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Sample records for phase doppler anemometry

  1. Evaluation of metered dose inhaler spray velocities using phase Doppler anemometry (PDA).

    PubMed

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

    2012-02-28

    Droplet velocity is an important parameter which can significantly influence inhalation drug delivery performance. Together with the droplet size, this parameter determines the efficiency of the deposition of MDI products at different sites within the lungs. In this study, phase Doppler anemometry (PDA) was used to investigate the instantaneous droplet velocity emitted from MDIs as well as the corresponding droplet size distribution. The nine commercial MDI products surveyed showed significantly different droplet velocities, indicating that droplet velocity could be used as a discriminating parameter for in vitro testing of MDI products. The droplet velocity for all tested MDI products decreased when the testing distance was increased from 3 cm to 6 cm from the front of mouthpiece, with CFC formulations showing a larger decrease than HFA formulations. The mean droplet diameters of the nine MDIs were also significantly different from one-another. Droplet size measurements made using PDA (a number-based technique) could not be directly compared to results obtained using laser light scattering measurements (a volume-based technique). This work demonstrates that PDA can provide unique information useful for characterizing MDI aerosol plumes and evaluating MDI drug delivery efficiency. PDA could also aid the evaluation of in vitro equivalence in support of formulation or manufacturing changes and in evaluation of abbreviated new drug applications (ANDAs) for MDIs. PMID:22183132

  2. Study of cyclic and steady particle motion in a realistic human airway model using phase-Doppler anemometry

    NASA Astrophysics Data System (ADS)

    Jedelský, Jan; Lízal, František; Jícha, Miroslav

    2012-04-01

    Transport and deposition of particles in human airways has been of research interest for many years. Various experimental methods such as constant temperature anemometry, particle image velocimetry and laser-Doppler based techniques were employed for study of aerosol transport in the past. We use Phase-Doppler Particle Analyser (P/DPA) for time resolved size and velocity measurement of liquid aerosol particles in a size range 1 to 8 μm. The di-2ethylhexyl sabacate (DEHS) particles were produced by condensation monodisperse aerosol generator. A thin-wall transparent model of human airways with non-symmetric bifurcations and non-planar geometry containing parts from throat to 3rd-4th generation of bronchi was fabricated for the study. Several cyclic (sinusoidal) breathing regimes were simulated using pneumatic breathing mechanism. Analogous steady-flow regimes were also investigated and used for comparison. An analysis of the particle velocity data was performed with aim to gain deeper understanding of the transport phenomena in the realistic bifurcating airway system. Flows of particles of different sizes in range 1 - 10 μm was found to slightly differ for extremely high Stokes numbers. Differences in steady and cyclic turbulence intensities were documented in the paper. Systematically higher turbulence intensity was found for cyclic flows and mainly in the expiration breathing phase. Negligible differences were found for behaviour of different particle size classes in the inspected range 1 to 8 μm. Possibility of velocity spectra estimation of air flow using the P/DPA data is discussed.

  3. Dual beam translator for use in Laser Doppler anemometry

    DOEpatents

    Brudnoy, David M.

    1987-01-01

    A method and apparatus for selectively translating the path of at least one pair of light beams in a Laser Doppler anemometry device whereby the light paths are translated in a direction parallel to the original beam paths so as to enable attainment of spacial coincidence of the two intersection volumes and permit accurate measurements of Reynolds shear stress.

  4. Dual beam translator for use in Laser Doppler anemometry

    DOEpatents

    Brudnoy, D.M.

    1984-04-12

    A method and apparatus for selectively translating the path of at least one pair of light beams in a Laser Doppler anemometry device whereby the light paths are translated in a direction parallel to the original beam paths so as to enable attainment of spacial coincidence of the two intersection volumes and permit accurate measurements of Reynolds shear stress.

  5. 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.

  6. Fiber optic laser Doppler anemometry in swirling jets

    NASA Technical Reports Server (NTRS)

    Taghavi, R.; Rice, E. J.

    1991-01-01

    Time-averaged and fluctuating quantities are measured in a free turbulent swirling jet. Data from a two-component laser Doppler anemometry (LDA) are compared to the measurements via hot-wire and 5-hole pitot probes. To acquire the proper seeding density near the axis of a swirling jet for LDA measurements proved difficult. This is due to an imbalance of the centrifugal force and radial pressure gradient, which throws the seeding material off the axis. Despite this problem, close agreement between various measurement techniques is obtained.

  7. Compensation for refractive-index variations in laser Doppler anemometry.

    PubMed

    Kehoe, A B; Desai, P V

    1987-07-01

    Techniques to compensate for index of refraction variations in the application of a laser Doppler anemometer are examined. For discontinuous plane-layered media a method of discrete elements is employed. An alternative set of equations is derived for continuous cylindrically layered media and simplified to make comparisons with available results for a single cylinder. Results of velocity measurements in a Plexiglas model of a cylindrically layered nuclear fuel assembly are presented to establish a positioning accuracy of the method to within 0.025 cm. PMID:20489924

  8. Laser Doppler anemometry measurements in the near-wake of an isolated Formula One wheel

    NASA Astrophysics Data System (ADS)

    Saddington, A. J.; Knowles, R. D.; Knowles, K.

    2007-05-01

    An experimental investigation was conducted to identify the main structures in the near wake of an isolated Formula One wheel rotating in ground contact. A 50 percent-scale isolated wheel assembly, geometrically similar to the configuration mounted on a Formula One racing car, was tested in a closed-return three-quarter open-jet wind tunnel. The test Reynolds number, based on wheel diameter was 6.8 × 105. Using laser doppler anemometry, three velocity components were measured with a total of 1966 data points across four planes and within one diameter downstream of the wheel axis. Based on analysis of these data, the main characteristics of the near-wake of an isolated wheel rotating in ground contact are presented. A revised model of the trailing vortex system induced in the wake of such a wheel is proposed, which clarifies the contradictory ones published in the literature to date.

  9. A microcomputer based frequency-domain processor for laser Doppler anemometry

    NASA Technical Reports Server (NTRS)

    Horne, W. Clifton; Adair, Desmond

    1988-01-01

    A prototype multi-channel laser Doppler anemometry (LDA) processor was assembled using a wideband transient recorder and a microcomputer with an array processor for fast Fourier transform (FFT) computations. The prototype instrument was used to acquire, process, and record signals from a three-component wind tunnel LDA system subject to various conditions of noise and flow turbulence. The recorded data was used to evaluate the effectiveness of burst acceptance criteria, processing algorithms, and selection of processing parameters such as record length. The recorded signals were also used to obtain comparative estimates of signal-to-noise ratio between time-domain and frequency-domain signal detection schemes. These comparisons show that the FFT processing scheme allows accurate processing of signals for which the signal-to-noise ratio is 10 to 15 dB less than is practical using counter processors.

  10. 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.

  11. 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

  12. Quantitative measurement of blood flow dynamics in chorioallantoic membrane of chicken embryo using laser Doppler anemometry

    NASA Astrophysics Data System (ADS)

    Borozdova, M. A.; Stiukhina, E. S.; Sdobnov, A. A.; Fedosov, I. V.; Postnov, D. E.; Tuchin, V. V.

    2016-04-01

    We report the results on in ovo application of developed Laser Doppler Anemometer (LDA) device. The chorioallantoic membrane (CAM) of 9-13 days chicken embryos was used as a biological model that allows an easy access to both arterial and venous vessels of different size. The key point of our study was to find out how the periodic and aperiodic pulsations of blood flow (which are inevitable in living organism) will affect the LDA functions and measuring capability. Specifically, we (i) developed the technique to extract and refine the pulse rhythm from the signal received from a vessel, and (ii) analyzed the changes in power spectra of LDA signal that are caused by heart beating and considerably complicate the reliable measurement of Doppler shift. Our main conclusion is that the algorithm of LDA data processing need to be improved, and this possibly can be done by counting the information on current phase of cardiac cycle.

  13. An LDA (Laser-Doppler Anemometry) investigation of three-dimensional normal shock wave boundary-layer interactions

    NASA Technical Reports Server (NTRS)

    Chriss, R. M.; Hingst, W. R.; Strazisar, A. J.; Keith, T. G., Jr.

    1989-01-01

    Nonintrusive measurements were made of a normal shock wave/boundary layer interaction. Two dimensional measurements were made throughout the interaction region while 3-D measurements were made in the vicinity of the shock wave. The measurements were made in the corner of the test section of a continuous supersonic wind tunnel in which a normal shock wave had been stabilized. Laser Doppler Anemometry, surface pressure measurement and flow visualization techniques were employed for two freestream Mach number test cases: 1.6 and 1.3. The former contained separated flow regions and a system of shock waves. The latter was found to be far less complicated. The results define the flow field structure in detail for each case.

  14. Droplet sizes and velocities in vaporizing sprays. [using laser Doppler anemometry

    NASA Technical Reports Server (NTRS)

    Yule, A. J.; Ereaut, P. R.; Ungut, A.

    1983-01-01

    A pulse height laser Doppler anemometer particle sizing technique has been refined to permit simultaneous particle size and velocity measurements in sprays. The improvements include (1) the use of a specially tailored 'top hat' light distribution, to provide unambiguous particle diameter-signal amplitude relations, (2) the use of back scattered light collection, and (3) the utilization of Mie theory to compute the relations between signal amplitude and particle diameter, in the backscatter mode. Twin-fluid atomized kerosene sprays have been investigated using the new technique. In these sprays distributions have been mapped of mean droplet diameters, droplet size distributions, and the local correlations between droplet diameters and velocities. The data show the variation of spray structure with atomizer input parameters, the preferential vaporization of smaller droplets, and the differing trajectories of the large and small droplets.

  15. Application of low-coherence optical fiber Doppler anemometry to fluid-flow measurement: optical system considerations

    NASA Astrophysics Data System (ADS)

    Boyle, William J. O.; Grattan, Kenneth T. V.; Palmer, Andrew W.; Meggitt, B. T.

    1991-08-01

    A fiber optic Doppler anemometric (FODA) sensor using an optical delay cavity technique and having the advantage of detecting velocity rather than simple speed is outlined. In this sensor the delay in a sensor cavity formed from light back-reflected from a fiber tip (Fresnel reflection) and light back-reflected from particles flowing in a fluid is balanced by the optical delay when light from this sensor cavity passes through a reference cavity formed by a combination of the zero and first diffraction orders produced by a Bragg cell inserted into the optical arrangement. The performance of an experimental sensor based on this scheme is investigated, and velocity measurements using the Doppler shift data from moving objects are presented. The sensitivity of the scheme is discussed, with reference to the other techniques of fluid flow measurement.

  16. Power spectral density of velocity fluctuations estimated from phase Doppler data

    NASA Astrophysics Data System (ADS)

    Jedelsky, Jan; Lizal, Frantisek; Jicha, Miroslav

    2012-04-01

    Laser Doppler Anemometry (LDA) and its modifications such as PhaseDoppler Particle Anemometry (P/DPA) is point-wise method for optical nonintrusive measurement of particle velocity with high data rate. Conversion of the LDA velocity data from temporal to frequency domain - calculation of power spectral density (PSD) of velocity fluctuations, is a non trivial task due to nonequidistant data sampling in time. We briefly discuss possibilities for the PSD estimation and specify limitations caused by seeding density and other factors of the flow and LDA setup. Arbitrary results of LDA measurements are compared with corresponding Hot Wire Anemometry (HWA) data in the frequency domain. Slot correlation (SC) method implemented in software program Kern by Nobach (2006) is used for the PSD estimation. Influence of several input parameters on resulting PSDs is described. Optimum setup of the software for our data of particle-laden air flow in realistic human airway model is documented. Typical character of the flow is described using PSD plots of velocity fluctuations with comments on specific properties of the flow. Some recommendations for improvements of future experiments to acquire better PSD results are given.

  17. Three-dimensional ray tracing through curvilinear interfaces with application to laser Doppler anemometry in a blood analogue fluid.

    PubMed

    Nugent, Allen H; Bertram, Christopher D

    2010-02-01

    Prediction of the effects of refractive index (RI) mismatch on laser Doppler anemometer (LDA) measurements within a curvilinear cavity (an artificial ventricle) was achieved by developing a general technique for modelling the paths of the convergent beams of the LDA system using 3D vector geometry. Validated by ray tracing through CAD drawings, the predicted maximum tolerance in RI between the solid model and the working fluid was +/- 0.0005, equivalent to focusing errors commensurate with the geometric and alignment uncertainties associated with the flow model and the LDA arrangement. This technique supports predictions of the effects of refraction within a complex geometry. Where the RI mismatch is unavoidable but known, it is possible not only to calculate the true position of the measuring volume (using the probe location and model geometry), but also to estimate degradation in signal quality arising from differential displacement and refraction of the laser beams. PMID:19669821

  18. Flow Velocities After Carotid Artery Stenting: Impact of Stent Design. A Fluid Dynamics Study in a Carotid Artery Model with Laser Doppler Anemometry

    SciTech Connect

    Greil, Oliver Kleinschmidt, Thomas; Weiss, Wolfgang; Wolf, Oliver; Heider, Peter; Schaffner, Silvio; Gianotti, Marc; Schmid, Thomas; Liepsch, Dieter; Berger, Hermann

    2005-01-15

    Purpose. To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model. Methods. Three different stents were positioned in silicone models of the carotid artery: a stainless steel stent (Wall-stent), a nitinol stent (SelfX), and a nitinol stent with a semipermeable membrane (MembraX). To increase the contact area of the membrane with the vessel wall, another MembranX model was modified at the outflow tract. The membrane consists of a biocompatible silicone-polyurethane copolymer (Elast-Eon) with a pore size of 100 {mu}m. All stents were deployed across the bifurcation and the external carotid artery origin. Flow velocity measurements were performed with laser Doppler anemometry (LDA), using pulsatile flow conditions (Re = 220; flow 0.39 l/min; flow rate ratio ICA:ECA = 70:30) in hemodynamically relevant cross-sections. The hemodynamic changes were analyzed by comparing velocity fluctuations of corresponding flow profiles. Results. The flow rate ratio ICA:ECA shifted significantly from 70/30 to 73.9/26.1 in the MembraX and remained nearly unchanged in the SelfX and Wallstent. There were no changes in the flow patterns at the inflow proximal to the stents. In the stent no relevant changes were found in the SelfX. In the Wallstent the separation zone shifted from the orifice of the ICA to the distal end of the stent. Four millimeters distal to the SelfX and the Wallstent the flow profile returned to normal. In the MembraX an increase in the central slipstreams was found with creation of a flow separation distal to the stent. With a modification of the membrane this flow separation vanished. In the ECA flow disturbances were seen at the inner wall distal to the stent struts in the SelfX and the Wallstent. With the MembraX a calming of flow could be observed in the ECA with a slight loss of flow volume. Conclusions. Stent placement across the carotid artery bifurcation induces alterations of the physiologic flow

  19. The joint estimation of differential delay, Doppler, and phase

    NASA Astrophysics Data System (ADS)

    Wax, M.

    1982-09-01

    In radio and sonar applications it sometimes happens that narrow-band signals, originated from a remote source and observed at a pair of receivers, differ by unknown differential phase and Doppler shift in addition to the differential delay corresponding to the range difference. The correspondence presents the joint maximum likelihood (ML) estimate of the differential delay, Doppler, and phase and examines their accuracy by deriving the Cramer-Rao bound. It is shown that joint ML estimators are the values of the delay and Doppler that maximize the magnitude of a generalized ambiguity function analogous to the one used in radar. It is also shown that for long observation time and high enough signal-to-noise ratio there is no degradation in the accuracy of the time-delay estimator due to the additional phase and Doppler uncertainty and that the differential Doppler is uncorrelated with the differential delay and phase estimators.

  20. Radiowave Phase Scintillation and Precision Doppler Tracking of Spacecraft

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.

    1997-01-01

    Phase scintillation cause by propagation through irregularities in the solar wind, ionosphere, and tropospher, introduces noise in spacecraft radio science experiments. The observations reported here are uses to refine the propagation noise model for Doppler tracking of deep space probes.

  1. Steady-state phase error for a phase-locked loop subjected to periodic Doppler inputs

    NASA Technical Reports Server (NTRS)

    Chen, C.-C.; Win, M. Z.

    1991-01-01

    The performance of a carrier phase locked loop (PLL) driven by a periodic Doppler input is studied. By expanding the Doppler input into a Fourier series and applying the linearized PLL approximations, it is easy to show that, for periodic frequency disturbances, the resulting steady state phase error is also periodic. Compared to the method of expanding frequency excursion into a power series, the Fourier expansion method can be used to predict the maximum phase error excursion for a periodic Doppler input. For systems with a large Doppler rate fluctuation, such as an optical transponder aboard an Earth orbiting spacecraft, the method can be applied to test whether a lower order tracking loop can provide satisfactory tracking and thereby save the effect of a higher order loop design.

  2. Spray Diagnostics in Rocket Engines Using Phase Doppler Analyzer

    NASA Technical Reports Server (NTRS)

    Isaac, Kakkattukuzhy M.

    1996-01-01

    Characteristics such as drop velocity, drop size, number density, volume flow rate, volume flux, and evaporation rate of the fuel spray in a rocket engine are directly related to engine performance. Several studies of shear coaxial atomization have been done in the past. However, additional work related to sprays at supercritical and transcritical conditions would be useful. The author undertook a study of the feasibility of using a phase Doppler particle analyzer (PDPA) for spray measurements in rocket engines as a part of the Summer Faculty Fellowship Program at the NASA Marshall Space Flight Center. The PDPA is a single particle counter (SPC) system based on light scattering from spherical particles. The PDPA instrument is based on refractive and reflective scattering as opposed to other instruments based on diffractive scattering. The main advantage of the PDPA instrument is its ability to provide point-wise information. The following sections describe the principle of operation of the PDPA system and the data obtained using a PDPA instrument in a spray formed by a commercially available fuel injection nozzle.

  3. Implementation and characterization of phase-resolved Doppler optical coherence tomography method for flow velocity measurement

    NASA Astrophysics Data System (ADS)

    Pongchalee, Pornthep; Palawong, Kunakorn; Meemon, Panomsak

    2014-06-01

    In this work, the system implementation and characterization of a Phase-Resolved Doppler Optical Coherence Tomography (PR-DOCT) is presented. The phase-resolved Doppler technique was implemented on a custom built Frequency Domain OCT (FD-OCT) that was recently developed at Suranaree University of Technology. Utilizing Doppler phase changed relation in a complex interference signal caused by moving samples, PR-DOCT can produce visualization and characterization of flow activity such as blood flow in biological samples. Here we report the performance of the implemented PR-DOCT system in term of the Velocity Dynamic Range (VDR), which is defined by the range from the minimum to the maximum detectable axial velocity. The minimum detectable velocity was quantified from a histogram distribution of phase difference between consecutive depth-scan signals when performing Doppler imaging of a stationary mirror. By applying a Gaussian curve fitting to the histogram, the Full Width at Half Maximum (FWHM) of the fitted curve was measured to represent the detectable minimum flow velocity of the system. The maximum detectable velocity was limited by the phase wrapping of the Doppler signal, which is governed by the acquisition speed of the system. We demonstrate the 3D Doppler imaging and velocity measurement of feed flow phantom using 100% milk pumped through a microfluidic chip by using a syringe pump system.

  4. A Method of Estimating Low Turbulence Levels in Near Real Time Using Laser Anemometry

    NASA Technical Reports Server (NTRS)

    Goldman, Louis J.; Seasholtz, Richard G.

    2004-01-01

    Laser anemometry was used to make two independent measurements of the flow velocity by capturing individual Doppler signals with high-speed digitizing boards. The two independent measurements were cross-correlated to reduce the contribution of photo detector shot noise on the frequency determination and subsequently on the turbulence estimate. In addition, criteria were developed to eliminate "bad" Doppler bursts from the data set, which then allowed reasonable low turbulence estimates to be made. The laser anemometer measurements were obtained at the inlet of an annular cascade and at the exit of a flow calibration nozzle and were compared with hot-wire data.

  5. Laser fringe anemometry for aero engine components

    NASA Technical Reports Server (NTRS)

    Strazisar, Anthony J.

    1986-01-01

    Advances in flow measurement techniques in turbomachinery continue to be paced by the need to obtain detailed data for use in validating numerical predictions of the flowfield and for use in the development of empirical models for those flow features which cannot be readily modelled numerically. The use of laser anemometry in turbomachinery research has grown over the last 14 years in response to these needs. Based on past applications and current developments, the key issues which are involved when considering the application of laser anemometry to the measurement of turbomachinery flowfields are discussed. Aspects of laser fringe anemometer optical design which are applicable to turbomachinery research are briefly reviewed. Application problems which are common to both laser fringe anemometry (LFA) and laser transit anemometry (LTA) such as seed particle injection, optical access to the flowfield, and measurement of rotor rotational position are covered. The efficiency of various data acquisition schemes is analyzed and issues related to data integrity and error estimation are addressed. Real-time data analysis techniques aimed at capturing flow physics in real time are discussed. Finally, data reduction and analysis techniques are discussed and illustrated using examples taken from several LFA turbomachinery applications.

  6. Laser fringe anemometry for aero engine components

    NASA Technical Reports Server (NTRS)

    Strazisar, A. J.

    1986-01-01

    Advances in flow measurement techniques in turbomachinery continue to be paced by the need to obtain detailed data for use in validating numerical predictions of the flowfield and for use in the development of empirical models for those flow features which cannot be readily modelled numerically. The use of laser anemometry in turbomachinery research has grown over the last 14 years in response to these needs. Based on past applications and current developments, this paper reviews the key issues which are involved when considering the application of laser anemometry to the measurement of turbomachinery flowfields. Aspects of laser fringe anemometer optical design which are applicable to turbomachinery research are briefly reviewed. Application problems which are common to both laser fringe anemometry (LFA) and laser transit anemometry (LTA) such as seed particle injection, optical access to the flowfield, and measurement of rotor rotational position are covered. The efficiency of various data acquisition schemes is analyzed and issues related to data integrity and error estimation are addressed. Real-time data analysis techniques aimed at capturing flow physics in real time are discussed. Finally, data reduction and analysis techniques are discussed and illustrated using examples taken from several LFA turbomachinery applications.

  7. Very low-phase noise, coherent 94GHz radar for micro-Doppler and vibrometry studies

    NASA Astrophysics Data System (ADS)

    Robertson, Duncan A.; Brooker, Graham M.; Beasley, Patrick D. L.

    2014-05-01

    Micro-Doppler and vibrometry measurements require coherent radars with low phase noise. We report the development of a novel, very low phase noise 94 GHz radar, called T-220, which offers superior performance for micro-Doppler and vibrometry studies compared with our previous work. The radar uses a combination of direct digital synthesis (DDS) chirp generation, frequency upconversion and frequency multiplication to yield very low phase noise and rapid, contiguous chirps, necessary for Doppler studies and other coherent processing applications. Dual fan beam antennas are used to achieve negligible transmit-receive leakage, with fine azimuth resolution and modest elevation coverage. The resulting PPI imagery is very high fidelity with little or no evidence of phase noise effects.

  8. A new fringeline-tracking approach for color Doppler ultrasound imaging phase unwrapping

    NASA Astrophysics Data System (ADS)

    Saad, Ashraf A.; Shapiro, Linda G.

    2008-03-01

    Color Doppler ultrasound imaging is a powerful non-invasive diagnostic tool for many clinical applications that involve examining the anatomy and hemodynamics of human blood vessels. These clinical applications include cardio-vascular diseases, obstetrics, and abdominal diseases. Since its commercial introduction in the early eighties, color Doppler ultrasound imaging has been used mainly as a qualitative tool with very little attempts to quantify its images. Many imaging artifacts hinder the quantification of the color Doppler images, the most important of which is the aliasing artifact that distorts the blood flow velocities measured by the color Doppler technique. In this work we will address the color Doppler aliasing problem and present a recovery methodology for the true flow velocities from the aliased ones. The problem is formulated as a 2D phase-unwrapping problem, which is a well-defined problem with solid theoretical foundations for other imaging domains, including synthetic aperture radar and magnetic resonance imaging. This paper documents the need for a phase unwrapping algorithm for use in color Doppler ultrasound image analysis. It describes a new phase-unwrapping algorithm that relies on the recently developed cutline detection approaches. The algorithm is novel in its use of heuristic information provided by the ultrasound imaging modality to guide the phase unwrapping process. Experiments have been performed on both in-vitro flow-phantom data and in-vivo human blood flow data. Both data types were acquired under a controlled acquisition protocol developed to minimize the distortion of the color Doppler data and hence to simplify the phase-unwrapping task. In addition to the qualitative assessment of the results, a quantitative assessment approach was developed to measure the success of the results. The results of our new algorithm have been compared on ultrasound data to those from other well-known algorithms, and it outperforms all of them.

  9. Third-Order Doppler Parameter Estimation of Bistatic Forward-Looking SAR Based on Modified Cubic Phase Function

    NASA Astrophysics Data System (ADS)

    Li, Wenchao; Yang, Jianyu; Huang, Yulin; Kong, Lingjiang

    For Doppler parameter estimation of forward-looking SAR, the third-order Doppler parameter can not be neglected. In this paper, the azimuth signal of the transmitter fixed bistatic forward-looking SAR is modeled as a cubic polynomial phase signal (CPPS) and multiple time-overlapped CPPSs, and the modified cubic phase function is presented to estimate the third-order Doppler parameter. By combining the cubic phase function (CPF) with Radon transform, the method can give an accurate estimation of the third-order Doppler parameter. Simulations validate the effectiveness of the algorithm.

  10. Further Studies Of Hot-Wire Anemometry

    NASA Technical Reports Server (NTRS)

    Mckenzie, Robert; Logan, Pamela; Bershader, Daniel

    1990-01-01

    Report discusses factors affecting readings of hot-wire anemometer in turbulent supersonic boundary layer. Represents extension of work described in "Hot-Wire Anemometry Versus Laser-Induced Fluorescence" (ARC-11802). Presents theoretical analysis of responses of hot-wire probe to changes in flow; also compares measurements by hot-wire probe with measurements of same flows by laser-induced fluorescence (LIF).

  11. Phase relationships between total electron content variations, Doppler velocity oscillations and geomagnetic pulsations

    SciTech Connect

    Liu, J.Y.; Berkey, F.T.

    1994-09-01

    The phase relationship between variations of ionospheric total electron content (TEC) and ground-level ULF geomagnetic pulsations has been examined for the advection and compression mechanisms. To determine the causal mechanism several earlier studies have examined the phase difference between oscillations of Doppler velocity in ionospherically reflected radio waves and simultaneous ULF geomagnetic pulsations. In most instances it was found that the phase relation varied from event to event. With the application of Euler`s formula this study shows that in low geomagnetic and midgeomagnetic latitudes the phase differences between variations of TEC and ULF pulsations in the northward component of the geomagnetic field due to the advection and compression mechanisms are 0{degrees} and 180{degrees}, respectively. The authors also found that TEC variations tend to lead ionospheric Doppler velocity oscillations by 90{degrees}. Furthermore, it is shown that the phase relationship between ionospheric Doppler velocity oscillations and ULF pulsations of the northward component of the geomagnetic field, caused by the advection and compression mechanisms, are functions of the scale length, frequency of ULF waves, and geomagnetic dip. 25 refs., 4 figs.

  12. Phase-coherent detection of an optical dipole force by Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Biercuk, M. J.; Uys, H.; Britton, J. W.; Vandevender, A. P.; Bollinger, J. J.

    2011-05-01

    We report phase-coherent Doppler detection of optical dipole forces using large ion crystals in a Penning trap. The technique is based on laser Doppler velocimetry using a cycling transition in $^{9}$Be$^{+}$ near 313 nm and the center-of-mass (COM) ion motional mode. The optical dipole force is tuned to excite the COM mode, and measurements of photon arrival times synchronized with the excitation potential show oscillations with a period commensurate with the COM motional frequency. Experimental results compare well with a quantitative model for a driven harmonic oscillator. This technique permits characterization of motional modes in ion crystals; the measurement of both frequency and phase information relative to the driving force is a key enabling capability -- comparable to lockin detection -- providing access to a parameter that is typically not available in time-averaged measurements. This additional information facilitates discrimination of nearly degenerate motional modes.

  13. Phase-coherent detection of an optical dipole force by Doppler velocimetry.

    PubMed

    Biercuk, M J; Uys, H; Britton, J W; Vandevender, A P; Bollinger, J J

    2011-05-23

    We report phase-coherent Doppler detection of optical dipole forces using large ion crystals in a Penning trap. The technique is based on laser Doppler velocimetry using a cycling transition in 9Be+ near 313 nm and the center-of-mass (COM) ion motional mode. The optical dipole force is tuned to excite the COM mode, and measurements of photon arrival times synchronized with the excitation potential show oscillations with a period commensurate with the COM motional frequency. Experimental results compare well with a quantitative model for a driven harmonic oscillator. This technique permits characterization of motional modes in ion crystals; the measurement of both frequency and phase information relative to the driving force is a key enabling capability--comparable to lockin detection - providing access to a parameter that is typically not available in time-averaged measurements. This additional information facilitates discrimination of nearly degenerate motional modes. PMID:21643288

  14. Doppler Radar Profiler for Launch Winds at the Kennedy Space Center (Phase 1a)

    NASA Technical Reports Server (NTRS)

    Murri, Daniel G.

    2011-01-01

    The NASA Engineering and Safety Center (NESC) received a request from the, NASA Technical Fellow for Flight Mechanics at Langley Research Center (LaRC), to develop a database from multiple Doppler radar wind profiler (DRWP) sources and develop data processing algorithms to construct high temporal resolution DRWP wind profiles for day-of-launch (DOL) vehicle assessment. This document contains the outcome of Phase 1a of the assessment including Findings, Observations, NESC Recommendations, and Lessons Learned.

  15. Phase control of probe response in a Doppler-broadened N-type four-level system

    SciTech Connect

    Fan Xijun; Liu Zhongbo; Liang Ying; Jia Kening; Tong Dianmin

    2011-04-15

    In this paper, we investigate theoretically the effect of the relative phase ({phi}) between the probe and driving fields on gain (absorption) and dispersion of the probe field in a Doppler-broadened N-type four-level system with spontaneously generated coherence from different respects. It is shown that gain (absorption) and dispersion are very sensitive to variations in the relative phase, and changing the Doppler width also has an obvious effect on the phase-dependent gain (absorption) and dispersion. When the probe and driving fields have the same propagation directions (copropagating), for the same Doppler width, the dispersion curve with {phi}={alpha} is the same as the gain (absorption) curve with {phi}={alpha}+{pi}/2; however, when the probe and driving fields have opposite propagation directions (counterpropagating), the dispersion curve and gain (absorption) curve are different and the difference becomes more considerable with an increase in Doppler width. In the co- and counterpropagating cases, gain (absorption) and dispersion always vary periodically with varying {phi}, and the period is 2{pi}. By adjusting the value of {phi}, the largest gain (absorption) and dispersion can be obtained, and a large index of refraction without absorption can be realized. Generally speaking, gain decreases with an increase in Doppler width, but by adjusting value of {phi}, at some special values of Doppler width, a larger gain than that without Doppler broadening can be obtained. Our study also shows that gain in the copropagating case is much larger than that in the counterpropagating case.

  16. Deceptive jamming for countering UWB-SAR based on Doppler frequency phase template of false target

    NASA Astrophysics Data System (ADS)

    He, Xiaodong; Tang, Bin

    2016-04-01

    A false target deceptive jamming method for countering ultra-wideband synthetic aperture radar (UWB-SAR) is proposed in this paper, which is based on dechirp processing to intercepted UWB-SAR signal and inverse dechirp to jamming signal. The jammer quadrature down-converts and dechirps the intercepted UWB-SAR signal using a linear frequency modulation (LFM) signal oscillator, which could reduce the bandwidth and sample rate of analog-to-digital converter. Then, the jammer utilises the azimuth direction Doppler frequency phase between the false target and the jammer, and backward reflection coefficient template to modulate the phase of the intercepted UWB-SAR signal, and then delayed the modulated phase and also modulated the range direction Doppler frequency phase to the that. Finally, the jammer uses LFM signal oscillator to up-convert the narrowband jamming signal in order to recover the bandwidth of the signal. Parameter errors analysis and simulation results have shown that the detected parameters and motion characteristic errors reduce the resolution and offset the expected position of the false target, but it still could obtain an expected false target image. Theoretical analysis and simulation results indicated that the jamming signal proposed in this paper could produce a false target in the UWB-SAR image, which provide a feasible method for countering UWB-SAR in real time.

  17. Signal phase estimation for measurement of respiration waveform using a microwave Doppler sensor.

    PubMed

    Noguchi, Hiroshi; Kubo, Hajime; Mori, Taketoshi; Sato, Tomomasa; Sanada, Hiromi

    2013-01-01

    This paper proposes and compares five methods for phase estimation to measure slight change of chest movement with respiration using a dual type microwave Doppler sensor. A body direction to the sensor affects the performance of the respiration measurement, because microwave reflection is sensitive to the surface direction. The phase estimation from two sensor signals is the most important part to measure respiration. Thus, we developed new five methods for phase estimation. These methods were evaluated by calculating correlation coefficients between estimated waveforms and reference ones. The results demonstrated that the phase estimation based on least square method is the best for respiration measurement with respect to both waveform estimation accuracy and calculation time. PMID:24111290

  18. A High Resolution Hydrometer Phase Classifier Based on Analysis of Cloud Radar Doppler Spectra.

    SciTech Connect

    Luke,E.; Kollias, P.

    2007-08-06

    The lifecycle and radiative properties of clouds are highly sensitive to the phase of their hydrometeors (i.e., liquid or ice). Knowledge of cloud phase is essential for specifying the optical properties of clouds, or else, large errors can be introduced in the calculation of the cloud radiative fluxes. Current parameterizations of cloud water partition in liquid and ice based on temperature are characterized by large uncertainty (Curry et al., 1996; Hobbs and Rangno, 1998; Intriery et al., 2002). This is particularly important in high geographical latitudes and temperature ranges where both liquid droplets and ice crystal phases can exist (mixed-phase cloud). The mixture of phases has a large effect on cloud radiative properties, and the parameterization of mixed-phase clouds has a large impact on climate simulations (e.g., Gregory and Morris, 1996). Furthermore, the presence of both ice and liquid affects the macroscopic properties of clouds, including their propensity to precipitate. Despite their importance, mixed-phase clouds are severely understudied compared to the arguably simpler single-phase clouds. In-situ measurements in mixed-phase clouds are hindered due to aircraft icing, difficulties distinguishing hydrometeor phase, and discrepancies in methods for deriving physical quantities (Wendisch et al. 1996, Lawson et al. 2001). Satellite-based retrievals of cloud phase in high latitudes are often hindered by the highly reflecting ice-covered ground and persistent temperature inversions. From the ground, the retrieval of mixed-phase cloud properties has been the subject of extensive research over the past 20 years using polarization lidars (e.g., Sassen et al. 1990), dual radar wavelengths (e.g., Gosset and Sauvageot 1992; Sekelsky and McIntosh, 1996), and recently radar Doppler spectra (Shupe et al. 2004). Millimeter-wavelength radars have substantially improved our ability to observe non-precipitating clouds (Kollias et al., 2007) due to their excellent

  19. Imaging and quantifying Brownian motion of micro- and nanoparticles using phase-resolved Doppler variance optical coherence tomography.

    PubMed

    Kim, Chang Soo; Qi, Wenjuan; Zhang, Jun; Kwon, Young Jik; Chen, Zhongping

    2013-03-01

    Different types and sizes of micro- and nanoparticles have been synthesized and developed for numerous applications. It is crucial to characterize the particle sizes. Traditional dynamic light scattering, a predominant method used to characterize particle size, is unable to provide depth resolved information or imaging functions. Doppler variance optical coherence tomography (OCT) measures the spectral bandwidth of the Doppler frequency shift due to the Brownian motion of the particles utilizing the phase-resolved approach and can provide quantitative information about particle size. Spectral bandwidths of Doppler frequency shifts for various sized particles were quantified and were demonstrated to be inversely proportional to the diameter of the particles. The study demonstrates the phase-resolved Doppler variance spectral domain OCT technique has the potential to be used to investigate the properties of particles in highly scattering media. PMID:23515863

  20. Measuring two-phase particle flux with a multi-frequency acoustic Doppler profiler.

    PubMed

    Wilson, Gregory W; Hay, Alex E

    2015-12-01

    A methodology is developed and tested for simultaneously extracting time-resolved one-dimensional profiles of the mass-concentration and velocity of two different particle types in a mixed suspension, using a multi-frequency pulse-to-pulse coherent Doppler instrument. The technique involves inversion of a model for frequency-dependent acoustic backscatter amplitude and phase. Results are presented from a laboratory settling column experiment, measuring a mixture of polystyrene beads (slowly-settling, strongly-scattering) and glass beads (quickly-settling, weakly-scattering) in a vertical pipe section. PMID:26723335

  1. A note on the phase relationship between ULF geomagnetic pulsations and HF-Doppler oscillations owing to the compressional mechanism

    NASA Astrophysics Data System (ADS)

    Liu, J. Y.

    Experimental scientists have indicated that an in-phase relationship between measurements of ionospheric Doppler velocity oscillations and ULF pulsations in the northward component of the geomagnetic field on the ground results from the compressional mechanism. A careful study of the theoretical models developed previously, however, shows that in low and middle geomagnetic latitudes, owing to the compressional mechanism the ionospheric Doppler velocity oscillations lead the ULF pulsations in the northward component of the geomagnetic field at ground level by 90 deg.

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

    PubMed

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

    1992-09-01

    Hot film anemometry, x-configuration probes were used in two experiments to evaluate their effectiveness at measurement of limb velocity. Data from tests with a probe attached to the end of a pendulum establish that the hot films measure velocity in the swing phase within 0.098 ms-1. The kinetic energy per unit mass of the pendulum was predicted within +/- 0.005 m2 s-2, from the measured velocity. In gait experiments with one human subject at speeds greater than 0.25 ms-1, the hot film anemometer and a video system predicted speeds within 0.083 ms-1. The hot film data are electronic signals that are easily stored and processed. The results from these experiments demonstrate that hot film anemometry is an effective and efficient method for direct measurement and analysis of the limb velocity. PMID:1405563

  3. Adaptive anisotropic diffusion for noise reduction of phase images in Fourier domain Doppler optical coherence tomography.

    PubMed

    Xia, Shaoyan; Huang, Yong; Peng, Shizhao; Wu, Yanfeng; Tan, Xiaodi

    2016-08-01

    Phase image in Fourier domain Doppler optical coherence tomography offers additional flow information of investigated samples, which provides valuable evidence towards accurate medical diagnosis. High quality phase images are thus desirable. We propose a noise reduction method for phase images by combining a synthetic noise estimation criteria based on local noise estimator (LNE) and distance median value (DMV) with anisotropic diffusion model. By identifying noise and signal pixels accurately and diffusing them with different coefficients respectively and adaptive iteration steps, we demonstrated the effectiveness of our proposed method in both phantom and mouse artery images. Comparison with other methods such as filtering method (mean, median filtering), wavelet method, probabilistic method and partial differential equation based methods in terms of peak signal-to-noise ratio (PSNR), equivalent number of looks (ENL) and contrast-to-noise ratio (CNR) showed the advantages of our method in reserving image energy and removing noise. PMID:27570687

  4. Adaptive anisotropic diffusion for noise reduction of phase images in Fourier domain Doppler optical coherence tomography

    PubMed Central

    Xia, Shaoyan; Huang, Yong; Peng, Shizhao; Wu, Yanfeng; Tan, Xiaodi

    2016-01-01

    Phase image in Fourier domain Doppler optical coherence tomography offers additional flow information of investigated samples, which provides valuable evidence towards accurate medical diagnosis. High quality phase images are thus desirable. We propose a noise reduction method for phase images by combining a synthetic noise estimation criteria based on local noise estimator (LNE) and distance median value (DMV) with anisotropic diffusion model. By identifying noise and signal pixels accurately and diffusing them with different coefficients respectively and adaptive iteration steps, we demonstrated the effectiveness of our proposed method in both phantom and mouse artery images. Comparison with other methods such as filtering method (mean, median filtering), wavelet method, probabilistic method and partial differential equation based methods in terms of peak signal-to-noise ratio (PSNR), equivalent number of looks (ENL) and contrast-to-noise ratio (CNR) showed the advantages of our method in reserving image energy and removing noise. PMID:27570687

  5. Estimating laser transit anemometry noise performance capabilities

    NASA Technical Reports Server (NTRS)

    Humphreys, William M., Jr.; Hunter, William W., Jr.

    1989-01-01

    A Monte Carlo based LTA (laser transit anemometry) simulation system has been used to perform a detailed evaluation of a set of processing algorithms proposed by Mayo and Smart (1984) for the extraction of two-dimensional flow parameters from LTA data sets collected in a plane normal to the optical axis of the system. The present evaluation includes data ensembles containing 0.0, 5.0, 10.0, and 20.0 percent background noise levels in the constituent correlograms. The results of these evaluations indicate that for turbulence levels of up to 10.0 percent the processing system is able to extract the necessary flow parameters accurately from the LTA data sets. Mean velocity magnitude and flow angle are measurable to within 2.0 percent for turbulence intensity levels of up to 14.0 percent. Standard deviations are measureable to within 10.0 percent over a turbulence range of 3.0-10.0 percent at the same noise levels. These results indicate that the algorithms described have applications in fluid flow surveys.

  6. Analysis of the ideal phase-Doppler System: Limitations imposed by the single-particle constraint

    SciTech Connect

    Edwards, C.F.; Marx, K.D.

    1991-06-01

    This paper explores the effects of particles statistics on the ability of a phase-Doppler system (or any single-particle diagnostic) to make accurate measurements of complex particle flows. This is accomplished by analyzing the response of an ideal phase-Doppler system to a postulated particle flux. The ideal system defined here senses particles of all sizes and velocities with perfect accuracy, but is subject to one constraint: in order for a measurement to be considered valid there must be only one particle in the probe volume at a time. A consequence of this constraint is that the measured flux of particles is similar to the true flux, but reduced by passage through two stages of filters. The first rejects particles for insufficient spacing and is controlled by a spatial Poisson process, while the second rejects particles for excessive residence time and is driven by a temporal Poisson process. The key filter parameters are the expected values of the number of particles in the probe volume and the number of particles entering the probe region during the residence time of a previous particle. Only if these values are kept below order 10{sup {minus}2} can the measured joint distribution function, flux rate, and derived quantities, be assumed to reflect the true nature of the flow. 8 refs., 30 figs., 2 tabs.

  7. Analysis of counting errors in the phase/Doppler particle analyzer

    NASA Technical Reports Server (NTRS)

    Oldenburg, John R.

    1987-01-01

    NASA is investigating the application of the Phase Doppler measurement technique to provide improved drop sizing and liquid water content measurements in icing research. The magnitude of counting errors were analyzed because these errors contribute to inaccurate liquid water content measurements. The Phase Doppler Particle Analyzer counting errors due to data transfer losses and coincidence losses were analyzed for data input rates from 10 samples/sec to 70,000 samples/sec. Coincidence losses were calculated by determining the Poisson probability of having more than one event occurring during the droplet signal time. The magnitude of the coincidence loss can be determined, and for less than a 15 percent loss, corrections can be made. The data transfer losses were estimated for representative data transfer rates. With direct memory access enabled, data transfer losses are less than 5 percent for input rates below 2000 samples/sec. With direct memory access disabled losses exceeded 20 percent at a rate of 50 samples/sec preventing accurate number density or mass flux measurements. The data transfer losses of a new signal processor were analyzed and found to be less than 1 percent for rates under 65,000 samples/sec.

  8. (Study of flow properties of wet solids using laser induced photochemical anemometry)

    SciTech Connect

    Falco, B.

    1990-07-23

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves that use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  9. (Study of flow properties of wet solids using laser induced photochemical anemometry)

    SciTech Connect

    Falco, B.

    1990-04-03

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  10. (Study of flow properties of wet solids using laser induced photochemical anemometry)

    SciTech Connect

    Falco, B.; Nocera, D.

    1990-01-23

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  11. (Study of flow properties of wet solids using laser induced photo chemical anemometry)

    SciTech Connect

    Falco, B.

    1992-04-09

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  12. 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.

  13. Comparison of twin-fluid atomizers using a phase Doppler analyser

    SciTech Connect

    Zaremba, Matouš E-mail: y145527@stud.fme.vutbr.cz E-mail: jicha@fme.vutbr.cz; Malý, Milan E-mail: y145527@stud.fme.vutbr.cz E-mail: jicha@fme.vutbr.cz; Jedelský, Jan E-mail: y145527@stud.fme.vutbr.cz E-mail: jicha@fme.vutbr.cz; Jícha, Miroslav E-mail: y145527@stud.fme.vutbr.cz E-mail: jicha@fme.vutbr.cz

    2014-08-06

    The quality of atomization is crucial in combustion processes, especially in cases of highly viscous fuels. Twin-fluid atomizers have been developed for atomizing heavy and waste fuels and they have undergone significant development in the last decades. Nevertheless, in order to design an atomizer for a given industrial application, a comparison of different atomizers at similar operating conditions is required. This paper focuses on the description and comparison of two internally mixed twin-fluid atomizers at the same operating regime. The Y-jet and the Inverse-effervescent atomizers were examined. The phase-Doppler analyzer was used to measure the velocity and size of droplets in a radial profile in the spray. Data were sorted out into classes with respect to the droplet size and the motion analysis was done for both atomizers.

  14. Effects of non-spherical drops on a phase Doppler spray analyzer

    NASA Technical Reports Server (NTRS)

    Alexander, D. R.; Wiles, K. J.; Schaub, S. A.; Seeman, M. P.

    1985-01-01

    A phase/Doppler spray analyzer (P/DSA) and a laser imaging system was used to study the response of a P/DSA to nonspherical particles. Methanol particles with an aspect ratio ranging from 0.7 to 1.4 were used in this investigation. Results indicated that the P/DSA was quite sensitive to particle shape. A Berglund-Liu generator was used to produce particles of 98 microns (volumetric diameter). The P/DSA instrument measured particle sizes ranging from 142 microns for a particle of aspect ratio 0.7, to 84 microns for an aspect ratio of 1.4. Particle diameters based on averaged x and y diameters for the laser imaging system ranged from 95 microns to 92 microns over the same range of aspect ratios.

  15. Hydrodynamic Nuclei Concentration Technique in Cavitation Research and Comparison to Phase-Doppler Measurements

    NASA Astrophysics Data System (ADS)

    Ebert, Eric; Kröger, Willfried; Damaschke, Nils

    2015-12-01

    Small particles, especially bubbles in the micro-meter range, influence the cavitation of the propellers. The prediction of cavitation inception and water quality measurements are important in cavitation research. The Hydrodynamic Nuclei Concentration (HDNC) technique can be used for reliable bubble concentration measurements in fluid flows. The HDNC technique bases on the analysis of scattered light from the cavitation nuclei in the water. The HDNC technique can distinguish between bubbles and solid particles. The particle type classification is important, because the number concentration of solid particles is often much higher than the nuclei concentration in cavitation tunnels and in seawater. Verification experiments show, that the HDNC technique reaches similar capabilities in number concentration estimation as Phase Doppler (PD) technique in much shorter acquisition time.

  16. Tricuspid and mitral regurgitation detected by color flow Doppler in the acute phase of Kawasaki disease

    SciTech Connect

    Suzuki, A.; Kamiya, T.; Tsuchiya, K.; Sato, I.; Arakaki, Y.; Kohata, T.; Ono, Y.

    1988-02-01

    Valvular lesions in the acute phase of Kawasaki disease were studied in 19 children. The patients were intensively observed by color flow Doppler every day from the day of hospitalization up to 12 days after the onset of the disease and 2 or more times a week thereafter, for up to 28 days. Mitral regurgitation (MR) was found in 9 patients (47%) and tricuspid regurgitation (TR) in 10 (53%). MRs were of transient type and confirmed from 7.5 +/- 1.6 (mean +/- standard deviation) to 13.1 +/- 6.5 days after the onset of the disease. Both types of valvular regurgitation were mild. The direction of regurgitation was from the center of valvular coaptation toward the posterior wall of the atrium. Neither valvular prolapse nor valvular deformity was noted. In patients with MR, left ventricular ejection fraction on M-mode echocardiography was significantly lower in the acute phase than in the convalescent phase of the disease (p less than 0.05). Using gallium-67 scintigram, the positive uptake of the isotope was noted in 7 (88%) of 8 patients with MR, but not found at all in 8 patients free of MR. These results suggest that MR and TR are often transient in the acute phase of Kawasaki disease and could be attributed to myocarditis.

  17. Mechanism Analysis of the Inverse Doppler Effect in Two-Dimensional Photonic Crystal based on Phase Evolution.

    PubMed

    Jiang, Qiang; Chen, Jiabi; Wang, Yan; Liang, Binming; Hu, Jinbing; Zhuang, Songlin

    2016-01-01

    Although the inverse Doppler effect has been observed experimentally at optical frequencies in photonic crystal with negative effective refractive index, its explanation is based on phenomenological theory rather than a strict theory. Elucidating the physical mechanism underlying the inverse Doppler shift is necessary. In this article, the primary electrical field component in the photonic crystal that leads to negative refraction was extracted, and the phase evolution of the entire process when light travels through a moving photonic crystal was investigated using static and dynamic finite different time domain methods. The analysis demonstrates the validity of the use of np (the effective refractive index of the photonic crystal in the light path) in these calculations, and reveals the origin of the inverse Doppler effect in photonic crystals. PMID:27102211

  18. Mechanism Analysis of the Inverse Doppler Effect in Two-Dimensional Photonic Crystal based on Phase Evolution

    NASA Astrophysics Data System (ADS)

    Jiang, Qiang; Chen, Jiabi; Wang, Yan; Liang, Binming; Hu, Jinbing; Zhuang, Songlin

    2016-04-01

    Although the inverse Doppler effect has been observed experimentally at optical frequencies in photonic crystal with negative effective refractive index, its explanation is based on phenomenological theory rather than a strict theory. Elucidating the physical mechanism underlying the inverse Doppler shift is necessary. In this article, the primary electrical field component in the photonic crystal that leads to negative refraction was extracted, and the phase evolution of the entire process when light travels through a moving photonic crystal was investigated using static and dynamic finite different time domain methods. The analysis demonstrates the validity of the use of np (the effective refractive index of the photonic crystal in the light path) in these calculations, and reveals the origin of the inverse Doppler effect in photonic crystals.

  19. Mechanism Analysis of the Inverse Doppler Effect in Two-Dimensional Photonic Crystal based on Phase Evolution

    PubMed Central

    Jiang, Qiang; Chen, Jiabi; Wang, Yan; Liang, Binming; Hu, Jinbing; Zhuang, Songlin

    2016-01-01

    Although the inverse Doppler effect has been observed experimentally at optical frequencies in photonic crystal with negative effective refractive index, its explanation is based on phenomenological theory rather than a strict theory. Elucidating the physical mechanism underlying the inverse Doppler shift is necessary. In this article, the primary electrical field component in the photonic crystal that leads to negative refraction was extracted, and the phase evolution of the entire process when light travels through a moving photonic crystal was investigated using static and dynamic finite different time domain methods. The analysis demonstrates the validity of the use of np (the effective refractive index of the photonic crystal in the light path) in these calculations, and reveals the origin of the inverse Doppler effect in photonic crystals. PMID:27102211

  20. 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

  1. 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.

  2. A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar

    PubMed Central

    Hyun, Eugin; Jin, Young-Seok; Lee, Jong-Hun

    2016-01-01

    For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW) radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT) is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method. PMID:26805835

  3. A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar.

    PubMed

    Hyun, Eugin; Jin, Young-Seok; Lee, Jong-Hun

    2016-01-01

    For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW) radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT) is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method. PMID:26805835

  4. Calibration of Direct Velocimetry Using Hot Wire Anemometry

    NASA Technical Reports Server (NTRS)

    Holland, Michael L.; DeSilva, Upul P.; Johnson, Joseph A., III

    1997-01-01

    We studied the functionality of the IFA300 Hot Wire Anemometry system and its feasibility for the calibration of Direct Estimator Velocimetry (DEV) using Laser Induced Florescence (LIF). The experimental setup consisted of a single-wire hot wire probe measuring one component of velocity, the anemometry computational hardware and software, an HP oscilloscope, and a table fan to produce a simple flow with fluctuations. Measurements were taken at several points in the stream wise and transverse directions in the flow and various parameters recorded such as mean velocities temperature, turbulence intensities, skewness coefficients and flatness coefficients. The IFA300 software also allowed us to perform statistical manipulations such as spectrum analysis on velocities samples and correlation. Utilization of data files, also produced by the anemometry software, and post analysis were performed to produce graphical representations of turbulent intensity versus probe position and a flow field velocity profile. We concluded that the IFA300 Hot Wire Anemometry system is a reliable and functional method for calibration of DEV using LIF. Our future intentions are to set up a test chamber such that both velocity measurement techniques can be applied simultaneously, thus the calibration.

  5. Application of laser anemometry in turbine engine research

    NASA Technical Reports Server (NTRS)

    Seasholtz, R. G.

    1983-01-01

    The application of laser anemometry to the study of flow fields in turbine engine components is reviewed. Included are discussions of optical configurations, seeding requirements, electronic signal processing, and data processing. Some typical results are presented along with a discussion of ongoing work.

  6. Application of laser anemometry in turbine engine research

    NASA Technical Reports Server (NTRS)

    Seasholtz, R. G.

    1982-01-01

    The application of laser anemometry to the study of flow fields in turbine engine components is reviewed. Included are discussions of optical configurations, seeding requirements, electronic signal processing, and data processing. Some typical results are presented along with a discussion of ongoing work.

  7. Hot-wire anemometry in hypersonic helium flow

    NASA Technical Reports Server (NTRS)

    Wagner, R. D.; Weinstein, L. M.

    1974-01-01

    Hot-wire anemometry techniques are described that have been developed and used for hypersonic-helium-flow studies. The short run time available dictated certain innovations in applying conventional hot-wire techniques. Some examples are given to show the application of the techniques used. Modifications to conventional equipment are described, including probe modifications and probe heating controls.

  8. First 3-Way Lunar Radio Phase Ranging and Doppler Experiment in Chang'E-3 Lander Mission

    NASA Astrophysics Data System (ADS)

    PING, J.; Meng, Q.; Tang, G.; Jian, N.; Wang, Z.; Li, W.; Chen, C.; Wang, M.; Wang, M.; Lu, Y.; Yu, Q.; Mao, Y.; Miao, C.; Lei, Y.; Shu, F.; Cao, J.

    2014-04-01

    Radio science experiments have been involved in all of the Chinese lunar missions with different research objectives. In Chang'E-3 landing mission, a 3-way open loop lunar radio phase ranging and Doppler technique was suggested and tested. This technique is modified and updated from early multi-channel oneway Doppler deep space tracking technique developed for Chinese Mars mission Yinghuo-1. In the 1st preliminary experiments, we obtained 1sps continuous phase ranging data before and after the successful landing period, with a resolution of 0.5 millimeter or better. This method, called Lunar Radio Phase Ranging (LRPR) can be a new space geodetic technique to measure the station position, earth tide and rotation, lunar orbit, tide and liberation, by means of independent observation, or to work together with Lunar Laser Ranging. Also, it can be used in future Mars mission.

  9. Using Doppler spectra to separate hydrometeor populations and analyze ice precipitation in multilayered mixed-phase clouds

    SciTech Connect

    Rambukkange, Mahlon P.; Verlinde, J.; Eloranta, E. W.; Flynn, Connor J.; Clothiaux, Eugene E.

    2011-01-31

    Multimodality of cloud radar Doppler spectra is used to partition cloud particle phases and to separate distinct ice populations in the radar sample volume, thereby facilitating analysis of individual ice showers in multilayered mixed-phase clouds. A 35-GHz cloud radar located at Barrow, Alaska, during the Mixed-Phase Arctic Cloud Experiment collected the Doppler spectra. Data from a pair of collocated depolarization lidars confirmed the presence of two liquid cloud layers reported in this study. Surprisingly, both of these cloud layers were embedded in ice precipitation yet maintained their liquid. Our spectral separation of the ice precipitation yielded two distinct ice populations: ice initiated within the two liquid cloud layers and ice precipitation formed in higher cloud layers. Comparisons of ice fall velocity versus radar reflectivity relationships derived for distinct showers reveal that a single relationship might not properly represent the ice showers during this period.

  10. Exploiting Cloud Radar Doppler Spectra of Mixed-Phase Clouds during ACCEPT Field Experiment to Identify Microphysical Processes

    NASA Astrophysics Data System (ADS)

    Kalesse, H.; Myagkov, A.; Seifert, P.; Buehl, J.

    2015-12-01

    Cloud radar Doppler spectra offer much information about cloud processes. By analyzing millimeter radar Doppler spectra from cloud-top to -base in mixed-phase clouds in which super-cooled liquid-layers are present we try to tell the microphysical evolution story of particles that are present by disentangling the contributions of the solid and liquid particles to the total radar returns. Instead of considering vertical profiles, dynamical effects are taken into account by following the particle population evolution along slanted paths which are caused by horizontal advection of the cloud. The goal is to identify regions in which different microphysical processes such as new particle formation (nucleation), water vapor deposition, aggregation, riming, or sublimation occurr. Cloud radar measurements are supplemented by Doppler lidar and Raman lidar observations as well as observations with MWR, wind profiler, and radio sondes. The presence of super-cooled liquid layers is identified by positive liquid water paths in MWR measurements, the vertical location of liquid layers (in non-raining systems and below lidar extinction) is derived from regions of high-backscatter and low depolarization in Raman lidar observations. In collocated cloud radar measurements, we try to identify cloud phase in the cloud radar Doppler spectrum via location of the Doppler peak(s), the existence of multi-modalities or the spectral skewness. Additionally, within the super-cooled liquid layers, the radar-identified liquid droplets are used as air motion tracer to correct the radar Doppler spectrum for vertical air motion w. These radar-derived estimates of w are validated by independent estimates of w from collocated Doppler lidar measurements. A 35 GHz vertically pointing cloud Doppler radar (METEK MIRA-35) in linear depolarization (LDR) mode is used. Data is from the deployment of the Leipzig Aerosol and Cloud Remote Observations System (LACROS) during the Analysis of the Composition of

  11. Doppler indices of gas phase formation in hypobaric environments: Time-intensity analysis

    NASA Technical Reports Server (NTRS)

    Powell, Michael R.

    1991-01-01

    A semi-quantitative method to analyze decompression data is described. It possesses the advantage that it allows a graded response to decompression rather than the dichotomous response generally employed. A generalized critical volume (C-V), or stoichiometric time-dependent equilibrium model is examined that relates the constant of the equation P sub i equals m P sub f plus b to variable tissue supersaturation and gas washout terms. The effects of the tissue ratio on gas phase formation indicate that a decreased ratio yields fewer individuals with Doppler detectable gas bubbles, but those individuals still present with Spencer Grade 3 or 4. This might indicate a local collapse of tissue saturation. The individuals with Grade 3 or 4 could be at risk for type 2 decompression sickness by transpulmonic arterialization. The primary regulator of the problems of decompression sickness is the reduction of local supersaturation, presumably governed by the presence and number of gas micronuclei. It is postulated that a reduction in these nuclei will favor a low incidence of decompression sickness in microgravity secondary to hypokinesia and adynamia.

