Electromagnetic field strength prediction in an urban environment: A useful tool for the planning of LMSS

NASA Technical Reports Server (NTRS)

Vandooren, G. A. J.; Herben, M. H. A. J.; Brussaard, G.; Sforza, M.; Poiaresbaptista, J. P. V.

1993-01-01

A model for the prediction of the electromagnetic field strength in an urban environment is presented. The ray model, that is based on the Uniform Theory of Diffraction (UTD), includes effects of the non-perfect conductivity of the obstacles and their surface roughness. The urban environment is transformed into a list of standardized obstacles that have various shapes and material properties. The model is capable of accurately predicting the field strength in the urban environment by calculating different types of wave contributions such as reflected, edge and corner diffracted waves, and combinations thereof. Also, antenna weight functions are introduced to simulate the spatial filtering by the mobile antenna. Communication channel parameters such as signal fading, time delay profiles, Doppler shifts and delay-Doppler spectra can be derived from the ray-tracing procedure using post-processing routines. The model has been tested against results from scaled measurements at 50 GHz and proves to be accurate.

A experiment on radio location of objects in the near-Earth space with VLBI in 2012

NASA Astrophysics Data System (ADS)

Nechaeva, M.; Antipenko, A.; Bezrukovs, V.; Bezrukov, D.; Dementjev, A.; Dugin, N.; Konovalenko, A.; Kulishenko, V.; Liu, X.; Nabatov, A.; Nesteruk, V.; Pupillo, G.; Reznichenko, A.; Salerno, E.; Shmeld, I.; Shulga, O.; Sybiryakova, Y.; Tikhomirov, Yu.; Tkachenko, A.; Volvach, A.; Yang, W.-J.

An experiment on radar location of space debris objects using of the method of VLBI was carried out in April, 2012. The radar VLBI experiment consisted in irradiation of some space debris objects (4 rocket stages and 5 inactive satellites) with a signal of the transmitter with RT-70 in Evpatoria, Ukraine. Reflected signals were received by a complex of radio telescopes in the VLBI mode. The following VLBI stations took part in the observations: Ventspils (RT-32), Urumqi (RT-25), Medicina (RT-32) and Simeiz (RT-22). The experiment included measurements of the Doppler frequency shift and the delay for orbit refining, and measurements of the rotation period and sizes of objects by the amplitudes of output interferometer signals. The cross-correlation of VLBI-data is performed at a correlator NIRFI-4 of Radiophysical Research Institute (Nizhny Novgorod). Preliminary data processing resulted in the series of Doppler frequency shifts, which comprised the information on radial velocities of the objects. Some results of the experiment are presented.

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.

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.

Radiometric Spacecraft Tracking for Deep Space Navigation

NASA Technical Reports Server (NTRS)

Lanyi, Gabor E.; Border, James S.; Shin, Dong K.

2008-01-01

Interplanetary spacecraft navigation relies on three types of terrestrial tracking observables.1) Ranging measures the distance between the observing site and the probe. 2) The line-of-sight velocity of the probe is inferred from Doppler-shift by measuring the frequency shift of the received signal with respect to the unshifted frequency. 3) Differential angular coordinates of the probe with respect to natural radio sources are nominally obtained via a differential delay technique of (Delta) DOR (Delta Differential One-way Ranging). The accuracy of spacecraft coordinate determination depends on the measurement uncertainties associated with each of these three techniques. We evaluate the corresponding sources of error and present a detailed error budget.

Propagation of Wide Bandwidth Signals through Strongly Turbulent Ionized Media

DTIC Science & Technology

1982-03-15

through random ionized media. This work is applicable to the problems of satel- lite communication and space based radar observation through a disturbed...REALIZATIONS 87 3.2 FORMULATION 88 3.2.1 Wide Bandwidth Signals 91 3.2.2 Total Phase Shift, Time Delay, and Doppler Frequency 95 3.2.3 Impulse Response...scattering limit. The 20 Gaussian form corresponds to pulse wander and dispersion while the expo- nential form corresponds to diffractive pulse spreading

Distribution of mean Doppler shift, spectral width, and skewness of coherent 50-MHz auroral radar backscatter

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

Watermann, J.; McNamara, A.G.; Sofko, G.J.

Some 7,700 radio aurora spectra obtained from a six link 50-MHz CW radar network set up on the Canadian prairies were analyzed with respect to the distributions of mean Doppler shift, spectral width and skewness. A comparison with recently published SABRE results obtained at 153 MHz shows substantial differences in the distributions which are probably due to different experimental and geophysical conditions. The spectra are mostly broad with mean Doppler shifts close to zero (type II spectra). The typical groupings of type I and type III spectra are clearly identified. All types appear to be in general much more symmetricmore » than those recorded with SABRE, and the skewness is only weakly dependent on the sign of the mean Doppler shift. Its distribution peaks near zero and shows a weak positive correlation with the type II Doppler shifts while the mostly positive type I Doppler shifts are slightly negatively correlated with the skewness.« less

Doppler color imaging. Principles and instrumentation.

PubMed

Kremkau, F W

1992-01-01

DCI acquires Doppler-shifted echoes from a cross-section of tissue scanned by an ultrasound beam. These echoes are then presented in color and superimposed on the gray-scale anatomic image of non-Doppler-shifted echoes received during the scan. The flow echoes are assigned colors according to the color map chosen. Usually red, yellow, or white indicates positive Doppler shifts (approaching flow) and blue, cyan, or white indicates negative shifts (receding flow). Green is added to indicate variance (disturbed or turbulent flow). Several pulses (the number is called the ensemble length) are needed to generate a color scan line. Linear, convex, phased, and annular arrays are used to acquire the gray-scale and color-flow information. Doppler color-flow instruments are pulsed-Doppler instruments and are subject to the same limitations, such as Doppler angle dependence and aliasing, as other Doppler instruments. Color controls include gain, TGC, map selection, variance on/off, persistence, ensemble length, color/gray priority. Nyquist limit (PRF), baseline shift, wall filter, and color window angle, location, and size. Doppler color-flow instruments generally have output intensities intermediate between those of gray-scale imaging and pulsed-Doppler duplex instruments. Although there is no known risk with the use of color-flow instruments, prudent practice dictates that they be used for medical indications and with the minimum exposure time and instrument output required to obtain the needed diagnostic information.

Application of Statistical Linear Time-Varying System Theory to Modeling of High Grazing Angle Sea Clutter

DTIC Science & Technology

2017-10-25

radar returns from a large object (such as a planet) in radio astronomy as a function of delay and Doppler shift using a so-called “scattering...from a planet in radar astronomy . Van Trees also briefly describes the scattering function in his 8 Corey D. Cooke most well-known book [7], as does... astronomy – communication via fluctuating multipath media,” rept. 234, MIT Lincoln Laboratory (October 1960). 6. P. E. Green, Jr., “Radar astronomy

Reversal of orbital angular momentum arising from an extreme Doppler shift

PubMed Central

Toninelli, Ermes; Horsley, Simon A. R.; Hendry, Euan; Phillips, David B.; Padgett, Miles J.

2018-01-01

The linear Doppler shift is familiar as the rise and fall in pitch of a siren as it passes by. Less well known is the rotational Doppler shift, proportional to the rotation rate between source and receiver, multiplied by the angular momentum carried by the beam. In extreme cases the Doppler shift can be larger than the rest-frame frequency and for a red shift, the observed frequency then becomes “negative.” In the linear case, this effect is associated with the time reversal of the received signal, but it can be observed only with supersonic relative motion between the source and receiver. However, the rotational case is different; if the radius of rotation is smaller than the wavelength, then the velocities required to observe negative frequencies are subsonic. Using an acoustic source at ≈100 Hz we create a rotational Doppler shift larger than the laboratory-frame frequency. We observe that once the red-shifted wave passes into the “negative frequency” regime, the angular momentum associated with the sound is reversed in sign compared with that of the laboratory frame. These low-velocity laboratory realizations of extreme Doppler shifts have relevance to superoscillatory fields and offer unique opportunities to probe interactions with rotating bodies and aspects of pseudorelativistic frame translation. PMID:29581257

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.

Orbit determination singularities in the Doppler tracking of a planetary orbiter

NASA Technical Reports Server (NTRS)

Wood, L. J.

1985-01-01

On a number of occasions, spacecraft launched by the U.S. have been placed into orbit about the moon, Venus, or Mars. It is pointed out that, in particular, in planetary orbiter missions two-way coherent Doppler data have provided the principal data type for orbit determination applications. The present investigation is concerned with the problem of orbit determination on the basis of Doppler tracking data in the case of a spacecraft in orbit about a natural body other than the earth or the sun. Attention is given to Doppler shift associated with a planetary orbiter, orbit determination using a zeroth-order model for the Doppler shift, and orbit determination using a first-order model for the Doppler shift.

Theory of Parabolic Arcs in Interstellar Scintillation Spectra

NASA Astrophysics Data System (ADS)

Cordes, James M.; Rickett, Barney J.; Stinebring, Daniel R.; Coles, William A.

2006-01-01

Interstellar scintillation (ISS), observed as time variation in the intensity of a compact radio source, is caused by small-scale structure in the electron density of the interstellar plasma. Dynamic spectra of ISS show modulation in radio frequency and time. Here we relate the (two-dimensional) power spectrum of the dynamic spectrum-the secondary spectrum-to the scattered image of the source. Recent work has identified remarkable parabolic arcs in secondary spectra. Each point in a secondary spectrum corresponds to interference between points in the scattered image with a certain Doppler shift and a certain delay. The parabolic arc corresponds to the quadratic relation between differential Doppler shift and delay through their common dependence on scattering angle. We show that arcs will occur in all media that scatter significant power at angles larger than the rms angle. Thus, effects such as source diameter, steep spectra, and dissipation scales, which truncate high angle scattering, also truncate arcs. Arcs are equally visible in simulations of nondispersive scattering. They are enhanced by anisotropic scattering when the spatial structure is elongated perpendicular to the velocity. In weak scattering the secondary spectrum is directly mapped from the scattered image, and this mapping can be inverted. We discuss additional observed phenomena including multiple arcs and reverse arclets oriented oppositely to the main arc. These phenomena persist for many refractive scattering times, suggesting that they are due to large-scale density structures, rather than low-frequency components of Kolmogorov turbulence.

Reversal of orbital angular momentum arising from an extreme Doppler shift.

PubMed

Gibson, Graham M; Toninelli, Ermes; Horsley, Simon A R; Spalding, Gabriel C; Hendry, Euan; Phillips, David B; Padgett, Miles J

2018-04-10

The linear Doppler shift is familiar as the rise and fall in pitch of a siren as it passes by. Less well known is the rotational Doppler shift, proportional to the rotation rate between source and receiver, multiplied by the angular momentum carried by the beam. In extreme cases the Doppler shift can be larger than the rest-frame frequency and for a red shift, the observed frequency then becomes "negative." In the linear case, this effect is associated with the time reversal of the received signal, but it can be observed only with supersonic relative motion between the source and receiver. However, the rotational case is different; if the radius of rotation is smaller than the wavelength, then the velocities required to observe negative frequencies are subsonic. Using an acoustic source at [Formula: see text]100 Hz we create a rotational Doppler shift larger than the laboratory-frame frequency. We observe that once the red-shifted wave passes into the "negative frequency" regime, the angular momentum associated with the sound is reversed in sign compared with that of the laboratory frame. These low-velocity laboratory realizations of extreme Doppler shifts have relevance to superoscillatory fields and offer unique opportunities to probe interactions with rotating bodies and aspects of pseudorelativistic frame translation. Copyright © 2018 the Author(s). Published by PNAS.

C IV Doppler shifts observed in active region filaments

NASA Technical Reports Server (NTRS)

Klimchuk, J. A.

1986-01-01

The Doppler shift properties of 21 active region filaments were studied using C IV Dopplergram data. Most are associated with corridors of weak magnetic field that separate opposite polarity strong fields seen in photospheric magnetograms. A majority of the filaments are relatively blue shifted, although several lie very close to the dividing lines between blue and red shift. Only one filament in the samples is clearly red shifted. A new calibration procedure for Dopplergrams indicates that sizable zero point offsets are often required. The center-to-limb behavior of the resulting absolute Doppler shifts suggests that filament flows are usually quite small. It is possible that they vanish.

The confrontation between general relativity and experiment

NASA Technical Reports Server (NTRS)

Will, C. M.

1980-01-01

Experiments that test the foundations of gravitation theory in terms of the Einstein equivalence principle are discussed along with solar system tests of general relativity at the post-Newtonian level. These include classical (light-deflection, time delay and perihelion shift) tests as well as tests of the strong equivalence principle. The binary pulsar is discussed as an extra-solar-system gravitational testing ground, and attention is given to the multipolarity of the waves and the amount of radiation damping. The mass function, periastron shift, redshift-Doppler parameter and rate of change of the orbit period (Pb) of the binary pulsar are also considered, and it is suggested that the measurement of Pb represents the first observation of the effects of gravitational radiation.

Photoacoustic Doppler effect from flowing small light-absorbing particles.

PubMed

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

2007-11-02

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.

Blocker-tolerant and high-sensitivity $Δ$$\\!$$Σ$ correlation digitizer for radar and coherent receiver applications

DOE PAGES

Mincey, John S.; Silva-Martinez, Jose; Karsilayan, AydinIlker; ...

2017-03-17

In this study, a coherent subsampling digitizer for pulsed Doppler radar systems is proposed. Prior to transmission, the radar system modulates the RF pulse with a known pseudorandom binary phase shift keying (BPSK) sequence. Upon reception, the radar digitizer uses a programmable sample-and-hold circuit to multiply the received waveform by a properly time-delayed version of the known a priori BPSK sequence. This operation demodulates the desired echo signal while suppressing the spectrum of all in-band noncorrelated interferers, making them appear as noise in the frequency domain. The resulting demodulated narrowband Doppler waveform is then subsampled at the IF frequency bymore » a delta-sigma modulator. Because the digitization bandwidth within the delta-sigma feedback loop is much less than the input bandwidth to the digitizer, the thermal noise outside of the Doppler bandwidth is effectively filtered prior to quantization, providing an increase in signal-to-noise ratio (SNR) at the digitizer's output compared with the input SNR. In this demonstration, a delta-sigma correlation digitizer is fabricated in a 0.18-μm CMOS technology. The digitizer has a power consumption of 1.12 mW with an IIP3 of 7.5 dBm. The digitizer is able to recover Doppler tones in the presence of blockers up to 40 dBm greater than the Doppler tone.« less

A Fiber Optic Doppler Sensor and Its Application in Debonding Detection for Composite Structures

PubMed Central

Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Meng, Guang; Ohsawa, Isamu; Shirai, Takehiro

2010-01-01

Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by using fiber optic Doppler (FOD) sensor with spiral shape. Interferometers based on two types of laser sources, namely the He-Ne laser and the infrared semiconductor laser, are proposed and compared in this study for the purpose of measuring Doppler frequency shift of the FOD sensor. Locations of the FOD sensors are optimized based on mechanical characteristics of lap splice joint. The FOD sensors are subsequently used to detect the guided ultrasonic waves propagating in the CFRP structures. By taking advantage of signal processing approaches, features of the guided wave signals can be revealed. The results demonstrate that debonding in the lap splice joint results in arrival time delay of the first package in the guided wave signals, which can be the characteristic for debonding damage inspection and damage extent estimation. PMID:22219698

A fiber optic Doppler sensor and its application in debonding detection for composite structures.

PubMed

Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Meng, Guang; Ohsawa, Isamu; Shirai, Takehiro

2010-01-01

Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by using fiber optic Doppler (FOD) sensor with spiral shape. Interferometers based on two types of laser sources, namely the He-Ne laser and the infrared semiconductor laser, are proposed and compared in this study for the purpose of measuring Doppler frequency shift of the FOD sensor. Locations of the FOD sensors are optimized based on mechanical characteristics of lap splice joint. The FOD sensors are subsequently used to detect the guided ultrasonic waves propagating in the CFRP structures. By taking advantage of signal processing approaches, features of the guided wave signals can be revealed. The results demonstrate that debonding in the lap splice joint results in arrival time delay of the first package in the guided wave signals, which can be the characteristic for debonding damage inspection and damage extent estimation.

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.

Digital second-order phase-locked loop

NASA Technical Reports Server (NTRS)

Holmes, J. K.; Carl, C. C.; Tagnelia, C. R.

1975-01-01

Actual tests with second-order digital phase-locked loop at simulated relative Doppler shift of 1x0.0001 produced phase lock with timing error of 6.5 deg and no appreciable Doppler bias. Loop thus appears to achieve subcarrier synchronization and to remove bias due to Doppler shift in range of interest.

Doppler-shifting effects on frequency spectra of gravity waves observed near the summer mesopause at high latitude

NASA Technical Reports Server (NTRS)

Fritts, David C.; Wang, Ding-Yi

1991-01-01

Results are presented of radar observations of horizontal and vertical velocities near the summer mesopause at Poker Flat (Alaska), showing that the observed vertical velocity spectra were influenced strongly by Doppler-shifting effects. The horizontal velocity spectra, however, were relatively insensitive to horizontal wind speed. The observed spectra are compared with predicted spectra for various models of the intrinsic motion spectrum and degrees of Doppler shifting.

Measurement of winds in Venus' upper mesosphere based on Doppler shifts of the 2.6-mm (C-12)O line

NASA Technical Reports Server (NTRS)

Shah, Kathryn P.; Muhleman, Duane O.; Berge, Glenn L.

1991-01-01

Venus observations conducted in 1988 at the first rotational transition of (C-12)O finely sampled this absorption line by means of a 32-channel filter bank; with this spatial and spectral resolution, it proved possible to measure Doppler shifts of the absorption line across the planet due to strong winds in Venus' upper mesosphere. The Doppler shifts change in a way that is indicative of westward horizontal winds. The radial wind speeds from the Doppler shifts were smoothed to reduce noise and then fitted in least-squares fashion to canonical forms of the lower atmosphere's westward zonal flow. The two flows exhibit a high correlation in orientation.

Comparing Goldstone Solar System Radar Earth-based Observations of Mars with Orbital Datasets

NASA Technical Reports Server (NTRS)

Haldemann, A. F. C.; Larsen, K. W.; Jurgens, R. F.; Slade, M. A.

2005-01-01

The Goldstone Solar System Radar (GSSR) has collected a self-consistent set of delay-Doppler near-nadir radar echo data from Mars since 1988. Prior to the Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA) global topography for Mars, these radar data provided local elevation information, along with radar scattering information with global coverage. Two kinds of GSSR Mars delay-Doppler data exist: low 5 km x 150 km resolution and, more recently, high (5 to 10 km) spatial resolution. Radar data, and non-imaging delay-Doppler data in particular, requires significant data processing to extract elevation, reflectivity and roughness of the reflecting surface. Interpretation of these parameters, while limited by the complexities of electromagnetic scattering, provide information directly relevant to geophysical and geomorphic analyses of Mars. In this presentation we want to demonstrate how to compare GSSR delay-Doppler data to other Mars datasets, including some idiosyncracies of the radar data. Additional information is included in the original extended abstract.

New Approaches For Asteroid Spin State and Shape Modeling From Delay-Doppler Radar Images

NASA Astrophysics Data System (ADS)

Raissi, Chedy; Lamee, Mehdi; Mosiane, Olorato; Vassallo, Corinne; Busch, Michael W.; Greenberg, Adam; Benner, Lance A. M.; Naidu, Shantanu P.; Duong, Nicholas

2016-10-01

Delay-Doppler radar imaging is a powerful technique to characterize the trajectories, shapes, and spin states of near-Earth asteroids; and has yielded detailed models of dozens of objects. Reconstructing objects' shapes and spins from delay-Doppler data is a computationally intensive inversion problem. Since the 1990s, delay-Doppler data has been analyzed using the SHAPE software. SHAPE performs sequential single-parameter fitting, and requires considerable computer runtime and human intervention (Hudson 1993, Magri et al. 2007). Recently, multiple-parameter fitting algorithms have been shown to more efficiently invert delay-Doppler datasets (Greenberg & Margot 2015) - decreasing runtime while improving accuracy. However, extensive human oversight of the shape modeling process is still required. We have explored two new techniques to better automate delay-Doppler shape modeling: Bayesian optimization and a machine-learning neural network.One of the most time-intensive steps of the shape modeling process is to perform a grid search to constrain the target's spin state. We have implemented a Bayesian optimization routine that uses SHAPE to autonomously search the space of spin-state parameters. To test the efficacy of this technique, we compared it to results with human-guided SHAPE for asteroids 1992 UY4, 2000 RS11, and 2008 EV5. Bayesian optimization yielded similar spin state constraints within a factor of 3 less computer runtime.The shape modeling process could be further accelerated using a deep neural network to replace iterative fitting. We have implemented a neural network with a variational autoencoder (VAE), using a subset of known asteroid shapes and a large set of synthetic radar images as inputs to train the network. Conditioning the VAE in this manner allows the user to give the network a set of radar images and get a 3D shape model as an output. Additional development will be required to train a network to reliably render shapes from delay-Doppler images.This work was supported by NASA Ames, NVIDIA, Autodesk and the SETI Institute as part of the NASA Frontier Development Lab program.

Lower-Hybrid-Drift Wave Turbulence in the Distant Magnetotail

DTIC Science & Technology

1978-05-01

kV ɘ with =• Y ~~ <» (Krall and Liewer, 1971). In this situation a Doppler shifted ,1; lower hybrid wave (u), - kV, . = ± u...satellite includes the relevant Doppler shifts since, in general, proton bulk flows are not directed parallel to the local magnetic field vector...theory of Section II predicts a relatively narrow frequency spectrum, the dominance of the Doppler shifting term k • Vp in Eq.(23)acts to

Sorting photons of different rotational Doppler shifts (RDS) by orbital angular momentum of single-photon with spin-orbit-RDS entanglement.

PubMed

Chen, Lixiang; She, Weilong

2008-09-15

We demonstrate that single photons from a rotating q-plate exhibit an entanglement in three degrees of freedom of spin, orbital angular momentum, and the rotational Doppler shift (RDS) due to the nonconservation of total spin and orbital angular momenta. We find that the rotational Doppler shift deltaomega = Omega((delta)s + deltal) , where s, l and Omega are quantum numbers of spin, orbital angular momentum, and rotating velocity of the q-plate, respectively. Of interest is that the rotational Doppler shift directly reflects the rotational symmetry of q-plates and can be also expressed as deltaomega = (Omega)n , where n = 2(q-1) denotes the fold number of rotational symmetry. Besides, based on this single-photon spin-orbit-RDS entanglement, we propose an experimental scheme to sort photons of different frequency shifts according to individual orbital angular momentum.

Experiments Using Cell Phones in Physics Classroom Education: The Computer-Aided g Determination

NASA Astrophysics Data System (ADS)

Vogt, Patrik; Kuhn, Jochen; Müller, Sebastian

2011-09-01

This paper continues the collection of experiments that describe the use of cell phones as experimental tools in physics classroom education.1-4 We describe a computer-aided determination of the free-fall acceleration g using the acoustical Doppler effect. The Doppler shift is a function of the speed of the source. Since a free-falling objects speed is changing linearly with time, the Doppler shift is also changing with time. It is possible to measure this shift using software that is both easy to use and readily available. Students will use the time-dependency of the Doppler shift to experimentally determine the acceleration due to gravity by using a cell phone as a freely falling object emitting a sound with constant frequency.

Electrostatic Ion-Cyclotron Waves in Magnetospheric Plasmas: Non-Local Aspects.

DTIC Science & Technology

1983-10-14

moving observer will see a Doppler shifted frequency --- S where is the velocity vector of the observer (satellite) and k is the wave vector. Since k...direction) will not see any Doppler -shift, irrespective of the size of ky . Such a statement could not be made in the purely local theory, since there...a local theory, a wide range of Doppler shifts would be produced, from -kivs to +kivs, since the maximum value of kx is k1. Some of the observations

Evaluation of a Delay-Doppler Imaging Algorithm Based on the Wigner-Ville Distribution

DTIC Science & Technology

1989-10-18

exchanging the frequency and time variables. 2.3 PROPERTIES OF THE WIGNER - VILLE DISTRIBUTION A partial list of the properties of the WVD is provided...ESD-TH-89-163 N Technical Report (N R55 00 Lfl Evaluation of a Delay-Doppler Imaging Algorithm Based on the Wigner - Ville Distribution K.I. Schultz 18...DOPPLER IMAGING ALGORITHM BASED ON THE WIGNER - VILLE DISTRIBUTION K.I. SCHULTZ Group 52 TECHNICAL REPORT 855 18 OCTOBER 1989 Approved for public release

Mercury Trapped Ion Frequency Standard for Ultra-Stable Reference Applications

NASA Technical Reports Server (NTRS)

Larsen, Kameron (Inventor); Burt, Eric A. (Inventor); Tjoelker, Robert L. (Inventor); Hamell, Robert L. (Inventor); Tucker, Blake C. (Inventor)

2017-01-01

An atomic clock including an ion trap assembly, a C-field coil positioned for generating a first magnetic field in the interrogation region of the ion trap assembly, a compensation coil positioned for generating a second magnetic field in the interrogation region, wherein the combination of the first and second magnetic fields produces an ion number-dependent second order Zeeman shift (Zeeman shift) in the resonance frequency that is opposite in sign to an ion number-dependent second order Doppler shift (Doppler shift) in the resonance frequency, the C-field coil has a radius selected using data indicating how changes in the radius affect an ion-number-dependent shift in the resonance frequency, such that a difference in magnitude between the Doppler shift and the Zeeman shift is controlled or reduced, and the resonance frequency, including the adjustment by the Zeeman shift, is used to obtain the frequency standard.

Spectroscopic Doppler analysis for visible-light optical coherence tomography

NASA Astrophysics Data System (ADS)

Shu, Xiao; Liu, Wenzhong; Duan, Lian; Zhang, Hao F.

2017-12-01

Retinal oxygen metabolic rate can be effectively measured by visible-light optical coherence tomography (vis-OCT), which simultaneously quantifies oxygen saturation and blood flow rate in retinal vessels through spectroscopic analysis and Doppler measurement, respectively. Doppler OCT relates phase variation between sequential A-lines to the axial flow velocity of the scattering medium. The detectable phase shift is between -π and π due to its periodicity, which limits the maximum measurable unambiguous velocity without phase unwrapping. Using shorter wavelengths, vis-OCT is more vulnerable to phase ambiguity since flow induced phase variation is linearly related to the center wavenumber of the probing light. We eliminated the need for phase unwrapping using spectroscopic Doppler analysis. We split the whole vis-OCT spectrum into a series of narrow subbands and reconstructed vis-OCT images to extract corresponding Doppler phase shifts in all the subbands. Then, we quantified flow velocity by analyzing subband-dependent phase shift using linear regression. In the phantom experiment, we showed that spectroscopic Doppler analysis extended the measurable absolute phase shift range without conducting phase unwrapping. We also tested this method to quantify retinal blood flow in rodents in vivo.

Off-axis targets maximize bearing Fisher Information in broadband active sonar.

PubMed

Kloepper, Laura N; Buck, John R; Liu, Yang; Nachtigall, Paul E

2018-01-01

Broadband active sonar systems estimate range from time delay and velocity from Doppler shift. Relatively little attention has been paid to how the received echo spectrum encodes information about the bearing of an object. This letter derives the bearing Fisher Information encoded in the frequency dependent transmitter beampattern. This leads to a counter-intuitive result: directing the sonar beam so that a target of interest is slightly off-axis maximizes the bearing information about the target. Beam aim data from a dolphin biosonar experiment agree closely with the angle predicted to maximize bearing information.

Observation of Doppler broadening in β -delayed proton- γ decay

DOE PAGES

Schwartz, S. B.; Wrede, C.; Bennett, M. B.; ...

2015-09-14

Background: The Doppler broadening of gamma-ray peaks is due to nuclear recoil from beta-delayed nucleon emission can be used to measure the energies of the nucleons. This method has never been tested using beta-delayed proton emission or applied to a recoil heavier than A = 10. Purpose: To test and apply this Doppler broadening method using gamma-ray peaks from the P-26(beta p gamma)Al-25 decay sequence. Methods: A fast beam of P-26 was implanted into a planar Ge detector, which was used as a P-26 beta-decay trigger. The SeGA array of high-purity Ge detectors was used to detect gamma rays frommore » the P-26(beta p gamma)Al-25 decay sequence. Results: Radiative Doppler broadening in beta-delayed proton-gamma decay was observed for the first time. Moreover, the Doppler broadening analysis method was verified using the 1613-keV gamma-ray line for which the proton energies were previously known. The 1776-keV gamma ray de-exciting the 2720 keV Al-25 level was observed in P-26(beta p gamma)Al-25 decay for the first time and used to determine that the center-of-mass energy of the proton emission feeding the 2720-keV level is 5.1 +/- 1.0 (stat.) +/- 0.6 (syst.) MeV, corresponding to a Si-26 excitation energy of 13.3 +/- 1.0 (stat.) +/- 0.6 (syst.) MeV for the proton-emitting level. Conclusions: Finally, the Doppler broadening method has been demonstrated to provide practical measurements of the energies for beta-delayed nucleon emissions populating excited states of nuclear recoils at least as heavy as A = 25.« less

Observation of Doppler broadening in β -delayed proton-γ decay

NASA Astrophysics Data System (ADS)

Schwartz, S. B.; Wrede, C.; Bennett, M. B.; Liddick, S. N.; Pérez-Loureiro, D.; Bowe, A.; Chen, A. A.; Chipps, K. A.; Cooper, N.; Irvine, D.; McNeice, E.; Montes, F.; Naqvi, F.; Ortez, R.; Pain, S. D.; Pereira, J.; Prokop, C.; Quaglia, J.; Quinn, S. J.; Sakstrup, J.; Santia, M.; Shanab, S.; Simon, A.; Spyrou, A.; Thiagalingam, E.

2015-09-01

Background: The Doppler broadening of γ -ray peaks due to nuclear recoil from β -delayed nucleon emission can be used to measure the energies of the nucleons. This method has never been tested using β -delayed proton emission or applied to a recoil heavier than A =10 . Purpose: To test and apply this Doppler broadening method using γ -ray peaks from the 26P(β p γ )25Al decay sequence. Methods: A fast beam of 26P was implanted into a planar Ge detector, which was used as a 26P β -decay trigger. The SeGA array of high-purity Ge detectors was used to detect γ rays from the 26P(β p γ )25Al decay sequence. Results: Radiative Doppler broadening in β -delayed proton-γ decay was observed for the first time. The Doppler broadening analysis method was verified using the 1613-keV γ -ray line for which the proton energies were previously known. The 1776-keV γ ray de-exciting the 2720 keV 25Al level was observed in 26P(β p γ )25Al decay for the first time and used to determine that the center-of-mass energy of the proton emission feeding the 2720-keV level is 5.1 ±1.0 (stat.) ±0.6 (syst.) MeV, corresponding to a 26Si excitation energy of 13.3 ±1.0 (stat.) ±0.6 (syst.) MeV for the proton-emitting level. Conclusions: The Doppler broadening method has been demonstrated to provide practical measurements of the energies for β -delayed nucleon emissions populating excited states of nuclear recoils at least as heavy as A =25 .

Use of global ionospheric maps for HF Doppler measurements interpretation

NASA Astrophysics Data System (ADS)

Petrova, I. R.; Bochkarev, V. V.; Latypov, R. R.

2018-04-01

The HF Doppler technique, a method of measurement of Doppler frequency shift of ionospheric signal, is one of the well-known and widely used techniques of ionosphere research. It allows investigation of various disturbances in the ionosphere. There are different sources of disturbances in the ionosphere such as geomagnetic storms, solar flashes, meteorological effects and atmospheric waves. The HF Doppler technique allows us to find out the influence of earthquakes, explosions and other processes on the ionosphere, which occurs near the Earth. HF Doppler technique has high sensitivity to small frequency variations and high time resolution but interpretation of results is difficult. In this paper, we attempt to use GPS data for Doppler measurements interpretation. Modeling of Doppler frequency shift variations with use of TEC allows separation of ionosphere disturbances of medium scale.

Observation of Doppler broadening in beta-delayed proton-gamma decay

NASA Astrophysics Data System (ADS)

Schwartz, Sarah

The Doppler broadening of gamma-ray peaks due to nuclear recoil from beta-delayed nucleon emission can be used to measure the energies of the nucleons. The purpose of this Thesis is to test and apply this Doppler broadening method using gamma-ray peaks from the 26P(betapgamma) 25Al decay sequence. A fast beam of 26P was implanted into a planar Ge detector, which was used as a 26P beta-decay trigger. The SeGA array of high-purity Ge detectors was used to detect gamma rays from the 26P(betapgamma)25Al decay sequence. Radiative Doppler broadening in beta-delayed proton-gamma decay was observed for the first time. The Doppler broadening analysis method was verified using the 1613 keV gamma-ray line for which the proton energies were previously known. The 1776 keV gamma ray de-exciting the 2720 keV 25Al level was observed in 26P(betapgamma) 25Al decay for the first time and used to determine that the center-of-mass energy of the proton emission feeding the 2720-keV level is 5.1 +/- 1.0 (stat.) +/- 0.6 (syst.) MeV, corresponding to a 26Si excitation energy of 13.3 +/- 1.0 (stat.) +/- 0.7 (syst.) MeV for the proton-emitting level. The Doppler broadening method has been demonstrated to provide practical measurements of the energies for beta-delayed nucleon emissions populating excited states of nuclear recoils at least as heavy as A = 25.

Galileo radio science investigations

NASA Technical Reports Server (NTRS)

Howard, H. T.; Eshleman, V. R.; Hinson, D. P.; Kliore, A. J.; Lindal, G. F.; Woo, R.; Bird, M. K.; Volland, H.; Edenhoffer, P.; Paetzold, M.

1992-01-01

Galileo radio-propagation experiments are based on measurements of absolute and differential propagation time delay, differential phase delay, Doppler shift, signal strength, and polarization. These measurements can be used to study: the atmospheric and ionospheric structure, constituents, and dynamics of Jupiter; the magnetic field of Jupiter; the diameter of Io, its ionospheric structure, and the distribution of plasma in the Io torus; the diameters of the other Galilean satellites, certain properties of their surfaces, and possibly their atmospheres and ionospheres; and the plasma dynamics and magnetic field of the solar corona. The spacecraft system provides linear rather than circular polarization on the S-band downlink signal, the capability to receive X-band uplink signals, and a differential downlink ranging mode. A highly-stable, dual-frequency, spacecraft radio system is developed that is suitable for simultaneous measurements of all the parameters normally attributed to radio waves.

Instrumentation for one-way satellite PTTI applications. [calibration and synchronization of clocks from navigation satellite

NASA Technical Reports Server (NTRS)

Osborne, A. E.

1973-01-01

A review of general principles and operational procedures illustrates how the typical passive user and omni receiving antenna can recover Precise Time and Time Interval (PTTI) information from a low altitude navigation satellite system for clock calibration and synchronization. Detailed discussions of concepts and theory of the receiver design are presented. The importance of RF correlation of the received and local PN encoded sequences is emphasized as a means of reducing delay uncertainties of the instrumentation to values compatible with nanosecond to submicrosecond PTTI objectives. Two receiver configurations were fabricated for use in satellite-to-laboratory experiments. In one receiver the delay-locked loop for PN signals synchronization used a dithered amplitude detection process while the second receiver used a complex sums phase detection method for measurement of delay error. The necessity for compensation of Doppler shift is discussed. Differences in theoretical signal acquisition and tracking performance of the design concepts are noted.

Frequency shift of the Bragg and Non-Bragg backscattering from periodic water wave

NASA Astrophysics Data System (ADS)

Wen, Biyang; Li, Ke

2016-08-01

Doppler effect is used to measure the relative speed of a moving target with respect to the radar, and is also used to interpret the frequency shift of the backscattering from the ocean wave according to the water-wave phase velocity. The widely known relationship between the Doppler shift and the water-wave phase velocity was deduced from the scattering measurements data collected from actual sea surface, and has not been verified under man-made conditions. Here we show that this ob- served frequency shift of the scattering data from the Bragg and Non-Bragg water wave is not the Doppler shift corresponding to the water-wave phase velocity as commonly believed, but is the water-wave frequency and its integral multiple frequency. The power spectrum of the backscatter from the periodic water wave consists of serials discrete peaks, which is equally spaced by water wave frequency. Only when the water-wave length is the integer multiples of the Bragg wave, and the radar range resolution is infinite, does the frequency shift of the backscattering mathematically equal the Doppler shift according to the water-wave phase velocity.

Method and apparatus for analyzing the fill characteristics of a packaging container

DOEpatents

Rodriguez, J.G.

1998-10-13

A system is described for analyzing the fill characteristics of a container. A container having a filling material therein is positioned adjacent a sound generator. Sound waves from the generator are applied to the container, causing it to vibrate. A vibration detector is used to determine the amount of container vibration. A preferred vibration detector involves a laser vibrometer which applies a reference laser beam to the vibrating container. The reference beam is reflected off of the container to generate a reflected laser beam. The reflected beam experiences a Doppler frequency shift compared with the reference beam which is caused by container vibration. The Doppler shift of the reflected beam is then compared with standardized Doppler shift data from a control container. Repeated Doppler shift measurements may also be undertaken which are converted into a vibration profile that is compared with a standardized vibration profile from a control container. 4 figs.

Method and apparatus for analyzing the fill characteristics of a packaging container

DOEpatents

Rodriguez, Julio G.

1998-01-01

A system for analyzing the fill characteristics of a container. A container having a filling material therein is positioned adjacent a sound generator. Sound waves from the generator are applied to the container, causing it to vibrate. A vibration detector is used to determine the amount of container vibration. A preferred vibration detector involves a laser vibrometer which applies a reference laser beam to the vibrating container. The reference beam is reflected off of the container to generate a reflected laser beam. The reflected beam experiences a Doppler frequency shift compared with the reference beam which is caused by container vibration. The Doppler shift of the reflected beam is then compared with standardized Doppler shift data from a control container. Repeated Doppler shift measurements may also be undertaken which are converted into a vibration profile that is compared with a standardized vibration profile from a control container.

On the role of mean flows in Doppler shifted frequencies

NASA Astrophysics Data System (ADS)

Gerkema, Theo; Maas, Leo R. M.; van Haren, Hans

2013-04-01

In the oceanographic literature, the term 'Doppler shift' often features in the context of mean flows and (internal) waves. Closer inspection reveals that the term is in fact used for two different things, which should be carefully distinguished, for their conflation results in incorrect interpretations. One refers to the difference in frequencies measured by two observers, one at a fixed position and one moving with the mean flow. The other definition is the one used in physics, where the frequency measured by an observer is compared to that of the source. In the latter sense, Doppler shifts occur only if the source and observer move with respect to each other; a steady mean flow cannot create a Doppler shift. We rehash the classical theory to straighten out some misconceptions and discuss how wave dispersion affects the classical relations and their application, for example on near-inertial internal waves.

Velocity measurement by vibro-acoustic Doppler.

PubMed

Nabavizadeh, Alireza; Urban, Matthew W; Kinnick, Randall R; Fatemi, Mostafa

2012-04-01

We describe the theoretical principles of a new Doppler method, which uses the acoustic response of a moving object to a highly localized dynamic radiation force of the ultrasound field to calculate the velocity of the moving object according to Doppler frequency shift. This method, named vibro-acoustic Doppler (VAD), employs two ultrasound beams separated by a slight frequency difference, Δf, transmitting in an X-focal configuration. Both ultrasound beams experience a frequency shift because of the moving objects and their interaction at the joint focal zone produces an acoustic frequency shift occurring around the low-frequency (Δf) acoustic emission signal. The acoustic emission field resulting from the vibration of the moving object is detected and used to calculate its velocity. We report the formula that describes the relation between Doppler frequency shift of the emitted acoustic field and the velocity of the moving object. To verify the theory, we used a string phantom. We also tested our method by measuring fluid velocity in a tube. The results show that the error calculated for both string and fluid velocities is less than 9.1%. Our theory shows that in the worst case, the error is 0.54% for a 25° angle variation for the VAD method compared with an error of -82.6% for a 25° angle variation for a conventional continuous wave Doppler method. An advantage of this method is that, unlike conventional Doppler, it is not sensitive to angles between the ultrasound beams and direction of motion.

