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21.
土壤腐殖酸的VIS-UV光谱特征和E465/E665的测定结果表明,各种土壤腐殖酸的VIS-UV吸收曲线相似,但吸收峰强度和E465/E665差异较大,进而推得它们的腐殖化程度排序为:紫色潮土腐殖酸>中性紫色土腐殖酸>酸性紫色土腐殖酸>腐殖土腐殖酸,说明它们在组成上有共同的本性,但结构和性质差异较大。在此基础上,研究它们对毒死蜱水解的影响。结果表明,不同来源土壤腐殖酸均促进了毒死蜱的水解,但它们的影响程度有明显的差异。对于腐殖化程度最低的腐殖土腐殖酸,浓度为120mg L-1时,对毒死蜱水解的促进作用最大,而随着腐殖酸浓度的增大,促进作用却越来越弱;而对于其它三种样品,腐殖酸溶液对毒死蜱水解的促进作用随着腐殖酸浓度增大而加强,其中以腐殖化程度较低的酸性紫色土的促进作用较为明显。可见,毒死蜱的水解速率与土壤腐殖酸的浓度和腐殖化程度有关。其中,腐殖酸腐殖化程度的影响机理主要与腐殖酸的酸性和腐殖酸的吸附—催化作用有关,其具体作用机理有待于进一步从定性和定量方面去研究,以更好地指导毒死蜱农药的合理施用和污染土壤的修复。 相似文献
22.
In the area of image retrieval from data bases and for copyright protection of large image collections there is a growing demand for unique but easily computable fingerprints for images. These fingerprints can be used to quickly identify every image within a larger set of possibly similar images. This paper introduces a novel method to automatically obtain such fingerprints from an image. It is based on a reinterpretation of an image as a Riemannian manifold. This representation is feasible for gray value images and color images. We discuss the use of the spectrum of eigenvalues of different variants of the Laplace operator as a fingerprint and show the usability of this approach in several use cases. Contrary to existing works in this area we do not only use the discrete Laplacian, but also with a particular emphasis the underlying continuous operator. This allows better results in comparing the resulting spectra and deeper insights in the problems arising. We show how the well known discrete Laplacian is related to the continuous Laplace-Beltrami operator. Furthermore, we introduce the new concept of solid height functions to overcome some potential limitations of the method. 相似文献
23.
W. Whaling W. H. C. Anderson M. T. Carle J. W. Brault H. A. Zarem 《Journal of research of the National Institute of Standards and Technology》2002,107(2):149-169
We report precision measurements by Fourier transform spectroscopy of the vacuum wavenumber, line width, and relative signal strength of 928 lines in the Ar I spectrum. Wavelength in air and classification of the transition are supplied for each line. A comparison of our results with other precision measurements illustrates the sensitivity of Ar I wavelengths to conditions in the light source. 相似文献
24.
25.
樊伟 《计算机工程与科学》2012,34(12):120-125
提出一种谱分解降维的模糊有监督局部保持投影策略。首先针对监督局部保持投影SLPP存在过学习和不能较好地保持图像空间的差异信息等问题,通过最小化局部离散度和最大化差异离散度准则提取投影方向,找到一种线性鉴别分析的等价形式。其次,通过采用模糊k近邻(FKNN)方法得到相应的样本分布隶属度信息,同时考虑到离群样本对整个分类结果的不利影响,提出一种模糊化方法,根据样本的隶属度对样本分布矩阵重定义所做的贡献,将每个样本的隶属度融入到SLPP特征抽取的过程中,从而得到完整有效的模糊样本特征向量集,有效解决了小样本问题的特征抽取问题。第三,提出一种谱分解的矩阵分析方法,在SLPP投影准则下,对散布矩阵实现降维。在ORL和NUST603人脸库上的实验结果验证了该方法的有效性。 相似文献
26.
27.
E. Q. Xie W. W. Wang N. Jiang D. Y. He Department of Physics Lanzhou University Lanzhou China 《金属学报(英文版)》2002,15(2):221-226
1. IntroductionThe transition metal silicides have attraeted much attention because of their potentialapplicatiOIl in very large scale integration (VLSI) de.ice[1]. Near-noble metal silicides canbe used as Schottky al1d ohn1ic col1tacts in silicon-based d… 相似文献
28.
Tetrahedral amorphous hydrogenated carbon (ta-C:H) films with various substrate bias voltages were prepared using a magnetic-field-filter plasma stream deposition system. The microstructural and optical properties were studied using ellipsometric spectra. The refractive index n of each sample was obtained by simulating their ellipsometric spectral using Tauc-Lorentz oscillator model, and then the relative sp3 C ratio of each sample was calculated using Bruggeman effective medium approximation. The sp3 C fraction of each sample was quantified by using electron energy-loss spectroscopy (EELS). The blood compatibility of the samples was evaluated by tests of platelet adhesion, kinetic clotting time and thrombin time. The quantity and morphology of the adherent platelets on the surface of these samples were investigated using scanning electron microscopy. Results show that the spectroscopic ellipsometry is a helpful method to evaluate the sp3 carbon fraction of the carbon films. The substrate bias voltage has an obvious effect on sp3 content and blood compatibility of ta-C:H films. The sample prepared with substrate bias voltage of − 20 V showed the best blood compatibility. A simple bio-physical hypothetical model was proposed to explain the experiment results. 相似文献
29.
In this paper the heteropoly complexes K_n[Ga(H_20)MW_(11)O_39)]·xH_20 [M=Cu(Ⅱ), Co(Ⅱ), Cr(Ⅲ),Fe(Ⅲ), Mn(Ⅳ)] have been prepared in this laboratory firstly. The products were characterized by chemicalanalysis, ionexchange, IR, UV and X-ray powder diffraction. 相似文献
30.
G. X. Zhao M. Zheng X. H. Lv X. H. Dong H. L. Li 《Metals and Materials International》2005,11(2):135-140
The corrosion behavior of 13Cr martensitic stainless steel in a CO2 environment in a stimulated oilfield was studied with potentiodynamic polarization and the impedance spectra technique. The
results showed that the microstructure of the surface scale clearly changed with temperature. This decreased the sensitivity
of pitting corrosion and increased the tendency toward general (or uniform) corrosion. The capacitance, the charge transfer
resistance, and the polarization resistance of the corrosion product scale decrease with increasing temperature from 90 to
120 °C, and thus the corrosion is a thermal activation controlled process. Charge transfer through the scale is difficult
and the corrosion is controlled by a diffusion process at a temperature of 150 °C. Resistance charge transfer through the
corrosion product layer is higher than that in the passive film. 相似文献