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1

Impedance matching for an asymmetric dielectric barrier discharge plasma actuator  

E-print Network

Impedance matching for an asymmetric dielectric barrier discharge plasma actuator Kunwar Pal Singh July 2007; published online 23 August 2007 A typical dielectric barrier discharge plasma actuator reflected power from the plasma actuator back to the power supply. This does not contribute to plasma

Roy, Subrata

2

On the mechanical efficiency of dielectric barrier discharge plasma actuators  

SciTech Connect

The mechanical power production and electrical power consumption of the dielectric barrier discharge plasma actuator is investigated for different operating conditions. The ratio of these two values delivers the mechanical efficiency of the actuator as a flow acceleration device. The general trend is that higher carrier frequencies and voltages lead to higher values of the efficiency. The values that were found for the mechanical efficiency are very small, the highest recorded value is only 0.18%.

Giepman, R. H. M.; Kotsonis, M. [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, Delft 2629HS (Netherlands)

2011-05-30

3

Force Production Mechanisms of a Dielectric-Barrier Discharge Plasma Actuator  

E-print Network

Force Production Mechanisms of a Dielectric-Barrier Discharge Plasma Actuator James W. Gregory* , C-barrier discharge plasma actuator. A theoretical derivation shows that the force produced is due to the acceleration affecting the amount of force produced by the plasma actuator. Nomenclature a = Acceleration b = Coefficient

Gregory, James W.

4

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

5

Simulation of an asymmetric single dielectric barrier plasma actuator K. P. Singha  

E-print Network

Simulation of an asymmetric single dielectric barrier plasma actuator K. P. Singha and Subrata Roy because of its applications in flow actuation in aerospace and many other areas.1,2 These actuators use plasma actuator is shown in Fig. 1. The grounded electrode for this configuration is em- bedded

Singh, Kunwar Pal

6

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

7

American Institute of Aeronautics and Astronautics On Multi-Barrier Plasma Actuators  

E-print Network

barrier plasma actuator at or near atmospheric pressures have been widely documented in the last one charged air which manifests itself as a primarily tangential wall jet. Varying aspectsAmerican Institute of Aeronautics and Astronautics 1 On Multi-Barrier Plasma Actuators Ryan

Roy, Subrata

8

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

9

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

10

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

11

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

NASA Astrophysics Data System (ADS)

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 Cm and Cg can be gotten by the calculation of the electric field, with the method of undetermined coefficients, while the value of Capacitance Cd is determined from the charge-voltage (Q-V) plot, also called Lissajous figure. It is found that the value of Capacitance Cd 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.

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

2014-05-01

12

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

13

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

14

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

15

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

16

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

17

Effect of external flow velocity on momentum transfer of dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

An experimental study is performed towards identifying cross-talk effects between DBD plasma actuators and external flow. An actuator is positioned in a boundary layer operated in a range of free stream velocities from 0 to 60 m/s, and tested both in counter-flow and co-flow forcing configurations. Electrical measurements are used for estimating the power consumption and the discharge formation is visualized using a CCD camera. The actuator's force is measured using a sensitive load cell. Results show the power consumption is constant for different flow velocities and actuator configurations. The plasma light emission is constant for co-flow forcing but shows a trend of increasing intensity with counter-flow forcing for increasing free stream velocities. The measured force is constant for free stream velocities larger than 20 m/s, with same magnitude and opposite direction for the counter-flow and co-flow configurations. In quiescent conditions, the measured force is smaller due to the change in wall shear force by the induced wall-jet. An analytical model is presented to estimate the influence of external flow on the actuator force. It is based on conservation of momentum through the ion-neutral collisional process while including the contribution of the wall shear force. Satisfactory agreement is found between the prediction of the model and experimental data at different external flow velocities.

Pereira, Ricardo; Ragni, Daniele; Kotsonis, Marios

2014-09-01

18

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

19

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

20

Contribution of positive and negative ions to the electrohydrodynamic force in a dielectric barrier discharge plasma actuator operating in air  

SciTech Connect

We present a parametric study of the electrohydrodynamic force generated by surface dielectric barrier discharge plasma actuators in air for sinusoidal voltage waveforms. The simulation results confirm that momentum is transferred from the charged particles to the neutral species in the same direction during both positive and negative parts of the cycle. The momentum transfer is due to positive ions during the positive part of the cycle (electrode above the dielectric layer is the anode), and to negative ions during the negative part of the cycle. The relative contribution of the positive and negative parts of the cycle depends on the voltage amplitude and frequency. The model predicts that the contribution of negative ions tends to be dominant at low voltage frequencies and high voltage amplitudes.

Boeuf, J. P.; Lagmich, Y.; Pitchford, L. C. [UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d'Energie), Universite de Toulouse, 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France); LAPLACE, CNRS, F-31062 Toulouse (France)

2009-07-15

21

Time-resolved measurements of plasma-induced momentum in air and nitrogen under dielectric barrier discharge actuation  

SciTech Connect

There has been much recent interest in boundary layer (BL) actuation by offset surface dielectric barrier discharges (SDBD). These discharges either act directly on the gas momentum through the mechanism of charge separation or they increase the flow stability through the creation of disturbances to the BL at a particular frequency. The objective of the work reported here is to clarify the physical mechanism of plasma-flow interaction. Two problems are considered in detail: the exact spatial/temporal distribution of the plasma-related force, and the specific role of negative ions in the net force budget. The experiments were made with an offset electrode configuration of SDBD at voltage amplitude U{<=}12 kV and frequency f=0.02-2 kHz. The main data were obtained by time-resolved Pitot tube pressure measurements in air and nitrogen at atmospheric pressure. Three main features of SDBD behavior were considered. First, the strong inhomogeneity in the spatial distribution of the plasma-induced flow were detected. Second, the principal role of negative ions in plasma-induced flow generation was established. Third, the two types of gas disturbances were observed: the thermal effect and momentum transfer effect (ion wind). To explain the aforementioned features of SDBD behavior in air and nitrogen the results of numerical simulation have been used.

Leonov, Sergey [Joint Institute for High Temperature, RAS, Moscow 125412 (Russian Federation); Opaits, Dmitry; Miles, Richard [Princeton University, Princeton, New Jersey 08544 (United States); Soloviev, Victor [Moscow Institute of Physics and Technology, Dolgoprudnyi, Moscow Region 141700 (Russian Federation)

2010-11-15

22

Modeling of dielectric barrier discharge plasma actuators driven by repetitive nanosecond pulses  

SciTech Connect

A detailed physical model for an asymmetric dielectric barrier discharge (DBD) in air driven by repetitive nanosecond voltage pulses is developed. In particular, modeling of DBD with high voltage repetitive negative and positive nanosecond pulses combined with positive dc bias is carried out. Operation at high voltage is compared with operation at low voltage, highlighting the advantage of high voltages, however the effect of backward-directed breakdown in the case of negative pulses results in a decrease of the integral momentum transferred to the gas. The use of positive repetitive pulses with dc bias is demonstrated to be promising for DBD performance improvement. The effects of the voltage waveform not only on force magnitude, but also on the spatial profile of the force, are shown. The crucial role of background photoionization in numerical modeling of ionization waves (streamers) in DBD plasmas is demonstrated.

Likhanskii, Alexandre V.; Shneider, Mikhail N.; Macheret, Sergey O.; Miles, Richard B. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Lockheed Martin Skunk Works, 1011 Lockheed Way, Palmdale, California 93599 (United States); Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

2007-07-15

23

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

24

Phase effect on flow control for dielectric barrier plasma actuators K. P. Singh and Subrata Roya  

E-print Network

power supply to the electrodes.1 The plasma when energized emits an acoustic signal which can provide low power a few watts levels, in a wide range of applications to suppress separation. Wings and fuselage of aircraft may be covered with a thin layer of glow discharge plasma which can pro- vide, through

Roy, Subrata

25

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.

26

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

27

Improving Wind Turbine Efficiency with Plasma Actuators  

NASA Astrophysics Data System (ADS)

As increasing the efficiency of modern wind turbines becomes more difficult, the use of active flow control now represents a more attractive means of possible improvement. This ongoing study examines utilizing single dielectric barrier discharge (SDBD) plasma actuators on wind turbine rotors to increase power generation. Blade element momentum (BEM) theory is used to identify regimes with the greatest potential for improvement and to estimate possible gains. Wind tunnel tests are conducted with plasma actuators to determine the amount of aerodynamic control achievable. In addition, the scope of a new "Laboratory for Enhanced Wind Energy Design" is outlined. Most critically, this resource includes two full-scale wind turbines to balance the known limitations of existing theory and wind tunnel testing by providing the capability to test novel blade designs and control strategies in the field.

Cooney, John; Corke, Thomas; Nelson, Robert

2010-11-01

28

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

29

Research on the Peristaltic Flow Acceleration Performance of Asynchronous and Duty Cycle Pulsed DBD Plasma Actuation  

NASA Astrophysics Data System (ADS)

Using a plexiglas plate model, the performance of peristaltic flow acceleration induced by multiple DBD (dielectric barrier discharge) plasma actuators was studied based on PIV (particle image velocimetry). The asynchronous and the duty cycle pulsed actuation modes were proposed and tested. The velocity fields induced by multiple DBD plasma actuators with different phase angles and duty cycle ratios were acquired and the momentum transfer characteristics of the flow field were discussed. Consequently, the mechanism of the peristalsis-acceleration multiple DBD plasma actuation was analyzed. The results show that the peristaltic flow acceleration effect of multiple plasma actuators occurs mainly in paraelectric direction, and the mechanism of peristaltic flow acceleration is ejection pushing effect rather than injection pumping effect. The asynchronous and the duty cycle pulsed actuation modes can, with energy consumption increase of merely 10%, achieve 65% and 42% increase of downstream velocity, and thus are promising in velocity improvement and energy saving.

Li, Feng; Gao, Chao; Zheng, Borui; Wang, Yushuai

2014-09-01

30

Strategies for control of transitional and turbulent flows using plasma-based actuators  

Microsoft Academic Search

An exploratory numerical study of the control of transitional and turbulent separated flows by means of dielectric-barrier-discharge (DBD) actuators is presented. The flow fields are simulated employing a high-fidelity Navier–Stokes solver augmented with a phenomenological model representing the plasma-induced body forces imparted by the actuator on the fluid. Several applications are considered, including interaction of an actuator with a laminar

Miguel R. Visbal

2010-01-01

31

Receptivity of Laminar Boundary Layers to Spanwise-Periodic Forcing by an Array of Plasma Actuators  

NASA Astrophysics Data System (ADS)

This work is concerned with the response of a Blasius boundary layer to dielectric-barrier- discharge (DBD) plasma actuators for the purpose of using these devices in bypass transition control. The plasma actuators consist of a spanwise-periodic array of high voltage electrodes, which are oriented to produce streamwise vortex pairs. The structure of actuator-induced streaks is measured using hot-wire anemometry over a streamwise distance of approximately 100 boundary layer thicknesses, and is decomposed into 4 span-wise Fourier modes. The modal content and corresponding streamwise growth characteristics are discussed for ten plasma actuator geometries over multiple excitation voltages and freestream velocities. Actuator power consumption was found to control the streak amplitude, whereas freestream velocity affected both amplitude and streamwise extent of the streaks. A common relationship between disturbance energy and power consumption was found among actuators of different dielectric thickness and similar electrode geometry.

Osmokrovic, Luke

32

The manipulation of an unstarting supersonic flow by plasma actuator  

NASA Astrophysics Data System (ADS)

The manipulation of an unstarting supersonic flow is demonstrated using a dielectric barrier discharge (DBD). Experiments are carried out in a Mach 4.7 model inlet flow. Flow features, such as boundary layers and shockwaves at low freestream static pressure (1 kPa) and temperature (60 K) are visualized with Rayleigh scattering from condensed CO2 particles. Flow unstart, initiated by mass injection, is studied for three model inlet flow configurations, distinguished by the initial conditions (untripped or tripped, plasma actuated or not) of the boundary layers. Unstart in the presence of thick, tripped boundary layers is characterized by the formation of an oblique unstart shock just upstream of a separating and propagating boundary layer. The presence of plasma actuation of this tripped boundary layer seems to arrest the boundary layer separation and leads to the formation of a quasi-stationary pseudo-shock, delaying unstart. The flow generated with DBD actuation is more characteristic of what is seen when unstart is generated in a model flow in which thin boundary layers grow naturally. Planar laser Rayleigh scattering visualizations suggest that the DBD actuation thins the tripped boundary layer over the exposed electrode region.

Im, S.; Do, H.; Cappelli, M. A.

2012-12-01

33

DNS Modeling of Plasma Array Flow Actuators  

NASA Astrophysics Data System (ADS)

As a part of a continuing effort toward the development of weakly ionized plasma actuators as a means for flow control, this study presents a numerical simulation of the response of the bulk flow to the actuators. For this simulation, solutions for the two-dimensional, unsteady, incompressible Navier-Stokes equations are obtained. The effect of the plasma is modeled as a body force in the momentum equations. Due to the Debye shielding effect, which leads to a localized body force near the electrodes, these equations are solved on a non-uniform grid using a 4th order compact finite-difference scheme. The code is initially validated on benchmark problems. In addition, digital PIV measurements are used to validate the simulations. The obtained results were found to favorably compare to the experiments. Our objective is to simulate the response of plasma actuators that are operated in different time-dependent conditions produced by transient or periodic inputs at different frequencies and phase shifts. The obtained results will be utilized to lead to optimum designs that enhance the actuators effectiveness at producing unsteady disturbances as a means to prevent or delay boundary layer separation.

Orlov, Dmitriy; Corke, Thomas; Haddad, Osamah

2003-11-01

34

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

35

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

36

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

E-print Network

as dielectric barrier discharge actuators (or OAUGDPTM , one atmosphere uniform glow discharge plasma1 of a high voltage, high frequency AC, a region of dielectric barrier discharge plasma is created­9 They are commonly produced by using an oscillating diaphragm mounted in a cavity that is embedded flush

Jacob, Jamey

37

Evaluation of thrust measurement techniques for dielectric barrier discharge actuators  

NASA Astrophysics Data System (ADS)

Despite its popularity in the recent literature, plasma actuators lack a consistent study to identify limitations, and remedy thereof, of various thrust measurement techniques. This paper focuses on comparing two different experimental techniques commonly used to measure the global, plasma-induced thrust. A force balance is used to make a direct measurement of the thrust produced, which is then compared with a control volume analysis on data obtained through particle image velocimetry. The local velocity measured by particle image velocimetry is also validated with a fine-tip pressure probe. For the direct thrust measurements, the effect of varying the actuator plate length upon which the induced flow acts is investigated. The results from these tests show that the length of the actuator plate is most influential at higher voltages with the measured thrust increasing as much as 20 % for a six times reduction in the length of the plate. For the indirect thrust measurement, the influence of the control volume size is analyzed. When the two methods are compared against each other, good agreement is found when the control volume size has a sufficient downstream extent. Also, the discharge length is optically measured using visible light emission. A linear correlation is found between the discharge length and the thrust measurements for the actuator configurations studied. Finally, the energy conversion efficiency curve for a representative actuator is also presented.

Durscher, Ryan; Roy, Subrata

2012-10-01

38

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

39

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

40

Influence of circulation on a rounded-trailing-edge airfoil using plasma actuators  

NASA Astrophysics Data System (ADS)

An experimental study on influence of circulation around a symmetric airfoil with a rounded trailing edge is presented. Flow control is achieved by the use of dielectric barrier discharge plasma actuators placed at the trailing edge of the airfoil. Direct lift and drag measurements are taken using an external load balance at freestream velocities of 10, 15 and 20 m/s corresponding to chord Reynolds number of 140,000, 210,000, 280,000. Additionally, time-resolved particle image velocimetry is used in order to elucidate the topology and dynamical response of the wake flow under the influence of actuation. Results indicate an increase in lift coefficient of approximately 0.1 for the lowest tested Reynolds number using the plasma actuator. Flowfield measurements indicate the successful manipulation of the Kutta condition enabled by the plasma actuator. The actuator is enhancing the mixing of the wake near the trailing edge while reducing the dominant shedding frequency. Proper orthogonal decomposition analysis reveals further details regarding the dynamics of the wake flow in presence of actuation, suggesting the sensitivity of the control concept to the positioning of the actuator as well as the angle of attack.

Kotsonis, Marios; Pul, Robin; Veldhuis, Leo

2014-07-01

41

Schlieren imaging in a dielectric barrier discharge actuator for airflow control  

NASA Astrophysics Data System (ADS)

The operation of a surface dielectric barrier discharge actuator for airflow control has been experimentally investigated. The actuator is constituted by an electrode pair separated by a dielectric Teflon sheet. Several ac supply conditions have been utilized. An electrohydrodynamics interaction was induced in still air, and several fluid-dynamic regimes were obtained. Visualization of the plasma boundary layer during the discharge ignition phase and during the steady state regime was obtained by utilizing a Schlieren diagnostic technique. The vortex morphology and propagation velocities at all supply conditions utilized have been evaluated. Velocity profiles perpendicular to the actuator surface, obtained from Pitot tube measurements, and line intensity profiles, determined by means of Schlieren imaging, have been determined for the steady regime operation. The integral along a line perpendicular to the actuator surface of the light intensity of the Schlieren image has been calculated. The profile obtained is in good agreement with the Pitot velocity profile in all the supply conditions investigated. Numerical simulations were also performed. The calculations confirm the relation between the flow velocity distribution in the boundary layer and the gas density distribution, which is the cause of the Schlieren image.

Cristofolini, A.; Neretti, G.; Roveda, F.; Borghi, C. A.

2012-02-01

42

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

43

Study of Transient and Unsteady Effects of Plasma Actuation in Transitional Flow over an SD7003 Airfoil  

E-print Network

at the trailing edge. Nomenclature c = Chord length Cd = Coefficient of drag Cf = Coefficient of skin friction Cl = Coefficient of lift Cm = Coefficient of moment Cp = Coefficient of pressure Dc = Nondimensional plasma force and plunging. The effects of Dielectric Barrier Discharge (DBD) plasma actuation as a flow control device have

Roy, Subrata

44

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

45

Electro-actuation characteristics of Cl2 and SF6 plasma-treated IPMC actuators  

Microsoft Academic Search

This paper describes plasma treatments that improve the actuation properties by modifying the surface morphology of ionic polymer metal composites (IPMC). The proposed Cl2 and SF6 plasmas change the surface appearance of the electroactive polymer, and scanning electron microscopy (SEM) of the plasma-treated surfaces reveals the development of round and cone-shaped microstructures. After electroless chemical metal plating, these microstructures significantly

Saim Saher; Woojin Kim; Sungwon Moon; H. Jin Kim; Yong Hyup Kim

2010-01-01

46

Boundary Layer Control by Means of Plasma Actuators  

SciTech Connect

The development of controlled transition in a flat-plate boundary layer is investigated using Large Eddy Simulations (LES) with the dynamic Smagorinsky model. The analysis of flow control with the objective to optimize the effects of Tollmien-Schlichting waves on a flat plate by means of plasma actuators was studied. The plasma effect is modeled as a body force in the momentum equations. These equations are solved in a uniform grid using a 2nd-order finite difference scheme in time and space. The response of plasma actuators operating in different time-dependent conditions, produced by transient or periodic inputs at different frequencies, is also analyzed.

Quadros, R. [UFRGS/PPGMAp-TUD-Stroemungslehre und Aerodynamik, Technische Universitaet Darmstadt, Petersenstr. 30, 64287 Darmstadt (Germany); Bortoli, A. L. de [UFRGS/DMPA-Departamento de Matematica Pura e Aplicada, Bento Goncalves 9500, Agronomia-P.O. Box 15080, Porto Alegre-RS (Brazil); Tropea, C. [TUD/SLA-Stroemungslehre und Aerodynamik, Technische Universitaet Darmstadt, Petersenstr. 30, 64287 Darmstadt (Germany)

2007-09-06

47

Active Flow Control in Turbomachinery Using Phased Plasma Actuators  

Microsoft Academic Search

This paper shall present the possibilities of new emerging active flow control techniques in turbomachinery using phased plasma actuators. The major gas turbine applications are low Reynolds number separation flow control in LPT turbine blades, active inlet flow control, active flow control on fan blades and compressor vanes, active control of tip clearance flows in the blade tip-casing region, plasma-assisted

B. Göksel; I. Rechenberg

48

Design of an Active Noise Control System using Plasma Actuators  

E-print Network

and analysed from sensors located in the test case (Figure 2 #12;U Trailing edge microphone Leading edgeDesign of an Active Noise Control System using Plasma Actuators Xun Huang, Sammie Chan, Xin Zhang variation in the flow field that can lead to the attenuation of flow-induced tonal noise [3, 4]. The plasma

Huang, Xun

49

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

50

Aerogel and ferroelectric dielectric materials for plasma actuators  

Microsoft Academic Search

This paper presents performance evaluation of two thick materials with extreme permittivity as dielectric barrier discharge actuators. Specifically, the use of silica aerogels and ferroelectrics is investigated. Due to high polarizability of the ferroelectric material the supplied power manifests itself primarily as heat generation with no measurable thrust. The silica aerogel, however, has a significant impact on thrust saturation as

Ryan Durscher; Subrata Roy

2012-01-01

51

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

52

Switching Behavior of a Plasma-Fluidic Actuator James W. Gregory*  

E-print Network

presents the plasma-fluidic actuator as a new type of flow control actuator. The device combines the best flow rates that current actuators cannot deliver. Jet thrust vectoring on a flight vehicle is oneSwitching Behavior of a Plasma-Fluidic Actuator James W. Gregory* , Joseph C. Ruotolo , Aaron R

Gregory, James W.

53

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

54

Force approximation for a plasma actuator operating in atmospheric air  

SciTech Connect

A plasma actuator has been studied using a self-consistent multibody system of quiescent air, plasma, and dielectric. Equations governing the motion of charged and neutral species have been solved with Poisson's equation. Based on first principles analysis, a functional relationship between electrodynamic force and electrical and physical control parameters has been approximated and numerically tested for air. The magnitude of approximated force increases with the fourth power of the amplitude of rf potential. Thus, the induced fluid velocity also increases. The induced velocity shows momentum injection very close to the actuator surface. There is, however, a very small increase in the induced velocity with the forcing frequency. For the specific range of operational parameters considered, the proposed force relation may help speed up the plasma actuator design process.

Singh, Kunwar Pal; Roy, Subrata [Computational Plasma Dynamics Laboratory and Test Facility, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2008-01-01

55

Suppression of Trailing-Edge Noise Using a Plasma Actuator  

NASA Astrophysics Data System (ADS)

Suppression control of noise generation from an airfoil trailing edge is examined experimentally by using a plasma actuator for a NACA0012 airfoil at an angle of attack of -2°, at a chord Reynolds number Re = 1.54 × 105. The boundary layer on the suction surface undergoes transition to turbulence at a location upstream of the trailing edge at the present flow condition and the generation of tonal trailing-edge noise is governed by vortex roll-up of boundary layer on the pressure surface in the vicinity of the trailing-edge which produces a strong acoustic (dipole) source by diffraction of vortex-induced fluctuations at the trailing-edge. When the plasma actuator is operated at an appropriate location on the pressure-side boundary layer, the trailing-edge noise is completely suppressed through delaying the development of the boundary-layer instability wave by the blowing effect of plasma actuator.

Inasawa, A.; Asai, M.; Itoh, K.; Kamijo, T.

2011-09-01

56

Numerical simulation of the effect of plasma aerodynamic actuation on improving film hole cooling performance  

NASA Astrophysics Data System (ADS)

The primary goal of this paper is to study film cooling performance for a cylindrical hole with plasma aerodynamic actuation. The simulation model of plasma aerodynamic actuation on improving film hole cooling effectiveness was established. The heat effect of plasma aerodynamic actuation model was taken into consideration. It was firstly found that the velocity and blowing ratio greatly affect the film cooling effectiveness. Then, position, power input, and the number of plasma actuators were particularly investigated.

Yu, Jin-Lu; He, Li-ming; Zhu, Yi-fei; Ding, Wei; Wang, Yu-qian

2013-06-01

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

Modelling of plasma aerodynamic actuation driven by nanosecond SDBD discharge  

NASA Astrophysics Data System (ADS)

A two-dimensional air plasma kinetics model (16 species and 44 processes) for nanosecond discharge under atmospheric pressure was developed to reveal the spatial and temporal distribution of discharge characteristics of a surface dielectric barrier discharge (SDBD) actuator. An energy transfer model, including two channels for energy release from external power source to gas, was developed to couple plasma with hydrodynamics directly in the same dimension. The governing equations included the Poisson equation for the electric potential, continuity equations for each species, electron energy equations for electrons taking part in reactions, and Navier-Stokes equations for non-isothermal fluid. The model was validated through current-voltage profile and electron temperature obtained from experiments. Calculations for discharge characteristics as well as the responses of fluid field from tens of nanoseconds to tens of seconds were performed. Results have shown that local air is heated to 1170 K within tens of nanoseconds and then decreases to 310 K at the end of a discharge period. 30% of the total power is transferred from electric field to electrons while only 20% of this energy is then released to gas through quenching processes. 9% of the total energy is released through ion collision. A micro-shock wave is formed and propagates at the speed of sound. High local density gradient and dynamic viscosity induces vortexes which whirl the heated air downstream. The combined effects of heating convection and vortexes in repetitive pulse discharges lead to the formation of a steady jet, in agreement with experimental results.

Zhu, Yifei; Wu, Yun; Cui, Wei; Li, Yinghong; Jia, Min

2013-09-01

59

Streamwise and spanwise plasma actuators for flow-induced cavity noise control  

E-print Network

March 2008 Plasma actuators operating in atmospheric air can induce a body force through collisions plasma actuators operating in at- mospheric pressure air2 holds the potential to reduce flow- induced/suction jets pose installation and maintenance is- sues. In contrast, plasma actuators are simple and cheap

Huang, Xun

60

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

E-print Network

of a turbulent channel flow with micro plasma actuators. Measurements are made by a laser Doppler velocimeter (LDV) at Re! = 297 and 602. We fabricate arrayed micro plasma actuators and reproduce spatially the exposed electrode. Okochi et al. (2009) fabricated micro plasma actuators for wall turbulence control

Kasagi, Nobuhide

61

Separation control in low pressure turbines using plasma actuators with passing wakes  

NASA Astrophysics Data System (ADS)

A Dielectric Barrier Discharge (DBD) plasma actuator is operated in flow over the suction surface of a Pack-B Low Pressure Turbine (LPT) airfoil at a Reynolds number of 50,000 (based on exit velocity and suction surface length) and inlet free-stream turbulence intensity of 2.5%. Preliminary characterization studies were made of the effect of varying actuator pulsing frequency and duty cycle, actuator edge effects, and orientation of the actuator with the flow. Flow control was demonstrated with the actuator imparting momentum opposite to the stream-wise flow direction, showing that it is possible to use disturbances alone to destabilize the flow and effect transition. No frequencies of strong influence were found over the range tested, indicating that a broad band of effective frequencies exists. Edge effects were found to considerably enhance separation control. Total pressure measurements of the flow without passing wakes were taken using a glass total-pressure tube. Corrections for streamline displacement due to shear and wall effects were made, and comparisons with previous hot-wire measurements were used to validate data. Performance features of conventional two-electrode and a novel three-electrode actuator configuration were compared. Hot-wire anemometry was used to take time-varying ensemble-averaged near-wall velocity measurements of the flow with periodic passing wakes. Corrections were made for near-wall effects, temperature effects, and interference of the electric field. The wakes were generated by a wake generator mechanism located upstream of the airfoil passage. The near-suction-surface total pressure field (flow without wakes) and velocity field (flow with wakes) in the trailing part of the airfoil passage, and the wall-normal gradient of these quantities, were used to demonstrate effective prevention of flow separation using the plasma actuator. Both flows (with and without passing wakes) showed fully attached flow (or very thin separation zones) when the actuator was activated. The flow with passing wakes and the actuator on showed relatively little time variation in the boundary layer, and qualitative similarities to the corresponding flow without passing wakes and with the actuator on were noted.

