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Sample records for doppler velocity measurements

  1. Laser Doppler Velocimeter particle velocity measurement system

    SciTech Connect

    Wilson, W.W.; Srikantaiah, D.V.; Philip, T.; George, A.

    1993-10-01

    This report gives a detailed description of the operation of the Laser Doppler Velocimeter (LDV) system maintained by DIAL at MSU. LDV is used for the measurement of flow velocities and turbulence levels in various fluid flow settings. Ills report details the operation and maintenance of the LDV system and provides a first-time user with pertinent information regarding the system`s setup for a particular application. Particular attention has been given to the use of the Doppler signal analyzer (DSA) and the burst spectrum analyzer (BSA) signal processors and data analysis.

  2. Velocity precision measurements using laser Doppler anemometry

    NASA Astrophysics Data System (ADS)

    Dopheide, D.; Taux, G.; Narjes, L.

    1985-07-01

    A Laser Doppler Anemometer (LDA) was calibrated to determine its applicability to high pressure measurements (up to 10 bars) for industrial purposes. The measurement procedure with LDA and the experimental computerized layouts are presented. The calibration procedure is based on absolute accuracy of Doppler frequency and calibration of interference strip intervals. A four-quadrant detector allows comparison of the interference strip distance measurements and computer profiles. Further development of LDA is recommended to increase accuracy (0.1% inaccuracy) and to apply the method industrially.

  3. Laser Doppler anemometer signal processing for blood flow velocity measurements

    SciTech Connect

    Borozdova, M A; Fedosov, I V; Tuchin, V V

    2015-03-31

    A new method for analysing the signal in a laser Doppler anemometer based on the differential scheme is proposed, which provides the flow velocity measurement in strongly scattering liquids, particularly, blood. A laser Doppler anemometer intended for measuring the absolute blood flow velocity in animal and human near-surface arterioles and venules is developed. The laser Doppler anemometer signal structure is experimentally studied for measuring the flow velocity in optically inhomogeneous media, such as blood and suspensions of scattering particles. The results of measuring the whole and diluted blood flow velocity in channels with a rectangular cross section are presented. (laser applications and other topics in quantum electronics)

  4. Exploratory Meeting on Airborne Doppler Lidar Wind Velocity Measurements

    NASA Technical Reports Server (NTRS)

    Fichtel, G. H. (Editor); Kaufman, J. W. (Editor); Vaughan, W. W. (Editor)

    1980-01-01

    The scientific interests and applications of the Airborne Doppler Lidar Wind Velocity Measurement System to severe storms and local weather are discussed. The main areas include convective phenomena, local circulation, atmospheric boundary layer, atmospheric dispersion, and industrial aerodynamics.

  5. Doppler velocity measurements from large and small arteries of mice

    PubMed Central

    Reddy, Anilkumar K.; Madala, Sridhar; Entman, Mark L.; Michael, Lloyd H.; Taffet, George E.

    2011-01-01

    With the growth of genetic engineering, mice have become increasingly common as models of human diseases, and this has stimulated the development of techniques to assess the murine cardiovascular system. Our group has developed nonimaging and dedicated Doppler techniques for measuring blood velocity in the large and small peripheral arteries of anesthetized mice. We translated technology originally designed for human vessels for use in smaller mouse vessels at higher heart rates by using higher ultrasonic frequencies, smaller transducers, and higher-speed signal processing. With these methods one can measure cardiac filling and ejection velocities, velocity pulse arrival times for determining pulse wave velocity, peripheral blood velocity and vessel wall motion waveforms, jet velocities for the calculation of the pressure drop across stenoses, and left main coronary velocity for the estimation of coronary flow reserve. These noninvasive methods are convenient and easy to apply, but care must be taken in interpreting measurements due to Doppler sample volume size and angle of incidence. Doppler methods have been used to characterize and evaluate numerous cardiovascular phenotypes in mice and have been particularly useful in evaluating the cardiac and vascular remodeling that occur following transverse aortic constriction. Although duplex ultrasonic echo-Doppler instruments are being applied to mice, dedicated Doppler systems are more suitable for some applications. The magnitudes and waveforms of blood velocities from both cardiac and peripheral sites are similar in mice and humans, such that much of what is learned using Doppler technology in mice may be translated back to humans. PMID:21572013

  6. Laser Doppler Measurement of Atmopsheric Wind Velocity

    NASA Technical Reports Server (NTRS)

    Schwiesow, R. L.; Abshire, N. L.; Derr, V. E.

    1973-01-01

    Our presentation consists of two parts: (1) a summary review of laser Doppler principles and applications, and (2) operational design and preliminary laboratory tests of a CO2 laser system for NOAA applications.

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

    PubMed

    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.

  8. Laser Doppler anemometer measurements using nonorthogonal velocity components - Error estimates

    NASA Technical Reports Server (NTRS)

    Orloff, K. L.; Snyder, P. K.

    1982-01-01

    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.

  9. Doppler aortic flow velocity measurement in healthy children.

    PubMed Central

    Sohn, S.; Kim, H. S.

    2001-01-01

    To determine normal values for Doppler parameters of left ventricular function, ascending aortic blood flow velocity was measured by pulsed wave Doppler echocardiography in 63 healthy children with body surface area (BSA) < 1 m(2) (age < 10 yr). Peak velocity was independent of sex, but increased with body size. Mean acceleration was related to peak velocity (r = 0.75, p < 0.0001). Both stroke distance and ejection time had strong negative correlations with heart rate and positive correlations with BSA, suggesting that these parameters should be evaluated in relation to heart rate and body size. Mean intra- and interobserver variability for peak velocity, ejection time, stroke and minute distance ranged from 3 to 7%, whereas variability for acceleration time was 9 to 13%. These data may be used as reference values for the assessment of hemodynamic states in young children with cardiac disease. PMID:11306737

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Simulated O VI Doppler dimming measurements of coronal outflow velocities

    NASA Technical Reports Server (NTRS)

    Strachan, Leonard; Gardner, L. D.; Kohl, John L.

    1992-01-01

    The possibility of determining O(5+) outflow velocities by using a Doppler dimming analysis of the resonantly scattered intensities of O VI lambda 1031.9 and lambda 1037.6 is addressed. The technique is sensitive to outflow velocities, W, in the range W greater than 30 and less than 250 km/s and can be used for probing regions of the inner solar corona, where significant coronal heating and solar wind acceleration may be occurring. These velocity measurements, when combined with measurements of other plasma parameters (temperatures and densities of ions and electrons) can be used to estimate the energy and mass flux of O(5+). In particular, it may be possible to locate where the flow changes from subsonic to supersonic and to identify source regions for the high and low speed solar wind. The velocity diagnostic technique is discussed with emphasis placed on the requirements needed for accurate outflow velocity determinations. Model determinations of outflow velocities based on simulated Doppler observations are presented.

  12. Velocity measurements in whole blood using acoustic resolution photoacoustic Doppler

    PubMed Central

    Brunker, Joanna; Beard, Paul

    2016-01-01

    Acoustic resolution photoacoustic Doppler velocimetry promises to overcome the spatial resolution and depth penetration limitations of current blood flow measuring methods. Despite successful implementation using blood-mimicking fluids, measurements in blood have proved challenging, thus preventing in vivo application. A common explanation for this difficulty is that whole blood is insufficiently heterogeneous relative to detector frequencies of tens of MHz compatible with deep tissue photoacoustic measurements. Through rigorous experimental measurements we provide new insight that refutes this assertion. We show for the first time that, by careful choice of the detector frequency and field-of-view, and by employing novel signal processing methods, it is possible to make velocity measurements in whole blood using transducers with frequencies in the tens of MHz range. These findings have important implications for the prospects of making deep tissue measurements of blood flow relevant to the study of microcirculatory abnormalities associated with cancer, diabetes, atherosclerosis and other conditions. PMID:27446707

  13. Velocity measurements in whole blood using acoustic resolution photoacoustic Doppler.

    PubMed

    Brunker, Joanna; Beard, Paul

    2016-07-01

    Acoustic resolution photoacoustic Doppler velocimetry promises to overcome the spatial resolution and depth penetration limitations of current blood flow measuring methods. Despite successful implementation using blood-mimicking fluids, measurements in blood have proved challenging, thus preventing in vivo application. A common explanation for this difficulty is that whole blood is insufficiently heterogeneous relative to detector frequencies of tens of MHz compatible with deep tissue photoacoustic measurements. Through rigorous experimental measurements we provide new insight that refutes this assertion. We show for the first time that, by careful choice of the detector frequency and field-of-view, and by employing novel signal processing methods, it is possible to make velocity measurements in whole blood using transducers with frequencies in the tens of MHz range. These findings have important implications for the prospects of making deep tissue measurements of blood flow relevant to the study of microcirculatory abnormalities associated with cancer, diabetes, atherosclerosis and other conditions.

  14. Laser Doppler velocity measurements of swirling flows with upstream influence

    NASA Technical Reports Server (NTRS)

    Rloff, K. L.; Bossel, H. H.

    1973-01-01

    Swirling flow in a rotating tube is studied by flow visualization at a moderate Reynolds number, and its velocity field is measured by laser-Doppler anemometry. The tube has constant diameter, and approximately uniform initial rigid rotation of the flow is assured by passing the flow through a rotating plug of porous metal before it enters the test section. At moderate swirl values, an object mounted on the tube centerline causes a closed bubble to form upstream of the obstacle, with a clearly defined stagnation point on the axis, and recirculating flow inside the bubble. The bubble length grows upstream as the swirl is increased, until it breaks up into a Taylor column reaching all the way upstream and downstream at swirl values above a certain critical value. A vortex jump (in the sense of Benjamin) occurs downstream of the obstacle except when the Taylor column is present. Using a laser-Doppler anemometer, axial and swirl velocity profiles are obtained at several stations upstream and downstream of the bubble, and in and around the bubble.

  15. Laser Doppler velocity measurement without directional ambiguity by using frequency shifted incident beams

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.

    1970-01-01

    Laser Doppler heterodyning system for velocity measurements without directional ambiguity, employing incident beams of different frequencies through rotating diffraction grating or Bragg cell application

  16. Doppler velocity measurements using a phase-stabilized michelson spectrometer

    NASA Astrophysics Data System (ADS)

    Smeets, G.

    1993-10-01

    Laser Doppler systems have become classical means of nonintrusively recording velocities in all kinds of flow fields. With the system mostly used, the so-called Doppler differential velocimeter, tracer particles incorporated in the flow are illuminated by two laser beams from slightly different directions, and the velocity is derived from the beating frequency of the two scattered light waves on the cathode of a photomultiplier. As the intersecting beams form equidistant light sheets within the probe volume by their interference, it is desirable, as is the case with any technique creating light barriers in space, that particles should pass the grid individually. The particles should be of a suitable size: large enough to scatter sufficient light for a good signal-to-noise ratio but small enough for negligible velocity relaxation and true indication of the turbulent velocity fluctuations. In most applications of this technique, e.g. in wind tunnel experiments, particles of controlled size and number density are seeded into the upstream flow.

  17. Ultrasonic distance and velocity measurement using a pair of LPM signals for cross-correlation method: improvement of Doppler-shift compensation and examination of Doppler velocity estimation.

    PubMed

    Hirata, Shinnosuke; Kurosawa, Minoru Kuribayashi

    2012-09-01

    Real-time distance measurement of a moving object with high accuracy and high resolution using an ultrasonic wave is difficult due to the influence of the Doppler effect or the limit of the calculation cost of signal processing. An over-sampling signal processing method using a pair of LPM signals has been proposed for ultrasonic distance and velocity measurement of moving objects with high accuracy and high resolution. The proposed method consists of cross correlation by single-bit signal processing, high-resolution Doppler velocity estimation with wide measurement range and low-calculation-cost Doppler-shift compensation. The over-sampling cross-correlation function is obtained from cross correlation by single-bit signal processing with low calculation cost. The Doppler velocity and distance of the object are determined from the peak interval and peak form in the cross-correlation function by the proposed method of Doppler velocity estimation and Doppler-shift compensation. In this paper, the proposed method of Doppler-shift compensation is improved. Accuracy of the determined distance was improved from approximately within ±140μm in the previous method to approximately within ±10μm in computer simulations. Then, the proposed method of Doppler velocity estimation is evaluated. In computer simulations, accuracy of the determined Doppler velocity and distance were demonstrated within ±8.471mm/s and ±13.87μm. In experiments, Doppler velocities of the motorized stage could be determined within ±27.9mm/s.

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

    NASA Technical Reports Server (NTRS)

    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.

  19. 3D velocity measurement by a single camera using Doppler phase-shifting holography

    NASA Astrophysics Data System (ADS)

    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.

  20. Monostatic Doppler lidar using an Nd:YAG laser for wind-velocity measurement

    NASA Astrophysics Data System (ADS)

    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.

  1. Doppler measurement of implosion velocity in fast Z-pinch x-ray sources

    NASA Astrophysics Data System (ADS)

    Jones, B.; Jennings, C. A.; Bailey, J. E.; Rochau, G. A.; Maron, Y.; Coverdale, C. A.; Yu, E. P.; Hansen, S. B.; Ampleford, D. J.; Lake, P. W.; Dunham, G.; Cuneo, M. E.; Deeney, C.; Fisher, D. V.; Fisher, V. I.; Bernshtam, V.; Starobinets, A.; Weingarten, L.

    2011-11-01

    The observation of Doppler splitting in K-shell x-ray lines emitted from optically thin dopants is used to infer implosion velocities of up to 70 cm/μs in wire-array and gas-puff Z pinches at drive currents of 15-20 MA. These data can benchmark numerical implosion models, which produce reasonable agreement with the measured velocity in the emitting region. Doppler splitting is obscured in lines with strong opacity, but red-shifted absorption produced by the cooler halo of material backlit by the hot core assembling on axis can be used to diagnose velocity in the trailing mass.

  2. Optimization of Doppler velocity echocardiographic measurements using an automatic contour detection method.

    PubMed

    Gaillard, E; Kadem, L; Pibarot, P; Durand, L-G

    2009-01-01

    Intra- and inter-observer variability in Doppler velocity echocardiographic measurements (DVEM) is a significant issue. Indeed, imprecisions of DVEM can lead to diagnostic errors, particularly in the quantification of the severity of heart valve dysfunction. To minimize the variability and rapidity of DVEM, we have developed an automatic method of Doppler velocity wave contour detection, based on active contour models. To validate our new method, results obtained with this method were compared to those obtained manually by an experienced echocardiographer on Doppler echocardiographic images of left ventricular outflow tract and transvalvular flow velocity signals recorded in 30 patients, 15 with aortic stenosis and 15 with mitral stenosis. We focused on three essential variables that are measured routinely by Doppler echocardiography in the clinical setting: the maximum velocity, the mean velocity and the velocity-time integral. Comparison between the two methods has shown a very good agreement (linear correlation coefficient R(2) = 0.99 between the automatically and the manually extracted variables). Moreover, the computation time was really short, about 5s. This new method applied to DVEM could, therefore, provide a useful tool to eliminate the intra- and inter-observer variabilities associated with DVEM and thereby to improve the diagnosis of cardiovascular disease. This automatic method could also allow the echocardiographer to realize these measurements within a much shorter period of time compared to standard manual tracing method. From a practical point of view, the model developed can be easily implanted in a standard echocardiographic system.

  3. Feasibility of using a reliable automated Doppler flow velocity measurements for research and clinical practices

    NASA Astrophysics Data System (ADS)

    Zolgharni, Massoud; Dhutia, Niti M.; Cole, Graham D.; Willson, Keith; Francis, Darrel P.

    2014-03-01

    Echocardiographers are often unkeen to make the considerable time investment to make additional multiple measurements of Doppler velocity. Main hurdle to obtaining multiple measurements is the time required to manually trace a series of Doppler traces. To make it easier to analyse more beats, we present an automated system for Doppler envelope quantification. It analyses long Doppler strips, spanning many heartbeats, and does not require the electrocardiogram to isolate individual beats. We tested its measurement of velocity-time-integral and peak-velocity against the reference standard defined as the average of three experts who each made three separate measurements. The automated measurements of velocity-time-integral showed strong correspondence (R2 = 0.94) and good Bland-Altman agreement (SD = 6.92%) with the reference consensus expert values, and indeed performed as well as the individual experts (R2 = 0.90 to 0.96, SD = 5.66% to 7.64%). The same performance was observed for peak-velocities; (R2 = 0.98, SD = 2.95%) and (R2 = 0.93 to 0.98, SD = 2.94% to 5.12%). This automated technology allows <10 times as many beats to be acquired and analysed compared to the conventional manual approach, with each beat maintaining its accuracy.

  4. Spray drop size and velocity measurements using the Phase/Doppler Particle Analyzer

    NASA Technical Reports Server (NTRS)

    Bachalo, W. D.; Houser, M. J.

    1987-01-01

    Detailed measurements of the drop size and velocity distributions were obtained for a swirl chamber pressure atomizer. These data were obtained with the Phase/Doppler Particle Analyzer manufactured by Aerometrics, Inc. Direct measurements of the size distributions revealed the evolving characteristics of the spray. Size velocity correlations were used to evaluate the effect of velocity relaxation on the size distributions. The simultaneous measurement of drop size and velocity was of major importance in accurately describing the changes in the local drop size distributions and mass flux.

  5. Application of the Dopplionogram to Doppler-sorted interferometry measurements of ionospheric drift velocity

    NASA Astrophysics Data System (ADS)

    Parkinson, M. L.; Breed, A. M.; Dyson, P. L.; Morris, R. J.

    1999-07-01

    The Dopplionogram was developed as a method of displaying Doppler shifts along the frequency axis of ionograms recorded using B-mode soundings of the Dynasonde, an early type of HF digital ionosonde. The basic idea of recording Doppler shifts in an ionogram format is applied and extended to the Doppler velocity mode of the Digisonde Portable Sounder-4 (DPS-4), a related and more recent type of digital ionosonde. In order to describe our mode of operation a Dopplionogram is redefined to mean a set of stepped-frequency soundings that yields a set of ionospheric Doppler shifts particular to the chosen transmission frequencies. Extension of the technique to include Doppler-sorted interferometry (DSI) analysis of the Doppler spectra facilitates a detailed analysis of ionospheric velocity variations in time and group height. This revitalized approach to DSI should prove useful for the study of ionospheric dynamics for which knowledge of the height profile of electric currents, drift velocity, and neutral winds is required. The technique is demonstrated using measurements of polar cap plasma winds obtained with a DPS-4 located at Casey, Antarctica (66.3°S, 110.5°E).

  6. Three interfering beams in laser Doppler velocimetry for particle position and microflow velocity profile measurements.

    PubMed

    Onofri, Fabrice

    2006-05-10

    It is proposed to use three interfering and coplanar laser beams to form the probe volume of laser Doppler systems. This allows us to obtain, for each particle crossing this probe volume, a Doppler signal whose frequency amplitude spectrum exhibits two characteristic peaks. Electromagnetic calculations and experimental validations clearly demonstrate that we can estimate simultaneously, from the analysis of these two frequency peaks, the particle position along the optical axis and one velocity component. This technique is expected to have great potentialities for velocity profile measurements in microfluidic or boundary layer flows, as well as for the sizing of spherical particles.

  7. Edge Ion Velocity Measurements with a Novel Doppler Spectrometer at the Alcator C-Mod Tokamak

    NASA Astrophysics Data System (ADS)

    Graf, Alexander; May, Mark; Beiersdorfer, Peter; Terry, Jim

    2006-10-01

    A high throughput, f/# ˜3.1, transmission grating Doppler spectrometer for visible light (3500-6700 å) is currently measuring ion or neutral velocities and temperatures at the Alcator C-Mod tokamak. The ion velocities are measured through the Doppler shift of impurities that are present in the plasma. A line width of as small as 0.4 å(velocity sensitivity of ˜10^5 cm/s) has been measured using calibration lamps. The spectrometer is fiber optically coupled and has access to toroidal and poloidal views. A spectral survey has been done with various views of the C-Mod plasma identifying various intrinsic impurities. The first Doppler measurements of B II were recorded with ˜15 ms per frame. Additional Doppler velocity and temperature measurements in both poloidal and toroidal directions for some of the brighter impurities (e.g. He II and N III), will be given. This work is supported was performed under the auspices of the DoE by UC LLNL under contract W-7405-ENG-48 and also under DoE Coop. Agreement DE-FC02-99ER54512.

  8. Comparison of carotid artery blood velocity measurements by vector and standard Doppler approaches.

    PubMed

    Tortoli, Piero; Lenge, Matteo; Righi, Daniele; Ciuti, Gabriele; Liebgott, Hervé; Ricci, Stefano

    2015-05-01

    Although severely affected by the angle dependency, carotid artery peak systolic velocity measurements are widely used for assessment of stenosis. In this study, blood peak systolic velocities in the common and internal carotid arteries of both healthy volunteers and patients with internal carotid artery stenosis were measured by two vector Doppler (VD) methods and compared with measurements obtained with the conventional spectral Doppler approach. Although the two VD techniques were completely different (using the transmission of focused beams and plane waves, respectively), the measurement results indicate that these techniques are nearly equivalent. The peak systolic velocities measured in 22 healthy common carotid arteries by the two VD techniques were very close (according to Bland-Altman analysis, the average difference was 3.2%, with limits of agreement of ± 8.6%). Application of Bland-Altman analysis to comparison of either VD technique with the spectral Doppler method provided a 21%-25% average difference with ± 13%-15% limits of agreement. Analysis of the results obtained from 15 internal carotid arteries led to similar conclusions, indicating significant overestimation of peak systolic velocity with the spectral Doppler method. Inter- and intra-operator repeatability measurements performed in a group of 8 healthy volunteers provided equivalent results for all of the methods (coefficients of variability in the range 2.7%-6.9%), even though the sonographers were not familiar with the VD methods. The results of this study suggest that the introduction of vector Doppler methods in commercial machines may finally be considered mature and capable of overcoming the angle-dependent overestimation typical of the standard spectral Doppler approach.

  9. Depth-encoded dual beam phase-resolved Doppler OCT for Doppler-angle-independent flow velocity measurement

    NASA Astrophysics Data System (ADS)

    Qian, Jie; Cheng, Wei; Cao, Zhaoyuan; Chen, Xinjian; Mo, Jianhua

    2017-02-01

    Phase-resolved Doppler optical coherence tomography (PR-D-OCT) is a functional OCT imaging technique that can provide high-speed and high-resolution depth-resolved measurement on flow in biological materials. However, a common problem with conventional PR-D-OCT is that this technique often measures the flow motion projected onto the OCT beam path. In other words, it needs the projection angle to extract the absolute velocity from PR-D-OCT measurement. In this paper, we proposed a novel dual-beam PR-D-OCT method to measure absolute flow velocity without separate measurement on the projection angle. Two parallel light beams are created in sample arm and focused into the sample at two different incident angles. The images produced by these two beams are encoded to different depths in single B-scan. Then the Doppler signals picked up by the two beams together with the incident angle difference can be used to calculate the absolute velocity. We validated our approach in vitro on an artificial flow phantom with our home-built 1060 nm swept source OCT. Experimental results demonstrated that our method can provide an accurate measurement of absolute flow velocity with independency on the projection angle.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  13. Measurement of rectus femoris muscle velocities during patellar tendon jerk using vector tissue doppler imaging.

    PubMed

    Sikdar, Siddhartha; Lebiedowska, Maria; Eranki, Avinash; Garmirian, Lindsay; Damiano, Diane

    2009-01-01

    We have developed a vector tissue Doppler imaging (TDI) system based on a clinical scanner that can be used to measure muscle velocities independent of the direction of motion. This method overcomes the limitations of conventional Doppler ultrasound, which can only measure velocity components along the ultrasound beam. In this study, we utilized this method to investigate the rectus femoris muscle velocities during a patellar tendon jerk test. Our goal was to investigate whether the muscle elongation velocities during a brisk tendon tap fall within the normal range of velocities that are expected due to rapid stretch of limb segments. In a preliminary study, we recruited six healthy volunteers (three men and three women) following informed consent. The stretch reflex response to tendon tap was evaluated by measuring: (1) the tapping force using an accelerometer instrumented to the neurological hammer (2) the angular velocities of the knee extension and flexion using a electrogoniometer (3) reflex activation using electromyography (EMG) and (4) muscle elongation, extension and flexion velocities using vector TDI. The passive joint angular velocity was linearly related to the passive muscle elongation velocity (R(2)=0.88). The maximum estimated joint angular velocity corresponding to muscle elongation due to tendon tap was less than 8.25 radians/s. This preliminary study demonstrates the feasibility of vector TDI for measuring longitudinal muscle velocities and indicates that the muscle elongation velocities during a clinical tendon tap test are within the normal range of values for rapid limb stretch encountered in daily life. With further refinement, vector TDI could become a powerful method for quantitative evaluation of muscle motion in musculoskeletal disorders.

  14. Optimization of Doppler echocardiographic velocity measurements using an automatic contour detection method.

    PubMed

    Gaillard, Emmanuel; Kadem, Lyes; Clavel, Marie-Annick; Pibarot, Philippe; Durand, Louis-Gilles

    2010-09-01

    Intra- and interobserver variability in Doppler echocardiographic velocity measurements (DEVM) is a significant issue. Indeed, imprecisions of DEVM can lead to diagnostic errors, particularly in the quantification of the severity of heart valve dysfunctions. To reduce the variability and rapidity of DEVM, we have developed an automatic method of Doppler velocity wave contour detection, based on active contour models. To validate our new method, results obtained with this method were compared with those obtained manually by two experienced echocardiographers on Doppler echocardiographic images of left ventricular outflow tract and transvalvular flow velocity signals recorded in 30 patients with aortic or mitral stenosis, 20 with normal sinus rhythm and 10 with atrial fibrillation. We focused on the three essential variables that are measured routinely using Doppler echocardiography in the clinical setting: the maximum velocity (Vmax), the mean velocity (Vmean) and the velocity-time integral (VTI). Comparison between the two methods has shown a very good agreement. A small bias value was found between the two methods (between -3.9% and 0.5% for Vmax, between -4.6% and -1.4% for Vmean and between -3.6% and 4.4% for VTI). Moreover, the computation time was short, approximately 5 s. This new method applied to DEVM could, therefore, provide a useful tool to eliminate the intra- and interobserver variabilities associated with DEVM and thereby to improve the accuracy of the diagnosis of cardiovascular disease. This automatic method could also allow the echocardiographer to realize these measurements within a much shorter period of time compared with the standard manual tracing method. From a practical point of view, the model developed can be easily implemented in a standard echocardiographic system.

  15. On the role of spectral resolution in velocity shear layer measurements by Doppler reflectometry

    SciTech Connect

    Happel, T.; Blanco, E.; Estrada, T.

    2010-10-15

    The signal quality of a Doppler reflectometer depends strongly on its spectral resolution, which is influenced by the microwave beam properties and the radius of curvature of the cutoff layer in the plasma. If measured close to a strong perpendicular velocity shear layer, the spectrum of the backscattered signal is influenced by different velocities. This can give rise to two Doppler shifted peaks in the spectrum as observed in TJ-II H-mode plasmas. It is shown by two-dimensional full wave simulations that the two peaks are separable provided the spectral resolution of the system is sufficient. However, if the spectral resolution is poor, the two peaks blend into one and yield an intermediate and incorrect velocity.

  16. Doppler ultrasound in the measurement of pulse wave velocity: agreement with the Complior method

    PubMed Central

    2011-01-01

    Aortic stiffness is an independent predictor factor for cardiovascular risk. Different methods for determining pulse wave velocity (PWV) are used, among which the most common are mechanical methods such as SphygmoCor or Complior, which require specific devices and are limited by technical difficulty in obtaining measurements. Doppler guided by 2D ultrasound is a good alternative to these methods. We studied 40 patients (29 male, aged 21 to 82 years) comparing the Complior method with Doppler. Agreement of both devices was high (R = 0.91, 0.84-0.95, 95% CI). The reproducibility analysis revealed no intra-nor interobserver differences. Based on these results, we conclude that Doppler ultrasound is a reliable and reproducible alternative to other established methods for the measurement of aortic PWV. PMID:21496271

  17. Direct and Doppler angle-independent measurement of blood flow velocity in small-diameter vessels using ultrasound microbubbles.

    PubMed

    Roy, Homagni Sikha; Zuo, Guoqing; Luo, Zhengchun; Wu, Hanping; Krupka, Tianyi M; Ran, Haitao; Li, Pan; Sun, Youping; Wang, Zhigang; Zheng, Yuanyi

    2012-01-01

    This article represents an initial attempt to demonstrate the feasibility of a novel method for measuring flow velocity in small vessels, which is a direct, noninvasive, ultrasound-guided, and Doppler angle-independent method. In vitro, experiments were designed to mimic blood flow inside tubes. Harmonic ultrasound imaging was used to track the movement of microbubbles, and the mean flow velocity was calculated. In vivo, the flow velocities were measured in the central arteries of rabbit ears. This method can be used whenever the Doppler ultrasound cannot measure the velocity in small vessels because of either low sensitivity or Doppler angle limitation. Copyright © 2012 Elsevier Inc. All rights reserved.

  18. Measurement of tendon velocities using vector tissue Doppler imaging: a feasibility study.

    PubMed

    Eranki, Avinash; Bellini, Lindsey; Prosser, Laura; Stanley, Christopher; Bland, Daniel; Alter, Katharine; Damiano, Diane; Sikdar, Siddhartha

    2010-01-01

    We have developed a vector Doppler ultrasound imaging method to directly quantify the magnitude and direction of muscle and tendon velocities during movement. The goal of this study was to evaluate the feasibility of using vector Tissue Doppler Imaging (vTDI) for estimating the tibialis anterior tendon velocities during dorsiflexion in children with cerebral palsy who have foot drop. Our preliminary results from this study show that tendon velocities estimated using vTDI have a strong linear correlation with the joint angular velocity estimated using a conventional 3D motion capture system. We observed a peak tendon velocity of 5.66±1.45 cm/s during dorsiflexion and a peak velocity of 8.83±2.13 cm/s during the passive relaxation phase of movement. We also obtained repeatable results from the same subject 3 weeks apart. Direct measurements of muscle and tendon velocities may be used as clinical outcome measures and for studying efficiency of movement control.

  19. Errors in acoustic doppler profiler velocity measurements caused by flow disturbance

    USGS Publications Warehouse

    Mueller, D.S.; Abad, J.D.; Garcia, C.M.; Gartner, J.W.; Garcia, M.H.; Oberg, K.A.

    2007-01-01

    Acoustic Doppler current profilers (ADCPs) are commonly used to measure streamflow and water velocities in rivers and streams. This paper presents laboratory, field, and numerical model evidence of errors in ADCP measurements caused by flow disturbance. A state-of-the-art three-dimensional computational fluid dynamic model is validated with and used to complement field and laboratory observations of flow disturbance and its effect on measured velocities. Results show that near the instrument, flow velocities measured by the ADCP are neither the undisturbed stream velocity nor the velocity of the flow field around the ADCP. The velocities measured by the ADCP are biased low due to the downward flow near the upstream face of the ADCP and upward recovering flow in the path of downstream transducer, which violate the flow homogeneity assumption used to transform beam velocities into Cartesian velocity components. The magnitude of the bias is dependent on the deployment configuration, the diameter of the instrument, and the approach velocity, and was observed to range from more than 25% at 5cm from the transducers to less than 1% at about 50cm from the transducers for the scenarios simulated. ?? 2007 ASCE.

  20. Development of fiber optic laser Doppler velocimeter for measurement of local blood velocity

    NASA Astrophysics Data System (ADS)

    Ohba, Kenkich; Fujiwara, Noboru

    1993-08-01

    In order to measure the local velocity field in opaque fluid flows like blood flow, a new laser Doppler velocimeter having a pickup consisting of a small distributed index lens attached to the tips of two fibers which are joined side by side in parallel has been newly developed. The distributed index lens is the shape of a truncated cone. The flow field around this sensor has been measured very precisely by means of an ordinary LDV. The effect of turbidity of fluid on the quality of the laser Doppler signal from this sensor has been examined by experiments. As a result, it has been shown that this LDV sensor has a high signal-to-noise ratio, and that the disturbance against flow by the sensor is very small, and it is very promising as a velocity sensor for opaque or semi-opaque fluid flow like blood flow.

  1. Volumetric vessel reconstruction method for absolute blood flow velocity measurement in Doppler OCT images

    NASA Astrophysics Data System (ADS)

    Qi, Li; Zhu, Jiang; Hancock, Aneeka M.; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D.; Chen, Zhongping

    2017-02-01

    Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it not only relates to the properties of the laser and the scattering particles, but also relates to the geometry of both directions of the laser beam and the flow. In this paper, focusing on the analysis of cerebral hemodynamics, we presents a method to quantify the total absolute blood flow velocity in middle cerebral artery (MCA) based on volumetric vessel reconstruction from pure DOCT images. A modified region growing segmentation method is first used to localize the MCA on successive DOCT B-scan images. Vessel skeletonization, followed by an averaging gradient angle calculation method, is then carried out to obtain Doppler angles along the entire MCA. Once the Doppler angles are determined, the absolute blood flow velocity of each position on the MCA is easily found. Given a seed point position on the MCA, our approach could achieve automatic quantification of the fully distributed absolute BFV. Based on experiments conducted using a swept-source optical coherence tomography system, our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches in the rodent brain.

  2. TU-A-9A-02: Analysis of Variations in Clinical Doppler Ultrasound Peak Velocity Measurements

    SciTech Connect

    Zhang, Y; Stekel, S; Tradup, D; Hangiandreou, N

    2014-06-15

    Purpose: Doppler ultrasound (US) peak velocity (Vmax) measurements show considerable variations due to intrinsic spectral broadening with different scanning techniques, machines and manufacturers. We developed a semi-automated Vmax estimation method and used this method to investigate the performance of a US system for clinical Doppler Vmax measurement. Methods: Semi-automated Vmax is defined as the velocity at which the computed mean spectral profile falls to within 1 background standard deviation of the background mean. GE LOGIQ E9 system with 9L and ML6-15 probes were studied with steady flow (5.3 – 12.5 ml/s) in a Gammex OPTIMIZER 1425A phantom. All Doppler spectra were acquired by 1 operator at the distal end of 5 mm angular tube using a modified clinical carotid artery protocol. Repeatability and variation of Vmax to scanning parameters and probes were analyzed and reported as percentage, i.e. (max-min)/mean. Results: Vmax estimation had good repeatability (3.1% over 6 days for 9L, and 3.6% for ML6-15). For 9L probe, varying gain, compression, scale, SV depth and length, and frequency had minimal impact on Vmax (all variations less than 4.0%). Beam steering had slightly higher influence (largest variations across flow rates were 4.9% for 9L and 6.9% for ML6-15). For both probes, Doppler angle had the greatest effect on Vmax. Percentage increase of Vmax was largely independent of actual flow rates. For Doppler angle varied from 30 to 60°, Vmax increased 24% for 9L, and 20% for ML6-15. Vmax measured by ML6-15 were lower than that by 9L at each Doppler angle with differences less than 5%. Conclusion: The proposed Vmax estimation method is shown to be a useful tool to evaluate clinical Doppler US system performance. For the tested system and probes, Doppler angle had largest impact in measured Vmax.

  3. Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

    DOE PAGES

    Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; ...

    2016-12-06

    Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (w'2) from zenith stares. But, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w'2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting formore » volume-averaging effects in the calculation of w'2 is also assessed. In addition, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w'2. And through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w'2. After the autocovariance technique is applied, values of w'2 from the Doppler lidars are generally in close agreement (R2 ≈ 0.95 -0.98) with those calculated from sonic anemometer measurements.« less

  4. Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

    NASA Astrophysics Data System (ADS)

    Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; Chilson, Phillip B.; Wharton, Sonia

    2016-12-01

    Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (w'2) from zenith stares. However, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w'2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting for volume-averaging effects in the calculation of w'2 is also assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w'2. Through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w'2. After the autocovariance technique is applied, values of w'2 from the Doppler lidars are generally in close agreement (R2 ≈ 0.95 - 0.98) with those calculated from sonic anemometer measurements.

  5. Acoustic resolution photoacoustic Doppler velocity measurements in fluids using time-domain cross-correlation

    NASA Astrophysics Data System (ADS)

    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

  6. Measurement of fast-changing low velocities by photonic Doppler velocimetry

    SciTech Connect

    Song Hongwei; Wu Xianqian; Huang Chenguang; Wei Yangpeng; Wang Xi

    2012-07-15

    Despite the increasing popularity of photonic Doppler velocimetry (PDV) in shock wave experiments, its capability of capturing low particle velocities while changing rapidly is still questionable. The paper discusses the performance of short time Fourier transform (STFT) and continuous wavelet transform (CWT) in processing fringe signals of fast-changing low velocities measured by PDV. Two typical experiments are carried out to evaluate the performance. In the laser shock peening test, the CWT gives a better interpretation to the free surface velocity history, where the elastic precursor, main plastic wave, and elastic release wave can be clearly identified. The velocities of stress waves, Hugoniot elastic limit, and the amplitude of shock pressure induced by laser can be obtained from the measurement. In the Kolsky-bar based tests, both methods show validity of processing the longitudinal velocity signal of incident bar, whereas CWT improperly interprets the radial velocity of the shocked sample at the beginning period, indicating the sensitiveness of the CWT to the background noise. STFT is relatively robust in extracting waveforms of low signal-to-noise ratio. Data processing method greatly affects the temporal resolution and velocity resolution of a given fringe signal, usually CWT demonstrates a better local temporal resolution and velocity resolution, due to its adaptability to the local frequency, also due to the finer time-frequency product according to the uncertainty principle.

  7. Measurement of velocities in gas-liquid two-phase flow using Laser Doppler Velocimetry

    SciTech Connect

    Vassallo, P.F.; Trabold, T.A.; Moore, W.E.; Kirouac, G.J.

    1992-09-01

    Measurements of bubble and liquid velocities in two-phase flow have been made using a new forward/backward scattering Laser Doppler Velocimetry (LDV) technique. This work was performed in a 6.4 by 11.1 mm vertical duct using known air/water mixtures. A standard LDV fiber optic probe was used to measure the bubble velocity, using direct backscattered light. A novel retro-reflector and lens assembly permitted the same probe to measure the liquid velocity with direct forward-scattered light. The bubble velocity was confirmed by independent measurements with a high-speed video system. The liquid velocity was confirmed by demonstrating the dominance of the liquid seed data rate in the forward-scatter measurement. Experimental data are presented to demonstrate the accuracy of the technique for a wide range of flow conditions, from bubbles as small as 0.75-mm-diam to slugs as large as 10-mm wide by 30-mm long. In the slug regime, the LDV technique performed velocity measurements for both phases, for void fractions up to 50%, which was the upper limit of our experimental investigation.

  8. Comparison of CO2 Doppler lidar and GPS rawinsonde wind velocity measurements

    NASA Astrophysics Data System (ADS)

    Roadcap, John R.; McNicholl, Patrick J.; Teets, Edward H., Jr.; Laird, Mitchell H.

    2001-09-01

    A comparison of CO2 Doppler lidar and GPS rawinsonde measurements of horizontal wind velocity was conducted during May 2000 at Hanscom AFB, Massachusetts. Seven days of side-by-side measurements using both lidar and GPS sondes were achieved comparing wind velocity as a function of altitude up to 6 km. The horizontal wind velocity was determined by the CO2 Doppler lidar using the Velocity Azimuth Display (VAD) method. Horizontal winds were also determined simultaneously using a differential GPS-tracked rawinsonde which provides GPS position coordinates once per second. Both lidar VAD wind speed Root Mean Squared Difference (RMS) and lidar vs. GPS sonde RMS were calculated and compared as a function of altitude, time, and stability regime. On average, significant increases in both the lidar VAD RMS and lidar vs. GPS RMS were observed during unstable conditions compared to stable conditions. Analyses of lidar VAD RMS show the smallest typical values average near 0.5 m/s over a single profile.

  9. [Transfontanellar Doppler ultrasound measurement of cerebral blood velocity before and after surgical treatment of hydrocephalus].

    PubMed

    de Assis, M C; Machado, H R

    1999-09-01

    Twenty-seven children with hydrocephalus of different etiologies diagnosed by clinical examination, neurosonography and computerized brain tomography were submitted to transfontanellar US-Doppler evaluation for measurement of blood flow velocity and for the calculation of resistance index (RI) in the anterior and middle cerebral arteries and internal carotids. All children were submitted to evaluation before surgery and on the 1st, 30th and 60th postoperative days. We conclude that neurosonography and US-Doppler technique is useful for determination of hydrocephalus, indication and control of cerebrospinal fluid shunts and monitoring of changes in RI, comparing data obtained immediately before and after surgery and during the late postoperative period. The results obtained when comparing the RI values for the various arteries during the different stages of the study also permitted us to conclude that the anterior cerebral arteries are representative of the maximal alterations that occur in cerebral vascular resistance in pediatric patients with hydrocephalus.

  10. Fiber-Based Doppler Lidar for Vector Velocity and Altitude Measurements

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

    A coherent Doppler lidar capable of providing accurate velocity and altitude data has been developed and demonstrated for future NASA missions to the solar system bodies requiring precision navigation and controlled soft landing.

  11. Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

    SciTech Connect

    Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; Chilson, Phillip B.; Wharton, Sonia

    2016-12-06

    Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (w'2) from zenith stares. But, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w'2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting for volume-averaging effects in the calculation of w'2 is also assessed. In addition, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w'2. And through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w'2. After the autocovariance technique is applied, values of w'2 from the Doppler lidars are generally in close agreement (R2 ≈ 0.95 -0.98) with those calculated from sonic anemometer measurements.

  12. MEASUREMENTS OF ANISOTROPIC ION TEMPERATURES, NON-THERMAL VELOCITIES, AND DOPPLER SHIFTS IN A CORONAL HOLE

    SciTech Connect

    Hahn, M.; Savin, D. W.

    2013-02-15

    We present a new diagnostic allowing one to measure the anisotropy of ion temperatures and non-thermal velocities, as well as Doppler shifts with respect to the ambient magnetic field. This method provides new results, as well as an independent test for previous measurements obtained with other techniques. Our spectral data come from observations of a low-latitude, on-disk coronal hole. A potential field source surface model was used to calculate the angle between the magnetic field lines and the line of sight for each spatial bin of the observation. A fit was performed to determine the line widths and Doppler shifts parallel and perpendicular to the magnetic field. For each line width component we derived ion temperatures T {sub i,} and T {sub i, Parallel-To} and non-thermal velocities v {sub nt,} and v {sub nt, Parallel-To }. T {sub i,} was cooler than off-limb polar coronal hole measurements, suggesting increasing collisional cooling with decreasing height. T {sub i, Parallel-To} is consistent with a uniform temperature of (1.8 {+-} 0.2) Multiplication-Sign 10{sup 6} K for each ion. Since parallel ion heating is expected to be weak, this ion temperature should reflect the proton temperature. A comparison between our results and others implies a large proton temperature gradient around 1.02 R {sub Sun }. The non-thermal velocities are thought to be proportional to the amplitudes of various waves. Our results for v {sub nt,} agree with Alfven wave amplitudes inferred from off-limb polar coronal hole line width measurements. Our v {sub nt, Parallel-To} results are consistent with slow magnetosonic wave amplitudes inferred from Fourier analysis of time-varying intensity fluctuations. Doppler shift measurements yield outflows of Almost-Equal-To 5 km s{sup -1} for ions formed over a broad temperature range. This differs from other studies that found a strong Doppler shift dependence on formation temperature.

  13. Ultrasonic Doppler measurements of blood flow velocity of rabbit retinal vessels using a 45-MHz needle transducer

    PubMed Central

    Matsuoka, Naoki; Paeng, Dong-Guk; Chen, Ruimin; Ameri, Hossein; Abdallah, Walid; Zhou, Qifa; Fawzi, Amani; Shung, K. K.

    2010-01-01

    Background The purpose of this study is to measure blood flow velocity of rabbit retinal vessels using a 45-MHz ultrasonic Doppler system with a needle transducer. Methods A high-frequency pulsed Doppler system that utilizes a 45-MHz PMN-PT needle transducer was developed to measure retinal blood flow velocity in situ. The pulsed Doppler allowed the differentiation of retinal from choroidal blood flow velocity. The needle transducer was inserted into the vitreous cavity through a 20-gauge incision port to access the retinal vessels. The first phase of the experiment evaluated the reproducibility of the measurements. The second phase measured velocities at four positions from the optic disc edge to the distal part of each vessel in nine eyes for the temporal and six eyes for the nasal portions. The angle between the transducer and the retinal vessel at each site was measured in enucleated rabbit eyes to estimate and compensate for measurement errors. Results In the first phase, the average measurement error was 5.97±1.34%. There was no significant difference comparing all eyes. In the second phase, the velocities gradually slowed from the disc edge to the distal part, and temporal velocities were faster than nasal velocities at all measurement sites. Conclusion This study demonstrated the feasibility of reliably measuring retinal blood flow velocity using a 45-MHz ultrasonic Doppler system with a needle transducer. PMID:20162299

  14. Vibration measurements using continuous scanning laser Doppler vibrometry: theoretical velocity sensitivity analysis with applications

    NASA Astrophysics Data System (ADS)

    Halkon, B. J.; Rothberg, S. J.

    2003-03-01

    It is readily accepted that a laser vibrometer measures target velocity in the direction of the incident laser beam, but this measured velocity must be considered in terms of the various components of the target velocity. This paper begins with a review of the theoretical description of the velocity sensed by a single laser beam incident in an arbitrary direction on a rotating target undergoing arbitrary vibration. The measured velocity is presented as the sum of six terms, each the product of a combination of geometric parameters, relating to the laser beam orientation, and a combination of motion parameters - the 'vibration sets'. This totally general velocity sensitivity model can be applied to any measurement configuration on any target. The model is also sufficiently versatile to incorporate time-dependent beam orientation and this is described in this paper, with reference to continuous scanning laser Doppler vibrometry. For continuous scanning applications, the velocity sensitivity model is shown formulated in two useful ways. The first is in terms of the laser beam orientation angles, developing the original model to include time dependency in the angles, whilst the second is an entirely new development in which the model is written in terms of the mirror scan angles, since it is these which the operator would seek to control in practice. In the original derivation, the illuminated section of the rotating target was assumed to be of rigid cross section but, since continuous scanning measurements are employed on targets with flexible cross sections, such as beams, panels and thin or bladed discs, the theory is developed in this paper for the first time to include provision for such flexibility.

  15. Fully distributed absolute blood flow velocity measurement for middle cerebral arteries using Doppler optical coherence tomography

    PubMed Central

    Qi, Li; Zhu, Jiang; Hancock, Aneeka M.; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D.; Chen, Zhongping

    2016-01-01

    Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it is related to vessel geometry. In this paper, we present a volumetric vessel reconstruction approach that is capable of measuring the absolute BFV distributed along the entire middle cerebral artery (MCA) within a large field-of-view. The Doppler angle at each point of the MCA, representing the vessel geometry, is derived analytically by localizing the artery from pure DOCT images through vessel segmentation and skeletonization. Our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches. Experiments on rodents using swept-source optical coherence tomography showed that our approach was able to reveal the consequences of permanent MCA occlusion with absolute BFV measurement. PMID:26977365

  16. Inertial Navigation System/Doppler Velocity Log (INS/DVL) Fusion with Partial DVL Measurements.

    PubMed

    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.

  17. Inertial Navigation System/Doppler Velocity Log (INS/DVL) Fusion with Partial DVL Measurements

    PubMed Central

    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

  18. Coherent Doppler Lidar for Measuring Altitude, Ground Velocity, and Air Velocity of Aircraft and Spaceborne Vehicles

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin (Inventor); Pierrottet, Diego F. (Inventor)

    2015-01-01

    A Doppler lidar sensor system includes a laser generator that produces a highly pure single frequency laser beam, and a frequency modulator that modulates the laser beam with a highly linear frequency waveform. A first portion of the frequency modulated laser beam is amplified, and parts thereof are transmitted through at least three separate transmit/receive lenses. A second portion of the laser beam is used as a local oscillator beam for optical heterodyne detection. Radiation from the parts of the laser beam transmitted via the transmit/receive lenses is received by the respective transmit/receive lenses that transmitted the respective part of the laser beam. The received reflected radiation is compared with the local oscillator beam to calculate the frequency difference there between to determine various navigational data.

  19. Navigation Doppler lidar sensor for precision altitude and vector velocity measurements: flight test results

    NASA Astrophysics Data System (ADS)

    Pierrottet, Diego; Amzajerdian, Farzin; Petway, Larry; Barnes, Bruce; Lockard, George; Hines, Glenn

    2011-06-01

    An all fiber Navigation Doppler Lidar (NDL) system is under development at NASA Langley Research Center (LaRC) for precision descent and landing applications on planetary bodies. The sensor produces high-resolution line of sight range, altitude above ground, ground relative attitude, and high precision velocity vector measurements. Previous helicopter flight test results demonstrated the NDL measurement concepts, including measurement precision, accuracies, and operational range. This paper discusses the results obtained from a recent campaign to test the improved sensor hardware, and various signal processing algorithms applicable to real-time processing. The NDL was mounted in an instrumentation pod aboard an Erickson Air-Crane helicopter and flown over various terrains. The sensor was one of several sensors tested in this field test by NASA's Autonomous Landing and Hazard Avoidance Technology (ALHAT) project.

  20. Navigation Doppler Lidar Sensor for Precision Altitude and Vector Velocity Measurements Flight Test Results

    NASA Technical Reports Server (NTRS)

    Pierrottet, Diego F.; Lockhard, George; Amzajerdian, Farzin; Petway, Larry B.; Barnes, Bruce; Hines, Glenn D.

    2011-01-01

    An all fiber Navigation Doppler Lidar (NDL) system is under development at NASA Langley Research Center (LaRC) for precision descent and landing applications on planetary bodies. The sensor produces high resolution line of sight range, altitude above ground, ground relative attitude, and high precision velocity vector measurements. Previous helicopter flight test results demonstrated the NDL measurement concepts, including measurement precision, accuracies, and operational range. This paper discusses the results obtained from a recent campaign to test the improved sensor hardware, and various signal processing algorithms applicable to real-time processing. The NDL was mounted in an instrumentation pod aboard an Erickson Air-Crane helicopter and flown over vegetation free terrain. The sensor was one of several sensors tested in this field test by NASA?s Autonomous Landing and Hazard Avoidance Technology (ALHAT) project.

  1. Elasticity Evaluation of Regenerating Cartilage Sample Based on Laser Doppler Measurement of Ultrasonic Particle Velocity

    NASA Astrophysics Data System (ADS)

    Nitta, Naotaka; Misawa, Masaki; Homma, Kazuhiro; Shiina, Tsuyoshi

    2012-07-01

    It is important for regenerative medicine to evaluate the maturity of regenerating tissue. In the maturity evaluation of regenerating cartilage, it is useful to measure the temporal change of elasticity because the maturity of regenerating tissue is closely related to its elasticity. In this study, an elasticity evaluation method for the extracted regenerating cartilage sample, which is based on the laser Doppler measurement of ultrasonic particle velocity, was experimentally investigated using agar-based phantoms with different elastic moduli and the regenerating cartilage samples extracted from beagles in animal experiments. In addition, the experimentally-obtained elasticity was compared with the result of a static compression test. These results verified the feasibility of the proposed method in the elasticity evaluation of regenerating cartilage samples.

  2. River habitat quality from river velocities measured using acoustic Doppler current profiler.

    PubMed

    Shields, F Douglas; Rigby, J R

    2005-10-01

    Prior research has demonstrated the utility of metrics based on spatial velocity gradients to characterize and describe stream habitat, with higher gradients generally indicative of higher levels of physical heterogeneity and thus habitat quality. However, detailed velocity data needed to compute these metrics are difficult to obtain. Acoustic Doppler current profilers (ADCP) may be used to rapidly collect detailed representations of river velocity fields. Herein we demonstrate use of ADCP to obtain ecologically relevant data and compute associated metrics. Data were collected from four reaches of the Little Tallahatchie River in northern Mississippi. Sampled reaches were selected to observe velocity regimes associated with three distinctly different conditions: downstream from a major flow obstruction (a low weir), downstream from the apices of each of two bends, and within an extremely long, straight reach created by channelization. Three-dimensional velocity data sets from each site were used to compute metrics of habitat quality proposed by others. A habitat metric based on the presence of rotational flow in the vertical plane proved to be the best discriminator among conditions within the sampled reaches. Two of four habitat quality metrics computed from these measured velocities were greatest for the sharpest meander bend. ADCP hold great potential for study of riverine physical aquatic habitats, particularly at the reach scale. Additional work is needed to develop generally applicable field protocols and data reduction tools. Specifically, guidelines for ADCP settings and configuration appropriate for a range of riverine site conditions must be developed. Advances in instrumentation are needed to allow collection of information in closer proximity to the free surface and solid boundaries.

  3. Dual-beam laser Doppler vibrometer for measurement of pulse wave velocity in elastic vessels

    NASA Astrophysics Data System (ADS)

    Campo, Adriaan; Dirckx, Joris

    2011-08-01

    When a fluid flowing through an elastic vessel is subjected to a sudden change in pressure gradient, pressure pulses will propagate through the fluid. Velocity of these pulse waves (PWV) can be determined by simultaneous detection of wall distension on two separate points on the vessel wall, along its trajectory. PWV depends on wall stiffness, and under certain circumstances, wall stiffness can be calculated from the propagation velocity. Optical interferometry is a noncontacting technique that allows measurement of wall distension on discrete locations. In this work we propose a miniaturized dual-beam laser Doppler vibrometer (LDV) to measure wall distension simultaneously at two locations. Our dual-beam LDV is based on a single laser source and one acousto-optic modulator with as much as possible of the interferometer optics shared among the different beams. The dual-beam LDV was used for simultaneous detection of wall distension of several elastic vessels of different stiffness. We found that PWV as measured in elastic vessels agrees well with theoretically expected values, and measurement precision is better than 5%. Moreover, the dual-beam LDV performs almost as good as commercial systems for detection of PWV. The dual-beam LDV can have applications in cardiovascular risk management. Stiffness of large arteries has a very good predictive value for cardiovascular disease and overall mortality. This parameter can be estimated from arterial PWV. Current methods to measure arterial PWV suffer from several shortcomings. A dual-beam LDV can offer substantial advantages over existing techniques.

  4. A dealiasing method for use with ultrasonic pulsed Doppler in measuring velocity profiles and flow rates in pipes

    NASA Astrophysics Data System (ADS)

    Murakawa, Hideki; Muramatsu, Ei; Sugimoto, Katsumi; Takenaka, Nobuyuki; Furuichi, Noriyuki

    2015-08-01

    The ultrasonic pulsed Doppler method (UDM) is a powerful tool for measuring velocity profiles in a pipe. However, the maximum detectable velocity is limited by the Nyquist sampling theorem. Furthermore, the maximum detectable velocity (also called Nyquist velocity), vmax, and the maximum measurable length are related and cannot be increased at the same time. If the velocity is greater than vmax, velocity aliasing occurs. Hence, the higher velocity that occurs with a larger pipe diameter, i.e. under higher flow rate conditions, cannot be measured with the conventional UDM. To overcome these limitations, dual-pulse repetition frequency (dual PRF) and feedback methods were employed in this study to measure velocity profiles in a pipe. The velocity distributions obtained with the feedback method were found to be more accurate than those obtained with the dual PRF method. However, misdetection of the Nyquist folding number using the feedback method was found to increase with the flow velocity. A feedback method with a moving average is proposed to improve the measurement accuracy. The method can accurately measure the velocity distributions at a velocity five times greater than the maximum velocity that can be measured with the conventional UDM. The measurement volume was found to be among the important parameters that must be considered in assessing the traceability of the reflector during the pulse emission interval. Hence, a larger measurement volume is required to measure higher velocities using the dual PRF method. Integrating velocity distributions measured using the feedback method with a moving average makes it possible to accurately determine flow rates six times greater than those that can be determined using the conventional pulsed Doppler method.

  5. Comparison of index velocity measurements made with a horizontal acoustic Doppler current profiler

    USGS Publications Warehouse

    Jackson, P. Ryan; Johnson, Kevin K.; Duncker, James J.

    2012-01-01

    The State of Illinois' annual withdrawal from Lake Michigan is limited by a U.S. Supreme Court decree, and the U.S. Geological Survey (USGS) is responsible for monitoring flows in the Chicago Sanitary and Ship Canal (CSSC) near Lemont, Illinois as a part of the Lake Michigan Diversion Accounting overseen by the U.S. Army Corps of Engineers, Chicago District. Every 5 years, a technical review committee consisting of practicing engineers and academics is convened to review the U.S. Geological Survey's streamgage practices in the CSSC near Lemont, Illinois. The sixth technical review committee raised a number of questions concerning the flows and streamgage practices in the CSSC near Lemont and this report provides answers to many of those questions. In addition, it is the purpose of this report to examine the index velocity meters in use at Lemont and determine whether the acoustic velocity meter (AVM), which is now the primary index velocity meter, can be replaced by the horizontal acoustic Doppler current profiler (H-ADCP), which is currently the backup meter. Application of the AVM and H-ADCP to index velocity measurements in the CSSC near Lemont, Illinois, has produced good ratings to date. The site is well suited to index velocity measurements in spite of the large range of velocities and highly unsteady flows at the site. Flow variability arises from a range of sources: operation of the waterway through control structures, lockage-generated disturbances, commercial and recreational traffic, industrial withdrawals and discharges, natural inflows, seiches, and storm events. The influences of these factors on the index velocity measurements at Lemont is examined in detail in this report. Results of detailed data comparisons and flow analyses show that use of bank-mounted instrumentation such as the AVM and H-ADCP appears to be the best option for index velocity measurement in the CSSC near Lemont. Comparison of the rating curves for the AVM and H-ADCP demonstrates

  6. Development of a laser-Doppler system for measurement of velocity fields in PVT crystal growth systems

    NASA Technical Reports Server (NTRS)

    Jones, O. C.; Glicksman, M. E.; Lin, J. T.; Kim, G. T.; Singh, N. B.

    1991-01-01

    A laser-Doppler velocimetry (LDV) system capable of measuring velocities as low as 10 exp -5 m/s is presented, and a calibration system for determining the accuracy of the LDV system at these velocities is described. The results obtained in mercurous chloride crystal grown in cylindrical ampoules at 300 C, using physical vapor transport (PVT) methods, are presented. It is concluded that the overall flow pattern observed is a unicellular, asymmetric pattern between Rayleigh number of 125 and 250.

  7. Modern spectral analysis techniques for blood flow velocity and spectral measurements with pulsed Doppler ultrasound.

    PubMed

    David, J Y; Jones, S A; Giddens, D P

    1991-06-01

    Four spectral analysis techniques were applied to pulsed Doppler ultrasonic quadrature signals to compare the relative merits of each technique for estimation of flow velocity and Doppler spectra. The four techniques were 1) the fast Fourier transform method, 2) the maximum likelihood method, 3) the Burg autoregressive algorithm, and 4) the modified covariance approach to autoregressive modeling. Both simulated signals and signals obtained from an in vitro flow system were studied. Optimal parameter values (e.g., model orders) were determined for each method, and the effects of signal-to-noise ratio and signal bandwidth were investigated. The modern spectral analysis techniques were shown to be superior to Fourier techniques in most circumstances, provided the model order was chosen appropriately. Robustness considerations tended to recommend the maximum likelihood method for both velocity and spectral estimation. Despite the restrictions of steady laminar flow, the results provide important basic information concerning the applicability of modern spectral analysis techniques to Doppler ultrasonic evaluation of arterial disease.

  8. Investigation of laser Doppler anemometry in developing a velocity-based measurement technique

    NASA Astrophysics Data System (ADS)

    Jung, Ki Won

    2009-12-01

    Acoustic properties, such as the characteristic impedance and the complex propagation constant, of porous materials have been traditionally characterized based on pressure-based measurement techniques using microphones. Although the microphone techniques have evolved since their introduction, the most general form of the microphone technique employs two microphones in characterizing the acoustic field for one continuous medium. The shortcomings of determining the acoustic field based on only two microphones can be overcome by using numerous microphones. However, the use of a number of microphones requires a careful and intricate calibration procedure. This dissertation uses laser Doppler anemometry (LDA) to establish a new measurement technique which can resolve issues that microphone techniques have: First, it is based on a single sensor, thus the calibration is unnecessary when only overall ratio of the acoustic field is required for the characterization of a system. This includes the measurements of the characteristic impedance and the complex propagation constant of a system. Second, it can handle multiple positional measurements without calibrating the signal at each position. Third, it can measure three dimensional components of velocity even in a system with a complex geometry. Fourth, it has a flexible adaptability which is not restricted to a certain type of apparatus only if the apparatus is transparent. LDA is known to possess several disadvantages, such as the requirement of a transparent apparatus, high cost, and necessity of seeding particles. The technique based on LDA combined with a curvefitting algorithm is validated through measurements on three systems. First, the complex propagation constant of the air is measured in a rigidly terminated cylindrical pipe which has very low dissipation. Second, the radiation impedance of an open-ended pipe is measured. These two parameters can be characterized by the ratio of acoustic field measured at multiple

  9. Remote measurement utilizing NASA's scanning laser Doppler systems. Volume 2: Laser Doppler dust devil velocity profile measurement program

    NASA Technical Reports Server (NTRS)

    Howle, R. E.; Krause, M. C.; Craven, C. E.; Gorzynski, E. J.; Edwards, B. B.

    1976-01-01

    The first detailed velocity profile data on thermally induced dust vortices are presented. These dust devils will be analyzed and studied to determine their flow fields and origin in an effort to correlate this phenomena with the generation and characteristics of tornadoes. A continuing effort to increase mankind's knowledge of vortex and other meteorological phenomena will hopefully allow the prediction of tornado occurrence, their path, and perhaps eventually even lead to some technique for their destruction.

  10. In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

    PubMed Central

    Blatter, Cedric; Meijer, Eelco F. J.; Nam, Ahhyun S.; Jones, Dennis; Bouma, Brett E.; Padera, Timothy P.; Vakoc, Benjamin J.

    2016-01-01

    Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence tomography platform that allows direct, label-free quantification of lymph velocity and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph velocity at sufficiently high temporal resolution to resolve the dynamic pulsatile flow in collecting lymphatic vessels. PMID:27377852

  11. In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Blatter, Cedric; Meijer, Eelco F. J.; Nam, Ahhyun S.; Jones, Dennis; Bouma, Brett E.; Padera, Timothy P.; Vakoc, Benjamin J.

    2016-07-01

    Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence tomography platform that allows direct, label-free quantification of lymph velocity and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph velocity at sufficiently high temporal resolution to resolve the dynamic pulsatile flow in collecting lymphatic vessels.

  12. The technology of grating laser Doppler velocimeter for measuring transverse velocity of objects

    NASA Astrophysics Data System (ADS)

    Zhang, Shu; Lu, Guangfeng; Fan, Zhenfang; Luo, Hui

    2014-12-01

    In order to lower production cost of Laser Doppler velocimeter (LDV) and simplify the system structure, a grating Doppler detection system has been designed. This LDV was carried out by differential measurement mode. Two beams of diffracted light from the grating are mixed, and the beat frequency will be detected by a detector when the grating is moving. Fundamentals also have been introduced and partial experiment results of this system are given out. The result indicates the experimental value is agreement with the theoretical value. Errors have been analyzed and the main factors affecting the accuracy were discussed. Upon inspection, the inexpensive and ease LDV is efficient to administer and feasible.

  13. Total velocity vector measurements in an axial-flow compressor using a 3-component laser Doppler anemometer

    NASA Astrophysics Data System (ADS)

    Chesnakas, Christopher J.; Dancey, Clinton L.