Using local correlation tracking to recover solar spectral information from a slitless spectrograph

NASA Astrophysics Data System (ADS)

Courrier, Hans T.; Kankelborg, Charles C.

2018-01-01

The Multi-Order Solar EUV Spectrograph (MOSES) is a sounding rocket instrument that utilizes a concave spherical diffraction grating to form simultaneous images in the diffraction orders m=0, +1, and -1. MOSES is designed to capture high-resolution cotemporal spectral and spatial information of solar features over a large two-dimensional field of view. Our goal is to estimate the Doppler shift as a function of position for every MOSES exposure. Since the instrument is designed to operate without an entrance slit, this requires disentangling overlapping spectral and spatial information in the m=±1 images. Dispersion in these images leads to a field-dependent displacement that is proportional to Doppler shift. We identify these Doppler shift-induced displacements for the single bright emission line in the instrument passband by comparing images from each spectral order. We demonstrate the use of local correlation tracking as a means to quantify these differences between a pair of cotemporal image orders. The resulting vector displacement field is interpreted as a measurement of the Doppler shift. Since three image orders are available, we generate three Doppler maps from each exposure. These may be compared to produce an error estimate.

Measuring Ocean Surface Waves using Signal Reflections from Geostationary Satellites

NASA Astrophysics Data System (ADS)

Ouellette, J. D.; Dowgiallo, D. J.; Hwang, P. A.; Toporkov, J. V.

2017-12-01

The delay-Doppler response of communications signals (such as GNSS) reflected off the ocean surface is well-known to have properties which strongly correlate with surface wind conditions and ocean surface roughness. This study extends reflectometry techniques currently applied to the GNSS constellation to include geostationary communications satellites such as XM Radio. In this study, ocean wind conditions and significant wave height will be characterized using the delay-Doppler response of XM Radio signals reflected off of ocean surface waves. Using geostationary satellites for reflectometry-based remote sensing of oceans presents two primary advantages. First, longer coherent integration times can be achieved, which boosts signal processing gain and allows for finer Doppler resolution. Second, being designed for wide-area broadcast communications, the ground-received power of these geostationary satellite signals tends to be many orders of magnitude stronger than e.g. GNSS signals. Reflections of such signals from the ocean are strong enough to be received well outside of the specular region. This flexibility of viewing geometry allows signal processing to be performed on data received from multiple incidence/reception angles, which can provide a more complete characterization of ocean surface roughness and surface wind vectors. This work will include studies of simulated and measured delay-Doppler behavior of XM Radio signals reflected from dynamic ocean surfaces. Simulation studies will include inter-comparison between a number of hydrodynamic and electromagnetic models. Results from simulations will be presented as delay-Doppler plots and will be compared with delay-Doppler behavior observed in measured data. Measured data will include field campaign results from early- to mid-2017 in which the US Naval Research Laboratory's in-house XM reflectometer-receiver was deployed near the coasts of Virginia and North Carolina to observe reflections from wind-driven ocean waves. Preliminary results from a significant wave height retrieval algorithm will also be presented.

Measurement of Ultracold Neutrons Produced by Using Doppler-shifted Bragg Reflection at a Pulsed-neutron Source

DOE R&D Accomplishments Database

Brun, T. O.; Carpenter, J. M.; Krohn, V. E.; Ringo, G. R.; Cronin, J. W.; Dombeck, T. W.; Lynn, J. W.; Werner, S. A.

1979-01-01

Ultracold neutrons (UCN) have been produced at the Argonne pulsed-neutron source by the Doppler shift of 400-m/s neutrons Bragg reflected from a moving crystal. The peak density of UCN produced at the crystal exceeds 0.1 n/cm{sup 3}.

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.

Optical frequency standards for gravitational wave detection using satellite velocimetry

NASA Astrophysics Data System (ADS)

Vutha, Amar

2015-04-01

Satellite Doppler velocimetry, building on the work of Kaufmann and Estabrook and Wahlquist, is a complementary technique to interferometric methods of gravitational wave detection. This method is based on the fact that the gravitational wave amplitude appears in the apparent Doppler shift of photons propagating from an emitter to a receiver. This apparent Doppler shift can be resolved provided that a frequency standard, capable of quickly averaging down to a high stability, is available. We present a design for a space-capable optical atomic frequency standard, and analyze the sensitivity of satellite Doppler velocimetry for gravitational wave astronomy in the milli-hertz frequency band.

Active Region Moss: Doppler Shifts from Hinode/EIS Observations

NASA Technical Reports Server (NTRS)

Tripathi, Durgesh; Mason, Helen E.; Klimchuk, James A.

2012-01-01

Studying the Doppler shifts and the temperature dependence of Doppler shifts in moss regions can help us understand the heating processes in the core of the active regions. In this paper we have used an active region observation recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) onboard Hinode on 12-Dec- 2007 to measure the Doppler shifts in the moss regions. We have distinguished the moss regions from the rest of the active region by defining a low density cut-off as derived by Tripathi et al. (2010). We have carried out a very careful analysis of the EIS wavelength calibration based on the method described in Young, O Dwyer and Mason (2012). For spectral lines having maximum sensitivity between log T = 5.85 and log T = 6.25 K, we find that the velocity distribution peaks at around 0 km/s with an estimated error of 4 km/s. The width of the distribution decreases with temperature. The mean of the distribution shows a blue shift which increases with increasing temperature and the distribution also shows asymmetries towards blue-shift. Comparing these results with observables predicted from different coronal heating models, we find that these results are consistent with both steady and impulsive heating scenarios. Further observational constraints are needed to distinguish between these two heating scenarios.

First planet confirmation with the exoplanet tracker

NASA Astrophysics Data System (ADS)

van Eyken, Julian C.; Ge, Jian C.; Mahadevan, Suvrath; DeWitt, Curtis; Ren, Deqing

2003-11-01

The Exoplanet Tracker (ET) is a new concept of instrument for measuring stellar radial velocity variations. ET is based on a dispersed fixed-delay interferometer, a combination of Michelson interferometer and medium resolution (R~6700) spectrograph which overlays interferometer fringes on a long-slit stellar spectrum. By measuring shifts in the fringes rather than the Doppler shifts in the absorption lines themselves, we are able to make accurate stellar radial velocity measurements with a high throughput and low cost instrument. The single-order operation of the instrument can also in principle allow multi-object observations. We plan eventually to conduct deep large scale surveys for extra-solar planets using this technique. We present confirmation of the planetary companion to 51Peg from our first stellar observations at the Kitt Peak 2.1m telescope, showing results consistent with previous observations. We outline the fundamentals of the instrument, and summarize our current progress in terms of accuracy and throughput.

Integrated Doppler Correction to TWSTFT Using Round-Trip Measurement

DTIC Science & Technology

2010-11-01

42 nd Annual Precise Time and Time Interval (PTTI) Meeting 251 INTEGRATED DOPPLER CORRECTION TO TWSTFT USING ROUND-TRIP MEASUREMENT Yi...Frequency Transfer ( TWSTFT ) data. It is necessary to correct the diurnal variation for comparing the time-scale difference. We focus on the up-/downlink...delay difference caused by satellite motion. In this paper, we propose to correct the TWSTFT data by using round-trip delay measurement. There are

Sea Ice Detection Based on Differential Delay-Doppler Maps from UK TechDemoSat-1

PubMed Central

Zhu, Yongchao; Yu, Kegen; Zou, Jingui; Wickert, Jens

2017-01-01

Global Navigation Satellite System (GNSS) signals can be exploited to remotely sense atmosphere and land and ocean surface to retrieve a range of geophysical parameters. This paper proposes two new methods, termed as power-summation of differential Delay-Doppler Maps (PS-D) and pixel-number of differential Delay-Doppler Maps (PN-D), to distinguish between sea ice and sea water using differential Delay-Doppler Maps (dDDMs). PS-D and PN-D make use of power-summation and pixel-number of dDDMs, respectively, to measure the degree of difference between two DDMs so as to determine the transition state (water-water, water-ice, ice-ice and ice-water) and hence ice and water are detected. Moreover, an adaptive incoherent averaging of DDMs is employed to improve the computational efficiency. A large number of DDMs recorded by UK TechDemoSat-1 (TDS-1) over the Arctic region are used to test the proposed sea ice detection methods. Through evaluating against ground-truth measurements from the Ocean Sea Ice SAF, the proposed PS-D and PN-D methods achieve a probability of detection of 99.72% and 99.69% respectively, while the probability of false detection is 0.28% and 0.31% respectively. PMID:28704948

3D atom microscopy in the presence of Doppler shift

NASA Astrophysics Data System (ADS)

Rahmatullah; Chuang, You-Lin; Lee, Ray-Kuang; Qamar, Sajid

2018-03-01

The interaction of hot atoms with laser fields produces a Doppler shift, which can severely affect the precise spatial measurement of an atom. We suggest an experimentally realizable scheme to address this issue in the three-dimensional position measurement of a single atom in vapors of rubidium atoms. A three-level Λ-type atom-field configuration is considered where a moving atom interacts with three orthogonal standing-wave laser fields and spatial information of the atom in 3D space is obtained via an upper-level population using a weak probe laser field. The atom moves with velocity v along the probe laser field, and due to the Doppler broadening the precision of the spatial information deteriorates significantly. It is found that via a microwave field, precision in the position measurement of a single hot rubidium atom can be attained, overcoming the limitation posed by the Doppler shift.

The doppler frequency shift caused by the inhomogeneities of a medium induced by pulses of intense laser radiation

NASA Astrophysics Data System (ADS)

Rozanov, N. N.; Kiselev, Al. S.; Kiselev, An. S.

2008-08-01

Self-reflection of pulses of intense laser radiation from an inhomogeneity induced by them in a medium with fast optical nonlinearity is analyzed. The reflected radiation is characterized by a considerable Doppler shift and by a signal magnitude that is sufficient for experimental detection.

Determining the near-surface current profile from measurements of the wave dispersion relation

NASA Astrophysics Data System (ADS)

Smeltzer, Benjamin; Maxwell, Peter; Aesøy, Eirik; Ellingsen, Simen

2017-11-01

The current-induced Doppler shifts of waves can yield information about the background mean flow, providing an attractive method of inferring the current profile in the upper layer of the ocean. We present measurements of waves propagating on shear currents in a laboratory water channel, as well as theoretical investigations of inversion techniques for determining the vertical current structure. Spatial and temporal measurements of the free surface profile obtained using a synthetic Schlieren method are analyzed to determine the wave dispersion relation and Doppler shifts as a function of wavelength. The vertical current profile can then be inferred from the Doppler shifts using an inversion algorithm. Most existing algorithms rely on a priori assumptions of the shape of the current profile, and developing a method that uses less stringent assumptions is a focus of this study, allowing for measurement of more general current profiles. The accuracy of current inversion algorithms are evaluated by comparison to measurements of the mean flow profile from particle image velocimetry (PIV), and a discussion of the sensitivity to errors in the Doppler shifts is presented.

The performance of differential VLBI delay during interplanetary cruise

NASA Technical Reports Server (NTRS)

Moultrie, B.; Wolff, P. J.; Taylor, T. H.

1984-01-01

Project Voyager radio metric data are used to evaluate the orbit determination abilities of several data strategies during spacecraft interplanetary cruise. Benchmark performance is established with an operational data strategy of conventional coherent doppler, coherent range, and explicitly differenced range data from two intercontinental baselines to ameliorate the low declination singularity of the doppler data. Employing a Voyager operations trajectory as a reference, the performance of the operational data strategy is compared to the performances of data strategies using differential VLBI delay data (spacecraft delay minus quasar delay) in combinations with the aforementioned conventional data types. The comparison of strategy performances indicates that high accuracy cruise orbit determination can be achieved with a data strategy employing differential VLBI delay data, where the quantity of coherent radio metric data has been greatly reduced.

Solitary waves of surface plasmon polariton via phase shifts under Doppler broadening and Kerr nonlinearity

NASA Astrophysics Data System (ADS)

Ahmad, S.; Ahmad, A.; Bacha, B. A.; Khan, A. A.; Abdul Jabar, M. S.

2017-12-01

Surface Plasmon Polaritons (SPPs) are theoretically investigated at the interface of a dielectric metal and gold. The output pulse from the dielectric is used as the input pulse for the generation of SPPs. The SPPs show soliton-like behavior at the interface. The solitary form of a SPP is maintained under the effects of Kerr nonlinearity, Doppler broadening and Fresnel dragging whereas its phase shift is significantly modified. A 0.3radian phase shift is calculated in the presence of both Kerr nonlinearity and Fresnel dragging in the absence of plasma motion. The phase shift is enhanced to 60radian due to the combined effect of Doppler broadening, Kerr nonlinearity and Fresnel dragging. The results may have significant applications in nano-photonics, optical tweezers, photovoltaic devices, plasmonster and sensing technology.

Statistics of biospeckles with application to diagnostics of periodontitis

NASA Astrophysics Data System (ADS)

Starukhin, Pavel Y.; Kharish, Natalia A.; Sedykh, Alexey V.; Ulyanov, Sergey S.; Lepilin, Alexander V.; Tuchin, Valery V.

1999-04-01

Results of Monte-Carlo simulations Doppler shift are presented for the model of random medium that contain moving particles. The single-layered and two-layered configurations of the medium are considered. Doppler shift of the frequency of laser light is investigated as a function of such parameters as absorption coefficient, scattering coefficient, and thickness of the medium. Possibility of application of speckle interferometry for diagnostics in dentistry has been analyzed. Problem of standardization of the measuring procedure has been studied. Deviation of output characteristics of Doppler system for blood microcirculation measurements has been investigated. Dependence of form of Doppler spectrum on the number of speckles, integration by aperture, has been studied in experiments in vivo.

Mercury exosphere. III: Energetic characterization of its sodium component

NASA Astrophysics Data System (ADS)

Leblanc, Francois; Chaufray, Jean-Yves; Doressoundiram, Alain; Berthelier, Jean-Jacques; Mangano, Valeria; López-Ariste, Arturo; Borin, Patrizia

2013-04-01

Mercury's sodium exosphere has been observed only few times with high spectral resolution from ground based observatories enabling the analysis of the emission spectra. These observations highlighted the energetic state of the sodium exospheric atoms relative to the surface temperature. More recently, the Doppler shift of the exospheric Na atoms was measured and interpreted as consistent with an exosphere moving outwards from the subsolar point (Potter, A.E., Morgan, T.H., Killen, R.E. [2009]. Icarus 204, 355-367). Using THEMIS solar telescope, we observed Mercury's sodium exosphere with very high spectral resolution at two opposite positions of its orbit. Using this very high spectral resolution and the scanning capabilities of THEMIS, we were able to reconstruct the 2D spatial distributions of the Doppler shifts and widths of the sodium atomic Na D2 and D1 lines. These observations revealed surprisingly large Doppler shift as well as spectral width consistent with previous observations. Starting from our 3D model of Mercury Na exosphere (Mercury Exosphere Global Circulation Model, Leblanc, F., Johnson, R.E. [2010]. Icarus 209, 280-300), we coupled this model with a 3D radiative transfer model described in a companion paper (Chaufray, J.Y., Leblanc, F. [2013]. Icarus, submitted for publication) which allows us to properly treat the non-maxwellian state of the simulated sodium exospheric population. Comparisons between THEMIS observations and simulations suggest that the previously observed energetic state of the Na exosphere might be essentially explained by a state of the Na exospheric atoms far from thermal equilibrium along with the Doppler shift dispersion of the Na atoms induced by the solar radiation pressure. However, the Doppler shift of the spectral lines cannot be explained by our modelling, suggesting either an exosphere spatially structured very differently than in our model or the inaccuracy of the spectral calibration when deriving the Doppler shift.

An Improved Wind Speed Retrieval Algorithm For The CYGNSS Mission

NASA Astrophysics Data System (ADS)

Ruf, C. S.; Clarizia, M. P.

2015-12-01

The NASA spaceborne Cyclone Global Navigation Satellite System (CYGNSS) mission is a constellation of 8 microsatellites focused on tropical cyclone (TC) inner core process studies. CYGNSS will be launched in October 2016, and will use GPS-Reflectometry (GPS-R) to measure ocean surface wind speed in all precipitating conditions, and with sufficient frequency to resolve genesis and rapid intensification. Here we present a modified and improved version of the current baseline Level 2 (L2) wind speed retrieval algorithm designed for CYGNSS. An overview of the current approach is first presented, which makes use of two different observables computed from 1-second Level 1b (L1b) delay-Doppler Maps (DDMs) of radar cross section. The first observable, the Delay-Doppler Map Average (DDMA), is the averaged radar cross section over a delay-Doppler window around the DDM peak (i.e. the specular reflection point coordinate in delay and Doppler). The second, the Leading Edge Slope (LES), is the leading edge of the Integrated Delay Waveform (IDW), obtained by integrating the DDM along the Doppler dimension. The observables are calculated over a limited range of time delays and Doppler frequencies to comply with baseline spatial resolution requirements for the retrieved winds, which in the case of CYGNSS is 25 km. In the current approach, the relationship between the observable value and the surface winds is described by an empirical Geophysical Model Function (GMF) that is characterized by a very high slope in the high wind regime, for both DDMA and LES observables, causing large errors in the retrieval at high winds. A simple mathematical modification of these observables is proposed, which linearizes the relationship between ocean surface roughness and the observables. This significantly reduces the non-linearity present in the GMF that relate the observables to the wind speed, and reduces the root-mean square error between true and retrieved winds, particularly in the high wind regime. The modified retrieval algorithm is tested using GPS-R synthetic data simulated using an End-to-End Simulator (E2ES) developed for CYGNSS, and it is then applied to GPS-R data from the TechDemoSat-1 (TDS-1) GPS-R experiment. An analysis of the algorithm performances for both synthetic and real data is illustrated.

Servomechanism for Doppler shift compensation in optical correlator for synthetic aperture radar

NASA Technical Reports Server (NTRS)

Constaninides, N. J.; Bicknell, T. J. (Inventor)

1980-01-01

A method and apparatus for correcting Doppler shifts in synthetic aperture radar data is described. An optical correlator for synthetic aperture radar data has a means for directing a laser beam at a signal film having radar return pulse intensity information recorded on it. A resultant laser beam passes through a range telescope, an azimuth telescope, and a Fourier transform filter located between the range and azimuth telescopes, and forms an image for recording on an image film. A compensation means for Doppler shift in the radar return pulse intensity information includes a beam splitter for reflecting the modulated laser beam, after having passed through the Fourier transform filter, to a detection screen having two photodiodes mounted on it.

Using Doppler Shifts of GPS Signals To Measure Angular Speed

NASA Technical Reports Server (NTRS)

Campbell, Charles E., Jr.

2006-01-01

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

Structured-illumination photoacoustic Doppler flowmetry of axial flow in homogeneous scattering media

NASA Astrophysics Data System (ADS)

Zhang, Ruiying; Yao, Junjie; Maslov, Konstantin I.; Wang, Lihong V.

2013-08-01

We propose a method for photoacoustic flow measurement based on the Doppler effect from a flowing homogeneous medium. Excited by spatially modulated laser pulses, the flowing medium induces a Doppler frequency shift in the received photoacoustic signals. The frequency shift is proportional to the component of the flow speed projected onto the acoustic beam axis, and the sign of the shift reflects the flow direction. Unlike conventional flowmetry, this method does not rely on particle heterogeneity in the medium; thus, it can tolerate extremely high particle density. A red-ink phantom flowing in a tube immersed in water was used to validate the method in both the frequency and time domains. The phantom flow immersed in an intralipid solution was also measured.

Swept-source based, single-shot, multi-detectable velocity range Doppler optical coherence tomography

PubMed Central

Meemon, Panomsak; Rolland, Jannick P.

2010-01-01

Phase-Resolved Doppler Optical Coherence Tomography (PR-DOCT) allows visualization and characterization of the location, direction, velocity, and profile of flow activity embedded in a static sample structure. The detectable Velocity Dynamic Range (VDR) of each particular PR-DOCT system is governed by a detectable Doppler phase shift, a flow angle, and an acquisition time interval used to determine the Doppler phase shift. In general, the lower boundary of the detectable Doppler phase shift is limited by the phase stability of the system, while the upper boundary is limited by the π phase ambiguity. For a given range of detectable Doppler phase shift, shortening the acquisition duration will increase not only the maximum detectable velocity but unfortunately also the minimum detectable velocity, which may lead to the invisibility of a slow flow. In this paper, we present an alternative acquisition scheme for PR-DOCT that extends the lower limit of the velocity dynamic range, while maintaining the maximum detectable velocity, hence increasing the overall VDR of PR-DOCT system. The essence of the approach is to implement a technique of multi-scale measurement to simultaneously acquire multiple VDRs in a single measurement. We demonstrate an example of implementation of the technique in a dual VDR DOCT, where two Doppler maps having different detectable VDRs were simultaneously detected, processed, and displayed in real time. One was a fixed VDR DOCT capable of measuring axial velocity of up to 10.9 mm/s without phase unwrapping. The other was a variable VDR DOCT capable of adjusting its detectable VDR to reveal slow flow information down to 11.3 μm/s. The technique is shown to effectively extend the overall detectable VDR of the PR-DOCT system. Examples of real time Doppler imaging of an African frog tadpole are demonstrated using the dual-VDR DOCT system. PMID:21258521

Ocean wind and roughness retrieval with spaceborne GNSS-Reflectometry: first results from the UK TechDemoSat-1 mission

NASA Astrophysics Data System (ADS)

Gommenginger, C.; Foti, G.

2015-12-01

GNSS-Reflectometry (GNSS-R) is a ground breaking ocean remote sensing technique that exploits reflected signals from Global Navigation Satellite Systems (GNSS) to retrieve geophysical information about the ocean surface such as near-surface winds above the ocean. Adopting a bistatic radar configuration, signals emitted by GNSS satellites flying in Medium Earth Orbit (MEO) are received by a GNSS-R receiver on a Low Earth Orbit (LEO) observatory utilizing both a zenith antenna to receive the direct signal from the GNSS and a nadir antenna to acquire the earth-reflected signal. The reflected signal originated from a glistening zone on the ocean surface sited around the Specular Point (SP), the geometrical point on the Earth surface where GNSS signals are forward scattered in the specular direction. The two signals are correlated for different shifts in time (delay) and frequency (Doppler) relative to the specular point (SP) to produce a so-called Delay Doppler Map (DDM) of forward-scattered electromagnetic power over the surface. This paper gives an overview of recent results obtained for wind speed and ocean roughness retrieval with the Low-Earth-Orbiting UK TechDemoSat-1 satellite (TDS-1). Launched in July 2014, TDS-1 provides the first new spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R) data since the pioneering UK-Disaster Monitoring Mission experiment in 2003. We present examples of onboard-processed delay Doppler Maps, including excellent DDM data quality for winds up to 27.9 m/s. The relationship between observed GNSS-R signals, wind speed and ocean roughness is explored using global collocated matchup datasets with METOP ASCAT scatterometer winds and WaveWatch3 numerical wave model output. Several Geophysical Model Functions are proposed, that make it possible to retrieve wind speed without bias and with a precision of the order of 2 m/s even without calibration. This work demonstrates the capabilities of low-cost, low-mass, low-power GNSS-R receivers ahead of their launch on the NASA CYGNSS constellation in 2016.

Frequency Correction for MIRO Chirp Transformation Spectroscopy Spectrum

NASA Technical Reports Server (NTRS)

Lee, Seungwon

2012-01-01

This software processes the flyby spectra of the Chirp Transform Spectrometer (CTS) of the Microwave Instrument for Rosetta Orbiter (MIRO). The tool corrects the effect of Doppler shift and local-oscillator (LO) frequency shift during the flyby mode of MIRO operations. The frequency correction for CTS flyby spectra is performed and is integrated with multiple spectra into a high signal-to-noise averaged spectrum at the rest-frame RF frequency. This innovation also generates the 8 molecular line spectra by dividing continuous 4,096-channel CTS spectra. The 8 line spectra can then be readily used for scientific investigations. A spectral line that is at its rest frequency in the frame of the Earth or an asteroid will be observed with a time-varying Doppler shift as seen by MIRO. The frequency shift is toward the higher RF frequencies on approach, and toward lower RF frequencies on departure. The magnitude of the shift depends on the flyby velocity. The result of time-varying Doppler shift is that of an observed spectral line will be seen to move from channel to channel in the CTS spectrometer. The direction (higher or lower frequency) in the spectrometer depends on the spectral line frequency under consideration. In order to analyze the flyby spectra, two steps are required. First, individual spectra must be corrected for the Doppler shift so that individual spectra can be superimposed at the same rest frequency for integration purposes. Second, a correction needs to be applied to the CTS spectra to account for the LO frequency shifts that are applied to asteroid mode.

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.

Blood flow velocity measurement by endovascular Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

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

2013-03-01

Blood flow velocity and volumetric flow measurements are important parameters for assessment of the severity of stenosis and the outcome of interventional therapy. However, feasibility of intravascular flow measurement using a rotational catheter based phase resolved Doppler optical coherence tomography (DOCT) is difficult. Motion artefacts induced by the rotating optical imaging catheter, and the radially dependent noise background of measured Doppler signals are the main challenges encountered. In this study, a custom-made data acquisition system and developed algorithms to remove non-uniform rotational distortion (NURD) induced phase shift artefact by tracking the phase shift observed on catheter sheath. The flow velocity is calculated from Doppler shift obtained by Kasai autocorrelation after motion artefact removal. Blood flow velocity profiles in porcine carotid arteries in vivo were obtained at 100 frames/s with 500 A-lines/frame and DOCT images were taken at 20 frames/s with 2500 A-lines/frame. Time-varying velocity profiles were obtained at an artery branch. Furthermore, the identification of a vein adjacent to the catheterized vessel based on the color Doppler signal was also observed. The absolute measurement of intravascular flow using a rotating fiber catheter can provide insights to different stages of interventional treatment of stenosis in carotid artery.

Non-Data Aided Doppler Shift Estimation for Underwater Acoustic Communication

DTIC Science & Technology

2014-05-01

in underwater acoustic wireless sensor networks . We analyzed the data collected from our experiments using non-data aided (blind) techniques such as...investigated different methods for blind Doppler shift estimation and compensation for a single carrier in underwater acoustic wireless sensor ...distributed underwater sensor networks . Detailed experimental and simulated results based on second order cyclostationary features of the received signals

Combined dispersive/interference spectroscopy for producing a vector spectrum

DOEpatents

Erskine, David J.

2002-01-01

A method of measuring the spectral properties of broadband waves that combines interferometry with a wavelength disperser having many spectral channels to produce a fringing spectrum. Spectral mapping, Doppler shifts, metrology of angles, distances and secondary effects such as temperature, pressure, and acceleration which change an interferometer cavity length can be measured accurately by a compact instrument using broadband illumination. Broadband illumination avoids the fringe skip ambiguities of monochromatic waves. The interferometer provides arbitrarily high spectral resolution, simple instrument response, compactness, low cost, high field of view and high efficiency. The inclusion of a disperser increases fringe visibility and signal to noise ratio over an interferometer used alone for broadband waves. The fringing spectrum is represented as a wavelength dependent 2-d vector, which describes the fringe amplitude and phase. Vector mathematics such as generalized dot products rapidly computes average broadband phase shifts to high accuracy. A Moire effect between the interferometer's sinusoidal transmission and the illumination heterodynes high resolution spectral detail to low spectral detail, allowing the use of a low resolution disperser. Multiple parallel interferometer cavities of fixed delay allow the instantaneous mapping of a spectrum, with an instrument more compact for the same spectral resolution than a conventional dispersive spectrometer, and not requiring a scanning delay.

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

Schwartz, S. B.; Wrede, C.; Bennett, M. B.

Background: The Doppler broadening of gamma-ray peaks is due to nuclear recoil from beta-delayed nucleon emission can be used to measure the energies of the nucleons. This method has never been tested using beta-delayed proton emission or applied to a recoil heavier than A = 10. Purpose: To test and apply this Doppler broadening method using gamma-ray peaks from the P-26(beta p gamma)Al-25 decay sequence. Methods: A fast beam of P-26 was implanted into a planar Ge detector, which was used as a P-26 beta-decay trigger. The SeGA array of high-purity Ge detectors was used to detect gamma rays frommore » the P-26(beta p gamma)Al-25 decay sequence. Results: Radiative Doppler broadening in beta-delayed proton-gamma decay was observed for the first time. Moreover, the Doppler broadening analysis method was verified using the 1613-keV gamma-ray line for which the proton energies were previously known. The 1776-keV gamma ray de-exciting the 2720 keV Al-25 level was observed in P-26(beta p gamma)Al-25 decay for the first time and used to determine that the center-of-mass energy of the proton emission feeding the 2720-keV level is 5.1 +/- 1.0 (stat.) +/- 0.6 (syst.) MeV, corresponding to a Si-26 excitation energy of 13.3 +/- 1.0 (stat.) +/- 0.6 (syst.) MeV for the proton-emitting level. Conclusions: Finally, the Doppler broadening method has been demonstrated to provide practical measurements of the energies for beta-delayed nucleon emissions populating excited states of nuclear recoils at least as heavy as A = 25.« less

Associations Between Renal Duplex Parameters and Adverse Cardiovascular Events in the Elderly: A Prospective Cohort Study

PubMed Central

Pearce, Jeffrey D.; Craven, Timothy E.; Edwards, Matthew S.; Corriere, Matthew A.; Crutchley, Teresa A.; Fleming, Shawn H.; Hansen, Kimberley J.

2010-01-01

Background Atherosclerotic renovascular disease is associated with an increased risk of cardiovascular disease (CVD) events. This study examines associations between Doppler-derived parameters from the renal artery and renal parenchyma and all-cause mortality and fatal and nonfatal CVD events in a cohort of elderly Americans. Study Design Cohort study. Setting A subset of participants from the Cardiovascular Health Study (CHS). Through an ancillary study, 870 (70% recruitment) Forsyth County, NC, CHS participants consented to undergo renal duplex sonography to define the prevalence of renovascular disease in the elderly, resulting in 726 (36% men; mean age, 77 years) technically adequate complete studies included in this investigation. Predictor Renal duplex sonography–derived Doppler signals from the main renal arteries and renal parenchyma. Spectral analysis from Doppler-shifted frequencies and angle of insonation were used to estimate renal artery peak systolic and end diastolic velocity (both in meters per second). Color Doppler was used to identify the corticomedullary junction. Using a 3-mm Doppler sample, the parenchymal peak systolic and end diastolic frequency shift (both in kilohertz) were obtained. Resistive index was calculated as (1 – [end diastolic frequency shift/peak systolic frequency shift]) using Doppler samples from the hilar arteries of the left or right kidney with the higher main renal artery peak systolic velocity. Outcomes & Measurements Proportional hazard regression analysis was used to determine associations between renal duplex sonography–derived Doppler signals and CVD events and all-cause mortality adjusted for accepted cardiovascular risk factors. Index CVD outcomes were defined as coronary events (angina, myocardial infarction, and coronary artery bypass grafting/percutaneous coronary intervention), cerebrovascular events (stroke or transient ischemic attack), and any CVD event (angina, congestive heart failure, myocardial infarction, stroke, transient ischemic attack, and coronary artery bypass grafting [CABG]/percutaneous transluminal coronary intervention [PTCI]). Results During follow-up, 221 deaths (31%), 229 CVD events (32%), 122 coronary events (17%), and 92 cerebrovascular events (13%) were observed. Renal duplex sonography–derived Doppler signals from the renal parenchyma were associated independently with all-cause mortality and CVD outcomes. In particular, increased parenchymal end diastolic frequency shift was associated significantly with any CVD event (HR, 0.73; 95% CI, 0.62-0.87; P < 0.001). Marginally significant associations were observed between increases in parenchymal end diastolic frequency shift and decreased risk of death (HR, 0.86; 95% CI, 0.73-1.00; P = 0.06) and decreased risk of cerebrovascular events (HR, 0.78; 95% CI, 0.61-1.01; P = 0.06). Parenchymal end diastolic frequency shift was not significantly predictive of coronary events (HR, 0.84; 95% CI, 0.67-1.06; P = 0.1). Limitations CHS participants showed a “healthy cohort” effect that may underestimate the rate of CVD events in the general population. Conclusion Renal duplex sonographic Doppler signals from the renal parenchyma showed significant associations with subsequent CVD events after controlling for other significant risk factors. In particular, a standard deviation increase in parenchymal end diastolic frequency shift was associated with 27% risk reduction in any CVD event. PMID:20116688

Absolute Doppler shift calibration of laser induced fluorescence signals using optogalvanic measurements in a hollow cathode lamp

NASA Technical Reports Server (NTRS)

Ruyten, Wilhelmus M.; Keefer, Dennis

1992-01-01

The paper investigates the use of optogalvanic (OG) measurements on the neutral 3P1 and 3P2 levels of argon in a hollow cathode lamp for the purpose of calibrating Doppler shifts of laser-induced fluorescence signals from an arcjet plume. It is shown that, even with non-Doppler-free OG detection, accuracy to better than 10 MHz is possible but that, depending on the experiment geometry, corrections of 10-35 MHz may be necessary to offset small axial drift velocities of neutral atoms in the hollow cathode lamp.

Development of the One-Sided Nonlinear Adaptive Doppler Shift Estimation

NASA Technical Reports Server (NTRS)

Beyon, Jeffrey Y.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.; Serror, Judith A.

2009-01-01

The new development of a one-sided nonlinear adaptive shift estimation technique (NADSET) is introduced. The background of the algorithm and a brief overview of NADSET are presented. The new technique is applied to the wind parameter estimates from a 2-micron wavelength coherent Doppler lidar system called VALIDAR located in NASA Langley Research Center in Virginia. The new technique enhances wind parameters such as Doppler shift and power estimates in low Signal-To-Noise-Ratio (SNR) regimes using the estimates in high SNR regimes as the algorithm scans the range bins from low to high altitude. The original NADSET utilizes the statistics in both the lower and the higher range bins to refine the wind parameter estimates in between. The results of the two different approaches of NADSET are compared.

Time delay occultation data of the Helios spacecraft for probing the electron density distribution in the solar corona

NASA Technical Reports Server (NTRS)

Edenhofer, P.; Lueneburg, E.; Esposito, P. B.; Martin, W. L.; Zygielbaum, A. I.; Hansen, R. T.; Hansen, S. F.

1978-01-01

S-band time delay measurements were collected from the spacecraft Helios A and B during three solar occultations in 1975/76 within heliocentric distances of about 3 and 215 earth radius in terms of range, Doppler frequency shift, and electron content. Characteristic features of measurement and data processing are described. Typical data sets are discussed to probe the electron density distribution near the sun (west and east limb as well) including the outer and extended corona. Steady-state and dynamical aspects of the solar corona are presented and compared with earth-bound-K-coronagraph measurements. Using a weighted least squares estimation, parameters of an average coronal electron density profile are derived in a preliminary analysis to yield electron densities at r = 3, 65, 215 earth radius. Transient phenomena are discussed and a velocity of propagation v is nearly equal to 900 km/s is determined for plasma ejecta from a solar flare observed during an extraordinary set of Helios B electron content measurements.

Speed of light demonstration using Doppler beat

NASA Astrophysics Data System (ADS)

Bernal, Luis; Bilbao, Luis

2018-05-01

From an apparatus previously designed for measuring the Doppler shift using a rotating mirror, an improved, versatile version was developed for speed of light demonstrations in a classroom or a teaching laboratory. By adding a second detector and adequate beam-splitter and mirrors, three different configurations are easily assembled. One configuration is used for time-of-flight measurements between a near and a far detector, allowing one to measure the speed of light provided that the path length between detectors is known. Another variation is the interferometric method obtained by superposing the far and near signals in such a way that a minimum of the combined signal is obtained when the time delay makes the signals arrive out of phase by π radians. Finally, the standard Doppler configuration allows the measurement of the frequency beat as a function of the rotation frequency. The main advantages of the apparatus are (a) the experimental setup is simple and completely accessible to undergraduate students, (b) the light is visible, students can see the rays, which, with the use of appropriate screens, can be blocked at any point along their paths, (c) the experiment can take place entirely within the teaching laboratory or demonstration room (using the interferometric method, the shortest distance to the far mirror was as small as 0.5 m), and (d) different configurations can be built, including some economical setups within the budget of teaching laboratories.

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.

Graphical Representation of the Doppler Shift: Classical and Relativistic

ERIC Educational Resources Information Center

Rojas, R.; Fuster, G.

2007-01-01

The Doppler shift is a frequency change of a repetitive effect, as measured by a receiver, due to the motion of the wave emitter, to the motion of the wave receiver, or both. A demonstration of the effect is provided by the sound of a car's horn that changes from a higher pitch to a lower pitch when a car drives past. Most derivations of the…

Imaging nanoparticle flow using magneto-motive optical Doppler tomography.

PubMed

Kim, Jeehyun; Oh, Junghwan; Milner, Thomas E; Nelson, J Stuart

2007-01-24

We introduce a novel approach for imaging solutions of superparamagnetic iron oxide (SPIO) nanoparticles using magneto-motive optical Doppler tomography (MM-ODT). MM-ODT combines an externally applied temporally oscillating high-strength magnetic field with ODT to detect nanoparticles flowing through a microfluidic channel. A solenoid with a cone-shaped ferrite core extensively increased the magnetic field strength (B(max) = 1 T, [Formula: see text]) at the tip of the core and also focused the magnetic field in microfluidic channels containing nanoparticle solutions. Nanoparticle contrast was demonstrated in a microfluidic channel filled with an SPIO solution by imaging the Doppler frequency shift which was observed independently of the nanoparticle flow rate and direction. Results suggest that MM-ODT may be applied to image Doppler shift of SPIO nanoparticles in microfluidic flows with high contrast.

Methods of Laser, Non-Linear, and Fiber Optics in Studying Fundamental Problems of Astrophysics

NASA Astrophysics Data System (ADS)

Kryukov, P. G.

2018-04-01

Precise measurements of Doppler shifts of lines in stellar spectra allowing the radial velocity to be measured are an important field of astrophysical studies. A remarkable feature of the Doppler spectroscopy is the possibility to reliably measure quite small variations of the radial velocities (its acceleration, in fact) during long periods of time. Influence of a planet on a star is an example of such a variation. Under the influence of a planet rotating around a star, the latter demonstrates periodic motion manifested in the Doppler shift of the stellar spectrum. Precise measurements of this shift made it possible to indirectly discover planets outside the Solar system (exoplanets). Along with this, searching for Earth-type exoplanets within the habitable zone is an important challenge. For this purpose, accuracy of spectral measurements has to allow one to determine radial velocity variations at the level of centimeters per second during the timespans of about a year. Suchmeasurements on the periods of 10-15 years also would serve as a directmethod for determination of assumed acceleration of the Universe expansion. However, the required accuracy of spectroscopic measurements for this exceeds the possibilities of the traditional spectroscopy (an iodine cell, spectral lamps). Methods of radical improvement of possibilities of astronomical Doppler spectroscopy allowing one to attain the required measurement accuracy of Doppler shifts are considered. The issue of precise calibration can be solved through creating a system of a laser optical frequency generator of an exceptionally high accuracy and stability.

Software for a GPS-Reflection Remote-Sensing System

NASA Technical Reports Server (NTRS)

Lowe, Stephen

2003-01-01

A special-purpose software Global Positioning System (GPS) receiver designed for remote sensing with reflected GPS signals is described in Delay/Doppler-Mapping GPS-Reflection Remote-Sensing System (NPO-30385), which appears elsewhere in this issue of NASA Tech Briefs. The input accepted by this program comprises raw (open-loop) digitized GPS signals sampled at a rate of about 20 MHz. The program processes the data samples to perform the following functions: detection of signals; tracking of phases and delays; mapping of delay, Doppler, and delay/Doppler waveforms; dual-frequency processing; coherent integrations as short as 125 s; decoding of navigation messages; and precise time tagging of observable quantities. The software can perform these functions on all detectable satellite signals without dead time. Open-loop data collected over water, land, or ice and processed by this software can be further processed to extract geophysical information. Possible examples include mean sea height, wind speed and direction, and significant wave height (for observations over the ocean); bistatic-radar terrain images and measures of soil moisture and biomass (for observations over land); and estimates of ice age, thickness, and surface density (for observations over ice).