Burman, Debashish

62

Suppression of Trailing-Edge Noise Using a Plasma Actuator  

Microsoft Academic Search

Suppression control of noise generation from an airfoil trailing edge is examined experimentally by using a plasma actuator for a NACA0012 airfoil at an angle of attack of -2°, at a chord Reynolds number Re = 1.54 × 105. The boundary layer on the suction surface undergoes transition to turbulence at a location upstream of the trailing edge at the

A. Inasawa; M. Asai; K. Itoh; T. Kamijo

2011-01-01

63

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

64

Unmanned air vehicle flow separation control using dielectric barrier discharge plasma at high wind speed  

NASA Astrophysics Data System (ADS)

The present paper described an experimental investigation of separation control of an Unmanned Aerial Vehicle (UAV) at high wind speeds. The plasma actuator was based on Dielectric Barrier Discharge (DBD) and operated in a steady manner. The flow over a wing of UAV was performed with smoke flow visualization in the ?0.75 m low speed wind tunnel to reveal the flow structure over the wing so that the locations of plasma actuators could be optimized. A full model of the UAV was experimentally investigated in the ?3.2 m low speed wind tunnel using a six-component internal strain gauge balance. The effects of the key parameters, including the locations of the plasma actuators, the applied voltage amplitude and the operating frequency, were obtained. The whole test model was made of aluminium and acted as a cathode of the actuator. The results showed that the plasma acting on the surface of UAV could obviously suppress the boundary layer separation and reduce the model vibration at the high wind speeds. It was found that the maximum lift coefficient of the UAV was increased by 2.5% and the lift/drag ratio was increased by about 80% at the wind speed of 100 m/s. The control mechanism of the plasma actuator at the test configuration was also analyzed.

Zhang, Xin; Huang, Yong; Wang, WanBo; Wang, XunNian; Li, HuaXing

2014-06-01

65

Force approximation for a plasma actuator operating in atmospheric air Kunwar Pal Singh and Subrata Roya  

E-print Network

Force approximation for a plasma actuator operating in atmospheric air Kunwar Pal Singh and Subrata November 2006; published online 10 January 2008 A plasma actuator has been studied using a self momentum injection very close to the actuator surface. There is, however, a very small increase

Roy, Subrata

66

Physics of plasma actuator operating in atmospheric air Kunwar Pal Singh and Subrata Roya  

E-print Network

Physics of plasma actuator operating in atmospheric air Kunwar Pal Singh and Subrata Roya; published online 19 March 2008 The physics of plasma actuator operating in the atmospheric air has been, and turbulent separation over a wall-mounted hump. Unsteady flow actuation with a duty factor seemed to perform

Roy, Subrata

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

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

69

Plasma actuator electron density measurement using microwave perturbation method  

NASA Astrophysics Data System (ADS)

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

2014-07-01

70

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

71

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

72

Vacuum application of thermal barrier plasma coatings  

NASA Technical Reports Server (NTRS)

Coatings are presently applied to Space Shuttle Main Engine (SSME) turbine blades for protection against the harsh environment realized in the engine during lift off-to-orbit. High performance nickel, chromium, aluminum, and yttrium (NiCrAlY) alloy coatings, which are applied by atmospheric plasma spraying, crack and spall off because of the severe thermal shock experienced during start-up and shut-down of the engine. Ceramic coatings of yttria stabilized zirconia (ZrO2-Y2O3) were applied initially as a thermal barrier over coating to the NiCrAlY but were removed because of even greater spalling. Utilizing a vacuum plasma spraying process, bond coatings of NiCrAlY were applied in a low pressure atmosphere of argon/helium, producing significantly improved coating-to-blade bonding. The improved coatings showed no spalling after 40 MSFC burner rig thermal shock cycles, cycling between 1700 and -423 F. The current atmospheric plasma NiCrAlY coatings spalled during 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2-Y2O3 to the turbine blades of first stage high-pressure fuel turbopumps utilizing the vacuum plasma process. The improved thermal barrier coating has successfully passed 40 burner rig thermal shock cycles without spalling. Hot firing in an SSME turbine engine is scheduled for the blades. Tooling was installed in preparation for vacuum plasma spray coating other SSME hardware, e.g., the titanium main fuel valve housing (MFVH) and the fuel turbopump nozzle/stator.

Holmes, R. R.; Mckechnie, T. N.

1988-01-01

73

Streamwise and spanwise plasma actuators for flow-induced cavity noise control  

SciTech Connect

Plasma actuators operating in atmospheric air can induce a body force through collisions between electrically charged particles and neutral air molecules by an externally applied electric field. The fast response and the simple structure make the plasma actuator a promising option in aerospace applications. In this work, experiments were performed with several alternative current excited plasma (streamwise and spanwise) actuators to control flow-induced noise from a cavity. It was found that the streamwise actuator induced three-dimensional variations in the shear layer. The spanwise actuator, however, has little influence on the global flow field. As a result, the streamwise actuator is more effective than the spanwise actuator in cavity noise attenuation.

Huang Xun; Zhang Xin [Aeronautics and Astronautics, School of Engineering Sciences, University of Southampton, Southampton SO17 1BJ (United Kingdom)

2008-03-15

74

Plasma morphology and induced airflow characterization of a DBD actuator with serrated electrode  

NASA Astrophysics Data System (ADS)

Plasma morphology and airflow induced by a dielectric barrier discharge (DBD) actuator, whose exposed electrode geometry is designed with a serrated configuration, are investigated in quiescent air and compared with a DBD actuator consisting of electrodes designed with a standard linear strip configuration. ICCD imaging, electrical measurements and three-component laser Doppler velocimetry were carried out to compare various features of these two actuators. With the serrated configuration, ICCD images of the discharge show that streamers are bent, whereas with the linear configuration they are straight. These curved streamers induce a three-dimensional flow topology, which is confirmed by friction line visualization and velocity measurements. Whereas a two-dimensional wall-jet is induced with the linear configuration, a transverse velocity component is measured with the serrated configuration, implying the creation of spanwise-periodic vorticity. Phase-averaged velocity measurements allow the temporal variation of this transverse velocity to be highlighted. On both sides of a tooth, it has qualitatively the same variation as the longitudinal velocity with respect to the negative or positive half-cycles of the high voltage signal. Moreover, with the same electrical operating parameters, the measured longitudinal velocity was higher, particularly at the tips.

Joussot, R.; Leroy, A.; Weber, R.; Rabat, H.; Loyer, S.; Hong, D.

2013-03-01

75

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

76

Response of a circular cylinder wake to a symmetric actuation by non-thermal plasma discharges  

NASA Astrophysics Data System (ADS)

In this study, the flow past a circular cylinder is manipulated by two plasma discharges placed on both sides of the model (at ±50°). A parametric investigation by force balance is conducted to define the sensitivity of the flow field to unsteady perturbations imparted by plasma actuators (dielectric barrier discharge) at 15.6 m/s ( Re D = 40,000). Effects of simple sinusoidal waveform, burst modulation and amplitude modulation are compared for low-frequency excitations. Regardless of the excitation mode, the cylinder experiences a large increase in the drag coefficient. The larger drag increase is observed for excitation related to the lock-on regime. Fast PIV measurements and triple decomposition by proper orthogonal decomposition are performed to extract the dynamical changes in the cylinder wake and to discriminate the control effects on the coherent and fluctuating turbulence. As expected, the control principally acts on the coherent flow structures. When forced, the vortices form closer to the base of the cylinder regardless of the actuation mode. This results in the drag increase observed by force measurements. The effectiveness of burst modulation is also due to the suppression of irregular shedding that is observed in the natural flow sequence and to a high level of correlation between the upper and lower vortex shedding. Finally, flow visualizations indicate that similar results can be obtained at higher Reynolds number ( Re D = 128,000, 50 m/s).

Benard, N.; Moreau, E.

2013-02-01

77

Effect of the charge surface distribution on the flow field induced by a dielectric barrier discharge actuator  

NASA Astrophysics Data System (ADS)

The Electro-Hydro-Dynamics (EHD) interaction induced by a surface dielectric barrier discharge in the aerodynamic boundary layer at one atmosphere still air has been investigated. Three different geometrical configurations of the actuator have been utilized. In the first configuration, an electrode pair separated by a 2 mm dielectric sheet has been used. The second and the third configurations have been obtained by adding a third electrode on the upper side of the dielectric surface. This electrode has been placed downstream of the upper electrode and has been connected to ground or has been left floating. Three different dielectric materials have been utilized. The high voltage upper electrode was fed by an a.c. electric tension. Measurements of the dielectric surface potential generated by the charge deposition have been done. The discharge has been switched off after positive and negative phases of the plasma current (the current phase was characterized by a positive or a negative value, respectively). The measurements have been carried out after both phases. The charge distribution strongly depended on the switching off phase and was heavily affected by the geometrical configuration. A remarkable decrease of the charge deposited on the dielectric surface has been detected when the third electrode was connected to ground. Velocity profiles were obtained by using a Pitot probe. They showed that the presence of the third electrode limits the fluid dynamics performance of the actuator. A relation between the charge surface distribution and the EHD interaction phenomenon has been found. Imaging of the plasma has been done to evaluate the discharge structure and the extension of the plasma in the configurations investigated.

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

2013-08-01

78

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

79

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

80

Bacterial Inactivation by Atmospheric Pressure Dielectric Barrier Discharge Plasma Jet  

Microsoft Academic Search

Bacillus subtilis and Escherichia coli seeded in two media (agar and filter papers) were exposed to after-glow plasma emitted from a atmospheric pressure dielectric barrier discharge (DBD) plasma jet generator in open air with a temperature of about 30-80 °C. In order to estimate the inactivation of microorganism using DBD plasma jet, various plasma conditions (such as treatment time and

Sanxi Deng; Cheng Cheng; Guohua Ni; Yuedong Meng; Hua Chen

2008-01-01

81

Physics of plasma actuator operating in atmospheric air  

SciTech Connect

The physics of plasma actuator operating in the atmospheric air has been numerically investigated. The O{sup -}, O{sub 2}{sup -}, O{sub 2}{sup +}, and N{sub 2}{sup +} ions have been included in the air chemistry to identify their role. For the specific case study, we find the density of positive ions is an order of magnitude higher at the positive peak of the cycle than that at the negative peak of the cycle. This difference in density levels of the species causes the development of the directional bias of the electrodynamic force. Numerical simulations indicate that positive ions play major role in the development of the positive force.

Singh, Kunwar Pal; Roy, Subrata [Computational Plasma Dynamics Laboratory and Test Facility, Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611-6300 (United States)

2008-03-17

82

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

83

Influence of the energy dissipation rate in the discharge of a plasma synthetic jet actuator  

Microsoft Academic Search

A promising actuator for high-speed flow control, referred to as a plasma synthetic jet (PSJ), is being studied by the DMAE department of the ONERA, and the Laplace laboratory of the CNRS, in France. This actuator was inspired by the 'sparkjet' device developed by the Johns Hopkins University Applied Physics Laboratory. The PSJ, which produces a synthetic jet with high

A. Belinger; P. Hardy; P. Barricau; J. P. Cambronne; D. Caruana

2011-01-01

84

Local and Bi-Global Stability Analysis of a Plasma Actuated Boundary Layer  

E-print Network

Local and Bi-Global Stability Analysis of a Plasma Actuated Boundary Layer Mark Riherd and Subrata discharge actuators on a laminar, zero pressure gradi- ent boundary layer. Both methods indicate layer. The general behavior of boundary layer stabilization is consistent with experimental results

Roy, Subrata

85

Low-Reynolds Number Flow Control Using Dielectric Barrier Discharge Actuators  

Microsoft Academic Search

Dielectric Barrier Discharges (DBD), operated at KHz and KV range, can create athermal plasma via collision processes and induce near wall jet. In this paper, we investigate the potential of using DBD to conduct flow control at low Reynolds numbers, motivated by micro air vehicle (MAV) applications. A previously developed computational methodology, based on the eN transition model and the

Balaji Jayaraman; Yongsheng Lian; Wei Shyy

2007-01-01

86

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

87

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

88

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

NASA Astrophysics Data System (ADS)

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; Nie, Wansheng; Shao, Tao; Tian, Xihui; Hou, Zhiyong; He, Haobo; Zhou, Penghui; Zhou, Siyin; Yang, Chao

2014-04-01

89

Investigation of the cylinder wake under spanwise periodic forcing with a segmented plasma actuator  

NASA Astrophysics Data System (ADS)

The wake response to three-dimensional forcing of flow over a circular cylinder was studied. Spanwise-segmented dielectric-barrier discharge plasma actuators were mounted on the cylinder in a square wave pattern for active forcing of the cylinder wake. The buried electrodes were placed periodically to create a spanwise-modulated blowing profile, with the aim of targeting three-dimensional instabilities in the wake. Considerable spanwise variation in the wake was achieved, which was a direct consequence of the difference in the location of shed spanwise vortices from the cylinder, along with the generation of streamwise vorticity. Two distinct power levels were used for forcing the flow, with different flow response observed between the two conditions. With low power, the segmented forcing caused the large-scale spanwise structures in the forcing region to lead those in the no-forcing region, with an accompanying shift away from the centerline and generation of streamwise vorticity. While vortex shedding was not substantially attenuated with low-power forcing, the shedding in the near wake was significantly attenuated with high-power forcing. This attenuation in the shedding strength was accompanied by a decrease in the peak shedding frequency, indicating an increase in the formation length. High-power forcing caused elongation of the Kármán vortices due to the induced strain field and strong differential development of the wake shedding frequency. In both forcing regimes, the wake three-dimensionality increased as shown by the increased width of the spectral peaks.

Bhattacharya, S.; Gregory, James W.

2015-01-01

90

Flow control around a circular cylinder using pulsed dielectric barrier discharge surface plasma  

SciTech Connect

Dielectric barrier discharge (DBD) plasma actuators have been used to control the flow around a circular cylinder at Re=15 000, where the near-wake structure was studied using time-resolved particle image velocimetry with simultaneous measurements of the dynamic lift and drag forces. It was shown that the vortex shedding was suppressed when the surface plasma placed near the natural separation point was activated in a pulsed mode at nondimensional frequency, f{sub p}{sup +}, above 0.6 with a force coefficient, C{sub p}, greater than 0.05%. Plasma actuator performance on flow control was summarized by mapping the changes in drag and lift fluctuations as a function of the forcing frequency and the force coefficient. They showed that more than 70% reduction in lift fluctuations was obtained with up to 32% drag reduction at f{sub p}{sup +}=2.0 and C{sub p}=0.32%. Here, narrowing of the wake was observed as the plasma promoted shear-layer roll-ups at the forcing frequency. This, however, did not affect the shear layer on the opposite side of the wake. At nondimensional forcing frequencies less than 0.6, the vortex shedding locked onto a multiple of the plasma frequency to amplify the wake oscillations. This caused more than 85% increase in lift fluctuations with 8% drag increase at f{sub p}{sup +}=0.2 and C{sub p}=0.01%. The efficiency of flow control using DBD plasma was found to be 1%-2% for drag reduction while around 6% for drag increase.

Jukes, Timothy N.; Choi, Kwing-So [Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

2009-08-15

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

Damping Tollmien-Schlichting waves in a boundary layer using plasma actuators  

NASA Astrophysics Data System (ADS)

The response of a zero pressure gradient boundary layer modified by flow-wise oriented momentum injection similar to that of a plasma actuator is calculated using a two-dimensional (bi-global) stability analysis. It is found that the addition of momentum into the boundary layer has a significant impact on Tollmien-Schlichting waves, which may be damped by up to two orders of magnitude. Changes to the exponential growth rate of the perturbations are also measured. These stabilizing effects are largely due to the momentum addition modifying the downstream boundary layer profiles, but localized stabilization effects are also noted. The relative stabilization of the TS wave appears to be a linear function with respect to the ratio of the plasma-induced wall jet velocity under quiescent conditions and the free-stream velocity for lower levels of plasma actuation (i.e. velocity ratios less than 0.1). For higher levels of plasma actuation, the relative stabilization of the TS wave appears to be exponential with respect to the total momentum addition to the boundary layer by the plasma actuator.

Riherd, Mark; Roy, Subrata

2013-12-01

93

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

94

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

95

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

96

Plasma sprayed and electrospark deposited zirconium metal diffusion barrier coatings  

Microsoft Academic Search

Zirconium metal coatings applied by plasma spraying and electrospark deposition (ESD) have been investigated for use as diffusion barrier coatings on low enrichment uranium fuel for research nuclear reactors. The coatings have been applied to both stainless steel as a surrogate and to simulated nuclear fuel uranium-molybdenum alloy substrates. Deposition parameter development accompanied by coating characterization has been performed. The

Kendall J Hollis; Maria I Pena

2010-01-01

97

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

98

Noise reduction in a heated Mach 1.3 jet using plasma actuators  

Microsoft Academic Search

Heating capabilities have recently been added to the free jet facility at the Gas Dynamics and Turbulence Laboratory (GDTL) of the Ohio State University using a storage-based off-line electric heater. This addition makes it possible to test the effectiveness of the localized arc filament plasma actuators (LAFPAs) for the purpose of either noise mitigation or mixing enhancement over a wide

Martin Kearney-Fischer; Mo Samimy

2009-01-01

99

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

100

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

101

Plasma bolometry using a multislit shutter with piezoelectric actuator  

NASA Astrophysics Data System (ADS)

We offer to apply a shutter with a piezoelectric bimorph actuator as a modulator of radiation and particle fluxes. Such shutters may be useful to provide measurements in steady state regimes of tokamaks and stellarators because they allow one to avoid amplifier drifts and to simplify diagnostics calibration. Signal modulation makes it possible to apply the lock-in amplification technique, increasing the sensitivity and reducing the neutron doze collected by sensors. Experiments with pyroelectric sensors (LiTaO3) at 350 Hz modulation frequency have demonstrated the detection limit at 30 Hz equal to 15 ?W/cm2, which is comparable to metallic bolometers.

Kuteev, Boris V.; Outkine, Andrew A.; Gabdullin, Pavel G.; Kostrioukov, Artem Yu.; Kapralov, Vladimir G.

2004-10-01

102

Performance enhancement of IPMC actuator by plasma surface treatment  

Microsoft Academic Search

IPMC (ionic polymer metal composite) is composed of ionic polymer and metal electrodes on both surfaces of the polymer. In this study, we changed the surface morphology of the ionic polymer by using plasma treatment. Plasma treatment made needle-shaped microstructures on the surface of the polymer and the microstructures helped to form a thicker uniform metal electrode which is deposited

Seong Jun Kim; In Taek Lee; Yong Hyup Kim

2007-01-01

103

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

104

Catalytic synthesis of carbon nanotubes in pulsed barrier discharge plasma  

NASA Astrophysics Data System (ADS)

It has been found that it is possible to activate the process of obtaining carbon nanotubes by vapor deposition due to the generation in the reaction zone of nonequilibrium plasma by the method of pulsed barrier discharge. It has been shown that depending on the catalytic substrate used (nickel wire, stainless steel, porous aluminum oxide with nickel deposited) in the pores, under the conditions of pulsed discharge both individual carbon nanotubes (straight or helical) and their ordered arrays can be obtained.

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

2007-11-01

105

Numerical study of boundary layer separation control using magnetogasdynamic plasma actuators  

NASA Astrophysics Data System (ADS)

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.

2009-10-01

106

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

107

Temporal modulation of plasma species in atmospheric dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

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-N2 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 N2 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; Liu, Dingxin; Rong, Mingzhe; Kong, Michael G.

2014-07-01

108

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

109

Active control of massively separated high-speed/base flows with electric arc plasma actuators  

NASA Astrophysics Data System (ADS)

The current project was undertaken to evaluate the effects of electric arc plasma actuators on high-speed separated flows. Two underlying goals motivated these experiments. The first goal was to provide a flow control technique that will result in enhanced flight performance for supersonic vehicles by altering the near-wake characteristics. The second goal was to gain a broader and more sophisticated understanding of these complex, supersonic, massively-separated, compressible, and turbulent flow fields. The attainment of the proposed objectives was facilitated through energy deposition from multiple electric-arc plasma discharges near the base corner separation point. The control authority of electric arc plasma actuators on a supersonic axisymmetric base flow was evaluated for several actuator geometries, frequencies, forcing modes, duty cycles/on-times, and currents. Initially, an electric arc plasma actuator power supply and control system were constructed to generate the arcs. Experiments were performed to evaluate the operational characteristics, electromagnetic emission, and fluidic effect of the actuators in quiescent ambient air. The maximum velocity induced by the arc when formed in a 5 mm x 1.6 mm x 2 mm deep cavity was about 40 m/s. During breakdown, the electromagnetic emission exhibited a rise and fall in intensity over a period of about 340 ns. After breakdown, the emission stabilized to a near-constant distribution. It was also observed that the plasma formed into two different modes: "high-voltage" and "low-voltage". It is believed that the plasma may be switching between an arc discharge and a glow discharge for these different modes. The two types of plasma do not appear to cause substantial differences on the induced fluidic effects of the actuator. In general, the characterization study provided a greater fundamental understanding of the operation of the actuators, as well as data for computational model comparison. Preliminary investigations of actuator geometry in the supersonic base flow determined that inclined cavity and normal cavity actuators positioned on the base near the base edge could produce significant disturbances in the shear layer. The disturbances were able to be tracked in time with phase-locked schlieren imaging and particle image velocimetry (PIV). The final set of flow control experiments were therefore performed with an eight-actuator base using the inclined cavity actuator geometry. The actuators were able to cause moderate influences on the axisymmetric shear layer velocity profile and base pressure. The most substantial changes to the shear layer and base pressure were noted for the highest current and duty cycle tests. At 1 A and 20% duty cycle, the base pressure was reduced by 3.5%. Similar changes were noted for all modes and a range of frequencies from about 10-30 kHz. Increases in duty cycle between 4% and 20% caused a nearly linear decrease in base pressure. Analysis of the shear layer velocity profiles acquired through PIV show a local thickening of the shear layer in the region of the disturbances caused by the actuator. A slight increase in thickness was also observed away from the disturbance. Disturbances were able to be tracked at all frequencies and translated along the shear layer at a convective velocity of 430 +/- 20 m/s. A fairly clear trend of increasing velocity disturbance amplitude correlating to increasing base pressure changes was noted. Moreover, the ability of the disturbances to stay well organized further down the shear layer also appears to be a significant factor in the actuators' effect on base pressure. Consistent with these observations, it appears that increased duty cycle causes increased shear layer disturbance amplitudes. The use of PIV has enabled substantial insight to be gained into the effects of the actuators on the ensemble-averaged flow field and on the variability of the instantaneous flow field with and without control. A sensitive bimodal recirculation region behavior was found in the no-control flow field tha

DeBlauw, Bradley G.

110

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

111

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

112

An experimental study of a plasma actuator in absence of free airflow: Ionic wind velocity profile  

SciTech Connect

In this study, we are interested in the direct current electrical corona discharge created between two wire electrodes. The experimental results are related to some electroaerodynamic actuators based on the direct current corona discharge at the surface of a dielectric material. Several geometrical forms are selected for the dielectric surface, such as a plate, a cylinder, and a NACA 0015 aircraft wing. The current density-electric field characteristics are presented for different cases in order to determine the discharge regimes. The corona discharge produces nonthermal plasma, so it is called plasma discharge. Plasma discharge creates a tangential ionic wind above the surface at the vicinity of the wall. The ionic wind induced by the corona discharge is measured in absence of free external airflow. The ionic wind velocity profiles and the maximum induced tangential force are given for different surface forms, so it is possible to compare the actuators effect based on the span of the ionic wind velocity and thrust values. The higher ionic wind velocity is obtained with the NACA profile, which shows the effectiveness of this actuator for the airflow control.

Mestiri, R.; Hadaji, R.; Ben Nasrallah, S. [Ecole Nationale d'Ingenieurs de Monastir, Monastir 5019 (Tunisia)

2010-08-15

113

One-dimensional analytical model development of a plasma-based actuator  

NASA Astrophysics Data System (ADS)

This dissertation provides a method for modeling the complex, multi-physics, multi-dimensional processes associated with a plasma-based flow control actuator, also known as the SparkJet, by using a one-dimensional analytical model derived from the Euler and thermodynamic equations, under varying assumptions. This model is compared to CFD simulations and experimental data to verify and/or modify the model where simplifying assumptions poorly represent the real actuator. The model was exercised to explore high-frequency actuation and methods of improving actuator performance. Using peak jet momentum as a performance metric, the model shows that a typical SparkJet design (1 mm orifice diameter, 84.8 mm3 cavity volume, and 0.5 J energy input) operated over a range of frequencies from 1 Hz to 10 kHz shows a decrease in peak momentum corresponding to an actuation cutoff frequency of 800 Hz. The model results show that the cutoff frequency is primarily a function of orifice diameter and cavity volume. To further verify model accuracy, experimental testing was performed involving time-dependent, cavity pressure and arc power measurements as a function of orifice diameter, cavity volume, input energy, and electrode gap. The cavity pressure measurements showed that pressure-based efficiency ranges from 20% to 40%. The arc power measurements exposed the deficiency in assuming instantaneous energy deposition and a calorically perfect gas and also showed that arc efficiency was approximately 80%. Additional comparisons between the pressure-based modeling and experimental results show that the model captures the actuator dependence on orifice diameter, cavity volume, and input energy but over-estimates the duration of the jet flow during Stage 2. The likely cause of the disagreement is an inaccurate representation of thermal heat transfer related to convective heat transfer or heat loss to the electrodes.

Popkin, Sarah Haack

114

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

115

Direct Measurement of Wall-Shear Stress of Plane Shear Layer with Plasma Synthetic Jet Actuator  

NASA Astrophysics Data System (ADS)

One of the useful ways to measure the effect of the flow control devise is to use the wall-shear stress sensor to measure the wall-shear stress directly. The sensor used in this paper measures the wall-shear stress, which is reduced by the flow control devise. In this paper, the wall-shear stress of the plane shear layer with the plasma synthetic jet actuator (PSJA) is investigated. PSJA is a flow control device composed of electrodes with A.C. signal. The actuator uses electrohydrodynamic (EHD) effect and induces flow around the electrodes. PSJA has great advantage such as miniaturization, maintenance free, and easy to control compared to other actuators. In this paper, the wall-shear stress of plane shear layer in a low-speed turbulent wind tunnel is observed to measure the effect of the PSJA. The results show that the PSJA changes the flow condition of shear layer by accelerating the flow in shear layer. The wall-shear stress reduces and increases according to the displacement of the wall-shear stress sensor and the actuator.

