The effect of different molar ratios of Y2O3 and Y（NO3）3 on the microstructure and electrical response of ZnO-Bi203-based varistor ceramics sintered at 1 000 ℃ was investigated, and the mechanism by which this dopi...The effect of different molar ratios of Y2O3 and Y（NO3）3 on the microstructure and electrical response of ZnO-Bi203-based varistor ceramics sintered at 1 000 ℃ was investigated, and the mechanism by which this doping improves the electrical characteristics of ZnO-Bi203-based varistor ceramics was discussed. With increasing amounts of Y（NO3）3 or Y2O3 in the starting composition, Y2O3, Sb204 and Y-containing Bi-rich phase form, and the average grain size significantly decreases. The average grain size significantly decreases as the contents of rare earth compounds of Y（NO3）3 or Y2O3 increase. The maximum value of the nonlinear coefficient is found at 0.16% Y（NO3）3 or 0.02% YaO3 （molar fraction） doped varistor ceramics, and there is an increase of 122% or 35% compared with the varistor ceramics without Y（NO3）3 or Y2O3. The threshold voltage VT of Y（NO3）3 and Y2O3 reaches at 1 460 V/mm and 1 035 V/ram, respectively. The results also show that varistor sample doped with Y（NO3）3 has a remarkably more homogeneous and denser microstructure in comparison to the sample doped with Y2O3.展开更多
Proton exchange membrane fuel cell (PEMFC) stack temperature and cathode stoichiometric oxygen are very important control parameters. The performance and lifespan of PEMFC stack are greatly dependent on the parameters...Proton exchange membrane fuel cell (PEMFC) stack temperature and cathode stoichiometric oxygen are very important control parameters. The performance and lifespan of PEMFC stack are greatly dependent on the parameters. So, in order to improve the performance index, tight control of two parameters within a given range and reducing their fluctuation are indispensable. However, control-oriented models and control strategies are very weak junctures in the PEMFC development. A predictive control algorithm was presented based on their model established by input-output data and operating experiences. It adjusts the operating temperature to 80 ℃. At the same time, the optimized region of stoichiometric oxygen is kept between 1.8?2.2. Furthermore, the control algorithm adjusts the variants quickly to the destination value and makes the fluctuation of the variants the least. According to the test results, compared with traditional fuzzy and PID controllers, the designed controller shows much better performance.展开更多
Solid oxide fuel cells (SOFCs) are considered to be one of the most important clean,distributed resources. However,SOFCs present a challenging control problem owing to their slow dynamics,nonlinearity and tight operat...Solid oxide fuel cells (SOFCs) are considered to be one of the most important clean,distributed resources. However,SOFCs present a challenging control problem owing to their slow dynamics,nonlinearity and tight operating constraints. A novel data-driven nonlinear control strategy was proposed to solve the SOFC control problem by combining a virtual reference feedback tuning (VRFT) method and support vector machine. In order to fulfill the requirement for fuel utilization and control constraints,a dynamic constraints unit and an anti-windup scheme were adopted. In addition,a feedforward loop was designed to deal with the current disturbance. Detailed simulations demonstrate that the fast response of fuel flow for the current demand disturbance and zero steady error of the output voltage are both achieved. Meanwhile,fuel utilization is kept almost within the safe region.展开更多
基金Project(BK2011243) supported by the Natural Science Foundation of Jiangsu Province, ChinaProject(EIPE11204) supported by the State Key Laboratory of Electrical Insulation and Power Equipment, China+4 种基金Project(KF201104) supported by the State Key Laboratory of New Ceramic and Fine Processing, ChinaProject(KFJJ201105) supported by the Opening Program of State key Laboratory of Electronic Thin Films and Integrated Devices, ChinaProject(2011-22) supported by the State Key Laboratory of Inorganic Synthesis and Preparative Chemistry of Jilin University, ChinaProject(10KJD430002) supported by the Universities Natural Science Research Project of Jiangsu Province, ChinaProject(11JDG084) supported by the Research Foundation of Jiangsu University, China
文摘The effect of different molar ratios of Y2O3 and Y（NO3）3 on the microstructure and electrical response of ZnO-Bi203-based varistor ceramics sintered at 1 000 ℃ was investigated, and the mechanism by which this doping improves the electrical characteristics of ZnO-Bi203-based varistor ceramics was discussed. With increasing amounts of Y（NO3）3 or Y2O3 in the starting composition, Y2O3, Sb204 and Y-containing Bi-rich phase form, and the average grain size significantly decreases. The average grain size significantly decreases as the contents of rare earth compounds of Y（NO3）3 or Y2O3 increase. The maximum value of the nonlinear coefficient is found at 0.16% Y（NO3）3 or 0.02% YaO3 （molar fraction） doped varistor ceramics, and there is an increase of 122% or 35% compared with the varistor ceramics without Y（NO3）3 or Y2O3. The threshold voltage VT of Y（NO3）3 and Y2O3 reaches at 1 460 V/mm and 1 035 V/ram, respectively. The results also show that varistor sample doped with Y（NO3）3 has a remarkably more homogeneous and denser microstructure in comparison to the sample doped with Y2O3.
基金Project (2003AA517020) supported by the National High-Tech Research and Development Program of China
文摘Proton exchange membrane fuel cell (PEMFC) stack temperature and cathode stoichiometric oxygen are very important control parameters. The performance and lifespan of PEMFC stack are greatly dependent on the parameters. So, in order to improve the performance index, tight control of two parameters within a given range and reducing their fluctuation are indispensable. However, control-oriented models and control strategies are very weak junctures in the PEMFC development. A predictive control algorithm was presented based on their model established by input-output data and operating experiences. It adjusts the operating temperature to 80 ℃. At the same time, the optimized region of stoichiometric oxygen is kept between 1.8?2.2. Furthermore, the control algorithm adjusts the variants quickly to the destination value and makes the fluctuation of the variants the least. According to the test results, compared with traditional fuzzy and PID controllers, the designed controller shows much better performance.
基金Projects(51076027,51036002) supported by the National Natural Science Foundation of ChinaProject(20090092110051) supported by the Doctoral Fund of Ministry of Education of China
文摘Solid oxide fuel cells (SOFCs) are considered to be one of the most important clean,distributed resources. However,SOFCs present a challenging control problem owing to their slow dynamics,nonlinearity and tight operating constraints. A novel data-driven nonlinear control strategy was proposed to solve the SOFC control problem by combining a virtual reference feedback tuning (VRFT) method and support vector machine. In order to fulfill the requirement for fuel utilization and control constraints,a dynamic constraints unit and an anti-windup scheme were adopted. In addition,a feedforward loop was designed to deal with the current disturbance. Detailed simulations demonstrate that the fast response of fuel flow for the current demand disturbance and zero steady error of the output voltage are both achieved. Meanwhile,fuel utilization is kept almost within the safe region.
