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131.
基因方法是基于自然选择和自然基因机制的并行随机自适应工程模型参数全局优化估计的通用数值方法。它不限制模型结构、优化准则、被估参数的数目、约束条件等,已开始广泛用于各种工程模型的优化设计之中。文中对它的原理、步骤、特点进行初步探讨,并针对基因方法的弱点,作者提出予以改进的加速基因方法,后者在最大流量频率曲线参数估计中得到成功应用 相似文献
132.
Chuan Pu Sangtae Park Chu P.B. Shi-Sheng Lee Ming Tsai Peale D. Bonadeo N.H. Brener I. 《IEEE journal of selected topics in quantum electronics》2004,10(3):472-477
We propose and demonstrate electrostatic sidewall-electrodes actuation of three-dimensional (3-D) microelectromechanical systems (MEMS) gimbal mirrors. The linearity of the mirror angle dependence on actuation voltage is improved with the sidewall-electrodes actuation. In addition, the undesired spring-softening effect commonly found in electrostatic actuation, where the mirror resonance frequency decreases with increased tilt angle, is significantly reduced. Sidewall actuation enables superior performance of 3-D MEMS mirrors including large pull-in angles, reduced actuation voltages, improved device reliability, and fast switching times. 相似文献
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134.
In this work, PdAg/Al2O3 composite membranes prepared by electroless co-deposition technique have been studied. Effects of plating time, Ag composition and total concentration of metal ions on surface morphologies, composition and microstructure of the resulting layers were investigated. Scanning electron microscope, energy dispersive spectrometer and nitrogen permeation technique were used to characterize the as-prepared composite membranes. From the experimental results, it shows that the surface morphology of the deposited PdAg layer is strongly affected by the Ag content of the plating bath. Since large differences of deposition rates and growth modes are observed between Pd and Ag grains, the PdAg layer exhibits the dendritic structure. As the Ag content is approximately 50%, the dendritic structured PdAg layer reveals the largest nitrogen permeability with the smallest size of residual pores. Furthermore, a comprehensive electrochemical analysis is proposed to interpret the composition and structure of the PdAg layer. Eventually, the experimental results are quite consistent with those predicted from the electrochemical analysis. 相似文献
135.
Calculating the elastic moduli of steel-fiber reinforced concrete using a dedicated empirical formula 总被引:1,自引:0,他引:1
The equivalent inclusion method (EIM) is adopted to study the characteristics of the equivalent material properties of steel-fiber reinforced concrete as a function of the volume fraction and the length to diameter ratio of the fibers. It is found that the equivalent material moduli of concrete reinforce with randomly orientated and distributed fibers are insensitive to the length to diameter ratio of the steel fibers. A set of empirical formulae is then proposed for the purposes of engineering applications. The proposed empirical model can simplify the calculation of the equivalent material moduli. Verifications of the proposed empirical formulae with the EIM model and with experimental data are performed with two examples. The first is a compression test. The second is 4 point bending test. The empirical formulae, based on the equivalent inclusion method proposed in this study, represent an alternative means of quickly calculating the effective elastic modulus of steel-fiber reinforced concrete materials. 相似文献
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137.
Newsome Mary R.; Steinberg Joel L.; Scheibel Randall S.; Troyanskaya Maya; Chu Z.; Hanten Gerri; Lu Hanzhang; Lane Summer; Lin Xiaodi; Hunter Jill V.; Vasquez Carmen; Zientz Jennifer; Li Xiaoqi; Wilde Elisabeth A.; Levin Harvey S. 《Canadian Metallurgical Quarterly》2008,22(4):419
Eight adolescents (ages 13-18 years) who sustained traumatic brain injury (TBI) and eight gender- and age-matched typically developing (TD) adolescents underwent event-related functional MRI (fMRI) while performing a Sternberg letter recognition task. Encoding, maintenance, and retrieval were examined with memory loads of one or four items during imaging. Both groups performed above a 70% accuracy criterion and did not differ in performance. TD adolescents showed greater increase in frontal and parietal activation during high-load relative to low-load maintenance than the TBI group. The TBI patients showed greater increase in activation during high-load relative to low-load encoding and retrieval than the TD group. Results from this preliminary study suggest that the capability to differentially allocate neural resources according to memory load is disrupted by TBI for the maintenance subcomponent of working memory. The overrecruitment of frontal and extrafrontal regions during encoding and retrieval following TBI may represent a compensatory process. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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139.
差分功耗分析攻击利用嵌入式加密系统功耗泄漏信号来获取加密系统密钥,将穷举问题转化为数据采集、处理问题.在对DES加密嵌入式系统攻击实验中,基于虚拟仪器的差分功耗分析平台令差分功耗分析攻击的数据采集过程由虚拟仪器应用程序控制进行,而后再对采集的功耗进行分析,能够快速、准确地找到加密系统密钥.较传统的穷举攻击而言,减少了消耗的时间和成本. 相似文献
140.