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1

Dielectric Barrier Discharge Plasma Actuators for Flow Control  

Microsoft Academic Search

The term plasma actuator has now been a part of the fluid dynamics flow-control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single-dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is

Thomas C. Corke; C. Lon Enloe; Stephen P. Wilkinson

2010-01-01

2

Dielectric barrier discharge plasma actuator for flow control  

Microsoft Academic Search

Electrohydrodynamic (EHD) and magnetohydrodynamic phenomena are being widely studied for aerodynamic applications. The major effects of these phenomena are heating of the gas, body force generation, and enthalpy addition or extraction, [1, 2, 3]. In particular, asymmetric dielectric barrier discharge (DBD) plasma actuators are known to be effective EHD device in aerodynamic control, [4, 5]. Experiments have demonstrated their effectiveness

Dmitry Florievich Opaits

2010-01-01

3

Bluff Body Flow Control Using Dielectric Barrier Discharge Plasma Actuators  

NASA Astrophysics Data System (ADS)

The results of an experimental investigation involving the use of dielectric barrier discharge plasma actuators to control bluff body flow is presented. The motivation for the work is plasma landing gear noise control for commercial transport aircraft. For these flow control experiments, the cylinder in cross-flow is chosen for study since it represents a generic flow geometry that is similar in all essential aspects to a landing gear strut. The current work is aimed both at extending the plasma flow control concept to Reynolds numbers typical of landing approach and take-off and on the development of optimum plasma actuation strategies. The cylinder wake flow with and without actuation are documented in detail using particle image velocimetry (PIV) and constant temperature hot-wire anemometry. The experiments are performed over a Reynolds number range extending to ReD=10^5. Using either steady or unsteady plasma actuation, it is demonstrated that even at the highest Reynolds number Karman shedding is totally eliminated and turbulence levels in the wake decrease by more than 50%. By minimizing the unsteady flow separation from the cylinder and associated large-scale wake vorticity, the radiated aerodynamic noise is also reduced.

Thomas, Flint; Kozlov, Alexey

2008-11-01

4

Dielectric Barrier Discharge Plasma Actuator for Flow Control  

NASA Technical Reports Server (NTRS)

This report is Part II of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. It includes a Ph.D. dissertation. The period of performance was January 1, 2007 to December 31, 2010. Part I of the final report is the overview published as NASA/CR-2012- 217654. Asymmetric dielectric barrier discharge (DBD) plasma actuators driven by nanosecond pulses superimposed on dc bias voltage are studied experimentally. This produces non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. The approach consisted of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low voltages. In view of practical applications certain questions have been also addressed, such as electrodynamic effects which accompany scaling of the actuators to real size models, and environmental effects of ozone production by the plasma actuators.

Opaits, Dmitry, F.

2012-01-01

5

Dielectric material degradation monitoring of dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

It is a known phenomenon that some dielectric materials used to construct plasma actuators degrade during operation. However, the rate at which this process occurs, to what extent, as well as a method to monitor is yet to be established. In this experimental study, it is shown that electrical measurements can be used to monitor changes in the material of the plasma actuators. The procedure we introduce for monitoring the actuators follows from the work of Kriegseis, Grundmann, and Tropea [Kriegseis et al., J. Appl. Phys. 110, 013305 (2011)], who used Lissajous figures to measure actuator power consumption and capacitance. In the present study, we quantify changes in both the power consumption and capacitance of the actuators over long operating durations. It is shown that the increase in the effective capacitance of the actuator is related to degradation (thinning) of the dielectric layer, which is accompanied by an increase in actuator power consumption. For actuators constructed from layers of Kapton® polyimide tape, these changes are self-limiting. Although the polyimide film degrades relatively quickly, the underlying adhesive layer appears to remain intact. Over time, the effective capacitance was found to increase by up to 36%, 25%, and 11% for actuators constructed with 2, 3, and 4 layers of Kapton tape, respectively. A method is presented to prevent erosion of the Kapton dielectric layer using a coating of Polydimethylsiloxane oil. It is shown the application of this treatment can delay the onset of degradation of the Kapton dielectric material.

Hanson, Ronald E.; Houser, Nicole M.; Lavoie, Philippe

2014-01-01

6

High-lift airfoil trailing edge separation control using a single dielectric barrier discharge plasma actuator  

Microsoft Academic Search

Control of flow separation from the deflected flap of a high-lift airfoil up to Reynolds numbers of 240,000 (15 m\\/s) is explored\\u000a using a single dielectric barrier discharge (DBD) plasma actuator near the flap shoulder. Results show that the plasma discharge\\u000a can increase or reduce the size of the time-averaged separated region over the flap depending on the frequency of actuation.

Jesse Little; Munetake Nishihara; Igor Adamovich; Mo Samimy

2010-01-01

7

Measurements and Simulations of Surface Dielectric Barrier Discharges Used as Plasma Actuators  

NASA Technical Reports Server (NTRS)

This report is a Ph.D. dissertation performed under NRA cooperative agreement and submitted as part of the final report. Asymmetric surface dielectric barrier discharges (DBDs) have shown promise for use as aerodynamic actuators for active flow control. In this project we studied DBD actuators experimentally and numerically. Our DBDs used a symmetric triangular high voltage waveform to generate plasma in atmospheric pressure air. Time-averaged measurements indicated that the induced force of a single barrier actuator design (one electrode insulated from the plasma) can be increased exponentially above the results of previous studies by decreasing both the length and thickness of the electrode exposed to the plasma. This increased force may allow these devices to control flow separation in a wider range of flow environments. Experiments using an intensified digital camera to examine the plasma on time scales of a few nanoseconds showed that, in addition to the previously-observed filamentary and jet-like plasma structures, discharges with very thin exposed electrodes exhibited a weak but constant plasma immediately adjacent to those electrodes. In double-barrier actuators (both electrodes insulated), decreasing the diameter of the narrower electrode lead to increasing forces, and recorded images showed the simultaneous existence of both filamentary and jet-like plasma structures. The development and application of a time-dependent, two-dimensional computational fluid plasma model has aided in understanding the detailed physics of surface DBDs at all-time scales. For simulated single-barrier discharges, the model qualitatively reproduced the filamentary and jet-like micro-discharge structures. The model was somewhat successful in reproducing the observed characteristics of double-barrier actuators. For both actuator geometries, the model indicated that the majority of the forces induced on the neutral gas occur in between micro-discharges as the plasmas decay.

Hoskinson, Alan R.

2012-01-01

8

Numerical analysis of plasma evolution on dielectric barrier discharge plasma actuator  

SciTech Connect

Time evolution of the discharge plasma in the dielectric barrier discharge (DBD) plasma actuator was simulated by the simple fluid model in which the electron and single positive ion species were considered. The characteristics of the discharge plasma evolution were investigated in detail, and the following results were obtained. When the positive-going voltage is applied, the streamer discharge is formed periodically. The periodically formed streamer expands from the exposed electrode, and its length becomes longer than the previous one. Periodic breakdown of the gas and step-by-step plasma expansion are also observed during the negative-going voltage; however, the streamer is not formed and the breakdown frequency is much higher. The simulation results with a triangular applied voltage waveform show the same characteristics as observed in the experiment; large discharge current spikes are observed during both the positive- and negative-going voltage phase, and the plasma in the negative-going voltage phase expands more smoothly than that in the positive phase because of its higher breakdown frequency. It was shown that even the simple numerical model could provide valuable insights into the physics of DBD plasma actuator; this indicates that the positive ions and electrons play a prominent role in determining the general characteristics of the plasma evolution.

Nishida, Hiroyuki [Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Abe, Takashi [Institute of Space and Astronautical Science, JAXA, Sagamihara, Kanagawa 229-8510 (Japan)

2011-07-01

9

Effect of dielectric barrier discharge plasma actuators on non-equilibrium hypersonic flows  

NASA Astrophysics Data System (ADS)

A numerical study employing discontinuous Galerkin method demonstrating net surface heat reduction for a cylindrical body in Mach 17 hypersonic flow is presented. This application focuses on using sinusoidal dielectric barrier discharge plasma actuators to inject momentum near the stagnation point. A 5 species finite rate air chemistry model completes the picture by analyzing the effect of the actuator on the flow chemistry. With low velocity near the stagnation point, the plasma actuator sufficiently modifies the fluid momentum. This results in redistribution of the integrated surface heating load on the body. Specifically, a particular configuration of normally pinching plasma actuation is predicted to reduce the surface heat flux at the stagnation point. An average reduction of 0.246% for the integrated and a maximum reduction of 7.68% are reported for the surface heat flux. The temperature contours in the fluid flow (with maximum temperature over 12 000 K) are pinched away from the stagnation point, thus resulting in reduced thermal load. Plasma actuation in this configuration also affects the species concentration distribution near the wall, in addition to the temperature gradient. The combined effect of both, thus results in an average reduction of 0.0986% and a maximum reduction of 4.04% for non-equilibrium calculations. Thus, this study successfully demonstrates the impact of sinusoidal dielectric barrier discharge plasma actuation on the reduction of thermal load on a hypersonic body.

Bhatia, Ankush; Roy, Subrata; Gosse, Ryan

2014-10-01

10

American Institute of Aeronautics and Astronautics Novel Multi-Barrier Plasma Actuators for Increased Thrust  

E-print Network

American Institute of Aeronautics and Astronautics 1 Novel Multi-Barrier Plasma Actuators by the American Institute of Aeronautics and Astronautics, Inc., with permission. #12;American Institute of Aeronautics and Astronautics 2 and 1-20 kHz, respectively. Such a high potential difference weakly ionizes

Roy, Subrata

11

Optical and electrical characterization of a surface dielectric barrier discharge plasma actuator  

NASA Astrophysics Data System (ADS)

An experimental characterization of the properties of asymmetric surface dielectric barrier discharges used as plasma actuators was performed. Optical emission spectroscopy was used to measure the radiated power and some plasma parameters such as the electron and vibrational temperature. Electrical characterization of the discharge was executed by recording individual current pulses with high temporal resolution, and collecting a large dataset of these events. Statistical analysis performed on them allowed one to correlate microdischarge (MD) properties with the voltage phase and to spot differences arising from the actual breakdown mechanism in such asymmetric configurations. In particular, the asymmetry between the two different half-cycles of the discharges was characterized, and it was found that it directly influences plasma actuator efficiency. Differences arising in the multiplicity, amplitude and temporal duration of the MDs were investigated. Some effects connected with the dielectric material and high voltage supply properties were evaluated and correlated with the induced velocity provided by the plasma actuators.

Biganzoli, I.; Barni, R.; Riccardi, C.; Gurioli, A.; Pertile, R.

2013-04-01

12

Force Measurements of Single and Double Barrier DBD Plasma Actuators in Quiescent Air  

NASA Technical Reports Server (NTRS)

We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators, as the electrode diameter decreased below those values previously studied the induced Force increases exponentially rather than linearly. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. In addition, we have shown the the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

2008-01-01

13

Phase effect on flow control for dielectric barrier plasma actuators  

SciTech Connect

Active control of flow has a wide range of applications. Specifically, mitigation of detachment due to the weakly ionized gas flow past a flat plate at an angle of attack is studied using two asymmetric sets of electrode pairs kept at a phase lag. The equations governing the dynamics of electrons, helium ions, and neutrals are solved self-consistently with charge-Poisson equation. The electrodynamic forces produced by two actuators largely depend on the relative phase between the potentials applied to rf electrodes and distance between them. A suitable phase and an optimum distance exist between two actuators for effective separation control.

Singh, K. P.; Roy, Subrata [Computational Plasma Dynamics Laboratory, Mechanical Engineering, Kettering University, Flint, Michigan 48504 (United States)

2006-07-03

14

Velocity-information-based force-term estimation of dielectric-barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

Particle image velocimetry measurements in close proximity to dielectric-barrier discharge plasma actuators are conducted to quantify the momentum transfer of the plasma to the surrounding air flow. Based on these data a comparative analysis of six existing approaches to estimate the induced body force is presented. Integral methods calculate an integral value for the actuator force based on the momentum-balance equation. Insight into the spatial distribution of the body force is provided by differential methods, which are based either on the Navier-Stokes equations or on the vorticity equation. It is demonstrated that the intensity as well as the domain of the force increase with increasing operating power levels. Emphasis is also placed on the issue of self-induced drag. It is shown that 30% of the induced momentum is consumed by wall friction. All results are validated with previously obtained balance force data and luminosity analysis of identical actuators.

Kriegseis, J.; Schwarz, C.; Tropea, C.; Grundmann, S.

2013-02-01

15

Characterization of nanosecond pulse driven dielectric barrier discharge plasma actuators for aerodynamic flow control  

NASA Astrophysics Data System (ADS)

Positive polarity nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuators are studied experimentally in quiescent atmosphere. Pulse energy and instantaneous pulse power (hereafter referred to as energy and power) are calculated using simultaneous voltage and current measurements. Electrical characteristics are evaluated as a function of peak voltage, pulse frequency, discharge length, and dielectric thickness. Schlieren imaging is used to provide a relative estimate of discharge energy that is coupled to the near surface gas as heat for the same parameters. Characteristics of the DBD load have a substantial effect on the individual voltage and current traces which are reflected in the energy and power values. Power is mainly dependent on actuator length which is inconsistent with schlieren data as expected. Higher per unit length energy indicates a stronger compression wave for a given actuator geometry, but this is not universally true across different actuators suggesting some constructions more efficiently couple energy to the gas. Energy and compression wave strength are linearly related. Higher pulse frequency produces higher energy but is primarily attributed to heating of the actuator and power supply components and not to an optimal discharge frequency. Both energy and wave strength increase as peak voltage to the power of approximately 3.5 over a substantial range similar to ac-DBD plasma actuators.

Dawson, Robert; Little, Jesse

2013-03-01

16

One-equation modeling and validation of dielectric barrier discharge plasma actuator thrust  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharge (DBD) plasma actuators with an asymmetric electrode configuration can generate a wall-bounded jet without mechanical moving parts, which require considerable modifications of existing aeronautical objects and which incur high maintenance costs. Despite this potential, one factor preventing the wider application of such actuators is the lack of a reliable actuator model. It is difficult to develop such a model because calculating the ion-electric field and fluid interaction consume a high amount calculation effort during the numerical analysis. Thus, the authors proposed a semi-empirical model which predicted the thrust of plasma actuators with a simple equation. It gave a numeric thrust value, and we implemented the value on a computational fluid dynamics (CFD) solver to describe the two-dimensional flow field induced by the actuator. However, the model had a narrow validation range, depending on the empirical formula, and it did not fully consider environment variables. This study presents an improved model by replacing the empirical formulae in the previous model with physical equations that take into account physical phenomena and environmental variables. During this process, additional operation parameters, such as pressure, temperature and ac waveforms, are newly taken to predict the thrust performance of the actuators with a wider range of existing parameters, the thickness of the dielectric barrier, the exposed electrode, the dielectric constant, the ac frequency and the voltage amplitude. Thrust prediction curves from the model are compared to those of earlier experimental results, showing that the average error is less than 5% for more than one hundred instances of data. As in the earlier work, the predicted thrust value is implemented on a CFD solver, and two-dimensional wall-jet velocity profiles induced by the actuator are compared to the previous experimental results.

Yoon, Jae-San; Han, Jae-Hung

2014-10-01

17

Refinement, validation, and implementation of lumped circuit element model for single dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

Single dielectric barrier discharge (SDBD) plasma actuators have been applied to a wide variety of aerodynamic flow control applications ranging from stall suppression of airfoils at high angles of attack to reducing tip leakage in jet engine turbine blades. With increased interest in applying plasma actuators to various engineering problems comes the need for an efficient model of the actuators that can be used in a CFD simulation. Prior to the current work, a model was developed that captured many of the spatial and temporal dynamics of the actuator by using circuits consisting of resistors and capacitors to model the plasma and dielectric material. In the current work, this model was refined by casting the governing equations in terms of a generalized coordinate system so that it can be applied to curved surfaces, the grid dependence of the model was eliminated, and the method of applying this model as a boundary condition to the electrostatic equations to calculate the body forces generated by the actuator was studied. This new formulation of the lumped circuit element model was then validated against various experimental observations including force vector orientation needed to produce observed induced flow, the scaling of the force with input voltage, and the directivity patterns and pressure time-series from acoustic measurements. The model was also implemented in a flow solver for the case of an impulsively started actuator on a flat plate and compared to experimental data found in literature. Finally, the utility of the model was demonstrated by simulating the use of actuators for flow control of the flow over a circular cylinder and a modified blunt trailing edge wind turbine blade.

Mertz, Benjamin E.

18

Capacitances and energy deposition curve of nanosecond pulse surface dielectric barrier discharge plasma actuator.  

PubMed

Nanosecond pulse surface dielectric barrier discharge (NPSDBD) plasma actuator is preferred to generate aerodynamic actuation which relies on the deposited energy during nanosecond time scale, named as the mechanism of fast thermalization. It is very important to understand the energy deposition process of NPSDBD plasma actuator. In this paper, an equivalent circuit model is presented to describe a typical asymmetric NPSDBD plasma actuator first. Of the three key capacitances in the equivalent circuit, the values of Capacitance C(m) and C(g) can be gotten by the calculation of the electric field, with the method of undetermined coefficients, while the value of Capacitance C(d) is determined from the charge-voltage (Q-V) plot, also called Lissajous figure. It is found that the value of Capacitance C(d) varies with the amplitude of applied pulse voltage, due to the change of the dimension of plasma sheet. Based on the circuit parameters and the measured waveforms of discharge voltage and current, the time varying characteristics of deposited energy can be obtained finally. It is indicated that the calculated results of deposited energy show a good agreement with conventional method. PMID:24880363

Pang, Lei; He, Kun; Di, Dongxu; Zhang, Qiaogen; Liu, Chunliang

2014-05-01

19

Simulation of an asymmetric single dielectric barrier plasma actuator  

SciTech Connect

Continuity equations governing electron and ion density are solved with Poisson's equation to obtain spatial and temporal profiles of electron density, ion density, and voltage. The motion of electrons and ions results in charge separation and generation of an electrostatic electric field. Electron deposition downstream of the overlap region of the electrode results in formation of a virtual negative electrode that always attracts the charge separation. The value of charge separation e(n{sub i}-n{sub e}) and the force per volume F=e(n{sub i}-n{sub e})E have been obtained near the dielectric surface for the 50th cycle. Domain integration of the force F=e(n{sub i}-n{sub e})E has been obtained for different plasma densities, frequencies, and rf voltage wave forms. The time average of the x force is positive and the y force is negative over the domain; therefore there is an average net force on the plasma in the positive x and negative y directions. This will result in a moving wave of plasma over the dielectric surface in the positive x direction, which can find application in flow control.

Singh, K.P.; Roy, Subrata [Computational Plasma Dynamics Laboratory, Mechanical Engineering, Kettering University, Flint, Michigan 48504 (United States)

2005-10-15

20

Effects of pulse polarity on nanosecond pulse driven dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

Nanosecond pulse driven dielectric barrier discharge plasma actuators are studied in quiescent air using a power supply capable of producing negative and positive polarity waveforms. High voltage pulses are applied to the exposed electrode of typical asymmetric actuator geometry. In addition to polarity, the effects of pulse amplitude, actuator length, and dielectric thickness are also investigated. Schlieren images are used to estimate the relative near surface gas heating, while electrical measurements are acquired simultaneously. Negative polarity pulses develop slightly more energy per unit length for thin dielectrics, while positive polarity is slightly higher for thick dielectrics. In most cases, the difference in per unit length energy produced by positive and negative pulses on equivalent actuators is not outside the measurement uncertainty. Negative polarity pulses are found to produce a stronger pressure wave for a given peak voltage and pulse energy across the test matrix. Results indicate that the negative polarity pulse more efficiently couples electrical energy to the near surface gas as heat. This suggests negative polarity pulses may be preferred for aerodynamic flow control applications employing this actuator arrangement.

Dawson, Robyn A.; Little, Jesse

2014-01-01

21

Experimental investigation of filamentary and non-filamentary regimes in a surface dielectric barrier plasma actuator  

NASA Astrophysics Data System (ADS)

Asymmetric surface dielectric barrier discharges fed by a high-voltage sinusoidal low-frequency drive are currently proposed as plasma actuators, because they can induce a directed airflow in the gas surrounding the surface. However, it is known that the induced airflow speed can not be increased as much as desired because a saturation is generally observed for sufficient high voltages. In this paper we show that when the voltage amplitude is increased enough the discharge does not appear uniform any more, but a pattern of plasma filaments becomes evident. We have thus studied plasma properties in both filamentary and nonfilamentary regimes, by means of a Rogowski coil for the measurement of the current associated to the discharge. This is interesting in order to understand what happens at high voltages, when the saturation of the induced airflow speed occurs.

Biganzoli, I.; Barni, R.; Gurioli, A.; Pertile, R.; Riccardi, C.

2014-11-01

22

Experimental investigation on a vectorized aerodynamic dielectric barrier discharge plasma actuator array  

NASA Astrophysics Data System (ADS)

The Electro-Hydro-Dynamics (EHD) interaction, induced in atmospheric pressure still air by a surface dielectric barrier discharge (DBD) actuator, had been experimentally studied. A plasma aerodynamic actuator array, able to produce a vectorized jet, with the induced airflow oriented toward the desired direction, had been developed. The array was constituted by a sequence of single surface DBD actuators with kapton as dielectric material. An ac voltage in the range of 0-6 kV peak at 15 kHz had been used. The vectorization had been obtained by feeding the upper electrodes with different voltages and by varying the electrical connections. The lower electrodes had been connected either to ground or to the high voltage source, to produce the desired jet orientation and to avoid plasma formation acting in an undesired direction. Voltage and current measurements had been carried out to evaluate waveforms and to estimate the active power delivered to the discharge. Schlieren imaging allowed to visualize the induced jet and to estimate its orientation. Pitot measurements had been performed to obtain velocity profiles for all jet configurations. A proportional relation between the jet deflection angle and the applied voltage had been found. Moreover, a linear relation had been obtained between the maximum speed in the jet direction and the applied voltage. The active power of the discharge is approximated by both a power law function and an exponential function of the applied voltage.

Neretti, Gabriele; Cristofolini, Andrea; Borghi, Carlo A.

2014-04-01

23

Electrical and mechanical characteristics of surface AC dielectric barrier discharge plasma actuators applied to airflow control  

NASA Astrophysics Data System (ADS)

The present paper is a wide review on AC surface dielectric barrier discharge (DBD) actuators applied to airflow control. Both electrical and mechanical characteristics of surface DBD are presented and discussed. The first half of the present paper gives the last results concerning typical single plate-to-plate surface DBDs supplied by a sine high voltage. The discharge current, the plasma extension and its morphology are firstly analyzed. Then, time-averaged and time-resolved measurements of the produced electrohydrodynamic force and of the resulting electric wind are commented. The second half of the paper concerns a partial list of approaches having demonstrated a significant modification in the discharge behavior and an increasing of its mechanical performances. Typically, single DBDs can produce mean force and electric wind velocity up to 1 mN/W and 7 m/s, respectively. With multi-DBD designs, velocity up to 11 m/s has been measured and force up to 350 mN/m.

Benard, Nicolas; Moreau, Eric

2014-11-01

24

Flow control over a NACA 0012 airfoil using dielectric-barrier-discharge plasma actuator with a Gurney flap  

NASA Astrophysics Data System (ADS)

Flow control study of a NACA 0012 airfoil with a Gurney flap was carried out in a wind tunnel, where it was demonstrated that a dielectric-barrier-discharge (DBD) plasma actuator attached to the flap could increase the lift further, but with a small drag penalty. Time-resolved PIV measurements of the near-wake region indicated that the plasma forcing shifted the wake downwards, reducing its recirculation length. Analysis of wake vortex dynamics suggested that the plasma actuator initially amplified the lower wake shear layer by adding momentum along the downstream surface of the Gurney flap. This enhanced mutual entrainment between the upper and lower wake vortices, leading to an increase in lift on the airfoil.

Feng, Li-Hao; Jukes, Timothy N.; Choi, Kwing-So; Wang, Jin-Jun

2012-06-01

25

Simulation Tool for Dielectric Barrier Discharge Plasma Actuators at Atmospheric and Sub-Atmospheric Pressures: SBIR Phase I Final Report  

NASA Technical Reports Server (NTRS)

This report is the final report of a SBIR Phase I project. It is identical to the final report submitted, after some proprietary information of administrative nature has been removed. The development of a numerical simulation tool for dielectric barrier discharge (DBD) plasma actuator is reported. The objectives of the project were to analyze and predict DBD operation at wide range of ambient gas pressures. It overcomes the limitations of traditional DBD codes which are limited to low-speed applications and have weak prediction capabilities. The software tool allows DBD actuator analysis and prediction for subsonic to hypersonic flow regime. The simulation tool is based on the VORPAL code developed by Tech-X Corporation. VORPAL's capability of modeling DBD plasma actuator at low pressures (0.1 to 10 torr) using kinetic plasma modeling approach, and at moderate to atmospheric pressures (1 to 10 atm) using hydrodynamic plasma modeling approach, were demonstrated. In addition, results of experiments with pulsed+bias DBD configuration that were performed for validation purposes are reported.

Likhanskii, Alexandre

2012-01-01

26

American Institute of Aeronautics and Astronautics Microscale Dielectric Barrier Discharge Plasma Actuators  

E-print Network

American Institute of Aeronautics and Astronautics 1 Microscale Dielectric Barrier Discharge Plasma by the Authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission of Aeronautics and Astronautics 2 d = damped frequency n = natural frequency = damping ratio I. Introduction

Roy, Subrata

27

Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias  

NASA Astrophysics Data System (ADS)

Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations with an arbitrary impedance load was developed. A new approach for nonintrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the schlieren technique, burst mode of plasma actuator operation, and two-dimensional numerical fluid modeling. The force and heating rate calculated by a plasma model was used as an input to two-dimensional viscous flow solver to predict the time-dependent dielectric barrier discharge induced flow field. This approach allowed us to restore the entire two-dimensional unsteady plasma induced flow pattern as well as characteristics of the plasma induced force. Both the experiments and computations showed the same vortex flow structures induced by the actuator. Parametric studies of the vortices at different bias voltages, pulse polarities, peak pulse voltages, and pulse repetition rates were conducted experimentally. The significance of charge buildup on the dielectric surface was demonstrated. The charge buildup decreases the effective electric field in the plasma and reduces the plasma actuator performance. The accumulated surface charge can be removed by switching the bias polarity, which leads to a newly proposed voltage waveform consisting of high-voltage nanosecond repetitive pulses superimposed on a high-voltage low frequency sinusoidal voltage. Advantages of the new voltage waveform were demonstrated experimentally.

Opaits, Dmitry F.; Likhanskii, Alexandre V.; Neretti, Gabriele; Zaidi, Sohail; Shneider, Mikhail N.; Miles, Richard B.; Macheret, Sergey O.

2008-08-01

28

Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias  

SciTech Connect

Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations with an arbitrary impedance load was developed. A new approach for nonintrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the schlieren technique, burst mode of plasma actuator operation, and two-dimensional numerical fluid modeling. The force and heating rate calculated by a plasma model was used as an input to two-dimensional viscous flow solver to predict the time-dependent dielectric barrier discharge induced flow field. This approach allowed us to restore the entire two-dimensional unsteady plasma induced flow pattern as well as characteristics of the plasma induced force. Both the experiments and computations showed the same vortex flow structures induced by the actuator. Parametric studies of the vortices at different bias voltages, pulse polarities, peak pulse voltages, and pulse repetition rates were conducted experimentally. The significance of charge buildup on the dielectric surface was demonstrated. The charge buildup decreases the effective electric field in the plasma and reduces the plasma actuator performance. The accumulated surface charge can be removed by switching the bias polarity, which leads to a newly proposed voltage waveform consisting of high-voltage nanosecond repetitive pulses superimposed on a high-voltage low frequency sinusoidal voltage. Advantages of the new voltage waveform were demonstrated experimentally.

Opaits, Dmitry F.; Likhanskii, Alexandre V.; Neretti, Gabriele; Zaidi, Sohail; Shneider, Mikhail N.; Miles, Richard B. [Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Macheret, Sergey O. [Lockheed Martin Aeronautics Company, Palmdale, California 93599 (United States)

2008-08-15

29

Plasma actuators for bluff body flow control  

NASA Astrophysics Data System (ADS)

The aerodynamic plasma actuators have shown to be efficient flow control devices in various applications. In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. This work is motivated by the need to reduce landing gear noise for commercial transport aircraft via an effective streamlining created by the actuators. The experiments are performed at Re D = 20,000...164,000. Circular cylinders in cross-flow are chosen for study since they represent a generic flow geometry that is similar in all essential aspects to a landing gear oleo or strut. The minimization of the unsteady flow separation from the models and associated large-scale wake vorticity by using actuators reduces the radiated aerodynamic noise. Using either steady or unsteady actuation at ReD = 25,000, Karman shedding is totally eliminated, turbulence levels in the wake decrease significantly and near-field sound pressure levels are reduced by 13.3 dB. Unsteady actuation at an excitation frequency of St D = 1 is found to be most effective. The unsteady actuation also has the advantage that total suppression of shedding is achieved for a duty cycle of only 25%. However, since unsteady actuation is associated with an unsteady body force and produces a tone at the actuation frequency, steady actuation is more suitable for noise control applications. Two actuation strategies are used at ReD = 82,000: spanwise and streamwise oriented actuators. Near field microphone measurements in an anechoic wind tunnel and detailed study of the near wake using LDA are presented in the study. Both spanwise and streamwise actuators give nearly the same noise reduction level of 11.2 dB and 14.2 dB, respectively, and similar changes in the wake velocity profiles. The contribution of the actuator induced noise is found to be small compared to the natural shedding noise. A tandem cylinder configuration with the plasma actuation on the upstream cylinder is investigated using surface dynamic pressure sensors. As a result of the plasma actuation, the surface pressure fluctuations on the downstream cylinder are reduced by about two times at the free-stream velocity of 40 m/s (ReD = 164,000). In addition, this study presents the results of a parametric experimental investigation aimed at optimizing the body force produced by single dielectric barrier discharge (SDBD) plasma actuators used for aerodynamic flow control. A primary goal of the study is the improvement of actuator authority for flow control applications at higher Reynolds number than previously possible. The study examines the effects of dielectric material and thickness, applied voltage amplitude and frequency, voltage waveform, exposed electrode geometry, covered electrode width and multiple actuator arrays. The metric used to evaluate the performance of the actuator in each case is the measured actuator-induced thrust which is proportional to the total body force. It is demonstrated that actuators constructed with thick dielectric material of low dielectric constant and operated at low frequency AC voltage produce a body force that is an order of magnitude larger than that obtained by the Kapton-based actuators used in many previous plasma flow control studies. These actuators allow operation at much higher applied voltages without the formation of discrete streamers which lead to body force saturation.

Kozlov, Alexey V.

30

Thrust Measurement of Dielectric Barrier Discharge (DBD) Plasma Actuators: New Anti-Thrust Hypothesis, Frequency Sweeps Methodology, Humidity and Enclosure Effects  

NASA Technical Reports Server (NTRS)

We discuss thrust measurements of Dielectric Barrier Discharge (DBD) plasma actuators devices used for aerodynamic active flow control. After a review of our experience with conventional thrust measurement and significant non-repeatability of the results, we devised a suspended actuator test setup, and now present a methodology of thrust measurements with decreased uncertainty. The methodology consists of frequency scans at constant voltages. The procedure consists of increasing the frequency in a step-wise fashion from several Hz to the maximum frequency of several kHz, followed by frequency decrease back down to the start frequency of several Hz. This sequence is performed first at the highest voltage of interest, then repeated at lower voltages. The data in the descending frequency direction is more consistent and selected for reporting. Sample results show strong dependence of thrust on humidity which also affects the consistency and fluctuations of the measurements. We also observed negative values of thrust, or "anti-thrust", at low frequencies between 4 Hz and up to 64 Hz. The anti-thrust is proportional to the mean-squared voltage and is frequency independent. Departures from the parabolic anti-thrust curve are correlated with appearance of visible plasma discharges. We propose the anti-thrust hypothesis. It states that the measured thrust is a sum of plasma thrust and anti-thrust, and assumes that the anti-thrust exists at all frequencies and voltages. The anti-thrust depends on actuator geometry and materials and on the test installation. It enables the separation of the plasma thrust from the measured total thrust. This approach enables more meaningful comparisons between actuators at different installations and laboratories. The dependence on test installation was validated by surrounding the actuator with a grounded large-diameter metal sleeve. Strong dependence on humidity is also shown; the thrust significantly increased with decreasing humidity, e.g., 44 percent increase as relative humidity changed from 18 percent and dew point 33 degF to 50 percent and dew point of 57 degF.

Ashpis, David E.; Laun, Matthew C.

2014-01-01

31

American Institute of Aeronautics and Astronautics Induced Flow from Serpentine Plasma Actuators Acting in  

E-print Network

American Institute of Aeronautics and Astronautics 1 Induced Flow from Serpentine Plasma Actuators on a dielectric barrier discharge (DBD) plasma actuator with the electrodes in a serpentine design of the actuator. In this work the serpentine configuration is constructed from patterned circular arcs

Roy, Subrata

32

Instability wave control in turbulent jet by plasma actuators  

NASA Astrophysics Data System (ADS)

Instability waves in the shear layer of turbulent jets are known to be a significant source of jet noise, which makes their suppression important for the aviation industry. In this study we apply plasma actuators in order to control instability waves in the shear layer of a turbulent air jet at atmospheric pressure. Three types of plasma actuators are studied: high-frequency dielectric barrier discharge, slipping surface discharge, and surface barrier corona discharge. Particle image velocimetry measurements of the shear layer demonstrate that the plasma actuators have control authority over instability waves and effectively suppress the instability waves artificially generated in the shear layer. It makes these actuators promising for application in active control systems for jet noise mitigation.

Kopiev, V. F.; Akishev, Y. S.; Belyaev, I. V.; Berezhetskaya, N. K.; Bityurin, V. A.; Faranosov, G. A.; Grushin, M. E.; Klimov, A. I.; Kopiev, V. A.; Kossyi, I. A.; Moralev, I. A.; Ostrikov, N. N.; Taktakishvili, M. I.; Trushkin, N. I.; Zaytsev, M. Yu

2014-12-01

33

SDBD plasma actuator with nanosecond pulse-periodic discharge  

Microsoft Academic Search

This paper presents a detailed explanation of the physical mechanism of the nanosecond pulsed surface dielectric barrier discharge (SDBD) effect on the flow. Actuator-induced gas velocities show near-zero values for nanosecond pulses. The measurements performed show overheating in the discharge region on fast (tau sime 1 µs) thermalization of the plasma input energy. The mean values of such heating of

A. Yu Starikovskii; A. A. Nikipelov; M. M. Nudnova; D. V. Roupassov

2009-01-01

34

Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias  

Microsoft Academic Search

Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations

Dmitry F. Opaits; Alexandre V. Likhanskii; Gabriele Neretti; Sohail Zaidi; Mikhail N. Shneider; Richard B. Miles; Sergey O. Macheret

2008-01-01

35

Stabilization of boundary layer streaks by plasma actuators  

NASA Astrophysics Data System (ADS)

A flow's transition from laminar to turbulent leads to increased levels of skin friction. In recent years, dielectric barrier discharge actuators have been shown to be able to delay the onset of turbulence in boundary layers. While the laminar to turbulent transition process can be initiated by several different instability mechanisms, so far, only stabilization of the Tollmien-Schlichting path to transition has received significant attention, leaving the stabilization of other transition paths using these actuators less explored. To fill that void, a bi-global stability analysis is used here to examine the stabilization of boundary layer streaks in a laminar boundary layer. These streaks, which are important to both transient and by-pass instability mechanisms, are damped by the addition of a flow-wise oriented plasma body force to the boundary layer. Depending on the magnitude of the plasma actuation, this damping can be up to 25% of the perturbation's kinetic energy. The damping mechanism appears to be due to highly localized effects in the immediate vicinity of the body force, and when examined using a linearized Reynolds-averaged Navier-Stokes energy balance, indicate negative production of the perturbation's kinetic energy. Parametric studies of the stabilization have also been performed, varying the magnitude of the plasma actuator's body force and the spanwise wavenumber of the actuation. Based on these parametric studies, the damping of the boundary layer streaks appears to be linear with respect to the total amount of body force applied to the flow.

Riherd, Mark; Roy, Subrata

2014-03-01

36

Surface plasma actuators modeling for flow control  

NASA Astrophysics Data System (ADS)

The surface plasma actuators over the entire speed region have been intensely investigated for flow control. Most of the fundamental phenomena have been firmly identified by experimental observations but ambiguities still remained. The direct computational simulation for multiple microdischarges is presently beyond our reach, thus the essential physics may be better understood on the framework of physics-based modeling. To achieve this objective, the drift-diffusion approximation is adopted as a transport property approximation to the nonequilibrium air plasma. The most challenging issue of electron impact ionization process at the low-temperature environment is addressed by the Townsend mechanism together with electron attachment, detachment, bulk, and ion-ion recombination. The effects and quantifications of Joule heating, periodic electrostatic force, as well as, the Lorentz acceleration for flow control are examined. The clarification to the hot spot of heat transfer in direct current discharge and the orientations of the periodic force associated with AC cycle of dielectric barrier discharge are also included.

Shang, J. S.; Huang, P. G.

2014-05-01

37

Use of Plasma Actuators as a Moving-Wake Generator  

NASA Technical Reports Server (NTRS)

The work documented in this report tests the concept of using plasma actuators as a simple and easy way to generate a simulated moving-wake and the disturbances associated with it in turbines. This wake is caused by the blades of the upstream stages of the turbine. Two types of devices, one constructed of arrays of NACA 0018 airfoils, and the one constructed of flat plates were studied. The airfoils or plates were equipped with surface mounted dielectric barrier discharge (DBD) plasma actuators, which were used to generate flow disturbances resembling moving-wakes. CTA hot-wire anemometry and flow visualization using a smoke-wire were used to investigate the wake independence at various spacings and downstream locations. The flat plates were found to produce better results than the airfoils in creating large velocity fluctuations in the free-stream flow. Different dielectric materials, plasma actuator locations, leading edge contours, angles of attack and plate spacings were investigated, some with positive results. The magnitudes of the velocity fluctuations were found to be comparable to existing mechanical moving-wake generators, thus proving the feasibility of using plasma actuators as a moving-wake generator.

Corke, Thomas C.; Thomas, Flint O.; Klapetzky Michael J.

2007-01-01

38

Three-dimensional effects of curved plasma actuators in quiescent air  

SciTech Connect

This paper presents results on a new class of curved plasma actuators for the inducement of three-dimensional vortical structures. The nature of the fluid flow inducement on a flat plate, in quiescent conditions, due to four different shapes of dielectric barrier discharge (DBD) plasma actuators is numerically investigated. The three-dimensional plasma kinetic equations are solved using our in-house, finite element based, multiscale ionized gas (MIG) flow code. Numerical results show electron temperature and three dimensional plasma force vectors for four shapes, which include linear, triangular, serpentine, and square actuators. Three-dimensional effects such as pinching and spreading the neighboring fluid are observed for serpentine and square actuators. The mechanisms of vorticity generation for DBD actuators are discussed. Also the influence of geometric wavelength ({lambda}) and amplitude ({Lambda}) of the serpentine and square actuators on vectored thrust inducement is predicted. This results in these actuators producing significantly better flow mixing downstream as compared to the standard linear actuator. Increasing the wavelengths of serpentine and square actuators in the spanwise direction is shown to enhance the pinching effect giving a much higher vertical velocity. On the contrary, changing the amplitude of the curved actuator varies the streamwise velocity significantly influencing the near wall jet. Experimental data for a serpentine actuator are also reported for validation purpose.

Wang Chincheng; Durscher, Ryan; Roy, Subrata

2011-04-15

39

Simulations of Serpentine Plasma Actuators in a Laminar Boundary Layer  

E-print Network

Simulations of Serpentine Plasma Actuators in a Laminar Boundary Layer Mark Riherd and Subrata Roy to the addition of the serpentine actuation are also measured. Nomenclature u, v, w Flow velocities p Pressure U geometry actuator,17,18 and the serpentine geometry actuator.18 The geometry relevant to the present work

Roy, Subrata

40

Scalability of Localized Arc Filament Plasma Actuators  

NASA Technical Reports Server (NTRS)

Temporal flow control of a jet has been widely studied in the past to enhance jet mixing or reduce jet noise. Most of this research, however, has been done using small diameter low Reynolds number jets that often have little resemblance to the much larger jets common in real world applications because the flow actuators available lacked either the power or bandwidth to sufficiently impact these larger higher energy jets. The Localized Arc Filament Plasma Actuators (LAFPA), developed at the Ohio State University (OSU), have demonstrated the ability to impact a small high speed jet in experiments conducted at OSU and the power to perturb a larger high Reynolds number jet in experiments conducted at the NASA Glenn Research Center. However, the response measured in the large-scale experiments was significantly reduced for the same number of actuators compared to the jet response found in the small-scale experiments. A computational study has been initiated to simulate the LAFPA system with additional actuators on a large-scale jet to determine the number of actuators required to achieve the same desired response for a given jet diameter. Central to this computational study is a model for the LAFPA that both accurately represents the physics of the actuator and can be implemented into a computational fluid dynamics solver. One possible model, based on pressure waves created by the rapid localized heating that occurs at the actuator, is investigated using simplified axisymmetric simulations. The results of these simulations will be used to determine the validity of the model before more realistic and time consuming three-dimensional simulations are conducted to ultimately determine the scalability of the LAFPA system.

Brown, Clifford A.

2008-01-01

41

Numerical simulation on a nanosecond-pulse surface dielectric barrier discharge actuator in near space  

Microsoft Academic Search

Lift-enhancement–drag-reduction technology is strongly required by near-space vehicles with low Reynolds number. It is known that a flow control method by a surface dielectric barrier discharge (SDBD) plasma can play an important role in this field. In order to obtain the discharge characteristics and evaluate the flow control effect of a SDBD actuator, the nanosecond-pulse discharge and induced flow field

Xueke Che; Tao Shao; Wansheng Nie; Ping Yan

2012-01-01

42

Comparisons of Force Measurement Methods for DBD Plasma Actuators in Quiescent Air  

NASA Technical Reports Server (NTRS)

We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators with cylindrical exposed electrodes, as the electrode diameter decrease the force efficiencies increase much faster than a previously reported linear trend. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. Actuators with rectangular cross-section exposed electrodes do not show the same rapid increase at small thicknesses. We have also shown that the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

2009-01-01

43

Single dielectric barrier discharge plasma enhanced aerodynamics: physics, modeling and applications  

Microsoft Academic Search

The term “plasma actuator” has been a part of the fluid dynamics flow control vernacular for more than a decade. A particular\\u000a type of plasma actuator that has gained wide use is based on a single dielectric barrier discharge (SDBD) mechanism that has\\u000a desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control

Thomas C. Corke; Martiqua L. Post; Dmitriy M. Orlov

2009-01-01

44

Shock Generation and Control Using DBD Plasma Actuators  

NASA Technical Reports Server (NTRS)

This report is the final report of a NASA Phase I SBIR contract, with some revisions to remove company proprietary data. The Shock Boundary Layer Interaction (SBLI) phenomena in a supersonic inlet involve mutual interaction of oblique shocks with boundary layers, forcing the boundary layer to separate from the inlet wall. To improve the inlet efficiency, it is desired to prevent or delay shock-induced boundary layer separation. In this effort, Innovative Technology Applications Company (ITAC), LLC and the University of Notre Dame (UND) jointly investigated the use of dielectric-barrier-discharge (DBD) plasma actuators for control of SBLI in a supersonic inlet. The research investigated the potential for DBD plasma actuators to suppress flow separation caused by a shock in a turbulent boundary layer. The research involved both numerical and experimental investigations of plasma flow control for a few different SBLI configurations: (a) a 12 wedge flow test case at Mach 1.5 (numerical and experimental), (b) an impinging shock test case at Mach 1.5 using an airfoil as a shock generator (numerical and experimental), and (c) a Mach 2.0 nozzle flow case in a simulated 15 X 15 cm wind tunnel with a shock generator (numerical). Numerical studies were performed for all three test cases to examine the feasibility of plasma flow control concepts. These results were used to guide the wind tunnel experiments conducted on the Mach 1.5 12 degree wedge flow (case a) and the Mach 1.5 impinging shock test case (case b) which were at similar flow conditions as the corresponding numerical studies to obtain experimental evidence of plasma control effects for SBLI control. The experiments also generated data that were used in validating the numerical studies for the baseline cases (without plasma actuators). The experiments were conducted in a Mach 1.5 test section in the University of Notre Dame Hessert Laboratory. The simulation results from cases a and b indicated that multiple spanwise actuators in series and at a voltage of 75 kVp-p could fully suppress the flow separation downstream of the shock. The simulation results from case c showed that the streamwise plasma actuators are highly effective in creating pairs of counter-rotating vortices, much like the mechanical vortex generators, and could also potentially have beneficial effects for SBLI control. However, to achieve these effects, the positioning and the quantity of the DBD actuators used must be optimized. The wind tunnel experiments mapped the baseline flow with good agreement to the numerical simulations. The experimental results were conducted with spanwise actuators for cases a and b, but were limited by the inability to generate a sufficiently high voltage due to arcing in the wind-tunnel test-section. The static pressure in the tunnel was lower than the static pressure in an inlet at flight conditions, promoting arching and degrading the actuator performance.

Patel, Mehul P.; Cain, Alan B.; Nelson, Christopher C.; Corke, Thomas C.; Matlis, Eric H.

2012-01-01

45

Turbulent Boundary Layer Separation Control on a Convex Ramp using Plasma Actuators  

NASA Astrophysics Data System (ADS)

This work is focused toward the development of active feedback control of turbulent boundary layer separation from a convex ramp surface. The work reported here is performed in a subsonic wind tunnel facility and utilizes single dielectric barrier discharge plasma actuators for separation control. Smoke and oil surface flow visualization are used to characterize the separation in the absence of actuation. The surface mounted plasma actuators are positioned upstream of the flow separation locations. Plasma-induced blowing transfers additional momentum to the boundary layer along the ramp surface and has a beneficial effect on flow reattachment. Experimental results are presented which demonstrate the effects of both steady and unsteady actuation. The effectiveness of the active flow control is documented through surface pressure measurements, LDV measurements, and downstream wake surveys.

Schatzman, David M.

2005-11-01

46

Low pressure characterization of dielectric barrier discharge actuators  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharge actuators tested for thrust inducement between 13 and 101 kPa ambient air pressure show that as the pressure decreases, the thrust increases to a maximum, then drops steadily approaching zero while the power consumption monotonically increases. The amplification in induced thrust at the peak ranges from a few percent to several folds of the thrust measured at atmospheric condition. The effect is more pronounced for thinner dielectrics at lower operating voltages than thicker dielectrics at higher operating voltages and is fairly independent of the ground electrode width. Results identify several optimal control parameters for high-altitude operations.

Soni, Jignesh; Roy, Subrata

2013-03-01

47

Evaluation of Dielectric-Barrier-Discharge Actuator Substrate Materials  

NASA Technical Reports Server (NTRS)

A key, enabling element of a dielectric barrier discharge (DBD) actuator is the dielectric substrate material. While various investigators have studied the performance of different homogeneous materials, most often in the context of related DBD experiments, fundamental studies focused solely on the dielectric materials have received less attention. The purpose of this study was to conduct an experimental assessment of the body-force-generating performance of a wide range of dielectric materials in search of opportunities to improve DBD actuator performance. Materials studied included commonly available plastics and glasses as well as a custom-fabricated polyimide aerogel. Diagnostics included static induced thrust, electrical circuit parameters for 2D surface discharges and 1D volume discharges, and dielectric material properties. Lumped-parameter circuit simulations for the 1D case were conducted showing good correspondence to experimental data provided that stray capacitances are included. The effect of atmospheric humidity on DBD performance was studied showing a large influence on thrust. The main conclusion is that for homogeneous, dielectric materials at forcing voltages less than that required for streamer formation, the material chemical composition appears to have no effect on body force generation when actuator impedance is properly accounted for.

Wilkinson, Stephen P.; Siochi, Emilie J.; Sauti, Godfrey; Xu, Tian-Bing; Meador, Mary Ann; Guo, Haiquan

2014-01-01

48

Noise control of subsonic cavity flows using plasma actuated receptive channels  

NASA Astrophysics Data System (ADS)

We introduce a passive receptive rectangular channel at the trailing edge of an open rectangular cavity to reduce the acoustic tones generated due to coherent shear layer impingement. The channel is numerically tested at Mach 0.3 using an unsteady three-dimensional large eddy simulation. Results show reduction in pressure fluctuations in the cavity due to which sound pressure levels are suppressed. Two linear dielectric barrier discharge plasma actuators are placed inside the channel to enhance the flow through it. Specifically, acoustic suppression of 7?dB was obtained for Mach 0.3 flow with the plasma actuated channel. Also, the drag coefficient for the cavity reduced by over three folds for the channel and over eight folds for the plasma actuated channel. Such a channel can be useful in noise and drag reduction for various applications, including weapons bay, landing gear and branched piping systems.

Das Gupta, Arnob; Roy, Subrata

2014-12-01

49

Plasma actuators for separation control on stationary and oscillating airfoils  

NASA Astrophysics Data System (ADS)

Given the importance of separation control associated with retreating blade stall on helicopters, the primary objective of this work was to develop a plasma actuator flow control device for its use in controlling leading-edge separation on stationary and oscillating airfoils. The plasma actuator consists of two copper electrodes separated by a dielectric insulator. When the voltage supplied to the electrodes is sufficiently high, the surrounding air ionizes forms plasma in the regions of high electrical field potential. The ionized air, in the presence of an electric field gradient, results in a body force on the flow. The effect of plasma actuator was experimentally investigated and characterized through a systematic set of experiments. It was then applied to NACA 66 3018 and NACA 0015 airfoils for the purpose of leading-edge separation control. The effectiveness of the actuator was documented through surface pressure measurements on the airfoil, mean wake velocity profiles, and flow visualization records. For the stationary airfoil, the actuator prevented flow separation for angles of attack up to 22°, which was 8° past the static stall angle. This resulted in as much as a 300% improvement in the lift-to-drag ratio. For the oscillating airfoil, the measurements were phase-conditioned to the oscillation motion. Three cases with the plasma actuator were investigated: steady actuation, unsteady plasma actuation, and so-called "smart" actuation in which the actuator is activated during portions of the oscillatory cycle. All of the cases exhibited a higher cycle-integrated lift and an improvement in the lift cycle hysteresis. The steady plasma actuation increased the lift over most of the cycle, except at the peak angle of attack where it was found to suppress the dynamic stall vortex. Because of this, the sharp drop in the lift coefficient past the maximum angle of attack was eliminated. The unsteady plasma actuation produced significant improvements in the lift coefficient during the pitch-down portion of the cycle, especially near the minimum angle of attack. A "smart" actuator approach produced the best improvement in the lift cycle with the highest integrated lift, and elimination of the sharp stall past the maximum angle of attack. It is possible that the "smart" actuation could be optimized further. However, these results are extremely promising for improving helicopter rotor performance.

Post, Martiqua L.

50

Turbine Tip Clearance Active Flow Control using Plasma Actuators  

NASA Astrophysics Data System (ADS)

A low-speed linear cascade was used to examine the tip gap leakage flow and leakage vortex that exists within the low pressure turbine stage of a gas-turbine engine. The cascade array is composed of nine Pratt & Whitney ``PakB" blades, with the center blade having a variable tip gap up to five percent chord. Reynolds numbers based on axial chord varied from 10^4 to 10^5. Static pressure taps located at the midspan and near the tip of the blade were used to characterize the blade pressure distribution. A five-hole probe was also traversed in the downstream blade wake to ascertain velocity vectors and total pressure loss. Flow control in the form of a single-dielectric-barrier plasma actuator mounted on the blade tip was used to alter the leakage vortex by acting on the blade tip separation bubble, the blade tip shear layer instability, or the gap flow jet instability through the production of high frequency unsteady disturbances. The flow was documented through measurements with and without flow control for varying tip gaps and Reynolds numbers. The effect of the actuation on the tip leakage vortex and efficiency are investigated.

