Browsing by Author "Wu, J. S."

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3D Direct Simulation Monte Carlo Modelling of the Inner Gas Coma of Comet 67P/Churyumov-Gerasimenko: A Parameter Study
(2016-03)
Liao, Y.
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Su, C. C.
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Marschall, R.
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Wu, J. S.
;
Rubin, M.
Direct Simulation Monte Carlo (DSMC) is a powerful numerical method to study rarefied gas flows such as cometary comae and has been used by several authors over the past decade to study cometary outflow. However, the investigation of the parameter space in simulations can be time consuming since 3D DSMC is computationally highly intensive. For the target of ESA\'s Rosetta mission, comet 67P/Churyumov-Gerasimenko, we have identified to what extent modification of several parameters influence the 3D flow and gas temperature fields and have attempted to establish the reliability of inferences about the initial conditions from in situ and remote sensing measurements. A large number of DSMC runs have been completed with varying input parameters. In this work, we present the simulation results and conclude on the sensitivity of solutions to certain inputs. It is found that among cases of water outgassing, the surface production rate distribution is the most influential variable to the flow field.
A comprehensive study of temperature-dependent reflectance and photoluminescence of Zn(1-x)Mn(x)O thin films grown on c-Al(2)O(3)
(2009-03-01)
Lin, D. Y.
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Lin, H. J.
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Wu, J. S.
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Chou, W. C.
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Yang, C. S.
We present a systematic study of temperature-dependent reflectance (R) and photoluminescence (PL) measurements on ZnMnO films grown by plasma-assisted molecular beam epitaxy. For the first time, the three free-exciton transitions FX(A) (Gamma(7c)-Gamma(u)(7v)), FX(B) (Gamma(7c)-Gamma(9v)), and FX(C) (Gamma(7c)-Gamma(l)(7v)) and the longitudinal-optical phonon replicas of FX(B) and FX(C) of ZnMnO films have been clearly observed in the R spectra. The parameters describing the activation energy and the temperature dependence of the transition energy and broadening have been extracted by fitting the experimental R and PL spectra. The spectral data of ZnMnO films not only show the deterioration of crystalline quality with increasing Mn composition fraction but also indicate the Mn clustering caused by Mn atom segregation.
A comprehensive study of temperature-dependent reflectance and photoluminescence of Zn1-xMnxO thin films grown on c-Al2O3
(2009-03-01)
Lin, D. Y.
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Lin, H. J.
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Wu, J. S.
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Chou, W. C.
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Yang, C. S.
We present a systematic study of temperature-dependent reflectance (R) and photoluminescence (PL) measurements on ZnMnO films grown by plasma-assisted molecular beam epitaxy. For the first time, the three free-exciton transitions FXA (Gamma(7c)-Gamma(u)(7v)), FXB (Gamma(7c)-Gamma(9v)), and FXC (Gamma(7c)-Gamma(l)(7v)) and the longitudinal-optical phonon replicas of FXB and FXC of ZnMnO films have been clearly observed in the R spectra. The parameters describing the activation energy and the temperature dependence of the transition energy and broadening have been extracted by fitting the experimental R and PL spectra. The spectral data of ZnMnO films not only show the deterioration of crystalline quality with increasing Mn composition fraction but also indicate the Mn clustering caused by Mn atom segregation.
Ab Initio Chemical Kinetic Study for Reactions of H Atoms with SiH(4) and Si(2)H(6): Comparison of Theory and Experiment
(2010-01-14)
Wu, S. Y.
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Raghunath, P.
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Wu, J. S.
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Lin, M. C.
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機械工程學系
The reactions of hydrogen atom with silane and disilane are relevant to the understanding of catalytic chemical vapor deposition (Cat-CVD) and plasma enhanced chemical vapor deposition (PECVD) processes. In the present study, these reactions have been investigated by means of A initio molecular-orbital and transition-state theory calculations. In both reactions, the most favorable pathway was found to be the H abstraction leading to the formation of SiH(3) and Si(2)H(5) products, with 5.1 and 4.0 kca/mol barriers, respectively. For H + Si(2)H(6), another possible reaction pathway giving SiH(3) + SiH(4) may take place with two different mechanisms with 4.3 and 6.7 kcal/mol barriers for H-atom attacking side-way and end-on, respectively. To validate the calculated energies of the reactions, two isodesmic reactions, SiH(3)+CH(4)-> SiH(4)+CH(3) and Si(2)H(5)+C(2)H(6)-> Si(2)H(6)+C(2)H(5) were employed; the predicted heats of the formation for SiH(3) (49.0 kcal/mol) and Si(2)H(5) (58.6 kcal/mol) were found to agree well with the experimental data. Finally, rate constants for both H-abstraction reactions predicted in the range of 290-2500 K agree well with experimental data. The result also shows that H+Si(2)H(6) producing H(2)+Si(2)H(5) is more favorable than SiH(3)+SiH(4).
