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1

Dielectric Barrier Discharge Plasma Actuators for Flow Control *  

NASA Astrophysics Data System (ADS)

The term plasma actuator has now been a part of the fluid dynamics flow-control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single-dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is through a generated body-force vector field that couples with the momentum in the external flow. The body force can be derived from first principles, and the effect of plasma actuators can be easily incorporated into flow solvers so that their placement and operation can be optimized. They have been used in a wide range of internal and external flow applications. Although initially considered useful only at low speeds, plasma actuators are effective in a number of applications at high subsonic, transonic, and supersonic Mach numbers, owing largely to more optimized actuator designs that were developed through better understanding and modeling of the actuator physics. New applications continue to appear through a growing number of programs in the United States, Germany, France, England, the Netherlands, Russia, Australia, Japan, and China. This review provides an overview of the physics and modeling of SDBD plasma actuators. It highlights some of the capabilities of plasma actuators through examples from experiments and simulations.

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

2010-01-01

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

Electrohydrodynamic force in dielectric barrier discharge plasma actuators  

Microsoft Academic Search

Surface dielectric barrier discharges (DBDs) have been proposed as actuators for flow control. In this paper we discuss the basic mechanisms responsible for the electrohydrodynamic (EHD) force exerted by the discharge on the gas molecules. A two-dimensional fluid model of the DBD is used to describe the plasma dynamics, to understand the basic physics associated with the EHD force and

J. P. Boeuf; Y. Lagmich; Th Unfer; Th Callegari; L. C. Pitchford

2007-01-01

4

Optical Comparison of Single and Double Dielectric barrier plasma actuators  

NASA Astrophysics Data System (ADS)

Time resolved ICCD pictures are taken for double and single surface barrier discharge plasma actuator for thick and thin powered electrodes. The filament and jet propagation minimum speeds are measured for both single and double barrier actuators. Optical emission spectra are measured using a monochromator. In a typical OES spectrum, O2, O^+, CO, OH, N, N2, N2^+ and also optical emission lines from exposed electrodes (stainless steel, copper and tungsten lines) were observed for single barrier actuators. The optical data are fit by SPECAIR code^1. The translational and rotational temperatures are found to be approximately room temperature while the vibrational temperatures were1700 K and 1200 K, the electron temperatures were 3200 K and 2400 K for thick and thin electrode respectively. The different regimes in a discharge will be discussed.

Hershkowitz, Noah; Oksuz, Lutfi; Hoskinson, Alan

2009-11-01

5

Optical studies of dielectric barrier plasma aerodynamic actuators  

NASA Astrophysics Data System (ADS)

The optical characteristics of surface dielectric barrier plasma actuators with a wire/planar electrode combination and 1 kHz triangular applied voltages were studied using an intensified charge-coupled device camera and a monochromator in atmospheric pressure air. The spatial and temporal images were recorded both parallel and perpendicular to the aerodynamic actuator surfaces on nanosecond time scales. Arc-shaped discharges jumping from above the powered wire across the dielectric above the grounded planar electrode were observed for the first time. Nitrogen molecular second and first positive band lines were observed and the discharge temperatures were calculated by matching the experimental spectra with SPECAIR lines (Laux et al 2003 Plasma Sources Sci. Technol. 12 125-138). The electron temperatures were found to be 6800 ± 400 K from the SPECAIR code.

Gulec, A.; Oksuz, L.; Hershkowitz, N.

2011-08-01

6

Temporal and spatial characteristics of Dielectric Barrier Plasma Actuators  

NASA Astrophysics Data System (ADS)

The temporal and spatial images of surface dielectric barrier plasma actuators with a wire/planar electrode combination and 1 kHz triangular applied voltages were taken using an intensified charge-coupled device (ICCD) camera and in addition a monochromator was used to measure the optical emission lines of discharges in air. Parallel and perpendicular images recorded with respect to discharge surface. Time resolved (nanosec order) images were used to calculate the discharge speed. Arc shaped discharges jumping from above the powered wire across the dielectric above the grounded planar electrode were observed for the first time. Nitrogen molecular second and first positive band lines were measured and electron and molecular temperatures were calculated using the SPECAIR code (Laux et al. Plasma Sources Sci. Technol. 2003,12,1255-138) and the Boltzmann plot method. The electron temperatures were found to be 6020 ± 1200 and 6800±400 K from the Boltzmann method and SPECAIR code respectively.

Oksuz, Lutfi; Hershkowitz, Noah; Gulec, Ali

2010-11-01

7

Surrogate modelling for characterising the performance of a dielectric barrier discharge plasma actuator  

Microsoft Academic Search

The dielectric barrier discharge (DBD) plasma actuator offers promising opportunities for flow control because of its fast response and non-moving parts. In this work, surrogate modelling is adopted to better understand the impact of the materials and operational parameters on the actuator performance, and to provide an efficient approach for performance estimation. The DBD model based on 2-species helium chemistry

Young-Chang Cho; Balaji Jayaraman; Felipe A. C. Viana; Raphael T. Haftka; Wei Shyy

2010-01-01

8

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

Microsoft Academic Search

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

Jesse Little; Munetake Nishihara; Igor Adamovich; Mo Samimy

2010-01-01

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

Lumped-element Circuit Model for Single-Dielectric Barrier Discharge Plasma Actuator  

NASA Astrophysics Data System (ADS)

This work presents an extension of our previous studies on a single-dielectric barrier discharge (SDBD) plasma actuators. The space-time lumped-element circuit model that had been developed for the actuator is intended to model the details of the ionization process to provide predictions of the body force for a range of parameters without the need of experimental calibration. In this model, the domain over the covered electrode is divided into several parallel equivalent circuit networks, each consisting of resistive and capacitive elements and zenor diodes. The results of this numerical model show very good agreement with the space-time resolved experimental observations of the plasma illumination over the dielectric surface for a range of applied voltage amplitudes and frequencies. These characteristics include plasma sweep-out velocity and spatial extent, and spatial intensity decay. The model provides the boundary conditions on the electric potential over the dielectric that is needed in solving for the actuator space-time body force. The plasma body force is then used in a Navier-Stokes flow solver to study the effects of the plasma actuator. Examples of simulations with the plasma actuator on a flat surface and the leading edge of an airfoil are presented. The simulations show good agreement with comparable experiments. Supported under a USAF SBIR Phase II Contract FA8650-04-C-3405.

Orlov, Dmitri; Corke, Thomas; Patel, Mehul

2006-11-01

11

Spatiotemporal structure of a millimetric annular dielectric barrier discharge plasma actuator  

NASA Astrophysics Data System (ADS)

The spatiotemporal structure of a millimetric annular dielectric barrier discharge plasma actuator is investigated using a photomultiplier tube, a high-sensitivity camera, particle image velocimetry, and electrohydrodynamics simulations. Plasma actuators have typically demonstrated their utility in flow separation control, but on a millimetric scale they have also shown to be promising in the control of crossflow instabilities in crossflow-dominated laminar-turbulent boundary-layer transition. In view of the subtleties associated with creating an initial disturbance to excite subcritical wavelengths, it is desirable to characterize the local plasma discharge structure, body force organization, and induced velocity field in detail. The results show that, similar to their linear centimetric counterpart, the plasma discharge has a highly dynamic and somewhat organized spatiotemporal structure. Under quiescent flow conditions, the actuator induces a velocity field that consists of two counter-rotating vortices, accompanied by a wall-normal synthetic jet region, which in three-dimensions describes a toroidal vortex around the aperture's periphery. The surprising result, however, is that these vortices rotate in the opposite direction to vortices generated by similar centimetric annular designs. Three-dimensional electrohydrodynamics simulations correctly reproduce this behavior. Because the body force organization may be qualitatively perceived as being the axisymmetric counterpart of the more classical linear actuator, this flow reversal is thought to be due to the actuator scale. When an array of millimetric actuators is considered in close proximity, an interaction takes place between the vortices created from each actuator and those of neighboring actuators, resulting in a significant reduction in vortex size compared with the single aperture case, accompanied by an increase in the maximum induced flow velocity magnitude.

Humble, R. A.; Craig, S. A.; Vadyak, J.; McClure, P. D.; Hofferth, J. W.; Saric, W. S.

2013-01-01

12

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

13

GASES, PLASMAS, AND ELECTRIC DISCHARGES: Optical Emission Spectroscopy Investigation of a Surface Dielectric Barrier Discharge Plasma Aerodynamic Actuator  

NASA Astrophysics Data System (ADS)

The optical emission spectroscopy of a surface dielectric barrier discharge plasma aerodynamic actuator is investigated with different electrode configurations, applied voltages and driving frequencies. The rotational temperature of N2(C3?u) molecule is calculated according to its rotational emission band near 380.5nm. The average electron energy of the discharge is evaluated by emission intensity ratio of first negative system to second positive system of N2. The rotational temperature is sensitive to the inner space of an electrode pair. The average electron energy shows insensitivity to the applied voltage, the driving frequency and the electrode configuration.

Li, Ying-Hong; Wu, Yun; Jia, Min; Zhou, Zhang-Wen; Guo, Zhi-Gang; Pu, Yi-Kang

2008-11-01

14

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

15

Power consumption, discharge capacitance and light emission as measures for thrust production of dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

A new procedure of determining the time resolved capacitance of a plasma actuator during operation is introduced, representing a simple diagnostic tool that provides insight into the phenomenological behavior of plasma actuators. The procedure is demonstrated by presenting example correlations between consumed electrical energy, size of the plasma region, and the operating voltage. It is shown that the capacitance of a plasma actuator is considerably increased by the presence of the plasma; hence a system that has previously been impedance matched can be considerably de-tuned when varying the operating voltage of the actuator. Such information is fundamental for any attempts to increase the energy efficiency of plasma-actuator systems. A combined analysis of the capacitance, light emission, size of the plasma region, force production, and power consumption is presented.

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

2011-07-01

16

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

17

Bluff Body Flow Control Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

In this study, the use of single dielectric barrier discharge plasma actuators for the control of bluff body flow separation is investigated. In particular, surface mounted plasma actuators are used to reduce both drag and unsteady vortex shedding from circular cylinders in cross-flow. It is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. Large reductions in vortex shedding and drag are demonstrated for Reynolds numbers ˜ 10^410^5. Both steady and unsteady plasma-induced surface blowing is explored. Results are presented from experiments involving both two and four surface mounted actuators.

Thomas, Flint

2005-11-01

18

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

19

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.

20

Novel applications of plasma actuators  

NASA Astrophysics Data System (ADS)

The current study investigates the effectiveness of two different dielectric barrier discharge plasma actuator configurations, a 3-D annular geometry for use in micro thrusters and internal duct aerodynamics and a jet vectoring actuator that acts as a vortex generator and flow control device. The first configuration consists of a closed circumferential arrangement which yields a body force when a voltage difference is applied across the inner and outer electrodes separated by a dielectric. The primary flow is driven by this zero-net mass flux jet at the wall that then entrains fluid in the core of the duct. PIV experiments in both quiescent flow and freestream are conducted on tubes of different diameters while varying parameters such as the modulation frequency, duty cycle and tunnel speed. The values of the induced velocities increase with the forcing frequency and duty cycle although there is a peak value for the forcing frequency after which the velocity and thrust decrease for each thruster. The velocities and thrust increase as the inner diameter of the tubes are increased while the velocity profiles show a great difference with the (l/di) ratio; recirculation occurs after going below a critical value. Experiments in the wind tunnel illustrate that the jet exit characteristics significantly change upon actuation in freestream flow but the effect tends to diminish with increasing inner diameters and tunnel speeds. Using staged arrays of these thrusters result in higher velocities while operating at both in phase and out of phase. The jet vectoring configuration consists of a single embedded electrode separated from two exposed electrodes on either side by the dielectric. The embedded electrode is grounded while the exposed electrodes are driven with a high frequency high voltage input signal. PIV measurements of the actuator in a freestream show that vectoring the jet yields stronger vortices than a linear configuration and increasing the difference between the duty cycles of the channels increases the vortex strength. It is seen that while the vortex is barely visible at the leading edge with little strength, it grows significantly large in the streamwise direction and reaches its maximum strength around mid-chord locations while the circulation distribution shows that the bulk of the circulation is added here. The motion of the vortex along this direction illustrates a braiding phenomena that can be observed via flow visualizations. Streamwise PIV data for this configuration on a wing with a NACA 0012 airfoil is used to plot the reverse flow probability, which in turn reveals that the use of the jet vectoring actuator as a vortex generator jet does suppress separation, but the actuator tends to lose its efficacy with increasing tunnel speeds.

Ozturk, Arzu Ceren

21

Microscale plasma actuators for improved thrust density  

NASA Astrophysics Data System (ADS)

We present a study of the dielectric barrier discharge (DBD) plasma actuators for microscale applications. Traditional macroscale DBD actuators suffer from relatively small actuation effect as characterized by small induced force density and resulting flow velocity. As a remedy we propose microscale plasma actuators that may induce orders of magnitude higher force density. We study the physics of such actuation using a multiscale ionized gas flow code based on the high-fidelity finite-element procedure. First, a two-dimensional volume discharge with nitrogen as a working gas is investigated using a first-principles approach solving coupled system of hydrodynamic plasma equations and Poisson equation for ion density, electron density, and electric field distribution. The quasi-neutral plasma and the sheath regions are identified. As the gap between electrodes is reduced, the sheath structure dominates the plasma region. Second, we simulate a first generation plasma micropump. We solve multiscale plasma-gas interaction inside a two-dimensional cross section of the microscale pump geometry. The result shows that a reasonable mass flow rate can be pumped using a set of small active electrodes.

Wang, Chin-Cheng; Roy, Subrata

2009-07-01

22

Cylinder Flow Control Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

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. Two optimized quartz dielectric plasma actuators mounted on the cylinder surface utilizing an improved saw-tooth waveform high-voltage generator allowed flow control at Reynolds number approaching supercritical. Using either steady or unsteady actuation, it is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. PIV based flow fields and wake velocity profiles obtained with hot-wire anemometry show large reductions in vortex shedding, wake width and turbulence intensity.

Kozlov, Alexey; Thomas, Flint

2007-11-01

23

Experimental Study of a Pulsed DC Plasma Flow Control Actuator.  

National Technical Information Service (NTIS)

An experiment on the effects of a pulsed DC plasma actuator on a separated flow in a low speed wind tunnel was conducted. The actuator consisted of two asymmetric copper electrodes oriented normal to the flow separated by a dielectric barrier and mounted ...

J. D. Wall

2006-01-01

24

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

National Technical Information Service (NTIS)

Dielectric Barrier Discharge (DBD) plasma actuators with serpentine shaped electrodes cause a change in the operational behavior of the flow control mechanism relative to the standard linear actuator due to the introduction of fully three dimensional vort...

M. Riherd M. Visbal S. Roy

2011-01-01

25

Feedback separation control using plasma actuators  

NASA Astrophysics Data System (ADS)

A single-dielectric barrier discharge plasma actuator is used to control the leading edge separation and thereby increase the maximum lift on a general wing section. The actuator is located at the leading edge and designed to direct high momentum air from the free-stream and accelerate it along the wall. A single pressure sensor with sufficient dynamic response, sensed the mean and unsteady pressure fluctuations near the leading edge (x/c=0.1). The wing section was mounted on a lift/drag balance. The time series from the pressure sensor was analyzed and correlated with the lift and drag measurements to determine real-time indicators of the flow separation state. This indicator function was used to control the plasma actuator. The experiments were conducted at chord Reynolds numbers, corrected for blockage, of 0.217× 10^6 and 0.307 × 10^6. The real-time separation control resulted in a substantial increase in both C_L_max and ?_stall, and an L/D improvement of as much as 340%. An optimum frequency corresponding to St=fc/U_?=1 was found to exist for unsteady excitation. Under this condition, the power to the actuator was only 2 Watts.

He, Chuan; Corke, Thomas; Patel, Mehul; Sowle, Zak

2004-11-01

26

Application of an AC barrier discharge actuator to control airflow separation above a NACA 0015 airfoil: Optimization of the actuation location along the chord  

Microsoft Academic Search

This paper deals with the control of airflow separation above a NACA 0015 airfoil with the help of a surface plasma actuator. A dielectric barrier discharge plasma is used to modify velocity in the boundary layer, tangentially to the wall. The goal of the actuation is to displace (upstream or downstream) the separation location, in either reattaching a naturally detached

Jérôme Jolibois; Maxime Forte; Éric Moreau

2008-01-01

27

Separation Control along a NACA 0015 Airfoil Using a Dielectric Barrier Discharge Actuator  

Microsoft Academic Search

\\u000a This paper deals with the control of airflow separation above a NACA 0015 airfoil using a surface plasma actuator. A dieletric\\u000a barrier discharge plasma is used to bring velocity in the boundary layer, tangentially to the wall. The goal of the actuation\\u000a is to displace (upstream or downstream) the separation point, in either reattaching a naturally detached airflow or in

Jérôme Jolibois; Maxime Forte; Eric Moreau

28

Airfoil Leading Edge Flow Separation Control using DBD Plasma Actuators driven by Nanosecond Pulses  

Microsoft Academic Search

This work continues an ongoing exploration of the use of dielectric barrier discharge plasma actuators driven by repetitive nanosecond pulses (NS-DBD hereafter) for aerodynamic flow control. The NS-DBD transfers very little momentum to the neutral air, but generates compression waves that manipulate flow instabilities similar to localized arc filament plasma actuators. Such devices which are believed to function through thermal

Jesse Little; Chris Rethmel; Keisuke Takashima; Chris Wiet; Igor Adamovich; Mo Samimy

2010-01-01

29

Micro Jet Generation with Annular Plasma Actuators  

NASA Astrophysics Data System (ADS)

The effectiveness of dielectric barrier discharge plasma actuators for use in micro thrusters and internal duct aerodynamics are investigated. The primary flow is driven by tha zero-net mass flux jet at the wall in a closed circumferential arrangemen that then entrains fluid in the core of the duct. This results in a unique configuration for studying impulsively started jet phenomena. Laser flow visualization is utilized to observe detailed flow structure wherein multiple vortex rings are formed immediately after pulsed actuation and evolve into a turbulent jet downstream. Measurements are made using PIV and the effects of modulation frequency and the duty cycle on the induced velocity and resulting thrust are observed. The values of the induced velocities increase with the forcing frequency and duty cycle although there is a peak value for the forcing frequency after which the velocity and thrust decrease. The influence of the length-to-diameter (l/di) ratio is also significant; the velocities and thrust increase as the inner diameter of the tubes are increased. Velocity profiles show a great difference with this ratio. As the inner diameter is increased, a recirculation region at the center of the tube with negative velocities can be observed. The effect of freestream on the induced veloicty profiles is also studied wherein the duct is placed inside a wind tunnel and tests are conducted at different Re.

Ozturk, Ceren; Jacob, Jamey

2008-11-01

30

Pulsed Plasma Actuators for Separation Flow Control  

Microsoft Academic Search

An experimental investigation of separation control using steady and pulsed plasma actuators was carried out on an Eppler E338 airfoil at typical micro air vehicle Reynolds numbers (20,000?Re?140,000). Pulsing was achieved by modulating the high frequency plasma excitation voltage. The actuators were calibrated directly using a laser dop- pler anemometer, with and without free-stream velocity, and this allowed the quantification

B. Göksel; D. Greenblatt; I. Rechenberg; Y. Singh; C. N. Nayeri; C. O. Paschereit

2006-01-01

31

On the role of oxygen in dielectric barrier discharge actuation of aerodynamic flows  

SciTech Connect

Phase-locked particle image velocimetry is used to study the mechanism of induced flow in the near field of a rf dielectric barrier discharge actuator mounted in the separated flow region of a bluff body. Flow actuation is found to be asymmetric, with suction toward the buried downstream electrode when it is biased positively relative to the upstream exposed electrode. Lesser flow is seen on the reverse voltage swing, where the buried electrode should attract positive ions. This phenomenon is enhanced when oxygen is added to the flow, suggesting that oxygen negative ions, possibly O{sub 2}{sup -}, play a dominant role in plasma actuation.

Kim, W.; Do, H.; Mungal, M. G.; Cappelli, M. A. [Mechanical Engineering Department, Stanford University, Stanford, California 94305-3032 (United States)

2007-10-29

32

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

33

Three-dimensional effects of curved plasma actuators in quiescent air  

NASA Astrophysics Data System (ADS)

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

Wang, Chin-Cheng; Durscher, Ryan; Roy, Subrata

2011-04-01

34

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

35

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 asymmetric dielectric-barrier-discharge (DBD) actuators is presented. The flow fields are simulated employ- ing an extensively validated high-fidelity Navier-Stokes s olver which is augmented with both phenomenological and first-principles models representing the plasma-induc ed body forces imparted by the actuator on the fluid. Several applications

Miguel R. Visbal; Datta V. Gaitonde; Subrata Roy

36

Modeling plasma actuators with air chemistry for effective flow control  

NASA Astrophysics Data System (ADS)

An asymmetric dielectric barrier discharge model is presented for real gas air chemistry using a self-consistent multibody system of plasma, dielectric, and neutral gas modeled together to predict the electrodynamic force imparted to the working gas. The equations governing the motion of charged and neutral species are solved with Poisson equation using finite element method using a Galerkin weak formulation. Electric field profile changes with the increase in grounded electrode and the density increases downstream. The electrodynamic force development mechanism is studied over a flat plate due to charge and neutral species production from adjacent air in a radio frequency driven barrier discharge. The time average of the force shows mostly acceleration above the actuator. Numerical simulation confirms that the magnitude of force increases very slightly with the increase in the length of grounded electrode.

Singh, Kunwar Pal; Roy, Subrata

2007-06-01

37

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

38

Experimental Investigation on the Characteristics of Sliding Discharge Plasma Aerodynamic Actuation  

NASA Astrophysics Data System (ADS)

A new electrical discharge called sliding discharge was developed to generate plasma aerodynamic actuation for flow control. A microsecond-pulse high voltage with a DC component was used to energize a three-electrode actuator to generate sliding discharge. The characteristics of plasma aerodynamic actuation by sliding discharge were experimentally investigated. Discharge morphology shows that sliding discharge is formed when energized by properly adjusting microsecond-pulse and DC voltage. Compared to dielectric barrier discharge (DBD), the plasma extension of sliding discharge is quasi-diffusive and stable but longer and more intensive. Results from particle image velocimetry (PIV) test indicate that plasma aerodynamic actuation by sliding discharge can induce a ‘starting vortex’ and a quasi-steady ‘near-wall jet’. Body force induced by plasma aerodynamic actuation is about the order of mN, which is stronger than that induced by single DBD. It is inferred that microsecond-pulse sliding discharge may be more effective to generate large-scale plasma aerodynamic actuation, which is very promising for improving aircraft aerodynamic characteristics and propulsion efficiency.

Song, Huimin; Li, Yinghong; Zhang, Qiaogen; Jia, Min; Wu, Yun

2011-10-01

39

Plasma actuators for separation control on stationary and oscillating airfoils  

Microsoft Academic Search

Given the importance of separation control associated with retreating blade stall on helicopters, the primary objective of this work was to develop a plasma actuator flow control device for its use in controlling leading-edge separation on stationary and oscillating airfoils. The plasma actuator consists of two copper electrodes separated by a dielectric insulator. When the voltage supplied to the electrodes

Martiqua L. Post

2004-01-01

40

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

NASA Astrophysics Data System (ADS)

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 alter the characteristics of the IPMC electrode. In plasma-treated IPMCs, the densely packed platinum nanoparticles have produced a relatively thick electrode layer. This configuration has led to the improvement in the electrical properties of the IPMC: surface resistance is noticeably decreased, whereas electrical capacitance is increased. These changes in the electrical properties have considerably enhanced the actuation parameters: displacement, force and operational life are increased by more than three times relative to the conventional IPMC. Our experimental data suggest a relationship between the IPMC actuator's electrical properties and actuation parameters: actuators with lower surface resistance generate large deflection and actuators with higher capacitance generate large actuation force. The actuation tests including coin lifting suggests the potential of the modified IPMC for artificial muscle applications.

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

2010-10-01

41

Numerical Simulation of Flow Control Over Airfoils Using Plasma Actuators  

Microsoft Academic Search

The goal of this work is to numerically simulate the application of weakly-ionized plasma actuators for improved aerodynamic performance of wings. Computations using the NASA Langley CFL3D unsteady thin layer Navier-Stokes solver have been carried out to calculate flow fields near NACA 0015 airfoil with plasma actuators installed on the suction surface in two different arrangements: one at the leading

Vladimir Voikov; Thomas Corke; Osamah Haddad

2004-01-01

42

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

43

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

44

Experimental Investigation of Hypersonic Flow and Plasma Aerodynamic Actuation Interaction  

NASA Astrophysics Data System (ADS)

For hypersonic flow, it was found that the most effective plasma actuator is derived from an electromagnetic perturbation. An experimental study was performed between hypersonic flow and plasma aerodynamic actuation interaction in a hypersonic shock tunnel, in which a Mach number of 7 was reached. The plasma discharging characteristic was acquired in static flows. In a hypersonic flow, the flow field can affect the plasma discharging characteristics. DC discharging without magnetic force is unstable, and the discharge channel cannot be maintained. When there is a magnetic field, the energy consumption of the plasma source is approximately three to four times larger than that without a magnetic field, and at the same time plasma discharge can also affect the hypersonic flow field. Through schlieren pictures and pressure measurement, it was found that plasma discharging could induce shockwaves and change the total pressure and wall pressure of the flow field.

Sun, Quan; Cheng, Bangqin; Li, Yinghong; Cui, Wei; Yu, Yonggui; Jie, Junhun

2013-09-01

45

Sensitivity of an asymmetric 3D diffuser to plasma-actuator induced inlet condition perturbations  

NASA Astrophysics Data System (ADS)

Experiments were conducted for the flow in a straight-walled 3D diffuser fed by a fully developed turbulent duct flow. Previous work found that this diffuser has a stable 3D separation bubble whose configuration is affected by the secondary flows in the upstream duct. Dielectric barrier discharge plasma actuators were used to produce low-momentum wall jets to determine if the separation behavior could be modified by weak forcing. Actuators producing a streamwise force along the wall where separation occurred in the baseline flow had a relatively small effect. However, spanwise acting plasma actuators that produced a pair of streamwise vortices in the inlet section of the diffuser had a strong effect on the diffuser pressure recovery. The diffuser performance could be either improved or degraded depending on the actuation parameters, including the actuator modulation frequency, duty cycle, and drive voltage. Velocity profile measurements in the diffuser inlet showed that the streamwise vortices affect the uniformity of the streamwise mean velocity accounting for some of the performance changes. However, phase-locked hotwire measurements at the diffuser exit indicate that the periodic nature of the forcing also plays an important role for cases with enhanced pressure recovery.

Grundmann, S.; Sayles, E. L.; Eaton, J. K.

2011-01-01

46

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

47

Numerical simulation of a plasma actuator based on ion transport  

NASA Astrophysics Data System (ADS)

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

2013-06-01

48

Numerical Simulation of Flow Control Over Airfoils Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

The goal of this work is to numerically simulate the application of weakly-ionized plasma actuators for improved aerodynamic performance of wings. Computations using the NASA Langley CFL3D unsteady thin layer Navier-Stokes solver have been carried out to calculate flow fields near NACA 0015 airfoil with plasma actuators installed on the suction surface in two different arrangements: one at the leading edge and the other at the trailing edge. Location of the plasma actuators was chosen to produce the effect of a wing leading edge slat and a trailing edge flap. The effect of plasma was modeled via body force terms in Navier-Stokes equations. The body force was obtained from the solution of the corresponding electrostatic problem. Based on predicted flow fields, the analysis of the effectiveness of plasma actuators for separation control on wings is presented. Computational tests were conducted at Reynolds number =217000 and Mach number =0.1 in order to compare the obtained numerical results with available experimental data, and assess the accuracy of the solver.

Voikov, Vladimir; Corke, Thomas; Haddad, Osamah

2004-11-01

49

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

50

Separation Control in a Centrifugal Bend Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

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

Arthur, Michael; Corke, Thomas

2011-11-01

51

Demonstration of Separation Delay with Glow-Discharge Plasma Actuators.  

National Technical Information Service (NTIS)

Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions ...

L. S. Hultgren D. E. Ashpis

2004-01-01

52

A large-scale multiple dielectric barrier discharge actuator based on an innovative three-electrode design  

NASA Astrophysics Data System (ADS)

For about 10 years, surface dielectric barrier discharges (DBDs) have been widely used as plasma actuators in subsonic airflow control applications. However, the extension length of a single surface DBD is limited to about 2 cm, which could restrict its use to small-scale applications. One way to extend the plasma actuation surface consists of using several single surface DBDs in series, energized by zero phase delayed or phase shifted high voltages. However, the mutual interaction between successive discharges affects the benefits of such standard multi-DBD actuators. This paper deals with a new design electrode for large-scale flow control applications. It consists of replacing each single two-electrode DBD by a three-electrode DBD where the third electrode acts as a shield between two successive DBDs. Experimental measurements by laser doppler velocimetry, pressure probe and time-resolved particle image velocimetry show that the mutual interactions can be strongly reduced, resulting in a constant electric wind velocity above the multi-DBD actuator.

Benard, N.; Mizuno, A.; Moreau, E.

2009-12-01

53

High Mach Number Leading-edge Flow Separation Control using AC DBD Plasma Actuators  

NASA Astrophysics Data System (ADS)

Wind tunnel experiments were conducted to quantify the effectiveness of alternating current dielectric barrier discharge flow control actuators to suppress leading-edge stall on a NASA energy efficient transport airfoil at compressible freestream speeds. The objective of this research was to increase lift, reduce drag, and improve the stall characteristics of the supercritical airfoil near stall by flow reattachment at relatively high Mach and Reynolds numbers. In addition, the effect of unsteady (or duty cycle) operation on these aerodynamic quantities was also investigated. The experiments were conducted for a range of Mach numbers between 0.1 and 0.4. corresponding to a Reynolds number range of 560,000 through 2,260,000. Lift, drag, quarter chord moment, and suction side pressures were measured near stall for baseline, steady actuation, and a scan of nondimensional duty cycle frequencies. The results show that the plasma actuators were effective at reattaching the leading-edge separated flow as evidenced by the increase in maximum lift coefficient and stall angle (as much as 2.5 degrees). The experiment also showed that lift was increased the most when the plasma actuator was operated unsteady with a nondimensional frequency of unity.

Kelley, Christopher; Bowles, Patrick; Cooney, John; He, Chuan; Corke, Thomas; Osborne, Bradley; Silkey, Joseph; Zehnle, Joseph

2011-11-01

54

Airflow control by non-thermal plasma actuators  

NASA Astrophysics Data System (ADS)

Active flow control is a topic in full expansion due to associated industrial applications of huge importance, particularly for aeronautics. Among all flow control methods, such as the use of mechanical flaps, wall synthetic jets or MEMS, plasma-based devices are very promising. The main advantages of such systems are their robustness, simplicity, low power consumption and ability for real-time control at high frequency. This paper is a review of the worldwide works on this topic, from its origin to the present. It is divided into two main parts. The first one is dedicated to the recent knowledge concerning the electric wind induced by surface non-thermal plasma actuators, acting in air at atmospheric pressure. Typically, it can reach 8 m s-1 at a distance of 0.5 mm from the wall. In the second part, works concerning active airflow control by these plasma actuators are presented. Very efficient results have been obtained for low-velocity subsonic airflows (typically U? <= 30 m s-1 and Reynolds number of a few 105), and promising results at higher velocities indicate that plasma actuators could be used in aeronautics.

Moreau, Eric

2007-02-01

55

Experimental Characterization of the Plasma Synthetic Jet Actuator  

NASA Astrophysics Data System (ADS)

The plasma synthetic jet is a novel active flow control method because of advantages such as fast response, high frequency and non-moving parts, and it has received more attention recently, especially regarding its application to high-speed flow control. In this paper, the experimental characterization of the plasma synthetic jet actuator is investigated. The actuator consists of a copper anode, a tungsten cathode and a ceramic shell, and with these three parts a cavity can be formed inside the actuator. A pulsed-DC power supply was adopted to generate the arc plasma between the electrodes, through which the gas inside was heated and expanded from the orifice. Discharge parameters such as voltage and current were recorded, respectively, by voltage and current probes. The schlieren system was used for flow visualization, and jet velocities with different discharge parameters were measured. The schlieren images showed that the strength of plasma jets in a series of pulses varies from each other. Through velocity measurement, it is found that at a fixed frequency, the jet velocity hardly increases when the discharge voltage ranges from 16 kV to 20 kV. However, with the discharge voltage fixed, the jet velocity suddenly decreases when the pulse frequency rises above 500 Hz, whereas at other testing frequencies no such decrease was observed. The maximum jet velocity measured in the experiment was up to 110 m/s, which is believed to be effective for high-speed flow control.