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

NASA Technical Reports Server (NTRS)

Mazumder, M. K.

1970-01-01

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

A Doppler-Cancellation Technique for Determining the Altitude Dependence of Gravitational Red Shift in an Earth Satellite

NASA Technical Reports Server (NTRS)

Badessa, R. S.; Kent, R. L.; Nowell, J. C.; Searle, C. L.

1960-01-01

A cancellation technique permits measurement of the frequency of a source moving relative to an observer without the obscuring effect of first-order Doppler shifts. The application of this method to a gravitational red shift experiment involving the use of an earth satellite containing a highly stable oscillator is described. The rapidity with which a measurement can be made permits the taking of data at various altitudes in a given elliptical orbit. Tropospheric and ionospheric effects upon the accuracy of results are estimated.

Trans-skull ultrasonic Doppler system aided by fuzzy logic

NASA Astrophysics Data System (ADS)

Hata, Yutaka; Nakamura, Masato; Yagi, Naomi; Ishikawa, Tomomoto

2012-06-01

This paper describes a trans-skull ultrasonic Doppler system for measuring the blood flow direction in brain under skull. In this system, we use an ultrasonic array probe with the center frequency of 1.0 MHz. The system determines the fuzzy degree of blood flow by Doppler Effect, thereby it locates blood vessel. This Doppler Effect is examined by the center of gravity shift of the frequency magnitudes. In in-vitro experiment, a cow bone was employed as the skull, and three silicon tubes were done as blood vessels, and bubble in water as blood. We received the ultrasonic waves through a protein, the skull and silicon tubes in order. In the system, fuzzy degrees are determined with respect to the Doppler shift, amplitude of the waves and attenuation of the tissues. The fuzzy degrees of bone and blood direction are calculated by them. The experimental results showed that the system successfully visualized the skull and flow direction, compared with the location and flow direction of the phantom. Thus, it detected the flow direction by Doppler Effect under skull, and automatically extracted the region of skull and blood vessel.

VLF wave growth and discrete emission triggering in the magnetosphere - A feedback model

NASA Technical Reports Server (NTRS)

Helliwell, R. A.; Inan, U. S.

1982-01-01

A simple nonlinear feedback model is presented to explain VLF wave growth and emission triggering observed in VLF transmission experiments. The model is formulated in terms of the interaction of electrons with a slowly varying wave in an inhomogeneous medium as in an unstable feedback amplifier with a delay line; constant frequency oscillations are generated on the magnetic equator, while risers and fallers are generated on the downstream and upstream sides of the equator, respectively. Quantitative expressions are obtained for the stimulated radiation produced by energy exchanged between energetic electrons and waves by Doppler-shifted cyclotron resonance, and feedback between the stimulated radiation and the phase bunched currents is incorporated in terms of a two-port discrete time model. The resulting model is capable of explaining the observed temporal growth and saturation effects, phase advance, retardation or frequency shift during growth in the context of a single parameter depending on the energetic particle distribution function, as well as pretermination triggering.

Special relativity corrections for space-based lidars.

PubMed

Gudimetla, V S; Kavaya, M J

1999-10-20

The theory of special relativity is used to analyze some of the physical phenomena associated with space-based coherent Doppler lidars aimed at Earth and the atmosphere. Two important cases of diffuse scattering and retroreflection by lidar targets are treated. For the case of diffuse scattering, we show that for a coaligned transmitter and receiver on the moving satellite, there is no angle between transmitted and returned radiation. However, the ray that enters the receiver does not correspond to a retroreflected ray by the target. For the retroreflection case there is misalignment between the transmitted ray and the received ray. In addition, the Doppler shift in the frequency and the amount of tip for the receiver aperture when needed are calculated. The error in estimating wind because of the Doppler shift in the frequency due to special relativity effects is examined. The results are then applied to a proposed space-based pulsed coherent Doppler lidar at NASA's Marshall Space Flight Center for wind and aerosol backscatter measurements. The lidar uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and the received frequencies to determine the atmospheric wind velocities. We show that the special relativity effects are small for the proposed system.

Special Relativity Corrections for Space-Based Lidars

NASA Technical Reports Server (NTRS)

RaoGudimetla, Venkata S.; Kavaya, Michael J.

1999-01-01

The theory of special relativity is used to analyze some of the physical phenomena associated with space-based coherent Doppler lidars aimed at Earth and the atmosphere. Two important cases of diffuse scattering and retroreflection by lidar targets are treated. For the case of diffuse scattering, we show that for a coaligned transmitter and receiver on the moving satellite, there is no angle between transmitted and returned radiation. However, the ray that enters the receiver does not correspond to a retroreflected ray by the target. For the retroreflection case there is misalignment between the transmitted ray and the received ray. In addition, the Doppler shift in the frequency and the amount of tip for the receiver aperture when needed are calculated, The error in estimating wind because of the Doppler shift in the frequency due to special relativity effects is examined. The results are then applied to a proposed space-based pulsed coherent Doppler lidar at NASA's Marshall Space Flight Center for wind and aerosol backscatter measurements. The lidar uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and the received frequencies to determine the atmospheric wind velocities. We show that the special relativity effects are small for the proposed system.

Transcranial Doppler ultrasound in the diagnosis of brain death. Is it useful or does it delay the diagnosis?

PubMed

Escudero, D; Otero, J; Quindós, B; Viña, L

2015-05-01

Transcranial Doppler ultrasound is able to demonstrate cerebral circulatory arrest associated to brain death, being especially useful in sedated patients, or in those in which complete neurological exploration is not possible. Transcranial Doppler ulstrasound is a portable, noninvasive and high-availability technique. Among its limitations, mention must be made of the absence of acoustic windows and false-negative cases. In patients clinically diagnosed with brain death, with open skulls or with anoxia as the cause of death, cerebral blood flow can be observed by ultrasound, since cerebral circulatory arrest is not always synchronized to the clinical diagnosis. The diagnostic rate is therefore time-dependent, and this fact that must be recognized in order to avoid delays in death certification. Despite its limitations, transcranial Doppler ulstrasound helps solve common diagnostic problems, avoids the unnecessary consumption of resources, and can optimize organ harvesting for transplantation. Copyright © 2014 Elsevier España, S.L.U. and SEMICYUC. All rights reserved.

Spread-Spectrum Carrier Estimation With Unknown Doppler Shift

NASA Technical Reports Server (NTRS)

DeLeon, Phillip L.; Scaife, Bradley J.

1998-01-01

We present a method for the frequency estimation of a BPSK modulated, spread-spectrum carrier with unknown Doppler shift. The approach relies on a classic periodogram in conjunction with a spectral matched filter. Simulation results indicate accurate carrier estimation with processing gains near 40. A DSP-based prototype has been implemented for real-time carrier estimation for use in New Mexico State University's proposal for NASA's Demand Assignment Multiple Access service.

Third-order-harmonic generation in coherently spinning molecules

NASA Astrophysics Data System (ADS)

Prost, E.; Zhang, H.; Hertz, E.; Billard, F.; Lavorel, B.; Bejot, P.; Zyss, Joseph; Averbukh, Ilya Sh.; Faucher, O.

2017-10-01

The rotational Doppler effect occurs when circularly polarized light interacts with a rotating anisotropic material. It is manifested by the appearance of a spectral shift ensuing from the transfer of angular momentum and energy between radiation and matter. Recently, we reported terahertz-range rotational Doppler shifts produced in third-order nonlinear optical conversion [O. Faucher et al., Phys. Rev. A 94, 051402(R) (2016), 10.1103/PhysRevA.94.051402]. The experiment was performed in an ensemble of coherently spinning molecules prepared by a short laser pulse exhibiting a twisted linear polarization. The present work provides an extensive analysis of the rotational Doppler effect in third-order-harmonic generation from spinning linear molecules. The underlying physics is investigated both experimentally and theoretically. The implication of the rotational Doppler effect in higher-order processes like high-order-harmonic generation is discussed.

Zero Autocorrelation Waveforms: A Doppler Statistic and Multifunction Problems

DTIC Science & Technology

2006-01-01

by ANSI Std Z39-18 It is natural to refer to A as the ambiguity function of u, since in the usual setting on the real line R, the analogue ambiguity...Doppler statistic |Cu,uek(j)| is excellent and provable for detecting deodorized Doppler frequency shift [11] (see Fig. 2). Also, if one graphs only

Advanced Receiver For Phase-Shift-Keyed Signals

NASA Technical Reports Server (NTRS)

Hinedi, Sami M.

1992-01-01

ARX II is second "breadboard" version of advanced receiver, a hybrid digital/analog receiving subsystem, extracting symbols and Doppler shifts from weak phase-shift-keyed signals. Useful in terrestrial digital communication systems.

Persistent Doppler Shift Oscillations Observed with HINODE-EIS in the Solar Corona: Spectroscopic Signatures of Alfvenic Waves and Recurring Upflows

NASA Technical Reports Server (NTRS)

Tian, Hui; McIntosh, Scott W.; Wang, Tongjiang; Offman, Leon; De Pontieu, Bart; Innes, Davina E.; Peter, Hardi

2012-01-01

Using data obtained by the EUV Imaging Spectrometer on board Hinode, we have performed a survey of obvious and persistent (without significant damping) Doppler shift oscillations in the corona. We have found mainly two types of oscillations from February to April in 2007. One type is found at loop footpoint regions, with a dominant period around 10 minutes. They are characterized by coherent behavior of all line parameters (line intensity, Doppler shift, line width, and profile asymmetry), and apparent blueshift and blueward asymmetry throughout almost the entire duration. Such oscillations are likely to be signatures of quasi-periodic upflows (small-scale jets, or coronal counterpart of type-II spicules), which may play an important role in the supply of mass and energy to the hot corona. The other type of oscillation is usually associated with the upper part of loops. They are most clearly seen in the Doppler shift of coronal lines with formation temperatures between one and two million degrees. The global wavelets of these oscillations usually peak sharply around a period in the range of three to six minutes. No obvious profile asymmetry is found and the variation of the line width is typically very small. The intensity variation is often less than 2%. These oscillations are more likely to be signatures of kink/Alfv´en waves rather than flows. In a few cases, there seems to be a p/2 phase shift between the intensity and Doppler shift oscillations, which may suggest the presence of slow-mode standing waves according to wave theories. However, we demonstrate that such a phase shift could also be produced by loops moving into and out of a spatial pixel as a result of Alfv´enic oscillations. In this scenario, the intensity oscillations associated with Alfv´enic waves are caused by loop displacement rather than density change. These coronal waves may be used to investigate properties of the coronal plasma and magnetic field.

Air-mass flux measurement system using Doppler-shifted filtered Rayleigh scattering

NASA Technical Reports Server (NTRS)

Shirley, John A.; Winter, Michael

1993-01-01

An optical system has been investigated to measure mass flux distributions in the inlet of a high speed air-breathing propulsion system. Rayleigh scattered light from air is proportional to the number density of molecules and hence can be used to ascertain the gas density in a calibrated system. Velocity field measurements are achieved by spectrally filtering the elastically-scattered Doppler-shifted light with an absorbing molecular filter. A novel anamorphic optical collection system is used which allows optical rays from different scattering angles, that have different Doppler shifts, to be recorded separately. This is shown to obviate the need to tune the laser through the absorption to determine velocities, while retaining the ability to make spatially-resolved measurements along a line. By properly selecting the laser tuning and filter parameters, simultaneous density measurements can be made. These properties are discussed in the paper and experiments demonstrating the velocimetry capability are described.

Doppler interpretation of quasar red shifts.

PubMed

Zapolsky, H S

1966-08-05

The hypothesis that the quasistellar sources (quasars) are local objects moving with velocities close to the speed of light is examined. Provided there is no observational cutoff on apparent bolometric magnitude for the quasars, the transverse Doppler effect leads to the expectation of fewer blue shifts than red shifts for an isotropic distribution of velocities. Such a distribution also yields a function N(z), the number of objects with red shift less than z which is not inconsistent with the present data. On the basis of two extreme assumptions concerning the origin of such rapidly moving sources, we computed curves of red shift plotted against magnitude. In particular, the curve obtained on the assumption that the quasars originated from an explosion in or nearby our own galaxy is in as good agreement with the observations as the curve of cosmological red shift plotted against magnitude.

Doppler-shifted self-reflected wave from a semiconductor

NASA Astrophysics Data System (ADS)

Schuelzgen, Alex; Hughes, S.; Peyghambarian, Nasser

1997-06-01

We report the first experimental observation of a self- reflected wave inside a very dense saturable absorber. An intense femtosecond pulse saturates the absorption and causes a density front moving into the semiconductor sample. Due to the motion of the boundary between saturated and unsaturated areas of the sample the light reflected at this boundary is red-shifted by the Doppler effect. The spectrally shifted reflection makes it possible to distinguish between surface reflection and self-reflection and is used to proof the concept of the dynamic nonlinear skin effect experimentally. Quite well agreement with model calculations is found.

Cross-calibrating ALES Envisat and CryoSat-2 Delay-Doppler: A coastal altimetry study in the Indonesian Seas

NASA Astrophysics Data System (ADS)

Passaro, Marcello; Dinardo, Salvatore; Quartly, Graham D.; Snaith, Helen M.; Benveniste, Jérôme; Cipollini, Paolo; Lucas, Bruno

2016-08-01

A regional cross-calibration between the first Delay-Doppler altimetry dataset from CryoSat-2 and a retracked Envisat dataset is here presented, in order to test the benefits of the Delay-Doppler processing and to expand the Envisat time series in the coastal ocean. The Indonesian Seas are chosen for the calibration, since the availability of altimetry data in this region is particularly beneficial due to the lack of in situ measurements and its importance for global ocean circulation. The Envisat data in the region are retracked with the Adaptive Leading Edge Subwaveform (ALES) retracker, which has been previously validated and applied successfully to coastal sea level research. The study demonstrates that CryoSat-2 is able to decrease the 1-Hz noise of sea level estimations by 0.3 cm within 50 km of the coast, when compared to the ALES-reprocessed Envisat dataset. It also shows that Envisat can be confidently used for detailed oceanographic research after the orbit change of October 2010. Cross-calibration at the crossover points indicates that in the region of study a sea state bias correction equal to 5% of the significant wave height is an acceptable approximation for Delay-Doppler altimetry. The analysis of the joint sea level time series reveals the geographic extent of the semiannual signal caused by Kelvin waves during the monsoon transitions, the larger amplitudes of the annual signal due to the Java Coastal Current and the impact of the strong La Niña event of 2010 on rising sea level trends.

Coherent Doppler lidar signal covariance including wind shear and wind turbulence

NASA Technical Reports Server (NTRS)

Frehlich, R. G.

1993-01-01

The performance of coherent Doppler lidar is determined by the statistics of the coherent Doppler signal. The derivation and calculation of the covariance of the Doppler lidar signal is presented for random atmospheric wind fields with wind shear. The random component is described by a Kolmogorov turbulence spectrum. The signal parameters are clarified for a general coherent Doppler lidar system. There are two distinct physical regimes: one where the transmitted pulse determines the signal statistics and the other where the wind field dominates the signal statistics. The Doppler shift of the signal is identified in terms of the wind field and system parameters.

Doppler-corrected Balmer spectroscopy of Rydberg positronium

NASA Astrophysics Data System (ADS)

Jones, A. C. L.; Hisakado, T. H.; Goldman, H. J.; Tom, H. W. K.; Mills, A. P.; Cassidy, D. B.

2014-07-01

The production of long-lived Rydberg positronium (Ps) and correction for Doppler shifts in the excitation laser frequencies are crucial elements of proposed measurements of the gravitational freefall of antimatter and for precision measurements of the optical spectrum of Ps. Using a two-step optical transition via 2P levels, we have prepared Ps atoms in Rydberg states up to the term limit. The spectra are corrected for the first-order Doppler shift using measured velocities, and the Balmer transitions are resolved for 15≤n≤31. The excitation signal amplitude begins to decrease for n >50, consistent with the onset of motional electric field ionization in the 3.5-mT magnetic field at the Ps formation target.

Sky-wave backscatter - A means for observing our environment at great distances.

NASA Technical Reports Server (NTRS)

Croft, T. A.

1972-01-01

During the last five years, much progress has been made in the understanding of sky-wave backscatter. An explanation of the various interacting phenomena is presented, as is a review of the current state of knowledge reflecting recent advances in observational methods and analytic techniques. New narrow-beam antennas, coupled with signal modulations that permit fine resolution in time delay, are beginning to yield information concerning the character of the scatterers, which now can be separately discerned. These narrow beams also permit study of polarization fading from small regions, and this shows promise as a means for learning the distant sea state. Doppler shifts of a fraction of a hertz on signals of tens of megahertz are separable, permitting isolation of sea returns from ground returns by virtue of the Doppler effect resulting from sea-wave speed; this also suggests a potential sea-monitoring principle. Despite these advances, there is little practical application of sky-wave backscatter as a means of environmental monitoring. This lack is attributed to the large remaining gaps in our understanding of the echoes and our inability to interpret the forms of data that can be acquired with equipment of reasonable cost.

DOPPLER SIGNATURES OF THE ATMOSPHERIC CIRCULATION ON HOT JUPITERS

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

Showman, Adam P.; Lewis, Nikole K.; Fortney, Jonathan J.

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 towardmore » 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.« less

The determination of the post-Newtonian parameter γ during the cruise phase of BepiColombo

NASA Astrophysics Data System (ADS)

Imperi, Luigi; Iess, Luciano

2017-04-01

The post-Newtonian parameter γ, unity in general relativity, controls the delay and the deflection of photons induced by the space-time curvature produced by any mass. A precise determination of this parameter can be attained by exploiting the Shapiro time delay and the corresponding Doppler shift affecting the propagation of radio signals between a ground antenna and a spacecraft near a superior solar conjunction. In its cruise phase to Mercury (from October 2018 to December 2025), the spacecraft BepiColombo will experience eleven superior solar conjunctions, thus offering an excellent opportunity to test general relativity. The experiment will benefit from very accurate range and Doppler measurements, enabled by a multi-frequency radio link in X and Ka bands (8 and 34 GHz) and a high rate (24 Mcps) pseudo-noise ranging code. The multi-frequency link configuration allows the suppression of the plasma noise due to the solar corona. In this paper, we report the results of a comprehensive analysis based on the latest spacecraft trajectory and numerical simulations. The ultimate accuracies will be determined by operational constraints, number of exploitable conjunctions, and dynamical noise acting on the spacecraft. We find that γ can be determined up to 6.2× {{10}-6} with just one conjunction in July 2022, thus improving by a factor of 4 the result obtained by the Cassini mission in 2002. This accuracy can be further increased by selecting a limited number of favourable superior solar conjunctions, down to 2.5× {{10}-6} when all of them are combined.

Analyses of solar viewing time, beta angle, and doppler shift for solar observations from the space shuttle

NASA Technical Reports Server (NTRS)

Brandon, J. P.

1972-01-01

Studies of solar physics phenomena are aided by the ability to observe the sun from earth orbit without periodic occultation. Charts are presented for the selection of suitable orbits about the earth at which a spacecraft is continuously illuminated through a period of a few days. Selection of the orbits considers the reduction of Doppler shift and wavefront attenuation due to relative orbital velocity and residual earth atmosphere.

Oscillations in the wake of a flare blast wave

NASA Astrophysics Data System (ADS)

Tothova, D.; Innes, D. E.; Stenborg, G.

2011-04-01

Context. Oscillations of coronal loops in the Sun have been reported in both imaging and spectral observations at the onset of flares. Images reveal transverse oscillations, whereas spectra detect line-of-sight velocity or Doppler-shift oscillations. The Doppler-shift oscillations are commonly interpreted as longitudinal modes. Aims: Our aim is to investigate the relationship between loop dynamics and flows seen in TRACE 195 Å images and Doppler shifts observed by SUMER in Si iii 1113.2 Å and FeXIX 1118.1 Å at the time of a C.8-class limb flare and an associated CME. Methods: We carefully co-aligned the sequence of TRACE 195 Å images to structures seen in the SUMER Si iii, CaX, and FeXIX emission lines. Additionally, Hα observations of a lifting prominence associated with the flare and the coronal mass ejection (CME) are available in three bands around 6563.3 Å. They give constraints on the timing and geometry. Results: Large-scale Doppler-shift oscillations in FeXIX and transverse oscillations in intensity images were observed over a large region of the corona after the passage of a wide bright extreme-ultraviolet (EUV) disturbance, which suggests ionization, heating, and acceleration of hot plasma in the wake of a blast wave. The online movie associated to Fig. 2 is available at http://www.aanda.org and at http://www.mps.mpg.de/data/outgoing/tothova/movie.gif

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)

Spacecraft Tests of General Relativity

NASA Technical Reports Server (NTRS)

Anderson, John D.

1997-01-01

Current spacecraft tests of general relativity depend on coherent radio tracking referred to atomic frequency standards at the ground stations. This paper addresses the possibility of improved tests using essentially the current system, but with the added possibility of a space-borne atomic clock. Outside of the obvious measurement of the gravitational frequency shift of the spacecraft clock, a successor to the suborbital flight of a Scout D rocket in 1976 (GP-A Project), other metric tests would benefit most directly by a possible improved sensitivity for the reduced coherent data. For purposes of illustration, two possible missions are discussed. The first is a highly eccentric Earth orbiter, and the second a solar-conjunction experiment to measure the Shapiro time delay using coherent Doppler data instead of the conventional ranging modulation.

Atrial electromechanical conduction delay in patients with neurocardiogenic syncope.

PubMed

Sucu, Murat; Ercan, Suleyman; Uku, Okkes; Davutoglu, Vedat; Altunbas, Gokhan

2014-05-01

We aimed to investigate the presence of atrial electromechanical conduction delay in patients with neurocardiogenic syncope, which was diagnosed with head-up tilt table test (HUTT). A total of 29 patients (mean age: 30.6 ± 15.9 years) with vasovagal syncope, as diagnosed by HUTT, and 23 healthy control subjects (mean age: 34.7 ± 16.3 years) with a negative HUTT were enrolled to the study. Atrial electromechanical conduction delay was defined as the time elapsed from the beginning of the P wave in the electrogardiogram to the beginning of the Am wave in tissue Doppler. There was no statistically significant difference between the groups in terms of interatrial conduction delay, whereas the difference was significant with regard to the right intraatrial electromechanical conduction delay (P < 0.01) and the left intraatrial electromechanical conduction delay (P < 0.0001). There was a negative correlation between the left intraatrial electromechanical conduction delay and the right intraatrial electromechanical conduction delay (r = -0.486, P = 0.001), whereas a positive correlation was present with the interatrial electromechanical conduction delay (r = 0.507, P = 0.001). In this study, the tissue Doppler method revealed that there is left and right intraatrial electromechanical conduction delay in patients with vasovagal syncope. The impact and role of atrial conduction delay as a pathophysiological determinant should be confirmed in further studies. ©2013 Wiley Periodicals, Inc.

Polarimetric Doppler spectrum of backscattered echoes from nonlinear sea surface damped by natural slicks

NASA Astrophysics Data System (ADS)

Yang, Pengju; Guo, Lixin

2016-11-01

Based on the Lombardini et al. model that can predict the hydrodynamic damping of rough sea surfaces in the presence of monomolecular slicks and the "choppy wave" model (CWM) that can describe the nonlinear interactions between ocean waves, the modeling of time-varying nonlinear sea surfaces damped by natural or organic sea slicks is presented in this paper. The polarimetric scattering model of second-order small-slope approximation (SSA-II) with tapered wave incidence is utilized for evaluating co- and cross-polarized backscattered echoes from clean and contaminated CWM nonlinear sea surfaces. The influence of natural sea slicks on Doppler shift and spectral bandwidth of radar sea echoes is investigated in detail by comparing the polarimetric Doppler spectra of contaminated sea surfaces with those of clean sea surfaces. A narrowing of Doppler spectra in the presence of oil slicks is observed for both co- and cross-polarization, which is qualitatively consistent with wave-tank measurements. Simulation results also show that the Doppler shifts in slicks can increase or decrease, depending on incidence angles and polarizations.

Improved measurements of mean sea surface velocity in the Nordic Seas from synthetic aperture radar

NASA Astrophysics Data System (ADS)

Wergeland Hansen, Morten; Johnsen, Harald; Engen, Geir; Øie Nilsen, Jan Even

2017-04-01

The warm and saline surface Atlantic Water (AW) flowing into the Nordic Seas across the Greenland-Scotland ridge transports heat into the Arctic, maintaining the ice-free oceans and regulating sea-ice extent. The AW influences the region's relatively mild climate and is the northern branch of the global thermohaline overturning circulation. Heat loss in the Norwegian Sea is key for both heat transport and deep water formation. In general, the ocean currents in the Nordic Seas and the North Atlantic Ocean is a complex system of topographically steered barotropic and baroclinic currents of which the wind stress and its variability is a driver of major importance. The synthetic aperture radar (SAR) Doppler centroid shift has been demonstrated to contain geophysical information about sea surface wind, waves and current at an accuracy of 5 Hz and pixel spacing of 3.5 - 9 × 8 km2. This corresponds to a horizontal surface velocity of about 20 cm/s at 35° incidence angle. The ESA Prodex ISAR project aims to implement new and improved SAR Doppler shift processing routines to enable reprocessing of the wide swath acquisitions available from the Envisat ASAR archive (2002-2012) at higher resolution and better accuracy than previously obtained, allowing combined use with Sentinel-1 and Radarsat-2 retrievals to build timeseries of the sea surface velocity in the Nordic Seas. Estimation of the geophysical Doppler shift from new SAR Doppler centroid shift retrievals will be demonstrated, addressing key issues relating to geometric (satellite orbit and attitude) and electronic (antenna mis-pointing) contributions and corrections. Geophysical Doppler shift retrievals from one month of data in January 2010 and the inverted surface velocity in the Nordic Seas are then addressed and compared to other direct and indirect estimates of the upper ocean current, in particular those obtained in the ESA GlobCurrent project.

An elementary approach to the gravitational Doppler shift

NASA Astrophysics Data System (ADS)

Wörner, C. H.; Rojas, Roberto

2017-01-01

In college physics courses, treatment of the Doppler effect is usually done far from the first introduction to kinematics. This paper aims to apply a graphical treatment to describe the gravitational redshift, by considering the Doppler effect in two accelerated reference frames and exercising the equivalence principle. This approach seems appropriate to discuss with beginner students and could serve to enrich the didactic processes.

A Microwave Interferometer on an Air Track.

ERIC Educational Resources Information Center

Polley, J. Patrick

1993-01-01

Uses an air track and microwave transmitters and receivers to make a Michelson interferometer. Includes three experiments: (1) measuring the wavelength of microwaves, (2) measuring the wavelength of microwaves by using the Doppler Effect, and (3) measuring the Doppler shift. (MVL)

Time synchronization via lunar radar.

NASA Technical Reports Server (NTRS)

Higa, W. H.

1972-01-01

The advent of round-trip radar measurements has permitted the determination of the ranges to the nearby planets with greater precision than was previously possible. When the distances to the planets are known with high precision, the propagation delay for electromagnetic waves reflected by the planets may be calculated and used to synchronize remotely located clocks. Details basic to the operation of a lunar radar indicate a capability for clock synchronization to plus or minus 20 microsec. One of the design goals for this system was to achieve a simple semiautomatic receiver for remotely located tracking stations. The lunar radar system is in operational use for deep space tracking at Jet Propulsion Laboratory and synchronizes five world-wide tracking stations with a master clock at Goldstone, Calif. Computers are programmed to correct the Goldstone transmissions for transit time delay and Doppler shifts so as to be received on time at the tracking stations; this dictates that only one station can be synchronized at a given time period and that the moon must be simultaneously visible to both the transmitter and receiver for a minimum time of 10 min.-

Time Delay Mechanical-noise Cancellation (TDMC) to Provide Order of Magnitude Improvements in Radio Science Observations

NASA Astrophysics Data System (ADS)

Atkinson, D. H.; Babuscia, A.; Lazio, J.; Asmar, S.

2017-12-01

Many Radio Science investigations, including the determinations of planetary masses, measurements of planetary atmospheres, studies of the solar wind, and solar system tests of relativistic gravity, rely heavily on precision Doppler tracking. Recent and currently proposed missions such as VERITAS, Bepi Colombo, Juno have shown that the largest error source in the precision Doppler tracking data is noise in the Doppler system. This noise is attributed to un-modeled motions of the ground antenna's phase center and is commonly referred to as "antenna mechanical noise." Attempting to reduce this mechanical noise has proven difficult since the deep space communications antennas utilize large steel structures that are already optimized for mechanical stability. Armstrong et al. (2008) have demonstrated the Time Delay Mechanical-noise Cancellation (TDMC) concept using Goldstone DSN antennas (70 m & 34 m) and the Cassinispacecraft to show that the mechanical noise of the 70 m antenna could be suppressed when two-way Doppler tracking from the 70 m antenna and the receive-only Doppler data from the smaller, stiffer 34 m antenna were combined with suitable delays. The proof-of-concept confirmed that the mechanical noise in the final Doppler observable was reduced to that of the stiffer, more stable antenna. Caltech's Owens Valley Radio Observatory (OVRO) near Bishop, CA now has six 10.4 m diameter antennas, a consequence of the closure of Combined Array for Research in Millimeter Astronomy (CARMA). In principle, a 10 m antenna can lead to an order-of-magnitude improvement for the mechanical noise correction, as the smaller dish offers better mechanical stability compared to a DSN 34-m antenna. These antennas also have existing Ka-band receiving systems, and preliminary discussions with the OVRO staff suggest that much of the existing signal path could be used for Radio Science observations.

Velocity measurements in the plume of an arcjet engine

NASA Technical Reports Server (NTRS)

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

1987-01-01

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

Radial velocity observations of the sun at night

NASA Technical Reports Server (NTRS)

Mcmillan, R. S.; Moore, T. L.; Perry, M. L.; Smith, P. H.

1993-01-01

The ability to detect planets orbiting stars has been evaluated through solar-spectrum Doppler shift measurements for 5 years, using the sunlit surface of the moon to furnish nighttime access to the solar spectrum integrated over the solar disk as though the sun were being observed at stellar distance. These lunar observations have indicated that the Doppler shift of the integrated solar photosphere disk in violet absorption lines has varied less that +/- 4 m/sec over the 1987-1992 interval studied.

Gyrotropic Guiding-Center Fluid Theory for the Turbulent Heating of Magnetospheric Ions in Downward Birkeland Current Regions

DTIC Science & Technology

2006-11-20

Doppler -shifted, quasistatic turbulence from the real, time- mogeneous medium,18 we can then estimate that k - k1 and dependent turbulence near the...ground is due to Doppler -shifted, spatially irregular, electric- field structures that are stationary in the ion frame. Sub- we have determined that the...erpnding cn ar ion tepeoratre- 18F J. Crary, M. V. Goldman , R. E. Ergun, and D. L. Newman, Geophys. sented in this paper gives the perpendicular ion

Spectroscopic planetary detection

NASA Technical Reports Server (NTRS)

Deming, Drake

1991-01-01

One of the most promising methods for the detection of extra-solar planets is the spectroscopic method, where a small Doppler shift (approx. 10 meter/sec) in the spectrum of the parent star reveals the presence of planetary companions. However, solar type stars may show spurious Doppler shifts due to surface activity. If these effects are periodic, as is the solar activity cycle, then they may masquerade as planetary companions. The goal of this study was to determine whether the solar cycle affects the Doppler stability of integrated sunlight. Observations of integrated sunlight were made in the near infrared (approx. 2 micron), using the Kitt Peak McMath Fourier transform spectrometer, with a N2O gas absorption cell for calibration. An accuracy of approx. 5 meter/sec was achieved.

Motion detector and analyzer

DOEpatents

Unruh, W.P.

1987-03-23

Method and apparatus are provided for deriving positive and negative Doppler spectrum to enable analysis of objects in motion, and particularly, objects having rotary motion. First and second returned radar signals are mixed with internal signals to obtain an in-phase process signal and a quadrature process signal. A broad-band phase shifter shifts the quadrature signal through 90/degree/ relative to the in-phase signal over a predetermined frequency range. A pair of signals is output from the broad-band phase shifter which are then combined to provide a first side band signal which is functionally related to a negative Doppler shift spectrum. The distinct positive and negative Doppler spectra may then be analyzed for the motion characteristics of the object being examined.

Doppler broadening in the β-proton- γ decay sequence

NASA Astrophysics Data System (ADS)

Schwartz, Sarah; Wrede, C.; Bennett, M. B.; Liddick, S. N.; Perez-Loureiro, D.; Bowe, A.; Chen, A. A.; Chipps, K. A.; Cooper, N.; Irvine, D.; McNeice, E.; Montes, F.; Naqvi, F.; Ortez, R.; Pain, S. D.; Pereira, J.; Prokop, C.; Quaglia, J.; Quinn, S. J.; Sakstrup, J.; Santia, M.; Shanab, S.; Simon, A.; Spyrou, A.; Thiagalingam, E.

2015-10-01

We report the first observation of Doppler-broadening in β delayed proton- γ decay. The broadening occurs because the daughter nucleus γ decays while recoiling from proton emission. A method to analyze β delayed nucleon emission was applied to two Doppler-broadened 25Al peaks from the 26P(βpγ)25Al decay. The method was first tested on the broad 1613 keV γ-ray peak using known center-of-mass proton energies as constraints. The method was then applied to the 1776 keV γ-ray peak from the 2720 keV excited state of 25Al. The broadening was used to determine a 26Si excitation energy of 13.3 +/- 1.0 (stat.) +/- 0.7 (syst.) MeV. This energy is consistent with proton emission from the known T = 2 isobaric analog state of 26P in 26Si.

A new method for blood velocity measurements using ultrasound FMCW signals.

PubMed

Kunita, Masanori; Sudo, Masamitsu; Inoue, Shinya; Akahane, Mutsuhiro

2010-05-01

The low peak power of frequency-modulated continuous wave (FMCW) radar makes it attractive for various applications, including vehicle collision warning systems and airborne radio altimeters. This paper describes a new ultrasound Doppler measurement system that measures blood flow velocity based on principles similar to those of FMCW radar. We propose a sinusoidal wave for FM modulation and introduce a new demodulation technique for obtaining Doppler information with high SNR and range resolution. Doppler signals are demodulated with a reference FMCW signal to adjust delay times so that they are equal to propagation times between the transmitter and the receiver. Analytical results suggest that Doppler signals can be obtained from a selected position, as with a sample volume in pulse wave Doppler systems, and that the resulting SNR is nearly identical to that obtained with continuous wave (CW) Doppler systems. Additionally, clutter power is less than that of CW Doppler systems. The analytical results were verified by experiments involving electronic circuits and Doppler ultrasound phantoms.

Insights on the Spectral Signatures of Stellar Activity and Planets from PCA

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

Davis, Allen B.; Fischer, Debra A.; Cisewski, Jessi

Photospheric velocities and stellar activity features such as spots and faculae produce measurable radial velocity signals that currently obscure the detection of sub-meter-per-second planetary signals. However, photospheric velocities are imprinted differently in a high-resolution spectrum than are Keplerian Doppler shifts. Photospheric activity produces subtle differences in the shapes of absorption lines due to differences in how temperature or pressure affects the atomic transitions. In contrast, Keplerian Doppler shifts affect every spectral line in the same way. With a high enough signal-to-noise (S/N) and resolution, statistical techniques can exploit differences in spectra to disentangle the photospheric velocities and detect lower-amplitude exoplanetmore » signals. We use simulated disk-integrated time-series spectra and principal component analysis (PCA) to show that photospheric signals introduce spectral line variability that is distinct from that of Doppler shifts. We quantify the impact of instrumental resolution and S/N for this work.« less

Doppler flowmeter

DOEpatents

Karplus, H.H.B.; Raptis, A.C.

1981-11-13

A Doppler flowmeter impulses an ultrasonic fixed-frequency signal obliquely into a slurry flowing in a pipe and a reflected signal is detected after having been scattered off of the slurry particles, whereby the shift in frequencies between the signals is proportional to the slurry velocity and hence slurry flow rate. This flowmeter filters the Doppler frequency-shift signal, compares the filtered and unfiltered shift signals in a divider to obtain a ratio, and then further compares this ratio against a preset fractional ratio. The flowmeter utilizes a voltage-to-frequency convertor to generate a pulsed signal having a determinable rate of repetition precisely proportional to the divergence of the ratios. The pulsed signal serves as the input control for a frequency-controlled low-pass filter, which provides thereby that the cutoff frequency of the filtered signal is known. The flowmeter provides a feedback control by minimizing the divergence. With the cutoff frequency and preset fractional ratio known, the slurry velocity and hence flow will also be determinable.

Doppler flowmeter

DOEpatents

Karplus, Henry H. B.; Raptis, Apostolos C.

1983-01-01

A Doppler flowmeter impulses an ultrasonic fixed-frequency signal obliquely into a slurry flowing in a pipe and a reflected signal is detected after having been scattered off of the slurry particles, whereby the shift in frequencies between the signals is proportional to the slurry velocity and hence slurry flow rate. This flowmeter filters the Doppler frequency-shift signal, compares the filtered and unfiltered shift signals in a divider to obtain a ratio, and then further compares this ratio against a preset fractional ratio. The flowmeter utilizes a voltage-to-frequency convertor to generate a pulsed signal having a determinable rate of repetition precisely proportional to the divergence of the ratios. The pulsed signal serves as the input control for a frequency-controlled low-pass filter, which provides thereby that the cutoff frequency of the filtered signal is known. The flowmeter provides a feedback control by minimizing the divergence. With the cutoff frequency and preset fractional ratio known, the slurry velocity and hence flow will also be determinable.

Scattering characteristics of relativistically moving concentrically layered spheres

NASA Astrophysics Data System (ADS)

Garner, Timothy J.; Lakhtakia, Akhlesh; Breakall, James K.; Bohren, Craig F.

2018-02-01

The energy extinction cross section of a concentrically layered sphere varies with velocity as the Doppler shift moves the spectral content of the incident signal in the sphere's co-moving inertial reference frame toward or away from resonances of the sphere. Computations for hollow gold nanospheres show that the energy extinction cross section is high when the Doppler shift moves the incident signal's spectral content in the co-moving frame near the wavelength of the sphere's localized surface plasmon resonance. The energy extinction cross section of a three-layer sphere consisting of an olivine-silicate core surrounded by a porous and a magnetite layer, which is used to explain extinction caused by interstellar dust, also depends strongly on velocity. For this sphere, computations show that the energy extinction cross section is high when the Doppler shift moves the spectral content of the incident signal near either of olivine-silicate's two localized surface phonon resonances at 9.7 μm and 18 μm.

Hardware Verification of Laser Noise Cancellation and Gravitational Wave Extraction using Time-Delay Interferometry

NASA Astrophysics Data System (ADS)

Mitryk, Shawn; Mueller, Guido

The Laser Interferometer Space Antenna (LISA) is a space-based modified Michelson interfer-ometer designed to measure gravitational radiation in the frequency range from 30 uHz to 1 Hz. The interferometer measurement system (IMS) utilizes one-way laser phase measurements to cancel the laser phase noise, reconstruct the proof-mass motion, and extract the gravitational wave (GW) induced laser phase modulations in post-processing using a technique called time-delay interferometry (TDI). Unfortunately, there exist few hard-ware verification experiments of the IMS. The University of Florida LISA Interferometry Simulator (UFLIS) is designed to perform hardware-in-the-loop simulations of the LISA interferometry system, modeling the characteris-tics of the LISA mission as accurately as possible. This depends, first, on replicating the laser pre-stabilization by locking the laser phase to an ultra-stable Zerodur cavity length reference using the PDH locking method. Phase measurements of LISA-like photodetector beat-notes are taken using the UF-phasemeter (PM) which can measure the laser BN frequency to within an accuracy of 0.22 uHz. The inter-space craft (SC) laser links including the time-delay due to the 5 Gm light travel time along the LISA arms, the laser Doppler shifts due to differential SC motion, and the GW induced laser phase modulations are simulated electronically using the electronic phase delay (EPD) unit. The EPD unit replicates the laser field propagation between SC by measuring a photodetector beat-note frequency with the UF-phasemeter and storing the information in memory. After the requested delay time, the frequency information is added to a Doppler offset and a GW-like frequency modulation. The signal is then regenerated with the inter-SC laser phase affects applied. Utilizing these components, I will present the first complete TDI simulations performed using the UFLIS. The LISA model is presented along-side the simulation, comparing the generation and measurement of LISA-like signals. Phasemeter measurements are used in post-processing and combined in the linear combinations defined by TDI, thus, canceling the laser phase and phase-lock loop noise to extract the applied GW modulation buried under the noise. Nine order of magnitude common mode laser noise cancellation is achieved at a frequency of 1 mHz and the GW signal is clearly visible after the laser and PLL noise cancellation.