Ab Initio Chemical Kinetic Study for Reactions of H Atoms with SiH4 and Si2H6: Comparison of Theory and Experiment
(2010-01-14)
Wu, S. Y.
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Raghunath, P.
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Wu, J. S.
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Lin, M. C.
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機械工程學系
The reactions of hydrogen atom with silane and disilane are relevant to the understanding of catalytic chemical vapor deposition (Cat-CVD) and plasma enhanced chemical vapor deposition (PECVD) processes. In the present study, these reactions have been investigated by means of A initio molecular-orbital and transition-state theory calculations. In both reactions, the most favorable pathway was found to be the H abstraction leading to the formation of SiH3 and Si2H5 products, with 5.1 and 4.0 kca/mol barriers, respectively. For H + Si2H6, another possible reaction pathway giving SiH3 + SiH4 may take place with two different mechanisms with 4.3 and 6.7 kcal/mol barriers for H-atom attacking side-way and end-on, respectively. To validate the calculated energies of the reactions, two isodesmic reactions, SiH3+CH4 -> SiH4+CH3 and Si2H5+C2H6 -> Si2H6+C2H5 were employed; the predicted heats of the formation for SiH3 (49.0 kcal/mol) and Si2H5 (58.6 kcal/mol) were found to agree well with the experimental data. Finally, rate constants for both H-abstraction reactions predicted in the range of 290-2500 K agree well with experimental data. The result also shows that H+Si2H6 producing H-2+Si2H5 is more favorable than SiH3+SiH4.
Ab Initio Chemical Kinetics for the Thermal Decomposition of SiH2+ and SiH3+ Ions and Related Reverse Ion-Molecule Reactions of Interest to PECVD of alpha-Si:H Films
(2019-11-01)
Nguyen, T. N.
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Lee, Y. M.
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Wu, J. S.
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Lin, M. C.
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交大名義發表
The mechanisms and kinetics for the thermal decomposition of SiH2+ and SiH3+ ions, and related reverse reactions involving their ion fragments have been investigated for the first time by using ab initio molecular orbital and variational RRKM calculations. Geometries of all species involved the title reactions have been optimized by the CCSD(T), CCSD, and MP2 methods with the Aug-CC-pVTZ basis set while their single point energies have been refined by the CCSD(T)/CBS calculation for all the three levels for comparison. The barrierless processes involved have been calculated at the CASPT2//CASSCF/Aug-CC-pVTZ level of theory. The potential energy surfaces indicate that the SiH2+ and SiH3+ ions can eliminate an H atom via barrierless processes with dissociation energies of 48.4 and 91.5 kcal mol(-1), respectively, or eliminate an H-2 molecule via tight transition states at TS1 (38.5 kcal mol(-1)) and TS3 (59.9 kcal mol(-1)) giving H-2(+) Si+ (21.3 kcal mol(-1)) and H-2(+) SiH+ (36.7 kcal mol(-1)), respectively, at the CCSD(T)/CBS//CCSD(T)/Aug-CC-pVTZ level of theory. The rate constants for the reactions predicted for a wide range of T,P-conditions reveal that they increase with rising temperature and pressure and H-2 elimination is the major channel in each of the decomposition reactions. The relative energies predicted by different methods agree closely; the predicted heats of formation for various species are in good agreement with available experimental values. The predicted rate constants for the forward and reverse reactions may be employed for kinetic modeling of PECVD processes.
Ab Initio Chemical Kinetics for the Thermal Decomposition of SiH4 (+) Ion and Related Reverse Ion-Molecule Reactions of Interest to PECVD of a-Si:H Films
(2017-07-01)
Nguyen, T. N.
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Lee, Y. M.
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Wu, J. S.
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Lin, M. C.