Jin, Di; Li, Yinghong; Jia, Min; Song, Huimin; Cui, Wei; Sun, Quan; Li, Fanyu

2013-10-01

56

Shearless transport barriers in magnetically confined plasmas  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

57

Airfoil Leading Edge Flow Separation Control using DBD Plasma Actuators driven by Nanosecond Pulses  

NASA Astrophysics Data System (ADS)

This work continues an ongoing exploration of the use of dielectric barrier discharge plasma actuators driven by repetitive nanosecond pulses (NS-DBD hereafter) for aerodynamic flow control. The NS-DBD transfers very little momentum to the neutral air, but generates compression waves that manipulate flow instabilities similar to localized arc filament plasma actuators. Such devices which are believed to function through thermal effects and instability manipulation could result in a significant improvement over conventional DBD (AC-DBD) plasmas that rely on momentum addition which limits their performance at high speeds. The efficacy of NS-DBDs has been demonstrated in our laboratory in a preliminary work on an airfoil leading edge up to Mach 0.17 and Re=1x106. The current work extends the investigation to higher Mach (0.27) and Re (1.15x106), the maximum operating conditions of our subsonic wind tunnel, using an 8 inch chord NACA 0015 airfoil. Results show the efficacy of the nanosecond pulse plasma discharge for attaching the nominally separated flow at various post stall angles of attack.

Little, Jesse; Rethmel, Chris; Takashima, Keisuke; Wiet, Chris; Adamovich, Igor; Samimy, Mo

2010-11-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

59

Induced flow direction of a single ehd plasma actuator using the one atmosphere uniform glow discharge plasma (OAUDGP)  

Microsoft Academic Search

Summary form only given. EHD plasma actuators have proven effective in delaying separation and re-attaching internal or external low speed flows in wind tunnel experiments that utilize drag balances, Pitot tubes, smoke flow visualization, and fluid dynamic modeling programs. Recent experiments showed that with the additional momentum from a single plasma actuator on its leading edge, the stall angle of

Xin Dai; J. Reece Roth

2006-01-01

60

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

61

Optimization of Airfoil Design for Flow Control with Plasma Actuators  

NASA Astrophysics Data System (ADS)

Using computer simulations and design optimization methods, this research examines the implementation of active flow control devices on wind turbine blades. Through modifications to blade geometry in order to maximize the effectiveness of flow control devices, increases in aerodynamic performance and control of aerodynamic performance are expected. Due to this compliant flow, an increase in the power output of wind turbines is able to be realized with minimal modification and investment to existing turbine blades. This is achieved through dynamic lift control via virtual camber control. Methods using strategic flow separation near the trailing edge are analyzed to obtain desired aerodynamic performance. FLUENT is used to determine the aerodynamic performance of potential turbine blade design, and the post-processing uses optimization techniques to determine an optimal blade geometry and plasma actuator operating parameters. This work motivates the research and development of novel blade designs with flow control devices that will be tested at Notre Dame's Laboratory for Enhanced Wind Energy Design.

Williams, Theodore; Corke, Thomas; Cooney, John

2011-11-01

62

Adaptive flow control of low-Reynolds number aerodynamics using dielectric barrier discharge actuator  

NASA Astrophysics Data System (ADS)

Aerodynamic performance of low-Reynolds number flyers, for a chord-based Reynolds number of 105 or below, is sensitive to wind gusts and flow separation. Active flow control offers insight into fluid physics as well as possible improvements in vehicle performance. While facilitating flow control by introducing feedback control and fluidic devices, major challenges of achieving a target aerodynamic performance under unsteady flow conditions lie on the high-dimensional nonlinear dynamics of the flow system. Therefore, a successful flow control framework requires a viable as well as accessible control scheme and understanding of underlying flow dynamics as key information of the flow system. On the other hand, promising devices have been developed recently to facilitate flow control in this flow regime. The dielectric barrier discharge (DBD) actuator is such an example; it does not have moving parts and provides fast impact on the flow field locally. In this paper, recent feedback flow control studies, especially those focusing on unsteady low-Reynolds number aerodynamics, are reviewed. As an example of an effective flow control framework, it is demonstrated that aerodynamic lift of a high angle-of-attack wing under fluctuating free-stream conditions can be stabilized using the DBD actuator and an adaptive algorithm based on general input-output models. System nonlinearities and control challenges are discussed by assessing control performance and the variation of the system parameters under various flow and actuation conditions. Other fundamental issues from the flow dynamics view point, such as the lift stabilization mechanism and the influence on drag fluctuation are also explored. Both potentiality and limitation of the linear modeling approach are discussed. In addition, guidelines on system identification and the controller and actuator setups are suggested.

Cho, Young-Chang; Shyy, Wei

2011-10-01

63

Pulsed Plasma Actuators for Active Flow Control at MAV Reynolds Numbers  

Microsoft Academic Search

An experimental investigation of separation control using steady and pulsed plasma actuators was carried out on an Eppler\\u000a E338 airfoil at typical micro air vehicle Reynolds numbers (20,000?Re?140,000). Pulsing was achieved by modulating the high frequency plasma excitation voltage. The actuators were calibrated\\u000a directly using a laser doppler anemometer, with and without free-stream velocity, and this allowed the quantification of

B. Göksel; D. Greenblatt; I. Rechenberg; Y. Kastantin; C. N. NAYERI; C. O. PASCHEREIT

64

Simulation of a Supersonic Jet Controlled by Plasma Actuators by the CESE Method  

Microsoft Academic Search

This paper reports preliminary CFD of an ideally expanded supersonic jet controlled by localized arc filament plasma actuators. The space-time Conservation Element and Solution Element (CESE) method was employed to solve the three-dimensional Euler equations with and without the application of plasma actuators. A fully expanded Mach 1.3 jet from a 2.54 mm diameter round nozzle is used as the

H. He; I. Adamovich; M. Samimy

2006-01-01

65

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

66

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

67

Lift and drag performances of an axisymmetric airfoil controlled by plasma actuator  

Microsoft Academic Search

A Dielectric Barrier Discharge (DBD) is mounted at the leading edge of a NACA 0015 airfoil model. The effects of steady and unsteady actuations on the lift and drag coefficients are investigated by time-averaged force measurements. Results demonstrate that the stall regime can be delayed of one or two degrees while the drag coefficient is reduced. The aerodynamic performances are

N. Benard; J. Jolibois; E. Moreau

2009-01-01

68

Active Separation Control over a NACA0024 by DBD Plasma Actuator and FBG Sensor  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharge plasma actuators (DBD-PA) and fiber Bragg grating (FBG) sensors have been investigated for active control of flow separation around a NACA0024 airfoil. Tangential jets were produced in the vicinity of the DBD-PA slightly aft of the leading edge of the airfoil. The flow separation control ability was evaluated at low Reynolds number in an open-circuit wind tunnel. Phase- and time-averaged velocity distributions around the airfoil were measured using Particle Image Velocimetry, and the flow separation control ability of the DBD-PA was assessed at 8°, 12° and 16° angle of attack. An FBG sensor was attached to a chord-wise cantilever near the trailing edge of the airfoil on the pressure surface. This was used to measure strain fluctuations in the cantilever root due to flow-induced oscillations. The feasibility of this system to detect flow separation was studied, where the standard deviations of strain fluctuations significantly increased when the flow was separated. This was utilized in an open-loop control system to detect flow separation by FBG then apply active control with the DBD-PA to reattach the flow.

Jukes, Timothy; Segawa, Takehiko; Walker, Seth; Furutani, Hirohide; Iki, Norihiko; Takekawa, Shinya

69

Design and characterization of a plasma actuator for controlling dynamic stall  

NASA Astrophysics Data System (ADS)

A repetitive pulsed spark discharge inside of a ˜1 mm cavity generates a high velocity (100-600 m/s) gas jets potentially capable of controlling dynamic stall on an airfoil at Re ˜1e6. High temperature compressible 2D CFD was used to determine the design and geometry of the actuator slot and plasma cavity. Experimental results measuring the time dependent plasma discharge emission and density variations (using gated ICCD and Schlieren) indicate that the plasma can be modeled as constant volume heating over 100 ns. The energy input to the actuator is controlled by the high voltage and capacitance initiating the discharge. During the discharge air in the cavity is rapidly heated. Temperature and pressure increase 5-10x, causing strong gradients and shocks. The flow is directed using an angled slot. In CFD designed geometries shock fronts and high temperature gas velocities are experimentally determined. The force generated by the actuator is also experimentally determined. Experimental results from the actuator show that velocities of 500 m/s can be achieved through 1mm2 orifices with energy inputs of 50 mJ. The CFD model predicts time scales and velocities similar to those observed, and it also indicates cavity cooling as important in optimizing the actuator pulse repetition rate.

Pollard, William; Staack, David

2012-10-01

70

On factors influencing arc filament plasma actuator performance in control of high speed jets  

NASA Astrophysics Data System (ADS)

Localized arc filament plasma actuators (LAFPAs) have been developed and used at The Gas Dynamics and Turbulence Laboratory for the purpose of controlling high-speed and high Reynolds number jets. The ability of LAFPAs for use in both subsonic and supersonic jets has been explored, and experiments to date have shown that these actuators have significant potential for mixing enhancement and noise control applications. While it has been established that the actuators manipulate instabilities of the jet, the exact nature of how the actuation couples to the flow is still unclear. All of the results previously reported have been based on a nozzle extension that has an azimuthal groove of 1 mm width and 0.5 mm depth along the inner surface approximately 1 mm upstream of nozzle extension exit. The ring groove was initially added to shield the plasma arcs from the high-momentum flow. However, the effect of the ring groove on the actuation mechanism is not known. To explore this effect, a new nozzle extension is designed, which relocates the actuators to the nozzle extension face and eliminates the ring groove. Schlieren images, particle image velocimetry and acoustic results of a Mach 0.9 jet of Reynolds number ~6.1 × 105 show similar trends and magnitudes with and without a ring groove. Thus, it is concluded that the ring groove does not play a primary role in the LAFPAs' control mechanism. Furthermore, the effect of the duty cycle of the actuator input pulse on the LAFPAs' control authority is investigated. The results show that the minimum duty cycle that provides complete plasma formation has the largest control over the jet.

Hahn, Casey; Kearney-Fischer, Martin; Samimy, Mo

2011-12-01

71

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

NASA Astrophysics Data System (ADS)

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

Reece Roth, J.

2005-10-01

72

Aerodynamic plasma actuators: A directional micro-jet device  

Microsoft Academic Search

In recent years electroaerodynamic actuators have been rather intensively studied in order to control airflow [H. Velkoff, R. Godfrey, J. of Heat Transfer 101 (1979) 157; S. El-Khabiry, G.M. Colver, Phys. Fluids 9 3 (1997) 587; A. Soldati, S. Banerjee, Phys. Fluids 10 (1998) 1742; R. Vilela Mendes, J.A. Dente, J. Fluids Eng. 120 (1998) 626; A. Schütze, et al.,

Nicolas Bénard; Jérôme Jolibois; Eric Moreau; Roberto Sosa; Guillermo Artana; Gérard Touchard

2008-01-01

73

DCT-TCI: Real Gas Characterization of Plasma Flow Control - An Integrated Approach.  

National Technical Information Service (NTIS)

This report presents results culminated partially from the AFOSR grant FA9550-09-1-0372 on experimental and numerical characterization of novel plasma actuators. Specifically the serpentine and multi-barrier plasma actuators are considered. The serpentine...

C. Wang R. Durscher S. Roy

2011-01-01

74

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

NASA Astrophysics Data System (ADS)

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, fp+, above 0.6 with a force coefficient, Cp, 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 fp+=2.0 and Cp=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 fp+=0.2 and Cp=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

2009-08-01

75

Preliminary numerical assessment of turbulent skin friction control with plasma actuators  

Microsoft Academic Search

Plasma actuators (PA) introduce a body force in the near-wall region of a fluid flow. This body force has already been successfully used for separation and transition flow control. We investigate the possibility of applying PAs to turbulent skin friction drag reduction by testing the effect of a modelled PA's body force in a numerically simulated turbulent channel flow. The

Bettina Frohnapfel; Antonio Criscione; Cameron Tropea; Yosuke Hasegawa; Nobuhide Kasagi

2009-01-01

76

EDITORIAL: Physics and phenomenology of plasma actuators for control of aeronautical flows  

NASA Astrophysics Data System (ADS)

The subject of atmospheric pressure plasma actuators for aerodynamic flow control originated in the mid-1990s and is now flourishing, particularly in the aeronautical, aerospace, and fluid dynamics literature. The rapid growth of this field can be illustrated by the figure below, which tracks the results of Google searches on 'plasma actuator' from August 2003, at which time there were 19 'hits', to the present, at which time there are more than 600 'hits'. The activity in this field has been growing exponentially, as the figure illustrates. Google plot This special Cluster within Journal of Physics D: Applied Physics begins with a broad survey of past and recent work done world-wide, proceeds with papers that look at the physics and phenomenology of several kinds of plasma actuators, and finally moves on to papers that look at the effects of the momentum addition by plasma actuators to subsonic and supersonic flows. This new technology is likely to have an important effect on military and commercial flight, and it is my hope that this Cluster will contribute to that end.

Reece Roth, J.

2007-02-01

77

Hydrogen sulfide dissociation in a barrier discharge plasma  

Microsoft Academic Search

The authors studied the decomposition of hydrogen sulfide in a barrier discharge. The choice of a barrier discharge was not made by chance. It possesses the following properties resulting in its having advantage over other types of discharges. (1) Use of a barrier discharge permits one to obtain superequilibrium atom concentrations for a given temperature owing to the nonisothermic plasma

F. A. Teimurova; A. M. Rasulov; N. T. Klimov

1992-01-01

78

Control of oblique shock wave/boundary layer interactions using plasma actuators  

NASA Astrophysics Data System (ADS)

Localized arc filament plasma actuators (LAFPAs) are used for shock wave/boundary layer interaction induced separation control in a Mach 2.3 flow. The boundary layer is fully turbulent with a Reynolds number based on the incompressible momentum thickness of 22,000 and shape factor of 1.37, and the impinging shock wave is generated by a 10° compression ramp. The LAFPAs are observed to have significant control authority over the interaction. The main effect is the displacement of the reflected shock and most of the interaction region upstream by approximately one boundary layer thickness (~5 mm). The initial goal of the control was to manipulate the low-frequency ( St~0.03) unsteadiness associated with the interaction region. A detailed investigation of the effect of actuator placement, frequency, and duty cycle on the control authority indicates the actuators' primary control mechanism is not the manipulation of low-frequency unsteadiness. Detailed measurements and analysis indicate that a modification to the boundary layer through heat addition by the actuators is the control mechanism, despite the extremely small power input of the actuators.

Webb, N.; Clifford, C.; Samimy, M.

2013-06-01

79

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

80

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

81

Control of the corner separation in a compressor cascade by steady and unsteady plasma aerodynamic actuation  

Microsoft Academic Search

This paper reports experimental results on using steady and unsteady plasma aerodynamic actuation to control the corner separation,\\u000a which forms over the suction surface and end wall corner of a compressor cascade blade passage. Total pressure recovery coefficient\\u000a distribution was adopted to evaluate the corner separation. Corner separation causes significant total pressure loss even\\u000a when the angle of attack is

Ying-hong LiYun; Yun Wu; Min Zhou; Chang-Bing Su; Xiong-Wei Zhang; Jun-Qiang Zhu

2010-01-01

82

Stall control at high angle of attack with plasma sheet actuators  

Microsoft Academic Search

We analyzed the modifications of the airflow around an NACA 0015 airfoil when the flow was perturbed with electrohydrodynamic\\u000a forces. The actuation was produced with a plasma sheet device (PSD) consisting in two bare electrodes flush mounted on the\\u000a surface of the wing profile operated to obtain a discharge contouring the body in the inter-electrode space. We analyze the\\u000a influence

Roberto Sosa; Guillermo Artana; Eric Moreau; Gérard Touchard

2007-01-01

83

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

NASA Astrophysics Data System (ADS)

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.

2010-08-01

84

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

85

Effects of plasma aerodynamic actuation on oblique shock wave in a cold supersonic flow  

NASA Astrophysics Data System (ADS)

Wedge oblique shock wave control using an arc discharge plasma aerodynamic actuator was investigated both experimentally and theoretically. Schlieren photography measurements in a small-scale short-duration supersonic wind tunnel indicated that the shock wave angle decreased and its start point shifted upstream with the plasma aerodynamic actuation. Also the shock wave intensity weakened, as shown by the decrease in the gas static pressure ratio of flow downstream and upstream of the shock wave. Moreover, the shock wave control effect was intensified when a static magnetic field was applied. Under test conditions of Mach 2.2, magnetic control and input voltage 3 kV, the start point of the shock wave shifted 4 mm upstream, while its angle and intensity decreased 8.6% and 8.8%, respectively. A thermal choking model was proposed to deduce the change laws of oblique shock wave control by surface arc discharge. The theoretical result was consistent with the experimental result, which demonstrated that the thermal choking model can effectively forecast the effect of plasma actuation on an oblique shock wave in a cold supersonic flow.

Wang, Jian; Li, Yinghong; Cheng, Bangqin; Su, Changbing; Song, Huimin; Wu, Yun

2009-08-01

86

FAST TRACK COMMUNICATION: Asymmetric surface barrier discharge plasma driven by pulsed 13.56 MHz power in atmospheric pressure air  

NASA Astrophysics Data System (ADS)

Barrier discharges are a proven method of generating plasmas at high pressures, having applications in industrial processing, materials science and aerodynamics. In this paper, we present new measurements of an asymmetric surface barrier discharge plasma driven by pulsed radio frequency (rf 13.56 MHz) power in atmospheric pressure air. The voltage, current and optical emission of the discharge are measured temporally using 2.4 kVp-p (peak to peak) 13.56 MHz rf pulses, 20 µs in duration. The results exhibit different characteristics to plasma actuators, which have similar discharge geometry but are typically driven at frequencies of up to about 10 kHz. However, the electrical measurements are similar to some other atmospheric pressure, rf capacitively coupled discharge systems with symmetric electrode configurations and different feed gases.

Dedrick, J.; Boswell, R. W.; Charles, C.

2010-09-01

87

Simulations of plasmas pentrating magnetic barriers  

Microsoft Academic Search

Perturbed currents perpendicular to the magnetic are generated by plasma motions in which the equilibrium magnetic field (and the corresponding equilibrium currents) are compressed, stretched, and deformed. One example of this is the Earth's magnetopause with its ever-present equilibrium transverse currents and its strong perturbations. Experiments have recently been performed using a plasma gun to shoot a plasma at a

Herbert Gunell; Tomas Hurtig; Mark Koepke; Nils Brenning; Hans Nilsson

2007-01-01

88

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

89

Stall control at high angle of attack with plasma sheet actuators  

NASA Astrophysics Data System (ADS)

We analyzed the modifications of the airflow around an NACA 0015 airfoil when the flow was perturbed with electrohydrodynamic forces. The actuation was produced with a plasma sheet device (PSD) consisting in two bare electrodes flush mounted on the surface of the wing profile operated to obtain a discharge contouring the body in the inter-electrode space. We analyze the influence of different parameters of the actuation (frequency, input power, electrodes position) on the aerodynamic performance of the airfoil, basing our study on measurements of the surface pressure distribution and of the flow fields with particle image velocimetry technique. The experiments indicated that at moderate Reynolds numbers (150,000 < Re < 333,000) and at high angles of attack, steady or periodic actuations enabled large improvement of the lift and drag/lift aerodynamic coefficients by reattaching the flow along the extrados. However, to attain the same results steady actuations required larger power consumption. When exciting the flow with a moderate value of non-dimensional power coefficient (ratio of electric power flow with the kinetic power flow), a frequency of excitation produced a peak on the coefficients that evaluate the airfoil performance. This peak in terms of a non-dimensional frequency was close to 0.4 and can be associated to an optimal frequency of excitation. However, our work indicates that this peak is not constant for all stalled flow conditions and should be analyzed considering scale factors that take into account the ratio of the length where the forcing acts and the cord length.

Sosa, Roberto; Artana, Guillermo; Moreau, Eric; Touchard, Gérard

2007-01-01

90

New technique deducing plasma potential by a capacitive coupling method in spraying dielectric barrier discharge plasmas  

SciTech Connect

A new method to measure the plasma potential in an atmospheric dielectric barrier discharge (DBD) plasmas is developed for a new spraying DBD plasma source, which is sustained by electric fields generated by flowing plasmas at the outer region of the electrodes, since conventional electric probe can not be applied due to arcing. The new technique is to measure the spatially averaged plasma potential by using a capacitive coupling method with calculation of collisional sheath thickness.

Choi, Yong-Sup; Chung, Kyu-Sun; Jung, Yong Ho; You, Hyun-Jong; Lee, Myoung-Jae [Electric Probe Applications Laboratory (ePAL), Hanyang University, Seoul 133-791 (Korea, Republic of)

2005-01-01

91

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

92

Processing of pollutants in dielectric-barrier plasma reactors  

SciTech Connect

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

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

1995-07-01

93

Effects of Plasma Spray Parameters on Two Layer Thermal Barrier.  

National Technical Information Service (NTIS)

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 ...

S. Stecura

1981-01-01

94

Coal Liquefaction by Using Dielectric Barrier Discharge Plasma  

NASA Astrophysics Data System (ADS)

An innovative method for coal liquefaction by using dielectric barrier discharge (DBD) plasma in a short reaction time was developed. Using tetralin as the reaction medium, DBD plasma as the energy source, and a reaction time of 10 min at 140°C, up to 10% of coal was converted to liquid material. The results showed the feasibility of coal's liquefaction by DBD plasma under relatively moderate conditions. Simultaneously, it was clarified that the effect of DBD plasma treatment was opposed to the thermal effect of heating. An acid plasma sheath could be formed on the coal powder surface in DBD conditions, liquefied reactions could be carried out in the absence of inorganic acid, and the products were nearly neutral and with low causticity.

Wang, Qiuying; Wu, Peng; Gu, Fan

2013-07-01

95

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

96

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

National Technical Information Service (NTIS)

The short term transient and long term periodic unsteady effects of pulsed plasma actuation are studied using an unsteady, compressible Navier- Stokes solver for the case of a partially separated transitional flow over an SD7003 airfoil at 4 deg angle of ...

D. Rizzetta M. Riherd M. Visbal S. Roy

2011-01-01

97

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

98

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

Microsoft Academic Search

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

Nicolas Benard; Eric Moreau

2011-01-01

99

Odor control using the AC barrier-type plasma reactors  

Microsoft Academic Search

Odor control from living environment has become of increased concern. In a previous paper, we investigated the removal of acetaldehyde (CH3CHO), which is one of the main odor components in cigarette smoke using the barrier-type packed-bed plasma reactor. In the present paper, we reported on the new results of acetaldehyde and ammonia (NH3) which is another odor component of cigarette

Masaaki Okubo; Tomoyuki Kuroki; Hideya Kametaka; Toshiaki Yamamoto

2001-01-01

100

Odor control using the AC barrier type plasma reactors  

Microsoft Academic Search

Odor control from living environment is becoming of increased concern. In the previous study, we investigated the removal of acetaldehyde (CH3CHO) which is one of the main odor components in tobacco smoke using the barrier type packed-bed plasma reactor. In the present paper, we reported on the new results of acetaldehyde, ammonia (NH3) which is another odor component and tobacco

M. Okubo; T. Kuroki; H. Kametaka; T. Yamamoto

2000-01-01

101

Diffusion barrier layer fabrication by plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

Plasma immersion Ion Implantation technique has been used to modify the diffusion barrier properties of titanium (Ti) metal layer against copper diffusion. Ti coated silicon wafer were implanted with doses viz. 1015ions/cm2 and 1017ions/cm2 corresponding to low and high dose regime. High dose of implantation of nitrogen ions in the film render it to become Ti(N). Cu/Ti(N)/Si structures were formed by depositing copper over the implanted samples. Diffusion barrier properties of Ti(N) was evaluated after annealing the samples up to 700ºC for 30 minutes. Sheet resistance, X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) measurements were carried out to investigate the effect of annealing. Low dose implanted Ti layer does not show any change in its diffusion barrier properties and fails at about 400ºC. The failure of diffusion barrier properties of low dose implanted samples is attributed to the chemical reaction between titanium and copper films. The high dose implanted layer stops the diffusion of Cu metal through it even at high annealing temperature. The enhancement in its diffusion barrier properties is supposed to be due to nitridation of titanium film which increases the activation energy involved for its chemical reaction with copper metal film.

Kumar, Mukesh; Rajkumar, %; Kumar, Dinesh; George, P. J.; Paul, A. K.

2003-04-01

102

Extremum Seeking Adaptive Separation Control on a Wing with Plasma Synthetic Jet Actuator  

NASA Astrophysics Data System (ADS)

Plasma synthetic jet actuator (PSJA) is a flow control device which has structure that insulator is tucked with electrode pair. It generates electrohydrodynamic (EHD) effect and induces a flow. The experiment was held to investigate the effect of flow control using extremum seeking with PSJA placed on the surface of NACA0012 wing installed in the wind tunnel. Frequency of the input signal to PSJA is modulated to maximize the effect of PSJA in flow control. The wake velocity fluctuation is one of indexes on separation control effect. The wake velocity is minimized over the input frequency by employing extremum seeking. The seeking algorithm calculates the correlation of the modulation frequency and wake velocity fluctuation. The modulation signal frequency where the correlation changes from negative to positive minimizes the wake velocity fluctuation. To detect a local minimum of the wake velocity fluctuation by extremum seeking, it is necessary to change the modulation signal frequency with time. Sine and square waves change the modulation signal frequency to PSJA. The wind tunnel speed was changed as an external factor. The experimental results show that the modulation signal frequency can track the optimum value when the wind tunnel speed is changed. This paper shows that adaptive flow control to optimize the modulation signal frequency with PSJA using extremum seeking enables to suppress turbulence on the flow field of wings.

Ogawara, Kakuji; Kojima, Ryota; Matsumoto, Shoji; Shingin, Hidenori

103

Inter- and intracellular signaling induced by magnetomechanical actuation of plasma membrane channels  

NASA Astrophysics Data System (ADS)

Magnetic particles allow for non-invasive control over their spatial orientation and motion which makes them ideally suitable for studying real-time processes in living cells. Lithographically defined ferromagnetic disks with spin-vortex ground state have the advantage of zero net magnetization in remanence. This eliminates long-range magnetic forces which otherwise lead to the interaction between particles and their agglomeration. Moreover, magnetically soft permalloy particles have high magnetization of saturation thus requiring very low external field for inducing high magnetomotive force, compared to superparamagnetic particles. Our group has previously demonstrated that micron-sized permalloy disks can be used for destruction of cancer cells (D.-H. Kim, E. A. Rozhkova, I. V. Ulasov, S. D. Bader, T. Rajh, M. S. Lesniak, V. Novosad, Nat. Mater. 9, 165-171 (2010). In this work, we investigate the effects of magnetomechanical stimulation of human brain cancer cells with these particles. It will be shown that the actuation of ion channels in cell plasma membrane induces, on the one hand side, intracellular signaling triggering cell apoptosis and, on the other hand, it stimulates the energy transfer between the cells which carries the information about apoptotic signal.

Vitol, Elina A.; Rozhkova, Elena A.; Novosad, Valentyn; Bader, Samuel D.

2012-02-01

104

Development and characterization of plasma actuators for high-speed jet control  

Microsoft Academic Search

Active control of high Reynolds number and high-speed jets has been hampered due to the lack of suitable actuators. Some of the attributes that would make an actuator suitable for such flows are: high amplitude and bandwidth; small size for distribution around the jet; phase-locking ability for jet azimuthal mode forcing; and sufficient ruggedness for hot jets. We have been

M. Samimy; I. Adamovich; B. Webb; J. Kastner; J. Hileman; S. Keshav; P. Palm

2004-01-01

105

MERCURY OXIDIZATION IN NON-THERMAL PLASMA BARRIER DISCHARGE SYSTEM  

SciTech Connect

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

V.K. Mathur

2003-02-01

106

The manipulation of atmospheric pressure dielectric barrier plasma jets  

NASA Astrophysics Data System (ADS)

Atmospheric pressure plasma jets offer a unique route to transport reactive chemical species generated under highly non-equilibrium conditions to a remote downstream sample; as such, they have become the device of choice in many biological and materials processing applications. This contribution explores techniques to manipulate the propagation dynamics of the fast moving ionization front generated in a dielectric barrier plasma jet, after it is launched from the powered electrode. To achieve this, the electric field in the region through which the ionization front propagates is manipulated on a sub-microsecond timescale. It is demonstrated that the application of voltage pulses of varying duration and delay to supplementary electrodes placed along the axis of propagation and tangential to it facilitates a considerable level of control over the velocity, intensity and direction of the ionization front. In doing so, the flux of reactive species transported to a specific point on a downstream substrate can be electrically modulated on a pulse to pulse basis, a finding that could significantly extend the application scope of plasma jet devices.

Walsh, J. L.; Olszewski, P.; Bradley, J. W.

2012-06-01

107

Surface discharge plasma actuator driven by a pulsed 13.56 MHz-5 kHz voltage waveform  

NASA Astrophysics Data System (ADS)

The effect of incorporating pulses of radio-frequency (rf: 13.56 MHz) voltage into the driving waveform of a surface discharge plasma actuator is investigated. Rf voltage is applied to the actuator to increase the production of ions and thereby increase the thrust that is generated by the discharge. This waveform is coupled to the powered electrode in 5 µs pulses and combined with a relatively low-frequency (LF) 5 kHz sinusoid to form a pulsed 13.56 MHz-5 kHz (rf-LF) driving voltage. Measurements of the applied voltage, rf and LF currents, effective power, and velocity field of the surrounding air are undertaken at atmospheric pressure. The thrust that is generated using the rf-LF waveform is estimated from the velocity fields using a momentum balance and is found to increase for increasing rf voltage when the LF voltage remains constant. Maximum thrust is achieved when the rf pulses are positioned at the LF voltage minima and this suggests the importance of negative ions. The efficacy of rf-LF actuation is investigated by comparing the thrust that is generated per unit increase in peak voltage with that obtained using an LF-driven discharge.

Dedrick, J.; Im, S.; Cappelli, M. A.; Boswell, R. W.; Charles, C.

2013-10-01

108

Core Internal Barrier Formation in Alcator C-Mod Plasmas  

NASA Astrophysics Data System (ADS)

Formation of internal transport barriers (ITB's) has been observed in the core region of Alcator C-Mod. Short lived ITB's form spontaneously following the H- to L-mode transition (Enhanced Neutron Mode, EN). They are also induced by lithium pellet injection into ohmic and RF heated discharges (PEP mode) and by ICRF heating outside of the q=1 surface. The H- to L-mode transition on Alcator C-Mod is typically followed by a strong increase in the global neutron rate, up to a factor of 8 with as much as 50% increase in central ion temperature. As the transition proceeds, the electron density collapses in the outer third of the plasma, resulting in a centrally peaked density profile and causing a local decrease of ?e in the region 0.3 < r/a < 0.5, from a value of 5 down to between 1 and 2. The ITB/PEP mode appears to be very similar to the ITB/EN phenomena, in that the density profiles are quite peaked, the neutron rate and ion temperature increase markedly, and impurities accumulate in the plasma center. In contrast, the central density and stored energy increase with ITB/PEP while for ITB/EN the central density is unchanged and the total stored energy decreases. The sawtooth activity in the two cases is also quite different.

Fiore, C. L.; Alcator C-Mod Group

2000-10-01

109

Core Internal Transport Barriers in Alcator C-Mod Plasmas  

NASA Astrophysics Data System (ADS)

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

Fiore, C. L.

2000-10-01

110

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

2013-08-07

111

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

Microsoft Academic Search

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

R. Mestiri; R. Hadaji; S. Ben Nasrallah

2010-01-01

112

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

Microsoft Academic Search

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

Jun Huang; Wei Chen; Hui Li; Xing-Quan Wang; Guo-Hua Lv; M. Latif Khohsa; Ming Guo; Ke-Cheng Feng; Peng-Ye Wang; Si-Ze Yang

2011-01-01

113

Transition phenomena and thermal transport properties in LHD plasmas with an electron internal transport barrier  

Microsoft Academic Search

Two types of improved core confinement were observed during centrally focused electron cyclotron heating (ECH) into plasmas sustained by counter (CNTR) and Co neutral beam injections (NBI) in the Large Helical Device. The CNTR NBI plasma displayed transition phenomena to the high-electron-temperature state and had a clear electron internal transport barrier, while the Co NBI plasma did not show a

T. Shimozuma; S. Kubo; H. Idei; S. Inagaki; N. Tamura; T. Tokuzawa; T. Morisaki; K. Y. Watanabe; K. Ida; I. Yamada; K. Narihara; S. Muto; M. Yokoyama; Y. Yoshimura; T. Notake; K. Ohkubo; T. Seki; K. Saito; R. Kumazawa; T. Mutoh; T. Watari; A. Komori

2005-01-01

114

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

115

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

National Technical Information Service (NTIS)

The sintering and creep of plasma-sprayed ceramic thermal barrier coatings under high temperature conditions are complex phenomena. Changes in thermomechanical and thermophysical properties and in the stress response of these coating systems as a result o...

