Profile measurements in the plasma edge of mega amp spherical tokamak using a ball pen probe

NASA Astrophysics Data System (ADS)

Walkden, N. R.; Adamek, J.; Allan, S.; Dudson, B. D.; Elmore, S.; Fishpool, G.; Harrison, J.; Kirk, A.; Komm, M.

2015-02-01

The ball pen probe (BPP) technique is used successfully to make profile measurements of plasma potential, electron temperature, and radial electric field on the Mega Amp Spherical Tokamak. The potential profile measured by the BPP is shown to significantly differ from the floating potential both in polarity and profile shape. By combining the BPP potential and the floating potential, the electron temperature can be measured, which is compared with the Thomson scattering (TS) diagnostic. Excellent agreement between the two diagnostics is obtained when secondary electron emission is accounted for in the floating potential. From the BPP profile, an estimate of the radial electric field is extracted which is shown to be of the order ˜1 kV/m and increases with plasma current. Corrections to the BPP measurement, constrained by the TS comparison, introduce uncertainty into the ER measurements. The uncertainty is most significant in the electric field well inside the separatrix. The electric field is used to estimate toroidal and poloidal rotation velocities from E × B motion. This paper further demonstrates the ability of the ball pen probe to make valuable and important measurements in the boundary plasma of a tokamak.

Floating potential in electronegative plasmas for non-zero ion temperatures

NASA Astrophysics Data System (ADS)

Regodón, Guillermo Fernando; Fernández Palop, José Ignacio; Tejero-del-Caz, Antonio; Díaz-Cabrera, Juan Manuel; Carmona-Cabezas, Rafael; Ballesteros, Jerónimo

2018-02-01

The floating potential of a Langmuir probe immersed in an electronegative plasma is studied theoretically under the assumption of radial positive ion fluid movement for non-zero positive ion temperature: both cylindrical and spherical geometries are studied. The model is solvable exactly. The special characteristics of the electronegative pre-sheath are found and the influence of the stratified electronegative pre-sheath is shown to be very small in practical applications. It is suggested that the use of the floating potential in the measurement of negative ions population density is convenient, in view of the numerical results obtained. The differences between the two radial geometries, which become very important for small probe radii of the order of magnitude of the Debye length, are studied.

Profile measurements in the plasma edge of mega amp spherical tokamak using a ball pen probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walkden, N. R., E-mail: nrw504@york.ac.uk; Department of Physics, York Plasma Institute, University of York, Heslington, York YO10 5DD; Adamek, J.

The ball pen probe (BPP) technique is used successfully to make profile measurements of plasma potential, electron temperature, and radial electric field on the Mega Amp Spherical Tokamak. The potential profile measured by the BPP is shown to significantly differ from the floating potential both in polarity and profile shape. By combining the BPP potential and the floating potential, the electron temperature can be measured, which is compared with the Thomson scattering (TS) diagnostic. Excellent agreement between the two diagnostics is obtained when secondary electron emission is accounted for in the floating potential. From the BPP profile, an estimate ofmore » the radial electric field is extracted which is shown to be of the order ∼1 kV/m and increases with plasma current. Corrections to the BPP measurement, constrained by the TS comparison, introduce uncertainty into the E{sub R} measurements. The uncertainty is most significant in the electric field well inside the separatrix. The electric field is used to estimate toroidal and poloidal rotation velocities from E × B motion. This paper further demonstrates the ability of the ball pen probe to make valuable and important measurements in the boundary plasma of a tokamak.« less

Langmuir Probe Measurements in a Grid-Assisted Magnetron Sputtering System

NASA Astrophysics Data System (ADS)

Sagás, Julio César; Pessoa, Rodrigo Sávio; Maciel, Homero Santiago

2018-02-01

The grid-assisted magnetron sputtering is a variation of the magnetron sputtering commonly used for thin film deposition. In this work, Langmuir probe measurements were performed in such a system by using the grid under two basic and practical electrical conditions, i.e., floating and grounded. The results show that grounding the grid leads to an enhancement of the plasma confinement and to increases in both floating and plasma potential, as inferred from the probe characteristics. The grounded grid drains electrons from the plasma, acting as an auxiliary anode and reducing the plasma diffusion toward the chamber walls. For the same discharge current, the improved confinement results in a lower electron temperature when compared to floating condition, although the electron densities are comparable in both cases.

Resolving an anomaly in electron temperature measurement using double and triple Langmuir probes

NASA Astrophysics Data System (ADS)

Ghosh, Soumen; Barada, K. K.; Chattopadhyay, P. K.; Ghosh, J.; Bora, D.

2015-02-01

Langmuir probes with variants such as single, double and triple probes remain the most common method of electron temperature measurement in low-temperature laboratory plasmas. However, proper estimation of electron temperature mainly using triple probe configuration requires the proper choice of compensation factor (W). Determination of the compensating factor is not very straightforward as it depends heavily on plasma floating potential (Vf), electron temperature (Te), the type of gas used for plasma production and the bias voltage applied to probe pins, especially in cases where there are substantial variations in floating potential. In this paper we highlight the anomaly in electron temperature measurement using double and triple Langmuir probe techniques as well as the proper determination of the compensation factor (W) to overcome this anomaly. Experiments are carried out with helicon antenna producing inductive radiofrequency plasmas, where significant variation of floating potential along the axis enables a detailed study of deviations introduced in Te measurements using triple probes compared to double and single probes. It is observed that the bias voltage between the probe pins of the triple probes plays an important role in the accurate determination of the compensating factor (W) and should be in the range (5Vd2 < Vd3 < 10Vd2), where Vd2 and Vd3 are the voltage between floating probe pins 2 and 1 and the bias voltage, respectively.

RP and RQA Analysis for Floating Potential Fluctuations in a DC Magnetron Sputtering Plasma

NASA Astrophysics Data System (ADS)

Sabavath, Gopikishan; Banerjee, I.; Mahapatra, S. K.

2016-04-01

The nonlinear dynamics of a direct current magnetron sputtering plasma is visualized using recurrence plot (RP) technique. RP comprises the recurrence quantification analysis (RQA) which is an efficient method to observe critical regime transitions in dynamics. Further, RQA provides insight information about the system’s behavior. We observed the floating potential fluctuations of the plasma as a function of discharge voltage by using Langmuir probe. The system exhibits quasi-periodic-chaotic-quasi-periodic-chaotic transitions. These transitions are quantified from determinism, Lmax, and entropy of RQA. Statistical investigations like kurtosis and skewness also studied for these transitions which are in well agreement with RQA results.

Analysis of ISS Plasma Interaction

NASA Technical Reports Server (NTRS)

Reddell, Brandon; Alred, John; Kramer, Leonard; Mikatarian, Ron; Minow, Joe; Koontz, Steve

2006-01-01

To date, the International Space Station (ISS) has been one of the largest objects flown in lower earth orbit (LEO). The ISS utilizes high voltage solar arrays (160V) that are negatively grounded leading to pressurized elements that can float negatively with respect to the plasma. Because laboratory measurements indicate a dielectric breakdown potential difference of 80V, arcing could occur on the ISS structure. To overcome the possibility of arcing and clamp the potential of the structure, two Plasma Contactor Units (PCUs) were designed, built, and flown. Also a limited amount of measurements of the floating potential for the present ISS configuration were made by a Floating Potential Probe (FPP), indicating a minimum potential of 24 Volts at the measurement location. A predictive tool, the ISS Plasma Interaction Model (PIM) has been developed accounting for the solar array electron collection, solar array mast wire and effective conductive area on the structure. The model has been used for predictions of the present ISS configuration. The conductive area has been inferred based on available floating potential measurements. Analysis of FPP and PCU data indicated distribution of the conductive area along the Russian segment of the ISS structure. A significant input to PIM is the plasma environment. The International Reference Ionosphere (IRI 2001) was initially used to obtain plasma temperature and density values. However, IRI provides mean parameters, leading to difficulties in interpretation of on-orbit data, especially at eclipse exit where maximum charging can occur. This limits our predicative capability. Satellite and Incoherent Scatter Radar (ISR) data of plasma parameters have also been collected. Approximately 130,000 electron temperature (Te) and density (Ne) pairs for typical ISS eclipse exit conditions have been extracted from the reduced Langmuir probe data flown aboard the NASA DE-2 satellite. Additionally, another 18,000 Te and Ne pairs of ISR data from several radar locations around the globe were used to assure consistency of the satellite data. PIM predictions for ISS charging made with this data correlated very well with FPP data, indicating that the general physics of spacecraft charging with high voltage solar arrays have been captured. The predictions also provided the probabilities of occurrences for ISS charging. These probabilities give a numerical measure of the number of times when the ISS will approach or exceed the vehicle plasma hazard conditions for each configuration. In this paper we shall present the interaction mechanisms between the ISS and the surrounding plasma and give an overview of the PIM components. PIM predictions are compared with available data followed by a discussion of the variability of plasma parameters and the conductive area on the ISS. The ISS PIM will be further tested and verified as data from the Floating Potential Measurement Unit become available, and construction of the ISS continues.

Observations of Transient ISS Floating Potential Variations During High Voltage Solar Array Operations

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Minow, Joseph I.; Parker, Linda N.; Pour, Maria Z. A.; Swenson, Charles; Nishikawa, Ken-ichi; Krause, Linda Habash

2016-01-01

The International Space Station (ISS) continues to be a world-class space research laboratory after over 15 years of operations, and it has proven to be a fantastic resource for observing spacecraft floating potential variations related to high voltage solar array operations in Low Earth Orbit (LEO). Measurements of the ionospheric electron density and temperature along the ISS orbit and variations in the ISS floating potential are obtained from the Floating Potential Measurement Unit (FPMU). In particular, rapid variations in ISS floating potential during solar array operations on time scales of tens of milliseconds can be recorded due to the 128 Hz sample rate of the Floating Potential Probe (FPP) pro- viding interesting insight into high voltage solar array interaction with the space plasma environment. Comparing the FPMU data with the ISS operations timeline and solar array data provides a means for correlating some of the more complex and interesting transient floating potential variations with mission operations. These complex variations are not reproduced by current models and require further study to understand the underlying physical processes. In this paper we present some of the floating potential transients observed over the past few years along with the relevant space environment parameters and solar array operations data.

Plasma sheath structure surrounding a large powered spacecraft

NASA Technical Reports Server (NTRS)

Mandell, M. J.; Jongeward, G. A.; Katz, I.

1984-01-01

Various factors determining the floating potential of a highly biased (about 4-kV) spacecraft in low earth orbit are discussed. While the common rule of thumb (90 percent negative; 10 percent positive) is usually a good guide, different biasing and grounding patterns can lead to high positive potentials. The NASCAP/LEO code can be used to predict spacecraft floating potential for complex three-dimensional spacecraft.

Initial Results from the Floating Potential Measurement Unit aboard the International Space Station

NASA Technical Reports Server (NTRS)

Wright, Kenneth H., Jr.; Swenson, Charles; Thompson, Don; Barjatya, Aroh; Koontz, Steven L.; Schneider, Todd; Vaughn, Jason; Minow, Joseph; Craven, Paul; Coffey, Victoria;

End-boundary sheath potential, electron and ion energy distribution in the low-pressure non-ambipolar electron plasma

NASA Astrophysics Data System (ADS)

Chen, Lee; Chen, Zhiying; Funk, Merritt

2013-12-01

The end-boundary floating-surface sheath potential, electron and ion energy distribution functions (EEDf, IEDf) in the low-pressure non-ambipolar electron plasma (NEP) are investigated. The NEP is heated by an electron beam extracted from an inductively coupled electron-source plasma (ICP) through a dielectric injector by an accelerator located inside the NEP. This plasma's EEDf has a Maxwellian bulk followed by a broad energy continuum connecting to the most energetic group with energies around the beam energy. The NEP pressure is 1-3 mTorr of N2 and the ICP pressure is 5-15 mTorr of Ar. The accelerator is biased positively from 80 to 600 V and the ICP power range is 200-300 W. The NEP EEDf and IEDf are determined using a retarding field energy analyser. The EEDf and IEDf are measured at various NEP pressures, ICP pressures and powers as a function of accelerator voltage. The accelerator current and sheath potential are also measured. The IEDf reveals mono-energetic ions with adjustable energy and it is proportionally controlled by the sheath potential. The NEP end-boundary floating surface is bombarded by a mono-energetic, space-charge-neutral plasma beam. When the injected energetic electron beam is adequately damped by the NEP, the sheath potential is linearly controlled at almost a 1 : 1 ratio by the accelerator voltage. If the NEP parameters cannot damp the electron beam sufficiently, leaving an excess amount of electron-beam power deposited on the floating surface, the sheath potential will collapse and become unresponsive to the accelerator voltage.

Role of electron temperature on charging of dust grains

NASA Astrophysics Data System (ADS)

Kausik, S. S.; Chakraborty, M.; Saikia, B. K.

2007-02-01

Dust grains are produced by evaporation of silver in an experimental setup consisting of a dust chamber, a plasma chamber, and a deflection chamber. Due to differential pressure between the dust and plasma chambers, the dust grains move upward and after passing through plasma they become negatively charged. These charged dust grains are then deflected by a dc field applied across a pair of deflector plates in the deflection chamber. Both from the amount of deflection and also from the floating potential, the number of charges collected on the dust grains is calculated. As the gas pressure is changed, the plasma density and the electron temperature changes. Dust charge is then calculated at each value of pressure from the deflection and floating potential. It is found that the electron temperature has a profound effect in the accumulation of charge on dust grains.

Tailoring the charged particle fluxes across the target surface of Magnum-PSI

NASA Astrophysics Data System (ADS)

Costin, C.; Anita, V.; Popa, G.; Scholten, J.; De Temmerman, G.

2016-04-01

Linear plasma generators are plasma devices designed to study fusion-relevant plasma-surface interactions. The first requirement for such devices is to operate with adjustable and well characterized plasma parameters. In the linear plasma device Magnum-PSI, the distribution of the charged particle flux across the target surface can be tailored by the target bias. The process is based on the radial inhomogeneity of the plasma column and it is evidenced by electrical measurements via a 2D multi-probe system installed as target. Typical results are reported for a hydrogen discharge operated at 125 A and confined by a magnetic field strength of 0.95 T in the middle of the coils. The probes were biased in the range of  -80 to  -25 V, while the floating potential of the target was about  -35 V. The results were obtained in steady-state regime of Magnum-PSI, being time-averaged over any type of fluctuations. Depending on the relative value of the target bias voltage with respect to the local floating potential in the plasma column, the entire target surface can be exposed to ion or electron dominated flux, respectively, or it can be divided into two adjacent zones: one exposed to electron flux and the other to ion flux. As a consequence of this effect, a floating conductive surface that interacts with an inhomogeneous plasma is exposed to non-zero local currents despite its overall null current and it is subjected to internal current flows.

A Novel Spacecraft Charge Monitor for LEO

NASA Technical Reports Server (NTRS)

Goembel, Luke

2004-01-01

Five years ago we introduced a new method for measuring spacecraft chassis floating potential relative to the space plasma (absolute spacecraft potential) in low Earth orbit. The method, based on a straightforward interpretation of photoelectron spectra, shows promise for numerous applications, but has not yet been tried. In the interest of testing the method, and ultimately supplying another tool for measuring absolute spacecraft charge, we are producing a flight prototype Spacecraft Charge Monitor (SCM) with support from NASA's Small Business Innovation Research (SBIR) program. Although insight into the technique came from data collected in space over two decades ago, very little data are available. The data indicate that it may be possible to determine spacecraft floating potential to within 0.1 volt each with the SCM second under certain conditions. It is debatable that spacecraft floating potential has ever been measured with such accuracy. The compact, easily deployed SCM also offers the advantage of long-term stability in calibration. Accurate floating potential determinations from the SCM could be used to correct biases in space plasma measurements and evaluate charge mitigation and/or sensing devices. Although this paper focuses on the device's use in low Earth orbit (LEO), the device may also be able to measure spacecraft charge at higher altitudes, in the solar wind, and in orbits around other planets. The flight prototype SCM we are producing for delivery to NASA in the third quarter of 2004 will measure floating potential from 0 to -150 volts with 0.1 volt precision, weigh approximately 600-700 grams, consume approximately 2 watts, and will measure approximately 8 x 10 x 17 cm.

Ionosphere Plasma State Determination in Low Earth Orbit from International Space Station Plasma Monitor

NASA Technical Reports Server (NTRS)

Kramer, Leonard

2014-01-01

A plasma diagnostic package is deployed on the International Space Station (ISS). The system - a Floating Potential Measurement Unit (FPMU) - is used by NASA to monitor the electrical floating potential of the vehicle to assure astronaut safety during extravehicular activity. However, data from the unit also reflects the ionosphere state and seems to represent an unutilized scientific resource in the form of an archive of scientific plasma state data. The unit comprises a Floating Potential probe and two Langmuir probes. There is also an unused but active plasma impedance probe. The data, at one second cadence, are collected, typically for a two week period surrounding extravehicular activity events. Data is also collected any time a visiting vehicle docks with ISS and also when any large solar events occur. The telemetry system is unusual because the package is mounted on a television camera stanchion and its data is impressed on a video signal that is transmitted to the ground and streamed by internet to two off center laboratory locations. The data quality has in the past been challenged by weaknesses in the integrated ground station and distribution systems. These issues, since mid-2010, have been largely resolved and the ground stations have been upgraded. Downstream data reduction has been developed using physics based modeling of the electron and ion collecting character in the plasma. Recursive algorithms determine plasma density and temperature from the raw Langmuir probe current voltage sweeps and this is made available in real time for situational awareness. The purpose of this paper is to describe and record the algorithm for data reduction and to show that the Floating probe and Langmuir probes are capable of providing long term plasma state measurement in the ionosphere. Geophysical features such as the Appleton anomaly and high latitude modulation at the edge of the Auroral zones are regularly observed in the nearly circular, 51 deg inclined, 400 km altitude ISS orbit. Evidence of waves in the ion collection current data is seen in geographic zones known to exhibit the spread-F phenomenon. An anomaly in the current collection characteristic of the cylindrical probe appears also too be organized by the geomagnetic field.

Spacecraft Charge Monitor

NASA Astrophysics Data System (ADS)

Goembel, L.

2003-12-01

We are currently developing a flight prototype Spacecraft Charge Monitor (SCM) with support from NASA's Small Business Innovation Research (SBIR) program. The device will use a recently proposed high energy-resolution electron spectroscopic technique to determine spacecraft floating potential. The inspiration for the technique came from data collected by the Atmosphere Explorer (AE) satellites in the 1970s. The data available from the AE satellites indicate that the SCM may be able to determine spacecraft floating potential to within 0.1 V under certain conditions. Such accurate measurement of spacecraft charge could be used to correct biases in space plasma measurements. The device may also be able to measure spacecraft floating potential in the solar wind and in orbit around other planets.

Correlation of ISS Electric Potential Variations with Mission Operations

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Minow, Joseph I.; Parker, Linda Neergaard

2014-01-01

Spacecraft charging on the International Space Station (ISS) is caused by a complex combination of the low Earth orbit plasma environment, space weather events, operations of the high voltage solar arrays, and changes in the ISS configuration and orbit parameters. Measurements of the ionospheric electron density and temperature along the ISS orbit and variations in the ISS electric potential are obtained from the Floating Potential Measurement Unit (FPMU) suite of four plasma instruments (two Langmuir probes, a Floating Potential Probe, and a Plasma Impedance Probe) on the ISS. These instruments provide a unique capability for monitoring the response of the ISS electric potential to variations in the space environment, changes in vehicle configuration, and operational solar array power manipulation. In particular, rapid variations in ISS potential during solar array operations on time scales of tens of milliseconds can be monitored due to the 128 Hz sample rate of the Floating Potential Probe providing an interesting insight into high voltage solar array interaction with the space plasma environment. Comparing the FPMU data with the ISS operations timeline and solar array data provides a means for correlating some of the more complex and interesting ISS electric potential variations with mission operations. In addition, recent extensions and improvements to the ISS data downlink capabilities have allowed more operating time for the FPMU than ever before. The FPMU was operated for over 200 days in 2013 resulting in the largest data set ever recorded in a single year for the ISS. In this paper we provide examples of a number of the more interesting ISS charging events observed during the 2013 operations including examples of rapid charging events due to solar array power operations, auroral charging events, and other charging behavior related to ISS mission operations.

Correlation of ISS Electric Potential Variations with Mission Operations

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Minow, Joseph I.; Parker, Linda Neergaard

2014-01-01

Spacecraft charging on the International Space Station (ISS) is caused by a complex mix of the low Earth orbit plasma environment, space weather events, operations of the high voltage solar arrays, and changes in the ISS configuration and orbit parameters. Measurements of the ionospheric electron density and temperature along the ISS orbit and variations in the ISS electric potential are obtained from the Floating Potential Measurement Unit (FPMU) suite of four plasma instruments (two Langmuir probes, a Floating Potential Probe, and a Plasma Impedance Probe) on the ISS. These instruments provide a unique capability for monitoring the response of the ISS electric potential to variations in the space environment, changes in vehicle configuration, and operational solar array power manipulation. In particular, rapid variations in ISS potential during solar array operations on time scales of tens of milliseconds can be monitored due to the 128 Hz sample rate of the Floating Potential Probe providing an interesting insight into high voltage solar array interaction with the space plasma environment. Comparing the FPMU data with the ISS operations timeline and solar array data provides a means for correlating some of the more complex and interesting ISS electric potential variations with mission operations. In addition, recent extensions and improvements to the ISS data downlink capabilities have allowed more operating time for the FPMU than ever before. The FPMU was operated for over 200 days in 2013 resulting in the largest data set ever recorded in a single year for the ISS. This presentation will provide examples of a number of the more interesting ISS charging events observed during the 2013 operations including examples of rapid charging events due to solar array power operations, auroral charging events, and other charging behavior related to ISS mission operations.

Effect of Trapped Ions on Shielding and Floating Potential of a Dust Grain in a Plasma

NASA Astrophysics Data System (ADS)

Lampe, Martin; Ganguli, Gurudas; Joyce, Glenn; Gavrishchaka, Valeriy

2001-10-01

The problem of electrostatic shielding around a small spherical collector immersed in plasma, and the related problem of electron and ion flow to the collector, date to the origins of plasma physics. Beginning with Mott-Smith and Langmuir (1926), calculations have typically neglected collisions, on the grounds that the mean free path is long compared to shielding length scales, i.e. the Debye length. However, investigators beginning with Bernstein and Rabinowitz (1959) have known that negative-energy trapped ions, created by occasional collisions, might be important. We present an analytic calculation of the density of trapped and untrapped ions, self-consistent with the potential. Under typical conditions for dust grains immersed in a discharge plasma, trapped ions dominate the shielding cloud in steady state, even in the limit of very long mean free path. As a result the shielded potential is different from the results of orbital motion limited theory. Collisions also greatly increase the ion current to the collector, thereby decreasing the floating potential and the grain charge by a factor as large as two to three.

Bunker probe: A plasma potential probe almost insensitive to its orientation with the magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costea, S., E-mail: stefan.costea@uibk.ac.at; Schneider, B. S.; Schrittwieser, R.

Due to their ability to suppress a large part of the electron current and thus measuring directly the plasma potential, ion sensitive probes have begun to be widely tested and used in fusion devices. For these probes to work, almost perfect alignment with the total magnetic field is necessary. This condition cannot always be fulfilled due to the curvature of magnetic fields, complex magnetic structure, or magnetic field reconnection. In this perspective, we have developed a plasma potential probe (named Bunker probe) based on the principle of the ion sensitive probe but almost insensitive to its orientation with the totalmore » magnetic field. Therefore it can be used to measure the plasma potential inside fusion devices, especially in regions with complex magnetic field topology. Experimental results are presented and compared with Ball-Pen probe measurements taken under identical conditions. We have observed that the floating potential of the Bunker probe is indeed little affected by its orientation with the magnetic field for angles ranging from 90° to 30°, in contrast to the Ball-Pen probe whose floating potential decreases towards that of a Langmuir probe if not properly aligned with the magnetic field.« less

Analytical study of spheroidal dust grains in plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zahed, H.; Mahmoodi, J.; Sobhanian, S.

2006-05-15

Using the modified spheroidal equations, the potential of a spheroidal conducting grain, floated in a plasma, is calculated. The electric field and capacitance for both prolate and oblate spheroidal grains are investigated. The solutions, obtained up to the second-order approximation, show that the plasma screening causes the equipotential surfaces around the grain to be more elongated or flattened than the potential spheroids of the Laplace equation. This leads to the variation of the plasma concentration around the grain.

Characterization of a medium-sized washer-gun for an axisymmetric mirror

NASA Astrophysics Data System (ADS)

Yi, Hongshen; Liu, Ming; Shi, Peiyun; Yang, Zhida; Zhu, Guanghui; Lu, Quanming; Sun, Xuan

2018-04-01

A new medium-sized washer gun is developed for a plasma start-up in a fully axisymmetric mirror. The gun is positioned at the east end of the Keda Mirror with AXisymmetricity facility and operated in the pulsed mode with an arc discharging time of 1.2 ms and a typical arc current of 8.5 kA with 1.5 kV discharge voltage. To optimize the operation, a systematic scan of the neutral pressure, the arc voltage, the bias voltage on a mesh grid 6 cm in front of the gun and an end electrode located on the west end of mirror, and the mirror ratio was performed. The streaming plasma was measured with triple probes in the three mirror cells and a diamagnetic loop in the central cell. Floating potential measurements suggest that the plasma could be divided into streaming and mirror-confined plasmas. The floating potential for the streaming plasma is negative, with an electric field pointing inwards. The mirror-confined plasma has a typical lifetime of 0.5 ms.

Characterization of a medium-sized washer-gun for an axisymmetric mirror.

PubMed

Yi, Hongshen; Liu, Ming; Shi, Peiyun; Yang, Zhida; Zhu, Guanghui; Lu, Quanming; Sun, Xuan

2018-04-01

A new medium-sized washer gun is developed for a plasma start-up in a fully axisymmetric mirror. The gun is positioned at the east end of the Keda Mirror with AXisymmetricity facility and operated in the pulsed mode with an arc discharging time of 1.2 ms and a typical arc current of 8.5 kA with 1.5 kV discharge voltage. To optimize the operation, a systematic scan of the neutral pressure, the arc voltage, the bias voltage on a mesh grid 6 cm in front of the gun and an end electrode located on the west end of mirror, and the mirror ratio was performed. The streaming plasma was measured with triple probes in the three mirror cells and a diamagnetic loop in the central cell. Floating potential measurements suggest that the plasma could be divided into streaming and mirror-confined plasmas. The floating potential for the streaming plasma is negative, with an electric field pointing inwards. The mirror-confined plasma has a typical lifetime of 0.5 ms.

Charge separation and transport of the n=2 instability in C-2 FRC plasmas

NASA Astrophysics Data System (ADS)

Deng, Bihe; Sun, Xuan; Tuszewski, Michel

2012-10-01

Charge separation is critical in the positive feedback loop for gravitational type instabilities to grow [1], such as in the case of the n=2 mode in the C-2 field reversed configuration (FRC) experiment [2]. A fast time response Langmuir probe with minimum perturbation to the plasma is inserted into the edge of the C-2 plasma to measure the plasma floating potential. With the combined plasma wobble motion and spin motion, 2-D scans of the plasma floating potential are obtained, and evidence of charge separation associated with the n=2 instability is observed. The transport due to charge separation is estimated. Charge neutralization can provide an alternative method to stabilize the n=2 mode. An experiment is proposed to test this method with two probes inserted into the plasma from two azimuthally separated ports and an external shorting circuit, to constantly neutralize the charge separation, thus suppress the growth of the n=2 mode. [4pt] [1] R.J. Goldston and P.H. Rutherford, Introduction to Plasma Physics (Institute of Physics Publishing, Bristol, 2000).[0pt] [2]. M.W. Binderbauer et al, Phys. Rev. Lett. 105, 045003 (2010).

ISS Charging Hazards and Low Earth Orbit Space Weather Effects

NASA Technical Reports Server (NTRS)

Minow, Joseph; Parker, L.; Coffey, V.; Wright K.; Koontz, S.; Edwards, D.

2008-01-01

Current collection by high voltage solar arrays on the International Space Station (ISS) drives the vehicle to negative floating potentials in the low Earth orbit daytime plasma environment. Pre-flight predictions of ISS floating potentials Phi greater than |-100 V| suggested a risk for degradation of dielectric thermal control coatings on surfaces in the U.S. sector due to arcing and an electrical shock hazard to astronauts during extravehicular activity (EVA). However, hazard studies conducted by the ISS program have demonstrated that the thermal control material degradation risk is effectively mitigated during the lifetime of the ISS vehicle by a sufficiently large ion collection area present on the vehicle to balance current collection by the solar arrays. To date, crew risk during EVA has been mitigated by operating one of two plasma contactors during EVA to control the vehicle potential within Phi less than or equal to |-40 V| with a backup process requiring reorientation of the solar arrays into a configuration which places the current collection surfaces into wake. This operation minimizes current collection by the solar arrays should the plasma contactors fail. This paper presents an analysis of F-region electron density and temperature variations at low and midlatitudes generated by space weather events to determine what range of conditions represent charging threats to ISS. We first use historical ionospheric plasma measurements from spacecraft operating at altitudes relevant to the 51.6 degree inclination ISS orbit to provide an extensive database of F-region plasma conditions over a variety of solar cycle conditions. Then, the statistical results from the historical data are compared to more recent in-situ measurements from the Floating Potential Measurement Unit (FPMU) operating on ISS in a campaign mode since its installation in August, 2006.

The Sheath-less Planar Langmuir Probe

NASA Astrophysics Data System (ADS)

Cooke, D. L.

2017-12-01

The Langmuir probe is one of the oldest plasma diagnostics, provided the plasma density and species temperature from analysis of a current-voltage curve as the voltage is swept over a practically chosen range. The analysis depends on a knowledge or theory of the many factors that influence the current-voltage curve including, probe shape, size, nearby perturbations, and the voltage reference. For applications in Low Earth Orbit, the Planar Langmuir Probe, PLP, is an attractive geometry because the ram ion current is very constant over many Volts of a sweep, allowing the ion density and electron temperature to be determined independently with the same instrument, at different points on the sweep. However, when the physical voltage reference is itself small and electrically floating as with a small spacecraft, the spacecraft and probe system become a double probe where the current collection theory depends on the interaction of the spacecraft with the plasma which is generally not as simple as the probe itself. The Sheath-less PLP, SPLP, interlaces on a single ram facing surface, two variably biased probe elements, broken into many small and intertwined segments on a scale smaller than the plasma Debye length. The SPLP is electrically isolated from the rest of the spacecraft. For relative bias potentials of a few volts, the ion current to all segments of each element will be constant, while the electron currents will vary as a function of the element potential and the electron temperature. Because the segments are small, intertwined, and floating, the assembly will always present the same floating potential to the plasma, with minimal growth as a function of voltage, thus sheath-less and still planar. This concept has been modelled with Nascap, and tested with a physical model inserted into a Low Earth Orbit-like chamber plasma. Results will be presented.

Validation of Ionospheric Measurements from the International Space Station (ISS)

NASA Technical Reports Server (NTRS)

Coffey, Victoria; Minow, Joseph; Wright, Kenneth

2009-01-01

The International Space Station orbit provides an ideal platform for in-situ studies of space weather effects on the mid and low-latitude F-2 region ionosphere. The Floating Potential Measurement Unit (FPMU) operating on the ISS since Aug 2006, is a suite of plasma instruments: a Floating Potential Probe (FPP), a Plasma Impedance Probe (PIP), a Wide-sweep Langmuir Probe (WLP), and a Narrow-Sweep Langmuir Probe. This instrument package provides a new opportunity for collaborative multi-instrument studies of the F-region ionosphere during both quiet and disturbed periods. This presentation first describes the operational parameters for each of the FPMU probes and shows examples of an intra-instrument validation. We then show comparisons with the plasma density and temperature measurements derived from the TIMED GUVI ultraviolet imager, the Millstone Hill ground based incoherent scatter radar, and DIAS digisondes, Finally we show one of several observations of night-time equatorial density holes demonstrating the capabilities of the probes for monitoring mid and low latitude plasma processes.

In-situ Observations of the Ionospheric F2-Region from the International Space Station

NASA Technical Reports Server (NTRS)

Coffey, Victoria N.; Wright, Kenneth H.; Minow, Joseph I.; Chandler, Michael O.; Parker, Linda N.

2008-01-01

The International Space Station orbit provides an ideal platform for in-situ studies of space weather effects on the mid and low latitude F-2 region ionosphere. The Floating Potential Measurement Unit (FPMU) operating on the ISS since Aug 2006, is a suite of plasma instruments: a Floating Potential Probe (FPP), a Plasma Impedance Probe (PIP), a Wide-sweep Langmuir Probe (WLP), and a Narrow-sweep Langmuir Probe (NLP). This instrument package provides a new opportunity for collaborative multi-instrument studies of the F-region ionosphere during both quiet and disturbed periods. This presentation first describes the operational parameters for each of the FPMU probes and shows examples of an intra-instrument validation. We then show comparisons with the plasma density and temperature measurements derived from the TIMED GUVI ultraviolet imager, the Millstone Hill ground based incoherent scatter radar, and DIAS digisondes, Finally we show one of several observations of night-time equatorial density holes demonstrating the capabilities of the probes for monitoring mid and low latitude plasma processes.

Computer modeling of high-voltage solar array experiment using the NASCAP/LEO (NASA Charging Analyzer Program/Low Earth Orbit) computer code

NASA Astrophysics Data System (ADS)

Reichl, Karl O., Jr.

1987-06-01

The relationship between the Interactions Measurement Payload for Shuttle (IMPS) flight experiment and the low Earth orbit plasma environment is discussed. Two interactions (parasitic current loss and electrostatic discharge on the array) may be detrimental to mission effectiveness. They result from the spacecraft's electrical potentials floating relative to plasma ground to achieve a charge flow equilibrium into the spacecraft. The floating potentials were driven by external biases applied to a solar array module of the Photovoltaic Array Space Power (PASP) experiment aboard the IMPS test pallet. The modeling was performed using the NASA Charging Analyzer Program/Low Earth Orbit (NASCAP/LEO) computer code which calculates the potentials and current collection of high-voltage objects in low Earth orbit. Models are developed by specifying the spacecraft, environment, and orbital parameters. Eight IMPS models were developed by varying the array's bias voltage and altering its orientation relative to its motion. The code modeled a typical low Earth equatorial orbit. NASCAP/LEO calculated a wide variety of possible floating potential and current collection scenarios. These varied directly with both the array bias voltage and with the vehicle's orbital orientation.

In-Situ F2-Region Plasma Density and Temperature Measurements from the International Space Station

NASA Technical Reports Server (NTRS)

Coffey, Victoria; Wright, Kenneth; Minow, Joseph

2008-01-01

The International Space Station orbit provides an ideal platform for in-situ studies of space weather effects on the mid and low latitude F-2 region ionosphere. The Floating Potential Measurement Unit (FPMU) operating on the ISS since Aug 2006. is a suite of plasma instruments: a Floating Potential Probe (FPP), a Plasma Impedance Probe (PIP), a Wide-sweep langmuir Probe (WLP), and a Narrow-sweep Langmuir Probe (NLP). This instrument package provides a new opportunity lor collaborative multi-instrument studies of the F-region ionosphere during both quiet and disturbed periods. This presentation first describes the operational parameters for each of the FPMU probes and shOWS examples of an intra-instrument validation. We then show comparisons with the plasma density and temperature measurements derived from the TIMED GUVI ultraviolet imager, the Millstone Hill ground based incoherent scatter radar, and DIAS digisondes, Finally we show one of several observations of night-time equatorial density holes demonstrating the capabilities of the probes lor monitoring mid and low latitude plasma processes.

Propagation characteristics of dust-acoustic waves in presence of a floating cylindrical object in the DC discharge plasma

NASA Astrophysics Data System (ADS)

Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.

2016-08-01

The experimental observation of the self-excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object is investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in a background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at low pressure. Excitation of such a low frequency wave is a result of the ion-dust streaming instability in the dust cloud. Characteristics of the propagating dust acoustic wave get modified in the presence of a floating cylindrical object of radius larger than that of the dust Debye length. Instead of propagation in the vertical direction, the DAWs are found to propagate obliquely in the presence of the floating object (kept either vertically or horizontally). In addition, a horizontally aligned floating object forms a wave structure in the cone shaped dust cloud in the sheath region. Such changes in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.

Summary of 2006 to 2010 FPMU Measurements of International Space Station Frame Potential Variations

NASA Technical Reports Server (NTRS)

Minow, Joseph I.; Wright, Kenneth H., Jr.; Chandler, Michael O.; Coffey, Victoria N.; Craven, Paul D.; Schneider, Todd A.; Parker, Linda N.; Ferguson, Dale C.; Koontz, Steve L.; Alred, John W.

2010-01-01

Electric potential variations on the International Space Station (ISS) structure in low Earth orbit are dominated by contributions from interactions of the United States (US) 160 volt solar arrays with the relatively high density, low temperature plasma environment and inductive potentials generated by motion of the large vehicle across the Earth?s magnetic field. The Floating Potential Measurement Unit (FPMU) instrument suite comprising two Langmuir probes, a plasma impedance probe, and a floating potential probe was deployed in August 2006 for use in characterizing variations in ISS potential, the state of the ionosphere along the ISS orbit and its effect on ISS charging, evaluating effects of payloads and visiting vehicles, and for supporting ISS plasma hazard assessments. This presentation summarizes observations of ISS frame potential variations obtained from the FPMU from deployment in 2006 through the current time. We first describe ISS potential variations due to current collection by solar arrays in the day time sector of the orbit including eclipse exit and entry charging events, potential variations due to plasma environment variations in the equatorial anomaly, and visiting vehicles docked to the ISS structure. Next, we discuss potential variations due to inductive electric fields generated by motion of the vehicle across the geomagnetic field and the effects of external electric fields in the ionosphere. Examples of night time potential variations at high latitudes and their possible relationship to auroral charging are described and, finally, we demonstrate effects on the ISS potential due to European Space Agency and US plasma contactor devices.

Plasma treatment switches the regime of wetting and floating of pepper seeds.

PubMed

Shapira, Yekaterina; Multanen, Victor; Whyman, Gene; Bormashenko, Yelena; Chaniel, Gilad; Barkay, Zahava; Bormashenko, Edward

2017-09-01

Cold radiofrequency plasma treatment modified wetting and floating regimes of pepper seeds. The wetting regime of plasma-treated seeds was switched from the Wenzel-like partial wetting to the complete wetting. No hydrophobic recovery following the plasma treatment was registered. Environmental scanning electron microscopy of the fine structure of the (three-phase) triple line observed with virgin and plasma-treated seeds is reported. Plasma treatment promoted rapid sinking of pepper seeds placed on the water/air interface. Plasma treatment did not influence the surface topography of pepper seeds, while charged them electrically. Electrostatic repulsion of floating plasma-treated seeds was observed. The surface charge density was estimated from the data extracted from floating of charged seeds and independently with the electrostatic pendulum as σ≈1-2μC/m 2 . Copyright © 2017 Elsevier B.V. All rights reserved.

Potential of an emissive cylindrical probe in plasma.

PubMed

Fruchtman, A; Zoler, D; Makrinich, G

2011-08-01

The floating potential of an emissive cylindrical probe in a plasma is calculated for an arbitrary ratio of Debye length to probe radius and for an arbitrary ion composition. In their motion to the probe the ions are assumed to be collisionless. For a small Debye length, a two-scale analysis for the quasineutral plasma and for the sheath provides analytical expressions for the emitted and collected currents and for the potential as functions of a generalized mass ratio. For a Debye length that is not small, it is demonstrated that, as the Debye length becomes larger, the probe potential approaches the plasma potential and that the ion density near the probe is not smaller but rather is larger than it is in the plasma bulk.

Irregular-regular mode oscillations inside plasma bubble and its fractal analysis in glow discharge magnetized plasma

NASA Astrophysics Data System (ADS)

Megalingam, Mariammal; Hari Prakash, N.; Solomon, Infant; Sarma, Arun; Sarma, Bornali

2017-04-01

Experimental evidence of different kinds of oscillations in floating potential fluctuations of glow discharge magnetized plasma is being reported. A spherical gridded cage is inserted into the ambient plasma volume for creating plasma bubbles. Plasma is produced between a spherical mesh grid and chamber. The spherical mesh grid of 80% optical transparency is connected to the positive terminal of power supply and considered as anode. Two Langmuir probes are kept in the ambient plasma to measure the floating potential fluctuations in different positions within the system, viz., inside and outside the spherical mesh grid. At certain conditions of discharge voltage (Vd) and magnetic field, irregular to regular mode appears, and it shows chronological changes with respect to magnetic field. Further various nonlinear analyses such as Recurrence Plot, Hurst exponent, and Lyapunov exponent have been carried out to investigate the dynamics of oscillation at a range of discharge voltages and external magnetic fields. Determinism, entropy, and Lmax are important measures of Recurrence Quantification Analysis which indicate an irregular to regular transition in the dynamics of the fluctuations. Furthermore, behavior of the plasma oscillation is characterized by the technique called multifractal detrended fluctuation analysis to explore the nature of the fluctuations. It reveals that it has a multifractal nature and behaves as a long range correlated process.

Ionospheric plasma flow about a system of electrically biased flat plates. M.S. Thesis - Cleveland State Univ. Final Report

NASA Technical Reports Server (NTRS)

Herr, Joel L.

1993-01-01

The steady state interaction of two electrically biased parallel plates immersed in a flowing plasma characteristic of low earth orbit is studied numerically. Fluid equations are developed to describe the motion of the cold positively charged plasma ions, and are solved using finite-differences in two dimensions on a Cartesian grid. The behavior of the plasma electrons is assumed to be described by the Maxwell-Boltzmann distribution. Results are compared to an analytical and a particle simulation technique for a simplified flow geometry consisting of a single semi-infinite negatively biased plate. Comparison of the extent of the electrical disturbance into the flowing plasma and the magnitude of the current collected by the plate is very good. The interaction of two equally biased parallel plates is studied as a function of applied potential. The separation distance at which the current collected by either plate decreases by five and twenty percent is determined as a function of applied potential. The percent decreases were based on a non-interacting case. The decrease in overall current is caused by a decrease in ionic density in the region between the plates. As the separation between the plates decreases, the plates collect the ions at a faster rate than they are supplied to the middle region by the oncoming plasma flow. The docking of spacecraft in orbit is simulated by moving two plates of unequal potential toward one another in a quasi-static manner. One plate is held at a large negative potential while the other floats electrically in the resulting potential field. It is found that the floating plate does not charge continuously negative as it approaches the other more negatively biased plate. Instead, it charges more and then less negative as ionic current decreases and then increases respectively upon approach. When the two plates come into contact, it is expected that the electrically floating plate will charge rapidly negative to a potential near that of the other plate.

Current leakage for low altitude satellites - Modeling applications. [simulation of high voltage solar cell array in ionospheric plasma environment

NASA Technical Reports Server (NTRS)

Konradi, A.; Mccoy, J. E.; Garriott, O. K.

1979-01-01

To simulate the behavior of a high voltage solar cell array in the ionospheric plasma environment, the large (90 ft x 55 ft diameter) vacuum chamber was used to measure the high-voltage plasma interactions of a 3 ft x 30 ft conductive panel. The chamber was filled with Nitrogen and Argon plasma at electron densities of up to 1,000,000 per cu cm. Measurements of current flow to the plasma were made in three configurations: (a) with one end of the panel grounded, (b) with the whole panel floating while a high bias was applied between the ends of the panel, and (c) with the whole panel at high negative voltage with respect to the chamber walls. The results indicate that a simple model with a constant panel conductivity and plasma resistance can adequately describe the voltage distribution along the panel and the plasma current flow. As expected, when a high potential difference is applied to the panel ends more than 95% of the panel floats negative with respect to the plasma.

Correlation of ISS Electric Potential Variations with Mission Operations

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Minow, Joseph I.; Parker, Linda Neergaard

2014-01-01

Orbiting approximately 400 km above the Earth, the International Space Station (ISS) is a unique research laboratory used to conduct ground-breaking science experiments in space. The ISS has eight Solar Array Wings (SAW), and each wing is 11.7 meters wide and 35.1 meters long. The SAWs are controlled individually to maximize power output, minimize stress to the ISS structure, and minimize interference with other ISS operations such as vehicle dockings and Extra-Vehicular Activities (EVA). The Solar Arrays are designed to operate at 160 Volts. These large, high power solar arrays are negatively grounded to the ISS and collect charged particles (predominately electrons) as they travel through the space plasma in the Earth's ionosphere. If not controlled, this collected charge causes floating potential variations which can result in arcing, causing injury to the crew during an EVA or damage to hardware [1]. The environmental catalysts for ISS floating potential variations include plasma density and temperature fluctuations and magnetic induction from the Earth's magnetic field. These alone are not enough to cause concern for ISS, but when they are coupled with the large positive potential on the solar arrays, floating potentials up to negative 95 Volts have been observed. Our goal is to differentiate the operationally induced fluctuations in floating potentials from the environmental causes. Differentiating will help to determine what charging can be controlled, and we can then design the proper operations controls for charge collection mitigation. Additionally, the knowledge of how high power solar arrays interact with the environment and what regulations or design techniques can be employed to minimize charging impacts can be applied to future programs.

Mirror Langmuir probe: a technique for real-time measurement of magnetized plasma conditions using a single Langmuir electrode.

PubMed

LaBombard, B; Lyons, L

2007-07-01

A new method for the real-time evaluation of the conditions in a magnetized plasma is described. The technique employs an electronic "mirror Langmuir probe" (MLP), constructed from bipolar rf transistors and associated high-bandwidth electronics. Utilizing a three-state bias wave form and active feedback control, the mirror probe's I-V characteristic is continuously adjusted to be a scaled replica of the "actual" Langmuir electrode immersed in a plasma. Real-time high-bandwidth measurements of the plasma's electron temperature, ion saturation current, and floating potential can thereby be obtained using only a single electrode. Initial tests of a prototype MLP system are reported, proving the concept. Fast-switching metal-oxide-semiconductor field-effect transistors produce the required three-state voltage bias wave form, completing a full cycle in under 1 mus. Real-time outputs of electron temperature, ion saturation current, and floating potential are demonstrated, which accurately track an independent computation of these values from digitally stored I-V characteristics. The MLP technique represents a significant improvement over existing real-time methods, eliminating the need for multiple electrodes and sampling all three plasma parameters at a single spatial location.

Positive ion temperature effect on the plasma-wall transition

NASA Astrophysics Data System (ADS)

Morales Crespo, R.

2018-06-01

This paper analyses the plasma-wall interaction of a plasma in contact with a conducting planar surface when the positive-ion temperature is not negligible compared with the electron one. The electric potential from the plasma to the wall is obtained by the appropriate formulation of the model as an initial-value problem as well as some features useful for experimental applications, such as the positive current-to-voltage characteristics, the saturation current density, the floating potential or an estimation of the sheath thickness. Finally, it is analysed how all these quantities depend on the ionization degree and the positive-ion temperature.

Cathodes Delivered for Space Station Plasma Contactor System

NASA Technical Reports Server (NTRS)

Patterson, Michael J.

1999-01-01

The International Space Station's (ISS) power system is designed with high-voltage solar arrays that typically operate at output voltages of 140 to 160 volts (V). The ISS grounding scheme electrically ties the habitat modules, structure, and radiators to the negative tap of the solar arrays. Without some active charge control method, this electrical configuration and the plasma current balance would cause the habitat modules, structure, and radiators to float to voltages as large as -120 V with respect to the ambient space plasma. With such large negative floating potentials, the ISS could have deleterious interactions with the space plasma. These interactions could include arcing through insulating surfaces and sputtering of conductive surfaces as ions are accelerated by the spacecraft plasma sheath. A plasma contactor system was baselined on the ISS to prevent arcing and sputtering. The sole requirement for the system is contained within a single directive (SSP 30000, paragraph 3.1.3.2.1.8): "The Space Station structure floating potential at all points on the Space Station shall be controlled to within 40 V of the ionospheric plasma potential using a plasma contactor." NASA is developing this plasma contactor as part of the ISS electrical power system. For ISS, efficient and rapid emission of high electron currents is required from the plasma contactor system under conditions of variable and uncertain current demand. A hollow cathode plasma source is well suited for this application and was, therefore, selected as the design approach for the station plasma contactor system. In addition to the plasma source, which is referred to as a hollow cathode assembly, or HCA, the plasma contactor system includes two other subsystems. These are the power electronics unit and the xenon gas feed system. The Rocketdyne Division of Boeing North American is responsible for the design, fabrication, assembly, test, and integration of the plasma contactor system. Because of technical and schedule considerations, the NASA Lewis Research Center was asked to manufacture and deliver the engineering model, the qualification model, and the flight HCA units for the plasma contactor system as government furnished equipment. To date, multiple units have been built. One cathode has demonstrated approximately 28 000-hr lifetime, two development HCA units have demonstrated over 15 000-hr lifetime, and one HCA unit has demonstrated more than 38 000 ignitions. All eight flight HCA's have been manufactured, acceptance tested, and are ready for delivery to the flight contractor.

Comparisons of Two Plasma Instruments on the International Space Station

NASA Astrophysics Data System (ADS)

Balthazor, R.; McHarg, M. G.; Minow, J. I.; Chandler, M. O.; Musick, J. D.; Feldmesser, H.; Darrin, M. A.; Osiander, R.

2011-12-01

The United States Air Force Academy's Canary instrument, a low-cost ion spectrometer with integrated charge multiplication, was installed on the International Space Station (ISS) on shuttle flight STS-134. The primary goal of the Canary experiment is to measure ion signals in the wake when ISS is flying in the standard +XVV attitude. However, the instrument is pointed (approximately) into ram and detects ambient Low Earth Orbit ions when the ISS is flying in the -XVV attitude. Simultaneous observations with NASA's Floating Plasma Measurement Unit (FPMU) have been taken during these times, and the results from each instrument are compared, in order to determine the origin of energy variations observed in the Canary ion signal. In addition, insights into the ISS floating plasma potential at the two different instrument locations can be obtained.

Initial experimental test of a helicon plasma based mass filter

NASA Astrophysics Data System (ADS)

Gueroult, R.; Evans, E. S.; Zweben, S. J.; Fisch, N. J.; Levinton, F.

2016-06-01

High throughput plasma mass separation requires rotation control in a high density multi-species plasmas. A preliminary mass separation device based on a helicon plasma operating in gas mixtures and featuring concentric biasable ring electrodes is introduced. Plasma profile shows strong response to electrode biasing. In light of floating potential measurements, the density response is interpreted as the consequence of a reshaping of the radial electric field in the plasma. This field can be made confining or de-confining depending on the imposed potential at the electrodes, in a way which is consistent with single particle orbit radial stability. Concurrent spatially resolved spectroscopic measurements suggest ion separation, with heavy to light ion emission line ratio increasing with radius when a specific potential gradient is applied to the electrodes.

Opportunities for Utilizing the International Space Station for Studies of F2- Region Plasma Science and High Voltage Solar Array Interactions with the Plasma Environment

NASA Technical Reports Server (NTRS)

Minow, Joseph I.; Coffey, Victoria; Wright, Kenneth; Craven, Paul; Koontz, Steven

2010-01-01

The near circular, 51.6deg inclination orbit of the International Space Station (ISS) is maintained within an altitude range of approximately 300 km to 400 km providing an ideal platform for conducting in-situ studies of space weather effects on the mid and low-latitude F-2 region ionosphere. The Floating Potential Measurement Unit (FPMU) is a suite of instruments installed on the ISS in August 2006 which includes a Floating Potential Probe (FPP), a Plasma Impedance Probe (PIP), a Wide-sweep Langmuir Probe (WLP), and a Narrow-sweep Langmuir Probe (NLP). The primary purpose for deploying the FPMU is to characterize ambient plasma temperatures and densities in which the ISS operates and to obtain measurements of the ISS potential relative to the space plasma environment for use in characterizing and mitigating spacecraft charging hazards to the vehicle and crew. In addition to the engineering goals, data from the FPMU instrument package is available for collaborative multi-satellite and ground based instrument studies of the F-region ionosphere during both quiet and disturbed periods. Finally, the FPMU measurements supported by ISS engineering telemetry data provides a unique opportunity to investigate interactions of the ISS high voltage (160 volt) solar array system with the plasma environment. This presentation will provide examples of FPMU measurements along the ISS orbit including night-time equatorial plasma density depletions sampled near the peak electron density in the F2-region ionosphere, charging phenomenon due to interaction of the ISS solar arrays with the plasma environment, and modification of ISS charging due to visiting vehicles demonstrating the capabilities of the FPMU probes for monitoring mid and low latitude plasma processes as well as vehicle interactions with the plasma environment.

Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

NASA Astrophysics Data System (ADS)

Zanáška, M.; Adámek, J.; Peterka, M.; Kudrna, P.; Tichý, M.

2015-03-01

The ball-pen probe (BPP) is used for direct plasma potential measurements in magnetized plasma. The probe can adjust the ratio of the electron and ion saturation currents Isat-/Isat+ to be close to one and therefore its I-V characteristic becomes nearly symmetric. If this is achieved, the floating potential of the BPP is close to the plasma potential. Because of its rather simple construction, it offers an attractive probe for measurements in magnetized plasma. Comparative measurements of plasma potential by BPPs of different dimensions as well as one Langmuir probe (LP) in an argon discharge plasma of a cylindrical magnetron were performed at various experimental conditions. An additional comparison by an emissive probe was also performed. All these types of probes provide similar values of plasma potential in a wide range of plasma parameters. Our results for three different BPP dimensions indicate that the BPP can be operated in a cylindrical magnetron DC argon discharge if the value of the ratio of the magnetic field and neutral gas pressure, B/p, is greater than approximately 10 mT/Pa.

A droplet in the inter-electrode gap during gas metal arc welding

NASA Astrophysics Data System (ADS)

Nemchinsky, Valerian

2011-11-01

Electrical current flowing through a metallic droplet after its detachment from the wire anode during gas metal arc welding (GMAW) is considered. Although the droplet has much higher electrical conductivity compared with the conductivity of the surrounding plasma, current cannot enter the droplet freely since doing so demands igniting of the cathode spot responsible for electron emission. A new mechanism of current flow through a metallic droplet is suggested: one part of the droplet has a potential, which is slightly below the floating potential; this part of the droplet collects ions from the plasma. The remaining portion of the droplet has a potential difference, which is slightly above the floating one. The latter section collects electrons which recombine with the ions collected by the rest of the droplet's surface. The maximum electric current that can flow through the droplet is estimated. It is shown that this current is on the order of a few tens of amperes.

Plasma heating, electric fields and plasma flow by electron beam ionospheric injection

NASA Technical Reports Server (NTRS)

Winckler, J. R.; Erickson, K. N.

1990-01-01

The electric fields and the floating potentials of a Plasma Diagnostics Payload (PDP) located near a powerful electron beam injected from a large sounding rocket into the auroral zone ionosphere have been studied. As the PDP drifted away from the beam laterally, it surveyed a region of hot plasma extending nearly to 60 m radius. Large polarization electric fields transverse to B were imbedded in this hot plasma, which displayed large ELF wave variations and also an average pattern which has led to a model of the plasma flow about the negative line potential of the beam resembling a hydrodynamic vortex in a uniform flow field. Most of the present results are derived from the ECHO 6 sounding rocket mission.

Removal of floating dust in glow discharge using plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ticos, C. M.; Jepu, I.; Lungu, C. P.

2010-07-05

Dust can be an inconvenient source of impurities in plasma processing reactors and in many cases it can cause damage to the plasma-treated surfaces. A technique for dust expulsion out of the trapping region in plasma is presented here, based on the wind force exerted on dust particles by a pulsed plasma jet. Its applicability is demonstrated by removing floating dust in the sheath of parallel-plate capacitive radio-frequency plasma.

Initial experimental test of a helicon plasma based mass filter

DOE PAGES

Gueroult, R.; Evans, E. S.; Zweben, S. J.; ...

2016-05-12

High throughput plasma mass separation requires rotation control in a high density multi-species plasmas. A preliminary mass separation device based on a helicon plasma operating in gas mixtures and featuring concentric biasable ring electrodes is introduced. Plasma profile shows strong response to electrode biasing. In light of floating potential measurements, the density response is interpreted as the consequence of a reshaping of the radial electric field in the plasma. This field can be made confining or de-confining depending on the imposed potential at the electrodes, in a way which is consistent with single particle orbit radial stability. In conclusion, concurrentmore » spatially resolved spectroscopic measurements suggest ion separation, with heavy to light ion emission line ratio increasing with radius when a specific potential gradient is applied to the electrodes.« less

Floating Potential Probe Deployed on the International Space Station

NASA Technical Reports Server (NTRS)

Ferguson, Dale C.

2001-01-01

In the spring and summer of 2000, at the request of the International Space Station (ISS) Program Office, a Plasma Contactor Unit Tiger Team was set up to investigate the threat of the ISS arcing in the event of a plasma contactor outage. Modeling and ground tests done under that effort showed that it is possible for the external structure of the ISS to become electrically charged to as much as -160 V under some conditions. Much of this work was done in anticipation of the deployment of the first large ISS solar array in November 2000. It was recognized that, with this deployment, the power system would be energized to its full voltage and that the predicted charging would pose an immediate threat to crewmembers involved in extravehicular activities (EVA's), as well as long-term damage to the station structure, were the ISS plasma contactors to be turned off or stop functioning. The Floating Potential Probe was conceived, designed, built, and deployed in record time by a crack team of scientists and engineers led by the NASA Glenn Research Center in response to ISS concerns about crew safety.

Numerical Model of the Plasma Sheath Generated by the Plasma Source Instrument Aboard the Polar Satellite

NASA Technical Reports Server (NTRS)

Leung, Wing C.; Singh, Nagendra; Moore, Thomas E.; Craven, Paul D.

2000-01-01

The plasma sheath generated by the operation of the Plasma Source Instrument (PSI) aboard the POLAR satellite is studied by using a 3-dimensional Particle-In-Cell (PIC) code. When the satellite passes through the region of low density plasma, the satellite charges to positive potentials as high as 4050Volts due to the photoelectrons emission. In such a case, ambient core ions cannot accurately be measured or detected. The goal of the onboard PSI is to reduce the floating potential of the satellite to a sufficiently low value so that the ions in the polar wind become detectable. When the PSI is operated, an ion-rich Xenon plasma is ejected from the satellite, such that the floating potential of the satellite is reduced and is maintained at about 2Volts. Accordingly, in our 3-dimensional PIC simulation, we considered that the potential of the satellite is 2Volts as a fixed bias. Considering the relatively high density of the Xenon plasma in the sheath (approx. 10 - 10(exp 3)/cc), the ambient plasma of low density (less than 1/cc) is neglected. In the simulations, the electric fields and plasma dynamics are calculated self-consistently. We found that an "Apple" shape positive potential sheath forms surrounding the satellite. In the region near the PSI emission, a high positive potential hill develops. Near the Thermal Ion Detection Experiment (TIDE) detector away from the PSI, the potentials are sufficiently low for the ambient polar wind ions to reach it. In the simulations, it takes about a hundred electron gyroperiods for the sheath to reach a quasi-steady state. This time is approximately the time taken by the heavy Xe(+) ions to expand up to about one average Larmor radius of electrons from the satellite surface. Using the steady state sheath, we performed trajectory calculations to characterize the detector response to a highly supersonic polar wind flow. The detected ions' velocity distribution shows significant deviations from a shifted Maxwellian in the ambient polar wind population. The deviations are caused by the effects of electric fields on the ions' motion as they traverse the sheath.

Electric field computation analysis for the Electric Field Detector (EFD) on board the China Seismic-Electromagnetic Satellite (CSES)

NASA Astrophysics Data System (ADS)

Diego, P.; Bertello, I.; Candidi, M.; Mura, A.; Coco, I.; Vannaroni, G.; Ubertini, P.; Badoni, D.

2017-11-01

The floating potential variability of the Electric Field Detector (EFD) probes, on board the Chinese Seismo-Electromagnetic Satellite (CSES), has been modeled, and the effects of several structural and environmental elements have been determined. The expected floating potentials of the probes are computed considering the ambient ionospheric plasma parameter variations. In addition, the ion collection variability, due to the different probe attitudes along the orbit, and its effect on each floating potential, are considered. Particular attention is given to the analysis of the shadow produced by the stubs, in order to determine the artificial electric field introduced by instrumental effects which has to be subtracted from the real measurements. The modulation of the altered electric field, due to the effect on shadowing of the ion drift, as measured by the ESA satellite Swarm A in a similar orbit, is also modeled. Such simulations are made in preparation of real EFD data analysis performed during the upcoming flight of CSES.

Laboratory simulation of the electrodynamic interactions of a tethered satellite with an ionospheric plasma

NASA Technical Reports Server (NTRS)

Bonifazi, C.; Lebreton, J. P.; Vannaroni, G.; Cosmovici, C.; Debrie, R.; Hamelin, M.; Pomathiod, L.; Arends, H.

1986-01-01

An improved experimental set-up in the Orleans Plasma Chamber allowed investigations of the I-V characteristics of a conductive spherical body (10 cm diameter) in a plasma environment. Moreover, the influence of a transversal magnetic field at 0.6 and 1.2 G was investigated, for the first time, both on the sheath potential profile and current collection. Floating potential profiles were measured at 16 different radial distances from the test body up to 9 body radii in 8 different angular positions. The test body potential could be increased in the range from -200 V up to +100 V. Preliminary results are shown and discussed.

Preliminary Results from the Flight of the Solar Array Module Plasma Interactions Experiment (SAMPIE)

NASA Technical Reports Server (NTRS)

Ferguson, Dale C.; Hillard, G. Barry

1994-01-01

SAMPIE, the Solar Array Module Plasma Interactions Experiment, flew in the Space Shuttle Columbia payload bay as part of the OAST-2 mission on STS-62, March, 1994. SAMPIE biased samples of solar arrays and space power materials to varying potentials with respect to the surrounding space plasma, and recorded the plasma currents collected and the arcs which occurred, along with a set of plasma diagnostics data. A large set of high quality data was obtained on the behavior of solar arrays and space power materials in the space environment. This paper is the first report on the data SAMPIE telemetered to the ground during the mission. It will be seen that the flight data promise to help determine arcing thresholds, snapover potentials and floating potentials for arrays and spacecraft in LEO.

Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zanáška, M.; Kudrna, P.; Tichý, M.

The ball-pen probe (BPP) is used for direct plasma potential measurements in magnetized plasma. The probe can adjust the ratio of the electron and ion saturation currents I{sub sat}{sup −}/I{sub sat}{sup +} to be close to one and therefore its I-V characteristic becomes nearly symmetric. If this is achieved, the floating potential of the BPP is close to the plasma potential. Because of its rather simple construction, it offers an attractive probe for measurements in magnetized plasma. Comparative measurements of plasma potential by BPPs of different dimensions as well as one Langmuir probe (LP) in an argon discharge plasma ofmore » a cylindrical magnetron were performed at various experimental conditions. An additional comparison by an emissive probe was also performed. All these types of probes provide similar values of plasma potential in a wide range of plasma parameters. Our results for three different BPP dimensions indicate that the BPP can be operated in a cylindrical magnetron DC argon discharge if the value of the ratio of the magnetic field and neutral gas pressure, B/p, is greater than approximately 10 mT/Pa.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choudhary, Mangilal, E-mail: mangilal@ipr.res.in; Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085; Mukherjee, S.

The experimental observation of the self–excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object is investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in a background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at low pressure. Excitation of such a low frequency wave is a resultmore » of the ion–dust streaming instability in the dust cloud. Characteristics of the propagating dust acoustic wave get modified in the presence of a floating cylindrical object of radius larger than that of the dust Debye length. Instead of propagation in the vertical direction, the DAWs are found to propagate obliquely in the presence of the floating object (kept either vertically or horizontally). In addition, a horizontally aligned floating object forms a wave structure in the cone shaped dust cloud in the sheath region. Such changes in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.« less

Electron density measurements in STPX plasmas

NASA Astrophysics Data System (ADS)

Clark, Jerry; Williams, R.; Titus, J. B.; Mezonlin, E. D.; Akpovo, C.; Thomas, E.

2017-10-01

Diagnostics have been installed to measure the electron density of Spheromak Turbulent Physics Experiment (STPX) plasmas at Florida A. & M. University. An insertable probe, provided by Auburn University, consisting of a combination of a triple-tipped Langmuir probe and a radial array consisting of three ion saturation current / floating potential rings has been installed to measure instantaneous plasma density, temperature and plasma potential. As the ramp-up of the experimental program commences, initial electron density measurements from the triple-probe show that the electron density is on the order of 1019 particles/m3. For a passive measurement, a CO2 interferometer system has been designed and installed for measuring line-averaged densities and to corroborate the Langmuir measurements. We describe the design, calibration, and performance of these diagnostic systems on large volume STPX plasmas.

Spacecraft charging analysis with the implicit particle-in-cell code iPic3D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deca, J.; Lapenta, G.; Marchand, R.

2013-10-15

We present the first results on the analysis of spacecraft charging with the implicit particle-in-cell code iPic3D, designed for running on massively parallel supercomputers. The numerical algorithm is presented, highlighting the implementation of the electrostatic solver and the immersed boundary algorithm; the latter which creates the possibility to handle complex spacecraft geometries. As a first step in the verification process, a comparison is made between the floating potential obtained with iPic3D and with Orbital Motion Limited theory for a spherical particle in a uniform stationary plasma. Second, the numerical model is verified for a CubeSat benchmark by comparing simulation resultsmore » with those of PTetra for space environment conditions with increasing levels of complexity. In particular, we consider spacecraft charging from plasma particle collection, photoelectron and secondary electron emission. The influence of a background magnetic field on the floating potential profile near the spacecraft is also considered. Although the numerical approaches in iPic3D and PTetra are rather different, good agreement is found between the two models, raising the level of confidence in both codes to predict and evaluate the complex plasma environment around spacecraft.« less

Preliminary results from the flight of the Solar Array Module Plasma Interactions Experiment (SAMPIE)

NASA Technical Reports Server (NTRS)

Ferguson, Dale C.; Hillard, G. Barry

1994-01-01

SAMPIE, the Solar Array Module Plasma Interactions Experiment, flew in the Space Shuttle Columbia payload bay as part of the Office of Aeronautics and Space Technology-2 (OAST-2) mission on STS-62, March, 1994. SAMPIE biased samples of solar arrays and space power materials to varying potentials with respect to the surrounding space plasma, and recorded the plasma currents collected and the arcs which occurred, along with a set of plasma diagnostics data. A large set of high quality data was obtained on the behavior of solar arrays and space power materials in the space environment. This paper is the first report on the data SAMPIE telemetered to the ground during the mission. It will be seen that the flight data promise to help determine arcing thresholds, snapover potentials, and floating potentials for arrays and spacecraft in LEO.

Improved understanding of the ball-pen probe through particle-in-cell simulations

NASA Astrophysics Data System (ADS)

Murphy-Sugrue, S.; Harrison, J.; Walkden, N. R.; Bryant, P.; Bradley, J. W.