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機械工程學系
The thermal unimolecular decomposition of SiH4 (+) ion and its related reverse reactions, SiH3 (+) + H and SiH2 (+) + H-2, have been investigated by ab initio molecular orbital and quantum statistical variational RRKM theory calculations. The potential energy surface has been calculated at different levels of theory; the results at the highest level, CCSD(T)/CBS//CCSD(T)/6-311++G(3df,2p), show that the decomposition of SiH4 (+) can mainly occur via a barrierless channel giving SiH2 (+) + H-2 lying 11.8 kcal/mol above the reactant, or via a transition state forming SiH3 (+)center dot center dot center dot H complex to be followed by a barrierless decomposition yielding SiH3 (+) + H lying 23.5 kcal/mol above the reactant. Barrierless processes were calculated using the CASPT2 and CASSCF methods with the 6-311++G(3df,2p) basis set and fitted with Morse potentials. The rate constants were predicted by solving master equations based on the RRKM theory at the E,J-resolved level; the results show that the channel SiH4 (+) -> SiH2 (+) + H-2 is predominate under PEVCD conditions. For H- and H-2-capturing by SiH3 (+) and SiH2 (+) ions, respectively, the rate constants were found to be weakly dependent on temperature at the high-pressure limit and decrease rapidly with pressure. The calculated heats of formation of the SiH (x) (+) (x = 2-4) ions are in close agreement with available thermochemical data.
Cliffs versus plains: Can ROSINA/COPS and OSIRIS data of comet 67P/Churyumov-Gerasimenko in autumn 2014 constrain inhomogeneous outgassing?
(2017-09-01)
Marschall, R.
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Mottola, S.
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Su, C. C.
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Liao, Y.
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Rubin, M.
Context. This paper describes the modelling of gas and dust data acquired in the period August to October 2014 from the European Space Agency's Rosetta spacecraft when it was in close proximity to the nucleus of comet 67P/Churyumov-Gerasimenko. Aims. With our 3D gas and dust comae models this work attempts to test the hypothesis that cliff activity on comet 67P/Churyumov-Gerasimenko can solely account for the local gas density data observed by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) and the dust brightnesses seen by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) in the considered time span. Methods. The model uses a previously developed shape model of the nucleus. From this, the water sublimation rates and gas temperatures at the surface are computed. The gas expansion is modelled with a 3D Direct Simulation Monte Carlo algorithm. A dust drag algorithm is then used to compute dust volume number densities in the coma, which are then converted to brightnesses using Mie theory and a line-of-sight integration. Furthermore we have studied the impact of topographic re-radiation on the models. Results. We show that gas activity from only cliff areas produces a fit to the ROSINA/COPS data that is as statistically good as a purely insolation-driven model. In contrast, pure cliff activity does not reproduce the dust brightness observed by OSIRIS and can thus be ruled out. On the other hand, gas activity from the Hapi region in addition to cliff activity produces a statistically better fit to the ROSINA/COPS data than purely insolation-driven outgassing and also fits the OSIRIS observations rather well. We found that topographic re-radiation does not contribute significantly to the sublimation behaviour of H2O but plays an important role in how the gas flux interacts with the irregular shape of the nucleus. Conclusions. We demonstrate that fits to the observations are non-unique. We can conclude however that gas and dust activity from cliffs and the Hapi region are consistent with the ROSINA/COPS and OSIRIS data sets for the considered time span and are thus a plausible solution. Models with activity from low gravitational slopes alone provide a statistically inferior solution.
COMPARISON OF THE PROPULSION PERFORMANCE OF AEROSPIKE AND BELL-SHAPED NOZZLE USING HYDROGEN PEROXIDE MONOPROPELLANT UNDER SEA-LEVEL CONDITION
(2019-06-01)
Lai, A.
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Wei, S. S.
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Lai, C. H.
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Chen, J. L.
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Liao, Y. H.
This study investigates numerically the performance of applying aerospike nozzle in a hydrogen peroxide mono-propellant propulsion system. A set of governing equations, including continuity, momentum, energy and species conservation equations with extended k-epsilon turbulence equations, are solved using the finite-volume method. The hydrogen peroxide mono-propellant is assumed to be fully decomposed into water vapor and oxygen after flowing through a catalyst bed before entering the nozzle. The aerospike nozzle is expected to have high performance even in deep throttling cases due to its self-compensating characteristics in a wide range of ambient pressure environments. The results show that the thrust coefficient efficiency (C-f,C-eta) of this work exceeds 90% of the theoretical value with a nozzle pressure ratio (PR) in the range of 20 similar to 45. Many complex gas dynamics phenomena in the aerospike nozzle are found and explained in the paper. In addition, performance of the aerospike nozzle is compared with that of the bell-shape nozzle.