D. Zhu R. A. Miller

1998-01-01

116

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

SciTech Connect

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

Subramanian, Ramesh (Oviedo, FL)

2001-01-01

117

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

DOEpatents

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

Subramanian, Ramesh (Oviedo, FL)

2001-01-01

118

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

119

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

120

Influence of heat treatment on nanocrystalline zirconia powder and plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Nanostructured zirconia top coat was deposited by air plasma spray and NiCoCrAlTaY bond coat was deposited on Ni substrate by low pressure plasma spray. Nanostructured and conventional thermal barrier coatings were heat-treated at temperature varying from 1050 to 1 250 °C for 2-20 h. The results show that obvious grain growth was found in both nanostructured and conventional thermal barrier

Xian-liang JIANG; Chun-bo LIU; Min LIU; Hui-zhao ZHU

2010-01-01

121

Tantalum oxide-based plasma-sprayed environmental barrier coatings  

NASA Astrophysics Data System (ADS)

Energy efficiency in gas turbine engines is linked to the high temperature capabilities of materials used in the hot section of the engine. To facilitate a significant increase in engine efficiency, tough structural ceramics have been developed that can handle the thermo-mechanical stresses that gas turbine components experience. Unfortunately, the high-temperature, high-pressure, and high-velocity combustion gases in a gas turbine contain water vapor and/or hydrogen which have been shown to volatilize the protective silica layer on silicon-based ceramics. This degradation leads to significant surface recession in ceramic gas turbine components. In order to maintain their structural integrity, an environmental barrier coating (EBC) could be used to protect ceramics from the harsh gas turbine environment. Due to its coefficient of thermal expansion and phase stability at elevated temperatures, tantalum oxide (Ta2O5) was examined as the base material for an air plasma-sprayed EBC on Si3N 4 ceramics. As-sprayed pure Ta2O5 was comprised of both low-temperature beta-Ta2O5 and high-temperature alpha-Ta 2O5 that was quenched into the structure. Residual stress measurements via X-ray diffraction determined the as-sprayed coating to be in tension and extensive vertical macrocracks were observed in the coating. Heat treatments of the pure coating led to conversion of alpha-Ta2 O5 to beta-Ta2O5, conversion of tensile stresses to compressive, localized buckling of the coating, and significant grain growth which caused microcracking in the coating. The pure coating was found to be an inadequate EBC. Al2O3 was investigated as a solid solution alloying addition designed to enhance the stability of beta-Ta2O 5, and reduce grain growth by slowing grain boundary diffusion. La 2O3 was investigated as an alloying addition designed to form second phase particles which would reduce grain growth through pinning. Al2O3 was successful at both stabilizing beta-Ta 2O5 and reducing grain growth, though AlTaO4 was found to form in the coatings. La2O3 additions led to the formation of LaTa7O19 which also contributed to grain growth reduction. Residual stresses in the alloyed coatings were generally found to be tensile. Microcracks were not observed in coatings that were alloyed with both Al2O3 and La2O3 with the most promising alloy being Ta2O5 + 1.5 wt.% Al 2O3 + 1.5 wt.% La2O3.

Weyant, Christopher M.

122

Ideal MHD stability of double transport barrier plasmas in DIII-D  

NASA Astrophysics Data System (ADS)

The ideal MHD stability for double transport barrier (DTB or DB) plasmas with varying edge and internal barrier width and height was investigated, using the ideal MHD stability code GATO. A moderate ratio of edge transport barriers (ETB) height to internal transport barriers (ITBs) height is found to be beneficial to MHD stability and the ?N is limited by global low n instabilities. For moderate ITB width DB plasmas, if the ETB is weak, the stability is limited by n = 1 (n is the toroidal mode number) global mode; whereas if the ETB is strong it is limited by intermediate-n edge peeling-ballooning modes. Broadening the ITB can improve stability if the ITB half width wi lsim 0.3. For very broad ITB width plasmas the stability is limited by stability to a low n (n > 1) global mode.

Li, G. Q.; Wang, S. J.; Lao, L. L.; Turnbull, A. D.; Chu, M. S.; Brennan, D. P.; Groebner, R. J.; Zhao, L.

2008-01-01

123

Recent Developments in the Field of Plasma-Sprayed Thermal Barrier Coatings  

Microsoft Academic Search

Thermal barrier coating (TBC) systems are widely used in gas turbines on thermally highly loaded parts as blades, vanes or combustion chamber to improve the performance of the engines. The standard plasma-sprayed systems consist of a vacuum plasma-sprayed (VPS) MCrAlY (M = Ni or Co) and an atmospherically plasma sprayed (APS) ceramic top layer made of yttria partially stabilised zirconia

R. Vaßen; J.-E. Döring; M. Dietrich; H. Lehmann; D. Stöver

124

A hypersonic plasma bullet train traveling in an atmospheric dielectric-barrier discharge jet  

Microsoft Academic Search

An experimental observation of fast-moving plasma bullets produced in an atmospheric dielectric-barrier discharge jet is reported in this paper. Nanosecond imaging suggests that the atmospheric discharge jet consists of a plasma bullet train traveling at a hypersonic speed from 7.0 km\\/s to 43.1 km\\/s. Yet on a millisecond scale, the bullet train appears as a plasma jet of several centimeters

Jianjun Shi; Fangchun Zhong; Jing Zhang; D. W. Liu; M. G. Kong

2008-01-01

125

Thermal behavior of bovine serum albumin after exposure to barrier discharge helium plasma jet  

NASA Astrophysics Data System (ADS)

Non-thermal plasma jets at atmospheric pressure are useful tools nowadays in plasma medicine. Various applications are tested such as cauterization, coagulation, wound healing, natural and artificial surfaces decontamination, and sterilization. In order to know more about the effects of gas plasma on biological supramolecules, we exposed protein powders to a barrier discharge helium plasma jet. Then, spectroscopic investigations were carried out in order to obtain information on protein secondary, tertiary, and quaternary structures. We obtained a reduction of the protein alpha-helix content after the plasma exposure and a different behavior, for both thermal denaturation/renaturation kinetics and thermal aggregation process.

Jijie, R.; Pohoata, V.; Topala, I.

2012-10-01

126

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

SciTech Connect

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

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

2006-05-01

127

Visualization by discharge illumination technique and modification by plasma actuator of rarefied Mach 2 airflow around a cylinder  

NASA Astrophysics Data System (ADS)

The use of plasma actuators for flow control has received considerable attention in recent years. This kind of device seems to be an appropriate means of raising abilities in flow control thanks to total electric control, no moving parts and a fast response time. The experimental work presented here shows, firstly, the non-intrusive character of the visualization of the density field of an airflow around a cylinder obtained using a plasma luminescence technique. Experiments are made in a continuous supersonic wind tunnel. The static pressure in the flow is 8 Pa, the mean free path is about 0.3 mm and the airflow velocity is 510 m s?1. Pressure measurements obtained by means of glass Pitot tube without the visualization discharge are proposed. Measured and simulated pressure profiles are in good agreement in the region near the cylinder. There is good correlation between numerical simulations of the supersonic flow field, analytical model predictions and experimental flow visualizations obtained by a plasma luminescence technique. Consequently, we show that the plasma luminescence technique is non-intrusive. Secondly, the effect of a dc discharge on a supersonic rarefied air flow around a cylinder is studied. An electrode is flush mounted on the cylinder. Stagnation pressure profiles are examined for different electrode positions on the cylinder. A shock wave modification depending on the electrode location is observed. The discharge placed at the upstream stagnation point induces an upstream shift of the bow shock, whereas a modification of the shock wave shape is observed when it is placed at 45° or 90°.

Leger, L.; Sellam, M.; Barbosa, E.; Depussay, E.

2013-06-01

128

Critical Threshold Behavior for Steady-State Internal Transport Barriers in Burning Plasmas  

SciTech Connect

Burning tokamak plasmas with internal transport barriers are investigated by means of integrated modeling simulations. The barrier sustainment in steady state, differently from the barrier formation process, is found to be characterized by a critical behavior, and the critical number of the phase transition is determined. Beyond a power threshold, alignment of self-generated and noninductively driven currents occurs and steady state becomes possible. This concept is applied to simulate a steady-state scenario within the specifications of the International Thermonuclear Experimental Reactor.

Garcia, J.; Giruzzi, G.; Artaud, J. F.; Basiuk, V.; Decker, J.; Imbeaux, F.; Peysson, Y.; Schneider, M. [Association EURATOM-CEA, CEA/DSM/IRFM, Cadarache, F-13108 St. Paul lez Durance (France)

2008-06-27

129

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

NASA Astrophysics Data System (ADS)

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 N2 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; Duan, Yixiang

2012-06-01

130

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

131

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

132

Dielectric-barrier-discharge vortex generators: characterisation and optimisation for flow separation control  

NASA Astrophysics Data System (ADS)

We investigated the use of dielectric-barrier-discharge plasma actuators as vortex generators for flow separation control applications. Plasma actuators were placed at a yaw angle to the oncoming flow, so that they produced a spanwise wall jet. Through interaction with the oncoming boundary layer, this created a streamwise longitudinal vortex. In this experimental investigation, the effect of yaw angle, actuator length and plasma-induced velocity ratio was studied. Particular attention was given to the vortex formation mechanism and its development downstream. The DBD plasma actuators were then applied in the form of co-rotating and counter-rotating vortex arrays to control flow separation over a trailing-edge ramp. It was found that the vortex generators were successful in reducing the separation region, even at plasma-to-free-stream velocity ratios of less than 10%.

Jukes, Timothy N.; Choi, Kwing-So

2012-02-01

133

Unraveling Quasiperiodic Relaxations of Transport Barriers with Gyrokinetic Simulations of Tokamak Plasmas  

NASA Astrophysics Data System (ADS)

The generation and dynamics of transport barriers governed by sheared poloidal flows are analyzed in flux-driven 5D gyrokinetic simulations of ion temperature gradient driven turbulence in tokamak plasmas. The transport barrier is triggered by a vorticity source that polarizes the system. The chosen source captures characteristic features of some experimental scenarios, namely, the generation of a sheared electric field coupled to anisotropic heating. For sufficiently large shearing rates, turbulent transport is suppressed and a transport barrier builds up, in agreement with the common understanding of transport barriers. The vorticity source also governs a secondary instability— driven by the temperature anisotropy (T??T?). Turbulence and its associated zonal flows are generated in the vicinity of the barrier, destroying the latter due to the screening of the polarization source by the zonal flows. These barrier relaxations occur quasiperiodically, and generically result from the decoupling between the dynamics of the barrier generation, triggered by the source driven sheared flow, and that of the crash, triggered by the secondary instability. This result underlines that barriers triggered by sheared flows are prone to relaxations whenever secondary instabilities come into play.

Strugarek, A.; Sarazin, Y.; Zarzoso, D.; Abiteboul, J.; Brun, A. S.; Cartier-Michaud, T.; Dif-Pradalier, G.; Garbet, X.; Ghendrih, Ph.; Grandgirard, V.; Latu, G.; Passeron, C.; Thomine, O.

2013-10-01

134

Underwater plasma processing of stabilized zirconia for thermal barrier coatings  

NASA Astrophysics Data System (ADS)

The influence of powder technology on the spraying process is growing. The use of powders of different morphologies results in a variety of coating properties. Plasma processing of ceramic composite powders underwater produces dense and spherical powders with excellent morphologies. Coatings of improved quality are produced by spraying these powders. This paper describes the concept of producing zirconia powders by a plasma process that is performed underwater. The most important parameters and standards are highlighted. Moreover, the influence of powder characteristics on coating properties will be described and some results presented.

Lugscheider, E.; Rass, I.

1992-03-01

135

VOCs Decomposition via Modified Ferroelectric Packed Bed Dielectric Barrier Discharge Plasma  

Microsoft Academic Search

A series of experiments are performed to remove toluene from a gaseous influent at room temperature and at- mospheric pressure by nonthermal plasma (NTP) generated di- electric barrier discharge. Four packed bed plasma reactors are compared in terms of energy density, toluene removal, energy efficiency, and other factors, with four conditions: no packing materials, ceramic materials, BaTiO3 rings, and Ba0.8Sr0.2Zr0.1Ti0.9O3

Tao Zhu; Yandong Wan; Hairong Li; Sha Chen; Yan Fang

2011-01-01

136

Improving the erosion resistance of plasma-sprayed zirconia thermal barrier coatings by laser glazing  

Microsoft Academic Search

In this study under review, substrates of 100 mm×25 mm×2 mm SUS 420 stainless steel coupons were first sprayed with a Ni–22Cr–10Al–1Y bond coat and then with a 19.5 wt.% yttria-stabilized zirconia (YSZ) top coat using an air-plasma spray system. After that, the plasma-sprayed yttria-stabilized zirconia thermal barrier coatings (TBCs) were glazed using a pulsed CO2 laser. The subsequent effects of laser glazing on

Pi-Chuen Tsai; Jiing-Herng Lee; Chi-Lung Chang

2007-01-01

137

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

138

Low-thermal-conductivity plasma-sprayed thermal barrier coatings with engineered microstructures  

Microsoft Academic Search

The solution precursor plasma spray (SPPS) process has been used to deposit ZrO2–7wt.% Y2O3 thermal barrier coatings (TBCs) that contain alternate layers of low and high porosities (layered-SPPS). The thermal conductivity of the layered-SPPS coating is found to be lower than those of both a SPPS coating with distributed porosity and an air-plasma-sprayed coating of the same composition, in the

Amol D. Jadhav; Nitin P. Padture; Eric H. Jordan; Maurice Gell; Pilar Miranzo; Edwin R. Fuller

2006-01-01

139

Investigations of plasma polymerized SiO x barrier films for polymer food packaging  

Microsoft Academic Search

Nano-scale SiOx layers were deposited on polyethylene terephthalate (PET) foils by plasma enhanced chemical vapor deposition (PECVD) in an electron cyclotron resonance (ECR) plasma process in order to enhance their barrier properties towards water vapor. Oxygen (O2) and hexamethyldisilazane (HMDSN) served as reactive gas and precursor, respectively. The effect of layer thickness and O2:HMDSN (x:1) gas mixture ratio on the

Simone Plog; Joachim Schneider; Matthias Walker; Andreas Schulz; Ulrich Stroth

2011-01-01

140

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

141

Degradation of malachite green by dielectric barrier discharge plasma.  

PubMed

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

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

2013-01-01

142

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

Microsoft Academic Search

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

Huixia Chen; Fengwu Bai; Zhilong Xiu

2010-01-01

143

FAST TRACK COMMUNICATION: Asymmetric surface barrier discharge plasma driven by pulsed 13.56 MHz power in atmospheric pressure air  

Microsoft Academic Search

Barrier discharges are a proven method of generating plasmas at high pressures, having applications in industrial processing, materials science and aerodynamics. In this paper, we present new measurements of an asymmetric surface barrier discharge plasma driven by pulsed radio frequency (rf 13.56 MHz) power in atmospheric pressure air. The voltage, current and optical emission of the discharge are measured temporally

J. Dedrick; R. W. Boswell; C. Charles

2010-01-01

144

The Effect of Air Plasma on Sterilization of Escherichia coli in Dielectric Barrier Discharge  

NASA Astrophysics Data System (ADS)

In this work, a Dielectric Barrier Discharge (DBD) air plasma was used to sterilize Escherichia coli (E. coli) on the surface of medical Polyethylene Terephthalate (PET) film. The leakage of cellular DNA and protein by optical absorbance measurement at 260 nm and 280 nm, together with transmission electron microscopy (TEM) about cell morphology were performed after sterilization to analyse inactivation mechanisms. The results indicated that the DBD air plasma was very effective in E. coli sterilization. The plasma germicidal efficiency depended on the plasma treatment time, the air-gap distance, and the applied voltage. Within 5 min of plasma treatment, the germicidal efficiency against E. coli could reach 99.99%. An etching action on cell membranes by electrons, ions and radicals is the primary mechanism for DBD air plasma sterilization, which leads to the effusion of cellular contents (DNA and protein) and bacterial death.

Hu, Miao; Guo, Yun

2012-08-01

145

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

146

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

SciTech Connect

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

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

2010-09-15

147

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

NASA Astrophysics Data System (ADS)

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.; O'Connell, D.

2011-09-01

148

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

NASA Astrophysics Data System (ADS)

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, Xing-Quan; Lv, Guo-Hua; Khohsa, M. Latif; Guo, Ming; Feng, Ke-Cheng; Wang, Peng-Ye; Yang, Si-Ze

2011-03-01

149

Measurement of the elastic modulus of a plasma-sprayed thermal barrier coating using spherical indentation  

Microsoft Academic Search

Failure in plasma-sprayed thermal barrier coatings systems mostly takes place in the ceramic topcoat or at the interface between the topcoat and the bondcoat. The failure normally occurs by spallation of the topcoat at shutdown operations from high temperatures where compressive thermal mismatch stresses are induced in the topcoat. In order to analyse the residual stresses, knowledge about the elastic

Mats Eskner; Rolf Sandström

2004-01-01

150

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

National Technical Information Service (NTIS)

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 stre...

S. R. Choi D. M. Zhu R. A. Miller

2004-01-01

151

Enhanced Oxygen Barrier and Interfacial Adhesion of Polystyrene\\/Clay Nanocomposites via Plasma Surface Modification  

Microsoft Academic Search

Bentonite layered-silicate was the selected nanofiller to be studied and filled in polystyrene, consequently represented PS\\/clay nanocomposites. The plasma technique developed in our laboratory was utilized as the clay pretreatment method to provide the radical sites on the clay surface prior to styrene grafting step. Gas barrier property and impact strength, one of the most serious deficiencies of polystyrene, were

Patchara Tasanatanachai; Rathanawan Magaraphan

2007-01-01

152

Plasma enhanced CVD of fluorocarbon films by low-pressure dielectric barrier discharge  

Microsoft Academic Search

Low-pressure dielectric barrier discharge (DBD) plasmas have been used to deposit polymerized fluorocarbon (FC) films on silicon substrates. The effects of discharge pressure and frequency of power supply on the film quality have been systematically investigated. The deposited films were characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and static contact angle measurements. Experimental results show that

Dongping Liu; Wei Li; Zhiqing Feng; Xiaodong Tan; Baoxiang Chen; Jinhai Niu; Yanhong Liu

2009-01-01

153

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

Microsoft Academic Search

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

Wenjun Liang; Jian Li; Jie Li; Yuquan Jin

2009-01-01

154

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

155

On the energy transport in internal transport barriers of RFP plasmas  

NASA Astrophysics Data System (ADS)

Single helical axis (SHAx) states obtained in high current reversed field pinch (RFP) plasmas feature an internal transport barrier delimiting the hot helical core region. The electron temperature jump across this region, and the related temperature gradient, display a clear relationship with the normalized amplitude of the secondary MHD modes. A transport analysis performed with the ASTRA code, taking into account the helical geometry, yields values of the thermal conductivity in the barrier region as low as 5 m2 s-1. The thermal conductivity is also related to the secondary mode amplitude. Since such amplitude is reduced when plasma current is increased, it is expected that higher current plasmas will display even steeper thermal gradients and hotter helical cores.

Lorenzini, R.; Alfier, A.; Auriemma, F.; Fassina, A.; Franz, P.; Innocente, P.; López-Bruna, D.; Martines, E.; Momo, B.; Pereverzev, G.; Piovesan, P.; Spizzo, G.; Spolaore, M.; Terranova, D.

2012-06-01

156

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

157

Thermomechanical behavior of plasma-sprayed zirconia thermal barrier coatings.  

SciTech Connect

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

Singh, J. P.

1998-04-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

159

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

2011-03-03

160

Phase transformation and bond coat oxidation behavior of plasma-sprayed zirconia thermal barrier coating  

Microsoft Academic Search

ZrO2–CeO2–Y2O3 and ZrO2–Y2O3 thermal barrier coatings were prepared using the air plasma spray process. Phase transformation in the ceramic top coating, bond coat oxidation and thermal barrier properties were investigated to compare ZrO2–CeO2–Y2O3 with ZrO2–Y2O3 at 1300°C under high temperature thermal cycles. In the as-sprayed condition, both coatings showed a 7?11% porosity fraction and typical lamellar structures formed by continuous

C. H. Lee; H. K. Kim; H. S. Choi; H. S. Ahn

2000-01-01

161

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

162

Mechanical property measurements of plasma-sprayed thermal-barrier coatings subjected to oxidation  

SciTech Connect

Techniques have been developed for measuring the tensile properties of plasma-sprayed coatings which are used in thermal barrier applications. The measurements have included the average Young's modulus, bond strength and elongation at failure. The oxidation behavior of the bond coat plays an important role in the integrity and adhesion of plasma-sprayed thermal barrier coatings. This work studies the nature of the high temperature degradation on the mechanical properties of the coating. Furnace tests have been carried out on U-700 alloy with bond coats of NiCrAlY or NiCrAlZr and an overlay of ZrO2-8 percent Y2O3. Weight gain measurements on the coatings have been examined with relation to the adhesion strength and failure observations. The results from an initial study are reported in this work. 13 references.

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

1984-07-01

163

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

SciTech Connect

The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value. 9 references.

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

1984-07-01

164

Coaxial rf atmospheric pressure dielectric barrier air-helium plasma characteristics  

NASA Astrophysics Data System (ADS)

The electrical and optical characteristics of a coaxial rf atmospheric pressure dielectric barrier discharge (DBD) with one electrode covered with glass and with helium in air were investigated. Optical measurements with an intensified charge coupled device (ICCD) camera combined with the voltage and power vs. current data provided identification of the ? to ? mode transitions. The coaxial design allowed operation with very low power density plasmas (0.18 W/cm3) and a much larger plasma size (13 mm) than the parallel plate designs.

Gulec, A.; Oksuz, L.; Hershkowitz, N.

2011-04-01

165

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

166

Creation of fluorocarbon barriers on surfaces of starch-based products through cold plasma treatment  

NASA Astrophysics Data System (ADS)

Two kinds of starch foam trays (starch and aspen-starch foam trays) were produced using a lab model baking machine. Surfaces of the trays were treated with CF4 and SF6 plasma to create fluorine-rich layers on the surfaces, which might show strong water resistance. The plasma parameters, such like RF power, gas pressure and reaction time, were varied to evaluate the effects of each parameter on fluorination of surfaces. The atomic concentrations of fluorine, oxygen and carbon on samples' surfaces were earned from ESCA (electron spectroscopy for chemical analysis) and contact angles of sample surfaces were measured for hydrophobicity. For water resistance of plasma treated surfaces, liquid water uptake and water vapor uptake test were performed. Also, equilibrium moisture contents of unmodified and plasma treated samples were measured to evaluate biodegradability of plasma treated samples. Fluorine-rich barriers were created on sample surfaces treated with CF 4 and SF6 plasma. The fluorine atomic concentrations of treated sample surfaces were ranged from 34.4% to 64.4% (CF4 treatment) and 43.6% to 57.9% (SF6 treatment). It was found at both plasma gases that plasma parameters affected total fluorine concentration and carbon-peak shapes in ESCA surveys, which imply different distributions of mono- or multi-fluoro carbon's contents. In various reaction times, it was found that total fluorine contents were decreased after a critical point as the reaction time was prolonged, which may imply that a dominant mechanism has been changed from deposition or functionalization to etching. Oxygen atomic concentration was decreased at sample surfaces treated by both plasmas. In the case of SF6 plasma, it was proved that the removal of oxygen surely occurred because there was no addition of sulfur species. Plasma treated sample surfaces had high contact angles with distilled water up to 150° and the high values of angles have been kept constant up to for 15 minutes. Fluorine-rich barriers created by plasma showed lower water liquid and vapor permeability than untreated surfaces did. Plasma treated samples had similar moisture contents with untreated samples at all relative humidity tested. AFM and SEM images were taken for sample surfaces' morphology and topography.

Han, Yousoo

167

Microstructure and Thermal Properties of Plasma Sprayed Thermal Barrier Coatings from Nanostructured YSZ  

Microsoft Academic Search

Nanostructured yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) were produced by atmospheric plasma spraying.\\u000a The microstructure of the sprayed coating was characterized by transmission electron microscope (TEM) and scanning electron\\u000a microscope (SEM). The nano-coating had a higher porosity of ~25% than the conventional coating, which is mainly attributed\\u000a to the large amount of intersplat gaps in the nano-coating. The thermal

Jing Wu; Hong-Bo Guo; Le Zhou; Lu Wang; Sheng-Kai Gong

2010-01-01

168

Mechanical properties of solution-precursor plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

The microstructure of thermal barrier coatings (TBCs) of 7 wt.% Y2O3 stabilized ZrO2 (7YSZ) deposited using the solution-precursor plasma spray (SPPS) method has: (i) controlled porosity, (ii) vertical cracks, and (iii) lack of large-scale “splat” boundaries. An unusual feature of such SPPS TBCs is that they are well-adherent in ultra-thick forms (~4 mm thickness), where most other types of ultra-thick ceramic coatings

Amol D. Jadhav; Nitin P. Padture

2008-01-01

169

Template Removal from ZSM-5 Zeolite Using Dielectric-Barrier Discharge Plasma  

Microsoft Academic Search

\\u000a Abstract  A dielectric-barrier discharge (DBD) plasma technique has been successfully applied for template removal from ZSM-5 zeolite.\\u000a The rate for template removal using DBD is about eight times higher than that using the conventional thermal calcination.\\u000a During the template removal using DBD, the highest temperature of the sample is about 125 °C. As such, the thermal effect\\u000a on the sample during the

Yuan Liu; Yun-xiang Pan; Pingyu Kuai; Chang-jun Liu

2010-01-01

170

Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species  

PubMed Central

Vascularization plays a key role in processes such as wound healing and tissue engineering. Non-thermal plasma, which primarily produces reactive oxygen species (ROS), has recently emerged as an efficient tool in medical applications including blood coagulation, sterilization and malignant cell apoptosis. Liquids and porcine aortic endothelial cells were treated with a non-thermal dielectric barrier discharge plasma in vitro. Plasma treatment of phosphate-buffered saline (PBS) and serum-free medium increased ROS concentration in a dose-dependent manner, with a higher concentration observed in serum-free medium compared with PBS. Species concentration inside cells peaked 1 h after treatment, followed by a decrease 3 h post treatment. Endothelial cells treated with a plasma dose of 4.2 J cm–2 had 1.7 times more cells than untreated samples 5 days after plasma treatment. The 4.2 J cm–2 plasma dose increased two-dimensional migration distance by 40 per cent compared with untreated control, while the number of cells that migrated through a three-dimensional collagen gel increased by 15 per cent. Tube formation was also enhanced by plasma treatment, with tube lengths in plasma-treated samples measuring 2.6 times longer than control samples. A fibroblast growth factor-2 (FGF-2) neutralizing antibody and ROS scavengers abrogated these angiogenic effects. These data indicate that plasma enhanced proliferation, migration and tube formation is due to FGF-2 release induced by plasma-produced ROS. Non-thermal plasma may be used as a potential tool for applying ROS in precise doses to enhance vascularization.

Arjunan, Krishna Priya; Friedman, Gary; Fridman, Alexander; Clyne, Alisa Morss

2012-01-01

171

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

2011-01-28

172

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

173

Multi-scale Phenomena and Structures Observed in Fabrication of Thermal Barrier Coatings by Using Plasma Spraying  

Microsoft Academic Search

Thermal barrier coatings (TBC) fabricated by plasma spray can exhibit a wide range of microstructures due to differences in feedstock powders and spraying conditions. Since different microstructures naturally result in different thermal and mechanical properties and service life as thermal barrier coatings, it is of great importance to understand the relationship among the feedstock characteristics, spray conditions and the coating

Seiji Kuroda; Hideyuki Murakami; Makoto Watanabe; Kaita Itoh; Kentaro Shinoda; Xiancheng Zhang

2010-01-01

174

Development of barrier coatings for cellulosic-based materials by cold plasma methods  

NASA Astrophysics Data System (ADS)

Cellulose-based materials are ideal candidates for future industries that need to be based on environmentally safe technologies and renewable resources. Wood represents an important raw material and its application as construction material is well established. Cellophane is one of the most important cellulosic material and it is widely used as packaging material in the food industry. Outdoor exposure of wood causes a combination of physical and chemical degradation processes due to the combined effects of sunlight, moisture, fungi, and bacteria. Cold-plasma-induced surface modifications are an attractive way for tailoring the characteristics of lignocellulosic substrates to prevent weathering degradation. Plasma-polymerized hexamethyldisiloxane (PPHMDSO) was deposited onto wood surfaces to create water repellent characteristics. The presence of a crosslinked macromolecular structure was detected. The plasma coated samples exhibited very high water contact angle values indicating the existence of hydrophobic surfaces. Reflective and electromagnetic radiation-absorbent substances were incorporated with a high-molecular-weight polydimethylsiloxane polymer in liquid phase and deposited as thin layers on wood surfaces. The macromolecular films, containing the dispersed materials, were then converted into a three dimensional solid state network by exposure to a oxygen-plasma. It was demonstrated that both UV-absorbent and reflectant components incorporated into the plasma-generated PDMSO matrix protected the wood from weathering degradation. Reduced oxidation and less degradation was observed after simulated weathering. High water contact angle values indicated a strong hydrophobic character of the oxygen plasma-treated PDMSO-coated samples. Plasma-enhanced surface modifications and coatings were employed to create water-vapor barrier layers on cellophane substrate surfaces. HMDSO was selected as a plasma gas and oxygen was used to ablate amorphous regions. Oxygen plasma treated cellophane and oxygen plasma treated and PPHMDSO coated cellophane surfaces were comparatively analyzed and the corresponding surface wettability characteristics were evaluated. The plasma generated surface topographies controlled the morphology of the PPHMDSO layers. Higher temperature HMDSO plasma-state environments lead to insoluble, crosslinked layers. Continuous and pulsed Csb2Fsb6 plasmas were also used for surface modification and excellent surface fluorination was achieved under the pulsed plasma conditions.

Denes, Agnes Reka

175

Global modeling of a dielectric barrier discharge in Ne–Xe mixtures for an alternating current plasma display panel  

Microsoft Academic Search

A global model of a dielectric barrier discharge in Ne–Xe mixtures for an alternating current plasma display panel was developed. This model was used to evaluate electron temperature, plasma density, densities of excited state atoms, wall charge density, current density, excimer density, and vacuum ultraviolet (VUV) intensity, and their gas composition-pressure dependencies, in order to analyze the mechanism of VUV

Y. Ikeda; J. P. Verboncoeur; P. J. Christenson; C. K. Birdsall

1999-01-01

176

Global modeling of a dielectric barrier discharge in Ne-Xe mixtures for an alternating current plasma display panel  

Microsoft Academic Search

A global model of a dielectric barrier discharge in Ne-Xe mixtures for an alternating current plasma display panel was developed. This model was used to evaluate electron temperature, plasma density, densities of excited state atoms, wall charge density, current density, excimer density, and vacuum ultraviolet (VUV) intensity, and their gas composition-pressure dependencies, in order to analyze the mechanism of VUV

Y. Ikeda; J. P. Verboncoeur; P. J. Christenson; C. K. Birdsall

1999-01-01

177

Plasma-enhanced catalysis at atmospheric pressure, using a dielectric barrier discharge.  

NASA Astrophysics Data System (ADS)

The combination of plasmas and catalysis under moderate temperatures is an emerging area. The techniques are commonly combined in one of two ways. In the first of these the catalyst is introduced into the plasma while in the second, the catalyst is placed down-stream of the discharge. The introduction of a plasma to a catalysis system may produce a change in the distribution or type of reactive species available for reaction or a change of catalyst properties, such as an increase in dispersion or a change in catalyst structure. In the present work, a micro-reactor that allows the study of catalysis using temperature-programmed techniques. The reactor also allows a dielectric barrier discharge (DBD) to be generated over the whole length of the catalyst region or to precede it. The DBD produces a cool plasma at atmospheric pressure and generates surface modifications of the catalyst and is a source of ions and radicals for reaction processes. Test reactions have been studied to show differences in reaction product distributions and activation temperatures when compared with the catalyst alone. Reaction product distributions were measured using a Hiden, capillary-inlet, mass spectrometer. A molecular beam inlet, mass/energy spectrometer was also used to study the constituents of the DBD plasma.

Rees, J. A.; Lundie, D. T.; Seymour, D. L.; Whitmore, T. D.