    1988-07-01

    A three-color, three-component laser Doppler anemometer (LDA) was used to simultaneously measure the three components of velocity in a low speed (2900 rpm) axial-flow compressor rotor blade passage. Although the mean velocities and entire Reynolds stress tensor were obtained with this system, only the mean velocity results are reported here. It is demonstrated that accurate measurements in the mean motion are possible over much of the blade passage and that the secondary motions can be captured. Confirmation of the observed mean flow results is obtained through a comparison of the three dimensional flow with limited stationary pressure probe measurements and simple irrotational flow assumptions. The presentation of the measurements is followed by a discussion of the difficulties encountered in making three-dimensional velocity measurements in blade passages with LDA and suggestions are made for improving the present system for this task.

  14. Accuracy of velocity and shear rate measurements using pulsed Doppler ultrasound: a comparison of signal analysis techniques.

    PubMed

    Markou, C P; Ku, D N

    1991-01-01

    An experimental investigation was instituted to evaluate the performance of Doppler ultrasound signal processing techniques for measuring fluid velocity under well-defined flow conditions using a 10-MHz multigated pulsed ultrasound instrument. Conditions of fully developed flow in a rigid, circular tube were varied over a Reynolds number range between 500 and 8000. The velocity across the tube was determined using analog and digital zero crossing detectors and three digital spectrum estimators. Determination of the Doppler frequency from analog or digital zero crossing detectors gave accurate velocity values for laminar and moderately turbulent flow away from the wall (0.969 less than or equal to r less than or equal to 0.986). Three digital spectrum estimators, Fast Fourier Transform, Burg autoregressive method, and minimum variance method, were slightly more accurate than the zero crossing detector (0.984 less than or equal to r less than or equal to 0.994), especially at points close to the walls and with higher levels of turbulence. Steep velocity gradients and transit-time-effects from high velocities produced significantly larger errors in velocity measurement. Wall shear rate estimates were most precise when calculated using the position of the wall and two velocity points. The calculated wall shears were within 20%-30% of theoretically predicted values.

  15. Doppler measurements of the H2O(+) ion velocity in the plasma tail of Comet Levy 1990c

    NASA Astrophysics Data System (ADS)

    Rauer, H.; Jockers, K.

    1993-03-01

    2D ion velocity fields have been obtained for the first time from measurements of the Doppler shift of ion emission lines in the plasma tail of the Comet Levy 1990c. Images of the comet obtained alternating with interferograms show the appearance of the plasma tail. Velocities from about 10 to 70 km/s are measured. The velocity fields show variations in speed and distribution of velocity values during the observing period. A clear correlation of velocity and ion distribution, as expected from momentum exchange with a stationary solar wind, could not be found in most cases. The flux of H2O(+) ion in the tail is calculated and shows variations from night to night. The mean production rate of 1.5 x 10 exp 27/s corresponds to only 18 percent of the expected value assuming photoionization to be the main ionization process.

  16. Laser Doppler measurement of relative blood velocity in the human optic nerve head

    SciTech Connect

    Riva, C.E.; Grunwald, J.E.; Sinclair, S.H.

    1982-02-01

    The Doppler shift frequency spectrum (DSFS) of laser light scattered from red blood cells (RBCs) moving in the microcirculation of the optic nerve head has been recorded in normal volunteers by means of a fundus camera laser Doppler velocimeter. The width of the DSFS, which varies in proportion to the speed of the RBCs, has been characterized by a parameter alpha. With the use of a model for the scattering of light by tissue and RBCs and for the RBC velocity distribution, values of alpha recorded at normal intraocular pressure (IOP) suggest that the RBCs that contribute to the Doppler signal are flowing in capillaries. The parameter alpha was found to vary markedly with the IOP and with the phase of the ocular pressure pulse at elevated IOP. The return of the speed of RBCs toward normal, which is observed after a step increase of IOP above normal and after a step decrease below normal, has been attributed to an autoregulatory response of the optic nerve circulation.

  17. Determination of left ventricular inflow by pulsed Doppler echocardiography: influence of mitral orifice area and blood velocity measurements.

    PubMed

    Tribouilloy, C; Slama, M; Shen, W F; Choquet, D; Delonca, J; Mertl, C; Dufosse, H; Lesbre, J P

    1991-01-01

    Pulsed Doppler echocardiography was performed in 30 patients to assess the influence of mitral orifice area and velocity on the determination of mitral stroke volume and inflow. Aortic forward stroke volume and outflow were measured at the centre of the aortic annulus, and compared with mitral flow measurements calculated by three methods. Both mitral stroke volume and inflow derived from an instantaneous velocity-area method showed an excellent correlation with aortic flow measurements. The other two methods, which determined mitral stroke volume and inflow based on a mean mitral valve area and diastolic velocity integral, significantly underestimated mitral flow measurements. This study indicates that the instantaneous velocity-area method offers a reliable means for quantitating left ventricular inflow.

  18. Method of radial velocities for the estimation of aircraft wake vortex parameters from data measured by coherent Doppler lidar.

    PubMed

    Smalikho, I N; Banakh, V A; Holzäpfel, F; Rahm, S

    2015-09-21

    The method of radial velocities (RV) is applied to estimate aircraft wake vortex parameters from measurements conducted with pulsed coherent Doppler lidar (PCDL). Operations of the Stream Line lidar and the 2-µm PCDL are simulated numerically to analyze the accuracy of the estimated wake vortex parameters with the RV method. The RV method is also used to estimate wake vortex trajectories and circulation from lidar measurements at Tomsk and Munich airports. The method of velocity envelopes and the RV method are compared employing data gathered with the 2-µm PCDL. The domain of applicability of the RV method is determined.

  19. Velocity surveys in a turbine stator annular-cascade facility using laser Doppler techniques. [flow measurement and flow characteristics

    NASA Technical Reports Server (NTRS)

    Goldman, L. J.; Seasholtz, R. G.; Mclallin, K. L.

    1976-01-01

    A laser Doppler velocimeter (LDV) was used to determine the flow conditions downstream of an annular cascade of stator blades operating at an exit critical velocity ratio of 0.87. Two modes of LDV operation (continuous scan and discrete point) were investigated. Conventional pressure probe measurements were also made for comparison with the LDV results. Biasing errors that occur in the LDV measurement of velocity components were also studied. In addition, the effect of pressure probe blockage on the flow conditions was determined with the LDV. Photographs and descriptions of the test equipment used are given.

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

    SciTech Connect

    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.

  1. Fiber-optic laser-Doppler anemometer microscope developed for the measurement of microvascular red cell velocity.

    PubMed

    Seki, J

    1990-11-01

    A fiber-optic laser-Doppler anemometer microscope (FLDAM) was developed and its applicability to the study of microvascular blood flow was examined by measuring red cell velocities in vivo and in vitro. The FLDAM consists of an intravital microscope equipped with a fringe-mode back-scatter LDA. A data processing method of the Doppler signal which used frequency averaging over the entire frequency range of the power spectrum was developed. Spatial resolution of the FLDAM varied from 17 to 200 microns with 50X to 5X objectives. In vitro experiments showed that the red cell velocity obtained by the FLDAM was equal to the mean flow velocity, within the accuracy of the measurements, for tube diameters from 35 to 100 microns, mean velocity from 0.7 to 17 mm/sec, and feed hematocrit of 20%, when 10X or 20X objectives were used. In vivo red cell velocity measurements conducted with the FLDAM in microvessels of rat mesentery with diameters from 6.5 to 49 microns showed that red cell velocities were about 1/1.6 times smaller than those obtained by the two-slit technique, which also suggests that the velocity obtained by the FLDAM corresponds to the mean flow velocity. This relationship was also established from theoretical considerations for the case where the FLDAM sampling volume covers the entire vessel cross section. Furthermore the frequency response of the FLDAM was established to be about 20 Hz, which was sufficient for measurement of pulsatile velocities in rat mesenteric microvessels.

  2. Measuring Solar Doppler Velocities in the He ii 30.38 nm Emission Using the EUV Variability Experiment (EVE)

    NASA Astrophysics Data System (ADS)

    Chamberlin, P. C.

    2016-08-01

    The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory has provided unprecedented measurements of the solar EUV irradiance at high temporal cadence with good spectral resolution and range since May 2010. The main purpose of EVE was to connect the Sun to the Earth by providing measurements of the EUV irradiance as a driver for space weather and Living With a Star studies, but after launch the instrument has demonstrated the significance of its measurements in contributing to studies looking at the sources of solar variability for pure solar physics purposes. This paper expands upon previous findings that EVE can in fact measure wavelength shifts during solar eruptive events and therefore provide Doppler velocities for plasma at all temperatures throughout the solar atmosphere from the chromosphere to hot flaring temperatures. This process is not straightforward as EVE was not designed or optimized for these types of measurements. In this paper we describe the many detailed instrumental characterizations needed to eliminate the optical effects in order to provide an absolute baseline for the Doppler shift studies. An example is given of a solar eruption on 7 September 2011 (SOL2011-09-07), associated with an X1.2 flare, where EVE Doppler analysis shows plasma ejected from the Sun in the He ii 30.38 nm emission at a velocity of almost 120 km s^{-1} along the line-of-sight.

  3. Measuring Solar Doppler Velocities in the He II 30.38 nm Emission Using the EUV Variability Experiment (EVE)

    NASA Technical Reports Server (NTRS)

    Chamberlin, Phillip Clyde

    2016-01-01

    The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory has provided unprecedented measurements of the solar EUV irradiance at high temporal cadence with good spectral resolution and range since May 2010. The main purpose of EVE was to connect the Sun to the Earth by providing measurements of the EUV irradianceas a driver for space weather and Living With a Star studies, but after launch the instrument has demonstrated the significance of its measurements in contributing to studies looking at the sources of solar variability for pure solar physics purposes. This paper expands upon previous findings that EVE can in fact measure wavelength shifts during solar eruptive events and therefore provide Doppler velocities for plasma at all temperatures throughout the solar atmosphere from the chromosphere to hot flaring temperatures. This process is not straightforward as EVE was not designed or optimized for these types of measurements. In this paper we describe the many detailed instrumental characterizations needed to eliminate the optical effects in order to provide an absolute baseline for the Doppler shift studies. An example is given of a solar eruption on 7 September 2011 (SOL2011-09-07), associated with an X1.2 flare, where EVE Doppler analysis shows plasma ejected from the Sun in the He II 30.38 nm emission at a velocity of almost 120 km s(exp -1) along the line-of-sight.

  4. Measuring Solar Doppler Velocities in the He II 30.38 nm Emission Using the EUV Variability Experiment (EVE)

    NASA Technical Reports Server (NTRS)

    Chamberlin, Phillip Clyde

    2016-01-01

    The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory has provided unprecedented measurements of the solar EUV irradiance at high temporal cadence with good spectral resolution and range since May 2010. The main purpose of EVE was to connect the Sun to the Earth by providing measurements of the EUV irradianceas a driver for space weather and Living With a Star studies, but after launch the instrument has demonstrated the significance of its measurements in contributing to studies looking at the sources of solar variability for pure solar physics purposes. This paper expands upon previous findings that EVE can in fact measure wavelength shifts during solar eruptive events and therefore provide Doppler velocities for plasma at all temperatures throughout the solar atmosphere from the chromosphere to hot flaring temperatures. This process is not straightforward as EVE was not designed or optimized for these types of measurements. In this paper we describe the many detailed instrumental characterizations needed to eliminate the optical effects in order to provide an absolute baseline for the Doppler shift studies. An example is given of a solar eruption on 7 September 2011 (SOL2011-09-07), associated with an X1.2 flare, where EVE Doppler analysis shows plasma ejected from the Sun in the He II 30.38 nm emission at a velocity of almost 120 km s(exp -1) along the line-of-sight.

  5. Vertical plasma drift velocities in the polarization jet observation by ground Doppler measurements and driftmeters on DMSP satellites

    NASA Astrophysics Data System (ADS)

    Khalipov, V. L.; Stepanov, A. E.; Kotova, G. A.; Kobyakova, S. E.; Bogdanov, V. V.; Kaisin, A. B.; Panchenko, V. A.

    2016-09-01

    Vertical and horizontal plasma drifts are investigated during the polarization jet (PJ) detection in the F2 ionospheric layer based on the Doppler measurements at the Yakutsk meridian chain of subauroral ionospheric stations. It is shown that the velocities of vertical and horizontal drifts are significantly higher than the background motion during PJ observation periods. The ionospheric plasma motion direction changes from upward to downward on the polar edge of the main ionospheric trough. Doppler measurements on the DPS-4 ionosondes are compared with the simultaneous measurements of the plasma drift on the DMSP satellites during their passage near the Yakutsk meridian. The two kinds of measurements are in good agreement with each other. During the magnetic storm of June 23, 2005, by measurements of the DMSP satellites, the velocities of upward plasma flows were 1.0-1.4 km/s at a satellite altitude of 850 km. In the ionospheric F region, this speed corresponds to 150 m/s. According to satellite measurements, the westward drift velocity reached 2.5 km/s. The development of the polarization jet in the ionosphere was accompanied by a tenfold decrease in the electron density in 15-30 min.

  6. A study of the geographic coverage properties of a satellite borne Doppler lidar wind velocity measuring system

    NASA Technical Reports Server (NTRS)

    Pate, T. H.

    1982-01-01

    Geographic coverage frequency and geographic shot density for a satellite borne Doppler lidar wind velocity measuring system are measured. The equations of motion of the light path on the ground were derived and a computer program devised to compute shot density and coverage frequency by latitude-longitude sections. The equations for the coverage boundaries were derived and a computer program developed to plot these boundaries, thus making it possible, after an application of a map coloring algorithm, to actually see the areas of multiple coverage. A theoretical cross-swath shot density function that gives close approximations in certain cases was also derived. This information should aid in the design of an efficient data-processing system for the Doppler lidar.

  7. Velocity variability in ultrasonic Doppler examinations.

    PubMed

    Hadlock, Jean; Beach, Kirk W

    2009-06-01

    Ultrasonic Doppler examination with spectral waveform has been used for the classification and surveillance of carotid artery stenosis for over 25 years. Progression/regression between examinations can be identified with 95% confidence if the velocity measurements change by more than two times the root mean square difference (RMSD) of the repeat measurement. Peak systolic velocity and end diastolic velocity measurements at a Doppler angle of 60 degrees were repeated in 47 carotid examinations. Measurement difference between sonographers and between instruments was tabulated. Root mean square difference was 11 cm/s (RMS%D = 11%) for systolic and 7 cm/s (RMS%D = 21%) for diastolic velocity measurements (excluding one severe stenosis case). Results for differences between sonographers and between instruments were similar to the overall results. In serial arterial studies using this Doppler velocimetry method, a difference exceeding 23 cm/s (21%) systolic, or 14 cm/s (42%) diastolic velocity indicates a significant (2 x RMSD) hemodynamic change.

  8. Resonant Doppler velocimeter. Ph.D. Thesis. Final Report, 1 Jul. 1974 - 31 Oct. 1979; [velocity, temperature, and pressure measurement

    NASA Technical Reports Server (NTRS)

    Zimmermann, M.

    1980-01-01

    A technique is presented for visualizing and quantitatively measuring velocity, temperature, and pressure by shining a single frequency laser beam into a gaseous flow which is seeded with an atomic species. The laser is tuned through the absorption frequencies of the seeded species and the absorption profile is detected by observing fluorescence as the atoms relax back to the ground state. The flow velocity is determined by observing the Doppler shift in the absorption frequency. Spectroscopic absorption line broadening mechanisms furnish information regarding the static temperature and pressure of the moving gas. Results of experiments conducted in the free stream and in the bow shock of a conical model mounted in a hypersonic wind tunnel indicate that the experimental uncertainties in the measurement of average values for the velocity, temperature and pressure of the flow are 0.1, 5 and 10 percent respectively.

  9. Accretion in young stars: measure of the stream velocity of TW Hya from the X-ray Doppler shift

    NASA Astrophysics Data System (ADS)

    Argiroffi, Costanza; Bonito, Rosaria; Orlando, Salvatore; Miceli, Marco; Peres, Giovanni

    2015-09-01

    High-resolution X-ray spectra are a unique tool to investigate the accretion process in young stars. In fact X-rays allow to investigate the accretion-shock region, where the infalling material is heated by strong shocks due to the impact with the denser stellar atmosphere. Here we show for the first time that it is possible to constrain the velocity of the accretion stream by measuring the Doppler shift of the emitted X-rays. To this aim we analyzed the deep Chandra/HETGS observation of the accreting young star TW Hya. We selected a sample of emission lines free from significant blends, fitted them with gaussian profiles, computed the radial velocity corresponding to each line, and averaged these velocities to obtain an accurate estimate of the global velocity of the X-ray emitting plasma. After correcting for Earth's motion, we compared this observed velocity with the photospheric radial velocity. In order to check this procedure we applied the same technique to other Chandra/HETGS spectra of single stars, whose X-rays are due only to coronal plasma. While spectra of pure coronal sources provide Doppler shifts in agreement with the known stellar radial velocity, we found that the X-ray spectrum of TW Hya is red-shifted by ~30-40 km/s with respect to the stellar photosphere. This proves that the X-ray emitting plasma on TW Hya is moving with respect to the stellar surface, definitively confirming that it originates in the accretion-shock region. The observed velocity suggests that the base of the accretion region is located at low latitudes of the stellar surface.

  10. Measuring caffeine-induced changes in middle cerebral artery blood velocity using transcranial Doppler in patients recovering from ischaemic stroke.

    PubMed

    Lunt, Michael J; Hanrahan, Andrew; Kerr, David; Jenkinson, Damian F

    2002-05-01

    Acute ingestion of caffeine is known to reduce cerebral blood flow in normal volunteers and in certain patient groups. There is no evidence that this causes problems in the normal population. However, there may be implications if a similar reduction occurs in patients recovering from an ischaemic stroke, in whom local blood flow has already been reduced. Transcranial Doppler provides a non-invasive method for measuring changes in middle cerebral artery (mca) blood velocity. A method for obtaining consistent. reliable measurements was developed and used in a double blind, randomized, crossover study on 20 patients (18 M, 2 F; mean age 70) recovering from ischaemic stroke in the mca territory. Middle cerebral artery blood velocity was measured bilaterally using transcranial Doppler before and after 250 mg caffeine (equivalent to about two cups of filter coffee) or matched placebo. Caffeine caused an average 12% reduction in blood velocity compared to placebo in the hemisphere affected by the stroke (95%c CI 8%-16%, p < 0.00001), and a 12% reduction in the non-affected hemisphere (95% CI 6%-18%, p < 0.001). The clinical implications are unclear at present, and imaging techniques will be required to establish whether caffeine does reduce flow to hypo-perfused regions.

  11. Blood flow velocity vector field reconstruction from dual-beam bidirectional Doppler OCT measurements in retinal veins

    PubMed Central

    Aschinger, Gerold C.; Schmetterer, Leopold; Doblhoff-Dier, Veronika; Leitgeb, Rainer A.; Garhöfer, Gerhard; Gröschl, Martin; Werkmeister, René M.

    2015-01-01

    In this paper, we demonstrate the possibility to reconstruct the actual blood flow velocity vector field in retinal microvessels from dual-beam bidirectional Doppler optical coherence tomography measurements. First, for a better understanding of measured phase patterns, several flow situations were simulated on the basis of the known dual beam measurement geometry. We were able to extract the vector field parameters that determine the measured phase pattern, allowing for the development of an algorithm to reconstruct the velocity vector field from measured phase data. In a next step, measurements were performed at a straight vessel section and at a venous convergence; the obtained phase data were evaluated by means of the new approach. For the straight vessel section, the reconstructed flow velocity vector field yielded a parabolic flow. For the venous convergence, however, the reconstructed vector field deviated from a parabolic profile, but was in very good accordance with the simulated vector field for the given vessel geometry. The proposed algorithm allows predictions of the velocity vector field. Moreover, the algorithm is also sensitive to directional changes of the flow velocity as small as <1°, thereby offering insight in the flow characteristics of the non-Newtonian fluid blood in microvessels. PMID:26137367

  12. A MAGNETIC CALIBRATION OF PHOTOSPHERIC DOPPLER VELOCITIES

    SciTech Connect

    Welsch, Brian T.; Fisher, George H.; Sun, Xudong

    2013-03-10

    The zero point of measured photospheric Doppler shifts is uncertain for at least two reasons: instrumental variations (from, e.g., thermal drifts); and the convective blueshift, a known correlation between intensity and upflows. Accurate knowledge of the zero point is, however, useful for (1) improving estimates of the Poynting flux of magnetic energy across the photosphere, and (2) constraining processes underlying flux cancellation, the mutual apparent loss of magnetic flux in closely spaced, opposite-polarity magnetogram features. We present a method to absolutely calibrate line-of-sight (LOS) velocities in solar active regions (ARs) near disk center using three successive vector magnetograms and one Dopplergram coincident with the central magnetogram. It exploits the fact that Doppler shifts measured along polarity inversion lines (PILs) of the LOS magnetic field determine one component of the velocity perpendicular to the magnetic field, and optimizes consistency between changes in LOS flux near PILs and the transport of transverse magnetic flux by LOS velocities, assuming that ideal electric fields govern the magnetic evolution. Previous calibrations fitted the center-to-limb variation of Doppler velocities, but this approach cannot, by itself, account for residual convective shifts at the limb. We apply our method to vector magnetograms of AR 11158, observed by the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory, and find clear evidence of offsets in the Doppler zero point in the range of 50-550 m s{sup -1}. In addition, we note that a simpler calibration can be determined from an LOS magnetogram and Dopplergram pair from the median Doppler velocity among all near-disk-center PIL pixels. We briefly discuss shortcomings in our initial implementation, and suggest ways to address these. In addition, as a step in our data reduction, we discuss the use of temporal continuity in the transverse magnetic field direction to correct apparently

  13. Nonmechanical scanning laser Doppler velocimeter for cross-sectional two-dimensional velocity measurement.

    PubMed

    Maru, Koichi; Hata, Takahiro

    2012-12-01

    We propose a two-dimensional scanning laser Doppler velocimeter (LDV) that does not require any moving mechanisms in its probe. In the proposed LDV, the measurement position can be scanned in two dimensions on a cross-sectional plane perpendicular to the direction of flow. The combination of the change in wavelength and change in port of the fiber array input to the probe is utilized for the scan. The experimental results using a sensor probe setup indicate that the measurement position can be scanned in two dimensions using the proposed method. The scanning range was estimated to be 39.7 mm in the axial direction over the wavelength range of 1536-1554 nm and 26.1 mm in the transverse direction for the use of 22 ports of the fiber array.

  14. A Microfluidics-based Pulpal Arteriole Blood Flow Phantom for Validation of Doppler Ultrasound Devices in Pulpal Blood Flow Velocity Measurement.

    PubMed

    Kim, Dohyun; Park, Sung-Ho

    2016-11-01

    Recently, Doppler ultrasound has been used for the measurement of pulpal blood flow in human teeth. However, the reliability of this method has not been verified. In this study, we developed a model to simulate arteriole blood flow within the dental pulp by using microfluidics. This arteriole simulator, or flow phantom, was used to determine the reliability of measurements obtained by using a Doppler ultrasound device. A microfluidic chip was fabricated by using the soft lithography technique, and blood-mimicking fluid was pumped through the channel by a microfluidic system. A Doppler ultrasound device was used for the measurement of flow velocity. The peak, mean, and minimal flow velocities obtained from the phantom and the Doppler ultrasound device were compared by using linear regression analysis and Pearson correlation coefficient. Bland-Altman analyses were performed to evaluate the velocity differences between the flow generated by the phantom and the flow measurements made with the Doppler ultrasound device. The microfluidic system was able to generate the flow profiles as intended, and the fluid flow could be monitored and controlled by the software program. There were excellent linear correlations between the peak, mean, and minimal flow velocities of the phantom and those of the Doppler ultrasound device (r = 0.94-0.996, P < .001). However, the velocities were overestimated by the Doppler ultrasound device. This phantom provides opportunities for research and education involving the Doppler ultrasound technique in dentistry. Although Doppler ultrasound can be an effective tool for the measurement of pulpal blood flow velocity, it is essential to validate and calibrate the device before clinical use. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  15. Vertical velocities within a Cirrus cloud from Doppler lidar and aircraft measurements during FIRE: Implications for particle growth

    NASA Technical Reports Server (NTRS)

    Gultepe, Ismail; Heymsfield, Andrew J.

    1990-01-01

    A large and comprehensive data set taken by the NOAA CO2 Doppler lidar, the NCAR King Air, and rawinsondes on 31 October 1986 during the FIRE (First ISCCP Regional Experiment) field program which took place in Wisconsin are presented. Vertical velocities are determined from the Doppler lidar data, and are compared with velocities derived from the aircraft microphysical data. The data are used for discussion of particle growth and dynamical processes operative within the cloud.

  16. Comparison of blood velocity measurements between ultrasound Doppler and accelerated phase-contrast MR angiography in small arteries with disturbed flow

    NASA Astrophysics Data System (ADS)

    Jiang, Jingfeng; Strother, Charles; Johnson, Kevin; Baker, Sara; Consigny, Dan; Wieben, Oliver; Zagzebski, James

    2011-03-01

    Ultrasound Doppler (UD) velocity measurements are commonly used to quantify blood flow velocities in vivo. The aim of our work was to investigate the accuracy of in vivo spectral Doppler measurements of velocity waveforms. Waveforms were derived from spectral Doppler signals and corrected for intrinsic spectral broadening errors by applying a previously published algorithm. The method was tested in a canine aneurysm model by determining velocities in small arteries (3-4 mm diameter) near the aneurysm where there was moderately disturbed flow. Doppler results were compared to velocity measurements in the same arteries acquired with a rapid volumetric phase contrast MR angiography technique named phase contrast vastly undersampled isotropic projection reconstruction magnetic resonance angiography (PC-VIPR MRA). After correcting for intrinsic spectral broadening, there was a high degree of correlation between velocities obtained by the real-time UD and the accelerated PC-MRA technique. The peak systolic velocity yielded a linear correlation coefficient of r = 0.83, end diastolic velocity resulted in r = 0.81, and temporally averaged mean velocity resulted in r = 0.76. The overall velocity waveforms obtained by the two techniques were also highly correlated (r = 0.89 ± 0.06). There were, however, only weak correlations for the pulsatility index (PI: 0.25) and resistive index (RI: 0.14) derived from the two techniques. Results demonstrate that to avoid overestimations of peak systolic velocities, the results for UD must be carefully corrected to compensate for errors caused by intrinsic spectral broadening.

  17. Comparison of Blood Velocity Measurements between Ultrasound Doppler and Accelerated Phase-Contrast MR Angiography in Small Arteries with Disturbed Flow

    PubMed Central

    Jiang, Jingfeng; Strother, Charles; Johnson, Kevin; Baker, Sara; Consigny, Dan; Wieben, Oliver; Zagzebski, James

    2011-01-01

    Ultrasound Doppler (UD) velocity measurements are commonly used to quantify blood flow velocities in vivo. The aim of our work was to investigate the accuracy of in vivo spectral Doppler measurements of velocity waveforms. Waveforms were derived from spectral Doppler signals and corrected for intrinsic spectral broadening errors by applying a previously published algorithm. The method was tested in a canine aneurysm model by determining velocities in small arteries (3-4 mm diameter) near the aneurysm where there was moderately disturbed flow. Doppler results were compared to velocity measurements in the same arteries acquired with a rapid volumetric phase contrast MR Angiography technique named PC-VIPR MRA. After correcting for intrinsic spectral broadening, there was a high degree of correlation between velocities obtained by the real-time UD and the accelerated PC-MRA technique. The peak systolic velocity yielded a linear correlation coefficient of r= 0.83; end diastolic velocity resulted in r= 0.81; and temporally-averaged mean velocity resulted in r= 0.76. The overall velocity waveforms obtained by the two techniques were also highly correlated (r=0.89 ± 0.06). There were, however, only weak correlations for the pulsatility index (PI; 0.25) and resistive index (RI; 0.14) derived from the two techniques. Results demonstrate that to avoid overestimations of peak systolic velocities, the results for UD must be carefully corrected to compensate for errors caused by intrinsic spectral broadening. PMID:21346280

  18. Modeling solar oscillation power spectra. II. Parametric model of spectral lines observed in Doppler-velocity measurements

    SciTech Connect

    Vorontsov, Sergei V.; Jefferies, Stuart M. E-mail: stuartj@ifa.hawaii.edu

    2013-11-20

    We describe a global parametric model for the observed power spectra of solar oscillations of intermediate and low degree. A physically motivated parameterization is used as a substitute for a direct description of mode excitation and damping as these mechanisms remain poorly understood. The model is targeted at the accurate fitting of power spectra coming from Doppler-velocity measurements and uses an adaptive response function that accounts for both the vertical and horizontal components of the velocity field on the solar surface and for possible instrumental and observational distortions. The model is continuous in frequency, can easily be adapted to intensity measurements, and extends naturally to the analysis of high-frequency pseudomodes (interference peaks at frequencies above the atmospheric acoustic cutoff).

  19. Doppler Velocity Estimation Based on Spectral Characteristics of M-Sequence-Modulated Signals in Ultrasonic Measurement for Moving Objects

    NASA Astrophysics Data System (ADS)

    Hirata, Shinnosuke; Hachiya, Hiroyuki

    2013-07-01

    Pulse compression using maximum-length sequence (M-sequence) can improve the signal-to-noise ratio (SNR) of the reflected echo and distance resolution in the pulse-echo method. In the case of a moving object, however, the echo is modulated due to the Doppler effect. The Doppler-shifted M-sequence-modulated signal cannot be correlated with the reference signal, which corresponds to the transmitted M-sequence-modulated signal. Therefore, Doppler velocity estimation before the correlation and cross correlation of the received signal with Doppler-shifted reference signals has been proposed. In this paper, the proposed Doppler velocity estimation based on spectral characteristics of cyclic M-sequence-modulated signals is described. Then, the Doppler velocity estimation is evaluated based on computer simulations. The Doppler velocity can be estimated from the Fourier-transformed spectral density of cycles of the M-sequence-modulated signal with high resolution even in noisy environments. According to the evaluation, furthermore, the cycle number and the number of carrier waves in 1 digit of the M-sequence-modulated signal should be decreased to improve the resolution and accuracy when the length of the transmitted signal is determined.

  20. Feasibility Study of Velocity and Temperature Measurements of an Arcjet Flow using Laser Resonance Doppler Velocimetric (LRDV) Technique

    NASA Technical Reports Server (NTRS)

    Rob, Mohammad A.

    1996-01-01

    Thermal Protection System (TPS) materials are used in space vehicles to shield from high heating environment encountered during their atmospheric reentry. Arcjet wind tunnels are used to simulate the flowfield encountered by the spacecrafts, and are used for testing TPS materials. How well these tests simulate the actual heating environment encountered by space vehicles depends on the characteristics of the simulated flow. The flow characterization requires the determination of temperature, concentration, and velocity of the various atomic and molecular species present in the flow. However, determining these parameters requires a complex set of both analytical and experimental procedures. The ability to properly simulate the flight environment is directly related to the accuracy with which these techniques can be used to define the arcjet Laser Resonance Doppler Velocimetric (LRDV) technique can be used to accurately determine the velocity and temperature of a gaseous species. In this technique, the medium is probed with a laser beam that is in resonance with an absorbing transition of the species. The absorption lineshape is Doppler-shifted due to the flow velocity of the species, and the frequency shift is detected as the variation in intensity of the fluorescence emitted by the species. Thus a measurement of the Doppler shift and the width of a spectral line can give both the temperature and the velocity of the flowfield. This summer, our project was to make a feasibility study to set up an experimental arrangement for the laser resonance Doppler velocimetric technique using a ring dye laser. Experiments required troubleshooting, cleaning, testing, and alignment of two lasers and several diagnostics instruments. All instruments and lasers necessary for the project worked well, but the output power of the broadband fundamental dye laser was limited to about 20 mW. This was quite low as compared to that necessary to obtain second harmonic oscillation at 327.49 nm

  1. Estimating mechanical blood trauma in a centrifugal blood pump: laser Doppler anemometer measurements of the mean velocity field.

    PubMed

    Pinotti, M; Paone, N

    1996-06-01

    A laser Doppler anemometer (LDA) was used to obtain the mean velocity and the Reynolds stress fields in the inner channels of a well-known centrifugal vaneless pump (Bio-pump). Effects of the excessive flow resistance against which an occlusive pump operates in some surgical situations, such as cardiopulmonary bypass, are illustrated. The velocity vector field obtained from LDA measurements reveals that the constraint-forced vortex provides pumping action in a restricted area in the core of the pump. In such situations, recirculating zones dominate the flow and consequently increase the damage to blood cells and raise the risk of thrombus formation in the device. Reynolds normal and shear stress fields were obtained in the entry flow for the channel formed by two rotating cones to illustrate the effects of flow disturbances on the potential for blood cell damage.

  2. Two-component laser Doppler anemometer for measurement of velocity and turbulent shear stress near prosthetic heart valves.

    PubMed

    Woo, Y R; Yoganathan, A P

    1985-01-01

    The velocity and turbulent shear stress measured in the immediate vicinity of prosthetic heart valves play a vital role in the design and evaluation of these devices. In the past hot wire/film and one-component laser Doppler anemometer (LDA) systems were used extensively to obtain these measurements. Hot wire/film anemometers, however, have some serious disadvantages, including the inability to measure the direction of the flow, the disturbance of the flow field caused by the probe, and the need for frequent calibration. One-component LDA systems do not have these problems, but they cannot measure turbulent shear stresses directly. Since these measurements are essential and are not available in the open literature, a two-component LDA system for measuring velocity and turbulent shear stress fields under pulsatile flow conditions was assembled under an FDA contract. The experimental methods used to create an in vitro data base of velocity and turbulent shear stress fields in the immediate vicinity of prosthetic heart valves of various designs in current clinical use are also discussed.

  3. Velocity measurement inside a motored internal combustion engine using three-component laser Doppler anemometry

    NASA Astrophysics Data System (ADS)

    Chan, V. S. S.; Turner, J. T.

    2000-10-01

    A three-component laser Doppler anemometry (LDA) system has been employed to investigate the structure of the flow inside the cylinder of a motored internal combustion engine. This model engine was reasonably representative of a typical, single cylinder, spark ignition engine although it did not permit firing. It was equipped with overhead valve gear and optical access was provided in the top and side walls of the cylinder. A principal objective was to study the influence of the inlet port design on the flow within the cylinder during the induction and compression strokes of the engine. Here, it can be noted that results obtained in an unfired engine are believed to be representative of the flow behaviour before combustion occurs in a fired engine (see P.O. Witze, Measurements of the spatial distribution and engine speed dependence of turbulent air motion in an i.c. engine, SAE Paper No. 770220, 1977; Witze, Sandia Laboratory Energy Report, SAND 79-8685, Sandia Laboratories, USA, 1979). Experimental data presented for an inclined inlet port configuration reveal the complex three-dimensional nature of the flow inside the model engine cylinder. Not surprisingly, the results also show that the inclined inlet port created flow conditions more favourable to mixing in the cylinder. Specifically, the inclined inlet flow was found to generate a region with a relatively high shear and strong recirculation zones in the cylinder. Inclining the inlet port also produced a more nearly homogeneous flow structure at top dead centre during the compression stroke. The paper identifies the special difficulties encountered in making the LDA measurements. The experimental findings are examined and the problems that arise in presenting time-varying three-dimensional data of this type are discussed. Finally, the future potential of this experimental approach is explored.

  4. Mathematical Models for Doppler Measurements

    NASA Technical Reports Server (NTRS)

    Lear, William M.

    1987-01-01

    Error analysis increases precision of navigation. Report presents improved mathematical models of analysis of Doppler measurements and measurement errors of spacecraft navigation. To take advantage of potential navigational accuracy of Doppler measurements, precise equations relate measured cycle count to position and velocity. Drifts and random variations in transmitter and receiver oscillator frequencies taken into account. Mathematical models also adapted to aircraft navigation, radar, sonar, lidar, and interferometry.

  5. A beam-scan type laser Doppler velocimeter for simultaneous and continuous measurement of velocity profiles

    NASA Astrophysics Data System (ADS)

    Hino, M.; Nadaoka, K.; Kobayashi, T.; Sato, Y.; Muramoto, T.

    A beam-scan-type LDV (SLV) with high spatial resolving power has been developed for the continuous measurement of nearly simultaneous velocity profiles in the cross sections of various flows. The SLV consists of a forward-scatter LDV and a beam-scan unit, using a reversed-scan method, capable of high-speed scanning of the measuring volume. An autofocusing device using an image sensor is employed to simplify the alignment of the receiving optics needed to match the transmitting optics. The SLV performance was validated by comparison of experimental results (for a wake flow of a circular cylinder, a reciprocally oscillatory flow, and a Karman vortex street flow) with flow visualization and computational results.

  6. Myocardial Tissue Doppler Velocity in Child Growth

    PubMed Central

    Choi, Sun-Ha; Kim, Nam Kyun; Jung, Jo Won; Choi, Jae Young

    2016-01-01

    Background In adults, tissue Doppler imaging (TDI) is a recommended component of routine echocardiography. However, TDI velocities are less accepted in pediatrics, due to their strong variability and age dependence in children. This study examines the distribution of myocardial tissue Doppler velocities in healthy children to assess the effect of age with cardiac growth on the various echocardiographic measurements. Methods Total 144 healthy children were enrolled in this study. They were recruited from the pediatric outpatient clinic for routine well-child visits. The statistical relationships between age and TDI values were analyzed. Also, the statistical relationships between body surface area (BSA) and TDI values, left ventricle end-diastolic dimension (LVEDD) and TDI values were analyzed. Also, we conducted multivariate analysis of cardiac growth parameters such as, age, BSA, LVEDD and TDI velocity data. Results All of the age, BSA, and LVEDD had positive correlations with deceleration time (DT), pressure half-time (PHT), peak early diastolic myocardial velocity, peak systolic myocardial velocity, and had negative correlations with peak late diastolic velocity (A) and the ratio of trans-mitral inflow velocity to early diastolic velocity of mitral annulus (E/E'). In the multivariate analysis, all of the age, BSA, and LVEDD had positive correlations with DT, PHT, and negative correlations with A and E/E'. Conclusion The cardiac growth parameters related alterations of E/E' may suggest that diastolic myocardial velocities are cardiac growth dependent, and diastolic function has positive correlation with cardiac growth in pediatric group. This cardiac growth related myocardial functional variation would be important for assessment of cardiac involvement either in healthy and sick child. PMID:27081443

  7. Phase/doppler spray analyzer for simultaneous measurements of drop size and velocity distributions

    NASA Technical Reports Server (NTRS)

    Bachalo, W. D.; Houser, M. J.

    1984-01-01

    Research was conducted on a laser light scatter detection method for measuring the size and velocity of spherical particles. The method is based upon the measurement of the interference fringe pattern produced by spheres passing through the intersection of two laser beams. A theoretical analysis of the method was carried out using the geometrical optics theory. The instrument response function was determined to be linear with drop size. Experimental verification of the theory was obtained by using monodisperse droplet streams. Several optical configurations were tested to identify all of the parametric effects upon the size measurements. Both off-axis forward-scatter and back-scatter light detection were utilized. Simulated spray environments and fuel spray nozzles were used in the evaluation of the method. The measurements of the monodisperse drops showed complete agreement with the theoretical predictions. The method was demonstrated to be independent of the beam intensity and extinction resulting from the surrounding drops. An instrument based on the concept has been developed.

  8. First Scientific Working Group Meeting of Airborne Doppler Lidar Wind Velocity Measurement Program

    NASA Technical Reports Server (NTRS)

    Kaufman, J. W. (Editor)

    1980-01-01

    The purpose of the first scientific working group meeting was fourfold: (1) to identify flight test options for engineering verification of the MSFC Doppler Lidar; (2) to identify flight test options for gathering data for scientific/technology applications; (3) to identify additional support equipment needed on the CV 990 aircraft for the flight tests; and (4) to identify postflight data processing and data sets requirements. The working group identified approximately ten flight options for gathering data on atmospheric dynamics processes, including turbulence, valley breezes, and thunderstorm cloud anvil and cold air outflow dynamics. These test options will be used as a basis for planning the fiscal year 1981 tests of the Doppler Lidar system.

  9. A NOVEL X-RAY IMAGING CRYSTAL SPECTROMETER FOR DOPPLER MEASUREMENTS OF ION TEMPERATURE AND PLASMA ROTATION VELOCITY PROFILES

    SciTech Connect

    Bitter, M; Hill, K W; Scott, S; Ince-Cushman, A; Reinke, M; Rice, J E; Beiersdorfer, P; Gu, M F; Lee, S G; Broennimann, C; Eikenberry, E F

    2008-06-06

    A new type of X-ray imaging crystal spectrometer has been implemented on Alcator CMod for Doppler measurements of ion temperature and plasma rotation velocity profiles. The instrument consists of two spherically bent (102)-quartz crystals with radii of curvature of 1444 and 1385 mm and four 'PILATUS II' detector modules. It records spectra of He-like argon from the entire, 72 cm high, elongated plasma cross-section and spectra of H-like argon from a 20 cm high, central region of the plasma, with a spatial resolution of 1.3 cm and a time resolution of less than 20 ms. The new spectrometer concept is also of interest for the diagnosis of burning plasmas on future machines. This paper presents recent experimental results from Aclator C-Mod and discusses challenges in X-ray spectroscopy for the diagnosis of fusion plasmas on future machines.

  10. Label-free in-vivo measurement of lymph flow velocity using Doppler optical coherence tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Blatter, Cedric; Meijer, Eelco F. J.; Nam, Ahhyun S.; Jones, Dennis; Padera, Timothy P.; Vakoc, Benjamin J.

    2016-03-01

    Alterations in lymphatic network function contribute to the lymphedema development, cancer progression and impairment in regional immune function. However, there are limited tools available to directly measure lymphatic vessel function and transport in vivo. Existing approaches such as fluorescence recovery after photo-bleaching (FRAP) require injection of exogenous labels which intrinsically alter the physiology of the local lymphatic network. A label-free approach to imaging lymph flow in vivo would provide direct and unaltered measurements of lymphatic vessel transport and could catalyze research in lymphatic biology. Here, we demonstrate and validate the use of Doppler optical coherence tomography (DOCT) to measure lymph flow in vivo at speeds as low as 50µm/s. Compared to blood, lymph is relatively acellular (under normal conditions), but contains similar soluble components to blood plasma. We demonstrate that the small but detectable scattering signal from lymph can be used to extract fluid velocity using a dedicated algorithm optimized for Doppler analysis in low signal-to-noise settings (0 to 6 dB typical). We demonstrate the accuracy of this technique by comparing DOCT to FRAP measurements, using an intralipid lymph proxy in microfluidic devices and in vivo in the mouse ear. Finally, we demonstrate the label free measurement of lymph speed in the hind-limb of mice with a temporal resolution of 0.25s that agree well with prior literature reports. We anticipate that DOCT can become a powerful new tool in preclinical lymphatic biology research—including the relationship between lymphatic function and metastasis formation—with the potential to later expand also to clinical settings.

  11. Measurements of the hole boring velocity from Doppler shifted harmonic emission from solid targets

    SciTech Connect

    Zepf, M.; Castro-Colin, M.; Chambers, D.; Preston, S.G.; Wark, J.S.; Zhang, J.; Danson, C.N.; Neely, D.; Norreys, P.A.; Dangor, A.E.; Dyson, A.; Lee, P.; Fews, A.P.; Gibbon, P.; Moustaizis, S.

    1996-09-01

    The fast ignitor scheme for inertial confinement fusion requires forward driving of the critical density surface by light pressure (hole boring) to allow energy deposition close to the dense fuel. The recession velocity of the critical density surface has been observed to be {ital v}/{ital c}=0.015 at an irradiance of 1.0{times}10{sup 19} Wcm{sup {minus}2} at a wavelength of 1.05 micron, in quantitative agreement with modeling. {copyright} {ital 1996 American Institute of Physics.}

  12. Cause and solution for false upstream boat velocities measured with a StreamPro acoustic doppler current profiler

    USGS Publications Warehouse

    Mueller, David S.; Rehmel, Mike S.; Wagner, Chad R.

    2007-01-01

    In 2003, Teledyne RD Instruments introduced the StreamPro acoustic Doppler current profiler which does not include an internal compass. During stationary moving-bed tests the StreamPro often tends to swim or kite from the end of the tether (the instrument rotates then moves laterally in the direction of the rotation). Because the StreamPro does not have an internal compass, it cannot account for the rotation. This rotation and lateral movement of the StreamPro on the end of the tether generates a false upstream velocity, which cannot be easily distinguished from a moving-bed bias velocity. A field test was completed to demonstrate that this rotation and lateral movement causes a false upstream boat velocity. The vector dot product of the boat velocity and the unit vector of the depth-averaged water velocity is shown to be an effective method to account for the effect of the rotation and lateral movement.

  13. Guidance for accurate and consistent tissue Doppler velocity measurement: comparison of echocardiographic methods using a simple vendor-independent method for local validation.

    PubMed

    Dhutia, Niti M; Zolgharni, Massoud; Willson, Keith; Cole, Graham; Nowbar, Alexandra N; Dawson, David; Zielke, Sayeh; Whelan, Carol; Newton, Jim; Mayet, Jamil; Manisty, Charlotte H; Francis, Darrel P

    2014-07-01

    Variability has been described between different echo machines and different modalities when measuring tissue velocities. We assessed the consistency of tissue velocity measurements across different modalities and different manufacturers in an in vitro model and in patients. Furthermore, we present freely available software tools to repeat these evaluations. We constructed a simple setup to generate reproducible motion and used it to compare velocities measured using three echocardiographic modalities: M-mode, speckle tracking, and tissue Doppler, with a straightforward, non-ultrasound, optical gold standard. In the clinical phase, 25 patients underwent M-mode, speckle tracking, and tissue Doppler measurements of s', e', and a' velocities. In vitro, the M-mode and speckle tracking velocities agreed with optical assessment. Of the three possible tissue Doppler measurement conventions (outer, middle, and inner edge) only the middle agreed with optical assessment (discrepancy -0.20 (95% CI -0.44 to 0.03) cm/s, P = 0.11, outer +5.19 (4.65 to 5.73) cm/s, P < 0.0001, inner -6.26 (-6.87 to -5.65) cm/s, P < 0.0001). A similar pattern occurred across all four studied manufacturers. M-mode was therefore chosen as the in vivo gold standard. Clinical measurements of s' velocities by speckle tracking and the middle line of the tissue Doppler showed concordance with M-mode, while the outer line overestimated significantly (+1.27(0.96 to 1.59) cm/s, P < 0.0001) and the inner line underestimated (-1.82 (-2.11 to -1.52) cm/s, P < 0.0001). Echocardiographic velocity measurements can be more consistent than previously suspected. The statistically modal velocity, found at the centre of the spectral pulsed wave tissue Doppler envelope, most closely represents true tissue velocity. This article includes downloadable, vendor-independent software enabling calibration of echocardiographic machines using a simple, inexpensive in vitro setup. Published on behalf of the European Society of

  14. Noninvasive Method for Measuring Local Pulse Wave Velocity by Dual Pulse Wave Doppler: In Vitro and In Vivo Studies

    PubMed Central

    Wang, Zhen; Yang, Yong; Yuan, Li-jun; Liu, Jie; Duan, Yun-you; Cao, Tie-sheng

    2015-01-01

    Objectives To evaluate the validity and reproducibility of a noninvasive dual pulse wave Doppler (DPWD) method, which involves simultaneous recording of flow velocity of two independent sample volumes with a measurable distance, for measuring the local arterial pulse wave velocity (PWV) through in vitro and in vivo studies. Methods The DPWD mode of Hitachi HI Vision Preirus ultrasound system with a 5–13MHz transducer was used. An in vitro model was designed to compare the PWV of a homogeneous rubber tubing with the local PWV of its middle part measured by DPWD method. In the in vivo study, local PWV of 45 hypertensive patients (25 male, 49.8±3.1 years) and 45 matched healthy subjects (25 male, 49.3±3.0 years) were investigated at the left common carotid artery (LCCA) by DPWD method. Results In the in vitro study, the local PWV measured by DPWP method and the PWV of the homogeneous rubber tubing did not show statistical difference (5.16 ± 0.28 m/s vs 5.03 ± 0.15 m/s, p = 0.075). The coefficient of variation (CV) of the intra- and inter- measurements for local PWV were 3.46% and 4.96%, for the PWV of the homogeneous rubber tubing were 0.99% and 1.98%. In the in vivo study, a significantly higher local PWV of LCCA was found in the hypertensive patients as compared to that in healthy subjects (6.29±1.04m/s vs. 5.31±0.72m/s, P = 0.019). The CV of the intra- and inter- measurements in hypertensive patients were 2.22% and 3.94%, in healthy subjects were 2.07% and 4.14%. Conclusions This study demonstrated the feasibility of the noninvasive DPWD method to determine the local PWV, which was accurate and reproducible not only in vitro but also in vivo studies. This noninvasive echocardiographic method may be illuminating to clinical use. PMID:25786124

  15. Transcranial measurement of blood velocities in the basal cerebral arteries using pulsed Doppler ultrasound: a method of assessing the Circle of Willis.

    PubMed

    Padayachee, T S; Kirkham, F J; Lewis, R R; Gillard, J; Hutchinson, M C; Gosling, R G

    1986-01-01

    Transcranial pulsed Doppler ultrasound and spectral analysis were used for detection of blood velocities in the basal cerebral arteries. The Doppler transducer was placed superior to the zygomatic arch and during insonation of the middle cerebral artery care was taken to obtain maximum Doppler-shift frequency signals since this allowed a small angle between the ultrasound beam and this artery. Doppler signals were obtained from the middle, anterior, and posterior cerebral arteries in 20 volunteers with the average depth of the Doppler gate at 4.9 (4.6-5.2 cm), 5.2 (4.9-5.4 cm), and 6.3 cm (6.0-6.9 cm), respectively. These measurements were in agreement with those obtained for 15 cadaver studies, in whom the distance from the proposed site of the Doppler transducer to each basal cerebral artery was measured as 4.7 +/- 0.6, 5.3 +/- 0.5, and 5.9 +/- 0.9 cm, respectively. The reproducibility of middle cerebral artery blood velocity values was tested in seven subjects and showed a variation of not more than 8% in any individual. The method was used in combination with common carotid compression to assess four patients who had occlusive extracranial carotid disease; in three the disease was more severe on one side and reversal of blood flow in the proximal ipsilateral anterior cerebral artery was demonstrated, consistent with cross flow from the contralateral side via the anterior communicating artery of the Circle of Willis. In the fourth patient augmentation of posterior cerebral artery blood velocities during common carotid compression indicated the major collateral source was from the vertebrobasilar system.

  16. Effects of transducer, velocity, Doppler angle, and instrument settings on the accuracy of color Doppler ultrasound.

    PubMed

    Stewart, S F

    2001-04-01

    The accuracy of a commercial color Doppler ultrasound (US) system was assessed in vitro using a rotating torus phantom. The phantom consisted of a thin rubber tube filled with a blood-mimicking fluid, joined at the ends to form a torus. The torus was mounted on a disk suspended in water, and rotated at constant speeds by a motor. The torus fluid was shown in a previous study to rotate as a solid body, so that the actual fluid velocity was dependent only on the motor speed and sample volume radius. The fluid velocity could, thus, be easily compared to the color Doppler-derived velocity. The effects of instrument settings, velocity and the Doppler angle was assessed in four transducers: a 2.0-MHz phased-array transducer designed for cardiac use, a 4.0-MHz curved-array transducer designed for general thoracic use, and two linear transducers designed for vascular use (one 4.0 MHz and one 6.0 MHz). The color Doppler accuracy was found to be significantly dependent on the transducer used, the pulse-repetition frequency and wall-filter frequency, the actual fluid velocity and the Doppler angle (p < 0.001 by analysis of variance). In particular, the phased array and curved array were observed to be significantly more accurate than the two linear arrays. The torus phantom was found to provide a sensitive measure of color Doppler accuracy. Clinicians need to be aware of these effects when performing color Doppler US exams.

  17. Doppler Lidar Vertical Velocity Statistics Value-Added Product

    SciTech Connect

    Newsom, R. K.; Sivaraman, C.; Shippert, T. R.; Riihimaki, L. D.

    2015-07-01

    Accurate height-resolved measurements of higher-order statistical moments of vertical velocity fluctuations are crucial for improved understanding of turbulent mixing and diffusion, convective initiation, and cloud life cycles. The Atmospheric Radiation Measurement (ARM) Climate Research Facility operates coherent Doppler lidar systems at several sites around the globe. These instruments provide measurements of clear-air vertical velocity profiles in the lower troposphere with a nominal temporal resolution of 1 sec and height resolution of 30 m. The purpose of the Doppler lidar vertical velocity statistics (DLWSTATS) value-added product (VAP) is to produce height- and time-resolved estimates of vertical velocity variance, skewness, and kurtosis from these raw measurements. The VAP also produces estimates of cloud properties, including cloud-base height (CBH), cloud frequency, cloud-base vertical velocity, and cloud-base updraft fraction.

  18. Measurement of velocities with an acoustic velocity meter, one side-looking and two upward-looking acoustic Doppler current profilers in the Chicago Sanitary and Ship Canal, Romeoville, Illinois

    USGS Publications Warehouse

    Oberg, Kevin A.; Duncker, James J.

    1999-01-01

    In 1998, a prototype 300 kHz, side-looking Acoustic Doppler Current Profiler (ADCP) was deployed in the Chicago Sanitary and Ship Canal (CSSC) at Romeoville, Illinois. Additionally, two upward-looking ADCP's were deployed in the same acoustic path as the side-looking ADCP and in the reach defined by the upstream and downstream acoustic velocity meter (AVM) paths. All three ADCP's were synchronized to the AVM clock at the gaging station so that data were sampled simultaneously. The three ADCP's were deployed for six weeks measuring flow velocities from 0.0 to 2.5 ft/s. Velocities measured by each ADCP were compared to AVM path velocities and to velocities measured by the other ADCP's.

  19. The effects of probe placement on measured flow velocity in transcranial Doppler ultrasound imaging in-vitro and in-vivo experiments

    NASA Astrophysics Data System (ADS)

    de Jong, Daan L. K.; Meel-van den Abeelen, Aisha S. S.; Lagro, Joep; Claassen, Jurgen A. H. R.; Slump, Cornelis H.

    2014-03-01

    The measurement of the blood flow in the middle cerebral artery (MCA) using transcranial Doppler ultrasound (US) imaging is clinically relevant for the study of cerebral autoregulation. Especially in the aging population, impairement of the autoregulation may coincide or relate to loss of perfusion and consequently loss of brain function. The cerebral autoregulation can be assessed by relating the blood pressure to the blood flow in the brain. Doppler US is a widely used, non-invasive method to measure the blood flow in the MCA. However, Doppler flow imaging is known to produce results that are dependent of the operator. The angle of the probe insonation with respect to the centerline of the blood vessel is a well known factor for output variability. In patients also the skull must be traversed and the MCA must be detected, influencing the US signal intensity. In this contribution we report two studies. We describe first an in-vitro setup to study the Doppler flow in a situation where the ground truth is known. Secondly, we report on a study with healthy volunteers where the effects of small probe displacements on the flow velocity signals are investigated. For the latter purpose, a special probe holder was designed to control the experiment.

  20. Simultaneous three-dimensional velocity and mixing measurements by use of laser Doppler velocimetry and fluorescence probes in a water tunnel

    NASA Technical Reports Server (NTRS)

    Neuhart, Dan H.; Wing, David J.; Henderson, Uleses C., Jr.

    1994-01-01

    A water tunnel investigation was conducted to demonstrate the capabilities of a laser-based instrument that can measure velocity and fluorescence intensity simultaneously. Fluorescence intensity of an excited fluorescent dye is directly related to concentration level and is used to indicate the extent of mixing in flow. This instrument is a three-dimensional laser Doppler velocimeter (LDV) in combination with a fluorometer for measuring fluorescence intensity variations. This capability allows simultaneous flow measurements of the three orthogonal velocity components and mixing within the same region. Two different flows which were generated by two models were studied: a generic nonaxisymmetric nozzle propulsion simulation model with an auxiliary internal water source that generated a jet flow and an axisymmetric forebody model with a circular sector strake that generated a vortex flow. The off-body flow fields around these models were investigated in the Langley 16- by 24-Inch Water Tunnel. The experimental results were used to calculate 17 quantities that included mean and fluctuating velocities, Reynolds stresses, mean and fluctuating dye fluorescence intensities (proportional to concentration), and fluctuating velocity and dye concentration correlations. An uncertainty analysis was performed to establish confidence levels in the experimental results. In general, uncertainties in mean velocities varied between 1 and 7 percent of free-stream velocity; uncertainties in fluctuating velocities varied between 1 and 5 percent of reference values. The results show characteristics that are unique to each type of flow.

  1. Velocity profile measurement of the Taylor vortex flow of a magnetic fluid using the ultrasonic Doppler method

    NASA Astrophysics Data System (ADS)

    Kikura, H.; Takeda, Y.; Durst, F.

    A successful application of the ultrasound velocity profile (UVP) measuring technique to investigations on the flow of magnetic fluids is described. The flow structure of a magnetic fluid in a concentric annular geometry with a large aspect ratio of 20 and a radius ratio of 0.65 was investigated for a inner cylinder rotation. Axial velocity distributions were measured using the UVP measuring technique. A non-uniform magnetic field was applied to the flow field using a permanent magnet located on the outside of the cylinders. The energy spectral density was calculated from the periodic axial velocity profiles. The critical Reynolds number was obtained for various magnetic field strengths, and the apparent viscosity caused by the applied magnetic field was estimated. The UVP method was demonstrated to provide useful information on the structure of Taylor vortex flow in a magnetic fluid.

  2. [Effective measurement of coronary flow velocity reserve (CFVR) with transthoracic Doppler echocardiography (TTDE) for plasma cell leukemia with hyperviscosity syndrome].

    PubMed

    Oka, Satoko; Yokote, Taiji; Akioka, Toshikazu; Hara, Satoshi; Yamano, Takeshi; Okabe, Taichi; Arishiro, Kumiko; Hoshiga, Masaaki; Shimizu, Akira; Tsuji, Motomu; Hanafusa, Toshiaki

    2006-01-01

    A 67-year-old woman was admitted with impaired general performance, suffering from fatigue, chest oppression on exertion, and paresthesia of the finger trips. The laboratory findings showed increased white blood cells with abnormal cells, and serum immunofixation test showed monoclonal IgM kappa paraprotein. On flow cytometric immunophenotyping with CD38 gating, most of the abnormal cells expressed surface CD20, CD138, cytoplasmic IgM, but neither surface CD56 nor surface IgM. Immunohistochemical staining of abnormal cells was positive for surface CD38, surface CD20 and cytoplasmic IgM. The final diagnosis was plasma cell leukemia IgM kappa type. Electrocardiography (ECG) on admission showed ST depression in II, III, aV(F), V4, V5, and V6. Coronary angiography (CAG) is invasive and difficult for patients with renal failure, therefore the patient underwent transthoracic Doppler echocardiography (TTDE), which revealed reduced coronary flow velocity reserve (CFVR). Two courses of VAD therapy were administered, then the condition improved, the serum IgM level decreased, abnormal cells were decreased in peripheral blood and bone marrow aspirates, and the creatinine levels improved. With the return of normal ECG findings and improved CFVR, the abnormal ECG and reduction in CFVR was thought to be associated with the hyperviscosity syndrome in PCL. Noninvasive assessment of CFVR by TTDE is significantly useful for the patients who have renal failure and need chemotherapy.

  3. Laser Doppler velocimeter measurements of boundary layer velocity and turbulent intensities in Mach 2.5 flow

    NASA Technical Reports Server (NTRS)

    Sewell, Jesse; Chew, Larry

    1994-01-01

    In recent years, the interest in developing a high-speed civil transport has increased. This has led to an increase in research activity on compressible supersonic flows, in particular the boundary layer. The structure of subsonic boundary layers has been extensively documented using conditional sampling techniques which exploit the knowledge of both u and v velocities. Researchers using these techniques have been able to explore some of the complex three-dimensional motions which are responsible for Reynolds stress production and transport in the boundary layer. As interest in turbulent structure has grown to include supersonic flows, a need for simultaneous multicomponent velocity measurements in these flows has developed. The success of conditional analysis in determining the characteristics of coherent motions and structures in the boundary layer relies on accurate, simultaneous measurement of two instantaneous velocity components.

  4. Measurements in the Turbulent Boundary Layer at Constant Pressure in Subsonic and Supersonic Flow. Part 2: Laser-Doppler Velocity Measurements

    NASA Technical Reports Server (NTRS)

    Dimotakis, P. E.; Collins, D. J.; Lang, D. B.

    1979-01-01

    A description of both the mean and the fluctuating components of the flow, and of the Reynolds stress as observed using a dual forward scattering laser-Doppler velocimeter is presented. A detailed description of the instrument and of the data analysis techniques were included in order to fully document the data. A detailed comparison was made between the laser-Doppler results and those presented in Part 1, and an assessment was made of the ability of the laser-Doppler velocimeter to measure the details of the flows involved.

  5. Effects of Isoflurane on Coronary Blood Flow Velocity in Young, Old, and ApoE−/− Mice Measured by Doppler Ultrasound

    PubMed Central

    Hartley, Craig J.; Reddy, Anilkumar K.; Madala, Sridhar; Michael, Lloyd H.; Entman, Mark L.; Taffet, George E.

    2007-01-01

    The commonly used anesthetic agent, isoflurane (ISO), is a potent coronary vasodilator which could potentially be used in the assessment of coronary reserve, but its effects on coronary blood flow in mice are unknown. Coronary reserve is reduced by age, coronary artery disease, and other cardiac pathologies in man, and some of these conditions can now be modeled in mice. Accordingly, we used Doppler ultrasound to measure coronary flow velocity in mice anesthetized at low (1%) and at high (2.5%) levels of ISO to generate baseline (B) and elevated hyperemic (H) coronary flows respectively. A 20 MHz Doppler probe was mounted in a micromanipulator and pointed transthoracically toward the origin of the left main coronary arteries of 10 6-wk (Y), 10 2-yr (O), and 20 2-yr apolipoprotein-E null (ApoE−/−) atherosclerotic (A) mice. In each mouse we measured (B) and (H) peak diastolic velocities. B was 35.4 +/− 1.4 cm/s (Y), 24.8 +/− 1.6 (O), and 51.7 +/− 6.4 (A); H was 83.5 +/− 1.3 (Y), 86.5 +/− 1.9 (O), and 120 +/− 16.9 (A); and H/B was 2.4 +/− 0.1 (Y), 3.6 +/− 0.2 (O), and 2.5 +/− 0.2 (A). The differences in baseline velocities and H/B between O and Y and between A and O were significant (P < 0.01), while the differences in hyperemic velocities were not (P > 0.05). H/B was higher in old mice due to decreased baseline flow rather than increased hyperemic flow velocity. In contrast ApoE−/− mice have increased baseline and hyperemic velocities perhaps due to coronary lesions. The differences in baseline velocities between young and old mice could be due to age-related changes in basal metabolism or to differential sensitivity to isoflurane. We conclude that Doppler ultrasound combined with coronary vasodilation via isoflurane could provide a convenient and noninvasive method to estimate coronary reserve in mice, but also that care must be taken when assessing coronary flow in mice under isoflurane anesthesia because of its potent coronary vasodilator

  6. Comparison of wind velocity in thunderstorms determined from measurements by a ground-based Doppler radar and an F-106B airplane

    NASA Technical Reports Server (NTRS)

    Usry, J. W.; Dunham, R. E., Jr.; Lee, J. T.

    1985-01-01

    As a part of the NASA Storm Hazards Program, the wind velocity in several thunderstorms was measured by an F-106B instrumented airplane and a ground-based Doppler radar. The results of five airplane penetrations of two storms in 1980 and six penetrations of one storm in 1981 are given. Comparisons were made between the radial wind velocity components measured by the radar and the airplane. The correlation coefficients for the 1980 data and part of the 1981 data were 0.88 and 0.78, respectively. It is suggested that larger values for these coefficients may be obtained by improving the experimental technique and in particular by slaving the radar to track the airplane during such tests.