2017-05-01

Ball-pen probes (BPP) have been deployed in the SOL of numerous tokamak experiments and low-temperature magnetised plasmas to make direct measurements of the plasma potential and electron temperature. Despite strong empirical evidence for the success of the BPP it lacks a theoretical underpinning of its collection mechanism. In this paper we investigate the capability of the probe to measure the plasma potential by means of particle-in-cell simulations. The BPP is found to float at a potential offset from the plasma potential by a factor {T}{{e}}{α }{{BPP}}. By simulating BPPs and Langmuir probes, excellent agreement has been found between the measured electron temperature and the specified source temperature. The transport mechanism for both ions and electrons has been determined. E × B drifts are observed to drive electrons and ions down the tunnel. This mechanism is sensitive to the diameter of the probe.

Self-confinement of finite dust clusters in isotropic plasmas.

PubMed

Miloshevsky, G V; Hassanein, A

2012-05-01

Finite two-dimensional dust clusters are systems of a small number of charged grains. The self-confinement of dust clusters in isotropic plasmas is studied using the particle-in-cell method. The energetically favorable configurations of grains in plasma are found that are due to the kinetic effects of plasma ions and electrons. The self-confinement phenomenon is attributed to the change in the plasma composition within a dust cluster resulting in grain attraction mediated by plasma ions. This is a self-consistent state of a dust cluster in which grain's repulsion is compensated by the reduced charge and floating potential on grains, overlapped ion clouds, and depleted electrons within a cluster. The common potential well is formed trapping dust clusters in the confined state. These results provide both valuable insights and a different perspective to the classical view on the formation of boundary-free dust clusters in isotropic plasmas.

The effect of radio-frequency self bias on ion acceleration in expanding argon plasmas in helicon sources

NASA Astrophysics Data System (ADS)

Wiebold, Matthew D.

Time-averaged plasma potential differences up to ˜ 165 V over several hundred Debye lengths are observed in low pressure (pn < 1 mTorr) expanding argon plasmas in the Madison Helicon Experiment. The potential gradient leads to ion acceleration exceeding Ei ≈ 7 kTe in some cases. Up to 1 kW of 13.56 MHz RF power is supplied to a half-turn, double-helix antenna in the presence of a nozzle magnetic field up to 1 kG. An RPA measures the IEDF and an emissive probe measures the plasma potential. Single and double probes measure the electron density and temperature. Two distinct mode hops, the capacitive-inductive (E-H) and inductive-helicon (H-W) transitions, are identified by jumps in electron density as RF power is increased. In the capacitive mode, large fluctuations of the plasma potential (Vp--p ≳ 140 V, Vp--p/Vp ≈ 150%) exist at the RF frequency, leading to formation of a self-bias voltage. The mobile electrons can flow from the upstream region during an RF cycle whereas ions cannot, leading to an initial imbalance of flux, and the self-bias voltage builds as a result. The plasma potential in the expansion chamber is held near the floating potential for argon (Vp ≈ 5kTe/e). In the capacitive mode, the ion acceleration is not well described by an ambipolar relation. The accelerated population decay is consistent with that predicted by charge-exchange collisions. Grounding the upstream endplate increases the self-bias voltage compared to a floating endplate. In the inductive and helicon modes, the ion acceleration more closely follows an ambipolar relation, a result of decreased capacitive coupling due to the decreased RF skin depth. The scaling of the potential gradient with the argon flow rate, magnetic field and RF power are investigated, with the highest potential gradients observed for the lowest flow rates in the capacitive mode. The magnitude of the self-bias voltage agrees well with that predicted for RF sheaths. Use of the self-bias effect in a plasma thruster is explored, possibly for a low thrust, high specific impulse mode in a multi-mode helicon thruster. This work could also explain similar potential gradients in expanding helicon plasmas that are ascribed to double layer formation in the literature.

Numerical Model of the Plasma Sheath Generated by the Plasma Source Instrument Aboard the Polar Satellite

NASA Technical Reports Server (NTRS)

Singh, N.; Leung, W. C.; Moore, T. E.; Craven, P. D.

2001-01-01

The plasma sheath generated by the operation of the Plasma Source Instrument (PSI) aboard the Polar satellite is studied by using a three-dimensional particle-in-cell (PIC) code. When the satellite passes through the region of low-density plasma, the satellite charges to positive potentials as high as 40-50 V, owing to the photoelectron emission. In such a case, ambient core ions cannot accurately be measured or detected. The goal of the onboard PSI is to reduce the floating potential of the satellite to a sufficiently low value so that the ions in the polar wind become detectable. When the PSI is operated, ion-rich xenon plasma is ejected from the satellite, such that the floating potential of the satellite is reduced and is maintained at approximately 2 V. Accordingly, in our three-dimensional PIC simulation we considered that the potential of the satellite is 2 V as a fixed bias. Considering the relatively high density of the xenon plasma in the sheath (10-10(exp 3)/cc), the ambient plasma of low density (<1/cc) is neglected. In the simulations the electric fields and plasma dynamics are calculated self-consistently. We found that an 'apple'-shape positive potential sheath forms surrounding the satellite. In the region near the PSI emission a high positive potential hill develops. Near the Thermal Ion Dynamics Experiment detector away from the PSI, the potentials are sufficiently low for the ambient polar wind ions to reach it. In the simulations it takes only about a couple of tens of electron gyroperiods for the sheath to reach a quasi steady state. This time is approximately the time taken by the heavy Xe(+) ions to expand up to about one average Larmor radius of electrons from the satellite surface. After this time the expansion of the sheath in directions transverse to the ambient magnetic field slows down because the electrons are magnetized. Using the quasi steady sheath, we performed trajectory calculations to characterize the detector response to a highly supersonic polar wind flow. The detected ions' velocity distribution shows significant deviations from a shifted Maxwellian in the ambient polar wind population. The deviations are caused by the effects of electric fields on the ions' motion as they traverse the sheath.

A Theory for Rapid Charging Events on the International Space Station

NASA Technical Reports Server (NTRS)

Ferguson, Dale C.; Craven, Paul D.; Minow, Joseph I.; Wright, Kenneth H., Jr.

2009-01-01

The Floating Potential Measurement Unit (FPMU) has detected high negative amplitude rapid charging events (RCEs) on the International Space Station (ISS) at the morning terminator. These events are larger and more rapid than the ISS morning charging events first seen by the Floating Potential Probe (FPP) on ISS in 2001. In this paper, we describe a theory for the RCEs that further elucidates the nature of spacecraft charging in low Earth orbit (LEO) in a non-equilibrium situation. The model accounts for all essential aspects of the newly discovered phenomenon, and is amenable to testing on-orbit. Predictions of the model for the amplitude of the ISS RCEs for the full set of ISS solar arrays and for the coming solar cycle are given, and the results of modeling by the Environments WorkBench (EWB) are compared to the observed events to show that the phenomenon can be explained by solar array driven charging. The situation is unique because the coverglasses have not yet reached equilibrium with the surrounding plasma during the RCEs. Finally, a prescription for further use of the ISS for investigating fundamental plasma physics in LEO is given. Already, plasma and charging monitoring instruments on ISS have taught us much about spacecraft interactions with the dense LEO plasma, and we expect they will continue to yield more valuable science when the Japanese Experiment Module (JEM) is in place.

Compensation of the sheath effects in cylindrical floating probes

NASA Astrophysics Data System (ADS)

Park, Ji-Hwan; Chung, Chin-Wook

2018-05-01

In cylindrical floating probe measurements, the plasma density and electron temperature are overestimated due to sheath expansion and oscillation. To reduce these sheath effects, a compensation method based on well-developed floating sheath theories is proposed and applied to the floating harmonic method. The iterative calculation of the Allen-Boyd-Reynolds equation can derive the floating sheath thickness, which can be used to calculate the effective ion collection area; in this way, an accurate ion density is obtained. The Child-Langmuir law is used to calculate the ion harmonic currents caused by sheath oscillation of the alternating-voltage-biased probe tip. Accurate plasma parameters can be obtained by subtracting these ion harmonic currents from the total measured harmonic currents. Herein, the measurement principles and compensation method are discussed in detail and an experimental demonstration is presented.

Recommended Practice for Use of Emissive Probes in Electric Propulsion Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheehan, J. P.; Raitses, Yevgeny; Hershkowitz, Noah

Here, this article provides recommended methods for building, operating, and taking plasma potential measurements from electron-emitting probes in electric propulsion devices, including Hall thrusters, gridded ion engines, and others. The two major techniques, the floating point technique and the inflection point technique, are described in detail as well as calibration and error-reduction methods. The major heating methods are described as well as the various considerations for emissive probe construction. Lastly, special considerations for electric propulsion plasmas are addressed, including high-energy densities, ion flows, magnetic fields, and potential fluctuations. Recommendations for probe design and operation are provided.

Recommended Practice for Use of Emissive Probes in Electric Propulsion Testing

DOE PAGES

Sheehan, J. P.; Raitses, Yevgeny; Hershkowitz, Noah; ...

2016-11-03

Here, this article provides recommended methods for building, operating, and taking plasma potential measurements from electron-emitting probes in electric propulsion devices, including Hall thrusters, gridded ion engines, and others. The two major techniques, the floating point technique and the inflection point technique, are described in detail as well as calibration and error-reduction methods. The major heating methods are described as well as the various considerations for emissive probe construction. Lastly, special considerations for electric propulsion plasmas are addressed, including high-energy densities, ion flows, magnetic fields, and potential fluctuations. Recommendations for probe design and operation are provided.

A Signature of Self-Organized Criticality in the HT-6M Edge Plasma Turbulence

NASA Astrophysics Data System (ADS)

Wang, Wen-Hao; Yu, Chang-Xuan; Wen, Yi-Zhi; Xu, Yu-Hong; Ling, Bi-Li; Gong, Xian-Zu; Liu, Bao-Hua; Wan, Bao-Nian

2001-03-01

Power spectra of electron density and floating potential fluctuations in the velocity shear layer of the HT-6M edge region have been measured and analysed. All the spectra have three distinct frequency regions with the spectral decay indices typical of self-organized criticality systems (0, -1 and -4) when Doppler shift effects induced by the plasma E×B flow velocity have been taken into account. These results are consistent with the predictions of the self-organized criticality models, which may be an indication of edge plasma turbulence in the HT-6M tokamak evolving into a critical state independent of local plasma parameters.

Self-organized criticality in a cold plasma

NASA Astrophysics Data System (ADS)

Alex, Prince; Carreras, Benjamin Andres; Arumugam, Saravanan; Sinha, Suraj Kumar

2017-12-01

We present direct evidence for the existence of self-organized critical behavior in cold plasma. A multiple anodic double layer structure generated in a double discharge plasma setup shows critical behavior for the anode bias above a threshold value. Analysis of the floating potential fluctuations reveals the existence of long-range time correlations and power law behavior in the tail of the probability distribution function of the fluctuations. The measured Hurst exponent and the power law tail in the rank function are strong indication of the self-organized critical behavior of the system and hence provide a condition under which complexities arise in cold plasma.

Design and validation of the ball-pen probe for measurements in a low-temperature magnetized plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bousselin, G.; Cavalier, J.; Pautex, J. F.

Ball-pen probes have been used in fusion devices for direct measurements of the plasma potential. Their application in low-temperature magnetized plasma devices is still subject to studies. In this context, a ball-pen probe has been recently implemented on the linear plasma device Mirabelle. Produced by a thermionic discharge, the plasma is characterized by a low electron temperature and a low density. Plasma confinement is provided by an axial magnetic field that goes up to 100 mT. The principle of the ball-pen probe is to adjust the saturation current ratio to 1 by reducing the electron current contribution. In that case,more » the floating potential of the probe is close to the plasma potential. A thorough study of the ball-pen probe operation is performed for different designs of the probe over a large set of plasma conditions. Comparisons between ball-pen, Langmuir, and emissive probes are conducted in the same plasma conditions. The ball-pen probe is successfully measuring the plasma potential in these specific plasma conditions only if an adapted electronics and an adapted probe size to the plasma characteristic lengths ({lambda}{sub D}, {rho}{sub ce}) are used.« less

High power impulse magnetron sputtering discharges: Instabilities and plasma self-organization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehiasarian, A. P.; New, R.; Hecimovic, A.

We report on instabilities in high power impulse magnetron sputtering plasmas which are likely to be of the generalized drift wave type. They are characterized by well defined regions of high and low plasma emissivity along the racetrack of the magnetron and cause periodic shifts in floating potential. The azimuthal mode number m depends on plasma current, plasma density, and gas pressure. The structures rotate in E-vectorxB-vector direction at velocities of {approx}10 km s{sup -1} and frequencies up to 200 kHz. Collisions with residual gas atoms slow down the rotating wave, whereas increasing ionization degree of the gas and plasmamore » conductivity speeds it up.« less

A New Kinetic Simulation Model with Self-Consistent Calculation of Regolith Layer Charging for Moon-Plasma Interactions

NASA Astrophysics Data System (ADS)

Han, D.; Wang, J.

2015-12-01

The moon-plasma interactions and the resulting surface charging have been subjects of extensive recent investigations. While many particle-in-cell (PIC) based simulation models have been developed, all existing PIC simulation models treat the surface of the Moon as a boundary condition to the plasma flow. In such models, the surface of the Moon is typically limited to simple geometry configurations, the surface floating potential is calculated from a simplified current balance condition, and the electric field inside the regolith layer cannot be resolved. This paper presents a new full particle PIC model to simulate local scale plasma flow and surface charging. A major feature of this new model is that the surface is treated as an "interface" between two mediums rather than a boundary, and the simulation domain includes not only the plasma but also the regolith layer and the bedrock underneath it. There are no limitations on the surface shape. An immersed-finite-element field solver is applied which calculates the regolith surface floating potential and the electric field inside the regolith layer directly from local charge deposition. The material property of the regolith layer is also explicitly included in simulation. This new model is capable of providing a self-consistent solution to the plasma flow field, lunar surface charging, the electric field inside the regolith layer and the bedrock for realistic surface terrain. This new model is applied to simulate lunar surface-plasma interactions and surface charging under various ambient plasma conditions. The focus is on the lunar terminator region, where the combined effects from the low sun elevation angle and the localized plasma wake generated by plasma flow over a rugged terrain can generate strongly differentially charged surfaces and complex dust dynamics. We discuss the effects of the regolith properties and regolith layer charging on the plasma flow field, dust levitation, and dust transport.

Thruster Plume Plasma Diagnostics: A Ground Chamber Experiment for a 2-Kilowatt Arcjet

NASA Technical Reports Server (NTRS)

Galofaro, Joel T.; Vayner, Boris V.; Hillard, G. Barry; Chornak, Michael T.

2005-01-01

Although detailed near field (0 to 3 cm) information regarding the exhaust plume of a two kilowatt arc jet is available (refs. 1 to 6), there is virtually little or no information (outside of theoretical extrapolations) available concerning the far field (2.6 to 6.1 m). Furthermore real information about the plasma at distances between (3 to 6 m) is of critical importance to high technology satellite companies in understanding the effect of arc jet plume exhausts on space based power systems. It is therefore of utmost importance that one understands the exact nature of the interaction between the arc jet plume, the spacecraft power system and the surrounding electrical plasma environment. A good first step in understanding the nature of the interactions lies in making the needed plume parameter measurements in the far field. All diagnostic measurements are performed inside a large vacuum system (12 m diameter by 18 m high) with a full scale arc jet and solar array panel in the required flight configuration geometry. Thus, necessary information regarding the plume plasma parameters in the far field is obtained. Measurements of the floating potential, the plasma potential, the electron temperature, number density, density distribution, debye length, and plasma frequency are obtained at various locations about the array (at vertical distances from the arc jet nozzle: 2.6, 2.7, 2.8, 3.2, 3.6, 4.0, 4.9, 5.0, 5.4, 5.75, and 6.14 m). Plasma diagnostic parameters are measured for both the floating and grounded configurations of the arc jet anode and array. Spectroscopic optical measurements are then acquired in close proximity to the nozzle, and contamination measurements are made in the vicinity of the array utilizing a mass spectrometer and two Quartz Crystal Microbalances (QCM's).

An analytical model for floating probes in AC plasma and its application to double probes for high density, high power RF discharges

NASA Astrophysics Data System (ADS)

Caneses, Juan Francisco; Blackwell, Boyd; Plasma Research Laboratory Team

2013-10-01

In this work we provide an analytical model that allows one to quantitatively assess the RF compensation performance and suitability of the double probe technique for use in RF generated plasma. The model is based in the theory of the self-bias effect as described in Braithwaite's work, which we extend to include the time resolved behavior of floating probes. We provide experimental verification for this model and show that the theory of transient RF self-bias probes and harmonic current detection probes are limiting cases of this extended model. Furthermore, the model shows that the RF compensation is solely dependent on the sheath impedance, the probe's stray capacitance to ground and RF frequency. In addition, we use these results to implement a double probe system for use in high density helicon plasma where heat loads could potentially damage the intricate components in an RF compensating circuit. Finally we use this model to (1) recommend ways to extend the operational regime of double probes where the plasma conditions would render them unsuitable and to (2) comment on the use of this model to aid design of RF compensated Langmuir probes.

Formulation development of gastroretentive tablets of lamivudine using the floating-bioadhesive potential of optimized polymer blends.

PubMed

Singh, Bhupinder; Garg, Babita; Chaturvedi, Subhash Chand; Arora, Sharry; Mandsaurwale, Rachana; Kapil, Rishi; Singh, Baljinder

2012-05-01

The current studies entail successful formulation of optimized gastroretentive tablets of lamivudine using the floating-bioadhesive potential of carbomers and cellulosic polymers, and their subsequent in-vitro and in-vivo evaluation in animals and humans. Effervescent floating-bioadhesive hydrophilic matrices were prepared and evaluated for in-vitro drug release, floatation and ex-vivo bioadhesive strength. The optimal composition of polymer blends was systematically chosen using central composite design and overlay plots. Pharmacokinetic studies were carried out in rabbits, and various levels of in-vitro/in-vivo correlation (IVIVC) were established. In-vivo gamma scintigraphic studies were performed in human volunteers using (99m) Tc to evaluate formulation retention in the gastric milieu. The optimized formulation exhibited excellent bioadhesive and floatational characteristics besides possessing adequate drug-release control and pharmacokinetic extension of plasma levels. The successful establishment of various levels of IVIVC substantiated the judicious choice of in-vitro dissolution media for simulating the in-vivo conditions. In-vivo gamma scintigraphic studies ratified the gastroretentive characteristics of the optimized formulation with a retention time of 5 h or more. Besides unravelling the polymer synergism, the study helped in developing an optimal once-a-day gastroretentive drug delivery system with improved bioavailability potential exhibiting excellent swelling, floating and bioadhesive characteristics. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

Effects of atmospheric pressure plasma jet with floating electrode on murine melanoma and fibroblast cells

NASA Astrophysics Data System (ADS)

Xu, G.; Liu, J.; Yao, C.; Chen, S.; Lin, F.; Li, P.; Shi, X.; Zhang, Guan-Jun

2017-08-01

Atmospheric pressure cold plasma jets have been recently shown as a highly promising tool in certain cancer therapies. In this paper, an atmospheric pressure plasma jet (APPJ) with a one inner floating and two outer electrode configuration using helium gas for medical applications is developed. Subjected to a range of applied voltages with a frequency of 19.8 kHz at a fixed rate of gas flow (i.e., 3 l/min), electrical and optical characteristics of the APPJ are investigated. Compared with the device only with two outer electrodes, higher discharge current, longer jet, and more active species in the plasma plume at the same applied voltage together with the lower gas breakdown voltage can be achieved through embedding a floating inner electrode. Employing the APPJ with a floating electrode, the effects of identical plasma treatment time durations on murine melanoma cancer and normal fibroblast cells cultured in vitro are evaluated. The results of cell viability, cell apoptosis, and DNA damage detection show that the plasma can inactivate melanoma cells in a time-dependent manner from 10 s to 60 s compared with the control group (p < 0.05). However, for fibroblast cells compared with their control group, the plasma with treatment time from 30 s to 60 s can induce significant changes (p < 0.05), showing a less cytotoxic effect than that on melanoma cells at the same treatment time. The different basal reactive oxygen species level and antioxidant superoxide dismutase level of two kinds of cells may account for their different responses towards the identical plasma exposure.

Numerical simulations of a sounding rocket in ionospheric plasma: Effects of magnetic field on the wake formation and rocket potential

NASA Astrophysics Data System (ADS)

Darian, D.; Marholm, S.; Paulsson, J. J. P.; Miyake, Y.; Usui, H.; Mortensen, M.; Miloch, W. J.

2017-09-01

The charging of a sounding rocket in subsonic and supersonic plasma flows with external magnetic field is studied with numerical particle-in-cell (PIC) simulations. A weakly magnetized plasma regime is considered that corresponds to the ionospheric F2 layer, with electrons being strongly magnetized, while the magnetization of ions is weak. It is demonstrated that the magnetic field orientation influences the floating potential of the rocket and that with increasing angle between the rocket axis and the magnetic field direction the rocket potential becomes less negative. External magnetic field gives rise to asymmetric wake downstream of the rocket. The simulated wake in the potential and density may extend as far as 30 electron Debye lengths; thus, it is important to account for these plasma perturbations when analyzing in situ measurements. A qualitative agreement between simulation results and the actual measurements with a sounding rocket is also shown.

Photon-assisted Beam Probes for Low Temperature Plasmas and Installation of Neutral Beam Probe in Helimak

NASA Astrophysics Data System (ADS)

Garcia de Gorordo, Alvaro; Hallock, Gary A.; Kandadai, Nirmala

2008-11-01

The Heavy Ion Beam Probe (HIBP) diagnostic has successfully measured the electric potential in a number of major plasma devices in the fusion community. In contrast to a Langmuir probe, the HIBP measures the exact electric potential rather than the floating potential. It is also has the advantage of being a very nonperturbing diagnostic. We propose a new photon-assisted beam probe technique that would extend the HIBP type of diagnostics into the low temperature plasma regime. We expect this method to probe plasmas colder than 10 eV. The novelty of the proposed diagnostic is a VUV laser that ionizes the probing particle. Excimer lasers produce the pulsed VUV radiation needed. The lasers on the market don't have a short enough wavelength too ionize any ion directly and so we calculate the population density of excited states in a NLTE plasma. These new photo-ionization techniques can take an instantaneous one-dimensional potential measurement of a plasma and are ideal for nonmagnitized plasmas where continuous time resolution is not required. Also the status of the Neutral Beam Probe installation on the Helimak experiment will be presented.

Behavior of collisional sheath in electronegative plasma with q-nonextensive electron distribution

NASA Astrophysics Data System (ADS)

Borgohain, Dima Rani; Saharia, K.

2018-03-01

Electronegative plasma sheath is addressed in a collisional unmagnetized plasma consisting of q-nonextensive electrons, Boltzmann distributed negative ions and cold fluid positive ions. Considering the positive ion-neutral collisions and ignoring the effects of ionization and collisions between negative species and positive ions (neutrals), a modified Bohm sheath criterion and hence floating potential are derived by using multifluid model. Using the modified Bohm sheath criterion, the sheath characteristics such as spatial profiles of density, potential and net space charge density have been numerically investigated. It is found that increasing values of q-nonextensivity, electronegativity and collisionality lead to a decrease of the sheath thickness and an increase of the sheath potential and the net space charge density. With increasing values of the electron temperature to negative ion temperature ratio, the sheath thickness increases and the sheath potential as well as the net space charge density in the sheath region decreases.

The effect of the ambient plasma conditions on the variation of charge on dust grains

NASA Astrophysics Data System (ADS)

Chakraborty, M.; Kausik, S. S.; Saikia, B. K.; Kakati, M.; Bujarbarua, S.

2003-02-01

An experimental study has been performed into the variation of charge on dust grains with change in the ambient plasma conditons. A dust beam containing submicron sized silver grains was passed through plasma. The dust grains were charged by the plasma particles as well as by primary electrons from the filament. An increase in the filament current increased both the plasma density and the number density of the primary electrons. The grain charge was found out both from the deflection of the dust grains and also from the floating potential. The experimental observations shows that the secondary emission caused by the primary electrons significantly influenced and played a prominent role in the establishment of charge on the grains.

Measurement of sheath potential by three emissive-probe methods in DC filament plasmas near a biased grid

NASA Astrophysics Data System (ADS)

Kang, In-Je; Park, In-Sun; Wackerbarth, Eugene; Bae, Min-Keun; Hershkowitz, Noah; Severn, Greg; Chung, Kyu-Sun

2017-10-01

Plasma potential structures are measured with an emissive probe near a negatively biased grid ( - 100 V , 80mm diam., 40 lines/cm) immersed in a hot filament DC discharge in Kr. Three different methods of analysis are compared: inflection point (IP), floating potential (FP) and separation point (SE) methods. The plasma device at the University of San Diego (length = 64 cm, diameter = 32 cm, source = filament DC discharge) was operated with 5 ×108

Effect of confining wall potential on charged collimated dust beam in low-pressure plasma

NASA Astrophysics Data System (ADS)

Kausik, S. S.; Kakati, B.; Saikia, B. K.

2013-05-01

The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10-4 millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (˜pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.

Cross-section analysis of the Magnum-PSI plasma beam using a 2D multi-probe system

NASA Astrophysics Data System (ADS)

Costin, C.; Anita, V.; Ghiorghiu, F.; Popa, G.; De Temmerman, G.; van den Berg, M. A.; Scholten, J.; Brons, S.

2015-02-01

The linear plasma generator Magnum-PSI was designed for the study of plasma-surface interactions under relevant conditions of fusion devices. A key factor for such studies is the knowledge of a set of parameters that characterize the plasma interacting with the solid surface. This paper reports on the electrical diagnosis of the plasma beam in Magnum-PSI using a multi-probe system consisting of 64 probes arranged in a 2D square matrix. Cross-section distributions of floating potential and ion current intensity were registered for a hydrogen plasma beam under various discharge currents (80-175 A) and magnetic field strengths (0.47-1.41 T in the middle of the coils). Probe measurements revealed a high level of flexibility of plasma beam parameters with respect to the operating conditions.

The transfer of atmospheric-pressure ionization waves via a metal wire

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Yang; Liu, Dongping, E-mail: Dongping.liu@dlnu.edu.cn; School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024

2016-01-15

Our study has shown that the atmospheric-pressure He ionization waves (IWs) may be transferred from one dielectric tube (tube 1) to the other one (tube 2) via a floating metal wire. The propagation of IWs along the two tubes is not affected by the diameter of a floating metal wire, however, their propagation is strongly dependent on the length of a floating metal wire. The propagation of one IW along the tube 1 may result in the second IW propagating reversely inside the tube in vicinity of a floating metal wire, which keeps from their further propagation through the tubemore » 1. After they merge together as one conduction channel inside the tube 1, the transferred plasma bullet starts to propagate along the tube 2. The propagation of transferred plasma bullets along the tube 2 is mainly determined by the capacitance and inductance effects, and their velocity and density can be controlled by the length of a floating metal wire.« less

Observation of high-temperature bubbles in an ECR plasma

NASA Astrophysics Data System (ADS)

Terasaka, K.; Yoshimura, S.; Tanaka, M. Y.

2018-05-01

Creation and annihilation of high-temperature bubbles have been observed in an electron cyclotron resonance plasma. The electron temperature in the bubble core is three times higher than that in the ambient region, and the size perpendicular to the magnetic field is much smaller than the plasma diameter. Formation of a bubble accompanies large negative spikes in the floating potential of a Langmuir probe, and the spatiotemporal behavior of the bubble has been visualized with a high-impedance wire grid detector. It is found that the bubble is in a prolate spheroidal shape with the axis along the magnetic field and occurs randomly in time and independently in space.

Evidence for breathing modes in direct current, pulsed, and high power impulse magnetron sputtering plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yuchen; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720; Zhou, Xue

2016-01-18

We present evidence for breathing modes in magnetron sputtering plasmas: periodic axial variations of plasma parameters with characteristic frequencies between 10 and 100 kHz. A set of azimuthally distributed probes shows synchronous oscillations of the floating potential. They appear most clearly when considering the intermediate current regime in which the direction of azimuthal spoke motion changes. Breathing oscillations were found to be superimposed on azimuthal spoke motion. Depending on pressure and current, one can also find a regime of chaotic fluctuations and one of stable discharges, the latter at high current. A pressure-current phase diagram for the different situations is proposed.

Observed Coupling Between the International Space Station PCU Plasma and a FPMU Langmuir Probe Facilitated by the Geomagnetic Field

NASA Technical Reports Server (NTRS)

Hartman, William; Koontz, Steven L.

2010-01-01

Electrical charging of the International Space Station (ISS) is a matter of serious concern resulting from the possibility of vehicle arcing and electrical shock hazard to crew during extravehicular activity (EVA). A Plasma Contactor Unit (PCU) was developed and integrated into ISS in order to control the ISS floating potential, thereby, minimize vehicle charging and associated hazards. One of the principle factors affecting ISS electrical charging is the ionosphere plasma state (i.e., electron temperature and density). To support ISS electrical charging studies a Floating Potential Monitoring Unit (FPMU) is also integrated into ISS in order to measure the ionosphere properties using Langmuir probes (LP). The FPMU was located on the Starboard side of ISS. The PCU is located near the center of ISS with its plasma exhaust pointed to port. From its integration on ISS in 2006 through November of 2009, the FPMU data exhibited nominal characteristics during PCU operation. On November 21, 2009 the FPMU was relocated from the Starboard location to a new Port location. After relocation significant enhanced noise was observed in both the LP current-voltage sweeps and the derived electron temperature data. The enhanced noise only occurred when the PCU was in discharge and at unique and repeatable locations of the ISS orbit. The cause of this enhanced noise was investigated. It was found that there is coupling occurring between the PCU plasma and the FPMU LP. In this paper we shall 1) present the on-orbit data and the presence of enhanced noise, 2) demonstrate that the coupling of the PCU plasma and the FPMU measurements is geomagnetically organized, 3) show that coupling of the PCU plasma and the FPMU is primarily due to and driven by particle-wave interaction and 4) show that the ionosphere conditions are adequate for Alfven waves to be generated by the PCU plasma.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duarte, V. N.; Clemente, R. A.

The steady one-dimensional planar plasma sheath problem, originally considered by Tonks and Langmuir, is revisited. Assuming continuously generated free-falling ions and isothermal electrons and taking into account electron inertia, it is possible to describe the problem in terms of three coupled integro-differential equations that can be numerically integrated. The inclusion of electron inertia in the model allows us to obtain the value of the plasma floating potential as resulting from an electron density discontinuity at the walls, where the electrons attain sound velocity and the electric potential is continuous. Results from numerical computation are presented in terms of plots formore » densities, electric potential, and particles velocities. Comparison with results from literature, corresponding to electron Maxwell-Boltzmann distribution (neglecting electron inertia), is also shown.« less

In-situ observation of the chemical erosion of graphite in the scrape-off-layer of TEXTOR

NASA Astrophysics Data System (ADS)

Philipps, V.; Vietzke, E.; Erdweg, M.

1989-04-01

A sniffer probe system has been used to investigate the chemical erosion during interaction of the TEXTOR scrape-off plasma with a pyrolytic graphite plate at temperatures up to 1400 °C. Floating potential conditions as well as 200 V bias has been applied at plasma ion fluxes of about 10 18ions/cm 2 sec.Methane formation was found to be 8 × 10 -3 CH 4/H and 1.5 × 10 -2 CD 4/D + for room temperature graphite and floating potential increasing by a factor of two at temperature around 500 °C. Biasing the graphite decreases the methane yield at room temperature and increase it in the maximum temperature range. CO formation due to chemical interaction of oxygen ions with the graphite reaches ratios between 3 and 6 × 10 -2 CO/D(H) near the limiter edge under normal TEXTOR scrape-off conditions and exceeds the chemical hydro-(deu-tero-carbon formation significantly. The results are discussed in view of the present status of hydro-(deutero-)carbon formation on graphite and carbon impurity observations made in fusion experiments.

Near Discharge Cathode Assembly Plasma Potential Measurements in a 30-cm NSTAR Type Ion Engine During Beam Extraction

NASA Technical Reports Server (NTRS)

Herman, Daniel A.; Gallimore, Alec D.

2006-01-01

Floating emissive probe plasma potential data are presented over a two-dimensional array of locations in the near Discharge Cathode Assembly (DCA) region of a 30-cm diameter ring-cusp ion thruster. Discharge plasma data are presented with beam extraction at throttling conditions comparable to the NASA TH Levels 8, 12, and 15. The operating conditions of the Extended Life Test (ELT) of the Deep Space One (DS1) flight spare ion engine, where anomalous discharge keeper erosion occurred, were TH 8 and TH 12 consequently they are of specific interest in investigating discharge keeper erosion phenomena. The data do not validate the presence of a potential hill plasma structure downstream of the DCA, which has been proposed as a possible erosion mechanism. The data are comparable in magnitude to data taken by other researchers in ring-cusp electron-bombardment ion thrusters. The plasma potential structures are insensitive to thruster throttling level with a minimum as low as 14 V measured at the DCA exit plane and increasing gradually in the axial direction. A sharp increase in plasma potential to the bulk discharge value of 26 to 28 volts, roughly 10 mm radially from DCA centerline, was observed. Plasma potential measurements indicate a low-potential plume structure that is roughly 20 mm in diameter emanating from the discharge cathode that may be attributed to a free-standing plasma double layer.

Axial distribution of plasma fluctuations, plasma parameters, deposition rate and grain size during copper deposition

NASA Astrophysics Data System (ADS)

Gopikishan, S.; Banerjee, I.; Pathak, Anand; Mahapatra, S. K.

2017-08-01

Floating potential fluctuations, plasma parameters and deposition rate have been investigated as a function of axial distance during deposition of copper in direct current (DC) magnetron sputtering system. Fluctuations were analyzed using phase space, power spectra and amplitude bifurcation plots. It has been observed that the fluctuations are modified from chaotic to ordered state with increase in the axial distance from cathode. Plasma parameters such as electron density (ne), electron temperature (Te) and deposition rate (Dr) were measured and correlated with plasma fluctuations. It was found that more the deposition rate, greater the grain size, higher the electron density, higher the electron temperature and more chaotic the oscillations near the cathode. This observation could be helpful to the thin film technology industry to optimize the required film.

Design of a toroidal device with a high temperature superconductor coil for non-neutral plasma trap

NASA Astrophysics Data System (ADS)

Ogawa, Yuichi; Morikawa, Junji; Nihei, Hitoshi; Ozawa, Daisaku; Yoshida, Zensho; Mito, Toshiyuki; Yanagi, Nagato; Iwakuma, Masataka

2002-01-01

The non-neutral plasma confinement device with a floating internal coil is under construction, where the high temperature superconductor (HTS) Ag-sheathed BSCCO-2223 is employed as the floating coil. We have two topics with this device: one is a trap of a non-neutral plasma consisting of one species, and another is an exploration of a high beta plasma based on two-fluid MHD relaxation theory. In the latter case the plasma should be non-neutralized in order to drive the plasma flow in the toroidal direction. The expected plasma parameters are discussed. Key elements of engineering issues have already developed. In addition, we have fabricated a small HTS coil and succeeded in levitating it within an accuracy of 25˜30 μm for 4 min or more.

Effect of secondary electron emission on the plasma sheath

NASA Astrophysics Data System (ADS)

Langendorf, S.; Walker, M.

2015-03-01

In this experiment, plasma sheath potential profiles are measured over boron nitride walls in argon plasma and the effect of secondary electron emission is observed. Results are compared to a kinetic model. Plasmas are generated with a number density of 3 × 1012 m-3 at a pressure of 10-4 Torr-Ar, with a 1%-16% fraction of energetic primary electrons. The sheath potential profile at the surface of each sample is measured with emissive probes. The electron number densities and temperatures are measured in the bulk plasma with a planar Langmuir probe. The plasma is non-Maxwellian, with isotropic and directed energetic electron populations from 50 to 200 eV and hot and cold Maxwellian populations from 3.6 to 6.4 eV and 0.3 to 1.3 eV, respectively. Plasma Debye lengths range from 4 to 7 mm and the ion-neutral mean free path is 0.8 m. Sheath thicknesses range from 20 to 50 mm, with the smaller thickness occurring near the critical secondary electron emission yield of the wall material. Measured floating potentials are within 16% of model predictions. Measured sheath potential profiles agree with model predictions within 5 V (˜1 Te), and in four out of six cases deviate less than the measurement uncertainty of 1 V.

Ground Simulations of Near-Surface Plasma Field and Charging at the Lunar Terminator

NASA Astrophysics Data System (ADS)

Polansky, J.; Ding, N.; Wang, J.; Craven, P.; Schneider, T.; Vaughn, J.

2012-12-01

Charging in the lunar terminator region is the most complex and is still not well understood. In this region, the surface potential is sensitively influenced by both solar illumination and plasma flow. The combined effects from localized shadow generated by low sun elevation angles and localized wake generated by plasma flow over the rugged terrain can generate strongly differentially charged surfaces. Few models currently exist that can accurately resolve the combined effects of plasma flow and solar illumination over realistic lunar terminator topographies. This paper presents an experimental investigation of lunar surface charging at the terminator region in simulated plasma environments in a vacuum chamber. The solar wind plasma flow is simulated using an electron bombardment gridded Argon ion source. An electrostatic Langmuir probe, nude Faraday probes, a floating emissive probe, and retarding potential analyzer are used to quantify the plasma flow field. Surface potentials of both conducting and dielectric materials immersed in the plasma flow are measured with a Trek surface potential probe. The conducting material surface potential will simultaneously be measured with a high impedance voltmeter to calibrate the Trek probe. Measurement results will be presented for flat surfaces and objects-on-surface for various angles of attack of the plasma flow. The implications on the generation of localized plasma wake and surface charging at the lunar terminator will be discussed. (This research is supported by the NASA Lunar Advanced Science and Exploration Research program.)

Scrape-off layer tokamak plasma turbulence

NASA Astrophysics Data System (ADS)

Bisai, N.; Singh, R.; Kaw, P. K.

2012-05-01

Two-dimensional (2D) interchange turbulence in the scrape-off layer of tokamak plasmas and their subsequent contribution to anomalous plasma transport has been studied in recent years using electron continuity, current balance, and electron energy equations. In this paper, numerically it is demonstrated that the inclusion of ion energy equation in the simulation changes the nature of plasma turbulence. Finite ion temperature reduces floating potential by about 15% compared with the cold ion temperature approximation and also reduces the radial electric field. Rotation of plasma blobs at an angular velocity about 1.5×105 rad/s has been observed. It is found that blob rotation keeps plasma blob charge separation at an angular position with respect to the vertical direction that gives a generation of radial electric field. Plasma blobs with high electron temperature gradients can align the charge separation almost in the radial direction. Influence of high ion temperature and its gradient has been presented.

Design, Fabrication, and Testing of Emissive Probes to Determine the Plasma Potential of the Plumes of Various Electric Thrusters

NASA Technical Reports Server (NTRS)

Chen, Erinna M.

2005-01-01

A significant problem in the use of electric thrusters in spacecraft is the formation of low-energy ions in the thruster plume. Low-energy ions are formed in the plume via random collisions between high-velocity ions ejected from the thruster and slow-moving neutral atoms of propellant effusing from the engine. The sputtering of spacecraft materials due to interactions with low-energy ions may result in erosion or contamination of the spacecraft. The trajectory of these ions is determined primarily by the plasma potential of the plume. Thus, accurate characterization of the plasma potential is essential to predicting low-energy ion contamination. Emissive probes were utilized to determine the plasma potential. When the ion and electron currents to the probe are balanced, the potential of such probes float to the plasma potential. Two emissive probes were fabricated; one utilizing a DC power supply, another utilizing a rectified AC power source. Labview programs were written to coordinate and automate probe motion in the thruster plume. Employing handshaking interaction, these motion programs were synchronized to various data acquisition programs to ensure precision and accuracy of the measurements. Comparing these experimental values to values from theoretical models will allow for a more accurate prediction of low-energy ion interaction.

Flowing Magnetized Plasma experiment

NASA Astrophysics Data System (ADS)

Wang, Zhehui; Si, Jiahe

2006-10-01

Results from the Flowing Magnetized Plasma experiment at Los Alamos are summarized. Plasmas are produced using a modified coaxial plasma gun with a center electrode extending into a cylindrical vacuum tank with 0.75 m in radius and 4.5 m long. The basic diagnostics are Bdot probes for edge and internal magnetic field, Mach probes and Doppler spectroscopy for plasma flow in the axial and azimuthal directions, and Langmuir probes for plasma floating potential, electron density and temperature. We have found two different plasma flow patterns associated with distinct IV characteristics of the coaxial plasma gun, indicating axial flow is strongly correlated with the plasma ejection from the plasma gun. Global electromagnetic oscillations at frequencies below ion cyclotron frequency are observed, indicating that familiar waves at these frequencies, e.g. Alfven wave or drift wave, are strongly modified by the finite plasma beta. We eliminate the possibility of ion sound waves since the ion and electron temperatures are comparable, and therefore, ion sound waves are strongly Landau damped.

Studies of Microdischarge Plasma Thrusters for Nanosatellite Propulsion

DTIC Science & Technology

2009-09-30

sections 0^ based on the Lennard - Jones interaction potentials14 are used to determine the neutral transport properties using vk = nk gkt^kb, where g... potential that exists between the MPT and the vacuum. The expulsion of hot gas and ions into the vacuum generates thrust. So far the MPT has been...cathode and e2 is at a potential between ej and e3. In fig. 3 b, ei is anode and e3 is cathode whereas e2 is floating. The power supply for ei is

Survey of International Space Station Charging Events

NASA Technical Reports Server (NTRS)

Craven, P. D.; Wright, Kenneth H., Jr.; Minow, Joseph I.; Coffey, Victoria N.; Schneider, Todd A.; Vaughn, Jason A.; Ferguson, Dale C.; Parker, Linda N.

2009-01-01

With the negative grounding of the 160V Photovoltaic (PV) arrays, the International Space Station (ISS) can experience varied and interesting charging events. Since August 2006, there has been a multi-probe p ackage, called the Floating Potential Measurement Unit (FPMU), availa ble to provide redundant measurements of the floating potential of th e ISS as well as the density and temperature of the local plasma environment. The FPMU has been operated during intermittent data campaigns since August 2006 and has collected over 160 days of information reg arding the charging of the ISS as it has progressed in configuration from one to three PV arrays and with various additional modules such as the European Space Agency?s Columbus laboratory and the Japan Aeros pace Exploration Agency's Kibo laboratory. This paper summarizes the charging of the ISS and the local environmental conditions that contr ibute to those charging events, both as measured by the FPMU.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tierno, S. P., E-mail: sp.tierno@upm.es; Donoso, J. M.; Domenech-Garret, J. L.

The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows amore » phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.« less

Validation of ISS Floating Potential Measurement Unit Electron Densities and Temperatures

NASA Technical Reports Server (NTRS)

Coffey, Victoria N.; Minow, Joseph I.; Parker, Linda N.; Bui, Them; Wright, Kenneth, Jr.; Koontz, Steven L.; Schneider, T.; Vaughn, J.; Craven, P.

2007-01-01

Validation of the Floating Potential Measurement Unit (FPMU) electron density and temperature measurements is an important step in the process of evaluating International Space Station spacecraft charging issues .including vehicle arcing and hazards to crew during extravehicular activities. The highest potentials observed on Space Station are due to the combined VxB effects on a large spacecraft and the collection of ionospheric electron and ion currents by the 160 V US solar array modules. Ionospheric electron environments are needed for input to the ISS spacecraft charging models used to predict the severity and frequency of occurrence of ISS charging hazards. Validation of these charging models requires comparing their predictions with measured FPMU values. Of course, the FPMU measurements themselves must also be validated independently for use in manned flight safety work. This presentation compares electron density and temperatures derived from the FPMU Langmuir probes and Plasma Impedance Probe against the independent density and temperature measurements from ultraviolet imagers, ground based incoherent scatter radar, and ionosonde sites.

Mode conversion at density irregularities in the LAPD

NASA Astrophysics Data System (ADS)

Kersten, Kristopher; Cattell, Cynthia; van Compernolle, Bart; Gekelman, Walter; Pribyl, Pat; Vincena, Steve

2010-11-01

Mode conversion of electrostatic plasma oscillations to electromagnetic radiation is commonly observed in space plasmas as Type II and III radio bursts. Much theoretical work has addressed the phenomenon, but due to the transient nature and generation location of the bursts, experimental verification via in situ observation has proved difficult. The Large Plasma Device (LAPD) provides a reproducible plasma environment that can be tailored for the study of space plasma phenomena. A highly configurable axial magnetic field and flexible diagnostics make the device well suited for the study of plasma instabilities at density gradients. We present preliminary results of mode conversion studies performed at the LAPD. The studies employed an electron beam source configured to drive Langmuir waves towards high density plasma near the cathode discharge. Internal floating potential probes show the expected plasma oscillations ahead of the beam cathode, and external microwave antenna signals reveal a strong band of radiation near the plasma frequency that persists into the low density plasma afterglow.

Campaign for Levitation in LDX

NASA Astrophysics Data System (ADS)

Garnier, D. T.; Hansen, A. K.; Mauel, M. E.; Ortiz, E. E.; Boxer, A. C.; Ellsworth, J. L.; Karim, I.; Kesner, J.; Michael, P. C.; Zhukovsky, A.

2006-10-01

In the past year, preparations have been made for the first flight of the Levitated Dipole Experiment (LDX). LDX, which consists of a 560 kg superconducting coil floating within a 5 m diameter vacuum chamber, is designed to study fusion relevant plasmas confined in a dipole magnetic field. During the spring, a high temperature superconducting levitation coil was integrated into the LDX facility. Testing was undertaken to verify the thermal performance of the coil under expected levitation conditions. In addition, a real-time operating system digital control system was developed that will be used for the levitation control. In July, plasma experiments were conducted with all superconducting magnets in operation. While still supported, roughly 75% of the weight of the floating coil was magnetically lifted by the levitation coil above. A series of plasma experiments were conducted with the same magnetic geometry as will be the case during levitation. During August, the second generation launcher system will be installed. The launcher, which retracts beyond the plasma's last closed field lines during operation, is designed to safely catch the floating coil following an unexpected loss of control. After this installation, levitation experiments will commence.

Cross-field electron transport inside an insulating cylinder of a baffled probe

NASA Astrophysics Data System (ADS)

Raitses, Yevgeny; Alt, Andrew

2017-10-01

Plasma-immersed wall experiments have been performed in a magnetized xenon plasma in a cross-field Penning configuration with density around 1012 cm-3 and an electron temperature around a few eV. A cylinder with an open end and diameter of 1.4 mm was placed across field lines so that electrons were blocked from reaching a wire recessed behind the shield while ions were unimpeded. The reduction of electron current to the wire causes it to float closer to the plasma potential, possibly making a device that can passively measure plasma potential. However, the measured electron current was much higher than expected even when the wire was recessed several electron gyroradii behind the baffle. Possible mechanisms for this electron conduction causing the short circuiting to the bulk plasma have been studied with numerical approaches and with a dedicated experiment designed to isolate this short circuit effect. The obtained results may be important for cross-field transport in a variety of other configurations in magnetized, low-temperature plasmas. This work was supported by DOE contract DE-AC02-09CH11466.

Irregular-regular-irregular mixed mode oscillations in a glow discharge plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Sabuj, E-mail: sabuj.ghosh@saha.ac.in; Shaw, Pankaj Kumar, E-mail: pankaj.shaw@saha.ac.in; Saha, Debajyoti, E-mail: debajyoti.saha@saha.ac.in

2015-05-15

Floating potential fluctuations of a glow discharge plasma are found to exhibit different kinds of mixed mode oscillations. Power spectrum analysis reveals that with change in the nature of the mixed mode oscillation (MMO), there occurs a transfer of power between the different harmonics and subharmonics. The variation in the chaoticity of different types of mmo was observed with the study of Lyapunov exponents. Estimates of correlation dimension and the Hurst exponent suggest that these MMOs are of low dimensional nature with an anti persistent character. Numerical modeling also reflects the experimentally found transitions between the different MMOs.

Design and Development of High Voltage Direct Current (DC) Sources for the Solar Array Module Plasma Interaction Experiment

NASA Technical Reports Server (NTRS)

Bibyk, Irene K.; Wald, Lawrence W.

1995-01-01

Two programmable, high voltage DC power supplies were developed as part of the flight electronics for the Solar Array Module Plasma Interaction Experiment (SAMPIE). SAMPIE's primary objectives were to study and characterize the high voltage arcing and parasitic current losses of various solar cells and metal samples within the space plasma of low earth orbit (LEO). High voltage arcing can cause large discontinuous changes in spacecraft potential which lead to damage of the power system materials and significant Electromagnetic Interference (EMI). Parasitic currents cause a change in floating potential which lead to reduced power efficiency. These primary SAMPIE objectives were accomplished by applying artificial biases across test samples over a voltage range from -600 VDC to +300 VDC. This paper chronicles the design, final development, and test of the two programmable high voltage sources for SAMPIE. The technical challenges to the design for these power supplies included vacuum, space plasma effects, thermal protection, Shuttle vibrations and accelerations.

Recent Results From Internal and Very-Near-Field Plasma Diagnostics of a High Specific Impulse Hall Thruster

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Gallimore, Alec D.; Jacobson, David (Technical Monitor)

2003-01-01

Floating potential and ion current density measurements were taken on the laboratory model NASA-173Mv2 in order to improve understanding of the physical processes affecting Hall thruster performance at high specific impulse. Floating potential was measured on discharge chamber centerline over axial positions spanning 10 mm from the anode to 100 mm downstream of the exit plane. Ion current density was mapped radially up to 300 mm from thruster centerline over axial positions in the very-near-field (10 to 250 mm from the exit plane). All data were collected using a planar probe in conjunction with a high-speed translation stage to minimize probe-induced thruster perturbations. Measurements of floating potential at a xenon flow rate of 10 mg/s have shown that the acceleration layer moved upstream 3 1 mm when the voltage increased from 300 to 600 V. The length of the acceleration layer was 14 2 mm and was approximately constant with voltage and magnetic field. Ion current density measurements indicated the annular ion beam crossed the thruster centerline 163 mm downstream of the exit plane. Radial integration of the ion current density at the cathode plane provided an estimate of the ion current fraction. At 500 V and 5 mg/s, the ion current fraction was calculated as 0.77.

Steady and oscillatory plasma properties in the near-field plume of a hollow cathode

NASA Astrophysics Data System (ADS)

Zun, ZHANG; Kan, XIE; Jiting, OUYANG; Ning, GUO; Yu, QIN; Qimeng, XIA; Song, BAI; Xianming, WU; Zengjie, GU

2018-02-01

Hollow cathodes serve as electron sources in Hall thrusters, ion thrusters and other electric propulsion systems. One of the vital problems in their application is the cathode erosion. However, the basic erosion mechanism and the source of high-energy ions cause of erosion are not fully understood. In this paper, both potential measurements and simulation analyses were performed to explain the formation of high-energy ions. A high-speed camera, a single Langmuir probe and a floating emissive probe were used to determine the steady and oscillatory plasma properties in the near-field plume of a hollow cathode. The temporal structure, electron temperature, electron density, and both static and oscillation of plasma potentials of the plume have been obtained by the diagnostics mentioned above. The experimental results show that there exists a potential hill (about 30 V) and also severe potential oscillations in the near-plume region. Moreover, a simple 2D particle-in-cell model was used to analyze the energy transition between the potential hill and/or its oscillations and the ions. The simulation results show that the energy of ions gained from the static potential background is about 20 eV, but it could reach to 60 eV when the plasma oscillates.

Multifractality in plasma edge electrostatic turbulence

NASA Astrophysics Data System (ADS)

Neto, C. Rodrigues; Guimarães-Filho, Z. O.; Caldas, I. L.; Nascimento, I. C.; Kuznetsov, Yu. K.

2008-08-01

Plasma edge turbulence in Tokamak Chauffage Alfvén Brésilien (TCABR) [R. M. O. Galvão et al., Plasma Phys. Contr. Fusion 43, 1181 (2001)] is investigated for multifractal properties of the fluctuating floating electrostatic potential measured by Langmuir probes. The multifractality in this signal is characterized by the full multifractal spectra determined by applying the wavelet transform modulus maxima. In this work, the dependence of the multifractal spectrum with the radial position is presented. The multifractality degree inside the plasma increases with the radial position reaching a maximum near the plasma edge and becoming almost constant in the scrape-off layer. Comparisons between these results with those obtained for random test time series with the same Hurst exponents and data length statistically confirm the reported multifractal behavior. Moreover, the persistence of these signals, characterized by their Hurst exponent, present radial profile similar to the deterministic component estimated from analysis based on dynamical recurrences.

Space Weather Monitoring for ISS Geomagnetic Storm Studies

NASA Technical Reports Server (NTRS)

Minow, Joseph I.; Parker, Neergaard

2013-01-01

The International Space Station (ISS) space environments community utilizes near real time space weather data to support a variety of ISS engineering and science activities. The team has operated the Floating Potential Measurement Unit (FPMU) suite of plasma instruments (two Langmuir probes, a floating potential probe, and a plasma impedance probe) on ISS since 2006 to obtain in-situ measurements of plasma density and temperature along the ISS orbit and variations in ISS frame potential due to electrostatic current collection from the plasma environment (spacecraft charging) and inductive (vxB) effects from the vehicle motion across the Earth s magnetic field. An ongoing effort is to use FPMU for measuring the ionospheric response to geomagnetic storms at ISS altitudes and investigate auroral charging of the vehicle as it passes through regions of precipitating auroral electrons. This work is challenged by restrictions on FPMU operations that limit observation time to less than about a third of a year. As a result, FPMU campaigns ranging in length from a few days to a few weeks are typically scheduled weeks in advance for ISS engineering and payload science activities. In order to capture geomagnetic storm data under these terms, we monitor near real time space weather data from NASA, NOAA, and ESA sources to determine solar wind disturbance arrival times at Earth likely to be geoeffective (including coronal mass ejections and high speed streams associated with coronal holes) and activate the FPMU ahead of the storm onset. Using this technique we have successfully captured FPMU data during a number of geomagnetic storm periods including periods with ISS auroral charging. This presentation will describe the strategies and challenges in capturing FPMU data during geomagnetic storms, the near real time space weather resources utilized for monitoring the space weather environment, and provide examples of auroral charging data obtained during storm operations.

Spacecraft-plasma-debris interaction in an ion beam shepherd mission

NASA Astrophysics Data System (ADS)

Cichocki, Filippo; Merino, Mario; Ahedo, Eduardo

2018-05-01

This paper presents a study of the interaction between a spacecraft, a plasma thruster plume and a free floating object, in the context of an active space debris removal mission based on the ion beam shepherd concept. The analysis is performed with the EP2PLUS hybrid code and includes the evaluation of the transferred force and torque to the target debris, its surface sputtering due to the impinging hypersonic ions, and the equivalent electric circuit of the spacecraft-plasma-debris interaction. The electric potential difference that builds up between the spacecraft and the debris, the ion backscattering and the backsputtering contamination of the shepherd satellite are evaluated for a nominal scenario. A sensitivity analysis is carried out to evaluate quantitatively the effects of electron thermodynamics, ambient plasma, heavy species collisions, and debris position.

Payload charging events in the mesosphere and their impact on Langmuir type electric probes

NASA Astrophysics Data System (ADS)

Bekkeng, T. A.; Barjatya, A.; Hoppe, U.-P.; Pedersen, A.; Moen, J. I.; Friedrich, M.; Rapp, M.

2013-02-01

Three sounding rockets were launched from Andøya Rocket Range in the ECOMA campaign in December 2010. The aim was to study the evolution of meteoric smoke particles during a major meteor shower. Of the various instruments onboard the rocket payload, this paper presents the data from a multi-Needle Langmuir Probe (m-NLP) and a charged dust detector. The payload floating potential, as observed using the m-NLP instrument, shows charging events on two of the three flights. These charging events cannot be explained using a simple charging model, and have implications towards the use of fixed bias Langmuir probes on sounding rockets investigating mesospheric altitudes. We show that for a reliable use of a single fixed bias Langmuir probe as a high spatial resolution relative density measurement, each payload should also carry an additional instrument to measure payload floating potential, and an instrument that is immune to spacecraft charging and measures absolute plasma density.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griswold, M. E., E-mail: mgriswold@trialphaenergy.com; Korepanov, S.; Thompson, M. C.

An end loss analyzer system consisting of electrostatic, gridded retarding-potential analyzers and pyroelectric crystal bolometers was developed to characterize the plasma loss along open field lines to the divertors of C-2U. The system measures the current and energy distribution of escaping ions as well as the total power flux to enable calculation of the energy lost per escaping electron/ion pair. Special care was taken in the construction of the analyzer elements so that they can be directly mounted to the divertor electrode. An attenuation plate at the entrance to the gridded retarding-potential analyzer reduces plasma density by a factor ofmore » 60 to prevent space charge limitations inside the device, without sacrificing its angular acceptance of ions. In addition, all of the electronics for the measurement are isolated from ground so that they can float to the bias potential of the electrode, 2 kV below ground.« less

Collective behavior of silver plasma during pulsed laser ablation

NASA Astrophysics Data System (ADS)

Dildar, I. M.; Rehman, S.; Khaleeq-ur-Rahman, M.; Bhatti, K. A.; Shuaib, A.

2015-07-01

The present work reports an electrical investigation of silver plasma using a self-fabricated Langmuir probe in air and under a low vacuum (~10-3 torr). A silver target was irradiated with a Q-switched Nd:YAG laser with the wavelength 1.064 µm, energy 10 mJ, pulse duration 9-14 ns and power 1.1 MW. The collective behavior of a silver plasma plume is studied using a Langmuir probe as an electrical diagnostic technique. By applying different positive and negative voltages to the probe, the respective signals are collected on a four channels digital storage oscilloscope having a frequency of 500 MHz. An I-V curve helps to measure electron temperature and electron density directly and plasma frequency, response time, Debye length and number of particles in ‘Debye’s sphere’ indirectly using the theory of Langmuir probe and mathematical formulas. The floating potential is measured as negative for laser induced silver plasma in air and vacuum, following the theory of plasma.

Oleyl group-functionalized insulating gate transistors for measuring extracellular pH of floating cells

NASA Astrophysics Data System (ADS)

Imaizumi, Yuki; Goda, Tatsuro; Toya, Yutaro; Matsumoto, Akira; Miyahara, Yuji

2016-01-01

The extracellular ionic microenvironment has a close relationship to biological activities such as by cellular respiration, cancer development, and immune response. A system composed of ion-sensitive field-effect transistors (ISFET), cells, and program-controlled fluidics has enabled the acquisition of real-time information about the integrity of the cell membrane via pH measurement. Here we aimed to extend this system toward floating cells such as T lymphocytes for investigating complement activation and pharmacokinetics through alternations in the plasma membrane integrity. We functionalized the surface of tantalum oxide gate insulator of ISFET with oleyl-tethered phosphonic acid for interacting with the plasma membranes of floating cells without affecting the cell signaling. The surface modification was characterized by X-ray photoelectron spectroscopy and water contact angle measurements. The Nernst response of -37.8 mV/pH was obtained for the surface-modified ISFET at 37 °C. The oleyl group-functionalized gate insulator successfully captured Jurkat T cells in a fluidic condition without acute cytotoxicity. The system was able to record the time course of pH changes at the cells/ISFET interface during the process of instant addition and withdrawal of ammonium chloride. Further, the plasma membrane injury of floating cells after exposure by detergent Triton™ X-100 was successfully determined using the modified ISFET with enhanced sensitivity as compared with conventional hemolysis assays.

Oleyl group-functionalized insulating gate transistors for measuring extracellular pH of floating cells

PubMed Central

Imaizumi, Yuki; Goda, Tatsuro; Toya, Yutaro; Matsumoto, Akira; Miyahara, Yuji

2016-01-01

Abstract The extracellular ionic microenvironment has a close relationship to biological activities such as by cellular respiration, cancer development, and immune response. A system composed of ion-sensitive field-effect transistors (ISFET), cells, and program-controlled fluidics has enabled the acquisition of real-time information about the integrity of the cell membrane via pH measurement. Here we aimed to extend this system toward floating cells such as T lymphocytes for investigating complement activation and pharmacokinetics through alternations in the plasma membrane integrity. We functionalized the surface of tantalum oxide gate insulator of ISFET with oleyl-tethered phosphonic acid for interacting with the plasma membranes of floating cells without affecting the cell signaling. The surface modification was characterized by X-ray photoelectron spectroscopy and water contact angle measurements. The Nernst response of −37.8 mV/pH was obtained for the surface-modified ISFET at 37 °C. The oleyl group-functionalized gate insulator successfully captured Jurkat T cells in a fluidic condition without acute cytotoxicity. The system was able to record the time course of pH changes at the cells/ISFET interface during the process of instant addition and withdrawal of ammonium chloride. Further, the plasma membrane injury of floating cells after exposure by detergent Triton™ X-100 was successfully determined using the modified ISFET with enhanced sensitivity as compared with conventional hemolysis assays. PMID:27877886

Product surface hardening in non-self-sustained glow discharge plasma before synthesis of superhard coatings

NASA Astrophysics Data System (ADS)

Krasnov, P. S.; Metel, A. S.; Nay, H. A.

2017-05-01

Before the synthesis of superhard coating, the product surface is hardened by means of plasma nitriding, which prevents the surface deformations and the coating brittle rupture. The product heating by ions accelerated from plasma by applied to the product bias voltage leads to overheating and blunting of the product sharp edges. To prevent the blunting, it is proposed to heat the products with a broad beam of fast nitrogen molecules. The beam injection into a working vacuum chamber results in filling of the chamber with quite homogeneous plasma suitable for nitriding. Immersion in the plasma of the electrode and heightening of its potential up to 50-100 V initiate a non-self-sustained glow discharge between the electrode and the chamber. It enhances the plasma density by an order of magnitude and reduces its spatial nonuniformity down to 5-10%. When a cutting tool is isolated from the chamber, it is bombarded by plasma ions with an energy corresponding to its floating potential, which is lower than the sputtering threshold. Hence, the sharp edges are sputtered only by fast nitrogen molecules with the same rate as other parts of the tool surface. This leads to sharpening of the cutting tools instead of blunting.

Characterization of the C-2W Plasma Guns

NASA Astrophysics Data System (ADS)

Dubois, Ami; Sokolov, Vladimir; Korepanov, Sergey; Osin, Dima; Player, Gabriel; TAE Team

2017-10-01

Previous use of coaxial arc discharge plasma guns on the C-2U device exhibited great success in plasma stabilization and improved confinement. On the C-2W experiment, arc discharge plasma guns will again be used to facilitate the electrical connection between the plasma core and the divertor electrodes in order to maintain the electrode edge biasing and induce E x B shear to control plasma rotation. Each plasma gun contains an internal solenoid used to shape the plasma stream. Characterization of electron density (ne) , electron temperature (Te) , floating potential (Vf) , and total plasma flux in an arc discharge lasting 6 ms without the internal solenoid are presented. A Langmuir probe located 27 cm axially outside of the plasma gun anode measures a bell-like radial ne profile with peak ne 1018 m-3 and Te 2 - 10 eV. Observed spectral lines of impurity ions provide an estimate of Te, and Balmer series line ratios of the main ion component are used to evaluate ne at both the probe location and near the plasma gun anode. A calorimeter measures the plasma flux to be constant and equivalent to 1 kA.

Are two plasma equilibrium states possible when the emission coefficient exceeds unity?

NASA Astrophysics Data System (ADS)

Campanell, M. D.; Umansky, M. V.

2017-05-01

Two floating sheath solutions with strong electron emission in planar geometry have been proposed, a "space-charge limited" (SCL) sheath and an "inverse" sheath. SCL and inverse models contain different assumptions about conditions outside the sheath (e.g., the velocity of ions entering the sheath). So it is not yet clear whether both sheaths are possible in practice, or only one. Here we treat the global presheath-sheath problem for a plasma produced volumetrically between two planar walls. We show that all equilibrium requirements (a) floating condition, (b) plasma shielding, and (c) presheath force balance, can indeed be satisfied in two different ways when the emission coefficient γ > 1. There is one solution with SCL sheaths and one with inverse sheaths, each with sharply different presheath distributions. As we show for the first time in 1D-1V simulations, a SCL and inverse equilibrium are both possible in plasmas with the same upstream properties (e.g., same N and Te). However, maintaining a true SCL equilibrium requires no ionization or charge exchange collisions in the sheath, or else cold ion accumulation in the SCL's "dip" forces a transition to the inverse. This suggests that only a monotonic inverse type sheath potential should exist at any plasma-facing surface with strong emission, whether be a divertor plate, emissive probe, dust grain, Hall thruster channel wall, sunlit object in space, etc. Nevertheless, SCL sheaths might still be possible if the ions in the dip can escape. Our simulations demonstrate ways in which SCL and inverse regimes might be distinguished experimentally based on large-scale presheath effects, without having to probe inside the sheath.

Are two plasma equilibrium states possible when the emission coefficient exceeds unity?

DOE PAGES

Campanell, Michael D.; Umansky, M. V.

2017-02-28

Two floating sheath solutions with strong electron emission in planar geometry have been proposed, a “space-charge limited” (SCL) sheath and an “inverse” sheath. SCL and inverse models contain different assumptions about conditions outside the sheath (e.g., the velocity of ions entering the sheath). So it is not yet clear whether both sheaths are possible in practice, or only one. Here we treat the global presheath-sheath problem for a plasma produced volumetrically between two planar walls. We show that all equilibrium requirements (a) floating condition, (b) plasma shielding, and (c) presheath force balance, can indeed be satisfied in two different waysmore » when the emission coefficient γ > 1. There is one solution with SCL sheaths and one with inverse sheaths, each with sharply different presheath distributions. As we show for the first time in 1D-1V simulations, a SCL and inverse equilibrium are both possible in plasmas with the same upstream properties (e.g., same N and Te). However, maintaining a true SCL equilibrium requires no ionization or charge exchange collisions in the sheath, or else cold ion accumulation in the SCL's “dip” forces a transition to the inverse. This suggests that only a monotonic inverse type sheath potential should exist at any plasma-facing surface with strong emission, whether be a divertor plate, emissive probe, dust grain, Hall thruster channel wall, sunlit object in space, etc. Nevertheless, SCL sheaths might still be possible if the ions in the dip can escape. Finally, our simulations demonstrate ways in which SCL and inverse regimes might be distinguished experimentally based on large-scale presheath effects, without having to probe inside the sheath.« less

Numerical investigation of the electric field distribution and the power deposition in the resonant cavity of a microwave electrothermal thruster

NASA Astrophysics Data System (ADS)

Yildiz, Mehmet Serhan; Celik, Murat

2017-04-01

Microwave electrothermal thruster (MET), an in-space propulsion concept, uses an electromagnetic resonant cavity as a heating chamber. In a MET system, electromagnetic energy is converted to thermal energy via a free floating plasma inside a resonant cavity. To optimize the power deposition inside the cavity, the factors that affect the electric field distribution and the resonance conditions must be accounted for. For MET thrusters, the length of the cavity, the dielectric plate that separates the plasma zone from the antenna, the antenna length and the formation of a free floating plasma have direct effects on the electromagnetic wave transmission and thus the power deposition. MET systems can be tuned by adjusting the lengths of the cavity or the antenna. This study presents the results of a 2-D axis symmetric model for the investigation of the effects of cavity length, antenna length, separation plate thickness, as well as the presence of free floating plasma on the power absorption. Specifically, electric field distribution inside the resonant cavity is calculated for a prototype MET system developed at the Bogazici University Space Technologies Laboratory. Simulations are conducted for a cavity fed with a constant power input of 1 kW at 2.45 GHz using COMSOL Multiphysics commercial software. Calculations are performed for maximum plasma electron densities ranging from 1019 to 1021 #/m3. It is determined that the optimum antenna length changes with changing plasma density. The calculations show that over 95% of the delivered power can be deposited to the plasma when the system is tuned by adjusting the cavity length.

