Jeng J.-S.,Far East University of Taiwan
Journal of Alloys and Compounds | Year: 2013
WO3-Sb thin films with and without Sb doping were prepared by the sol-gel spin-coating method. The surface morphology, crystal structure, and binding energy of the WO3-Sb films were investigated before and after annealing under O2 or N2 atmospheres. After spin-coating, Sb2O3 precipitates on the surface of the as-deposited amorphous WO3 films with different Sb/W molar ratios. After annealing in O2 or N2 ambients, the precipitates start to disappear and then microvoids appear on the surface of the crystalline WO3 films with 5% and 10% molar ratios of Sb. WO3-Sb thin films present the monoclinic phase after annealing at 700 °C in N2, whereas films show the tetragonal phase after annealing at the same temperature in O2. In addition, Sb segregation occurs on the surface of the WO 3 films with Sb additives after annealing at 700 °C in N 2 ambient. This study discusses the connection among the Sb additive of the WO3-Sb films and how they are influenced by the Sb/W molar ratios and the annealing atmospheres of WO3-Sb films. © 2012 Elsevier B.V. All rights reserved.
Lin C.-N.,Far East University of Taiwan
International Journal of Heat and Mass Transfer | Year: 2012
In this study, the characteristics of the three-dimensional heat and fluid flow fields generated by the vibrating fan are examined by performing numerical simulations and experimental measurements. This paper considers two different arrangements of the heat source, namely vertical and horizontal. In performing the simulations, the fluid domain is meshed using a dynamic meshing scheme in order to take account of the time-varying shape and position of the vibrating blade. The results show that the interaction between the normal force exerted on the air surrounding the moving blade and the impingement jet flow produced at the blade tip prompts the formation of two counter-rotating screw-type flow circulations on either edge of the blade. An infrared thermal camera is used to measure the temperature distribution on the heated surface to examine the numerical results. It is indicated that the piezoelectric fan improves the heat transfer coefficient by 1.6-3.4 times when the heat source is vertically arranged and 1.8-3.6 times when the heat source is horizontally arranged. © 2012 Elsevier Ltd. All rights reserved.
Jeng J.-S.,Far East University of Taiwan
Applied Surface Science | Year: 2012
SnO 2 films with and without Sb doping were prepared by the sol-gel spin-coating method. Material properties of the SnO 2 films with different Sb contents were investigated before and after annealing under O 2 or N 2. When SnO 2 films are annealed under N 2 or O 2, the resistivity decreases with increasing annealing temperature, which may be related to the increased crystallinity and reduced film defects. The intensity of SnO 2 peaks for both O 2- and N 2-annealed films increases as the annealing temperature increases. Small nodules are revealed on the surface of SnO 2 films after annealing in N 2 or O 2 atmospheres, and some voids are present on the surface of N 2-annealed SnO 2 films. After doping with Sb, the resistivity of SnO 2 films after annealing in O 2 is greater than that of N 2-annealed SnO 2 films. The surface morphology of SnO 2 films incorporating different molar ratios of Sb after annealing are similar to that of as-spun SnO 2 films with adding Sb. There were no voids found on the surfaces of N 2-annealed SnO 2:Sb films. In addition, the peak intensity of SnO 2:Sb films after O 2-annealing is higher than those films after N 2-annealing. The chemical binding states and Hall mobility of the high-temperature annealed SnO 2 films without and with adding Sb are also related to the annealing atmospheres. This study discusses the connection among the material properties of the SnO 2 films with different Sb contents and how these properties are influenced by the Sb-doping concentration and the annealing atmospheres of SnO 2 films. © 2012 Elsevier B.V. All rights reserved.
Yang S.-K.,Far East University of Taiwan
Asian Journal of Control | Year: 2012
This paper presents a new strategy for suppressing the windup effect caused by actuator saturation in proportional-integral-derivative (PID) controlled systems. In the proposed approach, the windup effect is modeled as an external disturbance imported to the PID controller and an observer-based auxiliary controller is designed to minimize the difference between the controller output signal and the system input signal in accordance with an H-infinite optimization criterion. It is shown that the proposed anti-windup (AW) scheme renders the performance of the controlled system more robust toward the effects of windup than conventional PID AW schemes and provides a better noise rejection capability. In addition, the proposed PID AW scheme is system independent and is an explicit function of the parameters of the original PID controller. As a result, the controller is easily implemented using either digital or analog circuits and facilitates a rapid, on-line tuning of the controller parameters as required in order to prevent the windup effect. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society.
Wang C.-C.,Far East University of Taiwan
Computers and Mathematics with Applications | Year: 2012
This paper studies the bifurcation and nonlinear behaviors of a united gas-lubricated bearing (UGB) system by a hybrid numerical method combining the differential transformation method and the finite difference method. The analytical results reveal a complex dynamic behavior comprising periodic, sub-harmonic, quasi-periodic and chaotic responses of the rotor center. Furthermore, the results reveal the changes which take place in the dynamic behavior of the bearing system as the rotor mass and bearing number are increased. The current analytical results are found to be in good agreement with those of other numerical methods. Therefore, the proposed method provides an effective means of gaining insights into the nonlinear dynamics of UGB systems. © 2011 Elsevier Ltd. All rights reserved.