  7. Some experiments in swirling flows: Detailed velocity measurements of a vortex breakdown using a laser Doppler anemometer. Ph.D. Thesis - Cornell Univ. Final Report

    NASA Technical Reports Server (NTRS)

    Faler, J. H.

    1976-01-01

    The results of an experimental study of spiraling flows in a slightly diverging, circular duct are reported. Seven types of flow disturbances were observed. In addition to the spiral and axisymmetric vortex breakdowns and the double helix mode, four other forms were identified and are reported. The type and axial location of the disturbance depended on the Reynolds and circulation numbers of the flow. Detailed velocity measurements were made by using a laser Doppler anemometer. Measurements made far upstream of any disturbance showed that the introduction of swirl resulted in the formation of a high axial velocity jet centered around the vortex center. A mapping of the velocity field of a so-called axisymmetric breakdown, formed at a Reynolds number of 2560, revealed that the recirculation zone is a two-celled structure, with four stagnation points on the vortex axis marking the axial extremes of the concentric cells. The dominant feature of the flow inside the bubble was the strong, periodic velocity fluctuations. Existing theoretical models do not predict the two-celled structure and the temporal velocity fluctuations that were observed.

  8. Self-mixing detection of backscattered radiation in a single-mode erbium fibre laser for Doppler spectroscopy and velocity measurements

    SciTech Connect

    Dmitriev, A K; Konovalov, A N; Ul'yanov, V A

    2014-04-28

    We report an experimental study of the self-mixing effect in a single-mode multifrequency erbium fibre laser when radiation backscattered from an external moving object arrives at its cavity. To eliminate resulting chaotic pulsations in the laser, we have proposed a technique for suppressing backscattered radiation through the use of multimode fibre for radiation delivery. The multifrequency operation of the laser has been shown to lead to strong fluctuations of the amplitude of the Doppler signal and a nonmonotonic variation of the amplitude with distance to the scattering object. In spite of these features, the self-mixing signal was detected with a high signal-to-noise ratio (above 10{sup 2}) when the radiation was scattered by a rotating disc, and the Doppler frequency shift, evaluated as the centroid of its spectrum, had high stability (0.15%) and linearity relative to the rotation rate. We conclude that the self-mixing effect in this type of fibre laser can be used for measuring the velocity of scattering objects and in Doppler spectroscopy for monitoring the laser evaporation of materials and biological tissues. (control of laser radiation parameters)

  9. Vertical Velocity Statistics Derived from the New ARM Doppler Lidars

    NASA Astrophysics Data System (ADS)

    Newsom, R. K.

    2012-12-01

    Accurate height-resolved measurements of higher-order statistical moments of vertical velocity fluctuations are crucial for improved understanding of convective initiation and the refinement of turbulence and surface layer parameterization schemes used in large eddy simulations and cloud resolving models. In October 2010 the US Department of Energy's Atmospheric Radiation Measurement (ARM) program added three coherent Doppler lidars to it's extensive suite of ground based instrumentation in order to fill a long-standing observational gap within the ARM program, i.e. measurement of clear-air vertical velocity profiles through the depth of the atmospheric boundary layer. The ARM Doppler lidars operate in the near-IR (1.5 microns) and are sensitive to backscatter from aerosol. The line-of-sight component of air velocity is obtained by measuring the Doppler shift induced by the motion of the aerosols. Vertical velocity measurements are thus obtained when the lidar beam is directed vertically. Under moderate to high signal-to-noise conditions the instruments are capable of making measurements with a precision of better than 10 cm s-1. The new systems have been deployed at ARM's Southern Great Plains (SGP) site in north central Oklahoma, the Tropical Western Pacific site in Darwin, Australia (TWP-Darwin), and the first ARM mobile facility. All three systems have proven to be highly reliable with nearly continuous operation since their initial deployments. The lidars are configured to spend the majority of their time in a vertical staring mode. The resulting datastreams consist of high spatial and temporal resolution, clear-air vertical velocity observations spanning multiple years. In this study, we present vertical velocity statistics derived from more than 18 months of 1 s resolution measurements taken at the two fixed sites, SGP and TWP-Darwin. The vertical structure of variance, skewness and kurtosis, as well as the diurnal and seasonal variability are compared and

  10. Reducing Spaceborne-Doppler-Radar Rainfall-Velocity Error

    NASA Technical Reports Server (NTRS)

    Tanelli, Simone; Im, Eastwood; Durden, Stephen L.

    2008-01-01

    A combined frequency-time (CFT) spectral moment estimation technique has been devised for calculating rainfall velocity from measurement data acquired by a nadir-looking spaceborne Doppler weather radar system. Prior spectral moment estimation techniques used for this purpose are based partly on the assumption that the radar resolution volume is uniformly filled with rainfall. The assumption is unrealistic in general but introduces negligible error in application to airborne radar systems. However, for spaceborne systems, the combination of this assumption and inhomogeneities in rainfall [denoted non-uniform beam filling (NUBF)] can result in velocity measurement errors of several meters per second. The present CFT spectral moment estimation technique includes coherent processing of a series of Doppler spectra generated in a standard manner from data over measurement volumes that are partially overlapping in the along-track direction. Performance simulation of this technique using high-resolution data from an airborne rain-mapping radar shows that a spaceborne Ku-band Doppler radar operating at signal-to-noise ratios greater than 10 dB can achieve root-mean-square accuracy between 0.5 and 0.6 m/s in vertical-velocity estimates.

  11. Ground and space based cloud-top wind velocities using CFHT/ESPaDOnS (Doppler velocimetry) and VEx/VIRTIS (cloud tracking) coordinated measurements

    NASA Astrophysics Data System (ADS)

    Machado, Pedro; Widemann, Thomas; Peralta, Javier; Gonçalves, Rúben; Donati, Jean-François; Luz, David

    2016-04-01

    We will present wind velocity results based in the measurements of the horizontal wind field at the cloud top level of the atmosphere of Venus, near 70 km altitude. Our aim is contribute to the characterisation of the zonal and meridional wind latitudinal profiles on hour and day-timescales. This will be done by tracking Doppler shift of solar and CO2 lines over the dayside hemisphere in coordination with ESA's Venus Express orbiter. Our observations measured winds at cloud tops at latitudes 60°S-60°N, while Vex/VIRTIS privileged southern latitudes poleward of 45°S. This coordination effort intended to provide a combined monitoring of short-term changes of wind amplitude and directions with extensive spatial coverage. We present results based on inter comparison of ground-based Doppler velocimetry of cloud-top winds and cloud tracking measurements from the Venus Express spacecraft. Doppler wind velocimetry obtained with the 3.60 m Canada-France-Hawaii telescope (CFHT) and the Visible Spectrograph ESPaDOnS in April 2014 consisted of high-resolution spectra of Fraunhofer lines in the visible range (0.37-1.05 μm) to measure the wind velocity using the Doppler shift of solar radiation scattered by cloud top particles in the observer's direction. The complete optical spectrum was collected at a phase angle Φ = (76 ± 0.3)°, at a resolution of about 80000. Both ground-based and Venus Express measurements show considerable day-to-day variability revealing wave propagation and angular momentum transport in latitude which needs to be carefully assessed. ESPaDOnS and the sequential technique of visible Doppler velocimetry has proven a reference technique to measure instantaneous winds. These measurements are necessary to help validating Global Circulation Models (GCMs), to extend the temporal coverage of available datasets. The ground-based observations in the base of this project are critical in their complementarity with Venus Express, which was recently

  12. Tangential velocity measurement using interferometric MTI radar

    SciTech Connect

    Doerry, Armin W.; Mileshosky, Brian P.; Bickel, Douglas L.

    2006-01-03

    Radar systems use time delay measurements between a transmitted signal and its echo to calculate range to a target. Ranges that change with time cause a Doppler offset in phase and frequency of the echo. Consequently, the closing velocity between target and radar can be measured by measuring the Doppler offset of the echo. The closing velocity is also known as radial velocity, or line-of-sight velocity. Doppler frequency is measured in a pulse-Doppler radar as a linear phase shift over a set of radar pulses during some Coherent Processing Interval (CPI). An Interferometric Moving Target Indicator (MTI) radar can be used to measure the tangential velocity component of a moving target. Multiple baselines, along with the conventional radial velocity measurement, allow estimating the true 3-D velocity of a target.

  13. Is Doppler tissue velocity during early left ventricular filling preload independent?

    NASA Technical Reports Server (NTRS)

    Yalcin, F.; Kaftan, A.; Muderrisoglu, H.; Korkmaz, M. E.; Flachskampf, F.; Garcia, M.; Thomas, J. D.

    2002-01-01

    BACKGROUND: Transmitral Doppler flow indices are used to evaluate diastolic function. Recently, velocities measured by Doppler tissue imaging have been used as an index of left ventricular relaxation. OBJECTIVE: To determine whether Doppler tissue velocities are influenced by alterations in preload. METHODS: Left ventricular preload was altered in 17 patients (all men, mean (SD) age, 49 (8) years) during echocardiographic measurements of left ventricular end diastolic volume, maximum left atrial area, peak early Doppler filling velocity, and left ventricular myocardial velocities during early filling. Preload altering manoeuvres included Trendelenberg (stage 1), reverse Trendelenberg (stage 2), and amyl nitrate (stage 3). Systolic blood pressure was measured at each stage. RESULTS: In comparison with baseline, left ventricular end diastolic volume (p = 0.001), left atrial area (p = 0.003), peak early mitral Doppler filling velocity (p = 0.01), and systolic blood pressures (p = 0.001) were all changed by preload altering manoeuvres. Only left ventricular myocardial velocity during early filling remained unchanged by these manoeuvres. CONCLUSIONS: In contrast to standard transmitral Doppler filling indices, Doppler tissue early diastolic velocities are not significantly affected by physiological manoeuvres that alter preload. Thus Doppler tissue velocities during early left ventricular diastole may provide a better index of diastolic function in cardiac patients by providing a preload independent assessment of left ventricular filling.

  14. Is Doppler tissue velocity during early left ventricular filling preload independent?

    NASA Technical Reports Server (NTRS)

    Yalcin, F.; Kaftan, A.; Muderrisoglu, H.; Korkmaz, M. E.; Flachskampf, F.; Garcia, M.; Thomas, J. D.

    2002-01-01

    BACKGROUND: Transmitral Doppler flow indices are used to evaluate diastolic function. Recently, velocities measured by Doppler tissue imaging have been used as an index of left ventricular relaxation. OBJECTIVE: To determine whether Doppler tissue velocities are influenced by alterations in preload. METHODS: Left ventricular preload was altered in 17 patients (all men, mean (SD) age, 49 (8) years) during echocardiographic measurements of left ventricular end diastolic volume, maximum left atrial area, peak early Doppler filling velocity, and left ventricular myocardial velocities during early filling. Preload altering manoeuvres included Trendelenberg (stage 1), reverse Trendelenberg (stage 2), and amyl nitrate (stage 3). Systolic blood pressure was measured at each stage. RESULTS: In comparison with baseline, left ventricular end diastolic volume (p = 0.001), left atrial area (p = 0.003), peak early mitral Doppler filling velocity (p = 0.01), and systolic blood pressures (p = 0.001) were all changed by preload altering manoeuvres. Only left ventricular myocardial velocity during early filling remained unchanged by these manoeuvres. CONCLUSIONS: In contrast to standard transmitral Doppler filling indices, Doppler tissue early diastolic velocities are not significantly affected by physiological manoeuvres that alter preload. Thus Doppler tissue velocities during early left ventricular diastole may provide a better index of diastolic function in cardiac patients by providing a preload independent assessment of left ventricular filling.

  15. Laser Doppler dust devil measurements

    NASA Technical Reports Server (NTRS)

    Bilbro, J. W.; Jeffreys, H. B.; Kaufman, J. W.; Weaver, E. A.

    1977-01-01

    A scanning laser doppler velocimeter (SLDV) system was used to detect, track, and measure the velocity flow field of naturally occurring tornado-like flows (dust devils) in the atmosphere. A general description of the dust devil phenomenon is given along with a description of the test program, measurement system, and data processing techniques used to collect information on the dust devil flow field. The general meteorological conditions occurring during the test program are also described, and the information collected on two selected dust devils are discussed in detail to show the type of information which can be obtained with a SLDV system. The results from these measurements agree well with those of other investigators and illustrate the potential for the SLDV in future endeavors.

  16. Time-dependent flow velocity measurement using two-dimensional color Doppler flow imaging and evaluation by Hagen-Poiseuille equation.

    PubMed

    Zhang, Bo; Sun, Yuqing; Xia, Lianghua; Gu, Junyi

    2015-12-01

    This paper aims to develop a technique to assess velocity flow profile and wall shear stress (WSS) spatial distribution across a vessel phantom representing an artery. Upon confirming the reliability of the technique, it was then used on a set of carotid arteries from a cohort of human subjects. We implemented color Doppler flow imaging (CDFI) for measurement of velocity profile in the artery cross section. Two dimensional instantaneous and time-dependent flow velocity and WSS vector fields were measured and their waveforms of peak velocities based on the technique were compared with WSS values generated by Hagen-Poiseuille equation. Seventy-five patients with intima-media thickening were prospectively enrolled and were divided into an IMT group. At the same time, another 75 healthy volunteers were enrolled as the control group. All the subjects were scanned and the DICOM files were imported into our in-house program. Next, we determine the velocity profile of carotid arteries in a set of 150 human subjects and compared them again. The peak velocities by the CDFI and Hagen-Poiseuille equation techniques were compared and statistically evaluated. The amounts of deviation for the two measured WSS profiles were performed and we demonstrated that they are not significantly different. At two different flow settings with peak flow velocity of 0.1, 0.5 (×10(-11)) m/s, the obtained WSS were 0.021 ± 0.04, 0.038 ± 0.05 m/s, respectively. For the patient population study, the mean WSS value calculated by Hagen-Poiseuille equation was 2.98 ± 0.15 dyne/cm(2), while it was 2.31 ± 0.14 dyne/cm(2) by our CDFI analysis program. The difference was not statistically significant (t = -1.057, P = 0.259). Similar to the Hagen-Poiseuille equation, a negative linear correlation was also found between the calculated WSS and intima-media thickness (P = 0.000). Using CDFI analysis, we found that the WSS distribution at the middle of the proximal plaque shoulder was larger than the top

  17. Application of acoustic-Doppler current profiler and expendable bathythermograph measurements to the study of the velocity structure and transport of the Gulf Stream

    NASA Technical Reports Server (NTRS)

    Joyce, T. M.; Dunworth, J. A.; Schubert, D. M.; Stalcup, M. C.; Barbour, R. L.

    1988-01-01

    The degree to which Acoustic-Doppler Current Profiler (ADCP) and expendable bathythermograph (XBT) data can provide quantitative measurements of the velocity structure and transport of the Gulf Stream is addressed. An algorithm is used to generate salinity from temperature and depth using an historical Temperature/Salinity relation for the NW Atlantic. Results have been simulated using CTD data and comparing real and pseudo salinity files. Errors are typically less than 2 dynamic cm for the upper 800 m out of a total signal of 80 cm (across the Gulf Stream). When combined with ADCP data for a near-surface reference velocity, transport errors in isopycnal layers are less than about 1 Sv (10 to the 6th power cu m/s), as is the difference in total transport for the upper 800 m between real and pseudo data. The method is capable of measuring the real variability of the Gulf Stream, and when combined with altimeter data, can provide estimates of the geoid slope with oceanic errors of a few parts in 10 to the 8th power over horizontal scales of 500 km.

  18. Relationship between the rheological properties of thickener solutions and their velocity through the pharynx as measured by the ultrasonic pulse Doppler method.

    PubMed

    Tashiro, Akiko; Hasegawa, Atsuko; Kohyama, Kaoru; Kumagai, Hitomi; Kumagai, Hitoshi

    2010-01-01

    The dependence of the dynamic viscoelastic parameters of carboxymethylcellulose (CMC), xanthan gum, and guar gum solutions on the angular frequency (omega) was compared with that of their viscosity (mu) on the shear rate (gamma). In addition, the effect of these rheological properties on the maximum velocity through the pharynx, V(max), as measured by the ultrasonic pulse Doppler method, was investigated. The CMC and guar gum solutions examined were taken as a dilute solution and a true polymer solution, respectively. The xanthan gum solution was taken as a weak gel above 0.5% and a true polymer solution below 0.2%. The maximum velocity, V(max), of the thickener solutions correlated well with mu, the dynamic viscosity eta', and the complex viscosity eta(*), especially those measured at gamma or omega of 20-30 s(-1) (or rad/s) and above, suggesting that mu, eta', and eta(*) are suitable indexes for care foods of the liquid type for dysphagic patients.

  19. Real-time high-velocity resolution color Doppler OCT

    NASA Astrophysics Data System (ADS)

    Westphal, Volker; Yazdanfar, Siavash; Rollins, Andrew M.; Izatt, Joseph A.

    2001-05-01

    Color Doppler optical coherence tomography (CDOCT), also called Optical Doppler Tomography) is a noninvasive optical imaging technique, which allows for micron-scale physiological flow mapping simultaneous with morphological OCT imaging. Current systems for real-time endoscopic optical coherence tomography (EOCT) would be enhanced by the capability to visualize sub-surface blood flow for applications in early cancer diagnosis and the management of bleeding ulcers. Unfortunately, previous implementations of CDOCT have either been sufficiently computationally expensive (employing Fourier or Hilbert transform techniques) to rule out real-time imaging of flow, or have been restricted to imaging of excessively high flow velocities when used in real time. We have developed a novel Doppler OCT signal-processing strategy capable of imaging physiological flow rates in real time. This strategy employs cross-correlation processing of sequential A-scans in an EOCT image, as opposed to autocorrelation processing as described previously. To measure Doppler shifts in the kHz range using this technique, it was necessary to stabilize the EOCT interferometer center frequency, eliminate parasitic phase noise, and to construct a digital cross correlation unit able to correlate signals of megahertz bandwidth by a fixed lag of up to a few ms. The performance of the color Doppler OCT system was demonstrated in a flow phantom, demonstrating a minimum detectable flow velocity of ~0.8 mm/s at a data acquisition rate of 8 images/second (with 480 A-scans/image) using a handheld probe. Dynamic flow as well as using it freehanded was shown. Flow was also detectable in a phantom in combination with a clinical usable endoscopic probe.

  20. Hydrokinetic canal measurements: inflow velocity, wake flow velocity, and turbulence

    DOE Data Explorer

    Gunawan, Budi

    2014-06-11

    The dataset consist of acoustic Doppler current profiler (ADCP) velocity measurements in the wake of a 3-meter diameter vertical-axis hydrokinetic turbine deployed in Roza Canal, Yakima, WA, USA. A normalized hub-centerline wake velocity profile and two cross-section velocity contours, 10 meters and 20 meters downstream of the turbine, are presented. Mean velocities and turbulence data, measured using acoustic Doppler velocimeter (ADV) at 50 meters upstream of the turbine, are also presented. Canal dimensions and hydraulic properties, and turbine-related information are also included.

  1. Optical Doppler tomographic imaging of fluid flow velocity in highly scattering media

    SciTech Connect

    Chen, Z.; Milner, T.E.; Dave, D.; Nelson, J.S.

    1997-01-01

    An optical Doppler tomography (ODT) system that permits imaging of fluid flow velocity in highly scattering media is described. ODT combines Doppler velocimetry with the high spatial resolution of low-coherence optical interferometry to measure fluid flow velocity at discrete spatial locations. Tomographic imaging of particle flow velocity within a circular conduit submerged 1mm below the surface in a highly scattering phantom of Intralipid is demonstrated. {copyright} {ital 1997} {ital Optical Society of America}

  2. Correction of Doppler Rada Data for Aircraft Motion Using Surface Measurements and Recursive Least-Squares Estimation

    NASA Technical Reports Server (NTRS)

    Durden, S.; Haddad, Z.

    1998-01-01

    Observations of Doppler velocity of hydrometeors form airborne Doppler weather radars normally contains a component due to the aircraft motion. Accurate hydrometeor velocity measurements thus require correction by subtracting this velocity from the observed velocity.

  3. Digital Doppler measurement with spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.; Hinedi, Sami M.; Labelle, Remi C.; Bevan, Roland P.; Del Castillo, Hector M.; Chong, Dwayne C.

    1991-01-01

    Digital and analog phase-locked loop (PLL) receivers were operated in parallel, each tracking the residual carrier from a spacecraft. The PLL tracked the downlink carrier and measured its instantaneous phase. This information, combined with a knowledge of the uplink carrier and the transponder ratio, permitted the computation of a Doppler observable. In this way, two separate Doppler measurements were obtained for one observation window. The two receivers agreed on the magnitude of the Doppler effect to within 1 mHz. There was less jitter on the data from the digital receiver. This was due to its smaller noise bandwidth. The demonstration and its results are described.

  4. Digital Doppler measurement with spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.; Hinedi, Sami M.; Labelle, Remi C.; Bevan, Roland P.; Del Castillo, Hector M.; Chong, Dwayne C.

    1991-01-01

    Digital and analog phase-locked loop (PLL) receivers were operated in parallel, each tracking the residual carrier from a spacecraft. The PLL tracked the downlink carrier and measured its instantaneous phase. This information, combined with a knowledge of the uplink carrier and the transponder ratio, permitted the computation of a Doppler observable. In this way, two separate Doppler measurements were obtained for one observation window. The two receivers agreed on the magnitude of the Doppler effect to within 1 mHz. There was less jitter on the data from the digital receiver. This was due to its smaller noise bandwidth. The demonstration and its results are described.

  5. Doppler effects on velocity spectra observed by MST radars

    NASA Technical Reports Server (NTRS)

    Scheffler, A. O.; Liu, C. H.

    1986-01-01

    Recently, wind data from mesophere-stratosphere-troposphere (MST) radars have been used to study the spectra of gravity waves in the atmosphere (Scheffler and Liu, 1985; VanZandt et al., 1985). Since MST radar measures the line-of-sight Doppler velocities, it senses the components of the wave-associated velocities along its beam directions. These components are related through the polarization relations which depend on the frequency and wave number of the wave. Therfore, the radar-observed velocity spectrum will be different from the original gravity-wave spectrum. Their relationship depends on the frequency and wave number of the wave as well as the propagation geometry. This relation can be used to interpret the observed data. It can also be used to test the assumption of gravity-wave spectrum (Scheffler and Liu, 1985). In deriving this relation, the background atmosphere has been assumed to be motionless. Obviously, the Doppler shift due to the background wind will change the shape of the gravity-wave power spectrum as well as its relation with the radar-observed spectrum. Here, researcher's investigate these changes.

  6. Doppler Measurements of the Suns Meridional Flow

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.

    1996-01-01

    Doppler velocity data obtained with the Global Oscillation Network Group (GONG) instruments in Tucson from 1992 August through 1995 April were analyzed to determine the structure and evolution of the Sun's meridional flow. Individual measurements of the flow were derived from line-of-sight velocity images averaged over 17 minutes to remove the p-mode oscillation signal. Typical flow velocities are poleward at approximately 20 m/s, but the results suggest that episodes may occur with much stronger flows. Such variations may help to explain some of the many disparate reports on the strength and structure of the Sun's meridional flow.

  7. Uterine artery, umbilical, and fetal cerebral Doppler velocities after epidural analgesia during labor.

    PubMed

    Valentin, Morgane; Ducarme, Guillaume; Ceccaldi, Pierre-François; Bougeois, Bernard; Luton, Dominique

    2012-08-01

    To evaluate the effects of epidural analgesia on uterine artery, umbilical, and fetal cerebral Doppler velocities during labor. In a prospective study at Beaujon Hospital, Paris, France, between September and December 2010, uterine artery, umbilical, and fetal cerebral Doppler flow velocities were measured in 12 pregnant women during spontaneous labor with epidural analgesia. The data were registered in a period of uterine relaxation before, and 20 and 60 minutes after the first administration of epidural analgesic drugs. The changes in Doppler velocimetry values and fetal heart rate after epidural analgesia were analyzed. Uterine artery velocities, but neither umbilical nor fetal cerebral Doppler velocities, were decreased significantly at 20 minutes and 1 hour after epidural analgesia (P<0.005). Women with the greatest decrease in uterine artery Doppler flow velocities delivered neonates with the lowest values of umbilical artery blood pH. The data suggest that the Doppler flow velocity of uterine arteries is affected by epidural analgesia during labor. Numerous Doppler flow studies of the effect of neuraxial blockade during labor on umbilical and uterine arteries have been published with incredibly variable and inconsistent results. Copyright © 2012 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.

  8. Doppler-Shifted Raman Spectroscopy Measures Flows

    NASA Technical Reports Server (NTRS)

    Exton, Reginald J.; Hillard, Mervin E., Jr.; Lempert, Walter R.; Covell, Peter F.; Miller, David S.

    1990-01-01

    Technique for measuring velocity, static pressure, and translational temperature of flowing molecules by use of stimulated Raman spectroscopy demonstrated in supersonic wind tunnel at NASA Langley Research Center. Nonintrusive, accurate wind-tunnel measurements obtained without seeding flows. Optical equipment for vibration-free Raman doppler velocimetry in wind tunnel includes specially designed retrometer that reduces sensitivity of system to vibrations. This capability very valuable in aerodynamic testing and proves useful in wide variety of laboratory, industrial, and engineering applications.

  9. Dust Particle Velocity Measurement in Shock Tubes.

    DTIC Science & Technology

    1985-12-08

    00. . .. 0 . 37 21 Photography of Electronic System for CERF 6’ Shock Tubeo..o..... 38 22 Record of a Typical Doppler Burst...2.1 PRINCIPLE OF OPERATION. Direct measurement of the particle velocity was obtained using Laser Doppler Velocimetry (LDV) [Ref. 2 and 3]. The...and transforms it into an electri- cal signal, known as Doppler burst. The period of the burst (T) is a function of the fringe spacing and the

  10. Velocity magnitude estimation with linear arrays using Doppler bandwidth.

    PubMed

    Tortoli, P; Guidi, G; Mantovani, L; Newhouse, V L

    2001-04-01

    The dependence of pulsed wave Doppler bandwidth on parameters typical of linear transducer arrays used in commercial Duplex and color flow mapping systems is investigated experimentally. For a single flow line it is observed that this bandwidth generally depends not only on the scatterer velocity and the beam-to-flow angle, but also on the flow line range and orientation. This is due to the fact that in Duplex and color flow systems the transducer is differently focused in the scan and elevation planes and its aperture and focal lengths are often made to vary, depending on the distance of the flow line from the transducer. It is however experimentally demonstrated that, at points where the ultrasound beamwidths in the scan and elevation planes are both comparable to the sample volume length, the Doppler bandwidth is independent of the beam-to-flow angle. It is also shown that this invariance can be extended to other ranges by appropriately modifying the array aperture. Finally, as an application of this independence, the flow-line velocity magnitude in these beam regions is estimated with better than 5% uncertainty through a simple bandwidth measurement.

  11. Is the measurement of inferior thyroid artery blood flow velocity by color-flow Doppler ultrasonography useful for differential diagnosis between gestational transient thyrotoxicosis and Graves' disease? A prospective study.

    PubMed

    Zuhur, Sayid Shafi; Ozel, Alper; Velet, Selvinaz; Buğdacı, Mehmet Sait; Cil, Esra; Altuntas, Yüksel

    2012-01-01

    To determine the role of peak systolic velocity, end-diastolic velocity and resistance indices of both the right and left inferior thyroid arteries measured by color-flow Doppler ultrasonography for a differential diagnosis between gestational transient thyrotoxicosis and Graves' disease during pregnancy. The right and left inferior thyroid artery-peak systolic velocity, end-diastolic velocity and resistance indices of 96 patients with thyrotoxicosis (41 with gestational transient thyrotoxicosis, 31 age-matched pregnant patients with Graves' disease and 24 age- and sex-matched non-pregnant patients with Graves' disease) and 25 age and sex-matched healthy euthyroid subjects were assessed with color-flow Doppler ultrasonography. The right and left inferior thyroid artery-peak systolic and end-diastolic velocities in patients with gestational transient thyrotoxicosis were found to be significantly lower than those of pregnant patients with Graves' disease and higher than those of healthy euthyroid subjects. However, the right and left inferior thyroid artery peak systolic and end-diastolic velocities in pregnant patients with Graves' disease were significantly lower than those of non-pregnant patients with Graves' disease. The right and left inferior thyroid artery peak systolic and end-diastolic velocities were positively correlated with TSH-receptor antibody levels. We found an overlap between the inferior thyroid artery-blood flow velocities in a considerable number of patients with gestational transient thyrotoxicosis and pregnant patients with Graves' disease. This study suggests that the measurement of inferior thyroid artery-blood flow velocities with color-flow Doppler ultrasonography does not have sufficient sensitivity and specificity to be recommended as an initial diagnostic test for a differential diagnosis between gestational transient thyrotoxicosis and Graves' disease during pregnancy.

  12. Blood flow velocity in monocular retinoblastoma assessed by color doppler

    PubMed Central

    Bonanomi, Maria Teresa B C; Saito, Osmar C; de Lima, Patricia Picciarelli; Bonanomi, Roberta Chizzotti; Chammas, Maria Cristina

    2015-01-01

    OBJECTIVE: To analyze the flow of retrobulbar vessels in retinoblastoma by color Doppler imaging. METHODS: A prospective study of monocular retinoblastoma treated by enucleation between 2010 and 2014. The examination comprised fundoscopy, magnetic resonance imaging, ultrasonography and color Doppler imaging. The peak blood velocities in the central retinal artery and central retinal vein of tumor-containing eyes (tuCRAv and tuCRVv, respectively) were assessed. The velocities were compared with those for normal eyes (nlCRAv and nlCRVv) and correlated with clinical and pathological findings. Tumor dimensions in the pathological sections were compared with those in magnetic resonance imaging and ultrasonography and were correlated with tuCRAv and tuCRVv. In tumor-containing eyes, the resistivity index in the central retinal artery and the pulse index in the central retinal vein were studied in relation to all variables. RESULTS: Eighteen patients were included. Comparisons between tuCRAv and nlCRAv and between tuCRVv and nlCRVv revealed higher velocities in tumor-containing eyes (p<0.001 for both), with a greater effect in the central retinal artery than in the central retinal vein (p=0.024). Magnetic resonance imaging and ultrasonography measurements were as reliable as pathology assessments (p=0.675 and p=0.375, respectively). A positive relationship was found between tuCRAv and the tumor volume (p=0.027). The pulse index in the central retinal vein was lower in male patients (p=0.017) and in eyes with optic nerve invasion (p=0.0088). CONCLUSIONS: TuCRAv and tuCRVv are higher in tumor-containing eyes than in normal eyes. Magnetic resonance imaging and ultrasonography measurements are reliable. The tumor volume is correlated with a higher tuCRAv and a reduced pulse in the central retinal vein is correlated with male sex and optic nerve invasion. PMID:26735219

  13. Effect of food intake on commonly used pulsed Doppler and tissue Doppler measurements.

    PubMed

    Dencker, Magnus; Björgell, Ola; Hlebowicz, Joanna

    2011-09-01

    This study evaluates the effect of food intake on commonly used pulsed Doppler and tissue Doppler measurements. Twenty-three healthy subjects aged 25.6 ± 4.5 years were investigated. A wide selection of pulsed Doppler and tissue Doppler variables were measured before a standardized meal as well as and 30 and 110 minutes afterwards. The following variables increased significantly (P < 0.05) 30 minutes after food intake: left ventricular stroke volume, left ventricular cardiac output, left ventricular outflow velocity-time integral, peak of early diastolic (E) and late diastolic (A) mitral flow velocities, pulmonary vein peak velocities in systole (S) and in diastole (D), S/D, pulsed tissue Doppler peak systolic velocities, and late diastolic velocities. Deceleration time of E-wave decreased significantly (P < 0.05). The change in measured variables between fasting and 30 minutes after the food intake ranged from 7% to 28%. There were no significant (P > 0.05) changes in E/A, early diastolic tissue Doppler velocities (e'), and E/e'. Most, but not all variables returned to baseline values 110 minutes after food intake. This study shows that food intake affects several echocardiographic variables used to routinely assess diastolic function and hemodynamics. Further studies are warranted in older healthy subjects and in patients with various cardiac diseases to determine whether the findings are reproducible in such populations. © 2011, Wiley Periodicals, Inc.

  14. Noise reduction in LOS wind velocity of Doppler lidar using discrete wavelet analysis

    NASA Astrophysics Data System (ADS)

    Wu, Songhua; Liu, Zhishen; Sun, Dapeng

    2003-12-01

    The line of sight (LOS) wind velocity can be determined from the incoherent Doppler lidar backscattering signals. Noise and interference in the measurement greatly degrade the inversion accuracy. In this paper, we apply the discrete wavelet denoising method by using biorthogonal wavelets and adopt a distancedependent thresholds algorithm to improve the accuracy of wind velocity measurement by incoherent Doppler lidar. The noisy simulation data are processed and compared with the true LOS wind velocity. The results are compared by the evaluation of both the standard deviation and correlation coefficient.The results suggest that wavelet denoising with distance-dependent thresholds can considerably reduce the noise and interfering turbulence for wind lidar measurement.

  15. Nearly automated analysis of coronary Doppler flow velocity from transthoracic ultrasound images: validation with manual tracings.

    PubMed

    Magagnin, V; Delfino, L; Cerutti, S; Turiel, M; Caiani, E G

    2007-05-01

    Coronary flow velocity reserve is obtained by manual tracings of transthoracic coronary Doppler flow velocity profiles as the ratio of stress versus baseline diastolic peak velocities. This approach introduces subjectivity in the measurements and limits the information which could be exploited from the Doppler velocity profile. Accordingly, our goals were to develop a technique for nearly automated detection of Doppler coronary flow velocity profile, and automatically compute both conventional and additional amplitude, derivative and temporal parameters, and validate it with manual tracings. A total of 100 patients (17 normals, 15 patients with severe coronary stenosis, 41 with connective tissue disease and 27 with diabetes mellitus) were studied. Linear correlation and Bland-Altman analyses showed that the proposed method was highly accurate and repeatable compared to the manual measurements. Comparison between groups evidenced significant differences in some of the automated parameters, thus representing potentially additional indices useful for the noninvasive diagnosis of microcirculatory or coronary artery disease.

  16. Laser Doppler measurement techniques for spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.; Gagliardi, Robert M.

    1986-01-01

    Two techniques are proposed for using laser links to measure the relative radial velocity of two spacecraft. The first technique determines the relative radial velocity from a measurement of the two-way Doppler shift on a transponded radio-frequency subcarrier. The subcarrier intensity-modulates reciprocating laser beams. The second technique determines the relative radial velocity from a measurement of the two-way Doppler shift on an optical frequency carrier which is transponded between spacecraft using optical Costas loops. The first technique might be used in conjunction with noncoherent optical communications, while the second technique is compatible with coherent optical communications. The first technique simultaneously exploits the diffraction advantage of laser beams and the maturity of radio-frequency phase-locked loop technology. The second technique exploits both the diffraction advantage of laser beams and the large Doppler effect at optical frequencies. The second technique has the potential for greater accuracy; unfortunately, it is more difficult to implement since it involves optical Costas loops.

  17. Measurement of aortic regurgitation by Doppler echocardiography.

    PubMed Central

    Zhang, Y; Nitter-Hauge, S; Ihlen, H; Rootwelt, K; Myhre, E

    1986-01-01

    In an attempt to develop a new approach to the non-invasive measurement of aortic regurgitation, transmitral volumetric flow (MF) and left ventricular total stroke volume (SV) were measured by Doppler and cross sectional echocardiography in 23 patients without aortic valve disease (group A) and in 26 patients with aortic regurgitation (group B). The transmitral volumetric flow was obtained by multiplying the corrected mitral orifice area by the diastolic velocity integral, and the left ventricular total stroke volume was derived by subtracting the left ventricular end systolic volume from the end diastolic volume. The aortic regurgitant fraction (RF) was calculated as: RF = 1 - MF/SV. In group A there was a close agreement between the transmitral volumetric flow and the left ventricular total stroke volume, and the difference between the two measurements did not differ significantly from zero. In group B the left ventricular total stroke volume was significantly larger than the transmitral volumetric flow, and there was good agreement between the regurgitant fractions determined by Doppler echocardiography and radionuclide ventriculography. Discrepancies between the two techniques were found in patients with combined aortic and mitral regurgitation or a low angiographic left ventricular ejection fraction (less than 35%). The effective cardiac output measured by Doppler echocardiography accorded well with that measured by the Fick method. Doppler echocardiography provides a new and promising approach to the non-invasive measurement of aortic regurgitation. PMID:3947478

  18. Validity and Reliability of Three-chamber-View Three-directional Encoded Phase-contrast Magnetic Resonance Velocity-Vector Mapping for Transmitral Velocity Measurements: Comparison with Doppler Echocardiography and Intra- and Inter-observer Variability.

    PubMed

    Suzuki, Munemura; Kotooka, Norihiko; Sakuma, Masashi; Nakazono, Takahiko; Node, Koichi; Irie, Hiroyuki

    2017-04-10

    Three-chamber view (3ch.) three-directional encoded phase-contrast magnetic resonance velocity vector mapping (PCMRVM) has been used for visualization and assessment of intra-cardiac flow. Although transmitral inflow velocity can be determined using this method by tracing mitral tips during the cardiac phase, its feasibility for clinical applications has not been established. Our aim was to investigate the validity and reproducibility of 3ch. PCMRVM for determining transmitral inflow velocity. We conducted 3ch. PCMRVM for 32 patients and eight healthy volunteers and analyzed the transmitral inflow pattern and early (E) and late (A) diastolic velocity. Nine patients also underwent Doppler echocardiography to evaluate correlations between the methods for E and A velocities and the E/A ratio. Intra- and inter-observer variability were calculated using intraclass correlation coefficients (ICC [1, 1] and ICC [2, 1]) for peak E and A velocities, Spearman's rank correlation coefficient for the E/A ratio, and Cohen's kappa coefficient for the inflow pattern. Bland-Altman plots indicated that 3ch. PCMRVM showed systemically lower velocities than Doppler echocardiography for E (3 [25.8] 48.6) and A (-6.28 [21] 48.3); however, a strong correlation was observed (r = 0.81, P < 0.0001). The E/A ratio was not statistically different between the two modalities (P = 0.21). The intra- and inter-observer variabilities for peak E and A velocities and the E/A ratio demonstrated nearly perfect agreement or strong correlations, except for the peak E velocity (ICC [2, 1] = 0.751). Based on these results, 3ch. PCMRVM can be used for both visualization and assessment of intra-cardiac flow and evaluation of the transmitral inflow velocity.

  19. Finding the peak velocity in a flow from its Doppler spectrum.

    PubMed

    Vilkomerson, David; Ricci, Stefano; Tortoli, Piero

    2013-10-01

    The signal backscattered by blood cells crossing a sample volume produces a Doppler power spectrum determined by the scatterers¿ velocity distribution. Because of intrinsic spectral broadening, the peak Doppler frequency observed does not correspond to the peak velocity in the flow. Several methods have been proposed for estimating the maximum velocity component--an important clinical parameter--but these methods are approximate, based on heuristic thresholds that can be inaccurate and strongly affected by noise. Reported here is a method of modeling the Doppler power spectrum of a flow, and from that model, determining what Doppler frequency on the descending slope of the power spectrum corresponds to the peak velocity in the insonated flow. It is shown that, for a fully insonated flow with a parabolic velocity distribution, the peak velocity corresponds to the Doppler frequency at the half-power point on that slope. The method is demonstrated to be robust with regard to the effects of noise and valid for a wide range of acquisition parameters. Experimental maximum velocity measurements on steady flows with rates between 100 and 300 mL/min (peak velocity range 6.6 cm/s to 19.9 cm/s) show a mean bias error that is smaller than 1%.

  20. Wing tip vortex measurements with laser Doppler systems

    NASA Technical Reports Server (NTRS)

    Fuller, C. E., III

    1973-01-01

    The vortex velocity field produced by a rectangular wing in a subsonic wind tunnel was measured using two laser Doppler velocimeter systems. One system made three dimensional mean velocity measurements and the other made one dimensional turbulence measurements. The systems and test procedures are described and comparisons of the measurements are made. The data defined a strong spiral motion in the vortex formation process.

  1. Normal Echocardiographic Measurements in a Korean Population Study: Part II. Doppler and Tissue Doppler Imaging

    PubMed Central

    Choi, Jin-Oh; Shin, Mi-Seung; Kim, Mi-Jeong; Jung, Hae Ok; Park, Jeong Rang; Sohn, Il Suk; Kim, Hyungseop; Park, Seong-Mi; Yoo, Nam Jin; Choi, Jung Hyun; Kim, Hyung-Kwan; Cho, Goo-Yeong; Lee, Mi-Rae; Park, Jin-Sun; Shim, Chi Young; Kim, Dae-Hee; Shin, Dae-Hee; Shin, Gil Ja; Shin, Sung Hee; Kim, Kye Hun; Park, Jae-Hyeong; Lee, Sang Yeub; Kim, Woo-Shik

    2016-01-01

    Background Hemodynamic and functional evaluation with Doppler and tissue Doppler study as a part of comprehensive echocardiography is essential but normal reference values have never been reported from Korean normal population especially according to age and sex. Methods Using Normal echOcaRdiographic Measurements in a KoreAn popuLation study subjects, we obtained normal reference values for Doppler and tissue Doppler echocardiography including tricuspid annular velocities according to current guidelines and compared values according to gender and age groups. Results Mitral early diastolic (E) and late diastolic (A) velocity as well as E/A ratio were significantly higher in women compared to those in men. Conversely, mitral peak systolic and late diastolic annular velocity in both septal and lateral mitral annulus were significantly lower in women compared to those in men. However, there were no significant differences in both septal and lateral mitral early diastolic annular (e') velocity between men and women. In both men and women, mitral E velocity and its deceleration time as well as both E/A and E/e' ratio considerably increased with age. There were no significant differences in tricuspid inflow velocities and tricuspid lateral annular velocities between men and women except e' velocity, which was significantly higher in women compared to that in men. However, changes in both tricuspid inflow and lateral annular velocities according to age were similar to those in mitral velocities. Conclusion Since there were significant differences in Doppler and tissue Doppler echocardiographic variables between men and women and changes according to age were even more considerable in both gender groups, normal Doppler echocardiographic values should be differentially applied based on age and sex. PMID:27358707

  2. Calibration of echocardiographic tissue doppler velocity, using simple universally applicable methods

    NASA Astrophysics Data System (ADS)

    Dhutia, Niti M.; Zolgharni, Massoud; Willson, Keith; Cole, Graham; Nowbar, Alexandra N.; Manisty, Charlotte H.; Francis, Darrel P.

    2014-03-01

    Some of the challenges with tissue Doppler measurement include: apparent inconsistency between manufacturers, uncertainty over which part of the trace to make measurements and a lack of calibration of measurements. We develop and test tools to solve these problems in echocardiography laboratories. We designed and constructed an actuator and phantom setup to produce automatic reproducible motion, and used it to compare velocities measured using 3 echocardiographic modalities: M-mode, speckle tracking, and tissue Doppler, against a non-ultrasound, optical gold standard. In the clinical phase, 25 patients underwent M-mode, speckle tracking and tissue Doppler measurements of tissue velocities. In-vitro, the M-mode and speckle tracking velocities were concordant with optical assessment. Of the three possible tissue Doppler measurement conventions (outer, middle and inner line) only the middle line agreed with the optical assessment (discrepancy -0.20 (95% confidence interval -0.44 to 0.03)cm/s, p=0.11, outer +5.19(4.65 to 5.73)cm/s, p<0.0001, inner -6.26(-6.87 to -5.65)cm/s, p<0.0001). All 4 studied manufacturers showed a similar pattern. M-mode was therefore chosen as the in-vivo gold standard. Clinical measurements of tissue velocities by speckle tracking and the middle line of the tissue Doppler were concordant with M-mode, while the outer line significantly overestimated (+1.27(0.96 to 1.59)cm/s, p<0.0001) and the inner line underestimated (-1.81(-2.11 to -1.52)cm/s, p<0.0001). Echocardiographic velocity measurements can be calibrated by simple, inexpensive tools. We found that the middle of the tissue Doppler trace represents velocity correctly. Echocardiographers requiring velocities to match between different equipment, settings or modalities should use the middle line as the "guideline".

  3. Analysis of placenta vascularization in patients with uterine altered artery Doppler flow velocity exams.

    PubMed

    Gilio, Daniel Bruno; Miranda Corrêa, Rosana Rosa; Souza de Oliveira Guimarães, Camila; Peres, Luiz Cesar; Marques Salge, Ana Karina; Cavellani, Camila Lourencini; de Paula Antunes Teixeira, Vicente; Costa da Cunha Castro, Eumenia

    2009-08-01

    One of the frequent questions in obstetric practice is to determine placental vascular changes that may account for abnormal Doppler flow velocity alterations in maternal uterine vessels from women and fetuses without pregnancy pathology. A retrospective morphometric study was realized using 27 placentas from patients submitted for Doppler flow velocity exam during pregnancy. The placentas were morphologically examined using hematoxylin-eosin staining. Measurements of villi were made with the use of a video camera coupled to a common light microscope and a computer with automatic image analyzing software. Of the 27 placentas, 13 (48%) were of patients showing unaltered Doppler and 14 (52%) showing altered Doppler. The number of stem villi vessels was significantly larger in the placentas of patients with Doppler exam alterations (P = 0.003). This group also presented greater stem villi vessel thickness, although without significant difference. The number of intermediary and terminal villi vessels was greater in the placentas of patients with altered Doppler exams (P < 0.001), and a greater terminal villi area was observed in these cases (P < 0.001). The morphological proof that uterine artery Doppler flow velocity exam alterations are associated with placental vascular alterations demonstrates the importance of this exam during prenatal care, even in the absence of maternal-fetal alterations.

  4. A Doppler dimming determination of coronal outflow velocity

    NASA Technical Reports Server (NTRS)

    Strachan, Leonard; Kohl, John L.; Weiser, Heinz; Withbroe, George L.; Munro, Richard H.

    1993-01-01

    Outflow velocities in a polar coronal hole are derived from observations made during a 1982 sounding rocket flight. The velocity results are derived from a Doppler dimming analysis of resonantly scattered H I Ly-alpha. This analysis indicates radial outflow velocities of 217 km/s at 2 solar radii from sun-center with an uncertainty range of 153 to 251 km/s at a confidence level of 67 percent. These results are best characterized as strong evidence for supersonic outflow within 2 solar radii of sun-center in a polar coronal hole. Several means for obtaining improved accuracy in future observations are discussed.

  5. Doppler Lidar for Wind Measurements on Venus

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Emmitt, George D.; Yu, Jirong; Kavaya, Michael J.

    2010-01-01

    NASA Langley Research Center has a long history of developing 2-micron laser transmitter for wind sensing. With support from NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement. The transmitter portion of the transceiver employs the high-pulse-energy, Ho:Tm:LuLiF, partially conductively cooled laser technology developed at NASA Langley. The transceiver is capable of 250 mJ pulses at 10 Hz. It is very similar to the technology envisioned for coherent Doppler lidar wind measurements from Earth and Mars orbit. The transceiver is coupled to the large optics and data acquisition system in the NASA Langley VALIDAR mobile trailer. The large optics consists of a 15-cm off-axis beam expanding telescope, and a full-hemispheric scanner. Vertical and horizontal vector winds are measured, as well as relative backscatter. The data acquisition system employs frequency domain velocity estimation and pulse accumulation. It permits real-time display of the processed winds and archival of all data. This lidar system was recently deployed at Howard University facility in Beltsville, Mary-land, along with other wind lidar systems. Coherent Doppler wind lidar ground-based wind measurements and comparisons with other sensors will be presented. A simulation and data product for wind measurement at Venus will be presented.

  6. Scanning laser Doppler Technique for velocity profile sensing on a moving surface.

    PubMed

    Sriram, P; Hanagud, S; Craig, J; Komerath, N M

    1990-06-01

    A scanning laser Doppler technique based on Chebyshev demodulation has been developed for the rapid measurement of spatially distributed velocity profiles. Scan frequencies up to 100 Hz can be used over scan lengths up to 270 mm. The Doppler signals are processed in the conventional manner using a frequency counter. The analog velocity output from the counter is post-processed to obtain the velocity profile. The Chebyshev demodulation post-processing technique for processing the velocity signals from solid surfaces has been introduced. The data processing technique directly yields the spatial velocity distribution in approximate functional form through frequency domain analysis of the scanning LDV velocity output. Results from a rotating disk setup are presented to illustrate the concept.

  7. Determination of the envelope function (maximum velocity curve) in Doppler ultrasound flow velocity diagrams

    NASA Astrophysics Data System (ADS)

    Tschirren, Juerg; Lauer, Ronald M.; Sonka, Milan

    2000-06-01

    This paper presents a new approach for the evaluation of Doppler flow velocity diagrams, obtained during brachial artery flow mediated dilatation (FMD) studies. The velocity diagrams are stored as image sequences on VCR tape. For this reason standard signal processing methods can not be used. A method for determination of blood velocity envelopes from image data is reported that uses Doppler-data specific heuristic to achieve high accuracy and robustness. The approach was tested in 40 Doppler blood flow images. Comparisons with manually defined independent standards demonstrated a very good correlation in determined peak velocity values (r equals 0.993) and flow envelope areas (r equals 0.996). The method is currently tested in a large volume clinical study.

  8. Doppler ultrasound tracking instrument for monitoring blood flow velocity.

    PubMed

    von Krüger, Marco Antônio; Evans, David H

    2002-01-01

    Doppler ultrasound (US) is potentially a valuable method for monitoring changes of blood flow velocity over a period of many minutes or even hours, but is seldom used in this way. One difficulty that may have contributed to this is the problem of maintaining a fixed geometry between the US beam and the blood vessel. A method of improving the success of monitoring might be to actively steer the US beam so as to maintain an adequate signal even when small displacements of the transducer occur. We have designed and built a prototype system for this purpose. The system comprises a continuous-wave phased-array transducer controlled by a purpose-built Doppler unit. The system constantly evaluates the quality of the returning Doppler signal in terms of total power and signal-to-noise ratio (SNR) (evaluated by assessing the quality of derived envelope signals), and steers the ultrasonic beam in a manner so as to improve the signal, should this be necessary. The system was tested in vitro, where the automatic tracking of the Doppler signal doubled the effective beam width of the transducer. Further developments that increase sensitivity and steering range should result in US Doppler systems that are better suited to long-term monitoring.

  9. Evaluation of the MV (CAPON) Coherent Doppler Lidar Velocity Estimator

    NASA Technical Reports Server (NTRS)

    Lottman, B.; Frehlich, R.

    1997-01-01

    The performance of the CAPON velocity estimator for coherent Doppler lidar is determined for typical space-based and ground-based parameter regimes. Optimal input parameters for the algorithm were determined for each regime. For weak signals, performance is described by the standard deviation of the good estimates and the fraction of outliers. For strong signals, the fraction of outliers is zero. Numerical effort was also determined.

  10. Concepts and trade-offs in velocity estimation with plane-wave contrast-enhanced Doppler.

    PubMed

    Tremblay-Darveau, Charles; Williams, Ross; Sheeran, Paul; Milot, Laurent; Bruce, Matthew; Burns, Peter

    2016-07-29

    While long Doppler ensembles are, in principle, beneficial for velocity estimates, short acoustic pulses must be used in microbubble contrast-enhanced Doppler to mitigate microbubble destruction. This introduces inherent trade-offs in velocity estimates with autocorrelators, which are studied here. A model of the autocorrelation function adapted to the microbubble Doppler signal, accounting for transit time, the echo frequency uncertainty and contrast-agent destruction is derived and validated in vitro. It is further demonstrated that a local measurement of the center frequency of the microbubble echo is essential in order to avoid significant bias in velocity estimates arising from the linear and nonlinear frequency-dependent scattering of microbubbles, and compensate the inherent speckle nature of the received echo frequency. For these reasons, broadband Doppler estimators (2D autocorrelator, Radon projection) are better suited than simpler narrowband estimators (1D autocorrelator, 1D Fourier transform) for contrast-enhanced flow assessment. A case study of perfusion in a VX-2 carcinoma using contrast-enhanced planewave Doppler is also shown. We demonstrate that even when considering all uncertainties associated with microbubble-related decorrelation (destruction, pulse bandwidth, transit time, flow gradient) and the need for real-time imaging, a coefficient of variation of 4% on the an axial velocity is achievable with planewave imaging.

  11. Concepts and Tradeoffs in Velocity Estimation With Plane-Wave Contrast-Enhanced Doppler.

    PubMed

    Tremblay-Darveau, Charles; Williams, Ross; Sheeran, Paul S; Milot, Laurent; Bruce, Matthew; Burns, Peter N

    2016-11-01

    While long Doppler ensembles are, in principle, beneficial for velocity estimates, short acoustic pulses must be used in microbubble contrast-enhanced (CE) Doppler to mitigate microbubble destruction. This introduces inherent tradeoffs in velocity estimates with autocorrelators, which are studied here. A model of the autocorrelation function adapted to the microbubble Doppler signal accounting for transit time, the echo frequency uncertainty, and contrast-agent destruction is derived and validated in vitro. It is further demonstrated that a local measurement of the center frequency of the microbubble echo is essential in order to avoid significant bias in velocity estimates arising from the linear and nonlinear frequency-dependent scattering of microbubbles and compensate for the inherent speckle nature of the received echo frequency. For these reasons, broadband Doppler estimators (2-D autocorrelator and Radon projection) are better suited than simpler narrow-band estimators (1-D autocorrelator and 1-D Fourier transform) for CE flow assessment. A case study of perfusion in a VX-2 carcinoma using CE plane-wave Doppler is also shown. We demonstrate that even when considering all uncertainties associated with microbubble-related decorrelation (destruction, pulse bandwidth, transit time, and flow gradient) and the need for real-time imaging, a coefficient of variation of 4% on the axial velocity is achievable with plane-wave imaging.

  12. Laboratory evaluation of microwave Doppler velocimeter for solid flow measurements

    NASA Astrophysics Data System (ADS)

    Wu, Z.; Wang, H. G.; Isa, M.; Liu, C. G.

    2014-04-01

    Pneumatic-conveyed solid flows are common in many industrial processes. The flow speed may be high and varying. The density of solids may also change with time. The mass flow rate is usually difficult to quantify for such multphase flows. On the other hand, microwave Doppler radar has been used as a device for velocity measurement or motion detection. It would be feasible to use such a device for solid flow measurements. In this paper, the principle of using microwave Doppler radar for such an application is investigated. Experimental results obtained using a microwave Doppler velocimeter for different types of solid flows in a laboratory environment are presented.

  13. Differences between Doppler velocities of ions and neutral atoms in a solar prominence

    NASA Astrophysics Data System (ADS)

    Anan, T.; Ichimoto, K.; Hillier, A.

    2017-05-01

    Context. In astrophysical systems with partially ionized plasma, the motion of ions is governed by the magnetic field while the neutral particles can only feel the magnetic field's Lorentz force indirectly through collisions with ions. The drift in the velocity between ionized and neutral species plays a key role in modifying important physical processes such as magnetic reconnection, damping of magnetohydrodynamic waves, transport of angular momentum in plasma through the magnetic field, and heating. Aims: This paper aims to investigate the differences between Doppler velocities of calcium ions and neutral hydrogen in a solar prominence to look for velocity differences between the neutral and ionized species. Methods: We simultaneously observed spectra of a prominence over an active region in H I 397 nm, H I 434 nm, Ca II 397 nm, and Ca II 854 nm using a high dispersion spectrograph of the Domeless Solar Telescope at Hida observatory. We compared the Doppler velocities, derived from the shift of the peak of the spectral lines presumably emitted from optically-thin plasma. Results: There are instances when the difference in velocities between neutral atoms and ions is significant, for example 1433 events ( 3% of sets of compared profiles) with a difference in velocity between neutral hydrogen atoms and calcium ions greater than 3σ of the measurement error. However, we also found significant differences between the Doppler velocities of two spectral lines emitted from the same species, and the probability density functions of velocity difference between the same species is not significantly different from those between neutral atoms and ions. Conclusions: We interpreted the difference of Doppler velocities as being a result of the motions of different components in the prominence along the line of sight, rather than the decoupling of neutral atoms from plasma. The movie attached to Fig. 1 is available at http://www.aanda.org

  14. [Aortic flow measurement by transesophageal Doppler effect].

    PubMed

    Cathignol, D; Lavandier, B; Muchada, R

    1985-01-01

    Continuous measurement of cardiac output by thermodilution is invasive, impractical and unpleasant for the patient. We propose to measure descending aortic blood flow with a specially designed intra-oesophageal Doppler echo probe. The apparatus is composed of two main parts. First an A scan system makes possible the measurement of the diameter of the vessel, second a continuous wave velocimeter is used to measure the spatial mean velocity of the blood. An output calculator determines the descending aortic blood flow. The oesophageal catheter contains three ultrasonic transducers at its tip mounted on an epoxy resin bracket produced by moulding. They are connected to a flexible hose placed inside a flexible polyvinyl sheath whose outer diameter is 6.8 mm and length is 50 cm. A cylindrical latex balloon is mounted on this sheath which is water inflated to minimum pressure, ensuring a good ultrasonic coupling between the transducers and the oesophageal wall. Connection between the probe and the apparatus is made by three coaxial cables. Three isolator-transformers are built into the connector cable to ensure a safe electrical circuit. After having bled the probe of any air, the balloon is deflated. The probe is gently introduced into the oesophagus by nasal or oral route until the transducers are situated between the 5th and 6th vertebra. The balloon is then inflated to minimum pressure with 10 ml of distilled water contained in a syringe. To find the aorta, the velocimeter is first used like a Doppler stethoscope. The probe is rotated into a position corresponding to the maximum level of Doppler signal.(ABSTRACT TRUNCATED AT 250 WORDS)

  15. Digital thermal monitoring (DTM) of vascular reactivity closely correlates with Doppler flow velocity.

    PubMed

    McQuilkin, Gary L; Panthagani, David; Metcalfe, Ralph W; Hassan, Haider; Yen, Albert A; Naghavi, Morteza; Hartley, Craig J

    2009-01-01

    The noninvasive measurement of peripheral vascular reactivity, as an indicator of vascular function, provides a valuable tool for cardiovascular screening of at-risk populations. Practical and economical considerations demand that such a test be low-cost and simple to use. To this end, it is advantageous to substitute digital thermal monitoring (DTM) for the more costly and complex Doppler system commonly used for this measurement. A signal processing model was developed to establish the basis for the relationship between finger temperature reactivity and blood flow reactivity following a transient brachial artery occlusion and reperfusion protocol (reactive hyperemia). Flow velocity signals were acquired from the radial artery of human subjects via an 8 MHz Doppler probe while simultaneous DTM signals were acquired from a distal fingertip via DTM sensors. The model transforms the DTM temperature signals into normalized flow signals via a deconvolution method which employs an exponential impulse function. The DTM normalized flow signals were compared to simultaneous, low-frequency, normalized flow signals computed from Doppler sensors. The normalized flow signals, derived from DTM and Doppler sensors, were found to yield similar reactivity responses during reperfusion. The reactivity areas derived from DTM and Doppler sensors, indicative of hyperemic volumes, were found to be within +/- 15%. In conclusion, this signal processing model provides a means to measure vascular reactivity using DTM sensors, that is equivalent to that obtained by more complex Doppler systems.

  16. Measuring velocity profiles by the LDA method

    NASA Astrophysics Data System (ADS)

    Kamil, Šimeček; Katarína, Ratkovská

    2017-09-01

    This article describes in details an experiment, which was done by the method Laser Doppler Anemometry (LDA). The experiment used the wind tunnel in the laboratory at the Department of Power System Engineering, Faculty of Mechanical Engineering. The result of measuring was air velocity profiles in the wind tunnel in cases with or without an obstacle in the airflow. The measurements take place in three planes perpendicular to the axis of the wind tunnel in the middle of the height of the tunnel end. Because the LDA method measures the velocity only in separated points, it is necessary to use traverse systems in the direction of measuring lines to make the velocity profiles. The results of this experiment are histograms (diagrams which show numbers of particulars values of velocity) and velocity profiles (for whole lines). These velocity profiles are compared with the results of the same experiment, which was measured by the method Particle Image Velocimetry (PIV).

  17. Potential for coherent Doppler wind velocity lidar using neodymium lasers

    NASA Technical Reports Server (NTRS)

    Kane, T. J.; Byer, R. L.; Zhou, B.

    1984-01-01

    Existing techniques for the frequency stabilization of Nd:YAG lasers operating at 1.06 micron, and the high-gain amplification of radiation at that wavelength, make possible the construction of a coherent Doppler wind velocity lidar using Nd:YAG. Velocity accuracy and range resolution are better at 1.06 micron than at 10.6 microns at the same level of the SNR. Backscatter from the atmosphere at 1.06 micron is greater than that at 10.6 microns by about 2 orders of magnitude, but the quantum-limited noise is higher by 100 also. Near-field attenuation and turbulent effects are more severe at 1.06 micron. In some configurations and environments, the 1.06-micron wavelength may be the better choice, and there may be technological advantages favoring the use of solid-state lasers in satellite systems.

  18. A Comprehensive Radial Velocity Error Budget for Next Generation Doppler Spectrometers

    NASA Technical Reports Server (NTRS)

    Halverson, Samuel; Ryan, Terrien; Mahadevan, Suvrath; Roy, Arpita; Bender, Chad; Stefansson, Guomundur Kari; Monson, Andrew; Levi, Eric; Hearty, Fred; Blake, Cullen; hide

    2016-01-01

    We describe a detailed radial velocity error budget for the NASA-NSF Extreme Precision Doppler Spectrometer instrument concept NEID (NN-explore Exoplanet Investigations with Doppler spectroscopy). Such an instrument performance budget is a necessity for both identifying the variety of noise sources currently limiting Doppler measurements, and estimating the achievable performance of next generation exoplanet hunting Doppler spectrometers. For these instruments, no single source of instrumental error is expected to set the overall measurement floor. Rather, the overall instrumental measurement precision is set by the contribution of many individual error sources. We use a combination of numerical simulations, educated estimates based on published materials, extrapolations of physical models, results from laboratory measurements of spectroscopic subsystems, and informed upper limits for a variety of error sources to identify likely sources of systematic error and construct our global instrument performance error budget. While natively focused on the performance of the NEID instrument, this modular performance budget is immediately adaptable to a number of current and future instruments. Such an approach is an important step in charting a path towards improving Doppler measurement precisions to the levels necessary for discovering Earth-like planets.

  19. A comprehensive radial velocity error budget for next generation Doppler spectrometers

    NASA Astrophysics Data System (ADS)

    Halverson, Samuel; Terrien, Ryan; Mahadevan, Suvrath; Roy, Arpita; Bender, Chad; Stefánsson, Gudmundur K.; Monson, Andrew; Levi, Eric; Hearty, Fred; Blake, Cullen; McElwain, Michael; Schwab, Christian; Ramsey, Lawrence; Wright, Jason; Wang, Sharon; Gong, Qian; Roberston, Paul

    2016-08-01

    We describe a detailed radial velocity error budget for the NASA-NSF Extreme Precision Doppler Spectrometer instrument concept NEID (NN-explore Exoplanet Investigations with Doppler spectroscopy). Such an instrument performance budget is a necessity for both identifying the variety of noise sources currently limiting Doppler measurements, and estimating the achievable performance of next generation exoplanet hunting Doppler spectrometers. For these instruments, no single source of instrumental error is expected to set the overall measurement floor. Rather, the overall instrumental measurement precision is set by the contribution of many individual error sources. We use a combination of numerical simulations, educated estimates based on published materials, extrapolations of physical models, results from laboratory measurements of spectroscopic subsystems, and informed upper limits for a variety of error sources to identify likely sources of systematic error and construct our global instrument performance error budget. While natively focused on the performance of the NEID instrument, this modular performance budget is immediately adaptable to a number of current and future instruments. Such an approach is an important step in charting a path towards improving Doppler measurement precisions to the levels necessary for discovering Earth-like planets.