Experimental investigation of differential confinement effects in a rotating helicon plasma

NASA Astrophysics Data System (ADS)

Gueroult, Renaud; Evans, Eugene; Zweben, Stewart J.; Fisch, Nathaniel J.; Levinton, Fred

2014-10-01

Although plasmas have long been considered for isotope separation, challenges presented by nuclear waste remediation and nuclear spent fuel reprocessing have recently sparked a renewed interest for high-throughput plasma based mass separation techniques. Different filter concepts relying on rotating plasmas have been proposed to address these needs. However, one of the challenges common to these concepts is the need to control the plasma rotation profile, which is generally assumed to be provided by means of dedicated electrodes. An experimental effort aiming to evaluate the practicality of these plasma filter concepts has recently been started at PPPL. For this purpose, a linear helicon plasma source is used in combination with concentric ring electrodes. Preliminary biasing experiments results indicate floating potential profiles locally suitable for mass discrimination for different gas mixtures (Ar/Ne, Ar/N2, Ar/Kr). Radially resolved spectroscopic measurements and neutral gas composition analysis at two different axial positions are being planned to assess the mass separation effect. Work supported by US DOE under Contract No. DE-AC02-09CH11466.

Increased water temperature renders single-housed C57BL/6J mice susceptible to antidepressant treatment in the forced swim test.

PubMed

Bächli, Heidi; Steiner, Michel A; Habersetzer, Ursula; Wotjak, Carsten T

2008-02-11

To investigate genotype x environment interactions in the forced swim test, we tested the influence of water temperature (20 degrees C, 25 degrees C, 30 degrees C) on floating behaviour in single-housed male C57BL/6J and BALB/c mice. We observed a contrasting relationship between floating and water temperature between the two strains, with C57BL/6J floating more and BALB/c floating less with increasing water temperature, independent of the lightening conditions and the time point of testing during the animals' circadian rhythm. Both strains showed an inverse relationship between plasma corticosterone concentration and water temperature, indicating that the differences in stress coping are unrelated to different perception of the aversive encounter. Treatment with desipramine (20mg/kg, i.p.) caused a reduction in immobility time in C57BL/6J mice if the animals were tested at 30 degrees C water temperature, with no effect at 25 degrees C and no effects on forced swim stress-induced corticosterone secretion. The same treatment failed to affect floating behaviour in BALB/c at any temperature, but caused a decrease in plasma corticosterone levels. Taken together we demonstrate that an increase in water temperature in the forced swim test exerts opposite effects on floating behaviour in C57BL/6J and BALB/c and renders single-housed C57BL/6J mice, but not BALB/c mice, susceptible to antidepressant-like behavioral effects of desipramine.

Cross-comparison of spacecraft-environment interaction model predictions applied to Solar Probe Plus near perihelion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marchand, R.; Miyake, Y.; Usui, H.

2014-06-15

Five spacecraft-plasma models are used to simulate the interaction of a simplified geometry Solar Probe Plus (SPP) satellite with the space environment under representative solar wind conditions near perihelion. By considering similarities and differences between results obtained with different numerical approaches under well defined conditions, the consistency and validity of our models can be assessed. The impact on model predictions of physical effects of importance in the SPP mission is also considered by comparing results obtained with and without these effects. Simulation results are presented and compared with increasing levels of complexity in the physics of interaction between solar environmentmore » and the SPP spacecraft. The comparisons focus particularly on spacecraft floating potentials, contributions to the currents collected and emitted by the spacecraft, and on the potential and density spatial profiles near the satellite. The physical effects considered include spacecraft charging, photoelectron and secondary electron emission, and the presence of a background magnetic field. Model predictions obtained with our different computational approaches are found to be in agreement within 2% when the same physical processes are taken into account and treated similarly. The comparisons thus indicate that, with the correct description of important physical effects, our simulation models should have the required skill to predict details of satellite-plasma interaction physics under relevant conditions, with a good level of confidence. Our models concur in predicting a negative floating potential V{sub fl}∼−10V for SPP at perihelion. They also predict a “saturated emission regime” whereby most emitted photo- and secondary electron will be reflected by a potential barrier near the surface, back to the spacecraft where they will be recollected.« less

ISS And Space Environment Interactions Without Operating Plasma Contactor

NASA Technical Reports Server (NTRS)

Carruth, M. R., Jr.; Ferguson, Dale; Suggs,Rob; McCollum, Matt

2001-01-01

The International Space Station (ISS) will be the largest, highest power spacecraft placed in orbit. Because of this the design of the electrical power system diverged markedly from previous systems. The solar arrays will operate at 160 V and the power distribution voltage will be 120 V. The structure is grounded to the negative side of the solar arrays so under the right circumstances it is possible to drive the ISS potential very negative. A plasma contactor has been added to the ISS to provide control of the ISS structure potential relative to the ambient plasma. The ISS requirement is that the ISS structure not be greater than 40 V positive or negative of local plasma. What are the ramifications of operating large structures with such high voltage power systems? The application of a plasma contactor on ISS controls the potential between the structure and the local plasma, preventing degrading effects. It is conceivable that there can be situations where the plasma contactor might be non-functional. This might be due to lack of power, the need to turn it off during some of the build-up sequences, the loss of functionality for both plasma contactors before a replacement can be installed, similar circumstances. A study was undertaken to understand how important it is to have the contactor functioning and how long it might be off before unacceptable degradation to ISS could occur. The details of interaction effects on spacecraft have not been addressed until driven by design. This was true for ISS. If the structure is allowed to float highly negative impinging ions can sputter exposed conductors which can degrade the primary surface and also generate contamination due to the sputtered material. Arcing has been known to occur on solar arrays that float negative of the ambient plasma. This can also generate electromagnetic interference and voltage transients. Much of the ISS structure and pressure module surfaces exposed to space is anodized aluminum. The anodization thickness is very thin to provide the required solar absorptance and emittance. For conditions where ISS structure can charge negative a large percentage of the array voltage, the dielectric strength of this layer is low, and dielectric breakdown (arcing) can occur. The energy stored capacitively in the structure can be delivered to the arc. The mechanisms by which this energy is delivered and how much of the energy is available hasn't been fully quantified. Questions have been raised regarding the possibility of whether a sustained arc might result due to current collected by the solar arrays from local plasma. It was postulated that even if dielectric breakdown didn't occur, impacts due to micrometeoroids and space debris could penetrate thin layers of dielectric on ISS and initiate an arc due to the coupling provided by the dense local plasma produced by the impact. This was proven in experiments conducted jointly by MSFC and Auburn University. A target chamber with a simulated ionospheric plasma and a biased, anodized aluminum plate and a 1-microfarad capacitor was used. The plate was then impacted by 75-micron particles accelerated to orbital velocity. Arc discharges were sustained for higher voltages but a threshold appears below which no discharge was initiated. Most items without an exposed power system will float electrically near the local plasma potential. This is true of the Space Shuttle, an Astronaut on EVA, and similar items. The structure of ISS might be at a large negative voltage. Therefore, capacitively stored energy can be transferred during docking, installing external boxes and equipment and Astronaut contact with ISS structure. The circumstances of when this can happen and the resulting effects are evaluated in this study. Also, a crewmember on EVA might be in the vicinity of an arc. All safety aspects of such an encounter including charging, molten particles from the arc site and EMI have been evaluated. This paper will report on the total results of this study focussed on the 4A configuration, scheduled to be complete in November, 2000. Interactions such as arcing, debris induced arcs, sustained arcs, sputtering, contamination from sputtering and arcing, docking interactions and Astronaut safety issues will all be addressed.

Characterizing ISS Charging Environments with On-Board Ionospheric Plasma Measurements

NASA Technical Reports Server (NTRS)

Minow, Jospeh I.; Craven, Paul D.; Coffey, Victoria N.; Schneider, Todd A.; Vaughn, Jason A.; Wright Jr, Kenneth; Parker, Paul D.; Mikatarian, Ronald R.; Kramer, Leonard; Hartman, William A.;

Investigation of Dusts Effect and Negative Ion in DC Plasmas by Electric Probes

NASA Astrophysics Data System (ADS)

Oh, Hye Taek; Kang, Inje; Bae, Min-Keun; Park, Insun; Lee, Seunghwa; Jeong, Seojin; Chung, Kyu-Sun

2017-10-01

Dust is typically negatively charged by electron attachment whose thermal velocities are fast compared to that of the heavier ions. The negatively charged particles can play a role of negative ions which affect the quasi-neutrality of background plasma. To investigate effect of metal dusts and negative ion on plasma and materials, metal dusts are injected into background Ar plasma which is generated by tungsten filament using dust dispenser on Cubical Plasma Device (CPD). The CPD has following conditions: size =24x24x24cm3, plasma source =DC filament plasma (ne 1x10x1010, Te 2eV), background gas =Ar, dusts =tungsten powder (diameter 1.89micron). The dust dispenser is developed to quantitate of metal dust by ultrasonic transducer. Electronegative plasmas are generated by adding O2 + Ar plasma to compare negative ion and dust effect. A few grams of micron-sized dusts are placed in the dust dispenser which is located at the upper side of the Cubical Plasma Device. The falling particles by dust dispenser are mainly charged up by the collection of the background plasma. The change in parameters due to negative ion production are characterized by measuring the floating and plasma potential, electron temperature and negative ion density using electric probes.

Effects of the guard electrode on the photoelectron distribution around an electric field sensor

NASA Astrophysics Data System (ADS)

Miyake, Y.; Usui, H.; Kojima, H.

2011-05-01

We have developed a numerical model of a double-probe electric field sensor equipped with a photoelectron guard electrode for the particle-in-cell simulation. The model includes typical elements of modern double-probe sensors on, e.g., BepiColombo/MMO, Cluster, and THEMIS spacecraft, such as a conducting boom and a preamplifier housing called a puck. The puck is also used for the guard electrode, and its potential is negatively biased by reference to the floating spacecraft potential. We apply the proposed model to an analysis of an equilibrium plasma environment around the sensor by assuming that the sun illuminates the spacecraft from the direction perpendicular to the sensor deployment axis. As a simulation result, it is confirmed that a substantial number of spacecraft-originating photoelectrons are once emitted sunward and then fall onto the puck and sensing element positions. In order to effectively repel such photoelectrons coming from the sun direction, a potential hump for electrons, i.e., a negative potential region, should be created in a plasma region around the sunlit side of the guard electrode surface. The simulation results reveal the significance of the guard electrode potential being not only lower than the spacecraft body but also lower than the background plasma potential of the region surrounding the puck and the sensing element. One solution for realizing such an operational condition is to bias the guard potential negatively by reference to the sensor potential because the sensor is usually operated nearly at the background plasma potential.

Temporal Evolution of the Plasma Sheath Surrounding Solar Cells in Low Earth Orbit

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Pour, Maria Z. A.

2017-01-01

High voltage solar array interactions with the space environment can have a significant impact on array performance and spacecraft charging. Over the past 10 years, data from the International Space Station has allowed for detailed observations of these interactions over long periods of time. Some of the surprising observations have been floating potential transients, which were not expected and are not reproduced by existing models. In order to understand the underlying processes producing these transients, the temporal evolution of the plasma sheath surrounding the solar cells in low Earth orbit is being investigated. This study includes lumped element modeling and particle-in-cell simulation methods. This presentation will focus on recent results from the on-going investigations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xian, Y. B.; Xu, H. T.; Lu, X. P., E-mail: luxinpei@hotmail.com

In this work, for better applications of atmospheric pressure plasma jets, the physics of plasma streamers in a glass tube with a part of it covered by a conductor is investigated. To better understand the propagation mechanism of plasma bullets in capillary tubes passing through a curved or narrow passage for some biomedical or material applications, the propagation of plasma streamers in a tube covered by a floating conductor is investigated. For a plasma streamer propagating in a tube covered by a conductor, the plasma streamer is suppressed and becomes shorter, and a secondary streamer is generated in the tubemore » at the downstream end of the conductor. The larger the area covered by the conductor, or the thinner the tube, the stronger the plasma streamer is inhibited. The electric potential of the conductor is measured to be as high as 6 kV. On the other hand, a higher voltage applied on the HV electrode, or a higher gas flow rate will make the secondary plasma streamer longer. It is found that the capacitor formed by the conductor outside the tube and the wall of the tube plays an important role in inhibiting the original plasma streamer and generating the secondary streamer. Moreover, the active species generated by the original plasma play important role in generating a secondary plasma streamer.« less

The Thermal Ion Dynamics Experiment and Plasma Source Instrument

NASA Technical Reports Server (NTRS)

Moore, T. E.; Chappell, C. R.; Chandler, M. O.; Fields, S. A.; Pollock, C. J.; Reasoner, D. L.; Young, D. T.; Burch, J. L.; Eaker, N.; Waite, J. H., Jr.;

High-voltage plasma interactions calculations using NASCAP/LEO

NASA Technical Reports Server (NTRS)

Mandell, M. J.; Katz, I.

1990-01-01

This paper reviews four previous simulations (two laboratory and two space-flight) of interactions of a high-voltage spacecraft with a plasma under low-earth orbit conditions, performed using a three-dimensional computer code NASCAP/LEO. Results show that NASCAP/LEO can perform meaningful simulations of high-voltage plasma interactions taking into account three-dimensional effects of geometry, spacecraft motion, and magnetic field. Two new calculations are presented: (1) for current collection by 1-mm pinholes in wires (showing that a pinhole in a wire can collect far more current than a similar pinhole in a flat plate); and (2) current collection by Charge-2 mother vehicle launched in December 1985. It is shown that the Charge-2 calculations predicted successfully ion collection at negative bias, the floating potential of a probe outside or inside the sheath under negative bias conditions, and magnetically limited electron collection under electron beam operation at high altitude.

Investigation of complexity dynamics in a DC glow discharge magnetized plasma using recurrence quantification analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitra, Vramori; Sarma, Bornali; Sarma, Arun

Recurrence is an ubiquitous feature which provides deep insights into the dynamics of real dynamical systems. A suitable tool for investigating recurrences is recurrence quantification analysis (RQA). It allows, e.g., the detection of regime transitions with respect to varying control parameters. We investigate the complexity of different coexisting nonlinear dynamical regimes of the plasma floating potential fluctuations at different magnetic fields and discharge voltages by using recurrence quantification variables, in particular, DET, L{sub max}, and Entropy. The recurrence analysis reveals that the predictability of the system strongly depends on discharge voltage. Furthermore, the persistent behaviour of the plasma time seriesmore » is characterized by the Detrended fluctuation analysis technique to explore the complexity in terms of long range correlation. The enhancement of the discharge voltage at constant magnetic field increases the nonlinear correlations; hence, the complexity of the system decreases, which corroborates the RQA analysis.« less

Investigation of dust transport on the lunar surface in laboratory plasmas

NASA Astrophysics Data System (ADS)

Wang, X.; Horanyi, M.; Robertson, S. H.

2009-12-01

There has been much evidence indicating dust levitation and transport on or near the lunar surface. Dust mobilization is likely to be caused by electrostatic forces acting on small lunar dust particles that are charged by UV radiation and solar wind plasma. To learn about the basic physical process, we investigated the dynamics of dust grains on a conducting surface in laboratory plasmas. The first experiment was conducted with a dust pile (JSC-Mars-1) sitting on a negatively biased surface in plasma. The dust pile spread and formed a diffusing dust ring. Dust hopping was confirmed by noticing grains on protruding surfaces. The electrostatic potential distributions measured above the dust pile show an outward pointing electrostatic force and a non-monotonic sheath above the dust pile, indicating a localized upward electrostatic force responsible for lifting dust off the surface. The second experiment was conducted with a dust pile sitting on an electrically floating conducting surface in plasma with an electron beam. Potential measurements show a horizontal electric field at the dust/surface boundary and an enhanced vertical electric field in the sheath above the dust pile when the electron beam current is set to be comparable to the Bohm ion current. Secondary electrons emitted from the surfaces play an important role in this case.

Plasma monitoring of the RLVIP-process with a Langmuir probe

NASA Astrophysics Data System (ADS)

Huber, D.; Hallbauer, A.; Pulker, H. K.

2005-09-01

The aim of this investigation was to study the characteristics of a reactive-low-voltage-high-current-ion-plating plasma and to correlate the observed plasma data with the properties of films deposited under such conditions. A Langmuir probe system (Smart Probe - Scientific Systems) was inserted into a Balzers BAP 800 ion plating plant above the e-gun evaporation source close to the insulated substrate holder. In this position during RLVIP deposition, plasma potential, floating potential, self-bias voltage, electron temperature, ion current density, and particle number density were measured and calculated, respectively. All measurements were performed in dependence of arc current (20-80A) and oxygen partial pressure (1 - 36 x 10-4mbar). With rising arc current the number of charged particles, the self-bias voltage between plasma and substrates as well as the energy of the condensing and bombarding species were increased. These data explain the increase of density, refractive index and mechanical stress of RLVIP-metal-oxide-layers, like Ta2O5 and Nb2O5, deposited with higher arc currents. An increase of gas pressure decreased the energy of the particles and therefore reduced slightly film density and refractive index. However, it improved chemistry and eliminated unwanted residual optical absorption and also decreased compressive mechanical film stress.

High-Resolution Measurement of the Turbulent Frequency-Wavenumber Power Spectrum in a Laboratory Magnetosphere

NASA Astrophysics Data System (ADS)

Qian, T. M.; Mauel, M. E.

2017-10-01

In a laboratory magnetosphere, plasma is confined by a strong dipole magnet, where interchange and entropy mode turbulence can be studied and controlled in near steady-state conditions. Whole-plasma imaging shows turbulence dominated by long wavelength modes having chaotic amplitudes and phases. Here, we report for the first time, high-resolution measurement of the frequency-wavenumber power spectrum by applying the method of Capon to simultaneous multi-point measurement of electrostatic entropy modes using an array of floating potential probes. Unlike previously reported measurements in which ensemble correlation between two probes detected only the dominant wavenumber, Capon's ``maximum likelihood method'' uses all available probes to produce a frequency-wavenumber spectrum, showing the existence of modes propagating in both electron and ion magnetic drift directions. We also discuss the wider application of this technique to laboratory and magnetospheric plasmas with simultaneous multi-point measurements. Supported by NSF-DOE Partnership in Plasma Science Grant DE-FG02-00ER54585.

Spacecraft-environment interaction model cross comparison applied to Solar Probe Plus

NASA Astrophysics Data System (ADS)

Lapenta, G.; Deca, J.; Markidis, S.; Marchand, R.; Guillemant, S.; Matéo Vélez, J.; Miyake, Y.; Usui, H.; Ergun, R.; Sturner, A. P.

2013-12-01

Given that our society becomes increasingly dependent on space technology, it is imperative to develop a good understanding of spacecraft-plasma interactions. Two main issues are important. First, one needs to be able to design a reliable spacecraft that can survive in the harsh solar wind conditions, and second a very good knowledge of the behaviour and plasma structure around the spacecraft is required to be able to interpret and correct measurements from onboard instruments and science experiments. In this work we present the results of a cross-comparison study between five spacecraft-plasma models (EMSES, iPic3D, LASP, PTetra, SPIS) used to simulate the interaction of the Solar Probe Plus (SPP) satellite with the space environment under representative solar wind conditions near perihelion. The purpose of this cross-comparison is to assess the consistency and validity of the different numerical approaches from the similarities and differences of their predictions under well defined conditions, with attention to the implicit PIC code iPic3D, which has never been used for spacecraft-environment interaction studies before. The physical effects considered are spacecraft charging, photoelectron and secondary electron emission, the presence of a background magnetic field and density variations. The latter of which can cause the floating potential of SPP to go from negative to positive or visa versa, depending on the solar wind conditions, and spacecraft material properties. Simulation results are presented and compared with increasing levels of complexity in the physics to evaluate the sensitivity of the model predictions to certain physical effects. The comparisons focus particularly on spacecraft floating potential, detailed contributions to the currents collected and emitted by the spacecraft, and on the potential and density spatial profiles near the satellite. Model predictions obtained with our different computational approaches are found to be in good agreement when the physical processes are treated similarly. The comparisons considered here indicate that, with the correct parameterization of important physical effects such as photoemission and secondary electron emission, our simulation models should have the required skill to predict details of satellite-plasma interaction physics with a high level of confidence. This work was supported by the International Space Science Institute in Bern Switzerland. The potential profile around the Solar Probe Plus spacecraft in orbital flow, from the iPic3D code. The physical model includes photo- and secondary electrons and a static magnetic field.

Direct measurements of classical and enhanced gradient-aligned cross-field ion flows in a helicon plasma source using laser-induced fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siddiqui, M. Umair, E-mail: musiddiqui@mail.wvu.edu; Thompson, Derek S.; McIlvain, Julianne M.

2015-12-15

Direct laser induced fluorescence measurements are shown of cross-field ion flows normal to an absorbing boundary that is aligned parallel to the axial magnetic field in a helicon plasma. We show Langmuir and emissive probe measurements of local density and plasma potential in the same region, as well as floating probe spectra near the boundary. With these measurements, we investigate the influence of ion-neutral collisionality on radial ion transport by varying the ratio of the ion gyro-radius, ρ{sub i}, to the ion-neutral collision length, λ, over the range 0.34 ≤ ρ{sub i}λ{sup −1} ≤ 1.60. Classical drift-diffusion transport along density and potential gradients ismore » sufficient to describe flow profiles for most cases. For two parameter regimes (ρ{sub i}λ{sup −1} = 0.65 and 0.44), low-frequency electrostatic fluctuations (f < 10 kHz) and enhanced cross-field bulk ion flow to the boundary are observed.« less

Oscillating plasma bubble and its associated nonlinear studies in presence of low magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Megalingam, Mariammal; Sarma, Bornali; Mitra, Vramori

Oscillating plasma bubbles have been created around a cylindrical mesh grid of 75% optical transparency in a DC plasma system with a low magnetic field. Plasma bubbles are created by developing ion density gradient around a cylindrical grid of 20 cm in diameter and 25 cm in height, inserted into the plasma. Relaxation and contraction of the plasma bubbles in the presence of external conditions, such as magnetic field and pressure, have been studied. A Langmuir probe has been used to detect the plasma floating potential fluctuations at different imposed experimental conditions. Nonlinear behavior of the system has been characterized by adoptingmore » nonlinear techniques such as Fast Fourier Transform, Phase Space Plot, and Recurrence Plot. It shows that the system creates highly nonlinear phenomena associated with the plasma bubble under the imposed experimental conditions. A theoretical and numerical model has also been developed to satisfy the observed experimental analysis. Moreover, observations are extended further to study the growth of instability associated with the plasma bubbles. The intention of the present work is to correlate the findings about plasma bubbles and their related instability with the one existing in the equatorial F-region of the ionosphere.« less

A comparative study of electrical probe techniques for plasma diagnostics

NASA Technical Reports Server (NTRS)

Szuszczewicz, E. P.

1972-01-01

Techniques for using electrical probes for plasma diagnostics are reviewed. Specific consideration is given to the simple Langmuir probe, the symmetric double probe of Johnson and Malter, the variable-area probe of Fetz and Oeschsner, and a floating probe technique. The advantages and disadvantages of each technique are discussed.

Further Studies of the Inhomgeneous Sheath as the Source of Collisionless Resistance in Plasmas in Spherical Geometry*

NASA Astrophysics Data System (ADS)

Walker, D. N.; Fernsler, R. F.; Blackwell, D. D.; Amatucci, W. E.; Messer, S. J.

2006-05-01

In a recently published work1 we use a simpler derivation of collisionless resistance in spherical geometry than previous authors, relying primarily on Gauss' law along with the continuity and cold fluid equations. The accompanying experimental work is based on measurements of the rf impedance characteristics of a small spherical probe immersed in a laboratory plasma. The data taken are from network analyzer measurements of the reflection coefficient obtained when applying a low level rf signal to the probe which is either near floating potential or negatively dc-biased in a low pressure plasma. The reduced density in the sheath alters the plasma impedance which becomes resistive, in spite of collisionless conditions, and hence the characterization of energy absorption as collisionless arises. Consistent with earlier work, the solutions obtained indicate that the plasma resistance is inversely proportional to the plasma density gradient evaluated at the location where the plasma frequency is equal to the applied frequency. Significant energy absorption is predicted and observed at frequencies generally near one-half the plasma frequency. *Work supported by ONR 1 Walker, D.N., R.F. Fernsler, D.D. Blackwell, W.A. Amatucci, S.J. Messer, Phys of Plasmas, To Appear 3/2006

Spacecraft potential control on ISEE-1

NASA Technical Reports Server (NTRS)

Gonfalone, A.; Pedersen, A.; Fahleson, U. V.; Faelthammar, C. G.; Mozer, F. S.; Torbert, R. B.

1979-01-01

Active control of the potential of the ISEE-1 satellite by the use of electron guns is reviewed. The electron guns contain a special cathode capable of emitting an electron current selectable between 10 to the -8th power and 10 to the -3rd power at energies from approximately .6 to 41 eV. Results obtained during flight show that the satellite potential can be stabilized at a value more positive than the normally positive floating potential. The electron guns also reduce the spin modulation of the spacecraft potential which is due to the aspect dependent photoemission of the long booms. Plasma parameters like electron temperature and density can be deduced from the variation of the spacecraft potential as a function of the gun current. The effects of electron beam emission on other experiments are briefly mentioned.

Langmuir Probe Diagnostics of Pulsed Plasma Doping System

NASA Astrophysics Data System (ADS)

Lei, Yu; Overzet, Lawrence J.; Felch, Susan B.; Fang, Ziwei; Koo, Bon-Woong; Goeckner, Matthew J.

2002-10-01

Pulsed plasma doping (P2LAD) is a potential solution to implement ultra-shallow junctions. In this study, Langmuir probe diagnostics techniques were investigated thoroughly for its application to P2LAD system, and the current sensing scheme using batteries and a 'downstairs' load resistor turned out to be the most reliable. Severe limitations of current transformers were found in diagnostics of pulsed plasma. A floating probe was proven to be good at monitoring the disturbances of the Langmuir probe and the cathode voltage. With the above technique, time-resolved Langmuir probe measurements have been carried out in a P2LAD system. The Langmuir probe data in Ar plasma indicate that during a 20 microns long implant pulse the plasma density ranges from 1E9 1E10 cm-3 and the electron temperature ranges from 0.4 to 14 eV. Between the pulses, the density keeps at the high level for 30 ms and then decays exponentially until reaching the range of 3E8 1E9 cm-3, which demonstrates the presence of residual plasma between pulses. A non-zero plasma density during the afterglow is also observed for BF3 plasma. Significant amounts of primary electron and electron beams are present during the ignition and ensuing steady region in both Ar and BF3 plasmas while they are much stronger in BF3 plasma. Plasma density is observed to increase with cathode voltage and pressure while the electron temperature is mainly influenced by the pressure. An overshoot of the cathode voltage during the afterglow region was found, and it significantly influences the plasma potential during the afterglow.

RF Rectification on LAPD and NSTX: the relationship between rectified currents and potentials

NASA Astrophysics Data System (ADS)

Perkins, R. J.; Carter, T.; Caughman, J. B.; van Compernolle, B.; Gekelman, W.; Hosea, J. C.; Jaworski, M. A.; Kramer, G. J.; Lau, C.; Martin, E. H.; Pribyl, P.; Tripathi, S. K. P.; Vincena, S.

2017-10-01

RF rectification is a sheath phenomenon important in the fusion community for impurity injection, hot spot formation on plasma-facing components, modifications of the scrape-off layer, and as a far-field sink of wave power. The latter is of particular concern for the National Spherical Torus eXperiment (NSTX), where a substantial fraction of the fast-wave power is lost to the divertor along scrape-off layer field lines. To assess the relationship between rectified currents and rectified voltages, detailed experiments have been performed on the Large Plasma Device (LAPD). An electron current is measured flowing out of the antenna and into the limiters, consistent with RF rectification with a higher RF potential at the antenna. The scaling of this current with RF power will be presented. The limiters are also floated to inhibit this DC current; the impact of this change on plasma-potential and wave-field measurements will be shown. Comparison to data from divertor probes in NSTX will be made. These experiments on a flexible mid-sized experiment will provide insight and guidance into the effects of ICRF on the edge plasma in larger fusion experiments. Funded by the DOE OFES (DE-FC02-07ER54918 and DE-AC02-09CH11466), NSF (NSF- PHY 1036140), and the Univ. of California (12-LR- 237124).

The potential of oceanic transport and onshore leaching of additive-derived lead by marine macro-plastic debris.

PubMed

Nakashima, Etsuko; Isobe, Atsuhiko; Kako, Shin'ichiro; Itai, Takaaki; Takahashi, Shin; Guo, Xinyu

2016-06-15

The long-distance transport potential of toxic lead (Pb) by plastic marine debris was examined by pure water leaching experiments using plastic fishery floats containing high level of additive-Pb such as 5100±74.3mgkg(-1). The leaching of Pb ended after sequential 480-h leaching experiments, and the total leaching amount is equivalent to approximately 0.1% of total Pb in a float. But it recovered when the float was scratched using sandpaper. We propose that a "low-Pb layer," in which Pb concentration is negligibly small, be generated on the float surface by the initial leaching process. Thickness of the layer is estimated at 2.5±1.2μm, much shallower than flaws on floats scratched by sandpaper and floats littering beaches. The result suggests that the low-Pb layer is broken by physical abrasion when floats are washed ashore, and that Pb inside the floats can thereafter leach into beaches. Copyright © 2016 Elsevier Ltd. All rights reserved.

HIT-SI Injector Voltage Measurements Using Injector Langmuir Probes

NASA Astrophysics Data System (ADS)

Aboul Hosn, Rabih; Smith, Roger; Jarboe, Thomas

2006-10-01

A pair of Langmuir probe arrays have been designed and built to measure floating potentials of the plasma at the injector mouth of the HIT-SI device. The Helicity Injected Torus using Steady Inductive Helicity Injection (HIT-SI) [1,2] is a ``bow tie'' spheromak using an electrodeless formation and sustainment concept. HIT-SI is powered by two inductive helicity injectors operated in quadrature to maintain a constant helicity injection rate. The electric probes consist of an array of four floating potential Langmuir probes measuring the voltage distribution in each injector from the shell to midpoint of the injector mouth. The probe measurements combine to determine the part of the injector loop voltage driving the n = 0 spheromak equilibrium region. Preliminary data suggest the spheromak voltage is the loop voltage minus the nearly constant injector voltage of 150-180 volts. These probe data will be used to calculate the helicity decay time of the spheromak. [1] T. R. Jarboe. Steady inductive helicity injection and its application to a high-beta spheromak. Fusion Technology, 36(1):85--91, July 1999. [2] P.E.Sieck et al., ``Demonstration of Steady Inductive Helicity Injection'', Nuc. Fusion, in press (2006).

What is the size of a floating sheath? An answer

NASA Astrophysics Data System (ADS)

Voigt, Farina; Naggary, Schabnam; Brinkmann, Ralf Peter

2016-09-01

The formation of a non-neutral boundary sheath in front of material surfaces is universal plasma phenomenon. Despite several decades of research, however, not all related issues are fully clarified. In a recent paper, Chabert pointed out that this lack of clarity applies even to the seemingly innocuous question ``What the size of a floating sheath?'' This contribution attempts to provide an answer that is not arbitrary: The size of a floating sheath is defined as the plate separation of an equivalent parallel plate capacitor. The consequences of the definition are explored with the help of a self-consistent sheath model, and a comparison is made with other sheath size definitions. Deutsche Forschungsgemeinschaft within SFB TR 87.

How does a probe inserted into the discharge influence the plasma structure?

NASA Astrophysics Data System (ADS)

Yordanov, D.; Lishev, St.; Shivarova, A.

2016-05-01

Shielding the bias applied to the probe by the sheath formed around it and determination of parameters of unperturbed plasmas are in the basis of the probe diagnostics. The results from a two-dimensional model of a discharge with a probe inserted in it show that the probe influences the spatial distribution of the plasma parameters in the entire discharge. The increase (although slight) in the electron temperature, due to the increased losses of charged particles on the additional wall in the discharge (mainly the probe holder), leads to redistribution of the plasma density and plasma potential, as shown by the results obtained at the floating potential of the probe. The deviations due to the bias applied to the probe tip are stronger in the ion saturation region of the probe characteristics. The pattern of the spatial redistribution of the plasma parameters advances together with the movement of the probe deeper in the discharge. Although probe sheaths and probe characteristics resulting from the model are shown, the study does not aim at discussions on the theories for determination of the plasma density from the ion saturation current. Regardless of the modifications in the plasma behavior in the entire discharge, the deviations of the plasma parameters at the position of the probe tip and, respectively, the uncertainty which should be added as an error when the accuracy of the probe diagnostics is estimated do not exceed 10%. Consequently, the electron density and temperature obtained, respectively, at the position of the plasma potential on the probe characteristics and from its transition region are in reasonable agreement with the results from the model of the discharge without a probe. Being in the scope of research on a source of negative hydrogen ions with the design of a matrix of small radius inductive discharges, the model is specified for a low-pressure hydrogen discharge sustained in a small-radius tube.

Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA 300M Hall Thruster

NASA Technical Reports Server (NTRS)

Herman, Daniel A; Shastry, Rohit; Huang, Wensheng; Soulas, George C.; KamHawi, Hani

2012-01-01

In order to aid in the design of high-power Hall thrusters and provide experimental validation for existing modeling efforts, plasma potential and Langmuir probe measurements were performed in the near-field plume of the NASA 300M Hall thruster. A probe array consisting of a Faraday probe, Langmuir probe, and emissive probe was used to interrogate the plume from approximately 0.1 - 2.0 DT,m downstream of the thruster exit plane at four operating conditions: 300 V, 400 V, and 500 V at 20 kW as well as 300 V at 10 kW. Results show that the acceleration zone and high-temperature region were contained within 0.3 DT,m from the exit plane at all operating conditions. Isothermal lines were shown to strongly follow magnetic field lines in the nearfield, with maximum temperatures ranging from 19 - 27 eV. The electron temperature spatial distribution created large drops in measured floating potentials in front of the magnetic pole surfaces where the plasma density was small, which suggests strong sheaths at these surfaces. The data taken have provided valuable information for future design and modeling validation, and complements ongoing internal measurement efforts on the NASA 300 M.

Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics.

PubMed

Boedo, J A; Rudakov, D L

2017-03-01

We present a method to calculate the ion saturation current, I sat , for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of I sat . It is noted that the I sat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating T e . We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuously biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and its use in reducing arcs.

Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boedo, J. A.; Rudakov, D. L.

Here we present a method to calculate the ion saturation current, I sat, for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of I sat. It is noted that the Isat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating T e. We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuouslymore » biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and it’s use in reducing arcs.« less

Characterization of Imposed Ordered Structures in MDPX

NASA Astrophysics Data System (ADS)

Hall, Taylor; Thomas, Edward; Konopka, Uwe; Merlino, Robert; Rosenberg, Marlene

2016-10-01

It is well understood that the microparticles in complex, or dusty, plasmas will form self-consistent crystalline patterns at the proper plasma parameters. In the Magnetized Dusty Plasma Experiment (MDPX) device, studies have been made of imposed, ordered structuring of the dust particles to a two dimensional grid. At high magnetic field (B >1 Tesla), the dust particles are shown to become spatially oriented to the structure of a wire mesh embedded in an electrically floating, upper electrode while the particles are suspended in a plasma that is generated by the powered, lower electrode in the experiment. With even higher magnetic field (B >2 Tesla), the particles become strongly confined to the mesh pattern with the particles constrained to a quasi-discreet motion that closely follows the mesh pattern. This presentation characterizes the structure of the potential energy well in which the dust particles are trapped through observation of particle motion and measurement of the thermal properties of the particles. This work is supported by funding from the U. S. Department of Energy Grant Number DE - SC0010485 and the NASA/Jet Propulsion Laboratory, JPL-1543114.

Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics

DOE PAGES

Boedo, J. A.; Rudakov, D. L.

2017-03-20

Here we present a method to calculate the ion saturation current, I sat, for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of I sat. It is noted that the Isat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating T e. We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuouslymore » biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and it’s use in reducing arcs.« less

Enhanced Discharge Performance in a Ring Cusp Plasma Source

NASA Technical Reports Server (NTRS)

Foster, John E.; Patterson, Michael J.

2000-01-01

There is a need for a lightweight, low power ion thruster for space science missions. Such an ion thruster is under development at NASA Glenn Research Center. In an effort to better understand the discharge performance of this thruster, a thruster discharge chamber with an anode containing electrically isolated electrodes at the cusps was fabricated and tested. Characteristics of this ring cusp ion discharge were measured without ion beam extraction. Discharge current was measured at collection electrodes located at the magnetic cusps and at the anode body itself. Discharge performance and plasma properties were measured as a function of power, which was varied between 20 and 50 W. It was found that ion production costs decreased by as much as 20 percent when the two most downstream cusp electrodes were allowed to float. Floating the electrodes did not give rise to a significant increase in discharge power even though the plasma density increased markedly. The improved performance is attributed to enhanced electron containment.

Internal Plasma Properties and Enhanced Performance of an 8 cm Ion Thruster Discharge

NASA Technical Reports Server (NTRS)

Foster, John E.; Patterson, Michael J.

1999-01-01

There is a need for a lightweight, low power ion thruster for space science missions. Such an ion thruster is under development at NASA Glenn Research Center. In an effort to better understand the discharge performance of this thruster. a version of this thruster with an anode containing electrically isolated electrodes at the cusps was fabricated and tested. Discharge characteristics of this ring cusp ion thruster were measured without ion beam extraction. Discharge current was measured at collection electrodes located at the cusps and at the anode body itself. Discharge performance and plasma properties were measured as a function of discharge power, which was varied between 20 and 50 W. It was found that ion production costs decreased by as much as 20 percent when the two most downstream cusp electrodes were allowed to float. Floating the electrodes did not give rise to a significant increase in discharge power even though the plasma density increased markedly. The improved performance is attributed to enhanced electron containment.

Electrostatic Discharge Issues in International Space Station Program EVAs

NASA Technical Reports Server (NTRS)

Bacon, John B.

2009-01-01

EVA activity in the ISS program encounters several dangerous ESD conditions. The ISS program has been aggressive for many years to find ways to mitigate or to eliminate the associated risks. Investments have included: (1) Major mods to EVA tools, suit connectors & analytical tools (2) Floating Potential Measurement Unit (3) Plasma Contactor Units (4) Certification of new ISS flight attitudes (5) Teraflops of computation (6) Thousands of hours of work by scores of specialists (7) Monthly management attention at the highest program levels. The risks are now mitigated to a level that is orders of magnitude safer than prior operations

Pharmacokinetics and analgesic effect of ketorolac floating delivery system.

PubMed

Radwan, Mahasen A; Abou El Ela, Amal El Sayeh F; Hassan, Maha A; El-Maraghy, Dalia A

2015-05-01

The efficacy of ketorolac tromethamine (KT) floating alginate beads as a drug delivery system for better control of KT release was investigated. The formulation with the highest drug loading, entrapment efficiency, swelling, buoyancy, and in vitro release would be selected for further in vivo analgesic effect in the mice and pharmacokinetics study in rats compared to the tablet dosage form. KT floating alginate beads were prepared by extrusion congealing technique. KT in plasma samples was analyzed using a UPLC MS/MS assay. The percentage yield, drug loading and encapsulation efficiency were increased proportionally with the hydroxypropylmethyl cellulose (HPMC) polymer amount in the KT floating beads. A reverse relationship was observed between HPMC amount in the beads and the KT in vitro release rate. F3-floating beads were selected, due to its better in vitro results (continued floating for >8 h) than others. A longer analgesic effect was observed for F3 in fed mice as compared to the tablets. After F3 administration to rats, the Cmax (2.2 ± 0.3 µg/ml) was achieved at ∼2 h and the decline in KT concentration was slower. F3 showed a significant increase in the AUC (1.89 fold) in rats as compared to the tablets. KT was successfully formulated as floating beads with prolonged in vitro release extended to a better in vivo characteristic with higher bioavailability in rats. KT in floating beads shows a superior analgesic effect over tablets, especially in fed mice.

Application of IRTAM to Support ISS Program Safety

NASA Technical Reports Server (NTRS)

Hartman, William A.; Schmidl, William D.; Mikatarian, Ronald; Koontz, Steven; Galkin, Ivan

2017-01-01

The International Space Station (ISS) orbits near the F-peak of the ionosphere (approximately 400 km altitude). Generally, satellites orbiting at this altitude would have a floating potential (FP) of approximately -1 V due to the electron temperature (Te). However, the ISS has 8 large negatively grounded 160 V solar array wings (SAW) that collect a significant electron current from the ionosphere. This current drives the ISS FP much more negative during insolation and is highly dependent on the electron density (Ne). Also, due to the size of the ISS, magnetic inductance caused by the geomagnetic field produces a delta potential up to 40 V across the truss, possibly producing positive potentials. During Extravehicular Activity (EVA) the negative FP can lead to an arcing hazard when it exceeds -45.5 V, and the positive FP can produce a DC current high enough to stimulate the astronaut's muscles and also cause a hazard. Data collected from the Floating Potential Monitoring Unit (FPMU) have shown that the probability of either of these hazards occurring during times with quiet to moderately disturbed geomagnetic activity is low enough to no longer be considered a risk. However, a study of the ionosphere Ne during severe geomagnetic storm activity has shown that the Ne can be enhanced by a factor of 6 in the ISS orbit. As a result, the ISS Safety Review Panel (SRP) requires that ionospheric conditions be monitored using the FPMU in conjunction with the ISS Plasma Interaction Model (PIM) to determine if a severe geomagnetic storm could result in a plasma environment that could produce a hazard. A 'Real-Time' plasma hazard assessment process was developed to support ISS Program real-time decision making providing constraint relief information for EVAs planning and operations. This process incorporates 'real time' ionospheric conditions, ISS solar arrays' orientation, ISS flight attitude, and where the EVA will be performed on the ISS. This assessment requires real time data that is presently provided by the FPMU including ISS floating potential, along with ionospheric Ne and Te, in order to determine the present environment. Once the present environment conditions are known to be either above, below, or near the current IRI values, the IRI is used to forecast what the environment could become in the event of a severe geomagnetic storm. If the FPMU should fail, the Space Environments team needs another source of data which is utilized to support a short-term forecast for EVAs. The IRI Real-Time Assimilative Mapping (IRTAM) model is an ionospheric model that uses real time measurements from approximately 70 digisondes to produce foF2 and hmF2 global maps in 15 minute cadence. The Boeing Space Environments team has used the IRI coefficients produced in IRTAM to calculate the Ne along the ISS orbital track. The results of the IRTAM model have been compared to FPMU measurements and show excellent agreement (figure 1). IRTAM has been identified as a potential FPMU back-up system will be used as a backup for the FPMU to support the ISS Program following completion of an FPMU/IRTAM validation campaign.

Floating marine litter as a raft for drifting voyages for Planes minutus (Crustacea: Decapoda: Grapsidae) and Liocarcinus navigator (Crustacea: Decapoda: Polybiidae).

PubMed

Tutman, P; Kapiris, K; Kirinčić, M; Pallaoro, A

2017-07-15

The Columbus crab Planes minutus and Arch-fronted swimming crab Liocarcinus navigator, within their distribution ranges in the Mediterranean, were found rafted on plastic macro-litter floating on the open south Adriatic. While P. minutus was recorded from inanimate flotsam outside of the Mediterranean, L. navigator is herein reported for the first time on floating marine litter. The role of floating litter as habitat or as a dispersal agent for marine invertebrates has received quite attention however, records of decapod crabs drifting on litter has been relatively sparse. Our results suggests that vast quantities of floating debris, comprised primarily of non-biodegradable plastic polymers, probably will augment natural floating substrates in the marine environment, potentially facilitating the spread of invasive species. The dispersion of rafting crabs through floating debris should be investigated given the high potential ecological risk of invasion by exotic species due to the increase in waste production (ecological risk assessment). Copyright © 2017 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yordanov, D., E-mail: yordanov@phys.uni-sofia.bg; Lishev, St.; Shivarova, A.

Shielding the bias applied to the probe by the sheath formed around it and determination of parameters of unperturbed plasmas are in the basis of the probe diagnostics. The results from a two-dimensional model of a discharge with a probe inserted in it show that the probe influences the spatial distribution of the plasma parameters in the entire discharge. The increase (although slight) in the electron temperature, due to the increased losses of charged particles on the additional wall in the discharge (mainly the probe holder), leads to redistribution of the plasma density and plasma potential, as shown by themore » results obtained at the floating potential of the probe. The deviations due to the bias applied to the probe tip are stronger in the ion saturation region of the probe characteristics. The pattern of the spatial redistribution of the plasma parameters advances together with the movement of the probe deeper in the discharge. Although probe sheaths and probe characteristics resulting from the model are shown, the study does not aim at discussions on the theories for determination of the plasma density from the ion saturation current. Regardless of the modifications in the plasma behavior in the entire discharge, the deviations of the plasma parameters at the position of the probe tip and, respectively, the uncertainty which should be added as an error when the accuracy of the probe diagnostics is estimated do not exceed 10%. Consequently, the electron density and temperature obtained, respectively, at the position of the plasma potential on the probe characteristics and from its transition region are in reasonable agreement with the results from the model of the discharge without a probe. Being in the scope of research on a source of negative hydrogen ions with the design of a matrix of small radius inductive discharges, the model is specified for a low-pressure hydrogen discharge sustained in a small-radius tube.« less

Adding high time resolution to charge-state-specific ion energy measurements for pulsed copper vacuum arc plasmas

NASA Astrophysics Data System (ADS)

Tanaka, Koichi; Han, Liang; Zhou, Xue; Anders, André

2015-08-01

Charge-state-resolved ion energy-time distributions of pulsed Cu arc plasma were obtained by using direct (time-dependent) acquisition of the ion detection signal from a commercial ion mass-per-charge and energy-per-charge analyzer. We find a shift of energies of Cu2+, Cu3+ and Cu4+ ions to lower values during the first few hundred microseconds after arc ignition, which is evidence for particle collisions in the plasma. The generation of Cu+ ions in the later part of the pulse, measured by the increase of Cu+ signal intensity and an associated slight reduction of the mean charge state, points to charge exchange reactions between ions and neutrals. At the very beginning of the pulse, when the plasma expands into vacuum and the plasma potential strongly fluctuates, ions with much higher energy (over 200 eV) are observed. Early in the pulse, the ion energies observed are approximately proportional to the ion charge state, and we conclude that the acceleration mechanism is primarily based on acceleration in an electric field. This field is directed away from the cathode, indicative of a potential hump. Measurements by a floating probe suggest that potential structures travel, and ions moving in the traveling field can gain high energies up to a few hundred electron-volts. Later in the pulse, the approximate proportionality is lost, which is related to increased smearing out of different energies due to collisions with neutrals, and/or to a change of the acceleration character from electrostatic to ‘gas-dynamic’, i.e. dominated by pressure gradient.

Effect of electron reflection on magnetized plasma sheath in an oblique magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ting-Ting; Ma, J. X., E-mail: jxma@ustc.edu.cn; Wei, Zi-An

Magnetized plasma sheaths in an oblique magnetic field were extensively investigated by conventionally assuming Boltzmann relation for electron density. This article presents the study of the magnetized sheath without using the Boltzmann relation but by considering the electron reflection along the magnetic field lines caused by the negative sheath potential. A generalized Bohm criterion is analytically derived, and sheath profiles are numerically obtained, which are compared with the results of the conventional model. The results show that the ion Mach number at the sheath edge normal to the wall has a strong dependence on the wall potential, which differs significantlymore » from the conventional model in which the Mach number is independent of the wall potential. The floating wall potential is lower in the present model than that in the conventional model. Furthermore, the sheath profiles are appreciably narrower in the present model when the wall bias is low, but approach the result of the conventional model when the wall bias is high. The sheath thickness decreases with the increase of ion-to-electron temperature ratio and magnetic field strength but has a complex relationship with the angle of the magnetic field.« less

Battery-powered pulsed high density inductively coupled plasma source for pre-ionization in laboratory astrophysics experiments.

PubMed

Chaplin, Vernon H; Bellan, Paul M

2015-07-01

An electrically floating radiofrequency (RF) pre-ionization plasma source has been developed to enable neutral gas breakdown at lower pressures and to access new experimental regimes in the Caltech laboratory astrophysics experiments. The source uses a customized 13.56 MHz class D RF power amplifier that is powered by AA batteries, allowing it to safely float at 3-6 kV with the electrodes of the high voltage pulsed power experiments. The amplifier, which is capable of 3 kW output power in pulsed (<1 ms) operation, couples electrical energy to the plasma through an antenna external to the 1.1 cm radius discharge tube. By comparing the predictions of a global equilibrium discharge model with the measured scalings of plasma density with RF power input and axial magnetic field strength, we demonstrate that inductive coupling (rather than capacitive coupling or wave damping) is the dominant energy transfer mechanism. Peak ion densities exceeding 5 × 10(19) m(-3) in argon gas at 30 mTorr have been achieved with and without a background field. Installation of the pre-ionization source on a magnetohydrodynamically driven jet experiment reduced the breakdown time and jitter and allowed for the creation of hotter, faster argon plasma jets than was previously possible.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rehder, J.B.

The project focuses on an appropriate technology for small-scale hydro power: floating waterwheels and turbines. For background, relic and existing systems such as early floating mills, traditional Amish waterwheels, and micro-hydro systems are examined. In the design phase of the project, new designs for Floating Hydro Power Systems include: an analysis of floatation materials and systems; a floating undershot waterwheel design; a floating cylinder (fiberglass storage tank) design; a submerged tube design; and a design for a floating platform with submerged propellers. Finally, in the applications phase, stream flow data from East Tennessee streams are used in a discussion ofmore » the potential applications of floating hydro power systems in small streams.« less

Controllable transition from positive space charge to negative space charge in an inverted cylindrical magnetron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rane, R., E-mail: ramu@ipr.res.in; Ranjan, M.; Mukherjee, S.

2016-01-15

The combined effect of magnetic field (B), gas pressure (P), and the corresponding discharge voltage on the discharge properties of argon in inverted cylindrical magnetron has been investigated. In the experiment, anode is biased with continuous 10 ms sinusoidal half wave. It is observed that at a comparatively higher magnetic field (i.e., >200 gauss) and lower operating pressure (i.e., <1 × 10{sup −3} mbar), the discharge extinguishes and demands a high voltage to reignite. Discharge current increases with increase in magnetic field and starts reducing at sufficiently higher magnetic field for a particular discharge voltage due to restricted electron diffusion towards the anode.more » It is observed that B/P ratio plays an important role in sustaining the discharge and is constant for a discharge voltage. The discharge is transformed to negative space charge regime from positive space charge regime at certain B/P ratio and this ratio varies linearly with the discharge voltage. The space charge reversal is indicated by the radial profile of the floating potential and plasma potential in between two electrodes for different magnetic fields. At a particular higher magnetic field (beyond 100 gauss), the floating potential increases gradually with the radial distance from cathode, whereas it remains almost constant at lower magnetic field.« less

Porcine intact and wounded skin responses to atmospheric nonthermal plasma.

PubMed

Wu, Andrew S; Kalghatgi, Sameer; Dobrynin, Danil; Sensenig, Rachel; Cerchar, Ekaternia; Podolsky, Erica; Dulaimi, Essel; Paff, Michelle; Wasko, Kimberly; Arjunan, Krishna Priya; Garcia, Kristin; Fridman, Gregory; Balasubramanian, Manjula; Ownbey, Robert; Barbee, Kenneth A; Fridman, Alexander; Friedman, Gary; Joshi, Suresh G; Brooks, Ari D

2013-01-01

Thermal plasma is a valued tool in surgery for its coagulative and ablative properties. We suggested through in vitro studies that nonthermal plasma can sterilize tissues, inactive pathogens, promote coagulation, and potentiate wound healing. The present research was undertaken to study acute toxicity in porcine skin tissues. We demonstrate that floating electrode-discharge barrier discharge (FE-DBD) nonthermal plasma is electrically safe to apply to living organisms for short periods. We investigated the effects of FE-DBD plasma on Yorkshire pigs on intact and wounded skin immediately after treatment or 24h posttreatment. Macroscopic or microscopic histological changes were identified using histological and immunohistochemical techniques. The changes were classified into four groups for intact skin: normal features, minimal changes or congestive changes, epidermal layer damage, and full burn and into three groups for wounded skin: normal, clot or scab, and full burn-like features. Immunohistochemical staining for laminin layer integrity showed compromise over time. A marker for double-stranded DNA breaks, γ-H2AX, increased over plasma-exposure time. These findings identified a threshold for plasma exposure of up to 900s at low power and <120s at high power. Nonthermal FE-DBD plasma can be considered safe for future studies of external use under these threshold conditions for evaluation of sterilization, coagulation, and wound healing. Copyright © 2013 Elsevier Inc. All rights reserved.

Deposition of silicon nitride from SiCl4 and NH3 in a low pressure RF plasma

NASA Technical Reports Server (NTRS)

Ron, Y.; Raveh, A.; Carmi, U.; Inspektor, A.; Avni, R.

1983-01-01

Silicon nitride coatings were deposited in a low-pressure (1-10 Torr) RF plasma from SiCl4 and NH3 in the presence of argon onto stainless martensitic steel grounded and floating substrates at 300 C and 440 C respectively. The heating of the substrates depends mainly on the position and the induced RF power. The coatings were identified as silicon nitride by X-ray investigation and were found to contain chlorine by energy-dispersive analysis of X-rays. The growth rate, the microhardness and the chlorine concentration of the coatings were determined as a function of the total gas pressure, the RF power input and the NH3-to-SiCl4 ratio. It was observed that the coatings on the floating substrates have higher deposition rates and are of superior quality.

Low Temperature Atmospheric Argon Plasma: Diagnostics and Medical Applications

NASA Astrophysics Data System (ADS)

Ermolaeva, Svetlana; Petrov, Oleg; Zigangirova, Nailya; Vasiliev, Mikhail; Sysolyatina, Elena; Antipov, Sergei; Alyapyshev, Maxim; Kolkova, Natalia; Mukhachev, Andrei; Naroditsky, Boris; Shimizu, Tetsuji; Grigoriev, Anatoly; Morfill, Gregor; Fortov, Vladimir; Gintsburg, Alexander

This study was devoted to diagnostic of low temperature plasma produced by microwave generator and investigation of its bactericidal effect against bacteria in biofilms and within eukaryotic cells. The profile of gas temperature near the torch outlet was measured. The spectrum in a wide range of wavelengths was derived by the method of optical emission spec-troscopy. Probe measurements of the floating potential of plasma were car-ried out. The estimation and adaptation of parameters of plasma flow (tem-perature, velocity, ion number density) according to medico-technical requirements were produced. The model of immersed surface-associated biofilms formed by Gram-negative bacteria, Pseudomonas aeruginosa and Burkholderia cenocepacia, and Gram-positive bacteria, Staphylococcus aureus, was used to assess bactericidal effects of plasma treatment. Reduction in the concentration of live bacteria in biofilms treated with plasma for 5 min was demonstrated by measuring Live/Dead fluorescent labeling and using direct plating. The intracellular infection model with the pathogenic bacterium, Chlamydia trachomatis, was used to study the efficacy of microwave argon plasma against intracellular parasites. A 2 min plasma treatment of mouse cells infected with C. trachomatis reduced infectious bacteria by a factor of 2×106. Plasma treatment diminished the number of viable host cells by about 20%. When the samples were covered with MgF2 glass to obstruct active particles and UV alone was applied, the bactericidal effect was re-duced by 5×104 fold compared to the whole plasma.

Ion sheath dynamics in a plasma for plasma-based ion implantation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yatsuzuka, M.; Miki, S.; Azuma, K.

1999-07-01

Spatial and temporal growth and collapse of ion sheath around an electrode of a negative high-voltage pulse (voltage: {minus}10 kV, pulse duration: 10 {micro}s) have been studied in a plasma for plasma-based ion implantation. A spherical electrode of 1.9 cm in a diameter is immersed in a nitrogen plasma with the plasma density range of 10{sup 9} to 10{sup 10} cm{sup {minus}3}, the electron temperature of 1.4 eV and the gas pressure of 8x10{sup {minus}4} Torr. The transient sheath dynamics was observed by the measurement of electron saturation current to a Langmuir probe, where a depletion of electron saturation currentmore » indicates the arrival time of sheath edge at the probe position. The expanding speed of sheath edge is higher than the ion acoustic speed until the sheath length reaches the steady-state extent determined by Child-Langmuir law. In the region beyond the steady-state extent, the rarefying disturbance produced by sheath expansion continues to propagate into the plasma at the ion acoustic peed. After the pulse voltage is returned to zero (more exactly, the floating potential), the electron current begins to recover. When the pulse fall time is shorter than the plasma transit time, the electron saturation current overshoots the steady-state saturation current at once, resulting in an excess of plasma density which propagates like a tidal wave into the plasma at the ion acoustic speed.« less

Electron temperature and heat load measurements in the COMPASS divertor using the new system of probes

NASA Astrophysics Data System (ADS)

Adamek, J.; Seidl, J.; Horacek, J.; Komm, M.; Eich, T.; Panek, R.; Cavalier, J.; Devitre, A.; Peterka, M.; Vondracek, P.; Stöckel, J.; Sestak, D.; Grover, O.; Bilkova, P.; Böhm, P.; Varju, J.; Havranek, A.; Weinzettl, V.; Lovell, J.; Dimitrova, M.; Mitosinkova, K.; Dejarnac, R.; Hron, M.; The COMPASS Team; The EUROfusion MST1 Team

2017-11-01

A new system of probes was recently installed in the divertor of tokamak COMPASS in order to investigate the ELM energy density with high spatial and temporal resolution. The new system consists of two arrays of rooftop-shaped Langmuir probes (LPs) used to measure the floating potential or the ion saturation current density and one array of Ball-pen probes (BPPs) used to measure the plasma potential with a spatial resolution of ~3.5 mm. The combination of floating BPPs and LPs yields the electron temperature with microsecond temporal resolution. We report on the design of the new divertor probe arrays and first results of electron temperature profile measurements in ELMy H-mode and L-mode. We also present comparative measurements of the parallel heat flux using the new probe arrays and fast infrared termography (IR) data during L-mode with excellent agreement between both techniques using a heat power transmission coefficient γ  =  7. The ELM energy density {{\\varepsilon }\\parallel } was measured during a set of NBI assisted ELMy H-mode discharges. The peak values of {{\\varepsilon }\\parallel } were compared with those predicted by model and with experimental data from JET, AUG and MAST with a good agreement.

A Floating Potential Method for Determining Ion Density

NASA Astrophysics Data System (ADS)

Evans, John D.; Chen, Francis F.

2001-10-01

The density n in partially ionized discharges is often found from the saturation ion current Ii of a cylindrical Langmuir probe. Collisionless probe theories, however, disagree with measured I - V curves probably because of collisions^1. We use a heuristic method that yields n from probe data agreeing with microwave interferometry. Probe current I is raised to the 4/3 power and fitted to a straight line on an I^4/3-V plot. The line is extrapolated to the floating potential V_f, thus approximating I_i(V_f). The sheath thickness d_sh for V = Vf is calculated from the Child-Langmuir (CL) law, and applying the Bohm sheath criterion to the surface at r_sh = Rp + d_sh yields n when Ii = I_i(V_f). This method works, but it cannot be justified by theory. Neglected are (a) cylindrical convergence of the ion charge, (b) finite ion energy at r = r_sh, (c) ions orbiting the probe, and (d) escape of ions axially. The Allen-Boyd-Reynolds theory, which treats (a) and (b) and neglects (c) and (d), gives too low n's. Apparently the errors self-cancel, and the simple Vf method gives the right result. ^1 F.F. Chen, Phys. Plasmas 8, 3029 (2001).

Vorticity Probes and the Characterization of Vortices in the Kelvin Helmholtz Instability in the LAPD

NASA Astrophysics Data System (ADS)

Horton, W.; Perez, J. C.; Bengtson, R. D.; Carter, T. A.; Gekelman, W.; Fassler, M.

2003-10-01

A new five-pin probe design called the Vorticity Probe is presented that explicitly measures the vorticity in the ExB flow from the floating potentials independent on any absolute calibration errors. The five Tantulum probe tips are arranged in a diamond pattern with 5mm tip spacing. The fluctuating floating potential at each tip is measured and used to compute a finite-difference approximation of the ExB vorticity. The probe is tested in the LAPD device run with a variable bias between the anode and the chamber wall that creates a sharply localized Er-profile at 30cm from the axis of the 100cm diameter chamber. The fluctuations observed are peaked in the shear flow layer and are being correlated with theoretical calculations of the Kelvin-Helmholtz instability for this plasma. Nonlinear calculations are presented and test particle motion in the mixture of waves and vortices are described. The spectrum at 15 to 30 kHz matches the theoretical prediction from the measured dEr/dr gradient that reaches 17kV/m^2 in the B=0.2T axial magnetic field. The parallel wavelength and azimuthal mode numbers are being measured for further comfirmation of the of the mode classification.

Long Distance Dispersal Potential of Two Seagrasses Thalassia hemprichii and Halophila ovalis

PubMed Central

Wu, Kuoyan; Chen, Ching-Nen Nathan; Soong, Keryea

2016-01-01

The wide distribution of many seagrasses may be attributable to exploitation of currents. However, many species have seeds heavier than seawater, limiting surface floating, and thus, deep water becomes a potential barrier between suitable habitats. In this investigation, we studied the dispersal potential of various life history stages of two species of seagrasses, Thalassia hemprichii and Halophila ovalis, at Dongsha Atoll and Penghu Islands in Taiwan Strait, west Pacific. The adult plants of both species, often dislodged naturally from substrate by waves, could float, but only that of T. hemprichii could float for months and still remain alive and potentially able to colonize new territories. The seedlings of T. hemprichii could also float for about a month once failing to anchor to substrate of coral sand, but that of H. ovalis could not. The fruits and seeds of T. hemprichii could both float, but for too short a duration to enable long distance travel; those seeds released from long floating fruits had low germination rates in our tests. Obviously, their seeds are not adaptive for long distance dispersal. Fruits and seeds of H. ovalis do not float. The potential of animals as vectors was tested by feeding fruits and seeds of both species to a goose, a duck, and two fish in the laboratory. The fruits and seeds of T. hemprichii were digested and could no longer germinate; those of H. ovalis could pass through the digestive tracts and have a much higher germination rates than uningested controls. Therefore, birds could be important vectors for long distance dispersal of H. ovalis. The two seagrasses adopted very different dispersal mechanisms for long distance travel, and both exploited traits originally adaptive for other purposes. PMID:27248695

Long Distance Dispersal Potential of Two Seagrasses Thalassia hemprichii and Halophila ovalis.

PubMed

Wu, Kuoyan; Chen, Ching-Nen Nathan; Soong, Keryea

2016-01-01

The wide distribution of many seagrasses may be attributable to exploitation of currents. However, many species have seeds heavier than seawater, limiting surface floating, and thus, deep water becomes a potential barrier between suitable habitats. In this investigation, we studied the dispersal potential of various life history stages of two species of seagrasses, Thalassia hemprichii and Halophila ovalis, at Dongsha Atoll and Penghu Islands in Taiwan Strait, west Pacific. The adult plants of both species, often dislodged naturally from substrate by waves, could float, but only that of T. hemprichii could float for months and still remain alive and potentially able to colonize new territories. The seedlings of T. hemprichii could also float for about a month once failing to anchor to substrate of coral sand, but that of H. ovalis could not. The fruits and seeds of T. hemprichii could both float, but for too short a duration to enable long distance travel; those seeds released from long floating fruits had low germination rates in our tests. Obviously, their seeds are not adaptive for long distance dispersal. Fruits and seeds of H. ovalis do not float. The potential of animals as vectors was tested by feeding fruits and seeds of both species to a goose, a duck, and two fish in the laboratory. The fruits and seeds of T. hemprichii were digested and could no longer germinate; those of H. ovalis could pass through the digestive tracts and have a much higher germination rates than uningested controls. Therefore, birds could be important vectors for long distance dispersal of H. ovalis. The two seagrasses adopted very different dispersal mechanisms for long distance travel, and both exploited traits originally adaptive for other purposes.

Performance of a Space-Based Wavelet Compressor for Plasma Count Data on the MMS Fast Plasma Investigation

NASA Technical Reports Server (NTRS)

Barrie, A. C.; Smith, S. E.; Dorelli, J. C.; Gershman, D. J.; Yeh, P.; Schiff, C.; Avanov, L. A.

2017-01-01

Data compression has been a staple of imaging instruments for years. Recently, plasma measurements have utilized compression with relatively low compression ratios. The Fast Plasma Investigation (FPI) on board the Magnetospheric Multiscale (MMS) mission generates data roughly 100 times faster than previous plasma instruments, requiring a higher compression ratio to fit within the telemetry allocation. This study investigates the performance of a space-based compression standard employing a Discrete Wavelet Transform and a Bit Plane Encoder (DWT/BPE) in compressing FPI plasma count data. Data from the first 6 months of FPI operation are analyzed to explore the error modes evident in the data and how to adapt to them. While approximately half of the Dual Electron Spectrometer (DES) maps had some level of loss, it was found that there is little effect on the plasma moments and that errors present in individual sky maps are typically minor. The majority of Dual Ion Spectrometer burst sky maps compressed in a lossless fashion, with no error introduced during compression. Because of induced compression error, the size limit for DES burst images has been increased for Phase 1B. Additionally, it was found that the floating point compression mode yielded better results when images have significant compression error, leading to floating point mode being used for the fast survey mode of operation for Phase 1B. Despite the suggested tweaks, it was found that wavelet-based compression, and a DWT/BPE algorithm in particular, is highly suitable to data compression for plasma measurement instruments and can be recommended for future missions.

Experimental study of plasma properties in the shadow of the T--10 mushroom limiter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alferov, A.A.; Vershkov, V.A.; Grashin, S.A.

1988-04-01

The plasma properties in the shadow of a mushroom-shaped limiter installed in a lower port of the tokamak have been studied. A study of the asymmetry of the plasma streams on the ion and electron sides of the limiter leads to the conclusion that there are two mechanisms for the occurrence of the asymmetry: the toroidal rotation of the plasma and a predominant escape of plasma to the wall through the outer part of the torus. The asymmetry observed in the plasma floating potentials near the limiter leads to the flow of a current close to the Spitzer value j/submore » S/ through the limiter. With increasing plasma density, the plasma density in the channels of the limiter increases, and the temperature of this plasma decreases, so the loss of charged particles to the limiter depends only weakly on the average density. This circumstance is related to the degradation of the plasma confinement with decreasing density. The total flux of charged particles to the limiter is comparable to the flux of these particles out of the plasma column. The plasma stream into the channels is approximately ambipolar, and the power levels drawn by the neutralization plate are on the order of 10j/sub S/T/sub e//e. The behavior of the neutral gas pressure in the volume near the limiter as a function of the plasma streams into the channels is nonlinear. The maximum pressure is 3x10/sup -2/ torr.« less

The hot plasma environment and floating potentials of an electron-beam-emitting rocket in the ionosphere

NASA Technical Reports Server (NTRS)

Arnoldy, R. L.; Winckler, J. R.

