Showing papers by "South China University of Technology published in 1996"

Genetic algorithms and their applications

Abstract: This article introduces the genetic algorithm (GA) as an emerging optimization algorithm for signal processing. After a discussion of traditional optimization techniques, it reviews the fundamental operations of a simple GA and discusses procedures to improve its functionality. The properties of the GA that relate to signal processing are summarized, and a number of applications, such as IIR adaptive filtering, time delay estimation, active noise control, and speech processing, that are being successfully implemented are described.

Growth and phycocyanin formation of Spirulina platensis in photoheterotrophic culture

Abstract: Glucose and acetate enhanced cell growth and phycocyanin production of S. platensis. The highest specific growth rate, cell concentration and phycocyanin production were respectively 0.62 d-1, 2.66 g/l and 322 mg/l on glucose and 0.52 d-1, 1.81 g/l and 246 mg/l on acetate. The specific growth rate of the alga on 2.5 g glucose/l was markedly increased with increasing light intensity up to 2 klux. Further increasing light intensity to 4 klux only resulted in a very slight increase in specific growth rate. At a light intensity above 4 klux, photoinhibition occurred. Light favoured phycocyanin formation. The highest phycocyanin content was obtained at a light intensity of 4 klux. When the light intensity decreased to 2 klux or less, the optimal glucose concentration for biomass production shifted from 2.5 g/l to 5.0 g/l.

Anelastic relaxation associated with the motion of domain walls in barium titanate ceramics

Abstract: The mechanical loss (Q −1) and shear modulus (G) were measured as a function of temperature in the range 130 K < T < 430 K for BaTiO3 ceramics by an inverted pendulum at low frequencies ranging between 1-0.01 Hz. The Q −1 (T) and G(T) curves exhibit the three phase transitions observed in BaTiO3. Each phase transition induces a loss peak and an anomaly in the elastic modulus. Moreover, three other loss peaks (R) are located below the phase transition temperature. These peaks can be described by an Arrhenius relationship, and the activation energies are determined as 0.92, 0.68, and 0.45 eV for the peak located in the tetragonal-, orthorhombic-, and rhombohedral-phase, respectively. These peaks are due to the interaction between the domain walls and the diffusion of oxygen vacancies in the domains.

Mechanical loss and Young's modulus associated with phase transitions in barium titanate based ceramics

Abstract: The mechanical loss (Q −1) and Young's modulus (E) were measured as a function of temperature in the range 100 K

Electrorheological properties of chitin suspensions

Abstract: Electrorheological suspensions are suspensions of solid particles whose rheological behavior can be strongly modified by the application of an electric field. In this article, the electrorheological properties of suspensions containing chitin particles (and its derivative-carboxylmethyl chitosan particles) in silicone oil are reported for a range of suspension weight concentrations, applied field strengths, shear rates, etc. In these suspensions, glycerin was used as an activator. The adsorbed amount of glycerin, one of the electrorheological parameters, was also studied experimentally. The ER effect of the chitin suspension reaches the maximum at about 11% of weight concentration. The dependence of the experimentally determined dynamic yield stress on particle concentration and field strength is found to be similar to that reported for other systems. The dynamic yield stress is found to increase with the particle concentration and the applied electric field strength.

Carbohydrate Digestibility and Resistant Starch of Steamed Bread

Abstract: Sixteen Australian hard and soft wheats and two U.S. hard wheats were milled into flours (break and reduction) for preparation of steamed breads. Chemical composition and rheological properties of the flour were determined. Steamed breads were analyzed for carbohydrate digestibility and resistant starch. There was no relationship between flour type, protein content and specific volume of steamed breads. Carbohydrate digestibility of steamed breads from soft wheat flour was higher than that of breads from hard wheat flour. Reduction flours produced steamed breads with higher carbohydrate digestibility than break flours. Resistant starch was higher in steamed breads from soft wheat flours than in those from hard wheat flours. Reduction flour produced higher resistant starch levels than break flours. Commercial white bread had resistant starch levels similar to those of steamed breads from soft wheat flour and hard wheat reduction flour. Verdaulichkeit der Kohlenhydrate und resistente Starke in bedampftem Brot. Sechzehn australische Hart- und Weichweizen sowie zwei U.S.-Hartweizen wurden zu Mehlen (grob und fein) vermahlen zur Herstellung von bedampften Broten. Die chemische Zusammensetzung und die rheologischen Eigenschaften des Mehls wurden bestimmt. Bedampfte Brote wurden hinsichtlich Verdaulichkeit und resistenter Starke analysiert. Es gab keinen Zusammenhang zwischen Mehyltype, Proteingehalt und spezifischem Volumen der bedampften Brote. Die Kohlenhydratverdaulichkeit bedampfter Brote von Weichweizenmehlen war hoher als die der Brote aus Hartweizenmehl. Feine Mehle ergaben bedampfte Brote mit hoherer Kohlenhydratverdaulichkeit als die aus Grobmehlen. Der Gehalt an resistenter Starke war bei Weichweizenmehlen hoher als bei Hartweizenmehlen. Feinweizenmehle erzeugten mehr resistente Starke als Grobmehle. Handelsubliches Weisbrot enthielt ahnliche Mengen an resistenter Starke wie bedampfte Brote aus Weichweizenmehl und Hartweizen-Feinmehl.

