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21.
This paper suggests a strategy for the imperfection sensitivity analysis of elastic thin-walled structures with notable residual stresses. The analysis is carried out by means of a Koiter's perturbation approach. The concept of imperfection, traditionally associated with geometric and load factors, is extended in this paper to the residual stresses. The strategy is implemented in a FEM code. A comparison of the obtained results allows a discussion on the accuracy and the influence of the different coefficients connected to the asymptotic analysis of the residual stresses. 相似文献
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本文主要介绍用改变空腔体积的直线外推法测量指形石墨电离室在石墨模体内的扰动修正因子 k_p 的方法和结果。采用一组形状和外径(φ=13.5mm)完全相同、空腔有效体积υ分别为0.4923、0.6832、0.9060、1.2092、1.4713和1.8818cm~3的6个指形石墨电离室,放置在距离模体表面深度 h为5.13g/cm~2的石墨模体内,在准直~(60)Co γ射线束照射下,测量了空腔内单位质量空气中的电离电荷 J_(?)随υ的变化曲线;由该曲线外推得到υ=0时的 J_a 值,即(J_a)_0;再求得 k_p=(J_a)_0/(J_a)_v)值及其随υ的变化曲线。得到回归方程为 k_p=1.000—8.24×10~(-3)υ。所得 k_p 值,可用于指形石墨电离室测量石墨模体内吸收剂量时的扰动修正。 相似文献
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有限精度混沌系统的m序列扰动实现 总被引:65,自引:3,他引:62
本文研究利用m序列的扰动来实现有限精度混沌系统的方法,考察了扰动序列的周期,幅度以及扰动分布对混沌信号特性的影响,研究表明,扰动m序列所需的阶数取决于混沌序列所需要达到的周期长度,扰动的位数取决于混沌映射的最大斜率,随着混沌系统实现粗度的提高,所需的扰动幅度呈指数减小。 相似文献
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Sergei Bulanov Francesco Pegoraro Jun-ichi Sakai 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1998,410(3):17-487
We discuss the formation of typical (structurally stable) singularities in nonlinear wave breaking in stable and unstable media. The wake wave-break due to the inhomogeneity of the Langmuir frequency is accompanied by electron injection into the acceleration phase. In a wake wave excited behind a finite width laser pulse, the wave-breaking mechanism involves the increase, with the distance behind the pulse, of the curvature of the wake front, followed by the self-intersection of the electron trajectories. In the long wavelength limit, the Weibel instability which leads to the generation of a strong magnetic field, the relativistic self focusing and the Rayleigh-Taylor instability of a thin plasma slab provide examples of a common behavior with the rarefaction wave-breaking in unstable media. We present a solution of the Cauchy problem that describes the evolution of nonlinear perturbations of the Rayleigh-Taylor instability in terms of analytical functions of a complex variable. 相似文献
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The problem of calculating the response of a distributed parameter system excited by a moving oscillator with random mass, velocity and acceleration is investigated. The system response is a stochastic process although its characteristics are assumed to be deterministic. In this paper, the distributed parameter system is assumed as a beam with Bernoulli–Euler type analytical behaviour. By adopting the Galerkin's method, a set of approximate governing equations of motion possessing time-dependent uncertain coefficients and forcing function is obtained. The statistical characteristics of the deflection of the beam are computed by using an improved perturbation approach with respect to mean value. The method, useful to gathering the stochastic structural effects due to the oscillator–beam interaction, is simple and leads to results very close to Monte Carlo simulation for a wide interval of variation of the uncertainties. 相似文献
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EFFECT OF INVOLUTE CONTACT RATIO ON THE DYNAMIC PERFORMANCE OF SPUR GEAR WITH NOTOOTH PROFILE MODIFICATION 总被引:1,自引:0,他引:1
Wang JianhongZhang QingweiRen HengbinInstitute of Mechanical Engineering Chongqing University Chongqing China 《机械工程学报(英文版)》2003,16(4):417-419
The effect of involute contact ratio on the torsional vibration behavior of spur gear-pair isstudied analytically through a mass-spring model. The tooth stiffness in model not only has a relationwith time, as many prior studies presented, but, more important, with involute contact ratio (ICR) aswell. The ICR embodies its impact on the spur gear's dynamic performance through changing theproportion of tooth stiffness when there are n+1 teeth in contact to tooth stiffness when there are n 相似文献