Vanness, Daniel

2005-11-01

51

Numerical and Experimental Investigation of Plasma Actuator Control of Modified Flat-back Airfoil  

NASA Astrophysics Data System (ADS)

Flat-back airfoil designs have been proposed for use on the inboard portion of large wind turbine blades because of their good structural characteristics. These structural characteristics are achieved by adding material to the aft portion of the airfoil while maintaining the camber of the origional airfoil shape. The result is a flat vertical trailing edge which increases the drag and noise produced by these airfoils. In order to improve the aerodynamic efficiency of these airfoils, the use of single dielectric barrier discharge (SDBD) plasma actuators was investigated experimentally and numerically. To accomplish this, a rounded trailing edge was added to traditional flat-back airfoil and plasma actuators were used symmetrically to control the flow separation casued by the blunt trailing edge. The actuators were used asymmetrically in order to vector the wake and increase the lift produced by the airfoil similar to adding camber.

Mertz, Benjamin; Corke, Thomas

2010-11-01

52

Separation Control from the Flap of a High-Lift Airfoil Using DBD Plasma Actuators  

NASA Astrophysics Data System (ADS)

Control of separation from the flap of a high-lift airfoil using a single dielectric barrier discharge (DBD) plasma actuator has been investigated experimentally. This project is motivated by the desire to replace existing multi-element flap configurations with a single simple flap to allow more efficient high-lift generation. The results show that a single DBD plasma actuator located at the flap shoulder can increase or reduce the size of the time-averaged separation bubble over the flap depending on the frequency of actuation. In the latter case, the lift on the airfoil is increased due to improved circulation around the model, but it does not result in full reattachment on the deflected flap. These findings are consistent with previous research on high-lift airfoil configurations. The work will be expanded by exploring the effect of multiple actuators as well as their geometry and location on the size and structure of the separated region over the flap. This portion of the work will be done with an emphasis on optimizing the relative phase of each actuator and its effect on the separated flow region.

Little, Jesse; Nishihara, Munetake; Adamovich, Igor; Samimy, Mo

2008-11-01

53

The use of plasma actuators for bluff body broadband noise control  

NASA Astrophysics Data System (ADS)

Experiments were conducted using plasma actuators to control broadband noise generated by a bluff body flow. The motivation behind the study was to explore the potential of plasma actuators to reduce landing gear noise during approach phase of an aircraft. The control effectiveness of both dielectric barrier discharge and sliding discharge plasma actuators were tested in laboratory environment, using a representative bluff body consisting of a circular cylinder and an oblique strut. Noise measurements were taken in an anechoic chamber using a phased microphone array and far-field microphones. Results showed that the upstream directed plasma forcing, located at ±90 deg on the upstream cylinder with respect to the approaching flow, could effectively attenuate the broadband noise radiated from the wake flow interaction with the downstream strut. With the same AC electrical power consumption, the sliding discharge with additional DC voltage was found to be more effective due to its elongated plasma distribution and higher induced flow momentum. Measurements using particle image velocimetry suggested that the flow speed impinging on the downstream strut was reduced by the upstream plasma forcing, contributing to the reduced noise.

Li, Yong; Zhang, Xin; Huang, Xun

2010-08-01

54

Shearless transport barriers in magnetically confined plasmas  

NASA Astrophysics Data System (ADS)

Shearless transport barriers appear in confined plasmas due to non-monotonic radial profiles and cause localized reduction of transport even after they have been broken. In this paper we summarize our recent theoretical and experimental research on shearless transport barriers in plasmas confined in toroidal devices. In particular, we discuss shearless barriers in Lagrangian magnetic field line transport caused by non-monotonic safety factor profiles. We also discuss evidence of particle transport barriers found in the TCABR Tokamak (University of São Paulo) and the Texas Helimak (University of Texas at Austin) in biased discharges with non-monotonic plasma flows.

Caldas, I. L.; Viana, R. L.; Abud, C. V.; Fonseca, J. C. D.; Guimarães Filho, Z. O.; Kroetz, T.; Marcus, F. A.; Schelin, A. B.; Szezech, J. D., Jr.; Toufen, D. L.; Benkadda, S.; Lopes, S. R.; Morrison, P. J.; Roberto, M.; Gentle, K.; Kuznetsov, Yu; Nascimento, I. C.

2012-12-01

55

Numerical simulation of nanosecond pulsed dielectric barrier discharge actuator in a quiescent flow  

NASA Astrophysics Data System (ADS)

We present a numerical study of nanosecond pulsed dielectric barrier discharge (DBD) actuator operating in quiescent air at atmospheric condition. Our study concentrates on plasma discharge induced fluid dynamics and on exploration of parametric space of interest for voltage pulse in an attempt to shed some light into elucidation of the mechanisms whereby the generated shock wave propagates through and affects the external flow. Specifically, a one-dimensional, self-similar, local ionization kinetic model recently developed to predict key parameters of nanosecond pulsed plasma discharge is coupled with the compressible Navier-Stokes equations possibly for the first time. Within the considered range of parameters of the plasma model which is justified for the modeling of surface nanosecond pulsed discharge at atmospheric pressure, our coupled method is able to provide satisfactory prediction of the shock structure generated by the actuator for comparison with experiment, not only in the qualitative shock wave shape but also in quantitative shock front displacement. We provide a comprehensive analysis of the gas heating, shock wave initiation and evolution processes. For example, the characteristic time of the rapid localized heating responsible for shock wave generation, which is yet to be quantified experimentally, is found to be ˜350 ns. We conduct a parametric investigation by varying the peak voltage from 10 kV to 50 kV and rise time from 5 ns to 150 ns. The pressure wave whose behavior is found to be dominated by input voltage amplitude, introduces highly transient, localized disturbance to the quiescent air. In addition, the vortex induced by the shock passage is relatively weak. The interplay of the induced flows by a few successive plasma discharges operating at continuous mode does not appear to be significant, especially at low voltage amplitude.

Zheng, J. G.; Zhao, Z. J.; Li, J.; Cui, Y. D.; Khoo, B. C.

2014-03-01

56

Numerical simulation of a plasma actuator based on ion transport  

SciTech Connect

Two-dimensional numerical simulation of ion transport and flow around a single dielectric barrier discharge plasma actuator (PA) is performed. Spatial distributions of ions and electrons as well as their time evolution are obtained by solving the transport equations of monovalent positive ions, monovalent negative ions, and electrons. Voltage and frequency of the driving alternating-current signal are assumed to be 8 kV and 5 kHz, respectively. Special focus is laid upon the effect of voltage gradient dV/dt on the magnitude of the body force. The validity of steady force models often used in flow simulation is also examined. The simulation results show that the magnitude of the body force induced by the PA increases as the voltage gradient dV/dt increases and its increase rate becomes milder at higher voltage. The mechanism of body force generation is explained from the time evolution of number density fields of ions and electrons. A comparison between flow simulations using a time-resolved body force and its time-averaged counterpart demonstrates that the time-averaged model gives sufficiently accurate results when the time scale of the flow is more than 30 times greater than that of the PA.

Yamamoto, Seiya; Fukagata, Koji [Department of Mechanical Engineering, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522 (Japan)] [Department of Mechanical Engineering, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522 (Japan)

2013-06-28

57

Plasma actuated heat transfer Subrata Roya  

E-print Network

with cold fluid film is common- place in many engineering problems including vertical/short takeoff in the vicinity of an actuator using an electrodynamic mechanism that induces attachment of cold jet to the work blade lifetime. In this process, cold gas is injected from a row of holes located spanwise into the hot

Roy, Subrata

58

Serpentine geometry plasma actuators for flow control Mark Riherd and Subrata Roy  

E-print Network

Serpentine geometry plasma actuators for flow control Mark Riherd and Subrata Roy Citation: J. Appl://jap.aip.org/authors #12;Serpentine geometry plasma actuators for flow control Mark Riherd and Subrata Roya) Applied. Plasma actuators with novel geometries, including the serpentine geometry, have been effective

Roy, Subrata

59

Broadband flow-induced sound control using plasma actuators  

NASA Astrophysics Data System (ADS)

Plasma actuators were used in this work to control flow-induced broadband noise radiated from a bluff body. The model consists of a cylinder and a component (torque link) that is installed on the lee side of the cylinder. The objective is to reduce the broadband noise mainly generated through the impingement of the cylinder wake on the torque link. The flow-structure interactions between the cylinder wake and the torque link are reduced by manipulating the cylinder wake with the externally imposed body force from the plasma actuators, which lead to the attenuation of the broadband noise. The control performance with the plasma actuators is studied in an anechoic chamber facility by examining far-field sound level and near-field acoustic source changes. At a free stream speed of 30 m/s, corresponding to the Reynolds number of 2.1×105, far-field measurements suggested that a reduction of up to 3.2 dB in overall sound pressure level. The near-field beamforming results also show approximately 3 dB reduction in the interested frequency ranges. The physical mechanisms related to broadband noise control were also discussed. This work suggests that plasma actuators offer the potential for solving flow-induced noise control problem at broadband frequencies.

Huang, Xun; Zhang, Xin; Li, Yong

2010-06-01

60

Separation Control in a Centrifugal Bend Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

An experiment and CFD simulation are presented to examine the use of plasma actuators to control flow separation in a 2-D channel with a 135^o inside-bend that is intended to represent a centrifugal bend in a gas turbine engine. The design inlet conditions are P=330,sia., T=1100^oF, and M=0.24. For these conditions, the flow separates on the inside radius of the bend. A CFD simulation was used to determine the location of the flow separation, and the conditions (location and voltage) of a plasma actuator that was needed to keep the flow attached. The plasma actuator body force model used in the simulation was updated to include the effect of high-pressure operation. An experiment was used to validate the simulation and to further investigate the effect of inlet pressure and Mach number on the flow separation control. This involved a transient high-pressure blow-down facility. The flow field is documented using an array of static pressure taps in the channel outside-radius side wall, and a rake of total pressure probes at the exit of the bend. The results as well as the pressure effect on the plasma actuators are presented.

Arthur, Michael; Corke, Thomas

2011-11-01

61

Rate of plasma thermalization of pulsed nanosecond surface dielectric barrier discharge  

Microsoft Academic Search

The paper presents a detailed explanation of the physical mechanism of the nanosecond pulsed surface dielectric barrier discharge (SDBD) effect on the flow. Actuator-induced gas velocities show near-zero values for nanosecond pulses. The measurements performed show overheating in the discharge region at fast (? ~ 1 us) thermalization of the plasma inputed energy. The mean values of such heating of

N. Aleksahdrov; M. Nudnova; S. Kindusheva; A. Starikovskiy

2010-01-01

62

Nanosecond-pulsed plasma actuation in quiescent air and laminar boundary layer  

NASA Astrophysics Data System (ADS)

An experimental investigation of the working principles of a nanosecond-pulsed dielectric barrier discharge (ns-DBD) plasma actuator has been conducted. Special emphasis is given on the thermal effects accompanying the rapid deposition of energy associated with this kind of actuation. A ns-DBD plasma actuator has been operated in quiescent air conditions as well as in a flat plate laminar boundary layer, with external flow velocity of 5 and 10 m s-1. Schlieren imaging and particle image velocimetry have been used to characterize the actuation. Additionally, the back-current shunt technique has been used for current measurements, from which energy input (per pulse) is calculated. Cases of 10-, 20- and 50-pulse bursts are tested. Schlieren imaging in still air conditions shows the formation of a high-temperature region in the vicinity of the discharge volume. The spatial extent of the visible ‘hot spot’ depends upon the number of pulses within the burst, following a power law. Schlieren imaging of the span-wise effect of the plasma actuator reveals weak compression waves originating from the loci of discharge filaments. The thermal ‘hot spots’ exhibit significant three-dimensionality. Particle image velocimetry is used to measure the velocity field resulting from the ns-DBDs acting on a laminar boundary layer. The disturbance leads to formation of a Tollmien-Schlichting wave train, with spectral content in good agreement with linear stability theory. It is observed that the group length of the wave train is proportional to the number of pulses within the burst.

Correale, G.; Michelis, T.; Ragni, D.; Kotsonis, M.; Scarano, F.

2014-03-01

63

Note: Background Oriented Schlieren as a diagnostics for airflow control by plasma actuators.  

PubMed

Background Oriented Schlieren (BOS) is an optical technique sensitive to the first spatial derivative of the refractive index inside a light-transmitting medium. Compared to other Schlieren-like techniques, BOS is more versatile and allows to capture bi-dimensional gradients rather than just one spatial component. We propose to adopt BOS for studying the capabilities of surface dielectric barrier discharges to work like plasma actuators in flow control applications. The characteristics of the BOS we implemented at this purpose are discussed, together with few results concerning the ionic wind produced by the discharge in absence of an external airflow. PMID:25725896

Biganzoli, I; Capone, C; Barni, R; Riccardi, C

2015-02-01

64

Note: Background Oriented Schlieren as a diagnostics for airflow control by plasma actuators  

NASA Astrophysics Data System (ADS)

Background Oriented Schlieren (BOS) is an optical technique sensitive to the first spatial derivative of the refractive index inside a light-transmitting medium. Compared to other Schlieren-like techniques, BOS is more versatile and allows to capture bi-dimensional gradients rather than just one spatial component. We propose to adopt BOS for studying the capabilities of surface dielectric barrier discharges to work like plasma actuators in flow control applications. The characteristics of the BOS we implemented at this purpose are discussed, together with few results concerning the ionic wind produced by the discharge in absence of an external airflow.

Biganzoli, I.; Capone, C.; Barni, R.; Riccardi, C.

2015-02-01

65

Progress Toward Accurate Measurements of Power Consumptions of DBD Plasma Actuators  

NASA Technical Reports Server (NTRS)

The accurate measurement of power consumption by Dielectric Barrier Discharge (DBD) plasma actuators is a challenge due to the characteristics of the actuator current signal. Micro-discharges generate high-amplitude, high-frequency current spike transients superimposed on a low-amplitude, low-frequency current. We have used a high-speed digital oscilloscope to measure the actuator power consumption using the Shunt Resistor method and the Monitor Capacitor method. The measurements were performed simultaneously and compared to each other in a time-accurate manner. It was found that low signal-to-noise ratios of the oscilloscopes used, in combination with the high dynamic range of the current spikes, make the Shunt Resistor method inaccurate. An innovative, nonlinear signal compression circuit was applied to the actuator current signal and yielded excellent agreement between the two methods. The paper describes the issues and challenges associated with performing accurate power measurements. It provides insights into the two methods including new insight into the Lissajous curve of the Monitor Capacitor method. Extension to a broad range of parameters and further development of the compression hardware will be performed in future work.

Ashpis, David E.; Laun, Matthew C.; Griebeler, Elmer L.

2012-01-01

66

Plasma actuator electron density measurement using microwave perturbation method  

SciTech Connect

A cylindrical dielectric barrier discharge plasma under five different pressures is generated in an evacuated glass tube. This plasma volume is located at the center of a rectangular copper waveguide cavity, where the electric field is maximum for the first mode and the magnetic field is very close to zero. The microwave perturbation method is used to measure electron density and plasma frequency for these five pressures. Simulations by a commercial microwave simulator are comparable to the experimental results.

Mirhosseini, Farid; Colpitts, Bruce [Electrical and Computer Engineering, University of New Brunswick, Fredericton, New Brunswick E3B 5A3 (Canada)

2014-07-21

67

Low pressure characterization of dielectric barrier discharge actuators Jignesh Soni and Subrata Roya)  

E-print Network

Low pressure characterization of dielectric barrier discharge actuators Jignesh Soni and Subrata kPa ambient air pressure show that as the pressure decreases, the thrust increases to a maximum parameters are well understood,7,8 the effect of operating pressure is yet to be fully explored. A the

Roy, Subrata

68

Competition between pressure effects and airflow influence for the performance of plasma actuators  

NASA Astrophysics Data System (ADS)

The present work addresses the combined influence of pressure variations and different airflow velocities on the discharge intensity of plasma actuators. Power consumption, plasma length, and discharge capacitance were investigated systematically for varying pressure levels (p = 0.1-1 bar) and airflow velocities (U?=0-100 m/s) to characterize and quantify the favorable and adverse effects on the discharge intensity. In accordance with previous reports, an increasing plasma actuator discharge intensity is observed for decreasing pressure levels. At constant pressure levels, an adverse airflow influence on the electric actuator performance is demonstrated. Despite the improved discharge intensity at lower pressure levels, the seemingly improved performance of the plasma actuators is accompanied with a more pronounced drop of the relative performance. These findings demonstrate the dependency of the (kinematic and thermodynamic) environmental conditions on the electric performance of plasma actuators, which in turn affects the control authority of plasma actuators for flow control applications.

Kriegseis, J.; Barckmann, K.; Frey, J.; Tropea, C.; Grundmann, S.

2014-05-01

69

Competition between pressure effects and airflow influence for the performance of plasma actuators  

SciTech Connect

The present work addresses the combined influence of pressure variations and different airflow velocities on the discharge intensity of plasma actuators. Power consumption, plasma length, and discharge capacitance were investigated systematically for varying pressure levels (p?=?0.1–1 bar) and airflow velocities (U{sub ?}=0?100 m/s) to characterize and quantify the favorable and adverse effects on the discharge intensity. In accordance with previous reports, an increasing plasma actuator discharge intensity is observed for decreasing pressure levels. At constant pressure levels, an adverse airflow influence on the electric actuator performance is demonstrated. Despite the improved discharge intensity at lower pressure levels, the seemingly improved performance of the plasma actuators is accompanied with a more pronounced drop of the relative performance. These findings demonstrate the dependency of the (kinematic and thermodynamic) environmental conditions on the electric performance of plasma actuators, which in turn affects the control authority of plasma actuators for flow control applications.

Kriegseis, J., E-mail: kriegseis@kit.edu [Institute of Fluid Mechanics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Barckmann, K.; Grundmann, S., E-mail: grundmann@csi.tu-darmstadt.de [Center of Smart Interfaces, Technische Universität Darmstadt, Darmstadt (Germany); Frey, J. [Institute for Aerospace Engineering, Technische Universität Dresden, Dresden (Germany); Tropea, C. [Center of Smart Interfaces, Technische Universität Darmstadt, Darmstadt (Germany); Institute of Fluid Mechanics and Aerodynamics, Technische Universität Darmstadt, Darmstadt (Germany)

2014-05-15

70

Combustion stabilization using serpentine plasma actuators Chin-Cheng Wang and Subrata Roya)  

E-print Network

Combustion stabilization using serpentine plasma actuators Chin-Cheng Wang and Subrata Roya 2011) This letter presents a numerical model for combustion stabilization with plasma actuators of Physics. [doi:10.1063/1.3615292] The topic of plasma assisted combustion (PAC) has been investigated

Roy, Subrata

71

Effect of a direct current bias on the electrohydrodynamic performance of a surface dielectric barrier discharge actuator for airflow control  

NASA Astrophysics Data System (ADS)

The effect of a DC bias on the electrohydrodynamics (EHD) force induced by a surface dielectric barrier AC discharge actuator for airflow control at the atmospheric pressure is investigated. The measurement of the surface potential due to charge deposition at different DC biases is carried out by using a special designed corona like discharge potential probe. From the surface potential data, the plasma electromotive force is shown not affected much by the DC biases except for some reduction of the DC bias near the exposed electrode edge for the sheath-like configuration. The total thrust is measured by an analytical balance, and an almost linear relationship to the potential voltage at the exposed electrode edge is found for the direct thrust force. The temporally averaged ionic wind characteristics are investigated by Pitot tube sensor and schlieren visualization system. It is found that the ionic wind velocity profiles with different DC biases are almost the same in the AC discharge plasma area but gradually diversified in the further downstream area as well as the upper space away from the discharge plasma area. Also, the DC bias can significantly modify the topology of the ionic wind produced by the AC discharge actuator. These results can provide an insight into how the DC biases to affect the force generation.

Yan, Huijie; Yang, Liang; Qi, Xiaohua; Ren, Chunsheng

2015-02-01

72

Plasma Actuators for Turbomachinery Flow Control  

NASA Technical Reports Server (NTRS)

This report is Part I of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. The period of performance was January 1, 2007 to December 31, 2010. This report includes the project summary, a list of publications and reprints of the publications that appeared in archival journals. Part II of the final report includes a Ph.D. dissertation and is published separately as NASA/CR-2012-2172655. The research performed under this project was focused on the operation of surface dielectric barrier discharge (DBD) devices driven by high voltage, nanosecond scale pulses plus constant or time varying bias voltages. The main interest was in momentum production and the range of voltages applied eliminated significant heating effects. The approach was experimental supplemented by computational modeling. All the experiments were conducted at Princeton University. The project provided comprehensive understanding of the associated physical phenomena. Limitations on the performance of the devices for the generation of high velocity surface jets were established and various means for overcoming those limitations were proposed and tested. The major limitations included the maximum velocity limit of the jet due to electrical breakdown in air and across the dielectric, the occurrence of backward breakdown during the short pulse causing reverse thrust, the buildup of surface charge in the dielectric offsetting the forward driving potential of the bias voltage, and the interaction of the surface jet with the surface through viscous losses. It was also noted that the best performance occurred when the nanosecond pulse and the bias voltage were of opposite sign. Solutions include the development of partially conducting surface coatings, the development of a semiconductor diode inlaid surface material to suppress the backward breakdown. Extension to long discharge channels was studied and a new ozone imaging method developed for more quantitative determination of surface jet properties.

Miles, Richard, B; Shneider, Mikhail, N.

2012-01-01

73

3rd AIAA Flow Control Conference, Jun. 58, 2006, San Francisco,CA Flow Control Using Plasma Actuators and  

E-print Network

Actuators and Linear/Annular Plasma Synthetic Jet Actuators Arvind Santhanakrishnan and Jamey D. Jacob Dept different actuator geometries have been tested: a conven- tional design using two rectangular strip electrodes (the linear actuator) that produces a nearly two-dimensional horizontal wall jet upon actuation

Jacob, Jamey

74

Single dielectric barrier discharge plasma enhanced aerodynamics: physics, modeling and applications  

NASA Astrophysics Data System (ADS)

The term “plasma actuator” has been a part of the fluid dynamics flow control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is through a generated body force vector that couples with the momentum in the external flow. The body force can be derived from first principles and the plasma actuator effect can be easily incorporated into flow solvers so that their placement and operation can be optimized. They have been used in a wide range of applications that include bluff body wake control; lift augmentation and separation control on a variety of lifting surfaces ranging from fixed wings with various degrees of sweep, wind turbine rotors and pitching airfoils simulating helicopter rotors; flow separation and tip-casing clearance flow control to reduce losses in turbines, to control flow surge and stall in compressors; and in exciting instabilities in boundary layers at subsonic to supersonic Mach numbers for turbulent transition control. New applications continue to appear through programs in a growing number of US universities and government laboratories, as well as in Germany, France, England, Netherland, Russia, Japan and China. This paper provides an overview of the physics, design and modeling of SDBD plasma actuators. It then presents their use in a number of applications that includes both numerical flow simulations and experiments together.

Corke, Thomas C.; Post, Martiqua L.; Orlov, Dmitriy M.

2009-01-01

75

Plasma sprayed functionally graded thermal barrier coatings  

Microsoft Academic Search

Functionally graded thermal barrier coatings of the system yttria stabilised zirconia\\/NiCoCrAlY were fabricated through plasma spraying using pre-alloyed composite powders as feedstock. Composite powders with different compositions (75% NiCoCrAlY:25% YSZ; 50% NiCoCrAly:50% YSZ and 25% NiCoCrAlY:75% YSZ) were prepared by mechanical alloying and plasma powder spheroidisation, and are subsequently sprayed successively in a single plasma torch to form the functionally

K. A. Khor; Z. L. Dong; Y. W. Gu

1999-01-01

76

Transient ejection phase modeling of a Plasma Synthetic Jet actuator  

NASA Astrophysics Data System (ADS)

For several years, a promising Plasma Synthetic Jet actuator for high-speed flow control has been under development at ONERA. So far, its confined geometry and small space-time scales at play have prevented its full experimental characterization. Complementary accurate numerical simulations are then considered in this study in order to provide a complete aerothermodynamic description of the actuator. Two major obstacles have to be overcome with this approach: the modeling of the energy deposited by the electric arc and the accurate computation of the transient response of the cavity generating the pulsed jet. To solve the first problem, an Euler solver coupled with an electric circuit model was used to evaluate the energy deposition in the cavity. Such a coupling is performed by considering the electric field between the two electrodes. The second issue was then addressed by injecting these source terms in large Eddy simulations of the entire actuator. Aerodynamic results were finally compared with Schlieren visualizations. Using the proposed methodology, the temporal evolution of the jet front is remarkably well predicted.

Laurendeau, F.; Chedevergne, F.; Casalis, G.

2014-12-01

77

On the benefits of hysteresis effects for closed-loop separation control using plasma actuation  

NASA Astrophysics Data System (ADS)

Flow separation control by a non-thermal plasma actuator is considered for a NACA 0015 airfoil at a chord Reynolds number of 1.9 × 105. Static hysteresis in the lift coefficient is demonstrated for increasing and then decreasing sinusoidal voltage amplitude supplying a typical single dielectric barrier discharge actuator at the leading edge of the model. In addition to these open-loop experiments, unsteady surface pressure signals are examined for transient processes involving forced reattachment and natural separation. The results show that strong pressure oscillations in the relatively slow separation process, compared to reattachment, precede the ultimate massive flow separation. To enhance the contrast between the parts of the signal related to the attached flow and those related to the incipient separation, RMS estimate of filtered values of Cp is used to define a flow separation predictor that is implemented in feedback control. Two simple controllers are proposed, one based on a predefined threshold of the unsteady Cp and another that utilizes the flow separation predictor to identify incipient separation. The latter effectively leverages the hysteresis in the post-stall regime to reduce the electrical power consumed by the actuator while maintaining continuously attached flow.

Benard, N.; Cattafesta, L. N.; Moreau, E.; Griffin, J.; Bonnet, J. P.

2011-08-01

78

Numerical Investigation of Serpentine Plasma Actuators for Separation Control at Low Reynolds Number  

E-print Network

1 Numerical Investigation of Serpentine Plasma Actuators for Separation Control at Low Reynolds Discharge (DBD) plasma actuators with serpentine shaped electrodes cause a change in the operational parameters, in particular the geometric amplitude of the serpentine geometry as it is flattened out

Roy, Subrata

79

Analytic model and frequency characteristics of plasma synthetic jet actuator  

NASA Astrophysics Data System (ADS)

This paper reports a novel analytic model of a plasma synthetic jet actuator (PSJA), considering both the heat transfer effect and the inertia of the throat gas. Both the whole cycle characteristics and the repetitive working process of PSJA can be predicted with this model. The frequency characteristics of a PSJA with 87 mm3 volume and different orifice diameters are investigated based on the analytic model combined with experiments. In the repetitive working mode, the actuator works initially in the transitional stage with 20 cycles and then in the dynamic balanced stage. During the transitional stage, major performance parameters of PSJA experience stepped growth, while during the dynamic balanced stage, these parameters are characterized by periodic variation. With a constant discharge energy of 6.9 mJ, there exists a saturated frequency of 4 kHz/6 kHz for an orifice diameter of 1 mm/1.5 mm, at which the time-averaged total pressure of the pulsed jet reaches a maximum. Between 0.5 mm and 1.5 mm, a larger orifice diameter leads to a higher saturated frequency due to the reduced jet duration time. As the actuation frequency increases, both the time-averaged cavity temperature and the peak jet velocity initially increase and then remain almost unchanged at 1600 K and 280 m/s, respectively. Besides, with increasing frequency, the mechanical energy incorporated in single pulsed jet, the expelled mass per pulse, and the time-averaged density in the cavity, decline in a stair stepping way, which is caused by the intermittent decrease of refresh stage duration in one period.

Zong, Hao-hua; Wu, Yun; Li, Ying-hong; Song, Hui-min; Zhang, Zhi-bo; Jia, Min

2015-02-01

80

Study of flow induced by sine wave and saw tooth plasma actuators  

NASA Astrophysics Data System (ADS)

The effect of plasma actuator that uses saw-tooth or sine-wave shape electrodes on boundary layer flows is experimentally investigated. The measurement results are compared with a corresponding standard configuration (conventional design using two rectangular strip electrodes)—the actuator that produces a nearly two-dimensional horizontal wall jet upon actuation. PIV measurements are used to characterize the actuators in a quiescent chamber. Operating in a steady manner, the new actuators result in the formation of streamwise and spanwise vortices. That is to say, the new actuators render the plasma actuators inducing three-dimensional variations in the shear layer, offering significant flexibility in flow control. The affected flowfield with the new actuators is significantly larger than that with the conventional linear actuators. While the conventional linear actuators affect primarily the boundary layer flow on a scale of about 1 cm above the wall, the new actuators affect the near wall region at a significantly larger scale. This new design broadens the applicability and enhances the flow control effects and it is potentially a more efficient flow control device.

Liu, Zhifeng; Wang, Lianze; Fu, Song

2011-11-01

81

Documentation and Control of Flow Separation on a Low Pressure Turbine Linear Cascade of Pak-B Blades Using Plasma Actuators  

NASA Technical Reports Server (NTRS)

This work involved the documentation and control of flow separation that occurs over low pressure turbine (LPT) blades at low Reynolds numbers. A specially constructed linear cascade was utilized to study the flow field over a generic LPT cascade consisting of Pratt & Whitney "Pak-B" shaped blades. Flow visualization, surface pressure measurements, LDV measurements, and hot-wire anemometry were conducted to examine the flow fields with and without separation control. Experimental conditions were chosen to give a range of chord Reynolds numbers (based on axial chord and inlet velocity) from 10,000 to 100,000, and a range of freestream turbulence intensities from u'/U(infinity) = 0.08 to 2.85 percent. The blade pressure distributions were measured and used to identify the region of separation that depends on Reynolds number and the turbulence intensity. Separation control was performed using dielectric barrier discharge (DBD) plasma actuators. Both steady and unsteady actuation were implemented and found to work well. The comparison between the steady and unsteady actuators showed that the unsteady actuators worked better than the steady ones. For the steady actuators, it was found that the separated region is significantly reduced. For the unsteady actuators, where the signal was pulsed, the separation was eliminated. The total pressure losses (a low Reynolds number) was reduced by approximately a factor of two. It was also found that lowest plasma duty cycle (10 percent in this work) was as effective as the highest plasma duty cycle (50 percent in this work). The mechanisms of the steady and unsteady plasma actuators were studied. It was suggested by the experimental results that the mechanism for the steady actuators is turbulence tripping, while the mechanism for the unsteady actuators is to generate a train of spanwise structures that promote mixing.

Corke, Thomas c.; Thomas, FLint, O.; Huang, Junhui

2007-01-01

82

Real time control of the plasma current and elongation in tokamaks using ECRH actuators  

Microsoft Academic Search

Real time control of the plasma elongation and plasma current using electron cyclotron resonance heating (ECRH) actuators has been demonstrated on TCV. Tokamak plasmas may be elongated by off-axis ECRH. The associated flattening of the current density profile increases the plasma's vertical stability, enabling higher elongations to be obtained, at lower currents than would be possible in Ohmic conditions. Successful

J. I. Paley; S. Coda

2007-01-01

83

DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines - Simulation of Flight Conditions in Test Chambers by Density Matching  

NASA Technical Reports Server (NTRS)

Dielectric Barrier Discharge (DBD) Plasma actuators for active flow control in aircraft and jet engines need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which, in turn, depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. The pressure and temperature at the actuator flight operation conditions need to be simultaneously set in the chamber. A simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density, while other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in operating flight conditions. The needed chamber pressures are shown for altitude flight of an air vehicle and for jet engines at sea-level takeoff and altitude cruise conditions. Atmospheric flight conditions are calculated from standard atmosphere with and without shock waves. The engine data was obtained from four generic engine models; 300-, 150-, and 50-passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and for altitude cruise conditions. The corresponding chamber pressures needed to test the actuators were calculated. The results show that, to simulate engine component flows at in-flight conditions, plasma actuator should be tested over a wide range of pressures. For the four model engines the range is from 12.4 to 0.03 atm, depending on the placement of the actuator in the engine. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it has to be tested at 12.4 atm for takeoff, and 6 atm for cruise conditions. If it is to be placed at the low-pressure turbine, it has to be tested at 0.5 and 0.2 atm, respectively. These results have implications for the feasibility and design of DBD plasma actuators for jet engine flow control applications. In addition, the distributions of unit Reynolds number, Mach number, and velocity along the engine are provided. The engine models are non-proprietary and this information can be used for evaluation of other types of actuators and for other purposes.

Ashpis, David E.; Thurman, Douglas R.

2011-01-01

84

Active Control of Flow around NACA 0015 Airfoil by Using DBD Plasma Actuator  

NASA Astrophysics Data System (ADS)

In this study, effect of plasma actuator on a flat plate and manipulation of flow separation on NACA0015 airfoil with plasma actuator at low Reynolds numbers were experimentally investigated. In the first section of the study, plasma actuator which consists of positive and grounded electrode couple and dielectric layer, located on a flat plate was actuated at different frequencies and peak to peak voltages in range of 3-5 kHz and 6-12 kV respectively. Theinduced air flow velocity on the surface of flat plate was measured by pitot tube at different locations behind the actuator. The influence of dielectricthickness and unsteady actuation with duty cycle was also examined. In the second section, the effect of plasma actuator on NACA0015 airfoil was studied atReynolds number 15000 and 30000. Four plasma actuators were placed at x/C = 0.1, 0.3, 0.5 and 0.9, and different electrode combinations were activated by sinusoidal signal. Flow visualizations were done when the attack angles were 0°, 5°, 10°, 15° and 20°. The results indicate that up to the 15° attack angle, the separated flow was reattached by plasma actuator at 12kV peak to peak voltage and 4 kHz frequency. However, 12 kVpp voltage was insufficient to reattach the flow at 20° angle of attack. The separated flow could be reattached by increasing the voltage up to 13 kV. Lift coefficient was also increased by the manipulated flow over the airfoil. Results showed that even high attack angles, the actuators can control the flow separation and prevent the airfoil from stall at low Reynolds numbers.

Akansu, Y. E.; Karakaya, F.; ?anl?soy, A.

2013-04-01

85

ACTIVE CONTROL OF NEAR-WALL TURBULENCE WITH PERIODIC FORCING BY PLASMA ACTUATOR  

E-print Network

undertaken to reduce skin friction drag by applying spatially periodic forcing in the near wall region of a turbulent channel flow with micro plasma actuators. Measurements are made by a laser Doppler velocimeter

Kasagi, Nobuhide

86

Variable Structure Model for Flow-Induced Tonal Noise Control with Plasma Actuators  

E-print Network

,14] demonstrated the use of plasma actuators for attenuating cavity tonal noise that is similar to landing gear bay motion to the surrounding neutral gas that can serve flow control applications [1­11]. Several types

Huang, Xun

87

Force generation due to three-dimensional plasma discharge on a conical forebody using pulsed direct current actuators  

E-print Network

Force generation due to three-dimensional plasma discharge on a conical forebody using pulsed Understanding the behavior of three-dimensional plasmas around a pulsed dc actuator can be useful for its direct current actuators Kunwar Pal Singh and Subrata Roya Computational Plasma Dynamics Laboratory

Roy, Subrata

88

Characterization of linear plasma synthetic jet actuators in an initially quiescent medium  

SciTech Connect

The plasma synthetic jet actuator (PSJA) is a geometrical variant of the aerodynamic plasma actuator that can be used to produce zero-mass flux jets similar to those created by mechanical devices. This jet can be either three-dimensional using annular electrode arrays (annular PSJA) or nearly two dimensional using two rectangular-strip exposed electrodes and one embedded electrode (linear PSJA). Unsteady pulsing of the PSJA at time scales decoupled to the ac input frequency results in a flow field dominated by counter-rotating vortical structures similar to conventional synthetic jets, and the peak velocity and momentum of the jet is found to be affected by a combination of the pulsing frequency and input power. This paper investigates the fluid dynamic characteristics of linear plasma synthetic jet actuators in an initially quiescent medium. Two-dimensional particle image velocimetry measurements on the actuator are used to validate a previously developed numerical model wherein the plasma behavior is introduced into the Navier-Stokes equations as an electrohydrodynamic force term calculated from Maxwell's equations and solved for the fluid momentum. The numerical model was implemented in an incompressible, unstructured grid code. The results of the simulations are observed to reproduce some aspects of the qualitative and quantitative experimental behavior of the jet for steady and pulsed modes of actuator operation. The self-similarity behavior of plasma synthetic jets are examined and compared to mechanically driven continuous and synthetic jets.

Santhanakrishnan, Arvind [Department of Mathematics, Phillips Hall, CB 3250, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3250 (United States); Reasor, Daniel A. Jr. [School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); LeBeau, Raymond P. Jr. [Department of Mechanical Engineering, University of Kentucky, Lexington, Kentucky 40506 (United States)

2009-04-15

89

Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air  

SciTech Connect

Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7?kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.

Che, Xueke, E-mail: chedk@163.com, E-mail: st@mail.iee.ac.cn; Nie, Wansheng; Tian, Xihui; Hou, Zhiyong; He, Haobo; Zhou, Penghui; Zhou, Siyin; Yang, Chao [Equipment Academy, Beijing 101416 (China)] [Equipment Academy, Beijing 101416 (China); Shao, Tao, E-mail: chedk@163.com, E-mail: st@mail.iee.ac.cn [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China)] [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China)

2014-04-15

90

Performance Envelope of Flow Velocity Induced by a Single OAUGDP^ Electrohydrodynamic (EHD) Plasma Actuator  

NASA Astrophysics Data System (ADS)

Electrohydrodynamic (EHD) plasma actuators using the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP^) are emerging as a promising aerodynamic flow control technology.^1 It has been found that a single plasma actuator on the leading edge of a NACA-0015 airfoil increased its stall angle from 15^o to 21^o at free-steam flow velocities up to 75 m/s,^2 promising flow control applications at aircraft take-off and landing speeds. We are conducting a research program to maximize the induced flow velocity and minimize the power consumption of plasma actuators by adjusting the electrode width, width ratio, gap distance, dielectric thickness, and dielectric material.^3 In this paper, we report the induced flow velocity and input power to the actuator as functions of the dielectric material, and RF voltage and frequency. We find that quartz and Teflon are superior dielectric materials. ^1J. R. Roth: Physics of Plasmas, Vol. 10, No. 5 (2003). ^2D.F.Opaits et al., 43rd AIAA Aerospace Sciences Meeting Reno, NV, January 10-14, 2005. ^3J. R. Roth, Xin Dai, Jozef Rahel, and D. M. Sherman, 43rd AIAA Aerospace Sciences Meeting Reno, NV, January 10-14, 2005

Reece Roth, J.

2005-10-01

91

Design of a DBD Plasma Actuator Array to Control Stationary Cross Flow Modes in a Supersonic Boundary Layer  

NASA Astrophysics Data System (ADS)

The control of cross flow dominated laminar turbulent transition is crucial for the improvement of efficiency of supersonic aircraft. Passive methods such as distributed micron sized roughness elements have proven to work efficiently as laminar flow control devices in subsonic and as we could recently show in supersonic flows. This study describes the replacement of micron sized roughness elements with an array of dielectric barrier discharge (DBD) plasma actuators in order to excite less amplified stationary cross flow modes. These are intended to suppress the growth of the naturally occurring most amplified stationary modes. The use of DBD plasma actuators allows for a dynamic control that can respond to changing flight conditions, which is difficult to achieve with traditional roughness elements. Experiments have been performed in the 0.5,Mach 3.5 NASA LaRC Supersonic Low Disturbance Tunnel on a 7^o half angle sharp cone at a 4.3^o angle of attack, and a unit Reynolds number of 250000/in.

Schuele, Chan-Yong; Matlis, Eric; Corke, Thomas; Wilkinson, Stephen

2010-11-01

92

Propagating-arc magnetohydrodynamic plasma actuator for directional high-authority flow control in atmospheric air  

NASA Astrophysics Data System (ADS)

A propagating-arc magnetohydrodynamic plasma actuator for aerodynamic flow control is reported. The actuator comprises two rail electrodes flush mounted on an aerodynamic surface. A pulsed arc is propelled down the length of the rails by Lorentz forces supported by a self-induced magnetic field. The arc induces a high velocity pulsed air wall jet due to the pushing and entrainment actions. Experiments in quiescent air demonstrate that the plasma arc achieves a peak velocity of around 100 m s-1 and requires a discharge energy on the order of 300 J per pulse. Wind tunnel tests on a 14.5 inch chord airfoil section, at a Reynolds number of 0.45 million show induced flow velocities on the order of 10's m s-1 with significant penetration of the flow actuation effect perpendicular to the wall surface.

Pafford, Brent; Sirohi, Jayant; Raja, Laxminarayan L.

2013-12-01

93

Flow and Noise Control in High Speed and High Reynolds Number Jets Using Plasma Actuators  

NASA Technical Reports Server (NTRS)

The idea of manipulating flow to change its characteristics is over a century old. Manipulating instabilities of a jet to increase its mixing and to reduce its radiated noise started in the 1970s. While the effort has been successful in low-speed and low Reynolds number jets, available actuators capabilities in terms of their amplitude, bandwidth, and phasing have fallen short in control of high-speed and high Reynolds number jets of practical interest. Localized arc filament plasma actuators have recently been developed and extensively used at Gas Dynamics and Turbulence Laboratory (GDTL) for control of highspeed and high Reynolds number jets. While the technique has been quite successful and is very promising, all the work up to this point had been carried out using small high subsonic and low supersonic jets from a 2.54 cm diameter nozzle exit with a Reynolds number of about a million. The preliminary work reported in this paper is a first attempt to evaluate the scalability of the technique. The power supply/plasma generator was designed and built in-house at GDTL to operate 8 actuators simultaneously over a large frequency range (0 to 200 kHz) with independent control over phase and duty cycle of each actuator. This allowed forcing the small jet at GDTL with azimuthal modes m = 0, 1, 2, 3, plus or minus 1, plus or minus 2, and plus or minus 4 over a large range of frequencies. This power supply was taken to and used, with minor modifications, at the NASA Nozzle Acoustic Test Rig (NATR). At NATR, 32 actuators were distributed around the 7.5 in. nozzle (a linear increase with nozzle exit diameter would require 60 actuators). With this arrangement only 8 actuators could operate simultaneously, thus limiting the forcing of the jet at NATR to only three azimuthal modes m = plus or minus 1, 4, and 8. Very preliminary results at NATR indicate that the trends observed in the larger NASA facility in terms of the effects of actuation frequency and azimuthal modes are similar in both small GDTL and larger NASA jets. However, the actuation authority seems to fall short in the larger jet at higher Mach numbers, resulting in decreased amplitude response compared to the small jet, which is attributed at this point to the lack of sufficient number of actuators. The preliminary results seem also to suggest that amplitude of actuation tones is similar in both the small and larger jets.

Samimy, M.; Kastner, J.; Kim, J.-H.; Utkin, Y.; Adamovich, I.; Brown, C. A.

2006-01-01

94

LES of a Jet Excited by the Localized Arc Filament Plasma Actuators  

NASA Technical Reports Server (NTRS)

The fluid dynamics of a high-speed jet are governed by the instability waves that form in the free-shear boundary layer of the jet. Jet excitation manipulates the growth and saturation of particular instability waves to control the unsteady flow structures that characterize the energy cascade in the jet.The results may include jet noise mitigation or a reduction in the infrared signature of the jet. The Localized Arc Filament Plasma Actuators (LAFPA) have demonstrated the ability to excite a high-speed jets in laboratory experiments. Extending and optimizing this excitation technology, however, is a complex process that will require many tests and trials. Computational simulations can play an important role in understanding and optimizing this actuator technology for real-world applications. Previous research has focused on developing a suitable actuator model and coupling it with the appropriate computational fluid dynamics (CFD) methods using two-dimensional spatial flow approximations. This work is now extended to three-dimensions (3-D) in space. The actuator model is adapted to a series of discrete actuators and a 3-D LES simulation of an excited jet is run. The results are used to study the fluid dynamics near the actuator and in the jet plume.

Brown, Clifford A.

2011-01-01

95

Toward the Design of Multi Asymmetric Surface Dielectric Barrier Discharge (ASDBD) Actuators  

NASA Astrophysics Data System (ADS)

This paper investigates the electrical behaviors of a single-ASDBD actuator and a two- ASDBD one supplied in sinusoidal mode (1-10 kHz). The main objective of our research is to determine the optimum frequency values for functioning of these actuators with a given power supply. For that purpose, we determine the electrical power density transmitted to the actuators versus frequency through two methods: i) a theoretical method, based on an impedance calculation, and ii) an experimental method, based on direct electrical measurements. These methods show that the addition of a second ASDBD changes the resonance frequency value of the actuator by moving it towards the low frequencies.

Zadeh, M.; Rohani, V.; Cauneau, F.; Fabry, F.; Fulcheri, L.

2014-11-01

96

Toward the Design of Multi Asymmetric Surface Dielectric Barrier Discharge (ASDBD) Actuators  

NASA Astrophysics Data System (ADS)

This paper investigates the electrical and mechanical behaviors of a single-ASDBD actuator and a two-ASDBD one supplied in sinusoidal mode (1–10 kHz). The main objective of our research is to determine the optimum frequency values for the function of these actuators with a given power supply. For this purpose, we determine the electrical power density input to the actuators versus frequency through two methods: i) a semi-theoretical method, based on an impedance calculation, and ii) an experimental method, based on direct electrical measurements. These methods show that the addition of a second ASDBD changes the resonance frequency value of the actuator by moving it towards low frequencies. After characterizing the aerodynamic mobile layer structure induced by the single-ASDBD actuator, we analyze experimentally the mechanical response of a two-ASDBD actuator as a function of the inter-ASDBD distance. The experiments demonstrate that the induced electric wind velocity and the electro-mechanical yield of a two-ASDBD actuator reach a maximum value for an optimum inter-ASDBD distance, which is a useful value for the design of highly efficient multi-ASDBD actuators.

Massiel, Zadeh; Rohani, V.; Cauneau, F.; Fabry, F.; Fulcheri, L.

2015-01-01

97

Processing of pollutants in dielectric-barrier plasma reactors  

SciTech Connect

Atmospheric-pressure dielectric barrier electrical discharges (silent discharges) can produce large-volume nonthermal plasmas and energetic electrons which can create substantial concentrations of free radicals. Gas-phase pollutants can be decomposed by these free radicals or by electron-induced dissociation. Basic plasma chemistry, laboratory-scale testing, reactor scale up, example applications, and specific electrical energy requirements for representative compounds are discussed in this paper.

Rosocha, L.A.; Coogan, J.J.

1995-07-01

98

Sterilization of Turmeric by Atmospheric Pressure Dielectric Barrier Discharge Plasma  

NASA Astrophysics Data System (ADS)

In this study atmospheric pressure dielectric barrier discharge (DBD) plasma has been employed for sterilizing dry turmeric powders. A 6 kV, 6 kHz frequency generator was used to generate plasma with Ar, Ar/O2, He, and He/O2 gases between the 5 mm gap of two quartz covered electrodes. The complete sterilization time of samples due to plasma treatment was measured. The most important contaminant of turmeric is bacillus subtilis. The results show that the shortest sterilization time of 15 min is achieved by exposing the samples to Ar/O2 plasma. Survival curves of samples are exponential functions of time and the addition of oxygen to plasma leads to a significant increase of the absolute value of time constant of the curves. Magnitudes of protein and DNA in treated samples were increased to a similar value for all samples. Taste, color, and solubility of samples were not changed after the plasma treatment.

Setareh, Salarieh; Davoud, Dorranian

2013-11-01

99

Two-dimensional plasma photonic crystals in dielectric barrier discharge  

SciTech Connect

A series of two-dimensional plasma photonic crystals have been obtained by filaments' self-organization in atmospheric dielectric barrier discharge with two water electrodes, which undergo the transition from square to square superlattice and finally to the hexagon. The spatio-temporal behaviors of the plasma photonic crystals in nanosecond scale have been studied by optical method, which show that the plasma photonic crystal is actually an integration of different transient sublattices. The photonic band diagrams of the transverse electric (TE) mode and transverse magnetic mode for each sublattice of these plasma photonic crystals have been investigated theoretically. A wide complete band gap is formed in the hexagonal plasma photonic crystal with the TE mode. The changes of the band edge frequencies and the band gap widths in the evolvement of different structures are studied. A kind of tunable plasma photonic crystal which can be controlled both in space and time is suggested.

Fan Weili; Dong Lifang [College of Physics Science and Technology, Hebei University, Baoding 071002 (China); Zhang Xinchun [School of Energy and Power Engineering, North China Electric Power University, Baoding 071003 (China)

2010-11-15

100

Plasma surface modification and hydrophobic barrier coating of paper  

Microsoft Academic Search

Development of new technologies for production of alternative paper properties with minimal environmental hazards was the goal of this project. In this study, the utilization of various chemicals under radio frequency (RF) plasma environments was investigated for creation of hydrophobic barrier properties and deposition of electrically conductive conjugated thin layers on the surface of paper. Four basic approaches have been

Halil Turgut Sahin

2001-01-01

101

Hot Isostatic Pressing of Plasma Sprayed Thermal Barrier Coating Systems  

Microsoft Academic Search

Thermal barrier coatings (TBC) are important to aerospace and high performance gas turbine engines because they help to keep the temperature experienced by the base metal low; thus, prolonging the life span of the material. Plasma spraying is a technique commonly used to deposit the ceramic-based TBC. An intermediate layer is applied to enhance the bond between the substrate and

K. A. Khor; N. L. Loh

1995-01-01

102

Numerical study of boundary layer separation control using magnetogasdynamic plasma actuators  

SciTech Connect

In this study, an efficient, time dependent, two-dimensional Navier-Stokes numerical code for shockwave boundary layer interaction in air is developed. Nonthermal surface plasma actuation is evaluated for effective shockwave induced boundary layer separation control within supersonic inlets. Specifically, high speed magnetogasdynamic plasma actuators are of interest. In these, localized ionization is produced close to the wall surface and then the flow is accelerated using strong magnetic fields. To replicate the experiments done at large boundary layer thickness, the code is divided into time independent and time dependent regimes to significantly reduce computation time. Computational results are in good agreement with experiments in terms of the flow structure as shown by Schlieren imaging, acetone planar laser scattering, and the static pressure profile on the test section wall.

Kalra, Chiranjeev S.; Shneider, Mikhail N.; Miles, Richard B. [Department of Mechanical and Aerospace Engineering, Applied Physics Group, Princeton University, Princeton, New Jersey 08544 (United States)

2009-10-15

103

Effects of plasma spray parameters on two layer thermal barrier  

NASA Technical Reports Server (NTRS)

The power level and the type of arc gas used during plasma spraying of a two layer thermal barrier system (TBS) were found to affect the life of the system. Life at 1095 C in a cyclic furnace test was improved by about 140 percent by increasing the power during plasma spray applications of the bond and thermal barrier coatings. This improvement is due to increases in the densities of the bond and thermal barrier coatings by 3 and 5 percent, respectively. These increases in densities are equivalent to about 45 and 30 percent reduction in mean porosities, respectively. The addition of hydrogen to the argon arc gas had the same effect as the reduction in power level and caused a reduction in TBS life.

Stecura, S.