2008-10-01

178

A simple dielectric barrier discharge device for generating slot homogeneous plasma in atmospheric pressure air  

NASA Astrophysics Data System (ADS)

We report a simple dielectric barrier discharge device for generating slot homogeneous plasma in atmospheric pressure air. It consists of two parallel water electrodes with a distance adjusting micrometer. With increasing the applied voltage, the discharge becomes homogeneous. The electron temperature, vibrational temperature (TV) of N2, and rotational temperature (TR) of N2+ are estimated by optical emission spectroscopy. Both TV and TR remain unchanged along the slot in the homogeneous discharge regime. The trend of the TV with respect to the applied voltage is opposite from that of TR, while the electron temperature keeps constant with the increasing applied voltage.

Dong, Lifang; Zhang, Yanzhao; Liu, Weiyuan; Yang, Li; Chen, Junying

2009-03-01

179

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

Microsoft Academic Search

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

Dongming Zhu; Robert A. Miller

1998-01-01

180

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

181

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.

Matthes, Rutger; Bender, Claudia; Schluter, Rabea; Koban, Ina; Bussiahn, Rene; Reuter, Stephan; Lademann, Jurgen; Weltmann, Klaus-Dieter; Kramer, Axel

2013-01-01

182

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

NASA Astrophysics Data System (ADS)

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 (Al2O3) 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, CHxNH2, etc.) which have been produced during the discharge of CH4/N2 mixture.

Majumdar, Abhijit; Hippler, Rainer

2007-07-01

183

Decomposition of trifluoromethane in a dielectric barrier discharge non-thermal plasma reactor.  

PubMed

The decomposition of trifluoromethane (CHF3) was carried out using non-thermal plasma generated in a dielectric barrier discharge (DBD) reactor. The effects of reactor temperature, electric power, initial concentration and oxygen content were examined. The DBD reactor was able to completely destroy CHF3 with alumina beads as a packing material. The decomposition efficiency increased with increasing electric power and reactor temperature. The destruction of CHF3 gradually increased with the addition of O2 up to 2%, but further increase in the oxygen content led to a decrease in the decomposition efficiency. The degradation pathways were explained with the identified by-products. The main by-products from CHF3 were found to be COF2, CF4, CO2 and CO although the COF2 and CF4 disappeared when the plasma were combined with alumina catalyst. PMID:23513444

Gandhi, M Sanjeeva; Mok, Y S

2012-01-01

184

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

2009-11-06

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

Quiescent double barrier high-confinement mode plasmas in the DIII-D tokamak  

NASA Astrophysics Data System (ADS)

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 Physics and Controlled Nuclear 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 that 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 s or >25 energy confinement times ?E), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved ?NH89=7 for up to 5 times the ?E of 150 ms. The ?NH89 values of 7 substantially exceed the value of 4 routinely achieved in the 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 magnetohydrodynamic (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.

2001-05-01

187

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

188

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

2013-09-01

189

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

190

Creep of plasma-sprayed-ZrO2 thermal-barrier coatings  

SciTech Connect

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

Firestone, R.F. (IIT Research Institute, Chicago, IL); Logan, W.R.

1982-09-01

191

Surface Modification of Polyethylene (PE) Films Using Dielectric Barrier Discharge Plasma at Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

Modification of the surface properties of polyethylene (PE) films is studied using air dielectric barrier discharge at atmospheric pressure. The treated samples are examined by water contact angle measurements, Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). With the increase in treating time, the water contact angle changes from 93.2° before treatment to a minimum of 53.3° after a treatment for 50 s. Both ATR and XPS results show some oxidized species are introduced into the sample surface by the plasma treatment and the tendency of the water contact angle with the treating time is the same as that of oxygen concentration on the treated sample surface. SEM result shows the surface roughness of PE samples increases with the treatment time increasing.

Wang, Kun; Li, Jian; Ren, Chunsheng; Wang, Dezhen; Wang, Younian

2008-08-01

192

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

193

Pellet injection into H-mode ITER plasma with the presence of internal transport barriers  

SciTech Connect

The impacts of pellet injection into ITER type-1 ELMy H-mode plasma with the presence of internal transport barriers (ITBs) are investigated using self-consistent core-edge simulations of 1.5D BALDUR integrated predictive modeling code. In these simulations, the plasma core transport is predicted using a combination of a semi-empirical Mixed B/gB anomalous transport model, which can self-consistently predict the formation of ITBs, and the NCLASS neoclassical model. For simplicity, it is assumed that toroidal velocity for {omega}{sub E Multiplication-Sign B} calculation is proportional to local ion temperature. In addition, the boundary conditions are predicted using the pedestal temperature model based on magnetic and flow shear stabilization width scaling; while the density of each plasma species, including both hydrogenic and impurity species, at the boundary are assumed to be a large fraction of its line averaged density. For the pellet's behaviors in the hot plasma, the Neutral Gas Shielding (NGS) model by Milora-Foster is used. It was found that the injection of pellet could result in further improvement of fusion performance from that of the formation of ITB. However, the impact of pellet injection is quite complicated. It is also found that the pellets cannot penetrate into a deep core of the plasma. The injection of the pellet results in a formation of density peak in the region close to the plasma edge. The injection of pellet can result in an improved nuclear fusion performance depending on the properties of pellet (i.e., increase up to 5% with a speed of 1 km/s and radius of 2 mm). A sensitivity analysis is carried out to determine the impact of pellet parameters, which are: the pellet radius, the pellet velocity, and the frequency of injection. The increase in the pellet radius and frequency were found to greatly improve the performance and effectiveness of fuelling. However, changing the velocity is observed to exert small impact.

Leekhaphan, P. [Thammasat University, School of Bio-Chemical Engineering and Technology, Sirindhorn International Institute of Technology (Thailand); Onjun, T. [Thammasat University, School of Manufacturing Systems and Mechanical Engineering, Sirindhorn International Institute of Technology (Thailand)

2011-04-15

194

High luminous efficiency characteristics of alternating current plasma display panel with delta color arrayed, enclosed barrier rib structure  

Microsoft Academic Search

The luminous efficiency characteristics of a new alternating current plasma display panel (ac PDP) structure with the segmented electrodes in delta color arrayed subpixels with enclosed barrier ribs (SDE) are investigated. The SDE structure which has a 4:3 horizontal to vertical cell dimension ratio showed higher luminance and luminous efficiency increment characteristics as the Xe partial pressure increased compared to

Tae Jun Kim; Cha Keun Yoon; Ki-Woong Whang

2006-01-01

195

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

196

Effects of plasma treatment in the tungsten process for chemical vapor deposition titanium nitride barrier film beyond nanometer technology  

Microsoft Academic Search

As the device shrunk to100 nm, the CVD TiN barrier filling would be limited by the process window of contact for both step coverage and plasma treatment. This limitation not only affects the step coverage capability but also poses a challenge to the treatment of the organic film with the small contact hole. In this study, we investigated whether the

K. W. Chen; Y. L. Wang; L. Chang; F. Y. Li; G. J. Hwang

2006-01-01

197

Enhanced Oxygen Barrier and Interfacial Adhesion of Polystyrene/Clay Nanocomposites via Plasma Surface Modification  

NASA Astrophysics Data System (ADS)

Bentonite layered-silicate was the selected nanofiller to be studied and filled in polystyrene, consequently represented PS/clay nanocomposites. The plasma technique developed in our laboratory was utilized as the clay pretreatment method to provide the radical sites on the clay surface prior to styrene grafting step. Gas barrier property and impact strength, one of the most serious deficiencies of polystyrene, were examined. Oxygen permeability was found to be decreased moderately even small amount of modified clay loaded. As the result of plasma surface modification, it was found that grafting of styrene was occurred mainly on the outer clay layer since FT-IR spectra showed the characteristic peak of polystyrene with the same basel-spacing like pristine clay. The broadening of diffraction peak of PS/clay nanocomposites produced by melt intercalation was observed suggesting the structure of both intercalation and partial exfoliation; however, the impact strength was reasonably improved which can imply to the enhancement of interfacial adhesion between clay particles and polystyrene matrix. In addition, the ratio of styrene and initiator played the significant role on these properties as well.

Tasanatanachai, Patchara; Magaraphan, Rathanawan

2007-03-01

198

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

2013-08-01

199

A cold plasma dielectric barrier discharge atomic emission detector for atmospheric mercury.  

PubMed

An automated atmospheric elemental mercury analyzer based on the dielectric barrier discharge (DBD) atomic emission technique was developed. The instrument is based on a gold-on tungsten coiled filament preconcentrator fashioned from commercial quartz-halogen lamps, a DBD excitation source and a radiation detector. An in-house program provided system control and data collection. Several types of radiation detectors, e.g., charge coupled device (CCD) array spectrometers, photomultiplier tubes (PMTs) and phototube (PT) are investigated. An argon plasma provided better performance than a nitrogen plasma. With approximately 0.88 standard liters per min sampling rate and preconcentration for 2min, the estimated (S/N=3) detection limit was 0.12ng/L (Hg(0)), the linear range extended at least to 6.6ngHg/L. Typical RSD values for determination at the single digit ng/L level ranged from 2.8 to 4.9%. In 19 separate calibrations conducted over 7 days, the calibration slope had a standard error of 1%. The system was applied to the determination of atmospheric mercury in two different locations. PMID:20298901

Puanngam, Mahitti; Ohira, Shin-Ichi; Unob, Fuangfa; Wang, Jian-Hua; Dasgupta, Purnendu K

2010-02-06

200

Simulataneous pentachlorophenol decomposition and granular activated carbon regeneration assisted by dielectric barrier discharge plasma.  

PubMed

An integrated granular activated carbon (GAC) adsorption/dielectric barrier discharge (DBD) process was applied to the treatment of high concentration pentachlorophenol (PCP) wastewater. The PCP in water firstly was adsorbed onto GAC, and then the degradation of PCP and regeneration of exhausted GAC were simultaneously carried out by DBD. The degradation mechanisms and products of PCP loaded on GAC were analyzed by EDX, FT-IR and GC-MS. The results suggested that the C-Cl bonds in PCP adsorbed by GAC were cleaved by DBD plasma, and some dechlorination and dehydroxylation products were identified. The adsorption capacity of adsorption/DBD treated GAC could maintain relatively high level, which confirmed that DBD treatment regenerated the GAC for subsequent reuse. The adsorption of N2, Boehm titration and XPS were used to investigate detailed surface characterizations of GAC. It could be found that DBD plasma not only increased the BET surface area and pore volume in micropore regions, but also had remarkably impact on the distribution of the oxygen-containing functional groups of GAC. PMID:19656621

Qu, Guang-Zhou; Lu, Na; Li, Jie; Wu, Yan; Li, Guo-Feng; Li, Duan

2009-07-16

201

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

202

Development and evaluation of suspension plasma sprayed yttria stabilized zirconia coatings as thermal barriers  

NASA Astrophysics Data System (ADS)

The insulating effects from thermal barrier coatings (TBCs) in gas turbine engines allow for increased operational efficiencies and longer service lifetimes. Consequently, improving TBCs can lead to enhanced gas turbine engine performance. This study was conducted to investigate if yttria-stabilized zirconia (YSZ) coatings, the standard industrial choice for TBCs, produced from nano-sized powder could provide better thermal insulation than current commericial YSZ coatings generated using micron-sized powders. The coatings for this research were made via the recently developed suspension plasma spraying (SPS) process. With SPS, powders are suspended in a solvent containing dispersing agents; the suspension is then injected directly into a plasma flow that evaporates the solvent and melts the powder while transporting it to the substrate. Although related to the industrial TBC production method of air plasma spraying (APS), SPS has two important differences---the ability to spray sub-micron diameter ceramic particles, and the ability to alloy the particles with chemicals dissolved in the solvent. These aspects of SPS were employed to generate a series of coatings from suspensions containing ˜100 nm diameter YSZ powder particles, some of which were alloyed with neodymium and ytterbium ions from the solvent. The SPS coatings contained columnar structures not observed in APS TBCs; thus, a theory was developed to explain the formation of these features. The thermal conductivity of the coatings was tested to evaluate the effects of these unique microstructures and the effects of the alloying process. The results for samples in the as-sprayed and heat-treated conditions were compared to conventional YSZ TBCs. This comparison showed that, relative to APS YSZ coatings, the unalloyed SPS samples typically exhibited higher as-sprayed and lower heat-treated thermal conductivities. All thermal conductivity values for the alloyed samples were lower than conventional YSZ TBCs. The different thermal conduction behaviors were linked to the porosity and compositional properties of the coatings using immersion density, SEM, and synchrotron radiation characterization techniques.

van Every, Kent J.

203

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

204

Properties of Dielectric-Barrier-Free Atmospheric Pressure Micro Plasma Driven by Sub-Micro Second DC Pulse Voltage  

NASA Astrophysics Data System (ADS)

An atmospheric pressure micro-plasma driven by a DC pulse has been developed. This device consists of He flowing two dielectric-free metal electrodes with a voltage pulse shorter than 500 ns, thus it maintains a glow discharge. Spatio-temporal measurements by the optical emission spectroscopy show that the change of partialpressure ratio between He and N2 is one of the most important factors affecting the discharge properties. The enhancement of the oxygen emissions for higher He flow rate mainly comes during afterglow, which suggests that the dissociative excitation of O2 by He metastable states is critical process for effective generation of oxygen radicals. As an alternative of atmospheric pressure micro plasma jet based on the dielectric barrier discharge or rf- driven micro plasma, dc pulse driven dielectric barrier-free configuration discharge can be used as an efficient and cost effective source for bio-medical and material processing applications.

Lee, Hae June; Ha, Chang Seung; Lee, Ho-Jun; Kim, Dong-Hyun

2009-10-01

205

Determination of fluorine, chlorine, bromine and iodine by barrier discharge radiofrequency helium plasma.  

PubMed

A determination method of fluorine (F), chlorine (Cl), bromine (Br) and iodine (I) by a barrier discharge radiofrequency helium plasma-atomic emission spectroscopy was developed. A borosilicate glass was wrapped by two copper film electrodes, one of which was earthed, and the other was supplied with a radiofrequency high voltage (98 kHz, 3.2 kV), resulting in a discharge inside of the tube. An optical emission from the discharge tube was introduced to a charge-coupled device (CCD)-spectrometer through an optical fiber, and was monitored in the wavelength range of 730-960 nm. The emission lines of F (733.2 nm, 739.9 nm), Cl (833.3 nm, 837.6 nm, 858.6 nm, 894.8 nm, 912.1 nm, etc.), Br (827.2 nm, 882.5 nm, 889.8 nm, 926.5 nm, etc.) and I (905.8 nm) were observed. The linearity of the calibration was determined for F and Cl over the range of 1-10 microg, and for Br of 0.1-1 microg. The relative emission intensity was in the order of Br > I > Cl >F. PMID:12458701

Watanabe, Nobuhisa; Buscher, Wolfgang; Böhm, Günter

2002-11-01

206

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

SciTech Connect

With a proper combination of applied voltage and the width of ground electrode, atmospheric pressure plasma jets extending beyond the ground electrode, whether it sits on the downstream or the upstream side, can be equally obtained with a dielectric barrier discharge setup, which can be ascribed to the overflow of deposited charges [J. Appl. Phys. 106, 013308 (2009)]. Here, we show that, by using narrower ground electrodes, such an overflow jet can be successfully launched at a much reduced voltage (down to below 10 kV). Moreover, by using transparent and triadic ground electrodes, development of charge overflow beneath the ground electrode was temporally and spatially resolved. Temporal evolution of discharge currents measured on the severed ground electrode helps establish the propagation dynamics of discharges along the dielectric surface beneath ground electrode, and also reinforces the conception that the streamer's head is in connection to the active electrode via a conducting channel. A small propagation velocity of 3.3x10{sup 3} m/s was measured for the ''overflow'' jet inside the dielectric tube. The availability of such overflow jets is enormously advantageous concerning their application to living bodies, to which the high voltage at active electrode is lethally dangerous.

Jiang Nan; Ji Ailing; Cao Zexian [Beijing National Laboratory for Condensed Matters, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China)

2010-08-15

207

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

2009-05-18

208

Influence of wall-charge accumulation on the gas dielectric barrier discharge in alternating current plasma display panel  

Microsoft Academic Search

Influences of wall-charge accumulation on gas dielectric barrier discharge (DBD) breakdown threshold and sustaining voltage margin of alternating current plasma display panel (AC-PDP) were investigated. It is observed that wall-charge accumulation results in a remarkable increase of gas DBD breakdown threshold during sustaining discharge period. Sustaining voltage margin is reduced by the threshold increase. A larger margin can be obtained

Bingang Guo; Wei Wei; Tsutae Shinoda; Chunliang Liu

2007-01-01

209

SiOâ-like film deposition by dielectric barrier discharge plasma gun at ambient temperature under an atmospheric pressure  

Microsoft Academic Search

A medium-frequency dielectric barrier discharge (DBD) plasma gun was used to deposit SiOâ-like films at ambient temperature under atmospheric pressure. SiOâ-like films were deposited on Si and stainless-steel surfaces by flowing Ar gas containing hexamethyldisiloxane (HMDSO) monomer through the gun. The authors found that the chemical structure of the deposited SiOâ-like film strongly depended on the HMDSO monomer ratio in

Chen Qiang; Zhang Yuefei; Han Erli; Ge Yuanjing

2006-01-01

210

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

Microsoft Academic Search

In order to investigate crack initiation sites and the crack propagation behavior in connection with the microstructure of thermal barrier coating (TBC) systems under creep and fatigue loadings, the failure behavior was observed in situ for plasma-sprayed TBC systems by optical microscopy, as a first step for elucidating the thermo-mechanical failure mechanism. Two types of TBC systems with differing top-coat

Satoru Takahashi; Yoshio Harada

2010-01-01

211

FAST TRACK COMMUNICATION: Atmospheric-pressure plasma CVD of TiO2 photocatalytic films using surface dielectric barrier discharge  

Microsoft Academic Search

Surface dielectric barrier discharge (DBD) was used for atmospheric-pressure plasma CVD of TiO2 films from TiCl4 and O2 for the first time. Under this experiment, the deposition rate was estimated at 22 nm min-1 by scanning electron microscope observation and the as-deposited TiO2 films were amorphous as evidenced by Raman analysis. The photocatalytic application of TiO2 films in removing HCHO

Lan-Bo Di; Xiao-Song Li; Chuan Shi; Yong Xu; De-Zhi Zhao; Ai-Min Zhu

2009-01-01

212

Optically driven nanotube actuators  

NASA Astrophysics Data System (ADS)

Optically driven actuators have been fabricated from single-wall carbon nanotube-polymer composite sheets. Like natural muscles, the millimetre-scale actuators are assemblies of millions of individual nanotube actuators processed into macroscopic length scales and bonded to an acrylic elastomer sheet to form an actuator that have been shown to generate higher stress than natural muscles and higher strains than high-modulus piezoelectric materials. Strain measurements revealed 0.01%-0.3% elastic strain generated due to electrostatic and thermal effects under visible light intensities of 5-120 mW cm-2. An optically actuated nanotube gripper is demonstrated to show manipulation of small objects. This actuation technology overcomes some of the fundamental limitations such as the use of high voltages or electrochemical solutions for actuation, opening up possibilities for remote light-induced actuation technologies.

Lu, Shaoxin; Panchapakesan, Balaji

2005-11-01

213

Uniaxial Electric Actuator  

NSDL National Science Digital Library

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

2012-12-19

214

Separation Spring Actuator.  

National Technical Information Service (NTIS)

The patent application relates to an actuator adapted for use in separating two interconnected bodies, while maintaining their respective desired directions. In the preferred embodiment, the actuator includes a housing which supports and guides a captive ...

C. F. Seifert

1975-01-01

215

Control of Smart Actuators.  

National Technical Information Service (NTIS)

Hysteresis in smart materials hinders wider applicability of such materials in actuators and sensors. In this dissertation we study modeling, identification and control of hysteresis in smart actuators. While the approaches are applicable to control of a ...

X. Tan

2002-01-01

216

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

217

Folded dielectric elastomer actuators  

Microsoft Academic Search

Polymer-based linear actuators with contractile ability are currently demanded for several types of applications. Within the class of dielectric elastomer actuators, two basic configurations are available today for such a purpose: the multi-layer stack and the helical structure. The first consists of several layers of elementary planar actuators stacked in series mechanically and parallel electrically. The second configuration relies on

Federico Carpi; Claudio Salaris; Danilo DeRossi

2007-01-01

218

Ultrathin-barrier AlN/GaN heterostructures grown by rf plasma-assisted molecular beam epitaxy on freestanding GaN substrates  

NASA Astrophysics Data System (ADS)

We report the structural and electrical properties of ultrathin-barrier AlN/GaN heterostructures grown on freestanding GaN substrates by rf plasma-assisted molecular beam epitaxy. Structures with barrier thicknesses between 1.5 nm and 7.5 nm were grown and characterized. We observe that AlN/GaN structures with barriers of 3.0 nm exhibit the highest Hall mobility, approximately 1700 cm2/Vs. Furthermore, the Hall mobility is much diminished in heterostructures with AlN barriers thicker than 4.5 nm, coincident with the onset of strain relaxation.

Storm, D. F.; Deen, D. A.; Katzer, D. S.; Meyer, D. J.; Binari, S. C.; Gougousi, T.; Paskova, T.; Preble, E. A.; Evans, K. R.; Smith, David J.

2013-10-01

219

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

220

Sintering and Fracture Behavior of Plasma-Sprayed Thermal Barrier Coatings.  

National Technical Information Service (NTIS)

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. There is a need to characterize the fundamental sintering and ...

D. Zhu S. R. Choi R. A. Miller

2004-01-01

221

Considerations for contractile electroactive materials and actuators  

NASA Astrophysics Data System (ADS)

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

Rasmussen, Lenore; Schramm, David; Rasmussen, Paul; Mullally, Kevin; Meixler, Lewis D.; Pearlman, Daniel; Kirk, Alice

2011-03-01

222

Considerations for Contractile Electroactive Materials and Actuators  

SciTech Connect

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

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

2011-05-23

223

Influence of wall-charge accumulation on the gas dielectric barrier discharge in alternating current plasma display panel  

SciTech Connect

Influences of wall-charge accumulation on gas dielectric barrier discharge (DBD) breakdown threshold and sustaining voltage margin of alternating current plasma display panel (AC-PDP) were investigated. It is observed that wall-charge accumulation results in a remarkable increase of gas DBD breakdown threshold during sustaining discharge period. Sustaining voltage margin is reduced by the threshold increase. A larger margin can be obtained when the threshold is decreased by removing unfavorable influence of wall-charge accumulation. Compared with normal margin, improved margin has a larger value and a faster linear increase with increasing wall-charge voltage. That indicates a way to improve AC-PDP performances remarkably.

Guo Bingang; Wei Wei; Shinoda, Tsutae; Liu Chunliang [Advanced Display Research Center, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba Meguro-Ku, Tokyo 153-8505 (Japan); Key Laboratory for Physical Electronics and Devices of the Ministry of Education of China, Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710049 (China)

2007-03-05

224

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

Microsoft Academic Search

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

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

2011-01-01

225

Control of plasma profiles in DIII-D discharges  

NASA Astrophysics Data System (ADS)

Active control of plasma profiles is an essential requirement for operating within plasma stability limits, for steady-state operation and for optimization of the plasma performance. In DIII-D, plasma profiles have been actively controlled using various actuators in the following manner: (a) real time closed loop control of the q profile evolution using electron cyclotron heating and neutral beam injection as actuators; (b) active control of the density and pressure profiles in quiescent H-mode and quiescent double barrier plasmas using electron cyclotron current drive (ECCD) and pellet injection; (c) active control of the edge profiles to suppress edge localized modes using resonant magnetic perturbation with toroidal mode number n = 3, (d) real time control of the current density profile to suppress neoclassical tearing modes using localized deposition of co-ECCD.

Gohil, P.; Evans, T. E.; Ferron, J. R.; Moyer, R. A.; Petty, C. C.; Burrell, K. H.; Casper, T. A.; Garofalo, A. M.; Hyatt, A. W.; Jayakumar, R. J.; Kessel, C.; Kim, J. Y.; La Haye, R. J.; Lohr, J.; Luce, T. C.; Makowski, M. A.; Mazon, D.; Menard, J.; Murakami, M.; Politzer, P. A.; Prater, R.; Wade, M. R.

2006-05-01

226

Characteristics of NOx Removal Combining Dielectric Barrier Discharge Plasma with Selective Catalytic Reduction by C3H6  

NASA Astrophysics Data System (ADS)

Characteristics of NOx removal combining dielectric barrier discharge (DBD) plasma with selective catalytic reduction (SCR) by C3H6 were investigated under the conditions of high NOx concentration and high space velocity at various temperatures. Experiment results show that there were no obvious removal of NOx and NO in the only C3H6-SCR system and only DBD system individually. But the high NOx removal rate was achieved in C3H6-SCR cooperating with DBD plasma system. Especially NOx removal rate can reach up to 88.5% at 150 °C simulating diesel engine exhaust temperature. It can be seen that when discharge comes into being, the catalystic activity was enhanced with discharge strengthened, so that the NOx was almost completely removed. In the course of NOx removal, DBD played an important role in oxidizing NO to NO2 and activating C3H6 and catalysts to reduce NOx.

Wang, Xing-Quan; Li, Yi; Chen, Wei; Lv, Guo-Hua; Huang, Jun; Zhu, Guo-Xian; Wang, Xiao-Qian; Zhang, Xian-Hui; Wang, Da-Cheng; Feng, Ke-Cheng; Yang, Si-Ze

2010-08-01

227

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

228

Characterization of ion heat conduction in JET and ASDEX Upgrade plasmas with and without internal transport barriers  

NASA Astrophysics Data System (ADS)

In ASDEX Upgrade and JET, the ion temperature profiles can be described by R/LTi which exhibits only little variations, both locally, when comparing different discharges, and radially over a wide range of the poloidal cross-section. Considering a change of the local ion heat flux of more than a factor of two, this behaviour indicates some degree of profile stiffness. In JET, covering a large ion temperature range from 1 to 25 keV, the normalized ion temperature gradient, R/LTi, shows a dependence on the electron to ion temperature ratio or toroidal rotational shear. In particular, in hot ion plasmas, produced predominantly by neutral beam heating at low densities, in which large Ti/Te is coupled to strong toroidal rotation, the effect of the two quantities cannot be distinguished. Both in ASDEX Upgrade and JET, plasmas with internal transport barriers (ITBs), including the PEP mode in JET, are characterized by a significant increase of R/LTi above the value of L- and H-mode plasmas. In agreement with previous ASDEX Upgrade results, no increase of the ion heat transport in reversed magnetic shear ITB plasmas is found in JET when raising the electron heating. Evidence is presented that magnetic shear directly influences R/LTi, namely decreasing the ion heat transport when going from weakly positive to negative magnetic shear.

Wolf, R. C.; Baranov, Y.; Garbet, X.; Hawkes, N.; Peeters, A. G.; Challis, C.; de Baar, M.; Giroud, C.; Joffrin, E.; Mantsinen, M.; Mazon, D.; Meister, H.; Suttrop, W.; Zastrow, K.-D.; ASDEX Upgrade Team; EFDA-JET Workprogramme, contributors to the

2003-09-01

229

Kinetic modeling of plasma methane conversion in a dielectric barrier discharge  

Microsoft Academic Search

Methane conversion by plasma offers a promising route to produce higher value-added products. As plasma reaction is a relatively complex process, kinetic modeling is necessary to obtain a general pattern of the complex interaction on the basis of chemical reaction and products. In this paper, we present a method to obtain the kinetic rate coefficient (k) from the experimental data.

Antonius Indartoa; Nowarat Coowanitwong; Jae-Wook Choi; Hwaung Lee; Hyung Keun Song

2008-01-01

230

Modelling of nitrogen plasma parameters in a ferro-electric packed bed barrier discharge  

Microsoft Academic Search

In order to optimize the operation of the ferro-electric packed bed reactor for gaseous pollution controls, a physical model was developed to predict various plasma parameters based on experimental current-voltage characteristics. The chemical kinetic model to predict ion and radical species was developed for pure nitrogen plasma. In this paper, we studied the effect of pellet dielectric constants, applied voltage

K. Takaki; M. B. Chang; T. Kawasaki; T. Ohkubo; S. Kanazawa; T. Nomoto; J. S. Chang

2001-01-01

231

Development and evaluation of suspension plasma sprayed yttria stabilized zirconia coatings as thermal barriers  

Microsoft Academic Search

The insulating effects from thermal barrier coatings (TBCs) in gas turbine engines allow for increased operational efficiencies and longer service lifetimes. Consequently, improving TBCs can lead to enhanced gas turbine engine performance. This study was conducted to investigate if yttria-stabilized zirconia (YSZ) coatings, the standard industrial choice for TBCs, produced from nano-sized powder could provide better thermal insulation than current

Kent J. van Every

2009-01-01

232

Analysis of the degradation mechanism of methylene blue by atmospheric pressure dielectric barrier discharge plasma  

Microsoft Academic Search

The degradation of a methylene blue solution using the dielectric barrier discharge (DBD) technique is proposed in this paper. The effect of pH on the degradation rate is also investigated. The concentration of oxidants in the liquid phase is tested through iodimetry. The key factors that affect the degradation rate of the methylene blue solution are analyzed. The intermediate and

Fangmin Huang; Li Chen; Honglin Wang; Zongcheng Yan

2010-01-01

233

An asymmetrically surface-modified graphene film electrochemical actuator.  

PubMed

It is critically important to develop actuator systems for diverse needs ranging from robots and sensors to memory chips. The advancement of mechanical actuators depends on the development of new materials and rational structure design. In this study, we have developed a novel graphene electrochemical actuator based on a rationally designed monolithic graphene film with asymmetrically modified surfaces. Hexane and O(2) plasma treatment were applied to the opposite sides of graphene film to induce the asymmetrical surface properties and hence asymmetrical electrochemical responses, responsible for actuation behaviors. The newly designed graphene actuator demonstrated here opens a new way for actuator fabrication and shows the potential of graphene film for applications in various electromechanical systems. PMID:20828146

Xie, Xuejun; Qu, Liangti; Zhou, Ce; Li, Yan; Zhu, Jia; Bai, Hua; Shi, Gaoquan; Dai, Liming

2010-10-26

234

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

235

Fast contracting polypyrrole actuators  

Microsoft Academic Search

Conducting polymer-based actuators are capable of producing at least 10 times more force for a given cross-sectional area (active stress) than skeletal muscle, and potentially 1000 times more, with strains typically between 1% and 10%. Low operating voltages make them particularly attractive for use in micro-electromechanical systems, in place of electrostatic and piezoelectric actuators. A drawback of conducting polymer actuators

John D Madden; Ryan A Cush; Tanya S Kanigan; Ian W Hunter

2000-01-01

236

Microbubble powered actuator  

Microsoft Academic Search

A micromechanical, bubble-powered actuator is presented which can produce mechanical displacements as large as 140 ?m of a polysilicon actuator plate in a direction perpendicular to the substrate with as little as 8.4 mA input current. This device has been designed, fabricated, and successfully tested to have controllable displacement in a nonconducting liquid (Fluorinert FC43). The principle of actuation is

Liwei Lin; Albert P. Pisano; Abraham P. Lee

1991-01-01

237

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

238

Surface structure and surface barrier characteristics of boron-doped diamond in electrolytes after CF 4 plasma treatment in RF-barrel reactor  

Microsoft Academic Search

We report on the effects of CF4 plasma process in technical RF barrel reactor on surface termination and the resulting electronic surface barrier of boron-doped diamond in electrolytes. The surface characteristics were evaluated for epitaxial single crystalline layers with sub-nm roughness. The capacitance–voltage characteristics of the processes electrodes implied a low electronic barrier at the fluorine-terminated areas, comparable to hydrogen

A. Denisenko; A. Romanyuk; C. Pietzka; J. Scharpf; E. Kohn

2010-01-01

239

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

Microsoft Academic Search

Surface microcompression is a very important technique to characterize the mechanical properties of film and coating systems. In this paper, surface microcompression simulation for La2Zr2O7 (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

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

2011-01-01

240

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

241

Resistive Fluid Turbulence in Diverted Tokamaks and the Edge Transport Barrier in H-Mode Plasmas.  

National Technical Information Service (NTIS)

The thermal and particle diffusivities driven by resistive fluid turbulence in diverted tokamak edge plasmas are calculated. Diverted tokamak geometry is characterized by increased global shear near the separatrix and the tendency of field lines to linger...