  12. Advances in Doppler OCT

    PubMed Central

    Liu, Gangjun; Chen, Zhongping

    2014-01-01

    We review the principle and some recent applications of Doppler optical coherence tomography (OCT). The advances of the phase-resolved Doppler OCT method are described. Functional OCT algorithms which are based on an extension of the phase-resolved scheme are also introduced. Recent applications of Doppler OCT for quantification of flow, imaging of microvasculature and vocal fold vibration, and optical coherence elastography are briefly discussed. PMID:24443649

  13. [Study of flow properties of wet solids using laser induced photochemical anemometry]. Quarterly technical progress report, April--June 1990

    SciTech Connect

    Falco, B.

    1990-07-23

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves that use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  14. [Study of flow properties of wet solids using laser induced photochemical anemometry]. Quarterly technical progress report, January--March 1990

    SciTech Connect

    Falco, B.

    1990-04-03

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  15. [Study of flow properties of wet solids using laser induced photochemical anemometry]. Quarterly technical progress report, October--December 1990

    SciTech Connect

    Falco, B.; Nocera, D.

    1990-01-23

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  16. Procedure for Determining Turbulence Length Scales Using Hotwire Anemometry

    NASA Technical Reports Server (NTRS)

    El-Gabry, Lamyaa A.; Thurman, Douglas R.; Poinsatte, Philip E.

    2014-01-01

    Hotwire anemometers are used to measure instantaneous velocity from which the mean velocity and the velocity fluctuation can be determined. Using a hotwire system, it is possible to deduce not only the velocity components and their fluctuation but to also analyze the energy spectra and from that the turbulence length scales. In this experiment, hotwire anemometry is used to measure the flow field turbulence for an array of film cooling holes. The objective of this paper is to document the procedure that is used to reduce the instantaneous velocity measurements to determine the turbulence length scales using data from the film-cooling experiments to illustrate the procedure.

  17. Comparison of laser transit anemometry data analysis techniques

    NASA Technical Reports Server (NTRS)

    Humphreys, William M., Jr.; Gartrell, Luther R.

    1991-01-01

    Two techniques for the extraction of two-dimensional flow information from laser transit anemometry (LTA) data sets are presented and compared via a simulation study and experimental investigation. The methods are a probability density function (PDF) estimation technique and a marginal distribution analysis technique. The simulation study builds on the results of previous work and provides a quantification of the accuracy of both techniques for various LTA data acquisition scenarios. The experimental comparison consists of using an LTA system to survey the flow downstream of a turbulence generator in a small low-speed wind tunnel. The collected data sets are analyzed and compared.

  18. Sonic anemometry to measure natural ventilation in greenhouses.

    PubMed

    López, Alejandro; Valera, Diego Luis; Molina-Aiz, Francisco

    2011-01-01

    The present work has developed a methodology for studying natural ventilation in Mediterranean greenhouses by means of sonic anemometry. In addition, specific calculation programmes have been designed to enable processing and analysis of the data recorded during the experiments. Sonic anemometry allows us to study the direction of the airflow at all the greenhouse vents. Knowing through which vents the air enters and leaves the greenhouse enables us to establish the airflow pattern of the greenhouse under natural ventilation conditions. In the greenhouse analysed in this work for Poniente wind (from the southwest), a roof vent designed to open towards the North (leeward) could allow a positive interaction between the wind and stack effects, improving the ventilation capacity of the greenhouse. The cooling effect produced by the mass of turbulent air oscillating between inside and outside the greenhouse at the side vents was limited to 2% (for high wind speed, u(o) ≥ 4 m s(-1)) reaching 36.3% when wind speed was lower (u(o) = 2 m s(-1)). PMID:22163728

  19. Sonic Anemometry to Measure Natural Ventilation in Greenhouses

    PubMed Central

    López, Alejandro; Valera, Diego Luis; Molina-Aiz, Francisco

    2011-01-01

    The present work has developed a methodology for studying natural ventilation in Mediterranean greenhouses by means of sonic anemometry. In addition, specific calculation programmes have been designed to enable processing and analysis of the data recorded during the experiments. Sonic anemometry allows us to study the direction of the airflow at all the greenhouse vents. Knowing through which vents the air enters and leaves the greenhouse enables us to establish the airflow pattern of the greenhouse under natural ventilation conditions. In the greenhouse analysed in this work for Poniente wind (from the southwest), a roof vent designed to open towards the North (leeward) could allow a positive interaction between the wind and stack effects, improving the ventilation capacity of the greenhouse. The cooling effect produced by the mass of turbulent air oscillating between inside and outside the greenhouse at the side vents was limited to 2% (for high wind speed, uo ≥ 4 m s−1) reaching 36.3% when wind speed was lower (uo = 2 m s−1). PMID:22163728

  20. Innovative Coal Solids-Flow Monitoring and Measurement Using Phase-Doppler and Mie Scattering Techniques

    SciTech Connect

    Stephen Seong Lee

    2010-01-19

    Fuel flow to individual burners is complicated and difficult to determine on coal fired boilers, since coal solids were transported in a gas suspension that is governed by the complex physics of two-phase flow. The objectives of the project were the measurements of suspended coal solids-flows in the simulated test conditions. Various extractive methods were performed manually and can give only a snapshot result of fuel distribution. In order to measure particle diameter & velocity, laser based phase-Doppler particle analyzer (PDPA) and particle image velocimetry (PIV) were carefully applied. Statistical methods were used to analyze particle characteristics to see which factors have significant effect. The transparent duct model was carefully designed and fabricated for the laser-based-instrumentation of solids-flow monitoring (LISM). The experiments were conducted with two different kinds of particles with four different particle diameters. The particle types were organic particles and saw dust particles with the diameter range of 75-150 micron, 150-250 micron, 250-355 micron and 355-425 micron. The densities of the particles were measured to see how the densities affected the test results. Also the experiment was conducted with humid particles and fog particles. To generate humid particles, the humidifier was used. A pipe was connected to the humidifier to lead the particle flow to the intersection of the laser beam. The test results of the particle diameter indicated that, the mean diameter of humid particles was between 6.1703 microns and 6.6947 microns when the humid particle flow was low. When the humid particle flow was high, the mean diameter was between 6.6728 microns and 7.1872 microns. The test results of the particle mean velocity indicated that the mean velocity was between 1.3394 m/sec and 1.4556 m/sec at low humid particle flow. When the humid particle flow was high, the mean velocity was between 1.5694 m/sec and 1.7856 m/sec. The Air Flow Module, TQ

  1. Reduction of phase-induced intensity noise in a fiber-based coherent Doppler lidar using polarization control.

    PubMed

    Rodrigo, Peter John; Pedersen, Christian

    2010-03-01

    Optimization of signal-to-noise ratio is an important aspect in the design of optical heterodyne detection systems such as a coherent Doppler lidar (CDL). In a CDL, optimal performance is achieved when the noise in the detector signal is dominated by local oscillator shot-noise. Most modern CDL systems are built using rugged and cost-efficient fiber optic components. Unfortunately, leakage signals such as residual reflections inherent within fiber components (e.g. circulator) can introduce phase-induced intensity noise (PIIN) to the Doppler spectrum in a CDL. Such excess noise may be a few orders of magnitude above the shot-noise level within the relevant CDL frequency bandwidth--corrupting the measurement of typically weak backscattered signals. In this study, observation of PIIN in a fiber-based CDL with a master-oscillator power-amplifier tapered semiconductor laser source is reported. Furthermore, we experimentally demonstrate what we believe is a newly proposed method using a simple polarization scheme to reduce PIIN by more than an order of magnitude. PMID:20389545

  2. Application of an integrated phase Doppler interferometer/rainbow thermometer/point-diffraction interferometer for characterizing burning droplets

    SciTech Connect

    Sankar, S.V.; Buermann, D.H.; Ibrahim, K.M.; Bachalo, W.D.

    1994-12-31

    A laser-based, nonintrusive diagnostic instrument has been developed for simultaneously measuring the velocity, size, temperature (refractive index) of burning droplets, and the gas-phase temperature field surrounding the burning droplet. The developed diagnostic is suitable for experimental studies involving single droplet/droplet array combustion. The size and velocity of the droplets are measured using the well-established phase Doppler interferometric technique. The temperature/refractive index of the droplets are determined by measuring the primary rainbow location with a linear charge coupled device (CCD) array. The gas-phase temperature distribution is inferred from interferograms obtained with point-diffraction interferometry (PDI). The three diagnostic techniques have been completely integrated to yield a single diagnostic instrument. New algorithms have been developed for extracting and normalizing the interferograms from noisy digital images. Methods for unambiguous phase unwrapping were also identified. The integrated diagnostic was tested by applying it to the case of isolated burning n-heptane droplets in motion. Using a combined experimental/theoretical approach, it was possible to extract the radial temperature profile of the gas phase surrounding the droplet in addition to the droplet velocity size, and temperature. The integrated diagnostic tool has significant potential for studying fundamental droplet combustion processes and for validating state-of-the-art droplet/spray combustion models.

  3. The Sphere Anemometer - A Fast Alternative to Cup Anemometry

    NASA Astrophysics Data System (ADS)

    Heißelmann, Hendrik; Hölling, Michael; Peinke, Joachim

    The main problem of cup anemometry is the different response time for increasing and decreasing wind velocities due to its moment of inertia. This results in an overestimation of wind speed under turbulent wind conditions, the so-called over-speeding. Additionally, routine calibrations are necessary due to the wear of bearings. Motivated by these problems the sphere anemometer, a new simple and robust sensor for wind velocity measurements without moving parts, was developed at the University of Oldenburg. In contrast to other known thrust-based sensors, the sphere anemometer uses the light pointer principle to detect the deflection of a bending tube caused by the drag force acting on a sphere mounted at its top. This technique allows the simultaneous determination of wind speed and direction via a two-dimensional position sensitive detector.

  4. Capacitive Ultrasonic Transducer Development for Acoustic Anemometry on Mars

    NASA Astrophysics Data System (ADS)

    Leonard-Pugh, Eurion; Wilson, C.; Calcutt, S.; Davis, L.

    2012-10-01

    Previous Mars missions have used either mechanical or thermal anemometry techniques. The moving parts of mechanical anemometers are prone to damage during launch and landing and their inertia makes them unsuited for turbulence studies. Thermal anemometers have been used successfully on Mars but are difficult to calibrate and susceptible to varying ambient temperatures. In ultrasonic anemometry, wind speed and sound speed are calculated from two-way time-of-flight measurements between pairs of transducers; three pairs of transducers are used to return a 3-D wind vector. These high-frequency measurements are highly reliable and immune from drift. Piezo-electric ultrasonic anemometers are widely used on Earth due to their full-range accuracy and high measurement frequency. However these transducers have high acoustic impedances and would not work on Mars. We are developing low-mass capacitive ultrasonic transducers for Mars missions which have significantly lower acoustic impedances and would therefore have a much stronger coupling to the Martian atmosphere. These transducers consist of a metallised polymer film pulled taught against a machined metal backplane. The film is drawn towards the backplane by a DC bias voltage. A varying signal is used on top of the DC bias to oscillate the film; generating acoustic waves. This poster will look at the operation of such sensors and the developments necessary to operate the devices under Martian conditions. Transducer performance is determined primarily by two elements; the front film and the backplane. The sensitivity of the transducer is affected by the thickness of the front film; as well as the diameter, curvature and roughness of the metal backplane. We present data on the performance of the sensors and instrument design considerations including signal shapes and transducer arrangements.

  5. Performance of the Phase Doppler Particle Analyzer icing cloud droplet sizing probe in the NASA Lewis Icing Research Tunnel

    NASA Technical Reports Server (NTRS)

    Rudoff, R. C.; Bachalo, E. J.; Bachalo, W. D.; Oldenburg, J. R.

    1992-01-01

    The design, development, and testing of an icing cloud droplet sizing probe based upon the Phase Doppler Particle Analyzer (PDPA) are discussed. This probe is an in-situ laser interferometry based single particle measuring device capable of determining size distributions. The probe is designed for use in harsh environments such as icing tunnels and natural icing clouds. From the measured size distribution, Median Volume Diameter (MVD) and Liquid Water Content (LWC) may be determined. Both the theory of measurement and the mechanical aspects of the probe design and development are discussed. The MVD results from the probe are compared to an existing calibration based upon different instruments in a series of tests in the NASA Lewis Icing Research Tunnel. Agreement between the PDPA probe and the existing calibration is close for MVDs between 15 to 30 microns, but the PDPA results are considerably smaller for MVDs under 15 microns.

  6. Liquid water content measurements using the Phase Doppler Particle Analyzer in the NASA Lewis Icing Research Tunnel

    NASA Technical Reports Server (NTRS)

    Rudoff, R. C.; Bachalo, E. J.; Bachalo, W. D.; Oldenburg, J. R.

    1993-01-01

    The performance of a Phase Doppler Particle Analyzer (PDPA) based icing probe suitable for use in icing tunnels and airborne applications is assessed. The instrument is shown to accurately and repeatably measure liquid water content (LWC) to within better than 20 percent of the nominal expected value in the NASA Lewis IRT. This was seen to be true over a wide range of tunnel operating conditions. The principles used by the PDPA for MVD and LWC determination are discussed. Calibration curves for the IRT median volume diameter are also determined and compared to the existing calibration determined via the PMS instruments. As has been shown in previous work, the PDPA is quite repeatable. The results are typically 3 to 5 microns smaller than the existing calibrations for a given run condition. Reasons for these differences are also discussed.

  7. Performance Of A Doppler-Corrected MDPSK Detector

    NASA Technical Reports Server (NTRS)

    Nguyen, Tien M.; Jedrey, Thomas C.; Hinedi, Sami; Agan, Martin J.

    1994-01-01

    Report presents theoretical analysis of effect of rate of change of Doppler shift of received multiple-differential-phase-shift-keyed (MDPSK) radio signal on performance of Doppler-corrected differential detector. In particular detector, phase of received signal corrected for Doppler shift by use of Doppler estimator designed to operate in presence of negligibly small Doppler rate.

  8. Phase relation between Pi2-associated ionospheric Doppler velocity and magnetic pulsations observed at a midlatitude MAGDAS station

    NASA Astrophysics Data System (ADS)

    Ikeda, Akihiro; Yumoto, Kiyohumi; Uozumi, Teiji; Shinohara, Manabu; Nozaki, Kenro; Yoshikawa, Akimasa; Bychkov, V. V.; Shevtsov, B. M.

    2010-02-01

    We examined the correlation between nighttime Pi2 pulsations detected simultaneously by a frequency modulated continuous wave (FM-CW) (HF) radar and by a ground magnetometer, both located at a midlatitude (L = 2.05) Magnetic Data Acquisition System station. Eighty-three Pi2 events were observed during the 43 day period from 23 September 2006 to 4 November 2006. The variations of the ground magnetic H component and ionospheric Doppler velocity (V*) exhibited high coherence for 80% of the 83 Pi2 events, for about a half of which the H and V* variations have the same dominant frequency. For such events, V* led H by 90° in phase, in the midnight sector of 2230-0300 LT. The average Ey (east-west electric field) amplitude derived from V* is 0.27 mV/m. The 90° phase delay was not found for the five events that were observed near dusk and dawn. The phase relation of H and V* for Pi2s in the midnight sector may be explained in terms of the radial standing structure of compressional waves, i.e., cavity mode oscillation.

  9. Time-resolved flowmetering of gas-liquid two-phase pipe flow by ultrasound pulse Doppler method

    NASA Astrophysics Data System (ADS)

    Murai, Yuichi; Tasaka, Yuji; Takeda, Yasushi

    2012-03-01

    Ultrasound pulse Doppler method is applied for componential volumetric flow rate measurement in multiphase pipe flow consisted of gas and liquid phases. The flowmetering is realized with integration of measured velocity profile over the cross section of the pipe within liquid phase. Spatio-temporal position of interface is detected also with the same ultrasound pulse, which further gives cross sectional void fraction. A series of experimental demonstration was shown by applying this principle of measurement to air-water two-phase flow in a horizontal tube of 40 mm in diameter, of which void fraction ranges from 0 to 90% at superficial velocity from 0 to 15 m/s. The measurement accuracy is verified with a volumetric type flowmeter. We also analyze the accuracy of area integration of liquid velocity distribution for many different patterns of ultrasound measurement lines assigned on the cross section of the tube. The present method is also identified to be pulsation sensor of flow rate that fluctuates with complex gas-liquid interface behavior.

  10. 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.

  11. [Study of flow properties of wet solids using laser induced photo chemical anemometry]. Quarterly technical progress report, July--September 1991

    SciTech Connect

    Falco, B.

    1992-04-09

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  12. Direct Blood Flow Measurements in a Free RPE-Choroid Graft with Phase-Resolved Doppler OCT

    PubMed Central

    van Zeeburg, Elsbeth J. T.; Braaf, Boy; Cereda, Matteo G.; van Meurs, Jan C.; de Boer, Johannes F.

    2015-01-01

    Purpose We directly demonstrated the revascularization in a free retinal pigment epithelium (RPE)-choroid graft with direct blood flow detection by experimental phase-resolved Doppler optical coherence tomography (PRD-OCT). Methods Seven patients with age-related macular degeneration underwent an RPE-choroid graft translocation in a prospective institutional cohort study. Spectral domain optical coherence tomography (SD-OCT) was used to measure the revascularization stage. With PRD-OCT the presence of flow was imaged postoperatively. Results The PRD-OCT confirmed flow in three patients when SD-OCT indicated the afferent vessel ingrowth stage, and in all seven patients when the SD-OCT indicated the efferent vessel ingrowth stage. Conclusions The PRD-OCT study was able to detect the presence of blood flow in a free RPE-choroid graft. The PRD-OCT findings directly confirmed the revascularization that was otherwise based on the more circumstantial evidence provided by SD-OCT images and angiography. Translational Relevance The use of both techniques to monitor the revascularization process in a free graft in patients are an interesting example of replacing more invasive by noninvasive techniques. There is potential future use of PRD-OCT for the visualization of vascularization patterns in other pathologies. PMID:25599010

  13. Comparison of digital holographic interferometry and constant temperature anemometry for measurement of temperature field in fluid

    NASA Astrophysics Data System (ADS)

    Doleček, Roman; Psota, Pavel; Lédl, Vít.; Vít, Tomáś; Dančová, Petra; Kopecký, Václav

    2015-05-01

    The presented paper shows possibility of using digital holographic interferometry (DHI) for temperature field measurement in moving fluids. This method uses a modified Twymann-Green setup having double sensitivity instead of commonly used Mach-Zehnder type of interferometer in order to obtain sufficient phases change of the field. On the other hand this setup is not light efficient as Mach-Zehnder interferometer. For measurement of the fast periodical phenomenon is not necessary to use always the high speed camera. One can consider this field to coherent phenomenon. With employing one digital camera synchronized to periodic field and external triggered one can capture whole period of the phenomenon. However the projections form one viewing direction of asymmetrical temperature field maybe misguided. Hence for sufficient examination of the asymmetrical field one should capture a large number of the phenomenon's projections from different viewing directions. This projections are later used for 3D tomographic reconstruction of the whole temperature field and its time evolution. One of the commonly used method for temperature field measurement in moving fluids is hot wire method - constant temperature anemometry (CTA). In contrast to whole field measurement of DHI it is an invasive point temperature measurement method. One of the limiting factor of using CTA in moving fluids is frequency of temperature changes. This changes should not exceed 1 kHz. This limitation could be overcome by using of optical methods such as DHI. The results of temperature field measurement achieved by both method are compared in the paper.

  14. Doppler echocardiography

    SciTech Connect

    Labovitz, A.J.; Williams, G.A.

    1988-01-01

    The authors are successful in presenting a basic book on clinical quantitative Doppler echocardiography. It is not intended to be a comprehensive text, but it does cover clinical applications in a succinct fashion. Only the more common diseases in the adult are considered. The subjects are presented logically and are easy to comprehend. The illustrations are good, and the book is paperbound. The basic principles of Doppler echocardiography are presented briefly. The book ends with chapters on left ventricular function (stroke volume and cardiac output), congenital heart disease, and color Doppler echo-cardiography. There are numerous references and a good glossary and index.

  15. Basic ideas and concepts in hot wire anemometry: an experimental approach for introductory physics students

    NASA Astrophysics Data System (ADS)

    El Abed, Mohamed

    2016-01-01

    The purpose of hot wire anemometry is to measure the speed of an air stream. The classical method is based on the measure of the value of a temperature dependant resistor inserted in a Wheatstone bridge (Lomas 1986 Fundamentals of Hot Wire Anemometry (Cambridge: Cambridge University Press)). In this paper we exhibit the physics behind this method and show that by using a wire whose resistance does not vary on the field of temperature explored (from 20 °C to 200 °C), it is however possible to make accurate measurements. Finally, limitations of the method are discussed.

  16. The Effect of Doppler Frequency Shift, Frequency Offset of the Local Oscillators, and Phase Noise on the Performance of Coherent OFDM Receivers

    NASA Technical Reports Server (NTRS)

    Xiong, Fuqin; Andro, Monty

    2001-01-01

    This paper first shows that the Doppler frequency shift affects the frequencies of the RF carrier, subcarriers, envelope, and symbol timing by the same percentage in an Orthogonal Frequency Division Multiplexing (OFDM) signal or any other modulated signals. Then the SNR degradation of an OFDM system due to Doppler frequency shift, frequency offset of the local oscillators and phase noise is analyzed. Expressions are given and values for 4-, 16-, 64-, and 256-QAM OFDM systems are calculated and plotted. The calculations show that the Doppler shift of the D3 project is about 305 kHz, and the degradation due to it is about 0.01 to 0.04 dB, which is negligible. The degradation due to frequency offset and phase noise of local oscillators will be the main source of degradation. To keep the SNR degradation under 0.1 dB, the relative frequency offset due to local oscillators must be below 0.01 for the 16 QAM-OFDM. This translates to an offset of 1.55 MHz (0.01 x 155 MHz) or a stability of 77.5 ppm (0.01 x 155 MHz/20 GHz) for the DI project. To keep the SNR degradation under 0.1 dB, the relative linewidth (0) due to phase noise of the local oscillators must be below 0.0004 for the 16 QAM-OFDM. This translates to a linewidth of 0.062 MHz (0.0004 x 155 MHz) of the 20 GHz RIF carrier. For a degradation of 1 dB, beta = 0.04, and the linewidth can be relaxed to 6.2 MHz.

  17. 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.

  18. Measurement of average density and relative volumes in a dispersed two-phase fluid

    DOEpatents

    Sreepada, Sastry R.; Rippel, Robert R.

    1992-01-01

    An apparatus and a method are disclosed for measuring the average density and relative volumes in an essentially transparent, dispersed two-phase fluid. A laser beam with a diameter no greater than 1% of the diameter of the bubbles, droplets, or particles of the dispersed phase is directed onto a diffraction grating. A single-order component of the diffracted beam is directed through the two-phase fluid and its refraction is measured. Preferably, the refracted beam exiting the fluid is incident upon a optical filter with linearly varing optical density and the intensity of the filtered beam is measured. The invention can be combined with other laser-based measurement systems, e.g., laser doppler anemometry.

  19. Application of laser anemometry to cryogenic wind tunnels

    NASA Technical Reports Server (NTRS)

    Hunter, W. W., Jr.; Honaker, W. C.; Gartrell, L. R.

    1983-01-01

    The installation and tests conducted with the laser Doppler and transit anemometer in the 0.3-Meter Transonic Cryogenic Tunnel are described. Using residual particulates in the flow field, a series of free stream velocity measurements were conducted which agreed to within 1-percent of predicted values for a range of Mach numbers, 0.2 to 0.85, and temperatures, 100 to 250 K. Measurements about a shock wave provided an estimate of scattering particulate size of 4 microns or less. The particle concentration is approximately 3 x 10 to the 5th to 1.6 x 10 to the 6th/cu m. Necessary isolation of the plenum wall windows from ambient air with slightly positive pressure of dry nitrogen gas to prevent condensation on the window surface was achieved. This was accomplished through the use of large enclosures fixed to the tunnel wall. A second method used an additional sheet of thin plate glass to create the dry gas pocket next to the plenum window. The installation of a laser anemometer in the National Transonic Facility is examined. The laser transit anemometer has been tentatively selected for the initial entry because of its compact laser-optics package.

  20. Interfacial shear modeling in two-phase annular flow

    SciTech Connect

    Kumar, R.; Edwards, D.P.

    1996-07-01

    A new interfacial shear stress model called the law of the interface model, based on the law of the wall approach in turbulent flows, has been developed and locally applied in a fully developed, adiabatic, two-phase annular flow in a duct. Numerical results have been obtained using this model in conjunction with other models available in the literature that are required for the closure of the continuity and momentum equations. These results have been compared with droplet velocity data (using laser Doppler velocimetry and hot film anemometry), void fraction data (using gamma densitometry) and pressure drop data obtained in a R-134A refrigerant test facility. Droplet velocity results match the experimental data well, however, the prediction of the void fraction is less accurate. The poor prediction of void fraction, especially for the low void fraction cases, appears to be due to the lack of a good mechanistic model for entrainment.

  1. Doppler tracking of planetary spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.

    1992-01-01

    This article concerns the measurement of Doppler shift on microwave links that connect planetary spacecraft with the Deep Space Network. Such measurements are made by tracking the Doppler effect with phase-locked loop receivers. A description of equipment and techniques as well as a summary of the appropriate mathematical models are given. The two-way Doppler shift is measured by transmitting a highly-stable microwave (uplink) carrier from a ground station, having the spacecraft coherently transpond this carrier, and using a phase-locked loop receiver at the ground station to track the returned (downlink) carrier. The largest sources of measurement error are usually plasma noise and thermal noise. The plasma noise, which may originate in the ionosphere or the solar corona, is discussed; and a technique to partially calibrate its effect, involving the use of two simultaneous downlink carriers that are coherently related, is described. Range measurements employing Doppler rate-aiding are also described.

  2. Planar Doppler Velocimetry for Large-Scale Wind Tunnel Applications

    NASA Technical Reports Server (NTRS)

    McKenzie, Robert L.

    1998-01-01

    Planar Doppler Velocimetry (PDV) concepts using a pulsed laser are described and the obtainable minimum resolved velocities in large-scale wind tunnels are evaluated. Velocity-field measurements are shown to be possible at ranges of tens of meters and with single pulse resolutions as low as 2 m/s. Velocity measurements in the flow of a low-speed, turbulent jet are reported that demonstrate the ability of PDV to acquire both average velocity fields and their fluctuation amplitudes, using procedures that are compatible with large-scale facility operations. The advantages of PDV over current Laser Doppler Anemometry and Particle Image Velocimetry techniques appear to be significant for applications to large facilities.

  3. Technical Training on High-Order Spectral Analysis and Thermal Anemometry Applications

    NASA Technical Reports Server (NTRS)

    Maslov, A. A.; Shiplyuk, A. N.; Sidirenko, A. A.; Bountin, D. A.

    2003-01-01

    The topics of thermal anemometry and high-order spectral analyses were the subject of the technical training. Specifically, the objective of the technical training was to study: (i) the recently introduced constant voltage anemometer (CVA) for high-speed boundary layer; and (ii) newly developed high-order spectral analysis techniques (HOSA). Both CVA and HOSA are relevant tools for studies of boundary layer transition and stability.

  4. Azimuthal Doppler Effect in Optical Vortex Spectroscopy

    NASA Astrophysics Data System (ADS)

    Aramaki, Mitsutoshi; Yoshimura, Shinji; Toda, Yasunori; Morisaki, Tomohiro; Terasaka, Kenichiro; Tanaka, Masayoshi

    2015-11-01

    Optical vortices (OV) are a set of solutions of the paraxial Helmholtz equation in the cylindrical coordinates, and its wave front has a spiral shape. Since the Doppler shift is caused by the phase change by the movement in a wave field, the observer in the OV, which has the three-dimensional structured wave front, feels a three-dimensional Doppler effect. Since the multi-dimensional Doppler components are mixed into a single Doppler spectrum, development of a decomposition method is required. We performed a modified saturated absorption spectroscopy to separate the components. The OV and plane wave are used as a probe beam and pump beam, respectively. Although the plane-wave pump laser cancels the z-direction Doppler shift, the azimuthal Doppler shift remains in the saturated dip. The spatial variation of the dip width gives the information of the azimuthal Doppler shift. The some results of optical vortex spectroscopy will be presented.

  5. Left ventricular dyssynchrony assessed by two three-dimensional imaging modalities: phase analysis of gated myocardial perfusion SPECT and tri-plane tissue Doppler imaging

    PubMed Central

    Ajmone Marsan, Nina; Henneman, Maureen M.; Chen, Ji; Ypenburg, Claudia; Dibbets, Petra; Ghio, Stefano; Bleeker, Gabe B.; Stokkel, Marcel P.; van der Wall, Ernst E.; Tavazzi, Luigi; Garcia, Ernest V.

    2007-01-01

    Purpose To compare left ventricular (LV) dyssynchrony assessment by phase analysis from gated myocardial perfusion SPECT (GMPS) with LV dyssynchrony assessment by tri-plane tissue Doppler imaging (TDI). Baseline LV dyssynchrony assessed with standard deviation (SD) of time-to-peak systolic velocity of 12 LV segments (Ts-SD) with TDI has proven to be a powerful predictor of response to CRT. Information on LV dyssynchrony can also be provided by GMPS with phase analysis of regional LV maximal count changes throughout the cardiac cycle. Methods Forty heart failure patients, referred for evaluation of potential eligibility for CRT, underwent both 3D echocardiography, with tri-plane TDI, and resting GMPS. From tri-plane TDI, Ts-SD was used as a validated parameter of LV dyssynchrony and compared with different indices (histogram bandwidth, phase SD, histogram skewness and kurtosis) derived from phase analysis of GMPS. Results Histogram bandwidth and phase SD showed good correlation with Ts-SD (r=0.77 and r=0.74, p<0.0001, respectively). Patients with substantial LV dyssynchrony assessed with tri-plane TDI (Ts-SD ≥33 ms) had also significantly higher values of histogram bandwidth and phase SD. Conclusions The results of this study support the use of phase analysis by GMPS to evaluate LV dyssynchrony. Histogram bandwidth and phase SD showed the best correlation with Ts-SD assessed with tri-plane TDI and appeared the most optimal variables for assessment of LV dyssynchrony with GMPS. PMID:17874098

  6. Ultrahigh-phase-stable swept source based on KTN electro-optic deflector towards Doppler OCT and polarization-sensitive OCT

    NASA Astrophysics Data System (ADS)

    Sasaki, Yuzo; Fujimoto, Masatoshi; Yagi, Shogo; Yamagishi, Shogo; Toyoda, Seiji; Kobayashi, Junya

    2014-03-01

    We have developed a wavelength-swept laser source with ultrahigh phase stability. Potassium tantalate niobate (KTa1- xNbxO3, KTN) single crystal was employed as an electro-optic deflector for a high-speed wavelength sweep in the laser cavity. A 200-kHz sweep rate was obtained with an average output power of 20 mW and a coherence length of 8 mm at the wavelength range exceeding 100 nm. Since the electro-optic effect in KTN crystal has a fast response of more than 500 MHz, the deflection of a KTN deflector can follow the applied voltage precisely. Considering this advantage, we demonstrated a swept source with ultrahigh phase stability in the 1.3 μm wavelength range as a result of the low-jitter operation of the deflector. The standard deviation of measured timing jitters between adjacent A-lines was confirmed to be less than 78 ps, which corresponds to a phase difference of 0.017 radians at a path difference of 1.5 mm of a Michelson interferometer. The phase stability can be increased with an improved voltage source because the timing jitter is still mainly caused by the voltage applied to KTN. In addition to realizing the phase stability of neighboring A-lines, the long-term stable sweep was demonstrated by eliminating the refresh operation that was previously needed to prevent output power decay. The ultrahigh phase stability we achieved makes our swept source promising for Doppler OCT and polarization-sensitive OCT.

  7. Doppler tracking

    NASA Astrophysics Data System (ADS)

    Thomas, Christopher Jacob

    This study addresses the development of a methodology using the Doppler Effect for high-resolution, short-range tracking of small projectiles and vehicles. Minimal impact on the design of the moving object is achieved by incorporating only a transmitter in it and using ground stations for all other components. This is particularly useful for tracking objects such as sports balls that have configurations and materials that are not conducive to housing onboard instrumentation. The methodology developed here uses four or more receivers to monitor a constant frequency signal emitted by the object. Efficient and accurate schemes for filtering the raw signals, determining the instantaneous frequencies, time synching the frequencies from each receiver, smoothing the synced frequencies, determining the relative velocity and radius of the object and solving the nonlinear system of equations for object position in three dimensions as a function of time are developed and described here.

  8. Zero to π Continuously Controllable Cross Phase Modulation in Doppler Broadened N-Type Electromagnetically Induced Transparency Medium

    PubMed Central

    Li, R. B.; Zhu, C. J.; Deng, L.; Hagley, E. W.

    2016-01-01

    We demonstrate an observation of zero to π continuously controllable cross-phase-modulation based on N-type electromagnetically induced transparency scheme in a room-temperature 87Rb vapor. We theoretically and experimentally show that the signal field acquires a π phase shift compared with the reference light in the presence of the phase-control field. Using the method of the optical Mach-Zehnder interferometer, we demonstrate that a zero to π continuously controllable phase gate can be built by modulating the phase-control field. In addition, our theoretical calculation agrees well with the experimental observation, and the results presented in this work hold the potential applications for the orthogonal polarization/vector gate in the quantum information processing.

  9. Doppler Optical Coherence Tomography

    PubMed Central

    Leitgeb, Rainer A.; Werkmeister, René M.; Blatter, Cedric; Schmetterer, Leopold

    2014-01-01

    Optical Coherence Tomography (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood velocity and blood flow from tissues. A common problem with the technique is that the Doppler angle is not known and several approaches have been realized to obtain absolute velocity and flow data from the retina. Additional studies are required to elucidate which of these techniques is most promising. In the recent years, however, several groups have shown that data can be obtained with high validity and reproducibility. In addition, several groups have published values for total retinal blood flow. Another promising application relates to non-invasive angiography. As compared to standard techniques such as fluorescein and indocyanine-green angiography the technique offers two major advantages: no dye is required and depth resolution is required is provided. As such Doppler OCT has the potential to improve our abilities to diagnose and monitor ocular vascular diseases. PMID:24704352

  10. Doppler optical coherence tomography.

    PubMed

    Leitgeb, Rainer A; Werkmeister, René M; Blatter, Cedric; Schmetterer, Leopold

    2014-07-01

    Optical Coherence Tomography (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood velocity and blood flow from tissues. A common problem with the technique is that the Doppler angle is not known and several approaches have been realized to obtain absolute velocity and flow data from the retina. Additional studies are required to elucidate which of these techniques is most promising. In the recent years, however, several groups have shown that data can be obtained with high validity and reproducibility. In addition, several groups have published values for total retinal blood flow. Another promising application relates to non-invasive angiography. As compared to standard techniques such as fluorescein and indocyanine-green angiography the technique offers two major advantages: no dye is required and depth resolution is required is provided. As such Doppler OCT has the potential to improve our abilities to diagnose and monitor ocular vascular diseases. PMID:24704352

  11. 4-D flow magnetic resonance imaging: blood flow quantification compared to 2-D phase-contrast magnetic resonance imaging and Doppler echocardiography

    PubMed Central

    Gabbour, Maya; Schnell, Susanne; Jarvis, Kelly; Robinson, Joshua D.; Markl, Michael

    2015-01-01

    Background Doppler echocardiography (echo) is the reference standard for blood flow velocity analysis, and two-dimensional (2-D) phase-contrast magnetic resonance imaging (MRI) is considered the reference standard for quantitative blood flow assessment. However, both clinical standard-of-care techniques are limited by 2-D acquisitions and single-direction velocity encoding and may make them inadequate to assess the complex three-dimensional hemodynamics seen in congenital heart disease. Four-dimensional flow MRI (4-D flow) enables qualitative and quantitative analysis of complex blood flow in the heart and great arteries. Objectives The objectives of this study are to compare 4-D flow with 2-D phase-contrast MRI for quantification of aortic and pulmonary flow and to evaluate the advantage of 4-D flow-based volumetric flow analysis compared to 2-D phase-contrast MRI and echo for peak velocity assessment in children and young adults. Materials and methods Two-dimensional phase-contrast MRI of the aortic root, main pulmonary artery (MPA), and right and left pulmonary arteries (RPA, LPA) and 4-D flow with volumetric coverage of the aorta and pulmonary arteries were performed in 50 patients (mean age: 13.1±6.4 years). Four-dimensional flow analyses included calculation of net flow and regurgitant fraction with 4-D flow analysis planes similarly positioned to 2-D planes. In addition, 4-D flow volumetric assessment of aortic root/ascending aorta and MPA peak velocities was performed and compared to 2-D phase-contrast MRI and echo. Results Excellent correlation and agreement were found between 2-D phase-contrast MRI and 4-D flow for net flow (r=0.97, P<0.001) and excellent correlation with good agreement was found for regurgitant fraction (r= 0.88, P<0.001) in all vessels. Two-dimensional phase-contrast MRI significantly underestimated aortic (P= 0.032) and MPA (P<0.001) peak velocities compared to echo, while volumetric 4-D flow analysis resulted in higher (aortic: P=0

  12. Hot-wire anemometry for in-flight measurement of aircraft wake vortices

    NASA Technical Reports Server (NTRS)

    Jacobsen, R. A.

    1977-01-01

    A development program has demonstrated that hot-wire anemometry can be used successfully on an aircraft in flight to make measurements of wake vortices produced by another aircraft. The probe, whose wires were made of platinum/rhodium, 10 microns in diameter, provides unambiguous results for inflow angles less than about 35 deg. off the probe axis. The high frequency response capability of the hot-wire system allows detailed measurement of the flow structure, and the study of aircraft hazards associated with wake turbulence.

  13. Flow distribution in a roller jet bit determined from hot-wire anemometry measurements

    SciTech Connect

    Gavignet, A.A.; Bradbury, L.J.; Quetier, F.P.

    1987-03-01

    In current practice, the optimization of drilling hydraulics consists of the selection of nozzle sizes that maximize either jet impact or hydraulic power at the nozzle. But what is required for a real optimization is the knowledge of the hydraulic forces available for cleaning at the rock face, not at the nozzle. This paper shows the results of hot-wire anemometry experiments that provide insight into the flow distribution in a jet bit. Direct measurements of the flow field, including turbulence levels, are reported and discussed.

  14. Development of a generalized theoretical model for the response of a phase/doppler measurement system to arbitrarily oriented fibers illuminated by gaussian beams.

    PubMed

    Schaub, S A; Lock, J A; Naqwi, A A

    1998-11-20

    We present a generalized theoretical model for the response of the phase/Doppler (P/D) measurement system to light scattered by cylindrical fibers. This theoretical model is valid for arbitrary fiber diameters and refractive indices, for Gaussian incident beams, and it accounts for arbitrary fiber orientations, fiber positions, and effects that are due to the two-dimensional receivers. The generalized P/D computer model (GPDCM) is the extension of an earlier study by the authors, combining past P/D simulation methodology with recent developments in modeling light scattering by tilted cylindrical fibers. A fortran computer program that implements the GPDCM theoretical development was written and tested against known P/D results and physical expectations. To illustrate the capabilities of the GPDCM, we present computation results, comparing the effect of fiber tilt, fiber position, and receiver aperture on the performance of P/D systems configured in backscatter and sidescatter arrangements. Calculations show that the effects of fiber tilt and position are most pronounced in the backscatter P/D arrangement, resulting in broadening of the measured phase distribution. The calculated mean phase shifts, however, were found to be essentially independent of the above factors. Computational results also showed that the effect of fiber tilt and position on phase-distribution measurements can be reduced through proper choice of aperture shape and by imposition of threshold criteria on measurable signal characteristics such as the amplitude ratio and visibilities. The GPDCM provides a computational tool that will be valuable in the design, optimization, and evaluation of P/D fiber measurement systems. PMID:18301627

  15. Identifying and discriminating phase transitions along decaying shocks with line imaging Doppler interferometric velocimetry and streaked optical pyrometry

    NASA Astrophysics Data System (ADS)

    Millot, Marius

    2016-01-01

    Ultrafast line-imaging velocity interferometer system for any reflector and streaked optical pyrometry are now commonly used to obtain high precision equation of state and electronic transport data under dynamic compression at major high energy density science facilities. We describe a simple way to improve distinguishing phase transformation signatures from other signals when monitoring decaying shock waves. The line-imaging capability of these optical diagnostics offers additional supporting evidence to the assignment of particular anomalies—such as plateaus or reversals—to the occurrence of a phase transition along the Hugoniot. We illustrate the discussion with two example datasets collected during laser driven shock compression of quartz and stishovite.

  16. Thermography and Sonic Anemometry to Analyze Air Heaters in Mediterranean Greenhouses

    PubMed Central

    López, Alejandro; Valera, Diego L.; Molina-Aiz, Francisco; Peña, Araceli

    2012-01-01

    The present work has developed a methodology based on thermography and sonic anemometry for studying the microclimate in Mediterranean greenhouses equipped with air heaters and polyethylene distribution ducts to distribute the warm air. Sonic anemometry allows us to identify the airflow pattern generated by the heaters and to analyze the temperature distribution inside the greenhouse, while thermography provides accurate crop temperature data. Air distribution by means of perforated polyethylene ducts at ground level, widely used in Mediterranean-type greenhouses, can generate heterogeneous temperature distributions inside the greenhouse when the system is not correctly designed. The system analyzed in this work used a polyethylene duct with a row of hot air outlet holes (all of equal diameter) that expel warm air toward the ground to avoid plant damage. We have observed that this design (the most widely used in Almería's greenhouses) produces stagnation of hot air in the highest part of the structure, reducing the heating of the crop zone. Using 88 kW heating power (146.7 W·m−2) the temperature inside the greenhouse is maintained 7.2 to 11.2 °C above the outside temperature. The crop temperature (17.6 to 19.9 °C) was maintained above the minimum recommended value of 10 °C. PMID:23202025

  17. Non-contact diagnostic system for sleep apnea-hypopnea syndrome based on amplitude and phase analysis of thoracic and abdominal Doppler radars.

    PubMed

    Kagawa, Masayuki; Tojima, Hirokazu; Matsui, Takemi

    2016-05-01

    Full-night polysomnography (PSG) has been recognized as the gold standard test for sleep apnea-hypopnea syndrome (SAHS). However, PSG examinees are physically restrained for the full night by many contact sensors and obtrusive connecting cables, inducing mental stress. We developed a non-contact SAHS diagnostic system that can detect apneic events without inducing stress in monitored individuals. Two Doppler radars were installed beneath the mattress to measure the vibrations of the chest and abdomen, respectively. Our system determines apnea and hypopnea events when the radar output amplitude decreases by <20 and 70 %, respectively, of the amplitude of a normal breath (without SAHS events). Additionally, we proposed a technique that detects paradoxical movements by focusing on phase differences between thoracic and abdominal movements, and were able to identify three types of sleep apnea: obstructive, central, and mixed. Respiratory disturbance indexes obtained showed a higher correlation (r = 94 %) with PSG than with pulse oximetry (r = 89 %). When predicting the severity of SAHS with an apnea-hypopnea index (AHI) of >15/h or >30/h using PSG as a reference, the radar system achieved a sensitivity of 96 and 90 %, and a specificity of 100 and 79 % with an AHI of >15/h and >30/h, respectively. The proposed radar system can be used as an alternative to the current airflow sensor, and to chest and abdomen belts for apnea-hypopnea evaluation. PMID:26307200

  18. Non-invasive classification of gas–liquid two-phase horizontal flow regimes using an ultrasonic Doppler sensor and a neural network

    NASA Astrophysics Data System (ADS)

    Musa Abbagoni, Baba; Yeung, Hoi

    2016-08-01

    The identification of flow pattern is a key issue in multiphase flow which is encountered in the petrochemical industry. It is difficult to identify the gas–liquid flow regimes objectively with the gas–liquid two-phase flow. This paper presents the feasibility of a clamp-on instrument for an objective flow regime classification of two-phase flow using an ultrasonic Doppler sensor and an artificial neural network, which records and processes the ultrasonic signals reflected from the two-phase flow. Experimental data is obtained on a horizontal test rig with a total pipe length of 21 m and 5.08 cm internal diameter carrying air-water two-phase flow under slug, elongated bubble, stratified-wavy and, stratified flow regimes. Multilayer perceptron neural networks (MLPNNs) are used to develop the classification model. The classifier requires features as an input which is representative of the signals. Ultrasound signal features are extracted by applying both power spectral density (PSD) and discrete wavelet transform (DWT) methods to the flow signals. A classification scheme of ‘1-of-C coding method for classification’ was adopted to classify features extracted into one of four flow regime categories. To improve the performance of the flow regime classifier network, a second level neural network was incorporated by using the output of a first level networks feature as an input feature. The addition of the two network models provided a combined neural network model which has achieved a higher accuracy than single neural network models. Classification accuracies are evaluated in the form of both the PSD and DWT features. The success rates of the two models are: (1) using PSD features, the classifier missed 3 datasets out of 24 test datasets of the classification and scored 87.5% accuracy; (2) with the DWT features, the network misclassified only one data point and it was able to classify the flow patterns up to 95.8% accuracy. This approach has demonstrated the

  19. Doppler-corrected differential detection system

    NASA Technical Reports Server (NTRS)

    Simon, Marvin K. (Inventor); Divsalar, Dariush (Inventor)

    1991-01-01

    Doppler in a communication system operating with a multiple differential phase-shift-keyed format (MDPSK) creates an adverse phase shift in an incoming signal. An open loop frequency estimation is derived from a Doppler-contaminated incoming signal. Based upon the recognition that, whereas the change in phase of the received signal over a full symbol contains both the differentially encoded data and the Doppler induced phase shift, the same change in phase over half a symbol (within a given symbol interval) contains only the Doppler induced phase shift, and the Doppler effect can be estimated and removed from the incoming signal. Doppler correction occurs prior to the receiver's final output of decoded data. A multiphase system can operate with two samplings per symbol interval at no penalty in signal-to-noise ratio provided that an ideal low pass pre-detection filter is employed, and two samples, at 1/4 and 3/4 of the symbol interval T sub s, are taken and summed together prior to incoming signal data detection.

  20. High-speed laser anemometry based on spectrally resolved Rayleigh scattering

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.

    1991-01-01

    Laser anemometry in unseeded flows based on the measurement of the spectrum of Rayleigh scattered laser light is reviewed. The use of molecular scattering avoids the well known problems (particle lag, biasing effects, seed generation, seed injection) of seeded flows. The fundamental limits on velocity measurement accuracy are determined using maximum likelihood methods. Measurement of the Rayleigh spectrum with scanning Fabry-Perot interferometers is analyzed and accuracy limits are established for both single pass and multipass configurations. Multipass configurations have much higher selectivity and are needed for measurements where there is a large amount of excess noise caused by stray laser light. It is shown that Rayleigh scattering is particularly useful for supersonic and hypersonic flows. The results of the analysis are compared with measurements obtained with a Rayleigh scattering diagnostic developed for study of the exhaust plume of a small hydrogen-oxygen rocket, where the velocities are in the range of 1000 to 5000 m/sec.

  1. Evaluation of concepts and methods for extraction of flow parameters from laser transit anemometry data

    NASA Technical Reports Server (NTRS)

    Humphreys, W. M., Jr.; Hunter, W. W., Jr.

    1988-01-01

    A Monte-Carlo type simulation system was developed to test concepts and associated algorithms proposed by Mayo and Smart (1984) for the extraction of two-dimensional flow parameters from laser transit anemometry data sets. The Monte-Carlo LTA simulation program models a flow field as well as the sample volume geometry of the LTA system, thereby permitting simulation of two-dimensional data acquisition in a three-dimensional flow field. The results of these tests on the proposed processing concepts suggest that the instrument is capable of measuring mean velocities to less than +0.15 percent error and flow angles to less then +0.3 percent for turbulence intensities of up to 15.0 percent.

  2. Turbulence measurements in hypersonic boundary layers using constant-temperature anemometry and Reynolds stress measurements in hypersonic boundary layers

    NASA Technical Reports Server (NTRS)

    Spina, Eric F.

    1995-01-01

    The primary objective in the two research investigations performed under NASA Langley sponsorship (Turbulence measurements in hypersonic boundary layers using constant temperature anemometry and Reynolds stress measurements in hypersonic boundary layers) has been to increase the understanding of the physics of hypersonic turbulent boundary layers. The study began with an extension of constant-temperature thermal anemometry techniques to a Mach 11 helium flow, including careful examinations of hot-wire construction techniques, system response, and system calibration. This was followed by the application of these techniques to the exploration of a Mach 11 helium turbulent boundary layer (To approximately 290 K). The data that was acquired over the course of more than two years consists of instantaneous streamwise mass flux measurements at a frequency response of about 500 kHz. The data are of exceptional quality in both the time and frequency domain and possess a high degree of repeatability. The data analysis that has been performed to date has added significantly to the body of knowledge on hypersonic turbulence, and the data reduction is continuing. An attempt was then made to extend these thermal anemometry techniques to higher enthalpy flows, starting with a Mach 6 air flow with a stagnation temperature just above that needed to prevent liquefaction (To approximately 475 F). Conventional hot-wire anemometry proved to be inadequate for the selected high-temperature, high dynamic pressure flow, with frequent wire breakage and poor system frequency response. The use of hot-film anemometry has since been investigated for these higher-enthalpy, severe environment flows. The difficulty with using hot-film probes for dynamic (turbulence) measurements is associated with construction limitations and conduction of heat into the film substrate. Work continues under a NASA GSRP grant on the development of a hot film probe that overcomes these shortcomings for hypersonic

  3. DOPPLER WEATHER SYSTEM

    SciTech Connect

    Berlin, Gary J.

    2002-08-05

    The SRS Doppler Weather System consists of a Doppler Server, A Master Server (also known as the Weather Server), several Doppler Slave Servers, and client-side software program called the Doppler Radar Client. This system is used to display near rel-time images taken from the SRS Weather Center's Doppler Radar computer. The Doppler Server is software that resides on the SRS Doppler Computer. It gathers raw data, 24-bit color weather images via screen scraping ever five minutes as requested by the Master Server. The Doppler Server then reduces the 24-bit color images to 8-bit color using a fixed color table for analysis and compression. This preserves the fidelity of the image color and arranges the colors in specific order for display. At the time of color reduction, the white color used for the city names on the background images are remapped to a different index (color) of white that the white on the weather scale. The Weather Server places a time stamp on the image, then compresses the image and passes it to all Doppler Slave servers. Each of the Doppler Slave servers mainitain a circular buffer of the eight most current images representing the last 40 minutes of weather data. As a new image is added, the oldest drops off. The Doppler Radar Client is an optional install program for any site-wide workstation. When a Client session is started, the Client requests Doppler Slave server assignment from the Master Server. Upon its initial request to the Slave Server, the Client obtains all eight current images and maintains its own circular buffer, updating its images every five minutes as the Doppler Slave is updated. Three background reference images are stored as part of the Client. The Client brings up the appropriate background image, decompresses the doppler data, and displays the doppler data on the background image.

  4. DOPPLER WEATHER SYSTEM

    Energy Science and Technology Software Center (ESTSC)

    2002-08-05

    The SRS Doppler Weather System consists of a Doppler Server, A Master Server (also known as the Weather Server), several Doppler Slave Servers, and client-side software program called the Doppler Radar Client. This system is used to display near rel-time images taken from the SRS Weather Center's Doppler Radar computer. The Doppler Server is software that resides on the SRS Doppler Computer. It gathers raw data, 24-bit color weather images via screen scraping ever fivemore » minutes as requested by the Master Server. The Doppler Server then reduces the 24-bit color images to 8-bit color using a fixed color table for analysis and compression. This preserves the fidelity of the image color and arranges the colors in specific order for display. At the time of color reduction, the white color used for the city names on the background images are remapped to a different index (color) of white that the white on the weather scale. The Weather Server places a time stamp on the image, then compresses the image and passes it to all Doppler Slave servers. Each of the Doppler Slave servers mainitain a circular buffer of the eight most current images representing the last 40 minutes of weather data. As a new image is added, the oldest drops off. The Doppler Radar Client is an optional install program for any site-wide workstation. When a Client session is started, the Client requests Doppler Slave server assignment from the Master Server. Upon its initial request to the Slave Server, the Client obtains all eight current images and maintains its own circular buffer, updating its images every five minutes as the Doppler Slave is updated. Three background reference images are stored as part of the Client. The Client brings up the appropriate background image, decompresses the doppler data, and displays the doppler data on the background image.« less

  5. Christian Doppler and the Doppler effect

    NASA Astrophysics Data System (ADS)

    Toman, Kurt

    1984-04-01

    A summary is given of Doppler's life and career. He was born 180 years ago on November 29, 1803, in Salzburg, Austria. He died on March 17, 1853 in Venice. The effect bearing his name was first announced in a presentation before the Royal Bohemian Society of the Sciences in Prague on May 25, 1842. Doppler considered his work a generalization of the aberration theorem as discovered by Bradley. With it came the inference that the perception of physical phenomena can change with the state of motion of the observer. Acceptance of the principle was not without controversy. In 1852, the mathematician Petzval claimed that no useful scientific deductions can be made from Doppler's elementary equations. In 1860, Ernst Mach resolved the misunderstanding that clouded this controversy. The Doppler effect is alive and well. Its role in radio science and related disciplines is enumerated.

  6. Comparing Pulsed Doppler LIDAR with SODAR and Direct Measurements for Wind Assessment

    SciTech Connect

    Kelley, N. D.; Jonkman, B. J.; Scott, G. N.; Pichugina, Y. L.

    2007-07-01

    There is a pressing need for good wind-speed measurements at greater and greater heights to assess the availability of the resource in terms of power production and to identify any frequently occurring atmospheric structural characteristics that may create turbulence that impacts the operational reliability and lifetime of wind turbines and their components. In this paper, we summarize the results of a short study that compares the relative accuracies of wind speeds derived from a high-resolution pulsed Doppler LIDAR operated by the National Oceanic and Atmospheric Administration (NOAA) and a midrange Doppler SODAR with wind speeds measured by four levels of tower-based sonic anemometry up to a height of 116 m.

  7. Implementing torsional-mode Doppler ladar.

    PubMed

    Fluckiger, David U

    2002-08-20

    Laguerre-Gaussian laser modes carry orbital angular momentum as a consequence of their helical-phase front screw dislocation. This torsional beam structure interacts with rotating targets, changing the orbital angular momentum (azimuthal Doppler) of the scattered beam because angular momentum is a conserved quantity. I show how to measure this change independently from the usual longitudinal momentum (normal Doppler shift) and derive the apropos coherent mixing efficiencies for monostatic, truncated Laguerre and Gaussian-mode ladar antenna patterns. PMID:12206220

  8. Doppler-corrected differential detection of MPSK

    NASA Technical Reports Server (NTRS)

    Simon, Marvin K.; Divsalar, Dariush

    1989-01-01

    An open-loop technique is presented for estimating and correcting Doppler frequency shift in an M-ary differential phase-shift-keyed (MDPSK) receiver. The novelty of the scheme is based on the observation that whereas the change in phase of the received signal over a full symbol contains the sum of the data (phase) and the Doppler-induced phase shift, the same change in phase over half a symbol (within a given symbol interval) contains only the Doppler-induced phase shift. Thus, by proper processing, the latter can be estimated and removed from the former. Analytical and simulation results are given for the variance of the above estimator, and the error probability performance of the MDPSK receiver is evaluated in the presence of the Doppler correction. Next, the practical considerations associated with the application of this technique on bandlimited Nyquist channels are discussed and incorporated into the final design. It is shown that the receiver can, in the absence of timing jitter, be designed to allow combined Doppler correction and data detection with no penalty due to intersymbol interference (ISI). The effects of ISI due to timing jitter are assessed by computer simulation.

  9. Advanced Doppler tracking experiments

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.

    1989-01-01

    The Doppler tracking method is currently the only technique available for broadband gravitational wave searches in the approx. 10(exp -4) to 10(exp -1) Hz low frequency band. A brief review is given of the Doppler method, a discussion of the main noise sources, and a review of experience with current spacecraft and the prospects for sensitivity improvements in an advanced Doppler tracking experiment.

  10. Hot-Film and Hot-Wire Anemometry for a Boundary Layer Active Flow Control Test

    NASA Technical Reports Server (NTRS)

    Lenahan, Keven C.; Schatzman, David M.; Wilson, Jacob Samuel

    2013-01-01

    Unsteady active flow control (AFC) has been used experimentally for many years to minimize bluff-body drag. This technology could significantly improve performance of rotorcraft by cleaning up flow separation. It is important, then, that new actuator technologies be studied for application to future vehicles. A boundary layer wind tunnel was constructed with a 1ft-x-3ft test section and unsteady measurement instrumentation to study how AFC manipulates the boundary layer to overcome adverse pressure gradients and flow separation. This unsteady flow control research requires unsteady measurement methods. In order to measure the boundary layer characteristics, both hot-wire and hot-film Constant Temperature Anemometry is used. A hot-wire probe is mounted in the flow to measure velocity while a hot-film array lays on the test surface to measure skin friction. Hot-film sensors are connected to an anemometer, a Wheatstone bridge circuit with an output that corresponds to the dynamic flow response. From this output, the time varying flow field, turbulence, and flow reversal can be characterized. Tuning the anemometers requires a fan test on the hot-film sensors to adjust each output. This is a delicate process as several variables drastically affect the data, including control resistance, signal input, trim, and gain settings.

  11. High-speed laser anemometry based on spectrally resolved Rayleigh scattering

    NASA Technical Reports Server (NTRS)

    Seasholtz, R. G.

    1991-01-01

    Laser anemometry in unseeded flows based on the measurement of the spectrum of Rayleigh scattered laser light is reviewed. The use of molecular scattering avoids the well-known problems (particle lag, biasing effects, seed generation, seed injection) of seeded flows. The fundamental limits on velocity measurement accuracy are determined using maximum likelihood methods. Measurement of the Rayleigh spectrum with scanning Fabry-Perot interferometers is analyzed and accuracy limits are established for both single pass and multi-pass configurations. Multi-pass configurations have much higher selectivity and are needed for measurements where there is a large amount of excess noise caused by stray laser light. It is shown that Rayleigh scattering is particularly useful for supersonic and hypersonic flows. The results of the analysis are compared with measurements obtained with a Rayleigh scattering diagnostic developed for study of the exhaust plume of a small hydrogen-oxygen rocket, where the velocities are in the range 1000 to 5000 m/sec.

  12. Developments in hot-film anemometry measurements of hydroacoustic particle motion

    NASA Astrophysics Data System (ADS)

    Dubbelday, Pieter S.; Apostolico, Virgil V.; Diebel, Dean L.