Compositional grading in GaAsSb grown on GaAs substrates
(2014-09-15)
Lin, Y. M.
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Chen, C. H.
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Wu, J. S.
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Lee, C. P.
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電子工程學系及電子研究所
The composition profile and lattice strain of GaAsSb grown on GaAs substrates by molecular beam epitaxy have been investigated using the Rutherford backscattering spectrometry (RBS) and X-ray reciprocal space mapping. Through RBS, we found that the Sb content in the layer increases from the interface to the top surface. The X-ray reciprocal space mapping shows that the GaAsSb lattice also gradually relaxes as the layer becomes thicker. The behavior of composition grading and gradual lattice relaxation is quite different from those of III-V ternary compounds with two group Ill atoms. (C) 2014 Elsevier B.V. All rights reserved.
Compositional grading in GaAsSb grown on GaAs substrates
(2014-09-15)
Lin, Y. M.
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Chen, C. H.
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Wu, J. S.
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Lee, C. P.
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電子工程學系及電子研究所
The composition profile and lattice strain of GaAsSb grown on GaAs substrates by molecular beam epitaxy have been investigated using the Rutherford backscattering spectrometry (RBS) and X-ray reciprocal space mapping. Through RBS, we found that the Sb content in the layer increases from the interface to the top surface. The X-ray reciprocal space mapping shows that the GaAsSb lattice also gradually relaxes as the layer becomes thicker. The behavior of composition grading and gradual lattice relaxation is quite different from those of III-V ternary compounds with two group Ill atoms. (C) 2014 Elsevier B.V. All rights reserved.
Development of a Parallel Explicit Finite-Volume Euler Equation Solver using the Immersed Boundary Method with Hybrid MPI-CUDA Paradigm
(2020-02-01)
Kuo, F. A.
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Chiang, C. H.
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Lo, M. C.
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Wu, J. S.
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機械工程學系
This study proposed the application of a novel immersed boundary method (IBM) for the treatment of irregular geometries using Cartesian computational grids for high speed compressible gas flows modelled using the unsteady Euler equations. Furthermore, the method is accelerated through the use of multiple Graphics Processing Units - specifically using Nvidia's CUDA together with MPI - due to the computationally intensive nature associated with the numerical solution to multi-dimensional continuity equations. Due to the high degree of locality required for efficient multiple GPU computation, the Split Harten-Lax-van-Leer (SHLL) scheme is employed for vector splitting of fluxes across cell interfaces. NVIDIA visual profiler shows that our proposed method having a computational speed of 98.6 GFLOPS and 61% efficiency based on the Roofline analysis that provides the theoretical computing speed of reaching 160 GLOPS with an average 2.225 operations/byte. To demonstrate the validity of the method, results from several benchmark problems covering both subsonic and supersonic flow regimes are presented. Performance testing using 96 GPU devices demonstrates a speed up of 89 times that of a single GPU (i.e. 92% efficiency) for a benchmark problem employing 48 million cells. Discussions regarding communication overhead and parallel efficiency for varying problem sizes are also presented.
DREAM: An Efficient Methodology for DSMC Simulation of Unsteady Processes
(2009)
Cave, H. M.
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Jermy, M. C.
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Tseng, K. C.
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Wu, J. S.
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機械工程學系
A technique called the DSMC Rapid Ensemble Averaging Method (DREAM) for reducing the statistical scatter in the output from unsteady DSMC simulations is introduced. During post-processing by DREAM, the DSMC algorithm is re-run multiple times over a short period before the temporal point of interest thus building up a combination of time- and ensemble-averaged sampling data. The particle data is regenerated several mean collision times before the output time using the particle data generated during the original DSMC run. This methodology conserves the original phase space data from the DSMC run and so is suitable for reducing the statistical scatter in highly non-equilibrium flows. In this paper, the DREAM-II method is investigated and verified in detail. Propagating shock waves at high Mach numbers (Mach 8 and 12) are simulated using a parallel DSMC code (PDSC) and then post-processed using DREAM. The ability of DREAM to obtain the correct particle velocity distribution in the shock structure is demonstrated and the reduction of statistical scatter in the output macroscopic properties is measured. DREAM is also used to reduce the statistical scatter in the results from the interaction of a Mach 4 shock with a square cavity and for the interaction of a Mach 12 shock on a wedge in a channel.
