WorldWideScience

Sample records for plasma velocity measurements

  1. Plasma flow velocity measurements using a modulated Michelson interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Howard, J. [Australian National Univ., Canberra, ACT (Australia). Plasma Research Lab.; Meijer, F.G. [FOM-Instituut voor Plasmafysica `Rijnhuizen`, Association Euratom-FOM, PO Box 1207, 3430 BE Nieuwegein (Netherlands)]|[Physics Faculty, University of Amsterdam, Amsterdam (Netherlands)

    1997-03-01

    This paper discusses the possibility of flow velocity reconstruction using passive spectroscopic techniques. We report some preliminary measurements of the toroidal flow velocity of hydrogen atoms in the RTP tokamak using a phase modulated Michelson interferometer. (orig.) 1 refs.

  2. Laser induced fluorescence measurements of axial velocity, velocity shear, and parallel ion temperature profiles during the route to plasma turbulence in a linear magnetized plasma device

    Science.gov (United States)

    Chakraborty Thakur, S.; Adriany, K.; Gosselin, J. J.; McKee, J.; Scime, E. E.; Sears, S. H.; Tynan, G. R.

    2016-11-01

    We report experimental measurements of the axial plasma flow and the parallel ion temperature in a magnetized linear plasma device. We used laser induced fluorescence to measure Doppler resolved ion velocity distribution functions in argon plasma to obtain spatially resolved axial velocities and parallel ion temperatures. We also show changes in the parallel velocity profiles during the transition from resistive drift wave dominated plasma to a state of weak turbulence driven by multiple plasma instabilities.

  3. Plasma flow velocity measurements using a modulated Michelson interferometer

    NARCIS (Netherlands)

    Howard, J.; Meijer, F. G.

    1997-01-01

    This paper discusses the possibility of flow velocity reconstruction using passive spectroscopic techniques. We report some preliminary measurements of the toroidal flow velocity of hydrogen atoms in the RTP tokamak using a phase modulated Michelson interferometer. (C) 1997 Elsevier Science S.A.

  4. Determination of the Ion Velocity Distribution in a Rotating Plasma from Measurements of Doppler Broadening

    DEFF Research Database (Denmark)

    Jørgensen, L. W.; Sillesen, Alfred Hegaard

    1979-01-01

    The Doppler-broadened profile of the He II 4685.75 AA line was measured along a chord in a rotating plasma, transverse to the magnetic field. Using a single-particle orbit picture, the corresponding velocity spectrum of ions confirm the measurements, so it can be concluded that the single......-particle orbit picture is valid for the discharge period under investigation, except for the first few microseconds during breakdown when a strong interaction between plasma and remaining neutral gas takes place by Alfvens critical velocity mechanism. A simple relation is given between the measured half......-width and shift of the Doppler profile and the macroscopic quantities of ion velocity and energy. Several Doppler-broadened profiles are shown for different plasma parameters....

  5. Hole boring velocity measurements in near critical density plasmas by a CO2 laser pulse

    Science.gov (United States)

    Gong, Chao; Tochitsky, Sergei; Pigeon, Jeremy; Joshi, Chan

    2014-10-01

    Measurements of plasma dynamics during the interaction of a high-power laser pulse with an above critical density plasma is important for understanding absorption, transport and particle acceleration mechanisms. An important process that affects these mechanisms is hole boring occurring at the critical density because of the radiation pressure of the laser pulse. Yet, no systematic measurements of the hole boring velocity's (vhb) dependence on laser intensity (I) have been made. In this talk, we present experimental results of vhb in near critical density plasmas produced by CO2 laser as a function of I in the range of 1*1015 to 1.6*1016 W/cm2. A novel four frame Mach-Zehnder interferometer using a 1 ps, 532 nm probe laser pulse was developed to record the evolution of the plasma density profile and the motion of the near critical density layer. Using this diagnostic, we observed the motion of the steepened plasma profile due to the incident, time-structured CO2 laser pulse. Experimental results show the hole boring velocity increases from 0.004c to 0.007c as the laser intensity is increased from 1*1015 to 1.6*1016 W/cm2. This work is supported by DOE grant DE-FG02-92-ER40727, NSF grant PHY-0936266 at UCLA.

  6. Ion rotational velocity of a field-reversed configuration plasma measured by neutral beam probe spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Y.; Tanjyo, M.; Ohi, S.; Goto, S.; Ishimura, T.

    1987-01-01

    The ion rotational angular velocity ..cap omega.. and the ion temperature T/sub i/ of a translated field-reversed configuration (FRC) plasma are measured using neutral beam probe spectroscopy. The value of ..cap omega.. is --(1.0--1.2) x ..cap omega..* at the onset time of the n = 2 rotational instability, where ..cap omega..* is the ion diamagnetic frequency for a rigid-rotor equilibrium. The ion rotational direction is the same as the ion diamagnetic direction. The value of ..cap omega.. is smaller than the angular frequency ..omega../sub re/ of the n = 2 instability, which can yield experimental evidence of the ion kinetic effects on the n = 2 instability in the FRC plasma. When the octupole field is applied to the plasma in order to suppress the n = 2 deformation, ..cap omega.. is slightly reduced. The ion temperature T/sub i/ is --70 eV at the onset time of the n = 2 instability.

  7. Measurements of the ion velocity distribution in an ultracold neutral plasma derived from a cold, dense Rydberg gas

    OpenAIRE

    S. D. Bergeson; Lyon, M

    2016-01-01

    We report measurements of the ion velocity distribution in an ultracold neutral plasma derived from a dense, cold Rydberg gas in a MOT. The Rydberg atoms are excited using a resonant two-step excitation pathway with lasers of 4 ns duration. The plasma forms spontaneously and rapidly. The rms width of the ion velocity distribution is determined by measuring laser-induced fluorescence (LIF) of the ions. The measured excitation efficiency is compared with a Monte-Carlo wavefunction calculation, ...

  8. Particle position and velocity measurement in dusty plasmas using particle tracking velocimetry

    Science.gov (United States)

    Feng, Yan; Goree, J.; Haralson, Zach; Wong, Chun-Shang; Kananovich, A.; Li, Wei

    2016-06-01

    > Methods of imaging and image analysis are presented for dusty plasma experiments. Micron-sized polymer spheres, electrically suspended in a partially ionized gas, are illuminated by a sheet of laser light and imaged by video cameras. Image analysis methods yield particle positions and velocities of individual particles in each video image. Methods to minimize errors in the particle positions and velocities, which are now commonly used in the dusty plasma community, are described.

  9. Measuring ion velocity distribution functions through high-aspect ratio holes in inductively coupled plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Cunge, G., E-mail: gilles.cunge@cea.fr; Darnon, M.; Dubois, J.; Bezard, P.; Mourey, O.; Petit-Etienne, C.; Vallier, L.; Despiau-Pujo, E.; Sadeghi, N. [Laboratoire des Technologies de la Microélectronique, CNRS, 17 rue des Martyrs, 38054 Grenoble (France)

    2016-02-29

    Several issues associated with plasma etching of high aspect ratio structures originate from the ions' bombardment of the sidewalls of the feature. The off normal angle incident ions are primarily due to their temperature at the sheath edge and possibly to charging effects. We have measured the ion velocity distribution function (IVDF) at the wafer surface in an industrial inductively coupled plasma reactor by using multigrid retarding field analyzers (RFA) in front of which we place 400 μm thick capillary plates with holes of 25, 50, and 100 μm diameters. The RFA then probes IVDF at the exit of the holes with Aspect Ratios (AR) of 16, 8, and 4, respectively. The results show that the ion flux dramatically drops with the increase in AR. By comparing the measured IVDF with an analytical model, we concluded that the ion temperature is 0.27 eV in our plasma conditions. The charging effects are also observed and are shown to significantly reduce the ion energy at the bottom of the feature but only with a “minor” effect on the ion flux and the shape of the IVDF.

  10. Measurements of 3D slip velocities and plasma column lengths of a gliding arc discharge

    DEFF Research Database (Denmark)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas

    2015-01-01

    , gives more realistic insight into the convection cooling process. Additionally, with the determination of the 3D slip velocity and the 3D length of the plasma column, we give more accurate estimates for the drag force, the electric field strength, the power per unit length, and the radius...... of the conducting zone of the plasma column. © 2015 AIP Publishing LLC....

  11. Measurements of 3D slip velocities and plasma column lengths of a gliding arc discharge

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas; Aldén, Marcus; Li, Zhongshan, E-mail: zhongshan.li@forbrf.lth.se, E-mail: alpers@ma.tum.de [Division of Combustion Physics, Lund University, P.O. Box 118, S-221 00 Lund (Sweden); Moseev, Dmitry [Max-Planck-Institut für Plasmaphysik, D-85748 Garching bei München (Germany); FOM Institute DIFFER, 3430 BE Nieuwegein (Netherlands); Kusano, Yukihiro [Department of Wind Energy, Section for Composites and Materials Mechanics, Technical University of Denmark, Risø Campus, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Salewski, Mirko [Department of Physics, Section for Plasma Physics and Fusion Energy, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Alpers, Andreas, E-mail: zhongshan.li@forbrf.lth.se, E-mail: alpers@ma.tum.de; Gritzmann, Peter; Schwenk, Martin [Zentrum Mathematik, Technische Universität München, D-85747 Garching bei München (Germany)

    2015-01-26

    A non-thermal gliding arc discharge was generated at atmospheric pressure in an air flow. The dynamics of the plasma column and tracer particles were recorded using two synchronized high-speed cameras. Whereas the data analysis for such systems has previously been performed in 2D (analyzing the single camera image), we provide here a 3D data analysis that includes 3D reconstructions of the plasma column and 3D particle tracking velocimetry based on discrete tomography methods. The 3D analysis, in particular, the determination of the 3D slip velocity between the plasma column and the gas flow, gives more realistic insight into the convection cooling process. Additionally, with the determination of the 3D slip velocity and the 3D length of the plasma column, we give more accurate estimates for the drag force, the electric field strength, the power per unit length, and the radius of the conducting zone of the plasma column.

  12. Fabry-Perot spectroscopy for kinetic temperature and velocity measurements of a high enthalpy air plasma flow

    Science.gov (United States)

    Zander, Fabian; Löhle, Stefan; Hermann, Tobias; Fulge, Hannes

    2017-08-01

    The atomic translational temperatures and velocities of a low pressure, high enthalpy air plasma are measured using Fabry-Perot spectroscopy. The measurements presented here are the first measurements using this system at this enthalpy level. The sub-picometre resolution of the unique system has allowed accurate translational temperature and velocity measurements of the atomic species in the plasma. The detection system allows the Doppler broadening of multiple atomic nitrogen and oxygen lines to be measured simultaneously. Additionally, having two optical paths, one perpendicular to the flow and one at 45 deg. allows the Doppler shift to be measured. Measurements were taken during three different plasma wind tunnel tests. Mean atomic nitrogen temperatures of 1.08+/- 0.11 × 104 K and atomic oxygen translational temperatures of 1.23+/- 0.12 ×104 K were measured. The thermal non-equilibrium determined verified earlier measurements of the same phenomena, however, the mechanism behind this has not yet been determined. The mean measured flow velocity was 3350+/- 840~m~s-1 and was consistent between the atomic species. The translational temperature and velocity contribute approximately 35% of the local enthalpy of the flow. The direct measurement of these parameters, removing previously required assumptions, increases the fidelity of the flow characterisation significantly. This allows high quality testing to be conducted in this flow field.

  13. Measurement and interpretation of the velocity space correlation of a laboratory plasma fluctuation with laser induced fluorescence

    Science.gov (United States)

    Mattingly, S. W.; Berumen, J.; Chu, F.; Hood, R.; Skiff, F.

    2013-11-01

    A technique for probing velocity space correlations has been developed using laser-induced fluorescence. In this paper, a description of the experimental setup is given, with results to follow in a later publication. The experiment consists of a cylindrical plasma column 3 m long and radius ~ 0.25 cm, holding singly-charged argon ions (Ar II) with density n ~ 109 cm-3, Te ~ 5 eV, Ti,|| ~ .06 eV, and a 1 kG axial magnetic field. Two separate metastable lines are excited by single frequency lasers at 611 nm and 668 nm. These lasers may tune with a precision of .01 pm. The separate lasers are used to measure independent slices of the velocity distribution function. To confirm the velocity distribution and magnetic field, the Doppler-broadened, sigma-polarized Zeeman line for each transition is measured. With this, the absolute parallel component of ion velocity subject to LIF can be determined. The two separate lasers then give us a signal as a function of two separate parallel ion velocities. Two point correlation is used to reduce the noise floor on the plasma fluctuation. This fluctuation is then investigated as a function of the difference in velocity.

  14. Measurements of the ion velocity distribution in an ultracold neutral plasma derived from a cold, dense Rydberg gas

    Science.gov (United States)

    Bergeson, Scott; Lyon, Mary

    2016-05-01

    We report measurements of the ion velocity distribution in an ultracold neutral plasma derived from a dense, cold Rydberg gas in a MOT. The Rydberg atoms are excited using a resonant two-step excitation pathway with lasers of 4 ns duration. The plasma forms spontaneously and rapidly. The rms width of the ion velocity distribution is determined by measuring laser-induced fluorescence (LIF) of the ions. The measured excitation efficiency is compared with a Monte-Carlo wavefunction calculation, and significant differences are observed. We discuss the conditions for blockaded Rydberg excitation and the subsequent spatial ordering of Rydberg atom domains. While the blockade interaction is greater than the Rabi frequency in portions of the atomic sample, no evidence for spatial ordering is observed. This research is supported in part by the Air Force Office of Scientific Research (Grant No. FA9950-12- 0308) and by the National Science Foundation (Grant No. PHY-1404488).

  15. Measurements of the ion velocity distribution in an ultracold neutral plasma derived from a cold, dense Rydberg gas

    CERN Document Server

    Bergeson, S D

    2016-01-01

    We report measurements of the ion velocity distribution in an ultracold neutral plasma derived from a dense, cold Rydberg gas in a MOT. The Rydberg atoms are excited using a resonant two-step excitation pathway with lasers of 4 ns duration. The plasma forms spontaneously and rapidly. The rms width of the ion velocity distribution is determined by measuring laser-induced fluorescence (LIF) of the ions. The measured excitation efficiency is compared with a Monte-Carlo wavefunction calculation, and significant differences are observed. We discuss the conditions for blockaded Rydberg excitation and the subsequent spatial ordering of Rydberg atom domains. While the blockade interaction is greater than the Rabi frequency in portions of the atomic sample, no evidence for spatial ordering is observed.

  16. Measurement of Plasma Ion Temperature and Flow Velocity from Chord-Averaged Emission Line Profile

    Indian Academy of Sciences (India)

    Xu Wei

    2011-03-01

    The distinction between Doppler broadening and Doppler shift has been analysed, the differences between Gaussian fitting and the distribution of chord-integral line shape have also been discussed. Local ion temperature and flow velocity have been derived from the chord-averaged emission line profile by a chosen-point Gaussian fitting technique.

  17. Temporal and spatial resolved SuperDARN line of sight velocity measurements corrected for plasma index of refraction using Bayesian inference

    Science.gov (United States)

    Spaleta, J.; Bristow, W. A.; Klein, J.

    2015-04-01

    Recent work by Gillies et al. (2012, 2009, 2010) has sought an explanation for the SuperDARN line-of-sight velocity underestimate of ionospheric plasma velocity. The reason for the underestimation is thought to be from the modification of the measured Doppler shift of the backscattered signal due to phase refractive index of the ionospheric plasma in the scattering region. Presented here is an analysis technique to estimate the plasma drift velocity, correcting for the index of the refraction of the scattering medium. The technique requires dual frequency SuperDARN observations and calculates velocity from the phase of the SuperDARN autocorrelation function (ACF). Both plasma velocity and plasma density are treated as independent unknowns, and self-consistent error estimates are generated for each. This new technique was employed at the McMurdo radar, resulting in estimates of plasma velocity on scales relevant to existing SuperDARN data products. The McMurdo dual frequency analysis also provides a new SuperDARN data product, an estimate for the plasma density in the ionospheric region derived wholly from SuperDARN backscatter.

  18. Measurements of 3D slip velocities and plasma column lengths of a gliding arc discharge

    NARCIS (Netherlands)

    Zhu, J.; Gao, J.; Ehn, A.; Alden, M.; Li, Z.; Moseev, D.; Kusano, Y.; Salewski, M.; Alpers, A.; Gritzmann, P.; Schwenk, M.

    2015-01-01

    A non-thermal gliding arc discharge was generated at atmospheric pressure in an air flow. The dynamics of the plasma column and tracer particles were recorded using two synchronized highspeed cameras. Whereas the data analysis for such systems has previously been performed in 2D (analyzing the singl

  19. Fine velocity structures collisional dissipation in plasmas

    Science.gov (United States)

    Pezzi, Oreste; Valentini, Francesco; Veltri, Pierluigi

    2016-04-01

    In a weakly collisional plasma, such as the solar wind, collisions are usually considered far too weak to produce any significant effect on the plasma dynamics [1]. However, the estimation of collisionality is often based on the restrictive assumption that the particle velocity distribution function (VDF) shape is close to Maxwellian [2]. On the other hand, in situ spacecraft measurements in the solar wind [3], as well as kinetic numerical experiments [4], indicate that marked non-Maxwellian features develop in the three-dimensional VDFs, (temperature anisotropies, generation of particle beams, ring-like modulations etc.) as a result of the kinetic turbulent cascade of energy towards short spatial scales. Therefore, since collisional effects are proportional to the velocity gradients of the VDF, the collisionless hypothesis may fail locally in velocity space. Here, the existence of several characteristic times during the collisional relaxation of fine velocity structures is investigated by means of Eulerian numerical simulations of a spatially homogeneous force-free weakly collisional plasma. The effect of smoothing out velocity gradients on the evolution of global quantities, such as temperature and entropy, is discussed, suggesting that plasma collisionality can increase locally due to the velocity space deformation of the particle velocity distribution. In particular, by means of Eulerian simulations of collisional relaxation of a spatially homogeneous force-free plasma, in which collisions among particles of the same species are modeled through the complete Landau operator, we show that the system entropy growth occurs over several time scales, inversely proportional to the steepness of the velocity gradients in the VDF. We report clear evidences that fine velocity structures are dissipated by collisions in a time much shorter than global non-Maxwellian features, like, for example, temperature anisotropies. Moreover we indicate that, if small-scale structures

  20. Laser-optical measurements of the velocities of the plasma jets formed from different gases in a kilojoule-range plasma focus facility

    Energy Technology Data Exchange (ETDEWEB)

    Polukhin, S. N., E-mail: snpol@lebedev.ru; Dzhamankulov, A. M.; Gurei, A. E.; Nikulin, V. Ya., E-mail: vnik@lebedev.ru; Peregudova, E. N.; Silin, P. V. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2016-12-15

    The velocities of the plasma jets formed from Ne, N{sub 2}, Ar, and Xe gases in plasma focus facilities were determined by means of laser-optical shadowgraphy of the shock waves generated at the jet leading edge. In spite of the almost tenfold ratio between the atomic weights of these gases, the outflow velocities of the plasma jets formed in experiments with these gases differ by less than twice, in the range of (0.7–1.1) × 10{sup 7} cm/s under similar discharge conditions. The energies of the jet ions were found to vary from 0.7 keV for nitrogen to 4 keV for xenon.

  1. Creating Non-Maxwellian Velocity Distributions in Ultracold Plasmas

    CERN Document Server

    Castro, J; McQuillen, P; Pohl, T; Killian, T C

    2011-01-01

    We present techniques to perturb, measure and model the ion velocity distribution in an ultracold neutral plasma produced by photoionization of strontium atoms. By optical pumping with circularly polarized light we promote ions with certain velocities to a different spin ground state, and probe the resulting perturbed velocity distribution through laser-induced fluorescence spectroscopy. We discuss various approaches to extract the velocity distribution from our measured spectra, and assess their quality through comparisons with molecular dynamic simulations

  2. Development of a compact thermal lithium atom beam source for measurements of electron velocity distribution function anisotropy in electron cyclotron resonance plasmas.

    Science.gov (United States)

    Nishioka, T; Shikama, T; Nagamizo, S; Fujii, K; Zushi, H; Uchida, M; Iwamae, A; Tanaka, H; Maekawa, T; Hasuo, M

    2013-07-01

    The anisotropy of the electron velocity distribution function (EVDF) in plasmas can be deduced from the polarization of emissions induced by anisotropic electron-impact excitation. In this paper, we develop a compact thermal lithium atom beam source for spatially resolved measurements of the EVDF anisotropy in electron cyclotron resonance (ECR) plasmas. The beam system is designed such that the ejected beam has a slab shape, and the beam direction is variable. The divergence and flux of the beam are evaluated by experiments and calculations. The developed beam system is installed in an ECR plasma device with a cusp magnetic field, and the LiI 2s-2p emission (670.8 nm) is observed in low-pressure helium plasma. The two-dimensional distributions of the degree and direction of the polarization in the LiI emission are measured by a polarization imaging system. The evaluated polarization distribution suggests the spatial variation of the EVDF anisotropy.

  3. Evaluation of arterial stiffness with plasma GGT levels and pulse wave velocity measurement in patients with FMF.

    Science.gov (United States)

    Yılmaz, Filiz; Ulu, Sena; Akcı, Önder; Ahsen, Ahmet; Demir, Kasım; Yüksel, Şeref

    2014-03-01

    Pulse wave velocity (PWV) is a non-invasive technique used to evaluate the arterial elasticity, which is an early indicator of atherosclerosis. Lately, gamma glutamyl transferase (GGT) is considered a determiner of arterial stiffness (AS). In this study, we aimed to evaluate the relationship between GGT levels and AS with PWV in patients with Familial Mediterranean fever (FMF). The study was conducted with 60 patients with FMF and 40 controls. Genetic analysis of the patients were performed. AS was assessed by PWV and, after the measurement of PWV, the presence of AS was determined. Mean PWV values and AS frequency were significantly higher in patients with FMF compared with the control group (pFMF patients were higher than in the control group but the difference was not statistically different. In the correlation analysis, PWV and AS were positively correlated with FMF (r=0349, pFMF duration and FMF were associated with GGT (r=0.300, p=0.02; r=0199, p=0.047, respectively). Increased PWV values in FMF patients may indicate arterial stiffness. These patients may be followed closely with PWV as an early indicator of atherosclerosis. Therefore, the cardiovascular risk can be determined in the early stages of disease and it may be possible to take necessary precautions.

  4. Measuring Kinetic Plasma Eigenmodes

    Science.gov (United States)

    Mattingly, Sean; Berumen, Jorge; Chu, Feng; Hood, Ryan; Skiff, Fred

    2015-11-01

    We present a method for measuring kinetic plasma eigenmodes of a cylindrical axially magnetized (1 kG) laboratory plasma (n ~109cm-3 , Te ~ 5eV , Ti ~ 0 . 06eV) by measuring velocity space correlation functions. This method simultaneously observes two separate laser induced fluorescence schemes. Each scheme has its own indepedently tunable laser and its own set of collection optics. With this setup, we are able to measure the time - averaged correlation function as a function of position on the cylindrical axis parallel to the magnetic field (z) and velocity on the deconvolved ion velocity distribution function (v) : C (z , v ,z' ,v' , τ) = t. The freedom of two lasers allows us to measure a two dimensional velocity correlation matrix. This matrix is investigated with the Vlasov equation in the collisionless and weakly collisional regime. The former case, which is continuous, is diagonalized with an integral transform defined by P. J. Morrison while the latter case, which is discrete, is diagonalized through the use of Hermite polynomials.

  5. Direct Measurements of the Spatial and Velocity Dependence of the Ion Density Fluctuation Spectrum of a Laboratory Plasma with Two Independent LIF Schemes

    Science.gov (United States)

    Mattingly, Sean; Berumen, Jorge; Chu, Feng; Hood, Ryan; Skiff, Fred

    2014-10-01

    By using two independently tunable lasers, each with its own collection optics and Ar II LIF transition scheme, we are able to investigate plasma ion density fluctuations as a function of not only spatial scales but also as a function of ion velocities as sampled on different points of a single Doppler-broadened spectral emission line. We do this by measuring the two point correlation C (x , v ,x' ,v' , τ) = t . With the current system, the two carriages determine x and x', while the velocities selected by each laser determine v and v'. Using the two lasers to make two point correlations in phase space demonstrates effects that are not fully understood. In this experiment, we explore the striking difference in correlations when, in the past, the particle orbits overlap in space versus when they do not overlap. This is performed on a small cylindrical laboratory plasma with n ~109 cm-3 , Te ~ 5 eV, Ti ~ 0 . 06 , and a 1 kG axial magnetic field. LIF is performed on ions at two locations aligned with the magnetic field line with a viewing volume comparable to the size of the Larmor radius. Results and interpretations from these experiments are presented and discussed. DOE Grant DE-FG02-99ER54543.

  6. Imaging thermal plasma mass and velocity analyzer

    Science.gov (United States)

    Yau, Andrew W.; Howarth, Andrew

    2016-07-01

    We present the design and principle of operation of the imaging ion mass and velocity analyzer on the Enhanced Polar Outflow Probe (e-POP), which measures low-energy (1-90 eV/e) ion mass composition (1-40 AMU/e) and velocity distributions using a hemispherical electrostatic analyzer (HEA), a time-of-flight (TOF) gate, and a pair of toroidal electrostatic deflectors (TED). The HEA and TOF gate measure the energy-per-charge and azimuth of each detected ion and the ion transit time inside the analyzer, respectively, providing the 2-D velocity distribution of each major ionospheric ion species and resolving the minor ion species under favorable conditions. The TED are in front of the TOF gate and optionally sample ions at different elevation angles up to ±60°, for measurement of 3-D velocity distribution. We present examples of observation data to illustrate the measurement capability of the analyzer, and show the occurrence of enhanced densities of heavy "minor" O++, N+, and molecular ions and intermittent, high-velocity (a few km/s) upward and downward flowing H+ ions in localized regions of the quiet time topside high-latitude ionosphere.

  7. Plasma Anemometer Measurements and Optimization

    Science.gov (United States)

    Marshall, Curtis; Matlis, Eric; Corke, Thomas; Gogineni, Sivaram

    2013-11-01

    Velocity measurements using a constant-current plasma anemometer were performed in a Mach 0.4 jet in order to further optimize the anemometer design. The plasma anemometer uses an AC glow discharge (plasma) formed in the air gap between two protruding low profile electrodes as the flow sensing element. The output from the anemometer is an amplitude modulated version of the AC voltage input that contains information about the mean fluctuating velocity components. Experiments were performed to investigate the effect of the electrode gap, AC current, and AC frequency on the mean and fluctuating velocity sensitivity and repeatability of the sensor. This involved mean velocity calibrations from 0 to 140 m/s and mean and fluctuating velocity profiles through the shear layer of the jet. Measurements with a constant temperature hot-wire anemometer were used for reference. The results showed an improvement in performance with increasing AC frequency that was attributed a more stable glow discharge. The agreement with the hot-wire were good, with the advantage of the plasma anemometer being its 100-times higher frequency response. Supported by Air Force SBIR Phase II FA8650-11-C-2199.

  8. Velocity Correction and Measurement Uncertainty Analysis of Light Screen Velocity Measuring Method

    Institute of Scientific and Technical Information of China (English)

    ZHENG Bin; ZUO Zhao-lu; HOU Wen

    2012-01-01

    Light screen velocity measuring method with unique advantages has been widely used in the velocity measurement of various moving bodies.For large air resistance and friction force which the big moving bodies are subjected to during the light screen velocity measuring,the principle of velocity correction was proposed and a velocity correction equation was derived.A light screen velocity measuring method was used to measure the velocity of big moving bodies which have complex velocity attenuation,and the better results were gained in practical tests.The measuring uncertainty after the velocity correction was calculated.

  9. Velocity Measurement Based on Laser Doppler Effect

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yan-Yan; HUO Yu-Jing; HE Shu-Fang; GONG Ke

    2010-01-01

    @@ A novel method for velocity measurement is presented.In this scheme,a parallel-linear-polarization dualfrequency laser is incident on the target and senses the target velocity with both the frequencies,which can increase the maximum measurable velocity significantly.The theoretical analysis and verification experiment of the novel method are presented,which show that high-velocity measurement can be achieved with high precision using this method.

  10. Inexpensive Time-of-Flight Velocity Measurements.

    Science.gov (United States)

    Everett, Glen E.; Wild, R. L.

    1979-01-01

    Describes a circuit designed to measure time-of-flight velocity and shows how to use it to determine bullet velocity in connection with the ballistic pendulum demonstration of momentum conservation. (Author/GA)

  11. Velocity Diagnosis of Critical Surface at Microwave Band in Laser-Induced Plasma

    Institute of Scientific and Technical Information of China (English)

    WU Ying; WANG Junyan; BAI Shunbo; CHEN Jianping; CHU Ran; YUN Xiaohua; NI Xiaowu

    2008-01-01

    The velocity of critical surface at microwave band in laser-induced plasma was mea-sured and the results are presented. The results indicate that the velocity of critical surface with low electron density is larger than that with the high one; and the velocity of critical surface increases with the laser power density.

  12. Low-Velocity Measurement in Water

    Science.gov (United States)

    Ellis, Christopher; Stefan, Heinz G.

    1986-09-01

    Water velocities in the centimeter per second range or less are measurable by only a few instruments. Experimental laboratory studies frequently require such measurements. A review of low water velocity measurement methods is presented. An inexpensive optical hydrogen bubble-tracing technique is described for velocity measurements in the range 0.5 to 8 cm/s. Modification to a thymol blue (pH) tracer method extends its applicability to the range 0.1 to 1.0 cm/s. Design and operational characteristics of the hydrogen bubble/thymol blue current meter are described.

  13. Position and velocity estimation through acceleration measurements

    OpenAIRE

    Estrada, Antonio; Efimov, Denis; Perruquetti, Wilfrid

    2014-01-01

    International audience; This paper proposes a solution to the problem of velocity and position estimation for a class of oscillating systems whose position, velocity and acceleration are zero mean signals. The proposed scheme considers that the dynamic model of the system is unknown and only noisy acceleration measurements are available.

  14. Measurement of Poloidal Velocity on the National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Ronald E. Bell and Russell Feder

    2010-06-04

    A diagnostic suite has been developed to measure impurity poloidal flow using charge exchange recombination spectroscopy on the National Spherical Torus Experiment. Toroidal and poloidal viewing systems measure all quantities required to determine the radial electric field. Two sets of up/down symmetric poloidal views are used to measure both active emission in the plane of the neutral heating beams and background emission in a radial plane away from the neutral beams. Differential velocity measurements isolate the line-integrated poloidal velocity from apparent flows due to the energy-dependent chargeexchange cross section. Six f/1.8 spectrometers measure 276 spectra to obtain 75 active and 63 background channels every 10 ms. Local measurements from a similar midplane toroidal viewing system are mapped into two dimensions to allow the inversion of poloidal line-integrated measurements to obtain local poloidal velocity profiles. Radial resolution after inversion is 0.6-1.8 cm from the plasma edge to the center.

  15. Measuring Bullet Velocity with a PC Soundcard

    CERN Document Server

    Courtney, M; Courtney, Michael; Edwards, Brian

    2006-01-01

    This article describes a simple method for using a PC soundcard to accurately measure bullet velocity. The method involves placing the microphone within a foot of the muzzle and firing at a steel target between 50 and 100 yards away. The time of flight for the bullet is simply the recorded time between muzzle blast and sound of the bullet hitting the target minus the time it takes the sound to return from the target to the microphone. The average bullet velocity is simply the distance from the muzzle to the target divided by the time of flight of the bullet. This method can also be applied to measurement of paintball velocities.

  16. Propagation velocities of laser-produced plasmas from copper wire targets and water droplets

    Science.gov (United States)

    Song, Kyo-Dong; Alexander, Dennis R.

    1994-01-01

    Experiments were performed to determine the plasma propagation velocities resulting from KrF laser irradiation of copper wire target (75 microns diameter) and water droplets (75 microns diameter) at irradiance levels ranging from 25 to 150 GW/sq cm. Plasma propagation velocities were measured using a streak camera system oriented orthogonally to the high-energy laser propagation axis. Plasma velocities were studied as a function of position in the focused beam. Results show that both the shape of the plasma formation and material removal from the copper wire are different and depend on whether the targets are focused or slightly defocused (approximately = 0.5 mm movement in the beam axis). Plasma formation and its position relative to the target is an important factor in determining the practical focal point during high-energy laser interaction with materials. At irradiance of 100 GW/sq cm, the air plasma has two weak-velocity components which propagate toward and away from the incident laser while a strong-velocity component propagates away from the laser beam as a detonation wave. Comparison of the measured breakdown velocities (in the range of 2.22-2.27 x 10(exp 5) m/s) for air and the value calculated by the nonlinear breakdown wave theory at irradiance of 100 GW/sq cm showed a quantitative agreement within approximately 50% while the linear theory and Gaussian pulse theory failed. The detonation wave velocities of plasma generated from water droplets and copper wire targets for different focused cases were measured and analyzed theoretically. The propagation velocities of laser-induced plasma liquid droplets obtained by previous research are compared with current work.

  17. Acoustic measurement of potato cannon velocity

    CERN Document Server

    Courtney, M; Courtney, Amy; Courtney, Michael

    2006-01-01

    This article describes measurement of potato cannon velocity with a digitized microphone signal. A microphone is attached to the potato cannon muzzle and a potato is fired at an aluminum target about 10 m away. The potato's flight time can be determined from the acoustic waveform by subtracting the time in the barrel and time for sound to return from the target. The potato velocity is simply the flight distance divided by the flight time.

  18. Driven phase space vortices in plasmas with nonextensive velocity distribution

    Science.gov (United States)

    Trivedi, Pallavi; Ganesh, Rajaraman

    2017-03-01

    The evolution of chirp-driven electrostatic waves in unmagnetized plasmas is numerically investigated by using a one-dimensional (1D) Vlasov-poisson solver with periodic boundary conditions. The initial velocity distribution of the 1D plasma is assumed to be governed by nonextensive q distribution [C. Tsallis, J. Stat. Phys. 52, 479 (1988)]. For an infinitesimal amplitude of an external drive, we investigate the effects of chirp driven dynamics that leads to the formation of giant phase space vortices (PSV) for both Maxwellian (q = 1) and non-Maxwellian ( q ≠ 1 ) plasmas. For non-Maxwellian plasmas, the formation of giant PSV with multiple extrema and phase velocities is shown to be dependent on the strength of "q". Novel features such as "shark"-like and transient "honeycomb"-like structures in phase space are discussed. Wherever relevant, we compare our results with previous work.

  19. Relative ion expansion velocity in laser-produced plasmas

    Science.gov (United States)

    Goldsmith, S.; Moreno, J. C.; Griem, H. R.; Cohen, Leonard; Richardson, M. C.

    1988-01-01

    The spectra of highly ionized titanium, Ti XIII through Ti XXI, and C VI Lyman lines were excited in laser-produced plasmas. The plasma was produced by uniformly irradiating spherical glass microballoons coated with thin layers of titanium and parylene. The 24-beam Omega laser system produced short, 0.6 ns, and high-intensity, 4 x 10 to the 14th W/sq cm, laser pulses at a wavelength of 351 nm. The measured wavelength for the 2p-3s Ti XIII resonance lines had an average shift of + 0.023 A relative to the C VI and Ti XX spectral lines. No shift was found between the C VI, Ti XIX, and Ti XX lines. The shift is attributed to a Doppler effect, resulting from a difference of (2.6 + or - 0.2) x 10 to the 7th cm/s in the expansion velocities of Ti XIX and Ti XX ions compared to Ti XIII ions.

  20. Radial variation of refractive index, plasma frequency and phase velocity in laser induced air plasma

    CSIR Research Space (South Africa)

    Mathuthu, M

    2006-12-01

    Full Text Available induced air plasma to study the spatial variation of plasma parameters in the axial direction of the laser beam. In this paper, the authors report investigation on the radial variation of the refractive index, plasma frequency, and phase velocity of a...

  1. Antarctica: measuring glacier velocity from satellite images.

    Science.gov (United States)

    Lucchitta, B K; Ferguson, H M

    1986-11-28

    Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

  2. Middle cerebral artery blood velocity and plasma catecholamines during exercise

    DEFF Research Database (Denmark)

    Pott, F; Jensen, K; Hansen, H;

    1996-01-01

    During dynamic exercise, mean blood velocity (Vmean) in the middle cerebral artery (MCA) demonstrates a graded increase to work rate and reflects regional cerebral blood flow. At a high work rate, however, vasoactive levels of plasma catecholamines could mediate vasoconstriction of the MCA...

  3. Numerical simulation of temperature and velocity fields in plasma spray

    Institute of Scientific and Technical Information of China (English)

    FAN Qun-bo; WANG Lu; WANG Fu-chi

    2007-01-01

    Based on the turbulence jet model, with respect to Ar-He mixture plasma gas injecting to ambient atmosphere, the temperature filed and velocity field under typical working conditions were investigated. Given the conditions of I=900 A, FAr=1.98 m3/h, FHe=0.85 m3/h, it is found that both the temperature and the velocity undergo a plateau region near the nozzle exit (0-10 mm) at the very first stage, then decrease abruptly from initial 13 543 K and 778.2 m/s to 4 000 K and 260.0 m/s, and finally decrease slowly again. Meanwhile, the radial temperature and radial velocity change relatively slow. The inner mechanism for such phenomena is due to the complex violent interaction between the high-temperature and high-velocity turbulent plasma jet and the ambient atmosphere. Compared with traditional methods, the initial working conditions can be directly related to the temperature and velocity fields of the plasma jet by deriving basic boundary conditions.

  4. Velocity Measurements of Thermoelectric Driven Flowing Liquid Lithium

    Science.gov (United States)

    Szott, Matthew; Xu, Wenyu; Fiflis, Peter; Haehnlein, Ian; Kapat, Aveek; Kalathiparambil, Kishor; Ruzic, David N.

    2014-10-01

    Liquid lithium has garnered additional attention as a PFC due to its several advantages over solid PFCs, including reduced erosion and thermal fatigue, increased heat transfer, higher device lifetime, and enhanced plasma performance due to the establishment of low recycling regimes at the wall. The Lithium Metal Infused Trenches concept (LiMIT) has demonstrated thermoelectric magnetohydrodynamic flow of liquid lithium through horizontal open-faced metal trenches with measured velocities varying from 3.7+/-0.5 cm/s in the 1.76 T field of HT-7 to 22+/-3 cm/s in the SLiDE facility at UIUC at 0.059 T. To demonstrate the versatility of the concept, a new LiMIT design using narrower trenches shows steady state, thermoelectric-driven flow at an arbitrary angle from horizontal. Velocity characteristics are measured and discussed. Based on this LiMIT concept, a new limiter design has been developed to be tested on the mid-plane of the EAST plasma. Preliminary modelling suggests lithium flow of 6 cm/s in this device. Additionally, recent testing at the Magnum-PSI facility has given encouraging results, and velocity measurements in relation to magnetic field strength and plasma flux are also presented.

  5. Device for measuring mechanical drilling velocity

    Energy Technology Data Exchange (ETDEWEB)

    Turchaninov, Y.N.; Ippolitova, L.G.; Khizgilov, A.I.; Rolik, V.A.

    1980-12-17

    A device is proposed for measuring the mechanical drilling velocity which includes a primary drilling tool supply transformer, control block, trigger, range switch; control block, block for determining motion direction, time counter and measurement instrument. In order to guarantee continuous measurement of the mechanical velocity and to improve the accuracy of measuring the average mechanical velocity during drilling at sea, it is equipped with a block for multiplying the number of pulses, four I circuits, supply counter, supply recorder, primary neutral transformer, two controllable frequency dividers, first frequency divider, generator of prime pulses consisting of a generatror of reference frequencies and second frequency divider, time recorder, counter and velocity recorder, time recorder and digital-analog transformer. In this case the outlet of the primary transformer for drilling tool supply is connected through a in-series connected block for determining the movement direction, block for multiplying the number of pulses, first circuit I and supply counter to one of the inlets of the supply counter. Its second inlet is connected through a block of control to the primary neutral transformer and one of the inlets of the time recorder. Its second inlet is connected through a in-series connected time counter, fourth I circuit, second frequency divider, generator of reference frequency, first frequency divider, third circuit I, second controllable frequency divider, counter and velocity recorder and digital-analog transformer of the measurement instrument. The outlet of the supply recorder is connected to one of the inlets of the first controllable divider. Its second inlet is connected to the second I circuit to the outlet of the first frequency divider, and the outlet is connected to one of the trigger inlets.

  6. Measurements of an expanding surface flashover plasma

    Energy Technology Data Exchange (ETDEWEB)

    Harris, J. R., E-mail: john.harris@colostate.edu [Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523 (United States)

    2014-05-21

    A better understanding of vacuum surface flashover and the plasma produced by it is of importance for electron and ion sources, as well as advanced accelerators and other vacuum electronic devices. This article describes time-of-flight and biased-probe measurements made on the expanding plasma generated from a vacuum surface flashover discharge. The plasma expanded at velocities of 1.2–6.5 cm/μs, and had typical densities of 10{sup 10}–10{sup 12} cm{sup −3}. The expansion velocity of the plasma leading edge often exhibited a sharp increase at distances of about 50 mm from the discharge site. Comparison with biased-probe data suggests that, under most conditions, the plasma leading edge was dominated by negative ions, with the apparent increase in velocity being due to fast H{sup −} overtaking slower, heavier ions. In some cases, biased-probe data also showed abrupt discontinuities in the plasma energy distribution co-located with large changes in the intercepted plasma current, suggesting the presence of a shock in the leading edge of the expanding plasma.

  7. Measurements of parallel electron velocity distributions using whistler wave absorption.

    Science.gov (United States)

    Thuecks, D J; Skiff, F; Kletzing, C A

    2012-08-01

    We describe a diagnostic to measure the parallel electron velocity distribution in a magnetized plasma that is overdense (ω(pe) > ω(ce)). This technique utilizes resonant absorption of whistler waves by electrons with velocities parallel to a background magnetic field. The whistler waves were launched and received by a pair of dipole antennas immersed in a cylindrical discharge plasma at two positions along an axial background magnetic field. The whistler wave frequency was swept from somewhat below and up to the electron cyclotron frequency ω(ce). As the frequency was swept, the wave was resonantly absorbed by the part of the electron phase space density which was Doppler shifted into resonance according to the relation ω - k([parallel])v([parallel]) = ω(ce). The measured absorption is directly related to the reduced parallel electron distribution function integrated along the wave trajectory. The background theory and initial results from this diagnostic are presented here. Though this diagnostic is best suited to detect tail populations of the parallel electron distribution function, these first results show that this diagnostic is also rather successful in measuring the bulk plasma density and temperature both during the plasma discharge and into the afterglow.

  8. Measurement of the velocity of a quantum object: A role of phase and group velocities

    Science.gov (United States)

    Lapinski, Mikaila; Rostovtsev, Yuri V.

    2017-08-01

    We consider the motion of a quantum particle in a free space. Introducing an explicit measurement procedure for velocity, we demonstrate that the measured velocity is related to the group and phase velocities of the corresponding matter waves. We show that for long distances the measured velocity coincides with the matter wave group velocity. We discuss the possibilities to demonstrate these effects for the optical pulses in coherently driven media or for radiation propagating in waveguides.

  9. Investigation on in-flight particle velocity in supersonic plasma spraying

    Institute of Scientific and Technical Information of China (English)

    Li Changqing; Ma Shining; Ye Xionglin

    2005-01-01

    In-flight particle velocity and flux distribution were measured using CCD thermal spray monitor system during supersonic plasma spray processing with nano-structured Al203-TiO2 feed stocks. According to the results of particle flux measurement, the largest radian of the divergent particle stream is about 0. 2. Within the measuring range, top speed of inflight particles reached 800 m/s. Particle acceleration was accomplished within 4 cm down stream of the nozzle. Average particle velocity ( about 450 m/s) exceeded local sound speed (340 m/s) even at a mean standoff distance of 17 cm. With increasing mean standoff distance, average velocity of in-flight particle decreased according to a parabolic rule approximately.Image diagnosis showed that the result of in-flight particle velocity measurement is credible.

  10. Associations between plasma fibulin-1, pulse wave velocity and diabetes in patients with coronary heart disease

    DEFF Research Database (Denmark)

    Hansen, Maria Lyck; Rasmussen, Lars Melholt

    2015-01-01

    BACKGROUND: Diabetes is related to increased risk of cardiovascular disease, and arterial stiffness and its consequences may be the factor connecting the two. Arterial stiffness is often measured by carotid-femoral pulse wave velocity (cf-PWV), but no plasma biomarker reflecting arterial stiffnes...

  11. Tomographic Particle Localization and Velocity Measurement

    Science.gov (United States)

    Kirner, S.; Forster, G.; Schein, J.

    2015-01-01

    Wire arc spraying is one of the most common and elementary thermal spray processes. Due to its easy handling, high deposition rate, and relative low process costs, it is a frequently used coating technology for the production of wear and corrosion resistant coatings. In order to produce reliable and reproducible coatings, it is necessary to be able to control the coating process. This can be achieved by analyzing the parameters of the particles deposited. Essential for the coating quality are, for example, the velocity, the size, and the temperature of the particles. In this work, an innovative diagnostic for particle velocity and location determination is presented. By the use of several synchronized CMOS-Cameras positioned around the particle jet, a series of images from different directions is simultaneously taken. The images contain the information that is necessary to calculate the 3D-location-vector of the particles and finally with the help of the exposure time the trajectory can be determined. In this work, the experimental setup of the tomographic diagnostic is presented, the mathematical method of the reconstruction is explained, and first measured velocity distributions are shown.

  12. Long velocity tails in plasmas and gravitational systems

    CERN Document Server

    Brenig, L; Filho, T M Rocha

    2016-01-01

    Long tails in the velocity distribution are observed in plasmas and gravitational systems. Some experiments and observations in far-from-equilibrium conditions show that these tails behave as 1/v^(5/2). We show here that such heavy tails are due to a universal mechanism related to the fluctuations of the total force field. Owing to the divergence in 1/r^2 of the binary interaction force, these fluctuations can be very large and their probability density exhibits a similar long tail. They induce large velocity fluctuations leading to the 1/v^(5/2) tail. We extract the mechanism causing these properties from the BBGKY hierarchy representation of Statistical Mechanics. This leads to a modification of the Vlasov equation by an additional term. The novel term involves a fractional power 3/4 of the Laplacian in velocity space and a fractional iterated time integral. Solving the new kinetic equation for a uniform system, we retrieve the observed 1/v^(5/2) tail for the velocity distribution. These results are confirm...

  13. VELOCITY SHEAR INSTABILITY IN DUSTY PLASMAS OF COMET

    Institute of Scientific and Technical Information of China (English)

    Lu Li; Li Zhongyuan

    2000-01-01

    The velocity shear instability in a magnetized, three-component dusty plasma is investigated for both positively and negatively charged dust particles. The critical shears as a function of the relative charge of dust grains for both positively and negatively charged dust grains are in the same form. The instability excitation is easier in colder proton's environment for positively charged dust, and so also in colder electron's environment for negatively charged dust. For a certain flow pattern, the instability excites in different direction for different sign of charged dust grains. This conclusion may be helpful in interpreting the helical structures and streamer splitted phenomena in a cometary tail.

  14. Selective measurement of digital nerve conduction velocity.

    Science.gov (United States)

    Terai, Y; Senda, M; Hashizume, H; Nagashima, H; Inoue, H

    2001-01-01

    We developed a new method to measure the nerve conduction velocity of a single digital nerve. In 27 volunteers (27 hands), we separately stimulated each digital nerve on the radial and ulnar sides of the middle and ring fingers. A double-peaked potential was recorded above the median nerve at the wrist joint when either the radial-side nerve or the ulnar-side nerve of the middle finger was stimulated. The first peak of this potential had disappeared after the digital nerve was blocked under the stimulating electrodes, and the peak appeared again coinciding with the decrease of anesthesia. Shifting the stimulating electrodes on the digital nerve resulted in no significant difference in the peak conduction velocity. It is possible that each peak of the potential was attributable to conduction of an action potential along one of the two digital nerves. This new method allows the assessment of a single digital nerve, and may be clinically useful for assessing the rupture of a digital nerve and the sensory nerve action potentials in carpal tunnel syndrome.

  15. Velocity Gradient Maps Directly Measured by PLF

    Science.gov (United States)

    Quintella, Cristina M.; Gonçalves, Cristiane C.; Lima, Angelo Mv; Pepe, Iuri M.

    2000-11-01

    Flows are macroscopically classified as laminar or turbulent due to their velocity distributions, nevertheless most chemical and biological phenomena are yield or enhanced by intermolecular orientation and microscopic turbulence. Here was studied a 100micra liquid sheet produced by a slit nozzle, both flowing freely into air and over a borosilicate surface (roughness bellow 5nm), ranging from 17 to 36Re (143 to 297cm/s, similar to muscles and brain blood flow). Mono ethylene glycol was used either pure, or with sodium alkyl benzene sulfated (ABS) surfactant (24.5mol/L, submicellar), or with poly(ethylene oxide) (PEO) (1409ppm, 4millions aw). Velocity gradients were directly measured by 514nm polarized laser induced fluorescence (PLF) with R6G as probe. Intermolecular alignment (IA) maps were obtained all over the flow (about 1,950 points, 0.02mm2 precision). The free jet average IA has increased 57% when flowing over borosilicate. With ABS, the IA increased, suggesting wall drag reduction. With PEO the IA decreases due to solvent intermolecular forces attenuation, generating wider turbulent areas. PLF proved to be an excellent method to evaluate IA within liquid thin flows. Chosen solute additions permits IA control over wide regions.

  16. Quantification of ultrasound correlation-based flow velocity mapping and edge velocity gradient measurement.

    Science.gov (United States)

    Park, Dae Woo; Kruger, Grant H; Rubin, Jonathan M; Hamilton, James; Gottschalk, Paul; Dodde, Robert E; Shih, Albert J; Weitzel, William F

    2013-10-01

    This study investigated the use of ultrasound speckle decorrelation- and correlation-based lateral speckle-tracking methods for transverse and longitudinal blood velocity profile measurement, respectively. By studying the blood velocity gradient at the vessel wall, vascular wall shear stress, which is important in vascular physiology as well as the pathophysiologic mechanisms of vascular diseases, can be obtained. Decorrelation-based blood velocity profile measurement transverse to the flow direction is a novel approach, which provides advantages for vascular wall shear stress measurement over longitudinal blood velocity measurement methods. Blood flow velocity profiles are obtained from measurements of frame-to-frame decorrelation. In this research, both decorrelation and lateral speckle-tracking flow estimation methods were compared with Poiseuille theory over physiologic flows ranging from 50 to 1000 mm/s. The decorrelation flow velocity measurement method demonstrated more accurate prediction of the flow velocity gradient at the wall edge than the correlation-based lateral speckle-tracking method. The novelty of this study is that speckle decorrelation-based flow velocity measurements determine the blood velocity across a vessel. In addition, speckle decorrelation-based flow velocity measurements have higher axial spatial resolution than Doppler ultrasound measurements to enable more accurate measurement of blood velocity near a vessel wall and determine the physiologically important wall shear.

  17. Velocity-space tomography of fusion plasmas by collective Thomson scattering of gyrotron radiation

    DEFF Research Database (Denmark)

    Salewski, Mirko; Jacobsen, A.S.; Jensen, Thomas;

    2016-01-01

    We propose a diagnostic capable of measuring 2D fast-ion velocity distribution functions 푓2퐷푣 in the MeV-range in magnetized fusion plasmas. Today velocity-space tomography based on fast-ion D훼 spectroscopy is regularly used to measure 푓2퐷푣 for ion energies below 100 keV. Unfortunately, the signal......-tonoise ratio becomes fairly low for MeV-range ions. Ions at any energy can be detected well by collective Thomson scattering of mm-wave radiation from a high-power gyrotron. We demonstrate how collective Thomson scattering can be used to measure 푓2퐷푣 in the MeV-range in reactor relevant plasmas...

  18. Agyrotropic pressure tensor induced by the plasma velocity shear

    Science.gov (United States)

    Pegoraro, Francesco; Del Sarto, Danele; Califano, Francesco

    2016-10-01

    We show that the spatial inhomogeneity of a shear flow in a fluid plasma is transferred to a pressure anisotropy that has both a gyrotropic and a non gyrotropic component. We investigate this process both analytically and numerically by including the full pressure tensor dynamics. We determine the time evolution of the pressure agyrotropy and in general of the pressure tensor anisotropization which arise from the action of both the magnetic eld and the flow strain tensor. This mechanism can affect the onset and development of shear-induced fluid instabilities in plasmas and is relevant to the understanding of the origin of some of the non-Maxwellian distribution functions evidenced both in Vlasov simulations and in space plasma measurements that exhibit pressure agyrotropy.

  19. Plasma Beam Measurements

    Science.gov (United States)

    1991-08-01

    GUN PLASMA BEAM / ,I 21 cm diameter = 0 GLASS DRIFT TUBE 50 cm diameter MCP CAMERA CLASS CROSSES (a) Gun muzzle /"- PLASA BEAM / TAROT z = 10 m MCP...discusses some of the hydrodynamic issues related to the calcula- tions. The reader may well wonder why hydrodynamics should be an issue in a 116 WL-TR-90...answer is yes for the slow beam cases and no for the fast beam cases. This is explained further. 118 WL-TR-90-83 The reader will recall the

  20. Measuring Global Monopole Velocities, one by one

    CERN Document Server

    Lopez-Eiguren, Asier; Achúcarro, Ana

    2016-01-01

    We present an estimation of the average velocity of a network of global monopoles in a cosmological setting using large numerical simulations. In order to obtain the value of the velocity, we improve some already known methods, and present a new one. This new method estimates individual global monopole velocities in a network, by means of detecting each monopole position in the lattice and following the path described by each one of them. Using our new estimate we can settle an open question previously posed in the literature: velocity-dependent one-scale (VOS) models for global monopoles predict two branches of scaling solutions, one with monopoles moving at subluminal speeds and one with monopoles moving at luminal speeds. Previous attempts to estimate monopole velocities had large uncertainties and were not able to settle that question. Our simulations find no evidence of a luminal branch. We also estimate the values of the parameters of the VOS model. With our new method we can also study the microphysics...

  1. Measuring global monopole velocities, one by one

    Science.gov (United States)

    Lopez-Eiguren, Asier; Urrestilla, Jon; Achúcarro, Ana

    2017-01-01

    We present an estimation of the average velocity of a network of global monopoles in a cosmological setting using large numerical simulations. In order to obtain the value of the velocity, we improve some already known methods, and present a new one. This new method estimates individual global monopole velocities in a network, by means of detecting each monopole position in the lattice and following the path described by each one of them. Using our new estimate we can settle an open question previously posed in the literature: velocity-dependent one-scale (VOS) models for global monopoles predict two branches of scaling solutions, one with monopoles moving at subluminal speeds and one with monopoles moving at luminal speeds. Previous attempts to estimate monopole velocities had large uncertainties and were not able to settle that question. Our simulations find no evidence of a luminal branch. We also estimate the values of the parameters of the VOS model. With our new method we can also study the microphysics of the complicated dynamics of individual monopoles. Finally we use our large simulation volume to compare the results from the different estimator methods, as well as to asses the validity of the numerical approximations made.

  2. A New Filtering Algorithm Utilizing Radial Velocity Measurement

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-feng; DU Zi-cheng; PAN Quan

    2005-01-01

    Pulse Doppler radar measurements consist of range, azimuth, elevation and radial velocity. Most of the radar tracking algorithms in engineering only utilize position measurement. The extended Kalman filter with radial velocity measureneut is presented, then a new filtering algorithm utilizing radial velocity measurement is proposed to improve tracking results and the theoretical analysis is also given. Simulation results of the new algorithm, converted measurement Kalman filter, extended Kalman filter are compared. The effectiveness of the new algorithm is verified by simulation results.

  3. Accurate Sound Velocity Measurement in Ocean Near-Surface Layer

    Science.gov (United States)

    Lizarralde, D.; Xu, B. L.

    2015-12-01

    Accurate sound velocity measurement is essential in oceanography because sound is the only wave that can propagate in sea water. Due to its measuring difficulties, sound velocity is often not measured directly but instead calculated from water temperature, salinity, and depth, which are much easier to obtain. This research develops a new method to directly measure the sound velocity in the ocean's near-surface layer using multi-channel seismic (MCS) hydrophones. This system consists of a device to make a sound pulse and a long cable with hundreds of hydrophones to record the sound. The distance between the source and each receiver is the offset. The time it takes the pulse to arrive to each receiver is the travel time.The errors of measuring offset and travel time will affect the accuracy of sound velocity if we calculated with just one offset and one travel time. However, by analyzing the direct arrival signal from hundreds of receivers, the velocity can be determined as the slope of a straight line in the travel time-offset graph. The errors in distance and time measurement result in only an up or down shift of the line and do not affect the slope. This research uses MCS data of survey MGL1408 obtained from the Marine Geoscience Data System and processed with Seismic Unix. The sound velocity can be directly measured to an accuracy of less than 1m/s. The included graph shows the directly measured velocity verses the calculated velocity along 100km across the Mid-Atlantic continental margin. The directly measured velocity shows a good coherence to the velocity computed from temperature and salinity. In addition, the fine variations in the sound velocity can be observed, which is hardly seen from the calculated velocity. Using this methodology, both large area acquisition and fine resolution can be achieved. This directly measured sound velocity will be a new and powerful tool in oceanography.

  4. Multi Point Velocity, Density and Temperature Measurements using LITA Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Laser induced thermal acoustics (LITA) is a nonintrusive, transient-grating optical technique that provides simultaneous high-accuracy measurements of velocity,...

  5. 大气压介质阻挡射流放电离子速度分布的测量%Measurement of ion velocity distribution in plasma jet with dielectric barrier geometry at atmospheric pressure

    Institute of Scientific and Technical Information of China (English)

    熊莉; 齐冰

    2016-01-01

    A new method based on fast Fourier transform, is presented to calculate ion velocity distribution by analyzing electromagnetic radiation signal from atmospheric nonequilibrium plasma. This method is based on a dipole model. Results show that the ion velocity distribution deviates from Maxwell distribution over time. The ion velocity and relative ion number fluctuate regularly with time.%通过测量大气压介质阻挡放电等离子体辐射信号,建立偶极子辐射模型,利用快速傅立叶变换,计算了大气压介质阻挡放电等离子体中离子速度分布。计算结果表明,速度分布偏离麦克斯韦分布,并且随着放电过程的进行,离子速度及相对离子数进行有规律的变化。

  6. A Study of DC Surface Plasma Discharge in Absence of Free Airflow: Ionic Wind Velocity Profile

    Directory of Open Access Journals (Sweden)

    M. Rafika

    2009-01-01

    Full Text Available In our study we are interested with the DC (Direct Current electric corona discharge created between two wire electrodes. We present experimental results related to some electroaerodynamic actuators based on the DC corona discharge at the surface of a dielectric material. We used different geometrical forms of dielectric surface such as a plate, a cylinder and a wing of aircraft of type NACA 0015. We present the current density-electric filed characteristics for different cases in order to determine the discharge regimes. The corona discharge produces non-thermal plasma so that it is called plasma discharge. Plasma discharge creates a tangential ionic wind above the surface at the vicinity of the wall. We have measured the ionic wind induced by the corona discharge in absence of free external airflow, we give the ionic wind velocity profiles for different surface forms and we compare the actuators effect based on the span of the ionic wind velocity values. We notice that the maximum ionic wind velocity is obtained with the NACA profile, which shows the effectiveness of this actuator for the airflow control.

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

    Science.gov (United States)

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

    2010-08-01

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

  8. Experimental Measurement for Shock Velocity-Mass Velocity Relationship of Liquid Argon Up to 46 GPa

    Institute of Scientific and Technical Information of China (English)

    孟川民; 施尚春; 董石; 杨向东; 谭华; 经福谦

    2003-01-01

    Shock properties of liquid argon were measured in the shock pressure up to 46 GPa by employing the two-stage light gas gun. Liquid nitrogen was used as coolant liquid. The cryogenic target system has been improved to compare with the previous work. Shock velocities were measured with self-shorting electrical probes. Impactor velocities were measured with an electrical-magnetic induction system. Mass velocities were obtained by mean of shock impedance matching method. The experimental data shows that the slope of experimental Hugoniot curve of liquid argon begins to decrease above 30 GPa.

  9. Accurate measurement of ultrasonic velocity by eliminating the diffraction effect

    Institute of Scientific and Technical Information of China (English)

    WEI Tingcun

    2003-01-01

    The accurate measurement method of ultrasonic velocity by the pulse interferencemethod with eliminating the diffraction effect has been investigated in VHF range experimen-tally. Two silicate glasses were taken as the specimens, their frequency dependences of longitu-dinal velocities were measured in the frequency range 50-350 MHz, and the phase advances ofultrasonic signals caused by diffraction effect were calculated using A. O. Williams' theoreticalexpression. For the frequency dependences of longitudinal velocities, the measurement resultswere in good agreement with the simulation ones in which the phase advances were included.It has been shown that the velocity error due to diffraction effect can be corrected very well bythis method.

  10. Turbulence measurements in fusion plasmas

    Science.gov (United States)

    Conway, G. D.