1981-01-01

The plasma environment surrounding the Echo III accelerator payload is examined with an extensive array of particle sensors. Suprathermal electrons are produced isotropically around the payload during the gun firings and decay away in approximately 32 ms. The largest directional intensities of this component are observed at the higher altitudes. Quick echo electrons are also observed to produce suprathermal electrons when they encounter the payload. The hot electrons surrounding the accelerator payload during gun injections bring sufficient charge to the payload to neutralize it provided the loss of charge by secondary production on the payload skin is small. Since the hot population exists for tens of milliseconds after the gun turnoff, it results in driving the payload up to 4 volts negative during this time. Quick echo electrons creating suprathermal electrons around the payload also drive the payload to a few volts negative.

Selection of floating-point or fixed-point for adaptive noise canceller in somatosensory evoked potential measurement.

PubMed

Shen, Chongfei; Liu, Hongtao; Xie, Xb; Luk, Keith Dk; Hu, Yong

2007-01-01

Adaptive noise canceller (ANC) has been used to improve signal to noise ratio (SNR) of somsatosensory evoked potential (SEP). In order to efficiently apply the ANC in hardware system, fixed-point algorithm based ANC can achieve fast, cost-efficient construction, and low-power consumption in FPGA design. However, it is still questionable whether the SNR improvement performance by fixed-point algorithm is as good as that by floating-point algorithm. This study is to compare the outputs of ANC by floating-point and fixed-point algorithm ANC when it was applied to SEP signals. The selection of step-size parameter (micro) was found different in fixed-point algorithm from floating-point algorithm. In this simulation study, the outputs of fixed-point ANC showed higher distortion from real SEP signals than that of floating-point ANC. However, the difference would be decreased with increasing micro value. In the optimal selection of micro, fixed-point ANC can get as good results as floating-point algorithm.

Parametric study of a pin-plane probe in moderately magnetized plasma

NASA Astrophysics Data System (ADS)

Binwal, S.; Gandhi, S.; Kabariya, H.; Karkari, S. K.

2015-12-01

The application of a planar Langmuir probe in magnetized plasma is found to be problematic due to significant perturbation of plasma along the magnetic field lines intercepting the probe surface. This causes the Ampere-Volts ‘I e(U)’ characteristics of the probe to deviate from its usual exponential law; in conjunction the electron saturation current I es is significantly reduced. Moreover estimating the electron temperature T e by considering the entire semi-log plot of I e(U) gives ambiguous values of T e. To address this problem, Pitts and Stangeby developed a formula for the reduction factor for I es. This formula depends on a number of uncertain parameters, namely; the ion temperature T +, electron cross-field diffusion coefficient {{D}\\bot ,\\text{e}} and the local potential hill V h estimated by applying a floating pin probe in the vicinity of the planar probe. Due to implicit dependence of these parameters on T e, the resulting analysis is not straightforward. This paper presents a parametric study of different parameters that influence the characteristics of a planar probe in magnetized plasma. For this purpose a pin-plane probe is constructed and applied in the magnetized plasma column. A comprehensive discussion is presented that highlights the practical methodology of using this technique for extracting useful information of plasma parameters in magnetized plasmas.

Spherical EUV and Plasma Spectrometer (seps) -a Monitor to Measure the Plasma and EUV Environment in Space

NASA Astrophysics Data System (ADS)

Brunner, Raimund; Schmidtke, Gerhard; Konz, Werner; Pfeffer, Wilfried

A low-cost monitor to measure the EUV and plasma environment in space is presented. The device consists of three (or more) isolated spheres, a metallic sphere, one or more highly trans-parent Inner Grids and Outer Grids. Each one is being connected to a sensitive floating elec-trometer. By setting different potentials to the grids as well as to the sphere and varying one or more of their voltages, measurements of spectral solar EUV irradiance (15-200 nm), of local plasma parameters such as electron and ion densities, electron energies and temperatures as well as ion compositions and debris events can be derived from the current recordings. This detector does not require any (solar) pointing device. The primary goal is to study the impact of solar activity events (e.g. CMEs) as well as subsequent reactions of the ionospheric/thermospheric systems (including space weather occurences). The capability of SEPS for measuring EUV pho-ton fluxes as well as plasma parameters in the energy range from 0 to +/-70 eV is demonstrated by laboratory measurements as performed in the IPM laboratory, at BESSY-PTB electron syn-chrotron in Berlin and at ESA/ESTEC plasma chamber. Based on the laboratory recording of plasma recombination EUV emission the sensor is suitable to detect also auroral and airglow radiations. -The state of the art in the development of this device is reported.

The land use potential of flood-prone rice fields using floating rice system in Bojonegoro regency in East Java

NASA Astrophysics Data System (ADS)

Irianto, H.; Mujiyo; Riptanti, E. W.; Qonita, A.

2018-03-01

Bojonegoro regency occupies the largest flood-prone rice fields of about 14,198 hectares, in East Java province. Floods commonly occur due to Bengawan Solo river over-burst, particularly in rainy season. The fields are potential for cultivating rice, but floods lasting for months causing these areas to be unproductive. The objective of this article is to examine the potential land use of flood prone rice fields in Bojonegoro regency using floating rice system as an effort to maintain productivity in rainy season. The method of this study is referential study about the rice production using floating cultivation system in other regions, which are later compared with the physical condition of the fields in Bojonegoro. The results of analysis show that rice cultivation using floating system can maintain rice production in flood prone areas during rainy season. The potential production of rice is 5-6 tons/ha. However, technical problems for cultivating rice cannot be ignored since farmers are not familiar with cultivating flooded fields. This article also explains alternatives of floating rice cultivation technique, which can be implemented effectively and efficiently. Pioneer work of developing floating rice in Bojonegoro that has been done by the Team of Faculty of Agriculture of UNS, Surakarta, is expected to serve as a medium for accelerating the adoption of cultivation technology innovation to farmers.

Formulation and In Vitro, In Vivo Evaluation of Effervescent Floating Sustained-Release Imatinib Mesylate Tablet

PubMed Central

Kadivar, Ali; Kamalidehghan, Behnam; Javar, Hamid Akbari; Davoudi, Ehsan Taghizadeh; Zaharuddin, Nurul Dhania; Sabeti, Bahareh; Chung, Lip Yong; Noordin, Mohamed Ibrahim

2015-01-01

Introduction Imatinib mesylate is an antineoplastic agent which has high absorption in the upper part of the gastrointestinal tract (GIT). Conventional imatinib mesylate (Gleevec) tablets produce rapid and relatively high peak blood levels and requires frequent administration to keep the plasma drug level at an effective range. This might cause side effects, reduced effectiveness and poor therapeutic management. Therefore, floating sustained-release Imatinib tablets were developed to allow the tablets to be released in the upper part of the GIT and overcome the inadequacy of conventional tablets. Methodology Floating sustained-release Imatinib mesylate tablets were prepared using the wet granulation method. Tablets were formulated using Hydroxypropyl Methylcellulose (HPMC K4M), with Sodium alginate (SA) and Carbomer 934P (CP) as release-retarding polymers, sodium bicarbonate (NaHCO3) as the effervescent agent and lactose as a filler. Floating behavior, in vitro drug release, and swelling index studies were conducted. Initial and total drug release duration was compared with a commercial tablet (Gleevec) in 0.1 N HCl (pH 1.2) at 37 ± 0.5°C for 24 hours. Tablets were then evaluated for various physical parameters, including weight variation, thickness, hardness, friability, and drug content. Consequently, 6 months of physical stability studies and in vitro gastro-retentive studies were conducted. Results and Discussion Statistical data analysis revealed that tablets containing a composition of 14.67% w/w HPMC K4M, 10.67%, w/w Na alginate, 1.33%, w/w Carbomer 934P and 9.33%, w/w NaHCO3 produced the most favorable formulation to develop 24-hour sustained-release tablets with optimum floating behavior and satisfactory physicochemical characteristics. Furthermore, in vitro release study revealed that the formulated SR tablet had significantly lower Cmax and higher Tmax compared to the conventional tablet (Gleevec). Thus, formulated SR tablets preserved persistent concentration of plasma up to 24 hours. Conclusion In conclusion, in order to suggest a better drug delivery system with constant favorable release, resulting in optimized absorption and less side effects, formulated CP-HPMC-SA based imatinib mesylate floating sustained-release tablets can be a promising candidate for cancer chemotherapy. PMID:26035710

Effect of the resonant magnetic perturbation on the plasma parameters in COMPASS tokamak’s divertor region

NASA Astrophysics Data System (ADS)

Dimitrova, M.; Cahyna, P.; Peterka, M.; Hasan, E.; Popov, Tsv K.; Ivanova, P.; Vasileva, E.; Panek, R.; Cavalier, J.; Seidl, J.; Markovic, T.; Havlicek, J.; Dejarnac, R.; Weinzettl, V.; Hacek, P.; Tomes, M.; the COMPASS Team; the EUROfusion MST1 Team

2018-02-01

The resonant magnetic perturbation (RMP) has proven to be a useful way to suppress edge-localized modes that under certain conditions can damage the device by the large power fluxes carried from the bulk plasma to the wall. The effect of RMP on the L-mode plasma parameters in the divertor region of the COMPASS tokamak was studied using the array of 39 Langmuir probes embedded into the divertor target. The current-voltage (IV) probe characteristics were processed by the first-derivative probe technique to obtain the plasma potential and the electron energy distribution function (EEDF) which was approximated by a bi-Maxwellian EEDF with a low-energy (4-6 eV) fraction and a high-energy (11-35 eV) one, the both factions having similar electron density. Clear splitting was observed during the RMP pulse in the low-field-side scrape-off-layer profiles of the floating potential U fl and the ion saturation current density J sat; these two quantities were obtained both by direct continuous measurement and by evaluation of the IV characteristics of probes with swept bias. The negative peaks of U fl induced by RMP spatially overlaps with the local minima of J sat (and n e) rather than with its local maxima which is partly caused by the spatial variation of the plasma potential and partly by the changed shape of the EEDF. The effective temperature of the whole EEDF is not correlated with the negative peaks of U fl, and the profile of the parallel power flux density shows secondary maxima due to RMP which mimic those of J sat.

Solving the Capacitive Effect in the High-Frequency sweep for Langmuir Probe in SYMPLE

NASA Astrophysics Data System (ADS)

Pramila; Patel, J. J.; Rajpal, R.; Hansalia, C. J.; Anitha, V. P.; Sathyanarayana, K.

2017-04-01

Langmuir Probe based measurements need to be routinely carried out to measure various plasma parameters such as the electron density (ne), the electron temperature (Te), the floating potential (Vf), and the plasma potential (Vp). For this, the diagnostic electronics along with the biasing power supplies is installed in standard industrial racks with a 2KV isolation transformer. The Signal Conditioning Electronics (SCE) system is populated inside the 4U-chassis based system with the front-end electronics, designed using high common mode differential amplifiers which can measure small differential signal in presence of high common mode dc- bias or ac ramp voltage used for biasing the probes. DC-biasing of the probe is most common method for getting its I-V characteristic but method of biasing the probe with a sweep at high frequency encounters the problem of corruption of signal due to capacitive effect specially when the sweep period and the discharge time is very fast and die down in the order of μs or lesser. This paper presents and summarises the method of removing such effects encountered while measuring the probe current.

On the use of the double floating probe method to infer the difference between the electron and the heavy particles temperatures in an atmospheric pressure, vortex-stabilized nitrogen plasma jet

NASA Astrophysics Data System (ADS)

Prevosto, L.; Kelly, H.; Mancinelli, B. R.

2014-05-01

Sweeping double probe measurements in an atmospheric pressure direct current vortex-stabilized plasma jet are reported (plasma conditions: 100 A discharge current, N2 gas flow rate of 25 Nl/min, thoriated tungsten rod-type cathode, copper anode with 5 mm inner diameter). The interpretation of the double probe characteristic was based on a generalization of the standard double floating probe formulae for non-uniform plasmas coupled to a non-equilibrium plasma composition model. Perturbations caused by the current to the probe together with collisional and thermal processes inside the probe perturbed region were taken into account. Radial values of the average electron and heavy particle temperatures as well as the electron density were obtained. The calculation of the temperature values did not require any specific assumption about a temperature relationship between different particle species. An electron temperature of 10 900 ± 900 K, a heavy particle temperature of 9300 ± 900 K, and an electron density of about 3.5 × 1022 m-3 were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found toward the outer border of the plasma jet. These results showed good agreement with those previously reported by the authors by using a single probe technique. The calculations have shown that this method is particularly useful for studying spraying-type plasma torches operated at power levels of about 15 kW.

On the use of the double floating probe method to infer the difference between the electron and the heavy particles temperatures in an atmospheric pressure, vortex-stabilized nitrogen plasma jet.

PubMed

Prevosto, L; Kelly, H; Mancinelli, B R

2014-05-01

Sweeping double probe measurements in an atmospheric pressure direct current vortex-stabilized plasma jet are reported (plasma conditions: 100 A discharge current, N2 gas flow rate of 25 Nl/min, thoriated tungsten rod-type cathode, copper anode with 5 mm inner diameter). The interpretation of the double probe characteristic was based on a generalization of the standard double floating probe formulae for non-uniform plasmas coupled to a non-equilibrium plasma composition model. Perturbations caused by the current to the probe together with collisional and thermal processes inside the probe perturbed region were taken into account. Radial values of the average electron and heavy particle temperatures as well as the electron density were obtained. The calculation of the temperature values did not require any specific assumption about a temperature relationship between different particle species. An electron temperature of 10,900 ± 900 K, a heavy particle temperature of 9300 ± 900 K, and an electron density of about 3.5 × 10(22) m(-3) were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found toward the outer border of the plasma jet. These results showed good agreement with those previously reported by the authors by using a single probe technique. The calculations have shown that this method is particularly useful for studying spraying-type plasma torches operated at power levels of about 15 kW.

Ion acceleration in a helicon source due to the self-bias effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiebold, Matt; Sung, Yung-Ta; Scharer, John E.

2012-05-15

Time-averaged plasma potential differences up to 165 V over several hundred Debye lengths are observed in low pressure (p{sub n} < 1 mTorr) expanding argon plasmas in the Madison Helicon eXperiment (MadHeX). The potential gradient leads to ion acceleration greater than that predicted by ambipolar expansion, exceeding E{sub i} Almost-Equal-To 7 kT{sub e} in some cases. RF power up to 500 W at 13.56 MHz is supplied to a half-turn, double-helix antenna in the presence of a nozzle magnetic field, adjustable up to 1 kG. A retarding potential analyzer (RPA) measures the ion energy distribution function (IEDF) and a sweptmore » emissive probe measures the plasma potential. Single and double probes measure the electron density and temperature. Two distinct mode hops, the capacitive-inductive (E-H) and inductive-helicon (H-W) transitions, are identified by jumps in density as RF power is increased. In the capacitive (E) mode, large fluctuations of the plasma potential (V{sub p-p} Greater-Than-Or-Equivalent-To 140V, V{sub p-p}/V{sub p} Almost-Equal-To 150%) exist at the RF frequency and its harmonics. The more mobile electrons can easily respond to RF-timescale gradients in the plasma potential whereas the inertially constrained ions cannot, leading to an initial flux imbalance and formation of a self-bias voltage between the source and expansion chambers. In the capacitive mode, the ion acceleration is not well described by an ambipolar relation, while in the inductive and helicon modes the ion acceleration more closely follows an ambipolar relation. The scaling of the potential gradient with the argon flow rate and RF power are investigated, with the largest potential gradients observed for the lowest flow rates in the capacitive mode. The magnitude of the self-bias voltage agrees with that predicted for RF self-bias at a wall. Rapid fluctuations in the plasma potential result in a time-dependent axial electron flux that acts to 'neutralize' the accelerated ion population, resulting in a zero net time-averaged current through the acceleration region when an insulating upstream boundary condition is enforced. Grounding the upstream endplate increases the self-bias voltage compared to a floating endplate.« less

Influence of Substrate Biasing on (Ba,Sr)TiO3 Films Prepared by Electron Cyclotron Resonance Plasma Sputtering

NASA Astrophysics Data System (ADS)

Matsumoto, Takeshi; Niino, Atsushi; Ohtsu, Yasunori; Misawa, Tatsuya; Yonesu, Akira; Fujita, Hiroharu; Miyake, Shoji

2004-03-01

(Ba,Sr)TiO3 (BST) films were deposited by electron cyclotron resonance (ECR) plasma sputtering with mirror confinement. DC bias voltage was applied to Pt/Ti/SiO2/Si substrates during deposition to vary the intensity of bombardment of energetic ions and to modify film properties. BST films deposited on the substrates at floating potential (approximately +20 V) were found to be amorphous, while films deposited on +40 V-biased substrates were crystalline in spite of a low substrate temperature below 648 K. In addition, atomic diffusion, which causes deterioration in the electrical properties of the films, was hardly observed in the crystallized films deposited with +40 V bias perhaps due to the low substrate temperature. Plasma diagnoses revealed that application of a positive bias to the substrate reduced the energy of ion bombardment and increased the density of excited neutral particles, which was assumed to result in the promotion of chemical reactions during deposition and the crystallization of BST films at a low temperature.

Development and characterization of floating spheroids of atorvastatin calcium loaded NLC for enhancement of oral bioavailability.

PubMed

Sharma, Kritika; Hallan, Supandeep Singh; Lal, Bharat; Bhardwaj, Ankur; Mishra, Neeraj

2016-09-01

The obejctive of the present study was to investigate the potential use of floating spheroids of Atorvastatin Calcium (ATS) Loaded nanostructured lipid carriers (NLCs). The final formula of floating spheroids was optimized on the basis of shape (spherical), diameter (0.47 mm), lag time (20 s), and floating time (> 32 h). The results were further confirmed by different pharmacokinetic parameters-it was observed that the developed optimized floating ATS spheroid-loaded NLCs formulation has significantly improved relative bioavailability, that is, 3.053-folds through oral route in comparison to marketed formulation.

Transfer of a cold atmospheric pressure plasma jet through a long flexible plastic tube

NASA Astrophysics Data System (ADS)

Kostov, Konstantin G.; Machida, Munemasa; Prysiazhnyi, Vadym; Honda, Roberto Y.

2015-04-01

This work proposes an experimental configuration for the generation of a cold atmospheric pressure plasma jet at the downstream end of a long flexible plastic tube. The device consists of a cylindrical dielectric chamber where an insulated metal rod that serves as high-voltage electrode is inserted. The chamber is connected to a long (up to 4 m) commercial flexible plastic tube, equipped with a thin floating Cu wire. The wire penetrates a few mm inside the discharge chamber, passes freely (with no special support) along the plastic tube and terminates a few millimeters before the tube end. The system is flushed with Ar and the dielectric barrier discharge (DBD) is ignited inside the dielectric chamber by a low frequency ac power supply. The gas flow is guided by the plastic tube while the metal wire, when in contact with the plasma inside the DBD reactor, acquires plasma potential. There is no discharge inside the plastic tube, however an Ar plasma jet can be extracted from the downstream tube end. The jet obtained by this method is cold enough to be put in direct contact with human skin without an electric shock. Therefore, by using this approach an Ar plasma jet can be generated at the tip of a long plastic tube far from the high-voltage discharge region, which provides the safe operation conditions and device flexibility required for medical treatment.

Cyclic powder formation during pulsed injection of hexamethyldisiloxane in an axially asymmetric radiofrequency argon discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Despax, B.; Makasheva, K.; CNRS, LAPLACE, F-31062 Toulouse cedex 09

2012-11-01

A new approach of periodic production of dusty plasma consisting of pulsed injection of hexamethyldisiloxane (HMDSO) in argon axially asymmetric radiofrequency (RF) discharge was investigated in this work. The range of plasma operating conditions in which this dusty plasma can exist was closely examined. The obtained results clearly show that a net periodicity in the formation/disappearance of dust particles in the plasma can be maintained on a very large scale of discharge duration. The significance of discharge axial asymmetry to the dust particles behaviour in the plasma is revealed by the development of an asymmetric in shape void shifted towardsmore » the powered RF electrode. The key role of the reactive gas and its pulsed injection on each stage of the oscillating process of formation/disappearance of dust particles is disclosed by optical and electrical measurements. It is shown that the period of dusty plasma formation/disappearance is inversely related to the HMDSO injection time. Moreover, the impact of time injection over short period (5 s) is examined. It indicates the conflicting role played by the HMDSO on the reduction of dusty plasma during the reactive gas injection and the reappearance of particles in the plasma during the time off. The electronegative behavior of the plasma in the presence of negatively charged particles seems to explain the energetic modifications in the discharge. A frequency analysis of the floating potential reveals all these cyclic processes. Particularly, in the 10-200 Hz frequency range, the presence and the evolution of dust particles in the plasma over one generation can be observed.« less

Plasma characteristics of direct current enhanced cylindrical inductively coupled plasma source

NASA Astrophysics Data System (ADS)

Yue, HUA; Jian, SONG; Zeyu, HAO; Chunsheng, REN

2018-06-01

Experimental results of a direct current enhanced inductively coupled plasma (DCE-ICP) source which consists of a typical cylindrical ICP source and a plate-to-grid DC electrode are reported. With the use of this new source, the plasma characteristic parameters, namely, electron density, electron temperature and plasma uniformity, are measured by Langmuir floating double probe. It is found that DC discharge enhances the electron density and decreases the electron temperature, dramatically. Moreover, the plasma uniformity is obviously improved with the operation of DC and radio frequency (RF) hybrid discharge. Furthermore, the nonlinear enhancement effect of electron density with DC + RF hybrid discharge is confirmed. The presented observation indicates that the DCE-ICP source provides an effective method to obtain high-density uniform plasma, which is desirable for practical industrial applications.

Measurement of plasma sheath overlap above a trench

NASA Astrophysics Data System (ADS)

Sheridan, T. E.; Steinberger, Thomas E.

2017-06-01

The plasma sheath above a rectangular trench has been experimentally characterized as the trench width is varied in a radio frequency (rf) plasma discharge for two different rf powers giving two different sets of plasma parameters. Measurements were made using the positions and all six normal mode frequencies of two dust particles floating just inside the sheath edge above the center of the trench. We find that sheath overlap occurs when the trench width ≲ 3 s 0 for a trench depth ≈0.7s0, where s0 is the planar sheath width. The electric field gradient inside the sheath edge increases with rf power.

77 FR 47876 - Intent To Prepare Environmental Impact Statements: Potential Commercial Wind Lease Issuance and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-10

... Statoil NA's proposed project, Hywind Maine, would consist of four 3-megawatt (MW) floating wind turbine... request by Statoil NA, is to construct a full-scale, deepwater floating wind turbine facility that... Prepare Environmental Impact Statements: Potential Commercial Wind Lease Issuance and Decision Regarding...

Observation of the hot electron interchange instability in a high beta dipolar confined plasma

NASA Astrophysics Data System (ADS)

Ortiz, Eugenio Enrique

In this thesis the first study of the high beta, hot electron interchange (HEI) instability in a laboratory, dipolar confined plasma is presented. The Levitated Dipole Experiment (LDX) is a new research facility that explores the confinement and stability of plasma created within the dipole field produced by a strong superconducting magnet. In initial experiments long-pulse, quasi-steady state microwave discharges lasting more than 10 sec have been produced with equilibria having peak beta values of 20%. Creation of high-pressure, high beta plasma is possible only when intense HEI instabilities are stabilized by sufficiently high background plasma density. LDX plasma exist within one of three regimes characterized by its response to heating and fueling. The observed HEI instability depends on the regime and can take one of three forms: as quasiperiodic bursts during the low density, low beta plasma regime, as local high beta relaxation events in the high beta plasma regime, and as global, intense energy relaxation bursts, both in the high beta and afterglow plasma regimes. Measurements of the HEI instability are made using high-impedance, floating potential probes and fast Mirnov coils. Analysis of these signals reveals the extent of the transport during high beta plasmas. During intense high beta HEI instabilities, fluctuations at the edge significantly exceed the magnitude of the equilibrium field generated by the high beta electrons and energetic electron confinement ends in under 100 musec. For heated plasmas, one of the consequences of the observed high beta transport is the presence of hysteresis in the neutral gas fueling required to stabilize and maintain the high beta plasma. Finally, a nonlinear, self-consistent numerical simulation of the growth and saturation of the HEI instability has been adapted for LDX and compared to experimental observations.

Self-sustained focusing of high-density streaming plasma

NASA Astrophysics Data System (ADS)

Bugaev, A.; Dobrovolskiy, A.; Goncharov, A.; Gushenets, V.; Litovko, I.; Naiko, I.; Oks, E.

2017-01-01

We describe our observations of the transport through an electrostatic plasma lens of a wide-aperture, high-current, low energy, metal-ion plasma flow produced by a cathodic arc discharge. The lens input aperture was 80 mm, the length of the lens was 140 mm, and there were three electrostatic ring electrodes located in a magnetic field formed by permanent magnets. The lens outer electrodes were grounded and the central electrode was biased up to -3 kV. The plasma was a copper plasma with directed (streaming) ion energy 20-40 eV, and the equivalent ion current was up to several amperes depending on the potential applied to the central lens electrode. We find that when the central lens electrode is electrically floating, the current density of the plasma flow at the lens focus increases by up to 40%-50%, a result that is in good agreement with a theoretical treatment based on plasma-optical principles of magnetic insulation of electrons and equipotentialization along magnetic field lines. When the central lens electrode is biased negatively, an on-axis stream of energetic electrons is formed, which can also provide a mechanism for focusing of the plasma flow. Optical emission spectra under these conditions show an increase in intensity of lines corresponding to both copper atoms and singly charged copper ions, indicating the presence of fast electrons within the lens volume. These energetic electrons, as well as accumulating on-axis and providing ion focusing, can also assist in reducing the microdroplet component in the dense, low-temperature, metal plasma.

Influence of an electric probe on the anode layer of a glow discharge in nitrogen

NASA Astrophysics Data System (ADS)

Taran, M. D.; Dyatko, N. A.; Kochetov, I. V.; Napartovich, A. P.; Akishev, Yu S.

2018-05-01

A two-dimensional (2D) numerical model of a DC glow discharge in nitrogen is developed for the case when the electric probe is mounted in the discharge gap. Within this model, calculations are performed for the gas pressure of 50 Torr and discharge current densities of 22 and 90 mA cm‑2. A cylindrical probe 1 mm in diameter is located parallel to the anode at a distance of 5 or 10 mm. The probe potential is varied in a wide range relative to the floating potential. Numerical simulations predict the 2D plasma perturbation pattern induced by the electric probe and the influence of the probe on anode layer characteristics. In particular, conditions are determined under which a region with no glow forms in the anode layer.

WindWaveFloat (WWF): Final Scientific Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alla Weinstein; Roddier, Dominique; Banister, Kevin

2012-03-30

Principle Power Inc. and National Renewable Energy Lab (NREL) have completed a contract to assess the technical and economic feasibility of integrating wave energy converters into the WindFloat, resulting in a new concept called the WindWaveFloat (WWF). The concentration of several devices on one platform could offer a potential for both economic and operational advantages. Wind and wave energy converters can share the electrical cable and power transfer equipment to transport the electricity to shore. Access to multiple generation devices could be simplified, resulting in cost saving at the operational level. Overall capital costs may also be reduced, provided thatmore » the design of the foundation can be adapted to multiple devices with minimum modifications. Finally, the WindWaveFloat confers the ability to increase energy production from individual floating support structures, potentially leading to a reduction in levelized energy costs, an increase in the overall capacity factor, and greater stability of the electrical power delivered to the grid. The research conducted under this grant investigated the integration of several wave energy device types into the WindFloat platform. Several of the resulting system designs demonstrated technical feasibility, but the size and design constraints of the wave energy converters (technical and economic) make the WindWaveFloat concept economically unfeasible at this time. Not enough additional generation could be produced to make the additional expense associated with wave energy conversion integration into the WindFloat worthwhile.« less

Commercial NiMH Cells in LEO Cycling: Thermal Vacuum Life Test Performed for the Floating Potential Probe (FPP)

NASA Technical Reports Server (NTRS)

Darcy, Eric; Strangways, Brad

2003-01-01

Contents include the following: 1. Introduction: What is the (Floating Potential Probe) FPP? Why was NiMH battery selected? Haw well would crimped seal cell performed in long term vacuum exposure? 2. Verification tests: Battery description. Test methods. Results. Main findings. FPP status.

Three-dimensional simulations of plasma turbulence in the RFX-mod scrape-off layer and comparison with experimental measurements

NASA Astrophysics Data System (ADS)

Riva, Fabio; Vianello, Nicola; Spolaore, Monica; Ricci, Paolo; Cavazzana, Roberto; Marrelli, Lionello; Spagnolo, Silvia

2018-02-01

The tokamak scrape-off layer (SOL) plasma dynamics is investigated in a circular limiter configuration with a low edge safety factor. Focusing on the experimental parameters of two ohmic tokamak inner-wall limited plasma discharges in RFX-mod [Sonato et al., Fusion Eng. Des. 74, 97 (2005)], nonlinear SOL plasma simulations are performed with the GBS code [Ricci et al., Plasma Phys. Controlled Fusion 54, 124047 (2012)]. The numerical results are compared with the experimental measurements, assessing the reliability of the GBS model in describing the RFX-mod SOL plasma dynamics. It is found that the simulations are able to quantitatively reproduce the RFX-mod experimental measurements of the electron plasma density, electron temperature, and ion saturation current density (jsat) equilibrium profiles. Moreover, there are indications that the turbulent transport is driven by the same instability in the simulations and in the experiment, with coherent structures having similar statistical properties. On the other hand, it is found that the simulation results are not able to correctly reproduce the floating potential equilibrium profile and the jsat fluctuation level. It is likely that these discrepancies are, at least in part, related to simulating only the tokamak SOL region, without including the plasma dynamics inside the last close flux surface, and to the limits of applicability of the drift approximation. The turbulence drive is then identified from the nonlinear simulations and with the linear theory. It results that the inertial drift wave is the instability driving most of the turbulent transport in the considered discharges.

A Numerical Characterization of the Gravito-Electrostatic Sheath Equilibrium Structure in Solar Plasma

NASA Astrophysics Data System (ADS)

Karmakar, Pralay Kumar

This article describes the equilibrium structure of the solar interior plasma (SIP) and solar wind plasma (SWP) in detail under the framework of the gravito-electrostatic sheath (GES) model. This model gives a precise definition of the solar surface boundary (SSB), surface origin mechanism of the subsonic SWP, and its supersonic acceleration. Equilibrium parameters like plasma potential, self-gravity, population density, flow, their gradients, and all the relevant inhomogeneity scale lengths are numerically calculated and analyzed as an initial value problem. Physical significance of the structure condition for the SSB is discussed. The plasma oscillation and Jeans time scales are also plotted and compared. In addition, different coupling parameters, and electric current profiles are also numerically studied. The current profiles exhibit an important behavior of directional reversibility, i.e., an electrodynamical transition from negative to positive value. It occurs beyond a few Jeans lengths away from the SSB. The virtual spherical surface lying at the current reversal point, where the net current becomes zero, has the property of a floating surface behavior of the real physical wall. Our investigation indicates that the SWP behaves as an ion current-carrying plasma system. The basic mechanism behind the GES formation and its distinctions from conventional plasma sheath are discussed. The electromagnetic properties of the Sun derived from our model with the most accurate available inputs are compared with those of others. These results are useful as an input element to study the properties of the linear and nonlinear dynamics of various solar plasma waves, oscillations and instabilities.

RFEA measurements of high-energy electrons in a helicon plasma device with expanding magnetic field

NASA Astrophysics Data System (ADS)

Gulbrandsen, Njål; Fredriksen, Åshild

2017-01-01

In the inductively coupled plasma of the Njord helicon device we have, for the same parameters as for which an ion beam exists, measured a downstream population of high-energy electrons emerging from the source. Separated measurements of energetic tail electrons was carried out by Retarding Field Energy Analyzer (RFEA) with a grounded entrance grid, operated in an electron collection mode. In a radial scan with the RFEA pointed toward the source, we found a significant population of high-energy electrons just inside the magnetic field line mapping to the edge of the source. A second peak in high-energy electrons density was observed in a radial position corresponding to the radius of the source. Also, throughout the main column a small contribution of high-energy electrons was observed. In a radial scan with a RFEA biased to collect ions a localized increase in the plasma ion density near the magnetic field line emerging from the plasma near the wall of the source was observed. This is interpreted as a signature of high-energy electrons ionizing the neutral gas. Also, a dip in the floating potential of a Langmuir probe is evident in this region where high-energy electrons is observed.

A dengue outbreak on a floating village at Cat Ba Island in Vietnam.

PubMed

Le Viet, Thanh; Choisy, Marc; Bryant, Juliet E; Vu Trong, Duoc; Pham Quang, Thai; Horby, Peter; Nguyen Tran, Hien; Tran Thi Kieu, Huong; Nguyen Vu, Trung; Nguyen Van, Kinh; Le Quynh, Mai; Wertheim, Heiman F L

2015-09-22

A dengue outbreak in an ecotourism destination spot in Vietnam, from September to November 2013, impacted a floating village of fishermen on the coastal island of Cat Ba. The outbreak raises questions about how tourism may impact disease spread in rural areas. Epidemiological data were obtained from the Hai Phong Preventive Medical Center (PMC), including case histories and residential location from all notified dengue cases from this outbreak. All household addresses were geo-located. Knox test, a spatio-temporal analysis that enables inference dengue clustering constrained by space and time, was performed on the geocoded locations. From the plasma available from two patients, positive for Dengue serotype 3 virus (DENV3), the Envelope (E) gene was sequenced, and their genetic relationships compared to other E sequences in the region. Of 192 dengue cases, the odds ratio of contracting dengue infections for people living in the floating villages compared to those living on the island was 4.9 (95 % CI: 3.6-6.7). The space-time analyses on 111 geocoded dengue residences found the risk of dengue infection to be the highest within 4 days and a radius of 20 m of a given case. Of the total of ten detected clusters with an excess risk greater than 2, the cluster with the highest number of cases was in the floating village area (24 patients for a total duration of 31 days). Phylogenetic analysis revealed a high homology of the two DENV3 strains (genotype III) from Cat Ba with DENV3 viruses circulating in Hanoi in the same year (99.1 %). Our study showed that dengue transmission is unlikely to be sustained on Cat Ba Island and that the 2013 epidemic likely originated through introduction of viruses from the mainland, potentially Hanoi. These findings suggest that prevention efforts should be focused on mainland rather than on the island.

Experimental evidence of the self-similarity and long-range correlations of the edge fluctuations in HT-6M tokamak

NASA Astrophysics Data System (ADS)

Wang, Wen-hao; Yu, Chang-xuan; Wen, Yi-zhi; Xu, Yu-hong; Ling, Bi-li; Gong, Xian-zu; Liu, Bao-hua; Wan, Bao-nian

2001-02-01

For a better understanding of long timescale transport dynamics, the rescaled range analysis techniques, the autocorrelation function (ACF) and the probability distribution function (PDF) are used to investigate long-range dependences in edge plasma fluctuations in an HT-6M tokamak. The results reveal the self-similar characters of the electrostatic fluctuations with self-similarity parameters (Hurst exponent) ranging from 0.64 to 0.79, taking into consideration the Er×B rotation-sheared effect. Fluctuation ACFs of both the ion saturation current and the floating potential, as well as PDF of the turbulence-induced particle flux, have two distinct timescales. One corresponds to the decorrelation timescale of local fluctuations (µs) and the other lasts to the order of the confinement time (ms). All these experimental results suggest that some of the mechanisms of the underlying turbulence are consistent with plasma transport as characterized by self-organized criticality (SOC).

Pulsed electromagnetic gas acceleration

NASA Technical Reports Server (NTRS)

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1974-01-01

Detailed measurements of the axial velocity profile and electromagnetic structure of a high power, quasi-steady MPD discharge are used to formulate a gasdynamic model of the acceleration process. Conceptually dividing the accelerated plasma into an inner flow and an outer flow, it is found that more than two-thirds of the total power in the plasma is deposited in the inner flow, accelerating it to an exhaust velocity of 12.5 km/sec. The outer flow, which is accelerated to a velocity of only 6.2 km/sec, appears to provide a current conduction path between the inner flow and the anode. Related cathode studies have shown that the critical current for the onset of terminal voltage fluctuations, which was recently shown to be a function of the cathode area, appears to reach an asymptote for cathodes of very large surface area. Detailed floating potential measurements show that the fluctuations are confined to the vicinity of the cathode and hence reflect a cathode emission process rather than a fundamental limit on MPD performance.

Continuous wavelet transform based time-scale and multifractal analysis of the nonlinear oscillations in a hollow cathode glow discharge plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nurujjaman, Md.; Narayanan, Ramesh; Iyengar, A. N. Sekar

2009-10-15

Continuous wavelet transform (CWT) based time-scale and multifractal analyses have been carried out on the anode glow related nonlinear floating potential fluctuations in a hollow cathode glow discharge plasma. CWT has been used to obtain the contour and ridge plots. Scale shift (or inversely frequency shift), which is a typical nonlinear behavior, has been detected from the undulating contours. From the ridge plots, we have identified the presence of nonlinearity and degree of chaoticity. Using the wavelet transform modulus maxima technique we have obtained the multifractal spectrum for the fluctuations at different discharge voltages and the spectrum was observed tomore » become a monofractal for periodic signals. These multifractal spectra were also used to estimate different quantities such as the correlation and fractal dimension, degree of multifractality, and complexity parameters. These estimations have been found to be consistent with the nonlinear time series analysis.« less

Design of an open-ended plenoptic camera for three-dimensional imaging of dusty plasmas

NASA Astrophysics Data System (ADS)

Sanpei, Akio; Tokunaga, Kazuya; Hayashi, Yasuaki

2017-08-01

Herein, the design of a plenoptic imaging system for three-dimensional reconstructions of dusty plasmas using an integral photography technique has been reported. This open-ended system is constructed with a multi-convex lens array and a typical reflex CMOS camera. We validated the design of the reconstruction system using known target particles. Additionally, the system has been applied to observations of fine particles floating in a horizontal, parallel-plate radio-frequency plasma. Furthermore, the system works well in the range of our dusty plasma experiment. We can identify the three-dimensional positions of dust particles from a single-exposure image obtained from one viewing port.

Optimization and evaluation of clarithromycin floating tablets using experimental mixture design.

PubMed

Uğurlu, Timucin; Karaçiçek, Uğur; Rayaman, Erkan

2014-01-01

The purpose of the study was to prepare and evaluate clarithromycin (CLA) floating tablets using experimental mixture design for treatment of Helicobacter pylori provided by prolonged gastric residence time and controlled plasma level. Ten different formulations were generated based on different molecular weight of hypromellose (HPMC K100, K4M, K15M) by using simplex lattice design (a sub-class of mixture design) with Minitab 16 software. Sodium bicarbonate and anhydrous citric acid were used as gas generating agents. Tablets were prepared by wet granulation technique. All of the process variables were fixed. Results of cumulative drug release at 8th h (CDR 8th) were statistically analyzed to get optimized formulation (OF). Optimized formulation, which gave floating lag time lower than 15 s and total floating time more than 10 h, was analyzed and compared with target for CDR 8th (80%). A good agreement was shown between predicted and actual values of CDR 8th with a variation lower than 1%. The activity of clarithromycin contained optimizedformula against H. pylori were quantified using well diffusion agar assay. Diameters of inhibition zones vs. log10 clarithromycin concentrations were plotted in order to obtain a standard curve and clarithromycin activity.

Attaining 2D Black Phosphorus and Investigations into Floating-Electrode Dielectric Barrier Discharge Treatment of Solutions

NASA Astrophysics Data System (ADS)

Smith, Joshua Benjamin

Since the discovery and isolation of the 2D carbon allotrope, graphene, research into additional 2D materials has significantly expanded. Electrical components continue to decrease in size so there is an ever-growing need for smaller circuitry to keep up with the demand. Research with graphene and additional 2D layered materials, such as transition metal dichalcogenides, brought about a realization of many unique properties that have never been previously explored for applications in electronics, photonics, and optoelectronics. Phosphorene, a novel 2D material isolated from bulk black phosphorus, is an intrinsic p-type material with a variable band gap for a variety of applications. However, these applications are limited by the inability to isolate films of phosphorene. This work investigates some of the previously found techniques for use with graphene isolation and their adaptations to phosphorene. Isolation of phosphorene from black phosphorus was investigated by exfoliation from bulk, chemical vapor deposition, and thin film conversion. Mechanical exfoliation with a tape method, drawing method, and tape/drawing method were used to isolate few-layer black phosphorus samples from bulk material. These methods were also briefly compared to liquid exfoliation of black phosphorus. A chemical vapor deposition approach led to the discovery of a novel method for growth of amorphous red phosphorus thin films from bulk red phosphorus/black phosphorus. An in situ chemical vapor deposition type approach was developed using these thin films for growth of a variety of 2D phosphorus allotropes. Successful conversion has provided fibrous phosphorus wires and hexagons, along with violet phosphorus and eventually black phosphorus. This approach demonstrates progress towards direct growth of 2D black phosphorus onto substrates with average areas >3 microm2 and thicknesses representing samples around 4 layers. Thicker samples were also observed with average areas >100 microm2. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy have confirmed successful growth of 2D black phosphorus from red phosphorus thin films for potential uses in 2D semiconductor applications. Additionally, this work discusses some of the chemistry occurring in solution as a result of nonthermal plasma treatment from a floating-electrode dielectric barrier discharge (FE-DBD) configuration. Nonthermal plasma generation allows for the treatment of heat sensitive materials. This has opened up the field to numerous clinical applications of nonthermal plasma treatment including sterilization and wound healing along with potentials in dentistry, dermatology, and even food industries. FE-DBD plasma treatment of water was found to provide a wide-range antimicrobial solution that remained active following 2 years of aging. This plasma-treated water was found to generate a number of ROS/RNS and the formation of these components was studied and verified with UV/Vis and ESR spectroscopy. Enhanced effects were observed when cell culture medium was plasma treated, suggesting the formation of additional reactive species from the plasma treatment of a variety of biomolecules. It is essential to understand these effects for a number of reasons. The possibility to generate a wide range of antimicrobial solutions from air, water, and basic biomolecules could provide a solution for those bacteria that have developed antibiotic resistances. Simultaneously, information into the reaction mechanisms of this FE-DBD plasma treatment can be investigated. All of the applications mentioned above involve complex networks of basic biomolecules, from skin tissue to bacteria cell walls. This work analyzes the effects of plasma treatment on several biomolecule solutions and simultaneously takes aim at understanding some of the potential mechanisms of plasma treatment. Studies were carried out using NMR and GC/MS. This information was used to investigate the possible targeted areas for FE-DBD plasma treatment and to simultaneously explain the antimicrobial effects.

Experimentally-based ExB drifts in the DIII-D divertor and SOL calculated from integration of Ohm's law using Thomson scattering measurements of T e and n e

DOE PAGES

Stangeby, Peter C.; Elder, J. David; McLean, Adam G.; ...

2017-03-27

We calculated the 2D spatial distributions of cross field drift velocities from 2D Thomson scattering measurements of T e and n e in the divertor and SOL of DIII-D. In contrast with the method that has been used on DIII-D where the 2D distribution of plasma potential V plasma is obtained from measurements of the probe floating potential of reciprocating probes, the present method does not require insertion of a probe into the plasma and can therefore be used in high power discharges. Furthermore, the 2D spatial distribution of V plasma is calculated from Ohm’s Law for the parallel electricmore » field E || along each flux tube, E || s || = -1.71dT e/ds || - T e/n edn e/ds ||, where the Thomson scattering values of T e and n e are used. To within a constant of integration, V plasma is obtained by integrating E || along the flux-tubes (field lines); the constant is obtained for each flux tube using the sheath drop at the target calculated from the characteristic of Langmuir probes built into the divertor tiles. The 2D distributions of E./01/2 = -dV4/ds./01/2, E452510/2 = -dV4/ds452510/2, v789 452510/2 = E./01/2/B and v789 ./01/2 = E452510/2/B are then calculated as well as the particle drift flux densities Γ789 452510/2 = nv789 452510/2 and Γ789 ./01/2 = nv789 ./01/2 for electrons, fuel ions and impurity ions, using the appropriate values of particle density, n.« less

Experimentally-based ExB drifts in the DIII-D divertor and SOL calculated from integration of Ohm's law using Thomson scattering measurements of T e and n e

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stangeby, Peter C.; Elder, J. David; McLean, Adam G.

We calculated the 2D spatial distributions of cross field drift velocities from 2D Thomson scattering measurements of T e and n e in the divertor and SOL of DIII-D. In contrast with the method that has been used on DIII-D where the 2D distribution of plasma potential V plasma is obtained from measurements of the probe floating potential of reciprocating probes, the present method does not require insertion of a probe into the plasma and can therefore be used in high power discharges. Furthermore, the 2D spatial distribution of V plasma is calculated from Ohm’s Law for the parallel electricmore » field E || along each flux tube, E || s || = -1.71dT e/ds || - T e/n edn e/ds ||, where the Thomson scattering values of T e and n e are used. To within a constant of integration, V plasma is obtained by integrating E || along the flux-tubes (field lines); the constant is obtained for each flux tube using the sheath drop at the target calculated from the characteristic of Langmuir probes built into the divertor tiles. The 2D distributions of E./01/2 = -dV4/ds./01/2, E452510/2 = -dV4/ds452510/2, v789 452510/2 = E./01/2/B and v789 ./01/2 = E452510/2/B are then calculated as well as the particle drift flux densities Γ789 452510/2 = nv789 452510/2 and Γ789 ./01/2 = nv789 ./01/2 for electrons, fuel ions and impurity ions, using the appropriate values of particle density, n.« less

The FIELDS experiment for Solar Probe Plus

NASA Astrophysics Data System (ADS)

Bale, S.; Spp/Fields Team

2010-12-01

Many of our basic ideas on the plasma physics of acceleration, energy flow, and dissipation, and structure of the solar wind have never been rigorously confronted by direct experimental measurements in the region where these processes are actually occurring. Although Alfven waves, shocks, and magnetic reconnection are often invoked as heating mechanisms, there have never been any direct measurements of Alfvenic waves nor the associated Poynting flux nor any measurements of ion or electron kinetic energy flux in the region from 10 R_s to 30 R_s where the final stages of wind acceleration are believed to occur. The radial profiles of both slow and fast solar wind acceleration are based on remote-sensing measurements and have been obtained for only a few selected events. Thus, the spatial radial and perpendicular scales of the acceleration process have been averaged by line-of-sight effects and the possibility of intense localized acceleration cannot be ruled out. The Solar Probe Plus (SPP) mission calls for the high quality fields and particles measurements required to solve the coronal heating and wind acceleration problem. The SPP 'FIELDS' experiment measures the electric and magnetic fields fundamental to the plasma physics of the structured and turbulent solar wind, flux ropes, collisionless shocks, and magnetic reconnection. FIELDS will make the first-ever measurements of the DC/Low-Frequency electric field inside of 1 AU allowing for in situ, high cadence measurements of the Poynting vector, the Elsasser variables, and E/B diagnostics of the wave spectrum to fce in the solar wind. SPP/FIELDS measures the radio wave (type III and II) signatures of microflares, energized electrons, and CME propagation. SPP/ FIELDS measures the plasma electron density to ~2% accuracy and the core electron temperature to ~5-10% accuracy more than 90% of the time at perihelion. FIELDS will also measure the in situ density fluctuation spectrum and structures at a very high cadence (≤ 10 kHz) and provide definitive signatures of the turbulent nature and heating of the solar wind plasma. Furthermore, SPP/FIELDS measures the impact rate and sig- natures of dust from micron- to nano-scales, by measuring the voltage signature of dust impacts on the spacecraft. FIELDS will also measure the floating potential of the SPP spacecraft, which is essential for correcting in situ electron data. The SPP/FIELDS experiment combines four (4) deployable electric antennas, fluxgate and search coil magnetometers and the associated signal processing electronics into a scientifically and technically integrated package. SPP/FIELDS makes very high cadence measurements of fields and density and employs an internal burst memory for intelligent data selection. FIELDS is required to measure very large plasma potentials and electric fields (~10V) and uses floating ground (+/- 100V) power preamplifiers. The SPP/FIELDS team has performed 3D plasma simulations of the SPP spacecraft plasma environ- ment, which reveal enormous voltage fluctuation levels in the plasma wake behind the spacecraft. This voltage noise dominates the true signal by orders of magnitude in the critical DC/LF frequency range. Therefore, we are proposing a design which places the four (4) electric antennas in front of the spacecraft ahead of the heat shield.

The floating anchored craniotomy

PubMed Central

Gutman, Matthew J.; How, Elena; Withers, Teresa

2017-01-01

Background: The “floating anchored” craniotomy is a technique utilized at our tertiary neurosurgery institution in which a traditional decompressive craniectomy has been substituted for a floating craniotomy. The hypothesized advantages of this technique include adequate decompression, reduction in the intracranial pressure, obviating the need for a secondary cranioplasty, maintained bone protection, preventing the syndrome of the trephined, and a potential reduction in axonal stretching. Methods: The bone plate is re-attached via multiple loosely affixed vicryl sutures, enabling decompression, but then ensuring the bone returns to its anatomical position once cerebral edema has subsided. Results: From the analysis of 57 consecutive patients analyzed at our institution, we have found that the floating anchored craniotomy is comparable to decompressive craniectomy for intracranial pressure reduction and has some significant theoretical advantages. Conclusions: Despite the potential advantages of techniques that avoid the need for a second cranioplasty, they have not been widely adopted and have been omitted from trials examining the utility of decompressive surgery. This retrospective analysis of prospectively collected data suggests that the floating anchored craniotomy may be applicable instead of decompressive craniectomy. PMID:28713633

Potential of water surface-floating microalgae for biodiesel production: Floating-biomass and lipid productivities.

PubMed

Muto, Masaki; Nojima, Daisuke; Yue, Liang; Kanehara, Hideyuki; Naruse, Hideaki; Ujiro, Asuka; Yoshino, Tomoko; Matsunaga, Tadashi; Tanaka, Tsuyoshi

2017-03-01

Microalgae have been accepted as a promising feedstock for biodiesel production owing to their capability of converting solar energy into lipids through photosynthesis. However, the high capital and operating costs, and high energy consumption, are hampering commercialization of microalgal biodiesel. In this study, the surface-floating microalga, strain AVFF007 (tentatively identified as Botryosphaerella sudetica), which naturally forms a biofilm on surfaces, was characterized for use in biodiesel production. The biofilm could be conveniently harvested from the surface of the water by adsorbing onto a polyethylene film. The lipid productivity of strain AVFF007 was 46.3 mg/L/day, allowing direct comparison to lipid productivities of other microalgal species. The moisture content of the surface-floating biomass was 86.0 ± 1.2%, which was much lower than that of the biomass harvested using centrifugation. These results reveal the potential of this surface-floating microalgal species as a biodiesel producer, employing a novel biomass harvesting and dewatering strategy. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Plant traits and environment: floating leaf blade production and turnover of waterlilies.

PubMed

Klok, Peter F; van der Velde, Gerard

2017-01-01

Floating leaf blades of waterlilies fulfill several functions in wetland ecosystems by production, decomposition and turnover as well as exchange processes. Production and turnover rates of floating leaf blades of three waterlily species, Nuphar lutea (L.) Sm., Nymphaea alba L. and Nymphaea candida Presl, were studied in three freshwater bodies, differing in trophic status, pH and alkalinity. Length and percentages of leaf loss of marked leaf blades were measured weekly during the growing season. Area and biomass were calculated based on leaf length and were used to calculate the turnover rate of floating leaf blades. Seasonal changes in floating leaf production showed that values decreased in the order: Nymphaea alba , Nuphar lutea , Nymphaea candida . The highest production was reached for Nuphar lutea and Nymphaea alba in alkaline, eutrophic water bodies. The production per leaf was relatively high for both species in the acid water body. Nymphaea candida showed a very short vegetation period and low turnover rates. The ratio Total potential leaf biomass/Maximum potential leaf biomass (P/B max ) of the three species ranged from 1.35-2.25. The ratio Vegetation period (Period with floating leaves)/Mean leaf life span ranged from 2.94-4.63, the ratio Growth period (Period with appearance of new floating leaves)/Vegetation period from 0.53-0.73. The clear differences between Nymphaea candida versus Nuphar lutea and Nymphaea alba , may be due to adaptations of Nymphaea candida to an Euro-Siberic climate with short-lasting summer conditions.

Plant traits and environment: floating leaf blade production and turnover of waterlilies

PubMed Central

2017-01-01

Floating leaf blades of waterlilies fulfill several functions in wetland ecosystems by production, decomposition and turnover as well as exchange processes. Production and turnover rates of floating leaf blades of three waterlily species, Nuphar lutea (L.) Sm., Nymphaea alba L. and Nymphaea candida Presl, were studied in three freshwater bodies, differing in trophic status, pH and alkalinity. Length and percentages of leaf loss of marked leaf blades were measured weekly during the growing season. Area and biomass were calculated based on leaf length and were used to calculate the turnover rate of floating leaf blades. Seasonal changes in floating leaf production showed that values decreased in the order: Nymphaea alba, Nuphar lutea, Nymphaea candida. The highest production was reached for Nuphar lutea and Nymphaea alba in alkaline, eutrophic water bodies. The production per leaf was relatively high for both species in the acid water body. Nymphaea candida showed a very short vegetation period and low turnover rates. The ratio Total potential leaf biomass/Maximum potential leaf biomass (P/Bmax) of the three species ranged from 1.35–2.25. The ratio Vegetation period (Period with floating leaves)/Mean leaf life span ranged from 2.94–4.63, the ratio Growth period (Period with appearance of new floating leaves)/Vegetation period from 0.53–0.73. The clear differences between Nymphaea candida versus Nuphar lutea and Nymphaea alba, may be due to adaptations of Nymphaea candida to an Euro-Siberic climate with short-lasting summer conditions. PMID:28462025

Evolution of Multiple Double Layer in Glow discharge and its inherent Properties

NASA Astrophysics Data System (ADS)

Alex, Prince; A, Saravanan; Sinha, Suraj

2016-10-01

Formation and evolution of multiple anodic double layers (MADLs) were experimentally studied in glow discharge plasma. The boundary condition for the existence of MADL was identified in terms of threshold bias and ambient working pressure. The MADL formation is accompanied by an explosive growth in anode current and consequent current-voltage characteristics follows a hysteresis loop. The analysis yield that stable MADLs is only observed when the control voltage V2 is between a certain critical values (Vq > νte MADL completely transforms to an intense high current carrying unstable anode glow. The floating potential analysis carried out using three axially positioned electrostatic probes shows a bipolar signature of DL with as the control parameter is varied. The floating potential analysis also shows that hysteresis arises due to the difference in magnitude of electric field required to align the space charges in the DL sheet at the control voltage changes forward and backward. The effect of pressure on MADL indicates that the MADL structure advances towards anode surface as the pressure is increases. The power dumped (W) in the MADL is estimated to decrease with increase in pressure while the same increase in the anode glow.

GAS AND BUBBLE PRODUCTION BY SIPHONOPHORES.

DTIC Science & Technology

Gas-filled siphonophore floats collected from a deep scattering layer (DSL) were photographed in the act of voluntarily expelling bubbles of nearly...Such free bubbles, together with the siphonophore floats themselves, constitute a biological family of potentially resonant sonar targets

Numerical study on aerodynamic damping of floating vertical axis wind turbines

NASA Astrophysics Data System (ADS)

Cheng, Zhengshun; Aagaard Madsen, Helge; Gao, Zhen; Moan, Torgeir

2016-09-01

Harvesting offshore wind energy resources using floating vertical axis wind turbines (VAWTs) has attracted an increasing interest in recent years. Due to its potential impact on fatigue damage, the aerodynamic damping should be considered in the preliminary design of a floating VAWT based on the frequency domain method. However, currently the study on aerodynamic damping of floating VAWTs is very limited. Due to the essential difference in aerodynamic load characteristics, the aerodynamic damping of a floating VAWT could be different from that of a floating horizontal axis wind turbine (HAWT). In this study, the aerodynamic damping of floating VAWTs was studied in a fully coupled manner, and its influential factors and its effects on the motions, especially the pitch motion, were demonstrated. Three straight-bladed floating VAWTs with identical solidity and with a blade number varying from two to four were considered. The aerodynamic damping under steady and turbulent wind conditions were estimated using fully coupled aero-hydro-servo-elastic time domain simulations. It is found that the aerodynamic damping ratio of the considered floating VAWTs ranges from 1.8% to 5.3%. Moreover, the aerodynamic damping is almost independent of the rotor azimuth angle, and is to some extent sensitive to the blade number.

Observation of the Kelvin–Helmholtz Instability in a Solar Prominence

NASA Astrophysics Data System (ADS)

Yang, Heesu; Xu, Zhi; Lim, Eun-Kyung; Kim, Sujin; Cho, Kyung-Suk; Kim, Yeon-Han; Chae, Jongchul; Cho, Kyuhyoun; Ji, Kaifan

2018-04-01

Many solar prominences end their lives in eruptions or abrupt disappearances that are associated with dynamical or thermal instabilities. Such instabilities are important because they may be responsible for energy transport and conversion. We present a clear observation of a streaming kink-mode Kelvin–Helmholtz Instability (KHI) taking place in a solar prominence using the Hα Lyot filter installed at the New Vacuum Solar Telescope, Fuxian-lake Solar Observatory in Yunnan, China. On one side of the prominence, a series of plasma blobs floated up from the chromosphere and streamed parallel to the limb. The plasma stream was accelerated to about 20–60 km s‑1 and then undulated. We found that 2″- and 5″-size vortices formed, floated along the stream, and then broke up. After the 5″-size vortex, a plasma ejection out of the stream was detected in the Solar Dynamics Observatory/Atmospheric Imaging Assembly images. Just before the formation of the 5″-size vortex, the stream displayed an oscillatory transverse motion with a period of 255 s with the amplitude growing at the rate of 0.001 s‑1. We attribute this oscillation of the stream and the subsequent formation of the vortex to the KHI triggered by velocity shear between the stream, guided by the magnetic field and the surrounding media. The plasma ejection suggests the transport of prominence material into the upper layer by the KHI in its nonlinear stage.

Classifying Floating Potential Measurement Unit Data Products as Science Data

NASA Technical Reports Server (NTRS)

Coffey, Victoria; Minow, Joseph

2015-01-01

We are Co-Investigators for the Floating Potential Measurement Unit (FPMU) on the International Space Station (ISS) and members of the FPMU operations and data analysis team. We are providing this memo for the purpose of classifying raw and processed FPMU data products and ancillary data as NASA science data with unrestricted, public availability in order to best support science uses of the data.

Enhancement of Biomass and Lipid Productivities of Water Surface-Floating Microalgae by Chemical Mutagenesis

PubMed Central

Nojima, Daisuke; Ishizuka, Yuki; Muto, Masaki; Ujiro, Asuka; Kodama, Fumito; Yoshino, Tomoko; Maeda, Yoshiaki; Matsunaga, Tadashi; Tanaka, Tsuyoshi

2017-01-01

Water surface-floating microalgae have great potential for biofuel applications due to the ease of the harvesting process, which is one of the most problematic steps in conventional microalgal biofuel production. We have collected promising water surface-floating microalgae and characterized their capacity for biomass and lipid production. In this study, we performed chemical mutagenesis of two water surface-floating microalgae to elevate productivity. Floating microalgal strains AVFF007 and FFG039 (tentatively identified as Botryosphaerella sp. and Chlorococcum sp., respectively) were exposed to ethyl methane sulfonate (EMS) or 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), and pale green mutants (PMs) were obtained. The most promising FFG039 PM formed robust biofilms on the surface of the culture medium, similar to those formed by wild type strains, and it exhibited 1.7-fold and 1.9-fold higher biomass and lipid productivities than those of the wild type. This study indicates that the chemical mutation strategy improves the lipid productivity of water surface-floating microalgae without inhibiting biofilm formation and floating ability. PMID:28555001

Enhancement of Biomass and Lipid Productivities of Water Surface-Floating Microalgae by Chemical Mutagenesis.

PubMed

Nojima, Daisuke; Ishizuka, Yuki; Muto, Masaki; Ujiro, Asuka; Kodama, Fumito; Yoshino, Tomoko; Maeda, Yoshiaki; Matsunaga, Tadashi; Tanaka, Tsuyoshi

2017-05-27

Water surface-floating microalgae have great potential for biofuel applications due to the ease of the harvesting process, which is one of the most problematic steps in conventional microalgal biofuel production. We have collected promising water surface-floating microalgae and characterized their capacity for biomass and lipid production. In this study, we performed chemical mutagenesis of two water surface-floating microalgae to elevate productivity. Floating microalgal strains AVFF007 and FFG039 (tentatively identified as Botryosphaerella sp. and Chlorococcum sp., respectively) were exposed to ethyl methane sulfonate (EMS) or 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), and pale green mutants (PMs) were obtained. The most promising FFG039 PM formed robust biofilms on the surface of the culture medium, similar to those formed by wild type strains, and it exhibited 1.7-fold and 1.9-fold higher biomass and lipid productivities than those of the wild type. This study indicates that the chemical mutation strategy improves the lipid productivity of water surface-floating microalgae without inhibiting biofilm formation and floating ability.

Near Real Time Tools for ISS Plasma Science and Engineering Applications

NASA Technical Reports Server (NTRS)

Minow, Joseph I.; Willis, Emily M.; Parker, Linda Neergaard; Shim, Ja Soon; Kuznetsova, Maria M.; Pulkkinen, Antti, A.

2013-01-01

The International Space Station (ISS) program utilizes a plasma environment forecast for estimating electrical charging hazards for crews during extravehicular activity (EVA). The process uses ionospheric electron density (Ne) and temperature (Te) measurements from the ISS Floating Potential Measurement Unit (FPMU) instrument suite with the assumption that the plasma conditions will remain constant for one to fourteen days with a low probability for a space weather event which would significantly change the environment before an EVA. FPMU data is typically not available during EVA's, therefore, the most recent FPMU data available for characterizing the state of the ionosphere during EVA is typically a day or two before the start of an EVA or after the EVA has been completed. Three near real time space weather tools under development for ISS applications are described here including: (a) Ne from ground based ionosonde measurements of foF2 (b) Ne from near real time satellite radio occultation measurements of electron density profiles (c) Ne, Te from a physics based ionosphere model These applications are used to characterize the ISS space plasma environment during EVA periods when FPMU data is not available, monitor for large changes in ionosphere density that could render the ionosphere forecast and plasma hazard assessment invalid, and validate the "persistence of conditions" forecast assumption. In addition, the tools are useful for providing space environment input to science payloads on ISS and anomaly investigations during periods the FPMU is not operating.

Direct experimental evidence of ion-ion co-stream instability excited in the sheath-presheath of Ar +He two-ion species plasma

NASA Astrophysics Data System (ADS)

Kella, Vara Prasad; Ghosh, Joydeep; Chattopadhyay, Prabal; Sharma, Devendra; Saxena, Yogesh

2017-10-01

Recent experimental measurements of ion flow speeds near the sheath edge of two-ion species plasma shows that, the ions reach the sheath edge with common sound speed other than their individual Bohm speeds at nearly equal ion concentrations. Baalrud et al., explain these results on the basis of ion-ion two-stream instability enhanced collisional friction between the ions. Some authors stipulate the existence of the instability indirectly, by measuring the ion flow speeds near the sheath edge. In these experiments, the instability is directly observed from the floating potential fluctuations from Langmuir probe placed near the sheath edge and from grid in Ar +He plasma. The frequency spectra shows broad band peaks with central frequency in the range 150-200 kHz. The intensity of the instability maximizes in the plasma produced with approximately equal ion concentrations of both the ion species. The frequency and amplitude of the peak decreases as the He+ to Ar+ concentration ratio decreases from unity. The phase velocity of the wave is measured as 11 +/-2 km/s and identified to be twice the ion-sound speed in the bulk ( 6.3 km/s), which is good agreement with earlier results of IAWs. The measured wave number and frequencies are compared with the theoretical dispersion relations. These observations confirm the existence of ion-ion co-stream instability in sheath-presheath of two-ion species plasma.

Particle-In-Cell Analysis of an Electric Antenna for the BepiColombo/MMO spacecraft

NASA Astrophysics Data System (ADS)

Miyake, Yohei; Usui, Hideyuki; Kojima, Hirotsugu

The BepiColombo/MMO spacecraft is planned to provide a first electric field measurement in Mercury's magnetosphere by mounting two types of the electric antennas: WPT and MEFISTO. The sophisticated calibration of such measurements should be performed based on precise knowledge of the antenna characteristics in space plasma. However, it is difficult to know prac-tical antenna characteristics considering the plasma kinetics and spacecraft-plasma interactions by means of theoretical approaches. Furthermore, some modern antenna designing techniques such as a "hockey puck" principle is applied to MEFISTO, which introduces much complexity in its overall configuration. Thus a strong demand arises regarding the establishment of a nu-merical method that can solve the complex configuration and plasma dynamics for evaluating the electric properties of the modern instrument. For the self-consistent antenna analysis, we have developed a particle simulation code named EMSES based on the particle-in-cell technique including a treatment antenna conductive sur-faces. In this paper, we mainly focus on electrostatic (ES) features and photoelectron distri-bution in the vicinity of MEFISTO. Our simulation model includes (1) a photoelectron guard electrode, (2) a bias current provided from the spacecraft body to the sensing element, (3) a floating potential treatment for the spacecraft body, and (4) photoelectron emission from sunlit surfaces of the conductive bodies. Of these, the photoelectron guard electrode is a key technol-ogy for producing an optimal condition of plasma environment around MEFISTO. Specifically, we introduced a pre-amplifier housing called puck located between the conductive boom and the sensor wire. The photoelectron guard is then simulated by forcibly fixing the potential difference between the puck surface and the spacecraft body. For the modeling, we use the Capacity Matrix technique in order to assure the conservation condition of total charge owned by the entire spacecraft body. We report some numerical analyses on the influence of the guard electrode on the surrounding plasma environment by using the developed model.

Observation of low magnetic field density peaks in helicon plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barada, Kshitish K.; Chattopadhyay, P. K.; Ghosh, J.

2013-04-15

Single density peak has been commonly observed in low magnetic field (<100 G) helicon discharges. In this paper, we report the observations of multiple density peaks in low magnetic field (<100 G) helicon discharges produced in the linear helicon plasma device [Barada et al., Rev. Sci. Instrum. 83, 063501 (2012)]. Experiments are carried out using argon gas with m = +1 right helical antenna operating at 13.56 MHz by varying the magnetic field from 0 G to 100 G. The plasma density varies with varying the magnetic field at constant input power and gas pressure and reaches to its peakmore » value at a magnetic field value of {approx}25 G. Another peak of smaller magnitude in density has been observed near 50 G. Measurement of amplitude and phase of the axial component of the wave using magnetic probes for two magnetic field values corresponding to the observed density peaks indicated the existence of radial modes. Measured parallel wave number together with the estimated perpendicular wave number suggests oblique mode propagation of helicon waves along the resonance cone boundary for these magnetic field values. Further, the observations of larger floating potential fluctuations measured with Langmuir probes at those magnetic field values indicate that near resonance cone boundary; these electrostatic fluctuations take energy from helicon wave and dump power to the plasma causing density peaks.« less

MOSFET Electric-Charge Sensor

NASA Technical Reports Server (NTRS)

Robinson, Paul A., Jr.

1988-01-01

Charged-particle probe compact and consumes little power. Proposed modification enables metal oxide/semiconductor field-effect transistor (MOSFET) to act as detector of static electric charges or energetic charged particles. Thickened gate insulation acts as control structure. During measurements metal gate allowed to "float" to potential of charge accumulated in insulation. Stack of modified MOSFET'S constitutes detector of energetic charged particles. Each gate "floats" to potential induced by charged-particle beam penetrating its layer.