T. S. Hahm P. H. Diamond

1986-01-01

242

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

2011-09-21

243

Study of plasma confinement in the L-2M stellarator during the formation of an edge transport barrier  

SciTech Connect

A plasma confinement mode characterized by the formation of an edge transport barrier (ETB) was discovered in the L-2M stellarator after boronization of the vacuum vessel wall. The transition into this mode is accompanied by a jump in the electron temperature by 100-200 eV at the plasma edge and a sharp increase in the gradient of the electron temperature T{sub e} in this region. The threshold power for the transition into the ETB confinement mode with an increased electron temperature gradient is P{sub thr}{sup {nabla}Te} = (60 {+-} 15)n{sub e} [10{sup 19} m{sup -3}] kW. The formation of the ETB manifests itself also in a substantial change in the electron density profile. A density peak with a steep gradient at the outer side forms at the plasma edge. The threshold power for the transition into the ETB confinement mode corresponding to a substantial increase in the plasma density gradient near r = a is P{sub thr}{sup {nabla}Te} = (67 {+-} 9)n{sub e} [10{sup 19} m{sup -3}] kW, which agrees to within experimental error with the threshold power for the transition into the ETB confinement mode determined from the sharp increase in the gradient of the electron temperature T{sub e}. The value of P{sub thr} for the L-2M stellarator agrees to within 25% with that obtained from the tokamak scaling. In the ETB confinement mode, the plasma energy W and the energy confinement time {tau}{sub E} determined from diamagnetic measurements increase by 20-30% as compared to those obtained from the stellarator scaling for the confinement mode without an ETB. When the heating power increases by a factor of 2-3 above the threshold value, the effects related to improved energy confinement disappear.

Voronov, G. S.; Akulina, D. K.; Batanov, G. M.; Berezhetskii, M. S.; Vasil'kov, D. G.; Vafin, I. Yu.; Voronova, E. V.; Grebenshchikov, S. E.; Grishina, I. A.; Kolik, L. V.; Larionova, N. F.; Logvinenko, V. P.; Malakhov, D. V.; Meshcheryakov, A. I.; Nechaev, Yu. I.; Petrov, A. E.; Sarksyan, K. A.; Saenko, V. V.; Skvortsova, N. N.; Fedyanin, O. I. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation)

2010-07-15

244

Study of plasma confinement in the L-2M stellarator during the formation of an edge transport barrier  

NASA Astrophysics Data System (ADS)

A plasma confinement mode characterized by the formation of an edge transport barrier (ETB) was discovered in the L-2M stellarator after boronization of the vacuum vessel wall. The transition into this mode is accompanied by a jump in the electron temperature by 100-200 eV at the plasma edge and a sharp increase in the gradient of the electron temperature T e in this region. The threshold power for the transition into the ETB confinement mode with an increased electron temperature gradient is P {thr/? Te } = (60 ± 15) n e [1019 m-3] kW. The formation of the ETB manifests itself also in a substantial change in the electron density profile. A density peak with a steep gradient at the outer side forms at the plasma edge. The threshold power for the transition into the ETB confinement mode corresponding to a substantial increase in the plasma density gradient near r = a is P {thr/? Te } = (67 ± 9) n e [1019 m-3] kW, which agrees to within experimental error with the threshold power for the transition into the ETB confinement mode determined from the sharp increase in the gradient of the electron temperature T e . The value of P thr for the L-2M stellarator agrees to within 25% with that obtained from the tokamak scaling. In the ETB confinement mode, the plasma energy W and the energy confinement time ? E determined from diamagnetic measurements increase by 20-30% as compared to those obtained from the stellarator scaling for the confinement mode without an ETB. When the heating power increases by a factor of 2-3 above the threshold value, the effects related to improved energy confinement disappear.

Voronov, G. S.; Akulina, D. K.; Batanov, G. M.; Berezhetskii, M. S.; Vasil'Kov, D. G.; Vafin, I. Yu.; Voronova, E. V.; Grebenshchikov, S. E.; Grishina, I. A.; Kolik, L. V.; Larionova, N. F.; Logvinenko, V. P.; Malakhov, D. V.; Meshcheryakov, A. I.; Nechaev, Yu. I.; Petrov, A. E.; Sarksyan, K. A.; Saenko, V. V.; Skvortsova, N. N.; Fedyanin, O. I.; Kharchev, N. K.; Khol'Nov, Yu. V.; Shchepetov, S. V.

2010-07-01

245

A study of remote plasma nitrided nGaAs\\/Au Schottky barrier  

Microsoft Academic Search

The use of GaN as an alternative interlayer for stable passivation of gallium arsenide surface is investigated. To this aim remote N2–H2 plasma nitridation of the n-doped gallium arsenide surface has been performed. The exposure time to N2–H2 plasmas has been varied in order to form ultrathin GaN layers with different thickness. Gallium nitride layer thickness and composition analysis have

M. Ambrico; M. Losurdo; P. Capezzuto; G. Bruno; T. Ligonzo; L. Schiavulli; I. Farella; V. Augelli

2005-01-01

246

Effective Actuation: High Bandwidth Actuators and Actuator Scaling Laws.  

National Technical Information Service (NTIS)

The project advances active flow control to enable new Air Force capabilities. Advances in both the development of new actuator hardware and in understanding the flow physics have been achieved. Four key new advances have been achieved in Phase I of this ...

A. B. Cain G. R. Raman E. J. Kerschen

2000-01-01

247

Terahertz dielectric properties of plasma-sprayed thermal-barrier coatings  

Microsoft Academic Search

We investigated the electromagnetic wave transmittance and dielectric properties of yttria partially stabilised zirconia thermal-barrier coatings by terahertz time-domain spectroscopy in which the samples were irradiated by a pulsed THz wave in the frequency range of 0.1–6.3THz. The coating microstructure was varied by changing the spray conditions and the THz transmittance and dielectric constants were examined as functions of frequency.

Makoto Watanabe; Seiji Kuroda; Hisashi Yamawaki; Mitsuharu Shiwa

2011-01-01

248

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

249

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

NASA Astrophysics Data System (ADS)

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 (INe) relative to Xe emission intensity (IXe) 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. INe/IXe 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; Uchida, Satoshi; Kajiyama, Hiroshi; Shinoda, Tsutae

2010-01-01

250

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

251

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

SciTech Connect

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

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

2008-07-15

252

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

253

Spectrally filtered ICCD-camera imaging of dielectric barrier discharge plasma jet using two crossed gas flows  

NASA Astrophysics Data System (ADS)

Temporally resolved imaging using an intensified charge-coupled device (ICCD) camera is one of the most effective ways for investigation of discharge behaviors in atmospheric-pressure plasmas. In a plasma jet using a dielectric barrier discharge (DBD) configuration with two crossed gas flows of pure He and Ar/acetone mixture, we have observed plasma jet propagations and transient glow discharge formation in the helium flow channel, and also a secondary discharge was ignited in the Ar/acetone flow channel when the applied voltage was in a falling slope. A transition point of the discharge between the He and Ar/acetone flows moved toward the upstream side. In order to analyze excited species formation in more detail, interference filters were used to identify discharge emissions from each excited species. From imaging results, by the spectrally filtered ICCD-camera, it was revealed that the transition point's movement was probably caused by the change of gas composition in the Ar/acetone flow, which was most likely due to the decomposition of acetone molecules by the collision with Ar metastable atoms. This effect was monitored from the time delayed C2 Swan band emission.

Urabe, Keiichiro; Sands, Brian; Sakai, Osamu; Ganguly, Biswa

2011-11-01

254

The effect of thermal aging on the thermal conductivity of plasma sprayed and EB-PVD thermal barrier coatings  

SciTech Connect

Thermal barrier coatings (TBCs) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBCs is of primary importance. Electron beam-physical vapor deposition (EV-PVD) and air plasma spraying (APS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The density of the APS coatings was controlled by varying the spray parameters. The low density APS yttria-partially stabilized zirconia (yttria-PSZ) coatings yielded a thermal conductivity that is lower than both the high density APS coatings and the EB-PVD coatings. The thermal aging of both fully and partially stabilized zirconia are compared. The thermal conductivity of the coatings permanently increases upon exposure to high temperatures. These increases are attributed to microstructural changes within the coatings. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the EB-PVD coatings are less susceptible to thermal aging effects, results suggest that they typically have a higher thermal conductivity than APS coatings before thermal aging. The increases in thermal conductivity due to thermal aging for plasma sprayed partially stabilized zirconia have been found to be less than for plasma sprayed fully stabilized zirconia coatings.

Dinwiddie, R.B.; Beecher, S.C.; Porter, W.D. [Oak Ridge National Lab., TN (United States); Nagaraj, B.A. [General Electric Co., Cincinnati, OH (United States). Aircraft Engine Group

1996-05-01

255

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

256

Helical dielectric elastomer actuators  

Microsoft Academic Search

This paper presents a new type of contractile polymer-based electromechanical linear actuator. The device belongs to the class of dielectric elastomer actuators, which are typically capable of undergoing large deformations induced by an applied electric field. It is based on a novel helical configuration, suitable for the generation of electrically driven axial contractions and radial expansions. The architecture, the principle

Federico Carpi; Antonio Migliore; Giorgio Serra; Danilo DeRossi

2005-01-01

257

Compliant actuator designs  

Microsoft Academic Search

In the growing fields of wearable robotics, rehabilitation robotics, prosthetics, and walking k robots, variable stiffness actuators (VSAs) or adjustable compliant actuators are being designed and implemented because of their ability to minimize large forces due to shocks, to safely interact with the user, and their ability to store and release energy in passive elastic elements. This review article describes

Ronald Ham; Thomas Sugar; Bram Vanderborght; Kevin Hollander; Dirk Lefeber

2009-01-01

258

Carbon Nanotube Actuators  

NASA Astrophysics Data System (ADS)

We have demonstrated a new type of electromechanical actuator, which is based on both a new type of actuator material (single-wall carbon nanotubes) and a new type of actuation mechanism (double-layer charge injection). Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. Higher stress generation capabilities than natural muscles and higher strains than high modulus ceramics were obtained in investigations of both all-solid-state and liquid-electrolyte-based devices. Evidence of giant charge injection is provided by in-situ measurements of electrochemical voltametry and Raman, UV-visible, and impedance spectroscopies. The results of ab initio quantum chemical calculations show that actuation arises from bond length changes that principally originate from quantum chemical effects, rather than electrostatic effects. Based on analysis of measurements, we conclude that nanotube actuators will eventually provide much higher specific work capacities and stress generation capabilities than alternative technologies, while operating at an order of magnitude lower voltages than ferroelectrics. We have demonstrated device operation to above 650 K, and conclude (based on observations of redox stability) that actuator operation to above 1300 K will eventually be feasible.

Baughman, Ray H.

2000-03-01

259

Smart Material-Actuated Rotor Technology – SMART  

Microsoft Academic Search

Vibration, noise, and aerodynamic design compromises are primary barriers to further improvements in effectiveness of the helicopter. The MD900 light utility helicopter main rotor system is modified to include in-blade smart material actuation for active control. A piezoelectric (PE)-driven trailing edge flap is used for vibration, noise, and aerodynamic performance improvements. A shape memory alloy (SMA)-driven trailing edge trim tab

Friedrich K. Straub; Dennis K. Kennedy; David B. Domzalski; Ahmed A. Hassan; Hieu Ngo; V. Anand; Terry Birchette

2004-01-01

260

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

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

Microstructure and indentation mechanical properties of plasma sprayed nano-bimodal and conventional ZrO 2-8wt%Y 2O 3 thermal barrier coatings  

Microsoft Academic Search

The nanostructured agglomerated feedstock used for plasma spraying was obtained by the nano-particle reconstituting technique. Nanostructured and conventional ZrO2-8wt%Y2O3 (8YSZ) thermal barrier coatings (TBCs) have been prepared by atmospheric plasma spraying (APS) on 45# steel substrates with the NiCrAlY as the bond-layer. The microstructure and phase composition of feedstocks and corresponding coatings were characterized. The top-layer of nanostructured 8YSZ TBCs

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

263

Measurement of the impulse produced by a pulsed surface discharge actuator in air  

NASA Astrophysics Data System (ADS)

The pulsed surface discharge in atmospheric pressure air generates a shock wave, thereby transferring an impulse to the surrounding gas. The aim of this work is to measure this impulse, using implementation of a plasma actuator based on linear surface discharges of length up to 10 cm, and of linear energy in a range 0.1–0.5 J cm?1. The shock wave generated by the discharge is visualized using a pulsed schlieren system and the impulse is measured with a dedicated balance. These measurements are correlated with 1D numerical simulations of pulsed energy depositions in a perfect gas. Experiments show that the discharge generates a cylindrical shock wave that travels at sonic speed after a few tens of microseconds, and produces an impulse that varies from 1 to 4 mN s m?1 and scales linearly with the linear energy density. This linearity agrees with the numerical simulations when 9.5% of the energy dissipated in the discharge is assumed to heat the gas. Overall, to produce a time-averaged force similar to the one achieved by dielectric barrier discharge (DBD) actuators, 2 to 3 times more power is required. However, surface discharge actuators do not saturate, and thus can induce time-averaged forces one or two orders of magnitude above DBD when pulsed at several hundreds of hertz.

Elias, P. Q.; Castera, P.

2013-09-01

264

Processing-structure-property relationships of thermal barrier coatings deposited using the solution precursor plasma spray process  

NASA Astrophysics Data System (ADS)

This research is intended to develop a novel process, solution-precursor plasma-spray (SPPS), for the deposition of highly durable thermal barrier coatings (TBCs). In the SPPS process a solution precursor feedstock, that results in ZrO2-7 wt% Y2O3 ceramic, is injected into the plasma jet and the coating is deposited on a metal substrate. The formed coating has the following novel microstructural features: (i) ultra-fine splats, (ii) through-thickness cracks, (iii) micrometer and nanometer porosity, and (iv) interpass boundaries. The deposition mechanisms of the solution precursor droplets injected into the different regions of the plasma jet were found to be different due to large temperature variation across the plasma jet. The solution precursor droplets injected into the core of the plasma jet are deposited on the substrate as ultra-fine splats that account for around 65 volume% of the coating. The other 35 volume% of the coating includes porosity and deposits formed from the solution precursor droplets injected into other regions of the plasma jet. The optimum processing condition for highly durable TBCs was determined using Taguchi design of experiments. Meanwhile, the relationship of the microstructural features and processing parameters was revealed. During thermal cycling, the unmelted particles in the coating were observed to pyloyze and/or sinter, while no sign of sintering was observed for the ultra-fine splats. The spacing of through-thickness cracks remains in the range of 160 to 190 mum throughout the thermal cycling test. Three stages of oxidation of the bond coat were observed. Failure of the SPPS TBC starts with the crack nucleation along the unmelted particles in the top coat and the Ni, Cr, Co-rich oxides of large thickness. These cracks propagate and coalesce with thermal cycling. The extensive cracking of the rapidly formed Ni, Cr, Co-rich oxides resulting from the depletion of aluminum in the bond coat leads to the development of large separation between TBC and substrate. When a separation of sufficient size emerges, the TBC starts to separate from the metal substrate by large scale buckling as a result of the small strain energy stored in the strain tolerant SPPS TBCs.

Xie, Liangde

265

MEMS actuated deformable mirror  

NASA Astrophysics Data System (ADS)

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, Alexandros; Olivier, Scot; Barbee, Troy; Walton, Chris; Cohn, Michael

2006-01-01

266

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

267

COMPARISON OF THERMAL PROPERTIES OF THERMAL BARRIER COATING DEPOSITED ON IN738 USING STANDARD AIR PLASMA SPRAY WITH 100HE PLASMA SPRAY SYSTEM  

SciTech Connect

A typical blade material is made of Nickel super alloy and can bear temperatures up to 950°C. But the operating temperature of a gas turbine is above the melting point of super alloy nearly at 1500°C. This could lead to hot corrosions, high temperature oxidation, creep, thermal fatigue may takes place on the blade material. Though the turbine has an internal cooling system, the cooling is not adequate to reduce the temperature of the blade substrate. Therefore to protect the blade material as well as increase the efficiency of the turbine, thermal barrier coatings (TBCs) must be used. A TBC coating of 250 ?m thick can reduce the temperature by up to 200° C. Air Plasma Spray Process (APS) and High Enthalpy Plasma Spray Process (100HE) were the processes used for coating the blades with the TBCs. Because thermal conductivity increases with increase in temperature, it is desired that these processes yield very low thermal conductivities at high temperatures in order not to damage the blade. An experiment was carried out using Flash line 5000 apparatus to compare the thermal conductivity of both processes.The apparatus could also be used to determine the thermal diffusivity and specific heat of the TBCs. 75 to 2800 K was the temperature range used in the experimentation. It was found out that though 100HE has high deposition efficiency, the thermal conductivity increases with increase in temperatures whiles APS yielded low thermal conductivities.

Uppu, N.; Mensah, P.F.; Ofori, D.

2006-07-01

268

Mullite-rich plasma electrolytic oxide coatings for thermal barrier applications  

Microsoft Academic Search

A study has been undertaken of the characteristics exhibited by mullite-rich plasma electrolytic oxide coatings grown on aluminium alloys by using silicate-rich electrolytes. It is found that they can be grown at a higher rate, and to a greater thickness, than alumina PEO coatings on aluminium. The thermal conductivity of these coatings has been measured using a steady-state method. It

J. A. Curran; H. Kalkanc?; Yu. Magurova; T. W. Clyne

2007-01-01

269

Anisotropic thermal conductivities of plasma-sprayed thermal barrier coatings in relation to the microstructure  

Microsoft Academic Search

Anisotropic thermal conductivities of the plasma-sprayed ceramic coating are explicitly expressed in terms of the microstructural\\u000a parameters. The dominant features of the porous space are identified as strongly oblate (cracklike) pores that tend to be\\u000a either parallel or normal to the substrate. The scatter in pore orientations is shown to have a pronounced effect on the effective\\u000a conductivities. The established

Igor Sevostianov; Mark Kachanov

2000-01-01

270

The deposition of oxygen containing plasma polymers for use as permeation barrier coatings  

Microsoft Academic Search

It has been found that common polymers containing oxygen have reduced hydrogen permeability. In this work we have incorporated oxygen into plasma polymer coatings as hydroxyl (OH) and carbonyl (C=O) side groups by codepositing organic vapors with HâO or HâOâ. We can vary the amount of oxygen incorporated up to 25 wt% oxygen. By adjusting the amount of incorporated oxygen

R. L. Crawley; J. L. Evans

1991-01-01

271

Use of indentation technique to measure elastic modulus of plasma-sprayed zirconia thermal barrier coating  

SciTech Connect

Elastic modulus of an yttria partially stabilized zirconia (YSZ) thermal barrier coating (TBC) was evaluated with a Knoop indentation technique. The measured elastic modulus values for the coating ranged from 68.4 {+-} 22.6 GPa at an indentation load of 50 g to 35.7 {+-} 9.8 at an indentation load of 300 g. At higher loads, the elastic modulus values did not change significantly. This steady-state value of 35.7 GPa for ZrO{sub 2} TBC agreed well with literature values obtained by the Hertzian indentation method. Furthermore, the measured elastic modulus for the TBC is lower than that reported for bulk ZrO{sub 2} ({approx} 190 GPa). This difference is believed to be due to the presence of a significant amount of porosity and microcracks in the TBCs. Hardness was also measured.

Singh, J.P.; Sutaria, M. [Argonne National Lab., IL (United States). Energy Technology Div.; Ferber, M. [Oak Ridge National Lab., TN (United States)

1997-01-01

272

Injection-molded PZT actuators  

NASA Astrophysics Data System (ADS)

Ceramics injection molding technology is being adapted for the fabrication of net shape piezoelectric actuators of lead zirconate titanate (PZT) and lead magnesium niobate (PMN). INjection molding offers low cost, high quality actuator components with a high degree of part-of-part reproducibility. Configurations under investigation include a proprietary high displacement linear element, air acoustic actuators, tube array actuators, benders, and various multilayer designs. Applications include conformable unidirectional patches for active noise and vibration control, high displacement bender actuators for active vortex generators and synthetic jets, high force-high displacement actuators for rotorblade flaps, and air acoustic actuators for active noise reduction.

Near, Craig D.; Schmidt, Gerald; McNeal, Kelley; Gentilman, Richard L.

1998-06-01

273

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

2013-02-05

274

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

275

Light actuated microfluidic devices  

Microsoft Academic Search

A light-actuated microfluidic device has been successfully fabricated to inject, move, separate, and merge liquid droplets with nano-liter volumes. Light actuation is realized by sandwiching the liquid droplets between two photosensitive surfaces whose wettability can be changed by light. By integrating a photoconductor with an electrowetting electrode, the surface tension at the liquid\\/solid interface above the electrode can be modified

Pei Yu Chiou; Zehao Chang; Ming C. Wu

2003-01-01

276

Laser Initiated Actuator study  

SciTech Connect

The program task was to design and study a laser initiated actuator. The design of the actuator is described, it being comprised of the fiber and body subassemblies. The energy source for all experiments was a Spectra Diode 2200-H2 laser diode. The diode is directly coupled to a 100 micron core, 0.3 numerical aperture fiber optic terminated with an SMA connector. The successful testing results are described and recommendations are made.

Watson, B.

1991-06-27

277

Local transport barrier formation and relaxation in reverse-shear plasmas on the TFTR tokamak  

SciTech Connect

The roles of turbulence stabilization by sheared E x B flow and Shafranov-shift gradients are examined for TFTR. Enhanced Reverse-Shear plasmas. Both effects in combination provide the basis of a positive-feedback model that predicts reinforced turbulence suppression with increasing pressure gradient. Local fluctuation behavior at the onset of ERS confinement is consistent with this framework. The power required for transitions into the ERS regime are lower when high power neutral beams are applied earlier in the current profile evolution, consistent with the suggestion that both effects play a role. Separation of the roles of E x B and Shafranov shift effects was performed by varying the E x B shear through changes in the toroidal velocity with nearly-steady-state pressure profiles. Transport and fluctuation levels increase only when E x B shearing rates are driven below a critical value that is comparable to the fastest linear growth rates of the dominant instabilities. While a turbulence suppression criterion that involves the ratio of shearing to linear growth rates is in accord with many of these results, the existence of hidden dependencies of the criterion is suggested in experiments where the toroidal field was varied. The forward transition into the ERS regime has also been examined in strongly rotating plasmas. The power threshold is higher with unidirectional injection than with balanced injection.

Synakowski, E.J.; Beer, M.A. [Princeton Univ., NJ (United States). Princeton Plasma Physics Lab.; Batha, S.H. [Fusion Physics and Technology, Torrance, CA (United States)] [and others

1997-02-01

278

A Simplified Numerical Study of the Kr/Cl2 Plasma Chemistry in Dielectric Barrier Discharge  

NASA Astrophysics Data System (ADS)

In this paper, the generation of excimers and exciplexe radiation in mixtures of rare gas with halogen by homogeneous dielectric barrier discharge (DBD) is investigated. The typical characteristics of an excilamp based on KrCl* exciplexe molecules and the kinetic processes for the formation and the decay of this molecules in the Kr/Cl2 mixture are studied. The computer model developed is based on the Kr/Cl2 mixture chemistry, the equivalent electric circuit and the Boltzmann equations. The importance in the kinetic processes of some species such as the metastable state of Krypton (Kr*(3P0,2)) and the negative ion of chloride (Cl?) is considered. The results illustrate the time variations of charged species (ne, Kr+, Cl?, Cl+, Cl+2, Kr+2), excited atoms and molecules (Kr*(3P0,2), Kr*(3P1), Cl*, Cl*2), the excimers (Kr*2, KrCl*(B), KrCl*(C), Kr2Cl*) and the UV photon concentrations (in 222 nm, 235 nm, 258 nm and 325 nm range). The effects of chlorine concentration and the total gas pressure in the Kr-Cl2 discharge on the electric parameters and radiation emissions are investigated.

N. Larbi Daho, Bachir; Belasri, A.

2013-04-01

279

FLUIDS, PLASMAS AND ELECTRIC DISCHARGES: The influence of the structures and compounds of DLC coatings on the barrier properties of PET bottles  

NASA Astrophysics Data System (ADS)

To reduce the oxygen transmission rate through a polyethylene terephthalate (PET) bottle (an organic plastic) diamond-like carbon (DLC) coatings on the inner surface of the PET bottle were deposited by radio frequency plasma-enhanced chemical vapour deposition (RF-PECVD) technology with C2H2 as the source of carbon and Ar as the diluted gas. As the barrier layer to humidity and gas permeation, this paper analyses the DLC film structure, composition, morphology and barrier properties by Fourier transform infrared, atomic force microscopy, scanning electron microscopy and oxygen transmission rate in detail. From the spectrum, it is found that the DLC film mainly consists of sp3 bonds. The barrier property of the films is significantly relevant to the sp3 bond concentration in the coating, the film thickness and morphology. Additionally, it is found that DLC film deposited in an inductively coupled plasma enhanced capacitively coupled plasma source shows a compact, homogeneous and crack-free surface, which is beneficial for a good gas barrier property in PET bottles.

Yang, Li; Wang, Zhen-Duo; Zhang, Shou-Ye; Yang, Li-Zhen; Chen, Qiang

2009-12-01

280

Considerations for Contractile Electroactive Materials and Actuators  

SciTech Connect

Ras Labs produces electroactive polymer (EAP) based materials and actuators that bend, swell, ripple and now contract (new development) with low electric input. This is an important attribute because of the ability of contraction to produce life-like motion. The mechanism of contraction is not well understood. Radionuclide-labeled experiments were conducted to follow the movement of electrolytes and water in these EAPs when activated. Extreme temperature experiments were performed on the contractile EAPs with very favorable results. One of the biggest challenges in developing these actuators, however, is the electrode-EAP interface because of the pronounced movement of the EAP. Plasma treatments of metallic electrodes were investigated in order to improve the attachment of the embedded electrodes to the EAP material. Surface analysis, adhesive testing, and mechanical testing were conducted to test metal surfaces and metal-polymer interfaces. The nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.

Lenore Rasmussen, Carl J. Erickson, Lewis D. Meixler, George Ascione, Charles A. Gentile, Carl Tilson, Stephen L. Bernasek, and Esta Abelev

2010-02-19

281

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

282

Impact of temperature increments on tunneling barrier height and effective electron mass for plasma nitrided thin SiO{sub 2} layer on a large wafer area  

SciTech Connect

Thermally grown SiO{sub 2} layers were treated by a plasma nitridation process realized in a vertical furnace. The combination of a pulsed-low frequency plasma and a microwave remote plasma with N{sub 2}/NH{sub 3}/He feed gas mixture was used to nitride the thermally grown SiO{sub 2} gate dielectrics of MIS structures. Temperature dependency of effective masses and the barrier heights for electrons in pure thermally grown SiO{sub 2} as well as plasma nitrided SiO{sub 2} in high electric field by means of Fowler-Nordheim regime was determined. It is frequently seen from the literature that either effective electron mass or barrier height (generally effective electron mass) is assumed to be a constant and, as a result, the second parameter is calculated under the chosen assumption. However, in contrast to general attitude of previous studies, this work does not make any such assumptions for the calculation of neither of these two important parameters of an oxide at temperature ranges from 23 to 110 deg. C for SiO{sub 2}, and 23 to 130 deg. C for nitrided oxide. It is also shown here that both parameters are affected from the temperature changes; respectively, the barrier height decreases while the effective mass increases as a result of elevated temperature in both pure SiO{sub 2} and plasma nitrided SiO{sub 2}. Therefore, one parameter could be miscalculated if the other parameter, i.e., effective mass of electron, was assumed to be a constant with respect to variable physical conditions like changing temperature. Additionally, the barrier heights were calculated just by taking constant effective masses for both types of oxides to be able to compare our results to common literature values.

Aygun, G. [Fraunhofer IISB, Schottkystrasse 10, 91058 Erlangen (Germany); Department of Physics, Izmir Institute of Technology, TR-35430 Urla, Izmir (Turkey); Roeder, G.; Erlbacher, T.; Wolf, M.; Schellenberger, M.; Pfitzner, L. [Fraunhofer IISB, Schottkystrasse 10, 91058 Erlangen (Germany)

2010-10-15

283

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

SciTech Connect

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

Taherzadeh, M.

1987-11-13

284

Thermo-mechanical behaviour of plasma sprayed yttria stabilized zirconia thermal barrier coatings  

NASA Astrophysics Data System (ADS)

Thermally sprayed ceramic coatings deposited from agglomerated feedstock powder have often demonstrated improved properties relative to coatings produced from conventional powders. These types of coatings have been reported to exhibit better wear resistance and higher adhesion strength compared to conventional deposits. In order to apply these types of coatings on turbine blades and diesel engine combustion chambers, the thermo-mechanical properties of plasma sprayed yttria stabilized zirconia coating were investigated. Creep strains and creep rates were measured using free standing thick coatings (3 mm) loaded in the four-point bend configuration at a range of temperatures (from 800 to 1200°C in air) and loads (27 to 49 N). Creep exponents and activation energy of the coatings were measured and the results were compared. Under the same test conditions the coating produced from agglomerated feedstock showed a lower creep strain than that produced from conventional powders. The creep strain of deposits was correlated to the microstructure of the coating. A model was developed to predict creep behaviour of coatings based on the thickness of splats. The results showed that the creep resistance is directly proportional to the splat thickness; the thicker the splat the higher is the creep resistance. The effect of splat interface on physical and mechanical properties of zirconia, such as thermal conductivity and elastic modulus of coatings, was investigated, too. It was shown that the high density of splat interfaces results in a lower thermal conductivity and elastic modulus.

Soltani, Reza

285

Diagnosis of hydrogen anions (H-,H3-) from the near-electrode region of dielectric-barrier-discharge plasmas  

NASA Astrophysics Data System (ADS)

Hydrogen anions (H-,H3-) from the near-ground-electrode region in dielectric barrier discharge hydrogen plasmas were characterized using a molecular-beam mass spectrometer under the pressure of 1.5-60 Torr. The measured H- current is more than one to a few orders of magnitude greater than that of H3- at pressure of 1.5-7.6 Torr with a peak-to-peak voltage of 40 kV and a 35 kHz ac power source. At the gas pressure range of 7.6-60 Torr, only the H- ionic signal is observed. The hydrogen-ion currents rise with the increasing of discharge voltage and ac frequency, but exhibit a maximum over the H2 pressure range studied. The dominant formation mechanism for the H- and H3- anions in the alternative and temporary cathode sheath near the discharge electrode has been discussed. The dependence of the mean energy of H- and H3- anions on H2 pressure has been also obtained.

Wang, Wenchun; Xu, Yong; Wang, Weiguo; Zhu, Aimin

2005-01-01

286

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

NASA Astrophysics Data System (ADS)

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

Takahashi, Satoru; Harada, Yoshio

287

Plasma binding and transport of diazepam across the blood-brain barrier. No evidence for in vivo enhanced dissociation.  

PubMed Central

The tissue uptake of extensively plasma-bound compounds is reportedly inconsistent with the conventional free-drug hypothesis limiting transport to unbound moiety in rapid intracapillary equilibrium with bound complex. Instead, protein-mediated/cell surface enhancement of dissociation has been postulated to occur in the microvasculature. This possibility was investigated by studying the passive transport of diazepam across the blood-brain barrier. Microdialysis probes placed within the vena cava and brain cortex were used to directly compare steady-state, interstitial unbound diazepam levels in both Wistar and genetically analbuminemic rats. The absence of albumin in the latter increased the unbound fraction of diazepam by almost fivefold; however, in both groups, the ratio of unbound concentrations in brain and blood at equilibrium was equal to unity. If enhanced dissociation occurred in the microvasculature, then the unbound brain level should have been greater than that in the systemic circulation. It is probable that earlier findings suggestive of protein-mediated transport reflect a nonequilibrium phenomenon. Comparison of the extent of diazepam's in vivo binding in blood by microdialysis to that estimated in vitro using conventional equilibrium dialysis with microcells showed good agreement, thus validating a widely accepted assumption of equivalency of these two values.

Dubey, R K; McAllister, C B; Inoue, M; Wilkinson, G R

1989-01-01

288

Streamer inhibition for improving force and electric wind produced by DBD actuators  

NASA Astrophysics Data System (ADS)

The use of thin wires from 13 to 300 µm in diameter as the exposed electrode of a surface dielectric barrier discharge (SDBD) plasma actuator is experimentally investigated by electrical and optical diagnostics, electrohydrodynamic force measurements and produced electric wind characterization from time-averaged and time-resolved measurements. The streamer inhibition and glow discharge enhancement due to the use of a thin wire active electrode fully modify the topology and the temporal behaviour of the thrust and the electric wind production. With a typical plate-to-plate DBD, the electric wind velocity increases during the negative going cycle. With a wire-to-plate design, both positive and negative going-cycle discharges result in an electric wind velocity increase. The four main quantitative results are as follows: (1) for a power consumption of 1 W cm-1, the force is increased from 65 to 95 mN m-1 when a 13 µm wire is used, (2) this corresponds to a 15% electric wind velocity enhancement, (3) electromechanical efficiency can be increased from 0.1% to 0.25%, (4) these improvements are applied for definition of a new multi-DBD design plasma actuator that allows us to produce a mean velocity of 10.5 m s-1.