  20. Laser Doppler velocimeter measurements in a turbine stator cascade facility

    NASA Technical Reports Server (NTRS)

    Seasholtz, R. G.

    1974-01-01

    A laser Doppler velocimeter (LDV) developed for mapping the flow velocity downstream from a 32-inch diameter annular cascade of turbine stator vanes in described. The LDV measurements were taken in a plane located approximately 0.5 inch downstream of the trailing edges of the vanes. Two components of the mean velocity (axial and circumferential) were measured. The flow velocities were in the high subsonic range. The LDV optics are of the dual scatter type with off-axis collection of the scattered light. The electronics system is based on the measurement of the time interval corresponding to eight periods of the Doppler signal and has a range of 10 to 80 MHz. The LDV measurements are compared with previous measurements made with a pressure probe.

  1. Laser Doppler velocimeter measurements in a turbine stator cascade facility

    NASA Technical Reports Server (NTRS)

    Seasholtz, R. G.

    1974-01-01

    A laser Doppler velocimeter (LDV) developed for mapping the flow velocity downstream from a 32-inch diameter annular cascade of turbine stator vanes is described. The LDV measurements were taken in a plane located approximately 0.5 inch downstream of the trailing edges of the vanes. Two components of the mean velocity (axial and circumferential) were measured. The flow velocities were in the high subsonic range. The LDV optics are of the dual scatter type with off-axis collection of the scattered light. The electronics system is based on the measurement of the time interval corresponding to eight periods of the Doppler signal and has a range of 10 to 80 MHz. The LDV measurements are compared with previous measurements made with a pressure probe.

  2. Long-term Variation of Temperatures and Wind Velocities from Earth based Doppler-wind and Temperature Measurements in Venus Upper Atmosphere between 1990 and 2013 using the Infrared Heterodyne Spectrometer THIS

    NASA Astrophysics Data System (ADS)

    Sornig, Manuela; Stangier, Tobias; Krause, Pia; Wischnewski, Caro; Kostiuk, Ted; Livengood, Tim

    2014-05-01

    Dynamics of the Venusian atmospheric transition zone between the sub-solar to anti-solar (SS-AS) flow dominated region above 120km and the superrotation dominated region below 90 km is not yet fully understood. Temperatures in the same region are not very well constrained and we lack in a comprehensive understanding of this atmospheric region. Therefore direct measurements of these parameters on various time scales and on different locations on the planet are essential for validation of global circulation models and a comprehensive understanding of the atmosphere. Such observations can be provided by the infrared heterodyne spectrometers THIS (University of Cologne) and HIPWAC (NASA GSFC). Operating around 10μm both instruments fully resolve CO2 non-LTE emission lines for Doppler-wind and temperature retrievals at an pressure level of 1μbar (~110 km). In addition to this "one-altitude" information the broader CO2 absorption lines can be used to gain information about the temperature profile lower down in the atmosphere (~60-90 km). Long term variability in Doppler-wind velocities and temperature at ~110km from campaigns between 1990 to 2013 will be presented. A report about local wave activities will be included. In addition recently retrieved temperature profiles from 60 to 90 km will be shown.

  3. Visualizing flow fields using acoustic Doppler current profilers and the Velocity Mapping Toolbox

    USGS Publications Warehouse

    Jackson, P. Ryan

    2013-01-01

    The purpose of this fact sheet is to provide examples of how the U.S. Geological Survey is using acoustic Doppler current profilers for much more than routine discharge measurements. These instruments are capable of mapping complex three-dimensional flow fields within rivers, lakes, and estuaries. Using the Velocity Mapping Toolbox to process the ADCP data allows detailed visualization of the data, providing valuable information for a range of studies and applications.

  4. Method and apparatus for optical Doppler tomographic imaging of fluid flow velocity in highly scattering media

    DOEpatents

    Nelson, John Stuart; Milner, Thomas Edward; Chen, Zhongping

    1999-01-01

    Optical Doppler tomography permits imaging of fluid flow velocity in highly scattering media. The tomography system combines Doppler velocimetry with high spatial resolution of partially coherent optical interferometry to measure fluid flow velocity at discrete spatial locations. Noninvasive in vivo imaging of blood flow dynamics and tissue structures with high spatial resolutions of the order of 2 to 10 microns is achieved in biological systems. The backscattered interference signals derived from the interferometer may be analyzed either through power spectrum determination to obtain the position and velocity of each particle in the fluid flow sample at each pixel, or the interference spectral density may be analyzed at each frequency in the spectrum to obtain the positions and velocities of the particles in a cross-section to which the interference spectral density corresponds. The realized resolutions of optical Doppler tomography allows noninvasive in vivo imaging of both blood microcirculation and tissue structure surrounding the vessel which has significance for biomedical research and clinical applications.

  5. Spaceborne Radar Measurements of Rainfall Vertical Velocity

    NASA Technical Reports Server (NTRS)

    Im, Eastwood; Tanelli, Simone; Giuli, Dino; Durden, Stephen L.; Facheris, Luca

    2000-01-01

    This paper studies the performance of a spaceborne precipitation radar in measuring vertical Doppler velocity of rainfall. As far as a downward pointing precipitation radar is concerned, one of the major problems affecting Doppler measurement at the nadir direction arises from the Non-Uniform Beam-Filling effect (NUBF). That is, when significant variation in rain rate is present within the radar IFOV (Instrument Field of View) in the along track direction. the Doppler shift caused by the radial component of the horizontal speed of the satellite is weighted differently among the portions of IFOV. The effects of this non-uniform weighting may dominate any other contribution. Under this condition, shape, average value and width of the Doppler spectrum may not be directly correlated with the vertical velocity of the precipitating particles. However, by using an inversion technique which over-samples the radar measurements in the along track direction, we show that the shift due to NUBF can be evaluated, and that the NUBF induced errors on average fall speed can be reduced.

  6. Velocity and turbulence measurements in combustion systems

    NASA Astrophysics Data System (ADS)

    Goldstein, R. J.; Lau, K. Y.; Leung, C. C.

    1983-06-01

    A laser-Doppler velocimeter is used in the measurement of high-temperature gas flows. A two-stage fluidization particle generator provides magnesium oxide particles to serve as optical scattering centers. The one-dimensional dual-beam system is frequency shifted to permit measurements of velocities up to 300 meters per second and turbulence intensities greater than 100 percent. Exiting flows from can-type gas turbine combustors and burners with pre-mixed oxy-acetylene flames are described in terms of the velocity, turbulence intensity, and temperature profiles. The results indicate the influence of the combustion process on turbulence.

  7. Miniature Laser Doppler Velocimeter for Measuring Wall Shear

    NASA Technical Reports Server (NTRS)

    Gharib, Morteza; Modarress, Darius; Forouhar, Siamak; Fourguette, Dominique; Taugwalder, Federic; Wilson, Daniel

    2005-01-01

    A miniature optoelectronic instrument has been invented as a nonintrusive means of measuring a velocity gradient proportional to a shear stress in a flow near a wall. The instrument, which can be mounted flush with the wall, is a variant of a basic laser Doppler velocimeter. The laser Doppler probe volume can be located close enough to the wall (as little as 100 micron from the surface) to lie within the viscosity-dominated sublayer of a turbulent boundary layer. The instrument includes a diode laser, the output of which is shaped by a diffractive optical element (DOE) into two beams that have elliptical cross sections with very high aspect ratios.

  8. Mixed-phase cloud phase partitioning using millimeter wavelength cloud radar Doppler velocity spectra

    NASA Astrophysics Data System (ADS)

    Yu, G.; Verlinde, J.; Clothiaux, E. E.; Chen, Y.-S.

    2014-06-01

    Retrieving and quantifying cloud liquid drop contributions to radar returns from mixed-phase clouds remains a challenge because the radar signal is frequently dominated by the returns from the ice particles within the radar sample volume. We present a technique that extracts the weak cloud liquid drop contributions from the total radar returns in profiling cloud radar Doppler velocity spectra. Individual spectra are first decomposed using a continuous wavelet transform, the resulting coefficients of which are used to identify the region in the spectra where cloud liquid drops contribute. By assuming that the liquid contribution to each Doppler spectrum is Gaussian shaped and centered on an appropriate peak in the wavelet coefficients, the cloud liquid drop contribution may be estimated by fitting a Gaussian distribution centered on the velocity of this peak to the original Doppler spectrum. The cloud liquid drop contribution to reflectivity, the volume mean vertical air motion, subvolume vertical velocity variance, and ice particle mean fall speed can be estimated based on the separation of the liquid contribution to the radar Doppler spectrum. The algorithm is evaluated using synthetic spectra produced from output of a state-of-the-art large eddy simulation model study of an Arctic mixed-phase cloud. The retrievals of cloud liquid drop mode reflectivities were generally consistent with the original model values with errors less than a factor of 2. The retrieved volume mean vertical air velocities reproduced the updraft and downdraft structures, but with an overall bias of approximately -0.06 m s-1. Retrievals based on Ka-band Atmospheric Radiation Measurement Program Zenith Radar observations from Barrow, Alaska, during October 2011 are also presented.

  9. A symmetrical laser Doppler velocity meter and its application to turbulence characterization

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.

    1972-01-01

    A symmetrical method of optical heterodyning of the Doppler shifted scattered laser radiation developed for velocity measurements with a minimal instrumental spectral broadening and a high signal-to-noise ratio. The method employs two laser beams incident on the moving scatterer and does not use any reference beam for heterodyning. The Doppler signal frequency is independent of the scattering angle and the signal possesses no receiving aperture broadening. Optical alignment is simple. Typical values of the instrumental spectral broadening were approximately 0.8 percent of the center frequency of the Doppler signal, and the signal-to-noise ratio was approximately 25 dB, obtained from an air flow system using submicron dioctylphthalate scattering aerosol. Experimental and theoretical studies were made on the characteristics of the Doppler signal and the effect of system parameters in turbulent flow measurement. The optimization process involved in the beam optics and in the use of a spatial filter is described. For localized flow measurement in any direction of the three-dimensional orthogonal coordinates, the system, using uncorrected optical components, had a sensing volume which can be described by a sensitive length of 600 microns and a diameter of 100 microns.

  10. Intra- and Inter-rater Reliability of Peripheral Arterial Blood Flow Velocity by Means of Doppler Ultrasound.

    PubMed

    Guirro, Elaine Caldeira de Oliveira; Leite, Gabriella de Paula Marcondes Ferreira; Dibai-Filho, Almir Vieira; Borges, Nathalia Cristina de Souza; Guirro, Rinaldo Roberto de Jesus

    2017-05-01

    Although it is possible to find studies that analyze the velocity of blood flow in different arteries, the reliability of Doppler ultrasound on peripheral arteries has not yet been completely established. Our objective was to evaluate intra- and inter-rater reliability of the measurement of blood flow velocity by Doppler ultrasound of brachial, radial, popliteal, and posterior tibial arteries. Fifty healthy individuals of both genders, aged between 18 and 45 years, were included in the study. For the evaluation of arterial blood flow velocity, a portable Doppler ultrasound device was used to measure the mean and maximum blood flow velocity of posterior tibial, popliteal, brachial, and radial arteries. Two examiners performed assessments of the same volunteers independently and twice, with an interval of 1 week between them. We found good to very good reliability for measuring the mean and maximum blood flow velocity of the arteries evaluated. The intraclass correlation coefficients ranged between 0.501 and 0.866, standard error of measurement ranged between 0.81 and 9.45 cm/s, and minimum detectable change ranged between 2.25 and 26.13 cm/s. The assessment of mean and maximum blood flow velocity of the brachial, radial, popliteal, and posterior tibial arteries by means of Doppler ultrasound presents acceptable reliability values, which supports the use of this evaluation method in research and clinical practice. Copyright © 2017. Published by Elsevier Inc.

  11. [Intracranial blood flow velocities evaluated by color Doppler (duplex) in preterm infants].

    PubMed

    de Assis, Marcelo Cardoso; Machado, Helio Rubens

    2004-03-01

    In order to ascertain the blood flow velocities in the intracranial arteries we evaluated 73 preterm neonates during a period ranging from June 1994 to March 1999. These preterm infants were divided in two separate groups, 18 healthy and 55 with intracranial hemorrhage. They were subjected to sequential measurements of blood flow velocities in the intracranial arteries. The gestational age of the whole group varied from 28 to 36 weeks and birth weights between 720 and 2530 g. The diagnosis of the intracerebral hemorrhages in these preterm neonates were done using high resolution gray and color scale transfontanellar ultrasonography brain scans. The ultrasound evaluations were performed in the initial 3rd, 7th and 14th day of life. The 73 preterm infants were evaluated with sequential measurements of blood flow velocity in the intracranial arteries using the Doppler technique through the anterior fontanelle. Doppler evaluation of the cerebral vessels were performed on days 3, 7, 30 and 90 of life. These evaluations were performed in the six intracranial arteries, meaning: right and left anterior and middle cerebral arteries and right and left internal carotid arteries. Doppler recordings were made using Duplex Color-Doppler system, pulse echo probe of 3,5; 5,0 and 7,5 MHz. Measuring the blood flow velocity in the cerebral arteries we obtained a maximum systolic velocity and end diastolic velocity with a rate in meters per second (m/s) for each cardiac cycle. After obtaining these numerical values for these velocities we obtained the resistance index (RI) or Pourcelot index. In a progressive way as the resistance index (RI) values were being obtained in each stage of this study they were also being checked in the cerebral arteries of healthy preterm infants and infants with intracranial hemorrhages. We also analyzed in a comparative method the values of the resistive index between the two groups of preterm infants observing their behaviour. The results obtained when

  12. Laser-Doppler velocity profile sensor with submicrometer spatial resolution that employs fiber optics and a diffractive lens.

    PubMed

    Büttner, Lars; Czarske, Jürgen; Knuppertz, Hans

    2005-04-20

    We report a novel laser-Doppler velocity profile sensor for microfluidic and nanofluidic applications and turbulence research. The sensors design is based on wavelength-division multiplexing. The high dispersion of a diffractive lens is used to generate a measurement volume with convergent and divergent interference fringes by means of two laser wavelengths. Evaluation of the scattered light from tracers allows velocity gradients to be measured in flows with submicrometer spatial resolution inside a measurement volume of 700-microm length. Using diffraction optics and fiber optics, we achieved a miniaturized and robust velocity profile sensor for highly resolved velocity measurements.

  13. Dual measurement terminal fall speeds and multiple Doppler winds

    NASA Technical Reports Server (NTRS)

    Grosh, R. C.

    1983-01-01

    It is shown that radar-derived terminal fall speed measurements can be useful in determining vertical air velocity in the middle troposphere by means of a network of Doppler radars. The theoretical principles of the dual measurement technique are described, and the relationship between measurement accuracies and theoretical estimates of terminal fall speeds is discussed. It is demonstrated that the use of differential reflectivity to estimate terminal fall speeds can reduce the standard error of vertical velocity estimates by 40-50 percent.

  14. Assessing the Capability of Doppler Global Velocimetry To Measure Vortical Flow Fields

    NASA Technical Reports Server (NTRS)

    Meyers, James F.; Usry, Jimmy W.; Miller, L. Scott

    1994-01-01

    A new nonintrusive flow diagnostics instrumentation system, Doppler global velocimetry, is presented. The system is capable of making simultaneous, three-component velocity measurements within a selected measurement plane at video camera rates. These velocity images can provide the researcher with spatial and temporal information about the flow field in a global sense. The investigation of a vortical flow above a 75-degree delta wing comparing standard three-component, fringe-type laser velocimetry measurements with Doppler global velocimetry measurements is presented.

  15. Comparison of pulsed wave and color Doppler myocardial velocity imaging in healthy dogs.

    PubMed

    Wess, G; Killich, M; Hartmann, K

    2010-01-01

    Tissue velocity imaging (TVI) is increasingly used in small animal cardiology. Tissue velocity of the myocardial wall can be measured by pulsed wave (PW) or color Doppler (CD) imaging methods. Currently, the same reference ranges are used for PW TVI and CD TVI methods. However, if and how both methods correlate, and whether they can be used interchangeably, have not been assessed in small animals. To compare the results of PW TVI and CD TVI measurements. Seventy-one healthy dogs. Longitudinal myocardial velocity profiles were recorded from the 4-chamber left apical view. Peak maximal systolic (S), early (E), and late diastolic (A) velocities were measured off-line in a blinded fashion in the septal and lateral left ventricular wall by PW TVI and CD TVI. Differences between peak PW TVI and CD TVI waves were analyzed by a paired t-test. Regression analysis and Bland-Altman difference plots also were used to assess agreement between methods. There was a significant correlation between PW TVI and CD TVI (P < .001). However, S, E, and A waves measured by PW TVI were significantly higher than the CD TVI values (P < .001). Peak systolic and diastolic PW velocities were approximately 2.20 cm/s higher than corresponding mean CD TVI velocities. PW TVI measurements are significantly higher compared with CD TVI measurements. Theses differences are clinically relevant. These methods should not be used interchangeably, and different reference ranges for PW TVI and CD TVI should be used.

  16. The effect of dead elements on the accuracy of Doppler ultrasound measurements.

    PubMed

    Vachutka, Jaromir; Dolezal, Ladislav; Kollmann, Christian; Klein, Jakob

    2014-01-01

    The objective of this study is to investigate the effect of multiple dead elements in an ultrasound probe on the accuracy of Doppler ultrasound measurements. For this work, we used a specially designed ultrasound imaging system, the Ultrasonix Sonix RP, that provides the user with the ability to disable selected elements in the probe. Using fully functional convex, linear, and phased array probes, we established a performance baseline by measuring the parameters of a laminar parabolic flow profile. These same parameters were then measured using probes with 1 to 10 disabled elements. The acquired velocity spectra from the functional probes and the probes with disabled elements were then analyzed to determine the overall Doppler power, maximum flow velocity, and average flow velocity. Color Flow Doppler images were also evaluated in a similar manner. The analysis of the Doppler spectra indicates that the overall Doppler power as well as the detected maximum and average velocities decrease with the increasing number of disabled elements. With multiple disabled elements, decreases in the detected maximum and average velocities greater than 20% were recorded. Similar results were also observed with Color Flow Doppler measurements. Our results confirmed that the degradation of the ultrasound probe through the loss of viable elements will negatively affect the quality of the Doppler-derived diagnostic information. We conclude that the results of Doppler measurements cannot be considered accurate or reliable if there are four or more contiguous dead elements in any given probe.

  17. Velocity Structure and Spatio-temporal Evolution in the Head Turbidity Currents based on Ultrasound Doppler Velocity Profiling

    NASA Astrophysics Data System (ADS)

    Nomura, Shun; Cesare Giovanni, De; Takeda, Yasushi; Yoshida, Taiki; Tasaka, Yuji; Sakaguchi, Hide

    2017-04-01

    Particle laden flow or turbidity current along the sea floor are important as a sediment conveyer and a formation factor of the submarine topography in the geological field. Especially, in the head of the flow, the kinematic energy is frequently exchanged through the boundary of the ambient water and the seabed floor, and it dominants the substantial dynamics of turbidity currents. An understanding of its turbulence structure helps to predict the sediment transport and layer development processes. To comprehend its dynamics precisely, flume test were conducted with continuously fed fluid quartz flour mixture supply. The flow velocities were measured at two different angles by the ultrasound Doppler velocity profiler UVP and both velocity components, in flow direction and on the vertical axis, were extracted. The fundamental velocity structure corresponds to the theories found in literature. Its spatio-temporal evolution was examined from the velocity distribution profiles along the downstream directions. Additionally, developing processes of head structures were also discussed through hydraulic statistic values such as mean velocity, Reynolds stress, and turbulent kinematic energy.

  18. Accuracy of velocity and power determination by the Doppler method

    NASA Technical Reports Server (NTRS)

    Rottger, J.

    1984-01-01

    When designing a Mesosphere-Stratosphere-Troposphere (MST) radar antenna one has to trade between the choices to optimize the effective aperture or to optimize the sidelobe suppression. An optimization of the aperture increases the sensitivity. Suppression of side-lobes by tapering attenuates undesirable signals which spoil the estimates of reflectivity and velocity. Generally, any sidelobe effects are equivalent to a broadening of the antenna beam. The return signal is due to a product of the antenna pattern with the varying atmospheric reflectivity structures. Thus, knowing the antenna pattern, it is in principle possible to find the signal spectra, which, however, may be a tedious computational and ambiguous procedure. For vertically pointing main beams the sidelobe effects are efficiently suppressed because of the aspect sensitivity. It follows that sidelobes are a minor problem for spaced antenna methods. However, they can be crucial for Doppler methods, which need off-vertical beams. If a sidelobe is pointing towards the zenith a larger power may be received from the vertical than off-vertical directions, but quantitative estimates of this effect are not yet known. To get an error estimate of sidelobe effects with an off-vertical main beam a 1-dimensional example is considered.

  19. Errors in radial velocity variance from Doppler wind lidar

    DOE PAGES

    Wang, H.; Barthelmie, R. J.; Doubrawa, P.; ...

    2016-08-29

    A high-fidelity lidar turbulence measurement technique relies on accurate estimates of radial velocity variance that are subject to both systematic and random errors determined by the autocorrelation function of radial velocity, the sampling rate, and the sampling duration. Our paper quantifies the effect of the volumetric averaging in lidar radial velocity measurements on the autocorrelation function and the dependence of the systematic and random errors on the sampling duration, using both statistically simulated and observed data. For current-generation scanning lidars and sampling durations of about 30 min and longer, during which the stationarity assumption is valid for atmospheric flows, themore » systematic error is negligible but the random error exceeds about 10%.« less

  20. Errors in radial velocity variance from Doppler wind lidar

    SciTech Connect

    Wang, H.; Barthelmie, R. J.; Doubrawa, P.; Pryor, S. C.

    2016-08-29

    A high-fidelity lidar turbulence measurement technique relies on accurate estimates of radial velocity variance that are subject to both systematic and random errors determined by the autocorrelation function of radial velocity, the sampling rate, and the sampling duration. Our paper quantifies the effect of the volumetric averaging in lidar radial velocity measurements on the autocorrelation function and the dependence of the systematic and random errors on the sampling duration, using both statistically simulated and observed data. For current-generation scanning lidars and sampling durations of about 30 min and longer, during which the stationarity assumption is valid for atmospheric flows, the systematic error is negligible but the random error exceeds about 10%.

  1. Acoustic Doppler discharge-measurement system

    USGS Publications Warehouse

    Simpson, Michael R.; Oltmann, Richard N.; ,

    1990-01-01

    A discharge-measurement system that uses a vessel-mounted acoustic Doppler current profiler has been developed and tested by the U.S. Geological Survey. Discharge measurements using the system require a fraction of the time needed for conventional current-meter discharge measurements and do not require shore-based navigational aids or tag lines for positioning the vessel.

  2. Recalibration of Mount Wilson Doppler measurements (Research note)

    NASA Technical Reports Server (NTRS)

    Snodgrass, H. B.; Howard, R.; Webster, L.

    1984-01-01

    The dispersion calibration of spectroscopic velocity measurements made with the 150-ft tower telescope at Mt. Wilson Observatory is revised upward by 0.55 percent on the basis of observations of the six lines of comparable shape and equivalent width nearest the 5250.2-A line of Fe-I used in the solar Doppler rate measurements. The dispersion results are presented in a graph, and the superiority of the Kitt Peak wavelength tables (Pierce and Breckenridge, 1973) over those of Moore et al. (1966) is demonstrated. As a result of the recalibration, all recent spectroscopic velocities from this telescope must be revised downward by 0.55 percent.

  3. Recalibration of Mount Wilson Doppler measurements (Research note)

    NASA Technical Reports Server (NTRS)

    Snodgrass, H. B.; Howard, R.; Webster, L.

    1984-01-01

    The dispersion calibration of spectroscopic velocity measurements made with the 150-ft tower telescope at Mt. Wilson Observatory is revised upward by 0.55 percent on the basis of observations of the six lines of comparable shape and equivalent width nearest the 5250.2-A line of Fe-I used in the solar Doppler rate measurements. The dispersion results are presented in a graph, and the superiority of the Kitt Peak wavelength tables (Pierce and Breckenridge, 1973) over those of Moore et al. (1966) is demonstrated. As a result of the recalibration, all recent spectroscopic velocities from this telescope must be revised downward by 0.55 percent.

  4. A comparison of a coaxial focused laser Doppler system in atmospheric measurements

    NASA Technical Reports Server (NTRS)

    Karaki, S.

    1973-01-01

    Measurements of atmospheric velocities and turbulence with the laser Doppler system were obtained, and the results compared with cup anemometer and hot-wire measurements in the same wind field. The laser Doppler velocimeter (LDV) is described along with the test procedures. It was found that mean values determined from the LDV data are within 5% of other anemometer data for long time periods, and the LDV measures higher velocities.

  5. Evaluation of gridded scanning ARM cloud radar reflectivity observations and vertical doppler velocity retrievals

    NASA Astrophysics Data System (ADS)

    Lamer, K.; Tatarevic, A.; Jo, I.; Kollias, P.

    2014-04-01

    The scanning Atmospheric Radiation Measurement (ARM) cloud radars (SACRs) provide continuous atmospheric observations aspiring to capture the 3-D cloud-scale structure. Sampling clouds in 3-D is challenging due to their temporal-spatial scales, the need to sample the sky at high elevations and cloud radar limitations. Thus, a suggested scan strategy is to repetitively slice the atmosphere from horizon to horizon as clouds advect over the radar (Cross-Wind Range-Height Indicator - CW-RHI). Here, the processing and gridding of the SACR CW-RHI scans are presented. First, the SACR sample observations from the ARM Southern Great Plains and Cape Cod sites are post-processed (detection mask, gaseous attenuation correction, insect filtering and velocity de-aliasing). The resulting radial Doppler moment fields are then mapped to Cartesian coordinates with time as one of the dimensions. Next the Cartesian-gridded Doppler velocity fields are decomposed into the horizontal wind velocity contribution and the vertical Doppler velocity component. For validation purposes, all gridded and retrieved fields are compared to collocated zenith-pointing ARM cloud radar measurements. We consider that the SACR sensitivity loss with range, the cloud type observed and the research purpose should be considered in determining the gridded domain size. Our results also demonstrate that the gridded SACR observations resolve the main features of low and high stratiform clouds. It is established that the CW-RHI observations complemented with processing techniques could lead to robust 3-D cloud dynamical representations up to 25-30 degrees off zenith. The proposed gridded products are expected to advance our understanding of 3-D cloud morphology, dynamics and anisotropy and lead to more realistic 3-D radiative transfer calculations.

  6. Comparison of blood flow velocity through the internal carotid artery based on Doppler ultrasound and numerical simulation.

    PubMed

    Hassani-Ardekani, Hajar; Ghalichi, Farzan; Niroomand-Oscuii, Hanieh; Farhoudi, Mehdi; Tarzmani, Mohammad Kazem

    2012-12-01

    Doppler ultrasound is a usual non-invasive method to estimate the stenosis percentage in large arteries such as carotid by measuring maximum velocity of blood flow. Based on clinical investigations, because of vessel wall motions, Doppler positioning and angle correction, some errors can arise in Doppler results which lead to incorrect diagnosis. The aim of this study was to compare the results of Doppler test and the numerical simulation of blood flow in the same case. For this evaluation, two patients including an 87-year-old man and a 72-year-old woman suffering from stenosis in the internal carotid artery were selected. First, clinical information of each patient such as CT-Angio scan images and Doppler ultrasound results on different locations of the stenosed artery were obtained. Then, the geometries were reconstructed and numerical simulations were carried out using ANSYS software. Results showed that the velocity profile of Doppler test and numerical simulation were in good agreement at the regions of pre-and post-stenosis. However, the value of maximum velocity at the stenotic region had significant differences.

  7. Doppler-shifted fluorescence imaging of velocity fields in supersonic reacting flows

    NASA Technical Reports Server (NTRS)

    Allen, M. G.; Davis, S. J.; Kessler, W. J.; Sonnenfroh, D. M.

    1992-01-01

    The application of Doppler-shifted fluorescence imaging of velocity fields in supersonic reacting flows is analyzed. Focussing on fluorescence of the OH molecule in typical H2-air Scramjet flows, the effects of uncharacterized variations in temperature, pressure, and collisional partner composition across the measurement plane are examined. Detailed measurements of the (1,0) band OH lineshape variations in H2-air combustions are used, along with single-pulse and time-averaged measurements of an excimer-pumped dye laser, to predict the performance of a model velocimeter with typical Scramjet flow properties. The analysis demonstrates the need for modification and control of the laser bandshape in order to permit accurate velocity measurements in the presence of multivariant flow properties.

  8. Doppler-shifted fluorescence imaging of velocity fields in supersonic reacting flows

    SciTech Connect

    Allen, M.G.; Davis, S.J.; Kessler, W.J.; Sonnenfroh, D.M. )

    1992-07-01

    The application of Doppler-shifted fluorescence imaging of velocity fields in supersonic reacting flows is analyzed. Focussing on fluorescence of the OH molecule in typical H2-air Scramjet flows, the effects of uncharacterized variations in temperature, pressure, and collisional partner composition across the measurement plane are examined. Detailed measurements of the (1,0) band OH lineshape variations in H2-air combustions are used, along with single-pulse and time-averaged measurements of an excimer-pumped dye laser, to predict the performance of a model velocimeter with typical Scramjet flow properties. The analysis demonstrates the need for modification and control of the laser bandshape in order to permit accurate velocity measurements in the presence of multivariant flow properties. 13 refs.

  9. Laser Doppler velocimeter aerial spray measurements

    NASA Technical Reports Server (NTRS)

    Zalay, A. D.; Eberle, W. R.; Howle, R. E.; Shrider, K. R.

    1978-01-01

    An experimental research program for measuring the location, spatial extent, and relative concentration of airborne spray clouds generated by agricultural aircraft is described. The measurements were conducted with a ground-based laser Doppler velocimeter. The remote sensing instrumentation, experimental tests, and the results of the flight tests are discussed. The cross section of the aerial spray cloud and the observed location, extent, and relative concentration of the airborne particulates are presented. It is feasible to use a mobile laser Doppler velocimeter to track and monitor the transport and dispersion of aerial spray generated by an agricultural aircraft.

  10. Acoustic Doppler Current Profiler Surveys of Velocity Downstream of Albeni Falls Dam

    SciTech Connect

    Perkins, William A.; Titzler, P. Scott; Richmond, Marshall C.; Serkowski, John A.; Kallio, Sara E.; Bellgraph, Brian J.

    2010-09-30

    The U.S. Army Corps of Engineers (USACE), Seattle District, is studying the potential to locate fish bypass systems at Albeni Falls Dam. The USACE requested Pacific Northwest National Laboratory (PNNL) to survey velocity magnitude and direction in the dam tailrace. The empirical data collected will be used to support future numerical modeling, physical modeling, and evaluation of fish bypass system alternatives. In May 2010, PNNL conducted velocity surveys of the Albeni Falls Dam using a boat-mounted acoustic Doppler current profiler. The surveys were conducted over three days (May 25 through 27). During the survey period, total river discharge at the dam varied between 30.2 and 31.0 kcfs. A small amount of spill discharge, 2 kcfs, was present on two days (May 26 and 27). This report presents data plots showing measured velocity direction and magnitude averaged over the entire depth and over 5-ft depth increments from 5 to 30 ft.

  11. Effect of velocity profile skewing on blood velocity and volume flow waveforms derived from maximum Doppler spectral velocity.

    PubMed

    Mynard, Jonathan P; Steinman, David A

    2013-05-01

    Given evidence that fully developed axisymmetric flow may be the exception rather than the rule, even in nominally straight arteries, maximum velocity (V(max)) can lie outside the Doppler sample volume (SV). The link between V(max) and derived quantities, such as volume flow (Q), may therefore be more complex than commonly thought. We performed idealized virtual Doppler ultrasound on data from image-based computational fluid dynamics (CFD) models of the normal human carotid artery and investigated how velocity profile skewing and choice of sample volume affected V(max) waveforms and derived Q variables, considering common assumptions about velocity profile shape (i.e., Poiseuille or Womersley). Severe velocity profile skewing caused substantial errors in V(max) waveforms when using a small, centered SV, although peak V(max) was reliably detected; errors with a long SV covering the vessel diameter were orientation dependent but lower overall. Cycle-averaged Q calculated from V(max) was typically within ±15%, although substantial skewing and use of a small SV caused 10%-25% underestimation. Peak Q derived from Womersley's theory was generally accurate to within ±10%. V(max) pulsatility and resistance indexes differed from Q-based values, although the Q-based resistance index could be predicted reliably. Skewing introduced significant error into V(max)-derived Q waveforms, particularly during mid-to-late systole. Our findings suggest that errors in the V(max) and Q waveforms related to velocity profile skewing and use of a small SV, or orientation-dependent errors for a long SV, could limit their use in wave analysis or for constructing characteristic or patient-specific flow boundary conditions for model studies.

  12. Evaluation of turbulence measurement techniques from a single Doppler lidar

    NASA Astrophysics Data System (ADS)

    Bonin, Timothy A.; Choukulkar, Aditya; Brewer, W. Alan; Sandberg, Scott P.; Weickmann, Ann M.; Pichugina, Yelena L.; Banta, Robert M.; Oncley, Steven P.; Wolfe, Daniel E.

    2017-08-01

    Measurements of turbulence are essential to understand and quantify the transport and dispersal of heat, moisture, momentum, and trace gases within the planetary boundary layer (PBL). Through the years, various techniques to measure turbulence using Doppler lidar observations have been proposed. However, the accuracy of these measurements has rarely been validated against trusted in situ instrumentation. Herein, data from the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) are used to verify Doppler lidar turbulence profiles through comparison with sonic anemometer measurements. For 17 days at the end of the experiment, a single scanning Doppler lidar continuously cycled through different turbulence measurement strategies: velocity-azimuth display (VAD), six-beam scans, and range-height indicators (RHIs) with a vertical stare.Measurements of turbulence kinetic energy (TKE), turbulence intensity, and stress velocity from these techniques are compared with sonic anemometer measurements at six heights on a 300 m tower. The six-beam technique is found to generally measure turbulence kinetic energy and turbulence intensity the most accurately at all heights (r2 ≈ 0.78), showing little bias in its observations (slope of ≈ 0. 95). Turbulence measurements from the velocity-azimuth display method tended to be biased low near the surface, as large eddies were not captured by the scan. None of the methods evaluated were able to consistently accurately measure the shear velocity (r2 = 0.15-0.17). Each of the scanning strategies assessed had its own strengths and limitations that need to be considered when selecting the method used in future experiments.

  13. Measurement of the Doppler power of flowing blood using ultrasound Doppler devices.

    PubMed

    Huang, Chih-Chung; Chou, Hung-Lung; Chen, Pay-Yu

    2015-02-01

    Measurement of the Doppler power of signals backscattered from flowing blood (henceforth referred to as the Doppler power of flowing blood) and the echogenicity of flowing blood have been used widely to assess the degree of red blood cell (RBC) aggregation for more than 20 y. Many studies have used Doppler flowmeters based on an analogue circuit design to obtain the Doppler shifts in the signals backscattered from flowing blood; however, some recent studies have mentioned that the analogue Doppler flowmeter exhibits a frequency-response problem whereby the backscattered energy is lost at higher Doppler shift frequencies. Therefore, the measured Doppler power of flowing blood and evaluations of RBC aggregation obtained using an analogue Doppler device may be inaccurate. To overcome this problem, the present study implemented a field-programmable gate array-based digital pulsed-wave Doppler flowmeter to measure the Doppler power of flowing blood, in the aim of providing more accurate assessments of RBC aggregation. A clinical duplex ultrasound imaging system that can acquire pulsed-wave Doppler spectrograms is now available, but its usefulness for estimating the ultrasound scattering properties of blood is still in doubt. Therefore, the echogenicity and Doppler power of flowing blood under the same flow conditions were measured using a laboratory pulser-receiver system and a clinical ultrasound system, respectively, for comparisons. The experiments were carried out using porcine blood under steady laminar flow with both RBC suspensions and whole blood. The experimental results indicated that a clinical ultrasound system used to measure the Doppler spectrograms is not suitable for quantifying Doppler power. However, the Doppler power measured using a digital Doppler flowmeter can reveal the relationship between backscattering signals and the properties of blood cells because the effects of frequency response are eliminated. The measurements of the Doppler power and

  14. Nonsearching Doppler parameter and velocity estimation method for synthetic aperture radar ground moving target imaging

    NASA Astrophysics Data System (ADS)

    Li, Zhongyu; Wu, Junjie; Huang, Yunlin; Yang, Haiguang; Yang, Jianyu

    2016-07-01

    For synthetic aperture radar (SAR), ground moving target (GMT) imaging necessitates the compensation of the additional azimuth modulation contributed by the unknown movement of the GMT. That is to say, it is necessary to estimate the Doppler parameters of the GMT without a priori knowledge of the GMT's motion parameters. This paper presents a Doppler parameter and velocity estimation method to refocus the GMT from its smeared response in SAR image. The main idea of this method is that an azimuth reference function is constructed to do the correlation integral with the azimuth signal of the GMT. And in general, the Doppler parameters of the presumed azimuth reference function are different from those of the GMT's azimuth signal since the velocity parameters of the GMT are unknown. Therefore, the correlation operation referred to here is actually mismatched, and the processing result of is shifted and defocused. The shifted and defocused result is utilized to get the real Doppler parameters and the velocity parameters of the GMT. One advantage of this method is that it is a nonsearching method. Another advantage is that both the Doppler centroid and the Doppler frequency rate of the GMT can be simultaneously estimated according to the relationships between the Doppler parameters and the smeared response of the GMT. In addition, the velocity of the GMT can also be obtained based on the estimated Doppler parameters. Numerical simulations and experimental data processing verify the validity of the method proposed.

  15. Radial pump impeller measurements using a laser Doppler velocimeter

    NASA Astrophysics Data System (ADS)

    Kannemans, H.

    1980-03-01

    A shrouded fully transparent radial pump impeller with thin backswept blades has been tested using a laser Doppler velocimeter. Two components of the velocity were measured relative to the laboratory reference frame in a plane perpendicular to the axis of rotation. The velocity distribution is presented relative to the blades at different radii and different flow rates over the whole blade passage. The results show that the flow is essentially unsteady and, at low flow rate, highly influenced by viscous effects. A comparison between the experimental data and a potential flow theory shows good agreement at high flow rates.

  16. Velocity measurements in the plume of an arcjet engine

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J.; Deininger, W. D.

    1987-01-01

    A nonintrusive technique has been used to conduct a radial survey in the flow field of an arcjet engine plume. The technique measures the Doppler shift of an optically thin line resulting from recombination and relaxation processes in the high Mach number stream, in order to determine flow velocities. Atom temperature can also be calculated from the same Doppler-broadened line widths, when these shifts are measured with a scanning Fabry-Perot spectrometer whose design is presented in detail.

  17. Velocity measurements in the plume of an arcjet engine

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J.; Deininger, W. D.

    1987-01-01

    A nonintrusive technique has been used to conduct a radial survey in the flow field of an arcjet engine plume. The technique measures the Doppler shift of an optically thin line resulting from recombination and relaxation processes in the high Mach number stream, in order to determine flow velocities. Atom temperature can also be calculated from the same Doppler-broadened line widths, when these shifts are measured with a scanning Fabry-Perot spectrometer whose design is presented in detail.

  18. Velocity measurements in the plume of an arcjet engine

    SciTech Connect

    Pivirotto, T.J.; Deininger, W.D.

    1987-05-01

    A nonintrusive technique has been used to conduct a radial survey in the flow field of an arcjet engine plume. The technique measures the Doppler shift of an optically thin line resulting from recombination and relaxation processes in the high Mach number stream, in order to determine flow velocities. Atom temperature can also be calculated from the same Doppler-broadened line widths, when these shifts are measured with a scanning Fabry-Perot spectrometer whose design is presented in detail. 19 references.

  19. Mean velocities measured with the double pulse technique

    NASA Astrophysics Data System (ADS)

    Nielsen, E.

    2004-10-01

    It was recently observed that double-pulse measurements of the mean velocities of a wide asymmetric spectrum are a function of the time lag between the pulses (Uspensky et al., 2004). Here we demonstrate that the observed relationship probably is influenced by the measurement technique in a way that is consistent with theoretical prediction. It is further shown that for small time lags the double pulse velocity is a good approximation to the mean Doppler velo-city.

  20. Wind measurements with the High Resolution Doppler Imager (HRDI)

    NASA Technical Reports Server (NTRS)

    Skinner, W. R.; Hays, P. B.; Abreu, V. J.

    1985-01-01

    The Upper Atmosphere Research Satellite (UARS), to be launched in 1989, is to provide a global data set required to understand the mechanisms controlling upper atmosphere structure and processes, as well as the response of the upper atmosphere to natural and human perturbations. The High Resolution Doppler Imager (HRDI) is the primary instrument for measuring the dynamics of the stratosphere and mesosphere. The goal of HRDI is to measure wind velocities in the stratosphere and mesosphere during the day and the mesosphere and thermosphere at night with an accuracy of 5 m/sec. HRDI will determine winds by measuring Doppler shifts of atmosphere absorption and emission features. Line of sight winds will be taken in two directions, thus allowing the wind vector to be formed. The HRDI instrument is overviewed. The basis of the measurement is explained, as is an outline of the instrument. Since neither instrument nor observational techniques is fully mature, only a brief sketch is presented.

  1. Doppler velocities in the ion tail of comet Levy 1990c

    NASA Technical Reports Server (NTRS)

    Jockers, Klaus; Rauer, H.; Debi-Prasad, C.; Geyer, E. H.

    1992-01-01

    We have obtained time alternating sequences of column density maps and Doppler velocity fields in the plasma tail of comet Levy 1990c. We describe the observing technique and data analysis, and we present first results.

  2. Fixed region of nondistensibility after coarctation repair: in vitro validation of its influence on Doppler peak velocities.

    PubMed

    Verhaaren, H; De Mey, S; Coomans, I; Segers, P; De Wolf, D; Matthys, D; Verdonck, P

    2001-06-01

    After coarctectomy, local loss of distensibility is noted in addition to mild anatomic narrowing. We hypothesize that the increased Doppler peak velocities measured at the aortic isthmus in these patients partly reflect obstruction secondary to the stiff surgical scar. The hypothesis was studied in a pulsatile hydraulic model. Thirty-one patients (13.0 +/- 4.0 years of age), 10.5 +/- 4.7 years after coarctectomy by end-to-end anastomosis, were studied clinically and echocardiographically. Indexes of distensibility were calculated. The effect of isolated increased stiffness was studied in vitro with a stiff and a compliant 1:1 scale latex model of the aorta mounted in a pulsatile full-scale circulation loop. Local stiffening was obtained by a rigid ring mounted around the aorta, fitted to the dimension of the unloaded aorta. For different pressure and flow regimens, pressures and Doppler velocities were measured across the ring. Mean peak velocities at the surgical scar were 2.2 +/- 0.4 m/s. Mild anatomic stenosis was present. All distensibility indexes indicated locally increased stiffness (P <.001). In the stiff latex model, Doppler peak velocities increased from 1.89 +/- 0.04 m/s to 2.32 +/- 0.06 m/s (P <.03); in the compliant model, from 1.15 +/- 0.03 m/s to 1.79 +/- 0.05 m/s (P <.001). The increase of Doppler peak velocities depends on model compliance only and is independent of flow rate, length of the noncompliant segment, and viscosity of the perfusion fluid. Velocities do not change when semicircular stiffening is applied. We have demonstrated in vitro that isolated local nondistensibility leads to vessel narrowing during vascular distension. The relative contribution of local scar stiffness in the increase of Doppler peak velocities after coarctectomy was hereby assessed.

  3. Arterial compliance measurement using a noninvasive laser Doppler measurement system

    NASA Astrophysics Data System (ADS)

    Hast, Jukka T.; Myllylae, Risto A.; Sorvoja, Hannu; Nissilae, Seppo M.

    2000-11-01

    The aim of this study was to study the elasticity of the arterial wall using a non-invasive laser Doppler measurement system. The elasticity of the arterial wall is described by its compliance factor, which can be determined when both blood pressure and the radial velocity of the arterial wall are known. To measure radical velocity we used a self- mixing interferometer. The compliance factors were measured from six healthy volunteers, whose ages were varied from 21 to 32. Although a single volunteer's compliance factor is presented as an example, this paper treated the volunteers as a group. First, the elastic modulus, which is inversely proportional to the compliance factor, was determined. Then, an exponential curve was fitted into the measured data and a characteristic equation for the elastic modulus of the arterial wall was determined. The elastic modulus was calculated at different pressures and the results were compared to the static incremental modulus of a dog's femoral artery. The results indicate that there is a correlation between human elastic and canine static incremental modulus for blood pressures varying from 60 to 110 mmHg.

  4. Evaluation of droplet velocity and size from nasal spray devices using phase Doppler anemometry (PDA).

    PubMed

    Liu, Xiaofei; Doub, William H; Guo, Changning

    2010-03-30

    To determine aerosol deposition during the inhalation drug delivery, it is important to understand the combination of velocity and droplet size together. In this study, phase Doppler anemometry (PDA) was used to simultaneously characterize the aerosol velocity and droplet size distribution (DSD) of three nasal spray pumps filled with water. Thirteen sampling positions were located in the horizontal cross-sectional area of the nasal spray plumes at a distance of 3cm from the pump orifice. The results showed droplet velocities near the center of the spray plume were higher and more consistent than those near the edge. The pumps examined showed significant differences in their aerosol velocity at the center of the spray plume, which suggest that this metric might be used as a discriminating parameter for in vitro testing of nasal sprays. Droplet size measurements performed using PDA were compared with results from laser light scattering measurements. The ability of PDA to provide simultaneous measurements of aerosol velocity and size makes it a powerful tool for the detailed investigation of nasal spray plume characteristics.

  5. A GIS-based Computational Tool for Multidimensional Flow Velocity by Acoustic Doppler Current Profilers

    NASA Astrophysics Data System (ADS)

    Kim, D.; Winkler, M.; Muste, M.

    2015-06-01

    Acoustic Doppler Current Profilers (ADCPs) provide efficient and reliable flow measurements compared to other tools for characteristics of the riverine environments. In addition to originally targeted discharge measurements, ADCPs are increasingly utilized to assess river flow characteristics. The newly developed VMS (Velocity Mapping Software) aims at providing an efficient process for quality assurance, mapping velocity vectors for visualization and facilitating comparison with physical and numerical model results. VMS was designed to provide efficient and smooth work flows for processing groups of transects. The software allows the user to select group of files and subsequently to conduct statistical and graphical quality assurance on the files as a group or individually as appropriate. VMS also enables spatial averaging in horizontal and vertical plane for ADCP data in a single or multiple transects over the same or consecutive cross sections. The analysis results are displayed in numerical and graphical formats.

  6. Changes in uterine artery Doppler flow velocity waveforms during the third stage of labor.

    PubMed

    Maymon, R; Herman, A; Halperin, R; Bukovsky, I; Weinraub, Z; Ariely, S

    1995-01-01

    Transabdominal Doppler velocity waveform measurements of the uterine arteries during the third stage of labor were performed upon 25 patients with uncomplicated vaginal deliveries and 5 with prolonged third stage in order to further assess third-stage mechanisms. Based on Doppler flow measurements, three phases of the third stage of labor were observed: (1) a latent phase with a systolic/diastolic ratio (S/D) and a pulsatility index (PI) of 2.14 +/- 0.49 and 0.89 +/- 0.17, respectively; (2) a contraction and detachment phase with an S/D and PI of 2.53 +/- 0.53 and 1.28 +/- 0.37, respectively, and (3) an expulsion phase with an S/D and PI of 2.20 +/- 0.34 and 0.91 +/- 0.20, respectively (p < 0.05). During the third stage of labor, it was shown that uterine contractions squeezed the uterine vessels as they traversed the myometrium, leading to an increase in the extrinsic resistance, which was reflected by high resistance flow. Following placental separation and changes in the placental-site wall, there was slight uterine relaxation resulting in decreased uterine vessel resistance. This observation encourages the authors to continue investigating the contribution of ultrasound and Doppler flow for studies of the postpartum period.

  7. Estimation of volume flow rate by surface integration of velocity vectors from color Doppler images.

    PubMed

    Sun, Y; Ask, P; Janerot-Sjöberg, B; Eidenvall, L; Loyd, D; Wranne, B

    1995-01-01

    A new Doppler echocardiographically based method has been developed to quantify volume flow rate by surface integration of velocity vectors (SIVV). Electrocardiographic-gated color Doppler images acquired in two orthogonal planes were used to estimate volume flow rate through a bowl-shaped surface at a given time and distance from the probe. To provide in vitro validation, the method was tested in a hydraulic model representing a pulsatile flow system with a restrictive orifice. Accurate estimates of stroke volume (+/- 10%) were obtained in a window between 1.2 and 1.6 cm proximal to the orifice, just before the region of prestenotic acceleration. By use of the Bernoulli's equation, the estimated flows were used to generate pressure gradient waveforms across the orifice, which agreed well with the measured flows. To demonstrate in vivo applicability, the SIVV method was applied retrospectively to the determination of stroke volume and subaortic flow from the apical three-chamber and five-chamber views in two patients. Stroke volume estimates along the left ventricular outflow tract showed a characteristic similar to that in the in vitro study and agreed well with those obtained by the Fick oxygen method. The region where accurate measurements can be obtained is affected by instrumental factors including Nyquist velocity limit, wall motion filter cutoff, and color flow sector angle. The SIVV principle should be useful for quantitative assessment of the severity of valvular abnormalities and noninvasive measurement of pulsatile volume flows in general.

  8. Assessment of the effect of vessel curvature on Doppler measurements in steady flow.

    PubMed

    Balbis, S; Guiot, C; Roatta, S; Arina, R; Todros, T

    2004-05-01

    Blood vessel curvature is responsible for the appearance of nonaxial velocity components and for minor changes in the pattern of the axial flow. All the velocity components are expected to contribute to the Doppler signal produced by the ultrasound (US) backscattered by the insonated blood cells, the axial velocity, contributing to the actual volumetric blood flow, and the transverse velocity, causing the recirculating vortices. A detailed, separate analysis of the velocity components is, therefore, mandatory to quantify how vessel curvature can affect results and clinical diagnosis. Both experimental in vitro measures and numerical simulations were performed on a curved tube and the Doppler power spectra so obtained were compared. The satisfactorily agreement of the above spectra shows that the nonaxial velocity components are easily detectable with clinical equipment and that their amplitude, as expected, is not negligible and can bias Doppler measurements and resulting clinical diagnosis.

  9. Molecular flow velocity using Doppler shifted Raman spectroscopy

    NASA Technical Reports Server (NTRS)

    Exton, Reginald J.; Hillard, Mervin E., Jr.; Lempert, Walter R.; Covell, Peter F.; Miller, David S.

    1987-01-01

    Measurements of molecular flow velocity, static pressure, and translational temperature in the free-stream of a supersonic wind tunnel and behind the shock of a simple model are reviewed. Based on the free-stream demonstration using inverse Raman spectroscopy, an experiment is outlined to investigate the lee-side flow field above a swept delta wing and simulated spectra expected for the leading-edge vortex are included. The extension of the technique to hypersonic wind tunnels is also explored through the use of simulated spectra.

  10. Power spectrum and blood flow velocity images obtained by dual-beam backscatter laser Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Ishida, Hiroki; Yasue, Youichi; Hachiga, Tadashi; Andoh, Tsugunobu; Akiguchi, Shunsuke; Kuraishi, Yasushi; Shimizu, Tadamichi

    2014-07-01

    We developed a micro multipoint laser Doppler velocimeter (μ-MLDV) for noninvasive in-vivo measurements of blood flow and we presented the results of demonstrations performed on experimental animals. In this paper, we investigate the validity of power spectrum analysis for determining the flow velocity and the minimum power of the semiconductor laser in the μ-MLDV. Although average velocity is generally estimated from a peak position ( f peak) in the power spectrum, the power spectrum of blood flow included an additional component in the high-frequency region. The conventional method for determining the average velocity of flows of transparent artificial fluids, which involves determining the average velocity from f peak, is unsuitable for in-vivo measurements of blood flow. The laser power was reduced from 140 to 30mW since 30mW was the minimum power at which images of blood flow velocity in microvessels could be obtained. About 30mW (power density of 15mW/mm2) is the maximum power which can be irradiated to humans. Further reduction in the laser power is necessary before this technique can be applied to humans.

  11. Pulsed photoacoustic Doppler flow measurements in blood-mimicking phantoms

    NASA Astrophysics Data System (ADS)

    Brunker, J.; Beard, P.

    2011-03-01

    The feasibility of making spatially resolved measurements of blood flow using pulsed photoacoustic Doppler techniques has been explored. Doppler time shifts were quantified via cross-correlation of pairs of photoacoustic waveforms generated within a blood-simulating phantom using pairs of laser light pulses. The photoacoustic waves were detected using a focussed or planar PZT ultrasound transducer. For each flow measurement, a series of 100 waveform pairs was collected. Previous data processing methods involved rejection of poorly correlated waveform pairs; the modal velocity value and standard deviation were then extracted from the selected distribution of velocity measurements. However, the data selection criteria used in this approach is to some extent arbitrary. A new data analysis protocol, which involves averaging the 100 cross-correlation functions and thus uses all of the measured data, has been designed in order to prevent exclusion of outliers. This more rigorous approach has proved effective for quantifying the linear motion of micron-scale absorbers imprinted on an acetate sheet moving with velocities in the range 0.14 to 1.25 ms-1. Experimental parameters, such as the time separation between the laser pulses and the transducer frequency response, were evaluated in terms of their effect on the accuracy, resolution and range of measurable velocities. The technique was subsequently applied to fluid phantoms flowing at rates less than 5 mms-1 along an optically transparent tube. Preliminary results are described for three different suspensions of phenolic resin microspheres, and also for whole blood. Velocity information was obtained even under non-optimal conditions using a low frequency transducer and a low pulse repetition frequency. The distinguishing advantage of pulsed rather than continuous-wave excitation is that spatially resolved velocity measurements can be made. This offers the prospect of mapping flow within the microcirculation and thus

  12. Noninvasive microstructural and velocity imaging in humans by color Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yazdanfar, Siavash

    The objective of this dissertation is to develop the optical instrumentation, electronics, and signal processing for high-resolution blood flow imaging using optical coherence tomography (OCT) in human subjects. In particular, in vivo OCT blood flow imaging, termed color Doppler OCT (CDOCT), is applied for the first time to measurements in human vasculature of the retina and skin. CDOCT is similar to color Doppler ultrasound, whereas depth-resolved flow information is extracted from reflectivity profiles obtained from phase-sensitive, low-coherence interferometry. Although CDOCT has been demonstrated in tissue-mimicking phantoms and in living animal models, the technique has not yet been extended to blood flow imaging in humans. In this project, CDOCT was integrated with a modified slit lamp biomicroscope for imaging of retinal blood flow, and additional technical requirements necessary for retinal flow imaging were met. This system was used to acquire the first high resolution, cross-sectional images of blood flow with OCT in humans. The image acquisition rate was increased to examine retinal hemodynamics in normal subjects. A method was introduced for improving the velocity resolution by approximately two orders of magnitude, down to ˜1 micrometer/sec, by calculating the change in the phase across sequential scans. This technique was used to achieve the highest velocity resolution to date in scattering media, and applied to imaging the human microvasculature down to the capillary level. Finally, a modification of CDOCT based on differential phase contrast was introduced for high resolution imaging in the presence of motion artifact. This technique measures the differential Doppler frequency between two beams of orthogonal polarization states that are laterally displaced on the sample. Using polarization diversity detection, the common-mode noise was removed, enabling the measurement of flow in scattering media down to the theoretical frequency resolution.

  13. Continuous cardiac output measurement - Aspects of Doppler frequency analysis

    NASA Technical Reports Server (NTRS)

    Mackay, R. S.; Hechtman, H. B.

    1975-01-01

    From the suprasternal notch blood flow velocity in the aorta can be measured non-invasively by a Doppler probe. Integration over systole after frequency analysis gives a measure of stroke volume if a separate diameter observation is incorporated. Frequency analysis by a zero crossing counter or by a set of parallel phaselock loops was less effective than a set of bandpass filters. Observations on dogs, baboons and humans before and after exercise or surgery suggest the indications to be useful. Application to judging heart failure by the effect of introducing a volume load is indicated. Changes in output also are measured in freely moving subjects.

  14. Continuous cardiac output measurement - Aspects of Doppler frequency analysis

    NASA Technical Reports Server (NTRS)

    Mackay, R. S.; Hechtman, H. B.

    1975-01-01

    From the suprasternal notch blood flow velocity in the aorta can be measured non-invasively by a Doppler probe. Integration over systole after frequency analysis gives a measure of stroke volume if a separate diameter observation is incorporated. Frequency analysis by a zero crossing counter or by a set of parallel phaselock loops was less effective than a set of bandpass filters. Observations on dogs, baboons and humans before and after exercise or surgery suggest the indications to be useful. Application to judging heart failure by the effect of introducing a volume load is indicated. Changes in output also are measured in freely moving subjects.

  15. Measurement Capabilities of Single-Pulse Planar Doppler Velocimetry

    NASA Technical Reports Server (NTRS)

    McKenzie, Robert L.; Kutler, Paul F. (Technical Monitor)

    1994-01-01

    Preliminary investigations are described of a method that is capable of measuring instantaneous, 3-D, velocity vectors everywhere in a light sheet generated by a pulsed laser. The technique, here called Planar Doppler Velocimetry (PDV), is a variation of a new concept for velocity measurements that was called Doppler Global Velocimetry (DGV) in its original disclosure. The concept relies on the use of a narrowband laser and measurements of the Doppler shift of scattered light from particles moving with a flow. The Doppler shift is recorded as a variation in transmission through a sharp-edged spectral filter provided by iodine vapor in a cell. Entire fields of velocity can be determined by using a solid-state camera to record the intensity variations throughout the field of view. However, the implementation of DGV has been centered principally on the use of high power, continuous-wave, ion lasers and measurement times that are determined by the 30-ms framing times of standard video cameras. Hence, they provide velocity fields that are averaged in time at least over that period. On the other hand, the PDV concept described in this presentation incorporates a high energy, repetitively pulsed, Nd-YAG laser that is injection-seeded to make it narrowband and then frequency-doubled to provide light at frequencies absorbed by the iodine vapor. The duration of each pulse is less than 10 nanoseconds. When used in combination with nonstandard, scientific quality, solid state cameras, a sequence of images can be obtained that provides instantaneous velocity vectors everywhere in the field of view. The investigations described in this paper include an accurate characterization of the iodine cell spectral behavior and its influence on the PDV measurements, a derivation of the PDV signal analysis requirements, and the unique aspects of the pulsed laser behavior related to this application. In addition, PDV measurements are to be demonstrated using data from a rotating wheel

  16. Differentiation of constrictive pericarditis from restrictive cardiomyopathy using mitral annular velocity by tissue Doppler echocardiography.

    PubMed

    Ha, Jong-Won; Ommen, Steve R; Tajik, A Jamil; Barnes, Marion E; Ammash, Naser M; Gertz, Morie A; Seward, James B; Oh, Jae K

    2004-08-01

    This study evaluated the diagnostic role of early diastolic mitral annular velocity (E') by tissue Doppler echocardiography for differentiating constrictive pericarditis from restrictive cardiomyopathy (primary restrictive cardiomyopathy and cardiac amyloidosis). The study group consisted of 75 patients (53 men, 22 women; mean age 62 years, range 27 to 87). Of these, 23 patients had surgically confirmed constrictive pericarditis, 38 had biopsy-proved systemic amyloidosis and typical echocardiographic features of cardiac involvement, and 14 had primary restrictive cardiomyopathy. Standard mitral inflow characteristics were measured. Tissue Doppler echocardiography was used to measure E' at the septal annulus. E' was significantly higher in patients with constrictive pericarditis than in those with primary restrictive cardiomyopathy or cardiac amyloidosis (12.3 vs 5.1 cm/second, p <0.001). An E' cut-off value > or =8 cm/second resulted in 95% sensitivity and 96% specificity for the diagnosis of constrictive pericarditis. There was no overlap of E' between patients who had constrictive pericarditis and those who had cardiac amyloidosis. In a subgroup analysis of restrictive cardiomyopathy, E' of patients who had cardiac amyloidosis was significantly lower than that of patients who had primary restrictive cardiomyopathy (4.6 vs 6.3 cm/second, p <0.001). Thus, E' velocity can distinguish between constrictive pericarditis and restrictive cardiomyopathy with a specific cut-off value in patients with clinical and echocardiographic evidence of diastolic heart failure.

  17. Effect of microbubble contrast on intracranial blood flow velocity assessed by transcranial Doppler.

    PubMed

    Logallo, Nicola; Fromm, Annette; Waje-Andreassen, Ulrike; Thomassen, Lars; Matre, Knut

    2014-03-01

    Ultrasound contrast agents (UCA) salvage a considerable number of transcranial Doppler (TCD) exams which would have failed because of poor bone window. UCA bolus injection causes an undesirable increase in measured blood flow velocity (BFV). The effect of UCA continuous infusion on measured BFV has not been investigated, and some in vitro experiments suggest that gain reduction during UCA administration may also influence measured BFV. This study aimed to investigate the effect of UCA continuous infusion on BFV measured by TCD and the influence of gain reduction on these measurements in a clinical setting. The right middle cerebral artery of ten patients with optimal bone window was insonated using a 2 MHz probe. UCA were administered using an infusion pump. BFV was measured (1) at baseline, (2) during UCA infusion, (3) during UCA infusion with gain reduction, and (4) after UCA wash-out phase. Gain reduction was based on the agreement between two neurosonographers on the degree of gain reduction necessary to restore baseline Doppler signal intensity (DSI). Actual DSI was estimated offline by analysis of raw data. BFV measured during UCA infusion with no gain adjustment was significantly higher than baseline BFV [peak systolic velocity (PSV): 85.1 ± 19.7 vs. 74.4 ± 19.7 cm/s, p < 0.0001; Mean velocity (MV): 56.5 ± 11.8 vs. 50.2 ± 12.3 cm/s, p < 0.0001]. BFV measured during UCA infusion with gain reduction was not significantly higher than baseline BFV (PSV: 74.3 ± 18.9 vs. 74.4 ± 19.4 cm/s, p = 0.8; MV: 49.4 ± 11.0 vs. 50.2 ± 12.3 cm/s, p = 0.8). Actual DSI during UCA infusion with gain reduction was not significantly higher than baseline DSI (13 ± 1 vs. 13 ± 1 dB). This study shows that UCA continuous infusion leads to an increase in measured BFV which may be counteracted by reducing Doppler gain thus restoring pre-contrast DSI.

  18. Application of Spectroscopic Doppler Velocimetry for Measurement of Streamwise Vorticity

    NASA Technical Reports Server (NTRS)

    Fagan, Amy; Zaman, Khairul B.; Elam, Kristie A.; Clem, Michelle M.

    2013-01-01

    A spectroscopic Doppler velocimetry technique has been developed for measuring two transverse components of velocity and hence streamwise vorticity in free jet flows. The nonintrusive optical measurement system uses Mie scattering from a 200 mW green continuous-wave laser interacting with dust and other tracer particulates naturally present in the air flow to measure the velocities. Scattered light is collected in two opposing directions to provide measurements of two orthogonal velocity components. An air-spaced Fabry-Perot interferometer is used for spectral analysis to determine the optical frequency shift between the incident laser light and the Mie scattered light. This frequency shift is directly proportional to the velocity component in the direction of the bisector of the incident and scattered light wave propagation vectors. Data were acquired for jet Mach numbers of 1.73 and 0.99 using a convergent 1.27-cm diameter round nozzle fitted with a single triangular "delta-tab". The velocity components and the streamwise vorticity calculated from the measurements are presented. The results demonstrate the ability of this novel optical system to obtain velocity and vorticity data without any artificial seeding and using a low power laser system.