Gastroprotective effects of the isopropanol extract of Artemisia princeps and its gastroretentive floating tablets on gastric mucosal injury.

PubMed

Kim, Joo-Il; Park, Sang-Wook; Lim, Jhong-Jae; Sohn, Se-Il; Shin, Ji-Su; Park, Sang Cheol; Jang, Young Pyo; Chung, Eun Kyoung; Lee, Hong-Woo; Lee, Kyung-Tae

2017-12-20

In this study, we investigated the gastroprotective effect of an isopropanol extract from the aerial parts of Artemisia princeps (IPAP) and developed a gastroretentive floating tablet of IPAP (IPAP-FR) for maximized local gastroprotective effects. Pre-treatment with IPAP ameliorated the gastric mucosal hemorrhagic lesions in ethanol/HCl- or indomethacin- treated rats. IPAP decreased mucosal hemorrhage of gastric ulcers induced by ethanol or indomethacin plus pyloric ligation in rats. The optimized floating tablet, IPAP-FR, floated on medium surface with more sustained eupatilin release compared to the non-floating control tablet. X-ray photographs in beagle dogs showed that IPAPFR was retained for > 2 h in the stomach. In the ethanol-induced gastric ulcer rat model, the gastric hemorrhagic lesion was improved more substantially with IPAP-FR compared to the non-floating control tablet. Based on these data, our data suggest that IPAP-FR has an improved therapeutic potential for the treatment of gastric ulcer.

Alginate/cashew gum floating bead as a matrix for larvicide release.

PubMed

Paula, Haroldo C B; de Oliveira, Erick F; Abreu, Flávia O M S; de Paula, Regina C M

2012-08-01

A polymeric floating system composed of Alginate (ALG) and Cashew gum (CG), loaded with an essential oil (Lippia sidoides-Ls) was prepared by ionotropic gelation, characterized regarding its physical-chemistry properties and evaluated on its potential as a controlled release system. The influence of process parameters on the buoyancy, loading, swelling and in vitro and in vivo release kinetics, was investigated. Results showed that beads produced with carbonate and Ls at high level contents exhibit good floatability (up to 5 days) and loading capacity (15.2-23.8%). In vitro release data showed a Fickian diffusion profile and in vivo experiments showed that ALG-CG floating system presented a superior and prolonged larvicide effect, in comparison with non-floating ones, presenting larvae mortality values of 85% and 33%, respectively, after 48 h. These results indicate that ALG-CG floating beads loaded with Ls presented enhanced oil entrapment efficiency, excellent floating ability, and suitable larvicide release pattern. Copyright © 2012 Elsevier B.V. All rights reserved.

Measurement of vehicle potential using a mother-daughter tethered rocket

NASA Technical Reports Server (NTRS)

Williamson, P. R.; Denig, W. F.; Banks, P. M.; Raitt, W. J.; Kawashima, N.; Hirao, K.; Oyama, K. I.; Sasaki, S.

1982-01-01

The equipment, experimental design, and results of mother-daughter tethered probes for measuring the potential of a spacecraft are described. The object was to inject a probe into the ionosphere by rocket and then lower an impedance voltage monitor-equipped section of the probe by means of a highly insulated wire. The mother probe, also carrying voltage monitors, would inject charges into the plasma that would be measured at both ends of the tether. Instrumentation on the daughter probe included voltage current monitors and a Langmuir probe, while the mother payload also carried a charge probe, floating probe, a Langmuir probe, and an impedance probe. The first launch was from Japan in 1980, and operations confirmed that Langmuir probes with area ratios less than 400:1 can produce changes in the vehicle potential if probe voltages of more than 10 V are applied in the collection mode. A ratio of 200:1 was sufficient for the daughter probe with voltages of 5 V. The experiment is concluded to verify the tethered probe method of measuring vehicle potential.

Investigation of high power impulse magnetron sputtering (HIPIMS) discharge using fast ICCD camera

NASA Astrophysics Data System (ADS)

Hecimovic, Ante

2012-10-01

High power impulse magnetron sputtering (HIPIMS) combines impulse glow discharges at power levels up to the MW range with conventional magnetron cathodes to achieve a highly ionised sputtered flux. The dynamics of the HIPIMS discharge was investigated using fast Intensified Charge Coupled Device (ICCD) camera. In the first experiment the HIPIMS plasma was recorded from the side with goal to analyse the plasma intensity using Abel inversion to obtain the emissivity maps of the plasma species. Resulting emissivity maps provide the information on the spatial distribution of Ar and sputtered material and evolution of the plasma chemistry above the cathode. In the second experiment the plasma emission was recorded with camera facing the target. The images show that the HIPIMS plasma develops drift wave type instabilities characterized by well defined regions of high and low plasma emissivity along the racetrack of the magnetron. The instabilities cause periodic shifts in the floating potential. The structures rotate in ExB direction at velocities of 10 kms-1 and frequencies up to 200 kHz. The high emissivity regions comprise Ar and metal ion emission with strong Ar and metal neutral emission depletion. A detailed analysis of the temporal evolution of the saturated instabilities using four consequently triggered fast ICCD cameras is presented. Furthermore working gas pressure and discharge current variation showed that the shape and the speed of the instability strongly depend on the working gas and target material combination. In order to better understand the mechanism of the instability, different optical interference band pass filters (of metal and gas atom, and ion lines) were used to observe the spatial distribution of each species within the instability.

Floating Potential Probe Langmuir Probe Data Reduction Results

NASA Technical Reports Server (NTRS)

Morton, Thomas L.; Minow, Joseph I.

2002-01-01

During its first five months of operations, the Langmuir Probe on the Floating Potential Probe (FPP) obtained data on ionospheric electron densities and temperatures in the ISS orbit. In this paper, the algorithms for data reduction are presented, and comparisons are made of FPP data with ground-based ionosonde and Incoherent Scattering Radar (ISR) results. Implications for ISS operations are detailed, and the need for a permanent FPP on ISS is examined.

Operating in the space plasma environment: A spacecraft charging study of the Solar X-ray Imager

NASA Technical Reports Server (NTRS)

Herr, Joel L.; Mccollum, Matthew B.; James, Bonnie F.

1994-01-01

This study presents the results of a spacecraft charging effects protection study conducted on the Solar X-ray Imager (SXI). The SXI is being developed by NASA Marshall Space Flight Center for NOAA's Space Environment Laboratory, and will be used to aid in forecasting energetic particle events and geomagnetic storms. Images will provide information on the intensity and location of solar flares, coronal mass ejections, and high speed solar streams. The SXI will be flown on a next-generation GOES sometime in the mid to late 1990's. Charging due to the encounter with a worst-case magnetic substorm environment is modeled using the NASCAP/GEO computer code. Charging levels of exterior surfaces and the floating potential of the spacecraft relative to plasma are determined as a function of spacecraft design, operational configuration, and orbital conditions. Areas where large surface voltage gradients exist on or near the SXI are identified as possible arc-discharge sites. Results of the charging analysis are then used to develop design recommendations that will limit the effects of spacecraft charging on the SXI operation.

Simultaneous extraction and quantification of lamotrigine, phenobarbital, and phenytoin in human plasma and urine samples using solidified floating organic drop microextraction and high-performance liquid chromatography.

PubMed

Asadi, Mohammad; Dadfarnia, Shayessteh; Haji Shabani, Ali Mohammad; Abbasi, Bijan

2015-07-01

A novel and simple method based on solidified floating organic drop microextraction followed by high-performance liquid chromatography with ultraviolet detection has been developed for simultaneous preconcentration and determination of phenobarbital, lamotrigine, and phenytoin in human plasma and urine samples. Factors affecting microextraction efficiency such as the type and volume of the extraction solvent, sample pH, extraction time, stirring rate, extraction temperature, ionic strength, and sample volume were optimized. Under the optimum conditions (i.e. extraction solvent, 1-undecanol (40 μL); sample pH, 8.0; temperature, 25°C; stirring rate, 500 rpm; sample volume, 7 mL; potassium chloride concentration, 5% and extraction time, 50 min), the limits of detection for phenobarbital, lamotrigine, and phenytoin were 1.0, 0.1, and 0.3 μg/L, respectively. Also, the calibration curves for phenobarbital, lamotrigine, and phenytoin were linear in the concentration range of 2.0-300.0, 0.3-200.0, and 1.0-200.0 μg/L, respectively. The relative standard deviations for six replicate extractions and determinations of phenobarbital, lamotrigine, and phenytoin at 50 μg/L level were less than 4.6%. The method was successfully applied to determine phenobarbital, lamotrigine, and phenytoin in plasma and urine samples. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental evidence of intermittent chaos in a glow discharge plasma without external forcing and its numerical modelling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, S., E-mail: sabuj.ghosh@saha.ac.in; Kumar Shaw, Pankaj; Sekar Iyengar, A. N.

Intermittent chaos was observed in a glow discharge plasma as the system evolved from regular type of relaxation oscillations (of larger amplitude) to an irregular type of oscillations (of smaller amplitude) as the discharge voltage was increased. Floating potential fluctuations were analyzed by different statistical and spectral methods. Features like a gradual change in the normal variance of the interpeak time intervals, a dip in the skewness, and a hump in the kurtosis with variation in the control parameter have been seen, which are strongly indicative of intermittent behavior in the system. Detailed analysis also suggests that the intrinsic noisemore » level in the experiment increases with the increasing discharge voltage. An attempt has been made to model the experimental observations by a second order nonlinear ordinary differential equation derived from the fluid equations for an unmagnetized plasma. Though the experiment had no external forcing, it was conjectured that the intrinsic noise in the experiment could be playing a vital role in the dynamics of the system. Hence, a constant bias and noise as forcing terms were included in the model. Results from the theoretical model are in close qualitative agreement with the experimental results.« less

Integration Assessment of Visiting Vehicle Induced Electrical Charging of the International Space Station Structure

NASA Technical Reports Server (NTRS)

Kramer, Leonard; Kerslake, Thomas W.; Galofaro, Joel T.

2010-01-01

The International Space Station (ISS) undergoes electrical charging in low Earth orbit (LEO) due to positively biased, exposed conductors on solar arrays that collect electrical charges from the space plasma. Exposed solar array conductors predominately collect negatively charged electrons and thus drive the metal ISS structure electrical ground to a negative floating potential (FP) relative to plasma. This FP is variable in location and time as a result of local ionospheric conditions. ISS motion through Earth s magnetic field creates an addition inductive voltage up to 20 positive and negative volts across ISS structure depending on its attitude and location in orbit. ISS Visiting Vehicles (VVs), such as the planned Orion crew exploration vehicle, contribute to the ISS plasma charging processes. Upon physical contact with ISS, the current collection properties of VVs combine with ISS. This is an ISS integration concern as FP must be controlled to minimize arcing of ISS surfaces and ensure proper management of extra vehicular activity crewman shock hazards. This report is an assessment of ISS induced charging from docked Orion vehicles employing negatively grounded, 130 volt class, UltraFlex (ATK Space Systems) solar arrays. To assess plasma electron current collection characteristics, Orion solar cell test coupons were constructed and subjected to plasma chamber current collection measurements. During these tests, coupon solar cells were biased between 0 and 120 V while immersed in a simulated LEO plasma. Tests were performed using several different simulated LEO plasma densities and temperatures. These data and associated theoretical scaling of plasma properties, were combined in a numerical model which was integrated into the Boeing Plasma Interaction Model. It was found that the solar array design for Orion will not affect the ISS FP by more than about 2 V during worst case charging conditions. This assessment also motivated a trade study to determine acceptable plasma electron current levels that can be collected by a single or combined fleet of ISS-docked VVs.

Reducing float coal dust

PubMed Central

Patts, J.R.; Colinet, J.F.; Janisko, S.J.; Barone, T.L.; Patts, L.D.

2016-01-01

Controlling float coal dust in underground coal mines before dispersal into the general airstream can reduce the risk of mine explosions while potentially achieving a more effective and efficient use of rock dust. A prototype flooded-bed scrubber was evaluated for float coal dust control in the return of a continuous miner section. The scrubber was installed inline between the face ventilation tubing and an exhausting auxiliary fan. Airborne and deposited dust mass measurements were collected over three days at set distances from the fan exhaust to assess changes in float coal dust levels in the return due to operation of the scrubber. Mass-based measurements were collected on a per-cut basis and normalized on the basis of per ton mined by the continuous miner. The results show that average float coal dust levels measured under baseline conditions were reduced by more than 90 percent when operating the scrubber. PMID:28018004

A semi-floating gate memory based on van der Waals heterostructures for quasi-non-volatile applications

NASA Astrophysics Data System (ADS)

Liu, Chunsen; Yan, Xiao; Song, Xiongfei; Ding, Shijin; Zhang, David Wei; Zhou, Peng

2018-05-01

As conventional circuits based on field-effect transistors are approaching their physical limits due to quantum phenomena, semi-floating gate transistors have emerged as an alternative ultrafast and silicon-compatible technology. Here, we show a quasi-non-volatile memory featuring a semi-floating gate architecture with band-engineered van der Waals heterostructures. This two-dimensional semi-floating gate memory demonstrates 156 times longer refresh time with respect to that of dynamic random access memory and ultrahigh-speed writing operations on nanosecond timescales. The semi-floating gate architecture greatly enhances the writing operation performance and is approximately 106 times faster than other memories based on two-dimensional materials. The demonstrated characteristics suggest that the quasi-non-volatile memory has the potential to bridge the gap between volatile and non-volatile memory technologies and decrease the power consumption required for frequent refresh operations, enabling a high-speed and low-power random access memory.

Electric field observations of equatorial bubbles

NASA Technical Reports Server (NTRS)

Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.

1992-01-01

Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

Review on the prevalence of diabetes and risk factors and situation of disease management in floating population in China.

PubMed

Han, Kaiyi; Yao, Jingjing; Yin, Xiao; Zhao, Mei; Sun, Qiang

2017-01-01

To give a comprehensive and basic understanding of diabetes and its risk factors in floating people in China. We use "(diabetes or type 2 diabetes or chronic disease) and (floating population or employed floating population)" as the key words to search in the China academic literature database (CNKI), Wan Fang database, PubMed and Web of Science for relevant literature and extract the data about the prevalence of diabetes, relevant risk factors and disease management of the floating population in China. Twenty-one literatures are entered into analysis finally, one is English and the rest are Chinese. According to the national survey, the prevalence rate of diabetes in floating population in China was 5. 1% (95%CI, 4.9% - 5.3%), which is lower than that of the general population(11.6%,95%CI, 11.3%-11.8%),and is consistent with the results of the local surveys. The comparison result between the prevalence of floating population and that of local population in each region differs in local surveys. In addition, the prevalence of male floating population is lower than that of the female population. Finally, as the age of the population rises, so does the prevalence of diabetes. As for the risk factors of chronical diseases, the overweight rate in every region is similar but the obesity rate differs in different regions (Ningxia,26.0%;Xiangshan,14.0%), and the obesity rate of the floating population is less than half of that of the general people(4.7%,11.9%). The awareness rate, treatment rate and control rate in the floating patients differ in the regional researches, but they all can't meet the goals set by the local health departments. Compared with the general population, the prevalence of diabetes in the floating population are lower. However, Considering the growing population number and the poor disease management of the floating patients, the potential threat brought by the diabetes in floating population is imponderable. The government should establish the national surveillance system of diabetes for the floating population, strengthen the construction of the primary medical institutions, and optimize the existing funding system.

Floating Gate sensor for in-vivo dosimetry in radiation therapies. Design and first characterization.

NASA Astrophysics Data System (ADS)

Faigon, A.; Martinez Vazquez, I.; Carbonetto, S.; García Inza, M.; G

2017-01-01

A floating gate dosimeter was designed and fabricated in a standard CMOS technology. The design guides and characterization are presented. The characterization included the controlled charging by tunneling of the floating gate, and its discharging under irradiation while measuring the transistor drain current whose change is the measure of the absorbed dose. The resolution of the obtained device is close to 1 cGy satisfying the requirements for most radiation therapies dosimetry. Pending statistical proofs, the dosimeter is a potential candidate for wide in-vivo control of radiotherapy treatments.

Spoke rotation reversal in magnetron discharges of aluminium, chromium and titanium

NASA Astrophysics Data System (ADS)

Hecimovic, A.; Maszl, C.; Schulz-von der Gathen, V.; Böke, M.; von Keudell, A.

2016-06-01

The rotation of localised ionisation zones, i.e. spokes, in magnetron discharge are frequently observed. The spokes are investigated by measuring floating potential oscillations with 12 flat probes placed azimuthally around a planar circular magnetron. The 12-probe setup provides sufficient temporal and spatial resolution to observe the properties of various spokes, such as rotation direction, mode number and angular velocity. The spokes are investigated as a function of discharge current, ranging from 10 mA (current density 0.5 mA cm-2) to 140 A (7 A cm-2). In the range from 10 mA to 600 mA the plasma was sustained in DC mode, and in the range from 1 A to 140 A the plasma was pulsed in high-power impulse magnetron sputtering mode. The presence of spokes throughout the complete discharge current range indicates that the spokes are an intrinsic property of a magnetron sputtering plasma discharge. The spokes may disappear at discharge currents above 80 A for Cr, as the plasma becomes homogeneously distributed over the racetrack. Up to discharge currents of several amperes (the exact value depends on the target material), the spokes rotate in a retrograde \\mathbf{E}× \\mathbf{B} direction with angular velocity in the range of 0.2-4 km s-1. Beyond a discharge current of several amperes, the spokes rotate in a \\mathbf{E}× \\mathbf{B} direction with angular velocity in the range of 5-15 km s-1. The spoke rotation reversal is explained by a transition from Ar-dominated to metal-dominated sputtering that shifts the plasma emission zone closer to the target. The spoke itself corresponds to a region of high electron density and therefore to a hump in the electrical potential. The electric field around the spoke dominates the spoke rotation direction. At low power, the plasma is further away from the target and it is dominated by the electric field to the anode, thus retrograde \\mathbf{E}× \\mathbf{B} rotation. At high power, the plasma is closer to the target and it is dominated by the electric field pointing to the target, thus \\mathbf{E}× \\mathbf{B} rotation.

The impact of the night float system on internal medicine residency programs.

PubMed

Trontell, M C; Carson, J L; Taragin, M I; Duff, A

1991-01-01

To study the design, method of implementation, perceived benefits, and problems associated with a night float system. Self-administered questionnaire completed by program directors, which included both structured and open-ended questions. The answers reflect resident and student opinions as well as those of the program directors, since program directors regularly obtain feedback from these groups. The 442 accredited internal medicine residency programs listed in the 1988-89 Directory of Graduate Medical Education Programs. Of the 442 programs, 79% responded, and 30% had experience with a night float system. The most frequent methods for initiating a night float system included: decreasing elective time (42.3%), hiring more residents (26.9%), creating a non-teaching service (12.5%), and reallocating housestaff time (9.6%). Positive effects cited include decreased fatigue, improved housestaff morale, improved recruiting, and better attitude toward internal medicine training. The quality of medical care was considered the same or better by most programs using it. The most commonly cited problems were decreased continuity of care, inadequate teaching of the night float team, and miscommunication. Residency programs using a night float system usually observe a positive effect on housestaff morale, recruitment, and working hours and no detrimental effect on the quality of patient care. Miscommunication and inadequate learning experience for the night float team are important potential problems. This survey suggests that the night float represents one solution to reducing resident working hours.

Fabrication of a Silicon Nanowire on a Bulk Substrate by Use of a Plasma Etching and Total Ionizing Dose Effects on a Gate-All-Around Field-Effect Transistor

NASA Technical Reports Server (NTRS)

Moon, Dong-Il; Han, Jin-Woo; Meyyappan, Meyya

2016-01-01

The gate all around transistor is investigated through experiment. The suspended silicon nanowire for the next generation is fabricated on bulk substrate by plasma etching method. The scallop pattern generated by Bosch process is utilized to form a floating silicon nanowire. By combining anisotropic and istropic silicon etch process, the shape of nanowire is accurately controlled. From the suspended nanowire, the gate all around transistor is demonstrated. As the silicon nanowire is fully surrounded by the gate, the device shows excellent electrostatic characteristics.

Effect of external electric and magnetic field on propagation of atmospheric pressure plasma jet

NASA Astrophysics Data System (ADS)

Zhu, Ping; Meng, Zhaozhong; Hu, Haixin; Ouyang, Jiting

2017-10-01

The behaviors of atmospheric pressure plasma jet produced by a coplanar dielectric barrier discharge (CDBD) in helium in external electrostatic and magnetic field are investigated experimentally. Time-resolved ICCD images of jet in electric field, magnetic field, and floating metal ring are recorded, respectively. The results show that the jet dynamics is affected significantly by a metal ring, an electric, and/or a magnetic field. In a transverse electric field, the jet shows behavior of deflection, broadening, and shortening according to the structure of electric field. In a transverse magnetic field, the jet deflects to up or down depending on the magnetic direction. The jet can be slowed down or obstructed by a floating metal ring on the jet path, but will still pass through the tube at higher applied voltages of DBD, without significant change in jet length or shape out of the tube compared with that without metal ring. A positive DC voltage on the metal ring helps to improve the jet length, but a negative voltage will reduce the length or completely stop the jet. The electric field to sustain the jet in helium is estimated to be about 24 ± 15 kV/cm from this experiment.

Quality of life associated with perceived stigma and discrimination among the floating population in Shanghai, China: a qualitative study.

PubMed

Wang, Ji-Wei; Cui, Zhi-Ting; Cui, Hong-Wei; Wei, Chang-Nian; Harada, Koichi; Minamoto, Keiko; Ueda, Kimiyo; Ingle, Kapilkumar N; Zhang, Cheng-Gang; Ueda, Atsushi

2010-12-01

The floating population refers to the large and increasing number of migrants without local household registration status and has become a new demographic phenomenon in China. Most of these migrants move from the rural areas of the central and western parts of China to the eastern and coastal metropolitan areas in pursuit of a better life. The floating population of China was composed of 121 million people in 2000, and this number was expected to increase to 300 million by 2010. Quality of life (QOL) studies of the floating population could provide a critical starting point for recognizing the potential of regions, cities and local communities to improve QOL. This study explored the construct of QOL of the floating population in Shanghai, China. We conducted eight focus groups with 58 members of the floating population (24 males and 34 females) and then performed a qualitative thematic analysis of the interviews. The following five QOL domains were identified from the analysis: personal development, jobs and career, family life, social relationships and social security. The results indicated that stigma and discrimination permeate these life domains and influence the framing of life expectations. Proposals were made for reducing stigma and discrimination against the floating population to improve the QOL of this population.

A Self-Powered Fast-Sampling Profiling Float in support of a Mesoscale Ocean Observing System in the Western North Pacific

NASA Astrophysics Data System (ADS)

Valdez, T.; Chao, Y.; Davis, R. E.; Jones, J.

2012-12-01

This talk will describe a new self-powered profiling float that can perform fast sampling over the upper ocean for long durations in support of a mesoscale ocean observing system in the Western North Pacific. The current state-of-the-art profiling floats can provide several hundreds profiles for the upper ocean every ten days. To quantify the role of the upper ocean in modulating the development of Typhoons requires at least an order of magnitude reduction for the sampling interval. With today's profiling float and battery technology, a fast sampling of one day or even a few hours will reduce the typical lifetime of profiling floats from years to months. Interactions between the ocean and typhoons often involves mesoscale eddies and fronts, which require a dense array of floats to reveal the 3-dimensional structure. To measure the mesoscale ocean over a large area like the Western North Pacific therefore requires a new technology that enables fast sampling and long duration at the same time. Harvesting the ocean renewable energy associated with the vertical temperature differentials has the potential to power profiling floats with fast sampling over long durations. Results from the development and deployment of a prototype self-powered profiling float (known as SOLO-TREC) will be presented. With eight hours sampling in the upper 500 meters, the upper ocean temperature and salinity reveal pronounced high frequency variations. Plans to use the SOLO-TREC technology in support of a dense array of fast sampling profiling floats in the Western North Pacific will be discussed.

Rydberg gas theory of a glow discharge plasma: I. Application to the electrical behaviour of a fast flowing glow discharge plasma.

PubMed

Mason, Rod S; Mitchell, David J; Dickinson, Paul M

2010-04-21

Current-voltage (I-V) curves have been measured, independent of the main discharge, for electricity passing through the steady state fast flowing 'afterglow' plasma of a low power dc glow discharge in Ar. Voltage profiles along the axial line of conduction have been mapped using fixed probes and potentiometry, and the mass spectra of cations emerging from the downstream sampling Cone, also acting as a probe anode, were recorded simultaneously. Floating double probe experiments were also carried out. The electrical behavior is consistent with the well established I-V characteristics of such discharges, but does not comply with classical plasma theory predictions. The plasma decays along the line of conduction, with a lifetime of approximately 1 ms, despite carrying a steady state current, and its potential is below that of the large surface area anode voltage; a situation which cannot exist in the presence of a conventional free ion-electron plasma, unless the electron temperature is super cold. Currents, large by comparison with the main discharge current, and independent of it, are induced to flow through the downstream plasma, from the Anode (acting as a cathode) to the anodic ion exit Cone, induced by electron impact ionisation at the anode, but without necessarily increasing the plasma density. It appears to be conducted by direct charge transfer between a part of the anode surface (acting as cathode to the auxiliary circuit) and the plasma, without secondary electron emission or heating, which suggests the direct involvement of Rydberg atom intermediates. The reaction energy defect (= the work function of the electrode surface) fits with the plasma potential threshold observed for the cathodic reaction to occur. A true free ion-electron plasma is readily detected by the observation of cations at the anode surface, when induced at the downstream anode, at high bias voltages, by the electron impact ionisation in the boundary region. In contrast to the classical model, the complex electrical (and mass spectrometric) behaviour fits qualitatively, but can be understood well, with the Rydberg gas model described in papers II and III (R. S. Mason, and R. S. Mason and P. Douglas, PCCP, 2010, DOI: 10.1039/b918081h and b918083d) over a wide range of probe bias voltages. The full cycle of behavior is then described for the development of a true secondary discharge within the downstream plasma.

A modified emulsion gelation technique to improve buoyancy of hydrogel tablets for floating drug delivery systems.

PubMed

Yom-Tov, Ortal; Seliktar, Dror; Bianco-Peled, Havazelet

2015-10-01

The use of buoyant or floating hydrogel tablets is of particular interest in the sustained release of drugs to the stomach. They have an ability to slow the release rates of drugs by prolonging their absorption window in the upper part of the gastrointestinal (GI) tract. In this study we synthesized bioactive hydrogels that have sustainable release rates for drugs in the stomach based on a hydrogel preparation technique that employs emulsifying surfactants. The emulsion gelation technique, which encapsulates oil droplets within the hydrogels during crosslinking, was used to decrease their specific gravity in aqueous environments, resulting in floating drug release depots. Properties such as swelling, buoyancy, density and drug release were manipulated by changing the polymer concentrations, surfactant percentages and the oil:polymer ratios. The relationship between these properties and the hydrogel's floating lag time was documented. The potential for this material to be used as a floating drug delivery system was demonstrated. Copyright © 2015 Elsevier B.V. All rights reserved.

Differential subcellular membrane recruitment of Src may specify its downstream signalling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diesbach, Philippe de; Medts, Thierry; Carpentier, Sarah

2008-04-15

Most Src family members are diacylated and constitutively associate with membrane 'lipid rafts' that coordinate signalling. Whether the monoacylated Src, frequently hyperactive in carcinomas, also localizes at 'rafts' remains controversial. Using polarized MDCK cells expressing the thermosensitive v-Src/tsLA31 variant, we here addressed how Src tyrosine-kinase activation may impact on its (i) membrane recruitment, in particular to 'lipid rafts'; (ii) subcellular localization; and (iii) signalling. The kinetics of Src-kinase thermoactivation correlated with its recruitment from the cytosol to sedimentable membranes where Src largely resisted solubilisation by non-ionic detergents at 4 deg. C and floated into sucrose density gradients like caveolin-1 andmore » flotillin-2, i.e. 'lipid rafts'. By immunofluorescence, activated Src showed a dual localization, at apical endosomes/macropinosomes and at the apical plasma membrane. The plasma membrane Src pool did not colocalize with caveolin-1 and flotillin-2, but extensively overlapped GM1 labelling by cholera toxin. Severe ({approx} 70%) cholesterol extraction with methyl-{beta}-cyclodextrin (M{beta}CD) did not abolish 'rafts' floatation, but strongly decreased Src association with floating 'rafts' and abolished its localization at the apical plasma membrane. Src activation independently activated first the MAP-kinase - ERK1/2 pathway, then the PI3-kinase - Akt pathway. MAP-kinase - ERK1/2 activation was insensitive to M{beta}CD, which suppressed Akt phosphorylation and apical endocytosis induced by Src, both depending on the PI3-kinase pathway. We therefore suggest that activated Src is recruited at two membrane compartments, allowing differential signalling, first via ERK1/2 at 'non-raft' domains on endosomes, then via PI3-kinase-Akt on a distinct set of 'rafts' at the apical plasma membrane. Whether this model is applicable to c-Src remains to be examined.« less

Preparation and investigation of novel gastro-floating tablets with 3D extrusion-based printing.

PubMed

Li, Qijun; Guan, Xiaoying; Cui, Mengsuo; Zhu, Zhihong; Chen, Kai; Wen, Haoyang; Jia, Danyang; Hou, Jian; Xu, Wenting; Yang, Xinggang; Pan, Weisan

2018-01-15

Three dimensional (3D) extrusion-based printing is a paste-based rapid prototyping process, which is capable of building complex 3D structures. The aim of this study was to explore the feasibility of 3D extrusion-based printing as a pharmaceutical manufacture technique for the fabrication of gastro-floating tablets. Novel low-density lattice internal structure gastro-floating tablets of dipyridamole were developed to prolong the gastric residence time in order to improve drug release rate and consequently, improve bioavailability and therapeutic efficacy. Excipients commonly employed in the pharmaceutical study could be efficiently applied in the room temperature 3D extrusion-based printing process. The tablets were designed with three kinds of infill percentage and prepared by hydroxypropyl methylcellulose (HPMC K4M) and hydroxypropyl methylcellulose (HPMC E15) as hydrophilic matrices and microcrystalline cellulose (MCC PH101) as extrusion molding agent. In vitro evaluation of the 3D printed gastro-floating tablets was performed by determining mechanical properties, content uniformity, and weight variation. Furthermore, re-floating ability, floating duration time, and drug release behavior were also evaluated. Dissolution profiles revealed the relationship between infill percentage and drug release behavior. The results of this study revealed the potential of 3D extrusion-based printing to fabricate gastro-floating tablets with more than 8h floating process with traditional pharmaceutical excipients and lattice internal structure design. Copyright © 2017. Published by Elsevier B.V.

Charging and shielding of a non-spherical dust grain in a plasma

NASA Astrophysics Data System (ADS)

Zhao, L.; Delzanno, G.

2013-12-01

The interaction of objects with a plasma is a classic problem of plasma physics. Originally, it was investigated in the framework of probe theory but more recently its interest has grown in connection with space and complex or dusty plasmas. It is customary to assume that the dust grains are spherical, and theories such as the Orbital Motion Limited (OML) theory are usually applied to calculate the dust charge. However, in nature dust grains have a variety of sizes and shapes. It is therefore natural to ask about the influence of the dust shape on the charging and shielding process. In order to answer this question, we study the charging and shielding of a non-spherical dust grain immersed in a Maxwellian plasma at rest. We consider prolate ellipsoids, varying parametrically the aspect ratio while keeping the surface area constant. The study is conducted with CPIC [1], a newly developed Particle-In-Cell code in curvilinear geometry that conforms to objects of arbitrary shape. For a plasma with temperature ratio equal to unity and for a dust grain with characteristic size of the order of the Debye length, it is shown that the floating potential has a very weak dependence on the geometry, while the charge on the grain increases by a factor of three when the aspect ratio changes from one (a sphere) to hundred (a needle-like ellipsoid). These results are consistent with the higher capacitance of ellipsoidal dust grains, but also indicate that the screening length depends on the geometry. Scaling studies of the dependence of the charging time and screening length on the aspect ratio and plasma conditions are presented, including theoretical considerations to support the numerical results. [1] G.L. Delzanno, et al, ';CPIC: a curvilinear Particle-In-Cell code for plasma-material interaction studies', under review.

Electron kinetics at the plasma interface

NASA Astrophysics Data System (ADS)

Bronold, Franz Xaver; Fehske, Holger; Pamperin, Mathias; Thiessen, Elena

2018-05-01

The most fundamental response of an ionized gas to a macroscopic object is the formation of the plasma sheath. It is an electron depleted space charge region, adjacent to the object, which screens the object's negative charge arising from the accumulation of electrons from the plasma. The plasma sheath is thus the positively charged part of an electric double layer whose negatively charged part is inside the wall. In the course of the Transregional Collaborative Research Center SFB/TRR24 we investigated, from a microscopic point of view, the elementary charge transfer processes responsible for the electric double layer at a floating plasma-wall interface and made first steps towards a description of the negative part of the layer inside the wall. Below we review our work in a colloquial manner, describe possible extensions, and identify key issues which need to be resolved to make further progress in the understanding of the electron kinetics across plasma-wall interfaces. Contribution to the Topical Issue "Fundamentals of Complex Plasmas", edited by Jürgen Meichsner, Michael Bonitz, Holger Fehske, Alexander Piel.

Potential Mapping of an Indium-Tin-Oxide Glass Box in a GEC Reference Cell

NASA Astrophysics Data System (ADS)

Kaplan, Rebecca; Carmona-Reyes, Jorge; Hyde, Truell; Matthews, Lorin; Casper Program Team

The use of indium-tin-oxide (ITO) coated boxes, as well as boxes coated with other substances, placed on or floating above the lower electrode in studies using Gaseous Electronics Conference Radio Frequency Reference Cells have increased in interest, as have the use of plain glass boxes. This increase in interest is due to the greater ability to control the confinement forces and in effect create dust chain structures which aid in studies within other areas of physics such as; entropy, kinetic dust temperature, plasma balls and coulomb explosions. Further analysis of the data obtained using these boxes shows what appear to be at least two different regions of confinement inside the boxes as well as some unexpected phenomena related to anomalous values and behavior of the electric field. These areas affect the dust to dust and dust to plasma interactions independently in the separate regions and are therefore of great interest. In this study electric potential and electric field maps created in MatLab with data obtained using two probes mounted on CASPER's S-100 nano-manipulator will be presented, connecting the information obtained from these maps to the behavior of the dust observed for different experimental conditions. All of this has been made possible by the opportunity and funding from the CASPER program and the National Science Foundation Grant Number PHY-1262031.

Experimental study of unipolar arcs in a low pressure mercury discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, C.T.

1979-12-31

An experimental study of unipolar arcs was conducted in a low pressure mercury discharge inductively heated with RF. The results were found to be consistent with the concept of a sheath mechanism for driving the unipolar arcs. Floating double-probe measurements of the unipolar arc plasma parameters yielded electron temperatures of approx. 2 eV and electron number densities of approx. 1 x 10/sup 11/ cm/sup -3/ assuming quasi-neutral plasma conditions. The variation of the unipolar arc current with: (1) the RF power input; and (2) the metal surface area exposed to the plasma verified the predicted dependence of the arc currentmore » on the plasma parameters and the metal surface area. Finally, alternative mechanisms for sustaining the observed arcs by high frequency rectification were ruled out on the basis of the recorded current waveforms of the unipolar arcs.« less

Interactions between large space power systems and low-Earth-orbit plasmas

NASA Technical Reports Server (NTRS)

Stevens, N. J.

1985-01-01

There is a growing tendency to plan space missions that will incorporate very large space power systems. These space power systems must function in the space plasma environment, which can impose operational limitations. As the power output increases, the operating voltage also must increase and this voltage, exposed at solar array interconnects, interacts with the local plasma. The implications of such interactions are considered. The available laboratory data for biased array segment tests are reviewed to demonstrate the basic interactions considered. A data set for a floating high voltage array test was used to generate approximate relationships for positive and negative current collection from plasmas. These relationships were applied to a hypothetical 100 kW power system operating in a 400 km, near equatorial orbit. It was found that discharges from the negative regions of the array are the most probable limiting factor in array operation.

Development of circuit model for arcing on solar panels

NASA Astrophysics Data System (ADS)

Mehta, Bhoomi K.; Deshpande, S. P.; Mukherjee, S.; Gupta, S. B.; Ranjan, M.; Rane, R.; Vaghela, N.; Acharya, V.; Sudhakar, M.; Sankaran, M.; Suresh, E. P.

2010-02-01

The increased requirements of payload capacity of the satellites have resulted in much higher power requirements of the satellites. In order to minimize the energy loss during power transmission due to cable loss, use of high voltage solar panels becomes necessary. When a satellite encounters space plasma it floats negatively with respect to the surrounding space plasma environment. At high voltage, charging and discharging on solar panels causes the power system breakdown. Once a solar panel surface is charged and potential difference between surface insulator and conductor exceeds certain value, electrostatic discharge (ESD) may occur. This ESD may trigger a secondary arc that can destroy the solar panel circuit. ESD is also called as primary or minor arc and secondary is called major arc. The energy of minor arc is supplied by the charge stored in the coverglass of solar array and is a pulse of typically several 100 ns to several 100 μs duration. The damage caused by minor arc is less compared to major arcs, but it is observed that the minor arc is cause of major arc. Therefore it is important to develop an understanding of minor arc and mitigation techniques. In this paper we present a linear circuit analysis for minor arcs on solar panels. To study arcing event, a ground experimental facility to simulate space plasma environment has been developed at Facilitation Centre for Industrial Plasma Technologies (Institute for Plasma Research) in collaboration with Indian Space Research Organization's ISRO Satellite Technology Centre (ISAC). A linear circuit model has been developed to explain the experimental results by representing the coverglass, solar cell interconnect and wiring by an LCR circuit and the primary arc by an equivalent LR circuit. The aim of the circuit analysis is to predict the arc current which flows through the arc plasma. It is established from the model that the current depends on various parameters like potential difference between insulator and conductor, arc resistance, stored charge in the solar cell coverglass and the external capacitor that simulates wire harness. A close correlation between the experiments and circuit model results has been observed.

Floating production platforms and their applications in the development of oil and gas fields in the South China Sea

NASA Astrophysics Data System (ADS)

Zhang, Dagang; Chen, Yongjun; Zhang, Tianyu

2014-03-01

This paper studies the current available options for floating production platforms in developing deepwater oil fields and the potential development models of future oil and gas exploration in the South China Sea. A detailed review of current deepwater platforms worldwide was performed through the examples of industry projects, and the pros and cons of each platform are discussed. Four types of platforms are currently used for the deepwater development: tension leg platform, Spar, semi-submersible platform, and the floating production system offloading. Among these, the TLP and Spar can be used for dry tree applications, and have gained popularity in recent years. The dry tree application enables the extension of the drilling application for fixed platforms into floating systems, and greatly reduces the cost and complexity of the subsea operation. Newly built wet tree semi-submersible production platforms for ultra deepwater are also getting their application, mainly due to the much needed payload for deepwater making the conversion of the old drilling semi-submersible platforms impossible. These platforms have been used in different fields around the world for different environments; each has its own advantages and disadvantages. There are many challenges with the successful use of these floating platforms. A lot of lessons have been learned and extensive experience accumulated through the many project applications. Key technologies are being reviewed for the successful use of floating platforms for field development, and potential future development needs are being discussed. Some of the technologies and experience of platform applications can be well used for the development of the South China Sea oil and gas field.

Compositional changes in lipid microdomains of air-blood barrier plasma membranes in pulmonary interstitial edema.

PubMed

Palestini, Paola; Calvi, Chiara; Conforti, Elena; Daffara, Rossella; Botto, Laura; Miserocchi, Giuseppe

2003-10-01

We evaluated in anesthetized rabbits the compositional changes of plasmalemmal lipid microdomains from lung tissue samples after inducing pulmonary interstitial edema (0.5 ml/kg for 3 h, leading to approximately 5% increase in extravascular water). Lipid microdomains (lipid rafts and caveolae) were present in the detergent-resistant fraction (DRF) obtained after discontinuous sucrose density gradient. DRF was enriched in caveolin-1, flotillin, aquaporin-1, GM1, cholesterol, sphingomyelin, and phosphatidylserine, and their contents significantly increased in interstitial edema. The higher DRF content in caveolin, flotillin, and aquaporin-1 and of the ganglioside GM1 suggests an increase both in caveolar domains and in lipid rafts, respectively. Compositional changes could be ascribed to endothelial and epithelial cells that provide most of plasma membrane surface area in the air-blood barrier. Alterations in lipid components in the plasma membrane may reflect rearrangement of floating lipid platforms within the membrane and/or lipid translocation from intracellular stores. Lipid traffic could be stimulated by the marked increase in hydraulic interstitial pressure after initial water accumulation, from approximately -10 to 5 cmH2O, due to the low compliance of the pulmonary tissue, in particular in the basement membranes and in the interfibrillar substance. Compositional changes in lipid microdomains represent a sign of cellular activation and suggest the potential role of mechanotransduction in response to developing interstitial edema.

Modeling Ionosphere Environments: Creating an ISS Electron Density Tool

NASA Technical Reports Server (NTRS)

Gurgew, Danielle N.; Minow, Joseph I.

2011-01-01

The International Space Station (ISS) maintains an altitude typically between 300 km and 400 km in low Earth orbit (LEO) which itself is situated in the Earth's ionosphere. The ionosphere is a region of partially ionized gas (plasma) formed by the photoionization of neutral atoms and molecules in the upper atmosphere of Earth. It is important to understand what electron density the spacecraft is/will be operating in because the ionized gas along the ISS orbit interacts with the electrical power system resulting in charging of the vehicle. One instrument that is already operational onboard the ISS with a goal of monitoring electron density, electron temperature, and ISS floating potential is the Floating Potential Measurement Unit (FPMU). Although this tool is a valuable addition to the ISS, there are limitations concerning the data collection periods. The FPMU uses the Ku band communication frequency to transmit data from orbit. Use of this band for FPMU data runs is often terminated due to necessary observation of higher priority Extravehicular Activities (EVAs) and other operations on ISS. Thus, large gaps are present in FPMU data. The purpose of this study is to solve the issue of missing environmental data by implementing a secondary electron density data source, derived from the COSMIC satellite constellation, to create a model of ISS orbital environments. Extrapolating data specific to ISS orbital altitudes, we model the ionospheric electron density along the ISS orbit track to supply a set of data when the FPMU is unavailable. This computer model also provides an additional new source of electron density data that is used to confirm FPMU is operating correctly and supplements the original environmental data taken by FPMU.

Dynamic response mitigation of floating wind turbine platforms using tuned liquid column dampers.

PubMed

Jaksic, V; Wright, C S; Murphy, J; Afeef, C; Ali, S F; Mandic, D P; Pakrashi, V

2015-02-28

In this paper, we experimentally study and compare the effects of three combinations of multiple tuned liquid column dampers (MTLCDs) on the dynamic performance of a model floating tension-leg platform (TLP) structure in a wave basin. The structural stability and safety of the floating structure during operation and maintenance is of concern for the performance of a renewable energy device that it might be supporting. The dynamic responses of the structure should thus be limited for these renewable energy devices to perform as intended. This issue is particularly important during the operation of a TLP in extreme weather conditions. Tuned liquid column dampers (TLCDs) can use the power of sloshing water to reduce surge motions of a floating TLP exposed to wind and waves. This paper demonstrates the potential of MTLCDs in reducing dynamic responses of a scaled TLP model through an experimental study. The potential of using output-only statistical markers for monitoring changes in structural conditions is also investigated through the application of a delay vector variance (DVV) marker for different conditions of control for the experiments. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Floating Offshore Wind in Hawaii: Potential for Jobs and Economic Impacts from Three Future Scenarios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jimenez, Tony; Keyser, David; Tegen, Suzanne

Construction of the first offshore wind power plant in the United States began in 2015, off the coast of Rhode Island, using fixed platform structures that are appropriate for shallow seafloors, like those located off the East Coast and mid-Atlantic. However, floating platforms, which have yet to be deployed commercially, will likely need to be anchored to the deeper seafloor if deployed in Hawaiian waters. To analyze the employment and economic potential for floating offshore wind off Hawaii's coasts, the Bureau of Ocean Energy Management commissioned the National Renewable Energy Laboratory (NREL) to analyze two hypothetical deployment scenarios for Hawaii:more » 400 MW of offshore wind by 2050 and 800 MW of offshore wind by 2050. The results of this analysis can be used to better understand the general scale of economic opportunities that could result from offshore wind development.« less

The design and implementation of the Dynamic Ionosphere Cubesat Experiment (DICE) science instruments

NASA Astrophysics Data System (ADS)

Burr, Steven Reed

Dynamic Ionosphere Cubesat Experiment (DICE) is a satellite project funded by the National Science Foundation (NSF) to study the ionosphere, more particularly Storm Enhanced Densities (SED) with a payload consisting of plasma diagnostic instrumentation. Three instruments onboard DICE include an Electric Field Probe (EFP), Ion Langmuir Probe (ILP), and Three Axis Magnetometer (TAM). The EFP measures electric fields from +/-8V and consists of three channels a DC to 40Hz channel, a Floating Potential Probe (FPP), and an spectrographic channel with four bands from 16Hz to 512Hz. The ILP measures plasma densities from 1x104 cm--3 to 2x107 cm--3. The TAM measures magnetic field strength with a range +/-0.5 Gauss with a sensitivity of 2nT. To achieve desired mission requirements careful selection of instrument requirements and planning of the instrumentation design to achieve mission success. The analog design of each instrument is described in addition to the digital framework required to sample the science data at a 70Hz rate and prepare the data for the Command and Data Handing (C&DH) system. Calibration results are also presented and show fulfillment of the mission and instrumentation requirements.

Near Real Time Tools for ISS Plasma Science and Engineering Applications

NASA Astrophysics Data System (ADS)

Minow, J. I.; Willis, E. M.; Parker, L. N.; Shim, J.; Kuznetsova, M. M.; Pulkkinen, A. A.

2013-12-01

The International Space Station (ISS) program utilizes a plasma environment forecast for estimating electrical charging hazards for crews during extravehicular activity (EVA). The process uses ionospheric electron density and temperature measurements from the ISS Floating Potential Measurement Unit (FPMU) instrument suite with the assumption that the plasma conditions will remain constant for one to fourteen days with a low probability for a space weather event which would significantly change the environment before an EVA. FPMU data is typically not available during EVA's, therefore, the most recent FPMU data available for characterizing the state of the ionosphere during EVA is typically a day or two before the start of an EVA or after the EVA has been completed. In addition to EVA support, information on ionospheric plasma densities is often needed for support of ISS science payloads and anomaly investigations during periods when the FPMU is not operating. This presentation describes the application of space weather tools developed by MSFC using data from near real time satellite radio occultation and ground based ionosonde measurements of ionospheric electron density and a first principle ionosphere model providing electron density and temperature run in a real time mode by GSFC. These applications are used to characterize the space environment during EVA periods when FPMU data is not available, monitor for large charges in ionosphere density that could render the ionosphere forecast and plasma hazard assessment invalid, and validate the assumption of 'persistence of conditions' used in deriving the hazard forecast. In addition, the tools are used to provide space environment input to science payloads on ISS and anomaly investigations during periods the FPMU is not operating.

Impact of floating windows on the accuracy of depth perception in games

NASA Astrophysics Data System (ADS)

Stanfield, Brodie; Zerebecki, Christopher; Hogue, Andrew; Kapralos, Bill; Collins, Karen

2013-03-01

The floating window technique is commonly employed by stereoscopic 3D filmmakers to reduce the effects of window violations by masking out portions of the screen that contain visual information that doesn't exist in one of the views. Although widely adopted in the film industry, and despite its potential benefits, the technique has not been adopted by video game developers to the same extent possibly because of the lack of understanding of how the floating window can be utilized in such an interactive medium. Here, we describe a quantitative study that investigates how the floating window technique affects users' depth perception in a simple game-like environment. Our goal is to determine how various stereoscopic 3D parameters such as the existence, shape, and size of the floating window affect the user experience and to devise a set of guidelines for game developers wishing to develop stereoscopic 3D content. Providing game designers with quantitative knowledge of how these parameters can affect user experience is invaluable when choosing to design interactive stereoscopic 3D content.

Nonthermal dielectric-barrier discharge plasma-induced inactivation involves oxidative DNA damage and membrane lipid peroxidation in Escherichia coli.

PubMed

Joshi, Suresh G; Cooper, Moogega; Yost, Adam; Paff, Michelle; Ercan, Utku K; Fridman, Gregory; Friedman, Gary; Fridman, Alexander; Brooks, Ari D

2011-03-01

Oxidative stress leads to membrane lipid peroxidation, which yields products causing variable degrees of detrimental oxidative modifications in cells. Reactive oxygen species (ROS) are the key regulators in this process and induce lipid peroxidation in Escherichia coli. Application of nonthermal (cold) plasma is increasingly used for inactivation of surface contaminants. Recently, we reported a successful application of nonthermal plasma, using a floating-electrode dielectric-barrier discharge (FE-DBD) technique for rapid inactivation of bacterial contaminants in normal atmospheric air (S. G. Joshi et al., Am. J. Infect. Control 38:293-301, 2010). In the present report, we demonstrate that FE-DBD plasma-mediated inactivation involves membrane lipid peroxidation in E. coli. Dose-dependent ROS, such as singlet oxygen and hydrogen peroxide-like species generated during plasma-induced oxidative stress, were responsible for membrane lipid peroxidation, and ROS scavengers, such as α-tocopherol (vitamin E), were able to significantly inhibit the extent of lipid peroxidation and oxidative DNA damage. These findings indicate that this is a major mechanism involved in FE-DBD plasma-mediated inactivation of bacteria.

Nonthermal Dielectric-Barrier Discharge Plasma-Induced Inactivation Involves Oxidative DNA Damage and Membrane Lipid Peroxidation in Escherichia coli▿

PubMed Central

Joshi, Suresh G.; Cooper, Moogega; Yost, Adam; Paff, Michelle; Ercan, Utku K.; Fridman, Gregory; Friedman, Gary; Fridman, Alexander; Brooks, Ari D.

2011-01-01

Oxidative stress leads to membrane lipid peroxidation, which yields products causing variable degrees of detrimental oxidative modifications in cells. Reactive oxygen species (ROS) are the key regulators in this process and induce lipid peroxidation in Escherichia coli. Application of nonthermal (cold) plasma is increasingly used for inactivation of surface contaminants. Recently, we reported a successful application of nonthermal plasma, using a floating-electrode dielectric-barrier discharge (FE-DBD) technique for rapid inactivation of bacterial contaminants in normal atmospheric air (S. G. Joshi et al., Am. J. Infect. Control 38:293-301, 2010). In the present report, we demonstrate that FE-DBD plasma-mediated inactivation involves membrane lipid peroxidation in E. coli. Dose-dependent ROS, such as singlet oxygen and hydrogen peroxide-like species generated during plasma-induced oxidative stress, were responsible for membrane lipid peroxidation, and ROS scavengers, such as α-tocopherol (vitamin E), were able to significantly inhibit the extent of lipid peroxidation and oxidative DNA damage. These findings indicate that this is a major mechanism involved in FE-DBD plasma-mediated inactivation of bacteria. PMID:21199923

Density-transition scale at quasiperpendicular collisionless shocks.

PubMed

Bale, S D; Mozer, F S; Horbury, T S

2003-12-31

Measurements of a spacecraft floating potential, on the four Cluster spacecraft, are used as a proxy for electron plasma density to study, for the first time, the macroscopic density transition scale at 98 crossings of the quasiperpendicular terrestrial bow shock. A timing analysis gives shock speeds and normals; the shock speed is used to convert the temporal measurement to a spatial one. A hyperbolic tangent function is fitted to each density transition, which captures the main shock transition, but not overshoot or undershoot nor foot features. We find that, at a low Mach number M, the density transition is consistent with both ion inertial scales c/omega(pi) and convected gyroradii v(sh,n)/Omega(ci,2), while at M>/=4-5 only the convected gyroradius is the preferred scale for the shock density transition and takes the value L approximately 0.4v(sh,n)/Omega(ci,2).

A compact, smart Langmuir Probe control module for MAST-Upgrade

NASA Astrophysics Data System (ADS)

Lovell, J.; Stephen, R.; Bray, S.; Naylor, G.; Elmore, S.; Willett, H.; Peterka, M.; Dimitrova, M.; Havranek, A.; Hron, M.; Sharples, R.

2017-11-01

A new control module for the MAST-Upgrade Langmuir Probe system has been developed. It is based on a Xilinx Zynq FPGA, which allows for excellent configurability and ease of retrieving data. The module is capable of arbitrary bias voltage waveform generation, and digitises current and voltage readings from 16 probes. The probes are biased and measured one at a time in a time multiplexed fashion, with the multiplexing sequence completely configurable. In addition, simultaneous digitisation of the floating potential of all unbiased probes is possible. A suite of these modules, each coupled with a high voltage amplifier, enables biasing and digitisation of 640 Langmuir Probes in the MAST-Upgrade Super-X divertor. The system has been successfully tested on the York Linear Plasma Device and on the COMPASS tokamak. It will be installed on MAST-Upgrade ready for operations in 2018.

Environmentally-induced voltage limitations in large space power systems

NASA Technical Reports Server (NTRS)

Stevens, N. J.

1984-01-01

Large power systems proposed for future space missions imply higher operating voltage requirements which, in turn, will interact with the space plasma environment. The effects of these interactions can only be inferred because of the limited data base of ground simulations, small test samples, and two space flight experiments. This report evaluates floating potentials for a 100 kW power system operating at 300, 500, 750, and 1000 volts in relation to this data base. Of primary concern is the possibility of discharging to space. The implications of such discharges were studied at the 500 volt operational setting. It was found that discharging can shut down the power system if the discharge current exceeds the array short circuit current. Otherwise, a power oscillation can result that ranges from 2 to 20 percent, depending upon the solar array area involved in the discharge. Means of reducing the effect are discussed.

A Flexible VHDL Floating Point Module for Control Algorithm Implementation in Space Applications

NASA Astrophysics Data System (ADS)

Padierna, A.; Nicoleau, C.; Sanchez, J.; Hidalgo, I.; Elvira, S.

2012-08-01

The implementation of control loops for space applications is an area with great potential. However, the characteristics of this kind of systems, such as its wide dynamic range of numeric values, make inadequate the use of fixed-point algorithms.However, because the generic chips available for the treatment of floating point data are, in general, not qualified to operate in space environments and the possibility of using an IP module in a FPGA/ASIC qualified for space is not viable due to the low amount of logic cells available for these type of devices, it is necessary to find a viable alternative.For these reasons, in this paper a VHDL Floating Point Module is presented. This proposal allows the design and execution of floating point algorithms with acceptable occupancy to be implemented in FPGAs/ASICs qualified for space environments.

A study of rotor and platform design trade-offs for large-scale floating vertical axis wind turbines

NASA Astrophysics Data System (ADS)

Griffith, D. Todd; Paquette, Joshua; Barone, Matthew; Goupee, Andrew J.; Fowler, Matthew J.; Bull, Diana; Owens, Brian

2016-09-01

Vertical axis wind turbines are receiving significant attention for offshore siting. In general, offshore wind offers proximity to large populations centers, a vast & more consistent wind resource, and a scale-up opportunity, to name a few beneficial characteristics. On the other hand, offshore wind suffers from high levelized cost of energy (LCOE) and in particular high balance of system (BoS) costs owing to accessibility challenges and limited project experience. To address these challenges associated with offshore wind, Sandia National Laboratories is researching large-scale (MW class) offshore floating vertical axis wind turbines (VAWTs). The motivation for this work is that floating VAWTs are a potential transformative technology solution to reduce offshore wind LCOE in deep-water locations. This paper explores performance and cost trade-offs within the design space for floating VAWTs between the configurations for the rotor and platform.

Floating plastic debris in the Central and Western Mediterranean Sea.

PubMed

Ruiz-Orejón, Luis F; Sardá, Rafael; Ramis-Pujol, Juan

2016-09-01

In two sea voyages throughout the Mediterranean (2011 and 2013) that repeated the historical travels of Archduke Ludwig Salvator of Austria (1847-1915), 71 samples of floating plastic debris were obtained with a Manta trawl. Floating plastic was observed in all the sampled sites, with an average weight concentration of 579.3 g dw km(-2) (maximum value of 9298.2 g dw km(-2)) and an average particle concentration of 147,500 items km(-2) (the maximum concentration was 1,164,403 items km(-2)). The plastic size distribution showed microplastics (<5 mm) in all the samples. The most abundant particles had a surface area of approximately 1 mm(2) (the mesh size was 333 μm). The general estimate obtained was a total value of 1455 tons dw of floating plastic in the entire Mediterranean region, with various potential spatial accumulation areas. Copyright © 2016 Elsevier Ltd. All rights reserved.

Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and Their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm

NASA Technical Reports Server (NTRS)

Coffey, Victoria; Sazykin, Stan; Chandler, Michael; Hairston, Marc; Minow, Joseph; Anderson, Brian

2017-01-01

The magnetic storm that commenced on June 22, 2015 was one of the largest storms in the current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated interplanetary shock waves. On June 22 at 18:36 UT the magnetosphere was impacted by the leading-edge shock wave and a sheath carrying a large and highly variable interplanetary magnetic field (IMF) Bz with values ranging from +25 to -40 nT. During the subsequent interval from 0000 to 0800 UT, there was a second intensification of the geomagnetic storm resulting from the impact of the CME. We present dramatic responses of simultaneous particle measurements from the high-altitude Magnetospheric Multiscale Mission (MMS) at high altitudes in the magnetosphere (approx. 9-12 Re) and from the low-altitude (F-region) Floating Potential Measurement Unit (FPMU) on board the International Space Station (ISS). We analyze potential causes of these dramatic particle flux dropouts by putting them in the context of storm-time electrodynamics, and support our results with numerical simulations of the global magnetosphere and ionosphere. During the sheath phase of the storm, the MMS spacecraft in the near-earth equatorial plane observed a rapid reconfiguration of the magnetic field near 1923 UT. Initially in the warm plasma sheet, particle flux dropouts were observed as they tracked the plasma-sheet to lobe transitions with the stretching and thinning of the plasma sheet. Anti-sunward flowing O+ ions of ionospheric origin were also measured during this period, confirming that the MMS spacecraft temporarily was in a lobe.

Diagnostic evaluations of a beam-shielded 8-cm mercury ion thruster

NASA Technical Reports Server (NTRS)

Nakanishi, S.

1978-01-01

An engineering model thruster fitted with a remotely actuated graphite fiber polyimide composite beam shield was tested in a 3- by 6.5-meter vacuum facility for in-situ assessment of beam shield effects on thruster performance. Accelerator drain current neutralizer floating potential and ion beam floating potential increased slightly when the shield was moved into position. A target exposed to the low density regions of the ion beam was used to map the boundaries of energetic fringe ions capable of sputtering. The particle efflux was evaluated by measurement of film deposits on cold, heated, bare, and enclosed glass slides.

Incident Energy Focused Design and Validation for the Floating Potential Probe

NASA Technical Reports Server (NTRS)

Fincannon, James

2002-01-01

Utilizing the spacecraft shadowing and incident energy analysis capabilities of the NASA Glenn Research Center Power and Propulsion Office's SPACE System Power Analysis for Capability Evaluation) computer code, this paper documents the analyses for various International Space Station (ISS) Floating Potential Probe (EPP) preliminary design options. These options include various solar panel orientations and configurations as well as deployment locations on the ISS. The incident energy for the final selected option is characterized. A good correlation between the predicted data and on-orbit operational telemetry is demonstrated. Minor deviations are postulated to be induced by degradation or sensor drift.

Dispersive liquid-liquid microextraction based on the solidification of floating organic drop followed by ICP-MS for the simultaneous determination of heavy metals in wastewaters

NASA Astrophysics Data System (ADS)

Li, Yong; Peng, Guilong; He, Qiang; Zhu, Hui; Al-Hamadani, Sulala M. Z. F.

2015-04-01

In the present work, a dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) combined with inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of Pb, Co, Cu, Ni, Zn. The influences of analytical parameters, including pH, extraction solvent volume, disperser solvent volume, concentration of chelating agent on the quantitative recoveries of Pb, Co, Cu, Ni, Zn were investigated. The effect of the interfering ions on the analytes recovery was also investigated. Under the optimized conditions, the limits of detection were 0.97-2.18 ng L-1. The relative standard deviations (RSDs) were 2.62-4.51% (n = 7, C = 20 ng L-1). The proposed method was successfully applied for the analysis of ultra trace metals in wastewater samples.

Solution processed molecular floating gate for flexible flash memories

NASA Astrophysics Data System (ADS)

Zhou, Ye; Han, Su-Ting; Yan, Yan; Huang, Long-Biao; Zhou, Li; Huang, Jing; Roy, V. A. L.

2013-10-01

Solution processed fullerene (C60) molecular floating gate layer has been employed in low voltage nonvolatile memory device on flexible substrates. We systematically studied the charge trapping mechanism of the fullerene floating gate for both p-type pentacene and n-type copper hexadecafluorophthalocyanine (F16CuPc) semiconductor in a transistor based flash memory architecture. The devices based on pentacene as semiconductor exhibited both hole and electron trapping ability, whereas devices with F16CuPc trapped electrons alone due to abundant electron density. All the devices exhibited large memory window, long charge retention time, good endurance property and excellent flexibility. The obtained results have great potential for application in large area flexible electronic devices.

Solution processed molecular floating gate for flexible flash memories

PubMed Central

Zhou, Ye; Han, Su-Ting; Yan, Yan; Huang, Long-Biao; Zhou, Li; Huang, Jing; Roy, V. A. L.

2013-01-01

Solution processed fullerene (C60) molecular floating gate layer has been employed in low voltage nonvolatile memory device on flexible substrates. We systematically studied the charge trapping mechanism of the fullerene floating gate for both p-type pentacene and n-type copper hexadecafluorophthalocyanine (F16CuPc) semiconductor in a transistor based flash memory architecture. The devices based on pentacene as semiconductor exhibited both hole and electron trapping ability, whereas devices with F16CuPc trapped electrons alone due to abundant electron density. All the devices exhibited large memory window, long charge retention time, good endurance property and excellent flexibility. The obtained results have great potential for application in large area flexible electronic devices. PMID:24172758

Direct probing of electron and hole trapping into nano-floating-gate in organic field-effect transistor nonvolatile memories

NASA Astrophysics Data System (ADS)

Cui, Ze-Qun; Wang, Shun; Chen, Jian-Mei; Gao, Xu; Dong, Bin; Chi, Li-Feng; Wang, Sui-Dong

2015-03-01

Electron and hole trapping into the nano-floating-gate of a pentacene-based organic field-effect transistor nonvolatile memory is directly probed by Kelvin probe force microscopy. The probing is straightforward and non-destructive. The measured surface potential change can quantitatively profile the charge trapping, and the surface characterization results are in good accord with the corresponding device behavior. Both electrons and holes can be trapped into the nano-floating-gate, with a preference of electron trapping than hole trapping. The trapped charge quantity has an approximately linear relation with the programming/erasing gate bias, indicating that the charge trapping in the device is a field-controlled process.

Profile measurements of the electron temperature on the ASDEX Upgrade, COMPASS, and ISTTOK tokamak using Thomson scattering, triple, and ball-pen probes

NASA Astrophysics Data System (ADS)

Adamek, J.; Müller, H. W.; Silva, C.; Schrittwieser, R.; Ionita, C.; Mehlmann, F.; Costea, S.; Horacek, J.; Kurzan, B.; Bilkova, P.; Böhm, P.; Aftanas, M.; Vondracek, P.; Stöckel, J.; Panek, R.; Fernandes, H.; Figueiredo, H.

2016-04-01

The ball-pen probe (BPP) technique is used successfully to make profile measurements of the electron temperature on the ASDEX Upgrade (Axially Symmetric Divertor Experiment), COMPASS (COMPact ASSembly), and ISTTOK (Instituto Superior Tecnico TOKamak) tokamak. The electron temperature is provided by a combination of the BPP potential (ΦBPP) and the floating potential (Vfl) of the Langmuir probe (LP), which is compared with the Thomson scattering diagnostic on ASDEX Upgrade and COMPASS. Excellent agreement between the two diagnostics is obtained for circular and diverted plasmas and different heating mechanisms (Ohmic, NBI, ECRH) in deuterium discharges with the same formula Te = (ΦBPP - Vfl)/2.2. The comparative measurements of the electron temperature using BPP/LP and triple probe (TP) techniques on the ISTTOK tokamak show good agreement of averaged values only inside the separatrix. It was also found that the TP provides the electron temperature with significantly higher standard deviation than BPP/LP. However, the resulting values of both techniques are well in the phase with the maximum of cross-correlation function being 0.8.

Profile measurements of the electron temperature on the ASDEX Upgrade, COMPASS, and ISTTOK tokamak using Thomson scattering, triple, and ball-pen probes.

PubMed

Adamek, J; Müller, H W; Silva, C; Schrittwieser, R; Ionita, C; Mehlmann, F; Costea, S; Horacek, J; Kurzan, B; Bilkova, P; Böhm, P; Aftanas, M; Vondracek, P; Stöckel, J; Panek, R; Fernandes, H; Figueiredo, H

2016-04-01

The ball-pen probe (BPP) technique is used successfully to make profile measurements of the electron temperature on the ASDEX Upgrade (Axially Symmetric Divertor Experiment), COMPASS (COMPact ASSembly), and ISTTOK (Instituto Superior Tecnico TOKamak) tokamak. The electron temperature is provided by a combination of the BPP potential (ΦBPP) and the floating potential (Vfl) of the Langmuir probe (LP), which is compared with the Thomson scattering diagnostic on ASDEX Upgrade and COMPASS. Excellent agreement between the two diagnostics is obtained for circular and diverted plasmas and different heating mechanisms (Ohmic, NBI, ECRH) in deuterium discharges with the same formula Te = (ΦBPP - Vfl)/2.2. The comparative measurements of the electron temperature using BPP/LP and triple probe (TP) techniques on the ISTTOK tokamak show good agreement of averaged values only inside the separatrix. It was also found that the TP provides the electron temperature with significantly higher standard deviation than BPP/LP. However, the resulting values of both techniques are well in the phase with the maximum of cross-correlation function being 0.8.

Dynamics modeling and loads analysis of an offshore floating wind turbine

NASA Astrophysics Data System (ADS)

Jonkman, Jason Mark

The vast deepwater wind resource represents a potential to use offshore floating wind turbines to power much of the world with renewable energy. Many floating wind turbine concepts have been proposed, but dynamics models, which account for the wind inflow, aerodynamics, elasticity, and controls of the wind turbine, along with the incident waves, sea current, hydrodynamics, and platform and mooring dynamics of the floater, were needed to determine their technical and economic feasibility. This work presents the development of a comprehensive simulation tool for modeling the coupled dynamic response of offshore floating wind turbines, the verification of the simulation tool through model-to-model comparisons, and the application of the simulation tool to an integrated loads analysis for one of the promising system concepts. A fully coupled aero-hydro-servo-elastic simulation tool was developed with enough sophistication to address the limitations of previous frequency- and time-domain studies and to have the features required to perform loads analyses for a variety of wind turbine, support platform, and mooring system configurations. The simulation capability was tested using model-to-model comparisons. The favorable results of all of the verification exercises provided confidence to perform more thorough analyses. The simulation tool was then applied in a preliminary loads analysis of a wind turbine supported by a barge with catenary moorings. A barge platform was chosen because of its simplicity in design, fabrication, and installation. The loads analysis aimed to characterize the dynamic response and to identify potential loads and instabilities resulting from the dynamic couplings between the turbine and the floating barge in the presence of combined wind and wave excitation. The coupling between the wind turbine response and the barge-pitch motion, in particular, produced larger extreme loads in the floating turbine than experienced by an equivalent land-based turbine. Instabilities were also found in the system. The influence of conventional wind turbine blade-pitch control actions on the pitch damping of the floating turbine was also assessed. Design modifications for reducing the platform motions, improving the turbine response, and eliminating the instabilities are suggested. These suggestions are aimed at obtaining cost-effective designs that achieve favorable performance while maintaining structural integrity.

