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1.
We describe high order numerical algorithms for the solution of second order elliptic equations in rectangular domains. These
algorithms are based on the Fourier method in combination with a subtraction procedure. The singularities at the corner points,
arising due to non-smoothness of the boundaries, are treated explicitly using properly constructed singular corner functions.
The present algorithm is a generalization of the Fast Poisson Solver developed in our previous paper.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Near-edge X-ray absorption spectroscopy (NEXAFS) is widely used to probe the chemistry and structure of surface layers. Moreover, using ultra-high brilliance polarised synchrotron light sources, it is possible to determine the molecular alignment of ultra-thin surface films. However, the quantitative analysis of NEXAFS data is complicated by many experimental factors and, historically, the essential methods of calibration, normalisation and artefact removal are presented in the literature in a somewhat fragmented manner, thus hindering their integrated implementation as well as their further development. This paper outlines a unified, systematic approach to the collection and quantitative analysis of NEXAFS data with a particular focus upon carbon K-edge spectra. As a consequence, we show that current methods neglect several important aspects of the data analysis process, which we address with a combination of novel and adapted techniques. We discuss multiple approaches in solving the issues commonly encountered in the analysis of NEXAFS data, revealing the inherent assumptions of each approach and providing guidelines for assessing their appropriateness in a broad range of experimental situations. 相似文献
3.
《Surface and interface analysis : SIA》2003,35(3):282-286
We have developed a high‐speed image processing CCD video camera for real‐time energy‐loss imaging using a conventional electron microscope with an energy‐loss imaging facility. As an initial demonstration of real‐time lock‐in energy‐loss imaging, a background‐subtracted energy‐loss image was observed by attaching the high‐speed image processing CCD video camera to an analytical electron microscope equipped with a floating‐type energy‐loss imaging analyser. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
An investigation has been carried out into the usefulness of the spectral subtraction technique in analyzing the infrared spectra of the clathrates of quinol and of Dianin's compound. Due to the flexibility of the quinol host lattice, it is not advisable to use guest-free -quinol as the reference if the host lattice in the clathrate is considerably distorted, as it is in the CH3CN clathrate. In this case it is advisable to use another clathrate as the reference provided that the spectrum of the new reference does not contain guest bands in the region of interest. The Dianin's compound host lattice is less flexible than that of quinol, and guest-free Dianin's compound can be used as the reference irrespective of the size of the guest molecule. With both clathrates the spectral subtraction technique has revealed guest molecule bands which were previously obscured by host lattice bands.Dedicated to Professor H. M. Powell. 相似文献
5.
Speech signals recorded with a distant microphone usually are interfered by the spatial reverberation in the room, which severely degrades the clarity and intelligibility of speech. A speech dereverberation method based on spectral subtraction and spectral line enhancement is proposed in this paper. Following the generalized statistical reverberation model, the power spectrum of late reverberation is estimated and removed from the reverberation speech by the spectral subtraction method. Then, according to the human auditory model, a spectral line enhancement technique based on adaptive post-filtering is adopted to further eliminate the reverberant components between adjacent speech formants. The proposed method can effectively suppress the spatial reverberation and improve the auditory perception of speech. The subjective and objective evaluation results reveal that the perceptual quality of speech is greatly improved by the proposed method. 相似文献
6.
In this work, a robust method for moving object detection in thermal video frames has been proposed by including Kullback–Leibler divergence (KLD) based threshold and background subtraction (BGS) technique. A trimmed-mean based background model has been developed that is capable enough to reduce noise or dynamic component of the background. This work assumed that each pixel has normally distributed. The KLD has computed between background pixel and a current pixel with the help of Gaussian mixture model. The proposed threshold is useful enough to classify the state of each pixel. The post-processing step uses morphological tool for edge linking, and then the flood-fill algorithm has applied for hole-filling, and finally the silhouette of targeted object has generated. The proposed methods run faster and have validated over various real-time based problematic thermal video sequences. In the experimental results, the average value of F1-score, area under the curve, the percentage of correct classification, Matthew’s correlation coefficient show higher values whereas total error and percentage of the wrong classification show minimum values. Moreover, the proposed-1 method achieved higher accuracy and execution speed with minimum false alarm rate that has been compared with proposed-2 as well as considered peer methods in the real-time thermal video. 相似文献
7.
J. Fang 《Optics & Laser Technology》1991,23(6):349-352
A rotational mismatch of gratings is used to generate a fringe carrier of an in-plane moiré pattern so that specimen deformation shows itself in the form of modulation of the carrier frequency. As both the unmodulated and modulated carriers are the patterns without fringe-loop or fringe-connection, they are automatically numbered with monotonical increasing orders by a digital image processing system without any ambiguity. The orders at every pixel of the image are determined by interpolation of the orders of the tracked fringes to establish two grey image files, from the difference of which, the orders of the in-plane displacement moiré are displayed with grey-level variation. 相似文献
8.
Mark T. Sims Laurence C. Abbott Robert M. Richardson John W. Goodby 《Liquid crystals》2019,46(1):11-24
An assessment of the data processing and analysis methods used to obtain the second- and fourth-rank orientational order parameters of liquid crystals from X-ray scattering experiments has been carried out, using experimental data from four extensively studied alkyl-cyanobiphenyls and calculated data generated from two general types of theoretical orientational distribution function. The application of a background subtraction and two different baseline correction methods to the scattering profiles is assessed, along with three different methods to analyse the processed data. The choice of baseline correction method is shown to have a significant effect: an offset to zero overestimates the order parameters from the experimental and calculated data sets, particularly for lower order parameters arising from broad distributions, whereas an offset to a value estimated from regions of low scattering intensity provides experimental values close to those reported from other experimental techniques. By contrast, the three different analysis methods are shown generally to result in relatively small absolute differences between the order parameters. We outline a straightforward general approach to experimental X-ray scattering data processing and analysis for uniaxial phases that results in order parameters that match well with those reported using other experimental techniques. 相似文献
9.
Transition from chaotic to ordered state has been observed during the initial stage of a discharge in a cylindrical DC glow
discharge plasma. Initially it shows a chaotic behavior but increasing the discharge voltage changes the characteristics of
the discharge glow and shows a period subtraction of order 7 period → 5 period → 3 period → 1 period, i.e. the system goes
to single mode through odd cycle subtraction. On further increasing the discharge voltage, the system goes through period
doubling, like 1 period → 2 period → 4 period. On further increasing the voltage, the system goes to stable state through
two period subtraction, like 4 period → 2 period → stable. 相似文献
10.
In this paper, we address the problem of finding low cost addition–subtraction sequences for situations where a doubling step is significantly cheaper than a non-doubling one. One application of this setting appears in the computation of the final exponentiation step of the reduced Tate pairing defined on ordinary elliptic curves. In particular, we report efficient addition–subtraction sequences for the Kachisa–Schaefer–Scott family of pairing-friendly elliptic curves, whose parameters involve computing the multi-exponentiation of relatively large sequences of exponents with a size of up to 26 bits. 相似文献