Flight Testing of the TWiLiTE Airborne Molecular Doppler Lidar

NASA Technical Reports Server (NTRS)

Gentry, Bruce; McGill, Matthew; Machan, Roman; Reed, Daniel; Cargo, Ryan; Wilkens, David J.; Hart, William; Yorks, John; Scott, Stan; Wake, Shane;

Sequential processing of GNSS-R delay-Doppler maps (DDM's) for ocean wind retrieval

NASA Astrophysics Data System (ADS)

Garrison, J. L.; Rodriguez-Alvarez, N.; Hoffman, R.; Annane, B.; Leidner, M.; Kaitie, S.

2016-12-01

The delay-Doppler map (DDM) is the fundamental data product from GNSS-Reflectometry (GNSS-R), generated by cross-correlating the scattered signal with a local signal model over a range of delays and Doppler frequencies. Delay and Doppler form a set of coordinates on the ocean surface and the shape of the DDM is related to the distribution of ocean slopes. Wind speed can thus be estimated by fitting a scattering model to the shape of the observed DDM or defining an observable (e.g. average power or leading edge slope) which characterizes the change in DDM shape. For spaceborne measurements, the DDM is composed of signals scattered from a glistening zone, which can extend for up to 100 km or more. Setting a reasonable resolution requirement (25 km or less) will limit the usable portion of the DDM at each observation to only a small region near the specular point. Cyclone-GNSS (CYGNSS) is a NASA mission to study developing tropical cyclones using GNSS-R. CYGNSS science requirements call for wind retrieval with an accuracy of 10 percent above 20 m/s within a 25 km resolution. This requirement can be met using an observable defined for DDM samples between +/- 0.25 chips in delay and +/- 1 kHz in Doppler, with some filtering of the observations using a minimum threshold for range corrected gain (RCG). An improved approach, to be reviewed in this presentation, sequentially processes multiple DDM's, to combine observations generated from different "looks" at the same points on the surface. Applying this sequential process to synthetic data indicates a significant improvement in wind retrieval accuracy over a 10 km grid covering a region around the specular point. The attached figure illustrates this improvement, using simulated CYGNSS DDM's generated using the wind fields from hurricanes Earl and Danielle (left). The middle plots show wind retrievals using only an observable defined within the 25 km resolution cell. The plots on the right side show the retrievals from sequential processing of multiple DDM's. Recently, the assimilation of GNSS-R retrievals into weather forecast models has been studied. The authors have begun to investigate the direct assimilation of other data products, such as the DDM itself, or the results of sequential processing.

Navigator alignment using radar scan

DOEpatents

Doerry, Armin W.; Marquette, Brandeis

2016-04-05

The various technologies presented herein relate to the determination of and correction of heading error of platform. Knowledge of at least one of a maximum Doppler frequency or a minimum Doppler bandwidth pertaining to a plurality of radar echoes can be utilized to facilitate correction of the heading error. Heading error can occur as a result of component drift. In an ideal situation, a boresight direction of an antenna or the front of an aircraft will have associated therewith at least one of a maximum Doppler frequency or a minimum Doppler bandwidth. As the boresight direction of the antenna strays from a direction of travel at least one of the maximum Doppler frequency or a minimum Doppler bandwidth will shift away, either left or right, from the ideal situation.

Impulsive EUV bursts observed in C IV with OSO-8. [UV solar spectra

NASA Technical Reports Server (NTRS)

Athay, R. G.; White, O. R.; Lites, B. W.; Bruner, E. C., Jr.

1980-01-01

Time sequences of profiles of the 1548 A line of C IV containing 51 EUV bursts observed in or near active regions are analyzed to determine the brightness, Doppler shift and line broadening characteristics of the bursts. The bursts have mean lifetimes of approximately 150 s, and mean increases in brightness at burst maximum of four-fold as observed with a field of view of 2 x 20 arc sec. Mean burst diameters are estimated to be 3 arc sec, or smaller. All but three of the bursts show Doppler shifts with velocities sometimes exceeding 75 km/s; 31 are dominated by red shifts and 17 are dominated by blue shifts. Approximately half of the latter group have red-shifted precursors. The bursts are interpreted as prominence material, such as surges and coronal rain, moving through the field of view of the spectrometer.

Doppler radar with multiphase modulation of transmitted and reflected signal

NASA Technical Reports Server (NTRS)

Shores, Paul W. (Inventor); Griffin, John W. (Inventor); Kobayashi, Herbert S. (Inventor)

1989-01-01

A microwave radar signal is generated and split by a circulator. A phase shifter introduces a series of phase shifts into a first part of the split signal which is then transmitted by antenna. A like number of phase shifts is introduced by the phase shifter into the return signal from the target. The circulator delivers the phase shifted return signal and the leakage signal from the circulator to a mixer which generates an IF signal output at the Doppler frequency. The IF signal is amplified, filtered, counted per unit of time, and the result displayed to provide indications of target sense and range rate. An oscillator controls rate of phase shift in the transmitted and received radar signals and provides a time base for the counter. The phase shift magnitude increases may be continuous and linear or discrete functions of time.

Development of Point Doppler Velocimetry for Flow Field Investigations

NASA Technical Reports Server (NTRS)

Cavone, Angelo A.; Meyers, James F.; Lee, Joseph W.

2006-01-01

A Point Doppler Velocimeter (pDv) has been developed using a vapor-limited iodine cell as the sensing medium. The iodine cell is utilized to directly measure the Doppler shift frequency of laser light scattered from submicron particles suspended within a fluid flow. The measured Doppler shift can then be used to compute the velocity of the particles, and hence the fluid. Since this approach does not require resolution of scattered light from individual particles, the potential exists to obtain temporally continuous signals that could be uniformly sampled in the manner as a hot wire anemometer. This leads to the possibility of obtaining flow turbulence power spectra without the limitations of fringe-type laser velocimetry. The development program consisted of a methodical investigation of the technology coupled with the solution of practical engineering problems to produce a usable measurement system. The paper outlines this development along with the evaluation of the resulting system as compared to primary standards and other measurement technologies.

OBSERVATIONAL EVIDENCE OF ELECTRON-DRIVEN EVAPORATION IN TWO SOLAR FLARES

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

Li, D.; Ning, Z. J.; Zhang, Q. M., E-mail: lidong@pmo.ac.cn

2015-11-01

We have explored the relationship between hard X-ray (HXR) emissions and Doppler velocities caused by the chromospheric evaporation in two X1.6 class solar flares on 2014 September 10 and October 22, respectively. Both events display double ribbons and the Interface Region Imaging Spectrograph slit is fixed on one of their ribbons from the flare onset. The explosive evaporations are detected in these two flares. The coronal line of Fe xxi 1354.09 Å shows blueshifts, but the chromospheric line of C i 1354.29 Å shows redshifts during the impulsive phase. The chromospheric evaporation tends to appear at the front of themore » flare ribbon. Both Fe xxi and C i display their Doppler velocities with an “increase-peak-decrease” pattern that is well related to the “rising-maximum-decay” phase of HXR emissions. Such anti-correlation between HXR emissions and Fe xxi Doppler shifts and correlation with C i Doppler shifts indicate the electron-driven evaporation in these two flares.« less

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.

Particle/fluid simulations of an eruptive flare: Identifying the field-aligned currents responsible for the hard x-rays

NASA Astrophysics Data System (ADS)

Winglee, R. M.

1994-09-01

While magnetohydrodynamics (MHD) can provide a reasonable description of the overall magnetic reconnection that is believed to drive flares, additional, and often separate processes have to be envoked to in order to explain the electron acceleration that is responsible for many of the observed flare emissions. A new model that incorporates the dynamic coronal current sheets, the reconnection site, and possible electron acceleration processes is developed through the use of two-dimensional particle and modified two-fluid simulations. The specific example of an eruptive flare driven by the coalescence of flux tubes supported by prescribed photospheric current elements is evaluated. It is shown that the electrons and ions have differential trajectories through the coronal current sheet which leads to the development of additonal plasma currents that flow around the surface of the current sheet. These surface currents are explicitly neglected in MHD but they are vital to the flare dynamics because they divert current from the coronal current sheet into the chromosphere, producing an effective resistivity that aids the development of fast reconnection. Because the surface currents are in the plane of the magnetic field, electrons in them experience strong acceleration and can account for the observed hard X-ray emissions. Model predictions are compared with observed time profiles of hard X-ray emissions and Doppler shifts seen in soft X-ray line emissions and are able to account for such features as (1) the asymmetry in the rise and decay time of the hard X-rays, (2) the apparent delay between the largest Doppler shifts and the hard X-ray peak, and (3) the relatively low intensity of the blue-shifted component. The use of particle and fluid simulations is important because it provides different, but complementary treatments of the electron acceleration, the global magnetic morphology, and the flare current system.

Doppler measurements of the ionosphere on the occasion of the Apollo-Soyuz test project. Part 1: Computer simulation of ionospheric-induced Doppler shifts

NASA Technical Reports Server (NTRS)

Grossi, M. D.; Gay, R. H.

1975-01-01

A computer simulation of the ionospheric experiment of the Apollo-Soyuz Test Project (ASTP) was performed. ASTP is the first example of USA/USSR cooperation in space and is scheduled for summer 1975. The experiment consists of performing dual-frequency Doppler measurements (at 162 and 324 MHz) between the Apollo Command Service Module (CSM) and the ASTP Docking Module (DM), both orbiting at 221-km height and at a relative distance of 300 km. The computer simulation showed that, with the Doppler measurement resolution of approximately 3 mHz provided by the instrumentation (in 10-sec integration time), ionospheric-induced Doppler shifts will be measurable accurately at all times, with some rare exceptions occurring when the radio path crosses regions of minimum ionospheric density. The computer simulation evaluated the ability of the experiment to measure changes of columnar electron content between CSM and DM (from which horizontal gradients of electron density at 221-km height can be obtained) and to measure variations in DM-to-ground columnar content (from which an averaged columnar content and the electron density at the DM can be deduced, under some simplifying assumptions).

New ion trap for atomic frequency standard applications

NASA Technical Reports Server (NTRS)

Prestage, J. D.; Dick, G. J.; Maleki, L.

1989-01-01

A novel linear ion trap that permits storage of a large number of ions with reduced susceptibility to the second-order Doppler effect caused by the radio frequency (RF) confining fields has been designed and built. This new trap should store about 20 times the number of ions a conventional RF trap stores with no corresponding increase in second-order Doppler shift from the confining field. In addition, the sensitivity of this shift to trapping parameters, i.e., RF voltage, RF frequency, and trap size, is greatly reduced.

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 of broadband emissions, which is an indicator for high magnitude inertial cavitation. Although the microbubble redistribution was shown to persist for the entire sonication period in dense populations, it was constrained to the first few milliseconds in lower concentrations. In conclusion, superharmonic microbubble Doppler effects can provide a quantitative measure of effective velocities of a sonicated microbubble population and could be used for monitoring ultrasound therapy in real-time.

Superharmonic microbubble Doppler effect in ultrasound therapy

PubMed Central

Pouliopoulos, Antonios N; Choi, James J

2016-01-01

Abstract 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 of broadband emissions, which is an indicator for high magnitude inertial cavitation. Although the microbubble redistribution was shown to persist for the entire sonication period in dense populations, it was constrained to the first few milliseconds in lower concentrations. In conclusion, superharmonic microbubble Doppler effects can provide a quantitative measure of effective velocities of a sonicated microbubble population and could be used for monitoring ultrasound therapy in real-time. PMID:27469394

Review of crop growth and soil moisture monitoring from a ground-based instrument implementing the Interference Pattern GNSS-R Technique

NASA Astrophysics Data System (ADS)

Rodriguez-Alvarez, N.; Bosch-Lluis, X.; Camps, A.; Aguasca, A.; Vall-Llossera, M.; Valencia, E.; Ramos-Perez, I.; Park, H.

2011-12-01

Reflectometry using Global Navigation Satellite Systems signals (GNSSR) has been the focus of many studies during the past few years for a number of applications over different scenarios as land, ocean or snow and ice surfaces. In the past decade, its potential has increased yearly, with improved receivers and signal processors, from generic GNSS receivers whose signals were recorded in magnetic tapes to instruments that measure full Delay Doppler Maps (the power distribution of the reflected GNSS signal over the 2-D space of delay offsets and Doppler shifts) in real time. At present, these techniques are considered to be promising tools to retrieve geophysical parameters such as soil moisture, vegetation height, topography, altimetry, sea state and ice and snow thickness, among others. This paper focuses on the land geophysical retrievals (topography, vegetation height and soil moisture) performed from a ground-based instrument using the Interference Pattern Technique (IPT). This technique consists of the measurement of the power fluctuations of the interference signal resulting from the simultaneous reception of the direct and the reflected GNSS signals. The latest experiment performed using this technique over a maize field is shown in this paper. After a review of the previous results, this paper presents the latest experiment performed using this technique over a maize field. This new study provides a deeper analysis on the soil moisture retrieval by observing three irrigation-drying cycles and comparing them to different depths soil moisture probes. Furthermore, the height of the maize, almost 300 cm, has allowed testing the capabilities of the technique over dense and packed vegetation layers, with high vegetation water content.

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).

Nonnegative Matrix Factorization for identification of unknown number of sources emitting delayed signals

PubMed Central

Iliev, Filip L.; Stanev, Valentin G.; Vesselinov, Velimir V.

2018-01-01

Factor analysis is broadly used as a powerful unsupervised machine learning tool for reconstruction of hidden features in recorded mixtures of signals. In the case of a linear approximation, the mixtures can be decomposed by a variety of model-free Blind Source Separation (BSS) algorithms. Most of the available BSS algorithms consider an instantaneous mixing of signals, while the case when the mixtures are linear combinations of signals with delays is less explored. Especially difficult is the case when the number of sources of the signals with delays is unknown and has to be determined from the data as well. To address this problem, in this paper, we present a new method based on Nonnegative Matrix Factorization (NMF) that is capable of identifying: (a) the unknown number of the sources, (b) the delays and speed of propagation of the signals, and (c) the locations of the sources. Our method can be used to decompose records of mixtures of signals with delays emitted by an unknown number of sources in a nondispersive medium, based only on recorded data. This is the case, for example, when electromagnetic signals from multiple antennas are received asynchronously; or mixtures of acoustic or seismic signals recorded by sensors located at different positions; or when a shift in frequency is induced by the Doppler effect. By applying our method to synthetic datasets, we demonstrate its ability to identify the unknown number of sources as well as the waveforms, the delays, and the strengths of the signals. Using Bayesian analysis, we also evaluate estimation uncertainties and identify the region of likelihood where the positions of the sources can be found. PMID:29518126

Nonnegative Matrix Factorization for identification of unknown number of sources emitting delayed signals.

PubMed

Iliev, Filip L; Stanev, Valentin G; Vesselinov, Velimir V; Alexandrov, Boian S

2018-01-01

Factor analysis is broadly used as a powerful unsupervised machine learning tool for reconstruction of hidden features in recorded mixtures of signals. In the case of a linear approximation, the mixtures can be decomposed by a variety of model-free Blind Source Separation (BSS) algorithms. Most of the available BSS algorithms consider an instantaneous mixing of signals, while the case when the mixtures are linear combinations of signals with delays is less explored. Especially difficult is the case when the number of sources of the signals with delays is unknown and has to be determined from the data as well. To address this problem, in this paper, we present a new method based on Nonnegative Matrix Factorization (NMF) that is capable of identifying: (a) the unknown number of the sources, (b) the delays and speed of propagation of the signals, and (c) the locations of the sources. Our method can be used to decompose records of mixtures of signals with delays emitted by an unknown number of sources in a nondispersive medium, based only on recorded data. This is the case, for example, when electromagnetic signals from multiple antennas are received asynchronously; or mixtures of acoustic or seismic signals recorded by sensors located at different positions; or when a shift in frequency is induced by the Doppler effect. By applying our method to synthetic datasets, we demonstrate its ability to identify the unknown number of sources as well as the waveforms, the delays, and the strengths of the signals. Using Bayesian analysis, we also evaluate estimation uncertainties and identify the region of likelihood where the positions of the sources can be found.

Data Acquisition and Processing System for Airborne Wind Profiling with a Pulsed, 2-Micron, Coherent-Detection, Doppler Lidar System

NASA Technical Reports Server (NTRS)

Beyon, J. Y.; Koch, G. J.; Kavaya, M. J.

2010-01-01

A data acquisition and signal processing system is being developed for a 2-micron airborne wind profiling coherent Doppler lidar system. This lidar, called the Doppler Aerosol Wind Lidar (DAWN), is based on a Ho:Tm:LuLiF laser transmitter and 15-cm diameter telescope. It is being packaged for flights onboard the NASA DC-8, with the first flights in the summer of 2010 in support of the NASA Genesis and Rapid Intensification Processes (GRIP) campaign for the study of hurricanes. The data acquisition and processing system is housed in a compact PCI chassis and consists of four components such as a digitizer, a digital signal processing (DSP) module, a video controller, and a serial port controller. The data acquisition and processing software (DAPS) is also being developed to control the system including real-time data analysis and display. The system detects an external 10 Hz trigger pulse and initiates the data acquisition and processing process, and displays selected wind profile parameters such as Doppler shift, power distribution, wind directions and velocities. Doppler shift created by aircraft motion is measured by an inertial navigation/GPS sensor and fed to the signal processing system for real-time removal of aircraft effects from wind measurements. A general overview of the system and the DAPS as well as the coherent Doppler lidar system is presented in this paper.

The EVE Doppler Sensitivity and Flare Observations

NASA Technical Reports Server (NTRS)

Hudson, H. S.; Woods, T. N.; Chamberlin, P. C.; Didkovsky, L.; Del Zanna, G.

2011-01-01

The Extreme-ultraviolet Variability Experiment (EVE) obtains continuous EUV spectra of the Sun viewed as a star. Its primary objective is the characterization of solar spectral irradiance, but its sensitivity and stability make it extremely interesting for observations of variability on time scales down to the limit imposed by its basic 10 s sample interval. In this paper we characterize the Doppler sensitivity of the EVE data. We find that the 30.4 nm line of He II has a random Doppler error below 0.001 nm (1 pm, better than 10 km/s as a redshift), with ample stability to detect the orbital motion of its satellite, the Solar Dynamics Observatory (SDO). Solar flares also displace the spectrum, both because of Doppler shifts and because of EVE's optical layout, which (as with a slitless spectrograph) confuses position and wavelength. As a flare develops, the centroid of the line displays variations that reflect Doppler shifts and therefore flare dynamics. For the impulsive phase of the flare SOL2010-06-12, we find the line centroid to have a redshift of 16.8 +/- 5.9 km/s relative to that of the flare gradual phase (statistical errors only). We find also that high-temperature lines, such as Fe XXIV 19.2 nm, have well-determined Doppler components for major flares, with decreasing apparent blueshifts as expected from chromospheric evaporation flows.

Explaining observed red and blue-shifts using multi-stranded coronal loops

NASA Astrophysics Data System (ADS)

Regnier, S.; Walsh, R. W.; Pearson, J.

2012-03-01

Magnetic plasma loops have been termed the building blocks of the solar atmosphere. However, it must be recognised that if the range of loop structures we can observe do consist of many ''sub-resolution'' elements, then current one-dimensional hydrodynamic models are really only applicable to an individual plasma element or strand. Thus a loop should be viewed is an amalgamation of these strands. They could operate in thermal isolation from one another with a wide range of temperatures occurring across the structural elements. This scenario could occur when the energy release mechanism consists of localised, discrete bursts of energy that are due to small scale reconnection sites within the coronal magnetic field- the nanoflare coronal heating mechanism. These energy bursts occur in a time-dependent manner, distributed along the loop/strand length, giving a heating function that depends on space and time. An important observational discovery with the Hinode/EIS spectrometer is the existence of red and blue-shifts in coronal loops depending on the location of the footpoints (inner or outer parts of the active region), and the temperature of the emission line in which the Doppler shifts are measured. Based on the multi-stranded model developed by Sarkar and Walsh (2008, ApJ, 683, 516), we show that red and blue-shifts exist in different simulated Hinode/EIS passbands: cooler lines (OV-SiVII) being dominated by red-shifts, whilst hotter lines (FeXV-CaXVII) are a combination of both. The distribution of blue-shifts depends on the energy input and not so much on the heating location. Characteristic Doppler shifts generated fit well with observed values. We also simulate the Hinode/EIS rasters to closely compare our simulation with the observations. Even if not statistically significant, loops can have footpoints with opposite Doppler shifts.

Red Shift, Blue Shift: Investigating Doppler Shifts, Blubber Thickness, and Migration as Explanations of Seasonal Variation in the Tonality of Antarctic Blue Whale Song

PubMed Central

Miller, Brian S.; Leaper, Russell; Calderan, Susannah; Gedamke, Jason

2014-01-01

The song of Antarctic blue whales (Balaenoptera musculus intermedia) comprises repeated, stereotyped, low-frequency calls. Measurements of these calls from recordings spanning many years have revealed a long-term linear decline as well as an intra-annual pattern in tonal frequency. While a number of hypotheses for this long-term decline have been investigated, including changes in population structure, changes in the physical environment, and changes in the behaviour of the whales, there have been relatively few attempts to explain the intra-annual pattern. An additional hypothesis that has not yet been investigated is that differences in the observed frequency from each call are due to the Doppler effect. The assumptions and implications of the Doppler effect on whale song are investigated using 1) vessel-based acoustic recordings of Antarctic blue whales with simultaneous observation of whale movement and 2) long-term acoustic recordings from both the subtropics and Antarctic. Results from vessel-based recordings of Antarctic blue whales indicate that variation in peak-frequency between calls produced by an individual whale was greater than would be expected by the movement of the whale alone. Furthermore, analysis of intra-annual frequency shift at Antarctic recording stations indicates that the Doppler effect is unlikely to fully explain the observations of intra-annual pattern in the frequency of Antarctic blue whale song. However, data do show cyclical changes in frequency in conjunction with season, thus suggesting that there might be a relationship among tonal frequency, body condition, and migration to and from Antarctic feeding grounds. PMID:25229644

Red shift, blue shift: investigating Doppler shifts, blubber thickness, and migration as explanations of seasonal variation in the tonality of Antarctic blue whale song.

PubMed

Miller, Brian S; Leaper, Russell; Calderan, Susannah; Gedamke, Jason

2014-01-01

The song of Antarctic blue whales (Balaenoptera musculus intermedia) comprises repeated, stereotyped, low-frequency calls. Measurements of these calls from recordings spanning many years have revealed a long-term linear decline as well as an intra-annual pattern in tonal frequency. While a number of hypotheses for this long-term decline have been investigated, including changes in population structure, changes in the physical environment, and changes in the behaviour of the whales, there have been relatively few attempts to explain the intra-annual pattern. An additional hypothesis that has not yet been investigated is that differences in the observed frequency from each call are due to the Doppler effect. The assumptions and implications of the Doppler effect on whale song are investigated using 1) vessel-based acoustic recordings of Antarctic blue whales with simultaneous observation of whale movement and 2) long-term acoustic recordings from both the subtropics and Antarctic. Results from vessel-based recordings of Antarctic blue whales indicate that variation in peak-frequency between calls produced by an individual whale was greater than would be expected by the movement of the whale alone. Furthermore, analysis of intra-annual frequency shift at Antarctic recording stations indicates that the Doppler effect is unlikely to fully explain the observations of intra-annual pattern in the frequency of Antarctic blue whale song. However, data do show cyclical changes in frequency in conjunction with season, thus suggesting that there might be a relationship among tonal frequency, body condition, and migration to and from Antarctic feeding grounds.

ACTIVE REGION MOSS: DOPPLER SHIFTS FROM HINODE/EXTREME-ULTRAVIOLET IMAGING SPECTROMETER OBSERVATIONS

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

Tripathi, Durgesh; Mason, Helen E.; Klimchuk, James A.

2012-07-01

Studying the Doppler shifts and the temperature dependence of Doppler shifts in moss regions can help us understand the heating processes in the core of the active regions. In this paper, we have used an active region observation recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode on 2007 December 12 to measure the Doppler shifts in the moss regions. We have distinguished the moss regions from the rest of the active region by defining a low-density cutoff as derived by Tripathi et al. in 2010. We have carried out a very careful analysis of the EIS wavelength calibrationmore » based on the method described by Young et al. in 2012. For spectral lines having maximum sensitivity between log T = 5.85 and log T = 6.25 K, we find that the velocity distribution peaks at around 0 km s{sup -1} with an estimated error of 4-5 km s{sup -1}. The width of the distribution decreases with temperature. The mean of the distribution shows a blueshift which increases with increasing temperature and the distribution also shows asymmetries toward blueshift. Comparing these results with observables predicted from different coronal heating models, we find that these results are consistent with both steady and impulsive heating scenarios. However, the fact that there are a significant number of pixels showing velocity amplitudes that exceed the uncertainty of 5 km s{sup -1} is suggestive of impulsive heating. Clearly, further observational constraints are needed to distinguish between these two heating scenarios.« less

Inverse Doppler shift and control field as coherence generators for the stability in superluminal light

NASA Astrophysics Data System (ADS)

Ghafoor, Fazal; Bacha, Bakht Amin; Khan, Salman

2015-05-01

A gain-based four-level atomic medium for the stability in superluminal light propagation using control field and inverse Doppler shift as coherence generators is studied. In regimes of weak and strong control field, a broadband and multiple controllable transparency windows are, respectively, identified with significantly enhanced group indices. The observed Doppler effect for the class of high atomic velocity of the medium is counterintuitive in comparison to the effect of the class of low atomic velocity. The intensity of each of the two pump fields is kept less than the optimum limit reported in [M. D. Stenner and D. J. Gauthier, Phys. Rev. A 67, 063801 (2003), 10.1103/PhysRevA.67.063801] for stability in the superluminal light pulse. Consequently, superluminal stable domains with the generated coherence are explored.

CONSTRAINING HIGH-SPEED WINDS IN EXOPLANET ATMOSPHERES THROUGH OBSERVATIONS OF ANOMALOUS DOPPLER SHIFTS DURING TRANSIT

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

Miller-Ricci Kempton, Eliza; Rauscher, Emily, E-mail: ekempton@ucolick.org

2012-06-01

Three-dimensional (3D) dynamical models of hot Jupiter atmospheres predict very strong wind speeds. For tidally locked hot Jupiters, winds at high altitude in the planet's atmosphere advect heat from the day side to the cooler night side of the planet. Net wind speeds on the order of 1-10 km s{sup -1} directed towards the night side of the planet are predicted at mbar pressures, which is the approximate pressure level probed by transmission spectroscopy. These winds should result in an observed blueshift of spectral lines in transmission on the order of the wind speed. Indeed, Snellen et al. recently observedmore » a 2 {+-} 1 km s{sup -1} blueshift of CO transmission features for HD 209458b, which has been interpreted as a detection of the day-to-night (substellar to anti-stellar) winds that have been predicted by 3D atmospheric dynamics modeling. Here, we present the results of a coupled 3D atmospheric dynamics and transmission spectrum model, which predicts the Doppler-shifted spectrum of a hot Jupiter during transit resulting from winds in the planet's atmosphere. We explore four different models for the hot Jupiter atmosphere using different prescriptions for atmospheric drag via interaction with planetary magnetic fields. We find that models with no magnetic drag produce net Doppler blueshifts in the transmission spectrum of {approx}2 km s{sup -1} and that lower Doppler shifts of {approx}1 km s{sup -1} are found for the higher drag cases, results consistent with-but not yet strongly constrained by-the Snellen et al. measurement. We additionally explore the possibility of recovering the average terminator wind speed as a function of altitude by measuring Doppler shifts of individual spectral lines and spatially resolving wind speeds across the leading and trailing terminators during ingress and egress.« less

Analysis of Nuclear Lifetimes Using the Gamma-ray Induced Doppler Shift Attenuation Method

NASA Astrophysics Data System (ADS)

Crespi, F. C. L.

2018-05-01

Lifetime measurements allow extraction of fundamental information on the nature of the excited states of a nuclear system. Since nuclear lifetimes cover many orders of magnitude, a number of experimental techniques and detection setups have been developed depending on the range of the lifetime of interest. The Gamma-ray Induced Doppler Shift Attenuation (GRIDSA) Method presented here is applied to the measurement of very short lifetimes, in the femtosecond range. It allows determining the nuclear lifetime by measuring the Doppler shift of a gamma ray emitted from the state of interest, in different directions with respect to a coincident preceding gamma ray, populating the same state and inducing a recoil of the nucleus in the target material with velocities of the order of 104-105 m/s. We realized an experiment in order to test the GRIDSA technique for the measurement of fs lifetimes after (n,γ) reactions. The measurement was performed at the Institut Laue-Langevin (ILL) with the 8 Ge-clover detectors of the FIPPS array. Preliminary results are discussed.

Long-term Doppler Shift and Line Profile Studies of Planetary Search Target Stars

NASA Technical Reports Server (NTRS)

McMillan, Robert S.

2002-01-01

This grant supported attempts to develop a method for measuring the Doppler shifts of solar-type stars more accurately. The expense of future space borne telescopes to search for solar systems like our own makes it worth trying to improve the relatively inexpensive pre-flight reconnaissance by ground-based telescopes. The concepts developed under this grant contributed to the groundwork for such improvements. They were focused on how to distinguish between extrasolar planets and stellar activity (convection) cycles. To measure the Doppler shift (radial velocity; RV) of the center of mass of a star in the presence of changing convection in the star's photosphere, one can either measure the effect of convection separately from that of the star's motion and subtract its contribution to the apparent RV, or measure the RV in a way that is insensitive to convection. This grant supported investigations into both of these approaches. We explored the use of a Fabry-Perot Etalon HE interferometer and a multichannel Fourier Transform Spectrometer (mFTS), and finished making a 1.8-m telescope operational and potentially available for this work.

Enhanced Multistatic Active Sonar via Innovative Signal Processing

DTIC Science & Technology

2015-09-30

3. DATES COVERED (From - To) Oct. 01, 2014-Sept. 30, 2015 4. TITLE AND SUBTITLE Enhanced Multistatic Active Sonar via Innovative Signal...active sonar (CAS) in the presence of strong direct blast is studied for the Doppler-tolerant linear frequency modulation waveform. A receiver design...beamformer variants is examined. 15. SUBJECT TERMS Pulsed active sonar (PAS), continuous active sonar (CAS), strong delay and Doppler-spread direct blast

Simultaneous transfer of optical frequency and time over 306 km long-haul optical fibre link

NASA Astrophysics Data System (ADS)

Hucl, Vaclav; Cizek, Martin; Pravdova, Lenka; Rerucha, Simon; Hrabina, Jan; Mikel, Bretislav; Smotlacha, Vladimir; Vojtech, Josef; Lazar, Josef; Cip, Ondrej

2016-12-01

Optical fibre links for distributing optical frequencies and time stamps were researched and experimentally tested in the past fifteen years. They have been used mainly for stability comparison of experimental optical clocks. But recent development puts demands on a technology transfer from laboratory experiments to the real industry. The remote calibration of interrogators of Fibre Bragg Grating strain sensory networks is one of important examples. The first step of the adoption the time and frequency broadcasting should be the drop-out free long-term operation of this technology between research laboratories connected via long-haul fibre links. We present a 306 km long-haul optical fibre link between the cities of Prague and Brno in the Czech Republic where a coherent transfer of stable optical frequency and a stable time signal has been firstly demonstrated. The link between ISI CAS Brno and CESNET Prague uses an internet communication fibre where a window of 1540-1546 nm is dedicated for the coherent transfer and 1PPS signal. The link is equipped with 6 bidirectional EDFA amplifiers. The optical frequency standard based on the highly-coherent laser Koheras Adjustik working at 1540.5 nm and stabilized with a saturation absorption spectroscopy technique was used for the coherent wave transfer. The suppression of the Doppler shift induced by the optical fibre was based on an accoustooptical modulator with a servo-loop including a fast PID controller processing the beat-note frequency given by mixing of the Adjustik laser (Brno) and the reflected frequency of this laser from the far end of 306 km long-haul fibre link (Prague). We verified the Doppler shift suppression for the coherent wave with a measuring method analysing the transport delay of the 1PPS signal.

Single-mode fiber, velocity interferometry

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

Krauter, K. G.; Jacobson, G. F.; Patterson, J. R.

2011-04-15

In this paper, we describe a velocity interferometer system based entirely on single-mode fiber optics. This paper includes a description of principles used in developing the single-mode velocity interferometry system (SMV). The SMV design is based on polarization-insensitive components. Polarization adjusters are included to eliminate the effects of residual birefringence and polarization dependent losses in the interferometers. Characterization measurements and calibration methods needed for data analysis and a method of data analysis are described. Calibration is performed directly using tunable lasers. During development, we demonstrated its operation using exploding-foil bridge-wire fliers up to 200 m/s. In a final test, wemore » demonstrated the SMV in a gas gun experiment up to 1.2 km/sec. As a basis for comparison in the gas gun experiment, we used another velocimetry technique that is also based on single-mode fiber optics: photonic Doppler velocimetry (PDV). For the gas gun experiment, we split the light returned from a single target spot and performed a direct comparison of the homodyne (SMV) and heterodyne (PDV) techniques concurrently. The two techniques had a negligible mean difference and a 1.5% standard deviation in the one-dimensional shock zone. Within one interferometer delay time after a sudden Doppler shift, a SMV unencumbered by multimode-fiber dispersion exhibits two color beats. These beats have the same period as PDV beats--this interference occurs between the ''recently'' shifted and ''formerly unshifted'' paths within the interferometer. We believe that recognizing this identity between homodyne and heterodyne beats is novel in the shock-physics field. SMV includes the conveniences of optical fiber, while removing the time resolution limitations associated with the multimode delivery fiber.« less

Single-mode fiber, velocity interferometry.

PubMed

Krauter, K G; Jacobson, G F; Patterson, J R; Nguyen, J H; Ambrose, W P

2011-04-01

In this paper, we describe a velocity interferometer system based entirely on single-mode fiber optics. This paper includes a description of principles used in developing the single-mode velocity interferometry system (SMV). The SMV design is based on polarization-insensitive components. Polarization adjusters are included to eliminate the effects of residual birefringence and polarization dependent losses in the interferometers. Characterization measurements and calibration methods needed for data analysis and a method of data analysis are described. Calibration is performed directly using tunable lasers. During development, we demonstrated its operation using exploding-foil bridge-wire fliers up to 200 m/s. In a final test, we demonstrated the SMV in a gas gun experiment up to 1.2 km/sec. As a basis for comparison in the gas gun experiment, we used another velocimetry technique that is also based on single-mode fiber optics: photonic Doppler velocimetry (PDV). For the gas gun experiment, we split the light returned from a single target spot and performed a direct comparison of the homodyne (SMV) and heterodyne (PDV) techniques concurrently. The two techniques had a negligible mean difference and a 1.5% standard deviation in the one-dimensional shock zone. Within one interferometer delay time after a sudden Doppler shift, a SMV unencumbered by multimode-fiber dispersion exhibits two color beats. These beats have the same period as PDV beats-this interference occurs between the "recently" shifted and "formerly unshifted" paths within the interferometer. We believe that recognizing this identity between homodyne and heterodyne beats is novel in the shock-physics field. SMV includes the conveniences of optical fiber, while removing the time resolution limitations associated with the multimode delivery fiber. © 2011 American Institute of Physics

Evaluation of atrial electromechanical conduction delay in case of hemodynamically insignificant rheumatic heart disease: A tissue Doppler study.

PubMed

Cagdas, Metin; Velibey, Yalcin; Guvenc, Tolga Sinan; Gungor, Baris; Guzelburc, Ozge; Calik, Nazmi; Ugur, Murat; Tekkesin, Ahmet Ilker; Gurkan, Kadir; Eren, Mehmet

2015-01-01

Atrial electromechanical delay (AEMD) that reflects delayed conduction may show us the clinical reflection of pathological changes in the atria. The main objective of the present study is to investigate AEMD in patients who had previous rheumatic carditis but without hemodynamically significant valvular disease. A total of 40 patients, previously diagnosed as rheumatic carditis but without significant valvular stenosis/regurgitation and atrial enlargement; and 39 age- and-sex matched controls were enrolled for the present study. Parameters of AEMD (lateral mitral annulus electromechanical delay, septal mitral annulus electromechanical delay and lateral tricuspid annulus electromechanical delay) were measured with tissue Doppler echocardiography and left intra-atrial and inter-atrial conduction times were calculated accordingly. A 24h ambulatory Holter monitoring was used in both groups to detect atrial fibrillation episodes and quantify atrial extrasystoles. Parameters of AEMD, including left intra-atrial and inter-atrial conduction times of subjects in the study group were longer compared to the control group (23.7 ± 7.0 vs. 18.3 ± 6.2). Increased AEMD is observed in patients with previous rheumatic carditis and no significant valvular stenosis/regurgitation and atrial enlargement, which may partly explain the increased incidence of atrial fibrillation observed in these patients.

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.

Center of Mass Estimation for a Spinning Spacecraft Using Doppler Shift of the GPS Carrier Frequency

NASA Technical Reports Server (NTRS)

Sedlak, Joseph E.

2016-01-01

A sequential filter is presented for estimating the center of mass (CM) of a spinning spacecraft using Doppler shift data from a set of onboard Global Positioning System (GPS) receivers. The advantage of the proposed method is that it is passive and can be run continuously in the background without using commanded thruster firings to excite spacecraft dynamical motion for observability. The NASA Magnetospheric Multiscale (MMS) mission is used as a test case for the CM estimator. The four MMS spacecraft carry star cameras for accurate attitude and spin rate estimation. The angle between the spacecraft nominal spin axis (for MMS this is the geometric body Z-axis) and the major principal axis of inertia is called the coning angle. The transverse components of the estimated rate provide a direct measure of the coning angle. The coning angle has been seen to shift slightly after every orbit and attitude maneuver. This change is attributed to a small asymmetry in the fuel distribution that changes with each burn. This paper shows a correlation between the apparent mass asymmetry deduced from the variations in the coning angle and the CM estimates made using the GPS Doppler data. The consistency between the changes in the coning angle and the CM provides validation of the proposed GPS Doppler method for estimation of the CM on spinning spacecraft.

Imaging doppler lidar for wind turbine wake profiling

DOEpatents

Bossert, David J.

2015-11-19

An imaging Doppler lidar (IDL) enables the measurement of the velocity distribution of a large volume, in parallel, and at high spatial resolution in the wake of a wind turbine. Because the IDL is non-scanning, it can be orders of magnitude faster than conventional coherent lidar approaches. Scattering can be obtained from naturally occurring aerosol particles. Furthermore, the wind velocity can be measured directly from Doppler shifts of the laser light, so the measurement can be accomplished at large standoff and at wide fields-of-view.

Radar Imaging of Asteroids

NASA Astrophysics Data System (ADS)

Ostro, S. J.