    2008-12-01

    Turbulence measurements in magnetically confined toroidal plasmas have a long history and relevance due to the detrimental role of turbulence induced transport on particle, energy, impurity and momentum confinement. The turbulence—the microscopic random fluctuations in particle density, temperature, potential and magnetic field—is generally driven by radial gradients in the plasma density and temperature. The correlation between the turbulence properties and global confinement, via enhanced diffusion, convection and direct conduction, is now well documented. Theory, together with recent measurements, also indicates that non-linear interactions within the turbulence generate large scale zonal flows and geodesic oscillations, which can feed back onto the turbulence and equilibrium profiles creating a complex interdependence. An overview of the current status and understanding of plasma turbulence measurements in the closed flux surface region of magnetic confinement fusion devices is presented, highlighting some recent developments and outstanding problems.

  11. Fat mass measured by DXA varies with scan velocity

    DEFF Research Database (Denmark)

    Black, Eva; Petersen, Liselotte; Kreutzer, Martin

    2002-01-01

    To study the influence of scan velocities of DXA on the measured size of fat mass, lean body mass, bone mineral content and density, and total body weight.......To study the influence of scan velocities of DXA on the measured size of fat mass, lean body mass, bone mineral content and density, and total body weight....

  12. Velocity-space sensitivity of neutron spectrometry measurements

    DEFF Research Database (Denmark)

    Jacobsen, Asger Schou; Salewski, Mirko; Eriksson, J.;

    2015-01-01

    Neutron emission spectrometry (NES) measures the energies of neutrons produced in fusion reactions. Here we present velocity-space weight functions for NES and neutron yield measurements. Weight functions show the sensitivity as well as the accessible regions in velocity space for a given range...

  13. On bias of kinetic temperature measurements in complex plasmas

    DEFF Research Database (Denmark)

    Kantor, M.; Moseev, D.; Salewski, Mirko

    2014-01-01

    The kinetic temperature in complex plasmas is often measured using particle tracking velocimetry. Here, we introduce a criterion which minimizes the probability of faulty tracking of particles with normally distributed random displacements in consecutive frames. Faulty particle tracking results...... in a measurement bias of the deduced velocity distribution function and hence the deduced kinetic temperature. For particles with a normal velocity distribution function, mistracking biases the obtained velocity distribution function towards small velocities at the expense of large velocities, i.e., the inferred...... velocity distribution is more peaked and its tail is less pronounced. The kinetic temperature is therefore systematically underestimated in measurements. We give a prescription to mitigate this type of error....

  14. Inertial Measurements Based Velocity-free Attitude Stabilization

    CERN Document Server

    Tayebi, A; Benallegue, A

    2012-01-01

    The existing attitude controllers (without angular velocity measurements) involve explicitly the orientation (\\textit{e.g.,} the unit-quaternion) in the feedback. Unfortunately, there does not exist any sensor that directly measures the orientation of a rigid body, and hence, the attitude must be reconstructed using a set of inertial vector measurements as well as the angular velocity (which is assumed to be unavailable in velocity-free control schemes). To overcome this \\textit{circular reasoning}-like problem, we propose a velocity-free attitude stabilization control scheme relying solely on inertial vector measurements. The originality of this control strategy stems from the fact that the reconstruction of the attitude as well as the angular velocity measurements are not required at all. Moreover, as a byproduct of our design approach, the proposed controller does not lead to the unwinding phenomenon encountered in unit-quaternion based attitude controllers.

  15. Sheared velocity flows as a source of pressure anisotropy in low collisionality plasmas

    Science.gov (United States)

    Del Sarto, Daniele; Pegoraro, Francesco; Cerri, Silvio Sergio; Califano, Francesco; Tenerani, Anna

    2015-04-01

    Non-Maxwellian metaequilibrium states may exist in low-collisionality plasmas as evidenced by direct (particle distributions) and indirect (e.g., instabilities driven by pressure anisotropy) satellite and laboratory measurements. These are directly observed in the solar wind (e.g. [1]), in magnetospheric reconnection events [2], in magnetically confined plasmas [3] or in simulations of Vlasov turbulence [4]. By including the full pressure tensor dynamics in a fluid plasma model, we show that a sheared velocity field can provide an effective mechanism that makes an initial isotropic state anisotropic. We discuss how the propagation of "magneto-elastic" waves can affect the pressure tensor anisotropization and the small scale formation that arise from the interplay between the gyrotropic terms due to the magnetic field and flow vorticity, and the non-gyropropic effect of the flow strain tensor. We support this analysis by a numerical integration of the nonlinear equations describing the pressure tensor evolution. This anisotropization mechanism might provide a good candidate for the understanding of the observed correlation between the presence of a sheared velocity flow and the signature of pressure anisotropies which are not yet explained within the standard models based e.g. on the CGL paradigm (see also [5]). Examples of these signatures are provided by the threshold lowering of ion-Weibel instabilities in the geomagnetic tail, observed in concomitance to the presence of a velocity shear in the near-earth plasma profile [6], or by the relatively stronger anisotropization measured for core protons in the fast solar wind [4,7] or in "space simulation" laboratory plasma experiments [3]. 1] E. Marsch et al., Journ. Geophys. Res. 109, A04120 (2004); Yu. V. Khotyainstev at el., Phys. Rev. Lett. 106, 165001 (2011). [2] N. Aunai et al., Ann. Geophys. 29, 1571 (2011); N. Aunai et al., Journ. Geophys. Res. 116, A09232 (2011). [3] E.E. Scime et al., Phys. Plasmas 7, 2157

  16. Supersonic Relative Velocity Effect on the Baryonic Acoustic Oscillation Measurements

    CERN Document Server

    Yoo, Jaiyul; Seljak, Uros

    2011-01-01

    We investigate the effect of supersonic relative velocities between baryons and dark matter, recently shown to arise generically at high redshift, on baryonic acoustic oscillation (BAO) measurements at low redshift. The amplitude of the relative velocity effect at low redshift is model-dependent, but can be parameterized by using an unknown bias. We find that if unaccounted, the relative velocity effect can shift the BAO peak position and bias estimates of the dark energy equation-of-state due to its non-smooth, out-of-phase oscillation structure around the BAO scale. Fortunately, the relative velocity effect can be easily modeled in constraining cosmological parameters without substantially inflating the error budget. We also demonstrate that the presence of the relative velocity effect gives rise to a unique signature in the galaxy bispectrum, which can be utilized to isolate this effect. Future dark energy surveys can accurately measure the relative velocity effect and subtract it from the power spectrum a...

  17. A new method of measuring the peculiar velocity power spectrum

    CERN Document Server

    Zhang, P; Juszkiewicz, R; Feldman, H A; Zhang, Pengjie; Stebbins, Albert; Juszkiewicz, Roman; Feldman, Hume

    2004-01-01

    We show that by directly correlating the cluster kinetic Sunyaev Zeldovich (KSZ) flux, the cluster peculiar velocity power spectrum can be measured to $\\sim 10%$ accuracy by future large sky coverage KSZ surveys. This method is almost free of systemics entangled in the usual velocity inversion method. The direct correlation brings extra information of density and velocity clustering. We utilize these information to construct two indicators of the Hubble constant and comoving angular distance and propose a novel method to constrain cosmology.

  18. Effects of beam velocity and density on an ion-beam pulse moving in magnetized plasmas

    CERN Document Server

    Zhao, Xiao-ying; Zhao, Yong-tao; Qi, Xin; Yang, Lei

    2016-01-01

    The wakefield and stopping power of an ion-beam pulse moving in magnetized plasmas are investigated by particle-in-cell (PIC) simulations. The effects of beam velocity and density on the wake and stopping power are discussed. In the presence of magnetic field, it is found that beside the longitudinal conversed V-shaped wakes, the strong whistler wave are observed when low-density and low-velocity pulses moving in plasmas. The corresponding stopping powers are enhanced due to the drag of these whistler waves. As beam velocities increase, the whistler waves disappear, and only are conversed V-shape wakes observed. The corresponding stopping powers are reduced compared with these in isotropic plasmas. When high-density pulses transport in the magnetized plasmas, the whistler waves are greatly inhibited for low-velocity pulses and disappear for high-velocity pulses. Additionally, the magnetic field reduces the stopping powers for all high-density cases.

  19. Interferometric measurement of the angular velocity of moving humans

    Science.gov (United States)

    Nanzer, Jeffrey A.

    2012-06-01

    This paper presents an analysis of the measurement of the angular velocity of walking humans using a millimeter-wave correlation interferometer. Measurement of the angular velocity of moving objects is a desirable function in remote sensing applications. Doppler radar sensors are able to measure the signature of moving humans based on micro-Doppler analysis; however, a person moving with little to no radial velocity produces negligible Doppler returns. Measurement of the angular movement of humans can be done with traditional radar techniques, however the process involves either continuous tracking with narrow beamwidth or angle-of-arrival estimation algorithms. A new method of measuring the angular velocity of moving objects using interferometry has recently been developed which measures the angular velocity of an object without tracking or complex processing. The frequency of the interferometer signal response is proportional to the angular velocity of the object as it passes through the interferometer beam pattern. In this paper, the theory of the interferometric measurement of angular velocity is covered and simulations of the response of a walking human are presented. Simulations are produced using a model of a walking human to show the significant features associated with the interferometer response, which may be used in classification algorithms.

  20. Influence of speckle effect on doppler velocity measurement

    Science.gov (United States)

    Zheng, Zheng; Changming, Zhao; Haiyang, Zhang; Suhui, Yang; Dehua, Zhang; Xingyuan, Zheng; Hongzhi, Yang

    2016-06-01

    In a coherent Lidar system, velocity measurement of a target is achieved by measuring Doppler frequency shift between the echo and local oscillator (LO) signals. The measurement accuracy is proportional to the spectrum width of Doppler signal. Actually, the speckle effect caused by the scattering of laser from a target will broaden the Doppler signal's spectrum and bring uncertainty to the velocity measurement. In this paper, a theoretical model is proposed to predict the broadening of Doppler spectrum with respect to different target's surface and motion parameters. The velocity measurement uncertainty caused by the broadening of spectrum is analyzed. Based on the analysis, we design a coherent Lidar system to measure the velocity of the targets with different surface roughness and transverse velocities. The experimental results are in good agreement with theoretical analysis. It is found that the target's surface roughness and transverse velocity can significantly affect the spectrum width of Doppler signal. With the increase of surface roughness and transverse velocity, the measurement accuracy becomes worse. However, the influence of surface roughness becomes weaker when the spot size of laser beam on the target is smaller.

  1. Simultaneous temperature and velocity Lagrangian measurements in turbulent thermal convection

    CERN Document Server

    Liot, O; Zonta, F; Chibbaro, S; Coudarchet, T; Gasteuil, Y; Pinton, J -F; Salort, J; Chillà, F

    2015-01-01

    We report joint Lagrangian velocity and temperature measurements in turbulent thermal convection. Measurements are performed using an improved version (extended autonomy) of the neutrally-buoyant instrumented particle that was used by to performed experiments in a parallelepipedic Rayleigh-Benard cell. The temperature signal is obtained from a RFtransmitter. Simultaneously, we determine particle's position and velocity with one camera, which grants access to the Lagrangian heat flux. Due to the extended autonomy of the present particle, we obtain well converged temperature and velocity statistics, as well as pseudo-eulerian maps of velocity and heat flux. Present experimental results have also been compared with the results obtained by a corresponding campaign of Direct Numerical Simulations and Lagrangian Tracking of massless tracers. The comparison between experimental and numerical results show the accuracy and reliability of our experimental measurements. Finally, the analysis of lagrangian velocity and t...

  2. Measurement of gas flow velocities by laser-induced gratings

    Energy Technology Data Exchange (ETDEWEB)

    Hemmerling, B.; Stampanoni-Panariello, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Kozlov, A.D.N. [General Physics Institute, Moscow (Russian Federation)

    1999-08-01

    Time resolved light scattering from laser-induced electrostrictive gratings was used for the determination of flow velocities in air at room temperature. By measuring the velocity profile across the width of a slit nozzle we demonstrated the high spatial resolution (about 200 mm) of this novel technique. (author) 3 figs., 1 ref.

  3. Electron drift velocity measurements in liquid krypton-methane mixtures

    CERN Document Server

    Folegani, M; Magri, M; Piemontese, L

    1999-01-01

    Electron drift velocities have been measured in liquid krypton, pure and mixed with methane at different concentrations (1-10% in volume) versus electric field strength, and a possible effect of methane on electron lifetime has been investigated. While no effect on lifetime could be detected, since lifetimes were in all cases longer than what measurable, a very large increase in drift velocity (up to a factor 6) has been measured.

  4. Measuring Oscillatory Velocity Fields Due to Swimming Algae

    CERN Document Server

    Guasto, Jeffrey S; Gollub, J P

    2010-01-01

    In this fluid dynamics video, we present the first time-resolved measurements of the oscillatory velocity field induced by swimming unicellular microorganisms. Confinement of the green alga C. reinhardtii in stabilized thin liquid films allows simultaneous tracking of cells and tracer particles. The measured velocity field reveals complex time-dependent flow structures, and scales inversely with distance. The instantaneous mechanical power generated by the cells is measured from the velocity fields and peaks at 15 fW. The dissipation per cycle is more than four times what steady swimming would require.

  5. Laser Doppler anemometer measurements using nonorthogonal velocity components: error estimates.

    Science.gov (United States)

    Orloff, K L; Snyder, P K

    1982-01-15

    Laser Doppler anemometers (LDAs) that are arranged to measure nonorthogonal velocity components (from which orthogonal components are computed through transformation equations) are more susceptible to calibration and sampling errors than are systems with uncoupled channels. In this paper uncertainty methods and estimation theory are used to evaluate, respectively, the systematic and statistical errors that are present when such devices are applied to the measurement of mean velocities in turbulent flows. Statistical errors are estimated for two-channel LDA data that are either correlated or uncorrelated. For uncorrelated data the directional uncertainty of the measured velocity vector is considered for applications where mean streamline patterns are desired.

  6. Measurements of neutral and ion velocity distribution functions in a Hall thruster

    Science.gov (United States)

    Svarnas, Panagiotis; Romadanov, Iavn; Diallo, Ahmed; Raitses, Yevgeny

    2015-11-01

    Hall thruster is a plasma device for space propulsion. It utilizes a cross-field discharge to generate a partially ionized weakly collisional plasma with magnetized electrons and non-magnetized ions. The ions are accelerated by the electric field to produce the thrust. There is a relatively large number of studies devoted to characterization of accelerated ions, including measurements of ion velocity distribution function using laser-induced fluorescence diagnostic. Interactions of these accelerated ions with neutral atoms in the thruster and the thruster plume is a subject of on-going studies, which require combined monitoring of ion and neutral velocity distributions. Herein, laser-induced fluorescence technique has been employed to study neutral and single-charged ion velocity distribution functions in a 200 W cylindrical Hall thruster operating with xenon propellant. An optical system is installed in the vacuum chamber enabling spatially resolved axial velocity measurements. The fluorescence signals are well separated from the plasma background emission by modulating the laser beam and using lock-in detectors. Measured velocity distribution functions of neutral atoms and ions at different operating parameters of the thruster are reported and analyzed. This work was supported by DOE contract DE-AC02-09CH11466.

  7. Unsteady Pressure and Velocity Measurements in Pumps

    Science.gov (United States)

    2006-11-01

    to reproduce the data with controlled experiments . For example, the rotor exit flow measured by means of a stationary high response probe will be...Turbomachinery by Means of High-Frequency Pressure Transducers. ASME, J. of Turbomachinery, Vol. 114, pp. 100-107. [3] Castorph, D. (1975): Messung ...Dreiß, A.; Kosyna, G. (1997): Experimental Investigations of Cavitation-States in a Radial Pump Impeller. JSME CENTENNIAL GRAND CONGRESS Proceedings of

  8. Three Component Velocity and Acceleration Measurement Using FLEET

    Science.gov (United States)

    Danehy, Paul M.; Bathel, Brett F.; Calvert, Nathan; Dogariu, Arthur; Miles, Richard P.

    2014-01-01

    The femtosecond laser electronic excitation and tagging (FLEET) method has been used to measure three components of velocity and acceleration for the first time. A jet of pure N2 issuing into atmospheric pressure air was probed by the FLEET system. The femtosecond laser was focused down to a point to create a small measurement volume in the flow. The long-lived lifetime of this fluorescence was used to measure the location of the tagged particles at different times. Simultaneous images of the flow were taken from two orthogonal views using a mirror assembly and a single intensified CCD camera, allowing two components of velocity to be measured in each view. These different velocity components were combined to determine three orthogonal velocity components. The differences between subsequent velocity components could be used to measure the acceleration. Velocity accuracy and precision were roughly estimated to be +/-4 m/s and +/-10 m/s respectively. These errors were small compared to the approx. 100 m/s velocity of the subsonic jet studied.

  9. Near-wall velocity profile measurement for nanofluids

    Science.gov (United States)

    Kanjirakat, Anoop; Sadr, Reza

    2016-01-01

    We perform near-wall velocity measurements of a SiO2-water nanofluid inside a microchannel. Nanoparticle image velocimetry measurements at three visible depths within 500 nm of the wall are conducted. We evaluate the optical properties of the nanofluid and their effect on the measurement technique. The results indicate that the small effect of the nanoparticles on the optical properties of the suspension have a negligible effect on the measurement technique. Our measurements show an increase in nanofluid velocity gradients near the walls, with no measurable slip, relative to the equivalent basefluid flow. We conjecture that particle migration induced by shear may have caused this increase. The effect of this increase in the measured near wall velocity gradient has implications on the viscosity measurement for these fluids.

  10. Near-wall velocity profile measurement for nanofluids

    Directory of Open Access Journals (Sweden)

    Anoop Kanjirakat

    2016-01-01

    Full Text Available We perform near-wall velocity measurements of a SiO2–water nanofluid inside a microchannel. Nanoparticle image velocimetry measurements at three visible depths within 500 nm of the wall are conducted. We evaluate the optical properties of the nanofluid and their effect on the measurement technique. The results indicate that the small effect of the nanoparticles on the optical properties of the suspension have a negligible effect on the measurement technique. Our measurements show an increase in nanofluid velocity gradients near the walls, with no measurable slip, relative to the equivalent basefluid flow. We conjecture that particle migration induced by shear may have caused this increase. The effect of this increase in the measured near wall velocity gradient has implications on the viscosity measurement for these fluids.

  11. Measuring surface flow velocity with smartphones: potential for citizen observatories

    Science.gov (United States)

    Weijs, Steven V.; Chen, Zichong; Brauchli, Tristan; Huwald, Hendrik

    2014-05-01

    Stream flow velocity is an important variable for discharge estimation and research on sediment dynamics. Given the influence of the latter on rating curves (stage-discharge relations), and the relative scarcity of direct streamflow measurements, surface velocity measurements can offer important information for, e.g., flood warning, hydropower, and hydrological science and engineering in general. With the growing amount of sensing and computing power in the hands of more outdoorsy individuals, and the advances in image processing techniques, there is now a tremendous potential to obtain hydrologically relevant data from motivated citizens. This is the main focus of the interdisciplinary "WeSenseIt" project, a citizen observatory of water. In this subproject, we investigate the feasibility of stream flow surface velocity measurements from movie clips taken by (smartphone-) cameras. First results from movie-clip derived velocity information will be shown and compared to reference measurements.

  12. Fluid approach to evaluate sound velocity in Yukawa systems (complex plasmas)

    CERN Document Server

    Khrapak, Sergey

    2015-01-01

    The conventional fluid description of multi-component plasma, supplemented by an appropriate equation of state for the macroparticle component, is used to evaluate the longitudinal sound velocity of Yukawa fluids. The obtained results are in very good agreement with those obtained earlier employing the quasi-localized charge approximation and molecular dynamics simulations in a rather broad parameter regime. Thus, a simple yet accurate tool to estimate the sound velocity across coupling regimes is proposed, which can be particularly helpful in estimating the dust-acoustic velocity in strongly coupled dusty (complex) plasmas. It is shown that, within the present approach, the sound velocity is completely determined by particle-particle correlations and the neutralizing medium (plasma), apart from providing screening of the Coulomb interaction, has no other effect on the sound propagation. The ratio of the actual sound velocity to its "ideal gas" (weak coupling) scale only weakly depends on the coupling strengt...

  13. Velocity measurement by coherent x-ray heterodyning

    Energy Technology Data Exchange (ETDEWEB)

    Lhermitte, Julien R. M.; Rogers, Michael C.; Manet, Sabine; Sutton, Mark

    2017-01-01

    We present a small-angle coherent x-ray scattering technique used for measuring flow velocities in slow moving materials. The technique is an extension of X-ray Photon Correlation Spectroscopy (XPCS): It involves mixing the scattering from moving tracer particles with a static reference that heterodynes the signal. This acts to elongate temporal effects caused by flow in homodyne measurements, allowing for a more robust measurement of flow properties. Using coherent x-ray heterodyning, velocities ranging from 0.1 to 10 μm/s were measured for a viscous fluid pushed through a rectangular channel. We describe experimental protocols and theory for making these Poiseuille flow profile measurements and also develop the relevant theory for using heterodyne XPCS to measure velocities in uniform and Couette flows.

  14. Velocity measurement by coherent x-ray heterodyning.

    Science.gov (United States)

    Lhermitte, Julien R M; Rogers, Michael C; Manet, Sabine; Sutton, Mark

    2017-01-01

    We present a small-angle coherent x-ray scattering technique used for measuring flow velocities in slow moving materials. The technique is an extension of X-ray Photon Correlation Spectroscopy (XPCS): It involves mixing the scattering from moving tracer particles with a static reference that heterodynes the signal. This acts to elongate temporal effects caused by flow in homodyne measurements, allowing for a more robust measurement of flow properties. Using coherent x-ray heterodyning, velocities ranging from 0.1 to 10 μm/s were measured for a viscous fluid pushed through a rectangular channel. We describe experimental protocols and theory for making these Poiseuille flow profile measurements and also develop the relevant theory for using heterodyne XPCS to measure velocities in uniform and Couette flows.

  15. Compton scattering measurements from dense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Glenzer, S H; Neumayer, P; Doeppner, T; Landen, L; Lee, R W; Wallace, R; Weber, S; Lee, H J; Kritcher, A L; Falcone, R; Regan, S P; Sawada, H; Meyerhofer, D D; Gregori, G; Fortmann, C; Schwarz, V; Redmer, R

    2007-10-02

    Compton scattering has been developed for accurate measurements of densities and temperatures in dense plasmas. One future challenge is the application of this technique to characterize compressed matter on the National Ignition Facility where hydrogen and beryllium will approach extremely dense states of matter of up to 1000 g/cc. In this regime, the density, compressibility, and capsule fuel adiabat may be directly measured from the Compton scattered spectrum of a high-energy x-ray line source. Specifically, the scattered spectra directly reflect the electron velocity distribution. In non-degenerate plasmas, the width provides an accurate measure of the electron temperatures, while in partially Fermi degenerate systems that occur in laser-compressed matter it provides the Fermi energy and hence the electron density. Both of these regimes have been accessed in experiments at the Omega laser by employing isochorically heated solid-density beryllium and moderately compressed beryllium foil targets. In the latter experiment, compressions by a factor of 3 at pressures of 40 Mbar have been measured in excellent agreement with radiation hydrodynamic modeling.

  16. Compton scattering measurements from dense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Glenzer, S H; Neumayer, P; Doeppner, T; Landen, O L; Lee, R W; Wallace, R J; Weber, S [Lawrence Livermore National Laboratory, Livermore, CA (United States); Lee, H J; Kritcher, A L; Falcone, R [University of California Berkeley, Berkeley, CA 94709 (United States); Regan, S P; Sawada, H; Meyerhofer, D D [Laboratory for Laser Energetics, Rochester, NY (United States); Gregori, G [Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Fortmann, C; Schwarz, V; Redmer, R [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany)], E-mail: glenzer1@llnl.gov

    2008-05-15

    Compton scattering techniques have been developed for accurate measurements of densities and temperatures in dense plasmas. One future challenge is the application of this technique to characterize compressed matter on the National Ignition Facility where hydrogen and beryllium will approach extremely dense states of matter of up to 1000 g/cc. In this regime, the density, compressibility, and capsule fuel adiabat may be directly measured from the Compton scattered spectrum of a high-energy x-ray line source. Specifically, the scattered spectra directly reflect the electron velocity distribution. In non-degenerate plasmas, the width provides an accurate measure of the electron temperatures, while in partially Fermi degenerate systems that occur in laser-compressed matter it provides the Fermi energy and hence the electron density. Both of these regimes have been accessed in experiments at the Omega laser by employing isochorically heated solid-density beryllium and moderately compressed beryllium foil targets. In the latter experiment, compressions by a factor of 3 at pressures of 40 Mbar have been measured in excellent agreement with radiation hydrodynamic modeling.

  17. Direct Ejecta Velocity Measurements of Tycho's Supernova Remnant

    CERN Document Server

    Sato, Toshiki

    2016-01-01

    We present the first direct ejecta velocity measurements of Tycho's supernova remnant (SNR). Chandra's high angular resolution images reveal a patchy structure of radial velocities in the ejecta that can be separated into distinct redshifted, blueshifted, and low velocity ejecta clumps or blobs. The typical velocities of the redshifted and blueshifted blobs are <~ 7,800 km/s and <~ 5,000 km/s, respectively. The highest velocity blobs are located near the center, while the low velocity ones appear near the edge as expected for a generally spherical expansion. Systematic uncertainty on the velocity measurements from gain calibration was assessed by carrying out joint fits of individual blobs with both the ACIS-I and ACIS-S detectors. We identified an annular region (~3.3'-3.5'), where the surface brightness in the Si, S, and Fe K lines reaches a peak while the line width reaches a minimum value. These minimum line widths correspond to ion temperatures of ~1 MeV for each of the three species, in excellent ...

  18. Near-wall velocity measurements by Particle-Shadow-Tracking

    CERN Document Server

    Lancien, Pierre; Métivier, François; 10.1007/s00348-007-0260-z

    2009-01-01

    We report a new method to measure the velocity of a fluid in the vicinity of a wall. The method, that we call Particle-Shadow Tracking (PST), simply consists in seeding the fluid with a small number of fine tracer particles of density close to that of the fluid. The position of each particle and of its shadow on the wall are then tracked simultaneously, allowing one to accurately determine the distance separating tracers from the wall and therefore to extract the velocity field. We present an application of the method to the determination of the velocity profile inside a laminar density current flowing along an inclined plane.

  19. Measurement of velocity field in parametrically excited solitary waves

    CERN Document Server

    Gordillo, Leonardo

    2014-01-01

    Paramerically excited solitary waves emerge as localized structures in high-aspect-ratio free surfaces subject to vertical vibrations. Herein, we provide the first experimental characterization of the hydrodynamics of thess waves using Particle Image Velocimetry. We show that the underlying velocity field of parametrically excited solitary waves is mainly composed by an oscillatory velocity field. Our results confirm the accuracy of Hamiltonian models with added dissipation in describing this field. Remarkably, our measurements also uncover the onset of a streaming velocity field which is shown to be as important as other crucial nonlinear terms in the current theory. The observed streaming pattern is particularly interesting due to the presence of oscillatory meniscii.

  20. Near-wall velocity profile measurement for nanofluids

    OpenAIRE

    Anoop Kanjirakat; Reza Sadr

    2016-01-01

    We perform near-wall velocity measurements of a SiO2–water nanofluid inside a microchannel. Nanoparticle image velocimetry measurements at three visible depths within 500 nm of the wall are conducted. We evaluate the optical properties of the nanofluid and their effect on the measurement technique. The results indicate that the small effect of the nanoparticles on the optical properties of the suspension have a negligible effect on the measurement technique. Our measurements show an increase ...

  1. Digital technique for the simultaneous measurement of velocity and temperature.

    Science.gov (United States)

    Keffer, J F; Budny, R S; Kawall, J G

    1978-09-01

    A computer-oriented, hot-wire anemometer technique for the simultaneous measurement of velocity and temperature in heated turbulent flows is described. This technique involves conversion of analogue anemometer voltage signals into digital forms and processing of these latter on a digital computer, in accordance with the anemometer response equations, to obtain instantaneous temperature and velocity. The technique was tested with a heated plane jet and found to be satisfactory.

  2. Measurements of electron drift velocity in pure isobutane

    Energy Technology Data Exchange (ETDEWEB)

    Vivaldini, Tulio C.; Lima, Iara B.; Goncalves, Josemary A.C.; Botelho, Suzana; Tobias, Carmen C.B., E-mail: ccbueno@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Ridenti, Marco A.; Pascholati, Paulo R. [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Fisica. Lab. do Acelerador Linear; Fonte, Paulo; Mangiarotti, Alessio [Universidade de Coimbra (Portugal). Dept de Fisica. Lab. de Instrumentacao e Fisica Experimental de Particulas

    2009-07-01

    In this work we report on preliminary results related to the dependence of the electron drift velocity for pure isobutane as a function of reduced electric field (E/N) in the range from 100 Td up to 216 Td. The measurements of electron drift velocity were based on the Pulsed Townsend technique. In order to validate the technique and analyzing non-uniformity effects, results for nitrogen are also presented and compared with a numerical simulation of the Bolsig+ code. (author)

  3. Temperature dynamics and velocity scaling laws for interchange driven, warm ion plasma filaments

    DEFF Research Database (Denmark)

    Olsen, Jeppe Miki Busk; Madsen, Jens; Nielsen, Anders Henry

    2016-01-01

    The influence of electron and ion temperature dynamics on the radial convection of isolated structures in magnetically confined plasmas is investigated by means of numerical simulations. It is demonstrated that the maximum radial velocity of these plasma blobs roughly follows the inertial velocit...

  4. Velocity Measurements of Turbulent Wake Flow Over a Circular Cylinder

    Science.gov (United States)

    Shih, Chang-Lung; Chen, Wei-Cheng; Chang, Keh-Chin; Wang, Muh-Rong

    2016-06-01

    There are two general concerns in the velocity measurements of turbulence. One is the temporal characteristics which governs the turbulent mixing process. Turbulence is rotational and is characterized by high levels of fluctuating vorticity. In order to obtain the information of vorticity dynamics, the spatial characteristics is the other concern. These varying needs can be satisfied by using a variety of diagnostic techniques such as invasive physical probes and non-invasive optical instruments. Probe techniques for the turbulent measurements are inherently simple and less expensive than optical methods. However, the presence of a physical probe may alter the flow field, and velocity measurements usually become questionable when probing recirculation zones. The non-invasive optical methods are mostly made of the foreign particles (or seeding) instead of the fluid flow and are, thus, of indirect method. The difference between the velocities of fluid and foreign particles is always an issue to be discussed particularly in the measurements of complicated turbulent flows. Velocity measurements of the turbulent wake flow over a circular cylinder will be made by using two invasive instruments, namely, a cross-type hot-wire anemometry (HWA) and a split-fiber hot-film anemometry (HFA), and a non-invasive optical instrument, namely, particle image velocimetry (PIV) in this study. Comparison results show that all three employed diagnostic techniques yield similar measurements in the mean velocity while somewhat deviated results in the root-mean-squared velocity, particularly for the PIV measurements. It is demonstrated that HFA possesses more capability than HWA in the flow measurements of wake flow. Wake width is determined in terms of either the flatness factor or shear-induced vorticity. It is demonstrated that flow data obtained with the three employed diagnostic techniques are capable of yielding accurate determination of wake width.

  5. Using embedded fibers to measure explosive detonation velocities

    Energy Technology Data Exchange (ETDEWEB)

    Podsednik, Jason W.; Parks, Shawn Michael; Navarro, Rudolfo J.

    2012-07-01

    Single-mode fibers were cleverly embedded into fixtures holding nitromethane, and used in conjunction with a photonic Doppler velocimeter (PDV) to measure the associated detonation velocity. These measurements have aided us in our understanding of energetic materials and enhanced our diagnostic capabilities.

  6. Measurement of Critical Impact Velocity of Copper in Tension

    Institute of Scientific and Technical Information of China (English)

    HU Jin-Wei; JIN Yang-Hui; CHEN Da-Nian; WU Shan-Xing; WANG Huan-Ran; MA Dong-Fang

    2008-01-01

    @@ Critical impact velocity (CIV) of oxygen-free high-conductivity (OFHC) copper is experimentally measured with a novel facility in a gas gun system.The results are compared with the theoretical predictions using the typical constitutive relations,and the measured CIV value is much lower than the predictions.

  7. Estimating Radar Velocity using Direction of Arrival Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Horndt, Volker [General Atomics Aeronautical Systems, Inc., San Diego, CA (United States); Bickel, Douglas Lloyd [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Naething, Richard M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-09-01

    Direction of Arrival (DOA) measurements, as with a monopulse antenna, can be compared against Doppler measurements in a Synthetic Aperture Radar ( SAR ) image to determine an aircraft's forward velocity as well as its crab angle, to assist the aircraft's navigation as well as improving high - performance SAR image formation and spatial calibration.

  8. Normalized velocity profiles of field-measured turbidity currents

    Science.gov (United States)

    Xu, Jingping

    2010-01-01

    Multiple turbidity currents were recorded in two submarine canyons with maximum speed as high as 280 cm/s. For each individual turbidity current measured at a fixed station, its depth-averaged velocity typically decreased over time while its thickness increased. Some turbidity currents gained in speed as they traveled downcanyon, suggesting a possible self-accelerating process. The measured velocity profiles, first in this high resolution, allowed normalizations with various schemes. Empirical functions, obtained from laboratory experiments whose spatial and time scales are two to three orders of magnitude smaller, were found to represent the field data fairly well. The best similarity collapse of the velocity profiles was achieved when the streamwise velocity and the elevation were normalized respectively by the depth-averaged velocity and the turbidity current thickness. This normalization scheme can be generalized to an empirical function Y = exp(–αXβ) for the jet region above the velocity maximum. Confirming theoretical arguments and laboratory results of other studies, the field turbidity currents are Froude-supercritical.

  9. Laboratory Measurements of Velocity and Attenuation in Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Zimmer, M A; Berge, P A; Bonner, B P; Prasad, M

    2004-06-08

    Laboratory measurements are required to establish relationships between the physical properties of unconsolidated sediments and P- and S-wave propagation through them. Previous work has either focused on measurements of compressional wave properties at depths greater than 500 m for oil industry applications or on measurements of dynamic shear properties at pressures corresponding to depths of less than 50 m for geotechnical applications. Therefore, the effects of lithology, fluid saturation, and compaction on impedance and P- and S-wave velocities of shallow soils are largely unknown. We describe two state-of-the-art laboratory experiments. One setup allows us to measure ultrasonic P-wave velocities at very low pressures in unconsolidated sediments (up to 0.1 MPa). The other experiment allows P- and S-wave velocity measurements at low to medium pressures (up to 20 MPa). We summarize the main velocity and attenuation results on sands and sand - clay mixtures under partially saturated and fully saturated conditions in two ranges of pressures (0 - 0.1 MPa and 0.1 - 20 MPa) representative of the top few meters and the top 1 km, respectively. Under hydrostatic pressures of 0.1 to 20 MPa, our measurements demonstrate a P- and S-wave velocity-dependence in dry sands around a fourth root (0.23 -0.26) with the pressure dependence for S-waves being slightly lower. The P- velocity-dependence in wet sands lies around 0.4. The Vp-Vs and the Qp-Qs ratios together can be useful tools to distinguish between different lithologies and between pressure and saturation effects. These experimental velocities at the frequency of measurement (200 kHz) are slightly higher that Gassmann's static result. For low pressures under uniaxial stress, Vp and Vs were a few hundred meters per second with velocities showing a strong dependence on packing, clay content, and microstructure. We provide a typical shallow soil scenario in a clean sand environment and reconstruct the velocity profile

  10. Signal processing method for shear wave velocity measurement

    Institute of Scientific and Technical Information of China (English)

    Hou Xingmin; Qu Shuying; Shi Xiangdong

    2007-01-01

    Soil shear wave velocity (SWV) is an important parameter in geotechnical engineering. To measure the soil SWV, three methods are generally used in China, including the single-hole method, cross-hole method and the surface-wave technique. An optimized approach based on a correlation function for single-hole SWV measurement is presented in this paper. In this approach, inherent inconsistencies of the artificial methods such as negative velocities, and too-large and too-small velocities, are eliminated from the single-hole method, and the efficiency of data processing is improved. In addition, verification using the cross-hole method of upper measuring points shows that the proposed optimized approach yields high precision in signal processing.

  11. Sound field separation with sound pressure and particle velocity measurements

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn; Leclère, Quentin

    2012-01-01

    separation techniques make it possible to distinguish between outgoing and incoming waves from the two sides, and thus NAH can be applied. In this paper, a separation method based on the measurement of the particle velocity in two layers and another method based on the measurement of the pressure...... and the velocity in a single layer are proposed. The two methods use an equivalent source formulation with separate transfer matrices for the outgoing and incoming waves, so that the sound from the two sides of the array can be modeled independently. A weighting scheme is proposed to account for the distance...... pressure-velocity method, although it requires an additional measurement surface. On the whole, the separation methods can be useful when the disturbance of the incoming field is significant. Otherwise the direct reconstruction is more accurate and straightforward. © 2012 Acoustical Society of America....

  12. Velocity of detonation (VOD measurement techniques - practical approach

    Directory of Open Access Journals (Sweden)

    Aruna Dhanraj Tete

    2013-06-01

    Full Text Available Velocity of Detonation (VOD is an important measure characteristics parameter of explosive material. The performance of explosive invariably depends on the velocity of detonation. The power/ strength of explosive to cause fragmentation of the solid structure determine the efficiency of the Blast performed. It is an established fact that measuring velocity of detonation gives a good indication of the strength and hence the performance of the explosive. In this survey various VOD measurement techniques such as electric, nonelectric and fibre optic have been discussed. To aid the discussion some commercially available VOD meter comparison are also presented. After review of the existing units available commercially and study of their respective merits and demerits, feature of an ideal system is proposed. 

  13. Sensors for Using Times of Flight to Measure Flow Velocities

    Science.gov (United States)

    Fralick, Gutave; Wrbanek, John D.; Hwang, Danny; Turso, James

    2006-01-01

    Thin-film sensors for measuring flow velocities in terms of times of flight are undergoing development. These sensors are very small and can be mounted flush with surfaces of airfoils, ducts, and other objects along which one might need to measure flows. Alternatively or in addition, these sensors can be mounted on small struts protruding from such surfaces for acquiring velocity measurements at various distances from the surfaces for the purpose of obtaining boundary-layer flow-velocity profiles. These sensors are related to, but not the same as, hot-wire anemometers. Each sensor includes a thin-film, electrically conductive loop, along which an electric current is made to flow to heat the loop to a temperature above that of the surrounding fluid. Instantaneous voltage fluctuations in segments of the loop are measured by means of electrical taps placed at intervals along the loop. These voltage fluctuations are caused by local fluctuations in electrical resistance that are, in turn, caused by local temperature fluctuations that are, in turn, caused by fluctuations in flow-induced cooling and, hence, in flow velocity. The differential voltage as a function of time, measured at each pair of taps, is subjected to cross-correlation processing with the corresponding quantities measured at other pairs of taps at different locations on the loop. The cross-correlations yield the times taken by elements of fluid to travel between the pairs of taps. Then the component of velocity along the line between any two pairs of taps is calculated simply as the distance between the pairs of taps divided by the travel time. Unlike in the case of hot-wire anemometers, there is no need to obtain calibration data on voltage fluctuations versus velocity fluctuations because, at least in principle, the correlation times are independent of the calibration data.

  14. Detailed Measurement of Horizontal Groundwater Velocities Without a Borehole

    Science.gov (United States)

    Bakker, M.; Calje, R.; Van der Made, K. J.; Schaars, F.

    2014-12-01

    A new methodology has been developed to measure horizontal groundwater velocities in unconsolidated aquifers. Groundwater velocities are measured with a heat tracer experiment. Temperature is measured along fiber optic cables using a Distributed Temperature Sensing (DTS) system. Fiber optic cables and a separate heating cable are pushed into the ground to depths of tens of meters. The groundwater is heated with the heating cable and the response is measured along several nearby fiber optic cables. The measured temperature responses are used to estimate the distribution of the magnitude and direction of the horizontal groundwater velocity over the entire depth of the cables. The methodology has been applied in a phreatic aquifer in the dune area along the Dutch coast. Significant variations of groundwater velocities with depth were observed even though the dune sand is relatively homogeneous. Major advantages of the new methodology are that the fiber optic cables are in direct contact with the groundwater and that the cables and installation are relatively cheap. No expensive boreholes are needed and consequently measurements are not affected by movement and mixing of water inside a borehole.

  15. Optic-microwave mixing velocimeter for superhigh velocity measurement

    Energy Technology Data Exchange (ETDEWEB)

    Weng Jidong; Wang Xiang; Tao Tianjiong; Liu Cangli; Tan Hua [Laboratory for Shock Waves and Detonation Physics Research, Institute of Fluid Physics, P.O. Box 919-102, Mianyang, Sichuan 621900 (China)

    2011-12-15

    The phenomenon that a light beam reflected off a moving object experiences a Doppler shift in its frequency underlies practical interferometric techniques for remote velocity measurements, such as velocity interferometer system for any reflector (VISAR), displacement interferometer system for any reflector (DISAR), and photonic Doppler velocimetry (PDV). While VISAR velocimeters are often bewildered by the fringe loss upon high-acceleration dynamic process diagnosis, the optic-fiber velocimeters such as DISAR and PDV, on the other hand, are puzzled by high velocity measurement over 10 km/s, due to the demand for the high bandwidth digitizer. Here, we describe a new optic-microwave mixing velocimeter (OMV) for super-high velocity measurements. By using currently available commercial microwave products, we have constructed a simple, compact, and reliable OMV device, and have successfully obtained, with a digitizer of bandwidth 6 GH only, the precise velocity history of an aluminum flyer plate being accelerated up to 11.2 km/s in a three stage gas-gun experiment.

  16. Measuring of the maximum measurable velocity for dual-frequency laser interferometer

    Institute of Scientific and Technical Information of China (English)

    Zhiping Zhang; Zhaogu Cheng; Zhaoyu Qin; Jianqiang Zhu

    2007-01-01

    There is an increasing demand on the measurable velocity of laser interferometer in manufacturing technologies. The maximum measurable velocity is limited by frequency difference of laser source, optical configuration, and electronics bandwidth. An experimental setup based on free falling movement has been demonstrated to measure the maximum easurable velocity for interferometers. Measurement results show that the maximum measurable velocity is less than its theoretical value. Moreover, the effect of kinds of factors upon the measurement results is analyzed, and the results can offer a reference for industrial applications.

  17. Velocity and rotation measurements in acoustically levitated droplets

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Abhishek [University of Central Florida, Orlando, FL 32816 (United States); Basu, Saptarshi [Indian Institute of Science, Bangalore 560012 (India); Kumar, Ranganathan, E-mail: ranganathan.kumar@ucf.edu [University of Central Florida, Orlando, FL 32816 (United States)

    2012-10-01

    The velocity scale inside an acoustically levitated droplet depends on the levitator and liquid properties. Using Particle Imaging Velocimetry (PIV), detailed velocity measurements have been made in a levitated droplet of different diameters and viscosity. The maximum velocity and rotation are normalized using frequency and amplitude of acoustic levitator, and droplet viscosity. The non-dimensional data are fitted for micrometer- and millimeter-sized droplets levitated in different levitators for different viscosity fluids. It is also shown that the rotational speed of nanosilica droplets at an advanced stage of vaporization compares well with that predicted by exponentially fitted parameters. -- Highlights: ► Demonstrates the importance of rotation in a levitated droplet that leads to controlled morphology. ► Provides detailed measurements of Particle Image Velocimetry inside levitated droplets. ► Shows variation of vortex strength with the droplet diameter and viscosity of the liquid.

  18. Measure Fly off Velocity of the Ion by Time of Flight Method

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Primary detector is the charge collector, i.e. Faraday cup to measure fly off velocity of the ion by time of flight method. It is simple and applied set up,When it irradiates on the solid plane targets that laser beam of high power is focused, a thin layer of the high temperature and tight density plasma is produced on the target surface. As this plasma expands in the vacuum, it has of its energy in from of directed kinetic energy of the ion. The ion current signals observed by the charge collector at a large distance will correspond to high

  19. Wind Velocity Decreasing Effects of Windbreak Fence for Snowfall Measurement

    Directory of Open Access Journals (Sweden)

    Ki-Pyo You

    2014-01-01

    Full Text Available Meteorological observatories use measuring boards on even ground in open areas to measure the amount of snowfall. In order to measure the amount of snowfall, areas unaffected by wind should be found. This study tried to determine the internal wind flow inside a windbreak fence, identifying an area unaffected by wind in order to measure the snowfall. We performed a computational fluid dynamics analysis and wind tunnel test, conducted field measurements of the type and height of the windbreak fence, and analyzed the wind flow inside the fence. The results showed that a double windbreak fence was better than a single windbreak fence for decreasing wind velocity. The double fence (width 4 m, height 60 cm, and fixed on the bottom has the greatest wind velocity decrease rate at the central part of octagonal windbreak.

  20. Langmuir-Probe Measurements in Flowing-Afterglow Plasmas

    Science.gov (United States)

    Johnsen, R.; Shunko, E. V.; Gougousi, T.; Golde, M. F.

    1994-01-01

    The validity of the orbital-motion theory for cylindrical Langmuir probes immersed in flowing- afterglow plasmas is investigated experimentally. It is found that the probe currents scale linearly with probe area only for electron-collecting but not for ion-collecting probes. In general, no agreement is found between the ion and electron densities derived from the probe currents. Measurements in recombining plasmas support the conclusion that only the electron densities derived from probe measurements can be trusted to be of acceptable accuracy. This paper also includes a brief derivation of the orbital-motion theory, a discussion of perturbations of the plasma by the probe current, and the interpretation of plasma velocities obtained from probe measurements.

  1. Micro-particle image velocimetry for velocity profile measurements of micro blood flows.

    Science.gov (United States)

    Pitts, Katie L; Fenech, Marianne

    2013-04-25

    Micro-particle image velocimetry (μPIV) is used to visualize paired images of micro particles seeded in blood flows. The images are cross-correlated to give an accurate velocity profile. A protocol is presented for μPIV measurements of blood flows in microchannels. At the scale of the microcirculation, blood cannot be considered a homogeneous fluid, as it is a suspension of flexible particles suspended in plasma, a Newtonian fluid. Shear rate, maximum velocity, velocity profile shape, and flow rate can be derived from these measurements. Several key parameters such as focal depth, particle concentration, and system compliance, are presented in order to ensure accurate, useful data along with examples and representative results for various hematocrits and flow conditions.

  2. Intraglottal velocity and pressure measurements in a hemilarynx model.

    Science.gov (United States)

    Oren, Liran; Gutmark, Ephraim; Khosla, Sid

    2015-02-01

    Determining the mechanisms of self-sustained oscillation of the vocal folds requires characterization of the pressures produced by intraglottal aerodynamics. Because most of the intraglottal aerodynamic forces cannot be measured in a tissue model of the larynx, current understanding of vocal fold vibration mechanism is derived from mechanical, analytical, and computational models. Previous studies have computed intraglottal pressures from measured intraglottal velocity fields and intraglottal geometry; however, this technique for determining pressures is not yet validated. In this study, intraglottal pressure measurements taken in a hemilarynx model are compared with pressure values that are computed from simultaneous velocity measurements. The results showed that significant negative pressure formed near the superior aspect of the folds during closing, which agrees with previous measurements in other hemilarynx models. Intraglottal velocity measurements show that the flow near the superior aspect separates from the glottal wall during closing and may develop into a vortex, which further augments the magnitude of negative pressure. Intraglottal pressure distributions, computed by solving the pressure Poisson equation, showed good agreement with pressure measurements. The match between the pressure computations and its measurements validates the current technique, which was previously used to estimate intraglottal pressure distribution in a full larynx model.

  3. Precise Measurement of Drift Velocities in Active-Target Detectors

    Science.gov (United States)

    Jensen, Louis

    2016-09-01

    Nuclear experiments with radioactive beams are needed to improve our understanding of nuclei structure far from stability. Radioactive beams typically have low beam rates, but active-target detectors can compensate for these low beam rates. In active-target detectors that are also Time-Projection Chambers (TPC), ionized electrons drift through an electric fieldto a detection device to imagethe trajectory of charged-particle ionization tracks within the chamber's gas volume. The measurement of the ionized electrons' drift velocity is crucial for the accurate imaging of these tracks. In order to measure this drift velocity, we will use a UV laser and photo-sensitive foil in a the ND-Cubedetector we are developing, periodically releasingelectrons from the foil at a known timesand a known distance from the electron detector, thereby precisely measuring the drift velocity in situ. We have surveyed several materials to find a material that will work well with typical solid-state UV lasers on the market. We plan to determine the best material and thickness of the foil to maximize the number of photoelectrons. The precision that will be afforded by this measurement of the drift velocity will allow us to eliminate a source of systematic uncertainty.

  4. Improved Measurement of Ejection Velocities From Craters Formed in Sand

    Science.gov (United States)

    Cintala, Mark J.; Byers, Terry; Cardenas, Francisco; Montes, Roland; Potter, Elliot E.

    2014-01-01

    A typical impact crater is formed by two major processes: compression of the target (essentially equivalent to a footprint in soil) and ejection of material. The Ejection-Velocity Measurement System (EVMS) in the Experimental Impact Laboratory has been used to study ejection velocities from impact craters formed in sand since the late 1990s. The original system used an early-generation Charge-Coupled Device (CCD) camera; custom-written software; and a complex, multicomponent optical system to direct laser light for illumination. Unfortunately, the electronic equipment was overtaken by age, and the software became obsolete in light of improved computer hardware.

  5. Velocity statistics in holographic fluids: magnetized quark-gluon plasma and superfluid flow

    Energy Technology Data Exchange (ETDEWEB)

    Areán, Daniel [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, D-80805, Munich (Germany); Zayas, Leopoldo A. Pando [The Abdus Salam International Centre for Theoretical Physics,Strada Costiera 11, 34014 Trieste (Italy); Michigan Center for Theoretical Physics, Department of Physics, University of Michigan,450 Church Street, Ann Arbor, MI 48109 (United States); Patiño, Leonardo; Villasante, Mario [Departamento de Física, Facultad de Ciencias, Universidad Nacional Autónoma de México,A.P. 70-542, México D.F. 04510 (Mexico)

    2016-10-28

    We study the velocity statistics distribution of an external heavy particle in holographic fluids. We argue that when the dual supergravity background has a finite temperature horizon the velocity statistics goes generically as 1/v, compatible with the jet-quenching intuition from the quark-gluon plasma. A careful analysis of the behavior of the classical string whose apparent world sheet horizon deviates from the background horizon reveals that other regimes are possible. We numerically discuss two cases: the magnetized quark-gluon plasma and a model of superfluid flow. We explore a range of parameters in these top-down supergravity solutions including, respectively, the magnetic field and the superfluid velocity. We determine that the velocity statistics goes largely as 1/v, however, as we leave the non-relativistic regime we observe some deviations.

  6. An inexpensive instrument for measuring wave exposure and water velocity

    Science.gov (United States)

    Figurski, J.D.; Malone, D.; Lacy, J.R.; Denny, M.

    2011-01-01

    Ocean waves drive a wide variety of nearshore physical processes, structuring entire ecosystems through their direct and indirect effects on the settlement, behavior, and survivorship of marine organisms. However, wave exposure remains difficult and expensive to measure. Here, we report on an inexpensive and easily constructed instrument for measuring wave-induced water velocities. The underwater relative swell kinetics instrument (URSKI) is a subsurface float tethered by a short (<1 m) line to the seafloor. Contained within the float is an accelerometer that records the tilt of the float in response to passing waves. During two field trials totaling 358 h, we confirmed the accuracy and precision of URSKI measurements through comparison to velocities measured by an in situ acoustic Doppler velocimeter and those predicted by a standard swell model, and we evaluated how the dimensions of the devices, its buoyancy, and sampling frequency can be modified for use in a variety of environments.

  7. Mean velocity, turbulence intensity and turbulence convection velocity measurements for a convergent nozzle in a free jet wind tunnel

    Science.gov (United States)

    Mccolgan, C. J.; Larson, R. S.

    1978-01-01

    The effect of light on the mean flow and turbulence properties of a 0.056 m circular jet were determined in a free jet wind tunnel. The nozzle exit velocity was 122 m/sec, and the wind tunnel velocity was set at 0, 12, 37, and 61 m/sec. Measurements of flow properties including mean velocity, turbulence intensity and spectra, and eddy convection velocity were carried out using two linearized hot wire anemometers. Normalization factors were determined for the mean velocity and turbulence convection velocity.

  8. Particle Velocity Measurement for Spherical Wave in Solid

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xue-feng; WANG Zhan-jiang; LIN Jun-de; SHEN Jun-yi

    2006-01-01

    An experimental technique for research on spherical divergent wave propagation in a solid has been developed,in which the source of generating spherical wave is a center initiating explosive charge designed in a mini-spherical shape with yield equivalent to 0.125 g and 0. 486 g TNT and a set of circular electromagnetic particle velocity gages is used to record the particle velocity histories. By using the circular electromagnetic particle velocity gages, the signal outputs not only are unattenuated due to the geometrical divergence, but also represent the average of the measured dynamic states of the medium over a circle on the wavefront. The distinctive features of this technique are very useful for the study of spherical divergent wave propagation in a solid, especially in an inhomogeneous solid, and the corresponding material dynamics.Many experimental measurements were conducted in polymethylmethacrylate (PMMA) and granite by means of the technique, and the reproducibility of tests was shown to be good. The measurement technique of the circular electromagnetic particle velocity gages is also suitable to the case of cylindrical wave.

  9. High resolved velocity measurements using Laser Cantilever Anemometry

    Science.gov (United States)

    Puczylowski, Jaroslaw; Hölling, Michael; Peinke, Joachim

    2016-11-01

    We have developed a new anemometer, namely the 2d-LCA (2d-Laser-Cantilever-Anemometer), that is capable of performing high resolved velocity measurements in fluids. The anemometer uses a micostructured cantilever made of silicon as a sensing element. The specific shape and the small dimensions (about 150µm) of the cantilever allow for precise measurements of two velocity component at a temporal resolution of about 150kHz. The angular acceptance range is 180° in total. The 2d-LCA is a simple to use alternative to x-wires and can be used in many areas of operation including measurements in liquids or in particle-laden flows. Unlike hot-wires, the resolution power of the 2d-LCA does not decrease with increasing flow velocity, making it particularly suitable for measurements in high-speed flows. In the recent past new cantilever designs were implemented with the goal to further improve the angular resolution and increase the stability. In addition, we have designed more robust cantilevers for measurements in rough environments such as offshore areas. Successful comparative measurements with hot-wires have been carried out in order to assess the performance of the 2d-LCA.

  10. The characteristics of the ion temperature and toroidal rotation velocity in the KSTAR plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Won Ha; Lee, Hyung Ho; Oh, Seung Tae [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    Charge exchange spectroscopy (CES) is one of the important diagnostics on the Korea Superconducting Tokamak Advanced Research (KSTAR) to get ion temperature and toroidal rotation velocity. We describe the current status and the improvements made over the last two years. The current system upgraded from a Czerny-Turner spectrometer consists of two spectroscopic systems looking at the KSTAR neutral beam which is modulated 5 Hz for special period. One system has a DS spectrometer (f/2.8) lent from NIFS with pitch-controlled double slit fiber bundle with back- illuminated CCD and the other system has Kspectrometer (F/2.0) made by NFRI with intensified CCD. The K-spectrometer has a grating number of 2400 g/mm, focal length of 200 mm. The upgrade of two high throughput spectrometers enables to improve the time resolution from 200 msec to around 10 msec. This article focuses on improved edge spatial interval from increasing of plasma viewing channels to 5 mm and enhanced time resolution from a high throughput spectrometer with back-illuminated CCD. The upgrade has allowed to measure pedestal ion temperature and toroidal rotation velocity profiles in KSTAR H-mode

  11. Dwarf Galaxies in the Coma Cluster: I. Velocity Dispersion Measurements

    CERN Document Server

    Kourkchi, E; Carter, D; Karick, A M; Mármol-Queraltó, E; Chiboucas, K; Tully, R B; Mobasher, B; Guzmán, R; Matković, A; Gruel, N

    2011-01-01

    We present the study of a large sample of early-type dwarf galaxies in the Coma cluster observed with DEIMOS on the Keck II to determine their internal velocity dispersion. We focus on a subsample of 41 member dwarf elliptical galaxies for which the velocity dispersion can be reliably measured, 26 of which were studied for the first time. The magnitude range of our sample is $-21measurement of the velocity dispersion and their error estimates. The measurements were performed using {\\it pPXF (penalised PiXel Fitting)} and using the Calcium triplet absorption lines. We use Monte Carlo bootstrapping to study various sources of uncertainty in our measurements, namely statistical uncertainty, template mismatch and other systematics. We find that the main source of uncertainty is the template mismatch effect which is reduced by using templates with a range of spectral types. Combining our measurements with those from the literature, we study the Faber-Jackson...

  12. Research on the photoelectric measuring method of warhead fragment velocity

    Science.gov (United States)

    Liu, Ji; Yu, Lixia; Zhang, Bin; Liu, Xiaoyan

    2016-09-01

    The velocity of warhead fragment is the key criteria to determine its mutilation efficiency. But owing to the small size, larger quantity, irregular shape, high speed, arbitrary direction, large dispersion of warhead fragment and adverse environment, the test of fragment velocity parameter is very difficult. The paper designed an optoelectronic system to measure the average velocity of warhead fragments accurately. The apparatus included two parallel laser screens spaced apart at a known fixed distance for providing time measurement between start and stop signals. The large effective screen area was composed of laser source, retro-reflector and large area photo-diode. Whenever a moving fragment interrupted two optical screens, the system would generate a target signal. Due to partial obscuration of the incident energy and the poor test condition of the explosion, fragment target signal is easily disturbed. Therefore, fragments signal processing technology has become a key technology of the system. The noise of signal was reduced by employing wavelet decomposition and reconstruction. The time of fragment passing though the target was obtained by adopting peak detection algorithm. Based on the method of search peak in different width scale and waveform trend by using optima wavelet, the problem of rolling waveform was solved. Lots of fragments experiments of the different types of the warheads were conducted. Experimental results show that: warhead fragments capture rate of system is better than 98%, which can give velocity of each fragment in the density of less than 20 pieces per m2.

  13. Investigation of gravity waves using horizontally resolved radial velocity measurements

    Directory of Open Access Journals (Sweden)

    G. Stober

    2013-06-01

    Full Text Available The Middle Atmosphere Alomar Radar System (MAARSY on the island Andøya in Northern Norway (69.3° N, 16.0° E observes polar mesospheric summer echoes (PMSE. These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of a pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g. horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  14. Velocity measurements in jets with application to noise source modeling

    Science.gov (United States)

    Morris, Philip J.; Zaman, K. B. M. Q.

    2010-02-01

    This paper describes an experimental investigation of the statistical properties of turbulent velocity fluctuations in an axisymmetric jet. The focus is on those properties that are relevant to the prediction of noise. Measurements are performed using two single hot-wire anemometers as well as a two-component anemometer. Two-point cross correlations of the axial velocity fluctuations and of the fluctuations in the square of the axial velocity fluctuations are presented. Several reference locations in the jet are used including points on the jet lip and centerline. The scales of the turbulence and the convection velocity are determined, both in an overall sense as well as a function of frequency. The relationship between the second and fourth order correlations is developed and compared with the experimental data. The implications of the use of dimensional as well as non-dimensional correlations are considered. Finally, a comparison is made between the length scales deduced from the flow measurements and a RANS CFD calculation.

  15. Investigation of gravity waves using horizontally resolved radial velocity measurements

    Science.gov (United States)

    Stober, G.; Sommer, S.; Rapp, M.; Latteck, R.

