Wen Shiush Chen

Contour Optimization of Suspension Insulators Using Dynamically Adjustable Genetic Algorithms

Electrical-field distribution along the insulator surface strongly depends upon the contour design, besides the effect of pollution. The insulator contour should be designed to reach a desired uniform and minimal tangential field to increase the onset voltage of surface flashover. In this paper, with the charge simulation method (CSM) integrated, the dynamically adjustable genetic algorithm (DAGA) approach is proposed for contour optimization of a suspension insulator. The aim of the contour optimization is to minimize and make the tangential electric field uniform and to minimize the size of the insulator, subject to design constraints. In the proposed approach, the cubic spline function based on control (or contour) points on the insulator surface is optimized to derive the desired contour. The results show that a rather uniform and minimal tangential field distribution with a smaller suspension insulator can be obtained through the proposed approach in comparison with the commercial insulator practically deployed in transmission systems.

Optimal Design of Support Insulators Using Hashing Integrated Genetic Algorithm and Optimized Charge Simulation Method

This paper proposes a combined approach of optimized charge simulation method (CSM) and hashing integrated adaptive genetic algorithm (HAGA) to the contour design of support insulators. In the combined approach, the HAGA determines the optimal displacement ratio and number of fictitious charges used in CSM, and then obtains the optimal contour design to minimize and uniform the tangential electric field along the dielectric boundary based on the optimized CSM. The proposed HAGA method considerably improves the execution efficiency by accessing the fitness values of the searched solutions saved a priori in a hashing table during the optimization process. To verify the effectiveness of the proposed method, three cases of different contours of support insulators have been studied. Results show that rather uniform and minimal tangential field distributions along the insulator surfaces can be effectively derived by the proposed approaches to achieve promising performance and higher probability free from flashover.

Fabrication of Ti-Doped ZnO Thin Films by Chemical Bath Deposition

Effect of thermal treatments on the structural and electrical properties of the chemical bath deposition derived Ti-doped ZnO thin films are studied. XRD results show that the annealed Ti-doped ZnO films with wurtzite structure are randomly oriented. Crystallite structure, carrier concentration, resistivity and mobility are found to be dependent on the treatment temperature. At a treatment temperature of 100°C, the Ti-doped ZnO film possesses a carrier concentration of 2.5×1020 cm-3, a resistivity of 2.8×10-3 Ω-cm, and a mobility of 12 cm2/Vs.

Electrical Characteristics of ZnTe Thermoelectric Thin Films

Thermal coating growth of ZnTe thermoelectric films were deposited on n-type Si substrate is studied. Structural analysis through x-ray diffraction (XRD) and scanning electron microscopy (SEM) were sensitive to the RTA treatment. The electrical properties and microstructure of these films were investigated with special emphasis on the effects of various annealing temperatures from 600°C to 800°C by RTA technique. The highest carrier concentration, lowest resistivity and mobility at an annealing temperature of 700°C are 3.5×1015 cm-3, 0.25 Ω-cm, and 49 cm2V-1S-1. The resultant electrical properties have made ZnTe films as very interesting materials for thermoelectric device applications.

Luminescence Properties of Tm3+ /Dy3+ Co-Doped Zinc-Aluminum Phosphate Glasses for White LED

Tm3+ and Dy3+ co-doped zinc-aluminum phosphate glasses were prepared in this study. Judd-Ofelt theory has been used to evaluate the three intensity parameters Ω2, Ω4 and Ω6 form the experimental oscillator strengths. The luminescence properties were investigated by excitation and emission spectra. White light emission could be induced by combined blue and yellow bands under UV excitation, and the variety of excitation wavelength could change the luminescence color.