The effect of Taurolidine on adherent and floating subpopulations of melanoma cells.

PubMed

Shrayer, D P; Lukoff, H; King, T; Calabresi, P

2003-04-01

The annual incidence of malignant melanoma is estimated at 10-12 per 100000 inhabitants in countries of Central Europe and the US, with more recent estimates showing a dramatic upward trend. Taurolidine (Carter/Wallace, Cranberry, NJ) is a novel, potentially effective, antitumor chemotherapeutic agent. We hypothesized that Taurolidine could inhibit the growth, induce apoptosis, affect the cell cycle and change morphology of melanoma cells. We expected this process to be different in adherent and floating subpopulations that may be reflective of solid tumors and their metastases. Analysis of MNT-1 human and B16F10 murine melanoma cells showed that at 72 h the IC(50) of Taurolidine was 25.4+/-3.3 microM for MNT-1 human melanoma cells and 30.9+/-3.6 microM for B16F10 murine melanoma cells. Taurolidine induced DNA fragmentation of melanoma cells in a dose-dependent manner. Taurolidine (75 and 100 microM) induced 52-97% Annexin-V binding (apoptosis), respectively. Evaluation of cell cycle after 72 h exposure to Taurolidine (0-100 microM) revealed that the percentage of melanoma cells in S phase increased from 27 to 40% in the adherent subpopulation and from 33 to 49% in the floating subpopulation. Phase contrast microscopy revealed a marked swelling of melanoma cells and decreasing cell numbers in adherent subpopulation starting at 24 h with 25 microM Taurolidine. Shrinkage of cells dominated at 75-100 microM Taurolidine. Using Cytospin assay in the floating population, we observed swelling of melanoma cells induced by 25-100 micro Taurolidine and appearance of giant (multinuclear) forms resulting from exposure to 75-100 micro Taurolidine. Some floating cells with normal morphology were observed with low concentrations of Taurolidine (0-25 microM). These data show that effects of Taurolidine may be different in adherent and floating subpopulations of melanoma cells. More importantly, floating subpopulations that may contain some viable melanoma cells, may be reflective of potential metastasis after treatment of solid tumors in vivo.

Atomic oxygen behavior at downstream of AC excited atmospheric pressure He plasma jet

NASA Astrophysics Data System (ADS)

Takeda, Keigo; Ishikawa, Kenji; Tanaka, Hiromasa; Sekine, Makoto; Hori, Masaru

2016-09-01

Applications of atmospheric pressure plasma jets (APPJ) have been investigated in the plasma medical fields such as cancer therapy, blood coagulation, etc. Reactive species generated by the plasma jet interacts with the biological surface. Therefore, the issue attracts much attentions to investigate the plasma effects on targets. In our group, a spot-size AC excited He APPJ have been used for the plasma medicine. From diagnostics of the APPJ using optical emission spectroscopy, the gas temperature and the electron density was estimated to be 299 K and 3.4 ×1015 cm-3. The AC excited He APPJ which affords high density plasma at room temperature is considered to be a powerful tool for the medical applications. In this study, by using vacuum ultraviolet absorption spectroscopy, the density of atomic oxygen on a floating copper as a target irradiated by the He APPJ was measured as a function of the distance between the plasma source and the copper wire. The measured density became a maximum value around 8 ×1013 cm-3 at 12 mm distance, and then decreased over the distance. It is considered that the behavior was due to the changes in the plasma density on the copper wire and influence of ambient air.

Preliminary investigation of high power microwave plasmas for electrothermal thruster use

NASA Technical Reports Server (NTRS)

Power, John L.; Sullivan, Daniel J.

1993-01-01

Results are reported from preliminary tests to evaluate the high power microwave electrothermal thruster (MET) concept, which employs a free-floating plasma discharge maintained by applied CW microwave power to heat a propellant gas flow. Stable plasmas have been created and maintained in helium (He), nitrogen (N2), and hydrogen (H2) as propellants in both the TM(sub 011) and TM(sub 012) modes at discharge pressures from 10 Pa to 69 kPa. Reproducible starting conditions of pressure and power have been documented for all the plasmas. Vortical inflow of the propellant gas was observed to cause the formation of on-axis 'spike' plasmas. The formation and unformation conditions of these plasmas were studied. Operation in the spike plasma condition enables maximum power absorption with minimum wall heating and offers maximum efficiency in heating the propellant gas. In the spike condition, plasmas of the three propellant gases were investigated in an open channel configuration to a maximum applied power level of 11.2 kW (in N2). Microwave power coupling efficiencies of over 90 percent were routinely obtained at absorbed power levels up to 2 kW. Magnetic nozzle effects were investigated with a superconducting solenoid Al magnet applying a high magnetic field to the plasmas in and exiting from the discharge tube.

Drift trajectories of a floating human body simulated in a hydraulic model of Puget Sound.

PubMed

Ebbesmeyer, C C; Haglund, W D

1994-01-01

After a young man jumped off a 221-foot (67 meters) high bridge, the drift of the body that beached 20 miles (32 km) away at Alki Point in Seattle, Washington was simulated with a hydraulic model. Simulations for the appropriate time period were performed using a small floating bead to represent the body in the hydraulic model at the University of Washington. Bead movements were videotaped and transferred to Computer Aided Drafting (AutoCAD) charts on a personal computer. Because of strong tidal currents in the narrow passage under the bridge (The Narrows near Tacoma, WA), small changes in the time of the jump (+/- 30 minutes) made large differences in the distance the body traveled (30 miles; 48 km). Hydraulic and other types of oceanographic models may be located by contacting technical experts known as physical oceanographers at local universities, and can be utilized to demonstrate trajectories of floating objects and the time required to arrive at selected locations. Potential applications for forensic death investigators include: to be able to set geographic and time limits for searches; determine potential origin of remains found floating or beached; and confirm and correlate information regarding entry into the water and sightings of remains.

Comparison of potentially pathogenic free-living amoeba hosts by Legionella spp. in substrate-associated biofilms and floating biofilms from spring environments.

PubMed

Hsu, Bing-Mu; Huang, Chin-Chun; Chen, Jung-Sheng; Chen, Nai-Hsiung; Huang, Jen-Te

2011-10-15

This study compares five genera of free-living amoebae (FLA) hosts by Legionella spp. in the fixed and floating biofilm samples from spring environments. Detection rate of Legionella spp. was 26.9% for the floating biofilms and 3.1% for the fixed biofilms. Acanthamoeba spp., Hartmanella vermiformis, and Naegleria spp. were more frequently detected in floating biofilm than in fixed biofilm samples. The percentage of pathogenic Acanthamoeba spp. among all the genus Acanthamoeba detected positive samples was 19.6%. The potential pathogenic Naegleria spp. (for example, Naegleria australiensis, Naegleria philippinensis, and Naegleria italica) was 54.2% to all the Naegleria detected positive samples. In the study, 12 serotypes of possible pneumonia causing Legionella spp. were detected, and their percentage in all the Legionella containing samples was 42.4%. The FLA parasitized by Legionella included unnamed Acanthamoeba genotype, Acanthamoeba griffini, Acanthamoeba jacobsi, H. vermiformis, and N. australiensis. Significant differences were also observed between the presence/absence of H. vermiformis and Legionella parasitism in FLA. Comparisons between the culture-confirmed method and the PCR-based detection method for detecting FLA and Legionella in biofilms showed great variation. Therefore, using these analysis methods together to detect FLA and Legionella is recommended. Copyright © 2011 Elsevier Ltd. All rights reserved.

Cascade Analysis of a Floating Wind Turbine Rotor

NASA Astrophysics Data System (ADS)

Eliassen, Lene; Jakobsen, Jasna B.; Knauer, Andreas; Nielsen, Finn Gunnar

2014-12-01

Mounting a wind turbine on a floating foundation introduces more complexity to the aerodynamic loading. The floater motion contains a wide range of frequencies. To study some of the basic dynamic load effect on the blades due to these motions, a two-dimensional cascade approach, combined with a potential vortex method, is used. This is an alternative method to study the aeroelastic behavior of wind turbines that is different from the traditional blade element momentum method. The analysis tool demands little computational power relative to a full three dimensional vortex method, and can handle unsteady flows. When using the cascade plane, a "cut" is made at a section of the wind turbine blade. The flow is viewed parallel to the blade axis at this cut. The cascade model is commonly used for analysis of turbo machineries. Due to the simplicity of the code it requires little computational resources, however it has limitations in its validity. It can only handle two-dimensional potential flow, i.e. including neither three-dimensional effects, such as the tip loss effect, nor boundary layers and stall effects are modeled. The computational tool can however be valuable in the overall analysis of floating wind turbines, and evaluation of the rotor control system. A check of the validity of the vortex panel code using an airfoil profile is performed, comparing the variation of the lift force, to the theoretically derived Wagner function. To analyse the floating wind turbine, a floating structure with hub height 90 m is chosen. An axial motion of the rotor is considered.

Quantifying Thin Mat Floating Marsh Strength and Interaction with Hydrodynamic Conditions

NASA Astrophysics Data System (ADS)

Collins, J. H., III; Sasser, C.; Willson, C. S.

2016-12-01

Louisiana possesses over 350,000 acres of unique floating vegetated systems known as floating marshes or flotants. Floating marshes make up 70% of the Terrebonne and Barataria basin wetlands and exist in several forms, mainly thick mat or thin mat. Salt-water intrusion, nutria grazing, and high-energy wave events are believed to be some contributing factors to the degradation of floating marshes; however, there has been little investigation into the hydrodynamic effects on their structural integrity. Due to their unique nature, floating marshes could be susceptible to changes in the hydrodynamic environment that may result from proposed river freshwater and sediment diversion projects introducing flow to areas that are typically somewhat isolated. This study aims to improve the understanding of how thin mat floating marshes respond to increased hydrodynamic stresses and, more specifically, how higher water velocities might increase the washout probability of this vegetation type. There are two major components of this research: 1) A thorough measurement of the material properties of the vegetative mats as a root-soil matrix composite material; and 2) An accurate numerical simulation of the hydrodynamics and forces imposed on the floating marsh mats by the flow. To achieve these goals, laboratory and field experiments were conducted using a customized device to measure the bulk properties of typical floating marshes. Additionally, Delft-3D FLOW and ANSYS FLUENT were used to simulate the flow around a series of simplified mat structures in order to estimate the hydrodynamic forcings on the mats. The hydrodynamic forcings are coupled with a material analysis, allowing for a thorough analysis of their interaction under various conditions. The 2-way Fluid Structure Interaction (F.S.I.) between the flow and the mat is achieved by coupling a Finite Element Analysis (F.E.A.) solver in ANSYS with FLUENT. The flow conditions necessary for the structural failure of the floating marshes are determined for a multitude of mat shapes and sizes, leading to a quantifiable critical velocity required for washout. Ultimately, through dimensional analysis, an equation for washout potential will be developed from the results, which could be used as a design guideline.

Analysis of the meal-dependent intragastric performance of a gastric-retentive tablet assessed by magnetic resonance imaging.

PubMed

Steingoetter, A; Kunz, P; Weishaupt, D; Mäder, K; Lengsfeld, H; Thumshirn, M; Boesiger, P; Fried, M; Schwizer, W

2003-10-01

Modern medical imaging modalities can trace labelled oral drug dosage forms in the gastrointestinal tract, and thus represent important tools for the evaluation of their in vivo performance. The application of gastric-retentive drug delivery systems to improve bioavailability and to avoid unwanted plasma peak concentrations of orally administered drugs is of special interest in clinical and pharmaceutical research. To determine the influence of meal composition and timing of tablet administration on the intragastric performance of a gastric-retentive floating tablet using magnetic resonance imaging in the sitting position. A tablet formulation was labelled with iron oxide particles as negative magnetic resonance contrast marker to allow the monitoring of the tablet position in the food-filled human stomach. Labelled tablet was administered, together with three different solid meals, to volunteers seated in a 0.5-T open-configuration magnetic resonance system. Volunteers were followed over a 4-h period. Labelled tablet was detectable in all subjects throughout the entire study. The tablet showed persistent good intragastric floating performance independent of meal composition. Unfavourable timing of tablet administration had a minor effect on the intragastric tablet residence time and floating performance. Magnetic resonance imaging can reliably monitor and analyse the in vivo performance of labelled gastric-retentive tablets in the human stomach.

[The Mechanism of Free-Floating Discussion in a Psychiatric/Mental Health Nursing Supervisory Group].

PubMed

Chiang, Hsien-Hsien

2015-06-01

Although the free-floating discussion format is widely used in group therapy, the application of this format in the context of supervisory groups has yet to be clarified. The purpose of this study was to explore the mechanisms involved in facilitating and learning the free-floating discussion format in a supervisory group. A phenomenological approach was used to investigate the group content and personal feedback of a psychiatric-nurse supervisory group. The group held on 12 sessions. Each session was conducted once weekly and lasting 150 minutes. The findings identified the functions of free-floating discussions in the context of supervisory groups as: embodied interaction and initiation by handling. Embodied interaction included: reflection on the experience of the other, sense of body, and present action. Initiation by handling included: facilitating the self-narrative, following the lead of the group, and reflecting in accordance with the group. The role of the facilitator is to parallel process rather than to lead in order to produce practical wisdom. Free-floating discussion and self-evidence from initiation by handling has the potential to promote spontaneity, creativity, and self-confidence in clinical practice and to promote deep learning.

The application of ceramsite ecological floating bed in aquaculture: its effects on water quality, phytoplankton, bacteria and fish production.

PubMed

Li, Xiao-Li; Marella, Thomas Kiran; Tao, Ling; Dai, Li-Li; Peng, Liang; Song, Chao-Feng; Li, Gu

2018-06-01

In recent years, biological floating bed technology has been applied increasingly in aquaculture ponds. In this study we developed a novel floating bed made from ceramsite and studied its effect on water quality, phytoplankton, bacteria and fish growth. Water quality was effectively regulated and controlled in ceramsite floating bed (CFB) ponds with an average transparency of 23.18 cm, ammonia nitrogen (NH 4 + -N) of 2.30 mg L -1 , total nitrogen (TN) of 5.09 mg L -1 and total phosphate (TP) of 1.32 mg L -1 which are lower than in control ponds without CFB. Increased phytoplankton species diversity, bacterial number, metabolic activity and microbial diversity was observed with CFB. At the end of growth stage, feed conversion ratio (FCR) was reduced with a total fish yield of 14,838 kg ha -1 at a survival rate of 77.2% in CFB ponds, which is significantly higher than control (P < 0.05). These results emphasize the potential of ecological floating bed to improve water quality, microalgal diversity, reduce the risk of harmful algal blooms and increase the number, activity and diversity of microorganisms as well as fish yield.

Outer midplane scrape-off layer profiles and turbulence in simulations of Alcator C-Mod inner-wall limited discharges

DOE PAGES

Halpern, Federico D.; LaBombard, Brian; Terry, James L.; ...

2017-06-27

A region of steep plasma gradients, the so-called ”narrow-feature”, has been found in the near scrape-off layer (SOL) of inner-wall limited (IWL) discharges. Dedicated IWL discharges were carried out in Alcator C-Mod [E.S. Marmar et al., Nucl. Fusion 55, (2015)] to study this phenomenon, allowing detailed observations of the plasma profiles and fluctuations. Langmuir probe (LP) measurements show a clear two decay length n e and T e profile structure at the outer midplane. The Gas-Puff Imaging (GPI) diagnostic shows large turbulent fluctuations across the last closed flux-surface, hence supporting the hypothesis that turbulent phenomena play a role in settingmore » the profile steepness. We have carried out the flux-driven non-linear turbulence simulations of two C-Mod discharges which allows a three-way comparison between LP, GPI, and simulation data. Observations and simulations correlate the steep gradient region characterizing the narrow feature with sheared poloidal flows and a deviation of the plasma potential from its floating value. Furthermore, the E x B shear rate exceeds the linear ballooning growth rate, indicating that the narrow feature could result from the effects of sheared flows, although causality could not be established. The fluctuation level in the narrow feature remains of order unity across the entire SOL, indicating that the transport reduction in the near-SOL cannot result from a simple quench rule.« less

Outer midplane scrape-off layer profiles and turbulence in simulations of Alcator C-Mod inner-wall limited discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halpern, Federico D.; LaBombard, Brian; Terry, James L.

A region of steep plasma gradients, the so-called ”narrow-feature”, has been found in the near scrape-off layer (SOL) of inner-wall limited (IWL) discharges. Dedicated IWL discharges were carried out in Alcator C-Mod [E.S. Marmar et al., Nucl. Fusion 55, (2015)] to study this phenomenon, allowing detailed observations of the plasma profiles and fluctuations. Langmuir probe (LP) measurements show a clear two decay length n e and T e profile structure at the outer midplane. The Gas-Puff Imaging (GPI) diagnostic shows large turbulent fluctuations across the last closed flux-surface, hence supporting the hypothesis that turbulent phenomena play a role in settingmore » the profile steepness. We have carried out the flux-driven non-linear turbulence simulations of two C-Mod discharges which allows a three-way comparison between LP, GPI, and simulation data. Observations and simulations correlate the steep gradient region characterizing the narrow feature with sheared poloidal flows and a deviation of the plasma potential from its floating value. Furthermore, the E x B shear rate exceeds the linear ballooning growth rate, indicating that the narrow feature could result from the effects of sheared flows, although causality could not be established. The fluctuation level in the narrow feature remains of order unity across the entire SOL, indicating that the transport reduction in the near-SOL cannot result from a simple quench rule.« less

Monitoring of the Spacecraft Potential in the Magetosphere With a Double Probe Instrument

NASA Astrophysics Data System (ADS)

Laakso, H.

1998-11-01

Measurements of the double probe instrument can be used for monitoring the variation of the spacecraft potential Vs in tenuous plasmas where the satellite usually floats at a positive potential. This study deals with the Vs variation of the Polar satellite in the magnetosphere, using three and half years of data in 1996-99. The observations are binned with the Kp index in order to investigate how the level of geomagnetic activity affects the average surface potential. Two different antenna baselines are used, 6 and 60 meters, which both can be used for monitoring the spacecraft potential. In a low-density environment, however, the short antenna measurements are more influenced by the charging sheath of the satellite, but the data are nevertheless qualitatively useful. In burst mode the sampling rate of the double probe experiment is 1-8 kHz, and then very fast spacecraft potential variations can be monitored. Typically Vs varies between 0 and 50 volts so that in the plasmasphere it is 0-1 volt, at the plasmapause it exhibits a steep increase by 3-5 volts, and outside the plasmasphere Vs is more than 5 volts. Highest Vs's occur in the high-altitude (> 4 RE) polar cap, where Vs is usually between 20 and 30 volts, and on auroral field lines where it frequently lies in the 30-50 volts range and occasionally above 50 volts.

Petrological and geochemical Highlights in the floating fragments of the October 2011 submarine eruption offshore El Hierro (Canary Islands): Relevance of submarine hydrothermal processes

NASA Astrophysics Data System (ADS)

Rodriguez-Losada, Jose A.; Eff-Darwich, Antonio; Hernandez, Luis E.; Viñas, Ronaldo; Pérez, Nemesio; Hernandez, Pedro; Melián, Gladys; Martinez-Frías, Jesús; Romero-Ruiz, M. Carmen; Coello-Bravo, Juan Jesús

2015-02-01

This paper describes the main physical, petrological and geochemical features of the floating fragments that were emitted in the initial stages of the 2011-2012 submarine eruption off the coast of the Canarian island of El Hierro, located 380 km from the Northwest African Coast. It attempts to assess the potential of radiometric analyses to discern the intriguing origin of the floating fragments and the differences between their constituent parts. In this regard, the material that conforms the core of the fragments contains the largest concentration of uranium (U) ever found in volcanic rocks of the Canary Islands. This enrichment in U is not found in the content of thorium (Th), hence the floating fragments have an unusual U/Th ratio, namely equal to or larger than 3. Although the origin of this material is under discussion, it is proposed that the enrichment in U is the result of hydrothermal processes.

Dragging a floating horizontal cylinder

NASA Astrophysics Data System (ADS)

Lee, Duck-Gyu; Kim, Ho-Young

2010-11-01

A cylinder immersed in a fluid stream experiences a drag, and it is well known that the drag coefficient is a function of the Reynolds number only. Here we study the force exerted on a long horizontal cylinder that is dragged perpendicular to its axis while floating on an air-water interface with a high Reynolds number. In addition to the flow-induced drag, the floating body is subjected to capillary forces along the contact line where the three phases of liquid/solid/gas meet. We first theoretically predict the meniscus profile around the horizontally moving cylinder assuming the potential flow, and show that the profile is in good agreement with that obtained experimentally. Then we compare our theoretical predictions and experimental measurement results for the drag coefficient of a floating horizontal cylinder that is given by a function of the Weber number and the Bond number. This study can help us to understand the horizontal motion of partially submerged objects at air-liquid interface, such as semi-aquatic insects and marine plants.

Fluid Surface Deformation by Objects in the Cheerios Effect

NASA Astrophysics Data System (ADS)

Nguyen, Khoi; Miller, Michael; Mandre, Shreyas; Mandre Lab Team

2012-11-01

Small objects floating on a fluid/air interface deform of the surface depending on material surface properties, density, and geometry. These objects attract each other through capillary interactions, a phenomenon dubbed the ``cheerios effect.'' The attractive force and torque exerted on these objects by the interface can be estimated if the meniscus deformation is known. In addition, the floating objects can also rotate due to such an interaction. We present a series of experiments focused on visualizing the the motions of the floating objects and the deformation of the interface. The experiments involve thin laser-cut acrylic pieces attracting each other on water in a large glass petri dish and a camera set-up to capture the process. Furthermore, optical distortion of a grid pattern is used to visualize the water surface deformation near the edge of the objects. This study of the deformation of the water surface around a floating object, of the attractive/repulsive forces, and of post-contact rotational dynamics are potentially instrumental in the study of colloidal self-assembly.

Experimental Study on New Multi-Column Tension-Leg-Type Floating Wind Turbine

NASA Astrophysics Data System (ADS)

Zhao, Yong-sheng; She, Xiao-he; He, Yan-ping; Yang, Jian-min; Peng, Tao; Kou, Yu-feng

2018-04-01

Deep-water regions often have winds favorable for offshore wind turbines, and floating turbines currently show the greatest potential to exploit such winds. This work established proper scaling laws for model tests, which were then implemented in the construction of a model wind turbine with optimally designed blades. The aerodynamic, hydrodynamic, and elastic characteristics of the proposed new multi-column tension-leg-type floating wind turbine (WindStar TLP system) were explored in the wave tank testing of a 1:50 scale model at the State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University. Tests were conducted under conditions of still water, white noise waves, irregular waves, and combined wind, wave, and current loads. The results established the natural periods of the motion, damping, motion response amplitude operators, and tendon tensions of the WindStar TLP system under different environmental conditions, and thus could serve as a reference for further research. Key words: floating wind turbine, model test, WindStar TLP, dynamic response

Intrinsic plasma rotation and Reynolds stress at the plasma edge in the HSX stellarator

DOE PAGES

Wilcox, Robert S.; Talmadge, J. N.; Anderson, David T.; ...

2016-02-05

Using multi-tipped Langmuir probes in the edge of the HSX stellarator, the radial electric field and parallel flows are found to deviate from the values calculated by the neoclassical transport code PENTA for the optimized quasi-helically symmetric (QHS) configuration. To understand whether Reynolds stress might explain the discrepancy, fluctuating floating potential measurements are made at two locations in the torus corresponding to the low field and high field sides of the device. The measurements at the two locations show clear evidence of a gradient in the Reynolds stress. However, the resulting flow due to the gradient in the stress ismore » found to be large and in opposite directions for the two locations. This makes an estimation of the flux surface average using a small number of measurement locations impractical from an experimental perspective. These results neither confirm nor rule out whether Reynolds stress plays an important role for the QHS configuration. Measurements made in configurations with the quasi-symmetry degraded show even larger flows and greater deviations from the neoclassically calculated velocity profiles than the QHS configuration while the fluctuation magnitudes are reduced. Lastly, for these configurations in particular, the Reynolds stress is most likely not responsible for the additional momentum.« less

Plasma properties and heating at the anode of a 1 kW arcjet using electrostatic probes

NASA Astrophysics Data System (ADS)

Tiliakos, Nicholas

A 1 kW hydrazine arcjet thruster has been modified for internal probing of the near-anode boundary layer with an array of fourteen electrostatic micro-probes. The main objectives of this experimental investigation were to: (1) obtain axial and azimuthal distributions of floating potential phisbf, anode sheath potential phisbs, probe current density at zero volts jsba, electron number density nsbes, electron temperature Tsbes, and anode heating due to electrons qsbe for arc currents Isbarc, between 7.8 and 10.6 A, propellant flow rates m = 40-60 mg/s, and specific energies, 18.8 MJ/kg ≤ P/m ≤ 27.4 MJ/kg; (2) probe the anode boundary layer using flush-mounted and cylindrical micro-probes; (3) verify azimuthal current symmetry; (4) understand what affects anode heating, a critical thruster lifetime issue; and (5) provide experimental data for validation of the Megli-Krier-Burton (MKB) model. All of the above objectives were met through the design, fabrication and implementation of fourteen electrostatic micro-probes, of sizes ranging from 0.170 mm to 0.43 mm in diameter. A technique for cleaning and implementing these probes was developed. Two configurations were used: flush-mounted planar probes and cylindrical probes extended 0.10-0.30 mm into the plasma flow. The main results of this investigation are: (1) electrostatic micro-probes can successfully be used in the harsh environment of an arcjet; (2) under all conditions tested the plasma is highly non-equilibrium in the near-anode region; (3) azimuthal current symmetry exists for most operating conditions; (4) the propellant flow rate affects the location of maximum anode sheath potential, current density, and anode heating more than the arc current; (5) the weighted anode sheath potential is always positive and varies from 8-17 V depending on thruster operating conditions; (6) the fraction of anode heating varies from 18-24% of the total input power over the range of specific energies tested; and (7) based on an energy loss factor of delta = 1200, reasonable correlation between the experimental data and the MKB model was found.

Triple probe interrogation of spokes in a HiPIMS discharge

NASA Astrophysics Data System (ADS)

Lockwood Estrin, F.; Karkari, S. K.; Bradley, J. W.

2017-07-01

Using a triple probe situated above the racetrack and inside the magnetic trap of a magnetron, rotating spoke-like structures have been clearly identified in a single HiPIMS pulse as periodic modulations of the electron temperature T e, electron density n e, ion saturation current I isat, floating potential V f and plasma potential V p. The spokes rotate in the E  ×  B direction with a velocity of ~8.8 km s-1. Defining the spoke shape from the footprint of the ion current, they deliver to flush-mounted probes embedded in the target, each spoke can be characterised by a dense but cool leading edge (n e ~ 2.0  ×  1019 m-3, T e ~ 2.1 eV) and a relatively hotter but more rarefied trailing edge (n e ~ 1  ×  1019 m-3, T e ~ 3.9 eV). Measurements of V p show a potential hump towards the rear of the spoke, separated from regions of the highest density, with plasma potentials up to 8 V more positive than the inter-spoke regions. Azimuthal electric fields of ~1 kV m-1 associated with these structures are calculated. Transforming the triple probe time-traces to functions of the azimuthal angle θ and assuming a Gaussian radial profile for the plasma parameters, 2D spatial maps of n e, T e and V p have been constructed as well as the target ion current density J p from the embedded probes. The phase relationship between T e, V p and n e can be clearly seen using this representation with n e leading T e and V p with a phase shift between them of ~50°. Regions of maximum ion current to the target, delivered by individual spokes, coincide with the overlap of regions of high n e and T e measured above the target at a height of 15 mm. Ions created at elevated positions above the target in the observed dense region will take several micro-seconds to reach that surface, so contributing to the target ion current in the following spokes.

Floating Offshore Wind in Oregon: Potential for Jobs and Economic Impacts from Two Future Scenarios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jimenez, Tony; Keyser, David; Tegen, Suzanne

Construction of the first offshore wind power plant in the United States began in 2015, off the coast of Rhode Island, using fixed platform structures that are appropriate for shallow seafloors, like those located off of the East Coast and mid-Atlantic. However, floating platforms, which have yet to be deployed commercially, will likely need to anchor to the deeper seafloor if deployed off of the West Coast. To analyze the employment and economic potential for floating offshore wind along the West Coast, the Bureau of Ocean Energy Management (BOEM) commissioned the National Renewable Energy Laboratory (NREL) to analyze two hypothetical,more » large-scale deployment scenarios for Oregon: 5,500 megawatts (MW) of offshore wind deployment in Oregon by 2050 (Scenario A), and 2,900 MW of offshore wind by 2050 (Scenario B). These levels of deployment could power approximately 1,600,000 homes (Scenario A) or 870,000 homes (Scenario B). Offshore wind would contribute to economic development in Oregon in the near future, and more substantially in the long term, especially if equipment and labor are sourced from within the state. According to the analysis, over the 2020-2050 period, Oregon floating offshore wind facilities could support 65,000-97,000 job-years and add $6.8 billion-$9.9 billion to the state GDP (Scenario A).« less

Wave excited motion of a body floating on water confined between two semi-infinite ice sheets

NASA Astrophysics Data System (ADS)

Ren, K.; Wu, G. X.; Thomas, G. A.

2016-12-01

The wave excited motion of a body floating on water confined between two semi-infinite ice sheets is investigated. The ice sheet is treated as an elastic thin plate and water is treated as an ideal and incompressible fluid. The linearized velocity potential theory is adopted in the frequency domain and problems are solved by the method of matched eigenfunctions expansion. The fluid domain is divided into sub-regions and in each sub-region the velocity potential is expanded into a series of eigenfunctions satisfying the governing equation and the boundary conditions on horizontal planes including the free surface and ice sheets. Matching is conducted at the interfaces of two neighbouring regions to ensure the continuity of the pressure and velocity, and the unknown coefficients in the expressions are obtained as a result. The behaviour of the added mass and damping coefficients of the floating body with the effect of the ice sheets and the excitation force are analysed. They are found to vary oscillatorily with the wave number, which is different from that for a floating body in the open sea. The motion of the body confined between ice sheets is investigated, in particular its resonant behaviour with extremely large motion found to be possible under certain conditions. Standing waves within the polynya are also observed.

Advances in petascale kinetic plasma simulation with VPIC and Roadrunner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowers, Kevin J; Albright, Brian J; Yin, Lin

2009-01-01

VPIC, a first-principles 3d electromagnetic charge-conserving relativistic kinetic particle-in-cell (PIC) code, was recently adapted to run on Los Alamos's Roadrunner, the first supercomputer to break a petaflop (10{sup 15} floating point operations per second) in the TOP500 supercomputer performance rankings. They give a brief overview of the modeling capabilities and optimization techniques used in VPIC and the computational characteristics of petascale supercomputers like Roadrunner. They then discuss three applications enabled by VPIC's unprecedented performance on Roadrunner: modeling laser plasma interaction in upcoming inertial confinement fusion experiments at the National Ignition Facility (NIF), modeling short pulse laser GeV ion acceleration andmore » modeling reconnection in magnetic confinement fusion experiments.« less

Investigating the potential of floating mires as record of palaeoenvironmental changes

NASA Astrophysics Data System (ADS)

Zaccone, C.; Adamo, P.; Giordano, S.; Miano, T. M.

2012-04-01

Peat-forming floating mires could provide an exceptional resource for palaeoenvironmental and environmental monitoring studies, as much of their own history, as well as the history of their surrounds, is recorded in their peat deposits. In his Naturalis historia (AD 77-79), Pliny the Elder described floating islands on Lake Vadimonis (now Posta Fibreno Lake, Italy). Actually, a small floating island (ca. 35 m of diameter and 3 m of submerged thickness) still occurs on this calcareous lake fed by karstic springs at the base of the Apennine Mountains. Here the southernmost Italian populations of Sphagnum palustre occur on the small surface of this floating mire known as "La Rota", i.e., a cup-formed core of Sphagnum peat and rhizomes of Helophytes, erratically floating on the water-body of a submerged doline, annexed to the easternmost edge of the lake, characterised by the extension of a large reed bed. Geological evidence point out the existence in the area of a large lacustrine basin since Late Pleistocene. The progressive filling of the lake caused by changing in climatic conditions and neotectonic events, brought about the formation of peat deposits in the area, following different depositional cycles in a swampy environment. Then, a round-shaped portion of fen, originated around lake margins in waterlogged areas, was somehow isolated from the bank and started to float. Coupling data about concentrations and fluxes of several major and trace elements of different origin (i.e., dust particles, volcanic emissions, cosmogenic dusts and marine aerosols), with climate records (plant micro- and macrofossils, pollens, isotopic ratios), biomolecular records (e.g., lipids), detailed age-depth modelling (i.e., 210Pb, 137Cs, 14C), and humification indexes, the present work is hoped to identify and better understand the reliability of this particular "archive", and thus possible relationships between biogeochemical processes occurring in this floating bog and environmental changes.

Open-air sprays for capturing and controlling airborne float coal dust on longwall faces

PubMed Central

Beck, T.W.; Seaman, C.E.; Shahan, M.R.; Mischler, S.E.

2018-01-01

Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 µm in diameter, in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity of 3.6 m/s (700 fpm). Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle should be operated at high fluid pressures to produce smaller droplets and move more air. These findings agree with past respirable dust control research, providing guidance on spray selection and spray array design in ongoing efforts to control airborne float dust over the entire longwall ventilated opening. PMID:29348700

Open-air sprays for capturing and controlling airborne float coal dust on longwall faces.

PubMed

Beck, T W; Seaman, C E; Shahan, M R; Mischler, S E

2018-01-01

Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 µm in diameter, in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity of 3.6 m/s (700 fpm). Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle should be operated at high fluid pressures to produce smaller droplets and move more air. These findings agree with past respirable dust control research, providing guidance on spray selection and spray array design in ongoing efforts to control airborne float dust over the entire longwall ventilated opening.

Removal of Metal Nanoparticles Colloidal Solutions by Water Plants

NASA Astrophysics Data System (ADS)

Olkhovych, Olga; Svietlova, Nataliia; Konotop, Yevheniia; Karaushu, Olena; Hrechishkina, Svitlana

2016-11-01

The ability of seven species of aquatic plants ( Elodea canadensis, Najas guadelupensis, Vallisneria spiralis L., Riccia fluitans L., Limnobium laevigatum, Pistia stratiotes L., and Salvinia natans L.) to absorb metal nanoparticles from colloidal solutions was studied. It was established that investigated aquatic plants have a high capacity for removal of metal nanoparticles from aqueous solution (30-100%) which indicates their high phytoremediation potential. Analysis of the water samples content for elements including the mixture of colloidal solutions of metal nanoparticles (Mn, Cu, Zn, Ag + Ag2O) before and after exposure to plants showed no significant differences when using submerged or free-floating hydrophytes so-called pleuston. However, it was found that the presence of submerged hydrophytes in aqueous medium ( E. canadensis, N. guadelupensis, V. spiralis L., and R. fluitans L.) and significant changes in the content of photosynthetic pigments, unlike free-floating hydrophytes ( L. laevigatum, P. stratiotes L., S. natans L.), had occur. Pleuston possesses higher potential for phytoremediation of contaminated water basins polluted by metal nanoparticles. In terms of removal of nanoparticles among studied free-floating hydrophytes, P. stratiotes L. and S. natans L. deserve on special attention.

Evaporation mitigation by floating modular devices

NASA Astrophysics Data System (ADS)

Hassan, M. M.; Peirson, W. L.

2016-05-01

Prolonged periods of drought and consequent evaporation from open water bodies in arid parts of Australia continue to be a threat to water availability for agricultural production. Over many parts of Australia, the annual average evaporation exceeds the annual precipitation by more than 5 times. Given its significance, it is surprising that no evaporation mitigation technique has gained widespread adoption to date. High capital and maintenance costs of manufactured products are a significant barrier to implementation. The use of directly recycled clean plastic containers as floating modular devices to mitigate evaporation has been investigated for the first time. A six-month trial at an arid zone site in Australia of this potential cost effective solution has been undertaken. The experiment was performed using clean conventional drinking water bottles as floating modules on the open water surface of 240-L tanks with three varying degrees of covering (nil, 34% and 68%). A systematic reduction in evaporation is demonstrated during the whole study period that is approximately linearly proportional to the covered surface. These results provide a potential foundation for robust evaporation mitigation with the prospect of implementing a cost-optimal design.

A Comparative Study of Three Different Chemical Vapor Deposition Techniques of Carbon Nanotube Growth on Diamond Films

DTIC Science & Technology

2012-11-01

microwave plasma-enhanced CVD (MPE-CVD) with presputtered metal catalyst, and floating catalyst thermal CVD (FCT-CVD) with xylene and ferrocene liquid...processes with nickel and iron catalysts, respectively. For the FCT-CVD approach, ferrocene is used as an iron source to promoteCNT growth. Based on...furnace is ramped up to the growth temperature of 750∘C. Ferrocene was dissolved into a xylene solvent in a 0.008 : 1molar volume ratio.The xylene

Physical and biological mechanisms of nanosecond- and microsecond-pulsed FE-DBD plasma interaction with biological objects

NASA Astrophysics Data System (ADS)

Dobrynin, Danil

2013-09-01

Mechanisms of plasma interaction with living tissues and cells can be quite complex, owing to the complexity of both the plasma and the tissue. Thus, unification of all the mechanisms under one umbrella might not be possible. Here, analysis of interaction of floating electrode dielectric barrier discharge (FE-DBD) with living tissues and cells is presented and biological and physical mechanisms are discussed. In physical mechanisms, charged species are identified as the major contributors to the desired effect and a mechanism of this interaction is proposed. Biological mechanisms are also addressed and a hypothesis of plasma selectivity and its effects is offered. Spatially uniform nanosecond and sub-nanosecond short-pulsed dielectric barrier discharge plasmas are gaining popularity in biological and medical applications due to their increased uniformity, lower plasma temperature, lower surface power density, and higher concentration of the active species produced. In this presentation we will compare microsecond pulsed plasmas with nanosecond driven systems and their applications in biology and medicine with specific focus on wound healing and tissue regeneration. Transition from negative to positive streamer will be discussed with proposed hypothesis of uniformity mechanisms of positive streamer and the reduced dependence on morphology and surface chemistry of the second electrode (human body) being treated. Uniform plasma offers a more uniform delivery of active species to the tissue/surface being treated thus leading to better control over the biological results.

Inhibition of Phosphatidylcholine-Specific Phospholipase C Interferes with Proliferation and Survival of Tumor Initiating Cells in Squamous Cell Carcinoma

PubMed Central

Ferri, Renata; Mercurio, Laura; Canevari, Silvana; Podo, Franca; Miotti, Silvia; Iorio, Egidio

2015-01-01

Purpose The role of phosphatidylcholine-specific phospholipase C (PC-PLC), the enzyme involved in cell differentiation and proliferation, has not yet been explored in tumor initiating cells (TICs). We investigated PC-PLC expression and effects of PC-PLC inhibition in two adherent (AD) squamous carcinoma cell lines (A431 and CaSki), with different proliferative and stemness potential, and in TIC-enriched floating spheres (SPH) originated from them. Results Compared with immortalized non-tumoral keratinocytes (HaCaT) A431-AD cells showed 2.5-fold higher PC-PLC activity, nuclear localization of a 66-kDa PC-PLC isoform, but a similar distribution of the enzyme on plasma membrane and in cytoplasmic compartments. Compared with A431-AD, A431-SPH cells showed about 2.8-fold lower PC-PLC protein and activity levels, but similar nuclear content. Exposure of adherent cells to the PC-PLC inhibitor D609 (48h) induced a 50% reduction of cell proliferation at doses comprised between 33 and 50 μg/ml, without inducing any relevant cytotoxic effect (cell viability 95±5%). In A431-SPH and CaSki-SPH D609 induced both cytostatic and cytotoxic effects at about 20 to 30-fold lower doses (IC50 ranging between 1.2 and 1.6 μg/ml). Furthermore, D609 treatment of A431-AD and CaSki-AD cells affected the sphere-forming efficiency, which dropped in both cells, and induced down-modulation of stem-related markers mRNA levels (Oct4, Nestin, Nanog and ALDH1 in A431; Nestin and ALDH1 in CaSki cells). Conclusions These data suggest that the inhibition of PC-PLC activity may represent a new therapeutic approach to selectively target the most aggressive and tumor promoting sub-population of floating spheres originated from squamous cancer cells possessing different proliferative and stemness potential. PMID:26402860

Can flexibility help you float?

NASA Astrophysics Data System (ADS)

Burton, L. J.; Bush, J. W. M.

2012-10-01

We consider the role of flexibility in the weight-bearing characteristics of bodies floating at an interface. Specifically, we develop a theoretical model for a two-dimensional thin floating plate that yields the maximum stable plate load and optimal stiffness for weight support. Plates small relative to the capillary length are primarily supported by surface tension, and their weight-bearing potential does not benefit from flexibility. Above a critical size comparable to the capillary length, flexibility assists interfacial flotation. For plates on the order of and larger than the capillary length, deflection from an initially flat shape increases the force resulting from hydrostatic pressure, allowing the plate to support a greater load. In this large plate limit, the shape that bears the most weight is a semicircle, which displaces the most fluid above the plate for a fixed plate length. Exact results for maximum weight-bearing plate shapes are compared to analytic approximations made in the limits of large and small plate sizes. The value of flexibility for floating to a number of biological organisms is discussed in light of our study.

Floating growth of large-scale freestanding TiO2 nanorod films at the gas-liquid interface for additive-free Li-ion battery applications.

PubMed

Xia, Hua-Rong; Li, Jia; Peng, Chen; Sun, Wen-Tao; Li, Long-Wei; Peng, Lian-Mao

2014-10-22

The floating growth process of large-scale freestanding TiO2 nanorod films at the gas-liquid interface was investigated. On the basis of the experiments, a self-templated growth scenario was developed to account for the self-assembly process. In the scenario, titanium complexes function not only as the Ti source for the growth of TiO2 but also as a soft template provider for the floating growth. According to the scenario, several new recipes of preparing freestanding TiO2 nanorod films at the gas-liquid interface were developed. The freestanding film was applied to a lithium ion battery as a binder-free and conducting agent-free anode, and good cyclability was obtained. This work may pave a new way to floating and freestanding TiO2 and other semiconductor materials, which has great potential not only in basic science but also in the applications such as materials engineering, Li-ion battery, photocatalyst, dye-sensitized solar cell, and flexible electronics.

Non-invasive probe diagnostic method for electron temperature and ion current density in atmospheric pressure plasma jet source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Young-Cheol; Kim, Yu-Sin; Lee, Hyo-Chang

2015-08-15

The electrical probe diagnostics are very hard to be applied to atmospheric plasmas due to severe perturbation by the electrical probes. To overcome this, the probe for measuring electron temperature and ion current density is indirectly contacted with an atmospheric jet source. The plasma parameters are obtained by using floating harmonic analysis. The probe is mounted on the quartz tube that surrounds plasma. When a sinusoidal voltage is applied to a probe contacting on a quartz tube, the electrons near the sheath at dielectric tube are collected and the probe current has harmonic components due to probe sheath nonlinearity. Frommore » the relation of the harmonic currents and amplitude of the sheath voltage, the electron temperature near the wall can be obtained with collisional sheath model. The electron temperatures and ion current densities measured at the discharge region are in the ranges of 2.7–3.4 eV and 1.7–5.2 mA/cm{sup 2} at various flow rates and input powers.« less

LETTER: Biased limiter experiments on the Advanced Toroidal Facility (ATF) torsatron

NASA Astrophysics Data System (ADS)

Uckan, T.; Isler, R. C.; Jernigan, T. C.; Lyon, J. F.; Mioduszewski, P. K.; Murakami, M.; Rasmussen, D. A.; Wilgen, J. B.; Aceto, S. C.; Zielinski, J. J.

1994-02-01

The Advanced Toroidal Facility (ATF) torsatron incorporates two rail limiters that can be positioned by external controls. The influence on the plasma parameters of biasing these limiters both positively and negatively with respect to the walls has been investigated. Experiments have been carried out in the electron cyclotron heated plasmas at 200 kW with a typical density of 5 × 1012 cm-3 and a central electron temperature of ~900 eV. Negative biasing produces only small changes in the plasma parameters, but positive biasing increases the particle confinement by about a factor of 5, although the plasma stored energy does fall at the higher voltages. In addition, positive biasing produces the following effects compared with floating limiter discharges: the core density profiles become peaked rather than hollow, the electric field at the edge becomes more negative (pointing radially inward), the magnitudes of the edge fluctuations and the fluctuation induced transport are reduced, the fluctuation wavelengths become longer and their propagation direction reverses from the electron to the ion diamagnetic direction. Neither polarity of biasing appears to affect the impurity content or transport

Profile measurements of the electron temperature on the ASDEX Upgrade, COMPASS, and ISTTOK tokamak using Thomson scattering, triple, and ball-pen probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamek, J., E-mail: adamek@ipp.cas.cz; Horacek, J.; Bilkova, P.

The ball-pen probe (BPP) technique is used successfully to make profile measurements of the electron temperature on the ASDEX Upgrade (Axially Symmetric Divertor Experiment), COMPASS (COMPact ASSembly), and ISTTOK (Instituto Superior Tecnico TOKamak) tokamak. The electron temperature is provided by a combination of the BPP potential (Φ{sub BPP}) and the floating potential (V{sub fl}) of the Langmuir probe (LP), which is compared with the Thomson scattering diagnostic on ASDEX Upgrade and COMPASS. Excellent agreement between the two diagnostics is obtained for circular and diverted plasmas and different heating mechanisms (Ohmic, NBI, ECRH) in deuterium discharges with the same formula T{submore » e} = (Φ{sub BPP} − V{sub fl})/2.2. The comparative measurements of the electron temperature using BPP/LP and triple probe (TP) techniques on the ISTTOK tokamak show good agreement of averaged values only inside the separatrix. It was also found that the TP provides the electron temperature with significantly higher standard deviation than BPP/LP. However, the resulting values of both techniques are well in the phase with the maximum of cross-correlation function being 0.8.« less

Observation of helicon wave with m = 0 antenna in a weakly magnetized inductively coupled plasma source

NASA Astrophysics Data System (ADS)

Ellingboe, Bert; Sirse, Nishant; Moloney, Rachel; McCarthy, John

2015-09-01

Bounded whistler wave, called ``helicon wave,'' is known to produce high-density plasmas and has been exploited as a high density plasma source for many applications, including electric propulsion for spacecraft. In a helicon plasma source, an antenna wrapped around the magnetized plasma column launches a low frequency wave, ωce/2 >ωhelicon >ωce/100, in the plasma which is responsible for maintaining high density plasma. Several antenna designs have been proposed in order to match efficiently the wave modes. In our experiment, helicon wave mode is observed using an m = 0 antenna. A floating B dot probe, compensated to the capacitively coupled E field, is employed to measure axial-wave-field-profiles (z, r, and θ components) in the plasma at multiple radial positions as a function of rf power and pressure. The Bθ component of the rf-field is observed to be unaffected as the wave propagates in the axial direction. Power coupling between the antenna and the plasma column is identified and agrees with the E, H, and wave coupling regimes previously seen in M =1 antenna systems. That is, the Bz component of the rf-field is observed at low plasma density as the Bz component from the antenna penetrates the plasma. The Bz component becomes very small at medium density due to shielding at the centre of the plasma column; however, with increasing density, a sudden ``jump'' occurs in the Bz component above which a standing wave under the antenna with a propagating wave away from the antenna are observed.

Particle Simulations of the Guard Electrode Effects on the Photoelectron Distribution Around an Electric Field Sensor

NASA Astrophysics Data System (ADS)

Miyake, Y.; Usui, H.; Kojima, H.

2010-12-01

In tenuous space plasma environment, photoelectrons emitted due to solar illumination produce a high-density photoelectron cloud localized in the vicinity of a spacecraft body and an electric field sensor. The photoelectron current emitted from the sensor has also received considerable attention because it becomes a primary factor in determining floating potentials of the sunlit spacecraft and sensor bodies. Considering the fact that asymmetric photoelectron distribution between sunlit and sunless sides of the spacecraft occasionally causes a spurious sunward electric field, we require quantitative evaluation of the photoelectron distribution around the spacecraft and its influence on electric field measurements by means of a numerical approach. In the current study, we applied the Particle-in-Cell plasma simulation to the analysis of the photoelectron environment around spacecraft. By using the PIC modeling, we can self-consistently consider the plasma kinetics. This enables us to simulate the formation of the photoelectron cloud as well as the spacecraft and sensor charging in a self-consistent manner. We report the progress of an analysis on photoelectron environment around MEFISTO, which is an electric field instrument for the BepiColombo/MMO spacecraft to Mercury’s magnetosphere. The photoelectron guard electrode is a key technology for ensuring an optimum photoelectron environment. We show some simulation results on the guard electrode effects on surrounding photoelectrons and discuss a guard operation condition for producing the optimum photoelectron environment. We also deal with another important issue, that is, how the guard electrode can mitigate an undesirable influence of an asymmetric photoelectron distribution on electric field measurements.

Circulation of Plasma in the Jovian Magnetosphere as Inferred from the Galileo Magnetometer Observations

NASA Astrophysics Data System (ADS)

Yu, Z. J.; Russell, C. T.; Kivelson, M. G.; Khurana, K. K.

2000-10-01

Massloading of the jovian magnetosphere by the addition of ions at the moon Io is the ultimate engine of the circulation of the magnetospheric plasma. In steady state the radial density profile enables the radial outflow velocity to be calculated from the mass addition rate. Some of these ions are lost from the field lines through pitch angle diffusion. Expected loss rates can be calculated from the fluctuation level in the magnetic field. Radial velocities can be calculated from observations of the Europa wake and force balance in the magnetodisk. The resulting transport times are shorter than the pitch angle scattering loss times so that most of the plasma is transported to the tail and lost by magnetic island formation. In turn the island formation process (reconnection) depletes magnetic field lines making them buoyant and allowing them to "float" back to the inner magnetosphere. In the torus these depleted flux tubes can be seen as thin tubes with stronger than the ambient field strength, implying plasma pressures about 2% of the magnetic field and ion temperatures principally in the range 30-150 eV. When the depleted flux tubes reach the orbit of Io where the energy density of the plasma drops these depleted flux tubes become indistinguishable from the ambient plasma, completing the circulation loop.

Removal of nutrients and veterinary antibiotics from swine wastewater by a constructed macrophyte floating bed system.

PubMed

Xian, Qiming; Hu, Lixia; Chen, Hancheng; Chang, Zhizhou; Zou, Huixian

2010-12-01

The potential of three varieties of Italian ryegrass (Lolium multiflorum Lam.), Dryan, Tachimasari and Waseyutaka, to improve the water quality of swine wastewater was evaluated using a constructed macrophyte floating bed system. With respect to reductions in levels of nutrients, chemical oxygen demand (COD), and sulfonamide antimicrobials (SAs, including sulfadiazine, sulfamethazine, and sulfamethoxazole), Dryan performed better than Tachimasari and Waseyutaka. For Dryan, total N was reduced by 84.0%, total P by 90.4%, COD by 83.4% and sulfonamide antimicrobials by 91.8-99.5%. Similar results were observed for Tachimasari and Waseyutaka. The results indicated that the treatment of swine wastewater using the constructed macrophyte floating bed system was effective in the removal of nutrients and veterinary antibiotics. Copyright © 2010 Elsevier Ltd. All rights reserved.

Cold Atmospheric Plasma, Created at the Tip of an Elongated Flexible Capillary Using Low Electric Current, Can Slow the Progression of Melanoma

PubMed Central

Binenbaum, Y.; Ben-David, G.; Gil, Z.; Slutsker, Ya. Z.; Ryzhkov, M. A.; Felsteiner, J.; Krasik, Ya. E.; Cohen, J. T.

2017-01-01

Introduction Cold Atmospheric Plasma Jet (CAPJ), with ion temperature close to room temperature, has tremendous potential in biomedical engineering, and can potentially offer a therapeutic option that allows cancer cell elimination without damaging healthy tissue. We developed a hand-held flexible device for the delivery of CAPJ to the treatment site, with a modified high-frequency pulse generator operating at a RMS voltage of <1.2 kV and gas flow in the range 0.3–3 l/min. The aims of our study were to characterize the CAPJ emitted from the device, and to evaluate its efficacy in elimination of cancer cells in-vitro and in-vivo. Methods and Results The power delivered by CAPJ was measured on a floating or grounded copper target. The power did not drastically change over distances of 0–14 mm, and was not dependent on the targets resistance. Temperature of CAPJ-treated target was 23°-36° C, and was dependent on the voltage applied. Spectroscopy indicated that excited OH- radicals were abundant both on dry and wet targets, placed at different distances from the plasma gun. An in-vitro cell proliferation assay demonstrated that CAPJ treatment of 60 seconds resulted in significant reduction in proliferation of all cancer cell lines tested, and that CAPJ activated medium was toxic to cancer cells. In-vivo, we treated cutaneous melanoma tumors in nude mice. Tumor volume was significantly decreased in CAPJ-treated tumors relatively to controls, and high dose per fraction was more effective than low dose per fraction treatment. Importantly, pathologic examination revealed that normal skin was not harmed by CAPJ treatment. Conclusion This preliminary study demonstrates the efficacy of flexible CAPJ delivery system against melanoma progression both in-vitro and in-vivo. It is envisioned that adaptation of CAPJ technology for different kinds of neoplasms use may provide a new modality for the treatment of solid tumors. PMID:28103270

Cold Atmospheric Plasma, Created at the Tip of an Elongated Flexible Capillary Using Low Electric Current, Can Slow the Progression of Melanoma.

PubMed

Binenbaum, Y; Ben-David, G; Gil, Z; Slutsker, Ya Z; Ryzhkov, M A; Felsteiner, J; Krasik, Ya E; Cohen, J T

2017-01-01

Cold Atmospheric Plasma Jet (CAPJ), with ion temperature close to room temperature, has tremendous potential in biomedical engineering, and can potentially offer a therapeutic option that allows cancer cell elimination without damaging healthy tissue. We developed a hand-held flexible device for the delivery of CAPJ to the treatment site, with a modified high-frequency pulse generator operating at a RMS voltage of <1.2 kV and gas flow in the range 0.3-3 l/min. The aims of our study were to characterize the CAPJ emitted from the device, and to evaluate its efficacy in elimination of cancer cells in-vitro and in-vivo. The power delivered by CAPJ was measured on a floating or grounded copper target. The power did not drastically change over distances of 0-14 mm, and was not dependent on the targets resistance. Temperature of CAPJ-treated target was 23°-36° C, and was dependent on the voltage applied. Spectroscopy indicated that excited OH- radicals were abundant both on dry and wet targets, placed at different distances from the plasma gun. An in-vitro cell proliferation assay demonstrated that CAPJ treatment of 60 seconds resulted in significant reduction in proliferation of all cancer cell lines tested, and that CAPJ activated medium was toxic to cancer cells. In-vivo, we treated cutaneous melanoma tumors in nude mice. Tumor volume was significantly decreased in CAPJ-treated tumors relatively to controls, and high dose per fraction was more effective than low dose per fraction treatment. Importantly, pathologic examination revealed that normal skin was not harmed by CAPJ treatment. This preliminary study demonstrates the efficacy of flexible CAPJ delivery system against melanoma progression both in-vitro and in-vivo. It is envisioned that adaptation of CAPJ technology for different kinds of neoplasms use may provide a new modality for the treatment of solid tumors.

Wave radiation and diffraction by a two-dimensional floating body with an opening near a side wall

NASA Astrophysics Data System (ADS)

Zhang, Hong-sheng; Zhou, Hua-wei

2013-08-01

The radiation and diffraction problem of a two-dimensional rectangular body with an opening floating on a semi-infinite fluid domain of finite water depth is analysed based on the linearized velocity potential theory through an analytical solution procedure. The expressions for potentials are obtained by the method of variation separation, in which the unknown coefficients are determined by the boundary condition and matching requirement on the interface. The effects of the position of the hole and the gap between the body and side wall on hydrodynamic characteristics are investigated. Some resonance is observed like piston motion in a moon pool and sloshing in a closed tank because of the existence of restricted fluid domains.

Production and study of high-beta plasma confined by a superconducting dipole magneta)

NASA Astrophysics Data System (ADS)

Garnier, D. T.; Hansen, A.; Mauel, M. E.; Ortiz, E.; Boxer, A. C.; Ellsworth, J.; Karim, I.; Kesner, J.; Mahar, S.; Roach, A.

2006-05-01

The Levitated Dipole Experiment (LDX) [J. Kesner et al., in Fusion Energy 1998, 1165 (1999)] is a new research facility that is exploring the confinement and stability of plasma created within the dipole field produced by a strong superconducting magnet. Unlike other configurations in which stability depends on curvature and magnetic shear, magnetohydrodynamic stability of a dipole derives from plasma compressibility. Theoretically, the dipole magnetic geometry can stabilize a centrally peaked plasma pressure that exceeds the local magnetic pressure (β>1), and the absence of magnetic shear allows particle and energy confinement to decouple. In initial experiments, long-pulse, quasi-steady-state microwave discharges lasting more than 10s have been produced that are consistent with equilibria having peak beta values of 20%. Detailed measurements have been made of discharge evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles, and plasma boundary shape. In these initial experiments, the high-field superconducting floating coil was supported by three thin supports. The plasma is created by multifrequency electron cyclotron resonance heating at 2.45 and 6.4GHz, and a population of energetic electrons, with mean energies above 50keV, dominates the plasma pressure. Creation of high-pressure, high-beta plasma is possible only when intense hot electron interchange instabilities are stabilized by sufficiently high background plasma density. A dramatic transition from a low-density, low-beta regime to a more quiescent, high-beta regime is observed when the plasma fueling rate and confinement time become sufficiently large.

[Further study on possibility of diffusion of Oncomelania hupensis with water in river channels of the east route of South-to-North Water Diversion Project].

PubMed

Huang, Yi-Xin; Hang, De-Rong; Tang, Hong-Ping; Sun, Dao-Kuan; Zhou, Can-Hua; Gao, Jin-Bin; Zheng, Bo; Hu, Gui-Quan; Li, Qian; Huang, Yong-Jun; She, Guang-Song; Ren, Zhi-Yuan

2014-12-01

To study the drifting law of floats and potential risks of Oncomelania hupensis diffusion in the water diversion rivers of the east route of South-to-North Water Diversion Project. The O. hupensis snails in the river channels were monitored by the salvage method and snail luring method with rice straw curtains, and the diffusion possibility of snails along with water was assessed through the drift test of floats with GPS. In the flood seasons from 2006 to 2013, totally 8 338.0 kg of floats were salvaged, and 2 100 rice straw curtains were put into water in the Li Canal and Jinbao shipping channel, but no Oncomelania snails were found. The drift test of floats with GPS before water diversion showed that the flow velocity on water surface (northbound) was 0.45 m/s, the average drift velocity of the floats was 0.56 - 0.60 m/s, and the average drift distances each time were 999.70 - 1 995.50 m in the Gaoshui River section, while there were no obvious drift in Jinbao shipping channel section. During the water diversion period, the flow velocity on water surface (northbound) was 0.45 m/s, the average drift velocity of the floats was 0.35 - 0.41m/s, and the average drift distances each time were 1 248.06 -1 289.44 m in the Gaoshui River, while in Jinbao shipping channel section, the flow velocity on water surface was 0.28 m/s, the average drift velocity of the floats was 0.25 - 0.27 m/s, and the average drift distances each time were 477.76 - 496.38 m. The drift test showed that the floats gradually closed to the river bank as affected by water flow, wind direction and ship waves, when blocked by the reeds, water plants or other obstacles, and they would stopped and could not continue to drift without outside help. There are no Oncomelania snails found in the river channels of the east route of South-to-North Water Diversion Project. The drifting distance of the floating debris along with the water is restricted by the flow rate and shore environment.

High-resolution Bio-Argo and Argo Measurements to Reveal Specific Oceanic Processes.

NASA Astrophysics Data System (ADS)

Poteau, A.; Claustre, H.; Briggs, N.; D'Ortenzio, F.; Schmechtig, C.; Prieur, L. M.; Boss, E.

2016-02-01

Together with temperature and salinity measurements, Bio-Argo profiling floats now measure a significant range of biogeochemical (e.g. O2, NO3) and bio-optical variables (Chla, backscattering coefficient and radiometry). To transmit the very large amount of data acquired by this new generation of floats, it was required to substitute the Argos telemetry (Argo program) with iridium telemetry. The obvious consequence is not only a much greater flexibly on data transmission but also on data acquisition thanks to the two-way communication allowed by iridium. Our group has now deployed and managed over 100 Bio-Argo floats of this type. In particular we have set up high-resolution mode of acquisition for certain periods of time or for dedicated portions of the water column. Here we illustrate with three examples the potential of conducting high-resolution measurement to identify and explore certain oceanic processes. (1) High resolution measurements of pressure, temperature and salinity (every 2 s) when the float is finishing its ascent (without any pump action) in the upper 10 m layer are analyzed with respect to sea state. We particularly focus on the study of the speed anomaly as compared to a nominal speed expected for a calm sea state. By comparison between speed anomaly of a float in the Mediterranean Sea and concurrent sea state measurements by a weather buoy in the same area, we suggest that float behaviour can be an indicator of sea state. (2) Each year, in response to springtime phytoplankton blooms, the resolution of bio-optical variables (backscattering and Chla) in the top 1000 m was increased to at least 1 m (every 10 s) for all floats in the North Atlantic and Southern Ocean. This resolution allowed accurate estimation of the concentration of large phytoplankton aggregates and revealed systematic differences in bulk aggregate sinking rate between ocean basins. (3) Finally we continuously record all the variables at a 10 min resolution during the float drift at 1000m. This allows us to characterize some events at this depth that can be related to bottom currents, high mixing or massive export of aggregates.

Toward Future Photovoltaic-Based Agriculture in Sea.

PubMed

Moustafa, Khaled

2016-04-01

To meet the challenges of climate change and water shortages, combining solar energy-based seawater desalination technologies with floating agriculture stations in one innovative hybrid system would be worthy of investigation for dry and sunny regions for seawater desalination and crop production within the same platform. Here, I discuss the feasibility of such a 'floating farm' or 'bluehouse' in the sea, by comparing it with the use of terrestrial greenhouses. I also debate the potential advantages and shortcomings of such a system. Copyright © 2015 Elsevier Ltd. All rights reserved.

Surface waves on floating liquids induced by ultrasound field

NASA Astrophysics Data System (ADS)

Geng, D. L.; Xie, W. J.; Yan, N.; Wei, B.

2013-01-01

We demonstrate a kind of wave pattern on the surface of floating liquids in a modulated ultrasound field. The waves are related to the liquid/solid phase transformation process. The nucleation sites of the eutectics locate at the center of these waves, and the eutectic growth direction is parallel to the propagation direction of the waves. It is revealed that such wave phenomenon can be ascribed to the interaction between ultrasound and eutectic growth at the liquid/solid interface. This result may provide a potential method for fabricating wave patterned surfaces on eutectic alloys.

Floating Offshore Wind in California: Gross Potential for Jobs and Economic Impacts from Two Future Scenarios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Speer, Bethany; Keyser, David; Tegen, Suzanne

Construction of the first offshore wind farm in the United States began in 2015, using fixed platform structures that are appropriate for shallow seafloors, like those located off of the East Coast and mid-Atlantic. However, floating platforms, which have yet to be deployed commercially, will likely need to anchor to the deeper seafloor if deployed off of the West Coast. To analyze the employment and economic potential for floating offshore wind along the West Coast, the Bureau of Ocean Energy Management (BOEM) has commissioned the National Renewable Energy Laboratory (NREL) to analyze two hypothetical, large-scale deployment scenarios for California: 16more » GW of offshore wind by 2050 (Scenario A) and 10 GW of offshore wind by 2050 (Scenario B). The results of this analysis can be used to better understand the general scales of economic opportunities that could result from offshore wind development. Results show total state gross domestic product (GDP) impacts of $16.2 billion in Scenario B or $39.7 billion in Scenario A for construction; and $3.5 billion in Scenario B or $7.9 billion in Scenario A for the operations phases.« less

A Radiation-Tolerant, Low-Power Non-Volatile Memory Based on Silicon Nanocrystal Quantum Dots

NASA Technical Reports Server (NTRS)

Bell, L. D.; Boer, E. A.; Ostraat, M. L.; Brongersma, M. L.; Flagan, R. C.; Atwater, H. A.; deBlauwe, J.; Green, M. L.

2001-01-01

Nanocrystal nonvolatile floating-gate memories are a good candidate for space applications - initial results suggest they are fast, more reliable and consume less power than conventional floating gate memories. In the nanocrystal based NVM device, charge is not stored on a continuous polysilicon layer (so-called floating gate), but instead on a layer of discrete nanocrystals. Charge injection and storage in dense arrays of silicon nanocrystals in SiO2 is a critical aspect of the performance of potential nanocrystal flash memory structures. The ultimate goal for this class of devices is few- or single-electron storage in a small number of nanocrystal elements. In addition, the nanocrystal layer fabrication technique should be simple, 8-inch wafer compatible and well controlled in program/erase threshold voltage swing was seen during 100,000 program and erase cycles. Additional near-term goals for this project include extensive testing for radiation hardness and the development of artificial layered tunnel barrier heterostructures which have the potential for large speed enhancements for read/write of nanocrystal memory elements, compared with conventional flash devices. Additional information is contained in the original extended abstract.