A study of platinum-thulium/KL zeolite reforming catalysts

Abstract: The Pt KL catalyst modified by Tm 2 O 3 has been characterized by the n-hexane, methylcyclopentane (MCP) and cyclohexane conversion reaction. The results show that the activity for the aromatization on Pt-Tm/KL zeolite catalysts containing thulium ranging from 0.05 to 0.2 wt.-% is higher than that on the Pt KL catalyst, and the stability of the modified catalysts is remarkably improved. The influence of thulium on the surface property of the Pt KL catalyst has also been studied with absorbed pyridine IR spectra and adsorption of methanol.

Elastic modulus and mechanical loss associated with phase transitions and domain walls motions in PZT based ceramics

Abstract: Elastic modulus (shear modulus G or Young's modulus E) and internal friction Q -1 were measured as a function of temperature on undoped Pb(Zr 50 Ti 50 )O 3 , Pb(Zr 22 T 48 )O 3 > Pb(Zr 54 Ti 46 )O 3 ceramics from -180°C to 500°C. Experiments were performed at low and medium frequencies (0.1 Hz - 4 kHz). The E(T) curves show two anomalies which are due to following phase transitions: tetragonal to cubic (Tc) and rhombohedral to tetragonal (TR-T). The Tc temperatures are in good agreement with phase diagram from litterature. The T R-T temperatures allow to complete the phase diagram of the morphotropic phase boundary of PZT in the low temperature range. Moreover,Q -1 (T) curves recorded at low frequencies show two relaxation peaks; their activation energy and relaxation time are determined using the Arrhenius plots. These two relaxation peaks could be attributed to the interaction of domain walls with point defects.

A new method of determining the stress state in microelectronic materials

Abstract: This paper introduces a new technique of determining the stress in microelectronic materials by combining photoelasticity and Fourier analysis. The approach uses a continuously rotating analyser to determine the photoelastic parameters from a Fourier analysis of the measured emerging light intensity. The principle of operation is discussed and the apparatus is described. An example is demonstrated to illustrate the application of the technique.

Chinese signature verification with moment invariants

Abstract: Zernike moment invariants have been widely used in pattern recognition and image processing. In this paper, Chinese signature verification using normalized Zernike moment invariants (NZMI) is proposed. Different orders of moment invariants are studied. Simulation results show that the proposed approach for signature verification is rotation-invariant and scale-invariant, and the preliminary results we got are very promising. Furthermore experiments using projection are also carried out. The results are compared with those of NZMI.

Factors Affecting the Determination of β-Cyclodextrin by Phenolphthalein Spectrophotometry

Abstract: The sensitivity of the phenolphthalein spectrophotometric method for the determination of the purity of β-cyclodextrin (β-CD) was studied under different conditions. The alkalinity of the phenolphthalein colorimetric solution and the concentration of phenolphthalein in the colorimetric solution affected the sensitivity of the spectrophotometric readings and the linear range of the calibration curve. The optimum conditions for a basic working solution at pH 10.53 were that 5 ml of phenolphthalein working solution and 5 ml of sodium borate working solution were made up to a total 50 ml of phenolphthalein colorimetric solution, and the optimum conditions for a basic working solution at pH 11.23 were that 5 ml of phenolphthalein working solution and 3 ml of sodium borate working solution were made up to 50 ml total solution. Because of the instability of the absorbance of phenolphthalein solutions, it is suggested that at over 98% purity, β-CD should be determined by other more accurate methods.