1981-01-01

104

Characteristics of sheath-driven tangential flow produced by a low-current DC surface glow discharge plasma actuator  

NASA Astrophysics Data System (ADS)

An experimental investigation of low-speed flow actuation at near-atmospheric pressure is presented. The flow actuation is achieved via low-current ( \\lesssim 1.0 mA) continuous or pulsed DC surface glow discharge plasma. The plasma actuator, consisting of two sharp-edged nickel electrodes, produces a tangential flow in a direction from anode to cathode, and is visualized using high-speed schlieren photography. The induced flow velocity estimated via the schlieren images reaches up to 5 m/s in test cases. The actuation capability increases with pressure and electrode gap distances, and the induced flow velocity increases logarithmically with the discharge power. Pulsed DC exhibits slightly improved actuation capability with better directionality. An analytic estimation of induced flow velocity obtained based on ion momentum in the cathode sheath and gas dynamics in one-dimensional flow yields values similar to those measured.

Shin, Jichul; Shajid Rahman, Mohammad

2014-08-01

105

Recent developments in DBD plasma flow control  

NASA Astrophysics Data System (ADS)

Flow control using DBD (dielectric-barrier-discharge) plasma actuators is a relatively new, but rapidly expanding area of research. There are a number of review papers available on this subject, but few discuss on their latest developments. The purpose of the present article is to “fill the gap” by reviewing the recent trend of plasma actuator design and to summarise aerodynamic control techniques. Here, we review new plasma actuators, such as plasma synthetic jet actuators, plasma spark jet actuators, three-dimensional plasma actuators and plasma vortex generators, which can induce three-dimensional flows away from the wall. We also review the starting vortex that leads to formation of a plasma wall jet. This is an important subject not only for a better understanding of the flow induced by DBD plasma actuators, but also as a database that can be used to calibrate the numerical models for plasma flow control. Design of DBD plasma actuators to obtain turbulent skin-friction reduction is shown and the modifications to near-wall turbulence structures are summarised. Novel applications of DBD plasma actuators for aerodynamic control are then discussed, including pitch and roll control, plasma jet vectoring, circulation control and plasma flap, showing a potential of DBD plasma actuators for replacing movable, aircraft control surfaces. Finally, vortex shedding control techniques by a number of different plasma actuators are surveyed.

Wang, Jin-Jun; Choi, Kwing-So; Feng, Li-Hao; Jukes, Timothy N.; Whalley, Richard D.

2013-10-01

106

Numerical Simulations of Flow Separation Control in Low-Pressure Turbines using Plasma Actuators  

NASA Technical Reports Server (NTRS)

A recently introduced phenomenological model to simulate flow control applications using plasma actuators has been further developed and improved in order to expand its use to complicated actuator geometries. The new modeling approach eliminates the requirement of an empirical charge density distribution shape by using the embedded electrode as a source for the charge density. The resulting model is validated against a flat plate experiment with quiescent environment. The modeling approach incorporates the effect of the plasma actuators on the external flow into Navier Stokes computations as a body force vector which is obtained as a product of the net charge density and the electric field. The model solves the Maxwell equation to obtain the electric field due to the applied AC voltage at the electrodes and an additional equation for the charge density distribution representing the plasma density. The new modeling approach solves the charge density equation in the computational domain assuming the embedded electrode as a source therefore automatically generating a charge density distribution on the surface exposed to the flow similar to that observed in the experiments without explicitly specifying an empirical distribution. The model is validated against a flat plate experiment with quiescent environment.

Suzen, Y. B.; Huang, P. G.; Ashpis, D. E.

2007-01-01

107

Shockwave—boundary layer interaction control by plasma aerodynamic actuation: An experimental investigation  

NASA Astrophysics Data System (ADS)

The potential of controlling shockwave—boundary layer interactions (SWBLIs) in air by plasma aerodynamic actuation is demonstrated. Experiments are conducted in a Mach 3 in-draft air tunnel. The separation-inducing shock is generated with a diamond-shaped shockwave generator located on the wall opposite to the surface electrodes, and the flow properties are studied with schlieren imaging and static wall pressure probes. The measurements show that the separation phenomenon is weakened with the plasma aerodynamic actuation, which is observed to have significant control authority over the interaction. The main effect is the displacement of the reflected shock. Perturbations of incident and reflected oblique shocks interacting with the separation bubble in a rectangular cross section supersonic test section are produced by the plasma actuation. This interaction results in a reduction of the separation bubble size, as detected by phase-lock schlieren images. The measured static wall pressure also shows that the separation-inducing shock is restrained. Our results suggest that the boundary layer separation control through heating is the primary control mechanism.

Sun, Quan; Cui, Wei; Li, Ying-Hong; Cheng, Bang-Qin; Jin, Di; Li, Jun

2014-07-01

108

Airflow control by non-thermal plasma actuators  

Microsoft Academic Search

Active flow control is a topic in full expansion due to associated industrial applications of huge importance, particularly for aeronautics. Among all flow control methods, such as the use of mechanical flaps, wall synthetic jets or MEMS, plasma-based devices are very promising. The main advantages of such systems are their robustness, simplicity, low power consumption and ability for real-time control

Eric Moreau

2007-01-01

109

Comparison of plasma treatment and sandblast preprocessing for IPMC actuator  

NASA Astrophysics Data System (ADS)

As a new kind of ionic-driven smart materials, ionic polymer metal composite (IPMC ) is normally fabricated by depositing noble metal (gold, platinum, palladium etc.) on both sides of base membrane (Nafion, Flemion etc.) and shows large bending deflection under low voltage. In the process of fabricating IPMC, surface roughening of base membrane has a significant effect on the performance of IPMC. At present, there are many ways to roughen the base membrane, including physical and chemical ways. In this paper, we analyze the effects of different surface treatment time by plasma etching on surface resistance and mechanical properties of IPMCs fabricated by the treated base membranes. Experimental results show that the base membrane treated by plasma etching displays uniform surface roughness, consequently reducing IPMC's surface resistance effectively and forming more uniform and homogeneous external and penetrative electrodes. However, due to the use of reactive gas, the plasma treatment leads to complex chemical reaction on Nafion surface, changing element composition and material properties and resulting in the performance degradation of IPMC. And sandblast way should be adopted and improved without any changes on element and material structure.

Zhang, Chi; Chen, Hualing; Wang, Yanjie; Wang, Yongquan; Jia, Shuhai

2014-03-01

110

Catalytic synthesis of carbon nanotubes in pulsed barrier discharge plasma  

Microsoft Academic Search

It has been found that it is possible to activate the process of obtaining carbon nanotubes by vapor deposition due to the\\u000a generation in the reaction zone of nonequilibrium plasma by the method of pulsed barrier discharge. It has been shown that\\u000a depending on the catalytic substrate used (nickel wire, stainless steel, porous aluminum oxide with nickel deposited) in the

S. A. Zhdanok; S. V. Gorbatov; A. A. Mikhailov; F. V. Plevako; K. F. Plevako; S. V. Shushkov; V. P. Savenko; A. L. Belanovich; G. L. Shchukin; D. V. Sviridov

2007-01-01

111

Control of supersonic axisymmetric base flows using passive splitter plates and pulsed plasma actuators  

NASA Astrophysics Data System (ADS)

An experimental investigation evaluating the effects of flow control on the near-wake downstream of a blunt-based axisymmetric body in supersonic flow has been conducted. To better understand and control the physical phenomena that govern these massively separated high-speed flows, this research examined both passive and active flow-control methodologies designed to alter the stability characteristics and structure of the near-wake. The passive control investigation consisted of inserting splitter plates into the recirculation region. The active control technique utilized energy deposition from multiple electric-arc plasma discharges placed around the base. The flow-control authority of both methodologies was evaluated with experimental diagnostics including particle image velocimetry, schlieren photography, surface flow visualization, pressure-sensitive paint, and discrete surface pressure measurements. Using a blowdown-type wind tunnel reconstructed specifically for these studies, baseline axisymmetric experiments without control were conducted for a nominal approach Mach number of 2.5. In addition to traditional base pressure measurements, mean velocity and turbulence quantities were acquired using two-component, planar particle image velocimetry. As a result, substantial insight was gained regarding the time-averaged and instantaneous near-wake flow fields. This dataset will supplement the previous benchmark point-wise laser Doppler velocimetry data of Herrin and Dutton (1994) for comparison with new computational predictive techniques. Next, experiments were conducted to study the effects of passive triangular splitter plates placed in the recirculation region behind a blunt-based axisymmetric body. By dividing the near-wake into 1/2, 1/3, and 1/4 cylindrical regions, the time-averaged base pressure distribution, time-series pressure fluctuations, and presumably the stability characteristics were altered. While the spatial base pressure distribution was influenced considerably, the area-integrated pressure was only slightly affected. Normalized RMS levels indicate that base pressure fluctuations were significantly reduced with the addition of the splitter plates. Power-spectral-density estimates revealed a spectral broadening of fluctuating energy for the 1/2 cylinder configuration and a bimodal distribution for the 1/3 and 1/4 cylinder configurations. It was concluded that the recirculation region is not the most sensitive location to apply flow control; rather, the shear layer may be a more influential site for implementing flow control methodologies. For active flow control, pulsed plasma-driven fluidic actuators were investigated. Initially, the performance of two plasma actuator designs was characterized to determine their potential as supersonic flow control devices. For the first actuator considered, the pulsed plasma jet, electro-thermal heating from an electric discharge heats and pressurizes gas in a small cavity which is exhausted through a circular orifice forming a synthetic jet. Depending on the electrical energy addition, peak jet velocities ranged between 130 to nearly 500 m/s when exhausted to quiescent, ambient conditions. The second plasma actuator investigated is the localized arc filament plasma actuator (LAFPA), which created fluidic perturbations through the rapid, local thermal heating, generated from an electric arc discharge between two electrodes within a shallow open cavity. Electrical and emission properties of the LAFPA were first documented as a function of pressure in a quiescent, no-flow environment. Rotational and vibrational temperatures from N2 spectra were obtained for select plasma conditions and ambient pressures. Results further validate that the assumption of optically thin conditions for these electric arc plasmas is not necessary valid, even at low ambient pressure. Breakdown voltage, sustained plasma voltage, power, and energy per pulse were demonstrated to decrease with decreasing pressure. Implementing an array of eight electric arcs circumferentially around the base nea

Reedy, Todd Mitchell

112

Temporal modulation of plasma species in atmospheric dielectric barrier discharges  

SciTech Connect

The atmospheric pressure dielectric barrier discharge in helium is a pulsed discharge in nature and the moment of maximum species densities is almost consistent with peak discharge current density. In this paper, a one-dimensional fluid model is used to investigate the temporal structure of plasma species in an atmospheric He-N{sub 2} dielectric barrier discharge (DBD). It is demonstrated that there exist microsecond delays of the moments of the maximum electron and ion densities from the peak of discharge current density. These time delays are caused by a competition between the electron impact and Penning ionizations, modulated by the N{sub 2} level in the plasma-forming gas. Besides, significant electron wall losses lead to the DBD being more positively charged and, with a distinct temporal separation in the peak electron and cation densities, the plasma is characterized with repetitive bursts of net positive charges. The temporal details of ionic and reactive plasma species may provide a new idea for some biological processes.

Yang, Aijun; Wang, Xiaohua, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn; Liu, Dingxin; Rong, Mingzhe, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn [Centre for Plasma Biomedicine, State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049 (China); Kong, Michael G. [Centre for Plasma Biomedicine, State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049 (China); Frank Reidy Research Center for Bioelectrics, Department of Electrical and Computer Engineering, Old Dominion University, Virginia 23508 (United States); Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States)

2014-07-15

113

Vacuum 65 (2002) 415425 Plasma spraying of micro-composite thermal barrier coatings  

E-print Network

Vacuum 65 (2002) 415­425 Plasma spraying of micro-composite thermal barrier coatings S. Sharafata. Keywords: Plasma spraying; Gas tunnel-type; Thermal barrier-composite coatings; Aluminum oxide; Zirconium, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan Abstract The thermal barrier coatings

Ghoniem, Nasr M.

114

Modeling of plasma remediation of VOCs in dielectric barrier discharges  

SciTech Connect

Since each year significant quantities of toxic wastes containing volatile organic compounds (VOCs) are produced by chemical and allied industries, destruction of these VOCs has become a major environmental concerns. Dielectric barrier discharges (DBDs) are promising low cost plasma sources for destruction of the VOCs. The efficient of plasma remediation depends on gas mixture, the dielectric constant and format of the voltage pulse. The authors have developed 1-d and 2-d plasma chemistry and hydrodynamic models to focus on the energy efficiency and optimum conditions for destruction of chlorinated hydrocarbons including CCI{sub 4} and CHCI{sub 3} which are widely used as industrial solvents. The plasma remediation model consists of circuit models, solution of Boltzmann`s equation for the electron energy distribution, plasma chemistry modules, and solution of the compressible Navier Stokes equations. CCI{sub 4} and CHCI{sub 3} can be initially destroyed by dissociative-electron-attachment which requires different discharge conditions than for generation of radicals for chemical remediation. These different operating regions are discussed. The authors present a detailed description of the major plasma chemical pathways and discuss the effects of varying parameters, such as applied voltage, dielectric constant, gas mixture content in the gas stream, and temperature on the amount and energy efficiency of remediation.

Xu, X.; Kushner, M.J. [Univ. of Illinois, Urbana, IL (United States). Dept. of Electrical and Computer Engineering

1997-12-31

115

Nonintrusive microwave diagnostics of collisional plasmas in Hall thrusters and dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

This research presents a numerical framework for diagnosing electron properties in collisional plasmas. Microwave diagnostics achieved a significant level of development during the middle part of the last century due to work in nuclear weapons and fusion plasma research. With the growing use of plasma-based devices in fields as diverse as space propulsion, materials processing and fluid flow control, there is a need for improved, flexible diagnostic techniques suitable for use under the practical constraints imposed by plasma fields generated in a wide variety of aerospace devices. Much of the current diagnostic methodology in the engineering literature is based on analytical diagnostic, or forward, models. The Appleton-Hartree formula is an oft-used analytical relation for the refractive index of a cold, collisional plasma. Most of the assumptions underlying the model are applicable to diagnostics for plasma fields such as those found in Hall Thrusters and dielectric barrier discharge (DBD) plasma actuators. Among the assumptions is uniform material properties, this assumption is relaxed in the present research by introducing a flexible, numerical model of diagnostic wave propagation that can capture the effects of spatial gradients in the plasma state. The numerical approach is chosen for its flexibility in handling future extensions such as multiple spatial dimensions to account for scattering effects when the spatial extent of the plasma is small relative to the probing beam's width, and velocity dependent collision frequency for situations where the constant collision frequency assumption is not justified. The numerical wave propagation model (forward model) is incorporated into a general tomographic reconstruction framework that enables the combination of multiple interferometry measurements. The combined measurements provide a quantitative picture of the spatial variation in the plasma properties. The benefit of combining multiple measurements in a coherent way (solving the inverse problem for the material properties) is the reconstruction provides a stronger empirical constraint on the predictions of high-fidelity predictive simulations than multiple un-reconstructed measurements in isolation. Use of the model for reconstructions informs the choice of numerical discretization technique. The model must be fast, low-storage and accurate to be useful for computing reconstructions. An important part of experimental work is error analysis, or uncertainty quantification. This becomes more difficult as sophistication of the measurement models increase. This research presents an uncertainty quantification technique based on complex-step sensitivity derivatives that is particularly well-suited for error propagation in sophisticated partial differential equation (PDE)-based measurement models, because it requires only trivial changes to the PDE solver to implement.

Stults, Joshua

116

Effect of Dielectric and Liquid on Plasma Sterilization Using Dielectric Barrier Discharge Plasma  

E-print Network

sterilization methods. Using a relatively small, low temperature, atmospheric, dielectric barrier discharge of liquid on the dielectric surface. Of the two dielectric substrates tested (FR4 and semi-ceramic (SC. Natural and fabricated plasmas occur over a wide range of pressures, temperatures and electron number

Roy, Subrata

117

Experimental study and optimization of Plasma Actuators for Flow control in subsonic regime  

NASA Astrophysics Data System (ADS)

The induced jet produced by a dielectric barrier discharge (DBD) setup is capable of preventing flow separation on airfoils at high angles of attack. The effect of various parameters on the velocity of this induced jet was studied experimentally. The glow discharge was created at atmospheric conditions by using a high voltage RF power supply. Flow visualization, photographic studies of the plasma, and hot-wire measurements on the induced jet were performed. The parametric investigation of the characteristics of the plasma show that the width of the plasma in the uniform glow discharge regime was an indication of the velocity induced. It was observed that the spanwise and streamwise overlap of the two electrodes, dielectric thickness, voltage and frequency of the applied voltage are the major parameters that govern the velocity and the extent of plasma. The effect of the optimized configuration on the performance characteristics of an airfoil was studied experimentally.

Moise, Pradeep; Mathew, Joseph; Venkatraman, Kartik; Thomas, Joy

2010-11-01

118

Plasma and ion barrier for electron beam spot stability  

SciTech Connect

The concept of a self-biased target to spatially confine the ions generated by the bombardment of intense electron beams on bremsstrahlung conversion targets has been predicted by computer simulation and further verified by experiments at the Integrated Test Stand for DARHT at Los Alamos National Laboratory. This technical article reports an alternative method of containing the plasmas and ions from the bremsstrahlung conversion target if the energy density of the electron beam is below a certain threshold. With the proposed changes of the electron beam parameters of the second axis of DARHT, the authors are able to show that a thin (0.5 mm) metallic barrier such as pure beryllium, or boron carbide with desirable thermal properties, is sufficiently transparent to the 20 MeV DARHT beam and at the same time able to confine the ions between the target and the barrier foil. The temperature rise in the foil due to energy deposited by the electron beam is expected to be below the melting point of the materials for the first three pulses. More important, they have shown in their time dependent particle-in-cell simulations that the deployment of a barrier situated 1 to 2 cm away from the converter target can achieve the ion confinement needed for the stability of the electron beam spot.

Kwan, T.J.T.; Snell, C.M.

1999-04-01

119

Coherent structures in plasma-actuator controlled supersonic jets: Axisymmetric and mixed azimuthal modes  

NASA Astrophysics Data System (ADS)

High-fidelity simulations are employed to study the effect of eight localized arc filament plasma actuators placed around the periphery of a Mach 1.3 converging-diverging nozzle exit. Emphasis is placed on understanding the coherent structures generated by axisymmetric (m = 0), flapping or first mixed (m = ±1) and second mixed (m = ±2) modes, which are excited at the jet column-mode frequency corresponding to a Strouhal number based on jet diameter of 0.3. Baseline (no control) and constant excitation (actuators on continuously) cases are also simulated. Comparisons with experimental results indicate that the computational model reproduces the main features induced by the actuators. Furthermore, the mean flow exhibits many similarities with the theoretical predictions of Cohen and Wygnanski [J. Fluid Mech. 176, 221 (1987)]. Overall, the results indicate a complex coherent structure generation, evolution, and disintegration process. For m = ±1, the phase-averaged flow reveals successive distorted elliptic vortex rings with axes in the flapping plane but alternating on either side of the jet axis. This generates a chain of structures each of which interacts with its predecessor on one side of the major plane and its successor on the other. Through self and mutual induction, the leading segment of each loop is pinched and passes through the previous ring before rapidly breaking up. The m = ±2 mode yields elliptic structures with major axes of successive rings being aligned with the two symmetry planes, which are orthogonal to each other. The minor axis side is pulled downstream faster than the rest of the structure because of the higher velocity near the jet centerline and self-induced effects, yielding a horse-shoe shape when viewed in profile. The m = 0 mode exhibits axisymmetric roll-up events, with vortex ribs in the braid regions connecting successive large coherent structures. The constant excitation (with largest energy input) and baseline cases are similar to each other, indicating that the direct effect of heating is negligible.

Gaitonde, D. V.; Samimy, M.

2011-09-01

120

44th AIAA Aerospace Sciences Meeting and Exhibit, Jan. 912, 2006, Reno, NV On Plasma Synthetic Jet Actuators  

E-print Network

44th AIAA Aerospace Sciences Meeting and Exhibit, Jan. 9­12, 2006, Reno, NV On Plasma Synthetic Jet (typ- ically rectangular strips) separated by dielectric material that can be used as active flow jet actuator (PSJA), is experimentally investigated in this paper. This particular geometry creates

Jacob, Jamey

121

Control of a high Reynolds number Mach 0.9 heated jet using plasma actuators  

SciTech Connect

The results of particle image velocimetry (PIV) measurements in a high subsonic, heated, jet forced using localized arc filament plasma actuators (LAFPAs) show that LAFPAs can consistently produce significant mixing enhancement over a wide range of temperatures. These actuators have been used successfully in high Reynolds number, high-speed unheated jets. The facility consists of an axisymmetric jet with different nozzle blocks of exit diameter of 2.54 cm and variable jet temperature in an anechoic chamber. The focus of this paper is on a high subsonic (M{sub j}=0.9) jet. Twelve experiments with various forcing azimuthal modes (m=0, 1, and {+-}1) and temperatures (T{sub o}/T{sub a}=1.0, 1.4, and 2.0) at a fixed forcing Strouhal number (St{sub DF}=0.3) have been conducted and PIV results compared with the baseline results to characterize the effectiveness of LAFPAs for mixing enhancement. Centerline velocity and turbulent kinetic energy as well as jet width are used for determining the LAFPAs' effectiveness. The characteristics of large-scale structures are analyzed through the use of Galilean streamlines and swirling strength. Across the range of temperatures collected, the effectiveness of LAFPAs improves as temperature increases. Possible reasons for the increase in effectiveness are discussed.

Kearney-Fischer, M.; Kim, J.-H.; Samimy, M. [Department of Mechanical Engineering, Gas Dynamics and Turbulence Laboratory, Ohio State University (GDTL/OSU), 2300 West Case Road, Columbus, Ohio 43235-7531 (United States)

2009-09-15

122

MERCURY OXIDIZATION IN NON-THERMAL PLASMA BARRIER DISCHARGE SYSTEM  

SciTech Connect

In the past decade, the emission of toxic elements from human activities has become a matter of great public concern. Hg, As, Se and Cd typically volatilize during a combustion process and are not easily caught with conventional air pollution control techniques. In addition, there is no pollution prevention technique available now or likely be available in the foreseeable future that can prevent the emission of these trace elements. These trace elements pose additional scientific challenge as they are present at only ppb levels in large gas streams. Mercury, in particular, has attracted significant attention due to its high volatility, toxicity and potential threat to human health. In the present research work, a non-thermal plasma dielectric barrier discharge technique has been used to oxidize Hg{sup 0}(g) to HgO. The basic premise of this approach is that Hg{sup 0} in vapor form cannot be easily removed in an absorption tower whereas HgO as a particulate is amiable to water scrubbing. The work presented in this report consists of three steps: (1) setting-up of an experimental apparatus to generate mercury vapors at a constant rate and modifying the existing non-thermal plasma reactor system, (2) solving the analytical challenge for measuring mercury vapor concentration at ppb level, and (3) conducting experiments on mercury oxidation under plasma conditions to establish proof of concept.

V.K. Mathur

2003-02-01

123

On the Vortex Dynamic of Airflow Reattachment Forced by a Single Non-thermal Plasma Discharge Actuator  

Microsoft Academic Search

Commercial and military aircrafts or miniature aerial vehicles can suffer from massive flow separation when high angles of\\u000a attack are required. Single dielectric barrier discharge (DBD) actuators have demonstrated their capability of controlling\\u000a such a separated flow at low external velocity. However, the processes resulting in the improvement of the flight performances\\u000a remain unclear. In the present study, the reattachment

Nicolas Benard; Eric Moreau

2011-01-01

124

AC Barrier Low-Frequency Plasma Source for Air Purifying System  

NASA Astrophysics Data System (ADS)

We have developed AC barrier low-frequency plasma source using AC (15kV, 60Hz) sources. Barrier material, such as rubber stabilizing the discharge plasma, is inserted between the electrodes. Large volume corona discharge was carried out at atmospheric pressure. Properties of AC barrier discharge will be presented. We investigated characteristics of treating acetaldehyde (CH3CHO), ammonia (NH4) and toluene (C6H5CH3) in a circulation test using AC barrier plasma generated beside catalyst filter. Purpose of this work is development of an efficient air purifying system. Our experiment was carried out to remove acetaldehyde and ammonia in tobacco smoke and toluene in air.

Kang Jung, G.; Lee Han, Y.; Uhm Han, S.; Yeom Bong, Y.; Park Jong, H.

2003-10-01

125

Distributed forcing flow control in the wake of a blunt trailing edge profiled body using plasma actuators  

NASA Astrophysics Data System (ADS)

A modern flow control technique for reducing the drag associated with the periodic shedding of von Kármán vortices in the wake of a blunt trailing edge profiled body is presented. The technique involves distributed forcing of the wake flow using an array of dielectric barrier discharge plasma actuators, with a spanwise spacing matched to the spanwise wavelength of the dominant secondary wake instability. The experiments include measurement of the velocity field in multiple vertical and horizontal planes in the wake using particle image velocimetry, as well as base pressure, at Reynolds numbers of 2000, 3000, and 5000 based on trailing edge thickness. The flow control technique causes elongation of the vortex formation region across the span, and significant reduction of the fluctuating and total drag forces, up to a maximum of 94% and 18%, respectively. The effectiveness of the flow control technique is shown to be dependent on the induced momentum coefficient. Proper orthogonal decomposition analysis is used to investigate the mechanism of interaction of the flow control technique with the wake flow. Two distinct flow regimes are observed depending on the induced momentum coefficient. The effect of the control on the wake flow structure in the first regime is similar to those observed in previous studies involving mild spanwise-periodic geometric perturbations at the trailing edge, where control leads to streamwise displacement of the vortices and a shift in shedding frequency. However, an incremental increase in the momentum coefficient leads to a second flow regime similar to those previously observed in the case of large-amplitude geometric perturbations, with an almost complete attenuation of vortex shedding in the near-wake region.

Naghib-Lahouti, A.; Hangan, H.; Lavoie, P.

2015-03-01

126

Failure analysis of plasma-sprayed thermal barrier coatings  

NASA Technical Reports Server (NTRS)

Thermally induced failure processes of plasma-sprayed thermal barrier coatings are examined. Cracking processes give rise to noise which was monitored by acoustic emission (AE) techniques. The sequential failure of coatings was examined from samples which were thermally cycled. Coatings of yttria-stabilized zirconia with and without a NiCrAlZr bond coat were plasma-sprayed onto U700 alloy rod. In some cases the substrate was intentionally overheated during deposition of the thermal protection system to check how this process variable influenced the AE response of the specimen. In this way a qualitative appraisal of how process variables affect coating integrity could be discerned in terms of cracking behavior. Results from up to seven consecutive thermal cycles are reported here. Coating failure was observed in all cases. Failure of the thermal protection system is progressive, since cracking and crack growth were observed prior to ultimate failure. Thus castastrophic failure occurs at some stage when there is a transformation from the microcrack to a macrocrack network.

Berndt, C. C.; Miller, R. A.

1984-01-01

127

Core Internal Transport Barriers in Alcator C-Mod Plasmas  

NASA Astrophysics Data System (ADS)

Formation of internal transport barriers (ITB's) has been observed frequently in the core region of Alcator C-MOD. Short lived ITB's form spontaneously following the H- to L-mode transition (Enhanced Neutron Mode). They are also induced by lithium pellet injection into ohmic and RF heated discharges (PEP mode) and in some cases by off-axis ICRF heating. The H- to L-mode transition on Alcator C-Mod is typically followed by a strong increase in the global neutron rate, up to a factor of 8 with up to a 50% increase in central ion temperature. As the transition proceeds, the electron density collapses in the outer third of the plasma, causing the electron density to be strongly peaked in the center. The steepening of the density profile results in a local decrease of the ratio of electron temperature scale length to electron density scale length (?_e) in the region 0.3 < r/a < 0.5, from a value of 5 down to between 1 and 2. Impurity accumulation in the plasma center occurs at the same time. The spontaneous ITB's occur following both RF and Ohmic H-modes, and typically last for less than 3 sawtooth cycles, about 40 ms. Slowing or stabilizing sawteeth appears to extend their lifetime. The ITB/PEP mode appears to be very similar to the ITB/EN phenomena, in that the density profiles are quite peaked, the neutron rate and ion temperature increase markedly, and impurities accumulate in the plasma center. In contrast, the central density and stored energy increase substantially with ITB/PEP while for ITB/EN the central density is unchanged and the total stored energy decreases. The sawtooth activity stops during ITB/PEP as the current profile at the center becomes hollow, while it continues unperturbed for nearly all ITB/EN occurrences. Comparison of these two modes presents a unique opportunity to explore core ITB formation and physics.

Fiore, C. L.

2000-10-01

128

Efficiency of plasma actuator ionization in shock wave modification in a rarefied supersonic flow over a flat plate  

NASA Astrophysics Data System (ADS)

This paper describes experimental and numerical investigations focused on the shock wave modification, induced by a dc glow discharge, of a Mach 2 flow under rarefied regime. The model under investigation is a flat plate equipped with a plasma actuator composed of two electrodes. The glow discharge is generated by applying a negative potential to the upstream electrode, enabling the creation of a weakly ionized plasma. The natural flow (i.e. without the plasma) exhibits a thick laminar boundary layer and a shock wave with a hyperbolic shape. Images of the flow obtained with an ICCD camera revealed that the plasma discharge induces an increase in the shock wave angle. Thermal effects (volumetric, and at the surface) and plasma effects (ionization, and thermal non-equilibrium) are the most relevant processes explaining the observed modifications. The effect induced by the heating of the flat plate surface is studied experimentally by replacing the upstream electrode by a heating element, and numerically by modifying the thermal boundary condition of the model surface. The results show that for a similar temperature distribution over the plate surface, modifications induced by the heating element are lower than those produced by the plasma. This difference shows that other effects than purely thermal effects are involved with the plasma actuator. Measurements of the electron density with a Langmuir probe highlight the fact that the ionization degree plays an important role into the modification of the flow. The gas properties, especially the isentropic exponent, are indeed modified by the plasma above the actuator and upstream the flat plate. This leads to a local modification of the flow conditions, inducing an increase in the shock wave angle.

Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis

2014-12-01

129

IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 35, NO. 3, JUNE 2007 693 Atmospheric Plasma Actuators for  

E-print Network

. The corresponding results were discussed in this paper. Index Terms--Aeroacoustics, atmospheric pressure glow dis- charges, flow control. I. INTRODUCTION PLASMA, operating in atmospheric pressure air conditions, holds] demonstrated the use of atmospheric pressure air glow discharges [2] for attenuating the tonal noise

Huang, Xun

130

Effect of dielectric and liquid on plasma sterilization using dielectric barrier discharge plasma.  

PubMed

Plasma sterilization offers a faster, less toxic and versatile alternative to conventional sterilization methods. Using a relatively small, low temperature, atmospheric, dielectric barrier discharge surface plasma generator, we achieved ? 6 log reduction in concentration of vegetative bacterial and yeast cells within 4 minutes and ? 6 log reduction of Geobacillus stearothermophilus spores within 20 minutes. Plasma sterilization is influenced by a wide variety of factors. Two factors studied in this particular paper are the effect of using different dielectric substrates and the significance of the amount of liquid on the dielectric surface. Of the two dielectric substrates tested (FR4 and semi-ceramic (SC)), it is noted that the FR4 is more efficient in terms of time taken for complete inactivation. FR4 is more efficient at generating plasma as shown by the intensity of spectral peaks, amount of ozone generated, the power used and the speed of killing vegetative cells. The surface temperature during plasma generation is also higher in the case of FR4. An inoculated FR4 or SC device produces less ozone than the respective clean devices. Temperature studies show that the surface temperatures reached during plasma generation are in the range of 30°C-66 °C (for FR4) and 20 °C-49 °C (for SC). Surface temperatures during plasma generation of inoculated devices are lower than the corresponding temperatures of clean devices. pH studies indicate a slight reduction in pH value due to plasma generation, which implies that while temperature and acidification may play a minor role in DBD plasma sterilization, the presence of the liquid on the dielectric surface hampers sterilization and as the liquid evaporates, sterilization improves. PMID:23951023

Mastanaiah, Navya; Johnson, Judith A; Roy, Subrata

2013-01-01

131

Research on Surface Modification of Polytetrafluoroethylene Coupled With Argon Dielectric Barrier Discharge Plasma Jet Characteristics  

Microsoft Academic Search

An argon dielectric barrier discharge (DBD) atmospheric-pressure plasma jet (APPJ) is designed and employed for surface modification of polytetrafluoroethylene (PTFE). The plasma diagnostics and dielectric surface analysis are coupled together to investigate the mechanisms of plasma modification. The discharge power is obtained by Lissajous figure, and electron excitation temperature (EET) is measured through an optical emission spectrum and calculated by

Xian-Jun Shao; Guan-Jun Zhang; Jiang-Yang Zhan; Gui-Min Xu

2011-01-01

132

Efficiency enhancement of a dielectric barrier plasma discharge by dielectric barrier optimization  

SciTech Connect

The characteristic feature of a dielectric barrier discharge (DBD) is the dielectric barrier placed between the electrodes. In the present work, the influence of the dielectric barrier to the properties of a DBD in air was investigated. Spectroscopic characterization of the DBD and electrical measurements were carried out. It was shown that the efficiency of a DBD can be considerably improved by optimizing the dielectric barrier. The dielectric material should possess an appropriate relative permittivity and thickness. For thin dielectric barriers, a high secondary emission coefficient becomes important. Additionally, the use of only one dielectric barrier is advantageous.

Meiners, Annette; Leck, Michael [Department of Science and Technology, University of Applied Science and Arts, Von-Ossietzky-Str. 99, 37085 Goettingen (Germany); Abel, Bernd [Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, University Leipzig, Linnestr. 2, 04103 Leipzig (Germany)

2010-11-15

133

Transient transport barriers in ohmic and electron cyclotron heated RTP plasmas: relation with rational magnetic surfaces  

NASA Astrophysics Data System (ADS)

Oblique pellet injection experiments have been performed in RTP ohmic and electron cyclotron (EC) heated plasmas. Peripheral cooling induces a transient rise of the electron temperature (Te) in the plasma core, with the formation of a region of a high Te gradient (transient transport barrier). The position of the barrier appears to be linked with the location of low-order rational magnetic surfaces. For Ohmic and EC heated plasmas with resonance moderately off-axis, the Te rise is peaked in the plasma centre and the footpoint of the barrier is located close to the q = 2 surface. For EC plasmas with far off-axis resonance, i.e. in plasmas exhibiting hollow Te profiles, the Te rise starts off-axis, near the innermost low order rational surface (typically q = 3). It then propagates to the centre in a seemingly diffusive way.

Gorini, G.; Mantica, P.; Hogeweij, G. M. D.; de Kloe, J.; Lopes Cardozo, N. J.; RTP Team

2000-05-01

134

Plasma Surface Modification of Polymer Backsheets: Origins of Future Interfacial Barrier/Backsheet Failure  

SciTech Connect

Flexible polymer substrates coated with inorganic oxide moisture barriers are a potential replacement for glass backsheets in thin film PV modules. Silicon oxynitride (SiOxNy) deposited by PECVD on polyethylene terephthalate (PET) represents one potential new backsheet candidate. Barrier deposition runs at NREL have typically included a nitrogen-rich plasma pretreatment prior to actual barrier deposition with the intention of cleaning the PET surface as well as enhancing adhesion of the SiOxNy barrier film to PET; however, test coupons of PET/barrier/EVA/TPE failed after damp heat exposure. PET substrates exposed to plasma conditions similar to those used in pre-treatment were examined by X-ray photoelectron spectroscopy (XPS) to reveal new low molecular weight PET fragments are created which are volatile upon heating and water soluble. Failure analysis of the coupons determined that the moisture barrier is, in fact, transferred to the encapsulant side.

Pankow, J. W.; Glick, S. H.

2005-11-01

135

Gas-confined barrier discharges: a simplified model for plasma dynamics in flame environments  

E-print Network

In this paper we evaluate the dynamics of non-thermal plasmas developing in extremely non-homogeneous environments. We present the gas-confined barrier discharge (GBD) concept and justify its importance as a first step to ...

Guerra-Garcia, Carmen

136

In-situ formation of multiphase air plasma sprayed barrier coatings for turbine components  

DOEpatents

A turbine component (10), such as a turbine blade, is provided which is made of a metal alloy (22) and a base, planar-grained thermal barrier layer (28) applied by air plasma spraying on the alloy surface, where a heat resistant ceramic oxide overlay material (32') covers the bottom thermal barrier coating (28), and the overlay material is the reaction product of the precursor ceramic oxide overlay material (32) and the base thermal barrier coating material (28).

Subramanian, Ramesh (Oviedo, FL)

2001-01-01

137

Fatigue testing of plasma-sprayed thermal barrier coatings, Volume 2. Final report  

SciTech Connect

A plasma sprayed thermal barrier coating for diesel engines were fatigue tested. Candidate thermal barrier coating materials were fatigue screened and a data base was generated for the selected candidate material. Specimen configurations are given for the bend fatigue tests, along with test setup, specimen preparation, test matrix and procedure, and data analysis.

Cruse, T.A.; Nagy, A.; Popelar, C.F.

1990-07-01

138

Fatigue testing of plasma-sprayed thermal barrier coatings, Volume 2. Final report  

Microsoft Academic Search

A plasma sprayed thermal barrier coating for diesel engines were fatigue tested. Candidate thermal barrier coating materials were fatigue screened and a data base was generated for the selected candidate material. Specimen configurations are given for the bend fatigue tests, along with test setup, specimen preparation, test matrix and procedure, and data analysis.

T. A. Cruse; A. Nagy; C. F. Popelar

1990-01-01

139

Fatigue testing of plasma-sprayed thermal barrier coatings, volume 2  

NASA Technical Reports Server (NTRS)

A plasma sprayed thermal barrier coating for diesel engines were fatigue tested. Candidate thermal barrier coating materials were fatigue screened and a data base was generated for the selected candidate material. Specimen configurations are given for the bend fatigue tests, along with test setup, specimen preparation, test matrix and procedure, and data analysis.

Cruse, T. A.; Nagy, A.; Popelar, C. F.

1990-01-01

140

Laser drilling of cooling holes through plasma sprayed thermal barrier coatings  

Microsoft Academic Search

Laser drilling is a non-contact process that can be used to form small holes in a wide variety of materials with a high degree of precision and reproducibility. The advantages of being able to drill difficult materials, specifically superalloys and ceramics, are exploited in the laser drilling of cooling holes in thermal barrier coated superalloys. Plasma sprayed thermal barrier coatings

K. T. Voisey; T. W. Clyne

2004-01-01

141

Plasma diagnostic techniques in thermal-barrier tandem-mirror fusion experiments  

SciTech Connect

We review two classes of plasma diagnostic techniques used in thermal-barrier tandem-mirror fusion experiments. The emphasis of the first class is to study mirror-trapped electrons at the thermal-barrier location. The focus of the second class is to measure the spatial and temporal behavior of the plasma space potential at various axial locations. The design and operation of the instruments in these two categories are discussed and data that are representative of their performance is presented.

Silver, E.H.; Clauser, J.F.; Carter, M.R.; Failor, B.H.; Foote, J.H.; Hornady, R.S.; James, R.A.; Lasnier, C.J.; Perkins, D.E.

1986-08-29

142

Failure modes of plasma-sprayed thermal barrier coatings  

NASA Astrophysics Data System (ADS)

Conventional plasma-sprayed thermal barrier coatings (TBCs) are known to fail by spallation of the yttria-stabilized zirconia (YSZ) topcoat exposing the underlying metal to high temperatures. Failure takes place by crack propagation in the YSZ just above the YSZ/thermally grown oxide (TGO) interface. Compressive stress in the TGO due to thermal expansion coefficient mismatch and oxidation is believed to play a key role in the failure. However, non-destructive measurement of the compressive stress in the TGO has been challenging due to the overlying ceramic top layer. In this study, TBC samples coated to current industrial specifications were thermally cycled to various fractions of their life to determine the failure mechanisms. The technique of Cr3+ piezospectroscopy was successfully applied to the plasma-sprayed samples for the first time in an effort to measure compressive stress in the TGO through the ceramic top layer. In addition, a new nano-grained plasma-sprayed TBC was studied in order to develop a next generation TBC with enhanced properties. Results from observations on cross-sections and spalled surfaces have identified two competing failure mechanisms for TBCs: (1) cracking along asperity tips at the TGO/bond coat interface, and (2) cracking in the ceramic between the asperity tips. TGO residual compressive stress was found to increase in the first 1 to 10 cycles and then decrease with increasing number of cycles. The standard deviation of the stress measurement, which is a measure of damage accumulation in the TGO layer, was found to increase at higher numbers of cycles. Measurement of compressive stress in the TGO using Cr3+ piezo-spectroscopy was limited to YSZ thicknesses of <50 mum due to an impurity present in the YSZ layer. When no impurity was present the limiting thickness was <170 mum due to scattering by microstructural defects such as solute, porosity, and most importantly splat boundaries. A new nano-grained TBC was fabricated with a resulting microstructure that contained no splat boundaries or microcracking. The coating had a high porosity, 22 vol%, and strain relieving vertical microcracks. When compared to conventional plasma-sprayed TBCs, the nano-grained TBCs have a similar cyclic lifetime and failure mechanism but a lower compressive stress in the TGO. Since thermal conductivity is a key physical property of interest in TBCs, a fundamental study was performed to understand the effects of grain boundaries and porosity on the thermal conductivity of YSZ. To that end, monolithic YSZ samples were manufactured using the fugitive sphere method to create tailored porosity utilizing polymer spheres. The grain boundaries were found to have little effect on the thermal conductivity while the porosity was found to have a small effect in the size range studied (5mum--15mum).

Schlichting, Kevin Walter

143

Examining the Role of Ozone in Surface Plasma Sterilization Using Dielectric Barrier  

E-print Network

Examining the Role of Ozone in Surface Plasma Sterilization Using Dielectric Barrier Discharge (DBD (DBD) devices are known ozone generators. Authors have previously demonstrated a DBD surface plasma and sterilization in 20 min (bacterial spores). The aim of this paper is to examine the role of the ozone in surface

Roy, Subrata

144

Plasma Surface Modification of Polymer Backsheets: Origins of Future Interfacial Barrier/Backsheet Failure (Poster)  

SciTech Connect

Flexible polymer substrates coated with inorganic oxide moisture barriers are a potential replacement for glass backsheets in thin-film PV (photovoltaic) modules. Silicon oxynitride (SiO{sub x}N{sub y}) deposited by plasma enhanced chemical vapor deposition (PECVD) on polyethylene terephthalate (PET) represents one potential new backsheet candidate. Barrier deposition runs at NREL have included a nitrogen-rich plasma pretreatment prior to barrier deposition with the intention of cleaning the PET surface and enhancing adhesion of the SiO{sub x}N{sub y} barrier film to PET; however, test coupons of PET/barrier/EVA/TPE failed after damp-heat exposure. (EVA is ethylene vinyl acetate and TPE is Tedlar{reg_sign}-PET-EVA). PET substrates exposed to plasma conditions similar to those used in pretreatment were examined by X-ray photoelectron spectroscopy (XPS) to reveal that new low molecular weight PET fragments were created at the PET surface. These fragments are responsible for barrier/PET interfacial failure and barrier transfer to the EVA encapsulant side following damp heat exposure.

Pankow, J. W.; Glick, S. H.

2006-05-01

145

Enhanced Design of Turbo-jet LPT by Separation Control Using Phased Plasma Actuators  

NASA Technical Reports Server (NTRS)

This work deals with the documentation and control of flow separation that occurs over turbine blades in the low-pressure turbine stage at low Reynolds numbers that exist at high altitude cruise. We utilize a specially constructed linear cascade that is designed to study the flow field over a generic LPT cascade consisting of Pratt & Whitney 'Pak B' shaped blades. This facility was constructed under a previous one-year NASA Glenn RC initiative. The center blade in the cascade is instrumented to measure the surface pressure coefficient distribution. Optical access allows two-component LDV measurement for boundary layer profiles. Experimental conditions have been chosen to give a range of chord Reynolds numbers from 10 to 100K, and a range of free-stream turbulence levels from u'/U(sub infinity)= 0.08 to 3 percent. The surface pressure measurements were used to define a region of separation and reattachment that depend on the free-stream conditions. The location of separation was found to be relatively insensitive to the experimental conditions. However, reattachment location was very sensitive to the turbulence level and Reynolds number. Excellent agreement was found between the measured pressure distributions and predictions from Euler and RANS simulations. Two-component LDV measurements are presently underway to document the mean and fluctuating velocity components in the boundary layer over the center blade for the range of experimental conditions. The fabrication of the plasma actuator is underway. These are designed to produce either streamwise vortices, or a downstream-directed wall jet. A precursor experiment for the former approach was performed with an array of vortex generators placed just upstream of the separation line. These led to reattachment except for the lowest Reynolds number. Progress has also been made on the proposed concept for a laterally moving wake. This involved constructing a smaller wind tunnel and molding an array of symmetric airfoils to form an array. Following its development, it will be scaled up and used to introduce lateral moving wakes upstream up the Pak-B cascade.

Ashpis, David (Technical Monitor); Corke, Thomas C.; Thomas, Flint O.

2003-01-01

146

INTERNAL TRANSPORT BARRIER AND ? LIMIT IN OHMICALLY HEATED PLASMA IN TUMAN-3M  

Microsoft Academic Search

An Internal Transport Barrier (ITB) was found in ohmically heated plasma in TUMAN-3M (R0 = 53 cm, al = 22 cm - circular limiter configuration, B t ? 0.7 T, Ip ? 175 kA, 6.0·10 19 m-3). The barrier reveals itself as a formation of a steep gradient on electron temperature and density radial profiles. The regions with reduced

M. V. Andreiko; L. G. Askinazi; V. E. Golant; N. A. Zhubr; V. A. Kornev; S. V. Krikunov; S. V. Lebedev; L. S. Levin; G. T. Razdobarin; V. V. Rozhdestvensky; V. A. Rozhansky; A. I. Smirnov; M. Tendler; A. S. Tukachinsky; S. P. Yaroshevich

147

Comparison of thermal cycling behavior of plasma-sprayed nanostructured and traditional thermal barrier coatings  

Microsoft Academic Search

Nanostructured and traditional thermal barrier coatings have been prepared by atmospherical plasma spraying (APS) on NiCrAlY-coated superalloy substrates. Nanostructured thermal barrier coating has relatively longer lifetime than the common coating after cyclic testing at 1050, 1100 and 1150°C. A transient thermal structural finite element solution was employed to analyze the stress distribution in the coatings. The reasons why the two

Chungen Zhou; Na Wang; Huibin Xu

2007-01-01

148

Thermal properties of plasma-sprayed functionally graded thermal barrier coatings  

Microsoft Academic Search

Plasma-sprayed thermal barrier coatings often have the problems of spallation and cracking in service owing to their poor bond strength and high residual stresses. Functionally graded thermal barrier coatings with a gradual compositional variation from heat resistant ceramics to fracture-resistant metals are proposed to mitigate these problems. In this paper, functionally graded yttria stabilized ZrO2\\/NiCoCrAlY coatings were prepared using pre-alloyed

K. A Khor; Y. W Gu

2000-01-01

149

A Comparison between Plasma Synthetic Jets and Conventional Jets  

Microsoft Academic Search

The flow field of a jet created by an actuator employing a surface dielectric barrier discharge (DBD) is investigated experimentally via PIV measurements, and a comparison of its fluid dynamic characteristics with mechanically driven continuous and synthetic jets is presented. The plasma synthetic jet actuator consists of two electrodes arranged asymmetrically separated by a dielectric material and under an input

Arvind Santhanakrishnan; Jamey Jacob

2007-01-01

150

SDBD plasma enhanced aerodynamics: concepts, optimization and applications  

Microsoft Academic Search

This paper provides an overview of the physics and design of single dielectric barrier discharge (SDBD) plasma actuators for enhanced aerodynamics in a variety of applications. The actuators consist of two electrodes, one exposed to the air and the other covered by a dielectric material. The electrodes are supplied with an ac voltage that at high enough levels, causes the

Thomas C. Corke; Martiqua L. Post; Dmitry M. Orlov

2007-01-01

151

Inactivation of Microcystis aeruginosa using dielectric barrier discharge low-temperature plasma  

SciTech Connect

The efficiency of Microcystis aeruginosa plasma inactivation was investigated using dielectric barrier discharge low-temperature plasma. The inactivation efficiency was characterized in terms of optical density. The influence of electrical and physicochemical parameters on M. aeruginosa inactivation was studied to determine the optimal experimental conditions. The influence of active species was studied. The proliferation of the M. aeruginosa cells was significantly decreased under plasma exposure. The morphologic changes in M. aeruginosa were characterized under scanning electron microscopy. These results suggest that the low-temperature plasma technology is a promising method for water pollution control.

Pu, Sichuan [School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049 (China)] [School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049 (China); Chen, Jierong [Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an 710049 (China)] [Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an 710049 (China); Wang, Gang [BMEI CO., LTD, Beijing 100027 (China)] [BMEI CO., LTD, Beijing 100027 (China); Li, Xiaoyong [School of Science, Xi'an Jiaotong University, Xi'an 710049 (China)] [School of Science, Xi'an Jiaotong University, Xi'an 710049 (China); Ma, Yun [School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049 (China) [School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049 (China); College of Chemistry and Chemical Engineering, Xi'an Shiyou University, Xi'an 710065 (China)

2013-05-13

152

Inactivation of Microcystis aeruginosa using dielectric barrier discharge low-temperature plasma  

NASA Astrophysics Data System (ADS)

The efficiency of Microcystis aeruginosa plasma inactivation was investigated using dielectric barrier discharge low-temperature plasma. The inactivation efficiency was characterized in terms of optical density. The influence of electrical and physicochemical parameters on M. aeruginosa inactivation was studied to determine the optimal experimental conditions. The influence of active species was studied. The proliferation of the M. aeruginosa cells was significantly decreased under plasma exposure. The morphologic changes in M. aeruginosa were characterized under scanning electron microscopy. These results suggest that the low-temperature plasma technology is a promising method for water pollution control.

Pu, Sichuan; Chen, Jierong; Wang, Gang; Li, Xiaoyong; Ma, Yun

2013-05-01

153

Tunable one-dimensional plasma photonic crystals in dielectric barrier discharge  

SciTech Connect

A tunable one-dimensional plasma photonic crystal is obtained by using a dielectric barrier discharge with two liquid electrodes. It is formed by the self-organization of the filaments, rather than that in an artificial array of electrodes. The dispersion relations of the plasma photonic crystals are calculated by solving the Helmholtz equation using a method analogous to Kronig-Penney's problem. The photonic band diagrams of the plasma photonic crystals are studied when changing the filling factor, the lattice constant, and the electron density, based on the experimental results. The critical electron density is given, beyond which the plasma photonic crystal will have a remarkable band structure.

Fan Weili; Dong Lifang [College of Physics Science and Technology, Hebei University, Baoding 071002 (China)

2010-07-15

154

Two-dimensional simulations of plasma flow and charge spreading across barrier pixels in AC plasma displays  

Microsoft Academic Search

Two-dimensional multispecies simulations of adjacent pixels separated by a barrier height 80% the gap height in a plasma display pixel cell are performed. The fill gas pressure is 400 torr with 2% xenon in helium. The simulations using a minimum number of excited states of helium and xenon are performed for different cell widths representing different display resolutions. The simulations

Ramana Veerasingam; Robert B. Campbell; Robert T. McGrath

1996-01-01

155

Technical note - Plasma-sprayed ceramic thermal barrier coatings for smooth intermetallic alloys  

NASA Technical Reports Server (NTRS)

A new approach for plasma spray deposition of ceramic thermal barrier coatings directly to smooth substrates is described. Ceramic thermal barrier coatings were directly applied to substrates that had been coated with low-pressure plasma sprayed NiCrAlY bond coats and then centerless ground to simulate a smooth oxidation-resistant substrate. As the high-temperature oxidation behavior of NiAl+Zr is superior to that of MCrALY alloy, the bond coat is not required for oxidation resistance.