Positive Voltage Hazard to EMU Crewman from Currents through Plasma

NASA Astrophysics Data System (ADS)

Kramer, Leonard; Hamilton, Doug; Mikatarian, Ronald; Thomas, Joseph; Koontz, Steven

2010-09-01

The International Space Station(ISS) in its transit through the ionosphere experiences a variable electrical potential between its bonded structure and the overlying ionospheric plasma. The 160 volt solar arrays on ISS are grounded negative and drive structure to negative floating potential(FP) relative to plasma. This potential is a result of the asymmetric collection properties of currents from ions and electrons moderated by geomagnetic; so called v Å~ B induction distributing an additional 20 volts both positive and negative across ISS’s main structural truss element. Since the space suit or extravehicular mobility unit(EMU) does not protect the crewperson from electrical shock, during extra vehicular activity(EVA) the person is exposed to a hazard from the potential when any of the several metallic suit penetrations come in direct contact with ISS structure. The moisture soaked garment worn by the crewperson and the large interior metal contact areas facilitate currents through the crewperson’s body. There are two hazards; Negative and Positive FP. The Negative hazard is the better known risk created by a shock hazard from arcing of anodized material on the EMU. Negative hazard has been controlled by plasma contactor units(PCU) containing a reserve of Xenon gas which is expelled from ISS. The PCU provide a ground path for the negative charge from the structure to flow to exterior plasma bringing ISS FP closer to zero. The understanding has now emerged that the operation of PCUs to protect the crewmen from negative voltage exposes him to low to moderate positive voltage(≤15V). Positive voltage is also a hazard as it focuses electrons onto exposed metal EMU penetrations completing a circuit from plasma through interior contact with the moist crewman’s body and on to ISS ground through any of several secondary isolated metal penetrations. The resulting direct current from positive voltage exposure is now identified as an electrical shock hazard. This paper describes the model of the EMU with a human body in the circuit that has been used by NASA to evaluate the low positive voltage hazard. The model utilizes the electron collection characterization from on orbit Langmuir probe data as representative of electron collection to a positive charged surface with a wide range of on orbit plasma temperature and density conditions. The data has been unified according to nonlinear theoretical temperature and density variation of the electron saturated probe current collection theory and used as a model for the electron collection at EMU surfaces. Vulnerable paths through the EMU connecting through the crewman’s body have been identified along with electrical impedance of the exposed body parts. The body impedance information is merged with the electron collection characteristics in circuit simulation software known as SPICE. The assessment shows that currents can be on the order of 20 mA for a 15 V exposure and of order 4 mA at 3V. These currents formally violate NASA protocol for electric current exposures. However the human factors associated with subjective consequences of noxious stimuli from low voltage exposure during the stressful conditions of EVA are an area of active inquiry.

Characterising the spatial variability of the tidal stream energy resource from floating turbines

NASA Astrophysics Data System (ADS)

Ward, Sophie; Neill, Simon; Robins, Peter

2017-04-01

The shelf seas, in particular the northwest European shelf seas surrounding the UK, contain significant tidal power potential. Tidal stream energy is both predictable and reliable providing that sites are well-selected based upon the hydrodynamic regime and the device specifics. In this high resolution three-dimensional tidal modelling study, we investigate how the tidal stream resource around the Welsh coast (UK) varies with water depth and location, with particular focus on the Pembrokeshire region. The potential extractable energy for a floating tidal stream energy converter is compared with that for a bottom-fixed device, highlighting the need to vary the resource characterisation criteria based on device specifics. We demonstrate how small variations in the tidal current speeds - with hub depth or due to tidal asymmetry - can lead to substantial variations in potential power output. Further, the results indicate that power generation from floating tidal energy converters will be more significantly influenced by tidal elevations in regions characterised by a lower tidal range (more progressive waves) than regions that experience a high tidal range (standing waves). As numerical modelling capacity improves and tidal stream energy converter technologies develop, ongoing improved quantification of the tidal resource is needed, as well as consideration of the possible feedbacks of the devices and energy extraction on the hydrodynamic regime and the surrounding area.

Evaluating the Cost, Safety, and Proliferation Risks of Small Floating Nuclear Reactors.

PubMed

Ford, Michael J; Abdulla, Ahmed; Morgan, M Granger

2017-11-01

It is hard to see how our energy system can be decarbonized if the world abandons nuclear power, but equally hard to introduce the technology in nonnuclear energy states. This is especially true in countries with limited technical, institutional, and regulatory capabilities, where safety and proliferation concerns are acute. Given the need to achieve serious emissions mitigation by mid-century, and the multidecadal effort required to develop robust nuclear governance institutions, we must look to other models that might facilitate nuclear plant deployment while mitigating the technology's risks. One such deployment paradigm is the build-own-operate-return model. Because returning small land-based reactors containing spent fuel is infeasible, we evaluate the cost, safety, and proliferation risks of a system in which small modular reactors are manufactured in a factory, and then deployed to a customer nation on a floating platform. This floating small modular reactor would be owned and operated by a single entity and returned unopened to the developed state for refueling. We developed a decision model that allows for a comparison of floating and land-based alternatives considering key International Atomic Energy Agency plant-siting criteria. Abandoning onsite refueling is beneficial, and floating reactors built in a central facility can potentially reduce the risk of cost overruns and the consequences of accidents. However, if the floating platform must be built to military-grade specifications, then the cost would be much higher than a land-based system. The analysis tool presented is flexible, and can assist planners in determining the scope of risks and uncertainty associated with different deployment options. © 2017 Society for Risk Analysis.

Large-scale environmental degradation results in inequitable impacts to already impoverished communities: A case study from the floating villages of Cambodia.

PubMed

Althor, Glenn; Mahood, Simon; Witt, Bradd; Colvin, Rebecca M; Watson, James E M

2018-02-19

Cambodian subsistence communities within the Tonle Sap Great Lake area rely on resource extraction from the lake to meet livelihood needs. These fishing communities-many of which consist of dwellings floating on the lake-face potentially profound livelihood challenges because of climate change and changing hydrology due to dam construction for hydroelectricity within the Mekong Basin. We conducted interviews across five village communities, with local subsistence fisher people in the Tonle Sap in 2015, and used thematic analysis methods to reveal a fishery system that is undergoing rapid ecological decline, with local fishing communities increasingly experiencing reductions in available fish stocks. As a result, over 100 000 people living in these communities are experiencing a direct loss of well-being and livelihood. We discuss these losses and consider their implications for the future viability of Cambodian floating village communities.

Nonadiabatic Ab Initio Molecular Dynamics with the Floating Occupation Molecular Orbital-Complete Active Space Configuration Interaction Method [Non-Adiabatic Ab Initio Molecular Dynamics with Floating Occupation Molecular Orbitals CASCI Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollas, Daniel; Sistik, Lukas; Hohenstein, Edward G.

Here, we show that the floating occupation molecular orbital complete active space configuration interaction (FOMO-CASCI) method is a promising alternative to the widely used complete active space self-consistent field (CASSCF) method in direct nonadiabatic dynamics simulations. We have simulated photodynamics of three archetypal molecules in photodynamics: ethylene, methaniminium cation, and malonaldehyde. We compared the time evolution of electronic populations and reaction mechanisms as revealed by the FOMO-CASCI and CASSCF approaches. Generally, the two approaches provide similar results. Some dynamical differences are observed, but these can be traced back to energetically minor differences in the potential energy surfaces. We suggest thatmore » the FOMO-CASCI method represents, due to its efficiency and stability, a promising approach for direct ab initio dynamics in the excited state.« less

Assessment of Experimental Uncertainty for a Floating Wind Semisubmersible under Hydrodynamic Loading: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robertson, Amy N; Wendt, Fabian F; Jonkman, Jason

The objective of this paper is to assess the sources of experimental uncertainty in an offshore wind validation campaign focused on better understanding the nonlinear hydrodynamic response behavior of a floating semisubmersible. The test specimen and conditions were simplified compared to other floating wind test campaigns to reduce potential sources of uncertainties and better focus on the hydrodynamic load attributes. Repeat tests were used to understand the repeatability of the test conditions and to assess the level of random uncertainty in the measurements. Attention was also given to understanding bias in all components of the test. The end goal ofmore » this work is to set uncertainty bounds on the response metrics of interest, which will be used in future work to evaluate the success of modeling tools in accurately calculating hydrodynamic loads and the associated motion responses of the system.« less

Borofloat and Starphire Float Glasses: A Comparison

DOE PAGES

Wereszczak, Andrew A.; Anderson Jr., Charles E.

2014-10-28

Borofloat ® borosilicate float glass and Starphire ® soda-lime silicate float glass are used in transparent protective systems. They are known to respond differently in some ballistic and triaxial loading conditions, and efforts are underway to understand the causes of those differences. Toward that, a suite of test and material characterizations were completed in the present study on both glasses so to identify what differences exist among them. Compositional, physical properties, elastic properties, flaw size distributions and concentrations, tensile/flexure strength, fracture toughness, spherical indentation and hardness, transmission electron microscopy, striae, high pressure responses via diamond anvil cell testing, laser shockmore » differences, and internal porosity were examined. Differences between these two float glasses were identified for many of these properties and characteristics, and the role of three (striae, high pressures where permanent densification can initiate, and sub-micron-sized porosity) lack understanding and deserve further attention. Lastly, the contributing roles of any of those properties or characteristics to triaxial or ballistic loading responses are not definitive; however, they provide potential correlations that may lead to improved understanding and management of loading responses in glasses used in transparent protective systems.« less

Assessing the effectiveness of pollutant removal by macrophytes in a floating wetland for wastewater treatment

NASA Astrophysics Data System (ADS)

Prajapati, Meera; van Bruggen, Johan J. A.; Dalu, Tatenda; Malla, Rabin

2017-12-01

The study aimed to evaluate the removal of pollutants by floating treatment wetlands (FTWs) using an edible floating plant, and emergent macrophytes. All experiments were performed under ambient conditions. Physico-chemical parameters were measured, along with microbiological analysis of biofilm within the roots, water column, and sludge and gravel zone. Nitrification and denitrification rates were high in the water zone of Azolla filiculoides, Lemna minor, Lactuca sativa, P. stratiotes, and Phragmites australis. Phosphate removal efficiencies were 23, 10, and 15% for the free-floating hydrophytes, emergent macrophytes, and control and edible plants, respectively. The microbial community was relatively more active in the root zone compared to other zones. Pistia stratiotes was found to be the efficient in ammonium (70%) and total nitrogen (59%) removal. Pistia stratiotes also showed the highest microbial activity of 1306 mg day-1, which was 62% of the total volume. Microbial activity was found in the water zone of all FTWs expect for P. australis. The use of P. stratiotes and the edible plant L. sativa could be a potential option to treat domestic wastewater due to relatively high nutrient and organic matter removal efficiency.

Invasive floating macrophytes reduce greenhouse gas emissions from a small tropical lake

PubMed Central

Attermeyer, K.; Flury, S.; Jayakumar, R.; Fiener, P.; Steger, K.; Arya, V.; Wilken, F.; van Geldern, R.; Premke, K.

2016-01-01

Floating macrophytes, including water hyacinth (Eichhornia crassipes), are dominant invasive organisms in tropical aquatic systems, and they may play an important role in modifying the gas exchange between water and the atmosphere. However, these systems are underrepresented in global datasets of greenhouse gas (GHG) emissions. This study investigated the carbon (C) turnover and GHG emissions from a small (0.6 km2) water-harvesting lake in South India and analysed the effect of floating macrophytes on these emissions. We measured carbon dioxide (CO2) and methane (CH4) emissions with gas chambers in the field as well as water C mineralization rates and physicochemical variables in both the open water and in water within stands of water hyacinths. The CO2 and CH4 emissions from areas covered by water hyacinths were reduced by 57% compared with that of open water. However, the C mineralization rates were not significantly different in the water between the two areas. We conclude that the increased invasion of water hyacinths and other floating macrophytes has the potential to change GHG emissions, a process that might be relevant in regional C budgets. PMID:26846590

Invasive floating macrophytes reduce greenhouse gas emissions from a small tropical lake

NASA Astrophysics Data System (ADS)

Attermeyer, K.; Flury, S.; Jayakumar, R.; Fiener, P.; Steger, K.; Arya, V.; Wilken, F.; van Geldern, R.; Premke, K.

2016-02-01

Floating macrophytes, including water hyacinth (Eichhornia crassipes), are dominant invasive organisms in tropical aquatic systems, and they may play an important role in modifying the gas exchange between water and the atmosphere. However, these systems are underrepresented in global datasets of greenhouse gas (GHG) emissions. This study investigated the carbon (C) turnover and GHG emissions from a small (0.6 km2) water-harvesting lake in South India and analysed the effect of floating macrophytes on these emissions. We measured carbon dioxide (CO2) and methane (CH4) emissions with gas chambers in the field as well as water C mineralization rates and physicochemical variables in both the open water and in water within stands of water hyacinths. The CO2 and CH4 emissions from areas covered by water hyacinths were reduced by 57% compared with that of open water. However, the C mineralization rates were not significantly different in the water between the two areas. We conclude that the increased invasion of water hyacinths and other floating macrophytes has the potential to change GHG emissions, a process that might be relevant in regional C budgets.

Production and Study of High-Beta Plasma Confined by a Superconducting Dipole Magnet

NASA Astrophysics Data System (ADS)

Garnier, Darren

2005-10-01

The Levitated Dipole Experiment (LDX)http://psfcwww2.psfc.mit.edu/ldx/ is a new research facility that is exploring the confinement and stability of plasma created within the dipole field produced by a strong superconducting magnet. Unlike other configurations in which stability depends on curvature and magnetic shear, MHD stability of a dipole derives from plasma compressibility. Theoretically, the dipole magnetic geometry can stabilize a centrally-peaked plasma pressure that exceeds the local magnetic pressure (β> 1), and the absence of magnetic shear allows particle and energy confinement to decouple. In this presentation, the first experiments using the LDX facility are reported. Long-pulse, quasi-steady state microwave discharges lasting up to 12 seconds have been produced that are consistent with equilibria having peak beta values of 10%. Detailed measurements have been made of discharge evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles, and plasma boundary shape. In these initial experiments, the high-field superconducting floating coil was supported by three thin supports and later the coil will be magnetically levitated. The plasma was created by multi- frequency electron cyclotron resonance heating at 2.45 and 6.4 GHz, and a population of energetic electrons, with mean energies above 50 keV, dominated the plasma pressure. Creation of high-pressure, high-beta plasma is only possible when intense hot electron interchange instabilities are stabilized sufficiently by a high background plasma density. A dramatic transition from a low-density, low-beta regime to a more quiescent, high-beta regime is observed when the plasma-fueling rate and confinement times are sufficiently long. External shaping coils are seen to modify the outer plasma boundary and affect the transition.

Renormalization group procedure for potential -g/r2

NASA Astrophysics Data System (ADS)

Dawid, S. M.; Gonsior, R.; Kwapisz, J.; Serafin, K.; Tobolski, M.; Głazek, S. D.

2018-02-01

Schrödinger equation with potential - g /r2 exhibits a limit cycle, described in the literature in a broad range of contexts using various regularizations of the singularity at r = 0. Instead, we use the renormalization group transformation based on Gaussian elimination, from the Hamiltonian eigenvalue problem, of high momentum modes above a finite, floating cutoff scale. The procedure identifies a richer structure than the one we found in the literature. Namely, it directly yields an equation that determines the renormalized Hamiltonians as functions of the floating cutoff: solutions to this equation exhibit, in addition to the limit-cycle, also the asymptotic-freedom, triviality, and fixed-point behaviors, the latter in vicinity of infinitely many separate pairs of fixed points in different partial waves for different values of g.

14 CFR 27.753 - Main float design.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main float design. 27.753 Section 27.753... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Floats and Hulls § 27.753 Main float design. (a) Bag floats. Each bag float must be designed to withstand— (1) The maximum pressure differential...

14 CFR 29.753 - Main float design.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main float design. 29.753 Section 29.753... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Floats and Hulls § 29.753 Main float design. (a) Bag floats. Each bag float must be designed to withstand— (1) The maximum pressure differential...

Formation of carbon allotrope aerosol by colliding plasmas in an inertial fusion reactor

NASA Astrophysics Data System (ADS)

Hirooka, Y.; Sato, H.; Ishihara, K.; Yabuuchi, T.; Tanaka, K. A.

2014-02-01

Along with repeated implosions, the interior of an inertial fusion target chamber is exposed to short pulses of high-energy x-ray, unburned DT-fuel particles, He-ash and pellet debris. As a result, chamber wall materials are subjected to ablation, emitting particles in the plasma state. Ablated particles will either be re-deposited elsewhere or collide with each other, perhaps in the centre-of-symmetry region of the chamber volume. Colliding ablation plasma particles can lead to the formation of clusters to grow into aerosol, possibly floating thereafter, which can deteriorate the subsequent implosion performance via laser scattering, etc. In a laboratory-scale YAG laser setup, the formation of nano-scale aerosol has been demonstrated in vacuum at irradiation power densities of the orders of 108-10 W cm-2 at 10 Hz, each 6 ns long, simulating the high-repetition rate inertial fusion reactor situation. Interestingly, carbon aerosol formation has been observed in the form of fullerene onion, nano- and micro-tubes when laser-ablated plasma plumes of carbon collide with each other. In contrast, colliding plasma plumes of metals tend to generate aerosol in the form of droplets under identical laser irradiation conditions. An atomic and molecular reaction model is proposed to interpret the process of carbon allotrope aerosol formation.

Interaction of atmospheric pressure plasmas with dry and wet wounded skin

NASA Astrophysics Data System (ADS)

Babaeva, Natalia; Kushner, Mark

2010-11-01

Non-equilibrium plasmas in direct contact with living tissue can produce therapeutic effects. Dielectric barrier discharge (DBD) devices used for this purpose contain the powered electrode while the tissue being treated is usually the floating electrode. The plasma produces beneficial effects through: (i) electric fields, (ii) production of radicals and charged species, (iii) photons and (iv) energetic ions impinging onto wounds and tissue surfaces. Using a 2-d plasma hydrodynamics model, we discuss the interaction of DBD filaments with human skin. We model the propagation of the streamer across the gap, its intersection with skin, the charging of cell surfaces and the generation of conduction and displacement currents, and electric fields in the cells. The cellular structure in the first few mm of human skin is incorporated into the computational mesh with permittivity and conductivity to represent the electrical properties of the intra- and inter-cell structures. In this talk, we concentrate on the effects of plasmas on open wounds which are either dry or filled with blood serum. We will discuss the penetration of electric fields through the blood serum and into the underlying cells, including the possible interactions with blood platelets, and the distribution of ion energies onto the liquid and cellular surfaces.

Characteristics of chiral plasma plumes generated in the absence of external magnetic field

NASA Astrophysics Data System (ADS)

Nie, LanLan; Liu, FengWu; Zhou, XinCai; Lu, XinPei; Xian, YuBin

2018-05-01

A chiral plasma plume has recently been generated inside a dielectric tube without the use of an external magnetic field. In this paper, we seek to further study the key properties of such a chiral plume to improve our understanding of how this interesting structure is generated and controlled. The chiral plume is generated by externally mounting a stainless steel helical coil or a ring onto the dielectric tube. By changing the pitch of the helical coil, the pitch of the plasma plume can be controlled, with the shape of the plume following the shape of the helical coil. The addition of the helical coil significantly expands the range of parameters under which the chiral plasma plume appears. When the frequency of the applied voltage increases, additional stable discharge channels appear between the adjacent helices. The addition of two helical coils results in the formation of two chiral plasma plumes, which follow the shape of the helical coils. When a metal ring is placed on the outside of the tube, there is no chiral plasma plume between the high voltage electrode and the ring; however, a chiral plasma plume appears on the right side of the ring if the distance between the ring and the high voltage electrode is small. These findings suggest that the chiral plasma can be effectively modulated and guided using an externally mounted helical coil, which acts as the floating/actual ground to reduce the impedance of the discharge and as such contributes to the emergence of the chiral plasma plume behavior.

International Space Station (ISS) Plasma Contactor Unit (PCU) Utilization Plan Assessment Update

NASA Technical Reports Server (NTRS)

Hernandez-Pellerano, Amri; Iannello, Christopher J.; Garrett, Henry B.; Ging, Andrew T.; Katz, Ira; Keith, R. Lloyd; Minow, Joseph I.; Willis, Emily M.; Schneider, Todd A.; Whittlesey, Edward J.;

40 CFR 65.45 - External floating roof converted into an internal floating roof.

Code of Federal Regulations, 2010 CFR

2010-07-01

... External floating roof converted into an internal floating roof. The owner or operator who elects to... 40 Protection of Environment 15 2010-07-01 2010-07-01 false External floating roof converted into an internal floating roof. 65.45 Section 65.45 Protection of Environment ENVIRONMENTAL PROTECTION...

Cycling and floating performance of symmetric supercapacitor derived from coconut shell biomass

NASA Astrophysics Data System (ADS)

Barzegar, Farshad; Khaleed, Abubakar A.; Ugbo, Faith U.; Oyeniran, Kabir O.; Momodu, Damilola Y.; Bello, Abdulhakeem; Dangbegnon, Julien K.; Manyala, Ncholu

2016-11-01

This work present two-step synthesizes route to low-cost mesoporous carbon from coconut shell. The electrochemical characterization of the coconut shell based activated carbon (CSAC) material as electrode for supercapacitor showed a specific capacitance of 186 F g-1, energy density of ˜11 Wh kg-1 and power density of 325 W kg-1 at a 0.5 A g-1 with an excellent stability after floating for 100 h and cycling for 10000 cycles in polymer gel electrolyte. The CSAC showed very good potential as a stable material for supercapacitors desirable for high power applications.

Dust impacts detected by Voyager-2 at Saturn and Uranus: A post-Halley view

NASA Astrophysics Data System (ADS)

Oberc, P.

1994-09-01

A new approach to the Voyager-2 dust impact observations near the ring plane of Saturn and Uranus is proposed in the paper, based on the experience from analyses of simulataneous dust and electric field observations by Vega-2 at Halley. Taking into account the impact geometry and the ambient plasma parameters, the possible responses of the two instruments, PRA (planetary radio astronomy) and PWS (plasma wave science), utilizing the same Voyager antenna, are evaluated as functions of the impact-induced charge. It is shown that the PRA instrument, which used the antenna elements as monopoles, responded mostly to pulses of the spacecraft potential, while the PWS instrument, working in dipole configuration, responded mostly to charge-separation electric fields. Due to the negative floating potential during both ring plane crossings the effect of charging the antenna was weak. The dust mass spectra near both ring planes are derived from the apparent impact rates and the V(rms) voltages, observed simultaneously by the PWS instrument. At Saturn's ring plane at 2.86 RS the obtained peak number density of particles bigger than 2 x 10-7g is 3.7 x 10-3/cu m, while the integral mass spectrum index alpha is about 1.5 at this mass magnitude and decreases toward lower masses down to values less than 1. In the ring plane region of Uranus at 4.51 RU the maximum number density for the limiting mass of 3.5 x 10-10g is found to be 4.4 x 10-4/cu m, while the index alpha at this mass is about 1.

Self-organized criticality: An interplay between stable and turbulent regimes of multiple anodic double layers in glow discharge plasma

NASA Astrophysics Data System (ADS)

Alex, Prince; Carreras, Benjamin Andres; Arumugam, Saravanan; Sinha, Suraj Kumar

2018-05-01

The role of self-organized criticality (SOC) in the transformation of multiple anodic double layers (MADLs) from the stable to turbulent regime has been investigated experimentally as the system approaches towards critical behavior. The experiment was performed in a modified glow discharge plasma setup, and the initial stable state of MADL comprising three concentric perceptible layers was produced when the drift velocity of electrons towards the anode exceeds the electron thermal velocity (νd ≥ 1.3νte). The macroscopic arrangement of both positive and negative charges in opposite layers of MADL is attributed to the self-organization scenario. Beyond νd ≥ 3νte, MADL begins to collapse and approaches critical and supercritical states through layer reduction which continue till the last remaining layer of the double layer is transformed into a highly unstable radiant anode glow. The avalanche resulting from the collapse of MADL leads to the rise of turbulence in the system. Long-range correlations, a key signature of SOC, have been explored in the turbulent floating potential fluctuations using the rescaled-range analysis technique. The result shows that the existence of the self-similarity regime with self-similarity parameter H varies between 0.55 and 0.91 for time lags longer than the decorrelation time. The power law tail in the rank function, slowly decaying tail of the autocorrelation function, and 1/f behavior of the power spectra of the fluctuations are consistent with the fact that SOC plays a conclusive role in the transformation of MADL from the stable to turbulent regime. Since the existence of SOC gives a measure of complexity in the system, the result provides the condition under which complexity arises in cold plasma.

Experimental Study of Arcing on High-voltage Solar Arrays

NASA Technical Reports Server (NTRS)

Vayner, Boris; Galofaro, Joel; Ferguson, Dale

2005-01-01

The main obstacle to the implementation of a high-voltage solar array in space is arcing on the conductor-dielectric junctions exposed to the surrounding plasma. One obvious solution to this problem would be the installation of fully encapsulated solar arrays which were not having exposed conductors at all. However, there are many technological difficulties that must be overcome before the employment of fully encapsulated arrays will turn into reality. An alternative solution to raise arc threshold by modifications of conventionally designed solar arrays looks more appealing, at least in the nearest future. A comprehensive study of arc inception mechanism [1-4] suggests that such modifications can be done in the following directions: i) to insulate conductor-dielectric junction from a plasma environment (wrapthrough interconnects); ii) to change a coverglass geometry (overhang); iii) to increase a coverglass thickness; iiii) to outgas areas of conductor-dielectric junctions. The operation of high-voltage array in LEO produces also the parasitic current power drain on the electrical system. Moreover, the current collected from space plasma by solar arrays determines the spacecraft floating potential that is very important for the design of spacecraft and its scientific apparatus. In order to verify the validity of suggested modifications and to measure current collection five different solar array samples have been tested in large vacuum chamber. Each sample (36 silicon based cells) consists of three strings containing 12 cells connected in series. Thus, arc rate and current collection can be measured on every string independently, or on a whole sample when strings are connected in parallel. The heater installed in the chamber provides the possibility to test samples under temperature as high as 80 C that simulates the LEO operational temperature. The experimental setup is described below.

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

NASA Astrophysics Data System (ADS)

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

2013-08-01

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

Experimental Study of Arcing on High-Voltage Solar Arrays

NASA Technical Reports Server (NTRS)

Vayner, Boris; Galofaro, Joel; Ferguson, Dale

2003-01-01

The main obstacle to the implementation of a high-voltage solar array in space is arcing on the conductor-dielectric junctions exposed to the surrounding plasma. One obvious solution to this problem would be the installation of fully encapsulated solar arrays which were not having exposed conductors at all. However, there are many technological difficulties that must be overcome before the employment of fully encapsulated arrays will turn into reality. An alternative solution to raise arc threshold by modifications of conventionally designed solar arrays looks more appealing, at least in the nearest future. A comprehensive study of arc inception mechanism suggests that such modifications can be done in the following directions: 1) To insulate conductor-dielectric junction from a plasma environment (wrapthrough interconnects); 2) To change a coverglass geometry (overhang); 3) To increase a coverglass thickness; 4) To outgas areas of conductor-dielectric junctions. The operation of high-voltage array in LEO produces also the parasitic current power drain on the electrical system. Moreover, the current collected from space plasma by solar arrays determines the spacecraft floating potential that is very important for the design of spacecraft and its scientific apparatus. In order to verify the validity of suggested modifications and to measure current collection five different solar array samples have been tested in a large vacuum chamber. Each sample (36 silicon based cells) consists of three strings containing 12 cells connected in series. Thus, arc rate and current collection can be measured on every string independently, or on a whole sample when strings are connected in parallel. The heater installed in the chamber provides the possibility to test samples under temperature as high as 80 C that stimulates the LEO operational temperature. The experimental setup is described below.

Dispersive liquid-liquid microextraction followed by high-performance liquid chromatography-ultraviolet detection to determination of opium alkaloids in human plasma.

PubMed

Ahmadi-Jouibari, Toraj; Fattahi, Nazir; Shamsipur, Mojtaba; Pirsaheb, Meghdad

2013-11-01

A novel, simple, rapid and sensitive dispersive liquid-liquid microextraction method based on the solidification of floating organic drop (DLLME-SFO) combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) was used to determine opium alkaloids in human plasma. During the extraction procedure, plasma protein was precipitated by using a mixture of zinc sulfate solution and acetonitrile. Some effective parameters on extraction were studied and optimized. Under the optimum conditions (extraction solvent: 30.0 μl 1-undecanol; disperser solvent: 470 μl acetone; pH: 9; salt addition: 1%(w/v) NaCl and extraction time: 0.5 min), calibration curves are linear in the range of 1.5-1000 μgl(-1) and limit of detections (LODs) are in the range of 0.5-5 μgl(-1). The relative standard deviations (RSDs) for 100 μgl(-1) of morphine and codeine, 10.0 μgl(-1) of papaverine and 20.0 μgl(-1) of noscapine in diluted human plasma are in the range of 4.3-7.4% (n=5). Finally, the method was successfully applied in the determination of opium alkaloids in the actual human plasma samples. The relative recoveries of plasma samples spiked with alkaloids are 88-110.5%. The obtained results show that DLLME-SFO combined with HPLC-UV is a fast and simple method for the determination of opium alkaloids in human plasma. Copyright © 2013 Elsevier B.V. All rights reserved.

76 FR 6118 - Endangered Species; File No. 14726

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-03

... potential Mississippi Canyon 252 oil exposure of pelagic sea turtles associated with floating Sargassum as part of the post-spill Natural Resources Damage Assessment of the BP Deepwater Horizon event. The...

In silico and in vitro methods to optimize the performance of experimental gastroretentive floating mini-tablets.

PubMed

Eberle, Veronika A; Häring, Armella; Schoelkopf, Joachim; Gane, Patrick A C; Huwyler, Jörg; Puchkov, Maxim

2016-01-01

Development of floating drug delivery systems (FDDS) is challenging. To facilitate this task, an evaluation method was proposed, which allows for a combined investigation of drug release and flotation. It was the aim of the study to use functionalized calcium carbonate (FCC)-based lipophilic mini-tablet formulations as a model system to design FDDS with a floating behavior characterized by no floating lag time, prolonged flotation and loss of floating capability after complete drug release. Release of the model drug caffeine from the mini-tablets was assessed in vitro by a custom-built stomach model. A cellular automata-based model was used to simulate tablet dissolution. Based on the in silico data, floating forces were calculated and analyzed as a function of caffeine release. Two floating behaviors were identified for mini-tablets: linear decrease of the floating force and maintaining of the floating capability until complete caffeine release. An optimal mini-tablet formulation with desired drug release time and floating behavior was developed and tested. A classification system for a range of varied floating behavior of FDDS was proposed. The FCC-based mini-tablets had an ideal floating behavior: duration of flotation is defined and floating capability decreases after completion of drug release.

A general theory for ball lightning structure and light output

NASA Astrophysics Data System (ADS)

Morrow, R.

2018-03-01

A general theory for free-floating ball lightning is presented which unifies the phantom plasma ball theory involving the production of very little light, with theories for ball lightning involving light output produced by burning particles from the soil. The mechanism for the formation of plasma balls is shown to be quite general, producing very similar plasma balls independent of initial ion densities over four orders of magnitude. All that is required is an excess of positive ions in the initial ball of ions. The central plasma density after 1 s is shown to be the reciprocal of the ion neutralization coefficient for all cases, both analytically and computationally. Further, the plasma region has zero electric field in all cases. Surrounding the plasma ball is a sphere of positive ions moving away from the centre via their own space-charge field; this space-charge field, which is the same in all cases near the plasma ball, drives negative ions and negative particles towards the plasma centre. The connection with burning particle theories is the proposition that the burning particles are highly-charged which is very likely after a lightning strike. Burning negatively charged particles would be driven into the plasma ball region and trapped while any positively charged particles would be driven away. The plasma ball structure is shown to last more than 10 s and the ‘burnout time’ for a typical coal particle (as an example) has been measured at 5-10 s this is comparable with the lifetimes observed for ball lightning. The light output from a few hundred particles is estimated to be ~1 W, a typical output for ball lightning. Finally, suggestions are made for the generation of ball lightning in the laboratory.

Effects of dc bias on the kinetics and electrical properties of silicon dioxide grown in an electron cyclotron resonance plasma

NASA Astrophysics Data System (ADS)

Carl, D. A.; Hess, D. W.; Lieberman, M. A.; Nguyen, T. D.; Gronsky, R.

1991-09-01

Thin (3-300-nm) oxides were grown on single-crystal silicon substrates at temperatures from 523 to 673 K in a low-pressure electron cyclotron resonance (ECR) oxygen plasma. Oxides were grown under floating, anodic or cathodic bias conditions, although only the oxides grown under floating or anodic bias conditions are acceptable for use as gate dielectrics in metal-oxide-semiconductor technology. Oxide thickness uniformity as measured by ellipsometry decreased with increasing oxidation time for all bias conditions. Oxidation kinetics under anodic conditions can be explained by negatively charged atomic oxygen, O-, transport limited growth. Constant current anodizations yielded three regions of growth: (1) a concentration gradient dominated regime for oxides thinner than 10 nm, (2) a field dominated regime with ohmic charged oxidant transport for oxide thickness in the range of 10 nm to approximately 100 nm, and (3) a space-charge limited regime for films thicker than approximately 100 nm. The relationship between oxide thickness (xox), overall potential drop (Vox) and ion current (ji) in the space-charge limited transport region was of the form: ji ∝ V2ox/x3ox. Transmission electron microscopy analysis of 5-60-nm-thick anodized films indicated that the silicon-silicon dioxide interface was indistinguishable from that of thermal oxides grown at 1123 K. High-frequency capacitance-voltage (C-V) and ramped bias current-voltage (I-V) studies performed on 5.4-30-nm gate thickness capacitors indicated that the as-grown ECR films had high levels of fixed oxide charge (≳1011 cm-2) and interface traps (≳1012 cm-2 eV-1). The fixed charge level could be reduced to ≊4×1010 cm-2 by a 20 min polysilicon gate activation anneal at 1123 K in nitrogen; the interface trap density at mid-band gap decreased to ≊(1-2)×1011 cm-2 eV-1 after this process. The mean breakdown strength for anodic oxides grown under optimum conditions was 10.87±0.83 MV cm-1. Electrical properties of the 5.4-8-nm gates compared well with thicker films and control dry thermal oxides of similar thicknesses.

Mercury ion thruster research, 1978

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1978-01-01

The effects of 8 cm thruster main and neutralizer cathode operating conditions on cathode orifice plate temperatures were studied. The effects of cathode operating conditions on insert temperature profiles and keeper voltages are presented for three different types of inserts. The bulk of the emission current is generally observed to come from the downstream end of the insert rather than from the cathode orifice plate. Results of a test in which the screen grid plasma sheath of a thruster was probed as the beam current was varied are shown. Grid performance obtained with a grid machined from glass ceramic is discussed. The effects of copper and nitrogen impurities on the sputtering rates of thruster materials are measured experimentally and a model describing the rate of nitrogen chemisorption on materials in either the beam or the discharge chamber is presented. The results of optimization of a radial field thruster design are presented. Performance of this device is shown to be comparable to that of a divergent field thruster and efficient operation with the screen grid biased to floating potential, where its susceptibility to sputter erosion damage is reduced, is demonstrated.

Geodesic acoustic mode (GAM) like oscillations and RMP effect in the STOR-M tokamak

NASA Astrophysics Data System (ADS)

Basu, Debjyoti; Nakajima, Masaru; Melnikov, A. V.; McColl, David; Rohollahi, Akbar; Elgriw, Sayf; Xiao, Chijin; Hirose, Akira

2018-02-01

A new kind of quasi-coherent mode was observed in ohmic plasma in the STOR-M tokamak. It is featured with a clear solitary peak around 30-35 kHz in the power spectra of the ion saturation current (I_sat) of Langmuir probe as well as poloidal and toroidal mode numbers (m  =  1,n  =  0) as per the prediction of conventional geodesic acoustic mode (GAM) theory. The dispersion relation of the mode is also similar to GAM and it also shows collisional damping. In contrast to conventional GAM, the floating potential ϕ of the observed GAM-like mode does not show similar symmetric poloidal and toroidal mode numbers (m  =  0,n  =  0), but has (m  =  1,n  =  1). The GAM-like mode has also a pronounced magnetic component with mixed poloidal modes (m=3~and~m=5; n=1 ), as observed by Mirnov coils. This mode is suppressed by the application of resonance magnetic perturbations.

Floating microbial fuel cells as energy harvesters for signal transmission from natural water bodies

NASA Astrophysics Data System (ADS)

Schievano, Andrea; Colombo, Alessandra; Grattieri, Matteo; Trasatti, Stefano P.; Liberale, Alessandro; Tremolada, Paolo; Pino, Claudio; Cristiani, Pierangela

2017-02-01

A new type of floating microbial fuel cell (fMFC) was developed for power supply of remote environmental sensors and data transmission. Ten operating fMFCs generated a cell potential in the range 100-800 mV depending on the external resistance applied. Power production peaked around 3-3.5 mW (power density of 22-28 mW m-2 cathode) after about 20-30 days of start-up period. The average of daily electrical energy harvested ranged between 10 and 35 mWh/d. Long-term performances were ensured in the presence of dense rice plants (Oryza Sativa). A power management system, based on a step-up DC/DC converter and a low-power data transmission system via SIGFOX™ technology, have been set up for the fMFCs. The tested fMFCs systems allowed to: i) harvest produced energy, ii) supply electronic devices (intermittent LED-light and a buzzer); iii) transmit remote data at low speed (three message of 12 bites each, in 6 s). Several 'floating garden' MFCs were set in the context of demonstrative events at EXPO2015 world exposition held in Milan between May-October 2015. Some of the 'floating garden' MFCs were operating for more than one year.

A comparison between the dynamics of horizontal and vertical axis offshore floating wind turbines.

PubMed

Borg, M; Collu, M

2015-02-28

The need to further exploit offshore wind resources in deeper waters has led to a re-emerging interest in vertical axis wind turbines (VAWTs) for floating foundation applications. However, there has been little effort to systematically compare VAWTs to the more conventional horizontal axis wind turbine (HAWT). This article initiates this comparison based on prime principles, focusing on the turbine aerodynamic forces and their impact on the floating wind turbine static and dynamic responses. VAWTs generate substantially different aerodynamic forces on the support structure, in particular, a potentially lower inclining moment and a substantially higher torque than HAWTs. Considering the static stability requirements, the advantages of a lower inclining moment, a lower wind turbine mass and a lower centre of gravity are illustrated, all of which are exploitable to have a less costly support structure. Floating VAWTs experience increased motion in the frequency range surrounding the turbine [number of blades]×[rotational speed] frequency. For very large VAWTs with slower rotational speeds, this frequency range may significantly overlap with the range of wave excitation forces. Quantitative considerations are undertaken comparing the reference NREL 5 MW HAWT with the NOVA 5 MW VAWT. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Potential area for floating net fishery in Lake Toba

NASA Astrophysics Data System (ADS)

Rustini, H. A.; Harsono, E.; Ridwansyah, I.

2018-02-01

Lake Toba in North Sumatera, Indonesia, is now designated to be a world-class tourism destination. Aside from its infrastructure development, this largest lake in the Southeast Asia needs to be restored, especially its water quality. While an oligotrophic status is required for tourism purposes, several studies showed that Toba is mesotrophic at its best and hyper-eutrophic at its worst. Numerous studies and reports blame floating net fishery (FNF) for water quality decline in Lake Toba and propose limitation for its production. While the central government allowed FNF to be positioned in certain areas according to its depth and distance from the lakeshore, increasing number of FNF means adding more nutrients to the lake and thus may inhibit the lake’s restoration process. Hence, it is important to identify which areas are potential for FNF location to assist the authorities to regulate FNF. This study used SPOT-6, SPOT-7, and Pleiades satellite imagery to locate the position of existing FNF and to analyse the result to identify a potential location for FNF.

On the Maas problem of seawater intrusion combated by infiltration

NASA Astrophysics Data System (ADS)

Kacimov, A. R.

2008-09-01

SummaryThe problem of Maas [Maas, K. 2007. Influence of climate change on a Ghijben-Herzberg lens. J. Hydrol. 347, 223-228] for infiltration inflow into a porous flat-roofed fresh water lens floating on the interface of an ascending Darcian saline water flow is shown to be in exact match with the Polubarinova-Kochina [Polubarinova-Kochina, P.Ya., 1977. Theory of Ground Water Movement. Nauka, Moscow (in Russian)] problem for flow in a lens capped by a cambered phreatic surface with a uniform accretion. The Maas complex potential in the domain of a heavy saline water seeping beneath the lens corresponds to one of an ideal fluid flow past an elliptical cylinder that makes possible conversion of this potential into ascending-descending seepage flows with floating (but stagnant) DNAPL-LNAPL volumes. Similar matching is possible for the velocity potential of an axisymmetric flow past an ellipsoid and hydrostatic pressure of a stagnant NAPL body stored in a semi-ellipsoidal pond.

Depth, ice thickness, and ice-out timing cause divergent hydrologic responses among Arctic lakes

USGS Publications Warehouse

Arp, Christopher D.; Jones, Benjamin M.; Liljedahl, Anna K.; Hinkel, Kenneth M.; Welker, Jeffery A.

2015-01-01

Lakes are prevalent in the Arctic and thus play a key role in regional hydrology. Since many Arctic lakes are shallow and ice grows thick (historically 2-m or greater), seasonal ice commonly freezes to the lake bed (bedfast ice) by winter's end. Bedfast ice fundamentally alters lake energy balance and melt-out processes compared to deeper lakes that exceed the maximum ice thickness (floating ice) and maintain perennial liquid water below floating ice. Our analysis of lakes in northern Alaska indicated that ice-out of bedfast ice lakes occurred on average 17 days earlier (22-June) than ice-out on adjacent floating ice lakes (9-July). Earlier ice-free conditions in bedfast ice lakes caused higher open-water evaporation, 28% on average, relative to floating ice lakes and this divergence increased in lakes closer to the coast and in cooler summers. Water isotopes (18O and 2H) indicated similar differences in evaporation between these lake types. Our analysis suggests that ice regimes created by the combination of lake depth relative to ice thickness and associated ice-out timing currently cause a strong hydrologic divergence among Arctic lakes. Thus understanding the distribution and dynamics of lakes by ice regime is essential for predicting regional hydrology. An observed regime shift in lakes to floating ice conditions due to thinner ice growth may initially offset lake drying because of lower evaporative loss from this lake type. This potential negative feedback caused by winter processes occurs in spite of an overall projected increase in evapotranspiration as the Arctic climate warms.

Characterizations of Plasticized Polymeric Film Coatings for Preparing Multiple-Unit Floating Drug Delivery Systems (muFDDSs) with Controlled-Release Characteristics

PubMed Central

Chen, Ying-Chen; Wang, Yu-Chun; Ho, Hsiu-O; Sheu, Ming-Thau

2014-01-01

Effervescent multiple-unit floating drug delivery systems (muFDDSs) consisting of drug (lorsartan)- and effervescent (sodium bicarbonate)-containing pellets were characterized in this study. The mechanical properties (stress and strain at rupture, Young’s modulus, and toughness) of these plasticized polymeric films of acrylic (Eudragit RS, RL, and NE) and cellulosic materials (ethyl cellulose (EC), and Surelease) were examined by a dynamic mechanical analyzer. Results demonstrated that polymeric films prepared from Surelease and EC were brittle with less elongation compared to acrylic films. Eudragit NE films were very flexible in both the dry and wet states. Because plasticizer leached from polymeric films during exposure to the aqueous medium, plasticization of wet Eudragit RS and RL films with 15% triethyl citrate (TEC) or diethyl phthalate (DEP) resulted in less elongation. DEP might be the plasticizer of choice among the plasticizers examined in this study for Eudragit RL to provide muFDDSs with a short time for all pellets to float (TPF) and a longer period of floating. Eudragit RL and RS at a 1∶1 ratio plasticized with 15% DEP were optimally selected as the coating membrane for the floating system. Although the release of losartan from the pellets was still too fast as a result of losartan being freely soluble in water, muFDDSs coated with Eudragit RL and RS at a 1∶1 ratio might have potential use for the sustained release of water-insoluble or the un-ionized form of drugs from gastroretentive drug delivery systems. PMID:24967594

Formulation and evaluation of floating tablet of H2-receptor antagonist.

PubMed

Kesarla, Rajesh S; Vora, Pratik Ashwinbhai; Sridhar, B K; Patel, Gunvant; Omri, Abdelwahab

2015-01-01

Conventional sustained dosage form of ranitidine hydrochloride (HCl) does not prevent frequent administration due to its degradation in colonic media and limited absorption in the upper part of GIT. Ranitidine HCl floating tablet was formulated with sublimation method to overcome the stated problem. Compatibility study for screening potential excipients was carried out using Fourier transform infrared spectroscopy (FT-IR) and differential scanning chromatography (DSC). Selected excipients were further evaluated for optimizing the formulation. Preliminary screening of binder, polymer and sublimating material was based on hardness and drug release, drug release with release kinetics and floating lag time with total floatation time, respectively. Selected excipients were subjected to 3(2) factorial design with polymer and sublimating material as independent factors. Matrix tablets were obtained by using 16/32" flat-faced beveled edges punches followed by sublimation. FT-IR and DSC indicated no significant incompatibility with selected excipients. Klucel-LF, POLYOX WSR N 60 K and l-menthol were selected as binder, polymer and sublimating material, respectively, for factorial design batches after preliminary screening. From the factorial design batches, optimum concentration to release the drug within 12 h was found to be 420 mg of POLYOX and 40 mg of l-menthol. Stability studies indicated the formulation as stable. Ranitidine HCl matrix floating tablets were formulated to release 90% of drug in stomach within 12 h. Hence, release of the drug could be sustained within narrow absorption site. Moreover, the dosage form was found to be floating within a fraction of second independent of the pH of media ensuring a robust formulation.

A compact, low cost Marx bank for generating capillary discharge plasmas.

PubMed

Dyson, A E; Thornton, C; Hooker, S M

2016-09-01

We describe in detail a low power Compact Marx Bank (CMB) circuit that can provide 20 kV, 500 A pulses of approximately 100-200 ns duration. One application is the generation of capillary discharge plasmas of density ≈10 18 cm -3 used in laser plasma accelerators. The CMB is triggered with a high speed solid state switch and gives a high voltage output pulse with a ns scale rise time into a 50 Ω load (coaxial cable) with <4 ns voltage jitter. Its small size (10 cm  ×  25 cm  ×  5 cm) means that it can be placed right next to the capillary discharge in the target chamber to avoid the need to impedance match. The electrical energy required per discharge is <1 J, and the CMB can be run at shot repetition rates of ≳1 Hz. This low power requirement means that the circuit can easily be powered by a small lead acid battery and, therefore, can be floated relative to laboratory earth. The CMB is readily scalable and pulses >45 kV are demonstrated in air discharges.

A compact, low cost Marx bank for generating capillary discharge plasmas

NASA Astrophysics Data System (ADS)

Dyson, A. E.; Thornton, C.; Hooker, S. M.

2016-09-01

We describe in detail a low power Compact Marx Bank (CMB) circuit that can provide 20 kV, 500 A pulses of approximately 100-200 ns duration. One application is the generation of capillary discharge plasmas of density ≈1018 cm-3 used in laser plasma accelerators. The CMB is triggered with a high speed solid state switch and gives a high voltage output pulse with a ns scale rise time into a 50 Ω load (coaxial cable) with <4 ns voltage jitter. Its small size (10 cm × 25 cm × 5 cm) means that it can be placed right next to the capillary discharge in the target chamber to avoid the need to impedance match. The electrical energy required per discharge is <1 J, and the CMB can be run at shot repetition rates of ≳1 Hz. This low power requirement means that the circuit can easily be powered by a small lead acid battery and, therefore, can be floated relative to laboratory earth. The CMB is readily scalable and pulses >45 kV are demonstrated in air discharges.

Floating Marine Debris in waters of the Mexican Central Pacific.

PubMed

Díaz-Torres, Evelyn R; Ortega-Ortiz, Christian D; Silva-Iñiguez, Lidia; Nene-Preciado, Alejandro; Orozco, Ernesto Torres

2017-02-15

The presence of marine debris has been reported recently in several oceans basins; there is very little information available for Mexican Pacific coasts, however. This research examined the composition, possible sources, distribution, and density of Floating Marine Debris (FMD) during nine research surveys conducted during 2010-2012 in the Mexican Central Pacific (MCP). Of 1820 floating objects recorded, 80% were plastic items. Sources of FMD were determined using key objects, which indicated that the most were related to the presence of the industrial harbor and of a growing fishing industry in the study area. Densities were relatively high, ranging from 40 to 2440objects/km 2 ; the highest densities were recorded in autumn. FMD were distributed near coastal regions, mainly in Jalisco, influenced by river outflow and surface currents. Our results seem to follow worldwide trends and highlight the need for further studies on potential ecological impacts within coastal waters of the MCP. Copyright © 2016 Elsevier Ltd. All rights reserved.

Theoretical simulation of solar spectra in the middle ultraviolet and visible for atmospheric trace constituent measurements

NASA Technical Reports Server (NTRS)

Goldman, A.

1978-01-01

Two balloon flights reaching float altitudes of approximately 30 and 40 km respectively, were used to obtain scans of the ultraviolet and visible solar spectra. Both flights covered the UV (2800-3500A) at approximately 0.3A resolution and the visible at approximately 0.6A. Numerous scans were obtained during ascent and from float for both flights. All spectral scans obtained at float, from high sun to low sun, were calibrated in wavelength by using several standard solar spectra for line position references. Comparisons of low sun scans and high sun scans show significant atmospheric continuum extinction and have the potential of being used to identify atmospheric lines superimposed on the attenuated solar spectrum. The resolution was mathematically degraded to approximately 5A to better see the broad band atmospheric extinction. This low resolution is also appropriate for the available low resolution absorption coefficients of NO2 and O3, allowing the identification of NO2 and O3 features on the sunset spectra.

Glow discharge detector

DOEpatents

Koo, Jackson C.; Yu, Conrad M.

2002-01-01

A highly sensitive electronic ion cell for the measurement of trace elements in He carrier gas which involves glow discharge. A constant wave (CW) glow discharge detector which is controlled through a biased resistor, can detect the change of electron density caused by impurities in the He carrier gas by many orders of magnitude larger than that caused by direct ionization or electron capture. The glow discharge detector utilizes a floating pseudo-electrode to form a probe in or near the plasma. By using this probe, the large variation of electron density due to trace amounts of impurities can be directly measured.

33 CFR 144.01-1 - Life floats.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Life floats. 144.01-1 Section 144... CONTINENTAL SHELF ACTIVITIES LIFESAVING APPLIANCES Manned Platforms § 144.01-1 Life floats. Each manned platform shall be provided with at least two approved life floats. The life floats shall have sufficient...

46 CFR 160.027-3 - Additional requirements for life floats.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 6 2010-10-01 2010-10-01 false Additional requirements for life floats. 160.027-3..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Life Floats for Merchant Vessels § 160.027-3 Additional requirements for life floats. (a) Each life float must have a platform designed...

46 CFR 160.027-3 - Additional requirements for life floats.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 6 2011-10-01 2011-10-01 false Additional requirements for life floats. 160.027-3..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Life Floats for Merchant Vessels § 160.027-3 Additional requirements for life floats. (a) Each life float must have a platform designed...

33 CFR 144.01-1 - Life floats.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Life floats. 144.01-1 Section 144... CONTINENTAL SHELF ACTIVITIES LIFESAVING APPLIANCES Manned Platforms § 144.01-1 Life floats. Each manned platform shall be provided with at least two approved life floats. The life floats shall have sufficient...

14 CFR 29.757 - Hull and auxiliary float strength.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Hull and auxiliary float strength. 29.757... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Floats and Hulls § 29.757 Hull and auxiliary float strength. The hull, and auxiliary floats if used, must withstand the...

33 CFR 144.01-1 - Life floats.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Life floats. 144.01-1 Section 144... CONTINENTAL SHELF ACTIVITIES LIFESAVING APPLIANCES Manned Platforms § 144.01-1 Life floats. Each manned platform shall be provided with at least two approved life floats. The life floats shall have sufficient...

33 CFR 144.01-1 - Life floats.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Life floats. 144.01-1 Section 144... CONTINENTAL SHELF ACTIVITIES LIFESAVING APPLIANCES Manned Platforms § 144.01-1 Life floats. Each manned platform shall be provided with at least two approved life floats. The life floats shall have sufficient...

33 CFR 144.01-1 - Life floats.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Life floats. 144.01-1 Section 144... CONTINENTAL SHELF ACTIVITIES LIFESAVING APPLIANCES Manned Platforms § 144.01-1 Life floats. Each manned platform shall be provided with at least two approved life floats. The life floats shall have sufficient...

46 CFR 160.027-3 - Additional requirements for life floats.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 6 2014-10-01 2014-10-01 false Additional requirements for life floats. 160.027-3..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Life Floats for Merchant Vessels § 160.027-3 Additional requirements for life floats. (a) Each life float must have a platform designed...

46 CFR 160.027-3 - Additional requirements for life floats.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 6 2013-10-01 2013-10-01 false Additional requirements for life floats. 160.027-3..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Life Floats for Merchant Vessels § 160.027-3 Additional requirements for life floats. (a) Each life float must have a platform designed...

46 CFR 160.027-3 - Additional requirements for life floats.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 6 2012-10-01 2012-10-01 false Additional requirements for life floats. 160.027-3..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Life Floats for Merchant Vessels § 160.027-3 Additional requirements for life floats. (a) Each life float must have a platform designed...

Load assumptions for the landing impact of seaplanes

NASA Technical Reports Server (NTRS)

Taub, Josef

1931-01-01

The formula for the impact of floats must include the enlargement factor itself as well as the type of enlargement. The latter is preferably characterized by the change in surface loading. It is shown that the enlargement of a small seaplane generally results in a changed float (or boat) loading as well as wing loading. The conditions of starting stipulate the retention of the float loading when changing from single-float (boat) to twin-float arrangement. This contingency is followed by an increased impact factor in the twin-float type against the otherwise equivalent single-float type.

Vegetation, substrate and hydrology in floating marshes in the Mississippi river delta plain wetlands, USA

USGS Publications Warehouse

Sasser, C.E.; Gosselink, J.G.; Swenson, E.M.; Swarzenski, C.M.; Leibowitz, N.C.

1996-01-01

In the 1940s extensive floating marshes (locally called 'flotant') were reported and mapped in coastal wetlands of the Mississippi River Delta Plain. These floating marshes included large areas of Panicum hemitomon-dominated freshwater marshes, and Spartina patens/Scirpus olneyi brackish marshes. Today these marshes appear to be quite different in extent and type. We describe five floating habitats and one non-floating, quaking habitat based on differences in buoyancy dynamics (timing and degree of floating), substrate characteristics, and dominant vegetation. All floating marshes have low bulk density, organic substrates. Nearly all are fresh marshes. Panicum hemitomon floating marshes presently occur within the general regions that were reported in the 1940's by O'Neil, but are reduced in extent. Some of the former Panicum hemitomon marshes have been replaced by seasonally or variably floating marshes dominated, or co-dominated by Sagittaria lancifolia or Eleocharis baldwinii. ?? 1996 Kluwer Academic Publishers.

Determinant Computation on the GPU using the Condensation Method

NASA Astrophysics Data System (ADS)

Anisul Haque, Sardar; Moreno Maza, Marc

2012-02-01

We report on a GPU implementation of the condensation method designed by Abdelmalek Salem and Kouachi Said for computing the determinant of a matrix. We consider two types of coefficients: modular integers and floating point numbers. We evaluate the performance of our code by measuring its effective bandwidth and argue that it is numerical stable in the floating point number case. In addition, we compare our code with serial implementation of determinant computation from well-known mathematical packages. Our results suggest that a GPU implementation of the condensation method has a large potential for improving those packages in terms of running time and numerical stability.

The Controllable Ball Joint Mechanism

NASA Astrophysics Data System (ADS)

Tung, Yung Cheng; Chieng, Wei-Hua; Ho, Shrwai

A controllable ball joint mechanism with three rotational degrees of freedom is proposed in this paper. The mechanism is composed of three bevel gears, one of which rotates with respect to a fixed frame and the others rotate with respect to individual floating frames. The output is the resultant motion of the differential motions by the motors that rotates the bevel gears at the fixed frame and the floating frames. The mechanism is capable of a large rotation, and the structure is potentially compact. The necessary inverse and forward kinematic analyses as well as the derivation of kinematic singularity are provided according to the kinematical equivalent structure described in this paper.

Electrically floating, near vertical incidence, skywave antenna

DOEpatents

Anderson, Allen A.; Kaser, Timothy G.; Tremblay, Paul A.; Mays, Belva L.

2014-07-08

An Electrically Floating, Near Vertical Incidence, Skywave (NVIS) Antenna comprising an antenna element, a floating ground element, and a grounding element. At least part of said floating ground element is positioned between said antenna element and said grounding element. The antenna is separated from the floating ground element and the grounding element by one or more electrical insulators. The floating ground element is separated from said antenna and said grounding element by one or more electrical insulators.

New insights on poly(vinyl acetate)-based coated floating tablets: characterisation of hydration and CO2 generation by benchtop MRI and its relation to drug release and floating strength.

PubMed

Strübing, Sandra; Abboud, Tâmara; Contri, Renata Vidor; Metz, Hendrik; Mäder, Karsten

2008-06-01

The purpose of this study was to investigate the mechanism of floating and drug release behaviour of poly(vinyl acetate)-based floating tablets with membrane controlled drug delivery. Propranolol HCl containing tablets with Kollidon SR as an excipient for direct compression and different Kollicoat SR 30 D/Kollicoat IR coats varying from 10 to 20mg polymer/cm2 were investigated regarding drug release in 0.1N HCl. Furthermore, the onset of floating, the floating duration and the floating strength of the device were determined. In addition, benchtop MRI studies of selected samples were performed. Coated tablets with 10mg polymer/cm2 SR/IR, 8.5:1.5 coat exhibited the shortest lag times prior to drug release and floating onset, the fastest increase in and highest maximum values of floating strength. The drug release was delayed efficiently within a time interval of 24 h by showing linear drug release characteristics. Poly(vinyl acetate) proved to be an appropriate excipient to ensure safe and reliable drug release. Floating strength measurements offered the possibility to quantify the floating ability of the developed systems and thus to compare different formulations more efficiently. Benchtop MRI studies allowed a deeper insight into drug release and floating mechanisms noninvasively and continuously.

14 CFR 23.753 - Main float design.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main float design. 23.753 Section 23.753... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Design and Construction Floats and Hulls § 23.753 Main float design. Each seaplane main float must meet the requirements of § 23.521. [Doc...

Floating Offshore WTG Integrated Load Analysis & Optimization Employing a Tuned Mass Damper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez Tsouroukdissian, Arturo; Lackner, Matt; Cross-Whiter, John

2015-09-25

Floating offshore wind turbines (FOWTs) present complex design challenges due to the coupled dynamics of the platform motion, mooring system, and turbine control systems, in response to wind and wave loading. This can lead to higher extreme and fatigue loads than a comparable fixed bottom or onshore system. Previous research[1] has shown the potential to reduced extreme and fatigue loads on FOWT using tuned mass dampers (TMD) for structural control. This project aims to reduce maximum loads using passive TMDs located at the tower top during extreme storm events, when grid supplied power for other controls systems may not bemore » available. The Alstom Haliade 6MW wind turbine is modelled on the Glosten Pelastar tension-leg platform (TLP). The primary objectives of this project are to provide a preliminary assessment of the load reduction potential of passive TMDs on real wind turbine and TLP designs.« less

Electron temperature and density probe for small aeronomy satellites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oyama, K.-I.; Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan, Taiwan; International Center for Space Weather Study and education, Kyushu University, Fukuoka

2015-08-15

A compact and low power consumption instrument for measuring the electron density and temperature in the ionosphere has been developed by modifying the previously developed Electron Temperature Probe (ETP). A circuit block which controls frequency of the sinusoidal signal is added to the ETP so that the instrument can measure both T{sub e} in low frequency mode and N{sub e} in high frequency mode from the floating potential shift of the electrode. The floating potential shift shows a minimum at the upper hybrid resonance frequency (f{sub UHR}). The instrument which is named “TeNeP” can be used for tiny satellites whichmore » do not have enough conductive surface area for conventional DC Langmuir probe measurements. The instrument also eliminates the serious problems associated with the contamination of satellite surface as well as the sensor electrode.« less

Parasitic current collection by PASP Plus solar arrays

NASA Technical Reports Server (NTRS)

Davis, Victoria Ann; Gardner, Barbara M.

1995-01-01

Solar cells at potentials positive with respect to a surrounding plasma collect electrons. Current is collected by the exposed high voltage surfaces: the interconnects and the sides of the solar cells. This current is a drain on the array power that can be significant for high-power arrays. In addition, this current influences the current balance that determines the floating potential of the spacecraft. One of the objectives of the Air Force (PL/GPS) PASP Plus (Photovoltaic Array Space Power Plus Diagnostics) experiment is an improved understanding fo parasitic current collection. We have done computer modeling of parasitic current collection and have examined current collection flight data from the first year of operations. Prior to the flight we did computer modeling to improve our understanding of the physical processes that control parasitic current collection. At high potentials, the current rapidly rises due to a phenomenon called snapover. Under snapover conditions, the equilibrium potential distribution across the dielectric surface is such that part of the area is at potentials greater than the first crossover of the secondary yield curve. Therefore, each incident electron generates more than one secondary electron. The net effect is that the high potential area and the collecting area increase. We did two-dimensional calculations for the various geometries to be flown. The calculations span the space of anticipated plasma conditions, applied potential, and material parameters. We used the calculations and early flight data to develop an analytic formula for the dependence of the current on the primary problem variables. The analytic formula was incorporated into the EPSAT computer code. EPSAT allows us to easily extend the results to other conditions. PASP Plus is the principal experiment integrated onto the Advanced Photovoltaic and Electronics Experiments (APEX) satellite bus. The experiment is testing twelve different solar array designs. Parasitic current collection is being measured for eight of the designs under various operational and environment conditions. We examined the current collected as a function of the various parameters for the six non-concentrator designs. The results are similar to those obtained in previous experiments and predicted by the calculations. We are using the flight data to validate the analytic formula developed. The formula can be used to quantify the parasitic current collected. Anticipating the parasitic current value allows the spacecraft designer to include this interaction when developing the design.

Turbine with radial acting seal

DOEpatents

Eng, Darryl S; Ebert, Todd A

2016-11-22

A floating brush seal in a rim cavity of a turbine in a gas turbine engine, where the floating brush seal includes a seal holder in which the floating brush seal floats, and a expandable seal that fits within two radial extending seal slots that maintains a seal with radial displacement of the floating brush seal and the seal holder.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Hyunsoo; Samsung Display Co. Ltd., Tangjeong, Chungcheongnam-Do 336-741; Choi, Hagyoung

2013-11-07

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

The Aerodynamic Drag of Five Models of Side Floats N.A.C.A. Models 51-E, 51-F, 51-G, 51-H, 51-J

NASA Technical Reports Server (NTRS)

House, R O

1938-01-01

The drag of five models of side floats was measured in the N.A.C.A. 7- by 10-foot wind tunnel. The most promising method of reducing the drag of floats indicated by these tests is lowering the angle at which the floats are rigged. The addition of a step to a float does not always increase the drag in the flying range, floats with steps sometimes having lower drag than similar floats without steps. Making the bow chine no higher than necessary might result in a reduction in air drag because of the lower angle of pitch of the chines. Since side floats are used formally to obtain lateral stability when the seaplane is operating on the water at slow speeds or at rest, greater consideration can be given to factors affecting aerodynamic drag than is possible for other types of floats and hulls.

Hydrodynamic and Aerodynamic Tests of Models of Floats for Single-float Seaplanes NACA Models 41-D, 41-E, 61-A, 73, and 73-A

NASA Technical Reports Server (NTRS)

Parkinson, J B; HOUSE R O

1938-01-01

Tests were made in the NACA tank and in the NACA 7 by 10 foot wind tunnel on two models of transverse step floats and three models of pointed step floats considered to be suitable for use with single float seaplanes. The object of the program was the reduction of water resistance and spray of single float seaplanes without reducing the angle of dead rise believed to be necessary for the satisfactory absorption of the shock loads. The results indicated that all the models have less resistance and spray than the model of the Mark V float and that the pointed step floats are somewhat superior to the transverse step floats in these respects. Models 41-D, 61-A, and 73 were tested by the general method over a wide range of loads and speeds. The results are presented in the form of curves and charts for use in design calculations.

Program Converts VAX Floating-Point Data To UNIX

NASA Technical Reports Server (NTRS)

Alves, Marcos; Chapman, Bruce; Chu, Eugene

1996-01-01

VAX Floating Point to Host Floating Point Conversion (VAXFC) software converts non-ASCII files to unformatted floating-point representation of UNIX machine. This is done by reading bytes bit by bit, converting them to floating-point numbers, then writing results to another file. Useful when data files created by VAX computer must be used on other machines. Written in C language.

CDC42 is required for epicardial and pro-epicardial development by mediating FGF receptor trafficking to the plasma membrane

PubMed Central

Li, Jingjing; Miao, Lianjie; Zhao, Chen; Shaikh Qureshi, Wasay Mohiuddin; Shieh, David; Guo, Hua; Lu, Yangyang; Hu, Saiyang; Huang, Alice; Zhang, Lu; Cai, Chen-leng; Wan, Leo Q.; Xin, Hongbo; Vincent, Peter; Singer, Harold A.; Zheng, Yi; Cleaver, Ondine; Fan, Zhen-Chuan

2017-01-01

The epicardium contributes to multiple cardiac lineages and is essential for cardiac development and regeneration. However, the mechanism of epicardium formation is unclear. This study aimed to establish the cellular and molecular mechanisms underlying the dissociation of pro-epicardial cells (PECs) from the pro-epicardium (PE) and their subsequent translocation to the heart to form the epicardium. We used lineage tracing, conditional deletion, mosaic analysis and ligand stimulation in mice to determine that both villous protrusions and floating cysts contribute to PEC translocation to myocardium in a CDC42-dependent manner. We resolved a controversy by demonstrating that physical contact of the PE with the myocardium constitutes a third mechanism for PEC translocation to myocardium, and observed a fourth mechanism in which PECs migrate along the surface of the inflow tract to reach the ventricles. Epicardial-specific Cdc42 deletion disrupted epicardium formation, and Cdc42 null PECs proliferated less, lost polarity and failed to form villous protrusions and floating cysts. FGF signaling promotes epicardium formation in vivo, and biochemical studies demonstrated that CDC42 is involved in the trafficking of FGF receptors to the cell membrane to regulate epicardium formation. PMID:28465335

76 FR 30309 - Marine Mammals and Endangered Species; File Nos. 14245, 1596-03, and 14726-01

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-25

..., condition, diet, and potential Mississippi Canyon 252 oil exposure of pelagic sea turtles associated with floating Sargassum as part of the post-spill Natural Resources Damage Assessment of the BP Deepwater...

Assessing biological and chemical signatures related to nutrient removal by floating islands in stormwater mesocosms.

PubMed

Chang, Ni-Bin; Islam, Kamrul; Marimon, Zachary; Wanielista, Martin P

2012-07-01

Aquatic floating plants on BioHaven mats were tested for their potential use as a Best Management Practice to be incorporated within existing stormwater detention ponds. Plants were analyzed for their capability to remove nutrient-pollution in parallel with the study of ecological dynamics. Experiments were carried out in cylindrical mesocosms of 5 m diameter and 1.2 m height, above-ground pools with a water volume of 14 m(3). The design parameters tested were for 5% and 10% vegetated floating island coverage of the mesocosm, both with and without shoreline plants called littoral zone. This littoral shelf was 0.5 m thick, graded at a downward slope of 1:5 toward the center using loamy soil with low organic matter content, excavated from below turf grass. Endemic plant species were chosen for the experimental location in central Florida based on a wetland identification manual by the Florida Department of Environmental Protection to ensure the study was not compromised by unique climate requirements of the plants. Nutrient and aquatic chemical conditions such as pH, dissolved oxygen, temperature, turbidity, and chlorophyll a were monitored to understand their relationships to the general wetland ecosystem. Real-time polymerase chain reaction analysis identified the microbial activity near the rhizospheric zone. Logistical placement considerations were made using spatial sampling across the horizontal plane of the mesocosms, beneath and around the root zone, to determine if nutrients tend to aggregate around the floating island. This study concluded that the application of floating islands as a stormwater technology can remove nutrients through plant uptake and biological activity. The most cost-effective size in the outdoor mesocosms was 5% surface area coverage of the mat. Copyright © 2012 Elsevier Ltd. All rights reserved.