Domain Walls Motions in Barium Titanate Ceramics

Abstract: The shear modulus and mechanical loss at low frequencies (0.01, 0.3, 1 Hz) are measured by an inverted pendulum for BaTiO 3 ceramic with large grain sizes. The permittivity and dielectric losses are also investigated for the same material at higher frequencies between 1 and 100 kHz as function of temperature. Those results show several relaxation peaks in the ferroelectric phases. The activation energy of each peak is obtained to be 0.29, 0.45, 0.68, 0.92 eV. The influences of strain amplitude and thermal treatments are studied specially for the mechanical relaxation peak located in the tetragonal phase. All the relaxation peaks could be associated to the interaction of oxygen vacancies in the domain with different configurations of domain walls by piezoelectric effect. The experimental results show there is one peak occurring in all the three ferroelectric phases, which could mean that the ferroelectric domain structures have certain memory effect.

Technical note Further results on robust bounds for large-scale time-delay systems with structured and unstructured uncertainties

Abstract: Robust stability conditions for the large-scale time-delay system with structured and unstructured uncertainties are established by the Lyapunov functional method together with matrix measures. As the delays under consideration can be arbitrary unknown but constant, all of the obtained results are delay-independent. An illustrative example is provided to compare with the existing results to show that much larger robust stability bounds can be obtained. Therefore, the proposed method is less conservative than current methods.

Grain refinement and microstructural effects on mechanical and tribological behaviours of Ti and B modified aluminium bronze

Abstract: Microstructural effects on mechanical and tribological behaviours have been studied for a series of aluminium bronzes with different microstructures. ASTM 1045 and 52100 steels were used as the counterparts in the friction and wear tests. Experimental data show that the coefficients of friction, wear rate and mechanical properties strongly depend on the volume fraction of α-phase present in the alloy and, to a lesser extent, on the average α-grain size. The minimum coefficients of friction and the wear rate correspond to a yield strength of 370 N mm−2 and a bulk hardness of HB 168. Except for extreme low average α-grain size (corresponding to low volume fraction), both the coefficients of friction and the wear rate show linear relations with the reciprocal of the yield strength of the alloy, but not to the reciprocal of the hardness as expected. Based on these results, a design principle for high strength wear-resistant aluminium bronze has been developed.

Diffusion-Deposition of Polyaniline onto Textiles with High Electric Conductivity and Improved Adhesion

Abstract: By aniline (ANI) diffusion and chemically oxidative polymerization, PANI was adherently deposited on PET fibres and Nylon fabrics PANI-PET fibres and PANI-Nylon fab rics doped with HCl have an electric conductivity as high as 0 42 S/cm and 0 45 S/cm respec tively With p-toluenesulfonic acid (p-TSA) and dodecylbenzene sulfonic acid (DBSA) and 5- sulfosalicylic acid (SSA) as dopants, the conductivity and final composites is one or two orders of magnitude lower than that with HCl A washing test was designed to investigate the interfacial ad hesion of PANI on textiles Results showed that the conductivity and interfacial adhesion of composites are improved greatly by preliminary aniline diffusion treatment of textiles Further in vestigations by SEM and WAXS and DSC showed that the improvement in properties of com posite textiles is mainly attributed to the increased interaction of macromolecules at the interface caused by the diffusion of PANI chains in the surface layer of the substrates

Application of exergoeconomics to the analysis and optimization of process systems

Abstract: The definitions and purposes of energy systems and process systems are compared in this paper by considering the role of energy in systems with emphasis on the differences in the methods used to optimize the exergoeconomic benefits of both types of systems. The process system exergoeconomic relationship primarily include the establishment of the Three-link model of process systems, the composition of objective functions, and the corresponding boundary constraint conditions for optimization. The Three-Link-Method (TLM) which is based on exergoeconomics, can be used to effectively optimize process systems. The TLM used to optimize process systems is outlined in this paper. Some aspects which need further development are also identified.

Stability for composite singular systems of differential equations with a delay

Abstract: In this paper, we gave an exponential estimate for the solutions of singular systems of differential equations with a delay and establish a comparison inequality for the systems. Based on this we estabish the criteria for asymptotic stability for the composite singular systems.