Higuchi, Takehiro; Ogawara, Kakuji; Mochizuki, Shinsuke

116

Plasma synthetic jet actuator: electrical and optical analysis of the discharge  

NASA Astrophysics Data System (ADS)

Active flow control is based on the development of robust actuators which are reliable, small and easy to integrate. A promising actuator referred to as plasma synthetic jet actuator produces a synthetic jet with high exhaust velocities and holds the promise of enabling high-speed flows. With this high velocity jet, it is possible to reduce fluid phenomena such as transition and turbulence, thus making it possible to increase an aircraft's performance whilst at the same time reducing its environmental impact. This high velocity jet is produced by a pulsed discharge in a microcavity. In this paper, we focus on the properties of the discharge in order to understand the functioning of the actuator. In the first part an electrical description of the discharge in presented. Afterwards, optical measurements (optical emission spectroscopy and ICCD photograph) enable the determination of temperature, volume and duration of the discharge. At the end of the paper we present an electrical model of the discharge, which can be obtained both from electrical measurements and from macroscopic properties of the discharge (temperature, volume). This electrical model can easily be included in electrical simulation software.

Belinger, A.; Naudé, N.; Cambronne, J. P.; Caruana, D.

2014-08-01

117

Destruction of 1,1,1-Trichloroethane Using Dielectric Barrier Discharge Nonthermal Plasma  

E-print Network

are not in thermal equilibrium. In nonthermal plasma, electrons, ions, and neutral species have differentDestruction of 1,1,1-Trichloroethane Using Dielectric Barrier Discharge Nonthermal Plasma Sandeep nonthermal plasma produced in a dielectric barrier discharge reactor to destroy 1,1,1-trichloroethane TCA

Cal, Mark P.

118

Feedback control of slowly-varying transient growth by an array of plasma actuators  

NASA Astrophysics Data System (ADS)

Closed-loop feedback control of boundary layer streaks embedded in a laminar boundary layer and experiencing transient growth, which is inherent to bypass boundary layer transition, is experimentally investigated. Streaky disturbances are introduced by a spanwise array of cylindrical roughness elements, and a counter disturbance is provided by a spanwise array of plasma actuators, which are capable of generating spanwise-periodic counter rotating vortices in the boundary layer. Feedback is provided by a spanwise array of shear stress sensors. An input/output model of the system is obtained from measurements of the boundary layer response to steady forcing, and used to design and analyze a proportional-integral controller, which targets a specific spanwise wavenumber of the disturbance. Attention is directed towards a quasi-steady case in which the controller update is slower than the convective time scale. This choice enables addressing issues pertinent to sensing, actuation, and control strategy that are also relevant to the control of unsteady disturbances but without the full complexity of transient effects. The feedback controller and plasma actuators perform well, attenuating the streamwise streaks both in the vicinity of the sensors and farther downstream. The controller remains effective for a range of off-design flow conditions, such as when the free-stream velocity is varied.

Hanson, Ronald E.; Bade, Kyle M.; Belson, Brandt A.; Lavoie, Philippe; Naguib, Ahmed M.; Rowley, Clarence W.

2014-02-01

119

Micro Actuators Electrostatic actuator  

E-print Network

film #12;W for PVDF film #12;Electrical to Mechanical l W t #12;#12;Bimorph Piezoelectric Actuators #12Micro Actuators ·Electrostatic actuator - comb drive actuator ·Magnetic actuator ·Thermal actuator ·Piezoelectric actuator ·Shape memory alloy actuator ·Pneumatic actuator Ref: AIP Handbook of Modern Sensors http

Leu, Tzong-Shyng "Jeremy"

120

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

121

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

122

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

SciTech Connect

Understanding the behavior of three-dimensional plasmas around a pulsed dc actuator can be useful for its efficient operation in many applications. The effect of such actuators is studied using a self-consistent multibody system of neutral oxygen species and its plasma. The equations governing the motion of charged species are solved with the drift diffusion approximation. The electrostatic potential is computed from Poisson's equation. The electric field and ionization level are the highest close to the junction of electrodes and dielectric. The plasma body force thus generated also follows a similar characteristic. Results also show some dc corona instabilities. The temporal average of such force shows mostly acceleration from anode to cathode above the actuator.

Singh, Kunwar Pal; Roy, Subrata [Computational Plasma Dynamics Laboratory and Test Facility, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2008-05-15

123

High-Barrier Schottky Diodes on N-Type Si(100) Due to Hydrogen Plasma  

Microsoft Academic Search

Electrical characteristics of Al\\/Si diodes exposed to hydrogen-containing plasmas have been measured. The Schottky barrier heights increase compared with that of a control diode. The Schottky barrier height increases consistently with an increase in an applied rf power or hydrogen concentration in the plasma. Furthermore, the Si surface exposed to argon or hydrogen plasma has been observed by X-ray photoelectron

Hiroaki Iwakuro; Toru Inoue; Tsukasa Kuroda

1991-01-01

124

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

125

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

126

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

127

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

128

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

NASA Astrophysics Data System (ADS)

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 (Mj=0.9) jet. Twelve experiments with various forcing azimuthal modes (m =0, 1, and ±1) and temperatures (To/Ta=1.0, 1.4, and 2.0) at a fixed forcing Strouhal number (StDF=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.

2009-09-01

129

Noise reduction in a heated Mach 1.3 jet using plasma actuators  

NASA Astrophysics Data System (ADS)

Heating capabilities have recently been added to the free jet facility at the Gas Dynamics and Turbulence Laboratory (GDTL) of the Ohio State University using a storage-based off-line electric heater. This addition makes it possible to test the effectiveness of the localized arc filament plasma actuators (LAFPAs) for the purpose of either noise mitigation or mixing enhancement over a wide range of temperatures. These actuators have been used successfully at GDTL in high Reynolds number, high-speed unheated jets. The facility consists of an axisymmetric jet of exit diameter 2.54 cm with different nozzle blocks and variable jet temperature in an anechoic chamber. Previous work with a Mach 0.9 jet has shown significant increases in noise reduction effectiveness with increasing temperature. The next step is to determine if and how this trend continues in supersonic heated jets. A number of combinations of forcing azimuthal mode and temperature ratio at a wide range of forcing frequencies are experimented in a perfectly-expanded Mach 1.3 axisymmetric jet to examine LAFPAs effectiveness for far-field noise mitigation. The preliminary results to be presented indicate that the trends observed in the previous work continue in this supersonic jet.

Kearney-Fischer, Martin; Samimy, Mo

2009-11-01

130

Atmospheric pressure plasma jets beyond ground electrode as charge overflow in a dielectric barrier discharge setup  

E-print Network

Atmospheric pressure plasma jets beyond ground electrode as charge overflow in a dielectric barrier voltage and the width of ground electrode, atmospheric pressure plasma jets extending beyond the ground, that surprisingly a plasma jet in the ambient air can penetrate the wall of a dielectric tube, and a secondary

Zexian, Cao

131

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

132

Micronucleus formation induced by dielectric barrier discharge plasma exposure in brain cancer cells  

NASA Astrophysics Data System (ADS)

Induction of micronucleus formation (cytogenetic damage) in brain cancer cells upon exposure of dielectric barrier discharge plasma has been investigated. We have investigated the influence of exposure and incubation times on T98G brain cancer cells by using growth kinetic, clonogenic, and micronucleus formation assay. We found that micronucleus formation rate directly depends on the plasma exposure time. It is also shown that colony formation capacity of cells has been inhibited by the treatment of plasma at all doses. Cell death and micronucleus formation are shown to be significantly elevated by 120 and 240 s exposure of dielectric barrier discharge plasma.

Kaushik, Nagendra K.; Uhm, Hansup; Ha Choi, Eun

2012-02-01

133

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

134

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

E-print Network

the power efficiency. Rather than using linear power amplifier [2], [8], our power supply uses power- marized. To improve the power efficiency, several plasma driving signals were tested on a real-time system the potential to reduce flow-induced noise generated during the takeoff and approach-to-landing of aircraft

Huang, Xun

135

Measurement of OH Radicals in Dielectric Barrier Discharge Plasmas by Cavity Ring-Down Spectroscopy  

Microsoft Academic Search

Near-infrared continuous wave cavity ring-down spectroscopy was applied to measure the OH radicals in dielectric barrier discharge plasmas, which play an important role in combustion systems, atmospheric chemistry and the removal of air pollutants by non-thermal plasmas. The P-branches of OH X2?i nu\\

Guoli Zhao; Aimin Zhu; Jiating Wu; Zhongwei Liu; Yong Xu

2010-01-01

136

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

137

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

138

Development of a stable dielectric-barrier discharge enhanced laminar plasma jet generated at atmospheric pressure  

SciTech Connect

A stable nonthermal laminar atmospheric-pressure plasma source equipped with dielectric-barrier discharge was developed to realize more efficient plasma generation, with the total energy consumption reduced to nearly 25% of the original. Temperature and emission spectra monitoring indicates that this plasma is uniform in the lateral direction of the jet core region. It is also found that this plasma contains not only abundant excited argon atoms but also sufficient excited N{sub 2} and OH. This is mainly resulted from the escape of abundant electrons from the exit, due to the sharp decrease of sustaining voltage and the coupling between ions and electrons.

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

2012-06-18

139

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

140

Atmospheric pressure resistive barrier air plasma jet induced bacterial inactivation in aqueous environment  

NASA Astrophysics Data System (ADS)

An atmospheric pressure resistive barrier air plasma jet is designed to inactivate bacteria in aqueous media in direct and indirect exposure modes of treatment. The resistive barrier plasma jet is designed to operate at both dc and standard 50-60 Hz low frequency ac power input and the ambient air at 50% humidity level was used as the operating gas. The voltage-current characteristics of the plasma jet were analyzed and the operating frequency of the discharge was measured to be 20 kHz and the plasma power was measured to be 26 W. The plasma jet rotational temperatures (Trot) are obtained from the optical emission spectra, from the N2C-B(2+) transitions by matching the experimental spectrum results with the Spectra Air (SPECAIR) simulation spectra. The reactive oxygen and nitrogen species were measured using optical emission spectroscopy and gas analyzers, for direct and indirect treatment modes. The nitric oxides (NO) were observed to be the predominant long lived reactive nitrogen species produced by the plasma. Three different bacteria including Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative), and Neisseria meningitidis (Gram-negative) were suspended in an aqueous media and treated by the resistive barrier air plasma jet in direct and indirect exposure modes. The results show that a near complete bacterial inactivation was achieved within 120 s for both direct and indirect plasma treatment of S. aureus and E. coli bacteria. Conversely, a partial inactivation of N. meningitidis was observed by 120 s direct plasma exposure and insignificant inactivation was observed for the indirect plasma exposure treatment. Plasma induced shifts in N. meningitidis gene expression was analyzed using pilC gene expression as a representative gene and the results showed a reduction in the expression of the pilC gene compared to untreated samples suggesting that the observed protection against NO may be regulated by other genes.

Thiyagarajan, Magesh; Sarani, Abdollah; Gonzales, Xavier

2013-03-01

141

Transport barriers and edge localized modes-like bursts in a plasma model with turbulent equipartition profiles  

E-print Network

Transport barriers and edge localized modes-like bursts in a plasma model with turbulent-consistent development of transport barriers is investigated analytically and numerically in flux driven interchange in the turbulence, prevent mixing, and constitute transport barriers for the turbulent fluxes

Nycander, Jonas

142

A study of barrier-torch plasma jet system at atmospheric pressure  

Microsoft Academic Search

We report on the application of barrier-torch plasma jet system — the novel plasma deposition system capable of working at\\u000a atmospheric pressure in open air. Properties of ZnO and TiO2 thin films were analyzed by XRD and AFM. In the contribution we present the first results of spectroscopic measurements of\\u000a Balmer H? line width aimed at estimating the electron density

M. Chichina; M. Tichý; P. Kudrna; A. Grinevich; O. Churpita; Z. Hubicka; S. Kment; J. Olejnícek

2006-01-01

143

Atmospheric-Pressure Dielectric Barrier Plasma Jets Elongated by Elevating External Electric Field  

Microsoft Academic Search

The discharge characteristics of the atmospheric- pressure plasma jets, generated by a capillary dielectric-barrier- discharge configuration with helium\\/neon gas flowing through and issuing out into the ambient air in different electric fields, have been investigated by an electron-multiplying CCD. We have com- pared plasma jets propagating in three configurations: 1) only one unipolar power electrode surrounding the capillary; 2) a

Qing Li; Yi-Kang Pu; Hideya Nishiyama

2011-01-01

144

Deactivation of A549 cancer cells in vitro by a dielectric barrier discharge plasma needle  

SciTech Connect

An inactivation mechanism study on A549 cancer cells by means of a dielectric barrier discharge plasma needle is presented. The neutral red uptake assay provides a quantitative estimation of cell viability after plasma treatment. Experimental results show that the efficiency of argon plasma for the inactivation process is very dependent on power and treatment time. A 27 W power and 120 s treatment time along with 900 standard cubic centimeter per minute Ar flow and a nozzle-to-sample separation of 3 mm are the best parameters of the process. According to the argon emission spectra of the plasma jet and the optical microscope images of the A549 cells after plasma treatment, it is concluded that the reactive species (for example, OH and O) in the argon plasma play a major role in the cell deactivation.

Huang Jun; Chen Wei; Li Hui; Wang Xingquan; Lv Guohua; Wang Pengye [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Khohsa, M. Latif [Pakistan Institute of Technology for Mineral and Advanced Engineering Material, Ferozepur Road, Lahore-54600 (Pakistan); Guo Ming; Feng Kecheng [College of Science, Changchun University of Science and Technology, Changchun 130022 (China); Yang Size [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Fujian Key Laboratory for Plasma and Magnetic Resonance, Department of Aeronautics, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005 (China)

2011-03-01

145

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

NASA Astrophysics Data System (ADS)

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.; Ioppolo, Tindaro; Ötügen, M. Volkan; Sheverev, Valery A.

2010-09-01

146

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

147

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

148

Formation of High Quality AlN Tunnel Barriers via an Inductively Couple Plasma  

NASA Astrophysics Data System (ADS)

Increasing operating frequencies of SIS receivers requires junctions that can operate at higher current densities. A major limiting factor of higher current density junctions is the increase in subgap leakage that occurs in AlOX barriers as current densities approach and exceed 10kA/cm2. AlN insulators are a promising alternative due to their lower leakage current at these high current densities. In this paper we present a more detailed analysis of the formation of AlN barriers using our previously reported inductively coupled plasma (ICP) source growth technique. The ICP allows for independent control of ion energy and current density in the plasma. Additionally, plasmas with very low ion energy (~20eV) and a high degree of dissociation (~80%) can be achieved. This improved control allows for the repeatable formation of high quality barriers. In particular, we report on the relationship between barrier thickness and plasma conditions as determined by in-situ discrete ellipsometry. Ellipsometry results were verified by fabricating Nb/Al-AlN/Nb junctions and measuring current-voltage, I(V), curves. dc I(V) curves for a range of current densities are presented.

Cecil, Thomas W.; Lichtenberger, Arthur W.; Kerr, Anthony R.

2008-04-01

149

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

150

Permeation barrier coating and plasma sterilization of PET bottles and foils  

NASA Astrophysics Data System (ADS)

Modern packaging materials such as polyethylene terephthalate (PET) offer various advantages over glass or metal containers. Beside this they only offer poor barrier properties against gas permeation. Therefore, the shelf-live of packaged food is reduced. Additionally, common sterilization methods like heat, hydrogen peroxide or peracetic acid may not be applicable due to reduced heat or chemical resistance of the plastic packaging material. For the plasma sterilization and permeation barrier coating of PET bottles and foils, a microwave driven low pressure plasma reactor is developed based on a modified Plasmaline antenna. The dependencies of important plasma parameters, such as gas mixture, process pressure, power and pulse conditions on oxygen permeation through packaging foil are investigated. A residual permeation as low as J = 1.0 ±0.3 cm^3m-2day-1bar-1 for 60 nm thick silicon oxide (SiOx) coated PET foils is achieved. To discuss this residual permeation, coating defects are visualized by capacitively coupled atomic oxygen plasma etching of coated substrate. A defect density of 3000 mm-2 is revealed responsible for permeation. For plasma sterilization, optimized plasma parameters based on fundamental research of plasma sterilization mechanisms permit short treatment times of a few seconds.

Steves, Simon; Deilmann, Michael; Bibinov, Nikita; Awakowicz, Peter

2009-10-01

151

Drug delivery through the skin barrier enhanced by treatment with tissue-tolerable plasma.  

PubMed

Most treatments in dermatology and cosmetology are based on the penetration of topically applied drugs into the skin or through the skin barrier to the target structure in the living tissue. In the case of healthy skin, scarcely 1% of the applied drugs pass the skin barrier, depending on their chemical properties. Therefore, different physical and chemical methods have been developed to stimulate the penetration process. All these methods are based on the partial destruction of the barrier. In this study, an electrical tissue-tolerable plasma (TTP) was used to increase the penetration of a topically applied model drug (fluorescent dye) through the skin barrier. Using laser scanning microscopy, the distribution of the model drug in different depths of the skin was investigated. It was found that the plasma treatment of the skin is a very efficient process to deliver topically applied substances into the living tissue. In the case of the non-plasma-treated skin, it was found that the fluorescent dye could be detected exclusively on the skin surface. If the dye was applied to the TTP-treated skin, it could be observed in high concentration also in deeper parts of the skin extending down to the stratum basale and the papillary structure. PMID:21371126

Lademann, Olaf; Richter, Heike; Meinke, Martina C; Patzelt, Alexa; Kramer, Axel; Hinz, Peter; Weltmann, Klaus-Dieter; Hartmann, Bernd; Koch, Stefan

2011-06-01

152

Plasma expansion of ZnO-coated surface barrier discharge in open air and its optical analysis  

SciTech Connect

Characteristics of the ZnO-coated surface barrier discharge in open air were diagnosed optically. Highly conductive ZnO film was deposited on the dielectric surface. We found that the increase of the surface conductivity induces wider discharge area. Moreover we analyzed the optical behavior of plasma transition of two barrier discharges by optical emission spectroscopy. Discharge characteristic of the normal dielectric barrier discharge is divided into only two modes: streamer and glow discharge. But in the case of ZnO-coated dielectric barrier discharge, pd range of glowlike discharge exists widely and this can be also an evidence of the enhancement of plasma uniformity.

Choi, Jai Hyuk; Han, Man Hyeop; Baik, Hong Koo; Song, Kie Moon [Department of Metallurgical Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemoon-Ku, Seoul 120-749 (Korea, Republic of); Department of Applied Physics, KonKuk University, Chungju 380-701 (Korea, Republic of)

2007-02-01

153

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 fairings can be applied, potentially leading to a reduction of radi- ated noise by shielding the downstream

Huang, Xun

154

Treatment of Candida albicans biofilms with low-temperature plasma induced by dielectric barrier discharge and atmospheric pressure plasma jet  

NASA Astrophysics Data System (ADS)

Because of some disadvantages of chemical disinfection in dental practice (especially denture cleaning), we investigated the effects of physical methods on Candida albicans biofilms. For this purpose, the antifungal efficacy of three different low-temperature plasma devices (an atmospheric pressure plasma jet and two different dielectric barrier discharges (DBDs)) on Candida albicans biofilms grown on titanium discs in vitro was investigated. As positive treatment controls, we used 0.1% chlorhexidine digluconate (CHX) and 0.6% sodium hypochlorite (NaOCl). The corresponding gas streams without plasma ignition served as negative treatment controls. The efficacy of the plasma treatment was determined evaluating the number of colony-forming units (CFU) recovered from titanium discs. The plasma treatment reduced the CFU significantly compared to chemical disinfectants. While 10 min CHX or NaOCl exposure led to a CFU log10 reduction factor of 1.5, the log10 reduction factor of DBD plasma was up to 5. In conclusion, the use of low-temperature plasma is a promising physical alternative to chemical antiseptics for dental practice.

Koban, Ina; Matthes, Rutger; Hübner, Nils-Olaf; Welk, Alexander; Meisel, Peter; Holtfreter, Birte; Sietmann, Rabea; Kindel, Eckhard; Weltmann, Klaus-Dieter; Kramer, Axel; Kocher, Thomas

2010-07-01

155

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

156

Study of non-thermal plasma jet with dielectric barrier configuration in nitrogen and argon  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharge (DBD) is advantageous in generating non-thermal plasma at atmospheric pressure, as it avoids transition to thermal arc and dispenses with costly vacuum system. It has found useful applications in treating heat-sensitive materials such as plastics and living tissue. In this work, the discharge formed between the Pyrex glass layer and the ground electrode is extruded through a nozzle to form the non-thermal plasma jet. The DBD characteristics were investigated in terms of charge transferred and mean power dissipated per cycle when operated in nitrogen and argon at various flow rates and applied voltages. These characteristics were then correlated to the dimension of the plasma jet. The mean power dissipated in the DBD was below 7 W giving an efficiency of 17 %. The length of the plasma jet was greatly limited to below 1 cm due to the configuration of the DBD system and nozzle.

Choo, C. Y.; Chin, O. H.

2014-03-01

157

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

158

Isothermal and cyclic oxidation of an air plasma-sprayed thermal barrier coating system  

SciTech Connect

Thermogravimetric methods for evaluating bond coat oxidation in plasma-sprayed thermal barrier coating (TBC) systems were assessed by high-temperature testing of TBC systems with air plasma-sprayed (APS) Ni-22Cr-10Al-1Y bond coatings and yttria-stabilized zirconia top coatings. High-mass thermogravimetric analysis (at 1150{sup degrees}C) was used to measure bond coat oxidation kinetics. Furnace cycling was used to evaluate APS TBC durability. This paper describes the experimental methods and relative oxidation kinetics of the various specimen types. Characterization of the APS TBCs and their reaction products is discussed.

Haynes, J.A.; Ferber, M.K.; Porter, W.D. [Oak Ridge National Lab., TN (United States); Rigney, E.D. [Alabama Univ., Birmingham, AL (United States). Dept. of Materials and Mechanical Engineering

1996-08-01

159

Oxidation and degradation of a plasma-sprayed thermal barrier coating system  

SciTech Connect

The isothermal oxidation behavior of thermal barrier coating (TBC) specimens consisting of single-crystal superalloy substrates, vacuum plasma-sprayed Ni-22Cr-10Al-1Y bond coatings and air plasma-sprayed 7.5 wt.% yttria stabilized zirconia top coatings was evaluated by thermogravimetric analysis at 1150{degrees}C for up to 200 hours. Coating durability was assessed by furnace cycling at 1150{degrees}C. Coatings and reaction products were identified by x-ray diffraction, field-emission scanning electron microscopy and energy dispersive spectroscopy.

Haynes, J.A. [Univ. of Alabama, Birmingham, AL (United States). Dept. of Materials and Mechanical Engineering; Ferber, M.K.; Porter, W.D. [Oak Ridge National Lab., TN (United States)

1996-04-01

160

Plasma-Catalytic Decomposition of Phenols in Atmospheric Pressure Dielectric Barrier Discharge  

Microsoft Academic Search

This study investigated the processes for the destruction of phenol and its derivatives (resorcin and pyrocatechol) in aqueous\\u000a solutions under the action of an oxygen dielectric barrier discharge (DBD) at atmospheric pressure in the presence or absence\\u000a of catalysts in the plasma zone. It was shown that the DBD had a high decomposition efficiency for phenol and its derivatives\\u000a (up

A. G. Bubnov; E. Yu. Burova; V. I. Grinevich; V. V. Rybkin; J.-K. Kim; H.-S. Choi

2006-01-01

161

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

162

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

163

Microscale plasma actuators for improved thrust density Chin-Cheng Wang and Subrata Roya  

E-print Network

is investigated using a first-principles approach solving coupled system of hydrodynamic plasma equations. © 2009 American Institute of Physics. DOI: 10.1063/1.3160304 I. INTRODUCTION The plasma that has been in which elect

Roy, Subrata

164

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

165

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

166

Surface modification of polypropylene non-woven fabric using atmospheric nitrogen dielectric barrier discharge plasma  

NASA Astrophysics Data System (ADS)

In this paper, a dielectric barrier discharge operating in nitrogen at atmospheric pressure has been used to improve the surface hydrophilic property of polypropylene (PP) non-woven fabric. The changes in the hydrophilic property of the modified PP samples are investigated by the contact angle measurements and the variation of water contact angle is obtained as a function of the energy density; micrographs of the PP before and after plasma treatment are observed by scanning electron microscopy (SEM) and the chemical composition of the PP surface before and after plasma treatment is also analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the surface hydrophilic property of the PP samples is greatly improved with plasma treatment for a few seconds, as evidenced by the fact that the contact angle of the treated PP samples significantly decreases after plasma treatment. The analysis of SEM shows that the surface roughness of the treated PP samples increases due to bonding and etching in plasma processing. The analyses of FTIR and the C1s peak in the high-resolution XPS indicate that oxygen-containing and nitrogen-containing polar functional groups are introduced into PP surface in plasma processing. It can be concluded that the surface hydrophilic property of the modified PP samples has been obviously improved due to the introduction of oxygen-containing and nitrogen-containing polar groups and the increase of the surface roughness on the PP surface.

Wang, Kunlei; Wang, Wenchun; Yang, Dezheng; Huo, Yan; Wang, Dezhen

2010-09-01

167

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

168

TECHNICAL NOTE: Performance enhancement of IPMC actuator by plasma surface treatment  

Microsoft Academic Search

IPMC (ionic polymer metal composite) is composed of ionic polymer and metal electrodes on both surfaces of the polymer. In this study, we changed the surface morphology of the ionic polymer by using plasma treatment. Plasma treatment made needle-shaped microstructures on the surface of the polymer and the microstructures helped to form a thicker uniform metal electrode which is deposited

Seong Jun Kim; In Taek Lee; Yong Hyup Kim

2007-01-01

169

The component content of active particles in a plasma-chemical reactor based on volume barrier discharge  

Microsoft Academic Search

In this paper the results of theoretical and experimental studies of the component content of active particles formed in a plasma-chemical reactor composed of a multiple-cell generator of active particles, based on volume barrier discharge, and a working chamber are presented. For calculation of the content of uncharged plasma components an approach is proposed which is based on averaging of

I. A. Soloshenko; V. V. Tsiolko; S. S. Pogulay; A. G. Terent'yeva; V. Yu Bazhenov; A. I. Shchedrin; A. V. Ryabtsev; A. I. Kuzmichev

2007-01-01

170

Dynamics of a potential barrier formed on the tail of a moving double layer in a collisionless plasma  

Microsoft Academic Search

A negative potential barrier on the low-potential side of a moving double layer gives rise to a current limitation in a collisionless plasma terminated by a positively biased cold collector plate in a Q machine. The double layer is produced in front of the plasma source and moves toward the collector during the limitation. When the double layer arrives at

S. Iizuka; P. Michelsen; J. J. Rasmussen; R. Schrittwieser; R. Hatakeyama; K. Saeki; N. Sato

1982-01-01

171

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

2014-09-01

172

Plasma-Sprayed Thermal Barrier Coatings: New Materials, Processing Issues, and Solutions  

NASA Astrophysics Data System (ADS)

Growing demands on thermal barrier coatings (TBCs) for gas turbines regarding their temperature and cyclic capabilities, corrosion resistance, and erosion performance have instigated the development of new materials and coating systems. Different pyrochlores, perovskites, doped yttria-stabilized zirconia, and hexaaluminates have been identified as promising candidates. However, processing these novel TBC materials by plasma spraying is often challenging. During the deposition process, stoichiometric changes, formation of undesired secondary phases or non-optimum amorphous contents, as well as detrimental microstructural effects can occur in particular. This article describes these difficulties and the development of process-related solutions by employing diagnostic tools.

