具有小密度差的两层流体中运动点源的二阶内波解

在具有自由面的两层流体中，运动点源生成的Kelvin船波存在两种模式，即表面波模式和内波模式。当上、下层流体密度比趋于1时，由内波模式计算的界面波幅趋于无穷大，这与实验事实相违背。为克服此困难，在自由面和界面作小波幅运动的假设，引入一个小密度差参数。研究了运动点源在无粘、不可压且具有小密度差的两层有限深流体中生成的高阶波动。首先利用摄动方法推导了各阶小参数满足的边值问题；其次，给出了小密度差情形下的可解性条件。证明了在密度比趋于1的极限情形，不存在导致界面波幅无穷大的内波模式；最后，利用Phillips的非线性共振相互作用理论，构造了具有自由面的两层有限深流体中Kelvin船波系的二阶一致有效波动解，并证明了该解在深水情形下退化为Newman关于均匀流体中自由面的二阶波动解。     

多任务实时系统提高实时性的方法及其在导航综合信号源系统中的应用

总结了在多任务条件下实时分布式计算机系统中提高实时性的基本原则，并结合某导航信号源系统的开发，详细介绍了在Windows环境下以C Builder为开发工具如何实现串行通信中的精确定时的方法。实验表明：运用该方法多任务系统能在毫秒级时间精度上可靠工作。     

Nonlinear H∞ control of structured uncertain stochastic neural networks with discrete and distributed time varying delays

This paper is concerned with the problem of robust H∞ control for structured uncertain stochastic neural networks with both discrete and distributed time varying delays. A sufficient condition is presented for the existence of H∞ control based on the Lyapunov stability theory. The stability criterion is described in terms of linear matrix inequalities （LMIs）, which can be easily checked in practice. An example is provided to demonstrate the effectiveness of the proposed result.     

Hydrodynamic Behavior in a Tapered Bubble Column

IntroductionBubble column( BC) and slurry bubble column( SBC) reactors have emerged as one of the mostpromising devices in chemical,biochemical and en-vironmental engineering operations because of theirsimple construction,isothermal conditions,highheat and mass transfer rates,and on- line catalystaddition and withdrawal[1_ 4] .The utilization of ta-pered slurry bubble column( TSBC) reactorshas re-cently received much attention ofsome scholars andscientists who are engaged in biochemical rea…     

分层递进教学在初中化学教学中的运用

本文运用智育心理学的研究成果,提出了“分层递进教学”,并配以“元认知”的学习策略。使分层递进教学真正符合学生认知发展和心理发展的客观规律,符合素质教育面向全体学生,使全体学生喜爱化学、学好化学。     

熔融插层法制备LLDPE/MgAl-LDH 剥离型纳米复合材料及其热性能研究

The interlayer surface of MgAl layered double hydroxide （MgAl-LDH） was modified by exchanging about half of the interlayer nitrate anions by dodecyl sulfate anions （DS） to get MgAl（H-DS） LDH, and then the MgAl（H-DS） was melt intercalated by LLDPE to get the LLDPE/MgAl-LDH exfoliation nanocomposites. The samples were characterized by Fourier transform infrared （PTIR） spectroscopy, X-ray diffraction （XRD）, ion chromatography, transmission electron microscopy （TEM）, and thermogravimetry analysis （TGA）. The nanoscale dispersion of MgAl-LDH layers in the LLDPE matrix was verified by the disappearance of （001） XRD reflection of the modified MgAl-LDH and by the TEM observation. The TGA profiles of LLDPE/MgAl-LDH nanocomposites show a faster charring process between 210 and 370 ℃ and a higher thermal stability above 370 ℃than LLDPE. The decomposition temperature of the nanocomposites with 10 wt% MgAl（H-DS） can be 42 ℃ higher than that of LLDPE at 40% weight loss.     

自分层涂料的研究进展

与常规的多次涂膜体系相比,自分层涂料可以实现多层涂膜一次涂装,解决层间附着力差的问题,节约生产成本,提高使用寿命。本文综述了白分层过程及其驱动力,详细讨论了相容性和表面张力等影响自分层的因素,分别从溶剂型、无溶剂型和水性涂料方面阐述了自分层涂料的研究进展。自分层涂料已在众多领域得到了广泛应用,环境友好型自分层涂料是其今...