具有可变电控光栅常数的液晶光栅

针对现有液晶光栅器件存在的光栅常数不能变化、电极尖端放电、边缘效应等缺点,设计了一种可转换光栅常数的液晶光栅。通过控制不同导电区的通断电,使液晶光栅不同区域产生透光与不透光,实现光栅常数的转换;液晶光栅梳状电极端部的圆弧状设计,避免了尖端放电现象,减小了边缘效应的影响。以He-Ne激光为光源,用WGD-8A型组合式多功能光栅光谱仪对所设计的液晶光栅器件进行了测量,结果表明：通过控制导电区的变化实现了光栅常数的转变,在2～3.4 V电压驱动下,具有3种不同光栅常数的液晶光栅的1级衍射光强逐渐增强,且其衍射光强的差值不断增大,达到了预期设计目的。设计的液晶光栅在视差栅栏、光栅尺等方面有好的应用前景。     

耦合边处理的特征无反射边界条件研究

详细分析特征无反射边界条件(Characteristic Non-reflecting Boundary Conditions)中边耦合处理方法,提出耦合处理的数学方法,数值模拟表明,该方法处理声波扰动时有明显的优势.对可压缩圆孔射流进行直接数值模拟,结果与试验吻合较好,表明提出的耦合边处理的特征边界数学分析方法是可行的.     

污泥中常规生物指标的检测

介绍了污泥中三种常规生物检测指标,即细菌总数、粪大肠菌群和蛔虫卵的检测方法。污泥中细菌总数的检测采用平皿计数法,先将污泥样品稀释后选取2~3个适宜的稀释度进行培养;污泥中粪大肠菌群的检测采用多管发酵法,分别将稀释后的污泥混悬液接种于乳糖蛋白胨培养基和EC培养液中进行初发酵和复发酵实验;污泥中蛔虫卵的检测采用漂浮法,利用饱和硝酸钠溶液的比重大于蛔虫卵的原理,通过分离、离心、洗涤等步骤将样品中的蛔虫卵集中于载物玻片上镜检计数。文章对污水处理厂检测及排放污泥有一定的指导意义。     

Pulsated free jets with polydisperse spray injection: Experiments and numerical simulations

In the present contribution, we consider acoustically pulsated free jets with a polydisperse spray injection in an axisymmetrical configuration. The acoustic excitation creates periodical large vortical structures, which are representative of the dynamics of gaseous flows in more complex configurations, and a strong interaction with the injected spray. In this context, we provide a series of detailed experimental measurements using laser diagnostics; we analyze droplet size distributions, associated size-conditioned dynamics and evaporation, for three liquids, leading to various droplet preferential concentrations due to the vortices. Besides the achievements in terms of diagnostics, we use the Eulerian multi-fluid model and dedicated robust numerical schemes in order to conduct simulations in the chosen configuration. Detailed comparisons between numerical simulations and experimental measurements are provided in terms of spray velocity and number density. Size-conditioned preferential concentration of both non-evaporating and evaporating sprays are observed and reproduced by the numerical simulations, which eventually yields a validation of the proposed model.     

Remote points and the like in pointfree topology

A point p of β, where X is a Tychonoff space, is called a remote point if for any nowhere dense D ⊆, X, p ∉ cl_βx D. A subset S of X is called round if whenever the closure in βX of a zero-set of X contains S, then it is a neighborhood of S. The purpose of this paper is to study these notions in the pointfree context. In the process, we introduce N-homomorphisms and show how the Stone extension of an N-homomorphism transfers remote points back and forth.      

Raman analysis of defects in n-type 4H-SiC

This paper employs micro-Raman technique for detailed analysis of the defects (both inside and outside) in bulk 4H-SiC. The main peaks of the first-order Raman spectrum obtained in the centre of defect agree well with those of perfect bulk 4H-SiC, which indicate that there is no parasitic polytype in the round pit and the hexagonal defect. Four electronic Raman scattering peaks from nitrogen defect levels are observed in the round pit (395\,cm$^{-1}$, 526\,cm$^{-1}$, 572\,cm$^{-1}$, and 635\,cm$^{-1})$, but cannot be found in the spectra of hexagonal defect. The theoretical analysis of the longitudinal optical plasmon--phonon coupled mode line shape indicates the nonuniformity of nitrogen distribution between the hexagonal defect and the outer area in 4H-SiC. The second-order Raman features of the defects in bulk 4H-SiC are well-defined using the selection rules for second-order scattering in wurtzite structure and compared with that in the free defect zone.     

NUMERICAL STUDY ON THE STABILITY AND MIXING OF VERTICAL ROUNE BUOYANT JET IN SHALLOW WATER

The k-epsilon model was applied to establish the mathematical model of vertical round buoyant jet discharging into confined depth, and it was solved using the Hybrid Finite Analytic Method ( HFAM ). The numerical predictions demonstrate two generic flow patterns for different jet discharge and environmental parameters: ( i ) a stable buoyant flow discharge with the mixed fluid leaving the near-field warm in a surface warm water layer;( ii ) an unstable buoyant flow discharge with recirculation and re-entrainment of warm water in the near field. Furthermore, the mixing characters of vertical round buoyant jet were numerically predicted. Both the stability criterion and numerical predictions of bulk dilutions are in excellent agreement with Lee and Jirka ' s experiments and theory.     

Secure state estimation for complex networks with multi-channel oriented round robin protocol

This paper focuses on the secure state estimation problem for complex networks (CNs) which are compromised by deception attack and constrained with limited communication resource. Firstly, a multi-channel oriented round robin (RR) protocol is proposed to schedule the data transferred over the communication network consisting of multiple transmission channels. The extended RR protocol can not only avoid the data collision caused by limited communication resource, but also fully utilize the sliced network bandwidth. Then, a state estimation error model is constructed by further considering the influence of deception attack. Following the model, efficient state estimators are designed based on analyzing the sufficient conditions that assuring the stability of the formulated state estimation error system. Finally, numerical results are presented to validate the theoretical outcomes.     

具有波阻抗不连续特性的粘弹性介质中的逆散射问题

在时间域内讨论了粘弹性介质的逆散射问题,其中粘弹性介质的波阻抗在远离入射波作用面一侧的交界面上是不连接的。介质的散射算子,传播算子所满足的微分积分方程可以用来反演未知的粘弹性介质的松弛模量,文中给出的反演过程只须利用介质层一侧的反射算子在一个走时来回的时间内的实验测量数据。最后,给出了数值算例,计算结果表明,利用方法可以较准确的反演得到材料松弛模量。