Archive for November, 2008
As the World Spins, Technology Spins Faster: A Global Long-Distance Education Program
In 2000, the educational leadership program of a major private U.S. university developed the Office of International Programs, designed to serve international educators and administrators in leadership positions. The student population grew from 10 students from nine countries in 2000 to 250 students from 63 countries in 2008. In the beginning, courses were delivered via asynchronous methods then later on, synchronous methods were integrated. Interviews were conducted in 2003 and follow-up online and paper-and-pencil surveys were administered in 2006 and 2008 respectively to examine students’ perceptions about international long distance learning, and the impact of the technologies used on their learning. › Continue reading
Influence of ZrO2 Nanoligands on the Catalytic Performance of Supported Pt/ZrO2/SiO2 Catalysts
A series of double-supported Pt/ZrO2/SiO2 catalysts were prepared to determine the influence of ZrO2 nanoparticle (NP) domain size on the reactivity of the catalytic active Pt component. The catalysts were synthesized by first impregnating zirconium tert-butoxide, Zr[OC(CH3)3]4, in toluene, drying and then calcining at 500 C to form ZrO2. In a second step, aqueous platinum tetra-ammine nitrate, Pt(NH3)4(NO3)2, was impregnated, dried and calcined in air at 500 C to form the final double-supported Pt/ZrO2/SiO2 catalyst. The ZrO2 loading was varied between 1% and 50% and the Pt loading was maintained constant at 0.1%. In situ Raman and UV-vis spectroscopy and TEM microscopic characterization revealed that the supported ZrO2 phase varied its domain size from isolated surface species to polymeric surface species to NPs (1-3 nm). TEM microscopy revealed that the supported Pt phase was present as 10-70 nm NPs for 1-20% ZrO2/SiO2, where the surface ZrOx species was present (1-12%) and a combination of surface ZrOx species and ZrO2 NPs (15-20%). The Pt NPs, however, were completely absent for higher zirconia loading where ZrO2 NPs are present and reflect the presence of a highly dispersed Pt phase on the ZrO2 NPs. The reactivity of the supported Pt phase was chemically probed with CH3OH oxidation (both steady-state and CH3OH-temperature programmed surface reaction (TPSR) spectroscopy). The reactivity of the methanol oxidation reaction was found to increase with the dimension of the Pt NPs, which also corresponds to lower ZrO2 domain size. Thus, the reactivity of the Pt catalytic active sites could be tuned by the domain size of the ZrO2 nanoligands.
Control of the Current Profile Evolution During the Ramp-Up Phase at DIII-D
Setting up a suitable current profile has been demonstrated to be a key condition for advanced scenarios with improved confinement and possible steady-state operation. Experiments at DIII-D focus on creating the desired q profile during the plasma current ramp-up and early attop phases with the aim of maintaining this profile during the subsequent phases of the discharge. Active feedback control of the q profile evolution at DIII-D has already been demonstrated [1], and an open-loop control scheme has been proposed [2] based on a simplified control-oriented dynamic model [3]. The use of Corsica for both control testing and design is reported, and results of open-loop current profile control experiments are presented.
[1] J.R. Ferron, et al., Nucl. Fusion 46 (2006) L13.
[2] Y. Ou, et al., Proc. American Control Conf., New York (2007).
[3] Y. Ou, et al., Fusion Eng. & Design 82 (2007) 1153.
Model-Based Shape Control Design for the National Spherical Torus Experiment (NSTX)
Plasma shape and position control is a challenging problem due to the difficulties associated with real-time shape identification, plasma parameters measurement, and control method selection. The recent implementation of the real-time equilibrium reconstruction code rtEFIT on NSTX allows plasma shaping by controlling the magnetic flux at the plasma boundary. A non-model-based shape controller that exploits this capability has been recently proposed [1]. We describe current efforts to develop a robust model-based multi-input-multi-output (MIMO) H∞ controller to provide real-time shaping and position control in the presence of disturbances and uncertainties in the plasma parameters. The control design is based on linear plasma response models derived from fundamental physics assumptions. Computer simulation results illustrate the performance of the model-based shape control method.
[1] D.A. Gates, et al., Nucl. Fusion 46 (2006) 17–23.
*Supported by the Pennsylvania Infrastructure Technology Alliance (PITA), the NSF CAREER award program (ECCS-0645086), and US DOE DE-FG03-99ER54522.