Dielectric Characteristics of (Ca0.2Sr0.8)3(ZrxTi1-x)2O7 Ceramics at Microwave Frequencies

(Ca0.2Sr0.8)3(ZrxTi1-x)2O7 (x = 0.02-0.1) ceramic prepared by the solid state method was investigated for its microstructure and microwave dielectric properties. The correlation between the microstructure and microwave dielectric properties was also investigated. By increasing x from 0.01 to 0.06, the dielectric constant and Q×f value of the specimen could be increased from 72 to a maximum of 74, and from 11000 GHz to a maximum of 18000 GHz, respectively. The εr value of 74, the Q×f value of 18,000 GHz, and the τf value of 418 ppm/oC were obtained for (Ca0.2Sr0.8)3(Zr0.06Ti0.94)2O7 ceramics sintering at 1520oC for 4h, and (Ca0.2Sr0.8)3(ZrxTi1-x)2O7 (x = 0.02-0.1) is proposed as a suitable material candidate for application in microwave ceramic temperature sensing antenna.

Effect of Sintering Behavior on Microwave Properties of (Ca0.8Sr0.2)ZrO3 Ceramics for Resonators

Microwave dielectric properties and microstructures of (Ca0.8Sr0.2)ZrO3 ceramics prepared by the conventional solid-state route have been studied. The values of the dielectric constant (εr) were 22-26. The Q×f values of 10400–11500 GHz were obtained when the sintering temperatures were in the range of 1400–1490°C. The temperature coefficient of the resonant frequency τf was not sensitive to the sintering temperature. The εr value of 26, the Q×f value of 11500 GHz, and the τf value of-9 ppm/°C were obtained for (Ca0.8Sr0.2)ZrO3 ceramics sintering at 1490°C. The ceramic, (Ca0.8Sr0.2)ZrO3 is proposed as a suitable candidate material for application in highly selective microwave ceramic passive components.

Effect of Sintering Behaviors on Microwave Dielectric Properties of (Ca0.3Sr0.1)Sm0.4TiO3 Ceramics

The microstructure and dielectric properties of the (Ca0.3Sr0.1)Sm0.4TiO3 ceramics with various sintering conditions have been investigated. The compounds were prepared by the conventional solid-state route with various sintering temperatures from 1340 to 1400°C and sintering duration from 3 h. The resultant microwave dielectric properties were analyzed based upon the densification, the X-ray diffraction patterns and the microstructures of the ceramics. The correlation between the microstructures, the microwave dielectric properties and sintering behaviors was also examined. The εr value of 96.7 and Q×f value of 11,600 GHz were obtained for (Ca0.3Sr0.1)Sm0.4TiO3 ceramics sintering at 1370°C for 3 h. The (Ca0.3Sr0.1)Sm0.4TiO3 ceramics had suitable dielectric properties can find applications in microwave devices such as resonator, filter and antenna.

Microstructural and Electrical Properties of ZnO Ceramics with ZnO-Na2O-P2O5 Glass Oxide Additions

The compositions, electrical properties and microstructures of zinc oxide ceramics with various 46.6ZnO-20Na2O-33.4P2O5 glass oxide additions prepared by solid-state method have been investigated. The structure of the materials is studied using X-Ray diffraction, and the microstructure is analyzed using scanning electron microscopy. The results indicated that the electrical properties were associated with the amount of 46.6ZnO-20Na2O-33.4P2O5 glass oxide additions and the sintering temperatures. The correlation between the microstructures, oxide additions and the sintering temperature was also discussed. From the results of electrical properties measurements, zinc oxide ceramics with various 46.6ZnO-20Na2O-33.4P2O5 glass oxide additions exhibits a good electrical behavior, which can be a suitable candidate material for electronic device applications.

Effect of Pressure Conditions on Characteristics of (Ca0.2Sr0.8)3Ti2O7 Dielectric Ceramics

The microwave dielectric properties of (Ca0.2Sr0.8)3Ti2O7 ceramic system have been investigated with various pressure conditions. The compounds were prepared by the conventional solid-state route with various pressure conditions from 60 to 80 Kg/cm2 and sintered at 1450oC for 4 h. The structure and microstructure were analyzed using X-ray diffraction and scanning electron microscopy techniques. The (Ca0.2Sr0.8)3Ti2O7 had excellent dielectric properties: Q×f ~ 50,000 (GHz) and εr ~ 63.2 for the sample at 70 Kg/cm2.