    2013-10-01

    The Middle Atmosphere Alomar Radar System (MAARSY) on the island of Andøya in Northern Norway (69.3° N, 16.0° E) observes polar mesospheric summer echoes (PMSE). These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first-order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g., horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  16. Investigation of gravity waves using horizontally resolved radial velocity measurements

    Directory of Open Access Journals (Sweden)

    G. Stober

    2013-10-01

    Full Text Available The Middle Atmosphere Alomar Radar System (MAARSY on the island of Andøya in Northern Norway (69.3° N, 16.0° E observes polar mesospheric summer echoes (PMSE. These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first-order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g., horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  17. Flow velocity measurement with the nonlinear acoustic wave scattering

    Science.gov (United States)

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    2015-10-01

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  18. Flow velocity measurement with the nonlinear acoustic wave scattering

    Energy Technology Data Exchange (ETDEWEB)

    Didenkulov, Igor, E-mail: din@appl.sci-nnov.ru [Institute of Applied Physics, 46 Ulyanov str., Nizhny Novgorod, 603950 (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 23 Gagarin ave., Nizhny Novgorod, 603950 (Russian Federation); Pronchatov-Rubtsov, Nikolay, E-mail: nikvas@rf.unn.ru [Lobachevsky State University of Nizhny Novgorod, 23 Gagarin ave., Nizhny Novgorod, 603950 (Russian Federation)

    2015-10-28

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  19. Measurement uncertainty budget of an interferometric flow velocity sensor

    Science.gov (United States)

    Bermuske, Mike; Büttner, Lars; Czarske, Jürgen

    2017-06-01

    Flow rate measurements are a common topic for process monitoring in chemical engineering and food industry. To achieve the requested low uncertainties of 0:1% for flow rate measurements, a precise measurement of the shear layers of such flows is necessary. The Laser Doppler Velocimeter (LDV) is an established method for measuring local flow velocities. For exact estimation of the flow rate, the flow profile in the shear layer is of importance. For standard LDV the axial resolution and therefore the number of measurement points in the shear layer is defined by the length of the measurement volume. A decrease of this length is accompanied by a larger fringe distance variation along the measurement axis which results in a rise of the measurement uncertainty for the flow velocity (uncertainty relation between spatial resolution and velocity uncertainty). As a unique advantage, the laser Doppler profile sensor (LDV-PS) overcomes this problem by using two fan-like fringe systems to obtain the position of the measured particles along the measurement axis and therefore achieve a high spatial resolution while it still offers a low velocity uncertainty. With this technique, the flow rate can be estimated with one order of magnitude lower uncertainty, down to 0:05% statistical uncertainty.1 And flow profiles especially in film flows can be measured more accurately. The problem for this technique is, in contrast to laboratory setups where the system is quite stable, that for industrial applications the sensor needs a reliable and robust traceability to the SI units, meter and second. Small deviations in the calibration can, because of the highly position depending calibration function, cause large systematic errors in the measurement result. Therefore, a simple, stable and accurate tool is needed, that can easily be used in industrial surroundings to check or recalibrate the sensor. In this work, different calibration methods are presented and their influences to the

  20. Coseismic and postseismic velocity changes measured by repeating earthquakes

    Science.gov (United States)

    Schaff, David P.; Beroza, Gregory C.

    2004-10-01

    Repeating earthquakes that rupture approximately the same fault patch and have nearly identical waveforms are a useful tool for measuring temporal changes in wave propagation in the Earth's crust. Since source and path effects are common to all earthquakes in a repeating earthquake sequence (multiplet), differences in their waveforms can be attributed to changes in the characteristics of the medium. We have identified over 20 multiplets containing between 5 and 40 repeating events in the aftershock zones of the 1989 Loma Prieta and 1984 Morgan Hill, California, earthquakes. Postmain shock events reveal delays of phases in the early S wave coda of as much as 0.2 s relative to premain shock events. The delay amounts to a path-averaged coseismic velocity decrease of about 1.5% for P waves and 3.5% for S waves. Since most of the multiplets are aftershocks and follow Omori's law, we have excellent temporal sampling in the immediate postmain shock period. We find that the amplitude of the velocity decrease decays logarithmically in time following the main shock. In some cases it returns to the premain shock values, while in others it does not. Similar results are obtained for the Morgan Hill main shock. Because the fractional change in S wave velocity is greater than the fractional change in P wave velocity, it suggests that the opening or connection of fluid-filled fractures is the underlying cause. The magnitude of the velocity change implies that low effective pressures are present in the source region of the velocity change. Our results suggest that the changes are predominantly near the stations and shallow, but we cannot exclude the possibility that changes occur at greater depth as well. If the variations are shallow, we may be detecting the lingering effects of nonlinearity during main shock strong ground motion. If the variations are deep, it suggests that pore pressures at seismogenic depths are high, which would likely play a key role in the earthquake process.

  1. Cross-correlation based time delay estimation for turbulent flow velocity measurements: Statistical considerations

    Energy Technology Data Exchange (ETDEWEB)

    Tal, Balazs; Bencze, Attila; Zoletnik, Sandor; Veres, Gabor [KFKI-Research Institute for Particle and Nuclear Physics, Association EURATOM, PO Box 49, H-1525 Budapest (Hungary); Por, Gabor [Department of Nuclear Techniques, Budapest University of Technology and Economics, Association EURATOM, Muegyetem rkp. 9., H-1111 Budapest (Hungary)

    2011-12-15

    Time delay estimation methods (TDE) are well-known techniques to investigate poloidal flows in hot magnetized plasmas through the propagation properties of turbulent structures in the medium. One of these methods is based on the estimation of the time lag at which the cross-correlation function (CCF) estimation reaches its maximum value. The uncertainty of the peak location refers to the smallest determinable flow velocity modulation, and therefore the standard deviation of the time delay imposes important limitation to the measurements. In this article, the relative standard deviation of the CCF estimation and the standard deviation of its peak location are calculated analytically using a simple model of turbulent signals. This model assumes independent (non interacting) overlapping events (coherent structures) with randomly distributed spatio-temporal origins moving with background flow. The result of our calculations is the derivation of a general formula for the CCF variance, which is valid not exclusively in the high event density limit, but also for arbitrary event densities. Our formula reproduces the well known expression for high event densities previously published in the literature. In this paper we also present a derivation of the variance of time delay estimation that turns out to be inversely proportional to the applied time window. The derived formulas were tested in real plasma measurements. The calculations are an extension of the earlier work of Bencze and Zoletnik [Phys. Plasmas 12, 052323 (2005)] where the autocorrelation-width technique was developed. Additionally, we show that velocities calculated by a TDE method possess a broadband noise which originates from this variance, its power spectral density cannot be decreased by worsening the time resolution and can be coherent with noises of other velocity measurements where the same turbulent structures are used. This noise should not be confused with the impact of zero mean frequency zonal flow

  2. The density and velocity of plasma bullets propagating along one dielectric tube

    Directory of Open Access Journals (Sweden)

    Longfei Ji

    2015-08-01

    Full Text Available This study shows that the propagation of plasma bullets along one dielectric tube is strongly affected by many discharge parameters, such as the waveform of applied voltage (AC or pulsed DC, peak voltage, He flow rate, and the frequency of AC voltage. Analysis indicates that the density and velocity of plasma bullets are mainly determined by the electric field at the front of plasma bullets. These discharge parameters may significantly influence the distribution of plasma potential along the tube, thus control the electric field at the front of plasma bullets and their propagation. An increase in the pulsed DC voltage with its rise time of <40-50 ns can lead to an obvious improvement in the electric field at the front of plasma bullets, resulting in generation of a plasma in the high density gas and a fast propagation of plasma bullets. He flowing through the tube can contribute to the surface diffusion of charged species, and greatly increase the electric field at the front of plasma bullets. During the propagation of plasma bullets, their density is decreased due to the surface recombination of charged species, such as electrons and ions.

  3. Hollow ballistic pendulum for plasma momentum measurements

    Science.gov (United States)

    Goncharov, S. F.; Pashinin, P. P.; Perov, V. Y.; Serov, R. V.; Yanovsky, V. P.

    1988-05-01

    A novel pendulum design—hollow ballistic pendulum—is suggested for plasma momentum measurements. It has an advantage over the pendula used earlier in laser plasma experiments of being insensitive to a momentum of matter evaporated and scattered by the pendulum wall exposed to the plasma, which usually exceeds plasma momentum to be measured. Simple expressions describing pendulum performance are derived, and requirements of shape and size are established. Using this kind of pendulum in experiments on laser acceleration of thin foils made it possible to measure the momentum of accelerated foil with an accuracy of about 10%.

  4. A potential issue for the OPERA neutrino velocity measurement

    CERN Document Server

    Palazzo, Antonio

    2011-01-01

    We discuss what we think may be a potential issue for the OPERA neutrino velocity measurement, in connection with the statistical procedure employed for the extraction of the neutrino time of flight. We show that such a potential problem may have eluded the Monte Carlo tests performed by the collaboration. Only the collaboration has the information necessary to clarify the issue, make quantitative estimates and trace definitive conclusions.

  5. Instantaneous velocity profile measurements in a turbulent boundary layer

    Science.gov (United States)

    Robinson, S. K.

    1986-01-01

    Instantaneous wall shear stress and streamwise velocities have been measured simultaneously in a flat-plate, turbulent boundary layer at moderate Reynolds number in an effort to provide experimental support for large eddy simulations. Data were obtained using a buried-wire, wall shear gage and a hot-wire rake positioned in the log region of the flow. Fluctuations of the instantaneous U(+) versus Y(+) profiles about a mean law of the wall are shown to be significant and complex. Peak cross-correlation values between wall shear stress and the velocities are high, and reflect the passage of a large structure inclined at a small angle to the wall. Estimates of this angle are consistent with those made by other investigators. Conditional sampling techniques were used to detect the passage of various sizes and types of flow disturbances (events), and to estimate their mean frequency of occurrence. Events characterized by large aand sudden streamwise accelerations were found to be highly coherent throughout the log region and were strongly correlated with large fluctuations in wall shear stress. Phase randomness between the near-wall quantities and the outer velocities was small. The results suggest that the flow events detected by conditional sampling applied to velocities in the log region may be related to the bursting process.

  6. Seeing-Induced Errors in Solar Doppler Velocity Measurements

    CERN Document Server

    Padinhatteeri, Sreejith; Sankarasubramanian, K; 10.1007/s11207-010-9597-1

    2010-01-01

    Imaging systems based on a narrow-band tunable filter are used to obtain Doppler velocity maps of solar features. These velocity maps are created by taking the difference between the blue- and red-wing intensity images of a chosen spectral line. This method has the inherent assumption that these two images are obtained under identical conditions. With the dynamical nature of the solar features as well as the Earth's atmosphere, systematic errors can be introduced in such measurements. In this paper, a quantitative estimate of the errors introduced due to variable seeing conditions for ground-based observations is simulated and compared with real observational data for identifying their reliability. It is shown, under such conditions, that there is a strong cross-talk from the total intensity to the velocity estimates. These spurious velocities are larger in magnitude for the umbral regions compared to the penumbra or quiet-sun regions surrounding the sunspots. The variable seeing can induce spurious velocitie...

  7. Measurement of a 2D fast-ion velocity distribution function by tomographic inversion of fast-ion D-alpha spectra

    DEFF Research Database (Denmark)

    Salewski, Mirko; Geiger, B.; Jacobsen, Asger Schou

    2014-01-01

    We present the first measurement of a local fast-ion 2D velocity distribution function f(v‖, v⊥). To this end, we heated a plasma in ASDEX Upgrade by neutral beam injection and measured spectra of fast-ion Dα (FIDA) light from the plasma centre in three views simultaneously. The measured spectra ...

  8. Collective Thomson scattering for ion temperature and velocity measurements on Magnum-PSI: a feasibility study

    Science.gov (United States)

    van der Meiden, H. J.

    2010-04-01

    In this paper, collective Thomson scattering (CTS) is proposed for measuring the ion temperature and axial/rotational velocity of a plasma jet in the linear plasma generator Magnum-PSI, where ITER-relevant plasma conditions will be simulated. CTS is feasible at Magnum-PSI, because high electron densities (ne) can be obtained at low electron temperatures, which means that small Debye lengths are achievable. Calculations show that CTS is possible at the fundamental wavelength (1064 nm) of a Nd : YAG laser. At this wavelength, a scattering angle of 17-35° is sufficiently small to achieve a scattering parameter 1 1.5 × 1021 m-3. The design considerations of the CTS diagnostic are described in this paper.

  9. Building a Dispersion Relation Solver for Hot Plasmas with Arbitrary Non-relativistic Parallel Velocity Distributions

    Science.gov (United States)

    Fu, X.; Waters, T.; Gary, S. P.

    2014-12-01

    Collisionless space plasmas often deviate from Maxwellian-like velocity distributions. To study kinetic waves and instabilities in such plasmas, the dispersion relation, which depends on the velocity distribution, needs to be solved numerically. Most current dispersion solvers (e.g. WHAMP) take advantage of mathematical properties of the Gaussian (or generalized Lorentzian) function, and assume that the velocity distributions can be modeled by a combination of several drift-Maxwellian (or drift-Lorentzian) components. In this study we are developing a kinetic dispersion solver that admits nearly arbitrary non-relativistic parallel velocity distributions. A key part of any dispersion solver is the evaluation of a Hilbert transform of the velocity distribution function and its derivative along Landau contours. Our new solver builds upon a recent method to compute the Hilbert transform accurately and efficiently using the fast Fourier transform, while simultaneously treating the singularities arising from resonances analytically. We have benchmarked our new solver against other codes dealing with Maxwellian distributions. As an example usage of our code, we will show results for several instabilities that occur for electron velocity distributions observed in the solar wind.

  10. Interferometer measurements in pulsed plasma experiments

    Energy Technology Data Exchange (ETDEWEB)

    Lisitsyn, I.V.; Kohno, Susumu; Kawauchi, Toshinori; Sueda, Tsuyoshi; Katsuki, Sunao; Akiyama, Hidenori [Kumamoto Univ. (Japan). Faculty of Engineering

    1997-11-01

    The interferometer measurements are extremely informative in plasma experiments allowing direct evaluations of the electron density. The primary goal of the work presented, is to build a laser interferometer which meets the requirements of the highest possible simplicity, economy, convenience and ease of construction. These requirements are successfully satisfied while maintaining high sensitivity ({+-}0.5deg - of phase shift) and a wide density range (10{sup 14} and 10{sup 19} cm{sup -2} - line-integrated) of the interferometer. In our experiments we used a low average power (5 mW) He-Ne laser without complicated and costly stabilization or detection environments. The He-Ne laser interferometer with the Michelson arrangement was used to measure the line-integrated plasma densities in various plasma experiments. Time- and spatially-resolved density measurements were performed for a plasma opening switch, a laser produced plasma, an electrothermal launcher and railgun plasmas. (author)

  11. Coherent Laser Instrument Would Measure Range and Velocity

    Science.gov (United States)

    Chang, Daniel; Cardell, Greg; San Martin, Alejandro; Spiers, Gary

    2005-01-01

    A proposed instrument would project a narrow laser beam that would be frequency-modulated with a pseudorandom noise (PN) code for simultaneous measurement of range and velocity along the beam. The instrument performs these functions in a low mass, power, and volume package using a novel combination of established techniques. Originally intended as a low resource- footprint guidance sensor for descent and landing of small spacecraft onto Mars or small bodies (e.g., asteroids), the basic instrument concept also lends itself well to a similar application guiding aircraft (especially, small unmanned aircraft), and to such other applications as ranging of topographical features and measuring velocities of airborne light-scattering particles as wind indicators. Several key features of the instrument s design contribute to its favorable performance and resource-consumption characteristics. A laser beam is intrinsically much narrower (for the same exit aperture telescope or antenna) than a radar beam, eliminating the need to correct for the effect of sloping terrain over the beam width, as is the case with radar. Furthermore, the use of continuous-wave (CW), erbium-doped fiber lasers with excellent spectral purity (narrow line width) permits greater velocity resolution, while reducing the laser s power requirement compared to a more typical pulsed solid-state laser. The use of CW also takes proper advantage of the increased sensitivity of coherent detection, necessary in the first place for direct measurement of velocity using the Doppler effect. However, measuring range with a CW beam requires modulation to "tag" portions of it for time-of-flight determination; typically, the modulation consists of a PN code. A novel element of the instrument s design is the use of frequency modulation (FM) to accomplish both the PN-modulation and the Doppler-bias frequency shift necessary for signed velocity measurements. This permits the use of a single low-power waveguide electrooptic

  12. Las Vegas Basin Seismic Response Project: Measured Shallow Soil Velocities

    Science.gov (United States)

    Luke, B. A.; Louie, J.; Beeston, H. E.; Skidmore, V.; Concha, A.

    2002-12-01

    The Las Vegas valley in Nevada is a deep (up to 5 km) alluvial basin filled with interlayered gravels, sands, and clays. The climate is arid. The water table ranges from a few meters to many tens of meters deep. Laterally extensive thin carbonate-cemented lenses are commonly found across parts of the valley. Lenses range beyond 2 m in thickness, and occur at depths exceeding 200 m. Shallow seismic datasets have been collected at approximately ten sites around the Las Vegas valley, to characterize shear and compression wave velocities in the near surface. Purposes for the surveys include modeling of ground response to dynamic loads, both natural and manmade, quantification of soil stiffness to aid structural foundation design, and non-intrusive materials identification. Borehole-based measurement techniques used include downhole and crosshole, to depths exceeding 100 m. Surface-based techniques used include refraction and three different methods involving inversion of surface-wave dispersion datasets. This latter group includes two active-source techniques, the Spectral Analysis of Surface Waves (SASW) method and the Multi-Channel Analysis of Surface Waves (MASW) method; and a new passive-source technique, the Refraction Mictrotremor (ReMi) method. Depths to halfspace for the active-source measurements ranged beyond 50 m. The passive-source method constrains shear wave velocities to 100 m depths. As expected, the stiff cemented layers profoundly affect local velocity gradients. Scale effects are evident in comparisons of (1) very local measurements typified by borehole methods, to (2) the broader coverage of the SASW and MASW measurements, to (3) the still broader and deeper resolution made possible by the ReMi measurements. The cemented layers appear as sharp spikes in the downhole datasets and are problematic in crosshole measurements due to refraction. The refraction method is useful only to locate the depth to the uppermost cemented layer. The surface

  13. Measurement of the velocity field behind the automotive vent

    Directory of Open Access Journals (Sweden)

    Jedelský Jan

    2012-04-01

    Full Text Available Passenger comfort in a personal vehicle cabin strongly depends on the appropriate function of the cabin ventilation system. Great attention is therefore paid to the effective functioning of the automotive vents. Various techniques can be employed to evaluate the proper formation of the flow behind the ventilation outlet. Constant Temperature Anemometry (CTA was used in our case for accurate measurement of the velocity field and consequent assessment of jet boundaries and jet axis. A novel methodology has been developed for the simulation of realistic conditions when using just a single vent under laboratory conditions instead of the complete vehicle ventilation system. A special technique has also been developed for determination of the terminal inclination angles of vent vanes for the particular vent type, which can be completely closed by the adjustable horizontal vanes. A two wire CTA probe was used for measurement of the actual velocity over predefined planes, which were specified according to smoke visualization. Mean velocities and the turbulence intensity were evaluated on the basis of the obtained data and are presented in a form of charts. Both jet boundary and orientation of the jet for a given setup of the vent are important characteristics of particular vent type. Effectiveness of different vents could be compared using our methodology and hence contribute to development of advanced ventilation system.

  14. Measurement of the velocity field behind the automotive vent

    Science.gov (United States)

    Ležovič, Tomáš; Lízal, František; Jedelský, Jan; Jícha, Miroslav

    2012-04-01

    Passenger comfort in a personal vehicle cabin strongly depends on the appropriate function of the cabin ventilation system. Great attention is therefore paid to the effective functioning of the automotive vents. Various techniques can be employed to evaluate the proper formation of the flow behind the ventilation outlet. Constant Temperature Anemometry (CTA) was used in our case for accurate measurement of the velocity field and consequent assessment of jet boundaries and jet axis. A novel methodology has been developed for the simulation of realistic conditions when using just a single vent under laboratory conditions instead of the complete vehicle ventilation system. A special technique has also been developed for determination of the terminal inclination angles of vent vanes for the particular vent type, which can be completely closed by the adjustable horizontal vanes. A two wire CTA probe was used for measurement of the actual velocity over predefined planes, which were specified according to smoke visualization. Mean velocities and the turbulence intensity were evaluated on the basis of the obtained data and are presented in a form of charts. Both jet boundary and orientation of the jet for a given setup of the vent are important characteristics of particular vent type. Effectiveness of different vents could be compared using our methodology and hence contribute to development of advanced ventilation system.

  15. Monitoring of the velocity field of the plasma motion under sounding of F ionospheric region by the probe waves

    Science.gov (United States)

    Sergeev, Evgeny; Komrakov, G. P.; Smyshlyaev, Sergey E.

    Results of investigations of the motions in F region of the ionosphere by means of the method of the space-frequency diversity reception are presented. Measurements of the vertical and horizontal plasma drift velocities have been performed over SURA facility (Russia) using of multifrequency dopler station for vertical sounding and diversity three point reception of the reflected radiosignals. Possibilities of a day (15 hours) monitoring of the drift velocity space at different altitudes were studied by using of the three fixed probe frequencies 4353 kHz, 5853 kHz and 7353 kHz. For another experimental series complex investigations of the pumped ionospheric volume were performed by its diagnostics at different frequencies with the short (¡ 200 mks) wide frequency band (˜ 500 kHz) and powerful (˜ 20 - 150 MW ERP) pulses. Data about a fine distribution structure of the vertical and horizontal plasma drift velocities in the turbulence plasma range were first obtained with a high frequency (˜ 1 kHz) and temporal (˜ 20 ms) resolution. The work was supported by RFBR grants 07-02-00464 and 06-02-17334.

  16. Measurement of Damage Velocities in Bullet Impacts of Transparent Armor

    Science.gov (United States)

    Anderson, Charles; Bigger, Rory; Weiss, Carl

    2013-06-01

    A series of impact experiments have been conducted to examine the response of transparent material to ballistic impact. The experiments consisted of impacting 15 mm of borosilicate glass back by 9.5 mm of Lexan. The projectile was a 0.30-cal hard steel bullet designed specifically for the experiments. Residual velocities and the residual length of the bullets (which were soft-recovered in a catch box) were measured as a function of impact velocity. High-speed imaging of the impact event and post-test analysis has permitted quantification of damage propagation and the rate of propagation. The results of several experiments are presented and compared to edge-on impact experiments that have been conducted by Strassburger et al..

  17. Deposition and properties of high-velocity-oxygen-fuel and plasma-sprayed Mo-Mo2C composite coatings

    Science.gov (United States)

    Prchlik, L.; Gutleber, J.; Sampath, S.

    2001-12-01

    Molybdenum thermal-spray coatings, dispersion strengthened by molybdenum oxides and molybdenum carbides, play an important role in industrial tribological applications. Traditionally, they have been prepared by plasma and wire flame spraying. High porosity and lower cohesion strength limit their application in situations where both galling and abrasion wear is involved. In this study, high-velocity-oxygen-fuel (HVOF) deposition of molybdenum and molybdenum carbide coatings was attempted. Deposition was achieved for all powders used. Composition, microstructure, mechanical, and wear properties of the HVOF synthesized coatings were evaluated and compared with plasma-sprayed counterparts. The HVOF coatings possessed a very good abrasion resistance, whereas plasma deposits performed better in dry sliding tests. Measurements showed a close relationship between the coating surface hardness and its abrasion resistance. Results also suggested correlation between molybdenum carbide distribution in the molybdenum matrix and the sliding friction response of Mo-Mo2C coatings.

  18. Measurement of the dynamo effect in a plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ji, H. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Prager, S.C.; Almagri, A.F.; Sarff, J.S. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Physics; Hirano, Y. [Electrotechnical Lab., Tsukuba, Ibaraki (Japan). Plasma Section; Toyama, H. [Univ. of Tokyo (Japan). Dept. of Physics

    1995-11-01

    A series of the detailed experiments has been conducted in three laboratory plasma devices to measure the dynamo electric field along the equilibrium field line (the {alpha} effect) arising from the correlation between the fluctuating flow velocity and magnetic field. The fluctuating flow velocity is obtained from probe measurement of the fluctuating E x B drift and electron diamagnetic drift. The three major findings are (1) the {alpha} effect accounts for the dynamo current generation, even in the time dependence through a ``sawtooth`` cycle; (2) at low collisionality the dynamo is explained primarily by the widely studied pressureless Magnetohydrodynamic (MHD) model, i.e., the fluctuating velocity is dominated by the E x B drift; (3) at high collisionality, a new ``electron diamagnetic dynamo`` is observed, in which the fluctuating velocity is dominated by the diamagnetic drift. In addition, direct measurements of the helicity flux indicate that the dynamo activity transports magnetic helicity from one part of the plasma to another, but the total helicity is roughly conserved, verifying J.B. Taylor`s conjecture.

  19. A high sensitivity momentum flux measuring instrument for plasma thruster exhausts and diffusive plasmas

    Energy Technology Data Exchange (ETDEWEB)

    West, Michael D.; Charles, Christine; Boswell, Rod W. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

    2009-05-15

    A high sensitivity momentum flux measuring instrument based on a compound pendulum has been developed for use with electric propulsion devices and radio frequency driven plasmas. A laser displacement system, which builds upon techniques used by the materials science community for surface stress measurements, is used to measure with high sensitivity the displacement of a target plate placed in a plasma thruster exhaust. The instrument has been installed inside a vacuum chamber and calibrated via two different methods and is able to measure forces in the range of 0.02-0.5 mN with a resolution of 15 {mu}N. Measurements have been made of the force produced from the cold gas flow and with a discharge ignited using argon propellant. The plasma is generated using a Helicon Double Layer Thruster prototype. The instrument target is placed about 1 mean free path for ion-neutral charge exchange collisions downstream of the thruster exit. At this position, the plasma consists of a low density ion beam (10%) and a much larger downstream component (90%). The results are in good agreement with those determined from the plasma parameters measured with diagnostic probes. Measurements at various flow rates show that variations in ion beam velocity and plasma density and the resulting momentum flux can be measured with this instrument. The instrument target is a simple, low cost device, and since the laser displacement system used is located outside the vacuum chamber, the measurement technique is free from radio frequency interference and thermal effects. It could be used to measure the thrust in the exhaust of other electric propulsion devices and the momentum flux of ion beams formed by expanding plasmas or fusion experiments.

  20. A high sensitivity momentum flux measuring instrument for plasma thruster exhausts and diffusive plasmas

    Science.gov (United States)

    West, Michael D.; Charles, Christine; Boswell, Rod W.

    2009-05-01

    A high sensitivity momentum flux measuring instrument based on a compound pendulum has been developed for use with electric propulsion devices and radio frequency driven plasmas. A laser displacement system, which builds upon techniques used by the materials science community for surface stress measurements, is used to measure with high sensitivity the displacement of a target plate placed in a plasma thruster exhaust. The instrument has been installed inside a vacuum chamber and calibrated via two different methods and is able to measure forces in the range of 0.02-0.5mN with a resolution of 15μN. Measurements have been made of the force produced from the cold gas flow and with a discharge ignited using argon propellant. The plasma is generated using a Helicon Double Layer Thruster prototype. The instrument target is placed about 1 mean free path for ion-neutral charge exchange collisions downstream of the thruster exit. At this position, the plasma consists of a low density ion beam (10%) and a much larger downstream component (90%). The results are in good agreement with those determined from the plasma parameters measured with diagnostic probes. Measurements at various flow rates show that variations in ion beam velocity and plasma density and the resulting momentum flux can be measured with this instrument. The instrument target is a simple, low cost device, and since the laser displacement system used is located outside the vacuum chamber, the measurement technique is free from radio frequency interference and thermal effects. It could be used to measure the thrust in the exhaust of other electric propulsion devices and the momentum flux of ion beams formed by expanding plasmas or fusion experiments.

  1. The ion velocity distribution of tokamak plasmas: Rutherford scattering at TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Tammen, H.F.

    1995-01-10

    One of the most promising ways to gererate electricity in the next century on a large scale is nuclear fusion. In this process two light nuclei fuse and create a new nucleus with a smaller mass than the total mass of the original nuclei, the mass deficit is released in the form of kinetic energy. Research into this field has already been carried out for some decades now, and will have to continue for several more decades before a commercially viable fusion reactor can be build. In order to obtain fusion, fuels of extremely high temperatures are needed to overcome the repulsive force of the nuclei involved. Under these circumstances the fuel is fully ionized: it consists of ions and electrons and is in the plasma state. The problem of confining such a hot substance is solved by using strong magnetic fields. One specific magnetic configuration, in common use, is called the tokamak. The plasma in this machine has a toroidal, i.e. doughnut shaped, configuration. For understanding the physical processes which take place in the plasma, a good temporally and spatially resolved knowledge of both the ion and electron velocity distribution is required. The situation concerning the electrons is favourable, but this is not the case for the ions. To improve the existing knowledge of the ion velocity distribution in tokamak plasmas, a Rutherford scattering diagnostic (RUSC), designed and built by the FOM-Institute for Plasmaphysics `Rijnhuizen`, was installed at the TEXTOR tokamak in Juelich (D). The principle of the diagnostic is as follows. A beam of monoenergetic particles (30 keV, He) is injected vertically into the plasma. A small part of these particles collides elastically with the moving plasma ions. By determining the energy of a scattered beam particle under a certain angle (7 ), the initial velocity of the plasma ion in one direction can be computed. (orig./WL).

  2. Unsteady velocity measurements in a realistic intracranial aneurysm model

    Science.gov (United States)

    Ugron, Ádám; Farinas, Marie-Isabelle; Kiss, László; Paál, György

    2012-01-01

    The initiation, growth and rupture of intracranial aneurysms are intensively studied by computational fluid dynamics. To gain confidence in the results of numerical simulations, validation of the results is necessary. To this end the unsteady flow was measured in a silicone phantom of a realistic intracranial aneurysm. A flow circuit was built with a novel unsteady flow rate generating method, used to model the idealised shape of the heartbeat. This allowed the measurement of the complex three-dimensional velocity distribution by means of laser-optical methods such as laser doppler anemometry (LDA) and particle image velocimetry (PIV). The PIV measurements, available with high temporal and spatial distribution, were found to have good agreement with the control LDA measurements. Furthermore, excellent agreement was found with the numerical results.

  3. Precision measurement of the carrier drift velocities in <100> silicon

    CERN Document Server

    Scharf, C

    2015-01-01

    Measurements of the drift velocities of electrons and holes as functions of electric field and temperature in high-purity n- and p-type silicon with crystal orientation are presented. The measurements cover electric field values between 2.4 and 50 kV/cm and temperatures between 233 and 333 K. Two methods have been used for extracting the drift velocities from current transient measurements: A time-of-flight (tof) method and fits of simulated transients to the measured transients, with the parameters describing the field and temperature dependence of the electron and hole mobilities as free parameters. A new mobility parametrization, which also provides a better description of existing data than previous ones, allowed an extension of the classical tof method to the situation of non-uniform fields. For the fit method, the use of the convolution theorem of Fourier transforms enabled us to precisely determine the electronics transfer function of the complete set-up, including the sensor properties. The agreement...

  4. Velocity and magnetic field measurements of Taylor plumes in SSX under different boundary conditions

    Science.gov (United States)

    Kaur, Manjit; Brown, M. R.; Han, J.; Shrock, J. E.; Schaffner, D. A.

    2016-10-01

    The SSX device has been modified by the addition of a 1 m long glass extension for accommodating pulsed theta pinch coils. The Taylor plumes are launched from a magnetized plasma gun and flow to an expansion volume downstream. The time of flight (TOF) measurements of these plumes are carried out using a linear array of Ḃ probes (separated by 10cm). TOF of the plasma plumes from one probe location to the next is determined by direct comparison of the magnetic field structures as well as by carrying out a cross-correlation analysis. With the glass boundary, the typical velocity of the Taylor plumes is found to be 25km /s , accompanied by a fast plasma (>= 50km /s) at the leading edge. Magnetic field embedded in the Taylor plumes is measured in the expansion chamber using a three-dimensional array of Ḃ probes and is found to be 700G . Some flux conservation of the Taylor plumes is provided by using a resistive (soak time 3 μs) and a mesh (soak time 170 μs > discharge time) liner around the glass tube for improving the downstream Taylor state velocity as well as the magnetic field. The results from these different boundary conditions will be presented. Work supported by DOE OFES and ARPA-E ALPHA programs.

  5. Spectroscopic measurement of ion temperature and ion velocity distributions in the flux-coil generated FRC

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, D.; Gota, H.; Hayashi, R.; Kiyashko, V.; Morehouse, M.; Primavera, S. [Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States); Bolte, N. [Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States); Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Marsili, P. [Department of Physics, University of Pisa, Largo B. Pontecorvo 3, 56127 Pisa (Italy); Roche, T. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Wessel, F. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States)

    2010-10-15

    One aim of the flux-coil generated field reversed configuration at Tri Alpha Energy (TAE) is to establish the plasma where the ion rotational energy is greater than the ion thermal energy. To verify this, an optical diagnostic was developed to simultaneously measure the Doppler velocity-shift and line-broadening using a 0.75 m, 1800 groves/mm, spectrometer. The output spectrum is magnified and imaged onto a 16-channel photomultiplier tube (PMT) array. The individual PMT outputs are coupled to high-gain, high-frequency, transimpedance amplifiers, providing fast-time response. The Doppler spectroscopy measurements, along with a survey spectrometer and photodiode-light detector, form a suite of diagnostics that provide insights into the time evolution of the plasma-ion distribution and current when accelerated by an azimuthal-electric field.

  6. Spectroscopic measurement of ion temperature and ion velocity distributions in the flux-coil generated FRC.

    Science.gov (United States)

    Gupta, D; Bolte, N; Gota, H; Hayashi, R; Kiyashko, V; Marsili, P; Morehouse, M; Primavera, S; Roche, T; Wessel, F

    2010-10-01

    One aim of the flux-coil generated field reversed configuration at Tri Alpha Energy (TAE) is to establish the plasma where the ion rotational energy is greater than the ion thermal energy. To verify this, an optical diagnostic was developed to simultaneously measure the Doppler velocity-shift and line-broadening using a 0.75 m, 1800 groves/mm, spectrometer. The output spectrum is magnified and imaged onto a 16-channel photomultiplier tube (PMT) array. The individual PMT outputs are coupled to high-gain, high-frequency, transimpedance amplifiers, providing fast-time response. The Doppler spectroscopy measurements, along with a survey spectrometer and photodiode-light detector, form a suite of diagnostics that provide insights into the time evolution of the plasma-ion distribution and current when accelerated by an azimuthal-electric field.

  7. Measurement of surface recombination velocity on heavily doped indium phosphide

    Science.gov (United States)

    Jenkins, Phillip; Ghalla-Goradia, Manju; Faur, Mircea; Faur, Maria; Bailey, Sheila

    1990-01-01

    Surface recombination velocity (SRV) on heavily doped n-type and p-type InP was measured as a function of surface treatment. For the limited range of substrates and surface treatments studied, SRV and surface stability depend strongly on the surface treatment. SRVs of 100,000 cm/sec in both p-type and n-type InP are obtainable, but in n-type the low-SRV surfaces were unstable, and the only stable surfaces on n-type had SRVs of more than 10to the 6th cm/sec.

  8. Velocity-selective EIT measurement of potassium Rydberg states

    CERN Document Server

    Xu, Wenchao

    2016-01-01

    We demonstrate a velocity selection scheme that mitigates suppression of electromagnetically induced transparency (EIT) by Doppler shifts for low--high EIT probe--coupling wavelength ordering. An optical pumping beam counter-propagating with the EIT probe beam transfers atoms between hyperfine states in a velocity selective fashion. Measurement of the transmitted probe beam synchronous with chopping of the optical pumping beam enables a Doppler-free EIT signal to be detected. Transition frequencies between 5P$_{1/2}$ and $n$S$_{1/2}$ states for $n=$26, 27, and 28 in $^{39}$K are obtained via EIT spectroscopy in a heated vapor cell with a probe beam stabilized to the 4S$_{1/2}\\rightarrow$5P$_{1/2}$ transition. Using previous high-resolution measurements of the 4S$_{1/2}\\rightarrow$nS$_{1/2}$ transitions, we make a determination of the absolute frequency of the 4S$_{1/2}\\rightarrow$5P$_{1/2}$ transition. Our measurement is shifted by 560 MHz from the currently accepted value with a two-fold improvement in uncer...

  9. Low-cost optoelectronic devices to measure velocity of detonation

    Science.gov (United States)

    Chan, Edwin M.; Lee, Vivian; Mickan, Samuel P.; Davies, Phil J.

    2005-02-01

    Velocity of Detonation (VoD) is an important measured characteristic parameter of explosive materials. When new explosives are developed, their VoD must be determined. Devices used to measure VoD are always destroyed in the process, however replacing these devices represents a considerable cost in the characterisation of new explosives. This paper reports the design and performance of three low-cost implementations of a point-to-point VoD measurement system, two using optical fibre and a third using piezoelectric polymers (PolyVinyliDine Flouride, PVDF). The devices were designed for short charges used under controlled laboratory conditions and were tested using the common explosive 'Composition B'. These new devices are a fraction of the cost of currently available VoD sensors and show promise in achieving comparable accuracy. Their future development will dramatically reduce the cost of testing and aid the characterisation of new explosives.

  10. Time window for magnetic reconnection in plasma configurations with velocity shear.

    Science.gov (United States)

    Faganello, M; Califano, F; Pegoraro, F

    2008-10-24

    It is shown that the rate of magnetic field line reconnection can be clocked by the evolution of the large-scale processes that are responsible for the formation of the current layers where reconnection can take place. In unsteady plasma configurations, such as those produced by the onset of the Kelvin-Helmholtz instability in a plasma with a velocity shear, qualitatively different magnetic structures are produced depending on how fast the reconnection process develops on the external clock set by the evolving large-scale configuration.

  11. Using piezoelectric sensors for ultrasonic pulse velocity measurements in concrete

    Science.gov (United States)

    Kee, Seong-Hoon; Zhu, Jinying

    2013-11-01

    The ultrasonic pulse velocity (UPV) test has been a widely used non-destructive testing method for concrete structures. However, the conventional UPV test has limitations in consistency of results and applicability in hard-to-access regions of structures. The authors explore the feasibility of embedded piezoelectric (PZT) sensors for ultrasonic measurements in concrete structures. Two PZT sensors were embedded in a reinforced concrete specimen. One sensor worked as an actuator driven by an ultrasonic pulse-receiver, and another sensor worked as a receiver. A series of ultrasonic tests were conducted to investigate the performance of the embedded sensors in crack-free concrete and concrete specimens having a surface-breaking crack under various external loadings. Signals measured by the embedded sensors show a broad bandwidth with a centre frequency around 80 kHz, and very good coherence in the frequency range from 30 to 180 kHz. Furthermore, experimental variability in ultrasonic pulse velocity and attenuation is substantially reduced compared to previously reported values from conventional UPV equipment. Findings from this study demonstrate that the embedded sensors have great potential as a low-cost solution for ultrasonic transducers for health monitoring of concrete in structures.

  12. Absolute velocity measurements in the solar transition region and corona

    Science.gov (United States)

    Hassler, D. M.; Rottman, G. J.; Orrall, F. Q.

    An experimental technique is presented to measure absolute velocities of minor ions formed in the solar transition region and corona. A sounding rocket experiment July 27 1987 obtained high resolution EUV spectra along a solar diameter with spatial resolution of 20 x 20 arcsec. The wavelengths of the 1533 Si II, 1548 C IV, and 770 Ne VIII emission lines were directly compared with wavelengths of known platinum lines generated by an inflight calibration lamp. On the assumption that horisontal motions cancel statistically so that the line-of-sight velocity approaches zero at the limb, a net radial downflow of approximately 7.5 + or - 1.0 km/s was found for C IV and upper limits were found on the radial flow for Si II and Ne VIII. This assumption was tested by direct comparison to the on-board wavelength reference using recently published laboratory rest wavelengths of the solar emission lines. Agreement was found within the published uncertainties of the laboratory wavelengths + or - 2 km/s in the case of C IV. It is suggested that improved laboratory wavelength measurements (+ or - 1 km/s) in conjunction with inflight wavelength calibration would improve constraints on models of transition region and coronal dynamics.

  13. Group velocity and pulse lengthening of mismatched laser pulses in plasma channels

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim

    2011-07-07

    Analytic solutions are presented to the non-paraxial wave equation describing an ultra-short, low-power, laser pulse propagating in aplasma channel. Expressions for the laser pulse centroid motion and laser group velocity are derived, valid for matched and mismatchedpropagation in a parabolic plasma channel, as well as in vacuum, for an arbitrary Laguerre-Gaussian laser mode. The group velocity of amismatched laser pulse, for which the laser spot size is strongly oscillating, is found to be independent of propagation distance andsignificantly less than that of a matched pulse. Laser pulse lengthening of a mismatched pulse owing to laser mode slippage isexamined and found to dominate over that due to dispersive pulse spreading for sufficiently long pulses. Analytic results are shown tobe in excellent agreement with numerical solutions of the full Maxwell equations coupled to the plasma response. Implications for plasmachannel diagnostics are discussed.

  14. Temperature dynamics and velocity scaling laws for interchange driven, warm ion plasma filaments

    Science.gov (United States)

    Olsen, Jeppe; Madsen, Jens; Nielsen, Anders Henry; Rasmussen, Jens Juul; Naulin, Volker

    2016-04-01

    The influence of electron and ion temperature dynamics on the radial convection of isolated structures in magnetically confined plasmas is investigated by means of numerical simulations. It is demonstrated that the maximum radial velocity of these plasma blobs roughly follows the inertial velocity scaling, which is proportional to the ion acoustic speed times the square root of the filament particle density times the sum of the electron and ion temperature perturbations. Only for small blobs the cross field convection does not follow this scaling. The influence of finite Larmor radius effects on the cross-field blob convection is shown not to depend strongly on the dynamical ion temperature field. The blob dynamics of constant finite and dynamical ion temperature blobs is similar. When the blob size is on the order of 10 times the ion Larmor radius the blobs stay coherent and decelerate slowly compared to larger blobs which dissipate faster due to fragmentation and turbulent mixing.

  15. Convective modes in plasma with the strong shear of ExB drift velocity

    Energy Technology Data Exchange (ETDEWEB)

    Timofeev, A.V. [RRC ' Kurchatov Institute' , Moscow, Russia 123182 (Russian Federation)

    2001-05-01

    The convective modes of an inhomogeneously drifting plasma in a shear magnetic field (a generalization of Suydam's problem) is considered. It is shown that a sufficiently great shear of ExB velocity drift suppresses the instability in the case of an arbitrary 'magnetic hill'. This result can be considered again as a Rayleigh theorem analogue. (author). Letter-to-the-editor.

  16. Improved technique for blood flow velocity measurement using Doppler effect

    Science.gov (United States)

    Valadares Oliveira, Eduardo J.; Nantes Button, Vera L. d. S.; Maia, Joaquim M.; Costa, Eduardo T.

    2002-04-01

    The Doppler velocimeter developed allows to determine the angle between the ultrasonic beam and the velocity vector of the flow, and to calculate the precise blood flow in a vessel. Four piezoelectric transducers constitute the Doppler velocimeter. Three of these transducers are positioned to form an equilateral triangle (base of a pyramid). When these transducers move simultaneously, backward or forward from the initial position, the emitted ultrasonic beams focalize on a position (peak of the pyramid) closer or farther from the transducers faces, according to the depth of the vessel where we intend to measure de flow. The angle between the transducers allows adjusting the height of this pyramid and the position of the focus (where the three beams meet). A forth transducer is used to determine the diameter of the vessel and monitor the position of the Doppler velocimeter relative to the vessel. Simulation results showed that with this technique is possible to accomplish precise measurement of blood flow.

  17. INCREASING MEASUREMENT ACCURACY IN ELECTRO-OPTICAL METHOD FOR MEASURING VELOCITY OF DETONATION

    Directory of Open Access Journals (Sweden)

    Mario Dobrilović

    2014-12-01

    Full Text Available In addition to other detonation parameters detonation velocity is a value that provides indirect information on the strength i.e. brisance of an explosive and explosive performance. In addition to that, detonation velocity is a value which can be measured in a relatively simpler and more precise manner, by developed and accessible methods when compared to other detonation parameters Due to its simple use, compact instruments and satisfactory accuracy, electro-optical method of detonation velocity measurement is widely used. The paper describes the electro-optical measurement method and points out the factors that affect its accuracy. The accuracy of measurement is increased and measurement uncertainty is reduced by the measurement result analysis with the application of different measurement setups.

  18. Measurement of ion velocity profiles in a magnetic reconnection layer via current sheet jogging

    Science.gov (United States)

    Stein, G.; Yoo, J.; Yamada, M.; Ji, H.; Dorfman, S.; Lawrence, E.; Myers, C.; Tharp, T.

    2011-10-01

    In many laboratory plasmas, constructing stationary Langmuir and Mach probe arrays with resolution on the order of electron skin depth is technically difficult, and can introduce significant plasma perturbations. However, complete two- dimensional profiles of plasma density, electron temperature, and ion flow are important for studying the transfer of energy from magnetic fields to particles during magnetic reconnection. Through the use of extra ``Shaping Field'' coils in the Magnetic Reconnection Experiment (MRX) at the Princeton Plasma Physics Laboratory, the inward motion of the current sheet in the reconnection layer can be accelerated, or ``jogged,'' allowing the measurement of different points across the sheet with stationary probes. By acquiring data from Langmuir probes and Mach probes at different locations in the MRX with respect to the current sheet center, profiles of electron density and temperature and a vector plot of two-dimensional ion velocity in the plane of reconnection are created. Results from probe measurements will be presented and compared to profiles generated from computer simulation.

  19. Velocity field measurements in the wake of a propeller model

    Science.gov (United States)

    Mukund, R.; Kumar, A. Chandan

    2016-10-01

    Turboprop configurations are being revisited for the modern-day regional transport aircrafts for their fuel efficiency. The use of laminar flow wings is an effort in this direction. One way to further improve their efficiency is by optimizing the flow over the wing in the propeller wake. Previous studies have focused on improving the gross aerodynamic characteristics of the wing. It is known that the propeller slipstream causes early transition of the boundary layer on the wing. However, an optimized design of the propeller and wing combination could delay this transition and decrease the skin friction drag. Such a wing design would require the detailed knowledge of the development of the slipstream in isolated conditions. There are very few studies in the literature addressing the requirements of transport aircraft having six-bladed propeller and cruising at a high propeller advance ratio. Low-speed wind tunnel experiments have been conducted on a powered propeller model in isolated conditions, measuring the velocity field in the vertical plane behind the propeller using two-component hot-wire anemometry. The data obtained clearly resolved the mean velocity, the turbulence, the ensemble phase averages and the structure and development of the tip vortex. The turbulence in the slipstream showed that transition could be close to the leading edge of the wing, making it a fine case for optimization. The development of the wake with distance shows some interesting flow features, and the data are valuable for flow computation and optimization.

  20. Force-velocity measurements of a few growing actin filaments.

    Directory of Open Access Journals (Sweden)

    Coraline Brangbour

    2011-04-01

    Full Text Available The polymerization of actin in filaments generates forces that play a pivotal role in many cellular processes. We introduce a novel technique to determine the force-velocity relation when a few independent anchored filaments grow between magnetic colloidal particles. When a magnetic field is applied, the colloidal particles assemble into chains under controlled loading or spacing. As the filaments elongate, the beads separate, allowing the force-velocity curve to be precisely measured. In the widely accepted Brownian ratchet model, the transduced force is associated with the slowing down of the on-rate polymerization. Unexpectedly, in our experiments, filaments are shown to grow at the same rate as when they are free in solution. However, as they elongate, filaments are more confined in the interspace between beads. Higher repulsive forces result from this higher confinement, which is associated with a lower entropy. In this mechanism, the production of force is not controlled by the polymerization rate, but is a consequence of the restriction of filaments' orientational fluctuations at their attachment point.

  1. Force-Velocity Measurements of a Few Growing Actin Filaments

    Science.gov (United States)

    Brangbour, Coraline; du Roure, Olivia; Helfer, Emmanuèle; Démoulin, Damien; Mazurier, Alexis; Fermigier, Marc; Carlier, Marie-France; Bibette, Jérôme; Baudry, Jean

    2011-01-01

    The polymerization of actin in filaments generates forces that play a pivotal role in many cellular processes. We introduce a novel technique to determine the force-velocity relation when a few independent anchored filaments grow between magnetic colloidal particles. When a magnetic field is applied, the colloidal particles assemble into chains under controlled loading or spacing. As the filaments elongate, the beads separate, allowing the force-velocity curve to be precisely measured. In the widely accepted Brownian ratchet model, the transduced force is associated with the slowing down of the on-rate polymerization. Unexpectedly, in our experiments, filaments are shown to grow at the same rate as when they are free in solution. However, as they elongate, filaments are more confined in the interspace between beads. Higher repulsive forces result from this higher confinement, which is associated with a lower entropy. In this mechanism, the production of force is not controlled by the polymerization rate, but is a consequence of the restriction of filaments' orientational fluctuations at their attachment point. PMID:21541364

  2. Thomson scattering measurements from asymmetric interpenetrating plasma flows

    Energy Technology Data Exchange (ETDEWEB)

    Ross, J. S., E-mail: ross36@llnl.gov; Moody, J. D.; Fiuza, F.; Ryutov, D.; Divol, L.; Huntington, C. M.; Park, H.-S. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States)

    2014-11-15

    Imaging Thomson scattering measurements of collective ion-acoustic fluctuations have been utilized to determine ion temperature and density from laser produced counter-streaming asymmetric flows. Two foils are heated with 8 laser beams each, 500 J per beam, at the Omega Laser facility. Measurements are made 4 mm from the foil surface using a 60 J 2ω probe laser with a 200 ps pulse length. Measuring the electron density and temperature from the electron-plasma fluctuations constrains the fit of the multi-ion species, asymmetric flows theoretical form factor for the ion feature such that the ion temperatures, ion densities, and flow velocities for each plasma flow are determined.

  3. Wind velocity measurements under turbulent conditions using a sphere anemometer

    Energy Technology Data Exchange (ETDEWEB)

    Heisselmann, Hendrik; Hoelling, Michael; Schulte, Bianca; Peinke, Joachim [Institute of Physics, University of Oldenburg (Germany)

    2008-07-01

    A well known problem of cup anemometry is the so-called overspeeding due to its momentum of inertia. As in nature turbulent flow conditions are predominant, cup anemometry leads to a wrong estimation of wind speeds. While cup anemometers do not provide the necessary time resolution to measure high frequency wind fluctuations, hot-wire anemometers are easily damaged under rough weather conditions. Therefore a robust, fast responding sphere anemometer was developed. The anemometer uses the thrust generated by the drag force on a sphere mounted on a flexible rod to detect wind velocities in two dimensions. The deflection of the rod is proportional to the drag force and can be measured either by means of a light pointer or by use of strain gauges. The two different measurement techniques were compared. The dynamic behaviour of the thrust anemometer was studied under laboratory conditions using a wind gust generator. The characteristics of different sphere-types and different rod materials were evaluated in order to optimize the setup. Results of open air measurements with hot-wire anemometer, sonic anemometer and sphere anemometer were compared by statistical methods.

  4. Monolithic interferometer for high precision radial velocity measurements

    Science.gov (United States)

    Wan, Xiaoke; Ge, Jian; Wang, Ji; Lee, Brian

    2009-08-01

    In high precision radial velocity (RV) measurements for extrasolar planets searching and studies, a stable wide field Michelson interferometer is very critical in Exoplanet Tracker (ET) instruments. Adopting a new design, monolithic interferometers are homogenous and continuous in thermal expansion, and field compensation and thermal compensation are both satisfied. Interferometer design and fabrication are decrypted in details. In performance evaluations, field angle is typically 22° and thermal sensitivity is typically -1.7 x 10-6/°C, which corresponds to ~500 m/s /°C in RV scale. In interferometer stability monitoring using a wavelength stabilized laser source, phase shift data was continuously recorded for nearly seven days. Appling a frequent calibration every 30 minutes as in typical star observations, the interferometer instability contributes less than 1.4 m/s in RV error, in a conservative estimation.

  5. Radio-controlled boat for measuring water velocities and bathymetry

    Science.gov (United States)

    Vidmar, Andrej; Bezak, Nejc; Sečnik, Matej

    2016-04-01

    Radio-controlled boat named "Hi3" was designed and developed in order to facilitate water velocity and bathymetry measurements. The boat is equipped with the SonTek RiverSurveyor M9 instrument that is designed for measuring open channel hydraulics (discharge and bathymetry). Usually channel cross sections measurements are performed either from a bridge or from a vessel. However, these approaches have some limitations such as performing bathymetry measurements close to the hydropower plant turbine or downstream from a hydropower plant gate where bathymetry changes are often the most extreme. Therefore, the radio-controlled boat was designed, built and tested in order overcome these limitations. The boat is made from a surf board and two additional small balance support floats. Additional floats are used to improve stability in fast flowing and turbulent parts of rivers. The boat is powered by two electric motors, steering is achieved with changing the power applied to left and right motor. Furthermore, remotely controlled boat "Hi3" can be powered in two ways, either by a gasoline electric generator or by lithium batteries. Lithium batteries are lighter, quieter, but they operation time is shorter compared to an electrical generator. With the radio-controlled boat "Hi3" we can perform measurements in potentially dangerous areas such as under the lock gates at hydroelectric power plant or near the turbine outflow. Until today, the boat "Hi3" has driven more than 200 km in lakes and rivers, performing various water speed and bathymetry measurements. Moreover, in future development the boat "Hi3" will be upgraded in order to be able to perform measurements automatically. The future plans are to develop and implement the autopilot. With this approach the user will define the route that has to be driven by the boat and the boat will drive the pre-defined route automatically. This will be possible because of the very accurate differential GPS from the Sontek River

  6. Optical Measurements of Dense Hypervelocity Plasmoids from Coaxial and Railgun Plasma Accelerators

    Science.gov (United States)

    Case, Andrew; Messer, Sarah; Bomgardner, Richard; Brockington, Samuel; Witherspoon, Douglas; Elton, Ray

    2009-11-01

    High velocity dense plasma jets are under continued experimental development for fusion applications including refueling, disruption mitigation, momentum injection/rotation drive, and magnetized target fusion. We present measurements taken on the plasmoids produced by a half-scale coaxial plasmoid accelerator, a full scale coaxial plasmoid accelerator, and a novel minirailgun accelerator. The data presented includes spectroscopic measurements of velocity and density, two point interferometric measurements of line integrated density and velocity, and fast framing camera imaging. Results from these measurements are in agreement with each other and with time of flight measurements taken using photodiodes, as well as total plasmoid momentum measurements taken using a ballistic pendulum technique. Plasma density is greater than 5 x10^15 cm-3, and velocities range up to 100 km/s, with a small component in some cases exceeding 120 km/s.

  7. Comparing radial velocities of atmospheric lines with radiosonde measurements

    CERN Document Server

    Figueira, P; Chacon, A; Lovis, C; Santos, N C; Curto, G Lo; Sarazin, M; Pepe, F

    2011-01-01

    The precision of radial velocity (RV) measurements depends on the precision attained on the wavelength calibration. One of the available options is using atmospheric lines as a natural, freely available wavelength reference. Figueira et al. (2010) measured the RV of O2 lines using HARPS and showed that the scatter was only of ~10 m/s over a timescale of 6 yr. Using a simple but physically motivated empirical model, they demonstrated a precision of 2 m/s, roughly twice the average photon noise contribution. In this paper we take advantage of a unique opportunity to confirm the sensitivity of the telluric absorption lines RV to different atmospheric and observing conditions: by means of contemporaneous in-situ wind measurements by radiosondes. The RV model fitting yielded similar results to that of Figueira et al. (2010), with lower wind magnitude values and varied wind direction. The probes confirmed the average low wind magnitude and suggested that the average wind direction is a function of time as well. The...

  8. Thomson Scattering Measurements of Plasma Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Holl, A; Redmer, R; Tschentscher, T; Toleikis, S; Forster, E; Cao, L; Glenzer, S H; Neumayer, P

    2006-03-29

    The authors propose to investigate the dynamics of plasmas in the warm dense matter (WDM) regime on ultra-short time scales. Accessible plasma conditions are in the density range of n = 10{sup 20} - 10{sup 23} cm{sup -3} and at moderate temperatures of T = 1 - 20 eV. These plasmas are of importance for laboratory astrophysics, high energy density science and inertial confinement fusion. They are characterized by a coupling parameter of {Lambda} {approx}> 1, where electromagnetic interactions are of the same order as the kinetic energy. The high density of the plasma makes it opaque to radiation in the visible range and, as a consequence, UV up to x-ray radiation can be used to probe such systems. Therefore a wide range in the temperature-density plane of WDM is presently unexplored and only the VUV-FEL opens for the first time the opportunity for its detailed investigation. In equilibrium, the macroscopic state of the plasma is completely characterized by its density and temperature. In pump-probe experiments however, the plasma is initially in a nonequilibrium state and relaxes towards equilibrium within the relaxation time {tau}{sub R}. For t > {tau}{sub R}, the plasma is in an equilibrium state and expands hydrodynamically on a time scale {tau}{sub H}. The proposed experiment measures the time-resolved Thomson scattering signal with the VUV-FEL radiation characterizing the plasma in equilibrium and nonequilibrium states. Both regimes are extremely interesting and will provide new insight into the following phenomena: (1) details of nonequilibrium correlations, (2) relaxation phenomena, (3) hydrodynamic expansion, (4) recombination kinetics. The time-resolved Thomson scattering signal is obtained in a pump-probe experiment by varying the delay between pump and probe. The final stage of the relaxation process (t {approx} {tau}{sub R}) is of special interest since the plasma components (electrons and ion species) can be assumed to be in quasi-equilibrium. This

  9. Influence of residual plasma drift velocity on the post-arc sheath expansion of vacuum circuit breakers

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Yongpeng; Shi, Zongqian; Jia, Shenli; Wang, Lijun [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Bai, Zhibin [State Grid Yulin Electric Power Supply Company, Shaanxi 719000 (China)

    2016-05-15

    The residual plasma in the inter-contact region of a vacuum circuit breaker moves towards the post-arc cathode at current zero, because the residual plasma mainly comes from the cathode spots during the arc burning process. In the most previous theoretical researches on the post-arc sheath expansion process of vacuum circuit breakers, only the thermal motion of residual plasma was taken into consideration. Alternately, the residual plasma was even assumed to be static at the moment of current zero in some simplified models. However, the influence of residual plasma drift velocity at current zero on the post-arc sheath expansion process was rarely investigated. In this paper, this effect is investigated by a one-dimensional particle-in-cell model. Simulation results indicate that the sheath expands slower with higher residual plasma drift velocity in the initial sheath expansion stage. However, with the increase of residual plasma drift velocity, the overall plasma density in the inter-contact region decreases faster, and the sheath expansion velocity increases earlier. Consequently, as a whole, it needs shorter time to expel the residual plasma from the inter-contact region. Furthermore, if the residual plasma drift velocity is high enough, the sheath expansion process ceases before it develops to the post-arc anode. Besides, the influence of the collisions between charges and neutrals is investigated as well in terms of the density of metal vapor. It shows that the residual plasma drift velocity takes remarkable effect only if the density of the metal vapor is relatively low, which corresponds to the circumstance of low-current interruptions.

  10. Influence of residual plasma drift velocity on the post-arc sheath expansion of vacuum circuit breakers

    Science.gov (United States)

    Mo, Yongpeng; Shi, Zongqian; Bai, Zhibin; Jia, Shenli; Wang, Lijun

    2016-05-01

    The residual plasma in the inter-contact region of a vacuum circuit breaker moves towards the post-arc cathode at current zero, because the residual plasma mainly comes from the cathode spots during the arc burning process. In the most previous theoretical researches on the post-arc sheath expansion process of vacuum circuit breakers, only the thermal motion of residual plasma was taken into consideration. Alternately, the residual plasma was even assumed to be static at the moment of current zero in some simplified models. However, the influence of residual plasma drift velocity at current zero on the post-arc sheath expansion process was rarely investigated. In this paper, this effect is investigated by a one-dimensional particle-in-cell model. Simulation results indicate that the sheath expands slower with higher residual plasma drift velocity in the initial sheath expansion stage. However, with the increase of residual plasma drift velocity, the overall plasma density in the inter-contact region decreases faster, and the sheath expansion velocity increases earlier. Consequently, as a whole, it needs shorter time to expel the residual plasma from the inter-contact region. Furthermore, if the residual plasma drift velocity is high enough, the sheath expansion process ceases before it develops to the post-arc anode. Besides, the influence of the collisions between charges and neutrals is investigated as well in terms of the density of metal vapor. It shows that the residual plasma drift velocity takes remarkable effect only if the density of the metal vapor is relatively low, which corresponds to the circumstance of low-current interruptions.

  11. The ''phase velocity'' of nonlinear plasma waves in the laser beat-wave accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Spence, W.L.

    1985-04-01

    A calculational scheme for beat-wave accelerators is introduced that includes all orders in velocity and in plasma density, and additionally accounts for the influence of plasma nonlinearities on the wave's phase velocity. The main assumption is that the laser frequencies are very large compared to the plasma frequency - under which it is possible to sum up all orders of forward Raman scattering. It is found that the nonlinear plasma wave does not have simply a single phase velocity, but that the beat-wave which drives it is usefully described by a non-local ''effective phase velocity'' function. A time-space domain approach is followed. (LEW)

  12. Complete velocity distribution in river cross-sections measured by acoustic instruments

    Science.gov (United States)

    Cheng, R.T.; Gartner, J.W.; ,

    2003-01-01

    To fully understand the hydraulic properties of natural rivers, velocity distribution in the river cross-section should be studied in detail. The measurement task is not straightforward because there is not an instrument that can measure the velocity distribution covering the entire cross-section. Particularly, the velocities in regions near the free surface and in the bottom boundary layer are difficult to measure, and yet the velocity properties in these regions play the most significant role in characterizing the hydraulic properties. To further characterize river hydraulics, two acoustic instruments, namely, an acoustic Doppler current profiler (ADCP), and a "BoogieDopp" (BD) were used on fixed platforms to measure the detailed velocity profiles across the river. Typically, 20 to 25 stations were used to represent a river cross-section. At each station, water velocity profiles were measured independently and/or concurrently by an ADCP and a BD. The measured velocity properties were compared and used in computation of river discharge. In a tow-tank evaluation of a BD, it has been confirmed that BD is capable of measuring water velocity at about 11 cm below the free-surface. Therefore, the surface velocity distribution across the river was extracted from the BD velocity measurements and used to compute the river discharge. These detailed velocity profiles and the composite velocity distribution were used to assess the validity of the classic theories of velocity distributions, conventional river discharge measurement methods, and for estimates of channel bottom roughness.