Debien, Antoine; Benard, Nicolas; Moreau, Eric

2012-05-01

289

Application of In-Situ Nitrogen Plasma Treated Amorphous-like Tungsten Silicide Film as Barrier Material in the Application of Copper Gate Electrode  

NASA Astrophysics Data System (ADS)

An amorphous-like tungsten silicide film, deposited by chemical vapor deposition at a higher flow ratio of 2.5 of WF6/SiH4, was used as the barrier layer in the copper gate electrode. This film processes superior barrier characteristics to those of the typical tungsten film at a lower flow ratio of 0.4 of WF6/SiH4 because it lacks the fast diffusion paths of columnar grain boundaries. We proved that the film successfully suppressed copper atom diffusion toward the gate oxide during annealing at 600°C for 30 min. We also found that the amorphous-like tungsten silicide film exhibits better barrier characteristics after in-situ nitrogen plasma treatment at 300°C for 5 min.

Deng, I-Chung

2002-11-01

290

Microrobot actuated by soft actuators based on dielectric elastomer  

Microsoft Academic Search

In this paper a microrobot, mimicking annelid animals like the earthworm, is presented. The robot is composed of several ring-like segments. Each segment is able to generate three degree-of-freedom motions such as pan\\/tilt\\/up-down respectively, and it is actuated by three soft actuators located equidistantly along the circumferential direction. The soft actuator, called antagonistically-driven linear actuator (ANTLA), is based on polymer

H. R. Choi; S. M. Ryew; K. M. Jung; H. M. Kim; J. W. Jeon; J. D. Nam; R. Maeda; K. Tanie

2002-01-01

291

Piezoelectric microflextensional actuator  

NASA Astrophysics Data System (ADS)

This paper presents a novel micro flextensional actuator design consisting of bulk PZT bonded to a silicon microbeam. The fabrication process includes boron doping, EDP etching, dicing, and bonding to produce actuators with large displacements (8.7 ?m) and gain factors (32) at 100V. The theoretical model predicts that a thin beam with properly designed initial imperfection maximizes the actuator displacement and gain factor. For large PZT displacement, small imperfection maximizes gain factor but may not gaurantee, the desired (up or down) displacement direction. For small PZT displacement, large initial imperfection improves performance and guarantees displacement in the (desired) direction of the initial imperfection. The theoretical model, based on the measured initial beam shape, predicts the experimentally measured direction and magnitude of beam displacement for two devices.

Cheong, Jongpil; Tadigadapa, Srinivas A.; Rahn, Christopher D.

2004-01-01

292

Cancer cells (MCF7, Colo-357, and LNCaP) viability on amorphous hydrogenated carbon nitride film deposited by dielectric barrier discharge plasma  

Microsoft Academic Search

Atmospheric pressure dielectric barrier discharge plasma in CH4\\/N2 (1:1) gas mixture has been employed to deposit amorphous hydrogenated carbon nitride (aH-CNx) film. In vitro studies with three different cancer cell lines were carried out on the coated surfaces. Preliminary biocompatibility and effect of CH4\\/N2 films have been investigated by measuring cell proliferation. Three different cancer cell (MCF-7, Colo-357, and LNCaP)

Abhijit Majumdar; Ramesh Ummanni; Karsten Schröder; Reinhard Walther; Rainer Hippler

2009-01-01

293

Miniature cybernetic actuators using piezoelectric device  

Microsoft Academic Search

A new type of miniature actuator, the so-called cybernetic actuator, for medical application has been proposed and developed. The cybernetic actuator has four driving states: free, increasing, decreasing and locked. A rotary-type cybernetic actuator and a linear-type cybernetic actuator driven by piezoelectric devices have been constructed. The feasibility of both actuators was verified by driving experiments

K. Ikuta; A. Kawahara; S. Yamazumi

1991-01-01

294

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

295

Recent developments in ceramic actuators  

NASA Astrophysics Data System (ADS)

In these several years, piezoelectric and electrostrictive materials have become key components in smart actuator/sensor systems such as precision positioners, miniature ultrasonic motors and adaptive mechanical dampers. This paper reviews recent developments of piezoelectric and related ceramic actuators with particular focus on the improvement of actuator materials, device designs and drive/control techniques of actuators. Developments will be compared among USA, Japan and Europe.

Uchino, Kenji

1998-04-01

296

On designing dielectric elastomer actuators  

Microsoft Academic Search

Subject to a voltage, a dielectric elastomer can deform substantially, making it a desirable material for actuators. Designing such an actuator, however, has been challenging due to nonlinear equations of state, as well as multiple modes of failure, parameters of design, and measures of performance. This paper explores these issues, using a spring-roll actuator as an example. We formulate the

Mickael Moscardo; Xuanhe Zhao; Zhigang Suo; Yuri Lapusta

2008-01-01

297

Response of dielectric elastomer actuators  

Microsoft Academic Search

Elastomer films sandwiched between compliant electrodes work as electrostatic actuators when a large electric field is applied over the electrodes. We have analyzed the mechanical and electrical response of actuators to a sinusoidal varying driving voltage. The actuator acts as a capacitor in the electric circuit, but due to very high strains, the capacitance changes during a work cycle. The

Peter Sommer-Larsen; Jacob C. Hooker; Guggi Kofod; Keld West; Mohammed Benslimane; Peter Gravesen

2001-01-01

298

Materials for dielectric elastomer actuators  

Microsoft Academic Search

Dielectric elastomer actuators consist of an elastomer film sandwiched between compliant electrodes. They work as electrostatic actuators: when a large electric field is applied over the electrodes, the rubber is compressed and the elastomer film elongates in the film plane. The performance of dielectric elastomer actuators (DEA), when a constant potential is applied, is expressed in a universal equation where

Peter Sommer-Larsen; Anne L. Larsen

2004-01-01

299

Electro-active paper actuators  

Microsoft Academic Search

In this paper, the actuation mechanism of electro-active paper (EAPap) actuators is addressed and the potential of the actuators is demonstrated. EAPap is a paper that produces large displacement with small force under an electrical excitation. EAPap is made with a chemically treated paper by constructing thin electrodes on both sides of the paper. When electrical voltage is applied on

Jaehwan Kim; Yung B. Seo

2002-01-01

300

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

SciTech Connect

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

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

2012-06-15

301

Design and fabrication of a micro thermal actuator for cellular grasping  

NASA Astrophysics Data System (ADS)

The development of a novel polymer-based micro robotic gripper that can be actuated in a fluidic medium is presented in this paper. Our current work is to explore new materials and designs for thermal actuators to achieve micromanipulation of live biological cells. We used parylene C to encapsulate a metal heater, resulting in effectively a tri-layered thermal actuator. Parylene C is a bio-compatible dielectric polymer that can serve as a barrier to various gases and chemicals. Therefore, it is suitable to serve as a thermal/electrical/chemical isolation material for protecting the metal heater from exposing to an aqueous environment. We have demonstrated parylene actuators (2 mm×100 ?m×0.5 ?m) to operate in an aqueous environment using 10 to 80 mW input power. The temperature of these actuators at full deflection was estimated to be ˜60°C, which is much lower than the typical requirement of >100°C to actuate other conventional MEMS actuators.Danio rerio follicles in fluidic medium were captured successfully using these actuators. Moreover, these actuators were found to be responsive to moderate rise in environmental temperature, and hence, we could vary the fluidic medium temperature to actuate trimorphs on a chip without any input of electrical energy, i.e., raising the fluidic temperature from 23°C to 60°C could actuate the trimorphs to grasp follicles of ˜1 mm size in diameter. At 60°C, the embryos inside the follicles were observed to be alive, i.e., they were still moving in the biological fluid isolated by the follicle membrane. The smallest follicles grasped were ˜500 ?m in diameter using 800 ?m×130 ?m×0.6 ?m actuators. The fabrication process, modeling, and optimization of the trimorph actuators are presented. Based on the successful operation of these polymer-based actuators, we are currently developing multifinger thermal microgrippers for cellular grasping and manipulation, which can potentially be hybridly integrated with circuits for computer control.

Chan, Ho-Yin; Li, Wen J.

2004-04-01

302

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

303

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

304

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

305

Encapsulated polypyrrole actuators  

Microsoft Academic Search

Conducting polymer-based actuators undergo volumetric changes as they are oxidized or reduced, from which mechanical work can be obtained. Polypyrrole [Q. Pei, O. Inganäs, Advanced Materials 4 (1992) 277; Q. Pei, O. Inganäs, Journal of Physical Chemistry 96 (1992) 10508; E. Smela, O. Inganäs, Q. Pei, I. Lundström, Advanced Materials 5 (1993) 630; E. Smela, O. Inganäs, I. Lundström, Science

John D. Madden; Ryan A. Cush; Tanya S. Kanigan; Colin J. Brenan; Ian W. Hunter

1999-01-01

306

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

307

Let me actuate you  

Microsoft Academic Search

In this paper we focus on two aspects of Tangible Interaction that have our particular interest: 1) the added value of tangibility when designing interfaces for toddlers and 2) the value of actuators. Especially the latter is something that in our opinion has been under-investigated within the field of Tangible and Embedded Interaction. In this paper we will address the

Bart Hengeveld; Caroline Hummels; Kees Overbeeke; Riny Voort; Hans Van Balkom; Jan De Moor

2008-01-01

308

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

309

Vortical flow control on a conical fore body cross section using an array of pulsed dc actuators  

SciTech Connect

Flow control on a conical fore body cross section of an aircraft is studied using plasma discharge by considering the neutral gas flow at 17.5 deg angle of attack. The equations governing the motion of electrons, ions as well as Poisson's equation are solved together with Navier-Stokes and energy equation for neutrals to study flow control. A single barrier discharge actuator is not sufficient to control the flow on the entire length of the fore body. An arrangement of multiple electrodes powered with pulsed dc voltage has been suggested for controlling such flows. The effects of joule heating of plasma, dielectric heating, and electrodynamic force have been investigated, separately and then combined on flow control. It is found that joule heating results in high temperature of the dielectric surface, however; electrodynamic force contributes prominently to flow control. A three-dimensional analysis is necessary to validate results with experiments.

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

2007-05-01

310

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

311

Self-organized pattern formation of an atmospheric pressure plasma jet in a dielectric barrier discharge configuration  

SciTech Connect

This letter reports the observation of self-organized patterns formed in a 29 mm wide atmospheric pressure plasma jet. By altering the gas flow rate and/or the applied voltage, the plasma jet is seen to have at least three different modes, namely, a diffuse-looking discharge, a self-organized discharge, and an unstable discharge with randomly occurring plasma channels. The self-organized discharge mode is characterized by several bright plasma channels embedded in a diffuse and dim plasma background. These plasma channels are regularly spaced from each other and their self-organized patterns are shown to evolve abruptly.

Nie Qiuyue; Ren Chunsheng; Wang Dezhen; Li Shouzhe; Zhang Jialiang; Kong, M. G. [State Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023 (China); Department of Electronic and Electrical Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU (United Kingdom)

2007-05-28

312

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

313

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

314

Solenoid actuator with fastener  

SciTech Connect

This patent describes a solenoid actuator comprising: a coil of electrically conductive wire wound about an axis; an enclosure for the coil; receptacle means carried by the enclosure for accommodating a mounting member of a device to be controlled by the solenoid actuator; a slideway carried by the enclosure extending transverse to the coil axis; a fastener movable within the slideway between a latched position in which it can engage the mounting member, to secure the enclosed coil to the device to be controlled, and an unlatched position in which it is disengaged from the mounting member, to permit separation of the enclosed coil from the device to be controlled. The means prevents separation of the fastener and the enclosure when the fastener is in its unlatched position.

Vollmer, D.J.; Greame, J.E.

1987-07-28

315

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

316

Dissolution actuated sample container  

DOEpatents

A sample collection vial and process of using a vial is provided. The sample collection vial has an opening secured by a dissolvable plug. When dissolved, liquids may enter into the interior of the collection vial passing along one or more edges of a dissolvable blocking member. As the blocking member is dissolved, a spring actuated closure is directed towards the opening of the vial which, when engaged, secures the vial contents against loss or contamination.

Nance, Thomas A.; McCoy, Frank T.

2013-03-26

317

Vacuum actuated gas delivery  

Microsoft Academic Search

The new Vacuum Actuated Cylinder (VACTM) gas source provides sub-atmospheric pressure delivery of the metal fluorides commonly used as dopants for ion implant. The VAC gas source is a mechanical system based on an embedded pressure control device located inside the cylinder. A pre-set sub-atmospheric pressure must be achieved in the delivery manifold before flow is permitted from the cylinder.

W. K. Olander; M. Donatucci; J. Mayer; L. Wang

2000-01-01

318

Microelectromechanical (MEM) thermal actuator  

SciTech Connect

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

319

Multiple current peaks in room-temperature atmospheric pressure homogenous dielectric barrier discharge plasma excited by high-voltage tunable nanosecond pulse in air  

NASA Astrophysics Data System (ADS)

Room temperature homogenous dielectric barrier discharge plasma with high instantaneous energy efficiency is acquired by using nanosecond pulse voltage with 20-200 ns tunable pulse width. Increasing the voltage pulse width can lead to the generation of regular and stable multiple current peaks in each discharge sequence. When the voltage pulse width is 200 ns, more than 5 organized current peaks can be observed under 26 kV peak voltage. Investigation also shows that the organized multiple current peaks only appear in homogenous discharge mode. When the discharge is filament mode, organized multiple current peaks are replaced by chaotic filament current peaks.

Yang, De-Zheng; Wang, Wen-Chun; Zhang, Shuai; Tang, Kai; Liu, Zhi-jie; Wang, Sen

2013-05-01

320

Linear Actuator for Rotary Manipulator Motion.  

National Technical Information Service (NTIS)

An improved, pressure tolerant, underwater actuator for rotary motion between two manipulator arm segments is presented which comprises a hydraulic linear actuator fastened to one manipulator arm segment, a ram shaft driven by the linear actuator, a linea...

R. L. Wernli

1983-01-01

321

Silicone dielectric elastomer actuators: Finite-elasticity model of actuation  

Microsoft Academic Search

A theory for the actuation strain of a silicone dielectric elastomer actuator with a simple geometry is developed. The stress is a function of two variables, the strain and the applied voltage. A lamination type stress–strain function was employed, due to the nature of the electrodes. All parameters are obtained from physical measurements. Then, measurements of the blocking force are

Guggi Kofod; Peter Sommer-Larsen

2005-01-01

322

Thermopneumatic actuator for tactile displays and smart actuation circuitry  

Microsoft Academic Search

This paper presents a thermopneumatic actuator to build large tactile displays as well as a smart activation circuitry to study and improve its performance. Since the main drawback of large tactile screens in the market is their cost, this proposal is intended to reduce the price because of the simplicity of the actuator and the potential low cost assembling. A

F. Vidal-Verdu; Manuel J. Madueno; Rafael Navas

2005-01-01

323

Self-organized pattern formation of an atmospheric pressure plasma jet in a dielectric barrier discharge configuration  

Microsoft Academic Search

This letter reports the observation of self-organized patterns formed in a 29 mm wide atmospheric pressure plasma jet. By altering the gas flow rate and\\/or the applied voltage, the plasma jet is seen to have at least three different modes, namely, a diffuse-looking discharge, a self-organized discharge, and an unstable discharge with randomly occurring plasma channels. The self-organized discharge mode

Qiu-Yue Nie; Chun-Sheng Ren; De-Zhen Wang; Shou-Zhe Li; Jia-Liang Zhang; M. G. Kong

2007-01-01

324

Retractable barrier strip  

SciTech Connect

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

325

CCMR: Plastic Actuators  

NSDL National Science Digital Library

Lately there has been a tremendous effort in the search for new ways for the development of better and more cost effective actuators and devices. The use for dielectric materials is preference. In this paper we search for the interaction between performance and preparation process. We take a look for the electric properties that laser annealing imparts on PVDF and ZnO, an enhancement in the conductivity of ZnO was found after laser irradiation. And we verify for any relation in its X-ray diffraction and the dielectric analysis we get from our experiments.

Colã³n Pã©rez, Luis M.

2005-08-17

326

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

327

Scalable synthetic muscle actuator  

NASA Astrophysics Data System (ADS)

We will discuss our work to build, characterize, and scale- up a metallized plastic muscle-like actuator called a Spiral Wound Transducer (SWT). Prototype SWTs have been built using microelectronics fabrication methods. The prototypes have demonstrated large amplitude motion and analog response. The prototypes, though small, have demonstrated forces equivalent to 12 grams for compressions of more than 15 percent at 30 Hz. The size of the SWTs is essentially unrestricted. Our work with commercially available metallized Mylar films to produce much larger, more powerful, and lower cost SWT devices will also be discussed.

Bobbio, Stephen M.; Pennington, Michael A.; Smith, Stephen W.; Zara, Jason; Leamy, Harry J.; Hudak, John A.; Pagan, Jennifer; Elliot, Paul C.

2000-06-01

328

Experimental and theoretical study of acetic-acid decomposition by a pulsed dielectric-barrier plasma in a gas-liquid two-phase flow  

NASA Astrophysics Data System (ADS)

Decomposition of acetic acid as a persistent material in water was demonstrated using a pulsed dielectric-barrier plasma in a gas-liquid two-phase flow. The plasma was driven by 35 kV, 200 Hz pulsed voltages and generated in oxygen bubbles in 20 ml solution having a concentration of 10-40 mgTOC l-1. The concentrations of ion species and hydrogen peroxide in the solution were analyzed by ion chromatography and absorptiometry, respectively. After 60 min of operation, the acetic acid was completely decomposed by the plasma. Optical measurements of the emission intensities of OH, H and O radicals suggest that the generated OH radicals are in the ground state in this study. A numerical calculation was carried out to analyze the radical generation processes in the gas phase and decomposition in the liquid phase. O-radical-induced generation of OH radical needed to be considered in the calculation of total organic carbon (TOC) and H2O2 concentrations in the solution. By considering such plasma-water interaction processes, data for the decomposition of acetic acid, which were in good agreement with experimental results, were obtained.

Matsui, Y.; Takeuchi, N.; Sasaki, K.; Hayashi, R.; Yasuoka, K.

2011-06-01

329

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

330

Modeling aspects concerning THUNDER actuators  

Microsoft Academic Search

This paper summarizes techniques for modeling geometric properties of THUNDER actuators which arise in the fabrication process. These actuators are high performance composites comprised of layers of piezoceramics in combination with aluminum, stainless steel, brass or titanium bonded with hot- melt adhesive. During the construction process, the assembly is heated under pressure to high temperatures, cooled and repoled to restore

M. Capozzoli; J. Gopalakrishnan; K. Hogan; J. Massad; T. Tokarchik; S. Wilmarth; H. Thomas Banks; Karla M. Mossi; Ralph C. Smith

1999-01-01

331

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

332

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

333

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

334

Hydrostatically Coupled Dielectric Elastomer Actuators  

Microsoft Academic Search

Within the emerging field of polymer-based mechatronics, soft materials showing intrinsic electromechanical transduction properties are being largely studied to develop new types of actuators. Among them, so-called dielectric elastomer (DE) actuators are one of the most promising. This paper presents a new class of such devices, which uses an incompressible fluid to mechanically couple an active part to a passive

Federico Carpi; Gabriele Frediani; Danilo De Rossi

2010-01-01

335

Electrostatically actuated conducting polymer microbridges  

Microsoft Academic Search

All-polymer microbridge electrostatic actuators based on a blended conductive polymer are fabricated using surface micromachining on glass substrates. A fabrication process is developed that allows the preservation of the electrical conductivity of the polymer structural layer and the suspension of the polymer microbridges. The electromechanical properties of the microbridges are studied using electrostatic actuation and optical and electrical detections. The

G. Zhang; V. Chu; J. P. Conde

2007-01-01

336

V-Stack piezoelectric actuator  

Microsoft Academic Search

Aeroelastic control of wings by means of a distributed, trailing-edge control surface is of interest with regards to maneuvers, gust alleviation, and flutter suppression. The use of high energy density, piezoelectric materials as motors provides an appealing solution to this problem. A comparative analysis of the state of the art actuators is currently being conducted. A new piezoelectric actuator design

Emil V. Ardelean; Robert L. Clark

2001-01-01

337

A new electromagnetic valve actuator  

Microsoft Academic Search

In conventional internal combustion (IC) engines, en- gine valve displacements are fixed relative to crankshaft position. If these valves are actuated as a variable function of crankshaft an- gle, significant improvements in fuel economy can be achieved. Ex- isting electromagnetically actuated variable-valve-timing (VVT) systems characteristically use springs to provide the large iner- tial power to move the engine valves. However,

W. S. Changt; T. A. Parlikart; M. D. Seemant; D. J. Perreaultt; J. G. Kassakian; T. A. Keirnl

2002-01-01

338

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.; Boyd, Robert D.

1999-10-15

339

A nonequilibrium argon-oxygen planar plasma jet using a half-confined dielectric barrier duct in ambient air  

NASA Astrophysics Data System (ADS)

A nonequilibrium argon plasma jet with oxygen addition, generated in a planar dielectric duct and issuing into ambient air with one edge stuck on a dielectric plane, is reported for the first time. This argon-oxygen plasma jet can be operated at low applied voltage as a filamentary discharge at atmospheric pressure. The addition of a small amount of oxygen results in the increase of produced ozone concentration and continuous emissions of centering at about 185 nm, 205 nm, 230 nm, and 253 nm. The synergistic generation of short wavelength ultraviolet emissions and active species is significantly important for plasma applications.

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

2012-03-01

340

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

341

GASES, PLASMAS, AND ELECTRIC DISCHARGES: Self-Consistent Model for Atmospheric Pressure Dielectric Barrier Discharges in Helium  

NASA Astrophysics Data System (ADS)

We show the necessity of leaving out the approximation of constant average electron energy in many fluid models. For this purpose a one-dimensional self-consistent model for He atmospheric barrier discharges is developed. With this model, the electron energy distribution function in the atmospheric pressure glow discharge is obtained without introducing much difficulty, and the new model is readily implemented for investigating discharges in complicated gases.

Sun, Ji-Zhong; Wang, Qi; Zhang, Jian-Hong; Wang, Yan-Hui; Wang, De-Zhen

2008-11-01

342

Evaluation of laser-glazed plasma-sprayed thermal barrier coatings under high temperature exposure to molten salts  

Microsoft Academic Search

Thermal Barrier Coating (TBC) systems are frequently used in gas turbine engines to provide thermal insulation to the hot-section metallic components and also to protect them from oxidation, hot corrosion and erosion. Surface sealing treatments, namely laser-glazing, have been showing a high potential for extending in-service lifetimes of these systems by improving chemical and thermo-mechanical resistance. In this investigation, both

C. Batista; A. Portinha; R. M. Ribeiro; V. Teixeira; C. R. Oliveira

2006-01-01

343

V-Stack piezoelectric actuator  

NASA Astrophysics Data System (ADS)

Aeroelastic control of wings by means of a distributed, trailing-edge control surface is of interest with regards to maneuvers, gust alleviation, and flutter suppression. The use of high energy density, piezoelectric materials as motors provides an appealing solution to this problem. A comparative analysis of the state of the art actuators is currently being conducted. A new piezoelectric actuator design is presented. This actuator meets the requirements for trailing edge flap actuation in both stroke and force. It is compact, simple, sturdy, and leverages stroke geometrically with minimum force penalties while displaying linearity over a wide range of stroke. The V-Stack Piezoelectric Actuator, consists of a base, a lever, two piezoelectric stacks, and a pre-tensioning element. The work is performed alternately by the two stacks, placed on both sides of the lever. Pre-tensioning can be readily applied using a torque wrench, obviating the need for elastic elements and this is for the benefit of the stiffness of the actuator. The characteristics of the actuator are easily modified by changing the base or the stacks. A prototype was constructed and tested experimentally to validate the theoretical model.

Ardelean, Emil V.; Clark, Robert L.

2001-07-01

344

Linear actuation in coextruded dielectric elastomer tubes  

Microsoft Academic Search

Cylindrical fibre actuators have been constructed by a coextrusion method using a thermoplastic polyurethane wall and a conductive grease filler. These actuators may be operated as single fibres or bundled together as actuating ropes. Key results include the validation of Carpi’s wall pressure model [F. Carpi, D.D. Rossi, Dielectric elastomer cylindrical actuators: electromechanical modelling and experimental evaluation, Mater. Sci. Eng.

Colin G. Cameron; Jeffrey P. Szabo; Stephen Johnstone; Jason Massey; Jacob Leidner

2008-01-01

345

High Specific Power Actuators for Robotic Manipulators  

Microsoft Academic Search

Recent advancements in actuator technology suggest that the implementation of reliable, high power-to-weight ratio pneumatic actuation systems is now possible for robotic platforms. Existing robotic manipulator arms for casualty extraction and patient placement use hydraulic actuation, whereas related robotic prosthetic devices typically use heavy actuator motors. We have developed an alternative solution that employs pneumatic artificial muscles (PAMs). The goal

Ryan M. Robinson; Curt S. Kothera; Benjamin K. S. Woods; Robert D. Vocke; Norman M. Wereley

2011-01-01

346

Study on the graphene-based actuator  

Microsoft Academic Search

Bilayer actuators comprising of MWCNT (Multi-walled carbon nanotubes) and Graphene oxide (GO) were studied for their actuation performance by using induction heating system. A simple fabrication method namely, filtration of the colloidal suspensions of MWCNT and GO through an Anodisc membrane was used to fabricate the actuators. In case of bilayer actuators, sequential filtration of MWCNTs and Graphene oxide dispersions

Liang Xu; Il Kwon Oh

2011-01-01

347

CMOS–MEMS Lateral Electrothermal Actuators  

Microsoft Academic Search

In this paper, a type of lateral electrothermal (ET) actuator fabricated with post-CMOS micromachining is presented. The actuator is a beam with a multimorph structure, composed of CMOS dielectric and metal interconnect. Following structural release, the actuators demonstrate self-assembly under the moments arising from residual stress. Actuation is achieved through the imbalanced thermal expansion of internal interconnect members, whose relative

Peter J. Gilgunn; Jingwei Liu; Niladri Sarkar; Gary K. Fedder

2008-01-01

348

Ultrasonic Linear Motor Using Multilayer Piezoelectric Actuators  

Microsoft Academic Search

In order to lower operating voltage and improve the lifetime of an ultrasonic linear motor, we have developed an ultrasonic oscillator with multilayer piezoelectric actuators. Multilayer piezoelectric actuators are operable at low voltage. However, the tensile strength of the multilayer piezoelectric actuator is small. Therefore, the multilayer piezoelectric actuators are build within an elastic body to lower the tensile stress

Tomoki Funakubo; Toshiharu Tsubata; Yoshihisa Taniguchi; Kazuhiro Kumei; Takanao Fujimura; Chikara Abe

1995-01-01

349

Electrically controlled polymeric gel actuators  

DOEpatents

Electrically controlled polymeric gel actuators or synthetic muscles capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots.

Adolf, Douglas B. (Albuquerque, NM); Shahinpoor, Mohsen (Albuquerque, NM); Segalman, Daniel J. (Albuquerque, NM); Witkowski, Walter R. (Albuquerque, NM)

1993-01-01

350

Electrically controlled polymeric gel actuators  

DOEpatents

Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

Adolf, D.B.; Shahinpoor, M.; Segalman, D.J.; Witkowski, W.R.

1993-10-05

351

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

352

Development of a Thermal Transport Database for Air Plasma Sprayed ZrO2-Y2O3 Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

Thermal diffusivities of air plasma sprayed (APS) thermal barrier coatings (TBCs) were measured by the laser flash method. The data were used to calculate thermal conductivity of TBCs when provided with density and specific heat data. Due to the complicated microstructure and other processing-related parameters, thermal diffusivity of TBCs can vary as much as three- to four-fold. Data collected from over 200 free-standing ZrO2-7-8wt.%Y2O3 TBCs are presented. The large database gives a clear picture of the expected "band" of thermal diffusivity values. When this band is used as a reference for thermal diffusivity of a specific TBC, the thermal transport property of the TBC can be more precisely described. This database is intended to serve researchers and manufacturers of TBCs as a valuable resource for the evaluation of TBCs.

Wang, Hsin; Dinwiddie, Ralph B.; Porter, Wallace D.

2010-09-01

353

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

354

Nanolayer biofilm coated on magnetic nanoparticles by using a dielectric barrier discharge glow plasma fluidized bed for immobilizing an antimicrobial peptide  

NASA Astrophysics Data System (ADS)

Using the monomer of acrylic acid and the novel technique of using a dielectric barrier discharge glow plasma fluidized bed (GPFB), a nanolayer biofilm of polyacrylic acid (PAA) was uniformly coated on the surface of magnetic nickel nanoparticles (NPs). Transmission electron microscopy, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy, etc, were used to characterize the modified NPs. The thickness of the biofilm was about 2 nm when the NPs were treated using the GPFB once, and the discharging conditions affected the density of the carboxyl group obviously. The PAA acting as an adhesion layer was used to immobilize the antimicrobial peptide LL-37, to kill the bacteria of Escherichia coli (E. coli), and the results indicated that the modified nickel NPs immobilizing a certain concentration of LL-37 could kill the bacteria effectively.

Chen, Guangliang; Zhou, Mingyan; Chen, Shihua; Lv, Guohua; Yao, Juming

2009-11-01

355

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.

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

2013-01-01

356

Effects of the fluorine plasma treatment on the surface potential and Schottky barrier height of AlxGa1-xN/GaN heterostructures  

NASA Astrophysics Data System (ADS)

The variations in surface potential and the Schottky barrier height ?B in fluorine-plasma-treated AlxGa1-xN/GaN heterostructures are systematically studied by x-ray photoelectron spectroscopy, providing insights to the mechanisms underlying the strong threshold voltage (Vth) modulation achieved by the F plasma treatment technology. It is found that a large amount of AlF3 appeared on the surface after the treatment, indicating a fluorinated surface. In addition, the surface potential of Al0.25Ga0.75N/GaN heterostructure was increased by ~0.38 eV during the first 60 s of the treatment and then rises slowly with additional treatment. Annealing at 400 °C in N2 ambient for 10 min does not affect the surface potential, but results in quick reduction in AlF3, consistent with the relative poor thermal stability of AlF3 reported in literature. ?B between Ni and F-plasma-treated Al0.25Ga0.75N surface was extrapolated from the shift in Ga 2p3/2 core-level and exhibits a small increase of 0.20 eV. The enhanced ?B is much smaller than the positive shift in Vth observed from high electron mobility transistors fabricated with the same treatment conditions, suggesting that the primary factor responsible for the conversion from depletion-mode to enhancement-mode AlxGa1-xN/GaN by F plasma treatment is not the surface modifications but rather the negative fixed charges carried by F ions in AlxGa1-xN/GaN heterostructures.

Huang, Sen; Chen, Hongwei; Chen, Kevin J.

2010-06-01

357

Fabrication of Polyurethane Dielectric Actuators.  

National Technical Information Service (NTIS)

This paper provides a summary of a 3-year Technology Investment Fund Project entitled 'Dielectric Polymer Actuators for Active/Passive Vibration Isolation,' which was completed in March 2005. The purpose of this project was to investigate dielectric polym...

J. P. Szabo

2005-01-01

358

Firewater system inadvertent actuation frequencies  

SciTech Connect

This paper presents some recommended generic values for fire protection system inadvertent actuation frequencies. The frequencies are based on actual data from Department of Energy and commercial reactor plant facilities.

Schroeder, J.A. [EG and G Idaho, Inc., Idaho Falls, ID (United States); Eide, S.A. [Los Alamos Technical Associates, Inc., Albuquerque, NM (United States)

1993-04-01

359

Firewater system inadvertent actuation frequencies  

SciTech Connect

This paper presents some recommended generic values for fire protection system inadvertent actuation frequencies. The frequencies are based on actual data from Department of Energy and commercial reactor plant facilities.

Schroeder, J.A. (EG and G Idaho, Inc., Idaho Falls, ID (United States)); Eide, S.A. (Los Alamos Technical Associates, Inc., Albuquerque, NM (United States))

1993-01-01

360

Hydraulically actuated well shifting tool  

SciTech Connect

This patent describes a hydraulically actuated shifting tool for actuating a sliding member in a well tool. It comprises: a housing having a hydraulic fluid bore therein; shifting dog means positioned on the housing for movement away and toward the housing; locking dog means positioned on the housing for movement away and toward the body; shifting dog hydraulic actuating means in fluid communication with the bore for causing engagement of the shifting dogs with the sliding member; locking dog hydraulic actuating means in communication with the bore for causing engagement of the locking dogs with the locking means; and hydraulic shifting means in communication with the bore for causing relative movement between the shifting dog means and the locking dog means for shifting the sliding sleeve.

