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Various TiO2/SiO2 composite nanoparticles were prepared by vapor phase hydrolysis of Titanium Tetraisopropoxide (TTIP) and Tetraethylorthosilicate (TEOS) in a tubular reactor heated by electrical furnace by changing the methods of reactant mixing, the molar ratio of the precursors and the set temperature of the furnace. These variables affected the average size and the bulk composition of the particles as well as their morphological and crystalline structures. The morphological structures of the particles were reconfirmed as T-S, S-T and T/S as in the previous study. Various correlations were obtained between the molar ratio of the precursors, and the size, the composition and the TiO2 main peak intensity of the particles as a parameter of the mode of reactant mixing. In general, it was found that high content of silicon constituent showed translucent envelopes surrounding primary particles, which increased the dispersion diameter of the particles, reduced the thermal stability, retarded the anatase-to-rutile transformation and the initial photocatalytic degradation of phenol in an aqueous solution.

A chaos maximizing optimal control problem is formulated and applied to Duffing's equation to maximize the largest Lyapunov exponent. The resulting bang-bang optimal controller yields a positive value of the largest Lyapunov exponent, indicating chaotic behavior. In fact, the largest Lyapunov exponent is approximately twice as large as that achieved with simple sinusoidal forcing at the same amplitude bounds. However, the resulting phase portrait of the optimal trajectory is a limit cycle and is not chaotic at all. This paradoxical result contradicts the basic theory that a bounded trajectory with at least one positive Lyapunov exponent must be chaotic. Details concerning the development of a chaos measurement that is viable for current optimal control theory, a method of continuous normalization, the paradoxical chaotic limit cycle, resolution of the paradox, and closed-loop optimal jump condition in an augmented space are presented. In particular, for systems of differential equations with only piecewise differentiable right-hand sides due to a switching control, a jump discontinuity condition must be imposed on the state perturbations in order to compute correct Lyapunov exponents.

When the response of a dynamical system is seemingly random and is confined in a finite region and shows extreme sensitivity to small changes in initial conditions, we say that the motion is chaotic. To represent chaos of a system precisely and quantitatively, we employ measurement quantity that represents the system's degree of chaos such as a Lyapunov exponent. A way of computing a Lyapunov exponent employs periodic renormalization for the state perturbation vector. However, the application of periodic renormalization for a Lyapunov exponent computation poses difficulties. One difficulty is exponential growth of the norm of the state perturbation vector. A common approach for avoiding this computational problem is periodic renormalization. However, periodic renormalization raises a discontinuity in the state perturbation vector that is not a standard case in optimal control theory as one wants to extremize chaos by manipulating a Lyapunov exponent. To circumvent the exponential growth in magnitude and the state perturbation vector discontinuity problem, one may employ a method of “continuous normalization” which replaces periodic discontinuous renormalization with differential equations that correspond to continuous normalization at each instant of time. This study provides details concerning the development of continuous normalization technique and presents an example for some systems. Also the comparison between the result produced by continuous normalization and that by the periodic renormalization of the state perturbation vector will be given.

The effect of the Pt electrode and the Pt-IrO/sub 2/ hybrid electrode on the performance of ferroelectric device was investigated. The modified Pt thin films with non-columnar structure significantly reduced the oxidation of TiN diffusion barrier layer, which rendered it possible to incorporate the simple stacked structure of Pt/TiN/poly-Si plug. When a Pt-IrO/sub 2/ hybrid electrode is applied, PZT thin film properties are influenced by the thickness and the partial coverage of the electrode layers. The optimized Pt-IrO/sub 2/ hybrid electrode significantly enhanced the fatigue properties with minimal leakage current.

In this paper, we describe a new speech/non-speech classification method that improves the endpoint detection performance for speech recognition in noisy environments. The proposed method uses multiple features to increase the robustness in noisy environments, and the classification and regression tree (CART) technique is applied to effectively combine these multiple features for classification of each frame. We evaluate the performance of the proposed method by conducting speech/non-speech classification experiments on noisy speech. We also investigate the importance of various features on speech/non-speech classification in noisy environments In particular, the proposed method is applied to the endpoint detection algorithm for isolated speech recognition of a voice-dialing cellular phone. We simulate the speech recognition experiments in various noise environments, and the effects of the proposed method on speech recognition performance are evaluated.

In the present study, in order to find out an grain refinement mechanism, 0.1wt.% Al-10wt.%Ti master alloy was added into A3003 alloy melt contained in graphite crucible and in alumina crucible, and then the melt holding time at 750°C was systematically changed from 1 min up to 120 min. It is interesting to note that the grain refinement and fading phenomena remarkably depend on the crucible material. The fading effect in the specimens using alumina crucible can be explained as the result of TiAl3 phase dissolution into molten aluminium matrix. In the specimens using graphite crucible, the grain refinement was occurred gradually with increasing holding time. It was suggest that the continuous grain refinement is due to transition of refinement mechanism from TiAl3 phase to TiC phase. It can be mentioned that the TiC formed from titanium and carbon solute in the aluminium melt, which came from the Al-10Ti alloy and the graphite crucible.