Noise Characteristics of an Instrumental Particle Absorbance Technique

Noise characteristics and noise reduction techniques for the particle soot absorption spectrometer (PSAP) are discussed. It is shown through elementary propagation of errors analysis and verified through simulations and by experiments that the PSAP signal noise varies as the ?3/2 power of the integration time and not the assumed ?1/2. It is also shown that neither simple boxcar averaging of independent absorptivity values nor the commonly used moving boxcar average allow realization of the maximum signal to noise ratio. Instead it is argued that maximal noise reduction is realized by post-processing of the raw reference and sample channel intensities. Finally the implications of these findings are demonstrated with representative field data.     

我真不是素描

<正>简单的纯白瓷块加上素描感十足的黑色包边,营造出立体插画般的视觉错觉。英国陶艺家Katharine Morling用坚硬的陶瓷创作出其他瓶瓶罐罐绝对没有的3D梦幻感。一台堪称古董级别的收银机内似乎装了太多的硬币,抽屉怎么也关不上,一旁放着订书机、记事本、笔筒等小杂物。如果不是有一圈黑色包边清晰地勾勒出轮廓,它们就像是微融的白巧克力。再仔细一看,似乎又像用柔软的纸张剪出的纸艺美物。然而轻轻敲几下,清脆     

Image-based finite element mesh construction for material microstructures

One way of computing the macroscopic behavior of a material sample with complex microstructure is to construct a finite element model based on a micrograph of a representative slice of the material. The quality of the results produced with such a model obviously depends on the quality of the constructed mesh. In this article, we describe a set of routines that modify and improve the quality of a 2D mesh. Most of the routines are guided by an effective element “energy” functional, which takes into account the shape quality of the elements and the homogeneity of the elements as determined from an underlying segmented image. The interfaces and boundaries in the image arise naturally from the segmentation process. From these routines, we construct a close-to-automatic mesh generator that requires only a few inputs, such as the linear sizes of the largest and smallest features in the micrograph.