This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The exp...This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The explicit dispersion relations are derived for the two cases when the propagation directions of SH waves are normal to the interface and parallel to the interface, respectively. The asymptotic expressions for dispersion relations are also given when the wave number is extremely small. Numerical results for stop band effect and phase velocity are presented for a periodic system of alternating BaTiO3 and Terfenol-D layers. The influence of volume fraction on stop band effect and dispersion behaviors is discussed and revealed.展开更多
H0i-eigenwave characteristics of a periodic iris-loaded circular waveguide (PICW) are examined, as concerns the ei-genmode behavior vs arbitrary variations of the geometric parameters and the Bragg bandwidths vs the p...H0i-eigenwave characteristics of a periodic iris-loaded circular waveguide (PICW) are examined, as concerns the ei-genmode behavior vs arbitrary variations of the geometric parameters and the Bragg bandwidths vs the parameter of filling extremums.展开更多
In order to describe the compressibility of traffic flows and determine the compression factors, the Mach number of gas dynamics is introduced, and the concept and the formula of the compression factor are obtained. A...In order to describe the compressibility of traffic flows and determine the compression factors, the Mach number of gas dynamics is introduced, and the concept and the formula of the compression factor are obtained. According to the concept of the compression factor and its differential equation, a stop-wave model is built. The theoretical value and the observed one are obtained by the survey data in Changchun city. The relative error between the two values is 20. 3%. The accuracy is improved 39% compared with the result from the traditional stop-wave model. The results show that the traffic flow is compressible, and the methods of research on gas compressibility is also applicable to the traffic flow. The stop-wave model obtained by the compression factor can better describe the phenomenon of the stop wave at a signalized intersection when compared with the traditional stop-wave model.展开更多
FMCWSAR将调频连续波与合成孔径成像技术结合于一体，是一种新近被提出来的成像雷达体制，它以其体积小、重量轻、成本低、分辨率高等一系列优点，引起越来越多的关注。然而，在FMCWSAR系统中，雷达连续不断地发射信号，调制信号周期相...FMCWSAR将调频连续波与合成孔径成像技术结合于一体，是一种新近被提出来的成像雷达体制，它以其体积小、重量轻、成本低、分辨率高等一系列优点，引起越来越多的关注。然而，在FMCWSAR系统中，雷达连续不断地发射信号，调制信号周期相对较长，停一走（STOP AND GO）近似不再成立，所以要用合适的算法来实现成像。针对FMCW SAR的特点，详细推导了停一走近似失效时FMCW SAR的信号模型及处理过程，提出了一种改进的RD算法。此方法是通过补偿连续运动引入的多普勒频移，消除连续运动的影响。展开更多
基金supported by the National Natural Science Foundation of China (Nos.10672108,10572069 and 10820101048)
文摘This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The explicit dispersion relations are derived for the two cases when the propagation directions of SH waves are normal to the interface and parallel to the interface, respectively. The asymptotic expressions for dispersion relations are also given when the wave number is extremely small. Numerical results for stop band effect and phase velocity are presented for a periodic system of alternating BaTiO3 and Terfenol-D layers. The influence of volume fraction on stop band effect and dispersion behaviors is discussed and revealed.
文摘H0i-eigenwave characteristics of a periodic iris-loaded circular waveguide (PICW) are examined, as concerns the ei-genmode behavior vs arbitrary variations of the geometric parameters and the Bragg bandwidths vs the parameter of filling extremums.
基金The National Basic Research Program of China (973Pro-gram)(No.2006CB705505)
文摘In order to describe the compressibility of traffic flows and determine the compression factors, the Mach number of gas dynamics is introduced, and the concept and the formula of the compression factor are obtained. According to the concept of the compression factor and its differential equation, a stop-wave model is built. The theoretical value and the observed one are obtained by the survey data in Changchun city. The relative error between the two values is 20. 3%. The accuracy is improved 39% compared with the result from the traditional stop-wave model. The results show that the traffic flow is compressible, and the methods of research on gas compressibility is also applicable to the traffic flow. The stop-wave model obtained by the compression factor can better describe the phenomenon of the stop wave at a signalized intersection when compared with the traditional stop-wave model.
文摘FMCWSAR将调频连续波与合成孔径成像技术结合于一体，是一种新近被提出来的成像雷达体制，它以其体积小、重量轻、成本低、分辨率高等一系列优点，引起越来越多的关注。然而，在FMCWSAR系统中，雷达连续不断地发射信号，调制信号周期相对较长，停一走（STOP AND GO）近似不再成立，所以要用合适的算法来实现成像。针对FMCW SAR的特点，详细推导了停一走近似失效时FMCW SAR的信号模型及处理过程，提出了一种改进的RD算法。此方法是通过补偿连续运动引入的多普勒频移，消除连续运动的影响。