  19. Real-time vector velocity assessment through multigate Doppler and plane waves.

    PubMed

    Ricci, Stefano; Bassi, Luca; Tortoli, Piero

    2014-02-01

    Several ultrasound (US) methods have been recently proposed to produce 2-D velocity vector fields with high temporal and spatial resolution. However, the real-time implementation in US scanners is heavily hampered by the high calculation power required. In this work, we report a real-time vector Doppler imaging method which has been integrated in an open research system. The proposed approach exploits the plane waves transmitted from two sub-arrays of a linear probe to estimate the velocity vectors in 512 sample volumes aligned along the probe axis. The method has been tested for accuracy and reproducibility through simulations and in vitro experiments. Simulations over a 0° to 90° angle range of a 0.5 m/s peak parabolic flow have yielded 0.75° bias and 1.1° standard deviation for direction measurement, and 0.6 cm/s bias with 3.1% coefficient of variation for velocity assessment. In vitro tests have supported the simulation results. Preliminary measurements on the carotid artery of a volunteer have highlighted the real-time system capability of imaging complex flow configurations in an intuitive, easy, and quick way, as shown in a sample supplementary movie. These features have allowed reproducible peak velocity measurements to be obtained, as needed for quantitative investigations on patients.

  20. Estimating Discharge using Multi-level Velocity Data from Acoustic Doppler Instruments

    NASA Astrophysics Data System (ADS)

    Bang Poulsen, J.; Rømer Rasmussen, K.; Bering Ovesen, N.

    2010-12-01

    In the majority of Danish streams, weed growth affects the effective stream width and bed roughness and therefore imposes temporal variations on the stage-discharge relationship. Small stream-gradients and firm ecology based restrictions prevent that hydraulic structures are made at the discharge stations and thus remove or limit such influences. Hence, estimation of the hydrograph is based on continuous stream gauging combined with monthly control measurements of discharge and assuming linear variation of bed roughness between the monthly measurements. As a result, any non-linear drift in weed density or structure which affect the frictional characteristics of the stream during both normal and peak flows are ignored. The present investigation studies if such temporal variation in the conveyance may be detected and eventually compensated for when estimating the hydrograph. Therefore acoustic Dopplers have been placed at the main discharge station in one of the largest Danish catchments (the Skjern). The instruments were set out in early February 2010 during the winter season and have been running since then. The long term average discharge at the station is near 14 m3/s and the cross sectional profile is roughly trapezoidal having width about 15 m., but slightly skew so that the stream is about 0.5 m. deeper off the right than off the left bank. During winter, the depths are typically near 2 m. while during summer they are about 1.5 m. During peak flows, when the discharge exceeds 35 m3/s, the depth increases to more than 3 m. The Doppler instruments (Nortek) are placed on a vertical pole about 2 m. off the right bank at three fixed elevations above the streambed (0.3, 0.6, and 1.3 m); the beams point horizontally towards the left bank perpendicularly to the average flow direction. At each depth, the Doppler sensor records 10 minute average stream velocities in the central 10 m. section of the stream. During summer periods with low flow, stream velocity has only

  1. Estimation of two-dimensional intraventricular velocity and pressure maps by digital processing conventional color-Doppler sequences

    NASA Astrophysics Data System (ADS)

    Garcia, Damien; Del Alamo, Juan C.; Tanne, David; Cortina, Cristina; Yotti, Raquel; Fernandez-Aviles, Francisco; Bermejo, Javier

    2008-11-01

    Clinical echocardiographic quantification of blood flow in the left ventricle is limited because Doppler methods only provide one velocity component. We developed a new technique to obtain two-dimensional flow maps from conventional transthoracic echocardiographic acquisitions. Velocity and pressure maps were calculated from color-Doppler velocity (apical long-axis view) by solving the continuity and Euler equations under the assumptions of zero transverse fluxes of mass and momentum. This technique is fast, clinically-compliant and does not require any specific training. Particle image velocimetry experiments performed in an atrioventricular duplicator showed that the circulation and size of the diastolic vortex was quantified accurately. Micromanometer measurements in pigs showed that apex-base pressure differences extracted from two-dimensional maps qualitatively agreed with micromanometer data. Initial clinical measurements in healthy volunteers showed a large prograde vortex. Additional retrograde vortices appeared in patients with dilated cardiomyopathy and left ventricular hypertrophy.

  2. Interferometric measurement of the angular velocity of moving humans

    NASA Astrophysics Data System (ADS)

    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.

  3. Echo machine-imposed limit on transmitral spectral Doppler velocity-profile analysis.

    PubMed

    Hall, A F; Bettlach, J; Nudelman, S P; Kovács, S J

    1997-01-01

    We have previously developed a kinematic model of ventricular filling. Its application to in vivo transmitral Doppler velocity profiles provides a quantitative characterization of filling. However, the model parameters computed by solving the "inverse problem" may depend on ultrasound machine type and setting (e.g., gain, baseline filter, dynamic range). To determine machine-based effects on the computed model parameters, we performed a flow phantom study using Acuson and HP echocardiography machines at various settings. We compared maximum velocity envelopes (MVEs), as well as the model fit to these MVEs, for 3 simulated waveforms imaged by both machines. For all 3 waveforms, the machines generated comparable MVEs, fit by the model within a mean-square difference of 5E-5 (m/s)2. The associated variations in model parameters for the 3 waveforms were not uniform. Two waveforms showed slight variation between machines, with model parameters varying by less than 6%. The shortest duration waveform showed model parameter variations of 10-15%. Analysis of the parameter space for this waveform showed a constant mean-square error contour that was larger than that for the other two, causing similar small variations in measured MVEs to result in larger differences in the parameter estimates for this waveform. Because this method completely eliminates inter- and intraobserver variability, we conclude that, within the limits established, the slight contour variations due to machine type and setting should not affect this method's applicability in clinical Doppler-flow analysis.

  4. Using Doppler Shifts of GPS Signals To Measure Angular Speed

    NASA Technical Reports Server (NTRS)

    Campbell, Charles E., Jr.

    2006-01-01

    A method has been proposed for extracting information on the rate of rotation of an aircraft, spacecraft, or other body from differential Doppler shifts of Global Positioning System (GPS) signals received by antennas mounted on the body. In principle, the method should be capable of yielding low-noise estimates of rates of rotation. The method could eliminate the need for gyroscopes to measure rates of rotation. The method is based on the fact that for a given signal of frequency ft transmitted by a given GPS satellite, the differential Doppler shift is attributable to the difference between those components of the instantaneous translational velocities of the antennas that lie along the line of sight from the antennas to the GPS satellite.

  5. Particle Velocity Measuring System

    NASA Technical Reports Server (NTRS)

    Arndt, G. Dickey (Inventor); Carl, James R. (Inventor)

    1998-01-01

    Method and apparatus are provided for determining the velocity of individual food particles within a liquid/solid food mixture that is cooked by an aseptic cooking method whereby the food mixture is heated as it flows through a flowline. At least one upstream and at least one downstream microwave transducer are provided to determine the minimum possible travel time of the fastest food particle through the flowline. In one embodiment, the upstream detector is not required. In another embodiment, a plurality of small dipole antenna markers are secured to a plurality of food particles to provide a plurality of signals as the markers pass the upstream and downstream transducers. The dipole antenna markers may also include a non-linear element to reradiate a harmonic frequency of a transmitter frequency. Upstream and downstream transducers include dipole antennas that are matched to the impedance of the food slurry and a signal transmission cable by various impedance matching means including unbalanced feed to the antennas.

  6. Analysis of Doppler measurements of people

    NASA Astrophysics Data System (ADS)

    Tan, Robert; Bender, Robert

    2006-05-01

    With the changing nature of international security it is of interest to the military to use remote sensors to detect and classify people as potential threats. We chose a millimeter wave (MMW) radar as our sensor to collect data on single and small groups of people that were either walking or running to determine how easily they could be detected. This work was done to support the concept of using Ka-band radar to detect people from an airborne platform. Fully-polarimetric Ka-Band radar data was collected of people walking and running at various orientations with respect to the radar. Micro-Doppler analysis reveals Doppler oscillations with time that are characteristic of people at all orientations measured.

  7. Estimating Radar Velocity using Direction of Arrival Measurements

    SciTech Connect

    Doerry, Armin Walter; Horndt, Volker; Bickel, Douglas Lloyd; Naething, Richard M.

    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. Using embedded fibers to measure explosive detonation velocities

    SciTech Connect

    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.

  9. Measuring Turbulence from Moored Acoustic Doppler Velocimeters. A Manual to Quantifying Inflow at Tidal Energy Sites

    SciTech Connect

    Kilcher, Levi; Thomson, Jim; Talbert, Joe; DeKlerk, Alex

    2016-03-01

    This work details a methodology for measuring hub height inflow turbulence using moored acoustic Doppler velocimiters (ADVs). This approach is motivated by the shortcomings of alternatives. For example, remote velocity measurements (i.e., from acoustic Doppler profilers) lack sufficient precision for device simulation, and rigid tower-mounted measurements are very expensive and technically challenging in the tidal environment. Moorings offer a low-cost, site-adaptable and robust deployment platform, and ADVs provide the necessary precision to accurately quantify turbulence.

  10. Photoacoustic Doppler flow measurement in optically scattering media

    NASA Astrophysics Data System (ADS)

    Fang, Hui; Maslov, Konstantin; Wang, Lihong V.

    2007-12-01

    We recently observed the photoacoustic Doppler effect from flowing small light-absorbing particles. Here, we apply the effect to measure blood-mimicking fluid flow in an optically scattering medium. The light scattering in the medium decreases the amplitude of the photoacoustic Doppler signal but does not affect either the magnitude or the directional discrimination of the photoacoustic Doppler shift. This technology may hold promise for a new Doppler method for measuring blood flow in microcirculation with high sensitivity.

  11. Blood viscosity measurement: an integral method using Doppler ultrasonic profiles

    NASA Astrophysics Data System (ADS)

    Flaud, P.; Bensalah, A.

    2005-12-01

    The aim of this work is to present a new indirect and noninvasive method for the measurement of the Newtonian blood viscosity. Based on an integral form of the axial Navier-Stokes equation, this method is particularly suited for in vivo investigations using ultrasonic arterial blood velocity profiles. Its main advantage is that it is applicable to periodic as well as non periodic flows. Moreover it does not require classical filtering methods enhancing signal to noise ratio of the physiological signals. This method only requires the knowledge of the velocimetric data measured inside a spatially and temporally optimized zone of the Doppler velocity profiles. The results obtained using numerical simulation as well as in vitro or in vivo experiments prove the effectiveness of the method. It is then well adapted to the clinical environment as a systematic quasi on-line method for the measurement of the blood viscosity.

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

    PubMed

    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.

  13. SIRHEN : a data reduction program for photonic Doppler velocimetry measurements.

    SciTech Connect

    Dolan, Daniel H., III; Ao, Tommy

    2010-06-01

    SIRHEN (Sandia InfraRed HEtrodyne aNalysis) is a program for reducing data from photonic Doppler velocimetry (PDV) measurements. SIRHEN uses the short-time Fourier transform method to extract velocity information. The program can be run in MATLAB (2008b or later) or as a Windows executable. This report describes the new Sandia InfraRed HEtrodyne aNalysis program (SIRHEN; pronounced 'siren') that has been developed for efficient and robust analysis of PDV data. The program was designed for easy use within Sandia's dynamic compression community.

  14. In vitro evaluation of volumetric flow from Doppler power-weighted and amplitude-weighted mean velocities.

    PubMed

    Minich, L L; Snider, A R; Meliones, J N; Yanock, C

    1993-01-01

    Ultrasound theory suggests that the volume of flow is directly related to the power and amplitude of the backscattered Doppler signals. To evaluate the accuracy of volume flow calculated with power-weighted and amplitude-weighted mean velocities (PWMV and AWMV), volume flows were measured in a pulsatile flow-tank system equipped with a 1.25 cm diameter simulated femoral artery. Analyses were performed throughout a range of physiologic flows, mean driving pressures, and pulse rates. At each hemodynamic setting, volume flow in the simulated artery was measured with an electromagnetic flow probe and with pulsed Doppler echocardiography by use of 7.0 and 3.5 MHz transducers. In addition, to determine the effects of vessel size and parabolic flow on the accuracy of the Doppler volumes, volume flow was evaluated in several differently sized vessels at sampling distances of 20 times the vessel diameter downstream from the orifice. On the ultrasound system, PWMV was calculated as the sum of the individual velocities multiplied by their respective power fractions (the fraction of the total instantaneous power represented by the individual signal power). The instantaneous PWMV was plotted continuously in time and superimposed on the spectral recording. Similarly, AWMV was calculated with amplitudes measured as the square root of the signal power. The PWMV and AWMV were integrated over the flow period and multiplied by the known cross-sectional area of flow to obtain the Doppler volume. In all analyses performed, volumetric flows calculated with Doppler echocardiography with PWMV and AWMV correlated extremely well with those measured with the electromagnetic flow probe. Thus, over a wide range of physiologic conditions, transducers frequencies, and vessel sizes, volume flow can be accurately calculated from PWMV and AWMV Doppler data. This technique provides an accurate, automatic method for on-line determination of volumetric flow.

  15. Doppler Global Velocimetry Measurements for Supersonic Flow Fields

    NASA Technical Reports Server (NTRS)

    Meyers, James F.

    2005-01-01

    The application of Doppler Global Velocimetry (DGV) to high-speed flows has its origins in the original development of the technology by Komine et al (1991). Komine used a small shop-air driven nozzle to generate a 200 m/s flow. This flow velocity was chosen since it produced a fairly large Doppler shift in the scattered light, resulting in a significant transmission loss as the light passed through the Iodine vapor. This proof-of-concept investigation showed that the technology was capable of measuring flow velocity within a measurement plane defined by a single-frequency laser light sheet. The effort also proved that velocity measurements could be made without resolving individual seed particles as required by other techniques such as Fringe- Type Laser Velocimetry and Particle Image Velocimetry. The promise of making planar velocity measurements with the possibility of using 0.1-micron condensation particles for seeding, Dibble et al (1989), resulted in the investigation of supersonic jet flow fields, Elliott et al (1993) and Smith and Northam (1995) - Mach 2.0 and 1.9 respectively. Meyers (1993) conducted a wind tunnel investigation above an inclined flat plate at Mach 2.5 and above a delta wing at Mach 2.8 and 4.6. Although these measurements were crude from an accuracy viewpoint, they did prove that the technology could be used to study supersonic flows using condensation as the scattering medium. Since then several research groups have studied the technology and developed solutions and methodologies to overcome most of the measurement accuracy limitations:

  16. Understanding the Influence of Flow Velocity, Wall Motion Filter, Pulse Repetition Frequency, and Aliasing on Power Doppler Image Quantification.

    PubMed

    Martins, Maricy R; Martins, Wellington P; Soares, Carlos A M; Miyague, Andre H; Kudla, Marek J; Pavan, Theo Z

    2017-07-24

    Although power Doppler imaging has been used to quantify tissue and organ vascularity, many studies showed that limitations in defining adequate ultrasound machine settings and attenuation make such measurements complex to be achieved. However, most of these studies were conducted by using the output of proprietary software, such as Virtual Organ computer-aided analysis (GE Healthcare, Kretz, Zipf, Austria); therefore, many conclusions may not be generalizable because of unknown settings and parameters used by the software. To overcome this limitation, our goal was to evaluate the impact of the flow velocity, pulse repetition frequency (PRF), and wall motion filter (WMF) on power Doppler image quantification using beam-formed ultrasonic radiofrequency data. The setup consisted of a blood-mimicking fluid flowing through a phantom. Radiofrequency signals were collected using PRFs ranging from 0.6 to 10 kHz for 6 different flow velocities (5-40 cm/s). Wall motion filter cutoff frequencies were varied between 50 and 250 Hz. The power Doppler magnitude was deeply influenced by the WMF cutoff frequency. The effect of using different WMF values varied with the PRF; therefore, the power Doppler signal intensity was dependent on the PRF. Finally, we verified that power Doppler quantification can be affected by the aliasing effect, especially when using a PRF lower than 1.3 kHz. The WMF and PRF greatly influenced power Doppler quantification, mainly when flow velocities lower than 20 cm/s were used. Although the experiments were conducted in a nonclinical environment, the evaluated parameters are equivalent to those used in clinical practice, which makes them valuable for aiding the interpretation of related data in future research. © 2017 by the American Institute of Ultrasound in Medicine.

  17. A real-time device for converting Doppler ultrasound audio signals into fluid flow velocity.

    PubMed

    Herr, Michael D; Hogeman, Cynthia S; Koch, Dennis W; Krishnan, Anandi; Momen, Afsana; Leuenberger, Urs A

    2010-05-01

    A Doppler signal converter has been developed to facilitate cardiovascular and exercise physiology research. This device directly converts audio signals from a clinical Doppler ultrasound imaging system into a real-time analog signal that accurately represents blood flow velocity and is easily recorded by any standard data acquisition system. This real-time flow velocity signal, when simultaneously recorded with other physiological signals of interest, permits the observation of transient flow response to experimental interventions in a manner not possible when using standard Doppler imaging devices. This converted flow velocity signal also permits a more robust and less subjective analysis of data in a fraction of the time required by previous analytic methods. This signal converter provides this capability inexpensively and requires no modification of either the imaging or data acquisition system.

  18. Cardiac tissue Doppler and tissue velocity imaging in anesthetized New Zealand white rabbits.

    PubMed

    Pelosi, Augusta; St John, Linda; Gaymer, Jean; Ferguson, Danielle; Goyal, Sandeep K; Abela, George S; Rubinstein, Jack

    2011-05-01

    New Zealand white rabbits are commonly used in cardiovascular research. Complete echocardiographic examination of the heart includes the evaluation of tissue Doppler (TDI) parameters, yet normal data are unavailable for rabbits. In addition, tissue velocity imaging (TV) is a potentially useful measure of myocardial function that has not yet been applied to rabbits. Anesthetized New Zealand white rabbits (n = 31) underwent echocardiography to establish the feasibility of performing TDI and TV and establishing corresponding reference values. Standard 2D, M-mode, and Doppler measurements were obtained in all rabbits and showed values comparable to previously published data. Interpretable TDI images were obtained in all 31 rabbits and TV in 24 of 31 rabbits. The values obtained were similar to those seen in healthy cats and are comparable to the values found in adult humans. TDI and TV can easily be added to standard echocardiographic evaluation in rabbits. The values from the current study, obtained in normal rabbits, can be used as reference values to improve characterization of cardiac disease in this species.

  19. Cardiac Tissue Doppler and Tissue Velocity Imaging in Anesthetized New Zealand White Rabbits

    PubMed Central

    Pelosi, Augusta; John, Linda St; Gaymer, Jean; Ferguson, Danielle; Goyal, Sandeep K; Abela, George S; Rubinstein, Jack

    2011-01-01

    New Zealand white rabbits are commonly used in cardiovascular research. Complete echocardiographic examination of the heart includes the evaluation of tissue Doppler (TDI) parameters, yet normal data are unavailable for rabbits. In addition, tissue velocity imaging (TV) is a potentially useful measure of myocardial function that has not yet been applied to rabbits. Anesthetized New Zealand white rabbits (n = 31) underwent echocardiography to establish the feasibility of performing TDI and TV and establishing corresponding reference values. Standard 2D, M-mode, and Doppler measurements were obtained in all rabbits and showed values comparable to previously published data. Interpretable TDI images were obtained in all 31 rabbits and TV in 24 of 31 rabbits. The values obtained were similar to those seen in healthy cats and are comparable to the values found in adult humans. TDI and TV can easily be added to standard echocardiographic evaluation in rabbits. The values from the current study, obtained in normal rabbits, can be used as reference values to improve characterization of cardiac disease in this species. PMID:21640025

  20. Arterial pulse wave propagation velocity in healthy dogs by pulse wave Doppler ultrasound.

    PubMed

    Nogueira, Rodrigo B; Pereira, Lucas A; Basso, Alice F; da Fonseca, Ingrid S; Alves, Lorena A

    2017-03-01

    The aim of this study was to prospectively evaluate the carotid-femoral pulse wave velocity (PWV) values in healthy dogs using pulse wave Doppler ultrasound. A secondary aim was to determine the feasibility of this method and to report the intra- and interobserver reproducibilities of the PWV in conscious dogs. The data were studied in 30 healthy, adult, male (n = 15) and female (n = 15) dogs. The time interval marked between the R wave peak of the electrocardiogram and the intersection of the blood flow wave upstroke of the Doppler spectrum with the baseline of zero frequency was determined for the carotid (T1) and for the femoral (T2) arteries. The distance covered by the pulse wave (L) was determined. The PWV was then calculated using the following formula: L/T2 - T1. The mean values of PWV calculated from the total sample (n = 30) evaluated were 13.41 ± 2.20 m/s. No significant statistical difference was observed for the PWV measurements between males (14.82 ± 3.18 m/s) and females (12.64 ± 2.45 m/s). The analysis revealed no intra nor interobserver differences. A reasonable reproducibility of the PWV measurements was showed by intraclass correlation coefficients (ICC), and the coefficients of variation (CV). These data demonstrate that noninvasive vascular Doppler analysis is a feasible and reproducible method to determine the carotid-femoral PWV in dogs.

  1. Wind turbine wake properties from Doppler lidar measurements

    NASA Astrophysics Data System (ADS)

    Pichugina, Y.; Banta, R. M.; Brewer, A.; Lundquist, J. K.

    2012-12-01

    Wake properties were estimated from the High-Resolution Doppler Lidar (HRDL) measurements during the Turbine Wake and Inflow Characterization Study (TWICS) in the spring of 2011. Velocity deficit, wake downwind extent, and wake meandering were obtained by detailed analysis of both lidar vertical-slice scans, performed straddling along the lidar-turbine centerline, and lidar conical scans, performed in narrow, nearly horizontal sectors that include the wind turbine inflow, and its wake at four levels. Simultaneous measurements of inflow and turbine outflow were corrected by terrain and wind direction to obtain mean wake properties. It has been found out that an operating wind turbine generates a wake with the maximum velocity deficit varying from 20% to 70% extending up to 10 rotor diameters downstream of the turbine, depending on the wind strength and atmospheric turbulence. Details including images and animations of the wake behavior will be presented.

  2. TURBULENCE SPECTRA FROM DOPPLER-BROADENED SPECTRAL LINES: TESTS OF THE VELOCITY CHANNEL ANALYSIS AND VELOCITY COORDINATE SPECTRUM TECHNIQUES

    SciTech Connect

    Chepurnov, A.; Lazarian, A.

    2009-03-10

    Turbulent motions induce Doppler shifts of observable emission and absorption lines motivating studies of turbulence using precision spectroscopy. We provide numerical testing of the two most promising techniques, velocity channel analysis and velocity coordinate spectrum (VCS). We obtain an expression for the shot noise that the discretization of the numerical data entails and successfully test it. We show that the numerical resolution required for recovering the underlying turbulent spectrum from observations depend on the spectral index of velocity fluctuations, which makes low-resolution testing misleading. We demonstrate numerically that, when dealing with absorption lines, sampling of turbulence along just a dozen directions provides a high quality spectrum with the VCS technique.

  3. Validation of streamflow measurements made with acoustic doppler current profilers

    USGS Publications Warehouse

    Oberg, K.; Mueller, D.S.

    2007-01-01

    The U.S. Geological Survey and other international agencies have collaborated to conduct laboratory and field validations of acoustic Doppler current profiler (ADCP) measurements of streamflow. Laboratory validations made in a large towing basin show that the mean differences between tow cart velocity and ADCP bottom-track and water-track velocities were -0.51 and -1.10%, respectively. Field validations of commercially available ADCPs were conducted by comparing streamflow measurements made with ADCPs to reference streamflow measurements obtained from concurrent mechanical current-meter measurements, stable rating curves, salt-dilution measurements, or acoustic velocity meters. Data from 1,032 transects, comprising 100 discharge measurements, were analyzed from 22 sites in the United States, Canada, Sweden, and The Netherlands. Results of these analyses show that broadband ADCP streamflow measurements are unbiased when compared to the reference discharges regardless of the water mode used for making the measurement. Measurement duration is more important than the number of transects for reducing the uncertainty of the ADCP streamflow measurement. ?? 2007 ASCE.

  4. Observation of Doppler-free electromagnetically induced transparency in atoms selected optically with specific velocity

    SciTech Connect

    Yu, Hoon; Kim, Kwan Su; Kim, Jung Dong; Lee, Hyun Kyung; Kim, Jung Bog

    2011-11-15

    We observed an electromagnetically induced transparency signal in a four-level system with optically selected rubidium atoms at specific velocities in a room-temperature vaporized cell. Since the atoms behave like cold atoms in the selected atomic view, the observed signals coincide with a trapped atomic system. According to this result, we can observe Doppler-free signals, which correspond from 1.2 to 1.0 K in a Doppler-broadened medium. And the selected atoms have velocity components of {+-}(131 {+-} 3) MHz per wave number. Our experimental results can provide insight for research in cold media.

  5. Effects of transducer beam geometry and flow velocity profile on the Doppler power spectrum: a theoretical study.

    PubMed

    Bascom, P A; Cobbold, R S

    1990-01-01

    A theoretical model is used to show how the Doppler spectrum for various axisymmetric velocity profiles is affected by beam misalignment and incomplete insonation. Results are presented for both circular and square beam geometries. Moreover, a closed-form expression is derived for the power spectral density received by an on-axis transducer with a Gaussian beam profile. It is shown that the error incurred in measuring the mean Doppler frequency with such a profile will generally be bounded by the results for the circular and square beam geometries. The effects of an ideal high-pass filter on the mean Doppler frequency and the backscattered Doppler power are examined. It is shown that such a filter can introduce large differences in the measured systolic to diastolic power ratios. Finally, theoretical expressions and results are presented for the spectral broadening index (SBI), normalized spectral variance (NSV), coefficient of kurtosis (CK), the coefficient of skewness (CS) as functions of the axisymmetric velocity profile shape assuming complete uniform insonation.

  6. High-flow-velocity and shear-rate imaging by use of color Doppler optical coherence tomography.

    PubMed

    van Leeuwen, T G; Kulkarni, M D; Yazdanfar, S; Rollins, A M; Izatt, J A

    1999-11-15

    Color Doppler optical coherence tomography (CDOCT) is capable of precise velocity mapping in turbid media. Previous CDOCT systems based on the short-time Fourier transform have been limited to maximum flow velocities of the order of tens of millimeters per second. We describe a technique, based on interference signal demodulation at multiple frequencies, to extend the physiological relevance of CDOCT by increasing the dynamic range of measurable velocities to hundreds of millimeters per second. The physiologically important parameter of shear rate is also derived from CDOCT measurements. The measured flow-velocity profiles and shear-rate distributions correlate very well with theoretical predictions. The multiple demodulation technique, therefore, may be useful to monitor blood flow in vivo and to identify regions with high and low shear rates.

  7. From HARPS to CODEX: exploring the limits of Doppler measurements

    NASA Astrophysics Data System (ADS)

    Pepe, F. A.; Lovis, C.

    2008-08-01

    Only 3 6 years ago, the Doppler technique was believed to have reached its final limitations in measuring stellar velocities and finding extra-solar planets. The 3 4 m s-1 precision level achieved, at that time, by various teams, was certainly limited by instrumental performances, but also constrained, as believed by a part of the community, by intrinsic stellar limitations. The advent of HARPS drastically changed this view. The instrument demonstrated, through its recent discoveries, that stars more 'stable' than 1 m s-1 actually exist, and that their radial velocity (RV) can be measured at that level of precision. Short-term precision of 20 cm s-1 rms and long-term precision of the order of 30 60 cm s-1 rms have been actually achieved on real stars, showing that RVs still harbor a great potential, and not only in the domain of extra-solar planets. Indeed, HARPS inspired the CODEX@ELT experiment for the direct determination of the expansion of the Universe, measuring the Doppler shift of Ly-α forest lines as a function of time. This experiment calls for a Doppler precision as low as 1 cm s-1, which in turn inspires new possibilities in the domain of extra-solar planets. We will investigate the obstacles on the way to cm s-1 precision. The discussion presented here will be based on our experience with HARPS and what we consider to be the current limitations set by the instrument, telescope, atmosphere and star. Finally, we will also provide an outlook on possible improvements and expected performances, which will finally define new scientific opportunities.

  8. Automated method for characterization of diastolic transmitral Doppler velocity contours: early rapid filling.

    PubMed

    Hall, A F; Kovács, S J

    1994-01-01

    Doppler echocardiographic studies of transmitral flow have become a routine clinical tool for the assessment and characterization of ventricular diastolic (filling) function. We have previously derived a parametrized diastolic filling (PDF) formalism for the purpose of diastolic function assessment using Doppler echocardiography. The model accommodates the mechanical "suction" feature of early diastolic filling of the heart by using a simple harmonic oscillator (SHO) as a paradigm for the kinematics of filling. PDF model predictions of transmitral flow velocity have shown excellent agreement with human echocardiographic Doppler contours (temporal profiles) when a visual, transparency overlay method of model fit to clinical Doppler contour comparison was used. The determination of PDF model parameters from the clinical Doppler contour is equivalent to the solution of the "inverse problem" of diastole. Previously, this determination consisted of a manual, iterative method of graphical overlay, in which model predicted contours were visually compared with the echocardiography machine generated Doppler contour using transparencies. To automate the process of model parameter estimation (i.e., solution of the "inverse problem") for the early or "rapid filling" phase of diastole (known in cardiology as the E-wave of the clinical Doppler velocity profile [DVP]) we recorded the acoustic pulsed Doppler signal using the forward channel of a commercial echocardiography machine. The Doppler spectrogram for a particular E-wave was recreated using short-time Fourier transform processing. The maximum velocity envelope (MVE) was extracted from the spectrogram. The PDF model was fit to the E-wave MVE using a Levenberg-Marquardt (iterative) algorithm by the requirement that the mean-square error between the clinical data (MVE) and the model be minimized. Because the model is linear, all of the PDF parameters for the Doppler E-wave can be uniquely determined. We show that: (1

  9. Ultrahigh-velocity resolution imaging of the microcirculation in-vivo using color Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yazdanfar, Siavash; Rollins, Andrew M.; Izatt, Joseph A.

    2001-05-01

    Color Doppler optical coherence tomography (CDOCT) is a method for noninvasive cross-sectional imaging of blood flow in vivo. In previous implementations, velocity estimates were obtained by measuring the frequency shift of discrete depth-resolved backscatter spectra, resulting in a velocity resolution on the order of 1 mm/s. We present a novel processing method that detects Doppler shifts calculated across sequential axial scans, enabling ultrahigh velocity resolution (~1 micron/s) flow measurement in scattering media. This method of sequential scan processing was calibrated with a moving mirror mounted on a precision motorized translator. Latex microspheres suspended in deuterium oxide were used as a highly scattering test phantom. Laminar flow profiles down to ~15 micron/s centerline velocity (0.02 cc/hr) were observed with a sensitivity of 1.2 micron/s. Finally, vessels on the order of 10 microns in diameter were imaged in living human skin, with a relative frequency sensitivity less than 4 x 10-5. To our knowledge, these results are the lowest velocities ever measured with CDOCT.

  10. On the Positive Bias of Peak Horizontal Velocity from an Idealized Doppler Profiler

    NASA Technical Reports Server (NTRS)

    Short, David A.; Merceret, Francis J.

    2004-01-01

    In the presence of 3-D turbulence, peak horizontal velocity estimates from an idealized Doppler profiler are found to be positively biased due to an incomplete specification of the vertical velocity field. The magnitude of the bias was estimated by assuming that the vertical and horizontal velocities can be separated into average and perturbation values and that the vertical and horizontal velocity perturbations are normally distributed. Under these assumptions, properties of the Type-I Extreme Value Distribution for maxima, known as the Gumbel distribution, can be used to obtain an analytical solution of the bias. The bias depends on geometric properties of the profiler configuration, the variance in the horizontal velocity, and the unresolved variance in the vertical velocity. When these variances are normalized by the average horizontal velocity, the bias can be mapped as a simple function of the normalized variances.

  11. Myocardial tissue Doppler velocity imaging in children: comparative study between two ultrasound systems.

    PubMed

    Koopman, Laurens P; Slorach, Cameron; Manlhiot, Cedric; McCrindle, Brian W; Friedberg, Mark K; Mertens, Luc; Jaeggi, Edgar T

    2010-09-01

    The investigators compared pulsed-wave tissue Doppler (PWTD) and color tissue Doppler (CTD) ventricular tissue velocities obtained using Vivid 7 (GE) and iE33 (Philips) ultrasound systems within a 30-minute time frame and examined interobserver and intraobserver variability. Longitudinal PWTD and CTD images were prospectively acquired in 49 children from the base of the right and left ventricular free wall and septum and stored for offline analysis. Intraobserver and interobserver coefficients of variation for PWTD velocities ranged from 4% to 6% and 5% to 10% for GE and from 1% to 10% and 2% to 14% for Philips, respectively. Intraobserver and interobserver coefficients of variation for CTD velocities ranged from 4% to 15% and 6% to 24% for GE and from 6% to 19% and 7% to 25% for Philips, respectively. Mean biases between the two systems for PWTD velocities, expressed as percentage differences, were around 0%, with the narrowest limits of agreement for systolic velocities at the septal annulus and the widest limits of agreement for early diastolic velocities at the lateral tricuspid valve annulus, respectively. Peak CTD-derived velocities were significantly and consistently lower for Philips compared with GE. Agreement between GE-derived and Philips-derived PWTD velocities was reasonable, whereas CTD-derived velocities differed substantially. 2010 American Society of Echocardiography. Published by Mosby, Inc. All rights reserved.

  12. Numerical performance analysis of acoustic Doppler velocity profilers in the wake of an axial-flow marine hydrokinetic turbine

    SciTech Connect

    Richmond, Marshall C.; Harding, Samuel F.; Romero Gomez, Pedro DJ

    2015-09-01

    The use of acoustic Doppler current profilers (ADCPs) for the characterization of flow conditions in the vicinity of both experimental and full scale marine hydrokinetic (MHK) turbines is becoming increasingly prevalent. The computation of a three dimensional velocity measurement from divergent acoustic beams requires the assumption that the flow conditions are homogeneous between all beams at a particular axial distance from the instrument. In the near wake of MHK devices, the mean fluid motion is observed to be highly spatially dependent as a result of torque generation and energy extraction. This paper examines the performance of ADCP measurements in such scenarios through the modelling of a virtual ADCP (VADCP) instrument in the velocity field in the wake of an MHK turbine resolved using unsteady computational fluid dynamics (CFD). This is achieved by sampling the CFD velocity field at equivalent locations to the sample bins of an ADCP and performing the coordinate transformation from beam coordinates to instrument coordinates and finally to global coordinates. The error in the mean velocity calculated by the VADCP relative to the reference velocity along the instrument axis is calculated for a range of instrument locations and orientations. The stream-wise velocity deficit and tangential swirl velocity caused by the rotor rotation lead to significant misrepresentation of the true flow velocity profiles by the VADCP, with the most significant errors in the transverse (cross-flow) velocity direction.

  13. Measurement of Turbulence with Acoustic Doppler Current Profilers - Sources of Error and Laboratory Results

    USGS Publications Warehouse

    Nystrom, E.A.; Oberg, K.A.; Rehmann, C.R.; ,

    2002-01-01

    Acoustic Doppler current profilers (ADCPs) provide a promising method for measuring surface-water turbulence because they can provide data from a large spatial range in a relatively short time with relative ease. Some potential sources of errors in turbulence measurements made with ADCPs include inaccuracy of Doppler-shift measurements, poor temporal and spatial measurement resolution, and inaccuracy of multi-dimensional velocities resolved from one-dimensional velocities measured at separate locations. Results from laboratory measurements of mean velocity and turbulence statistics made with two pulse-coherent ADCPs in 0.87 meters of water are used to illustrate several of inherent sources of error in ADCP turbulence measurements. Results show that processing algorithms and beam configurations have important effects on turbulence measurements. ADCPs can provide reasonable estimates of many turbulence parameters; however, the accuracy of turbulence measurements made with commercially available ADCPs is often poor in comparison to standard measurement techniques.

  14. Celestial-mechanical interpretation of the two-way radio measurements of radial velocity of spacecraft for scientific applications

    NASA Astrophysics Data System (ADS)

    Komovkin, S. V.; Lavrenov, S. M.; Tuchin, A. G.; Tuchin, D. A.; Yaroshevsky, V. S.

    2016-12-01

    The article describes a model of the two-way measurements of radial velocity based on the Doppler effect. The relations are presented for the instantaneous value of the increment range at the time of measurement and the radial velocity of the mid-dimensional interval. The compensation of methodological errors of interpretation of the two-way Doppler measurements is considered.

  15. Measuring with laser Doppler vibrometer on moving frame (LDVMF)

    NASA Astrophysics Data System (ADS)

    Rahimi, Siamand; Li, Zili; Dollevoet, Rolf

    2014-05-01

    Structural dynamic gives insight into structural properties such as mass, eigenfrequencies, eigenmodes, modal damping and strain distribution and can be utilized in structural health monitoring, dynamic sub-structuring, etc. In this context structural vibration is measured and used. The measurement is done by means of conventional sensors such as accelerometers or non destructively using Laser Doppler Vibrometer (LDV), for instance. The non-destructive, non-contact measurement techniques preserve the integrity of the structure and don't add mass and stiffness to the structure under test. When one deals with civil structures such as rail and road ways, pipelines and catenary the importance of these techniques becomes more evident as they allow standoff measurement on a moving frame. Nevertheless when LDV is employed due to the relative in-plane motion between the LDV and the target speckle noise is generated which degrades the signal quality and makes this application not very straightforward but challenging. One of the first Laser Doppler Vibrometer on moving frame is adopted to measure and monitor the ground vibration, aiming at detection of buried land mines. The major addressed difficulty in this application is the speckle noise present in the acquired signal. In general the signal quality and the Signal to Noise Ratio (SNR) are a function of the laser spot size and wave length, measurement distance, relative velocity and sampling frequency. A trade-off between these factors, which are not always intuitive would help to minimize the noise floor due to the speckle noise. In this paper a test rig is presented which allows to study the speckle noise at different measurement ranges, between 1.8 and 2.8 m, and different velocities, up to 150 km/h. The results might serve as a guideline to the design process of a LDVMF.

  16. - and Frequency-Domain Signatures of Velocity Changing Collisions in Sub-Doppler Saturation Spectra and Pressure Broadening

    NASA Astrophysics Data System (ADS)

    Hall, Gregory; Xu, Hong; Forthomme, Damien; Dagdigian, Paul; Sears, Trevor

    2017-06-01

    We have combined experimental and theoretical approaches to the competition between elastic and inelastic collisions of CN radicals with Ar, and how this competition influences time-resolved saturation spectra. Experimentally, we have measured transient, two-color sub-Doppler saturation spectra of CN radicals with an amplitude chopped saturation laser tuned to selected Doppler offsets within rotational lines of the A-X (2-0) band, while scanning a frequency modulated probe laser across the hyperfine-resolved saturation features of corresponding rotational lines of the A-X (1-0) band. A steady-state depletion spectrum includes off-resonant contributions ascribed to velocity diffusion, and the saturation recovery rates depend on the sub-Doppler detuning. The experimental results are compared with Monte Carlo solutions to the Boltzmann equation for the collisional evolution of the velocity distributions of CN radicals, combined with a pressure-dependent and speed-dependent lifetime broadening. Velocity changing collisions are included by appropriately sampling the energy resolved differential cross sections for elastic scattering of selected rotational states of CN (X). The velocity space diffusion of Doppler tagged molecules proceeds through a series of small-angle scattering events, eventually terminating in an inelastic collision that removes the molecule from the coherently driven ensemble of interest. Collision energy-dependent total cross sections and differential cross sections for elastic scattering of selected CN rotational states with Ar were computed with Hibridon quantum scattering calculations, and used for sampling in the Monte Carlo modeling. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-SC0012704 with the U.S. Department of Energy, Office of Science, and supported by its Division of Chemical Sciences, Geosciences and Biosciences within the Office of Basic Energy Sciences.

  17. Conventional color Doppler velocity sonography versus color Doppler energy sonography for the diagnosis of acute experimental torsion of the spermatic cord.

    PubMed

    Lee, F T; Winter, D B; Madsen, F A; Zagzebski, J A; Pozniak, M A; Chosy, S G; Scanlan, K A

    1996-09-01

    We compared color Doppler velocity sonography and color Doppler energy sonography for the diagnosis of spermatic cord torsion in a canine model and determined the degree of torsion necessary to acutely halt testicular blood flow. Spermatic cord torsion was created in five dogs by exposing and rotating the ipsilateral testis 0 degree, 180 degrees, 270 degrees, 360 degrees, 450 degrees, and 540 degrees. Detorsion followed. The testicles were scanned at each torsion stop using both color Doppler velocity sonography and color Doppler energy sonography. Doppler parameters were optimized (by phantom and test scans) and maintained at a tolerable noise level throughout the experiment. Readers who were unaware of the degree of torsion compared flow in the rotated and contralateral control testes. Flow became undetectable by color Doppler velocity sonography and color Doppler energy sonography at 450 degrees in four of five cases and at 540 degrees in one of five cases. We found no significant difference between the velocity and the energy techniques for detecting this absence of flow (p > .05, Wilcoxon test). We found a significant difference in degree of flow for both techniques when comparing controls and all degrees of torsion combined (p < .006, Mann-Whitney test), but significance was achieved at lesser degrees of torsion with the velocity technique than with the energy technique (180 degrees and 360 degrees, respectively, Wilcoxon test). Color Doppler energy sonography was not significantly more sensitive than color Doppler velocity sonography for the diagnosis of spermatic cord torsion in this model. Complete occlusion of arterial inflow occurred at 450-540 degrees of torsion.

  18. Wind Field Measurements With Airborne Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Menzies, Robert T.

    1999-01-01

    In collaboration with lidar atmospheric remote sensing groups at NASA Marshall Space Flight Center and National Oceanic and Atmospheric Administration (NOAA) Environmental Technology Laboratory, we have developed and flown the Multi-center Airborne Coherent Atmospheric Wind Sensor (MACAWS) lidar on the NASA DC-8 research aircraft. The scientific motivations for this effort are: to obtain measurements of subgrid scale (i.e. 2-200 km) processes and features which may be used to improve parameterizations in global/regional-scale models; to improve understanding and predictive capabilities on the mesoscale; and to assess the performance of Earth-orbiting Doppler lidar for global tropospheric wind measurements. MACAWS is a scanning Doppler lidar using a pulsed transmitter and coherent detection; the use of the scanner allows 3-D wind fields to be produced from the data. The instrument can also be radiometrically calibrated and used to study aerosol, cloud, and surface scattering characteristics at the lidar wavelength in the thermal infrared. MACAWS was used to study surface winds off the California coast near Point Arena, with an example depicted in the figure below. The northerly flow here is due to the Pacific subtropical high. The coastal topography interacts with the northerly flow in the marine inversion layer, and when the flow passes a cape or point that juts into the winds, structures called "hydraulic expansion fans" are observed. These are marked by strong variation along the vertical and cross-shore directions. The plots below show three horizontal slices at different heights above sea level (ASL). Bottom plots are enlargements of the area marked by dotted boxes above. The terrain contours are in 200-m increments, with the white spots being above 600-m elevation. Additional information is contained in the original.

  19. Doppler cooling with coherent trains of laser pulses and a tunable velocity comb

    SciTech Connect

    Ilinova, Ekaterina; Ahmad, Mahmoud; Derevianko, Andrei

    2011-09-15

    We explore the possibility of decelerating and Doppler cooling an ensemble of two-level atoms by a coherent train of short, nonoverlapping laser pulses. We derive analytical expressions for mechanical force exerted by the train. In frequency space the force pattern reflects the underlying frequency comb structure. The pattern depends strongly on the ratio of the atomic lifetime to the repetition time between the pulses and pulse area. For example, in the limit of short lifetimes, the frequency-space peaks of the optical force wash out. We propose to tune the carrier-envelope offset frequency to follow the Doppler-shifted detuning as atoms decelerate; this leads to compression of atomic velocity distribution about comb teeth and results in a ''velocity comb''--a series of narrow equidistant peaks in the velocity space.

  20. Estimation of neutral wind velocity in the ionospheric heights by HF-Doppler technique

    NASA Technical Reports Server (NTRS)

    Kitamura, T.; Takefu, M.; Hiroshige, N.

    1985-01-01

    Three net stations located about 100 kilometers apart were set up around the station of the standard frequency and time signals (JJY) in central Japan and measurements of atmospheric gravity waves in the ionospheric heights (F-region, 200 to 400 km) were made by means of the HF-Doppler technique during the period of February 1983 to December 1983. The frequencies of the signals received are 5.0, 8.0 and 10.0 MHz, but only the 8.0 MHz signals are used for the present study, because no ambiguities due to the interference among other stations such as BPM, BSF, etc. exist by the use of 8.0 MHz. Two main results concerning the horizontal phase velocity of the atmospheric gravity waves with periods of 40 to 70 min may be summarized as follows: (1) the value of the phase velocity ranges from 50 m/s to 300 m/s; (2) the direction of the gravity wave propagation shows a definite seasonal variation. The prevailing direction of the gravity waves in winter is from north to south, which is consistent with the results obtained from other investigations. On the other hand, the two directions, from northeast to southwest and from southeast to northeast, dominate in summer.

  1. Estimation of neutral wind velocity in the ionospheric heights by HF-Doppler technique

    NASA Technical Reports Server (NTRS)

    Kitamura, T.; Takefu, M.; Hiroshige, N.

    1985-01-01

    Three net stations located about 100 kilometers apart were set up around the station of the standard frequency and time signals (JJY) in central Japan and measurements of atmospheric gravity waves in the ionospheric heights (F-region, 200 to 400 km) were made by means of the HF-Doppler technique during the period of February 1983 to December 1983. The frequencies of the signals received are 5.0, 8.0 and 10.0 MHz, but only the 8.0 MHz signals are used for the present study, because no ambiguities due to the interference among other stations such as BPM, BSF, etc. exist by the use of 8.0 MHz. Two main results concerning the horizontal phase velocity of the atmospheric gravity waves with periods of 40 to 70 min may be summarized as follows: (1) the value of the phase velocity ranges from 50 m/s to 300 m/s; (2) the direction of the gravity wave propagation shows a definite seasonal variation. The prevailing direction of the gravity waves in winter is from north to south, which is consistent with the results obtained from other investigations. On the other hand, the two directions, from northeast to southwest and from southeast to northeast, dominate in summer.

  2. Velocity gradients in spatially-resolved laser Doppler flowmetry and dynamic light scattering with confocal and coherence gating

    PubMed Central

    Uribe-Patarroyo, Néstor; Bouma, Brett E.

    2016-01-01

    Dynamic light scattering (DLS) is widely used to characterize diffusive motion to obtain precise information on colloidal suspensions by calculating the autocorrelation function of the signal from a heterodyne optical system. DLS can also be used to determine the flow velocity field in systems that exhibit mass transport by incorporating the effects of the deterministic motion of scatterers on the autocorrelation function, a technique commonly known as laser Doppler flowmetry. DLS measurements can be localized with confocal and coherence gating techniques such as confocal microscopy and optical coherence tomography, thereby enabling the determination of the spatially-resolved velocity field in three dimensions. It has been thought that spatially-resolved DLS can determine the axial velocity as well as the lateral speed in a single measurement. We demonstrate, however, that gradients in the axial velocity of scatterers exert a fundamental influence on the autocorrelation function even in well-behaved, non-turbulent flow. By obtaining the explicit functional relation between axial-velocity gradients and the autocorrelation function, we show that the velocity field and its derivatives are intimately related and their contributions cannot be separated. Therefore, a single DLS measurement cannot univocally determine the velocity field. Our extended theoretical model was found to be in good agreement with experimental measurements. PMID:27627357

  3. Velocity gradients in spatially resolved laser Doppler flowmetry and dynamic light scattering with confocal and coherence gating

    NASA Astrophysics Data System (ADS)

    Uribe-Patarroyo, Néstor; Bouma, Brett E.

    2016-08-01

    Dynamic light scattering (DLS) is widely used to characterize diffusive motion to obtain precise information on colloidal suspensions by calculating the autocorrelation function of the signal from a heterodyne optical system. DLS can also be used to determine the flow velocity field in systems that exhibit mass transport by incorporating the effects of the deterministic motion of scatterers on the autocorrelation function, a technique commonly known as laser Doppler flowmetry. DLS measurements can be localized with confocal and coherence gating techniques such as confocal microscopy and optical coherence tomography, thereby enabling the determination of the spatially resolved velocity field in three dimensions. It has been thought that spatially resolved DLS can determine the axial velocity as well as the lateral speed in a single measurement. We demonstrate, however, that gradients in the axial velocity of scatterers exert a fundamental influence on the autocorrelation function even in well-behaved, nonturbulent flow. By obtaining the explicit functional relation between axial-velocity gradients and the autocorrelation function, we show that the velocity field and its derivatives are intimately related and their contributions cannot be separated. Therefore, a single DLS measurement cannot univocally determine the velocity field. Our extended theoretical model was found to be in good agreement with experimental measurements.

  4. Saturn's Doppler velocimetry wind measurements with VLT/UVES

    NASA Astrophysics Data System (ADS)

    Silva, Miguel; Mota Machado, Pedro; Luz, David; Sanchez-Lavega, Agustin; Hueso, Ricardo; Peralta, Javier

    2016-10-01

    We present Doppler wind velocity results of Saturn's zonal flow at ~0.4 mbar pressure level. Our aim is help to constrain the characterization of the equatorial jet at the referred altitude and the latitudinal variation of the zonal winds, to contribute to monitor the spatial and temporal variability in order to achieve a better understanding of the dynamics of Saturn's zonal winds, which Sánchez-Lavega et al. (2003, Nature, 423, 623) have found to have strongly changed in recent years, as the planet approached southern summer solstice.The UVES/VLT instrument has been used, which simultaneously achieves high spectral resolving power and high spatial resolution. The field has been derotated in order to have the aperture aligned perpendicularly to Saturn's rotation axis. In this configuration, spatial information in the East-West direction is preserved in a set of spectra in the direction perpendicular to dispersion.The technique of absolute accelerometry (AA, Connes, 1985, ApSS 110, 211) has been applied to the backscattered solar spectrum in order to determine the Doppler shift associated with the zonal circulation. Our measurements have been made in the wavelength range of 480-680 nm. Previously we successfully adapted this Doppler velocimetry technique for measuring winds at Venus cloud tops (Machado et al. 2012).The observations consisted of 4 blocks of 15 exposures of 90 sec, plus two shorter blocks of 9 exposures, totalling 7.3 hours of telescope time. In order to cover the whole disk the aperture has been offset by 1 arcsec in the North-South direction between consecutive exposures. Most of the northern hemisphere was covered by the rings. Saturn's diameter was 17.4 arcsec, and the slit aperture was 0.3x25 arcsec. The aperture offset between consecutive exposures was 1 arcsec. Two observations blocks of 9 exposures only covered the central part of the disk, and four others covered the whole disk. The sub-terrestrial point was at -26.1 degrees South. The

  5. Wind Measurements from Arc Scans with Doppler Wind Lidar

    SciTech Connect

    Wang, H.; Barthelmie, R. J.; Clifton, Andy; Pryor, S. C.

    2015-11-25

    When defining optimal scanning geometries for scanning lidars for wind energy applications, we found that it is still an active field of research. Our paper evaluates uncertainties associated with arc scan geometries and presents recommendations regarding optimal configurations in the atmospheric boundary layer. The analysis is based on arc scan data from a Doppler wind lidar with one elevation angle and seven azimuth angles spanning 30° and focuses on an estimation of 10-min mean wind speed and direction. When flow is horizontally uniform, this approach can provide accurate wind measurements required for wind resource assessments in part because of its high resampling rate. Retrieved wind velocities at a single range gate exhibit good correlation to data from a sonic anemometer on a nearby meteorological tower, and vertical profiles of horizontal wind speed, though derived from range gates located on a conical surface, match those measured by mast-mounted cup anemometers. Uncertainties in the retrieved wind velocity are related to high turbulent wind fluctuation and an inhomogeneous horizontal wind field. Moreover, the radial velocity variance is found to be a robust measure of the uncertainty of the retrieved wind speed because of its relationship to turbulence properties. It is further shown that the standard error of wind speed estimates can be minimized by increasing the azimuthal range beyond 30° and using five to seven azimuth angles.

  6. Wind Measurements from Arc Scans with Doppler Wind Lidar

    DOE PAGES

    Wang, H.; Barthelmie, R. J.; Clifton, Andy; ...

    2015-11-25

    When defining optimal scanning geometries for scanning lidars for wind energy applications, we found that it is still an active field of research. Our paper evaluates uncertainties associated with arc scan geometries and presents recommendations regarding optimal configurations in the atmospheric boundary layer. The analysis is based on arc scan data from a Doppler wind lidar with one elevation angle and seven azimuth angles spanning 30° and focuses on an estimation of 10-min mean wind speed and direction. When flow is horizontally uniform, this approach can provide accurate wind measurements required for wind resource assessments in part because of itsmore » high resampling rate. Retrieved wind velocities at a single range gate exhibit good correlation to data from a sonic anemometer on a nearby meteorological tower, and vertical profiles of horizontal wind speed, though derived from range gates located on a conical surface, match those measured by mast-mounted cup anemometers. Uncertainties in the retrieved wind velocity are related to high turbulent wind fluctuation and an inhomogeneous horizontal wind field. Moreover, the radial velocity variance is found to be a robust measure of the uncertainty of the retrieved wind speed because of its relationship to turbulence properties. It is further shown that the standard error of wind speed estimates can be minimized by increasing the azimuthal range beyond 30° and using five to seven azimuth angles.« less

  7. Measuring discharge with ADCPs: Inferences from synthetic velocity profiles

    USGS Publications Warehouse

    Rehmann, C.R.; Mueller, D.S.; Oberg, K.A.

    2009-01-01

    Synthetic velocity profiles are used to determine guidelines for sampling discharge with acoustic Doppler current profilers (ADCPs). The analysis allows the effects of instrument characteristics, sampling parameters, and properties of the flow to be studied systematically. For mid-section measurements, the averaging time required for a single profile measurement always exceeded the 40 s usually recommended for velocity measurements, and it increased with increasing sample interval and increasing time scale of the large eddies. Similarly, simulations of transect measurements show that discharge error decreases as the number of large eddies sampled increases. The simulations allow sampling criteria that account for the physics of the flow to be developed. ?? 2009 ASCE.

  8. Velocity profiles inside volcanic clouds from three-dimensional scanning microwave dual-polarization Doppler radars

    NASA Astrophysics Data System (ADS)

    Montopoli, Mario

    2016-07-01

    In this work, velocity profiles within a volcanic tephra cloud obtained by dual-polarization Doppler radar acquisitions with three-dimensional (3-D) mechanical scanning capability are analyzed. A method for segmenting the radar volumes into three velocity regimes: vertical updraft, vertical fallout, and horizontal wind advection within a volcanic tephra cloud using dual-polarization Doppler radar moments is proposed. The horizontal and vertical velocity components within the regimes are retrieved using a novel procedure that makes assumptions concerning the characteristics of the winds inside these regimes. The vertical velocities retrieved are combined with 1-D simulations to derive additional parameters including particle fallout, mass flux, and particle sizes. The explosive event occurred on 23 November 2013 at the Mount Etna volcano (Sicily, Italy), is considered a demonstrative case in which to analyze the radar Doppler signal inside the tephra column. The X-band radar (3 cm wavelength) in the Catania, Italy, airport observed the 3-D scenes of the Etna tephra cloud ~32 km from the volcano vent every 10 min. From the radar-derived vertical velocity profiles of updraft, particle fallout, and horizontal transportation, an exit velocity of 150 m/s, mass flux rate of 1.37 • 107 kg/s, particle fallout velocity of 18 m/s, and diameters of precipitating tephra particles equal to 0.8 cm are estimated on average. These numbers are shown to be consistent with theoretical 1-D simulations of plume dynamics and local reports at the ground, respectively. A thickness of 3 ± 0.36 km for the downwind ash cloud is also inferred by differentiating the radar-derived cloud top and the height of transition between the convective and buoyancy regions, the latter being inferred by the estimated vertical updraft velocity profile. The unique nature of the case study as well as the novelty of the segmentation and retrieval methods presented potentially give new insights into the

  9. Phase noise in pulsed Doppler lidar and limitations on achievable single-shot velocity accuracy

    NASA Astrophysics Data System (ADS)

    McNicholl, P.; Alejandro, S.

    1992-07-01

    The smaller sampling volumes afforded by Doppler lidars compared to radars allows for spatial resolutions at and below some sheer and turbulence wind structure scale sizes. This has brought new emphasis on achieving the optimum product of wind velocity and range resolutions. Several recent studies have considered the effects of amplitude noise, reduction algorithms, and possible hardware related signal artifacts on obtainable velocity accuracy. We discuss here the limitation on this accuracy resulting from the incoherent nature and finite temporal extent of backscatter from aerosols. For a lidar return from a hard (or slab) target, the phase of the intermediate frequency (IF) signal is random and the total return energy fluctuates from shot to shot due to speckle; however, the offset from the transmitted frequency is determinable with an accuracy subject only to instrumental effects and the signal to noise ratio (SNR), the noise being determined by the LO power in the shot noise limited regime. This is not the case for a return from a media extending over a range on the order of or greater than the spatial extent of the transmitted pulse, such as from atmospheric aerosols. In this case, the phase of the IF signal will exhibit a temporal random walk like behavior. It will be uncorrelated over times greater than the pulse duration as the transmitted pulse samples non-overlapping volumes of scattering centers. Frequency analysis of the IF signal in a window similar to the transmitted pulse envelope will therefore show shot-to-shot frequency deviations on the order of the inverse pulse duration reflecting the random phase rate variations. Like speckle, these deviations arise from the incoherent nature of the scattering process and diminish if the IF signal is averaged over times greater than a single range resolution cell (here the pulse duration). Apart from limiting the high SNR performance of a Doppler lidar, this shot-to-shot variance in velocity estimates has a

  10. Phase noise in pulsed Doppler lidar and limitations on achievable single-shot velocity accuracy

    NASA Technical Reports Server (NTRS)

    Mcnicholl, P.; Alejandro, S.

    1992-01-01

    The smaller sampling volumes afforded by Doppler lidars compared to radars allows for spatial resolutions at and below some sheer and turbulence wind structure scale sizes. This has brought new emphasis on achieving the optimum product of wind velocity and range resolutions. Several recent studies have considered the effects of amplitude noise, reduction algorithms, and possible hardware related signal artifacts on obtainable velocity accuracy. We discuss here the limitation on this accuracy resulting from the incoherent nature and finite temporal extent of backscatter from aerosols. For a lidar return from a hard (or slab) target, the phase of the intermediate frequency (IF) signal is random and the total return energy fluctuates from shot to shot due to speckle; however, the offset from the transmitted frequency is determinable with an accuracy subject only to instrumental effects and the signal to noise ratio (SNR), the noise being determined by the LO power in the shot noise limited regime. This is not the case for a return from a media extending over a range on the order of or greater than the spatial extent of the transmitted pulse, such as from atmospheric aerosols. In this case, the phase of the IF signal will exhibit a temporal random walk like behavior. It will be uncorrelated over times greater than the pulse duration as the transmitted pulse samples non-overlapping volumes of scattering centers. Frequency analysis of the IF signal in a window similar to the transmitted pulse envelope will therefore show shot-to-shot frequency deviations on the order of the inverse pulse duration reflecting the random phase rate variations. Like speckle, these deviations arise from the incoherent nature of the scattering process and diminish if the IF signal is averaged over times greater than a single range resolution cell (here the pulse duration). Apart from limiting the high SNR performance of a Doppler lidar, this shot-to-shot variance in velocity estimates has a

  11. An inertial velocity reference for the NASA airborne Doppler lidar

    NASA Technical Reports Server (NTRS)

    Keck, Thomas S.; Telford, James W.

    1988-01-01

    The following four tasks were studied: (1) modification of the calibration routines to calibrate the Inertial Measurement Unit gyroscope drifts with fixed platform heading; (2) modification of the calibration routines to calibrate the Inertial Measurement Unit accelerometers; (3) checking overall software again for errors; and (4) providing documentation on the above work describing changes to the present software, results of these changes and future operating procedures.

  12. An acoustic doppler current profiler survey of flow velocities in St. Clair River, a connecting channel of the Great Lakes

    USGS Publications Warehouse

    Holtschlag, David J.; Koschik, John A.

    2003-01-01

    Acoustic Doppler current profilers (ADCP) were used to measure flow velocities in St. Clair River during a survey in May and June of 2002, as part of a study to assess the susceptibility of public water intakes to contaminants on the St. Clair-Detroit River Waterway. The survey provides 2.7 million point velocity measurements at 104 cross sections. Sections are spaced about 1,630 ft apart along the river from Port Huron to Algonac, Michigan, a distance of 28.6 miles. Two transects were obtained at each cross section, one in each direction across the river. Along each transect, velocity profiles were obtained 2-4 ft apart. At each velocity profile, average water velocity data were obtained at 1.64 ft intervals of depth. The raw position and velocity data from the ADCP field survey were adjusted for local magnetic anomalies using global positioning system (GPS) measurements at the end points of the transects. The adjusted velocity and ancillary data can be retrieved through the internet and extracted to column-oriented data files.

  13. Horizontal velocities of MSTIDs over Taiwan observed by continuous HF Doppler sounding

    NASA Astrophysics Data System (ADS)

    Fišer, Jiří; Chum, Jaroslav

    2016-04-01

    Medium scale traveling ionospheric disturbances (MSTIDs) are signatures of gravity waves (GWs) which propagatein the termosphere. Since GWs play an important role in the coupling between the lower atmospheric layers and the thermosphere it is important to study their properties and source mechanisms. In this contribution we present an experimental study focused on horizontal velocities of MSTIDs over Taiwan in the nearly two year long period starting in April 2014. We observe MSTIDs by multipath continuous HF Doppler sounding system. The movement of ionospheric plasma induced via collisions by gravity waves is detected as Doppler shift of the sounding radio signal. We investigate seasonal and diurnal variations of MSTIDs horizontal propagation parameters and compare them with horizontal wind model (HWM) and also compare them with results obtained in other locations in middle a low latitudes where similar HF Doppler sounding systems are installed.

  14. Characterization of Measurement Error Sources in Doppler Global Velocimetry

    NASA Technical Reports Server (NTRS)

    Meyers, James F.; Lee, Joseph W.; Schwartz, Richard J.

    2001-01-01

    Doppler global velocimetry uses the absorption characteristics of iodine vapor to provide instantaneous three-component measurements of flow velocity within a plane defined by a laser light sheet. Although the technology is straightforward, its utilization as a flow diagnostics tool requires hardening of the optical system and careful attention to detail during data acquisition and processing if routine use in wind tunnel applications is to be achieved. A development program that reaches these goals is presented. Theoretical and experimental investigations were conducted on each technology element to determine methods that increase measurement accuracy and repeatability. Enhancements resulting from these investigations included methods to ensure iodine vapor calibration stability, single frequency operation of the laser and image alignment to sub-pixel accuracies. Methods were also developed to improve system calibration, and eliminate spatial variations of optical frequency in the laser output, spatial variations in optical transmissivity and perspective and optical distortions in the data images. Each of these enhancements is described and experimental examples given to illustrate the improved measurement performance obtained by the enhancement. The culmination of this investigation was the measured velocity profile of a rotating wheel resulting in a 1.75% error in the mean with a standard deviation of 0.5 m/s. Comparing measurements of a jet flow with corresponding Pitot measurements validated the use of these methods for flow field applications.

