Probability of capture for the second fundamental model of resonance

The extension of the adiabatic invariant theory for one-degree of freedom Hamiltonian systems with varying parameters proposes a way of evaluating the probability of capture from one domain of the phase space into another. We derive here analytic expressions for these probabilities for a typical model of resonance of orderN. We show that the probabilities depend only upon two parameters and not four as expected a priori.     

Directions of anhysteretic and rotational remanent magnetizations in rotating samples

Summary. These experiments support Stephenson's predictions that partial anhysteretic remanent magnetizations produced in rotating samples deviate from the steady field direction, which is collinear with the rotation axis, by amounts depending on the angle, between the alternating magnetic field axis and the rotation axis. A similar effect was observed for partial rotational remanent magnetizations. Possible differences between the two remanence types were noted.     

Nonlinear interaction of axisymmetric circulation and nonaxisymmetric disturbances in hurricanes

The nonlinear interaction of axisymmetric circulation and nonaxisymmetric disturbances in hurricanes is numerically studied with a quasigeostrophic barotropic model of a higher resolution. It is pointed out that the interaction may be divided into two categories. In the first category, nonaxisymmetric disturbances decay, the coordinate locus of maximum.relative vortic-ity (?)max is seemingly unordered, and the central pressure of hurricane rises; while in the second one, nonaxisymmetric disturbances develop, the locus of (?)max shows an ordered limit cycle pattern, and the central pressure falls remarkably. A succinct criterion is given to judge which category the interaction belongs to, i.e. the vortex beta Rossby number at the initial time Rβ< 1 belongs to the decaying category and Rβ> 1 to the developing one. Finally, practical applications of theoretical results of the rotational adaptation process presented by Zeng and numerical results in this paper to the hurricane intensity prediction in China     

Global Geometric Analysis of Ship Rolling and Capsizing in Random Waves

The nonlinear biased ship rolling motion and capsizing in random waves are studied by utilizing a global geometric method.Thompson's α-parameterized family of restoring functions is adopted in the vessel equation of motion for the representation of bias.To take into account the presence of randomness in the excitation and the response,a stochastic Melnikov method is developed and a mean-square criterion is obtained to provide an upper bound on the domain of the potential chaotic rolling motion.This criterion can be used to predict the qualitative nature of the invariant manifolds which represent the boundary between safe and unsafe initial conditions,and how these depend on system parameters of the specific ship model.Phase space transport theory and lobe dynamics are used to demonstrate how motions starting from initial conditions inside the regions bounded by the intersected manifolds will evolve and how unexpected capsizing can occur.     

DEM辅助下的倾斜航摄影像匹配方法

在倾斜航空摄影测量中,倾斜影像间由于视角差异较大,具有较大几何变形,而具备仿射尺度不变性的ASIFT算法存在效率较低的问题,提出一种DEM辅助下的倾斜航摄影像匹配方法。该方法通过利用影像的粗略外方位元素和测区的DEM数据,首先对倾斜影像进行仿射变换来减弱几何变形;然后通过SIFT特征匹配算法来获取同名点对,并使用RANSAC剔除误匹配;最后将同名点对根据单应矩阵反算回原影像,以基础矩阵估计法剔除误匹配,获得最终匹配点对。通过对多组数据进行实验,结果表明,该算法的计算效率较高,获得的匹配点对在数量和分布情况上也更为理想。     

面向宽基线立体影像匹配的高质量仿射不变特征提取方法

针对宽基线影像匹配问题,提出基于信息量和空间分布均衡性双重约束的多层次特征筛选方法,并在此基础上探讨集成该特征筛选方法、MSER(Maximally Stable Extremal Region detector)、SIFT(Scale Invariant Scale Transformation)的特征提取算法,以达到提取高质量(高信息量、空间分布均衡、高重复率)仿射不变特征的目的。实验表明,相对现有最优算法,本文方法具有更高的重复率和匹配成功率,更有利于后续的(宽基线)立体匹配。     

Kinetic Energy Budgets during the Rapid Intensification of Typhoon Rammasun (2014)

In this study, Typhoon Rammasun(2014) was simulated using the Weather Research and Forecasting model to examine the kinetic energy during rapid intensification(RI). Budget analyses revealed that in the inner area of the typhoon,the conversion from symmetric divergent kinetic energy associated with the collocation of strong cyclonic circulation and inward flow led to an increase in the symmetric rotational kinetic energy in the lower troposphere. The increase in the symmetric rotational kinetic e...     

小波域遥感图像不变纹理分类

分析了有限脊小波变换可以实现图像的旋转不变性和平移不变性,提出了结合两种小波变换提取图像纹理特征的方法,实现了在小波域中进行图像的不变纹理分类.     

基于PCA与不变矩的车标定位与识别

在车牌位置确定的情况下,利用车标边缘特点在车牌上方一定范围内检测车标.提出车标似真度的概念,将检测到的车标图像映入PCA生成的特征车标空间,得到的重构图像与原图像进行车标真实性检测,减少车标的误定位;然后利用不变矩的旋转、尺度及平移均不变的特性,定义不变矩的最小矩距离进行车标识别.通过实测车标图像的定位和识别实验表明,该方法是有效和可行的.