A cylindrical dielectric barrier discharge (DBD) reactor has been developed for the conversion of undiluted CO2 into CO and O2 at atmospheric pressure and low temperatures. Both the physical and chemical effects on reaction performance have been investigated for the addition of BaTiO3 and glass beads into the discharge gap. The presence of these packing materials in the DBD reactor changes the physical characteristics of the discharge and leads to a shift of the discharge mode from a typical filamentary discharge with no packing to a combination of filamentary discharge and surface discharge with packing. Highest CO2 conversion and energy efficiency are achieved when the BaTiO3 beads are fully packed into the discharge gap. It is found that adding the BaTiO3 beads into the plasma system enhances the average electric field and mean electron energy of the CO2 discharge by a factor of 2, which significantly contributes to the enhancement of CO2 conversion, CO yield and energy efficiency of the plasma process. In addition, highly energetic electrons (> 3.0 eV) generated by the discharge could activate BaTiO3 photocatalyst to form electron-hole pairs on its surface, which contributes to the enhanced conversion of CO2.

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In this work, a coaxial dielectric barrier discharge reactor has been developed for the decomposition of CO 2 at atmospheric pressure. The response surface methodology based on a three-factor, three-level Box-Behnken design has been developed to investigate the effects of key independent process parameters (discharge power, feed flow rate, and discharge length) and their interactions on the reaction performance in terms of CO 2 conversion and the energy efficiency of the plasma process. Two quadratic polynomial regression models have been established to understand the relationships between the plasma process parameters and the performance of the CO 2 conversion process. The results indicate that the discharge power is the most important factor affecting CO 2 conversion, while the feed flow rate has the most significant impact on the energy efficiency of the process. The interactions between different plasma process parameters have a very weak effect on the conversion of CO 2 . However, the interactions of the discharge length with either discharge power or gas flow rate have a significant effect on the energy efficiency of the plasma process. The optimal process performance-CO 2 conversion (14.3%) and energy efficiency (8.0%) for the plasma CO 2 conversion process is achieved at a discharge power of 15.8 W, a feed flow rate of 41.9 ml Á min À1 and a discharge length of 150 mm as the highest global desirability of 0.816 is obtained at these conditions. The reproducibility of the experimental results successfully demonstrates the feasibility and reliability of the design of experiments approach for the optimization of the plasma CO 2 conversion process.

|The design of a bilateral teleoperation controller is a nontrivial problem. The goal is to achieve a stable system with optimal performance in the possible presence of time delays, disturbances, uncertainties and or measurement noise. In this paper, a general design strategy based on H1 theory is presented. This approach allows a convenient means to tradeo the optimization of various performance criteria and system robustness. The control approach is applied to a motion-scaling teleoperation system and simulations and experiments with the resulting controllers demonstrate that the strategy is e ective.

A comparative study of the two most popular turbulence models, the Prandtl mixing length model and the K-epsilon model, has been carried out for turbulent SF 6 arcs burning in a supersonic nozzle under direct current conditions. The computed radial temperature profiles are compared with those measured previously by Leseberg and Pietsch at currents of 100 A, 600 A and 1800 A, respectively. It has been found that the turbulence parameters of the K-epsilon model are dependent upon the arcing current while those of the Prandtl mixing length model are applicable for all the currents investigated. For turbulent SF 6 arcs in a supersonic nozzle, consideration of the range of applicability of the turbulence parameters and the cost of computation have made the Prandtl mixing length model preferable to the K-epsilon model.