    1988-08-01

    Hot film anemometry may be used to measure particle motion in hydroacoustic fields. Since the cylindrical sensors used thus far are very fragile, the method is little suited for use outside the laboratory. The measurement of the response of a more rugged conical sensor is reported here. Another way of protecting the sensor consists of packaging the sensor in a rubber liquid filled boot. This also prevents fouling and bubble formation on the heated film. The response shows a resonance at low frequency, ascribed to the liquid filled boot, which may be used for enhanced response in a limited frequency region. The response of a hot film anemometer to vertical hydroacoustic particle motion is influenced by free convection, which acts as a bias flow. The output was shown to be proportional to particle displacement for a wide range of parameters. It was expected that an imposed bias flow would increase the output and remove the dependence on the direction of gravity. Therefore, a hot-film sensor (diameter d) was subjected to an underwater jet from a nozzle. The output showed a transition from being proportional to particle speed, to being proportional to particle displacement, depending on the angular frequency omega and imposed flow speed omega. The transition takes place when a dimensionless number omega, defined as omega = omega/nu is of order 1.

  13. Velocity measurements in PFBC cyclone separator systems dip legs with thermal anemometry

    SciTech Connect

    Romeo, L.M.; Velilla, J.

    1999-07-01

    In order to improve the operational behavior (efficiency and stability) of the cyclone separator system in Escatron PFBC power plant, a laboratory-scale cold model has been built. Scaling laws have been applied to simulate the hydrodynamics and performance of the systems, in order to obtain valuable and relevant results for commercial PFBC technology. It has been demonstrated that the filtration effect of the cyclones in a PFBC power plant is extended down to the dipleg. Previous studies in a laboratory-scale cold model have pointed out the importance of the vortex inside the dipleg and its influence in the separation efficiency. It is due to the fact that the cyclone effect is still active in the dipleg. These studies are based in pressure drop dipleg measurements. Thermal anemometry has been used to measure the gas velocity and turbulence of several installations. In this case it has been used in order to check the vortex activity in the upper section of the dipleg of a cyclone separator system for a PFBC power plant. This paper deals with the results and conclusions of the research about the velocity field inside the dipleg. The possibility of improving cyclone efficiency by means of extending the vortex, the study of the variables affecting the vortex (and also the cyclone efficiency) and the establishment of a flow-pattern in the dipleg are the main objectives of the research and the paper.

  14. Turbulent Channel Flow Measurements with a Nano-scale Thermal Anemometry Probe

    NASA Astrophysics Data System (ADS)

    Bailey, Sean; Witte, Brandon

    2014-11-01

    Using a Nano-scale Thermal Anemometry Probe (NSTAP), streamwise velocity was measured in a turbulent channel flow wind tunnel at Reynolds numbers ranging from Reτ = 500 to Reτ = 4000 . Use of these probes results in the a sensing-length-to-viscous-length-scale ratio of just 5 at the highest Reynolds number measured. Thus measured results can be considered free of spatial filtering effects. Point statistics are compared to recently published DNS and LDV data at similar Reynolds numbers and the results are found to be in good agreement. However, comparison of the measured spectra provide further evidence of aliasing at long wavelengths due to application of Taylor's frozen flow hypothesis, with increased aliasing evident with increasing Reynolds numbers. In addition to conventional point statistics, the dissipative scales of turbulence are investigated with focus on the wall-dependent scaling. Results support the existence of a universal pdf distribution of these scales once scaled to account for large-scale anisotropy. This research is supported by KSEF Award KSEF-2685-RDE-015.

  15. The Cognitive Doppler.

    ERIC Educational Resources Information Center

    Kozoil, Micah E.

    1989-01-01

    Discusses the learning needs of students in the concrete operational stage in mathematics. Identifies the phenomenon of reduced cognitive performance in an out-of-class environment as the "Cognitive Doppler." Suggests methods of reducing the pronounced effects of the Cognitive Doppler by capitalizing on the students' ability to memorize effective…

  16. 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.

  17. Interferometric millimeter wave and THz wave doppler radar

    DOEpatents

    Liao, Shaolin; Gopalsami, Nachappa; Bakhtiari, Sasan; Raptis, Apostolos C.; Elmer, Thomas

    2015-08-11

    A mixerless high frequency interferometric Doppler radar system and methods has been invented, numerically validated and experimentally tested. A continuous wave source, phase modulator (e.g., a continuously oscillating reference mirror) and intensity detector are utilized. The intensity detector measures the intensity of the combined reflected Doppler signal and the modulated reference beam. Rigorous mathematics formulas have been developed to extract bot amplitude and phase from the measured intensity signal. Software in Matlab has been developed and used to extract such amplitude and phase information from the experimental data. Both amplitude and phase are calculated and the Doppler frequency signature of the object is determined.

  18. Airflow Measurement of the Car HVAC Unit Using Hot-wire Anemometry

    NASA Astrophysics Data System (ADS)

    Fojtlín, Miloš; Planka, Michal; Fišer, Jan; Pokorný, Jan; Jícha, Miroslav

    2016-03-01

    Thermal environment in a vehicular cabin significantly influence drivers' fatigue and passengers' thermal comfort. This environment is traditionally managed by HVAC cabin system that distributes air and modifies its properties. In order to simulate cabin thermal behaviour, amount of the air led through car vents must be determined. The aim of this study was to develop methodology to measure airflow from the vents, and consequently calculate corresponding air distribution coefficients. Three climatic cases were selected to match European winter, summer, and spring / fall conditions. Experiments were conducted on a test vehicle in a climatic chamber. The car HVAC system was set to automatic control mode, and the measurements were executed after the system stabilisation—each case was independently measured three times. To be able to evaluate precision of the method, the airflow was determined at the system inlet (HVAC suction) and outlet (each vent), and the total airflow values were compared. The airflow was calculated by determining a mean value of the air velocity multiplied by an area of inlet / outlet cross-section. Hot-wire anemometry was involved to measure the air velocity. Regarding the summer case, total airflow entering the cabin was around 57 l s-1 with 60 % of the air entering the cabin through dashboard vents; no air was supplied to the feet compartment. The remaining cases had the same total airflow of around 42 l s-1, and the air distribution was focused mainly on feet and windows. The inlet and outlet airflow values show a good match with a maximum mass differential of 8.3 %.

  19. Doppler radar flowmeter

    DOEpatents

    Petlevich, Walter J.; Sverdrup, Edward F.

    1978-01-01

    A Doppler radar flowmeter comprises a transceiver which produces an audio frequency output related to the Doppler shift in frequency between radio waves backscattered from particulate matter carried in a fluid and the radiated radio waves. A variable gain amplifier and low pass filter are provided for amplifying and filtering the transceiver output. A frequency counter having a variable triggering level is also provided to determine the magnitude of the Doppler shift. A calibration method is disclosed wherein the amplifier gain and frequency counter trigger level are adjusted to achieve plateaus in the output of the frequency counter and thereby allow calibration without the necessity of being able to visually observe the flow.

  20. A study for developing an ultrasonic Doppler flowmeter

    NASA Astrophysics Data System (ADS)

    Biermans, M.; Bregman, R.

    1984-06-01

    The system parameters for low cost ultrasonic Doppler flowmeters for medical applications were investigated. A flowmeter was built. A phase locked loop is used to find the correct Doppler shift. Laboratory and field tests prove the success of the development, although very often insufficient reflectors exist in the liquids. The accuracy is + or - 5%; the reproducibility is + or - 0.5%.

  1. Calibration, Data Acquisition, and Post Analysis of Turbulent Fluid Flow in a Calibration Jet Using Hot-wire Anemometry

    NASA Technical Reports Server (NTRS)

    Moreno, Michelle

    2004-01-01

    The Turbine Branch concentrates on the following areas: Computational Fluid Dynamics (CFD), and implementing experimental procedures to obtain physical modeling data. Hot-wire Anemometry is a valuable tool for obtaining physical modeling data. Hot-wire Anemometry is likely to remain the principal research tool for most turbulent air/gas flow studies. The Hot-wire anemometer consists of a fine wire heated by electric current. When placed in a fluid stream, the hot-wire loses heat to the fluid by forced convection. In forced convection, energy transfer is due to molecular motion imposed by an extraneous force moving fluid parcels. When the hot-wire is in "equilibrium", the rate of heat input to the wire is equal to the rate of heat loss at the wire ends. The equality between heat input and heat loss is the basis for King s equation, which relates the electrical parameters of the hot-wire to the flow parameters of the fluid. Hot-wire anemometry is based on convective heat transfer from a heated wire element placed in a fluid flow. Any change in the fluid flow condition that affects the heat transfer from the heated element will be detected virtually instantaneously by a constant-temperature Hot-wire anemometry system. The system implemented for this research is the IFA 300. The system is a fully-integrated, thermal anemometer-based system that measures mean and fluctuating velocity components in air, water, and other fluids. It also measures turbulence and makes localized temperature measurements. A constant-temperature anemometer is a bridge and amplifier circuit that controls a tiny wire at constant temperature. As a fluid flow passes over the heated sensor, the amplifier senses the bridge off-balance and adjusts the voltage to the top of the bridge, keeping the bridge in balance. The voltage on top of the bridge can then be related to the velocity of the flow. The bridge voltage is sensitive to temperature as well as velocity and so the built-in thermocouple

  2. TiCl4 as a source of TiO2 particles for laser anemometry measurements in hot gas

    NASA Technical Reports Server (NTRS)

    Weikle, Donald H.; Seasholtz, Richard G.; Oberle, Lawrence G.

    1990-01-01

    A method of reacting TiCl4 with water saturated gaseous nitrogen (GN2) at the entrance into a high temperature gas flow is described. The TiO2 particles formed are then entrained in the gas flow and used as seed particles for making laser anemometry (LA) measurements of the flow velocity distribution in the hot gas. Scanning electron microscope photographs of the TiO2 particles are shown. Data rate of the LA processor was measured to determine the amount of TiO2 formed. The TiCl4 and mixing gas flow diagram is shown. This work was performed in an open jet burner.

  3. Doppler Lidar (DL) Handbook

    SciTech Connect

    Newsom, RK

    2012-02-13

    The Doppler lidar (DL) is an active remote sensing instrument that provides range- and time-resolved measurements of radial velocity and attenuated backscatter. The principle of operation is similar to radar in that pulses of energy are transmitted into the atmosphere; the energy scattered back to the transceiver is collected and measured as a time-resolved signal. From the time delay between each outgoing transmitted pulse and the backscattered signal, the distance to the scatterer is inferred. The radial or line-of-sight velocity of the scatterers is determined from the Doppler frequency shift of the backscattered radiation. The DL uses a heterodyne detection technique in which the return signal is mixed with a reference laser beam (i.e., local oscillator) of known frequency. An onboard signal processing computer then determines the Doppler frequency shift from the spectra of the heterodyne signal. The energy content of the Doppler spectra can also be used to determine attenuated backscatter.

  4. Color Doppler flow imaging.

    PubMed

    Foley, W D; Erickson, S J

    1991-01-01

    The performance requirements and operational parameters of a color Doppler system are outlined. The ability of an operator to recognize normal and abnormal variations in physiologic flow and artifacts caused by noise and aliasing is emphasized. The use of color Doppler flow imaging is described for the vessels of the neck and extremities, upper abdomen and abdominal transplants, obstetrics and gynecology, dialysis fistulas, and testicular and penile flow imaging. PMID:1898567

  5. An electronic Doppler signal generator for assessing continuous-wave ultrasonic Doppler flowmeters

    NASA Astrophysics Data System (ADS)

    Smallwood, R. H.; Dixon, P.

    1986-03-01

    The design and performance of the electric Doppler signal generator are described. The features of the CW ultrasonic Doppler flowmeter, which operates in the 2-10 MHz range, that are relevant to the design of the generator are examined. Methods for evaluating the bandwidth, dynamic range, directional separation, and linearity of the zero-crossing detector are discussed. The use of a polyphase network as a phase shifter to generate a single sideband (SSB) signal is analyzed. The SSB generation is performed at a frequency of 100 kHz and the advantages of generation at this frequency are stated. The selection of proper SSB signals for the system is investigated. The performance of the Doppler signal generator is evaluated with a frequency analyzer; sideband rejection ratios and phase error in the quadrature oscillator are calculated. The Doppler generator was applied to a CW flowmeter and output signal levels were measured. The test reveals that the Doppler signal generator's performance exceeds the flowmeter requirements; rejection of the unwanted sideband exceeds 40 dB for Doppler frequencies up to 10 kHz, which is the minimum upper frequency for 10 MHz flowmeters.

  6. Laser Doppler And Range Systems For Spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, P. W.; Gagliardi, R. M.

    1990-01-01

    Report discusses two types of proposed laser systems containing active transponders measuring distance (range) and line-of-sight velocity (via Doppler effect) between deep space vehicle and earth-orbiting satellite. Laser system offers diffraction advantage over microwave system. Delivers comparable power to distant receiver while using smaller transmitting and receiving antennas and less-powerful transmitter. Less subject to phase scintillations caused by passage through such inhomogeneous media as solar corona. One type of system called "incoherent" because range and Doppler measurements do not require coherence with laser carrier signals. Other type of system called "coherent" because successful operation requires coherent tracking of laser signals.

  7. Ultrasonic Doppler Modes

    NASA Astrophysics Data System (ADS)

    Tortoli, Piero; Fidanzati, Paolo; Luca, Bassi

    Any US equipment includes Doppler facilities capable of providing information about moving structures inside the human body. In most cases, the primary interest is in the investigation of blood flow dynamics, since this may be helpful for early diagnosis of cardiovascular diseases. However, there is also an increasing interest in tracking the movements of human tissues, since such movements can give an indirect evaluation of their elastic properties, which are valuable indicators of the possible presence of pathologies. This paper aims at presenting an overview of the different ways in which the Doppler technique has been developed and used in medical ultrasound (US), from early continuous wave (CW) systems to advanced pulsed wave (PW) colour-Doppler equipment. In particular, the most important technical features and clinical applications of CW, single-gate PW, multi-gate PW and flow-imaging systems are reviewed. The main signal processing approaches used for detection of Doppler frequencies are described, including time-domain and frequency-domain (spectral) methods, as well as novel strategies like, e.g., harmonic Doppler mode, which have been recently introduced to exploit the benefits of US contrast agents.

  8. Quantitative Measurement of the Doppler Shift at an Ultrasonic Frequency

    ERIC Educational Resources Information Center

    Nerbun, R. C.; Leskovec, R. A.

    1976-01-01

    Discussed is a Doppler shift laboratory experiment for an introductory college physics course. Ultrasonic transducers and a digital phase detector circuit "black box" are used to overcome room noise and "standing waves" and to produce an observable frequency shift. (SL)

  9. Compression of polyphase codes with Doppler shift

    NASA Astrophysics Data System (ADS)

    Wirth, W. D.

    It is shown that pulse compression with sufficient Doppler tolerance may be achieved with polyphase codes derived from linear frequency modulation (LFM) and nonlinear frequency modulation (NLFM). Low sidelobes in range and Doppler are required especially for the radar search function. These may be achieved by an LFM derived phase coder together with Hamming weighting or by applying a PNL polyphase code derived from NLFM. For a discrete and known Doppler frequency with an expanded and mismatched reference vector a sidelobe reduction is possible. The compression is then achieved without a loss in resolution. A set up for the expanded reference gives zero sidelobes only in an interval around the signal peak or a least square minimization for all range elements. This version may be useful for target tracking.

  10. Measurement of blood velocity using laser Doppler method for the designing module

    NASA Astrophysics Data System (ADS)

    Chen, Guo-Liang; Lee, Jen-Ai; Lu, Tung-Wu; Chen, Zhao-Cheng; Chen, Chien-Ming

    2005-04-01

    We built the Dual Beam Mode of the LDA (Laser Doppler Anemometry) frame, set the photodetector at the same side with light source which collect the scattering light of blood cell. It's proper to reduce LDA optical path and convenient for our designing module. The concentration of chicken blood in this study is about 1% and we measured the relations actually between flood velocity and the angle of beams cross on particles, temperature, and the diameter of aqueduct. We found better results while the cross angle was less than 38.8 degree, diameter of aqueduct was 6 mm, and temperature of blood was set to 36 . These parameters can also provide important basis for the LDA module kit that we are designing.

  11. An experimental study of a three-dimensional thrust augmenting ejector using laser Doppler velocimetry

    NASA Technical Reports Server (NTRS)

    Storms, Bruce Lowell

    1989-01-01

    Flow field measurements were obtained in a three-dimensional thrust augmenting ejector using laser Doppler velocimetry and hot wire anemometry. The primary nozzle, segmented into twelve slots of aspect ratio 3.0, was tested at a pressure ratio of 1.15. Results are presented on the mean velocity, turbulence intensity, and Reynolds stress progressions in the mixing chamber of the constant area ejector. The segmented nozzle was found to produce streamwise vortices that may increase the mixing efficiency of the ejector flow field. Compared to free jet results, the jet development is reduced by the presence of the ejector walls. The resulting thrust augmentation ratio of this ejector was also calculated to be 1.34.

  12. Pulsed Doppler lidar airborne scanner

    NASA Technical Reports Server (NTRS)

    Dimarzio, C. A.; Mcvicker, D. B.; Morrow, C. E.; Negus, C. C.

    1985-01-01

    This report covers the work accomplished during the reporting period on Pulsed Doppler Lidar Airborne Scanner and describes plans for the next reporting period. The objectives during the current phase of the contract are divided into four phases. Phase 1 includes ground testing of the system and analysis of data from the 1981 Severe Storms Test Flights. Phase 2 consists of preflight preparation and planning for the 1983 flight series. The flight test itself will be performed during Phase 3, and Phase 4 consists of post-flight analysis and operation of the system after that flight test. The range profile from five samples taken during Flight 10, around 1700 Z is given. The lowest curve is taken from data collected upwind of Mt. Shasta at about 10,000 feet of altitude, in a clear atmosphere, where no signals were observed. It thus is a good representation of the noise level as a function of range. The next curve was taken downwind of the mountain, and shows evidence of atmospheric returns. There is some question as to whether the data are valid at all ranges, or some ranges are contaminated by the others.

  13. Pulsed Doppler lidar airborne scanner

    NASA Astrophysics Data System (ADS)

    Dimarzio, C. A.; McVicker, D. B.; Morrow, C. E.; Negus, C. C.

    1985-10-01

    This report covers the work accomplished during the reporting period on Pulsed Doppler Lidar Airborne Scanner and describes plans for the next reporting period. The objectives during the current phase of the contract are divided into four phases. Phase 1 includes ground testing of the system and analysis of data from the 1981 Severe Storms Test Flights. Phase 2 consists of preflight preparation and planning for the 1983 flight series. The flight test itself will be performed during Phase 3, and Phase 4 consists of post-flight analysis and operation of the system after that flight test. The range profile from five samples taken during Flight 10, around 1700 Z is given. The lowest curve is taken from data collected upwind of Mt. Shasta at about 10,000 feet of altitude, in a clear atmosphere, where no signals were observed. It thus is a good representation of the noise level as a function of range. The next curve was taken downwind of the mountain, and shows evidence of atmospheric returns. There is some question as to whether the data are valid at all ranges, or some ranges are contaminated by the others.

  14. Polarimetric Doppler Weather Radar

    NASA Astrophysics Data System (ADS)

    Bringi, V. N.; Chandrasekar, V.

    2001-10-01

    This work provides a detailed introduction to the principles of Doppler and polarimetric radar, focusing in particular on their use in the analysis of weather systems. The authors first discuss underlying topics such as electromagnetic scattering, polarization, and wave propagation. They then detail the engineering aspects of pulsed Doppler polarimetric radar, before examining key applications in meteorology and remote sensing. The book is aimed at graduate students of electrical engineering and atmospheric science as well as practitioners involved in the applications of polarimetric radar.

  15. Dual-Polarised Doppler X-band Radar Observations of Mixed Phased Clouds from the UK's Ice in Clouds Experiment-Dust (ICE-D)

    NASA Astrophysics Data System (ADS)

    Neely, R. R., III; Blyth, A. M.; Bennett, L.; Dufton, D.; Cui, Z.; Huang, Y.

    2015-12-01

    Here we present dual-polarised Doppler X-band radar observations of convective, altocumulus and altostratus clouds relatively close to the Sahara desert in order to examine the impact of dust on the formation of ice and precipitation. These initial results come the UK's Ice in Clouds Experiment - Dust (UK ICE-D). UK ICE-D was an aircraft and ground-based project based in Cape Verde off the coast of Senegal, Africa during August 2015. The overall goal of this experiment was to determine how desert dust affects primary nucleation of ice particles in convective and layer clouds as well as the subsequent development of precipitation and glaciation of the clouds. This was accomplished by making focused observations when dust was present in high concentrations and when almost no dust was present. Here we focus on examining the differences in hydrometeor types derived from the dual-polarised X-band radar observations observed in the high and low dust loadings with specific emphasis on the role of supercooled rain drops in these two situations.

  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. PMID:11368866

  17. Finnish Meteorological Institute Doppler Lidar

    SciTech Connect

    Ewan OConnor

    2015-03-27

    This doppler lidar system provides co-polar and cross polar attenuated backscatter coefficients,signal strength, and doppler velocities in the cloud and in the boundary level, including uncertainties for all parameters. Using the doppler beam swinging DBS technique, and Vertical Azimuthal Display (VAD) this system also provides vertical profiles of horizontal winds.

  18. Basic principles of pulsed-wind Doppler lidars with multitime coherence

    NASA Astrophysics Data System (ADS)

    Matvienko, G. G.; Polyakov, S. N.; Oshlakov, V. K.

    2008-11-01

    A concept of multitime coherence (MTC) of optical beams is proposed. Two versions of fiber multiplicator topologies are presented, which are intended for the generation of multiple fiber pulses (MFP) possessing the MTC property. The fiber multiplicators may be a useful tool for Doppler laser anemometry of spatially separated scattering objects. Moreover, their use makes feasible the implementation of low-coherence wind Doppler lidars on the base of laser sources having a limited-time coherence (from one to a few tens of nanoseconds) and a high-velocity measurement resolution. Different lidar systems that feature a ring-fiber resonator (RFR) for reference wave generation are proposed. Two systems are also considered: (i) one based on a multimode fiber topology, which provides for the sensing ns-pulse generation and for the reference and probe wave multiplication; (ii) one based on a single-mode fiber topology, which provides for ns-pulse sensing and for the signal and reference wave multiplication. The concept of a low-coherence Doppler lidar system intended for atmospheric-sensing applications, which makes use of reference and signal waves possessing the MTC properties, is formulated for the first time.

  19. The Doppler Pendulum Experiment

    ERIC Educational Resources Information Center

    Lee, C. K.; Wong, H. K.

    2011-01-01

    An experiment to verify the Doppler effect of sound waves is described. An ultrasonic source is mounted at the end of a simple pendulum. As the pendulum swings, the rapid change of frequency can be recorded by a stationary receiver using a simple frequency-to-voltage converter. The experimental results are in close agreement with the Doppler…

  20. Wind observations above an urban river using a new lidar technique, scintillometry and anemometry.

    PubMed

    Wood, C R; Pauscher, L; Ward, H C; Kotthaus, S; Barlow, J F; Gouvea, M; Lane, S E; Grimmond, C S B

    2013-01-01

    Airflow along rivers might provide a key mechanism for ventilation in cities: important for air quality and thermal comfort. Airflow varies in space and time in the vicinity of rivers. Consequently, there is limited utility in point measurements. Ground-based remote sensing offers the opportunity to study 3D airflow in locations which are difficult to observe with conventional approaches. For three months in the winter and spring of 2011, the airflow above the River Thames in central London was observed using a scanning Doppler lidar, a scintillometer and sonic anemometers. First, an inter-comparison showed that lidar-derived mean wind-speed estimates compare almost as well to sonic anemometers (root-mean-square error (rmse) 0.65-0.68 ms(-1)) as comparisons between sonic anemometers (0.35-0.73 ms(-1)). Second, the lidar duo-beam operating strategy provided horizontal transects of wind vectors (comparison with scintillometer rmse 1.12-1.63 ms(-1)) which revealed mean and turbulent airflow across the river and surrounds; in particular, channelled airflow along the river and changes in turbulence quantities consistent with the roughness changes between built and river environments. The results have important consequences for air quality and dispersion around urban rivers, especially given that many cities have high traffic rates on roads located on riverbanks. PMID:23201607

  1. Mitigating Doppler shift effect in HF multitone data modem

    NASA Astrophysics Data System (ADS)

    Sonlu, Yasar

    1989-09-01

    Digital communications over High Frequency (HF) radio channels are getting important in recent years. Current HF requirements are for data transmission at rates 2.4 kbps or more to accommodate computer data links and digital secure voice. HF modems which were produced to meet these speeds are, serial modems and parallel modems. On the other hand, the HF sky-wave communication medium, the ionosphere, has some propagation problems such as multipath and Doppler shift. The effect of Doppler shift in a parallel modem which employs Differential Quadrature Phase Shift Keying (DQPSK) modulation is considered and a correction method to mitigate the Doppler Shift effect is introduced.

  2. Design of a Doppler reflectometer for KSTAR

    SciTech Connect

    Lee, K. D. Nam, Y. U.; Seo, Seong-Heon; Kim, Y. S.

    2014-11-15

    A Doppler reflectometer has been designed to measure the poloidal propagation velocity on the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. It has the operating frequency range of V-band (50-75 GHz) and the monostatic antenna configuration with extraordinary mode (X-mode). The single sideband modulation with an intermediate frequency of 50 MHz is used for the heterodyne measurement with the 200 MHz in-phase and quadrature (I/Q) phase detector. The corrugated conical horn antenna is used to approximate the Gaussian beam propagation and it is installed together with the oversized rectangular waveguides in the vacuum vessel. The first commissioning test of the Doppler reflectometer system on the KSTAR tokamak is planned in the 2014 KSTAR experimental campaign.

  3. Doppler ultrasound studies in pelvic inflammatory disease.

    PubMed

    Tinkanen, H; Kujansuu, E

    1992-01-01

    Ten women with tubo-ovarian abscess caused by pelvic inflammatory disease (PID) were investigated by transvaginal Doppler ultrasound during the acute and healing phases of the infection. The pulsatility index (PI) of the uterine arteries was measured and compared with the values obtained from 19 healthy women. Each control patient was investigated three times during a single menstrual cycle. In PID patients, the PI values were significantly lower than in controls in the same phase of the menstrual cycle. When C-reactive protein was > 50, the PI values were lowest and reverted to normal values when the infection subsided. In a case of chronic infection, the PI did not rise to normal despite normal infection parameters. Doppler ultrasound seems to offer a new method of assessing PID. PMID:1487185

  4. Doppler radar results

    NASA Technical Reports Server (NTRS)

    Bracalente, Emedio M.

    1992-01-01

    The topics are covered in viewgraph form and include the following: (1) a summary of radar flight data collected; (2) a video of combined aft cockpit, nose camera, and radar hazard displays; (3) a comparison of airborne radar F-factor measurements with in situ and Terminal Doppler Weather Radar (TDWR) F-factors for some sample events; and (4) a summary of wind shear detection performance.

  5. Laser double Doppler flowmeter

    NASA Astrophysics Data System (ADS)

    Poffo, L.; Goujon, J.-M.; Le Page, R.; Lemaitre, J.; Guendouz, M.; Lorrain, N.; Bosc, D.

    2014-05-01

    The Laser Doppler flowmetry (LDF) is a non-invasive method for estimating the tissular blood flow and speed at a microscopic scale (microcirculation). It is used for medical research as well as for the diagnosis of diseases related to circulatory system tissues and organs including the issues of microvascular flow (perfusion). It is based on the Doppler effect, created by the interaction between the laser light and tissues. LDF measures the mean blood flow in a volume formed by the single laser beam, that penetrate into the skin. The size of this measurement volume is crucial and depends on skin absorption, and is not directly reachable. Therefore, current developments of the LDF are focused on the use of always more complex and sophisticated signal processing methods. On the other hand, laser Double Doppler Flowmeter (FL2D) proposes to use two laser beams to generate the measurement volume. This volume would be perfectly stable and localized at the intersection of the two laser beams. With FL2D we will be able to determine the absolute blood flow of a specific artery. One aimed application would be to help clinical physicians in health care units.

  6. Clinical applications of doppler ultrasound

    SciTech Connect

    Taylor, K.J.W.; Burns, P.N.; Well, P.N.T.

    1987-01-01

    This book introduces a guide to the physical principles and instrumentation of duplex Doppler ultrasound and its applications in obstetrics, gynecology, neonatology, gastroentology, and evaluation of peripheral vascular disease. The book provides information needed to perform Doppler ultrasound examinations and interpret the results. An introduction to Doppler physics and instrumentation is followed by a thorough review of hemodynamics, which explains the principles underlying interpretation of Doppler signals. Of special note is the state-of-the-art coverage of new applications of Doppler in recognition of high-risk pregnancy, diagnosis of intrauterine growth retardation, investigation of neonatal blood flow, evaluation of first-trimester pregnancy, and diagnosis of gastrointestinal disease. The book also offers guidelines on the use of Doppler ultrasound in diagnosing carotid disease, deep venous thrombosis, and aorta/femoral disease.

  7. Laser Doppler diagnostics for orthodontia

    NASA Astrophysics Data System (ADS)

    Ryzhkova, Anastasia V.; Lebedeva, Nina G.; Sedykh, Alexey V.; Ulyanov, Sergey S.; Lepilin, Alexander V.; Kharish, Natalia A.

    2004-06-01

    The results of statistical analysis of Doppler spectra of intensity fluctuations of light, scattered from mucous membrane of oral cavity of healthy volunteers and patients, abused by the orthodontic diseases, are presented. Analysis of Doppler spectra, obtained from tooth pulp of patients, is carried out. New approach to monitoring of blood microcirculation in orthodontics is suggested. Influence of own noise of Doppler measuring system on formation of the output signal is studied.

  8. Duplex Doppler ultrasound study of the temporomandibular joint

    PubMed Central

    Stagnitti, A.; Marini, A.; Impara, L.; Drudi, F.M.; Lo mele, L.; Lillo Odoardi, G.

    2012-01-01

    Introduction The anatomy and physiology of the temporomandibular joint can be studied clinically and by diagnostic imaging. Magnetic resonance imaging (MRI), radiography (X-ray) and computed tomography (CT) have thus for many years contributed to the study of the kinetics in the mandibular condyle. However, also duplex Doppler ultrasound (US) examination is widely used in the study of structures during movement, particularly vascular structures. Materials and methods A total of 30 patients were referred by the Department of Orthodontics to the Department of Radiological, Oncological and Pathological Sciences, University of Rome “La Sapienza”. All patients underwent duplex Doppler ultrasound (US) examination of the temporomandibular joint using Toshiba APLIO SSA-770A equipment and duplex Doppler multi-display technique, which allows simultaneous display of US images and color Doppler signals. A linear phased array probe with crystal elements was used operating at a basic frequency of 6 MHz during pulsed Doppler spectral analysis and 7.5 MHz during US imaging. Results In normal patients a regular alternation in the spectral Doppler waveforms was obtained, while in patients with temporomandibular joint meniscus dysfunction there was no regularity in the sum of the Fourier series with an unsteady waveform pattern related to irregular movements of the temporomandibular joint. Conclusions In all cases duplex Doppler US examination proved able to differentiate between normal and pathological patients and among the latter this technique permitted identification of the most significant aspects of the dysfunctional diseases. PMID:23397016

  9. A combined experimental and theoretical study of supercooling by two-phase mist flows

    SciTech Connect

    Yang Zhihua.

    1991-01-01

    A combined experimental and theoretical study of cooling enhancement by mist flow was performed for a square channel with a smooth wall. A new method is proposed for the turbulent deposition of droplets from two-phase mist flow into the wall of the channel. The proposed analytical model shows satisfactory agreement with observations from an experimental measurement using a particle-sizing two-dimensional reference-model laser-Doppler anemometry technique. Supercooling is defined as the simultaneous attainment of high heat flux and a low temperature of a surface to be cooled. Surface cooling is by evaporation from the exposed side of the film. The film is maintained by the continuous deposition of a stream of turbulent mist. An analytical model is provided for the heat-transfer enhancement coefficient due to mist supercooling. Also, experiments were carried out to investigate cooling enhancement. A substantial supercooling by mist flow is reported. The effects on supercooling of flow rate, droplet concentration and size, and wall heat flux are also reported.

  10. Terminal Doppler weather radar

    NASA Astrophysics Data System (ADS)

    Michelson, M.; Shrader, W. W.; Wieler, J. G.

    1990-02-01

    The terminal Doppler weather radar (TDWR) system, now under development, will provide automatic detection of microbursts and low-level wind shear. This paper discusses the TDWR performance parameters and describes its structural elements, including the antenna subsystem, the transmitter, the receiver/exciter, the digital signal processor, and the radar product generator/remote monitoring subsystem. Attention is also given to the processes of the base data formation, point target removal, signal-to-noise thresholding, and velocity de-aliasing and to the TDWR algorithms and displays. A schematic diagram of the TDWR system is presented.

  11. Laser Doppler velocimetry primer

    NASA Technical Reports Server (NTRS)

    Bachalo, William D.

    1985-01-01

    Advanced research in experimental fluid dynamics required a familiarity with sophisticated measurement techniques. In some cases, the development and application of new techniques is required for difficult measurements. Optical methods and in particular, the laser Doppler velocimeter (LDV) are now recognized as the most reliable means for performing measurements in complex turbulent flows. And such, the experimental fluid dynamicist should be familiar with the principles of operation of the method and the details associated with its application. Thus, the goals of this primer are to efficiently transmit the basic concepts of the LDV method to potential users and to provide references that describe the specific areas in greater detail.

  12. Impact of manakin motion on particle transport in the breathing zone

    EPA Science Inventory

    The current experimental investigation is focused on particle measurements using Phase Doppler Anemometry (PDA) in the breathing zone of a seated, breathing, thermal manikin under stationary and rotational conditions. Particle size, concentration, flux, and velocity data were co...

  13. Apparatus and method for noninvasive particle detection using doppler spectroscopy

    DOEpatents

    Sinha, Dipen N.

    2016-05-31

    An apparatus and method for noninvasively detecting the presence of solid particulate matter suspended in a fluid flowing through a pipe or an oil and gas wellbore are described. Fluid flowing through a conduit containing the particulate solids is exposed to a fixed frequency (>1 MHz) of ultrasonic vibrations from a transducer attached to the outside of the pipe. The returning Doppler frequency shifted signal derived from the scattering of sound from the moving solid particles is detected by an adjacent transducer. The transmitted signal and the Doppler signal are combined to provide sensitive particulate detection. The magnitude of the signal and the Doppler frequency shift are used to determine the particle size distribution and the velocity of the particles. Measurement of the phase shift between the applied frequency and the detected Doppler shifted may be used to determine the direction of motion of the particles.

  14. ANL Doppler flowmeter

    NASA Astrophysics Data System (ADS)

    Karplus, H. B.; Raptis, A. C.; Lee, S.; Simpson, T.

    1985-10-01

    A flowmeter has been developed for measuring flow velocity in hot slurries. The flowmeter works on an ultrasonic Doppler principle in which ultrasound is injected into the flowing fluid through the solid pipe wall. Isolating waveguides separate the hot pipe from conventional ultrasonic transducers. Special clamp-on high-temperature transducers also can be adapted to work well in this application. Typical flows in pilot plants were found to be laminar, giving rise to broad-band Doppler spectra. A special circuit based on a servomechanism sensor was devised to determine the frequency average of such a broad spectrum. The device was tested at different pilot plants. Slurries with particulates greater than 70 microns (0.003 in.) yielded good signals, but slurries with extremely fine particulates were unpredictable. Small bubbles can replace the coarse particles to provide a good signal if there are not too many. Successful operation with very fine particulate slurries may have been enhanced by the presence of microbubbles.

  15. Doppler Beats or Interference Fringes?

    ERIC Educational Resources Information Center

    Kelly, Paul S.

    1979-01-01

    Discusses the following: another version of Doppler beats; alternate proof of spin-1 sin-1/2 problems; some mechanisms related to Dirac's strings; Doppler redshift in oblique approach of source and observer; undergraduate experiment on noise thermometry; use of the time evolution operator; resolution of an entropy maximization controversy;…

  16. Manipulating the spin-dependent splitting by geometric Doppler effect.

    PubMed

    Liu, Yachao; Ke, Yougang; Zhou, Junxiao; Luo, Hailu; Wen, Shuangchun

    2015-06-29

    We report the manipulation of spin-dependent splitting by geometric Doppler effect based on dielectric metasurfaces. The extrapolation of rotational Doppler effect from temporal to spatial coordinate gives the phase change when the local optical axes of dielectric metasurfaces are rotating in space. Therefore, the continuous variation of local optical axes in a certain direction will introduce a phase gradient in the same direction at the beam cross section. This is additive to the phase gradient appeared when breaking the rotational symmetry of linearly polarized cylindrical vector beams, which leads to the deflections of different spin components of light, i.e., photonic spin Hall effect. Hence, it is possible to manipulate the spin-dependent splitting by introducing the geometric Doppler effect. Theoretically and experimentally, we show that the magnitude and orientation of the spin-dependent splitting are both tunable when changing the spatial rotation rate of local optical axes and incident polarization. PMID:26191680

  17. Measurements of velocity spectra using time-resolving Doppler global velocimetry with laser frequency modulation and a detector array

    NASA Astrophysics Data System (ADS)

    Fischer, Andreas; Büttner, Lars; Czarske, Jürgen; Eggert, Michael; Müller, Harald

    2009-10-01

    Measuring velocity spectra in turbulent flows requires methods providing a high temporal resolution and a low measurement uncertainty. Hot-wire anemometry is often used, but it is intrusive. Laser Doppler anemometry is non-intrusive, but due to the statistical arrival of individual tracers provides no constant measurement rate. We therefore propose the use of Doppler global velocimetry (DGV), which is a contactless method allowing temporally equidistant measurements of continuous signals. Additionally, 2d measurements are possible instead of single point measurements. The commonly applied slow cameras are substituted by a fibre coupled detector array consisting of 25 avalanche photo diodes, which increases temporal resolution up to 10 μs. Contrarily to conventional DGV, a sinusoidal laser frequency modulation enables omitting the reference detector array. A correction of beam splitting and image misalignment errors is thus not necessary, but disturbances due to temporal fluctuations of the scattered light can occur and have to be reduced by increasing the modulation frequency. We validate the proposed system capability of synchronously measuring velocity spectra at multiple points in turbulent flows by presenting experimental results. The acquired velocity spectra in a wind tunnel experiment show good agreement with hot-wire comparison measurements within 0.1 m/s. An uncertainty analysis is given, which allows the achievable measurement uncertainty to be estimated as a function of the desired temporal resolution. An uncertainty down to 0.2 m/s can, for example, be achieved assuming a desired temporal resolution of 1 ms. These promising results open new perspectives for turbulence and correlation studies in flows such as to investigate the turbulence characteristics behind a truncated cylinder attached to a plate or the inlet of an aircraft turbine for flow characterisation in industry.

  18. ADVANCED COMPUTATIONAL MODEL FOR THREE-PHASE SLURRY REACTORS

    SciTech Connect

    Goodarz Ahmadi

    2004-10-01

    In this project, an Eulerian-Lagrangian formulation for analyzing three-phase slurry flows in a bubble column was developed. The approach used an Eulerian analysis of liquid flows in the bubble column, and made use of the Lagrangian trajectory analysis for the bubbles and particle motions. The bubble-bubble and particle-particle collisions are included the model. The model predictions are compared with the experimental data and good agreement was found An experimental setup for studying two-dimensional bubble columns was developed. The multiphase flow conditions in the bubble column were measured using optical image processing and Particle Image Velocimetry techniques (PIV). A simple shear flow device for bubble motion in a constant shear flow field was also developed. The flow conditions in simple shear flow device were studied using PIV method. Concentration and velocity of particles of different sizes near a wall in a duct flow was also measured. The technique of Phase-Doppler anemometry was used in these studies. An Eulerian volume of fluid (VOF) computational model for the flow condition in the two-dimensional bubble column was also developed. The liquid and bubble motions were analyzed and the results were compared with observed flow patterns in the experimental setup. Solid-fluid mixture flows in ducts and passages at different angle of orientations were also analyzed. The model predictions were compared with the experimental data and good agreement was found. Gravity chute flows of solid-liquid mixtures were also studied. The simulation results were compared with the experimental data and discussed A thermodynamically consistent model for multiphase slurry flows with and without chemical reaction in a state of turbulent motion was developed. The balance laws were obtained and the constitutive laws established.

  19. High resolution Doppler lidar

    NASA Technical Reports Server (NTRS)

    Abreu, Vincent J.; Hays, Paul B.; Barnes, John E.

    1989-01-01

    A high resolution lidar system was implemented to measure winds in the lower atmosphere. The wind speed along the line of sight was determined by measuring the Doppler shift of the aerosol backscattered laser signal. The system in its present configuration is stable, and behaves as indicated by theoretical simulations. This system was built to demonstrate the capabilities of the detector system as a prototype for a spaceborne lidar. The detector system investigated consisted of a plane Fabry-Perot etalon, and a 12-ring anode detector. This system is generically similar to the Fabry-Perot interferometer developed for passive wind measurements on board the Dynamics Explorer satellite. That this detector system performs well in a lidar configuration was demonstrated.

  20. 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.

  1. Doppler ultrasound--basics revisited.

    PubMed

    Eagle, Mary

    Palpation of pedal pulses alone is known to be an unreliable indicator for the presence of arterial disease. Using portable Doppler ultrasound to measure the resting ankle brachial pressure index is superior to palpation of peripheral pulses as an assessment of the adequacy pf the arterial supply in the lower limb. Revisiting basics, this article aims to aid the clinician to understand and perform hand-held Doppler ultrasound effectively while involving the client or patient in the process. The author describes the basics of Doppler ultrasound, how to select correct equipment for the process, and interpretation of results to further enhance clinicians' knowledge. PMID:16835512

  2. Evaluation of meteorological airborne Doppler radar

    NASA Technical Reports Server (NTRS)

    Hildebrand, P. H.; Mueller, C. K.

    1984-01-01

    This paper will discuss the capabilities of airborne Doppler radar for atmospheric sciences research. The evaluation is based on airborne and ground based Doppler radar observations of convective storms. The capability of airborne Doppler radar to measure horizontal and vertical air motions is evaluated. Airborne Doppler radar is shown to be a viable tool for atmospheric sciences research.

  3. Dual-Doppler Feasibility Study

    NASA Technical Reports Server (NTRS)

    Huddleston, Lisa L.

    2012-01-01

    When two or more Doppler weather radar systems are monitoring the same region, the Doppler velocities can be combined to form a three-dimensional (3-D) wind vector field thus providing for a more intuitive analysis of the wind field. A real-time display of the 3-D winds can assist forecasters in predicting the onset of convection and severe weather. The data can also be used to initialize local numerical weather prediction models. Two operational Doppler Radar systems are in the vicinity of Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS); these systems are operated by the 45th Space Wing (45 SW) and the National Weather Service Melbourne, Fla. (NWS MLB). Dual-Doppler applications were considered by the 45 SW in choosing the site for the new radar. Accordingly, the 45th Weather Squadron (45 WS), NWS MLB and the National Aeronautics and Space Administration tasked the Applied Meteorology Unit (AMU) to investigate the feasibility of establishing dual-Doppler capability using the two existing systems. This study investigated technical, hardware, and software requirements necessary to enable the establishment of a dual-Doppler capability. Review of the available literature pertaining to the dual-Doppler technique and consultation with experts revealed that the physical locations and resulting beam crossing angles of the 45 SW and NWS MLB radars make them ideally suited for a dual-Doppler capability. The dual-Doppler equations were derived to facilitate complete understanding of dual-Doppler synthesis; to determine the technical information requirements; and to determine the components of wind velocity from the equation of continuity and radial velocity data collected by the two Doppler radars. Analysis confirmed the suitability of the existing systems to provide the desired capability. In addition, it is possible that both 45 SW radar data and Terminal Doppler Weather Radar data from Orlando International Airport could be used to alleviate any

  4. Doppler characteristics of sea clutter.

    SciTech Connect

    Raynal, Ann Marie; Doerry, Armin Walter

    2010-06-01

    Doppler radars can distinguish targets from clutter if the target's velocity along the radar line of sight is beyond that of the clutter. Some targets of interest may have a Doppler shift similar to that of clutter. The nature of sea clutter is different in the clutter and exo-clutter regions. This behavior requires special consideration regarding where a radar can expect to find sea-clutter returns in Doppler space and what detection algorithms are most appropriate to help mitigate false alarms and increase probability of detection of a target. This paper studies the existing state-of-the-art in the understanding of Doppler characteristics of sea clutter and scattering from the ocean to better understand the design and performance choices of a radar in differentiating targets from clutter under prevailing sea conditions.

  5. Segmentation of Doppler optical coherence tomography signatures using a support-vector machine

    PubMed Central

    Singh, Amardeep S. G.; Schmoll, Tilman; Leitgeb, Rainer A.

    2011-01-01

    When processing Doppler optical coherence tomography images, there is a need to segment the Doppler signatures of the vessels. This can be used for visualization, for finding the center point of the flow areas or to facilitate the quantitative analysis of the vessel flow. We propose the use of a support-vector machine classifier in order to segment the flow. It uses the phase values of the Doppler image as well as texture information. We show that superior results compared to conventional simple threshold-based methods can be achieved in conditions of significant phase noise, which inhibit the use of a simple threshold of the phase values. PMID:21559144

  6. 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.

  7. High Resolution Doppler Lidar

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This Grant supported the development of an incoherent lidar system to measure winds and aerosols in the lower atmosphere. During this period the following activities occurred: (1) an active feedback system was developed to improve the laser frequency stability; (2) a detailed forward model of the instrument was developed to take into account many subtle effects, such as detector non-linearity; (3) a non-linear least squares inversion method was developed to recover the Doppler shift and aerosol backscatter without requiring assumptions about the molecular component of the signal; (4) a study was done of the effects of systematic errors due to multiple etalon misalignment. It was discovered that even for small offsets and high aerosol loadings, the wind determination can be biased by as much as 1 m/s. The forward model and inversion process were modified to account for this effect; and (5) the lidar measurements were validated using rawinsonde balloon measurements. The measurements were found to be in agreement within 1-2 m/s.

  8. Compact Doppler magnetograph

    NASA Astrophysics Data System (ADS)

    Ruzmaikin, Alexander; Moynihan, Philip I.; Vaughan, Arthur H.; Cacciani, Alessandro

    1998-11-01

    We designed a low-cost flight instrument that images the full solar disk through two narrow band filters at the red nd blue 'wings' of the solar potassium absorption line. The images are produced on a 1024 X 1024 charge-coupled device with a resolution of 2 arcsec per pixel. Four filtergrams taken in a very short time at both wings in the left and right states of circular polarization are used to yield a Dopplergram and a magnetogram simultaneously. The noise-equivalent velocity associated with each pixel is less than 3 m/s. The measured signal is linearly proportional to the velocity in the range +/- 4000 m/s. The range of magnetic fields is from 3 to 3000 Gauss. The optical system of the instrument is simple and easily aligned. With a pixel size of 12 micrometers , the effective focal length is 126 cm. A Raleigh resolution limit of 4 arcsec is achieved with a 5-cm entrance apertures, providing an f/25 focal ratio. The foreoptic is a two-component telephoto lens serving to limit the overall optical length to 89 cm or less. The mass of the instrument is 14 kg. the power required is less than 30 Watts. The Compact Doppler Magnetograph can be used in space mission with severe mass and power requirements. It can also be effectively used for ground-based observations: large telescope, dome or other observatory facilities are not required.

  9. High Resolution Doppler Imager

    NASA Technical Reports Server (NTRS)

    Hays, Paul B.

    1999-01-01

    This report summarizes the accomplishments of the High Resolution Doppler Imager (HRDI) on UARS spacecraft during the period 4/l/96 - 3/31/99. During this period, HRDI operation, data processing, and data analysis continued, and there was a high level of vitality in the HRDI project. The HRDI has been collecting data from the stratosphere, mesosphere, and lower thermosphere since instrument activation on October 1, 1991. The HRDI team has stressed three areas since operations commenced: 1) operation of the instrument in a manner which maximizes the quality and versatility of the collected data; 2) algorithm development and validation to produce a high-quality data product; and 3) scientific studies, primarily of the dynamics of the middle atmosphere. There has been no significant degradation in the HRDI instrument since operations began nearly 8 years ago. HRDI operations are fairly routine, although we have continued to look for ways to improve the quality of the scientific product, either by improving existing modes, or by designing new ones. The HRDI instrument has been programmed to collect data for new scientific studies, such as measurements of fluorescence from plants, measuring cloud top heights, and lower atmosphere H2O.

  10. NASA LaRC FIB Multi-Channel Anemometry Recording System-User's Manual. [conducted at the Langley Low-Turbulence Pressure Tunnel

    NASA Technical Reports Server (NTRS)

    Johnson, Sherylene (Compiler); Bertelrud, Arild (Compiler); Anders, J. B. (Technical Monitor)

    2002-01-01

    This report is part of a series of reports describing a flow physics high-lift experiment conducted in NASA Langley Research Center's Low-Turbulence Pressure Tunnel (LTPT) in 1996. The anemometry system used in the experiment was originally designed for and used in flight tests with NASA's Boeing 737 airplane. Information that may be useful in the evaluation or use of the experimental data has been compiled. The report also contains details regarding record structure, how to read the embedded time code, as well as the output file formats used in the code reading the binary data.

  11. HF Doppler Acoustic Imaging of the Ocean Surface and Interior

    NASA Astrophysics Data System (ADS)

    Pinkel, Robert; Smith, Jerome A.

    2004-11-01

    HF phased array Doppler sonar represents a new tool for obtaining Three-dimensional (r,q,t) images of the oceanic surface and interior velocity field. While the capabilities of the approach are unique, the design constraints are also unusual. Examples of both are presented in this work.

  12. Power Doppler imaging: clinical experience and correlation with color Doppler US and other imaging modalities.

    PubMed

    Hamper, U M; DeJong, M R; Caskey, C I; Sheth, S

    1997-01-01

    Power Doppler imaging has recently gained attention as an additional color flow imaging technique that overcomes some of the limitations of conventional color Doppler ultrasound (US). Limitations of conventional color Doppler US include angle dependence, aliasing, and difficulty in separating background noise from true flow in slow-flow states. Owing to its increased sensitivity to flow, power Doppler sonography is valuable in low-flow states and when optimal Doppler angles cannot be obtained. Longer segments of vessels and more individual vessels can be visualized with power Doppler US than with conventional color Doppler sonography. Power Doppler sonography increases diagnostic confidence when verifying or excluding testicular or ovarian torsion and confirming thrombosis or occlusion of vessels. Power Doppler sonography also improves evaluation of parenchymal flow and decreases examination times in technically challenging cases. Power Doppler US is a useful adjunct to mean-frequency color Doppler sonography, especially when color Doppler US cannot adequately obtain or display diagnostic information. PMID:9084086

  13. Experimental and Theoretical Studies on Two-Phase Flows.

    NASA Astrophysics Data System (ADS)

    Koh, Christopher James

    This thesis, comprised of two parts, deals with the flow of suspensions. Part I concerns specifically with the stability of a single drop translating through a quiescent, unbounded suspending fluid at low Reynolds number. The evolution of the shape of an initially nonspherical drop as it translates is studied numerically and experimentally. For finite capillary numbers, it is shown that the drop reverts to a sphere provided that the initial deformation is small enough. However, beyond certain critical initial deformation, the drop deforms continuously. For initially prolate shapes, the drop elongates with the formation of a tail; for initially oblate shapes, the drop flattens with the formation of a cavity at its rear. Experiments extend the numerical results. It is found that initially unstable prolate drops break up into multiple droplets, while initially unstable oblate drops deform in double-emulsion drops. Part II of this thesis considers the flow of high concentration solid suspensions through a rectangular channel. By adapting the well-known Laser Doppler Anemometry, an experimental technique is developed to measure the velocity as well as particle volume fraction of the suspension. A crucial element in these experiments is the reduction of the optical turbidity of the suspension. To accomplish this goal, a systematic method based on refractive-index-matching of the two phases is employed. Experimental results show that the velocity profile is blunted while the concentration profile has a maximum near the center. The qualitative features of the experimental data compare reasonably well with theoretical predictions based on the shear-induced particle migration theory.

  14. [Color Doppler sonography of focal abdominal lesions].

    PubMed

    Licanin, Zoran; Lincender, Lidija; Djurović, V; Salihefendić, Nizama; Smajlović, Fahrudin

    2004-01-01

    Color Doppler sonography (CDS--spectral, color and power), harmonic imaging techniques (THI, PHI), possibility of 3D analysis of picture, usage of contrast agents, have raised the values of ultrasound as a diagnostic method to a very high level. THI--non-linear gray scale modality, is based on the processing of higher reflected frequencies, that has improved a picture resolution, which is presented with less artifacts and limiting effects of obesity and gases. Ultrasound contrast agents improve analysis of micro and macro circulation of the examined area, and with the assessment of velocity of supply in ROI (wash in), distribution and time of signal weakening (wash out), are significantly increasing diagnostic value of ultrasound. Besides the anatomical and topographic presentation of examined region (color, power), Color Doppler sonography gives us haemodynamic-functional information on vascularisation of that region, as well as on pathologic vascularisation if present. Avascular aspect of a focal pathologic lesion corresponds to a cyst or haematoma, while coloration and positive spectral curve discover that anechogenic lesions actually represents aneurysms, pseudoaneurysms or AVF. In local inflammatory lesion, abscess in an acute phase, CDS shows first increased, and then decreased central perfusion, while in a chronic phase, a pericapsular vascularisation is present. Contribution of CDS in differentiation of hepatic tumors (hemangioma, HCC and metastasis) is very significant. Central color dots along the peripheral blood vessels and the blush phenomenon are characteristics of capillary hemangioma, peritumoral vascular ring "basket" of HCC, and "detour" sign of metastasis. The central artery, RI from 0.45 to 0.60 and radial spreading characterize FNH. Hepatic adenoma is characterized by an intratumoral vein, and rarely by a vascular hallo. Further on, blood velocity in tumor defined by Color Doppler, distinguishes malignant from benign lesion, where 40 cm/s is a

  15. One way Doppler Extractor. Volume 2: Digital VCO technique

    NASA Technical Reports Server (NTRS)

    Nossen, E. J.; Starner, E. R.

    1974-01-01

    A feasibility analysis and trade-offs for a one-way Doppler extractor using digital VCO techniques is presented. The method of Doppler measurement involves the use of a digital phase lock loop; once this loop is locked to the incoming signal, the precise frequency and hence the Doppler component can be determined directly from the contents of the digital control register. The only serious error source is due to internally generated noise. Techniques are presented for minimizing this error source and achieving an accuracy of 0.01 Hz in a one second averaging period. A number of digitally controlled oscillators were analyzed from a performance and complexity point of view. The most promising technique uses an arithmetic synthesizer as a digital waveform generator.

  16. Theoretical analysis and experimental verification on optical rotational Doppler effect.

    PubMed

    Zhou, Hailong; Fu, Dongzhi; Dong, Jianji; Zhang, Pei; Zhang, Xinliang

    2016-05-01

    We present a theoretical model to sufficiently investigate the optical rotational Doppler effect based on modal expansion method. We find that the frequency shift content is only determined by the surface of spinning object and the reduced Doppler shift is linear to the difference of mode index between input and output orbital angular momentum (OAM) light, and linear to the rotating speed of spinning object as well. An experiment is carried out to verify the theoretical model. We explicitly suggest that the spatial spiral phase distribution of spinning object determines the frequency content. The theoretical model makes us better understand the physical processes of rotational Doppler effect, and thus has many related application fields, such as detection of rotating bodies, imaging of surface and measurement of OAM light. PMID:27137615

  17. Theoretical analysis and experimental verification on optical rotational Doppler effect

    NASA Astrophysics Data System (ADS)

    Zhou, Hailong; Fu, Dongzhi; Dong, Jianji; Zhang, Pei; Zhang, Xinliang

    2016-05-01

    We present a theoretical model to sufficiently investigate the optical rotational Doppler effect based on modal expansion method. We find that the frequency shift content is only determined by the surface of spinning object and the reduced Doppler shift is linear to the difference of mode index between input and output orbital angular momentum (OAM) light, and linear to the rotating speed of spinning object as well. An experiment is carried out to verify the theoretical model. We explicitly suggest that the spatial spiral phase distribution of spinning object determines the frequency content. The theoretical model makes us better understand the physical processes of rotational Doppler effect, and thus has many related application fields, such as detection of rotating bodies, imaging of surface and measurement of OAM light.

  18. Planetary Doppler Imaging

    NASA Astrophysics Data System (ADS)

    Murphy, N.; Jefferies, S.; Hart, M.; Hubbard, W. B.; Showman, A. P.; Hernandez, G.; Rudd, L.

    2014-12-01

    Determining the internal structure of the solar system's gas and ice giant planets is key to understanding their formation and evolution (Hubbard et al., 1999, 2002, Guillot 2005), and in turn the formation and evolution of the solar system. While internal structure can be constrained theoretically, measurements of internal density distributions are needed to uncover the details of the deep interior where significant ambiguities exist. To date the interiors of giant planets have been probed by measuring gravitational moments using spacecraft passing close to, or in orbit around the planet. Gravity measurements are effective in determining structure in the outer envelope of a planet, and also probing dynamics (e.g. the Cassini and Juno missions), but are less effective in probing deep structure or the presence of discrete boundaries. A promising technique for overcoming this limitation is planetary seismology (analogous to helioseismology in the solar case), postulated by Vorontsov, 1976. Using trapped pressure waves to probe giant planet interiors allows insight into the density and temperature distribution (via the sound speed) down to the planetary core, and is also sensitive to sharp boundaries, for example at the molecular to metallic hydrogen transition or at the core-envelope interface. Detecting such boundaries is not only important in understanding the overall structure of the planet, but also has implications for our understanding of the basic properties of matter at extreme pressures. Recent Doppler measurements of Jupiter by Gaulme et al (2011) claimed a promising detection of trapped oscillations, while Hedman and Nicholson (2013) have shown that trapped waves in Saturn cause detectable perturbations in Saturn's C ring. Both these papers have fueled interest in using seismology as a tool for studying the solar system's giant planets. To fully exploit planetary seismology as a tool for understanding giant planet structure, measurements need to be made

  19. A FORTRAN code for the calculation of probe volume geometry changes in a laser anemometry system caused by window refraction

    NASA Technical Reports Server (NTRS)

    Owen, Albert K.

    1987-01-01

    A computer code was written which utilizes ray tracing techniques to predict the changes in position and geometry of a laser Doppler velocimeter probe volume resulting from refraction effects. The code predicts the position change, changes in beam crossing angle, and the amount of uncrossing that occur when the beams traverse a region with a changed index of refraction, such as a glass window. The code calculates the changes for flat plate, cylinder, general axisymmetric and general surface windows and is currently operational on a VAX 8600 computer system.

  20. Understanding Doppler Broadening of Gamma Rays

    SciTech Connect

    Rawool-Sullivan, Mohini; Sullivan, John P.

