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Two-stage densification of ultrafine transition alumina seeded with a-phase particulates
W.J.Wei,H.C.Kao,C.Y.Huang 한양대학교 세라믹연구소 2003 Journal of Ceramic Processing Research Vol.4 No.1
Highly densified Al2O3 was prepared from a transition (mainly q-phase) Al2O3 powder doped with a-seeds. Two thermal processing steps resulted in the densification and the q- to a-phase transformation were characterized by thermomechanical analysis (TMA), porosimetry, scanning and transmission electron microscopies (SEM and TEM). The evolution of the grain growth and porosity were observed. The results showed that the first-stage densification in association with the q- to a-phase transformation could be controlled to form ultrafine and uniform microstructures, and that would benefit the second-stage densification. The additional a-seeds do not only enhance the transformation rate and give a narrower pore size, but also allow the growth of uniform a-grains to sizes ca. 60 nm. The final densification properties of two seeded samples by thermal treatments were investigated revealing the effects of the transformation in the first stage and the influence of two sintering parameters, e.g. temperature and soaking time on the sintered microstructure.
Huang, Y.L.,Chen, H.J.,Rosowsky, D.V.,Kao, Y.G. Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.10 No.1
This paper proposes a simple numerical model for use in a finite analysis (FEA) of scaffold-shoring systems. The structural model consists of a single set of multiple-story scaffolds with constraints in the out-of-plane direction at every connection joint between stories. Although this model has only two dimensions (termed the 2-D model), it is derived from the analysis of a complete scaffold-shoring system and represents the structural behavior of a complete three-dimensional system. Experimental testing of scaffolds up to three stories in height conducted in the laboratory, along with an outdoor test of a five-story scaffold system, were used to validate the 2-D model. Both failure modes and critical loads were compared. In the comparison of failure modes, the computational results agree very well with the test results. However, in the comparison of critical loads, computational results were consistently somewhat greater than test results. The decreasing trends of critical loads with number of stories in both the test and simulation results were similar. After investigations to explain the differences between the computationally and experimentally determined critical loads, it was recommended that the 2-D model be used as the numerical model in subsequent analysis. In addition, the computational critical loads were calibrated and revised in accordance with the experimental critical loads, and the revised critical loads were then used as load-carrying capacities for scaffold-shoring systems for any number of stories. Finally, a simple procedure is suggested for determining load-carrying capacities of scaffold-shoring systems of heights other than those considered in this study.
Qi, W.,Park, J.H.,Cheng, J.,Kao, Y.,Gao, X. Elsevier Science B. V., Amsterdam 2017 NONLINEAR ANALYSIS HYBRID SYSTEMS Vol.26 No.-
This paper treats the problem of anti-windup design for stochastic Markovian switching systems with mode-dependent time-varying delays and saturation nonlinearity. The anti-windup compensator is designed such that the resulting system with mode-dependent time-varying delays and saturating actuator is stochastically stable and the domain of attraction is maximized. Sufficient conditions for the corresponding problem are proposed in terms of linear matrix inequalities. Finally, an example about RLC serial circuit demonstrates the validity of the proposed results.
T.H. Hsieh,C.H. Hsu,C.Y. Wu,J.Y. Kao,C.Y. Hsu 한국물리학회 2018 Current Applied Physics Vol.18 No.5
High-entropy alloy (AlCrNbSiTiV)N nitride films are prepared using direct current (dc) reactive magnetron sputtering, with an equiatomic AlCrNbSiTiV alloy target. Experiments using the grey-Taguchi method are conducted to determine the effect of deposition parameters (dc power, substrate temperature, N2/(N2+Ar) flow rate and substrate bias) on the microstructure, mechanical and tribological properties. Orthogonal array (L9 34), signal-to-noise ratio and analysis of variance are used to analyze the effect of the deposition parameters. The coated films are examined using scanning electron microscopy, an atomic force microscope, transmission electron microscopy (TEM), a tribometer and a nanoindenter. The TEM patterns confirm that the (AlCrNbSiTiV)N nitride films have a simple face-center-cubic structure. The experimental results show that a (AlCrNbSiTiV)N film coating significantly improves the mechanical properties. In the confirmation runs, using grey relational analysis, the improvement in friction coefficient is 32.5%, in corrosion current is 28.6%, in hardness H is 29.4%, in elastic modulus E is −18.3%, in H/E is 57.1 and in H3/E2 is 225.0%. The samples with (AlCrNbSiTiV)N film coating are classified as HF1 and exhibit good adhesive strength.