Electric field filamentation and higher harmonic generation in very high frequency capacitive discharges
(2019-09-04)
Sharma, Sarveshwar
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Sirse, N.
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Sen, A.
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Wu, J. S.
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Turner, M. M.
The effects of the discharge voltage on the formation and nature of electric field transients in a symmetric, collisionless, very high frequency, capacitively coupled plasma are studied using a self-consistent particle-in-cell (PIC) simulation code. At a driving frequency of 60 MHz and 5 mTorr of argon gas pressure, the discharge voltage is varied from 10 V to 150 V for a fixed discharge gap. It is observed that an increase in the discharge voltage causes filamentation in the electric field transients and to create multiple higher harmonics in the bulk plasma. Correspondingly, higher harmonics, up to 7th harmonic, in the discharge current are also observed. The power in the higher harmonics increases with a rise in the discharge voltage. The plasma density continues to increase with the discharge voltage but in a nonlinear manner, whereas, the bulk electron temperature decreases. Meanwhile, the electron energy distribution function evolves from a Maxwellian at lower discharge voltages to a bi-Maxwellian at higher discharge voltages.
Enhancement of VUV Emission from a Coaxial Xenon Excimer Ultraviolet Lamp Driven by Distorted Bipolar Square Voltages
(2011-12-01)
Jou, S. Y.
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Hung, C. T.
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Chiu, Y. M.
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Wu, J. S.
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Wei, B. Y.
Enhancement of vacuum UV emission (172 nm VUV) from a coaxial xenon excimer UV lamp (EUV) driven by distorted 50 kHz bipolar square voltages, as compared to that by sinusoidal voltages, is investigated numerically in this paper. A self-consistent radial one-dimensional fluid model, taking into consideration non-local electron energy balance, is employed to simulate the discharge physics and chemistry. The discharge is divided into two three-period portions; these include: the pre-discharge, the discharge (most intense at 172 nm VUV emission) and the post-discharge periods. The results show that the efficiency of VUV emission using the distorted bipolar square voltages is much greater than when using sinusoidal voltages; this is attributed to two major mechanisms. The first is the much larger rate of change of the voltage in bipolar square voltages, in which only the electrons can efficiently absorb the power in a very short period of time. Energetic electrons then generate a higher concentration of metastable (and also excited dimer) xenon that is distributed more uniformly across the gap, for a longer period of time during the discharge process. The second is the comparably smaller amount of "wasted" power deposition by Xe(2)(+) in the post-discharge period, as driven by distorted bipolar square voltages, because of the nearly vanishing gap voltage caused by the shielding effect resulting from accumulated charges on both dielectric surfaces. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Experimental investigation of the effect of nozzle throat diameter on the performance of a hybrid rocket motor with swirling injection of high-concentration hydrogen peroxide
(2019-11-01)
Wei, S. S.
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Lee, M. C.
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Chien, Y. H.
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Chou, T. H.
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Wu, J. S.
One of the issues of using a normal graphite nozzle for the hybrid rocket propulsion is the serious throat erosion due to combustion with a higher O/F ratio. This may undermine the throttling capability of the hybrid rocket engine. In this study, we would like to address how the propulsion performance changes under the conditions of different nozzle throat diameters and O/F ratios. We designed and tested a 40-kgf class single-port hybrid rocket motor with the swirling injection of oxidizer, which utilizes the 90 wt% hydrogen peroxide and polypropylene (PP) as oxidizer and fuel, respectively. Three different diameters of graphite nozzle throat (10, 11, and 12 mm) were used to approximate various conditions of nozzle erosion, while the mass flow rates of the injected oxidizer were kept the same. The hot-fire test results indicated that the thrust was nearly the same even the nozzle throat diameters and O/F ratios were different. Especially, the discrepancies among the measured thrusts and oxidizer ISP under various test conditions were found to be less than 1%, which is highly beneficial for the purpose of the thrust control using mass flow rate control of the oxidizer for a hybrid rocket engine with swirling injection of high-concentration hydrogen peroxide.
Implementation of a transient adaptive sub-cell module for the parallel-DSMC code using unstructured grids
(2010-08-01)
Su, C. C.
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Tseng, K. C.
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Cave, H. M.
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Wu, J. S.
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Lian, Y. Y.