    2014-07-03

    Doppler-broadened gamma ray peaks are observed routinely in the collection and analysis of gamma-ray spectra. If not recognized and understood, the appearance of Doppler broadening can complicate the interpretation of a spectrum and the correct identification of the gamma ray-emitting material. We have conducted a study using a simulation code to demonstrate how Doppler broadening arises and provide a real-world example in which Doppler broadening is found. This report describes that study and its results.

  1. Comparison of Triature Doppler Velocimetry and VISAR

    SciTech Connect

    Cenobio H Gallegos, Bruce Marshall, Matthew Teel, Vincent T Romero, Abel Diaz, and Michael Berninger

    2010-01-01

    Triature Photonic Doppler Velocimetry (TDV) is an adaptation of Photonic Doppler Velocimetry (PDV) that rejects common-mode data noise after splitting PDV three ways, with each signal 120° out of phase from each other. Testing has demonstrated that TDV also improves temporal resolution from the typical five nanoseconds of PDV to a subnanosecond range. This paper compares the temporal response of TDV with that of PDV and VISAR [velocity interferometer system for any reflector] in an experiment with a subnanosecond (~120-picosecond rise time) shock source. Laboratory tests were performed using a high-power laser on targets of copper and aluminum. A Buce Marshall fast VISAR with a single-point PDV and a prototype TDV were used. A special probe that combined PDV, TDV, and fast VISAR made simultaneous velocity measurements. Breakout velocities of 1.3 km/second on copper and 2.5 km/second on aluminum were observed, where TDV resolved rise times of ~200 ps. This resolution was better than that of a fast VISAR, which can achieve ~500 ps temporal resolution. Test methods and results are presented.

  2. The Doppler Effect--A New Approach

    ERIC Educational Resources Information Center

    Allen, J.

    1973-01-01

    Discusses the Doppler effect as it applies to different situations, such as a stationary source of sound with the observer moving, a stationary observer, and the sound source and observer both moving. Police radar, satellite surveillance radar, radar astronomy, and the Doppler navigator, are discussed as applications of Doppler shift. (JR)

  3. JAWS multiple Doppler derived winds

    NASA Technical Reports Server (NTRS)

    Elmore, Kimberly L.

    1987-01-01

    An elementary working knowledge is given of the advantages and limitations of the multiple Doppler radar analyses that have recently become available from the Joint Airport Weather Studies (JAWS) project. What Doppler radar is and what it does is addressed and the way Doppler radars were used in the JAWS project to gather wind shear data is described. The working definition of wind shear used is winds that affect aircraft flight over a span of 15 to 45 seconds and turbulence is defined as air motion that cause abrupt aircraft motions. The JAWS data current available contain no turbulence data. The concept of multiple Doppler analysis and the geometry of how it works are described, followed by an explanation of how data gathered in radar space are interpolated to a common Cartesian coordinate system and the limitations involved. A discussion is also presented of the analysis grid and how it was constructed. What the user actually gets is discussed, followed by a discussion of the expected errors in the three orthogonal wind components. Finally, a discussion is presented of why JAWS data are significant.

  4. Doppler observations of solar rotation

    NASA Technical Reports Server (NTRS)

    Scherrer, P. H.; Wilcox, J. M.

    1980-01-01

    Daily observations of the photospheric equatorial rotation rate using the Doppler effect are made at the Stanford Solar Observatory. These observations show no variations in the rotation rate that exceed the observational error of about 1%. The average rotation rate is indistinguishable from that of sunspots and large-scale magnetic field structures.

  5. Doppler observations of solar rotation

    NASA Technical Reports Server (NTRS)

    Scherrer, P. H.

    1980-01-01

    Daily observations of the photospheric equatorial rotation rate using the Doppler effect mode at the Sanford Solar Observatory are presented. These observations show no variations in the rotation rate that exceed the observational error of about one percent. The average rotation rate is indistinguishable from that of sunspots and large scale magnetic field structures.

  6. Laser Doppler field sensor for high resolution flow velocity imaging without camera

    SciTech Connect

    Voigt, Andreas; Bayer, Christian; Shirai, Katsuaki; Buettner, Lars; Czarske, Juergen

    2008-09-20

    In this paper we present a laser sensor for highly spatially resolved flow imaging without using a camera. The sensor is an extension of the principle of laser Doppler anemometry (LDA). Instead of a parallel fringe system, diverging and converging fringes are employed. This method facilitates the determination of the tracer particle position within the measurement volume and leads to an increased spatial and velocity resolution compared to conventional LDA. Using a total number of four fringe systems the flow is resolved in two spatial dimensions and the orthogonal velocity component. Since no camera is used, the resolution of the sensor is not influenced by pixel size effects. A spatial resolution of 4 {mu}m in the x direction and 16 {mu}m in the y direction and a relative velocity resolution of 1x10{sup -3} have been demonstrated up to now. As a first application we present the velocity measurement of an injection nozzle flow. The sensor is also highly suitable for applications in nano- and microfluidics, e.g., for the measurement of flow rates.

  7. Segmental Comparison of Peripheral Arteries by Doppler Ultrasound and CT Angiography

    PubMed Central

    Swaminathan, Ram Kumar; Ganesan, Prakash; Mayavan, Manibharathi

    2016-01-01

    Introduction Diseases of peripheral arterial system are one of the common causes of limb pain, especially in elderly patients. Here we analyse non invasive imaging of peripheral arterial segments. Aim Aim of the study was to compare arterial diseases of extremities using Doppler ultrasound and CT angiography, and to find the better non-invasive modality of choice. Materials and Methods Fifty patients {14 patients with upper limb complaints (15 upper limbs) and 36 patients with lower limb complaints (72 lower limbs)} of peripheral arterial disease underwent Doppler ultrasound (USG) and CT Angiogram (CTA). Arterial systems divided into anatomic segments and luminal narrowing were compared using gray scale Doppler ultrasound and axial images of arterial phase of CT angiogram. Using statistical methods, sensitivity, specificity and accuracy of Doppler ultrasound and CT angiography were determined. Results Six hundred and nineteen arterial segments were studied with CT angiography and Doppler ultrasound. Of which 226 diseased segments were identified in CT angiography. Doppler overestimated narrowing by one grade in 47 segments, by two grade in 11 segments, by three grades in 30 segments and by four grades in 22 segments; underestimated by one grade in 28 segments, by two grades in 9 segments, by three grades in 5 segments and by four grades in 3 segments. Significant statistical difference exists between Doppler USG and CT angiography. Doppler showed good correlation with CT angiography in 74%, but, Doppler overestimated stenosis grade in a significant percentage. The sensitivity, specificity and accuracy of Doppler USG compared with CT angiography was 93.36%, 82.44%, and 86.42%. Conclusion Duplex Doppler can be the first investigation in excluding peripheral arterial disease, especially for evaluation of infra inguinal region of lower limbs and from second part of the subclavian artery in upper limbs. PMID:27042556

  8. Flashing liquid jets and two-phase droplet dispersion I. Experiments for derivation of droplet atomisation correlations.

    PubMed

    Cleary, Vincent; Bowen, Phil; Witlox, Henk

    2007-04-11

    The large-scale release of a liquid contained at upstream conditions above its local atmospheric boiling point is a scenario often given consideration in process industry risk analysis. Current-hazard quantification software often employs simplistic equilibrium two-phase approaches. Scaled water experiments have been carried out measuring droplet velocity and droplet size distributions for a range of exit orifice aspect ratios (L/d) and conditions representing low to high superheat. 2D Phase-Doppler Anemometry has been utilised to characterise droplet kinematics and spray quality. Droplet size correlations have been developed for non-flashing, the transition between non-flashing and flashing, and fully flashing jets. Using high-speed shadowography, transition between regimes is defined in terms of criteria identified in the external flow structure. An overview companion paper provides a wider overview of the problem and reports implementation of these correlations into consequence models and subsequent validation. The fluid utilised throughout is water, hence droplet correlations are developed in non-dimensional form to allow extrapolation to other fluids through similarity scaling, although verification of model performance for other fluids is required in future studies. Data is reduced via non-dimensionalisation in terms of the Weber number and Jakob number, essentially representing the fluid mechanics and thermodynamics of the system, respectively. A droplet-size distribution correlation has also been developed, conveniently presented as a volume undersize distribution based on the Rosin-Rammler distribution. Separate correlations are provided for sub-cooled mechanical break-up and fully flashing jets. This form of correlation facilitates rapid estimates of likely mass rainout quantities, as well as full distribution information for more rigorous two-phase thermodynamic modelling in the future. PMID:16956721

  9. Reducing Antenna Mechanical Noise in Precision Doppler Tracking

    NASA Astrophysics Data System (ADS)

    Armstrong, J. W.; Estabrook, F. B.; Asmar, S. W.; Iess, L.; Tortora, P.

    2006-05-01

    Precision Doppler tracking of deep-space probes is central to spacecraft navigation and many radio science investigations. The most sensitive Doppler observations to date have been taken using the NASA/JPL Deep Space Network (DSN) antenna DSS 25, a 34-m-diameter beam-waveguide station especially instrumented with simultaneous X-band (approximately 8.4-GHz) and Ka-band (approximately 32-GHz) links and tropospheric scintillation calibration equipment, tracking the Cassini spacecraft. These Cassini observations achieved Doppler fractional frequency stability (Doppler frequency fluctuation divided by center frequency, Delta f / f_o ) of approximately 3 x 10^-15 at tau = 1000 s integration. In those very-high-sensitivity tracks, the leading disturbance was antenna mechanical noise: time-dependent unmodeled physical motion of the ground antenna's phase center caused by antenna sag as the elevation angle changed, unmodeled subreflector motion, wind loading, bulk motion of the antenna as it rolled over irregularities in the supporting azimuth ring, differential thermal expansion of the structure, etc. This noise has seemed irreducible at reasonable cost, since it is unclear how to build a practical, large, moving, steel structure having mechanical stability significantly better than that of current tracking stations. Here we show how the mechanical noise of a large tracking antenna can effectively be removed when two-way Doppler tracking data from an existing DSN antenna are suitably combined with simultaneous tracking data using an ancillary (smaller and stiffer) antenna. Using our method, the mechanical noise in the final Doppler observable can be reduced, substantially, to that of the stiffer antenna.

  10. Browsing a wealth of millimeter-wavelength doppler spectra data

    SciTech Connect

    Johnson,K.; Luke,E.; Kollias, P.; Remillard, J.; Widener, K.; Jensen, M.

    2010-03-15

    The ARM Climate Research Facility has collected an extensive archive of vertically pointing millimeter wavelength Doppler radar spectra at both 35 and 95 GHz. These data are a rich potential source of detailed microphysical and dynamical cloud and precipitation information. The recording of spectra, which is ongoing, began at the Southern Great Plains site in September of 2003, at the North Slope of Alaska site in April 2004, and at Tropical Western Pacific sites in 2006. Spectra are also being collected during ARM Mobile Facility deployments. The data’s temporal resolution is as high as two seconds, at height intervals of 45 to 90 m. However, the sheer volume of available data can be somewhat daunting to access and search for specific features of interest. Here we present a user interface for spectra browsing, which allows the user to view time-height images of radar moments, select a time or height of interest, and then “drill down” through images of spectrograms to individual Doppler spectra or time- and height-sequences of spectra. Also available are images summarizing spectral characteristics, such as number of spectral peaks, spectral shape information (skewness and kurtosis), moment uncertainty estimates, and hydrometeor vs. clutter identification as produced by the ARM MicroARSCL (Microphysical Active Remote Sensing of Clouds) value-added product. In addition to the access and visualization tools, we are developing a Doppler spectra simulator capable of generating Doppler spectra from liquid, mixed-phase, and solid cloud constituents and precipitation. The Doppler spectra simulator can be used as an interface between explicit microphysics models and Doppler spectra observations from the ARM radars. The plan is to ultimately make the spectra simulator available from within the spectra browser, allowing a user to associate observed spectra with the microphysical conditions capable of producing them.

  11. Applications of Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Xu, Zhiqiang

    longitudinal resolution and the imaging depth for OCT imaging. Doppler OCT is becoming an increasingly popular field of investigation within optical coherence tomography with potentially important applications in cardiovascular and microfluidic research. We have spent some of the effort on searching for accurate and efficient methods for processing the experimental data. We applied the pseudo Wigner time-frequency distribution method to the data processing of Doppler OCT and compared its performance to that of the short-time Fourier transform method, the Hilbert-based phase-resolved method and the autocorrelation method. We concluded that the pseudo Wigner-distribution signal processing method is overall more precise than other often-used methods in Doppler OCT for the analysis of cross-sectional velocity distributions, especially in the high velocity regime. We also discovered the advantage of using the time-domain instead of the frequency domain for Doppler OCT for some applications where precise Doppler-speed metrology is essential. Based on the fact that the obtained local OCT interference signal is almost a single periodic waveform, we have developed a novel, simple and less time-consuming processing method based on the zero-crossing points in an OCT signal for the measurement of the Doppler frequency in a laminar flow. This method was compared to other processing approaches currently used in Doppler OCT. The results show that in the case of laminar flow, the zero-crossing method gives the more precise results, especially in the higher velocity regime with a substantial economy in processing time and an increase in dynamic range which can reach 70 dB. This feature becomes a major advantage in metrology if one wants to measure velocities over several orders of magnitude. We have applied this technique to some real flow models and the preliminary results on flow velocity distributions obtained in the case of a microfluidic circuit and in that of a phantom of a blood vessel

  12. Spacecraft Doppler tracking with a VLBI antenna

    NASA Technical Reports Server (NTRS)

    Comoretto, G.; Iess, L.; Bertotti, B.; Brenkle, J. P.; Horton, T.

    1990-01-01

    Preliminary results are reported from Doppler-shift measurements to the Voyager-2 spacecraft at a distance of 26 AU, obtained using the 32-m VLBI antenna at Medicina (Italy) during July and August 1988. The apparatus comprises the el-az antenna, an S-X-band receiver, a hydrogen maser to generate the reference signal, a Mark III VLBI terminal, and a digital tone extractor capable of isolating a tone of known frequency from a noisy signal and giving its phase and amplitude. A signal transmitted in S-band from the NASA Deep Space Network (DSN) station in Australia and retransmitted coherently in X-band by Voyager, was received 7 h 6 min later at Medicina and at the DSN station in Madrid. Sample data are presented graphically and shown to be of generally high quality; further in-depth analysis is under way.

  13. 3D reconstruction and quantitative assessment method of mitral eccentric regurgitation from color Doppler echocardiography

    NASA Astrophysics Data System (ADS)

    Liu, Qi; Ge, Yi Nan; Wang, Tian Fu; Zheng, Chang Qiong; Zheng, Yi

    2005-10-01

    Based on the two-dimensional color Doppler image in this article, multilane transesophageal rotational scanning method is used to acquire original Doppler echocardiography while echocardiogram is recorded synchronously. After filtering and interpolation, the surface rendering and volume rendering methods are performed. Through analyzing the color-bar information and the color Doppler flow image's superposition principle, the grayscale mitral anatomical structure and color-coded regurgitation velocity parameter were separated from color Doppler flow images, three-dimensional reconstruction of mitral structure and regurgitation velocity distribution was implemented separately, fusion visualization of the reconstructed regurgitation velocity distribution parameter with its corresponding 3D mitral anatomical structures was realized, which can be used in observing the position, phase, direction and measuring the jet length, area, volume, space distribution and severity level of the mitral regurgitation. In addition, in patients with eccentric mitral regurgitation, this new modality overcomes the inherent limitations of two-dimensional color Doppler flow image by depicting the full extent of the jet trajectory, the area of eccentric regurgitation on three-dimensional image was much larger than that on two-dimensional image, the area variation tendency and volume variation tendency of regurgitation have been shown in figure at different angle and different systolic phase. The study shows that three-dimensional color Doppler provides quantitative measurements of eccentric mitral regurgitation that are more accurate and reproducible than conventional color Doppler.

  14. ADVANCED COMPUTATIONAL MODEL FOR THREE-PHASE SLURRY REACTORS

    SciTech Connect

    Goodarz Ahmadi

    2001-10-01

    In the second year of the project, the Eulerian-Lagrangian formulation for analyzing three-phase slurry flows in a bubble column is further developed. The approach uses an Eulerian analysis of liquid flows in the bubble column, and makes use of the Lagrangian trajectory analysis for the bubbles and particle motions. An experimental set for studying a two-dimensional bubble column is also developed. The operation of the bubble column is being tested and diagnostic methodology for quantitative measurements is being developed. An Eulerian computational model for the flow condition in the two-dimensional bubble column is also being developed. The liquid and bubble motions are being analyzed and the results are being compared with the experimental setup. Solid-fluid mixture flows in ducts and passages at different angle of orientations were analyzed. The model predictions were compared with the experimental data and good agreement was found. Gravity chute flows of solid-liquid mixtures is also being studied. Further progress was also made in developing a thermodynamically consistent model for multiphase slurry flows with and without chemical reaction in a state of turbulent motion. The balance laws are obtained and the constitutive laws are being developed. Progress was also made in measuring concentration and velocity of particles of different sizes near a wall in a duct flow. The technique of Phase-Doppler anemometry was used in these studies. The general objective of this project is to provide the needed fundamental understanding of three-phase slurry reactors in Fischer-Tropsch (F-T) liquid fuel synthesis. The other main goal is to develop a computational capability for predicting the transport and processing of three-phase coal slurries. The specific objectives are: (1) To develop a thermodynamically consistent rate-dependent anisotropic model for multiphase slurry flows with and without chemical reaction for application to coal liquefaction. Also establish the

  15. Doppler velocity detection limitations in spectrometer-based versus swept-source optical coherence tomography

    PubMed Central

    Hendargo, Hansford C.; McNabb, Ryan P.; Dhalla, Al-Hafeez; Shepherd, Neal; Izatt, Joseph A.

    2011-01-01

    Recent advances in Doppler techniques have enabled high sensitivity imaging of biological flow to measure blood velocities and vascular perfusion. Here we compare spectrometer-based and wavelength-swept Doppler OCT implementations theoretically and experimentally, characterizing the lower and upper observable velocity limits in each configuration. We specifically characterize the washout limit for Doppler OCT, the velocity at which signal degradation results in loss of flow information, which is valid for both quantitative and qualitative flow imaging techniques. We also clearly differentiate the washout effect from the separate phenomenon of phase wrapping. We demonstrate that the maximum detectable Doppler velocity is determined by the fringe washout limit and not phase wrapping. Both theory and experimental results from phantom flow data and retinal blood flow data demonstrate the superiority of the swept-source technique for imaging vessels with high flow rates. PMID:21833356

  16. Doppler ultrasound evaluation in preeclampsia

    PubMed Central

    2013-01-01

    Background Worldwide preeclampsia (PE) is the leading cause of maternal death and affects 5 to 8% of pregnant women. PE is characterized by elevated blood pressure and proteinuria. Doppler Ultrasound (US) evaluation has been considered a useful method for prediction of PE; however, there is no complete data about the most frequently altered US parameters in the pathology. The aim of this study was to evaluate the uterine, umbilical, and the middle cerebral arteries using Doppler US parameters [resistance index (RI), pulsatility index (PI), notch (N), systolic peak (SP) and their combinations] in pregnant women, in order to make a global evaluation of hemodynamic repercussion caused by the established PE. Results A total of 102 pregnant Mexican women (65 PE women and 37 normotensive women) were recruited in a cases and controls study. Blood velocity waveforms from uterine, umbilical, and middle cerebral arteries, in pregnancies from 24 to 37 weeks of gestation were recorded by trans-abdominal examination with a Toshiba Ultrasound Power Vision 6000 SSA-370A, with a 3.5 MHz convex transducer. Abnormal general Doppler US profile showed a positive association with PE [odds ratio (OR) = 2.93, 95% confidence interval (CI) = 1.2 - 7.3, P = 0.021)], and a specificity and predictive positive value of 89.2% and 88.6%, respectively. Other parameters like N presence, RI and PI of umbilical artery, as well as the PI of middle cerebral artery, showed differences between groups (P values < 0.05). Conclusion General Doppler US result, as well as N from uterine vessel, RI from umbilical artery, and PI from umbilical and middle cerebral arteries in their individual form, may be considered as tools to determine hemodynamic repercussion caused by PE. PMID:24252303

  17. Coherent homodyne receiver with a compensator of Doppler shifts for inter orbit optical communication

    NASA Astrophysics Data System (ADS)

    Ando, Toshiyuki; Haraguchi, Eisuke; Tajima, Kenichi; Hirano, Yoshihito; Hanada, Tatsuyuki; Yamakawa, Shiro

    2011-03-01

    This paper presents Bread Board Model (BBM) of coherent homodyne receiver with an optical phase locked loop and a frequency compensator of Doppler shifts for inter satellite optical communication link. 2.5Gbps BPSK data has been demodulated with sensitivity of -49.1dBm at bit rate of 1e-6 under initial frequency offset of +/-7 GHz simulated as Doppler shifts due to variation of distance between each satellite.

  18. In vivo feasibility of endovascular Doppler optical coherence tomography

    PubMed Central

    Sun, Cuiru; Nolte, Felix; Cheng, Kyle H. Y.; Vuong, Barry; Lee, Kenneth K. C.; Standish, Beau A.; Courtney, Brian; Marotta, Thomas R.; Mariampillai, Adrian; Yang, Victor X. D.

    2012-01-01

    Feasibility of detecting intravascular flow using a catheter based endovascular optical coherence tomography (OCT) system is demonstrated in a porcine carotid model in vivo. The effects of A-line density, radial distance, signal-to-noise ratio, non-uniform rotational distortion (NURD), phase stability of the swept wavelength laser and interferometer system on Doppler shift detection limit were investigated in stationary and flow phantoms. Techniques for NURD induced phase shift artifact removal were developed by tracking the catheter sheath. Detection of high flow velocity (~51 cm/s) present in the porcine carotid artery was obtained by phase unwrapping techniques and compared to numerical simulation, taking into consideration flow profile distortion by the eccentrically positioned imaging catheter. Using diluted blood in saline mixture as clearing agent, simultaneous Doppler OCT imaging of intravascular flow and structural OCT imaging of the carotid artery wall was feasible. To our knowledge, this is the first in vivo demonstration of Doppler imaging and absolute measurement of intravascular flow using a rotating fiber catheter in carotid artery. PMID:23082299

  19. 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

  20. Generic Doppler processor speeds radar analysis

    NASA Astrophysics Data System (ADS)

    Engler, Harold F., Jr.; West, Philip D.; Austin, Mark D.; Gardos, Thomas R.

    1991-03-01

    The design and operation of a generic Doppler processor (GDP) are described in detail and illustrated with diagrams. The GDP was developed to facilitate the selection of a Doppler processing method for a radar system; it operates on an industrial desktop computer and makes it possible to switch rapidly among different Doppler processing bandwidths and center frequencies, filtering methods (FFT, analog, etc.), windowing methods, numbers of bits for quantization, and output display formats. The principal components are a programmable baseband clutter filter module, a Doppler processor chassis, a synthetic range-Doppler display, and a spectrum-analyzer-type real-Doppler display. The GDP provides + or - 5O kHz coverage with filter bandwidth 200 Hz, a maximum of 512 channels, 10 range gates, and an instantaneous dynamic range of 60 dB. Also discussed is the efficient finite-impulse-response filter design used to simulate analog filter banks.

  1. Mapping of airborne Doppler radar data

    SciTech Connect

    Lee, W.; Dodge, P.; Marks, F.D. Jr.; Hildebrand, P.H. NOAA, Miami, FL )

    1994-04-01

    Two sets of equations are derived to (1) map airborne Doppler radar data from an aircraft-relative coordinate system to an earth-relative coordinate system, and (2) remove the platform motion from the observed Doppler velocities. These equations can be applied to data collected by the National Oceanic and Atmospheric Administration WP-3D system, the National Center for Atmospheric Research Electra Doppler Radar (ELDORA) system, and other airborne radar systems.

  2. Doppler effects on periodicities in Saturn's magnetosphere

    NASA Astrophysics Data System (ADS)

    Carbary, J. F.

    2015-11-01

    The magnetosphere of Saturn exhibits a wide variety of periodic phenomena in magnetic fields, charged particles, and radio emissions. The periodicities are observed from a moving spacecraft, so an issue arises about the periodicities being influenced by the Doppler effects. Doppler effects can be investigated using models of the periodicities and then flying the spacecraft through the model, effectively measuring any Doppler phenomena with the simulation. Using 200 days of typical elliptical orbits from the Cassini mission at Saturn, three models were tested: an azimuthal wave (or "searchlight") model, a radial wave (or "pond ripple") model, and a model of an outwardly traveling spiral wave. The azimuthal wave model produced virtually no Doppler effects in the periodicities because its wave vector is nearly perpendicular to the spacecraft trajectory. The radial wave model generated strong Doppler effects of an upshifted and a downshifted signal (a dual period) on either side of the true period, because the wave vector is either parallel or antiparallel to the spacecraft trajectory. Being intermediate to the searchlight and radial waves, the spiral wave produced Doppler effects but only for low wave speeds (<10 RS/h). For higher wave speeds the Doppler effects were not as clear. The Doppler effects can be mitigated by employing only observations beyond ~15 RS where the spacecraft speed is low compared to the wave speed. The observed periodicities over the same 200 day interval do not show evidence of Doppler effects but generally display a single feature at the expected ~10.7 h period.

  3. Transthoracic Ultrafast Doppler Imaging of Human Left Ventricular Hemodynamic Function

    PubMed Central

    Osmanski, Bruno-Félix; Maresca, David; Messas, Emmanuel; Tanter, Mickael; Pernot, Mathieu

    2016-01-01

    Heart diseases can affect intraventricular blood flow patterns. Real-time imaging of blood flow patterns is challenging because it requires both a high frame rate and a large field of view. To date, standard Doppler techniques can only perform blood flow estimation with high temporal resolution within small regions of interest. In this work, we used ultrafast imaging to map in 2D human left ventricular blood flow patterns during the whole cardiac cycle. Cylindrical waves were transmitted at 4800 Hz with a transthoracic phased array probe to achieve ultrafast Doppler imaging of the left ventricle. The high spatio-temporal sampling of ultrafast imaging permits to rely on a much more effective wall filtering and to increase sensitivity when mapping blood flow patterns during the pre-ejection, ejection, early diastole, diastasis and late diastole phases of the heart cycle. The superior sensitivity and temporal resolution of ultrafast Doppler imaging makes it a promising tool for the noninvasive study of intraventricular hemodynamic function. PMID:25073134

  4. Stimulated acoustic emission: pseudo-Doppler shifts seen during the destruction of nonmoving microbubbles.

    PubMed

    Tiemann, K; Pohl, C; Schlosser, T; Goenechea, J; Bruce, M; Veltmann, C; Kuntz, S; Bangard, M; Becher, H

    2000-09-01

    The purpose of this study was to evaluate the appearance and the characteristics of stimulated acoustic emission (SAE) as an echo contrast-specific color Doppler phenomenon with impact on myocardial contrast echocardiography (MCE). Stationary microbubbles of the new contrast agent SH-U 563A (Schering AG) were embedded within a tissue-mimicking gel material. Harmonic power Doppler imaging (H-PDI), color Doppler and pulse-wave Doppler data were acquired using an HDI-5000 equipped with a phased-array transducer (1.67/3.3 MHz). In color Doppler mode, bubble destruction resulted in random noise like Doppler signals. PW-Doppler revealed short "pseudo-Doppler" shifts with a broadband frequency spectrum. Quantification of SAE events by H-PDI demonstrated an exponential decay of signal intensities over successive frames. A strong linear relationship was found between bubble concentration and the square root of the linearized H-PDI signal for a range of concentrations of more than two orders of magnitude (R = 0.993, p < 0.0001). Intensity of the H-PDI signals correlated well with emission power (R = 0.96, p = 0.0014). SAE results from disintegration of microbubbles and can be demonstrated by all Doppler imaging modalities, including H-PDI. Intensity of SAE signals is influenced by the applied acoustic power and correlates highly with the concentration of microbubbles. Because intensity of SAE signals correlates highly with echo contrast concentrations, analysis of SAE signals might be used for quantitative MCE. PMID:11053751

  5. The design of an onboard digital Doppler processor for a spaceborne scatterometer

    NASA Technical Reports Server (NTRS)

    Long, David G.; Chi, Chong-Yung; Li, Fuk K.

    1988-01-01

    A digital Doppler processor, which will permit the Doppler center frequency of the measurement cell bandwidths to be adjusted to compensate for the effects of the earth's rotation, will be used in the next NASA spaceborn scatterometer known as NSCAT. The authors describe the design and genesis of the NSCAT digital Doppler processor and discusses the performance tradeoff issues that were evaluated during the design phase. In this FFT (fast Fourier transform)-based technique, computation of the adjustment to the cell center frequencies will be done onboard using an approximate expression for the Doppler shift of the cell center versus orbit time. This technique also permits modification of the parameters used to locate the radar-backscatter-coefficient measurement cells by ground command in response to orbit changes.

  6. Effects of geomagnetic pulsations on the Doppler shift of HF backscatter radar echoes

    NASA Astrophysics Data System (ADS)

    Bourdillon, A.; Delloue, J.; Parent, J.

    1989-04-01

    Three mechanisms are considered for studying the effects of geomagnetic pulsations on the Doppler shifts of HF backscatter radar echoes: (1) variation of the phase refractive index under the influence of the varying magnetic component, (2) modulation of the plasma density, and (3) electrodynamic drift of the ionosphere. The electrodynamic drift is shown to be the most probable efficient mechanism to account for the measured Doppler shifts. In this model the Doppler shift on F-region propagation modes is sensitive to the eastward electric field of the wave, while E-region propagation modes are sensitive to the northward and eastward components with weights depending on the reflection height. Pi 2 and Pc 3 effects on the Doppler shift are presented, along with an example of the effects of Pi 2 pulsations on F-region and Es-region propagation modes.

  7. Airborne Differential Doppler Weather Radar

    NASA Technical Reports Server (NTRS)

    Meneghini, R.; Bidwell, S.; Liao, L.; Rincon, R.; Heymsfield, G.; Hildebrand, Peter H. (Technical Monitor)

    2001-01-01

    The Precipitation Radar aboard the Tropical Rain Measuring Mission (TRMM) Satellite has shown the potential for spaceborne sensing of snow and rain by means of an incoherent pulsed radar operating at 13.8 GHz. The primary advantage of radar relative to passive instruments arises from the fact that the radar can image the 3-dimensional structure of storms. As a consequence, the radar data can be used to determine the vertical rain structure, rain type (convective/stratiform) effective storm height, and location of the melting layer. The radar, moreover, can be used to detect snow and improve the estimation of rain rate over land. To move toward spaceborne weather radars that can be deployed routinely as part of an instrument set consisting of passive and active sensors will require the development of less expensive, lighter-weight radars that consume less power. At the same time, the addition of a second frequency and an upgrade to Doppler capability are features that are needed to retrieve information on the characteristics of the drop size distribution, vertical air motion and storm dynamics. One approach to the problem is to use a single broad-band transmitter-receiver and antenna where two narrow-band frequencies are spaced apart by 5% to 10% of the center frequency. Use of Ka-band frequencies (26.5 GHz - 40 GHz) affords two advantages: adequate spatial resolution can be attained with a relatively small antenna and the differential reflectivity and mean Doppler signals are directly related to the median mass diameter of the snow and raindrop size distributions. The differential mean Doppler signal has the additional property that this quantity depends only on that part of the radial speed of the hydrometeors that is drop-size dependent. In principle, the mean and differential mean Doppler from a near-nadir viewing radar can be used to retrieve vertical air motion as well as the total mean radial velocity. In the paper, we present theoretical calculations for the

  8. Doppler photoacoustic and Doppler ultrasound in blood with optical contrast agent

    NASA Astrophysics Data System (ADS)

    Sheinfeld, Adi; Eyal, Avishay

    2013-03-01

    Photoacoustic Doppler flowmetry as well as Doppler ultrasound were performed in acoustic resolution regime on tubes filled with flowing blood with indocyanine green (ICG) at different concentrations. The photoacoustic excitation utilized a pair of directly-modulated fiber-coupled 830nm laser-diodes, modulated with either CW or tone-bursts for depthresolved measurements. The amplitude of the Doppler peak in photoacoustic Doppler measurements was found to be proportional to the ICG concentration. Photoacoustic Doppler was measured in ICG at human safe concentrations, but not in whole blood. Comparing the results between the two modalities implied that using a wavelength with higher optical absorption may improve the photoacoustic signal in blood.

  9. Development of the doppler electron velocimeter: theory.

    SciTech Connect

    Reu, Phillip L.

    2007-03-01

    Measurement of dynamic events at the nano-scale is currently impossible. This paper presents the theoretical underpinnings of a method for making these measurements using electron microscopes. Building on the work of Moellenstedt and Lichte who demonstrated Doppler shifting of an electron beam with a moving electron mirror, further work is proposed to perfect and utilize this concept in dynamic measurements. Specifically, using the concept of ''fringe-counting'' with the current principles of transmission electron holography, an extension of these methods to dynamic measurements is proposed. A presentation of the theory of Doppler electron wave shifting is given, starting from the development of the de Broglie wave, up through the equations describing interference effects and Doppler shifting in electron waves. A mathematical demonstration that Doppler shifting is identical to the conceptually easier to understand idea of counting moving fringes is given by analogy to optical interferometry. Finally, potential developmental experiments and uses of a Doppler electron microscope are discussed.

  10. Observation of the Zero Doppler Effect

    PubMed Central

    Ran, Jia; Zhang, Yewen; Chen, Xiaodong; Fang, Kai; Zhao, Junfei; Chen, Hong

    2016-01-01

    The normal Doppler effect has well-established applications in many areas of science and technology. Recently, a few experimental demonstrations of the inverse Doppler effect have begun to appear in negative-index metamaterials. Here we report an experimental observation of the zero Doppler effect, that is, no frequency shift irrespective of the relative motion between the wave signal source and the detector in a zero-index metamaterial. This unique phenomenon, accompanied by the normal and inverse Doppler effects, is generated by reflecting a wave from a moving discontinuity in a composite right/left-handed transmission line loaded with varactors when operating in the near zero-index passband, or the right/left-handed passband. This work has revealed a complete picture of the Doppler effect in metamaterials and may lead to potential applications in electromagnetic wave related metrology. PMID:27046395

  11. Inverse Doppler Effects in Broadband Acoustic Metamaterials.

    PubMed

    Zhai, S L; Zhao, X P; Liu, S; Shen, F L; Li, L L; Luo, C R

    2016-01-01

    The Doppler effect refers to the change in frequency of a wave source as a consequence of the relative motion between the source and an observer. Veselago theoretically predicted that materials with negative refractions can induce inverse Doppler effects. With the development of metamaterials, inverse Doppler effects have been extensively investigated. However, the ideal material parameters prescribed by these metamaterial design approaches are complex and also challenging to obtain experimentally. Here, we demonstrated a method of designing and experimentally characterising arbitrary broadband acoustic metamaterials. These omni-directional, double-negative, acoustic metamaterials are constructed with 'flute-like' acoustic meta-cluster sets with seven double meta-molecules; these metamaterials also overcome the limitations of broadband negative bulk modulus and mass density to provide a region of negative refraction and inverse Doppler effects. It was also shown that inverse Doppler effects can be detected in a flute, which has been popular for thousands of years in Asia and Europe. PMID:27578317

  12. Observation of the Zero Doppler Effect

    NASA Astrophysics Data System (ADS)

    Ran, Jia; Zhang, Yewen; Chen, Xiaodong; Fang, Kai; Zhao, Junfei; Chen, Hong

    2016-04-01

    The normal Doppler effect has well-established applications in many areas of science and technology. Recently, a few experimental demonstrations of the inverse Doppler effect have begun to appear in negative-index metamaterials. Here we report an experimental observation of the zero Doppler effect, that is, no frequency shift irrespective of the relative motion between the wave signal source and the detector in a zero-index metamaterial. This unique phenomenon, accompanied by the normal and inverse Doppler effects, is generated by reflecting a wave from a moving discontinuity in a composite right/left-handed transmission line loaded with varactors when operating in the near zero-index passband, or the right/left-handed passband. This work has revealed a complete picture of the Doppler effect in metamaterials and may lead to potential applications in electromagnetic wave related metrology.

  13. Observation of the Zero Doppler Effect.

    PubMed

    Ran, Jia; Zhang, Yewen; Chen, Xiaodong; Fang, Kai; Zhao, Junfei; Chen, Hong

    2016-01-01

    The normal Doppler effect has well-established applications in many areas of science and technology. Recently, a few experimental demonstrations of the inverse Doppler effect have begun to appear in negative-index metamaterials. Here we report an experimental observation of the zero Doppler effect, that is, no frequency shift irrespective of the relative motion between the wave signal source and the detector in a zero-index metamaterial. This unique phenomenon, accompanied by the normal and inverse Doppler effects, is generated by reflecting a wave from a moving discontinuity in a composite right/left-handed transmission line loaded with varactors when operating in the near zero-index passband, or the right/left-handed passband. This work has revealed a complete picture of the Doppler effect in metamaterials and may lead to potential applications in electromagnetic wave related metrology. PMID:27046395

  14. International Symposium on Laser Anemometry, 3rd, ASME Winter Annual Meeting, Boston, MA, Dec. 13-18, 1987, Proceedings

    NASA Astrophysics Data System (ADS)

    Dybbs, A.; Ali, F.; Morrison, G.

    The conference presents papers on instrumentation and signal processing; internal flows; turbulence; jets, boundary layers, and two-phase flows; and industrial and geological flows. Particular attention is given to the application of a two-axis Bragg cell to achieve a lower cost microcomputer controlled two-component LDA, a new signal processor for noisy LDV signals, uncertainties due to visibility and phase response functions of LDV optical single particle counters, a comparison of measured near-wall velocity profiles and flow visualization in a separated flow, and turbulence production over a rough wall at Mach 3. Other topics include two-step finite difference methods for fluid transient analysis, a three-dimensional microlaser anemometer for boundary layer studies, and LDA measurement of the passage flow field in an annular airfoil cascade.

  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. Techniques in Doppler gravity inversion

    NASA Technical Reports Server (NTRS)

    Phillips, R. J.

    1974-01-01

    The types of Doppler gravity data available for local as opposed to planetwide geophysical modeling are reviewed. Those gravity fields that are determined dynamically in orbit determination programs yield a smoothed representation of the local gravity field that may be used for quantitative modeling. An estimate of the difference between smoothed and true fields can be considered as a noise limitation in generating local gravity models. A nonlinear inversion for the geometry, depth, and density of the Mare Serenitatis mascon using an ellipsoidal model yielded a global least squares minimum in horizontal dimensions, depth, and thickness-density contrast product. It was subsequently found, by using a linear model, that there were an infinite number of solutions corresponding to various combinations of depth and lateral inhomogeneity. Linear modeling was performed by means of generalized inverse theory.

  17. Global Doppler frequency shift detection with near-resonant interferometry

    NASA Astrophysics Data System (ADS)

    Landolt, Andrin; Roesgen, Thomas

    2009-10-01

    The recent development in measuring 2D Doppler shift distributions for flow velocimetry using the dispersive properties of atomic line filters is presented. On the basis of velocity field measurements on a subsonic jet flow and a tip vortex flow in a medium-sized wind tunnel, the technique was assessed. Atomic line filters near a resonant transition combine imaging capabilities with a sharp frequency cutoff and an associated region of strong anomalous dispersion. While conventional Doppler global velocimetry relies on the absorption of the filter to convert frequency shifts to intensity variations, near-resonant interferometry uses its dispersion to detect frequency shifts as phase changes in an interference pattern. In the present setup, an iodine vapor cell in an imaging Michelson interferometer is used. With the illuminating laser frequency tuned near a resonant transition, the cell’s dispersion converts the frequency content of the field of view into a distortion of the carrier-fringe pattern recorded at the image plane of the interferometer. The phase distribution in the fringe images is reconstructed by filtering the individual images with a 2D Gabor filter pair tuned to the spatial frequencies of the basic carrier-fringe pattern. The post-processing is concluded with subsequent phase-unwrapping and subtraction of the carrier reference fringe phase. The method and the setup were demonstrated and calibrated experimentally on a rotating disc. The capability of the technique to operate in a real experimental environment was validated in a free subsonic jet and a tip vortex flow behind a wing section in a medium-sized wind tunnel facility. The measurements were found to be in generally good agreement with the theoretically predicted system characteristics and the reference measurements. As with other Doppler global techniques, the stability of the pulsed laser system and the secondary scattering in the test volume were identified as the main error sources.

  18. Application of Doppler Global Velocimetry to Supersonic Flows

    NASA Technical Reports Server (NTRS)

    Meyers, James F.

    1996-01-01

    The design and implementation of Doppler Global Velocimetry (DGV) for testing in the Langley Unitary Plan Wind Tunnel is presented. The discussion begins by outlining the characteristics of the tunnel and the test environment, with potential problem areas highlighted. Modifications to the optical system design to implement solutions for these problems are described. Since this tunnel entry was the first ever use of DGV in a supersonic wind tunnel, the test series was divided into three phases, each with its own goal. Phase I determined if condensation provided sufficient scattered light for DGV applications. Phase II studied particle lag by measuring the flow about an oblique shock above an inclined flat plate. Phase III investigated the supersonic vortical flow field above a 75-degree delta wing at 24-degrees angle of attack. Example results from these tests are presented.

  19. Doppler radar detection of vortex hazard indicators

    NASA Technical Reports Server (NTRS)

    Nespor, Jerald D.; Hudson, B.; Stegall, R. L.; Freedman, Jerome E.

    1994-01-01

    Wake vortex experiments were conducted at White Sands Missile Range, NM using the AN/MPS-39 Multiple Object Tracking Radar (MOTR). The purpose of these experiments was twofold. The first objective was to verify that radar returns from wake vortex are observed for some time after the passage of an aircraft. The second objective was to verify that other vortex hazard indicators such as ambient wind speed and direction could also be detected. The present study addresses the Doppler characteristics of wake vortex and clear air returns based upon measurements employing MOTR, a very sensitive C-Band phased array radar. In this regard, the experiment was conducted so that the spectral characteristics could be determined on a dwell to-dwell basis. Results are presented from measurements of the backscattered power (equivalent structure constant), radial velocity and spectral width when the aircraft flies transverse and axial to the radar beam. The statistics of the backscattered power and spectral width for each case are given. In addition, the scan strategy, experimental test procedure and radar parameters are presented.

  20. Staggered Multiple-PRF Ultrafast Color Doppler.

    PubMed

    Posada, Daniel; Poree, Jonathan; Pellissier, Arnaud; Chayer, Boris; Tournoux, Francois; Cloutier, Guy; Garcia, Damien

    2016-06-01

    Color Doppler imaging is an established pulsed ultrasound technique to visualize blood flow non-invasively. High-frame-rate (ultrafast) color Doppler, by emissions of plane or circular wavefronts, allows severalfold increase in frame rates. Conventional and ultrafast color Doppler are both limited by the range-velocity dilemma, which may result in velocity folding (aliasing) for large depths and/or large velocities. We investigated multiple pulse-repetition-frequency (PRF) emissions arranged in a series of staggered intervals to remove aliasing in ultrafast color Doppler. Staggered PRF is an emission process where time delays between successive pulse transmissions change in an alternating way. We tested staggered dual- and triple-PRF ultrafast color Doppler, 1) in vitro in a spinning disc and a free jet flow, and 2) in vivo in a human left ventricle. The in vitro results showed that the Nyquist velocity could be extended to up to 6 times the conventional limit. We found coefficients of determination r(2) ≥ 0.98 between the de-aliased and ground-truth velocities. Consistent de-aliased Doppler images were also obtained in the human left heart. Our results demonstrate that staggered multiple-PRF ultrafast color Doppler is efficient for high-velocity high-frame-rate blood flow imaging. This is particularly relevant for new developments in ultrasound imaging relying on accurate velocity measurements. PMID:26780789

  1. Rotational Doppler effect in nonlinear optics

    NASA Astrophysics Data System (ADS)

    Li, Guixin; Zentgraf, Thomas; Zhang, Shuang

    2016-08-01

    The translational Doppler effect of electromagnetic and sound waves has been successfully applied in measurements of the speed and direction of vehicles, astronomical objects and blood flow in human bodies, and for the Global Positioning System. The Doppler effect plays a key role for some important quantum phenomena such as the broadened emission spectra of atoms and has benefited cooling and trapping of atoms with laser light. Despite numerous successful applications of the translational Doppler effect, it fails to measure the rotation frequency of a spinning object when the probing wave propagates along its rotation axis. This constraint was circumvented by deploying the angular momentum of electromagnetic waves--the so-called rotational Doppler effect. Here, we report on the demonstration of rotational Doppler shift in nonlinear optics. The Doppler frequency shift is determined for the second harmonic generation of a circularly polarized beam passing through a spinning nonlinear optical crystal with three-fold rotational symmetry. We find that the second harmonic generation signal with circular polarization opposite to that of the fundamental beam experiences a Doppler shift of three times the rotation frequency of the optical crystal. This demonstration is of fundamental significance in nonlinear optics, as it provides us with insight into the interaction of light with moving media in the nonlinear optical regime.

  2. Doppler images of DI Piscium during 2004-2006

    NASA Astrophysics Data System (ADS)

    Lindborg, M.; Hackman, T.; Mantere, M. J.; Korhonen, H.; Ilyin, I.; Kochukhov, O.; Piskunov, N.

    2014-02-01

    Aims: DI Psc (HD 217352) is a Li-rich, rapidly rotating single K giant. We set out to study the spot configuration and activity level by calculating surface temperature maps of the star. Methods: We apply the Doppler imaging method on high-resolution optical spectroscopy obtained during 2004-2006. Results: In July-August 2004, no clear spot structures were visible, but the spot coverage increased in July 2005, and cool spots emerged, especially at intermediate latitudes. Later on in September 2006, the spot coverage increased and cool spots were visible on both sides of the equator. However, the map of 2006 suffers from bad phase coverage, meaning it is not possible to draw definite conclusions on the spot locations during that season. Conclusions: Compared with earlier Doppler maps of DI Psc and temperature maps obtained for other late-type stars with similar rotation rates, DI Psc seems to be in a low activity state especially during the observing season of July-August 2004. During the 2005 and 2006 observing seasons, the spot activity seen in the spectral line profiles and inferred from Doppler images increases, and the temperature contrast in our last map is more comparable to what was reported in an earlier study. Therefore, it can be concluded that the spot activity level of the star is variable over time. However, the present and previous Doppler images form too short a time series to draw conclusions about a possible activity cycle in DI Psc. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  3. The Next Generation Airborne Polarimetric Doppler Radar

    NASA Astrophysics Data System (ADS)

    Vivekanandan, J.; Lee, Wen-Chau; Loew, Eric; Salazar, Jorge; Chandrasekar, V.

    2013-04-01

    aircraft in its fleet for airborne atmospheric measurements, including dropsonde, and in situ sampling and remote sensing of clouds, chemistry and aerosols. Therefore, the addition of a precipitation radar to the NSF/NCAR C-130 platform will produce transformational change in its mission. This new design can be cloned for C-130s operated by a number of agencies, including NOAA and the Air Force hurricane reconnaissance fleet. This paper presents a possible configuration of a novel, airborne phased array radar (APAR) to be installed on the NSF/NCAR C-130 aircraft with improved spatial resolution and polarimetric capability to meet or exceed that of ELDORA. The preliminary design, an update of the APAR project, and a future plan will be presented. References: Bell, M. M. , M. T. Montgomery, 2008: Observed Structure, Evolution, and Potential Intensity of Category 5 Hurricane Isabel (2003) from 12 to 14 September. Monthly Weather Review, Vol. 136, Issue 6, pp. 2023-2046. Hildebrand, P. H., W.-C. Lee, C. A. Walther, C. Frush, M. Randall, E. Loew, R. Neitzel, R. Parsons, J. Testud, F. Baudin, and A. LeCornec, 1996: The ELDORA/ASTRAIA airborne Doppler weather radar: High resolution observations from TOGA COARE. Bull. Amer. Metoro. Soc., 77, 213-232 Howard B. Bluestein, Roger M. Wakimoto, 2003: Mobile Radar Observations of Severe Convective Storms re Convective Storms. Meteorological Monographs, Vol. 30, Issue 52, pp. 105-105. Montgomery, M. T., M. M. Bell, S. D. Aberson, M. L. Black, 2006: Hurricane Isabel (2003): New Insights into the Physics of Intense Storms. Part I: Mean Vortex Structure and Maximum Intensity Estimates. Bull. of the American Meteorl. Soc., Vol. 87, Issue 10, pp. 1335-1347.

  4. IIP Update: A Packaged Coherent Doppler Wind Lidar Transceiver. Doppler Aerosol WiNd Lidar (DAWN)

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Koch, Grady J.; Yu, Jirong; Trieu, Bo C.; Amzajerdian, Farzin; Singh, Upendra N.; Petros, Mulugeta

    2006-01-01

    The state-of-the-art 2-micron coherent Doppler wind lidar breadboard at NASA/LaRC will be engineered and compactly packaged consistent with future aircraft flights. The packaged transceiver will be integrated into a coherent Doppler wind lidar system test bed at LaRC. Atmospheric wind measurements will be made to validate the packaged technology. This will greatly advance the coherent part of the hybrid Doppler wind lidar solution to the need for global tropospheric wind measurements.

  5. Doppler Lidar Descent Sensor for Planetary Landing

    NASA Astrophysics Data System (ADS)

    Amzajerdian, F.; Pierrottet, D. F.; Petway, L. B.; Hines, G. D.; Barnes, B. W.

    2012-06-01

    Future robotic and manned missions to Mars demand accurate knowledge of ground velocity and altitude to ensure soft landing at the designated landing location. To meet this requirement, a prototype Doppler lidar has been developed and demonstrated.

  6. Generalized Doppler Formula in a Nonstatic Universe

    ERIC Educational Resources Information Center

    Gross, Peter G.

    1977-01-01

    Derives the general Doppler formula in a nonstatic universe using assumptions of special relativity, homogeneity and isotropy of the universe. Examples of applications to physical cosmology are given. (SL)

  7. Evaluation of a pulsed ultrasonic Doppler flowmeter

    NASA Technical Reports Server (NTRS)

    Wells, M. K.

    1973-01-01

    The in vivo application of the pulsed ultrasound Doppler velocity meter (PUDVM) for measuring arterial velocity waveforms is reported. In particular, the performance of the PUDVM is compared with a hot film anemometer of proven accuracy.

  8. Student Microwave Experiments Involving the Doppler Effect.

    ERIC Educational Resources Information Center

    Weber, F. Neff; And Others

    1980-01-01

    Described is the use of the Doppler Effect with microwaves in the measurement of the acceleration due to gravity of falling objects. The experiments described add to the repertoire of quantitative student microwave experiments. (Author/DS)

  9. High range resolution micro-Doppler analysis

    NASA Astrophysics Data System (ADS)

    Cammenga, Zachary A.; Smith, Graeme E.; Baker, Christopher J.

    2015-05-01

    This paper addresses use of the micro-Doppler effect and the use of high range-resolution profiles to observe complex targets in complex target scenes. The combination of micro-Doppler and high range-resolution provides the ability to separate the motion of complex targets from one another. This ability leads to the differentiation of targets based on their micro-Doppler signatures. Without the high-range resolution, this would not be possible because the individual signatures would not be separable. This paper also addresses the use of the micro-Doppler information and high range-resolution profiles to generate an approximation of the scattering properties of a complex target. This approximation gives insight into the structure of the complex target and, critically, is created without using a pre-determined target model.

  10. Laser anemometry measurements of natural circulation flow in a scale model PWR reactor system. [Pressurized Water Reactor

    NASA Technical Reports Server (NTRS)

    Kadambi, J. R.; Schneider, S. J.; Stewart, W. A.

    1986-01-01

    The natural circulation of a single phase fluid in a scale model of a pressurized water reactor system during a postulated grade core accident is analyzed. The fluids utilized were water and SF6. The design of the reactor model and the similitude requirements are described. Four LDA tests were conducted: water with 28 kW of heat in the simulated core, with and without the participation of simulated steam generators; water with 28 kW of heat in the simulated core, with the participation of simulated steam generators and with cold upflow of 12 lbm/min from the lower plenum; and SF6 with 0.9 kW of heat in the simulated core and without the participation of the simulated steam generators. For the water tests, the velocity of the water in the center of the core increases with vertical height and continues to increase in the upper plenum. For SF6, it is observed that the velocities are an order of magnitude higher than those of water; however, the velocity patterns are similar.

  11. High-latitude HF Doppler observations of ULF waves. 1. Waves with large spatial scale sizes

    NASA Astrophysics Data System (ADS)

    Wright, D. M.; Yeoman, T. K.; Chapman, P. J.

    1997-12-01

    A quantitative study of observations of the ionospheric signatures of magnetospheric ultra low frequency (ULF) waves by a high-latitude (geographic: 69.6°N 19.2°E) high-frequency Doppler sounder has been undertaken. The signatures, which are clearly correlated with pulsations in ground magnetometer data, exhibit periods in the range 100-400 s and have azimuthal wave numbers in the range 3-8. They are interpreted here as local field line resonances. Phase information provided by O- and X-mode Doppler data support the view that these are associated with field line resonances having large azimuthal scale sizes. The relative phases and amplitudes of the signatures in the Doppler and ground magnetometer data are compared with a model for the generation of Doppler signatures from incident ULF waves. The outcome suggests that the dominant mechanism involved in producing the Doppler signature is the vertical component of an E × B bulk motion of the local plasma caused by the electric field perturbation of the ULF wave.

  12. The application of noncoherent Doppler data types for Deep Space Navigation

    NASA Technical Reports Server (NTRS)

    Bhaskaran, S.

    1995-01-01

    Recent improvements in computational capability and DSN technology have renewed interest in examining the possibility of using one-way Doppler data alone to navigate interplanetary spacecraft. The one-way data can be formulated as the standard differenced-count Doppler or as phase measurements, and the data can be received at a single station or differenced if obtained simultaneously at two stations. A covariance analysis, which analyzes the accuracy obtainable by combinations of one-way Doppler data, is performed and compared with similar results using standard two-way Doppler and range. The sample interplanetary trajectory used was that of the Mars Pathfinder mission to Mars. It is shown that differenced one-way data are capable of determining the angular position of the spacecraft to fairly high accuracy, but have relatively poor sensitivity to the range. When combined with single-station data, the position dispersions are roughly an order of magnitude larger in range and comparable in angular position as compared to dispersions obtained with standard two-way data types. It was also found that the phase formulation is less sensitive to data weight variations and data coverage than the differenced-count Doppler formulation.

  13. Application of non-coherent Doppler data types for deep space navigation

    NASA Technical Reports Server (NTRS)

    Bhaskaran, Shyam

    1995-01-01

    Recent improvements in computational capability and Deep Space Network technology have renewed interest in examining the possibility of using one-way Doppler data alone to navigate interplanetary spacecraft. The one-way data can be formulated as the standard differenced-count Doppler or as phase measurements, and the data can be received at a single station or differenced if obtained simultaneously at two stations. A covariance analysis is performed which analyzes the accuracy obtainable by combinations of one-way Doppler data and compared with similar results using standard two-way Doppler and range. The sample interplanetary trajectory used was that of the Mars Pathfinder mission to Mars. It is shown that differenced one-way data is capable of determining the angular position of the spacecraft to fairly high accuracy, but has relatively poor sensitivity to the range. When combined with single station data, the position dispersions are roughly an order of magnitude larger in range and comparable in angular position as compared to dispersions obtained with standard data two-way types. It was also found that the phase formulation is less sensitive to data weight variations and data coverage than the differenced-count Doppler formulation.

  14. Doppler micro sense and avoid radar

    NASA Astrophysics Data System (ADS)

    Gorwara, Ashok; Molchanov, Pavlo; Asmolova, Olga

    2015-10-01

    There is a need for small Sense and Avoid (SAA) systems for small and micro Unmanned Aerial Systems (UAS) to avoid collisions with obstacles and other aircraft. The proposed SAA systems will give drones the ability to "see" close up and give them the agility to maneuver through tight areas. Doppler radar is proposed for use in this sense and avoid system because in contrast to optical or infrared (IR) systems Doppler can work in more harsh conditions such as at dusk, and in rain and snow. And in contrast to ultrasound based systems, Doppler can better sense small sized obstacles such as wires and it can provide a sensing range from a few inches to several miles. An SAA systems comprised of Doppler radar modules and an array of directional antennas that are distributed around the perimeter of the drone can cover the entire sky. These modules are designed so that they can provide the direction to the obstacle and simultaneously generate an alarm signal if the obstacle enters within the SAA system's adjustable "Protection Border". The alarm signal alerts the drone's autopilot to automatically initiate an avoidance maneuver. A series of Doppler radar modules with different ranges, angles of view and transmitting power have been designed for drones of different sizes and applications. The proposed Doppler radar micro SAA system has simple circuitry, works from a 5 volt source and has low power consumption. It is light weight, inexpensive and it can be used for a variety of small unmanned aircraft.

  15. Signal simulator model A-111. [signal source for Doppler tracking high data rate receivers

    NASA Technical Reports Server (NTRS)

    Flattau, T.; Mellars, J.

    1974-01-01

    A signal simulator designed to function as a signal source for Doppler tracking high data rate receivers is described. The simulator produces modulated signals whose carrier frequency can be varied between 200 and 900 MHz at rates greater than 20 MHz/sec. The modulation is phase shift keying with data rate up to 300 megabits per second.

  16. Retroreflector for photonic Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Lagoski, Thomas J.; Coutu, Ronald A., Jr.; Starman, LaVern A.

    2009-08-01

    In order to meet the goals of the Department of Defense (DoD) for smaller and more accurate weapons, numerous projects are currently investigating the miniaturization of weapons and munition fuze components. One of these efforts is to characterize the performance of small detonators. The velocity of the flyer, the key component needed to initiate a detonation sequence, can be measured using a photonic Doppler velocimeter (PDV). The purpose of this research was to develop a microelectromechanical system (MEMS) device that would act as an optimal retroreflective surface for the PDV. Two MEMS solutions were explored: one using the PolyMUMPsTM fabrication process and one in-house fabrication design using silicon on insulator (SOI) wafers. The in-house design consisted of an array of corner reflectors created using an SOI wafer. Each corner reflector consisted of three separate mirror plates which were self-assembled by photoresist pad hinges. When heated to a critical temperature (typically 140-160 °C), the photoresist pads melted and the resulting surface tension caused each mirror to rotate into place. The resulting array of corner reflectors was then coated with a thin layer of gold to increase reflectivity. Despite the successful assembly of a PolyMUMPsTM corner reflector, assembling an array of these reflectors was found to be unfeasible. Although the SOI corner reflector design was completed, these devices were not fabricated in time for testing during this research. However, the bidirectional reflectance distribution function (BRDF) and optical cross section (OCS) of commercially available retroreflective tapes were measured. These results can be used as a baseline comparison for future testing of a fabricated SOI corner reflector array.