Miller, R. A.; Doychak, J.

1992-01-01

156

RESEARCH ARTICLE The use of plasma actuators for bluff body broadband  

E-print Network

actuators to reduce landing gear noise during approach phase of an aircraft. The control effectiveness Exp Fluids DOI 10.1007/s00348-009-0806-3 #12;source of airframe noise is the landing gears where the approach to landing phase, especially when the aircraft is equipped with modern high bypass ratio engines

Huang, Xun

157

Improving plasma actuator performance at low pressure, and an analysis of the pointing capabilities of cubeSats using Plasmonic Force Propulsion (PFP) thrusters  

NASA Astrophysics Data System (ADS)

This thesis details the work done on two unrelated projects, plasma actuators, an aerodynamic flow control device, and Plasmonic Force Propulsion (PFP) thrusters, a space propulsion system for small satellites. The first half of the thesis is a paper published in the International Journal of Flow Control on plasma actuators. In this paper the thrust and power consumption of plasma actuators with varying geometries was studied at varying pressure. It was found that actuators with longer buried electrodes produce the most thrust over all and that they substantially improved thrust at low pressure. In particular actuators with 75 mm buried electrodes produced 26% more thrust overall and 34% more thrust at low pressure than the standard 15 mm design. The second half details work done modeling small satellite attitude and reaction control systems in order to compare the use of Plasmonic Force Propulsion thrusters with other state of the art reaction control systems. The model uses bang bang control algorithms and assumes the worst case scenario solar radiation pressure is the only disturbing force. It was found that the estimated 50-500 nN of thrust produced by PFP thrusters would allow the spacecraft which use them extremely high pointing and positioning accuracies (<10-9 degrees and 3 pm). PFP thrusters still face many developmental challenges such as increasing specific impulse which require more research, however, they have great potential to be an enabling technology for future NASA missions such as the Laser Interferometer Space Antenna, and The Stellar Imager.

Friz, Paul Daniel

158

Oxidative Stress Induced in Saccharomyces Cerevisiae Exposed to Dielectric Barrier Discharge Plasma in Air at Atmospheric Pressure  

Microsoft Academic Search

Nonthermal plasmas are considered to be effective methods for sterilization. However, the changes that occur within the cells of microorganism during sterilization are rarely reported. This paper investigated the effects of dielectric barrier discharge air plasma at atmospheric pressure on yeast Saccharomyces cerevisiae ATCC 4126 suspended in water. S. cerevisiae showed extensive cell death after plasma discharge. For plasma-treated cells,

Huixia Chen; Fengwu Bai; Zhilong Xiu

2010-01-01

159

Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys  

NASA Technical Reports Server (NTRS)

A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

Miller, Robert A. (inventor); Doychak, Joseph (inventor)

1994-01-01

160

Grain-Boundary Grooving of Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings  

E-print Network

- sponsible for the microstructural changes of plasma-sprayed 7 wt% Y2O3­ZrO2 thermal barrier coatings of a yttria-stabilized zircon- ia (YSZ) top coat with a composition of 6­8 wt% Y2O3­ZrO2 plasma sprayed over as t0 -ZrO2.8,9 Non-transform- able zirconia is a non-equilibrium phase as the concentration of yttrium

Trice, Rodney W.

161

Life modeling of atmospheric and low pressure plasma-sprayed thermal-barrier coating  

NASA Technical Reports Server (NTRS)

The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value.

Miller, R. A.; Argarwal, P.; Duderstadt, E. C.

1984-01-01

162

Surface modification of acrylate intraocular lenses with dielectric barrier discharge plasma at atmospheric pressure  

Microsoft Academic Search

Surface modification with dielectric barrier discharge (DBD) plasma was carried out at atmospheric pressure (argon as the\\u000a discharge gas) to improve the biocompatibility of hydrophobic acrylate intraocular lens (IOL). Changes of the plasma-treated\\u000a IOL surface in chemical composition, morphology and hydrophilicity were comprehensively evaluated by X-ray photoelectron spectroscopy\\u000a (XPS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and

Yao Wang; ZhenMei Liu; ZhiKang Xu; Ke Yao

2009-01-01

163

Potential Barrier around an Emitting Body an a Plasma  

NASA Astrophysics Data System (ADS)

We present a self-consistent, kinetic theory for the charging and shielding of an object at rest in a collisionless plasma [1]. The body is an electron emitter according to thermionic emission, photoemission or secondary emission. The theory is formulated for positively charged bodies, derived under the assumption of spherical symmetry so that conservation of energy and angular momentum can be used to calculate the plasma distribution functions at any given point in phase space. Far away from the body the plasma is assumed unperturbed, described by a Maxwellian distribution function at rest. Thus, the unperturbed plasma acts as a source of particles balancing the absorptions from the body and a steady state is eventually reached. The theory is shown to be in good agreement with PIC simulations [1-2]. Further on, several cases (focusing on parameters typical of laboratory experiments) are presented for the three different emission mechanisms, showing that shielding potentials having an attractive well are possible for all of them.[1] G. L. Delzanno, A. Bruno, G. Sorasio, G. Lapenta, Phys. Plasmas 12, 062102 (2005).[2] G. L. Delzanno, G. Lapenta, M. Rosenberg, Phys. Rev. Lett. 92 (3), 035002 (2004).

Bruno, Antonio; Luca Delzanno, Gian; Sorasio, Gianfranco; Lapenta, Giovanni

2005-10-01

164

Electron dynamics and plasma jet formation in a helium atmospheric pressure dielectric barrier discharge jet  

SciTech Connect

The excitation dynamics within the main plasma production region and the plasma jets of a kHz atmospheric pressure dielectric barrier discharge (DBD) jet operated in helium was investigated. Within the dielectric tube, the plasma ignites as a streamer-type discharge. Plasma jets are emitted from both the powered and grounded electrode end; their dynamics are compared and contrasted. Ignition of these jets are quite different; the jet emitted from the powered electrode is ignited with a slight time delay to plasma ignition inside the dielectric tube, while breakdown of the jet at the grounded electrode end is from charging of the dielectric and is therefore dependent on plasma production and transport within the dielectric tube. Present streamer theories can explain these dynamics.

Algwari, Q. Th. [Centre for Plasma Physics, School of Maths and Physics, Queen's University Belfast, University Road, Belfast, Northern Ireland BT7 1NN (United Kingdom); Electronic Department, College of Electronics Engineering, Mosul University, Mosul 41002 (Iraq); O'Connell, D. [Centre for Plasma Physics, School of Maths and Physics, Queen's University Belfast, University Road, Belfast, Northern Ireland BT7 1NN (United Kingdom); York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)

2011-09-19

165

Attenuation of single-tone ultrasound by an atmospheric glow discharge plasma barrier  

SciTech Connect

Propagation of 143 kHz ultrasound through an atmospheric pressure glow discharge in air was studied experimentally. The plasma was a continuous dc discharge formed by a multipin electrode system. Distributions of the gas temperature were also obtained in and around the plasma using laser-induced Rayleigh scattering technique. Results show significant attenuation of the ultrasound by the glow discharge plasma barrier (up to -24 dB). The results indicate that sound attenuation does not depend on the thickness of the plasma and attenuation is caused primarily by reflection of the sound waves from the plasma due to the sharp gas temperatures gradients that form at the plasma boundary. These gradients can be as high as 80 K/mm.

Stepaniuk, Vadim P. [Lenterra Inc., 7 Tenney Road, West Orange, New Jersey 07052 (United States); Ioppolo, Tindaro; Oetuegen, M. Volkan [Southern Methodist University, 3101 Dyer Street, Dallas, Texas 75205 (United States); Sheverev, Valery A. [Lenterra Inc., 7 Tenney Road, West Orange, New Jersey 07052 (United States); Polytechnic Institute of NYU, 6 Metrotech Center, Brooklyn, New York 11201 (United States)

2010-09-15

166

Fast Opening Microwave Barrier and Independency of Polarization in Plasma tubes  

NASA Astrophysics Data System (ADS)

Plasma barriers are used to protect sensitive microwave apparatus from potentially damaging electronic warfare signals. We have found both experimentally and theoretically that we can open such a barrier on a time scale of microseconds instead of typically many milliseconds. We do this by increasing the plasma density rather than waiting for it to decay. We produce a standing wave between the two layers that results in microwave transmission, analogous to the transmission found in an optical Fabry-Perot Resonator. The plasma tubes work extremely well in intercepting microwave radiation when the incident wave electric field is parallel to the tubes. However, if the electric field is perpendicular to the tubes, the normally induced plasma current cannot flow, and the plasma effects are not expected to appear. To our surprise, when the plasma tubes were experimentally tested with the electric field perpendicular to the tubes, the plasma tubes not only intercepted the microwave signal, but the observed cut-off with a pulsed plasma lasted about twice as long. The effect appears to be due to an electrostatic resonance, and preliminary calculations suggest that a normally ignored term in Maxwell's Equations is responsible.

Anderson, Ted; Alexeff, Igor; Farshi, Esmaeil; Dyer, Fred; Peck, Jeffry; Pradeep, Eric P.; Pulsani, Nanditha; Karnam, Naresh

2007-11-01

167

Mechanism of Blood Coagulation by Nonthermal Atmospheric Pressure Dielectric Barrier Discharge Plasma  

Microsoft Academic Search

Mechanisms of blood coagulation by direct contact of nonthermal atmospheric pressure dielectric barrier discharge (DBD) plasma are investigated. This paper shows that no significant changes occur in the pH or Ca2+ concentration of blood during discharge treatment. Thermal effects and electric field effects are also shown to be negligible. Investigating the hypothesis that the discharge treatment acts directly on blood

Sameer U. Kalghatgi; Gregory Fridman; Moogega Cooper; Gayathri Nagaraj; Marie Peddinghaus; Manjula Balasubramanian; Victor N. Vasilets; Alexander F. Gutsol; Alexander Fridman; Gary Friedman

2007-01-01

168

Attenuation of single-tone ultrasound by an atmospheric glow discharge plasma barrier  

E-print Network

was a continuous dc discharge formed by a multipin electrode system. Distributions of the gas temperature were also its temperature. At the boundary be- tween hot discharge and cold gas regions the acoustic speedAttenuation of single-tone ultrasound by an atmospheric glow discharge plasma barrier Vadim P

�tügen, Volkan

169

Removal of SO2 from gas streams using a dielectric barrier discharge and combined plasma photolysis  

E-print Network

Removal of SO2 from gas streams using a dielectric barrier discharge and combined plasma photolysis H. Balbach University of Illinois. Department of Electrical and Computer Engineering, 1406 W Green Engineering, I406 F! Green Street, Urbana, Illinois 61801 (Received 8 November 1990; accepted for publication

Kushner, Mark

170

Non-destructive evaluation of plasma sprayed functionally graded thermal barrier coatings  

Microsoft Academic Search

Acoustic emission (AE) as a non-destructive evaluation technique has recently been used in a number of studies to investigate the performance and failure behavior of plasma sprayed thermal barrier coatings. The mechanism of coating failure is complex, especially when considering the composite nature of the coating. In the present paper, the thermal shock tests with in situ acoustic emission are

L Fu; K. A Khor; H. W Ng; T. N Teo

2000-01-01

171

Gas-confined barrier discharges: a simplified model for plasma dynamics in flame environments  

NASA Astrophysics Data System (ADS)

In this paper we evaluate the dynamics of non-thermal plasmas developing in extremely non-homogeneous environments. We present the gas-confined barrier discharge (GBD) concept and justify its importance as a first step to understanding the dynamics of non-thermal plasmas in flame environments. In this concept, cold (in a generalized sense) barriers of gas play the role of the dielectrics, with some major differences in behaviour with respect to solid barriers. We present an analytical evaluation of the discharge appearance modes, new experimental results using helium-nitrogen layers that confirm the possibility of avoiding breakdown in the cold layers and a numerical evaluation that helps interpret the development of streamers once they reach a non-ionizing region.

Guerra-Garcia, C.; Martinez-Sanchez, M.

2013-08-01

172

Degradation of malachite green by dielectric barrier discharge plasma.  

PubMed

Oxidative decomposition of aqueous organic pollutant malachite green (MG) was studied in a dielectric barrier discharge reactor operated under ambient conditions. Total organic carbon content analysis confirmed the mineralization of the pollutant leading to the formation of carbon dioxide, which was confirmed by an infrared analyzer. Typical results indicated that the degradation rate increases with increasing applied voltage and decreases with increasing concentration. Dye degradation followed first order kinetics. The intermediate products formed during the degradation of MG were identified by a high resolution mass spectrometer (HR-MS) and proposed a plausible mechanism for the mineralization process. PMID:23416603

Manoj Kumar Reddy, P; Ramaraju, B; Subrahmanyam, Ch

2013-01-01

173

Dielectric barrier plasma dynamics for active control of separated flows  

SciTech Connect

The dynamics of separation mitigation with asymmetric dielectric barrier discharges is explored by considering the gas flow past a flat plate at an angle of attack. A self-consistent model utilizing motion of electrons, ions, and neutrals is employed to couple the electric force field to the momentum of the fluid. The charge separation and concomitant electric field yield a time-averaged body force which is oriented predominantly downstream, with a smaller transverse component towards the wall. This induces a wall-jet-like feature that effectively eliminates the separation bubble. The impact of several geometric and electrical operating parameters is elucidated.

Roy, Subrata; Singh, K.P.; Gaitonde, Datta V. [Computational Plasma Dynamics Laboratory, Mechanical Engineering, Kettering University, Flint, Michigan 48504 (United States); Computational Sciences Branch, Air Vehicles Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio 45433 (United States)

2006-03-20

174

Plasma and ion barrier for electron beam spot stability  

SciTech Connect

High-current electron beams of small spot size are used for high-resolution x-ray radiography of dense objects. Intense energy deposition in the bremsstrahlung target causes generation of ions which can propagate upstream and disrupt the electron beam. We have investigated the use of a thin beryllium foil placed 1-2 cm in front of the target, which serves as a barrier for the ions but is essentially transparent to the incoming electron beam. Analysis and computer simulations confirm that this confinement method will halt ion propagation and preserve the spot size stability of the electron beam. (c) 2000 American Institute of Physics.

Kwan, Thomas J. T. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Snell, Charles M. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2000-03-01

175

Compact High-Velocity Atmospheric Pressure Dielectric Barrier Plasma Jet in Ambient Air  

NASA Astrophysics Data System (ADS)

In this paper, a non-thermal atmospheric pressure plasma jet at high streaming velocity operating with ambient air is highlighted. In the present technological approach, the employment of air poses a significant challenge. The high oxygen concentration in air results in a reduced concentration of reactive species in combination with a short species lifetime. The plasma jet assembly presented here contains a special dielectric barrier with a high secondary emission coefficient. In this way, the electron density and in turn the density of reactive species is increased. In addition, the plasma jet assembly is equipped with a short electrode. This leads to a higher voltage across the discharge gap and in turn to an increased density of reactive plasma species. The plasma jet is formed within and emitted by a small conical nozzle. A high-speed gas flow with gas velocity of 340 m/s was achieved at the end of the nozzle. In the jet the concentration of toxic and unwanted neutral plasma species like O3 or NOx is significantly reduced because of the shorter residence time within the plasma. The range of short-lived active plasma species is in turn considerably enhanced. The jet efficiency and action range measured through the oxidation of a test surface were determined by measuring the increase of surface tension of a polypropylene substrate via contact angle measurements after plasma treatment. Numerical modeling of the plasma plume indicates that oxygen atoms are in fact the main active species in the plasma plume.

Annette, Meiners; Michael, Leck; Bernd, Abel

2015-01-01

176

Towards Feedback Control of Bypass Transition: Numerical Simulations of Laminar Boundary Layer Response to a Plamsa Actuator  

NASA Astrophysics Data System (ADS)

We study the effects of single dielectric barrier discharge (SDBD) plasma actuators as a means to delay bypass transition in the Blasius boundary layer, with the eventual goal of closed-loop control. Since streamwise streaks are the structures with the largest transient growth, we orient an array of plasma actuators so as to produce spanwise forces and streamwise vorticity, and thus directly cancel the streaks. We use a pseudo-spectral solver to perform direct numerical simulations of the effect of plasma actuators, implemented as body forces. We compare two different models for the plasma actuator, and then apply each model to our spanwise geometry. We go on to compare each model's simulation results with experiments carried out by our collaborators at University of Toronto and Michigan State University as part of a multi-university research project.

Belson, Brandt; Rowley, Clarence

2010-11-01

177

Instrumented tensile adhesion tests on plasma sprayed thermal barrier coatings  

Microsoft Academic Search

Tensile adhesion tests (TATs) which are normally utilized for industrial quality control procedures have been used for research\\u000a purposes to examine failure mechanisms of plasma sprayed coatings. This work is applied to two layer coatings (NiCrAlY or\\u000a NiCrAlZr bond coat with a yttria stabilized zirconia ceramic overlay) which are tested in tension perpendicular to the surface.\\u000a The mechanical behavior of

Christopher C. Berndt

1989-01-01

178

Growth Control of Dry Yeast Using Scalable Atmospheric-Pressure Dielectric Barrier Discharge Plasma Irradiation  

NASA Astrophysics Data System (ADS)

We have investigated the effects of plasma irradiation on the growth of dry yeast (Saccharomyces cerevisiae) using a scalable atmospheric-pressure dielectric barrier discharge (DBD) device. NO of 380 ppm, NO2 of 10 ppm and O3 of 560 ppm were detected 1 mm below the discharges, which were produced by the DBD plasmas. DBD plasma irradiation of 10 to 100 s enhances the growth of yeast in the lag phase, whereas that of 120 and 150 s suppresses the growth. O3, NO2, photons, and heat generated by the plasma irradiation are not responsible for the growth enhancement of the dry yeast. Plasma etching has little effect on the growth of dry yeast cells. NO plays a key role in the growth enhancement of dry yeast cells.

Kitazaki, Satoshi; Koga, Kazunori; Shiratani, Masaharu; Hayashi, Nobuya

2012-11-01

179

Decomposition of L-valine under nonthermal dielectric barrier discharge plasma.  

PubMed

L-Valine solutions in water and phosphate buffer were treated with nonthermal plasma generated by using a dielectric barrier discharge (DBD) device and the products generated after plasma treatments were characterized by (1)H NMR and GC-MS. Our results demonstrate that L-valine is decomposed to acetone, formic acid, acetic acid, threo-methylaspartic acid, erythro-methlyaspartic acid, and pyruvic acid after direct exposure to DBD plasma. The concentrations of these compounds are time-dependent with plasma treatment. The mechanisms of L-valine under the DBD plasma are also proposed in this study. Acetone, pyruvic acid, and organic radicals (•)CHO, CH3COCH2OO(•) (acetonylperoxy), and CH3COC(OH)2OO(•) (1,1-dihydroxypropan-2-one peroxy) may be the determining chemicals in DNA damage. PMID:24450953

Li, Yingying; Kojtari, Arben; Friedman, Gary; Brooks, Ari D; Fridman, Alex; Ji, Hai-Feng

2014-02-13

180

The parametric investigation of influence of DBD actuator on the boundary layer under various Reynolds number  

NASA Astrophysics Data System (ADS)

In the previous research, the wall-jet-like flow or vortical structures were generated using a single dielectric barrier discharge (DBD) actuator in still air. It has been shown that the actuator can generated so-called vortex train if it is powered by modulated voltage waveform. Now, the plasma DBD actuator is placed inside a rectangular channel and an interaction with boundary layer (BL) is studied. The characteristics of the BL are modifying by varying inlet velocity. The actuator is adjusted to be set in spanwise orientation which means that the generated wall-jet-like flow is oriented in the same meaning as the main flow or in the opposite direction. The interaction of vortical structures generated by actuator with BL will be described quantitatively from mean flow field.

Procházka, P.; Uruba, V.

2014-08-01

181

Thermomechanical behavior of plasma-sprayed zirconia thermal barrier coatings.  

SciTech Connect

The effect of coating porosity and thickness on the resistance to damage of yttria stabilized zirconia thermal barrier coatings in an oxidizing environment by thermal cycling was evaluated. Hardness and elastic modulus of an as-processed porous coating were lower than those of a dense coating and the porous coating failed after fewer thermal cycles. Similarly, specimen with a thicker coating failed after fewer thermal cycles than specimen with a thinner coating. The earlier failure of the porous coating is due to lower fracture toughness and enhanced oxidation of the coating/substrate interface, whereas, the earlier failure of the thick coating is due to higher thermal transient stresses that developed in the coating during thermal cycling. Generally, an increase in coating density led to initial increase in both hardness and elastic modulus with increasing thermal cycles. However, hardness and density gradually decreased as the number of thermal cycles increase because of microcracks formation and growth. Microscopic observations indicated that the formation of multiple microcracks and their subsequent growth and coalescence led to final coating failure.

Singh, J. P.

1998-04-01

182

Inactivation of Campylobacter jejuni with dielectric barrier discharge plasma using air and nitrogen gases.  

PubMed

Air and nitrogen gas are commonly used feed gases for plasma generation and are economically useful in industrial applications. The two gases were compared in dielectric barrier discharge plasma for the inactivation of Campylobacter jejuni on an agar surface. Plasma treatment with nitrogen gas for 20 s did not yield any reduction (p>0.05) in viable cell count. However, a 0.8-log reduction (p<0.05) in colony-forming units (CFU) occurred when the nitrogen gas was supplemented with 2% (vol/vol) air. The use of air only, air supplemented with 2% (vol/vol) nitrogen, or oxygen only further decreased the viable cell counts by 0.7-1.7-log CFU (p<0.05). These results suggest that oxygen in plasma generation is critically important for the increased inactivation effect. Scanning electron microscopy analysis showed much cell debris including fragmented flagella in the sample exposed to air plasma, while no cell debris was found in the sample exposed to nitrogen plasma. In transmission electron microscopy analysis, many C. jejuni cells exposed to air plasma had truncated flagella with sharp bends, while the cells exposed to nitrogen plasma were normal, strongly suggesting that the air plasma can reduce the virulence of C. jejuni. A BacLight assay showed that air plasma damaged the cellular membrane (p<0.05), whereas nitrogen plasma did not after 5- or 20-s treatment. The damage to the membrane was consistent with the reduced viable cell count. Based on confocal microscopic analysis, the similar results were found by visualizing the fluorescent-dye-stained cells. In addition, the prolonged nitrogen plasma for 2 min also damaged many cellular membranes. This study shows that air, especially oxygen, is more effective and destructive than nitrogen and provides evidence that membrane damage may be a major mechanism for the inactivation of C. jejuni exposed to plasma. PMID:24971667

Kim, Joo-Sung; Lee, Eun-Jung; Kim, Yun-Ji

2014-08-01

183

Detection of hydroxyl radicals during regeneration of granular activated carbon in dielectric barrier discharge plasma system  

NASA Astrophysics Data System (ADS)

To understand the reactions taking place in the dielectric barrier discharge (DBD) plasma system of activated carbon regeneration, the determination of active species is necessary. A method based on High Performance Liquid Chromatography with radical trapping by salicylic acid, has been developed to measure hydroxyl radical (•OH) in the DBD plasma reactor. The effects of applied voltage, treatment time, and gas flow rate and atmosphere were investigated. Experimental results indicated that increasing voltage, treatment time and air flow rate could enhance the formation of •OH. Oxygen atmosphere and a suitable GAC water content were contributed to •OH generation. The results give an insight into plasma chemical processes, and can be helpful to optimize the design and application for the plasma system.

Tang, Shoufeng; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

2013-03-01

184

Carbon dioxide splitting in a dielectric barrier discharge plasma: a combined experimental and computational study.  

PubMed

Plasma technology is gaining increasing interest for the splitting of CO2 into CO and O2 . We have performed experiments to study this process in a dielectric barrier discharge (DBD) plasma with a wide range of parameters. The frequency and dielectric material did not affect the CO2 conversion and energy efficiency, but the discharge gap can have a considerable effect. The specific energy input has the most important effect on the CO2 conversion and energy efficiency. We have also presented a plasma chemistry model for CO2 splitting, which shows reasonable agreement with the experimental conversion and energy efficiency. This model is used to elucidate the critical reactions that are mostly responsible for the CO2 conversion. Finally, we have compared our results with other CO2 splitting techniques and we identified the limitations as well as the benefits and future possibilities in terms of modifications of DBD plasmas for greenhouse gas conversion in general. PMID:25641832

Aerts, Robby; Somers, Wesley; Bogaerts, Annemie

2015-02-01

185

Generation of tunable plasma photonic crystals in meshed dielectric barrier discharge  

SciTech Connect

Tunable superlattice plasma photonic crystals are obtained in a meshed dielectric barrier discharge. These plasma photonic crystals are composed of thin artificial lattices and thick self-organized lattices, and can be tuned easily by adjusting the applied voltage. A plasma photonic crystal with self-organized hexagonal lattice coupled to artificial square lattice is first realized. The dispersion relations of the square sublattices with different radii, which are recorded by an intensified charge-coupled device camera, are calculated. The results show that the thick square sublattice has the higher band edge frequencies and wider band widths. Band gaps of superlattice plasma photonic crystals are actually temporal integrations of those of transient sublattices.

Wang, Yongjie; Dong, Lifang, E-mail: donglfhbu@163.com; Liu, Weibo; He, Yafeng; Li, Yonghui [College of Physics Science and Technology, Hebei University, Baoding 071002, China and Hebei Key Laboratory of Optic-electronic Information Materials, Baoding 071002 (China)

2014-07-15

186

Generation of tunable plasma photonic crystals in meshed dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

Tunable superlattice plasma photonic crystals are obtained in a meshed dielectric barrier discharge. These plasma photonic crystals are composed of thin artificial lattices and thick self-organized lattices, and can be tuned easily by adjusting the applied voltage. A plasma photonic crystal with self-organized hexagonal lattice coupled to artificial square lattice is first realized. The dispersion relations of the square sublattices with different radii, which are recorded by an intensified charge-coupled device camera, are calculated. The results show that the thick square sublattice has the higher band edge frequencies and wider band widths. Band gaps of superlattice plasma photonic crystals are actually temporal integrations of those of transient sublattices.

Wang, Yongjie; Dong, Lifang; Liu, Weibo; He, Yafeng; Li, Yonghui

2014-07-01

187

Nanocapsules for drug delivery through the skin barrier by tissue-tolerable plasma  

NASA Astrophysics Data System (ADS)

For many years, several attempts have been made to enhance skin penetration by chemical, physical or mechanical manipulation to reduce the barrier function of the skin. The present study demonstrates the possibility of penetration enhancement for 400 nm sized nanocapsules loaded with a model drug consisting of a fluorescent dye by the application of tissue-tolerable plasma (TTP). Therefore, the stability of the nanocapsules and their penetration through the skin barrier prior to and in combination with TTP application was evaluated. The results revealed that the penetration of the nanocapsules could be effectively enhanced when applied in combination with TTP, hence delivering the model drug unaffected by plasma into deeper skin layers. The stability testing showed no significant structural changes of the nanocapsules after contact with TTP. Thus, the present study introduces a new strategy for the penetration enhancement of substances by the combined utilization of nanocapsules and TTP.

Lademann, J.; Patzelt, A.; Richter, H.; Lademann, O.; Baier, G.; Breucker, L.; Landfester, K.

2013-08-01

188

A dielectric-barrier discharge enhanced plasma brush array at atmospheric pressure  

SciTech Connect

This study developed a large volume cold atmospheric plasma brush array, which was enhanced by a dielectric barrier discharge by integrating a pair of DC glow discharge in parallel. A platinum sheet electrode was placed in the middle of the discharge chamber, which effectively reduced the breakdown voltage and working voltage. Emission spectroscopy diagnosis indicated that many excited argon atoms were distributed almost symmetrically in the lateral direction of the plasma. The concentration variations of reactive species relative to the gas flow rate and discharge current were also examined.

Li Xuemei; Zhan Xuefang; Yuan Xin; Zhao Zhongjun; Yan Yanyue; Duan Yixiang [Research Center of Analytical Instrumentation, Analytical Testing Center, College of Chemistry, Sichuan University, Chengdu (China); Tang Jie [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an (China)

2013-07-15

189

A Brief Study on the Ignition of the Non-Thermal Atmospheric Pressure Plasma Jet from a Double Dielectric Barrier Configured Plasma Pencil  

NASA Astrophysics Data System (ADS)

To understand the self sustained propagation of the plasma jet/bullet in air under atmospheric pressure, the ignition of the plasma jet/bullet, the plasma jet/bullet ignition point in the plasma pencil, the formation time and the formation criteria from a dielectric barrier configured plasma pencil were investigated in this study. The results were confirmed by comparing these results with the plasma jet ignition process in the plasma pencil without a dielectric barrier. Electrical, optical, and imaging techniques were used to study the formation of the plasma jet from the ignition of discharge in a double dielectric barrier configured plasma pencil. The investigation results show that the plasma jet forms at the outlet of the plasma pencil as a donut shaped discharge front because of the electric field line along the outlet's surface. It is shown that the required time for the formation of the plasma jet changes with the input voltage of the discharge. The input power calculation for the gap discharge and for the whole system shows that 56% of the average input power is used by the first gap discharge. The estimated electron density inside the gap discharge is in the order of 1011 cm-3. If helium is used as a feeding gas, a minimum 1.48×10-8 C charge is required per pulse in the gap discharge to generate a plasma jet.

Asma, Begum; Mounir, Laroussi; R. Pervez, M.

2013-07-01

190

Plasma Flow Characteristics in a Spray-Type Dielectric Barrier Discharge Reactor  

Microsoft Academic Search

A numerical simulation on the spray-type dielectric barrier discharge (DBD) is carried out for a mixture gas of nitrogen (N2) and sulfur hexafluoride (SF6) at atmospheric pressure to understand the electrical characteristics and the plasma flow dynamics that depend on design parameters and operating conditions. A 2-D axi-symmetric nonuniform grid is employed in the simulation code consisting of the following

Hyun-Su Kim; Woo Seok Kang; Gon-Ho Kim; Sang Hee Hong

2009-01-01

191

Energy confinement scaling for reversed-shear plasmas with internal transport barrier in JT-60U  

Microsoft Academic Search

An energy confinement scaling for reversed-shear plasmas with box-type internal transport barrier (ITB) and L-mode edge is developed based on the JT-60U data. The stored energy is divided into two parts: L-mode base part and core part surrounded by the ITB. The core stored energy Wcore does not simply increase with the net heating power Pnet. A scaling of core

T. Takizuka; Y. Sakamoto; T. Fukuda; T. Fujita; Y. Kamada; T. Suzuki; S. Ide; H. Shirai

2002-01-01

192

Changes induced in the permeability barrier of the yeast plasma membrane by cupric ion. [Saccharomyces cerevisiae  

Microsoft Academic Search

A specific effect of Cu\\/sup 2 +\\/ eliciting selective changes in the permeability of intact Saccharomyces cerevisiae cells is described. When 200 ..mu..M CuClâ was added to a cell suspension in a buffer of low ionic strength, the permeability barrier of the plasma membranes of the cells was lost within 2 min at 25°C. The release of amino acids was

Y. Ohsumi; K. Kitamoto; Y. Anraku

1988-01-01

193

Skeletal Cell Differentiation Is Enhanced by Atmospheric Dielectric Barrier Discharge Plasma Treatment  

PubMed Central

Enhancing chondrogenic and osteogenic differentiation is of paramount importance in providing effective regenerative therapies and improving the rate of fracture healing. This study investigated the potential of non-thermal atmospheric dielectric barrier discharge plasma (NT-plasma) to enhance chondrocyte and osteoblast proliferation and differentiation. Although the exact mechanism by which NT-plasma interacts with cells is undefined, it is known that during treatment the atmosphere is ionized generating extracellular reactive oxygen and nitrogen species (ROS and RNS) and an electric field. Appropriate NT-plasma conditions were determined using lactate-dehydrogenase release, flow cytometric live/dead assay, flow cytometric cell cycle analysis, and Western blots to evaluate DNA damage and mitochondrial integrity. We observed that specific NT-plasma conditions were required to prevent cell death, and that loss of pre-osteoblastic cell viability was dependent on intracellular ROS and RNS production. To further investigate the involvement of intracellular ROS, fluorescent intracellular dyes Mitosox (superoxide) and dihydrorhodamine (peroxide) were used to assess onset and duration after NT-plasma treatment. Both intracellular superoxide and peroxide were found to increase immediately post NT-plasma treatment. These increases were sustained for one hour but returned to control levels by 24 hr. Using the same treatment conditions, osteogenic differentiation by NT-plasma was assessed and compared to peroxide or osteogenic media containing ?-glycerolphosphate. Although both NT-plasma and peroxide induced differentiation-specific gene expression, neither was as effective as the osteogenic media. However, treatment of cells with NT-plasma after 24 hr in osteogenic or chondrogenic media significantly enhanced differentiation as compared to differentiation media alone. The results of this study show that NT-plasma can selectively initiate and amplify ROS signaling to enhance differentiation, and suggest this technology could be used to enhance bone fusion and improve healing after skeletal injury. PMID:24349203

Zhang, Jun; Kurpad, Deepa S.; Fridman, Gregory; Fridman, Alexander; Freeman, Theresa A.

2013-01-01

194

Radio frequency plasma power dependence of the moisture permeation barrier characteristics of Al{sub 2}O{sub 3} films deposited by remote plasma atomic layer deposition  

SciTech Connect

In the present study, we investigated the gas and moisture permeation barrier properties of Al{sub 2}O{sub 3} films deposited on polyethersulfone films (PES) by capacitively coupled plasma (CCP) type Remote Plasma Atomic Layer Deposition (RPALD) at Radio Frequency (RF) plasma powers ranging from 100 W to 400 W in 100 W increments using Trimethylaluminum [TMA, Al(CH{sub 3}){sub 3}] as the Al source and O{sub 2} plasma as the reactant. To study the gas and moisture permeation barrier properties of 100-nm-thick Al{sub 2}O{sub 3} at various plasma powers, the Water Vapor Transmission Rate (WVTR) was measured using an electrical Ca degradation test. WVTR decreased as plasma power increased with WVTR values for 400 W and 100 W of 2.6 × 10{sup ?4} gm{sup ?2}day{sup ?1} and 1.2 × 10{sup ?3} gm{sup ?2}day{sup ?1}, respectively. The trends for life time, Al-O and O-H bond, density, and stoichiometry were similar to that of WVTR with improvement associated with increasing plasma power. Further, among plasma power ranging from 100 W to 400 W, the highest power of 400 W resulted in the best moisture permeation barrier properties. This result was attributed to differences in volume and amount of ion and radical fluxes, to join the ALD process, generated by O{sub 2} plasma as the plasma power changed during ALD process, which was determined using a plasma diagnosis technique called the Floating Harmonic Method (FHM). Plasma diagnosis by FHM revealed an increase in ion flux with increasing plasma power. With respect to the ALD process, our results indicated that higher plasma power generated increased ion and radical flux compared with lower plasma power. Thus, a higher plasma power provides the best gas and moisture permeation barrier properties.

Jung, Hyunsoo [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of) [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Samsung Display Co. Ltd., Tangjeong, Chungcheongnam-Do 336-741 (Korea, Republic of); Choi, Hagyoung; Lee, Sanghun [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)] [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jeon, Heeyoung [Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)] [Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jeon, Hyeongtag [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of) [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

2013-11-07

195

Boundary-Layer Separation Control under Low-Pressure Turbine Airfoil Conditions using Glow-Discharge Plasma Actuators  

NASA Technical Reports Server (NTRS)

Modem low-pressure turbines, in general, utilize highly loaded airfoils in an effort to improve efficiency and to lower the number of airfoils needed. Typically, the airfoil boundary layers are turbulent and fully attached at takeoff conditions, whereas a substantial fraction of the boundary layers on the airfoils may be transitional at cruise conditions due to the change of density with altitude. The strong adverse pressure gradients on the suction side of these airfoils can lead to boundary-layer separation at the latter low Reynolds number conditions. Large separation bubbles, particularly those which fail to reattach, cause a significant degradation of engine efficiency. A component efficiency drop of the order 2% may occur between takeoff and cruise conditions for large commercial transport engines and could be as large as 7% for smaller engines at higher altitude. An efficient means of of separation elimination/reduction is, therefore, crucial to improved turbine design. Because the large change in the Reynolds number from takeoff to cruise leads to a distinct change in the airfoil flow physics, a separation control strategy intended for cruise conditions will need to be carefully constructed so as to incur minimum impact/penalty at takeoff. A complicating factor, but also a potential advantage in the quest for an efficient strategy, is the intricate interplay between separation and transition for the situation at hand. Volino gives a comprehensive discussion of several recent studies on transition and separation under low-pressure-turbine conditions, among them one in the present facility. Transition may begin before or after separation, depending on the Reynolds number and other flow conditions. If the transition occurs early in the boundary layer then separation may be reduced or completely eliminated. Transition in the shear layer of a separation bubble can lead to rapid reattachment. This suggests using control mechanisms to trigger and enhance early transition. Gad-el-Hak provides a review of various techniques for flow control in general and Volino discusses recent studies on separation control under low-pressure-turbine conditions utilizing passive as well as active devices. As pointed out by Volino, passive devices optimized for separation control at low Reynolds numbers tend to increase losses at high Reynolds numbers, Active devices have the attractive feature that they can be utilized only in operational regimes where they are needed and when turned off would not affect the flow. The focus in the present paper is an experimental Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil ('Pak-B'). The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) Gee-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface- flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control. of active separation control using glow discharge plasma actuators.

Hultgren, Lennart S.; Ashpis, David E.

2003-01-01

196

The cold and atmospheric-pressure air surface barrier discharge plasma for large-area sterilization applications  

SciTech Connect

This letter reports a stable air surface barrier discharge device for large-area sterilization applications at room temperature. This design may result in visually uniform plasmas with the electrode area scaled up (or down) to the required size. A comparison for the survival rates of Escherichia coli from air, N{sub 2} and O{sub 2} surface barrier discharge plasmas is presented, and the air surface plasma consisting of strong filamentary discharges can efficiently kill Escherichia coli. Optical emission measurements indicate that reactive species such as O and OH generated in the room temperature air plasmas play a significant role in the sterilization process.

Wang Dacheng [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Zhao Di [Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); School of Photoelectrical Engineering, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Feng Kecheng [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Zhang Xianhui [Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Liu Dongping [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); School of Physics and Materials Engineering, Dalian Nationalities University, Dalian 116600 (China); Yang Size [Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100080 (China)

2011-04-18

197

Controlled drug release through a plasma polymerized tetramethylcyclo-tetrasiloxane coating barrier.  

PubMed

A plasma polymerized tetramethylcyclo-tetrasiloxane (TMCTS) coating was deposited onto a metallic biomaterial, 316 stainless steel, to control the release rate of drugs, including daunomycin, rapamycin and NPC-15199 (N-(9-fluorenylmethoxy-carbonyl)-leucine), from the substrate surface. The plasma-state polymerized TMCTS thin film was deposited in a vacuum plasma reactor operated at a radio-frequency of 13.56 MHz, and was highly adhesive to the stainless steel, providing a smooth and hard coating layer for drugs coated on the substrate. To investigate the influence of plasma coating thickness on the drug diffusion profile, coatings were deposited at various time lengths from 20 s to 6 min, depending on the type of drug. Atomic force spectroscopy (AFM) was utilized to characterize coating thickness. Drug elution was measured using a spectrophotometer or high-performance liquid chromatography (HPLC) system. The experimental results indicate that plasma polymerized TMCTS can be used as an over-coating to control drug elution at the desired release rate. The drug-release rate was also found to be dependent on the molecular weight of the drug with plasma coating barrier on top of it. The in vitro cytotoxicity test result suggested that the TMCTS plasma coatings did not produce a cytotoxic response to mammalian cells. The non-cytotoxicity of TMCTS coating plus its high thrombo-resistance and biocompatibility are very beneficial to drug-eluting devices that contact blood. PMID:21294969

Osaki, Shigemasa; Chen, Meng; Zamora, Paul O

2012-01-01

198

Effect of atmospheric pressure dielectric barrier discharge plasma on the biological activity of naringin.  

PubMed

The biological activity of naringin treated with atmospheric pressure plasma was evaluated to investigate whether exposure to plasma can be used as a method to improve the biological activity of natural materials. Naringin was dissolved in methanol (at 500 ppm) and transferred to a container. A dielectric barrier discharge (DBD) (250 W, 15 kHz, ambient air) was then generated. Treatment with the plasma for 20 min increased the radical-scavenging activity, FRAP value, and the total phenolic compound content of naringin from 1.45% to 38.20%, from 27.78 to 207.78 ?M/g, and from 172.50 to 225.83 ppm, respectively. Moreover, the tyrosinase-inhibition effect of naringin increased from 6.12% to 83.30% upon plasma treatment. Naringin treated with plasma exhibited antimicrobial activity against foodborne pathogens, especially Salmonella Typhimurium; an activity that was absent before plasma treatment. Structural modifications induced in the naringin molecule by plasma might be responsible for improving the biological activity of naringin. PMID:24799234

Kim, Hyun-Joo; Yong, Hae In; Park, Sanghoo; Kim, Kijung; Kim, Tae Hoon; Choe, Wonho; Jo, Cheorun

2014-10-01

199

Two-dimensional simulations of plasma flow and charge spreading across barrier pixels in AC plasma displays  

SciTech Connect

Two-dimensional multispecies simulations of adjacent pixels separated by a barrier height 80% the gap height in a plasma display pixel cell are performed. The fill gas pressure is 400 torr with 2% xenon in helium. The simulations using a minimum number of excited states of helium and xenon are performed for different cell widths representing different display resolutions. The simulations show plasma transport through the gap to the adjacent pixel which is in the sustained off state. In a sustained off state, there is no discharge in the pixel at the sustained voltage. The simulations show that for low-resolution displays, the plasma overflow does not cause a discharge in the adjacent pixel that is in the sustained off mode, while for a high-resolution display a 20% gap in the barrier height could result in a breakdown in the adjacent off pixel. A higher pixel resolution, or equivalently smaller pixel pitch, requires higher firing and sustained voltages due primarily to increased particle losses as a result of the reduced particle transit times. Finally, using a larger number of excited xenon atomic states, an isolated single pixel is simulated to model the transport of excited states including the radiative states. The model shows that the density profiles peak in the cathode fall region spreading out to the side walls with decreasing intensity.

Veerasingam, R.; Campbell, R.B.; McGrath, R.T. [Sandia National Labs., Albuquerque, NM (United States)] [Sandia National Labs., Albuquerque, NM (United States)

1996-12-01

200

Observation of particle transport barriers in reverse shear plasmas on the Tokamak Fusion Test Reactor  

SciTech Connect

Perturbative experiments on the Tokamak Fusion Test Reactor [Phys. Plasmas {bold 4}, 1736 (1997)] (TFTR) have investigated transport in reverse shear plasmas. On TFTR, reverse magnetic shear plasmas bifurcate into two states with different transport properties: reverse shear (RS) and enhanced reverse shear (ERS) with improved core confinement. Measurements of the 14 MeV t(d,n){alpha} neutrons and charge-exchange recombination radiation spectra are used to infer the trace tritium and helium profiles, respectively. The profile evolution indicate the formation of core particle transport barriers in ERS plasmas. The transport barrier is manifested by an order-of-magnitude reduction in the particle diffusivity (D{sub T},D{sub He}) and a smaller reduction in the pinch within the reverse shear region. The low diffusivities are consistent with neoclassical predictions. Furthermore, D{sub T} and D{sub He}{approx}{chi}{sub eff}, the effective thermal diffusivity. Although the measured coefficients imply no helium ash accumulation, the situation is uncertain in a reactor due to unknown {chi}{sub eff} scaling. {copyright} {ital 1998} {ital American Institute of Physics}

Efthimion, P.C.; von Goeler, S.; Houlberg, W.A.; Synakowski, E.J.; Zarnstorff, M.C.; Batha, S.H.; Bell, R.E.; Bitter, M.; Bush, C.E.; Levinton, F.M.; Mazzucato, E.; McCune, D.; Mueller, D.; Park, H.; Ramsey, A.T.; Roquemore, A.L.; Taylor, G. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey08543 (United States)

1998-05-01

201

Surface treatment of para-aramid fiber by argon dielectric barrier discharge plasma at atmospheric pressure  

NASA Astrophysics Data System (ADS)

This paper is focused on influence of argon dielectric barrier discharge (DBD) plasma on the adhesive performance and wettability of para-aramid fibers and three parameters including treated power, exposure time and argon flux were detected. The interfacial shear strength (IFSS) was greatly increased by 28% with 300 W, 60 s, 2 L min-1 argon flux plasma treatment. The content of oxygen atom and oxygen-containing polar functional groups were enhanced after the argon plasma treated, so as the surface roughness, which contributed to the improvement of surface wettability and the decrease of contact angle with water. However, long-time exposure, exorbitant power or overlarge argon flux could partly destroy the prior effects of the treatment and damage the mechanical properties of fibers to some degree.

Gu, Ruxi; Yu, Junrong; Hu, Chengcheng; Chen, Lei; Zhu, Jing; Hu, Zuming

2012-10-01

202

Direct current dielectric barrier assistant discharge to get homogeneous plasma in capacitive coupled discharge  

SciTech Connect

In this paper, we propose a method to get more homogeneous plasma in the geometrically asymmetric capacitive coupled plasma (CCP) discharge. The dielectric barrier discharge (DBD) is used for the auxiliary discharge system to improve the homogeneity of the geometrically asymmetric CCP discharge. The single Langmuir probe measurement shows that the DBD can increase the electron density in the low density volume, where the DBD electrodes are mounted, when the pressure is higher than 5?Pa. By this manner, we are able to improve the homogeneity of the plasma production and increase the overall density in the target volume. At last, the finite element simulation results show that the DC bias, applied to the DBD electrodes, can increase the homogeneity of the electron density in the CCP discharge. The simulation results show a good agreement with the experiment results.

Du, Yinchang, E-mail: ycdu@mail.ustc.edu.cn [Modern Physics Department, University of Science and Technology of China, Hefei, Anhui 230026 (China); Max-Planck Institute for Extraterrestrial Physics, D-85748 Garching (Germany); Li, Yangfang [Max-Planck Institute for Extraterrestrial Physics, D-85748 Garching (Germany); Cao, Jinxiang; Liu, Yu; Wang, Jian; Zheng, Zhe [Modern Physics Department, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2014-06-15

203

Integrated Plasma Simulation of Ion Cyclotron and Lower Hybrid Range of Frequencies Actuators in Tokamaks  

NASA Astrophysics Data System (ADS)

Recent upgrades to the ion cyclotron RF (ICRF) and lower hybrid RF (LHRF) components of the Integrated Plasma Simulator [1] have made it possible to simulate LH current drive in the presence of ICRF minority heating and mode conversion electron heating. The background plasma is evolved in these simulations using the TSC transport code [2]. The driven LH current density profiles are computed using advanced ray tracing (GENRAY) and Fokker Planck (CQL3D) [3] components and predictions from GENRAY/CQL3D are compared with a ``reduced'' model for LHCD (the LSC [4] code). The ICRF TORIC solver is used for minority heating with a simplified (bi-Maxwellian) model for the non-thermal ion tail. Simulation results will be presented for LHCD in the presence of ICRF heating in Alcator C-Mod. [4pt] [1] D. Batchelor et al, Journal of Physics: Conf. Series 125, 012039 (2008).[0pt] [2] S. C. Jardin et al, J. Comp. Phys. 66, 481 (1986).[0pt] [3] R. W. Harvey and M. G. McCoy, Proc. of the IAEA Tech. Comm. Meeting on Simulation and Modeling of Therm. Plasmas, Montreal, Canada (1992).[0pt] [4] D. Ignat et al, Nucl. Fus. 34, 837 (1994).[0pt] [5] M. Brambilla, Plasma Phys. and Cont. Fusion 41,1 (1999).

Bonoli, P. T.; Shiraiwa, S.; Wright, J. C.; Harvey, R. W.; Batchelor, D. B.; Berry, L. A.; Chen, Jin; Poli, F.; Kessel, C. E.; Jardin, S. C.

2012-10-01

204

Development of a dielectric barrier discharge enhanced plasma jet in atmospheric pressure air  

SciTech Connect

A plasma jet equipped with dielectric barrier discharge (DBD) is developed to generate diffuse air plasma with fairly large gap and cross sectional area. The diffuse air plasma has two discharge modes under different gap widths from the nozzle to the ground plate electrode. For large gap width, a diffuse plume fills the whole space between the nozzle and the plate electrode after coaxial DBD is ignited when the applied voltage reaches a certain value. Rather than diffuse plasma plume, a bright plasma column bridges the nozzle and the plate electrode with further increasing the applied voltage under small gap width. By optical and electrical measurement, results show that the macroscopically diffuse discharge in air is obtained by the superimposition of radially distributed streamers that appear at different cycles of the applied voltage, and the bright plasma column belongs to atmospheric pressure glow discharge. The molecular vibrational temperature and the gas temperature are given as functions of the peak value of the applied voltage.

Li Xuechen; Chang Yuanyuan; Jia Pengying [College of Physics Science and Technology, Hebei University, Baoding 071002 (China); Xu Longfei; Fang Tongzhen; Wang Long [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2012-09-15

205

Comparison Between Dielectric Barrier Discharge Plasma and Ozone Regenerations of Activated Carbon Exhausted with Pentachlorophenol  

NASA Astrophysics Data System (ADS)

In this study, two regeneration methods (dielectric barrier discharge (DBD) plasma and ozone (O3) regeneration) of saturated granular activated carbon (GAC) with pentachlorophenol (PCP) were compared. The results show that the two regeneration methods can eliminate contaminants from GAC and recover its adsorption properties to some extent. Comparing the DBD plasma with O3 regeneration, the adsorption rate and the capacity of the GAC samples after DBD plasma regeneration are greater than those after O3 regeneration. O3 regeneration decreases the specific surface area of GAC and increases the acidic surface oxygen groups on the surface of GAC, which causes a decrease in PCP on GAC uptake. With increasing regeneration cycles, the regeneration efficiencies of the two methods decrease, but the decrease in the regeneration efficiencies of GAC after O3 regeneration is very obvious compared with that after DBD plasma regeneration. Furthermore, the equilibrium data were fitted by the Freundlich and Langmuir models using the non-linear regression technique, and all the adsorption equilibrium isotherms fit the Langmuir model fairly well, which demonstrates that the DBD plasma and ozone regeneration processes do not appear to modify the adsorption process, but to shift the equilibrium towards lower adsorption concentrations. Analyses of the weight loss of GAC show that O3 regeneration has a lower weight loss than DBD plasma regeneration.

Qu, Guangzhou; Liang, Dongli; Qu, Dong; Huang, Yimei; Li, Jie

2014-06-01

206

Localized arc filament plasma actuators for noise mitigation and mixing enhancement  

NASA Technical Reports Server (NTRS)

A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

2008-01-01

207

Localized arc filament plasma actuators for noise mitigation and mixing enhancement  

NASA Technical Reports Server (NTRS)

A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

2010-01-01

208

Characterization of a Direct-Current Glow Discharge Plasma Actuator in Low-Pressure Supersonic Flow  

Microsoft Academic Search

DOI: 10.2514\\/1.27197 An experimental study of a direct-current, nonequilibrium glow plasma discharge in the presence of a Mach 2.85 supersonic flow is presented. The discharge is generated with pinlike electrodes flush-mounted on a plane surface with sustaining currents between 25 to 300 mA. In the presence of a supersonic flow, two distinct discharge modes (diffuse and constricted) are observed depending

Jichul Shin; V. Narayanaswamy; Laxminarayan L. Raja; Noel T. Clemens

2007-01-01

209

Plasma Treatment of Industrial Landfill Leachate by Atmospheric Pressure Dielectric Barrier Discharges  

NASA Astrophysics Data System (ADS)

An dielectric barrier discharge (DBD) system in atmospheric pressure utilized for the treatment of industrial landfill leachate is reported. The discharge parameters, such as the operating frequency, gas flow rate, and treating duration, were found to affect significantly the removal of ammonia nitrogen (AN) in industrial landfill leachate. An increase in treating duration leads to an obvious increase in the removal efficiency of AN (up to 83%) and the leachate color changed from deep grey-black to transparent. Thus the dielectric barrier discharges in atmospheric pressure could degrade the landfill leachate effectively. Typical waveforms of both applied voltage and discharge current were also presented for analyzing the discharge processes under different discharge parameters. Optical emission spectra measurements indicate that oxidation species generated in oxygen DBD plasma play a crucial role in removing AN, oxidizing organic and inorganic substances and decolorizing the landfill leachate.

