Large-Scale Turbulent Vortical Structures inside a Sudden Expansion Cylinder Chamber

A large eddy simulation (LES) is performed for turbulent flow around a bluff body inside a sudden expansion cylinder chamber, a configuration which resembles a premixed gas turbine combustor. To promote turbulent mixing and to accommodate flame stability, a flame holder is installed inside the combustion chamber. The Smagorinsky model and the Lagrangian dynamic subgrid-scale model are employed and tested. The calculated Reynolds number is 5,000 based on the bulk velocity and the diameter of inlet pipe. The simulation code is constructed by using a general coordinate system based on the physical contravariant velocity components. The predicted turbulent statistics are evaluated by comparing with the laser-doppler velocimetry (LDV) measurement data. The agreement of LES with the experimental data is shown to be satisfactory. Emphasis is placed on the time-dependent evolutions of turbulent vortical structures behind the flame holder. The numerical flow visualizations depict the behavior of large-scale vortices. The turbulent behavior behind the flame holder is analyzed by visualizing the sectional views of vortical structure. This revised version was published online in July 2006 with corrections to the Cover Date.     

Products of Michael spaces and completely metrizable spaces

For disjoint subsets of the Michael space has the topology obtained by isolating the points in and letting the points in retain the neighborhoods inherited from . We study normality of the product of Michael spaces with complete metric spaces. There is a ZFC example of a Lindelöf Michael space , of minimal weight , with Lindelöf but with not normal. ( denotes the countable product of a discrete space of cardinality .) If denotes , the normality of implies the normality of for any complete metric space (of arbitrary weight). However, the statement `` normal implies normal' is axiom sensitive.

     

二维各向异性光子晶体完全带隙的增宽

介绍了光子晶体能带设计的一种新机制,利用各向异性材料制作二维光子晶体,可以大大提高光子晶体的完全带隙宽度。     

光纤超外差干涉测量系统的研究

提出了一种用于绝对距离测量的光纤超外差干涉系统,简述了该方案的原理,给出了信号处理的框图,并进行了初步实验。对系统的误差分析表明,在光强较弱、信噪比差的情况下,光学元件的非理想特性以及测量信号与参考信号之间的耦合是引起测量误差的主要原因。     

气相多组分反应流场的一种新算法

本文提出气相多组分方程组采用时间推进法,把混合气连续方程同状态方程相联系,把密度的调整量转化为压力的调整量,计算绝对压力场,对大温差下的有化学反应的多组分炉内流场进行计算,获得成功．     

半导体光电探测器响应度测试装置的研制

分析了半导体光电探测器光谱响应度的测试原理;研制了一套波长为０．４～１．１μｍ的光谱响度测试装置。该装置采用双光路替代法,可以测试绝对光谱响应度、相对光谱响应度和量子效率,并可减小光源不稳定性对测试结果的影响,最终给出了测试结果比对。     

双波长绝对距离外差干涉仪的研究

提出了一种采用双纵模稳频激光器的新型绝对距离测量外差干涉仪。该干涉仪探测两个波长各自的外差信号, 通过测量两信号的相位差, 直接测量出合成波的小数级次。指出了两波长间的相互耦合对测量精度的影响, 提出了补偿方法, 在２５ ｍ 的测量范围取得了 １４０ μｍ 的测量精度。     

Interaction induced delocalization of two particles: large system size calculations and dependence on interaction strength

The localization length L₂ of two interacting particles in a one-dimensional disordered system is studied for very large system sizes by an efficient and accurate variant of the Green function method. The numerical results (at the band center) can be well described by the functional form L ₂ =L ₁ [0.5+c(U) L ₁ ] where L₁ is the one-particle localization length and the coefficient depends on the strength U of the on-site Hubbard interaction. The Breit-Wigner width or equivalently the (inverse) life time of non-interacting pair states is analytically calculated for small disorder and taking into account the energy dependence of the one-particle localization length. This provides a consistent theoretical explanation of the numerically found U-dependence of c(U). Received 16 September 1998     

Contact shape optimization based on the reciprocal variational formulation

The paper deals with a class of optimal shape design problems for elastic bodies unilaterally supported by a rigid foundation. Cost and constraint functionals defining the problem depend on contact stresses, i.e. their control is of primal interest. To this end, the so-called reciprocal variational formulation of contact problems making it possible to approximate directly the contact stresses is used. The existence and approximation results are established. The sensitivity analysis is carried out.     

Лypbe控制系统绝对稳定的新判据

本文导出了控制系统零解绝对稳定的新的必要条件,给出几类控制系统零解绝对稳定的新判据。