Bifurcation and Chaos Analysis of Stochastic Duffing System Under Harmonic Excitations

The Chebyshev polynomial approximation is applied to the dynamic response problem of a stochastic Duffing system with bounded random parameters, subject to harmonic excitations. The stochastic Duffing system is first reduced into an equivalent deterministic non-linear one for substitution. Then basic non-linear phenomena, such as stochastic saddle-node bifurcation, stochastic symmetry-breaking bifurcation, stochastic period-doubling bifurcation, coexistence of different kinds of steady-state stochastic responses, and stochastic chaos, are studied by numerical simulations. The main feature of stochastic chaos is explored. The suggested method provides a new approach to stochastic dynamic response problems of some dissipative stochastic systems with polynomial non-linearity.     

估计区间特征值问题特征值界的一种新方法

在对称矩阵的性质和谱半径的单调性质等矩阵计算理论的基础上,给出了一种计算标准区间特征值问题特征值上下界的新方法.最后用两个数值例子与已有的方法进行了比较,进一步验证了本文方法的正确性和有效性.     

Dynamic characteristics of a beam specimen featuring electrorheological fluids

The experimental investigations are focused on evaluating the elastodynamic response characteristics of beams fabricated in electrorheological (ER) fluids when the beams are subjected to forced vibration. The beams used in this experiment are composed of three kinds of materials: structural material, damping material and sealant material. Beams with different ER fluids and different structural material are made and tested. The results demonstrate clearly the ability to significantly change the vibrational characteristics of beams fabricated in smart composites by changing the electric field intensity imposed on the fluid domains. With the ASTM standard E756-83 equations, the Young's modulus of the beams and the shear modulus of ER fluids are evaluated.     

冲击波负压与肺损伤

着重研究不同水平的冲击波负压峰值对大白鼠和家兔肺的影响。将Ｗｉｓｔａｒ系大白鼠分为６组，每组１０只，其中一组为正常对照组，其余５组分别暴露于平均峰值为－５３．７ｋＰａ至－８５．９ｋＰａ的冲击波负压环境中。伤后立即解剖动物，重点观察肺伤情，同时用６只家兔暴露于冲击波负压环境中，另６只为对照组。实验结果:在上述冲击波负压环境中，肺可出现从无伤至极重度伤的伤情，肺出血充血以及肺表面压痕与肺冲击伤的表现非常相似。随着冲击波负压峰值的变化，各组肺伤情亦随着变化，且相关非常显著，各实验组动物肺伤情与对照组相应的肺伤情相差显著。实验证明，一定条件下的冲击波负压对大白鼠和家兔肺具有明显的致伤作用。     

单丝探头测量数据分析方法

本文介绍了用单丝热线探头测量三维湍流流场时的数据分析方法。文中着重研究了联系相关值和均方根值的相关系数及瞬时速度的泰勒级数的收敛性问题，认为在高湍流度流场中Ｋｉｎｇ的相关系数假定值宜作适当的修正，而当泰勒级数不满足余项收敛条件，本文提出了一种简便的计算方法，并用这种方法处理了圆柱体近尾区的实验数据，其结果与Ｏｎｇ用图表法处理实验数据的结果相符     

随机剪切柱在地震激励下的演变随机响应

随机剪切柱是指固连于地面的剪切柱的某些物理参数是随机变量 ,该模型在Niigata地震激励下的响应属于演变随机响应。本文将新近发展起来的演变随机响应问题的统一解法 ,推广到用于求解随机结构振动响应问题。首先用这一方法求出每个样本结构的随机响应 ,然后用MonteCarlo法来进一步求随机结构的集合随机响应特性。这样 ,与单纯用Monte Carlo法进行数字模拟相比 ,可使计算工作量大为减少。本文用随机剪切柱的演变随机响应问题加以说明     

A novel coding method for high vividness three-dimensional holographic display

The quality of the reconstructed holographic three-dimensional image is seriously influenced by the noise. A novel encoded algorithm combining the Burch code with the four-step phase shifting method is presented to remove the noise and improve the contrast and resolution of the reconstructed image. The reconstructed three-dimensional images are compared with the results of the median filtering. The performance parameters of two methods are analyzed. The experimental results show that the zero-order light spot, conjugate image and speckle noise are suppressed effectively. The quality of the reconstructed image is noticeably improved.     

Generation of high-order harmonic continuum with two-hump-structure infrared laser pulse

We experimentally investigate the high-order harmonic generation in argon gas cell driven by a multi-cycle broadband infrared laser pulse from a tunable optical-parametric-amplifier （OPA） source. The generation of high-order harmonic continuum with the cut-off photon energy up to 110 eV is observed by tuning the chirp of the 800-nm laser pulse which pumps OPA source. The generation of harmonic continuum is understood in terms of the two-hump structure of the OPA output spectrum and the optimal relative phase of the two humps. The demonstrated scheme is of importance for the generation of extreme ultraviolet （XUV） continuum at higher photon energy region.     

束流轨道与相关环境参数的同步诊断技术

粒子加速器由于受地基振动、环境温度、热效应等因素的影响,导致束流位置探头(BPM)所在真空盒的机械中心相对四极铁磁中心的漂移较大,因此很难提高束流轨道的绝对测量精度。探索利用电容式探头实时检测该漂移量的方法。首先分析了电容式探头的测量原理,并设计了轨道振动同步诊断方案,然后设计了专用探头,并利用数据采集设备对探头的线性度、精度和频率响应进行实验室测试。结果显示电容式探头能检测到2μm的相对位移,且可有效检测300Hz以下的振动频率,可用于束流轨道与相关环境参数的同步诊断。     

Mixed volumes and measures of asymmetry

The mixed volume and the measure of asymmetry for convex bodies are two important topics in convex geometry.In this paper,we first reveal a close connection between the Lp-mixed volumes proposed by E.Lutwak and the p-measures of asymmetry,which have the Minkowski measure as a special case,introduced by Q.Guo.Then,a family of measures of asymmetry is defined in terms of the Orlicz mixed volumes introduced by R.J.Gardner,D.Hug and W.Weil recently,which is an extension of the p-measures.