Zhao, Di; Wang, Dacheng; Yan, Gui; Ma, Hong; Xiong, Xiaojing; Luo, Jinjing; Zhang, Xianhui; Liu, Dongping; Yang, Size

2011-10-01

210

Plasma-assisted atomic layer deposition of Al2O3 moisture permeation barriers on polymers  

NASA Astrophysics Data System (ADS)

Thin Al2O3 films of different thicknesses (10-40nm) were deposited by plasma-assisted atomic layer deposition on substrates of poly(2,6-ethylenenaphthalate) (PEN), and the water vapor transmission rate (WVTR) values were measured by means of the calcium test. The permeation barrier properties improved with decreasing substrate temperature and a good WVTR of 5×10-3gm-2day-1 (WVTRPEN=0.5gm-2day-1) was measured for a 20nm thick Al2O3 film deposited at room temperature using short purging times. Such ultrathin, low-temperature deposited, high-quality moisture permeation barriers are an essential requirement for the implementation of polymeric substrates in flexible electronic and display applications.

Langereis, E.; Creatore, M.; Heil, S. B. S.; van de Sanden, M. C. M.; Kessels, W. M. M.

2006-08-01

211

Plasma From Patients With HELLP Syndrome Increases Blood-Brain Barrier Permeability.  

PubMed

Circulating inflammatory factors and endothelial dysfunction have been proposed to contribute to the pathophysiology of hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. To date, the occurrence of neurological complications in these women has been reported, but few studies have examined whether impairment in blood-brain barrier (BBB) permeability or cerebrovascular reactivity is present in women having HELLP syndrome. We hypothesized that plasma from women with HELLP syndrome causes increased BBB permeability and cerebrovascular dysfunction. Posterior cerebral arteries from female nonpregnant rats were perfused with 20% serum from women with normal pregnancies (n = 5) or women with HELLP syndrome (n = 5), and BBB permeability and vascular reactivity were compared. Plasma from women with HELLP syndrome increased BBB permeability while not changing myogenic tone and reactivity to pressure. Addition of the nitric oxide (NO) synthase inhibitor N(?)-nitro-l-arginine methyl ester caused constriction of arteries that was not different with the different plasmas nor was dilation to the NO donor sodium nitroprusside different between the 2 groups. However, dilation to the small- and intermediate-conductance, calcium-activated potassium channel activator NS309 was decreased in vessels exposed to HELLP plasma. Thus, increased BBB permeability in response to HELLP plasma was associated with selective endothelial dysfunction. PMID:25194151

Wallace, Kedra; Tremble, Sarah M; Owens, Michelle Y; Morris, Rachael; Cipolla, Marilyn J

2015-03-01

212

Surface treatment of aramid fiber by air dielectric barrier discharge plasma at atmospheric pressure  

NASA Astrophysics Data System (ADS)

Aramid fiber samples are treated by air dielectric barrier discharge (DBD) plasma at atmospheric pressure; the plasma treatment time is investigated as the major parameter. The effects of this treatment on the fiber surface physical and chemical properties are studied by using surface characterization techniques. Scanning electron microscopy (SEM) is performed to determine the surface morphology changes, X-ray photoelectron spectroscopy (XPS) is analyzed to reveal the surface chemical composition variations and dynamic contact angle analysis (DCAA) is used to examine the changes of the fiber surface wettability. In addition, the wetting behavior of a kind of thermoplastic resin, poly(phthalazinone ether sulfone ketone) (PPESK), on aramid fiber surface is also observed by SEM photos. The study shows that there seems to be an optimum treatment condition for surface modification of aramid fiber by the air DBD plasma. In this paper, after the 12 s, 27.6 W/cm3 plasma treatment the aramid fiber surface roughness is significantly improved, some new oxygen-containing groups such as C-O, Cdbnd O and Odbnd C-O are generated on the fiber surface and the fiber surface wettability is greatly enhanced, which results in the better wetting behavior of PPESK resin on the plasma-treated aramid fiber.

Jia, Caixia; Chen, Ping; Liu, Wei; Li, Bin; Wang, Qian

2011-02-01

213

Damage evolution and residual stresses in plasma-sprayed zirconia thermal barrier coatings.  

SciTech Connect

Air-plasma-sprayed zirconia thermal barrier coatings were subjected to thermal cycling and residual stress evolution in thermally grown oxide scale was studied by micro- and macro-ruby fluorescence spectroscopy. The macro approach reveals that compressive stress in the oxide scale increases with increasing number of thermal cycles (and thus increasing scale thickness), reaching a value of 1.8 GPa at a scale thickness of 3-4 {micro}m (80 cycles). Micro-ruby fluorescence spectroscopy indicates that protrusions of the zirconia top coat into the bond coat act as localized areas of high stress concentration, leading to damage initiation during thermal cycling.

Singh, J. P.

1999-02-03

214

Sintering and creep behavior of plasma-sprayed zirconia- and hafnia-based thermal barrier coatings  

Microsoft Academic Search

The sintering and creep of plasma-sprayed ceramic thermal barrier coatings under high temperature conditions are complex phenomena. Changes in thermomechanical and thermophysical properties and in the stress response of these coating systems as a result of the sintering and creep processes are detrimental to coating thermal fatigue resistance and performance. In this paper, the sintering characteristics of ZrO2–8wt%Y2O3, ZrO2–25wt%CeO2–2.5wt%Y2O3, ZrO2–6w%NiO–9wt%Y2O3,

Dongming Zhu; Robert A. Miller

1998-01-01

215

Process, properties and environmental response of plasma sprayed thermal barrier coatings  

NASA Technical Reports Server (NTRS)

Experimental results are shown which demonstrate that the properties of plasma sprayed fully stabilized zirconia are strongly influenced by the process parameters. Properties of the coatings in the as-sprayed condition are shown to be additionally influenced by environmental exposure. This behavior is dependent on raw material considerations and processing conditions as well as exposure time and temperature. Process control methodology is described which can take into consideration these complex interactions and help to produce thermal barrier coatings in a cost effective way while meeting coating technical requirements.

Novak, R. C.

1995-01-01

216

Process, properties, and environmental response of plasma sprayed thermal barrier coatings  

NASA Technical Reports Server (NTRS)

Experimental results are shown which demonstrate that the properties of plasma sprayed fully stabilized zirconia are strongly influenced by the process parameters. Properties of the coatings in the as-sprayed condition are shown to be additionally influenced by environmental exposure. This behavior is dependent on raw material considerations and processing conditions as well as exposure time and temperature. Process control methodology is described which can take into consideration these complex interactions and help to produce thermal barrier coatings in a cost effective way while meeting coating technical requirements.

Novak, Richard C.

1995-01-01

217

Antimicrobial Efficacy of Two Surface Barrier Discharges with Air Plasma against In Vitro Biofilms  

PubMed Central

The treatment of infected wounds is one possible therapeutic aspect of plasma medicine. Chronic wounds are often associated with microbial biofilms which limit the efficacy of antiseptics. The present study investigates two different surface barrier discharges with air plasma to compare their efficacy against microbial biofilms with chlorhexidine digluconate solution (CHX) as representative of an important antibiofilm antiseptic. Pseudomonas aeruginosa SG81 and Staphylococcus epidermidis RP62A were cultivated on polycarbonate discs. The biofilms were treated for 30, 60, 150, 300 or 600 s with plasma or for 600 s with 0.1% CHX, respectively. After treatment, biofilms were dispensed by ultrasound and the antimicrobial effects were determined as difference in the number of the colony forming units by microbial culture. A high antimicrobial efficacy on biofilms of both plasma sources in comparison to CHX treatment was shown. The efficacy differs between the used strains and plasma sources. For illustration, the biofilms were examined under a scanning electron microscope before and after treatment. Additionally, cytotoxicity was determined by the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay with L929 mouse fibroblast cell line. The cell toxicity of the used plasma limits its applicability on human tissue to maximally 150 s. The emitted UV irradiance was measured to estimate whether UV could limit the application on human tissue at the given parameters. It was found that the UV emission is negligibly low. In conclusion, the results support the assumption that air plasma could be an option for therapy of chronic wounds. PMID:23894661

Matthes, Rutger; Bender, Claudia; Schlüter, Rabea; Koban, Ina; Bussiahn, René; Reuter, Stephan; Lademann, Jürgen; Weltmann, Klaus-Dieter; Kramer, Axel

2013-01-01

218

Nanocomposite Lanthanum Zirconate Thermal Barrier Coating Deposited by Suspension Plasma Spray Process  

NASA Astrophysics Data System (ADS)

This work seeks to develop an innovative nanocomposite thermal barrier coating (TBC) exhibiting low thermal conductivity and high durability compared with that of current TBCs. To achieve this objective, nanosized lanthanum zirconate particles were selected for the topcoat of the TBC system, and a new process—suspension plasma spray—was employed to produce desirable microstructural features: the nanocomposite lanthanum zirconate TBC contains ultrafine splats and high volume porosity, for lower thermal conductivity, and better durability. The parameters of plasma spray experiment included two main variables: (i) spray distance varying from 40 to 80 mm and (ii) the concentration of suspension 20, 25, and 30 wt.%, respectively. The microstructure of obtained coatings was characterized with scanning electron microscope and x-ray diffraction. The porosity of coatings is in the range of 6-10%, and the single phase in the as-sprayed coatings was pyrochlore lanthanum zirconate.

Wang, Chaohui; Wang, You; Wang, Liang; Hao, Guangzhao; Sun, Xiaoguang; Shan, Fan; Zou, Zhiwei

2014-10-01

219

Factors affecting the microstructural stability and durability of thermal barrier coatings fabricated by air plasma spraying  

SciTech Connect

The high-temperature behavior of high-purity, low-density (HP-LD) air plasma sprayed (APS) thermal barrier coatings (TBCs) with NiCoCrAlY bond coats deposited by argon-shrouded plasma spraying is described. The high purity yttria-stabilized zirconia resulted in top coats which are highly resistant to sintering and transformation from the metastable tetragonal phase to the equilibrium mixture of monoclinic and cubic phases. The thermal conductivity of the as-processed TBC is low but increases during high temperature exposure even before densification occurs. The porous topcoat microstructure also resulted in good spallation resistance during thermal cycling. The actual failure mechanisms of the APS coatings were found to depend on topcoat thickness, topcoat density, and the thermal cycle frequency. The failure mechanisms are described and the durability of the HP-LD coatings is compared with that of state-of-the-art electron beam physical vapor deposition TBCs.

Helminiak, M. A.; Yanar, N. M.; Pettit, F. S.; Taylor, T. A.; Meier, G. H.

2012-10-01

220

Effects of Dielectric Barrier Discharge Plasma Treatment on Pentachlorophenol Removal of Granular Activated Carbon  

NASA Astrophysics Data System (ADS)

The pentachlorophenol (PCP) adsorbed granular activated carbon (GAC) was treated by dielectric barrier discharge (DBD) plasma. The effects of DBD plasma on the structure of GAC and PCP decomposition were analyzed by N2 adsorption, thermogravimetric, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and gas chromatography mass spectrometry (GC-MS). The experimental data of adsorption kinetics and thermodynamics of PCP on GAC were fitted with different kinetics and isotherm models, respectively. The results indicate that the types of N2 adsorption isotherm of GAC are not changed by DBD plasma, while the specific surface area and pore volume increase after DBD plasma treatment. It is found that the weight loss of the saturated GAC is the highest, on the contrary, the weight loss of DBD treated GAC is the least because of reduced PCP residue on the GAC. The XPS spectra and SEM image suggest that some PCP on the GAC is removed by DBD plasma, and the surface of GAC treated by DBD plasma presents irregular and heterogeneous morphology. The GC-MS identification of by-products shows that two main dechlorination intermediate products, tetrachlorophenol and trichlorophenol, are distinguished. The fitting results of experimental data of adsorption kinetics and thermodynamics indicate that the pseudo-first-order and pseudo-second order models can be used for the prediction of the kinetics of virgin GAC and DBD treated GAC for PCP adsorption, and the Langmuir isotherm model fits better with the data of adsorption isotherm than the Freundlich isotherm in the adsorption of PCP on virgin GAC and DBD treated GAC.

Ji, Puhui; Qu, Guangzhou; Li, Jie

2013-10-01

221

QUIESCENT DOUBLE BARRIER H-MODE PLASMAS IN THE DIII-D TOKAMAK  

SciTech Connect

High confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D [J.L. Luxon, et al., Plasma Phys. and Contr. Nucl. Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987) Vol. I, p. 159] this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation which is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 seconds or >25 energy confinement times {tau}{sub E}), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved {beta}{sub N} H{sub 89} = 7 for up to 5 times the {tau}{sub E} of 150 ms. The {beta}{sub N} H{sub 89} values of 7 substantially exceed the value of 4 routinely achieved in standard ELMing H-mode. The key factors in creating the quiescent H-mode operation are neutral beam injection in the direction opposite to the plasma current (counter injection) plus cryopumping to reduce the density. Density and impurity control in the quiescent H-mode is possible because of the presence of an edge magnetic hydrodynamic (MHD) oscillation, the edge harmonic oscillation, which enhances the edge particle transport while leaving the energy transport unaffected.

K.H. BURRELL; M.E. AUSTIN; D.P. BRENNAN; J.C. DeBOO; E.J. DOYLE; C. FENZI; C. FUCHS; P. GOHIL; R.J. GROEBNER; L.L. LAO; T.C. LUCE; M.A. MAKOWSKI; G.R. McKEE; R.A. MOYER; C.C. PETTY; M. PORKOLAB; C.L.RETTIG; T.L. RHODES; J.C. ROST; B.W. STALLARD; E.J. STRAIT; E.J. SYNAKOWSKI; M.R. WADE; J.G. WATKINS; W.P. WEST

2000-11-01

222

Evaluation of damage induced by inductively coupled plasma etching of 6H-SiC using Au Schottky barrier diodes  

Microsoft Academic Search

Surface damage of 6H-SiC induced by inductively coupled plasma (ICP) etching with a CF4\\/O2 gas mixture has been evaluated by Au Schottky barrier diodes formed on the etched surfaces. The influence of substrate dc bias has been studied. It is found that there is an optimum dc bias for ICP etching. Under the optimum dc bias voltage, Schottky barrier diodes

Binghui Li; Lihui Cao; Jian H. Zhao

1998-01-01

223

Method and Process Development of Advanced Atmospheric Plasma Spraying for Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

Over the last few years, global economic growth has triggered a dramatic increase in the demand for resources, resulting in steady rise in prices for energy and raw materials. In the gas turbine manufacturing sector, process optimizations of cost-intensive production steps involve a heightened potential of savings and form the basis for securing future competitive advantages in the market. In this context, the atmospheric plasma spraying (APS) process for thermal barrier coatings (TBC) has been optimized. A constraint for the optimization of the APS coating process is the use of the existing coating equipment. Furthermore, the current coating quality and characteristics must not change so as to avoid new qualification and testing. Using experience in APS and empirically gained data, the process optimization plan included the variation of e.g. the plasma gas composition and flow-rate, the electrical power, the arrangement and angle of the powder injectors in relation to the plasma jet, the grain size distribution of the spray powder and the plasma torch movement procedures such as spray distance, offset and iteration. In particular, plasma properties (enthalpy, velocity and temperature), powder injection conditions (injection point, injection speed, grain size and distribution) and the coating lamination (coating pattern and spraying distance) are examined. The optimized process and resulting coating were compared to the current situation using several diagnostic methods. The improved process significantly reduces costs and achieves the requirement of comparable coating quality. Furthermore, a contribution was made towards better comprehension of the APS of ceramics and the definition of a better method for future process developments.

Mihm, Sebastian; Duda, Thomas; Gruner, Heiko; Thomas, Georg; Dzur, Birger

2012-06-01

224

Improving Atmospheric Plasma Spraying of Zirconate Thermal Barrier Coatings Based on Particle Diagnostics  

NASA Astrophysics Data System (ADS)

Lanthanum zirconate (La2Zr2O7) has been proposed as a promising material for thermal barrier coatings. During atmospheric plasma spraying (APS) of La2Zr2O7 a considerable amount of La2O3 can evaporate in the plasma flame, resulting in a non-stoichiometric coating. As indicated in the phase diagram of the La2O3-ZrO2 system, in the composition range of pyrochlore structure, the stoichiometric La2Zr2O7 has the highest melting point and other compositions are eutectic. APS experiments were performed with a TriplexPro™-200 plasma torch at different power levels to achieve different degrees of evaporation and thus stoichiometry. For comparison, some investigations on gadolinium zirconate (Gd2Zr2O7) were included, which is less prone to evaporation and formation of non-stoichiometry. Particle temperature distributions were measured by the DPV-2000 diagnostic system. In these distributions, characteristic peaks were detected at specific torch input powers indicating evaporation and solidification processes. Based on this, process parameters can be defined to provide stoichiometric coatings that show good thermal cycling performance.

Mauer, Georg; Sebold, Doris; Vaßen, Robert; Stöver, Detlev

2012-06-01

225

Efficient barrier for charge injection in polyethylene by silver nanoparticles/plasma polymer stack  

NASA Astrophysics Data System (ADS)

Charge injection from a metal/insulator contact is a process promoting the formation of space charge in polymeric insulation largely used in thick layers in high voltage equipment. The internal charge perturbs the field distribution and can lead to catastrophic failure either through its electrostatic effects or through energetic processes initiated under charge recombination and/or hot electrons effects. Injection is still ill-described in polymeric insulation due to the complexity of the contact between the polymer chains and the electrodes. Barrier heights derived from the metal work function and the polymer electronic affinity do not provide a good description of the measurements [Taleb et al., IEEE Trans. Dielectr. Electr. Insul. 20, 311-320 (2013)]. Considering the difficulty to describe the contact properties and the need to prevent charge injection in polymers for high voltage applications, we developed an alternative approach by tailoring the interface properties by the silver nanoparticles (AgNPs)/plasma polymer stack, deposited on the polymer film. Due to their small size, the AgNPs, covered by a very thin film of plasma polymer, act as deep traps for the injected charges thereby stabilizing the interface from the point of view of charge injection. After a quick description of the method for elaborating the nanostructured layer near the contact, it is demonstrated how the AgNPs/plasma polymer stack effectively prevents, in a spectacular way, the formation of bulk space charge.

Milliere, L.; Makasheva, K.; Laurent, C.; Despax, B.; Teyssedre, G.

2014-09-01

226

Model for toroidal velocity in H-mode plasmas in the presence of internal transport barriers  

NASA Astrophysics Data System (ADS)

A model for predicting toroidal velocity in H-mode plasmas in the presence of internal transport barriers (ITBs) is developed using an empirical approach. In this model, it is assumed that the toroidal velocity is directly proportional to the local ion temperature. This model is implemented in the BALDUR integrated predictive modelling code so that simulations of ITB plasmas can be carried out self-consistently. In these simulations, a combination of a semi-empirical mixed Bohm/gyro-Bohm (mixed B/gB) core transport model that includes ITB effects and NCLASS neoclassical transport is used to compute a core transport. The boundary is taken to be at the top of the pedestal, where the pedestal values are described using a theory-based pedestal model based on a combination of magnetic and flow shear stabilization pedestal width scaling and an infinite-n ballooning pressure gradient model. The combination of the mixed B/gB core transport model with ITB effects, together with the pedestal and the toroidal velocity models, is used to simulate the time evolution of plasma current, temperature and density profiles of 10 JET optimized shear discharges. It is found that the simulations can reproduce an ITB formation in these discharges. Statistical analyses including root mean square error (RMSE) and offset are used to quantify the agreement. It is found that the averaged RMSE and offset among these discharges are about 24.59% and -0.14%, respectively.

Chatthong, B.; Onjun, T.; Singhsomroje, W.

2010-06-01

227

Evaluation of pathogen inactivation on sliced cheese induced by encapsulated atmospheric pressure dielectric barrier discharge plasma.  

PubMed

Pathogen inactivation induced by atmospheric pressure dielectric barrier discharge (DBD) (250 W, 15 kHz, air discharge) produced in a rectangular plastic container and the effect of post-treatment storage time on inactivation were evaluated using agar plates and cheese slices. When agar plates were treated with plasma, populations of Escherichia coli, Salmonella Typhimurium, and Listeria monocytogenes showed 3.57, 6.69, and 6.53 decimal reductions at 60 s, 45 s, and 7 min, respectively. When the pathogens tested were inoculated on cheese slices, 2.67, 3.10, and 1.65 decimal reductions were achieved at the same respective treatment times. The post-treatment storage duration following plasma treatment potently affected further reduction in pathogen populations. Therefore, the newly developed encapsulated DBD-plasma system for use in a container can be applied to improve the safety of sliced cheese, and increasing post-treatment storage time can greatly enhance the system's pathogen-inactivation efficiency. PMID:25475265

Yong, Hae In; Kim, Hyun-Joo; Park, Sanghoo; Alahakoon, Amali U; Kim, Kijung; Choe, Wonho; Jo, Cheorun

2015-04-01

228

Experimental investigation of a surface DBD plasma actuator at atmospheric pressure in different N2/O2 gas mixtures  

NASA Astrophysics Data System (ADS)

This paper presents an investigation of the influence of nitrogen and oxygen on the behavior of a surface dielectric barrier discharge (SDBD) used for active flow control. The SDBD operated in a controlled atmosphere under several N2/O2 gas mixture ratios. For each gas mixture, the consumed power was measured as a function of voltage amplitude. Then, for a given applied high voltage, the plasma morphology was recorded and commented and lastly, ionic wind velocity measurements were performed. Results show that the induced ionic wind velocity is mainly due to oxygen negative ions during the negative half-cycle. Nevertheless, the contribution of nitrogen to velocity is not negligible during the positive half-cycle. Moreover, the propagation of negative spark filaments during the negative half-cycle is linked to the proportion of O2 in the gas mixture. Increasing this proportion beyond 20% leads to a shift in the saturation effect to lower voltages and to a decrease in the maximum ionic wind velocity value.

Audier, P.; Rabat, H.; Leroy, A.; Hong, D.

2014-12-01

229

Mechanical Properties of Plasma-Sprayed ZrO2-8 wt% Y2O3 Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

Mechanical behavior of free standing, plasma-sprayed ZrO2-8 wt% Y2O3 thermal barrier coatings, including strength, fracture toughness, fatigue, constitutive relation, elastic modulus, and directionality, has been determined under various loading-specimen configurations. This report presents and describes a summary of mechanical properties of the plasma-sprayed coating material to provide them as a design database.

Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

2004-01-01

230

Creep of plasma-sprayed-ZrO2 thermal-barrier coatings  

NASA Technical Reports Server (NTRS)

Specimens of plasma-sprayed-zirconia thermal-barrier coatings with three different porosities and different initial particle sizes were deformed in compression at initial loads of 6900, 13,800, and 24,100 kPa (1000, 2000, and 3500 psi) and temperatures of 1100, 1250, and 1400 C. The coatings were stabilized with lime, MgO, and two different concentrations of Y2O3. Creep began as soon as the load was applied and continued at a constantly decreasing rate until the load was removed. Temperature and stabilization had a pronounced effect on creep rate while the stress, particle size, and porosity had a lesser effect. Creep deformation was due to cracking and particle sliding.

Firestone, R. F.; Logan, W. R.; Adams, J. W.; Bill, R. C., Jr.

1982-01-01

231

Pattern formation and dynamics of plasma filaments in dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharges (DBDs) operating in a transient glow discharge regime offer a large variety of self-organized filamentary static or dynamical structures and constitute an excellent physical system for the study of nonlinear dynamics and pattern formation. The plasma filaments of DBDs can exhibit particle-like behavior, with motion, generation, annihilation, and scattering as well as collective effects leading to self-organized structures (hexagons, stripes, concentric rings, spirals, etc) that are typical of reaction–diffusion systems. The purpose of this paper is to analyze the detailed physics of pattern formation in DBDs on the basis of numerical fluid simulations and experiments in order to provide a deeper understanding of the nonlinear mechanisms responsible for the self-organization and dynamics of filaments.

Callegari, T.; Bernecker, B.; Boeuf, J. P.

2014-10-01

232

Degradation of selected organophosphate pesticides in wastewater by dielectric barrier discharge plasma.  

PubMed

In this paper, degradation of selected organophosphate pesticides (dichlorvos and dimethoate) in wastewater by dielectric barrier discharge plasma (DBD) was studied. DBD parameters, i.e. discharge powers and air-gap distances, differently affect their degradation efficiency. The results show that better degradation efficiency is obtained with a higher discharge power and a shorter air-gap distance. The effect of radical intervention degradation was also investigated by adding radical scavenger (tert-butyl alcohol) to the pesticide solution during the experiments. The result shows that the degradation efficiency is restrained in the presence of radical scavenger. It clearly demonstrates that hydroxyl radicals are most likely the main driver for degradation process. Moreover, the kinetics indicate that the disappearance rate of pesticides follows the first-order rate law when the initial concentration of the solution is low, but shifts to zero-order at a higher initial concentration. PMID:23835613

Hu, Yingmei; Bai, Yanhong; Yu, Hu; Zhang, Chunhong; Chen, Jierong

2013-09-01

233

Monitoring Delamination of Plasma-Sprayed Thermal Barrier Coatings by Reflectance-Enhanced Luminescence  

NASA Technical Reports Server (NTRS)

Highly scattering plasma-sprayed thermal barrier coatings (TBCs) present a challenge for optical diagnostic methods to monitor TBC delamination because scattering attenuates light transmitted through the TBC and usually degrades contrast between attached and delaminated regions of the TBC. This paper presents a new approach where reflectance-enhanced luminescence from a luminescent sublayer incorporated along the bottom of the TBC is used to identify regions of TBC delamination. Because of the higher survival rate of luminescence reflecting off the back surface of a delaminated TBC, the strong scattering exhibited by plasma-sprayed TBCs actually accentuates contrast between attached and delaminated regions by making it more likely that multiple reflections of luminescence off the back surface occur before exiting the top surface of the TBC. A freestanding coating containing sections designed to model an attached or delaminated TBC was prepared by depositing a luminescent Eu-doped or Er-doped yttria-stabilized zirconia (YSZ) luminescent layer below a plasma-sprayed undoped YSZ layer and utilizing a NiCr backing layer to represent an attached substrate. For specimens with a Eu-doped YSZ luminescent sublayer, luminescence intensity maps showed excellent contrast between unbacked and NiCr-backed sections even at a plasma-sprayed overlayer thickness of 300 m. Discernable contrast between unbacked and NiCr-backed sections was not observed for specimens with a Er-doped YSZ luminescent sublayer because luminescence from Er impurities in the undoped YSZ layer overwhelmed luminescence originating form the Er-doped YSZ sublayer.

Eldridge, Jeffrey I.; Bencic, Timothy J.

2006-01-01

234

Removal of Tricholoethylene from Air Streams by a Superimposed Barrier Discharge Plasma Reactor  

NASA Astrophysics Data System (ADS)

In this work, superimposed barrier discharge - activated carbon filter hybrid systems are used to remove TCE from air streams, and the mechanism of TCE decomposition is investigated. The superimposed barrier discharge consisted of silent and a surface discharges. Experiments are conducted for the gas flow rate from 0.1 to 10 L/min, applied power from 0 to 7 W and TCE initial concentration from 0 to 2,000 ppm for 60 Hz ac applied voltage conditions. Discharge by-products are measured by FTIR, GC and TLV VOC detector. The results shows that; 1) TCE decomposition rate nonmonotonically increases with increasing applied power up to discharge power around 4 W and decreases with increasing applied power; 2) Approximately 50% of TCE is removed by plasma reactors and the other 50% is removed by activated carbon filters; 3) TCE is decomposition to form CO, CO2, H2O, HCl and Cl2, and HCl and Cl2 are adsorbed in activated carbon filters; 4) No COCl2 is observed in a discharge by-products for the present range of experiments; 5) Aerosol particles are also observed as a discharge by-products.

Urashima, Kuniko; Ito, Tairo; Chang, Jen-Shih

1996-10-01

235

Effect of Sintering on Mechanical and Physical Properties of Plasma-Sprayed Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

The effect of sintering on mechanical and physical properties of free-standing plasma-sprayed ZrO2-8 wt% Y2O3 thermal barrier coatings (TBCs) was determined by annealing them at 1316 C in air. Mechanical and physical properties of the TBCs, including strength, modes I and II fracture toughness, elastic modulus, Poisson s response, density, microhardness, fractography, and phase stability, were determined at ambient temperature as a function of annealing time ranging from 0 to 500 h. All mechanical and physical properties, except for the amount of monoclinic phase, increased significantly in 5 to 100 h and then reached a plateau above 100 h. Annealing resulted in healing of microcracks and pores and in grain growth, accompanying densification of the TBC s body due to the sintering effect. However, an inevitable adverse effect also occurred such that the desired lower thermal conductivity and good expansivity, which makes the TBCs unique in thermal barrier applications, were degraded upon annealing. A model was proposed to assess and quantify all the property variables in response to annealing in a normalized scheme. Directionality of as-sprayed TBCs appeared to have an insignificant effect on their properties, as determined via fracture toughness, microhardness, and elastic modulus measurements.

Choi, Sung R.; Zhu, Dong-Ming; Miller, Robert A.

2004-01-01

236

Physical and Barrier Properties of Plasma Enhanced Chemical Vapor Deposition ?-SiC:N:H Films  

NASA Astrophysics Data System (ADS)

In this work, we investigate the thermal stability and physical and barrier properties of three species of plasma enhanced chemical vapor deposition (PECVD) ?-SiC:N:H silicon carbide films with different carbon and nitrogen contents and dielectric constants less than a value of 5.5. For comparison, one species of ?-SiN:H film with a k value of 7.2 is also studied. It is found that the dielectric constant decreases with increasing content of carbon and decreasing content of nitrogen in the ?-SiC:N:H film. All of the three species of ?-SiC:N:H and the one species of ?-SiN:H films are thermally stable at temperatures up to 500°C. However, degraded barrier capability and moisture resistance were observed for the ?-SiC:N:H film with a k value of 3.5, which has a C/Si atomic ratio of 0.875. This is presumably due to the poorly crosslinked molecular structure and porosity enhancement caused by the abundant amount of carbon in the ?-SiC:N:H film.

Chiang, Chiu-Chih; Wu, Zhen-Cheng; Wu, Wei-Hao; Chen, Mao-Chieh; Ko, Chung-Chi; Chen, Hsi-Ping; Jang, Syun-Ming; Yu, Chen-Hua; Liang, Mong-Song

2003-07-01

237

Characterization and Properties of Electroless Nickel Plated Poly (ethylene terephthalate) Nonwoven Fabric Enhanced by Dielectric Barrier Discharge Plasma Pretreatment  

Microsoft Academic Search

In order to develop a more economical pretreatment method for electroless nickel plating, a dielectric barrier discharge (DBD) plasma at atmospheric pressure was used to improve the hydrophilicity and adhesion of poly (ethylene terephthalate) (PET) nonwoven fabric. The properties of the PET nonwoven fabric including its liquid absorptive capacity (WA), aging behavior, surface chemical composition, morphology of the surface, adhesion

Yamin Geng; Canhui Lu; Mei Liang; Wei Zhang

2010-01-01

238

Rotary actuators  

Microsoft Academic Search

Rotary actuators are electromagnetic devices developing mechanical torque with limited rotary motion. Because of their simplicity and low cost they are finding more and more applications, especially in the automotive field. This paper describes a novel homopolar rotary actuator with a ring-type radially-magnetized multipolar permanent magnet featuring a high force density “transverse flux” configuration which performs a spring action by

A. M. Pawlak; S. Schultz; V. Gangla

1994-01-01

239

Improved Ethanol Production from Xylose by Candida shehatae Induced by Dielectric Barrier Discharge Air Plasma  

NASA Astrophysics Data System (ADS)

Xylose fermentation is essential for ethanol production from lignocellulosic biomass. Exposure of the xylose-fermenting yeast Candida shehatae (C. shehatae) CICC1766 to atmospheric pressure dielectric barrier discharge (DBD) air plasma yields a clone (designated as C81015) with stability, which exhibits a higher ethanol fermentation rate from xylose, giving a maximal enhancement in ethanol production of 36.2% compared to the control (untreated). However, the biomass production of C81015 is lower than that of the control. Analysis of the NADH (nicotinamide adenine dinucleotide)- and NADPH (nicotinamide adenine dinucleotide phosphate)-linked xylose reductases and NAD+-linked xylitol dehydrogenase indicates that their activities are enhanced by 34.1%, 61.5% and 66.3%, respectively, suggesting that the activities of these three enzymes are responsible for improving ethanol fermentation in C81015 with xylose as a substrate. The results of this study show that DBD air plasma could serve as a novel and effective means of generating microbial strains that can better use xylose for ethanol fermentation.

Chen, Huixia; Xiu, Zhilong; Bai, Fengwu

2014-06-01

240

Neutron and X-ray diffraction of plasma-sprayed zirconia-yttria thermal barrier coatings  

NASA Technical Reports Server (NTRS)

ZrO2-7.8mol. pct. YO1.5, a fused powder, and ZrO2-8.7mol. pct. YO1.5, a prereacted powder, were plasma-sprayed onto steel substrates. Neutron diffraction and X-ray diffraction of the as-received powder, the powder plasma sprayed into water, as-sprayed coatings, and coatings heat-treated for 10 and 100 h were carried out to study phase transformations and ordering of the oxygen ions on the oxygen sublattice. The as-received fused powder has a much lower monoclinic percentage than does the pre-reacted powder, this resulting in a much lower monoclinic percentage in the coating. Heat treatment increases the percentages of the cubic and monoclinic phases, while decreasing the tetragonal content. An ordered tetragonal phase is detected by the presence of extra neutron diffraction peaks. These phase transformations and ordering will result in volume changes. The implications of these transformations on the performance of partially stabilized zirconia thermal barrier coatings is discussed.

Shankar, N. R.; Herman, H.; Singhal, S. P.; Berndt, C. C.

1984-01-01

241

Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor.  

PubMed

A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80â"ƒ in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 × 10 (-3) gm (-2) d (-1) at 60â"ƒ and 90% relative humidity could be observed. PMID:24936155

Bülow, Tim; Gargouri, Hassan; Siebert, Mirko; Rudolph, Rolf; Johannes, Hans-Hermann; Kowalsky, Wolfgang

2014-01-01

242

Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor  

NASA Astrophysics Data System (ADS)

A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80℃ in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 × 10 -3 g m -2 d -1 at 60℃ and 90% relative humidity could be observed.

Bülow, Tim; Gargouri, Hassan; Siebert, Mirko; Rudolph, Rolf; Johannes, Hans-Hermann; Kowalsky, Wolfgang

2014-05-01

243

Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor  

PubMed Central

A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80℃ in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 × 10 ?3 gm?2d?1 at 60℃ and 90% relative humidity could be observed. PMID:24936155

2014-01-01

244

A diffuse plasma generated by bipolar nanosecond pulsed dielectric barrier discharge in nitrogen  

NASA Astrophysics Data System (ADS)

In this study, a bipolar high-voltage pulse with 20 ns rising time is employed to generate diffuse dielectric barrier discharge plasma using wire-plate electrode configuration in nitrogen at atmospheric pressure. The gas temperature of the plasma is determined by comparing the experimental and the best fitted optical emission spectra of the second positive bands of N2(C3?u ? B3 ?g, 0-2) and the first negative bands of N2+ (B2 ?u+ ? X2 ?g+, 0-0). The effects of the concentration of argon and oxygen on the emission intensities of N2 (C3?u ? B3?g, 0-0, 337.1 nm), OH (A 2? ? X2?, 0-0) and N2+ (B2 ?u+ ? X2 ?g+, 0-0, 391.4 nm) are investigated. It is shown that the plasma gas temperature keeps almost constant with the pulse repetition rate and pulse peak voltage increasing. The emission intensities of N2 (C3?u ? B3?g, 0-0, 337.1 nm), OH(A2? ? X2?, 0-0) and N2+ (B2 ?u+ ? X2 ?g+, 0-0, 391.4 nm) rise with increasing the concentration of argon, but decrease with increasing the concentration of oxygen, and the influences of oxygen concentration on the emission intensities of N2(C3?u ? B3?g, 0-0, 337.1 nm) and OH (A2? ? X2?, 0-0) are more greater than that on the emission intensity of N2+ (B2 ?u+ ? X2 ?g+, 0-0, 391.4 nm).

Jia, Li; Yang, De-Zheng; Shi, Heng-Chao; Wang, Wen-Chun; Wang, Sen

2014-05-01

245

Digital Actuator Technology  

SciTech Connect

There are significant developments underway in new types of actuators for power plant active components. Many of these make use of digital technology to provide a wide array of benefits in performance of the actuators and in reduced burden to maintain them. These new product offerings have gained considerable acceptance in use in process plants. In addition, they have been used in conventional power generation very successfully. This technology has been proven to deliver the benefits promised and substantiate the claims of improved performance. The nuclear industry has been reluctant to incorporate digital actuator technology into nuclear plant designs due to concerns due to a number of concerns. These could be summarized as cost, regulatory uncertainty, and a certain comfort factor with legacy analog technology. The replacement opportunity for these types of components represents a decision point for whether to invest in more modern technology that would provide superior operational and maintenance benefits. Yet, the application of digital technology has been problematic for the nuclear industry, due to qualification and regulatory issues. With some notable exceptions, the result has been a continuing reluctance to undertake the risks and uncertainties of implementing digital actuator technology when replacement opportunities present themselves. Rather, utilities would typically prefer to accept the performance limitations of the legacy analog actuator technologies to avoid impacts to project costs and schedules. The purpose of this report is to demonstrate that the benefits of digital actuator technology can be significant in terms of plant performance and that it is worthwhile to address the barriers currently holding back the widespread development and use of this technology. It addresses two important objectives in pursuit of the beneficial use of digital actuator technology for nuclear power plants: 1. To demonstrate the benefits of digital actuator technology over legacy analog sensor technology in both quantitative and qualitative ways. 2. To recognize and address the added difficulty of digital technology qualification, especially in regard to software common cause failure (SCCF), that is introduced by the use of digital actuator technology.

Ken Thomas; Ted Quinn; Jerry Mauck; Richard Bockhorst

2014-09-01

246

Effects of electrode geometry on the performance of dielectric barrier/packed-bed discharge plasmas in benzene degradation.  

PubMed

In this study, the effects of electrode geometry on benzene degradation in a dielectric barrier/packed-bed discharge plasma reactor with different electrodes were systematically investigated. Three electrodes were employed in the experiments, these were coil, bolt, and rod geometries. The reactor using the coil electrode showed better performance in reducing the dielectric loss in the barrier compared to that using the bolt or rod electrodes. In the case of the coil electrode, both the benzene degradation efficiency and energy yield were higher than those for the other electrodes, which can be attributed to the increased role of surface mediated reactions. Irrespective of the electrode geometry, the packed-bed discharge plasma was superior to the dielectric barrier discharge plasma in benzene degradation at any specific applied voltage. The main gaseous products of benzene degradation were CO, CO2, H2O, and formic acid. Discharge products such as O3, N2O, N2O5, and HNO3 were also detected in the outlet gas. Moreover, the presence of benzene inhibited the formation of ozone because of the competing reaction of oxygen atoms with benzene. This study is expected to offer an optimized approach combining dielectric barrier discharge and packed-bed discharge to improve the degradation of gaseous pollutants. PMID:24061216

Jiang, Nan; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

2013-11-15

247

Effect of dielectric barrier discharge plasma actuators on non-equilibrium hypersonic Ankush Bhatia, Subrata Roy, and Ryan Gosse  

E-print Network

. Phys. 113, 243302 (2013); 10.1063/1.4809975 Momentum transfer and flow induction in a dielectric of Mechanical and Aerospace Engineering, University of Florida, Gainesville 32611, USA 2 Computational Sciences Center of Excellence, Air Force Research Laboratory, AFRL/RQHV, Bldg 146B, 2210 Eighth St., WPAFB, Ohio

Roy, Subrata

248

On the use of pulsed Dielectric Barrier Discharges to control the gas-phase composition of atmospheric pressure air plasmas  

NASA Astrophysics Data System (ADS)

We presents results obtained from the numerical simulation of the gas-phase chemical kinetics in atmospheric pressure air non-equilibrium plasmas. In particular we have addressed the effect of pulsed operation mode of a plane dielectric barrier discharge. It was conjectured that the large difference in the time scales involved in the fast dissociation of oxygen molecules in plasma and their subsequent reactions to produce ozone and nitrogen oxides, makes the presence of a continuously repeated plasma production unnecessary and a waste of electrical power and thus efficiency. In order to test such suggestion we have performed a numerical study of the composition and the temporal evolution of the gas-phase of atmospheric pressure air non-equilibrium plasmas. Comparison with experimental findings in a dielectric barrier discharge with an electrode configuration symmetrical and almost ideally plane is briefly addressed too, using plasma diagnostics to extract the properties of the single micro-discharges and a sensor to measure the concentration of ozone produced by the plasma.

Barni, R.; Biganzoli, I.; Dell'Orto, E.; Riccardi, C.

2014-11-01

249

Driving reactions: Surmounting activation barriers in solid state chemistry using hydroxide melts and RF plasmas  

NASA Astrophysics Data System (ADS)

This thesis explores several techniques for surmounting activation barriers in solid state chemistry. The two major issues addressed are the use of a solution-based molten hydroxide system to increase the rate of reactant diffusion over that in the solid state, and the use of an RF plasma to break bonds in gaseous reactants for subsequent reaction with a solid. Part I describes the use of molten alkali metal hydroxides as a low-temperature solvent system for both electrodeposition and precipitation of high valent copper oxides. Cyclic voltammetry was used to determine the effects of various reaction conditions on copper dissolved in the melts, including copper activity, temperature, and atmosphere composition. The results of this study indicate that copper oxide phases become less soluble at higher copper activities, temperatures, and pHsb2O values. Also, the Cu(II)/Cu(III) redox wave, important for the electrodeposition of cuprate phases with high copper formal oxidation states, is observed below 300sp°C in air and at 350sp°C in dry argon. NaCuOsb2 was electrodeposited under constant current conditions. Iodometric titrations and annealing studies indicate that NaCuOsb2 is oxygen deficient and tends to lose additional oxygen on heating. The hydroxide method was also successful in the deposition of thin films of superconducting EuBasb2Cusb4Osb8 on SrTiOsb3 substrates. The films were found to be superconducting with a Tsbc of 75 K in the absence of annealing. In Part II, the idea of circumventing activation energy barriers is applied to the problem of environmentally harmful perfluorocarbons (PFCs). Mass spectrometry was used to determine the PFC emissions from two semiconductor manufacturing processes: oxide etch and post-CVD chamber clean. Because of radical recombination to thermodynamically stable species, most of the PFCs used in these processes are emitted to the atmosphere. A prototype abatement device which uses an RF plasma to provide the activation energy to break the strong carbon-fluorine bonds in PFCs was built and tested. Breaking these bonds causes the production of highly reactive radicals, which react with CaO to produce CaFsb2. The maximum observed yield of the process was 34%.

Friedman, Todd Lawrence

1997-11-01

250

Removal of priority pollutants from water by means of dielectric barrier discharge atmospheric plasma.  

PubMed

Two different nonthermal plasma reactors at atmospheric pressure were assessed for the removal of organic micropollutants (atrazine, chlorfenvinfos, 2,4-dibromophenol, and lindane) from aqueous solutions (1-5 mg L(-1)) at laboratory scale. Both devices were dielectric barrier discharge (DBD) reactors; one was a conventional batch reactor (R1) and the other a coaxial thin-falling-water-film reactor (R2). A first-order degradation kinetics was proposed for both experiments. The kinetic constants (k) were slightly faster in R1 (0.534 min(-1) for atrazine; 0.567 min(-1) for chlorfenvinfos; 0.802 min(-1) for 2,4-dibromophenol; 0.389 min(-1) for lindane) than in R2 (0.104 min(-1) for atrazine; 0.523 min(-1) for chlorfenvinfos; 0.273 min(-1) for 2,4-dibromophenol; 0.294 min(-1) for lindane). However, energy efficiencies were about one order of magnitude higher in R2 (89 mg kW(-1) h(-1) for atrazine; 447 mg kW(-1) h(-1) for c hlorfenvinfos; 47 mg kW(-1) h(-1) for 2,4-dibromophenol; 50 mg kW(-1) h(-1) for lindane) than in R1. Degradation by -products of all four compounds were identified in R1. As expected, when the plasma treatment (R1) was applied to industrial wastewater spiked with atrazine or lindane, micropollutant removal was also achieved, although at a lower rate than with aqueous solutions (k = 0.117 min(-1) for atrazine; k = 0.061 min(-1) for lindane). PMID:24121639

Hijosa-Valsero, María; Molina, Ricardo; Schikora, Hendrik; Müller, Michael; Bayona, Josep M

2013-11-15

251

Development of a diffuse air-argon plasma source using a dielectric-barrier discharge at atmospheric pressure  

SciTech Connect

A stable diffuse large-volume air plasma source was developed by using argon-induced dielectric-barrier discharges at atmospheric pressure. This plasma source can be operated in a filamentary discharge with the average areal power density of 0.27 W/cm{sup 2} and the gas temperature of 315{+-}3 K. Spatial measurement of emission spectrum and temperature indicates that this plasma is uniform in the central region along the transverse direction. It is also found that the formation of diffuse air plasma mainly lies in the creation of sufficient seed electrons by the Penning effect through collisions between two argon or nitrogen metastables at low electric fields.

Tang Jie; Jiang Weiman; Zhao Wei; Wang Yishan; Li Shibo; Wang Haojing [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an 710119 (China)] [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an 710119 (China); Duan Yixiang [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an 710119 (China) [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an 710119 (China); Research Center of Analytical Instrumentation, Sichuan University, Chengdu 610064 (China)

2013-01-21

252

Sintering and Creep Behavior of Plasma-Sprayed Zirconia and Hafnia Based Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

The sintering and creep of plasma-sprayed ceramic thermal barrier coatings under high temperature conditions are complex phenomena. Changes in thermomechanical and thermophysical properties and in the stress response of these coating systems as a result of the sintering and creep processes are detrimental to coating thermal fatigue resistance and performance. In this paper, the sintering characteristics of ZrO2-8wt%y2O3, ZrO2-25wt%CeO2-2.5wt%Y2O3, ZrO2-6w%NiO- 9wt%Y2O3, ZrO2-6wt%Sc2O3-2wt%y2O3 and HfO2-27wt%y2O3 coating materials were investigated using dilatometry. It was found that the HfO2-Y2O3 and baseline ZrO2-Y2O3 exhibited the best sintering resistance, while the NiO-doped ZrO2-Y2O3 showed the highest shrinkage strain rates during the tests. Higher shrinkage strain rates of the coating materials were also observed when the specimens were tested in Ar+5%H2 as compared to in air. This phenomenon was attributed to an enhanced metal cation interstitial diffusion mechanism under the reducing conditions. It is proposed that increased chemical stability of coating materials will improve the material sintering resistance.

Zhu, Dongming; Miller, Robert A.

1998-01-01

253

Acetamiprid removal in wastewater by the low-temperature plasma using dielectric barrier discharge.  

PubMed

Degradation of acetamiprid in wastewater was studied in a dielectric barrier discharge (DBD) reactor. This reactor produces ultraviolet light and reactive species like ozone (O?) can be used for the treatment of wastewater. We examined the factors that could affect the degradation process, including the discharge power, and the initial concentrations of acetamiprid, and O? which is generated by the DBD reactor. We also investigated the effect of adding Na?B?O? as a radical scavenger to probe the role of hydroxyl radical in the reaction. The results indicated that acetamiprid could be removed from aqueous solution effectively and hydroxyl radicals played an important role during the degradation by the low temperature plasma. The degradation process of acetamiprid fits the first-order kinetics. The degradation efficiency was 83.48 percent at 200 min when the discharge power was 170 W and the initial acetamiprid concentration was 50 mg/L. The removal efficiency of acetamiprid decreased with the increasing concentration of Na?B?O? because B?O?(2-) is an excellent radical scavenger that inhibited the generation of OH during the DBD process. The removal efficiency of acetamiprid improved in the presence of O?. The main reason was that O? can oxidize certain organic compounds directly or indirectly by generating hydroxyl radicals. The degradation products of acetamiprid were characterized qualitatively and quantitatively using high performance liquid chromatography, mass spectrometry and UV-vis spectroscopy. PMID:24840877

Li, Shanping; Ma, Xiaolong; Jiang, Yanyan; Cao, Xiaohong

2014-08-01

254

[Influence of pressure on plasma temperature of octagon structure in dielectric barrier discharge].  

PubMed

Octagon structure consisting of the spots and lines was firstly observed in discharge in argon and air mixture by using a dielectric barrier discharge device with water electrodes. Plasma temperatures of the spots and lines in octagon structure at different gas pressure were studied by using optical emission spectra. The emission spectra of the N2 second positive band (C3IIu-->B3IIg)were measured, and the molecule vibrational temperatures of the spots and lines were calculated by the emission intensities. Based on the relative intensity of the line at 391.4 nm and the N2 line at 394.1 nm, the average electron energy of the spots and lines were investigated. The spectral lines of Ar I 763.26 nm ((2)P6-1Ss) and 772.13 nm ((2)P2-->1S3) were chosen to estimate electron excitation temperature of the spots and lines by the relative intensity ratio method. The molecule vibrational temperature, average electron energy, and electron excitation temperature of the lines are higher than those of the spots at the same pressure. The molecule vibrational temperature, average electron energy, and electron excitation temperature of the spots and lines decrease with pressure increasing from 40 to 60 kPa. PMID:24369624

Dong, Li-fang; Zhao, Long-hu; Wang, Yong-jie; Tong, Guo-liang; Di, Cong

2013-09-01

255

Optical emission characteristics of surface nanosecond pulsed dielectric barrier discharge plasma  

SciTech Connect

This paper reports an experimental study of the optical emission characteristics of the surface dielectric barrier discharge plasma excited by nanosecond pulsed voltage. N{sub 2}(C{sup 3}{Pi}{sub u}) rotational and vibrational temperatures are almost the same with upper electrode powered with positive polarity and lower electrode grounded or upper electrode grounded and lower electrode powered with positive polarity. While the electron temperature is 12% higher with upper electrode powered with positive polarity and lower electrode grounded. When the frequency is below 2000 Hz, there is almost no influence of applied voltage amplitude and frequency on N{sub 2}(C{sup 3}{Pi}{sub u}) rotational, vibrational temperature and electron temperature. As the pressure decreases from 760 Torr to 5 Torr, N{sub 2}(C{sup 3}{Pi}{sub u}) rotational temperature remains almost unchanged, while its vibrational temperature decreases initially and then increases. The discharge mode changes from a filamentary type to a glow type around 80 Torr. In the filamentary mode, the electron temperature remains almost unchanged. In the glow mode, the electron temperature increases while the pressure decreases.