Mauer, Georg; Jarligo, Maria Ophelia; Mack, Daniel Emil; Vaßen, Robert

2013-06-01

173

Mechanisms of degradation and failure in a plasma deposited thermal barrier coating  

NASA Technical Reports Server (NTRS)

Failure of a two layer plasma deposited thermal barrier coating is caused by cyclic thermal exposure and occurs by spallation of the outer ceramic layer. Spallation life is quantitatively predictable, based on the severity of cyclic thermal exposure. This paper describes and attempts to explain unusual constitutive behavior observed in the insulative ceramic coating layer, and presents details of the ceramic cracking damage accumulation process which is responsible for spallation failure. Comments also are offered to rationalize the previously documented influence of interfacial oxidation on ceramic damage accumulation and spallation life.

Demasi-Marcin, Jeanine T.; Sheffler, Keith D.; Bose, Sudhangshu

1989-01-01

174

Antimicrobial efficacy of two surface barrier discharges with air plasma against in vitro biofilms.  

PubMed

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

175

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

176

Formaldehyde removal from gas streams by means of NaNO2 dielectric barrier discharge plasma.  

PubMed

Destruction of formaldehyde by means of NaNO2 ferro-electric packed bed dielectric barrier discharge plasma in a coaxial cylindrical reactor was carried out at atmospheric pressure and room temperature. The difference among four kinds of NaNO2 ferro-electric reactors was compared in terms of specific energy density (SED), energy yield (EY), and HCHO decomposition. In addition, by-products during the decomposition of HCHO and destruction mechanism were also investigated. The removal efficiency of HCHO increased by means of NaNO2 DBD plasma significantly and enhanced with increasing SED distinctly. More amount of NaNO2 contributed to higher HCHO removal efficiency in the reactors. Reactor C had the highest HCHO removal efficiency among the reactors. As an important by-product, ozone concentration increased with higher SED. The possible main products in the outlet effluent were CO, CO(2) and H(2)O. PMID:19896770

Liang, Wen-Jun; Li, Jian; Li, Jing-Xin; Zhu, Tao; Jin, Yu-Quan

2010-03-15

177

Origin of darkening in 8 wt% yttria-zirconia plasma-sprayed thermal barrier coatings  

SciTech Connect

This paper reports on the origins of darkening of 8 wt% Y{sub 2}O{sub 3}-ZrO{sub 2} air plasma-sprayed (APS) and low-pressure plasma-sprayed (LPPS) thermal barrier coatings (TBC) studied using x-ray photoelectron spectroscopy. The change of valence states of zirconium, due to the reduction of ZrO{sub 2} to Zr{sub 2}O{sub 3}, was responsible for darkening of TBC. Quantification of Zr{sup 3+} oxide was related both to the black color of TBC and to the spraying technologies and parameters. Furthermore, impurity (Fe, Al, Si, and Na) segregation and exsolution phenomena were monitored as a function of the air thermal treatment (up to 1473 K) and it was demonstrated not to be the origin of darkening.

Ingo, G.M. (Inst. di Teoria e Struttura Elettronica del CNR, CP 10, 00016 Monterotondo Stazione, Roma (IT))

1991-02-01

178

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. [National Energy Technology Laboratory (NETL) and Univ. of Pittsburgh, PA (United States); Yanar, N. M. [National Energy Technology Laboratory (NETL) and Univ. of Pittsburgh, PA (United States); Pettit, F. S. [National Energy Technology Laboratory (NETL) and Univ. of Pittsburgh, PA (United States); Taylor, T. A. [Praxair Surface Technologies, Inc., Indianapolis, IN (United States); Meier, G. H. [National Energy Technology Laboratory (NETL) and Univ. of Pittsburgh, PA (United States)

2012-10-01

179

Deposition and Characteristics of Submicrometer-Structured Thermal Barrier Coatings by Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

In the field of thermal barrier coatings (TBCs) for gas turbines, suspension plasma sprayed (SPS) submicrometer-structured coatings often show unique mechanical, thermal, and optical properties compared to conventional atmospheric plasma sprayed ones. They have thus the potential of providing increased TBC performances under severe thermo-mechanical loading. Experimental results showed the capability of SPS to obtain yttria stabilized zirconia coatings with very fine porosity and high density of vertical segmentation cracks, yielding high strain tolerance, and low Young's modulus. The evolution of the coating microstructure and properties during thermal cycling test at very high surface temperature (1400 °C) in our burner rigs and under isothermal annealing was investigated. Results showed that, while segmentation cracks survive, sintering occurs quickly during the first hours of exposure, leading to pore coarsening and stiffening of the coating. In-situ measurements at 1400 °C of the elastic modulus were performed to investigate in more detail the sintering-related stiffening.

Guignard, Alexandre; Mauer, Georg; Vaßen, Robert; Stöver, Detlev

2012-06-01

180

Hybrid Plasma-Sprayed Thermal Barrier Coatings Using Powder and Solution Precursor Feedstock  

NASA Astrophysics Data System (ADS)

A novel approach of hybridizing the conventional atmospheric plasma spraying (APS) technique with the solution precursor plasma spray (SPPS) route to achieve thermal barrier coatings (TBCs) with tailored configurations is presented. Such a hybrid process can be conveniently adopted for forming composite, multi-layered and graded coatings employing simultaneous and/or sequential feeding of solution precursor as well as powder feedstock, yielding distinct TBC microstructures that bear promise to further extend coating durability. TBC specimens generated using conventional APS technique, the SPPS method and through APS-SPPS hybrid processing have been comprehensively characterized for microstructure, phase constitution, hardness and thermal cycling life, and the results were compared to demonstrate the advantages that can ensue from hybrid processing.

Joshi, S. V.; Sivakumar, G.; Raghuveer, T.; Dusane, R. O.

2014-04-01

181

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

182

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

E-print Network

, the power used and the speed of killing vegetative cells. The surface temperature during plasma generation States of America, 2 Department of Pathology, Immunology and Laboratory Medicine, College of Medicine and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America

Roy, Subrata

183

Plasma-Enhanced-Polymerization Thin-Film as a Drift Barrier for Cu Ions  

NASA Astrophysics Data System (ADS)

The barrier properties of divinyl siloxane-benzocyclobutene (DVS-BCB) films formed by plasma-enhanced polymerization were studied for ultralow-k porous silica (po-SiO) interlayer dielectrics. Time-dependent dielectric breakdown (TDDB) measurements of blanket Cu/BCB/Si metal-insulator-semiconductor (MIS) capacitors showed no polarity dependence of the bias-temperature stresses at 200 °C under 2 MV/cm, indicating that Cu ions hardly drifted into the BCB film with the positive bias stress. On the other hand, Cu/SiOC/Si MIS capacitors under the positively biased Cu showed a significant degradation in the TDDB lifetime compared with the negative bias case. The barrier effect of the thin BCB was confirmed from the TDDB measurements using Cu/BCB/ultralow-k-po-SiO/Si stacked MIS structures. The TDDB lifetime of the stacked MIS capacitor was improved more than 30-fold by the use of 15-nm-thick BCB on po-SiO. The electric field and temperature dependences of the TDDB lifetime of the stacked MIS structure indicated that the TDDB lifetime of po-SiO capped with 15-nm-thick BCB is longer than 10 years at 125 °C and 1.4 MV/cm. We conclude that the barrier property of BCB that is as thin as 15 nm is effective for preventing Cu ion drift into interlayer dielectrics.

Yoshino, Takenobu; Hata, Nobuhiro; Kawahara, Jun; Shishida, Yoshinori; Kikkawa, Takamaro

2007-04-01

184

Plasma-Deposited SiOxCyHz Barrier Coatings for Organic Device Encapsulation  

NASA Astrophysics Data System (ADS)

A plasma-deposited SiOxCyHz barrier coating was investigated for the encapsulation of an organic photovoltaic (OPV). A closed drift linear plasma source, which is a modified extended layer linear ion source, was used to deposit SiOxCyHz films without any plasma damage due to plasma heating and ion bombardment on the organic devices. The deposition precursor was a gas mixture of hexamethyldisiloxane (HMDSO) and oxygen. The effect of the HMDSO/(HMDSO+O2) ratio over the range from 3.7 to 14.2% on the silicon content in Si(-O)x bonding was studied. HMDSO reacted effectively with oxygen radicals to form pure SiO2 bonds at the ratio of 3.7%. However, additional HMDSO injection led to insufficient HMDSO oxidation resulting in SiOxCyHz film deposition. In this work, a SiO2 single layer deposited at the ratio of 3.7% was adapted for the encapsulation of OPV. The encapsulated OPV showed an original power conversion efficiency (PCE) of ˜2% without any degradation.

Lee, Seunghun; Kang, Yong-Jin; Jung, Sunghoon; Kim, Jong-Kuk; Kim, Do-Geun

2013-07-01

185

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

186

Dielectric barrier discharge for high efficiency plasma-chemical vapor generation of cadmium.  

PubMed

A novel approach for Cd vapor generation was developed on the basis of a plasma-assisted chemical process. The generated Cd vapor was subsequently measured by atomic fluorescence spectrometry. Dissolved Cd species were readily converted into volatile species by reaction with hydrogen in a coaxial thin-film dielectric barrier discharge (DBD) plasma reactor. Both atomic and molecular Cd species were produced when a solution containing Cd(2+) was exposed to hydrogen-containing DBD plasma. Fast and efficient vapor generation of Cd was achieved simply in plain (neutral) water medium. Optimal conditions for the DBD-plasma Cd vapor generator were identified. The performance of this thin-film DBD plasma-chemical vapor generation (CVG) was evaluated through comparison with that arising from the conventional HCl-KBH4 system. The vapor generation efficiency of the proposed method (He-DBD) was found to be superior to the conventional CVG approach. Under the optimized conditions, the detection limits of Cd were found to be from 0.03 ng mL(-1) (Ar-DBD) to 0.008 ng mL(-1) (He-DBD) with a heated quartz tube atomizer (QTA); good repeatability (relative standard deviation (RSD) = 1.4%, n = 5) was obtained for a 1 ng mL(-1) standard. The new thin-film DBD plasma-CVG provides several additional advantages including simple setup, easy coupling with flow injection, low power consumption (?18 W), cost-effectiveness, and long operation lifetime. The accuracy of the proposed method was validated through analysis of cadmium in reference material of simulated natural water sample GBW(E)080402 and rice reference material GBW10045. The concentration of cadmium determined by the present method agreed well with the reference values. PMID:23485066

Zhu, Zhenli; Wu, Qingju; Liu, Zhifu; Liu, Lu; Zheng, Hongtao; Hu, Shenghong

2013-04-16

187

Physical and plasmachemical aspects of diffuse coplanar barrier discharge as a novel atmospheric-pressure plasma source  

NASA Astrophysics Data System (ADS)

Collaborating Czech and Slovakian university teams have recently developed an innovative plasma source, the so-called Diffuse Coplanar Surface Barrier Discharge (DCSBD), which has the potential to move a step closer to the industry requirement for in-line treatment of low-added-value materials using a highly-nonequlibrium ambient air plasma (Simor et al. 2002, The idea is to generate a thin (on the order of 0.1 mm) layer of highly-nonequlibrium plasma with a high power density (up to 100 W/cm^3) in the immediate vicinity of the treated surface and bring it into a close contact with the treated surface. Comparing to atmospheric-pressure glow discharge, volume dielectric barrier discharge, and plasma jet plasmas, such a diffuse plasma layer is believed to provide substantial advantages in energy consumption, exposure time, and technical simplicity. A brief outline of physical mechanism and basic properties of DCSBD will given using the results of emission spectroscopy, high-speed camera, and spatially resolved cross-correlation spectroscopy studies. The presentation will review also a current state of the art in in-line plasma treatment of low-cost materials and opportunities for the use of the so-called Diffuse Coplanar Surface Dielectric Barrier Discharge (DCSBD). The results obtained on the ambient air plasma treatments of textile, paper, wood, and glass illustrate that DCSBD offers outstanding performance with extremely low energy consumption for large area, uniform surface modifications of materials under continuous process conditions.

Cernak, M.; Kovacik, D.; Zahoranova, A.; Rahel, J.

2008-07-01

188

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

189

American Institute of Aeronautics and Astronautics Physics Based Analysis of Horseshoe Plasma Actuator for Improving  

E-print Network

1 American Institute of Aeronautics and Astronautics Physics Based Analysis of Horseshoe Plasma. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. #12;2 American Institute of Aeronautics and Astronautics I. Introduction rossflow jets have been widely used in many

Roy, Subrata

190

Characteristics of Plasma-Treated Amorphous Ta-Si-C Film as a Diffusion Barrier for Copper Metallization  

NASA Astrophysics Data System (ADS)

Ta-Si-C film was prepared by magnetron sputtering, and the thermal stability of the plasma-treated film as a copper diffusion barrier was evaluated. The barrier properties and failure behaviors of the studied films were elucidated using a four-point probe, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The as-deposited Ta-Si-C film had an amorphous structure, and the structure remained stable at an elevated temperature, allowing the film to be adopted as a barrier to inhibit Cu diffusion. The Cu/Ta26Si41C32/Si stacked structure had a failure temperature of 750°C/1 min when the 5-nm-thick Ta26Si41C32 film was treated by exposure to Ar/H2 plasma mixture, while the stacked film failed at 800°C/1 min when treated by exposure to Ar/N2 plasma mixture. Using the Ar/N2 plasma treatment favorably enhanced the thermal stability of the Ta26Si41C32 thin film as a barrier for Cu interconnections. When the Ta-Si-C film thickness was further reduced to 2 nm, the film retained the barrier effect at 650°C, 700°C, and 750°C for Ta34Si47C18, Ta30Si44C25, and Ta26Si41C32 compositions, respectively.

Fang, Jau-Shiung; Su, Wu-Jia; Huang, Meng-Shuo; Chiu, Chin-Fu; Chin, Tsung-Shune

2014-01-01

191

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

192

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

193

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

194

Columnar-Structured Mg-Al-Spinel Thermal Barrier Coatings (TBCs) by Suspension Plasma Spraying (SPS)  

NASA Astrophysics Data System (ADS)

The suspension plasma spraying (SPS) process has been developed to permit the feeding of sub-micrometer-sized powder into the plasma plume. In contrast to electron beam-physical vapor deposition and plasma spray-physical vapor deposition, SPS enables the cost-efficient deposition of columnar-structured coatings. Due to their strain tolerance, these coatings play an important role in the field of thermal barrier coatings (TBCs). In addition to the cost-efficient process, attention was turned to the TBC material. Nowadays, yttria partially stabilized zirconia (YSZ) is used as standard TBC material. However, its long-term application at temperatures higher than 1200 °C is problematic. At these high temperatures, phase transitions and sintering effects lead to the degradation of the TBC system. To overcome those deficits of YSZ, Mg-Al-spinel was chosen as TBC material. Even though it has a lower melting point (~2135 °C) and a higher thermal conductivity (~2.5 W/m/K) than YSZ, Mg-Al-spinel provides phase stability at high temperatures in contrast to YSZ. The Mg-Al-spinel deposition by SPS resulted in columnar-structured coatings, which have been tested for their thermal cycling lifetime. Furthermore, the influence of substrate cooling during the spraying process on thermal cycling behavior, phase composition, and stoichiometry of the Mg-Al-spinel has been investigated.

Schlegel, N.; Ebert, S.; Mauer, G.; Vaßen, R.

2014-08-01

195

Columnar-Structured Mg-Al-Spinel Thermal Barrier Coatings (TBCs) by Suspension Plasma Spraying (SPS)  

NASA Astrophysics Data System (ADS)

The suspension plasma spraying (SPS) process has been developed to permit the feeding of sub-micrometer-sized powder into the plasma plume. In contrast to electron beam-physical vapor deposition and plasma spray-physical vapor deposition, SPS enables the cost-efficient deposition of columnar-structured coatings. Due to their strain tolerance, these coatings play an important role in the field of thermal barrier coatings (TBCs). In addition to the cost-efficient process, attention was turned to the TBC material. Nowadays, yttria partially stabilized zirconia (YSZ) is used as standard TBC material. However, its long-term application at temperatures higher than 1200 °C is problematic. At these high temperatures, phase transitions and sintering effects lead to the degradation of the TBC system. To overcome those deficits of YSZ, Mg-Al-spinel was chosen as TBC material. Even though it has a lower melting point (~2135 °C) and a higher thermal conductivity (~2.5 W/m/K) than YSZ, Mg-Al-spinel provides phase stability at high temperatures in contrast to YSZ. The Mg-Al-spinel deposition by SPS resulted in columnar-structured coatings, which have been tested for their thermal cycling lifetime. Furthermore, the influence of substrate cooling during the spraying process on thermal cycling behavior, phase composition, and stoichiometry of the Mg-Al-spinel has been investigated.

Schlegel, N.; Ebert, S.; Mauer, G.; Vaßen, R.

2015-01-01

196

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

197

Synthesis of Polystyrene Thin Films by Means of an Atmospheric-Pressure Plasma Torch and a Dielectric Barrier Discharge  

Microsoft Academic Search

In this paper, the deposition and characterization of plasma-polymerized polystyrene (pp-PS) using PECVD under atmospheric pressure on a variety of substrates was investigated. An atmospheric RF plasma torch and an HF dielectric-barrier-discharge (DBD) system were used to deposit thin pp-PS coatings on PTFE, HDPE, stainless steel, glass, and silicon wafer. The styrene vapor was carried by Ar or He. The

Delphine Merche; Claude Poleunis; Patrick Bertrand; Michele Sferrazza; François Reniers

2009-01-01

198

Characterization and Application of a Planar Radio - Inductively-Coupled Plasma Source for the Production of Barrier Coatings  

Microsoft Academic Search

A planar radio-frequency (rf) inductively-coupled plasma (ICP) source is used to produce fluorocarbon discharges (CF_4\\/Ar) to fluorinate the surface of high-density polyethylene (HDPE). Using this system, concurrent studies of discharge characteristics, permeation properties of treated polymers and polymer surface characteristics are conducted to advance the use of plasma-fluorinated polymer surfaces as a barrier layer for automotive applications. Langmuir probes are

Leonard Joseph Mahoney

1994-01-01

199

Investigation of Plasma Polymerized Maleic Anhydride Film in a Middle Frequency Dielectric Barrier Discharge  

NASA Astrophysics Data System (ADS)

Plasma polymerized maleic anhydride (MA) was carried out by using maleic anhydride supersaturated ethanol solution as a precursor in a dielectric barrier discharge (DBD). The film properties were characterized by water contact angle (WCA), Fourier transfer infrared (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) analysis, and a thickness profilometer. The influence of the processing parameters on the film properties such as the power frequency and polymerization zone was investigated. The results show that anhydride group incorporated into the growing films is favorable at the frequency of 80 kHz and working pressure of 50 Pa. The poly (maleic anhydride) film is uniform and compact at an average deposition rate of 8 nm/min.

Tang, Wenjie; Chen, Qiang; Zhang, Yuefei; Ge, Yuanjing

2008-04-01

200

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

201

Effect of Thermal Exposure on Mechanical Properties of a Plasma-Sprayed Nanostructured Thermal Barrier Coating  

NASA Astrophysics Data System (ADS)

A nanostructured thermal barrier coating (TBC) was deposited by air plasma spraying. The effect of microstructural evolution on nano-hardness and Young's modulus has been investigated by nanoindentation technique after exposure at 1200 °C in air for different times. The results showed that the sintering process of nanostructured TBC at 1200 °C was divided into two stages. TBC completely kept the nanostructure with the grain size <100 nm at the first stage of 10 h thermal exposure. The nanostructure was lost gradually at the second stage from 10 to 200 h thermal exposure. During the first stage, nano-hardness and Young's modulus increased rapidly for TBC densification, and Weibull bimodal distribution of both Young's modulus and nano-hardness disappeared as grain grew and most microcracks were healed. The structure of TBC did not change basically, and nano-hardness and Young's modulus increased slightly at the second stage.

Wu, Zilong; Ni, Liyong; Yu, Qinghe; Zhou, Chungen

2012-01-01

202

The role of a diffusion barrier in plasma display panel with the high gamma cathode layer  

NASA Astrophysics Data System (ADS)

Plasma display panel (PDP) with MgO-SrO double cathode layer and SiO2 diffusion barrier is proposed to make the SrO layer free of contaminations. Time of flight-secondary ion mass spectrometry (TOF-SIMS) analysis shows the diffusion of impurities, like Na and K, can be effectively blocked while a new SrO layer is formed on top of the MgO layer. This structure shows that high Xe gases can be used to improve the luminous efficacy 2.3 times and decrease the voltage margin more than 10 V compared to the conventional PDP using Ne-Xe 15%. The aging time was also significantly decreased to 3-4 h.

Lee, Tae-Ho; Cheong, Hee-Woon; Kwon, Ohyung; Whang, Ki-Woong; Ole Steinmüller, Sven; Janek, Jürgen

2011-10-01

203

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 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} H89 = 7 for up to 5 times the {tau}{sub E} of 150 ms. The {beta}{sub N} H89 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.

Burrell, K H; Austin, M E; Brennan, D P; DeBoo, J C; Doyle, E J; Fenzi, C; Fuchs, C; Gohil, P; Greenfield, C M; Groebner, R J; Lao, L L; Luce, T C; Makowski, M A; McKee, G R; Moyer, R A; Petty, C C; Porkolab, M; Rettig, C L; Rhodes, T L; Rost, J C; Stallard, B W; Strait, E J; Synakowski, E J; Wade, M R; Watkins, J G; West, W P

2000-11-01

204

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

205

Improvement of oxygen barrier of polyethylene terepthalate film by plasma-source ion implantation of carbon  

NASA Astrophysics Data System (ADS)

The surface of polyethylene terepthalate (PET) film has been successfully modified to amorphous carbon by plasma source ion implantation (PSII) as a means of improving the oxygen barrier characteristics of the PET film. The process was performed using high negative pulsed voltage in an radio frequency field with C2H2 gas. The amorphous carbon layer is found to consist primarily of graphite crystal with C-H, C-H2 and C-H3 components, and to reduce the oxygen transmission rate of the film by up to 100 times that of unmodified PET film at a thickness of only 70-300 nm. Raman spectra reveal that the amorphous carbon layer has diamond-like carbon characteristics, yet is soft compared to other diamond-like carbon films with hydrogen contents of >20 at. %. A stronger graphite character in the x-ray photoelectron spectroscopy spectra is found to represent the fineness of the carbon structure and correlate well with the improvement of oxygen barrier characteristics. copyright 2002 American Vacuum Society.

Yoshida, M.; Tanaka, T.; Shinohara, M.; Watanabe, S.; Lee, J. W.; Takagi, T.

2002-09-01

206

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

207

Copper barrier properties of a low-dielectric-constant organocyclosiloxane prepared by plasma-enhanced polymerization  

NASA Astrophysics Data System (ADS)

An excellent barrier effect against copper (Cu) ion drift of an organocyclosiloxane (OCS) low-dielectric-constant film is studied by electric measurements. The OCS film, which was formed by plasma-enhanced polymerization, had two kinds of organic groups such as alkyl and vinyl groups extending from each silicon (Si) atom in a six-membered ring of silica (Si-O). Time to breakdown of Cu/OCS/Si metal-insulator-semiconductor (MIS) capacitors measured with positive bias stress was equal to that with negative bias stress, and an almost zero flatband voltage shift was observed after applying a bias-temperature stress. From these results, the authors conclude that Cu+ ion drift into OCS is suppressed. By forming 30-nm-thick OCS on a porous silica (po-SiO) film, the predicted lifetime of Cu/OCS/po-SiO MIS structure exceeds 10yr at 473K under 0.2MV/cm, suggesting that thin OCS is attractive for po-SiO as a drift barrier for Cu+ ions. It is proposed that the contact between Cu and Si-O skeletal bonds is suppressed by organic groups in OCS, preventing the ionization of Cu atoms and their drift.

Yoshino, Takenobu; Hata, Nobuhiro; Kawahara, Jun; Kikkawa, Takamaro

2007-04-01

208

Treatment of PET and PU polymers by atmospheric pressure plasma generated in dielectric barrier discharge in air  

Microsoft Academic Search

Plasma treatments are frequently employed to modify surface properties of materials such as adhesivity, hydrophobicity, oleophobicity etc. Present work deals with surface modification of common commercial polymers such as polyethylene terephthalate (PET) and polyurethane (PU) by an air dielectric barrier discharge (DBD) at atmospheric pressure. The DBD treatment was performed in a plain reactor in wire-duct geometry (non-uniform field reactor),

K. G. Kostov; A. L. R. dos Santos; R. Y. Honda; P. A. P. Nascente; M. E. Kayama; M. A. Algatti; R. P. Mota

2010-01-01

209

Compartmentalisation of the sperm plasma membrane: a FRAP, FLIP and SPFI analysis of putative diffusion barriers on the sperm head  

Microsoft Academic Search

Spermatozoa are highly polarised cells with a compartmentalised distribution of lipids and proteins in their plasma membrane. It is not known how these compartments are stably maintained in what is essentially a fluid environment. In this investigation we have examined the hypothesis that intramembranous diffusion barriers selectively retain some components within compartments, while allowing free passage of others. A fluorescence

Peter S. James; Conor Hennessy; Torunn Berge; Roy Jones

2004-01-01

210

Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition  

SciTech Connect

Cost effective and a very simple dielectric barrier discharge plasma processing apparatus for thin film deposition and mass spectroscopic analysis of organic gas mixture has been described. The interesting features of the apparatus are the construction of the dielectric electrodes made of aluminum oxide or alumina (Al{sub 2}O{sub 3}) and glass and the generation of high ignition voltage from the spark plug transformer taken from car. Metal capacitor is introduced in between ground and oscilloscope to measure the executing power during the discharge and the average electron density in the plasma region. The organic polymer films have been deposited on Si (100) substrate using several organic gas compositions. The experimental setup provides a unique drainage system from the reaction chamber controlled by a membrane pump to suck out and remove the poisonous gases or residuals (cyanogens, H-CN, CH{sub x}NH{sub 2}, etc.) which have been produced during the discharge of CH{sub 4}/N{sub 2} mixture.

Majumdar, Abhijit; Hippler, Rainer [Institut fuer Physik, Ernst-Moritz-Arndt-Universitaet Greifswald, Felix-Hausdorff-Strasse 6, 17489 Greifswald (Germany)

2007-07-15

211

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

212

Degradation of aqueous 3,4-dichloroaniline by a novel dielectric barrier discharge plasma reactor.  

