Showing papers by "Donghua University published in 2000"

Fuzzy self-tuning immune feedback controller for tissue hyperthermia

Abstract: A new universal controller structure suitable for various low or high order plants is presented. The controller includes a basic fuzzy self-tuning P-type immune controller inspired from the immune feedback mechanism of biological immune systems and an incremental block with the purpose to treat with the order of the plants. The P-type immune feedback law is automatically tuned by a fuzzy logic controller. The effectiveness of this control approach is examined by designing a fuzzy self-tuning PID-type immune controller to control tissue temperature during hyperthermia. Computer simulation results demonstrate that the control performance of the immune controller is superior to that of the corresponding linear controller.

DNA genetic algorithms for design of fuzzy systems

Abstract: A new DNA genetic algorithm (DNA-GA) based on the mechanism of biological DNA and genetic information is proposed. The genetic operators of the DNA-GA are discussed. The DNA encoding method is suitable for the representation of complex knowledge. The DNA-GA is employed to design effective generalized fuzzy systems (GFS) for the modeling and control applications. GFS employ arbitrary fuzzy rules, e(-|/spl alpha//sub 1/x/sub 1/+/spl alpha//sub 2/|)-type input fuzzy sets containing almost arbitrary continuous input fuzzy sets, arbitrary singleton output fuzzy sets, arbitrary fuzzy logic AND, and the generalized defuzzifier containing the widely-used centroid defuzzifier as a special case. The DNA-GA is used to select input variables and to tune the design parameters and membership functions of GFS. As such, the fuzzy rule sets of GFS can be obtained. The work in this paper provides a useful way for the design of fuzzy controllers and fuzzy models.

Optimization of Thermal Storage Based on Load Graph of Thermal Energy System

Abstract: Thermal energy storage (TES) can average the loads of thermal energy systems, thus increases their energetic and exergetic efficiencies. The steam boiler plant with violently fluctuating loads is a typical example when a steam accumulator is added to it. However, the comparatively big first cost constitutes a barrier to wide use of TES. The cost will notably be reduced through minimizing the necessary thermal capacity of TES. A computer program for performing the optimization is illustrated in the paper. This program was applied to an existing boiler plant equipped with a steam accumulator. The results show that there would have been a remarkable reduction in the necessary capacity, if the capacity of this steam accumulator had been optimized. Four conclusions have been reached.

Actual air separation across multilayer composite membranes

Abstract: Multilayer composite membranes are fabricated from six types of thin films as selective layers, an ethyl cellulose (EC) thin film as a flexible spacer, and poly(ether sulfone) (PES) with 15–45 nm pore size or 100–120 μm thickness as a porous support layer. The effects of the thin-film type and its layer number, operating temperature, and transmembrane pressure difference, as well as the operational time on the actual air-separation properties through the composite membranes, are investigated by a constant pressure-variable volume method. The results show that a pure polystyrene thin-film composite membrane exhibits poor actual air-separation performance due to its brittleness, although it has a higher ideal oxygen over nitrogen separation factor. The oxygen-enrichment air (OEA) flux through all of the composite membranes tested increases significantly with increasing operating temperature and pressure difference. The oxygen concentration in the OEA increases slightly with an increase in operating temperature, and the oxygen concentration through the polystyrene/cholesteryl oleyl carbonate blend, top layer composite membrane exhibits the maximal value. As the transmembrane pressure difference increases, the oxygen concentration in the OEA also exhibits the maximal value. The maximum oxygen concentration can reach 39.1%, which is achieved by the multilayer composite membrane consisting of a polystyrene/cholesteryl oleyl carbonate (95/5) monolayer, an EC single flexible spacer, and a PES support at 35°C and a transmembrane pressure difference of 550 kPa. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2396–2403, 2000

Optimal investment consumption model with a higher interest rate for borrowing

Abstract: This paper considers a consumption and investment decision problem with a higher interest rate for borrowing as well as the dividend rate. Wealth is divided into a riskless asset and risky asset with logrithmic Brownian motion price fluctuations. The stochastic control problem of maximizating expected utility from terminal wealth and consumption is studied. Equivalent conditions for optimality are obtained. By using duality methods the existence of optimal portfolio consumption is proved, and the explicit solutions leading to feedback formulae are derived for deteministic coefficients.

A prototype of fault diagnosis based on Petri nets

Abstract: A Petri net modeling tool using the object oriented method is introduced in this paper. With this tool, a Petri net-based prototype of fault diagnosis was developed using the model-based method. The prototype was connected to the database by DAO technique, and the firing mechanism and analytic methods of Petri net were used to form the DLL documents. Compared with the method of rule-based expert system, the Petri net-based one has the following advantages: 1) with direct knowledge representation; 2) with convenient knowledge storage in a form of mathematical matrix; and 3) making inference more quickly and effectively.

An improved generation algorithm for fractal patterns based on fuzzy stochastic iterated system

Abstract: The general concept of an iterated function system is introduced and fuzzy theory is drawn into the iterated function system when the probability relative to each affine transformation is chosen, therefore the fuzzy probability is put forward as well as an improved generation algorithm of fractal patterns based on a fuzzy stochastic iterated function system. The algorithm adjusts the probability distribution of each affine transformation in the iterated function system by a fuzzy adjusting factor, thus it better controls the shape and density of the patterns of fractal attractors, and this has been well tested and verified by examples.