基于光散射技术的两种能见度探测方法的比较分析

为了提高大气能见度的仪器探测水平,并验证自行研制的车载式拉曼激光雷达探测大气水平能见度的可靠性,使用1种基于可见光波段的前向散射能见度仪,与基于后向散射原理的拉曼激光雷达进行了联合试验,对两者测量结果,进行了分析和讨论,结果表明这两种探测手段具有较高的相关性.同时,通过对前向散射原理的探讨,为能见度仪的国产化提供了参考,也检验了国内首台车载式拉曼激光雷达在测量能见度方面的可靠性,扩展了它的应用领域.     

A modification for the mask-filtering approach by superposing anisotropic derivatives in an image

We demonstrate a novel method to modify the mask-filtering approach by enlarging the gray-level difference of any two nearby pixels in an image. Derivatives are calculated in different directions respectively instead of isotropically. Some higher spatial frequencies are then selectively magnified. The final image has better sharpened fine characteristics than that enhanced by the conventional technique.     

Non-stretchable pseudo-visibility graphs

We exhibit a family of graphs which can be realized as pseudo-visibility graphs of pseudo-polygons, but not of straight-line polygons. The example is based on the characterization of vertex-edge pseudo-visibility graphs of O'Rourke and Streinu [Proc. ACM Symp. Comput. Geometry, Nice, France, 1997, pp. 119–128] and extends a recent result of the author [Proc. ACM Symp. Comput. Geometry, Miami Beach, 1999, pp. 274–280] on non-stretchable vertex-edge visibility graphs. We construct a pseudo-visibility graph for which there exists a unique compatible vertex-edge visibility graph, which is then shown to be non-stretchable. The construction is then extended to an infinite family.     

On the visibility in well-behaved random sets in Euclidean space

In Calka et al. (2009), the decay of the probability of reaching distance at least r in some direction from a given point without hitting any ball, in the Poisson Boolean model of continuum percolation, was studied. The methods used in Calka et al. (2009) include coverage techniques, and the most precise results were obtained in dimension 2. In this note, we strengthen some of the results obtained in Calka et al. (2009) to dimension 3 and higher and at the same time extend them to more general random sets.     

Improving the sharpness of an image with non-uniform illumination

We demonstrate a new method to sharpen a non-uniformly illuminated image by use of wavelet transformation employing Harr function. Both the fine characteristics and object edges in the image are well enhanced without degrading the contrast. This method provides some superiority compared to the conventional algorithms.     

A climbing girl's reflections about angles

The main research question in this paper is whether a climbing discourse can be a resource for a school-geometry discourse. The text is based on a 12-year old girl's story from an exciting climbing trip during her summer holiday. The girl uncovers some of her knowledge that had been invisible to her; she is guided to see some relations between her climbing and her understanding of angles. In the beginning, this girl believes her story does not concern angles at all. The tools for uncovering angles in her story are based on different levels of visibility and objects of the climbing discourse combined with different conceptions of space. The girl develops her consciousness about angles as natural elements in her climbing activity and she is guided to see the angle as an object of her climbing discourse.     

Investigating the time dynamics of seismicity by using the visibility graph approach: Application to seismicity of Mexican subduction zone

By using the method of the visibility graph (VG), five magnitude time series extracted from the seismic catalog of the Mexican subduction zone were investigated. The five seismic sequences represent the seismicity which occurred between 2005 and 2012 in five seismic areas: Guerrero, Chiapas, Oaxaca, Jalisco and Michoacán. Among the five seismic sequences, the Jalisco sequence shows VG properties significantly different from those shown by the other four. Such a difference could be inherent in the different tectonic settings of Jalisco with respect to those characterizing the other four areas. The VG properties of the seismic sequences have been put in relationship with the more typical seismological characteristics (b$b$-value and a$a$-value of the Gutenberg–Richter law).     

空中目标多波段红外辐射特性描述与仿真分析

针对空中目标在复杂背景下的探测需求,根据实际目标的运动特性,分析目标在飞行高度、飞行姿态角改变时的辐射特点,基于MODTRAN计算得到大气辐射和衰减数据,建立目标的三维模型、热辐射和反射模型,搭建空中目标的红外成像仿真系统.分析和仿真结果表明:在中波波段,目标尾焰的红外辐射比蒙皮强很多,在长波波段,蒙皮的红外辐射比较强,仿真图像的细节比较多,尾焰的红外辐射虽然有所减弱,红外成像效果依旧很好;相同探测条件下,由于位置越高大气越稀薄,探测器的可探测距离会变得比较远.目标红外辐射特性的分析和红外仿真系统的搭建对缩短红外探测器的研制周期和进一步确定探测器波段和系统分辨率等指标提供了参考依据.