1996-09-01

Measurements of the distribution of echo power in time delay (range) and Doppler frequency (line-of-sight velocity) can synthesize images of near-Earth and main-belt asteroids (NEAs and MBAs) that traverse the detectability windows of groundbased radar telescopes. Under ideal circumstances, current radar waveforms can achieve decameter surface resolution. The number of useful pixels obtainable in an imaging data set is of the same order as the signal-to-noise ratio, SNR, of an optimally filtered, weighted sum of all the data. (SNR increases as the square root of the integration time.) The upgraded Arecibo telescope which is about to become operational, should be able to achieve single-date SNRs {\\underline>} (20,100) for an average of (35,5) MBAs per year and single-date SNRs {\\underline>} (20,100,1000) for an average of (10,6,2) of the currently catalogued NEAs per year; optical surveying of the NEA population could increase the frequency of opportunities by an order of magnitude. The strongest imaging opportunities predicted for Arecibo between now and the end of 1997 include (the peak SNR/date is in parentheses): 9 Metis (110), 27 Euterpe (170), 80 Sappho (100), 139 Juewa (140), 144 Vibilia (140), 253 Mathilde (100), 2102 Tantalus (570), 3671 Dionysus (170), 3908 1980PA (4400), 4179 Toutatis (16000), 4197 1982TA (1200), 1991VK (700), and 1994PC1 (7400). A delay-Doppler image projects the echo power distribution onto the target's apparent equatorial plane. One cannot know a priori whether one or two (or more) points on the asteroid contributed power to a given pixel, so accurate interpretation of delay-Doppler images requires modeling (Hudson, 1993, Remote Sensing Rev. 8, 195-203). Inversion of an imaging sequence with enough orientational coverage can remove "north/south" ambiguities and can provide estimates of the target's three-dimensional shape, spin state, radar scattering properties, and delay-Doppler trajectory (e.g., Ostro et al. 1995, Science 270, 80-83; Hudson and Ostro 1995, Science 270, 84-86).

Two-photon absorption dispersion spectrometer for 1.53 μm eye-safe Doppler LIDAR.

PubMed

Vance, J D

2012-07-01

Based upon resonant two-photon absorption within a rubidium cell and 780 nm pump light, a birefringent medium for 1.530 μm is induced that changes rapidly with frequency. The birefringence is exploited to build a spectrometer that is capable of measuring the Doppler shift of scattered photons.

High Speed A/D DSP Interface for Carrier Doppler Tracking

NASA Technical Reports Server (NTRS)

Baggett, Timothy

1998-01-01

As on-board satellite systems continue to increase in ability to perform self diagnostic checks, it will become more important for satellites to initiate ground communications contact. Currently, the NASA Space Network requires users to pre-arranged times for satellite communications links through the Tracking and Data Relay Satellite (TDRS). One of the challenges in implementing an on-demand access protocol into the Space Network, is the fact that a low Earth orbiting (LEO) satellite's communications will be subject to a doppler shift which is outside the capability of the NASA ground station to lock onto. In a prearranged system, the satellite's doppler is known a priori, and the ground station is able to lock onto the satellite's signal. This paper describes the development of a high speed analog to digital interface into a Digital Signal Processor (DSP). This system will be used for identifying the doppler shift of a LEO satellite through the Space Network, and aiding the ground station equipment in locking onto the signal. Although this interface is specific to one application, it can be used as a basis for interfacing other devices with a DSP.

Extended Kalman Doppler tracking and model determination for multi-sensor short-range radar

NASA Astrophysics Data System (ADS)

Mittermaier, Thomas J.; Siart, Uwe; Eibert, Thomas F.; Bonerz, Stefan

2016-09-01

A tracking solution for collision avoidance in industrial machine tools based on short-range millimeter-wave radar Doppler observations is presented. At the core of the tracking algorithm there is an Extended Kalman Filter (EKF) that provides dynamic estimation and localization in real-time. The underlying sensor platform consists of several homodyne continuous wave (CW) radar modules. Based on In-phase-Quadrature (IQ) processing and down-conversion, they provide only Doppler shift information about the observed target. Localization with Doppler shift estimates is a nonlinear problem that needs to be linearized before the linear KF can be applied. The accuracy of state estimation depends highly on the introduced linearization errors, the initialization and the models that represent the true physics as well as the stochastic properties. The important issue of filter consistency is addressed and an initialization procedure based on data fitting and maximum likelihood estimation is suggested. Models for both, measurement and process noise are developed. Tracking results from typical three-dimensional courses of movement at short distances in front of a multi-sensor radar platform are presented.

Red Shifts with Obliquely Approaching Light Sources.

ERIC Educational Resources Information Center

Head, C. E.; Moore-Head, M. E.

1988-01-01

Refutes the Doppler effect as the explanation of large red shifts in the spectra of distant galaxies and explains the relativistic effects in which the light sources approach the observer obliquely. Provides several diagrams and graphs. (YP)

The effect of the duration of jet aircraft flyover sounds on judged annoyance. [noise predictions and noise measurements of jet aircrafts and human reactions to the noise intensity

NASA Technical Reports Server (NTRS)

Shepherd, K. P.

1979-01-01

The effect of the duration of jet aircraft flyover sounds on humans and the annoyance factor are examined. A nine point numerical category scaling technique is utilized for the study. Changes in the spectral characteristics of aircraft sounds caused by atmospheric attenuation are discussed. The effect of Doppler shifts using aircraft noises with minimal pure tone content is reported. The spectral content of sounds independent of duration and Doppler shift are examined by analysis of variance.

Titan's dunes revealed by the delay/Doppler processing of the Cassini radar altimeter data

NASA Astrophysics Data System (ADS)

Poggiali, V.; Mastrogiuseppe, M.; Hayes, A.; Seu, R.; Bonnefoy, L.; Mullen, J.; Lunine, J. I.

2017-12-01

Doppler Beam Sharpened techniques can be exploited for the Cassini radar altimeter data to resolve features far smaller than the footprint in the along-track direction [1]. We applied the delay/Doppler algorithm [2] which performs an incoherent sum of the echoes relative to specific along-track Doppler-limited areas. The algorithm allows to preserve the radiometric resolution and to improve the geometric one by a factor of ten with respect to the conventional processing. The generation of topographic profiles with km-scale along-track spacing is essential to our understanding of the processes that shape Titan's surfaces and lead to the formation of morphologic units like dunes, hummocks, fluvial valleys, and lacustrine basins. Dunes are one of the most extensive units on Titan, covering vast portions of Titan's equatorial latitudes and almost all longitudes. In SAR images, they have a linear bright-dark pattern extending hundreds of kilometers. Delay/Doppler processing of the altimetry data allows us to resolve individual longitudinal dunes both spatially and vertically for the first time. Comparing radar altimetry backscatter to the dune backscattering from SAR images, we can obtain new information about their geometric and dielectric characteristics. Current models using radarclinometry [3], SAR swath pairs [4], or unresolved altimetry [5] estimate dune heights of 40-150 m, but are unable to resolve the topography of individual dune crests. This will permit also a more accurate estimation of the sediment budget of the dunes, a necessary step towards understanding their formation and evolution. References: [1] Picardi, G. et al., IGARSS `98 Proc., vol. 5, pp. 2643-2645, 1998; [2] Raney, R.K., IEEE TGRS 36, n. 5, 1998; [3] Lorenz, R.D. et al., Science 312, 724-727, 2006; [4] Callegari, M. et al., IEEE vol. 8, n. 3, p. 1295-1306; [5] Mastrogiuseppe, M. et al., Icarus 230, p. 191-197, 2014.

Doppler measurements of the ionosphere on the occasion of the Apollo-Soyuz test project. Part 2: Inversion of differential and rotating Doppler shifts

NASA Technical Reports Server (NTRS)

Gay, R. H.; Grossi, M. D.

1975-01-01

The preparation of the analytical approach and of the related software used in the inversion of the differential and rotating Doppler data obtained from the ionospheric experiment of the Apollo-Soyuz Test Project (ASTP) is discussed. These data were collected in space-to-space paths (between the ASTP Docking Module (DM) and the Apollo Command Service Module and in space-to-ground paths (between the DM and ground). The Doppler links operated at 162 and 324 MHz and have an accuracy better than 3 MHz over 10-sec integration time. The inversion approach was tested with dummy data obtained with a computer simulation. It was found that a measurement accuracy of 1 to 10% in the value of the horizontal electron density gradient at 221-km altitude can be achieved, in space-to-space paths. For space-to-ground paths near the orbital plane, possible effects of the horizontal gradients on the received differential Doppler shifts were identified. It was possible to reduce the gradient-associated errors in the inversion that leads to the columnar electron content by approximately one-half. Accuracies of 5 to 10% in columnar electron content are achievable, with this gradient-compensation technique.

Detection of Transionospheric SuperDARN HF Waves by the Radio Receiver Instrument on the enhanced Polar Outflow Probe Satellite

NASA Astrophysics Data System (ADS)

Gillies, R. G.; Yau, A. W.; James, H. G.; Hussey, G. C.; McWilliams, K. A.

2014-12-01

The enhanced Polar Outflow Probe (ePOP) Canadian small-satellite was launched in September 2013. Included in this suite of eight scientific instruments is the Radio Receiver Instrument (RRI). The RRI has been used to measure VLF and HF radio waves from various ground and spontaneous ionospheric sources. The first dedicated ground transmission that was detected by RRI was from the Saskatoon Super Dual Auroral Radar Network (SuperDARN) radar on Nov. 7, 2013 at 14 MHz. Several other passes over the Saskatoon SuperDARN radar have been recorded since then. Ground transmissions have also been observed from other radars, such as the SPEAR, HAARP, and SURA ionospheric heaters. However, the focus of this study will be on the results obtained from the SuperDARN passes. An analysis of the signal recorded by the RRI provides estimates of signal power, Doppler shift, polarization, absolute time delay, differential mode delay, and angle of arrival. By comparing these parameters to similar parameters derived from ray tracing simulations, ionospheric electron density structures may be detected and measured. Further analysis of the results from the other ground transmitters and future SuperDARN passes will be used to refine these results.

Rapid Cerebral Hemodynamic Modulation during Set Shifting: Evidence of Time-Locked Associations with Cognitive Control in Females

ERIC Educational Resources Information Center

Schuepbach, Daniel; Huizinga, Mariette; Duschek, Stefan; Grimm, Simone; Boeker, Heinz; Hell, Daniel

2009-01-01

Set shifting provokes specific alterations of cerebral hemodynamics in basal cerebral arteries. However, no gender differences have been reported. In the following functional transcranial Doppler study, we introduced cerebral hemodynamic modulation to the aspects of set shifting during Wisconsin Card Sorting Test (WCST). Twenty-one subjects…

Presence and Implication of Temporal Nonuniformity of Early Diastolic Left Ventricular Wall Expansion in Patients With Heart Failure.

PubMed

Iwano, Hiroyuki; Kamimura, Daisuke; Fox, Ervin R; Hall, Michael E; Vlachos, Pavlos; Little, William C

2016-12-01

Early-diastolic left ventricular (LV) longitudinal expansion is delayed with diastolic dysfunction. We hypothesized that, in patients with heart failure (HF), regardless of LV ejection fraction (EF), there is diastolic temporal nonuniformity with a delay of longitudinal relative to circumferential expansion. Echocardiography was performed in 143 HF patients-50 with preserved EF (HFpEF) and 93 with reduced EF (HFrEF)-as well as 31 normal control subjects. The delay of early-diastolic mitral annular velocity from the mitral Doppler E (T E-e' ) was measured as a parameter of the longitudinal expansion delay. The delay of the longitudinal early-diastolic global strain rate (SR E ) relative to circumferential SR E (Delay C-L ) was calculated as a parameter of temporal nonuniformity. Intra-LV pressure difference (IVPD) was estimated with the use of color M-mode Doppler data as a parameter of LV diastolic suction. Although normal control subjects had symmetric LV expansion in early diastole, T E-e' and Delay C-L were significantly prolonged in HF regardless of EF (P < .01 vs control for all). Multivariate analysis revealed that Delay C-L was the independent determinant of IVPD among the parameters of LV geometry and contraction (β = -0.21; P < .05). An abnormal temporal nonuniformity of early-diastolic expansion is present in HF regardless of EF, which was associated with reduced LV suction. Copyright © 2016 Elsevier Inc. All rights reserved.

The Martian rotation from Doppler measurements: Simulations of future radioscience experiments

NASA Astrophysics Data System (ADS)

Péters, Marie-Julie; Yseboodt, Marie; Dehant, Véronique; Le Maistre, Sebastien; Marty, Jean-Charles

2016-10-01

The radioscience experiment onboard the future InSight and ExoMars missions consists in two-way Doppler shift measurement from a X-band radio link between a lander on Mars and the ground stations on Earth. The Doppler effect on the radio signal is related to the revolution of the planets around the Sun and to the variations of the orientation and the rotation of Mars. The variations of the orientation of the rotation axis are the precession and nutations, related to the deep interior of Mars and the variations of the rotation rate are the length-of-day variation, related to the dynamic of the atmosphere.We perform numerical simulations of the Doppler measurements in order to quantify the precision that can be achieved on the determination of the Mars rotation and orientation parameters (MOP). For this purpose, we use the GINS (Géodésie par Intégrations Numériques Simultanées) software developed by the CNES and further adapted at the Royal Observatory of Belgium for planetary geodesy applications. This software enables to simulate the relative motion of the lander at the surface of Mars relative to the ground stations and to compute the MOP signature on the Doppler shift. The signature is the difference between the Doppler observable estimated taking into account a MOP and the Doppler estimated without this parameter.The objective is to build a strategy to be applied to future data processing in order to improve our estimation of the MOP. We study the effect of the elevation of the Earth in the sky of the lander, of the tracking duration and number of pass per week, of the tracking time, of the lander position and of Doppler geometry on the signatures. Indeed, due to the geometry, the Doppler data are highly sensitive to the position variations along the line of sight.

DE-Sync: A Doppler-Enhanced Time Synchronization for Mobile Underwater Sensor Networks.

PubMed

Zhou, Feng; Wang, Qi; Nie, DongHu; Qiao, Gang

2018-05-25

Time synchronization is the foundation of cooperative work among nodes of underwater sensor networks; it takes a critical role in the research and application of underwater sensor networks. Although numerous time synchronization protocols have been proposed for terrestrial wireless sensor networks, they cannot be directly applied to underwater sensor networks. This is because most of them typically assume that the propagation delay among sensor nodes is negligible, which is not the case in underwater sensor networks. Time synchronization is mainly affected by a long propagation delay among sensor nodes due to the low propagation speed of acoustic signals. Furthermore, sensor nodes in underwater tend to experience some degree of mobility due to wind or ocean current, or some other nodes are on self-propelled vehicles, such as autonomous underwater vehicles (AUVs). In this paper, we propose a Doppler-enhanced time synchronization scheme for mobile underwater sensor networks, called DE-Sync. Our new scheme considers the effect of the clock skew during the process of estimating the Doppler scale factor and directly substitutes the Doppler scale factor into linear regression to achieve the estimation of the clock skew and offset. Simulation results show that DE-Sync outperforms existing time synchronization protocols in both accuracy and energy efficiency.

Precoding based channel prediction for underwater acoustic OFDM

NASA Astrophysics Data System (ADS)

Cheng, En; Lin, Na; Sun, Hai-xin; Yan, Jia-quan; Qi, Jie

2017-04-01

The life duration of underwater cooperative network has been the hot topic in recent years. And the problem of node energy consuming is the key technology to maintain the energy balance among all nodes. To ensure energy efficiency of some special nodes and obtain a longer lifetime of the underwater cooperative network, this paper focuses on adopting precoding strategy to preprocess the signal at the transmitter and simplify the receiver structure. Meanwhile, it takes into account the presence of Doppler shifts and long feedback transmission delay in an underwater acoustic communication system. Precoding technique is applied based on channel prediction to realize energy saving and improve system performance. Different precoding methods are compared. Simulated results and experimental results show that the proposed scheme has a better performance, and it can provide a simple receiver and realize energy saving for some special nodes in a cooperative communication.

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.

Water Surface Currents, Short Gravity-Capillary Waves and Radar Backscatter

NASA Technical Reports Server (NTRS)

Atakturk, Serhad S.; Katsaros, Kristina B.

1993-01-01

Despite their importance for air-sea interaction and microwave remote sensing of the ocean surface, intrinsic properties of short gravity-capillary waves are not well established. This is largely due to water surface currents and their effects on the direct measurements of wave parameters conducted at a fixed point. Frequencies of small scale waves propagating on a surface which itself is in motion, are subject to Doppler shifts. Hence, the high frequency tail of the wave spectra obtained from such temporal observations is smeared. Conversion of this smeared measured-frequency spectra to intrinsic-frequency (or wavenumber) spectra requires corrections for the Doppler shifts. Such attempts in the past have not been very successful in particular when field data were used. This becomes evident if the amplitude modulation of short waves by underlying long waves is considered. Microwave radar studies show that the amplitude of a short wave component attains its maximum value near the crests and its minimum in the troughs of the long waves. Doppler-shifted wave data yield similar results but much larger in modulation magnitude, as expected. In general, Doppler shift corrections reduce the modulation magnitude. Overcorrection may result in a negligible modulation or even in a strong modulation with the maximum amplitude in the wave troughs. The latter situation is clearly contradictory to our visual observations as well as the radar results and imply that the advection by currents is overestimated. In this study, a differential-advection approach is used in which small scale waves are advected by the currents evaluated not at the free surface, but at a depth proportional to their wavelengths. Applicability of this approach is verified by the excellent agreement in phase and magnitude of short-wave modulation between results based on radar and on wave-gauge measurements conducted on a lake.

Doppler characteristics of sea clutter.

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

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 characteristicsmore » 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.« less

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.

Quantification of absolute blood velocity using LDA

NASA Astrophysics Data System (ADS)

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

2018-04-01

We developed novel schematics of a Laser Doppler anemometer where measuring volume is comparable with the red blood cell (RBC) size and a small period of interference fringes improves device resolution. The technique was used to estimate Doppler frequency shift at flow velocity measurements. It has been shown that technique is applicable for measurements in whole blood.

The high-resolution Doppler imager on the Upper Atmosphere Research Satellite

NASA Technical Reports Server (NTRS)

Hays, Paul B.; Abreu, Vincent J.; Dobbs, Michael E.; Gell, David A.; Grassl, Heinz J.; Skinner, Wilbert R.

1993-01-01

The high-resolution Doppler imager (HRDI) on the Upper Atmosphere Research Satellite is a triple-etalon Fabry-Perot interferometer designed to measure winds in the stratosphere, mesosphere, and lower thermosphere. Winds are determined by measuring the Doppler shifts of rotational lines of the O2 atmospheric band, which are observed in emission in the mesosphere and lower thermosphere and in absorption in the stratosphere. The interferometer has high resolution (0.05/cm), good offhand rejection, aud excellent stability. This paper provides details of the design and capabilities of the HRDI instrument.

Doppler search for a gravitational background radiation with two spacecraft

NASA Astrophysics Data System (ADS)

Bertotti, B.; Iess, L.

1985-11-01

The prospect of detecting a gravitational wave background by means of a simultaneous Doppler tracking of two spacecraft are discussed. It is found that the cross spectrum of the Doppler shifts of the two spacecraft is a filtered expression of the energy density spectrum of the background. The filter function, which is expressed as a series in terms of Legendre polynomials, is obtained by an integration over the rotation group, assuming the background to be isotropic. The main noise sources are examined, and the advantages of a measurement with two spacecraft are noted.

Doppler imaging using spectrally-encoded endoscopy

PubMed Central

Yelin, Dvir; Bouma, B. E.; Rosowsky, J. J.; Tearney, G. J.

2009-01-01

The capability to image tissue motion such as blood flow through an endoscope could have many applications in medicine. Spectrally encoded endoscopy (SEE) is a recently introduced technique that utilizes a single optical fiber and miniature diffractive optics to obtain endoscopic images through small diameter probes. Using spectral-domain interferometry, SEE is furthermore capable of three-dimensional volume imaging at video rates. Here we show that by measuring relative spectral phases, this technology can additionally measure Doppler shifts. Doppler SEE is demonstrated in flowing Intralipid phantoms and vibrating middle ear ossicles. PMID:18795020

Method and apparatus for Doppler frequency modulation of radiation

NASA Technical Reports Server (NTRS)

Margolis, J. S.; Mccleese, D. J.; Shumate, M. S.; Seaman, C. H. (Inventor)

1980-01-01

A method and apparatus are described for frequency modulating radiation, such as from a laser, for optoacoustic detectors, interferometers, heterodyne spectrometers, and similar devices. Two oppositely reciprocating cats-eye retroreflectors are used to Doppler modulate the radiation. By reciprocally moving both retroreflectors, the center of mass is maintained constant to permit smooth operation at many Hertz. By slightly offsetting the axis of one retroreflector relative to the other, multiple passes of a light beam may be achieved for greater Doppler shifts with the same reciprocating motion of the retroreflectors.

Long-range, noncoherent laser Doppler velocimeter.

PubMed

Bloom, S H; Kremer, R; Searcy, P A; Rivers, M; Menders, J; Korevaar, E

1991-11-15

An experimental demonstration of a long-range, noncoherent laser Doppler velocimeter (LDV) is presented. The LDV detects incoming Doppler-shifted signal photons by using the sharp spectral absorption features in atomic or molecular vapors. The edge of the absorption feature is used to convert changes in frequency to large changes in transmission. Preliminary measurements of wind velocity using seeded aerosols showed that the LDV results agreed with mechanical anemometer measurements to within the accuracy of the LDV measurements. With optimization the LDV will provide accurate range-resolved and vibration-tolerant wind-speed measurements at large distances.

Recent Developments in Microwave Ion Clocks

NASA Astrophysics Data System (ADS)

Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

We review the development of microwave-frequency standards based on trapped ions. Following two distinct paths, microwave ion clocks have evolved greatly in the last twenty years since the earliest Paul-trap-based units. Laser-cooled ion frequency standards reduce the second-order Doppler shift from ion micromotion and thermal secular motion achieving good signal-to-noise ratios via cycling transitions where as many as ~10^8 photons per second per ion may be scattered. Today, laser-cooled ion standards are based on linear Paul traps which hold ions near the node line of the trapping electric field, minimizing micromotion at the trapping-field frequency and the consequent second-order Doppler frequency shift. These quadrupole (radial) field traps tightly confine tens of ions to a crystalline single-line structure. As more ions are trapped, space charge forces some ions away from the node-line axis and the second-order Doppler effect grows larger, even at negligibly small secular temperatures. Buffer-gas-cooled clocks rely on large numbers of ions, typically ~10^7, optically pumped by a discharge lamp at a scattering rate of a few photons per second per ion. To reduce the second-order Doppler shift from space charge repulsion of ions from the trap node line, novel multipole ion traps are now being developed where ions are weakly bound with confining fields that are effectively zero through the trap interior and grow rapidly near the trap electrode ``walls''.

Extreme Doppler Shifting of Io's Neutral Jets

NASA Astrophysics Data System (ADS)

Schmidt, Carl

2017-08-01

The dynamics and the extension of Jupiter's magnetosphere are determined by the massive internal plasma sources combined with the fast rotation. The vast majority of the plasma originates from the atmosphere of the moon Io, the most volcanically active body in our solar system. Here we propose to characterize the density and velocity of energetic neutral atoms escaping from Io's atmosphere. Exploiting the high resolution and sensitivity of the COS G130M spectral mode, we will measure the Doppler velocities of atomic O, S and Cl streams, which are energized through charge exchange and dissociative recombination of molecular ions. Prior COS observations of Io revealed a large number of emission lines from several ion and neutral species with excellent S/N, obtained over a single HST orbit. Those spectra were obtained surrounding eclipse geometry, where Doppler shifts are minimized and were restricted to Io itself rather than the stream region. Here we will target the extended clouds with only two orbits total when the moon is at eastern and western elongation for maximum Doppler shifts. The observations will provide new constraints on the diffuse large-scale cloud structures in the Jovian system and significantly improve our understanding of the transport of mass and energy within the Io-torus interaction. The absolute brightness, in combination with plasma parameters from line ratios/collision strengths, will allow us to quantify the outflow of energetic neutral atoms from Io's main sulfur-oxygen atmosphere for the first time.

A theoretical framework for the changing spectral properties of meter-scale Farley-Buneman waves between 90 and 125 km altitudes

NASA Astrophysics Data System (ADS)

St.-Maurice, Jean-Pierre; Chau, Jorge L.

2016-10-01

Stimulated by recent observations described in a companion paper, we have revisited existing theories of the Farley-Buneman instability throughout the altitude range 90 to 125 km. We have assumed that the irregularities detected by radars at a given altitude are dominated by structures moving at the threshold speed in a direction associated with maximum linear growth rate conditions. We included recent nonisothermal electron and ion theories, which can modify threshold speeds by considerable amounts. We included altitude-dependent models of ion and electron temperature and of the ion motion in the phase velocity calculations. Our treatment of the instability explains why some spectra are slow (Doppler shifts typically 200 m/s) and narrow, while others are fast (1500 m/s or close to the E × B) and narrow. These narrow spectra have all the characteristics of what has been labeled as "Type III" and "Type IV" in the past. Our calculations also offer an explanation for the observation of a strong asymmetry in the number of events with positive Doppler shifts near the nominal ion-acoustic speed and those with negative Doppler shifts of the same magnitude.

Long microwave delay fiber-optic link for radar testing

NASA Astrophysics Data System (ADS)

Newberg, I. L.; Gee, C. M.; Thurmond, G. D.; Yen, H. W.

1990-05-01

A long fiberoptic delay line is used as a radar repeater to improve radar testing capabilities. The first known generation of 152 microsec delayed ideal target at X-band (10 GHz) frequencies having the phase stability and signal-to-noise ratio (SNR) needed for testing modern high-resolution Doppler radars is demonstrated with a 31.6-km experimental externally modulated fiberoptic link with a distributed-feedback (DFB) laser. The test application, link configuration, and link testing are discussed.

Carrier Estimation Using Classic Spectral Estimation Techniques for the Proposed Demand Assignment Multiple Access Service

NASA Technical Reports Server (NTRS)

Scaife, Bradley James

1999-01-01

In any satellite communication, the Doppler shift associated with the satellite's position and velocity must be calculated in order to determine the carrier frequency. If the satellite state vector is unknown then some estimate must be formed of the Doppler-shifted carrier frequency. One elementary technique is to examine the signal spectrum and base the estimate on the dominant spectral component. If, however, the carrier is spread (as in most satellite communications) this technique may fail unless the chip rate-to-data rate ratio (processing gain) associated with the carrier is small. In this case, there may be enough spectral energy to allow peak detection against a noise background. In this thesis, we present a method to estimate the frequency (without knowledge of the Doppler shift) of a spread-spectrum carrier assuming a small processing gain and binary-phase shift keying (BPSK) modulation. Our method relies on an averaged discrete Fourier transform along with peak detection on spectral match filtered data. We provide theory and simulation results indicating the accuracy of this method. In addition, we will describe an all-digital hardware design based around a Motorola DSP56303 and high-speed A/D which implements this technique in real-time. The hardware design is to be used in NMSU's implementation of NASA's demand assignment, multiple access (DAMA) service.

Asteroid orbit fitting with radar and angular observations

NASA Astrophysics Data System (ADS)

Baturin, A. P.

2013-12-01

The asteroid orbit fitting problem using their radar and angular observations has been considered. The problem was solved in a standanrd way by means of minimization of weighted sum of squares of residuals. In the orbit fitting both kinds of radar observa-tions have been used: the observations of time delays and of Doppler frequency shifts. The weight for angular observations has been set the same for all of them and has been determined as inverse mean-square residual obtained in the orbit fitting using just angular observations. The weights of radar observations have been set as inverse squared errors of these observations published together with them in the Minor Planet Center electronical circulars (MPECs). For the orbit fitting some five asteroids have been taken from these circulars. The asteroids have been chosen fulfilling the requirement of more than six radar observations of them to be available. The asteroids are 1950 DA, 1999 RQ36, 2002 NY40, 2004 DC and 2005 EU2. Several orbit fittings for these aster-oids have been done: with just angular observations; with just radar observations; with both angular and radar observations. The obtained results are quite acceptable because in the last case the mean-square angular residuals are approximately equal to the same ones obtained in the fitting with just angular observations. As to radar observations mean-square residuals, the time delay residuals for three asteroids do not exceed 1 μs, for two others ˜ 10 μs and the Doppler shift residuals for three asteroids do not exceed 1 Hz, for two others ˜ 10 Hz. The motion equations included perturbations from 9 planets and the Moon using their ephemerides DE422. The numerical integration has been performed with Everhart 27-order method with variable step. All calculations have been exe-cuted to a 34-digit decimal precision (i.e. using 128-bit floating-point numbers). Further, the sizes of confidence ellipsoids of im-proved orbit parameters have been compared. It has been accepted that an indicator of ellipsoid size is a geometric mean of its six semi-axes. A comparison of sizes has shown that confidence ellipsoids obtained in orbit fitting with both angular and radar obser-vations are several times less than ellipsoids obtained with just angular observations.

Experiments Using Cell Phones in Physics Classroom Education: The Computer-Aided "g" Determination

ERIC Educational Resources Information Center

Vogt, Patrik; Kuhn, Jochen; Muller, Sebastian

2011-01-01

This paper continues the collection of experiments that describe the use of cell phones as experimental tools in physics classroom education. We describe a computer-aided determination of the free-fall acceleration "g" using the acoustical Doppler effect. The Doppler shift is a function of the speed of the source. Since a free-falling objects…

System for Processing Coded OFDM Under Doppler and Fading

NASA Technical Reports Server (NTRS)

Tsou, Haiping; Darden, Scott; Lee, Dennis; Yan, Tsun-Yee

2005-01-01

An advanced communication system has been proposed for transmitting and receiving coded digital data conveyed as a form of quadrature amplitude modulation (QAM) on orthogonal frequency-division multiplexing (OFDM) signals in the presence of such adverse propagation-channel effects as large dynamic Doppler shifts and frequency-selective multipath fading. Such adverse channel effects are typical of data communications between mobile units or between mobile and stationary units (e.g., telemetric transmissions from aircraft to ground stations). The proposed system incorporates novel signal processing techniques intended to reduce the losses associated with adverse channel effects while maintaining compatibility with the high-speed physical layer specifications defined for wireless local area networks (LANs) as the standard 802.11a of the Institute of Electrical and Electronics Engineers (IEEE 802.11a). OFDM is a multi-carrier modulation technique that is widely used for wireless transmission of data in LANs and in metropolitan area networks (MANs). OFDM has been adopted in IEEE 802.11a and some other industry standards because it affords robust performance under frequency-selective fading. However, its intrinsic frequency-diversity feature is highly sensitive to synchronization errors; this sensitivity poses a challenge to preserve coherence between the component subcarriers of an OFDM system in order to avoid intercarrier interference in the presence of large dynamic Doppler shifts as well as frequency-selective fading. As a result, heretofore, the use of OFDM has been limited primarily to applications involving small or zero Doppler shifts. The proposed system includes a digital coherent OFDM communication system that would utilize enhanced 802.1la-compatible signal-processing algorithms to overcome effects of frequency-selective fading and large dynamic Doppler shifts. The overall transceiver design would implement a two-frequency-channel architecture (see figure) that would afford frequency diversity for reducing the adverse effects of multipath fading. By using parallel concatenated convolutional codes (also known as Turbo codes) across the dual-channel and advanced OFDM signal processing within each channel, the proposed system is intended to achieve at least an order of magnitude improvement in received signal-to-noise ratio under adverse channel effects while preserving spectral efficiency.

A level 2 wind speed retrieval algorithm for the CYGNSS mission

NASA Astrophysics Data System (ADS)

Clarizia, Maria Paola; Ruf, Christopher; O'Brien, Andrew; Gleason, Scott

2014-05-01

The NASA EV-2 Cyclone Global Navigation Satellite System (CYGNSS) is a spaceborne mission focused on tropical cyclone (TC) inner core process studies. CYGNSS consists of a constellation of 8 microsatellites, which will measure ocean surface wind speed in all precipitating conditions, including those experienced in the TC eyewall, and with sufficient frequency to resolve genesis and rapid intensification. It does so through the use of an innovative remote sensing technique, known as Global Navigation Satellite System-Reflectometry, or GNSS-R. GNSS-R uses signals of opportunity from navigation constellations (e.g. GPS, GLONASS, Galileo), scattered by the surface of the ocean, to retrieve the surface wind speed. The dense space-time sampling capabilities, the ability of L-band signals to penetrate well through rain, and the possibility of simple, low-cost/low-power GNSS receivers, make GNSS-R ideal for the CYGNSS goals. Here we present an overview of a Level 2 (L2) wind speed retrieval algorithm, which would be particularly suitable for CYGNSS, and could be used to estimate winds from GNSS-R in general. The approach makes use of two different observables computed from 1-second Level 2a (L2a) delay-Doppler Maps (DDMs) of radar cross section. The first observable is called Delay-Doppler Map Average (DDMA), and it's the averaged radar cross section over a delay-Doppler window around the DDM peak (i.e. the specular reflection point coordinate in delay and Doppler). The second is called the Leading Edge Slope (LES), and it's the leading edge of the Integrated Delay Waveform (IDW), obtained by integrating the DDM along the Doppler dimension. The observables are calculated over a limited range of delays and Doppler frequencies, to comply with baseline spatial resolution requirements for the retrieved winds, which in the case of CYGNSS is 25 km x 25 km. If the observable from the 1-second DDM corresponds to a resolution higher than the specified one, time-averaging between consecutive observables is also applied, to reduce further the noise in the observables. The observables are correlated with wind speed, allowing one to develop an empirical Geophysical Model Function (GMF) that relates the observable value to the ground truth matchup winds, using a training dataset. The empirical GMF can then be used to estimate the winds from a generic dataset of observables, independent from the training one. In addition to that, the degree of decorrelation existing between winds retrieved from DDMA and from LES leads to the development of a Minimum Variance (MV) estimator, which provides improved wind estimates compared to those from DDMA or LES alone. The retrieval algorithm is applied in this study to GNSS-R synthetic data simulated using an End-to-End Simulator (E2ES) developed for CYGNSS, and using the true wind speeds that constitute the input to the simulations, as the ground-truth matchups. The performances of the retrieval algorithm will be presented in the form of Root Mean Square (RMS) error between the true and retrieved winds, highlighting that, for those specular points acquired with high enough gain of the receiver antenna, the RMS error meets the CYGNSS requirements on the wind speed uncertainty, which must be the greatest between 2 m/s or 10% of the measured wind.

Doppler optical coherence tomography of retinal circulation.

PubMed

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

2012-09-18

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 practicality of making these measurements in clinical studies and routine clinical practice.

Thermospheric nighttime wind and temperature analysis from some 2014 stormy nights monitored at Oukaimeden Observatory by RENOIR instrument

NASA Astrophysics Data System (ADS)

Bounhir, Aziza; Benkhaldoun, Zouhair; Kaab, Mohamed; Makela, Jonathan J.; Harding, Brian; Fisher, Daniel J.; Lagheryeb, Amine; Khalifa, Malki; Lazrek, Mohamed; Daassou, Ahmed

2015-08-01

In this paper we report on the thermospheric winds and temperatures over Oukaimeden Observatory in Morocco in some stormy nights during the year 2014. These results are based on Fabry-Perot interferometer (FPI) measurements of Doppler shifts and Doppler broadenings of the 630.0nm spectral emission and pertain to the lower thermosphere region, near 250km altitude. This FPI is a part of RENOIR experiment installed thanks to scientific cooperation program with university of Illinois Urbana (USA).The storm energy input modify the global circulation in the thermosphere resulting in significant changes in the ionospheric plasma properties. Thermospheric and ionospheric storms are closely connected.We first set up the climatological behavior of the thermospheric winds and temperature during quiet nights. These results will be presented in this session in a separate abstract (M. Kaab & Z. Benkhaldoun et al) . Then we investigate the departure of the winds and the temperatures from their climatological behavior during some magnetic storms. The winds present many features. We can notice westward winds and an enhancement of the equatorward winds with sometimes an appearance of a poleward component. We also notice a significant increase of the temperature that last several hours. By looking trough the geomagnetic indices we investigate the delay of thermospheric storm time in our region and its effects on the winds and temperature patterns.

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.

Geodetic positioning using a global positioning system of satellites

NASA Technical Reports Server (NTRS)

Fell, P. J.

1980-01-01

Geodetic positioning using range, integrated Doppler, and interferometric observations from a constellation of twenty-four Global Positioning System satellites is analyzed. A summary of the proposals for geodetic positioning and baseline determination is given which includes a description of measurement techniques and comments on rank deficiency and error sources. An analysis of variance comparison of range, Doppler, and interferometric time delay to determine their relative geometric strength for baseline determination is included. An analytic examination to the effect of a priori constraints on positioning using simultaneous observations from two stations is presented. Dynamic point positioning and baseline determination using range and Doppler is examined in detail. Models for the error sources influencing dynamic positioning are developed. Included is a discussion of atomic clock stability, and range and Doppler observation error statistics based on random correlated atomic clock error are derived.

Reconsidering Dark Matter

NASA Astrophysics Data System (ADS)

Aisenberg, Sol

2012-02-01

There is a difference between (a) distances of remote standard candles, SN Type Ia, and (b) distances based upon their red shifts. It was believed that these galaxies had accelerated and used Dark Energy. There are 2 assumptions not supported by observations. The first is that the red shifts for remote galaxies are due to the Doppler Effect associated with receding velocity. Hubble only observed red shifts as a function of distances of known stars, and never measured receding velocities. He suggested the Doppler Effect as a cause, but expressed doubt about the suggestion. There are other causes for a red shift - gravity red shift of light from the sun, and loss of photon energy by gravity interaction of photons with dust and gas in interstellar space. The second assumption is that Hubble's linear relationship between the observed red shift and the distance will be valid at very large distances. Increasing red shift corresponds to a decrease of photon energy towards zero, and cannot be used for very remote stars - where the photon energy approaches zero and the red shift dependence becomes nonlinear and asymptotic to a constant value. This predicts the difference between the galaxy distances and the distances determined from their observed red shifts. The recent Nobel Prize (to Schmidt, Reis, and Perlmutter) needs reexamination. Two basic assumptions that are the foundation of their work may not be accurate. Details are in my earlier essays in ``The Misunderstood Universe'', 2009. .

Detection and characterization of Budd-Chiari syndrome with inferior vena cava obstruction: Comparison of fixed and flexible delayed scan time of computed tomography venography.

PubMed

Zhou, Peng-Li; Wu, Gang; Han, Xin-Wei; Bi, Yong-Hua; Zhang, Wen-Guang; Wu, Zheng-Yang

2017-06-01

To compare the results of computed tomography venography (CTV) with a fixed and a flexible delayed scan time for Budd-Chiari syndrome (BCS) with inferior vena cava (IVC) obstruction. A total of 209 consecutive BCS patients with IVC obstruction underwent either a CTV with a fixed delayed scan time of 180s (n=87) or a flexible delayed scan time for good image quality according to IVC blood flow in color Doppler ultrasonography (n=122). The IVC blood flow velocity was measured using a color Doppler ultrasound prior to CT scan. Image quality was classified as either good, moderate, or poor. Image quality, surrounding structures and the morphology of the IVC obstruction were compared between the two groups using a χ 2 -test or paired or unpaired t-tests as appropriate. Inter-observer agreement was assessed using Kappa statistics. There was no significant difference in IVC blood flow velocity between the two groups. Overall image quality, surrounding structures and IVC obstruction morphology delineation on the flexible delayed scan time of CTV images were rated better relative to those obtained by fixed delayed scan time of CTV images (p<0.001). Evaluation of CTV data sets was significantly facilitated with flexible delayed scan time of CTV. There were no significant differences in Kappa statistics between Group A and Group B. The flexible delayed scan time of CTV was associated with better detection and more reliable characterization of BCS with IVC obstruction compared to a fixed delayed scan time. Copyright © 2017 Elsevier B.V. All rights reserved.

Mass defect effects in atomic clocks

NASA Astrophysics Data System (ADS)

Yudin, Valeriy; Taichenachev, Alexey

2018-03-01

We consider some implications of the mass defect on the frequency of atomic transitions. We have found that some well-known frequency shifts (the gravitational shift and motion-induced shifts such as quadratic Doppler and micromotion shifts) can be interpreted as consequences of the mass defect in quantum atomic physics, i.e. without the need for the concept of time dilation used in special and general relativity theories. Moreover, we show that the inclusion of the mass defect leads to previously unknown shifts for clocks based on trapped ions.

