充分发展湍流场中Pr数对被动标量输运的影响

采用直接数值模拟方法,研究壁湍流中分子Pr数对湍流被动标量输运的影响.发现在槽道湍流的外层,湍流雷诺平均普朗特数PrT与分子普朗特数的倒数呈线性关系;湍流亚格子普朗特数PrT与分子普朗特数的关系较为复杂,在分子普朗特数为1附近时,湍流亚格子Prt数出现极小值.     

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     

Observer-based passive control for uncertain linear systems with delay in state and control input

This paper deals with the robust passivity synthesis problem for a class of uncertain linear systems with time-varying delay in state and control input. The parameter uncertainties are norm-bounded and allowed to appear in all matrices of the model. The problem aims at designing an observer-based dynamic output-feedback controller that robustly stabilizes the uncertain systems and achieves the strict passivity of closed-loop systems for all admissible uncertainties. By converting the problem at hand into a class of strictly passive control problem for a parameterized system, the explicit solution is established and expressed in terms of a linear matrix inequality. A numerical example is provided to demonstrate the validity of the proposed approach.     

Self-assembled luminescent CdSe-ZnS quantum dot bioconjugates prepared using engineered poly-histidine terminated proteins

We report a simple and versatile approach for the conjugation of luminescent CdSe-ZnS core-shell quantum dots (QDs) to proteins through coordination of engineered C-terminal oligohistidine sequences. Several histidine tail containing proteins were self-assembled onto the QD surface using this method. A recombinant antibody specific for the high explosive 2,4,6-trinitrotoluene (TNT) was conjugated to QDs through a carboxy terminal histidine tail and the bioconjugate used to detect TNT by competitive immunoassay. TNT was detected over the range of 10 μg/ml down to 41 ng/ml using the scFv conjugated to QDs. These results open up the possibility to conjugate luminescent QDs to a whole range of proteins to form QD bioconjugates that can be effectively used in bio-oriented applications, such as sensing, imaging, immunoassay and other diagnostics.     

The effect of the change in the microscopic structures of the iron on corrosion resistance and passivated properties

The passive film of iron showed n‐type semiconductor characteristic in borate buffer solution, and its donor concentration increased slightly after tensile strain in the present study. However, comparing with solution‐annealed sample, the anodic passive film formed on tensile‐strained one was highly protective. The more dislocations on tensile‐strained sample promoted the diffusion of iron and oxygen vacancy. Moreover, more donor density (mainly oxygen vacancies) promoted the diffusion of oxygen. They all facilitated tensile‐strained sample to form Fe₂O₃ and thicker passive film on the surface. More Fe₂O₃ and thicker passive film on the surface of tensile‐strained iron could improve corrosion resistance. Copyright © 2014 John Wiley & Sons, Ltd.     

供应链集中决策下RFID技术应用决策分析

RFID技术可以对供应链系统中的产品信息进行有效追溯和实时共享,以化解系统管理效率、安全防范、监控和保障能力极其低下等问题.但是,由于应用成本的制约,使很多附加值较低的行业仍望而却步,严重制约了RFID技术的发展和普及.以单个零售商和供应商组成的供应链系统为研究对象,首先,对基于RFID的供应链产品入库及日常盘点管理流程进行了简要分析;在此基础上,分别构建了集中决策下采用与不采用RFID技术时的供应链利润模型,并对其最优决策问题进行详细分析,得出供应链系统在集中决策下实施RFID技术的投资决策条件,所得结论可以为供应链系统在集中决策下实施RFID技术应用决策问题提供理论支持.     

点涡动力系统的Lyapunov指数

平面上理想流体的三点涡系统是可积的Hamilton系统, 但其运动仍然相当复杂, 这给研究被动微粒在三点涡系统中运动带来了很大的困难. 着眼于点涡系统的被动微粒对初始小扰动的稳定性, 通过Oseledec定理定义被动微粒的Lyapunov指数, 给出了点涡系统中被动微粒稳定性的定量刻画. 同时, 由Hamilton系统的保体积性质得到的关于Lyapunov指数的简洁表达式, 避免了计算的繁琐. 利用这个定义, 点涡系的瞬时流场可以被划分成若干区域, 被动微粒的混沌运动只能在近涡的特定区域出现.      

Modeling of isothermal processes in porous materials on the basis of the concept of an ensemble of pores

A class of models of porous media based on the concept of an ensemble of pores with a certain distribution of the main geometric parameters (for example, the pore size) is considered. The cases of pores saturated with single-and two-phase multicomponent liquid mixtures are investigated. The properties of equilibrium states of the mixture are derived from the minimum free energy condition and the transfer laws from the decreasing free energy condition. The hydrodynamic connectivity of the pores is described by two types of kernels: one describes the spatial connectivity and the other the connectivity in an elementary macrovolume. Analytically and numerically, the one-dimensional problems of establishment of a steady-state regime, propagation of a passive admixture, and two-phase flow (an analog of the Buckley-Leverett problem) are investigated. A relationship between the models in question and relaxational filtration models is demonstrated. A simple model of capillary hysteresis related with the non-monotonicity of the pore area to volume ratio function is proposed.     

被动谐波锁模Er3+/Yb3+共掺双包层光纤环形腔激光器

为了实现高重复频率和高功率的光脉冲,实验采用Er3+/Yb3+共掺双包层光纤作为增益介质,稳定的中心波长为976 nm的高功率半导体激光器作为泵浦源,利用非线性偏振旋转锁模技术,得到稳定的自起振锁模光脉冲。当泵浦功率为2.4 W时,激光器输出重复频率为8.829 MHz的连续锁模光脉冲,平均输出功率为52.5 mW,自起振锁模泵浦阈值功率为0.6 W,并观测到了稳定的高阶谐波锁模、调Q和调Q-锁模光脉冲输出。     

装甲结构对被动电磁装甲防护射流性能的影响

为了实现被动电磁装甲对射流产生更加充分的破坏作用,减小装甲结构设计对射流参数的依赖性,提出了多层板结构被动电磁装甲。通过对多层板装甲等效电路的分析可知,在射流电阻占系统电阻主导的情况下,随着装甲板层数的增加,通过射流和装甲板的脉冲电流将大大提高。同时对多层装甲板电感计算可知,多层装甲板能够有效减小系统电感。通过对射流在多层装甲板间运动规律的分析,建立了脉冲电流对射流作用的数学模型,通过数值计算可知多层装甲板结构能有效减小射流头部和尾部的有效侵彻长度,并增加脉冲电流对射流的作用时间。