  17. The leicester Doppler phantom--a digital electronic phantom for ultrasound pulsed Doppler system testing.

    PubMed

    Gittins, John; Martin, Kevin

    2010-04-01

    Doppler flow and string phantoms have been used to assess the performance of ultrasound Doppler systems in terms of parameters such as sensitivity, velocity accuracy and sample volume registration. However, because of the nature of their construction, they cannot challenge the accuracy and repeatability of modern digital ultrasound systems or give objective measures of system performance. Electronic Doppler phantoms are able to make use of electronically generated test signals, which may be controlled precisely in terms of frequency, amplitude and timing. The Leicester Electronic Doppler Phantom uses modern digital signal processing methods and field programmable gate array technology to overcome some of the limitations of previously described electronic phantoms. In its present form, it is able to give quantitative graphical assessments of frequency response and range gate characteristics, as well as measures of dynamic range and velocity measurement accuracy. The use of direct acoustic coupling eliminates uncertainties caused by Doppler beam effects, such as intrinsic spectral broadening, but prevents their evaluation. PMID:20350689

  18. Passive component based multifunctional Jones matrix swept source optical coherence tomography for Doppler and polarization imaging.

    PubMed

    Lim, Yiheng; Hong, Young-Joo; Duan, Lian; Yamanari, Masahiro; Yasuno, Yoshiaki

    2012-06-01

    We present a fiber based multifunctional Jones matrix swept source optical coherence tomography (SS-OCT) system for Doppler and polarization imaging. Jones matrix measurement without using active components such as electro-optic modulators is realized by incident polarization multiplexing based on independent delay of two orthogonal polarization states and polarization diversity detection. In addition to polarization sensitivity, this system measures Doppler flow without extra hardware for phase stabilized SS-OCT detection. An eighth-wave plate was measured to demonstrate the polarization detection accuracy. The optic nerve head of a retina was measured in vivo. Detailed vasculature and birefringent structures were investigated simultaneously. PMID:22660086

  19. Atom localization in a Doppler broadened medium via two standing-wave fields

    NASA Astrophysics Data System (ADS)

    Abd-Elnabi, Somia; Osman, Kariman I.

    2016-01-01

    The atom localization has been achieved in a four-level V-type atomic system interacting with two classical unidirectional standing-wave fields and weak probe field in a Doppler broadened medium under several conditions at very low temperature. The precision of the atom localization is compared with the system in the presence and absence of the Doppler broadened medium. The influence of some parameters such as the amplitude, wave vectors and the phase shift of the standing-wave fields on the atom localization is studied and has been found to obtain various atom localization patterns with symmetric shape.

  20. 3-D Ultrafast Doppler Imaging Applied to the Noninvasive and Quantitative Imaging of Blood Vessels in Vivo

    PubMed Central

    Provost, J.; Papadacci, C.; Demene, C.; Gennisson, J-L.; Tanter, M.; Pernot, M.

    2016-01-01

    Ultrafast Doppler Imaging was introduced as a technique to quantify blood flow in an entire 2-D field of view, expanding the field of application of ultrasound imaging to the highly sensitive anatomical and functional mapping of blood vessels. We have recently developed 3-D Ultrafast Ultrasound Imaging, a technique that can produce thousands of ultrasound volumes per second, based on three-dimensional plane and diverging wave emissions, and demonstrated its clinical feasibility in human subjects in vivo. In this study, we show that non-invasive 3-D Ultrafast Power Doppler, Pulsed Doppler, and Color Doppler Imaging can be used to perform quantitative imaging of blood vessels in humans when using coherent compounding of three-dimensional tilted plane waves. A customized, programmable, 1024-channel ultrasound system was designed to perform 3-D Ultrafast Imaging. Using a 32X32, 3-MHz matrix phased array (Vermon, France), volumes were beamformed by coherently compounding successive tilted plane wave emissions. Doppler processing was then applied in a voxel-wise fashion. 3-D Ultrafast Power Doppler Imaging was first validated by imaging Tygon tubes of varying diameter and its in vivo feasibility was demonstrated by imaging small vessels in the human thyroid. Simultaneous 3-D Color and Pulsed Doppler Imaging using compounded emissions were also applied in the carotid artery and the jugular vein in one healthy volunteer. PMID:26276956

  1. Doppler shift simulation of scattered HF signals during the Tromsø HF pumping experiment on 16 February 1996

    NASA Astrophysics Data System (ADS)

    Borisova, T. D.; Blagoveshchenskaya, N. F.; Moskvin, I. V.; Rietveld, M. T.; Kosch, M. J.; Thidé, B.

    2002-09-01

    Comparisons between bistatic scatter measurements and simulation results during the Tromsø HF pumping experiment on 16 February 1996 are made. Doppler measurements of an HF diagnostic signal scattered from the field-aligned irregularities (FAIs) in the auroral E-region were carried out on the London Tromsø St. Petersburg path at 9410 kHz from 21:00 to 22:00 UT. The scattered signals were observed both from natural and artificial ionospheric irregularities located in the vicinity of Tromsø. To simulate the Doppler frequency shifts, fd , of scattered signals, a radio channel model, named CONE, was developed. The model allows for ray tracing, group and phase paths, and Doppler frequency shift calculations. The calculated Doppler shifts were analyzed for dependence on the magnitude and direction of plasma velocities in the scattering volume. It was found that the velocity components in the north-south direction are crucial for explaining the Doppler frequency shifts of the scattered diagnostic signals. To simulate fd , real velocities obtained from the EISCAT UHF radar at an altitude of 278 km and from the digital all-sky imager during the experiment were employed. The simulation results of Doppler frequency shift variations with time are in reasonable agreement with the experimental Doppler shifts of scattered signals on the London Tromsø St. Petersburg path.

  2. Modeling of Doppler frequency shift in multipath radiochannels

    NASA Astrophysics Data System (ADS)

    Penzin, Maksim; Iyin, Nikolay

    2016-06-01

    We discuss the modeling of propagation of a quasi-monochromatic radio signal, represented by a coherent pulse sequence, in a non-stationary multipath radio channel. In such a channel, signal propagation results in the observed frequency shift for each ray (Doppler effect). The modeling is based on the assumption that during propagation of a single pulse a channel can be considered stationary. A phase change in the channel transfer function is shown to cause the observed frequency shift in the received signal. Thus, instead of measuring the Doppler frequency shift, we can measure the rate of change in the mean phase of one pulse relative to another. The modeling is carried out within the framework of the method of normal waves. The method enables us to model the dynamics of the electromagnetic field at a given point with the required accuracy. The modeling reveals that a local change in ionospheric conditions more severely affects the rays whose reflection region is in the area where the changes occur.

  3. Measurement of the rotational Doppler frequency shift of a spinning object using a radio frequency orbital angular momentum beam.

    PubMed

    Zhao, Mingyang; Gao, Xinlu; Xie, Mutong; Zhai, Wensheng; Xu, Wenjing; Huang, Shanguo; Gu, Wanyi

    2016-06-01

    An indirect approach based on phase measurement is proposed to measure the rotational Doppler frequency shift, which takes full advantage of the phase structure of orbital angular momentum (OAM) beams in radio domain, using a vector network analyzer (VNA) as a phase discriminator. A proof-of-concept experiment is established by an optical-controlled system with the OAM state of 1. By analyzing the experiment's results, the rotational Doppler frequency shift is measured as 24.83 Hz (max error rate 0.67%) at 50π rad/s rotational velocity, deducing the rotational velocity as 50.18π (average error rate 0.36%). PMID:27244411

  4. Doppler imaging with dual-detection full-range frequency domain optical coherence tomography

    PubMed Central

    Meemon, Panomsak; Lee, Kye-Sung; Rolland, Jannick P.

    2010-01-01

    Most of full-range techniques for Frequency Domain Optical Coherence Tomography (FD-OCT) reported to date utilize the phase relation between consecutive axial lines to reconstruct a complex interference signal and hence may exhibit degradation in either mirror image suppression performance or detectable velocity dynamic range or both when monitoring a moving sample such as flow activity. We have previously reported a technique of mirror image removal by simultaneous detection of the quadrature components of a complex spectral interference called a Dual-Detection Frequency Domain OCT (DD-FD-OCT) [Opt. Lett. 35, 1058-1060 (2010)]. The technique enables full range imaging without any loss of acquisition speed and is intrinsically less sensitive to phase errors generated by involuntary movements of the subject. In this paper, we demonstrate the application of the DD-FD-OCT to a phase-resolved Doppler imaging without degradation in either mirror image suppression performance or detectable velocity dynamic range that were observed in other full-range Doppler methods. In order to accommodate for Doppler imaging, we have developed a fiber-based DD-FD-OCT that more efficiently utilizes the source power compared with the previous free-space DD-FD-OCT. In addition, the velocity sensitivity of the phase-resolved DD-FD-OCT was investigated, and the relation between the measured Doppler phase shift and set flow velocity of a flow phantom was verified. Finally, we demonstrate the Doppler imaging using the DD-FD-OCT in a biological sample. PMID:21258488

  5. Spacecraft Doppler Tracking as a Xylophone Detector

    NASA Technical Reports Server (NTRS)

    Tinto, Massimo

    1996-01-01

    We discuss spacecraft Doppler tracking in which Doppler data recorded on the ground are linearly combined with Doppler measurements made on board a spacecraft. By using the four-link radio system first proposed by Vessot and Levine, we derive a new method for removing from the combined data the frequency fluctuations due to the Earth troposphere, ionosphere, and mechanical vibrations of the antenna on the ground. Our method provides also for reducing by several orders of magnitude, at selected Fourier components, the frequency fluctuations due to other noise sources, such as the clock on board the spacecraft or the antenna and buffeting of the probe by non-gravitational forces. In this respect spacecraft Doppler tracking can be regarded as a xylophone detector. Estimates of the sensitivities achievable by this xylophone are presented for two tests of Einstein's theory of relativity: searches for gravitational waves and measurements of the gravitational red shift. This experimental technique could be extended to other tests of the theory of relativity, and to radio science experiments that rely on high-precision Doppler measurements.

  6. Inverse Doppler Effects in Broadband Acoustic Metamaterials

    PubMed Central

    Zhai, S. L.; Zhao, X. P.; Liu, S.; Shen, F. L.; Li, L. L.; Luo, C. R.

    2016-01-01

    The Doppler effect refers to the change in frequency of a wave source as a consequence of the relative motion between the source and an observer. Veselago theoretically predicted that materials with negative refractions can induce inverse Doppler effects. With the development of metamaterials, inverse Doppler effects have been extensively investigated. However, the ideal material parameters prescribed by these metamaterial design approaches are complex and also challenging to obtain experimentally. Here, we demonstrated a method of designing and experimentally characterising arbitrary broadband acoustic metamaterials. These omni-directional, double-negative, acoustic metamaterials are constructed with ‘flute-like’ acoustic meta-cluster sets with seven double meta-molecules; these metamaterials also overcome the limitations of broadband negative bulk modulus and mass density to provide a region of negative refraction and inverse Doppler effects. It was also shown that inverse Doppler effects can be detected in a flute, which has been popular for thousands of years in Asia and Europe. PMID:27578317

  7. A pseudo-dual-Doppler analysis of cyclic tornadogenesis

    NASA Astrophysics Data System (ADS)

    Dowell, David Collin

    2000-06-01

    Several tornadic storms formed in the Texas Panhandle on 8 June 1995, the date of the last mission of VORTEX (Verification of the Origins of Rotation in Tornadoes EXperiment). The southernmost storm in this severe weather outbreak produced a family of at least five tornadoes near the town of McLean. Airborne Doppler radar scans of this storm by the ELDORA (ELectra DOppler RAdar) offer the most detailed look to date at a storm producing a family of tornadoes. The goals of this study were twofold. The first was to determine a pseudo-dual-Doppler wind synthesis method in Cartesian coordinates appropriate for the analysis of the ELDORA data. Unique aspects of this part of the study include a comparison of wind synthesis methods based on variational formulations and the use of a non-uniform moving reference frame for the syntheses. A dual-Doppler formulation in which the radial velocity and continuity equations are all satisfied as weak constraints (Gamache 1997, Shapiro and Mewes 1999) yields a more accurate wind field than traditional (and variational) methods in which the radial velocity equations are satisfied exactly. The second goal of this study was to diagnose both the cyclic process and the formation of individual tornadoes. The McLean storm produced three large tornadoes at 18 min intervals. The last of these then lasted much longer (over one hour) and was stronger than the previous tornadoes. New pre-tornadic vortices formed on the east side of the updraft by tilting of strong environmental low-level horizontal vorticity into the vertical and then stretching of the vertical vorticity within the updraft. The vortices did not mature at low levels until they migrated to the west side of the updraft. Indirect evidence indicates that both baroclinic generation of horizontal vorticity and the rear downdraft may have played roles in tornado formation at this stage. The tornadic potential of a storm appears-to be related to the relative strength of low-level storm

  8. An atlas of Doppler emission-line tomography of cataclysmic variable stars

    NASA Technical Reports Server (NTRS)

    Kaitchuck, Ronald H.; Schlegel, Eric M.; Honeycutt, R. Kent; Horne, Keith; Marsh, T. R.; White, J. C., II; Mansperger, Cathy S.

    1994-01-01

    Doppler emission-line tomography is a technique similar to medical tomography. In this atlas the emission-line profiles of cataclysmic variable stars, seen at different orbital phases, are transformed into velocity space images. This transformation makes many of the complex line profile changes easier to interpret. The emission contributions of the disk and the s-wave are clearly separated in these images, and any emission from the stream and the secondary star can often be identified. In this atlas, Doppler tomograms of Hbeta, He I lambda 4471, and He II lambda 4686 emission lines of 18 cataclysmic variable stars are presented. The Doppler images provide insights into the individual systems and a better technique for measuring and radial velocity amplitude of the white dwarf.

  9. A 3-D PW ultrasonic Doppler flowmeter: theory and experimental characterization.

    PubMed

    Calzolai, M; Capineri, L; Fort, A; Masotti, L; Rocchi, S; Scabia, M

    1999-01-01

    A complete 3-D ultrasonic pulsed Doppler system has been developed to measure quantitatively the velocity vector field of a fluid flow independently of the probe position. The probe consists of four 2.5 MHz piezocomposite ultrasonic transducers (one central transmitter and three receivers separated by 120 degrees ) to measure the velocity projections along three different directions. The Doppler shift of the three channels is calculated by analog phase and quadrature demodulation, then digitally processed to extract the mean velocity from the complex spectrum. The accuracy of the 3-D Doppler technique has been tested on a moving string phantom providing an error of about 4% for both amplitude and direction with an acquisition window of 100 ms. PMID:18238403

  10. The Windvan pulsed CO2 Doppler lidar wide-area wind sensor

    NASA Technical Reports Server (NTRS)

    Lawrence, Rhidian

    1990-01-01

    Wind sensing using a Doppler lidar is achieved by sensing the Doppler content of narrow frequency laser light backscattered by the ambient atmospheric aerosols. The derived radial wind components along several directions are used to generate wind vectors, typically using the Velocity Azimuth Display (VAD) method described below. Range resolved information is obtained by range gating the continuous scattered return. For a CO2 laser (10.6 mu) the Doppler velocity scaling factor is 188 kHz/ms(exp -1). In the VAD scan method the zenith angle of the pointing direction is fixed and its azimuth is continuously varied through 2 pi. A spatially uniform wind field at a particular altitude yields a sinusoidal variation of the radial component vs. azimuth. The amplitude, phase and dc component of this sinusoid yield the horizontal wind speed, direction and vertical component of the wind respectively. In a nonuniform wind field the Fourier components of the variation yields the required information.

  11. Application of vector analysis on study of illuminated area and Doppler characteristics of airborne pulse radar

    NASA Astrophysics Data System (ADS)

    Wang, Haijiang; Yang, Ling

    2014-12-01

    In this paper, the application of vector analysis tool in the illuminated area and the Doppler frequency distribution research for the airborne pulse radar is studied. An important feature of vector analysis is that it can closely combine the geometric ideas with algebraic calculations. Through coordinate transform, the relationship between the frame of radar antenna and the ground, under aircraft motion attitude, is derived. Under the time-space analysis, the overlap area between the footprint of radar beam and the pulse-illuminated zone is obtained. Furthermore, the Doppler frequency expression is successfully deduced. In addition, the Doppler frequency distribution is plotted finally. Using the time-space analysis results, some important parameters of a specified airborne radar system are obtained. Simultaneously, the results are applied to correct the phase error brought by attitude change in airborne synthetic aperture radar (SAR) imaging.

  12. Orbit-determination performance of Doppler data for interplanetary cruise trajectories. Part 1: Error analysis methodology

    NASA Technical Reports Server (NTRS)

    Ulvestad, J. S.; Thurman, S. W.

    1992-01-01

    An error covariance analysis methodology is used to investigate different weighting schemes for two-way (coherent) Doppler data in the presence of transmission-media and observing-platform calibration errors. The analysis focuses on orbit-determination performance in the interplanetary cruise phase of deep-space missions. Analytical models for the Doppler observable and for transmission-media and observing-platform calibration errors are presented, drawn primarily from previous work. Previously published analytical models were improved upon by the following: (1) considering the effects of errors in the calibration of radio signal propagation through the troposphere and ionosphere as well as station-location errors; (2) modelling the spacecraft state transition matrix using a more accurate piecewise-linear approximation to represent the evolution of the spacecraft trajectory; and (3) incorporating Doppler data weighting functions that are functions of elevation angle, which reduce the sensitivity of the estimated spacecraft trajectory to troposphere and ionosphere calibration errors. The analysis is motivated by the need to develop suitable weighting functions for two-way Doppler data acquired at 8.4 GHz (X-band) and 32 GHz (Ka-band). This weighting is likely to be different from that in the weighting functions currently in use; the current functions were constructed originally for use with 2.3 GHz (S-band) Doppler data, which are affected much more strongly by the ionosphere than are the higher frequency data.

  13. Advanced multi-contrast Jones matrix optical coherence tomography for Doppler and polarization sensitive imaging.

    PubMed

    Ju, Myeong Jin; Hong, Young-Joo; Makita, Shuichi; Lim, Yiheng; Kurokawa, Kazuhiro; Duan, Lian; Miura, Masahiro; Tang, Shuo; Yasuno, Yoshiaki

    2013-08-12

    An advanced version of Jones matrix optical coherence tomography (JMT) is demonstrated for Doppler and polarization sensitive imaging of the posterior eye. JMT is capable of providing localized flow tomography by Doppler detection and investigating the birefringence property of tissue through a three-dimensional (3-D) Jones matrix measurement. Owing to an incident polarization multiplexing scheme based on passive optical components, this system is stable, safe in a clinical environment, and cost effective. Since the properties of this version of JMT provide intrinsic compensation for system imperfection, the system is easy to calibrate. Compared with the previous version of JMT, this advanced JMT achieves a sufficiently long depth measurement range for clinical cases of posterior eye disease. Furthermore, a fine spectral shift compensation method based on the cross-correlation of calibration signals was devised for stabilizing the phase of OCT, which enables a high sensitivity Doppler OCT measurement. In addition, a new theory of JMT which integrates the Jones matrix measurement, Doppler measurement, and scattering measurement is presented. This theory enables a sensitivity-enhanced scattering OCT and high-sensitivity Doppler OCT. These new features enable the application of this system to clinical cases. A healthy subject and a geographic atrophy patient were measured in vivo, and simultaneous imaging of choroidal vasculature and birefringence structures are demonstrated. PMID:23938857

  14. Some effects of quantization on a noiseless phase-locked loop. [sampling phase errors

    NASA Technical Reports Server (NTRS)

    Greenhall, C. A.

    1979-01-01

    If the VCO of a phase-locked receiver is to be replaced by a digitally programmed synthesizer, the phase error signal must be sampled and quantized. Effects of quantizing after the loop filter (frequency quantization) or before (phase error quantization) are investigated. Constant Doppler or Doppler rate noiseless inputs are assumed. The main result gives the phase jitter due to frequency quantization for a Doppler-rate input. By itself, however, frequency quantization is impractical because it makes the loop dynamic range too small.

  15. Investigation of Measurement Errors in Doppler Global Velocimetry

    NASA Technical Reports Server (NTRS)

    Meyers, James F.; Lee, Joseph W.

    1999-01-01

    While the initial development phase of Doppler Global Velocimetry (DGV) has been successfully completed, there remains a critical next phase to be conducted, namely the determination of an error budget to provide quantitative bounds for measurements obtained by this technology. This paper describes a laboratory investigation that consisted of a detailed interrogation of potential error sources to determine their contribution to the overall DGV error budget. A few sources of error were obvious; e.g., iodine vapor adsorption lines, optical systems, and camera characteristics. However, additional non-obvious sources were also discovered; e.g., laser frequency and single-frequency stability, media scattering characteristics, and interference fringes. This paper describes each identified error source, its effect on the overall error budget, and where possible, corrective procedures to reduce or eliminate its effect.

  16. Inline Ultrasonic Rheometry by Pulsed Doppler

    SciTech Connect

    Pfund, David M.; Greenwood, Margaret S.; Bamberger, Judith A.; Pappas, Richard A.

    2006-12-22

    This will be a discussion of the non-invasive determination of the viscosity of a non-Newtonian fluid in laminar pipe flow over the range of shear rates present in the pipe. The procedure used requires knowledge of the flow profile in and the pressure drop along a long straight run of pipe. The profile is determined by using a pulsed ultrasonic Doppler velocimeter. This approach is ideal for making non-invasive, real-time measurements for monitoring and control. Rheograms of a shear thinning, thixotropic gel will be presented. The operating parameters and limitations of the Doppler-based instrument will be discussed. The most significant limitation is velocity gradient broadening of the Doppler spectra near the walls of the pipe. This limitation can be significant for strongly shear thinning fluids (depending also on the ratio of beam to pipe diameter and the transducer's insertion angle).

  17. Doppler tomography of accretion in binaries

    NASA Astrophysics Data System (ADS)

    Steeghs, D.

    2004-03-01

    Since its conception, Doppler tomography has matured into a versatile and widely used tool. It exploits the information contained in the highly-structured spectral line-profiles typically observed in mass-transferring binaries. Using inversion techniques akin to medical imaging, it permits the reconstruction of Doppler maps that image the accretion flow on micro-arcsecond scales. I summarise the basic concepts behind the technique and highlight two recent results; the use of donor star emission as a means to system parameter determination, and the real-time movies of the evolving accretion flow in the cataclysmic variable WZ Sge during its 2001 outburst. I conclude with future opportunities in Doppler tomography by exploiting the combination of superior data sets, second generation reconstruction codes and simulated theoretical tomograms to delve deeper into the physics of accretion flows.

  18. Doppler experiments with Cassini radio system

    NASA Technical Reports Server (NTRS)

    Comoretto, G.; Bertotti, B.; Iess, L.; Ambrosini, R.

    1992-01-01

    The radio system of the Cassini orbiter will include a K-alpha band downlink channel, mainly intended for telemetry. A K-alpha uplink has also been proposed to allow for a highly accurate gravitational wave experiment. The fourfold increase in frequency will reduce the plasma noise by a factor of 12 and will allow a Doppler accuracy better than 10 exp -15 for time scales of 10 exp 3 - 10 exp 4 s. Extensive Doppler measurements of the gravitational field of Saturn and its satellites can be performed, exploiting the induced change in the velocity of the spacecraft. Possible sources of low-frequency gravitational waves and errors in the Doppler link are discussed.

  19. Rubidium Atomic Line Filtered (RALF) Doppler Velocimetry

    NASA Astrophysics Data System (ADS)

    Fajardo, Mario; Molek, Christopher; Vesely, Annamaria; Lasem Team

    2013-06-01

    We report our progress towards adapting the well-known Global Dopper Velocimetry (GDV) technique, popular in the aerodynamics community, to the order-of-magnitude higher velocities pertinent to shock experiments. In GDV, the narrow-line illumination laser is tuned to an edge of a molecular iodine absorption line; an iodine gas cell converts the Doppler shift of the reflected light to transmitted intensity. We follow the suggestion in the original 1990 patent by Komine and broaden the absorption lines of alkali metal atoms by adding a buffer gas, thereby tuning the transmission edge spectrum to match the Doppler shift (surface velocity) range of interest. We use atomic rubidium vapor cells, with 0 to 1 atmosphere pressures of molecular nitrogen buffer gas, and coin the name ``Rubidium Atomic Line Filtered'' (RALF) Doppler velocimetry. [96ABW-2013-0036

  20. Analysis of Doppler lidar wind measurements

    NASA Technical Reports Server (NTRS)

    Srivastava, R. C.

    1986-01-01

    Doppler lidar and multiple Doppler radar data were obtained in a convectively mixed planetary boundary layer. The lidar measurements were possible due to scattering from existing aerosols; radar reflecting chaff was released in the atmosphere to make it visible to the multiple Doppler radar network. The data were analyzed to obtain detailed horizontal wind structures. The divergence of the horizontal wind was calculated and the anelastic continuity equation integrated to obtain vertical air motions. Differences between the areally averaged quantities and the grid point values provided a measure of the fluctuations in the wind components or the turbulent wind fluctuations. Vertical profiles of the mean winds and quantities related to the turbulent kinetic energy components and the turbulent momentum transfers were also calculated.

  1. HF Doppler radar observations of low-latitude spread F

    NASA Astrophysics Data System (ADS)

    Reddi, C. R.; Sarma, M. S. S. R. K. N.; Niranjan, K.

    2009-06-01

    HF (5.5 MHz) Doppler radar observations of nonspread F and spread F echoes over Visakhapatnam (17.7°N, 83.3°E; dip 20°) are presented. The echoes appearing suddenly and nearly simultaneously in 16 successive range bins at 7.5 km intervals in association with spread F have been investigated. Two to five episodes of spread F activity were found to appear at intervals of 1-2 hours during individual nights. At the time of onset of spread F conditions, the Doppler velocity for each range bin changed rapidly from a negative maximum to a positive maximum followed by a gradual decrease to a steady ±10-15 m/s or to a large negative velocity and then again to a large positive. At the time of small constant velocity or velocity change from negative to positive, the spread F echoes were weak or even below the detection level of the radar. This disappearance in the higher ranges causes the decrease in range extent of spread F echoes. The positive and negative maximum velocities of spread F were in the range of +70 to -60 m/s. The maximum upward and downward velocity is not the same in all events of spread F activity. The width of the Doppler velocity spectrum for spread F echoes was found to vary with velocity. For zero velocity the width was a minimum of 50 m/s in contrast to 25 m/s for nonspread F events. These features were consistently observed for all spread F incidences. The observed results are compared with already reported HF/VHF observations and are discussed in the light of equatorial plasma dynamics during the growth phase of Rayleigh Taylor instability leading the incidence of spread F.

  2. Broad-band acoustic Doppler current profiler

    USGS Publications Warehouse

    Cobb, E.D.

    1993-01-01

    The broad-band acoustic Doppler current profiler is an instrument that determines velocity based on the Doppler principle by reflecting acoustic signals off sediment particles in the water. The instrument is capable of measuring velocity magnitude and direction throughout a water column and of measuring water depth. It is also capable of bottom tracking and can, therefore, keep track of its own relative position as it is moved across a channel. Discharge measurements can be made quickly and, based on limited tests, accurately with this instrument. ?? 1993.

  3. 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.

  4. A visual demo of the Doppler effect

    NASA Astrophysics Data System (ADS)

    Papacosta, Pangratios

    2010-09-01

    Most physics teachers are familiar with the standard classroom demonstration of the Doppler effect. We invite students to explain the periodic variation of the pitch produced when we swirl a sounding buzzer over our heads. Students are quick to connect this phenomenon to everyday life experiences such as listening to the sound of the siren of a fast-approaching police car or the bell of an approaching train. In addition to these aural experiences, our understanding of the Doppler effect can be strengthened with a useful visual metaphor.

  5. Ultrasonographic Doppler Use for Female Reproduction Management.

    PubMed

    Bollwein, Heinrich; Heppelmann, Maike; Lüttgenau, Johannes

    2016-03-01

    Transrectal color Doppler ultrasonography is a useful technique to get new information about physiologic and pathophysiologic alterations of the uterus and ovaries in female cattle. During all reproductive stages characteristic changes in uterine blood flow are observed. Cows with puerperal disturbances show delayed decrease in uterine blood flow in the first few weeks postparturition compared with healthy cows. Measurement of follicular blood flow is used to identify normally developing follicles and predict superovulatory response. Determination of luteal blood is more reliable than B-mode sonography to distinguish between functional and nonfunctional corpora lutea. Color Doppler ultrasonography is a promising tool to improve reproductive management in female cattle. PMID:26922117

  6. 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.

  7. Selection effects in Doppler velocity planet searches

    NASA Astrophysics Data System (ADS)

    O'Toole, Simon; Tinney, Chris; Jones, Hugh

    2008-05-01

    The majority of extra-solar planets have been discovered by measuring the Doppler velocities of the host star. Like all exoplanet detection methods, the Doppler method is rife with observational biases. Before any robust comparison of mass, orbital period and eccentricity distributions can be made with theory, a detailed understanding of these selection effects is required, something which up to now is lacking. We present here a progress report on our analysis of the selection effects present in Anglo-Australian Planet Search data, including the methodology used and some preliminary results.

  8. Photoacoustic Doppler Effect from Flowing Small Light-Absorbing Particles

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    From the flow of a suspension of micrometer-scale carbon particles, the photoacoustic Doppler shift is observed. As predicted theoretically, the observed Doppler shift equals half of that in Doppler ultrasound and does not depend on the direction of laser illumination. This new physical phenomenon provides a basis for developing photoacoustic Doppler flowmetry, which can potentially be used for detecting fluid flow in optically scattering media and especially low-speed blood flow of relatively deep microcirculation in biological tissue.

  9. Chaotic system for self-synchronizing Doppler measurement.

    PubMed

    Carroll, Thomas L

    2005-03-01

    In a radar system, it is necessary to measure both range and velocity of a target. The movement of the target causes a Doppler shift of the radar signal, and the size of the Doppler shift is used to measure the velocity of the target. In this work, a chaotic drive-response system is simulated that detects a Doppler shift in a chaotic signal. The response system can detect Doppler shifts in more than one signal at a time. PMID:15836263

  10. Doppler disc tomography applied to low-mass AGN spin

    NASA Astrophysics Data System (ADS)

    Middleton, Matthew J.; Ingram, Adam R.

    2015-01-01

    Doppler tomography can provide a powerful means of determining black hole spin when our view to the central regions are revealed and obscured by optically thick orbiting material, and can provide an independent estimate that does not suffer as many degeneracies as traditional methods. For low-mass active galactic nuclei (AGN), time-dependent obscuration is expected to leave a signature in the changing spectrum of the disc emission which extends into the soft X-ray bandpass. We create a spectral model incorporating Doppler tomography and apply it to the case of the low-mass (8 × 105 M⊙) AGN, RX J1301.9+2747 which shows unusual timing properties in the form of short-lived flares that we argue are best explained by the orbit of a window through an optically thick wind. Modelling the phase-resolved spectrum over the course of the highest data quality flare indicates a very low spin even when we relax our constraints. This is the lowest mass AGN for which a spin has been measured and the first via this technique. We note that, as the mass and spin are very low, this appears to favour supermassive black hole (SMBH) growth by chaotic rather than constant accretion.

  11. The first Doppler images of the eclipsing binary SZ Piscium

    NASA Astrophysics Data System (ADS)

    Xiang, Yue; Gu, Shenghong; Cameron, A. Collier; Barnes, J. R.; Zhang, Liyun

    2016-02-01

    We present the first Doppler images of the active eclipsing binary system SZ Psc, based on the high-resolution spectral data sets obtained in 2004 November and 2006 September-December. The least-squares deconvolution technique was applied to derive high signal-to-noise profiles from the observed spectra of SZ Psc. Absorption features contributed by a third component of the system were detected in the LSD profiles at all observed phases. We estimated the mass and period of the third component to be about 0.9 M⊙ and 1283 ± 10 d, respectively. After removing the contribution of the third body from the least-squares deconvolved profiles, we derived the surface maps of SZ Psc. The resulting Doppler images indicate significant star-spot activities on the surface of the K subgiant component. The distributions of star-spots are more complex than that revealed by previous photometric studies. The cooler K component exhibited pronounced high-latitude spots as well as numerous low- and intermediate-latitude spot groups during the entire observing seasons, but did not show any large, stable polar cap, different from many other active RS CVn-type binaries.

  12. Particle sizing experiments with the laser Doppler velocimeter: Final report

    SciTech Connect

    Giel, T.V. Jr.; Son, J.Y.

    1988-06-01

    Measurement techniques for in-situ simultaneous measurements of particle size distributions and particle velocities using the dual beam laser Doppler velocimeter (LV) were analytically and experimentally investigated. This investigation examined the different signal characteristics of the LV for determination of particle size and particle velocity, simultaneously. The different size related signal components were evaluated not only singularly but also as simultaneous measurements to determine which characteristic, or combination of characteristics, provided the best measure of particle size. The evaluation concentrated on the 0.5 to 5 ..mu..m particle size range, in which the LV light scattering characteristics are complex often non-monotonic functions of the particle size as well as functions of index of refraction, the laser light wavelength, laser intensity and polarization, and the location and response characteristics of the detector. Different components of the LV signal were considered, but analysis concentrated on Doppler phase, visibility and scatter-intensity because they show the greatest promise. These signals characteristics were initially defined analytically for numerous optical configurations over the 0.5 to 5 ..mu..m diameter range with 0.1 ..mu..m segmentation, for refractive index values from 1.0 to 3.0 with absorptive (imaginary) components varied form 0 to 1.0. Collector orientation and effective f/No., as well as fringe spacing, beam polarization and wavelength, were varied in this analytical evaluation. 18 refs., 42 figs., 5 tabs.

  13. Simultaneous 2D Doppler backscattering from edge turbulence

    NASA Astrophysics Data System (ADS)

    Thomas, David; Brunner, Kai; Freethy, Simon; Huang, Billy; Shevchenko, Vladimir; Vann, Roddy

    2015-11-01

    The Synthetic Aperture Microwave Imaging (SAMI) diagnostic (previously at MAST and now at NSTX-U) actively probes the plasma edge using a wide (80 degree beam width) and broadband (10-34.5 GHz) beam. It digitizes the phase and amplitude of the Doppler backscattered signal using a receiving array of eight antennas which can be focused in any direction post shot to an angular range of 6-24 degree FWHM. This allows Doppler BackScattering (DBS) experiments to be conducted in every direction within the field of view simultaneously. This capability is unique to SAMI and is a novel way of conducting DBS experiments. SAMI has measured the magnetic pitch angle in the edge for the first time using a backscattering diagnostic. This is possible with simultaneous 2D DBS because the maximum backscattered power is perpendicular to the turbulence and turbulence is elongated along the magnetic field. SAMI has also studied the effect of NBI and the L-H transition on turbulent velocity, and turbulence suppression in the edge during H-mode. Initial results from all of these studies will be presented. This work is supported by the Engineering and Physical Sciences Research Council Grants EP/K504178 and EP/H016732.

  14. Conventional ultrasonography and color Doppler velocimetry of uterine leiomyomas.

    PubMed

    Caruso, A; Caforio, L; Testa, A C; Pomini, F; Ciampelli, M; Mancuso, S

    1998-01-01

    The role of uterine leiomyomas as causative factor of sterility is controversial. Submucosal myomas, in particular, can interfere with fertility and be associated to obstetric complications as abruption of placenta, post-partum metrorrhagia and puerperal sepsis. With ultrasonography, immediate and long-term information can be drawn on changes in the features of myomas. However, to-date, there are no reliable noninvasive exams to assess the nature and growth pattern of myomas. With Doppler velocimetry in ovarian malignancies a vascularization significantly different from that observed in benign tumors, is detected. It has been hypothesized that within benign tumors, as myomatous masses, tissues with different cell proliferation rates could be characterized by different vascular patterns. In a group of myomas shown to have central arterial vessels at Doppler examination, significant correlations were assessed between resistance indices of analyzed vessels and percentage of cell in the proliferative phase evaluated with cytofluorimetry. The myomatous tissue with high cell proliferation rate seems to have higher vascular resistances. PMID:10191660

  15. 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.

  16. Coherent-array HF Doppler sounding of traveling ionospheric disturbances. I - Basic technique

    NASA Astrophysics Data System (ADS)

    Jacobson, A. R.; Carlos, R. C.

    1989-04-01

    The paper presents an introduction to the use of phase-coherent, multireceiver HF Doppler sounding arrays for measuring the horizontal velocity of traveling ionospheric disturbances (TIDs). The point of departure is the theorem of Pfister (1971) relating ray Doppler to ray zenith angle for a monostatic full reflection sounder. Retaining the simple model of a specular, smooth ionospheric reflector which is deformed by a propagating undulation, the theorem is first generalyzed to bistatic sounding geometry and then the effects of amplitude are included in addition to phase. Next, these results are cast into an algorithm for treating multireceiver phase sounders containing many diverse baselines, in order to obtain an accurate and unambiguous solution in the plane of wave slowness (inverse of velocity). The point spread function of this solution is controlled gy process bandwidth and by array geometry.

  17. Traveling Ionospheric Disturbance Characteristics Over Texas Using the TIDDBIT HF Doppler Radar

    NASA Astrophysics Data System (ADS)

    Wene, G.; Crowley, G.; Fessler, B.; Bronn, J.

    2004-05-01

    Atmospheric gravity waves (AGW) are generated by numerous lower atmospheric processes, such as storms, and by auroral processes in the ionosphere. At ionospheric heights, the motion of the neutral gas in the AGW sets the ionosphere into motion. The waves displace the isoionic contours, resulting in a travelling ionospheric disturbance (TID). TIDs can be thought of as traveling corrugations in the ionosphere, and they can seriously affect HF radio communications and surveillance systems. Consequently, one of the most sensitive methods for detecting transient changes in the ionosphere is the HF Doppler technique operating in the 3-10 MHz band. A simple Doppler system consists of a CW (continuous wave) radio transmitter and receiver, which are highly frequency-stable. When a HF radio wave is reflected from the ionosphere, movement of the reflection point during passage of a TID produces a change in phase path and a Doppler shift proportional to the time rate of change of the phase path. The Doppler system is sensitive to motions of the ionospheric reflection point, and it therefore provides an accurate measure of both the TID and AGW periods. Similarly, because the TID velocity is determined simply from triangulation using the time-delays between perturbations at different reflection points, the TID velocities are also an accurate estimate of the underlying gravity wave horizontal and vertical trace velocities. HF Doppler systems have advantages over all other techniques for the measurement of TID characteristics. They are more amenable to analysis than data from ionosonde chains, and their time resolution (30 sec) is much higher than that of ionosondes . Unlike total electron content (TEC) methods, which respond to height-integrated TID effects, the HF Doppler radar responds to TIDs at the altitude of the radio reflection point. Finally, HF Doppler systems have low power consumption, so that both spatial and temporal resolution can be maintained for many days without

  18. Doppler effect of subluminal and superluminal sources in eight dimensions

    NASA Astrophysics Data System (ADS)

    Chandola, H. C.; Rajput, B. S.

    1984-06-01

    The study of the relativistic Doppler effect of subliminal and superluminal sources has been undertaken in the eight-dimensional space. It has been shown that correct Doppler shifts are obtained in the external spaces of these sources and the conformal correspondence between Doppler effect curves holds in case of approaching and receeding sources but not in the transverse case.

  19. Satellite Doppler data processing using a microcomputer

    NASA Technical Reports Server (NTRS)

    Schmid, P. E.; Lynn, J. J.

    1977-01-01

    A microcomputer which was developed to compute ground radio beacon position locations using satellite measurements of Doppler frequency shift is described. Both the computational algorithms and the microcomputer hardware incorporating these algorithms were discussed. Results are presented where the microcomputer in conjunction with the NIMBUS-6 random access measurement system provides real time calculation of beacon latitude and longitude.

  20. 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.

  1. Method for Canceling Ionospheric Doppler Effect

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.

    1982-01-01

    Unified transponder system with hydrogen-maser oscillators at both stations can compensate for both motional and ionospheric components of Doppler shift. Appropriate choices of frequency shift in output of mixer m3. System exploits proportionality between dispersive component of frequency shift and reciprocal of frequency to achieve cancellation of dispersive component at output.

  2. Analysis of Doppler radar windshear data

    NASA Technical Reports Server (NTRS)

    Williams, F.; Mckinney, P.; Ozmen, F.

    1989-01-01

    The objective of this analysis is to process Lincoln Laboratory Doppler radar data obtained during FLOWS testing at Huntsville, Alabama, in the summer of 1986, to characterize windshear events. The processing includes plotting velocity and F-factor profiles, histogram analysis to summarize statistics, and correlation analysis to demonstrate any correlation between different data fields.

  3. Three-dimensional power Doppler angiography

    NASA Astrophysics Data System (ADS)

    Guo, Zhenyu; Durand, Louis-Gilles; Holdsworth, David W.; Fenster, Aaron

    1997-05-01

    The purpose of the present study is to improve the quantification of peripheral arterial stenosis using 3D power Doppler angiography and investigate the potential of this technique for generating the arterial tree of the lower limb for surgery planning. Stenotic wall-less agar arteries were created to simulate the femoral and carotid arteries. 3D power Doppler angiograms of those arteries were generated under different hemodynamic conditions using a 3D ultrasound imaging system developed by the Life Imaging System Inc. The effect of multiple stenoses on the 3D power Doppler angiograms was investigated using the femoral arterial phantoms. Using the carotid arterial phantoms, 3D power Doppler angiograms of the carotid arteries were generated and compared with the known geometry. To image a whole lower limb arterial tree for lower limb salvage surgery planning, multiple scans are required to cover the entire field-of- view interested by using a water-coupled scanner. Preliminary in vivo test was performed using water-coupled scanning.

  4. Atmospheric laser Doppler velocimetry - An overview

    NASA Technical Reports Server (NTRS)

    Bilbro, J. W.

    1980-01-01

    Research, development, and application of atmospheric laser Doppler velocimetry are overviewed. Consideration is given to operation principles of CO2 heterodyne systems. Global wind, pollution, V/STOL flow, and true airspeed measurements are outlined. Wind energy, dust devils, water spouts, tornadoes, and aircraft wake vortices are covered.

  5. Cross-frequency Doppler sensitive signal processing

    NASA Astrophysics Data System (ADS)

    Wagstaff, Ronald A.

    2005-04-01

    When there is relative motion between an acoustic source and a receiver, a signal can be Doppler shifted in frequency and enter or leave the processing bins of the conventional signal processor. The amount of the shift is determined by the frequency and the rate of change in the distance between the source and the receiver. This frequency Doppler shifting can cause severe reductions in the processors performance. Special cross-frequency signal processing algorithms have recently been developed to mitigate the effects of Doppler. They do this by using calculation paths that cut across frequency bins in order to follow signals during frequency shifting. Cross-frequency spectral grams of a fast-flying sound source were compared to conventional grams, to evaluate the performance of this new signal processing method. The Doppler shifts in the data ranged up to 70 contiguous frequency bins. The resulting cross-frequency grams showed that three paths provided small to no improvement. Four paths showed improvements for either up-frequency or down-frequency shifting, but not for both. Two paths showed substantial improvement for both up-frequency and down-frequency shifting. The cross-frequency paths will be defined, and comparisons between conventional and cross-frequency grams will be presented. [Work supported by Miltec Corporation.

  6. Calculating "g" from Acoustic Doppler Data

    ERIC Educational Resources Information Center

    Torres, Sebastian; Gonzalez-Espada, Wilson J.

    2006-01-01

    Traditionally, the Doppler effect for sound is introduced in high school and college physics courses. Students calculate the perceived frequency for several scenarios relating a stationary or moving observer and a stationary or moving sound source. These calculations assume a constant velocity of the observer and/or source. Although seldom…

  7. Assessing the quality of ionogram interpretation using the HF Doppler technique

    NASA Astrophysics Data System (ADS)

    Buresova, D.; Krasnov, V.; Drobzheva, Ya.; Lastovicka, J.; Chum, J.; Hruska, F.

    2007-05-01

    The first joint common volume measurements by the Digisonde Portable Sounder (DPS-4) and a new Doppler type system has been run at the Pruhonice ionospheric observatory (49.99° N, 14.54° E) since January 2004. The measurement of the Doppler shift is carried out continuously on a frequency of 3.6 MHz, thus the radio wave is reflected predominantly from the ionospheric F layer. To compare digisonde measurements with the Doppler data, a phase path was calculated from both Doppler and digisonde records. Under stormy conditions and in the case where a sporadic E layer was present, a significant disagreement between both measurements has been found. The discrepancies could be related to the uncertainties of the observational inputs and to the interpretation of the digisonde data. The comparison of the phase paths shows that during geomagnetically quiet days, in the absence of the sporadic E layer, and when high quality ionograms are available and correctly scaled, the electron density N(h) profiles, calculated by the Automatic Real Time Ionogram Scaler with True height algorithm (ARTIST), can be considered reliable.

  8. Doppler optical coherence tomography of retinal circulation.

    PubMed

    Tan, Ou; Wang, Yimin; Konduru, Ranjith K; Zhang, Xinbo; Sadda, SriniVas R; Huang, David

    2012-01-01

    Noncontact retinal blood flow measurements are performed with a Fourier domain optical coherence tomography (OCT) system using a circumpapillary double circular scan (CDCS) that scans around the optic nerve head at 3.40 mm and 3.75 mm diameters. The double concentric circles are performed 6 times consecutively over 2 sec. The CDCS scan is saved with Doppler shift information from which flow can be calculated. The standard clinical protocol calls for 3 CDCS scans made with the OCT beam passing through the superonasal edge of the pupil and 3 CDCS scan through the inferonal pupil. This double-angle protocol ensures that acceptable Doppler angle is obtained on each retinal branch vessel in at least 1 scan. The CDCS scan data, a 3-dimensional volumetric OCT scan of the optic disc scan, and a color photograph of the optic disc are used together to obtain retinal blood flow measurement on an eye. We have developed a blood flow measurement software called "Doppler optical coherence tomography of retinal circulation" (DOCTORC). This semi-automated software is used to measure total retinal blood flow, vessel cross section area, and average blood velocity. The flow of each vessel is calculated from the Doppler shift in the vessel cross-sectional area and the Doppler angle between the vessel and the OCT beam. Total retinal blood flow measurement is summed from the veins around the optic disc. The results obtained at our Doppler OCT reading center showed good reproducibility between graders and methods (<10%). Total retinal blood flow could be useful in the management of glaucoma, other retinal diseases, and retinal diseases. In glaucoma patients, OCT retinal blood flow measurement was highly correlated with visual field loss (R(2)>0.57 with visual field pattern deviation). Doppler OCT is a new method to perform rapid, noncontact, and repeatable measurement of total retinal blood flow using widely available Fourier-domain OCT instrumentation. This new technology may improve the

  9. Planetary Radio Interferometry and Doppler Experiment (PRIDE) for Planetary Atmospheric Studies

    NASA Astrophysics Data System (ADS)

    Bocanegra Bahamon, Tatiana; Cimo, Giuseppe; Duev, Dmitry; Gurvits, Leonid; Molera Calves, Guifre; Pogrebenko, Sergei

    2015-04-01

    The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that allows the determination of the radial velocity and lateral coordinates of planetary spacecraft with very high accuracy (Duev, 2012). The setup of the experiment consists of several ground stations from the European VLBI Network (EVN) located around the globe, which simultaneously perform Doppler tracking of a spacecraft carrier radio signal, and are subsequently processed in a VLBI-style in phase referencing mode. Because of the accurate examination of the changes in phase and amplitude of the radio signal propagating from the spacecraft to the multiple stations on Earth, the PRIDE technique can be used for several fields of planetary research, among which planetary atmospheric studies, gravimetry and ultra-precise celestial mechanics of planetary systems. In the study at hand the application of this technique for planetary atmospheric investigations is demonstrated. As a test case, radio occultation experiments were conducted with PRIDE having as target ESA's Venus Express, during different observing sessions with multiple ground stations in April 2012 and March 2014. Once each of the stations conducts the observation, the raw data is delivered to the correlation center at the Joint Institute for VLBI in Europe (JIVE) located in the Netherlands. The signals are processed with a high spectral resolution and phase detection software package from which Doppler observables of each station are derived. Subsequently the Doppler corrected signals are correlated to derive the VLBI observables. These two sets of observables are used for precise orbit determination. The reconstructed orbit along with the Doppler observables are used as input for the radio occultation processing software, which consists of mainly two modules, the geometrical optics module and the ray tracing inversion module, from which vertical density profiles, and subsequently, temperature and pressure profiles of Venus

  10. 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

  11. Acute hemodialysis effects on doppler echocardiographic indices.

    PubMed

    Abid, Leila; Rekik, Hajer; Jarraya, Fayçal; Kharrat, Ilyes; Hachicha, Jamil; Kammoun, Samir

    2014-07-01

    Conventional echocardiographic (ECHO) parameters of systolic and diastolic function of the left ventricular (LV) have been shown to be load dependent. However, the impact of pre-load reduction on tissue Doppler (TD) parameters of LV function is incompletely understood. To evaluate the effect of a single hemodialysis (HD) session on LV systolic and diastolic function using pulsed Doppler echocardiography and pulsed tissue Doppler imaging (TDI), we studied 81 chronic HD patients (40 males; mean age 52.4 ± 16.4 years) with these tools. ECHO parameters were obtained 30 min before and 30 min after HD. Fluid volume removed by HD was 1640 ± 730 cm³. HD led to reduction in LV end-diastolic volume (P <0.001), end-systolic volume (P <0.001), left atrium area (P <0.001), peak early (E-wave) trans-mitral flow velocity (P <0.001), the ratio of early to late Doppler velocities of diastolic mitral inflow (P <0.001) and aortic time velocity integral (P <0.001). No significant change in peak S velocity of pulmonary vein flow after HD was noted. Early and late diastolic (E') TDI velocities and the ratio of early to late TDI diastolic velocities (E'/A') on the lateral side of the mitral annulus decreased significantly after HD (P = 0.013; P = 0.007 and P = 0.008, respectively). Velocity of flow progression (Vp) during diastole was not affected by pre-load reduction. Pulmonary artery systolic pressure and the diameter of the inferior vena cava decreased significantly (P <0.001 and P <0.001, respectively) after HD. We conclude that most of the Doppler-derived indices of diastolic function are pre-load-dependent and velocity of flow progression was minimally affected by pre-load reduction in HD patients. PMID:24969184

  12. The Novel Nonlinear Adaptive Doppler Shift Estimation Technique and the Coherent Doppler Lidar System Validation Lidar

    NASA Technical Reports Server (NTRS)

    Beyon, Jeffrey Y.; Koch, Grady J.

    2006-01-01

    The signal processing aspect of a 2-m wavelength coherent Doppler lidar system under development at NASA Langley Research Center in Virginia is investigated in this paper. The lidar system is named VALIDAR (validation lidar) and its signal processing program estimates and displays various wind parameters in real-time as data acquisition occurs. The goal is to improve the quality of the current estimates such as power, Doppler shift, wind speed, and wind direction, especially in low signal-to-noise-ratio (SNR) regime. A novel Nonlinear Adaptive Doppler Shift Estimation Technique (NADSET) is developed on such behalf and its performance is analyzed using the wind data acquired over a long period of time by VALIDAR. The quality of Doppler shift and power estimations by conventional Fourier-transform-based spectrum estimation methods deteriorates rapidly as SNR decreases. NADSET compensates such deterioration in the quality of wind parameter estimates by adaptively utilizing the statistics of Doppler shift estimate in a strong SNR range and identifying sporadic range bins where good Doppler shift estimates are found. The authenticity of NADSET is established by comparing the trend of wind parameters with and without NADSET applied to the long-period lidar return data.

  13. Sub-Doppler cooling of sodium atoms in gray molasses

    NASA Astrophysics Data System (ADS)

    Colzi, Giacomo; Durastante, Gianmaria; Fava, Eleonora; Serafini, Simone; Lamporesi, Giacomo; Ferrari, Gabriele

    2016-02-01

    We report on the realization of sub-Doppler laser cooling of sodium atoms in gray molasses using the D1 optical transition (3 s 1/2 2S →3 p 1/2 2P) at 589.8 nm. The technique is applied to samples containing 3 ×109 atoms, previously cooled to 350 μ K in a magneto-optical trap, and it leads to temperatures as low as 9 μ K and phase-space densities in the range of 10-4. The capture efficiency of the gray molasses is larger than 2/3, and we observe no density-dependent heating for densities up to 1011cm-3 .

  14. Doppler-Shifted Flare Emissions Observed by SDO/EVE

    NASA Technical Reports Server (NTRS)

    Chamberlin, Phillip C.

    2012-01-01

    The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO) has been obtaining unprecedented observations of solar variation on times scales of seconds during flares and over the rising phase of Solar Cycle 24 since its start of normal operations in May 2010. Unexpectedly, as first pointed out in Hudson et. al., Ap.j. (2011), even with EVE's spectral resolution of 0.1 nm and 'irradiance' measurements, EVE has the ability to very accurately determine Doppler shifts in all emissions during solar flares and coronal mass ejections (CMEs). The technique for deriving these absolute velocities is not straightforward, as the optical and instrumental effects must first be eliminated in order to separate the absolute plasma velocities from the instrument effects. This talk will discuss these efforts to eliminate the instrumental component, as well as show some of the first results of absolute velocities of multiple emissions at a wide range of temperatures during solar flares.

  15. Externally Dispersed Interferometry for Resolution Boosting and Doppler Velocimetry

    SciTech Connect

    Erskine, D J

    2003-12-01

    Externally dispersed interferometry (EDI) is a rapidly advancing technique for wide bandwidth spectroscopy and radial velocimetry. By placing a small angle-independent interferometer near the slit of an existing spectrograph system, periodic fiducials are embedded on the recorded spectrum. The multiplication of the stellar spectrum times the sinusoidal fiducial net creates a moire pattern, which manifests high detailed spectral information heterodyned down to low spatial frequencies. The latter can more accurately survive the blurring, distortions and CCD Nyquist limitations of the spectrograph. Hence lower resolution spectrographs can be used to perform high resolution spectroscopy and radial velocimetry (under a Doppler shift the entire moir{acute e} pattern shifts in phase). A demonstration of {approx}2x resolution boosting (100,000 from 50,000) on the Lick Obs. echelle spectrograph is shown. Preliminary data indicating {approx}8x resolution boost (170,000 from 20,000) using multiple delays has been taken on a linear grating spectrograph.

  16. Optical coherence Doppler tomography for quantitative cerebral blood flow imaging

    PubMed Central

    You, Jiang; Du, Congwu; Volkow, Nora D.; Pan, Yingtian

    2014-01-01

    Optical coherence Doppler tomography (ODT) is a promising neurotechnique that permits 3D imaging of the cerebral blood flow (CBF) network; however, quantitative CBF velocity (CBFv) imaging remains challenging. Here we present a simple phase summation method to enhance slow capillary flow detection sensitivity without sacrificing dynamic range for fast flow and vessel tracking to improve angle correction for absolute CBFv quantification. Flow phantom validation indicated that the CBFv quantification accuracy increased from 15% to 91% and the coefficient of variation (CV) decreased 9.3-fold; in vivo mouse brain validation showed that CV decreased 4.4-/10.8- fold for venular/arteriolar flows. ODT was able to identify cocaine-elicited microischemia and quantify CBFv disruption in branch vessels and capillaries that otherwise would have not been possible. PMID:25401033

  17. Planar Particle Imaging and Doppler Velocimetry System and Method

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P. (Inventor)

    2003-01-01

    A planar velocity measurement system (100) is operative to measure all three velocity components of a flowing fluid (106) across an illuminated plane (108) using only a single line of sight. The fluid flow is seeded with small particles which accurately follow the flow field fluctuations. The seeded flow field is illuminated with pulsed laser light source (102) and the positions of the particles in the flow are recorded on CCD cameras (122,124). The in-plane velocities are measured by determining the in-plane particle displacements. The out-of-plane velocity component is determined by measuring the Doppler shift of the light scattered by the particles. Both gas and liquid velocities can be measured, as well as two-phase flows.

  18. Non-contact displacement estimation using Doppler radar.

    PubMed

    Gao, Xiaomeng; Singh, Aditya; Yavari, Ehsan; Lubecke, Victor; Boric-Lubecke, Olga

    2012-01-01

    Non-contact Doppler radar has been used extensively for detection of physiological motion. Most of the results published to date have been focused on estimation of the physiological rates, such as respiratory rate and heart rate, with CW and modulated waveforms in various settings. Accurate assessment of chest displacement may take this type of monitoring to the new level, by enabling the estimation of associated cardiopulmonary volumes, and possibly pulse pressure. To obtain absolute chest displacement with highest precision, full nonlinear phase demodulation of the quadrature radar outputs must be performed. The accuracy of this type of demodulation is limited by the drifting received RF power, varying dc offset, and channel quadrature imbalance. In this paper we demonstrate that if relatively large motion is used to calibrate the system, smaller motion displacement may be acquired with the accuracy on the order of 30 µm. PMID:23366212

  19. Doppler lidar results from the San Gorgonio Pass experiments

    NASA Technical Reports Server (NTRS)

    Cliff, W. C.; Skarda, J. R.; Renne, D. S.

    1984-01-01

    During FY-84, the Doppler Lidar data from the San Gorgonio Pass experiments were analyzed, evaluated, and interpreted with regard to signal strength, signal width, magnitude and direction of velocity component and a goodness parameter associated with the expected noise level of the signal. From these parameters, a screening criteria was developed to eliminate questionable data. For the most part analysis supports the validity of Doppler Lidar data obtained at San Gorgonio Pass with respect to the mean velocity magnitude and direction. The question as to whether the Doppler width could be interpreted as a measure of the variance of the turbulence within the Doppler Lidar System (DLS) focal volume was not resolved. The stochastic nature of the Doppler broadening from finite residence time of the particles in the beam as well as other Doppler broadening phenomenon tend to mask the Doppler spread associated with small scale turbulence. Future tests with longer pulses may assist in better understanding.

  20. Superharmonic microbubble Doppler effect in ultrasound therapy.

    PubMed

    Pouliopoulos, Antonios N; Choi, James J

    2016-08-21

    The introduction of microbubbles in focused ultrasound therapies has enabled a diverse range of non-invasive technologies: sonoporation to deliver drugs into cells, sonothrombolysis to dissolve blood clots, and blood-brain barrier opening to deliver drugs into the brain. Current methods for passively monitoring the microbubble dynamics responsible for these therapeutic effects can identify the cavitation position by passive acoustic mapping and cavitation mode by spectral analysis. Here, we introduce a new feature that can be monitored: microbubble effective velocity. Previous studies have shown that echoes from short imaging pulses had a Doppler shift that was produced by the movement of microbubbles. Therapeutic pulses are longer (>1 000 cycles) and thus produce a larger alteration of microbubble distribution due to primary and secondary acoustic radiation force effects which cannot be monitored using pulse-echo techniques. In our experiments, we captured and analyzed the Doppler shift during long therapeutic pulses using a passive cavitation detector. A population of microbubbles (5  ×  10(4)-5  ×  10(7) microbubbles ml(-1)) was embedded in a vessel (inner diameter: 4 mm) and sonicated using a 0.5 MHz focused ultrasound transducer (peak-rarefactional pressure: 75-366 kPa, pulse length: 50 000 cycles or 100 ms) within a water tank. Microbubble acoustic emissions were captured with a coaxially aligned 7.5 MHz passive cavitation detector and spectrally analyzed to measure the Doppler shift for multiple harmonics above the 10th harmonic (i.e. superharmonics). A Doppler shift was observed on the order of tens of kHz with respect to the primary superharmonic peak and is due to the axial movement of the microbubbles. The position, amplitude and width of the Doppler peaks depended on the acoustic pressure and the microbubble concentration. Higher pressures increased the effective velocity of the microbubbles up to 3 m s(-1), prior to the onset

  1. Superharmonic microbubble Doppler effect in ultrasound therapy

    NASA Astrophysics Data System (ADS)

    Pouliopoulos, Antonios N.; Choi, James J.

