Numerical simulation of Richtmyer-Meshkov instability

The compressible Navier-Stokes equations discretized with a fourth order accurate compact finite difference scheme with group velocity control are used to simulate the Richtmyer-Meshkov (R-M) instability problem produced by cylindrical shock-cylindrical material interface with shock Mach number Ms=1.2 and density ratio 1:20 (interior density/outer density). Effect of shock refraction, reflection, interaction of the reflected shock with the material interface, and effect of initial perturbation modes on R-M instability are investigated numerically. It is noted that the shock refraction is a main physical mechanism of the initial phase changing of the material surface. The multiple interactions of the reflected shock from the origin with the interface and the R-M instability near the material interface are the reason for formation of the spike-bubble structures. Different viscosities lead to different spike-bubble structure characteristics. The vortex pairing phenomenon is found in the initial double mode simulation. The mode interaction is the main factor of small structures production near the interface.

     

Kinetics and Modeling of Vinyl Acetate Graft Polymerization from Poly(ethylene glycol)

A kinetic model for the graft polymerization of VAc from PEG was developed using the method of moments. Experiments were carried out to verify the model. The effect of various parameters, such as initiator concentration, temperature, and PEG molecular weight on the polymerization kinetics was examined. Polymerization rate, grafting efficiency, graft copolymer molecular weight, and PEG grafted ratio were measured. The model was in good agreement with the experimental data. No gel effect was observed at the studied PEG/VAc weight ratio of 1:1. The chain transfer constant to PEG was correlated to be . The model was also applied in a semi‐batch reaction and compared with the experimental results.

     

Preparation and SO2 Absorption/Desorption Properties of Crosslinked Poly(1,1,3,3‐Tetramethylguanidine Acrylate) Porous Particles

Summary: Novel crosslinked porous particles based on the ionic copolymer of 1,1,3,3‐tetramethylguanidine acrylate (TMGA) and N,N‐methylenebisacrylamide (MBA) were prepared via an inverse suspension polymerization using cyclohexane as continuous phase and Span 60 as the dispersant. The SO₂ absorption–desorption properties of the P(TMGA‐co‐MBA) particles were studied for the first time. The particles showed excellent SO₂ absorption properties: high capacity and rate. These absorption properties, as well as the particle volume, shape, and morphology, remained unchanged during the SO₂ absorption–desorption cycles. The material appeared to be a good candidate as SO₂ absorbent for fuel gas desulfurization (FGD) and purification of other SO₂‐containing gases.

Optical microscope image of the P(TMGA‐co‐MBA) porous particles.     

Speciation of Fe(III) and Fe(II) in water samples by liquid–liquid extraction combined with low-temperature electrothermal vaporization (ETV) ICP-AES

The use of 1-phenyl-3-methyl-4-benzoylpyrazolone (PMBP) as extractant for separation of Fe(III) and Fe(II) and low-temperature vaporization of the Fe(III)–PMBP chelate into ICP-AES for their speciation analysis was investigated. The factors affecting the formation of Fe(PMBP)₃ chelate and its vaporization behavior were investigated in detail. PMBP was used not only as the extractant for the separation of Fe(III) and Fe(II) but also as the chemical modifier for the low-temperature ETV-ICP-AES determination of iron. Under the optimized conditions, the detection limit for iron(III) and iron(II) are both 3.2?ng/mL, with relative standard deviations of 3.9 and 4.5%, respectively. The proposed method was applied to the determination of trace iron in biological standard reference materials and the species in East Lake water samples, and the results obtained were satisfactory.     

基于δ算子的网络控制系统最优控制方法

针对具有时延的网络控制系统研究其最优控制问题.利用线性离散系统有限时域的增量式差分变换来取代传统的离散变换,在δ算子域内应用动态规划理论,设计线性离散二次型最优控制律,将包含时延参数的当前状态量和前一时刻的控制信号组成增广向量并进行闭环反馈控制律设计.经过理论和仿真验证,当采样周期趋于无穷小时,δ算子域离散系统的模型参数逼近于相应的连续时间模型参数.     

衍射微透镜列阵的研究与应用

本文研究了衍射微透镜列阵的设计与制作工艺方法，在此基础上研制出一系列衍射微透镜列阵，衍射效率均大于８５％，在深紫外、可见及红外波前传感器中得到了成功应用。     

可燃气体检测报警器计量检定与计量管理的探讨

指出了可燃气体检测报警器计量检定的重要性,结合河南省南阳市辖区内可燃气体检测报警器计量检定的现状,着重分析了计量检定与计量管理存在的问题和难点,并且提出了相关建议。     

Regio- and stereoselective synthesis of highly functionalized vinyl ethers via coiodination of acetylenic ketones

A Cu(OTf)₂-catalyzed highly regio- and stereoselective coiodination of acetylenic ketones was reported, providing a mild and convenient method for the synthesis of (Z)-β-carbonyl-β-iodoenol ethers in good yields.     

基于多版本冗余进程的容侵系统

针对利用多样性防御入侵和容忍入侵的典型方法的不足,提出了一种在操作系统的系统调用层上实现的多版本冗余进程的容侵系统。采用指令集随机化实现了多版本的冗余进程,并且利用冗余进程间系统调用的一致性,通过封装Linux内核中系统调用,实现了容侵系统的分发器、比较器。实验证明:该系统能有效地容忍针对恶意代码注入类型的入侵。     

Stochastic bounded consensus tracking of leader–follower multi-agent systems with measurement noises based on sampled-data with small sampling delay

This paper is concerned with the stochastic bounded consensus tracking problems of leader–follower multi-agent systems, where the control input of an agent can only use the information measured at the sampling instants from its neighborhood agents or a virtual leader with a time-varying reference state, the measurements are corrupted by random noises, and the signal sampling process induces a small sampling delay. The augmented matrix method, probability limit theory and algebra graph theory are employed to derive the necessary and sufficient conditions guaranteeing mean square bounded consensus tracking. It turns out that the convergence of the proposed protocol simultaneously depends on the constant feedback gains, the network topology, the sampling period and the sampling delay, and that the static consensus tracking error depends on not only the above-mentioned factors, but also the noise intensity, the number of agents and the upper bound of the changing rate of the virtual leader’s state. The obtained results cover no sampling delay as a special case. Simulations are provided to demonstrate the effectiveness of the theoretical results.