PubMed

Degradation of aqueous 3,4-dichloroaniline (3,4-DCA) was conducted in a novel dielectric barrier discharge (DBD) plasma reactor. The factors affecting the degradation efficiency of 3,4-DCA and the degradation mechanism of 3,4-DCA were investigated. The experimental results indicated that the degradation efficiency of 3,4-DCA increased with increasing input power intensity, and the degradation of 3,4-DCA by the novel DBD plasma reactor fitted pseudo-first-order kinetics. Higher degradation efficiency of 3,4-DCA was observed in acidic conditions. The degradation efficiency of 3,4-DCA, the removal rate of total organic carbon (TOC), and the detected Cl(-) increased dramatically with adding Fe(2+) or Fe(3+). Degradation of 3,4-DCA could be accelerated or inhibited in the presence of H2O2 depending on the dosage. Several degradation intermediates of 3,4-DCA such as 1,2-dichlorobenzene, 2-chloro-1,4-benzoquinone, 3,4-dichlorophenyl isocyanate, 2-chlorohydroquinone, 3,4-dichloronitrobenzene, and 3,4-dichlorophenol were identified by gas chromatography mass spectrometry (GC-MS) analysis. Based on the identification of aromatic intermediates, acetic acid, formic acid, oxalic acid, and Cl(-) released, a possible mineralization pathway of 3,4-DCA was proposed. PMID:25315933

Feng, Jingwei; Liu, Runlong; Chen, Pei; Yuan, Shoujun; Zhao, Dayong; Zhang, Jibiao; Zheng, Zheng

2014-10-15

213

Isothermal Oxidation Behavior of Supersonic Atmospheric Plasma-Sprayed Thermal Barrier Coating System  

NASA Astrophysics Data System (ADS)

In this work, Y2O3 stabilized zirconia-based thermal barrier coatings (TBCs) were deposited by conventional atmospheric plasma spraying (APS) and high efficiency supersonic atmospheric plasma spraying (SAPS), respectively. The effect of Al2O3 layer stability on the isothermal growth behavior of thermally grown oxides (TGOs) was studied. The results revealed that the Al2O3 layer experienced a three-stage change process, i.e., (1) instantaneous growth stage, (2) steady-state growth stage, and (3) depletion stage. The thickness of Al2O3 scale was proved to be an important factor for the growth rate of TGOs. The SAPS-TBCs exhibited a higher Al2O3 stability and better oxidation resistance as compared with the APS-TBCs. Additionally, it was found that inner oxides, especially nucleated on the top of the crest, continually grew and swallowed the previously formed Al2O3 layer, leading to the granulation and disappearance of continuous Al2O3 scale, which was finally replaced by the mixed oxides and spinel.

Bai, Yu; Ding, Chunhua; Li, Hongqiang; Han, Zhihai; Ding, Bingjun; Wang, Tiejun; Yu, Lie

2013-10-01

214

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

215

Improving the thermal shock resistance of plasma sprayed CYSZ thermal barrier coatings by laser surface modification  

NASA Astrophysics Data System (ADS)

In this study, substrates of Inconel 738 LC superalloy coupons were first sprayed with a NiCoCrAlY bondcoat and then with a ceria and yttria stabilized zirconia (CYSZ) topcoat by air plasma spraying (APS). After that, the plasma sprayed CYSZ thermal barrier coatings (TBCs) were treated using a pulsed Nd:YAG laser. The effects of laser glazing on the microstructure and thermal shock resistance of the coatings were evaluated. Thermal shock test was administered by holding specimens at 950 °C for 5 min and then water quenching. More than 20% of the spalled region of the surface of the topcoat was adopted as the criterion for the failure of samples. The microstructures of both the as processed and the tested TBCs were investigated using scanning electron microscope (SEM). The phases of the coatings were analyzed with X-ray diffractometry (XRD). XRD analysis revealed that both as sprayed and laser glazed topcoats consisted of nonequilibrium tetragonal (T') phase. The results showed that the life times of the as sprayed TBCs were enhanced around fourfold by the formation of a continuous network of segmented cracks perpendicular to the surface and the increase in strain accommodation.

Ahmadi-Pidani, Raheleh; Shoja-Razavi, Reza; Mozafarinia, Reza; Jamali, Hossein

2012-05-01

216

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

217

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

218

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

219

Diamond-like carbon produced by plasma source ion implantation as a corrosion barrier  

SciTech Connect

There currently exists a broad range of applications for which the ability to produce an adherent, hard, wear and, corrosion-resistant coating plays a vital role. These applications include engine components, orthopedic devices, textile manufacturing components, hard disk media, optical coatings, and cutting and machining tools (e.g., punches, taps, scoring dies, and extrusion dies). Ion beam processing can play an important role in all of these technologies. Plasma source ion implantation (PSII) is an emerging technology which has the potential to overcome the limitations of conventional ion implantation by: (1) reducing the time and expense for implanting onto complex shapes and large areas and (2) extending the thickness of the modification zone through ion beam enhanced plasma growth of surface coatings. In PSII, targets are placed directly in a plasma source and then pulse biased to produce a non-line-of-sight process for complex-shaped targets without complex fixturing. If the pulse bias is a relatively high negative potential (20 to 100 kV) ion implantation will result. If however, a low voltage (50--1,200 eV) high duty cycle pulse bias is applied, film deposition from the chamber gas will result, thereby increasing the extent of the surface modification into the 1--10 micron regime. To evaluate the potential for DLC to be used as a corrosion barrier, Electrochemical Impedance Spectroscopy (EIS) and traditional electrochemistry techniques were used to investigate the breakdown mechanism in chloride and nonchloride containing environments. The effect of surface preparation on coating breakdown was also evaluated.

Lillard, R.S.; Butt, D.P.; Taylor, T.N.; Walter, K.C.; Nastasi, M.

1998-03-01

220

Gentle dry etching of P(VDF-TrFE) multilayer micro actuator structures by use of an inductive coupled plasma  

Microsoft Academic Search

To fully utilize the actuator properties of poly(vinylidenefluoride) (P(VDF))-based polymers, the electric field has to be rather high and one way to accomplish this, in particular with low voltage drive signals, is to build multilayered structures. This paper focuses on how to structure poly(vinylidenefluoride-trifluoroethylene) P(VDF-TrFE) by presenting an etch method to create multilayered miniaturized actuators, with intermediate aluminium electrodes. To

E. Edqvist; N. Snis; S. Johansson

2008-01-01

221

Abatement of toluene from gas streams via ferro-electric packed bed dielectric barrier discharge plasma.  

PubMed

Destruction of gaseous toluene via ferro-electric packed bed dielectric barrier discharge plasma in a coaxial cylindrical reactor was carried out at atmospheric pressure and room temperature. The difference among three kinds of reactors was compared in terms of specific energy density (SED), energy yield (EY), toluene decomposition. In order to optimize the geometry of the reactor, the removal efficiency of toluene was compared for various inner electrode diameters. In addition, qualitative analysis on by-products and particular discussion on toluene abatement mechanisms were also presented. It has been found that ferro-electric packed bed DBD reactor could effectively decompose toluene. Toluene removal efficiency enhanced with increasing SED. With respect to toluene conversion, 1.62 mm electrode appeared to be superior to 1.06 mm electrodes. BaTiO3 reactor had the highest toluene removal efficiency among the reactors. For NaNO2 reactor, the highest EY could reach 17.0 mg/kWh to a certain extent. PMID:19515490

Liang, Wenjun; Li, Jian; Li, Jie; Jin, Yuquan

2009-10-30

222

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

223

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

224

[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

225

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

226

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

227

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

228

Treatment of raw poultry with nonthermal dielectric barrier discharge plasma to reduce Campylobacter jejuni and Salmonella enterica.  

PubMed

Nonthermal plasma has been shown to be effective in reducing pathogens on the surface of a range of fresh produce products. The research presented here investigated the effectiveness of nonthermal dielectric barrier discharge plasma on Salmonella enterica and Campylobacter jejuni inoculated onto the surface of boneless skinless chicken breast and chicken thigh with skin. Chicken samples were inoculated with antibiotic-resistant strains of S. enterica and C. jejuni at levels of 10(1) to 10(4) CFU and exposed to plasma for a range of time points (0 to 180 s in 15-s intervals). Surviving antibiotic-resistant pathogens were recovered and counted on appropriate agar. In order to determine the effect of plasma on background microflora, noninoculated skinless chicken breast and thighs with skin were exposed to air plasma at ambient pressure. Treatment with plasma resulted in elimination of low levels (10(1) CFU) of both S. enterica and C. jejuni on chicken breasts and C. jejuni from chicken skin, but viable S. enterica cells remained on chicken skin even after 20 s of exposure to plasma. Inoculum levels of 10(2), 10(3), and 10(4) CFU of S. enterica on chicken breast and chicken skin resulted in maximum reduction levels of 1.85, 2.61, and 2.54 log, respectively, on chicken breast and 1.25, 1.08, and 1.31 log, respectively, on chicken skin following 3 min of plasma exposure. Inoculum levels of 10(2), 10(3), and 10(4) CFU of C. jejuni on chicken breast and chicken skin resulted in maximum reduction levels of 1.65, 2.45, and 2.45 log, respectively, on chicken breast and 1.42, 1.87, and 3.11 log, respectively, on chicken skin following 3 min of plasma exposure. Plasma exposure for 30 s reduced background microflora on breast and skin by an average of 0.85 and 0.21 log, respectively. This research demonstrates the feasibility of nonthermal dielectric barrier discharge plasma as an intervention to help reduce foodborne pathogens on the surface of raw poultry. PMID:22221351

Dirks, Brian P; Dobrynin, Danil; Fridman, Gregory; Mukhin, Yuri; Fridman, Alexander; Quinlan, Jennifer J

2012-01-01

229

Improved Oxidation Life of Segmented Plasma Sprayed 8YSZ Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

Unconventional plasma sprayed thermal barrier coating (TBC) systems were produced and evaluated by interrupted or cyclic furnace oxidation life testing. First, approximately 250 µm thick 8YSZ coatings were directly sprayed onto grit blasted surfaces of PWA 1484, without a bond coat, to take advantage of the excellent oxidation resistance of this superalloy. For nominal sulfur (S) contents of 1 ppmw, total coating separation took place at relatively short times (200 h at 1100°C). Reductions in the S content, by melt desulfurization commercially (0.3 ppmw) or by hydrogen (H2) annealing in the laboratory (0.01 ppmw), improved scale adhesion and extended life appreciably, by factors of 5-10. However, edge-initiated failure persisted, producing massive delamination as one sheet of coating. Secondly, surfaces of melt desulfurized PWA 1484 were machined with a grid of grooves or ribs (˜250 µm wide and high), resulting in a segmented TBC surface macrostructure, for the purpose of subverting this failure mechanism. In this case, failure occurred only as independent, single-segment events. For grooved samples, 1100 °C segment life was extended to ˜1000h for 5 mm wide segments, with no failure observed out to 2000 h for segments ?2.5 mm wide. Ribbed samples were even more durable, and segments ?6 mm remained intact for 2000 h. Larger segments failed by buckling at times inversely related to the segment width and decreased by oxidation effects at higher temperatures. This critical buckling size was consistent with that predicted for elastic buckling of a TBC plate subject to thermal expansion mismatch stresses. Thus, low S substrates demonstrate appreciable coating lives without a bond coat, while rib segmenting extends life considerably.

Smialek, James L.

2004-03-01

230

Induction of apoptosis in human myeloid leukemia cells by remote exposure of resistive barrier cold plasma.  

PubMed

Cold atmospheric plasma (CAP), an ambient temperature ionized gas, is gaining extensive interest as a promising addition to anti-tumor therapy primarily due to the ability to generate and control delivery of electrons, ions, excited molecules, UV photons, and reactive species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) to a specific site. The heterogeneous composition of CAP offers the opportunity to mediate several signaling pathways that regulate tumor cells. Consequently, the array of CAP generated products has limited the identification of the mechanisms of action on tumor cells. The aim of this work is to assess the cell death response of human myeloid leukemia cells by remote exposure to CAP generated RNS by utilizing a novel resistive barrier discharge system that primarily produces RNS. The effect of variable treatments of CAP generated RNS was tested in THP-1 cell (human monocytic leukemia cell line), a model for hematological malignancy. The number of viable cells was evaluated with erythrosine-B staining, while apoptosis and necrosis was assessed by endonuclease cleavage observed by agarose gel electrophoresis and detection of cells with the exclusionary dye propidium iodide and fluorescently labeled annexin-V by flow cytometry and fluorescent microscopy. Our observations indicate that treatment dosage levels of 45 s of exposure to CAP emitted RNS-induced apoptotic cell death and for higher dosage conditions of ?50 s of exposure to CAP induced necrosis. Overall the results suggest that CAP emitted RNS play a significant role in the anti-tumor potential of CAP. PMID:24022746

Thiyagarajan, Magesh; Anderson, Heather; Gonzales, Xavier F

2014-03-01

231

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

PubMed Central

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

232

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

233

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

234

Polymeric Actuators.  

PubMed

Actuators are materials and devices that are able to change their shape in response to changes in environmental conditions and perform mechanical work on nano-, micro-, and macroscales. Among the huge variety of different actuators, polymer-based ones are highly attractive because of a number of properties such as sensitivity to a broad range of stimuli and good mechanical properties. The goal of this review is to provide a general picture of different mechanisms and working principles of polymeric actuators as well as to show a palette of their applications. PMID:25386998

Ionov, Leonid

2014-11-11

235

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

236

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

237

Electromechanical actuators  

NASA Technical Reports Server (NTRS)

Materials illustrating a presentation on the development of electromechanical actuators (EMA) for electric flight systems are presented. Technology issues are identified, and major steps relative to EMA development, NASA's role, and a technology procurement plan are outlined.

Bigham, J.

1982-01-01

238

Silicon oxide barrier films deposited on PET foils in pulsed plasmas: influence of substrate bias on deposition process and film properties  

NASA Astrophysics Data System (ADS)

A widely used plastic for packaging, polyethylene terephtalate (PET) offers limited barrier properties against gas permeation. For many applications of PET (from food packaging to micro electronics) improved barrier properties are essential. A silicon oxide barrier coating of PET foils is applied by means of a pulsed microwave driven low-pressure plasma. While the adjustment of the microwave power allows for a control of the ion production during the plasma pulse, a substrate bias controls the energy of ions impinging on the substrate. Detailed analysis of deposited films applying oxygen permeation measurements, x-ray photoelectron spectroscopy and atomic force microscopy are correlated with results from plasma diagnostics describing the deposition process. The influence of a change in process parameters such as gas mixture and substrate bias on the gas temperature, electron density, mean electron energy, ion energy and the atomic oxygen density is studied. An additional substrate bias results in an increase in atomic oxygen density up to a factor of 6, although plasma parameter such as electron density of ne = 3.8 ± 0.8 × 1017 m-3 and electron temperature of kBTe = 1.7 ± 0.1 eV are unmodified. It is shown that atomic oxygen densities measured during deposition process higher than nO = 1.8 × 1021 m-3 yield in barrier films with a barrier improvement factor up to 150. Good barrier films are highly cross-linked and show a smooth morphology.

Steves, S.; Ozkaya, B.; Liu, C.-N.; Ozcan, O.; Bibinov, N.; Grundmeier, G.; Awakowicz, P.

2013-02-01

239

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

240

Deposition and characterization of plasma sprayed Ni-5A1/ magnesia stabilized zirconia based functionally graded thermal barrier coating  

NASA Astrophysics Data System (ADS)

Thermal barrier coatings (TBCs) are employed to protect hot section components in industrial and aerospace gas turbine engines. Conventional TBCs frequently fail due to high residual stresses and difference between coefficient of thermal expansion (CTE) of the substrate & coatings. Functionally graded thermal barrier coatings (FG-TBCs) with gradual variation in composition have been proposed to minimize the problem. In this work, a five layered functionally graded thermal barrier coating system was deposited by atmospheric plasma spray (APS) technique on Nimonic 90 substrates using Ni-5Al as bond coat (BC) and magnesia stabilized zirconia as top coat (TC). The coatings were characterized by SEM, EDS, XRD & optical profilometer. Microhardness and coefficient of thermal expansion of the five layers deposited as individual coatings were also measured. The deposited coating system was oxidized at 800°C. SEM analysis showed that five layers were successfully deposited by APS to produce a FG-TBC. The results also showed that roughness (Ra) of the individual layers decreased with an increase in TC content in the coatings. It was found that microhardness and CTE values gradually changed from bond coat to cermet layers to top coat. The oxidized coated sample revealed parabolic behavior and changes in the surface morphology and composition of coating.

Baig, M. N.; Khalid, F. A.

2014-06-01

241

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

242

Dielectric barrier plasma dynamics for active control of separated flows Subrata Roya  

E-print Network

. Singh Computational Plasma Dynamics Laboratory, Mechanical Engineering, Kettering University, Flint, Michigan 48504 Datta V. Gaitonde Computational Sciences Branch, Air Vehicles Directorate, Air Force

Roy, Subrata

243

Nonthermal Dielectric Barrier Discharge (DBD) Plasma Suppresses Herpes Simplex Virus Type 1 (HSV-1) Replication in Corneal Epithelium  

PubMed Central

Purpose Herpes keratitis (HK) is the leading cause of cornea-derived and infection-associated blindness in the developed world. Despite the availability of effective antivirals, some patients develop refractory disease, drug-resistant infection, and topical toxicity. A nonpharmaceutical treatment modality may offer a unique advantage in the management of such cases. This study investigated the antiviral effect of nonthermal dielectric barrier discharge (DBD) plasma, a partially ionized gas that can be applied to organic substances to produce various biological effects. Methods Human corneal epithelial cells and explanted corneas were infected with herpes simplex virus type 1 (HSV-1) and exposed to culture medium treated with nonthermal DBD plasma. The extent of infection was measured by plaque assay, quantitative PCR, and Western blot. Corneal toxicity assessment was performed with fluorescein staining, histologic examination, and 8-OHdG detection. Results Application of DBD plasma–treated medium to human corneal epithelial cells and explanted corneas produced a dose-dependent reduction of the cytopathic effect, viral genome replication, and the overall production of infectious viral progeny. Toxicity studies showed lack of detrimental effects in explanted human corneas. Conclusions Nonthermal DBD plasma substantially suppresses corneal HSV-1 infection in vitro and ex vivo without causing pronounced toxicity. Translational Relevance Nonthermal plasma is a versatile tool that holds great biomedical potential for ophthalmology, where it is being investigated for wound healing and sterilization and is already in use for ocular microsurgery. The anti-HSV-1 activity of DBD plasma demonstrated here could be directly translated to the clinic for use against drug-resistant herpes keratitis. PMID:24757592

Alekseev, Oleg; Donovan, Kelly; Limonnik, Vladimir; Azizkhan-Clifford, Jane

2014-01-01

244

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

245

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

246

Interaction between soot particles and NOx during dielectric barrier discharge plasma remediation of simulated diesel exhaust  

E-print Network

in actual exhausts and may, through heterogeneous chemistry, affect the remediation process. In this article, a computational investigation of the effect of soot on the plasma chemistry of NOx removal in a simulated diesel. INTRODUCTION The use of atmospheric nonthermal plasma processing in tandem with selective catalytic reduction

Kushner, Mark

247

Collective Phenomena In Volume And Surface Barrier Discharges  

NASA Astrophysics Data System (ADS)

Barrier discharges are increasingly used as a cost-effective means to produce non-equilibrium plasmas at atmospheric pressure. This way, copious amounts of electrons, ions, free radicals and excited species can be generated without appreciable gas heating. In most applications the barrier is made of dielectric material. In laboratory experiments also the use of resistive, ferroelectric and semiconducting materials has been investigated, also porous ceramic layers and dielectric barriers with controlled surface conductivity. Major applications utilizing mainly dielectric barriers include ozone generation, surface cleaning and modification, polymer and textile treatment, sterilization, pollution control, CO2 lasers, excimer lamps, plasma display panels (flat TV screens). More recent research efforts are also devoted to biomedical applications and to plasma actuators for flow control. Sinu- soidal feeding voltages at various frequencies as well as pulsed excitation schemes are used. Volume as well as surface barrier discharges can exist in the form of filamentary, regularly patterned or laterally homogeneous discharges. Reviews of the subject and the older literature on barrier discharges were published by Kogelschatz (2002, 2003), by Wagner et al. (2003) and by Fridman et al. (2005). A detailed discussion of various properties of barrier discharges can also be found in the recent book "Non-Equilibrium Air Plasmas at Atmospheric Pressure" by Becker et al. (2005). The physical effects leading to collective phenomena in volume and surface barrier discharges will be discussed in detail. Special attention will be given to self-organization of current filaments. Main similarities and differences of the two types of barrier discharges will be elaborated.

Kogelschatz, U.

2010-07-01

248

The efficient plasma plume extraction from atmospheric pressure parallal dielectric barrier discharge jet  

Microsoft Academic Search

Summary form only given. Planar dielectric barrier discharges (DBDs) have a large number of industrial applications because of simple structure and no need for cumbersome impedance matching systems. However, planar DBD still have some disadvantages such as the limit of gap distance and the non-uniformity due to the characteristics of microdischarge intercepting electrodes. Therefore the DBD jet has been introduced.

Joo Hyon Noh; Man Hyeop Han; Jai Hyuk Choi; Yong Ki Lee; Hong Koo Baik

2006-01-01

249

Coplanar ac discharges between cylindrical electrodes with a nanoporous alumina dielectric: Modular dielectric barrier plasma devices  

Microsoft Academic Search

Dielectric barrier discharges between coplanar Al rods having an ?2-?m-thick layer of nanoporous alumina dielectric at the surface have been investigated. Rods 3 mm in diameter, 7 cm in length, and spaced by 5 mm produce stable and intense glow discharges in 50 torr of Ne when pairs of rods are driven by an alternating current (bipolar) waveform for which

J. H. Cho; K.-W. Lee; S.-J. Park; J. G. Eden

2005-01-01

250

Blood-nerve barrier: distribution of anionic sites on the endothelial plasma membrane and basal lamina of dorsal root ganglia.  

PubMed

Previous investigations of the blood-nerve barrier have correlated the greater permeability of ganglionic endoneurial vessels, compared to those of nerve trunks, with the presence of fenestrations and open intercellular junctions. Recent studies have demonstrated reduced endothelial cell surface charge in blood vessels showing greater permeability. To determine the distribution of anionic sites on the plasma membranes and basal laminae of endothelial cells in dorsal root ganglia, cationic colloidal gold and cationic ferritin were used. Electron microscopy revealed the existence of endothelial microdomains with differing labelling densities. Labelling indicated that caveolar and fenestral diaphragms and basal laminae are highly anionic at physiological pH, luminal plasma membranes and endothelial processes are moderately charged and abluminal plasma membranes are weakly anionic. Tracers did not occur in caveolae or cytoplasmic vesicles. In vitro tracer experiments at pH values of 7.3, 5.0, 3.5 and 2.0 indicated that the anionic charge on the various endothelial domains was contributed by chemical groups with differing pKa values. In summary, the labelling of ganglionic and sciatic nerve vessels was similar except for the heavy labelling of diaphragms in a minority of endoneurial vessels in ganglia. This difference is likely to account in part for the greater permeability of ganglionic endoneurial vessels. The results are discussed with regard to the blood-nerve and -brain barriers and vascular permeability in other tissues and a comparison made between the ultrastructure and anionic microdomains of epi-, peri- and endoneurial vessels of dorsal root ganglia and sciatic nerves. PMID:1960538

Bush, M S; Reid, A R; Allt, G

1991-09-01

251

Dielectric barrier discharge-plasma induced vaporization and its application to the determination of mercury by atomic fluorescence spectrometry.  

PubMed

This paper describes a low-temperature dielectric barrier discharge (DBD)-plasma induced vaporization technique using mercury as a model analyte. The evaporation and atomization of dissolved mercury species in the sample solution can be achieved rapidly in one step, allowing mercury to be directly detected by atomic fluorescence spectrometry. The DBD plasma was generated concentrically in-between two quartz tube (outer tube: i.d. 5 mm and o.d. 6 mm, inner tube: i.d. 2 mm and o.d. 3 mm). A copper electrode was embedded inside the inner quartz tube and sample solution was applied onto the outer surface of the inner tube. The effects of operating parameters such as plasma power, plasma gas identity, plasma gas flow rate and interferences from concomitant elements have been investigated. The difference in the sensitivities of Hg(2+), methylmercury (MeHg) and ethylmercury (EtHg) was found to be negligible in the presence of formic acid (?1% v/v). The analytical performance of the present technique was evaluated under optimized conditions. The limits of detection were calculated to be 0.02 ng mL(-1) for Hg(2+), MeHg and EtHg, and repeatability was 6.2%, 4.9% and 4.3% RSD (n = 11) for 1 ng mL(-1) of Hg(2+), MeHg and EtHg, respectively. This provides a simple mercury detection method for small-volume samples with an absolute limit of detection at femtogram level. The accuracy of the system was verified by the determination of mercury in reference materials including freeze-dried urine ZK020-2, simulated water matrix reference material GBW(E) 080392 and tuna fish GBW10029, and the concentration of mercury determined by the present method agreed well with the reference values. PMID:21935545

Liu, Zhifu; Zhu, Zhenli; Wu, Qingju; Hu, Shenghong; Zheng, Hongtao

2011-11-01

252

Microstructure Evolution of the TaNx (x=0--1) Diffusion Barriers by NH3 Plasma Treatment for the Electroless Copper Deposition  

NASA Astrophysics Data System (ADS)

Microstructure evolution during NH3 plasma treatment of the surface of TaNx barrier films was investigated using transmission electron microscopy (TEM) in order to understand how the plasma treatment improves the palladium activation process for electroless copper deposition. Plan view TEM and selected area diffraction pattern (SADP) results showed that the outermost surface of the crystalline TaNx layer was transformed to the amorphous phase by the NH3 plasma treatment. The surface energy, evaluated by contact angle measurement, of TaNx films was increased by the NH3 plasma treatment. The increase in the surface energy of TaNx films by the plasma treatment seems to increase the nucleation sites for palladium activation. It is thought that the enhancement of the palladium activation process by the NH3 plasma treatment was caused by an increase in the surface energy of TaNx films during the plasma treatment.

Hong, Seok Woo; Lee, Yong Sun; Park, Jong-Wan

2004-10-01

253

Thermal cycling behavior of plasma-sprayed thermal barrier coatings with various MCrAlX bond coats  

NASA Astrophysics Data System (ADS)

The influence of bond coat composition on the spallation resistance of plasma-sprayed thermal barrier coatings (TBCs) on single-crystal René N5 substrates was assessed by furnace thermal cycle testing of TBCs with various vacuum plasma spray (VPS) or air plasma-spray (APS) MCrAlX (M=Ni and/or Co; and X=Y, Hf, and/or Si) bond coats. The TBC specimens with VPS bond coats were fabricated using identical parameters, with the exception of bond coat composition. The TBC lifetimes were compared with respect to MCrAlX composition (before and after oxidation testing) and MCrAlX properties (surface roughness, thermal expansion, hardness, and Young’s modulus). The average TBC spallation lifetimes varied significantly (from 174 to 344 1 h cycles at 1150 °C) as a function of bond coat composition. Results suggested a relationship between TBC durability and bond coat thermal expansion behavior below 900 °C. Although there were only slight differences in their relative rates of cyclic oxidation weight gain, VPS MCrAlX bond coats with better oxide scale adhesion provided superior TBC lifetimes.

Haynes, J. A.; Ferber, M. K.; Porter, W. D.

2000-03-01

254

Effects of surface modification by atmospheric oxygen dielectric barrier discharge plasma on PBO fibers and its composites  

NASA Astrophysics Data System (ADS)

In this paper, oxygen dielectric barrier discharge (oxy-DBD) plasma was employed to modify PBO fibers and enhance the interfacial adhesion of PBO fiber/bismaleimide composites. The interlaminar shear strength (ILSS) of the composites was improved greatly to 62.0 MPa with an increment of 41.2% at 30 W/cm3, 24 s. The SEM images of fracture morphology indicated that the failure place shifted from the interface to the matrix, and the water absorption decreased from 1.96 to 1.53%, the two results demonstrated the improved adhesive strength in other ways. In addition, the ILSS retention ratio of PBO/BMI composites after boiling in water were about 90%, confirming good humid resistance of the composites. The results obtained from XPS and AFM revealed that some polar groups were introduced onto PBO fibers and the surface morphology of PBO fibers was roughened. As a result, the wettability, reactivity and roughness of PBO fibers were all improved, they contributed to the improvement of the ILSS of the composites. The comparisons with air-DBD plasma showed that the chemical changes of PBO fibers were not alike because of different plasma gases.