    2016-08-01

    The introduction of microbubbles in focused ultrasound therapies has enabled a diverse range of non-invasive technologies: sonoporation to deliver drugs into cells, sonothrombolysis to dissolve blood clots, and blood-brain barrier opening to deliver drugs into the brain. Current methods for passively monitoring the microbubble dynamics responsible for these therapeutic effects can identify the cavitation position by passive acoustic mapping and cavitation mode by spectral analysis. Here, we introduce a new feature that can be monitored: microbubble effective velocity. Previous studies have shown that echoes from short imaging pulses had a Doppler shift that was produced by the movement of microbubbles. Therapeutic pulses are longer (>1 000 cycles) and thus produce a larger alteration of microbubble distribution due to primary and secondary acoustic radiation force effects which cannot be monitored using pulse-echo techniques. In our experiments, we captured and analyzed the Doppler shift during long therapeutic pulses using a passive cavitation detector. A population of microbubbles (5  ×  104–5  ×  107 microbubbles ml‑1) was embedded in a vessel (inner diameter: 4 mm) and sonicated using a 0.5 MHz focused ultrasound transducer (peak-rarefactional pressure: 75–366 kPa, pulse length: 50 000 cycles or 100 ms) within a water tank. Microbubble acoustic emissions were captured with a coaxially aligned 7.5 MHz passive cavitation detector and spectrally analyzed to measure the Doppler shift for multiple harmonics above the 10th harmonic (i.e. superharmonics). A Doppler shift was observed on the order of tens of kHz with respect to the primary superharmonic peak and is due to the axial movement of the microbubbles. The position, amplitude and width of the Doppler peaks depended on the acoustic pressure and the microbubble concentration. Higher pressures increased the effective velocity of the microbubbles up to 3 m s‑1, prior to the onset

  2. Magnetic Doppler imaging of the chemically peculiar star HD 125248

    NASA Astrophysics Data System (ADS)

    Rusomarov, N.; Kochukhov, O.; Ryabchikova, T.; Ilyin, I.

    2016-04-01

    Context. Intermediate-mass, chemically peculiar stars with strong magnetic fields provide an excellent opportunity to study the topology of their surface magnetic fields and the interplay between magnetic geometries and abundance inhomogeneities in the atmospheres of these stars. Aims: We reconstruct detailed maps of the surface magnetic field and abundance distributions for the magnetic Ap star HD 125248. Methods: We performed the analysis based on phase-resolved, four Stokes parameter spectropolarimetric observations obtained with the HARPSpol instrument. These data were interpreted with the help of magnetic Doppler imaging techniques and model atmospheres taking the effects of strong magnetic fields and nonsolar chemical composition into account. Results: We improved the atmospheric parameters of the star, Teff = 9850 ± 250 K and log g = 4.05 ± 0.10. We performed detailed abundance analysis, which confirmed that HD 125248 has abundances typical of other Ap stars, and discovered significant vertical stratification effects for the Fe ii and Cr ii ions. We computed LSD Stokes profiles using several line masks corresponding to Fe-peak and rare earth elements, and studied their behavior with rotational phase. Combining previous longitudinal field measurements with our own observations, we improved the rotational period of the star Prot = 9.29558 ± 0.00006 d. Magnetic Doppler imaging of HD 125248 showed that its magnetic field is mostly poloidal and quasi-dipolar with two large spots of different polarity and field strength. The chemical maps of Fe, Cr, Ce, Nd, Gd, and Ti show abundance contrasts of 0.9-3.5 dex. Among these elements, the Fe abundance map does not show high-contrast features. Cr is overabundant around the negative magnetic pole and has 3.5 dex abundance range. The rare earth elements and Ti are overabundant near the positive magnetic pole. Conclusions: The magnetic field of HD 125248 has strong deviations from the classical oblique dipole field

  3. Description and availability of airborne Doppler radar data

    NASA Technical Reports Server (NTRS)

    Harrah, S. D.; Bracalente, E. M.; Schaffner, P. R.; Baxa, E. G.

    1993-01-01

    An airborne, forward-looking, pulse, Doppler radar has been developed in conjunction with the joint FAA/NASA Wind Shear Program. This radar represents a first in an emerging technology. The radar was developed to assess the applicability of an airborne radar to detect low altitude hazardous wind shears for civil aviation applications. Such a radar must be capable of looking down into the ground clutter environment and extracting wind estimates from relatively low reflectivity weather targets. These weather targets often have reflectivities several orders of magnitude lower than the surrounding ground clutter. The NASA radar design incorporates numerous technological and engineering achievements in order to accomplish this task. The basic R/T unit evolved from a standard Collins 708 weather radar, which supports specific pulse widths of 1-7 microns and Pulse Repetition Frequencies (PRF) of less than 1-10 kHz. It was modified to allow for the output of the first IF signal, which fed a NASA developed receiver/detector subsystem. The NASA receiver incorporated a distributed, high-speed digital attenuator, producing a range bin to range bin automatic gain control system with 65 dB of dynamic range. Using group speed information supplied by the aircraft's navigation system, the radar signal is frequency demodulated back to base band (zero Doppler relative to stationary ground). The In-phase & Quadrature-phase (I/Q) components of the measured voltage signal are then digitized by a 12-bit A-D converter (producing an additional 36 dB of dynamic range). The raw I/Q signal for each range bin is then recorded (along with the current radar & aircraft state parameters) by a high-speed Kodak tape recorder.

  4. 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

  5. ROTATIONAL DOPPLER BEAMING IN ECLIPSING BINARIES

    SciTech Connect

    Groot, Paul J.

    2012-01-20

    In eclipsing binaries the stellar rotation of the two components will cause a rotational Doppler beaming during eclipse ingress and egress when only part of the eclipsed component is covered. For eclipsing binaries with fast spinning components this photometric analog of the well-known spectroscopic Rossiter-McLaughlin effect can exceed the strength of the orbital effect. Example light curves are shown for a detached double white dwarf binary, a massive O-star binary and a transiting exoplanet case, similar to WASP-33b. Inclusion of the rotational Doppler beaming in eclipsing systems is a prerequisite for deriving the correct stellar parameters from fitting high-quality photometric light curves and can be used to determine stellar obliquities as well as, e.g., an independent measure of the rotational velocity in those systems that may be expected to be fully synchronized.

  6. Uterine artery Doppler and prediction of preeclampsia.

    PubMed

    Lovgren, Todd R; Dugoff, Lorraine; Galan, Henry L

    2010-12-01

    Identifying patients at risk for preeclampsia would allow an increase in perinatal surveillance and possibly decrease the inherent maternal and fetal morbidity and mortality associated with severe preeclampsia and eclampsia. First and second trimester uterine artery Doppler velocimetry is a sensitive screening tool for the detection of preeclampsia and intrauterine growth retardation (IUGR) requiring delivery before 34 weeks. The performance of uterine artery Doppler velocimetry as a screening test depends on the prevalence of the adverse outcome in the studied population and whether the adverse outcomes are assessed individually or collectively as a group. Future research in this area should focus on identification of additional markers that may be incorporated into a prediction model for early identification of patients at risk for adverse outcomes. PMID:21048456

  7. The Doppler spread theory and parameterization revisited

    NASA Astrophysics Data System (ADS)

    Hines, Colin O.

    2004-07-01

    The author's earlier Doppler Spread Theory (DST) and Doppler Spread Parameterization (DSP) are revisited with a new understanding of the dichotomous roles played by nonlinearity in Eulerian and Lagrangian coordinates, respectively. An embryo Lagrangian DST is introduced and employed to assess the original DST. Earlier results near the Eulerian spectral peak are found to be reasonably valid, whereas those at greater vertical wavenumber are confirmed to have produced too much spreading. The earlier DSP is found to need little if any change, though specific values are suggested for its two most important ``fudge factors''. In a more general context, the continuing identity of a wave undergoing certain nonlinear interactions with other waves is discussed.

  8. Minior Actinide Doppler Coefficient Measurement Assessment

    SciTech Connect

    Nolan E. Hertel; Dwayne Blaylock

    2008-04-10

    The "Minor Actinide Doppler Coefficient Measurement Assessment" was a Department of Energy (DOE) U-NERI funded project intended to assess the viability of using either the FLATTOP or the COMET critical assembly to measure high temperature Doppler coefficients. The goal of the project was to calculate using the MCNP5 code the gram amounts of Np-237, Pu-238, Pu-239, Pu-241, AM-241, AM-242m, Am-243, and CM-244 needed to produce a 1E-5 in reactivity for a change in operating temperature 800C to 1000C. After determining the viability of using the assemblies and calculating the amounts of each actinide an experiment will be designed to verify the calculated results. The calculations and any doncuted experiments are designed to support the Advanced Fuel Cycle Initiative in conducting safety analysis of advanced fast reactor or acceoerator-driven transmutation systems with fuel containing high minor actinide content.

  9. Measuring Doppler Beaming with Kepler and TESS

    NASA Astrophysics Data System (ADS)

    Mayorga, Laura; Jackiewicz, Jason

    2016-01-01

    The Kepler mission offered unparalleled insight into stellar systems. Due to Kepler's high precision photometry, we can study the reflected light from a planet, the ellipsoidal variations of a star, and the small Doppler beaming signal due to the gravitational interaction between a planet and host star. To predict how the beaming signal varies as a function of stellar system parameters, we numerically simulate the beaming signals both Kepler and the upcoming Transiting Exoplanet Survey Satellite (TESS) would detect. We predict what mass planets TESS will be capable of detecting given the solar neighborhood population of stars and known population of exoplanets. Doppler beaming is largest for massive, short-period planets around cool stars and is more easily detectable by Kepler than TESS. Kepler's advantage is its bluer bandpass, longer time baseline, and higher precision.

  10. Straylight correction to Doppler rotation measurements

    NASA Astrophysics Data System (ADS)

    Andersen, B. N.

    1985-07-01

    The correction of the Pierce and LoPresto (1984) Doppler data on the plasma rotation rate for stray light increases the observed equatorial rotation velocity from 1977 to 2004 m/sec. This correction has an uncertainty of approximately 10 m/sec, because the accurate form of the stray light function is not available. The correction is noted to be largest for the blue lines, in virtue of increased scattering, and for the weak lines, due to the limb effect.

  11. Doppler, Johann Christian Andreas (1803-53)

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Born in Salzburg, Austria, Doppler studied and taught mathematics in Vienna. On the verge, because of economic hardship, of emigrating to America, he was offered posts in Prague. Despite huge teaching loads, he was able to carry out some research of his own (in the face of complaints of neglect by his students). In 1842 read a paper to the Royal Bohemian Society `On the colored light of the doubl...

  12. Directional acoustic measurements by laser Doppler velocimeters

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Overbey, R. L.; Testerman, M. K.

    1976-01-01

    Laser Doppler velocimeters (LDVs) are used as velocity microphones to measure sound pressure level in the range from 90 to 130 dB, spectral components, and two-point correlation functions for acoustic-noise source identification. Close agreement between LDV and microphone data is observed. 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 noise.

  13. Doppler Lidar Wind Value-Added Product

    SciTech Connect

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

    2015-07-01

    Wind speed and direction, together with pressure, temperature, and relative humidity, are the most fundamental atmospheric state parameters. Accurate measurement of these parameters is crucial for numerical weather prediction. Vertically resolved wind measurements in the atmospheric boundary layer are particularly important for modeling pollutant and aerosol transport. Raw data from a scanning coherent Doppler lidar system can be processed to generate accurate height-resolved measurements of wind speed and direction in the atmospheric boundary layer.

  14. Coastal salinity measurement using a Doppler Radiometer

    NASA Astrophysics Data System (ADS)

    Schwarz, Benjamin S.; Tatnall, Adrian R. L.; Lewis, Hugh G.

    2012-10-01

    Coastal salinity is characterised by large and variable salinity contrasts on relatively small scales. Measurements of salinity at a resolution compatible with these coastal regions on a regular basis would provide a rich source of information that could be used for a number of applications that have a fundamental bearing on the world's lifestyle. Doppler radiometry offers an approach to capture such measurements, as it reduces the number of required antennas needed to form an image, compared with an Interferometer type instrument. In this work, a Doppler Radiometer type instrument on free-flying satellites is introduced. This approach removes the need for a physical connection between all the antennas, affords the system a degree of reconfigurability, yet is still able to provide data of sufficient resolution. A Y-shaped central hub (similar to the SMOS configuration) is employed with additional antennas mounted on free flying platforms surrounding the central hub. The additional baselines formed between the antennas of the free flying satellites and central hub as well as between the free flying satellites extend the u-v coverage beyond that of just the central hub. The spatial resolution of a Doppler Radiometer system with a Y-shaped hub with a SMOS configuration of antennas, with each arm extended by five 6 m spaced free flying antennas would be of the order of 5 km, when imaging from 800 km. This paper will present some initial results from a study into an instrument concept that could provide coastal salinity measurements at microwave wavelengths. The study focuses on antenna array design and on quantifying the improvement in spatial resolution available by using this method, and includes an investigation into the effects of the relative motion between the hub and the free flying satellites on the imaging. Further, whilst this paper focuses on the application of the Doppler Radiometer to salinity measurement, the techniques described are applicable to other

  15. Laser Doppler systems in pollution monitoring

    NASA Technical Reports Server (NTRS)

    Miller, C. R.; Sonnenschein, C. M.; Herget, W. F.; Huffaker, R. M.

    1976-01-01

    The paper reports on a program undertaken to determine the feasibility of using a laser Doppler velocimeter (LDV) to measure smoke-stack gas exit velocity, particulate concentration, and mass flow. Measurements made with a CO2 laser Doppler radar system at a coal-burning power plant are compared with in-stack measurements made by a pitot tube. The operational principles of a LDV are briefly described along with the system employed in the present study. Data discussed include typical Doppler spectra from smoke-stack effluents at various laser elevation angles, the measured velocity profile across the stack exit, and the LDV-measured exit velocity as a function of the exit velocity measured by the in-stack instrument. The in-stack velocity is found to be about 14% higher than the LDV velocity, but this discrepancy is regarded as a systematic error. In general, linear relationships are observed between the laser data, the exit velocity, and the particulate concentration. It is concluded that an LDV has the capability of determining both the mass concentration and the mass flow from a power-plant smoke stack.

  16. 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.

  17. Validation of a radar doppler spectra simulator using measurements from the ARM cloud radars

    SciTech Connect

    Remillard, J.; Luke, E.; Kollias, P.

    2010-03-15

    The use of forward models as an alternative approach to compare models with observations contains advantages and challenges. Radar Doppler spectra simulators are not new; their application in high- resolution models with bin microphysics schemes could help to compare model output with the Doppler spectra recorded from the vertically pointing cloud radars at the ARM Climate Research Facility sites. The input parameters to a Doppler spectra simulator are both microphysical (e.g., particle size, shape, phase, and number concentration) and dynamical (e.g., resolved wind components and sub-grid turbulent kinetic energy). Libraries for spherical and non-spherical particles are then used to compute the backscattering cross-section and fall velocities, while the turbulence is parameterized as a Gaussian function with a prescribed width. The Signal-to-Noise Ratio (SNR) is used to determine the amount of noise added throughout the spectrum, and the spectral smoothing due to spectral averages is included to reproduce the averaging realized by cloud radars on successive returns. Thus, realistic Doppler spectra are obtained, and several parameters that relate to the morphological characteristics of the synthetically generated spectra are computed. Here, the results are compared to the new ARM microARSCL data products in an attempt to validate the simulator. Drizzling data obtained at the SGP site by the MMCR and the AMF site at Azores using the WACR are used to ensure the liquid part and the turbulence representation part of the simulator are properly accounted in the forward model.

  18. 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. PMID:23478764

  19. Power broadening and Doppler effects of coherent dark resonances in Rb

    NASA Astrophysics Data System (ADS)

    Erhard, Michael; Nußmann, Stefan; Helm, Hanspeter

    2000-12-01

    Using a phase-locked laser pair we have observed dark resonances with linewidths below 30 Hz in a rubidium cell filled with neon as buffer gas. A model allowing for pressure broadening correctly reproduces the dependence of the width on the laser intensity. Consideration of velocity changing collisions reveals the absence of Doppler effects in the position and width of the dark resonance at high buffer-gas pressure.

  20. Computer vision approach for ultrasound Doppler angle estimation.

    PubMed

    Saad, Ashraf A; Loupas, Thanasis; Shapiro, Linda G

    2009-12-01

    Doppler ultrasound is an important noninvasive diagnostic tool for cardiovascular diseases. Modern ultrasound imaging systems utilize spectral Doppler techniques for quantitative evaluation of blood flow velocities, and these measurements play a crucial rule in the diagnosis and grading of arterial stenosis. One drawback of Doppler-based blood flow quantification is that the operator has to manually specify the angle between the Doppler ultrasound beam and the vessel orientation, which is called the Doppler angle, in order to calculate flow velocities. In this paper, we will describe a computer vision approach to automate the Doppler angle estimation. Our approach starts with the segmentation of blood vessels in ultrasound color Doppler images. The segmentation step is followed by an estimation technique for the Doppler angle based on a skeleton representation of the segmented vessel. We conducted preliminary clinical experiments to evaluate the agreement between the expert operator's angle specification and the new automated method. Statistical regression analysis showed strong agreement between the manual and automated methods. We hypothesize that the automation of the Doppler angle will enhance the workflow of the ultrasound Doppler exam and achieve more standardized clinical outcome. PMID:18488268

  1. Doppler Wind Measurements of Mars Atmospheric Circulation

    NASA Astrophysics Data System (ADS)

    Clancy, R. T.; Sandor, B. J.; Moriarty-Schieven, G. H.

    2003-05-01

    The late August 2003 opposition of Mars, which occurs very near Mars perihelion, presents its largest angular diameter (25 arcsec) over the previous and subsequent 20 years. Sub-millimeter observations from the James Clerk Maxwell Telescope (JCMT) on August 27 (also scheduled for September 3) will provide 345 Ghz CO line integrations at five beam positions on the Mars disk. Differencing spectral line absorptions observed at east, west, south, and north offset positions from a disk center spectrum yields highly accurate measurements of projected doppler velocities relative to the disk center. As demonstrated in similar Venus mesospheric (90-110 km altitude) wind measurements obtained from JCMT in March 2001 and November 2002 (Clancy et al., 2002), this method provides excellent sensitivity (5 m/sec at 40-80 km altitudes) for short integration periods (10-15 minutes). Systematic uncertainties associated with the absorption lineshape and spectrometer baseline and channel characteristics are minimized, and the steep sub-millimeter line core shapes provide improved doppler shift sensitivity relative to millimeter measurements. Direct wind measurements for the Mars atmosphere are extremely important for validation of Mars general circulation models (GCM, e.g. Forget et al., 1999), yet remain beyond current spacecraft mission capabilities. Lellouch et al. (1993) obtained equinoctial (Ls=200) wind determinations in significant disagreement with Mars GCM predictions, employing 230 Ghz CO doppler line shifts from IRAM. JCMT sub-millimeter CO doppler shifts observed during the August 2003 Mars opposition should be much more accurate, with critical zonal and meridional resolution during the key southern summer season. Atmospheric pressure-temperature profiles (0-75km) will also be retrieved from each disk position 12CO spectrum, complementing the Ls dependence of disk average measurements obtained from previous whole disk JCMT Mars 12CO observations. In addition to doppler

  2. Imaging shear wave propagation for elastic measurement using OCT Doppler variance method

    NASA Astrophysics Data System (ADS)

    Zhu, Jiang; Miao, Yusi; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K. Kirk; Zhou, Qifa; Chen, Zhongping

    2016-03-01

    In this study, we have developed an acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) method for the visualization of the shear wave and the calculation of the shear modulus based on the OCT Doppler variance method. The vibration perpendicular to the OCT detection direction is induced by the remote acoustic radiation force (ARF) and the shear wave propagating along the OCT beam is visualized by the OCT M-scan. The homogeneous agar phantom and two-layer agar phantom are measured using the ARFOE-OCE system. The results show that the ARFOE-OCE system has the ability to measure the shear modulus beyond the OCT imaging depth. The OCT Doppler variance method, instead of the OCT Doppler phase method, is used for vibration detection without the need of high phase stability and phase wrapping correction. An M-scan instead of the B-scan for the visualization of the shear wave also simplifies the data processing.

  3. The delta Doppler technique for LDV measurements at long distances

    NASA Technical Reports Server (NTRS)

    Cliff, W. C.

    1976-01-01

    A technique for measuring velocity, referred to as a Delta Doppler technique, was presented. This technique determines scattering source velocities by measuring the difference in Doppler shifts of two different frequencies. By transmitting the two frequencies along the same path, a moving fringe pattern is established such that a nonmoving scatterer at the sensing volume would see an intensity variation exactly equal to the difference in the transmitted frequencies. If the particle has a velocity component along an axis which bisects the angle formed by the transmitter and receiver axes, a Doppler shift in the difference frequency can be measured and the velocity component computed. The frequency measured would correspond to the difference in Doppler frequencies that two laser Doppler velocimeters using separate frequencies (the same frequencies as used previously) would have measured, thus the term Delta Doppler.

  4. The portable Doppler: practical applications in EMS care.

    PubMed

    O'Keefe, K M; Bookman, L

    1976-12-01

    The practical application of a new, commercially available, portable Doppler ultrasound device to the operation of a busy city-county emergency department and ambulance service was investigated. An initial evaluation using healthy volunteers confirmed accuracy and reproducibility of the Doppler blood pressure readings comparable to that of auscultatory and palpatory measurement. In selected patients, the Doppler readings correlated well with readings from patients who had intra-arterial lines. When used in several low flow states, such as testing adequacy of cardiopulmonary resuscitation (CPR) and verification of electromechanical dissociation, the Doppler aided the clinical evaluation and treatment in many cases where traditional methods were useless. The Doppler was also helpful in the evaluation of local arterial injury but this unit was not found sensitive enough for venous disease. Finally, the Doppler enhanced the obtaining of vital signs in the noisy environment of our ambulances. PMID:1018378

  5. Spacecraft Doppler Tracking as a Xylophone Detector of Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Tinto, M.

    1995-01-01

    Spacecraft Doppler tracking is discussed for detecting gravitational waves in which Doppler data recorded on the ground are linearly combined with Doppler measurements made on board a spacecraft. A new method is derived for removing from combined data the frequency fluctuations due to the Earth troposphere, ionosphere, and mechanical vibrations of the antenna on the ground. The remaining non-zero gravitational wave signal could be used for detecting gravitational waves.

  6. Applications of Doppler ultrasound in clinical vascular disease

    NASA Technical Reports Server (NTRS)

    Barnes, R. W.; Hokanson, D. E.; Sumner, D. S.; Strandness, D. E., Jr.

    1975-01-01

    Doppler ultrasound has become the most useful and versatile noninvasive technique for objective evaluation of clinical vascular disease. Commercially available continuous-wave instruments provide qualitative and quantitative assessment of venous and arterial disease. Pulsed Doppler ultrasound was developed to provide longitudinal and transverse cross-sectional images of the arterial lumen with a resolution approaching that of conventional X-ray techniques. Application of Doppler ultrasound in venous, peripheral arterial, and cerebrovascular diseases is reviewed.

  7. Doppler and speckle methods for diagnostics in dentistry

    NASA Astrophysics Data System (ADS)

    Ulyanov, Sergey S.; Lepilin, Alexander V.; Lebedeva, Nina G.; Sedykh, Alexey V.; Kharish, Natalia A.; Osipova, Yulia; Karpovich, Alexander

    2002-02-01

    The results of statistical analysis of Doppler spectra of scattered intensity, obtained from tissues of oral cavity membrane of healthy volunteers, are presented. The dependence of the spectral moments of Doppler signal on cutoff frequency is investigated. Some results of statistical analysis of Doppler spectra, obtained from tooth pulp of patients, are presented. New approach for monitoring of blood microcirculation in orthodontics is suggested. Influence of own noise of measuring system on formation of speckle-interferometric signal is studied.

  8. Effects of the gaseous and liquid water content of the atmosphere on range delay and Doppler frequency

    NASA Technical Reports Server (NTRS)

    Flock, W. L.

    1981-01-01

    When high precision is required for range measurement on Earth space paths, it is necessary to correct as accurately as possible for excess range delays due to the dry air, water vapor, and liquid water content of the atmosphere. Calculations based on representative values of atmospheric parameters are useful for illustrating the order of magnitude of the expected delays. Range delay, time delay, and phase delay are simply and directly related. Doppler frequency variations or noise are proportional to the time rate of change of excess range delay. Tropospheric effects were examined as part of an overall consideration of the capability of precision two way ranging and Doppler systems.

  9. HF Doppler and VHF radar observations of upper atmospheric disturbances caused by weak cold front during winter time

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Lee, C. C.; Gao, M.; Johnson, D. L.; Yang, F. W.

    1990-01-01

    The simultaneous use of the Taiwan VHF radar and the HF Doppler sounder for remote measurement of three-dimensional winds, gravity waves, and density perturbations at mesospheric and thermospheric heights is demonstrated. A special event of atmospheric disturbances caused by propagating gravity waves excited by weak convective motions in winter time were investigated. The three-dimensional wind velocities at different heights were determined, and the frequency, horizontal wavelength, vertical wavelength, and phase velocity of the gravity waves were measured. The subtropical, low-latitude site makes the VHF radar and HF Doppler array systems unique, and the observations especially valuable for space projects dealing with low-latitude atmosphere.

  10. High-Frame-Rate Echocardiography Using Coherent Compounding With Doppler-Based Motion-Compensation.

    PubMed

    Poree, Jonathan; Posada, Daniel; Hodzic, Amir; Tournoux, Francois; Cloutier, Guy; Garcia, Damien

    2016-07-01

    High-frame-rate ultrasonography based on coherent compounding of unfocused beams can potentially transform the assessment of cardiac function. As it requires successive waves to be combined coherently, this approach is sensitive to high-velocity tissue motion. We investigated coherent compounding of tilted diverging waves, emitted from a 2.5 MHz clinical phased array transducer. To cope with high myocardial velocities, a triangle transmit sequence of diverging waves is proposed, combined with tissue Doppler imaging to perform motion compensation (MoCo). The compound sequence with integrated MoCo was adjusted from simulations and was tested in vitro and in vivo. Realistic myocardial velocities were analyzed in an in vitro spinning disk with anechoic cysts. While a 8 dB decrease (no motion versus high motion) was observed without MoCo, the contrast-to-noise ratio of the cysts was preserved with the MoCo approach. With this method, we could provide high-quality in vivo B-mode cardiac images with tissue Doppler at 250 frames per second. Although the septum and the anterior mitral leaflet were poorly apparent without MoCo, they became well perceptible and well contrasted with MoCo. The septal and lateral mitral annulus velocities determined by tissue Doppler were concordant with those measured by pulsed-wave Doppler with a clinical scanner (r(2)=0.7,y=0.9 x+0.5,N=60) . To conclude, high-contrast echo cardiographic B-mode and tissue Doppler images can be obtained with diverging beams when motion compensation is integrated in the coherent compounding process. PMID:26863650

  11. Eliminating Doppler Effects in Synthetic-Aperture Radar Optical Processors

    NASA Technical Reports Server (NTRS)

    Constantindes, N. J.; Bicknell, T. J.

    1984-01-01

    Pair of photodetectors generates correction signals. Instrument detects Doppler shifts in radar and corrects processing parameters so ambiguities caused by shifts not manifested as double or overlapping images.

  12. PRECISE DOPPLER MONITORING OF BARNARD'S STAR

    SciTech Connect

    Choi, Jieun; Marcy, Geoffrey W.; Howard, Andrew W.; Isaacson, Howard; McCarthy, Chris; Fischer, Debra A.; Johnson, John A.; Wright, Jason T.

    2013-02-20

    We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the second nearest star system to Earth, obtained from Lick and Keck Observatories during the 25 years between 1987 and 2012. The early precision was 20 m s{sup -1} but was 2 m s{sup -1} during the last 8 years, constituting the most extensive and sensitive search for Doppler signatures of planets around this stellar neighbor. We carefully analyze the 136 Keck radial velocities spanning 8 years by first applying a periodogram analysis to search for nearly circular orbits. We find no significant periodic Doppler signals with amplitudes above {approx}2 m s{sup -1}, setting firm upper limits on the minimum mass (Msin i) of any planets with orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for circular orbits, we determine that planetary companions to Barnard's Star with masses above 2 M {sub Circled-Plus} and periods below 10 days would have been detected. Planets with periods up to 2 years and masses above 10 M {sub Circled-Plus} (0.03 M {sub Jup}) are also ruled out. A similar analysis allowing for eccentric orbits yields comparable mass limits. The habitable zone of Barnard's Star appears to be devoid of roughly Earth-mass planets or larger, save for face-on orbits. Previous claims of planets around the star by van de Kamp are strongly refuted. The radial velocity of Barnard's Star increases with time at 4.515 {+-} 0.002 m s{sup -1} yr{sup -1}, consistent with the predicted geometrical effect, secular acceleration, that exchanges transverse for radial components of velocity.

  13. Christian Doppler is 200 years young.

    PubMed

    Bollinger, Alfred; Partsch, Hugo

    2003-11-01

    Christian Doppler was born 200 years ago in Salzburg, Austria, on November 29, 1803, worked in Prague and Vienna and died 150 years ago in Venice. In an article of eight pages he described the principle, which made him famous. It appeared in 1842 with the exotic title: "On the Coloured Light of the Double Stars and Certain Other Stars of the Heaven". The validity of his principle for velocity measurement was confirmed by trumpet sounds produced on a train moving towards and away from the observer. Around 1960 Japanese scientists suggested that flow velocity in blood vessels could be determined by analysing the difference of frequency between emitted and backscattered ultrasound. Rushmer and coworkers built machines suitable for medicine in Seattle, where Eugene Strandness recognized their potential and applied them in first studies. In 1967 the technique jumped to Europe and started to be used worldwide. Already by using continuous wave ultrasound it was possible to diagnose occlusive disease of neck and limb arteries, venous thrombosis and valvular insufficiency with accuracy. Measurements of postestenotic ankle blood pressure were facilitated by Doppler sensing. Over the years more sophisticated instruments were developed. Pulsed emission of ultrasound waves opened a way to study flow velocity profiles across large vessels. By combining the method with A or B mode ultrasound blood flow could be quantified and finally perfused segments of blood vessels visualized. Duplex scanning in its simple and then in its colour coded version is nowadays the standard non-invasive technique that nobody would like to miss. Vascular territories like intracranial, renal and intestinal arteries can also be explored. For the assessment of microvascular flow in skin and mucosae laser Doppler instruments were introduced. PMID:14694774

  14. Current-induced spin wave Doppler shift

    NASA Astrophysics Data System (ADS)

    Bailleul, Matthieu

    2010-03-01

    In metal ferromagnets -namely Fe, Co and Ni and their alloys- magnetism and electrical transport are strongly entangled (itinerant magnetism). This results in a number of properties such as the tunnel and giant magnetoresistance (i.e. the dependence of the electrical resistance on the magnetic state) and the more recently addressed spin transfer (i.e. the ability to manipulate the magnetic state with the help of an electrical current). The spin waves, being the low-energy elementary excitations of any ferromagnet, also exist in itinerant magnets, but they are expected to exhibit some peculiar properties due the itinerant character of the carriers. Accessing these specific properties experimentally could shed a new light on the microscopic mechanism governing itinerant magnetism, which -in turn- could help in optimizing material properties for spintronics applications. As a simple example of these specific properties, it was predicted theoretically that forcing a DC current through a ferromagnetic metal should induce a shift of the frequency of the spin waves [1,2]. This shift can be identified to a Doppler shift undergone by the electron system when it is put in motion by the electrical current. We will show how detailed spin wave measurements allow one to access this current-induced Doppler shift [3]. From an experimental point of view, we will discuss the peculiarities of propagating spin wave spectroscopy experiments carried out at a sub-micrometer length-scale and with MHz frequency resolution. Then, we will discuss the measured value of the Doppler shift in the context of both the old two-current model of spin-polarized transport and the more recent model of adiabatic spin transfer torque. [4pt] [1] P.Lederer and D.L. Mills, Phys.Rev. 148, 542 (1966).[0pt] [2] J. Fernandez-Rossier et al., Phys. Rev. B 69, 174412 (2004)[0pt] [3] V. Vlaminck and M. Bailleul, Science 322, 410 (2008).

  15. An improved instantaneous laser Doppler velocity system

    NASA Astrophysics Data System (ADS)

    Desio, Charles V.; Olcmen, Semih; Schinetsky, Philip

    2016-02-01

    In this paper, improvements made on a single velocity component instantaneous laser Doppler velocimetry (ILDV) system are detailed. The ILDV system developed in this research effort is capable of measuring a single velocity component at a rate as high as two megahertz. The current system accounts for the effects of the laser intensity variation on the measured velocity and eliminates the use of a Pockels cell used in previous ILDV systems. The system developed in the current effort was tested using compressible, subsonic jet flows. The ILDV system developed would be most beneficial where a high data capture rate is needed such as in shock tubes, and high-speed wind tunnels.

  16. Left ventricular performance indices by transesophageal Doppler.

    PubMed

    Thys, D M; Hillel, Z

    1988-11-01

    The purpose of this study was to assess whether blood flow velocity signals, obtained by esophageal continuous-wave Doppler, reflect changes in ventricular performance. Ventricular performance has previously been determined by analysis of blood flow velocity signals sampled in the ascending aorta. In this investigation velocity signals were acquired from the descending aorta, with the use of an esophageal Doppler transducer. Maximum blood flow velocity (Vm), maximum blood flow volume acceleration (Accv), and maximum linear blood flow acceleration (Acc) were the velocity signals used to evaluate left ventricular performance. Twenty-six patients scheduled for myocardial revascularization and anesthetized with fentanyl (50 micrograms/kg) and pancuronium (0.15 mg/kg) were studied. In seven patients (Group I) a good correlation (r = 0.91) was observed between Accv in the ascending and descending aorta. In 10 patients (Group 2), halothane (0.5 and 1.0 MAC end-tidal) was added to the anesthetic. At these halothane concentrations Vm, Accv, and Acc measured in the descending aorta remained unchanged. Decreases were noted in the product of mean arterial pressure (MAP) and Acc (P-Acc; decreased 20% at 0.5 MAC and 39% at 1 MAC) and the product of systemic vascular resistance and Acc (R-Acc; decreased 25% at 1 MAC). In nine patients (Group 3), phenylephrine was used to reverse the decrease in MAP induced by 1 MAC halothane. Under these conditions Vm, Accv, Acc, and P-Acc showed similar decreases (approximately 30% of baseline values), whereas R-Acc returned to baseline values. In summary, indices of blood flow in the descending aorta were easily determined with a commercial transesophageal continuous-wave Doppler device. Descending and ascending aortic blood flow Accv correlated well, and the changes in the product of MAP and Acc in the descending aorta reflected the anticipated, halothane-induced, changes in left ventricular performance. In conclusion, descending aortic blood

  17. Everyday relativity and the Doppler effect

    NASA Astrophysics Data System (ADS)

    Picton Drake, Samuel; Purvis, Alan

    2014-01-01

    It is generally believed that special relativistic effects are important only when studying objects moving at speeds close to that of light. This belief leaves many practicing scientists and engineers with the impression that an understanding of relativity is not necessary for their day jobs. Our aim is to show that the ideas and mathematics of the special theory of relativity are used in practical applications involving objects moving much slower than the speed of light. In particular, we show how the Doppler shift for sound and light can be calculated from the postulates of relativity.

  18. Applying Zeeman Doppler imaging to solar spectra

    NASA Astrophysics Data System (ADS)

    Hussain, G. A. J.; Saar, S. H.; Collier Cameron, A.

    2004-03-01

    A new generation of spectro-polarimeters with high throughput (e.g. CFHT/ESPADONS and LBT/PEPSI) is becoming available. This opportunity can be exploited using Zeeman Doppler imaging (ZDI), a technique that inverts time-series of Stokes V spectra to map stellar surface magnetic fields (Semel 1989). ZDI is assisted by ``Least squares deconvolution'' (LSD), which sums up the signal from 1000's of photospheric lines to produce a mean deconvolved profile with higher S:N (Donati & Collier Cameron 1997).

  19. Short pulse C-band Doppler scatterometer

    NASA Astrophysics Data System (ADS)

    Arakelyan, Artashes K.; Hambaryan, Astghik K.; Smolin, Aleksander I.; Karyan, Vanik V.; Hovhannesyan, Gagik G.; Alaverdyan, Eduard R.; Arakelyan, Arsen A.; Hambaryan, Vardan K.

    2005-05-01

    In this paper C-band (~5.75GHz), dual polarization, Doppler scatterometer is developed, for short distance remote sensing of water surface microwave reflective and spectrum characteristics simultaneous and coincident measurements, under laboratory-control conditions. Developed system will be set on a mobile bogie moving on the height of 6.5m along a stationary platform of 32m of length. It will allow carry out polarimetric (vv, vh, hh, hv), simultaneous and coincident microwave active measurements of pool water surface parameters at angles of incidence from the while of 0-40o.

  20. In-suit Doppler technology assessment

    NASA Technical Reports Server (NTRS)

    Schulze, Arthur E.; Greene, Ernest R.; Nadeau, John J.

    1991-01-01

    The objective of this program was to perform a technology assessment survey of non-invasive air embolism detection utilizing Doppler ultrasound methodologies. The primary application of this technology will be a continuous monitor for astronauts while performing extravehicular activities (EVA's). The technology assessment was to include: (1) development of a full understanding of all relevant background research; and (2) a survey of the medical ultrasound marketplace for expertise, information, and technical capability relevant to this development. Upon completion of the assessment, LSR was to provide an overview of technological approaches and R&D/manufacturing organizations.

  1. Solar Doppler shifts - Sources of continuous spectra

    NASA Technical Reports Server (NTRS)

    Duvall, T. L., Jr.; Harvey, J. W.

    1986-01-01

    Oscillation observations can be used to study nonoscillatory solar phenomena that exhibit Doppler shifts. The paper discusses several effects of these phenomena and their associated temporal and spatial power spectra: (1) they limit the signal-to-noise ratio and sometimes detectability of oscillation modes; (2) there is the potential for better understanding and/or detection of solar phenomena; (3) large-scale convection may spatially modulate oscillation modes, leading to a continuous background spectrum; and (4) in regions of the spectrum where the resolution to separate modes is lacking one can determine upper limits for the integrated effects of modes.

  2. Transmission media effects on precise Doppler tracking

    NASA Technical Reports Server (NTRS)

    Callahan, P. S.

    1978-01-01

    The effects of the transmission media - the earth's troposphere and ionosphere, and the solar wind - on precise Doppler tracking are discussed. The charged particle effects can be largely removed by dual frequency observations; however there are limitations to these corrections (besides system noise and/or finite integration times) including the effects of magnetic fields, diffraction, and differential refraction, all of which must be carefully evaluated. The earth's troposphere can contribute an error of delta f/f approximately 10 to the minus 14th power.

  3. The new Adelaide medium frequency Doppler radar

    NASA Astrophysics Data System (ADS)

    Reid, I. M.; Vandepeer, B. G. W.; Dillon, S.; Fuller, B.

    1993-08-01

    The Buckland Park Aerial Array (35 deg S, 138 deg E) is situated about 40 km north of Adelaide on a flat coastal plain. It was designed by Basil Briggs and Graham Elford, and constructed between 1965 and 1968. The first results were published in the late 1960's. Some aspects of the history of the array are described in Briggs (1993). A new MF Doppler Radar utilizing the array has been developed. This paper describes some of the technical details of this new facility.

  4. Coronary Artery Imaging with Transthoracic Doppler Echocardiography.

    PubMed

    Takeuchi, Masaaki; Nakazono, Akemi

    2016-07-01

    Coronary artery imaging with transthoracic Doppler echocardiography is a simple and useful technique to diagnose significant coronary artery stenosis. The visualization of mosaic flow in the proximal left coronary artery provides a direct indication of the presence of significant stenosis at the corresponding site during routine echocardiography. Coronary flow velocity reserve (CFVR) has a high diagnostic accuracy and feasibility in detecting the presence of functionally significant coronary stenosis in the left anterior descending coronary artery (LAD) and in the right coronary artery. The measurement of CFVR in the LAD also provides prognostic information in patients with intermediate coronary stenosis. This review summarizes the utility of transthoracic coronary artery imaging. PMID:27216843

  5. Detection of microemboli by transcranial Doppler ultrasound.

    PubMed Central

    Grosset, D G; Georgiadis, D; Kelman, A W; Cowburn, P; Stirling, S; Lees, K R; Faichney, A; Mallinson, A; Quin, R; Bone, I; Pettigrew, L; Brodie, E; MacKay, T; Wheatley, D J

    1996-01-01

    Doppler ultrasound detection of abnormally high-pitched signals within the arterial waveform offers a new method for diagnosis, and potentially for prediction, of embolic complications in at-risk patients. The nature of Doppler "microembolic" signals is of particular interest in patients with prosthetic heart valves, where a high prevalence of these signals is observed. Monitoring the middle cerebral artery with 2-MHz transcranial Doppler ultrasound (TC-2000, Nicolet Biomedical; Warwick, UK), we looked for microemboli signals in 150 patients (95 women and 55 men), and found 1 or more signals during a 30-min recording in 89% of 70 patients with Bjork-Shiley valves (principally monostrut), 54% of 50 patients with Medtronic-Hall valves, and 50% of 30 patients with Carpentier-Edwards valves (p < 0.001, chi 2). In the patients with Bjork-Shiley valves, the mean number of signals per hour was 59 (range, 42-86; 95% confidence interval), which was significantly higher than the mean in patients with Medtronic-Hall and Carpentier-Edwards valves (1.5[range, 0.5-2.5] and 1 [range, 0-5.3], respectively; both p < 0.04, multiple comparisons. Bonferroni correction). In the patients undergoing serial pre- and postoperative studies, the causative role of the valve implant was emphasized. There was no correlation between the number of emboli signals and a prior history of neurologic deficit, cardiac rhythm, previous cardiac surgery, or the intensity of oral anticoagulation, in patients with prosthetic heart valves. In Bjork-Shiley patients, dual (mitral and aortic) valves were associated with more signals than were single valves. In Medtronic-Hall patients, the signal count was greater for valves in the aortic position than it was for valves in the mitral position. Comparative studies of Doppler emboli signals in other clinical settings suggest a difference in composition or size of the underlying maternal between prosthetic valve patients and patients with carotid stenosis. These

  6. Doppler cooling to the quantum limit.

    PubMed

    Chalony, M; Kastberg, A; Klappauf, B; Wilkowski, D

    2011-12-01

    Doppler cooling on a narrow transition is limited by the noise of single scattering events. It shows novel features, which are in sharp contrast with cooling on a broad transition, such as a non-gaussian momentum distribution, and divergence of its mean square value close to the resonance. We have observed those features using 1D cooling on an intercombination transition in strontium, and compared the measurements with theoretical predictions and Monte Carlo simulations. We also find that for very a narrow transition, cooling can be improved using a dipole trap, where the clock shift is canceled. PMID:22242994

  7. Catadioptric optics for laser Doppler velocimeter applications

    NASA Technical Reports Server (NTRS)

    Dunagan, Stephen E.

    1989-01-01

    This paper examines the adaptation of low-cost Schmidt-Cassegrain astronomical telescopes to perform the laser-beam-focusing and scattered-light collection tasks associated with dual-beam laser Doppler velocimetry. A generic telescope design is analyzed using ray-tracing methods and Gaussian beam-propagation theory. A straightforward modification procedure to convert from infinite to near unity conjugate-ratio operation with very low residual aberration is identified and tested with a 200-mm-aperture telescope modified for f/10 operation. Performance data for this modified telescope configuration are near the diffraction limit and agree well with predictions.

  8. Respiratory effort energy estimation using Doppler radar.

    PubMed

    Shahhaidar, Ehsaneh; Yavari, Ehsan; Young, Jared; Boric-Lubecke, Olga; Stickley, Cris

    2012-01-01

    Human respiratory effort can be harvested to power wearable biosensors and mobile electronic devices. The very first step toward designing a harvester is to estimate available energy and power. This paper describes an estimation of the available power and energy due to the movements of the torso during breathing, using Doppler radar by detecting breathing rate, torso displacement, torso movement velocity and acceleration along the sagittal movement of the torso. The accuracy of the detected variables is verified by two reference methods. The experimental result obtained from a healthy female human subject shows that the available power from circumferential movement can be higher than the power from the sagittal movement. PMID:23365993

  9. Ultrasonic detection of photothermal interaction of lasers with tissue using a pulsed Doppler system

    NASA Astrophysics Data System (ADS)

    Ying, Hao; Azeemi, Aamer; Hartley, Craig J.; Motamedi, Massoud; Bell, Brent A.; Rastegar, Sohi; Sheppard, L. C.

    1995-05-01

    Thermal therapy using various heating sources such as lasers or microwaves to destroy benign and malignant lesions has recently gained widespread acceptance. However, the accurate prediction of thermal damage in tissue according to theoretical or computer modeling is difficult and unreliable due to target variability with respect to physical properties, geometry, and blood perfusion. Thus, one of the major obstacles to application of thermal therapies has been the lack of a noninvasive, real-time method that could determine the extent and geometry of treated tissue. To evaluate the effects of laser heating on tissue, we have developed an analog-digital hybrid Doppler ultrasound system to measure the phase and amplitude of ultrasonic echoes returned from the heated tissue. The system consists of an eight-gate pulsed Doppler detector, a 16-channel 12-bit A/D converter, and a signal analysis and visualization software package. In vitro studies using canine liver showed two distinct types of modulation of the echoes along the ultrasound beam path during laser irradiation using an 810 nm diode laser. Type 1 signals showed a small and slow variation in amplitude and phase, and were attributed to tissue coagulation. Type 1 signals showed a small and slow variation in amplitude and phase, and were attributed to tissue coagulation. Type 2 signals showed large and rapid variations in amplitude and phase which usually appeared after tissue surface explosion and were indicative of tissue ablation. We hypothesize that the observed phase changes in type 1 signals are due to thermal effects within the tissue consistent with tissue expansion and contraction while the phase changes in type 2 signals are likely due to formation and motion of gas bubbles in the tissue. A further development of the Doppler ultrasound technique could lead to the generation of feedback information needed for monitoring and automatic control of thermal treatment using various heating modalities such as

  10. A Method for Characteristic Extraction of Ultrasound Doppler Signal with Peak-valley Relationship under Heavy Noise.

    PubMed

    Lin, Zhang; Liu Dong, C; Jiliu, Zhou

    2005-01-01

    This paper proposes a real-time algorithm estimating clinical useful parameters from the maximum frequency curve of ultrasound Doppler spectrum. Traditional methods always apply some pre-calculations to the frequency waveform, for instance, filtering or scaling transformation, which have limitations on real-time features detection and waveform display. In this paper, we propose and maintain a process unit as a section of the waveform with the help of its phase information and the idea of the changeable scaling in the wavelet, to determine the Doppler waveform parameters in real time. From a set of in vivo Doppler waveforms, our proposed algorithm can pick up right parameters even in very noisy environment. PMID:17282933

  11. Analysis and improved design considerations for airborne pulse Doppler radar signal processing in the detection of hazardous windshear

    NASA Technical Reports Server (NTRS)

    Lee, Jonggil

    1990-01-01

    High resolution windspeed profile measurements are needed to provide reliable detection of hazardous low altitude windshear with an airborne pulse Doppler radar. The system phase noise in a Doppler weather radar may degrade the spectrum moment estimation quality and the clutter cancellation capability which are important in windshear detection. Also the bias due to weather return Doppler spectrum skewness may cause large errors in pulse pair spectral parameter estimates. These effects are analyzed for the improvement of an airborne Doppler weather radar signal processing design. A method is presented for the direct measurement of windspeed gradient using low pulse repetition frequency (PRF) radar. This spatial gradient is essential in obtaining the windshear hazard index. As an alternative, the modified Prony method is suggested as a spectrum mode estimator for both the clutter and weather signal. Estimation of Doppler spectrum modes may provide the desired windshear hazard information without the need of any preliminary processing requirement such as clutter filtering. The results obtained by processing a NASA simulation model output support consideration of mode identification as one component of a windshear detection algorithm.

  12. Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique: A test case of the Mars Express Phobos fly-by

    NASA Astrophysics Data System (ADS)

    Duev, D. A.; Pogrebenko, S. V.; Cimò, G.; Molera Calvés, G.; Bocanegra Bahamón, T. M.; Gurvits, L. I.; Kettenis, M. M.; Kania, J.; Tudose, V.; Rosenblatt, P.; Marty, J.-C.; Lainey, V.; de Vicente, P.; Quick, J.; Nickola, M.; Neidhardt, A.; Kronschnabl, G.; Ploetz, C.; Haas, R.; Lindqvist, M.; Orlati, A.; Ipatov, A. V.; Kharinov, M. A.; Mikhailov, A. G.; Lovell, J. E. J.; McCallum, J. N.; Stevens, J.; Gulyaev, S. A.; Natush, T.; Weston, S.; Wang, W. H.; Xia, B.; Yang, W. J.; Hao, L.-F.; Kallunki, J.; Witasse, O.

    2016-09-01

    Context. The closest ever fly-by of the Martian moon Phobos, performed by the European Space Agency's Mars Express spacecraft, gives a unique opportunity to sharpen and test the Planetary Radio Interferometry and Doppler Experiments (PRIDE) technique in the interest of studying planet-satellite systems. Aims: The aim of this work is to demonstrate a technique of providing high precision positional and Doppler measurements of planetary spacecraft using the Mars Express spacecraft. The technique will be used in the framework of Planetary Radio Interferometry and Doppler Experiments in various planetary missions, in particular in fly-by mode. Methods: We advanced a novel approach to spacecraft data processing using the techniques of Doppler and phase-referenced very long baseline interferometry spacecraft tracking. Results: We achieved, on average, mHz precision (30 μm/s at a 10 s integration time) for radial three-way Doppler estimates and sub-nanoradian precision for lateral position measurements, which in a linear measure (at a distance of 1.4 AU) corresponds to ~50 m.

  13. Detection of Traveling Ionospheric Disturbances by Medium Frequency Doppler Sounding Using AM Radio Transmissions

    NASA Astrophysics Data System (ADS)

    Chilcote, M. A.; Labelle, J. W.; Lind, F. D.; Coster, A. J.; Galkin, I. A.; Miller, E.; Weatherwax, A. T.

    2013-12-01

    Nighttime traveling ionosphere disturbances (TIDs) propagating in the lower F region of the ionosphere were detected from time variations in the Doppler shifts of commercial AM radio broadcast stations. Three separately deployed receivers, components of the Intercepted Signals for Ionospheric Science (ISIS) Array software radio instrumentation network, recorded signals from two radio stations during eleven nights in March-April, 2012. Combining these measurements established that variations in the frequencies of the received signals, with amplitudes up to a few tenths of a Hertz, resulted from Doppler shifts produced by the ionosphere. At times, TIDs were detected as large amplitude variations in the Doppler shift with approximately 40-minute period correlated across the array. For one study interval, 0000-0400 UT on April 13, 2012, simultaneous GPS-TEC, digisonde, and superDARN coherent backscatter radar measurements confirmed the detection of TIDs with the same period. Detection of the AM signals at widely spaced receivers allowed the phase velocity and wavelength of the TIDs to be inferred, with some limitations due to differing reflection heights for the different frequencies. These measurements will be compared to phase velocities and wavelengths determined from combining an array of GPS receivers; discrepancies due to the altitude sensitivity of the techniques or other effects will be discussed. These results demonstrate that AM radio signals can be used for detection of nighttime TIDs.

  14. The mobile Sousy-Doppler radar: Technical design and first results

    NASA Technical Reports Server (NTRS)

    Czechowsky, P.; Schmidt, G.; Ruster, R.

    1983-01-01

    A mobile VHF Doppler system was developed. The electronic part is installed in a 20 ft container and tested using a special log periodic aerial to illuminate the 300 m dish. The system was extended by designing a mobile phased antenna array with finally 576 Yagi elements. The grouping of the single Yagis, the system of transmission lines, the phase shifters, the power splitters and the T/R switch are described. Results from the first two campaigns and a survey of future programs demonstrating the flexibility of this mobile system are summarized.

  15. Characterizing Ocean Turbulence from Argo, Acoustic Doppler, and Simulation Data

    NASA Astrophysics Data System (ADS)

    McCaffrey, Katherine

    the tidal channel. TurbSim models statistics at the height of a turbine hub (5m) well, but do not model coherent events, while the LES does create these events, but not realistically in this configuration, based on comparisons with observations. Each of the datasets have disadvantages when it comes to observing turbulence. The Argo network is sparse in space, and few measurements are taken simultaneously in time. Therefore spatial and temporal averaging is needed, which requires the turbulence to be homogeneous and stationary if it is to be generalized. Though the acoustic Doppler current profiler provides a vertical profile of velocities, the fluctuations are dominated by instrument noise and beam spread, preventing it from being used for most turbulence metrics. ADV measurements have much less noise, and no beam spread, but the observations are made at one point in space, limiting us to temporal statistics or an assumption of "frozen turbulence" to infer spatial scales. As for the models, TurbSim does not have any real-world forcing, and uses parameterized spectra, and coherence functions and randomizes phase information, while LES models must make assumptions about sub-grid scales, which may be inaccurate. Additionally, all models are set up with idealizations of the forcing and domain, which may make the results unlike observations in a particular location and time. Despite these difficulties in observing and characterizing turbulence, I present several quantities that use the imperfect, yet still valuable observations, to attain a better description of the turbulence in the oceans.

  16. Is Doppler ultrasound useful for evaluating gestational trophoblastic disease?

    PubMed Central

    Lin, Lawrence H; Bernardes, Lisandra S; Hase, Eliane A; Fushida, Koji; Francisco, Rossana P V

    2015-01-01

    Doppler ultrasound is a non-invasive method for evaluating vascularization and is widely used in clinical practice. Gestational trophoblastic neoplasia includes a group of highly vascularized malignancies derived from placental cells. This review summarizes data found in the literature regarding the applications of Doppler ultrasound in managing patients with gestational trophoblastic neoplasia. The PubMed/Medline, Web of Science, Cochrane and LILACS databases were searched for articles published in English until 2014 using the following keywords: “Gestational trophoblastic disease AND Ultrasonography, Doppler.” Twenty-eight articles met the inclusion criteria and were separated into the 4 following groups according to the aim of the study. 1 Doppler ultrasound does not seem to be capable of differentiating partial from complete moles, but it might be useful when evaluating pregnancies in which a complete mole coexists with a normal fetus. 2 There is controversy in the role of uterine artery Doppler velocimetry in the prediction of development of gestational trophoblastic neoplasia. 3 Doppler ultrasound is a useful tool in the diagnosis of gestational trophoblastic neoplasia because abnormal myometrial vascularization and lower uterine artery Doppler indices seem to be correlated with invasive disease. 4 Lower uterine artery Doppler indices in the diagnosis of gestational trophoblastic neoplasia are associated with methotrexate resistance and might play a role in prognosis. CONCLUSION: Several studies support the importance of Doppler ultrasound in the management of patients with gestational trophoblastic neoplasia, particularly the role of Doppler velocimetry in the prediction of trophoblastic neoplasia and the chemoresistance of trophoblastic tumors. Doppler findings should be used as ancillary tools, along with human chorionic gonadotropin assessment, in the diagnosis of gestational trophoblastic neoplasia. PMID:26735221

  17. Localization of Living-Bodies Using Single-Frequency Multistatic Doppler Radar System

    NASA Astrophysics Data System (ADS)

    Miwa, Takashi; Ogiwara, Shun; Yamakoshi, Yoshiki

    Recently, it has become important to rapidly detect human subjects buried under collapsed houses, rubble and soil due to earthquakes and avalanches to reduce the casualties in a disaster. Such detection systems have already been developed as one kind of microwave displacement sensors that are based on phase difference generated by the motion of the subject's breast. Because almost all the systems consist of single transmitter and receiver pair, it is difficult to rapidly scan a wide area. In this paper, we propose a single-frequency multistatic radar system to detect breathing human subjects which exist in the area surrounded by the transmitting and receiving array. The vibrating targets can be localized by the MUSIC algorithm with the complex amplitude in the Doppler frequency. This algorithm is validated by the simulated signals synthesized with a rigorous solution of a dielectric spherical target model. We show experimental 3D localization results using a developed multistatic Doppler radar system around 250MHz.

  18. An automated method for analysis and visualization of laser Doppler velocimetry data.

    PubMed

    Healy, T M; Ellis, J T; Fontaine, A A; Jarrett, C A; Yoganathan, A P

    1997-01-01

    The analysis and visualization of large data sets collected by use of laser Doppler velocimetry has presented a challenge to researchers using this technique to investigate complex flow fields. This paper describes an automated procedure for analysis and animation of two- and three-dimensional laser Doppler velocimetry data. The procedure consists of a suite of FORTRAN programs for calculating phase window averages of velocity and the Reynolds stress tensor, calculating the principal normal stresses, maximum shear stresses, and preparation of data files for input into Plot-3D compatible data visualization software. An example application of these techniques to data collected from an in vitro investigation of the retrograde flow field associated with a bileaflet mechanical heart valve is also presented. PMID:9084838

  19. Surface Brightness Variation of the Contact Binary SW Lac: Clues From Doppler Imaging

    NASA Astrophysics Data System (ADS)

    Şenavcı, Hakan Volkan

    2012-04-01

    In this study, we present the preliminary light curve analysis of the contact binary SW Lac, using B, V light curves of the system spanning 2 years (2009 - 2010). During the spot modeling process, we used the information coming from the Doppler maps of the system, which was performed using the high resolution and phase dependent spectra obtained at the 2.1m Otto Struve Telescope of the McDonald Observatory, in 2009. The results showed that the spot modeling from the light curve analysis are in accordance with the Doppler maps, while the non-circular spot modeling technique is needed in order to obtain much better and reliable spot models.

  20. Users guide for an Airborne Windshear Doppler Radar Simulation (AWDRS) program

    NASA Technical Reports Server (NTRS)

    Britt, Charles L.

    1990-01-01

    A description is provided of the Airborne Windshear Doppler Radar Simulation (AWDRS) program developed for NASA-Langley by the Research Triangle Institute. The radar simulation program is a comprehensive calculation of the signal characteristics and expected outputs of an airborne coherent pulsed Doppler radar system viewing a low level microburst along or near the approach path of the aircraft. The detailed nature of the simulation permits the quick evaluation of proposed trade-offs in radar system parameters and the evaluation of the performance of proposed configurations in various microburst/clutter environments. The simulation also provides a test bed for various proposed signal processing techniques for minimizing the effects of noise, phase jitter, and ground clutter and maximizing the useful information derived for avoidance of microburst windshear by aircraft.