A method of transient adaptive sub-cells (TAS) suitable for unstructured grids that is modified from the existing one for the structured grids of DSMC is Introduced. The TAS algorithm is implemented within the framework of a parallelized DSMC code (PDSC). Benchmarking tests are conducted for steady driven cavity flow, steady hypersonic flow over a two-dimensional cylinder, steady hypersonic flow over a cylinder/flare and the unsteady vortex shedding behind a two-dimensional cylinder The use of TAS enables a reduction in the computational expense of the simulation since larger sampling cells and less simulation particles can be employed. Furthermore, the collision quality of the simulation is maintained or improved and the preservation of property gradients and vorticity at the scale of the sub-cells enables correct unsteady vortex shedding frequencies to be predicted The use of TAS in a parallel-DSMC code allows simulations of unsteady processes at a level to be carried out efficiently, accurately and with acceptable computational time (C) 2010 Elsevier Ltd All rights reserved
Implementation of Fuchs' model of ion diffusion charging of nanoparticles considering the electron contribution in dc-corona chargers in high charge densities
(2009-06-21)
Aliat, A.
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Hung, C. T.
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Tsai, C. J.
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Wu, J. S.
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機械工程學系
A 1D corona discharge model coupled to a 2D-axisymmetric particle charging model are proposed in this paper to simulate nanoparticle charging process within a wire-tube air corona discharge subjected to an applied positive or negative dc voltage. This 1D discharge model provides the distribution of the electric field, the air ion and free electron concentrations for the 2D charging model which in turn solves the spatial distributions of the various charged nanoparticles within the tube. This 2D charging model takes into account the effect of electrons, on the basis of Fuchs' law usually employed in the literature for modelling of ion diffusion nanoparticle charging. The current approach is valid when the concentration of nanoparticles is much lower than the concentration of ionic species in the gas. Numerical results show that the positive air ions can be assumed to be solely responsible for the charging process in a positive air corona charger, while both the negative air ions and electrons play an important role in the negative charging. At high negative charge intensities, the effect of the electrons becomes appreciable due to their high conduction velocity. In general, the numerical results obtained are in good agreement with the experimental data reported in the literature.
Implementation of the Transient Adaptive Sub-Cell Module for the Parallel DSMC Code
(2009)
Tseng, K. C.
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Cave, H. M.
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Kuo, T. C.
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Jermy, M. C.
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Krumdieck, S. P.
A method of transient adaptive sub-cells (TAS) suitable for unstructured grids in Direct Simulation Monte Carlo (DSMC) simulations is introduced. The TAS algorithm is implemented within the frame work of a parallelized DSMC code (PDSC). Benchmarking tests are conducted for driven cavity (low, hypersonic flow over a two-dimensional cylinder and the unsteady vortex shedding behind a two-dimensional cylinder. The use of TAS enabled a reduction in the computational expense of the simulation since larger sampling cells and less simulation particles could be employed. Furthermore, the collision quality of the simulation was maintained or improved and the preservation of property gradients and vorticity at the scale of the sub-cells enabled correct unsteady vortex shedding frequencies to be predicted. The use of TAS in a parallel DSMC code allows simulations of unsteady processes at a near continuum level to be carried out efficiently, accurately and with acceptable computational times.
Inactivation of E. coli and B. subtilis by a parallel-plate dielectric barrier discharge jet
(2010-08-15)
Chiang, M. H.
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Wu, J. Y.
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Li, Y. H.
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Wu, J. S.
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Chen, S. H.
Inactivation of Escherichia coli and Bacillus subtilis using the jet region of a parallel-plate air dielectric barrier discharge (DBD) driven by a distorted sinusoidal voltage power supply under atmospheric-pressure condition is reported. Various types of working gases, including pure N(2), pure O(2), and compressed air, were tested. Discharges were characterized electrically by measuring the discharge current, applied voltage and absorbed power, and optically by measuring the optical emission spectra in the UV-visible range and absorption spectra in the IR range. Results of survival rate show that both E. coil and B. subtilis cells (up to 10(7) CFU/mL) can be effectively inactivated using less than 18 passes (1.8 s of residence time in total) of exposure to the post-discharge jet region of compressed air and oxygen discharges at different treating distances in the range of 4-20 mm. Among these, the compressed-air discharge performs the best in inactivating both two types of the bacterial cells, because of the abundant ozone generation and probably through the assistance of nitrous oxide generated in the discharge. In summary, the post-discharge jet region of an oxygen-contained parallel-plate DBD driven by a distorted sinusoidal voltage power driven is very effective in inactivating both E. coli and B. subtilis cells under the present test conditions. Crown Copyright (c) 2010 Published by Elsevier B.V. All rights reserved.