Wu Yun; Li Yinghong; Jia Min; Song Huimin; Liang Hua [Science and Technology on Plasma Dynamics Lab, Aeronautics and Astronautics Engineering College, Air Force Engineering University, Xi'an 710038 (China)

2013-01-21

256

Quasistatic vs. Dynamic Modulus Measurements Of Plasma-Sprayed Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

Plasma-sprayed 8wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) have been demonstrated to exhibit nonlinear hysteretic elastic behavior by quasistatic cyclic compression and cylindrical punch indentation measurements. In particular, the instantaneous (tangential) elastic modulus increases with applied stress and exhibits significant hysteresis during cycling. Sound velocity (dynamic) measurements also show an increase in TBC modulus with applied compressive stress, but in contrast show no significant hysteresis for the modulus during cycling. The nonlinear elastic behavior of the TBCs evidenced by these tests is attributed to coating compaction and internal sliding. The differences between the quasistatic and dynamic measurements are explained by the relative absence of the effect of internal sliding in the dynamic modulus measurements. By incorporating short load reversals into the larger loading cycle and measuring the instantaneous modulus at the start of each load reversal, the effects of internal sliding can be substantially reduced in the quasistatic measurements, and the resulting modulus values show good agreement with the modulus values determined by dynamic sound velocity measurements.

Eldridge, J. I.; Morscher, G. N.; Choi, S. R.

2002-01-01

257

High Temperature Multilayer Environmental Barrier Coatings Deposited Via Plasma Spray-Physical Vapor Deposition  

NASA Technical Reports Server (NTRS)

Si-based ceramic matrix composites (CMCs) require environmental barrier coatings (EBCs) in combustion environments to avoid rapid material loss. Candidate EBC materials have use temperatures only marginally above current technology, but the addition of a columnar oxide topcoat can substantially increase the durability. Plasma Spray-Physical Vapor Deposition (PS-PVD) allows application of these multilayer EBCs in a single process. The PS-PVD technique is a unique method that combines conventional thermal spray and vapor phase methods, allowing for tailoring of thin, dense layers or columnar microstructures by varying deposition conditions. Multilayer coatings were deposited on CMC specimens and assessed for durability under high heat flux and load. Coated samples with surface temperatures ranging from 2400-2700F and 10 ksi loads using the high heat flux laser rigs at NASA Glenn. Coating morphology was characterized in the as-sprayed condition and after thermomechanical loading using electron microscopy and the phase structure was tracked using X-ray diffraction.

Harder, Bryan James; Zhu, Dongming; Schmitt, Michael P.; Wolfe, Douglas E.

2014-01-01

258

Altered antioxidant system stimulates dielectric barrier discharge plasma-induced cell death for solid tumor cell treatment.  

PubMed

This study reports the experimental findings and plasma delivery approach developed at the Plasma Bioscience Research Center, Korea for the assessment of antitumor activity of dielectric barrier discharge (DBD) for cancer treatment. Detailed investigation of biological effects occurring after atmospheric pressure non-thermal (APNT) plasma application during in vitro experiments revealed the role of reactive oxygen species (ROS) in modulation of the antioxidant defense system, cellular metabolic activity, and apoptosis induction in cancer cells. To understand basic cellular mechanisms, we investigated the effects of APNT DBD plasma on antioxidant defense against oxidative stress in various malignant cells as well as normal cells. T98G glioblastoma, SNU80 thyroid carcinoma, KB oral carcinoma and a non-malignant HEK293 embryonic human cell lines were treated with APNT DBD plasma and cellular effects due to reactive oxygen species were observed. Plasma significantly decreased the metabolic viability and clonogenicity of T98G, SNU80, KB and HEK293 cell lines. Enhanced ROS in the cells led to death via alteration of total antioxidant activity, and NADP+/NADPH and GSH/GSSG ratios 24 hours (h) post plasma treatment. This effect was confirmed by annexin V-FITC and propidium iodide staining. These consequences suggested that the failure of antioxidant defense machinery, with compromised redox status, might have led to sensitization of the malignant cells. These findings suggest a promising approach for solid tumor therapy by delivering a lethal dose of APNT plasma to tumor cells while sparing normal healthy tissues. PMID:25068311

Kaushik, Nagendra K; Kaushik, Neha; Park, Daehoon; Choi, Eun H

2014-01-01

259

Simulation of stresses and delamination in a plasma-sprayed thermal barrier system upon thermal cycling  

E-print Network

spray coatings; Thermal barrier systems; Computer simulation; Layered materials; Fatigue 1. Introduction resistance, a thermal barrier coating (TBC) that imparts the thermal insulation and a thermally-grown oxide blasting, before depositing the thermal barrier material. This contrasts with the preference for bond coat

Hutchinson, John W.

260

Propagation Structure of a 13.56MHz Asymmetric Surface Barrier Discharge Plasma in Atmospheric-Pressure Air  

Microsoft Academic Search

The global structure of a pulse-modulated 13.56-MHz asymmetric surface barrier discharge plasma has been investigated in atmospheric-pressure air. Intensified-CCD images were exposed over 20-µs radio-frequency pulses for three input power cases. The discharges do not appear to move significantly during the pulses, even though they are integrated over more than 200 oscillations of the applied voltage, and this allows for

James Dedrick; Rod W. Boswell; Pierre Audier; Dunpin Hong; Christine Charles

2011-01-01

261

Thermally Actuated Hydraulic Pumps  

NASA Technical Reports Server (NTRS)

Thermally actuated hydraulic pumps have been proposed for diverse applications in which direct electrical or mechanical actuation is undesirable and the relative slowness of thermal actuation can be tolerated. The proposed pumps would not contain any sliding (wearing) parts in their compressors and, hence, could have long operational lifetimes. The basic principle of a pump according to the proposal is to utilize the thermal expansion and contraction of a wax or other phase-change material in contact with a hydraulic fluid in a rigid chamber. Heating the chamber and its contents from below to above the melting temperature of the phase-change material would cause the material to expand significantly, thus causing a substantial increase in hydraulic pressure and/or a substantial displacement of hydraulic fluid out of the chamber. Similarly, cooling the chamber and its contents from above to below the melting temperature of the phase-change material would cause the material to contract significantly, thus causing a substantial decrease in hydraulic pressure and/or a substantial displacement of hydraulic fluid into the chamber. The displacement of the hydraulic fluid could be used to drive a piston. The figure illustrates a simple example of a hydraulic jack driven by a thermally actuated hydraulic pump. The pump chamber would be a cylinder containing encapsulated wax pellets and containing radial fins to facilitate transfer of heat to and from the wax. The plastic encapsulation would serve as an oil/wax barrier and the remaining interior space could be filled with hydraulic oil. A filter would retain the encapsulated wax particles in the pump chamber while allowing the hydraulic oil to flow into and out of the chamber. In one important class of potential applications, thermally actuated hydraulic pumps, exploiting vertical ocean temperature gradients for heating and cooling as needed, would be used to vary hydraulic pressures to control buoyancy in undersea research vessels. Heretofore, electrically actuated hydraulic pumps have been used for this purpose. By eliminating the demand for electrical energy for pumping, the use of the thermally actuated hydraulic pumps could prolong the intervals between battery charges, thus making it possible to greatly increase the durations of undersea exploratory missions.

Jones, Jack; Ross, Ronald; Chao, Yi

2008-01-01

262

Failure of thick, low density air plasma sprayed thermal barrier coatings  

NASA Astrophysics Data System (ADS)

This research was directed at developing fundamental understandings of the variables that influence the performance of air plasma sprayed (APS) yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC). Focus was placed on understanding how and why each variable influenced the performance of the TBC system along with how the individual variables interacted with one another. It includes research on the effect of surface roughness of NiCoCrAlY bond coats deposited by argon-shrouded plasma spraying, the interdiffusion behavior of bond coats coupled to commercial superalloys, and the microstructural and compositional control of APS topcoats to maximize the coating thicknesses that can be applied without spallation. The specimens used for this research were prepared by Praxair Surface Technologies and have been evaluated using cyclic oxidation and thermal shock tests. TBC performance was sensitive to bond coat roughness with the rougher bond coats having improved cyclic performance than the smoother bond coats. The explanation being the rough bond coat surface hindered the propagation of the delamination cracks. The failure mechanisms of the APS coatings were found to depend on a combination of the topcoat thickness, topcoat microstructure and the coefficient of thermal expansion (CTE) mismatch between the superalloy and topcoat. Thinner topcoats tended to fail at the topcoat/TGO interface due to bond coat oxidation whereas thicker topcoats failed within the topcoat due to the strain energy release rate of the thicker coating exceeding the fracture strength of the topcoat. Properties of free-standing high and conventional purity YSZ topcoats of both a lowdensity (LD) and dense-vertically fissure (DVF) microstructures were evaluated. The densification rate and phase evolution were sensitive to the YSZ purity and the starting microstructure. Increasing the impurity content resulted in enhanced sintering and phase decomposition rates, with the exception of the conventional-purity DVF which exhibited a density decrease during sintering. A combination of the DVF and LD topcoat microstructures (dual TBC) resulted in significant increase in cyclic durability. A 1275 mum thick dual TBC coating was found to have a comparable furnace cyclic life to that of a 100 im LD TBC.

Helminiak, Michael Aaron

263

Sintering and Fracture Behavior of Plasma-sprayed Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. There is a need to characterize the fundamental sintering and fracture behavior of the current ZrO2-(7 to 8)wt%Y2O3 coating, in order to fully take advantage of the coating capability. In addition, a thorough evaluation of the coating behavior and temperature limits will be useful for more accurately assessing the benefit gained from future advanced coating systems. In this study, the sintering behavior of plasma-sprayed ZrO2-8wt%Y2O3 coatings was systematically investigated as a function of temperature and time using a dilatometer in the temperature range of 1200-1500 C. The coating sintering kinetics obtained by dilatometry were compared with the coating thermal conductivity increase kinetics, determined by a steady-state laser heat-flux testing approach, under high temperature and thermal gradient sintering conditions. The mode I, mode II, and mixed mode I-mode II fracture behavior of as-processed and sintering-annealed coatings was determined in asymmetric flexure loading at ambient and elevated temperatures in order to evaluate the coating sintering effects on the fracture envelope of K(sub I) versus K(sub II). The coating thermal conductivity cyclic response associated with the interface delamination of the coating systems under simulated engine heat-flux conditions will be discussed in conjunction with the sintering and fracture testing results.

Zhu, Dongming; Choi, Sung R.; Miller, Robert A.

2004-01-01

264

Structural modification of the skin barrier by OH radicals: a reactive molecular dynamics study for plasma medicine  

NASA Astrophysics Data System (ADS)

While plasma treatment of skin diseases and wound healing has been proven highly effective, the underlying mechanisms, and more generally the effect of plasma radicals on skin tissue, are not yet completely understood. In this paper, we perform ReaxFF-based reactive molecular dynamics simulations to investigate the interaction of plasma generated OH radicals with a model system composed of free fatty acids, ceramides, and cholesterol molecules. This model system is an approximation of the upper layer of the skin (stratum corneum). All interaction mechanisms observed in our simulations are initiated by H-abstraction from one of the ceramides. This reaction, in turn, often starts a cascade of other reactions, which eventually lead to the formation of aldehydes, the dissociation of ceramides or the elimination of formaldehyde, and thus eventually to the degradation of the skin barrier function.

Van der Paal, J.; Verlackt, C. C.; Yusupov, M.; Neyts, E. C.; Bogaerts, A.

2015-04-01

265

Preferential killing of human lung cancer cell lines with mitochondrial dysfunction by nonthermal dielectric barrier discharge plasma.  

PubMed

The distinctive cellular and mitochondrial dysfunctions of two human lung cancer cell lines (H460 and HCC1588) from two human lung normal cell lines (MRC5 and L132) have been studied by dielectric barrier discharge (DBD) plasma treatment. This cytotoxicity is exposure time-dependent, which is strongly mediated by the large amount of H2O2 and NOx in culture media generated by DBD nonthermal plasma. It is found that the cell number of lung cancer cells has been reduced more than that of the lung normal cells. The mitochondrial vulnerability to reactive species in H460 may induce distinctively selective responses. Differential mitochondrial membrane potential decrease, mitochondrial enzymatic dysfunction, and mitochondrial morphological alteration are exhibited in two cell lines. These results suggest the nonthermal plasma treatment as an efficacious modality in lung cancer therapy. PMID:23703387

Panngom, K; Baik, K Y; Nam, M K; Han, J H; Rhim, H; Choi, E H

2013-01-01

266

Actuated atomizer  

NASA Technical Reports Server (NTRS)

An actuated atomizer is adapted for spray cooling or other applications wherein a well-developed, homogeneous and generally conical spray mist is required. The actuated atomizer includes an outer shell formed by an inner ring; an outer ring; an actuator insert and a cap. A nozzle framework is positioned within the actuator insert. A base of the nozzle framework defines swirl inlets, a swirl chamber and a swirl chamber. A nozzle insert defines a center inlet and feed ports. A spool is positioned within the coil housing, and carries the coil windings having a number of turns calculated to result in a magnetic field of sufficient strength to overcome the bias of the spring. A plunger moves in response to the magnetic field of the windings. A stop prevents the pintle from being withdrawn excessively. A pintle, positioned by the plunger, moves between first and second positions. In the first position, the head of the pintle blocks the discharge passage of the nozzle framework, thereby preventing the atomizer from discharging fluid. In the second position, the pintle is withdrawn from the swirl chamber, allowing the atomizer to release atomized fluid. A spring biases the pintle to block the discharge passage. The strength of the spring is overcome, however, by the magnetic field created by the windings positioned on the spool, which withdraws the plunger into the spool and further compresses the spring.

Tilton, Charles (Inventor); Weiler, Jeff (Inventor); Palmer, Randall (Inventor); Appel, Philip (Inventor)

2008-01-01

267

Analysis and experimental study on formation conditions of large-scale barrier-free diffuse atmospheric pressure air plasmas in repetitive pulse mode  

SciTech Connect

Atmospheric air diffuse plasmas have enormous application potential in various fields of science and technology. Without dielectric barrier, generating large-scale air diffuse plasmas is always a challenging issue. This paper discusses and analyses the formation mechanism of cold homogenous plasma. It is proposed that generating stable diffuse atmospheric plasmas in open air should meet the three conditions: high transient power with low average power, excitation in low average E-field with locally high E-field region, and multiple overlapping electron avalanches. Accordingly, an experimental configuration of generating large-scale barrier-free diffuse air plasmas is designed. Based on runaway electron theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as a discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform E-field are structured. Experimental results show that the volume-scaleable, barrier-free, homogeneous air non-thermal plasmas have been obtained between the gap spacing with the copper-wire electrodes. The area of air cold plasmas has been up to hundreds of square centimeters. The proposed formation conditions of large-scale barrier-free diffuse air plasmas are proved to be reasonable and feasible.

Li, Lee, E-mail: leeli@mail.hust.edu.cn; Liu, Lun; Liu, Yun-Long; Bin, Yu; Ge, Ya-Feng; Lin, Fo-Chang [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electric and Electronic Engineering, HuaZhong University of Science and Technology (HUST), Wuhan 430074 (China)

2014-01-14

268

Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures  

NASA Technical Reports Server (NTRS)

The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2- 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of K(sub I)/K(sub II) were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma-sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

2003-01-01

269

Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures  

NASA Technical Reports Server (NTRS)

The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2 - 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of KI/KII were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma- sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

2003-01-01

270

Measurement of turbulence decorrelation during transport barrier evolution in a high-temperature fusion plasma.  

PubMed

A low power polychromatic beam of microwaves is used to diagnose the behavior of turbulent fluctuations in the core of the JT-60U tokamak during the evolution of the internal transport barrier. A continuous reduction in the size of turbulent structures is observed concomitant with the reduction of the density scale length during the evolution of the internal transport barrier. The density correlation length decreases to the order of the ion gyroradius, in contrast with the much longer scale lengths observed earlier in the discharge, while the density fluctuation level remain similar to the level before transport barrier formation. PMID:15904000

Nazikian, R; Shinohara, K; Kramer, G J; Valeo, E; Hill, K; Hahm, T S; Rewoldt, G; Ide, S; Koide, Y; Oyama, Y; Shirai, H; Tang, W

2005-04-01

271

Measurement of Turbulence Decorrelation during Transport Barrier Evolution in a High Temperature Fusion Plasma  

SciTech Connect

A low power polychromatic beam of microwaves is used to diagnose the behavior of turbulent fluctuations in the core of the JT-60U tokamak during the evolution of the internal transport barrier. A continuous reduction in the size of turbulent structures is observed concomitant with the reduction of the density scale length during the evolution of the internal transport barrier. The density correlation length decreases to the order of the ion gyroradius, in contrast to the much longer scale lengths observed earlier in the discharge, while the density fluctuation level remain similar to the level before transport barrier formation.

R. Nazikian; K. Shinohara; G.J. Kramer; E. Valeo; K. Hill; T.S. Hahm; G. Rewoldt; S. Ide; Y. Koide; Y. Oyama; H. Shirai; W. Tang

2005-03-29

272

High-speed photographs of a dielectric barrier atmospheric pressure plasma jet  

Microsoft Academic Search

The propagation of an atmospheric pressure plasma jet (APPJ) is investigated by use of an intensified charge coupled device (ICCD) camera. It is shown that the APPJ is mainly an electrical phenomenon and not a flow related one. The jet does not consist of a voluminous plasma. Much more, the presented plasma source acts like a \\

M. Teschke; J. Kedzierski; E. G. Finantu-Dinu; D. Korzec; J. Engemann

2005-01-01

273

Characterisation of thermal barrier coatings and ultra high temperature composites deposited in a low pressure plasma reactor  

Microsoft Academic Search

A low pressure plasma process working at 600–800Pa was used to deposit from aqueous solution ZrO2–4mol% Y2O3 (Yttria partially stabilized Zirconia–YpSZ) layers and stacks of Ta2O5\\/YpSZ layers for use as thermal barrier coatings (TBC). The observation of the cross section revealed a high porosity. The thermal diffusivity of the layers (1×10?7m2s?1) was measured by a laser flash technique and compared

C. Fourmond; G. Da Rold; F. Rousseau; C. Guyon; S. Cavadias; D. Morvan; R. Mévrel

2011-01-01

274

Barriers to Antiretroviral Therapy Adherence and Plasma HIV RNA Suppression Among AIDS Clinical Trials Group Study Participants.  

PubMed

We conducted a secondary data analysis of 11 AIDS Clinical Trials Group (ACTG) studies to examine longitudinal associations between 14 self-reported antiretroviral therapy (ART) adherence barriers (at 12 weeks) and plasma HIV RNA (at 24 weeks) and to discern the relative importance of these barriers in explaining virologic detectability. Studies enrolled from 1997 to 2003 and concluded between 2002 and 2012. We included 1496 (54.2% of the original sample) with complete data. The most commonly selected barriers were "away from home" (21.9%), "simply forgot" (19.6%), "change in daily routine" (19.5%), and "fell asleep/slept through dosing time" (18.9%). In bivariate analyses, "too many pills to take" (OR=0.43, p<0.001), "wanted to avoid side effects" (OR=0.54, p=0.001), "felt drug was toxic/harmful" (OR=0.44, p<0.001), "felt sick or ill" (OR=0.49, p<0.001), "felt depressed/overwhelmed" (OR=0.58, p=0.004), and "problem taking pills at specified time" (OR=0.71, p=0.04) were associated with a lower odds of an undetectable HIV RNA. "Too many pills to take," "wanted to avoid side effects," "felt drug was toxic/harmful," "felt sick/ill,", and "felt depressed/overwhelmed" had the highest relative importance in explaining virologic detectability. "Simply forgot" was not associated with HIV RNA (OR=0.99, p=0.95) and was ninth in its relative importance. Adherence interventions should prioritize barriers with highest importance in explaining virologic outcomes rather than focusing on more commonly reported barriers. PMID:25615029

Saberi, Parya; Neilands, Torsten B; Vittinghoff, Eric; Johnson, Mallory O; Chesney, Margaret; Cohn, Susan E

2015-03-01

275

Electrorepulsive actuator  

NASA Technical Reports Server (NTRS)

The invention is a linear actuator that operates under the principle that like charges repel and opposite charges attract. The linear actuator consists of first and second pairs of spaced opposed conductors where one member of each pair of conductors is attached to a fixed member, and where the other member of each pair of conductors is attached to a movable member such as an elongated rod. The two pairs of spaced conductors may be provided in the form of two spacedly interwound helical vanes where the conductors are located on the opposite sides of the two helical vanes. One helical vane extends inwardly from a housing and the other helical vane extends outwardly from an elongated rod. The elongated rod may be caused to move linearly with respect to the housing by applying appropriate charges of like or opposite polarity to the electrical conductors on the helical vanes.

Collins, Earl R., Jr. (inventor); Curry, Kenneth C. (inventor)

1992-01-01

276

Modular droplet actuator drive  

NASA Technical Reports Server (NTRS)

A droplet actuator drive including a detection apparatus for sensing a property of a droplet on a droplet actuator; circuitry for controlling the detection apparatus electronically coupled to the detection apparatus; a droplet actuator cartridge connector arranged so that when a droplet actuator cartridge electronically is coupled thereto: the droplet actuator cartridge is aligned with the detection apparatus; and the detection apparatus can sense the property of the droplet on a droplet actuator; circuitry for controlling a droplet actuator coupled to the droplet actuator connector; and the droplet actuator circuitry may be coupled to a processor.

Pollack, Michael G. (Inventor); Paik, Philip (Inventor)

2011-01-01

277

1316 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 36, NO. 4, AUGUST 2008 Schlieren Imaging of Flow Actuation Produced  

E-print Network

1316 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 36, NO. 4, AUGUST 2008 Schlieren Imaging of Flow, and Laxminarayan L. Raja Abstract--Schlieren imaging of flow field structure produced by direct-current surface of a 30 wedge. Schlieren imaging reveals that for cathodes located upstream of the anodes, the discharge

Raja, Laxminarayan L.

278

Assessment of a dielectric barrier discharge plasma reactor at atmospheric pressure for the removal of bisphenol A and tributyltin.  

PubMed

The ability of a laboratory-scale dielectric barrier discharge (DBD) nonthermal plasma reactor at atmospheric pressure was assessed for the removal of bisphenol A (1 mg L(-1)) and tributyltin (10 mg L(-1)) from aqueous solutions. The elimination of both the compounds followed an exponential decay equation, and a first-order degradation kinetics was proposed for them (k = 0.662 min(-1) for bisphenol A and k = 0.800 min(-1) for tributyltin), reaching in both cases about 96% removal after 5-min treatment. Accordingly, plasma DBD reactors could be used as alternative advanced oxidation technologies for the removal of some persistent and toxic pollutants from water and wastewater, although further research should be performed to evaluate the effluent toxicity. PMID:24701940

Hijosa-Valsero, Maria; Molina, Ricardo; Bayona, Josep M

2014-01-01

279

Low Thermal Conductivity Yttria-Stabilized Zirconia Thermal Barrier Coatings Using the Solution Precursor Plasma Spray Process  

NASA Astrophysics Data System (ADS)

The primary function of thermal barrier coatings (TBCs) is to insulate the underlying metal from high temperature gases in gas turbine engines. As a consequence, low thermal conductivity and high durability are the primary properties of interest. In this work, the solution precursor plasma spray (SPPS) process was used to create layered porosity, called inter-pass boundaries, in yttria-stabilized zirconia (YSZ) TBCs. IPBs have been shown to be effective in reducing thermal conductivity. Optimization of the IPB microstructure by the SPPS process produced YSZ TBCs with a thermal conductivity of 0.6 W/mK, an approximately 50% reduction compared to standard air plasma sprayed (APS) coatings. In preliminary tests, SPPS YSZ with IPBs exhibited equal or greater furnace thermal cycles and erosion resistance compared to regular SPPS and commercially made APS YSZ TBCs.

Jordan, Eric H.; Jiang, Chen; Roth, Jeffrey; Gell, Maurice

2014-06-01

280

Functionalization of Hydrogen-free Diamond-like Carbon Films using Open-air Dielectric Barrier Discharge Atmospheric Plasma Treatments  

SciTech Connect

A dielectric barrier discharge (DBD) technique has been employed to produce uniform atmospheric plasmas of He and N2 gas mixtures in open air in order to functionalize the surface of filtered-arc deposited hydrogen-free diamond-like carbon (DLC) films. XPS measurements were carried out on both untreated and He/N2 DBD plasma treated DLC surfaces. Chemical states of the C 1s and N 1s peaks were collected and used to characterize the surface bonds. Contact angle measurements were also used to record the short- and long-term variations in wettability of treated and untreated DLC. In addition, cell viability tests were performed to determine the influence of various He/N2 atmospheric plasma treatments on the attachment of osteoblast MC3T3 cells. Current evidence shows the feasibility of atmospheric plasmas in producing long-lasting variations in the surface bonding and surface energy of hydrogen-free DLC and consequently the potential for this technique in the functionalization of DLC coated devices.

Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Instituto de Materiales de Madrid, C.S.I.C., Cantoblanco, 28049 Madrid, Spain; Instituto de Quimica-Fisica"Rocasolano"C.S.I.C., 28006 Madrid, Spain; Mahasarakham University, Mahasarakham 44150, Thailand; CASTI, CNR-INFM Regional Laboratory, L'Aquila 67100, Italy; SUNY Upstate Medical University, Syracuse, NY 13210, USA; Endrino, Jose; Endrino, J. L.; Marco, J. F.; Poolcharuansin, P.; Phani, A.R.; Allen, M.; Albella, J. M.; Anders, A.

2007-12-28

281

Improvement of plasma uniformity using ZnO-coated dielectric barrier discharge in open air  

NASA Astrophysics Data System (ADS)

The discharge behavior in atmospheric pressure dielectric barrier discharge using ZnO-coated dielectric layer is examined. ZnO thin film on alumina using rf magnetron sputter causes about a factor of a million higher surface conductivity than bare alumina surface. Experimental result shows that discharge uniformity is improved definitely in the case of ZnO-coated dielectric barrier discharge. Increase of surface conductivity stimulates charges to spread over the dielectric surface widely. These charge spreading enhances the uniformity and the stability of atmospheric pressure discharge in open air by initiation of consecutive streamers.

Choi, Jai Hyuk; Lee, Tae Il; Han, Inho; Oh, Byeong-Yun; Jeong, Min-Chang; Myoung, Jae-Min; Baik, Hong Koo; Song, Kie Moon; Lim, Yong Sik

2006-08-01

282

Microstreamer dynamics during plasma remediation of NO using atmospheric pressure dielectric barrier discharges  

E-print Network

Microstreamer dynamics during plasma remediation of NO using atmospheric pressure dielectric- ate toxins from atmospheric pressure gas streams. Plasma remediation is one technique which has been methods for the removal of oxides of nitrogen NxOy from atmospheric gas streams and among those techniques

Kushner, Mark

283

Mechanical properties and oxidation resistance of plasma-sprayed multilayered Al 2O 3\\/ZrO 2 thermal barrier coatings  

Microsoft Academic Search

Coupled with functionally graded materials (FGM) concept, Al2O3 was proposed as a potential candidate as an interlayer to improve the oxidation resistance of thermal barrier coating (TBC) system due to its low oxygen diffusivity. Plasma spray process was utilized to produce Al2O3\\/ZrO2 functionally graded thermal barrier coating (FG-TBC). This article discusses physical and mechanical properties, thermal behavior, and high-temperature oxidation

Andi M. Limarga; Sujanto Widjaja; Tick Hon Yip

2005-01-01

284

Mach 5 bow shock control by a nanosecond pulse surface dielectric barrier discharge  

Microsoft Academic Search

Bow shock perturbations in a Mach 5 air flow, produced by low-temperature, nanosecond pulse, and surface dielectric barrier discharge (DBD), are detected by phase-locked schlieren imaging. A diffuse nanosecond pulse discharge is generated in a DBD plasma actuator on a surface of a cylinder model placed in air flow in a small scale blow-down supersonic wind tunnel. Discharge energy coupled

M. Nishihara; K. Takashima; J. W. Rich; I. V. Adamovich

2011-01-01

285

Single-chamber plasma enhanced chemical vapor deposition of transparent organic/inorganic multilayer barrier coating at low temperature  

SciTech Connect

Deposition of organic/inorganic multilayers is usually carried out by two different process steps by two different deposition methods. A single-chamber process for the deposition of multilayer stacks can make the process and deposition system simpler. In this work, SiOCH and plasma-polymerized methylcyclohexane (pp-MCH) films and their multilayer stacks for application to transparent diffusion barrier coatings were deposited in a single low-temperature plasma enhanced chemical vapor deposition reactor using hexamethyldisilazane/N{sub 2}O/O{sub 2}/Ar and methylcyclohexane/Ar mixtures for SiOCH and pp-MCH layers, respectively. The deposition rates of the SiOCH and pp-MCH layers were increased with increasing the N{sub 2}O:O{sub 2} gas flow ratio and rf plasma power, respectively. Oxygen concentration in the SiOCH films was decreased and carbon and hydrogen incorporation was increased when increasing the N{sub 2}O:O{sub 2} gas flow ratio from 0:1 to 3:1. In this work, the water vapor transmission rate of polyester sulfone substrate could be reduced from a level of 50 (bare substrate) to 0.8 g/m{sup 2} day after deposition of a pp-MCH/SiOCH/pp-MCH multilayer coating.

Park, S. M.; Kim, D. J.; Kim, S. I.; Lee, N.-E. [School of Advanced Materials Science and Engineering, Center for Advanced Plasma Surface Technology, Sungkyunkwan University, Suwon, Kyunggi-do 440-746 (Korea, Republic of)

2008-07-15

286

Analysis of transient electron energy in a micro dielectric barrier discharge for a high performance plasma display panel  

SciTech Connect

We present here analysis of electron energy of a micro dielectric barrier discharge (micro-DBD) for alternating-current plasma display panel (ac-PDP) with Ne/Xe gas mixture by using the optical emission spectroscopy (OES). The OES method is quite useful to evaluate a variety of electron energy in a high pressure DBD ignited in a PDP small cell. Experiment shows that the ratio of Ne emission intensity (I{sub Ne}) relative to Xe emission intensity (I{sub Xe}) drastically decreases with time. This temporal profile is well consistent with dynamic behavior of electron temperature in a micro-DBD, calculated in one-dimensional fluid model. I{sub Ne}/I{sub Xe} also decreases with an increase in Xe gas pressure and a decrease in applied voltage especially in the initial stage of discharge, and these reflect the basic features of electron temperature in a micro-DBD. The influences of plasma parameters such as electron temperature on luminous efficacy are also theoretically analyzed using one-dimensional fluid model. The low electron temperature, which is attained at high Xe gas pressure, realizes the efficient Xe excitation for vacuum ultraviolet radiation. The high Xe-pressure condition also induces the rapid growth of discharge and consequent high plasma density, resulting in high electron heating efficiency.

Uchida, Giichiro; Kajiyama, Hiroshi; Shinoda, Tsutae [Graduate School of Advanced Science of Matter, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan); Uchida, Satoshi [Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachiouji 192-0397 (Japan)

2010-01-15

287

Low temperature plasma-enhanced atomic layer deposition of thin vanadium nitride layers for copper diffusion barriers  

SciTech Connect

Thin vanadium nitride (VN) layers were grown by atomic layer deposition using tetrakis(ethylmethylamino)vanadium and NH{sub 3} plasma at deposition temperatures between 70 Degree-Sign C and 150 Degree-Sign C on silicon substrates and polymer foil. X-ray photoelectron spectroscopy revealed a composition close to stoichiometric VN, while x-ray diffraction showed the {delta}-VN crystal structure. The resistivity was as low as 200 {mu}{Omega} cm for the as deposited films and further reduced to 143 {mu}{Omega} cm and 93 {mu}{Omega} cm by annealing in N{sub 2} and H{sub 2}/He/N{sub 2}, respectively. A 5 nm VN layer proved to be effective as a diffusion barrier for copper up to a temperature of 720 Degree-Sign C.

Rampelberg, Geert; Devloo-Casier, Kilian; Deduytsche, Davy; Detavernier, Christophe [Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, B-9000 Ghent (Belgium)] [Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, B-9000 Ghent (Belgium); Schaekers, Marc [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium)] [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Blasco, Nicolas [Air Liquide Electronics US, L.P., 46401 Landing Parkway, Fremont, California 94538 (United States)] [Air Liquide Electronics US, L.P., 46401 Landing Parkway, Fremont, California 94538 (United States)

2013-03-18

288

Destruction of Gaseous Styrene with a Low-Temperature Plasma Induced by a Tubular Multilayer Dielectric Barrier Discharge  

NASA Astrophysics Data System (ADS)

The destruction of gaseous styrene was studied using a low-temperature plasma induced by tubular multilayer dielectric barrier discharge (DBD). The results indicate that the applied voltage, gas flow rate, inlet styrene concentration and reactor configuration play important roles in styrene removal efficiency (?styrene) and energy yield (EY). Values of ?styrene and EY reached 96% and 15567 mg/kWh when the applied voltage, gas flow rate, inlet styrene concentration and layers of quartz tubes were set at 10.8 kV, 5.0 m/s, 229 mg/m3 and 5 layers, respectively. A qualitative analysis of the byproducts and a detailed discussion of the reaction mechanism are also presented. The results could facilitate industrial applications of the new DBD reactor for waste gas treatment.

Zhang, Jiahui; Liu, Juanjuan; Zhang, Renxi; Hou, Huiqi; Chen, Shanping; Zhang, Yi

2015-01-01

289

Flight control actuation system  

NASA Technical Reports Server (NTRS)

A flight control actuation system comprises a controller, electromechanical actuator and a pneumatic actuator. During normal operation, only the electromechanical actuator is needed to operate a flight control surface. When the electromechanical actuator load level exceeds 40 amps positive, the controller activates the pneumatic actuator to offset electromechanical actuator loads to assist the manipulation of flight control surfaces. The assistance from the pneumatic load assist actuator enables the use of an electromechanical actuator that is smaller in size and mass, requires less power, needs less cooling processes, achieves high output forces and adapts to electrical current variations. The flight control actuation system is adapted for aircraft, spacecraft, missiles, and other flight vehicles, especially flight vehicles that are large in size and travel at high velocities.

Wingett, Paul T. (Inventor); Gaines, Louie T. (Inventor); Evans, Paul S. (Inventor); Kern, James I. (Inventor)

2004-01-01

290

New ZrO2-Yb2O3 plasma-sprayed coatings for thermal barrier applications  

NASA Technical Reports Server (NTRS)

New thermal barrier coatings, whose compositions were chosen on the basis of a limited study of the ZrO2-Yb2O3 system, were evaluated by cyclic testing in a furnace at 1120 C. On Ni-16.2Cr-5.9Al-0.15Y bond coating, ZrO2-12.4Yb2O3, ZrO2-14.7Yb2O3 and ZrO2-17.4Yb2O3 coatings have respectively 60, 30, and 15 percent longer lives than the near-optimum ZrO2-6.1Y2O3 coating. On Ni-18.3Cr-6.4Al-0.22Yb coating, ZrO2-12.4Yb2O3 has about 40 percent longer life than the ZrO2-6.1Y2O3 coating. The optimum Yb2O3 concentration in ZrO2 at which the maximum life is obtained is believed to be between 12.4 and 14.7 wt pct. The ZrO2-Yb2O3 thermal barrier systems failed through the formation of a crack or cracks in the thermal barrier coating near the bond coating interface. As-received ZrO2-Yb2O3 plasma spray powders had a nonhomogeneous distribution of Yb2O3. Monoclinic, cubic, and tetragonal phases in addition to Zr3Yb4O12 and an unknown phase were present.

Stecura, Stephan

1987-01-01

291

An atmospheric pressure quasiuniform planar plasma jet generated by using a dielectric barrier configuration  

SciTech Connect

A stable nonthermal quasiuniform planar plasma jet, originating from a planar dielectric duct with a rectangular exit and issuing into ambient air at atmospheric pressure, is reported in the present work. Current-voltage characteristics, one discharge current pulse per sinusoidal half voltage cycle, show that the discharge is not filamentary. Its spatial uniformity in the transverse direction is shown to be excellent by monitoring optical emission spectra in the jet core region except jet boundaries. This is possibly resulted from high preionization in the upstream region, and it is a challenge to the traditional single streamer explanation for nonthermal plasma jets.

Li Qing [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Takana, Hidemasa; Nishiyama, Hideya [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Pu Yikang [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2011-06-13

292

An atmospheric pressure quasiuniform planar plasma jet generated by using a dielectric barrier configuration  

NASA Astrophysics Data System (ADS)

A stable nonthermal quasiuniform planar plasma jet, originating from a planar dielectric duct with a rectangular exit and issuing into ambient air at atmospheric pressure, is reported in the present work. Current-voltage characteristics, one discharge current pulse per sinusoidal half voltage cycle, show that the discharge is not filamentary. Its spatial uniformity in the transverse direction is shown to be excellent by monitoring optical emission spectra in the jet core region except jet boundaries. This is possibly resulted from high preionization in the upstream region, and it is a challenge to the traditional single streamer explanation for nonthermal plasma jets.

Li, Qing; Takana, Hidemasa; Pu, Yi-Kang; Nishiyama, Hideya

2011-06-01

293

Microprocessor controlled force actuator  

NASA Technical Reports Server (NTRS)

The mechanical and electrical design of a prototype force actuator for vibration control of large space structures (LSS) is described. The force actuator is an electromagnetic system that produces a force by reacting against a proof-mass. The actuator has two colocated sensors, a digital microcontroller, and a power amplifier. The total weight of actuator is .998 kg. The actuator has a steady state force output of approximately 2.75 N from approximately 2 Hz to well beyond 1000 Hz.

Zimmerman, D. C.; Inman, D. J.; Horner, G. C.

1986-01-01

294

Mixed Mode Fracture of Plasma Sprayed Thermal Barrier Coatings: Effects of Anisotropy and Heterogeneity  

NASA Technical Reports Server (NTRS)

The combined mode I-mode II fracture behavior of anisotropic ZrO2-8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of KI/KII were also determined. The mixed-mode fracture behavior of the microsplat coating material was modeled using Finite Element approach to account for anisotropy and micro cracked structures, and predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

Zhu, Dongming; Choi, Sung R.; Ghosn, Louis L.

2008-01-01

295

Is the mammalian cell plasma membrane a barrier to oxygen transport?  

Microsoft Academic Search

Oxygen transport in the Chinese hamster ovary (CHO) plasma membrane has been studied by observing the collision of molecular oxygen with nitroxide radical spin labels placed in the lipid bilayer portion of the membrane at various distances from the membrane surface using the long-pulse saturation- recovery electron spin resonance (ESR) technique. The collision rate was estimated for 5-, 12-, and

WITOLD K. SUBCZYNSKI; LARRY E. HOPWOOD; JAMES S. HYDE

1992-01-01

296

Damage Accumulation and Failure of Plasma-Sprayed Thermal Barrier Coatings under Thermal Gradient Cyclic Conditions  

NASA Technical Reports Server (NTRS)

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. A fundamental understanding of the sintering and thermal cycling induced delamination of thermal barrier coating systems under engine-like heat flux conditions will potentially help to improve the coating temperature capability. In this study, a test approach is established to emphasize the real-time monitoring and assessment of the coating thermal conductivity, which can initially increase under the steady-state high temperature thermal gradient test due to coating sintering, and later decrease under the thermal gradient cyclic test due to coating cracking and delamination. Thermal conductivity prediction models have been established for a ZrO2-(7- 8wt%)Y2O3 model coating system in terms of heat flux, time, and testing temperatures. The coating delamination accumulation is then assessed based on the observed thermal conductivity response under the combined steady-state and cyclic thermal gradient tests. The coating thermal gradient cycling associated delaminations and failure mechanisms under simulated engine heat-flux conditions will be discussed in conjunction with the coating sintering and fracture testing results.

Zhu, Dongming; Choi, Sung R.; Ghosn, Louis J.; Miller, rober A.

2005-01-01

297

Evaluation of the degradation of plasma sprayed thermal barrier coatings using nano-indentation.  

PubMed

In this study, the disk type of a thermal barrier coating (TBC) system for a gas turbine blade was isothermally aged at 1100 degrees C for various times up to 400 hours. For each aging condition, the thickness of the thermally grown oxide (TGO) was measured by optical microscope and mechanical properties such as the elastic modulus and hardness were measured by micro-indentation and nano-indentation on the cross-section of a coating specimen. In the case of micro-indentation, the mechanical properties of a Ni-base superalloy substrate and MCrAlY bond coat material did not significantly change with an increase in exposure time. In the case of nano-indentation, the gamma-Ni phase and beta-NiAl phase in the bond coat and top coat material show no significant change in their properties. However, the elastic modulus and the hardness of TGO show a remarkable decrease from 100 h to 200 h then remain nearly constant after 200 h due to the internal delamination of TBC. It has been confirmed that the nano-indentation technique is a very effective way to evaluate the degradation of a thermal barrier coating system. PMID:19908771

Kim, Dae-Jin; Cho, Sung-Keun; Choi, Jung-Hun; Koo, Jae-Mean; Seok, Chang-Sung; Kim, Moon-Young

2009-12-01

298

A low-power magnetic-field-assisted plasma jet generated by dielectric-barrier discharge enhanced direct-current glow discharge at atmospheric pressure  

SciTech Connect

A magnetic field is introduced to the dielectric-barrier discharge enhanced direct-current glow discharge for efficient plasma generation, with the discharge power of 2.7?W and total energy consumption reduced to 34% of the original. By spatially examining the emission spectra and plasma temperature, it is found that their peaks shift from edges to the center and the negative and anode glows merge into the positive column and disappear, accompanied by improvement of uniformity and chemical activity of the enlarged plasma. This lies in the enhancement of ionization in the curved and lengthened electron path and the dispersion of discharge domains.

Jiang, Weiman; Tang, Jie, E-mail: tangjie1979@opt.ac.cn; Wang, Yishan; Zhao, Wei [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an 710119 (China)] [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an 710119 (China); Duan, Yixiang [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an 710119 (China) [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an 710119 (China); Research Center of Analytical Instrumentation, Sichuan University, Chengdu 610064 (China)

2014-01-06

299

Plasma-assisted conversion of CO2 in a dielectric barrier discharge reactor: understanding the effect of packing materials  

NASA Astrophysics Data System (ADS)

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 two, which significantly contributes to the enhancement of CO2 conversion, CO yield, and energy efficiency of the plasma process. In addition, the highly energetic electrons (>3.0 eV) generated by the discharge could activate the BaTiO3 photocatalyst to form electron–hole pairs on its surface, which contributes to the enhanced conversion of CO2.

Mei, Danhua; Zhu, Xinbo; He, Ya-Ling; Yan, Joseph D.; Tu, Xin

2015-02-01

300

Effect of heat treatment on the thermal conductivity of plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

The effect of heat treatment on the thermal conductivity of plasma-sprayed Y2O3 stabilized ZrO2 (YSZ) and Al2O3 coatings was investigated. A heat treatment of 1300 °C in flowing argon for 50 h was found to significantly increase the\\u000a thermal conductivity of the coatings when compared to measurements in the assprayed condition. Transmission electron microscopy\\u000a (TEM) examination of the microstructures of

Rollie Dutton; Robert Wheeler; K. S. Ravichandran; K. An

2000-01-01

301

Study on the Generation Characteristics of Dielectric Barrier Discharge Plasmas on Water Surface  

NASA Astrophysics Data System (ADS)

A new contact glow discharge electrode on the surface of water was designed and employed in this study. Because of the strong field strength in the small air gap formed by the electrode and the water surface, glow discharge plasmas were generated and used to treat waste water. The electric field distribution of the designed electrode model was simulated by MAXWELL 3D® simulation software, and the discharge parameters were measured. Through a series of experiments, we investigated the impact of optimal designs, such as the dielectric of the electrode, immersion depths, and curvature radii of the electrode on the generation characteristics of plasmas. In addition, we designed an equipotential multi-electrode configuration to treat a Methyl Violet solution and observe the discoloration effect. The experimental and simulation results indicate that the designed electrodes can realize glow discharge with a relative low voltage, and the generated plasmas covered a large area and were in stable state. The efficiency of water treatment is improved and optimized with the designed electrodes.

Liu, Wenzheng; Li, Chuanhui

2014-01-01

302

Superconducting linear actuator  

NASA Technical Reports Server (NTRS)

Special actuators are needed to control the orientation of large structures in space-based precision pointing systems. Electromagnetic actuators that presently exist are too large in size and their bandwidth is too low. Hydraulic fluid actuation also presents problems for many space-based applications. Hydraulic oil can escape in space and contaminate the environment around the spacecraft. A research study was performed that selected an electrically-powered linear actuator that can be used to control the orientation of a large pointed structure. This research surveyed available products, analyzed the capabilities of conventional linear actuators, and designed a first-cut candidate superconducting linear actuator. The study first examined theoretical capabilities of electrical actuators and determined their problems with respect to the application and then determined if any presently available actuators or any modifications to available actuator designs would meet the required performance. The best actuator was then selected based on available design, modified design, or new design for this application. The last task was to proceed with a conceptual design. No commercially-available linear actuator or modification capable of meeting the specifications was found. A conventional moving-coil dc linear actuator would meet the specification, but the back-iron for this actuator would weigh approximately 12,000 lbs. A superconducting field coil, however, eliminates the need for back iron, resulting in an actuator weight of approximately 1000 lbs.

Johnson, Bruce; Hockney, Richard

1993-01-01

303

Iodine excitation in a dielectric barrier discharge micro-plasma and its determination by optical emission spectrometry.  

PubMed

A low temperature micro-plasma generated in a dielectric barrier discharge (DBD) was used as a radiation source for the excitation of iodine and its determination by vapor generation-optical emission spectrometry. A piece of ceramic tube served as an excitation chamber to provide a small gas path for introducing a helium stream to generate a DBD micro-plasma by using a neon power supply. Iodine was on-line vaporized by reaction of iodide in sample solution (or iodate pre-reduced to iodide by ascorbic acid) with H(2)O(2). The vapor was subsequently separated and transferred into the DBD excitation chamber by a helium stream for performing optical emission and detection at a 905 nm emission line. The emission spectra were measured with a QE65000 charge-coupled device spectrometer. A few important issues governing the performance of the entire system, e.g., selection of the analytical emission line, elimination of the DBD micro-plasma background variation and optimization of the experimental parameters, were investigated. With a sampling volume of 1.0 mL, a linear range of 0.1-10.0 mg L(-1) was obtained along with a detection limit of 0.03 mg L(-1). A precision of 2.1% RSD was achieved at the concentration level of 2 mg L(-1) iodine. The present system was applied in the determination of trace iodine in real samples, i.e., GBW10023 laver, table salt and cydiodine buccal tablets, giving rise to satisfactory results. PMID:23383405

Yu, Yong-Liang; Dou, Shuai; Chen, Ming-Li; Wang, Jian-Hua

2013-03-21

304

Finite Element Modeling of the Different Failure Mechanisms of a Plasma Sprayed Thermal Barrier Coatings System  

NASA Astrophysics Data System (ADS)

A new finite element model is used to investigate catastrophic failures of a thermal barrier coatings system due to crack propagation along the interfaces between the ceramic top-coat, thermally grown oxide, and bond-coat layers, as well as between the lamellas structure of the ceramic layer. The thermo-mechanical model is designed to take into account a non-homogenous temperature distribution and the effects of the residual stresses generated during the coating process. Crack propagation is simulated using the contact tool "Debond" present in the ABAQUS finite element code. Simulations are performed with a geometry corresponding to similar or dissimilar amplitudes of asperity, and for different thicknesses of the oxide layer. The numerical results have shown that crack evolution depends crucially on the ratio of the loading rate caused by growth and swelling of the oxide layer and also on the interface roughness obtained during the spraying of coatings.

Ranjbar-Far, M.; Absi, J.; Mariaux, G.

2012-12-01

305

Spatial and temporal evolution of microdischarges in Surface Dielectric Barrier Discharges for aeronautical applications plasmas  

NASA Astrophysics Data System (ADS)

Surface Dielectric Barrier Discharges have been proposed long ago as a tool to improve aerodynamics and flow performances. Such electrical discharges could be employed to energize the gas phase and to induce flows. The discharge itself consists of a large number of repetitions of single electric current pulses, with short duration and limited spatial extension filling the region near electrodes. The connection between such macroscopic effect and the properties of the single microdischarge events has been investigated. In particular we have measured the direction and the velocity of propagation of the ionization wave during the different phases of the voltage cycle. Light collected from different parts of the gap arrives at a photomultiplier tube with a delay proportional to the velocity of the ionization wave. The measured propagation velocity was estimated as about 220 km/s in the so called backward discharge phase.

Barni, R.; Biganzoli, I.; Riccardi, C.

2014-11-01

306

High Temperature Damping Behavior of Plasma-Sprayed Thermal Barrier and Protective Coatings  

NASA Technical Reports Server (NTRS)

A high temperature damping test apparatus has been developed using a high heat flux CO 2 laser rig in conjunction with a TIRA S540 25 kHz Shaker and Polytec OFV 5000 Vibrometer system. The test rig has been successfully used to determine the damping performance of metallic and ceramic protective coating systems at high temperature for turbine engine applications. The initial work has been primarily focused on the microstructure and processing effects on the coating temperature-dependence damping behavior. Advanced ceramic coatings, including multicomponent tetragonal and cubic phase thermal barrier coatings, along with composite bond coats, have also been investigated. The coating high temperature damping mechanisms will also be discussed.

Zhu, Dongming; Miller, Robert A.; Duffy, Kirsten P.; Ghosn, Louis J.

2010-01-01

307

Piston actuated nastic materials  

E-print Network

piston actuators distributed through the beam?s outer core provide the internal work needed. By actuating the piston elements in their axial direction, which is transverse to the beam?s central axis, the beam twists as desired. This study?s objective...?s shape. An actuator?s design depends on the application?s requirements and available methods for pressurizing the system internally. The actuator?s shape provides maximum work energy density in the axial direction. Nastic material?s concept...

Shah, Viral

2009-05-15

308

Properties of Plasma Enhanced Chemical Vapor Deposition Barrier Coatings and Encapsulated Polymer Solar Cells  

NASA Astrophysics Data System (ADS)

In this paper, we report silicon oxide coatings deposited by plasma enhanced chemical vapor deposition technology (PECVD) on 125 ?m polyethyleneterephthalate (PET) surfaces for the purpose of the shelf lifetime extension of sealed polymer solar cells. After optimization of the processing parameters, we achieved a water vapor transmission rate (WVTR) of ca. 10-3 g/m2/day with the oxygen transmission rate (OTR) less than 0.05 cc/m2/day, and succeeded in extending the shelf lifetime to about 400 h in encapsulated solar cells. And then the chemical structure of coatings related to the properties of encapsulated cell was investigated in detail.

Qi, Lei; Zhang, Chunmei; Chen, Qiang

2014-01-01

309

Enhancement of antioxidant effects of naringin after atmospheric pressure dielectric barrier discharge plasma treatment.  

PubMed

Naringin is the natural chief bitter flavonoid found in Citrus species. Herein, bitter naringin was treated with atmospheric pressure plasma to afford two new converted flavonoids, narinplasmins A (2) and B (3), along with the known compound, 2R-naringin. The structures of the two new naringin derivatives were elucidated on the basis of spectroscopic methods. The antioxidant activity of all isolates was evaluated based on 1,1-diphenyl-2-picrylhydrazyl and peroxynitrite (ONOO(-)) scavenging assays. The new flavanone glycoside 2 containing a methoxyalkyl group exhibited significantly improved antioxidant properties in these assays relative to the parent naringin. PMID:25677658

Kim, Tae Hoon; Jang, Soo Jeung; Chung, Hyung-Wook; Kim, Hyun-Joo; Yong, Hae In; Choe, Wonho; Jo, Cheorun

2015-03-15

310

Turbulent boundary-layer control with plasma spanwise travelling waves  

NASA Astrophysics Data System (ADS)

Arrays of dielectric-barrier-discharge plasma actuators have been designed to generate spanwise travelling waves in the turbulent boundary layer for possible skin-friction drag reductions. Particle image velocimetry was used to elucidate the modifications to turbulence structures created by the plasma spanwise travelling waves. It has been observed that the plasma spanwise travelling waves amalgamated streamwise vortices, lifting low-speed fluid from the near-wall region up and around the peripheries of their cores to form wide ribbons of low-speed streamwise velocity within the viscous sublayer.