Collaborative Visual Seafloor Imaging using a Photographic AUV and a Lagrangian Imaging Float

NASA Astrophysics Data System (ADS)

Friedman, A.; Pizarro, O.; Roman, C.; Toohey, L.; Snyder, W.; Johnson-Roberson, M.; Iscar, E.; Williams, S. B.

2016-02-01

High resolution seafloor imaging from mobile autonomous platforms has become a valuable tool for habitat classification, stock assessment and seafloor exploration. This abstract addresses the concept of joint seafloor survey planning using both navigable and drifting platforms, and presents results from an experiment using a bottom surveying AUV and a drifting Lagrangian camera float. We consider two classes of vehicles; one which is able to self propel and execute structured surveys, and one which is Lagrangian and moves only with the currents. The navigable vehicle is the more capable and the more expensives asset of the two. The Lagrangian platforms is a low cost imaging tool that can actively control its altitude above the seafloor to obtain high quality images but can not otherwise control its trajectory over the bottom. When used together the vehicles offer several scenarios for joint operations. When used in an exploratory manner the Lagrangian float is an inexpensive way to collect images from an unknown area. Depending on the collected images, a follow on structured survey with the navigable AUV can collect additional information if the cost is acceptable given the need and prior data. When used simultaneously the drifting float can guide the AUV trajectory over an area. When both platforms are equipped with acoustic tracking and communications the AUV trajectory can be automatically redirected to follow the Lagrangian float using one of many patterns. This capability allows for surveys that are potentially more representative of the near bottom oceanographic conditions at the desired location. Results will be presented from a cruise to Scott Reef, Australia, where both platforms were used as part of a coral habitat monitoring project.

Autonomous magnetic float zone microgravity crystal growth application to TiC and GaAs

NASA Astrophysics Data System (ADS)

Chan, Tony Y.-T.; Choi, Sang-Keun

1992-10-01

The floating zone process is ideal for high temperature (greater than 3000 K) growth of titanium carbide because it is containerless. However, float zoning requires small melt volumes in order to maintain a stable melt configuration. The short melt columns make it difficult to achieve a controlled thermal profile, a necessity for producing crystals of high quality. Thus, an automated control strategy based upon continuous monitoring of the growth process with processing parameters adjusted to values based upon the physical transport processes of the growth process is very desirable for maintaining stability and reproducibility of the process. The present work developed a Float-zone Acquisition and Control Technology (FACT) system which uses relations derived by combining empirical relations with a knowledge data base deduced from detailed numerical analysis of fluid mechanics and thermal transport of the growth process. The FACT system was assembled, tested and employed to grow two TiC ingots. One of the ingots was characterized by x-ray diffraction at different axial locations. The x-ray rocking curves showed consistent characteristics of a manually grown ingot. It was also found that with the FACT system, the process conditions can be operated closer to the stability limits, due to fast response time and repetitive amounts of adjustment from the FACT system. The FACT system shows a major potential in growing quality TiC crystals in a cost-effective manner.

Atomic Force Microscope Studies of the Fusion of Floating Lipid Bilayers

PubMed Central

Abdulreda, Midhat H.; Moy, Vincent T.

2007-01-01

This study investigated the fusion of apposing floating bilayers of egg L-α-phosphatidylcholine (egg PC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine. Atomic force microscope measurements of fusion forces under different compression rates were acquired to reveal the energy landscape of the fusion process under varied lipid composition and temperature. Between compression rates of ∼1000 and ∼100,000 pN/s, applied forces in the range from ∼100 to ∼500 pN resulted in fusion of floating bilayers. Our atomic force microscope measurements indicated that one main energy barrier dominated the fusion process. The acquired dynamic force spectra were fit with a simple model based on the transition state theory with the assumption that the fusion activation potential is linear. A significant shift in the energy landscape was observed when bilayer fluidity and composition were modified, respectively, by temperature and different cholesterol concentrations (15% ≤ chol ≤ 25%). Such modifications resulted in a more than twofold increase in the width of the fusion energy barrier for egg PC and 1,2-dimyristoyl-sn-glycero-3-phosphocholine floating bilayers. The addition of 25% cholesterol to egg PC bilayers increased the activation energy by ∼1.0 kBT compared with that of bilayers with egg PC alone. These results reveal that widening of the energy barrier and consequently reduction in its slope facilitated membrane fusion. PMID:17400691

Atomic force microscope studies of the fusion of floating lipid bilayers.

PubMed

Abdulreda, Midhat H; Moy, Vincent T

2007-06-15

This study investigated the fusion of apposing floating bilayers of egg L-alpha-phosphatidylcholine (egg PC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine. Atomic force microscope measurements of fusion forces under different compression rates were acquired to reveal the energy landscape of the fusion process under varied lipid composition and temperature. Between compression rates of approximately 1000 and approximately 100,000 pN/s, applied forces in the range from approximately 100 to approximately 500 pN resulted in fusion of floating bilayers. Our atomic force microscope measurements indicated that one main energy barrier dominated the fusion process. The acquired dynamic force spectra were fit with a simple model based on the transition state theory with the assumption that the fusion activation potential is linear. A significant shift in the energy landscape was observed when bilayer fluidity and composition were modified, respectively, by temperature and different cholesterol concentrations (15% < or = chol < or = 25%). Such modifications resulted in a more than twofold increase in the width of the fusion energy barrier for egg PC and 1,2-dimyristoyl-sn-glycero-3-phosphocholine floating bilayers. The addition of 25% cholesterol to egg PC bilayers increased the activation energy by approximately 1.0 k(B)T compared with that of bilayers with egg PC alone. These results reveal that widening of the energy barrier and consequently reduction in its slope facilitated membrane fusion.

Characterization of cement float buoyancy in the stalked barnacle Dosima fascicularis (Crustacea, Cirripedia).

PubMed

Zheden, Vanessa; Kovalev, Alexander; Gorb, Stanislav N; Klepal, Waltraud

2015-02-06

Dosima fascicularis is the only barnacle which can drift autonomously at the water surface with a foam-like cement float. The cement secreted by the animal contains numerous gas-filled cells of different size. When several individuals share one float, their size and not their number is crucial for the production of both volume and mass of the float. The gas content within the cells of the foam gives positive static buoyancy to the whole float. The volume of the float, the gas volume and the positive static buoyancy are positively correlated. The density of the cement float without gas is greater than that of seawater. This study shows that the secreted cement consists of more than 90% water and the gas volume is on average 18.5%. Our experiments demonstrate that the intact foam-like cement float is sealed to the surrounding water.

Characterization of cement float buoyancy in the stalked barnacle Dosima fascicularis (Crustacea, Cirripedia)

PubMed Central

Zheden, Vanessa; Kovalev, Alexander; Gorb, Stanislav N.; Klepal, Waltraud

2015-01-01

Dosima fascicularis is the only barnacle which can drift autonomously at the water surface with a foam-like cement float. The cement secreted by the animal contains numerous gas-filled cells of different size. When several individuals share one float, their size and not their number is crucial for the production of both volume and mass of the float. The gas content within the cells of the foam gives positive static buoyancy to the whole float. The volume of the float, the gas volume and the positive static buoyancy are positively correlated. The density of the cement float without gas is greater than that of seawater. This study shows that the secreted cement consists of more than 90% water and the gas volume is on average 18.5%. Our experiments demonstrate that the intact foam-like cement float is sealed to the surrounding water. PMID:25657839

Autonomous Microstructure EM-APEX Floats

DTIC Science & Technology

2016-01-01

Autonomous Microstructure_EM-APEX_Float 4/8/16 at 3:21 PM 1 Title: Autonomous Microstructure EM-APEX Floats Authors: Ren-Chieh Lien1,2...Street Seattle, WA 98105 rcl@uw.edu Abstract: Fast responding FP-07 thermistors have been incorporated on profiling EM-APEX floats to measure...storage board. The raw and processed temperature observations are stored on a microSD card. Results from eight microstructure EM-APEX floats

First measurements with Argo flots in the Southern Baltic Sea

NASA Astrophysics Data System (ADS)

Walczowski, Waldemar; Goszczko, Ilona; Wieczorek, Piotr; Merchel, Malgorzata; Rak, Daniel

2017-04-01

The Argo programme is one of the most important elements of the ocean observing system. Currently almost 4000 Argo floats profile global oceans and deliver real time data. Originally Argo floats were developed for open ocean observations. Therefore a standard float can dive up to 2000 m and deep Argo floats are under development. However in the last years the shallow shelf seas become also interesting for Argo users. Institute of Oceanology Polish Academy of Sciences (IOPAN) participates in the Euro-Argo research infrastructure, the European contribution to Argo system. A legal and governance framework (Euro-Argo ERIC) was set up in May 2014. For a few years IOPAN has deployed floats mostly in the Nordic Seas and the European Arctic region. In the end of 2016 the first Polish Argo float was deployed in the Southern Baltic Sea. Building on the successful experience with Argo floats deployed by the Finnish oceanographers in the Bothnian Sea and Gotland Basin, the IOPAN float was launched in the Bornholm Deep during the fall cruise of IOPAN research vessel Oceania. The standard APEX float equipped with 2-way Iridium communication was used and different modes of operation, required for the specific conditions in the shallow and low saline Baltic Sea, were tested. Settings for the Baltic float are different than for the oceanic mode and were frequently changed during the mission to find the optimum solution. Changing the float parking depth during the mission allows for the limited control of the float drift direction. Results of a high resolution numerical forecast model for the Baltic Sea proved to be a valuable tool for determining the parking depth of the float in the different flow regimes. Trajectory and drift velocity of the Argo float deployed in the Southern Baltic depended strongly on the atmospheric forcing (in particular wind speed and direction), what was clearly manifested during the 'Axel' storm passing over the deployment area in January 2017. The first deployment showed clearly that Argo floats can be a useful tool for the Baltic Sea monitoring as the important element of a more complex, multidisciplinary observing system.

Comparison of Bispectral Index™ values during the flotation restricted environmental stimulation technique and results for stage I sleep: a prospective pilot investigation.

PubMed

Dunham, C Michael; McClain, Jesse V; Burger, Amanda

2017-11-29

To determine whether Bispectral Index™ values obtained during flotation-restricted environment stimulation technique have a similar profile in a single observation compared to literature-derived results found during sleep and other relaxation-induction interventions. Bispectral Index™ values were as follows: awake-state, 96.6; float session-1, 84.3; float session-2, 82.3; relaxation-induction, 82.8; stage I sleep, 86.0; stage II sleep, 66.2; and stages III-IV sleep, 45.1. Awake-state values differed from float session-1 (%difference 12.7%; Cohen's d = 3.6) and float session-2 (%difference 14.8%; Cohen's d = 4.6). Relaxation-induction values were similar to float session-1 (%difference 1.8%; Cohen's d = 0.3) and float session-2 (%difference 0.5%; Cohen's d = 0.1). Stage I sleep values were similar to float session-1 (%difference 1.9%; Cohen's d = 0.4) and float session-2 (%difference 4.3%; Cohen's d = 1.0). Stage II sleep values differed from float session-1 (%difference 21.5%; Cohen's d = 4.3) and float session-2 (%difference 19.6%; Cohen's d = 4.0). Stages III-IV sleep values differed from float session-1 (%difference 46.5%; Cohen's d = 5.6) and float session-2 (%difference 45.2%; Cohen's d = 5.4). Bispectral Index™ values during flotation were comparable to those found in stage I sleep and nadir values described with other relaxation-induction techniques.

Floating electrode dielectrophoresis.

PubMed

Golan, Saar; Elata, David; Orenstein, Meir; Dinnar, Uri

2006-12-01

In practice, dielectrophoresis (DEP) devices are based on micropatterned electrodes. When subjected to applied voltages, the electrodes generate nonuniform electric fields that are necessary for the DEP manipulation of particles. In this study, electrically floating electrodes are used in DEP devices. It is demonstrated that effective DEP forces can be achieved by using floating electrodes. Additionally, DEP forces generated by floating electrodes are different from DEP forces generated by excited electrodes. The floating electrodes' capabilities are explained theoretically by calculating the electric field gradients and demonstrated experimentally by using test-devices. The test-devices show that floating electrodes can be used to collect erythrocytes (red blood cells). DEP devices which contain many floating electrodes ought to have fewer connections to external signal sources. Therefore, the use of floating electrodes may considerably facilitate the fabrication and operation of DEP devices. It can also reduce device dimensions. However, the key point is that DEP devices can integrate excited electrodes fabricated by microtechnology processes and floating electrodes fabricated by nanotechnology processes. Such integration is expected to promote the use of DEP devices in the manipulation of nanoparticles.

Radiation tolerance of boron doped dendritic web silicon solar cells

NASA Technical Reports Server (NTRS)

Rohatgi, A.

1980-01-01

The potential of dendritic web silicon for giving radiation hard solar cells is compared with the float zone silicon material. Solar cells with n(+)-p-P(+) structure and approximately 15% (AMl) efficiency were subjected to 1 MeV electron irradiation. Radiation tolerance of web cell efficiency was found to be at least as good as that of the float zone silicon cell. A study of the annealing behavior of radiation-induced defects via deep level transient spectroscopy revealed that E sub v + 0.31 eV defect, attributed to boron-oxygen-vacancy complex, is responsible for the reverse annealing of the irradiated cells in the temperature range of 150 to 350 C.

Nonvolatile floating gate organic memory device based on pentacene/CdSe quantum dot heterojuction

NASA Astrophysics Data System (ADS)

Shin, Ik-Soo; Kim, Jung-Min; Jeun, Jun-Ho; Yoo, Seok-Hyun; Ge, Ziyi; Hong, Jong-In; Ho Bang, Jin; Kim, Yong-Sang

2012-04-01

An organic floating-gate memory device using CdSe quantum dots (QDs) as a charge-trapping element was fabricated. CdSe QDs were localized beneath a pentacene without any tunneling insulator, and the QD layer played a role as hole-trapping sites. The band bending formed at the junction between pentacene and QD layers inhibited back-injection of holes trapped in CdSe into pentacene, which appeared as a hysteretic capacitance-voltage response during the operation of the device. Nearly, 60% of trapped charge was sustained even after 104 s in programmed state, and this long retention time can be potentially useful in practical applications of non-volatile memory.

A novel control process of cyanobacterial bloom using cyanobacteriolytic bacteria immobilized in floating biodegradable plastic carriers.

PubMed

Nakamura, N; Nakano, K; Sugiura, N; Matsumura, M

2003-12-01

A process using a floating carrier for immobilization of cyanobacteriolytic bacteria, B.cereus N-14, was proposed to realize an effective in situ control of natural floating cyanobacterial blooms. The critical concentrations of the cyanobacteriolytic substance and B.cereus N-14 cells required to exhibit cyanobacteriolytic activity were investigated. The results indicated the necessity of cell growth to produce sufficiently high amounts of the cyanobacteriolytic substance to exhibit its activity and also for conditions enabling good contact between high concentrations of the cyanobacteriolytic substance and cyanobacteria. Floating biodegradable plastics made of starch were applied as a carrier material to maintain close contact between the immobilized cyanobacteriolytic bacteria and floating cyanobacteria. The floating starch-carriers could eliminate 99% of floating cyanobacteria in 4 d. Since B.cereus N-14 could produce the cyanobacteriolytic substance under the presence of starch and some amino acids, the cyanobacteriolytic activity could be attributed to carbon source fed from starch carrier and amino acids eluted from lysed cyanobacteria. Therefore, the effect of using a floating starch-carrier was confirmed from both view points as a carrier for immobilization and a nutrient source to stimulate cyanobacteriolytic activity. The new concept to apply a floating carrier immobilizing useful microorganisms for intensive treatment of a nuisance floating target was demonstrated.

77 FR 16116 - Public Input on the Development and Potential Issuance of Treasury Floating Rate Notes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-19

... appropriate coupon payment frequency of a Treasury FRN? 5. What changes to trading, settlement and accounting systems would be needed to accommodate FRNs? 6. Are there any other operational issues that Treasury...

Development of novel gastroretentive floating particulate drug delivery system of gliclazide.

PubMed

Awasthi, Rajendra; Kulkarni, Giriraj T

2012-09-01

The objective of present project was to improve the dissolution profile of gliclazide by developing floating alginate beads using various biodegradable polymers like gelatin, pectin and hydroxypropylmethylcellulose (HPMC). The floating beads were prepared by a simple ionotropic gelatin method using calcium carbonate as gas generating agent. The developed beads were characterized by Fourier transform infrared spectroscopy analysis, differential scanning calorimetry, X-ray diffraction analysis and scanning electron microscopy (SEM). The prepared beads showed good in vitro floatation, which was dependent on the concentration of gas-forming agent. SEM photomicrographs confirmed that the developed beads were spherical in shape and had particle size in the range of 730 to 890 μm. The incorporation efficiency was found to be in the range of 59.96 to 85.1%. The cumulative percent drug release from the beads after 10 h dissolution study at pH 1.2 and pH 5.8 was in the range of 33 to 46% and 82 to 95% respectively. The concentration of the gas generating agent was found to influence the release rate. The mechanism of drug release was Fickian diffusion with swelling. The in vivo sub-acute hypoglycemic study in high fat diet induced diabetic C57BL/6J mice demonstrated significant (p < 0.05) hypoglycemic effect over a period of 12 h and 24 h, respectively, with HPMC and pectin beads. A significant (p & 0.05) reduction in fasting and non-fasting blood glucose levels, reduction in fasting plasma insulin level and a significant improvement in glucose tolerance were observed in animals treated with formulations. The developed beads were suitable carriers for improving the systemic absorption of gliclazide and maintaining reduced blood glucose levels.

40 CFR 426.50 - Applicability; description of the float glass manufacturing subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... float glass manufacturing subcategory. 426.50 Section 426.50 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Float Glass Manufacturing Subcategory § 426.50 Applicability; description of the float glass...

40 CFR 426.50 - Applicability; description of the float glass manufacturing subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... float glass manufacturing subcategory. 426.50 Section 426.50 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Float Glass Manufacturing Subcategory § 426.50 Applicability; description of the float glass...

Tethered float liquid level sensor

DOEpatents

Daily, III, William Dean

2016-09-06

An apparatus for sensing the level of a liquid includes a float, a tether attached to the float, a pulley attached to the tether, a rotation sensor connected to the pulley that senses vertical movement of said float and senses the level of the liquid.

40 CFR 264.1085 - Standards: Surface impoundments.

Code of Federal Regulations, 2010 CFR

2010-07-01

... the surface impoundment by installing and operating either of the following: (1) A floating membrane... from a surface impoundment using a floating membrane cover shall meet the requirements specified in... floating membrane cover designed to meet the following specifications: (i) The floating membrane cover...

Preliminary results from DIMES: Dispersion in the ACC

NASA Astrophysics Data System (ADS)

Balwada, D.; Speer, K.; LaCasce, J. H.; Owens, B.

2012-04-01

The Diapycnal and Isopynal Mixing Experiment in the Southern Ocean (DIMES) is a CLIVAR process study designed to study mixing in the Antarctic Circumpolar Current. The experiment includes tracer release, float, and small-scale turbulence components. This presentation will report on some results of the float component, from floats deployed across the ACC in the Southeast Pacific Ocean. These are the first subsurface Lagrangian trajectories from the ACC. Floats were deployed to follow approximately a constant density surface for a period of 1-3 years. To help aid the experimental results virtual floats were advected using AVISO data and basic statistics were derived from both deployed and virtual float trajectories. Experimental design, initial results, comparison to virtual floats and single particle and relative dispersion calculations will be presented.

Floating macro-litter along the Mediterranean French coast: Composition, density, distribution and overlap with cetacean range.

PubMed

Di-Méglio, Nathalie; Campana, Ilaria

2017-05-15

This study investigated the composition, density and distribution of floating macro-litter along the Liguro-Provençal basin with respect to cetaceans presence. Survey transects were performed in summer between 2006 and 2015 from sailing vessels with simultaneous cetaceans observations. During 5171km travelled, 1993 floating items were recorded, widespread in the whole study area. Plastics was the predominant category, with bags/packaging always representing >45% of total items. Overall mean density (14.98 items/km 2 ) was stable with significant increase reported only in 2010-2011; monthly analysis showed lower litter densities in July-September, suggesting possible seasonal patterns. Kernel density estimation for plastics revealed ubiquitous distribution rather than high accumulation areas, mainly due to the circulation dynamics of this area. The presence range of cetaceans (259 sightings, 6 species) corresponded by ~50% with plastic distribution, indicating high potential of interaction, especially in the eastern part of the area, but effective risks for marine species might be underrepresented. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nutrient removal by up-scaling a hybrid floating treatment bed (HFTB) using plant and periphyton: From laboratory tank to polluted river.

PubMed

Liu, Junzhuo; Wang, Fengwu; Liu, Wei; Tang, Cilai; Wu, Chenxi; Wu, Yonghong

2016-05-01

Planted floating treatment bed (FTB) is an innovative technique of removing nutrients from polluted water but limited in deep water and cold seasons. Periphyton was integrated into FTB for a hybrid floating treatment bed (HFTB) to improve its nutrient removal capacity. To assess its potential for treating nutrient-polluted rivers, HFTB was up-scaled from 5L laboratory tanks to 350L outdoor tanks and then to a commercial-scale 900m section of polluted river. Plants and periphyton interacted in HFTB with periphyton limiting plant root growth and plants having shading effects on periphyton. Non-overlapping distribution of plants and periphyton can minimize the negative interactions in HFTB. HFTB successfully kept TN and TP of the river at less than 2.0 and 0.02mgL(-1), respectively. This study indicates that HFTB can be easily up-scaled for nutrients removal from polluted rivers in different seasons providing a long-term, environmentally-friendly method to remediate polluted ecosystems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Biotransformation of arsenite and bacterial aox activity in drinking water produced from surface water of floating houses: Arsenic contamination in Cambodia.

PubMed

Chang, Jin-Soo

2015-11-01

The potential arsenite bioteansformation activity of arsenic was investigated by examining bacterial arsenic arsenite-oxidizing gene such as aoxS, aoxR, aoxA, aoxB, aoxC, and aoxD in high arsenic-contaminated drinking water produced from the surface water of floating houses. There is a biogeochemical cycle of activity involving arsenite oxidase aox system and the ars (arsenic resistance system) gene operon and aoxR leader gene activity in Alcaligenes faecalis SRR-11 and aoxS leader gene activity in Achromobacter xylosoxidans TSL-66. Batch experiments showed that SRR-11 and TSL-66 completely oxidized 1 mM of As (III) to As (V) within 35-40 h. The leaders of aoxS and aoxR are important for gene activity, and their effects in arsenic bioremediation and mobility in natural water has a significant ecological role because it allows arsenite oxidase in bacteria to control the biogeochemical cycle of arsenic-contaminated drinking water produced from surface water of floating houses. Copyright © 2015 Elsevier Ltd. All rights reserved.

Red Sea Outflow Experiment (REDSOX): DLD2 RAFOS Float Data Report February 2001 - March 2003

DTIC Science & Technology

2005-01-01

1 2. Description of the DLD2 Float and Dual-Release System ................................................................... 2 3. Sound Sources...processing are described in detail. 2. Description of the DLD2 Float and Dual-Release System The DLD2 is a second-generation RAFOS (Ranging And Fixing Of...Sound) float with several improvements over the traditional RAFOS float (see Rossby et al., 1986, for a complete description of the RAFOS system ). A

A new amoxicillin/clavulanate therapeutic system: preparation, in vitro and pharmacokinetic evaluation.

PubMed

Kerc, Janez; Opara, Jerneja

2007-04-20

A new peroral amoxicillin/clavulanate therapeutic system composed of immediate release tablet and controlled release floating capsule was developed and evaluated by in vivo bioavailability study. Pharmacokinetic (PK) parameters for amoxicillin and clavulanic acid of the new therapeutic systems: AUCt, AUCi, (AUCt/AUCi), Cmax, Tmax, kel, T(1/2) and additionally for amoxicillin T(4) and T(2) were calculated from the plasma levels. The study confirmed enhanced pharmacokinetic parameters of a newly developed therapeutic system containing 1500 mg of amoxicillin and 125 mg of clavulanic acid. Prolonged time over MIC of amoxicillin in relation to a regular immediate release amoxicillin/clavulanate formulation was confirmed.

BIO ARGO floats: tools for operational monitoring of the Black Sea

NASA Astrophysics Data System (ADS)

Palazov, Atanas; Slabakova, Violeta; Peneva, Elisaveta; Stanev, Emil

2014-05-01

The assessment of ecological status in the context of the Water Framework Directive (WFD) and Marine Strategy Framework Directive (MSFD) requires comprehensive knowledge and understanding of the physical and biogeochemical processes that determine the functioning of marine ecosystems. One of the main challenges however is the need of data with frequency relevant to the spatial and temporal scales of the ecological processes. The majority of in situ observations that are commonly used for ecological monitoring of the Black Sea are generally based on near-shore monitoring programs or irregular oceanographic cruises that provide either non-synoptic, coarse resolution realizations of large scale processes or detailed, but time and site specific snapshots of local features. These gaps can be filled by two independent sources: satellite observation and profiling floats. In fact satellite ocean color sensors allows for determination at synoptic scale of water quality parameters through its absorption properties. However the satellite ocean color methods have a number of limitations such as: measurements can only be made during daylight hours; require cloud-free conditions and are sensitive to atmospheric aerosols; provide information only for the upper layer of the ocean (approximately the depth of 10% incident light); algorithms developed for global applications are a source of large uncertainties in the marginal seas and costal areas. These constrains of the optical remote sensing observations can be avoided by using miniature biogeochemical sensors and autonomous platforms that offer remarkable perspectives for observing the "biological" ocean, notably at critical spatiotemporal scales which have been out of reach until recently (Claustre et al., 2010). In the frame of "E-AIMS: Euro-Argo Improvements for the GMES marine Service" 7 EC FP project two Bio Argo floats were deployed in the Black Sea. Beside the traditionally CTD the floats were equipped with biogeochemical sensors (oxygen, irradiance, chl-a and backscattering). The selection of the deployment locations was limited only to the Bulgarian Black Sea waters, so that the optimal deployment strategy that has been chosen was the floats to be deployed in the maximum distant positions from each other along the Black Sea geostrophic current at depth ~ 1800 m. Coincident biogeochemical and in-water radiometric measurements were collected at the time of each float deployment to ensure intercalibration of the instruments mounted on the floats and as well as to find empirical relationship between optical data and biogeochemical variables. The data obtained form Bio floats will be used to: investigate the seasonal evolution of oxygen in the upper layers, including the subsurface oxygen maximum; study the seasonal and inter annual dynamics of phytoplankton blooms in the deeper Black Sea; cross validation of satellite derived Chl-a and backscattering. References: Claustre et al. (2010). Bio-optical profiling floats as new observational tools for biogeochemical and ecosystem studies: potential synergies with ocean color remote sensing. Proceedings of the "OceanObs'09: Sustained Ocean Observations and Information for Society" Conference, Venice/Italy.

Identification of mothball powder composition by float tests and melting point tests.

PubMed

Tang, Ka Yuen

2018-07-01

The aim of the study was to identify the composition, as either camphor, naphthalene, or paradichlorobenzene, of mothballs in the form of powder or tiny fragments by float tests and melting point tests. Naphthalene, paradichlorobenzene and camphor mothballs were blended into powder and tiny fragments (with sizes <1/10 of the size of an intact mothball). In the float tests, the mothball powder and tiny fragments were placed in water, saturated salt solution and 50% dextrose solution (D50), and the extent to which they floated or sank in the liquids was observed. In the melting point tests, the mothball powder and tiny fragments were placed in hot water with a temperature between 53 and 80 °C, and the extent to which they melted was observed. Both the float and melting point tests were then repeated using intact mothballs. Three emergency physicians blinded to the identities of samples and solutions visually evaluated each sample. In the float tests, paradichlorobenzene powder partially floated and partially sank in all three liquids, while naphthalene powder partially floated and partially sank in water. Naphthalene powder did not sink in D50 or saturated salt solution. Camphor powder floated in all three liquids. Float tests identified the compositions of intact mothball accurately. In the melting point tests, paradichlorobenzene powder melted completely in hot water within 1 min while naphthalene powder and camphor powder did not melt. The melted portions of paradichlorobenzene mothballs were sometimes too small to be observed in 1 min but the mothballs either partially or completely melted in 5 min. Both camphor and naphthalene intact mothballs did not melt in hot water. For mothball powder, the melting point tests were more accurate than the float tests in differentiating between paradichlorobenzene and non-paradichlorobenzene (naphthalene or camphor). For intact mothballs, float tests performed better than melting point tests. Float tests can identify camphor mothballs but melting point tests cannot. We suggest melting point tests for identifying mothball powder and tiny fragments while float tests are recommended for intact mothball and large fragments.

Changing Patterns of the Floating Population in China during 2000-2010*

PubMed Central

Liang, Zai; Li, Zhen; Ma, Zhongdong

2015-01-01

Using data from the 2000 and 2010 Chinese Population Censuses and applying a consistent definition of migration, this paper examines changing patterns of China's floating population during 2000-2010. We find that during the first decade of the 21st century, there have been significant changes in China's floating population, as reflected in continuing rise of interprovincial floating population and the rise of the floating population in China's western and interior regions, geographic diversification of destinations for the floating population, a major increase in interprovincial return migration, and significant improvement in education and occupational profiles among the floating population. We argue that these patterns are driven by a combination of complex domestic and international factors, including the newly released Labor Law, removal of agricultural tax, the western China development program, increased investment in education by the Chinese government, and the global financial crisis. We also discuss several challenges facing the floating population in the coming years, which include equality of educational opportunity for migrant children and adequate housing and social welfare protection for the floating population. Finally, we reflect on the future of migration research in China. PMID:26213427

Assessment of the nutrient removal effectiveness of floating treatment wetlands applied to urban retention ponds.

PubMed

Wang, Chih-Yu; Sample, David J

2014-05-01

The application of floating treatment wetlands (FTWs) in point and non-point source pollution control has received much attention recently. Although the potential of this emerging technology is supported by various studies, quantifying FTW performance in urban retention ponds remains elusive due to significant research gaps. Actual urban retention pond water was utilized in this mesocosm study to evaluate phosphorus and nitrogen removal efficiency of FTWs. Multiple treatments were used to investigate the contribution of each component in the FTW system with a seven-day retention time. The four treatments included a control, floating mat, pickerelweed (Pontederia cordata L.), and softstem bulrush (Schoenoplectus tabernaemontani). The water samples collected on Day 0 (initial) and 7 were analyzed for total phosphorus (TP), total particulate phosphorus, orthophosphate, total nitrogen (TN), organic nitrogen, ammonia nitrogen, nitrate-nitrite nitrogen, and chlorophyll-a. Statistical tests were used to evaluate the differences between the four treatments. The effects of temperature on TP and TN removal rates of the FTWs were described by the modified Arrhenius equation. Our results indicated that all three FTW designs, planted and unplanted floating mats, could significantly improve phosphorus and nitrogen removal efficiency (%, E-TP and E-TN) compared to the control treatment during the growing season, i.e., May through August. The E-TP and E-TN was enhanced by 8.2% and 18.2% in the FTW treatments planted with the pickerelweed and softstem bulrush, respectively. Organic matter decomposition was likely to be the primary contributor of nutrient removal by FTWs in urban retention ponds. Such a mechanism is fostered by microbes within the attached biofilms on the floating mats and plant root surfaces. Among the results of the four treatments, the FTWs planted with pickerelweed had the highest E-TP, and behaved similarly with the other two FTW treatments for nitrogen removal during the growth period. The temperature effects described by the modified Arrhenius equation revealed that pickerelweed is sensitive to temperature and provides considerable phosphorus removal when water temperature is greater than 25 °C. However, the nutrient removal effectiveness of this plant species may be negligible for water temperatures below 15 °C. The study also assessed potential effects of shading from the FTW mats on water temperature, DO, pH, and attached-to-substrate periphyton/vegetation. Copyright © 2014 Elsevier Ltd. All rights reserved.

14 CFR 25.753 - Main float design.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main float design. 25.753 Section 25.753 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Design and Construction Floats and Hulls § 25.753 Main float design...

40 CFR 265.1086 - Standards: Surface impoundments.

Code of Federal Regulations, 2010 CFR

2010-07-01

... floating membrane cover in accordance with the provisions specified in paragraph (c) of this section; or (2... emissions from a surface impoundment using a floating membrane cover shall meet the requirements specified... with a floating membrane cover designed to meet the following specifications: (i) The floating membrane...

40 CFR 65.44 - External floating roof (EFR).

Code of Federal Regulations, 2013 CFR

2013-07-01

... external floating roof except for automatic bleeder vents (vacuum breaker vents) and rim space vents does... floating roof shall meet the following specifications: (i) Except for automatic bleeder vents (vacuum breaker vents) and rim space vents, each opening in the noncontact external floating roof shall provide a...

40 CFR 65.44 - External floating roof (EFR).

Code of Federal Regulations, 2014 CFR

2014-07-01

... external floating roof except for automatic bleeder vents (vacuum breaker vents) and rim space vents does... floating roof shall meet the following specifications: (i) Except for automatic bleeder vents (vacuum breaker vents) and rim space vents, each opening in the noncontact external floating roof shall provide a...

40 CFR 65.44 - External floating roof (EFR).

Code of Federal Regulations, 2012 CFR

2012-07-01

... external floating roof except for automatic bleeder vents (vacuum breaker vents) and rim space vents does... floating roof shall meet the following specifications: (i) Except for automatic bleeder vents (vacuum breaker vents) and rim space vents, each opening in the noncontact external floating roof shall provide a...

Seven centuries of atmospheric Pb deposition recorded in a floating mire from Central Italy

NASA Astrophysics Data System (ADS)

Zaccone, Claudio; Lobianco, Daniela; D'Orazio, Valeria; Miano, Teodoro M.; Shotyk, William

2016-04-01

Floating mires generally consist of emergent vegetation rooted in highly organic buoyant mats that rise and fall with changes in water level. Generally speaking, the entire floating mass (mat) is divided into a mat root zone and an underlying mat peat zone. Floating mires are distributed world-wide; large areas of floating marsh occur along rivers and lakes in Africa, the Danube Delta in Romania, the Amazon River in South America, and in the Mississippi River delta in USA, whereas smaller areas occur also in The Netherlands, Australia and Canada. While peat cores from ombrotrophic bogs have been often (and successfully) used to reconstruct changes in the atmospheric deposition of several metals (including Pb), no studies are present in literature about the possibility to use peat profiles from floating mires. To test the hypothesis that peat-forming floating mires could provide an exceptional tool for environmental studies, a complete, 4-m deep peat profile was collected in July 2012 from the floating island of Posta Fibreno, a relic mire in the Central Italy. This floating island has a diameter of ca. 30 m, a submerged thickness of about 3 m, and the vegetation is organized in concentric belts, from the Carex paniculata palisade to the Sphagnum palustre centre. The whole core was frozen cut each 1-to-2 cm (n =231), and Pb determined by quadrupole ICP-MS (at the ultraclean SWAMP lab, University of Alberta, Canada) in each sample throughout the first 100 cm, and in each odd-numbered slice for the remaining 300 cm. The 14C age dating of organic sediments (silty peat) isolated from the sample at 385 cm of depth revealed that the island probably formed ca. 700 yrs ago. Lead concentration trend shows at least two main zones of interest, i.e., a clear peak (ranging from 200 to 1600 ppm) between 110-115 cm of depth, probably corresponding to early 1960's - late 1970's, and a broad band (80-160 ppm) between 295-320 cm of depth, corresponding to approximately AD 1480-1650. Lead concentrations were normalized to those of Th, a conservative, lithophile element often used as an indicator of the abundance of mineral particles. Crustal enrichment factor values, calculated by normalizing the Pb/Th ratio in peat samples to the corresponding ratio for the Upper Continental Crust, clearly show that almost all the Pb reaching this floating isle in the last seven centuries is of anthropogenic origin. In particular, while the big peak around 100-115 cm of depth is associated with that of Sb, the band around 300 cm characterized also the trend of several other major and trace elements (i.e., Ag, Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sr, Th, Tl, U, V, Y, Zn) with the exception of Sb. Although γ-spectrometry measurement (210Pb, 137Cs and 241Am) for the first 100 cm of this core is still on-going, at the best of our knowledge, this work may provide the first Pb chronology obtained from a (4 m) deep floating mire. Furthermore, it is to note that a) this floating mire could consist of the southernmost European population of Sphagnum, and b) this core shows a great potential to be used as archive of environmental changes, especially considering its high resolution (1 cm = 0.5 yr in the first 100 cm, and 2-2.5 yrs in the remaining 300 cm of depth). The Authors thank the Municipality of Posta Fibreno, Managing Authority of the Regional Natural Reserve of Lake Posta Fibreno, for allowing peat cores sampling.

Formulation and in-vitro evaluation of floating bilayer tablet of lisinopril maleate and metoprolol tartrate.

PubMed

Ijaz, Hira; Qureshi, Junaid; Danish, Zeeshan; Zaman, Muhammad; Abdel-Daim, Mohamed; Hanif, Muhammad; Waheed, Imran; Mohammad, Imran Shair

2015-11-01

The purpose of this study was to introduce the technology for the development of rate-controlled oral drug delivery system to overcome various physiological problems. Several approaches are being used for the purpose of increasing the gastric retentive time, including floating drug delivery system. Gastric floating lisinopril maleate and metoprolol tartrate bilayer tablets were formulated by direct compression method using the sodium starch glycolate, crosscarmellose sodium for IR layer. Eudragit L100, pectin, acacia as sustained release polymers in different ratios for SR metoprolol tartrate layer and sodium bicarbonate, citric acid as gas generating agents for the floating extended release layer. The floating bilayer tablets of lisinopril maleate and metoprolol tartrate were designed to overcome the various problems associated with conventional oral dosage form. Floating tablets were evaluated for floating lag time, drug contents and in-vitro dissolution profile and different kinetic release models were applied. It was clear that the different ratios of polymers affected the drug release and floating time. L2 and M4 showed good drug release profile and floating behavior. The linear regression and model fitting showed that all formulation followed Higuchi model of drug release model except M4 that followed zero order kinetic. From the study it is evident that a promising controlled release by floating bilyer tablets of lisinopril maleate and metoprolol tartrate can be developed successfully.

Formulation and statistical optimization of gastric floating alginate/oil/chitosan capsules loading procyanidins: in vitro and in vivo evaluations.

PubMed

Chen, Rencai; Guo, Xiaomin; Liu, Xuecong; Cui, Haiming; Wang, Rui; Han, Jing

2018-03-01

The aim of the present work was to develop gastric floating capsules containing oil-entrapped beads loading procyanidins. The floating beads were prepared by ionotropic gelation method using sodium alginate, CaCl 2 and chitosan. The effect of three independent parameters (concentration of sodium alginate, CaCl 2 and chitosan) on entrapment efficiency were analyzed by Box-Behnken design. The floating beads were evaluated for surface morphology, particle size, density, entrapment efficiency, buoyancy, release behavior in vitro and floating ability in vivo. The prepared beads were grossly spherical in shape and the mean size was approximately 1.54±0.17mm. The density was 0.97g/cm 3 . And the optimal conditions were as follows: concentration of sodium alginate, CaCl 2 and chitosan were 33.75mg/mL, 9.84mg/mL and 9.05mg/mL, respectively. The optimized formulation showed entrapment efficiency of 88.84±1.04% within small error-value (0.65). The release mechanism of floating capsules followed Korsmeyer-Peppas model (r 2 =0.9902) with non-Fickian release. The gastric floating capsules exhibited 100% floating percentage in vitro and they could float on the top of gastric juice for 5h in vivo. Therefore, the floating capsules are able to prolong the gastroretentive delivery of procyanidins. Copyright © 2017 Elsevier B.V. All rights reserved.

Bethany Speer | NREL

Science.gov Websites

Strategic Energy Analysis Center. Areas of Expertise International economic policy Climate change mitigation Markets Climate change mitigation policies Education M.A. in global finance, trade and economic Keyser, Suzanne Tegen. 2016. Floating Offshore Wind in California: Gross Potential for Jobs and Economic

Memory operations in Au nanoparticle single-electron transistors with floating gate electrodes

NASA Astrophysics Data System (ADS)

Azuma, Yasuo; Sakamoto, Masanori; Teranishi, Toshiharu; Majima, Yutaka

2016-11-01

Floating gate memory operations are demonstrated in a single-electron transistor (SET) fabricated by a chemical assembly using the Au nanogap electrodes and the chemisorbed Au nanoparticles. By applying pulse voltages to the control gate, phase shifts were clearly and stably observed both in the Coulomb oscillations and in the Coulomb diamonds. Writing and erasing operations on the floating gate memory were reproducibly observed, and the charges on the floating gate electrodes were maintained for at least 12 h. By considering the capacitance of the floating gate electrode, the number of electrons in the floating gate electrode was estimated as 260. Owing to the stability of the fabricated SET, these writing and erasing operations on the floating gate memory can be applied to reconfigurable SET circuits fabricated by a chemically assembled technique.

Transforming Ocean Observations of the Carbon Budget, Acidification, Hypoxia, Nutrients, and Biological Productivity: a Global Array of Biogeochemical Argo Floats

NASA Astrophysics Data System (ADS)

Talley, L. D.; Johnson, K. S.; Claustre, H.; Boss, E.; Emerson, S. R.; Westberry, T. K.; Sarmiento, J. L.; Mazloff, M. R.; Riser, S.; Russell, J. L.

2017-12-01

Our ability to detect changes in biogeochemical (BGC) processes in the ocean that may be driven by increasing atmospheric CO2, as well as by natural climate variability, is greatly hindered by undersampling in vast areas of the open ocean. Argo is a major international program that measures ocean heat content and salinity with about 4000 floats distributed throughout the ocean, profiling to 2000 m every 10 days. Extending this approach to a global BGC-Argo float array, using recent, proven sensor technology, and in close synergy with satellite systems, will drive a transformative shift in observing and predicting the effects of climate change on ocean metabolism, carbon uptake, acidification, deoxygenation, and living marine resource management. BGC-Argo will add sensors for pH, oxygen, nitrate, chlorophyll, suspended particles, and downwelling irradiance, with sufficient accuracy for climate studies. Observing System Simulation Experiments (OSSEs) using BGC models indicate that 1000 BGC floats would provide sufficient coverage, hence equipping 1/4 of the Argo array. BGC-Argo (http://biogeochemical-argo.org) will enhance current sustained observational programs such as Argo, GO-SHIP, and long-term ocean time series. BGC-Argo will benefit from deployments on GO-SHIP vessels, which provide sensor verification. Empirically derived algorithms that relate the observed BGC float parameters to the carbon system parameters will provide global information on seasonal ocean-atmosphere carbon exchange. BGC Argo measurements could be paired with other emerging technology, such as pCO2 measurements from ships of opportunity and wave gliders, to extend and validate exchange estimates. BGC-Argo prototype programs already show the potential of a global observing system that can measure seasonal to decadal variability. Various countries have developed regional BGC arrays: Southern Ocean (SOCCOM), North Atlantic Subpolar Gyre (remOcean), Mediterranean (NAOS), the Kuroshio (INBOX), and Indian Ocean (IOBioArgo). As examples, bio-optical sensors are identifying regional anomalies in light attenuation/scattering, with implications for ocean productivity and carbon export; SOCCOM floats show high CO2 outgassing in the Antarctic Circumpolar Current, due to previously unmeasured winter fluxes.

Classification scheme for sedimentary and igneous rocks in Gale crater, Mars

NASA Astrophysics Data System (ADS)

Mangold, N.; Schmidt, M. E.; Fisk, M. R.; Forni, O.; McLennan, S. M.; Ming, D. W.; Sautter, V.; Sumner, D.; Williams, A. J.; Clegg, S. M.; Cousin, A.; Gasnault, O.; Gellert, R.; Grotzinger, J. P.; Wiens, R. C.

2017-03-01

Rocks analyzed by the Curiosity rover in Gale crater include a variety of clastic sedimentary rocks and igneous float rocks transported by fluvial and impact processes. To facilitate the discussion of the range of lithologies, we present in this article a petrological classification framework adapting terrestrial classification schemes to Mars compositions (such as Fe abundances typically higher than for comparable lithologies on Earth), to specific Curiosity observations (such as common alkali-rich rocks), and to the capabilities of the rover instruments. Mineralogy was acquired only locally for a few drilled rocks, and so it does not suffice as a systematic classification tool, in contrast to classical terrestrial rock classification. The core of this classification involves (1) the characterization of rock texture as sedimentary, igneous or undefined according to grain/crystal sizes and shapes using imaging from the ChemCam Remote Micro-Imager (RMI), Mars Hand Lens Imager (MAHLI) and Mastcam instruments, and (2) the assignment of geochemical modifiers based on the abundances of Fe, Si, alkali, and S determined by the Alpha Particle X-ray Spectrometer (APXS) and ChemCam instruments. The aims are to help understand Gale crater geology by highlighting the various categories of rocks analyzed by the rover. Several implications are proposed from the cross-comparisons of rocks of various texture and composition, for instance between in place outcrops and float rocks. All outcrops analyzed by the rover are sedimentary; no igneous outcrops have been observed. However, some igneous rocks are clasts in conglomerates, suggesting that part of them are derived from the crater rim. The compositions of in-place sedimentary rocks contrast significantly with the compositions of igneous float rocks. While some of the differences between sedimentary rocks and igneous floats may be related to physical sorting and diagenesis of the sediments, some of the sedimentary rocks (e.g., potassic rocks) cannot be paired with any igneous rocks analyzed so far. In contrast, many float rocks, which cannot be classified from their poorly defined texture, plot on chemistry diagrams close to float rocks defined as igneous from their textures, potentially constraining their nature.

Classification scheme for sedimentary and igneous rocks in Gale crater, Mars

DOE PAGES

Mangold, Nicolas; Schmidt, Mariek E.; Fisk, Martin R.; ...

2016-11-05

Rocks analyzed by the Curiosity rover in Gale crater include a variety of clastic sedimentary rocks and igneous float rocks transported by fluvial and impact processes. Here, to facilitate the discussion of the range of lithologies, we present in this article a petrological classification framework adapting terrestrial classification schemes to Mars compositions (such as Fe abundances typically higher than for comparable lithologies on Earth), to specific Curiosity observations (such as common alkali-rich rocks), and to the capabilities of the rover instruments. Mineralogy was acquired only locally for a few drilled rocks, and so it does not suffice as a systematicmore » classification tool, in contrast to classical terrestrial rock classification. The core of this classification involves (1) the characterization of rock texture as sedimentary, igneous or undefined according to grain/crystal sizes and shapes using imaging from the ChemCam Remote Micro-Imager (RMI), Mars Hand Lens Imager (MAHLI) and Mastcam instruments, and (2) the assignment of geochemical modifiers based on the abundances of Fe, Si, alkali, and S determined by the Alpha Particle X-ray Spectrometer (APXS) and ChemCam instruments. The aims are to help understand Gale crater geology by highlighting the various categories of rocks analyzed by the rover. Several implications are proposed from the cross-comparisons of rocks of various texture and composition, for instance between in place outcrops and float rocks. All outcrops analyzed by the rover are sedimentary; no igneous outcrops have been observed. However, some igneous rocks are clasts in conglomerates, suggesting that part of them are derived from the crater rim. The compositions of in-place sedimentary rocks contrast significantly with the compositions of igneous float rocks. While some of the differences between sedimentary rocks and igneous floats may be related to physical sorting and diagenesis of the sediments, some of the sedimentary rocks (e.g., potassic rocks) cannot be paired with any igneous rocks analyzed so far. Finally, in contrast, many float rocks, which cannot be classified from their poorly defined texture, plot on chemistry diagrams close to float rocks defined as igneous from their textures, potentially constraining their nature.« less

Classification scheme for sedimentary and igneous rocks in Gale crater, Mars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mangold, Nicolas; Schmidt, Mariek E.; Fisk, Martin R.

Rocks analyzed by the Curiosity rover in Gale crater include a variety of clastic sedimentary rocks and igneous float rocks transported by fluvial and impact processes. Here, to facilitate the discussion of the range of lithologies, we present in this article a petrological classification framework adapting terrestrial classification schemes to Mars compositions (such as Fe abundances typically higher than for comparable lithologies on Earth), to specific Curiosity observations (such as common alkali-rich rocks), and to the capabilities of the rover instruments. Mineralogy was acquired only locally for a few drilled rocks, and so it does not suffice as a systematicmore » classification tool, in contrast to classical terrestrial rock classification. The core of this classification involves (1) the characterization of rock texture as sedimentary, igneous or undefined according to grain/crystal sizes and shapes using imaging from the ChemCam Remote Micro-Imager (RMI), Mars Hand Lens Imager (MAHLI) and Mastcam instruments, and (2) the assignment of geochemical modifiers based on the abundances of Fe, Si, alkali, and S determined by the Alpha Particle X-ray Spectrometer (APXS) and ChemCam instruments. The aims are to help understand Gale crater geology by highlighting the various categories of rocks analyzed by the rover. Several implications are proposed from the cross-comparisons of rocks of various texture and composition, for instance between in place outcrops and float rocks. All outcrops analyzed by the rover are sedimentary; no igneous outcrops have been observed. However, some igneous rocks are clasts in conglomerates, suggesting that part of them are derived from the crater rim. The compositions of in-place sedimentary rocks contrast significantly with the compositions of igneous float rocks. While some of the differences between sedimentary rocks and igneous floats may be related to physical sorting and diagenesis of the sediments, some of the sedimentary rocks (e.g., potassic rocks) cannot be paired with any igneous rocks analyzed so far. Finally, in contrast, many float rocks, which cannot be classified from their poorly defined texture, plot on chemistry diagrams close to float rocks defined as igneous from their textures, potentially constraining their nature.« less

Experimental investigations of electron density and ion energy distributions in dual-frequency capacitively coupled plasmas for Ar/CF{sub 4} and Ar/O{sub 2}/CF{sub 4} discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jia; Liu, Yong-Xin; Gao, Fei

2014-01-07

The electron density and ion energy distribution (IED) are investigated in low-pressure dual-frequency capacitively coupled Ar/CF{sub 4} (90%/10%) and Ar/O{sub 2}/CF{sub 4} (80%/10%/10%) plasmas. The relations between controllable parameters, such as high-frequency (HF) power, low-frequency (LF) power and gas pressure, and plasma parameters, such as electron density and IEDs, are studied in detail by utilizing a floating hairpin probe and an energy resolved quadrupole mass spectrometer, respectively. In our experiment, the electron density is mainly determined by the HF power and slightly influenced by the LF power. With increasing gas pressure, the electron density first goes up rapidly to amore » maximum value and then decreases at various HF and LF powers. The HF power also plays a considerable role in affecting the IEDs under certain conditions and the ion energy independently controlled by the LF source is discussed here. For clarity, some numerical results obtained from a two-dimensional fluid model are presented.« less

40 CFR 65.44 - External floating roof (EFR).

Code of Federal Regulations, 2010 CFR

2010-07-01

... design requirements. The owner or operator who elects to control storage vessel regulated material emissions by using an external floating roof shall comply with the design requirements listed in paragraphs (a)(1) through (3) of this section. (1) The external floating roof shall be designed to float on the...

40 CFR 65.44 - External floating roof (EFR).

Code of Federal Regulations, 2011 CFR

2011-07-01

... design requirements. The owner or operator who elects to control storage vessel regulated material emissions by using an external floating roof shall comply with the design requirements listed in paragraphs (a)(1) through (3) of this section. (1) The external floating roof shall be designed to float on the...

14 CFR 29.757 - Hull and auxiliary float strength.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Hull and auxiliary float strength. 29.757 Section 29.757 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... § 29.757 Hull and auxiliary float strength. The hull, and auxiliary floats if used, must withstand the...

40 CFR 63.1063 - Floating roof requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... the point of refloating the floating roof shall be continuous and shall be performed as soon as... 40 Protection of Environment 10 2010-07-01 2010-07-01 false Floating roof requirements. 63.1063...) National Emission Standards for Storage Vessels (Tanks)-Control Level 2 § 63.1063 Floating roof...

50 CFR 679.94 - Economic data report (EDR) for the Amendment 80 sector.

Code of Federal Regulations, 2010 CFR

2010-10-01

...: NMFS, Alaska Fisheries Science Center, Economic Data Reports, 7600 Sand Point Way NE, F/AKC2, Seattle... Operation Description of code Code NMFS Alaska region ADF&G FCP Catcher/processor Floating catcher processor. FLD Mothership Floating domestic mothership. IFP Stationary Floating Processor Inshore floating...

Have Floating Rates Been a Success?

ERIC Educational Resources Information Center

Higham, David

1983-01-01

Floating exchange rates have not lived up to all expectations, but neither have they performed as badly as some critics have suggested. Examined are the impact of floating rates on balance of payments adjustment, domestic economic policy, and inflation and the claim that floating rates have displayed excessive fluctuations. (Author/RM)

Potential alteration of fjordal circulation due to a large floating structure—Numerical investigation with application to Hood Canal basin in Puget Sound

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khangaonkar, Tarang; Wang, Taiping

Circulation in typical fjords is characterized by a shallow brackish layer at the surface over a deep long and narrow saltwater column. This surface layer is responsible for the outflow of water from the fjord, is easily disrupted by external forces, such as wind, and is influenced by freshwater inflow. In this paper, we postulate that the stability of fjordal circulation may also be vulnerable to impacts from anthropogenic alterations, such as floating structures, that could constrict the mixing and transport in the upper layers of the water column. The potential for alteration of circulation in Hood Canal, a silled-fjordmore » located inside Puget Sound, Washington, has been examined. Using classical analytical treatments along the lines formulated by Hansen and Rattray [1965], Rattray [1967], Dyer [1973] and more recently, MacCready [2004], we develop a solution applicable to a range of estuary classifications varying from a partially mixed estuary regime to classical fjord conditions. Both estuary types exist in the Puget Sound system, and we compare our analytical solution with observed data. The analysis is based on an exponential variation of eddy viscosity with depth, and it has been extended further with modifications of the free surface boundary conditions to develop a solution representing the presence of a floating bridge at the estuary/fjord entrance. The model results show that tidally averaged mean circulation under the influence of such a constraint could reduce by as much as 30 to 50 percent. The overall water quality of fjords and narrow estuaries is dependent on net circulation and flushing. A potential decrease in residual flow or a corresponding increase in residence time of this magnitude merits further study.« less

Multi-input and binary reproducible, high bandwidth floating point adder in a collective network

DOEpatents

Chen, Dong; Eisley, Noel A.; Heidelberger, Philip; Steinmacher-Burow, Burkhard

2016-11-15

To add floating point numbers in a parallel computing system, a collective logic device receives the floating point numbers from computing nodes. The collective logic devices converts the floating point numbers to integer numbers. The collective logic device adds the integer numbers and generating a summation of the integer numbers. The collective logic device converts the summation to a floating point number. The collective logic device performs the receiving, the converting the floating point numbers, the adding, the generating and the converting the summation in one pass. One pass indicates that the computing nodes send inputs only once to the collective logic device and receive outputs only once from the collective logic device.

Quantification of scaling exponent with Crossover type phenomena for different types of forcing in DC glow discharge plasma

NASA Astrophysics Data System (ADS)

Saha, Debajyoti; Shaw, Pankaj Kumar; Ghosh, Sabuj; Janaki, M. S.; Sekar Iyengar, A. N.

2018-01-01

We have carried out a detailed study of scaling region using detrended fractal analysis test by applying different forcing likewise noise, sinusoidal, square on the floating potential fluctuations acquired under different pressures in a DC glow discharge plasma. The transition in the dynamics is observed through recurrence plot techniques which is an efficient method to observe the critical regime transitions in dynamics. The complexity of the nonlinear fluctuation has been revealed with the help of recurrence quantification analysis which is a suitable tool for investigating recurrence, an ubiquitous feature providing a deep insight into the dynamics of real dynamical system. An informal test for stationarity which checks for the compatibility of nonlinear approximations to the dynamics made in different segments in a time series has been proposed. In case of sinusoidal, noise, square forcing applied on fluctuation acquired at P = 0.12 mbar only one dominant scaling region is observed whereas the forcing applied on fluctuation (P = 0.04 mbar) two prominent scaling regions have been explored reliably using different forcing amplitudes indicating the signature of crossover phenomena. Furthermore a persistence long range behavior has been observed in one of these scaling regions. A comprehensive study of the quantification of scaling exponents has been carried out with the increase in amplitude and frequency of sinusoidal, square type of forcings. The scalings exponent is envisaged to be the roughness of the time series. The method provides a single quantitative idea of the scaling exponent to quantify the correlation properties of a signal.

Characterization of poly(vinyl acetate) based floating matrix tablets.

PubMed

Strübing, Sandra; Metz, Hendrik; Mäder, Karsten

2008-03-03

Floating Kollidon SR matrix tablets containing Propranolol HCl were developed and characterized with respect to drug release characteristics and floating strength. Kollidon SR was able to delay Propranolol HCl release efficiently. Drug release kinetics was evaluated using the Korsmeyer-Peppas model and found to be governed by Fickian diffusion. Tablet floating started immediately and continued for 24 h. It was possible to monitor the floating strength of the matrix devices using a simple experimental setup. Floating strength was related to Kollidon SR level with improved floating characteristics for samples with a high polymer/drug ratio. Swelling characteristics of the tablets were analyzed by applying the equation according to Therien-Aubin et al. The influence of the polymer content on swelling characteristics was found to be only marginal. Furthermore, the new method of benchtop MRI was introduced to study the water diffusion and swelling behaviour non-invasively and continuously.

Investigation of Tank 241-AW-104 Composite Floating Layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meznarich, H. K.; Bolling, S. D.; Lachut, J. S.

Seven grab samples and one field blank were taken from Tank 241-AW-104 (AW-104) on June 2, 2017, and received at 222-S Laboratory on June 5, 2017. A visible layer with brown solids was observed floating on the top of two surface tank waste samples (4AW-17-02 and 4AW 17 02DUP). The floating layer from both samples was collected, composited, and submitted for chemical analyses and solid phase characterization in order to understand the composition of the floating layer. Tributyl phosphate and tridecane were higher in the floating layer than in the aqueous phase. Density in the floating layer was slightly lowermore » than the mean density of all grab samples. Sodium nitrate and sodium carbonate were major components with a trace of gibbsite and very small size agglomerates were present in the solids of the floating layer. The supernate consisted of organics, soluble salt, and particulates.« less

The Situational Awareness Sensor Suite for the ISS (SASSI): A Mission Concept to Investigate ISS Charging and Wake Effects

NASA Technical Reports Server (NTRS)

Krause, L. Habash; Minow, J. I.; Coffey, V. N.; Gilchrist, Brian E.; Hoegy, W. R.

2014-01-01

The complex interaction between the International Space Station (ISS) and the surrounding plasma environment often generates unpredictable environmental situations that affect operations. Examples of affected systems include extravehicular activity (EVA) safety, solar panel efficiency, and scientific instrument integrity. Models and heuristically-derived best practices are well-suited for routine operations, but when it comes to unusual or anomalous events or situations, especially those driven by space weather, there is no substitute for real-time monitoring. Space environment data collected in real-time (or near-real time) can be used operationally for both real-time alarms and data sources in assimilative models to predict environmental conditions important for operational planning. Fixed space weather instruments mounted to the ISS can be used for monitoring the ambient space environment, but knowing whether or not (or to what extent) the ISS affects the measurements themselves requires adequate space situational awareness (SSA) local to the ISS. This paper presents a mission concept to use a suite of plasma instruments mounted at the end of the ISS robotic arm to systematically explore the interaction between the Space Station structure and its surrounding environment. The Situational Awareness Sensor Suite for the ISS (SASSI) would be deployed and operated on the ISS Express Logistics Carrier (ELC) for long-term "survey mode" observations and the Space Station Remote Manipulator System (SSRMS) for short-term "campaign mode" observations. Specific areas of investigation include: 1) ISS frame and surface charging during perturbations of the local ISS space environment, 2) calibration of the ISS Floating Point Measurement Unit (FPMU), 3) long baseline measurements of ambient ionospheric electric potential structures, 4) electromotive force-induced currents within large structures moving through a magnetized plasma, and 5) wake-induced ion waves in both electrostatic (i.e. particles) and electromagnetic modes. SASSI will advance the understanding of plasma-boundary interaction phenomena, demonstrate a suite a sensors acting in concert to provide effective SSA, and validate and/or calibrate existing ISS space environment instruments and models.

33 CFR 147.815 - ExxonMobil Hoover Floating OCS Facility safety zone.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false ExxonMobil Hoover Floating OCS... HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.815 ExxonMobil Hoover Floating OCS Facility safety zone. (a) Description. The ExxonMobil Hoover Floating OCS Facility, Alaminos...

33 CFR 147.815 - ExxonMobil Hoover Floating OCS Facility safety zone.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false ExxonMobil Hoover Floating OCS... HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.815 ExxonMobil Hoover Floating OCS Facility safety zone. (a) Description. The ExxonMobil Hoover Floating OCS Facility, Alaminos...

33 CFR 147.815 - ExxonMobil Hoover Floating OCS Facility safety zone.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false ExxonMobil Hoover Floating OCS... HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.815 ExxonMobil Hoover Floating OCS Facility safety zone. (a) Description. The ExxonMobil Hoover Floating OCS Facility, Alaminos...

33 CFR 147.815 - ExxonMobil Hoover Floating OCS Facility safety zone.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false ExxonMobil Hoover Floating OCS... HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.815 ExxonMobil Hoover Floating OCS Facility safety zone. (a) Description. The ExxonMobil Hoover Floating OCS Facility, Alaminos...

33 CFR 144.01-15 - Alternates for life floats.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Alternates for life floats. 144... for life floats. (a) Approved lifeboats, approved life rafts or approved inflatable life rafts may be used in lieu of approved life floats for either all or part of the capacity required. When either...

33 CFR 144.01-5 - Location and launching of life floats.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Location and launching of life floats. 144.01-5 Section 144.01-5 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Location and launching of life floats. The life floats shall be distributed in accessible locations and...

33 CFR 144.01-15 - Alternates for life floats.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Alternates for life floats. 144... for life floats. (a) Approved lifeboats, approved life rafts or approved inflatable life rafts may be used in lieu of approved life floats for either all or part of the capacity required. When either...

14 CFR 23.529 - Hull and main float landing conditions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Hull and main float landing conditions. 23... Water Loads § 23.529 Hull and main float landing conditions. (a) Symmetrical step, bow, and stern... directed perpendicularly to the keel line. (b) Unsymmetrical landing for hull and single float seaplanes...

46 CFR 131.870 - Life floats and buoyant apparatus.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Life floats and buoyant apparatus. 131.870 Section 131... OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.870 Life floats and buoyant apparatus. (a) The name of the vessel must be plainly marked or painted on each life float or buoyant apparatus...

33 CFR 144.01-5 - Location and launching of life floats.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Location and launching of life floats. 144.01-5 Section 144.01-5 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Location and launching of life floats. The life floats shall be distributed in accessible locations and...

46 CFR 131.870 - Life floats and buoyant apparatus.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Life floats and buoyant apparatus. 131.870 Section 131... OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.870 Life floats and buoyant apparatus. (a) The name of the vessel must be plainly marked or painted on each life float or buoyant apparatus...

46 CFR 131.870 - Life floats and buoyant apparatus.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Life floats and buoyant apparatus. 131.870 Section 131... OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.870 Life floats and buoyant apparatus. (a) The name of the vessel must be plainly marked or painted on each life float or buoyant apparatus...

46 CFR 131.870 - Life floats and buoyant apparatus.

Code of Federal Regulations, 2011 CFR

2011-10-01

... OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.870 Life floats and buoyant apparatus. (a) The name of the vessel must be plainly marked or painted on each life float or buoyant apparatus... 46 Shipping 4 2011-10-01 2011-10-01 false Life floats and buoyant apparatus. 131.870 Section 131...

46 CFR 131.870 - Life floats and buoyant apparatus.

Code of Federal Regulations, 2010 CFR

2010-10-01

... OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.870 Life floats and buoyant apparatus. (a) The name of the vessel must be plainly marked or painted on each life float or buoyant apparatus... 46 Shipping 4 2010-10-01 2010-10-01 false Life floats and buoyant apparatus. 131.870 Section 131...

77 FR 44544 - Safety Zone; Gilmerton Bridge Center Span Float-In, Elizabeth River; Norfolk, Portsmouth, and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-30

...-AA00 Safety Zone; Gilmerton Bridge Center Span Float-In, Elizabeth River; Norfolk, Portsmouth, and... withdrawing its proposed rule concerning the Gilmerton Bridge Center Span Float-in and bridge construction of... ``Safety Zone; Gilmerton Bridge Center Span Float-in, Elizabeth River; Norfolk, Portsmouth, and Chesapeake...

On the manifestation of coexisting nontrivial equilibria leading to potential well escapes in an inhomogeneous floating body

NASA Astrophysics Data System (ADS)

Sequeira, Dane; Wang, Xue-She; Mann, B. P.

2018-02-01

This paper examines the bifurcation and stability behavior of inhomogeneous floating bodies, specifically a rectangular prism with asymmetric mass distribution. A nonlinear model is developed to determine the stability of the upright and tilted equilibrium positions as a function of the vertical position of the center of mass within the prism. These equilibria positions are defined by an angle of rotation and a vertical position where rotational motion is restricted to a two dimensional plane. Numerical investigations are conducted using path-following continuation methods to determine equilibria solutions and evaluate stability. Bifurcation diagrams and basins of attraction that illustrate the stability of the equilibrium positions as a function of the vertical position of the center of mass within the prism are generated. These results reveal complex stability behavior with many coexisting solutions. Static experiments are conducted to validate equilibria orientations against numerical predictions with results showing good agreement. Dynamic experiments that examine potential well hopping behavior in a waveflume for various wave conditions are also conducted.

Impact of anti-tacking agents on properties of gas-entrapped membrane and effervescent floating tablets.

PubMed

Kriangkrai, Worawut; Puttipipatkhachorn, Satit; Sriamornsak, Pornsak; Pongjanyakul, Thaned; Sungthongjeen, Srisagul

2014-12-01

Tackiness caused by the gas-entrapped membrane (Eudragit(®)RL 30D) was usually observed during storage of the effervescent floating tablets, leading to failure in floatation and sustained release. In this work, common anti-tacking agents (glyceryl monostearate (GMS) and talc) were used to solve this tackiness problem. The impact of anti-tacking agent on the properties of free films and corresponding floating tablets was investigated. GMS was more effective than talc in reducing tackiness of the film. Addition and increasing amount of anti-tacking agents lowered the film mechanical strength, but the coating films were still strong and flexible enough to resist the generated gas pressure inside the floating tablet. Wettability and water vapor permeability of the film decreased with increasing level of anti-tacking agents as a result of their hydrophobicity. No interaction between anti-tacking agents and polymer was observed as confirmed by Fourier transform infrared spectroscopy, powder X-ray diffractometry, and differential scanning calorimetry studies. Increasing amount of anti-tacking agents decreased time to float and tended to retard drug release of the floating tablets. Floating properties and drug release were also influenced by type of anti-tacking agents. The obtained floating tablets still possessed good floating properties and controlled drug release even though anti-tacking agent had some effects. The results demonstrated that the tackiness problem of the floating tablets could be solved by incorporating anti-tacking agent into the gas-entrapped membrane.