  15. Application of acoustic doppler velocimeters for streamflow measurements

    USGS Publications Warehouse

    Rehmel, M.

    2007-01-01

    The U.S. Geological Survey (USGS) principally has used Price AA and Price pygmy mechanical current meters for measurement of discharge. New technologies have resulted in the introduction of alternatives to the Price meters. One alternative, the FlowTracker acoustic Doppler velocimeter, was designed by SonTek/YSI to make streamflow measurements in wadeable conditions. The device measures a point velocity and can be used with standard midsection method algorithms to compute streamflow. The USGS collected 55 quality-assurance measurements with the FlowTracker at 43 different USGS streamflow-gaging stations across the United States, with mean depths from 0.05to0.67m, mean velocities from 13 to 60 cm/s, and discharges from 0.02 to 12.4m3/s. These measurements were compared with Price mechanical current meter measurements. Analysis of the comparisons shows that the FlowTracker discharges were not statistically different from the Price meter discharges at a 95% confidence level. ?? 2007 ASCE.

  16. Measurement of retinal blood velocity

    NASA Astrophysics Data System (ADS)

    Winchester, Leonard W., Jr.; Chou, Nee-Yin

    2006-02-01

    A fundus camera was modified to illuminate the retina of a rabbit model with low power laser light in order to obtain laser speckle images. A fast-exposure charge-coupled device (CCD) camera was used to capture laser speckle images of the retina. Image acquisition was synchronized with the arterial pulses of the rabbit to ensure that all images are obtained at the same point in the cardiac cycle. The rabbits were sedated and a speculum was inserted to prevent the eyelid from closing. Both albino (New Zealand; pigmented (Dutch belted) rabbits were used in the study. The rabbit retina is almost avascular. The measurements are obtained for choroidal tissue as well as retinal tissue. Because the retina is in a region of high metabolism, blood velocity is strongly affected by blood oxygen saturation. Measurements of blood velocity obtained over a wide range of O II saturations (58%-100%) showed that blood velocity increases with decreasing O II saturation. For most experiments, the left eye of the rabbit was used for laser measurements whereas the right eye served as a control. No observable difference between pre- and post-experimented eye was noted. Histological examinations of retinal tissue subjected to repeated laser measurements showed no indication of tissue damage.

  17. Tangential Velocity Measurement Using Interferometric MTI Radar

    SciTech Connect

    DOERRY, ARMIN W.; MILESHOSKY, BRIAN P.; BICKEL, DOUGLAS L.

    2002-11-01

    An Interferometric Moving Target Indicator radar can be used to measure the tangential velocity component of a moving target. Multiple baselines, along with the conventional radial velocity measurement, allow estimating the true 3-D velocity vector of a target.

  18. Free-surface velocity measurements using an optically recording velocity interferometer

    NASA Astrophysics Data System (ADS)

    Lu, Jian-xin; Wang, Zhao; Liang, Jing; Shan, Yu-sheng; Zhou, Chuang-zhi; Xiang, Yi-huai; Lu, Ze; Tang, Xiu-zhang

    2007-01-01

    An optically recording velocity interferometer system (ORVIS) was developed for the free-surface velocity measurements in the equation of state experiments. The time history of free-surface velocity and the particle velocity in laser deduced shockwaves experiments can be recorded by the electronic streak camera in ORVIS. The interference fringe shifts recorded by the ORVIS is proportional to the Doppler shift of a laser beam induced by being reflected from the back suface of the monitored target. In the experiments, ORVIS got an 179 ps time resolution, and a higher time resolution could be got by minimizing the delay time. The equation of state experiments were carried out on the high power excimer laser system called "Heaven I", the velocity of iron and aluminium was researched.

  19. Measuring mean velocities with Pogo

    SciTech Connect

    Rossby, T.; Fontaine, J.; Hummon, J. )

    1991-10-01

    Pogo is a sample technique for measuring water transport between the surface and some preselected depth. Equipped with a 12-kHz pinger for tracking and range measurements, a xenon flasher for nighttime relocation, and a VHF beacon for daytime recovery, it has been used over 200 times in the Gulf Stream to measure volume transport and to provide a reference velocity (transport) for geostrophic calculations from pairs of hydrographic stations. This note gives a brief technical description of Pogo and how it is used. Loran C was used for navigation in this study, but with the advent of the Global Positioning System (GPS), Pogo can be used worldwide. 6 refs.

  20. Advance particle and Doppler measurement methods

    NASA Technical Reports Server (NTRS)

    Busch, C.

    1985-01-01

    Particle environments, i.e., rain, ice, and snow particles are discussed. Two types of particles addressed are: (1) the natural environment in which airplanes fly and conduct test flights; and (2) simulation environments that are encountered in ground-test facilities such as wind tunnels, ranges, etc. There are characteristics of the natural environment that one wishes to measure. The liquid water content (LWC) is the one that seems to be of most importance; size distribution may be of importance in some applications. Like snow, the shape of the particle may be an important parameter to measure. As one goes on to environment in simulated tests, additional parameters may be required such as velocity distribution, the velocity lag of the particle relative to the aerodynamic flow, and the trajectory of the particle as it goes through the aerodynamic flow and impacts on the test object.

  1. Investigation into the selection of viewing configurations for three-component planar Doppler velocimetry measurements

    SciTech Connect

    Charrett, Tom O. H.; Nobes, David S.; Tatam, Ralph P

    2007-07-01

    A method for the calculation of three orthogonal velocity components in planar Doppler velocimetry (PDV) using four or more measured velocity components (to the three typically used) is presented. The advantages and disadvantages are assessed by use of a Monte Carlo simulation and experimental measurements of the velocity field of a rotating disk. The addition of a fourth velocity component has been shown to lead to reductions inthe final errors of up to 25%. The selection of viewing configurations for experiments is discussed by simulation of the level of errors in measured velocity components and investigation of the final level of errors in the orthogonal velocity components. Experimental measurements of the velocity field of a rotating disk are presented, demonstrating the effectof the viewing configuration on the final level of error.

  2. Turbulence as observed by concurrent measurements made at NSSL using weather radar, Doppler radar, Doppler lidar and aircraft

    NASA Technical Reports Server (NTRS)

    Lee, Jean T.

    1987-01-01

    As air traffic increases and aircraft capability increases in range and operating altitude, the exposure to weather hazards increases. Turbulence and wind shears are two of the most important of these hazards that must be taken into account if safe flight operations are to be accomplished. Beginning in the early 1960's, Project Rough Rider began thunderstorm investigations. Past and present efforts at the National Severe Storm Laboratory (NSSL) to measure these flight safety hazards and to describe the use of Doppler radar to detect and qualify these hazards are summarized. In particular, the evolution of the Doppler-measured radial velocity spectrum width and its applicability to the problem of safe flight is presented.

  3. An acoustic doppler current profiler survey of flow velocities in Detroit River, a connecting channel of the Great Lakes

    USGS Publications Warehouse

    Holtschlag, David J.; Koschik, John A.

    2003-01-01

    Acoustic Doppler current profilers (ADCP) were used to survey flow velocities in Detroit River from July 8-19, 2002, as part of a study to assess the susceptibility of public water intakes to contaminants on the St. Clair-Detroit River Waterway. More than 3.5 million point velocities were measured at 130 cross sections. Cross sections were generally spaced about 1,800 ft apart along the river from the head of Detroit River at the outlet of Lake St. Clair to the mouth of Detroit River on Lake Erie. Two transects were surveyed at each cross section, one in each direction across the river. Along each transect, velocity profiles were generally obtained 0.8-2.2 ft apart. At each velocity profile, average water velocity data were obtained at 1.64 ft intervals of depth. The raw position and velocity data from the ADCP field survey were adjusted for local magnetic anomalies using global positioning system (GPS) measurements at the end points of the transects. The adjusted velocity and ancillary data can be retrieved though the internet and extracted to column-oriented data files.

  4. Spatial and temporal resolution of aortic Doppler blood velocity signals in normal human subjects.

    PubMed

    Targett, R C; McIlroy, M B

    1985-01-01

    We have used digital, microcomputer-based methods for the numerical analysis of pulsed, range-gated, ultrasonic Doppler blood velocity signals recorded with an axially aimed transducer from the ascending aorta of normal subjects. We investigated the spatial, temporal and amplitude resolution of our methods for recording and analysis, comparing aortic signals with test signals from a sine wave function generator. The spatial resolution of our system was found to be adequate in spite of the use of a relatively large sample volume. The temporal resolution was significantly influenced by the rate of change of velocity which affected the results of discrete fast Fourier transform analysis. The rate of increase in aortic blood velocity at the start of ejection was linear, following an initial jump in velocity. The amplitude resolution was affected by fluctuations in the amplitude of the Doppler signals. We conclude that our methods do not exaggerate the bluntness of the aortic velocity profile or the linearity of the increase in blood velocity at the start of left ventricular ejection.

  5. Shape and vibration measurement of fast rotating objects employing novel laser Doppler techniques

    NASA Astrophysics Data System (ADS)

    Pfister, Thorsten; Günther, Philipp; Büttner, Lars; Czarske, Jürgen

    2007-06-01

    This contribution presents novel laser Doppler techniques, which allow simultaneous measurement of radial position and tangential velocity and, thus, determination of the shape of rotating objects with one single sensor. Conventional laser Doppler velocimeters measure only velocities. A concurrent position measurement can be realized by generating two fan-like interference fringe systems with contrary fringe spacing gradients and evaluating the quotient of the two resulting Doppler frequencies. Alternatively, two tilted fringe systems in combination with phase evaluation can be employed. It is shown that the position uncertainty of this sensor is not only independent of the surface roughness but, most notably, that it is in principle independent of the object velocity. Thus, in contrast to conventional distance sensors, the novel laser Doppler position sensor offers high temporal resolution below 3 μs and high position resolution in the micrometer range simultaneously. The sensor was applied to automatic 3D shape measurements of turning parts and to monitoring rotor unbalance and dynamic deformations. Furthermore, in situ measurements of tip clearance and rotor vibrations at turbo machines for up to 600 m/s blade tip velocity are reported. The results are in excellent agreement with those of triangulation and capacitive probes, respectively.

  6. Use of High Sensitivity GNSS Receiver Doppler Measurements for Indoor Pedestrian Dead Reckoning

    PubMed Central

    He, Zhe; Renaudin, Valérie; Petovello, Mark G.; Lachapelle, Gérard

    2013-01-01

    Dead-reckoning (DR) algorithms, which use self-contained inertial sensors combined with gait analysis, have proven to be effective for pedestrian navigation purposes. In such DR systems, the primary error is often due to accumulated heading drifts. By tightly integrating global navigation satellite system (GNSS) Doppler measurements with DR, such accumulated heading errors can usually be accurately compensated. Under weak signal conditions, high sensitivity GNSS (HSGNSS) receivers with block processing techniques are often used, however, the Doppler quality of such receivers is relatively poor due to multipath, fading and signal attenuation. This often limits the benefits of integrating HSGNSS Doppler with DR. This paper investigates the benefits of using Doppler measurements from a novel direct vector HSGNSS receiver with pedestrian dead-reckoning (PDR) for indoor navigation. An indoor signal and multipath model is introduced which explains how conventional HSGNSS Doppler measurements are affected by indoor multipath. Velocity and Doppler estimated by using direct vector receivers are introduced and discussed. Real experimental data is processed and analyzed to assess the veracity of proposed method. It is shown when integrating HSGNSS Doppler with PDR algorithm, the proposed direct vector method are more helpful than conventional block processing method for the indoor environments considered herein. PMID:23539033

  7. Use of high sensitivity GNSS receiver Doppler measurements for indoor pedestrian dead reckoning.

    PubMed

    He, Zhe; Renaudin, Valérie; Petovello, Mark G; Lachapelle, Gérard

    2013-03-28

    Dead-reckoning (DR) algorithms, which use self-contained inertial sensors combined with gait analysis, have proven to be effective for pedestrian navigation purposes. In such DR systems, the primary error is often due to accumulated heading drifts. By tightly integrating global navigation satellite system (GNSS) Doppler measurements with DR, such accumulated heading errors can usually be accurately compensated. Under weak signal conditions, high sensitivity GNSS (HSGNSS) receivers with block processing techniques are often used, however, the Doppler quality of such receivers is relatively poor due to multipath, fading and signal attenuation. This often limits the benefits of integrating HSGNSS Doppler with DR. This paper investigates the benefits of using Doppler measurements from a novel direct vector HSGNSS receiver with pedestrian dead-reckoning (PDR) for indoor navigation. An indoor signal and multipath model is introduced which explains how conventional HSGNSS Doppler measurements are affected by indoor multipath. Velocity and Doppler estimated by using direct vector receivers are introduced and discussed. Real experimental data is processed and analyzed to assess the veracity of proposed method. It is shown when integrating HSGNSS Doppler with PDR algorithm, the proposed direct vector method are more helpful than conventional block processing method for the indoor environments considered herein.

  8. Validation of volumetric flow measurements by means of a Doppler-tipped coronary angioplasty guide wire.

    PubMed

    Labovitz, A J; Anthonis, D M; Cravens, T L; Kern, M J

    1993-12-01

    We used an in vitro model to validate volumetric flow measurements obtained with an 0.018-inch angioplasty guidewire with a 12 MHz transducer mounted on its tip. By using a modified two-head roller pump device, flow was adjusted incrementally from a minimum of 90 ml/min to a maximum of 550 ml/min. Flow was measured with the Doppler guide wire in tubing ranging from 1.9 mm to 6.0 mm internal diameter, as the product of the spectral Doppler velocity integral and the cross-sectional area of the tubing, over a 1-minute period. It was an excellent correlation between the Doppler calculated flow rates and actual flow, regardless of tubing diameter (r = 0.99). These results suggest that the Doppler spectral output of this device might be accurately applied to estimates of volumetric flow in human coronary arteries.

  9. Gulf stream velocity structure through combined inversion of hydrographic and acoustic Doppler data

    NASA Technical Reports Server (NTRS)

    Pierce, S. D.

    1986-01-01

    Near-surface velocities from an acoustic Doppler instrument are used in conjunction with CTD/O2 data to produce estimates of the absolute flow field off Cape Hatteras. The data set consists of two transects across the Gulf Stream made by the R/V Endeavor cruise EN88 in August 1982. An inverse procedure is applied which makes use of both the acoustic Doppler data and property conservation constraints. Velocity sections at approximately 73 deg. W and 71 deg. W are presented with formal errors of 1-2 cm/s. The net Gulf Stream transports are estimated to be 116 + or - 2 Sv across the south leg and 161 + or - 4 Sv across the north. A Deep Western Boundary Current transport of 4 + or - 1 Sv is also estimated. While these values do not necessarily represent the mean, they are accurate estimates of the synoptic flow field in the region.

  10. Hemodynamic numerical simulations of the disturbance due to intracoronary flow measurements by a Doppler guide wire.

    PubMed

    Chodzyński, Kamil J; Gremmo, Simone; Eker, Omer F; Lalmand, Jacques; Aminian, Adel; de Sousa, Daniel Ribeiro; Boudjeltia, Karim Zouaoui; Coussement, Grégory

    2016-10-10

    Since hemodynamics plays a key role in the development and evolution of cardiovascular pathologies, physician's decision must be based on proper monitoring of relevant physiological flow quantities. A numerical analysis of the error introduced by an intravascular Doppler guide wire on the peak velocity measurements has been carried out. The effect of probe misalignment (±10°) with respect to the vessel axis was investigated. Numerical simulations were performed on a realistic 3D geometry, reconstructed from coronary angiography images. Furthermore, instead of using Poiseuille or Womersley approximations, the unsteady pulsatile inlet boundary condition has been calculated from experimental peak-velocity measurements inside the vessel through a new approach based on an iterative Newton's algorithm. The results show that the presence of the guide modifies significantly both the maximum velocity and the peak position in the section plane; the difference is between 6 and 17 % of the maximum measured velocity depending on the distance from the probe tip and the instantaneous vessel flow rate. Furthermore, a misalignment of the probe may lead to a wrong estimation of the peak velocity with an error up to 10 % depending on the probe orientation angle. The Doppler probe does affect the maximum velocity and its position during intravascular Doppler measurements. Moreover, the Doppler-probe-wire sampling volume at 5.2 and 10 mm far from the probe tip is not sufficient to prevent its influence on the measurement. This should be taken into account in clinical practice by physicians during intravascular Doppler quantification. The new numerical approach used in this work could potentially be helpful in future numerical simulations to set plausible inlet boundary conditions.

  11. Ductus Venosus Doppler Flow Velocity after Transplacental and Non-transplacental Amniocentesis during Midtrimester.

    PubMed

    Artunc Ulkumen, Burcu; Pala, Halil Gursoy; Baytur, Yesim Bulbul; Koyuncu, Faik Mumtaz

    2014-09-01

    We aimed to evaluate ductus venosus Doppler waveforms before and after amniocentesis in order to investigate any effect of amniocentesis on fetal myocardial hemodynamics. We also evaluated the umbilical artery, uterine artery and fetal mid-cerebral artery Doppler waveforms in order to investigate any relationship with ductus venosus Doppler changes. The study population consisted of 56 singleton pregnancies having genetic amniocentesis. Twenty seven of them had transplacental needle insertion; whereas 29 of them had non-transplacental amniocentesis. Uterine artery, umbilical artery, mid-cerebral artery and ductus venosus pulsatiliy index and resistance index were measured just before and after amniocentesis. Amniocentesis does not cause any significant changes in fetal ductus venosus Doppler waveforms. There is also no significant changes in uterine artery, umbilical artery, mid-cerebral artery pulsatility and resistance index. Amniocentesis-whether transplacental or not- does not cause any significant effect on fetal myocardial hemodynamics.

  12. Ductus Venosus Doppler Flow Velocity after Transplacental and Non-transplacental Amniocentesis during Midtrimester

    PubMed Central

    Ulkumen, Burcu Artunc; Pala, Halil Gursoy; Baytur, Yesim Bulbul; Koyuncu, Faik Mumtaz

    2014-01-01

    Objective: We aimed to evaluate ductus venosus Doppler waveforms before and after amniocentesis in order to investigate any effect of amniocentesis on fetal myocardial hemodynamics. We also evaluated the umbilical artery, uterine artery and fetal mid-cerebral artery Doppler waveforms in order to investigate any relationship with ductus venosus Doppler changes. Methods: The study population consisted of 56 singleton pregnancies having genetic amniocentesis. Twenty seven of them had transplacental needle insertion; whereas 29 of them had non-transplacental amniocentesis. Uterine artery, umbilical artery, mid-cerebral artery and ductus venosus pulsatiliy index and resistance index were measured just before and after amniocentesis. Results: Amniocentesis does not cause any significant changes in fetal ductus venosus Doppler waveforms. There is also no significant changes in uterine artery, umbilical artery, mid-cerebral artery pulsatility and resistance index. Conclusion: Amniocentesis-whether transplacental or not- does not cause any significant effect on fetal myocardial hemodynamics. PMID:25225513

  13. Flow velocity measurement with the nonlinear acoustic wave scattering

    SciTech Connect

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    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.

  14. The impact of charge transfer inefficiency on Extreme Precision Doppler measurements

    NASA Astrophysics Data System (ADS)

    Blake, C. H.; Halverson, S.; Roy, A.

    2017-04-01

    A new generation of ``Extreme Precision'' astronomical spectrometers is currently being designed to detect Earth-mass planets orbiting nearby stars using the Doppler method. Measuring the subtle shifts in stellar absorption features resulting from stellar radial velocity variations of tens of centimeters per second is a significant technological challenge. Currently, there are several instruments around the world capable of measuring stellar radial velocities at the 1 m s-1 level. Moving beyond this level of precision, CCD effects may become important and could limit the ultimate measurement precision in complex ways. Here, we simulate the impact of Charge Transfer Inefficiency (CTI) in CCDs on radial velocity measurements. We show that CTI can manifest as a significant source of systematic error in high precision Doppler measurements, though these effects can likely be mitigated using optimized observing strategies and empirical flux corrections.

  15. Shear wave transmissivity measurement by color Doppler shear wave imaging

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Yamazaki, Mayuko; Kasahara, Toshihiro; Sunaguchi, Naoki; Yuminaka, Yasushi

    2016-07-01

    Shear wave elastography is a useful method for evaluating tissue stiffness. We have proposed a novel shear wave imaging method (color Doppler shear wave imaging: CD SWI), which utilizes a signal processing unit in ultrasound color flow imaging in order to detect the shear wave wavefront in real time. Shear wave velocity is adopted to characterize tissue stiffness; however, it is difficult to measure tissue stiffness with high spatial resolution because of the artifact produced by shear wave diffraction. Spatial average processing in the image reconstruction method also degrades the spatial resolution. In this paper, we propose a novel measurement method for the shear wave transmissivity of a tissue boundary. Shear wave wavefront maps are acquired by changing the displacement amplitude of the shear wave and the transmissivity of the shear wave, which gives the difference in shear wave velocity between two mediums separated by the boundary, is measured from the ratio of two threshold voltages required to form the shear wave wavefronts in the two mediums. From this method, a high-resolution shear wave amplitude imaging method that reconstructs a tissue boundary is proposed.

  16. Laser Doppler techniques for the combined measurement of inlet flow and valve motion in IC engines

    NASA Astrophysics Data System (ADS)

    Gasparetti, M.; Paone, N.; Tomasini, E. P.

    1996-04-01

    A measurement methodology and a test set-up for the experimental investigation of internal combustion engines are presented. This system is based on a laser Doppler anemometer and a laser Doppler vibrometer which measure in a co-ordinated or simultaneous mode both the velocity of the intake flow and the motion of the inlet poppet valve. A synchronized data acquisition procedure allows the use of two optical instruments to analyse the effects of valve jumps and bounces on the inlet flow field. At high rpm, anomalous valve behaviour may appear. Fluid velocity measurements are taken inside the cylinder and the manifold of a motored automotive engine head at different rpm, up to a speed at which anomalous valve behaviour regularly occurs. Velocity data are processed in both time and frequency domains. This measurement system also represents a valuable tool to study resonance phenomena in ducts.

  17. Automated assessment of mitral regurgitant volume and regurgitant fraction by a newly developed digital color Doppler velocity profile integration method.

    PubMed

    Hozumi, T; Yoshida, K; Akasaka, T; Takagi, T; Yamamuro, A; Yagi, T; Yoshikawa, J

    1997-11-15

    Recent development of the automated cardiac flow measurement (ACFM) method has provided automated measurement of stroke volume and cardiac output by spatial and temporal integration of digital Doppler velocity profile data. The purpose of this study was to evaluate the clinical usefulness of the ACFM method using digital color Doppler velocity profile integration in the assessment of mitral regurgitant volume and regurgitant fraction from measurements of both aortic outflow and mitral inflow volumes. We calculated both aortic outflow and mitral inflow volumes from the apical approach with the ACFM and pulsed Doppler (PD) methods in 20 patients with isolated mitral regurgitation. Mitral regurgitant volume and regurgitant fraction were calculated by the following equation: mitral regurgitant volume = (mitral inflow volume) - (aortic outflow volume), % regurgitant fraction = (mitral regurgitant volume)/(mitral inflow volume) x 100. Mitral regurgitant volume and regurgitant fraction were compared with that determined by the PD method. Mitral regurgitant volume measurement by the ACFM method showed a good correlation with that measured by the PD method (r = 0.90, y = 0.77x + 11.6, SEE = 9.0 ml); the mean differences between PD and ACFM measurements was -1.7 +/- 12.5 ml. Regurgitant fraction estimated by the ACFM method correlated well with that of the PD method (r = 0.92, y = 0.98x + 2.1, SEE = 8.8%). The mean difference for the measurement of regurgitant fraction between the PD and ACFM methods was 0.8 +/- 6.6%. Total time required for mitral regurgitant volume calculation in 1 cardiac cycle by the ACFM method was significantly shorter than that of the PD method (126 +/- 15 seconds vs 228 +/- 36 seconds, p <0.01). In conclusion, the newly developed ACFM method is simple, quick, and accurate in the automated assessment of mitral regurgitant volume and regurgitant fraction.

  18. First Measurements of Simulated Upper Atmospheric Winds Using a Monolithic Doppler Asymmetric Spatial Heterodyne (DASH) Interferometer

    NASA Astrophysics Data System (ADS)

    Babcock, D. D.; Harlander, J.; Englert, C. R.; Roesler, F. L.; Pedersen, T. R.; Feldman, R.

    2010-12-01

    Results of the first calibrated Doppler measurements taken with a Doppler Asymmetric Spatial Heterodyne (DASH) instrument optimized for measuring simulated upper atmospheric winds using the O(1D) red line at 630nm will be presented. A space flight prototype DASH instrument has been designed, built, and is currently operational through funding from the Air Force Research Laboratory (AFRL) and in-kind support from the Naval Research Laboratory (NRL). The DASH instrument named ARROW (Atmospheric Redline inteRferometer for dOppler Winds) includes an internal emission line source for simultaneous calibration of the Doppler shift measurements, measured a laboratory emission line source which was Doppler shifted by known velocities. The comparison between the Doppler shifts that were retrieved from the DASH data and the shifts that were imposed on the laboratory emission line source demonstrate the accuracy of the measurements. This laboratory validation contributes significantly to our efforts to rapidly increase the technical readiness level of the DASH optical interferometric technique.

  19. Variability of Vertical Velocity Statistics in the Cloud-Free Convective Boundary Layer as Revealed by Doppler Lidar

    NASA Astrophysics Data System (ADS)

    Berg, L. K.; Newsom, R. K.; Turner, D. D.

    2016-12-01

    The majority of our understanding of the behavior of vertical velocity in the convective boundary layer is based on a small number of short-term observations made using either in situ or with remote sensing techniques over a limited number of sites. Analysis of long-term statistics have been lacking due to the scarcity of appropriate measurements. The US Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility is addressing this shortcoming through the deployment of a suite of scanning Doppler Lidars at a number of locations, associated with reconfiguration of the ARM Southern Great Plains site and the recent Holistic Interaction of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) field campaign. In this study, we utilize data collected by a Doppler Lidar system that has operated continuously from 2011 to the present at a location in north-central Oklahoma to examine the long-term behavior of the vertical velocity variance, skewness, and kurtosis. The application of standard normalization techniques, such as the mixed-layer depth and Deardorff convective velocity scale, do a good job in collapsing the data onto a single curve during periods in which the boundary layer is well developed, albeit with considerable amounts of scatter. During non-steady conditions, such as those found in the morning, scaling using the Deardorff convective velocity scale is found to work poorly. This behavior is likely due to the eddy turnover time and the growth rate of the boundary-layer depth. Systematic differences in the turbulence statistics are found by season, for non-stationary conditions, or periods with relatively small and large values of the surface friction velocity measured at the surface, amount of static instability, and wind shear across the boundary-layer top.

  20. A Preliminary Evaluation of Near-Transducer Velocities Collected with Low-Blank Acoustic Doppler Current Profiler

    USGS Publications Warehouse

    Gartner, J.W.; Ganju, N.K.; ,

    2002-01-01

    Many streams and rivers for which the US Geological Survey must provide discharge measurements are too shallow to apply existing acoustic Doppler current profiler techniques for flow measurements of satisfactory quality. Because the same transducer is used for both transmitting and receiving acoustic signals in most Doppler current profilers, some small time delay is required for acoustic "ringing" to be damped out of transducers before meaningful measurements can be made. The result of that time delay is that velocity measurements cannot be made close to the transducer thus limiting the usefulness of these instruments in shallow regions. Manufacturers and users are constantly striving for improvements to acoustic instruments which would permit useful discharge measurements in shallow rivers and streams that are still often measured with techniques and instruments more than a century old. One promising area of advance appeared to be reduction of time delay (blank) required between transmitting and receiving signals during acoustic velocity measurements. Development of a low- or zero-blank transducer by RD Instruments3 held promise that velocity measurements could be made much closer to the transducer and thus in much shallower water. Initial experience indicates that this is not the case; limitation of measurement quality appears to be related to the physical presence of the transducer itself within the flow field. The limitation may be the result of changes to water flow pattern close to the transducer rather than transducer ringing characteristics as a function of blanking distance. Results of field experiments are discussed that support this conclusion and some minimum measurement distances from transducer are suggested based on water current speed and ADCP sample modes.

  1. Minimally destructive Doppler measurement of a quantized, superfluid flow

    NASA Astrophysics Data System (ADS)

    Anderson, Neil; Kumar, Avinash; Eckel, Stephen; Stringari, Sandro; Campbell, Gretchen

    2016-05-01

    Ring shaped Bose-Einstein condensates are of interest because they support the existence of quantized, persistent currents. These currents arise because in a ring trap, the wavefunction of the condensate must be single valued, and thus the azimuthal velocity is quantized. Previously, these persistent current states have only been measured in a destructive fashion via either interference with a phase reference or using the size of a central vortex-like structure that appears in time of flight. Here, we demonstrate a minimally destructive, in-situ measurement of the winding number of a ring shaped BEC. We excite a standing wave of phonon modes in the ring BEC using a perturbation. If the condensate is in a nonzero circulation state, then the frequency of these phonon modes are Doppler shifted, causing the standing wave to precess about the ring. From the direction and velocity of this precession, we can infer the winding number of the flow. For certain parameters, this technique can detect individual winding numbers with approximately 90% fidelity.

  2. Direct measurement of Lorentz transformation with Doppler effects

    NASA Astrophysics Data System (ADS)

    Chen, Shao-Guang

    For space science and astronomy the fundamentality of one-way velocity of light (OWVL) is selfevident. The measurement of OWVL (distance/interval) and the clock synchronization with light-signal transfer make a logical circulation. This means that OWVL could not be directly measured but only come indirectly from astronomical method (Romer's Io eclipse and Bradley's sidereal aberration), furthermore, the light-year by definitional OWVL and the trigonometry distance with AU are also un-measurable. For to solve this problem two methods of clock synchronization were proposed: The direct method is that at one end of dual-speed transmissionline with single clock measure the arriving-time difference of longitudinal wave and transverse wave or ordinary light and extraordinary light, again to calculate the collective sending-time of two wave with Yang's /shear elastic-modulus ratio (E/k) or extraordinary/ordinary light refractive-index ratio (ne/no), which work as one earthquake-station with single clock measures first-shake time and the distance to epicenter; The indirect method is that the one-way wavelength l is measured by dual-counters Ca and Cb and computer's real-time operation of reading difference (Nb - Na) of two counters, the frequency f is also simultaneously measured, then l f is just OWVL. Therefore, with classical Newtonian mechanics and ether wave optics, OWVL can be measured in the Galileo coordinate system with an isotropic length unit (1889 international meter definition). Without any hypotheses special relativity can entirely establish on the metrical results. When a certain wavelength l is defined as length unit, foregoing measurement of one-way wavelength l will become as the measurement of rod's length. Let a rigidity-rod connecting Ca and Cb moves relative to lamp-house with velocity v, rod's length L = (Nb - Na) l will change follow v by known Doppler effect, i.e., L(q) =L0 (1+ (v/c) cos q), where L0 is the proper length when v= 0, v• r = v cos q

  3. Spline function approximation for velocimeter Doppler frequency measurement

    NASA Technical Reports Server (NTRS)

    Savakis, Andreas E.; Stoughton, John W.; Kanetkar, Sharad V.

    1989-01-01

    A spline function approximation approach for measuring the Doppler spectral peak frequency in a laser Doppler velocimeter system is presented. The processor is designed for signal bursts with mean Doppler shift frequencies up to 100 MHz, input turbulence up to 20 percent, and photon counts as low as 300. The frequency-domain processor uses a bank of digital bandpass filters for the capture of the energy spectrum of each signal burst. The average values of the filter output energies, as a function of normalized frequency, are modeled as deterministic spline functions which are linearly weighted to evaluate the spectral peak location associated with the Doppler shift. The weighting coefficients are chosen to minimize the mean square error. Performance evaluation by simulation yields average errors in estimating mean Doppler frequencies within 0.5 percent for poor signal-to-noise conditions associated with a low photon count of 300 photons/burst.

  4. Optic-microwave mixing velocimeter for superhigh velocity measurement

    NASA Astrophysics Data System (ADS)

    Weng, Jidong; Wang, Xiang; Tao, Tianjiong; Liu, Cangli; Tan, Hua

    2011-12-01

    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.

  5. Optic-microwave mixing velocimeter for superhigh velocity measurement

    SciTech Connect

    Weng Jidong; Wang Xiang; Tao Tianjiong; Liu Cangli; Tan Hua

    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.

  6. Effects of volume averaging on the line spectra of vertical velocity from multiple-Doppler radar observations

    NASA Technical Reports Server (NTRS)

    Gal-Chen, T.; Wyngaard, J. C.

    1982-01-01

    Calculations of the ratio of the true one-dimensional spectrum of vertical velocity and that measured with multiple-Doppler radar beams are presented. It was assumed that the effects of pulse volume averaging and objective analysis routines is replacement of a point measurement with a volume integral. A u and v estimate was assumed to be feasible when orthogonal radars are not available. Also, the target fluid was configured as having an infinite vertical dimension, zero vertical velocity at the top and bottom, and having homogeneous and isotropic turbulence with a Kolmogorov energy spectrum. The ratio obtained indicated that equal resolutions among radars yields a monotonically decreasing, wavenumber-dependent response function. A gain of 0.95 was demonstrated in an experimental situation with 40 levels. Possible errors introduced when using unequal resolution radars were discussed. Finally, it was found that, for some flows, the extent of attenuation depends on the number of vertical levels resolvable by the radars.

  7. Effects of volume averaging on the line spectra of vertical velocity from multiple-Doppler radar observations

    NASA Technical Reports Server (NTRS)

    Gal-Chen, T.; Wyngaard, J. C.

    1982-01-01

    Calculations of the ratio of the true one-dimensional spectrum of vertical velocity and that measured with multiple-Doppler radar beams are presented. It was assumed that the effects of pulse volume averaging and objective analysis routines is replacement of a point measurement with a volume integral. A u and v estimate was assumed to be feasible when orthogonal radars are not available. Also, the target fluid was configured as having an infinite vertical dimension, zero vertical velocity at the top and bottom, and having homogeneous and isotropic turbulence with a Kolmogorov energy spectrum. The ratio obtained indicated that equal resolutions among radars yields a monotonically decreasing, wavenumber-dependent response function. A gain of 0.95 was demonstrated in an experimental situation with 40 levels. Possible errors introduced when using unequal resolution radars were discussed. Finally, it was found that, for some flows, the extent of attenuation depends on the number of vertical levels resolvable by the radars.

  8. Relative velocity measurement from the spectral phase of a match-filtered linear frequency modulated pulse.

    PubMed

    Pinson, Samuel; Holland, Charles W

    2016-08-01

    Linear frequency modulated signals are commonly used to perform underwater acoustic measurements since they can achieve high signal-to-noise ratios with relatively low source levels. However, such signals present a drawback if the source or receiver or target is moving. The Doppler effect affects signal amplitude, delay, and resolution. To perform a correct match filtering that includes the Doppler shift requires prior knowledge of the relative velocity. In this paper, the relative velocity is extracted directly from the Doppler cross-power spectrum. More precisely, the quadratic coefficient of the Doppler cross-power-spectrum phase is proportional to the relative velocity. The proposed method achieves velocity estimates that compare favorably with Global Positioning System ground truth and the ambiguity method.

  9. Hydroxyurea lowers transcranial Doppler flow velocities in children with sickle cell anaemia in a Nigerian cohort.

    PubMed

    Lagunju, IkeOluwa; Brown, Biobele J; Sodeinde, Olugbemiro

    2015-09-01

    Sickle cell anaemia (SCA) is the leading genetic disorder in Nigeria. Elevated velocities ≥170 cm/sec occur in about a third of Nigerian children with SCA. Chronic blood transfusion for stroke prevention is faced with a myriad of challenges in our practice. To evaluate the effectiveness of hydroxyurea (HU) in reducing flow velocities in a cohort of Nigerian children with SCA and elevated velocities treated with HU. An observational study was carried out on a cohort of Nigerian children with SCA and elevated velocities identified on routine transcranial Doppler (TCD) screening. HU was recommended in those with TCD velocities ≥ 170cm/sec as stipulated in our hospital protocol. Outcomes were compared after ≥12 months of observation. Fifty children with elevated TCD velocities were studied; 31 consented to HU therapy and 19 declined. Children on HU showed a statistically significant decline in mean velocities from 199.7 [17.1] cm/sec to 165.8 [20.7] cm/sec (P < 0.001) with a significant increase in mean packed cell volume from 21.1 [3.4] to 25.0 [2.8]%. Children without treatment had a significant rise in mean velocities from 190.2 [10.8] cm/sec to 199.7 [14.9] cm/sec (P = 0.003). Children with conditional risk velocities on HU were less likely to convert to abnormal risk (P < 0.001). Two stroke events occurred, one in each group. No adverse effects of HU were recorded in the cohort. HU appears to significantly reduce TCD velocities in Nigerian children with SCA and elevated velocities ≥170 cm/sec with beneficial effect on the haematological profile. HU may provide an effective approach to primary stroke prevention, particularly in Africa. © 2015 Wiley Periodicals, Inc.

  10. Tissue perfusion measurements: multiple-exposure laser speckle analysis generates laser Doppler-like spectra.

    PubMed

    Thompson, Oliver B; Andrews, Michael K

    2010-01-01

    Variations in skin perfusion are easily detected by laser speckle contrast maps, but a robust interpretation of the information has been lacking. We show that multiple-exposure laser speckle methods produce the same spectral information as laser Doppler methods when applied to targets with embedded moving scatterers. This enables laser speckle measurements to be interpreted more quantitatively. We do this by using computer simulation of speckle data, and by experimental measurements on Brownian motion and skin perfusion using a laser Doppler system and a multiple-exposure laser speckle system. The power spectral density measurements of the light fluctuations derived using both techniques are exactly equivalent. Dermal perfusion can therefore be measured by laser Doppler or laser speckle contrast methods. In particular, multiexposure laser speckle can be rapidly processed to generate a full-field map of the perfusion index proportional to the concentration and mean velocity of red blood cells.

  11. Laser Doppler position sensor for position and shape measurements of fast rotating objects

    NASA Astrophysics Data System (ADS)

    Czarske, Jürgen; Pfister, Thorsten; Büttner, Lars

    2006-08-01

    We report about a novel optical method based on laser Doppler velocimetry for position and shape measurements of moved solid state surfaces with approximately one micrometer position resolution. 3D shape measurements of a rotating cylinder inside a turning machine as well as tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm and 586 m/s blade tip velocity are presented. All results are in good agreement with conventional reference probes. The measurement accuracy of the laser Doppler position sensor is investigated in dependence of the speckle pattern. Furthermore, it is shown that this sensor offers high temporal resolution and high position resolution simultaneously and that shading can be reduced compared to triangulation. Consequently, the presented laser Doppler position sensor opens up new perspectives in the field of real-time manufacturing metrology and process control, for example controlling the turning and the grinding process or for future developments of turbo machines.

  12. Study on Water Distribution Imaging in the Sand Using Propagation Velocity of Sound with Scanning Laser Doppler Vibrometer

    NASA Astrophysics Data System (ADS)

    Sugimoto, Tsuneyoshi; Nakagawa, Yutaka; Shirakawa, Takashi; Sano, Motoaki; Ohaba, Motoyoshi; Shibusawa, Sakae

    2013-07-01

    We propose a method for the monitoring and imaging of the water distribution in the rooting zone of plants using sound vibration. In this study, the water distribution measurement in the horizontal and vertical directions in the soil layer was examined to confirm whether a temporal change in the volume water content of the soil could be estimated from a temporal changes in propagation velocity. A scanning laser Doppler vibrometer (SLDV) is used for measurement of the vibration velocity of the soil surface, because the highly precise vibration velocity measurement of several many points can be carried out automatically. Sand with a uniform particle size distribution is used for the soil, as it has high plasticity; that is, the sand can return to a dry state easily even if it is soaked with water. A giant magnetostriction vibrator or a flat speaker is used as a sound source. Also, a soil moisture sensor, which measures the water content of the soil using the electric permittivity, is installed in the sand. From the experimental results of the vibration measurement and soil moisture sensors, we can confirm that the temporal changes of the water distribution in sand using the negative pressure irrigation system in both the horizontal and vertical directions can be estimated using the propagation velocity of sound. Therefore, in the future, we plan to develop an insertion-type sound source and receiver using the acceleration sensors, and we intend to examine whether our method can be applied even in commercial soil with growing plants.

  13. Retrieval of Hydrometeor Drop Size Distributions from TRMM Field Campaign Profiler Doppler Velocity Spectra Observations

    NASA Technical Reports Server (NTRS)

    Williams, Christopher R.; Gage, Kenneth S.

    2003-01-01

    Consistent with the original proposal and work plan, this project focused on estimating the raindrop size distributions (DSDs) retrieved from vertically pointing Doppler radar profilers and analyzing the relationship of the retrieved DSDs with the dynamics of the precipitation processes. The first phase of this project focused on developing the model to retrieve the DSD from the observed Doppler velocity spectra. The second phase used this model to perform DSD retrievals from the profiler observations made during the TRMM Ground Validation Field Campaigns of TEFLUN-B, TRMM-LBA, and KWAJEX. The third phase of this project established collaborations with scientists involved with each field campaign in order to validate the profiler DSD estimates and to enable the profiler retrievals to be used in their research. Through these collaborations, the retrieved DSDs were placed into context with the dynamical processes of the observed precipitating cloud systems.

  14. Classification of transcranial Doppler signals using their chaotic invariant measures.

    PubMed

    Ozturk, Ali; Arslan, Ahmet

    2007-05-01

    In this study, chaos analysis was performed on the transcranial Doppler (TCD) signals recorded from the temporal region of the brain of 82 patients as well as of 24 healthy people. Two chaotic invariant measures, i.e. the maximum Lyapunov exponent and the correlation dimension, were calculated for the TCD signals after applying nonlinearity and stationarity tests to them. The sonograms obtained via Burg autoregressive (AR) method demonstrated that the chaotic invariant measures represented the unpredictability and complexity levels of the TCD signals. According to the multiple linear regression analysis, the chaotic invariant measures were found to be highly significant for the regression equation which fitted to the data. This result suggested that the chaotic invariant measures could be used for automatically differentiating various cerebrovascular conditions via an appropriate classifier. For comparison purposes, we investigated several different classification algorithms. The k-nearest neighbour algorithm outperformed all the other classifiers with a classification accuracy of 94.44% on the test data. We used the receiver operating characteristic (ROC) curves in order to assess the performance of the classifiers. The results suggested that the classification systems which use the chaotic invariant measures as input have potential in detecting the blood flow velocity changes due to various brain diseases.

  15. Supersonic-nitrogen flow-field measurements with the resonant Doppler velocimeter

    NASA Technical Reports Server (NTRS)

    Cheng, S.; Zimmermann, M.; Miles, R. B.

    1983-01-01

    The application of the resonant Doppler velocimeter (RDV) for obtaining the mean velocity, temperature, and pressure measurements and flow-field visualization in a supersonic free nitrogen jet is reported. This method utilizes laser-induced fluorescence to determine the spectral absorption of an atomic or molecular species seeded into the flow. A narrow linewidth tunable laser is directed into the flow and the total fluorescence from any point is obtained as the laser is tuned. The velocity of the flow is obtained from the Doppler shifted absorption frequency, and the temperature and pressure of the gas are determined from line broadening measurements. Results are presented for the use of this technique to determine the velocity, temperature, and pressure of the flow of sodium atoms seeded into a supersonic nitrogen jet. It is concluded that the visible signal is sufficiently intense for spatially resolved flow visualization purposes.

  16. Directional acoustic measurements by laser Doppler velocimeters. [for jet aircraft noise

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Overbey, R. L.; Testerman, M. K.

    1976-01-01

    Laser Doppler velocimeters (LDVs) were used as velocity microphones to measure sound pressure level in the range of 90-130 db, spectral components, and two-point cross correlation functions for acoustic noise source identification. Close agreement between LDV and microphone data is observed. It was concluded that directional sensitivity and the ability to measure remotely make LDVs useful tools for acoustic measurement where placement of any physical probe is difficult or undesirable, as in the diagnosis of jet aircraft noise.

  17. Use of Doppler radar to assess ice cloud particle fall velocity-size relations for remote sensing and climate studies

    NASA Astrophysics Data System (ADS)

    Matrosov, Sergey Y.; Heymsfield, Andrew J.

    2000-09-01

    Knowledge of ice crystal terminal velocities, both for individual crystals and for size distributions, is important for an adequate representation of ice particle sedimentation in climate models. While the terminal velocities (υt) of individual crystals of simple shapes have been measured, theoretical relations of the form υt = ADB (where D is the maximum particle dimension), obtained using expressions for the aerodynamic drag force, are often more useful because they can be applied to a wide range of particle sizes and heights and temperatures in the atmosphere. For high tropospheric ice clouds the coefficient A has been found to vary over 1 order of magnitude; the exponent B is generally within the range 0.7-1.4. Aerodynamic drag force calculations show that A and B are related. A and B can also be used to characterize terminal-velocity-particle characteristic size relations for size distributions. In this study we use collocated, vertically pointing measurements of ice cloud radar reflectivity, Doppler velocity, and IR brightness temperatures to estimate the vertical profiles of cloud particle characteristic size, cloud ice water content, and vertically averaged value of the coefficient A, emphasizing cirrus clouds. We analyze variations in terminal-velocity-size relations for individual particles and corresponding variations for ensembles of particles: for example, in relations between the reflectivity-weighted terminal velocity and the median volume size and between the mass-weighted terminal velocity and the median volume size. The retrievals indicate that A ranges from ˜250 to almost 4000 (cgs units), similar to the range found from the theoretical calculations. The coefficient A tends to decrease as a characteristic particle size (e.g., median size) increases. As a simplification for climate modeling efforts, we present an empirical relation between median size and A, although there is a fair amount of variability about this relation. Using the Doppler

  18. Determinants of diastolic myocardial tissue Doppler velocities: influences of relaxation and preload

    NASA Technical Reports Server (NTRS)

    Firstenberg, M. S.; Greenberg, N. L.; Main, M. L.; Drinko, J. K.; Odabashian, J. A.; Thomas, J. D.; Garcia, M. J.

    2001-01-01

    Myocardial tissue Doppler echocardiography (TDE) has been proposed as a tool for the assessment of diastolic function. Controversy exists regarding whether TDE measurements are influenced by preload. In this study, left ventricular volume and high-fidelity pressures were obtained in eight closed-chest dogs during intermittent caval occlusion. The time constant of isovolumic ventricular relaxation (tau) was altered with varying doses of dobutamine and esmolol. Peak early diastolic myocardial (E(m)) and transmitral (E) velocities were measured before and after preload reduction. The relative effects of changes in preload and relaxation were determined for E(m) and compared with their effects on E. The following results were observed: caval occlusion significantly decreased E (DeltaE = 16.4 +/- 3.3 cm/s, 36.6 +/- 13.7%, P < 0.01) and E(m) (DeltaE(m) = 1. 3 +/- 0.4 cm/s, 32.5 +/- 26.1%, P < 0.01) under baseline conditions. However, preload reduction was similar for E under all lusitropic conditions (P = not significant), but these effects on E(m) decreased with worsening relaxation. At tau < 50 ms, changes in E(m) with preload reduction were significantly greater (DeltaE(m) = 2.8 +/- 0.6 cm/s) than at tau = 50-65 ms (DeltaE(m) = 1.2 +/- 0.2 cm/s) and at tau >65 ms (DeltaE(m) = 0.5 +/- 0.1 cm/s, P < 0.05). We concluded that TDE E(m) is preload dependent. However, this effect decreases with worsening relaxation.

  19. Field Assessment of Acoustic-Doppler Based Discharge Measurements

    USGS Publications Warehouse

    Mueller, D.S.; ,

    2002-01-01

    The use of equipment based on the Doppler principle for measuring water velocity and computing discharge is common within the U.S. Geological Survey (USGS). The instruments and software have changed appreciably during the last 5 years; therefore, the USGS has begun a field validation of the instruments currently (2002) available for making discharge measurements from a moving boat in streams of various sizes. Instruments manufactured by SonTek/YSI2 and RD Instruments, Inc. were used to collect discharge data at five different sites. One or more traditional discharge measurements were made by the use of a Price AA current meter and standard USGS procedures with the acoustic instruments at each site during data collection. The discharges measured with the acoustic instruments were compared with the discharges measured with Price AA meters and the current USGS stage-discharge rating for each site. The mean discharges measured by each acoustic instrument were within 5 percent of the Price AA-based measurement and (or) discharge from the stage-discharge rating. Additional analysis of the data collected indicates that the coefficient of variation of the discharge measurements consistently was less for the RD Instruments, Inc. Rio Grandes than it was for the SonTek/YSI RiverSurveyors. The bottom-tracking referenced measurement had a lower coefficient of variation than the differentially corrected global positioning system referenced measurements. It was observed that the higher frequency RiverSurveyors measured a moving bed more often than the lower frequency Rio Grandes. The detection of a moving bed caused RiverSurveyors to be consistently biased low when referenced to bottom tracking. Differentially corrected global positioning system data may be used to remove the bias observed in the bottom-tracking referenced measurements.

  20. Correction of Dual-PRF Doppler Velocity Outliers in the Presence of Aliasing

    DOE PAGES

    Altube, Patricia; Bech, Joan; Argemí, Oriol; ...

    2017-07-18

    In Doppler weather radars, the presence of unfolding errors or outliers is a well-known quality issue for radial velocity fields estimated using the dual–pulse repetition frequency (PRF) technique. Postprocessing methods have been developed to correct dual-PRF outliers, but these need prior application of a dealiasing algorithm for an adequate correction. Our paper presents an alternative procedure based on circular statistics that corrects dual-PRF errors in the presence of extended Nyquist aliasing. The correction potential of the proposed method is quantitatively tested by means of velocity field simulations and is exemplified in the application to real cases, including severe storm events.more » The comparison with two other existing correction methods indicates an improved performance in the correction of clustered outliers. The technique we propose is well suited for real-time applications requiring high-quality Doppler radar velocity fields, such as wind shear and mesocyclone detection algorithms, or assimilation in numerical weather prediction models.« less

  1. Evaluation of mean velocity and turbulence measurements with ADCPs

    USGS Publications Warehouse

    Nystrom, E.A.; Rehmann, C.R.; Oberg, K.A.

    2007-01-01

    To test the ability of acoustic Doppler current profilers (ADCPs) to measure turbulence, profiles measured with two pulse-to-pulse coherent ADCPs in a laboratory flume were compared to profiles measured with an acoustic Doppler velocimeter, and time series measured in the acoustic beam of the ADCPs were examined. A four-beam ADCP was used at a downstream station, while a three-beam ADCP was used at a downstream station and an upstream station. At the downstream station, where the turbulence intensity was low, both ADCPs reproduced the mean velocity profile well away from the flume boundaries; errors near the boundaries were due to transducer ringing, flow disturbance, and sidelobe interference. At the upstream station, where the turbulence intensity was higher, errors in the mean velocity were large. The four-beam ADCP measured the Reynolds stress profile accurately away from the bottom boundary, and these measurements can be used to estimate shear velocity. Estimates of Reynolds stress with a three-beam ADCP and turbulent kinetic energy with both ADCPs cannot be computed without further assumptions, and they are affected by flow inhomogeneity. Neither ADCP measured integral time scales to within 60%. ?? 2007 ASCE.

  2. CARS measurement of velocity in a supersonic jet

    NASA Technical Reports Server (NTRS)

    Gustafson, E. K.; Mcdaniel, J. C.; Byer, R. L.

    1981-01-01

    It is shown that CW CARS can be used to measure velocity in supersonic flows. The accuracy with which the Doppler shift can be measured is determined through the drift in the laser frequencies. In the experiment described here, it is found that a laser drift error of 10 MHz during the recording of a spectrum would limit the velocity resolution to 34 m/s. It is noted that improved frequency stabilization of the laser sources could lead to a velocity measurement accuracy of several m/s. In the experiment, a 4-W single axial mode argon ion laser is the pump source, and the Stokes-shifted frequency is generated by a 100-mW tunable dye laser.

  3. Doppler lidar atmospheric wind sensors - A comparative performance evaluation for global measurement applications from earth orbit

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.

    1986-01-01

    A comparison is made of four prominent Doppler lidar systems, ranging in wavelength from the near UV to the middle IR, which are presently being studied for their potential in an earth-orbiting global tropospheric wind field measurement application. The comparison is restricted to relative photon efficiencies, i.e., the required number of transmitted photons per pulse is calculated for each system for midtropospheric velocity estimate uncertainties ranging from + or - 1 to + or - 4 m/s. The results are converted to laser transmitter pulse energy and power requirements. The analysis indicates that a coherent CO2 Doppler lidar operating at 9.11-micron wavelength is the most efficient.

  4. Orientation-independent rapid pulsatile flow measurement using dual-angle Doppler OCT

    PubMed Central

    Peterson, Lindsy M; Gu, Shi; Jenkins, Michael W; Rollins, Andrew M

    2014-01-01

    Doppler OCT (DOCT) can provide blood flow velocity information which is valuable for investigation of microvascular structure and function. However, DOCT is only sensitive to motion parallel with the imaging beam, so that knowledge of flow direction is needed for absolute velocity determination. Here, absolute volumetric flow is calculated by integrating velocity components perpendicular to the B-scan plane. These components are acquired using two illumination beams with a predetermined angular separation, produced by a delay encoded technique. This technology enables rapid pulsatile flow measurement from single B-scans without the need for 3-D volumetric data or knowledge of blood vessel orientation. PMID:24575344

  5. Air-mass flux measurement system using Doppler-shifted filtered Rayleigh scattering

    NASA Technical Reports Server (NTRS)

    Shirley, John A.; Winter, Michael

    1993-01-01

    An optical system has been investigated to measure mass flux distributions in the inlet of a high speed air-breathing propulsion system. Rayleigh scattered light from air is proportional to the number density of molecules and hence can be used to ascertain the gas density in a calibrated system. Velocity field measurements are achieved by spectrally filtering the elastically-scattered Doppler-shifted light with an absorbing molecular filter. A novel anamorphic optical collection system is used which allows optical rays from different scattering angles, that have different Doppler shifts, to be recorded separately. This is shown to obviate the need to tune the laser through the absorption to determine velocities, while retaining the ability to make spatially-resolved measurements along a line. By properly selecting the laser tuning and filter parameters, simultaneous density measurements can be made. These properties are discussed in the paper and experiments demonstrating the velocimetry capability are described.

  6. Absolute and dynamic position and shape measurement of fast moving objects employing novel laser Doppler techniques

    NASA Astrophysics Data System (ADS)

    Pfister, Thorsten; Günther, Philipp; Büttner, Lars; Czarske, Jürgen

    2008-09-01

    In this contribution a novel laser Doppler distance (LDD) sensor is presented, which allows simultaneous measurement of axial position and tangential velocity and, thus, determination of the shape of moving and especially rotating objects with one single sensor. Conventional laser Doppler velocimeters measure only velocities. A concurrent position measurement can be realized by generating two fan-shaped interference fringe systems with contrary fringe spacing gradients and evaluating the quotient of the two resulting Doppler frequencies. Alternatively, two tilted fringe systems in combination with phase evaluation can be employed. It will be shown that, in contrast to conventional distance sensors, high temporal resolution below 3 μs and high position resolution of about 1 μm can be achieved simultaneously, because the position uncertainty of the LDD sensor is in principle independent of the object velocity. This is advantageous especially for monitoring highly dynamic processes e.g. at turbo machines, where in-process measurements of tip clearance and rotor vibrations are reported for up to 600 m/s blade tip velocity.

  7. Turbine-scale wind field measurements using dual-Doppler lidar

    SciTech Connect

    Newsom, Rob K.; Berg, Larry K.; Shaw, William J.; Fischer, Marc

    2015-02-01

    Spatially resolved measurements of micro-scale winds are retrieved using scanning dual-Doppler lidar, and validated against independent in situ wind measurements. Data for this study were obtained during a month-long field campaign conducted at a site in north-central Oklahoma in November of 2010. Observational platforms include one heavily instrumented 60-m meteorological tower and two scanning coherent Doppler lidars. The lidars were configured to perform coordinated dual-Doppler scans surrounding the 60-m tower, and the resulting radial velocity observations were processed to retrieve the 3-component velocity vector field on surfaces defined by the intersecting scan planes. Raw radial velocity measurements from the lidars were calibrated by direct comparison to a sonic anemometer located at the 60 m level on the tower. Wind retrievals were performed using both calibrated and uncalibrated measurements, and validated against the 60-m sonic anemometer observations. Retrievals using uncalibrated radial velocity data show a significant slow bias in the wind speed of about 14%; whereas the retrievals using the calibrated data show a much smaller slow bias of 1.2%. Retrievals using either the calibrated or uncalibrated data exhibit negligible bias in the wind direction (<0.2o), and excellent correlation in the wind speeds (>0.96).

  8. Stroke volume and mitral annular velocities. Insights from tissue Doppler imaging.

    PubMed

    Bruch, C; Stypmann, J; Gradaus, R; Breithardt, G; Wichter, T

    2004-10-01

    The aim of this study was to assess the impact of stroke volume (SV) on mitral annular velocities derived from tissue Doppler imaging (TDI). To this end, conventional echocardiographic variables and TDI derived mitral annular velocities (S', E', A') were obtained in 14 patients (pts) with increased SV (due to primary mitral (n=12) (ISV group)), in 41 pts with reduced SV (due to ischemic (n=27) or dilated cardiomyopathy (n=9) or hypertensive heart disease (n=5) (RSV group)) and 29 asymptomatic controls with normal SV (CON group). Systolic (S') and early diastolic (E') mitral annular velocities were elevated in the ISV group in the comparison to the CON group, but were significantly reduced in the RSV group. Late diastolic annular velocities (A') did not differ between the ISV and the CON group, but were lowest in the RSV group. On simple linear regression analysis, SV was significantly related to S' (r=0.74, p<0.001), to E' (r=0.74, p<0.001) and to A' (r=0.43, p<0.01). On multiple regression analysis, SV was a stronger independent predictor of S' and E' than conventional systolic or diastolic echocardiographic variables. Thus, stroke volume has a significant impact on TDI derived systolic (S') and early diastolic (E') mitral annular velocities. This should be considered, when TDI is used in the evaluation of LV performance or in the estimation of filling pressures.

  9. Millimeter-wave micro-Doppler measurements of small UAVs

    NASA Astrophysics Data System (ADS)

    Rahman, Samiur; Robertson, Duncan A.

    2017-05-01

    This paper discusses the micro-Doppler signatures of small UAVs obtained from a millimeter-wave radar system. At first, simulation results are shown to demonstrate the theoretical concept. It is illustrated that whilst the propeller rotation rate of the small UAVs is quite high, millimeter-wave radar systems are capable of capturing the full micro-Doppler spread. Measurements of small UAVs have been performed with both CW and FMCW radars operating at 94 GHz. The CW radar was used for obtaining micro-Doppler signatures of individual propellers. The field test data of a flying small UAV was collected with the FMCW radar and was processed to extract micro-Doppler signatures. The high fidelity results clearly reveal features such as blade flashes and propeller rotation modulation lines which can be used to classify targets. This work confirms that millimeter-wave radar is suitable for the detection and classification of small UAVs at usefully long ranges.

  10. Bubbly flow velocity measurements near a heated cylindrical conductor

    SciTech Connect

    Canaan, R.E.; Hassan, Y.A. )

    1990-01-01

    The objective of this study is to apply recent advances and improvements in the digital pulsed laser velocimetry (DPLV) technique to the analysis of two-phase bubbly flow about a cylindrical conductor emitting a constant heat flux within a transparent rectangular enclosure. Pulsed laser velocimetry is a rapidly advancing fluid flow visualization technique that determines full-field instantaneous velocity vectors of a quantitative nature such that the flow field remains undisturbed by the measurement. The DPLV method offers several significant advantages over more traditional fluid velocity measurement techniques such as hot wire/film anemometry and laser Doppler anemometry because reliable instantaneous velocity data may be acquired over substantial flow areas in a single experiment.

  11. Particle and gas velocity measurements in a dc plasma jet

    SciTech Connect

    Lesinski, J.; Mizera-Lesinska, B.; Jurewicz, J.; Boulos, M.I.

    1980-01-01

    Measurements were made, using Laser Doppler Anemometry (LDA), of the velocity of 53 ..mu..m alumina particles as they are injected in a dc plasma jet operated with an argon-nitrogen mixture (18.9 l/min argon and 4.7 l/min nitrogen) at a power level of 15.2 kW. Results obtained at distances between 5 and 150 mm from the nozzle showed the particles to penetrate the plasma jet and attain the gas velocity at about 50 mm from their point of injection. Plasma velocity measurements in the core region of the jet proved to be particularly difficult. Limitations of the LDA system with regard to its spatial resolution and seeding requirements are discussed.

  12. A proposed method for wind velocity measurement from space

    NASA Technical Reports Server (NTRS)

    Censor, D.; Levine, D. M.

    1980-01-01

    An investigation was made of the feasibility of making wind velocity measurements from space by monitoring the apparent change in the refractive index of the atmosphere induced by motion of the air. The physical principle is the same as that resulting in the phase changes measured in the Fizeau experiment. It is proposed that this phase change could be measured using a three cornered arrangement of satellite borne source and reflectors, around which two laser beams propagate in opposite directions. It is shown that even though the velocity of the satellites is much larger than the wind velocity, factors such as change in satellite position and Doppler shifts can be taken into account in a reasonable manner and the Fizeau phase measured. This phase measurement yields an average wind velocity along the ray path through the atmosphere. The method requires neither high accuracy for satellite position or velocity, nor precise knowledge of the refractive index or its gradient in the atmosphere. However, the method intrinsically yields wind velocity integrated along the ray path; hence to obtain higher spatial resolution, inversion techniques are required.

  13. Inexpensive Time-of-Flight Velocity Measurements.

    ERIC Educational Resources Information Center

    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)

  14. Inexpensive Time-of-Flight Velocity Measurements.

    ERIC Educational Resources Information Center

    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)

  15. Laser Doppler pulp vitality measurements: simulation and measurement

    NASA Astrophysics Data System (ADS)

    Ertl, T.

    2017-02-01

    Frequently pulp vitality measurement is done in a dental practice by pressing a frozen cotton pellet on the tooth. This method is subjective, as the patient's response is required, sometimes painful and has moderate sensitivity and specificity. Other methods, based on optical or electrical measurement have been published, but didńt find wide spread application in the dental offices. Laser Doppler measurement of the blood flow in the pulp could be an objective method to measure pulp vitality, but the influence of the gingival blood flow on the measurements is a concern. Therefore experiments and simulations were done to learn more about the gingival blood flow in relation to the pulpal blood flow and how to minimize the influence. First patient measurements were done to show the feasibility clinically. Results: Monte Carlo simulations and bench experiments simulating the blood flow in and around a tooth show that both basic configurations, transmission and reflection measurements are possible. Most favorable is a multi-point measurement with different distances from the gingiva. Preliminary sensitivity / specificity are promising and might allow an objective and painless measurement of tooth vitality.

  16. Doppler ultrasound of blood flow velocities in ophthalmic and central retinal arteries during the early neonatal period.