Whalley, Richard D.; Choi, Kwing-So

2014-08-01

311

Uniaxial Electric Actuator  

NSDL National Science Digital Library

This site includes a cut-away animation of how a uniaxial electric actuator operates. Objective: Describe how the uniaxial electric actuator works. You can find this animation under the heading "Automation Technology."

312

Micromachined electrostatic vertical actuator  

DOEpatents

A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

Lee, Abraham P. (Walnut Creek, CA); Sommargren, Gary E. (Santa Cruz, CA); McConaghy, Charles F. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

1999-10-19

313

Failure during thermal cycling of plasma-sprayed thermal barrier coatings  

NASA Technical Reports Server (NTRS)

The thermal cycling behavior of plasma-sprayed ZrO2-12 wt pct Y2O3 coatings was studied. Coatings were produced with and without bond coats of Ni-Cr-Al-Zr and in some cases the substrates were heated to above the optimum temperature prior to spraying. The coatings (attached to the substrate) were thermal cycled to 1200 C and their cracking behavior was followed by acoustic emission (AE) techniques. It was possible to examine the failure mechanisms by statistical analysis of the AE data and to evaluate the influence of preheating and bond coating. It is shown that the AE spectrum changes when a bond coat is used because of the presence of microcracks which, in turn, dissipate energy and improve the coating integrity. The preheating effect is reflected by a decrease in the peak count rate and an increase in the temperature at which AE activity is initiated.

Berndt, C. C.; Herman, H.

1983-01-01

314

The algorithm and program complex for splitting on a parts the records of acoustic waves recorded during the work of plasma actuator flush-mounted in the model plane nozzle with the purpose of analyzing their robust spectral and correlation characteristics  

NASA Astrophysics Data System (ADS)

Currently acute problem of developing new technologies by reducing the noise of aircraft engines, including the directional impact on the noise on the basis of the interaction of plasma disturbances and sound generation pulsations. One of the devices built on this principle being developed in GPI RAS. They are plasma actuators (group of related to each other gaps, built on the perimeter of the nozzle) of various shapes and forms. In this paper an algorithm was developed which allows to separate impulses from the received experimental data, acquired during the work of plasma actuator flush-mounted in the model plane nozzle. The algorithm can be adjusted manually under a variety of situations (work of actuator in a nozzle with or without airflow, adjustment to different frequencies and pulse duration of the actuator). And program complex is developed on the basis of MatLab software, designed for building sustainable robust spectral and autocovariation functions of acoustic signals recorded during the experiments with the model of a nozzle with working actuator.

Chernousov, A. D.; Malakhov, D. V.; Skvortsova, N. N.

2014-03-01

315

Considerations for Contractile Electroactive Materials and Actuators  

SciTech Connect

Ras Labs produces contractile electroactive polymer (EAP) based materials and actuators that bend, swell, ripple, and contract (new development) with low electric input. In addition, Ras Labs produces EAP materials that quickly contract and expand, repeatedly, by reversing the polarity of the electric input, which can be cycled. This phenomenon was explored using molecular modeling, followed by experimentation. Applied voltage step functions were also investigated. High voltage steps followed by low voltage steps produced a larger contraction followed by a smaller contraction. Actuator control by simply adjusting the electric input is extremely useful for biomimetic applications. Muscles are able to partially contract. If muscles could only completely contract, nobody could hold an egg, for example, without breaking it. A combination of high and low voltage step functions could produce gross motor function and fine manipulation within the same actuator unit. Plasma treated electrodes with various geometries were investigated as a means of providing for more durable actuation.

Lenore Rasmussen, David Schramm, Paul Rasmussen, Kevin Mullaly, Ras Labs, LLC, Intelligent Materials for Prosthetics & Automation, Lewis D. Meixler, Daniel Pearlman and Alice Kirk

2011-05-23

316

Performance of Cobalt-Based Fischer-Tropsch Synthesis Catalysts Using Dielectric-Barrier Discharge Plasma as an Alternative to Thermal Calcination  

NASA Astrophysics Data System (ADS)

Co-based catalysts were prepared by using dielectric-barrier discharge (DBD) plasma as an alternative method to conventional thermal calcination. The characterization results of N2-physisorption, temperature programmed reduction (TPR), transmission electron microscope (TEM), and X-ray diffraction (XRD) indicated that the catalysts prepared by DBD plasma had a higher specific surface area, lower reduction temperature, smaller particle size and higher cobalt dispersion as compared to calcined catalysts. The DBD plasma method can prevent the sintering and aggregation of active particles on the support due to the decreased treatment time (0.5 h) at lower temperature compared to the longer thermal calcination at higher temperature (at 500° C for 5 h). As a result, the catalytic performance of the Fischer-Tropsch synthesis on DBD plasma treated Co/SiO2 catalyst showed an enhanced activity, C5+ selectivity and catalytic stability as compared to the conventional thermal calcined Co/SiO2 catalyst.

Bai, Suli; Huang, Chengdu; Lv, Jing; Li, Zhenhua

2012-01-01

317

Thermal Shock Behavior of Air Plasma Sprayed CoNiCrAlY/YSZ Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

The structural changes and failure mechanism of thermal barrier coatings (TBCs) during thermal shock cycling were investigated. TBCs consisting of CoNiCrAlY bond coat and partially yttria-stabilized zirconia (YSZ) top coat were deposited by atmospheric plasma spraying (APS) on a nickel-based alloy substrate and its thermal shock resistance performance was evaluated. TBCs were heated at 1100°C for 15 min followed by cold water quenching to ambient temperature. Microstructural evaluation and elemental analysis of TBCs were performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The crack features of YSZ coatings in TBCs during thermal shock cycling, including those of horizontal (parallel to the substrate) and vertical cracks (perpendicular to the substrate), were particularly investigated by means of SEM and image analysis. Results show that horizontal and vertical cracks have different influences on the thermal shock resistance of the coatings. Horizontal cracks that occur at the interface of YSZ and thermally growth oxidation (TGO) cause partial or large-area spalling of coatings. When vertical and horizontal cracks encounter, network segments are formed which lead to partial spalling of the coatings.

Liu, Zi Wei; Wu, Wei; Hua, Jia Jie; Lin, Chu Cheng; Zheng, Xue Bin; Zeng, Yi

2014-07-01

318

Thermal Aging Behavior of Axial Suspension Plasma-Sprayed Yttria-Stabilized Zirconia (YSZ) Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

7.5YSZ thermal barrier coatings (TBCs) were deposited onto the stainless steel substrates using axial suspension plasma spraying (ASPS). Free-standing coatings were isothermally aged in air from 1200 to 1600 °C for 24 h and at 1550 °C for 20 to 100 h, respectively. Thermal aging behavior such as phase composition, microstructure evolutions, grain growth, and mechanical properties for thermal-aged coatings were investigated. Results show that the as-sprayed metastable tetragonal (t'-ZrO2) phase decomposes into equilibrium tetragonal (t-ZrO2) and cubic (c-ZrO2) phases during high-temperature exposures. Upon further cooling, the c-ZrO2 may be retained or transform into another metastable tetragonal (t?-ZrO2) phase, and tetragonal ? monoclinic phase transformation occurred after 1550 °C/40 h aging treatment. The coating exhibits a unique structure with segmentation cracks and micro/nano-size grains, and the grains grow gradually with increasing aging temperature and time. In addition, the hardness ( H) and Young's modulus ( E) significantly increased as a function of temperature due to healing of pores or cracks and grain growth of the coating. And a nonmonotonic variation is found in the coatings thermal aged at a constant temperature (1550 °C) with prolonged time, this is a synergetic effect of coating sintering and m-ZrO2 phase formation.

Zhao, Yuexing; Wang, Liang; Yang, Jiasheng; Li, Dachuan; Zhong, Xinghua; Zhao, Huayu; Shao, Fang; Tao, Shunyan

2015-02-01

319

[Investigation of plasma parameters of the square pattern with two kinds of spatiotemporal symmetry in dielectric barrier discharge].  

PubMed

Two kinds of square patterns with different spatiotemporal symmetry were observed in dielectric barrier discharge, and their plasma parameters were measured by using optical emission spectra. It was found that the spatiotemporal symmetry of the square pattern at lower gas pressure is different from the one at higher gas pressure. Six spectral lines in the emission spectrum of the N2 second positive band were chosen to estimate the vibrational temperature, and the ratio of I391.4/I394.1 was used to represent the average electron energy. The excitation temperature was determined by the ratio of I763.2/I772.1. Furthermore, the width and shift of Ar I 696.54 nm were used to estimate the electron density. The results show that the vibrational temperature, excitation temperature and electron energy of the square pattern at lower gas pressure are higher than those at higher gas pressure, while the electron density is lower than that at higher gas pressure. PMID:25269284

Wang, Yong-Jie; Dong, Li-Fang; Zhao, Long-Hu; Liu, Wei-Bo; Zhang, Xin-Pu; Zhang, Chao

2014-07-01

320

Metal carbonyl vapor generation coupled with dielectric barrier discharge to avoid plasma quench for optical emission spectrometry.  

PubMed

The scope of dielectric barrier discharge (DBD) microplasma as a radiation source for optical emission spectrometry (OES) is extended by nickel carbonyl vapor generation. We proved that metal carbonyl completely avoids the extinguishing of plasma, and it is much more suitable for matching the DBD excitation and OES detection with respect to significant DBD quenching by concomitant hydrogen when hydride generation is used. A concentric quartz UV reactor allows sample solution to flow through the central channel wherein to efficiently receive the uniformly distributed UV irradiation in the confined cylindrical space between the concentric tubes, which facilitates effective carbonyl generation in a nickel solution. The carbonyl is transferred into the DBD excitation chamber by an argon stream for nickel excitation, and the characteristic emission of nickel at 232.0 nm is detected by a charge-coupled device (CCD) spectrometer. A 1.0 mL sample solution results in a linear range of 5-100 ?g L(-1) along with a detection limit of 1.3 ?g L(-1) and a precision of 2.4% RSD at 50 ?g L(-1). The present DBD-OES system is validated by nickel in certified reference materials. PMID:25511607

Cai, Yi; Li, Shao-Hua; Dou, Shuai; Yu, Yong-Liang; Wang, Jian-Hua

2015-01-20

321

Effects of driving voltage frequency on the discharge characteristics of atmospheric dielectric-barrier-discharge plasma jet  

NASA Astrophysics Data System (ADS)

We present here the analysis of the discharge characteristics of a He dielectric-barrier-discharge (DBD) plasma jet operated in the frequency range of 0.6 to 30 kHz under an open-air condition. Discharge strength is sensitive to driving voltage frequency, and an increasing driving frequency induces a weak pulse discharge with a small plume length. We also performed time-resolved optical emission measurements in a transient pulse discharge driven by various voltage frequencies. A strong optical emission from O atoms is observed near the quartz-tube outlet at a low driving voltage frequency of about 5 kHz, where more than 90% of the total O emission intensity is detected in the after-discharge period. The observations indicate that low-frequency discharge operation can generate a large number of reactive excited O atoms near the quartz-tube outlet, and this is ascribed to the chemical reactions in the after-discharge period.

Uchida, Giichiro; Takenaka, Kosuke; Kawabata, Kazufumi; Miyazaki, Atsushi; Setsuhara, Yuichi

2014-11-01

322

Nanosecond barrier discharge in a krypton/helium mixture containing mercury dibromide: Optical emission and plasma parameters  

NASA Astrophysics Data System (ADS)

Spectral and electrical characteristics of atmospheric-pressure nanosecond barrier discharge plasma in a HgBr2/Kr/He mixture have been investigated. The discharge was initiated by positive 10-kV voltage pulses with a rise time of 4 ns and a half-amplitude duration of 28 ns. Emission from exciplex HgBr ( B 2?{1/2/+} - X 2?{1/2/+}) and KrBr ( B 2?{1/2/+} - X 2?{1/2/+}, C3/2-A?1/2, D1/2-A?1/2) molecules have been studied. From the time evolution of the B-X transition spectra of the HgBr molecule (502 nm) and KrBr molecule (207 nm), a mechanism of the formation of the exciplex molecules in the nanosecond discharge has been deduced. The distributions of the energies and rates of the processes responsible for emission from HgBr and KrBr molecules have been analyzed by numerically solving the Boltzmann equation for the electron distribution function. Experiments have confirmed the possibility of optimizing the voltage supply pulse for maximizing the efficiency of simultaneous emission in the UV and visible (green) spectral ranges from atmospheric-pressure discharge in the HgBr2/Kr/He mixture.

Malinina, A. A.; Starikovskaya, S. M.; Malinin, A. N.

2015-01-01

323

In Situ Observation of Creep and Fatigue Failure Behavior for Plasma-Sprayed Thermal Barrier Coating Systems  

NASA Astrophysics Data System (ADS)

In order to investigate crack initiation sites and the crack propagation behavior in connection with the microstructure of thermal barrier coating (TBC) systems under creep and fatigue loadings, the failure behavior was observed in situ for plasma-sprayed TBC systems by optical microscopy, as a first step for elucidating the thermo-mechanical failure mechanism. Two types of TBC systems with differing top-coat (TC) microstructures were prepared by changing the processing conditions. The mechanical failure behavior of TBC system was found to depend strongly on the loading conditions. Under static creep loading, many segmentation cracks in the TC widened with increasing creep strain in the substrate. However, the propagation of these cracks into the bond-coat (BC) and alloy substrate was prevented due to the stress relief induced by plastic flow in the BC layer at elevated temperatures. As a result, the TBC system exhibited typical creep rupture behavior with nucleation and coalescence of microcracks in the alloy substrate interior regardless of the TC microstructure. Under dynamic fatigue loading, on the other hand, many fatigue cracks initiated not only from the tips of segmentation cracks in the TC layer but also from the TC/BC interface. Furthermore, it was found that the fatigue cracks propagated into the BC and alloy substrate even at elevated temperatures above the ductile-brittle transition temperature of the BC; the fatigue failure behavior under dynamic fatigue loading was dependent on the TC microstructure and the properties of the TC/BC interface.

Takahashi, Satoru; Harada, Yoshio

324

Analysis of Plasma-Sprayed Thermal Barrier Coatings With Homogeneous and Heterogeneous Bond Coats Under Spatially Uniform Cyclic Thermal Loading  

NASA Technical Reports Server (NTRS)

This report summarizes the results of a numerical investigation into the spallation mechanism in plasma-sprayed thermal barrier coatings observed under spatially-uniform cyclic thermal loading. The analysis focuses on the evolution of local stress and inelastic strain fields in the vicinity of the rough top/bond coat interface during thermal cycling, and how these fields are influenced by the presence of an oxide film and spatially uniform and graded distributions of alumina particles in the metallic bond coat aimed at reducing the top/bond coat thermal expansion mismatch. The impact of these factors on the potential growth of a local horizontal delamination at the rough interface's crest is included. The analysis is conducted using the Higher-Order Theory for Functionally Graded Materials with creep/relaxation constituent modeling capabilities. For two-phase bond coat microstructures, both the actual and homogenized properties are employed in the analysis. The results reveal the important contributions of both the normal and shear stress components to the delamination growth potential in the presence of an oxide film, and suggest mixed-mode crack propagation. The use of bond coats with uniform or graded microstructures is shown to increase the potential for delamination growth by increasing the magnitude of the crack-tip shear stress component.

Arnold, Steven M.; Pindera, Marek-Jerzy; Aboudi, Jacob

2003-01-01

325

Dielectric barrier discharge plasma treatment on E. coli: Influence of CH4/N2, O2, N2/O2, N2, and Ar gases  

NASA Astrophysics Data System (ADS)

Atmospheric pressure dielectric barrier discharge (DBD) plasma has been employed on Gram-negative bacteria, Escherichia coli BL21. Treatment was carried out using plasma generated with different compositions of gases: CH4/N2 (1:2), O2, N2/O2 (1:1), N2, and Ar, and by varying plasma power and treatment time. E. coli cells were exposed under the DBD plasma in triplicates, and their surviving numbers were observed in terms of colony forming units. It has been observed that the CH4/N2 plasma exhibits relatively higher sterilization property toward E. coli compared to plasma generated by using O2, N2/O2, N2, and Ar gas mixtures. The time to kill up to 90% of the initial population of the E. coli cells was found to be about 2-3 min for CH4/N2 and O2 gas mixture DBD plasma. A prolongation of treatment time and an increase in the dissipated power significantly improved the E. coli killing efficiency of the atmospheric pressure DBD plasma.

Majumdar, Abhijit; Singh, Rajesh Kumar; Palm, Gottfried J.; Hippler, Rainer

2009-10-01

326

Plasma Separation Process: Betacell (BCELL) code: User's manual. [Bipolar barrier junction  

SciTech Connect

The emergence of clearly defined applications for (small or large) amounts of long-life and reliable power sources has given the design and production of betavoltaic systems a new life. Moreover, because of the availability of the plasma separation program, (PSP) at TRW, it is now possible to separate the most desirable radioisotopes for betacell power generating devices. A computer code, named BCELL, has been developed to model the betavoltaic concept by utilizing the available up-to-date source/cell parameters. In this program, attempts have been made to determine the betacell energy device maximum efficiency, degradation due to the emitting source radiation and source/cell lifetime power reduction processes. Additionally, comparison is made between the Schottky and PN junction devices for betacell battery design purposes. Certain computer code runs have been made to determine the JV distribution function and the upper limit of the betacell generated power for specified energy sources. A Ni beta emitting radioisotope was used for the energy source and certain semiconductors were used for the converter subsystem of the betacell system. Some results for a Promethium source are also given here for comparison. 16 refs.

Taherzadeh, M.

1987-11-13

327

Bimorphic polymeric photomechanical actuator  

NASA Technical Reports Server (NTRS)

A bimorphic polymeric photomechanical actuator, in one embodiment using polyvinylidene fluoride (PVDF) as a photosensitive body, transmitting light over fiber optic cables, and controlling the shape and pulse duration of the light pulse to control movement of the actuator. Multiple light beams are utilized to generate different ranges of motion for the actuator from a single photomechanical body and alternative designs use multiple light beams and multiple photomechanical bodies to provide controlled movement. Actuator movement using one or more ranges of motion is utilized to control motion to position an actuating element in three dimensional space.

Sarkisov, Sergey S. (Inventor); Curley, Michael J. (Inventor); Adamovsky, Grigory (Inventor); Sarkisov, Jr., Sergey S. (Inventor); Fields, Aisha B. (Inventor)

2006-01-01

328

Omnidirectional Actuator Handle  

NASA Technical Reports Server (NTRS)

Proposed actuator handle comprises two normally concentric rings, cables, and pulleys arranged such that relative displacement of rings from concentricity results in pulling of cable and consequent actuation of associated mechanism. Unlike conventional actuator handles like levers on farm implements, actuated from one or two directions only, proposed handle reached from almost any direction and actuated by pulling or pushing inner ring in any direction with respect to outer ring. Flanges installed on inner ring to cover gap between inner ring and housing to prevent clothing from being caught.

Moetteli, John B.

1995-01-01

329

Deposition of Ethylene-Hexafluoropropene Gradient Plasma-Copolymer Using Dielectric Barrier Discharge Reactor at Atmospheric Pressure: Application to Release Coatings on Pressure-Sensitive Tape  

Microsoft Academic Search

Plasma-polymerized hexafluoropropene (PPHFP) film deposited using a dielectric barrier discharge reactor at atmospheric pressure had low enough adhesive strength, 22.2 Nm-1, for use as a release coating of pressure-sensitive adhesive tapes, but the bond strength between PPHFP film and a poly (ethylene terephthalate) (PET) substrate film was slightly weak: some part of the PPHFP deposits could be peeled from the

Kunihito Tanaka; Masuhiro Kogoma

2003-01-01

330

Structural studies of plasma polymers obtained in pulsed dielectric barrier discharge of TEOS and HMDSO on nylon 66 fabrics  

Microsoft Academic Search

Plasma-enhanced chemical vapour deposition of two monomers, namely tetraethylorthosilicate (TEOS) and hexamethyldisiloxane (HMDSO) was carried out on nylon 66 fabrics. Pulsed discharge at variable duty cycle was used for analysing the effect of different pulse parameters on the structural properties of plasma polymers. HMDSO plasma yielded more hydrophobic surfaces than TEOS plasma. The surface chemical composition of plasma-treated fabrics was

Kiran H. Kale; Shital S. Palaskar

2012-01-01

331

Treatment surfaces with atomic oxygen excited in dielectric barrier discharge plasma of O{sub 2} admixed to N{sub 2}  

SciTech Connect

This paper describes the increase in surface energy of substrates by their treatment with gas composition generated in plasmas of DBD (Dielectric Barrier Discharge) in O2 admixed with N2. Operating gas dissociation and excitation was occurred in plasmas developed in two types of reactors of capacitively-coupled dielectric barrier configurations: coaxial cylindrical, and flat rectangular. The coaxial cylindrical type comprised an inner cylindrical electrode encapsulated in a ceramic sheath installed coaxially inside a cylindrical ceramic (quartz) tube passing through an annular outer electrode. Components of the flat rectangular type were a flat ceramic tube of a narrow rectangular cross section supplied with two flat electrodes mounted against one another outside of the long parallel walls of this tube. The operating gas, mixture of N{sub 2} and O{sub 2}, was flowing in a completely insulated discharge gap formed between insulated electrodes of the devices with an average velocity of gas inlet of about 7 to 9 m/s. Dielectric barrier discharge plasma was excited in the operating gaps with a bipolar pulse voltage of about 6 kV for 2 ms at 50 kHz repetition rate applied to the electrodes of the coaxial device, and of about 14 kV for 7 ms at 30 kHz repetition rate for the flat linear device. A lifetime of excited to the 2s{sup 2}2p{sup 4}({sup 1}S{sub 0}) state in DBD plasma and streaming to the surfaces with a gas flow atomic oxygen, responsible presumably for treating surfaces, exceeded 10 ms in certain cases, that simplified its separation from DBD plasma and delivery to substrates. As it was found in particular, surfaces of glass and some of polymers revealed significant enhancement in wettability after treatment.

Shun'ko, E. V.; Belkin, V. S. [WINTEK Electro-Optics Corporation, 1665 Highland Dr., Ann Arbor, Michigan 48108 (United States)

2012-06-15

332

Microstructure and properties of in-flight rare-earth doped thermal barrier coatings prepared by suspension plasma spray  

NASA Astrophysics Data System (ADS)

Thermal barrier coatings with lower thermal conductivity improve the efficiency of gas turbine engines by allowing higher operating temperatures. Recent studies were shown that coatings containing a pair of rare-earth oxides with equal molar ratio have lower thermal conductivity and improved sintering resistance compared to the undoped 4-4.5 mol.% yttria-stabilized zirconia (YSZ). In the present work, rare-earth doped coatings were fabricated via suspension plasma spray by spraying YSZ powder-ethanol suspensions that contained dissolved rare-earth nitrates. The compositions of the coatings determined by inductively coupled plasma mass spectroscopy verified that 68 +/- 8% of the rare-earth nitrates added into the suspension was incorporated into the coatings. Two coatings containing different concentrations of the same dopant pair (Nd2O3/Yb2O3), and three coatings having similar concentrations of different dopant pairs (Nd 2O3/Yb2O3, Nd2O3/Gd 2O3, and Gd2O3/Yb2O 3) were produced and compared. The effect of dopant concentration and dopant pair type on the microstructure and properties of the coatings in the as-sprayed and heat treated conditions were investigated using XRD, SEM, TEM, STEM-EDX, and the laser flash method. The cross-sectional morphology of all coatings displayed columnar structure. The porosity content of the coating was found to increase with increasing dopant concentration, but did not significantly change with dopant pairs. Similarly, increasing the Nd2O3/Yb2O 3 concentration lowered the thermal conductivity of the as-sprayed coatings. Although the effect of changing dopant pair type is not as significant as increasing the dopant concentration, the coating that contained Gd2O 3/Yb2O3 exhibited the lowest conductivity compared to coatings that had other dopant pairs. Thermal conductivity measurement performed on the heat treated coatings indicated a larger conductivity increase for the rare-earth doped coatings. A detailed study on the microstructural change of the coatings after various heat treatments at 1200°C and 1300°C showed evidence of crack healing and grain growth. Comparison between the rare-earth dopant distribution of a selected coating before and after a 1300°C/50 hr heat treatment suggests the possibility of dopant rearrangement, which can further increase the thermal conductivity. An explanation on the difference in the properties of the rare-earth doped coatings produced by SPS and conventional processes was discussed.

Gong, Stephanie

333

Determination of Scattering and Absorption Coefficients for Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."

Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.

2009-01-01

334

MEMS fluidic actuator  

DOEpatents

The present invention comprises a novel, lightweight, massively parallel device comprising microelectromechanical (MEMS) fluidic actuators, to reconfigure the profile, of a surface. Each microfluidic actuator comprises an independent bladder that can act as both a sensor and an actuator. A MEMS sensor, and a MEMS valve within each microfluidic actuator, operate cooperatively to monitor the fluid within each bladder, and regulate the flow of the fluid entering and exiting each bladder. When adjacently spaced in a array, microfluidic actuators can create arbitrary surface profiles in response to a change in the operating environment of the surface. In an embodiment of the invention, the profile of an airfoil is controlled by independent extension and contraction of a plurality of actuators, that operate to displace a compliant cover.

Kholwadwala, Deepesh K. (Albuquerque, NM); Johnston, Gabriel A. (Trophy Club, TX); Rohrer, Brandon R. (Albuquerque, NM); Galambos, Paul C. (Albuquerque, NM); Okandan, Murat (Albuquerque, NM)

2007-07-24

335

Flexible thin-layer dielectric barrier discharge plasma treatment of pork butt and beef loin: effects on pathogen inactivation and meat-quality attributes.  

PubMed

The effects of a flexible thin-layer dielectric barrier discharge (DBD) plasma system using a sealed package on microbial inactivation and quality attributes of fresh pork and beef were tested. Following a 10-min treatment, the microbial-load reductions of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium were 2.04, 2.54, and 2.68 Log CFU/g in pork-butt samples and 1.90, 2.57, and 2.58 Log CFU/g in beef-loin samples, respectively. Colorimetric analysis showed that DBD-plasma treatment did not significantly affect L* values (lightness) of pork and beef samples, but lowered a* values (redness) significantly after 5- and 7.5-min exposures. The plasma treatment significantly influenced lipid oxidation only after a 10-min exposure. The texture of both types of meat was unaffected by plasma treatment. All sensory parameters of treated and non-treated samples were comparable except for taste, which was negatively influenced by the plasma treatment (P < 0.05). This thin-layer DBD-plasma system can be applied to inactivate foodborne pathogens. The observed minor deterioration of meat quality might be prevented by the use of hurdle technology. PMID:25475266

Jayasena, Dinesh D; Kim, Hyun Joo; Yong, Hae In; Park, Sanghoo; Kim, Kijung; Choe, Wonho; Jo, Cheorun

2015-04-01

336

Modeling piezoelectric actuators  

Microsoft Academic Search

The piezoelectric actuator (PEA) is a well-known device for managing extremely small displacements in the range from 10 pm to 100 ?m. When developing a control system for a piezo-actuated positioning mechanism, the actuator dynamics have to be taken into account. An electromechanical piezo model, based on physical principles, is presented in this paper. In this model, a first-order differential

H. J. M. T. S. Adriaens; W. L. De Koning; R. Banning

2000-01-01

337

Remote switch actuator  

DOEpatents

The invention provides a device and method for actuating electrical switches remotely. The device is removably attached to the switch and is actuated through the transfer of a user's force. The user is able to remain physically removed from the switch site obviating need for protective equipment. The device and method allow rapid, safe actuation of high-voltage or high-current carrying electrical switches or circuit breakers.

Haas, Edwin Gerard; Beauman, Ronald; Palo, Jr., Stefan

2013-01-29

338

Hydrostatic actuation in MEMS  

NASA Astrophysics Data System (ADS)

Hydrostatic actuation is a novel method of actuation in Micro Electro Mechanical Systems (MEMS) and provides advantages over other actuation techniques in current use. Hydrostatic actuation utilises a contained pressurised medium to straighten a bent hollow beam, similar to the Bourdon tube used to measure pressure in the macro world. Research has commenced at RMIT University to design and fabricate a microgripper prototype to validate this work. To simplify the design of this microgripper a virtual prototype has been initiated. This paper looks at the work carried out and verification of this virtual prototype using mathematical and finite element modelling. Further work to be undertaken will also be discussed.

Mutzenich, Simon; Vinay, Thurai; Rosengarten, Gary

2002-11-01

339

Improved Electrohydraulic Linear Actuators  

NASA Technical Reports Server (NTRS)

A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to many industrial uses, such as steam turbines, process control valves, dampers, motion control, etc. The advantageous features of the improved electrohydraulic linear actuators are best described with respect to shortcomings of prior electrohydraulic linear actuators that the improved ones are intended to supplant. The flow of hydraulic fluid to the two ports of the actuator cylinder is controlled by a servo valve that is controlled by a signal from a servo amplifier that, in turn, receives an analog position-command signal (a current having a value between 4 and 20 mA) from a supervisory control system of the facility. As the position command changes, the servo valve shifts, causing a greater flow of hydraulic fluid to one side of the cylinder and thereby causing the actuator piston to move to extend or retract a piston rod from the actuator body. A linear variable differential transformer (LVDT) directly linked to the piston provides a position-feedback signal, which is compared with the position-command signal in the servo amplifier. When the position-feedback and position-command signals match, the servo valve moves to its null position, in which it holds the actuator piston at a steady position.

Hamtil, James

2004-01-01

340

Destruction of volatile organic compounds in air by a superimposed barrier discharge plasma reactor and activated carbon filter hybrid system  

Microsoft Academic Search

The superimposed barrier discharge and activated carbon filter hybrid systems are used to remove toluene and trichloro-ethylene (TCE) from air streams. The superimposed barrier discharge consists of silent and surface discharges. Experiments are conducted for the gas flow rate from 1 to 10 L\\/min., applied power from 0 to 7 W and toluene and TCE initial concentration from 0 to

K. Urashima; J. S. Chang; T. Ito

1997-01-01

341

Cost-effective actuator tester  

NASA Technical Reports Server (NTRS)

Group of preprogrammed plug-in cards and control module converts breadboard control electronics of actuator assembly to actuator tester. System utilizes electronic control, and hydraulic systems of breadboard actuator into which it is installed.

Kopp, G. F.; Wyllie, C. E.

1977-01-01

342

Carbon nanotube array actuators  

NASA Astrophysics Data System (ADS)

Experimental investigations of highly vertically aligned carbon nanotubes (CNTs), also known as CNT-arrays, are the main focus of this paper. The free strain as result of an active material behavior is analyzed via a novel experimental setup. Previous test experiences of papers made of randomly oriented CNTs, also called Bucky-papers, reveal comparably low free strain. The anisotropy of aligned CNTs promises better performance. Via synthesis techniques like chemical vapor deposition (CVD) or plasma enhanced CVD (PECVD), highly aligned arrays of multi-walled carbon nanotubes (MWCNTs) are synthesized. Two different types of CNT-arrays are analyzed, morphologically first, and optically tested for their active characteristics afterwards. One type of the analyzed arrays features tube lengths of 750-2000 ?m with a large variety of diameters between 20 and 50 nm and a wave-like CNT-shape. The second type features a maximum, almost uniform, length of 12 ?m and a constant diameter of 50 nm. Different CNT-lengths and array types are tested due to their active behavior. As result of the presented tests, it is reported that the quality of orientation is the most decisive property for excellent active behavior. Due to their alignment, CNT-arrays feature the opportunity to clarify the actuation mechanism of architectures made of CNTs.

Geier, S.; Mahrholz, T.; Wierach, P.; Sinapius, M.

2013-09-01

343

Dielectric barrier discharge micro-plasma emission source for the determination of lead in water samples by tungsten coil electro-thermal vaporization.  

PubMed

In this study, a fast and simple approach to directly determinate lead in water samples by a low power dielectric barrier discharge (DBD) excitation source was developed using tungsten coil electro-thermal vaporization (WC ETV) for liquid microsample introduction. A 20 ?L sample was dropped onto the WC, and then the sample went through the drying, pyrolysis, subsequently the analyte was vaporized and swept directly into the dielectric barrier discharge micro-plasma for emission, and the whole process took only 3 min. The effects of operating parameters such as plasma gas flow rate, plasma input voltage, pyrolysis current, vaporization current and interferences from concomitant elements were investigated. Under the optimal conditions, the limit of detection (LODs, 3?) was calculated to be 7.7 ?g L(-1). Repeatability, expressed as the relative standard deviation of the spectral peak height, was 4.6% (n=11) for 0.1 mg L(-1) lead standard solution. The proposed method was successfully applied to the determinations of Pb in water samples. PMID:25476285

Zheng, Hongtao; Ma, Jingzhi; Zhu, Zhenli; Tang, Zhiyong; Hu, Shenghong

2015-01-01

344

AlN/GaN double-barrier resonant tunneling diodes grown by rf-plasma-assisted molecular-beam epitaxy  

NASA Astrophysics Data System (ADS)

AlN/GaN double-barrier resonant tunneling diodes (DB-RTDs) were fabricated on (0001) Al2O3 substrates by molecular-beam epitaxy, using a rf-plasma nitrogen source. The AlN/GaN DB-RTDs were designed to have a 3-ML-thick GaN quantum well and 4-ML-thick AlN barrier layers sandwiched by Si-doped n-type GaN contact layers. The current-voltage characteristics of mesa diode samples showed clear negative differential resistance (NDR) at room temperature. The NDR was observed at 2.4 V with a peak current of 2.9 mA, which corresponds to 180 A/cm2. A peak-to-valley current ratio as high as 32 was obtained.

Kikuchi, Akihiko; Bannai, Ryo; Kishino, Katsumi; Lee, Chia-Ming; Chyi, Jen-Inn

2002-08-01

345

The interaction between plasma filaments in dielectric barrier discharges and liquid covered wounds: electric fields delivered to model platelets and cells  

NASA Astrophysics Data System (ADS)

The treatment of wounds by atmospheric pressure plasmas in the context of plasma medicine typically proceeds through a liquid layer covering exposed cells. The wounds and their liquid covering often have irregular shapes with electrical properties (i.e. conductivity and permittivities) that may differ not only from wound-to-wound but also for a single wound as healing proceeds. The differing shapes and electrical properties extend into the liquid within the wound that typically contains cellular materials such as blood platelets. The plasma, wound, liquid and intra-liquid cellular components represent an interacting system of mutual dependence. In this paper, we discuss the results from a computational investigation of the treatment of small, liquid-covered wounds by filamentary dielectric barrier discharges. The sizes of the wounds are of the order of the plasma filaments and the liquid within the wound, an approximation of blood serum, contains idealized blood platelets. We find that the electrical properties of a wound can have significant effects on the spreading of the plasma on its surface by virtue of the deformation of the vacuum electric fields due to the shape, the effective capacitance of the wound and the discontinuities in electrical permittivity. This in turn effects the penetration of the electric field to cells under the liquid. The orientation and permittivity of the platelets relative to the liquid determines the electric fields that may stimulate the platelets.

Babaeva, Natalia Yu; Tian, Wei; Kushner, Mark J.

2014-06-01

346

High Displacement Actuator (HDA)  

NASA Technical Reports Server (NTRS)

Positioned beneath a fiber optic displacement sensor is the new High Displacement Actuator (HDA) developed by scientists at NASA Langley Research Center. The high displacement actuator significantly improves the state-of-the-art piezoelectric technology and provides inordinately large mechanical displacements. The HDA is also applicable to high performance sensor applications such as microphones, non-destructive testing, and vibration sensing. Test results on the high displacement actuators show displacements 50 times greater than device thickness and several orders of magnitude increase over state-of-the-art devices. The actuators can be used from DC to frequencies in excess of a megahertz and with displacement loads exceeding 10 Kg (25 lbs). The actuator can also produce displacements comparable to state-of-the-art devices with an order reduction in operating voltage. The high displacement actuators are reliable. They have been laboratory tested to beyond 400 million cycles without failure. The highly efficient electrically- insulated actuator can be operated in a vacuum, in liquids, and in the upper atmosphere. The HDA is versatile and rugged allowing for use in harsh environments for hundreds of commercial applications. In many device applications the high displacement actuator wafer itself can serve the function of several components, e.g. in simple pumps it take the place of piston, piston-rod and crank. The HDA is a packaged flexible laminate of pre-stressed polymeric materials and a piezoelectric ceramic that form a robust, low cost, user friendly device.

1994-01-01

347

Self-actuated device  

DOEpatents

A self-actuated device, of particular use as a valve or an orifice for nuclear reactor fuel and blanket assemblies, in which a gas produced by a neutron induced nuclear reaction gradually accumulates as a function of neutron fluence. The gas pressure increase occasioned by such accumulation of gas is used to actuate the device.

Hecht, Samuel L. (Richland, WA)

1984-01-01

348

Multiple current peaks in room-temperature atmospheric pressure homogenous dielectric barrier discharge plasma excited by high-voltage tunable nanosecond pulse in air  

SciTech Connect

Room temperature homogenous dielectric barrier discharge plasma with high instantaneous energy efficiency is acquired by using nanosecond pulse voltage with 20-200 ns tunable pulse width. Increasing the voltage pulse width can lead to the generation of regular and stable multiple current peaks in each discharge sequence. When the voltage pulse width is 200 ns, more than 5 organized current peaks can be observed under 26 kV peak voltage. Investigation also shows that the organized multiple current peaks only appear in homogenous discharge mode. When the discharge is filament mode, organized multiple current peaks are replaced by chaotic filament current peaks.

Yang, De-Zheng; Wang, Wen-Chun; Zhang, Shuai; Tang, Kai; Liu, Zhi-jie; Wang, Sen [Key Lab of Materials Modification, Dalian University of Technology, Ministry of Education, Dalian 116024 (China)] [Key Lab of Materials Modification, Dalian University of Technology, Ministry of Education, Dalian 116024 (China)

2013-05-13

349

The effect of sintering and CMAS on the stability of plasma-sprayed zirconia thermal barrier coatings  

E-print Network

State of the art thermal barrier coatings (TBCs) for gas turbine applications comprise (7 wt.%) yttria partially stabilized zirconia (7YSZ). 7YSZ offers a range of attractive functional properties – low thermal conductivity, high thermal expansion...

Shinozaki, Maya

2013-07-09

350

Cryogenic Piezoelectric Actuator  

NASA Technical Reports Server (NTRS)

In this paper, PMN-PT single crystal piezoelectric stack actuators and flextensional actuators were designed, prototyped and characterized for space optics applications. Single crystal stack actuators with footprint of 10 mm x10 mm and the height of 50 mm were assembled using 10 mm x10mm x0.15mm PMN-PT plates. These actuators showed stroke > 65 - 85 microns at 150 V at room temperature, and > 30 microns stroke at 77 K. Flextensional actuators with dimension of 10mm x 5 mm x 7.6 mm showed stroke of >50 microns at room temperature at driving voltage of 150 V. A flextensional stack actuator with dimension of 10 mm x 5 mm x 47 mm showed stroke of approx. 285 microns at 150 V at room temperature and > 100 microns at 77K under driving of 150 V should be expected. The large cryogenic stroke and high precision of these actuators are promising for cryogenic optics applications.

Jiang, Xiaoning; Cook, William B.; Hackenberger, Wesley S.

2009-01-01

351

Electro-Mechanical Actuators  

NASA Technical Reports Server (NTRS)

The electro-mechanical actuator, a new electronics technology, is an electronic system that provides the force needed to move valves that control the flow of propellant to the engine. It is proving to be advantageous for the main propulsion system plarned for a second generation reusable launch vehicle. Hydraulic actuators have been used successfully in rocket propulsion systems. However, they can leak when high pressure is exerted on such a fluid-filled hydraulic system. Also, hydraulic systems require significant maintenance and support equipment. The electro-mechanical actuator is proving to be low maintenance and the system weighs less than a hydraulic system. The electronic controller is a separate unit powering the actuator. Each actuator has its own control box. If a problem is detected, it can be replaced by simply removing one defective unit. The hydraulic systems must sustain significant hydraulic pressures in a rocket engine regardless of demand. The electro-mechanical actuator utilizes power only when needed. A goal of the Second Generation Reusable Launch Vehicle Program is to substantially improve safety and reliability while reducing the high cost of space travel. The electro-mechanical actuator was developed by the Propulsion Projects Office of the Second Generation Reusable Launch Vehicle Program at the Marshall Space Flight Center.

2001-01-01

352

Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses  

SciTech Connect

This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18?×?15?×?15?cm{sup 3}, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

Teng, Yun; Li, Lee, E-mail: leeli@mail.hust.edu.cn; Liu, Yun-Long; Liu, Lun; Liu, Minghai [State Key Laboratory of AEET, School of Electric and Electronic Engineering, HuaZhong University of Science and Technology (HUST), Wuhan 430074 (China)

2014-10-15

353

Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses  

NASA Astrophysics Data System (ADS)

This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm3, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

Teng, Yun; Li, Lee; Liu, Yun-Long; Liu, Lun; Liu, Minghai

2014-10-01

354

Considerations for Contractile Electroactive Materials and Actuators  

SciTech Connect

Ras Labs produces electroactive polymer (EAP) based materials and actuators that bend, swell, ripple and now contract (new development) with low electric input. This is an important attribute because of the ability of contraction to produce life-like motion. The mechanism of contraction is not well understood. Radionuclide-labeled experiments were conducted to follow the movement of electrolytes and water in these EAPs when activated. Extreme temperature experiments were performed on the contractile EAPs with very favorable results. One of the biggest challenges in developing these actuators, however, is the electrode-EAP interface because of the pronounced movement of the EAP. Plasma treatments of metallic electrodes were investigated in order to improve the attachment of the embedded electrodes to the EAP material. Surface analysis, adhesive testing, and mechanical testing were conducted to test metal surfaces and metal-polymer interfaces. The nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.

Rasmussen, Lenore; Erickson, Carl J.; Meixler, Lewis D.; Ascione, George; Gentile, Charles A.; Tilson, Carl; Bernasek, Stephen L.; Abelev, Esta

2010-02-19

355

Furnace Cyclic Behavior of Plasma-Sprayed Zirconia-Yttria and Multi-Component Rare Earth Oxide Doped Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

Ceramic thermal barrier coatings will play an increasingly important role in advanced gas turbine engines because of their ability to enable further increases in engine temperatures. However, the coating performance and durability become a major concern under the increasingly harsh thermal cycling conditions. Advanced zirconia- and hafnia-based cluster oxide thermal barrier coatings with lower thermal conductivity and improved thermal stability are being developed using a high-heat-flux laser-rig based test approach. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of numerous candidate coating materials was carried out using conventional furnace cyclic tests. In this paper, furnace thermal cyclic behavior of the advanced plasma-sprayed zirconia-yttria-based thermal barrier coatings that were co-doped with multi-component rare earth oxides was investigated at 1163 C using 45 min hot cycles. The ceramic coating failure mechanisms were studied by using scanning electron microscopy combined with X-ray diffraction phase analysis after the furnace tests. The coating cyclic lifetime will be discussed in relation to coating phase structures, total dopant concentrations, and other properties.

Zhu, Dongming; Nesbitt, James A.; McCue, Terry R.; Barrett, Charles A.; Miller, Robert A.

2002-01-01

356

Muscle Motion Solenoid Actuator  

NASA Astrophysics Data System (ADS)

It is one of our dreams to mechanically recover the lost body for damaged humans. Realistic humanoid robots composed of such machines require muscle motion actuators controlled by all pulling actions. Particularly, antagonistic pairs of bi-articular muscles are very important in animal's motions. A system of actuators is proposed using the electromagnetic force of the solenoids with the abilities of the stroke length over 10 cm and the strength about 20 N, which are needed to move the real human arm. The devised actuators are based on developments of recent modern electro-magnetic materials, where old time materials can not give such possibility. Composite actuators are controlled by a high ability computer and software making genuine motions.

Obata, Shuji

357

Magnetically Actuated Seal  

NASA Technical Reports Server (NTRS)

This invention is a magnetically actuated seal in which either a single electromagnet, or multiple electromagnets, are used to control the seal's position. This system can either be an open/ close type of system or an actively controlled system.

Pinera, Alex

2013-01-01

358

Rotary Series Elastic Actuator  

NASA Technical Reports Server (NTRS)

A rotary actuator assembly is provided for actuation of an upper arm assembly for a dexterous humanoid robot. The upper arm assembly for the humanoid robot includes a plurality of arm support frames each defining an axis. A plurality of rotary actuator assemblies are each mounted to one of the plurality of arm support frames about the respective axes. Each rotary actuator assembly includes a motor mounted about the respective axis, a gear drive rotatably connected to the motor, and a torsion spring. The torsion spring has a spring input that is rotatably connected to an output of the gear drive and a spring output that is connected to an output for the joint.

Ihrke, Chris A. (Inventor); Mehling, Joshua S. (Inventor); Parsons, Adam H. (Inventor); Griffith, Bryan Kristian (Inventor); Radford, Nicolaus A. (Inventor); Permenter, Frank Noble (Inventor); Davis, Donald R. (Inventor); Ambrose, Robert O. (Inventor); Junkin, Lucien Q. (Inventor)

2013-01-01

359

Vortical flow control on a conical fore body cross section using an array of pulsed dc actuators  

NASA Astrophysics Data System (ADS)

Flow control on a conical fore body cross section of an aircraft is studied using plasma discharge by considering the neutral gas flow at 17.5 deg angle of attack. The equations governing the motion of electrons, ions as well as Poisson's equation are solved together with Navier-Stokes and energy equation for neutrals to study flow control. A single barrier discharge actuator is not sufficient to control the flow on the entire length of the fore body. An arrangement of multiple electrodes powered with pulsed dc voltage has been suggested for controlling such flows. The effects of joule heating of plasma, dielectric heating, and electrodynamic force have been investigated, separately and then combined on flow control. It is found that joule heating results in high temperature of the dielectric surface, however; electrodynamic force contributes prominently to flow control. A three-dimensional analysis is necessary to validate results with experiments.

Singh, Kunwar Pal; Roy, Subrata

2007-05-01

360

Piezoelectrically actuated tunable capacitor  

Microsoft Academic Search

This paper describes the design, fabrication, and characterization of the first MEMS piezoelectric tunable capacitors employing zinc oxide (ZnO) actuation. Relatively simple design rules for the device-structure optimization for largest deflection are shown from simulation results based on theoretical equations. The ZnO-actuated tunable capacitors are accordingly designed and fabricated with both surface and bulk micromachining techniques. Through the surface micromachining

Chuang-Yuan Lee; Eun Sok Kim

2006-01-01

361

Electrostatic Linear Actuator  

NASA Technical Reports Server (NTRS)

Electrically charged helices attract or repel each other. Proposed electrostatic linear actuator made with intertwined dual helices, which holds charge-bearing surfaces. Dual-helix configuration provides relatively large unbroken facing charged surfaces (relatively large electrostatic force) within small volume. Inner helix slides axially in outer helix in response to voltages applied to conductors. Spiral form also makes components more rigid. Actuator conceived to have few moving parts and to be operable after long intervals of inactivity.

Collins, Earl R., Jr.; Curry, Kenneth C.

1990-01-01

362

Inertial Linear Actuators  

NASA Technical Reports Server (NTRS)

Inertial linear actuators developed to suppress residual accelerations of nominally stationary or steadily moving platforms. Function like long-stroke version of voice coil in conventional loudspeaker, with superimposed linear variable-differential transformer. Basic concept also applicable to suppression of vibrations of terrestrial platforms. For example, laboratory table equipped with such actuators plus suitable vibration sensors and control circuits made to vibrate much less in presence of seismic, vehicular, and other environmental vibrational disturbances.

Laughlin, Darren

1995-01-01

363

Combustion powered linear actuator  

DOEpatents

The present invention provides robotic vehicles having wheeled and hopping mobilities that are capable of traversing (e.g. by hopping over) obstacles that are large in size relative to the robot and, are capable of operation in unpredictable terrain over long range. The present invention further provides combustion powered linear actuators, which can include latching mechanisms to facilitate pressurized fueling of the actuators, as can be used to provide wheeled vehicles with a hopping mobility.

Fischer, Gary J. (Albuquerque, NM)

2007-09-04

364

Development of ionic polymer actuator arrays  

NASA Astrophysics Data System (ADS)

Ionic polymer metal composites (IPMC) are bending type actuators which are soft, and show large deformation at low voltage. This work explored the creation of IPMC actuator arrays to take advantage of the unique features of IPMCs, in applications such as pump and valve arrays for micro-fluidic devices, microwave switch arrays etc. In the design of the arrays, the concept of integration is key, to make the actuator array reliable, compact and scalable. The arrays are created as a single physical part, by electrode patterning on the ionic polymer and material engineering. Gold chemical plating was used to create the flexible electrodes with large capacitance on Flemion and Nafion. Patterning was done with masks created in various ways. Nafion, because of its high flexibility, can be made into diaphragm actuators with very good dynamic properties. Flemion in cantilever mode was found to generate large forces without relaxation, a key feature for the design of IPMC switches and valves. A new electrode fabrication technique was developed based on plasma polymerization on an amine monomer on the membrane and subsequent self assembly of Au colloids. A 14-micron thick Flemion sample with 10 layers of 13nm diameter Au colloids showed actuation at +/-1.5V. The demonstration of actuation of IPMC with self-assembled electrodes is a milestone for the future application of IPMC to MEMS. Finally the actuation mechanisms of Nafion and Flemion were modeled. Two dominant contributions in the actuation of IPMC were considered: electro-osmosis, and equilibrium volume which can change upon cation redistribution. A large volume transition upon pH change was observed for Flemion, whereas Nafion proved indifferent to pH. It is proposed that Flemion is generally weakly ionized and has many ionic groups in acid form. Upon cation redistribution, this structure is perturbed and the ionization increases at the cathode side because of the increase in sodium concentration, leading to an increase in equilibrium volume at the cathode and permanent bending. Nafion is always fully ionized and therefore does not show such transition. Its actuation is believed to be dominated by electro-osmosis through its highly swollen network of ionic clusters and channels.

Le Guilly, Marie

365

Compact electrostatic comb actuator  

DOEpatents

A compact electrostatic comb actuator is disclosed for microelectromechanical (MEM) applications. The actuator is based upon a plurality of meshed electrostatic combs, some of which are stationary and others of which are moveable. One or more restoring springs are fabricated within an outline of the electrostatic combs (i.e. superposed with the moveable electrostatic combs) to considerably reduce the space required for the actuator. Additionally, a truss structure is provided to support the moveable electrostatic combs and prevent bending or distortion of these combs due to unbalanced electrostatic forces or external loading. The truss structure formed about the moveable electrostatic combs allows the spacing between the interdigitated fingers of the combs to be reduced to about one micron or less, thereby substantially increasing the number of active fingers which can be provided in a given area. Finally, electrostatic shields can be used in the actuator to substantially reduce unwanted electrostatic fields to further improve performance of the device. As a result, the compact electrostatic comb actuator of the present invention occupies only a fraction of the space required for conventional electrostatic comb actuators, while providing a substantial increase in the available drive force (up to one-hundred times).

Rodgers, M. Steven (Albuquerque, NM); Burg, Michael S. (Albuquerque, NM); Jensen, Brian D. (Albuquerque, NM); Miller, Samuel L. (Albuquerque, NM); Barnes, Stephen M. (Albuquerque, NM)

2000-01-01

366

Actuation of polypyrrole nanowires  

NASA Astrophysics Data System (ADS)

Nanoscale actuators are essential components of the NEMS (nanoelectromechanical systems) and nanorobots of the future, and are expected to become a major area of development within nanotechnology. This paper demonstrates for the first time that individual polypyrrole (PPy) nanowires with diameters under 100 nm exhibit actuation behavior, and therefore can potentially be used for constructing nanoscale actuators. PPy is an electroactive polymer which can change volume on the basis of its oxidation state. PPy-based macroscale and microscale actuators have been demonstrated, but their nanoscale counterparts have not been realized until now. The research reported here answers positively the fundamental question of whether PPy wires still exhibit useful volume changes at the nanoscale. Nanowires with a 50 nm diameter and a length of approximately 6 µm, are fabricated by chemical polymerization using track-etched polycarbonate membranes as templates. Their actuation response as a function of oxidation state is investigated by electrochemical AFM (atomic force microscopy). An estimate of the minimum actuation force is made, based on the displacement of the AFM cantilever.

