In this work, a semi-empirical 1.5D plasma fluid model (PFM) is proposed to model a single microdischarge (MD) in atmospheric pressure air dielectric barrier discharges (APADBDs). The species continuity equations and the electron energy density equation are solved in onedimensional domain, while the Poisson equation is solved in the axisymmetric domain to capture the enhancement of the electric field in front of the streamer. The framework of air chemistry is considered and the effect of photoionization is modeled in the axisymmetric domain. The accumulation factor (AF) is introduced and determined by experimental data to model the accumulation of charged particles on the dielectric surface. The simulated results in two gaps are compared with experimental measurements. In the gap of 1.4 mm, the simulated electric current reaches 72 mA, which is close to the typically measured electric current. The simulated maximum wave velocity is around 1.7×10 6 m s −1 , which is close to the available experimental data. The change of simulated charge density implies that the average accumulation of charged particles on the dielectric surface during each half period (HP) is around 40 nC cm −2 , which is in the same order of magnitude as the average charge density evaluated in the previous measurements as 51.5 nC cm −2 . The effect of AF is studied and shows that the AF determines both peak and duration of the electric current. In the gap of 2.0 mm, the simulated current reaches 113 mA, which is close to the typically measured current. Although the gap voltage of the 2.0 mm gap is higher than that of the 1.4 mm gap, the average electric field of the 2.0 mm gap is lower than that of the 1.4 mm gap before breakdown due to larger gap distance. The maximum wave velocity is faster than that simulated in the gap of 1.4 mm due to the longer gap distance for developing higher wave velocity as 2.4×10 6 m s −1 . During each HP, the average accumulation of charge density on the dielectric surface reaches around 40 nC cm −2 which is almost identical to that simulated in the gap of 1.4 mm as observed experimentally. In general, the proposed semi-empirical 1.5D PFM captures the dynamics of a single MD in APADBDs.
The dynamic behavior of ozonation with pollutant in a rotating packed bed is studied for the model establishment. o-Cresol is chosen as the model pollutant. The concentrations of the residual o-cresol, effluent dissolved oxygen, and off-gas ozone at various times are measured simultaneously. The validity of the model is demonstrated by comparing the predicted results with the experimental data. Furthermore, the assumption of complete as well as partial wetting of packing is examined by comparison of the prediction with the experimental data. The patterns of the concentration profiles in the packed bed vary with the ozonation time in the transient state until reaching the steady state. It usually needs about 2 hydraulic retention times to reach steady state under the conditions of this study. The effects of dimensionless system parameters such as Damköhler and Stanton numbers on the performance of the ozonation process are also investigated.
A quartz crystal microbalance (QCM) serving as a biosensor to detect the target biomolecules (analytes) often suffers from the time consuming process, especially in the case of diffusion-limited reaction. In this experimental work, we modify the reaction chamber of a conventional QCM by integrating into the multimicroelectrodes to produce electrothermal vortex flow which can efficiently drive the analytes moving toward the sensor surface, where the analytes were captured by the immobilized ligands. The microelectrodes are placed on the top surface of the chamber opposite to the sensor, which is located on the bottom of the chamber. Besides, the height of reaction chamber is reduced to assure that the suspended analytes in the fluid can be effectively drived to the sensor surface by induced electrothermal vortex flow, and also the sample costs are saved. A series of frequency shift measurements associated with the adding mass due to the specific binding of the analytes in the fluid flow and the immobilized ligands on the QCM sensor surface are performed with or without applying electrothermal effect (ETE). The experimental results show that electrothermal vortex flow does effectively accelerate the specific binding and make the frequency shift measurement more sensible. In addition, the images of the binding surfaces of the sensors with or without applying electrothermal effect are taken through the scanning electron microscopy. By comparing the images, it also clearly indicates that ETE does raise the specific binding of the analytes and ligands and efficiently improves the performance of the QCM sensor. V C 2014 AIP Publishing LLC. [http://dx
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