Microwave imaging of spinning object using orbital angular momentum

NASA Astrophysics Data System (ADS)

Liu, Kang; Li, Xiang; Gao, Yue; Wang, Hongqiang; Cheng, Yongqiang

2017-09-01

The linear Doppler shift used for the detection of a spinning object becomes significantly weakened when the line of sight (LOS) is perpendicular to the object, which will result in the failure of detection. In this paper, a new detection and imaging technique for spinning objects is developed. The rotational Doppler phenomenon is observed by using the microwave carrying orbital angular momentum (OAM). To converge the radiation energy on the area where objects might exist, the generation method of OAM beams is proposed based on the frequency diversity principle, and the imaging model is derived accordingly. The detection method of the rotational Doppler shift and the imaging approach of the azimuthal profiles are proposed, which are verified by proof-of-concept experiments. Simulation and experimental results demonstrate that OAM beams can still be used to obtain the azimuthal profiles of spinning objects even when the LOS is perpendicular to the object. This work remedies the insufficiency in existing microwave sensing technology and offers a new solution to the object identification problem.

Doppler effect for sound emitted by a moving airborne source and received by acoustic sensors located above and below the sea surface.

PubMed

Ferguson, B G

1993-12-01

The acoustic emissions from a propeller-driven aircraft are received by a microphone mounted just above ground level and then by a hydrophone located below the sea surface. The dominant feature in the output spectrum of each acoustic sensor is the spectral line corresponding to the propeller blade rate. A frequency estimation technique is applied to the acoustic data from each sensor so that the Doppler shift in the blade rate can be observed at short time intervals during the aircraft's transit overhead. For each acoustic sensor, the observed variation with time of the Doppler-shifted blade rate is compared with the variation predicted by a simple ray-theory model that assumes the atmosphere and the sea are distinct isospeed sound propagation media separated by a plane boundary. The results of the comparison are shown for an aircraft flying with a speed of about 250 kn at altitudes of 500, 700, and 1000 ft.

Detection of mitral valve abnormalities by carotid Doppler flow study: implications for the management of patients with cerebrovascular disease.

PubMed

Weinberger, J; Goldman, M

1985-01-01

Patients with symptoms of cerebral ischemia are often evaluated with non-invasive carotid artery testing. An abnormal carotid Doppler ultrasound frequency shift pattern of early systolic flutter (ESF) was demonstrated by auscultation and velocity wave form analysis in patients with normal carotid bifurcations. Ten of these patients were studied with echocardiography (echo) and eight had mitral valve prolapse (MVP). To evaluate the association between ESF and MVP, a prospective blinded study was performed, recording carotid Doppler frequency shift in 50 patients referred for routine echocardiography. A total of 18 patients had ESF: 9/12 patients with MVP by echocardiography had ESF. Nine additional patients without MVP had ESF (two with mitral regurgitation and two with redundant mitral valves). The association of ESF with MVP was significant (p less than 0.001). The findings of ESF with a normal carotid artery by non-invasive testing suggests a possible mitral valve origin for symptoms of cerebrovascular disease.

Electronic Warfare and Radar Systems Engineering Handbook. 4th Edition

DTIC Science & Technology

2013-10-01

and Maintainability R&M Reliability and Maintainability RAT Ram Air Turbine RBOC Rapid Blooming Offboard Chaff RCP or RHCP Right-hand Circular...Doppler shifted return (see Figure 10). Reflections off rotating jet engine compressor blades, aircraft propellers, ram air turbine (RAT...Doppler techniques, in order to precisely predict aircraft ground speed and direction of motion. Wind influences are taken into account, such that

Wind Profiles Obtained with a Molecular Direct Detection Doppler Lidar During IHOP-2002

NASA Technical Reports Server (NTRS)

Gentry, Bruce M.; Chen, Huai-Lin; Li, Steven X.; Mathur, Savyasachee; Dobler, Jeremy; Hasselbrack, William; Comer, Joseph

2004-01-01

The Goddard Lidar Observatory for Winds (GLOW) is a mobile direct detection Doppler lidar system which uses the double edge technique to measure the Doppler shift of the molecular backscattered laser signal at a wavelength of 355 nm. In the spring of 2002 GLOW was deployed to the western Oklahoma profiling site (36 deg 33.500 min. N, 100 deg. 36.371 min. W) to participate in the International H2O Project (IHOP). During the IHOP campaign over 240 hours of wind profiles were obtained with the GLOW lidar in support of a variety of scientific investigations.

Fraunhofer filters to reduce solar background for optical communications

NASA Technical Reports Server (NTRS)

Kerr, E. L.

1986-01-01

A wavelength that lies within a spectral interval of reduced solar emission (a Fraunhofer line) can carry optical communications with reduced interference from direct or reflected background sunlight. Suitable Fraunhofer lines are located within the tuning range of good candidate lasers. The laser should be tunable dynamically to track Doppler shifts in the sunlight incident on any solar system body that may appear in the background as viewed by the receiver. A Fraunhofer filter used with a direct-detection receiver should be tuned to match the Doppler shifts of the source and background. The required tuning calculated here for various situations is also required if, instead, one uses a heterodyne receiver with limited post-detection bandwidth.

Specialization of the auditory system for the processing of bio-sonar information in the frequency domain: Mustached bats.

PubMed

Suga, Nobuo

2018-04-01

For echolocation, mustached bats emit velocity-sensitive orientation sounds (pulses) containing a constant-frequency component consisting of four harmonics (CF 1-4 ). They show unique behavior called Doppler-shift compensation for Doppler-shifted echoes and hunting behavior for frequency and amplitude modulated echoes from fluttering insects. Their peripheral auditory system is highly specialized for fine frequency analysis of CF 2 (∼61.0 kHz) and detecting echo CF 2 from fluttering insects. In their central auditory system, lateral inhibition occurring at multiple levels sharpens V-shaped frequency-tuning curves at the periphery and creates sharp spindle-shaped tuning curves and amplitude tuning. The large CF 2 -tuned area of the auditory cortex systematically represents the frequency and amplitude of CF 2 in a frequency-versus-amplitude map. "CF/CF" neurons are tuned to a specific combination of pulse CF 1 and Doppler-shifted echo CF 2 or 3 . They are tuned to specific velocities. CF/CF neurons cluster in the CC ("C" stands for CF) and DIF (dorsal intrafossa) areas of the auditory cortex. The CC area has the velocity map for Doppler imaging. The DIF area is particularly for Dopper imaging of other bats approaching in cruising flight. To optimize the processing of behaviorally relevant sounds, cortico-cortical interactions and corticofugal feedback modulate the frequency tuning of cortical and sub-cortical auditory neurons and cochlear hair cells through a neural net consisting of positive feedback associated with lateral inhibition. Copyright © 2018 Elsevier B.V. All rights reserved.

Moving target parameter estimation of SAR after two looks cancellation

NASA Astrophysics Data System (ADS)

Gan, Rongbing; Wang, Jianguo; Gao, Xiang

2005-11-01

Moving target detection of synthetic aperture radar (SAR) by two looks cancellation is studied. First, two looks are got by the first and second half of the synthetic aperture. After two looks cancellation, the moving targets are reserved and stationary targets are removed. After that, a Constant False Alarm Rate (CFAR) detector detects moving targets. The ground range velocity and cross-range velocity of moving target can be got by the position shift between the two looks. We developed a method to estimate the cross-range shift due to slant range moving. we estimate cross-range shift by Doppler frequency center. Wigner-Ville Distribution (WVD) is used to estimate the Doppler frequency center (DFC). Because the range position and cross range before correction is known, estimation of DFC is much easier and efficient. Finally experiments results show that our algorithms have good performance. With the algorithms we can estimate the moving target parameter accurately.

Search for Doppler-shifted gamma-ray emission from SS 433 using the SMM spectrometer

NASA Technical Reports Server (NTRS)

Geldzahler, B. J.; Share, G. H.; Kinzer, R. L.; Magura, J.; Chupp, E. L.

1989-01-01

Data accumulated from 1980 to 1983 with the Gamma Ray Spectrometer aboard NASA's Solar Maximum Mission (SMM) satellite were searched for evidence of red and blue Doppler-shifted 1.37 MeV Mg-24 nuclear lines from SS 433. The SMM data base covers 270 days when SS 433 was in the field of view and includes periods of radio flaring and quiescence. No evidence was found for Doppler-shifted line emission in any of the spectra. The range of 3-sigma upper limits for individual 9 day integration periods was 0.0008-0.0023 photons/sq cm per sec for the blue beam, encompassing the reported about 1.5 MeV line, and 0.0008-0.002 photons/sq cm per sec for the red beam, encompassing the reported about 1.2 MeV line; the average 3-sigma upper limit in each beam for shifted about 1.37 MeV lines is 0.0015 photons/sq cm per sec for single 9 day integrations. The 3-sigma upper limit on 1.37 MeV gamma-ray emission over 23 9-day integration intervals for the red beam and 28 intervals for the blue beam is 0.0002 photons/sq cm per sec. These new limits from SMM can be reconciled with the HEAO 3 results only if SS 433 emits gamma radiation at or above the SMM sensitivity limit on rare occasions due to variable physical conditions in the system.

Short wavelength ion waves upstream of the earth's bow shock

NASA Technical Reports Server (NTRS)

Fuselier, S. A.; Gurnett, D. A.

1984-01-01

The identification and explanation of short wavelength antenna interference effects observed in spacecraft plasma wave data have provided an important new method of determining limits on the wavelength, direction of propagation, and Doppler shift of short wavelength electrostatic waves. Using the ISEE-1 wideband electric field data, antenna interference effects have been identified in the ion waves upstream of the earth's bow shock. This identification implies that wavelengths of the upstream ion waves are shorter than the antenna length. The interference effects also provide new measurements of the direction of propagation of the ion waves. The new measurements show that the wave vectors of the ion waves are not parallel to the interplanetary magnetic field (IMF) as previously reported. The direction of propagation does not appear to be controlled by the IMF. In addition, analysis of the Doppler shift of the short wavelength ion waves has provided a measurement of the dispersion relation. The upper limit of the rest frame frequency was found to be on the order of the ion plasma frequency. At this frequency, the wavelength is on the order of a few times the Debye length. The results of this study now provide strong evidence that the ion waves in the upstream region are Doppler-shifted ion acoustic waves. Previously announced in STAR as N83-36328

Spacecraft-to-Earth Communications for Juno and Mars Science Laboratory Critical Events

NASA Technical Reports Server (NTRS)

Soriano, Melissa; Finley, Susan; Jongeling, Andre; Fort, David; Goodhart, Charles; Rogstad, David; Navarro, Robert

2012-01-01

Deep Space communications typically utilize closed loop receivers and Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK). Critical spacecraft events include orbit insertion and entry, descent, and landing.---Low gain antennas--> low signal -to-noise-ratio.---High dynamics such as parachute deployment or spin --> Doppler shift. During critical events, open loop receivers and Multiple Frequency Shift Keying (MFSK) used. Entry, Descent, Landing (EDL) Data Analysis (EDA) system detects tones in real-time.

Interstellar holography

NASA Astrophysics Data System (ADS)

Walker, M. A.; Koopmans, L. V. E.; Stinebring, D. R.; van Straten, W.

2008-08-01

The dynamic spectrum of a radio pulsar is an in-line digital hologram of the ionized interstellar medium. It has previously been demonstrated that such holograms permit image reconstruction, in the sense that one can determine an approximation to the complex electric field values as a function of Doppler shift and delay, but to date the quality of the reconstructions has been poor. Here we report a substantial improvement in the method which we have achieved by simultaneous optimization of the thousands of coefficients that describe the electric field. For our test spectrum of PSRB0834+06 we find that the model provides an accurate representation of the data over the full 63dB dynamic range of the observations: residual differences between model and data are noise like. The advent of interstellar holography enables detailed quantitative investigation of the interstellar radio-wave propagation paths for a given pulsar at each epoch of observation. We illustrate this using our test data which show the scattering material to be structured and highly anisotropic. The temporal response of the medium exhibits a scattering tail which extends to beyond 100μs, and the centroid of the pulse at this frequency and this epoch of observation is delayed by approximately 15μs as a result of multipath propagation in the interstellar medium.

Differential correction capability of the GTDS using TDRSS data

NASA Technical Reports Server (NTRS)

Liu, S. Y.; Soskey, D. G.; Jacintho, J.

1980-01-01

A differential correction (DC) capability was implemented in the Goddard Trajectory Determination System (GTDS) to process satellite tracking data acquired via the Tracking and Data Relay Satellite System (TRDRSS). Configuration of the TDRSS is reviewed, observation modeling is presented, and major features of the capability are discussed. The following types of TDRSS data can be processed by GTDS: two way relay range and Doppler measurements, hybrid relay range and Doppler measurements, one way relay Doppler measurements, and differenced one way relay Doppler measurements. These data may be combined with conventional ground based direct tracking data. By using Bayesian weighted least squares techniques, the software allows the simultaneous determination of the trajectories of up to four different satellites - one user satellite and three relay satellites. In addition to satellite trajectories, the following parameters can be optionally solved: for drag coefficient, reflectivity of a satellite for solar radiation pressure, transponder delay, station position, and biases.

Source motion detection, estimation, and compensation for underwater acoustics inversion by wideband ambiguity lag-Doppler filtering.

PubMed

Josso, Nicolas F; Ioana, Cornel; Mars, Jérôme I; Gervaise, Cédric

2010-12-01

Acoustic channel properties in a shallow water environment with moving source and receiver are difficult to investigate. In fact, when the source-receiver relative position changes, the underwater environment causes multipath and Doppler scale changes on the transmitted signal over low-to-medium frequencies (300 Hz-20 kHz). This is the result of a combination of multiple paths propagation, source and receiver motions, as well as sea surface motion or water column fast changes. This paper investigates underwater acoustic channel properties in a shallow water (up to 150 m depth) and moving source-receiver conditions using extracted time-scale features of the propagation channel model for low-to-medium frequencies. An average impulse response of one transmission is estimated using the physical characteristics of propagation and the wideband ambiguity plane. Since a different Doppler scale should be considered for each propagating signal, a time-warping filtering method is proposed to estimate the channel time delay and Doppler scale attributes for each propagating path. The proposed method enables the estimation of motion-compensated impulse responses, where different Doppler scaling factors are considered for the different time delays. It was validated for channel profiles using real data from the BASE'07 experiment conducted by the North Atlantic Treaty Organization Undersea Research Center in the shallow water environment of the Malta Plateau, South Sicily. This paper provides a contribution to many field applications including passive ocean tomography with unknown natural sources position and movement. Another example is active ocean tomography where sources motion enables to rapidly cover one operational area for rapid environmental assessment and hydrophones may be drifting in order to avoid additional flow noise.

Design of a fast echo matching algorithm to reduce crosstalk with Doppler shifts in ultrasonic ranging

NASA Astrophysics Data System (ADS)

Liu, Lei; Guo, Rui; Wu, Jun-an

2017-02-01

Crosstalk is a main factor for wrong distance measurement by ultrasonic sensors, and this problem becomes more difficult to deal with under Doppler effects. In this paper, crosstalk reduction with Doppler shifts on small platforms is focused on, and a fast echo matching algorithm (FEMA) is proposed on the basis of chaotic sequences and pulse coding technology, then verified through applying it to match practical echoes. Finally, we introduce how to select both better mapping methods for chaotic sequences, and algorithm parameters for higher achievable maximum of cross-correlation peaks. The results indicate the following: logistic mapping is preferred to generate good chaotic sequences, with high autocorrelation even when the length is very limited; FEMA can not only match echoes and calculate distance accurately with an error degree mostly below 5%, but also generates nearly the same calculation cost level for static or kinematic ranging, much lower than that by direct Doppler compensation (DDC) with the same frequency compensation step; The sensitivity to threshold value selection and performance of FEMA depend significantly on the achievable maximum of cross-correlation peaks, and a higher peak is preferred, which can be considered as a criterion for algorithm parameter optimization under practical conditions.

Multi-Component, Multi-Point Interferometric Rayleigh/Mie Doppler Velocimeter

NASA Technical Reports Server (NTRS)

Danehy, Paul M.; Lee, Joseph W.; Bivolaru, Daniel

2012-01-01

An interferometric Rayleigh scattering system was developed to enable the measurement of multiple, orthogonal velocity components at several points within very-high-speed or high-temperature flows. The velocity of a gaseous flow can be optically measured by sending laser light into the gas flow, and then measuring the scattered light signal that is returned from matter within the flow. Scattering can arise from either gas molecules within the flow itself, known as Rayleigh scattering, or from particles within the flow, known as Mie scattering. Measuring Mie scattering is the basis of all commercial laser Doppler and particle imaging velocimetry systems, but particle seeding is problematic when measuring high-speed and high-temperature flows. The velocimeter is designed to measure the Doppler shift from only Rayleigh scattering, and does not require, but can also measure, particles within the flow. The system combines a direct-view, large-optic interferometric setup that calculates the Doppler shift from fringe patterns collected with a digital camera, and a subsystem to capture and re-circulate scattered light to maximize signal density. By measuring two orthogonal components of the velocity at multiple positions in the flow volume, the accuracy and usefulness of the flow measurement increase significantly over single or nonorthogonal component approaches.

Detection of cavernous transformation of the portal vein by contrast-enhanced ultrasound.

PubMed

Hwang, Misun; Thimm, Matthew A; Guerrerio, Anthony L

2018-06-01

Cavernous transformation of the portal vein can be missed on color Doppler exam or arterial phase cross-sectional imaging due to their slow flow and delayed enhancement. Contrast-enhanced ultrasound (CEUS) offers many advantages over other imaging techniques and can be used to successfully detect cavernous transformations of the portal vein. A 10-month-old female was followed for repeat episodes of hematemesis. Computed tomography angiography (CTA) and magnetic resonance arteriogram (MRA) and portal venography were performed. Color Doppler exam of the portal vein was performed followed by administration of Lumason, a microbubble US contrast agent. Magnetic resonance arteriogram, CTA, and color Doppler exam at the time of initial presentation was unremarkable without obvious vascular malformation within the limits of motion degraded exam. At 8-month follow-up, esophagogastroduodenoscopy revealed a vascular malformation in the distal esophagus which was sclerosed. At 6 month after sclerosis of the lesion, portal venography revealed occlusion of the portal vein with extensive collateralization. Color Doppler revealed subtle hyperarterialization and periportal collaterals. CEUS following color Doppler exam demonstrated extensive enhancement of periportal collaterals. Repeat color Doppler after contrast administration demonstrated extensive Doppler signal in the collateral vessels, suggestive of cavernous transformation. We describe a case of cavernous transformation of the portal vein missed on initial color Doppler, CTA and MRA, but detected with contrast-enhanced ultrasound technique.

Doppler lidar wind measurement with the edge technique

NASA Technical Reports Server (NTRS)

Korb, C. Laurence; Gentry, Bruce M.

1992-01-01

The edge technique is a new and powerful method for measuring small frequency shifts. Range resolved lidar measurements of winds can be made with high accuracy and high vertical resolution using the edge technique to measure the Doppler shift of an atmospheric backscattered signal from a pulsed laser. The edge technique can be used at near-infrared or visible wavelengths using well developed solid state lasers and detectors with various edge filters. In the edge technique, the laser frequency is located on the steep slope of the spectral response function of a high resolution optical filter. Due to the steep slope of the edge, very small frequency shifts cause large changes in measured signal. The frequency of the outgoing laser pulse is determined by measuring its location on the edge of the filter. This is accomplished by sending a small portion of the beam to the edge detection setup where the incoming light is split into two channels - an edge filter and an energy monitor channel. The energy monitor signal is used to normalize the edge filter signal for magnitude. The laser return backscattered from the atmosphere is collected by a telescope and directed through the edge detection setup to determine its frequency (location on the edge) in a similar manner for each range element. The Doppler shift, and thus the wind, is determined from a differential measurement of the frequency of the outgoing laser pulse and the frequency of the laser return backscattered from the atmosphere. We have conducted simulations of the performance of an edge lidar system using an injection seeded pulsed Nd:YAG laser at 1.06 microns. The central fringe of a Fabry-Perot etalon is used as a high resolution edge filter to measure the shift of the aerosol return.

Optical Interferometric Measurement of Skin Vibration for the Diagnosis of Cardiovascular Diseases.

NASA Astrophysics Data System (ADS)

Hong, Hyundae

A system has been developed based on the measurement of skin surface vibration which is related to the underlying vascular wall motion for the superficial arteries and coronary movement for the chest wall. Data obtained suggests that the information detected by such measurements can be related to the derivative of the intravascular pressure, an important physiological parameter. These results are in contrast to conventional optical Doppler techniques which have been utilized to measure blood perfusion in the skin layers and blood flow within the superficial arteries. These techniques relied on the interaction between incident photons and moving red blood cells. The present system uses an optical interferometer with a 633 nm HeNe laser to detect μm displacements of the skin surface. A photodiode detects an optical Doppler shift signal of frequency, 2 v/ lambda, where v and lambda are the skin vibration velocity and the wavelength of the laser, respectively. The electronic processing system we developed enhances, cleans and processes the raw Doppler signal to produce two main outputs: Doppler audio, and a time domain profile of the skin velocity. The audio signal changes its tone according to the velocity of skin movement which is related to the first derivative of the intravascular pressure, and the internal structure of the intervening tissue layers between the vessel and the surface. The results obtained demonstrated that the skin velocity waveforms near each artery and the chest signals at the auscultation points for the four heart valve sounds were unique in their profiles. It also proved to be possible to measure the magnitude, harmonics, and the cardiovascular propagation delay for pulse waves. The theoretical and experimental results demonstrated that the system detected the skin velocity, which is related to the time derivative of the pressure. It also reduces the loading effect on the pulsation signals and heart sounds produced by the conventional piezoelectric vibration sensors. The system sensitivity, which could potentially be optimized further was 366.2 mum/sec for the present research. Overall, optical cardiovascular vibrometry has the potential to become a simple non invasive approach to cardiovascular screening.

An Externally Dispersed Interferometer for Sensitive Doppler Extrasolar Planet Searches

NASA Astrophysics Data System (ADS)

Ge, Jian; Erskine, David J.; Rushford, Mike

2002-09-01

A new kind of instrument for sensitive Doppler extrasolar planet searches, called an externally dispersed interferometer, is described in this paper. It is a combination of an optical Michelson-type interferometer and an intermediate-resolution grating spectrometer. The interferometer measures Doppler radial velocity (RV) variations of starlight through the phase shifts of moiré fringes, created by multiplication of the interferometer fringes with stellar absorption lines. The intermediate-resolution spectrograph disperses the moiré fringes into thousands of parallel-wavelength channels. This increases the instrument bandwidth and fringe visibility by preventing fringe cross-talk between neighboring spectral lines. This results in a net increase in the signal-to-noise ratio over an interferometer used alone with broadband light. Compared to current echelle spectrometers for extrasolar planet searches, this instrument offers two unique instrument properties: a simple, stable, well-defined sinusoidal instrument response function (point-spread function) and magnification of Doppler motion through moiré fringe techniques. Since instrument noise is chiefly limited by the ability to characterize the instrument response, this new technique provides unprecedented low instrumental noise in an economical compact apparatus, enabling higher precision for Doppler RV measurements. In practice, the moiré magnification can be 5-10 times depending on the interferometer comb angle. This instrument has better sensitivity for smaller Doppler shifts than echelle spectrometers. The instrument can be designed with much lower spectral resolving power without losing Doppler sensitivity and optimized for higher throughput than echelle spectrometers to allow a potential survey for planets around fainter stars than current magnitude limits. Lab-based experiments with a prototype instrument with a spectral resolution of R~20,000 demonstrated ~0.7 m s-1 precision for short-term RV measurements. A fiber-fed version of the prototype with R~5600 was tested with starlight at the Lick 1 m telescope and demonstrated ~7 m s-1 RV precision at 340 Å bandwidth. The increased velocity noise is attributed to the lower spectral resolution, lower fringe visibility, and uncontrolled instrument environment.

The Causes of Logging Truck Delays on Two West Virginia Logging Operations

Treesearch

John E. Baumgras

1978-01-01

Logging truck downtime increases timber harvesting costs. To determine the extent and causes of truck delays, four logging trucks on two separate operations were monitored for a 7-month period by recording speedometers and with tallies of delay causes. The results show the number of truck delays per shift, their duration, and the total delay time per shift for eight...

Biventricular pacemaker optimization guided by comprehensive echocardiography-preliminary observations regarding the effects on systolic and diastolic ventricular function and third heart sound.

PubMed

Taha, Nima; Zhang, Jing; Ranjan, Rupesh; Daneshvar, Samuel; Castillo, Edilzar; Guillen, Elizabeth; Montoya, Martha C; Velasquez, Giovanna; Naqvi, Tasneem Z

2010-08-01

Doppler echocardiography of mitral inflow or aortic outflow or both has been validated and advocated to guide biventricular (Biv) pacemaker optimization. A comprehensive and tailored Doppler echocardiographic evaluation may be required in patients with heart failure to assist with Biv pacemaker optimization. The third heart sound (S(3)), an acoustic cardiographic parameter, has been demonstrated to be a highly specific finding for hemodynamic evaluation in patients with heart failure. The aims of this study were to evaluate the use of comprehensive Doppler echocardiography as a guide during Biv pacemaker optimization in patients after cardiac resynchronization therapy and to evaluate the feasibility of S(3) intensity to be a cost-efficient parameter for Biv pacemaker optimization compared with Doppler echocardiography. Comprehensive Doppler echocardiographic evaluations were performed during Biv pacemaker optimization in 44 patients referred for pacemaker optimization (mean age, 71 + or - 12 years; mean left ventricular ejection fraction, 34 + or - 11%). Blinded assessment of S(3) intensity was performed simultaneously using acoustic cardiography. The correlation and improvement in cardiac hemodynamics were analyzed between the methods. Echocardiographically guided optimization resulted in significant improvements in the left ventricular outflow velocity-time integral (15.92 + or - 4.77 to 18.51 + or - 5.19 cm, P < .001), ejection time (278 + or - 40 to 293 + or - 40 ms, P < .001), myocardial performance index (0.57 + or - 0.19 to 0.44 + or - 0.14, P < .002), and peak pulmonary artery systolic pressure (42 + or - 13 to 36 + or - 11 mm Hg, P < .04) and decreased S(3) intensity from 4.81 + or - 1.84 at baseline to 3.96 + or - 1.22 after optimization (P < .02) for the overall study group and from 6.63 + or - 1.37 to 4.85 + or - 1.13 (P < .001) in the 18 patients with baseline S(3) intensity > 5.0. The correlation between echocardiographic and acoustic cardiographic S(3) intensity for optimal atrioventricular delay was 0.86 (P < .001) and for optimal interventricular delay was 0.64 (P < .001). Optimal atrioventricular delay was identical by echocardiographic and acoustic cardiographic S(3) intensity in 56%, and optimal interventricular delay was identical in 75% of patients. Pacemakers were permanently programmed on the basis of echocardiographic evaluation. In 35 patients available for follow up, the mean New York Heart Association class reduced from 2.55 + or - 0.81 to 1.77 + or - 0.90 (P < .001) and the mean quality-of-life score as assessed by Minnesota Living With Heart Failure Questionnaire improved from 45 + or - 28 to 32 + or - 28 (P = .08) at 2.5 + or - 2.1 months. Comprehensive echocardiographically guided Biv pacemaker optimization produces significant improvement in Doppler echocardiographic hemodynamics, a reduction in S(3) intensity, and an improvement in functional class in patients after cardiac resynchronization therapy. Copyright 2010 American Society of Echocardiography. Published by Mosby, Inc. All rights reserved.

Noise normalization and windowing functions for VALIDAR in wind parameter estimation

NASA Astrophysics Data System (ADS)

Beyon, Jeffrey Y.; Koch, Grady J.; Li, Zhiwen

2006-05-01

The wind parameter estimates from a state-of-the-art 2-μm coherent lidar system located at NASA Langley, Virginia, named VALIDAR (validation lidar), were compared after normalizing the noise by its estimated power spectra via the periodogram and the linear predictive coding (LPC) scheme. The power spectra and the Doppler shift estimates were the main parameter estimates for comparison. Different types of windowing functions were implemented in VALIDAR data processing algorithm and their impact on the wind parameter estimates was observed. Time and frequency independent windowing functions such as Rectangular, Hanning, and Kaiser-Bessel and time and frequency dependent apodized windowing function were compared. The briefing of current nonlinear algorithm development for Doppler shift correction subsequently follows.

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

Aerial ultrasonic micro Doppler sonar detection range in outdoor environments.

PubMed

Bradley, Marshall; Sabatier, James M

2012-03-01

Current research demonstrates that micro Doppler sonar has the capability to uniquely identify the presence of a moving human, making it an attractive component in surveillance systems for border security applications. Primary environmental factors that limit sonar performance are two-way spreading losses, ultrasonic absorption, and backscattered energy from the ground that appears at zero Doppler shift in the sonar signal processor. Spectral leakage from the backscatter component has a significant effect on sonar performance for slow moving targets. Sonar performance is shown to rapidly decay as the sensor is moved closer to the ground due to increasing surface backscatter levels. © 2012 Acoustical Society of America

Measuring Gravitation Using Polarization Spectroscopy

NASA Technical Reports Server (NTRS)

Matsko, Andrey; Yu, Nan; Maleki, Lute

2004-01-01

A proposed method of measuring gravitational acceleration would involve the application of polarization spectroscopy to an ultracold, vertically moving cloud of atoms (an atomic fountain). A related proposed method involving measurements of absorption of light pulses like those used in conventional atomic interferometry would yield an estimate of the number of atoms participating in the interferometric interaction. The basis of the first-mentioned proposed method is that the rotation of polarization of light is affected by the acceleration of atoms along the path of propagation of the light. The rotation of polarization is associated with a phase shift: When an atom moving in a laboratory reference interacts with an electromagnetic wave, the energy levels of the atom are Doppler-shifted, relative to where they would be if the atom were stationary. The Doppler shift gives rise to changes in the detuning of the light from the corresponding atomic transitions. This detuning, in turn, causes the electromagnetic wave to undergo a phase shift that can be measured by conventional means. One would infer the gravitational acceleration and/or the gradient of the gravitational acceleration from the phase measurements.

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.

Editorial special issue on "Laser Doppler vibrometry"

NASA Astrophysics Data System (ADS)

Vanlanduit, Steve; Dirckx, Joris

2017-12-01

The invention of the laser in 1960 has opened up many opportunities in the field of measurement science and technology. Just a few years after the invention of the laser, a novel fluid flow measurement technique based on the Doppler effect was introduced: at that moment the laser Doppler anemometer or shortly LDA [1] was born. The technique enabled fluid velocity measurement by using the light of a He-Ne beam which was scattered by very small polystyrene spheres entrained in the fluid. Later on, in the late nineteen seventees it was recognized that the detection of the Doppler frequency shift that occurs when light is scattered by a moving surface can also be used to measure the vibration velocity of an object. The instrument to perform these vibration measurements was called the laser Doppler vibrometer or LDV [2]. In the last decades several technological advances were made in the field of laser Doppler vibrometry. The result is that nowadays, velocity measurements of fluids (using LDA) and vibrating objects (using LDV) are performed in many challenging applications in different fields (microelectronics, civil structures, biomedical engineering, material science, etc.).

Flight phasemeter on the Laser Ranging Interferometer on the GRACE Follow-On mission

NASA Astrophysics Data System (ADS)

Bachman, B.; de Vine, G.; Dickson, J.; Dubovitsky, S.; Liu, J.; Klipstein, W.; McKenzie, K.; Spero, R.; Sutton, A.; Ware, B.; Woodruff, C.

2017-05-01

As the first inter-spacecraft laser interferometer, the Laser Ranging Interferometer (LRI) on the GRACE Follow-On Mission will demonstrate interferometry technology relevant to the LISA mission. This paper focuses on the completed LRI Laser Ranging Processor (LRP), which includes heterodyne signal phase tracking at μ {{cycle/}}\\sqrt{{{Hz}}} precision, differential wavefront sensing, offset frequency phase locking and Pound-Drever-Hall laser stabilization. The LRI design has characteristics that are similar to those for LISA: 1064 nm NPRO laser source, science bandwidth in the mHz range, MHz-range intermediate frequency and Doppler shift, detected optical power of tens of picoWatts. Laser frequency stabilization has been demonstrated at a level below 30{{Hz/}}\\sqrt{{{Hz}}}, better than the LISA requirement of 300{{Hz/}}\\sqrt{{{Hz}}}. The LRP has completed all performance testing and environmental qualification and has been delivered to the GRACE Follow-On spacecraft. The LRI is poised to test the LISA techniques of tone-assisted time delay interferometry and arm-locking. GRACE Follow-On launches in 2017.

A review of ionospheric effects on Earth-space propagation

NASA Technical Reports Server (NTRS)

Klobuchar, J. A.

1984-01-01

A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.

Compressed Sensing in On-Grid MIMO Radar.

PubMed

Minner, Michael F

2015-01-01

The accurate detection of targets is a significant problem in multiple-input multiple-output (MIMO) radar. Recent advances of Compressive Sensing offer a means of efficiently accomplishing this task. The sparsity constraints needed to apply the techniques of Compressive Sensing to problems in radar systems have led to discretizations of the target scene in various domains, such as azimuth, time delay, and Doppler. Building upon recent work, we investigate the feasibility of on-grid Compressive Sensing-based MIMO radar via a threefold azimuth-delay-Doppler discretization for target detection and parameter estimation. We utilize a colocated random sensor array and transmit distinct linear chirps to a small scene with few, slowly moving targets. Relying upon standard far-field and narrowband assumptions, we analyze the efficacy of various recovery algorithms in determining the parameters of the scene through numerical simulations, with particular focus on the ℓ 1-squared Nonnegative Regularization method.

Predicting fluctuations-caused regime shifts in a time delayed dynamics of an invading species

NASA Astrophysics Data System (ADS)

Xie, Qingshuang; Wang, Tonghuan; Zeng, Chunhua; Dong, Xiaohui; Guan, Lin

2018-03-01

In this paper, we investigate early warning signals (EWS) of regime shifts in a density-dependent invading population model with time delay, in which the population density is assumed to be disturbed by intrinsic and extrinsic fluctuations. It is shown that the time delay and noises can cause the regime shifts between low and high population density states. The regime shift time (RST) as a function of noise intensity exhibits a maximum, which identifies the signature of the noise-enhanced stability of the low density state, while the time delay weakens the stability of the low density state. Applying the Kramers time technique, we also discuss the intersection point of the RST between low and high population density states, i.e., a critical point in the RST is found. Therefore, the critical point may give an EWS of regime shifts from one alternative state to another one for the changes in the noise parameters and time delay.

Method for ambiguity resolution in range-Doppler measurements

NASA Technical Reports Server (NTRS)

Heymsfield, Gerald M. (Inventor); Miller, Lee S. (Inventor)

1994-01-01

A method for resolving range and Doppler target ambiguities when the target has substantial range or has a high relative velocity in which a first signal is generated and a second signal is also generated which is coherent with the first signal but at a slightly different frequency such that there exists a difference in frequency between these two signals of Delta f(sub t). The first and second signals are converted into a dual-frequency pulsed signal, amplified, and the dual-frequency pulsed signal is transmitted towards a target. A reflected dual-frequency signal is received from the target, amplified, and changed to an intermediate dual-frequency signal. The intermediate dual-frequency signal is amplified, with extracting of a shifted difference frequency Delta f(sub r) from the amplified intermediate dual-frequency signal done by a nonlinear detector. The final step is generating two quadrature signals from the difference frequency Delta f(sub t) and the shifted difference frequency Delta f(sub r) and processing the two quadrature signals to determine range and Doppler information of the target.

Evaluation of atrial electromechanical delay and left atrial mechanical function in patients with obstructive sleep apnea : Cardiac involvement in patients with OSA.

PubMed

Karabag, Turgut; Aydin, Mustafa; Altin, Remzi; Dogan, Sait M; Cil, Cem; Buyukuysal, Cagatay; Sayin, Muhammet R

2012-07-01

The aim of this study was to evaluate atrial electromechanical delay measured by tissue Doppler imaging and left atrial mechanical function in patients with obstructive sleep apnea (OSA). Fourty-seven moderate-to-severe OSA patients who were newly diagnosed by polysomnography (Apnea-hypopnea index ≥ 15 events/h, 32 males, mean age 49.4 ± 11.5) and 30 patients who had no OSA in polysomnography (Apnea-hypopnea index < 5 events/h, 21 males, mean age 45.4 ± 9.1) were included in the study. Using tissue Doppler, diastolic functions, atrial electromechanical coupling were measured from the lateral mitral, septal, and tricuspid annulus. Inter, intra, and left atrial electromechanical delay were calculated (lateral-tricuspid, septum-tricuspid, lateral-septal). Left atrial volumes (maximal, minimal, and presystolic) were measured by the method of discs in the apical four-chamber view and were indexed to body surface area. Mechanical function parameters of the left atrium were also calculated. Interatrial, intraatrial, and left atrial electromechanical delays were significantly higher in the OSA group compared to the control group. Passive emptying fraction was significantly decreased, volume at the beginning of atrial systole and active emptying volume were significantly increased in OSA patients compared to the controls. The apnea-hypopnea index was significantly associated with interatrial and intraatrial electromechanical delay, passive emptying fraction, and conduit volume. Electromechanical delay was markedly prolonged and left atrial electromechanical function was impaired in untreated OSA patients. These impairments worsen with increasing severity of OSA.

Functional brain development in growth-restricted and constitutionally small fetuses: a fetal magnetoencephalography case-control study.

PubMed

Morin, E C; Schleger, F; Preissl, H; Braendle, J; Eswaran, H; Abele, H; Brucker, S; Kiefer-Schmidt, I

2015-08-01

Fetal magnetoencephalography records fetal brain activity non-invasively. Delayed brain responses were reported for fetuses weighing below the tenth percentile. To investigate whether this delay indicates delayed brain maturation resulting from placental insufficiency, this study distinguished two groups of fetuses below the tenth percentile: growth-restricted fetuses with abnormal umbilical artery Doppler velocity (IUGR) and constitutionally small-for-gestational-age fetuses with normal umbilical artery Doppler findings (SGA) were compared with fetuses of adequate weight for gestational age (AGA), matched for age and behavioural state. A case-control study of matched pairs. Fetal magnetoencephalography-Center at the University Hospital of Tuebingen. Fourteen IUGR fetuses and 23 SGA fetuses were matched for gestational age and fetal behavioural state with 37 healthy, normal-sized fetuses. A 156-channel fetal magentoencephalography system was used to record fetal brain activity. Light flashes as visual stimulation were applied to the fetus. The Student's t-test for paired groups was performed. Latency of fetal visual evoked magnetic responses (VER). The IUGR fetuses showed delayed VERs compared with controls (IUGR, 233.1 ms; controls, 184.6 ms; P = 0.032). SGA fetuses had similar evoked response latencies compared with controls (SGA, 216.1 ms; controls, 219.9 ms; P = 0.828). Behavioural states were similarly distributed. Visual evoked responses are delayed in IUGR fetuses, but not in SGA. Fetal behavioural state as an influencing factor of brain response latency was accounted for in the comparison. This reinforces that delayed brain maturation is the result of placental insufficiency. © 2015 Royal College of Obstetricians and Gynaecologists.

TIME EVOLUTION OF PLASMA PARAMETERS DURING THE RISE OF A SOLAR PROMINENCE INSTABILITY

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

Orozco Suárez, D.; Asensio Ramos, A.; Trujillo Bueno, J.