    PubMed

    Papacci, P; Romagnoli, C; Favuzzi, A; Luciano, R; Giannini, R; De Carolis, M P; Tortorolo, G

    1998-11-01

    To obtain standard values of blood flow velocity in the ophthalmic artery and central retinal artery in the neonatal period and to compare blood flow velocity of orbital vessels with that of the anterior cerebral artery and middle cerebral artery. Forty-five healthy neonates (gestational age, 39.2 +/- 1.2 weeks; birth weight, 3,210 +/- 567 g) on the first and third postnatal days (90 eyes each time) and on the fifth day of life (34 eyes) were included in a clinical trial. A duplex scanner with mechanical sector probe was used for measuring blood flow velocity in the ophthalmic artery, central retinal artery, anterior cerebral artery, and middle cerebral artery. A nominal imaging frequency of 7.5 MHz, a transmitted Doppler frequency of 5 MHz, and a wall filter setting of 50 Hz were used in each case. Systolic, end-diastolic, and mean-enveloped velocities were measured for the studied vessels and the resistance and pulsatility indices were calculated. On the first postnatal day, blood flow velocities and indices in the ophthalmic artery were systolic 14 +/- 2.4 cm/sec, end-diastolic 3.8 +/- 0.6 cm/sec, mean-enveloped 7.3 +/- 1.3 cm/sec, resistance index 0.73 +/- 0.03, and pulsatility index 1.5 +/- 0.2. Central retinal artery blood flow velocities and indices were systolic 8.7 +/- 1.8 cm/sec, end-diastolic 2.7 +/- 0.7 cm/sec, mean-enveloped 5.0 +/- 1.1 cm/sec, resistance index 0.70 +/- 0.04, and pulsatility index 1.3 +/- 0.1. There were no significant differences in ophthalmic artery and central retinal artery flow velocities between right and left eyes. Doppler values of the central retinal artery were significantly lower (P = .0005) than those of the ophthalmic artery for each day studied. The Doppler data for the central retinal artery and ophthalmic artery were significantly lower (from P = .005 to .0001) than those observed in the anterior cerebral artery and middle cerebral artery at the same postnatal age. No significant differences in flow variables were found

  17. EFFECT OF TRANSFUSION THERAPY ON TRANSCRANIAL DOPPLER ULTRASONOGRAPHY VELOCITIES IN CHILDREN WITH SICKLE CELL DISEASE

    PubMed Central

    Kwiatkowski, Janet L.; Yim, Eunsil; Miller, Scott; Adams, Robert J.

    2011-01-01

    Background Children with sickle cell disease and abnormal transcranial Doppler (TCD) ultrasonography have a high risk of stroke, but this risk is greatly reduced when chronic transfusion therapy is administered. The change in TCD velocities during chronic transfusion therapy and rate and frequency of normalization of TCD findings have not been studied extensively. Procedures Using data from children with sickle cell disease enrolled as potential subjects in the Optimizing Primary Stroke Prevention in Sickle Cell Anemia (STOP 2) trial, we characterized the change in TCD velocities on transfusion therapy and identified predictors of developing a normal TCD. Results Among 88 children with serial TCD data after starting transfusions for abnormal TCD 46 (52%) converted to normal TCD after a mean of 4.3 months (median 3.0; range 0.85-14.3 months) of transfusions. TCD studies remained abnormal in 19/88 (21.6%) after a mean of 2.4 years of transfusion. The median TCD velocity was lowered by 38 cm/s within three months of initiating transfusions, followed by a more gradual decline then stabilization of velocities, although with significant individual variation. Factors associated with conversion to normal TCD included lower initial TCD velocity, younger age, and higher pre-transfusion hemoglobin level during transfusion therapy. Conclusion Younger children with higher pre-transfusion hemoglobin levels and lower abnormal TCD velocities are most likely to have rapid normalization of TCD on transfusions. Long-term follow-up of children with persistently abnormal exams or worsening velocities on transfusion is needed to determine if these children are at higher risk of stroke. PMID:21370410

  18. Measurements of velocity and discharge, Grand Canyon, Arizona, May 1994

    USGS Publications Warehouse

    Oberg, Kevin A.; Fisk, Gregory G.; ,

    1995-01-01

    The U.S. Geological Survey (USGS) evaluated the feasibility of utilizing an acoustic Doppler current profiler (ADCP) to collect velocity and discharge data in the Colorado River in Grand Canyon, Arizona, in May 1994. An ADCP is an instrument that can be used to measure water velocity and discharge from a moving boat. Measurements of velocity and discharge were made with an ADCP at 54 cross sections along the Colorado River between the Little Colorado River and Diamond Creek. Concurrent measurements of discharge with an ADCP and a Price-AA current meter were made at three U.S. Geological Survey streamflow-gaging stations: Colorado River above the Little Colorado River near Desert View, Colorado River near Grand Canyon, and Colorado River above Diamond Creek near Peach Springs. Discharges measured with an ADCP were within 3 percent of the rated discharge at each streamflow-gaging station. Discharges measured with the ADCP were within 4 percent of discharges measured with a Price-AA meter, except at the Colorado River above Diamond Creek. Vertical velocity profiles were measured with the ADCP from a stationary position at four cross sections along the Colorado River. Graphs of selected vertical velocity profiles collected in a cross section near National Canyon show considerable temporal variation among profile.

  19. Velocity profiles, Reynolds stresses and bed roughness from an autonomous field deployed Acoustic Doppler Velocity Profiler in a mixed sediment tidal estuary

    NASA Astrophysics Data System (ADS)

    O'Boyle, Louise; Thorne, Peter; Cooke, Richard; Cohbed Team

    2014-05-01

    Estuaries are among some of the most important global landscapes in terms of population density, ecology and economy. Understanding the dynamics of these natural mixed sediment environments is of particular interest amid growing concerns over sea level rise, climate variations and estuarine response to these changes. Many predictors exist for bed form formation and sand transport in sandy coastal zones; however less work has been published on mixed sediments. This paper details a field study which forms part of the COHBED project aiming to increase understanding of bed forms in a biotic mixed sediment estuarine environment. The study was carried out in the Dee Estuary, in the eastern Irish Sea between England and Wales from the 21st May to 4th June 2013. A state of the art instrumentation frame, known as SEDbed, was deployed at three sites of differing sediment properties and biological makeup within the intertidal zone of the estuary. The SEDbed deployment consisted of a suite of optical and acoustic instrumentation, including an Acoustic Doppler Velocity Profiler (ADVP), Acoustic Doppler Velocimeter (ADV) and a three dimensional acoustic ripple profiler, 3D-ARP. Supplementary field samples and measurements were recorded alongside the frame during each deployment. This paper focuses on the use of new technological developments for the investigation of sediment dynamics. The hydrodynamics at each of the deployment sites are presented including centimetre resolution velocity profiles in the near bed region of the water column, obtained from the ADVP, which is presently the only autonomous field deployed coherent Doppler profiler . Based on these high resolution profiles variations in frictional velocity, bed shear stress and roughness length are calculated. Comparisons are made with theoretical models and with Reynolds stress values obtained from ADV data at a single point within the ADVP profile and from ADVP data itself. Predictions of bed roughness at each

  20. Simultaneous spatial and spectral mapping of flow using photoacoustic Doppler measurement

    NASA Astrophysics Data System (ADS)

    Sheinfeld, Adi; Gilead, Sharon; Eyal, Avishay

    2010-11-01

    We demonstrate the use of tone-burst excitation and time-gated spectral analysis for photoacoustic Doppler mapping of flow in an unperturbed vessel phantom and in a vessel with a spatially varying lumen. The method, which mimics pulsed Doppler ultrasound, enables simultaneous measurement of axial position and flow as well as complete characterization of the Doppler spectrum over a wide range of mean velocities (3.5 to 200 mm/s). To generate the required optical excitation, a continuous cw laser source followed by an external electro-optic modulator is used. Stenoses at various levels are emulated in a C-flex tube with a flowing suspension of micrometer-scale carbon particles. Two-dimensional maps of spectral content versus axial position at different points along the vessel and for various levels of perturbations demonstrate the potential use of the method for characterization of flow irregularities.

  1. Doppler and the Doppler Effect.

    DTIC Science & Technology

    1984-06-01

    Doppler Applications Doppler Effect Roemer Doppler Principle Bradley Relative motion Velocity History Light Velocity 20. ABSTRACT (Continue on reverse...of Colorado, Boulder, CO 11-14 Jan 1984 5 1. Historical Background The astronomer Olaf Roemer determined the velocity of light in 1676 from time...approached Jupiter and longer when it receded from Jupiter. In effect, Roemer used a Doppler method in determining the velocity of light . [2 ] In 1727

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

    USGS Publications Warehouse

    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.

  3. Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length

    SciTech Connect

    Liu, Wenzhong; Yi, Ji; Chen, Siyu; Jiao, Shuliang; Zhang, Hao F.

    2015-09-15

    Purpose: Doppler optical coherence tomography (OCT) is widely used for measuring retinal blood flow. Existing Doppler OCT methods require the eyeball axial length, in which empirical values are usually used. However, variations in the axial length can create a bias unaccounted for in the retinal blood flow measurement. The authors plan to develop a Doppler OCT method that can measure the total retinal blood flow rate without requiring the eyeball axial length. Methods: The authors measured the retinal blood flow rate using a dual-ring scanning protocol. The small and large scanning rings entered the eye at different incident angles (small ring: 4°; large ring: 6°), focused on different locations on the retina, and detected the projected velocities/phase shifts along the probing beams. The authors calculated the ratio of the projected velocities between the two rings, and then used this ratio to estimate absolute flow velocity. The authors tested this method in both Intralipid phantoms and in vivo rats. Results: In the Intralipid flow phantom experiments, the preset and measured flow rates were consistent with the coefficient of determination as 0.97. Linear fitting between preset and measured flow rates determined the fitting slope as 1.07 and the intercept as −0.28. In in vivo rat experiments, the measured average total retinal blood flow was 7.02 ± 0.31μl/min among four wild-type rats. The authors’ measured flow rates were consistent with results in the literature. Conclusions: By using a dual-ring scanning protocol with carefully controlled incident angle difference between the two scanning rings in Doppler OCT, the authors demonstrated that it is feasible to measure the absolute retinal blood flow without knowing the eyeball axial length.

  4. Absolute Retinal Blood Flow Measurement With a Dual-Beam Doppler Optical Coherence Tomography

    PubMed Central

    Dai, Cuixia; Liu, Xiaojing; Zhang, Hao F.; Puliafito, Carmen A.; Jiao, Shuliang

    2013-01-01

    Purpose. To test the capability of a novel dual-beam Doppler optical coherence tomography (OCT) technique for simultaneous in vivo measurement of the Doppler angle and, thus, the absolute retinal blood velocity and the retinal flow rate, without the influence of motion artifacts. Methods. A novel dual-beam Doppler spectral domain OCT (SD-OCT) was developed. The two probing beams are separated with a controllable distance along an arbitrary direction, both of which are controlled by two independent 2D optical scanners. Two sets of optical Doppler tomography (ODT) images are acquired simultaneously. The Doppler angle of each blood vessel segment is calculated from the relative coordinates of the centers of the blood vessel in the two corresponding ODT images. The absolute blood flow velocity and the volumetric blood flow rate can then be calculated. To measure the total retinal blood flow, we used a circular scan pattern centered at the optic disc to obtain two sets of concentric OCT/ODT images simultaneously. Results. We imaged two normal human subjects at ages of 48 and 34 years. The total retinal blood flow rates of the two human subjects were calculated to be 47.01 μL/min (older subject) and 51.37 μL/min (younger subject), respectively. Results showed that the performance of this imaging system is immune to eye movement, since the two sets of ODT images were acquired simultaneously. Conclusions. The dual-beam OCT/ODT system is successful in measuring the absolute retinal blood velocity and the volumetric flow rate. The advantage of the technique is that the two sets of ODT images used for the calculation are acquired simultaneously, which eliminates the influence of eye motion and ensures the accuracy of the calculated hemodynamic parameters. PMID:24222303

  5. Use of Acoustic Doppler Instruments for Measuring Discharge in Streams with Appreciable Sediment Transport

    USGS Publications Warehouse

    Mueller, D.S.; ,

    2002-01-01

    The use of Acoustic Doppler current profilers (ADCP) for measuring discharge in streams with sediment transport was discussed. The studies show that the acoustic frequency of an ADCP in combination with the sediment transport characteristics in a river causes the ADCP bottom-tracking algorithms to detect a moving bottom. A moving bottom causes bottom-tracking-referenced water velocities and discharges to be biased low. The results also show that the use of differential global positioning system (DGPS) data allows accurate measurement of water velocities and discharges in such cases.

  6. Measurements of solar transition zone velocities and line broadening using the ultraviolet spectrometer and polarimeter on the Solar Maximum Mission

    NASA Technical Reports Server (NTRS)

    Simon, G.; Mein, P.; Vial, J. C.; Shine, R. A.; Woodgate, B. E.

    1982-01-01

    The UVSP instrument on SMM is able to observe solar regions at two wavelengths in the same line with a band-pass of 0.3 A. Intensity and Doppler velocity maps are derived. It is shown that the numerical values are sensitive to the adopted Doppler width and the range of velocities is limited to within 30 km/sec. A method called Double Dopplergram Determination (DDD) is described for deriving both the Doppler width and the velocity (up to 80 km/sec), and the main sources of uncertainties are discussed. To illustrate the method, a set of C IV 1548 A observations is analyzed according to this procedure. The mean C IV Doppler width measured (0.15 A) is comparable to previous determinations. A relation is found between bright regions and down-flows. Large Doppler widths correspond to strong velocity gradients.

  7. 39 GHz Interferometer System for Measuring Detonation Velocity

    SciTech Connect

    Ross, Patrick W.; Tran, Vu; Waltman, Thomas B.; Tringe, Joe; May, Chadd; Cradick, Jerry; Hodgin, Ralph; Kane, Ron

    2015-05-13

    A new 39 GHz RF interferometer system is presented for use in velocity measurements of high explosives (HE) detonations. The frequency was chosen to compliment the currently available suite, and provide more spatial information. An RF signal is generated and coupled to a waveguide adapter serving as an antenna. The HE is initially transparent to the RF. When the HE detonates, the detonation front becomes reflective to the RF. This reflection is picked up by the waveguide adapter and mixed with an unperturbed RF signal to give a low frequency signal which can be digitized with an oscilloscope. By comparing the signal with a reference signal, velocity information can be obtained using Fourier Transforms and wavelet models. Bench test results using a “slapper” are shown. The 39 GHz microwave interferometer is used in Deflagration to Detonation shots. The signal is reflected off a moving surface, and the Doppler shift of the reflected signal is used to calculate the velocity.

  8. Monitoring of drug and stimulation induced cerebral blood flow velocity changes in rat sensory cortex using spectral domain Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wang, Chuan; Yang, Yong; Ding, Zhihua; Meng, Jie; Wang, Kai; Yang, Wenwei; Xu, Ying

    2011-04-01

    Doppler optical coherence tomography (DOCT) provides a novel method to measure blood flow velocity in vessels with diameter at micrometer scale. In this study, a developed spectral domain DOCT system is applied to monitor cerebral blood flow velocity changes in a rat. An animal model with a cranial window is used, and by application of a drug, light, and electric stimulations, changes in blood flow velocity of the pial artery in sensory cortex are measured in real time. The results show significant differences in blood flow velocity before and after drug administration or light and electric stimulations, demonstrating the feasibility of DOCT in cerebral microcirculation study. Given its noninvasive nature, high spatial resolution, high velocity sensitivity, and high imaging speed, DOCT shows great promise in brain research by imaging blood flow changes at micrometer scale vessels, which helps to understand the pathogenesis of cerebral diseases and neurodegenerative diseases.

  9. Photonic systems for high precision radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Halverson, Samuel P.

    The discovery of Earth-like exoplanets has profound implications for our understanding of the origins and diversity of life in our universe. As such, developing new and improved Doppler radial velocity (RV) spectrometers capable of discovering and characterizing these planets is a high priority in the astronomical community. However, detection of true Earth-analogs remains beyond the technical reach of current Doppler RV instruments. This thesis discusses a number of technological developments designed specifically to overcome classical instrumental limitations of high precision Doppler RV measurements. These technologies are essential components of next generation instruments that aim to achieve the RV precision necessary to detect low-mass planets. This instrumentation research is driven by the development of the Habitable-zone Planet Finder (HPF), a near-infrared (NIR) Doppler spectrograph currently under development at Penn State that will detect terrestrial-mass planets orbiting nearby M-dwarfs. Furthermore, many technologies discussed will also be applied to the NASA-NSF Extreme Precision Doppler Spectrometer concept NEID, a Doppler RV instrument for the 3.5 meter WIYN telescope, slated for delivery in 2019. NEID is an ultra-stable, high resolution optical spectrometer also under development at Penn State. This thesis describes new specialized optical fiber delivery systems, designed to significantly improve instrument illumination stability, modal noise suppression systems, which suppress mode interference in optical fibers and allow spectrometers to fully realize the exquisite precision of modern wavelength calibration sources, and new photonic calibration sources, which show significant promise as potential Doppler wavelength references. These technologies represent important steps in enabling next generation instruments to reach precisions sufficient to detect terrestrial-mass planets orbiting in the Habitable-zones of nearby stars. Improving measurement

  10. Accommodations assessment: Spaceborne Doppler lidar wind measuring system

    NASA Technical Reports Server (NTRS)

    1981-01-01

    An accommodations analysis performed by the MSFC Preliminary Design Office for a spaceborne Doppler lidar wind measuring system is summarized. A dedicated, free-flying spacecraft design concept is described. Mass and beginning-of-life power requirements are estimated at 2260 kg and 6.0 - 8.5 kW respectively, to support a pulsed, CO2, Doppler lidar having a pulse energy of 10 J, pulse rate of 8 Hz, and efficiency of approximately 5%. Under the assumptions of the analysis, such a system would provide wind measurements on a global scale, with accuracies of a few meters per second.

  11. Three-dimensional velocity measurements using LDA

    NASA Astrophysics Data System (ADS)

    Buchhave, Preben

    The design requirements for and development of an LDA that measures the three components of the fluid velocity vector are described. The problems encountered in LDA measurements in highly turbulent flows, multivariate response, velocity bias, spatial resolution, temporal resolution, and dynamic range, are discussed. The use of the fringe and/or the reference beam methods to measure the three velocity components, and the use of color, frequency shift, and polarization to separate three velocity projections are examined. Consideration is given to the coordinate transformation, the presentation of three-dimensional LDA data, and the possibility of three-dimensional bias correction. Procedures for conducting three-dimensional LDA measurements are proposed.

  12. Two-wave photon Doppler velocimetry measurements in direct impact Hopkinson pressure bar experiments

    NASA Astrophysics Data System (ADS)

    Lea, Lewis J.; Jardine, Andrew P.

    2015-09-01

    Direct impact Hopkinson pressure bar systems offer many potential advantages over split Hopkinson pressure bars, including access to higher strain rates, higher strains for equivalent striker velocity and system length, lower dispersion and faster achievement of force equilibrium. Currently advantages are gained at a significant cost: the fact that input bar data is unavailable removes all information about the striker impacted specimen face, preventing the determination of force equilibrium, and requiring approximations to be made on the sample deformation history. Recently photon Doppler velocimetry methods have been developed, which can replace strain gauges on Hopkinson bars. In this paper we discuss an experimental method and complementary data analysis for using Doppler velocimetry to measure surface velocities of the striker and output bars in a direct impact bar experiment, allowing similar data to be recorded as in a split bar system, with the same level of convenience. We discuss extracting velocity and force measurements, and improving the accuracy and convenience of Doppler velocimetry on Hopkinson bars. Results obtained using the technique are compared to equivalent split bar tests, showing improved stress measurements for the lowest and highest strains.

  13. Near bottom velocity measurements in San Francisco Bay, California

    USGS Publications Warehouse

    Gartner, Jeffrey W.; Cheng, Ralph T.; ,

    1996-01-01

    The ability to accurately measure long-term time-series of tidal currents in bays and estuaries is critical in estuarine hydrodynamic studies. Accurate measurements of tidal currents near the air-water interface and in the bottom boundary layer remain difficult in spite of the significant advances in technology for measuring tidal currents which have been achieved in recent years. One of the objectives of this study is to demonstrate that turbulent mean velocity distribution within the bottom boundary layer can be determined accurately by using a broad-band acoustic Doppler current profiler (BB-ADCP). A suite of instruments, including two BB-ADCPs and four electromagnetic (EM) current meters was deployed in San Francisco Bay, California in an investigation of resuspension and transport of sediment during March 1995. The velocity measurements obtained in the bottom boundary layer by BB-ADCP were highly coherent (r2>0.94) with the velocity measurements obtained by EM current meters. During early March 1995, both BB-ADCPs and EM current meters recorded a very unusual flow event. Agreement among independent measurements by these instruments in describing such an atypical hydrodynamic occurrence further validates the velocity measurements obtained by BB-ADCP in the bottom boundary layer.

  14. Interhemispheric comparisons of cerebral blood flow velocity changes during mental tasks with transcranial Doppler sonography.

    PubMed

    Lin, Tzu-Kang; Ryu, Shan-Jin; Hsu, Peng-Wei

    2009-11-01

    The purpose of this study was to evaluate hemispheric asymmetry of cerebral blood flow changes during various mental tests by applying transcranial Doppler sonography (TCD) to simultaneously monitor bilateral cerebral blood flow velocity changes. Twenty-one participants without cerebrovascular disease performed 3 left hemispheric tasks (reading, calculation, and color scaling) and 3 right hemispheric tasks (face recognition, space imagination, and line orientation). Mean velocities of the rest and performing periods did not differ significantly between the left and right hemispheric tasks. Although greater acceleration of blood flow velocity was observed on the left than on the right in most of the 6 tasks except line orientation (mean left - right ratio difference [D(l-r)] ranged from -0.018 to 0.071), this difference was larger for left hemispheric tasks (mean D(l-r) ranged from 0.050 to 0.071) than right hemispheric tasks (mean D(l-r) ranged from -0.018 to 0.034; P < .001). Further comparisons of each pair of (ie, left and right) hemispheric tasks revealed that the most suitable left and right hemispheric tasks to show hemispheric asymmetry were reading and line orientation, respectively (P < .001). Hemispheric asymmetry of cerebral blood flow changes during mental tests is demonstrable with TCD only when comparing the D(l-r) in response to suitable paired left and right hemispheric tasks.

  15. A novel approach for Doppler blood flow measurement.

    PubMed

    McNamara, D M; Goli, A; Ziarani, A K

    2008-01-01

    A new approach to frequency estimation for the velocity estimation in Doppler ultrasound blood flow analysis is presented. The basis of the approach is an adaptive sinusoid-tracking algorithm which is effective in extracting nonstationary signals from within noise and estimating their time-varying parameters, such as the frequency, over time. The preliminary studies conducted using simulated signals show the potential of this approach in estimating Doppler frequency shifts under noisy conditions. A qualitative comparison with the short-time Fourier transform (STFT) is presented to show the advantages of the proposed technique over the STFT. The proposed approach offers advantages over conventional time-frequency analysis techniques in terms of high time-frequency resolution and high noise immunity.

  16. Relative blood flow changes measured using calibrated frequency-weighted Doppler power at different hematocrit levels.

    PubMed

    Wallace, Sean; Logallo, Nicola; Faiz, Kashif W; Lund, Christian; Brucher, Rainer; Russell, David

    2014-04-01

    In theory, the power of a trans-cranial Doppler signal may be used to measure changes in blood flow and vessel diameter in addition to velocity. In this study, a flow index (FI) of relative changes in blood flow was derived from frequency-weighted Doppler power signals. The FI, plotted against velocity, was calibrated to the zero intercept with absent flow to reduce the effects of non-uniform vessel insonation. An area index was also calculated. FIs were compared with actual flow in four silicone tubes of different diameter at increasing flow rates and increasing hematocrit (Hct) in a closed-loop phantom model. FI values were strongly correlated with actual flow, at constant Hct, but varied substantially with changes in Hct. Percentage changes in area indexes, relative to the 4-mm tube, were strongly correlated with tube cross-sectional area. The implications of these results for in vivo use are discussed.

  17. Velocity space evolution of a minority energetic electron population undergoing the anomalous Doppler instability

    SciTech Connect

    Lai, W. N.; Chapman, S. C.; Dendy, R. O.

    2015-11-15

    The kinetic evolution in velocity space of a minority suprathermal electron population that is undergoing the anomalous Doppler instability (ADI) is investigated using the results from fully nonlinear numerical simulations that self-consistently evolve particles and fields in a plasma. Electron trajectories in phase space during different stages of the ADI are captured, and are analysed in relation to the characteristics of the excited electric fields and of the overall distribution of particles. For some electrons, trapping and mirroring effects are observed during the saturation phase. A relationship between the second order moments of the perpendicular electron distribution function and time is established, and is used to investigate the range of applicability of analytical approximations drawn from classical theory, that involve a quasilinear wave-driven diffusion operator.

  18. Doppler effect in optical velocimetry

    NASA Astrophysics Data System (ADS)

    Rinkevichius, Bronius S.

    1996-02-01

    The current state of the optical metrology based on the Doppler effect has been reviewed. Some historical and scientific information is given, in addition the contemporary optical methods of the velocity measurement using the Doppler effect are analyzed. The Doppler effect applications in astrophysics, plasma physics, investigations of gas and liquid flows, acoustics, mechanics of the deforming solid body and of the rotational motion are considered. The description is presented for the following techniques of the velocity measurement: laser Doppler anemometry, laser Doppler vibrometry, laser gyroscopy.

  19. Acoustic Doppler velocimeter-induced acoustic streaming and its implications for measurement

    NASA Astrophysics Data System (ADS)

    Poindexter, C. M.; Rusello, P. J.; Variano, E. A.

    2011-05-01

    The acoustic Doppler velocimeter (ADV) is widely used for the characterization of fluid flow. Secondary flows ("acoustic streaming") generated by the ADV's acoustic pulses may affect the accuracy of measurements in experiments with small velocities. We assessed the impact of acoustic streaming on flow measurement using particle image velocimetry. The probes of two different ADVs were successively mounted in a tank of quiescent water. The probes' ultrasound emitters were aligned with a laser light sheet. Observed flow was primarily in the axial direction, accelerating from the ultrasound emitter and peaking within centimeters of the velocimeter sampling volume before dropping off. We measured the dependence of acoustic streaming velocity on ADV configuration, finding that different settings induce streaming ranging from negligible to more than 2.0 cm s-1. From these results, we describe cases where acoustic streaming affects velocity measurements and also cases where ADVs accurately measure their own acoustic streaming.

  20. A comprehensive method of estimating electric fields from vector magnetic field and Doppler measurements

    SciTech Connect

    Kazachenko, Maria D.; Fisher, George H.; Welsch, Brian T.

    2014-11-01

    Photospheric electric fields, estimated from sequences of vector magnetic field and Doppler measurements, can be used to estimate the flux of magnetic energy (the Poynting flux) into the corona and as time-dependent boundary conditions for dynamic models of the coronal magnetic field. We have modified and extended an existing method to estimate photospheric electric fields that combines a poloidal-toroidal decomposition (PTD) of the evolving magnetic field vector with Doppler and horizontal plasma velocities. Our current, more comprehensive method, which we dub the 'PTD-Doppler-FLCT Ideal' (PDFI) technique, can now incorporate Doppler velocities from non-normal viewing angles. It uses the FISHPACK software package to solve several two-dimensional Poisson equations, a faster and more robust approach than our previous implementations. Here, we describe systematic, quantitative tests of the accuracy and robustness of the PDFI technique using synthetic data from anelastic MHD (ANMHD) simulations, which have been used in similar tests in the past. We find that the PDFI method has less than 1% error in the total Poynting flux and a 10% error in the helicity flux rate at a normal viewing angle (θ = 0) and less than 25% and 10% errors, respectively, at large viewing angles (θ < 60°). We compare our results with other inversion methods at zero viewing angle and find that our method's estimates of the fluxes of magnetic energy and helicity are comparable to or more accurate than other methods. We also discuss the limitations of the PDFI method and its uncertainties.

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

    PubMed

    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

  2. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Laser Doppler visualisation of the velocity field by excluding the influence of multiparticle scattering

    NASA Astrophysics Data System (ADS)

    Dubnishchev, Yu N.; Chugui, Yu V.; Kompenhans, J.

    2009-10-01

    The method of laser Doppler visualisation and measurement of the velocity field in gas and liquid flows by suppressing the influence of multiparticle scattering is discussed. The cross section of the flow under study is illuminated by a laser beam transformed by an anamorphic optical system into a laser sheet. The effect of multiparticle scattering is eliminated by obtaining differential combinations of frequency-demodulated images of the laser sheet in different regions of the angular spectrum of scattered light.

  3. 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

    NASA Astrophysics Data System (ADS)

    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.

  4. Left ventricular long axis tissue Doppler systolic velocity is independently related to heart rate and body size.

    PubMed

    Peverill, Roger E; Chou, Bon; Donelan, Lesley

    2017-01-01

    The physiological factors which affect left ventricular (LV) long-axis function are not fully defined. We investigated the relationships of resting heart rate and body size with the peak velocities and amplitudes of LV systolic and early diastolic long axis motion, and also with long-axis contraction duration. Two groups of adults free of cardiac disease underwent pulsed-wave tissue Doppler imaging at the septal and lateral mitral annular borders. Group 1 (n = 77) were healthy subjects <50 years of age and Group 2 (n = 65) were subjects between 40-80 years of age referred for stress echocardiography. Systolic excursion (SExc), duration (SDur) and peak velocity (s') and early diastolic excursion (EDExc) and peak velocity (e') were measured. SExc was not correlated with heart rate, height or body surface area (BSA) for either LV wall in either group, but SDur was inversely correlated with heart rate for both walls and both groups, and after adjustment for heart rate, males in both groups had a shorter septal SDur. Septal and lateral s` were independently and positively correlated with SExc, heart rate and height in both groups, independent of sex and age. There were no correlations of heart rate, height or BSA with either e` or EDExc for either wall in either group. Heart rate and height independently modify the relationship between s` and SExc, but neither are related to EDExc or e`. These findings suggest that s` and SExc cannot be used interchangeably for the assessment of LV long-axis contraction.

  5. Effects of intravenous bolus injection of nicorandil on renal artery flow velocity assessed by color Doppler ultrasound.

    PubMed

    Shimamoto, Yukiko; Kubo, Takashi; Tanabe, Kazumi; Emori, Hiroki; Katayama, Yosuke; Nishiguchi, Tsuyoshi; Taruya, Akira; Kameyama, Takeyoshi; Orii, Makoto; Yamano, Takashi; Kuroi, Akio; Yamaguchi, Tomoyuki; Takemoto, Kazushi; Matsuo, Yoshiki; Ino, Yasushi; Tanaka, Atsushi; Hozumi, Takeshi; Terada, Masaki; Akasaka, Takashi

    2017-01-01

    Previous animal studies have shown that a potassium channel opener, nicorandil, provokes vasodilation in renal microvasculature and increases renal blood flow. We conducted a clinical study that aimed to evaluate the effect of nicorandil on renal artery blood flow in comparison with nitroglycerin by using color Doppler ultrasound. The present study enrolled 40 patients with stable coronary artery disease who had no renal arterial stenosis and renal parenchymal disease. The patients received intravenous administration of nicorandil (n=20) or nitroglycerin (n=20). Before and after the administration, renal artery blood flow velocity was measured by color-guided pulsed-wave Doppler. The peak-systolic, end-diastolic, and mean renal artery blood flow velocities before the administration were not different between the nicorandil group and the nitroglycerin group. The peak-systolic (79±15cm/s to 99±21cm/s, p<0.001; and 78±19cm/s to 85±19cm/s, p=0.004), end-diastolic (22±5cm/s to 28±8cm/s, p<0.001; and 24±6cm/s to 26±6cm/s, p=0.005) and mean (41±6cm/s to 49±9cm/s, p<0.001; and 43±9cm/s to 45±9cm/s, p=0.009) renal artery flow velocities increased significantly in either group. The nominal changes in the peak-systolic (20±10cm/s vs. 7±8cm/s, p<0.001), end-diastolic (5±4cm/s vs. 2±3cm/s, p=0.001), and mean (8±5cm/s vs. 2±2cm/s, p<0.001) renal artery blood flow velocities were significantly greater in the nicorandil group compared with the nitroglycerin group. Intravenous nicorandil increased renal artery blood flow velocity in comparison with nitroglycerin. Nicorandil has a significant effect on renal hemodynamics. Copyright © 2016 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

  6. Exploitation of SAR data for measurement of ocean currents and wave velocities

    NASA Technical Reports Server (NTRS)

    Shuchman, R. A.; Lyzenga, D. R.; Klooster, A., Jr.

    1981-01-01

    Methods of extracting information on ocean currents and wave orbital velocities from SAR data by an analysis of the Doppler frequency content of the data are discussed. The theory and data analysis methods are discussed, and results are presented for both aircraft and satellite (SEASAT) data sets. A method of measuring the phase velocity of a gravity wave field is also described. This method uses the shift in position of the wave crests on two images generated from the same data set using two separate Doppler bands. Results of the current measurements are pesented for 11 aircraft data sets and 4 SEASAT data sets.

  7. Phase Control of Group Velocity in a Doppler-Broadened Λ-Type Three-Level System

    NASA Astrophysics Data System (ADS)

    Qiu, Tian-Hui; Xie, Min

    2016-06-01

    We theoretically investigate the phase control role on the group velocity of a weak probe field in a Doppler-broadened Λ-type three-level atomic system with the spontaneously generated coherence effect enhanced by an incoherence pump. We find that the absorption-dispersion of the probe field behaves phase and Doppler broadening-dependent phenomena, and testify that the quite large group index can be realized. The group velocity of the probe field can be switched from subluminal to superluminal or vice versa by modulating the relative phase of the two applied light fields. In contrast to the counterpropagating setting, the copropagating case is more suitable for the purpose considered in this paper due to the effectiveness of Doppler-free.

  8. Measuring hemodynamics in the developing heart tube with four-dimensional gated Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Jenkins, Michael W.; Peterson, Lindsy; Gu, Shi; Gargesha, Madhusudhana; Wilson, David L.; Watanabe, Michiko; Rollins, Andrew M.

    2010-11-01

    Hemodynamics is thought to play a major role in heart development, yet tools to quantitatively assess hemodynamics in the embryo are sorely lacking. The especially challenging analysis of hemodynamics in the early embryo requires new technology. Small changes in blood flow could indicate when anomalies are initiated even before structural changes can be detected. Furthermore, small changes in the early embryo that affect blood flow could lead to profound abnormalities at later stages. We present a demonstration of 4-D Doppler optical coherence tomography (OCT) imaging of structure and flow, and present several new hemodynamic measurements on embryonic avian hearts at early stages prior to the formation of the four chambers. Using 4-D data, pulsed Doppler measurements could accurately be attained in the inflow and outflow of the heart tube. Also, by employing an en-face slice from the 4-D Doppler image set, measurements of stroke volume and cardiac output are obtained without the need to determine absolute velocity. Finally, an image plane orthogonal to the blood flow is used to determine shear stress by calculating the velocity gradient normal to the endocardium. Hemodynamic measurements will be crucial to identifying genetic and environmental factors that lead to congenital heart defects.

  9. Design of a Non-scanning Lidar for Wind Velocity and Direction Measurement

    NASA Astrophysics Data System (ADS)

    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.

  10. Effect of Age on Transcranial Doppler Velocities in Patients with Aneurysmal Subarachnoid Hemorrhage.

    PubMed

    Da Silva, Ivan R; Gomes, Joao A; Wachsman, Ari; Rodriguez de Freitas, Gabriel; Provencio, Jose Javier

    2016-01-01

    It is not well understood whether age impacts transcranial Doppler (TCD) mean flow velocities (MFVs) in patients with aneurysmal subarachnoid hemorrhage (SAH) with or without delayed cerebral ischemia (DCI). The aim of our study was to analyze the behavior of TCD MFV during the first 7 days after SAH in patients of different ages and correlate them with the occurrence of DCI. This study is a databank analysis of patients with SAH admitted between 2010 and 2012 in a single center. We analyzed mean MFV of bilateral middle cerebral arteries (MCAs) in all patients enrolled in the study on days 1, 3 and 7. The correlation between age and TCD MFV was analyzed using a univariate linear regression model. Fifty-five patients were studied. Starting on the third day after the bleeding, increasing age was associated with slower MFVs. This trend was not affected by the interrogation of the right or left MCA. After correction to include only patients who developed DCI, the same findings persisted on days 3 and 7. Older age was correlated with a significant decrease on TCD velocities in patients with SAH, even after correction for patients who developed DCI. © 2016 S. Karger AG, Basel.

  11. Measuring D(d,p)T fusion reactant energy spectra with Doppler shifted fusion products

    SciTech Connect

    Boris, D. R.; Kulcinski, G. L.; Santarius, J. F.; Donovan, D. C.; Piefer, G. R.

    2010-06-15

    Deuterium fusion reactant energy spectra have been measured using a diagnostic that records the Doppler shift imparted to charged particle fusion products of the D(d,p)T reaction by the center-of-mass velocity of the deuterium reactants. This diagnostic, known as the fusion ion Doppler shift diagnostic (FIDO) measures fast deuterium energy spectra in the inertial electrostatic confinement (IEC) experiment at the University of Wisconsin-Madison {l_brace}Santarius et al. [Fusion Sci. Technol. 47, 1238 (2005)]{r_brace}, a device to confine high energy light ions in a spherically symmetric, electrostatic potential well. This article details the first measurements of the fusion reactant energy spectra in an IEC device as well as the design and principles of operation of the FIDO diagnostic. Scaling of reactant energy spectra with a variety of experimental parameters have been explored.

  12. Modeling measured glottal volume velocity waveforms.

    PubMed

    Verneuil, Andrew; Berry, David A; Kreiman, Jody; Gerratt, Bruce R; Ye, Ming; Berke, Gerald S

    2003-02-01

    The source-filter theory of speech production describes a glottal energy source (volume velocity waveform) that is filtered by the vocal tract and radiates from the mouth as phonation. The characteristics of the volume velocity waveform, the source that drives phonation, have been estimated, but never directly measured at the glottis. To accomplish this measurement, constant temperature anemometer probes were used in an in vivo canine constant pressure model of phonation. A 3-probe array was positioned supraglottically, and an endoscopic camera was positioned subglottically. Simultaneous recordings of airflow velocity (using anemometry) and glottal area (using stroboscopy) were made in 3 animals. Glottal airflow velocities and areas were combined to produce direct measurements of glottal volume velocity waveforms. The anterior and middle parts of the glottis contributed significantly to the volume velocity waveform, with less contribution from the posterior part of the glottis. The measured volume velocity waveforms were successfully fitted to a well-known laryngeal airflow model. A noninvasive measured volume velocity waveform holds promise for future clinical use.

  13. Validating precision estimates in horizontal wind measurements from a Doppler lidar

    DOE PAGES

    Newsom, Rob K.; Brewer, W. Alan; Wilczak, James M.; ...

    2017-03-30

    Results from a recent field campaign are used to assess the accuracy of wind speed and direction precision estimates produced by a Doppler lidar wind retrieval algorithm. The algorithm, which is based on the traditional velocity-azimuth-display (VAD) technique, estimates the wind speed and direction measurement precision using standard error propagation techniques, assuming the input data (i.e., radial velocities) to be contaminated by random, zero-mean, errors. For this study, the lidar was configured to execute an 8-beam plan-position-indicator (PPI) scan once every 12 min during the 6-week deployment period. Several wind retrieval trials were conducted using different schemes for estimating themore » precision in the radial velocity measurements. Here, the resulting wind speed and direction precision estimates were compared to differences in wind speed and direction between the VAD algorithm and sonic anemometer measurements taken on a nearby 300 m tower.« less

  14. Non-contact measurement of facial surface vibration patterns during singing by scanning laser Doppler vibrometer

    PubMed Central

    Kitamura, Tatsuya; Ohtani, Keisuke

    2015-01-01

    This paper presents a method of measuring the vibration patterns on facial surfaces by using a scanning laser Doppler vibrometer (LDV). The surfaces of the face, neck, and body vibrate during phonation and, according to Titze (2001), these vibrations occur when aerodynamic energy is efficiently converted into acoustic energy at the glottis. A vocalist's vibration velocity patterns may therefore indicate his or her phonatory status or singing skills. LDVs enable laser-based non-contact measurement of the vibration velocity and displacement of a certain point on a vibrating object, and scanning LDVs permit multipoint measurements. The benefits of scanning LDVs originate from the facts that they do not affect the vibrations of measured objects and that they can rapidly measure the vibration patterns across planes. A case study is presented herein to demonstrate the method of measuring vibration velocity patterns with a scanning LDV. The objective of the experiment was to measure the vibration velocity differences between the modal and falsetto registers while three professional soprano singers sang sustained vowels at four pitch frequencies. The results suggest that there is a possibility that pitch frequency are correlated with vibration velocity. However, further investigations are necessary to clarify the relationships between vibration velocity patterns and phonation status and singing skills. PMID:26579054

  15. MULTI-CHANNEL PULSED DOPPLER SIGNAL PROCESSING FOR VASCULAR MEASUREMENTS IN MICE

    PubMed Central

    Reddy, Anilkumar K.; Madala, Sridhar; Jones, Alan D.; Caro, Walter A.; Eberth, John F.; Pham, Thuy T.; Taffet, George E.; Hartley, Craig J.

    2009-01-01

    The small size, high heart rate, and small tissue displacement of a mouse require small sensors that are capable of high spatial and temporal tissue displacement resolutions and multichannel data acquisition systems with high sampling rates for simultaneous measurement of high fidelity signals. We developed and evaluated an ultrasound-based mouse vascular research system (MVRS) that can be used to characterize vascular physiology in normal, transgenic, surgically altered, and disease models of mice. The system consists of multiple 10/20MHz ultrasound transducers, analog electronics for Doppler displacement and velocity measurement, signal acquisition and processing electronics, and personal computer based software for real-time and offline analysis. In-vitro testing of the system showed that it is capable of measuring tissue displacement as low as 0.1 µm and tissue velocity (µm/s) starting from 0. The system can measure blood velocities up to 9 m/s (with 10 MHz Doppler at a PRF of 125 kHz) and has a temporal resolution of 0.1 milliseconds. Ex-vivo tracking of an excised mouse carotid artery wall using our Doppler technique and a video pixel tracking technique showed high correlation (R2=0.99). The system can be used to measure diameter changes, augmentation index, impedance spectra, pulse wave velocity, characteristic impedance, forward and backward waves, reflection coefficients, coronary flow reserve, and cardiac motion in murine models. The system will facilitate the study of mouse vascular mechanics and arterial abnormalities resulting in significant impact on the evaluation and screening of vascular disease in mice. PMID:19854566

  16. Neuronavigated microvascular Doppler sonography for intraoperative monitoring of blood flow velocity changes during aneurysm surgery - a feasible monitoring technique.

    PubMed

    Malinova, Vesna; von Eckardstein, Kajetan; Rohde, Veit; Mielke, Dorothee

    2015-10-01

    The intraoperative microvascular Doppler sonography (iMDS) is a well-established tool in vascular surgery for blood flow velocity (BFV) monitoring, capable of detecting vessel occlusion. However, identification of subtotal vessel compromise is more difficult, since the measured BFV may substantially vary with changing insonation angles and insonated vessel segments. To keep these parameters constant we combined neuronavigation with iMDS (niMDS). The question was if niMDS allows the detection of subtotal vessel compromise in aneurysm surgery. During surgery, the 3-dimensional reconstruction of the CT-angiography, which was obtained routinely prior to surgery, was displayed by the neuronavigational system. Prior to clipping, neuronavigation was used to define target point and trajectory, which, by coupling the neuronavigational pointer with the Doppler probe, correspond to the insonated vessel segment and the insonation angle. After clipping, for each vessel segment, the same trajectory was used for all consecutive measurements. The mean BFVs pre- and post-clipping were documented. We performed 82 BFV-measurements in 39 aneurysm surgeries. Mean deviation between pre- and post-clipping BFV values was 2.12cm/s. There was a significant correlation between the mean BFV values before and after clipping (r=0.45 [95% CI 17-66%]; p=0.002). One patient experienced new neurological deficits due to occlusion of a perforating vessel that was not insonated. The study could not answer the question if niMDS can detect BFV changes after clipping indicating vessel compromise, as no subtotal vessel occlusion occurred in the 39 operations. However, we proofed that niMDS-measured BFVs only varied minimally in uncompromised vessels pre- and post-clipping, suggesting that vessel compromises might be easily detected during aneurysm surgery. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. VizieR Online Data Catalog: GJ667C Doppler and activity measurements (Anglada-Escude+, 2013)

    NASA Astrophysics Data System (ADS)

    Anglada-Escude, G.; Tuomi, M.; Gerlach, E.; Barnes, R.; Heller, R.; Jenkins, J. S.; Wende, S.; Vogt, S. S.; Butler, R. P.; Reiners, A.; Jones, H. R. A.

    2013-06-01

    HARPS-TERRA Doppler and activity measurements of GJ 667C. Doppler Measurements are in the Barycenter of the Solar System and corrected for perspective acceleration. The median has been velocity has been subtracted for cosmetic purposes. Nominal uncertainties in FWHM and BIS are 2.0 and 2.35 times the corresponding UNCCCF. No consistent CCF measurement could be obtained for the last two spectra because of conflicting HARPS-DRS software versions (different binary masks) used to produce them. Except for those two spectra and according to the ESO archive documentation, all CCF measurements were generated using the default M2 binary mask. (1 data file).

  18. Relaxation effects of lavender aromatherapy improve coronary flow velocity reserve in healthy men evaluated by transthoracic Doppler echocardiography.

    PubMed

    Shiina, Yumi; Funabashi, Nobusada; Lee, Kwangho; Toyoda, Tomohiko; Sekine, Tai; Honjo, Sachiko; Hasegawa, Rei; Kawata, Takayuki; Wakatsuki, Yu; Hayashi, Shinichiro; Murakami, Shio; Koike, Kazuo; Daimon, Masao; Komuro, Issei

    2008-09-26

    It has been reported that mental stress is an independent risk factor for cardiovascular events and impairs coronary circulation. Lavender aromatherapy, one of the most popular complementary treatments, is recognized as a beneficial mental relaxation therapy. However, no study has examined the effect of this therapy on coronary circulation. We aimed to assess the effect of lavender aromatherapy on coronary circulation by measuring coronary flow velocity reserve (CFVR) with noninvasive transthoracic Doppler echocardiography (TTDE). We enrolled 30 young healthy men (mean age 34+/-4.7 years, range 24-40 years). Coronary flow velocities in the left anterior descending coronary artery were recorded by TTDE at rest and during hyperemia induced with an intravenous infusion of adenosine triphosphate (ATP). CFVR was calculated as the ratio of hyperemic to basal mean diastolic flow velocity. CFVR was assessed at baseline and immediately after lavender aromatherapy (four drops of essential oil diluted with 20 ml of hot water and inhaled for 30 min). Simultaneously, serum cortisol was measured as a marker of stress hormones. To exclude the relaxation effects of rest, the same measurements were repeated in the same volunteers without aromatherapy as a control study. CFVR measurements were obtained in all volunteers (100%). Blood pressure and heart rate responses to ATP infusion were not affected by lavender aromatherapy. Serum cortisol significantly decreased after lavender aromatherapy (8.4+/-3.6 to 6.3+/-3.3, p<0.05), but remained unchanged in controls (9.1+/-3.5 to 8.1+/-3.9, p=ns). In addition, CFVR significantly increased after lavender aromatherapy (3.8+/-0.87 to 4.7+/-0.90, p<0.001), but not in controls (3.9+/-0.8 to 3.9+/-0.8, p=ns). Lavender aromatherapy reduced serum cortisol and improved CFVR in healthy men. These findings suggest that lavender aromatherapy has relaxation effects and may have beneficial acute effects on coronary circulation.

  19. Doppler lidar for measurement of atmospheric wind fields

    SciTech Connect

    Menzies, R.T. )

    1991-01-01

    Measurements of wind fields in the earth's troposphere with daily global coverage is widely considered as a significant advance for forecasting and transport studies. For optimal use by NWP (Numerical Weather Prediction) models the horizontal and vertical resolutions should be approximately 100 km and 1 km, respectively. For boundary layer studies vertical resolution of a few hundred meters seems essential. Earth-orbiting Doppler lidar has a unique capability to measure global winds in the troposphere with the high vertical resolution required. The lidar approach depends on transmission of pulses with high spectral purity and backscattering from the atmospheric aerosol particles or layered clouds to provide a return signal. Recent field measurement campaigns using NASA research aircraft have resulted in collection of aerosol and cloud data which can be used to optimize the Doppler lidar instrument design and measurement strategy. 5 refs.

  20. Identification and Minimization of Errors in Doppler Global Velocimetry Measurements

    NASA Technical Reports Server (NTRS)

    Meyers, James F.; Lee, Joseph W.

    2000-01-01

    A systematic laboratory investigation was conducted to identify potential measurement error sources in Doppler Global Velocimetry technology. Once identified, methods were developed to eliminate or at least minimize the effects of these errors. The areas considered included the Iodine vapor cell, optical alignment, scattered light characteristics, noise sources, and the laser. Upon completion the demonstrated measurement uncertainty was reduced to 0.5 m/sec.

  1. Wind Measurements with High Energy 2 Micron Coherent Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Barnes, Bruce W.; Koch, Grady J.; Petros, Mulugeta; Beyon, Jeffrey Y.; Amzajerdian, Farzin; Yu, Ji-Rong; Kavaya, Michael J.; Singh, Upendra N.

    2004-01-01

    A coherent Doppler lidar based on an injection seeded Ho:Tm:YLF pulsed laser was developed for wind measurements. A transmitted pulse energy over 75 mJ at 5 Hz repetition rate has been demonstrated. Designs are presented on the laser, injection seeding, receiver, and signal processing subsystems. Sample data of atmospheric measurements are presented including a wind profile extending from the atmospheric boundary layer (ABL) to the free troposphere.

  2. Measurement uncertainty budget of an interferometric flow velocity sensor

    NASA Astrophysics Data System (ADS)

    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

  3. Multisource Localization from Delay and Doppler Measurements.

    DTIC Science & Technology

    1986-07-01

    trademark of SCT. 4 ’, . .. . . . . . Table 1. Enviromental information for the four simulation cases. (Note: all distances are measured in meters...14675 N Bearing cosines Lis: (.368,.927,.075) RD noise standard deviation a 1.0 Table I describes the enviromental information (source location, range...errors in the Euclidean 3D source coordinates and errors in range. We find that the SI method produces estimates with a bias which is small compared

  4. Unsteady velocity measurements in a realistic intracranial aneurysm model

    NASA Astrophysics Data System (ADS)

    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.

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

    USGS Publications Warehouse

    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.

  6. Laser-induced fluorescence diagnostic for temperature and velocity measurements in a hydrogen arcjet plume.

    PubMed

    Liebeskind, J G; Hanson, R K; Cappelli, M A

    1993-10-20

    A diagnostic has been developed to measure velocity and translational temperature in the plume of a 1-kW-class arcjet thruster operating on hydrogen. Laser-induced fluorescence with a narrow-band cw laser is used to probe the Balmer α transition of excited atomic hydrogen. The velocity is determined from the Doppler shift of the fluorescence excitation spectrum, whereas the temperature is inferred from the lineshape. Analysis shows that although Doppler broadening is the only significant broadening mechanism, the fine structure of the transition must be taken into account. Near the exit plane, axial velocities vary from 4 to 14 km/s, radial velocities vary from 0 to 4 km/s, and swirl velocities are shown to be relatively small. Temperatures from 1000 to 5000 K indicate high dissociation fractions.

  7. Achromatic Emission Velocity Measurements in Luminous Flows

    NASA Technical Reports Server (NTRS)

    Schneider, S. J.; Fulghum, S. F.; Rostler, P. S.

    1997-01-01

    A new velocity measurement instrument for luminous flows was developed by Science Research Laboratory for NASA. The SIEVE (Segmented Image Emission VElocimeter) instrument uses broadband light emitted by the flow for the velocity measurement. This differs from other velocimetry techniques in that it does not depend on laser illumination and/or light scattering from particles in the flow. The SIEVE is a passive, non-intrusive diagnostic. By moving and adjusting the imaging optics, the SIEVE can provide three-dimensional mapping of a flow field and determine turbulence scale size. A SIEVE instrument was demonstrated on an illuminated rotating disk to evaluate instrument response and noise and on an oxy-acetylene torch to measure flame velocities. The luminous flow in rocket combustors and plumes is an ideal subject for the SIEVE velocity measurement technique.

  8. An improved version of the extended velocity-azimuth display analysis of single-Doppler radar data

    NASA Astrophysics Data System (ADS)

    Matejka, Thomas; Srivastava, Ramesh C.

    1991-08-01

    Extended velocity-azimuth display (EVAD) analysis is useful for obtaining vertical profiles of horizontal divergence, vertical air velocity, vertical hydrometer velocity, and hydrometeor terminal fall speed in widespread precipitation. The technique uses a volume of velocity data collected with a single Doppler radar. Several improvements to the previously reported EVAD technique are discussed. They include the weighting of Fourier series coefficients to reflect their estimated error, a correction for heteroscedasticity (the systematic variation of residuals) in the regression analysis, and the weighting of data from different elevation angles to compensate for the finite thickness of the layers in which each analysis is performed. Vertical air velocity is obtained through a variational procedure. Procedures for dealiasing the velocity data and for rejecting outliers from the dataset are summarized. Recommendations for collecting radar data for use in EVAD analysis are made.

  9. The variation in frequency locations in Doppler ultrasound spectra for maximum blood flow velocities in narrowed vessels.

    PubMed

    Zhang, Yingyun; Zhang, Yufeng; Gao, Lian; Deng, Li; Hu, Xiao; Zhang, Kexin; Li, Haiyan

    2017-07-28

    This study assessed the variation in the frequency locations in the Doppler ultrasound spectra for the maximum blood flow velocities of in vessels with different degrees of bilaterally axisymmetric stenosis. This was done by comparing the relationship between the velocity distributions and corresponding Doppler power spectra. First, a geometric vessel model with axisymmetric stenosis was established. This made it possible to obtain the blood flow velocity distributions for different degrees of stenosis from the solutions of the Navier-Stokes equations. Then, the Doppler spectra were calculated for the entire segment of the vessel that was covered by the sound field. Finally, the maximum frequency locations for the spectra were determined based on the intersections of the maximum values chosen from the calculated blood flow velocity distributions and their corresponding spectra. The computational analysis showed that the maximum frequencies, which corresponded to the maximum blood flow velocities for different degrees of stenosis, were located at different positions along the spectral falling edges. The location for a normal (stenosis free) vessel was in the middle of the falling edge. For vessels with increasing degrees of stenosis, this location shifted approximately linearly downward along the falling edge. For 40% stenosis, the location reached a position at the falling edge of 0.32. Results obtained using the Field II simulation tool demonstrated the validity of the theoretical analysis and calculations, and may help to improve the maximum velocity estimation accuracy for Doppler blood flow spectra in stenosed vessels. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

  10. Endothelial-mediated coronary flow reserve and its relation to mitral annular tissue Doppler velocities in offspring of hypertensive parents.

    PubMed

    Mahfouz, Ragab A; Dwidar, Ashraf Elsaied; El Tahlawi, Mohammad A

    2011-11-01

    Although coronary flow reserve (CFR) is reduced in hypertensive patients, data regarding the endothelial response of coronary vasomotion and its relation to left ventricular (LV) function in their offspring is limited. To investigate the endothelial response of coronary flow, using cold pressor test (CPT), in offspring of hypertensive parents and its impact on LV diastolic function. The study population consisted of 32 healthy young offspring (mean age 23.5 ± 7.1 years) of hypertensive parents and 26 aged matched volunteers (healthy offspring of normotensive parents) as controls. Coronary blood flow velocities were recorded in all subjects at rest and after CPT; a stimulus that can be considered totally endothelium-dependent. CFR was calculated as the ratio of hyperemic-to-resting diastolic peak velocities. Doppler echocardiographic assessment was performed using both conventional and tissue Doppler assessment. Coronary diastolic peak velocities at rest was comparable between the two groups (27.1 ± 6.2 vs 26.4 ± 5.8; P > 0.05); but the velocities were significantly lower after CPT in offspring of hypertensive parents (P < 0.02), with highly significant lower CFR (P < 0.0001). Conventional echo-Doppler variables were comparable in both groups, whereas tissue Doppler assessment demonstrated significant LV diastolic dysfunction among offspring of hypertensive parents. The CPT-CFR was significantly correlated to tissue Doppler diastolic dysfunction in this group (For Em, Am and Em/Am, r was 0.65, 0.59 and 0.61, respectively, and P < 0.001). Offspring of hypertensive parents have coronary endothelial dysfunction that appears in response to physiological stimuli (CPT). The coronary endothelial dysfunction is associated with latent LV diastolic dysfunction. © 2011, Wiley Periodicals, Inc.

  11. Three Dimensional Measurements of Boundary Layer Statistics using Scanning Doppler Lidar

    NASA Astrophysics Data System (ADS)

    Frehlich, R.

    2008-12-01

    Accurate measurements and modeling of the boundary layer is challenging, especially for the stable night time boundary layer, the highly turbulent boundary layer, and the early morning transition to convection. High quality profiles of mean and turbulent statistics of the night time boundary layer are logistically difficult using instrumented towers or instrumented research aircraft. One of the fundamental limits to the accuracy of atmospheric estimates of mean and turbulent quantities is the number of independent samples of the relevant processes. Traditional measurements from towers, sodars, radar profilers, and instrumented aircraft essentially produce a spatial sample of the atmosphere along a line defined by the mean wind (or aircraft trajectory). Advanced three dimensional measurements of the boundary layer provides the highest statistical accuracy which is essential to understand complex rapidly changing processes. The development of eye-safe scanning Doppler lidars and processing algorithms to correct for the spatial filtering by the laser pulse smoothing and the contribution from estimation error have produced profiles of the mean velocity and key turbulence statistics (the energy dissipation rate, velocity variance, and turbulence length scale) for two orthogonal horizontal velocity components. This requires accurate information about the sensing volume of the lidar measurements as well as the statistical properties of the estimation error. The various processing techniques and fundamental assumptions for the analysis of scanning Doppler lidar data will be presented for various atmospheric conditions. Unresolved issues for future work will also be outlined.

  12. [Measurement of the blood flow velocity in the pulmonary arteries using the magnetic resonance technique].

    PubMed

    Gamroth, A H; Schad, L R; Wacker, C M; Gehling, U; Knopp, M V; Betsch, B; Clorius, J H; van Kaick, G

    1992-04-01

    MR blood velocity measurements were performed by the RACE technique in a plane perpendicular to the flow of the pulmonary arteries. MR findings were correlated with those of perfusion scintigraphy, Doppler US and right heart catheter (thermodilution). The ratio of MR blood flow measurements of right and left pulmonary arteries correlated well with the results of perfusion scintigraphy (RPA to LPA) and Doppler. Poor correlation was found when comparing MR blood flow measurements with right heart catheter since absolute flow measurements can be superimposed by neighboring blood vessels in complex anatomic situations.

  13. Measurement of two-dimensional Doppler wind fields using a field widened Michelson interferometer.

    PubMed

    Langille, Jeffery A; Ward, William E; Scott, Alan; Arsenault, Dennis L

    2013-03-10

    An implementation of the field widened Michelson concept has been applied to obtain high resolution two-dimensional (2D) images of low velocity (<50 m/s) Doppler wind fields in the lab. Procedures and techniques have been developed that allow Doppler wind and irradiance measurements to be determined on a bin by bin basis with an accuracy of less than 2.5 m/s from CCD images over the observed field of view. The interferometer scanning mirror position is controlled to subangstrom precision with subnanometer repeatability using the multi-application low-voltage piezoelectric instrument control electronics developed by COM DEV Ltd.; it is the first implementation of this system as a phase stepping Michelson. In this paper the calibration and characterization of the Doppler imaging system is described and the planned implementation of this new technique for imaging 2D wind and irradiance fields using the earth's airglow is introduced. Observations of Doppler winds produced by a rotating wheel are reported and shown to be of sufficient precision for buoyancy wave observations in airglow in the mesopause region of the terrestrial atmosphere.

  14. Ultrasonic Doppler measurement of renal artery blood flow

    NASA Technical Reports Server (NTRS)

    Freund, W. R.; Meindl, J. D.

    1975-01-01

    An extensive evaluation of the practical and theoretical limitations encountered in the use of totally implantable CW Doppler flowmeters is provided. Theoretical analyses, computer models, in-vitro and in-vivo calibration studies describe the sources and magnitudes of potential errors in the measurement of blood flow through the renal artery, as well as larger vessels in the circulatory system. The evaluation of new flowmeter/transducer systems and their use in physiological investigations is reported.

  15. The remote measurement of tornado-like flows employing a scanning laser Doppler system

    NASA Technical Reports Server (NTRS)

    Jeffreys, H. B.; Bilbro, J. W.; Dimarzio, C.; Sonnenschein, C.; Toomey, D.

    1977-01-01

    The paper deals with a scanning laser Doppler velocimeter system employed in a test program for measuring naturally occurring tornado-like phenomena, known as dust devils. A description of the system and the test program is followed by a discussion of the data processing techniques and data analysis. The system uses a stable 15-W CO2 laser with the beam expanded and focused by a 12-inch telescope. Range resolution is obtained by focusing the optical system. The velocity of each volume of air (scanned in a horizontal plane) is determined from spectral analysis of the heterodyne signal. Results derived from the measurement program and data/system analyses are examined.

  16. The remote measurement of tornado-like flows employing a scanning laser Doppler system

    NASA Technical Reports Server (NTRS)

    Jeffreys, H. B.; Bilbro, J. W.; Dimarzio, C.; Sonnenschein, C.; Toomey, D.

    1977-01-01

    The paper deals with a scanning laser Doppler velocimeter system employed in a test program for measuring naturally occurring tornado-like phenomena, known as dust devils. A description of the system and the test program is followed by a discussion of the data processing techniques and data analysis. The system uses a stable 15-W CO2 laser with the beam expanded and focused by a 12-inch telescope. Range resolution is obtained by focusing the optical system. The velocity of each volume of air (scanned in a horizontal plane) is determined from spectral analysis of the heterodyne signal. Results derived from the measurement program and data/system analyses are examined.

  17. Doppler Global Velocimetry Measurements of the Vortical Flow Above an F/A-18

    NASA Technical Reports Server (NTRS)

    Lee, Joseph W.; Meyers, James F.; Cavone, Angelo A.; Suzuki, Karen E.

    1993-01-01

    A Doppler global velocimeter was used to investigate the vortical flow above an F/A-18 model at 25-degrees angle of attack. The measurements indicate that the flow had the same characteristics as the vortical flow above a standard delta wing. The flow pattern indicating transition from stable to burst conditions found above the delta wing was also found at the 440 station above the F/A-18. Measurements downstream at the 524 station found that the flow velocity varied considerably, with standard deviations reaching 30 percent of free stream. However, individual data images indicated that the flow was spatially coherent, and not chaotic as expected.

  18. Prognostication of valvular aortic stenosis using tissue Doppler echocardiography: underappreciated importance of late diastolic mitral annular velocity.

    PubMed

    Poh, Kian-Keong; Chan, Mark Yan-Yee; Yang, Hong; Yong, Quek-Wei; Chan, Yiong-Huak; Ling, Lieng H

    2008-05-01

    Intact left atrial booster pump function helps maintain cardiac compensation in patients with aortic valve stenosis (AS). Because late diastolic mitral annular (A') velocity reflects left atrial systolic function, we hypothesized that A' velocity correlates with plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) level and clinical outcome in AS. We prospectively enrolled 53 consecutive patients (median age 74 years) with variable degrees of AS, in sinus rhythm, and left ventricular ejection fraction greater than 50%. Indices of valvular stenosis, left ventricular diastolic dysfunction, and mitral annular motion were correlated with plasma NT-proBNP and a composite clinical end point comprising cardiac death and symptom-driven aortic valve replacement. Tissue Doppler echocardiographic parameters, including early diastolic (E') velocity and A' velocity and ratio of early diastolic transmitral (E) to E' velocity (E/E') at the annular septum correlated better with NT-proBNP levels than body surface area-indexed aortic valve area. Eighteen patients had the composite end point, which was univariately predicted by body surface area-indexed aortic valve area, NT-proBNP, and all tissue Doppler echocardiographic indices. This outcome was most strongly predicted by the combination of septal A' velocity and E/E' ratio in bivariate Cox modeling. Septal annular A' velocity less than 9.6 cm/s was associated with significantly reduced event-free survival (Kaplan Meier log rank = 27.3, P < .0001) and predicted the end point with a sensitivity, specificity, and accuracy of 94%, 80%, and 85%, respectively. In patients with AS and normal ejection fraction, annular tissue Doppler echocardiographic indices may better reflect the physiologic consequences of afterload burden on the left ventricle than body surface area-indexed aortic valve area. Lower A' velocity is a predictor of cardiac death and need for valve surgery, suggesting an important role for compensatory left atrial

  19. Assessment of the severity of aortic regurgitation with pulsed wave Doppler velocity profile in the descending aorta.