Liu, Zhe; Chen, Ping; Zhang, Xiaoliang; Yu, Qi; Ma, Keming; Ding, Zhenfeng

2013-10-01

255

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

256

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

NASA Astrophysics Data System (ADS)

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 strength, surface electrical resistivity and electromagnetic interference (EMI)- shielding effectiveness (SE) were studied. The liquid absorptive capacity (WA) increased due to the incorporation of oxygen-containing and nitrogen-containing functional groups on the surface of PET nonwoven fabric after DBD air-plasma treatment. The surface morphology of the nonwoven fibers became rougher after plasma treatment. Therefore, the surface was more prone to absorb tin sensitizer and palladium catalyst to form an active layer for the deposition of electroless nickel. SEM and X-ray diffraction (XRD) measurements indicated that a uniform coating of nickel was formed on the PET nonwoven fabric. The average EMI-SE of Ni-plating of PET nonwoven fabric maintained a relatively stable value (38.2 dB to 37.3 dB) in a frequency range of 50 MHz to 1500 MHz. It is concluded that DBD is feasible for pretreatment of nonwoven fabric for electroless nickel plating to prepare functional material with good EMI-SE properties.

Geng, Yamin; Lu, Canhui; Liang, Mei; Zhang, Wei

2010-12-01

257

Observation of an impurity hole in a plasma with an ion internal transport barrier in the Large Helical Device  

SciTech Connect

Extremely hollow profiles of impurities (denoted as 'impurity hole') are observed in the plasma with a steep gradient of the ion temperature after the formation of an internal transport barrier (ITB) in the ion temperature transport in the Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. The radial profile of carbon becomes hollow during the ITB phase and the central carbon density keeps dropping and reaches 0.1%-0.3% of plasma density at the end of the ion ITB phase. The diffusion coefficient and the convective velocity of impurities are evaluated from the time evolution of carbon profiles assuming the diffusion and the convection velocity are constant in time after the formation of the ITB. The transport analysis gives a low diffusion of 0.1-0.2 m{sup 2}/s and the outward convection velocity of {approx}1 m/s at half of the minor radius, which is in contrast to the tendency in tokamak plasmas for the impurity density to increase due to an inward convection and low diffusion in the ITB region. The outward convection is considered to be driven by turbulence because the sign of the convection velocity contradicts the neoclassical theory where a negative electric field and an inward convection are predicted.

Ida, K.; Yoshinuma, M.; Osakabe, M.; Nagaoka, K.; Yokoyama, M.; Funaba, H.; Suzuki, C.; Ido, T.; Shimizu, A.; Murakami, I.; Tamura, N.; Kasahara, H.; Takeiri, Y.; Ikeda, K.; Tsumori, K.; Kaneko, O.; Morita, S.; Goto, M.; Tanaka, K.; Narihara, K. [National Institute for Fusion Sciences, Toki, Gifu 509-5292 (Japan)] (and others)

2009-05-15

258

Spectroscopic diagnostics of barrier discharge plasmas in mixtures of zinc diiodide with inert gases  

Microsoft Academic Search

The spectral characteristics of the emission of gas discharge atmospheric pressure plasmas in mixtures of zinc diiodide vapor\\u000a with inert gases (He, Ne, Ar, Kr, and Xe) are investigated. The formation of a gas discharge plasma and the excitation of\\u000a the components of a working mixture were performed in a high-frequency (with a repetition frequency of sinusoidal voltage\\u000a pulses of

N. N. Guivan; A. N. Malinin

2005-01-01

259

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

260

Actuator-valve interface optimization. [Explosive actuators  

SciTech Connect

The interface of explosive actuator driven valves can be optimized to maximize the velocity of the valve plunger by using the computer code Actuator-Valve Response. Details of the AVR model of the actuator driven valve plunger and the results of optimizing an actuator-valve interface with AVR are presented. 5 refs., 5 figs., 3 tabs.

Burchett, O.L.; Jones, R.L.

1987-02-01

261

Optimizing Compliance and Thermal Conductivity of Plasma Sprayed Thermal Barrier Coatings via Controlled Powders and Processing Strategies  

NASA Astrophysics Data System (ADS)

The properties and performance of plasma-sprayed thermal barrier coatings (TBCs) are strongly dependent on the microstructural defects, which are affected by starting powder morphology and processing conditions. Of particular interest is the use of hollow powders which not only allow for efficient melting of zirconia ceramics but also produce lower conductivity and more compliant coatings. Typical industrial hollow spray powders have an assortment of densities resulting in masking potential advantages of the hollow morphology. In this study, we have conducted process mapping strategies using a novel uniform shell thickness hollow powder to control the defect microstructure and properties. Correlations among coating properties, microstructure, and processing reveal feasibility to produce highly compliant and low conductivity TBC through a combination of optimized feedstock and processing conditions. The results are presented through the framework of process maps establishing correlations among process, microstructure, and properties and providing opportunities for optimization of TBCs.

Tan, Yang; Srinivasan, Vasudevan; Nakamura, Toshio; Sampath, Sanjay; Bertrand, Pierre; Bertrand, Ghislaine

2012-09-01

262

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

263

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

264

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

265

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

266

Nitridation of thin metal layers by plasma immersion ion implantation for diffusion barrier applications  

NASA Astrophysics Data System (ADS)

For this study, Ti/Si and Ta/Si structures were implanted with two doses of nitrogen 10 15 ions/cm2 (low dose) and 10 17 ions/cm2 (high dose) at 10KeV and 20KeV energy. Characterization was performed by Sheet resistance measurement and X-Ray diffraction (XRD) techniques. Results shows that implantation of 10 15 ions/cm2 dose of nitrogen does not cause any nitridation, while in case of high dose implanted samples formation of tantalum nitride phase was observed. Nitride layers formed this way was used as diffusion barrier layers for copper metallization in Silicon based integrated circuits.

Kumar, Mukesh; Rajkumar, -; Kumar, Dinesh

2006-01-01

267

Contrib. Plasma Phys. 47, No. 1-2, 26 33 (2007) / DOI 10.1002/ctpp.200710005 Progress in Spectroscopic Diagnostics of Barrier Discharges  

E-print Network

Contrib. Plasma Phys. 47, No. 1-2, 26 ­ 33 (2007) / DOI 10.1002/ctpp.200710005 Progress in Spectroscopic Diagnostics of Barrier Discharges K. V. Kozlov1 and H.-E. Wagner2 1 Department of Chemistry, at the improvement of the measurement technique and development of the data processing procedures, and on the other

Greifswald, Ernst-Moritz-Arndt-Universität

268

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

Microsoft Academic Search

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

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

2011-01-01

269

Oxidative Conversion of PFC via Plasma Processing with Dielectric Barrier Discharges  

Microsoft Academic Search

Perfluorocompounds (PFCs) have been extensively used as plasma etching andchemical vapor deposition (CVD) gases for semiconductor manufacturingprocesses. PFCs have significant effects on the global warming and havevery long atmospheric lifetimes. Laboratory-scale experiments were performedto evaluate the effectiveness of CF4 conversion by using dielectric barrierdischarges (DBD). The results of this study revealed that the removalefficiency of CF4 increased with application of

Sheng Jen Yu; Moo Been Chang

2001-01-01

270

Characterization and Application of a Planar Radio - Inductively-Coupled Plasma Source for the Production of Barrier Coatings.  

NASA Astrophysics Data System (ADS)

A planar radio-frequency (rf) inductively-coupled plasma (ICP) source is used to produce fluorocarbon discharges (CF_4/Ar) to fluorinate the surface of high-density polyethylene (HDPE). Using this system, concurrent studies of discharge characteristics, permeation properties of treated polymers and polymer surface characteristics are conducted to advance the use of plasma-fluorinated polymer surfaces as a barrier layer for automotive applications. Langmuir probes are used to determine spatial distribution of charged-particle and space-potential characteristics in Ar and CF_4/Ar discharges and to show the influence of the spatial distribution of the heating regions and the reactor boundaries on the discharge uniformity. Langmuir probes are also used to identify rf anisotropic drift motion of electrons in the heating regions of the source and transient high-energy electron features in pulsed discharges. These latter features allow pulsed ICP sources to be operated at low time-averaged powers that are necessary to treat thermally sensitive polymers. Fourier Transform Infrared (FITR) spectroscopy is used to measure the dissociation of fluorocarbon gases and to explore differences between pulsed- and continuous -power operation. Dissociation levels of CF_4 (50-85%) using pulsed-power operation are as high as that for continuous operation, even though the net time -averaged power is far less with pulsed operation. The result suggests that pulsed fluorocarbon discharges possess high concentrations of chemically-active species needed for rapid surface fluorination. A gravimetric permeation cup method is used to measure the permeation rate of test fuels through HDPE membranes, and electron spectroscopy for chemical analysis (ESCA) studies are performed to determine the stoichiometry and thickness of the barrier layer. From these studies we find that a 50-70 A thick, polar, fluoro-hydrocarbon over layer reduces the permeation of isooctane/toluene/methanol mixtures by a factor of 4. To increase the permeation resistance for automotive applications, this result points towards the deposition of a 1000 A thick fluoro-hydrocarbon barrier coating with stoichiometry and bond structures similar to the CF_4/Ar treated HDPE.

Mahoney, Leonard Joseph

271

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

272

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

273

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

274

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

275

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

276

Plasma membrane and actin cytoskeleton as synergistic barriers to nanowire cell penetration.  

PubMed

Nanowires are a rapidly emerging platform for manipulation of and material delivery directly into the cell cytosol. These high aspect ratio structures can breach the lipid membrane; however, the yield of penetrant structures is low, and the mechanism is largely unknown. In particular, some nanostructures appear to defeat the membrane transiently, while others can retain long-term access. Here, we examine if local dissolution of the lipid membrane, actin cytoskeleton, or both can enhance nanowire penetration. It is possible that, during cell contact, membrane rupture occurs; however, if the nanostructures do not penetrate the cytoskeleton, the membrane may reclose over a relatively short time frame. We show with quantitative analysis of the number of penetrating nanowires that the lipid bilayer and actin cytoskeleton are synergistic barriers to nanowire cell access, yet chemical poration through both is still insufficient to increase long-term access for adhered cells. PMID:25244597

Aalipour, Amin; Xu, Alexander M; Leal-Ortiz, Sergio; Garner, Craig C; Melosh, Nicholas A

2014-10-21

277

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

278

Memory metal actuator  

NASA Technical Reports Server (NTRS)

A mechanical actuator can be constructed by employing a plurality of memory metal actuator elements in parallel to control the amount of actuating force. In order to facilitate direct control by digital control signals provided by a computer or the like, the actuating elements may vary in stiffness according to a binary relationship. The cooling or reset time of the actuator elements can be reduced by employing Peltier junction cooling assemblies in the actuator.

Ruoff, C. F. (inventor)

1985-01-01

279

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

280

Effect of Processing Conditions on the Anelastic Behavior of Plasma Sprayed Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

Plasma sprayed ceramic materials contain an assortment of micro-structural defects, including pores, cracks, and interfaces arising from the droplet based assemblage of the spray deposition technique. The defective architecture of the deposits introduces a novel "anelastic" response in the coatings comprising of their non-linear and hysteretic stress-strain relationship under mechanical loading. It has been established that this anelasticity can be attributed to the relative movement of the embedded defects under varying stresses. While the non-linear response of the coatings arises from the opening/closure of defects, hysteresis is produced by the frictional sliding among defect surfaces. Recent studies have indicated that anelastic behavior of coatings can be a unique descriptor of their mechanical behavior and related to the defect configuration. In this dissertation, a multi-variable study employing systematic processing strategies was conducted to augment the understanding on various aspects of the reported anelastic behavior. A bi-layer curvature measurement technique was adapted to measure the anelastic properties of plasma sprayed ceramic. The quantification of anelastic parameters was done using a non-linear model proposed by Nakamura et.al. An error analysis was conducted on the technique to know the available margins for both experimental as well as computational errors. The error analysis was extended to evaluate its sensitivity towards different coating microstructure. For this purpose, three coatings with significantly different microstructures were fabricated via tuning of process parameters. Later the three coatings were also subjected to different strain ranges systematically, in order to understand the origin and evolution of anelasticity on different microstructures. The last segment of this thesis attempts to capture the intricacies on the processing front and tries to evaluate and establish a correlation between them and the anelastic parameters.

Viswanathan, Vaishak

2011-12-01

281

Multi-scale modelling of pulsed nanosecond dielectric barrier plasma discharges in plane-to-plane geometry  

NASA Astrophysics Data System (ADS)

An integrated theoretical and numerical framework is developed to study the dynamics of energy coupling, gas heating and generation of active species by repetitively pulsed nanosecond dielectric barrier discharges (NS DBDs) in air. The work represents one of the first attempts to simulate, in a self-consistent manner, multiple (more than 100) nanosecond pulses. Detailed information is obtained about the electric-field transients during each voltage pulse, and accumulation of plasma generated species and gas heating over ms timescales. The plasma is modelled using a two-temperature, detailed chemistry scheme, with ions and neutral species in thermal equilibrium at the gas temperature, and electrons in thermal nonequilibrium. The analysis is conducted with pressures and pulsing frequency in the range 40-100 Torr and 1-105 Hz, respectively. The input electrical energy is directly proportional to the number density, and remains fairly constant on a per molecule basis from pulse to pulse. Repetitive pulsing results in uniform production of atomic oxygen in the discharge volume via electron-impact dissociation during voltage pulses, and through quenching of excited nitrogen molecules in the afterglow. The ion Joule effect causes rapid gas heating of ˜40 K/pulse in the cathode sheath and generates weak acoustic waves. Conductive heat loss to the walls during the time interval between voltage pulses prevents overheating of the cathode layer and development of ionization instabilities. A uniform ‘hat-shaped’ temperature profile develops in the discharge volume after multiple pulses, due to chemical heat release from quenching of excited species. This finding may explain experimentally observed volumetric ignition (as opposed to hot-spot ignition) in fuel-air mixtures subject to NS DBD.

Nagaraja, Sharath; Yang, Vigor; Adamovich, Igor

2013-04-01

282

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

283

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

284

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

285

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

286

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

287

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

288

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)

2006-01-01

289

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

290

Nanotube micro-optomechanical actuators  

Microsoft Academic Search

In this letter we demonstrate a simple carbon nanotube patterning technique that combines nanotube film bonding, photolithography, and O2 plasma etching. Well defined carbon nanotube film structures with line widths less than ~1.5 mum and thickness ranging from 40 to 780 nm were readily fabricated. A micro-optomechanical actuator based on this process has been demonstrated. This patterning process can be

Shaoxin Lu; Balaji Panchapakesan

2006-01-01

291

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

292

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

293

Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work  

NASA Astrophysics Data System (ADS)

A review is presented of how heat transfer takes place in plasma-sprayed (zirconia-based) thermal barrier coatings (TBCs) during operation of gas turbines. These characteristics of TBCs are naturally of central importance to their function. Current state-of-the-art TBCs have relatively high levels of porosity (~15%) and the pore architecture (i.e., its morphology, connectivity, and scale) has a strong influence on the heat flow. Contributions from convective, conductive and radiative heat transfer are considered, under a range of operating conditions, and the characteristics are illustrated with experimental data and modeling predictions. In fact, convective heat flow within TBCs usually makes a negligible contribution to the overall heat transfer through the coating, although what might be described as convection can be important if there are gross through-thickness defects such as segmentation cracks. Radiative heat transfer, on the other hand, can be significant within TBCs, depending on temperature and radiation scattering lengths, which in turn are sensitive to the grain structure and the pore architecture. Under most conditions of current interest, conductive heat transfer is largely predominant. However, it is not only conduction through solid ceramic that is important. Depending on the pore architecture, conduction through gas in the pores can play a significant role, particularly at the high gas pressures typically acting in gas turbines (although rarely applied in laboratory measurements of conductivity). The durability of the pore structure under service conditions is also of importance, and this review covers some recent work on how the pore architecture, and hence the conductivity, is affected by sintering phenomena. Some information is presented concerning the areas in which research and development work needs to be focussed if improvements in coating performance are to be achieved.

Golosnoy, I. O.; Cipitria, A.; Clyne, T. W.

2009-12-01

294

A Comparison between Plasma Synthetic Jets and Conventional Jets  

NASA Astrophysics Data System (ADS)

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 of high voltage, high frequency AC at ambient conditions of pressure and temperature, a region of DBD plasma is formed starting from the edges of the exposed electrode. In an initially quiescent medium, this plasma region is observed to induce and sustain entrainment of near wall fluid, the volume of which is ejected out from the base of the actuator in the form of a jet. The electrodes are shaped either in the form of annular arrays for rendering a circular jet, or linear arrays for rendering a rectangular jet. 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. The jet outputs are found to be affected by a variety of system inputs, including the input electrical power, pulsing frequency, and actuator dimension. The effects of varying the above parameters on the self similarity behavior of plasma synthetic jets are examined and compared to mechanically driven jets.

Santhanakrishnan, Arvind; Jacob, Jamey

2007-11-01

295

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

296

Carbon nanotube actuators  

PubMed

Electromechanical actuators based on sheets of single-walled carbon nanotubes were shown to generate higher stresses than natural muscle and higher strains than high-modulus ferroelectrics. Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. The actuation mechanism (quantum chemical-based expansion due to electrochemical double-layer charging) does not require ion intercalation, which limits the life and rate of faradaic conducting polymer actuators. Unlike conventional ferroelectric actuators, low operating voltages of a few volts generate large actuator strains. Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology. PMID:10334985

Baughman; Cui; Zakhidov; Iqbal; Barisci; Spinks; Wallace; Mazzoldi; De Rossi D; Rinzler; Jaschinski; Roth; Kertesz

1999-05-21

297

Influence of pores on the surface microcompression mechanical response of thermal barrier coatings fabricated by atmospheric plasma spray—Finite element simulation  

NASA Astrophysics Data System (ADS)

Surface microcompression is a very important technique to characterize the mechanical properties of film and coating systems. In this paper, surface microcompression simulation for La 2Zr 2O 7 (LZ) thermal barrier coatings (TBCs) was implemented by finite element method, especially, the influence of pores on the surface microcompression mechanical response of the thermal barrier coatings fabricated by atmospheric plasma spray (APS) was focused on. The simulation results indicate that the pores not only affect the stress distribution beneath the contact area between the indenter and coating surface, but also affect the shape of the force-displacement curve and the plastic deformation behavior of TBCs. The micromechanism was discussed in detail in this study. At the same time, by using the surface microcompression technique, a new direction or method was proposed to characterize the pore content of the coating quantitatively.

Wang, L.; Wang, Y.; Sun, X. G.; Pan, Z. Y.; He, J. Q.; Li, C. G.

2011-01-01

298

Electromagnetic rotational actuation.  

SciTech Connect

There are many applications that need a meso-scale rotational actuator. These applications have been left by the wayside because of the lack of actuation at this scale. Sandia National Laboratories has many unique fabrication technologies that could be used to create an electromagnetic actuator at this scale. There are also many designs to be explored. In this internship exploration of the designs and fabrications technologies to find an inexpensive design that can be used for prototyping the electromagnetic rotational actuator.

Hogan, Alexander Lee

2010-08-01

299

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 3min. 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?gL(-1). Repeatability, expressed as the relative standard deviation of the spectral peak height, was 4.6% (n=11) for 0.1mgL(-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

2015-01-15

300

Influence of low energy argon plasma treatment on the moisture barrier performance of hot wire-CVD grown SiNx multilayers  

NASA Astrophysics Data System (ADS)

The reliability and stability are key issues for the commercial utilization of organic photovoltaic devices based on flexible polymer substrates. To increase the shelf-lifetime of these devices, transparent moisture barriers of silicon nitride (SiNx) films are deposited at low temperature by hot wire CVD (HW-CVD) process. Instead of the conventional route based on organic/inorganic hybrid structures, this work defines a new route consisting in depositing multilayer stacks of SiNx thin films, each single layer being treated by argon plasma. The plasma treatment allows creating smoother surface and surface atom rearrangement. We define a critical thickness of the single layer film and focus our attention on the effect of increasing the number of SiNx single-layers on the barrier properties. A water vapor transmission rate (WVTR) of 2 × 10-4 g/(m2·day) is reported for SiNx multilayer stack and a physical interpretation of the plasma treatment effect is given.

Majee, Subimal; Fátima Cerqueira, Maria; Tondelier, Denis; Geffroy, Bernard; Bonnassieux, Yvan; Alpuim, Pedro; Bourée, Jean Eric

2014-01-01

301

Distributed electrostatic micro actuator  

Microsoft Academic Search

A micro actuator that is called a distributed electrostatic actuator, because it consists of many driving units, and that is driven by electrostatic force is described. Each driving unit has wavelike electrodes, which are insulated and pull each other by the electrostatic force. The deformation of this actuator depends on the electrostatic force, the elasticity of the structure, and the

Motoharu Yamaguchi; Shuji Kawamura; Kazuyuki Minami; Masayoshi Esashi

1993-01-01

302

Introduction to Actuators LM  

NSDL National Science Digital Library

This page from the Southwest Center for Microsystems Education covers an overview of actuators. The documents in this learning module are designed to introduce students to actuators in the micro and macro scales. Included are a student guide, instructor guide, and narrated presentation to the Introduction to Actuators lesson.

2014-07-09

303

An electrochemical micro actuator  

Microsoft Academic Search

In this paper an investigation of the feasibility of a new electrochemical micro actuator is presented. The actuator is fabricated using silicon micro-machining techniques. A gas pressure is generated by electrolysis of an aqueous electrolyte solution. The build up pressure is used to change the deflection of a membrane. The actuator has three states: the electrolysis state, in which the

M. W. Hamberg; C. R. Neagu; J. G. E. Gardeniers; D. J. Ijntema; M. C. Elwenspoek

1995-01-01

304

Plasma-Enhanced Atomic Layer Deposition of Ruthenium-Titanium Nitride Mixed-Phase Layers for Direct-Plate Liner and Copper Diffusion Barrier Applications  

NASA Astrophysics Data System (ADS)

Current interconnect networks in semiconductor processing utilize a sputtered TaN diffusion barrier, Ta liner, and Cu seed to improve the adhesion, microstructure, and electromigration resistance of electrochemically deposited copper that fills interconnect wires and vias. However, as wire/via widths shrink due to device scaling, it becomes increasingly difficult to have the volume of a wire/via be occupied with ECD Cu which increases line resistance and increases the delay in signal propagation in IC chips. A single layer that could serve the purpose of a Cu diffusion barrier and ECD Cu adhesion promoter could allow ECD Cu to occupy a larger volume of a wire/via, leading to a decrease in line resistance and decrease in signal delay. Previous work has shown RuTaN, RuWCN, and RuCo films can act as Cu diffusion barriers and be directly platable to thickness of 2-3nm. However, other material selections may prove as effective or possibly better. Mixed-phase films of ruthenium titanium nitride grown by atomic layer deposition (ALD) were investigated for their performance as a Cu diffusion barrier and as a surface for the direct plating of ECD Cu. All Ru was deposited by plasma-enhanced atomic layer deposition (PEALD) while TiN was deposited by either thermal ALD or PEALD. RuTiN, films with thermal ALD TiN and a Ru:Ti of 20:1 showed barrier performance comparable to PVD TaN at 3-4 nm thickness and 15 nm planar films were directly platable. Follow up work is certainly needed for this material set, yet initial results indicate RuTiN could serve as an effective direct plate liner for Cu interconnects.

Gildea, Adam James

305

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

306

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

307

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

308

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

309

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

310

Optical emission characteristics of medium- to high-pressure N{sub 2} dielectric barrier discharge plasmas during surface modification of polymers  

SciTech Connect

The authors measured the band spectra (first and second positive systems) of the nitrogen molecule by optical emission spectroscopy with an aim to understand the mechanism of surface processing by medium- to high-pressure dielectric barrier discharge (DBD) plasmas. The experimentally measured and calculated spectra were compared to determine the vibrational and rotational temperatures of the N{sub 2} (C{sup 3}{Pi}{sub u}) state in the generated plasmas. The authors generated the N{sub 2} DBD plasmas at a driving frequency of 1-7 kHz and a discharge pressure of 20-10{sup 5} Pa for the surface modification of a polyethylene terephthalate (PET) sample. It was found that the vibrational temperature was greatly affected by the N{sub 2} pressure while the rotational temperature remained constant in the N{sub 2} pressure range of 20-10{sup 5} Pa. The emission intensity of N{sub 2} first positive system (B{sup 3}{Pi}{yields}A{sup 3}{Sigma}) rapidly decreased at an increasing N{sub 2} pressure due to the collisional relaxation process of the B{sup 3}{Pi} state with N{sub 2} molecules. The N{sub 2}{sup +}(B{sup 2}{Sigma}{sub u}{sup +}{yields}X{sup 2}{Sigma}{sub g}{sup +}) radiative transition was observed in the low-pressure DBD plasmas, which was attributed to the direct electron impact ionization of N{sub 2} molecules. The surface characterizations of treated PET samples by contact angle measurement and atomic force microscopy indicate that the low-pressure N{sub 2} DBD plasma is an effective method for the surface modification of polymers. Analysis indicates the plasma characteristics such as electron temperature and ion energy are mainly dependent on the N{sub 2} pressure, which turn to determine the surface properties of treated PET samples.

Liu Dongping; Niu Jinhai; Yu Naisen [School of Physics and Materials Engineering, Dalian Nationalities University, Dalian 116600 (China) and Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005 (China); School of Physics and Materials Engineering, Dalian Nationalities University, Dalian 116600 (China)

2011-11-15

311

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

312

Sensors and Actuators  

NSDL National Science Digital Library

Sensors and Actuators A (SAAA) disseminates "...information on all aspects of research and development of solid-state devices for transducing physical signals." Sensors and Actuators B (SAAB) "...is an interdisciplinary journal dedicated to covering research and development in the field of chemical sensors, actuators and microsystems." Issues of SAAA available range from September 1999 to the present; issues of SAAB cover January 2000-present.

2001-01-01

313

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

314

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

315

Retractable barrier strip  

DOEpatents

A portable barrier strip 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 stable 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.

Marts, Donna J. (Idaho Falls, ID); Barker, Stacey G. (Idaho Falls, ID); McQueen, Miles A. (Idaho Falls, ID)

1996-01-01

316

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

317

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

318

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

319

Dyeing mechanism and optimization of polyamide 6,6 functionalized with double barrier discharge (DBD) plasma in air  

NASA Astrophysics Data System (ADS)

The physico-chemical improvements occasioned by DBD plasma discharge in dyeing process of polyamide 6,6 (PA66) fibers were investigated. The SEM, fluorescence microscopy, UV-vis spectroscopy, surface energy, FTIR, XPS and pH of aqueous extracts confirm the high polar functionalization of PA66 fibers due to plasma incorporation of oxygen atoms from atmospheric air. DBD plasma-generated reactive species preferentially break the CN bonds, and not the aliphatic C-C chain of PA66. Formation of low-molecular weight acidic molecules that act as dye "carrier" and creation of micro-channels onto PA66 surface seems to favor dye diffusion into the fiber cores. Plasma treatment allows high level of direct dye diffusion and fixation in PA66 fibers at lower temperatures and shorter dyeing times than traditional dyeing methods.

