to co, there exist many solutions for a fixed conductance ratio. The unsymmetrical walls have great effects on velocity distribution. Unsymmetrical jets may form with a stronger one near the low conductive wall, which may introduce stronger MHD instability. The pressure gradient distributions as a function of Hartmann number are given, in which the wall effects on the distributions are well illustrated.