We present high-spatial resolution spectropolarimetric observations of a quiescent hedgerow prominence taken in the He I 1083.0 nm triplet. The observation consisted of a time series in sit-and-stare mode of ∼36 minutes duration. The spectrograph's slit crossed the prominence body and we recorded the time evolution of individual vertical threads. Eventually, we observed the development of a dark Rayleigh-Taylor plume that propagated upward with a velocity, projected onto the plane of the sky, of 17 km s{sup –1}. Interestingly, the plume apex collided with the prominence threads pushing them aside. We inferred Doppler shifts, Doppler widths, and magnetic field strength variations bymore » interpreting the He I Stokes profiles with the HAZEL code. The Doppler shifts show that clusters of threads move coherently while individual threads have oscillatory patterns. Regarding the plume we found strong redshifts (∼9-12 km s{sup –1}) and large Doppler widths (∼10 km s{sup –1}) at the plume apex when it passed through the prominence body and before it disintegrated. We associate the redshifts with perspective effects while the Doppler widths are more likely due to an increase in the local temperature. No local variations of the magnetic field strength associated with the passage of the plume were found; this leads us to conclude that the plumes are no more magnetized than the surroundings. Finally, we found that some of the threads' oscillations are locally damped, what allowed us to apply prominence seismology techniques to infer additional prominence physical parameters.« less

Toward Two-Color Sub-Doppler Saturation Recovery Kinetics in CN (x, v = 0, J)

NASA Astrophysics Data System (ADS)

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

2015-06-01

Collision-induced rotational energy transfer among rotational levels of ground state CN (X 2σ+, v = 0) radicals has been probed by saturation recovery experiments, using high-resolution, polarized transient FM spectroscopy to probe the recovery of population and the decay of alignment following ns pulsed laser depletion of selected CN rotational levels. Despite the lack of Doppler selection in the pulsed depletion and the thermal distribution of collision velocities, the recovery kinetics are found to depend on the probed Doppler shift of the depleted signal. The observed Doppler-shift-dependent recovery rates are a measure of the velocity dependence of the inelastic cross sections, combined with the moderating effects of velocity-changing elastic collisions. New experiments are underway, in which the pulsed saturation is performed with sub-Doppler velocity selection. The time evolution of the spectral hole bleached in the initially thermal CN absorption spectrum can characterize speed-dependent inelastic collisions along with competing elastic velocity-changing collisions, all as a function of the initially bleached velocity group and rotational state. The initial time evolution of the depletion recovery spectrum can be compared to a stochastic model, using differential cross sections for elastic scattering as well as speed-dependent total inelastic cross sections, derived from ab initio scattering calculations. Progress to date will be reported. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-AC02-98CH10886 and DE-SC0012704 with the U.S. Department of Energy and supported by its Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences.

Use of speckle for determining the response characteristics of Doppler imaging radars

NASA Technical Reports Server (NTRS)

Tilley, D. G.

1986-01-01

An optical model is developed for imaging optical radars such as the SAR on Seasat and the Shuttle Imaging Radar (SIR-B) by analyzing the Doppler shift of individual speckles in the image. The signal received at the spacecraft is treated in terms of a Fresnel-Kirchhoff integration over all backscattered radiation within a Huygen aperture at the earth. Account is taken of the movement of the spacecraft along the orbital path between emission and reception. The individual points are described by integration of the point source amplitude with a Green's function scattering kernel. Doppler data at each point furnishes the coordinates for visual representations. A Rayleigh-Poisson model of the surface scattering characteristics is used with Monte Carlo methods to generate simulations of Doppler radar speckle that compare well with Seasat SAR data SIR-B data.

Development of Rayleigh Doppler lidar for measuring middle atmosphere winds

NASA Astrophysics Data System (ADS)

Raghunath, K.; Patra, A. K.; Narayana Rao, D.

Interpretation of most of the middle and upper atmospheric dynamical and chemical data relies on the climatological description of the wind field Rayleigh Doppler lidar is one instrument which monitors wind profiles continuously though continuity is limited to clear meteorological conditions in the middle atmosphere A Doppler wind lidar operating in incoherent mode gives excellent wind and temperature information at these altitudes with necessary spectral sensitivity It observes atmospheric winds by measuring the spectral shift of the scattered light due to the motions of atmospheric molecules with background winds and temperature by spectral broadening The presentation is about the design and development of Incoherent Doppler lidar to obtain wind information in the height regions of 30-65 km The paper analyses and describes various types of techniques that can be adopted viz Edge technique and Fringe Imaging technique The paper brings out the scientific objectives configuration simulations error sources and technical challenges involved in the development of Rayleigh Doppler lidar The presentation also gives a novel technique for calibrating the lidar

Childhood cognitive development after fetal growth restriction.

PubMed

Llurba, E; Baschat, A A; Turan, O M; Harding, J; McCowan, L M

2013-04-01

To examine the relationship between prenatal umbilical artery (UA) and internal carotid artery (ICA) Doppler findings and cognitive development at 3 and 6 years in low-birth-weight children. This was a study of 209 low-birth-weight (< 10(th) centile) children born after 28 gestational weeks with UA resistance index (RI) measured within 2 weeks before delivery. Children with normal UA- and ICA-RI were defined as small-for-gestational age (SGA) and those with abnormal UA or ICA Doppler findings as having fetal growth restriction (FGR). Cognitive ability at 3 and 6 years' corrected age was assessed using the fourth edition of the Stanford-Binet Intelligence Scale (SBIS) and compared between SGA and FGR groups. An SBIS score < 85 was considered to indicate delayed development. The median gestational age at diagnosis of abnormal fetal growth was 36.6 (range, 28-41) weeks. There were 87 (41.6%) children classified as having FGR and 122 (58.4%) as SGA. The mean global SBIS score at 3 years was 109.4 (SD, 22.8) and at 6 years it was 110.5 (SD, 13.9). Overall, 22 (10.5%) children had delayed development at 3 years. Total SBIS scores and individual domain scores did not differ between FGR and SGA groups at 3 or 6 years and similar proportions in each group had delayed development. Abnormal prenatal UA and ICA Doppler findings are not associated with lower developmental scores in low-birth-weight children delivered in the third trimester of pregnancy. Copyright © 2013 ISUOG. Published by John Wiley & Sons, Ltd.

Evidence of mass outflow in the low corona over a large sunspot

NASA Astrophysics Data System (ADS)

Neupert, W. M.; Brosius, J. W.; Thomas, R. J.; Thompson, W. T.

1994-04-01

An extreme ultraviolet (EUV) imaging spectrograph designed for sounding rocket flight has been used to search for velocity fields in the low solar corona. During a flight in May, 1989, we obtained emission line profile measurements along a chord through an active region on the Sun. Relative Doppler velocities were measured in emission lines of Mg IX, Fe XV, and Fe XVI with a sensitivity of 2-3 km/s at 350 A. The only Doppler shift appreciably greater than this level was observed in the line of Mg IX at 368.1 A over the umbra of the large sunspot. The maximum shift measured at that location corresponded to a velocity toward the observer of 14 plus or minus 3 km/s relative to the mean of measurements in that emission line made elsewhere over the active region. The magnetic field in the low corona was aligned to within 10 deg of the line of sight at the location of maximum Doppler shift. Depending on the magnetic field geometry, this mass outflow could either re-appear as a downflow of material in distant footprints of closed coronal loops or, if along open field lines, could contribute to the solar wind. The site of the sunspot was near a major photospheric magnetic field boundary. Such boundaries have been associated with low-speed solar winds as observed in interplanetary plasmas.

The Weyl Definition of Redshifts

ERIC Educational Resources Information Center

Harvey, Alex

2012-01-01

In 1923, Weyl published a (not widely known) protocol for the calculation of redshifts. It is completely independent of the origin of the shift and treats it as a pure Doppler shift. The method is comprehensive and depends solely on the relation between the world lines of source and observer. It has the merit of simplicity of statement and…

Target Super-Resolution Compensation for Coherent Airborne Radar Utilizing Spread Spectrum Waveforms.

DTIC Science & Technology

1983-12-01

effects of the transmitted waveform. This will be accomplished via comparisons of signal-to-noise ratios for non-coherent filtering vs. coherent narrowband...form of frequency or phase modulation. The simulation will assume we are processing the video (baseband) signal which resu fr i an enviroment (target...range, they can be resolved in doppler if AWD/2 > Fr where &wD is the doppler-shift difference. A similiar consideration of target resolution for a

SINA: A test system for proximity fuses

NASA Astrophysics Data System (ADS)

Ruizenaar, M. G. A.

1989-04-01

SINA, a signal generator that can be used for testing proximity fuses, is described. The circuitry of proximity fuses is presented; the output signal of the RF circuit results from a mixing of the emitted signal and received signal that is Doppler shifted in frequency by the relative motion of the fuse with respect to the reflecting target of surface. With SINA, digitized and stored target and clutter signals (previously measured) can be transformed to Doppler signals, for example during a real flight. SINA can be used for testing fuse circuitry, for example in the verification of results of computer simulations of the low frequency Doppler signal processing. The software of SINA and its use are explained.

Laser Doppler velocimetry using a modified computer mouse

NASA Astrophysics Data System (ADS)

Zaron, Edward D.

2016-10-01

A computer mouse has been modified for use as a low-cost laser Doppler interferometer and used to measure the two-component fluid velocity of a flowing soap film. The mouse sensor contains two vertical cavity surface emitting lasers, photodiodes, and signal processing hardware integrated into a single package, approximately 1 cm2 in size, and interfaces to a host computer via a standard USB port. Using the principle of self-mixing interferometry, whereby laser light re-enters the laser cavity after being scattered from a moving target, the Doppler shift and velocity of scatterers dispersed in the flow are measured. Observations of the boundary layer in a turbulent soap film channel flow demonstrate the capabilities of the sensor.

Estimating the delay-Doppler of target echo in a high clutter underwater environment using wideband linear chirp signals: Evaluation of performance with experimental data.

PubMed

Yu, Ge; Yang, T C; Piao, Shengchun

2017-10-01

A chirp signal is a signal with linearly varying instantaneous frequency over the signal bandwidth, also known as a linear frequency modulated (LFM) signal. It is widely used in communication, radar, active sonar, and other applications due to its Doppler tolerance property in signal detection using the matched filter (MF) processing. Modern sonar uses high-gain, wideband signals to improve the signal to reverberation ratio. High gain implies a high product of the signal bandwidth and duration. However, wideband and/or long duration LFM signals are no longer Doppler tolerant. The shortcoming of the standard MF processing is loss of performance, and bias in range estimation. This paper uses the wideband ambiguity function and the fractional Fourier transform method to estimate the target velocity and restore the performance. Target velocity or Doppler provides a clue for differentiating the target from the background reverberation and clutter. The methods are applied to simulated and experimental data.

Echocardiography for cardiac resynchronization therapy: recommendations for performance and reporting--a report from the American Society of Echocardiography Dyssynchrony Writing Group endorsed by the Heart Rhythm Society.

PubMed

Gorcsan, John; Abraham, Theodore; Agler, Deborah A; Bax, Jeroen J; Derumeaux, Genevieve; Grimm, Richard A; Martin, Randy; Steinberg, Jonathan S; Sutton, Martin St John; Yu, Cheuk-Man

2008-03-01

Echocardiography plays an evolving and important role in the care of heart failure patients treated with biventricular pacing, or cardiac resynchronization therapy (CRT). Numerous recent published reports have utilized echocardiographic techniques to potentially aide in patient selection for CRT prior to implantation and to optimized device settings afterwards. However, no ideal approach has yet been found. This consensus report evaluates the contemporary applications of echocardiography for CRT including relative strengths and technical limitations of several techniques and proposes guidelines regarding current and possible future clinical applications. Principal methods advised to qualify abnormalities in regional ventricular activation, known as dyssynchrony, include longitudinal velocities by color-coded tissue Doppler and the difference in left ventricular to right ventricular ejection using routine pulsed Doppler, or interventricular mechanical delay. Supplemental measures of radial dynamics which may be of additive value include septal-to-posterior wall delay using M-mode in patients with non-ischemic disease with technically high quality data, or using speckle tracking radial strain. A simplified post-CRT screening for atrioventricular optimization using Doppler mitral inflow velocities is also proposed. Since this is rapidly changing field with new information being added frequently, future modification and refinements in approach are anticipated to continue.

Magnetic Compensation for Second-Order Doppler Shift in LITS

NASA Technical Reports Server (NTRS)

Burt, Eric; Tjoelker, Robert

2008-01-01

The uncertainty in the frequency of a linear-ion-trap frequency standard (LITS) can be reduced substantially by use of a very small magnetic inhomogeneity tailored to compensate for the residual second-order Doppler shift. An effect associated with the relativistic time dilatation, one cause of the second-order Doppler shift, is ion motion that is attributable to the trapping radio-frequency (RF)electromagnetic field used to trap ions. The second-order Doppler shift is reduced by using a multi-pole trap; however it is still the largest source of systematic frequency shift in the latest generation of LITSs, which are among the most stable clocks in the world. The present compensation scheme reduces the frequency instability of the affected LITS to about a tenth of its previous value. The basic principles of prior generation LITSs were discussed in several prior NASA Tech Briefs articles. Below are recapitulated only those items of basic information necessary to place the present development in context. A LITS includes a microwave local oscillator, the frequency of which is stabilized by comparison with the frequency of the ground state hyperfine transition of 199Hg+ ions. The comparison involves a combination of optical and microwave excitation and interrogation of the ions in a linear ion trap in the presence of a nominally uniform magnetic field. In the current version of the LITS, there are two connected traps (see figure): (1) a quadrupole trap wherein the optical excitation and measurement take place and (2) a 12-pole trap (denoted the resonance trap), wherein the microwave interrogation takes place. The ions are initially loaded into the quadrupole trap and are thereafter shuttled between the two traps. Shuttling ions into the resonance trap allows sensitive microwave interrogation to take place well away from loading interference. The axial magnetic field for the resonance trap is generated by an electric current in a finely wound wire coil surrounded by magnetic shields. In the quadrupole and 12-pole traps, the potentials are produced by RF voltages applied to even numbers (4 and 12, respectively) of parallel rods equally spaced around a circle. The polarity of the voltage on each rod is opposite that of the voltage on the adjacent rod. As a result, the amplitude of the RF trapping field is zero along the centerline and increases, with radius, to a maximum value near the rods.

Design and implementation of a smartphone-based portable ultrasound pulsed-wave Doppler device for blood flow measurement.

PubMed

Huang, Chih-Chung; Lee, Po-Yang; Chen, Pay-Yu; Liu, Ting-Yu

2012-01-01

Blood flow measurement using Doppler ultrasound has become a useful tool for diagnosing cardiovascular diseases and as a physiological monitor. Recently, pocket-sized ultrasound scanners have been introduced for portable diagnosis. The present paper reports the implementation of a portable ultrasound pulsed-wave (PW) Doppler flowmeter using a smartphone. A 10-MHz ultrasonic surface transducer was designed for the dynamic monitoring of blood flow velocity. The directional baseband Doppler shift signals were obtained using a portable analog circuit system. After hardware processing, the Doppler signals were fed directly to a smartphone for Doppler spectrogram analysis and display in real time. To the best of our knowledge, this is the first report of the use of this system for medical ultrasound Doppler signal processing. A Couette flow phantom, consisting of two parallel disks with a 2-mm gap, was used to evaluate and calibrate the device. Doppler spectrograms of porcine blood flow were measured using this stand-alone portable device under the pulsatile condition. Subsequently, in vivo portable system verification was performed by measuring the arterial blood flow of a rat and comparing the results with the measurement from a commercial ultrasound duplex scanner. All of the results demonstrated the potential for using a smartphone as a novel embedded system for portable medical ultrasound applications. © 2012 IEEE

Early Calibration Results of CYGNSS Mission

NASA Astrophysics Data System (ADS)

Balasubramaniam, R.; Ruf, C. S.; McKague, D. S.; Clarizia, M. P.; Gleason, S.

2017-12-01

The first of its kind, GNSS-R complete orbital mission, CYGNSS was successfully launched on Dec 15 2016. The goal of this mission is to accurately forecast the intensification of tropical cyclones by modelling its inner core. The 8 micro observatories of CYGNSS carry a passive instrument called Delay Doppler Mapping Instrument (DDMI). The DDMIs form a 2D representation called the Delay-Doppler Map (DDM) of the forward scattered power signal. Each DDMI outputs 4 DDMs per second which are compressed and sent to the ground resulting in a total of 32 sea-surface measurements produced by the CYGNSS constellation per second. These are subsequently used in the Level-2 wind retrieval algorithm to extract wind speed information. In this paper, we perform calibration and validation of CYGNSS measurements for accurate extraction of wind speed information. The calibration stage involves identification and correction for dependence of the CYGNSS observables namely Normalised Bistatic Radar Cross Section and Leading Edge Slope of the Integrated Delay Waveform over instrument parameters, geometry etc. The validation stage involves training of the Geophysical Model Function over a multitude of ground truth sources during the Atlantic hurricane season and also refined validation of high wind speed data products.

Doppler-shift estimation of flat underwater channel using data-aided least-square approach

NASA Astrophysics Data System (ADS)

Pan, Weiqiang; Liu, Ping; Chen, Fangjiong; Ji, Fei; Feng, Jing

2015-06-01

In this paper we proposed a dada-aided Doppler estimation method for underwater acoustic communication. The training sequence is non-dedicate, hence it can be designed for Doppler estimation as well as channel equalization. We assume the channel has been equalized and consider only flat-fading channel. First, based on the training symbols the theoretical received sequence is composed. Next the least square principle is applied to build the objective function, which minimizes the error between the composed and the actual received signal. Then an iterative approach is applied to solve the least square problem. The proposed approach involves an outer loop and inner loop, which resolve the channel gain and Doppler coefficient, respectively. The theoretical performance bound, i.e. the Cramer-Rao Lower Bound (CRLB) of estimation is also derived. Computer simulations results show that the proposed algorithm achieves the CRLB in medium to high SNR cases.

Acceleration and heating of heavy ions in high speed solar wind streams

NASA Technical Reports Server (NTRS)

Gomberoff, L.; Gratton, F. T.; Gnavi, G.

1995-01-01

Left hand polarized Alfven waves generated in coronal holes propagate in the direction of high speed solar wind streams, accelerating and heating heavy ions. As the solar wind expands, the ratio between the frequency of the Alfven waves and the proton gyrofrequency increases, due to the decrease of the interplanetary magnetic field, and encounter first the local ion gyrofrequency of the species with the largest M(sub l) = m(sub l)/z(sub l)m(sub p) (m(sub l) is the mass of species l, m(sub p) is the proton mass and z(sub l) is the degree of ionization of species l). It is shown that the Alfven waves experience there strong absorption and cannot propagate any further until the ions are accelerated and heated. Once this occurs, the Alfven waves continue to propagate until they meet the gyrofrequency of the next species giving rise to a similar phenomenon. In order to show this contention, we use the linear dispersion relation of ion cyclotron waves in a multicomponent plasma consisting of oxygen ions, alpha particles and protons. We assume that at any distance from the sun, the Alfven waves follow the local dispersion relation of electromagnetic ion cyclotron waves. To illustrate the results, we solve the dispersion relation for oxygen ions and alpha particles drifting relative to the protons. The dispersion relation has three branches. The first branch starts at zero frequency and goes to the Doppler-shifted oxygen ion gyrofrequency. The second branch starts close to the oxygen gyrofrequency, and goes to the Doppler-shifted alpha particle gyrofrequency. The third branch starts close to the alpha particle gyrofrequency, and goes to the proton gyrofrequency. The Alfven waves propagate following the first branch of the dispersion relation. When they reach the Doppler-shifted oxygen ion gyrofrequency, the ions are accelerated and heated to some definite values. When these values are reached, the dispersion relation changes, and it is now the first branch of the dispersion relation, the one which goes to the Doppler-shifted alpha particle gyrofrequency. The Alfven waves continue to propagate along the first branch of the dispersion relation and proceed to accelerate and heat the alpha particles.

Strategies and methodologies to develop techniques for computer-assisted analysis of gas phase formation during altitude decompression

NASA Technical Reports Server (NTRS)

Powell, Michael R.; Hall, W. A.

1993-01-01

It would be of operational significance if one possessed a device that would indicate the presence of gas phase formation in the body during hypobaric decompression. Automated analysis of Doppler gas bubble signals has been attempted for 2 decades but with generally unfavorable results, except with surgically implanted transducers. Recently, efforts have intensified with the introduction of low-cost computer programs. Current NASA work is directed towards the development of a computer-assisted method specifically targeted to EVA, and we are most interested in Spencer Grade 4. We note that Spencer Doppler Grades 1 to 3 have increased in the FFT sonogram and spectrogram in the amplitude domain, and the frequency domain is sometimes increased over that created by the normal blood flow envelope. The amplitude perturbations are of very short duration, in both systole and diastole and at random temporal positions. Grade 4 is characteristic in the amplitude domain but with modest increases in the FFT sonogram and spectral frequency power from 2K to 4K over all of the cardiac cycle. Heart valve motion appears to characteristic display signals: (1) the demodulated Doppler signal amplitude is considerably above the Doppler-shifted blow flow signal (even Grade 4); and (2) demodulated Doppler frequency shifts are considerably greater (often several kHz) than the upper edge of the blood flow envelope. Knowledge of these facts will aid in the construction of a real-time, computer-assisted discriminator to eliminate cardiac motion artifacts. There could also exist perturbations in the following: (1) modifications of the pattern of blood flow in accordance with Poiseuille's Law, (2) flow changes with a change in the Reynolds number, (3) an increase in the pulsatility index, and/or (4) diminished diastolic flow or 'runoff.' Doppler ultrasound devices have been constructed with a three-transducer array and a pulsed frequency generator.

Two AFC Loops For Low CNR And High Dynamics

NASA Technical Reports Server (NTRS)

Hinedi, Sami M.; Aguirre, Sergio

1992-01-01

Two alternative digital automatic-frequency-control (AFC) loops proposed to acquire (or reacquire) and track frequency of received carrier radio signal. Intended for use where carrier-to-noise ratios (CNR's) low and carrier frequency characterized by high Doppler shift and Doppler rate because of high relative speed and acceleration, respectively, between transmitter and receiver. Either AFC loops used in place of phase-locked loop. New loop concepts integrate ideas from classical spectrum-estimation, digital-phase-locked-loop, and Kalman-Filter theories.

Laser Doppler spectrometer method of particle sizing. [for air pollution

NASA Technical Reports Server (NTRS)

Weber, F. N.

1976-01-01

A spectrometer for the detection of airborne particulate pollution in the submicron size range is described. In this device, airborne particles are accelerated through a supersonic nozzle, with different sizes achieving different velocities in the gas flow. Information about the velocities of the accelerated particles is obtained with a laser-heterodyne optical system through the Doppler shift of light scattered from the particles. Detection is accomplished by means of a photomultiplier. Nozzle design and signal processing techniques are also discussed.

Assessment of atrial electromechanical delay by tissue Doppler echocardiography in obese subjects.

PubMed

Yagmur, Julide; Cansel, Mehmet; Acikgoz, Nusret; Ermis, Necip; Yagmur, Murat; Atas, Halil; Tasolar, Hakan; Karakus, Yasin; Pekdemir, Hasan; Ozdemir, Ramazan

2011-04-01

Our aim was to evaluate whether atrial electromechanical delay measured by tissue Doppler imaging (TDI), which is an early predictor of atrial fibrillation (AF) development, is prolonged in obese subjects. A total of 40 obese and 40 normal-weight subjects with normal coronary angiograms were included in this study. P-wave dispersion (PWD) was calculated on the 12-lead electrocardiogram (ECG). Systolic and diastolic left ventricular (LV) functions, inter- and intra-atrial electromechanical delay were measured by TDI and conventional echocardiography. Inter- and intra-atrial electromechanical delay were significantly longer in the obese subjects compared with the controls (44.08 ± 10.06 vs. 19.35 ± 5.94 ms and 23.63 ± 6.41 vs. 5.13 ± 2.67 ms, P < 0.0001 for both, respectively). PWD was higher in obese subjects (53.40 ± 5.49 vs. 35.95 ± 5.93 ms, P < 0.0001). Left atrial (LA) diameter, LA volume index and LV diastolic parameters were significantly different between the groups. Interatrial electromechanical delay was correlated with PWD (r = 0.409, P = 0.009), high-sensitivity C-reactive protein (hsCRP) levels (r = 0.588, P < 0.0001). Interatrial electromechanical delay was positively correlated with LA diameter, LA volume index, and LV diastolic function parameters consisting of mitral early wave (E) deceleration time (DT) and isovolumetric relaxation time (IVRT; r = 0.323, P = 0.042; r = 0.387, P = 0.014; r = 0.339, P = 0.033; r = 0.325, P = 0.041; respectively) and, negatively correlated with mitral early (E) to late (A) wave ratio (E/A) (r = -0.380, P = 0.016) and myocardial early-to-late diastolic wave ratio (E(m)/A(m)) (r = -0.326, P = 0.040). This study showed that atrial electromechanical delay is prolonged in obese subjects. Prolonged atrial electromechanical delay is due to provoked low-grade inflammation as well as LA enlargement and early LV diastolic dysfunction in obese subjects.

Imaging and characterizing shear wave and shear modulus under orthogonal acoustic radiation force excitation using OCT Doppler variance method.

PubMed

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

2015-05-01

We report on a novel acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) technique for imaging shear wave and quantifying shear modulus under orthogonal acoustic radiation force (ARF) excitation using the optical coherence tomography (OCT) Doppler variance method. The ARF perpendicular to the OCT beam is produced by a remote ultrasonic transducer. A shear wave induced by ARF excitation propagates parallel to the OCT beam. The OCT Doppler variance method, which is sensitive to the transverse vibration, is used to measure the ARF-induced vibration. For analysis of the shear modulus, the Doppler variance method is utilized to visualize shear wave propagation instead of Doppler OCT method, and the propagation velocity of the shear wave is measured at different depths of one location with the M scan. In order to quantify shear modulus beyond the OCT imaging depth, we move ARF to a deeper layer at a known step and measure the time delay of the shear wave propagating to the same OCT imaging depth. We also quantitatively map the shear modulus of a cross-section in a tissue-equivalent phantom after employing the B scan.

Investigation of mixed ionospheric and fround scatter using high spectral content pulse sequences for SuperDARN radars

NASA Astrophysics Data System (ADS)

Spaleta, J.; Bristow, W. A.

2013-12-01

SuperDARN radars estimate plasma drift velocities from the Doppler shift observed on signals scattered from field-aligned density irregularities. These field-aligned density irregularities are embedded in the ionospheric plasma, and move at the same velocity as background plasma. As a result, the electromagnetic signals scattered from these irregularities are Doppler shifted. The SuperDARN radars routinely observe ionospheric scatter Doppler velocities ranging from zero to thousands of meters per second. The radars determine the Doppler shift of the ionospheric scatter by linear fitting the phase of an auto correlation function derived from the radar pulse sequence. The phase fitting technique employed assumes a single dominant velocity is present in the signal. In addition, the SuperDARN radars can also observe signals scattered from the ground. Once refracted by the ionospheric plasma and bent earthward, the radar pulses eventually reach the ground where they scatter, sending signal back to the radar. This ground-scatter signal is characterized as having a low Doppler shift and low spectral width. The SuperDARN radars are able to use these signal characteristics to discriminate the ground scatter signal from the ionospheric scatter, when regions of ground scatter are isolated from ionospheric scatter returns. The phase fitting assumption of a single dominate target can easily be violated at ranges where ground and ionospheric scatter mix together. Due to the wide elevation angle extent of the SuperDARN radar design, ground and ionospheric scatter from different propagation paths can mix together in the return signal. When this happens, the fitting algorithm attempts to fit to the dominant signal, and if ground scatter dominates, information about the ionospheric scatter at that range can be unresolved. One way to address the mix scatter situation is to use a high spectral content pulse sequence together with a spectral estimation technique. The high spectral content pulse sequence consists of twice as many pulses and five times as many distinct lags over which to calculate the auto correlation function. This additional spectral information makes it possible to use spectral estimator techniques, that are robust against aperiodic time series data, to calculate the existence of multiple scatter modes in the signal. A comparison of the operation of the traditional SuperDARN pulse sequence and high spectral content pulse sequence will be presented for both synthetic examples and real SuperDARN radar mixed scatter situation.

High-Resolution Radar Imagery of Mars

NASA Astrophysics Data System (ADS)

Harmon, John K.; Nolan, M. C.

2009-09-01

We present high-resolution radar images of Mars obtained during the 2005 and 2007 oppositions. The images were constructed from long-code delay-Doppler observations made with the Arecibo S-band (13-cm) radar. The average image resolution of 3 km represented a better than order-of-magnitude improvement over pre-upgrade Arecibo imagery of the planet. Images of depolarized reflectivity (an indicator primarily of wavelength-scale surface roughness) show the same bright volcanic flow features seen in earlier imagery, but with much finer detail. A new image of the Elysium region shows fine detail in the radar-bright channels of Athabasca Vallis, Marte Vallis, and Grjota Vallis. The new images of Tharsis and Olympus Mons also show a complex array of radar-bright and radar-dark features. Southern Amazonis exhibits some of the most complex and puzzling radar-bright structure on the planet. Another curiosity is the Chryse/Xanthe/Channels region, where we find some radar-bright features in or adjacent to fluvial chaos structures. Chryse/Xanthe is also the only region of Mars showing radar-bright craters (which are rare on Mars but common on the Moon and Mercury). We also obtained the first delay-Doppler image showing the enhanced backscatter from the residual south polar ice cap. In addition to the depolarized imagery, we were able to make the first delay-Doppler images of the circular polarization ratio (an important diagnostic for surface roughness texture). We find that vast areas of the radar-bright volcanic regions have polarization ratios close to unity. Such high ratios are rare for terrestrial lava flows and only seen for extremely blocky surfaces giving high levels of multiple scattering.

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

USGS Publications Warehouse

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

2002-01-01

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

Fabrication of 94Zr thin target for recoil distance doppler shift method of lifetime measurement

NASA Astrophysics Data System (ADS)

Gupta, C. K.; Rohilla, Aman; Abhilash, S. R.; Kabiraj, D.; Singh, R. P.; Mehta, D.; Chamoli, S. K.

2014-11-01

A thin isotopic 94Zr target of thickness 520 μg /cm2 has been prepared for recoil distance Doppler shift method (RDM) lifetime measurement by using an electron beam deposition method on tantalum backing of 3.5 mg/cm2 thickness at Inter University Accelerator Center (IUAC), New Delhi. To meet the special requirement of smoothness of surface for RDM lifetime measurement and also to protect the outer layer of 94Zr from peeling off, a very thin layer of gold has been evaporated on a 94Zr target on a specially designed substrate holder. In all, 143 mg of 99.6% enriched 94Zr target material was utilized for the fabrication of 94Zr targets. The target has been successfully used in a recent RDM lifetime measurement experiment at IUAC.

Nodding motions of accretion rings and disks - A short-term period in SS 433

NASA Technical Reports Server (NTRS)

Katz, J. I.; Anderson, S. F.; Grandi, S. A.; Margon, B.

1982-01-01

It is pointed out that accretion disks and rings in mass transfer binaries have been observed spectroscopically and calculated theoretically for many years. The present investigation is partly based on the availability of several years of spectroscopic observations of the Doppler shifts of the moving lines in SS433. A formalism is presented to compute frequencies and amplitudes of short-term 'nodding' motions in precessing accretion disks in close binary systems. This formalism is applied to an analysis of the moving-line Doppler shifts in SS433. The 35d X-ray cycle of Hercules X-1 is also discussed. In the considered model, the companion star exerts a gravitational torque on the disk rim. Averaged over the binary orbit, this yields a steady torque which results in the mean driven counterprecession of the disk.

First fast-ion D-alpha (FIDA) measurements and simulations on C-2U

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

Bolte, N. G., E-mail: nbolte@TriAlphaEnergy.com; Gupta, D.; Onofri, M.

2016-11-15

The first measurements of fast-ion D-alpha (FIDA) radiation have been acquired on C-2U, Tri Alpha Energy’s advanced, beam-driven field-reversed configuration (FRC). These measurements are also forward modeled by FIDASIM. This is the first measurement and simulation of FIDA carried out on an FRC topology. FIDA measurements are made of Doppler-shifted Balmer-alpha light from neutralized fast ions using a bandpass filter and photomultiplier tube. One adjustable line-of-sight measured signals at eight locations and eight times during the FRC lifetime over 26 discharges. Filtered signals include only the highest energy ions (>6 keV) and share some salient features with the FIDASIM result.more » Highly Doppler-shifted beam radiation is also measured with a high-speed camera and is spatially well-correlated with FIDASIM.« less

Fast and robust standard-deviation-based method for bulk motion compensation in phase-based functional OCT.

PubMed

Wei, Xiang; Camino, Acner; Pi, Shaohua; Cepurna, William; Huang, David; Morrison, John C; Jia, Yali

2018-05-01

Phase-based optical coherence tomography (OCT), such as OCT angiography (OCTA) and Doppler OCT, is sensitive to the confounding phase shift introduced by subject bulk motion. Traditional bulk motion compensation methods are limited by their accuracy and computing cost-effectiveness. In this Letter, to the best of our knowledge, we present a novel bulk motion compensation method for phase-based functional OCT. Bulk motion associated phase shift can be directly derived by solving its equation using a standard deviation of phase-based OCTA and Doppler OCT flow signals. This method was evaluated on rodent retinal images acquired by a prototype visible light OCT and human retinal images acquired by a commercial system. The image quality and computational speed were significantly improved, compared to two conventional phase compensation methods.

Narrow bandwidth detection of vibration signature using fiber lasers

DOEpatents

Moore, Sean; Soh, Daniel B.S.

2018-05-08

The various technologies presented herein relate to extracting a portion of each pulse in a series of pulses reflected from a target to facilitate determination of a Doppler-shifted frequency for each pulse and, subsequently, a vibration frequency for the series of pulses. Each pulse can have a square-wave configuration, whereby each pulse can be time-gated to facilitate discarding the leading edge and the trailing edge (and associated non-linear effects) of each pulse and accordingly, capture of the central portion of the pulse from which the Doppler-shifted frequency, and ultimately, the vibration frequency of the target can be determined. Determination of the vibration velocity facilitates identification of the target being in a state of motion. The plurality of pulses can be formed from a laser beam (e.g., a continuous wave), the laser beam having a narrow bandwidth.

Doppler-based motion compensation algorithm for focusing the signature of a rotorcraft.

PubMed

Goldman, Geoffrey H

2013-02-01

A computationally efficient algorithm was developed and tested to compensate for the effects of motion on the acoustic signature of a rotorcraft. For target signatures with large spectral peaks that vary slowly in amplitude and have near constant frequency, the time-varying Doppler shift can be tracked and then removed from the data. The algorithm can be used to preprocess data for classification, tracking, and nulling algorithms. The algorithm was tested on rotorcraft data. The average instantaneous frequency of the first harmonic of a rotorcraft was tracked with a fixed-lag smoother. Then, state space estimates of the frequency were used to calculate a time warping that removed the effect of a time-varying Doppler shift from the data. The algorithm was evaluated by analyzing the increase in the amplitude of the harmonics in the spectrum of a rotorcraft. The results depended upon the frequency of the harmonics and the processing interval duration. Under good conditions, the results for the fundamental frequency of the target (~11 Hz) almost achieved an estimated upper bound. The results for higher frequency harmonics had larger increases in the amplitude of the peaks, but significantly lower than the estimated upper bounds.

Raman Doppler velocimetry - A unified approach for measuring molecular flow velocity, temperature, and pressure

NASA Technical Reports Server (NTRS)

Exton, R. J.; Hillard, M. E.

1986-01-01

Molecular flow velocity (one component), translational temperature, and static pressure of N2 are measured in a supersonic wind tunnel using inverse Raman spectroscopy. For velocity, the technique employs the large Doppler shift exhibited by the molecules when the pump and probe laser beams are counterpropagating (backward scattering). A retrometer system is employed to yield an optical configuration insensitive to mechanical vibration, which has the additional advantage of simultaneously obtaining both the forward and backward scattered spectra. The forward and backward line breadths and their relative Doppler shift can be used to determine the static pressure, translational temperature, and molecular flow velocity. A demonstration of the technique was performed in a continuous airflow supersonic wind tunnel in which data were obtained under the following conditions: (1) free-stream operation at five set Mach number levels over the 2.50-4.63 range; (2) free-stream operation over a range of Reynolds number (at a fixed Mach number) to vary systematically the static pressure; and (3) operation in the flow field of a simple aerodynamic model to assess beam steering effects in traversing the attached shock layer.

Complex regression Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Elahi, Sahar; Gu, Shi; Thrane, Lars; Rollins, Andrew M.; Jenkins, Michael W.

2018-04-01

We introduce a new method to measure Doppler shifts more accurately and extend the dynamic range of Doppler optical coherence tomography (OCT). The two-point estimate of the conventional Doppler method is replaced with a regression that is applied to high-density B-scans in polar coordinates. We built a high-speed OCT system using a 1.68-MHz Fourier domain mode locked laser to acquire high-density B-scans (16,000 A-lines) at high enough frame rates (˜100 fps) to accurately capture the dynamics of the beating embryonic heart. Flow phantom experiments confirm that the complex regression lowers the minimum detectable velocity from 12.25 mm / s to 374 μm / s, whereas the maximum velocity of 400 mm / s is measured without phase wrapping. Complex regression Doppler OCT also demonstrates higher accuracy and precision compared with the conventional method, particularly when signal-to-noise ratio is low. The extended dynamic range allows monitoring of blood flow over several stages of development in embryos without adjusting the imaging parameters. In addition, applying complex averaging recovers hidden features in structural images.

The Cassini/Huygens Doppler Wind Experiment: Results from the Titan Descent

NASA Technical Reports Server (NTRS)

Bird, M. K.; Dutta-Roy, R.; Allison, M.; Asmar, S. W.; Atkinson, D. H.; Edenhofer, P.; Plettemeier, D.; Tyler, G. L.

2005-01-01

The primary objective of the Doppler Wind Experiment (DWE), one of the six scientific investigations comprising the payload of the ESA Huygens Probe, is a determination of the wind velocity in Titan's atmosphere. Measurements of the Doppler shift of the S-band (2040 MHz) carrier signal to the Cassini Orbiter and to Earth were recorded during the Probe descent in order to deduce wind-induced motion of the Probe to an accuracy better than 1 m s-1. An experiment with the same scientific goal was performed with the Galileo Probe at Jupiter. Analogous to the Galileo experience, it was anticipated that the frequency of the Huygens radio signal could be measured on Earth to obtain an additional component of the horizontal winds. Specific secondary science objectives of DWE include measurements of: (a) Doppler fluctuations to determine the turbulence spectrum and possible wave activity in the Titan atmosphere; (b) Doppler and signal level modulation to monitor Probe descent dynamics (e.g., spinrate/spinphase, parachute swing); (c) Probe coordinates and orientation during descent and after impact on Titan.

Relationship of spaced antenna and Doppler techniques for velocity measurements (keynote paper), part 3

NASA Technical Reports Server (NTRS)

Vincent, R. A.

1984-01-01

The Doppler, spaced-antenna and interferometric methods of measuring wind velocities all use the same basic information, the Doppler shifts imposed on backscattered radio waves, but they process it in different ways. The Doppler technique is most commonly used at VHF since the narrow radar beams are readily available. However, the spaced antenna (SA) method has been successfully used with the SOUSY and Adelaide radars. At MF/HF the spaced antenna method is widely used since the large antenna arrays (diameter 1 km) required to generate narrow beams are expensive to construct. Where such arrays of this size are available then the Doppler method has been successfully used (e.g., Adelaide and Brisbane). In principle, the factors which influence the choice of beam pointing angle, the optimum antenna spacing will be the same whether operation is at MF or VHF. Many of the parameters which govern the efficient use of wind measuring systems have been discussed at previous MST workshops. Some of the points raised by these workshops are summarized.

A Control Allocation System for Automatic Detection and Compensation of Phase Shift Due to Actuator Rate Limiting

NASA Technical Reports Server (NTRS)

Yildiz, Yidiray; Kolmanovsky, Ilya V.; Acosta, Diana

2011-01-01

This paper proposes a control allocation system that can detect and compensate the phase shift between the desired and the actual total control effort due to rate limiting of the actuators. Phase shifting is an important problem in control system applications since it effectively introduces a time delay which may destabilize the closed loop dynamics. A relevant example comes from flight control where aggressive pilot commands, high gain of the flight control system or some anomaly in the system may cause actuator rate limiting and effective time delay introduction. This time delay can instigate Pilot Induced Oscillations (PIO), which is an abnormal coupling between the pilot and the aircraft resulting in unintentional and undesired oscillations. The proposed control allocation system reduces the effective time delay by first detecting the phase shift and then minimizing it using constrained optimization techniques. Flight control simulation results for an unstable aircraft with inertial cross coupling are reported, which demonstrate phase shift minimization and recovery from a PIO event.