Lee, Alexander S.; Peteu, Serban F.; Ly, James V.; Requicha, Aristides A. G.; Thompson, Mark E.; Zhou, Chongwu

2008-04-01

367

Actuation of polypyrrole nanowires.  

PubMed

Nanoscale actuators are essential components of the NEMS (nanoelectromechanical systems) and nanorobots of the future, and are expected to become a major area of development within nanotechnology. This paper demonstrates for the first time that individual polypyrrole (PPy) nanowires with diameters under 100 nm exhibit actuation behavior, and therefore can potentially be used for constructing nanoscale actuators. PPy is an electroactive polymer which can change volume on the basis of its oxidation state. PPy-based macroscale and microscale actuators have been demonstrated, but their nanoscale counterparts have not been realized until now. The research reported here answers positively the fundamental question of whether PPy wires still exhibit useful volume changes at the nanoscale. Nanowires with a 50 nm diameter and a length of approximately 6 µm, are fabricated by chemical polymerization using track-etched polycarbonate membranes as templates. Their actuation response as a function of oxidation state is investigated by electrochemical AFM (atomic force microscopy). An estimate of the minimum actuation force is made, based on the displacement of the AFM cantilever. PMID:21825643

Lee, Alexander S; Peteu, Serban F; Ly, James V; Requicha, Aristides A G; Thompson, Mark E; Zhou, Chongwu

2008-04-23

368

GEC Student Award for Excellence Finalist: Interaction of Non-Thermal Dielectric Barrier Discharge Plasma with DNA inside Cells  

NASA Astrophysics Data System (ADS)

Direct non-thermal plasma is now being widely considered for various medical applications, viz; cancer treatment, coagulation, wound healing. However, the understanding of the interaction between non-thermal plasma and cells is lacking. Here we study the possibility that effects of the plasma treatment can penetrate though cellular membranes without destroying them. One of the most important of such effects to investigate would be DNA double strand breaks (DSB's) since these are some of the important events in a cell's life cycle. We measured DNA DSB's in mammalian cells using immunofluorescence and western blots. Hydrogen peroxide treatment was used as a positive control since it is known to induce massive DNA double strand breaks. The results indicate that short (5 seconds) direct plasma treatment at low power (0.2 W/cm^2) does produce DNA DSB's in mammalian cells. This means that somehow plasma penetrates inside the cells. Several questions arise about what is the mechanism of penetration and do the cells repair the DNA DSB's. We show that the cells do repair the DNA DSB's produced by short exposure of low power plasma. Although the detailed mechanisms are being investigated we confirmed that reactive oxygen species mediate interaction between plasma and DNA.

Kalghatgi, Sameer; Kelly, Crystal; Fridman, Gregory; Clifford-Azizkhan, Jane; Fridman, Alexander; Friedman, Gary

2008-10-01

369

Retractable barrier strip  

DOEpatents

A portable barrier strip is described having retractable tire-puncture means for puncturing a vehicle tire. The tire-puncture means, such as spikes, have an armed position for puncturing a tire and a retracted position for not puncturing a tire. The strip comprises a plurality of barrier blocks having the tire-puncture means removably disposed in a shaft that is rotatably disposed in each barrier block. The shaft removably and pivotally interconnects the plurality of barrier blocks. Actuation cables cause the shaft to rotate the tire-puncture means to the armed position for puncturing a vehicle tire and to the retracted position for not puncturing the tire. Each tire-puncture means is received in a hollow-bed portion of its respective barrier block when in the retracted position. The barrier strip rests in its deployed position and substantially motionless as a tire rolls thereon and over. The strip is rolled up for retrieval, portability, and storage purposes, and extended and unrolled in its deployed position for use. 13 figs.

Marts, D.J.; Barker, S.G.; McQueen, M.A.

1996-04-16

370

Cold vapor generation of Zn based on dielectric barrier discharge induced plasma chemical process for the determination of water samples by atomic fluorescence spectrometry.  

PubMed

A new plasma chemical vapor generation (plasma-CVG) method for Zn was developed by dielectric barrier discharge (DBD). The dissolved Zn ions was readily converted to volatile species by DBD plasma in the presence of hydrogen and then, the generated Zn vapor, Zn(0), was detected by cold vapor atomic fluorescence spectrometry (AFS). It eliminated the use of unstable tetrahydroborate-reducing reagent and high-purity acids. The operating conditions for the DBD plasma-CVG system were optimized for the efficient vapor generation of Zn. In addition, possible interferences from coexisting ions on the plasma-CVG of Zn were also examined. No appreciable matrix interference was found from most of the examined ions at concentration of 1 mg L(-1). However, severe depression of the Zn vapor generation efficiency was observed in the presence of ions at 10 mg L(-1). Under the optimal conditions, the limit of detection (LOD) was calculated to be 0.2 ?g L(-1); good repeatability (relative standard deviation (RSD)?=?2.6%, n?=?11) was obtained for a 20 Zn ?g L(-1) standard. The accuracy of the proposed method was validated though analysis of Zn in reference material of simulated natural water sample GSB07-1184-2000 and the determined result was in good agreement with the reference value. The proposed method has also been successfully applied to the determination of Zn in Changjiang River water, Wuhan East Lake water, and Wuhan tap water samples. It provides an alternative green vapor generation method for Zn. PMID:24871865

Zhu, Zhenli; Liu, Lu; Li, Yixiao; Peng, Huan; Liu, Zhifu; Guo, Wei; Hu, Shenghong

2014-11-01

371

Hybrid electromechanical actuator and actuation system  

NASA Technical Reports Server (NTRS)

A hybrid electromechanical actuator has two different types of electromechanical elements, one that expands in a transverse direction when electric power is applied thereto and one that contracts in a transverse direction when electric power is applied thereto. The two electromechanical elements are (i) disposed in relation to one another such that the transverse directions thereof are parallel to one another, and (ii) mechanically coupled to one another at least at two opposing edges thereof. Electric power is applied simultaneously to the elements.

Su, Ji (Inventor); Xu, Tian-Bing (Inventor)

2008-01-01

372

Barrier properties to surrogates of hydrogenated carbon nano-films deposited on PET by plasma-enhanced chemical vapour deposition.  

PubMed

Poly(ethylene terephthalate) resin was contaminated with a series of surrogates using a US Food and Drug Administration protocol. The contaminated samples were coated with two different kinds of hydrogenated amorphous carbon thin films (a-C:H): one with diamond-like hydrogenated amorphous carbon and another with polymer-like hydrogenated carbon (PLCH) phases. To evaluate the barrier properties of the a-C:H films, migration assays were performed using food simulants. After the tests, analysis by gas chromatography with different detectors was carried out. The appearance of the films before and after the migration experiments was studied by field emission scanning electron microscopy. The results showed that a-C:H films have good barrier properties for most of the evaluated compounds, mainly when they are deposited as PLCH phase. PMID:25254307

Oliveira, Éder C; Echegoyen, Yolanda; Nerin, Cristina; Cruz, Sandra A

2014-01-01

373

Modeling of residual stresses in a plasma-sprayed zirconia\\/alumina functionally graded-thermal barrier coating  

Microsoft Academic Search

Thermal barrier coating (TBC) structures composed of Al2O3 and ZrO2 with different chemical compositions on the NiCoCrAlY bondcoat are proposed to improve the oxidation resistance of TBC systems. The concept of functionally graded materials is applied to manage residual stresses due to sharp interface between dissimilar materials that can lead to a premature failure of TBC system. A numerical study

Sujanto Widjaja; Andi M. Limarga; Tick Hon Yip

2003-01-01

374

Ideal magnetohydrodynamic instabilities with low toroidal mode numbers localized near an internal transport barrier in high-betap mode plasmas in the Japan Atomic Energy Research Institute Tokamak60 Upgrade  

Microsoft Academic Search

Local steep pressure gradient generated near an internal transport barrier drives a radially localized magnetohydrodynamic (MHD) instability with low toroidal mode number (n) in the high-?p mode plasma in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [Y. Koide &etal;, Phys. Plasmas 4, 1623 (1997)]. The instability occurs in the ?p regime lower than that for the ?p-collapse and

S. Takeji; Y. Kamada; T. Ozeki; S. Ishida; T. Takizuka; Y. Neyatani; S. Tokuda

1997-01-01

375

Ideal magnetohydrodynamic instabilities with low toroidal mode numbers localized near an internal transport barrier in high-β{sub p} mode plasmas in the Japan Atomic Energy Research Institute Tokamak60 Upgrade  

Microsoft Academic Search

Local steep pressure gradient generated near an internal transport barrier drives a radially localized magnetohydrodynamic (MHD) instability with low toroidal mode number (n) in the high-β{sub p} mode plasma in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [Y. Koide {ital et al.}, Phys. Plasmas {bold 4}, 1623 (1997)]. The instability occurs in the β{sub p} regime lower than

S. Takeji; Y. Kamada; T. Ozeki; S. Ishida; T. Takizuka; Y. Neyatani; S. Tokuda

1997-01-01

376

The actuated Workbench : 2D actuation in tabletop tangible interfaces  

E-print Network

The Actuated Workbench is a new actuation mechanism that uses magnetic forces to control the two-dimensional movement of physical objects on flat surfaces. This mechanism is intended for use with existing tabletop Tangible ...

Pangaro, Gian Antonio, 1976-

2003-01-01

377

Acoustic Measurements in a Hexamethyldisiloxane-Loaded Low-Temperature Direct Barrier Discharge (DBD) Plasma Effluent: Nozzle Cleaning  

NASA Astrophysics Data System (ADS)

Acoustic emission (AE) measurements as well as laser light scattering experiments were performed during SiO2 layer deposition. SiO2 was generated in low-temperature atmospheric plasma torches (?500 W), which were seeded with hexamethyldisiloxane. These AE measurements can be used to detect the necessity for nozzle cleaning online. The plasma torches were used to obtain high-quality SiO2 coatings. For electrical power of less than 350 W, we observed parasitic SiO2 deposition in the burner nozzle, which decreases the nozzle aperture within several hours of operation time. No parasitic SiO2 deposition inside the burner nozzle was observed when the plasma source was operated at more than 350 W. The reduced nozzle aperture causes increased plasma velocities and acoustic noise. Especially burst-like increases of this acoustic emission were assumed to be correlated to the ejection of particles. This hypothesis could be confirmed by measurements of scattered light from a sheet of laser light at 248 nm. The obtained correlations suggest using a microphone as a low-cost monitor for the degree of parasitic deposition inside the plasma burner nozzle. The threshold for acoustic noise detection has to be chosen low enough to avoid burst-like emission of particles.

Burkert, A.; Müller, D.; Paa, W.

2015-02-01

378

Thermally actuated mechanical systems  

NASA Astrophysics Data System (ADS)

This thesis will discuss the generation of controlled sub-micron motions using novel micro actuators. Our research focuses on the development of an arm-type actuator and a free-motion locomotive walking device. Nano-science and nano-technology focuses on the creation of novel functional materials and also at the development of new fabrication techniques incorporating them. In the fields of novel fabrication techniques, manipulations of micron or sub-micron objects by micro actuators have been suggested in the science and engineering societies for mainly two reasons. From a scientific standpoint, new tools enable new prospective sciences, as is evident from the development of the atomic force microscope. From an engineering standpoint, the miniaturization of manipulation tools will require less material and less energy during a material's production. In spite of such importance, progress in the actuator miniaturization is in a primitive state, especially for the micro mobile devices. The thesis will be a key step in pursuit of this goal with an emphasis on generating motions. Our static actuator uses the excellent elastic properties of multiwall carbon nanotubes as a template for a bimorph system. Deflections in response to temperature variations are demonstrated. The mobile device itself is a bimorph system consisting of thin metal films. Control mechanisms for its velocity and steering are discussed. Finally, fundamental limits on the capabilities of the two devices in a more general sense are discussed under via laws of physics.

Sul, Onejae

379

Folded dielectric elastomer actuators  

NASA Astrophysics Data System (ADS)

Polymer-based linear actuators with contractile ability are currently demanded for several types of applications. Within the class of dielectric elastomer actuators, two basic configurations are available today for such a purpose: the multi-layer stack and the helical structure. The first consists of several layers of elementary planar actuators stacked in series mechanically and parallel electrically. The second configuration relies on a couple of helical compliant electrodes alternated with a couple of helical dielectrics. The fabrication of both these configurations presents some specific drawbacks today, arising from the peculiarity of each structure. Accordingly, the availability of simpler solutions may boost the short-term use of contractile actuators in practical applications. For this purpose, a new configuration is here described. It consists of a monolithic structure made of an electroded sheet, which is folded up and compacted. The resulting device is functionally equivalent to a multi-layer stack with interdigitated electrodes. However, with respect to a stack the new configuration is advantageously not discontinuous and can be manufactured in one single phase, avoiding layer-by-layer multi-step procedures. The development and preliminary testing of prototype samples of this new actuator made of a silicone elastomer are presented here.

Carpi, Federico; Salaris, Claudio; DeRossi, Danilo

2007-04-01

380

Responses of OH (X2?) and OH (A2?+) to high-energy electrons of dielectric barrier discharge in plasma-assisted burner flame  

NASA Astrophysics Data System (ADS)

We examined the responses of OH(X2?) and OH(A2?+) in a premixed CH4 flame to high-energy electrons produced by a dielectric barrier discharge. The density of OH(X2?) did not respond to the pulsed production of high-energy electrons; however, we observed a pulsed increase in the density of chemically produced OH(A2?+). In addition, we observed that OH(A2?+) produced at the same time as high-energy electrons had a lower rotational temperature. We discussed possible key reactions in plasma-assisted combustion on the basis of the experimental observation showing the production of cold OH(A2?+).

Zaima, Kazunori; Sasaki, Koichi

2014-11-01

381

Measurement of ion density in an atmospheric pressure argon with pin-to-plate dielectric barrier discharge by resonance of plasma radiation  

NASA Astrophysics Data System (ADS)

The measurements of the ion densities in the atmospheric AC barrier corona argon discharge are carried out by receiving and analyzing the frequencies of the electromagnetic radiation emitted from the plasma. An auxiliary excitation source composed of a pin-to-pin discharge system is introduced to excite the oscillations of the main discharge. To analyze the resonance mechanism, a complemented model based on a one-dimensional description of forced vibrations is given. Calculations indicate that Ar2 + is the dominant ion ( ˜ 89 % in number density). By analyzing resonance frequencies, the ion densities of Ar2 + are in the order of 10 19 ˜ 10 20 m - 3 and increase slowly as the applied voltage increases.

Qi, Bing; Pan, Lizhu; Zhou, Qiujiao; Huang, Jianjun; Liu, Ying

2014-12-01

382

Study of barrier properties and chemical resistance of recycled PET coated with amorphous carbon through a plasma enhanced chemical vapour deposition (PECVD) process.  

PubMed

Many studies have been carried out in order to make bottle-to-bottle recycling feasible. The problem is that residual contaminants in recycled plastic intended for food packaging could be a risk to public health. One option is to use a layer of virgin material, named functional barrier, which prevents the contaminants migration process. This paper shows the feasibility of using polyethylene terephthalate (PET) recycled for food packaging employing a functional barrier made from hydrogen amorphous carbon film deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) process. PET samples were deliberately contaminated with a series of surrogates using a FDA protocol. After that, PET samples were coated with approximately 600 and 1200 Angstrons thickness of amorphous carbon film. Then, the migration tests using as food simulants: water, 10% ethanol, 3% acetic acid, and isooctane were applied to the sample in order to check the chemical resistance of the new coated material. After the tests, the liquid extracts were analysed using a solid-phase microextraction device (SPME) coupled to GC-MS. PMID:16393820

Cruz, S A; Zanin, M; Nerin, C; De Moraes, M A B

2006-01-01

383

Dielectric barrier discharge plasma in Ar/O{sub 2} promoting apoptosis behavior in A549 cancer cells  

SciTech Connect

The Ar/O{sub 2} plasma needle in the induction of A549 cancer cells apoptosis process is studied by means of real-time observation. The entire process of programmed cell death is observed. The typical morphological changes of A549 apoptosis are detected by 4', 6-diamidino-2-phenylindole staining, for example, chromatin condensation and nuclear fragmentation. Cell viability is determined and quantified by neutral red uptake assay, and the survival rate of A549 from Ar/O{sub 2} plasmas is presented. Further spectral analysis indicates the reactive species, including O and OH play crucial roles in the cell inactivation.

Huang Jun; Li Hui; Chen Wei; Lv Guohua; Wang Xingquan; Zhang Guoping; Wang Pengye [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Ostrikov, Kostya [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, New South Wales 2070 (Australia); School of Physics, The University of Sydney, Sydney, New South Wales 2006 (Australia); Yang Size [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005 (China)

2011-12-19

384

Conducting polymer actuators : temperature effects  

E-print Network

In order to utilize conducting polymer actuators as a viable engineering solution, it is necessary to produce usable levels of force with a reasonable bandwidth. Polypyrrole actuated at temperatures as high as 100 °C ...

Del Zio, Michael R. (Michael Robert), 1982-

2006-01-01

385

Low-Shock Pyrotechnic Actuator  

NASA Technical Reports Server (NTRS)

Miniature 1-ampere, 1-watt pyrotechnic actuator enclosed in flexible metal bellows. Bellows confines outgassing products, and pyrotechnic shock reduction achieved by action of bellows, gas cushion within device, and minimum use of pyrotechnic material. Actuator inexpensive, compact, and lightweight.

Lucy, M. H.

1984-01-01

386

Torsional Ratcheting Actuating System  

SciTech Connect

A new type of surface micromachined ratcheting actuation system has been developed at the Microelectronics Development Laboratory at Sandia National Laboratories. The actuator uses a torsional electrostatic comb drive that is coupled to an external ring gear through a ratcheting scheme. The actuator can be operated with a single square wave, has minimal rubbing surfaces, maximizes comb finger density, and can be used for open-loop position control. The prototypes function as intended with a minimum demonstrated operating voltage of 18V. The equations of motion are developed for the torsional electrostatic comb drive. The resonant frequency, voltage vs. displacement and force delivery characteristics are predicted and compared with the fabricated device's performance.

BARNES,STEPHEN MATTHEW; MILLER,SAMUEL L.; RODGERS,M. STEVEN; BITSIE,FERNANDO

2000-01-24

387

Hydraulically actuated artificial muscles  

NASA Astrophysics Data System (ADS)

Hydraulic Artificial Muscles (HAMs) consisting of a polymer tube constrained by a nylon mesh are presented in this paper. Despite the actuation mechanism being similar to its popular counterpart, which are pneumatically actuated (PAM), HAMs have not been studied in depth. HAMs offer the advantage of compliance, large force to weight ratio, low maintenance, and low cost over traditional hydraulic cylinders. Muscle characterization for isometric and isobaric tests are discussed and compared to PAMs. A model incorporating the effect of mesh angle and friction have also been developed. In addition, differential swelling of the muscle on actuation has also been included in the model. An application of lab fabricated HAMs for a meso-scale robotic system is also presented.

Meller, M. A.; Tiwari, R.; Wajcs, K. B.; Moses, C.; Reveles, I.; Garcia, E.

2012-04-01

388

Hydraulic involute cam actuator  

DOEpatents

Mechanical joints are provided in which the angle between a first coupled member and a second coupled member may be varied by mechanical actuators. In some embodiments the angle may be varied around a pivot axis in one plane and in some embodiments the angle may be varied around two pivot axes in two orthogonal planes. The joints typically utilize a cam assembly having two lobes with an involute surface. Actuators are configured to push against the lobes to vary the rotation angle between the first and second coupled member.

Love, Lonnie J. (Knoxville, TN); Lind, Randall F. (Loudon, TX)

2011-11-01

389

Fault tolerant linear actuator  

DOEpatents

In varying embodiments, the fault tolerant linear actuator of the present invention is a new and improved linear actuator with fault tolerance and positional control that may incorporate velocity summing, force summing, or a combination of the two. In one embodiment, the invention offers a velocity summing arrangement with a differential gear between two prime movers driving a cage, which then drives a linear spindle screw transmission. Other embodiments feature two prime movers driving separate linear spindle screw transmissions, one internal and one external, in a totally concentric and compact integrated module.

Tesar, Delbert

2004-09-14

390

Isotropic nitride etching for thin nitride barrier self-aligned contact (TNBSAC) in an inductively coupled plasma chemical etcher  

NASA Astrophysics Data System (ADS)

The bitline contact hole and the storage node contact hole of 0.22 micrometers in 1G DRAM device manufacturing of 0.18 micrometers design rule were formed with thin nitride barrier self- aligned contact (TNBSAC) technology. In this work the isotropic dry etching process for the removal of nitride used as an oxide etching barrier in TNBSAC was characterized with respect to the parameters such as O2/(NF3 + O2) flow rate ratio, total flow rate, pressure, chiller temperature. From these tests, an isotropic nitride etching recipe was evaluated as the following: 0.8Torr 900Watt 60NF3 140O2 10 degrees C, nitride etch rate equals 1200 angstrom/min, selectivity of nitride to middle temperature oxide (MTO) equals 7.2, selectivity to Boro Phosphor Silicate Glass equals 7. When this condition was applied to TNBSAC technology, good etching characteristics was achieved enough to be implemented into device manufacturing like MTO loss less 100 angstrom on wordline corner, no Si substrate damage and contact hole CD bias about 160 angstrom. When the bitline contact hole and the storage node contact hole in 1G DRAM device fully processed form isolation to metallization were defined with TNBSAC technology, the electrical characterization of the bitline contact hole was investigated comparing TNBSAC with sidewall oxide spacer contact (SOSCON) technology. TNBSAC employing the isotopic nitride etching showed the short free connection, the lower junction leakage current and the lower contact resistance compared with SOSCON.

Kim, Jeong-Ho; Ryu, Jae-Ok; Kim, Jong-Sam; Kim, Jin-Woong; Seol, Yeo-Song

1998-09-01

391

Detection of segmentation cracks in top coat of thermal barrier coatings during plasma spraying by non-contact acoustic emission method  

NASA Astrophysics Data System (ADS)

Numerous cracks can be observed in the top coat of thermal barrier coatings (TBCs) deposited by the atmospheric plasma spraying (APS) method. These cracks can be classified into vertical and horizontal ones and they have opposite impact on the properties of TBCs. Vertical cracks reduce the residual stress in the top coat and provide strain tolerance. On the contrary, horizontal cracks trigger delamination of the top coat. However, monitoring methods of cracks generation during APS are rare even though they are strongly desired. Therefore, an in situ, non-contact and non-destructive evaluation method for this objective was developed in this study with the laser acoustic emission (AE) technique by using laser interferometers as a sensor. More AE events could be detected by introducing an improved noise reduction filter and AE event detection procedures with multiple thresholds. Generation of vertical cracks was successfully separated from horizontal cracks by a newly introduced scanning pattern of a plasma torch. Thus, generation of vertical cracks was detected with certainty by this monitoring method because AE events were detected only during spraying and a positive correlation was observed between the development degree of vertical cracks and the total AE energy in one experiment.

Ito, Kaita; Kuriki, Hitoshi; Araki, Hiroshi; Kuroda, Seiji; Enoki, Manabu

2014-06-01

392

Surface modification of thermoplastic poly(vinyl alcohol)/saponite nanocomposites via surface-initiated atom transfer radical polymerization enhanced by air dielectric discharges barrier plasma treatment  

NASA Astrophysics Data System (ADS)

To improve the water resistance of thermoplastic poly(vinyl alcohol)/saponite nanocomposites (TPVA), a simple two-step method was developed for the covalent immobilization of atom transfer radical polymerization (ATRP) initiators on the TPVA surfaces enhanced by air dielectric barrier discharges (DBD) plasma treatment, and hydrophobic poly(methyl methacrylate) (PMMA) brushes were then grafted onto the surface of TPVA via surface-initiated atom transfer radical polymerization (SI-ATRP). The chemical composition, morphology and hydrophobicity of the modified TPVA surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The water resistance of the surface-functionalized PMMA was evaluated by the contact angle and water adsorption method. It was shown that air DBD plasma treatment activated the TPVA surface and accelerated the immobilization of ATRP initiator on the TPVA surface. Compared with TPVA control, TPVA modified by SI-ATRP can be grafted well-defined and covalently tethered network PMMA brushes onto the surface and the hydrophobicity of TPVA were significantly enhanced.

Zhen, Weijun; Lu, Canhui

2012-07-01

393

Optical characteristics and parameters of the plasma of a barrier discharge excited in a mixture of mercury dibromide vapor with nitrogen and helium  

SciTech Connect

Results are presented from experimental and theoretical studies of the optical characteristics and parameters of the plasma of an atmospheric-pressure barrier discharge excited in a HgBr{sub 2}: N{sub 2}: He mixture, which was used as the working medium of a small-size (with a radiation area of 8 cm{sup 2}) exciplex gas-discharge radiation source. The mean radiation power of 87 mW was achieved at the radiation wavelength {lambda}{sub max} = 502 nm. The electron energy distribution function, the transport characteristics, the specific energy lost in the processes involving electrons, the electron temperature and density, and the rate constants of elastic and inelastic electron scattering by the components of the working mixture were calculated as functions of the reduced field E/N. The plasma of a discharge excited in a HgBr{sub 2}: N{sub 2}: He mixture can be used as the working medium of a small-size blue-green radiation source. Such a source can find application in biotechnology, photonics, and medicine and can also be used to manufacture gas-discharge display panels.

Malinina, A. A.; Guivan, N. N.; Shimon, L. L.; Shuaibov, A. K. [Uzhgorod National University (Ukraine)

2010-09-15

394

Computational study of temporal behavior of incident species impinging on a water surface in dielectric barrier discharge for the understanding of plasma–liquid interface  

NASA Astrophysics Data System (ADS)

A lipid bilayer is a basic structure of the cell membrane and is stable in liquid solution. In this study, we analyzed dielectric barrier discharge (DBD) containing water on a quartz substrate using a one-dimensional fluid model. To simulate atmospheric pressure plasma for practical use, a tiny amount of N2 gas (0.5 ppm) was added to He gas ambient as an impure gas. The calculated current–voltage (I–V) characteristics reproduced the measured ones qualitatively. We focused on the behavior of DBD at the plasma–liquid interface and analyzed the temporal behavior of the electric field strength and incident fluxes of charged, excited, and radical species on the water surface. By varying the gap length, it was shown that the maximum electric field strength in an AC cycle saturated at gap lengths ?0.15 cm. The incident fluxes of N2+ and He2+ on the water surface are almost the same and show strong correlations with the electric field in the vicinity of the water surface.

Suda, Yoshiyuki; Oda, Akinori; Kato, Ryo; Yamashita, Ryuma; Tanoue, Hideto; Takikawa, Hirofumi; Tero, Ryugo

2015-01-01

395

Investigation of Crack Propagation Behavior of Atmospheric Plasma-Sprayed Thermal Barrier Coatings under Uniaxial Tension Using the Acoustic Emission Technique  

NASA Astrophysics Data System (ADS)

Uniaxial tension is a common technique to characterize the adhesive strength of plasma-sprayed thermal barrier coatings (TBCs). In this work, the crack initiation, growth, and propagation behavior of atmospheric plasma-sprayed TBCs during uniaxial tension testing was investigated using the acoustic emission (AE) technique, x-ray diffraction analysis, scanning electron microscopy, and the finite-element method (FEM). The experimental results indicated that the position of crack initiation was usually located within the ceramic layer, and the crack tended to propagate along the tension direction, with some key horizontal cracks reaching the metallic layer/ceramic layer interface, after which vertical cracks initiating at the middle and lower segments of the horizontal cracks propagated along the interface. When some critical cracks were formed at the interface and a series of assembled splats separated from the coating, the coating failed completely. The AE signal could be divided into three typical stages, corresponding to the three stages of the stress-stain curve under uniaxial tension. Detailed analysis of the AE signal associated with the failure behavior was performed. The dynamic propagation patterns of the key cracks in the ceramic layer during the tension process were simulated using the FEM, whose results further confirmed the conclusions drawn from the experimental results.

Wang, L.; Liu, C. G.; Zhong, X. H.; Zhao, Y. X.; Zhao, H. Y.; Yang, J. S.; Tao, S. Y.; Wang, Y.

2015-02-01

396

Sensor-actuator placement for flexible structures with actuator dynamics  

NASA Technical Reports Server (NTRS)

A novel approach for placement of sensors and actuators in control of flexible space structures is developed. Using an approximation of the control forces and output measurements by spatially continuous functions, the approach follows a nonlinear programming technique to determine optimal locations for sensors and actuators. Two different criteria are considered for the placement of sensors and actuators. The first criterion optimizes the location of the sensors and actuators in order to move the transmission zeros of the system farther to the left of the imaginary axis. The second criterion, however, places the sensors and actuators to optimize a function of the singular values of the Hankel matrix, which includes both measures of controllability and observability. Moreover, the effect of actuator dynamics in the placement of sensors and actuators is investigated.

Maghami, P. G.; Joshi, S. M.

1991-01-01

397

Thermal Barrier Coatings  

NASA Technical Reports Server (NTRS)

In order to reduce heat transfer between a hot gas heat source and a metallic engine component, a thermal insulating layer of material is placed between them. This thermal barrier coating is applied by plasma spray processing the thin films. The coating has been successfully employed in aerospace applications for many years. Lewis Research Center, a leader in the development engine components coating technology, has assisted Caterpillar, Inc. in applying ceramic thermal barrier coatings on engines. Because these large engines use heavy fuels containing vanadium, engine valve life is sharply decreased. The barrier coating controls temperatures, extends valve life and reduces operating cost. Additional applications are currently under development.

1993-01-01

398

Series elastic actuators  

Microsoft Academic Search

It is traditional to make the interface between an actuator and its load as stiff as possible. Despite this tradition, reducing interface stiffness offers a number of advantages, including greater shock tolerance, lower reflected inertia, more accurate and stable force control, less inadvertent damage to the environment, and the capacity for energy storage. As a trade-off, reducing interface stiffness also

Gill A. Pratt; Matthew M. Williamson

1995-01-01

399

"Mighty Worm" Piezoelectric Actuator  

NASA Technical Reports Server (NTRS)

"Mighty Worm" piezoelectric actuator used as adjustable-length structural member, active vibrator or vibration suppressor, and acts as simple (fixed-length) structural member when inactive. Load force not applied to piezoelectric element in simple-structural-member mode. Piezoelectric element removed from load path when not in use.

Bamford, Robert M.; Wada, Ben K.; Moore, Donald M.

1994-01-01

400

Electromechanical flight control actuator  

NASA Technical Reports Server (NTRS)

The feasibility of using an electromechanical actuator (EMA) as the primary flight control equipment in aerospace flight is examined. The EMA motor design is presented utilizing improved permanent magnet materials. The necessary equipment to complete a single channel EMA using the single channel power electronics breadboard is reported. The design and development of an improved rotor position sensor/tachometer is investigated.

1979-01-01

401

Piezoelectric linear actuator  

NASA Technical Reports Server (NTRS)

Actuator exerts linear force that is controllable and reproducible to microinch tolerance. It is constructed for extremely accurate control of a valve but can also be used as a variable venturi meter, micropositioner, microthruster, and in fluidics and reaction-control systems.

Lehrer, S.

1969-01-01

402

Bistable microelectromechanical actuator  

DOEpatents

A bistable microelectromechanical (MEM) actuator is formed on a substrate and includes a stressed membrane of generally rectangular shape that upon release assumes a curvilinear cross-sectional shape due to attachment at a midpoint to a resilient member and at opposing edges to a pair of elongate supports. The stressed membrane can be electrostatically switched between a pair of mechanical states having mirror-image symmetry, with the MEM actuator remaining in a quiescent state after a programming voltage is removed. The bistable MEM actuator according to various embodiments of the present invention can be used to form a nonvolatile memory element, an optical modulator (with a pair of mirrors supported above the membrane and moving in synchronism as the membrane is switched), a switchable mirror (with a single mirror supported above the membrane at the midpoint thereof) and a latching relay (with a pair of contacts that open and close as the membrane is switched). Arrays of bistable MEM actuators can be formed for applications including nonvolatile memories, optical displays and optical computing. 49 figs.

Fleming, J.G.

1999-02-02

403

Evolution of the plasma-sprayed microstructure in 7 wt% yttria-stabilized zirconia thermal barrier coatings during uniaxial stress relaxation and the concomitant changes in material properties  

NASA Astrophysics Data System (ADS)

The understanding of failure mechanisms in plasma sprayed 7 wt% yttria stabilized zirconia (YSZ) is a key step toward optimizing thermal barrier coating (TBC) usage, design, and life prediction. The purpose of the present work is to characterize and understand the stress relaxation behavior occurring in plasma-sprayed YSZ coatings, so that the correlating magnitude of unfavorable tensile stress, which coatings experienced upon cooling, may be reduced through microstructural design. The microstructure and properties of as-sprayed coatings changes immensely during service at high temperature, and therefore the effects of long heat-treatment times, and the concomitant change within the microstructure, on the time-dependent mechanical behavior of stand-alone YSZ coatings was studied in parallel with the as-sprayed coating condition. Aside from influencing the mechanical properties, stress relaxation also affects the insulating efficiency of plasma-sprayed 7wt% YSZ coatings. Directionally dependent changes in microstructure due to stress relaxation of a uniaxially applied stress at 1200°C were observed in plasma-sprayed coatings. Small angle neutron scattering (SANS) investigation of coatings after stress relaxation displayed a 46% reduction in the specific surface area connected to the load-orientation dependent closure of void surface area perpendicular to the applied load when compared to coatings sintered in air, i.e. no applied load. These anisotropic microstructural changes were linked to the thermal properties of the coating. For example, a coating stress relaxed from 60 MPa for 5-min at 1200°C exhibited a thermal conductivity of 2.1 W/m-K. A coating that was only heat-treated for 5-min at 1200°C (i.e. no stress applied) exhibited a thermal conductivity of 1.7 W/m·K. In the current study, uniaxial stress relaxation in plasma-sprayed 7wt% YSZ coatings was determined the result of: (1) A more uniform distribution of the applied load with time, (2) A reduction in the SSA associated with void systems due to sintering, specifically the closing and healing of intralamellar cracks perpendicular to the applied stress, and (3) A compaction and closure of void systems under the applied load. These anisotropic changes in microstructure result in distinguishable changes in thermo-mechanical properties, with very minute changes to the overall bulk density.

Petorak, Christopher

404

Control of vortex on a non-slender delta wing by a nanosecond pulse surface dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

Wind tunnel experiments are conducted for improving the aerodynamic performance of delta wing using a leading-edge pulsed nanosecond dielectric barrier discharge (NS-DBD). The whole effects of pulsed NS-DBD on the aerodynamic performance of the delta wing are studied by balanced force measurements. Pressure measurements and particle image velocimetry (PIV) measurements are conducted to investigate the formation of leading-edge vortices affected by the pulsed NS-DBD, compared to completely stalled flow without actuation. Various pulsed actuation frequencies of the plasma actuator are examined with the freestream velocity up to 50 m/s. Stall has been delayed substantially and significant shifts in the aerodynamic forces can be achieved at the post-stall regions when the actuator works at the optimum reduced frequency of F + = 2. The upper surface pressure measurements show that the largest change of static pressure occurs at the forward part of the wing at the stall region. The time-averaged flow pattern obtained from the PIV measurement shows that flow reattachment is promoted with excitation, and a vortex flow pattern develops. The time-averaged locations of the secondary separation line and the center of the vortical region both move outboard with excitation.

Zhao, Guang-yin; Li, Ying-hong; Liang, Hua; Han, Meng-hu; Hua, Wei-zhuo

2015-01-01

405

Considerations For Contractile Electroactive Materials and Actuators  

SciTech Connect

Electroactive polymers (EAPs) that bend, swell, ripple (first generation materials), and now contract with low electric input (new development) have been produced. The mechanism of contraction is not well understood. Radionuclide-labeled experiments, molecular modeling, electrolyte experiments, pH experiments, and an ionic concentration experiment were used to determine the chain of events that occur during contraction and, reciprocally, expansion when the polarity is reversed, in these ionic EAPs. Plasma treatment of the electrodes, along with other strategies, allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface, analogous to nerves and tendons moving with muscles during movement. Challenges involved with prototyping actuation using contractile EAPs are also discussed.

Lenore Rasmussen, Lewis D. Meixler and Charles A. Gentile

2012-02-29

406

Hot corrosion behaviors of gas tunnel type plasma sprayed La 2Zr 2O 7 thermal barrier coatings  

Microsoft Academic Search

Gas tunnel type plasma sprayed free-standing La2Zr2O7 coating specimens with a thickness of 300–400?m were prepared under optimized operating conditions and were subjected to hot corrosion test in the presence of corrosive impurities such as V2O5, Na2SO4, and Na2SO4+V2O5 mixtures (60:40wt%) at two different temperatures for duration of 5h, i.e. 1000 and 1350K for V2O5 and Na2SO4+V2O5 mixtures, 1200 and

S. Yugeswaran; Akira Kobayashi; P. V. Ananthapadmanabhan

407

Microwave power for smart material actuators  

NASA Astrophysics Data System (ADS)

The concept of microwave-driven smart material actuators was envisioned and developed as the best option to alleviate the complexity and weight associated with a hard-wire-networked power and control system for smart actuator arrays. The patch rectenna array was initially designed for high current output, but has undergone further development for high voltage output devices used in shape control applications. Test results show that more than 200 V of output were obtained from a 6 × 6 array at a far-field exposure (1.8 m away) with an X-band input power of 18 W. The 6 × 6 array patch rectenna was designed to theoretically generate voltages up to 540 V, but practically it has generated voltages in the range between 200 and 300 V. Testing was also performed with a thin layer composite unimorph ferroelectric driver and sensor and electro-active paper as smart actuators attached to the 6 × 6 array. Flexible dipole rectenna arrays built on thin-film-based flexible membranes are most applicable for NASA's various missions, such as microwave-driven shape controls for aircraft morphing and large, ultra-lightweight space structures. An array of dipole rectennas was designed for high voltage output by densely populating Schottky barrier diodes to drive piezoelectric or electrostrictive actuators. The dipole rectenna array will eventually be integrated with a power allocation and distribution logic circuit and microbatteries for storage of excessive power. The roadmap for the development of wireless power drivers based on the rectenna array for shape control requires the development of new membrane materials with proper dielectric constants that are suitable for dipole rectenna arrays.

Choi, Sang H.; Song, Kyo D.; Golembiewskii, Walter; Chu, Sang-Hyon; King, Glen C.

2004-02-01

408

Dielectric Actuation of Polymers  

NASA Astrophysics Data System (ADS)

Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy densities, high coupling efficiency, quiet operation, and light weight. One focus of this dissertation is on the design of DE materials with high performance and easy processing. UV radiation curing of reactive species is studied as a generic synthesis methodology to provide a platform for material scientists to customize their own DE materials. Oligomers/monomers, crosslinkers, and other additives are mixed and cured at appropriate ratios to control the stress-strain response, suppress electromechanical instability of the resulting polymers, and provide stable actuation strains larger than 100% and energy densities higher than 1 J/g. The processing is largely simplified in the new material system by removal of the prestretching step. Multilayer stack actuators with 11% linear strain are demonstrated in a procedure fully compatible with industrial production. A multifunctional DE derivative material, bistable electroactive polymer (BSEP), is invented enabling repeatable rigid-to-rigid deformation without bulky external structures. Bistable actuation allows the polymer actuator to have two distinct states that can support external load without device failure. Plasticizers are used to lower the glass transition temperature to 45 °C. Interpenetrating polymer network structure is established inside the BSEP to suppress electromechanical instability, providing a breakdown field of 194 MV/m and a stable bistable strain as large as 228% with a 97% strain fixity. The application of BSEP in tactile display is investigated by the prototyping of a large scale refreshable Braille display device. Braille is a critical way for the vision impaired community to learn literacy and improve life quality. Current piezoelectrics-based refreshable Braille display technologies are limited to up to 1 line of Braille text, due to the bulky size of bimorph actuators. Based on the unique actuation feature of BSEP, refreshable Braille display devices up to smartphone-size have been demonstrated by polymer sheet laminates. Dots in the devices can be individually controlled via incorporated field-driven BSEP actuators and Joule heater units. A composite material consisting of silver nanowires (AgNW) embedded in a polymer substrate is brought up as a compliant electrode candidate for BSEP application. The AgNW composite is highly conductive (Rs: 10 ?/sq) and remains conductive at strains as high as 140% (Rs: <10 3 ?/sq). The baseline conductivity has only small changes up to 90% strain, which makes it low enough for both field driving and stretchable Joule heating. An out-of-plane bistable area strain up to 68% under Joule heating is achieved.

Niu, Xiaofan

409

GaN-based high-electron-mobility transistor structures with homogeneous lattice-matched InAlN barriers grown by plasma-assisted molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Metal-polar In0.17Al0.83N barriers, lattice-matched to GaN, were grown under N-rich conditions by plasma-assisted molecular beam epitaxy. The compositional homogeneity of these barriers was confirmed by plan-view high-angle annular dark-field scanning transmission electron microscopy and atom probe tomography. Metal-polar In0.17Al0.83N/(GaN)/(AlN)/GaN structures were grown with a range of AlN and GaN interlayer (IL) thicknesses to determine the optimal structure for achieving a low two-dimensional electron gas (2DEG) sheet resistance. It was determined that the presence of a GaN IL was necessary to yield a 2DEG sheet density above 2 × 1013 cm-2. By including AlN and GaN ILs with thicknesses of 3 nm and 2 nm, respectively, a metal-polar In0.17Al0.83N/GaN/AlN/GaN structure regrown on a GaN-on-sapphire template yielded a room temperature (RT) 2DEG sheet resistance of 163 ?/?. This structure had a threading dislocation density (TDD) of ˜5 × 108 cm-2. Through regrowth on a free-standing GaN template with low TDD (˜5 × 107 cm-2), an optimized metal-polar In0.17Al0.83N/GaN/AlN/GaN structure achieved a RT 2DEG sheet resistance of 145 ?/? and mobility of 1822 cm2 V-1 s-1. High-electron-mobility transistors with output current densities above 1 A mm-1 were also demonstrated on the low-TDD structure.

Kaun, Stephen W.; Ahmadi, Elaheh; Mazumder, Baishakhi; Wu, Feng; Kyle, Erin C. H.; Burke, Peter G.; Mishra, Umesh K.; Speck, James S.

2014-04-01

410

Cylindrical Piezoelectric Fiber Composite Actuators  

NASA Technical Reports Server (NTRS)

The use of piezoelectric devices has become widespread since Pierre and Jacques Curie discovered the piezoelectric effect in 1880. Examples of current applications of piezoelectric devices include ultrasonic transducers, micro-positioning devices, buzzers, strain sensors, and clocks. The invention of such lightweight, relatively inexpensive piezoceramic-fiber-composite actuators as macro fiber composite (MFC) actuators has made it possible to obtain strains and displacements greater than those that could be generated by prior actuators based on monolithic piezoceramic sheet materials. MFC actuators are flat, flexible actuators designed for bonding to structures to apply or detect strains. Bonding multiple layers of MFC actuators together could increase force capability, but not strain or displacement capability. Cylindrical piezoelectric fiber composite (CPFC) actuators have been invented as alternatives to MFC actuators for applications in which greater forces and/or strains or displacements may be required. In essence, a CPFC actuator is an MFC or other piezoceramic fiber composite actuator fabricated in a cylindrical instead of its conventional flat shape. Cylindrical is used here in the general sense, encompassing shapes that can have circular, elliptical, rectangular or other cross-sectional shapes in the planes perpendicular to their longitudinal axes.

Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.

2008-01-01

411

Contact damping in microelectromechanical actuators  

NASA Astrophysics Data System (ADS)

We examine the significance of the energy loss mechanisms active in electrostatic MEMS actuators. We find that the dominant loss mechanism changes depending on the actuator mode of operation. We find that the active mechanisms in the order of their significance are: fluid-structure interactions dominant for actuators operating in air, actuator-substrate interactions dominant for actuators in contact with a substrate under vacuum, and intrinsic loss mechanisms dominant for actuators in-flight under vacuum. Further, experimental results show that the quality factor of an electrostatic MEMS actuator drops drastically as the actuator first comes into line contact with a substrate. As the contact area expands along the actuator length, the quality factor increases. Measurements under 1 Torr vacuum show a three-fold increase in the quality factor as the contact area expands from a line to 30% of the actuator area. This increase in the quality factor is attributed to the drop in the contribution of friction forces into energy losses as contact expands and adhesion forces increase.

Khater, M. E.; Akhtar, S.; Park, S.; Ozdemir, S.; Abdel-Rahman, E.; Vyasarayani, C. P.; Yavuz, M.

2014-12-01

412

Microfabricated therapeutic actuators  

DOEpatents

Microfabricated therapeutic actuators are fabricated using a shape memory polymer (SMP), a polyurethane-based material that undergoes a phase transformation at a specified temperature (Tg). At a temperature above temperature Tg material is soft and can be easily reshaped into another configuration. As the temperature is lowered below temperature Tg the new shape is fixed and locked in as long as the material stays below temperature Tg. Upon reheating the material to a temperature above Tg, the material will return to its original shape. By the use of such SMP material, SMP microtubing can be used as a release actuator for the delivery of embolic coils through catheters into aneurysms, for example. The microtubing can be manufactured in various sizes and the phase change temperature Tg is determinate for an intended temperature target and intended use. 8 figs.

Lee, A.P.; Northrup, M.A.; Ciarlo, D.R.; Krulevitch, P.A.; Benett, W.J.

1999-06-15

413

Microfabricated therapeutic actuator mechanisms  

DOEpatents

Electromechanical microstructures (microgrippers), either integrated circuit (IC) silicon-based or precision machined, to extend and improve the application of catheter-based interventional therapies for the repair of aneurysms in the brain or other interventional clinical therapies. These micromechanisms can be specifically applied to release platinum coils or other materials into bulging portions of the blood vessels also known as aneurysms. The ``micro`` size of the release mechanism is necessary since the brain vessels are the smallest in the body. Through a catheter more than one meter long, the micromechanism located at one end of the catheter can be manipulated from the other end thereof. The microgripper (micromechanism) of the invention will also find applications in non-medical areas where a remotely actuated microgripper or similar actuator would be useful or where micro-assembling is needed. 22 figs.

Northrup, M.A.; Ciarlo, D.R.; Lee, A.P.; Krulevitch, P.A.

1997-07-08

414

Sensors and Actuators  

NSDL National Science Digital Library

This module is part of the course “Intro to Mechatronics” at Lawrence Technological University and was developed through seed funding from the CAAT. This module consists of a PowerPoint presentation and accelerometer LabVIEW lab. Discussed in the Power Point are automotive sensors, actuators, and their use in powertrain (energy use, drivability and performance), body (occupant needs), and chassis (vehicle handling and safety). Some of the types of these sensors are rotational (crank or cam position), pressure (EVAP system or MAP), exhaust gas (oxygen sensor), and actuators (air bag inflators, relays, and injectors). Also included is a section on DC and AC motors operation and their automotive applications (traction motor, window motor, and seat motor). The lab will introduce students to developing data acquisition for sensors using National Instruments LabVIEW software. For instructors who would like solutions to the lab, please contact the CAAT.

Lawrence Technological University

415

Electrical Actuation Technology Bridging  

NASA Technical Reports Server (NTRS)

This document contains the proceedings of the NASA Electrical Actuation Technology Bridging (ELA-TB) Workshop held in Huntsville, Alabama, September 29-October 1, 1992. The workshop was sponsored by the NASA Office of Space Systems Development and Marshall Space Flight Center (MSFC). The workshop addressed key technologies bridging the entire field of electrical actuation including systems methodology, control electronics, power source systems, reliability, maintainability, and vehicle health management with special emphasis on thrust vector control (TVC) applications on NASA launch vehicles. Speakers were drawn primarily from industry with participation from universities and government. In addition, prototype hardware demonstrations were held at the MSFC Propulsion Laboratory each afternoon. Splinter sessions held on the final day afforded the opportunity to discuss key issues and to provide overall recommendations. Presentations are included in this document.

Hammond, Monica (compiler); Sharkey, John (compiler)

1993-01-01

416

Scissor thrust valve actuator  

DOEpatents

Apparatus for actuating a valve includes a support frame and at least one valve driving linkage arm, one end of which is rotatably connected to a valve stem of the valve and the other end of which is rotatably connected to a screw block. A motor connected to the frame is operatively connected to a motor driven shaft which is in threaded screw driving relationship with the screw block. The motor rotates the motor driven shaft which drives translational movement of the screw block which drives rotatable movement of the valve driving linkage arm which drives translational movement of the valve stem. The valve actuator may further include a sensory control element disposed in operative relationship with the valve stem, the sensory control element being adapted to provide control over the position of the valve stem by at least sensing the travel and/or position of the valve stem.

DeWall, Kevin G.; Watkins, John C; Nitzel, Michael E.

2006-08-29

417

Microfabricated therapeutic actuators  

DOEpatents

Microfabricated therapeutic actuators are fabricated using a shape memory polymer (SMP), a polyurethane-based material that undergoes a phase transformation at a specified temperature (Tg). At a temperature above temperature Tg material is soft and can be easily reshaped into another configuration. As the temperature is lowered below temperature Tg the new shape is fixed and locked in as long as the material stays below temperature Tg. Upon reheating the material to a temperature above Tg, the material will return to its original shape. By the use of such SMP material, SMP microtubing can be used as a release actuator for the delivery of embolic coils through catheters into aneurysms, for example. The microtubing can be manufactured in various sizes and the phase change temperature Tg is determinate for an intended temperature target and intended use.

Lee, Abraham P. (Walnut Creek, CA); Northrup, M. Allen (Berkeley, CA); Ciarlo, Dino R. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA); Benett, William J. (Livermore, CA)

1999-01-01

418

Dissolution actuated sample container  

DOEpatents

A sample collection vial and process of using a vial is provided. The sample collection vial has an opening secured by a dissolvable plug. When dissolved, liquids may enter into the interior of the collection vial passing along one or more edges of a dissolvable blocking member. As the blocking member is dissolved, a spring actuated closure is directed towards the opening of the vial which, when engaged, secures the vial contents against loss or contamination.

Nance, Thomas A.; McCoy, Frank T.

2013-03-26

419

Thermally actuated thermionic switch  

DOEpatents

A thermally actuated thermionic switch which responds to an increase of temperature by changing from a high impedance to a low impedance at a predictable temperature set point. The switch has a bistable operation mode switching only on temperature increases. The thermionic material may be a metal which is liquid at the desired operation temperature and held in matrix in a graphite block reservoir, and which changes state (ionizes, for example) so as to be electrically conductive at a desired temperature.

Barrus, D.M.; Shires, C.D.

1982-09-30

420

Linear mass actuator  

NASA Technical Reports Server (NTRS)

A linear mass actuator includes an upper housing and a lower housing connectable to each other and having a central passageway passing axially through a mass that is linearly movable in the central passageway. Rollers mounted in the upper and lower housings in frictional engagement with the mass translate the mass linearly in the central passageway and drive motors operatively coupled to the roller means, for rotating the rollers and driving the mass axially in the central passageway.

Holloway, Sidney E., III (inventor); Crossley, Edward A., Jr. (inventor); Jones, Irby W. (inventor); Miller, James B. (inventor); Davis, C. Calvin (inventor); Behun, Vaughn D. (inventor); Goodrich, Lewis R., Sr. (inventor)

1992-01-01