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991.
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993.
随机数在密码学、保密通信和国家安全等领域具有重要的作用,因此寻求一种提高随机数测试通过率的方法具有重要意义.对美国NIST SP800-22测试标准中的部分测试标准进行了分析,并针对其中的单比特频数测试、游程测试、块内最大游程测试以及子块测试分别给出了其物理意义和改进随机数发生器性能的硬件措施. 相似文献
994.
Hydrogenated nanocomposite aluminum/carbon thin films (Al/a‐C:H) were fabricated on stainless steel and silicon wafer substrates via unbalanced reactive magnetron sputtering from an Al target in CH4/Ar plasma. The composition and structure of Al/a‐C:H films were investigated by high‐resolution transmission electron microscope (HRTEM), XPS and micro‐Raman spectroscopy. Nanoindenter, interferometer and ball‐on‐disc tribometer were carried out to evaluate the hardness, internal stress and tribological properties of Al/a‐C:H films. HRTEM observations confirmed that the metallic Al nanocrystallites were uniformly dispersed in the amorphous carbon matrix. XPS and Raman analyses indicated that the sp2 content increased with the increase of Al content in the films. Nanoindenter and interferometer tests exhibited that the uniform incorporation of Al nanocrystallites can diminish drastically the magnitude of internal stress with maintaining the higher hardness of as‐deposited films. Especially, the ball‐on‐disc tribometer measurements revealed that the nanocomposite film with 2.3 at.% Al content exhibited relatively better wear resistance and self‐lubrication performance with a friction coefficient of 0.06 and wear rate of 3.1 × 10?16 m3/ N·m under ambient air, which can be attributed to the relatively higher hardness, the formation of continuous graphitized transfer film on counterface and the reduced reaction of oxygen with carbon. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
995.
996.
Applying the multidimensional Lindstedt-Poincaré (MDLP) method, we study the forced vibrations with internal resonance of a clamped-clamped pipe conveying fluid under external periodic excitation. The frequency-amplitude response curves of the first-mode resonance with internal resonance are obtained and its characteristics are discussed; moreover, the motions of the first two modes are also analyzed in detail. The present results reveal rich and complex dynamic behaviors caused by internal resonance and that some of the internal resonances are decided by the excitation amplitude. The MDLP method is also proved to be a simple and efficient technique to deal with nonlinear dynamics. 相似文献
997.
激光烧蚀-等离子体质谱结合归一定量方法原位线扫描检测石榴石多种元素 总被引:4,自引:0,他引:4
探讨了基体归一定量技术在实际应用中存在的问题.外标结合内标归一校正法避免了内标法中需要采用其它微区技术测定内标含量的繁琐步骤,可方便地用于具有环带结构等难以找到均匀分布的内标元素的地质样品的元素空间分布测定,解决了在采用直接外标法进行基体归一时,不能同时采用多外标进行校正的缺陷.激光线扫取样的最大优势是快速、省时.采用线扫的激光取样方式,结合归一定量技术,对具有环带结构的天然石榴石样品中的45种元素进行了分析测定,并与传统的激光打坑结果作对比,结果令人满意. 相似文献
998.
Christian Rühle Graham T. Eyres Sylvia Urban Jean-Pierre Dufour Paul D. Morrison Philip J. Marriott 《Journal of chromatography. A》2009,1216(30):5740-5747
The preparative scale isolation of multiple components from an essential oil matrix is described using multidimensional gas chromatography (prep-MDGC) which allows their further characterisation by mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. Menthol, linalyl acetate, carvone and geraniol were isolated individually, and were also collected in various combinations. It was demonstrated to be possible to collect multiple selected components from numerous repeat injections of the sample, to permit increased mass recovery from an external cryotrap collection device. Peak retention times remained reproducible (<0.3 s) over the repeated injections and switching events. This methodology may be utilised to confirm peak identity or to produce unique mixed-component reference standards, for instance to allow their identification in other samples using GC/MS, or identify them in comprehensive two-dimensional gas chromatography (GC × GC) analysis. 相似文献
999.
Nabil Vaeli Nadia Esfandiari Zahra Arab Aboosadi 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2019,25(3):261-283
The experimental feasibility of extracting carvacrol or cymophenol from local and medicinal Oliveria decumbens by supercritical carbon dioxide through using ultrasound waves was investigated in this study. The extraction modelling was carried out in two forms: Internal and external. The internal model was adopted to simulate the concentration distribution of the phytochemicals in the plant particles. In this model, the extracted cell was assumed to be a filled substrate and two mechanisms of molecular permeability and mass transfer had the greatest effect. The comparison of the experimental data obtained from modelling revealed that both the internal and external models are compatible with the experimental data as much as 80%, indicating an acceptable accuracy. Furthermore, the empirical data is completely in line with the model at the final time (40 min), which is the time to reach the equilibrium. 相似文献
1000.
This paper considers the dividend optimization problem for an insurance company under the consideration of internal competition between different units inside the company. The objective is to find a reinsurance policy and a dividend payment scheme so as to maximize the expected discounted value of the dividend payment, and the expected present value of an amount which the insurer earns until the time of ruin. By solving the corresponding constrained Hamilton-Jacobi-Bellman (HJB) equation, we obtain the value function and the optimal reinsurance policy and dividend payment. 相似文献