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941.
进气道作为飞机强散射源之一,准确评估其雷达散射截面(RCS)特性一直是当今计算电磁学的研究热点.研究了一种加入阻抗边界条件、前后向迭代的迭代物理光学法,提出一种盒体分割法用于处理几何消隐工作.通过软件开发实现任意金属/介质腔体RCS特性评估,并用相关算例校验软件准确性.在此基础上应用该软件对金属/涂敷介质矩形S弯扩压5器进行数值模拟,获得了扩压器在入射波长0.03 m下的RCS变化规律.改进后的迭代物理光学法适用于任意腔体改型和涂敷吸波材料研究,缩短设计周期. 相似文献
942.
943.
Wai-Sum Chan 《International Journal of Mathematical Education in Science & Technology》2013,44(5):745-748
Most introductory textbooks on simple linear regression analysis mention the fact that extreme data points have a great influence on ordinary least-squares (OLS) regression estimation. However, not many textbooks provide a rigorous mathematical explanation of this phenomenon. In this note a way is suggested to fill this gap by teaching students the concept of breakdown point. 相似文献
944.
Elizabeth A. Baker Perla Rittigstein John M. Torkelson Connie B. Roth 《Journal of polymer science. Part A, Polymer chemistry》2009,47(24):2509-2519
Existing studies in the research literature showing conflicting changes in physical aging rates with decreasing film thickness in nanoconfined polymer films highlight the need for a single experimental technique to efficiently characterize physical aging rates in thin polymer films of varying chemical structure. To that end, we have developed a streamlined ellipsometry procedure to measure the structural relaxation of thin glassy polymer films. We evaluate different methods of calculating a physical aging rate β from the measured thickness h(t) and index of refraction n(t) data. We present extensive measurements of β as a function of aging temperature and aging time for polystyrene (PS) films supported on silicon, and determine that the physical aging rate β can be easily and reliably determined from β = −1/h0 dh/d(log t), where h0 is the initial measure of the film thickness at an aging time of 10 min. We have also carried out oxygen permeation studies on poly(methyl methacrylate) (PMMA) films from 800 μm down to 190 nm in thickness, and find no change in the permeability with film thickness or physical aging at room temperature for up to 65 days, which suggests that gas permeation may be insensitive to physical aging in such low free volume polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2509–2519, 2009 相似文献
945.
Guanjun Chang Lin Zhang Runxiong Lin 《Journal of Macromolecular Science: Physics》2013,52(12):2499-2504
Six kinds of poly(imino ketone)s (PIKs) with different structures were designed, involving different ratios of carbonyl and imino groups, and the insertion of two types of bulky groups in the main chain. Under 3D periodic boundary conditions, simulations of physical and chemical properties for PIKs with six different structures on the molecular level, including fractional free volume (FFV) and melt density, solubility, and glass transition temperature, were carried out. 相似文献
946.
H. Zessin 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2008,43(1):50-58
A fundamental theorem of Mürmann [2] characterizing equilibrium distributions of physical clusters is reconsidered. We recover
this result by means of the integration by parts formula approach to Gibbs processes due to Nguyen Xuan Xanh and Hans Zessin
[4].
Dedicated to Reinhard Lang on the occasion of his 60 th birthday. 相似文献
947.
This review deals with the dynamics of quantum systems that are subject to high frequency external perturbations. Though the
problem may look hopelessly time-dependent, and poised on the extreme opposite side of adiabaticity, there exists a ‘Kapitza
Window’ over which the dynamics can be treated in terms of effective time-independent Hamiltonians. The consequent results
are important in the context of atomic traps as well as quantum optic properties of atoms in intense and high-frequency electromagnetic
fields.
相似文献
948.
Guérin Fabrice 《商业与工业应用随机模型》2010,26(5):502-508
The paper written by M. Li, S. D. Holland and W. Q. Meeker [Applied Stochastic Models in Business and Industry] presents statistical methods for automatic Crack detection based on vibrothermography sequence‐of‐image data. In particular, a matched filter used to increase the signal‐to‐noise ratio is developed. The review gives suggestions about physical approach and detection criteria. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
949.
《Physics and Chemistry of Liquids》2012,50(4):514-533
Densities, speeds of sound and the refractive indices of binary systems containing alkanes (hexane, heptane, octane and nonane) with aromatic compounds (benzene, toluene and ethylbenzene) at T = 283.15 and 298.15 K under atmospheric pressure were determined over the whole composition range. From the experimental results, the derived and excess properties (excess molar volumes, isentropic compressibility, excess molar isentropic compressibility and refractive index deviations) at T = 283.15 and 298.15 K were calculated and satisfactorily fitted to the Redlich–Kister equation. 相似文献
950.
为研究青海高原道地药材羌活和铁棒锤的特性,采用电热板消解法处理样品,原子吸收分光光度法测定了两种药材中Ca、Mg、Cu、Zn、Fe、Mn 6种金属元素的含量。结果表明,Ca、Mg、Cu、Zn、Fe、Mn 6种微量元素含量在两种道地药材中,含量最高的是Ca,平均值分别为(55.78±12.10)mg/g和(26.48±5.79)mg/g;含量最低的元素为Cu,其值分别为(0.28±0.28)mg/g和(0.09±0.06)mg/g;其它元素含量从高到低依次为Mg,Fe,Zn,Mn。可见不同地区的羌活其微量元素的含量有明显的差异,且羌活微量元素含量也存在种间差异,细叶羌活的Ca、Mg元素含量比宽叶羌活的要低,相反,Fe,Cu,Zn 3种元素含量细叶羌活的比宽叶的要高。 相似文献