  1. Cas A Dynamics: Doppler and Proper Motion

    NASA Astrophysics Data System (ADS)

    DeLaney, Tracey; Smith, J.; Rudnick, L.; Ennis, J.; Rho, J.; Reach, W.; Kozasa, T.; Gomez, H.

    2006-06-01

    We present Doppler velocity images of the young supernova remnant Cassiopeia A in the infrared emission lines of Ar, Ne, Si, and S observed with the Spitzer IRS and covering nearly the whole extent of the remnant. The measured infrared velocities of the shocked ejecta range from -4000 km/s to +6000 km/s. The Si and S emission near the center of the remnant, that is associated with ejecta that have not yet encountered the reverse shock, also shows both red- and blue-shifted structures with velocities between -3000 km/s and +3000 km/s. These unshocked ejecta provide a unique opportunity to study the kinematics of the explosion free from the influences of the reverse shock and CSM. The infrared kinematics are compared to optical and X-ray Doppler velocities and optical, X-ray, and radio proper motions. This work was performed for the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the United States Government under Prime Contract between California Institute of Technology and NASA.

  2. Windowed multipole for cross section Doppler broadening

    NASA Astrophysics Data System (ADS)

    Josey, C.; Ducru, P.; Forget, B.; Smith, K.

    2016-02-01

    This paper presents an in-depth analysis on the accuracy and performance of the windowed multipole Doppler broadening method. The basic theory behind cross section data is described, along with the basic multipole formalism followed by the approximations leading to windowed multipole method and the algorithm used to efficiently evaluate Doppler broadened cross sections. The method is tested by simulating the BEAVRS benchmark with a windowed multipole library composed of 70 nuclides. Accuracy of the method is demonstrated on a single assembly case where total neutron production rates and 238U capture rates compare within 0.1% to ACE format files at the same temperature. With regards to performance, clock cycle counts and cache misses were measured for single temperature ACE table lookup and for windowed multipole. The windowed multipole method was found to require 39.6% more clock cycles to evaluate, translating to a 7.9% performance loss overall. However, the algorithm has significantly better last-level cache performance, with 3 fewer misses per evaluation, or a 65% reduction in last-level misses. This is due to the small memory footprint of the windowed multipole method and better memory access pattern of the algorithm.

  3. Doppler global velocimetry data in circular jets

    NASA Astrophysics Data System (ADS)

    Kuhlman, John; Burton, Lucinda; Scarberry, Tom

    2002-07-01

    A two-component Doppler global velocimeter (DGV) system has been improved through the use of vapour-limited iodine cells that have temperature-independent responses, along with nonpolarizing beam splitters and lower f-number lenses. Two-component DGV velocity measurements have been obtained for a 1 inch diameter uniform circular jet flow at a nominal exit velocity of 60 m s-1, as well as for an annular jet and a swirling jet. These data generally agree with earlier point Doppler velocimeter and hot wire anemometer results to within about 2-4 m s-1, and display a total variability from a smooth curve of ±2-3 m s-1. This level of accuracy has been obtained for a system that uses a cw argon ion laser and eight-bit CCD cameras and digitizers. Exceptions to this level of accuracy are noted in regions of significant secondary scattering, due to scattered laser light that is reflected off the lip of the jet nozzle, as well as in regions of low smoke seeding levels, resulting in low signal-to-noise ratios. A significant amount of the variability of the data from a smooth curve is due to the flat field correction.

  4. Ambiguity resolution for satellite Doppler positioning systems

    NASA Technical Reports Server (NTRS)

    Argentiero, P.; Marini, J.

    1979-01-01

    The implementation of satellite-based Doppler positioning systems frequently requires the recovery of transmitter position from a single pass of Doppler data. The least-squares approach to the problem yields conjugate solutions on either side of the satellite subtrack. It is important to develop a procedure for choosing the proper solution which is correct in a high percentage of cases. A test for ambiguity resolution which is the most powerful in the sense that it maximizes the probability of a correct decision is derived. When systematic error sources are properly included in the least-squares reduction process to yield an optimal solution the test reduces to choosing the solution which provides the smaller valuation of the least-squares loss function. When systematic error sources are ignored in the least-squares reduction, the most powerful test is a quadratic form comparison with the weighting matrix of the quadratic form obtained by computing the pseudoinverse of a reduced-rank square matrix. A formula for computing the power of the most powerful test is provided. Numerical examples are included in which the power of the test is computed for situations that are relevant to the design of a satellite-aided search and rescue system.

  5. Exploring inside-out Doppler tomography: non-magnetic cataclysmic variables

    NASA Astrophysics Data System (ADS)

    Kotze, E. J.; Potter, S. B.; McBride, V. A.

    2015-07-01

    Context. Doppler tomography is a technique that has revolutionised the interpretation of the phase-resolved spectroscopic observations of interacting binary systems. Aims: We present the results of our investigation of reversing the velocity axis to create an inside-out Doppler coordinate framework with the intent to expose overly compacted and enhance washed out emission details in the standard Doppler framework. Methods: The inside-out tomogram is constructed independently of the standard tomogram by directly projecting phase-resolved spectra onto an inside-out velocity coordinate frame. For the inside-out framework, the zero-velocity origin is transposed to the outer circumference and the maximum velocities to the origin of the velocity space. We test the technique on a simulated system and two real systems with easily identifiable features, namely the accretion disc and bright spot in WZ Sge, and spiral shocks in IP Peg. Results: Our tests show that there is a redistribution of the relative brightness of emission components throughout the tomograms, i.e., where the standard framework tends to concentrate and enhance lower velocity features towards the origin, the inside-out velocity framework tends to concentrate and enhance higher velocity features towards the origin. Conversely, the standard framework disperses and smears the higher velocities farther away from the origin whereas the inside-out framework disperses and smears the lower velocities. In addition, the projection of the accretion disc in velocity space now appears correctly orientated with the inner edge close to the maximum velocity origin and its outer edge closer to the zero-velocity outer circumference. Furthermore, the gas stream and secondary star are projected on the outside of the disc with the bright spot of the stream-disc impact region on the disc's outer edge in the inside-out velocity space. Conclusions: We conclude that inside-out Doppler tomography complements the already powerful

  6. Investigations of atmospheric dynamics using a CW Doppler sounder array

    NASA Technical Reports Server (NTRS)

    Rao, G. L.

    1974-01-01

    A three-dimensional CW Doppler sounding system currently under operation at the NASA-Marshall Space Flight Center, Alabama is described. The properties of the neutral atmosphere are discussed along with the theory of Doppler sounding technique. Methods of data analyses used to investigate the dynamical phenomena at the ionospheric heights are presented and suggestions for future investigations provided.

  7. Doppler weather radar with predictive wind shear detection capabilities

    NASA Technical Reports Server (NTRS)

    Kuntman, Daryal

    1991-01-01

    The status of Bendix research on Doppler weather radar with predictive wind shear detection capability is given in viewgraph form. Information is given on the RDR-4A, a fully coherent, solid state transmitter having Doppler turbulence capability. Frequency generation data, plans, modifications, system characteristics and certification requirements are covered.

  8. New Doppler echocardiographic applications for the study of diastolic function

    NASA Technical Reports Server (NTRS)

    Garcia, M. J.; Thomas, J. D.; Klein, A. L.

    1998-01-01

    Doppler echocardiography is one of the most useful clinical tools for the assessment of left ventricular (LV) diastolic function. Doppler indices of LV filling and pulmonary venous (PV) flow are used not only for diagnostic purposes but also for establishing prognosis and evaluating the effect of therapeutic interventions. The utility of these indices is limited, however, by the confounding effects of different physiologic variables such as LV relaxation, compliance and filling pressure. Since alterations in these variables result in changes in Doppler indices of opposite direction, it is often difficult to determine the status of a given variable when a specific Doppler filling pattern is observed. Recently, color M-mode and tissue Doppler have provided useful insights in the study of diastolic function. These new Doppler applications have been shown to provide an accurate estimate of LV relaxation and appear to be relatively insensitive to the effects of preload compensation. This review will focus on the complementary role of color M-mode and tissue Doppler echocardiography and traditional Doppler indices of LV filling and PV flow in the assessment of diastolic function.

  9. 21 CFR 892.1550 - Ultrasonic pulsed doppler imaging system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ultrasonic pulsed doppler imaging system. 892.1550 Section 892.1550 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1550 Ultrasonic pulsed doppler...

  10. Micro-Doppler classification of riders and riderless horses

    NASA Astrophysics Data System (ADS)

    Tahmoush, David

    2014-05-01

    Micro-range Micro-Doppler can be used to isolate particular parts of the radar signature, and in this case we demonstrate the differences in the signature between a walking horse versus a walking horse with a rider. Using micro-range micro-Doppler, we can distinguish the radar returns from the rider as separate from the radar returns of the horse.

  11. Imaging doppler velocimeter with downward heterodyning in the optical domain

    DOEpatents

    Reu, Phillip L; Hansche, Bruce D

    2013-05-21

    In a Doppler velocimeter, the incoming Doppler-shifted beams are heterodyned to reduce their frequencies into the bandwidth of a digital camera. This permits the digital camera to produce at every sampling interval a complete two-dimensional array of pixel values. This sequence of pixel value arrays provides a velocity image of the target.

  12. Rotational Doppler effect in x-ray photoionization

    SciTech Connect

    Sun Yuping; Wang Chuankui; Gel'mukhanov, Faris

    2010-11-15

    The energy of the photoelectron experiences a red or blue Doppler shift when the molecule recedes from the detector or approaches him. This results in a broadening of the photoelectron line due to the translational thermal motion. However, the molecules also have rotational degrees of freedom and we show that the translational Doppler effect has its rotational counterpart. This rotational Doppler effect leads to an additional broadening of the spectral line of the same magnitude as the Doppler broadening caused by translational thermal motion. The rotational Doppler broadening as well as the rotational recoil broadening is sensitive to the molecular orbital from which the photoelectron is ejected. This broadening should be taken into account in analysis of x-ray photoemission spectra of super-high resolution and it can be directly observed using x-ray pump-probe spectroscopy.

  13. Doppler-cancelled response to VLF gravitational waves

    NASA Technical Reports Server (NTRS)

    Caporali, A.

    1981-01-01

    The interaction of long periodic gravitational waves with a three link microwave system known as the Doppler Cancelling System is discussed. This system, which was developed for a gravitational redshift experiment, uses one-way and two-way Doppler informatin to construct the beat signal of two reference oscillators moving with respect to each other. The geometric optics approximation is used to derive the frequency shift produced on a light signal propagating in a gravitational wave space-time. The signature left on the Doppler-cancelled beat by burst and continuous gravitational waves is analyzed. A comparison is made between the response to gravitational waves of the Doppler Cancelling System and that of a Doppler tracking system which employs two-way, round-trip radio waves. A three-fold repetition of the gravitational wave form is found to be a common feature of the response functions of both systems. These two functions otherwise exhibit interesting differences.

  14. One way Doppler extractor. Volume 1: Vernier technique

    NASA Technical Reports Server (NTRS)

    Blasco, R. W.; Klein, S.; Nossen, E. J.; Starner, E. R.; Yanosov, J. A.

    1974-01-01

    A feasibility analysis, trade-offs, and implementation for a One Way Doppler Extraction system are discussed. A Doppler error analysis shows that quantization error is a primary source of Doppler measurement error. Several competing extraction techniques are compared and a Vernier technique is developed which obtains high Doppler resolution with low speed logic. Parameter trade-offs and sensitivities for the Vernier technique are analyzed, leading to a hardware design configuration. A detailed design, operation, and performance evaluation of the resulting breadboard model is presented which verifies the theoretical performance predictions. Performance tests have verified that the breadboard is capable of extracting Doppler, on an S-band signal, to an accuracy of less than 0.02 Hertz for a one second averaging period. This corresponds to a range rate error of no more than 3 millimeters per second.

  15. The superiority of combined continuous wave Doppler examination over periorbital Doppler for the detection of extracranial carotid disease.

    PubMed Central

    Trockel, U; Hennerici, M; Aulich, A; Sandmann, W

    1984-01-01

    Non-invasive examination of 431 vessels in 333 patients with cerebrovascular disease in all stages was performed in order to compare the reliability of the periorbital Doppler test alone and together with the more difficult insonation of the carotid arteries in the neck (combined Doppler). These findings were compared with those of subsequent arteriography. Extracranial obstructive (greater than 50%) carotid disease was detected with 100% sensitivity by the combined Doppler, but with only 48% sensitivity by the periorbital indirect test. The specific ability of both methods to identify non-stenotic carotid arteries (less than 50%) was similar at about 98%. Only the combined Doppler examination reliably differentiated various degrees of obstruction, comparable to that obtained with arteriography. Non-obstructive plaques could not be detected or excluded by either Doppler test. More refined methods will be necessary for their evaluation. Images PMID:6693913

  16. Lunar gravity - Apollo 15 Doppler radio tracking

    NASA Technical Reports Server (NTRS)

    Muller, P. M.; Sjogren, W. L.; Wollenhaupt, W. R.

    1974-01-01

    Analysis and interpretation of the lunar gravity measurements obtained from Apollo 15 Doppler radio tracking data. The extent of surface coverage was limited to the trajectory paths of the command and service module during revolutions 3 through 11, when it was at a relatively low periapsis altitude just prior to undocking with the lunar module. The trajectory was close to the most optimal for study of the details of the Serenitatis and Crisium mascons. The periapsis altitude was about 12 km at the center of Mare Serenitatis, one of the largest mascons, and the one in the most favorable viewing geometry. The results obtained strengthen Booker's (1970) contention that all mascons have approximately the same thickness.

  17. Hands-Free Transcranial Color Doppler Probe

    NASA Technical Reports Server (NTRS)

    Chin, Robert; Madala, Srihdar; Sattler, Graham

    2012-01-01

    Current transcranial color Doppler (TCD) transducer probes are bulky and difficult to move in tiny increments to search and optimize TCD signals. This invention provides miniature motions of a TCD transducer probe to optimize TCD signals. The mechanical probe uses spherical bearing in guiding and locating the tilting crystal face. The lateral motion of the crystal face as it tilts across the full range of motion was achieved by minimizing the distance between the pivot location and the crystal face. The smallest commonly available metal spherical bearing was used with an outer diameter of 12 mm, a 3-mm tall retaining ring, and 5-mm overall height. Small geared motors were used that would provide sufficient power in a very compact package. After confirming the validity of the basic positioning concept, optimization design loops were completed to yield the final design.

  18. Microscale Heat Conduction Models and Doppler Feedback

    SciTech Connect

    Hawari, Ayman I.; Ougouag, Abderrafi

    2015-01-22

    The objective of this project is to establish an approach for providing the fundamental input that is needed to estimate the magnitude and time-dependence of the Doppler feedback mechanism in Very High Temperature reactors. This mechanism is the foremost contributor to the passive safety of gas-cooled, graphite-moderated high temperature reactors that use fuel based on Tristructural-Isotropic (TRISO) coated particles. Therefore, its correct prediction is essential to the conduct of safety analyses for these reactors. Since the effect is directly dependent on the actual temperature reached by the fuel during transients, the underlying phenomena of heat deposition, heat transfer and temperature rise must be correctly predicted. To achieve the above objective, this project will explore an approach that accounts for lattice effects as well as local temperature variations and the correct definition of temperature and related local effects.

  19. Role of transcranial Doppler in cerebrovascular disease.

    PubMed

    Kulkarni, Amit A; Sharma, Vijay K

    2016-01-01

    Transcranial Doppler (TCD) is the only noninvasive modality for the assessment of real-time cerebral blood flow. It complements various anatomic imaging modalities by providing physiological-flow related information. It is relatively cheap, easily available, and can be performed at the bedside. It has been suggested as an essential component of a comprehensive stroke centre. In addition to its importance in acute cerebrovascular ischemia, its role is expanding in the evaluation of cerebral hemodynamics in various disorders of the brain. The "established" clinical indications for the use of TCD include cerebral ischemia, sickle cell disease, detection of right-to-left shunts, subarachnoid hemorrhage, periprocedural or surgical monitoring, and brain death. We present the role of TCD in acute cerebrovascular ischemia, sonothrombolysis, and intracranial stenosis. PMID:27625245

  20. Pulsed laser Doppler measurements of wind shear

    NASA Technical Reports Server (NTRS)

    Dimarzio, C.; Harris, C.; Bilbro, J. W.; Weaver, E. A.; Burnham, D. C.; Hallock, J. N.

    1979-01-01

    There is a need for a sensor at the airport that can remotely detect, identify, and track wind shears near the airport in order to assure aircraft safety. To determine the viability of a laser wind-shear system, the NASA pulsed coherent Doppler CO2 lidar (Jelalian et al., 1972) was installed in a semitrailer van with a rooftop-mounted hemispherical scanner and was used to monitor thunderstorm gust fronts. Wind shears associated with the gust fronts at the Kennedy Space Center (KSC) between 5 July and 4 August 1978 were measured and tracked. The most significant data collected at KSC are discussed. The wind shears were clearly visible in both real-time velocity vs. azimuth plots and in postprocessing displays of velocities vs. position. The results indicate that a lidar system cannot be used effectively when moderate precipitation exists between the sensor and the region of interest.

  1. Color Doppler imaging of retinal diseases.

    PubMed

    Dimitrova, Galina; Kato, Satoshi

    2010-01-01

    Color Doppler imaging (CDI) is a widely used method for evaluating ocular circulation that has been used in a number of studies on retinal diseases. CDI assesses blood velocity parameters by using ultrasound waves. In ophthalmology, these assessments are mainly performed on the retrobulbar blood vessels: the ophthalmic, the central retinal, and the short posterior ciliary arteries. In this review, we discuss CDI use for the assessment of retinal diseases classified into the following: vascular diseases, degenerations, dystrophies, and detachment. The retinal vascular diseases that have been investigated by CDI include diabetic retinopathy, retinal vein occlusions, retinal artery occlusions, ocular ischemic conditions, and retinopathy of prematurity. Degenerations and dystrophies included in this review are age-related macular degeneration, myopia, and retinitis pigmentosa. CDI has been used for the differential diagnosis of retinal detachment, as well as the evaluation of retrobulbar circulation in this condition. CDI is valuable for research and is a potentially useful diagnostic tool in the clinical setting. PMID:20385332

  2. DC coupled Doppler radar physiological monitor.

    PubMed

    Zhao, Xi; Song, Chenyan; Lubecke, Victor; Boric-Lubecke, Olga

    2011-01-01

    One of the challenges in Doppler radar systems for physiological monitoring is a large DC offset in baseband outputs. Typically, AC coupling is used to eliminate this DC offset. Since the physiological signals of interest include frequency content near DC, it is not desirable to simply use AC coupling on the radar outputs. While AC coupling effectively removes DC offset, it also introduces a large time delay and distortion. This paper presents the first DC coupled IQ demodulator printed circuit board (PCB) design and measurements. The DC coupling is achieved by using a mixer with high LO to RF port isolation, resulting in a very low radar DC offset on the order of mV. The DC coupled signals from the PCB radar system were successfully detected with significant LNA gain without saturation. Compared to the AC coupled results, the DC coupled results show great advantages of less signal distortion and more accurate rate estimation. PMID:22254704

  3. Laser Doppler systems in atmospheric turbulence

    NASA Technical Reports Server (NTRS)

    Murty, S. S. R.

    1976-01-01

    The loss of heterodyne signal power for the Marshall Space Flight Center laser Doppler system due to the random changes in the atmospheric index of refraction is investigated. The current status in the physics of low energy laser propagation through turbulent atmosphere is presented. The analysis and approximate evaluation of the loss of the heterodyne signal power due to the atmospheric absorption, scattering, and turbulence are estimated for the conditions of the January 1973 flight tests. Theoretical and experimental signal to noise values are compared. Maximum and minimum values of the atmospheric attenuation over a two way path of 20 km range are calculated as a function of altitude using models of atmosphere, aerosol concentration, and turbulence.

  4. Doppler cooling and trapping on forbidden transitions.

    PubMed

    Binnewies, T; Wilpers, G; Sterr, U; Riehle, F; Helmcke, J; Mehlstäubler, T E; Rasel, E M; Ertmer, W

    2001-09-17

    Ultracold atoms at temperatures close to the recoil limit have been achieved by extending Doppler cooling to forbidden transitions. A cloud of (40)Ca atoms has been cooled and trapped to a temperature as low as 6 microK by operating a magnetooptical trap on the spin-forbidden intercombination transition. Quenching the long-lived excited state with an additional laser enhanced the scattering rate by a factor of 15, while a high selectivity in velocity was preserved. With this method, more than 10% of precooled atoms from a standard magnetooptical trap have been transferred to the ultracold trap. Monte Carlo simulations of the cooling process are in good agreement with the experiments. PMID:11580503

  5. The solar oscillations investigation: Michelson Doppler imager

    NASA Technical Reports Server (NTRS)

    Hoeksema, J. Todd; Scherrer, P. H.; Bush, R. I.; Title, A.; Tarbell, T.

    1992-01-01

    The Solar Oscillations Investigation (SOI) developed the Michelson Doppler Imager (MDI) to investigate the properties of the solar interior using the tools of helioseismology and of the photosphere and corona using more conventional techniques. The fundamental goal is to understand the Sun by determining its structure and observing its dynamics. The basic observables, velocity, intensity, and magnetic field, are computed on board from up to twenty 1024 by 1024 filtergrams made each minute. Subsequent analysis will extend the region to be explored downward into the solar interior and upward into the corona. While the instrument is dedicated to producing an uninterrupted series of helioseismology data, several magnetograms will be made each day and special eight hour campaigns are being developed to address specific scientific questions, some in coordination with other SOHO (Solar and Heliospheric Observatory) instruments.

  6. Parallax effects in laser Doppler spectroscopy

    SciTech Connect

    Smirnov, V I

    1999-12-31

    Parallax effects in laser Doppler spectroscopy, associated with the variation of the scattering angle during motion of a particle through the probed volume, were investigated by a numerical simulation method based on the Mie scattering theory. It was found that, in general, the shifts of the spectral profile parameters (the average frequency, broadening, asymmetry, and kurtosis) become significant as the parallax number N{sub {psi}{alpha}=}(2/{pi}){psi}{alpha} ({psi} is the angular size of the probed volume, {alpha} = {pi}d/{lambda} is the relative particle diameter) increases. The anomalous ranges of the parameters of the particle and of the optical system, in which marked distortions (such as the polymodal nature and the splitting of the spectral profile) are observed even for a low parallax number (N{sub {psi}{alpha}} || 1), were discovered. (laser applications and other topics in quantum electronics)

  7. Widefield laser doppler velocimeter: development and theory.

    SciTech Connect

    Hansche, Bruce David; Reu, Phillip L.; Massad, Jordan Elias

    2007-03-01

    The widefield laser Doppler velocimeter is a new measurement technique that significantly expands the functionality of a traditional scanning system. This new technique allows full-field velocity measurements without scanning, a drawback of traditional measurement techniques. This is particularly important for tests in which the sample is destroyed or the motion of the sample is non-repetitive. The goal of creating ''velocity movies'' was accomplished during the research, and this report describes the current functionality and operation of the system. The mathematical underpinnings and system setup are thoroughly described. Two prototype experiments are then presented to show the practical use of the current system. Details of the corresponding hardware used to collect the data and the associated software to analyze the data are presented.

  8. Planar Particle Imaging Doppler Velocimetry Developed

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P.

    2000-01-01

    Two current techniques exist for the measurement of planar, three-component velocity fields. Both techniques require multiple views of the illumination plane in order to extract all three velocity components. Particle image velocimetry (PIV) is a high-resolution, high accuracy, planar velocimetry technique that provides valuable instantaneous velocity information in aeropropulsion test facilities. PIV can provide three-component flow-field measurements using a two-camera, stereo viewing configuration. Doppler global velocimetry (DGV) is another planar velocimetry technique that can provide three component flow-field measurements; however, it requires three detector systems that must be located at oblique angles from the measurement plane. The three-dimensional configurations of either technique require multiple (DGV) or at least large (stereo PIV) optical access ports in the facility in which the measurements are being conducted. Optical access is extremely limited in aeropropulsion test facilities. In many cases, only one optical access port is available. A hybrid measurement technique has been developed at the NASA Glenn Research Center, planar particle image and Doppler velocimetry (PPIDV), which combines elements from both the PIV and DGV techniques into a single detection system that can measure all three components of velocity across a planar region of a flow field through a single optical access port. In the standard PIV technique, a pulsed laser is used to illuminate the flow field at two closely spaced instances in time, which are recorded on a "frame-straddling" camera, yielding a pair of single-exposure image frames. The PIV camera is oriented perpendicular to the light sheet, and the processed PIV data yield the two-component velocity field in the plane of the light sheet. In the standard DGV technique, an injection-seeded Nd:YAG pulsed laser light sheet illuminates the seeded flow field, and three receiver systems are used to measure three components

  9. 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.

  10. 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

  11. Vapor core turbulence in annular two-phase flow

    SciTech Connect

    Trabold, T.A.; Kumar, R.

    1998-06-01

    This paper reports a new technique to measure vapor turbulence in two-phase flows using hot-film anemometry. Continuous vapor turbulence measurements along with local void fraction, droplet frequency, droplet velocity and droplet diameter were measured in a thin, vertical duct. By first eliminating the portion of the output voltage signal resulting from the interaction of dispersed liquid droplets with the HFA sensor, the discrete voltage samples associated with the vapor phase were separately analyzed. The data revealed that, over the range of liquid droplet sizes and concentrations encountered, the presence of the droplet field acts to enhance vapor turbulence. In addition, there is evidence that vapor turbulence is significantly influenced by the wall-bounded liquid film. The present results are qualitatively consistent with the limited data available in the open literature.

  12. Theory of sub-Doppler cooling of three-level {Lambda} atoms in standing light waves

    SciTech Connect

    Kosachev, D.V.; Rozhdestvenskii, Yu.V.

    1994-12-01

    A general theory of cooling of three-level {Lambda} atoms in two standing light waves between which there is a relative spatial phase shift is presented for arbitrary ratios of the intensity and detuning. It is shown that in the case of equal detuning of the light waves, deep (sub-Doppler) cooling of three-level atoms occurs for any values of the spatial phase shift. For zero spatial phase shift, the atoms are strongly cooled due to coherent population trapping in the given atom-field interaction scheme. On the other hand, for the case of different frequency detunings, sub-Doppler cooling of {Lambda} atoms is possible only with a nonzero relative phase shift; it is shown that this is associated with the so-called {open_quotes}Sisyphus{close_quotes} cooling mechanism. The authors underscore that in their scheme neither a polarization gradient of the exciting waves nor a magnetic field is required to achieve this type of cooling pattern; two standing waves acting on different transitions of a {Lambda} atom are sufficient. 13 refs., 10 figs.

  13. Laser Doppler vibrometry experiment on a piezo-driven slot synthetic jet in water

    NASA Astrophysics Data System (ADS)

    Broučková, Zuzana; Vít, Tomáš; Trávníček, Zdeněk

    2015-05-01

    The present study deals with a slot synthetic jet (SJ) issuing from an actuator into quiescent surroundings and driven by a piezoceramic transducer. The actuator slot width was 0.36 mm, with a drive frequency proposed near the theoretical natural frequency of the actuator. The working fluid was water at room temperature. The present experiments used flow visualization (a laser-induced fluorescence technique) and laser Doppler vibrometry methods. Flow visualization was used to identify SJ formation, to demonstrate its function, and to estimate SJ velocity. Laser Doppler vibrometry was used to quantify diaphragm displacement and refine operating parameters. Phase averaging yielded a spatial and temporal diaphragm deflection during the actuation period. Taking incompressibility and continuity into consideration, the velocity in the actuator slot and the Reynolds number of the SJ were evaluated as 0.21 m/s and 157, respectively. The present results confirmed a SJ actuator function at the resonance frequency of approximately 46 Hz, which corresponds closely with the theoretical evaluation. The laser Doppler vibrometry results corresponded closely with an estimation of SJ velocity by the present flow visualization.

  14. Doppler Tomography and Photometry of the Cataclysmic Variable 1RXS J064434.5+334451

    NASA Astrophysics Data System (ADS)

    Echevarria, Juan

    2015-08-01

    We have obtained simultaneous photometric and spectroscopic observations of the cataclysmic variable 1RXS J064434.5+334451. We have calibrated the spectra for slit losses using the simultaneous photometry. This has been used to construct reliable Doppler images from Hα, Hβ and He II 4686 Å emission lines. We have also analyzed the radial velocity curve of the emission lines to derive its semi-amplitude, and used a co-phasing method to determine the semi-amplitude of the secondary. We have improved the ephemeris of the object based on new photometric eclipse timings to obtain HJD = 2453403.759533 + 0.26937446E. Some eclipses present a clear internal structure which we attribute to a central blob of He II emission surrounding the white dwarf, a finding supported by the Doppler Tomography. This indicates that the system has a large inclination angle i = 78o ± 2. We discuss which radial velocity semi-amplitudes indicator yields a better result for the mass ratio of the system. We derive the masses of the components: M1 = 0.76 ± 0.04 M⊙, M2 = 0.57 ± 0.04 M⊙ and their separation a = 1.92 ± 0.04R⊙ . The Doppler tomography and other observed features in this nova-like system strongly suggests that this is an SW Sex type system.

  15. 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.

  16. Microvascular anastomosis in rodent model evaluated by Fourier domain Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Huang, Yong; Tong, Dedi; Zhu, Shan; Wu, Lehao; Ibrahim, Zuhaib; Lee, WP Andrew; Brandacher, Gerald; Kang, Jin U.

    2014-03-01

    Vascular and microvascular anastomosis are critical components of reconstructive microsurgery, vascular surgery and transplant surgery. Imaging modality that provides immediate, real-time in-depth view and 3D structure and flow information of the surgical site can be a great valuable tool for the surgeon to evaluate surgical outcome following both conventional and innovative anastomosis techniques, thus potentially increase the surgical success rate. Microvascular anastomosis for vessels with outer diameter smaller than 1.0 mm is extremely challenging and effective evaluation of the outcome is very difficult if not impossible using computed tomography (CT) angiograms, magnetic resonance (MR) angiograms and ultrasound Doppler. Optical coherence tomography (OCT) is a non-invasive high-resolution (micron level), high-speed, 3D imaging modality that has been adopted widely in biomedical and clinical applications. Phaseresolved Doppler OCT that explores the phase information of OCT signals has been shown to be capable of characterizing dynamic blood flow clinically. In this work, we explore the capability of Fourier domain Doppler OCT as an evaluation tool to detect commonly encountered post-operative complications that will cause surgical failure and to confirm positive result with surgeon's observation. Both suture and cuff based techniques were evaluated on the femoral artery and vein in the rodent model.

  17. Ultra-fast displaying Spectral Domain Optical Doppler Tomography system using a Graphics Processing Unit.

    PubMed

    Jeong, Hyosang; Cho, Nam Hyun; Jung, Unsang; Lee, Changho; Kim, Jeong-Yeon; Kim, Jeehyun

    2012-01-01

    We demonstrate an ultrafast displaying Spectral Domain Optical Doppler Tomography system using Graphics Processing Unit (GPU) computing. The calculation of FFT and the Doppler frequency shift is accelerated by the GPU. Our system can display processed OCT and ODT images simultaneously in real time at 120 fps for 1,024 pixels × 512 lateral A-scans. The computing time for the Doppler information was dependent on the size of the moving average window, but with a window size of 32 pixels the ODT computation time is only 8.3 ms, which is comparable to the data acquisition time. Also the phase noise decreases significantly with the window size. Since the performance of a real-time display for OCT/ODT is very important for clinical applications that need immediate diagnosis for screening or biopsy. Intraoperative surgery can take much benefit from the real-time display flow rate information from the technology. Moreover, the GPU is an attractive tool for clinical and commercial systems for functional OCT features as well. PMID:22969328

  18. Infrared Doppler instrument for the Subaru Telescope (IRD)

    NASA Astrophysics Data System (ADS)

    Tamura, M.; Suto, H.; Nishikawa, J.; Kotani, T.; Sato, B.; Aoki, W.; Usuda, T.; Kurokawa, T.; Kashiwagi, K.; Nishiyama, S.; Ikeda, Y.; Hall, D.; Hodapp, K.; Hashimoto, J.; Morino, J.; Inoue, S.; Mizuno, Y.; Washizaki, Y.; Tanaka, Y.; Suzuki, S.; Kwon, J.; Suenaga, T.; Oh, D.; Narita, N.; Kokubo, E.; Hayano, Y.; Izumiura, H.; Kambe, E.; Kudo, T.; Kusakabe, N.; Ikoma, M.; Hori, Ya.; Omiya, M.; Genda, H.; Fukui, A.; Fujii, Y.; Guyon, O.; Harakawa, H.; Hayashi, M.; Hidai, M.; Hirano, T.; Kuzuhara, M.; Machida, M.; Matsuo, T.; Nagata, T.; Ohnuki, H.; Ogihara, M.; Oshino, S.; Suzuki, R.; Takami, H.; Takato, N.; Takahashi, Y.; Tachinami, C.; Terada, H.

    2012-09-01

    IRD is the near-infrared high-precision radial velocity instrument for the Subaru 8.2-m telescope. It is a relatively compact (~1m size) spectrometer with a new echelle-grating and Volume-Phase Holographic gratings covering 1-2 micron wavelengths combined with an original frequency comb using optical pulse synthesizer. The spectrometer will employ a 4096x4096-pixel HgCdTe array under testing at IfA, University of Hawaii. Both the telescope/Adaptive Optics and comb beams are fed to the spectrometer via optical fibers, while the instrument is placed at the Nasmyth platform of the Subaru telescope. Expected accuracy of the Doppler-shifted velocity measurements is about 1 m s-1. Helped with the large collecting area and high image quality of the Subaru telescope, IRD can conduct systematic radial velocity surveys of nearby middle-to-late M stars aiming for down to one Earth-mass planet. Systematic observational and theoretical studies of M stars and their planets for the IRD science are also ongoing. We will report the design and preliminary development progresses of the whole and each component of IRD.

  19. Cardiorespiratory interactions: Noncontact assessment using laser Doppler vibrometry.

    PubMed

    Sirevaag, Erik J; Casaccia, Sara; Richter, Edward A; O'Sullivan, Joseph A; Scalise, Lorenzo; Rohrbaugh, John W

    2016-06-01

    The application of a noncontact physiological recording technique, based on the method of laser Doppler vibrometry (LDV), is described. The effectiveness of the LDV method as a physiological recording modality lies in the ability to detect very small movements of the skin, associated with internal mechanophysiological activities. The method is validated for a range of cardiovascular variables, extracted from the contour of the carotid pulse waveform as a function of phase of the respiration cycle. Data were obtained from 32 young healthy participants, while resting and breathing spontaneously. Individual beats were assigned to four segments, corresponding with inspiration and expiration peaks and transitional periods. Measures relating to cardiac and vascular dynamics are shown to agree with the pattern of effects seen in the substantial body of literature based on human and animal experiments, and with selected signals recorded simultaneously with conventional sensors. These effects include changes in heart rate, systolic time intervals, and stroke volume. There was also some evidence for vascular adjustments over the respiration cycle. The effectiveness of custom algorithmic approaches for extracting the key signal features was confirmed. The advantages of the LDV method are discussed in terms of the metrological properties and utility in psychophysiological research. Although used here within a suite of conventional sensors and electrodes, the LDV method can be used on a stand-alone, noncontact basis, with no requirement for skin preparation, and can be used in harsh environments including the MR scanner. PMID:26970208

  20. Doppler imaging of LQ Hydrae for 1998-2002

    NASA Astrophysics Data System (ADS)

    Cole, E. M.; Hackman, T.; Käpylä, M. J.; Ilyin, I.; Kochukhov, O.; Piskunov, N.

    2015-09-01

    Aims: We study the spot distribution on the surface of LQ Hya during the observing seasons October 1998-November 2002. We look for persistent active longitudes, trends in the level of spot activity and compare to photometric data. Methods: We apply the Doppler imaging technique on photospheric spectral lines using an inversion code to retrieve images of the surface temperature. Results: We present new temperature maps using multiple spectral lines for a total of 7 seasons. Conclusions: We find no evidence for active longitudes persisting over multiple observing seasons. The spot activity appears to be concentrated to two latitude regions. Using the currently accepted rotation period, we find spot structures to show a trend in the phase-time plot, indicative of a need for a longer period. We conclude that the long-term activity of LQ Hya is more chaotic than that of some magnetically active binary stars analyzed with similar methods, but still with clear indications of an activity cycle from the photometry. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Table 2 is available in electronic form at http://www.aanda.org

  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. Fractal dimensions of laser doppler flowmetry time series.

    PubMed

    Carolan-Rees, G; Tweddel, A C; Naka, K K; Griffith, T M

    2002-01-01

    Laser Doppler flowmetry (LDF) provides a non-invasive method of assessing cutaneous perfusion. As the microvasculature under the probe is not defined the measured flux cannot be given absolute units, but the technique has nevertheless proved valuable for assessing relative changes in perfusion in response to physiological stress. LDF signals normally show pronounced temporal variability, both as a consequence of the pulsatile nature of blood flow and local changes in dynamic vasomotor activity. The aim of the present study was to investigate the use of methods of nonlinear analysis in characterizing temporal fluctuations in LDF signals. Data were collected under standardised conditions from the forearm of 16 normal subjects at rest, during exercise and on recovery. Surrogate data was then generated from the original time series by phase randomization. Dispersional analysis demonstrated that the LDF data was fractal with two distinct scaling regions, thus allowing the calculation of a fractal dimension which decreased significantly from 1.23 +/- 0.09 to 1.04 +/- 0.02 during exercise. By contrast, dispersional analysis of the surrogate data showed no scaling region. PMID:11891142

  3. Use of Doppler ultrasound for non-invasive urodynamic diagnosis

    PubMed Central

    Ozawa, Hideo; Watanabe, Toyohiko; Uematsu, Katsutoshi; Sasaki, Katsumi; Inoue, Miyabi; Kumon, Hiromi

    2009-01-01

    Objectives: A totally non-invasive transperineal urodynamic technique using Doppler ultrasonography has been developed. Methods: Since normal urine does not have blood cells, urine was thought not to produce the Doppler effects. However, basic studies confirmed that the decrease of pressure at high velocity (Bernouilli effect) caused dissolved gas to form microbubbles, which are detected by Doppler ultrasonography. Subjects sat and the probe was advanced via remote control to achieve gentle contact with the perineal skin. The digital uroflow data signals and the color Doppler ultrasound video images were processed on a personal computer. The flow-velocity curves from two sites; the distal prostatic urethra just above the external sphincter (V1) and the sphincteric urethra (V2) were plotted against time. The parameters of both the pressure-flow studies and the Doppler ultrasound urodynamic studies were compared in men who had various degrees of obstruction. Results: Functional cross-sectional area at prostatic urethra (A1), calculated by Qmax/V1, was lower in the group of bladder outlet obstruction (BOO) vs. control group. Velocity ratio (VR), which was calculated by V1/V2, was the parameter having the best correlation with BOO index, though A1 had a similar correlation. This method is viable to diagnose the degree of BOO. Conclusions: The development of non-invasive Doppler ultrasound videourodynamics (Doppler UDS) will dramatically expand the information on voiding function. PMID:19468440

  4. Pulsed Doppler echocardiographic analysis of mitral regurgitation after myocardial infarction.

    PubMed

    Loperfido, F; Biasucci, L M; Pennestri, F; Laurenzi, F; Gimigliano, F; Vigna, C; Rossi, E; Favuzzi, A; Santarelli, P; Manzoli, U

    1986-10-01

    In 72 patients with previous myocardial infarction (MI), mitral regurgitation (MR) was assessed by pulsed-wave Doppler echocardiography and compared with physical and 2-dimensional echocardiographic findings. MR was found by Doppler in 29 of 42 patients (62%) with anterior MI, 11 of 30 (37%) with inferior MI (p less than 0.01) and in none of 20 normal control subjects. MR was more frequent in patients who underwent Doppler study 3 months after MI than in those who underwent Doppler at discharge (anterior MI = 83% vs 50%, p less than 0.01; inferior MI = 47% vs 27%, p = not significant). Of 15 patients who underwent Doppler studies both times, 3 (all with anterior MI) had MR only on the second study. Of the patients with Doppler MR, 12 of 27 (44%) with a left ventricular (LV) ejection fraction (EF) greater than 30% and 1 of 13 (8%) with an EF of 30% or less (p less than 0.01) had an MR systolic murmur. Mitral prolapse or eversion and papillary muscle fibrosis were infrequent in MI patients, whether or not Doppler MR was present. The degree of Doppler MR correlated with EF (r = -0.61), LV systolic volume (r = 0.47), and systolic and diastolic mitral anulus circumference (r = 0.52 and 0.51, respectively). Doppler MR was present in 24 of 28 patients (86%) with an EF of 40% or less and in 16 of 44 (36%) with EF more than 40% (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3766410

  5. Multi-epoch Doppler tomography and polarimetry of QQ Vul

    NASA Astrophysics Data System (ADS)

    Schwope, Axel D.; Catalán, Maria S.; Beuermann, Klaus; Metzner, André; Smith, Robert Connon; Steeghs, Danny

    2000-04-01

    We present multi-epoch high-resolution spectroscopy and photoelectric polarimetry of the long-period polar (AM Herculis star) QQ Vul. The blue emission lines show several distinct components, the sharpest of which can unequivocally be assigned to the illuminated hemisphere of the secondary star and used to trace its orbital motion. This narrow emission line can be used in combination with Nai absorption lines from the photosphere of the companion to build a stable long-term ephemeris for the star: inferior conjunction of the companion occurs at HJD=2448446.4710(5)+Ex0.15452011 day (11). The polarization curves are dissimilar at different epochs, thus supporting the idea of fundamental changes of the accretion geometry, e.g., between one- and two-pole accretion modes. The linear polarization pulses display a random scatter by 0.2 phase units and are not suitable for the determination of the binary period. The polarization data suggest that the magnetic (dipolar) axis has a colatitude of 23 deg, an azimuth of -50 deg, and an orbital inclination between 50 deg and 70 deg. Doppler images of blue emission and red absorption lines show a clear separation between the illuminated and non-illuminated hemispheres of the secondary star. The absorption lines on their own can be used to determine the mass ratio of the binary by Doppler tomography with an accuracy of 15-20 per cent. The narrow emission lines of different atomic species show remarkably different radial velocity amplitudes: K=85-130kms-1. Emission lines from the most highly ionized species, Heii, originate closest to the inner Lagrangian point L1. We can discern two kinematic components within the accretion stream; one is associated with the ballistic part, and the other with the magnetically threaded part of the stream. The location of the emission component associated with the ballistic accretion stream appears displaced between different epochs. Whether this displacement indicates a dislocation of the ballistic

  6. Doppler velocimetry of a current driven spin helix

    NASA Astrophysics Data System (ADS)

    Yang, Luyi

    2012-02-01

    We present direct observation of the translational motion of spin helices in GaAs quantum wells under the influence of applied electric fields. Previously, the lifetime of such helices was observed by time-resolving the amplitude of light diffracted from the periodic spin polarization [1]. This technique cannot be applied to tracking the motion of current-driven spin helices because diffraction amplitude is insensitive to translation of the center of mass of a periodic structure. In this talk, we describe a new experimental technique, Doppler spin velocimetry, capable of resolving displacements of spin polarization at the level of 1 nm on a picosecond time scale [2]. This is accomplished through the use of heterodyne detection to measure the optical phase of the diffracted light. We discuss experiments in which this technique is used to measure the motion of spin helices as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. Several striking observations will be reported -- for example, the spin helix velocity changes sign as a function of wavevector and is zero at the wavevector that yields the largest spin lifetime. Another important observation is that the velocity of spin polarization packets becomes equal to the drift velocity of the high-mobility electron gas in the limit of small spin helix amplitude. Finally, we show that spin helices continue propagate at the same speed as the Fermi sea even when the electron drift velocity exceeds the Fermi velocity of 10^7 cm-s-1. In collaboration with J. D. Koralek and J. Orenstein, UC Berkeley and LBNL, D. R. Tibbetts, J. L. Reno, and M. P. Lilly, SNL. Supported by DOE under Contract No. DE-AC02-05CH11231 and DE-AC04-94AL85000. [4pt] [1] J. D. Koralek et al., ``Emergency of the persistent spin helix in semiconductor quantum wells,'' Nature 458, 610-613 (2009). [0pt] [2] L. Yang et al, ``Doppler velocimetry of spin propagation in a two-dimensional electron gas,'' to appear

  7. In vivo photoacoustic tomography of total blood flow and Doppler angle

    NASA Astrophysics Data System (ADS)

    Yao, Junjie; Maslov, Konstantin I.; Wang, Lihong V.

    2012-02-01

    As two hallmarks of cancer, angiogenesis and hypermetabolism are closely related to increased blood flow. Volumetric blood flow measurement is important to understanding the tumor microenvironment and developing new means to treat cancer. Current photoacoustic blood flow estimation methods focus on either the axial or transverse component of the flow vector. Here, we propose a method to compute the total flow speed and Doppler angle by combining the axial and transverse flow measurements. Both the components are measured in M-mode. Collating the A-lines side by side yields a 2D matrix. The columns are Hilbert transformed to compare the phases for the computation of the axial flow. The rows are Fourier transformed to quantify the bandwidth for the computation of the transverse flow. From the axial and transverse flow components, the total flow speed and Doppler angle can be derived. The method has been verified by flowing bovine blood in a plastic tube at various speeds from 0 to 7.5 mm/s and at Doppler angles from 30 to 330°. The measurement error for total flow speed was experimentally determined to be less than 0.3 mm/s; for the Doppler angle, it was less than 15°. In addition, the method was tested in vivo on a mouse ear. The advantage of this method is simplicity: No system modification or additional data acquisition is required to use our existing system. We believe that the proposed method has the potential to be used for cancer angiogenesis and hypermetabolism imaging.

  8. Ultrasonic Doppler measurement of renal artery blood flow

    NASA Technical Reports Server (NTRS)

    Freund, W. R.; Beaver, W. L.; Meindl, J. D.

    1976-01-01

    Studies were made of (1) blood flow redistribution during lower body negative pressure (LBNP), (2) the profile of blood flow across the mitral annulus of the heart (both perpendicular and parallel to the commissures), (3) testing and evaluation of a number of pulsed Doppler systems, (4) acute calibration of perivascular Doppler transducers, (5) redesign of the mitral flow transducers to improve reliability and ease of construction, and (6) a frequency offset generator designed for use in distinguishing forward and reverse components of blood flow by producing frequencies above and below the offset frequency. Finally methodology was developed and initial results were obtained from a computer analysis of time-varying Doppler spectra.

  9. Relativistic formulation for the Doppler-broadened line profile

    SciTech Connect

    Huang, Young-Sea; Chiue, Juang-Han; Huang, Yi-Chi; Hsiung, Te-Chih

    2010-07-15

    Profiles of spectral lines due to the thermal motion of light-emitting particles are formulated based on the classical and the relativistic Doppler effects, respectively. For the classical case, the well-known Doppler-broadened line profile is reproduced. For the relativistic case, the line profile obtained is asymmetrically broadened with increasing temperature. However, the peak frequency remains unshifted, in contrast to blueshifted, as has been predicted in the current literature. Reasoning is given as to why the relativistic Doppler-broadened line profile currently accepted is probably invalid.

  10. [Feasibility study of the Doppler exploration of the renal artery].

    PubMed

    Milon, P; Clavier, E; Genevois, A; Benozio, M

    1990-03-01

    Using arteriography as a reference, the authors investigate the feasibility of pulsed doppler exploration of the normal or pathological renal arteries in 46 successive patients. The poor sensitivity of pulsed doppler, mainly due to the considerable anatomical variations of the renal pedicle, does not currently allow using this technique for the detection of renal arterial stenosis. When combined with angiography, pulsed doppler becomes a definite asset in therapeutic radiology to help in the choice of a treatment and in follow-up. PMID:2191123

  11. Sub-Doppler laser cooling of potassium atoms

    NASA Astrophysics Data System (ADS)

    Landini, M.; Roy, S.; Carcagní, L.; Trypogeorgos, D.; Fattori, M.; Inguscio, M.; Modugno, G.

    2011-10-01

    We investigate the sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of system and an adiabatic ramping of the laser parameters allows us to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25±3 μK and 47±5 μK in high-density samples of the two isotopes 39K and 41K, respectively. Our findings should find application to other atomic systems.

  12. Advances in Direct Detection Doppler Lidar Technology and Techniques

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce; Einaudi, Franco (Technical Monitor)

    2001-01-01

    In this paper we will describe the ground based Doppler lidar system which is mounted in a modified delivery van to allow field deployment and operations. The system includes an aerosol double edge receiver optimized for aerosol backscatter Doppler measurements at 1064 nm and a molecular double edge receiver which operates at 355 nm. The lidar system will be described including details of the injection seeded diode pumped laser transmitter and the piezoelectrically tunable high spectral resolution Fabry Perot etalon which is used to measure the Doppler shift. Examples of tropospheric wind profiles obtained with the system will also be presented to demonstrate its capabilities.

  13. Is tissue Doppler echocardiography the Holy Grail for the intensivist?

    PubMed Central

    Poelaert, Jan; Roosens, Carl

    2007-01-01

    Assessment of left ventricular diastolic function in the critically ill patient remains a difficult issue in clinical practice. Combined use of routine transmitral and pulmonary venous Doppler patterns in conjunction with tissue Doppler imaging have been claimed to allow bedside diagnosis of diastolic dysfunction. Although in the previous issue of Critical Care it was clearly demonstrated there might be a difference in load dependency of the early myocardial tissue Doppler velocity between lateral and septal placed sample volume, there remain still several unanswered questions, particularly with respect to the preload dependency of these indices. PMID:17567926

  14. Sub-Doppler laser cooling of potassium atoms

    SciTech Connect

    Landini, M.; Roy, S.; Carcagni, L.; Trypogeorgos, D.; Fattori, M.; Inguscio, M.; Modugno, G.

    2011-10-15

    We investigate the sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of system and an adiabatic ramping of the laser parameters allows us to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25{+-}3 {mu}K and 47{+-}5 {mu}K in high-density samples of the two isotopes {sup 39}K and {sup 41}K, respectively. Our findings should find application to other atomic systems.

  15. Doppler ultrasound signal denoising based on wavelet frames.

    PubMed

    Zhang, Y; Wang, Y; Wang, W; Liu, B

    2001-05-01

    A novel approach was proposed to denoise the Doppler ultrasound signal. Using this method, wavelet coefficients of the Doppler signal at multiple scales were first obtained using the discrete wavelet frame analysis. Then, a soft thresholding-based denoising algorithm was employed to deal with these coefficients to get the denoised signal. In the simulation experiments, the SNR improvements and the maximum frequency estimation precision were studied for the denoised signal. From the simulation and clinical studies, it was concluded that the performance of this discrete wavelet frame (DWF) approach is higher than that of the standard (critically sampled) wavelet transform (DWT) for the Doppler ultrasound signal denoising. PMID:11381694

  16. Rotational Doppler Effect and Barnett Field in Spinning NMR

    NASA Astrophysics Data System (ADS)

    Chudo, Hiroyuki; Harii, Kazuya; Matsuo, Mamoru; Ieda, Jun'ichi; Ono, Masao; Maekawa, Sadamichi; Saitoh, Eiji

    2015-04-01

    We report the observation of the rotational Doppler effect using nuclear magnetic resonance (NMR). We have developed a coil-spinning technique that enables measurements by rotating a detector and fixing a sample. We found that the rotational Doppler effect gives rise to NMR frequency shifts equal to the rotation frequency. We formulate the rotational Doppler effect and the Barnett field using a vector model for the nuclear magnetic moment. This formulation reveals that, with just the sample rotating, both effects cancel each other, thereby explaining the absence of an NMR frequency shift in conventional sample-spinning NMR measurements.

  17. Studying Venus' atmosphere and ionosphere with Planetary Radio Interferometry and Doppler Experiment (PRIDE)

    NASA Astrophysics Data System (ADS)

    Bocanegra-Bahamon, T. M.; Cimo, G.; Duev, D. A.; Gurvits, L. I.; Marty, J. Ch.; Pogrebenko, S. V.; Rosenblatt, P.

    2014-04-01

    The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that can provide a multi-disciplinary enhancement of the science return of planetary missions. By performing precise Doppler tracking of a spacecraft carrier radio signal, at Earth-based radio telescopes, and VLBI-style processing of these signals in phase-referencing mode, the technique allows the determination of the radial velocity and lateral coordinates of the spacecraft with very high accuracy[1]. Because of the accurate examination of the changes in phase and amplitude of the radio signal propagating from the spacecraft to the multiple stations on Earth, the PRIDE technique can be used for several fields of planetary research. The application of this technique for atmospheric studies has been assessed by observing ESA's Venus Express (VEX) during Venus occultation events in 2012 and 2014, and by participating in one of the Venus Express Atmospheric Drag Experiment (VExADE) campaigns in 2012. Both studies are contributing to the characterization efforts of the atmosphere and ionosphere of Venus. During the Venus Express Atmospheric Drag Experiment (VExADE) campaigns VEX's orbit pericenter was lowered into an altitude range of approximately 165 to 175 km in order to probe Venus upper atmosphere above its north pole. The first VExADE campaigns were carried out between 2009-2010 using Doppler tracking data acquired by the VEX radio science experiment (VeRa), which provided the first in situ measurements of the density of Venus' polar thermosphere at solar minimum conditions [2]. In the December 2012 campaign the PRIDE-team participated by tracking VEX with several radio telescopes from the European VLBI Network (EVN) during pericenter passage. A Doppler frequency drop of ∼40 mHz was detected as VEX reached the lowest altitudes at around 170 km. The tracking data for each pericenter pass is fitted for precise orbit determination, from which drag acceleration estimates and the

  18. 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.

  19. On the synthesis of sample volumes for real-time spectral Doppler ultrasound simulation.

    PubMed

    Aguilar, Luis A; Steinman, David A; Cobbold, Richard S C

    2010-12-01

    A variety of methods for simulating the ultrasound field produced by transducers are currently used in ultrasound imaging system design. However, simulations can be time-consuming, making them difficult to apply in real-time environments when the observation field changes rapidly with time. This is particularly true for interactive real-time Doppler and B-mode ultrasound simulators designed for use as training tools. In this paper, it is demonstrated that the use of a distribution of monopole sources can be used to simulate the field from a phased linear array and the accuracy should be sufficient for simulating pulsed spectral Doppler. Very good agreement can be achieved in comparison with that obtained by a more exact method and, because of the simplicity of the calculations, real-time simulations of flow in the arterial system becomes possible. Specifically, quantitative measurements were made and compared against an analytic solution for the case of a piston transducer and against Field II for the phased array. The root-mean-square error shows that it is possible to achieve 10% or less error for the latter case. For comparable conditions, the computational speed for the transmit field of phased array using the Field II method as compared with the monopole approach was found to be at least an order of magnitude faster. It is pointed out that the simplicity of the monopole approach provides the opportunity for a further order of magnitude gain. Our findings can have direct application on the simulation of spectral Doppler and other ultrasound techniques for the purpose of teaching and training. PMID:20950935

  20. Absolute velocity measurement using three-beam spectral-domain Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Sharma, P.; Verma, Y.; Kumar, S.; Gupta, P. K.

    2015-09-01

    We report the development of a three-beam spectral-domain Doppler optical coherence tomography setup that allows single interferometer-based measurement of absolute flow velocity. The setup makes use of galvo-based phase shifting to remove complex conjugate mirror artifact and a beam displacer in the sample arm to avoid cross talk image. The results show that the developed approach allows efficient utilization of the imaging range of the spectral-domain optical coherence tomography setup for three-beam-based velocity measurement.

  1. Observations of the quasi 2-day wave from the High Resolution Doppler Imager on UARS

    NASA Technical Reports Server (NTRS)

    Wu, D. L.; Hays, P. B.; Skinner, W. R.; Marshall, A. R.; Burrage, M. D.; Lieberman, R. S.; Ortland, D. A.

    1993-01-01

    A strong westward traveling oscillation, with a period of 2 days and zonal wave number 3, is observed in the mesospheric and lower thermospheric winds from the High Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS). The important events happen in January, July, and September/October, of which the occurrence in January is the strongest with an amplitude over 60 m/s. Detailed analyses for the periods of January 1992 and January 1993 reveal a cause-and-effect relationship in the wave developing process at 95 km. The global structures of the wave amplitude and phase are also presented.

  2. Adaptive Doppler separation by quadratic detection of distance-confused radar signals

    NASA Astrophysics Data System (ADS)

    de Reffye, Jerome

    1988-02-01

    Possible improvements in the Doppler radar processing necessary to separate two targets whose distance ranges are confused are considered, with special attention given to the case of the detection of a missile in the presence of an aircraft. Real-time adaptive filtering methods are developed which permit the rejection of harmonics in nonwhite noise. Procedures for the quadratic integration of frequency-modulated signals representing the missile in the acceleration phase are then studied. Finally, the developed techniques are applied to a nonlinear problem.

  3. Interference of Backscatter from Two Droplets in a Focused Continuous Wave CO2 Doppler Lidar Beam

    NASA Technical Reports Server (NTRS)

    Jarzembski, Maurice A.; Srivastava, Vandana

    1998-01-01

    Using a focused continuous wave CO2 Doppler lidar at wavelength 9.1 microns the interference of the superposition of backscatter from two approx. 14.12 microns diameter silicone oil droplets in the lidar beam was observed. This interference results in a single backscatter pulse from the two droplets with a distinct periodic structure. The interference is due to the phase difference in backscatter from the two droplets while they are traversing the lidar beam because they are moving at different speeds and, thus, the droplet separation is not constant. The complete cycle of interference, with periodicity of 2(Pi), gives excellent agreement between measurements and lidar theory.

  4. Filtering for unwrapping noisy Doppler optical coherence tomography images for extended microscopic fluid velocity measurement range.

    PubMed

    Xu, Yang; Darga, Donald; Smid, Jason; Zysk, Adam M; Teh, Daniel; Boppart, Stephen A; Scott Carney, P

    2016-09-01

    In this Letter, we report the first application of two phase denoising algorithms to Doppler optical coherence tomography (DOCT) velocity maps. When combined with unwrapping algorithms, significantly extended fluid velocity dynamic range is achieved. Instead of the physical upper bound, the fluid velocity dynamic range is now limited by noise level. We show comparisons between physical simulated ideal velocity maps and the experimental results of both algorithms. We demonstrate unwrapped DOCT velocity maps having a peak velocity nearly 10 times the theoretical measurement range. PMID:27607963

  5. Doppler electron velocimetry : notes on creating a practical tool.

    SciTech Connect

    Reu, Phillip L.; Milster, Tom

    2008-11-01

    The Doppler electron velocimeter (DEV) has been shown to be theoretically possible. This report attempts to answer the next logical question: Is it a practical instrument? The answer hinges upon whether enough electrons are available to create a time-varying Doppler current to be measured by a detector with enough sensitivity and bandwidth. The answer to both of these questions is a qualified yes. A target Doppler frequency of 1 MHz was set as a minimum rate of interest. At this target a theoretical beam current signal-to-noise ratio of 25-to-1 is shown for existing electron holography equipment. A detector is also demonstrated with a bandwidth of 1-MHz at a current of 10 pA. Additionally, a Linnik-type interferometer that would increase the available beam current is shown that would offer a more flexible arrangement for Doppler electron measurements over the traditional biprism.

