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A contraction-expansion Helical Mixer in the Laminar Regime

Chinese Journal of Chemical Engineering 2014年第3期22卷 261-266页

作者：梁栋张淑芬 State Key Laboratory of Fine Chemicals Dalian University of Technology

A contraction-expansion helical mixer which combines several features, viz. helical pipes for induction of secondary flows and sudden expansion and contraction array tor expansion vortices, has been designed to en- hance flow mixing. A fast competitive-consecutive diazo coupling reaction is used to test the mixing efficiency of contraction-expansion helical mixer. Furthermore, an image processing technique is applied for data visualization and monitoring the extent of mixing. The mixing performance is found to be superior in comparison to the regular helical mixer in the range of Reynolds number from 170 to 1540. Moreover, the mixing time of contraction-expansion helical mixer was found to be reduced by more than 25% compared to the regular helical pipe. Finally, a simple correlation is proposed for predicting the mixing time.

关键词： contraction-expansion helical pipe mixing laminar flow

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Variable universe stable adaptive fuzzy control of nonlinear system

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Science China(Technological Sciences) 2002年第3期45卷 225-240页

作者：李洪兴苗志宏王加银 1. Department of Mathematics Beijing Normal University 100875 Beijing China 2. Department of Mathematics Sichuan Normal University 610066 Chengdu China 3. Department of Automation Tsinghua University 100084 Beijing China

A kind of stable adaptive fuzzy control of nonlinear system is implemented using variable universe method. First of all, the basic structure of variable universe adaptive fuzzy controllers is briefly introduced. Then the contraction-expansion factor that is a key tool of variable universe method is defined by means of integral regulation idea, and a kind of adaptive fuzzy controllers is designed by using such a contraction-expansion factor. The simulation on first order nonlinear system is done. Secondly, it is proved that the variable universe adaptive fuzzy control is asymptotically stable by use of Lyapunov theory. The simulation on the second order nonlinear system shows that its simulation effect is also quite good. Finally a useful tool, called symbolic factor, is proposed, which may be of universal significance. It can greatly reduce the settling time and enhance the robustness of the system.

关键词： nonlinear systems, variable universe adaptive fuzzy control, contraction-expansion factor, symbolic factor, stable domain.

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Adaptive fuzzy controllers based on variable universe

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Science China(Technological Sciences) 1999年第1期42卷 10-20页

作者：李洪兴 1. Department of Mathematics Beijing Normal University 100875 Beijing China

Adaptive fuzzy controllers by means of variable universe are proposed based on interpolation forms of fuzzy control. First, monotonicity of control rules is defined, and it is proved that the monotonicity of interpolation functions of fuzzy control is equivalent to the monotonicity of control rules. This means that there is not any contradiction among the control rules under the condition for the control rules being monotonic. Then structure of the contraction-expansion factor is discussed. At last, three models of adaptive fuzzy control based on variable universe are given which are adaptive fuzzy control model with potential heredity, adaptive fuzzy control model with obvious heredity and adaptive fuzzy control model with successively obvious heredity.

关键词： fuzzy control variable universe contraction-expansion factor interpolator adaptive fuzzy control.

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