Direct numerical simulation of passive scalar in decaying compressible turbulence

1IntroductionDirectnumericalsimulation(DNS)becomesanimportanttoolinrecentresearchofturbulence[1].DNSofcompressibleturbulenceismoredifficultthanthatoftheincompressibleturbulence.WhentheturbulentMachnumberisgreaterthan0.3theshockletsmayappearinthecompressibleturbulentflowfields.Thereasonandmechanismofshockletsexistencearenotclearyet.TheturbulentMachnumberinDNScannotbeveryhighwiththepresentexistingnumericalmethodsandcomputerresource.Fortheproblemofcompressibleisotropicturbulencewiththeinitia…     

Exact Anomalous Dimensions of Composite Operators in the Obukhov–Kraichnan Model

We consider two stochastic equations that describe the turbulent transfer of a passive scalar field (x)(t,x) and generalize the known Obukhov–Kraichnan model to the case of a possible compressibility and large-scale anisotropy. The pair correlation function of the field (x) is characterized by an infinite collection of anomalous indices, which have previously been found exactly using the zero-mode method. In the quantum field formulation, these indices are identified with the critical dimensions of an infinite family of tensor composite operators that are quadratic in the field (x), which allows obtaining exact values for the latter (the values not restricted to the -expansion) and then using them to find the corresponding renormalization constants. The identification of the correlation function indices with the composite-operator dimensions itself is supported by a direct calculation of the critical dimensions in the one-loop approximation.     

响应面方法计算HTR-10余热排出系统物理过程的失效概率

在核电站安全研究中，概率安全评价方法已经得到了广泛的应用.但是对于采用非能动设计的核电站系统，其可靠性分析的研究还处于初级阶段.非能动系统的失效不但要考虑常规可靠性分析中考虑的设备失效，还要考虑物理过程的失效.物理过程失效概率的计算方法和能动系统可靠性分析方法完全不同.本文给出物理过程失效的数学描述，介绍了一次二阶矩法、响应面方法，并且应用响应面方法计算了清华大学核能技术设计研究院10MW高温气冷实验堆(HTR-10)余热排出系统失效概率的近似值. 关键词： 概率安全评价 非能动系统 可靠性 响应面     

基于XRD的镀锌钝化膜残余应力试验研究

利用XRD技术测试了镀锌钝化膜结合界面的残余应力，同时通过电解抛光法检测了其厚度方向残余应力的分布规律，分析了残余应力对镀锌钝化膜结合强度的影响. 试验结果表明，镀锌钝化膜的残余应力均表现为压应力，并随着基体表面残余应力的增大而减小；钝化膜在2—10μm厚度方向的残应力为-274.5—-428.3MPa，其应力为梯度分布；镀锌钝化膜与基体的界面结合强度与其残余应力成反比，减小薄膜残余应力，有利于提高镀锌钝化膜与基体的结合强度. 关键词： X射线衍射法(XRD) 镀锌钝化膜 结合强度 残余应力     

添加钇提高不锈钢耐蚀性能的AES研究

用俄歇能谱仪对比研究了添加０．２％Ｙ对高硅不锈钢在９３％Ｈ２ＳＯ４介质中所形成的钝化膜中各元素浓度分布的影响，添加０．２％Ｙ增大了ＳｉＯ２在不锈钢钝化膜中的比例，从而使合金中Ｓｉ可充分形成富ＳｉＯ２的钝化膜。     

Spectral reduction for control systems modeling passive integrated circuits

Linear control systems modeling passive integrated circuits are examined. A new algebraic method of spectral reduction equipped with efficient tools for preserving passivity is proposed and justified. For RC networks (circuits), this method is similar to and can be regarded as an extension of the well-known PACT method, which is based on congruence transforms. Up to now, such an extension seemed to be impossible, and different techniques were used for the reduction of RCL and RCLM networks. Some numerical results are presented.     

STUDIES ON THE MESOZOIC MARGINAL ARC SYSTEM OF THE SOUTHEAST COAST AND TAIWAN IN CHINA

The southeast coastal Zhejiang, Fujian, Guangdong provinces and Taiwan in China comprised an important area in ancient Asia where the Yenshanian continental margin magmatic arc well developed in the late Mesozoic time. It is believed that the oceanic trench and subduction zone are situated on the east side of the Central Range in Taiwan. It seems unlikely that the so-called Hercynian-Indosinian ancient island arc folded system would have occurred in this region.     

Selective area rare-earth doping of planar glass samples for monolithic integration of optically passive and active waveguides

Successful demonstration of selective area doping of planar glass samples for monolithic integration of optically passive and active devices on a single chip is presented. Salt solution of erbium was delivered onto pre-sintered germano-silicate samples via a syringe. The samples were then consolidated to form dense glass layers containing regions doped with rare earth. Erbium tri-chloride solution, 0.1 M, was used during the solution doping phase, with the resulting erbium atomic percentage ranging from more than 0.1-0.4%, increasing linearly with the number of drips applied.     

Nearly Vertical Hopf Bifurcation for a Passively Q-Switched Microchip Laser

Passively Q-switched microchip lasers generate strongly pulsating intensity oscillations that emerge from a Hopf bifurcation point. We show that this bifurcation is nearly vertical and explain why strongly pulsating oscillations are immediately observed as we pass the Hopf bifurcation point. The laser dynamical problem is mathematically a singular perturbation problem which we investigate. The leading order problem is conservative and corresponds to Lotka–Volterra equations.     

Asymmetric solution-phase mixture aldol reaction using oligomeric ethylene glycol tagged chiral oxazolidinones

Sorting tags are oligomeric structures that can be used as protecting groups or chiral auxiliaries enabling solution-phase mixture syntheses of multiple tagged compounds in one pot and allowing for facile and predictable chromatographic separation of products at the end of synthetic sequences. Perfluorinated hydrocarbon and oligomeric ethylene glycol (OEG) derivatives are known classes of sorting tags. Herein we describe the preparation of OEGylated chiral oxazolidinones and their use in asymmetric solution-phase mixture aldol reactions. Through the use of such oxazolidinones based on tyrosine four different individually tagged aldol adducts were obtained as a mixture, chromatographically demixed, detagged, and it was shown that these processes gave the desired aldol products in good yield and enantioselectivity.