Roth, B.A.

1992-10-20

361

High torque miniature rotary actuator  

NASA Astrophysics Data System (ADS)

This paper summarizes the design and the development of a miniature rotary actuator (36 mm diameter by 100 mm length) used in spacecraft mechanisms requiring high torques and/or ultra-fine step resolution. This actuator lends itself to applications requiring high torque but with strict volume limitations which challenge the use of conventional rotary actuators. The design challenge was to develop a lightweight (less than 500 grams), very compact, high bandwidth, low power, thermally stable rotary actuator capable of producing torques in excess of 50 N.m and step resolutions as fine as 0.003 degrees. To achieve a relatively high torsional stiffness in excess of 1000 Nm/radian, the design utilizes a combination of harmonic drive and multistage planetary gearing. The unique design feature of this actuator that contributes to its light weight and extremely precise motion capability is a redundant stepper motor driving the output through a multistage reducing gearbox. The rotary actuator is powered by a high reliability space-rated stepper motor designed and constructed by Moog, Inc. The motor is a three-phase stepper motor of 15 degree step angle, producing twenty-four full steps per revolution. Since micro-stepping is not used in the design, and un-powered holding torque is exhibited at every commanded step, the rotary actuator is capable of reacting to torques as high as 35 Nm by holding position with the power off. The output is driven through a gear transmission having a total train ratio of 5120:1, resulting in a resolution of 0.003 degrees output rotation per motor step. The modular design of the multi-stage output transmission makes possible the addition of designs having different output parameters, such as lower torque and higher output speed capability. Some examples of an actuator family based on this growth capability will be presented in the paper.

Nalbandian, Ruben

2005-07-01

362

13 Microfabrication: conjugated polymer actuators  

Microsoft Academic Search

Conjugated polymers actuators can be operated in aqueous media, which makes them attractive for laboratories -on-a-chip and applications in physiological conditions. One of the most stable conjugated polymers under these conditions is polypyrrole, which can be patterned using standard photolithography. Polypyrrole-gold bilayer actuators that bend out of the plane of the wafer have been microfabricated in our laboratory. These can

Edwin W. H. JAGER; Elisabeth SMELA; Olle Ingan

2001-01-01

363

Firewater system inadvertent actuation frequency  

SciTech Connect

The purpose of this analysis was to determine generic and plant-specific firewater inadvertent actuation frequencies for wetpipe and preaction firewater systems at the Advanced Test Reactor (ATR). Firewater systems of both kinds are installed throughout the ATR facility. When installed for the protection of reactor equipment, firewater systems may also adversely affect the equipment they are meant to protect. This occurs when inadvertent actuation of a firewater system causes wetting and subsequent damage to equipment.

Schroeder, J.A.; Eide, S.A.

1991-08-01

364

Enzyme actuated bioresponsive hydrogels  

NASA Astrophysics Data System (ADS)

Bioresponsive hydrogels are emerging with technological significance in targeted drug delivery, biosensors and regenerative medicine. Conferred with the ability to respond to specific biologically derived stimuli, the design challenge is in effectively linking the conferred biospecificity with an engineered response tailored to the needs of a particular application. Moreover, the fundamental phenomena governing the response must support an appropriate dynamic range and limit of detection. The design of these systems is inherently complicated due to the high interdependency of the governing phenomena that guide the sensing, transduction, and the actuation response of hydrogels. To investigate the dynamics of these materials, model systems may be used which seek to interrogate the system dynamics by uni-variable experimentation and limit confounding phenomena such as: polymer-solute interactions, polymer swelling dynamics and biomolecular reaction-diffusion concerns. To this end, a model system, alpha-chymotrypsin (Cht) (a protease) and a cleavable peptide-chromogen (pro-drug) covalently incorporated into a hydrogel, was investigated to understand the mechanisms of covalent loading and release by enzymatic cleavage in bio-responsive delivery systems. Using EDC and Sulfo-NHS, terminal carboxyl groups of N-succinyl-Ala-Ala-Pro-Phe p-nitroanilide, a cleavable chromogen, were conjugated to primary amines of a hydrated poly(HEMA)-based hydrogel. Hydrogel discs were incubated in buffered Cht causing enzyme-mediated cleavage of the peptide and concomitant release of the chromophore for monitoring. To investigate substrate loading and the effects of hydrogel morphology on the system, the concentration of the amino groups (5, 10, 20, and 30 mol%) and the cross-linked density (1, 5, 7, 9 and 12 mol%) were independently varied. Loading-Release Efficiency of the chromogen was shown to exhibit a positive relation to increasing amino groups (AEMA). The release rates demonstrated a negative relation to increasing cross-linked density attributed to decreasing void fractions and increasing tortuosities. The diffusion coefficient of Cht, D0, Cht, was determined to be 6.9 +/- 0.5 x 10-7 cm2 s -1, and the range of Deff of Cht for 1 to 12 mol% TEGDA was determined to 6.9 x10-8 to 0.1 x 10 -8cm2 s-1. We show how these parameters may be optimized and used to achieve programmed release rates in engineered bio-responsive systems. The field of bioresponsive hydrogels is continuing to expand as the need for such materials persists. Future work will enable more control over the loading and release of therapeutic and diagnostic moieties. Continued research regarding in enzymatically actuated hydrogels will involve pre-polymerization loading methodologies; in silico diffusion-reaction multiphysics modeling; enzyme actuated degradation of the polymer; and substation of various mediating enzyme, cleavable peptides, and release molecules.

Wilson, Andrew Nolan

365

Considerations for Contractile Electroactive Polymeric Materials and Actuators  

SciTech Connect

Ras Labs produces electroactive polymer (EAP) based materials and actuators that bend, swell, ripple and now contract (new development) with low electric input. This is an important attribute because of the ability of contraction to produce life-like motion. The mechanism of contraction is not well understood. Radionuclide-labeled experiments were conducted to follow the movement of electrolytes and water in these EAPs when activated. Extreme temperature experiments were performed on the contractile EAPs with very favorable results. One of the biggest challenges in developing these actuators, however, is the electrode-EAP interface because of the pronounced movement of the EAP. Plasma treatments of metallic electrodes were investigated in order to improve the attachment of the embedded electrodes to the EAP material. Surface analysis, adhesive testing, and mechanical testing were conducted to test metal surfaces and metal-polymer interfaces. The nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.

Lenore Rasmussen, Carl J. Erickson, Lewis D. Meixler, George Ascione, Charles A. Gentile, Carl Tilson, Stephen L. Bernasek, Esta Abelev

2009-06-16

366

Lu2O3-SiO2-ZrO2 Coatings for Environmental Barrier Application by Solution Precursor Plasma Spraying and Influence of Precursor Chemistry  

NASA Astrophysics Data System (ADS)

As environmental barrier coatings are subjected to thermal stress in gas turbine engines, the introduction of a secondary phase as zircon (ZrSiO4) is likely to increase the stress resistance of Lu2Si2O7 coatings generated by induction plasma spraying using liquid precursors. In a first step, precursor chemistry effect is investigated by the synthesis of ZrO2-SiO2 nanopowders by induction plasma nanopowder synthesis technique. Tetraethyl orthosilicate (TEOS) as silicon precursor and zirconium oxynitrate and zirconium ethoxide as zirconium precursors are mixed in ethanol and produce a mixture of tetragonal zirconia and amorphous silica nanoparticles. The use of zirconium ethoxide precursor results in zirconia particles with diameter below 50 nm because of exothermic thermal decomposition of the ethoxide and its high boiling point with respect to solvent, while larger particles are formed when zirconium oxynitrate is employed. The formation temperature of zircon from zirconia and silica oxides is found at 1425 °C. Second, coatings are synthesized in Lu2O3-ZrO2-SiO2 system. After heat treatment, the doping effect of lutetium on zirconia grains totally inhibits the zircon formation. Dense coatings are obtained with the use of zirconium ethoxide because denser particles with a homogeneous diameter distribution constitute the coating.

Darthout, Émilien; Quet, Aurélie; Braidy, Nadi; Gitzhofer, François

2013-09-01

367

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

368

Optical characteristics and parameters of the plasma of a barrier discharge excited in a mixture of mercury dibromide vapor with nitrogen and helium  

NASA Astrophysics Data System (ADS)

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 HgBr2: N2: He mixture, which was used as the working medium of a small-size (with a radiation area of 8 cm2) exciplex gas-discharge radiation source. The mean radiation power of 87 mW was achieved at the radiation wavelength ?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 HgBr2: N2: 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.

2010-09-01

369

Nanotube Nano-actuators  

NASA Astrophysics Data System (ADS)

In 1999 it was found that a thin sheet of single wall carbon nanotubes (buckypaper) can act as an electromechanical transducer (an actuator), converting an applied voltage into a dimensional change, with the potential to do work.[1] The mechanism proposed for the effect is quite fundamental, relying on modification of the nearest neighbor carbon-carbon distance due to charge injected into the nanotube pi-orbital system. Because the experiment relied on buckypaper, which possesses nanoscale pores (where gas generation might also account for dimensional changes), as well as creep (where ropes sliding against one another make it difficult to determine the magnitude of the effect in the fundamental unit), the demonstration was less than ideal. Using an atomic force microscope for detection, we have now performed corresponding measurements on individual ropes of nanotubes tethered across micromachined trenches in silicon substrates. The experiment and results will be described. 1. R. H. Baughman, C. X. Cui, A. A. Zakhidov, Z. Iqbal, J. N. Barisci, G. M. Spinks, G. G. Wallace, A. Mazzoldi, D DeRossi, A. G. Rinzler, O. Jaschinski, S. Roth, M. Kertesz, Science, 284, 1340 (1999).

Jennifer, Sippel; Arnason, Steve; Baughman, Ray; Rinzler, Andrew

2002-03-01

370

Laser melted ZrO 2–Y 2O 3 thermal barrier obtained by plasma spraying method  

Microsoft Academic Search

The aim of the paper is to determine the influence of laser melting upon the selected physical properties of ZrO2–Y2O3 ceramic coatings deposited by APS method on super-alloys which function as TBC. Laser melting which helps to eliminate pores and other structural defects of coatings deposited by plasma spraying method should contribute to the improvement of their density and durability

Krystyna Kobyla?ska Szkaradek

2010-01-01

371

Preparation of Diamond-Like Carbon Film Assisted in the Plasma of Dielectric Barrier Discharge at Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharge at atmospheric presure has been applied to prepare hydrocarbon films on large- area glass and silicon substrates. When hydrogen and methane mixture(2:1) is used as discharge gas and the substrate is heated to 300 °C, hard hydrogenated amorphous carbon film is deposited. From the IR deconvolution analysis of the C-H stretching absorption for the coating, the hydrocarbon group ration (CH3:CH2:CH) and C-C bond type ratio (sp3c/sp2c) are about 10%: 21%: 69% and 3:1-6:1, respectively. Their Knoop hardness is up to 10Gpa. No film is deposited when the content of methane in the mixed gases is decreased to 5% at 300 °C silicon substrate.

Liu, Dong-ping; Ma, Teng-cai; Yu, Shi-ji; Song, Zhi-min; Yang, Xun-feng

1999-12-01

372

Assessment of hepatobiliary function and placental barrier integrity in pregnant rats by combination of bromosulphophthalein and fluorescein isothiocyanate plasma disappearance tests.  

PubMed Central

The permeability of the placental barrier to bromosulphophthalein (BSP) is believed to be very low. Whether this property is shared by other cholephilic organic anions, such as fluorescein isothiocyanate (FITC), is not known. When BSP was injected (140 mumol/kg body wt) into the left jugular vein of non-pregnant or pregnant female rats (at the 21st day of pregnancy), a similar and rapid plasma disappearance was observed during the first few minutes; afterwards, a slower disappearance phase was found. This phase was different in these groups, that is, a longer retention of BSP in the maternal bloodstream of pregnant rats was accompanied by a slower BSP output into bile. It was impossible to demonstrate the presence of BSP in fetal blood or the placenta by colorimetric methods. These results are consistent with the modifications occurring in the hepatic handling of BSP during pregnancy together with a marked impermeability of the placenta to the dye, at least in the mother-to-fetus direction. After intravenous FITC (10 mumol/kg body wt) administration to the mother, the compound was rapidly transferred into both the maternal bile and the fetal blood. Thereafter, FITC refluxed back from the fetal-placental compartment to the maternal blood as soon as the maternal liver reduced its plasma concentrations, which were first higher (approximately threefold) and then similar to those found in fetal blood. The reversible retention of FITC by the fetal-placental compartment accounts for a significant delay in both FITC bile output and plasma disappearance as compared with those observed in non-pregnant rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Villaneuva, G. R.; Sanchez-Abarca, L. I.; Bravo, P.; el-Mir, M. Y.; Marin, J. J.

1995-01-01

373

A fluidic micro-actuator with an integrated inductive position sensor  

NASA Astrophysics Data System (ADS)

An important technological barrier in the development of microrobotic systems is the lack of compact sensor-actuator systems. This paper presents a piston-cylinder fluidic microactuator with an integrated inductive position sensor. Such positioning systems offer great opportunities for all devices that need to control a large number of degrees of freedom in a restricted volume. The main advantage of fluidic actuators is their high force and power density at microscale. The outside diameter of the actuator developed in this research is 1.3 mm and the length is 15 mm. The stroke is 12 mm, and the actuation force is more than 0.4 N at a supply pressure of 550 kPa. The position sensor consists of two coils wound around the cylinder of the actuator. The measurement principle is based on the change in coupling factor between the coils as the piston moves in the actuator. The sensor is extremely small since one layer of 25 µm copper wire is sufficient to achieve an accuracy of 10 µm over the total stroke. Measurements showed that the actuator achieves a positioning accuracy of 20 µm in closed loop control.

De Volder, M.; Coosemans, J.; Ceyssens, F.; Peirs, J.; Puers, R.; Reynaerts, D.

2007-01-01

374

Development of a deformable mirror based on conductive polymer actuator arrays for adaptive optics  

NASA Astrophysics Data System (ADS)

Adaptive optical systems incorporate active components that compensate for wavefront aberrations introduced by optical defects. The increase in resolution is limited by the stroke of the adaptive components underlying actuating mechanism and the differential stroke of neighbouring actuators. Development of high-density nano-scale polypyrrole bilayer actuator arrays may deliver superior performance over conventional adaptive optics actuator technologies such as electrostatic electrodes or piezoelectric mirrors. This study establishes key performance requirements for adaptive optics systems and proposes a prototypical design of a novel deformable mirror based on conductive polymers. The associated fabrication methods are evaluated and critical technological barriers pertinent to future development are identified. The implications of this technology range from more powerful astronomical telescopes to improved retinal tissue diagnosis.

Price, Aaron D.; Naguib, Hani E.; Ben Amara, Foued

2010-03-01

375

Slope seeking for autonomous lift improvement by plasma surface discharge  

NASA Astrophysics Data System (ADS)

The present paper describes an experimental investigation of closed-loop separation control using plasma actuators. The post-stall-separated flow over a NACA 0015 airfoil is controlled using a single dielectric barrier discharge actuator located at the leading edge. Open-loop measurements are first performed to highlight the effects of the voltage amplitude on the control authority for freestream velocities of 10-30 m/s (chord Re = 1.3 × 105 to 4 × 105). The results indicate that partial or full reattachment can be achieved and motivate the choice of the slope seeking approach as the control algorithm. A single-input/single-output algorithm is used to autonomously seek the optimal voltage required to achieve the control objective (full flow reattachment associated with maximum lift). The paper briefly introduces the concept of slope seeking, and a detailed parameterization of the controller is considered. Static (fixed speed) closed-loop experiments are then discussed, which demonstrate the capability of the algorithm. In each case, the flow can be reattached in an autonomous fashion. The last part of the paper demonstrates the robustness of the gradient-based, model-free scheme for dynamic freestream conditions. This paper highlights the capability of slope seeking to autonomously achieve high lift when used to drive the voltage of a plasma actuator. It also describes the advantages and drawbacks of such a closed-loop approach.

Benard, Nicolas; Moreau, Eric; Griffin, John; Cattafesta, Louis N., III

2010-05-01

376

Hot corrosion behaviors of gas tunnel type plasma sprayed La 2Zr 2O 7 thermal barrier coatings  

Microsoft Academic Search

Gas tunnel type plasma sprayed free-standing La2Zr2O7 coating specimens with a thickness of 300–400?m were prepared under optimized operating conditions and were subjected to hot corrosion test in the presence of corrosive impurities such as V2O5, Na2SO4, and Na2SO4+V2O5 mixtures (60:40wt%) at two different temperatures for duration of 5h, i.e. 1000 and 1350K for V2O5 and Na2SO4+V2O5 mixtures, 1200 and

S. Yugeswaran; Akira Kobayashi; P. V. Ananthapadmanabhan

377

Steam injection packer actuator and method  

SciTech Connect

This patent describes a downhole apparatus for controlling fluid pressure in a hydraulic packer actuable from the surface by injecting fluid at a packer actuating pressure sufficient to set the packer in a subterranean petroleum recovery well subjected to temperature variations, comprising: the downhole apparatus including a first fluid chamber in fluid communication with the hydraulic packer for housing a portion of the fluid; closure means for automatically sealing the fluid in the first fluid chamber from downhole fluid exterior to the apparatus; fluid pressure compensator means including a second variable volume chamber and first movably responsive barrier means separating the first fluid chamber and the second chamber. It is movably responsive to the varying pressure of the fluid in the first chamber caused by the temperature variations for increasing the volume of the first chamber while decreasing the volume of the second chamber; accumulator means including a third variable volume chamber for housing a compressible gas and second movable fluid barrier means separating the first fluid chamber and the third chamber. It is movably responsive to the varying pressure of the fluid in the first chamber caused by the temperature variations for preventing excessive fluid pressure in the first chamber by increasing the volume of the first chamber while compressing the gas in the third chamber; and pressure release means for releasing fluid pressure from the first chamber to unset the packer.

Halbardier, F.A.

1987-04-07

378

Fabrication of TiNi shape memory actuator for micropump  

NASA Astrophysics Data System (ADS)

We are attempting to develop a shape memory alloy (SMA) actuated micropump as a component for use in micro analysis or micro dosage systems. In this paper, we will discuss the fabrication process and dynamic actuation properties of an SMA actuator. TiNi thin film of about 6 micrometers in thickness was deposited onto a Si wafer with a square recess on its reverse side, and annealed at 500 degrees C for 1h in a vacuum to memorize an initial flat shape. The TiNi thin film and a Pyrex glass cap of 500 micrometers thickness with a square recess were then anodically bonded together in a vacuum to form a chamber to which a bias pressure was to be applied to deform the TiNi thin film. After removing the remaining 50 $mUm thick Si layer beneath the TiNi thin film by RIE in SF6 plasma, a shape memory diaphragm of 5mm square in size was completed. The fabricated actuator was driven by resistive heating and air-cooling under a bias pressure of 200 kPa, which was applied by a nitrogen gas flow through a small hole pieced in the Pyrex glass cap. Under these conditions, the actuator gave displacements of about 95 micrometers at the center during repeated thermal cycles. A Si check valve structure, to be assembled with the actuator to construct a micropump, was also fabricated through a process of anisotropic etching and fusion bonding. The flow resistance for forward flow proved to be about one-three hundredths of that for backward flow.

Makino, Eiji; Mitsuya, Takashi; Shibata, Takayuki

1999-09-01

379

Novel photomechanical actuators  

NASA Astrophysics Data System (ADS)

The importance of research in optical nano-engineering today is comparable to that of research in semiconductors 60 years ago. Biologically inspired photoactive isomers are being engineered and incorporated into substrates to construct optically addressable nanomachine "laser controlled molecular actuators" which will provide non-contact active figure control, allowing a robust response of lightweight optics to pointing slewing, thermal perturbations, and misalignment. The ability of photoactive molecules to change structure within a matrix in response to light has application to minimizing optical element mass while drastically improving control authority of active optics. Ongoing experiments are providing a foundation for applications in the development of novel optically addressable light-activated shape control of deformable mirrors, as well as addressing issues like damping vibrations after re-pointing large space telescopes. Several types of systems are being studied. The goal is to design and then synthesize materials, generate a picture of molecular scale mechanical forces, bulk geometric distortions, and then to optimize the systems for active optical elements. This requires the design and synthesis of novel photoactive materials. Understanding the molecular-scale motion of photomechanical nano-machines require chemical studies, novel synthesis and fabrication techniques, spectroscopy, imaging molecular-scale mechanical responses and surfaces, optical metrology, and development of novel control techniques. After synthesizing appropriate photoactive substances, active substrates will be produced. A test apparatus is being developed to quantify control authority. Once the chemistry has evolved, a down selection will occur, and new substrates will be fabricated and tested. This talk will report results of this effort.

Ritter, Joseph M.; Brozik, James A.; Emmert, Luke; Fallbach, Mike; Bradford, Rodney; Leo, Donald J.; Meissner, Ken E.

2004-02-01

380

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES: Determination of Ionization Coefficient of Atmospheric Helium in Dielectric Barrier Discharge  

NASA Astrophysics Data System (ADS)

A weakly luminous layer close to the anode is observed at time far ahead of the current pulse in dielectric barrier discharge of helium at atmospheric pressure and it is considered as the result of a very weak Townsend discharge. Based on the assumption that the space charge produced by this Townsend discharge is too small to distort the uniform electric field in the gas gap, the electrons have more or less the same energy over the entire gap and the spatial distribution of the discharge light is proportional to the distribution of electron density. This light distribution is obtained by processing side-view photograph of discharge gap using an intensified charge coupled device camera with an exposure time of 20 ns. By fitting a theoretically derived formula with the measured curve of light distribution, the Townsend electron ionization coefficient a is determined to be 31 cm-1 at E/p = 3.6 V·cm-1·Torr-1, which is much higher than that obtained by solving the Boltzmann equation of pure helium. It is believed that penning ionization of helium metastables with impurity of nitrogen molecules makes great contribution to the experimentally determined ? value. The contribution of this penning ionization to ? is roughly estimated.

Liang, Zhuo; Luo, Hai-Yun; Wang, Xin-Xin; Lv, Bo; Guan, Zhi-Cheng; Wang, Li-Ming

2008-06-01

381

Getting into the cilia: Nature of the barrier(s).  

PubMed

Abstract The primary cilium that protrudes from the plasma membrane of many eukaryotic cell types is very much a cellular organelle in its own right. Its unique membrane and luminal composition is effectively compartmentalized by diffusion barrier at its base, known as the transition zone. Recent works have now shed light on the molecular components of this diffusion barrier, and revealed intriguing functional similarities with other better characterized cellular barriers. PMID:24099335

Lim, Yi Shan; Tang, Bor Luen

2013-10-08

382

A Parylene Bellows Electrochemical Actuator  

PubMed Central

We present the first electrochemical actuator with Parylene bellows for large-deflection operation. The bellows diaphragm was fabricated using a polyethylene-glycol-based sacrificial molding technique followed by coating in Parylene C. Bellows were mechanically characterized and integrated with a pair of interdigitated electrodes to form an electrochemical actuator that is suitable for low-power pumping of fluids. Pump performance (gas generation rate and pump efficiency) was optimized through a careful examination of geometrical factors. Overall, a maximum pump efficiency of 90% was achieved in the case of electroplated electrodes, and a deflection of over 1.5 mm was demonstrated. Real-time wireless operation was achieved. The complete fabrication process and the materials used in this actuator are bio-compatible, which makes it suitable for biological and medical applications.

Li, Po-Ying; Sheybani, Roya; Gutierrez, Christian A.; Kuo, Jonathan T. W.; Meng, Ellis

2011-01-01

383

Deformable Mirrors with Thermal Actuators  

NASA Astrophysics Data System (ADS)

Adaptive optics is applied in lasers, scientific instrumentation, ultrafast sciences, ophthalmology and material processing. For successful use in these applications, the deformable mirrors must be simple, inexpensive, reliable and efficient. Most of the currently used technologies based on piezoelectric, electrostrictive, electromagnetic and electrostatic actuation are rather expensive. We report on a novel type of ultra-low-cost deformable mirror with actuators based on thermal expansion. The 19-channel one inch deformable mirror has response time of ? 15 s, actuator stroke of about 6 ?m, temporal stability of about ?/10 rms in the visible range. The mirror has shown good correction ability for low-order Zernike polynomials, therefore it can be used for correction of rather large aberrations with slow changing amplitudes in both temporal and spatial domains.

Vdovin, G.; Loktev, M.

384

New electrode materials for dielectric elastomer actuators  

NASA Astrophysics Data System (ADS)

Dielectric elastomer actuators exert strain due to an applied electric field. With advantageous properties such as high efficiency and their light weight, these actuators are attractive for a variety of applications ranging from biomimetic robots, medical prosthetics to conventional pumps and valves. The performance and reliability however, are limited by dielectric breakdown which occurs primarily from localized defects inherently present in the polymer film during actuation. These defects lead to electric arcing, causing a short circuit that shuts down the entire actuator and can lead to actuator failure at fields significantly lower than the intrinsic strength of the material. This limitation is particularly a problem in actuators using large-area films. Our recent studies have shown that the gap between the strength of the intrinsic material and the strength of large-area actuators can be reduced by electrically isolating defects in the dielectric film. As a result, the performance and reliability of dielectric elastomers actuators can be substantially improved.

Yuan, Wei; Lam, Tuling; Biggs, James; Hu, Liangbing; Yu, Zhibin; Ha, Soonmok; Xi, Dongjuan; Senesky, Matthew K.; Grüner, George; Pei, Qibing

2007-04-01

385

Miniature linear-to-rotary motion actuator  

NASA Astrophysics Data System (ADS)

A miniature hydraulic actuation system capable of converting linear actuator motion to control surface rotary motion has been designed for application to active controls on dynamic wind tunnel models. Due to space constraints and the torque requirements of an oscillating control surface at frequencies up to 50 Hertz, a new actuation system was developed to meet research objectives. This new actuation system was designed and developed to overcome the output torque limitations and fluid loss/sealing difficulties associated with an existing vane type actuator. Static control surface deflections and dynamic control surface oscillations through a given angle are provided by the actuation system. The actuator design has been incorporated into a transonic flutter model with an active trailing edge flap and two active spoilers. The model is scheduled for testing in the LaRC 16 Foot Transonic Dynamics Tunnel during Summer 1993. This paper will discuss the actuation system, its design, development difficulties, test results, and application to aerospace vehicles.

Sorokach, Michael R., Jr.

1993-05-01

386

Engineered Muscle Actuators: Cells and Tissues.  

National Technical Information Service (NTIS)

We report the completion of Phase II of a technological development program for the production of living muscle mechanical actuators for robotic and prosthetic applications. Our primary objectives were to engineer living skeletal muscle actuators in cultu...

E. Arruda H. Herr K. K. Parker L. Larkin R. G. Dennis

2007-01-01

387

Optimization of a magnetic disk drive actuator with small skew actuation  

Microsoft Academic Search

Currently the utilization of the voice-coil motor for actuating read\\/write head elements in magnetic hard disk drives results in a skewed actuation, which necessitates an involved microjogging process and thus a complicated servo system. Furthermore, in perpendicular recording systems, a small skew actuation will relax the requirement on pole trimming. This article presents a magnetic hard disk drive actuator and

Zhimin He; Eng Hong Ong; Guoxiao Guo

2002-01-01

388

Electrostatically actuatable light modulating device  

DOEpatents

The electrostatically actuatable light modulator utilizes an opaque substrate plate patterned with an array of aperture cells, the cells comprised of physically positionable dielectric shutters and electrostatic actuators. With incorporation of a light source and a viewing screen, a projection display system is effected. Inclusion of a color filter array aligned with the aperture cells accomplishes a color display. The system is realized in terms of a silicon based manufacturing technology allowing fabrication of a high resolution capability in a physically small device which with the utilization of included magnification optics allows both large and small projection displays.

Koehler, Dale R. (1332 Wagontrain Dr., Albuquerque, NM 87123)

1991-01-01

389

Fast-acting valve actuator  

DOEpatents

A fast-acting valve actuator utilizes a spring driven pneumatically loaded piston to drive a valve gate. Rapid exhaust of pressurized gas from the pneumatically loaded side of the piston facilitates an extremely rapid piston stroke. A flexible selector diaphragm opens and closes an exhaust port in response to pressure differentials created by energizing and de-energizing a solenoid which controls the pneumatic input to the actuator as well as selectively providing a venting action to one side of the selector diaphragm.

Cho, Nakwon (Knoxville, TN)

1980-01-01

390

A self-sensing dielectric elastomer actuator  

Microsoft Academic Search

A novel self-sensing method based on the dielectric elastomer (DE) actuator\\/sensor, was successfully developed and evaluated in order to extract accurate displacement information during the actuation process without using any additional sensing device. The proposed self-sensing method is based on a capacitance characteristic of a DE actuator. The DE actuator with a serial external resistor can serve as an electrical

Kwangmok Jung; Kwang J. Kim; Hyouk Ryeol Choi

2008-01-01

391

Note: A novel rotary actuator driven by only one piezoelectric actuator.  

PubMed

This paper presents a novel piezo-driven rotary actuator based on the parasitic motion principle. Output performances of the rotary actuator were tested and discussed. Experiment results indicate that using only one piezoelectric actuator and simple sawtooth wave control, the rotary actuator reaches the rotation velocity of about 20?097 ?rad?s when the driving voltage is 100 V and the driving frequency is 90 Hz. The actuator can rotate stably with the minimum resolution of 0.7 ?rad. This paper verifies feasibility of the parasitic motion principle for applications of rotary actuators, providing new design ideas for precision piezoelectric rotary actuators. PMID:24089880

Huang, Hu; Fu, Lu; Zhao, Hongwei; Shi, Chengli; Ren, Luquan; Li, Jianping; Qu, Han

2013-09-01

392

Note: A novel rotary actuator driven by only one piezoelectric actuator  

NASA Astrophysics Data System (ADS)

This paper presents a novel piezo-driven rotary actuator based on the parasitic motion principle. Output performances of the rotary actuator were tested and discussed. Experiment results indicate that using only one piezoelectric actuator and simple sawtooth wave control, the rotary actuator reaches the rotation velocity of about 20 097 ?rad/s when the driving voltage is 100 V and the driving frequency is 90 Hz. The actuator can rotate stably with the minimum resolution of 0.7 ?rad. This paper verifies feasibility of the parasitic motion principle for applications of rotary actuators, providing new design ideas for precision piezoelectric rotary actuators.

Huang, Hu; Fu, Lu; Zhao, Hongwei; Shi, Chengli; Ren, Luquan; Li, Jianping; Qu, Han

2013-09-01

393

Optimization of a magnetic disk drive actuator with small skew actuation  

NASA Astrophysics Data System (ADS)

Currently the utilization of the voice-coil motor for actuating read/write head elements in magnetic hard disk drives results in a skewed actuation, which necessitates an involved microjogging process and thus a complicated servo system. Furthermore, in perpendicular recording systems, a small skew actuation will relax the requirement on pole trimming. This article presents a magnetic hard disk drive actuator and suspension assembly with small skew actuation. In the present study, the distance from the actuator pivot to the read/write head is chosen so that the skew angle variation is minimized. After that, the suspension head is assembled to the actuator arm at a slant angle with respect to the actuator longitudinal direction to achieve an absolute small skew actuation. Finite element modeling and experimental measurements reveal that there are no significant changes of the actuator assembly dynamic performance with and without the slant angle.