  13. Photonic systems for high precision radial velocity measurements

    Science.gov (United States)

    Halverson, Samuel

    2016-01-01

    I will discuss new instrumentation and techniques designed to maximize the Doppler radial velocity (RV) measurement precision of next generation exoplanet discovery instruments. These systems include a novel wavelength calibration device based on an all-fiber fabry-perot interferometer, a compact and efficient optical fiber image scrambler based on a single high-index ball lens, and a unique optical fiber mode mixer. These systems have been developed specifically to overcome three technological hurdles that have classically hindered high precision RV measurements in both the optical and near-infrared (NIR), namely: lack of available wavelength calibration sources, inadequate decoupling of the spectrograph from variable telescope illumination, and speckle-induced noise due to mode interference in optical fibers. The instrumentation presented here will be applied to the Habitable-zone Planet Finder, a NIR RV instrument designed to detect rocky planets orbiting in the habitable zones of nearby M-dwarfs, and represents a critical technological step towards the detection of potentially habitable Earth-like planets. While primarily focused in the NIR, many of these systems will be adapted to future optical RV instruments as well, such as NASA's new Extreme Precision Doppler Spectrometer for the WIYN telescope.

  14. Rotation Rate of Saturn's Magnetosphere using CAPS Plasma Measurements

    Science.gov (United States)

    Sittler, E.; Cooper, J.; Hartle, R.; Simpson, D.; Johnson, R.; Thomsen, M.; Arridge, C.

    2011-01-01

    We present the present status of an investigation of the rotation rate of Saturn's magnetosphere using a 3D velocity moment technique being developed at Goddard which is similar to the 2D version used by Sittler et al. for SOI and similar to that used by Thomsen et al.. This technique allows one to nearly cover the full energy range of the Cassini Plasma Spectrometer (CAPS) IMS from 1 V . E/Q work during roll maneuvers. We make comparisons with the bi-Maxwellian fitting technique developed by Wilson et al. and the similar velocity moment technique by Thomsen et al. . We concentrate our analysis when ion composition data is available, which is used to weight the non-compositional data, referred to as singles data, to separate H+, H2+ and water group ions (W+) from each other. The chosen periods have high enough telemetry rates (4 kbps or higher) so that coincidence ion data, similar to that used by Sittler et al. for SOI is available. The ion data set is especially valuable for measuring flow velocities for protons, which are more difficult to derive using singles data within the inner magnetosphere, where the signal is dominated by heavy ions (i.e., proton peak merges with W+ peak as low energy shoulder). Our technique uses a flux function, which is zero in the proper plasma flow frame, to estimate fluid parameter uncertainties. The comparisons investigate the experimental errors and potential for systematic errors in the analyses, including ours. The rolls provide the best data set when it comes to getting 4PI coverage of the plasma but are more susceptible to time aliasing effects. In the future we will then make comparisons with magnetic field observations, Saturn ionosphere conductivities as presently known and the field aligned currents necessary for the planet to enforce corotation of the rotating plasma.

  15. Gyrokinetic simulations of fusion plasmas using a spectral velocity space representation

    CERN Document Server

    Parker, Joseph Thomas

    2016-01-01

    Magnetic confinement fusion reactors suffer severely from heat and particle losses through turbulent transport, which has inspired the construction of ever larger and more expensive reactors. Numerical simulations are vital to their design and operation, but particle collisions are too infrequent for fluid descriptions to be valid. Instead, strongly magnetised fusion plasmas are described by the gyrokinetic equations, a nonlinear integro-differential system for evolving the particle distribution functions in a five-dimensional position and velocity space, and the consequent electromagnetic field. Due to the high dimensionality, simulations of small reactor sections require hundreds of thousands of CPU hours on High Performance Computing platforms. We develop a Hankel-Hermite spectral representation for velocity space that exploits structural features of the gyrokinetic system. The representation exactly conserves discrete free energy in the absence of explicit dissipation, while our Hermite hypercollision ope...

  16. Video Measurement of the Muzzle Velocity of a Potato Gun

    Science.gov (United States)

    Jasperson, Christopher; Pollman, Anthony

    2011-01-01

    Using first principles, a theoretical equation for the maximum and actual muzzle velocities for a pneumatic cannon was recently derived. For a fixed barrel length, this equation suggests that the muzzle velocity can be enhanced by maximizing the product of the initial pressure and the volume of the propellant gas and decreasing the projectile…

  17. Video Measurement of the Muzzle Velocity of a Potato Gun

    Science.gov (United States)

    Jasperson, Christopher; Pollman, Anthony

    2011-01-01

    Using first principles, a theoretical equation for the maximum and actual muzzle velocities for a pneumatic cannon was recently derived. For a fixed barrel length, this equation suggests that the muzzle velocity can be enhanced by maximizing the product of the initial pressure and the volume of the propellant gas and decreasing the projectile…

  18. PCN magnetic index and average convection velocity in the polar cap inferred from SuperDARN radar measurements

    Science.gov (United States)

    Fiori, R. A. D.; Koustov, A. V.; Boteler, D.; Makarevich, R. A.

    2009-07-01

    The relationship between the polar cap north (PCN) magnetic index and the average convection velocity of the plasma flow across the polar cap is investigated using data from both the Rankin Inlet (RKN) polar cap Super Dual Auroral Radar Network (SuperDARN) radar and the entire SuperDARN network. Correlation between the PCN index and the average velocity, determined from the median RKN line of sight (LOS) velocity, maximizes near magnetic noon and midnight when the radar field of view is roughly aligned with the noon-midnight meridian. For observations between 1000 and 1100 MLT, a roughly linear increase of the average velocity was found for a PCN index between 0 and 2, but the rate of increase is ˜2 times faster than in previous publications in which the average velocity was estimated from DMSP ion drift measurements. Comparisons between the PCN index with the cross-polar cap velocity estimated from (1) SuperDARN convection maps and (2) median RKN LOS velocities show similar trends. Both the average cross-polar cap velocity (estimated by two methods) and the cross-polar cap potential show a tendency for saturation at PCN > 2. No significant seasonal change in the nature of the relationships was found.

  19. VELOCITY MEASUREMENTS FOR A SOLAR ACTIVE REGION FAN LOOP FROM HINODE/EIS OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Young, P. R. [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States); O' Dwyer, B.; Mason, H. E. [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)

    2012-01-01

    The velocity pattern of a fan loop structure within a solar active region over the temperature range 0.15-1.5 MK is derived using data from the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. The loop is aligned toward the observer's line of sight and shows downflows (redshifts) of around 15 km s{sup -1} up to a temperature of 0.8 MK, but for temperatures of 1.0 MK and above the measured velocity shifts are consistent with no net flow. This velocity result applies over a projected spatial distance of 9 Mm and demonstrates that the cooler, redshifted plasma is physically disconnected from the hotter, stationary plasma. A scenario in which the fan loops consist of at least two groups of 'strands'-one cooler and downflowing, the other hotter and stationary-is suggested. The cooler strands may represent a later evolutionary stage of the hotter strands. A density diagnostic of Mg VII was used to show that the electron density at around 0.8 MK falls from 3.2 Multiplication-Sign 10{sup 9} cm{sup -3} at the loop base, to 5.0 Multiplication-Sign 10{sup 8} cm{sup -3} at a projected height of 15 Mm. A filling factor of 0.2 is found at temperatures close to the formation temperature of Mg VII (0.8 MK), confirming that the cooler, downflowing plasma occupies only a fraction of the apparent loop volume. The fan loop is rooted within a so-called outflow region that displays low intensity and blueshifts of up to 25 km s{sup -1} in Fe XII {lambda}195.12 (formed at 1.5 MK), in contrast to the loop's redshifts of 15 km s{sup -1} at 0.8 MK. A new technique for obtaining an absolute wavelength calibration for the EIS instrument is presented and an instrumental effect, possibly related to a distorted point-spread function, that affects velocity measurements is identified.

  20. Tidally induced velocity variations of the Beardmore Glacier, Antarctica, and their representation in satellite measurements of ice velocity

    Directory of Open Access Journals (Sweden)

    O. J. Marsh

    2013-09-01

    Full Text Available Ocean tides close to the grounding line of outlet glaciers around Antarctica have been shown to directly influence ice velocity, both linearly and non-linearly. These fluctuations can be significant and have the potential to affect satellite measurements of ice discharge, which assume displacement between satellite passes to be consistent and representative of annual means. Satellite observations of horizontal velocity variation in the grounding zone are also contaminated by vertical tidal effects, the importance of which is highlighted here in speckle tracking measurements. Eight TerraSAR-X scenes from the grounding zone of the Beardmore Glacier are analysed in conjunction with GPS measurements to determine short-term and decadal trends in ice velocity. Diurnal tides produce horizontal velocity fluctuations of >50% on the ice shelf, recorded in the GPS data 4 km downstream of the grounding line. This variability decreases rapidly to <5% only 15 km upstream of the grounding line. Daily fluctuations are smoothed to <1% in the 11-day repeat pass TerraSAR-X imagery, but fortnightly variations over this period are still visible and show that satellite-velocity measurements can be affected by tides over longer periods. The measured tidal displacement observed in radar look direction over floating ice also allows the grounding line to be identified, using differential speckle tracking where phase information cannot be easily unwrapped.

  1. Methods of Measurement of High Air Velocities by the Hot-wire Method

    Science.gov (United States)

    Weske, John R.

    1943-01-01

    Investigations of strengths of hot wires at high velocities were conducted with platinum, nickel, and tungsten at approximately 200 Degrees Celcius hot-wire temperature. The results appear to disqualify platinum for velocities approaching the sonic range; whereas nickel withstands sound velocity, and tungsten may be used for supersonic velocities under standard atmospheric conditions. Hot wires must be supported by rigid prolongs at high velocities to avoid wire breakage. Resting current measurements for constant temperature show agreement with King's relation.

  2. Structure of parallel-velocity-shear driven mode in toroidal plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Dong, J.Q.; Xu, W.B.; Zhang, Y.Z. [Southwestern Inst. of Physics, Chengdu (China); Horton, W. [Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies

    1998-09-15

    It is shown that the Fourier-ballooning representation is appropriate for the study of short wavelength drift-like perturbation in toroidal plasmas with a parallel velocity shear (PVS). The radial structure of the mode driven by a PVS is investigated in a torus. The Reynolds stress created by PVS turbulence and proposed as one of the sources for a sheared poloidal plasma rotation is analyzed. It is demonstrated that a finite ion temperature may strongly enhance the Reynolds stress creation ability from PVS driven turbulence. The correlation of this observation with the requirement that ion heating power be higher than a threshold value for the formation of an internal transport barrier is discussed.

  3. Flowing dusty plasma experiments: generation of flow and measurement techniques

    Science.gov (United States)

    Jaiswal, S.; Bandyopadhyay, P.; Sen, A.

    2016-12-01

    A variety of experimental techniques for the generation of subsonic/supersonic dust fluid flows and means of measuring such flow velocities are presented. The experiments have been carried out in a \\Pi -shaped dusty plasma experimental device with micron size kaolin/melamine formaldehyde particles embedded in a background of argon plasma created by a direct current glow discharge. A stationary dust cloud is formed over the cathode region by precisely balancing the pumping speed and gas flow rate. A flow of dust particles/fluid is generated by additional gas injection from a single or dual locations or by altering the dust confining potential. The flow velocity is then estimated by three different techniques, namely, by super particle identification code, particle image velocimetry analysis and the excitation of dust acoustic waves. The results obtained from these three different techniques along with their merits and demerits are discussed. An estimation of the neutral drag force responsible for the generation as well as the attenuation of the dust fluid flow is made. These techniques can be usefully employed in laboratory devices to investigate linear and non-linear collective excitations in a flowing dusty plasma.

  4. Sound velocity measurement methods for porous sandstone. Measurements, finite element modelling, and diffraction correction

    CERN Document Server

    Sæther, Mathias; Ersland, Geir

    2016-01-01

    Acoustic material parameters of gas hydrate bearing porous rocks are important for evaluation of methods to exploit the vast methane gas resources present in the earth's subsurface, potentially combined with CO2 injection. A solid buffer method for measuring changes of the compressional wave velocity in porous rocks with changing methane hydrate contents under high-pressure hydrate-forming conditions, is tested and evaluated with respect to effects influencing on the measurement accuracy. The limited space available in the pressure chamber represents a challenge for the measurement method. Several effects affect the measured compressional wave velocity, such as interference from sidewall reflections, diffraction effects, the amount of torque (force) used to achieve acoustic coupling, and water draining of the watersaturated rock specimen. Test measurements using the solid buffer method in the pressure chamber at atmospheric conditions are compared to independent measurements using a water-bath immersion measu...

  5. Inductive Measurement of Plasma Jet Electrical Conductivity

    Science.gov (United States)

    Turner, Matthew W.; Hawk, Clark W.; Litchford, Ron J.

    2005-01-01

    An inductive probing scheme, originally developed for shock tube studies, has been adapted to measure explosive plasma jet conductivities. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-inch diameter probe was designed and constructed, and calibration was accomplished by firing an aluminum slug through the probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-gram high explosive shaped charges. Measured conductivities were in the range of 3 kS/m for unseeded octol charges and 20 kS/m for seeded octol charges containing 2% potassium carbonate by mass.

  6. Comparison between x-ray scattering and velocity-interferometry measurements from shocked liquid deuterium

    Science.gov (United States)

    Falk, K.; Regan, S. P.; Vorberger, J.; Crowley, B. J. B.; Glenzer, S. H.; Hu, S. X.; Murphy, C. D.; Radha, P. B.; Jephcoat, A. P.; Wark, J. S.; Gericke, D. O.; Gregori, G.

    2013-04-01

    The equation of state of light elements is essential to understand the structure of Jovian planets and inertial confinement fusion research. The Omega laser was used to drive a planar shock wave in the cryogenically cooled deuterium, creating warm dense matter conditions. X-ray scattering was used to determine the spectrum near the boundary of the collective and noncollective scattering regimes using a narrow band x-ray source in backscattering geometry. Our scattering spectra are thus sensitive to the individual electron motion as well as the collective plasma behavior and provide a measurement of the electron density, temperature, and ionization state. Our data are consistent with velocity-interferometry measurements previously taken on the same shocked deuterium conditions and presented by K. Falk [High Energy Density Phys.10.1016/j.hedp.2011.11.006 8, 76 (2012)]. This work presents a comparison of the two diagnostic systems and offers a detailed discussion of challenges encountered.

  7. Comparison between x-ray scattering and velocity-interferometry measurements from shocked liquid deuterium.

    Science.gov (United States)

    Falk, K; Regan, S P; Vorberger, J; Crowley, B J B; Glenzer, S H; Hu, S X; Murphy, C D; Radha, P B; Jephcoat, A P; Wark, J S; Gericke, D O; Gregori, G

    2013-04-01

    The equation of state of light elements is essential to understand the structure of Jovian planets and inertial confinement fusion research. The Omega laser was used to drive a planar shock wave in the cryogenically cooled deuterium, creating warm dense matter conditions. X-ray scattering was used to determine the spectrum near the boundary of the collective and noncollective scattering regimes using a narrow band x-ray source in backscattering geometry. Our scattering spectra are thus sensitive to the individual electron motion as well as the collective plasma behavior and provide a measurement of the electron density, temperature, and ionization state. Our data are consistent with velocity-interferometry measurements previously taken on the same shocked deuterium conditions and presented by K. Falk et al. [High Energy Density Phys. 8, 76 (2012)]. This work presents a comparison of the two diagnostic systems and offers a detailed discussion of challenges encountered.

  8. Shock wave velocity measuring system based on vernier VISAR-type interferometers

    Science.gov (United States)

    Gubskii, K. L.; Koshkin, D. S.; Antonov, A. S.; Mikhailuk, A. V.; Pirog, V. A.; Kuznetsov, A. P.

    2015-11-01

    The paper presents a multi-line diagnostic system for measuring the surface velocity in shock physics experiments. This system is designed for simultaneous measurement of surface velocity at multiple points. It is free from ambiguity caused by harmonic dependence of interference signals on the velocity and has a time resolution of 0.8 ns.

  9. Velocity measurement of model vertical axis wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.A.; McWilliam, M. [Waterloo Univ., ON (Canada). Dept. of Mechanical Engineering

    2006-07-01

    An increasingly popular solution to future energy demand is wind energy. Wind turbine designs can be grouped according to their axis of rotation, either horizontal or vertical. Horizontal axis wind turbines have higher power output in a good wind regime than vertical axis turbines and are used in most commercial class designs. Vertical axis Savonius-based wind turbine designs are still widely used in some applications because of their simplistic design and low wind speed performance. There are many design variables that must be considered in order to optimize the power output in a given wind regime in a typical wind turbine design. Using particle image velocimetry, a study of the air flow around five different model vertical axis wind turbines was conducted in a closed loop wind tunnel. A standard Savonius design with two semi-circular blades overlapping, and two variations of this design, a deep blade and a shallow blade design were among the turbine models included in this study. It also evaluated alternate designs that attempt to increase the performance of the standard design by allowing compound blade curvature. Measurements were collected at a constant phase angle and also at random rotor orientations. It was found that evaluation of the flow patterns and measured velocities revealed consistent and stable flow patterns at any given phase angle. Large scale flow structures are evident in all designs such as vortices shed from blade surfaces. An important performance parameter was considered to be the ability of the flow to remain attached to the forward blade and redirect and reorient the flow to the following blade. 6 refs., 18 figs.

  10. Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines

    Directory of Open Access Journals (Sweden)

    P. Guio

    Full Text Available The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.

    Key words. Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response function

  11. Astrometric radial velocities. I. Non-spectroscopic methods for measuring stellar radial velocity

    OpenAIRE

    1999-01-01

    High-accuracy astrometry permits the determination of not only stellar tangential motion, but also the component along the line-of-sight. Such non-spectroscopic (i.e. astrometric) radial velocities are independent of stellar atmospheric dynamics, spectral complexity and variability, as well as of gravitational redshift. Three methods are analysed: (1) changing annual parallax, (2) changing proper motion and (3) changing angular extent of a moving group of stars. All three have significant pot...

  12. Experimental measurement of non-Markovian dynamics and self-diffusion in a strongly coupled plasma

    CERN Document Server

    Strickler, T S; McQuillen, P; Daligault, J; Killian, T C

    2015-01-01

    We present a study of the collisional relaxation of ion velocities in a strongly coupled, ultracold neutral plasma on short timescales compared to the inverse collision rate. Non-exponential decay towards equilibrium for the average velocity of a tagged population of ions heralds non-Markovian dynamics and a breakdown of assumptions underlying standard kinetic theory. We prove the equivalence of the average-velocity curve to the velocity autocorrelation function, a fundamental statistical quantity that provides access to equilibrium transport coefficients and aspects of individual particle trajectories in a regime where experimental measurements have been lacking. From our data, we calculate the ion self-diffusion constant. This demonstrates the utility of ultracold neutral plasmas for isolating the effects of strong coupling on collisional processes, which is of interest for dense laboratory and astrophysical plasmas.

  13. Quantitative measurement of high flow velocities by a spin echo MR technique

    Energy Technology Data Exchange (ETDEWEB)

    Lin Yigun (First Military Medical Coll., Quangzhou, FJ (China)); Kojima, Akihiro; Shinzato, Jintetsu; Sakamoto, Yuji; Ueno, Sukeyoshi; Takahashi, Mutsumasa; Higashida, Yoshiharu

    A new method of flow measurement using a spin echo (SE) technique has been developed on the basis of the flow effect that at high velocities signal intensity decreases linearly with increasing flow velocity. Flow velocity is calculated from the signal intensity ratio of the flowing material in two images with the same imaging parameters but different echo times. The linear relationship between the signal intensity and flow velocity was examined with a steady flow phantom. When assessed with steady flows in the phantom, flow velocities calculated by this method were in good agreement with velocities measured by a flow meter. This method was used with ECG gating to measure the blood flow of the right common carotid artery of a healthy volunteer. The measured peak flow velocity and the pattern of flow velocities during systole correlated well with the results obtained by Doppler ultrasound. (author).

  14. Video measurements of fluid velocities and water levels in breaking waves

    CSIR Research Space (South Africa)

    Govender, K

    2002-01-01

    Full Text Available The cost-effective measurement of the velocity flow fields in breaking water waves, using particle and correlation image velocimetry, is described. The fluid velocities are estimated by tracking the motion of neutrally buoyant particles and aeration...

  15. General review of maximal aerobic velocity measurement at laboratory. Proposition of a new simplified protocol for maximal aerobic velocity assessment.

    Science.gov (United States)

    Berthon, P; Fellmann, N

    2002-09-01

    The maximal aerobic velocity concept developed since eighties is considered as either the minimal velocity which elicits the maximal aerobic consumption or as the "velocity associated to maximal oxygen consumption". Different methods for measuring maximal aerobic velocity on treadmill in laboratory conditions have been elaborated, but all these specific protocols measure V(amax) either during a maximal oxygen consumption test or with an association of such a test. An inaccurate method presents a certain number of problems in the subsequent use of the results, for example in the elaboration of training programs, in the study of repeatability or in the determination of individual limit time. This study analyzes 14 different methods to understand their interests and limits in view to propose a general methodology for measuring V(amax). In brief, the test should be progressive and maximal without any rest period and of 17 to 20 min total duration. It should begin with a five min warm-up at 60-70% of the maximal aerobic power of the subjects. The beginning of the trial should be fixed so that four or five steps have to be run. The duration of the steps should be three min with a 1% slope and an increasing speed of 1.5 km x h(-1) until complete exhaustion. The last steps could be reduced at two min for a 1 km x h(-1) increment. The maximal aerobic velocity is adjusted in relation to duration of the last step.

  16. Calibration of Instruments for Measuring Wind Velocity and Direction

    Science.gov (United States)

    Vogler, Raymond D.; Pilny, Miroslav J.

    1950-01-01

    Signal Corps wind equipment AN/GMQ-1 consisting of a 3-cup anemometer and wind vane was calibrated for wind velocities from 1 to 200 miles per hour. Cup-shaft failure prevented calibration at higher wind velocities. The action of the wind vane was checked and found to have very poor directional accuracy below a velocity of 8 miles per hour. After shaft failure was reported to the Signal Corps, the cup rotors were redesigned by strengthening the shafts for better operation at high velocities. The anemometer with the redesigned cup rotors was recalibrated, but cup-shaft failure occurred again at a wind velocity of approximately 220 miles per hour. In the course of this calibration two standard generators were checked for signal output variation, and a wind-speed meter was calibrated for use with each of the redesigned cup rotors. The variation of pressure coefficient with air-flow direction at four orifices on a disk-shaped pitot head was obtained for wind velocities of 37.79 53.6, and 98.9 miles per hour. A pitot-static tube mounted in the nose of a vane was calibrated up to a dynamic pressure of 155 pounds per square foot, or approximately 256 miles per hour,

  17. A study of the river velocity measurement techniques and analysis methods

    Science.gov (United States)

    Chung Yang, Han; Lun Chiang, Jie

    2013-04-01

    Velocity measurement technology can be traced back to the pitot tube velocity measurement method in the 18th century and today's velocity measurement technology use the acoustic and radar technology, with the Doppler principle developed technology advances, in order to develop the measurement method is more suitable for the measurement of velocity, the purpose is to get a more accurate measurement data and with the surface velocity theory, the maximum velocity theory and the indicator theory to obtain the mean velocity. As the main research direction of this article is to review the literature of the velocity measurement techniques and analysis methods, and to explore the applicability of the measurement method of the velocity measurement instruments, and then to describe the advantages and disadvantages of the different mean velocity profiles analysis method. Adequate review of the references of this study will be able to provide a reference for follow-up study of the velocity measurement. Review velocity measurement literature that different velocity measurement is required to follow the different flow conditions measured be upgraded its accuracy, because each flow rate measurement method has its advantages and disadvantages. Traditional velocity instrument can be used at low flow and RiverRAD microwave radar or imaging technology measurement method may be applied in high flow. In the tidal river can use the ADCP to quickly measure river vertical velocity distribution. In addition, urban rivers may be used the CW radar to set up on the bridge, and wide rivers can be used RiverRAD microwave radar to measure the velocities. Review the relevant literature also found that using Ultrasonic Doppler Current Profiler with the Chiu's theory to the velocity of observing automation work can save manpower and resources to improve measurement accuracy, reduce the risk of measurement, but the great variability of river characteristics in Taiwan and a lot of drifting floating

  18. Measuring Velocities in the Early Stage of an Eruption: Using “Overlappogram” Data from Hinode EIS

    Science.gov (United States)

    Harra, Louise K.; Hara, Hirohisa; Doschek, George A.; Matthews, Sarah; Warren, Harry; Culhane, J. Leonard; Woods, Magnus M.

    2017-06-01

    In order to understand the onset phase of a solar eruption, plasma parameter measurements in the early phases are key to constraining models. There are two current instrument types that allow us to make such measurements: narrow-band imagers and spectrometers. In the former case, even narrow-band filters contain multiple emission lines, creating some temperature confusion. With imagers, however, rapid cadences are achievable and the field of view can be large. Velocities of the erupting structures can be measured by feature tracking. In the spectrometer case, slit spectrometers can provide spectrally pure images by “rastering” the slit to build up an image. This method provides limited temporal resolution, but the plasma parameters can be accurately measured, including velocities along the line of sight. Both methods have benefits and are often used in tandem. In this paper we demonstrate for the first time that data from the wide slot on the Hinode EUV Imaging Spectrometer, along with imaging data from AIA, can be used to deconvolve velocity information at the start of an eruption, providing line-of-sight velocities across an extended field of view. Using He ii 256 Å slot data at flare onset, we observe broadening or shift(s) of the emission line of up to ±280 km s-1. These are seen at different locations—the redshifted plasma is seen where the hard X-ray source is later seen (energy deposition site). In addition, blueshifted plasma shows the very early onset of the fast rise of the filament.

  19. Toroidal momentum pinch velocity due to the coriolis drift effect on small scale instabilities in a toroidal plasma.

    Science.gov (United States)

    Peeters, A G; Angioni, C; Strintzi, D

    2007-06-29

    In this Letter, the influence of the "Coriolis drift" on small scale instabilities in toroidal plasmas is shown to generate a toroidal momentum pinch velocity. Such a pinch results because the Coriolis drift generates a coupling between the density and temperature perturbations on the one hand and the perturbed parallel flow velocity on the other. A simple fluid model is used to highlight the physics mechanism and gyro-kinetic calculations are performed to accurately assess the magnitude of the pinch. The derived pinch velocity leads to a radial gradient of the toroidal velocity profile even in the absence of a torque on the plasma and is predicted to generate a peaking of the toroidal velocity profile similar to the peaking of the density profile. Finally, the pinch also affects the interpretation of current experiments.

  20. Plasma dynamics near critical density inferred from direct measurements of laser hole boring.

    Science.gov (United States)

    Gong, Chao; Tochitsky, Sergei Ya; Fiuza, Frederico; Pigeon, Jeremy J; Joshi, Chan

    2016-06-01

    We have used multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, v_{HB}, of the density cavity pushed forward by a train of CO_{2} laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the v_{HB} falls rapidly as the laser pulse intensity falls at the back of the laser pulse train. A heuristic theory is presented that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. The measured values of v_{HB}, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.

  1. Measuring 3D Velocity Vectors using the Transverse Oscillation Method

    DEFF Research Database (Denmark)

    Pihl, Michael Johannes; Jensen, Jørgen Arendt

    2012-01-01

    Experimentally obtained estimates of threedimensional (3D) velocity vectors using the 3D Transverse Oscillation (TO) method are presented. The method employs a 2D transducer and synthesizes two double-oscillating fields in receive to obtain the axial, transverse, and elevation velocity components...... simultaneously. Experimental data are acquired using the ultrasound research scanner SARUS. The double-oscillating TO fields are investigated in an experimental scanning tank setup. The results demonstrate that the created fields only oscillate in the axial plus either the transverse or the elevation direction...

  2. Velocity measurement technique for high-speed targets based on digital fine spectral line tracking

    Institute of Scientific and Technical Information of China (English)

    Wen Shuliang; Yuan Qi

    2006-01-01

    Target velocity and acceleration are two of the most important features for identification of warheads and decoys in ballistic missile defense phased array radar systems. Velocity compensation is also the necessary step for one-dimensional range profile imaging. According to the high-velocity characteristics of ballistic objects and the low data rate of phased array radars with multiple target tracking, a fine spectral line digital velocity tracking frame is presented and a new method is developed to extract velocity error and resolve the velocity ambiguity in the measurement loop. Simulation results demonstrate the effectiveness of the proposed technique.

  3. Astrometric radial velocities. I. Non-spectroscopic methods for measuring stellar radial velocity

    Science.gov (United States)

    Dravins, Dainis; Lindegren, Lennart; Madsen, Søren

    1999-08-01

    High-accuracy astrometry permits the determination of not only stellar tangential motion, but also the component along the line-of-sight. Such non-spectroscopic (i.e. astrometric) radial velocities are independent of stellar atmospheric dynamics, spectral complexity and variability, as well as of gravitational redshift. Three methods are analysed: (1) changing annual parallax, (2) changing proper motion and (3) changing angular extent of a moving group of stars. All three have significant potential in planned astrometric projects. Current accuracies are still inadequate for the first method, while the second is marginally feasible and is here applied to 16 stars. The third method reaches high accuracy (accuracy limit is set by uncertainties in the cluster expansion rate. Based (in part) on observations by the ESA Hipparcos satellite

  4. Astrometric radial velocities; 1, Non-spectroscopic methods for measuring stellar radial velocity

    CERN Document Server

    Dravins, D; Madsen, S; Dravins, Dainis; Lindegren, Lennart; Madsen, Soren

    1999-01-01

    High-accuracy astrometry permits the determination of not only stellar tangential motion, but also the component along the line-of-sight. Such non-spectroscopic (i.e. astrometric) radial velocities are independent of stellar atmospheric dynamics, spectral complexity and variability, as well as of gravitational redshift. Three methods are analysed: (1) changing annual parallax, (2) changing proper motion and (3) changing angular extent of a moving group of stars. All three have significant potential in planned astrometric projects. Current accuracies are still inadequate for the first method, while the second is marginally feasible and is here applied to 16 stars. The third method reaches high accuracy (<1 km/s) already with present data, although for some clusters an accuracy limit is set by uncertainties in the cluster expansion rate.

  5. Aortic pulse wave velocity measurement in systemic sclerosis patients

    Directory of Open Access Journals (Sweden)

    M. Sebastiani

    2012-12-01

    Full Text Available Background. Systemic sclerosis (SSc is characterized by endothelial dysfunction and widespread microangiopathy. However, a macrovascular damage could be also associated. Aortic pulse wave velocity (aPWV is known to be a reliable indicator of arterial stiffness and a useful prognostic predictor of cardiovascular events. Moreover, aPWV may be easily measured by non-invasive, user-friendly tool. Aim of our study was to evaluate aPWV alterations in a series of SSc patients. Methods. The aPWV was evaluated in 35 consecutive female SSc patients and 26 sex- and age-matched healthy controls. aPWV alterations were correlated with cardiopulmonary involvement. Results. A significant increase of aPWV was observed in SSc patients compared to controls (9.4±3.2 m/s vs 7.3±1 m/s; P=0.002. In particular, 14/35 (40% SSc patients and only 1/26 (4% controls (P=0.0009 showed increased aPWV (>9 m/s cut-off value. Moreover, echocardiography evaluation showed an increased prevalence of right atrial and ventricular dilatation (atrial volume: 23.6±6.2 mL vs 20.3±4.3 mL, P=0.026; ventricular diameter 19.5±4.9 mm vs 15.9±1.6 mm; P=0.001 associated to higher values of pulmonary arterial systolic pressure (PAPs in SSc patients (31.5±10.4 mmHg vs 21.6±2.9 mmHg; P50 years old. Furthermore, altered aPWV was more frequently associated with limited cutaneous pattern, longer disease duration (≥5 years, and/or presence of anticentromere antibody (ACA. Conclusions. A significantly higher prevalence of abnormally increased aPWV was evidenced in SSc patients compared to healthy controls. The possibility of more pronounced and diffuse vascular damage in a particular SSc subset (ACA-positive subjects with limited cutaneous scleroderma and longer disease duration might be raised.

  6. Measuring surface current velocities in the Agulhas region with ASAR

    CSIR Research Space (South Africa)

    Rouault, MJ

    2010-01-01

    Full Text Available velocities for oceanographic research in the Agulhas Current are assessed. Comparisons between radar, altimetry and surface drifters observations of the surface currents show that accurate wind fields are a strong pre-requisite to the derivation of meaningful...

  7. Measurements of ion temperature and flow of pulsed plasmas produced by a magnetized coaxial plasma gun device using an ion Doppler spectrometer

    Science.gov (United States)

    Kitagawa, Y.; Sakuma, I.; Iwamoto, D.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2012-10-01

    It is important to know surface damage characteristics of plasma-facing component materials during transient heat and particle loads such as type I ELMs. A magnetized coaxial plasma gun (MCPG) device has been used as transient heat and particle source in ELM simulation experiments. Characteristics of pulsed plasmas produced by the MCPG device play an important role for the plasma material interaction. In this study, ion temperature and flow velocity of pulsed He plasmas were measured by an ion Doppler spectrometer (IDS). The IDS system consists of a light collection system including optical fibers, 1m-spectrometer and a 16 channel photomultiplier tube (PMT) detector. The IDS system measures the width and Doppler shift of HeII (468.58 nm) emission line with the time resolution of 1 μs. The Doppler broadened and shifted spectra were measured with 45 and 135 degree angles with respect to the plasmoid traveling direction. The observed emission line profile was represented by sum of two Gaussian components to determine the temperature and flow velocity. The minor component at around the wavelength of zero-velocity was produced by the stationary plasma. As the results, the ion velocity and temperature were 68 km/s and 19 eV, respectively. Thus, the He ion flow energy is 97 eV. The observed flow velocity agrees with that measured by a time of flight technique.

  8. Mathematical Relationships Between Two Sets of Laser Anemometer Measurements for Resolving the Total Velocity Vector

    Science.gov (United States)

    Owen, Albert K.

    1993-01-01

    The mathematical relations between the measured velocity fields for the same compressor rotor flow field resolved by two fringe type laser anemometers at different observational locations are developed in this report. The relations allow the two sets of velocity measurements to be combined to produce a total velocity vector field for the compressor rotor. This report presents the derivation of the mathematical relations, beginning with the specification of the coordinate systems and the velocity projections in those coordinate systems. The vector projections are then transformed into a common coordinate system. The transformed vector coordinates are then combined to determine the total velocity vector. A numerical example showing the solution procedure is included.

  9. The velocity distribution of pickup He{sup +} measured at 0.3 AU by MESSENGER

    Energy Technology Data Exchange (ETDEWEB)

    Gershman, Daniel J. [Geospace Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Fisk, Lennard A.; Gloeckler, George; Raines, Jim M.; Slavin, James A.; Zurbuchen, Thomas H. [Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Solomon, Sean C., E-mail: djgersh@umich.edu [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States)

    2014-06-20

    During its interplanetary trajectory in 2007-2009, the MErcury Surface, Space ENvrionment, GEochemistry, and Ranging (MESSENGER) spacecraft passed through the gravitational focusing cone for interstellar helium multiple times at a heliocentric distance R ≈ 0.3 AU. Observations of He{sup +} interstellar pickup ions made by the Fast Imaging Plasma Spectrometer sensor on MESSENGER during these transits provide a glimpse into the structure of newly formed inner heliospheric pickup-ion distributions. This close to the Sun, these ions are picked up in a nearly radial interplanetary magnetic field. Compared with the near-Earth environment, pickup ions observed near 0.3 AU will not have had sufficient time to be energized substantially. Such an environment results in a nearly pristine velocity distribution function that should depend only on pickup-ion injection velocities (related to the interstellar gas), pitch-angle scattering, and cooling processes. From measured energy-per-charge spectra obtained during multiple spacecraft observational geometries, we have deduced the phase-space density of He{sup +} as a function of magnetic pitch angle. Our measurements are most consistent with a distribution that decreases nearly monotonically with increasing pitch angle, rather than the more commonly modeled isotropic or hemispherically symmetric forms. These results imply that pitch-angle scattering of He{sup +} may not be instantaneous, as is often assumed, and instead may reflect the velocity distribution of initially injected particles. In a slow solar wind stream, we find a parallel-scattering mean free path of λ {sub ||} ∼ 0.1 AU and a He{sup +} production rate of ∼0.05 m{sup –3} s{sup –1} within 0.3 AU.

  10. Speckle-based three-dimensional velocity measurement using spatial filtering velocimetry

    DEFF Research Database (Denmark)

    Iversen, Theis Faber Quist; Jakobsen, Michael Linde; Hanson, Steen Grüner

    2011-01-01

    We present an optical method for measuring the real-time three-dimensional (3D) translational velocity of a diffusely scattering rigid object observed through an imaging system. The method is based on a combination of the motion of random speckle patterns and regular fringe patterns. The speckle...... spatial filters designed to measure the three components of the object’s translational velocity. Furthermore, experimental data are presented that demonstrate full 3D velocity measurement....

  11. Flowing dusty plasma experiments: Generation of flow and measurement techniques

    CERN Document Server

    Jaiswal, S; Sen, A

    2016-01-01

    A variety of experimental techniques for the generation of subsonic/supersonic dust fluid flows and means of measuring such flow velocities are presented. The experiments have been carried out in a $\\Pi-$shaped Dusty Plasma Experimental (DPEx) device with micron size kaolin/Melamine Formaldehyde (MF) particles embedded in a background of Argon plasma created by a direct current (DC) glow discharge. A stationary dust cloud is formed over the cathode region by precisely balancing the pumping speed and gas flow rate. A flow of dust particles/fluid is generated by additional gas injection from a single or dual locations or by altering the dust confining potential. The flow velocity is then estimated by three different techniques, namely, by super Particle Identification (sPIT) code, Particle Image Velocimetry (PIV) analysis and the excitation of Dust Acoustic Waves (DAWs). The results obtained from these three different techniques along with their merits and demerits are discussed. An estimation of the neutral dr...

  12. Measuring In-Situ Mdf Velocity Of Detonation

    Science.gov (United States)

    Horine, Frank M.; James, Jr., Forrest B.

    2005-10-25

    A system for determining the velocity of detonation of a mild detonation fuse mounted on the surface of a device includes placing the device in a predetermined position with respect to an apparatus that carries a couple of sensors that sense the passage of a detonation wave at first and second spaced locations along the fuse. The sensors operate a timer and the time and distance between the locations is used to determine the velocity of detonation. The sensors are preferably electrical contacts that are held spaced from but close to the fuse such that expansion of the fuse caused by detonation causes the fuse to touch the contact, causing an electrical signal to actuate the timer.

  13. Retinal hemodynamic oxygen reactivity assessed by perfusion velocity, blood oximetry and vessel diameter measurements

    DEFF Research Database (Denmark)

    Klefter, Oliver Niels; Lauritsen, Anne Øberg; Larsen, Michael

    2015-01-01

    PURPOSE: To test the oxygen reactivity of a fundus photographic method of measuring macular perfusion velocity and to integrate macular perfusion velocities with measurements of retinal vessel diameters and blood oxygen saturation. METHODS: Sixteen eyes in 16 healthy volunteers were studied at two...... measurements may provide comprehensive information about retinal metabolism....

  14. Electrical conductivity and velocity of highly ionized plasma flows - Theory and experiment.

    Science.gov (United States)

    Vendell, E. W.; Park, C.; Posch, R. E.

    1972-01-01

    Use of an immersible, three-coil, magnetic-induction probe, previously tested in a low-density supersonic argon jet, to measure electrical conductivity and velocity profiles of a highly ionized high-density nitrogen jet in the continuum flow regime where effects due to probe bow shocks and boundary layers might not be negligible. Measured centerline values of electrical conductivity and velocity were compared with predictions based on a theoretical analysis previously developed to study the gas as it expanded adiabatically and inviscidly from an equilibrium sonic state to the nozzle exit. The resulting numerical exit plane values for electron density and electron temperature were then substituted into the Spitzer-Haerm conductivity formula to compute a theoretical conductivity which agreed within 40% of the measured conductivity, while the calculated and experimental velocity values differed by as much as 50%. The lack of agreement was attributed to the possible use of invalid assumptions and boundary conditions in the computer analysis or to the unknown effects of shocks on the probe data.

  15. Characterization of High-Velocity Single Particle Impacts on Plasma-Sprayed Ceramic Coatings

    Science.gov (United States)

    Kiilakoski, Jarkko; Lindroos, Matti; Apostol, Marian; Koivuluoto, Heli; Kuokkala, Veli-Tapani; Vuoristo, Petri

    2016-08-01

    High-velocity impact wear can have a significant effect on the lifetime of thermally sprayed coatings in multiple applications, e.g., in the process and paper industries. Plasma-sprayed oxide coatings, such as Cr2O3- and TiO2-based coatings, are often used in these industries in wear and corrosion applications. An experimental impact study was performed on thermally sprayed ceramic coatings using the High-Velocity Particle Impactor (HVPI) at oblique angles to investigate the damage, failure, and deformation of the coated structures. The impact site was characterized by profilometry, optical microscopy, and scanning electron microscopy (SEM). Furthermore, the connection between the microstructural details and impact behavior was studied in order to reveal the damage and failure characteristics at a more comprehensive level. Differences in the fracture behavior were found between the thermally sprayed Cr2O3 and TiO2 coatings, and a concept of critical impact energy is presented here. The superior cohesion of the TiO2 coating inhibited interlamellar cracking while the Cr2O3 coating suffered greater damage at high impact energies. The HVPI experiment has proven to be able to produce valuable information about the deformation behavior of coatings under high strain rates and could be utilized further in the development of wear-resistant coatings.

  16. Scaling of X-ray emission and ion velocity in laser produced Cu plasmas

    Science.gov (United States)

    Prasad, Y. B. S. R.; Senecha, V. K.; Pant, H. C.; Kamath, M. P.; Solanki, G. S.; Tripathi, P. K.; Kulkarni, A. P.; Gupta, S.; Pareek, R.; Joshi, A. S.; Sreedhar, N.; Nigam, Sameer; Navathe, C. P.

    2000-11-01

    The x-ray emission from slab targets of copper irradiated by Nd:glass laser (1.054 m m, 5 and 15 ns) at intensities between 1012 and 1014 W/cm2 has been studied. The x-ray emissions were monitored with the help of high quantum efficiency x-ray silicon photo diodes and vacuum photo diodes, all covered with aluminium filters of different thickness. The x-ray intensity vs the laser intensity has a scaling factor of (1.2--1.92). The relative x-ray conversion efficiency follows an empirical relationship which is in close agreement with the one reported by Babonneau et al. The ion velocities were monitored using Langmuir probes placed at different angles and radial distances from the target position. The variation of the ion velocity with the laser intensity follows a scaling of the form Fb where b ~ 0.22 which is in good agreement with the reported scaling factor values. The results on the x-ray emission from Cu plasma are reported.

  17. Scaling of x-ray emission and ion velocity in laser produced Cu plasmas

    Indian Academy of Sciences (India)

    Y B S R Prasad; V K Senecha; H C Pant; M P Kamath; G S Solanki; P K Tripathi; A P Kulkarni; S Gupta; R Pareek; A S Joshi; N Sreedhar; Sameer Nigam; C P Navathe

    2000-11-01

    The x-ray emission from slab targets of copper irradiated by Nd:glass laser (1.054 m, 5 and 15 ns) at intensities between 1012 and 1014W/cm2 has been studied. The x-ray emissions were monitored with the help of high quantum efficiency x-ray silicon photo diodes and vacuum photo diodes, all covered with aluminium filters of different thickness. The x-ray intensity vs the laser intensity has a scaling factor of (1.2–1.92). The relative x-ray conversion efficiency follows an empirical relationship which is in close agreement with the one reported by Babonneau et al. The ion velocities were monitored using Langmuir probes placed at different angles and radial distances from the target position. The variation of the ion velocity with the laser intensity follows a scaling of the form where ∼ 0.22 which is in good agreement with the reported scaling factor values. The results on the x-ray emission from Cu plasma are reported.

  18. Plasma Density Measurements in Cable Gun Experiments with a Sensitive He-Ne Interferometer

    Institute of Scientific and Technical Information of China (English)

    CHEN Lin; HE An; JIANG Wei; XU Min; WU Shoudong; LI Ye

    2007-01-01

    A time-resolved sensitive He-Ne laser interferometer without complicated active stabilization was built up and applied to low-density plasma measurements. A precision of about 0.2° in phase measurements was achieved with a minimum line-integrated plasma density as low as 8.3×l013 cm-2. With this interferometer, the characteristics of the plasma generated by a cable plasma gun was investigated systematically. The reproducibility, spatial and temporal distributions and the averaged injection velocity of the plasma are presented. In addition, the interaction of the plasma flow with a conductor was studied by placing a metal plate in the downstream of the cable gun.

  19. Plasma Density Measurements on Refuelling by Solid Hydrogen Pellets in a Rotating Plasma

    DEFF Research Database (Denmark)

    Jørgensen, L. W.; Sillesen, A. H.

    1978-01-01

    The authors used laser interferometry to directly measure the increase in plasma density caused by the ablation of a solid hydrogen pellet situated in a rotating plasma.......The authors used laser interferometry to directly measure the increase in plasma density caused by the ablation of a solid hydrogen pellet situated in a rotating plasma....

  20. Measurements of Spatially Resolved Velocity Variations in Shock Compressed Heterogeneous Materials Using a Line-Imaging Velocity Interferometer

    Energy Technology Data Exchange (ETDEWEB)

    ASAY,JAMES R.; CHHABILDAS,LALIT C.; KNUDSON,MARCUS D.; TROTT,WAYNE M.

    1999-09-01

    Relatively straightforward changes in the optical design of a conventional optically recording velocity interferometer system (ORVIS) can be used to produce a line-imaging velocity interferometer wherein both temporal and spatial resolution can be adjusted over a wide range. As a result line-imaging ORVIS can be tailored to a variety of specific applications involving dynamic deformation of heterogeneous materials as required by the characteristic length scale of these materials (ranging from a few {micro}m for ferroelectric ceramics to a few mm for concrete). A line-imaging ORVIS has been successfully interfaced to the target chamber of a compressed gas gun driver and fielded on numerous tests in combination with simultaneous measurements using a dual delay-leg, ''push-pull'' VISAR system. These tests include shock loading of glass-reinforced polyester composites, foam reverberation experiments (measurements at the free surface of a thin aluminum plate impacted by foam), and measurements of dispersive velocity in a shock-loaded explosive simulant (sugar). Comparison of detailed spatially-resolved material response to the spatially averaged VISAR measurements will be discussed.

  1. Plasma ion composition measurements for Europa

    Science.gov (United States)

    Sittler, E. C.; Cooper, J. F.; Hartle, R. E.; Paterson, W. R.; Christian, E. R.; Lipatov, A. S.; Mahaffy, P. R.; Paschalidis, N. P.; Coplan, M. A.; Cassidy, T. A.; Richardson, J. D.; Fegley, B.; Andre, N.

    2013-11-01

    Jupiter magnetospheric interactions and surface composition, both important to subsurface ocean detection for the Galilean icy moons Europa, Ganymede, and Callisto, can be measured using plasma ion mass spectrometry on either an orbiting spacecraft or one designed for multiple flybys of these moons. Detection of emergent oceanic materials at the Europa surface is more likely than at Ganymede and Callisto. A key challenge is to resolve potential intrinsic Europan materials from the space weathering patina of iogenic species implanted onto the sensible surface by magnetospheric interactions. Species-resolved measurements of pickup ion currents are also critical to extraction of oceanic induced magnetic fields from magnetospheric interaction background dominated by these currents. In general the chemical astrobiological potential of Europa should be determined through the combination of surface, ionospheric, and pickup ion composition measurements. The requisite Ion Mass Spectrometer (IMS) for these measurements would need to work in the high radiation environment of Jupiter's magnetosphere between the orbits of Europa and Ganymede, and beyond. A 3D hybrid model of the moon-magnetosphere interaction is also needed to construct a global model of the electric and magnetic fields, and the plasma environment, around Europa. Europa's ionosphere is probably usually dominated by hot pickup ions with 100-1000 eV temperatures, excursions to a "classical" cold ionosphere likely being infrequent. A field aligned ionospheric wind driven by the electron polarization electric field should arise and be measurable.

  2. Multiwavelength Observations of Supersonic Plasma Blob Triggered by Reconnection Generated Velocity Pulse in AR10808

    CERN Document Server

    Srivastava, A K; Murawski, K; Kumar, Pankaj

    2012-01-01

    Using multi-wavelength observations of Solar and Heliospheric Observatory (SoHO)/Michelson Doppler Imager (MDI), Transition Region and Coronal Explorer (TRACE) 171 \\AA, and H$\\alpha$ from Culgoora Solar Observatory at Narrabri, Australia, we present a unique observational signature of a propagating supersonic plasma blob before an M6.2 class solar flare in AR10808 on 9th September 2005. The blob was observed between 05:27 UT to 05:32 UT with almost a constant shape for the first 2-3 minutes, and thereafter it quickly vanished in the corona. The observed lower bound speed of the blob is estimated as $\\sim$215 km s$^{-1}$ in its dynamical phase. The evidence of the blob with almost similar shape and velocity concurrent in H$\\alpha$ and TRACE 171 \\AA\\ supports its formation by multi-temperature plasma. The energy release by a recurrent 3-D reconnection process via the separator dome below the magnetic null point, between the emerging flux and pre-existing field lines in the lower solar atmosphere, is found to be...

  3. A generalized AZ-non-Maxwellian velocity distribution function for space plasmas

    Science.gov (United States)

    Abid, A. A.; Khan, M. Z.; Lu, Quanming; Yap, S. L.

    2017-03-01

    A more generalized form of the non-Maxwellian distribution function, i.e., the AZ-distribution function is presented. Its fundamental properties are numerically observed by the variation of three parameters: α (rate of energetic particles on the shoulder), r (energetic particles on a broad shoulder), and q (superthermality on the tail of the velocity distribution curve of the plasma species). It has been observed that (i) the A Z - distribution function reduces to the ( r , q ) - distribution for α → 0 ; (ii) the A Z - distribution function reduces to the q - distribution for α → 0 , and r → 0 ; (iii) the A Z -distribution reduces to Cairns-distribution function for r → 0 , and q → ∞ ; (iv) the AZ-distribution reduces to Vasyliunas Cairns distribution for r → 0 , and q = κ + 1 ; (v) the AZ-distribution reduces to kappa distribution for α → 0 , r → 0 , and q = κ + 1 ; and (vi) finally, the AZ-distribution reduces to Maxwellian distribution for α → 0 , r → 0 , and q → ∞ . The uses of this more generalized A Z - distribution function in various space plasmas are briefly discussed.

  4. Embedded Fiber Optic Probes to Measure Detonation Velocities Using the Photonic Doppler Velocimeter

    Energy Technology Data Exchange (ETDEWEB)

    Hare, D E; Holtkamp, D B; Strand, O T

    2010-03-02

    Detonation velocities for high explosives can be in the 7 to 8 km/s range. Previous work has shown that these velocities may be measured by inserting an optical fiber probe into the explosive assembly and recording the velocity time history using a Fabry-Perot velocimeter. The measured velocity using this method, however, is the actual velocity multiplied times the refractive index of the fiber core, which is on the order of 1.5. This means that the velocimeter diagnostic must be capable of measuring velocities as high as 12 km/s. Until recently, a velocity of 12 km/s was beyond the maximum velocity limit of a homodyne-based velocimeter. The limiting component in a homodyne system is usually the digitizer. Recently, however, digitizers have come on the market with 20 GHz bandwidth and 50 GS/s sample rate. Such a digitizer coupled with high bandwidth detectors now have the total bandwidth required to make velocity measurements in the 12 km/s range. This paper describes measurements made of detonation velocities using a high bandwidth homodyne system.

  5. Measurements of electron drift velocity in isobutane using the pulsed Townsend technique

    Energy Technology Data Exchange (ETDEWEB)

    Vivaldini, Tulio C.; Lima, Iara B.; Goncalves, Josemary A.C.; Botelho, Suzana; Tobias, Carmen C.B. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Ridenti, Marco A.; Pascholati, Paulo R. [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica. Lab. do Acelerador Linear; Fonte, Paulo; Mangiarotti, Alessio [Universidade de Coimbra (Portugal). Dept. de Fisica. Lab. de Instrumentacao e Fisica Experimental de Particulas

    2010-07-01

    Full text. The electron drift velocity characterizes the electric conductivity of weakly ionized gases and is one of the most important transport parameters for simulation and modeling of radiation detectors and plasma discharges. This work presents the results of electron drift velocity as a function of the reduced electric field obtained in nitrogen and isobutane by the Pulsed Townsend technique. Due to its excellent timing properties, isobutane is a common component of standard mixtures used in RPCs (Resistive Plate Chambers), however, at moderate electric fields strength (50 Td <= E/N <= 200 Td), there are insufficient data available in literature for this gas. In our experimental apparatus, electrons are liberated from an aluminum cathode (40mm diameter) due to the incidence of a nitrogen laser beam (MNL202-LD LTB) and are accelerated by the applied electric field toward the anode, made of a high resistivity glass (2 x 10{sup 10} {Omega}{center_dot}m). The fast electric signals generated is amplified and were digitalized in a 1 GHz bandwidth oscilloscope to measure the electrons transit time and to calculate the electron drift velocity in different gaps between anode and cathode. As the timing information presented in the fast electric signal originated in the anode is significant in our application, the amplifier circuit had to hold special features in order to preserve the signal shape. The linear amplifier used, based on the BGM1013 integrated circuit (Philips R), reaches up to 2.1 GHz bandwidth with 35.5 dB gain and was developed and built at Laboratory of Instrumentation and Experimental Particles Physics/Portugal. In order to validate this method, measurements were initially carried out in pure nitrogen, in reduced electric fields ranging from 148 to 194 Td. These results showed good agreement with those found in the literature for this largely investigated gas. The measurements of electron drift velocities in pure isobutane were performed as a function

  6. Rotation Rate of Saturn's Magnetosphere using CAPS Plasma Measurements

    Science.gov (United States)

    Sittler, E.; Cooper, J.; Simpson, D.; Paterson, W.

    2012-01-01

    We present the present status of an investigation of the rotation rate of Saturn 's magnetosphere using a 3D velocity moment technique being developed at Goddard which is similar to the 2D version used by Sittler et al. (2005) [1] for SOI and similar to that used by Thomsen et al. (2010). This technique allows one to nearly cover the full energy range of the CAPS IMS from 1 V less than or equal to E/Q less than 50 kV. Since our technique maps the observations into a local inertial frame, it does work during roll manoeuvres. We have made comparisons with Wilson et al. (2008) [2] (2005-358 and 2005-284) who performs a bi-Maxwellian fit to the ion singles data and our results are nearly identical. We will also make comparisons with results by Thomsen et al. (2010) [3]. Our analysis uses ion composition data to weight the non-compositional data, referred to as singles data, to separate H+, H2+ and water group ions (W+) from each other. The ion data set is especially valuable for measuring flow velocities for protons, which are more difficult to derive using singles data within the inner magnetosphere, where the signal is dominated by heavy ions (i.e., proton peak merges with W+ peak as low energy shoulder). Our technique uses a flux function, which is zero in the proper plasma flow frame, to estimate fluid parameter uncertainties. The comparisons investigate the experimental errors and potential for systematic errors in the analyses, including ours. The rolls provide the best data set when it comes to getting 4PI coverage of the plasma but are more susceptible to time aliasing effects. Since our analysis is a velocity moments technique it will work within the inner magnetosphere where pickup ions are important and velocity distributions are non-Maxwellian. So, we will present results inside Enceladus' L shell and determine if mass loading is important. In the future we plan to make comparisons with magnetic field observations, use Saturn ionosphere conductivities as

  7. Measurement of velocity of air flow in the sinus maxillaris.

    Science.gov (United States)

    Müsebeck, K; Rosenberg, H

    1979-03-01

    Anemometry with the hot wire and hot film technique previously described, enables the rhinologist to record slow and rapidly changing air flow in the maxillary sinus. The advantages and disadvantages of this method are considered. Anemometry together with manometry may be designated sinumetry and used as a diagnostic procedure following sinuscopy in chronic maxillary sinus disease. The value of the function from velocity of time allows the estimation of flow-volume in the sinus. Furthermore, the method is useful to evaluate the optimal therapy to restore ventilation in the case of an obstructed ostium demonstrated before and after surgical opening in the inferior meatus.

  8. Velocity distribution measurements in atomic beams generated using laser induced back-ablation

    CERN Document Server

    Denning, A; Lee, S; Ammonson, M; Bergeson, S D

    2008-01-01

    We present measurements of the velocity distribution of calcium atoms in an atomic beam generated using a dual-stage laser back-ablation apparatus. Distributions are measured using a velocity selective Doppler time-of-flight technique. They are Boltzmann-like with rms velocities corresponding to temperatures above the melting point for calcium. Contrary to a recent report in the literature, this method does not generate a sub-thermal atomic beam.

  9. Uncertainty in velocity measurement based on diode-laser absorption in nonuniform flows

    OpenAIRE

    Li, Fei; Yu, XiLong; Cai, Weiwei; Ma, Lin

    2012-01-01

    This work investigates the error caused by nonuniformities along the line-of-sight in velocity measurement using tunable diode-laser absorption spectroscopy (TDLAS). Past work has demonstrated TDLAS as an attractive diagnostic technique for measuring velocity, which is inferred from the Doppler shift of two absorption features using two crossing laser beams. However, because TDLAS is line-of-sight in nature, the obtained velocity is a spatially averaged value along the probing laser beams. As...

  10. Precision measurement of transverse velocity distribution of a strontium atomic beam

    OpenAIRE

    Gao, F.; H. Liu; Xu, P.; X. Tian; Y. Wang; Ren, J; Haibin Wu; Hong Chang

    2014-01-01

    We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that the resolution of the measured velocity can reach 0.13 m/s, corresponding to 90$\\mu K$ in energy units. The experimental results are in very good agreement with the results of theoretical calculations. Based on the spectroscopic techniques use...

  11. Application of image cross-correlation to the measurement of glacier velocity using satellite image data

    Science.gov (United States)

    Scambos, Theodore A.; Dutkiewicz, Melanie J.; Wison, Jeremy C.; Bindschadler, Robert A.

    1992-01-01

    A high-resolution map of the velocity field of the central portion of Ice Stream E in West Antarctica, generated by the displacement-measuring technique, is presented. The use of cross-correlation software is found to be a significant improvement over previous manually based photogrammetric methods for velocity measurement, and is far more cost-effective than in situ methods in remote polar areas. A hue-intensity-saturation image of Ice Stream E and its velocity field is shown.

  12. Increase of the Density, Temperature and Velocity of Plasma Jets driven by a Ring of High Energy Laser Beams

    OpenAIRE

    Fu, Wen; Liang, Edison P.; Fatenejad, Milad; Lamb, Donald Q.; Grosskopf, Michael; Park, Hye-Sook; Remington, Bruce; Spitkovsky, Anatoly

    2012-01-01

    Supersonic plasma outflows driven by multi-beam, high-energy lasers, such as Omega and NIF, have been and will be used as platforms for a variety of laboratory astrophysics experiments. Here we propose a new way of launching high density and high velocity, plasma jets using multiple intense laser beams in a hollow ring formation. We show that such jets provide a more flexible and versatile platform for future laboratory astrophysics experiments. Using high resolution hydrodynamic simulations,...

  13. Velocity measurements of low Reynolds number tube flow using fiber-optic technology

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, J.C.

    1993-03-01

    In 1988 Nielsen started work to measure the spatial variability of the mass flux vector being transported in a porous medium. To measure the spatial variability of the mass flux vector, the spatial variability of its components(velocity, concentration) must be measured. Nielsen was successful in measuring the pore level concentration at many different pores and in verifying the assumption that a nonuniform concentration field exists within the mixing zone between two miscible fluids. However, Nielsen was unable to conduct the necessary pore level velocity measurements needed. Nielsen's work is being continued and a probe is being developed that will measure both velocity and concentration components at pore level. The probe is essentially the same probe used to make the pore level concentration measurements with added capabilities needed to make the velocity measurements. This probe has several design variables, dealing primarily with the velocity component, that need further investigation. The research presented in this thesis investigates these parameters by performing experiments in a capillary tube. The tube is a controlled system where the velocity of the fluid can be determined from the volumetric flow rate using Poiseuille's solution for viscous flow. Also, a statistically based relationship between the velocity measured with the probe and the velocity determined from the volumetric flow rate has been developed.