Oliveira, Fernando Ribeiro; Zille, Andrea; Souto, Antonio Pedro

2014-02-01

320

Atmospheric Pressure Plasma Jet (APPJ) and Dielectric Barrier Atmospheric Pressure Glow Discharge (DB-APGD) in Comparison  

Microsoft Academic Search

In this work two prominent types of low temperature atmospheric pressure plasma sources are compared. First, a plane-parallel 13.56 MHz RF-excited atmospheric pressure plasma jet (APPJ) operated with 2 m3\\/h helium feed gas containing 0.5 % molecular oxygen is investigated. Its stainless steel electrodes' area measures 8 x 4 cm2 and the discharge gap is 1.1 mm. The effluent leaving

S. Reuter; V. Schulz-von der Gathen; H. F. Döbele

2007-01-01

321

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

322

Electrostatic curved electrode actuators  

Microsoft Academic Search

In this paper, the design, fabrication, and first experimental results of electrostatic curved electrode actuators are addressed. The actuator design is based upon the deformation of a movable micromechanical structure by electrostatic forces using a fixed curved electrode. When a voltage is applied, an electrostatic force is created that will deform the free structure along the outline of the fixed

Rob Legtenberg; Erwin Berenschot; Miko Elwenspoek; J. H. J. Fluitman

1995-01-01

323

Piezoceramic actuated aperture antennas  

Microsoft Academic Search

Recently, it has been demonstrated that aperture antennas can have their performance improved by utilizing PVDF as a shape controlling actuator. Since PVDF is a polymer with limited control authority, these antennas can only be employed in space based applications. This study examines more robust antenna structures devised of a thick metalized substrate with surface bonded piezoceramic (PZT) actuators. In

Hwan-Sik Yoon; Gregory Washington

1998-01-01

324

Electrostatic parallelogram actuators  

Microsoft Academic Search

Surface micromachined actuators composed of polysilicon, parallelogram flexible supports are described. The parallelogram actuators transform both the direction and the magnitude of the attractive, electrostatic force developed between the drive electrodes. In a typical configuration, one vertex of the parallelogram is fixed, two opposing, suspended vertices are pulled by the attractive electrostatic force, and the fourth, suspended vertex moves towards

N. Takeshima; K. J. Gabrielt; M. Ozaki; J. Takahashi; H. Horiguchi; H. Fujita

1991-01-01

325

Remotely controllable actuating device  

NASA Technical Reports Server (NTRS)

An actuating device can change a position of an active member that remains in substantially the same position in the absence of a force of a predetermined magnitude on the active member. The actuating device comprises a shape-memory alloy actuating member for exerting a force when actuated by changing the temperature thereof, which shape-memory alloy actuating member has a portion for connection to the active member for exerting thereon a force having a magnitude at least as large as the predetermined magnitude for moving the active member to a desired position. Actuation circuitry is provided for actuating the shape-memory alloy actuating member by changing the temperature thereof only for the time necessary to move the active member to the desired position. The invention is particularly useful for changing the position of a camber-adjusting tab on a helicopter rotor blade by using two shape-memory alloy members that can act against each other to adjust dynamic properties of the rotor blade as it is rotating.

McKillip, Jr., Robert M. (Inventor)

1998-01-01

326

Dependency of temperature on polarization in CH{sub 4}/N{sub 2} dielectric barrier discharge plasma: A crude assumption  

SciTech Connect

We have investigated the variations of polarization (P) and the temperature ({Delta}T) at the electrode surfaces during the deposition of C-N layer in CH{sub 4}/N{sub 2} (1:2) dielectric barrier discharge plasma. The reactive deposition process influences the surface temperature, polarization, and the value of the in situ dielectric constant. We have developed a crude model that correlates the surface temperature and surface polarization with thin film properties. We assume that during the thin film deposition process, the atomic mean kinetic energy is equal to the electrostatic energy stored in the electrode surface area. Theoretically estimated temperature is found to agree well with the experimental results. However, the linear model thus developed cannot be used to explain the phenomena in the interfacial polarization stage that requires a nonlinear theory.

Majumdar, Abhijit; Hippler, Rainer [Institut of Physics, University of Greifswald, Felix Hausdorff Strasse 6, 17489 Greifswald (Germany); Ghosh, Basudev [Jadavpur University, Kolkata 700032, West Bengal (India)

2010-11-15

327

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

328

The Cortical Acto-Myosin Network: From Diffusion Barrier to Functional Gateway in the Transport of Neurosecretory Vesicles to the Plasma Membrane  

PubMed Central

Dysregulation of regulated exocytosis is linked to an array of pathological conditions, including neurodegenerative disorders, asthma, and diabetes. Understanding the molecular mechanisms underpinning neuroexocytosis including the processes that allow neurosecretory vesicles to access and fuse with the plasma membrane and to recycle post-fusion, is therefore critical to the design of future therapeutic drugs that will efficiently tackle these diseases. Despite considerable efforts to determine the principles of vesicular fusion, the mechanisms controlling the approach of vesicles to the plasma membrane in order to undergo tethering, docking, priming, and fusion remain poorly understood. All these steps involve the cortical actin network, a dense mesh of actin filaments localized beneath the plasma membrane. Recent work overturned the long-held belief that the cortical actin network only plays a passive constraining role in neuroexocytosis functioning as a physical barrier that partly breaks down upon entry of Ca2+ to allow secretory vesicles to reach the plasma membrane. A multitude of new roles for the cortical actin network in regulated exocytosis have now emerged and point to highly dynamic novel functions of key myosin molecular motors. Myosins are not only believed to help bring about dynamic changes in the actin cytoskeleton, tethering and guiding vesicles to their fusion sites, but they also regulate the size and duration of the fusion pore, thereby directly contributing to the release of neurotransmitters and hormones. Here we discuss the functions of the cortical actin network, myosins, and their effectors in controlling the processes that lead to tethering, directed transport, docking, and fusion of exocytotic vesicles in regulated exocytosis. PMID:24155741

Papadopulos, Andreas; Tomatis, Vanesa M.; Kasula, Ravikiran; Meunier, Frederic A.

2013-01-01

329

The cortical acto-Myosin network: from diffusion barrier to functional gateway in the transport of neurosecretory vesicles to the plasma membrane.  

PubMed

Dysregulation of regulated exocytosis is linked to an array of pathological conditions, including neurodegenerative disorders, asthma, and diabetes. Understanding the molecular mechanisms underpinning neuroexocytosis including the processes that allow neurosecretory vesicles to access and fuse with the plasma membrane and to recycle post-fusion, is therefore critical to the design of future therapeutic drugs that will efficiently tackle these diseases. Despite considerable efforts to determine the principles of vesicular fusion, the mechanisms controlling the approach of vesicles to the plasma membrane in order to undergo tethering, docking, priming, and fusion remain poorly understood. All these steps involve the cortical actin network, a dense mesh of actin filaments localized beneath the plasma membrane. Recent work overturned the long-held belief that the cortical actin network only plays a passive constraining role in neuroexocytosis functioning as a physical barrier that partly breaks down upon entry of Ca(2+) to allow secretory vesicles to reach the plasma membrane. A multitude of new roles for the cortical actin network in regulated exocytosis have now emerged and point to highly dynamic novel functions of key myosin molecular motors. Myosins are not only believed to help bring about dynamic changes in the actin cytoskeleton, tethering and guiding vesicles to their fusion sites, but they also regulate the size and duration of the fusion pore, thereby directly contributing to the release of neurotransmitters and hormones. Here we discuss the functions of the cortical actin network, myosins, and their effectors in controlling the processes that lead to tethering, directed transport, docking, and fusion of exocytotic vesicles in regulated exocytosis. PMID:24155741

Papadopulos, Andreas; Tomatis, Vanesa M; Kasula, Ravikiran; Meunier, Frederic A

2013-01-01

330

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

331

MEMS Actuated Deformable Mirror  

SciTech Connect

This ongoing work concerns the creation of a deformable mirror by the integration of MEMS actuators with Nanolaminate foils through metal compression boning. These mirrors will use the advantages of these disparate technologies to achieve dense actuation of a high-quality, continuous mirror surface. They will enable advanced adaptive optics systems in large terrestrial telescopes. While MEMS actuators provide very dense actuation with high precision they can not provide large forces typically necessary to deform conventional mirror surfaces. Nanolaminate foils can be fabricated with very high surface quality while their extraordinary mechanical properties enable very thin, flexible foils to survive the rigors of fabrication. Precise metal compression bonding allows the attachment of the fragile MEMS actuators to the thin nanolaminate foils without creating distortions at the bond sites. This paper will describe work in four major areas: (1) modeling and design, (2) bonding development, (3) nanolaminate foil development, (4) producing a prototype. A first-principles analytical model was created and used to determine the design parameters. A method of bonding was determined that is both strong, and minimizes the localized deformation or print through. Work has also been done to produce nanolaminate foils that are sufficiently thin, flexible and flat to be deformed by the MEMS actuators. Finally a prototype was produced by bonding thin, flexible nanolaminate foils to commercially available MEMS actuators.

Papavasiliou, A; Olivier, S; Barbee, T; Walton, C; Cohn, M

2005-11-10

332

Compact piezohydraulic actuation system  

NASA Astrophysics Data System (ADS)

Design and analysis of a scalable piezohydraulic actuation system is presented. Efficiency analysis of frequency rectification demonstrates that hydraulic actuation transfers the maximum amount of work from the actuator to the load. The ratio of peak electrical power to average power delivered caries from 8 percent to 25 percent depending on the piezoelectric coupling coefficient, highlighting the need for efficient power electronics to minimize heat dissipation in the system and minimize volume. A lumped parameter system model demonstrates that fluid compliance is the limiting facto in the stiffness of a bidirectional actuator that does not require hydraulic accumulators or four-way valves. A benchtop experiment consisting of a piezoelectric shock actuator, pumping chamber, and a linear hydraulic cylinder is developed and tested to determine the effect of friction on the micron- level motion of the actuator. The effects of friction are minimized by applying a pneumatic precharge to the system and driving the actuator at its maximum voltage level. Friction is not deemed a limiting factor to the development of a piezohydraulic system with stroke outputs on the order of 100 micrometers per cycle.

Nasser, Khalil; Leo, Donald J.; Cudney, Harley H.

2000-06-01

333

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

334

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

335

A Novel Plasma-Sprayed Durable Thermal Barrier Coating with a Well-Bonded YSZ Interlayer Between Porous YSZ and Bond Coat  

NASA Astrophysics Data System (ADS)

Atmospheric plasma-sprayed YSZ (yttria-stabilized zirconia) thermal barrier coatings (TBCs) are widely used in industrial gas turbine engines to protect the superalloy blades from failure. The failure of TBCs in service occurs by the spalling of YSZ coating. Crack propagation leading to the failure of plasma-sprayed TBCs usually occurs within the YSZ coating near the YSZ/bond coat interface. In the present study, a novel durable TBC consisting of a YSZ interlayer of well-bonded lamellae between the bond coat and the conventional YSZ porous top coat was introduced. The YSZ interlayer was deposited at different coating surface temperatures, which resulted in the formation of YSZ with significantly improved interlamellar bonding. The result shows that the thermal cyclic lifetime of the novel TBCs with the 20-30-?m-thick YSZ interlayer increased by a factor of 4 compared with that of the conventional one. The improved thermal cyclic lifetime was attributed to the controlled transition of the cracking path from near the YSZ/bond coat interface to the YSZ top layer. The effect of the YSZ interlayer thickness on the lifetime of TBCs was also investigated.

Li, Chang-Jiu; Li, Yong; Yang, Guan-Jun; Li, Cheng-Xin

2012-06-01

336

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.

2015-01-01

337

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

338

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

339

Effect of Coating Process Condition on High-Temperature Oxidation and Mechanical Failure Behavior for Plasma Sprayed Thermal Barrier Coating Systems  

NASA Astrophysics Data System (ADS)

In order to clarify the thermal and/or mechanical failure behavior of the plasma sprayed thermal barrier coating (TBC) system in connection with their coating characteristics depending on the coating process condition, two kinds of the failure analytical tests were conducted for TBC systems processed under different conditions. One was the high-temperature oxidation test, which was conducted at 1100°C under both the isothermal and thermal cycle conditions. The other was the in-situ observation of mechanical failure behavior, which was conducted under the static loadings at ambient temperature; as the most fundamental aspect, by means of an optical microscopy. It was found that the thermal and mechanical failure behavior of TBC system depends strongly on the top-coat (TC)/bond-coat (BC) interfacial condition, the reheat-treatment (RHT) after spraying and so on. For the TBC system with vacuum plasma sprayed (VPS) BC as well as for that with atmospheric plasma sprayed (APS) BC, in particular, the RHT at an appropriate temperature in Ar atmosphere was found to be effective for improving the oxidation property. For the TBC system with APS-BC, however, it was impossible to prevent the crack growth into the BC interior under the tensile loading in spite of conducting the RHT, since the microdefects such as oxides within the APS-BC tend to provide an easy crack propagation path. Furthermore, it was clarified that the smoothening process on the BC surface is able to prevent perfectly the occurrence of the wart-like oxide during oxidation, but at the same time increases also the risk of the TC spalling under the mechanical loading.

Takahashi, Satoru; Yoshiba, Masayuki; Harada, Yoshio

340

Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Films by Dielectric Barrier Discharge in TiCl4/O2/N2 Gas Mixtures  

NASA Astrophysics Data System (ADS)

Low-pressure dielectric barrier discharge (DBD) TiCl4/O2 and N2 plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A homemade large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy, and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15°. Compared to titanium oxide films deposited in TiCl4/O2 gas mixtures, those in TiCl4/O2/N2 gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl4/O2/N2 gas mixtures with the addition of 50% N2 and 20% TiCl4 is still smaller than 20°, while that of undoped titanium oxide films is larger than 64° when they are measured after one week. The low-pressure TiCl4/O2 plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film's fragmentation due to the over-high film stress. Optical emission spectra (OES) of TiCl4/O2 DBD plasmas at various power supply driving frequencies are presented.

Niu, Jinhai; Zhang, Zhihui; Fan, Hongyu; Yang, Qi; Liu, Dongping; Qiu, Jieshan

2014-07-01

341

Tendon Driven Finger Actuation System  

NASA Technical Reports Server (NTRS)

A humanoid robot includes a robotic hand having at least one finger. An actuation system for the robotic finger includes an actuator assembly which is supported by the robot and is spaced apart from the finger. A tendon extends from the actuator assembly to the at least one finger and ends in a tendon terminator. The actuator assembly is operable to actuate the tendon to move the tendon terminator and, thus, the finger.

Ihrke, Chris A. (Inventor); Reich, David M. (Inventor); Bridgwater, Lyndon (Inventor); Linn, Douglas Martin (Inventor); Askew, Scott R. (Inventor); Diftler, Myron A. (Inventor); Platt, Robert (Inventor); Hargrave, Brian (Inventor); Valvo, Michael C. (Inventor); Abdallah, Muhammad E. (Inventor); Permenter, Frank Noble (Inventor); Mehling, Joshua S. (Inventor)

2013-01-01

342

Torsional Micromirrors with Lateral Actuators  

Microsoft Academic Search

We report the first implementation of laterally actuated high aspect ratio torsionally suspended micromirrors. In-plane actuation is transformed into out-of- plane motion and rotation, enabling monolithic integration of a wide variety of SOI-MEMS sensors, actuators and micromirrors. The new actuation methodology features highly controllable and agile micromirror devices for optical communications. Two types of device structures integrated with comb-drive actuators

Veljko Milanovic; Matthew Last; Kristofer S. J. Pister

2001-01-01

343

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

344

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

345

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

346

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

347

Linear Proof Mass Actuator  

NASA Technical Reports Server (NTRS)

This paper describes the mechanical design, analysis, fabrication, testing, and lessons learned by developing a uniquely designed spaceflight-like actuator. The linear proof mass actuator (LPMA) was designed to attach to both a large space structure and a ground test model without modification. Previous designs lacked the power to perform in a terrestrial environment while other designs failed to produce the desired accelerations or frequency range for spaceflight applications. Thus, the design for a unique actuator was conceived and developed at NASA Langley Research Center. The basic design consists of four large mechanical parts (mass, upper housing, lower housing, and center support) and numerous smaller supporting components including an accelerometer, encoder, and four drive motors. Fabrication personnel were included early in the design phase of the LPMA as part of an integrated manufacturing process to alleviate potential difficulties in machining an already challenging design. Operating testing of the LPMA demonstrated that the actuator is capable of various types of load functions.

Holloway, Sidney E., III

1994-01-01

348

Combustion powered linear actuator  

SciTech Connect

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

349

Hydrogels for Actuators  

Microsoft Academic Search

\\u000a In microsystem technology research a material with such a diversity and significance like silicon in microelectronics has\\u000a not been established for the last 20 years. Recently in microfluidics and in special imaging systems hydrogels get ready to\\u000a take this place. Here we present a review on hydrogel based microsystems with actuator or sensor-actuator functionalities.\\u000a Automatic microfluidic systems based on the

Andreas Richter

350

Magnetic micro-actuator  

Microsoft Academic Search

The characteristics of three types of magnetic microactuators made by silicon-based microfabrication are described. The microfabrication, actuator configuration, and dynamic characteristics of a fabricated microactuator with a planar coil are examined. This microactuator is shown to operate in the nanometer range. It has a conical soft-magnetic tip 10 microns high with a one-turn copper coil. This actuator will be applied

K. Yanagisawa; A. Tago; T. Ohkubo; H. Kuwano

1991-01-01

351

Polypyrrole micro actuators  

Microsoft Academic Search

The doping and undoping of conjugated polymers is accompanied by a volume change. This volume change can be used to make micro-actuators. We have built polypyrrole (PPy) gold bilayer structures. The volume change of PPy induces a bending of the bilayer. We have made micro-actuators based on this principle, which have been examined with video-microscopy. Some applications for these microactuators

Edwin W. H. Jager; Elisabeth Smela; Olle Inganäs; Ingemar Lundström

1999-01-01

352

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

353

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

354

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

355

Backed Bending Actuator  

NASA Technical Reports Server (NTRS)

Bending actuators of a proposed type would partly resemble ordinary bending actuators, but would include simple additional components that would render them capable of exerting large forces at small displacements. Like an ordinary bending actuator, an actuator according to the proposal would include a thin rectangular strip that would comprise two bonded layers (possibly made of electroactive polymers with surface electrodes) and would be clamped at one end in the manner of a cantilever beam. Unlike an ordinary bending actuator, the proposed device would include a rigid flat backplate that would support part of the bending strip against backward displacement; because of this feature, the proposed device is called a backed bending actuator. When an ordinary bending actuator is inactive, the strip typically lies flat, the tip displacement is zero, and the force exerted by the tip is zero. During activation, the tip exerts a transverse force and undergoes a bending displacement that results from the expansion or contraction of one or more of the bonded layers. The tip force of an ordinary bending actuator is inversely proportional to its length; hence, a long actuator tends to be weak. The figure depicts an ordinary bending actuator and the corresponding backed bending actuator. The bending, the tip displacement (d(sub t)), and the tip force (F) exerted by the ordinary bending actuator are well approximated by the conventional equations for the loading and deflection of a cantilever beam subject to a bending moment which, in this case, is applied by the differential expansion or contraction of the bonded layers. The bending, displacement, and tip force of the backed bending actuator are calculated similarly, except that it is necessary to account for the fact that the force F(sub b) that resists the displacement of the tip could be sufficient to push part of the strip against the backplate; in such a condition, the cantilever beam would be effectively shortened (length L*) and thereby stiffened and, hence, made capable of exerting a greater tip force for a given degree of differential expansion or contraction of the bonded layers. Taking all of these effects into account, the cantilever-beam equations show that F(sub b) would be approximately inversely proportional to d(sup 1/2) for d less than a calculable amount, denoted the transition displacement (dt). For d less than d(sub t), part of the strip would be pressed against the backplate. Therefore, the force F(sub b) would be very large for d at or near zero and would decrease as d increases toward d(sub t). At d greater than d(sub t), none of the strip would be pressed against the backplate and F(sub b) would equal the tip force F of the corresponding ordinary bending actuator. The advantage of the proposal is that a backed bending actuator could be made long to obtain large displacement when it encountered little resistance but it could also exert a large zero-displacement force, so that it could more easily start the movement of a large mass, throw a mechanical switch, or release a stuck mechanism.

Costen, Robert C.; Su, Ji

2004-01-01

356

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

357

Barrier Thickness Dependence of Electrical Properties and DC Device Characteristics of AlGaN\\/GaN Heterostructure Field-Effect Transistors Grown by Plasma-Assisted Molecular-Beam Epitaxy  

Microsoft Academic Search

We report on the barrier thickness dependence of the electrical properties and DC device characteristics of Al0.4Ga0.6N\\/GaN heterostructure field-effect transistors (HFETs). The HFET structures with 8-25-nm-thick AlGaN barrier layers were grown on sapphire substrates by plasma-assisted molecular-beam epitaxy. All of the fabricated HFET devices with a gate length of 1 mum showed a good DC performance and an excellent pinch-off

Masataka Higashiwaki; Toshiaki Matsui

2004-01-01

358

Non-collinear valve actuator  

NASA Technical Reports Server (NTRS)

A non-collinear valve actuator includes a primary actuating system and a return spring system with each applying forces to a linkage system in order to regulate the flow of a quarter-turn valve. The primary actuating system and return spring system are positioned non-collinearly, which simply means the primary actuating system and return spring system are not in line with each other. By positioning the primary actuating system and return spring system in this manner, the primary actuating system can undergo a larger stroke while the return spring system experiences significantly less displacement. This allows the length of the return spring to be reduced due to the minimization of displacement thereby reducing the weight of the return spring system. By allowing the primary actuating system to undergo longer strokes, the weight of the primary actuating system may also be reduced. Accordingly, the weight of the non-collinear valve actuator is reduced.

Richard, James A. (Inventor)

2012-01-01

359

Electrothermally actuated polymer microvalves  

NASA Astrophysics Data System (ADS)

A new family of thermally activated microactuators that provide both large displacements and forces based on a thin polymer actuating layer are presented. The actuators use the high volumetric expansion of a sealed, surface micromachined patch of paraffin heated near its melting point to deform a sealing diaphragm. The paraffin microactuators have been used as the active elements for microfluidic valves. The paraffin actuated microvalves presented in this work offer good performance for valuing gases and liquids in microchannels with low actuation powers. In addition, many valves can be fabricated on a single die making possible integrated microfluidic systems. The paraffin actuated microvalves are suitable for applications requiring many devices on a single die, low processing temperatures, and simple, non-bonded process technology. Two types of actuators have been fabricated using a simple two mask fabrication process. Two types of microfluidic valves have been fabricated and tested which use a paraffin microactuator as the active element. The normally-open blocking microvalve structure has been used to fabricate a precision flow control system of microvalves consisting of four normally-open, paraffin actuated, blocking valve structures. The control valve is designed to operate over a 0.01--5.0 sccm flow range at a differential pressure of 800 Torr. Flow rates ranging from 0.02 to 4.996 sccm have been measured. Leak rates as low as 5.4 x 10-4 sccm have been measured for single valves. System leak rates as low as 3.2 x 10 -3 sccm have been measured. Finally, a second normally-open, paraffin actuated microvalve structure which uses a piston element is fabricated inside a capillary. The piston element encloses a sealed paraffin actuation layer which can deflect thus stopping flow inside the microchannel. This simple device requires low actuation power, can be batch fabricated and is easily integrated with other fluidic or microelectronic systems. In addition, many valves can be fabricated on a single die permitting the implementation of complex integrated microfluidic systems on the same substrate. Preliminary test results show that the normally-open inline valve stops liquid flow with about 25 mW input electrical power. (Abstract shortened by UMI.)

Carlen, Edwin Thomas

360

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

361

Dielectric Barrier Discharge control on an unstarting supersonic flow  

NASA Astrophysics Data System (ADS)

The control of unstarting supersonic model inlet flow using Dielectric Barrier Discharge (DBD) is experimentally demonstrated at Mach 4.7 flow condition. Planar Laser Rayleigh Scattering (PLRS) technique is utilized to visualize important flow features, such as boundary layers and shockwaves, at low static temperature (˜60K) and pressure (˜1kPa) freestream condition. The unstart which is initiated by jet injection in three different model inlet flow, a laminar boundary layer, tripped boundary layer without actuation, and tripped boundary layer with actuation, is demonstrated with PLRS technique. The delay of unstart process is observed through the DBD actuation of the tripped boundary layer when a single DBD actuator pair is oriented parallel to the freestream flow, generates spanwise disturbances. However, this actuation on unstart process is limited to a region of actuation.

Im, Seong-Kyun; Do, Hyungrok; Bak, Moonsoo; Cappelli, Mark

2011-11-01

362

Parallel Coupled Micro-Macro Actuators  

E-print Network

This thesis presents a new actuator system consisting of a micro-actuator and a macro-actuator coupled in parallel via a compliant transmission. The system is called the Parallel Coupled Micro-Macro Actuator, or PaCMMA. ...

Morrell, John Bryant

1996-01-01

363

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

364

Rapid thermal annealing effect on amorphous hydrocarbon film deposited by CH{sub 4}/Ar dielectric barrier discharge plasma on Si wafer: Surface morphology and chemical evaluation  

SciTech Connect

The effects of rapid thermal annealing (RTA) on amorphous hydrogenated carbon-coated film on Si wafer, deposited by CH{sub 4}/Ar dielectric barrier discharge plasma (at half of the atmospheric pressure), was examined. Bubbles-like structures were formed on the surface of the deposited carbon-coated film. The surface morphology studied by scanning electron microscopy (SEM), which showed that the effect of RTA on the film changing the morphological property drastically at 600 deg. C and most of the bubbles started evaporating above 200 deg. C. The inbuilt energy dispersive x-ray in SEM gives the quantitative analysis of the annealed surface. X-ray photoelectron spectroscopy results of the as-deposited films agree with the IR results in that the percent of Si-CH{sub 3}, Si-O-Si and C-O(H) stretching vibrational band in the film. Most of these bands disappeared as the sample was annealed at 600 deg. C in Ar medium.

Majumdar, Abhijit; Hippler, Rainer [Institut fuer Physik, Ernst-Moritz-Arndt-Universitaet Greifswald, Felix-Hausdorff-Str. 6, 17489 Greifswald (Germany); Bhattacharayya, S. R. [Surface Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata 700 064 (India)

2009-05-01

365

CMAS-Resistant Plasma Sprayed Thermal Barrier Coatings Based on Y2O3-Stabilized ZrO2 with Al3+ and Ti4+ Solute Additions  

NASA Astrophysics Data System (ADS)

The higher operating temperatures in gas-turbine engines made possible by thermal barrier coatings (TBCs) are engendering a new problem: environmentally ingested airborne silicate particles (sand, ash) melt on the hot TBC surfaces and form calcium-magnesium-alumino-silicate (CMAS) glass deposits. The molten CMAS glass degrades the TBCs, leading to their premature failure. Here, we demonstrate the use of a commercially manufactured feedstock powder, in conjunction with air plasma spray process, to deposit CMAS-resistant yttria-stabilized zirconia-based TBCs containing Al3+ and Ti4+ in solid solution. Results from the characterization of these new TBCs and CMAS/TBCs interaction experiments are presented. The CMAS mitigation mechanisms in these new TBCs involve the crystallization of the anorthite phase. Raman microscopy is used to generate large area maps of the anorthite phase in the CMAS-interacted TBCs demonstrating the potential usefulness of this method for studying CMAS/TBCs interactions. The ubiquity of airborne sand/ash particles and the ever-increasing demand for higher operating temperatures in future high efficiency gas-turbine engines will necessitate CMAS resistance in all hot-section components of those engines. In this context, the versatility, ease of processing, and low cost offered by the process demonstrated here could benefit the development of these new CMAS-resistant TBCs.