He, Zhimin; Ong, Eng Hong; Guo, Guoxiao

2002-05-01

394

Investigations on actuation characteristics of IPMC artificial muscle actuator  

Microsoft Academic Search

Electromechanical response characteristics of ion-exchange polymer metal composite (IPMC), known as a material for artificial muscle actuators, varies extremely depending on the driving method. With respect to the power management the driving method is one of the important considerations though it has not been investigated sufficiently up to now. Its efficiency is critical to enhance the performance of an IPMC

Kwangmok Jung; Jaedo Nam; Hyoukryeol Choi

2003-01-01

395

Control system design for docking actuator  

Microsoft Academic Search

Research on the control system design for actuators used in a space docking system is presented. The phase of velocity matching and that of attenuation in the soft docking process are investigated by utilizing an experimental docking test facility which includes an electromechanical actuator and an air-lifted docking target. In the matching phase, the actuator is accelerated to match the

S. Niwa; M. Suzuki; J. Zhou; A. Miyata

1991-01-01

396

Dielectric elastomer actuators for tactile displays  

Microsoft Academic Search

In this paper we discuss dielectric elastomer actuators (DEA) as one of the most promising technologies in electroactive polymers (EAP). For tactile display applications a large number of actuator elements is essential. The multilayer technology presented here offers the possibility to build up independent actuators and arrays at a high density within one substrate. The functional principle of these electromechanical

Marc Matysek; Peter Lotz; Thomas Winterstein; Helmut F. Schlaak

2009-01-01

397

Performance of dielectric elastomer actuators and materials  

Microsoft Academic Search

Dielectric elastomer actuators performance depends on their construction and the way they are driven. We describe the governing equations for the dynamic performance of actuators and show examples of their use. Both the properties of the base elastomer material and the compliant electrodes influence the actuators performance. The mechanical and electrical properties of elastomers are discussed with a focus on

Peter Sommer-Larsen; Guggi Kofod; M. H. Shridhar; Mohammed Benslimane; Peter Gravesen

2002-01-01

398

Dielectric elastomer based prototype fiber actuators  

Microsoft Academic Search

Dielectric elastomer based prototype fiber actuators have been developed and evaluated. The work is motivated by the tremendous potential offered by the current multicomponent fiber forming technologies as a means to fabricate fiber actuators. To explore the potential, prototype fiber actuators have been fabricated using commercially available dielectric elastomer tubes and by applying appropriate compliant electrodes to inner cavity and

Sohil Arora; Tushar Ghosh; John Muth

2007-01-01

399

Application of smart material-hydraulic actuators  

Microsoft Academic Search

The application of a new class of actuators is considered. The actuators under development combine a high energy density smart material, specifically a piezoelectric material, with internal servohydraulic components. Large displacement outputs are produced, while the high force capacity of the stiff smart material is retained, for a net high-energy output. The actuator is considered \\

Eric H. Anderson; Gregory L. Bales; Edward V. White

2003-01-01

400

Application of Smart Material-Hydraulic Actuators  

Microsoft Academic Search

The application of a new class of actuators is considered. The actuators under development combine a high energy density smart material, specifically a piezoelectric material, with internal servohydraulic components. Large displacement outputs are produced, while the high force capacity of the stiff smart material is retained, for a net high- energy output. The actuator is considered \\

Eric H. Anderson; Gregory L. Bales; Edward V. White

401

Active suspension with multilayer dielectric elastomer actuator  

Microsoft Academic Search

A promising application for dielectric elastomer actuators (DEA) is the active vibration control in the low frequency range (0 - 200 Hz). The active and passive properties of the actuator can be joined to eliminate the disturbances in the whole frequency range. These actuators can be used for protection of lightweight sensible equipment like optic e. g. components. This paper

Roman Karsten; Peter Lotz; Helmut F. Schlaak

2011-01-01

402

The LDCM actuator for vibration suppression  

Microsoft Academic Search

A linear DC motor (LDCM) has been proposed as an actuator for the COFS I Mast and the COFS program ground test Mini-Mast. The basic principles of operation of the LDCM as an actuator for vibration suppression in large flexible structures are reviewed. Because of force and stroke limitations, control loops are required to stabilize the actuator, which results in

E. N. Ide; D. K. Lindner

1988-01-01

403

The LDCM actuator for vibration suppression  

Microsoft Academic Search

A linear dc motor (LDCM) has been proposed as an actuator for the COFS I mast and the COFS program ground test Mini-Mast. The basic principles of operation of the LDCM as an actuator for vibration suppression in large flexible structures are reviewed. Because of force and stroke limitations, control loops are required to stabilize the actuator, which results in

Eric N. Ide; Douglas K. Lindner

1988-01-01

404

Modelling surface-micromachined electrothermal actuators  

Microsoft Academic Search

A method for the accurate simulation of electrothermal actuators is presented. The model accounts for variations in material parameters that occur over the temperature range at which polysilicon electrothermal actuators are operated. The paper then presents the steps necessary to perform a sequential electrothermal-mechanical analysis using ANSYS modelling software. The model is compared against actuators fabricated using a surface-micromachining process

R. W. Johnstone; M. Parameswaran

2004-01-01

405

A vacuum-driven peristaltic micropump with valved actuation chambers  

NASA Astrophysics Data System (ADS)

This paper presents a simple peristaltic micropump design incorporated with valved actuation chambers and propelled by a pulsed vacuum source. The vacuum-driven peristaltic micropump offers high pumping rates, low backflow, appreciable tolerance to air bubbles, and minimal destruction to fluid contents. The pumping device, fabricated by laser micromachining and plasma bonding of three polydimethylsiloxane (PDMS) layers, includes a pneumatic network, actuation membranes, and microfluidic channels. As the key to peristaltic motion, the sequential deflection of the elastic membranes is achieved by periodic pressure waveforms (negative) traveling through the pneumatic network, provided by a vacuum source regulated by an electromagnetic valve. This configuration eliminates the complicated control logic typically required in peristaltic motion. Importantly, the valved actuation chambers substantially reduce backflow and improve the pumping rates. In addition, the pneumatic network with negative pressure provides a means to effectively remove air bubbles present in the microflow through the gas-permeable PDMS membrane, which can be highly desired in handling complex fluidic samples. Experimental characterization of the micropump performance has been conducted by controlling the resistance of the pneumatic network, the number of normally closed valves, the vacuum pressure, and the frequency of pressure pulses. A maximal flow rate of 600 µL min-1 has been optimized at the pulsed vacuum frequency of 30 Hz with a vacuum pressure of 50 kPa, which is comparable to that of compressed air-actuated peristaltic micropumps.

Cui, Jianguo; Pan, Tingrui

2011-06-01

406

Actuation Compensation for Flexible Surgical Snakelike Robots with Redundant Remote Actuation  

Microsoft Academic Search

This paper presents two actuation compensation methods for a snake-like robot implementing multi flexible backbones and actuation redundancy. This snake-like robot is designed for distal dexterity enhancement in MIS surgery of the throat. Actuation compensation is required to account for the flexibility of the actuation lines that connect this snake-like robot with its remote actuation units. The paper presents both

Kai Xu; Nabil Simaan

2006-01-01

407

Discharge-Mode Transition in Jet-Type Dielectric Barrier Discharge Using Argon/Acetone Gas Flow Ignited by Small Helium Plasma Jet  

NASA Astrophysics Data System (ADS)

A discharge-mode transition in a jet-type dielectric barrier discharge (DBD) was triggered by a small fraction of acetone vapor added to an argon (Ar) gas flow at atmospheric pressure. In order to trigger a stable discharge in the Ar/acetone gas flow with a relatively small applied voltage, we used an additional small plasma jet using a He gas flow on the side of the main flow. The transition from filamentary to glow like discharge modes took place upon increasing the acetone-vapor ratio, with the transition occurring at an acetone content of approximately 0.3 vol %. We compared discharge currents, optical emission spectra, and deposited materials on the substrate in each discharge mode to characterize the discharge phenomena. The experimental results clearly indicate that the characteristics of the jet-type DBD show nonlinear dependence on the acetone-vapor ratio, especially around the transition to the discharge mode. It was also found by microscopic observations that the surface morphologies of the deposited materials were completely different in the filamentary and glow like modes.

Urabe, Keiichiro; Yamada, Keitaro; Sakai, Osamu

2011-11-01

408

Diagnosis of hydrogen ions (H+, H_{2}^{+} , H_{3}^{+} , H-) from the near-electrode region of dielectric barrier discharge plasmas  

NASA Astrophysics Data System (ADS)

Hydrogen ions (H+, H_{2}^{+} , H_{3}^{+} ) from the near-ground-electrode region in dielectric barrier discharge plasmas were characterized using a molecular beam mass spectrometer under a hydrogen pressure of 1-80 Torr. The measured H+ current is more than one to a few orders of magnitude greater than the currents of H_{2}^{+} and H_{3}^{+} at a pressure of 1-15 Torr, with a peak-to-peak voltage of 50 kV and 35 kHz ac power source. At a gas pressure range of 15-80 Torr, only the H+ ionic signal is observed. The hydrogen ion currents rise with increasing discharge voltage and ac frequency but exhibit a maximum over the H2 pressure range studied. The H- ionic signal is also detected under certain discharge conditions within a hydrogen pressure of 1.5-35 Torr. The main physicochemical processes of interaction between hydrogen ions, neutrals and electrons in the alternative and temporary cathode sheath near the discharge electrode have been discussed. The dependence of the mean energy of H- ions on H2 pressure has also been obtained.

Wang, Wenchun; Xu, Yong; Wang, Weiguo; Zhu, Aimin

2004-04-01

409

NOx remediation in oxygen-rich exhaust gas using atmospheric pressure non-thermal plasma generated by a pulsed nanosecond dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

It is clearly seen that the application of non-thermal plasmas (NTP) to remove NOx from gas mixture containing a large amount of oxygen (O2) is dominated by NO to NO2 oxidation. Experiments have been conducted using a NTP generated by a nanosecond pulsed dielectric barrier discharge in synthetic exhaust gas, prepared from N2, O2, NO, H2O, and C3H6, over a large range of gas temperature (20-300\\r{}C). Results show that the NOx removal rate significantly increased with increasing specific energy deposition. For example, at a temperature of 100\\r{}C and an energy deposition of 27 J l-1, 92% of the NO molecules have been removed. The W values for NO is dramatically reduced to values scaling from ?15 eV at 27 J l-1 down to ?4 eV at 7 J l-1. NOx removal efficiency around 43% was obtained at a temperature of 260\\r{}C and a space velocity of 60 000 h-1 for a specific input energy of 27 J l-1. W values for NOx were less than ?30 eV. Such treatments in exhaust gas with and without the presence of water vapour induced reactions leading to the production of a large variety of by-products such as acetaldehyde, propylene oxide, formic acid, methyl nitrate, and nitromethane.

Khacef, A.; Cormier, J. M.; Pouvesle, J. M.

2002-07-01

410

Innovative approach to high stroke electrostatic actuators  

NASA Astrophysics Data System (ADS)

The electrostatic actuation is still a preferred principle in modern microelectromechanical systems (MEMS). Based on the Coulomb attraction between two different point charges, the electrostatic actuation is a surface effect and thus volume-independent. In addition, the efficiency of electrostatic actuation increases with a decreasing gap size between the electrodes. The relatively simple morphology of an electrostatic actuator allows low-cost wafer-level fabrication, making it a versatile and convenient principle for MEMS actuators. Although the electrostatic principle seems only to be applicable for actuators in micrometer scale, this paper presents the successful upscaling of an electrostatic actuator to the millimeter scale, still utilizing the major advantages, including wafer-level fabrication, of the said principle and providing a high stroke with low actuation voltage. For such an actuator, we replace the common silicon with the non-conducting OrmoComp, a UV-curable hybrid polymer, suitable for wafer-level fabrication. With a significantly lower elastic modulus, only a fraction of actuation voltage is necessary for a similar deflection. The electrodes are realized with additional coatings of thin metal layers. To achieve a high stroke, while maintaining a relatively low voltage, the actuator design is based on a redesigned zipper actuator. With our developed fabrication process, we are able to create a highly displaced out-of-plane actuator, while almost eliminating the initial gap between the electrodes. Experimental results of a wafer-level fabricated zipper actuator show an out-of-plane motion up to 470 ?m at an actuation voltage of 374 V.

Lange, N.; Wippermann, F.; Beckert, E.; Eberhardt, R.; Tünnermann, A.

2013-03-01

411

Stick and slip actuators (SSA)  

NASA Astrophysics Data System (ADS)

Stick and Skip Actuators (SSA) are particularly well adapted to micro- robotics. A simple design, a very high intrinsic resolution (a few nanometers) and a high rigidity make them especially interesting in high precision micro-manipulations. Moreover, a smart design allows to combine the guiding and actuating function. The mechanical interface between the piezo-elements and the guiding mechanisms in an important point of the stick and slip actuators. The design of this interface and the choice of the material are very important. Both aspects have an impact on the rigidity, which has an influence on the behavior of the actuator. They have also an incidence onf the reliability (lifetime) because the design gives the contact condition and the material the wear resistance. In addition, a loading system allowing to keep the mechanical contact at this interface has a direct effect on the contact pressure. In order to confirm the performance of SSA, prototypes have been developed at the ISR. Their designs have bene made for application in optical microscopy, for manipulators in industrial assembly of micro- engineering products, for micro-factory, chemical and bio-engineering equipment for research or routine tasks, such as testing, screening etc. This paper presents a short description of several SSA made by the IRS and describes the parameters characterizing the stick and slip motion and the mechanical interface.

Schmitt, Carl; Breguet, Jean-Marc; Bergander, Arvid; Clavel, Reymond

2000-10-01

412

Applications of dielectric elastomer actuators  

Microsoft Academic Search

Dielectric elastomer actuators, based on the field-induced deformation of elastomeric polymers with compliant electrodes, can produce a large strain response, combined with a fast response time and high electromechanical efficiency. This unique performance, combined with other factors such as low cost, suggests many potential applications, a wide range of which are under investigation. Applications that effectively exploit the properties of

Ron Pelrine; Peter Sommer-Larsen; Roy D. Kornbluh; Richard Heydt; Guggi Kofod; Qibing Pei; Peter Gravesen

2001-01-01

413

Shape-memory actuated gimbal  

Microsoft Academic Search

Future spacecraft systems will require advanced positioning systems to meet stringent reliability, vibration, lightweighting, and cost requirements. Current devices employing stepping motor and gear reduction assemblies may not be able to meet future design needs. A shape memory alloy (SMA) actuated multiaxis gimbal has been developed that provides solutions to these mechanism issues. SMAs utilize a thermally activated reversible phase

Bernie F. Carpenter; R. J. Head; Russ Gehling

1995-01-01

414

Distributed structural actuation with electrostrictors  

Microsoft Academic Search

This paper develops a model for the behavior of an electrostrictively coupled electromechanical system. The framework for the derivation of the governing equations is sufficiently general to model the dynamics of any nonlinear electroceramic actuated system which can be described by a set of constitutive relationships. The constitutive relations for electrostrictors are reviewed and are simplified to contain a single

Michael L. Fripp; Nesbitt W. Hagood; Lana Luoma

1994-01-01

415

Electro-active paper actuators  

NASA Astrophysics Data System (ADS)

In this paper, the actuation mechanism of electro-active paper (EAPap) actuators is addressed and the potential of the actuators is demonstrated. EAPap is a paper that produces large displacement with small force under an electrical excitation. EAPap is made with a chemically treated paper by constructing thin electrodes on both sides of the paper. When electrical voltage is applied on the electrodes the EAPap produces bending displacement. However, the displacement output has been unstable and degraded with timescale. To improve the bending performance of EAPap, different paper fibers - softwood, hardwood, bacteria cellulose, cellophane, carbon mixture paper, electrolyte containing paper and Korean traditional paper, in conjunction with additive chemicals, were tested. Two attempts were made to construct the electrodes: the direct use of aluminum foil and the gold sputtering technique. It was found that a cellophane paper exhibits a remarkable bending performance. When 2 MV m-1 excitation voltage was applied to the paper actuator, more than 3 mm tip displacement was observed from the 30 mm long paper beam. This is quite a low excitation voltage compared with that of other EAPs. Details of the experiments and results are addressed.

Kim, Jaehwan; Seo, Yung B.

2002-06-01

416

Rotary actuator with energy conservation  

Microsoft Academic Search

An energy conserving air motor with rotary actuation includes a pair of cooperating different diameter pistons coaxially arranged and connected rigidly to one another by a central connecting member provided with spur gear section adaptable of receiving a meshing pinion assembled inside an elongated housing provided with a diffential diameter bore passing therethrough and adaptable of receiving inside a larger

Pauliukonis

1984-01-01

417

Electromagnetically actuated ball valve micropumps  

Microsoft Academic Search

We present two types of oscillating diaphragm micropumps configured with passive ball valves and using electromagnetic actuation. One type is made out of poly(methyl methacrylate) (PMMA), while the other one is made out of borosilicate glass. Both were produced using the powder blasting microfabrication method. The pumping resonant frequency was measured to be within the range of 20-30 Hz for

Christophe Yamahata; Frédéric Lacharme; Jan Matter; Silvan Schnydrig; Yves Burri; Martin A. M. Gijs

2005-01-01

418

Piezoelectric multilayer actuator life test.  

PubMed

Potential NASA optical missions such as the Space Interferometer Mission require actuators for precision positioning to accuracies of the order of nanometers. Commercially available multilayer piezoelectric stack actuators are being considered for driving these precision mirror positioning mechanisms. These mechanisms have potential mission operational requirements that exceed 5 years for one mission life. To test the feasibility of using these commercial actuators for these applications and to determine their reliability and the redundancy requirements, a life test study was undertaken. The nominal actuator requirements for the most critical actuators on the Space Interferometry Mission (SIM) in terms of number of cycles was estimated from the Modulation Optics Mechanism (MOM) and Pathlength control Optics Mechanism (POM) and these requirements were used to define the study. At a nominal drive frequency of 250 Hz, one mission life is calculated to be 40 billion cycles. In this study, a set of commercial PZT stacks configured in a potential flight actuator configuration (pre-stressed to 18 MPa and bonded in flexures) were tested for up to 100 billion cycles. Each test flexure allowed for two sets of primary and redundant stacks to be mechanically connected in series. The tests were controlled using an automated software control and data acquisition system that set up the test parameters and monitored the waveform of the stack electrical current and voltage. The samples were driven between 0 and 20 V at 2000 Hz to accelerate the life test and mimic the voltage amplitude that is expected to be applied to the stacks during operation. During the life test, 10 primary stacks were driven and 10 redundant stacks, mechanically in series with the driven stacks, were open-circuited. The stroke determined from a strain gauge, the temperature and humidity in the chamber, and the temperature of each individual stack were recorded. Other properties of the stacks, including the displacement from a capacitance gap sensor and impedance spectra were measured at specific intervals. The average degradation in the stroke over the life test was found to be small (<3%) for the primary stacks and <4% for the redundant stacks. It was noted that about half of the stroke reduction occurred within the first 10 billion cycles. At the end of the life test, it was found that the actuator could recover about half of the lost stroke by applying a dc voltage of 100 V at room temperature. The data up to 100 billion cycles for these tests and the analysis of the experimental results are presented in this paper. PMID:21507759

Sherrit, Stewart; Bao, Xiaoqi; Jones, Christopher M; Aldrich, Jack B; Blodget, Chad J; Moore, James D; Carson, John W; Goullioud, Renaud

2011-04-01

419

Study of flapping actuator modules using IPMC  

NASA Astrophysics Data System (ADS)

The Ionic Polymer Metal Composite (IPMC), an electro-active polymer, has many advantages including bending actuation, low weight, low power consumption, and flexibility. These advantages coincide with the requirements of flapping-wing motion. Thus, IPMC can be an adequate smart material for the generation of the flapping-wing motions. In this research, a flapping actuator module operated at the resonant frequency is developed using an IPMC actuator. First, IPMC actuators are fabricated to investigate the mechanical characteristics of IPMC as an actuator. The performances of the IPMC actuators, including the deformation, blocking force and natural frequency, are then obtained according to the input voltage and IPMC dimensions. Second, the empirical performance model and the equivalent stiffness model of the IPMC actuator are established. Third, flapping actuator modules using the first resonance frequency are developed, and their flapping frequency and stroke characteristics are investigated. Fourth, adequate flapping models for a flapping actuator module are selected, and dimensional data such as wing area and wing mass are obtained. Finally, the flapping actuator module is designed and manufactured to adjust the flapping models and its performance is tested. Experimental results demonstrate the potential IPMC has for use as a flapping actuator.

Kim, Hong-Il; Kim, Dae-Kwan; Han, Jae-Hung

2007-04-01

420

Enhanced IPMC actuation by thermal cycling  

NASA Astrophysics Data System (ADS)

IPMCs are bi-polar actuators capable of large, rapid actuation in flexural configurations. The limit of actuation is defined by the maximal voltage that can be applied to the IPMC, above which electrolysis of the electrolyte and damage to the IPMC may occur. In this paper we present preliminary results that indicate how this actuation limit could be tuned and even exceeded through controlled thermal cycling of gold-plated Nafion IPMCs. Thermal cycling is used to move the centre point of the actuation stroke. Subsequent voltage stimulation actuates the structure around this new centre point. It is shown that by further thermal cycling this centre point naturally returns to its initial position. By exploiting this shape memory characteristic as part of a control system it is expected that more sophisticated IPMC actuation will be achievable.

Rossiter, Jonathan; Takashima, Kazuto; Mukai, Toshiharu

2012-03-01

421

Plasma chemical reactions in C2H2/N2, C2H4/N2, and C2H6/N2 gas mixtures of a laboratory dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

Plasma chemical reactions in C2H2/N2, C2H4/N2, and C2H6/N2 gas mixtures have been studied by means of mass spectrometry at a medium pressure of 300 mbar in a laboratory dielectric barrier discharge. A major reaction scheme is production of larger hydrocarbons like CnHm with n up to 12 including formation of functional CN groups.

Thejaswini, H. C.; Majumdar, Abhijit; Maung Tun, Tin; Hippler, Rainer

2011-09-01

422

Characteristics of SiO x N y films deposited by inductively coupled plasma enhanced chemical vapor deposition using HMDS\\/NH 3\\/O 2\\/Ar for water vapor diffusion barrier  

Microsoft Academic Search

SiOxNy thin films were deposited by inductively coupled plasma enhanced chemical vapor deposition (ICP-PECVD) using hexamethyldisilazane (HMDS, 99.9%)\\/NH3\\/O2\\/Ar at a low temperature, and examined for use as a water vapor diffusion barrier. The film characteristics were investigated as a function of the O2:NH3 ratio. An increase in the O2:NH3 ratio decreased the level of impurities such as –CHx, N–H in

J. H. Lee; C. H. Jeong; H. B. Kim; J. T. Lim; S. J. Kyung; G. Y. Yeom

2006-01-01

423

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

424

Thermopneumatic actuator for tactile displays and smart actuation circuitry  

NASA Astrophysics Data System (ADS)

This paper presents a thermopneumatic actuator to build large tactile displays as well as a smart activation circuitry to study and improve its performance. Since the main drawback of large tactile screens in the market is their cost, this proposal is intended to reduce the price because of the simplicity of the actuator and the potential low cost assembling. A small display with 4 x 4 taxels and 2.54mm of distance between centres has been built to show the viability of the proposal. Furthermore, a smart actuation strategy is implemented where the heater element (a diode) is also used as sensor in a feedback control loop that improves the dynamic response. Such strategy consists in sensing the voltage drop in the diode to measure its temperature, thus it can be heated up quickly without being destroyed because power supply is decreased once the target temperature is reached. We have measured rise times around 2 seconds and fall times around 4 seconds, while the maximum force and stroke are above 10grams (0.1N) and 1mm respectively. The obtained results are good, specially to implement a large tactile screen. Power consumption is high, but it could be lower if latching mechanisms are used to keep the taxel active without power supply.

Vidal-Verdu, F.; Madueno, Manuel J.; Navas, Rafael

2005-07-01

425

Enhancing the force capability of permanent magnet latching actuators for electromechanical valve actuation systems  

NASA Astrophysics Data System (ADS)

This article introduces a topology of parallel-polarized permanent magnet latching actuator for use in electromagnetic valve actuation systems for internal combustion engines. The actuator has a number of advantages over reluctance actuators, commonly employed in such systems, in terms of reduced starting currents and fail-safe capability. The influence of a number of design features on actuator performance, such as tooth tapering, additional magnets to improve the main magnet flux path and prevent the onset of saturation, and mechanical clearances required to protect the permanent magnet from shock loads are investigated. The design study findings are verified by measurements on a prototype actuator.

Rens, J.; Clark, R. E.; Jewell, G. W.; Howe, D.

2005-05-01

426

Design of Nafion actuator with enhanced displacement  

NASA Astrophysics Data System (ADS)

A new actuator system has been developed. This actuator uses Nafion, a solid electrolyte, in combination with Platinum Copper (Pt-Cu) electrodes and mobile ions of Cu2+ to create much larger actuation displacement at smaller levels of applied voltage (1V or less). This actuator provides bending deformation. Large deformation is provided by electrode reaction of copper. Since this reaction is reversible, Cu electrode is not consumed by using polarity change of applied voltage. This actuation mechanism is different from others. Because the induction of the large deflection of Nafion, the large number of the mobile cations is essential. Although it is possible to induce a large deflection by applying a higher electric field as alternative way, this would introduce the electrolysis of water that is not desired unless the device is always submerged in water. To convert bending deformation to liner actuation, we designed a device using a pair of Nafion actuator, which is termed as loop actuator. This loop actuator can be designed into the device with large force by making parallel array. Solid polymer electrolyte-metal composite actuator contains water inside. Therefore coating that prevents water from evaporation is needed for its use in dry condition.

Uchida, Mikio; Xu, Chunye; Le Guilly, Marie; Taya, Minoru

2002-07-01

427

Piezoelectric step-motion actuator  

SciTech Connect

A step-motion actuator using piezoelectric material to launch a flight mass which, in turn, actuates a drive pawl to progressively engage and drive a toothed wheel or rod to accomplish stepped motion. Thus, the piezoelectric material converts electrical energy into kinetic energy of the mass, and the drive pawl and toothed wheel or rod convert the kinetic energy of the mass into the desired rotary or linear stepped motion. A compression frame may be secured about the piezoelectric element and adapted to pre-compress the piezoelectric material so as to reduce tensile loads thereon. A return spring may be used to return the mass to its resting position against the compression frame or piezoelectric material following launch. Alternative embodiment are possible, including an alternative first embodiment wherein two masses are launched in substantially different directions, and an alternative second embodiment wherein the mass is eliminated in favor of the piezoelectric material launching itself.

Mentesana; Charles P. (Leawood, KS)

2006-10-10

428

Smart aerodynamic control surface actuator  

NASA Astrophysics Data System (ADS)

Integral control surfaces in rear sections of airfoils can be used to actively control camber. This has potential applications in individual blade cyclic control of helicopters and in aeroelastic control of fixed-wing aircraft. When analyzed as actuators, integral control surfaces will have a characteristically misbehaved frequency response function (FRF). Taking tip displacement as a result of a force input, one would expect either highly peaked resonances characteristic of such a substructure or large areas of very low response depending on what part of the frequency domain the observation is made. In this paper, active control is used locally to convert the FRF of a proposed integral actuator into a more favorable flat-gain FRF in a frequency range of interest. This is accomplished while still exploiting at least some of the gain of the open loop first structural resonance. Both experiment and analysis are presented.

Griffin, Steven F.; Hanagud, Sathya V.

1994-05-01

429

Electrostatically actuated conducting polymer microbridges  

NASA Astrophysics Data System (ADS)

All-polymer microbridge electrostatic actuators based on a blended conductive polymer are fabricated using surface micromachining on glass substrates. A fabrication process is developed that allows the preservation of the electrical conductivity of the polymer structural layer and the suspension of the polymer microbridges. The electromechanical properties of the microbridges are studied using electrostatic actuation and optical and electrical detections. The pull-in phenomena and a dependence of the bridge deflection with the square of the applied voltage are observed. Compared to the silicon-based microbridges, the polymer structures present higher deflection amplitude for the same applied electrical force. The resonance frequency of the polymer bridges occurs in the megahertz range with quality factors of the order of 100 when measured in vacuum. The mechanical properties of the polymer device are affected by residual stress.

Zhang, G.; Chu, V.; Conde, J. P.

2007-03-01

430

Microelectromagnetic ferrofluid-based actuator  

NASA Astrophysics Data System (ADS)

Computer simulations were used to investigate the performance of a microscale ferrofluid-based magnetic actuator developed for liquid dispensing in microfluidic channels. The actuation was based on the movement of a ferrofluid plug in a magnetic field gradient generated by on-chip effectively infinite parallel conductors. The movement, positioning, and retaining of ferrofluid plugs with different lengths at various locations along a microfluidic channel were investigated for two cases. In case (a), the magnetic field gradient was generated by a single conductor; when the ferrofluid reached its equilibrium position, the current was switched off and the nearest neighbor conductor was energized. A similar, consecutive on/off current switching was performed for case (b), where a set of conductors was energized simultaneously.

Melikhov, Y.; Lee, S. J.; Jiles, D. C.; Schmidt, D. H.; Porter, M. D.; Shinar, R.

2003-05-01

431

Propeller pitch change actuation system  

SciTech Connect

An apparatus is described for adjusting the pitch of a variable pitch propeller blade characterized by: an actuator for setting the pitch of the propeller blade the actuator having; a rotatable screw for setting propeller pitch, a nut mounted for longitudinal motion along the screw as the screw is rotated, means for connecting the nut to the propeller blade to adjust the pitch of the propeller blade as the screw rotates, and a rotatable means mounted within the nut for locking the nut against longitudinal motion if the rotatable means is not rotating with the longitudinal motion of the nut and for allowing the nut to move longitudinally if the rotatable means is rotating with the longitudinal motion of the nut.

Kusiak, E.H.

1988-06-28

432

Electrospun polymer-CNT actuators  

NASA Astrophysics Data System (ADS)

Electrospun polymer-MWCNTs fibers were prepared using a precursor solution that consists of multiwall carbon nanotubes (MWCNTs), Poly(dymethylsiloxane) and Poly(methylmethacrylate) in Tetrahydrofuran (THF) and Dimethylformamide (DMF). Before adding them into the precursor, the MWCNTs were dispersed in Sodium Dodecyl Sulfate (SDS) and water. We report evidence of UV photo-conduction and photo-actuation in electrospun PDMS/PMMA-CNT composite fibers.

Crespo, J. P.; Rosa, S.; Meléndez, A.; Santiago-Avilés, J. J.; Ramos, I.; Campo, E. M.

2011-09-01

433

Ferrofluid-Impregnated Paper Actuators  

Microsoft Academic Search

In this paper, we report on an inexpensive method of fabricating miniature magnetic actuators using ferrofluid- impregnated paper. Different types of papers (including soft tissue paper, cleanroom paper, Whatman-1 filter paper, printer paper, and newspaper) were loaded with oil-based ferrofluid, microma- chined by a CO2 laser and coated with a thin layer of parylene-C. The soaking capability of the different

Zhenwen Ding; Pinghung Wei; Girish Chitnis; Babak Ziaie

2011-01-01

434

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

435

Cryomechanism: a cryogenic rotating actuator  

NASA Astrophysics Data System (ADS)

Fifteen years ago, CEA started the development of cryogenic rotating actuators for the astrophysical infrared camera (VISIR) that is set on the Very Large Telescope (VLT). At the time of the VISIR first light in 2004, 10 cryogenic rotating actuators, also known as "CryoMechanisms" (CM), were present in the instrument. Today VISIR is still operating and the CM that are actuated several times a day, have no reported failure up to now. In continuation of the VISIR project, CEA undertook space qualification tests with the aim of making the CM compatible with space missions. Relying on this background, a smaller model of the mechanism has been built and tested at cryogenic temperatures. Today, the cryomechanisms are selected for the ESA/EUCLID [1] space mission. The qualification program will run throughout 2014. This paper first describes the VISIR's baseline specification, the CM design and its operation principle. Then, the upgrades for the space constrains are shown and the qualification plan with respect to vibrations, thermal cycling and life testing campaigns is given. Some results of the tests carried out on a qualification model are addressed. At end, the design improvements for the EUCLID project are presented and a summary of the CM capabilities is highlighted.

Barriere, J.-C.; Berthé, M.; Carty, M.; Duboué, B.; Fontignie, J.; Leboeuf, D.; Martignac, J.; Cara, C.; Charon, P.; Durand, G. A.; Bachet, D.

2013-09-01

436

Dielectric Elastomer Actuators for A Portable Force Feedback Device  

Microsoft Academic Search

This paper focuses on the development of novel actuators for a portable force feedback glove for, but not limited to, the simulation of organ palpations. A conceptual design of a chain-like actuator based on electroactive polymers is introduced. One elementary actuator of this chain was built in order to explore and optimize the actuator manufac- turing process. Actuators manufactured with

Rui Zhang; Andreas Kunz; Gabor Kovacs; Silvain Michel; Andrea Mazzone

437

Design of a smart material actuator for rotor control  

Microsoft Academic Search

The results of a study to conceptually define an on-blade smart material actuator for primary and active control on a servoflap rotor are presented. Actuator design drivers, goals, and requirements are defined. For a previously developed hybrid actuator concept, the design of the cyclic and active (high speed) control actuator and feasibility of the collective (low speed) actuator and stroke

Friedrich K. Straub; Donald J. Merkley

1995-01-01

438

Design of a smart material actuator for rotor control  

Microsoft Academic Search

The results of a study to conceptually define an on-blade smart material actuator for primary and active control on a servoflap rotor are presented. Actuator design drivers, goals, and requirements are defined. For a previously developed hybrid actuator concept, the design of the cyclic and active (high speed) control actuator and feasibility of the collective (low speed) actuator and stroke

Friedrich K. Straub; Donald J. Merkley

1997-01-01

439

Fundamental behavior of piezoceramic sheet actuators  

NASA Astrophysics Data System (ADS)

This paper investigates the behavior of piezoceramic actuators under different typ