  14. Velocity measurements of low Reynolds number tube flow using fiber-optic technology

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, J. Christopher [Univ. of Vermont, Burlington, VT (United States)

    1993-03-01

    In 1988 Nielsen started work to measure the spatial variability of the mass flux vector being transported in a porous medium. To measure the spatial variability of the mass flux vector, the spatial variability of its components(velocity, concentration) must be measured. Nielsen was successful in measuring the pore level concentration at many different pores and in verifying the assumption that a nonuniform concentration field exists within the mixing zone between two miscible fluids. However, Nielsen was unable to conduct the necessary pore level velocity measurements needed. Nielsen`s work is being continued and a probe is being developed that will measure both velocity and concentration components at pore level. The probe is essentially the same probe used to make the pore level concentration measurements with added capabilities needed to make the velocity measurements. This probe has several design variables, dealing primarily with the velocity component, that need further investigation. The research presented in this thesis investigates these parameters by performing experiments in a capillary tube. The tube is a controlled system where the velocity of the fluid can be determined from the volumetric flow rate using Poiseuille`s solution for viscous flow. Also, a statistically based relationship between the velocity measured with the probe and the velocity determined from the volumetric flow rate has been developed.

  15. Near-field acoustic holography with sound pressure and particle velocity measurements

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren

    of particle velocity measurements and combined pressure-velocity measurements in NAH, the relation between the near-field and the far-field radiation from sound sources via the supersonic acoustic intensity, and finally, the reconstruction of sound fields using rigid spherical microphone arrays. Measurement...... of the particle velocity has notable potential in NAH, and furthermore, combined measurement of sound pressure and particle velocity opens a new range of possibilities that are examined in this study. On this basis, sound field separation methods have been studied, and a new measurement principle based on double...... layer measurements of the particle velocity has been proposed. Also, the relation between near-field and far-field radiation from sound sources has been examined using the concept of the supersonic intensity. The calculation of this quantity has been extended to other holographic methods, and studied...

  16. ECE Measurements of Helical Plasmas in LHD

    Science.gov (United States)

    Nagayama, Y.; Inagaki, S.; Ito, Y.; Kawahata, K.; Sasao, H.; de Vries, P.

    1999-11-01

    This paper presents ECE measurements on LHD, which is the l=2, n=10 heriotron with the major radius of 3.8 m, with the averaged minor radius of 60 cm and with the helical field of up to 3 T. The ECE is collected from both inner and outer sides, since the magnetic field has a peaked profile. ECE is detcted with Michelson, GPC and 70 GHz and 140 GHz radiometers. The LHD plasma is generated using ECH of up to 1 MW and is heated using NBI of up to 8 GW. Notch filters reduce the ECH leakage. The polarization of ECE is theoretically and experimentally investigated in the heriotoron system, where the field angle rotates -30 to 30^o. The polarization follows as the field angle changes. Since the density profile is flat, ECE is cut off in the edge region in the high density LHD plasma. An interesting observation is the breathing phenomena, which is as follows: the electron temperature and other plasma parameters oscillate with frequency of 0.5-1Hz like a sine-wave when the NBI power is about 1 MW.

  17. Velocity distribution measurements in a fishway like open channel by Laser Doppler Anemometry (LDA)

    Science.gov (United States)

    Sayeed-Bin-Asad, S. M.; Lundström, T. S.; Andersson, A. G.; Hellström, J. G. I.

    2016-03-01

    Experiments in an open channel flume with placing a vertical half cylinder barrier have been performed in order to investigate how the upstream velocity profiles are affected by a barrier. An experimental technique using Laser Doppler Velocimetry (LDV) was adopted to measure these velocity distributions in the channel for four different discharge rates. Velocity profiles were measured very close to wall and at 25, 50 and 100 mm upstream of the cylinder wall. For comparing these profiles with well-known logarithmic velocity profiles, velocity profiles were also measured in smooth open channel flow for all same four discharge rates. The results indicate that regaining the logarithmic velocity profiles upstream of the half cylindrical barrier occurs at 100 mm upstream of the cylinder wall.

  18. Velocity distribution measurements in a fishway like open channel by Laser Doppler Anemometry (LDA

    Directory of Open Access Journals (Sweden)

    Sayeed-Bin-Asad S.M.

    2016-01-01

    Full Text Available Experiments in an open channel flume with placing a vertical half cylinder barrier have been performed in order to investigate how the upstream velocity profiles are affected by a barrier. An experimental technique using Laser Doppler Velocimetry (LDV was adopted to measure these velocity distributions in the channel for four different discharge rates. Velocity profiles were measured very close to wall and at 25, 50 and 100 mm upstream of the cylinder wall. For comparing these profiles with well-known logarithmic velocity profiles, velocity profiles were also measured in smooth open channel flow for all same four discharge rates. The results indicate that regaining the logarithmic velocity profiles upstream of the half cylindrical barrier occurs at 100 mm upstream of the cylinder wall.

  19. Development of ultrasonic pulse-train Doppler method for velocity profile and flowrate measurement

    Science.gov (United States)

    Wada, Sanehiro; Furuichi, Noriyuki; Shimada, Takashi

    2016-11-01

    We present a novel technique for measuring the velocity profile and flowrate in a pipe. This method, named the ultrasonic pulse-train Doppler method (UPTD), has the advantages of expanding the velocity range and setting the smaller measurement volume with low calculation and instrument costs in comparison with the conventional ultrasonic pulse Doppler method. The conventional method has limited measurement of the velocity range due to the Nyquist sampling theorem. In addition, previous reports indicate that a smaller measurement volume increases the accuracy of the measurement. In consideration of the application of the conventional method to actual flow fields, such as industrial facilities and power plants, the issues of velocity range and measurement volume are important. The UPTD algorithm, which exploits two pulses of ultrasound with a short interval and envelope detection, is proposed. Velocity profiles calculated by this algorithm were examined through simulations and excellent agreement was found in all cases. The influence of the signal-to-noise ratio (SNR) on the algorithm was also estimated. The result indicates that UPTD can measure velocity profiles with high accuracy, even under a small SNR. Experimental measurements were conducted and the results were evaluated at the national standard calibration facility of water flowrate in Japan. Every detected signal forms a set of two pulses and the enveloped line can be observed clearly. The results show that UPTD can measure the velocity profiles over the pipe diameter, even if the velocities exceed the measurable velocity range. The measured flowrates were under 0.6% and the standard deviations for all flowrate conditions were within  ±0.38%, which is the uncertainty of the flowrate measurement estimated in the previous report. In conclusion, UPTD provides superior accuracy and expansion of the velocity range.

  20. Temporal evolution of confined fast-ion velocity distributions measured by collective Thomson scattering in TEXTOR

    DEFF Research Database (Denmark)

    Nielsen, Stefan Kragh; Bindslev, Henrik; Porte, L.

    2008-01-01

    of scattering locations and different resolved velocity components can be measured. The temporal resolution is 4 ms while the spatial resolution is similar to 10 cm depending on the scattering geometry. Fast-ion velocity distributions in a variety of scenarios are measured, including the evolution...

  1. A Raman anemometer for component-selective velocity measurements of particles in a flow

    NARCIS (Netherlands)

    Florisson, O.; Mul, de F.F.M.; Winter, de H.G.

    1981-01-01

    An anemometer for the measurement of the velocity of particles of different components in a flow, separate and apart from that of the flow itself, is described. As a component-selective mechanism Raman scattering is used. The velocity is measured by relating the autocorrelated scattering signal to t

  2. Total uncertainty of low velocity thermal anemometers for measurement of indoor air movements

    DEFF Research Database (Denmark)

    Jørgensen, F.; Popiolek, Z.; Melikov, Arsen Krikor

    2004-01-01

    For a specific thermal anemometer with omnidirectional velocity sensor the expanded total uncertainty in measured mean velocity Û(Vmean) and the expanded total uncertainty in measured turbulence intensity Û(Tu) due to different error sources are estimated. The values are based on a previously dev...

  3. Electron Velocity Distributions Measured with Soft-X-Ray PHA at RTP

    NARCIS (Netherlands)

    Da Cruz, D. F.; Meijer, J. H.; Donne, A. J. H.

    1992-01-01

    A soft x-ray pulse height analysis (PHA) system is begin used at the Rijhuizen Tokamak Project to study the electron velocity distribution. A liquid nitrogen cooled Si(Li) detector is used to view the plasma along a tangential line of sight. A gas cell in combination with Al foils is used for filter

  4. LASER ULTRASONIC FOR MEASUREMENTS OF VELOCITY DISTRIBUTION IN PIPES

    Directory of Open Access Journals (Sweden)

    M. Navarrete

    2004-12-01

    Full Text Available The present work describes the development of a photoacoustic flowmeter with probe-beam deflection. A pulsedlaser beam produces an acoustic pulse, whose propagation is registered by its deflection effects on two cw probebeams. The acoustic pulse in a flowing fluid is produced by absorption of a laser pulse (30 ns, 1.1 mJ focused overa path flow line. The acoustic propagations, along and against the flow, are monitored by two cw probe beams. Inthe interaction, the probe beam undergoes a transient deflection that is detected by a fast response photodiode.The velocity distribution data profile of a square pipe is obtained by means of the acoustic pulse arrival timemeasured through its cross section applying the cylindrical shockwave model developed by Vlasses. The profilesdetermined with this experimental technique are compared with two turbulent pipe flow models.

  5. Measuring drift velocity and electric field in mirror machine by fast photography

    Science.gov (United States)

    Be'ery, I.; Seemann, O.; Fruchtman, A.; Fisher, A.; Nemirovsky, J.

    2013-02-01

    The flute instability in mirror machines is driven by spatial charge accumulation and the resulting E × B plasma drift. On the other hand, E × B drift due to external electrodes or coils can be used as a stabilizing feedback mechanism. Fast photography is used to visualize Hydrogen plasma in a small mirror machine and infer the plasma drift and the internal electric field distribution. Using incompressible flow and monotonic decay assumptions we obtain components of the velocity field from the temporal evolution of the plasma cross section. The electric field perpendicular to the density gradient is then deduced from E=-V × B. With this technique we analyzed the electric field of flute perturbations and the field induced by electrodes immersed in the plasma.

  6. Usefulness of early diastolic mitral annular velocity to predict plasma levels of brain natriuretic peptide and transient heart failure development after device closure of atrial septal defect.

    Science.gov (United States)

    Masutani, Satoshi; Taketazu, Mio; Mihara, Chihiro; Mimura, Yuko; Ishido, Hirotaka; Matsunaga, Tamotsu; Kobayashi, Toshiki; Senzaki, Hideaki

    2009-12-15

    Device closure of atrial septal defect (ASD) is sometimes followed by elevation of plasma brain natriuretic peptide (BNP), a marker of heart failure, and progression to heart failure. This study tested the hypothesis that the underlying diastolic dysfunction, assessed on tissue Doppler images (TDI) before device closure, can predict BNP level after ASD closure. The study subjects were 39 consecutive patients (age 27.5 +/- 16.3 years, range 5 to 63) who underwent device closure for ASD. Echocardiographic evaluation using TDI and 2-dimensional and pulse wave Doppler were performed, together with plasma BNP measurement 1 day before and 2 days after ASD closure. Before ASD closure, an age-dependent decrease was noted in left ventricular relaxation, assessed by early diastolic mitral annular velocity. ASD closure resulted in a decrease in early diastolic mitral annular velocity (from 14.7 to 12.3 cm/s, p linear regression identified early diastolic mitral annular velocity before ASD closure and age as independent predictors of BNP levels after ASD closure (p annular velocity developed exertional dyspnea after the procedure. In conclusion, our results indicate that TDI measurements could be useful to detect underlying diastolic dysfunction that can potentially cause heart failure after ASD closure and emphasize the importance of ASD closure at a young age before impairment of left ventricular relaxation.

  7. Precise Measurement of Subsurface Seismic Velocity Variation by Coda Wave Interferometry

    Institute of Scientific and Technical Information of China (English)

    Xia Yu; Wang Baoshan; Ge Hongkui; Chen Yong

    2008-01-01

    A filed experiment was conducted continuously for three days,and the velocity variation was measured using coda wave interferometry.The measurement error is estimated to be around 10-4,which coincides well with the theoretical error.The velocity variation during this period is up to 10-3.The relationship between velocity variation and changes in air temperature,barometric pressure and solid earth tide was analyzed with linear least square fitting.The velocity has no dependence on air temperature,but displayed change of the order of 10-6~10-7 when the barometer or earth tide changed one Pa.

  8. A Device for Measuring Sonic Velocity and Compressor Mach Number

    Science.gov (United States)

    1948-07-01

    resonator (the only 4 NACA TN No. 1664 accurate measurement required) is measured, as shomn in figure 1, by means of a mercury manometer . The compressor Mach...tube vs not connected to the ccmpressor inlet until after calibration. The pressure in the device was measured by means of the mercury manometer . Fram

  9. On the phase velocity of plasma waves in a self-modulated laser wake-field accelerator

    NARCIS (Netherlands)

    Andreev, N. E.; Kirsanov, V. I.; Sakharov, A. S.; van Amersfoort, P. W.; Goloviznin, V. V.

    1996-01-01

    The properties of the wake field excited by a flattop laser pulse with a sharp leading edge and a power below the critical one for relativistic self-focusing are studied analytically and numerically with emphasis on the phase velocity of the plasma wave. The paraxial model describing modulation of t

  10. On the phase velocity of plasma waves in a self-modulated laser wake-field accelerator

    NARCIS (Netherlands)

    Andreev, N. E.; Kirsanov, V. I.; Sakharov, A. S.; van Amersfoort, P. W.; Goloviznin, V. V.

    1996-01-01

    The properties of the wake field excited by a flattop laser pulse with a sharp leading edge and a power below the critical one for relativistic self-focusing are studied analytically and numerically with emphasis on the phase velocity of the plasma wave. The paraxial model describing modulation of t

  11. Laser-Induced Fluorescence Velocity Measurements in Supersonic Underexpanded Impinging Jets

    Science.gov (United States)

    Inman, Jennifer A.; Danehy, Paul M.; Barthel, Brett; Alderfer, David W.; Novak, Robert J.

    2010-01-01

    We report on an application of nitric oxide (NO) flow-tagging velocimetry to impinging underexpanded jet flows issuing from a Mach 2.6 nozzle. The technique reported herein utilizes a single laser, single camera system to obtain planar maps of the streamwise component of velocity. Whereas typical applications of this technique involve comparing two images acquired at different time delays, this application uses a single image and time delay. The technique extracts velocity by assuming that particular regions outside the jet flowfield have negligible velocity and may therefore serve as a stationary reference against which to measure motion of the jet flowfield. By taking the average of measurements made in 100 single-shot images for each flow condition, streamwise velocities of between -200 and +1,000 m/s with accuracies of between 15 and 50 m/s are reported within the jets. Velocity measurements are shown to explain otherwise seemingly anomalous impingement surface pressure measurements.

  12. Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity

    Science.gov (United States)

    Yost, William T.; Cantrell, John H.; Kushnick, Peter W.

    1991-10-01

    A new instrument based on a constant-frequency pulsed phase-locked-loop (CFPPLL) concept has been developed to accurately measure the ultrasonic wave velocity in liquids and changes in ultrasonic wave velocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency-dependent effects that plague other techniques. Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measure velocities, as well as for monitoring small changes in velocity without the sensitivity to frequency-dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 10 to the 7th.

  13. Bounds imposed on the sheath velocity of a dense plasma focus by conservation laws and ionization stability condition

    CERN Document Server

    Auluck, S K H

    2014-01-01

    Experimental data compiled over five decades of dense plasma focus research is consistent with the snowplow model of sheath propagation, based on the hypothetical balance between magnetic pressure driving the plasma into neutral gas ahead and wind pressure resisting its motion. The resulting sheath velocity, or the numerically proportional drive parameter, is known to be approximately constant for devices optimized for neutron production over 8 decades of capacitor bank energy. This paper shows that the validity of the snowplow hypothesis, with some correction, as well as the non-dependence of sheath velocity on device parameters, have their roots in local conservation laws for mass, momentum and energy coupled with the ionization stability condition. Both upper and lower bounds on sheath velocity are shown to be related to material constants of the working gas and independent of the device geometry and capacitor bank impedance.

  14. Bounds imposed on the sheath velocity of a dense plasma focus by conservation laws and ionization stability condition

    Science.gov (United States)

    Auluck, S. K. H.

    2014-09-01

    Experimental data compiled over five decades of dense plasma focus research are consistent with the snowplow model of sheath propagation, based on the hypothetical balance between magnetic pressure driving the plasma into neutral gas ahead and "wind pressure" resisting its motion. The resulting sheath velocity, or the numerically proportional "drive parameter," is known to be approximately constant for devices optimized for neutron production over 8 decades of capacitor bank energy. This paper shows that the validity of the snowplow hypothesis, with some correction, as well as the non-dependence of sheath velocity on device parameters, have their roots in local conservation laws for mass, momentum, and energy coupled with the ionization stability condition. Both upper and lower bounds on sheath velocity are shown to be related to material constants of the working gas and independent of the device geometry and capacitor bank impedance.

  15. Predictions for the energy loss of light ions in laser-generated plasmas at low and medium velocities.

    Science.gov (United States)

    Cayzac, W; Bagnoud, V; Basko, M M; Blažević, A; Frank, A; Gericke, D O; Hallo, L; Malka, G; Ortner, A; Tauschwitz, An; Vorberger, J; Roth, M

    2015-11-01

    The energy loss of light ions in dense plasmas is investigated with special focus on low to medium projectile energies, i.e., at velocities where the maximum of the stopping power occurs. In this region, exceptionally large theoretical uncertainties remain and no conclusive experimental data are available. We perform simulations of beam-plasma configurations well suited for an experimental test of ion energy loss in highly ionized, laser-generated carbon plasmas. The plasma parameters are extracted from two-dimensional hydrodynamic simulations, and a Monte Carlo calculation of the charge-state distribution of the projectile ion beam determines the dynamics of the ion charge state over the whole plasma profile. We show that the discrepancies in the energy loss predicted by different theoretical models are as high as 20-30%, making these theories well distinguishable in suitable experiments.

  16. Interpreting Power Anisotropy Measurements in Plasma Turbulence

    CERN Document Server

    Chen, C H K; Horbury, T S; Schekochihin, A A

    2009-01-01

    A relationship between power anisotropy and wavevector anisotropy in turbulent fluctuations is derived. This can be used to interpret plasma turbulence measurements, for example in the solar wind. If fluctuations are anisotropic in shape then the ion gyroscale break point in spectra in the directions parallel and perpendicular to the magnetic field would not occur at the same frequency, and similarly for the electron gyroscale break point. This is an important consideration when interpreting solar wind observations in terms of anisotropic turbulence theories. Model magnetic field power spectra are presented assuming a cascade of critically balanced Alfven waves in the inertial range and kinetic Alfven waves in the dissipation range. The variation of power anisotropy with scale is compared to existing solar wind measurements and the similarities and differences are discussed.

  17. Laser transit anemometer measurements of a JANNAF nozzle base velocity flow field

    Science.gov (United States)

    Hunter, William W., Jr.; Russ, C. E., Jr.; Clemmons, J. I., Jr.

    1990-01-01

    Velocity flow fields of a nozzle jet exhausting into a supersonic flow were surveyed. The measurements were obtained with a laser transit anemometer (LTA) system in the time domain with a correlation instrument. The LTA data is transformed into the velocity domain to remove the error that occurs when the data is analyzed in the time domain. The final data is shown in velocity vector plots for positions upstream, downstream, and in the exhaust plane of the jet nozzle.

  18. High Precision UTDR Measurements by Sonic Velocity Compensation with Reference Transducer

    Directory of Open Access Journals (Sweden)

    Sam Stade

    2014-07-01

    Full Text Available An ultrasonic sensor design with sonic velocity compensation is developed to improve the accuracy of distance measurement in membrane modules. High accuracy real-time distance measurements are needed in membrane fouling and compaction studies. The benefits of the sonic velocity compensation with a reference transducer are compared to the sonic velocity calculated with the measured temperature and pressure using the model by Belogol’skii, Sekoyan et al. In the experiments the temperature was changed from 25 to 60 °C at pressures of 0.1, 0.3 and 0.5 MPa. The set measurement distance was 17.8 mm. Distance measurements with sonic velocity compensation were over ten times more accurate than the ones calculated based on the model. Using the reference transducer measured sonic velocity, the standard deviations for the distance measurements varied from 0.6 to 2.0 µm, while using the calculated sonic velocity the standard deviations were 21–39 µm. In industrial liquors, not only the temperature and the pressure, which were studied in this paper, but also the properties of the filtered solution, such as solute concentration, density, viscosity, etc., may vary greatly, leading to inaccuracy in the use of the Belogol’skii, Sekoyan et al. model. Therefore, calibration of the sonic velocity with reference transducers is needed for accurate distance measurements.

  19. Dissipated power and induced velocity fields data of a micro single dielectric barrier discharge plasma actuator for active flow control☆

    Science.gov (United States)

    Pescini, E.; Martínez, D.S.; De Giorgi, M.G.; Francioso, L.; Ficarella, A.

    2015-01-01

    In recent years, single dielectric barrier discharge (SDBD) plasma actuators have gained great interest among all the active flow control devices typically employed in aerospace and turbomachinery applications [1,2]. Compared with the macro SDBDs, the micro single dielectric barrier discharge (MSDBD) actuators showed a higher efficiency in conversion of input electrical power to delivered mechanical power [3,4]. This article provides data regarding the performances of a MSDBD plasma actuator [5,6]. The power dissipation values [5] and the experimental and numerical induced velocity fields [6] are provided. The present data support and enrich the research article entitled “Optimization of micro single dielectric barrier discharge plasma actuator models based on experimental velocity and body force fields” by Pescini et al. [6]. PMID:26425667

  20. Predicting stroke outcome using DCE-CT measured blood velocity

    Science.gov (United States)

    Oosterbroek, Jaap; Bennink, Edwin; Dankbaar, Jan Willem; Horsch, Alexander D.; Viergever, Max A.; Velthuis, Birgitta K.; de Jong, Hugo W. A. M.

    2015-03-01

    CT plays an important role in the diagnosis of acute stroke patients. Dynamic contrast enhanced CT (DCE-CT) can estimate local tissue perfusion and extent of ischemia. However, hemodynamic information of the large intracranial vessels may also be obtained from DCE-CT data and may contain valuable diagnostic information. We describe a novel method to estimate intravascular blood velocity (IBV) in large cerebral vessels using DCE-CT data, which may be useful to help predict stroke outcome. DCE-CT scans from 34 patients with isolated M1 occlusions were included from a large prospective multi-center cohort study of patients with acute ischemic stroke. Gaussians fitted to the intravascular data yielded the time-to-peak (TTP) and cerebral-blood-volume (CBV). IBV was computed by taking the inverse of the TTP gradient magnitude. Voxels with a CBV of at least 10% of the CBV found in the arterial input function were considered part of a vessel. Mid-sagittal planes were drawn manually and averages of the IBV over all vessel-voxels (arterial and venous) were computed for each hemisphere. Mean-hemisphere IBV differences, mean-hemisphere TTP differences, and hemisphere vessel volume differences were used to differentiate between patients with good and bad outcome (modified Rankin Scale score <3 versus ≥3 at 90 days) using ROC analysis. AUCs from the ROC for IBV, TTP, and vessel volume were 0.80, 0.67 and 0.62 respectively. In conclusion, IBV was found to be a better predictor of patient outcome than the parameters used to compute it and may be a promising new parameter for stroke outcome prediction.

  1. A simple measuring technique of surface flow velocity to analyze the behavior of velocity fields in hydraulic engineering applications.

    Science.gov (United States)

    Tellez, Jackson; Gomez, Manuel; Russo, Beniamino; Redondo, Jose M.

    2015-04-01

    An important achievement in hydraulic engineering is the proposal and development of new techniques for the measurement of field velocities in hydraulic problems. The technological advances in digital cameras with high resolution and high speed found in the market, and the advances in digital image processing techniques now provides a tremendous potential to measure and study the behavior of the water surface flows. This technique was applied at the Laboratory of Hydraulics at the Technical University of Catalonia - Barcelona Tech to study the 2D velocity fields in the vicinity of a grate inlet. We used a platform to test grate inlets capacity with dimensions of 5.5 m long and 4 m wide allowing a zone of useful study of 5.5m x 3m, where the width is similar of the urban road lane. The platform allows you to modify the longitudinal slopes from 0% to 10% and transversal slope from 0% to 4%. Flow rates can arrive to 200 l/s. In addition a high resolution camera with 1280 x 1024 pixels resolution with maximum speed of 488 frames per second was used. A novel technique using particle image velocimetry to measure surface flow velocities has been developed and validated with the experimental data from the grate inlets capacity. In this case, the proposed methodology can become a useful tools to understand the velocity fields of the flow approaching the inlet where the traditional measuring equipment have serious problems and limitations. References DigiFlow User Guide. (2012), (June). Russo, B., Gómez, M., & Tellez, J. (2013). Methodology to Estimate the Hydraulic Efficiency of Nontested Continuous Transverse Grates. Journal of Irrigation and Drainage Engineering, 139(10), 864-871. doi:10.1061/(ASCE)IR.1943-4774.0000625 Teresa Vila (1), Jackson Tellez (1), Jesus Maria Sanchez (2), Laura Sotillos (1), Margarita Diez (3, 1), and J., & (1), M. R. (2014). Diffusion in fractal wakes and convective thermoelectric flows. Geophysical Research Abstracts - EGU General Assembly 2014

  2. Effect of diffraction on the ultrasonic velocity measured by the pulse interference method in VHF range

    Institute of Scientific and Technical Information of China (English)

    WEI Tingcun

    2002-01-01

    The effect of diffraction on the ultrasonic velocity measured by the pulse interference method has been investigated in VHF range theoretically and experimentally. Two silicate glasses are taken as the specimens, their frequency dependences of longitudinal velocities are measured in the frequency range of 50-350 MHz, and the phase advances of ultrasonic signals caused by diffraction effect are calculated using A. O. Williams' theoretical expression. For the velocity error due to diffraction effect, the experimental results are in good agreement with the theoretical prediction. It has been shown that the velocity error due to diffraction effect is directly proportional to d θ21 (f)/df, where θ21 (f) is the phase advances difference between the two partial reflection signals used in velocity measurement and f is the ultrasonic frequency.

  3. Validation of Doppler ultrasound and magnetic resonance imaging velocity measurements by means of a test object

    NARCIS (Netherlands)

    Oostayen, J.A. van; Bezemer, R.A.; Wasser, M.N.J.M.; Teirlinck, C.J.P.M.

    1996-01-01

    Objective: To validate Doppler ultrasound and MRI mean velocity measurements in a test object in which mean velocities are known and can be chosen within a range of 10-100 cm/s in tubes of 4 and 8 mm. This validation was carried out to check the performance of a duplex Doppler ultrasound system that

  4. A Fabry-Perot interferometer system for high-speed velocity measurement

    NARCIS (Netherlands)

    Cheng, L.K.; Bruinsma, A.J.A.; Prinse, W.C.; Smorenburg, C.

    1997-01-01

    The Fabry-Perot Velocity Interferometer System (F-PVIS) is designed and built for measuring the Doppler shift of light by recording positional changes in the interferometric pattern behind the Fabry-Perot interferometer. The velocity of a surface can be deduced from the Doppler shift which is caused

  5. Measuring of Settling Velocity of Fine Sediment Using a Recirculated Settling Column

    DEFF Research Database (Denmark)

    Johansen, Claus; Larsen, Torben

    1998-01-01

    The paper describes a new experimental method for the measurement of the settling velocity of fine sediments. The method includes determination of the influence of turbulence and concentration. The paper also illustrates the method by giving results of the settling velocity of kaolinite for varyi...

  6. Measurement of Settling Velocity of Fine Sediment using a Recirculated Settling Column

    DEFF Research Database (Denmark)

    Johansen, C.; Larsen, Torben

    1997-01-01

    The paper describes a new experimental method for the measurement of the settling velocity of fine sediments. The method includes determination of the influence of turbulence and concentration. The paper also illustrates the method by giving results of the settling velocity of kaolinite for varyi...

  7. A Fabry-Perot interferometer system for high-speed velocity measurement

    NARCIS (Netherlands)

    Cheng, L.K.; Bruinsma, A.J.A.; Prinse, W.C.; Smorenburg, C.

    1997-01-01

    The Fabry-Perot Velocity Interferometer System (F-PVIS) is designed and built for measuring the Doppler shift of light by recording positional changes in the interferometric pattern behind the Fabry-Perot interferometer. The velocity of a surface can be deduced from the Doppler shift which is caused

  8. Glacier Surface Velocity Measurements from Radar Interferometry and the Principle of Mass Conservation

    OpenAIRE

    Mohr, Johan Jacob; Reeh, Niels

    2002-01-01

    Presents a relation between the three glacier surface velocity components, the surface flux-divergence, glacier thickness and bottom melt and displacement. The relation can be used as an extension to the surface parallel flow assumption often used with interferometric synthetic aperture measurements of glacier velocities. The assumptions for the derivation are described and important limitations high-lighted.

  9. Measurement of Settling Velocity of Fine Sediment using a Recirculated Settling Column

    DEFF Research Database (Denmark)

    Johansen, C.; Larsen, Torben

    1997-01-01

    The paper describes a new experimental method for the measurement of the settling velocity of fine sediments. The method includes determination of the influence of turbulence and concentration. The paper also illustrates the method by giving results of the settling velocity of kaolinite for varying...

  10. Precision measurement of transverse velocity distribution of a Strontium atomic beam

    CERN Document Server

    Gao, F; Xu, P; Tian, X; Wang, Y; Ren, J; Wu, Haibin; Chang, Hong

    2013-01-01

    We measure precisely the transverse velocity distribution in a thermal Sr atomic beam with a velocity selective saturated fluorescence spectroscopy. By using the ultrastable laser system and narrow intercombination transition line of Sr atoms, the resolution of the velocity measured can be reached 0.13m/s, corresponding to 90$\\mu K$ in energy unit. The experimental results are agreement very well with a theoretical calculation. With the spectroscopic techniques, the absolute frequency of the intercombination transition of $^{88}$Sr is measured by an optical-frequency comb generator referenced to the SI second through an H maser, which is given by 434 829 121 318(10)kHz.

  11. Multipoint Vernier VISAR Interferometer System for Measuring Mass Velocity in Shock Wave Experiments

    Science.gov (United States)

    Gubskii, K. L.; Koshkin, D. S.; Mikhaylyuk, A. V.; Korolev, A. M.; Pirog, V. A.; Kuznetsov, A. P.

    The results of development of a laser interferometer designed to measure the mass velocity of condensed substances in shock wave experiments in the field of high energy density physics are presented. The developed laser system allows measurements of the velocity of free surfaces of samples in shockwave experiments with accuracy no worse than 10 m/s for the entire range of velocities attained experimentally. The time resolution of measurements is limited by the response speed of the used PMTs and amounts to 2.5 ns.

  12. Smart Laser Interferometer with Electrically Tunable Lenses for Flow Velocity Measurements through Disturbing Interfaces

    Directory of Open Access Journals (Sweden)

    Jürgen W. Czarske

    2015-01-01

    Full Text Available Interferometric velocity measurements are of great importance at flow investigations. However, the laser beams can be distorted at the interfaces between optical media of different refractive indices. Temporal fluctuations of these distortions will cause a deterioration of the laser interferometer signals. We have harnessed the power of programmable photonics devices to eliminate this signal deterioration. Non-invasive flow velocity measurements through a rapidly fluctuating media interface with large strokes of about 100 microns are presented. Our work represents a paradigm shift for interferometric velocity measurement techniques from using static to dynamic optical elements.

  13. On Improving Impedance Probe Plasma Potential Measurements

    Science.gov (United States)

    2014-02-21

    assumption of a collisionless, stationary Maxwellian plasma and are seen to work well in non -flowing plasmas of sufficient density. However, as plasma...collection area. For Maxwellian electrons, np = n exp(Vp-φp)/Te and so at low frequency from Eq. (1) above, the resistive component of the ac

  14. Measurement of the Velocity of the Neutrino with MINOS

    CERN Document Server

    Adamson, P; Bumgarner, R

    2014-01-01

    The MINOS experiment uses a beam of predominantly muon-type neutrinos generated using protons from the Main Injector at Fermilab in Batavia, IL, and travelling 735 km through the Earth to a disused iron mine in Soudan, MN. The 10{\\mu}s-long beam pulse contains fine time structure which allows a precise measurement of the neutrino time of flight to be made. The time structure of the parent proton pulse is measured in the beamline after extraction from the Main Injector, and neutrino interactions are timestamped at the Fermilab site in the Near Detector (ND), and at the Soudan site in the Far Detector (FD). Small, transportable auxiliary detectors, consisting of scintillator planes and associated readout electronics, are used to measure the relative latency between the two large detectors. Time at each location is measured with respect to HP5071A Cesium clocks, and time is transferred using GPS Precise Point Positioning (PPP) solutions for the clock offset at each location. We describe the timing calibration of...

  15. Photon trajectories, anomalous velocities, and weak measurements: A classical interpretation

    CERN Document Server

    Bliokh, Konstantin Y; Nori, Franco

    2013-01-01

    Recently, Kocsis et al. reported the observation of "average trajectories of single photons" in a two-slit interference experiment [Science 332, 1170 (2011)]. This was possible by using the quantum weak-measurements method, which implies averaging over many events, i.e., in fact, a multi-photon limit of classical optics. We give a classical-optics interpretation to this experiment and other related problems. It appears that weak measurements of the local momentum of photons made by Kocsis et al. represent measurements of the Poynting vector in an optical field. We consider both the real and imaginary parts of the local momentum, and show that their measurements have been realized in classical optics using small probe particles. We also examine the appearance of "anomalous" values of the local momentum: either negative (backflow) or exceeding the wavenumber (superluminal propagation). These features appear to be closely related to vortices and evanescent waves. Finally, we revisit a number of older works and f...

  16. Method for Measuring Velocity of Warhead Fragments Based on Photoelectric Detection

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    For measuring velocity and impacting position of single fragment of warhead, a non-contact measuring method is proposed, in which a six-light-screen array, a position indicator, a multi-channel chronograph and a computer are used.The principle of measurement is described. The key device of the system is a light screen array sensor which consists of six light screens allocated with certain geometrical parameters. When the fragment flies through the light screen array, the time of passing through each of the screens is recorded by the multi-channel chronograph. According to the time data and the geometrical parameters of the array, the velocity vector and the location of the fragment can be calculated immediately. The presented method can be used to locate the fragment and to measure the real velocity on its flying direction. It can also be used to measure the velocity of a fragment swarm after the system is engineered further.

  17. Highly spatially resolved velocity measurements of a turbulent channel flow by a fiber-optic heterodyne laser-Doppler velocity-profile sensor

    Energy Technology Data Exchange (ETDEWEB)

    Shirai, K.; Pfister, T.; Buettner, L.; Czarske, J. [Dresden University of Technology (TU Dresden), Department of Electrical Engineering and Information Technology, Chair for Measurement and Testing Techniques, Dresden (Germany); Mueller, H. [Physikalisch-Technische Bundesanstalt Braunschweig (PTB), Department 1.4 Gas Flow, Braunschweig (Germany); Becker, S.; Lienhart, H.; Durst, F. [Institute of Fluid Mechanics (LSTM), Friedrich-Alexander-University Erlangen-Nuernberg, Erlangen (Germany)

    2006-03-15

    Velocity measurements with a high spatial resolution are important in turbulent flow research. In this paper, we report on the development of a new fiber-optic laser-Doppler velocity-profile sensor exhibiting a spatial resolution of up to 5 {mu}m and its application to turbulent boundary layers. The sensor developed in the present work employs a frequency-division-multiplexing technique in order to separate two measurement signals from the two fringe systems. Velocity measurements close to zero at the solid wall were realized using heterodyne technique. The use of fiber optics improved a robustness of the sensor. The measurement accuracy of the sensor was experimentally investigated with respect to the spatial resolution and velocity. Universal velocity profile of a turbulent flow was obtained in a fully developed channel flow. Mean and fluctuating velocity are presented with a high spatial resolution. (orig.)

  18. Electron Temperature and Plasma Flow Measurements of NIF Hohlraum Plasmas

    Science.gov (United States)

    Barrios, M. A.; Liedahl, D. A.; Schneider, M. B.; Jones, O.; Brow, G. V.; Regan, S. P.; Fournier, K. B.; Moore, A. S.; Ross, J. S.; Eder, D.; Landen, O.; Kauffman, R. L.; Nikroo, A.; Kroll, J.; Jaquez, J.; Huang, H.; Hansen, S. B.; Callahan, D. A.; Hinkel, D. E.; Bradley, D.; Moody, J. D.; LLNL Collaboration; LLE Collaboration; GA Collaboration; SNL Collaboration

    2016-10-01

    Characterizing the plasma conditions inside NIF hohlraums, in particular mapping the plasma Te, is critical to gaining insight into mechanisms that affect energy coupling and transport in the hohlraum. The dot spectroscopy platform provides a temporal history of the localized Te and plasma flow inside a NIF hohlraum, by introducing a Mn-Co tracer dot, at strategic locations inside the hohlraum, that comes to equilibrium with the local plasma. K-shell X-ray spectroscopy of the tracer dot is recorded onto an absolutely calibrated X-ray streak spectrometer. Isoelectronic and interstage line ratios are used to infer localized Te through comparison with atomic physics calculations using SCRAM. Time resolved X-ray images are simultaneously taken of the expanding dot, providing plasma (ion) flow information. We present recent results provided by this platform and compare with simulations using HYDRA. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

  19. Determination of wave intensity in flexible tubes using measured diameter and velocity.

    Science.gov (United States)

    Feng, J; Khir, A W

    2007-01-01

    Wave intensity (WI) is a hemodynamics index, which is the product of changes in pressure and velocity across the wave-front. Wave Intensity Analysis, which is a time domain technique allows for the separation of running waves into their forward and backward directions and traditionally uses the measured pressure and velocity waveforms. However, due to the possible difficulty in obtaining reliable pressure waveforms non-invasively, investigating the use of wall displacement instead of pressure signals in calculating WI may have clinical merits. In this paper, we developed an algorithm in which we use the measured diameter of flexible tube's wall and flow velocity to separate the velocity waveform into its forward and backward directions. The new algorithm is also used to separate wave intensity into its forward and backward directions. In vitro experiments were carried out in two sized flexible tubes, 12mm and 16mm in diameters, each is of 2 m in length. Pressure, velocity and diameter were taken at three measuring sites. A semi-sinusoidal wave was generated using a piston pump, which ejected 40cc water into each tube. The results show that separated wave intensity into the forward and backward directions of the new algorithm using the measured diameter and velocity are almost identical in shape to those traditionally using the measured pressure and velocity. We conclude that the new algorithm presented in this work, could have clinical advantages since the required information can be obtained non-invasively.

  20. Measuring the velocity field from type Ia supernovae in an LSST-like sky survey

    CERN Document Server

    Odderskov, Io

    2016-01-01

    With the upcoming sky survey with the Large Synoptic Survey Telescope a great sample of type Ia supernovae will be observed, allowing for a precise mapping of the velocity structure of the universe. Since the source of peculiar velocities is variations in the density field, cosmological parameters related to the matter distribution can subsequently be extracted from the velocity power spectrum. One way to quantify this is through the angular power spectrum of radial peculiar velocities on spheres at different redshifts. We investigate how well this observable can be measured, despite the problems caused by areas with no information. To obtain a realistic distribution of supernovae, we create mock supernova catalogs by using a semi-analytical code for galaxy formation on the merger trees extracted from N-body simulations. We measure the cosmic variance in the velocity power spectrum by repeating the procedure many times for differently located observers, and vary different aspects of the analysis, such as the ...

  1. Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

    Science.gov (United States)

    Prisiazhniuk, D.; Krämer-Flecken, A.; Conway, G. D.; Happel, T.; Lebschy, A.; Manz, P.; Nikolaeva, V.; Stroth, U.; the ASDEX Upgrade Team

    2017-02-01

    In fusion machines, turbulent eddies are expected to be aligned with the direction of the magnetic field lines and to propagate in the perpendicular direction. Time delay measurements of density fluctuations can be used to calculate the magnetic field pitch angle α and perpendicular velocity {{v}\\bot} profiles. The method is applied to poloidal correlation reflectometry installed at ASDEX Upgrade and TEXTOR, which measure density fluctuations from poloidally and toroidally separated antennas. Validation of the method is achieved by comparing the perpendicular velocity (composed of the E× B drift and the phase velocity of turbulence {{v}\\bot}={{v}E× B}+{{v}\\text{ph}} ) with Doppler reflectometry measurements and with neoclassical {{v}E× B} calculations. An important condition for the application of the method is the presence of turbulence with a sufficiently long decorrelation time. It is shown that at the shear layer the decorrelation time is reduced, limiting the application of the method. The magnetic field pitch angle measured by this method shows the expected dependence on the magnetic field, plasma current and radial position. The profile of the pitch angle reproduces the expected shape and values. However, comparison with the equilibrium reconstruction code cliste suggests an additional inclination of turbulent eddies at the pedestal position (2-3°). This additional angle decreases towards the core and at the edge.

  2. Measuring Collisionless Damping in Heliospheric Plasmas using Field-Particle Correlations

    CERN Document Server

    Klein, Kristopher G

    2016-01-01

    An innovative field-particle correlation technique is proposed that uses single-point measurements of the electromagnetic fields and particle velocity distribution functions to investigate the net transfer of energy from fields to particles associated with the collisionless damping of turbulent fluctuations in weakly collisional plasmas, such as the solar wind. In addition to providing a direct estimate of the local rate of energy transfer between fields and particles, it provides vital new information about the distribution of that energy transfer in velocity space. This velocity-space signature can potentially be used to identify the dominant collisionless mechanism responsible for the damping of turbulent fluctuations in the solar wind. The application of this novel field-particle correlation technique is illustrated using the simplified case of the Landau damping of Langmuir waves in an electrostatic 1D-1V Vlasov-Poisson plasma, showing that the procedure both estimates the local rate of energy transfer f...

  3. A pulsed wire probe for the measurement of velocity and flow direction in slowly moving air.

    Science.gov (United States)

    Olson, D E; Parker, K H; Snyder, B

    1984-02-01

    This report describes the theory and operation of a pulsed-probe anemometer designed to measure steady three-dimensional velocity fields typical of pulmonary tracheo-bronchial airflows. Local velocities are determined by measuring the transport time and orientation of a thermal pulse initiated at an upstream wire and sensed at a downstream wire. The transport time is a reproducible function of velocity and the probe wire spacing, as verified by a theoretical model of convective heat transfer. When calibrated the anemometer yields measurements of velocity accurate to +/- 5 percent and resolves flow direction to within 1 deg at airspeeds greater than or equal to 10 cm/s. Spatial resolution is +/- 0.5 mm. Measured flow patterns typical of curved circular pipes are included as examples of its application.

  4. Use of hot wire anemometry to measure velocity of the limb during human movement.

    Science.gov (United States)

    Sun, S C; Mote, C D; Skinner, H B

    1992-09-01

    Hot film anemometry, x-configuration probes were used in two experiments to evaluate their effectiveness at measurement of limb velocity. Data from tests with a probe attached to the end of a pendulum establish that the hot films measure velocity in the swing phase within 0.098 ms-1. The kinetic energy per unit mass of the pendulum was predicted within +/- 0.005 m2 s-2, from the measured velocity. In gait experiments with one human subject at speeds greater than 0.25 ms-1, the hot film anemometer and a video system predicted speeds within 0.083 ms-1. The hot film data are electronic signals that are easily stored and processed. The results from these experiments demonstrate that hot film anemometry is an effective and efficient method for direct measurement and analysis of the limb velocity.

  5. Correlation of Spherical Thermistor for the Measurement of Low Velocity Air Flow

    Institute of Scientific and Technical Information of China (English)

    Xin-GangLiang; Ying-PingZhang; 等

    1998-01-01

    A spherical thermistor,an accurate temperature sensor is employed as an air velocity sensor in this work.The measuring principle is derived and the effects of the insulation layer,air temperature,netural convection and thermal radiation are discussed.Two different correlation relations for velocity measurements are proposed based on theoretical analyses and experimental calibrations,Experiments have shown that spherical thermistor is a good velocity sensor for speed between 0.1-2.5m/s at room temperature and the insulation layer hardly influences the accuracy of the thermistor used in the present work,Modification of correlation can even further imporve measurement accuracy.Since the thermistor is small and cheap,it is possible to apply this method to multi-Point velocity measurement with a low disturbance to the flow field.

  6. Thrust Stand Measurements of a Conical Pulsed Inductive Plasma Thruster

    Science.gov (United States)

    Hallock, Ashley K.; Polzin, Kurt A.; Emsellem, Gregory D.

    2012-01-01

    Pulsed inductive plasma thrusters [1-3] are spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10-100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, pulsed inductive plasma thrusters can su er from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. The Microwave Assisted Discharge Inductive Plasma Accelerator (MAD-IPA)[4], shown in Fig. 1 is a pulsed inductive plasma thruster that is able to operate at lower pulse energies by partially ionizing propellant with an electron cyclotron resonance (ECR) discharge inside a conical inductive coil whose geometry serves to potentially increase propellant and plasma plume containment relative to at coil geometries. The ECR plasma is created with the use of permanent mag- nets arranged to produce a thin resonance region along the inner surface of the coil, restricting plasma formation and, in turn, current sheet formation to areas of high magnetic coupling to the driving coil.

  7. EVIDENCE OF HOT HIGH VELOCITY PHOTOIONIZED PLASMA FALLING ON ACTIVELY ACCRETING T TAURI STARS

    Energy Technology Data Exchange (ETDEWEB)

    Gómez de Castro, Ana Ines [Grupo de Investigación Complutense AEGORA and S.D. Astronomía y Geodesia, Fac. de CC Matemáticas, Universidad Complutense, E-28040 Madrid (Spain)

    2013-10-01

    The He II (1640 Å) line and the resonance doublet of N V (UV1) provide a good diagnostic tool to constrain the excitation mechanism of hot (T{sub e} > 40,000 K) atmospheric/magnetospheric plasmas in T Tauri stars (TTSs). Making use of the data available in the Hubble Space Telescope archive, this work shows that there are at least two distinct physical components contributing to the radiation in these tracers: the accretion flow sliding on the magnetosphere and the atmosphere. The N V profiles in most sources are symmetric and at rest with respect to the star. The velocity dispersion of the profile increases from non-accreting (σ = 40 km s{sup –1}) to accreting (σ = 120 km s{sup –1}) TTSs, suggesting that the macroturbulence field in the line formation region decreases as the stars approach the main sequence. Evidence of the N V line being formed in a hot solar-like wind has been found in RW Aur, HN Tau, and AA Tau. The He II profile has a strong narrow component that dominates the line flux; the dispersion of this component ranges from 20 to 60 km s{sup –1}. Current data suggest that both accretion shocks and atmospheric emission might contribute to the line flux. In some sources, the He II line shows a broad and redward-shifted emission component often accompanied by semiforbidden O III] emission that has a critical electron density of ∼3.4 × 10{sup 10} cm{sup 3}. In spite of their different origins (inferred from the kinematics of the line formation region), N V and He II fluxes are strongly correlated, with only the possible exception of some of the heaviest accretors.

  8. Measuring Ultrasonic Acoustic Velocity in a Thin Sheet of Graphite Epoxy Composite

    Science.gov (United States)

    2008-01-01

    A method for measuring the acoustic velocity in a thin sheet of a graphite epoxy composite (GEC) material was investigated. This method uses two identical acoustic-emission (AE) sensors, one to transmit and one to receive. The delay time as a function of distance between sensors determines a bulk velocity. A lightweight fixture (balsa wood in the current implementation) provides a consistent method of positioning the sensors, thus providing multiple measurements of the time delay between sensors at different known distances. A linear fit to separation, x, versus delay time, t, will yield an estimate of the velocity from the slope of the line.

  9. Coherent Doppler Lidar for Measuring Velocity and Altitude of Space and Arial Vehicles

    Science.gov (United States)

    Amzajerdian, Farzin; Pierrottet, Diego; Hines, Glenn D.; Petway, Larry; Barnes, Bruce W.

    2016-01-01

    A coherent Doppler lidar has been developed to support future NASA missions to planetary bodies. The lidar transmits three laser beams and measures line-of-sight range and velocity along each beam using a frequency modulated continuous wave (FMCW) technique. Accurate altitude and velocity vector data, derived from the line-of-sight measurements, enables the landing vehicle to precisely navigate from several kilometers above the ground to the designated location and execute a gentle touchdown. The same lidar sensor can also benefit terrestrial applications that cannot rely on GPS or require surface-relative altitude and velocity data.

  10. Computer signal processing for ultrasonic attenuation and velocity measurements for material property characterizations

    Science.gov (United States)

    Vary, A.

    1979-01-01

    This report deals with instrumentation and computer programming concepts that have been developed for ultrasonic materials characterization. Methods that facilitate velocity and attenuation measurements are described. The apparatus described is based on a broadband, buffered contact probe using a pulse-echo approach for simultaneously measuring velocity and attenuation. Instrumentation, specimen condition, and signal acquisition and acceptance criteria are discussed. Typical results with some representative materials are presented.

  11. Comparative study of electrostatic sensors with circular and probe electrodes for velocity measurement of pulverised coal

    Institute of Scientific and Technical Information of China (English)

    Shao Jiaqing; Krabicka Jan; Yah Yong

    2007-01-01

    This paper presents recent progress on the velocity measurement of pulverised coal in pneumatic pipelines using electrostatic sensors in combination with correlation signal processing techniques. A comparative study of electrostatic sensors with circular and probe electrodes was conducted on a 94 mm bore horizontal pipeline in a 4 MW furnace. The advantages and limitations of both sensors are discussed. Experimental results demonstrate that both sensors are capable of providing pulverised coal velocity measurement with excellent repeatability and dynamic response.

  12. Measuring two-dimensional components of a flow velocity vector using a hot-wire probe.

    Science.gov (United States)

    Kiełbasa, Jan

    2007-08-01

    The article presents a single-hot-wire probe adapted to detect the direction of flow velocity. The modification consists of the introduction of a third support which allows to measure voltage at the central point of the wire. The sign of voltage difference DeltaU between both parts of the wire is the measure of the direction of flow velocity in a system of coordinates associated with the probe.

  13. Use of the Hot Wire Anemometry for Velocity and Temperature Measurements in a Turbomachine

    OpenAIRE

    Blidi, Sami; Miton, Hubert

    1995-01-01

    The hot film anemometry in a highly heterogeneous unsteady flow is a quite complex measurement technique. The velocity is determined from the heat flux measurement. The part of the signal related to velocity must be kept apart from one related to temperature and to pressure of flow. After a brief return to the principle of hot wire anemometry and the different heat transfer models between hot wire and flow, an experimentally established heat flux expression is presented. This study was achiev...

  14. Experimental determination of the onset of turbulence on inclined plates using hot wire velocity measurements

    OpenAIRE

    Rodríguez Sevillano, Angel; Pérez Grande, María Isabel; Meseguer Ruiz, José

    2010-01-01

    The problem of determination of the turbulence onset in natural convection on heated inclined plates in an air environment has been experimentally revisited. The transition has been detected by using hot wire velocity measurements. The onset of turbulence has been considered to take place where velocity fluctuations (measured through turbulence intensity) start to grow. Experiments have shown that the distance to the plate edge where the onset begins depends both on the plate inclinatio...

  15. 3D velocity measurement by a single camera using Doppler phase-shifting holography

    Science.gov (United States)

    Ninomiya, Nao; Kubo, Yamato; Barada, Daisuke; Kiire, Tomohiro

    2016-10-01

    In order to understand the details of the flow field in micro- and nano-fluidic devices, it is necessary to measure the 3D velocities under a microscopy. Thus, there is a strong need for the development of a new measuring technique for 3D velocity by a single camera. One solution is the use of holography, but it is well known that the accuracy in the depth direction is very poor for the commonly used in-line holography. At present, the Doppler phase-shifting holography is used for the 3D measurement of an object. This method extracts the signal of a fixed frequency caused by the Doppler beat between the object light and the reference light. It can measure the 3D shape precisely. Here, the frequency of the Doppler beat is determined by the velocity difference between the object light and the reference light. This implies that the velocity of an object can be calculated by the Doppler frequency. In this study, a Japanese 5 yen coin was traversed at a constant speed and its holography has been observed by a high-speed camera. By extracting only the first order diffraction signal at the Doppler frequency, a precise measurement of the shape and the position of a 5 yen coin has been achieved. At the same time, the longitudinal velocity of a 5 yen coin can be measured by the Doppler frequency. Furthermore, the lateral velocities are obtained by particle image velocimetry (PIV) method. A 5 yen coin has been traversed at different angles and its shapes and the 3D velocities have been measured accurately. This method can be applied to the particle flows in the micro- or nano-devices, and the 3D velocities will be measured under microscopes.

  16. Laser and acoustic Doppler techniques for the measurement of fluid velocities

    Science.gov (United States)

    Cliff, W. C.

    1975-01-01

    An overview of current laser and acoustic Doppler techniques is presented. Results obtained by Doppler anemometry and conventional sensors are compared. Comparisons include simultaneous velocity measurements by hot wire and a three-dimensional laser anemometer made in a gaseous pipe flow as well as direct comparisons of atmospheric velocities measured with propeller and cup anemometry. Scanning techniques are also discussed. Conclusions and recommendations for future work are presented.

  17. Penetrative convection in stratified fluids: velocity and temperature measurements

    Directory of Open Access Journals (Sweden)

    M. Moroni

    2006-01-01

    Full Text Available The flux through the interface between a mixing layer and a stable layer plays a fundamental role in characterizing and forecasting the quality of water in stratified lakes and in the oceans, and the quality of air in the atmosphere. The evolution of the mixing layer in a stably stratified fluid body is simulated in the laboratory when "Penetrative Convection" occurs. The laboratory model consists of a tank filled with water and subjected to heating from below. The methods employed to detect the mixing layer growth were thermocouples for temperature data and two image analysis techniques, namely Laser Induced Fluorescence (LIF and Feature Tracking (FT. LIF allows the mixing layer evolution to be visualized. Feature Tracking is used to detect tracer particle trajectories moving within the measurement volume. Pollutant dispersion phenomena are naturally described in the Lagrangian approach as the pollutant acts as a tag of the fluid particles. The transilient matrix represents one of the possible tools available for quantifying particle dispersion during the evolution of the phenomenon.

  18. Large density amplification measured on jets ejected from a magnetized plasma gun

    OpenAIRE

    Yun, Gunsu S.; You, Setthivoine; Bellan, Paul M.

    2007-01-01

    Observation of a large density amplification in the collimating plasma jet ejected from a coplanar coaxial plasma gun is reported. The jet velocity is ~30 km s^-1 and the electron density increases from ~10^20 to 10^(22–23) m^-3. In previous spheromak experiments, electron density of the order 10^(19–21) m^-3 had been measured in the flux conserver region, but no density measurement had been reported for the source gun region. The coplanar geometry of our electrodes permits direct observation...

  19. Diode Laser Velocity Measurements by Modulated Filtered Rayleigh Scattering

    Science.gov (United States)

    Mach, J. J.; Varghese, P. L.; Jagodzinski, J. J.

    1999-01-01

    The ability of solid-state lasers to be tuned in operating frequency at MHz rates by input current modulation, while maintaining a relatively narrow line-width, has made them useful for spectroscopic measurements. Their other advantages include low cost, reliability, durability, compact size, and modest power requirements, making them a good choice for a laser source in micro-gravity experiments in drop-towers and in flight. For their size, they are also very bright. In a filtered Rayleigh scattering (FRS) experiment, a diode laser can be used to scan across an atomic or molecular absorption line, generating large changes in transmission at the resonances for very small changes in frequency. The hyperfine structure components of atomic lines of alkali metal vapors are closely spaced and very strong, which makes such atomic filters excellent candidates for sensitive Doppler shift detection and therefore for high-resolution velocimetry. In the work we describe here we use a Rubidium vapor filter, and work with the strong D(sub 2) transitions at 780 nm that are conveniently accessed by near infrared diode lasers. The low power output of infrared laser diodes is their primary drawback relative to other laser systems commonly used for velocimetry. However, the capability to modulate the laser frequency rapidly and continuously helps mitigate this. Using modulation spectroscopy and a heterodyne detection scheme with a lock-in amplifier, one can extract sub-microvolt signals occurring at a specific frequency from a background that is orders of magnitude stronger. The diode laser modulation is simply achieved by adding a small current modulation to the laser bias current. It may also be swept repetitively in wavelength using an additional lower frequency current ramp.

  20. Axis and velocity determination for quasi two-dimensional plasma/field structures from Faraday's law: A second look

    Science.gov (United States)

    Sonnerup, Bengt U. Ö.; Denton, Richard E.; Hasegawa, Hiroshi; Swisdak, M.

    2013-05-01

    We re-examine the basic premises of a single-spacecraft data analysis method, developed by Sonnerup and Hasegawa (2005), for determining the axis orientation and proper frame velocity of quasi two-dimensional, quasi-steady structures of magnetic field and plasma. The method, which is based on Faraday's law, makes use of magnetic and electric field data measured by a single spacecraft traversing the structure, although in many circumstances the convection electric field, - v × B, can serve as a proxy for E. It has been used with success for flux ropes observed at the magnetopause but has usually failed to provide acceptable results when applied to real space data from reconnection events as well as to virtual data from numerical MHD simulations of such events. In the present paper, the reasons for these shortcomings are identified, analyzed, and discussed in detail. Certain basic properties of the method are presented in the form of five theorems, the last of which makes use of singular value decomposition to treat the special case where the magnetic variance matrix is non-invertible. These theorems are illustrated using data from analytical models of flux ropes and also from MHD simulations as well as a 2-D kinetic simulation of reconnection. The results make clear that the method requires the presence of a significant, non-removable electric field distribution in the plane transverse to the invariant direction and that it is sensitive to deviations from strict two-dimensionality and strict time stationarity.

  1. Increase of the Density, Temperature and Velocity of Plasma Jets driven by a Ring of High Energy Laser Beams

    CERN Document Server

    Fu, Wen; Fatenejad, Milad; Lamb, Donald Q; Grosskopf, Michael; Park, Hye-Sook; Remington, Bruce; Spitkovsky, Anatoly

    2012-01-01

    Supersonic plasma outflows driven by multi-beam, high-energy lasers, such as Omega and NIF, have been and will be used as platforms for a variety of laboratory astrophysics experiments. Here we propose a new way of launching high density and high velocity, plasma jets using multiple intense laser beams in a hollow ring formation. We show that such jets provide a more flexible and versatile platform for future laboratory astrophysics experiments. Using high resolution hydrodynamic simulations, we demonstrate that the collimated jets can achieve much higher density, temperature and velocity when multiple laser beams are focused to form a hollow ring pattern at the target, instead of focused onto a single spot. We carried out simulations with different ring radii and studied their effects on the jet properties. Implications for laboratory collisionless shock experiments are discussed.

  2. A Vector Measurement-based Angular Velocity Estimation Scheme for Maneuvering Spacecraft

    Science.gov (United States)

    Jo, Sujang; Bang, Hyochoong; Leeghim, Henzeh

    2017-09-01

    A new practical approach to estimate the body angular velocity of maneuvering spacecraft using only vector measurements is presented. Several algorithms have been introduced in previous studies to estimate the angular velocity directly from vector measurements at two time instants. However, these direct methods are based on the constant angular velocity assumption, and estimation results may be invalid for attitude maneuvers. In this paper, an estimation scheme to consider attitude disturbances and control torques is proposed. The effects of angular velocity variation on estimation results are quantitatively evaluated, and an algorithm to minimize estimation errors is designed by selecting the optimal time interval between vector measurements. Without losing the simplicity of direct methods, the design parameters of the algorithm are restricted to the expected covariance of disturbances and the maximum angular acceleration. By applying the proposed estimation scheme, gyroscopes can be directly replaced by attitude sensors such as star trackers.

  3. Front-Crawl Instantaneous Velocity Estimation Using a Wearable Inertial Measurement Unit

    Directory of Open Access Journals (Sweden)

    Kamiar Aminian

    2012-09-01

    Full Text Available Monitoring the performance is a crucial task for elite sports during both training and competition. Velocity is the key parameter of performance in swimming, but swimming performance evaluation remains immature due to the complexities of measurements in water. The purpose of this study is to use a single inertial measurement unit (IMU to estimate front crawl velocity. Thirty swimmers, equipped with an IMU on the sacrum, each performed four different velocity trials of 25 m in ascending order. A tethered speedometer was used as the velocity measurement reference. Deployment of biomechanical constraints of front crawl locomotion and change detection framework on acceleration signal paved the way for a drift-free integration of forward acceleration using IMU to estimate the swimmers velocity. A difference of 0.6 ± 5.4 cm·s−1 on mean cycle velocity and an RMS difference of 11.3 cm·s−1 in instantaneous velocity estimation were observed between IMU and the reference. The most important contribution of the study is a new practical tool for objective evaluation of swimming performance. A single body-worn IMU provides timely feedback for coaches and sport scientists without any complicated setup or restraining the swimmer’s natural technique.

  4. A Catalytic Sensor for Measurement of Radical Density in CO2 Plasmas

    Directory of Open Access Journals (Sweden)

    Alenka Vesel

    2012-11-01

    Full Text Available A catalytic sensor for the measurement of radical density in weakly ionized CO2 plasmas, created in a low-pressure electrodeless discharge, is presented. The CO2 plasma was created in a 4 cm wide borosilicate glass tube inside a copper coil connected to a radio frequency generator operating at 27.12 MHz with a nominal power of 250 W. The dissociation fraction of the CO2 molecules was measured in the early afterglow at pressures ranging from 10 Pa to 100 Pa, and at distances of up to 35 cm along the gas stream from the glowing plasma. The radical density peaked (2 × 1020 m–3 at 80 Pa. The density quickly decreased with increasing distance from the glowing plasma despite a rather large drift velocity. The dissociation fraction showed similar behavior, except that the maximum was obtained at somewhat lower pressure. The results were explained by rather intense surface recombination of radicals.