    PubMed

    Kalaycı, Belma; Kalaycı, Süleyman; Türker Bayır, Pınar; Duyuler, Serkan; Güven, Saadet; Sen, Taner; Tüfekçioğlu, Omaç

    2014-08-01

    The quantitative parameters which are used to assess the severity of aortic regurgitation (AR) provide the most accurate information whereas these parameters are difficult and time-consuming. The aim of this study was to get a practical parameter to use in daily practice for assessing the severity of aortic regurgitation. The study was an observational cohort study on diagnostic accuracy of severity of aortic regurgitation. Thirty-seven patients with aortic regurgitation determined by quantitative parameters (18 patients with severe aortic regurgitation and 19 patients with moderate aortic regurgitation) were included in this study. Each patient's diastolic flow pattern in the descending aorta was examined by pulsed wave Doppler. Systolic and diastolic flow time-velocity integral (TVI), TVI time, systolic and diastolic TVI ratio in the descending aorta were evaluated. In addition to these parameters, dP/dt, peak acceleration time and end-diastolic flow velocity in the diastolic flow were determined. We investigated whether there a significant difference between two groups or not. Receiver operating characteristic (ROC) analysis was used to determine the optimal cut-off values of echocardiographic parameters which were used to identify the severity of aortic regurgitation. The study population was composed of 16 female and 21 male patients. Their mean age was 46.5 years. The mean diastolic flow TVI of patients who had moderate and severe aortic regurgitation was found 10.1 cm and 18.6 cm, respectively (p<0.001). In the ROC curve analysis, the values of diastolic flow TVI above 13.5 cm was found to have 83% sensitivity and 90% specifity to predict the severity of aortic regurgitation (AUC: 0.91, 95% CI 0.80-1.0, p<0.001). Also we investigated the other parameters like systolic flow TVI, the ratio of systolic and diastolic flow TVI, mean diastolic flow time, mean systolic flow time, the ratio of systolic and diastolic flow time, end-diastolic velocity, peak

  20. An example of scaling MST Doppler spectra using median spectra, spectral smoothing, and velocity tracing

    NASA Technical Reports Server (NTRS)

    Green, J. L.

    1986-01-01

    Although automatic, computer scaling methods appeared at the start of the MST (mesosphere stratosphere troposphere) radar technique, there is a continuing need for scaling algorithms that perform editing functions and increase the sensitivity of radar by post processing. The scaling method presented is an adaptation of the method of scaling MST Doppler spectra presented by Rastogi (1984). A brief overview of this method is as follows: a median spectrum is calculated from several sequential spectra; the median noise value is subtracted from this derived spectrum; the median spectrum is smoothed; the detection/nondetection decision is made by comparing the smoothed spectrum to the variance of the smoothed noise; and if a signal is detected, then the half-power points of the smoothed echo spectrum are used to place limits on the evaluation of the first two moments of the unsmoothed median spectrum. In all of the above steps, the algorithm is guided by tracing the expected velocity range upward from the lowest range as far as possible. The method is discussed in more detail.

  1. Determination of U, V, and W from single station Doppler radar radial velocities

    NASA Technical Reports Server (NTRS)

    Clark, W. L.; Green, J. L.; Warnock, J. M.

    1986-01-01

    The ST/MST (stratosphere troposphere/mesosphere stratosphere troposphere) clear air Doppler radar, or wind profiler, is an important tool in observational meteorology because of its capability to remote observe dynamic parameters of the atmosphere. There are difficulties in transforming the observed radial velocities into meteorological wind components. How this problem has been treated in the past is reviewed, and some of the analysis is recast to a form more suited to the high diagnostic abilities of a number of fixed beam configurations with reference to a linear wind field. The results, in conjunction with other works which treats problems such as the effects of finite sample volumes in the presence of nonhomogeneous atmospheric reflectivity, have implications important to the design of both individual MST/ST radars and MST/ST radar networks. The key parameters to uncoupling terms in the scaling equations are w sub x and w sub y. Whenever the stratiform condition, which states that these two parameters are negligible, is satisfied, a five beam ST radar may determine unbiased values of u, v, and w for sample volumes directly above the radar. The divergence and partial deformation of the flow may also be determined. Three beam systems can determine w and w sub z, but are unable to obtain u and v wind components uncontaminated by vertical sheer terms, even when the stratiform condition is satisfied.

  2. Effect of food intake on left and right ventricular systolic tissue Doppler measurements.

    PubMed

    Dieden, Anna; Gårdinger, Ylva; Hlebowicz, Joanna; Björgell, Ola; Dencker, Magnus

    2016-09-01

    Systolic tissue Doppler measurements (s') have been used to measure the velocity in myocardial motion and are a valuable tool for evaluating the systolic function of the left and right ventricles. Digestion of food is known to significantly alter hemodynamics and may therefore affect s'. The effect of food intake on s' parameters has not yet been studied. We assessed whether s' is affected by food intake. Nineteen healthy subjects aged 26·2 ± 4·2 years were investigated. s' was measured with pulsed tissue Doppler imaging in the right and left ventricles before the subjects ate a standardized meal and also 30 and 110 min after the meal. Three measurements were taken in each projection, and a mean value was calculated for each. s' increased significantly (P<0·05) from fasting to 30 min after food intake in every measured site except in the left inferolateral wall (P = 0·15, NS). Several, but not all, variables returned to base value 110 min after food intake. This study shows that food intake affects the tissue Doppler variables used to evaluate systolic heart function. Further studies are needed in older healthy subjects and older subjects with various cardiovascular diseases. © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

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

    NASA Astrophysics Data System (ADS)

    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

  4. Application of a single laser Doppler system to the measurement of atmospheric winds

    NASA Technical Reports Server (NTRS)

    Cliff, W. C.; Huffaker, R. M.

    1974-01-01

    The feasibility of employing a single laser Doppler velocimeter (LDV) system to remotely measure one-, two-, and three-dimensional velocity components in atmospheric flow fields is presented. A focused continuous wave CO2 laser emitting at the 10.6 mu wavelength is used as the laser source. Scan configurations employed by the LDV system were single-point, two-point, conical, and spiral conical. Test results are presented, which include favorable comparisons of velocity components measured by conventional anemometry and the LDV system. The feasibility using a single-beam LDV employing a conical scan technique for measuring two- and three-dimensional mean winds. Measurements to 300 m in dense fogs showed the ability of the LDV system to operate in dense fogs.

  5. Reference measurements on a Francis model turbine with 2D Laser-Doppler-Anemometry

    NASA Astrophysics Data System (ADS)

    Frey, A.; Kirschner, O.; Riedelbauch, S.; Jester-Zuerker, R.; Jung, A.

    2016-11-01

    To validate the investigations of a high-resolution CFD simulation of a Francis turbine, measurements with 2D Laser-Doppler-Anemometry are carried out. The turbine is operated in part load, where a rotating vortex rope occurs. To validate both, mean velocities and velocity fluctuations, the measurements are classified relative to the vortex rope position. Several acrylic glass windows are installed in the turbine walls such as upstream of the spiral case inlet, in the vaneless space and in the draft tube. The current investigation is focused on a measurement plane below the runner. 2D velocity components are measured on this whole plane by measuring several narrow spaced radial lines. To avoid optical refraction of the laser beam a plan parallel window is inserted in the cone wall. The laser probe is positioned with a 2D traverse system consisting of a circumferential rail and a radial aligned linear traverse. The velocity data are synchronized with the rotational frequency of the rotating vortex rope. The results of one measurement line show the dependency of the axial and circumferential velocities on the vortex rope position.

  6. Spall velocity measurements from laboratory impact craters

    NASA Astrophysics Data System (ADS)

    Polanskey, Carol A.; Ahrens, Thomas J.

    Spall velocities were measured for a series of impacts into San Marcos gabbro. Impact velocities ranged from 1 to 6.5 km/sec. Projectiles varied in material and size with a maximum mass of 4g for a lead bullet to a minimum of 0.04 g for an aluminum sphere. The spall velocities were calculated both from measurements taken from films of the events and from estimates based on range measurements of the spall fragments. The maximum spall velocity observed was 27 m/sec, or 0.5 percent of the impact velocity. The measured spall velocities were within the range predicted by the Melosh (1984) spallation model for the given experimental parameters. The compatability between the Melosh model for large planetary impacts and the results of these small scale experiments is considered in detail. The targets were also bisected to observe the internal fractures. A series of fractures were observed whose location coincided with the boundary of the theoretical near surface zone predicted by Melosh. Above this boundary the target material should receive reduced levels of compressive stress as compared to the more highly shocked region below.

  7. Spall velocity measurements from laboratory impact craters

    NASA Technical Reports Server (NTRS)

    Polanskey, Carol A.; Ahrens, Thomas J.

    1986-01-01

    Spall velocities were measured for a series of impacts into San Marcos gabbro. Impact velocities ranged from 1 to 6.5 km/sec. Projectiles varied in material and size with a maximum mass of 4g for a lead bullet to a minimum of 0.04 g for an aluminum sphere. The spall velocities were calculated both from measurements taken from films of the events and from estimates based on range measurements of the spall fragments. The maximum spall velocity observed was 27 m/sec, or 0.5 percent of the impact velocity. The measured spall velocities were within the range predicted by the Melosh (1984) spallation model for the given experimental parameters. The compatability between the Melosh model for large planetary impacts and the results of these small scale experiments is considered in detail. The targets were also bisected to observe the internal fractures. A series of fractures were observed whose location coincided with the boundary of the theoretical near surface zone predicted by Melosh. Above this boundary the target material should receive reduced levels of compressive stress as compared to the more highly shocked region below.

  8. Coherent Laser Instrument Would Measure Range and Velocity

    NASA Technical Reports Server (NTRS)

    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

  9. Doppler ultrasound velocities and resistive indexes immediately after pediatric liver transplantation: normal ranges and predictors of failure.

    PubMed

    Jamieson, Lucy H; Arys, Bo; Low, Gavin; Bhargava, Ravi; Kumbla, Surekha; Jaremko, Jacob L

    2014-07-01

    We sought to determine the ranges of Doppler ultrasound findings immediately after pediatric liver transplantation that are associated with successful outcomes or postoperative complications. This study included consecutive children who underwent Doppler ultrasound less than 48 hours after liver transplantation from 2001 to 2011. Operative reports and clinical outcome data were recorded. We had 110 patients (54% girls) with mean age at transplantation of 2.9 years (median, 1.3 years; range, 0-14 years) and a median follow-up interval of 3.5 years. Two pediatric radiologists reviewed ultrasound images in consensus. We computed descriptive statistics, interindex correlations, and analysis of variance. Twenty-four of 110 patients had a vascular complication, most commonly hepatic arterial thrombosis (seven patients). Compared with published adult normal values, normal pediatric Doppler parameters at postoperative day 1 trended toward higher normal velocities and resistive indexes (up to 0.95). Absent or low-velocity common hepatic artery flow less than 50 cm/s or a common hepatic artery resistive index less than 0.50 were significantly associated with hepatic artery thrombosis, whereas absent or low-velocity portal venous flow less than 30 cm/s or low-velocity hepatic venous flow less than 25 cm/s were significantly associated with vascular complications and a monotonic hepatic venous waveform was significantly associated with venous complications. Flow in a pediatric liver on the first day after transplantation is normally hyperdynamic, especially in the youngest transplant recipients, and, as a result, low velocities or resistive indexes are particularly concerning for complications. The pediatric-specific ranges of expected posttransplantation Doppler ultrasound findings presented in this article should assist in identifying normal variation and potentially life-threatening complications.

  10. Effects of inflow velocity profile on two-dimensional hemodynamic analysis by ordinary and ultrasonic-measurement-integrated simulations.

    PubMed

    Kato, Takaumi; Sone, Shusaku; Funamoto, Kenichi; Hayase, Toshiyuki; Kadowaki, Hiroko; Taniguchi, Nobuyuki

    2016-09-01

    Two-dimensional ultrasonic-measurement-integrated (2D-UMI) simulation correctly reproduces hemodynamics even with an inexact inflow velocity distribution. This study aimed to investigate which is superior, a two-dimensional ordinary (2D-O) simulation with an accurate inflow velocity distribution or a 2D-UMI simulation with an inaccurate one. 2D-O and 2D-UMI simulations were performed for blood flow in a carotid artery with four upstream velocity boundary conditions: a velocity profile with backprojected measured Doppler velocities (condition A), and velocity profiles with a measured Doppler velocity distribution, a parabolic one, and a uniform one, magnitude being obtained by inflow velocity estimation (conditions B, C, and D, respectively). The error of Doppler velocity against the measurement data was sensitive to the inflow velocity distribution in the 2D-O simulation, but not in the 2D-UMI simulation with the inflow velocity estimation. Among the results in conditions B, C, and D, the error in the worst 2D-UMI simulation with condition D was 31 % of that in the best 2D-O simulation with condition B, implying the superiority of the 2D-UMI simulation with an inaccurate inflow velocity distribution over the 2D-O simulation with an exact one. Condition A resulted in a larger error than the other conditions in both the 2D-O and 2D-UMI simulations.

  11. Internal Detonation Velocity Measurements Inside High Explosives

    SciTech Connect

    Benterou, J; Bennett, C V; Cole, G; Hare, D E; May, C; Udd, E

    2009-01-16

    In order to fully calibrate hydrocodes and dynamic chemistry burn models, initiation models and detonation models of high explosives, the ability to continuously measure the detonation velocity within an explosive is required. Progress on an embedded velocity diagnostic using a 125 micron diameter optical fiber containing a chirped fiber Bragg grating is reported. As the chirped fiber Bragg grating is consumed by the moving detonation wave, the physical length of the unconsumed Bragg grating is monitored with a fast InGaAs photodiode. Experimental details of the associated equipment and data in the form of continuous detonation velocity records within PBX-9502 are presented. This small diameter fiber sensor has the potential to measure internal detonation velocities on the order of 10 mm/{micro}sec along path lengths tens of millimeters long.

  12. Left ventricular long axis tissue Doppler systolic velocity is independently related to heart rate and body size

    PubMed Central

    Peverill, Roger E.; Chou, Bon; Donelan, Lesley

    2017-01-01

    Background The physiological factors which affect left ventricular (LV) long-axis function are not fully defined. We investigated the relationships of resting heart rate and body size with the peak velocities and amplitudes of LV systolic and early diastolic long axis motion, and also with long-axis contraction duration. Methods Two groups of adults free of cardiac disease underwent pulsed-wave tissue Doppler imaging at the septal and lateral mitral annular borders. Group 1 (n = 77) were healthy subjects <50 years of age and Group 2 (n = 65) were subjects between 40–80 years of age referred for stress echocardiography. Systolic excursion (SExc), duration (SDur) and peak velocity (s') and early diastolic excursion (EDExc) and peak velocity (e') were measured. Results SExc was not correlated with heart rate, height or body surface area (BSA) for either LV wall in either group, but SDur was inversely correlated with heart rate for both walls and both groups, and after adjustment for heart rate, males in both groups had a shorter septal SDur. Septal and lateral s` were independently and positively correlated with SExc, heart rate and height in both groups, independent of sex and age. There were no correlations of heart rate, height or BSA with either e` or EDExc for either wall in either group. Conclusion Heart rate and height independently modify the relationship between s` and SExc, but neither are related to EDExc or e`. These findings suggest that s` and SExc cannot be used interchangeably for the assessment of LV long-axis contraction. PMID:28288162

  13. Design study for a spatial heterodyne Doppler coherence imaging system for flow measurements on NSTX-U

    NASA Astrophysics Data System (ADS)

    Schwartz, Jacob; Jaworski, M. A.; Diallo, A.; Kaita, R.; Nichols, J. H.

    2015-11-01

    Measuring the flow of impurities in the SOL of NSTX-U can lead to understanding of main ion flow and heat transport. Spatial heterodyne Doppler coherence imaging is a technique that allows a single camera frame to record both the brightness and Doppler shift of an emitted spectral line over the entire field of view. With a tangential view on NSTX-U it is possible to tomographically reconstruct 2d (r-z) profiles of emissivity and flow velocity for an imaged impurity ion by assuming axisymmetry and field-aligned flow. One can derive the main ion parallel flow velocity by making four measurements and using additional assumptions. Imaging of two spectral lines each from two ion species allows solving for ne, Te, and the density of the two ion species by using ADAS emissivity tables. Since measurements of the velocity of two impurities are planned, it is possible to derive a main ion parallel velocity by using a reconstructed ni and Ti (from other diagnostics), a 1d conduction-limited SOL model, and a 1d model of forces on impurities. With fewer than four measurements, it is possible to derive the main ion velocity if the impurities are entrained in the flow. A design study for such a spatial heterodyne Doppler coherence imaging system on NSTX-U will be presented. Supported by U.S. DOE Contract No. DE-AC02-09CH11466.

  14. Color M-mode Doppler flow propagation velocity is a preload insensitive index of left ventricular relaxation: animal and human validation

    NASA Technical Reports Server (NTRS)

    Garcia, M. J.; Smedira, N. G.; Greenberg, N. L.; Main, M.; Firstenberg, M. S.; Odabashian, J.; Thomas, J. D.

    2000-01-01

    OBJECTIVES: To determine the effect of preload in color M-mode Doppler flow propagation velocity (v(p)). BACKGROUND: The interpretation of Doppler filling patterns is limited by confounding effects of left ventricular (LV) relaxation and preload. Color M-mode v(p) has been proposed as a new index of LV relaxation. METHODS: We studied four dogs before and during inferior caval (IVC) occlusion at five different inotropic stages and 14 patients before and during partial cardiopulmonary bypass. Left ventricular (LV) end-diastolic volumes (LV-EDV), the time constant of isovolumic relaxation (tau), left atrial (LA) pre-A and LV end-diastolic pressures (LV-EDP) were measured. Peak velocity during early filling (E) and v(p) were extracted by digital analysis of color M-mode Doppler images. RESULTS: In both animals and humans, LV-EDV and LV-EDP decreased significantly from baseline to IVC occlusion (both p < 0.001). Peak early filling (E) velocity decreased in animals from 56 +/- 21 to 42 +/- 17 cm/s (p < 0.001) without change in v(p) (from 35 +/- 15 to 35 +/- 16, p = 0.99). Results were similar in humans (from 69 +/- 15 to 53 +/- 22 cm/s, p < 0.001, and 37 +/- 12 to 34 +/- 16, p = 0.30). In both species, there was a strong correlation between LV relaxation (tau) and v(p) (r = 0.78, p < 0.001, r = 0.86, p < 0.001). CONCLUSIONS: Our results indicate that color M-mode Doppler v(p) is not affected by preload alterations and confirms that LV relaxation is its main physiologic determinant in both animals during varying lusitropic conditions and in humans with heart disease.

  15. Color M-mode Doppler flow propagation velocity is a preload insensitive index of left ventricular relaxation: animal and human validation

    NASA Technical Reports Server (NTRS)

    Garcia, M. J.; Smedira, N. G.; Greenberg, N. L.; Main, M.; Firstenberg, M. S.; Odabashian, J.; Thomas, J. D.

    2000-01-01

    OBJECTIVES: To determine the effect of preload in color M-mode Doppler flow propagation velocity (v(p)). BACKGROUND: The interpretation of Doppler filling patterns is limited by confounding effects of left ventricular (LV) relaxation and preload. Color M-mode v(p) has been proposed as a new index of LV relaxation. METHODS: We studied four dogs before and during inferior caval (IVC) occlusion at five different inotropic stages and 14 patients before and during partial cardiopulmonary bypass. Left ventricular (LV) end-diastolic volumes (LV-EDV), the time constant of isovolumic relaxation (tau), left atrial (LA) pre-A and LV end-diastolic pressures (LV-EDP) were measured. Peak velocity during early filling (E) and v(p) were extracted by digital analysis of color M-mode Doppler images. RESULTS: In both animals and humans, LV-EDV and LV-EDP decreased significantly from baseline to IVC occlusion (both p < 0.001). Peak early filling (E) velocity decreased in animals from 56 +/- 21 to 42 +/- 17 cm/s (p < 0.001) without change in v(p) (from 35 +/- 15 to 35 +/- 16, p = 0.99). Results were similar in humans (from 69 +/- 15 to 53 +/- 22 cm/s, p < 0.001, and 37 +/- 12 to 34 +/- 16, p = 0.30). In both species, there was a strong correlation between LV relaxation (tau) and v(p) (r = 0.78, p < 0.001, r = 0.86, p < 0.001). CONCLUSIONS: Our results indicate that color M-mode Doppler v(p) is not affected by preload alterations and confirms that LV relaxation is its main physiologic determinant in both animals during varying lusitropic conditions and in humans with heart disease.

  16. ELODIE: A spectrograph for accurate radial velocity measurements.

    NASA Astrophysics Data System (ADS)

    Baranne, A.; Queloz, D.; Mayor, M.; Adrianzyk, G.; Knispel, G.; Kohler, D.; Lacroix, D.; Meunier, J.-P.; Rimbaud, G.; Vin, A.

    1996-10-01

    The fibre-fed echelle spectrograph of Observatoire de Haute-Provence, ELODIE, is presented. This instrument has been in operation since the end of 1993 on the 1.93 m telescope. ELODIE is designed as an updated version of the cross-correlation spectrometer CORAVEL, to perform very accurate radial velocity measurements such as needed in the search, by Doppler shift, for brown-dwarfs or giant planets orbiting around nearby stars. In one single exposure a spectrum at a resolution of 42000 (λ/{DELTA}λ) ranging from 3906A to 6811A is recorded on a 1024x1024 CCD. This performance is achieved by using a tanθ=4 echelle grating and a combination of a prism and a grism as cross-disperser. An automatic on-line data treatment reduces all the ELODIE echelle spectra and computes cross-correlation functions. The instrument design and the data reduction algorithms are described in this paper. The efficiency and accuracy of the instrument and its long term instrumental stability allow us to measure radial velocities with an accuracy better than 15m/s for stars up to 9th magnitude in less than 30 minutes exposure time. Observations of 16th magnitude stars are also possible to measure velocities at about 1km/s accuracy. For classic spectroscopic studies (S/N>100) 9th magnitude stars can be observed in one hour exposure time.

  17. A comparison of vertical velocity in cirrus obtained from aircraft and lidar divergence measurements during FIRE. [First ISCCP Regional Experiment

    NASA Technical Reports Server (NTRS)

    Gultepe, Ismail; Heymsfield, A. J.; Lenschow, D. H.

    1990-01-01

    Techniques are presented to obtain vertical velocity in cirrus clouds from in situ aircraft lateral wind measurements and from ground-based remote Doppler lidar measurements. The approach used is to calculate w from the integral of the divergence of the horizontal velocity around a closed path. Divergence measurements from both aircraft and Doppler lidar are discussed. The principal errors in the calculation of w from aircraft lateral wind measurements are bias in the lateral wind, ground speed errors, and error due to vertical shear of the horizontal wind. For Doppler lidar measurements the principal errors are in the estimate of mean terminal velocity and the zeroth order coefficients of the Fourier series that is fitted to the data. The technique is applied to a cirrus cloud investigated during the FIRE (First International Satellite Cloud Climatology Regional Experiment) Cirrus Intensive Field Observation Program. The results indicate that the error in w is about + or - 14 cm/s from the aircraft technique; this can be reduced to about + or - 2 to 3 cm/s with technical improvements in both ground speed and lateral velocity measurements. The error in w from Doppler lidar measurements, which is about + or - 8 cm/s, can be reduced to about + or - 5 cm/s by improvements in the Doppler velocity measurements with technology that is currently available.

  18. A comparison of vertical velocity in cirrus obtained from aircraft and lidar divergence measurements during FIRE. [First ISCCP Regional Experiment

    NASA Technical Reports Server (NTRS)

    Gultepe, Ismail; Heymsfield, A. J.; Lenschow, D. H.

    1990-01-01

    Techniques are presented to obtain vertical velocity in cirrus clouds from in situ aircraft lateral wind measurements and from ground-based remote Doppler lidar measurements. The approach used is to calculate w from the integral of the divergence of the horizontal velocity around a closed path. Divergence measurements from both aircraft and Doppler lidar are discussed. The principal errors in the calculation of w from aircraft lateral wind measurements are bias in the lateral wind, ground speed errors, and error due to vertical shear of the horizontal wind. For Doppler lidar measurements the principal errors are in the estimate of mean terminal velocity and the zeroth order coefficients of the Fourier series that is fitted to the data. The technique is applied to a cirrus cloud investigated during the FIRE (First International Satellite Cloud Climatology Regional Experiment) Cirrus Intensive Field Observation Program. The results indicate that the error in w is about + or - 14 cm/s from the aircraft technique; this can be reduced to about + or - 2 to 3 cm/s with technical improvements in both ground speed and lateral velocity measurements. The error in w from Doppler lidar measurements, which is about + or - 8 cm/s, can be reduced to about + or - 5 cm/s by improvements in the Doppler velocity measurements with technology that is currently available.

  19. Method for ambiguity resolution in range-Doppler measurements

    NASA Technical Reports Server (NTRS)

    Heymsfield, Gerald M. (Inventor); Miller, Lee S. (Inventor)

    1994-01-01

    A method for resolving range and Doppler target ambiguities when the target has substantial range or has a high relative velocity in which a first signal is generated and a second signal is also generated which is coherent with the first signal but at a slightly different frequency such that there exists a difference in frequency between these two signals of Delta f(sub t). The first and second signals are converted into a dual-frequency pulsed signal, amplified, and the dual-frequency pulsed signal is transmitted towards a target. A reflected dual-frequency signal is received from the target, amplified, and changed to an intermediate dual-frequency signal. The intermediate dual-frequency signal is amplified, with extracting of a shifted difference frequency Delta f(sub r) from the amplified intermediate dual-frequency signal done by a nonlinear detector. The final step is generating two quadrature signals from the difference frequency Delta f(sub t) and the shifted difference frequency Delta f(sub r) and processing the two quadrature signals to determine range and Doppler information of the target.

  20. Laser Doppler velocimeter measurement in the tip region of a compressor rotor

    NASA Technical Reports Server (NTRS)

    Murthy, K. N. S.; Lakshminarayana, B.

    1984-01-01

    The axial and tangential velocity components near the tip region of a compressor rotor were measured by a laser Doppler velocimeter. The measurements were taken at 25 radial locations in the outer twenty percent of the blade span and at 10 axial locations upstream, inside and at the exit of the rotor. The results are interpreted to derive the behavior of the leakage flow, annulus wall boundary layer growth, inviscid effects and the rotor wake decay characteristics in the tip region. The inviscid and annulus wall boundary layer effects dominate up to quarter chord, beyond which the leakage phenomena has a major influence in altering the flow characteristics in the outer ten percent of the blade span. The annulus wall boundary layer undergoes drastic change through the passage. The velocity field measured near the leading edge reveals the effects of rapid acceleration near the suction surface and the stagnation point on the pressure surface.

  1. Thermal tests for laser Doppler perfusion measurements in Raynaud's syndrome

    NASA Astrophysics Data System (ADS)

    Kacprzak, Michal; Skora, A.; Obidzinska, J.; Zbiec, A.; Maniewski, Roman; Staszkiewicz, W.

    2004-07-01

    The laser Doppler method offers a non-invasive, real time technique for monitoring of blood perfusion in microcirculation. In practical measurements the perfusion index is given only in relative values. Thus, accurate and reproducible results can be only obtained when using a well controlled stimulation test. The aim of this study was evaluation of the thermal stimulation test, which is frequently used to investigate microcirculation in patients with Raynaud's syndrome. Three types of thermal tests, in which air or water with temperature in range 5°C - 40°C were used. Ten normal volunteers and fifteen patients with clinical symptoms of the primary Raynaud's syndrome were enrolled in this study. To estimate skin microcirculation changes during the thermal test, the multichannel laser Doppler system and laser Doppler scanner were used. The obtained results were analyzed from the point of view of the efficiency of these methods and the thermal provocative tests in differentiation of normal subjects and patient with Raynaud's syndrome.

  2. Measurement of the velocity of a quantum object: a role of group velocity

    NASA Astrophysics Data System (ADS)

    Rostovtsev, Yuri V.

    2013-03-01

    We consider a free motion of a quantum particle. 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.

  3. Caffeine can affect velocity in the middle cerebral artery during hyperventilation, hypoventilation, and thinking: a transcranial Doppler study.

    PubMed

    Perod, A L; Roberts, A E; McKinney, W M

    2000-01-01

    This study examined possible caffeine-mediated changes in blood flow velocity in the middle cerebral artery (VMCA) induced by tests of cerebrovascular responsiveness. Transcranial Doppler (TCD) sonography provided simultaneous bilateral VMCA measures while healthy college students hypoventilated, hyperventilated, and performed cognitive activities (short-term remembering, generating an autobiographical image, solving problems), each in 31-second tests. VMCA measures were obtained from the same persons, in separate testing sessions, when they were noncaffeinated and under two levels of caffeine: a smaller amount (from a cola, 45 mg/12 oz) and a larger amount (from coffee, 117 mg/8 oz). Compared with the no-caffeine control condition, a smaller amount of caffeine had no significant effects on global VMCA, but a larger amount suppressed VMCA by 5.8%. Time-course analyses showed that VMCA (1) followed a triphasic pattern to increase over baselines during hypoventilation regardless of caffeine condition, (2) slowed below baselines during hyperventilation (with the degree of slowing attenuated under caffeine), and (3) increased over baselines during all cognitive activities (ranges 3.8-6.9%). It is concluded that a large amount of caffeine can suppress VMCA, and this possibility should be anticipated when TCD is used to assess cerebral hemovelocity.

  4. Novel Optical Technique Developed and Tested for Measuring Two-Point Velocity Correlations in Turbulent Flows

    NASA Technical Reports Server (NTRS)

    Zimmerli, Gregory A.; Goldburg, Walter I.

    2002-01-01

    A novel technique for characterizing turbulent flows was developed and tested at the NASA Glenn Research Center. The work is being done in collaboration with the University of Pittsburgh, through a grant from the NASA Microgravity Fluid Physics Program. The technique we are using, Homodyne Correlation Spectroscopy (HCS), is a laser-light-scattering technique that measures the Doppler frequency shift of light scattered from microscopic particles in the fluid flow. Whereas Laser Doppler Velocimetry gives a local (single-point) measurement of the fluid velocity, the HCS technique measures correlations between fluid velocities at two separate points in the flow at the same instant of time. Velocity correlations in the flow field are of fundamental interest to turbulence researchers and are of practical importance in many engineering applications, such as aeronautics.

  5. Ultrasound safety in early pregnancy: reduced energy setting does not compromise obstetric Doppler measurements.

    PubMed

    Sande, R K; Matre, K; Eide, G E; Kiserud, T

    2012-04-01

    We hypothesized that first-trimester Doppler ultrasonography can be carried out at lower output energies than the currently advocated limits without compromising clinically important information. We recruited 42 pregnant women for an ultrasound examination at 12 weeks' gestation. Twenty-one women were examined with a transvaginal transducer, the rest with a transabdominal transducer. We used pulsed Doppler to measure pulsatility index (PI) and peak systolic velocity (PSV) in five clinically relevant fetal and maternal blood vessels. The energy indicator thermal index for bone (TIb) was set at 1.0, 0.5 and 0.1. Each measurement was repeated three times. A mixed linear regression model accounting for correlation between measurements was used to assess the effect of different TIb levels and transducers. We were able to visualize the vessels by color Doppler and measure PI and PSV in all vessels at all energy levels in all the participants with the exception of the ductus venosus in two participants, yielding 1872 recordings for statistical analysis. A reduction in TIb from 1.0 to 0.5 and 0.1 had no effect on the PI or PSV values, nor was there any trend towards higher parameter variance with decreasing TIb. There was no difference between measured values of PI and PSV between the transducers, but the transabdominal technique was associated with a greater parameter variance. Reliable first-trimester Doppler data can be obtained with output energy reduced to a TIb of 0.5 or 0.1. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.

  6. Antarctica: measuring glacier velocity from satellite images

    SciTech Connect

    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.

  7. Antarctica: measuring glacier velocity from satellite images.

    PubMed

    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.

  8. Antarctica: Measuring glacier velocity from satellite images

    USGS Publications Warehouse

    Lucchitta, B.K.; Ferguson, H.M.

    1986-01-01

    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.

  9. Feasibility of Acoustic Doppler Velocity Meters for the Production of Discharge Records from U.S. Geological Survey Streamflow-Gaging Stations

    USGS Publications Warehouse

    Morlock, Scott E.; Nguyen, Hieu T.; Ross, Jerry H.

    2002-01-01

    It is feasible to use acoustic Doppler velocity meters (ADVM's) installed at U.S. Geological Survey (USGS) streamflow-gaging stations to compute records of river discharge. ADVM's are small acoustic current meters that use the Doppler principle to measure water velocities in a two-dimensional plane. Records of river discharge can be computed from stage and ADVM velocity data using the 'index velocity' method. The ADVM-measured velocities are used as an estimator or 'index' of the mean velocity in the channel. In evaluations of ADVM's for the computation of records of river discharge, the USGS installed ADVM's at three streamflow-gaging stations in Indiana: Kankakee River at Davis, Fall Creek at Millersville, and Iroquois River near Foresman. The ADVM evaluation study period was from June 1999 to February 2001. Discharge records were computed, using ADVM data from each station. Discharge records also were computed using conventional stage-discharge methods of the USGS. The records produced from ADVM and conventional methods were compared with discharge record hydrographs and statistics. Overall, the records compared closely from the Kankakee River and Fall Creek stations. For the Iroquois River station, variable backwater was present and affected the comparison; because the ADVM record compensates for backwater, the ADVM record may be superior to the conventional record. For the three stations, the ADVM records were judged to be of a quality acceptable to USGS standards for publications and near realtime ADVM-computed discharges are served on USGS real-time data World Wide Web pages.

  10. Influence of myocardial infarction size on radionuclide and Doppler echocardiographic measurements of diastolic function

    SciTech Connect

    Johannessen, K.A.; Cerqueira, M.D.; Stratton, J.R. )

    1990-03-15

    To assess the relation between myocardial infarction size and diastolic function as measured by radionuclide ventriculography and Doppler echocardiography, 83 patients (aged 58 +/- 9 years) without significant valvular disease were studied 8 to 12 weeks after an acute myocardial infarction. Myocardial infarction size was measured by resting thallium-201 tomography. Peak early filling rate (in end-diastolic volumes/s) was measured by gated blood pool scintigraphy. Doppler measures of mitral inflow were peak early (E) and atrial (A) filling velocities, slopes of E and A, percent E and A filling, E/A ratio and diastolic filling period. In univariate analyses, there was a significant inverse correlation between infarction size and the peak early filling rate (r = -0.59, p less than 0.001), and this remained significant (r = -0.63, p less than 0.0001) in an analysis that included 2 other determinants of the filling rate, age and diastolic filling period. Infarction size was directly correlated to the peak E velocity (r = 0.37, p less than 0.01), deceleration of E (r = 0.41, p less than 0.01) and percent E filling (r = 0.31, p less than 0.01), and was inversely correlated to peak A (r = -0.27, p less than 0.05) and percent A filling (r = -0.26, p less than 0.05).

  11. Fringe mode transmittance laser Doppler microscope anemometer: its adaptation for measurement in the microcirculation.

    PubMed

    Einav, S; Berman, H J

    1988-10-01

    Blood flow analysis in the microcirculation requires accurate measurement of velocity, volume flow and shear-rate versus shear-stress relationships. The resolution of most anemometers is too limited to obtain useful measurements, especially near the blood vessel wall and at branches and bifurcations. To make such measurements possible with a noninvasive, high resolution, accurate technique, we have developed a fringe mode, transmittance laser Doppler microscope anemometer (LDMA). This system has an intrinsically high spatial resolution (10 x 12 microns), and does not require a high concentration (10(6)/cm3) of scatters or red blood cells (RBC) as in our application. Preliminary measurements of water flow in a rectangular channel were conducted to ascertain the reliability and accuracy of velocity measurements using the LDMA. Velocity profiles were then measured by the LDMA system in arterioles 38-135 microns in diameter, in the transparent, everted cheek pouch of the anaesthetized hamster. The extremely high resolution of the optical system, and the ultra-fine traversing mechanism of the microscope stage, made velocity readings larger than 0.02 mm/s with accuracy and reproducibility better than 1%, possible near the wall to within 7-10 microns.

  12. Mesospheric wind measurements using a medium-frequency imaging Doppler interferometer

    NASA Technical Reports Server (NTRS)

    Adams, G. W.; scatterers.

    1986-01-01

    Wind results from a medium-frequency radar operated as an imaging Doppler interferometer are presented. Ten independent antennas, together with mesospheric wind motions, were used to Doppler-sort and then echo-locate individual scattering points. The three-dimensional location and radial velocity of each discrete scattering point was determined. Mean winds were then determined by a least squares fit to the radial velocities of the ensemble of scatterers.

  13. Absolute Doppler shift calibration of laser induced fluorescence signals using optogalvanic measurements in a hollow cathode lamp

    NASA Technical Reports Server (NTRS)

    Ruyten, Wilhelmus M.; Keefer, Dennis

    1992-01-01

    The paper investigates the use of optogalvanic (OG) measurements on the neutral 3P1 and 3P2 levels of argon in a hollow cathode lamp for the purpose of calibrating Doppler shifts of laser-induced fluorescence signals from an arcjet plume. It is shown that, even with non-Doppler-free OG detection, accuracy to better than 10 MHz is possible but that, depending on the experiment geometry, corrections of 10-35 MHz may be necessary to offset small axial drift velocities of neutral atoms in the hollow cathode lamp.

  14. Measurement of the Rotation Rate of Jovian Planets with Doppler Spectroscopy

    NASA Astrophysics Data System (ADS)

    Reid, Piper

    2013-06-01

    Jupiter and Saturn are the two gas giants in our solar system. These huge planets rotate very quickly and are composed of gas with no rock or ice surface like many of the other planets in our solar system. Determining the rotational velocity of these planets is of interest to scientists as this information can help in the understanding of the origins of these gas giants and the formation of our solar system. With an amateur astronomer’s telescope in a backyard observatory, is it possible to determine the speed of rotation of Jupiter and Saturn by measuring the Doppler shift of the Hydrogen-α emission lines from each side of the planet? Two Jovian planets, Jupiter and Saturn were studied. The rotational velocity was calculated by aligning the spectroscope slit with the equatorial axis of the Jovian planet and capturing a spectrum that shows tilt in the characteristic emission lines then analyzing the tilt of the emission lines and calculating the amount of Doppler shift implied by this spectral shift. By careful use of consumer grade astronomical equipment it is possible for an amateur astronomer to determine the rotational velocity of the Jovian planets from a backyard home observatory in a suburban setting.

  15. Field evaluation of boat-mounted acoustic Doppler instruments used to measure streamflow

    USGS Publications Warehouse

    Mueller, D.S.; ,

    2003-01-01

    The use of instruments based on the Doppler principle for measuring water velocity and computing discharge is common within the U.S. Geological Survey (USGS). The instruments and software have changed appreciably during the last 5 years; therefore, the USGS has begun field validation of the instruments used to make discharge measurements from a moving boat. Instruments manufactured by SonTek/YSI and RD Instruments, Inc. were used to collect discharge data at five different sites. One or more traditional discharge measurements were made using a Price AA current meter and standard USGS procedures concurrent with the acoustic instruments at each site. Discharges measured with the acoustic instruments were compared with discharges measured with Price AA current meters and the USGS stage-discharge rating for each site. The mean discharges measured by each acoustic instrument were within 5 percent of the Price AA-based measurement and (or) discharge from the stage-discharge rating.

  16. Three Component Doppler Global Velocimeter Measurements of the Flow Above A Delta Wing

    NASA Technical Reports Server (NTRS)

    Meyers, James F.; Lee, Joseph W.; Covone, Angelo A.

    1992-01-01

    A new measurement technique is being developed by NASA to measure off-surface flow fields. This method, Doppler global velocimetry, will allow quantification of complex three-dimensional flow fields at video camera rates. The entire flow field structure within a selected plane is measured simultaneously rather than by scanned, point-by-point measurements using conventional laser velocimetry. To assess the capability of this new technique, three - component velocity measurements of the vortical flow field above a thin 75-degree delta wing were made in the NASA Langley Basic Aerodynamics Research Tunnel. Measurements were made of the flow field at the 70-percent chord location at angles-of-attack of 20.5 and 40.0 degrees to investigate unburst and burst vortices. For comparison, previous fringe-type laser velocimeter measurements of the flow field at the same conditions are included.

  17. A technique to measure the size of particles in laser Doppler velocimetry applications

    NASA Technical Reports Server (NTRS)

    Hess, C. F.

    1985-01-01

    A method to measure the size of particles in Laser Doppler Velocimeter (LDV) applications is discussed. Since in LDV the velocity of the flow is assocated with the velocity of particles to establish how well they follow the flow, in the present method the interferometric probe volume is surrounded by a larger beam of different polarization or wavelength. The particle size is then measured from the absolute intensity scattered from the large beam by particles crossing the fringes. Experiments using polystrene particles between 1.1 and 3.3 microns and larger glass beads are reported. It is shown that the method has an excellent size resolution and its accuracy is better than 10% for the particle size studied.

  18. Analysis of airborne Doppler lidar, Doppler radar and tall tower measurements of atmospheric flows in quiescent and stormy weather

    NASA Technical Reports Server (NTRS)

    Bluestein, H. B.; Doviak, R. J.; Eilts, M. D.; Mccaul, E. W.; Rabin, R.; Sundara-Rajan, A.; Zrnic, D. S.

    1986-01-01

    The first experiment to combine airborne Doppler Lidar and ground-based dual Doppler Radar measurements of wind to detail the lower tropospheric flows in quiescent and stormy weather was conducted in central Oklahoma during four days in June-July 1981. Data from these unique remote sensing instruments, coupled with data from conventional in-situ facilities, i.e., 500-m meteorological tower, rawinsonde, and surface based sensors, were analyzed to enhance understanding of wind, waves and turbulence. The purposes of the study were to: (1) compare winds mapped by ground-based dual Doppler radars, airborne Doppler lidar, and anemometers on a tower; (2) compare measured atmospheric boundary layer flow with flows predicted by theoretical models; (3) investigate the kinematic structure of air mass boundaries that precede the development of severe storms; and (4) study the kinematic structure of thunderstorm phenomena (downdrafts, gust fronts, etc.) that produce wind shear and turbulence hazardous to aircraft operations. The report consists of three parts: Part 1, Intercomparison of Wind Data from Airborne Lidar, Ground-Based Radars and Instrumented 444 m Tower; Part 2, The Structure of the Convective Atmospheric Boundary Layer as Revealed by Lidar and Doppler Radars; and Part 3, Doppler Lidar Observations in Thunderstorm Environments.

  19. Measurement Capabilities of Planar Doppler Velocimetry in Large-Scale Wind Tunnels

    NASA Technical Reports Server (NTRS)

    McKenzie, Robert L.; Warmbrodt, William (Technical Monitor)

    1997-01-01

    Over the past few years, Planar Doppler Velocimetry (PDT) has been shown by several laboratories to offer an attractive means for measuring three-dimensional velocity vectors everywhere in a light sheet placed in a flow. Unlike some other optical means of measuring flow velocities, PDT is particularly attractive for use in large wind tunnels where distances to the sample region may be several meters, because it does not require the spatial resolution and tracking of individual scattering particles or the alignment of crossed beams at large distances. To date, demonstrations of PDT (also called Doppler Global Velocimetry by some authors) have been made either in low speed flows without quantitative comparison to other measurements, or in supersonic flows where the Doppler shift is large and its measurement is relatively insensitive to instrumental errors. Moreover, most reported applications have relied on the use of continuous-wave lasers, which limit the measurement to time-averaged velocity fields. This work summarizes the results of two previous studies of PDT in which the use of pulsed lasers to obtain instantaneous velocity vector fields is evaluated. The objective has been to quantitatively define and demonstrate PDT capabilities for applications in large-scale wind tunnels that are intended primarily for the testing of rotorcraft and subsonic aircraft at speeds typically less than 100 m/s. For such applications, the adequate resolution of low-speed flow fields requires accurate measurements of small Doppler shifts that are obtained at distances of several meters from the sample region and with a field of view that is sufficient to encompass the entire region of interest. The use of pulsed lasers provides the unique capability to obtain not only time-averaged fields, but also their statistical fluctuation amplitudes and the spatial excursions of unsteady flow regions such as wakes, separations, and rotor-tip vortices. To accomplish the objectives of these

  20. Measurement Capabilities of Planar Doppler Velocimetry in Large-Scale Wind Tunnels

    NASA Technical Reports Server (NTRS)

    McKenzie, Robert L.; Warmbrodt, William (Technical Monitor)

    1997-01-01

    Over the past few years, Planar Doppler Velocimetry (PDT) has been shown by several laboratories to offer an attractive means for measuring three-dimensional velocity vectors everywhere in a light sheet placed in a flow. Unlike some other optical means of measuring flow velocities, PDT is particularly attractive for use in large wind tunnels where distances to the sample region may be several meters, because it does not require the spatial resolution and tracking of individual scattering particles or the alignment of crossed beams at large distances. To date, demonstrations of PDT (also called Doppler Global Velocimetry by some authors) have been made either in low speed flows without quantitative comparison to other measurements, or in supersonic flows where the Doppler shift is large and its measurement is relatively insensitive to instrumental errors. Moreover, most reported applications have relied on the use of continuous-wave lasers, which limit the measurement to time-averaged velocity fields. This work summarizes the results of two previous studies of PDT in which the use of pulsed lasers to obtain instantaneous velocity vector fields is evaluated. The objective has been to quantitatively define and demonstrate PDT capabilities for applications in large-scale wind tunnels that are intended primarily for the testing of rotorcraft and subsonic aircraft at speeds typically less than 100 m/s. For such applications, the adequate resolution of low-speed flow fields requires accurate measurements of small Doppler shifts that are obtained at distances of several meters from the sample region and with a field of view that is sufficient to encompass the entire region of interest. The use of pulsed lasers provides the unique capability to obtain not only time-averaged fields, but also their statistical fluctuation amplitudes and the spatial excursions of unsteady flow regions such as wakes, separations, and rotor-tip vortices. To accomplish the objectives of these

  1. Wave measurements using GPS velocity signals.

    PubMed

    Doong, Dong-Jiing; Lee, Beng-Chun; Kao, Chia Chuen

    2011-01-01

    This study presents the idea of using GPS-output velocity signals to obtain wave measurement data. The application of the transformation from a velocity spectrum to a displacement spectrum in conjunction with the directional wave spectral theory are the core concepts in this study. Laboratory experiments were conducted to verify the accuracy of the inversed displacement of the surface of the sea. A GPS device was installed on a moored accelerometer buoy to verify the GPS-derived wave parameters. It was determined that loss or drifting of the GPS signal, as well as energy spikes occurring in the low frequency band led to erroneous measurements. Through the application of moving average skill and a process of frequency cut-off to the GPS output velocity, correlations between GPS-derived, and accelerometer buoy-measured significant wave heights and periods were both improved to 0.95. The GPS-derived one-dimensional and directional wave spectra were in agreement with the measurements. Despite the direction verification showing a 10° bias, this exercise still provided useful information with sufficient accuracy for a number of specific purposes. The results presented in this study indicate that using GPS output velocity is a reasonable alternative for the measurement of ocean waves.

  2. Wave Measurements Using GPS Velocity Signals

    PubMed Central

    Doong, Dong-Jiing; Lee, Beng-Chun; Kao, Chia Chuen

    2011-01-01

    This study presents the idea of using GPS-output velocity signals to obtain wave measurement data. The application of the transformation from a velocity spectrum to a displacement spectrum in conjunction with the directional wave spectral theory are the core concepts in this study. Laboratory experiments were conducted to verify the accuracy of the inversed displacement of the surface of the sea. A GPS device was installed on a moored accelerometer buoy to verify the GPS-derived wave parameters. It was determined that loss or drifting of the GPS signal, as well as energy spikes occurring in the low frequency band led to erroneous measurements. Through the application of moving average skill and a process of frequency cut-off to the GPS output velocity, correlations between GPS-derived, and accelerometer buoy-measured significant wave heights and periods were both improved to 0.95. The GPS-derived one-dimensional and directional wave spectra were in agreement with the measurements. Despite the direction verification showing a 10° bias, this exercise still provided useful information with sufficient accuracy for a number of specific purposes. The results presented in this study indicate that using GPS output velocity is a reasonable alternative for the measurement of ocean waves. PMID:22346618

  3. Reference values for ductus venosus Doppler flow measurements at 10-14 weeks of gestation.

    PubMed

    Prefumo, F; Risso, D; Venturini, P L; De Biasio, P

    2002-07-01

    To calculate reference ranges for ductus venosus Doppler measurements obtained transabdominally at 10-14 weeks of gestation. Two hundred and one normal fetuses with a crown-rump length (CRL) ranging from 38 to 88 mm were examined in a cross-sectional study. The pulsatility index for veins (PIV), peak velocity during ventricular systole (S-wave), lowest forward velocity during atrial contraction (A-wave) and time-averaged maximum velocity (TAMXV) were recorded from the ductus venosus. Flow velocity waveforms were also classified as normal or abnormal according to the presence (normal) or absence or reversal (abnormal) of frequencies during atrial contraction. Three of 201 fetuses showed an abnormal flow pattern (1.5%; 95% exact confidence interval, 0.3-4.3%). In the 198 fetuses with a normal flow pattern, the mean PIV ranged from 1.07 at a CRL of 38 mm to 1.00 at a CRL of 88 mm (r = -0.093; P = 0.19). A significant increase in mean blood flow velocity with increasing CRL was noted for the S-wave (27.0 cm/s to 33.6 cm/s; r = 0.17; P = 0.02), the A-wave (5.9 cm/s to 7.8 cm/s; r = 0.14; P = 0.04) and the TAMXV (19.4 cm/s to 25.3 cm/s; r = 0.19; P < 0.01). Crown-rump length-specific reference ranges for each parameter were calculated using the method of scaled absolute residuals. Abnormal ductus venosus flow patterns could be observed in normal fetuses, even if they ocurred with a low prevalence. Reference values for Doppler measurements were established in fetuses with normal patterns of flow.

  4. Estimation of acoustical streaming: theoretical model, Doppler measurements and optical visualisation.

    PubMed

    Nowicki, A; Kowalewski, T; Secomski, W; Wójcik, J

    1998-02-01

    An approximate solution for the streaming velocity generated by flat and weakly focused transducers was derived by directly solving the Dirichlet boundary conditions for the Poisson equation, the solution of the Navier-Stokes equation for the axial components of the streaming velocity. The theoretical model was verified experimentally using a 32 MHz pulsed Doppler unit. The experimental acoustical fields were produced by three different 4 mm diameter flat and focused transducers driven by the transmitter generating the average acoustic power within the range from 1 microW to 6 mW. The streaming velocity was measured along the ultrasonic beam from 0 to 2 cm. Streaming was induced in a solution of water and corn starch. The experimental results showed that for a given acoustic power the streaming velocity was independent of the starch density in water, changed from 0.3 to 40 grams of starch in 1 l of distilled water. For applied acoustic powers, the streaming velocity changed linearly from 0.2 to 40 mm/s. Both, the theoretical solutions for plane and focused waves and the experimental results were in good agreement. The streaming velocity field was also visualised using the particle image velocimetry (PIV) and two different evaluation methods. The first based on the FFT-based cross-correlation analysis between small sections for each pair of images and the second employing the algorithm of searching for local displacements between several images.

  5. The Göttingen Solar Radial Velocity Project: Sub-m s-1 Doppler Precision from FTS Observations of the Sun as a Star

    NASA Astrophysics Data System (ADS)

    Lemke, U.; Reiners, A.

    2016-09-01

    Radial velocity observations of stars are entering the sub-m s-1 domain revealing fundamental barriers for Doppler precision experiments. Observations of the Sun as a star can easily overcome the m s-1 photon limit but face other obstacles. We introduce the Göttingen Solar Radial Velocity Project with the goal of obtaining high-precision (cm s-1) radial velocity measurements of the Sun as a star with a Fourier Transform Spectrograph. In this first paper, we present the project and first results. The photon limit of our 2 minute observations is at the 2 cm s-1 level but is currently limited by strong instrumental systematics. A drift of a few m s-1 hr-1 is visible in all observing days, probably caused by vignetting of the solar disk in our fiber-coupled setup, and imperfections of our guiding system add further offsets in our data. Binning the data into 30 minute groups shows m s-1 stability after correcting for a daily and linear instrumental trend. Our results show the potential of Sun-as-a-star radial velocity measurements that can possibly be achieved after a substantial upgrade of our spectrograph coupling strategy. Sun-as-a-star observations can provide crucial empirical information about the radial velocity signal of convective motion and stellar activity and on the wavelength dependence of radial velocity signals caused by stellar line profile variations.

  6. Spatiotemporal Dynamics of the Wind Velocity from Minisodar Measurement Data

    NASA Astrophysics Data System (ADS)

    Simakhin, V. A.; Cherepanov, O. S.; Shamanaeva, L. G.

    2016-04-01

    The spatiotemporal dynamics of the three wind velocity components in the atmospheric boundary layer is analyzed on the basis of Doppler minisodar measurements. The data were processed and analyzed with the help of robust nonparametric methods based on the weighted maximum likelihood method and classical methods. Distribution laws were obtained for each wind velocity component. There are outliers in the distribution functions; both right and left asymmetry of the distributions are observed. For the x- and ycomponents, the width of the distribution increases as the observation altitude is increased, but the maximum of the distribution function decreases, which is in agreement with the data available in the literature. For the zcomponents the width of the distribution remains practically constant, but the value of the maximum also decreases with altitude. Analysis of the hourly semidiurnal dynamics showed that all three components have maxima in the morning and evening hours. For the y- and z-components the maxima in the evening hours are more strongly expressed than in the morning hours. For the x- and y-components the horizontal wind shear is closely tracked in the evening hours. It is shown that adaptive estimates on the efficiency significantly exceed the classical parametric estimates and allow one to analyze the spatiotemporal dynamics of the wind velocity, and reveal jets and detect wind shears.

  7. Acoustic Measurement of Potato Cannon Velocity

    ERIC Educational Resources Information Center

    Courtney, Michael; Courtney, Amy

    2007-01-01

    Potato cannon velocity can be measured 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. 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…

  8. Optoelectronic System for Measuring Warhead Fragments Velocity

    NASA Astrophysics Data System (ADS)

    Liu, Ji; Zhao, Donge; Li, Yangjun; Zhou, Hanchang

    2011-02-01

    High-speed warhead fragments velocity measurement is one of the key technologies in investigating damage efficiency of warhead. We have designed and constructed a system to accurately determine the velocity of warhead fragments by measuring the time of flight between two parallel laser screens is presented. Each screen is formed by a laser source, a large photodetector and a retro-reflector. Optical output of the laser source is a collimated beam. The beam passes through cylindrical lens and the slit of photodetector reach to retro-reflector .The energy, reflected by retro-reflector; focus on the active area of photodetector. The system utilizes reflected ray by scotchlite retro-reflector as the start and end signal. And utilizes wideband circuit and data acquiring system to condition and sample signals. Experimental results show the system can measurement velocity are within the range from 20m/s to 2000m/s on target area of 1m2 and can perform satisfactorily with a wide range from 2000 lx to100,000lx. The measurement system also can be used to test velocity of projectile.

  9. Acoustic Measurement of Potato Cannon Velocity

    ERIC Educational Resources Information Center

    Courtney, Michael; Courtney, Amy

    2007-01-01

    Potato cannon velocity can be measured 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. 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…

  10. Minimally destructive, Doppler measurement of a quantized flow in a ring-shaped Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Anderson, N.; Phillips, W. D.; Eckel, S.; Campbell, G. K.; Stringari, S.

    2016-02-01

    The Doppler effect, the shift in the frequency of sound due to motion, is present in both classical gases and quantum superfluids. Here, we perform an in situ, minimally destructive measurement, of the persistent current in a ring-shaped, superfluid Bose-Einstein condensate using the Doppler effect. Phonon modes generated in this condensate have their frequencies Doppler shifted by a persistent current. This frequency shift will cause a standing-wave phonon mode to be ‘dragged’ along with the persistent current. By measuring this precession, one can extract the background flow velocity. This technique will find utility in experiments where the winding number is important, such as in emerging ‘atomtronic’ devices.

  11. Optical fiber-based system for continuous measurement of in-bore projectile velocity

    NASA Astrophysics Data System (ADS)

    Wang, Guohua; Sun, Jinglin; Li, Qiang

    2014-08-01

    This paper reports the design of an optical fiber-based velocity measurement system and its application in measuring the in-bore projectile velocity. The measurement principle of the implemented system is based on Doppler effect and heterodyne detection technique. The analysis of the velocity measurement principle deduces the relationship between the projectile velocity and the instantaneous frequency (IF) of the optical fiber-based system output signal. To extract the IF of the fast-changing signal carrying the velocity information, an IF extraction algorithm based on the continuous wavelet transforms is detailed. Besides, the performance of the algorithm is analyzed by performing corresponding simulation. At last, an in-bore projectile velocity measurement experiment with a sniper rifle having a 720 m/s muzzle velocity is performed to verify the feasibility of the optical fiber-based velocity measurement system. Experiment results show that the measured muzzle velocity is 718.61 m/s, and the relative uncertainty of the measured muzzle velocity is approximately 0.021%.

  12. Optical fiber-based system for continuous measurement of in-bore projectile velocity.

    PubMed

    Wang, Guohua; Sun, Jinglin; Li, Qiang

    2014-08-01

    This paper reports the design of an optical fiber-based velocity measurement system and its application in measuring the in-bore projectile velocity. The measurement principle of the implemented system is based on Doppler effect and heterodyne detection technique. The analysis of the velocity measurement principle deduces the relationship between the projectile velocity and the instantaneous frequency (IF) of the optical fiber-based system output signal. To extract the IF of the fast-changing signal carrying the velocity information, an IF extraction algorithm based on the continuous wavelet transforms is detailed. Besides, the performance of the algorithm is analyzed by performing corresponding simulation. At last, an in-bore projectile velocity measurement experiment with a sniper rifle having a 720 m/s muzzle velocity is performed to verify the feasibility of the optical fiber-based velocity measurement system. Experiment results show that the measured muzzle velocity is 718.61 m/s, and the relative uncertainty of the measured muzzle velocity is approximately 0.021%.

  13. Evaluation of acoustic doppler velocity meters to quantify flow from Comal Springs and San Marcos Springs, Texas

    USGS Publications Warehouse

    Gary, Marcus O.; Gary, Robin H.; Asquith, William H.

    2008-01-01

    Comal Springs and San Marcos Springs are the two largest springs in Texas, are major discharge points for the San Antonio segment of the Edwards aquifer, and provide habitat for several Federally listed endangered species that depend on adequate springflows for survival. It is therefore imperative that the Edwards Aquifer Authority have accurate and timely springflow data to guide resource management. Discharge points for Comal Springs and San Marcos Springs are submerged in Landa Lake and in Spring Lake, respectively. Flows from the springs currently (2008) are estimated by the U.S Geological Survey in real time as surface-water discharge from conventional stage-discharge ratings at sites downstream from each spring. Recent technological advances and availability of acoustic Doppler velocity meters (ADVMs) now provide tools to collect data (stream velocity) related to springflow that could increase accuracy of real-time estimates of the springflows. The U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, did a study during May 2006 through September 2007 to evaluate ADVMs to quantify flow from Comal and San Marcos Springs. The evaluation was based on two monitoring approaches: (1) placement of ADVMs in important spring orifices - spring run 3 and spring 7 at Comal Springs, and diversion spring at San Marcos Springs; and (2) placement of ADVMs at the nearest flowing streams - Comal River new and old channels for Comal Springs, Spring Lake west and east outflow channels and current (2008) San Marcos River streamflow-gaging site for San Marcos Springs. For Comal Springs, ADVM application at spring run 3 and spring 7 was intended to indicate whether the flows of spring run 3 and spring 7 can be related to total springflow. The findings indicate that velocity data from both discharge features, while reflecting changes in flow, do not reliably show a direct relation to measured streamflow and thus to total Comal Springs flow. ADVMs at the Comal

  14. Novel laser Doppler flowmeter for pulpal blood flow measurements

    NASA Astrophysics Data System (ADS)

    Zang, De Yu; Millerd, James E.; Wilder-Smith, Petra B. B.; Arrastia-Jitosho, Anna-Marie A.

    1996-04-01

    We have proposed and experimentally demonstrated a new configuration of laser Doppler flowmetry for dental pulpal blood flow measurements. To date, the vitality of a tooth can be determined only by subjective thermal or electric tests, which are of questionable reliability and may induced pain in patient. Non-invasive techniques for determining pulpal vascular reactions to injury, treatment, and medication are in great demand. The laser Doppler flowmetry technique is non-invasive; however, clinical studies have shown that when used to measure pulpal blood flow the conventional back-scattering Doppler method suffers from low signal-to-noise ratio (SNR) and unreliable flux readings rendering it impossible to calibrate. A simplified theoretical model indicates that by using a forward scattered geometry the detected signal has a much higher SNR and can be calibrated. The forward scattered signal is readily detectable due to the fact that teeth are relatively thin organs with moderate optical loss. A preliminary experiment comparing forward scattered detection with conventional back- scattered detection was carried out using an extracted human molar. The results validated the findings of the simple theoretical model and clearly showed the utility of the forward scattering geometry. The back-scattering method had readings that fluctuated by as much as 187% in response to small changes in sensor position relative to the tooth. The forward scattered method had consistent readings (within 10%) that were independent of the sensor position, a signal-to-noise ratio that was at least 5.6 times higher than the back-scattering method, and a linear response to flow rate.

  15. Laser Doppler anemometry measurements of steady flow through two bi-leaflet prosthetic heart valves.

    PubMed

    Bazan, Ovandir; Ortiz, Jayme Pinto; Vieira, Francisco Ubaldo; Vieira, Reinaldo Wilson; Antunes, Nilson; Tabacow, Fabio Bittencourt Dutra; Costa, Eduardo Tavares; Petrucci, Orlando

    2013-01-01

    In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hydrodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench. To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream. To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min.) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements. It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found. Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves.

  16. Laser Doppler anemometry measurements of steady flow through two bi-leaflet prosthetic heart valves

    PubMed Central

    Bazan, Ovandir; Ortiz, Jayme Pinto; Vieira Junior, Francisco Ubaldo; Vieira, Reinaldo Wilson; Antunes, Nilson; Tabacow, Fabio Bittencourt Dutra; Costa, Eduardo Tavares; Petrucci Junior, Orlando

    2013-01-01

    Introduction In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hydrodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench. Objective To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream. Methods To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min. ) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements. Results It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found. Conclusions Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves. PMID:24598950

  17. Measurement uncertainty and temporal resolution of Doppler global velocimetry using laser frequency modulation

    SciTech Connect

    Fischer, Andreas; Buettner, Lars; Czarske, Juergen; Eggert, Michael; Mueller, Harald

    2008-07-20

    A Doppler global velocimetry (DGV) measurement technique with a sinusoidal laser frequency modulation is presented for measuring velocity fields in fluid flows. A cesium absorption