提高窗口傅立叶变换精度的方法

由于CCD采集的变形条纹图是空域有限的,在对其作窗口傅立叶变换处理时,高斯窗在图像边缘的不完整会产生测量误差。针对这种情况,提出了采用Gerchberg迭代法对条纹进行外插延拓,扩展窗口傅立叶变换处理的有效区域范围,进而改善窗口傅立叶变换的测量精度。     

基于傅立叶变换的岩屑纹理特征提取及岩性识别方法研究

针对在PDC钻头条件下石油录井过程中的岩屑岩性难以用肉眼识别,以及人工分类速度较慢的问题,该文利用傅立叶周向谱能量法原理,将岩屑图像在频域中按照频率由低到高对周向谱能量进行分级,将各级能量占总能量的比率作为该图像的特征量,然后应用Bayes分类器对其进行分类处理,将所得结果与人工分类结果做比较,并验证了方法的可靠性。实验证明,这种方法能更好的分析岩屑的岩性,对泥岩的分类准确率高达99.44%。     

生物降解稠油极性化合物负离子电喷雾傅立叶变换离子回旋共振质谱分析

为研究生物降解对原油中极性化合物组成影响,采用傅立叶变换离子回旋共振质谱分析技术,研究了准噶尔盆地三台—北三台地区生物降解稠油中极性大分子化合物的组成。结果显示,生物降解稠油中含杂原子化合物类型较为复杂,主要有N₁、N₁O₁、N₁O₂、O₁、O₁S₁、O₂、O₂S₁、O₃、O₃S₁和O₄;不同生物降解程度稠油中极性化合物组成具有明显差异,随着生物降解作用加剧,稠油中O₂类化合物相对丰度明显升高,N₁、O₁S₁、O₂S₁、O₃、O₃S₁和O₄类化合物呈现逐渐降低的变化规律。通过对极性化合物中相对丰度较高的N₁和O₂类化合物的分析发现,随着生物降解程度增大,N₁和O₂类极性化合物缩合度整体增高,指示高缩合度的极性化合物抗生物降解能力更强,更易富集,长烷基支链取代化合物更易被生物降解。在严重生物降解稠油中,O₂类极性化合物相对丰度最高,其中酸性组分以一环至四环环烷酸(分子缩合度DBE为2~5)为主。傅立叶变换离子回旋共振质谱分析技术具有超高质量分辨分析能力,可以从分子层次研究原油中极性大分子化合物的化学组成,为石油地球化学研究提供了新的技术手段。     

小波分析及其在时变滤波和信号分离中的应用

利用小波变换具有的多时频分辨率特性，对地震勘探和测井信号这类非平衡信号进行分析，可以充分利用信号的时间－频率特性。文中介绍了小波变换的基本概念及其在地震勘探信号的时变滤波和声波全波列测井信号的信号分离中的应用，实例表明，小波变换在地球物理信号中具有广阔的应用前景。图５参７     

Fiber optic sensing for ultrasonic NDE

An innovative approach to nondestructive evaluation (NDE) using noncontacting optical sensors has demonstrated. In this effort a single mode optical fiber interferometer (OFI) was used to sense the presence and form of Rayleigh waves traveling along the surface of a steel test bar at a velocity of nearly 3mm/µs. Acousto-optic time-domain data was successfully used to detect the presence and locate the position of a test flaw (a machined slot) in the bar, and spectrum analysis was used to estimate its geometry and size. This approach has many potential applications in the ultrasonic evaluation of real flaws in structures with complex geometries. Coupled with the authors' earlier work demonstrating the feasibility of generating acoustic waves in metals using laser light pulses transmitted through the fiber optic probes, this latest achievement points to the development of a fully noncontacting, fiber optic based thermal-acousto-photonic (TAP) NDE system, with potential applications to the reliability testing of many important structures where composition, scale, geometry, or restricted access preclude the use of conventional NDE techniques.     

Understanding the effects of various edible coatings on the storability of fresh cherry

n this work, cherries, which have a very short shelf life, were packaged after being coated with various edible coatings [whey protein isolate (WPI), chitosan and shellac]. The changes in gas composition, weight loss, Brix, pH, electrical conductivity and firmness were measured periodically up to 11 days after harvest to compare the effects of the applied coatings. Fourier transform near‐infrared (FT‐NIR) spectroscopymeasurements were also taken individually. After storage, the gas composition within trays was about 1–10% O₂ and 14–47% CO₂. The lowest weight loss (25.56%) was observed in the shellac‐coated cherries, while the highest loss (48.58%) occurred in the control group. Coated cherries exhibited a significantly lower pH and electrical conductivity than the uncoated ones. The control group presented the highest total soluble solid (TSS) values (21.29) and shellac coating had (17.25) the lowest. At the end of storage, the highest ascorbic acid (AA) content was 0.64 mg/100 ml in the shellac‐coated cherries, and the lowest AA content of 0.40 mg/100 ml was measured in the control group. Firmness was maintained by coating, especially with shellac (3.734 N), whereas the control had the lowest firmness measured (2.138 N) at the end of storage. There were differences between the absorbance spectra for the coated and control cherries at the end of storage. This research concludes that shellac coating is more effective in reducing the respiration rate and maintaining the quality parameters of cherries than chitosan and WPI coatings. Major benefits of coatings were observed in lessening the weight‐loss process and in maintaining firmness, which were also supported by the FT‐NIR measurements. Copyright © 2010 John Wiley & Sons, Ltd.     