  5. S-wave velocity structures of the Taipei Basin, Taiwan, using microtremor array measurements

    Science.gov (United States)

    Huang, Huey-Chu; Wu, Cheng-Feng; Lee, Feng-Mei; Hwang, Ruey-Der

    2015-04-01

    The S-wave velocity structures of the Taipei Basin in Taiwan are investigated using the array records of microtremors at 15 sites. Dispersion curves at these sites are calculated using the frequency-wavenumber (F-K) spectrum method. The S-wave velocity structures in the Taipei Basin are then estimated by employing surface wave inversion technique. Harder strata sites have higher phase velocities than softer sites. If the S-wave velocity of the Tertiary Basement is assumed to be 1000 m/s, then the Quaternary alluvial thicknesses in the Taipei Basin are between about 100 m and 650 m. The thickness of the alluvium gradually increases from the southeast to the northwest. The inversion results are also in good agreement with well-logging data and seismic reflection studies of the Taipei Basin. The study concludes that microtremor array measurement is a useful tool for estimating S-wave velocity structure.

  6. In vivo lateral blood flow velocity measurement using speckle size estimation.

    Science.gov (United States)

    Xu, Tiantian; Hozan, Mohsen; Bashford, Gregory R

    2014-05-01

    In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is "smeared") if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method

  7. Comparison of H-mode plasma simulations using toroidal velocity models depending on plasma current density and ion temperature in presence of an ITB

    Directory of Open Access Journals (Sweden)

    Boonyarit Chatthong

    2014-06-01

    Full Text Available Two different approaches for predicting plasma toroidal velocity (v are developed and used in self-consistent simulations of H-mode plasmas with the presence of ITB using BALDUR integrated predictive modelling code. In the first approach, the toroidal velocity depends on the plasma current density; while in the second approach the toroidal velocity is directly proportional to the ion temperature. The profile of v is used to calculate the ExB flow shear which is a main mechanism for plasma transport suppression, leading to the ITB formation. In all simulations, the core transport model is a combination of NCLASS neoclassical transport and semi-empirical Mixed Bohm/gyro-Bohm model that includes the ITB effects. The boundary condition is set at top of the pedestal and is estimated using a pedestal model based on a combination of magnetic and flow shear stabilization pedestal width scaling and an infinite-n ballooning pressure gradient. Two toroidal velocity models are used to simulate the time evolution of plasma temperature and density profiles of 10 JET discharges. The root mean square error (RMSE is used to compare simulation results of those 10 JET discharges with experimental data. It is found that RMSE of Ti , Te , ne are 28.1%, 31.8%, and 15.0% for the first toroidal velocity model and 25.5%, 30.2%, and 15.1% for the second toroidal velocity model, respectively. Furthermore, this suite of codes is used to predict the ITER performance under standard type I ELMy H-mode. It is found that the simulation yields formation of a narrow ITB near r/a = 0.7 in the simulation using the current density dependent model and a wide ITB from r/a = 0.5 to 0.8 in the simulation using the ion temperature dependent model. The average of central ion temperature, total fusion power output and alpha power are predicted to be 36 keV, 159 MW and 492 MW for the current density dependent model and 49 keV, 218 MW and 786 MW for the ion temperature dependent

  8. Number-conserving linear response study of low-velocity ion stopping in a collisional magnetized classical plasma

    Directory of Open Access Journals (Sweden)

    Nersisyan Hrachya B.

    2013-11-01

    Full Text Available The low-velocity stopping power of ions in a magnetized collisional plasma is studied through the linear response theory. The collisions are taken into account through a number-conserving relaxation time approximation. One of the major objectives of this study is to compare and contrast our theoretical results with those obtained through a diffusion coefficient formulation based on Dufty-Berkovsky relation.

  9. Reliability of the Measured Velocity Anisotropy of the Milky Way Stellar Halo

    Science.gov (United States)

    Hattori, Kohei; Valluri, Monica; Loebman, Sarah R.; Bell, Eric F.

    2017-06-01

    Determining the velocity distribution of halo stars is essential for estimating the mass of the Milky Way and for inferring its formation history. Since the stellar halo is a dynamically hot system, the velocity distribution of halo stars is well described by the three-dimensional velocity dispersions ({σ }r,{σ }θ ,{σ }φ ) or by the velocity anisotropy parameter β =1-({σ }θ 2+{σ }φ 2)/(2{σ }r2). Direct measurements of ({σ }r,{σ }θ ,{σ }φ ) consistently suggest β = 0.5-0.7 for nearby halo stars. In contrast, the value of β at large Galactocentric radius r is still controversial, since reliable proper motion data are available for only a handful of stars. In the last decade, several authors have tried to estimate β for distant halo stars by fitting the observed line-of-sight velocities at each radius with simple velocity distribution models (local fitting methods). Some results of local fitting methods imply β < 0 at r≳ 20 {kpc}, which is inconsistent with recent predictions from cosmological simulations. Here we perform mock-catalog analyses to show that the estimates of β based on local fitting methods are reliable only at r≤slant 15 {kpc} with the current sample size (˜103 stars at a given radius). As r increases, the line-of-sight velocity (corrected for the solar reflex motion) becomes increasingly closer to the Galactocentric radial velocity, so it becomes increasingly more difficult to estimate the tangential velocity dispersion ({σ }θ ,{σ }φ ) from the line-of-sight velocity distribution. Our results suggest that the forthcoming Gaia data will be crucial for understanding the velocity distribution of halo stars at r≥slant 20 {kpc}.

  10. The Measurement of cloud velocity using the pulsed laser and image tracking technique

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Seong-Ouk; Baik, Seung-Hoon; Park, Seung-Kyu; Park, Nak-Gyu; Kim, Dong-lyul; Ahn, Yong-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    The height of the clouds is also important for the three dimensional radiative interaction of aerosols and clouds, since the radiative effects vary strongly depending whether the cloud is above, below or even embedded in an aerosol layer. Clouds play an important role in climate change, in the prediction of local weather, and also in aviation safety when instrument assisted flying is unavailable. Presently, various ground-based instruments used for the measurements of the cloud base height or velocity. Lidar techniques are powerful and have many applications in climate studies, including the clouds' temperature measurement, the aerosol particle properties, etc. Otherwise, it is very circumscribed in cloud velocity measurements In this paper, we propose a new method to measure the cloud velocity. In this paper, we presented a method for the measurement of the cloud altitude and velocity using lidar's range detection and the tracking system. For the lidar system, we used an injection-seeded pulsed Nd:YAG laser as the transmitter to measure the distance to the target clouds. We used the DIC system to track the cloud image and calculate the actual displacement per unit time. The configured lidar system acquired the lidar signal of clouds at a distance of about 4 km. The developed fast correlation algorithm of the tracking, which is used to track the fast moving cloud relatively, was efficient for measuring the cloud velocity in real time. The measurement values had a linear distribution.

  11. Modifications to the pulsar kick velocity due to magnetic interactions in dense plasma

    Science.gov (United States)

    Adhya, S. P.; Roy, P. K.; Dutt-Mazumder, A. K.

    2014-02-01

    In this work we calculate the pulsar kick velocity of a magnetized neutron star (NS) composed of a degenerate quark matter core with non-Fermi liquid (NFL) correction. Both the leading order (LO) and next to LO (NLO) corrections to the kick velocity have been incorporated. In addition, the NFL corrections to the specific heat of magnetized quark matter have been presented. This has been taken into account to calculate the kick velocity of the NS. The results show a significant departure from the normal Fermi liquid estimates. The relation between radius and temperature has been shown with a kick velocity of 100 km s-1 with and without NFL corrections.

  12. Measurements of solids concentration and axial solids velocity in gas-solid two-phase flows.

    NARCIS (Netherlands)

    Nieuwland, J.J.; Meijer, R.; Kuipers, J.A.M.; Swaaij, van W.P.M.

    1996-01-01

    Several techniques reported in the literature for measuring solids concentration and solids velocity in (dense) gas-solid two-phase flow have been briefly reviewed. An optical measuring system, based on detection of light reflected by the suspended particles, has been developed to measure local soli

  13. Molecular Rayleigh Scattering Diagnostic for Dynamic Temperature, Velocity, and Density Measurements

    Science.gov (United States)

    Mielke, Amy R.; Elam, Kristie A.; Sung, Chi-Jen

    2006-01-01

    A molecular Rayleigh scattering technique is developed to measure dynamic gas temperature, velocity, and density in unseeded turbulent flows at sampling rates up to 16 kHz. A high power CW laser beam is focused at a point in an air jet plume and Rayleigh scattered light is collected and spectrally resolved. The spectrum of the light, which contains information about the temperature and velocity of the flow, is analyzed using a Fabry-Perot interferometer. The circular interference fringe pattern is divided into four concentric regions and sampled at 1 and 16 kHz using photon counting electronics. Monitoring the relative change in intensity within each region allows for measurement of gas temperature and velocity. Independently monitoring the total scattered light intensity provides a measure of gas density. A low speed heated jet is used to validate the measurement of temperature fluctuations and an acoustically excited nozzle flow is studied to validate velocity fluctuation measurements. Power spectral density calculations of the property fluctuations, as well as mean and fluctuating quantities are presented. Temperature fluctuation results are compared with constant current anemometry measurements and velocity fluctuation results are compared with constant temperature anemometry measurements at the same locations.

  14. Comparing shear-wave velocity profiles inverted from multichannel surface wave with borehole measurements

    Science.gov (United States)

    Xia, J.; Miller, R.D.; Park, C.B.; Hunter, J.A.; Harris, J.B.; Ivanov, J.

    2002-01-01

    Recent field tests illustrate the accuracy and consistency of calculating near-surface shear (S)-wave velocities using multichannel analysis of surface waves (MASW). S-wave velocity profiles (S-wave velocity vs. depth) derived from MASW compared favorably to direct borehole measurements at sites in Kansas, British Columbia, and Wyoming. Effects of changing the total number of recording channels, sampling interval, source offset, and receiver spacing on the inverted S-wave velocity were studied at a test site in Lawrence, Kansas. On the average, the difference between MASW calculated Vs and borehole measured Vs in eight wells along the Fraser River in Vancouver, Canada was less than 15%. One of the eight wells was a blind test well with the calculated overall difference between MASW and borehole measurements less than 9%. No systematic differences were observed in derived Vs values from any of the eight test sites. Surface wave analysis performed on surface data from Wyoming provided S-wave velocities in near-surface materials. Velocity profiles from MASW were confirmed by measurements based on suspension log analysis. ?? 2002 Elsevier Science Ltd. All rights reserved.

  15. Classical Heat-Flux Measurements in Coronal Plasmas from Collective Thomson-Scattering Spectra

    Science.gov (United States)

    Henchen, R. J.; Hu, S. X.; Katz, J.; Froula, D. H.; Rozmus, W.

    2016-10-01

    Collective Thomson scattering was used to measure heat flux in coronal plasmas. The relative amplitude of the Thomson-scattered power into the up- and downshifted electron plasma wave features was used to determine the flux of electrons moving along the temperature gradient at three to four times the electron thermal velocity. Simultaneously, the ion-acoustic wave features were measured. Their relative amplitude was used to measure the flux of the return-current electrons. The frequencies of these ion-acoustic and electron plasma wave features provide local measurements of the electron temperature and density. These spectra were obtained at five locations along the temperature gradient in a laser-produced blowoff plasma. These measurements of plasma parameters are used to infer the Spitzer-Härm flux (qSH = - κ∇Te ) and are in good agreement with the values of the heat flux measured from the scattering-feature asymmetries. Additional experiments probed plasma waves perpendicular to the temperature gradient. The data show small effects resulting from heat flux compared to probing waves along the temperature gradient. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  16. A dual-phantom system for validation of velocity measurements in stenosis models under steady flow.

    Science.gov (United States)

    Blake, James R; Easson, William J; Hoskins, Peter R

    2009-09-01

    A dual-phantom system is developed for validation of velocity measurements in stenosis models. Pairs of phantoms with identical geometry and flow conditions are manufactured, one for ultrasound and one for particle image velocimetry (PIV). The PIV model is made from silicone rubber, and a new PIV fluid is made that matches the refractive index of 1.41 of silicone. Dynamic scaling was performed to correct for the increased viscosity of the PIV fluid compared with that of the ultrasound blood mimic. The degree of stenosis in the models pairs agreed to less than 1%. The velocities in the laminar flow region up to the peak velocity location agreed to within 15%, and the difference could be explained by errors in ultrasound velocity estimation. At low flow rates and in mild stenoses, good agreement was observed in the distal flow fields, excepting the maximum velocities. At high flow rates, there was considerable difference in velocities in the poststenosis flow field (maximum centreline differences of 30%), which would seem to represent real differences in hydrodynamic behavior between the two models. Sources of error included: variation of viscosity because of temperature (random error, which could account for differences of up to 7%); ultrasound velocity estimation errors (systematic errors); and geometry effects in each model, particularly because of imperfect connectors and corners (systematic errors, potentially affecting the inlet length and flow stability). The current system is best placed to investigate measurement errors in the laminar flow region rather than the poststenosis turbulent flow region.

  17. Profile Measurement of Ion Temperature and Toroidal Rotation Velocity with Charge Exchange Recombination Spectroscopy Diagnostics in the HL-2A Tokamak

    Institute of Scientific and Technical Information of China (English)

    吴静; 姚列明; 朱建华; 韩晓玉; 李文柱

    2012-01-01

    This paper deals with the profile measurement of impurity ion temperature and toroidal rotation velocity that can be achieved by using the charge exchange recombination spectrum (CXRS) diagnostics tool built on the HL-2A toknmak. By using CXRS, an accurate impurity ion temperature and toroidal plasma rotation velocity profile can be achieved under the condition of neutrM beam injection (NBI) heating. Considering the edge effect of the line of CVI 529.06 nm (n= 8-7), which contains three lines (active exciting spectral line (ACX), passivity exciting spectral line (PCX) and electron exciting spectral line (ICE)), and using three Gaussian fitted curves, we obtain the following experimental results: the core ion temperature of HL-2A device is nearly thousands of eV, and the plasma rotation velocity reaches about 104 m· s^-1. At the end of paper, some explanations are presented for the relationship between the curves and the inner physical mechanism.

  18. Profile Measurement of Ion Temperature and Toroidal Rotation Velocity with Charge Exchange Recombination Spectroscopy Diagnostics in the HL-2A Tokamak

    Science.gov (United States)

    Wu, Jing; Yao, Lieming; Zhu, Jianhua; Han, Xiaoyu; Li, Wenzhu

    2012-11-01

    This paper deals with the profile measurement of impurity ion temperature and toroidal rotation velocity that can be achieved by using the charge exchange recombination spectrum (CXRS) diagnostics tool built on the HL-2A tokamak. By using CXRS, an accurate impurity ion temperature and toroidal plasma rotation velocity profile can be achieved under the condition of neutral beam injection (NBI) heating. Considering the edge effect of the line of CVI 529.06 nm (n = 8~7), which contains three lines (active exciting spectral line (ACX), passivity exciting spectral line (PCX) and electron exciting spectral line (ICE)), and using three Gaussian fitted curves, we obtain the following experimental results: the core ion temperature of HL-2A device is nearly thousands of eV, and the plasma rotation velocity reaches about 104 m · s-1. At the end of paper, some explanations are presented for the relationship between the curves and the inner physical mechanism.

  19. Measurement of the electron drift velocity for directional dark matter detectors

    CERN Document Server

    Mayet, F; Bosson, G; Bourrion, O; Guillaudin, O; Lamblin, J; Richer, J P; Riffard, Q; Santos, D; Iguaz, F J; Lebreton, L; Maire, D

    2014-01-01

    Three-dimensional track reconstruction is a key issue for directional Dark Matter detection. It requires a precise knowledge of the electron drift velocity. Magboltz simulations are known to give a good evaluation of this parameter. However, large TPC operated underground on long time scale may be characterized by an effective electron drift velocity that may differ from the value evaluated by simulation. In situ measurement of this key parameter is hence a way to avoid bias in the 3D track reconstruction. We present a dedicated method for the measurement of the electron drift velocity with the MIMAC detector. It is tested on two gas mixtures : $\\rm CF_4$ and $\\rm CF_4+CHF_3$. We also show that adding $\\rm CHF_3$ allows us to lower the electron drift velocity while keeping almost the same Fluorine content of the gas mixture.

  20. Measurement of gas flow velocity: anemometer with a vibrating hot wire.

    Science.gov (United States)

    Kiełbasa, Jan

    2010-01-01

    I propose a new method to measure velocity of a gas flow, which utilizes the time derivative of the voltage observed on a vibrating hot-wire sensor. The wire vibrates with an amplitude a and a frequency f, and is kept perpendicular to the gas flow direction in the plane containing the flow velocity vector v(g). When the parameters of vibrations are tuned, the number of zeros per vibration period of the hot-wire voltage function changes. I demonstrate that at the point of change, the unknown gas velocity is directly expressed by the parameters of vibrations v(g)=2pifa. Therefore, the velocity can be measured without any prior calibration of the hot-wire speed-voltage curve and the method can be used for gases of slowly changing temperature or composition.

  1. An experiment to measure the one-way velocity of propagation of electromagnetic radiation

    Science.gov (United States)

    Kolen, P.; Torr, D. G.

    1982-01-01

    An experiment involving commercially available instrumentation to measure the velocity of the earth with respect to absolute space is described. The experiment involves the measurement of the one-way propagation velocity of electromagnetic radiation down a high-quality coaxial cable. It is demonstrated that the experiment is both physically meaningful and exceedingly simple in concept and in implementation. It is shown that with currently available commercial equipment one might expect to detect a threshold value for the component of velocity of the earth's motion with respect to absolute space in the equatorial plane of approximately 10 km/s, which greatly exceeds the velocity resolution required to detect the motion of the solar system with respect to the center of the galaxy.

  2. Main-ion temperature and plasma rotation measurements based on scattering of electron cyclotron heating waves in ASDEX Upgrade

    DEFF Research Database (Denmark)

    Pedersen, Morten Stejner; Rasmussen, Jesper; Nielsen, Stefan Kragh

    2017-01-01

    We demonstrate measurements of spectra of O-mode electron cyclotron resonance heating (ECRH) waves scattered collectively from microscopic plasma fluctuations in ASDEX Upgrade discharges with an ITER-like ECRH scenario. The measured spectra are shown to allow determination of the main ion...... temperature and plasma rotation velocity. This demonstrates that ECRH systems can be exploited for diagnostic purposes alongside their primary heating purpose in a reactor relevant scenario....

  3. Main-ion temperature and plasma rotation measurements based on scattering of electron cyclotron heating waves in ASDEX Upgrade

    Science.gov (United States)

    Stejner, M.; Rasmussen, J.; Nielsen, S. K.; Jacobsen, A. S.; Korsholm, S. B.; Leipold, F.; McDermott, R. M.; Salewski, M.; Schubert, M.; Stober, J.; Wagner, D. H.; the ASDEX Upgrade Team; the EUROfusion MST1 Team

    2017-07-01

    We demonstrate measurements of spectra of O-mode electron cyclotron resonance heating (ECRH) waves scattered collectively from microscopic plasma fluctuations in ASDEX Upgrade discharges with an ITER-like ECRH scenario. The measured spectra are shown to allow determination of the main ion temperature and plasma rotation velocity. This demonstrates that ECRH systems can be exploited for diagnostic purposes alongside their primary heating purpose in a reactor relevant scenario.

  4. Plasma levels of the arterial wall protein fibulin-1 are associated with carotid-femoral pulse wave velocity

    DEFF Research Database (Denmark)

    Laugesen, Esben; Høyem, Pernille; Christiansen, Jens Sandahl;

    2013-01-01

    -associated extracellular matrix protein, fibulin-1, was recently found in higher concentrations in the arterial wall and in plasma in patients with long duration type 2 diabetes. Furthermore, plasma fibulin-1 independently predicted total mortality and was associated with pulse pressure, an indirect measure of arterial...

  5. Inversion methods for fast-ion velocity-space tomography in fusion plasmas

    DEFF Research Database (Denmark)

    Jacobsen, Asger Schou; Stagner, L.; Salewski, Mirko

    2016-01-01

    Velocity-space tomography has been used to infer 2D fast-ion velocity distribution functions. Here we compare the performance of five different tomographic inversion methods: truncated singular value decomposition, maximum entropy, minimum Fisher information and zeroth and first-order Tikhonov re...

  6. 信息动态%Sound Velocity Measurement of Mesoscale Objects Using Laser Ultrasonics Technique

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    A laser-based ultrasound system was designed and built to measure the sound velocity of mesoscale (tens of micrometer to millimeter-sized) objects. The system uses a Q-switch laser with 6.3 ns pulse width for excitation of broadband ultrasonic waves,and an optical fiber displacement interferometer for detection. The longitudinal acoustic wave velocities of the copper foils with different thicknesses were presented, which exhibit a relatively high degree of accuracy.

  7. Adaptive method for quantifying uncertainty in discharge measurements using velocity-area method.

    Science.gov (United States)

    Despax, Aurélien; Favre, Anne-Catherine; Belleville, Arnaud

    2015-04-01

    Streamflow information provided by hydrometric services such as EDF-DTG allow real time monitoring of rivers, streamflow forecasting, paramount hydrological studies and engineering design. In open channels, the traditional approach to measure flow uses a rating curve, which is an indirect method to estimate the discharge in rivers based on water level and punctual discharge measurements. A large proportion of these discharge measurements are performed using the velocity-area method; it consists in integrating flow velocities and depths through the cross-section [1]. The velocity field is estimated by choosing a number m of verticals, distributed across the river, where vertical velocity profile is sampled by a current-meter at ni different depths. Uncertainties coming from several sources are related to the measurement process. To date, the framework for assessing uncertainty in velocity-area discharge measurements is the method presented in the ISO 748 standard [2] which follows the GUM [3] approach. The equation for the combined uncertainty in measured discharge u(Q), at 68% level of confidence, proposed by the ISO 748 standard is expressed as: Σ 2 2 2 -q2i[u2(Bi)+-u2(Di)+-u2p(Vi)+-(1ni) ×-[u2c(Vi)+-u2exp(Vi)

  8. Laboratory measurement of longitudinal wave velocity of artificial gas hydrate under different temperatures and pressures

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The longitudinal wave velocity and attenuation measurements of artificial gas hy- drate samples at a low temperature are reported. And the temperature and pressure dependence of longitudinal wave velocity is also investigated. In order to under- stand the acoustic properties of gas hydrate, the pure ice, the pure tetrahydrofuran (THF), the pure gas hydrate samples and sand sediment containing gas hydrate are measured at a low temperature between 0℃ and –15℃. For the pure ice, the pure THF and the pure gas hydrate samples, whose density is 898 kg/m3, 895 kg/m3 and 475 kg/m3, the velocity of longitudinal wave is respectively 3574 m/s, 3428 m/s and 2439 m/s. For synthesized and compacted samples, the velocity of synthesized samples is lower than that of compacted samples. The velocities increase when the densities of the samples increase, while the attenuation decreases. Under the con- dition of low temperature, the results show that the velocity is slightly affected by the temperature. The results also show that wave velocities increase with the in- crease of piston pressures. For example, the velocity of one sample increases from 3049 up to 3337 m/s and the other increases from 2315 up to 2995 m/s. But wave velocity decreases from 3800 to 3546 m/s when the temperature increases from –15℃ to 5℃ and changes significantly close to the melting point. Formation con- ditions of the two samples are the same but with different conversion ratios of wa- ter. The results of the experiment are important for exploration of the gas hydrate resources and development of acoustic techniques.

  9. Measurements of dust deposition velocity in a wind-tunnel experiment

    Directory of Open Access Journals (Sweden)

    J. Zhang

    2014-04-01

    Full Text Available In this study, we present the results of a wind-tunnel experiment on dust deposition. A new method is proposed to derive dust deposition velocity from the PDA (Particle Dynamics Analysis particle-velocity and particle-size measurements. This method has the advantage that the motions of individual dust particles are directly observed and all relevant data for computing dust deposition velocity is collected using a single instrument, and therefore the measurement uncertainties are reduced. The method is used in the wind-tunnel experiment to measure the dust deposition velocities for different particle sizes, wind speeds and surface conditions. For a sticky-smooth wood surface and a water surface, the observed dust deposition velocities are compared with the predictions using a dust deposition scheme, and the entire dataset is compared with the data found in the literature. From the wind-tunnel experiments, a relatively reliable dataset of dust deposition velocity is obtained, which is of considerable value for the development and validation of dust deposition schemes.

  10. Velocity and Vorticity Measurements of Jupiter's Great Red Spot Using Automated Cloud Feature Tracking

    CERN Document Server

    Choi, David S; Gierasch, Peter J; Showman, Adam P; 10.1016/j.icarus.2006.10.037

    2013-01-01

    We have produced mosaics of the Great Red Spot (GRS) using images taken by the Galileo spacecraft in May 2000, and have measured the winds of the GRS using an automated algorithm that does not require manual cloud tracking. Our technique yields a high-density, regular grid of wind velocity vectors that is advantageous over a limited number of scattered wind vectors that result from manual cloud tracking. The high-velocity collar of the GRS is clearly seen from our velocity vector map, and highest wind velocities are measured to be around 170 m/s. The high resolution of the mosaics have also enabled us to map turbulent eddies inside the chaotic central region of the GRS, similar to those mapped by Sada et al. (1996) and Vasavada et al. (1998). Using the wind velocity measurements, we computed particle trajectories around the GRS as well as maps of relative and absolute vorticities. We have discovered a narrow ring of cyclonic vorticity that surrounds the main anti-cyclonic high-velocity collar. This narrow rin...

  11. Mean Velocity, Turbulence Intensity and Turbulence Convection Velocity Measurements for a Convergent Nozzle in a Free Jet Wind Tunnel. Comprehensive Data Report

    Science.gov (United States)

    Mccolgan, C. J.; Larson, R. S.

    1977-01-01

    The effect of flight on the mean flow and turbulence properties of a 0.056m circular jet were determined in a free jet wind tunnel. The nozzle exit velocity was 122 m/sec, and the wind tunnel velocity was set at 0, 12, 37, and 61 m/sec. Measurements of flow properties including mean velocity, turbulence intensity and spectra, and eddy convection velocity were carried out using two linearized hot wire anemometers. This report contains the raw data and graphical presentations. The final technical report includes a description of the test facilities, test hardware, along with significant test results and conclusions.

  12. Plasma Diagnostics by Antenna Impedance Measurements

    Science.gov (United States)

    Swenson, C. M.; Baker, K. D.; Pound, E.; Jensen, M. D.

    1993-01-01

    The impedance of an electrically short antenna immersed in a plasma provides an excellent in situ diagnostic tool for electron density and other plasma parameters. By electrically short we mean that the wavelength of the free-space electromagnetic wave that would be excited at the driving frequency is much longer than the physical size of the antenna. Probes using this impedance technique have had a long history with sounding rockets and satellites, stretching back to the early 1960s. This active technique could provide information on composition and temperature of plasmas for comet or planetary missions. Advantages of the impedance probe technique are discussed and two classes of instruments built and flown by SDL-USU for determining electron density (the capacitance and plasma frequency probes) are described.

  13. Assimilation of Sonic Velocity and Thin Section Measurements from the NEEM Ice Core

    Science.gov (United States)

    Hay, Michael; Pettit, Erin; Kluskiewicz, Dan; Waddington, Edwin

    2016-04-01

    We examine the measurement of crystal orientation fabric (COF) in ice cores using thin sections and sound-wave velocities, focusing on the NEEM core in Greenland. Ice crystals have substantial plastic anisotropy, with shear orthogonal to the crystallographic c-axis occuring far more easily than deformation in other orientations. Due to strain-induced grain-rotation, COFs can become highly anisotropic, resulting in bulk anisotropic flow. Thin-section measurements taken from ice cores allow sampling of the crystal fabric distribution. Thin-section measurements, however, suffer from sampling error, as they sample a small amount of ice, usually on the order of a hundred grans. They are typically only taken at intervals of several meters, which means that meter-scale variations in crystal fabric are difficult to capture. Measuring sonic velocities in ice cores provides an alternate method of determining crystal fabric. The speed of vertical compression waves is affected by the vertical clustering of c-axes, but is insensitive to azimuthal fabric anisotropy. By measuring splitting between the fast and slow shear-wave directions, information on the azimuthal distribution of orientations can be captured. Sonic-velocity measurements cannot capture detailed information on the orientation distribution of the COF, but they complement thin-section measurements with several advantages. Sonic-logging measurements can be taken at very short intervals, eliminating spatial gaps. In addition, sonic logging samples a large volume of ice with each measurement, reducing sampling error. Our logging tool has a depth resolution of around 3m/s, and can measure velocity features on the order of 1m/s. Here, we show the results of compression-wave measurements at NEEM. We also combine sonic-velocity measurements and thin-section measurements to produce a more accurate and spatially-complete representation of ice-crystal orientations in the vicinity of the NEEM core.

  14. Molecular Rayleigh Scattering Techniques Developed for Measuring Gas Flow Velocity, Density, Temperature, and Turbulence

    Science.gov (United States)

    Mielke, Amy F.; Seasholtz, Richard G.; Elam, Kristie A.; Panda, Jayanta

    2005-01-01

    Nonintrusive optical point-wise measurement techniques utilizing the principles of molecular Rayleigh scattering have been developed at the NASA Glenn Research Center to obtain time-averaged information about gas velocity, density, temperature, and turbulence, or dynamic information about gas velocity and density in unseeded flows. These techniques enable measurements that are necessary for validating computational fluid dynamics (CFD) and computational aeroacoustic (CAA) codes. Dynamic measurements allow the calculation of power spectra for the various flow properties. This type of information is currently being used in jet noise studies, correlating sound pressure fluctuations with velocity and density fluctuations to determine noise sources in jets. These nonintrusive techniques are particularly useful in supersonic flows, where seeding the flow with particles is not an option, and where the environment is too harsh for hot-wire measurements.

  15. Wave solutions of ion cyclotron heated plasmas with self-consistent velocity distributions in a tokamak

    Science.gov (United States)

    Lee, Jungpyo; Wright, John; Bonoli, Paul; Harvey, Robert

    2015-11-01

    We describe a numerical model for the propagation and absorption of ion cyclotron waves in a tokamak with a non-Maxwellian velocity space distribution function. The non-Maxwellian distribution is calculated by solving Maxwell's equations and the Fokker-Plank equation self-consistently. This approach will be useful to interpret measurements of minority hydrogen tail formation during ICRF heating experiments in Alcator C-Mod. To couple the Maxwell equation solver with Fokker-Plank equation solver, the quasilinear diffusion coefficients for the fundamental ion cyclotron absorption and the first harmonic absorption are calculated. In a previous study, the all-orders spectral algorithm wave solver (AORSA) was coupled with the Fokker-Plank code (CQL3D) to find the self-consistent non-Maxwellian distribution. We derive the modified quasilinear diffusion coefficients for the finite Larmor radius (FLR) approximation using a significantly faster wave solver (TORIC) following the approach by Jaeger. The coupled TORIC-CQL3D model will be compared against results from AORSA-CQL3D in order to verify the accuracy of the reduced FLR physics in TORIC. Work supported by US Department of Energy Contract No. DE-FC02-01ER54648.

  16. Plasma scattering of electromagnetic radiation theory and measurement techniques

    CERN Document Server

    Froula, Dustin H; Luhmann, Neville C Jr; Sheffield, John

    2011-01-01

    This work presents one of the most powerful methods of plasma diagnosis in exquisite detail to guide researchers in the theory and measurement techniques of light scattering in plasmas. Light scattering in plasmas is essential in the research and development of fusion energy, environmental solutions, and electronics.Referred to as the "Bible" by researchers the work encompasses fusion and industrial applications essential in plasma research. It is the only comprehensive resource specific to the plasma scattering technique. It provides a wide-range of experimental examples and discussion of the

  17. The Enhanced-model Ladar Wind Sensor and Its Application in Planetary Wind Velocity Measurements

    Science.gov (United States)

    Soreide, D. C.; Mcgann, R. L.; Erwin, L. L.; Morris, D. J.

    1993-01-01

    For several years we have been developing an optical air-speed sensor that has a clear application as a meteorological wind-speed sensor for the Mars landers. This sensor has been developed for aircraft use to replace the familiar, pressure-based Pitot probe. Our approach utilizes a new concept in the laser-based optical measurement of air velocity (the Enhanced-Mode Ladar), which allows us to make velocity measurements with significantly lower laser power than conventional methods. The application of the Enhanced-Mode Ladar to measuring wind speeds in the martian atmosphere is discussed.

  18. Deep S-wave velocity structure at Hawaii Islands obtained by microtremor array measurements

    Science.gov (United States)

    Hayashi, K.

    2015-12-01

    Microtremor array measurements and three-component microtremor measurements have been performed at the west coast of Hawaii Island (Figure.1). Two seismographs with three-component accelerometers were used for data acquisition. At each site, one seismograph was fixed in one place and data was acquired at that location for the entire survey. Data was acquired by a second seismograph at larger separations ranging from 5 to 3403m from the fixed seismograph. Data acquisition was repeated at each new separation. In each measurement, 10 to 60 minutes of ambient noise was recorded. As the separations of seismographs increased, the record length of ambient noise was increased. The sampling interval used was 10msec. An entire measurement took several hours. Data acquisition was performed in the day-time and the seismographs were placed in relatively quiet places such as in parks or residential areas. A spatial autocorrelation was used for calculating phase velocity and a clear dispersion curve (Figure 2a) was obtained in frequency range from 0.2 to 30 Hz. A joint inversion was applied to the observed dispersion curve, and H/V spectrum, and S-wave velocity model was analyzed for the site. In the inversion, phase velocities of the dispersion curve and the absolute value and peak frequencies of the H/V spectra were used as observation data. The unknown parameters were layer thickness and S-wave velocity. A Genetic Algorithm was used for optimization. Theoretical H/V spectra and phase velocities are generated by calculating the weighted average of the fundamental mode and higher modes (up to the 5th mode) based on medium response. Figure 2b shows an S-wave velocity model obtained by the inversion. We can see that a low velocity layer with S-wave velocity from 250 to 700 m/s exists to a depth of 90 m. A velocity layer with S-wave velocity from 900 to 1500 m/s exists at a depth range of 90 to 1300 m. Bedrock with S-wave velocity about 3000 m/s exists at a depth of 2200 m.

  19. Measurement of bubble velocity using Capacitively Coupled Contactless Conductivity Detection (C4D) technique

    Institute of Scientific and Technical Information of China (English)

    Baoliang Wang; Ying Zhou; Haifeng Ji; Zhiyao Huang; Haiqing Li

    2013-01-01

    The feasibility of applying Capacitively Coupled Contactless Conductivity Detection (C4D) technique to measurement of bubble velocity in gas-liquid two-phase flow in millimeter-scale pipe is investigated.And,a new method,which combines the C4D technique and the principle of cross-correlation velocity measurement,is proposed for the measurement of bubble velocity.This research includes two parts.First,based on the principle of C4D,a new five-electrode C4D sensor is developed.Then,with two conductivity signals obtained by the C4D sensor,the velocity measurement of bubble is implemented according to the principle of cross-correlation.The research results indicate that the C4D technique is highly effective and anticipates a broad potential in the field of two-phase flow.Experimental results show that the fiveelectrode C4D sensor is suitable for measuring the velocity of single bubbles with a relative error of less than 5%.

  20. Study of Influence of Experimental Technique on Measured Particle Velocity Distributions in Fluidized Bed

    Science.gov (United States)

    Gopalan, Balaji; Shaffer, Frank

    2013-11-01

    Fluid flows that are loaded with high concentration of solid particles are common in oil and chemical processing industries. However, the opaque nature of the flow fields and the complex nature of the flow have hampered the experimental and computational study of these processes. This has led to the development of a number of customized experimental techniques for high concentration particle flows for evaluation and improvement of CFD models. This includes techniques that track few individual particles, measures average particle velocity over a small sample volume and those over a large sample volume. In this work novel high speed PIV (HsPIV), with individual particle tracking, was utilized to measure velocities of individual particles in gas-particle flow fields at the walls circulating and bubbling fluidized bed. The HsPIV measurement technique has the ability to simultaneously recognize and track thousands of individual particles in flows of high particle concentration. To determine the effect of the size of the sample volume on particle velocity measurements, the PDF of Lagrangian particle velocity was compared with the PDF of Eulerian for different domain sizes over a range of flow conditions. The results will show that measured particle velocity distribution can vary from technique to technique and this bias has to be accounted in comparison with CFD simulations.

  1. Simultaneous measurement of droplet size and velocity field by an interferometric imaging technique in spray combustion

    Energy Technology Data Exchange (ETDEWEB)

    Fujisawa, N.; Hosokawa, A.; Tomimatsu, S. [Niigata Univ. (Japan). Dept. of Mechanical and Production Engineering

    2003-08-01

    The present paper describes an experimental technique of droplet sizing and velocity measurement for application to a luminous flame in spray combustion. The size measurement of unburnt fuel droplets in combustion is carried out by using an interferometric imaging method, while the corresponding velocity field is measured by particle tracking velocimetry (PTV) in combination with the rotary shutter to avoid the high intensity noise of the luminous flame in spray combustion. The measurements are successfully applied to the spray flow from a gun-type burner with and without combustion. The experimental results in spray combustion indicate that the smaller size of fuel droplets are almost burnt in the centre of the flame and the unburnt droplets of larger size remain in the outer region of the burner flow. It was found that the mean droplet velocity measured by the present PTV technique in combustion is almost independent of the droplet size and agrees closely with the gas velocity. However, the velocity magnitude with combustion is increased in comparison with the case without combustion, which suggests the influence of gas expansion at high temperatures. (author)

  2. Particle image velocimetry measurements of 2-dimensional velocity field around twisted tape

    Energy Technology Data Exchange (ETDEWEB)

    Song, Min Seop; Park, So Hyun; Kim, Eung Soo, E-mail: kes7741@snu.ac.kr

    2016-11-01

    Highlights: • Measurements of the flow field in a pipe with twisted tape were conducted by particle image velocimetry (PIV). • A novel matching index of refraction technique utilizing 3D printing and oil mixture was adopted to make the test section transparent. • Undistorted particle images were clearly captured in the presence of twisted tape. • 2D flow field in the pipe with twisted tape revealed the characteristic two-peak velocity profile. - Abstract: Twisted tape is a passive component used to enhance heat exchange in various devices. It induces swirl flow that increases the mixing of fluid. Thus, ITER selected the twisted tape as one of the candidates for turbulence promoting in the divertor cooling. Previous study was mainly focused on the thermohydraulic performance of the twisted tape. As detailed data on the velocity field around the twisted tape was insufficient, flow visualization study was performed to provide fundamental data on velocity field. To visualize the flow in a complex structure, novel matching index of refraction technique was used with 3-D printing and mixture of anise and mineral oil. This technique enables the camera to capture undistorted particle image for velocity field measurement. Velocity fields at Reynolds number 1370–9591 for 3 different measurement plane were obtained through particle image velocimetry. The 2-dimensional averaged velocity field data were obtained from 177 pair of instantaneous velocity fields. It reveals the characteristic two-peak flow motion in axial direction. In addition, the normalized velocity profiles were converged with increase of Reynolds numbers. Finally, the uncertainty of the result data was analyzed.

  3. Spatially Resolved Measurements of a Double Layer in an Argon Helicon Plasma

    Science.gov (United States)

    Aguirre, Evan; Siddiqui, Umair; McKee, John; Scime, Earl

    2015-11-01

    We report 2-dimensional, spatially resolved observations of a double layer in an expanding helicon plasma. These new measurements investigate the origins of previously observed multiple ion beam populations in the downstream plasma. We use Laser Induced Fluorescence (LIF) to measure the ion velocity distribution functions (IVDFs) of argon ions and neutrals both parallel and perpendicular to the background magnetic field and an rf-compensated Langmuir probe to determine the local plasma potential. These are the first multi-dimensional LIF measurements of ion acceleration in a current-free double layer and were obtained with a recently installed, internal scanning probe system in the HELIX-LEIA experimental facility. This work is supported by US National Science Foundation grant number PHY-1360278.

  4. Water Velocity Measurements on a Vertical Barrier Screen at the Bonneville Dam Second Powerhouse

    Directory of Open Access Journals (Sweden)

    Yong Yuan

    2011-11-01

    Full Text Available Fish screens at hydroelectric dams help to protect rearing and migrating fish by preventing them from passing through the turbines and directing them towards the bypass channels by means of a sweeping flow parallel to the screen. However, fish screens may actually be harmful to fish if the fish become impinged on the surface of the screen or become disoriented due to poor flow conditions near the screen. Recent modifications to the vertical barrier screens (VBS in the gate wells at the Bonneville Dam second powerhouse (B2 were intended to increase the guidance of juvenile salmonids into the juvenile bypass system but have resulted in higher mortality and descaling rates of hatchery subyearling Chinook salmon during the 2008 juvenile salmonid passage season. To investigate the potential cause of the high mortality and descaling rates, an in situ water velocity measurement study was conducted using acoustic Doppler velocimeters in the gate well slots at turbine units 12A and 14A of B2. From the measurements collected, the average approach velocity, sweep velocity, and the root mean square value of the velocity fluctuations were calculated. The approach velocities measured across the face of the VBS were variable and typically less than 0.3 m/s, but fewer than 50% were less than or equal to 0.12 m/s. There was also large variance in sweep velocities across the face of the VBS with most measurements recorded at less than 1.5 m/s. Results of this study revealed that the approach velocities in the gate wells exceeded criteria intended to improve fish passage conditions that were recommended by National Marine Fisheries Service and the Washington State Department of Fish and Wildlife. The turbulence measured in the gate well may also result in suboptimal fish passage conditions but no established guidelines to contrast those results have been published.

  5. Experimental Measurement of Self-Diffusion in a Strongly Coupled Plasma

    Science.gov (United States)

    2016-08-04

    Kubo relation D ¼ Z ∞ 0 ZðtÞdt; which describes the long-time mean -square displacement of a given particle through D ¼ limt→∞hjrðtÞ − rð0Þj2i=6t [25...Experimental Measurement of Self-Diffusion in a Strongly Coupled Plasma T. S. Strickler,1 T. K. Langin,1 P. McQuillen,1 J. Daligault,2 and T. C...collisional relaxation of ion velocities in a strongly coupled , ultracold neutral plasma on short time scales compared to the inverse collision rate. The

  6. Design of a Non-scanning Lidar for Wind Velocity and Direction Measurement

    Science.gov (United States)

    Liu, Bo; Peng, Zhangxian

    2016-06-01

    A Doppler lidar system for wind velocity and direction measurement is presented. The lidar use a wide field of view (FOV) objective lens as an optical antenna for both beam transmitting and signal receiving. By four fibers coupled on different position on the focal plane, the lidar can implement wind vector measurement without any scanning movement.

  7. Design of a Non-scanning Lidar for Wind Velocity and Direction Measurement

    Directory of Open Access Journals (Sweden)

    Liu Bo

    2016-01-01

    Full Text Available A Doppler lidar system for wind velocity and direction measurement is presented. The lidar use a wide field of view (FOV objective lens as an optical antenna for both beam transmitting and signal receiving. By four fibers coupled on different position on the focal plane, the lidar can implement wind vector measurement without any scanning movement.

  8. Feasibility of Velocity Measurements by a Drifter in the Yangon River

    NARCIS (Netherlands)

    Janssen, M.P.J.; Koning, R.J.

    2016-01-01

    Myanmar is dealing with a large data deficit, which is in contrast with the substantial need for it. The implementation of measuring techniques to obtain hydro- and morphodynamic data is an upcoming process. Measuring velocities can be valuable for calibrating models or giving estimates of sediment

  9. Measuring the Phase Velocity of Light in a Magnetic Field with the PVLAS Detector

    OpenAIRE

    Melissinos, A. C.

    2002-01-01

    A method is suggested for measuring the velocity of light in a magnetic field using the PVLAS detector. It is proposed to modulate the linear polarization of the input light. In that case the feedback signal necessary to keep the high finesse Fabry-Perot cavity on resonance is a measure of the change in the speed of light for the two orthogonal polarizations.

  10. Estimated carotid-femoral pulse wave velocity has similar predictive value as measured carotid-femoral pulse wave velocity

    DEFF Research Database (Denmark)

    Greve, Sara V; Blicher, Marie K; Kruger, Ruan;

    2016-01-01

    BACKGROUND: Carotid-femoral pulse wave velocity (cfPWV) adds significantly to traditional cardiovascular risk prediction, but is not widely available. Therefore, it would be helpful if cfPWV could be replaced by an estimated carotid-femoral pulse wave velocity (ePWV) using age and mean blood pres...

  11. A first comparison of irregularity and ion drift velocity measurements in the E-region

    Directory of Open Access Journals (Sweden)

    R. A. Makarevich

    2006-09-01

    Full Text Available E-region irregularity velocity measurements at large flow angles with the STARE Finland coherent VHF radar are considered in context of the ion and electron velocity data provided by the EISCAT tristatic radar system, CUTLASS Finland coherent HF radar, and IMAGE fluxgate magnetometers. The data have been collected during a special experiment on 27 March 2004 during which EISCAT was scanning between several E- and one F-region altitudes along the magnetic field line. Within the E-region, the EISCAT measurements at two altitudes of 110 and 115 km are considered while the electron velocity is inferred from the EISCAT ion velocity measurements at 278 km. The line-of-sight (l-o-s VHF velocity measured by STARE VHF los is compared to the ion and electron velocity components (Vi0 comp and Ve0 comp along the STARE l-o-s direction. The comparison with Ve0 comp for the entire event shows that the measurements exhibit large scatter and small positive correlation. The correlation with Ve0 comp was substantial in the first half of the interval under study when Ve0 comp was larger in magnitude. The comparison with Vi0 comp at 110 and 115 km shows a considerable positive correlation, with VHF velocity being typically larger (smaller in magnitude than Vi0 comp at 110 km (115 km so that VVHF los appears to be bounded by the ion velocity components at two altitudes. It is also demonstrated that the difference between VVHF los and Vi0 comp at 110 km can be treated, in the first approximation, as a linear function of the effective backscatter height heff also counted from 110 km; heff varies in the range 108–114 km due to the altitude integration effects in the scattering cross-section. Our results are consistent with the notion that VHF

  12. Acoustic resolution photoacoustic Doppler velocity measurements in fluids using time-domain cross-correlation

    Science.gov (United States)

    Brunker, J.; Beard, P.

    2013-03-01

    Blood flow measurements have been demonstrated using the acoustic resolution mode of photoacoustic sensing. This is unlike previous flowmetry methods using the optical resolution mode, which limits the maximum penetration depth to approximately 1mm. Here we describe a pulsed time correlation photoacoustic Doppler technique that is inherently flexible, lending itself to both resolution modes. Doppler time shifts are quantified via cross-correlation of pairs of photoacoustic waveforms generated in moving absorbers using pairs of laser light pulses, and the photoacoustic waves detected using an ultrasound transducer. The acoustic resolution mode is employed by using the transducer focal width, rather than the large illuminated volume, to define the lateral spatial resolution. The use of short laser pulses allows depth-resolved measurements to be obtained with high spatial resolution, offering the prospect of mapping flow within microcirculation. Whilst our previous work has been limited to a non-fluid phantom, we now demonstrate measurements in more realistic blood-mimicking phantoms incorporating fluid suspensions of microspheres flowing along an optically transparent tube. Velocities up to 110 mm/s were measured with accuracies approaching 1% of the known velocities, and resolutions of a few mm/s. The velocity range and resolution are scalable with excitation pulse separation, but the maximum measurable velocity was considerably smaller than the value expected from the detector focal beam width. Measurements were also made for blood flowing at velocities up to 13.5 mm/s. This was for a sample reduced to 5% of the normal haematocrit; increasing the red blood cell concentration limited the maximum measurable velocity so that no results were obtained for concentrations greater than 20% of a physiologically realistic haematocrit. There are several possible causes for this limitation; these include the detector bandwidth and irregularities in the flow pattern. Better

  13. Correlation and spectral measurements of fluctuating pressures and velocities in annular turbulent flow. [PWR; BWR

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, R.J.; Jones, B.G.; Roy, R.P.

    1980-02-01

    An experimental study of the fluctuating velocity field, the fluctuating static wall pressure and the in-stream fluctuating static pressure in an annular turbulent air flow system with a radius ratio of 4.314 has been conducted. The study included direct measurements of the mean velocity profile, turbulent velocity field; fluctuating static wall pressure and in-stream fluctuating static pressure from which the statistical values of the turbulent intensity levels, power spectral densities of the turbulent quantities, the cross-correlation between the fluctuating static wall pressure and the fluctuating static pressure in the core region of the flow and the cross-correlation between the fluctuating static wall pressure and the fluctuating velocity field in the core region of the flow were obtained.

  14. Measurements of Dendritic Growth Velocities in Undercooled Melts of Pure Nickel Under Static Magnetic Fields

    Science.gov (United States)

    Gao, Jianrong; Zhang, Zongning; Zhang, Yingjie

    2012-01-01

    Dendritic growth velocities in undercooled melts of pure Ni have been intensively studied over the past fifty years. However, the literature data are at marked variance with the prediction of the widely accepted model for rapid dendritic growth both at small and at large undercoolings. In the present work, bulk melts of pure Ni samples of high purity were undercooled by glass fluxing treatment under a static magnetic field. The recalescence processes of the samples at different undercoolings were recorded using a high-speed camera, and were modeled using a software to determine the dendritic growth velocities. The present data confirmed the effect of melt flow on dendritic growth velocities at undercoolings below 100 K. A comparison of the present data with previous measurements on a lower purity material suggested an effect of impurities on dendritic growth velocities at undercoolings larger than 200 K as well.

  15. Ice Velocity Measurement from SAR: Comparison of Sentinel-1A and RADARSAT-2

    DEFF Research Database (Denmark)

    Kusk, Anders; Dall, Jørgen

    Mapping the velocity fields of the continental ice sheets and their outlet glaciers is important in order to monitor and model the response of the cryosphere to global climate change. Since the mid 1990s, space-based SAR data have enabled measurement of ice velocities on a continental scale...... fields. Two Greenland-wide RADARSAT-2 campaigns were carried out during January-March 2014, and a smaller one in December 2014-February 2015. Ice velocity maps from both campaigns will be presented. A preliminary ice velocity map from the former campaign is attached with this abstract, while the latter...... with this abstract. The overlapping temporal coverage of the second RADARSAT-2 campaign and the first Sentinel-1 campaign allows a comparison of the two sensors in terms of: Impact of differing imaging modes (stripmap vs TOPS). The better coverage of Sentinel-1 is at the cost of a reduced azimuth resolution, however...

  16. Planar Velocity Distribution of Viscous Debris Flow at Jiangjia Ravine, Yunnan, China: A Field Measurement Using Two Radar Velocimeters

    Institute of Scientific and Technical Information of China (English)

    FU Xudong; WANG Guangqian; KANG Zhicheng; FEI Xiangjun

    2007-01-01

    Characteristics of planar velocity distribution of viscous debris flow were analyzed using the measured data at Jiangjia Ravine, Yunnan, China. The velocity data were measured through using two radar velocimeters. The cross-sectional mean velocities were calculated and used to examine Kang et al's (2004) relationship, which was established for converting the flow velocity at river centerline measured by a radar velocimeter into the mean velocity based on the stop-watch method. The velocity coefficient, K, defined by the ratio of the mean velocity to the maximum velocity, ranges from 0.2 to 0.6. Kang et al's (2004) relationship was found being inapplicable to flows with K smaller than 0.43. This paper contributes to show the complexity of the planar velocity distribution of viscous debris flows and the applicability of Kang et al's relationship.

  17. Thrust Stand Measurements of the Microwave Assisted Discharge Inductive Plasma Accelerator

    Science.gov (United States)

    Hallock, Ashley K.; Polzin, Kurt A.; Emsellem, Gregory D.

    2011-01-01

    Pulsed inductive plasma thrusters [1-3] are spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. This type of pulsed thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10-100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, pulsed inductive plasma thrusters require high pulse energies to inductively ionize propellant. The Microwave Assisted Dis- charge Inductive Plasma Accelerator (MAD-IPA), shown in Fig. 1, is a pulsed inductive plasma thruster that addressees this issue by partially ionizing propellant inside a conical inductive coil before the main current pulse via an electron cyclotron resonance (ECR) discharge. The ECR plasma is produced using microwaves and a static magnetic field from a set of permanent magnets arranged to create a thin resonance region along the inner surface of the coil, restricting plasma formation, and in turn current sheet formation, to a region where the magnetic coupling between the plasma and the theta-pinch coil is high. The use of a conical theta-pinch coil also serves to provide neutral propellant containment and plasma plume focusing that is improved relative to the more common planar geometry of the Pulsed Inductive Thruster (PIT) [1, 2]. In this paper, we describe thrust stand measurements performed to characterize the performance (specific impulse, thrust efficiency) of the MAD-IPA thruster. Impulse data are obtained at various pulse energies, mass flow rates and inductive coil geometries. Dependencies on these experimental parameters are discussed in the context of the current sheet formation and electromagnetic plasma

  18. Stiffness matrix determination of composite materials using lamb wave group velocity measurements

    Science.gov (United States)

    Putkis, O.; Croxford, A. J.

    2013-04-01

    The use of Lamb waves in Non-Destructive Evaluation (NDE) and Structural Health Monitoring (SHM) is gaining popularity due to their ability to travel long distances without significant attenuation, therefore offering large area inspections with a small number of sensors. The design of a Lamb-wave-based NDE/SHM system for composite materials is more complicated than for metallic materials due to the directional dependence of Lamb wave propagation characteristics such as dispersion and group velocity. Propagation parameters can be theoretically predicted from known material properties, specifically the stiffness matrix and density. However, in practice it is difficult to obtain the stiffness matrix of a particular material or structure with high accuracy, hence introducing errors in theoretical predictions and inaccuracies in the resulting propagation parameters. Measured Lamb wave phase velocities can be used to infer the stiffness matrix, but the measurements are limited to the principal directions due to the steering effect (different propagation directions of phase and corresponding group velocities). This paper proposes determination of the stiffness matrix from the measured group velocities, which can be unambiguously measured in any direction. A highly anisotropic carbon-fibre-reinforced polymer plate is chosen for the study. The influence of different stiffness matrix elements on the directional group velocity profile is investigated. Thermodynamic Simulated Annealing (TSA) is used as a tool for inverse, multi variable inference of the stiffness matrix. A good estimation is achieved for particular matrix elements.

  19. System identification of velocity mechanomyogram measured with a capacitor microphone for muscle stiffness estimation.

    Science.gov (United States)

    Uchiyama, Takanori; Tomoshige, Taiki

    2017-04-01

    A mechanomyogram (MMG) measured with a displacement sensor (displacement MMG) can provide a better estimation of longitudinal muscle stiffness than that measured with an acceleration sensor (acceleration MMG), but the displacement MMG cannot provide transverse muscle stiffness. We propose a method to estimate both longitudinal and transverse muscle stiffness from a velocity MMG using a system identification technique. The aims of this study are to show the advantages of the proposed method. The velocity MMG was measured using a capacitor microphone and a differential circuit, and the MMG, evoked by electrical stimulation, of the tibialis anterior muscle was measured five times in seven healthy young male volunteers. The evoked MMG system was identified using the singular value decomposition method and was approximated with a fourth-order model, which provides two undamped natural frequencies corresponding to the longitudinal and transverse muscle stiffness. The fluctuation of the undamped natural frequencies estimated from the velocity MMG was significantly smaller than that from the acceleration MMG. There was no significant difference between the fluctuations of the undamped natural frequencies estimated from the velocity MMG and that from the displacement MMG. The proposed method using the velocity MMG is thus more advantageous for muscle stiffness estimation.

  20. Theory and signal processing of acoustic correlation techniques for current velocity measurement

    Institute of Scientific and Technical Information of China (English)

    ZHU Weiqing; FENG Lei; WANG Changhong; WANG Yuling; QIU Wei

    2008-01-01

    A theoretical model and signal processing of acoustic correlation measurements to estimate current velocity are discussed. The sonar space-time correlation function of vol-ume reverberations within Fraunhofer zone is derived. The function, which is in exponential forms, is the theoretical model of acoustic correlation measurements. The characteristics of the correlation values around the maximum of the amplitude of the correlation function, where most information about current velocity is contained, are primarily analyzed. Localized Least Mean Squares (LLMS) criterion is put forward for velocity estimation. Sequential Quadratic Programming (SQP) method is adopted as the optimization method. So the systematic sig-nal processing method of acoustic correlation techniques for current velocity measurement is established. A prototype acoustic correlation current profiler (ACCP) underwent several sea trials, the results show that theoretical model approximately coincides with experimental re-sults. Current profiles including the speed and direction from ACCP are compared with those from acoustic Doppler current profiler (ADCP). The current profiles by both instruments agree reasonably well. Also, the standard deviation of velocity measurement by ACCP is statistically calculated and it is a little larger than predicted value.

  1. Spectroscopic measurements of plasma emission light for plasma-based acceleration experiments

    Science.gov (United States)

    Filippi, F.; Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Ferrario, M.; Mostacci, A.; Palumbo, L.; Zigler, A.

    2016-09-01

    Advanced particle accelerators are based on the excitation of large amplitude plasma waves driven by either electron or laser beams. Future experiments scheduled at the SPARC_LAB test facility aim to demonstrate the acceleration of high brightness electron beams through the so-called resonant Plasma Wakefield Acceleration scheme in which a train of electron bunches (drivers) resonantly excites wakefields into a preformed hydrogen plasma; the last bunch (witness) injected at the proper accelerating phase gains energy from the wake. The quality of the accelerated beam depends strongly on plasma density and its distribution along the acceleration length. The measurements of plasma density of the order of 1016-1017 cm-3 can be performed with spectroscopic measurements of the plasma-emitted light. The measured density distribution for hydrogen filled capillary discharge with both Balmer alpha and Balmer beta lines and shot-to-shot variation are here reported.

  2. Precision measurement of transverse velocity distribution of a strontium atomic beam

    Science.gov (United States)

    Gao, F.; Liu, H.; Xu, P.; Tian, X.; Wang, Y.; Ren, J.; Wu, Haibin; Chang, Hong

    2014-02-01

    We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that the resolution of the measured velocity can reach 0.13 m/s, corresponding to 90 μK in energy units. The experimental results are in very good agreement with the results of theoretical calculations. Based on the spectroscopic techniques used here, the absolute frequency of the intercombination transition of 88Sr is measured using an optical-frequency comb generator referenced to the SI second through an H maser, and is given as 434 829 121 318(10) kHz.

  3. Precision measurement of transverse velocity distribution of a strontium atomic beam

    Directory of Open Access Journals (Sweden)

    F. Gao

    2014-02-01

    Full Text Available We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that the resolution of the measured velocity can reach 0.13 m/s, corresponding to 90 μK in energy units. The experimental results are in very good agreement with the results of theoretical calculations. Based on the spectroscopic techniques used here, the absolute frequency of the intercombination transition of 88Sr is measured using an optical-frequency comb generator referenced to the SI second through an H maser, and is given as 434 829 121 318(10 kHz.

  4. Simultaneous measurement of particle velocity and size based on gray difference and autocorrelation

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The gray of two images of a same particle taken by a digital camera with different exposure times is different too. Based on the gray difference of particle images in a double-exposed photo and autocorrelation processing of digital images,this paper proposes a method for measuring particle velocities and sizes simultaneously. This paper also introduces the theoretical foundation of this method,the process of particle imaging and image processing,and the simultaneous measurement of velocity and size of a low speed flow field with 35 μm and 75 μm standard particles. The graphical measurement results can really reflect the flow characteristics of the flow field. In addition,although the measured velocity and size histograms of these two kinds of standard particles are slightly wider than the theoretical ones,they are all still similar to the normal distribution,and the peak velocities and diameters of the histograms are consistent with the default values. Therefore,this measurement method is capable of providing moderate measurement accuracy,and it can be further developed for high-speed flow field measurements.

  5. Measurement of non-Maxwellian electron velocity distributions in a reflex discharge

    Science.gov (United States)

    Phipps, C. R., Jr.; Bershader, D.

    1978-01-01

    The results of a ruby laser Thomson scattering study of the space and time-resolved electron velocity distributions in a pulsed Penning discharge in hydrogen are presented. Electron densities were to the order of 10 to the 13th/cu cm and temperatures were roughly 3 eV. This point is just prior to the cessation of the discharge ohmic heating pulse. For magnetic strengths less than 200 G, Maxwellian distributions were found over an energy range six times thermal energy. Temperatures agreed with Langmuir probe data. For fields of 450 G, chaotic plasma potentials were observed to be unstable and the Thomson scattering showed that the electron velocity distributions had central temperatures of 2 eV and wing temperatures of 15-12 eV.