  6. Extracting and analyzing micro-Doppler from ladar signatures

    NASA Astrophysics Data System (ADS)

    Tahmoush, Dave

    2015-05-01

    Ladar and other 3D imaging modalities have the capability of creating 3D micro-Doppler to analyze the micro-motions of human subjects. An additional capability to the recognition of micro-motion is the recognition of the moving part, such as the hand or arm. Combined with measured RCS values of the body, ladar imaging can be used to ground-truth the more sensitive radar micro-Doppler measurements and associate the moving part of the subject with the measured Doppler and RCS from the radar system. The 3D ladar signatures can also be used to classify activities and actions on their own, achieving an 86% accuracy using a micro-Doppler based classification strategy.

  7. Laser Doppler technology applied to atmospheric environmental operating problems

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    Carbon dioxide laser Doppler ground wind data were very favorably compared with data from standard anemometers. As a result of these measurements, two breadboard systems were developed for taking research data: a continuous wave velocimeter and a pulsed Doppler system. The scanning continuous wave laser Doppler velocimeter developed for detecting, tracking and measuring aircraft wake vortices was successfully tested at an airport where it located vortices to an accuracy of 3 meters at a range of 150 meters. The airborne pulsed laser Doppler system was developed to detect and measure clear air turbulence (CAT). This system was tested aboard an aircraft, but jet stream CAT was not encountered. However, low altitude turbulence in cumulus clouds near a mountain range was detected by the system and encountered by the aircraft at the predicted time.

  8. Modifications and Moving Measurements of Mobile Doppler LIDAR

    NASA Astrophysics Data System (ADS)

    Liu, Bing-Yi; Liu, Zhi-Shen; Song, Xiao-Quan; Wu, Song-Hua; Bi, De-Cang; Wang, Xi-Tao; Yin, Qi-Wei; Reitebuch, Oliver

    2010-10-01

    In the last annual report of ID. 5291 LIDAR Cal/Val, a mobile Doppler lidar had been developed for 3D wind measurements by the Chinese partners from Ocean Remote Sensing Institute, Ocean University of China. In this year, in order to further improve the mobility of the mobile Doppler lidar for lidar calibration and validation, both GPS and inertial navigation system are integrated on the vehicle for performing measurements during movement. The modifications of the system and the results of the moving measurements are presented. This work simplifies the construction of the mobile Doppler system and makes the lidar more flexible for ground-based wind measurements and validation with the ADM-Aeolus spaceborne Doppler lidar.

  9. 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.

  10. A digital multigate Doppler method for high frequency ultrasound.

    PubMed

    Qiu, Weibao; Ye, Zongying; Yu, Yanyan; Chen, Yan; Chi, Liyang; Mu, Peitian; Li, Guofeng; Wang, Congzhi; Xiao, Yang; Dai, Jiyan; Sun, Lei; Zheng, Hairong

    2014-01-01

    Noninvasive visualization of blood flow with high frequency Doppler ultrasound has been extensively used to assess the morphology and hemodynamics of the microcirculation. A completely digital implementation of multigate pulsed-wave (PW) Doppler method was proposed in this paper for high frequency ultrasound applications. Analog mixer was eliminated by a digital demodulator and the same data acquisition path was shared with traditional B-mode imaging which made the design compact and flexible. Hilbert transform based quadrature demodulation scheme was employed to achieve the multigate Doppler acquisition. A programmable high frequency ultrasound platform was also proposed to facilitate the multigate flow visualization. Experimental results showed good performance of the proposed method. Parabolic velocity gradient inside the vessel and velocity profile with different time slots were acquired to demonstrate the functionality of the multigate Doppler. Slow wall motion was also recorded by the proposed method. PMID:25061836

  11. Laser Doppler instrument measures fluid velocity without reference beam

    NASA Technical Reports Server (NTRS)

    Bourquin, K. R.; Shigemoto, F. H.

    1971-01-01

    Fluid velocity is measured by focusing laser beam on moving fluid and measuring Doppler shift in frequency which results when radiation is scattered by particles either originally present or deliberately injected into moving fluid.

  12. Numerical studies of HF Doppler variations caused by ionospheric disturbances

    NASA Astrophysics Data System (ADS)

    Takefu, M.; Hiroshige, N.

    HF Doppler variations caused by ionospheric disturbances are studied using an ionosphere model containing sinusoidal traveling electron density fluctuations. The present study uses a more realistic ionosphere model and a more accurate numerical method than previous works using corrugated specular reflector models. The study gives a clue to estimate the TID-associated fluctuations of ionospheric electron density by means of HF Doppler measurements. It is shown that some kinds of characteristic HF Doppler traces result depending on the wavelength of the disturbance and its traveling direction. Numerical results suggest that more or less 5 percent of the background electron density can explain most of the quasi-periodic variations on the observed HF Doppler records.

  13. A Digital Multigate Doppler Method for High Frequency Ultrasound

    PubMed Central

    Qiu, Weibao; Ye, Zongying; Yu, Yanyan; Chen, Yan; Chi, Liyang; Mu, Peitian; Li, Guofeng; Wang, Congzhi; Xiao, Yang; Dai, Jiyan; Sun, Lei; Zheng, Hairong

    2014-01-01

    Noninvasive visualization of blood flow with high frequency Doppler ultrasound has been extensively used to assess the morphology and hemodynamics of the microcirculation. A completely digital implementation of multigate pulsed-wave (PW) Doppler method was proposed in this paper for high frequency ultrasound applications. Analog mixer was eliminated by a digital demodulator and the same data acquisition path was shared with traditional B-mode imaging which made the design compact and flexible. Hilbert transform based quadrature demodulation scheme was employed to achieve the multigate Doppler acquisition. A programmable high frequency ultrasound platform was also proposed to facilitate the multigate flow visualization. Experimental results showed good performance of the proposed method. Parabolic velocity gradient inside the vessel and velocity profile with different time slots were acquired to demonstrate the functionality of the multigate Doppler. Slow wall motion was also recorded by the proposed method. PMID:25061836

  14. Coherent Doppler Lidar for Precision Navigation of Spacecrafts

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    A fiber-based coherent Doppler lidar, utilizing an FMCW technique, has been developed and its capabilities demonstrated through two successful helicopter flight test campaigns. This Doppler lidar is expected to play a critical role in future planetary exploration missions because of its ability in providing the necessary data for soft landing on the planetary bodies and for landing missions requiring precision navigation to the designated location on the ground. Compared with radars, the Doppler lidar can provide significantly higher precision velocity and altitude data at a much higher rate without concerns for measurement ambiguity or target clutter. Future work calls for testing the Doppler lidar onboard a rocket-powered free-flyer platform operating in a closed-loop with the vehicle s guidance, navigation, and control (GN&C) unit.

  15. The Doppler Effect: A Consideration of Quasar Redshifts.

    ERIC Educational Resources Information Center

    Gordon, Kurtiss J.

    1980-01-01

    Provides information on the calculation of the redshift to blueshift ratio introduced by the transverse Doppler effect at relativistic speeds. Indicates that this shift should be mentioned in discussions of whether quasars are "local" rather than "cosmological" objects. (GS)

  16. Doing the Doppler. How to Drive This Concept Home.

    ERIC Educational Resources Information Center

    Koser, John F.

    1990-01-01

    An outdoor activity that demonstrates the Doppler effect is described. Class predictions are verified by actual involvement in collecting data. Presented is a method of analyzing data. Safety concerns are discussed. (KR)

  17. X-ray pulsars/Doppler integrated navigation for Mars final approach

    NASA Astrophysics Data System (ADS)

    Cui, Pingyuan; Wang, Shuo; Gao, Ai; Yu, Zhengshi

    2016-05-01

    The performance of the navigation system during the Mars final approach phase determines the initial accuracy of Mars entry phase, which is critical for a pin-point landing. An X-ray pulsars/Doppler integrated navigation strategy is proposed to improve the estimation accuracy of the spacecraft's entry state, as well as to enhance the autonomy, real-time and reliability. The navigation system uses the X-ray pulsar measurements and Doppler velocity measurements which are complementary to each other. The performance degradation in velocity estimation at the end of the final approach phase for X-ray pulsar based navigation can thus be eliminated. The nonlinearity of the system and the performance of Extended Kalman Filter are analyzed in this paper. Furthermore, in order to optimize the navigation scheme, a principle for navigation beacons selection based on the Fisher information matrix is used. Finally, a navigation scenario based on the 2012 encounter at Mars of Mars Science Laboratory spacecraft is considered to demonstrate the feasibility and accuracy of the proposed scheme. Simulation results also indicate that the proposed navigation scheme has reference value for the design of the future Mars explorations.

  18. Using doppler radar images to estimate aircraft navigational heading error

    DOEpatents

    Doerry, Armin W.; Jordan, Jay D.; Kim, Theodore J.

    2012-07-03

    A yaw angle error of a motion measurement system carried on an aircraft for navigation is estimated from Doppler radar images captured using the aircraft. At least two radar pulses aimed at respectively different physical locations in a targeted area are transmitted from a radar antenna carried on the aircraft. At least two Doppler radar images that respectively correspond to the at least two transmitted radar pulses are produced. These images are used to produce an estimate of the yaw angle error.

  19. Digital Doppler extraction demonstration with the advanced receiver

    NASA Technical Reports Server (NTRS)

    Hinedi, S.; Bevan, R.; Delcastillo, H.; Kinman, P.; Chong, D.; Labelle, R.

    1990-01-01

    A digital Doppler extraction demonstration with the Advanced Receiver 2 (ARX 2) tracking Pioneer 10 and Voyager 2 is described. The measured results are compared with those of the Block 4 receiver that was operating in parallel with the ARX 2. It is shown that the ARX 2 outperforms the Block 4 receiver in terms of Allan variance of the Doppler residuals, the amount of which depends on the scenario of interest.

  20. Software For Clear-Air Doppler-Radar Display

    NASA Technical Reports Server (NTRS)

    Johnston, Bruce W.

    1990-01-01

    System of software developed to present plan-position-indicator scans of clear-air Doppler radar station on color graphical cathode-ray-tube display. Designed to incorporate latest accepted standards for equipment, computer programs, and meteorological data bases. Includes use of Ada programming language, of "Graphical-Kernel-System-like" graphics interface, and of Common Doppler Radar Exchange Format. Features include portability and maintainability. Use of Ada software packages produced number of software modules reused on other related projects.

  1. Monitoring and Analysis of Respiratory Patterns Using Microwave Doppler Radar

    PubMed Central

    Pathirana, Pubudu N.; Steinfort, Christopher Louis; Caelli, Terry

    2014-01-01

    Noncontact detection characteristic of Doppler radar provides an unobtrusive means of respiration detection and monitoring. This avoids additional preparations, such as physical sensor attachment or special clothing, which can be useful for certain healthcare applications. Furthermore, robustness of Doppler radar against environmental factors, such as light, ambient temperature, interference from other signals occupying the same bandwidth, fading effects, reduce environmental constraints and strengthens the possibility of employing Doppler radar in long-term respiration detection, and monitoring applications such as sleep studies. This paper presents an evaluation in the of use of microwave Doppler radar for capturing different dynamics of breathing patterns in addition to the respiration rate. Although finding the respiration rate is essential, identifying abnormal breathing patterns in real-time could be used to gain further insights into respiratory disorders and refine diagnostic procedures. Several known breathing disorders were professionally role played and captured in a real-time laboratory environment using a noncontact Doppler radar to evaluate the feasibility of this noncontact form of measurement in capturing breathing patterns under different conditions associated with certain breathing disorders. In addition to that, inhalation and exhalation flow patterns under different breathing scenarios were investigated to further support the feasibility of Doppler radar to accurately estimate the tidal volume. The results obtained for both experiments were compared with the gold standard measurement schemes, such as respiration belt and spirometry readings, yielding significant correlations with the Doppler radar-based information. In summary, Doppler radar is highlighted as an alternative approach not only for determining respiration rates, but also for identifying breathing patterns and tidal volumes as a preferred nonwearable alternative to the conventional

  2. Muscle activity characterization by laser Doppler Myography

    NASA Astrophysics Data System (ADS)

    Scalise, Lorenzo; Casaccia, Sara; Marchionni, Paolo; Ercoli, Ilaria; Primo Tomasini, Enrico

    2013-09-01

    Electromiography (EMG) is the gold-standard technique used for the evaluation of muscle activity. This technique is used in biomechanics, sport medicine, neurology and rehabilitation therapy and it provides the electrical activity produced by skeletal muscles. Among the parameters measured with EMG, two very important quantities are: signal amplitude and duration of muscle contraction, muscle fatigue and maximum muscle power. Recently, a new measurement procedure, named Laser Doppler Myography (LDMi), for the non contact assessment of muscle activity has been proposed to measure the vibro-mechanical behaviour of the muscle. The aim of this study is to present the LDMi technique and to evaluate its capacity to measure some characteristic features proper of the muscle. In this paper LDMi is compared with standard superficial EMG (sEMG) requiring the application of sensors on the skin of each patient. sEMG and LDMi signals have been simultaneously acquired and processed to test correlations. Three parameters has been analyzed to compare these techniques: Muscle activation timing, signal amplitude and muscle fatigue. LDMi appears to be a reliable and promising measurement technique allowing the measurements without contact with the patient skin.

  3. Doppler-resolved kinetics of saturation recovery

    SciTech Connect

    Forthomme, Damien; Hause, Michael L.; Yu, Hua -Gen; Dagdigian, Paul J.; Sears, Trevor J.; Hall, Gregory E.

    2015-04-08

    Frequency modulated laser transient absorption has been used to monitor the ground state rotational energy transfer rates of CN radicals in a double-resonance, depletion recovery experiment. When a pulsed laser is used to burn a hole in the equilibrium ground state population of one rotational state without velocity selection, the population recovery rate is found to depend strongly on the Doppler detuning of a narrow-band probe laser. Similar effects should be apparent for any relaxation rate process that competes effectively with velocity randomization. Alternative methods of extracting thermal rate constants in the presence of these non-thermal conditions are evaluated. Total recovery rate constants, analogous to total removal rate constants in an experiment preparing a single initial rotational level, are in good agreement with quantum scattering calculations, but are slower than previously reported experiments and show qualitatively different rotational state dependence between Ar and He collision partners. As a result, quasi-classical trajectory studies confirm that the differing rotational state dependence is primarily a kinematic effect.

  4. Atmospheric aerosol and Doppler lidar studies

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeff; Bowdle, D. A.; Srivastava, V.; Jarzembski, M.; Cutten, D.; Mccaul, E. W., Jr.

    1991-01-01

    Experimental and theoretical studies were performed of atmospheric aerosol backscatter and atmospheric dynamics with Doppler lidar as a primary tool. Activities include field and laboratory measurement and analysis efforts. The primary focus of activities related to understanding aerosol backscatter is the GLObal Backscatter Experiment (GLOBE) program. GLOBE is a multi-element effort designed toward developing a global aerosol model to describe tropospheric clean background backscatter conditions that Laser Atmospheric Wind Sounder (LAWS) is likely to encounter. Two survey missions were designed and flown in the NASA DC-8 in November 1989 and May to June 1990 over the remote Pacific Ocean, a region where backscatter values are low and where LAWS wind measurements could make a major contribution. The instrument complement consisted of pulsed and continuous-wave (CW) CO2 gas and solid state lidars measuring aerosol backscatter, optical particle counters measuring aerosol concentration, size distribution, and chemical composition, a filter/impactor system collecting aerosol samples for subsequent analysis, and integrating nephelometers measuring visible scattering coefficients. The GLOBE instrument package and survey missions were carefully planned to achieve complementary measurements under clean background backscatter conditions.

  5. Doppler-resolved kinetics of saturation recovery

    DOE PAGESBeta

    Forthomme, Damien; Hause, Michael L.; Yu, Hua -Gen; Dagdigian, Paul J.; Sears, Trevor J.; Hall, Gregory E.

    2015-04-08

    Frequency modulated laser transient absorption has been used to monitor the ground state rotational energy transfer rates of CN radicals in a double-resonance, depletion recovery experiment. When a pulsed laser is used to burn a hole in the equilibrium ground state population of one rotational state without velocity selection, the population recovery rate is found to depend strongly on the Doppler detuning of a narrow-band probe laser. Similar effects should be apparent for any relaxation rate process that competes effectively with velocity randomization. Alternative methods of extracting thermal rate constants in the presence of these non-thermal conditions are evaluated. Totalmore » recovery rate constants, analogous to total removal rate constants in an experiment preparing a single initial rotational level, are in good agreement with quantum scattering calculations, but are slower than previously reported experiments and show qualitatively different rotational state dependence between Ar and He collision partners. As a result, quasi-classical trajectory studies confirm that the differing rotational state dependence is primarily a kinematic effect.« less

  6. Doppler effect induced spin relaxation boom.

    PubMed

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-01-01

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures. PMID:26996253

  7. Doppler effect induced spin relaxation boom

    PubMed Central

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-01-01

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures. PMID:26996253

  8. Doppler effect induced spin relaxation boom

    NASA Astrophysics Data System (ADS)

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-03-01

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures.

  9. Evaluating microcirculation by pulsatile laser Doppler signal

    NASA Astrophysics Data System (ADS)

    Chao, P. T.; Jan, M. Y.; Hsiu, H.; Hsu, T. L.; Wang, W. K.; Wang, Y. Y. Lin

    2006-02-01

    Laser Doppler flowmetry (LDF) is a popular method for monitoring the microcirculation, but it does not provide absolute measurements. Instead, the mean flux response or energy distribution in the frequency domain is generally compared before and after stimulus. Using the heartbeat as a trigger, we investigated whether the relation between pressure and flux can be used to discriminate different microcirculatory conditions. We propose the following three pulsatile indices for evaluating the microcirculation condition from the normalized pressure and flux segment with a synchronized-averaging method: peak delay time (PDT), pressure rise time and flux rise time (FRT). The abdominal aortic blood pressure and renal cortex flux (RCF) signals were measured in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). The mean value of the RCF did not differ between SHR and WKY. However, the PDT was longer in SHR (87.14 ± 5.54 ms, mean ± SD) than in WKY (76.92 ± 2.62 ms; p < 0.001). The FRT was also longer in SHR (66.56 ± 1.98 ms) than in WKY (58.02 ± 1.77 ms; p < 0.001). We propose that a new dimension for comparing the LDF signals, which the results from the present study show, can be used to discriminate RCF signals that cannot be discriminated using traditional methods.

  10. Resonant Doppler imaging with common path OCT

    NASA Astrophysics Data System (ADS)

    Koch, Edmund; Hammer, Daniel; Wang, Siqian; Cuevas, Maximiliano; Walther, Julia

    2009-07-01

    Resonant Doppler flow imaging based on optical coherence tomography (OCT) is a recently developed imaging modality that provides, besides the structural information, dynamic blood flow information. We show that this method can be applied to a common path OCT system by mounting the mirror in the reference arm on a small piezo actor leading to a simpler and more stable system design. Besides the known 3 state cycle, we describe other cycles with any number of states leading to higher measurement speed or larger velocity range. The hysteresis of the piezo actor is compensated by applying an optimized electrical signal. Two different approaches, one using a Levenberg-Marquardt optimization, the other using the Prandtl-Ishlinskii model for compensation of hysteresis, are applied to generate the optimized control signal. Besides providing an analytical formula for the calculation of the axial velocity for cycles having certain spacings in the reference velocity, we describe deviations from the signal degradation caused by the transversal part of the motion causing errors in the velocity estimation. The performance of the system with two and three states is first evaluated with a mirror on a loud speaker. Measurements with a flow phantom consisting of 1 % Intralipid dilution flowing through small diameter capillaries show the suitability of the system and the expected deviations at high velocities.

  11. Differenced Range Versus Integrated Doppler (DRVID) ionospheric analysis of metric tracking in the Tracking and Data Relay Satellite System (TDRSS)

    NASA Technical Reports Server (NTRS)

    Radomski, M. S.; Doll, C. E.

    1995-01-01

    The Differenced Range (DR) Versus Integrated Doppler (ID) (DRVID) method exploits the opposition of high-frequency signal versus phase retardation by plasma media to obtain information about the plasma's corruption of simultaneous range and Doppler spacecraft tracking measurements. Thus, DR Plus ID (DRPID) is an observable independent of plasma refraction, while actual DRVID (DR minus ID) measures the time variation of the path electron content independently of spacecraft motion. The DRVID principle has been known since 1961. It has been used to observe interplanetary plasmas, is implemented in Deep Space Network tracking hardware, and has recently been applied to single-frequency Global Positioning System user navigation This paper discusses exploration at the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) of DRVID synthesized from simultaneous two-way range and Doppler tracking for low Earth-orbiting missions supported by the Tracking and Data Relay Satellite System (TDRSS) The paper presents comparisons of actual DR and ID residuals and relates those comparisons to predictions of the Bent model. The complications due to the pilot tone influence on relayed Doppler measurements are considered. Further use of DRVID to evaluate ionospheric models is discussed, as is use of DRPID in reducing dependence on ionospheric modeling in orbit determination.

  12. 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

  13. Sub-Doppler laser cooling of fermionic 40K atoms in three-dimensional gray optical molasses

    NASA Astrophysics Data System (ADS)

    Rio Fernandes, D.; Sievers, F.; Kretzschmar, N.; Wu, S.; Salomon, C.; Chevy, F.

    2012-12-01

    We demonstrate sub-Doppler cooling of 40K on the D1 atomic transition. Using a gray-molasses scheme, we efficiently cool a compressed cloud of 6.5 × 108 atoms from ˜4 mK to 20 μK in 8 ms. After transfer to a quadrupole magnetic trap, we measure a phase space density of ˜10-5. This technique offers a promising route for fast evaporation of fermionic 40K.

  14. Planetary Radio Interferometry and Doppler Experiment (PRIDE) for studying the thermosphere of Venus

    NASA Astrophysics Data System (ADS)

    Bocanegra Bahamón, T. M.; Cimò, G.; Duev, D. A.; Gurvits, L. I.; Marty, J. C.; Molera Calvés, G.; Pogrebenko, S. V.; Rosenblatt, P.

    2013-09-01

    Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a generic experimental setup of on-board and Earth-based radio devices and facilities, which serves as an enhancement of the science return of planetary missions. The main goal of this technique is to provide precise estimates of the spacecraft state vectors, by performing precise Doppler tracking of the spacecraft carrier signal, at one or more Earth-based radio telescopes, and VLBI-style correlation of these signals in phase referencing mode [1]. By allowing an accurate examination of the changes in phase and amplitude of the radio signal propagating from the spacecraft to the multiple stations on Earth, the PRIDE technique can be used for several fields of research, among them: atmospheric and ionospheric structure of planets and their satellites, planetary gravity fields, planets' shapes, masses and ephemerides, solar plasma and different aspects of the theory of general relativity. The PRIDE-team is participating in the so-called Venus Express Atmospheric Drag Experiment (VEx-ADE) campaigns by tracking ESA's Venus Express with multiple radio telescopes on Earth. During each campaign, VEX's orbit pericenter is lowered into an altitude range of approximately 165 to 175 km in order to probe Venus upper atmosphere above its north pole. The first VExADE campaigns were carried out between 2009-2010 using Doppler tracking data acquired by the VEX radio science experiment (VeRa), which provided the first in situ measurements of the density of Venus' polar thermosphere at solar minimum conditions [2]. The last campaign was conducted in December 2012, in which the PRIDE-team participated by tracking VEX with several radio telescopes from the European VLBI Network (EVN) during pericenter passage. A Doppler frequency drop of ∼40 mHz was detected as VEX reached the lowest altitudes at around 170 km. The tracking data for each pericenter pass is fitted for precise orbit determination, from which drag

  15. 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.

  16. Developments in laser Doppler accelerometry (LDAc) and comparison with laser Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Rothberg, Steve; Hocknell, Alan; Coupland, Jeremy

    This paper outlines the principles and early development of an interferometric technique for remote measurement of vibration acceleration — laser Doppler accelerometry (LDAc). One of the key advantages of LDAc over laser Doppler velocimetry (LDV) is its ability to measure extremely high vibration accelerations and shocks, effectively without limit, and this point is expanded upon in the paper. Early LDAc development showed how unwanted, velocity-dependent optical beats could occur on the photodetector but novel use of a frequency shifting device, whose primary purpose was for direction discrimination, was successful in isolating the required acceleration-dependent beat. A problem remained in the rate at which the velocity-dependent and acceleration-dependent beats broadened during target motion. In a further development, it was possible to 'select' a back reflection to produce a velocity-dependent beat that was NOT modulated in the presence of target motion. The acceleration-dependent beat could then be demodulated and preliminary results are given to demonstrate this outcome.

  17. Developments in laser Doppler accelerometry (LDAc) and comparison with laser Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Rothberg, Steve; Hocknell, Alan; Coupland, Jeremy

    1999-12-01

    This paper outlines the principles and early development of an interferometric technique for remote measurement of vibration acceleration - laser Doppler accelerometry (LDAc). One of the key advantages of LDAc over laser Doppler velocimetry (LDV) is its ability to measure extremely high vibration accelerations and shocks, effectively without limit, and this point is expanded upon in the paper. Early LDAc development showed how unwanted, velocity-dependent optical beats could occur on the photodetector but novel use of a frequency shifting device, whose primary purpose was for direction discrimination, was successful in isolating the required acceleration-dependent beat. A problem remained in the rate at which the velocity-dependent and acceleration-dependent beats broadened during target motion. In a further development, it was possible to 'select' a back reflection to produce a velocity-dependent beat that was NOT modulated in the presence of target motion. The acceleration-dependent beat could then be demodulated and preliminary results are given to demonstrate this outcome.

  18. In-situ position and vibration measurement of rough surfaces using laser Doppler distance sensors

    NASA Astrophysics Data System (ADS)

    Czarske, J.; Pfister, T.; Günther, P.; Büttner, L.

    2009-06-01

    In-situ measurement of distances and shapes as well as dynamic deformations and vibrations of fast moving and especially rotating objects, such as gear shafts and turbine blades, is an important task at process control. We recently developed a laser Doppler distance frequency sensor, employing two superposed fan-shaped interference fringe systems with contrary fringe spacing gradients. Via two Doppler frequency evaluations the non-incremental position (i.e. distance) and the tangential velocity of rotating bodies are determined simultaneously. The distance uncertainty is in contrast to e.g. triangulation in principle independent of the object velocity. This unique feature allows micrometer resolutions of fast moved rough surfaces. The novel sensor was applied at turbo machines in order to control the tip clearance. The measurements at a transonic centrifugal compressor were performed during operation at up to 50,000 rpm, i.e. 586 m/s velocity of the blade tips. Due to the operational conditions such as temperatures of up to 300 °C, a flexible and robust measurement system with a passive fiber-coupled sensor, using diffractive optics, has been realized. Since the tip clearance of individual blades could be temporally resolved an analysis of blade vibrations was possible. A Fourier transformation of the blade distances results in an average period of 3 revolutions corresponding to a frequency of 1/3 of the rotary frequency. Additionally, a laser Doppler distance sensor using two tilted fringe systems and phase evaluation will be presented. This phase sensor exhibits a minimum position resolution of σz = 140 nm. It allows precise in-situ shape measurements at grinding and turning processes.

  19. Sub-Doppler Spectroscopy of H_3^+

    NASA Astrophysics Data System (ADS)

    Hodges, James N.; Perry, Adam J.; Siller, Brian M.; McCall, Benjamin J.

    2013-06-01

    Spectroscopy of H_3^+ is of fundamental interest for advancing ab initio efforts to calculate spectra with high precision and accuracy. H_3^+ is the simplest polyatomic ion, which is why it is an excellent benchmark for theory. In order to perform calculations with spectroscopic accuracy, relativistic and non-adiabatic corrections to the Born-Oppenhiemer approximation must be included; calculations with these considerations agree to within hundredths of a wavenumber. Increasing the precision of the calculations further will require a treatment of quantum electrodynamic effects, as has already been implemented for the diatomic case, and testing these calculations will require higher-precision experimental data to guide ab initio calculations. Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy, or NICE-OHVMS, is a highly sensitive, highly precise technique that we have employed to observe transitions in the ν_2 fundamental band of H_3^+. It combines the advantages of cavity enhancement and heterodyne detection with the ion-neutral discrimination afforded by velocity modulation. Combining a cavity with a high power mid-infrared light source, we can saturate rovibrational transitions. The resulting Lamb dips may be fit in order to determine line centers to a much higher precision than is possible for ordinary Doppler broadened profiles. Additionally, a frequency comb is used to surpass the limited accuracy and precision of a wavemeter. Here we present the results from comb calibrated H_3^+ transitions observed via NICE-OHVMS. Precision and accuracy of ˜ 1 MHz were achieved representing the most accurate and precise H_3^+ line list that has been obtained to date. O. L. Polyansky, J. Tennyson, J. Chem. Phys. (1999), 110, 5056--5064. J. Komasa, et al. J. Chem. Theor. Comp. (2011), 7, 3105--3115. B. M. Siller, et al. Opt. Express (2011), 19, 24822--7. K. N. Crabtree, et al. Chem. Phys. Lett. (2012), 551, 1--6.

  20. Right Ventricular Tissue Doppler in Space Flight

    NASA Technical Reports Server (NTRS)

    Hamilton, Douglas R.; Barratt, Michael R.; Sargsyan, Ashot E.; Ebert, Douglas; Garcia, Kathleen M.; Martin, David S.; Dulchavsky, Scott A.; Duncan, J. Michael

    2009-01-01

    Tissue Doppler (TD) registers movement of a given sample of cardiac tissue throughout the cardiac cycle. TD spectra of the right ventricle (RV) were obtained from a long-duration ISS crewmember as a portion of an ongoing experiment ("Braslet" test objective). To our knowledge, this is the first report of RV TD conducted in space flight, and the data represent reproducibility and fidelity of this application in space and serve as the first "space normal" data set. Methods RV TD was performed by astronaut scientists remotely guided by an ultrasound expert from Mission Control Center, Houston, TX. In four of the subjects, RV TD was acquired from the free wall near the tricuspid annulus in two separate sessions 4 to 7 days apart. A fifth subject had only one session. All digital DICOM frames were exported for off-line analysis. Systolic (S ), early diastolic (E ) and late diastolic (A ) velocities were measured. RV Tei-index was calculated using diastolic and systolic time intervals as a combined measure of myocardial performance. Results and Discussion The mean values from the first 4 subjects (8 sessions) were used as the on-orbit reference data, and subject 5 was considered as a hypothetical patient for comparison (see Table). The greatest difference was in the early diastolic A (31 %) yet the standard deviation (a) for A amongst the reference subjects was 2.25 (mean = 16.02). Of interest is the Tei index, a simple and feasible indicator of overall ventricular function; it was similar amongst all the subjects. The late diastolic A seems to compensate for the variance in E . Normal Tei index for the RV is < 0.3, yet our data show all but one subject consistently above this level, notwithstanding their nominal responses to daily exercise in microgravity. These data remind us that the physiology of RV preload in altered gravity environments is still not completely understood.

  1. Hands-Free Transcranial Color Doppler Probe

    NASA Technical Reports Server (NTRS)

    Chin, Robert; Madala, Srihdar; Sattler, Graham

    2012-01-01

    Current transcranial color Doppler (TCD) transducer probes are bulky and difficult to move in tiny increments to search and optimize TCD signals. This invention provides miniature motions of a TCD transducer probe to optimize TCD signals. The mechanical probe uses a spherical bearing in guiding and locating the tilting crystal face. The lateral motion of the crystal face as it tilts across the full range of motion was achieved by minimizing the distance between the pivot location and the crystal face. The smallest commonly available metal spherical bearing was used with an outer diameter of 12 mm, a 3-mm tall retaining ring, and 5-mm overall height. Small geared motors were used that would provide sufficient power in a very compact package. After confirming the validity of the basic positioning concept, optimization design loops were completed to yield the final design. A parallel motor configuration was used to minimize the amount of space wasted inside the probe case while minimizing the overall case dimensions. The distance from the front edge of the crystal to the edge of the case was also minimized to allow positioning of the probe very close to the ear on the temporal lobe. The mechanical probe is able to achieve a +/-20deg tip and tilt with smooth repeatable action in a very compact package. The enclosed probe is about 7 cm long, 4 cm wide, and 1.8 cm tall. The device is compact, hands-free, and can be adjusted via an innovative touchscreen. Positioning of the probe to the head is performed via conventional transducer gels and pillows. This device is amendable to having advanced software, which could intelligently focus and optimize the TCD signal.

  2. Single Mode, Extreme Precision Doppler Spectrographs

    NASA Astrophysics Data System (ADS)

    Schwab, Christian; Leon-Saval, Sergio G.; Betters, Christopher H.; Bland-Hawthorn, Joss; Mahadevan, Suvrath

    2014-04-01

    The `holy grail' of exoplanet research today is the detection of an earth-like planet: a rocky planet in the habitable zone around a main-sequence star. Extremely precise Doppler spectroscopy is an indispensable tool to find and characterize earth-like planets; however, to find these planets around solar-type stars, we need nearly one order of magnitude better radial velocity (RV) precision than the best current spectrographs provide. Recent developments in astrophotonics (Bland-Hawthorn & Horton 2006, Bland-Hawthorn et al. 2010) and adaptive optics (AO) enable single mode fiber (SMF) fed, high resolution spectrographs, which can realize the next step in precision. SMF feeds have intrinsic advantages over multimode fiber or slit coupled spectrographs: The intensity distribution at the fiber exit is extremely stable, and as a result the line spread function of a well-designed spectrograph is fully decoupled from input coupling conditions, like guiding or seeing variations (Ihle et al. 2010). Modal noise, a limiting factor in current multimode fiber fed instruments (Baudrand & Walker 2001), can be eliminated by proper design, and the diffraction limited input to the spectrograph allows for very compact instrument designs, which provide excellent optomechanical stability. A SMF is the ideal interface for new, very precise wavelength calibrators, like laser frequency combs (Steinmetz et al. 2008, Osterman et al. 2012), or SMF based Fabry-Perot Etalons (Halverson et al. 2013). At near infrared wavelengths, these technologies are ready to be implemented in on-sky instruments, or already in use. We discuss a novel concept for such a spectrograph.

  3. Doppler findings in intrapartum fetal distress.

    PubMed

    Eslamian, Laleh; Tooba, Khatereh

    2011-01-01

    The umbilical vein (UV) has a non pulsating and even pattern in normal fetuses. Pulsation of UV has been described in severely growth restricted fetuses with chronic hypoxia. We wanted to see whether UV pulsations could also be seen in fetuses with heart deceleration during labor, as an adjunctive measure to assess the intra partum hypoxia. In a prospective study Doppler examination was performed on 34 fetuses with normal cardiotocography (CGT) and 26 fetuses with abnormal CTGs (GA>37w and cervical dilatation>3cm). Perinatal outcome was assessed according to presence or absence of UV pulsations. The 2 groups were similar regarding gestational age, cervical dilatation, Umbilical artery blood pH, S/D ratio,Pulsatility Index( PI) and Resistance Index (RI). Intraabdominal UV pulsation were present in 6 (23.1%) of abnormal CTG group but no case were seen in normal CTG group (P= 0.005). Five of 6 (83.3%) fetuses with UV pulsation underwent cesarean delivery. The rate of cesarean delivery was 90% in abnormal CTG group without pulsation and 14.7% in normal CTG group. The frequency of Apgar score <7 was more in fetuses with UV pulsations (16.7% vs 5%) although not statistically significant. NICU admission was considerably more in UV pulsation group (33% vs 5%, P= 0.123). After exclusion of LBW fetuses the UV pulsation was present in 4 (19%) of abnormal CTG group, who 3 of them underwent cesarean section. Neither umbilical artery pH<7 nor Apger score <7 or NICU admission were seen in these 4 neonates. Pulsation in UV was seen in 23% of fetuses with abnormal CTG during intra partum period. Cesarean delivery and NICU admission was increased in fetuses with UV pulsations, although not statistically significant. When LBW fetuses were excluded no case of UA pH<7, Apgar sore <7or NICU admission were seen. PMID:22009812

  4. Doppler images of II Pegasi for 2004-2010

    NASA Astrophysics Data System (ADS)

    Hackman, T.; Mantere, M. J.; Lindborg, M.; Ilyin, I.; Kochukhov, O.; Piskunov, N.; Tuominen, I.

    2012-02-01

    Aims: We study the spot activity of II Peg during the years 2004-2010 to determine long- and short-term changes in the magnetic activity. In a previous study, we detected a persistent active longitude, as well as major changes in the spot configuration occurring on a timescale of shorter than a year. The main objective of this study is to determine whether the same phenomena persist in the star during these six years of spectroscopic monitoring. Methods: The observations were collected with the high-resolution SOFIN spectrograph at the Nordic Optical Telescope. The temperature maps were calculated using a Doppler imaging code based on Tikhonov regularization. Results: We present 12 new temperature maps that show spots distributed mainly over high and intermediate latitudes. In each image, 1-3 main active regions can be identified. The activity level of the star is clearly lower than during our previous study for the years 1994-2002. In contrast to the previous observations, we detect no clear drift of the active regions with respect to the rotation of the star. Conclusions: Having shown a systematic longitudinal drift of the spot-generating mechanism during 1994-2002, the star has clearly switched to a low-activity state for 2004-2010, during which the spot locations appear more random over phase space. It could be that the star is near to a minimum of its activity cycle. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

  5. DOPPLER SIGNATURES OF THE ATMOSPHERIC CIRCULATION ON HOT JUPITERS

    SciTech Connect

    Showman, Adam P.; Lewis, Nikole K.; Fortney, Jonathan J.; Shabram, Megan

    2013-01-01

    The meteorology of hot Jupiters has been characterized primarily with thermal measurements, but recent observations suggest the possibility of directly detecting the winds by observing the Doppler shift of spectral lines seen during transit. Motivated by these observations, we show how Doppler measurements can place powerful constraints on the meteorology. We show that the atmospheric circulation-and Doppler signature-of hot Jupiters splits into two regimes. Under weak stellar insolation, the day-night thermal forcing generates fast zonal jet streams from the interaction of atmospheric waves with the mean flow. In this regime, air along the terminator (as seen during transit) flows toward Earth in some regions and away from Earth in others, leading to a Doppler signature exhibiting superposed blueshifted and redshifted components. Under intense stellar insolation, however, the strong thermal forcing damps these planetary-scale waves, inhibiting their ability to generate jets. Strong frictional drag likewise damps these waves and inhibits jet formation. As a result, this second regime exhibits a circulation dominated by high-altitude, day-to-night airflow, leading to a predominantly blueshifted Doppler signature during transit. We present state-of-the-art circulation models including non-gray radiative transfer to quantify this regime shift and the resulting Doppler signatures; these models suggest that cool planets like GJ 436b lie in the first regime, HD 189733b is transitional, while planets hotter than HD 209458b lie in the second regime. Moreover, we show how the amplitude of the Doppler shifts constrains the strength of frictional drag in the upper atmospheres of hot Jupiters. If due to winds, the {approx}2 km s{sup -1} blueshift inferred on HD 209458b may require drag time constants as short as 10{sup 4}-10{sup 6} s, possibly the result of Lorentz-force braking on this planet's hot dayside.

  6. Cross-correlation Doppler global velocimetry (CC-DGV)

    NASA Astrophysics Data System (ADS)

    Cadel, Daniel R.; Lowe, K. Todd

    2015-08-01

    A flow velocimetry method, cross-correlation Doppler global velocimetry (CC-DGV), is presented as a robust, simplified, and high dynamic range implementation of the Doppler global/planar Doppler velocimetry technique. A sweep of several gigahertz of the vapor absorption spectrum is used for each velocity sample, with signals acquired from both Doppler-shifted scattered light within the flow and a non-Doppler shifted reference beam. Cross-correlation of these signals yields the Doppler shift between them, averaged over the duration of the scan. With presently available equipment, velocities from 0 ms-1 to over 3000 ms-1 can notionally be measured simultaneously, making the technique ideal for high speed flows. The processing routine is shown to be robust against large changes in the vapor pressure of the iodine cell, benefiting performance of the system in facilities where ambient conditions cannot be easily regulated. Validation of the system was performed with measurements of a model wind turbine blade boundary layer made in a 1.83 m by 1.83 m subsonic wind tunnel for which laser Doppler velocimetry (LDV) measurements were acquired alongside the CC-DGV results. CC-DGV uncertainties of ±1.30 ms-1, ±0.64 ms-1, and ±1.11 ms-1 were determined for the orthogonal stream-wise, transverse-horizontal, and transverse-vertical velocity components, and root-mean-square deviations of 2.77 ms-1 and 1.34 ms-1 from the LDV validation results were observed for Reynolds numbers of 1.5 million and 2 million, respectively. Volumetric mean velocity measurements are also presented for a supersonic jet, with velocity uncertainties of ±4.48 ms-1, ±16.93 ms-1, and ±0.50 ms-1 for the orthogonal components, and self-validation done by collapsing the data with a physical scaling.

  7. Enhanced models for stellar Doppler noise reveal hints of a 13-year activity cycle of 55 Cancri

    NASA Astrophysics Data System (ADS)

    Baluev, Roman V.

    2015-01-01

    We consider the impact of Doppler noise models on the statistical robustness of the exoplanetary radial velocity fits. We show that the traditional model of the Doppler noise with an additive jitter can generate large non-linearity effects, decreasing the reliability of the fit, especially in the cases when a correlated Doppler noise is involved. We introduce a regularization of the additive noise model that can gracefully eliminate its singularities together with the associated non-linearity effects. We apply this approach to Doppler time series data of several exoplanetary systems. It demonstrates that our new regularized noise model yields orbital fits that have either increased or at least the same statistical robustness, in comparison with the simple additive jitter. Various statistical uncertainties in the parametric estimations are often reduced, while planet detection significance is often increased. Concerning the 55 Cnc five-planet system, we show that its Doppler data contain significant correlated (`red') noise. Its correlation time-scale is in the range from days to months, and its magnitude is much larger than the effect of the planetary N-body perturbations in the radial velocity (these perturbations thus appear undetectable). Characteristics of the red noise depend on the spectrograph/observatory, and also show a cyclic time variation in phase with the public Ca II H&K and photometry measurements. We interpret this modulation as a hint of the long-term activity cycle of 55 Cnc, similar to the solar 11-yr cycle. We estimate the 55 Cnc activity period by 12.6± ^{2.5}_{1.0} yr, with the nearest minimum presumably expected in 2014 or 2015.

  8. The study of ovarian artery hemodynamics in patients with infertility by color Doppler energy.

    PubMed

    Xiao, X; Le, G; Zhang, Y; Li, C

    2001-01-01

    Seventy-four cases of infertility were examined to study the hemodynamics of the bilateral ovarian arteries at 21st day during the corpus luteum phase by color Doppler energy(CDE) and color Doppler flow imaging (CDFI). All the patients were verified by laparoscopy, fallopian tube patency examination and ovarian function test. Twenty-two healthy women served as controls. The results showed that the difference of resistance index(RI) and pulsatility index (PI) of bilateral ovarian arteries between the infertility and the normal controls had statistical significance (P < 0.01), and the PI showed negative correlation with the thickness of endometrium (left side: r = 0.724, P < 0.01; right side: r = 0.756, P < 0.01). The results also showed that CDE was more sensitive than CDFI in displaying the ovarian arteries. It could be concluded that the elevated resistance of ovarian artery during the corpus luteum phase was one of the important factors that resulted in infertility. PMID:11523245

  9. Microstructure Evaluation of Fe-BASED Amorphous Alloys Investigated by Doppler Broadening Positron Annihilation Technique

    NASA Astrophysics Data System (ADS)

    Lu, Wei; Huang, Ping; Wang, Yuxin; Yan, Biao

    2013-07-01

    Microstructure of Fe-based amorphous and nanocrystalline soft magnetic alloy has been investigated by X-ray diffraction (XRD), transmission electronic microscopy (TEM) and Doppler broadening positron annihilation technique (PAT). Doppler broadening measurement reveals that amorphous alloys (Finemet, Type I) which can form a nanocrystalline phase have more defects (free volume) than alloys (Metglas, Type II) which cannot form this microstructure. XRD and TEM characterization indicates that the nanocrystallization of amorphous Finemet alloy occurs at 460°C, where nanocrystallites of α-Fe with an average grain size of a few nanometers are formed in an amorphous matrix. With increasing annealing temperature up to 500°C, the average grain size increases up to around 12 nm. During the annealing of Finemet alloy, it has been demonstrated that positron annihilates in quenched-in defect, crystalline nanophase and amorphous-nanocrystalline interfaces. The change of line shape parameter S with annealing temperature in Finemet alloy is mainly due to the structural relaxation, the pre-nucleation of Cu nucleus and the nanocrystallization of α-Fe(Si) phase during annealing. This study throws new insights into positron behavior in the nanocrystallization of metallic glasses, especially in the presence of single or multiple nanophases embedded in the amorphous matrix.

  10. Symmetrical modified dual tree complex wavelet transform for processing quadrature Doppler ultrasound signals.

    PubMed

    Serbes, G; Aydin, N

    2011-01-01

    Dual-tree complex wavelet transform (DTCWT), which is a shift invariant transform with limited redundancy, is an improved version of discrete wavelet transform. Complex quadrature signals are dual channel signals obtained from the systems employing quadrature demodulation. An example of such signals is quadrature Doppler signal obtained from blood flow analysis systems. Prior to processing Doppler signals using the DTCWT, directional flow signals must be obtained and then two separate DTCWT applied, increasing the computational complexity. In this study, in order to decrease computational complexity, a symmetrical modified DTCWT algorithm is proposed (SMDTCWT). A comparison between the new transform and the symmetrical phasing-filter technique is presented. Additionally denoising performance of SMDTCWT is compared with the DWT and the DTCWT using simulated signals. The results show that the proposed method gives the same output as the symmetrical phasing-filter method, the computational complexity for processing quadrature signals using DTCWT is greatly reduced and finally the SMDTCWT based denoising outperforms conventional DWT with same computational complexity. PMID:22255416

  11. Differential atrial filling after Mustard and Senning repairs. Detection by transcutaneous Doppler ultrasound.

    PubMed Central

    Wyse, R K; Macartney, F J; Rohmer, J; Ottenkamp, J; Brom, A G

    1980-01-01

    The dominance of Mustard's operation for transposition of the great arteries has been challenged by the recent revival of Senning's repair because it promises better long-term results in terms of venous obstruction and atrial haemodynamics. These hypotheses were tested by recording jugular venous flow waveforms transcutaneously in 24 postoperative patients with simple complete transposition using a bidirectional Doppler blood velocimeter. Eight patients had undergone Mustard's operation and 16 the Senning alternative; all had previously had a postoperative cardiac catheterisation. Both groups of patients had similar left ventricular, pulmonary arterial, and systemic venous atrial pressures. No child showed any evidence at catheterisation of either mitral regurgitation or of superior vena caval pathway obstruction. These two findings were endorsed by the transcutaneous Doppler recordings. Jugular venous flow in normal children exhibits two maxima, one of atrial filling during ventricular systole, the other of ventricular filling occurs once the tricuspid valve has opened. Both operative procedures diminished the size of the former phase, but the Mustard did so more. After Mustard's operation forward flow during the atrial filling phase was absent in approximately half the cardiac cycles recorded, and severely diminished in the rest. By contrast, there was approximately a 90 per cent appearance of atrial filling waves after Senning's operation which also provided significantly better atrial function than Mustard's procedure in terms of peak velocity of blood entering the atrium and total atrial filling. It is therefore concluded that both procedures compromise atrial volume and compliance but Senning's repair to a much lesser extent. PMID:7459153

  12. New measurements of Venus winds with ground-based Doppler velocimetry at CFHT

    NASA Astrophysics Data System (ADS)

    Machado, P.; Widemann, T.; Luz, D.; Peralta, J.; Berry, D. L.

    2012-04-01

    Since Venus Express spacecraft operations started in 2006, an ongoing effort has been made to coordinate its operations with observations from the ground using various techniques and spectral domains (Lellouch and Witasse, 2008). We present an analysis of Venus Doppler winds at cloud tops based on observations made at the Canada France Hawaii 3.6-m telescope (CFHT) with the ESPaDOnS visible spectrograph. These observations consisted of high-resolution spectra of Fraunhofer lines in the visible range (0.37-1.05 μm) to measure the winds at cloud tops using the Doppler shift of solar radiation scattered by cloud top particles in the observer's direction (Widemann et al., 2007, 2008). The observations were made during 19-20 February 2011 and were coordinated with Visual Monitoring Camera (VMC) observations by Venus Express. The complete optical spectrum was collected over 40 spectral orders at each point with 2-5 seconds exposures, at a resolution of about 80000. The observations included various points of the dayside hemisphere at a phase angle of 67°, between +10° and -60° latitude, in steps of 10° , and from +70° to -12° longitude relative to sub-Earth meridian in steps of 12°. The Doppler shift measured in scattered solar light on Venus dayside results from two instantaneous motions: (1) a motion between the Sun and Venus upper cloud particles; (2) a motion between the observer and Venus clouds. The measured Doppler shift, which results from these two terms combined, varies with the planetocentric longitude and latitude and is minimum at meridian ΦN = ΦSun - ΦEarth where the two components subtract to each other for a pure zonal regime. Due to the need for maintaining a stable velocity reference during the course of acquisition using high resolution spectroscopy, we measure relative Doppler shifts to ΦN. The main purpose of our work is to provide variable wind measurements with respect to the background atmosphere, complementary to simultaneous

  13. Influence of speckle effect on doppler velocity measurement

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  14. Results of the international ionospheric Doppler sounder network

    NASA Astrophysics Data System (ADS)

    Lastovicka, Jan; Chum, Jaroslav

    2016-07-01

    This paper summarizes main recent results reached by the Czech-lead international network of ionospheric Doppler sounders. The network consists of Doppler sounders in the western half of Czechia (5 measuring paths, 3 frequencies with central receivers in Prague), northern Taiwan (3 transmitters, two separated receivers, 1 frequency), and three similar systems (3 measuring paths with 1 receiver and 1 frequency) in Tucuman (north-western Argentina), Hermanus (the southernmost South Africa) and Luisville (northern South Africa). Three main areas of research have been (1) statistical properties of gravity waves, (2) ionospheric effects of earthquakes, and (3) low latitude/equatorial phenomena. Some results: (1) the theoretically expected dominance of gravity wave propagation against wind has been confirmed; (2) impact of the Tohoku 2001 M9.0 earthquake was registered in the ionosphere over the Czech Republic as long-period infrasound on the distance of about 9000 km from epicenter; analysis of ionospheric infrasound excited by the Nepal 2015 M7.8 earthquake observed by the Czech and Taiwan Doppler sounders showed that the intensity of ionospheric signal is significantly height dependent and that the Doppler shift depends not only on the advection (up and down motion) of the reflecting layer but also on the compression/rarefaction of the electron gas; (3) spread F structures observed by Doppler sounders in Tucuman and Taiwan (both under the crest of equatorial ionization anomaly) provide results consistent with S4 scintillation data and with previous optical, GPS and satellite measurements.

  15. A rotating torus phantom for assessing color Doppler accuracy.

    PubMed

    Stewart, S F

    1999-10-01

    A rotating torus phantom was designed to assess the accuracy of color Doppler ultrasound. A thin rubber tube was filled with blood analog fluid and joined at the ends to form a torus, then mounted on a disk submerged in water and rotated at constant speeds by a motor. Flow visualization experiments and finite element analyses demonstrated that the fluid accelerates quickly to the speed of the torus and spins as a solid body. The actual fluid velocity was found to be dependent only on the motor speed and location of the sample volume. The phantom was used to assess the accuracy of Doppler-derived velocities during two-dimensional (2-D) color imaging using a commercial ultrasound system. The Doppler-derived velocities averaged 0.81 +/- 0.11 of the imposed velocity, with the variations significantly dependent on velocity, pulse-repetition frequency and wall filter frequency (p < 0.001). The torus phantom was found to have certain advantages over currently available Doppler accuracy phantoms: 1. It has a high maximum velocity; 2. it has low velocity gradients, simplifying the calibration of 2-D color Doppler; and 3. it uses a real moving fluid that gives a realistic backscatter signal. PMID:10576268

  16. Ultrasonic bistatic Doppler sonar in air for personnel motion detection

    NASA Astrophysics Data System (ADS)

    Ekimov, Alexander; Hickey, Craig J.

    2012-06-01

    The National Center for Physical Acoustics (NCPA) at the University of Mississippi is working on the application of ultrasonic Doppler sonars in air for personnel motion detection. Two traditional Doppler sonar configurations, a monostatic and a bistatic, are being studied. In the monostatic configuration, the distance between the transmitter and the receiver is small. The proximity of the source to the receiver places a limitation on the system associated with the overloading of the receivers' input due to acoustic energy leakage from the transmitters' output. The maximum range of detection is therefore limited by the dynamic range of the acquisition system. In a bistatic Doppler ultrasonic sonar, the source and receiver are spaced apart and the acoustic energy along the direct path does not constrain the maximum acoustic power level output of the transmitter. In a monostatic configuration the acoustic signal suffers from beam spreading and natural absorption during propagation from the transmitter to the target and from the target back to the receiver. In a bistatic configuration the acoustic propagation is in one direction only and theoretically the detection distance can be twice the monostatic distance. For comparison the experiments of a human walking in a building hallway using the bistatic and monostaic Doppler sonars in air were conducted. The experimental results for human signatures from these Doppler sonars are presented and discussed.

  17. GEOS 3 STDN S band Doppler tracking investigation

    NASA Technical Reports Server (NTRS)

    Rosenbaum, B.

    1979-01-01

    GEOS 3S Doppler band and laser ranging data, acquired from August 1975 to March 1976 in the spacecraft altimeter calibration area, are examined. An evaluation of two-way and three-way Doppler data, for the positioning of Spaceflight Tracking and Data Network S band stations is presented, as well as the Goddard Space Flight Center laser system that is used to reference the exact position of the Doppler stations. The two-way and three-way Doppler tracking devices, situated at Rosman and Bermuda, have yielded data for the recovery of GEOS 3 arc height with an uncertainty of only 1 m. Attention is given to the effects of beacon signal frequency instability, controlled by a temperature sensitive auxiliary crystal oscillator on board the spacecraft, and to the one-way range rate tracking noise that was found to be within a range of 2 to 10 cm/s. 1- and 2-way passes and their different arc meters are graphed, showing the Doppler tracking interval. It was concluded that other accurate computations and recovery of station coordinates could be performed employing tracking data from S band stations.

  18. Temporal enhancement of two-dimensional color doppler echocardiography

    NASA Astrophysics Data System (ADS)

    Terentjev, Alexey B.; Settlemier, Scott H.; Perrin, Douglas P.; del Nido, Pedro J.; Shturts, Igor V.; Vasilyev, Nikolay V.

    2016-03-01

    Two-dimensional color Doppler echocardiography is widely used for assessing blood flow inside the heart and blood vessels. Currently, frame acquisition time for this method varies from tens to hundreds of milliseconds, depending on Doppler sector parameters. This leads to low frame rates of resulting video sequences equal to tens of Hz, which is insufficient for some diagnostic purposes, especially in pediatrics. In this paper, we present a new approach for reconstruction of 2D color Doppler cardiac images, which results in the frame rate being increased to hundreds of Hz. This approach relies on a modified method of frame reordering originally applied to real-time 3D echocardiography. There are no previous publications describing application of this method to 2D Color Doppler data. The approach has been tested on several in-vivo cardiac 2D color Doppler datasets with approximate duration of 30 sec and native frame rate of 15 Hz. The resulting image sequences had equivalent frame rates to 500Hz.

  19. High-resolution Doppler model of the human gait

    NASA Astrophysics Data System (ADS)

    Geisheimer, Jonathan L.; Greneker, Eugene F., III; Marshall, William S.

    2002-07-01

    A high resolution Doppler model of the walking human was developed for analyzing the continuous wave (CW) radar gait signature. Data for twenty subjects were collected simultaneously using an infrared motion capture system along with a two channel 10.525 GHz CW radar. The motion capture system recorded three-dimensional coordinates of infrared markers placed on the body. These body marker coordinates were used as inputs to create the theoretical Doppler output using a model constructed in MATLAB. The outputs of the model are the simulated Doppler signals due to each of the major limbs and the thorax. An estimated radar cross section for each part of the body was assigned using the Lund & Browder chart of estimated body surface area. The resultant Doppler model was then compared with the actual recorded Doppler gait signature in the frequency domain using the spectrogram. Comparison of the two sets of data has revealed several identifiable biomechanical features in the radar gait signature due to leg and body motion. The result of the research shows that a wealth of information can be unlocked from the radar gait signature, which may be useful in security and biometric applications.

  20. The Solar Oscillations Investigation - Michelson Doppler Imager

    NASA Astrophysics Data System (ADS)

    Scherrer, P. H.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.; Kosovichev, A. G.; Schou, J.; Rosenberg, W.; Springer, L.; Tarbell, T. D.; Title, A.; Wolfson, C. J.; Zayer, I.; MDI Engineering Team

    1995-12-01

    The Solar Oscillations Investigation (SOI) uses the Michelson Doppler Imager (MDI) instrument to probe the interior of the Sun by measuring the photospheric manifestations of solar oscillations. Characteristics of the modes reveal the static and dynamic properties of the convection zone and core. Knowledge of these properties will improve our understanding of the solar cycle and of stellar evolution. Other photospheric observations will contribute to our knowledge of the solar magnetic field and surface motions. The investigation consists of coordinated efforts by several teams pursuing specific scientific objectives. The instrument images the Sun on a 10242 CCD camera through a series of increasingly narrow spectral filters. The final elements, a pair of tunable Michelson interferometers, enable MDI to record filtergrams with a FWHM bandwidth of 94 mÅ. Normally 20 images centered at 5 wavelengths near the Ni I 6768 spectral line are recorded each minute. MDI calculates velocity and continuum intensity from the filtergrams with a resolution of 4″ over the whole disk. An extensive calibration program has verified the end-to-end performance of the instrument. To provide continuous observations of the longest-lived modes that reveal the internal structure of the Sun, a carefully-selected set of spatial averages are computed and downlinked at all times. About half the time MDI will also be able to downlink complete velocity and intensity images each minute. This high rate telemetry (HRT) coverage is available for at least a continuous 60-day interval each year and for 8 hours each day during the rest of the year. During the 8-hour HRT intervals, 10 of the exposures each minute can be programmed for other observations, such as measurements in MDI's higher resolution (1.25″) field centered about 160″ north of the equator; meanwhile, the continuous structure program proceeds during the other half minute. Several times each day, polarizers will be inserted to