Cerium incorporating into MCM-41 mesoporous materials for CO oxidation

Ceria doped MCM-41 materials were synthesized by surfactant-assisted hydrothermal and wet impregnation methods. All the obtained Ce-MCM-41 materials were characterized by N₂ physical adsorption, X-ray diffraction (XRD), diffuse reflectance UV–visible spectroscopy (DRUV–vis), infrared spectroscopy (IR), solid-state cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy (CP/MAS-NMR), and transmission electron microscopy (TEM). The catalytic properties were evaluated in CO oxidation under atmospheric pressure and various temperatures. The results showed that in the materials synthesized by hydrothermal method, most of Ce ions were well incorporated in the tetrahedral coordinated sites into the framework of the MCM-41 as Si/Ce molar ratio is 30 and 50. High cerium content may lead to mesostructure partial collapsing and ceria particles segregation. For CO oxidation, the catalytic activity of Ce-MCM-41 synthesized by hydrothermal method was significantly greater than that of the materials prepared by impregnation route. Over the Ce-MCM-41 materials prepared via hydrothermal technique, 100% CO conversion was achieved at 504, 514 and 528 K, respectively, as the Si/Ce molar ratio decreased from 50 to 30 and 10. For the first time, we found an interesting correlation of Q₃ species relative area in the ²⁹Si CP/MAS-NMR spectra of the Ce-MCM-41materials with the reaction rates of CO oxidation, which indicates that both surface hydroxyls and tetrahedral-coordinated Ce⁴⁺ ions in the MCM-41 take important roles in the CO oxidation.     

基于傅里叶卷积和多特征调制的图像修复网络

目的 解决大面积破损难以修复且修复过程中感受野、特征空间信息利用不足,导致修复后的孔洞区域与背景之间出现结构、纹理、风格不一致的问题。方法 基于傅里叶卷积和多特征调制的修复网络FFC-MFMGAN,傅里叶卷积在网络的浅层便具有较大的感受野,尤其是在宽掩码时能够跳过掩码区域,捕获到有效特征,多特征调制生成网络能够分别利用完整区域的信息和随机样式操纵,增强与未受损区域的语义连贯性,以及大空洞率下修复的多样性。结果 在Place 2数据集上,将文中方法与其他图像修复方法进行了对比实验,经过测试,各类指标均得到明显改善,峰值信噪比提高了1.4%,结构相似性提高了4.5%,平均绝对误差降低了12.6%,基于学习的感知图像块相似性降低了9.1%。结论 FFC-MFMGAN网络能够较好地修复大面积不规则孔洞,同时增强修复图像的全局结构性和清晰度,对实际包装印刷图像的缺陷修复也有一定参考价值。     

Three-in-One Strategy Constructing the First High-Performance Nonlinear Optical Sulfide Crystallizing with the P43 Space Group

The balance between large nonlinear optical (NLO) effect and wide bandgap is the key scientific issue for the exploration of infrared NLO materials. Targeting this issue, two new pentanary chalcogenides KGaGe_1.37Sn_0.63S₆ ( 1 ) and KGaGe_1.37Sn_0.63Se₆ ( 2 ) are obtained by the three-in-one strategy, viz. three types of fourfold-coordinated metal elements co-occupying the same site. They crystallize in the tetragonal P4₃ ( 1 ) and monoclinic Cc ( 2 ) space group. Their structures can be evolved from benchmark AgGaS₂ (AGS) by suitable substitution. Remarkably, 1 is the first NLO sulfide crystallizing with the P4₃ space group, representing a new structure-type NLO material. The structural relationship between 1 and 2 and the evolution from 1 , 2 to AGS are also analyzed. Both 1 and 2 show balanced NLO properties. Specifically, 1 exhibits phase-matchable SHG response of 0.6 × AGS, a wide bandgap of 3.50 eV, and a high laser damage threshold of 6.24 × AGS. Theoretical calculation results suggest that the Ga/Ge/Sn element ratios of the co-occupied sites of 1 and 2 are the most appropriate for stabilizing the structures. The strategy adopted here will provide some inspiration for exploring new high-performance NLO materials.