  6. Ultrasonic position and velocity measurement for a moving object by M-sequence pulse compression using Doppler velocity estimation by spectrum-pattern analysis

    Science.gov (United States)

    Ikari, Yohei; Hirata, Shinnosuke; Hachiya, Hiroyuki

    2015-07-01

    Pulse compression using a maximum-length sequence (M-sequence) can improve the signal-to-noise ratio (SNR) of the reflected echo in the pulse-echo method. In the case of a moving object, however, the echo is modulated owing to the Doppler effect. The Doppler-shifted M-sequence-modulated signal cannot be correlated with the reference signal that corresponds to the transmitted M-sequence-modulated signal. Therefore, Doppler velocity estimation by spectrum-pattern analysis of a cyclic M-sequence-modulated signal and cross correlations with Doppler-shifted reference signals that correspond to the estimated Doppler velocities has been proposed. In this paper, measurements of the position and velocity of a moving object by the proposed method are described. First, Doppler velocities of the object are estimated using a microphone array. Secondly, the received signal from each microphone is correlated with each Doppler-shifted reference signal. Then, the position of the object is determined from the B-mode image formed from all cross-correlation functions. After that, the velocity of the object is calculated from velocity components estimated from the Doppler velocities and the position. Finally, the estimated Doppler velocities, determined positions, and calculated velocities are evaluated.

  7. Planar measurements of velocity and concentration of turbulent mixing in a T-junction

    DEFF Research Database (Denmark)

    Ingvorsen, Kristian Mark; Meyer, Knud Erik; Nielsen, N. F.

    Turbulent mixing of two isothermal air streams in a T-junction of square ducts are investigated. Three dimensional velocity fields and turbulent kinetic energy are measured with stereoscopic Particle Image Velocimetry (PIV). The concentration field is obtained with a planar Mie scattering technique...... using the stereoscopic PIV setup. The concentration measurement method is developed in the present study and the accuracy of the technique is investigated. The resulting data are two dimensional concentration fields taken at 4Hz. The combination of velocity, turbulence and concentration fields give...

  8. A technique for measuring velocity and attenuation of ultrasound in liquid foams

    CERN Document Server

    Pierre, Juliette; Leroy, Valentin

    2012-01-01

    We describe an experimental setup specifically designed for measuring the ultrasonic transmission through liquid foams, over a broad range of frequencies (60-600 kHz). The question of determining the ultrasonic properties of the foam (density, phase velocity and attenuation) from the transmission measurements is addressed. An inversion method is proposed, tested on synthetic data, and applied to a liquid foam at different times during the coarsening. The ultrasonic velocity and attenuation are found to be very sensitive to the foam bubble sizes, suggesting that a spectroscopy technique could be developed for liquid foams.

  9. MR velocity mapping measurement of renal artery blood flow in patients with impaired kidney function

    DEFF Research Database (Denmark)

    Cortsen, M; Petersen, L.J.; Stahlberg, F

    1996-01-01

    Renal blood flow (RBF) was measured in 9 patients with chronic impaired kidney function using MR velocity mapping and compared to PAH clearance and 99mTc-DTPA scintigraphy. An image plane suitable for flow measurement perpendicular to the renal arteries was chosen from 2-dimensional MR angiography...... by 99mTc-DTPA scintigraphy. A reduction of RBF was found, and there was a significant correlation between PAH clearance multiplied by 1/(1-hematocrit) and RBF determined by MR velocity mapping. Furthermore, a significant correlation between the distribution of renal function and the percent distribution...

  10. An industrial light-field camera applied for 3D velocity measurements in a slot jet

    Science.gov (United States)

    Seredkin, A. V.; Shestakov, M. V.; Tokarev, M. P.

    2016-10-01

    Modern light-field cameras have found their application in different areas like photography, surveillance and quality control in industry. A number of studies have been reported relatively low spatial resolution of 3D profiles of registered objects along the optical axis of the camera. This article describes a method for 3D velocity measurements in fluid flows using an industrial light-field camera and an alternative reconstruction algorithm based on a statistical approach. This method is more accurate than triangulation when applied for tracking small registered objects like tracer particles in images. The technique was used to measure 3D velocity fields in a turbulent slot jet.

  11. The measurement of abrasive particles velocities in the process of abrasive water jet generation

    Science.gov (United States)

    Zeleňák, Michal; Foldyna, Josef; Říha, Zdeněk

    2014-08-01

    An optimization of the design of the abrasive cutting head using the numerical simulation requires gathering as much information about processes occurring in the cutting head as possible. Detailed knowledge of velocities of abrasive particles in the process of abrasive water jet generation is vital for the verification of the numerical model. A method of measurement of abrasive particles at the exit of focusing tube using the FPIV technique was proposed and preliminary tests are described in the paper. Results of analysis of measured velocity fields are presented in the paper.

  12. Measuring preheat in laser-drive aluminum using velocity interferometer system for any reflector: Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Shu, Hua; Fu, Sizu; Huang, Xiuguang; Wu, Jiang; Xie, Zhiyong; Zhang, Fan; Ye, Junjian; Jia, Guo; Zhou, Huazhen [Shanghai Institute of Laser Plasma, P.O. BOX 800-229, Shanghai 201800 (China)

    2014-08-15

    In this paper, we systematically study preheating in laser-direct-drive shocks by using a velocity interferometer system for any reflector (VISAR). Using the VISAR, we measured free surface velocity histories of Al samples over time, 10–70 μm thick, driven directly by a laser at different frequencies (2ω, 3ω). Analyzing our experimental results, we concluded that the dominant preheating source was X-ray radiation. We also discussed how preheating affected the material initial density and the measurement of Hugoniot data for high-Z materials (such as Au) using impedance matching. To reduce preheating, we proposed and tested three kinds of targets.

  13. Measurement of Flow Velocity and Inference of Liquid Viscosity in a Microfluidic Channel by Fluorescence Photobleaching

    DEFF Research Database (Denmark)

    Carroll, Nick J.; Jensen, Kaare Hartvig; Parsa, Shima

    2014-01-01

    We present a simple, noninvasive method for simultaneous measurement of flow velocity and inference of liquid viscosity in a microfluidic channel. We track the dynamics of a sharp front of photobleached fluorescent dye using a confocal microscope and measure the intensity at a single point...... downstream of the initial front position. We fit an exact solution of the advection diffusion equation to the fluorescence intensity recovery curve to determine the average flow velocity and the diffusion coefficient of the tracer dye. The dye diffusivity is correlated to solute concentration to infer...

  14. Laser-strophometry high-resolution technique for velocity gradient measurements in fluid flows

    CERN Document Server

    Staude, Wilfried

    2001-01-01

    This book describes techniques that allow the measurement of arbitrary velocity gradient components in fluids with high spatial and temporal resolution, e.g. turbulent fluids. The techniques are based on the properties of scattered laser light. The book gives a detailed and rigorous treatment of the physical and mathematical background in a pedagogical presentation accessible to students in physics and engineering. From both the theoretical and experimental points of view, four different schemes are discussed in detail; the schemes differ in the way the velocity of the moving pattern of the scattered laser light is measured.

  15. Measuring melt and velocity of Alaskan mountain glaciers using phase-sensitive radar and differential GPS

    Science.gov (United States)

    Neuhaus, S.; Tulaczyk, S. M.

    2015-12-01

    Alaskan glaciers show some of the highest rates of retreat worldwide, contributing to sea level rise. This retreat is due to both increased velocity and increased melt. We seek to understand the role of glacial meltwater on velocity. Matanuska glacier, a land terminating glacier in Alaska, has been well-studied using traditional glaciological techniques, but new technology has emerged that allows us to measure melt and velocity more accurately. We employed high-resolution differential GPS to create surface velocity profiles across flow in the ablation zone during the summer of 2015. We also measured surface ablation using stakes and measured basal melt using phase-sensitive radar designed by the British Antarctic Survey. The positions acquired by differential GPS are obtained to a resolution of less than 0.5m, while feature tracking using time-lapse photography for the same time period yields positions with greater and more variable uncertainty. The phase-sensitive radar provides ice thinning rates. Phase-sensitive radar together with ground penetrating radar provides us with an understanding of the internal structure of the glacier. This suite of data allows us to determine the relative importance of surface melt, basal melt, and internal deformation on ice velocity in warm mountain glaciers.

  16. Turbulent velocity and concentration measurements in a macro-scale multi-inlet vortex nanoprecipitation reactor

    Science.gov (United States)

    Liu, Zhenping; Fox, Rodney; Hill, James; Olsen, Michael

    2013-11-01

    Flash Nanoprecipitation (FNP) is a technique to produce monodisperse functional nanoparticles. Microscale multi-inlet vortex reactors (MIVR) have been effectively applied to FNP due to their ability to provide rapid mixing and flexibility of inlet flow conditions. A scaled-up MIVR could potentially generate large quantities of functional nanoparticles, giving FNP wider applicability in industry. In the presented research, the turbulent velocity field inside a scaled-up, macroscale MIVR is measured by particle image velocimetry (PIV). Within the reactor, velocity is measured using both two-dimensional and stereoscopic PIV at two Reynolds numbers (3500 and 8750) based on the flow at each inlet. Data have been collected at numerous locations in the inlet channels, the reaction chamber, and the reactor outlet. Mean velocity and Reynolds stresses have been obtained based on 5000 instantaneous velocity realizations at each measurement location. The turbulent mixing process has also been investigated with passive scalar planar laser-induced fluorescence and simultaneous PIV/PLIF. Velocity and concentration results are compared to results from previous experiments in a microscale MIVR. Scaled profiles of turbulent quantities are similar to those previously found in the microscale MIVR.

  17. Comprehensive spatiotemporal glacier and ice sheet velocity measurements from Landsat 8

    Science.gov (United States)

    Moon, Twila; Fahnestock, Mark; Scambos, Ted; Klinger, Marin; Haran, Terry

    2015-04-01

    Combining newly developed software with Landsat 8 image returns, we are now producing broad-coverage ice velocity measurements on weekly to monthly scales across ice sheets and glaciers. Using new image-to-image cross correlation software, named PyCorr, we take advantage of the improved radiometric resolution of the Landsat 8 panchromatic band to create velocity maps with sub-pixel accuracy. Landsat 8's 12-bit radiometric resolution supports measurement of ice flow in uncrevassed regions based on persistent sastrugi patterns lasting weeks to a few months. We also leverage these improvements to allow for ice sheet surface roughness measurements. Landsat 8's 16-day repeat orbit and increased image acquisition across the Greenland and Antarctic ice sheets supports development of seasonal to annual ice sheet velocity mosaics with full coverage of coastal regions. We also create time series for examining sub-seasonal change with near real time processing in areas such as the Amundsen Sea Embayment and fast flowing Greenland outlet glaciers. In addition, excellent geolocation accuracy enables velocity mapping of smaller ice caps and glaciers, which we have already applied in Alaska and Patagonia. Finally, PyCorr can be used for velocity mapping with other remote sensing imagery, including high resolution WorldView satellite data.

  18. Assimilation of Sonic Velocity and Thin-Section Measurements from the NEEM Ice-Core

    Science.gov (United States)

    Hay, M.; Pettit, E. C.; Waddington, E. D.

    2016-12-01

    We examine the measurement of crystal orientation fabric (COF) in ice cores using thin sections and sound-wave velocities, focusing on the NEEM core in Greenland. Ice crystals have substantial plastic anisotropy, with shear orthogonal to the crystallographic c-axis occurring far more easily than deformation in other orientations. Due to strain-induced grain-rotation, COFs can become highly anisotropic, resulting in bulk anisotropic flow. Thin-section measurements taken from ice cores allow sampling of the crystal fabric distribution. Thin-section measurements, however, suffer from sampling error, as they sample a small amount of ice, usually on the order of a hundred grans. They are typically only taken at intervals of several meters, which means that meter-scale variations in crystal fabric are difficult to capture. Measuring sonic velocities in ice cores provides an alternate method of determining crystal fabric. The speed of vertical compression waves is affected by the vertical clustering of c-axes, but is insensitive to azimuthal fabric anisotropy. By measuring splitting between the fast and slow shear-wave directions, information on the azimuthal distribution of orientations can be captured. Sonic-velocity measurements cannot capture detailed information on the orientation distribution of the COF, but they complement thin-section measurements with several advantages. Sonic-logging measurements can be taken at very short intervals, eliminating spatial gaps. In addition, sonic logging samples a large volume of ice with each measurement, reducing sampling error. Our logging tool has a depth resolution of around 3m/s, and can measure velocity features on the order of 1m/s. Here, we show the results of compression-wave measurements at NEEM. We also assimilate the sonic measurements with the thin-section data using a Bayesian inference procedure. This procedure allows us to combine the respective strengths of the two fabric measurement methods, to produce a more

  19. Plasma actuator electron density measurement using microwave perturbation method

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-21

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

  20. Measurement of a 2D fast-ion velocity distribution function by tomographic inversion of fast-ion D-alpha spectra

    CERN Document Server

    Salewski, Mirko; Jacobsen, Asger Schou; Garcıa-Munoz, Manuel; Heidbrink, Bill; Korsholm, Soren Bang; Leipold, Frank; Madsen, Jens; Moseev, Dmitry; Nielsen, Stefan Kragh; Rasmussen, Jesper; Stejner, Morten; Tardini, Giovanni; Weiland, Markus

    2015-01-01

    We present the first measurement of a local fast-ion 2D velocity distribution function $f(v_\\parallel, v_\\perp)$. To this end, we heated a plasma in ASDEX Upgrade by neutral beam injection and measured spectra of fast-ion D-alpha (FIDA) light from the plasma center in three views simultaneously. The measured spectra agree very well with synthetic spectra calculated from a TRANSP/NUBEAM simulation. Based on the measured FIDA spectra alone, we infer $f(v_\\parallel, v_\\perp)$ by tomographic inversion. Salient features of our measurement of $f(v_\\parallel, v_\\perp)$ agree reasonably well with the simulation: the measured as well as the simulated $f(v_\\parallel, v_\\perp)$ are lopsided towards negative velocities parallel to the magnetic field, and they have similar shapes. Further, the peaks in the simulation of $f(v_\\parallel, v_\\perp)$ at full and half injection energies of the neutral beam also appear in the measurement at similar velocity-space locations. We expect that we can measure spectra in up to seven vi...

  1. Measurements of the laminar burning velocity of hydrogen-air premixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Pareja, Jhon; Burbano, Hugo J. [Science and Technology of Gases and Rational Use of Energy Group, Faculty of Engineering, University of Antioquia, Calle 67 N 53, 108 Bloque 20, 447 Medellin (Colombia); Ogami, Yasuhiro [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan)

    2010-02-15

    Experimental and numerical studies on laminar burning velocities of hydrogen-air mixtures were performed at standard pressure and room temperature varying the equivalence ratio from 0.8 to 3.0. The flames were generated using a contoured slot-type nozzle burner (4 mm x 10 mm). Measurements of laminar burning velocity were conducted using particle tracking velocimetry (PTV) combined with Schlieren photography. This technique provides the information of instantaneous local burning velocities in the whole region of the flame front, and laminar burning velocities were determined using the mean value of local burning velocities in the region of non-stretch. Additionally, average laminar burning velocities were determined using the angle method and compared with the data obtained with the PTV method. Numerical calculations were also conducted using detailed reaction mechanisms and transport properties. The experimental results from the PTV method are in good agreement with the numerical results at every equivalence ratio of the range of study. Differences between the results obtained with the angle method and those with the PTV method are reasonably small when the effects of flame stretch and curvature are reduced by using a contoured slot-type nozzle. (author)

  2. Velocity-space sensitivities of neutron emission spectrometers at the tokamaks JET and ASDEX Upgrade in deuterium plasmas

    Science.gov (United States)

    Jacobsen, A. S.; Binda, F.; Cazzaniga, C.; Eriksson, J.; Hjalmarsson, A.; Nocente, M.; Salewski, M.; Tardini, G.

    2017-07-01

    Future fusion reactors are foreseen to be heated by the energetic alpha particles produced in fusion reactions. For this to happen, it is important that the energetic ions are sufficiently confined. In present day fusion experiments, energetic ions are primarily produced using external heating systems such as neutral beam injection and ion cyclotron resonance heating. In order to diagnose these fast ions, several different fast-ion diagnostics have been developed and implemented in the various experiments around the world. The velocity-space sensitivities of fast-ion diagnostics are given by so-called weight functions. Here instrument-specific weight functions are derived for neutron emission spectrometry detectors at the tokamaks JET and ASDEX Upgrade for the 2.45 MeV neutrons produced in deuterium-deuterium reactions in deuterium plasmas. Using these, it is possible to directly determine which part of velocity space each detector observes.

  3. Measurements of temperature and velocity fluctuations in oscillating flows using thermal anemometry – application to thermoacoustic refrigerators

    OpenAIRE

    Berson, Arganthaël; Poignand, Gaelle; Jondeau, Emmanuel; Blanc-Benon, Philippe; Comte-Bellot, Geneviève

    2012-01-01

    International audience; This paper summarizes our recent work on the development of thermal anemometry to measure velocity and temperature fluctuations in oscillating flows. First, we demonstrate that velocity cannot be measured accurately by hot-wire anemometry in oscillating flows when the flow reverses its direction. Indeed, there is no unique and well-defined correlation between the flow velocity and heat transfer near flow reversal, which prevents the recovery of velocity fluctuations fr...

  4. Lamb-shift and electric field measurements in plasmas

    Science.gov (United States)

    Doveil, F.; Chérigier-Kovacic, L.; Ström, P.

    2017-01-01

    The electric field is a quantity of particular relevance in plasma physics. Indeed, its fluctuations are responsible for different macroscopic phenomena such as anomalous transport in fusion plasmas. Answering a long-standing challenge, we offer a new method to locally and non-intrusively measure weak electric fields and their fluctuations in plasmas, by means of a beam of hydrogen ions or atoms. We present measurements of the electric field in vacuum and in a plasma where Debye shielding is measured. For the first time, we have used the Lamb-shift resonance to measure oscillating electric fields around 1 GHz and observed the strong enhancement of the Lyman-α signal. The measurement is both direct and non-intrusive. This method provides sensitivity (mV cm-1) and temporal resolution (ns) that are three orders higher compared to current diagnostics. It thus allows measuring fluctuations of the electric field at scales not previously reached experimentally.

  5. Measurement of Velocity Distribution in Atomic Beam by Diode Laser with Narrow Line width

    Institute of Scientific and Technical Information of China (English)

    CHEN Jingbiao; WANG Fengzhi; YANG Donghai; WANG YiQiu

    2001-01-01

    In this paper, by using the detecting laser beam interacts with the atomic beam at a sharp angle and the Doppler frequency shift effect, the velocity distribution in cesium atomic beam is measured with a diode laser of narrow linewidth of 1 MHz. The effects of the atomic natural line width and cycling transition detecting factor on the measured results have been analyzed. Finally, the measured results have been compared with the theoretical calculation.

  6. Development of new measuring technique using sound velocity for CO2 concentration in Cameroonian volcanic lakes

    Science.gov (United States)

    Sanemasa, M.; Saiki, K.; Kaneko, K.; Ohba, T.; Kusakabe, M.; Tanyileke, G.; Hell, J.

    2012-12-01

    1. Introduction Limnic eruptions at Lakes Monoun and Nyos in Cameroon, which are sudden degassing of magmatic CO2 dissolved in the lake water, occurred in 1984 and 1986, respectively. The disasters killed about 1800 people around the lakes. Because of ongoing CO2 accumulation in the bottom water of the lakes, tragedy of limnic eruptions will possibly occur again. To prevent from further disasters, artificial degassing of CO2 from the lake waters has been undergoing. Additionally, CO2 monitoring of the lake waters is needed. Nevertheless, CO2 measurement is done only once or twice a year because current methods of CO2 measurement, which require chemical analysis of water samples, are not suitable for frequent measurement. In engineering field, on the other hand, a method to measure salt concentration using sound velocity has been proposed (Kleis and Sanchez, 1990). This method allows us to evaluate solute concentration fast. We applied the method to dissolved CO2 and examined the correlation between sound velocity and CO2 concentration in laboratory experiment. Furthermore, using the obtained correlation, we tried to estimate the CO2 concentration of waters in the Cameroonian lakes. 2. Laboratory experiment We examined the correlation between sound velocity and CO2 concentration. A profiler (Minos X, made by AML oceanography) and pure water were packed in cylindrical stainless vessel and high-pressure CO2 gas was injected to produce carbonated water. The profiler recorded temperature, pressure and sound velocity. Change of sound velocity was defined as difference of sound velocity between carbonated water and pure water under the same temperature and pressure conditions. CO2 concentration was calculated by Henry's law. The result indicated that the change of sound velocity [m s-1] is proportional to CO2 concentration [mmol kg-1], and the coefficient is 0.021 [m kg s-1 mmol-1]. 3. Field application Depth profiles of sound velocity, pressure, and temperature of Lakes

  7. Hemolysis interference in measuring fish plasma biochemical indicators.

    Science.gov (United States)

    Mirghaed, Ali Taheri; Ghelichpour, Melika; Hoseini, Seyyed Morteza; Amini, Kourosh

    2017-08-01

    The present study aimed to determine hemolysis interference in measurement of plasma biochemical parameters in fish specimens. For this purpose, blood samples were harvested from 24 Huso huso juveniles. After centrifugation, each plasma sample was divided into seven portions to make seven levels of hemolysis. Hemolysis was induced by addition of different percentages of the corresponding whole blood [0 (non-hemolyzed control group), 1, 3, 5, 10, 15, and 20% of whole blood]. Albumin, total protein, calcium, phosphorus, glucose, sodium, potassium, chloride, alkaline phosphatase (ALP), aspartate transaminase (AST), and alanine transaminase (ALT) were measured in different samples. Results showed that plasma albumin, ALP, potassium, and AST significantly increased (more than 200% at the highest hemolysis level) in the hemolyzed samples. Also, plasma total protein and phosphorus showed significant elevation in the hemolyzed samples (more than 70% at the highest hemolysis level). Plasma glucose, calcium, chloride, and ALT showed narrow but significant increase in hemolyzed samples (11.8-35.2% at the highest hemolysis level). Plasma sodium showed no significant changes in the hemolyzed samples. In conclusion, the present results show that hemolysis markedly affects plasma parameters levels, which interferes with plasma results interpretation. Therefore, analysis of hemolyzed samples should be avoided or the results should be interpreted with caution. This study encourages further investigations to develop methods for omitting the effects of hemolysis by sample blanking and/or presenting correction coefficients for measurement of plasma parameters in samples with different levels of hemolysis.

  8. Measurements of the coupling between the tumbling of rods and the velocity gradient tensor in turbulence

    CERN Document Server

    Ni, Rui; Ouellette, Nicholas T; Voth, Greg A

    2014-01-01

    We present simultaneous experimental measurements of the dynamics of anisotropic particles transported by a turbulent flow and the velocity gradient tensor of the flow surrounding them. We track both rod-shaped particles and small spherical flow tracers using stereoscopic particle tracking. By using scanned illumination, we are able to obtain a high enough seeding density of tracers to measure the full velocity gradient tensor near the rod. The alignment of rods with the vorticity and the eigenvectors of the strain rate show agreement with numerical simulations. A full description of the tumbling of rods in turbulence requires specifying a seven-dimensional joint probability density function (PDF) of five scalars characterizing the velocity gradient tensor and two scalars describing the relative orientation of the rod. If these seven parameters are known, then Jeffery's equation specifies the rod tumbling rate and any statistic of rod rotations can be obtained as a weighted average over the joint PDF. To look...

  9. Determination and sensitivity analysis of the seismic velocity of a shallow layer from refraction traveltimes measures

    Directory of Open Access Journals (Sweden)

    S Zein

    2016-03-01

    Full Text Available In this paper, we are interested in determining the seismic velocity of ashallow under-ground layer from refraction traveltimes measures. Wepresent a study case taken from an experimental seismic survey. The studycase is a wide-angle seismic inversion using experimental traveltimesmeasures and based on ray tracing technique and genetic algorithms. Thehypothesis on the velocity distribution, coming from the seismicexperiment, makes the computation of some seismic rays expensive intime. We propose to reduce the computations time by introducing aformulation of the inverse problem that avoids such costly rays, hence theinversion becomes feasible.Also we present a sensitivity analysis based on a singular valuedecomposition of the jacobian of the traveltimes with respect to velocity.We give the relationship between the traveltimes measure errors and thevelocity estimation error. We discuss the advantages of this method overthe classical one based on the resolution matrix.

  10. Two-phase velocity measurements around cylinders using particle image velocimetry

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Y.A.; Philip, O.G.; Schmidl, W.D. [Texas A& M Univ., College Station, TX (United States)] [and others

    1995-09-01

    The particle Image Velocimetry flow measurement technique was used to study both single-phase flow and two-phase flow across a cylindrical rod inserted in a channel. First, a flow consisting of only a single-phase fluid was studied. The experiment consisted of running a laminar flow over four rods inserted in a channel. The water flow rate was 126 cm{sup 3}/s. Then a two-phase flow was studied. A mixture of water and small air bubbles was used. The water flow rate was 378 cm{sup 3}/s and the air flow rate was approximately 30 cm{sup 3}/s. The data are analyzed to obtain the velocity fields for both experiments. After interpretation of the velocity data, forces acting on a bubble entrained by the vortex were calculated successfully. The lift and drag coefficients were calculated using the velocity measurements and the force data.

  11. Velocity measurement in life combustion systems with high temperature anemometer - HTA

    Energy Technology Data Exchange (ETDEWEB)

    Staudinger, G.; Mory, A.; Pilz, R.; Zimmel, M. [Technische Universitaet Graz, Graz (Austria). Inst. fuer Verfahrenstechnik, Abt. fuer Apparatebau und Mechanische Verfahrenstechnik

    1998-12-31

    An anemometer was developed which allows to measure velocities in dusty atmospheres at temperatures up to 1200{degree}C in a range between 1 and 40 m/s. The most important features of this vane-anemometer are its frictionless aerostatic bearing and the internal air cooling. The frequency of rotation is detected with a high temperature resistant optical fibre. In the project velocities and velocity-fields were measured in the combustion chambers of a 300 MW{sub el} power plant, a 27 MW{sub th} waste incinerator and in different pilot- and semi-industrial plants. The fuels used were coal, biomass, and municipal waste. 11 figs., 2 tabs.

  12. Temperature, Pressure and Velocity measurements on the Ranque-Hilsch Vortex Tube

    Science.gov (United States)

    Liew, R.; Zeegers, J. C. H.; Kuerten, J. G. M.; Michałek, W. R.

    2012-11-01

    Temperatures, pressures and velocities were measured in a Ranque-Hilsch vortex tube. Results show that the cooling power is larger than the heating power due to a heat loss to the surroundings. This heat loss became the more dominant thermodynamic process at large cold fractions (the ratio of cold mass flow over total mass flow). The velocities were obtained by means of Laser Doppler Anemometry. By this method, the three dimensional velocities of the gas and their standard deviations in the vortex tube are revealed by an non-intrusive measurement method. The turbulent fluctuations, characterized by the standard deviations, show that the turbulence is isotropic in the core region of the vortex tube.

  13. Measurement of velocity profiles of nanofluids in laminar channel flow using Particle Image Velocimetry

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, Arun K.; Kulkarni, Parimal P.; Singh, R.K.; Verma, Pumendra [Bhabha Atomic Research Centre (BARC), Mumbai (India). Reactor Engineering Div.; Gandhi, Mayur [University Institute of Chemical Technology, Mumbai (India). Dept. of Chemical Engineering

    2014-06-15

    The objective of the paper is to measure the velocity profiles of water based nanofluids for flow through channels in order to understand whether the nanofluids behave Newtonian. For this purpose, experiments were carried for flow through a rectangular channel in laminar regime. Four different nanofluids were used, i.e. Al{sub 2}O{sub 3}, CuO, TiO{sub 2} and SiO{sub 2} with base fluid as water. Experiments were conducted at low concentration of these particles. The velocity profiles were measured using Particle Image Velocimetry. The results indicate that the velocity profiles are similar for all the fluids indicating the flows to be Newtonian. (orig.)

  14. PRESSURE-VELOCITY JOINT MEASUREMENTS OF A WALL-BOUNDED TURBULENT SHEAR FLOW

    Institute of Scientific and Technical Information of China (English)

    LIU Ying-zheng; KE Feng; WANG Wei-zhe; CAO Zhao-min

    2006-01-01

    The unsteady behavior of the large-scale vortical structures buried in a wall-bounded turbulent shear layer flow was extensively investigated using pressure-velocity joint measurements. The wall pressure fluctuations and flow field velocity fluctuations were measured simultaneously by using a microphone and an X-type hotwire, respectively. The spatially and temporally strong coupling between the convecting flow structures and the wall pressure fluctuations were meticulously investigated in terms of the continuous wavelet transform, cross-correlation and coherence of the wall pressure and flow field. The characteristics of the large-scale vortical structures, e.g., the shedding frequency, averaged convection velocity, convective motion, and structure pattern were revealed.

  15. The equilibrium velocity of spherical particles in rectangular microfluidic channels for size measurement.

    Science.gov (United States)

    Sommer, Christian; Quint, Stephan; Spang, Peter; Walther, Thomas; Bassler, Michael

    2014-07-01

    According to the Segré-Silberberg effect, spherical particles migrate to a lateral equilibrium position in parabolic flow profiles. Here, for the first time, the corresponding equilibrium velocity is studied experimentally for micro particles in channels with rectangular cross section. Micro channels are fabricated in PMMA substrate based on a hot embossing process. To measure individual particle velocities at very high precision, the technique of spatially modulated emission is applied. It is found that the equilibrium velocity is size-dependent and the method offers a new way to measure particle size in microfluidic systems. The method is of particular interest for microfluidic flow cytometry as it delivers an alternative to the scatter signal for cell size determination.

  16. Unsteady Velocity Measurements Taken Behind a Model Helicopter Rotor Hub in Forward Flight

    Science.gov (United States)

    Berry, John D.

    1997-01-01

    Drag caused by separated flow behind the hub of a helicopter has an adverse effect on aerodynamic performance of the aircraft. To determine the effect of separated flow on a configuration used extensively for helicopter aerodynamic investigations, an experiment was conducted using a laser velocimeter to measure velocities in the wake of a model helicopter hub operating at Mach-scaled conditions in forward flight. Velocity measurements were taken using a laser velocimeter with components in the vertical and downstream directions. Measurements were taken at 13 stations downstream from the rotor hub. At each station, measurements were taken in both a horizontal and vertical row of locations. These measurements were analyzed for harmonic content based on the rotor period of revolution. After accounting for these periodic velocities, the remaining unsteady velocities were treated as turbulence. Turbulence intensity distributions are presented. Average turbulent intensities ranged from approximately 2 percent of free stream to over 15 percent of free stream at specific locations and azimuths. The maximum average value of turbulence was located near the rear-facing region of the fuselage.

  17. Interference effects in the long-time tail of the velocity auto-correlation function for a dense one-component plasma in a magnetic field

    NARCIS (Netherlands)

    Suttorp, L.G.; Schoolderman, A.J.

    1987-01-01

    The long-time behaviour of the velocity autocorrelation function that describes the motion of a tagged particle through a one-component plasma in a uniform magnetic field has been determined with the use of mode-coupling theory. The long-time tail depends on the orientation of the velocity with resp

  18. On the theory of MHD modes driven by strong ExB velocity shear in tokamaks. Addendum. 2000 Plasma Phys. Control. Fusion 42 57

    Energy Technology Data Exchange (ETDEWEB)

    Mikhailovskii, A.B.; Sharapov, S.E.; Timofeev, A.V. [JET Joint Undertaking, Abingdon, Oxfordshire OX14 3EA (United Kingdom)

    2000-07-01

    The theory of MHD modes driven by strong ExB velocity shear in tokamaks given by Mikhailovskii and Sharapov (2000 Plasma Phys. Control. Fusion 42 57) is revised. It is suggested that, in the approximations taken by these authors, there are no MHD eigenmodes if the cross-field velocity shear is larger then the Alfven frequency shear. (author)

  19. New experimental technique for the measurement of the velocity field in thin films falling over obstacles

    Science.gov (United States)

    Landel, Julien R.; Daglis, Ana; McEvoy, Harry; Dalziel, Stuart B.

    2014-11-01

    We present a new experimental technique to measure the surface velocity of a thin falling film. Thin falling films are important in various processes such as cooling in heat exchangers or cleaning processes. For instance, in a household dishwasher cleaning depends on the ability of a thin draining film to remove material from a substrate. We are interested in the impact of obstacles attached to a substrate on the velocity field of a thin film flowing over them. Measuring the velocity field of thin falling films is a challenging experimental problem due to the small depth of the flow and the large velocity gradient across its depth. We propose a new technique based on PIV to measure the plane components of the velocity at the surface of the film over an arbitrarily large area and an arbitrarily large resolution, depending mostly on the image acquisition technique. We perform experiments with thin films of water flowing on a flat inclined surface, made of glass or stainless steel. The typical Reynolds number of the film is of the order of 100 to 1000, computed using the surface velocity, the film thickness and the kinematic viscosity of the film. We measure the modification to the flow field, from a viscous-gravity regime, caused by small solid obstacles, such as three-dimensional hemispherical obstacles and two-dimensional steps. We compare our results with past theoretical and numerical studies. This material is based upon work supported by the Defense Threat Reduction Agency under Contract No. HDTRA1-12-D-0003-0001.

  20. Inertial Navigation System/Doppler Velocity Log (INS/DVL Fusion with Partial DVL Measurements

    Directory of Open Access Journals (Sweden)

    Asaf Tal

    2017-02-01

    Full Text Available The Technion autonomous underwater vehicle (TAUV is an ongoing project aiming to develop and produce a small AUV to carry on research missions, including payload dropping, and to demonstrate acoustic communication. Its navigation system is based on an inertial navigation system (INS aided by a Doppler velocity log (DVL, magnetometer, and pressure sensor (PS. In many INSs, such as the one used in TAUV, only the velocity vector (provided by the DVL can be used for aiding the INS, i.e., enabling only a loosely coupled integration approach. In cases of partial DVL measurements, such as failure to maintain bottom lock, the DVL cannot estimate the vehicle velocity. Thus, in partial DVL situations no velocity data can be integrated into the TAUV INS, and as a result its navigation solution will drift in time. To circumvent that problem, we propose a DVL-based vehicle velocity solution using the measured partial raw data of the DVL and additional information, thereby deriving an extended loosely coupled (ELC approach. The implementation of the ELC approach requires only software modification. In addition, we present the TAUV six degrees of freedom (6DOF simulation that includes all functional subsystems. Using this simulation, the proposed approach is evaluated and the benefit of using it is shown.

  1. Inertial Navigation System/Doppler Velocity Log (INS/DVL) Fusion with Partial DVL Measurements

    Science.gov (United States)

    Tal, Asaf; Klein, Itzik; Katz, Reuven

    2017-01-01

    The Technion autonomous underwater vehicle (TAUV) is an ongoing project aiming to develop and produce a small AUV to carry on research missions, including payload dropping, and to demonstrate acoustic communication. Its navigation system is based on an inertial navigation system (INS) aided by a Doppler velocity log (DVL), magnetometer, and pressure sensor (PS). In many INSs, such as the one used in TAUV, only the velocity vector (provided by the DVL) can be used for aiding the INS, i.e., enabling only a loosely coupled integration approach. In cases of partial DVL measurements, such as failure to maintain bottom lock, the DVL cannot estimate the vehicle velocity. Thus, in partial DVL situations no velocity data can be integrated into the TAUV INS, and as a result its navigation solution will drift in time. To circumvent that problem, we propose a DVL-based vehicle velocity solution using the measured partial raw data of the DVL and additional information, thereby deriving an extended loosely coupled (ELC) approach. The implementation of the ELC approach requires only software modification. In addition, we present the TAUV six degrees of freedom (6DOF) simulation that includes all functional subsystems. Using this simulation, the proposed approach is evaluated and the benefit of using it is shown. PMID:28241410

  2. Inertial Navigation System/Doppler Velocity Log (INS/DVL) Fusion with Partial DVL Measurements.

    Science.gov (United States)

    Tal, Asaf; Klein, Itzik; Katz, Reuven

    2017-02-22

    The Technion autonomous underwater vehicle (TAUV) is an ongoing project aiming to develop and produce a small AUV to carry on research missions, including payload dropping, and to demonstrate acoustic communication. Its navigation system is based on an inertial navigation system (INS) aided by a Doppler velocity log (DVL), magnetometer, and pressure sensor (PS). In many INSs, such as the one used in TAUV, only the velocity vector (provided by the DVL) can be used for aiding the INS, i.e., enabling only a loosely coupled integration approach. In cases of partial DVL measurements, such as failure to maintain bottom lock, the DVL cannot estimate the vehicle velocity. Thus, in partial DVL situations no velocity data can be integrated into the TAUV INS, and as a result its navigation solution will drift in time. To circumvent that problem, we propose a DVL-based vehicle velocity solution using the measured partial raw data of the DVL and additional information, thereby deriving an extended loosely coupled (ELC) approach. The implementation of the ELC approach requires only software modification. In addition, we present the TAUV six degrees of freedom (6DOF) simulation that includes all functional subsystems. Using this simulation, the proposed approach is evaluated and the benefit of using it is shown.

  3. A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running.

    Science.gov (United States)

    Samozino, P; Rabita, G; Dorel, S; Slawinski, J; Peyrot, N; Saez de Villarreal, E; Morin, J-B

    2016-06-01

    This study aimed to validate a simple field method for determining force- and power-velocity relationships and mechanical effectiveness of force application during sprint running. The proposed method, based on an inverse dynamic approach applied to the body center of mass, estimates the step-averaged ground reaction forces in runner's sagittal plane of motion during overground sprint acceleration from only anthropometric and spatiotemporal data. Force- and power-velocity relationships, the associated variables, and mechanical effectiveness were determined (a) on nine sprinters using both the proposed method and force plate measurements and (b) on six other sprinters using the proposed method during several consecutive trials to assess the inter-trial reliability. The low bias (<5%) and narrow limits of agreement between both methods for maximal horizontal force (638 ± 84 N), velocity (10.5 ± 0.74 m/s), and power output (1680 ± 280 W); for the slope of the force-velocity relationships; and for the mechanical effectiveness of force application showed high concurrent validity of the proposed method. The low standard errors of measurements between trials (<5%) highlighted the high reliability of the method. These findings support the validity of the proposed simple method, convenient for field use, to determine power, force, velocity properties, and mechanical effectiveness in sprint running.

  4. An Inexpensive Field-Widened Monolithic Michelson Interferometer for Precision Radial Velocity Measurements

    Science.gov (United States)

    Mahadevan, Suvrath; Ge, Jian; Fleming, Scott W.; Wan, Xiaoke; DeWitt, Curtis; van Eyken, Julian C.; McDavitt, Dan

    2008-09-01

    We have constructed a thermally compensated field-widened monolithic Michelson interferometer that can be used with a medium-resolution spectrograph to measure precise Doppler radial velocities of stars. Our prototype monolithic fixed-delay interferometer is constructed with off-the-shelf components and assembled using a hydrolysis bonding technique. We installed and tested this interferometer in the Exoplanet Tracker (ET) instrument at the Kitt Peak 2.1 m telescope, an instrument built to demonstrate the principles of dispersed fixed-delay interferometry. An iodine cell allows the interferometer drift to be accurately calibrated, relaxing the stability requirements on the interferometer itself. When using our monolithic interferometer, the ET instrument has no moving parts (except the iodine cell), greatly simplifying its operation. We demonstrate differential radial velocity precision of a few m s-1 on well known radial velocity standards and planet bearing stars when using this interferometer. Such monolithic interferometers will make it possible to build relatively inexpensive instruments that are easy to operate and capable of precision radial velocity measurements. A larger multiobject version of the Exoplanet Tracker will be used to conduct a large scale survey for planetary systems as part of the Sloan Digital Sky Survey III (SDSS III). Variants of the techniques and principles discussed in this paper can be directly applied to build large monolithic interferometers for such applications, enabling the construction of instruments capable of efficiently observing many stars simultaneously at high velocity precision.

  5. Trace projection transformation: a new method for measurement of debris flow surface velocity fields

    Science.gov (United States)

    Yan, Yan; Cui, Peng; Guo, Xiaojun; Ge, Yonggang

    2016-12-01

    Spatiotemporal variation of velocity is important for debris flow dynamics. This paper presents a new method, the trace projection transformation, for accurate, non-contact measurement of a debris-flow surface velocity field based on a combination of dense optical flow and perspective projection transformation. The algorithm for interpreting and processing is implemented in C ++ and realized in Visual Studio 2012. The method allows quantitative analysis of flow motion through videos from various angles (camera positioned at the opposite direction of fluid motion). It yields the spatiotemporal distribution of surface velocity field at pixel level and thus provides a quantitative description of the surface processes. The trace projection transformation is superior to conventional measurement methods in that it obtains the full surface velocity field by computing the optical flow of all pixels. The result achieves a 90% accuracy of when comparing with the observed values. As a case study, the method is applied to the quantitative analysis of surface velocity field of a specific debris flow.

  6. Estimation of pressure-particle velocity impedance measurement uncertainty using the Monte Carlo method.

    Science.gov (United States)

    Brandão, Eric; Flesch, Rodolfo C C; Lenzi, Arcanjo; Flesch, Carlos A

    2011-07-01

    The pressure-particle velocity (PU) impedance measurement technique is an experimental method used to measure the surface impedance and the absorption coefficient of acoustic samples in situ or under free-field conditions. In this paper, the measurement uncertainty of the the absorption coefficient determined using the PU technique is explored applying the Monte Carlo method. It is shown that because of the uncertainty, it is particularly difficult to measure samples with low absorption and that difficulties associated with the localization of the acoustic centers of the sound source and the PU sensor affect the quality of the measurement roughly to the same extent as the errors in the transfer function between pressure and particle velocity do.

  7. Measurement of ion and electron drift velocity and electronic attachment in air for ionization chambers

    CERN Document Server

    Boissonnat, Guillaume; Colin, Jean; Remadi, Aurelien; Salvador, Samuel

    2016-01-01

    Air-ionization chambers have been used in radiotherapy and particle therapy for decades. However, fundamental parameters in action in the detector responses are sparsely studied. In this work we aimed to measure the electronic attachment, electrons and ions mobilities of an ionization chamber (IC) in air. The main idea is to extract these from the actual response of the IC to a single ionizing particle in order to insure that they were measured in the same condition they are to be used while neglecting undesired phenomena: recombination and space charge effect. The non-standard signal shape analysis performed here were also confronted to a more standard drift chamber measurements using time-of-flight. It was found that both detectors displayed compatible results concerning positive and negative ions drift velocities where literature data is well spread out. In the same time, electron attachment measurements sit in the middle of known measurements while electron drift velocities seemed to show an offset compar...

  8. Interferometric velocity measurements through a fluctuating gas-liquid interface employing adaptive optics.

    Science.gov (United States)

    Büttner, Lars; Leithold, Christoph; Czarske, Jürgen

    2013-12-16

    Optical transmission through fluctuating interfaces of mediums with different refractive indexes is limited by the occurring distortions. Temporal fluctuations of such distortions deteriorate optical measurements. In order to overcome this shortcoming we propose the use of adaptive optics. For the first time, an interferometric velocity measurement technique with embedded adaptive optics is presented for flow velocity measurements through a fluctuating air-water interface. A low order distortion correction technique using a fast deformable mirror and a Hartmann-Shack camera with high frame rate is employed. The obtained high control bandwidth enables precise measurements also at fast fluctuating media interfaces. This methodology paves the way for several kinds of optical flow measurements in various complex environments.

  9. In situ impedance measurement of microwave atmospheric pressure plasma

    Science.gov (United States)

    Lee, S. T.; Nam, W. J.; Lee, J. K.; Yun, G. S.

    2017-04-01

    The impedance of atmospheric pressure argon plasma jets driven by microwave frequency is determined in situ by a novel ‘two frequency method’. In the conventional method of reflection coefficient ({{S}}11) measurement, the frequency of the driving microwave power is scanned, which inevitably affects the plasma characters and leads to uncertainty in the estimated plasma impedance. In our proposed method, the frequency-scanning signal additional to the driving power is used to measure {{S}}11 over a wide frequency range, which enables accurate determination of the plasma impedance based on an equivalent circuit model. The measured resistance and reactance of the plasma increase with the driving power in agreement with the transmission line theory. Based on this in situ measurement of the plasma impedance, the net power coupled to the plasma has been determined. The overall power efficiency remains approximately unchanged around 45% for different input power levels owing to the competing effects between the impedance mismatch and the volume change of the plasma.

  10. Toroidal and poloidal plasma rotation measurements in Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Hess, W.R.; Garbet, X.; Guirlet, R.; Hesse, M.; Payan, J. [Association Euratom-CEA, Centre d`Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee

    1993-12-31

    Plasma rotation measurements by visible spectroscopy and by a CO{sub 2}-laser scattering experiment (ALTAIR) are presented. The ALTAIR diagnostic is used to study the turbulence changes at the plasma edge during operation of the ergodic divertor (ED). Heterodyne detection allows discrimination between waves propagating in the electron or in the ion diamagnetic direction. (author) 6 refs., 4 figs.

  11. Electro-optic probe measurements of electric fields in plasmas

    Science.gov (United States)

    Nishiura, M.; Yoshida, Z.; Mushiake, T.; Kawazura, Y.; Osawa, R.; Fujinami, K.; Yano, Y.; Saitoh, H.; Yamasaki, M.; Kashyap, A.; Takahashi, N.; Nakatsuka, M.; Fukuyama, A.

    2017-02-01

    The direct measurements of high-frequency electric fields in a plasma bring about significant advances in the physics and engineering of various waves. We have developed an electro-optic sensor system based on the Pockels effect. Since the signal is transmitted through an optical fiber, the system has high tolerance for electromagnetic noises. To demonstrate its applicability to plasma experiments, we report the first result of measurement of the ion-cyclotron wave excited in the RT-1 magnetosphere device. This study compares the results of experimental field measurements with simulation results of electric fields in plasmas.

  12. Thrust Stand Measurements of a Conical Inductive Pulsed Plasma Thruster

    Science.gov (United States)

    Hallock, Ashley K.; Polzin, Kurt A.

    2013-01-01

    Inductive Pulsed Plasma Thrusters (iPPT) spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current Propellant is accelerated and expelled at a high exhaust velocity (O(10 -- 100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, inductive pulsed plasma thrusters can suffer from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, inductive pulsed plasma thrusters can suffer from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. A conical coil geometry may offer higher propellant utilization efficiency over that of a at inductive coil, however an increase in propellant utilization may be met with a decrease in axial electromagnetic acceleration, and in turn, a decrease in the total axially-directed kinetic energy imparted to the propellant.

  13. A comparison of measured and modeled velocity fields for a laminar flow in a porous medium

    Science.gov (United States)

    Wood, B. D.; Apte, S. V.; Liburdy, J. A.; Ziazi, R. M.; He, X.; Finn, J. R.; Patil, V. A.

    2015-11-01

    Obtaining highly-resolved velocity data from experimental measurements in porous media is a significant challenge. The goal of this work is to compare the velocity fields measured in a randomly-packed porous medium obtained from particle image velocimetry (PIV) with corresponding fields predicted from direct numerical simulation (DNS). Experimentally, the porous medium was comprised of 15 mm diameter spherical beads made of optical glass placed in a glass flow cell to create the packed bed. A solution of ammonium thiocyanate was refractive-index matched to the glass creating a medium that could be illuminated with a laser sheet without distortion. The bead center locations were quantified using the imaging system so that the geometry of the porous medium was known very accurately. Two-dimensional PIV data were collected and processed to provide high-resolution velocity fields at a single plane within the porous medium. A Cartesian-grid-based fictitious domain approach was adopted for the direct numerical simulation of flow through the same geometry as the experimental measurements and without any adjustable parameters. The uncertainties associated with characterization of the pore geometry, PIV measurements, and DNS predictions were all systematically quantified. Although uncertainties in bead position measurements led to minor discrepancies in the comparison of the velocity fields, the axial and normal velocity deviations exhibited normalized root mean squared deviations (NRMSD) of only 11.32% and 4.74%, respectively. The high fidelity of both the experimental and numerical methods have significant implications for understanding and even for engineering the micro-macro relationship in porous materials. The ability to measure and model sub-pore-scale flow features also has relevance to the development of upscaled models for flow in porous media, where physically reasonable closure models must be developed at the sub-pore scale. These results provide valuable data

  14. Measurement and analysis of angular velocity variations of twelve-cylinder diesel engine crankshaft

    Science.gov (United States)

    Bulatović, Ž. M.; Štavljanin, M. S.; Tomić, M. V.; Knežević, D. M.; Biočanin, S. Lj.

    2011-11-01

    This paper presents the procedures for measuring and analyzing the angular velocity variation of twelve-cylinder diesel engine crankshaft on its free end and on the power-output end. In addition, the paper deals with important aspects of the measurement of crankshaft torsional oscillations. The method is based on digital encoders placed at two distances, and one of them is a sensor not inserted directly on the shaft, i.e. a non-contact method with a toothed disc is used. The principle based on toothed disc is also used to measure the actual camshaft angular velocity of in-line compact high-pressure pump the engine is equipped with, and this paper aims to demonstrate the possibility of measuring the actual angular velocity of any rotating shaft in the engine, on which it is physically possible to mount a toothed disc. The method was created completely independently during long-range development and research tests of V46 family engines. This method is specific for its particular adaptability for use on larger engines with extensive vibrations and torsional oscillations. The main purpose of this paper is a practical contribution to all the more interesting research of the use of engine crankshaft angular velocity as a diagnostic tool for identifying the engine irregular running.

  15. Localized measurement of longitudinal and transverse flow velocities in colloidal suspensions using optical coherence tomography

    NARCIS (Netherlands)

    Weiss, N.; Van Leeuwen, T.G.; Kalkman, J.

    2013-01-01

    We report on localized measurement of the longitudinal and transverse flow velocities in a colloidal suspension using optical coherence tomography. We present a model for the path-length resolved autocorrelation function including diffusion and flow, which we experimentally verify. For flow that is

  16. On measuring surface wave phase velocity from station–station cross-correlation of ambient signal

    DEFF Research Database (Denmark)

    Boschi, Lapo; Weemstra, Cornelis; Verbeke, Julie

    2012-01-01

    We apply two different algorithms to measure surface wave phase velocity, as a function of frequency, from seismic ambient noise recorded at pairs of stations from a large European network. The two methods are based on consistent theoretical formulations, but differ in the implementation: one met...

  17. Velocity field measurements in an evaporating sessile droplet by means of micro-PIV technique

    Directory of Open Access Journals (Sweden)

    Yagodnitsyna Anna

    2016-01-01

    Full Text Available Velocity fields are measured in evaporating sessile droplets on two substrates with different contact angles and contact angle hysteresis using micro resolution particle image velocimetry technique. Different flow patterns are observed in different stages of droplet evaporation: a flow with vortices and a radial flow. Flow structure is found to be similar for droplets on different substrates.

  18. In Vivo Three-Dimensional Velocity Vector Imaging and Volumetric Flow Rate Measurements

    DEFF Research Database (Denmark)

    Pihl, Michael Johannes; Stuart, Matthias Bo; Tomov, Borislav Gueorguiev

    2013-01-01

    scanner SARUS. Measurements are conducted on a carotid artery flow phantom from Danish Phantom Design, and 20 frames are acquired with a constant flow rate of 16.7±0.17 mL/s provided by a Shelley Medical Imaging Technologies CompuFlow 1000 system. The peak velocity magnitude in the vessel is found...

  19. Uncertainty in velocity measurement based on diode-laser absorption in nonuniform flows.

    Science.gov (United States)

    Li, Fei; Yu, Xilong; Cai, Weiwei; Ma, Lin

    2012-07-10

    This work investigates the error caused by nonuniformities along the line-of-sight in velocity measurement using tunable diode-laser absorption spectroscopy (TDLAS). Past work has demonstrated TDLAS as an attractive diagnostic technique for measuring velocity, which is inferred from the Doppler shift of two absorption features using two crossing laser beams. However, because TDLAS is line-of-sight in nature, the obtained velocity is a spatially averaged value along the probing laser beams. As a result, nonuniformities in the flow can cause uncertainty in the velocity measurement. Therefore, it is the goal of this work to quantify the uncertainty caused by various nonuniformities typically encountered in practice, including boundary layer effects, the divergence/convergence of the flow, and the methods used to fit the Doppler shift. Systematic analyses are performed to quantify the uncertainty under various conditions, and case studies are reported to illustrate the usefulness of such analysis in interpreting experimental data obtained from a scramjet facility. We expect this work to be valuable for the design and optimization of TDLAS-based velocimetry, and also for the quantitative interpretation of the measurements.

  20. Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

    DEFF Research Database (Denmark)

    Salewski, Mirko; Geiger, B.; Nielsen, Stefan Kragh;

    2012-01-01

    We compute tomographies of 2D fast-ion velocity distribution functions from synthetic collective Thomson scattering (CTS) and fast-ion D (FIDA) 1D measurements using a new reconstruction prescription. Contradicting conventional wisdom we demonstrate that one single 1D CTS or FIDA view suffices to...

  1. MEASUREMENT OF MOTION CORRECTED WIND VELOCITY USING AN AEROSTAT LOFTED SONIC ANEMOMETER

    Science.gov (United States)

    An aerostat-lofted, sonic anemometer was used to determine instantaneous 3 dimensional wind velocities at altitudes relevant to fire plume dispersion modeling. An integrated GPS, inertial measurement unit, and attitude heading and reference system corrected the wind data for th...

  2. Comparison of sprinkler droplet size and velocity measurements using a laser precipitation meter and photographic method

    Science.gov (United States)

    Kinetic energy of water droplets has a substantial effect on development of a soil surface seal and infiltration rate of bare soil. Methods for measuring sprinkler droplet size and velocity needed to calculate droplet kinetic energy have been developed and tested over the past 50 years, each with ad...

  3. Concentration and Velocity Measurements of Both Phases in Liquid-Solid Slurries

    Science.gov (United States)

    Altobelli, Stephen; Hill, Kimberly; Caprihan, Arvind

    2007-03-01

    Natural and industrial slurry flows abound. They are difficult to calculate and to measure. We demonstrate a simple technique for studying steady slurries. We previously used time-of-flight techniques to study pressure driven slurry flow in pipes. Only the continuous phase velocity and concentration fields were measured. The discrete phase concentration was inferred. In slurries composed of spherical, oil-filled pills and poly-methyl-siloxane oils, we were able to use inversion nulling to measure the concentration and velocity fields of both phases. Pills are available in 1-5mm diameter and silicone oils are available in a wide range of viscosities, so a range of flows can be studied. We demonstrated the technique in horizontal, rotating cylinder flows. We combined two tried and true methods to do these experiments. The first used the difference in T1 to select between phases. The second used gradient waveforms with controlled first moments to produce velocity dependent phase shifts. One novel processing method was developed that allows us to use static continuous phase measurements to reference both the continuous and discrete phase velocity images. ?

  4. Role of grain size and particle velocity distribution in secondary electron emission in space plasmas

    Science.gov (United States)

    Chow, V. W.; Mendis, D. A.; Rosenberg, M.

    1993-01-01

    By virtue of being generally immersed in a plasma environment, cosmic dust is necessarily electrically charged. The fact that secondary emission plays an important role in determining the equilibrium grain potential has long been recognized, but the fact that the grain size plays a crucial role in this equilibrium potential, when secondary emission is important, has not been widely appreciated. Using both conducting and insulating spherical grains of various sizes and also both Maxwellian and generalized Lorentzian plasmas (which are believed to represent certain space plasmas), we have made a detailed study of this problem. In general, we find that the secondary emission yield delta increases with decreasing size and becomes very large for grains whose dimensions are comparable to the primary electron penetration depth, such as in the case of the very small grains observed at comet Halley and inferred in the interstellar medium. Moreover, we observed that delta is larger for insulators and equilibrium potentials are generally more positive when the plasma has a broad non-Maxwellian tail. Interestingly, we find that for thermal energies that are expected in several cosmic regions, grains of different sizes can have opposite charge, the smaller ones being positive while the larger ones are negative. This may have important consequences for grain accretion in polydisperse dusty space plasmas.

  5. Effect of Gas Velocity on the Dust Sediment Layer in the Coupled Field of Corona Plasma and Cyclone

    Science.gov (United States)

    Wei, Mingshan; Ma, Chaochen; Li, Minghua; S, N. Danish

    2006-09-01

    A dust sediment layer was found on the outer tube wall when the ESCP (electrostatic centrifugal precipitator) trapped diesel particulates or ganister sand. The Compton back scatter method was used to measure the sediment thickness during the experiment. The effect of the inlet gas velocity on the dust sediment layer was investigated. PIV (Particle Image Velocimetry) was used to measure the velocity field between the inner barb tube wall and the outer tube wall. Experiments showed that the thickness of the sediment increased with time, and the sediment layer at the lower end was much thicker than that at the upper end. The agglomeration on the outer tube wall could be removed when the inlet gas velocity was increased to a certain value.

  6. Ultrasonic laboratory measurements of the seismic velocity changes due to CO2 injection

    Science.gov (United States)

    Park, K. G.; Choi, H.; Park, Y. C.; Hwang, S.

    2009-04-01

    Monitoring the behavior and movement of carbon dioxide (CO2) in the subsurface is a quite important in sequestration of CO2 in geological formation because such information provides a basis for demonstrating the safety of CO2 sequestration. Recent several applications in many commercial and pilot scale projects and researches show that 4D surface or borehole seismic methods are among the most promising techniques for this purpose. However, such information interpreted from the seismic velocity changes can be quite subjective and qualitative without petrophysical characterization for the effect of CO2 saturation on the seismic changes since seismic wave velocity depends on various factors and parameters like mineralogical composition, hydrogeological factors, in-situ conditions. In this respect, we have developed an ultrasonic laboratory measurement system and have carried out measurements for a porous sandstone sample to characterize the effects of CO2 injection to seismic velocity and amplitude. Measurements are done by ultrasonic piezoelectric transducer mounted on both ends of cylindrical core sample under various pressure, temperature, and saturation conditions. According to our fundamental experiments, injected CO2 introduces the decrease of seismic velocity and amplitude. We identified that the velocity decreases about 6% or more until fully saturated by CO2, but the attenuation of seismic amplitude is more drastically than the velocity decrease. We also identified that Vs/Vp or elastic modulus is more sensitive to CO2 saturation. We note that this means seismic amplitude and elastic modulus change can be an alternative target anomaly of seismic techniques in CO2 sequestration monitoring. Thus, we expect that we can estimate more quantitative petrophysical relationships between the changes of seismic attributes and CO2 concentration, which can provide basic relation for the quantitative assessment of CO2 sequestration by further researches.

  7. Acute elevation of plasma non-esterified fatty acids increases pulse wave velocity and induces peripheral vasodilation in humans in vivo

    NARCIS (Netherlands)

    Riksen, Niels P.; Bosselaar, Marlies; Bakker, Stephan J. L.; Heine, Robert J.; Rongen, Gerard A.; Tack, Cees J.; Smits, Paul

    2007-01-01

    Plasma NEFA (non-esterified fatty acid) concentrations are elevated in patients with obesity. In the present study we first aimed to provide an integral haemodynamic profile of elevated plasma NEFAs by the simultaneous assessment of blood pressure, pulse wave velocity, FBF (forearm blood flow) and s

  8. Comparative experimental study on several methods for measuring elastic wave velocities in rocks at high pressure

    Institute of Scientific and Technical Information of China (English)

    XIE; Hongsen(谢鸿森); ZHOU; Wenge; 周文戈); LIU; Yonggang; (刘永刚); GUO; Jie; (郭捷); HOU; Wei; (侯渭); ZHAO; Zhidan(赵志丹)

    2002-01-01

    To measure elastic wave velocities in rocks at high temperature and high pressure is an important way to acquire the mechanics and thermodynamics data of rocks in the earth's interior and also a substantial approach to studying the structure and composition of materials there. In recent years, a rapid progress has been made in methodology pertaining to the measurements of elastic wave velocities in rocks at high temperature and high pressure with solids as the pressure-transfer media. However, no strict comparisons have been made of the elastic wave velocity data of rocks measured at high temperature and high pressure by various laboratories. In order to compare the experimental results from various laboratories, we have conducted a comparative experimental study on three measuring methods and made a strict comparison with the results obtained by using the transmission method with fluid as the pressure-transfer medium. Our experimental results have shown that the measurements obtained by the three methods are comparable in the pressure ranges of their application. The cubic sample pulse transmission method used by Kern is applicable to measuring elastic wave velocities in crustal rocks at lower temperature and lower pressure. The prism sample pulse reflection-transmission method has some advantages in pressure range, heating temperature and measuring precision. Although the measurements obtained under relatively low pressure conditions by the prism sample pulse transmission method are relatively low in precision, the samples are large in length and their assemblage is simple. So this method is suitable to the experiments that require large quantities of samples and higher pressures. Therefore, in practical application the latter two methods are usually recommended because their measurements can be mutually corrected and supplemented.

  9. Measurements of ammonia concentrations, fluxes and dry deposition velocities to a spruce forest 1991-1995

    DEFF Research Database (Denmark)

    Andersen, H.V.; Hovmand, M.F.; Hummelshøj, P.;

    1999-01-01

    at conditions with easterly winds, the air have passed central Jutland with large emission areas. Some of the relatively low deposition velocities or emissions were observed during conditions with low ammonia concentration and westerly winds. These observations might relate to a compensation point of the forest...... measuring period characterized by easterly winds with dry conditions and high ammonia concentrations, and the emissions might relate to evaporation from ammonia saturated surfaces or emission from mineralization in the forest soil. In general, relatively high net deposition velocities were observed during...