Senturk, Bilge S.; Garces, Hector F.; Ortiz, Angel L.; Dwivedi, Gopal; Sampath, Sanjay; Padture, Nitin P.

2014-04-01

366

Direct Quantification of Chemical Warfare Agents and Related Compounds at Low ppt Levels: Comparing Active Capillary Dielectric Barrier Discharge Plasma Ionization and Secondary Electrospray Ionization Mass Spectrometry.  

PubMed

A novel active capillary dielectric barrier discharge plasma ionization (DBDI) technique for mass spectrometry is applied to the direct detection of 13 chemical warfare related compounds, including sarin, and compared to secondary electrospray ionization (SESI) in terms of selectivity and sensitivity. The investigated compounds include an intact chemical warfare agent and structurally related molecules, hydrolysis products and/or precursors of highly toxic nerve agents (G-series, V-series, and "new" nerve agents), and blistering and incapacitating warfare agents. Well-defined analyte gas phase concentrations were generated by a pressure-assisted nanospray with consecutive thermal evaporation and dilution. Identification was achieved by selected reaction monitoring (SRM). The most abundant fragment ion intensity of each compound was used for quantification. For DBDI and SESI, absolute gas phase detection limits in the low ppt range (in MS/MS mode) were achieved for all compounds investigated. Although the sensitivity of both methods was comparable, the active capillary DBDI sensitivity was found to be dependent on the applied AC voltage, thus enabling direct tuning of the sensitivity and the in-source fragmentation, which may become a key feature in terms of field applicability. Our findings underline the applicability of DBDI and SESI for the direct, sensitive detection and quantification of several CWA types and their degradation products. Furthermore, they suggest the use of DBDI in combination with hand-held instruments for CWAs on-site monitoring. PMID:25427190

Wolf, Jan-Christoph; Schaer, Martin; Siegenthaler, Peter; Zenobi, Renato

2015-01-01

367

Osteoconductive Potential of Barrier NanoSiO2 PLGA Membranes Functionalized by Plasma Enhanced Chemical Vapour Deposition  

PubMed Central

The possibility of tailoring membrane surfaces with osteoconductive potential, in particular in biodegradable devices, to create modified biomaterials that stimulate osteoblast response should make them more suitable for clinical use, hopefully enhancing bone regeneration. Bioactive inorganic materials, such as silica, have been suggested to improve the bioactivity of synthetic biopolymers. An in vitro study on HOB human osteoblasts was performed to assess biocompatibility and bioactivity of SiO2 functionalized poly(lactide-co-glycolide) (PLGA) membranes, prior to clinical use. A 15?nm SiO2 layer was deposited by plasma enhanced chemical vapour deposition (PECVD), onto a resorbable PLGA membrane. Samples were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and infrared spectroscopy (FT-IR). HOB cells were seeded on sterilized test surfaces where cell morphology, spreading, actin cytoskeletal organization, and focal adhesion expression were assessed. As proved by the FT-IR analysis of samples, the deposition by PECVD of the SiO2 onto the PLGA membrane did not alter the composition and other characteristics of the organic membrane. A temporal and spatial reorganization of cytoskeleton and focal adhesions and morphological changes in response to SiO2 nanolayer were identified in our model. The novedous SiO2 deposition method is compatible with the standard sterilization protocols and reveals as a valuable tool to increase bioactivity of resorbable PLGA membranes. PMID:24883304

Terriza, Antonia; Vilches-Pérez, Jose I.; de la Orden, Emilio; Yubero, Francisco; Gonzalez-Caballero, Juan L.; González-Elipe, Agustin R.; Vilches, José; Salido, Mercedes

2014-01-01

368

Studies of micro actuators in Japan  

Microsoft Academic Search

Various kinds of driving principles are proposed for micro actuators. Electrostatic, superconducting, piezoelectric, and shape-memory alloy actuators are studied, with emphasis on work done in Japan. Electrostatic actuators, a superconducting actuator, an actuator which simulates muscles, a microfluid system with piezoelectric actuators, and a cell fusion system based on a fluid integration circuit are described. Microactuators and the micro machines

Hiroyuki Fujita

1989-01-01

369

Attempting a classification for electrical polymeric actuators  

Microsoft Academic Search

Polymeric actuators, electroactive polymer actuators, electromechanical polymeric actuators, artificial muscles, and other, are usual expressions to name actuators developed during the last 15-20 years based on interactions between the electric energy and polymer films. The polymeric actuators can be divided into two main fields: electromechanical actuators working by electrostatic interactions between the polymer and the applied electric fields, and electrochemomechanical

T. F. Otero; J. López Cascales; A. J. Fernández-Romero

2007-01-01

370

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

371

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

372

Pneumatic Actuator Systems  

NSDL National Science Digital Library

In this interactive activity adapted from MATEC, learn about pneumatic actuator systems, which use compressed air to transmit motion. Animations illustrate the components of a typical pneumatic actuator system: the computer, communication module, programmable logic controller, input/output module, solenoid valve, and pneumatic device. Observe how the system functions as a whole, and learn more about some common pneumatic devices.The interactive is accompanied by a background essay, standards alignment, and discussion questions. Users who sign up for a free account can save the resource and download it as well.

2012-06-04

373

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

374

Modeling hysteresis in piezoceramic actuators  

Microsoft Academic Search

A major deficiency of piezoceramic actuators is that their open-loop control accuracy is seriously limited by hysteresis. This paper discusses the adaptation of the Preisach model to describe the nonlinear hysteresis behavior of these actuators. The adapted model is used to predict the response of a piezoceramic actuator to a sinusoidal input and a triangular input. The predictions are compared

Ping Ge; Musa Jouaneh

1995-01-01

375

Paraffin actuated surface micromachined valves  

Microsoft Academic Search

A new, active, normally-open blocking microvalve that uses the thermal expansion of a sealed, thin paraffin patch for actuation has been fabricated and tested. The entire structure is batch-fabricated by surface micromachining the actuator and channel materials on top of a single substrate. The paraffin actuated microvalves are suitable for applications requiring many devices on a single die, low processing

E. T. Carlen; C. H. Mastrangelo

2000-01-01

376

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

377

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

378

Magnetorheologic fluids for actuators  

Microsoft Academic Search

Magnetorheologic fluids (MRF) are suspensions consisting of a synthetic oil and very small soft-magnetic particles. In a magnetic field, the particles are locked to long chains. In consequence of it, the viscosity and the flow behaviour of the fluid are considerably changed. This reversible effect can be used in actuators, especially for controlled damping of shocks and vibrations, or in

L. Zipser; L. Richter; U. Lange

2001-01-01

379

Gravity actuated thermal motor  

Microsoft Academic Search

The invention discloses a gravity actuated thermal motor which includes a rotor preferably in the form of a ring-shaped annulus which is filled with water. A plurality of collapsible bellows are connected to and extend inwardly from the outer peripheral wall of the annulus into the water-filled chamber. In communication with each of the bellows and extending outwardly from the

Schur

1978-01-01

380

Electrostatic curved electrode actuators  

Microsoft Academic Search

This paper presents the design and performance of an electrostatic actuator consisting of a laterally compliant cantilever beam and a fixed curved electrode, both suspended above a ground plane. A theoretical description of the static behavior of the cantilever as it is pulled into contact with the rigid fixed-electrode structure is given. Two models are presented: a simplified semi-analytical model

Rob Legtenberg; John Gilbert; Stephen D. Senturia; Miko Elwenspoek

1997-01-01

381

Shape Memory Alloy Actuator  

NASA Technical Reports Server (NTRS)

The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

Baumbick, Robert J. (Inventor)

2000-01-01

382

Shape Memory Alloy Actuator  

NASA Technical Reports Server (NTRS)

The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

Baumbick, Robert J. (Inventor)

2002-01-01

383

Piezoelectric actuators control unit  

Microsoft Academic Search

Superconductive cavities for future linear accelerators, such as ILC, have extremely large quality factors that require an effective stabilization with both slow and fast tuners. Piezoelectric actuators are the most common choice for fast tuners, but one drawback for large scale applications is the limited bandwidth and the large cost of commercially available drivers. In this paper we present a

Franco Bedeschi; Stefano Galeotti; Alberto Gennai; Carlo Magazzu; Diego Passuello; Elena Pedreschi; Franco Spinella; Federico Paoletti

2010-01-01

384

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

385

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

386

"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

387

Piezoceramic actuated aperture antennae  

Microsoft Academic Search

Recently, it has been demonstrated that aperture antennae can have their performance improved by employing shape control on the antenna surface. The antennae previously studied were actuated utilizing polyvinylidene fluoride (PVDF). Since PVDF is a polymer with limited control authority, these antennae can only be employed in space based applications. This study examines more robust antenna structures devised of a

Hwan-Sik Yoon; Gregory Washington

1998-01-01

388

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.

Fleming, James G. (Albuquerque, NM)

1999-01-01

389

Thermomagnetic metal flexure actuators  

Microsoft Academic Search

Deep X-ray lithography and metal plating when coupled with a sacrificial layer, SLIGA, lends itself to the fabrication of very high aspect ratio metal structures which are mechanically stiff in the substrate direction and can be very flexible in the direction parallel to the substrate. These properties can be exploited by producing a family of new flexure actuators which can

H. Guckel; J. Klein; T. Christenson; K. Skrobis; M. Laudon; E. G. Lovell

1992-01-01

390

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

391

Ultrasonically Actuated Tools for Abrading Rock Surfaces  

NASA Technical Reports Server (NTRS)

An ultrasonic rock-abrasion tool (URAT) was developed using the same principle of ultrasonic/sonic actuation as that of the tools described in two prior NASA Tech Briefs articles: Ultrasonic/ Sonic Drill/Corers With Integrated Sensors (NPO-20856), Vol. 25, No. 1 (January 2001), page 38 and Ultrasonic/ Sonic Mechanisms for Drilling and Coring (NPO-30291), Vol. 27, No. 9 (September 2003), page 65. Hence, like those tools, the URAT offers the same advantages of low power demand, mechanical simplicity, compactness, and ability to function with very small axial loading (very small contact force between tool and rock). Like a tool described in the second of the cited previous articles, a URAT includes (1) a drive mechanism that comprises a piezoelectric ultrasonic actuator, an amplification horn, and a mass that is free to move axially over a limited range and (2) an abrasion tool bit. A URAT tool bit is a disk that has been machined or otherwise formed to have a large number of teeth and an overall shape chosen to impart the desired shape (which could be flat or curved) to the rock surface to be abraded. In operation, the disk and thus the teeth are vibrated in contact with the rock surface. The concentrated stresses at the tips of the impinging teeth repeatedly induce microfractures and thereby abrade the rock. The motion of the tool induces an ultrasonic transport effect that displaces the cuttings from the abraded area. The figure shows a prototype URAT. A piezoelectric-stack/horn actuator is housed in a cylindrical container. The movement of the actuator and bit with respect to the housing is aided by use of mechanical sliders. A set of springs accommodates the motion of the actuator and bit into or out of the housing through an axial range between 5 and 7 mm. The springs impose an approximately constant force of contact between the tool bit and the rock to be abraded. A dust shield surrounds the bit, serving as a barrier to reduce the migration of rock debris to sensitive instrumentation or mechanisms in the vicinity. A bushing at the tool-bit end of the housing reduces the flow of dust into the actuator and retains the bit when no axial load is applied.

Dolgin, Benjamin; Sherrit, Stewart; Bar-Cohen, Yoseph; Rainen, Richard; Askin, Steve; Bickler, Donald; Lewis, Donald; Carson, John; Dawson, Stephen; Bao, Xiaoqi; Chang, Zensheu; Peterson, Thomas

2006-01-01

392

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

393

Vehicle barrier  

DOEpatents

A vehicle security barrier which can be conveniently placed across a gate opening as well as readily removed from the gate opening to allow for easy passage. The security barrier includes a barrier gate in the form of a cable/gate member in combination with laterally attached pipe sections fixed by way of the cable to the gate member and lateral, security fixed vertical pipe posts. The security barrier of the present invention provides for the use of cable restraints across gate openings to provide necessary security while at the same time allowing for quick opening and closing of the gate areas without compromising security.

Hirsh, Robert A. (Bethel Park, PA)

1991-01-01

394

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

395

Effects of Post-SiH4 and Plasma Treatments on Chemical Vapor Deposited Cu Seeds with Chemical Vapor Deposited TiN Barrier in Porous Low Dielectric Constant and Cu Integration  

NASA Astrophysics Data System (ADS)

A Cu seed deposited by chemical vapor deposition (CVD) was integrated with a CVD TiN barrier and electroplated Cu in a double level metal interconnect scheme using a dual damascene process. The post-SiH4 treatment of CVD TiN inhibits agglomeration of thin Cu by improving the wettability of Cu seeds as well as reducing the TiN sheet resistance. Post-plasma treatment on CVD Cu seeds decreases impurities in CVD Cu and eliminates interface voids between the CVD Cu seed and electroplated Cu, improving the gap filling properties of electroplated Cu layers. Inherently poor adhesion of the CVD Cu layers between the Cu barrier metal and the electroplated Cu is overcome by CVD TiN post treatments and CVD Cu post-plasma treatment. Bias-thermal-stress (BTS) tests were performed to verify the effect of post-SiH4 treatment. The SiH4 treated CVD TiN barrier and CVD Cu seed show feasibility for 65-nm technology in terms of low via resistance and chain yields.

Pyo, Sung Gyu; Park, Shangkyun; Park, Hansoo; Lee, Donghyun

2011-07-01

396

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

397

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

398

Telescoping cylindrical piezoelectric fiber composite actuator assemblies  

NASA Technical Reports Server (NTRS)

A telescoping actuator assembly includes a plurality of cylindrical actuators in a concentric arrangement. Each cylindrical actuator is at least one piezoelectric fiber composite actuator having a plurality of piezoelectric fibers extending parallel to one another and to the concentric arrangement's longitudinal axis. Each cylindrical actuator is coupled to concentrically-adjacent ones of the cylindrical actuators such that the plurality of cylindrical actuators can experience telescopic movement. An electrical energy source coupled to the cylindrical actuators applies actuation energy thereto to generate the telescopic movement.

Allison, Sidney G. (Inventor); Shams, Qamar A. (Inventor); Fox, Robert L. (Inventor); Fox, legal representative, Christopher L. (Inventor); Fox Chattin, legal representative, Melanie L. (Inventor)

2010-01-01

399

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.

Northrup, Milton A. (Berkeley, CA); Ciarlo, Dino R. (Livermore, CA); Lee, Abraham P. (Walnut Creek, CA); Krulevitch, Peter A. (Los Altos, CA)

1997-01-01

400

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

401

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

402

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

403

High displacement ceramic metal composite actuators (moonies)  

Microsoft Academic Search

The two most common type of piezoelectric actuators are the multilayer actuator with internal electrodes and the cantilevered bimorph actuator. A new type of composite ceramic actuator is the multilayered multistacked moonie (multi-multi moonie). Normal multilayer actuators produce a large generative force, but only a small displacement. Conversely, bimorphs produce large displacements but the forces are very small. The moonie

Aydin Dogan; Qichang Xu; Katsuhiko Onitsuka; Shoko Yoshikawa; Kenji Uchino; Robert E. Newnham

1994-01-01

404

Empirical model of a bending IPMC actuator  

Microsoft Academic Search

We study ionomeric polymer-metal composite (IPMC) actuators in situations where the strip of actuator acts either on maximum mechanical power or maximum amplitude of actuation. We apply a modified equivalent circuit of IPMC muscle which takes into account the surface resistance change while material bends. In case of series of bending acts, the first actuation of IPMC actuator is performed

Andres Punning; Mart Anton; Maarja Kruusmaa; Alvo Aabloo

2006-01-01

405

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

406

Micro bellow actuators  

Microsoft Academic Search

We report here a novel micromachined bellow-style actuator (microbellow) which uses a smaller real estate but is capable of larger deflections compared to a flat membrane of the same size. In this first demonstration, three-layer silicon nitride microbellows have been successfully fabricated by using polysilicon\\/TMAH sacrificial layer etching technology. Inside the bellows, runs of sacrificial layer are designed at the

Xing Yang; Yu-Chong Tai; Chih-Ming Ho

1997-01-01

407

Shape memory alloy actuator  

DOEpatents

An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.

Varma, Venugopal K. (Knoxville, TN)

2001-01-01

408

Magnetically actuated, addressable microstructures  

Microsoft Academic Search

Surface-micromachined, batch-fabricated structures that combine plated-nickel films with polysilicon mechanical flexures to produce individually addressable, magnetically activated devices have been fabricated and tested. Individual microactuator control has been achieved in two ways: (1) by actuating devices using the magnetic field generated by coils integrated around each device and (2) by using electrostatic forces to clamp selected devices to an insulated

Jack W. Judy; Richard S. Muller

1997-01-01

409

Microelectromechanical (MEM) thermal actuator  

DOEpatents

Microelectromechanical (MEM) buckling beam thermal actuators are disclosed wherein the buckling direction of a beam is constrained to a desired direction of actuation, which can be in-plane or out-of-plane with respect to a support substrate. The actuators comprise as-fabricated, linear beams of uniform cross section supported above the substrate by supports which rigidly attach a beam to the substrate. The beams can be heated by methods including the passage of an electrical current through them. The buckling direction of an initially straight beam upon heating and expansion is controlled by incorporating one or more directional constraints attached to the substrate and proximal to the mid-point of the beam. In the event that the beam initially buckles in an undesired direction, deformation of the beam induced by contact with a directional constraint generates an opposing force to re-direct the buckling beam into the desired direction. The displacement and force generated by the movement of the buckling beam can be harnessed to perform useful work, such as closing contacts in an electrical switch.

Garcia, Ernest J. (Albuquerque, NM); Fulcher, Clay W. G. (Sandia Park, NM)

2012-07-31

410

IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 35, NO. 5, OCTOBER 2007 1301 Simulation of Direct-Current Surface Plasma  

E-print Network

­100 W) compared to thermal arcs (1 kW) [9]. Glow discharge plasma actuators therefore pro- videIEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 35, NO. 5, OCTOBER 2007 1301 Simulation of Direct-Current Surface Plasma Discharge Phenomena in High-Speed Flow Actuation Thomas Deconinck, Shankar Mahadevan

Raja, Laxminarayan L.

411

Direct drive field actuator motors  

DOEpatents

A positive-drive field actuator motor is described which includes a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately. 62 figs.

Grahn, A.R.

1998-03-10

412

Direct drive field actuator motors  

SciTech Connect

A positive-drive field actuator motor including a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately.

Grahn, Allen R. (Salt Lake City, UT)

1998-01-01

413

Continuously-Variable Series-Elastic Actuator  

E-print Network

Actuator efficiency is an important factor in the design of powered leg prostheses, orthoses, exoskeletons, and legged robots. A continuously-variable series-elastic actuator (CV-SEA) is presented as an efficient actuator ...

Mooney, Luke M.

414

Parallel-Coupled Micro-Macro Actuators  

Microsoft Academic Search

This paper presents a new actuator system consisting of a micro- actuator and a macro-actuator coupled in parallel via a compliant transmission. The system is called the parallel-coupled micro-macro actuator, or PaCMMA.In this system, the micro-actuator is capable of high-bandwidth force control owing to its low mass and direct-drive connection to the output shaft. The compliant transmission of the macro-actuator

John B. Morrell; J. Kenneth Salisbury

1998-01-01

415

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

NASA Astrophysics Data System (ADS)

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 to the actuator is 7.3-7.8 mJ/pulse. Plasma temperature inferred from nitrogen emission spectra is a few tens of degrees higher than flow stagnation temperature, T = 340 ± 30 K. Phase-locked Schlieren images are used to detect compression waves generated by individual nanosecond discharge pulses near the actuator surface. The compression wave propagates upstream toward the baseline bow shock standing in front of the cylinder model. Interaction of the compression wave and the bow shock causes its displacement in the upstream direction, increasing shock stand-off distance by up to 25%. The compression wave speed behind the bow shock and the perturbed bow shock velocity are inferred from the Schlieren images. The effect of compression waves generated by nanosecond discharge pulses on shock stand-off distance is demonstrated in a single-pulse regime (at pulse repetition rates of a few hundred Hz) and in a quasi-continuous mode (using a two-pulse sequence at a pulse repetition rate of 100 kHz). The results demonstrate feasibility of hypersonic flow control by low-temperature, repetitive nanosecond pulse discharges.

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

2011-06-01

416

Conducting polymer actuator enhancement through microstructuring  

E-print Network

Electroactive conducting polymers, such as polypyrrole, polyaniline, and polythiophenes are currently studied as novel biologically inspired actuators. The actuation mechanisms in these materials are based on the diffusion ...

Pillai, Priam Vasudevan

2007-01-01

417

Piezoelectric actuated gimbal  

DOEpatents

A gimbal is described and which includes a fixed base member defining an axis of rotation; a second member concentrically oriented relative to the axis of rotation; a linear actuator oriented in immediate, adjoining force transmitting relation relative to the base member or to the second member, and which applies force along a linear axis which is tangential to the axis of rotation so as to cause the second member to rotate coaxially relative to the fixed base member; and an object of interest mounted to the second member such that the object of interest is selectively moved relative to the base member about the axis of rotation.

Tschaggeny, Charles W. (Woods Cross, UT); Jones, Warren F. (Idaho Falls, ID); Bamberg, Eberhard (Salt Lake City, UT)

2011-09-13

418

Compact valve actuation mechanism  

NASA Technical Reports Server (NTRS)

A valve actuation device. The device may include a free floating valve bridge movably supported within a cavity in the engine housing. The bridge may be provided with a cavity and an orifice arrangement for pumping gases entrained with lubricating fluid toward the piston stems as the bridge reciprocates back and forth. The device may also include a rocker arm that has a U-shaped cross-sectional shape for receiving at least a portion of the valve bridge, valve stem valve spring and spring retainer therein. The rocker arm may be provided with lubrication passages for directing lubrication to the point wherein it is pivotally affixed to the engine housing.

Brogdon, James William (Inventor); Gill, David Keith (Inventor)

2000-01-01

419

Modelling of Microspring Thermal Actuator  

Microsoft Academic Search

The deflection of a chevron actuator strongly depends on the length and the angle of the beams; a larger deflection is produced if a smaller angle is used. The drawback is that it is a single beam like device. To deliver a larger displacement, even longer beams are required for chevron actuators. This is problematical in term of fabrication and

J. K. Luo; A. J. Flewitt; S. M. Spearing; N. A. Fleck; W. I. Milne

420

Piezoelectric actuators for dynamic applications  

Microsoft Academic Search

The main advantages of piezoelectrical actuators are their high resolution in motion and their excellent dynamic behavior. Especially the very short response times of solid state actuators presents new opportunities in developing high dynamical systems with unsurpassable characteristics. New concepts of piezoelectrically driven microoptical devices, e.g. optical fiber switches, intensity modulators and choppers, can be developed. Very compact systems with

Peter Buecker; Bernt Goetz; Thomas Martin

1998-01-01

421

Linear electric actuators and generators  

Microsoft Academic Search

Linear electric actuators and generators (LEAGs) are electromagnetic devices which develop directly short-travel progressive (or oscillatory) linear motion. Machine tool sliding tables, pen recorders and free piston power machines are typical industrial applications for LEAGs. Their recent revival in applications in compressors, pumps, electromagnetic valve actuators, active shock absorbers, vibrators, etc. Prompts this review, which presents main LEAGs configurations, their

I. Boldea; S. A. Nasar

1999-01-01

422

Bi-stable optical actuator  

DOEpatents

The present invention is a bi-stable optical actuator device that is depowered in both stable positions. A bearing is used to transfer motion and smoothly transition from one state to another. The optical actuator device may be maintained in a stable position either by gravity or a restraining device.

Holdener, Fred R. (Tracy, CA); Boyd, Robert D. (Livermore, CA)

2000-01-01

423

Linear electric actuators and generators  

Microsoft Academic Search

Linear electric actuators and generators (LEAGs) are electromagnetic devices which develop directly short-travel progressive (or oscillatory) linear motion. Machine tool sliding tables, pen recorders, and free piston power machines are typical industrial applications for LEAGs. Their revival in applications in compressors, pumps, electromagnetic valve actuators, active shock absorbers, vibrators, etc. prompts this review, which presents main LEAGs configurations, their principles

I. Boldea; S. A. Nasar

1997-01-01

424

Biosensing and actuation for microbiorobots  

Microsoft Academic Search

One of the great challenges in nano\\/micro scale science and engineering is the independent manipulation of cells and man-made objects with active sensing. For such work, there is a need for controllable actuators. Actuation can be realized using inorganic components; however, these systems are expensive to produce and require sophisticated fabrication techniques. Furthermore, they do not have integrated biosensing elements

Mahmut Selman Sakar; Edward B. Steager; A. Agung Julius; MinJun Kim; Vijay Kumar; George J. Pappas

2010-01-01

425

Rectenna performances for smart membrane actuators  

NASA Astrophysics Data System (ADS)

The patch rectenna array was initially designed for high voltage output in shape control applications. The test results show that more than 200 volts of output was obtained from a 6 X 6 array at a far-field exposure (1.8 meters away) with an x-band input power of 18 watts. The 6 X 6 array patch rectenna was designed to generate theoretical voltages of up to 540 volts, but normal output was range 200 and 300 volts. Test were also performed with a THUNDER actuator attached to the 6 x 6 array. Flexible dipole rectenna arrays built on thin-film based flexible membranes are envisioned as the best option for NASA applications, such as microwave-driven shape controls for aircraft morphing and large ultra lightweight space structures. An array of dipole rectennas was designed for a high voltage output by densely populating it with Schottky barrier diodes to drive piezoelectric or electrostrictive actuators. The dipole rectenna array will eventually be integrated with a PAD logic circuit for power allocation and distribution and microbatteries for storage of excess power. The development of rectenna array-based wireless power drivers for shape control requires the development of new membrane materials with dielectric constants that are suitable for dipole rectenna arrays.

Choi, Sang H.; Song, Kyo D.; King, Glen C.; Woodall, Charles

2002-07-01

426

Actuator-valve interface optimization  

SciTech Connect

A computer code, Actuator Valve Response (AVR), has been developed to optimize the explosive actuator-valve interface parameters so that the valve plunger velocity is at a maximum when the plunger reaches the valve tubes. The code considers three forces to act on the valve plunger before the plunger reaches the valve tubes. These are the pressure force produced by the actuator, the shear force necessary to shear the seal disks on the actuator and the valve plunger, and the friction force caused by friction between the plunger and the plunger bore. The three forces are modeled by expressions that are explicitly functions of the plunger displacement. A particular actuator-valve combination was analyzed with the computer code AVR with four different combinations of valve plunger seal disk shear strength and initial friction force. (LEW)

Burchett, O.L.; Jones, R.L.

1986-01-01