  10. A new method of measuring the cluster peculiar velocity power spectrum

    CERN Document Server

    Zhang, Pengjie; Juszkiewicz, Roman; Stebbins, Albert

    2008-01-01

    We propose to use spatial correlations of the kinetic Sunyaev-Zeldovich (KSZ) flux as an estimator of the peculiar velocity power spectrum. In contrast with conventional techniques, our new method does not require measurements of the thermal SZ signal or the X-ray temperature. Moreover, this method has the special advantage that the expected systematic errors are always sub-dominant to statistical errors on all scales and redshifts of interest. We show that future large sky coverage KSZ surveys may allow a peculiar velocity power spectrum estimates of an accuracy reaching ~10%.

  11. Galileo, measurement of the velocity of light, and the reaction times.

    Science.gov (United States)

    Foschi, Renato; Leone, Matteo

    2009-01-01

    According to the commonly accepted view, Galileo Galilei devised in 1638 an experiment that seemed able to show that the velocity of light is finite. An analysis of archival material shows that two decades later members of the Florence scientific society Accademia del Cimento followed Galileo guidelines by actually attempting to measure the velocity of light and suggesting improvements. This analysis also reveals a fundamental difference between Galileo's and Florence academy's methodologies and that Galileo's experiment was, in some respects, a pioneering work affecting also the history of the psychology of perception.

  12. Preliminary measurements of velocity, density and total temperature fluctuations in compressible subsonic flow

    Science.gov (United States)

    Stainback, P. C.; Johnson, C. B.; Basnett, C. B.

    1983-01-01

    The heat transfer characteristics of a three-wire hot-wire probe operated with a constant temperature anemometer were investigated in the subsonic compressible flow regime. The sensitivity coefficients, with respect to velocity, density and total temperature, were measured and the results were used to calculate the velocity, density, and total temperature fluctuations in the test section of the Langley 0.3-m Transonic Cryogenic Tunnel (TCT). These results were extended to give estimates for fluctuations due to vorticity, sound, and entropy. In addition, attempts were made to determine the major source of disturbances in the 0.3-m TCT.

  13. A 4-spot time-of-flight anemometer for small centrifugal compressor velocity measurements

    Science.gov (United States)

    Wernet, Mark P.; Skoch, Gary J.

    1992-01-01

    The application of laser anemometry techniques in turbomachinery facilities is a challenging dilemma requiring an anemometer system with special qualities. Here, we describe the use of a novel laser anemometry technique applied to a small 4.5 kg/s, 4:1 pressure ratio centrifugal compressor. Sample velocity profiles across the blade pitch are presented for a single location along the rotor. The results of the intra-blade passage velocity measurements will ultimately be used to verify CFD 3-D viscous code predictions.

  14. Improved measurement of the neutron absorption cross section for very low velocities

    Science.gov (United States)

    Schroffenegger, J.; Fierlinger, P.; Hollering, A.; Geltenbort, P.; Lauer, T.; Rauch, H.; Zechlau, T.

    2016-01-01

    The absorption cross section of natural Gd and isotopic enriched 157Gd for ultra-cold neutrons (UCN) as a function of the velocity has been measured within a time-of-flight-experiment. Particular attention is paid to small velocities in the region of a few m/s. This is intended to determine the validity of the 1 / v-law governing absorption cross sections in this region and the resulting divergence at v = 0. The experiment does not show any significant violation of 1 / v for v > 3 m /s.

  15. Improved measurement of the neutron absorption cross section for very low velocities

    Directory of Open Access Journals (Sweden)

    J. Schroffenegger

    2016-01-01

    Full Text Available The absorption cross section of natural Gd and isotopic enriched 157Gd for ultra-cold neutrons (UCN as a function of the velocity has been measured within a time-of-flight-experiment. Particular attention is paid to small velocities in the region of a few m/s. This is intended to determine the validity of the 1/v-law governing absorption cross sections in this region and the resulting divergence at v=0. The experiment does not show any significant violation of 1/v for v>3 m/s.

  16. Improved measurement of the neutron absorption cross section for very low velocities

    OpenAIRE

    J. Schroffenegger; Fierlinger, P.; Hollering, A.; Geltenbort, P; Lauer, T.(Forschungsneutronenquelle Heinz Maier-Leibnitz, Technische Universität München, Garching, D-85748, Germany); Rauch, H.; Zechlau, T.

    2016-01-01

    The absorption cross section of natural Gd and isotopic enriched 157 Gd for ultra-cold neutrons (UCN) as a function of the velocity has been measured within a time-of-flight-experiment. Particular attention is paid to small velocities in the region of a few m/s. This is intended to determine the validity of the 1/v -law governing absorption cross sections in this region and the resulting divergence at v=0 . The experiment does not show any significant violation of 1/v for v>3 m/s .

  17. In vivo noninvasive method for measuring local wave velocity in femoral arteries of pig

    Science.gov (United States)

    Zhang, Xiaoming; Kinnick, Randall; Pislaru, Cristina; Fatemi, Mostafa; Greenleaf, James

    2005-09-01

    We have proposed generating a bending wave in the arterial wall using ultrasound radiation force and measuring the wave velocity along the arterial wall [Zhang et al., IEEE Trans. Ultrason. Ferroelectr. Freq. Control 52, 642-652 (2005)]. Here, we report the results of in vivo studies on pigs. The pig was anesthetized, and a micromanometer tip catheter was inserted into the femoral artery to measure luminal pressure. A water bath was created on the animal's groin to allow unimpeded access of the ultrasound beams to the femoral artery. The femoral artery was first located using a 13-MHz linear-array transducer. Then, a vibro-acoustography image was obtained to ensure precise positioning of the excitation force relative to the artery. The artery was excited by the force transducer and the resulting vibration of the arterial wall was measured by a sensing Doppler transceiver. Measured wave velocity was 3.1 m/s at 300 Hz. With this new method wave velocity over a distance of 5 mm, and therefore stiffness of arteries, can be measured locally and non-invasively. Measurement time is short in a few tens of milliseconds, which allows pressure dependence and pharmacological effect on the wall properties to be measured at different cardiac times.

  18. Errors and uncertainties in the measurement of ultrasonic wave attenuation and phase velocity.

    Science.gov (United States)

    Kalashnikov, Alexander N; Challis, Richard E

    2005-10-01

    This paper presents an analysis of the error generation mechanisms that affect the accuracy of measurements of ultrasonic wave attenuation coefficient and phase velocity as functions of frequency. In the first stage of the analysis we show that electronic system noise, expressed in the frequency domain, maps into errors in the attenuation and the phase velocity spectra in a highly nonlinear way; the condition for minimum error is when the total measured attenuation is around 1 Neper. The maximum measurable total attenuation has a practical limit of around 6 Nepers and the minimum measurable value is around 0.1 Neper. In the second part of the paper we consider electronic noise as the primary source of measurement error; errors in attenuation result from additive noise whereas errors in phase velocity result from both additive noise and system timing jitter. Quantization noise can be neglected if the amplitude of the additive noise is comparable with the quantization step, and coherent averaging is employed. Experimental results are presented which confirm the relationship between electronic noise and measurement errors. The analytical technique is applicable to the design of ultrasonic spectrometers, formal assessment of the accuracy of ultrasonic measurements, and the optimization of signal processing procedures to achieve a specified accuracy.

  19. Mass spectrometry of planetary exospheres at high relative velocity: direct comparison of open- and closed-source measurements

    Science.gov (United States)

    Meyer, Stefan; Tulej, Marek; Wurz, Peter

    2017-01-01

    The exploration of habitable environments on or inside icy moons around the gas giants in the solar system is of major interest in upcoming planetary missions. Exactly this theme is addressed by the JUpiter ICy moons Explorer (JUICE) mission of ESA, which will characterise Ganymede, Europa and Callisto as planetary objects and potential habitats. We developed a prototype of the Neutral Gas and Ion Mass spectrometer (NIM) of the Particle Environment Package (PEP) for the JUICE mission intended for composition measurements of neutral gas and thermal plasma. NIM/PEP will be used to measure the chemical composition of the exospheres of the icy Jovian moons. Besides direct ion measurement, the NIM instrument is able to measure the inflowing neutral gas in two different modes: in neutral mode, where the gas enters directly the ion source (open source), and in thermal mode, where the gas gets thermally accommodated to the wall temperature by several collisions inside an equilibrium sphere, called antechamber, before entering the ion source (closed source). We performed measurements with the prototype NIM using a neutral gas beam of 1 up to 4.5 km s-1 velocity in the neutral and thermal mode. The current trajectory of JUICE foresees a flyby velocity of 4 km s-1 at Europa; other flybys are in the range of 1 up to 7 km s-1 and orbital velocity in Ganymede orbits is around 2 km s-1. Different species are used for the gas beam, such as noble gases Ne, Ar, Kr as well as molecules like H2, methane, ethane, propane and more complex ones. The NIM prototype was successfully tested under realistic JUICE mission conditions. In addition, we find that the antechamber (closed source) behaves as expected with predictable density enhancement over the specified mass range and within the JUICE mission phase velocities. Furthermore, with the open source and the closed source we measure almost the same composition for noble gases, as well as for molecules, indicating no additional

  20. In vivo μPIV measurements of blood velocity in small vessels of a rat model

    Science.gov (United States)

    Leong, Chia Min; Russell, John; Connor, Nadine; Honkanen, Markus; Wei, Timothy

    2009-11-01

    Aging-related muscular changes have been shown to affect voice production. There is correlation between muscular changes and changes in capillary hemodynamics and structure with aging. Alterations in oxygen transport to cells and tissues at the capillary level has been hypothesized as one of the key factors that causes muscular changes thus voice production. Since oxygen transport is related to hemodynamics, we start by measuring blood velocity in capillaries of cremaster muscle of a living rat. The μPIV technique is adapted for measuring blood velocity where red blood cells are used as `seeding particles'. The accuracy of the μPIV measurements are determined by comparison with results obtained using other techniques such as particle tracking velocimetry (PTV). Finally, challenges in measuring flow through three-dimensional larynx geometry will be discussed.

  1. Acoustic velocity measurement across the diameter of a liquid metal column

    Energy Technology Data Exchange (ETDEWEB)

    Calder, C.A.; Wilcox, W.W.

    1978-05-15

    Present techniques for measuring sound velocity in liquid metals have been limited by the use of transducers which cannot survive in extreme temperature conditions. These methods also require relatively long measurement times. An optical noncontacting method has been developed which may be used for extremely short experimental times and very high temperatures and pressures. This technique is being incorporated into an isobaric expansion apparatus in which a 1 mm diam wire sample in a high pressure argon gas environment is resistively heated to melt within a time period of only a few microseconds. Before instability of the liquid column occurs, thermal expansion, enthalpy, and temperature are measured. The addition of the sound velocity measurement permits a more complete determination of the thermophysical properties of the liquid metal.

  2. Exploiting SENTINEL-1 Amplitude Data for Glacier Surface Velocity Field Measurements: Feasibility Demonstration on Baltoro Glacier

    Science.gov (United States)

    Nascetti, A.; Nocchi, F.; Camplani, A.; Di Rico, C.; Crespi, M.

    2016-06-01

    The leading idea of this work is to continuously retrieve glaciers surface velocity through SAR imagery, in particular using the amplitude data from the new ESA satellite sensor Sentinel-1 imagery. These imagery key aspects are the free access policy, the very short revisit time (down to 6 days with the launch of the Sentinel-1B satellite) and the high amplitude resolution (up to 5 m). In order to verify the reliability of the proposed approach, a first experiment has been performed using Sentinel-1 imagery acquired over the Karakoram mountain range (North Pakistan) and Baltoro and other three glaciers have been investigated. During this study, a stack of 11 images acquired in the period from October 2014 to September 2015 has been used in order to investigate the potentialities of the Sentinel-1 SAR sensor to retrieve the glacier surface velocity every month. The aim of this test was to measure the glacier surface velocity between each subsequent pair, in order to produce a time series of the surface velocity fields along the investigated period. The necessary coregistration procedure between the images has been performed and subsequently the glaciers areas have been sampled using a regular grid with a 250 × 250 meters posting. Finally the surface velocity field has been estimated, for each image pair, using a template matching procedure, and an outlier filtering procedure based on the signal to noise ratio values has been applied, in order to exclude from the analysis unreliable points. The achieved velocity values range from 10 to 25 meters/month and they are coherent to those obtained in previous studies carried out on the same glaciers and the results highlight that it is possible to have a continuous update of the glacier surface velocity field through free Sentinel-1 imagery, that could be very useful to investigate the seasonal effects on the glaciers fluid-dynamics.

  3. Seismic structure beneath the Gulf of California: a contribution from group velocity measurements

    Science.gov (United States)

    Di Luccio, F.; Persaud, P.; Clayton, R. W.

    2014-12-01

    Rayleigh wave group velocity dispersion measurements from local and regional earthquakes are used to interpret the lithospheric structure in the Gulf of California region. We compute group velocity maps for Rayleigh waves from 10 to 150 s using earthquakes recorded by broad-band stations of the Network of Autonomously Recording Seismographs in Baja California and Mexico mainland, UNM in Mexico, BOR, DPP and GOR in southern California and TUC in Arizona. The study area is gridded in 120 longitude cells by 180 latitude cells, with an equal spacing of 10 × 10 km. Assuming that each gridpoint is laterally homogeneous, for each period the tomographic maps are inverted to produce a 3-D lithospheric shear wave velocity model for the region. Near the Gulf of California rift axis, we found three prominent low shear wave velocity regions, which are associated with mantle upwelling near the Cerro Prieto volcanic field, the Ballenas Transform Fault and the East Pacific Rise. Upwelling of the mantle at lithospheric and asthenospheric depths characterizes most of the Gulf. This more detailed finding is new when compared to previous surface wave studies in the region. A low-velocity zone in northcentral Baja at ˜28ºN which extends east-south-eastwards is interpreted as an asthenospheric window. In addition, we also identify a well-defined high-velocity zone in the upper mantle beneath central-western Baja California, which correlates with the previously interpreted location of the stalled Guadalupe and Magdalena microplates. We interpret locations of the fossil slab and slab window in light of the distribution of unique post-subduction volcanic rocks in the Gulf of California and Baja California. We also observe a high-velocity anomaly at 50-km depth extending down to ˜130 km near the southwestern Baja coastline and beneath Baja, which may represent another remnant of the Farallon slab.

  4. Gas Temperature Measurements of Fluctuating Coal - MHD Plasmas Using Modified Line Reversal.

    Science.gov (United States)

    Winkleman, Bradley Carl

    The technique of modified line reversal is investigated and developed to allow accurate measurements on fluctuating coal fired magnetohydrodynamic plasmas and flows. Generalized modified line reversal equations applicable to any geometry and optical system are developed and presented. The generalized equations are specialized to the two most common optical systems, focussed and collimated, employed for modified line reversal measurements. Approximations introduced by specializing to the specific optical systems are investigated. Vignetting of the optical system images is shown to introduce large biases in the temperature measurement for certain optical configurations commonly applied. It is shown that symmetric optical systems are unacceptable for line reversal measurements. The errors introduced by non-simultaneous measurement of the required line reversal parameters due to rapidly fluctuating plasma characteristics are characterized. Line reversal signal and temperature measurements made on a coal fired MHD plasma are used to quantify the error in the temperature measurement due to non-simultaneous sampling of the measured line reversal parameters. A simple modified line reversal system based on interference filters and photodiodes that employs spatial separation to obtain the required line reversal parameters is described. Gas temperatures measured with devices using both the spatial and temporal separation techniques are compared. Modified line reversal temperature measurements are compared to theoretically predicted temperatures as well as CARS and high velocity thermocouple temperature measurements.

  5. Sample Disturbance in Resonant Column Test Measurement of Small-Strain Shear-Wave Velocity

    Science.gov (United States)

    Chiara, Nicola; Stokoe, K. H.

    The accurate assessment of dynamic soil properties is a crucial step in the solution process of geotechnical earthquake engineering problems. The resonant column test is one of the ordinary procedures for dynamic characterization of soil. In this paper, the impact of sample disturbance on the resonant column test measurement of small-strain S-wave velocity is examined. Sample disturbance is shown to be a function of the ratio of the laboratory to field S-wave velocities: Vs, lab/Vs,field. The influence of four parameters - soil stiffness, soil plasticity index, in-situ sample depth and in-situ effective mean confining pressure - on sample disturbance is investigated both qualitatively and quantitatively. The relative importance of each parameter in predicting the small-strain field S-wave velocity from the resonant column test values is illustrated and predictive equations are presented.

  6. An Inexpensive Field-Widened Monolithic Michelson Interferometer for Precision Radial Velocity Measurements

    CERN Document Server

    Mahadevan, Suvrath; Fleming, Scott W; Wan, Xiaoke; DeWitt, Curtis; van Eyken, Julian C; McDavitt, Dan

    2008-01-01

    We have constructed a thermally compensated field-widened monolithic Michelson interferometer that can be used with a medium-resolution spectrograph to measure precise Doppler radial velocities of stars. Our prototype monolithic fixed-delay interferometer is constructed with off-the-shelf components and assembled using a hydrolysis bonding technique. We installed and tested this interferometer in the Exoplanet Tracker (ET) instrument at the Kitt Peak 2.1m telescope, an instrument built to demonstrate the principles of dispersed fixed delay interferometry. An iodine cell allows the interferometer drift to be accurately calibrated, relaxing the stability requirements on the interferometer itself. When using our monolithic interferometer, the ET instrument has no moving parts (except the iodine cell), greatly simplifying its operation. We demonstrate differential radial velocity precision of a few m s$^{-1}$ on well known radial velocity standards and planet bearing stars when using this interferometer. Such mon...

  7. Optical measurements of pore geometry and fluid velocity in a bed of irregularly packed spheres

    Science.gov (United States)

    Huang, Alice Y. L.; Huang, Michelle Y. F.; Capart, Hervé; Chen, Rong-Her

    2008-08-01

    Imaging methods are proposed for the characterisation of liquid flows through transparent porous media of matched refractive index. The methods are based on the analysis of laser-illuminated slices, and specialized for the case in which the porous medium is composed of irregularly packed spheres. They include algorithms for the reconstruction of the three-dimensional (3D) sphere arrangement based on a laser scan of the packed bed, particle tracking velocimetry applied to the motions of micro-tracers in a laser-illuminated plane, and techniques for the co-registration of geometry and velocity measurements acquired from different slices. The methods are applied to a cylindrical flow cell filled with mono-sized spheres and operated at Reynolds number Re = 28. The data produced include the full 3D geometry of the packed spheres assembly, the 2D fluid velocity field in the axial centre-plane of the flow cell, and the corresponding porosity and velocity distributions.

  8. Measuring the translational and rotational velocity of particles in helical motion using structured light

    CERN Document Server

    Rosales-Guzmán, Carmelo; Belmonte, Aniceto; Torres, Juan P

    2014-01-01

    We measure the rotational and translational velocity components of particles moving in helical motion using the frequency shift they induced to the structured light beam illuminating them. Under Laguerre-Gaussian mode illumination, a particle with a helical motion reflects light that acquires an additional frequency shift proportional to the angular velocity of rotation in the transverse plane, on top of the usual frequency shift due to the longitudinal motion. We determined both the translational and rotational velocities of the particles by switching between two modes: by illuminating with a Gaussian beam, we can isolate the longitudinal frequency shift; and by using a Laguerre-Gaussian mode, the frequency shift due to the rotation can be determined. Our technique can be used to characterize the motility of microorganisms with a full three-dimensional movement.

  9. Using smartphones' pressure sensors to measure vertical velocities in elevators, stairways and drones

    CERN Document Server

    Monteiro, Martin

    2016-01-01

    By means of smartphones' pressure sensors we measure vertical velocities of elevators, pedestrians climbing stairways and flying unmanned aerial vehicles (or \\textit{drones}). The barometric pressure obtained with the smartphone is related, thanks to the hydrostatic approximation, to the altitude of the device. From the altitude values, the vertical velocity is accordingly derived. The approximation considered is valid in the first hundreds meters of the inner layers of the atmosphere. Simultaneously to the pressure, the acceleration values, reported by the buit-in accelerometers, are also recorded. Integrating numerically the acceleration, vertical velocity and altitude are also obtained. We show that data obtained with the pressure sensor is considerable less noisy than that obtained with the accelerometer in the experiments proposed here. Accumulatioin of errors are also evident in the numerical integration of the acceleration values. The comparison with reference values taken from the architectural plans ...

  10. Measurement of the group velocity of light in sea water at the ANTARES site

    Science.gov (United States)

    Adrián-Martínez, S.; Al Samarai, I.; Albert, A.; André, M.; Anghinolfi, M.; Anton, G.; Anvar, S.; Ardid, M.; Assis Jesus, A. C.; Astraatmadja, T.; Aubert, J.-J.; Baret, B.; Basa, S.; Bertin, V.; Biagi, S.; Bigi, A.; Bigongiari, C.; Bogazzi, C.; Bou-Cabo, M.; Bouhou, B.; Bouwhuis, M. C.; Brunner, J.; Busto, J.; Camarena, F.; Capone, A.; Cârloganu, C.; Carminati, G.; Carr, J.; Cecchini, S.; Charif, Z.; Charvis, Ph.; Chiarusi, T.; Circella, M.; Costantini, H.; Coyle, P.; Curtil, C.; De Bonis, G.; Decowski, M. P.; Dekeyser, I.; Deschamps, A.; Distefano, C.; Donzaud, C.; Dornic, D.; Dorosti, Q.; Drouhin, D.; Eberl, T.; Emanuele, U.; Enzenhöfer, A.; Ernenwein, J.-P.; Escoffier, S.; Fermani, P.; Ferri, M.; Flaminio, V.; Folger, F.; Fritsch, U.; Fuda, J.-L.; Galatà, S.; Gay, P.; Geyer, K.; Giacomelli, G.; Giordano, V.; Gómez-González, J. P.; Graf, K.; Guillard, G.; Halladjian, G.; Hallewell, G.; van Haren, H.; Hartman, J.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Herold, B.; Hößl, J.; Hsu, C. C.; de Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U.; Kavatsyuk, O.; Kooijman, P.; Kopper, C.; Kouchner, A.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lamare, P.; Larosa, G.; Lattuada, D.; Lefèvre, D.; Lim, G.; Lo Presti, D.; Loehner, H.; Loucatos, S.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martínez-Mora, J. A.; McMillan, J. E.; Meli, A.; Montaruli, T.; Moscoso, L.; Motz, H.; Neff, M.; Nezri, E.; Palioselitis, D.; Păvălaş, G. E.; Payet, K.; Payre, P.; Petrovic, J.; Piattelli, P.; Picot-Clemente, N.; Popa, V.; Pradier, T.; Presani, E.; Racca, C.; Reed, C.; Riccobene, G.; Richardt, C.; Richter, R.; Rivière, C.; Robert, A.; Roensch, K.; Rostovtsev, A.; Ruiz-Rivas, J.; Rujoiu, M.; Russo, G. V.; Salesa, F.; Samtleben, D. F. E.; Sapienza, P.; Schöck, F.; Schuller, J.-P.; Schüssler, F.; Seitz, T.; Shanidze, R.; Simeone, F.; Spies, A.; Spurio, M.; Steijger, J. J. M.; Stolarczyk, Th.; Sánchez-Losa, A.; Taiuti, M.; Tamburini, C.; Thompson, L. F.; Toscano, S.; Vallage, B.; Van Elewyck, V.; Vannoni, G.; Vecchi, M.; Vernin, P.; Wagner, S.; Wijnker, G.; Wilms, J.; de Wolf, E.; Yepes, H.; Zaborov, D.; Zornoza, J. D.; Zúñiga, J.

    2012-04-01

    The group velocity of light has been measured at eight different wavelengths between 385 nm and 532 nm in the Mediterranean Sea at a depth of about 2.2 km with the ANTARES optical beacon systems. A parametrisation of the dependence of the refractive index on wavelength based on the salinity, pressure and temperature of the sea water at the ANTARES site is in good agreement with these measurements.

  11. Measurement of the Group Velocity of Light in Sea Water at the ANTARES Site

    CERN Document Server

    Adrián-Martínez, S; Albert, A; André, M; Anghinolfi, M; Anton, G; Anvar, S; Ardid, M; Jesus, A C Assis; Astraatmadja, T; Aubert, J-J; Baret, B; Basa, S; Bertin, V; Biagi, S; Bigi, A; Bigongiari, C; Bogazzi, C; Bou-Cabo, M; Bouhou, B; Bouwhuis, M C; Brunner, J; Busto, J; Camarena, F; Capone, A; Carloganu, C; Carminati, G; Carr, J; Cecchini, S; Charif, Z; Charvis, Ph; Chiarusi, T; Circella, M; Costantini, H; Coyle, P; Curtil, C; De Bonis, G; Decowski, M P; Dekeyser, I; Deschamps, A; Distefano, C; Donzaud, C; Dornic, D; Dorosti, Q; Drouhin, D; Eberl, T; Emanuele, U; Enzenhöfer, A; Ernenwein, J-P; Escoffier, S; Fermani, P; Ferri, M; Flaminio, V; Folger, F; Fritsch, U; Fuda, J-L; Galatá, S; Gay, P; Geyer, K; Giacomelli, G; Giordano, V; Gómez-González, J P; Graf, K; Guillard, G; Halladjian, G; Hallewell, G; van Haren, H; Hartman, J; Heijboer, A J; Hello, Y; Hernández-Rey, J J; Herold, B; Hößl, J; Hsu, C C; de Jong, M; Kadler, M; Kalekin, O; Kappes, A; Katz, U; Kavatsyuk, O; Kooijman, P; Kopper, C; Kouchner, A; Kreykenbohm, I; Kulikovskiy, V; Lahmann, R; Lamare, P; Larosa, G; Lattuada, D; Lefévre, D; Lim, G; Presti, D Lo; Loehner, H; Loucatos, S; Mangano, S; Marcelin, M; Margiotta, A; Martínez-Mora, J A; Meli, A; Montaruli, T; Moscoso, L; Motz, H; Neff, M; Nezri, E; Palioselitis, D; Păvălaş, G E; Payet, K; Payre, P; Petrovic, J; Piattelli, P; Picot-Clemente, N; Popa, V; Pradier, T; Presani, E; Racca, C; Reed, C; Riccobene, G; Richardt, C; Richter, R; Riviére, C; Robert, A; Roensch, K; Rostovtsev, A; Ruiz-Rivas, J; Rujoiu, M; Russo, G V; Salesa, F; Samtleben, D F E; Sapienza, P; Schöck, F; Schuller, J-P; Schüssler, F; Seitz, T; Shanidze, R; Simeone, F; Spies, A; Spurio, M; Steijger, J J M; Stolarczyk, Th; Sánchez-Losa, A; Taiuti, M; Tamburini, C; Toscano, S; Vallage, B; Van Elewyck, V; Vannoni, G; Vecchi, M; Vernin, P; Wagner, S; Wijnker, G; Wilms, J; de Wolf, E; Yepes, H; Zaborov, D; Zornoza, J D; Zúñiga, J

    2011-01-01

    The group velocity of light has been measured at eight different wavelengths between 385 nm and 532 nm in the Mediterranean Sea at a depth of about 2.2 km with the ANTARES optical beacon systems. A parametrisation of the dependence of the refractive index on wavelength based on the salinity, pressure and temperature of the sea water at the ANTARES site is in good agreement with these measurements.

  12. Monostatic Doppler lidar using an Nd:YAG laser for wind-velocity measurement

    Science.gov (United States)

    Bersenev, V. I.; Kaptsov, L. N.; Priezzhev, A. V.

    1987-10-01

    A monostatic Doppler lidar using a CW Nd:YAG laser has been developed for measurements of wind velocity. A series of atmospheric measurements using this lidar was carried out. At medium turbulence levels, the limiting lidar range is 200 m. As compared with a CO2 Doppler lidar, the Nd:YAG lidar has a better spatial resolution, is more convenient to use, and does not require a cooled photodetector.

  13. Measurement of the near-wall velocity profile for a nanofluid flow inside a microchannel

    Science.gov (United States)

    Kanjirakat, Anoop; Sadr, Reza

    2015-11-01

    Hydrodynamics and anomalous heat transfer enhancements have been reported in the past for colloidal suspensions of nano-sized particles dispersed in a fluid (nanofluids). However, such augmentations may manifest itself by study of fluid flow characteristics near in the wall region. Present experimental study reports near-wall velocity profile for nanofluids (silicon dioxide nanoparticles in water) measured inside a microchannel. An objective-based nano-Particle Image Velocimetry (nPIV) technique is used to measure fluid velocity within three visible depths, O(100nm), from the wall. The near-wall fluid velocity profile is estimated after implementing the required corrections for optical properties and effects caused by hindered Brownian motion, wall-particle interactions, and non-uniform exponential illumination on the measurement technique. The fluid velocities of nanofluids at each of the three visible depths are observed to be higher than that of the base fluid resulting in a higher shear rate in this region. The relative increase in shear rates for nanofluids is believed to be the result of the near-wall shear-induced particle migration along with the Brownian motion of the nanoparticles. This research is funded by NPRP grant # 08-574-2-239 from the Qatar National Research Fund (a member of Qatar Foundation).

  14. Shock Initiation of New and Aged PBX 9501 Measured with Embedded Electromagnetic Particle Velocity Gauges

    Energy Technology Data Exchange (ETDEWEB)

    L. G. Hill; R. L. Gustavsen; R. R. Alcon; S. A. Sheffield

    1999-09-01

    We have used an embedded electromagnetic particle velocity gauge technique to measure the shock initiation behavior in PBX 9501 explosive. Up to twelve separate particle velocity wave profile measurements have been made at different depths in a single experiment. These detail the growth from an input shock to a detonation. In addition, another gauge element called a ''shock tracker'' has been used to monitor the progress of the shock front as a function of time and position as it moves through the explosive sample. This provides data similar to that obtained in a traditional explosively driven wedge test and is used to determine the position and time that the wave attains detonation. Run distance-to-detonation vs. input pressure (Pop-plot) data and particle velocity wave profile data have been obtained on new PBX 9501 pressed to densities of 1.826, 1.830, and 1.837 g/cm{sup 3}. In addition, the same measurements were performed on aged material recovered from dismantled W76 and W78 weapons. The input pressure range covered was 3.0 to 5.2 GPa. All results to date show shock sensitivity to be a function only of the initial density and not of age. PBX 9501 shock initiates the same after 17 years in stockpile as it does on the day it is pressed. Particle velocity wave profiles show mixed heterogeneous initiation (growth in the front) and homogeneous initiation (growth behind the front).

  15. On the evaluation of vorticity using cardiovascular magnetic resonance velocity measurements.

    Science.gov (United States)

    Garcia, J; Larose, E; Pibarot, P; Kadem, L

    2013-12-01

    Vorticity and vortical structures play a fundamental role affecting the evaluation of energetic aspects (mainly left ventricle work) of cardiovascular function. Vorticity can be derived from cardiovascular magnetic resonance (CMR) imaging velocity measurements. However, several numerical schemes can be used to evaluate the vorticity field. The main objective of this work is to assess different numerical schemes used to evaluate the vorticity field derived from CMR velocity measurements. We compared the vorticity field obtained using direct differentiation schemes (eight-point circulation and Chapra) and derivate differentiation schemes (Richardson 4* and compact Richardson 4*) from a theoretical velocity field and in vivo CMR velocity measurements. In all cases, the effect of artificial spatial resolution up-sampling and signal-to-noise ratio (SNR) on vorticity computation was evaluated. Theoretical and in vivo results showed that the eight-point circulation method underestimated vorticity. Up-sampling evaluation showed that the artificial improvement of spatial resolution had no effect on mean absolute vorticity estimation but it affected SNR for all methods. The Richardson 4* method and its compact version were the most accurate and stable methods for vorticity magnitude evaluation. Vorticity field determination using the eight-point circulation method, the most common method used in CMR, has reduced accuracy compared to other vorticity schemes. Richardson 4* and its compact version showed stable SNR using both theoretical and in vivo data.

  16. Measurements of the sound velocity of shock-compressed liquid silica to 1100 GPa

    Science.gov (United States)

    McCoy, C. A.; Gregor, M. C.; Polsin, D. N.; Fratanduono, D. E.; Celliers, P. M.; Boehly, T. R.; Meyerhofer, D. D.

    2016-12-01

    The sound velocity in a shocked material provides information about its off-Hugoniot behavior of a material at high pressures. This information can be used to extend the knowledge gained in Hugoniot experiments and to model the re-shock and release behavior. Silica is one of the most important materials for equation of state studies because of its prevalence in the earth's interior and the well-defined properties of α-quartz. This article presents the sound velocity measurements of amorphous fused silica over the range 200 to 1100 GPa using laser-driven shocks and an α-quartz standard. These measurements demonstrate the technique proposed by Fratanduono et al. [J. Appl. Phys. 116, 033517 (2014)] to determine the sound velocity from the arrival of acoustic perturbations. The results compare favorably to the SESAME 7386 equation-of-state table. The Grüneisen parameter was calculated from the sound velocity data and found to be Γ=0.66 ±0.05 at densities above 6 g/cm3, an increase in precision by a factor of two over previous measurements.

  17. Real time mass flux measurements of gas-solid suspensions at low velocities

    Energy Technology Data Exchange (ETDEWEB)

    Saunders, J H; Chao, B T; Soo, S L

    1981-01-01

    In previous work, measurement of the particulate mass flux was made based upon a novel electrostatic technique. A small conducting wire sensor was inserted in the flow and as each particle hit the sensor an individual pulse of current was identified. Through suitable electronic circuitry, the number of pulses in a given time were counted. This was a direct measure of the number of particle-probe collisions which was related to local particle mass flow. The technique is currently limited to monodisperse suspensions. A primary advantage of the impact counter system is that the output does not depend upon the magnitude of the actual charge transfer. As long as the pulses are sufficiently above the noise level, variations in charge transfer will not affect the measurement. For the current work, the technique was applied to vertical gas-solid flow where the fluid velocity was slightly above the particle terminal velocity. Under these conditions a sufficient signal to noise ratio was not found. The Cheng-Soo charge transfer theory indicated that the low particle-sensor impact velocity was responsible. The probe system was then modified by extracting a particulate sample isokinetically and accelerating the particles to a sufficient velocity by an area reduction in the sampling tube. With this technique the signal to noise ratio was about 12 to 1. Mass flux results are shown to compare favorably with filter collection and weighing.

  18. LOCAL VELOCITY PROFILES MEASURED BY PIV IN AN VESSEL AGITATED BY RUSHTON TURBINE

    Directory of Open Access Journals (Sweden)

    Radek Šulc

    2014-12-01

    Full Text Available The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV. The experiments were carried out in a fully baffled cylindrical flat bottom vessel 300 mm in inner diameter. The tank was agitated by a Rushton turbine 100 mm in diameter. The velocity fields were measured for three impeller rotation speeds 300 rpm, 450 rpm and 600 rpm and the corresponding Reynolds numbers in the range 50 000 < Re < 100 000, which means that the fully-developed turbulent flow was reached. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller rotational speed. The velocity profiles were averaged, and were expressed by Chebyshev polynomials of the 1st order. Although the experimentally investigated area was relatively far from the impeller, and it was located in upward flow to the impeller, no state of local isotropy was found. The ratio of the axial rms fluctuation velocity to the radial component was found to be in the range from 0.523 to 0.768. The axial turbulence intensity was found to be in the range from 0.293 to 0.667, which corresponds to a high turbulence intensity.

  19. Direct velocity measurement and enhanced mixing in laminar flows over ultrahydrophobic surfaces

    Science.gov (United States)

    Ou, Jia

    2005-11-01

    A series of experiment are presented studying the kinematics of water flowing over drag-reducing ultrahydrophobic surfaces. The surfaces are fabricated from silicon wafers using photolithography and are designed to incorporate patterns of microridges with precise spacing and alignment. These surfaces are reacted with an organosilane to achieve high hydrophobicity. Microridges with different widths, spacing and alignments are tested in a microchannel flow cell with rectangular cross-section. The velocity profile across the microchannel is measured with micro particle image velocimetry (μ-PIV) capable of resolving the flow down to length scales well below the size of the surface features. A maximum slip velocity of >60% of the average velocity in the flow is observed at the center of the air-water interface supported between these hydrophobic microridges, and the no-slip boundary condition is found at the hydrophobic microridges. The μ-PIV measurements demonstrate that slip along the shear-free air-water interface supported between the hydrophobic micron-sized ridges is the primary mechanism responsible for the drag reduction. The experiment velocity and pressure drop measurement are compared with the prediction of numerical simulation and an analytical model. By aligning the hydrophobic microridges at an acute angle to the flow direction a secondary flow is produced which can significantly enhance mixing in this laminar flow.

  20. Measurment of threshold friction velocities at potential dust sources in semi-arid regions

    Science.gov (United States)

    King, Matthew A.

    The threshold friction velocities of potential dust sources in the US Southwest were measured in the field using a Portable Wind Tunnel, which is based on the Desert Research Institute's Portable In-Situ Wind Erosion Laboratory (PI-SWERL). A mix of both disturbed and undisturbed surfaces were included in this study. It was found that disturbed surfaces, such as those at the Iron King Mine tailings site, which is part of the EPA's Superfund program and contains surface concentrations of arsenic and lead reaching as high as 0.5% (w/w), had lower threshold friction velocities (0.32 m s -1 to 0.40 m s-1) in comparison to those of undisturbed surfaces (0.48 to 0.61 m s-1). Surface characteristics, such as particle size distribution, had effects on the threshold friction velocity (smaller grain sized distributions resulted in lower threshold friction velocities). Overall, the threshold friction velocities of disturbed surfaces were within the range of natural wind conditions, indicating that surfaces disturbed by human activity are more prone to causing windblown dust.

  1. Simultaneous PIV and PTV measurements of wind and sand particle velocities

    Science.gov (United States)

    Zhang, Wei; Wang, Yuan; Lee, Sang Joon

    2008-08-01

    Wind-blown sand is a typical example of two-phase particle-laden flows. Owing to lack of simultaneous measured data of the wind and wind-blown sand, interactions between them have not yet been fully understood. In this study, natural sand of 100-125 μm taken from Taklimakan Desert was tested at the freestream wind speed of 8.3 m/s in an atmospheric boundary layer wind tunnel. The captured flow images containing both saltating sand and small wind tracer particles, were separated by using a digital phase mask technique. The 2-D PIV (particle imaging velocimetry) and PTV (particle tracking velocimetry) techniques were employed to extract simultaneously the wind velocity field and the velocity field of dispersed sand particles, respectively. Comparison of the mean streamwise wind velocity profile and the turbulence statistics with and without sand transportation reveal a significant influence of sand movement on the wind field, especially in the dense saltating sand layer ( y/ δ < 0.1). The ensemble-averaged streamwise velocity profile of sand particles was also evaluated to investigate the velocity lag between the sand and the wind. This study would be helpful in improving the understanding of interactions between the wind and the wind-blown sand.

  2. Development and testing of a novel single-wire sensor for wide range flow velocity measurements

    Science.gov (United States)

    Al-Salaymeh, A.; Durst, F.

    2004-05-01

    Thermal flow sensors with a wide dynamic range, e.g. 1:1000 and more, are currently not available in spite of the great demand for such sensors in practical fluid flow measurements. The present paper introduces a sensor of this kind. The new sensor is mechanically the same as the 'sending' wire of the two-wire thermal flow sensor described by Durst et al, but it is excited by discrete, widely separated, square waves of electrical current rather than a continuous sinusoidal current. The nominal 'output' of the new sensor is the increase in wire temperature so that an integral of the resistance over the pulse length can be used for measurements. This 'output' is a function of the time constant ('thermal inertia') of the heated wire and thus also of the velocity of flow. The time constant decreases as the flow velocity increases, while the heat transfer increases. At very low flow velocities the response is determined almost entirely by the time constant of the wire while at high velocities the device acts almost like a 'constant current' hot-wire anemometer. That is, the effect of thermal inertia augments the output signal of the basic hot wire, thus increasing the flow rate range/sensitivity of the device, especially at the low-velocity end, above than that of a simple hot-wire flowmeter. The sensor described here was developed for slowly changing unidirectional flows, and uses one wire of 12.5 µm diameter. It is excited at 30 Hz frequency and its usable flow velocity range is 0.01-25 m s-1.

  3. Ion temperature gradient driven mode in presence of transverse velocity shear in magnetized plasmas

    DEFF Research Database (Denmark)

    Chakrabarti, N.; Juul Rasmussen, J.; Michelsen, Poul

    2005-01-01

    The effect of sheared poloidal flow on the toroidal branch of the ion temperature gradient driven mode of magnetized nonuniform plasma is studied. A novel "nonmodal" calculation is used to analyze the problem. It is shown that the transverse shear flow considerably reduced the growth...

  4. Measurement of Heat Propagation in a Laser Produced Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Gregori, G; Glenzer, S H; Knight, J; Niemann, C; Price, D; Froula, D H; Edwards, J; Town, R P J; Brantov, A; Bychenkov, V Y; Rozmus, W

    2003-08-22

    We present the observation of a nonlocal heat wave by measuring spatially and temporally resolved electron temperature profiles in a laser produced nitrogen plasma. Absolutely calibrated measurements have been performed by resolving the ion-acoustic wave spectra across the plasma volume with Thomson scattering. We find that the experimental electron temperature profiles disagree with flux-limited models, but are consistent with transport models that account for the nonlocal effects in heat conduction by fast electrons.

  5. Light scattering by a dense ionization plasma wave with a tunable velocity

    Science.gov (United States)

    Zhidkov, Alexei; Fujii, Takashi; Esirkepov, Timur; Koga, James; Nemoto, Koshichi; Bulanov, Sergei

    2009-11-01

    An optically-dense ionization wave (IW) produced by two femtosecond laser pulses focused cylindrically and crossing each other is shown to be an efficient coherent x-ray converter. The resulting velocity of a quasi-plane IW in the vicinity of pulse intersection increases with the angle between the pulses from the group velocity of ionizing pulses to infinity allowing an easy tuning the wavelength of x-rays. We study the conversion of a coherent light to x-rays by means of particle-in-cell simulation and by solution of continuous equation with the correct current. The x-ray spectra of a converted, lower frequency coherent light change from the monochromatic to a high order harmonic-like with the duration of ionizing pulses and the intensity of scattered pulses; the spectrum are not symmetrical at Vc.

  6. Design and testing of miniaturized plasma sensor for measuring hypervelocity impact plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Goel, A., E-mail: ashish09@stanford.edu; Tarantino, P. M.; Lauben, D. S.; Close, S. [Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305 (United States)

    2015-04-15

    An increasingly notable component of the space environment pertains to the impact of meteoroids and orbital debris on spacecraft and the resulting mechanical and electrical damages. Traveling at speeds of tens of km/s, when these particles, collectively referred to as hypervelocity particles, impact a satellite, they vaporize, ionize, and produce a radially expanding plasma that can generate electrically harmful radio frequency emission or serve as a trigger for electrostatic discharge. In order to measure the flux, composition, energy distribution, and temperature of ions and electrons in this plasma, a miniaturized plasma sensor has been developed for carrying out in-situ measurements in space. The sensor comprises an array of electrostatic analyzer wells split into 16 different channels, catering to different species and energy ranges in the plasma. We present results from numerical simulation based optimization of sensor geometry. A novel approach of fabricating the sensor using printed circuit boards is implemented. We also describe the test setup used for calibrating the sensor and show results demonstrating the energy band pass characteristics of the sensor. In addition to the hypervelocity impact plasmas, the plasma sensor developed can also be used to carry out measurements of ionospheric plasma, diagnostics of plasma propulsion systems, and in other space physics experiments.

  7. Design and testing of miniaturized plasma sensor for measuring hypervelocity impact plasmas

    Science.gov (United States)

    Goel, A.; Tarantino, P. M.; Lauben, D. S.; Close, S.

    2015-04-01

    An increasingly notable component of the space environment pertains to the impact of meteoroids and orbital debris on spacecraft and the resulting mechanical and electrical damages. Traveling at speeds of tens of km/s, when these particles, collectively referred to as hypervelocity particles, impact a satellite, they vaporize, ionize, and produce a radially expanding plasma that can generate electrically harmful radio frequency emission or serve as a trigger for electrostatic discharge. In order to measure the flux, composition, energy distribution, and temperature of ions and electrons in this plasma, a miniaturized plasma sensor has been developed for carrying out in-situ measurements in space. The sensor comprises an array of electrostatic analyzer wells split into 16 different channels, catering to different species and energy ranges in the plasma. We present results from numerical simulation based optimization of sensor geometry. A novel approach of fabricating the sensor using printed circuit boards is implemented. We also describe the test setup used for calibrating the sensor and show results demonstrating the energy band pass characteristics of the sensor. In addition to the hypervelocity impact plasmas, the plasma sensor developed can also be used to carry out measurements of ionospheric plasma, diagnostics of plasma propulsion systems, and in other space physics experiments.

  8. Measurements of outflow velocities in on-disk plumes from EIS/Hinode observations

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Hui; Xia, Lidong; Li, Bo; Huang, Zhenghua; Jiao, Fangran; Mou, Chaozhou, E-mail: xld@sdu.edu.cn [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Shandong University, Weihai 264209 (China)

    2014-10-20

    The contribution of plumes to the solar wind has been subject to hot debate in the past decades. The EUV Imaging Spectrometer (EIS) on board Hinode provides a unique means to deduce outflow velocities at coronal heights via direct Doppler shift measurements of coronal emission lines. Such direct Doppler shift measurements were not possible with previous spectrometers. We measure the outflow velocity at coronal heights in several on-disk long-duration plumes, which are located in coronal holes (CHs) and show significant blueshifts throughout the entire observational period. In one case, a plume is measured four hours apart. The deduced outflow velocities are consistent, suggesting that the flows are quasi-steady. Furthermore, we provide an outflow velocity profile along the plumes, finding that the velocity corrected for the line-of-sight effect can reach 10 km s{sup –1} at 1.02 R {sub ☉}, 15 km s{sup –1} at 1.03 R {sub ☉}, and 25 km s{sup –1} at 1.05 R {sub ☉}. This clear signature of steady acceleration, combined with the fact that there is no significant blueshift at the base of plumes, provides an important constraint on plume models. At the height of 1.03 R {sub ☉}, EIS also deduced a density of 1.3 × 10{sup 8} cm{sup –3}, resulting in a proton flux of about 4.2 × 10{sup 9} cm{sup –2} s{sup –1} scaled to 1 AU, which is an order of magnitude higher than the proton input to a typical solar wind if a radial expansion is assumed. This suggests that CH plumes may be an important source of the solar wind.

  9. Comparison of solar wind velocity measurements with a theoretical acceleration model

    Energy Technology Data Exchange (ETDEWEB)

    Coles, W.A. (Univ. of California, La Jolla (United States)); Esser, R. (Univ. of Tromsoe (Norway)); Loevhaug, U.P. (EISCAT, Ramfjordbotn (Norway)); Markkanen, J. (Geophysical Observatory, Sodankyla (Finland))

    1991-08-01

    Interplanetary radio scintillation (IPS) measurements of the solar wind velocity were made using the receiving antennas of the European Incoherent Scatter Facility (EISCAT) radar system in northern Scandinavia from June through October 1990. The observations, which cover the distance range from 11 to 90 R{sub s} from Sun center, were taken with sufficient density to measure the same stream at two (or more) different distances. The deduced velocities are in the range 100 {approx lt} U {approx lt} 540 km s{sup {minus}1}. The authors selected from 192 observations, 16 examples of streams observed with good radial alignment, of which 12 were observed unchanged for several days. The measured velocities are compared with calculations based on a two-fluid solar wind model with Alfven waves. In eight cases the measurements are in good agreement with the model when a moderate amount of wave energy is added to the flow. In four cases the observed streams show low or moderate velocities below, say, 20 R{sub s} but then accelerate fast at larger distances from the Sun. This delayed acceleration is much steeper than the acceleration in the model at these distances. In the remaining four cases the streams seem to reach their final velocities much closer to the base than in other cases, and they are not observed to accelerate much between 10 and 90 R{sub s}. At these distances all related solar wind models they have seen give the same results; they all fit half the data, and none can fit the other half.

  10. Plasma absorption evidence via chirped pulse spectral transmission measurements

    Energy Technology Data Exchange (ETDEWEB)

    Jedrkiewicz, Ottavia, E-mail: ottavia.jedrkiewicz@ifn.cnr.it [Istituto di Fotonica e Nanotecnologie, CNR and CNISM UdR Como, Via Valleggio 11, I-22100 Como (Italy); Minardi, Stefano [Institute of Applied Physics, Friedrich-Schiller-University Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Couairon, Arnaud; Jukna, Vytautas [Centre de Physique Theorique, CNRS, Ecole Polytechnique, F-91128 Palaiseau (France); Selva, Marco; Di Trapani, Paolo [Dipartimento di Scienza e Alta Tecnologia, University of Insubria and CNISM UdR Como, Via Valleggio 11, I-22100 Como (Italy)

    2015-06-08

    This work aims at highlighting the plasma generation dynamics and absorption when a Bessel beam propagates in glass. We developed a simple diagnostics allowing us to retrieve clear indications of the formation of the plasma in the material, thanks to transmission measurements in the angular and wavelength domains. This technique featured by the use of a single chirped pulse having the role of pump and probe simultaneously leads to results showing the plasma nonlinear absorption effect on the trailing part of the pulse, thanks to the spectral-temporal correspondence in the measured signal, which is also confirmed by numerical simulations.

  11. Comparison of treadmill and cycle ergometer measurements of force-velocity relationships and power output.

    Science.gov (United States)

    Jaskólska, A; Goossens, P; Veenstra, B; Jaskólski, A; Skinner, J S

    1999-04-01

    Since body balance and weight-bearing factors present while running on the treadmill might cause additional muscle recruitment and thus could influence the force-velocity relationship and power, the present study was undertaken to find out whether the F-V and F-P relationships measured while running on the treadmill are different from the respective indices measured during cycling. On two separate occasions, 32 male subjects were tested using a series of 5 sec, all-out sprints against different braking forces on the Gymrol Sprint treadmill and on the Monark ergometer. The maximal peak power (PPmax) and maximal mean power (MPmax) were measured. The equation: EP = 0.5 maximal force (Fo) x0.5 maximal velocity (Vo) was used to calculate the estimated values of peak power (EPP) and mean power (EMP). The F-V relationship was linear in both cycle ergometer and treadmill measurements. PPmax, MPmax, EPP, and EMP values on the treadmill were lower than the respective values on the ergometer. EPP on the ergometer and on the treadmill, as well as EMP values on the ergometer, were slightly higher than the corresponding measured values of PPmax and MPmax. The levels of braking force at which PP, MP, PPmax, and MPmax were obtained were lower on the ergometer than on the treadmill. High correlation coefficients were found between PPmax, MPmax, EPP, and EMP measured on the ergometer and on the treadmill (r = 0.86, r = 0.84, r = 0.71, r = 0.78, respectively, P<0.01). In both tests, significant relationships between PPmax, MPmax, EPP, and EMP were observed. It is concluded that independent of the type of ergometry the force-velocity relationship is similar in the measured range of velocities which suggests that the number of muscle groups and joints engaged in movement are more important than body balance and weight-bearing factors present while running on a treadmill.

  12. Plasma Measurements: An Overview of Requirements and Status

    Energy Technology Data Exchange (ETDEWEB)

    Kenneth M. Young

    2008-01-04

    This paper introduces this special issue on plasma diagnostics for magnetic fusion devices. Its primary purpose is to relate the measurements of plasma parameters to the physics challenges to be faced on operating and planned devices, and also to identify the diagnostic techniques that are used to make these measurements. The specific physics involved in the application of the techniques will be addressed in subsequent chapters. This chapter is biased toward measurements for tokamaks because of their proximity to the burning plasma frontier, and to set the scene for the development work associated with ITER. Hence, there is some emphasis on measurements for alpha-physics studies and the needs for plasma measurements as input to actuators to control the plasma, both for optimizing the device performance and for protection of the surrounding material. The very different approach to the engineering of diagnostics for a burning plasma is considered, emphasizing the needs for new calibration ideas, reliability and hardness against, and compatibility with, radiation. New ideas take a long time to be converted into "work-horse" sophisticated diagnostics so that investment in new developments is essential for ITER, particularly for the measurement of alpha-particles.

  13. Measurements of shock-front structure in multi-species plasmas on OMEGA

    Science.gov (United States)

    Rinderknecht, Hans G.; Park, H.-S.; Ross, J. S.; Wilks, S. C.; Amendt, P. A.; Heeter, R. F.; Katz, J.; Hoffman, N. M.; Vold, E.; Taitano, W.; Simakov, A.; Chacon, L.

    2016-10-01

    The structure of a shock front in a plasma with multiple ion species is measured for the first time in experiments on the OMEGA laser. Thomson scattering of a 263.25 nm probe beam is used to diagnose electron density, electron and ion temperature, ion species concentration, and flow velocity in strong shocks (M 5) propagating through low-density (ρ 0.1 mg/cc) plasmas composed of H(98%)+Ne(2%) and H(98%)+C(2%). Separation of the ion species within the shock front is inferred. Although shocks play an important role in ICF and astrophysical plasmas, the intrinsically kinetic nature of the shock front indicates the need for experiments to benchmark hydrodynamic models. Comparison with PIC, Vlasov-Fokker-Planck, and multi-component hydrodynamic simulations will be presented. This work performed under auspices of U.S. DOE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  14. S-wave velocity measurements applied to the seismic microzonation of Basel, Upper Rhine Graben

    Science.gov (United States)

    Havenith, Hans-Balder; Fäh, Donat; Polom, Ulrich; Roullé, Agathe

    2007-07-01

    An extensive S-wave velocity survey had been carried out in the frame of a recent seismic microzonation study of Basel and the border areas between Switzerland, France and Germany. The aim was to better constrain the seismic amplification potential of the surface layers. The survey included single station (H/V spectral ratios) and ambient vibration array measurements carried out by the Swiss team, as well as active S-wave velocity measurements performed by the German and French partners. This paper is focused on the application of the array technique, which consists in recording ambient vibrations with a number of seismological stations. Several practical aspects related to the field measurements are outlined. The signal processing aims to determine the dispersion curves of surface waves contained in the ambient vibrations. The inversion of the dispersion curve provides a 1-D S-wave velocity model for the investigated site down to a depth related to the size of the array. Since the size of arrays is theoretically not limited, arrays are known to be well adapted for investigations in deep sediment basins, such as the Upper Rhine Graben including the area of the city of Basel. In this region, 27 array measurements with varying station configurations have been carried out to determine the S-wave velocity properties of the geological layers down to a depth of 100-250 m. For eight sites, the outputs of the array measurements have been compared with the results of the other investigations using active sources, the spectral analysis of surface waves (SASW) and S-wave reflection seismics. Borehole information available for a few sites could be used to calibrate the geophysical measurements. By this comparison, the advantages and disadvantages of the array method and the other techniques are outlined with regard to the effectiveness of the methods and the required investigation depth. The dispersion curves measured with the arrays and the SASW technique were also combined

  15. A multi-method approach to radial-velocity measurement for single-object spectra

    CERN Document Server

    David, M; Frémat, Y; Damerdji, Y; Luche, C Delle; Gosset, E; Katz, D; Viala, Y

    2014-01-01

    The derivation of radial velocities from large numbers of spectra that typically result from survey work, requires automation. However, except for the classical cases of slowly rotating late-type spectra, existing methods of measuring Doppler shifts require fine-tuning to avoid a loss of accuracy due to the idiosyncrasies of individual spectra. The radial velocity spectrometer (RVS) on the Gaia mission, which will start operating very soon, prompted a new attempt at creating a measurement pipeline to handle a wide variety of spectral types. The present paper describes the theoretical background on which this software is based. However, apart from the assumption that only synthetic templates are used, we do not rely on any of the characteristics of this instrument, so our results should be relevant for most telescope-detector combinations. We propose an approach based on the simultaneous use of several alternative measurement methods, each having its own merits and drawbacks, and conveying the spectral informa...

  16. Optical Flow Cell for Measuring Size, Velocity and Composition of Flowing Droplets

    Directory of Open Access Journals (Sweden)

    Sammer-ul Hassan

    2017-02-01

    Full Text Available Here an optical flow cell with two light paths is reported that can accurately quantify the size and velocity of droplets flowing through a microchannel. The flow cell can measure the time taken for droplets to pass between and through two conjoined light paths, and thereby is capable of measuring the velocities (0.2–5.45 mm/s and sizes of droplets (length > 0.8 mm. The composition of the droplet can also be accurately quantified via optical absorption measurements. The device has a small footprint and uses low-powered, low-cost components, which make it ideally suited for use in field-deployable and portable analytical devices.

  17. Distributed tracking for networked Euler-Lagrange systems without velocity measurements

    Institute of Scientific and Technical Information of China (English)

    Qingkai Yang; Hao Fang; Yutian Mao; Jie Huang

    2014-01-01

    The problem of distributed coordinated tracking control for networked Euler-Lagrange systems without velocity measure-ments is investigated. Under the condition that only a portion of the fol owers have access to the leader, sliding mode estimators are developed to estimate the states of the dynamic leader in fi-nite time. To cope with the absence of velocity measurements, the distributed observers which only use position information are designed. Based on the outputs of the estimators and observers, distributed tracking control laws are proposed such that al the fol-lowers with parameter uncertainties can track the dynamic leader under a directed graph containing a spanning tree. It is shown that the distributed observer-control er guarantees asymptotical stabil-ity of the closed-loop system. Numerical simulations are worked out to il ustrate the effectiveness of the control laws.

  18. Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity

    Energy Technology Data Exchange (ETDEWEB)

    Yost, William T; Cantrell, John H; Kushnick, Peter W

    1991-10-01

    A new instrument based on a constant frequency pulsed phase-locked-loop (CFPPLL) concept has been developed to accurately measure the ultrasonicwavevelocity in liquids and changes in ultrasonicwavevelocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency-dependent effects that plague other techniques including the constant phase shifts of reflectors placed in the path of the ultrasonicwave.Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measurevelocities, as well as for monitoring small changes in velocity without the sensitivity to frequency-dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 10{sup 7}.

  19. Automated inter-station phase velocity measurements across the eastern Mediterranean and Middle East

    Science.gov (United States)

    El-Sharkawy, Amr; Weidle, Christian; Christiano, Luigia; Soomro, Riaz; Lebedev, Sergi; Meier, Thomas

    2016-04-01

    The structure of the lithosphere in northeastern Africa, eastern Mediterranean and the Middle East is highly variable. It ranges from young oceanic lithosphere in the Red Sea to what is considered the oldest oceanic lithosphere on Earth in the Mediterranean Sea north of Libya, and from highly deformed continental lithosphere at the east-Mediterranean margins to more stable continental lithosphere of Phanerozoic origin and to cratonic lithosphere beneath the Arabian Peninsula. Details of the lithospheric structure are, however, poorly known. Surface waves are ideally suited for studies of the lithosphere and the sublithospheric mantle. Our goal is to better define the 3D lithospheric shear-wave velocity structure within this region by surface wave tomography. Using regional to teleseismic Rayleigh and Love waves that traverse the area we can obtain information about its seismic structure by examining phase velocities as a function of frequency. A newly developed algorithm for automated inter-station phase velocity measurements (Soomro et al. 2016) is applied here to obtain both Rayleigh and Love fundamental mode phase velocities. We utilize a database consisting of more than 3800 regional and teleseismic earthquakes recorded by more than 1850 broadband seismic stations within the area, provided by the European Integrated Data Archive (WebDc/EIDA) and IRIS. Moreover, for the first time, data from the Egyptian National Seismological Network (ENSN), recorded by up to 25 broad band seismic stations, is also included in the analysis. For each station pair approximately located on the same great circle path, the recorded waveforms are cross correlated and the dispersion curves of fundamental modes are calculated from the phase of the weighted cross correlation functions. Path average dispersion curves are obtained by averaging the smooth parts of single-event dispersion curves. Parameters tests and preliminary results of automatically measured phase velocities are

  20. Luminescent two-color tracer particles for simultaneous velocity and temperature measurements in microfluidics

    Science.gov (United States)

    Massing, J.; Kaden, D.; Kähler, C. J.; Cierpka, C.

    2016-11-01

    The simultaneous and non-intrusive measurement of temperature and velocity fields in flows is of great scientific and technological interest. To sample the velocity and temperature, tracer particle based approaches have been developed, where the velocity is measured using PIV or PTV and the temperature is obtained from the intensity (LIF, thermographic phosphors) or frequency (TLC) of the light emitted or reflected by the tracer particles. In this article, a measurement technique is introduced, that relates the luminescent intensity ratio of individual dual-color luminescent tracer particles to temperature. Different processing algorithms are tested on synthetic particle images and compared with respect to their accuracy in estimating the intensity ratio. Furthermore, polymer particles which are doped with the temperature sensitive dye europium (III) thenoyltrifluoroacetonate (EuTTA) and the nearly temperature insensitive reference dye perylene are characterized as valid tracers. The results show a reduction of the temperature measurement uncertainty of almost 40% (95% confidence interval) compared to previously reported luminescent particle based measurement techniques for microfluidics.