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

NASA Technical Reports Server (NTRS)

Chamberlin, Phillip Clyde

2016-01-01

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

Geo-Acoustic Doppler Spectroscopy: A Novel Acoustic Technique For Surveying The Seabed

NASA Astrophysics Data System (ADS)

Buckingham, Michael J.

2010-09-01

An acoustic inversion technique, known as Geo-Acoustic Doppler Spectroscopy, has recently been developed for estimating the geo-acoustic parameters of the seabed in shallow water. The technique is unusual in that it utilizes a low-flying, propeller-driven light aircraft as an acoustic source. Both the engine and propeller produce sound and, since they are rotating sources, the acoustic signature of each takes the form of a sequence of narrow-band harmonics. Although the coupling of the harmonics across the air-sea interface is inefficient, due to the large impedance mismatch between air and water, sufficient energy penetrates the sea surface to provide a useable underwater signal at sensors either in the water column or buried in the sediment. The received signals, which are significantly Doppler shifted due to the motion of the aircraft, will have experienced a number of reflections from the seabed and thus they contain information about the sediment. A geo-acoustic inversion of the Doppler-shifted modes associated with each harmonic yields an estimate of the sound speed in the sediment; and, once the sound speed has been determined, the known correlations between it and the remaining geo-acoustic parameters allow all of the latter to be computed. This inversion technique has been applied to aircraft data collected in the shallow water north of Scripps pier, returning values of the sound speed, shear speed, porosity, density and grain size that are consistent with the known properties of the sandy sediment in the channel.

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

NASA Astrophysics Data System (ADS)

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

2012-10-01

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

Spread-Spectrum Beamforming and Clutter Filtering for Plane-Wave Color Doppler Imaging.

PubMed

Mansour, Omar; Poepping, Tamie L; Lacefield, James C

2016-07-21

Plane-wave imaging is desirable for its ability to achieve high frame rates, allowing the capture of fast dynamic events and continuous Doppler data. In most implementations of plane-wave imaging, multiple low-resolution images from different plane wave tilt angles are compounded to form a single high-resolution image, thereby reducing the frame rate. Compounding improves the lateral beam profile in the high-resolution image, but it also acts as a low-pass filter in slow time that causes attenuation and aliasing of signals with high Doppler shifts. This paper introduces a spread-spectrum color Doppler imaging method that produces high-resolution images without the use of compounding, thereby eliminating the tradeoff between beam quality, maximum unaliased Doppler frequency, and frame rate. The method uses a long, random sequence of transmit angles rather than a linear sweep of plane wave directions. The random angle sequence randomizes the phase of off-focus (clutter) signals, thereby spreading the clutter power in the Doppler spectrum, while keeping the spectrum of the in-focus signal intact. The ensemble of randomly tilted low-resolution frames also acts as the Doppler ensemble, so it can be much longer than a conventional linear sweep, thereby improving beam formation while also making the slow-time Doppler sampling frequency equal to the pulse repetition frequency. Experiments performed using a carotid artery phantom with constant flow demonstrate that the spread-spectrum method more accurately measures the parabolic flow profile of the vessel and outperforms conventional plane-wave Doppler in both contrast resolution and estimation of high flow velocities. The spread-spectrum method is expected to be valuable for Doppler applications that require measurement of high velocities at high frame rates.

Non-Doppler shift related experimental shock wave measurements using velocity interferometer systems for any reflector.

PubMed

Forsman, A C; Kyrala, G A

2001-05-01

Velocity interferometer system for any reflectors (VISARs), are becoming increasingly popular in the measurement of shock waves in solids and liquids. VISAR techniques are used in measurements of transit time, speed of shock waves in flight in transparent media [L. C. Chhabildas and J. L. Wise, in Proceedings of the 4th APS Topical Conference on Shock Waves in Condensed Matter, Spokane, Washington, 1985, edited by Y. M. Gupta (Plenum, New York, 1986); P. M. Celliers et al., Appl. Phys. Lett. 73, 1320 (1998)], and in measurements of particle velocity. However, in cases where shock compression or release may change the index of refraction n+ik of the material being studied, the VISAR technique must be applied with care. Changes in n and k introduce phase shifts into the VISAR results that are not associated with changes in velocity. This paper presents a derivation of the theoretical output of a line VISAR that includes the effects of changing n and k and an experimental observation of a non-Doppler shift related effect.

A Simple Snap Oscillator with Coexisting Attractors, Its Time-Delayed Form, Physical Realization, and Communication Designs

NASA Astrophysics Data System (ADS)

Rajagopal, Karthikeyan; Jafari, Sajad; Akgul, Akif; Karthikeyan, Anitha; Çiçek, Serdar; Shekofteh, Yasser

2018-05-01

In this paper, we report a novel chaotic snap oscillator with one nonlinear function. Dynamic analysis of the system shows the existence of bistability. To study the time delay effects on the proposed snap oscillator, we introduce multiple time delay in the fourth state equation. Investigation of dynamical properties of the time-delayed system shows that the snap oscillator exhibits the same multistable properties as the nondelayed system. The new multistable hyperjerk chaotic system has been tested in chaos shift keying and symmetric choc shift keying modulated communication designs for engineering applications. It has been determined that the symmetric chaos shift keying modulated communication system implemented with the new chaotic system is more successful than the chaos shift keying modulation for secure communication. Also, circuit implementation of the chaotic snap oscillator with tangent function is carried out showing its feasibility.

Left Ventricular Stroke Volume Quantification by Contrast Echocardiography – Comparison of Linear and Flow-Based Methods to Cardiac Magnetic Resonance

PubMed Central

Dele-Michael, Abiola O.; Fujikura, Kana; Devereux, Richard B; Islam, Fahmida; Hriljac, Ingrid; Wilson, Sean R.; Lin, Fay; Weinsaft, Jonathan W.

2014-01-01

Background Echocardiography (echo) quantified LV stroke volume (SV) is widely used to assess systolic performance after acute myocardial infarction (AMI). This study compared two common echo approaches – predicated on flow (Doppler) and linear chamber dimensions (Teichholz) – to volumetric SV and global infarct parameters quantified by cardiac magnetic resonance (CMR). Methods Multimodality imaging was performed as part of a post-AMI registry. For echo, SV was measured by Doppler and Teichholz methods. Cine-CMR was used for volumetric SV and LVEF quantification, and delayed-enhancement CMR for infarct size. Results 142 patients underwent same-day echo and CMR. On echo, mean SV by Teichholz (78±17ml) was slightly higher than Doppler (75±16ml; Δ=3±13ml, p=0.02). Compared to SV on CMR (78±18ml), mean difference by Teichholz (Δ=−0.2±14; p=0.89) was slightly smaller than Doppler (Δ−3±14; p=0.02) but limits of agreement were similar between CMR and echo methods (Teichholz: −28, 27 ml, Doppler: −31, 24ml). For Teichholz, differences with CMR SV were greatest among patients with anteroseptal or lateral wall hypokinesis (p<0.05). For Doppler, differences were associated with aortic valve abnormalities or root dilation (p=0.01). SV by both echo methods decreased stepwise in relation to global LV injury as assessed by CMR-quantified LVEF and infarct size (p<0.01). Conclusions Teichholz and Doppler calculated SV yield similar magnitude of agreement with CMR. Teichholz differences with CMR increase with septal or lateral wall contractile dysfunction, whereas Doppler yields increased offsets in patients with aortic remodeling. PMID:23488864

Wind turbine generators with active radar signature control blades

NASA Astrophysics Data System (ADS)

Tennant, Alan; Chambers, Barry

2004-07-01

The large radar cross section of wind turbine generator (WTG) blades combined with high tip speeds can produce significant Doppler returns when illuminated by a radar. Normally, an air traffic control radar system will filter out large returns from stationary targets, however the Doppler shifts introduced by the WTG are interpreted as moving aircraft that can confuse radar operators and compromise safety. A possible solution to this problem that we are investigating is to incorporate an active layer into the structure of the WTG blades that can be used to dynamically modulate the RCS of the blade return. The active blade can operate in one of two modes: firstly the blade RCS can be modulated to provide a Doppler return that is outside the detectable range of the radar receiver system so that it is rejected: a second mode of operation is to introduce specific coding on to the Doppler returns so that they may be uniquely identified and rejected. The active layer used in the system consists of a frequency selective surface controlled by semiconductor diodes and is a development of techniques that we have developed for active radar absorbers. Results of experimental work using a 10GHz Doppler radar and scale model WTG with active Doppler imparting blades are presented.

SDP_mharwit_1: Demonstration of HIFI Linear Polarization Analysis of Spectral Features

NASA Astrophysics Data System (ADS)

Harwit, M.

2010-03-01

We propose to observe the polarization of the 621 GHz water vapor maser in VY Canis Majoris to demonstrate the capability of HIFI to make polarization observations of Far-Infrared/Submillimeter spectral lines. The proposed Demonstration Phase would: - Show that HIFI is capable of interesting linear polarization measurements of spectral lines; - Test out the highest spectral resolving power to sort out closely spaced Doppler components; - Determine whether the relative intensities predicted by Neufeld and Melnick are correct; - Record the degree and direction of linear polarization for the closely-Doppler shifted peaks.

SPACE COMMUNICATIONS TECHNIQUES

DTIC Science & Technology

A description is given of the expansion of interim simplex space communication facilities at Rome, N . Y ., and Trinidad to full duplex for use in...communications baseband demod ulator, doppler-shift tracking, and passive radar tracking at Rome, N . Y . are discussed.

On the detectability of key-MeV solar protons through their nonthermal Lyman-alpha emission

NASA Technical Reports Server (NTRS)

Canfield, R. C.; Chang, C. R.

1985-01-01

The intensity and timescale of nonthermal Doppler-shifted hydrogen L alpha photon emission as diagnostics of 10 keV to 10 MeV protons bombarding the solar chromosphere during flares are investigated. The steady-state excitation and ionization balance of the proton beam are determined, taking into account all important atomic interactions with the ambient chromosphere. For a proton energy flux comparable to the electron energy flux commonly inferred for large flares, L alpha wing intensities orders of magnitude larger than observed nonflaring values were found. Investigation of timescales for ionization and charge exchange leads researchers to conclude that over a wide range of values of mean proton energy and beam parameters, Doppler-shifted nonthermal L alpha emission is a useful observational diagnostic of the presence of 10 keV to 10 MeV superthermal proton beams in the solar flare chromosphere.

Continuous wave dye-laser technique for simultaneous, spatially resolved measurements of temperature, pressure, and velocity of NO in an underexpanded free jet

NASA Technical Reports Server (NTRS)

Di Rosa, Michael D.; Chang, Albert Y.; Hanson, Ronald K.

1993-01-01

Gas dynamic quantities within an underexpanded nitrogen free jet, seeded with 0.5 percent NO, were measured nonintrusively by using an intracavity-doubled, rapid-tuning, CW ring dye laser. The UV beam passed obliquely through the jet axis, and its frequency repetitively scanned across adjacent rotational lines in the NO gamma band near 225 nm at a rate of 4 kHz. Spatially resolved excitation scans were obtained by monitoring the induced broadband fluoresence. Modeling the Doppler-shifted excitation scans with Voigt profiles permitted simultaneous determinations of NO velocity, rotational temperature, and pressure. Zero Doppler shift was referenced to an absorption trace obtained across a static cell and recorded concurrently with the excitation scan. Typically, the measured and predicted axial distributions agreed within 10 percent. At high Mach numbers there was evidence of rotational freezing of NO.

Acoustic sounding of wind velocity profiles in a stratified moving atmosphere.

PubMed

Ostashev, V E; Georges, T M; Clifford, S F; Goedecke, G H

2001-06-01

The paper deals with analytical and numerical studies of the effects of atmospheric stratification on acoustic remote sensing of wind velocity profiles by sodars. Both bistatic and monostatic schemes are considered. Formulas for the Doppler shift of an acoustic echo signal scattered by atmospheric turbulence advected with the mean wind in a stratified moving atmosphere are derived. Numerical studies of these formulas show that errors in retrieving wind velocity can be of the order of 1 m/s if atmospheric stratification is ignored. Formulas for the height at which wind velocity is retrieved are also derived. Approaches are proposed which allow one to take into account the effects of atmospheric stratification when restoring the wind velocity profile from measured values of the Doppler shift and the time interval of acoustic impulse propagation from a sodar to the scattering volume and back to the ground.

Low collectivity of the first 2+ states of 212,210Po

NASA Astrophysics Data System (ADS)

Kocheva, D.; Rainovski, G.; Jolie, J.; Pietralla, N.; Blazhev, A.; Astier, A.; Altenkirch, R.; Bast, M.; Beckers, M.; Ansari, S.; Braunroth, Th.; Cappellazzo, M.; Cortés, M. L.; Dewald, A.; Diel, F.; Djongolov, M.; Fransen, C.; Gladnishki, K.; Goldkuhle, A.; Hennig, A.; Karayonchev, V.; Keatings, J. M.; Kluge, E.; Kröll, Th.; Litzinger, J.; Moschner, K.; Müller-Gatermann, C.; Petkov, P.; Rudigier, M.; Scheck, M.; Spagnoletti, P.; Scholz, Ph.; Schmidt, T.; Spieker, M.; Stahl, C.; Stegmann, R.; Stolz, A.; Vogt, A.; Stoyanova, M.; Thöle, P.; Warr, N.; Werner, V.; Witt, W.; Wölk, D.; Zamora, J. C.; Zell, K. O.; Van Isacker, P.; Ponomarev, V. Yu.

2018-05-01

The lifetimes of the first 2+ excited states of 212,210Po were measured in two transfer reactions 208Pb(12C,8Be)212Po and 208Pb(12C,10Be)210Po by the Recoil Distance Doppler Shift (RDDS) method and by the Doppler Shift Attenuation method (DSAM), respectively. The derived absolute B(E2) values of 2.6(3) W.u. for 212Po and 1.83(28) W.u. for 210Po indicate low collectivity. It is shown that the properties of the yrast {2}1+, {4}1+, {6}1+ and {8}1+ states in both nuclei cannot be described consistently in the framework of nuclear shell models. It is also demonstrated in the case of 210Po that Quasi-particle Phonon Model (QPM) calculations cannot overcome this problem thus indicating the existence of a peculiarity which is neglected in both theoretical approaches.

Fringe chasing by three-point spatial phase shifting for discrimination of the motion direction in the long-range homodyne laser Doppler vibrometry

NASA Astrophysics Data System (ADS)

Daemi, Mohammad Hossein; Rasouli, Saifollah

2018-07-01

In this work, a three-point spatial phase shifting (SPS) method is implemented for chasing of the moving interference fringes in the homodyne laser Doppler vibrometry (HoLDV). By the use of SPS method, we remove disability of the HoLDV in the discrimination of the motion direction for long-range displacements. From the phase increments histogram, phase unwrapping tolerance value is selected, and adequacy of the data acquisition rate and required bandwidth limit are determined. Also in this paper, a detailed investigation on the effect of detectors positioning errors and influence of the Gaussian profile of the interfering beams on the measurements are presented. Performance of the method is verified by measuring a given harmonic vibration produced by a loudspeaker. Also, by the proposed method, vibration of mounting system of a disk laser gain medium is characterized.

Complex phase error and motion estimation in synthetic aperture radar imaging

NASA Astrophysics Data System (ADS)

Soumekh, M.; Yang, H.

1991-06-01

Attention is given to a SAR wave equation-based system model that accurately represents the interaction of the impinging radar signal with the target to be imaged. The model is used to estimate the complex phase error across the synthesized aperture from the measured corrupted SAR data by combining the two wave equation models governing the collected SAR data at two temporal frequencies of the radar signal. The SAR system model shows that the motion of an object in a static scene results in coupled Doppler shifts in both the temporal frequency domain and the spatial frequency domain of the synthetic aperture. The velocity of the moving object is estimated through these two Doppler shifts. It is shown that once the dynamic target's velocity is known, its reconstruction can be formulated via a squint-mode SAR geometry with parameters that depend upon the dynamic target's velocity.

Vacancy-fluorine complexes and their impact on the properties of metal-oxide transistors with high-k gate dielectrics studied using monoenergetic positron beams

NASA Astrophysics Data System (ADS)

Uedono, A.; Inumiya, S.; Matsuki, T.; Aoyama, T.; Nara, Y.; Ishibashi, S.; Ohdaira, T.; Suzuki, R.; Miyazaki, S.; Yamada, K.

2007-09-01

Vacancy-fluorine complexes in metal-oxide semiconductors (MOS) with high-k gate dielectrics were studied using a positron annihilation technique. F+ ions were implanted into Si substrates before the deposition of gate dielectrics (HfSiON). The shift of threshold voltage (Vth) in MOS capacitors and an increase in Fermi level position below the HfSiON/Si interface were observed after F+ implantation. Doppler broadening spectra of the annihilation radiation and positron lifetimes were measured before and after HfSiON fabrication processes. From a comparison between Doppler broadening spectra and those obtained by first-principles calculation, the major defect species in Si substrates after annealing treatment (1050 °C, 5 s) was identified as vacancy-fluorine complexes (V3F2). The origin of the Vth shift in the MOS capacitors was attributed to V3F2 located in channel regions.

Molecular velocimetry using stimulated Raman spectroscopy

NASA Technical Reports Server (NTRS)

Exton, R. J.; Hillard, M. E.

1984-01-01

Molecular flow velocity of N2 was measured in a supersonic wind tunnel using inverse Raman spectroscopy. This technique employs the large Doppler shift exhibited by the molecules when the pump and probe laser beams are counter-propagating (backward scattering). A retrometer system is employed to yield a vibration-free optical configuration which has the additional advantage of obtaining both the forward and backward scattered spectra simultaneously. The linebreadths and their relative Doppler shift can be used to determine the static pressure, translational temperature, and molecular flow velocity. A demonstration of the concept was performed in a supersonic wind tunnel and included: (1) measurements over the Mach number range 2.50 to 4.63; (2) static pressure measurements (at Mach 2.50) corresponding to a Reynolds number per foot range of 1 to 5 x 10 to the 6th power; and (3) measurements behind the shock wave of a flat plate model.

Localization and tracking of moving objects in two-dimensional space by echolocation.

PubMed

Matsuo, Ikuo

2013-02-01

Bats use frequency-modulated echolocation to identify and capture moving objects in real three-dimensional space. Experimental evidence indicates that bats are capable of locating static objects with a range accuracy of less than 1 μs. A previously introduced model estimates ranges of multiple, static objects using linear frequency modulation (LFM) sound and Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates. The delay time for a single object was estimated with an accuracy of about 1.3 μs by measuring the echo at a low signal-to-noise ratio (SNR). The range accuracy was dependent not only on the SNR but also the Doppler shift, which was dependent on the movements. However, it was unclear whether this model could estimate the moving object range at each timepoint. In this study, echoes were measured from the rotating pole at two receiving points by intermittently emitting LFM sounds. The model was shown to localize moving objects in two-dimensional space by accurately estimating the object's range at each timepoint.

Radial plasma drifts deduced from VLF whistler mode signals - A modelling study

NASA Astrophysics Data System (ADS)

Poulter, E. M.; Andrews, M. K.; Bailey, G. J.; Moffett, R. J.

1984-05-01

VLF whistler mode signals have previously been used to infer radial plasma drifts in the equatorial plane of the plasmasphere and the field-aligned ionosphere-protonosphere coupling fluxes. Physical models of the plasmasphere consisting of O(+) adn H(+) ions along dipole magnetic field lines, and including radial E x B drifts, are applied to a mid-latitude flux tube appropriate to whistler mode signals received at Wellington, New Zealand, from the fixed frequency VLF transmitter NLK (18.6 kHz) in Seattle, U.S.A. These models are first shown to provide a good representation of the recorded Doppler shift and group delay data. They are then used to simulate the process of deducing the drifts and fluxes from the recorded data. Provided the initial whistler mode duct latitude and the ionospheric contributions are known, the drifts at the equatorial plane can be estimated to about + or - 20 m/s (approximately 10-15 percent), and the two hemisphere ionosphere-protonosphere coupling fluxes to about + or - 10 to the 12th/sq m-sec (approximately 40 percent).

On the detection of a stochastic background of gravitational radiation by the Doppler tracking of spacecraft

NASA Technical Reports Server (NTRS)

Mashhoon, B.; Grishchuk, L. P.

1980-01-01

Consideration is given to the possibility of detection of an isotropic background gravitational radiation of a stochastic nature by the method of Doppler tracking of spacecraft. Attention is given in the geometrical optics limit, to the general formula for the frequency shift of an electromagnetic signal in the gravitational radiation field, and it is shown to be gauge independent. The propagation of a free electromagnetic wave in a gravitational radiation field is examined with the conclusion that no resonance phenomena can be expected. Finally, the 'Doppler noise' due to a stochastic background is evaluated, and it is shown to depend on the total energy density of the background and a parameter that is a characteristic of the radiation spectrum and the detection system used.

Theoretical and experimental signal-to-noise ratio assessment in new direction sensing continuous-wave Doppler lidar

NASA Astrophysics Data System (ADS)

Tegtmeier Pedersen, A.; Abari, C. F.; Mann, J.; Mikkelsen, T.

2014-06-01

A new direction sensing continuous-wave Doppler lidar based on an image-reject homodyne receiver has recently been demonstrated at DTU Wind Energy, Technical University of Denmark. In this contribution we analyse the signal-to-noise ratio resulting from two different data processing methods both leading to the direction sensing capability. It is found that using the auto spectrum of the complex signal to determine the wind speed leads to a signal-to-noise ratio equivalent to that of a standard self-heterodyne receiver. Using the imaginary part of the cross spectrum to estimate the Doppler shift has the benefit of a zero-mean background spectrum, but comes at the expense of a decrease in the signal-to noise ratio by a factor of √2.

Resonant Doppler velocimetry in supersonic nitrogen flow. Ph.D. Thesis. Final Report, 31 Oct. 1979 - 31 Jul. 1982

NASA Technical Reports Server (NTRS)

Cheng, S. W. S.

1982-01-01

The development of the Resonant Doppler Velocimeter (RDV) is discussed. It is a new nonintrusive laser technique for flow diagnosis. The RDV technique is applied to supersonic nitrogen flow with sodium atoms as tracer particles. The measurements are achieved by shining a tunable single frequency laser beam into the flow. The resonant absorption spectrum of the seeded species is determined by observing the fluorescence signal intensity as a function of excitation wavelength. By comparing the peak absorption wavelength with a reference frequency marker, the flow velocity along the excitation beam can be obtained through the Doppler shift relation. By fitting the spectrum with a theoretical line profile, the static temperature and pressure of the flow an be determined.

Radar research on thunderstorms and lightning

NASA Technical Reports Server (NTRS)

Rust, W. D.; Doviak, R. J.

1982-01-01

Applications of Doppler radar to detection of storm hazards are reviewed. Normal radar sweeps reveal data on reflectivity fields of rain drops, ionized lightning paths, and irregularities in humidity and temperature. Doppler radar permits identification of the targets' speed toward or away from the transmitter through interpretation of the shifts in the microwave frequency. Wind velocity fields can be characterized in three dimensions by the use of two radar units, with a Nyquist limit on the highest wind speeds that may be recorded. Comparisons with models numerically derived from Doppler radar data show substantial agreement in storm formation predictions based on information gathered before the storm. Examples are provided of tornado observations with expanded Nyquist limits, gust fronts, turbulence, lightning and storm structures. Obtaining vertical velocities from reflectivity spectra is discussed.

Measurement of movements in the ionosphere using radio reflections

NASA Astrophysics Data System (ADS)

Whitehead, J. D.; From, W. R.; Jones, K. L.; Monro, P. E.

1983-05-01

Movements of the ionosphere may be measured using radio reflections either by observing the movement of the diffraction, or interference, pattern along the ground; or by using the Doppler shifts of the echo as a radar beam is scanned across the sky. The two methods may use the same experimental arrangement and even the same data. The error in the drift velocity measured for scattered echoes is inversely proportional to the square of the array size for both methods. More detail of the random motion may be observed with the Doppler method. When the radio reflections are from an undulating surface in the ionosphere which changes its form as it moves, the Doppler method combined with further analysis is required to measure the movement and change of the undulating surface.

Correction of I/Q channel errors without calibration

DOEpatents

Doerry, Armin W.; Tise, Bertice L.

2002-01-01

A method of providing a balanced demodular output for a signal such as a Doppler radar having an analog pulsed input; includes adding a variable phase shift as a function of time to the input signal, applying the phase shifted input signal to a demodulator; and generating a baseband signal from the input signal. The baseband signal is low-pass filtered and converted to a digital output signal. By removing the variable phase shift from the digital output signal, a complex data output is formed that is representative of the output of a balanced demodulator.

On-chip programmable ultra-wideband microwave photonic phase shifter and true time delay unit.

PubMed

Burla, Maurizio; Cortés, Luis Romero; Li, Ming; Wang, Xu; Chrostowski, Lukas; Azaña, José

2014-11-01

We proposed and experimentally demonstrated an ultra-broadband on-chip microwave photonic processor that can operate both as RF phase shifter (PS) and true-time-delay (TTD) line, with continuous tuning. The processor is based on a silicon dual-phase-shifted waveguide Bragg grating (DPS-WBG) realized with a CMOS compatible process. We experimentally demonstrated the generation of delay up to 19.4 ps over 10 GHz instantaneous bandwidth and a phase shift of approximately 160° over the bandwidth 22-29 GHz. The available RF measurement setup ultimately limits the phase shifting demonstration as the device is capable of providing up to 300° phase shift for RF frequencies over a record bandwidth approaching 1 THz.

1998 NASA Review: Center for Space Telemetering and Telecommunication Systems

NASA Technical Reports Server (NTRS)

Cunningham, Garry

1998-01-01

The following topics are included in the conference proceedings following the program overview: (1) Coding and Carrier Recovery Techniques; (2) Carrier Frequency Estimation Under Unknown Doppler Shifts; (3) Small Satellite Experiments; (4) Bandwidth Efficient Modulation/Equalization Techniques.

Virtual Ionosonde Construction by using ITS and IRI-2012 models

NASA Astrophysics Data System (ADS)

Kabasakal, Mehmet; Toker, Cenk

2016-07-01

Ionosonde is a kind of radar which is used to examine several properties of the ionosphere, including the electron density and drift velocity. Ionosonde is an expensive device and its installation requires special expertise and a proper area clear of sources of radio interference. In order to overcome the difficulties of installing an ionosonde hardware, the target of this study is to construct a virtual ionosonde based on communication channel models where the model parameters are determined by ray tracing obtained by the PHaRLAP software and the International Reference Ionosphere (IRI-2012) model. Although narrowband high frequency (HF) communication models have been widely used to represent the behaviour of the radio channel, they are applicable to a limited set of actual propagation conditions and wideband models are needed to better understand the HF channel. In 1997, the Institute for Telecommunication Science (ITS) developed a wideband HF ionospheric model, the so-called ITS model, however, it has some restrictions in real life applications. The ITS model parameters are grouped into two parts; the deterministic and the stochastic parameters. The deterministic parameters are the delay time (tau _{c}) of each reflection path based on the penetration frequency (f _{p}), the height (h _{0}) of the maximum electron density and the half thickness (sigma) of the reflective layer. The stochastic parameters, delay spread (sigma _{tau}), delay rise time (sigma _{c}), Doppler spread (sigma _{D}), Doppler shift (f _{s}), are to calculate the impulse response of the channel. These parameters are generally difficult to obtain and are based on the measured data which may not be available in all cases. In order to obtain these parameters, we propose to integrate the PHaRLAP ray tracing toolbox and the IRI-2012 model. When Total Electron Content (TEC) estimates obtained from GNSS measurements are input to IRI-2012, the model generates electron density profiles close to the actual profiles, which are used for ray tracing between the user defined geographical coordinates. Then, ITS model parameters are obtained from both ray tracing and also the IRI-2012 model. Finally, an ionosonde signal waveform is transmitted through the channel obtained from the ITS model to generate the ionogram. As an application, oblique sounding between two points is simulated with ITS channel model. M-sequence, Barker sequence and complementary sequences are used as sounding waveforms. The effects of channel on the oblique ionogram and sounding waveform characteristics are also investigated.

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

NASA Technical Reports Server (NTRS)

Mazumder, M. K.

1972-01-01

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

Signature management of radar returns from wind turbine generators

NASA Astrophysics Data System (ADS)

Tennant, A.; Chambers, B.

2006-04-01

The large radar cross section of wind turbine generator (WTG) blades combined with high tip speeds can produce significant Doppler returns when illuminated by a radar. Normally, an air traffic control radar system will filter out large returns from stationary targets, but the Doppler shifts introduced by the WTG blades are interpreted as moving aircraft that can confuse radar operators and compromise safety. A possible solution to this problem is to incorporate an active layer into the structure of the WTG blades that can be used to dynamically modulate the radar cross section (RCS) of the blade return. The active blade can operate in one of two modes: first the blade RCS can be modulated to provide a Doppler return that is outside the detectable range of the radar receiver system so that it is rejected; a second mode of operation is to introduce specific coding onto the Doppler returns so that they may be uniquely identified and rejected. The active layer used in the system consists of a frequency selective surface controlled by semiconductor diodes and is a development of techniques developed for active radar absorbers. Results of theoretical and experimental work using a 10 GHz Doppler radar and scale-model WTG are presented.

Christian Andreas Doppler--the man and his legacy.

PubMed

Coman, I M

2005-01-01

Reminding the life and legacy of the Austrian Scientist who discovered the famous 'Doppler Effect'. C.A. Doppler was born the 29th of November 1803 in Salzburg. After studies in Linz and Vienna, he graduated in mathematics, became assistant at the University and later worked as a professor in Prague. Back to Vienna, he was appointed as professor at the Polytechnic School and --in 1850--as first director of the new Institute of Physics. C.A. Doppler did publish on magnetism, electricity, optics, and astronomy. He remains in the history of science due to the discovery presented (May 25, 1842) at the Royal Bohemian Society of Science entitled "On the colored light of the double stars and certain other stars of the heavens"; the paper described (applied to light) the shift of frequency which bears nowadays his name. The theory was later experimentally proven and--extended for any electromagnetic and acoustic waves--got myriads if applications in astronomy, physics, aviation, meteorology, and health science. Satomura in Japan (1955) published it's first ultrasound vascular application--with successive achievements in the next decades. Doppler ultrasonagraphy became the main noninvasive instrument for functional assesment of heart and vessels.

Transverse Wave Induced Kelvin–Helmholtz Rolls in Spicules

NASA Astrophysics Data System (ADS)

Antolin, P.; Schmit, D.; Pereira, T. M. D.; De Pontieu, B.; De Moortel, I.

2018-03-01

In addition to their jet-like dynamic behavior, spicules usually exhibit strong transverse speeds, multi-stranded structure, and heating from chromospheric to transition region temperatures. In this work we first analyze Hinode and IRIS observations of spicules and find different behaviors in terms of their Doppler velocity evolution and collective motion of their sub-structure. Some have a Doppler shift sign change that is rather fixed along the spicule axis, and lack coherence in the oscillatory motion of strand-like structure, matching rotation models, or long-wavelength torsional Alfvén waves. Others exhibit a Doppler shift sign change at maximum displacement and coherent motion of their strands, suggesting a collective magnetohydrodynamic (MHD) wave. By comparing with an idealized 3D MHD simulation combined with radiative transfer modeling, we analyze the role of transverse MHD waves and associated instabilities in spicule-like features. We find that transverse wave induced Kelvin–Helmholtz (TWIKH) rolls lead to coherence of strand-like structure in imaging and spectral maps, as seen in some observations. The rapid transverse dynamics and the density and temperature gradients at the spicule boundary lead to ring-shaped Mg II k and Ca II H source functions in the transverse cross-section, potentially allowing IRIS to capture the Kelvin–Helmholtz instability dynamics. Twists and currents propagate along the spicule at Alfvénic speeds, and the temperature variations within TWIKH rolls, produce the sudden appearance/disappearance of strands seen in Doppler velocity and in Ca II H intensity. However, only a mild intensity increase in higher-temperature lines is obtained, suggesting there is an additional heating mechanism at work in spicules.

Impact of nonabsorbing control rod tips on kinetics feedback for BWR turbine trip without bypass RETRAN-03 analyses

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

Feltus, M.A.; Knerr, R.; Shoop, U.

1993-01-01

RETRAN-03 studies were performed for the boiling water reactor (BWR) turbine trip without bypass (TTWOB) event to investigate how the non-neutron-absorbing material on control rod tips affect scram delay timing and reactivity feedback. Scram delay, Doppler temperature, and moderator void (density) feedback were varied to assess their relative impact on kinetics behavior. Although a generic point-kinetics RETRAN-03 TTWOB model 2 was employed, actual plant information was used to develop the basic and parametric cases.

Experimental study of the effect of 2/1 classical tearing mode on (intermediate, small)-scale microturbulence in the core of an EAST L mode plasma

NASA Astrophysics Data System (ADS)

Sun, P. J.; Li, Y. D.; Ren, Y.; Zhang, X. D.; Wu, G. J.; Lyu, B.; Shi, T. H.; Xu, L. Q.; Wang, F. D.; Li, Q.; Zhang, J. Z.; Hu, L. Q.; Li, J. G.; the EAST Team

2018-02-01

In this paper, we report an experimental study of the effect of a m/n = -2/-1 (m, n being poloidal and toroidal mode number, separately) classical tearing mode on (intermediate, small)-scale microturbulence (see the definition in section 1) in the core of an EAST L mode plasma discharge. The microturbulence at different scales k ⊥ = 10, 18 and 26 cm-1 (i.e., {k}\\perp {ρ }i˜ 2, 3.6 and 5.2, respectively. Here, {ρ }i is the ion gyroradius and k ⊥ is the perpendicular wavenumber) were measured simultaneously by the EAST multi-channel tangential CO2 laser collective scattering diagnostics. Experimental results confirm that the decrease of microturbulent Doppler shift ({f}{{Doppler}}={k}t{v}t/2π ), inversely correlated to the increase of microturbulent mean frequency (defined in equation (1)), is due to the 2/1 tearing mode. Temporal evolution of frequency-integrated spectral power S tot of microturbulence, found to be correlated with the width of 2/1 magnetic island, suggests the modulation effect on microturbulence by the tearing mode beyond Doppler shift effect. Modulation effects on microturbulence by the tearing mode are further demonstrated by the correlation between microturbulent envelope and magnetic fluctuations.

Luminosity Dependence and Search Doppler

NASA Technical Reports Server (NTRS)

VanParadijs, Johannes A.

1998-01-01

The research supported by this grant covered two projects: (1) a study of the luminosity dependence of the properties of atoll sources; and (2) a search for Doppler shifts in the pulse arrival times of the anomalous pulsar 4U 0142+61. Following the discovery of kilohertz quasi-periodic oscillations (QPOS) in Sco X-1 studies of the X-ray properties of atoll sources have been dominated by searches for these QPOS, and the study of their dependence on other source properties, such as X-ray luminosity and spectral state. In the project supported by grant NAG5-3269 we have detected kHz QPOs for several atoll sources. The physical interpretation of these QPO is as yet unclear, but simple models (such as the Keplerian beat frequency model) can probably be excluded. The results of this research have been reported. We have studied the X-ray pulsations of the anomalous X-ray pulsar 4U 0142+61 using the Rossi XTE. A detailed search for Doppler shifts did not lead to a positive detection. The upper limits exclude almost all types of possible companion stars, except white dwarfs. However, the latter can be excluded since anomalous X-ray pulsars are very young objects. We therefore conclude that anomalous X-ray pulsars are single neutron stars.

Local time distribution of the SSC-associated HF-Doppler frequency shifts

NASA Technical Reports Server (NTRS)

Kikuchi, T.; Sugiuchi, H.; Ishimine, T.

1985-01-01

The HF-Doppler frequency shift observed at the storm's sudden commencement is composed of a frequency increase (+) and decrease (-), and classified into four types, SCF(+ -), SCF(- +), SCF(+) and SCF(-). Since the latter two types are special cases of the former two types, two different kinds of electrical field exist in the F region and cause the ExB drift motion of plasma. HUANG (1976) interpreted the frequency increase of SCF(+ -) as due to the westward induction electric field proportional to delta H/ delta t and the succeeding frequency decrease due to the eastward conduction electric field which produces ionospheric currents responsible for the magnetic increase on the ground. In spite of his success in interpreting the SCF(+ -), some other interpretations are needed for the explanation of the whole set of SCF's, particularly SCF(- +). Local time distributions of the SCF's are derived from 41 SCF's which are observed on the HF standard signal (JJY) as received in Okinawa (path length =1600 km) and Kokubunji (60 km). It is shown that the SCF(+ -) appears mainly during the day, whereas the SCF(- +) is observed during the night. The results indicate that the preliminary frequency shift (+) of SCF(+ -) and (-) of SCF(- +) is caused by a westward electric field in the dayside hemisphere, while by an eastward electric field in the nightside hemisphere. The main frequency shift (-) of SCF(+ -) and (+) of SCF(- +) is caused by the reversed electric field. Consequently, the preliminary frequency shift is caused by the dusk-to-dawn electric field, while the main frequency shift by the dawn-to-dusk electric field.

Phase delaying the human circadian clock with a single light pulse and moderate delay of the sleep/dark episode: no influence of iris color.

PubMed

Canton, Jillian L; Smith, Mark R; Choi, Ho-Sun; Eastman, Charmane I

2009-07-17

Light exposure in the late evening and nighttime and a delay of the sleep/dark episode can phase delay the circadian clock. This study assessed the size of the phase delay produced by a single light pulse combined with a moderate delay of the sleep/dark episode for one day. Because iris color or race has been reported to influence light-induced melatonin suppression, and we have recently reported racial differences in free-running circadian period and circadian phase shifting in response to light pulses, we also tested for differences in the magnitude of the phase delay in subjects with blue and brown irises. Subjects (blue-eyed n = 7; brown eyed n = 6) maintained a regular sleep schedule for 1 week before coming to the laboratory for a baseline phase assessment, during which saliva was collected every 30 minutes to determine the time of the dim light melatonin onset (DLMO). Immediately following the baseline phase assessment, which ended 2 hours after baseline bedtime, subjects received a 2-hour bright light pulse (~4,000 lux). An 8-hour sleep episode followed the light pulse (i.e. was delayed 4 hours from baseline). A final phase assessment was conducted the subsequent night to determine the phase shift of the DLMO from the baseline to final phase assessment.Phase delays of the DLMO were compared in subjects with blue and brown irises. Iris color was also quantified from photographs using the three dimensions of red-green-blue color axes, as well as a lightness scale. These variables were correlated with phase shift of the DLMO, with the hypothesis that subjects with lighter irises would have larger phase delays. The average phase delay of the DLMO was -1.3 +/- 0.6 h, with a maximum delay of ~2 hours, and was similar for subjects with blue and brown irises. There were no significant correlations between any of the iris color variables and the magnitude of the phase delay. A single 2-hour bright light pulse combined with a moderate delay of the sleep/dark episode delayed the circadian clock an average of ~1.5 hours. There was no evidence that iris color influenced the magnitude of the phase shift. Future studies are needed to replicate our findings that iris color does not impact the magnitude of light-induced circadian phase shifts, and that the previously reported differences may be due to race.

Direct measurement of Lorentz transformation with Doppler effects

NASA Astrophysics Data System (ADS)

Chen, Shao-Guang

For space science and astronomy the fundamentality of one-way velocity of light (OWVL) is selfevident. The measurement of OWVL (distance/interval) and the clock synchronization with light-signal transfer make a logical circulation. This means that OWVL could not be directly measured but only come indirectly from astronomical method (Romer's Io eclipse and Bradley's sidereal aberration), furthermore, the light-year by definitional OWVL and the trigonometry distance with AU are also un-measurable. For to solve this problem two methods of clock synchronization were proposed: The direct method is that at one end of dual-speed transmissionline with single clock measure the arriving-time difference of longitudinal wave and transverse wave or ordinary light and extraordinary light, again to calculate the collective sending-time of two wave with Yang's /shear elastic-modulus ratio (E/k) or extraordinary/ordinary light refractive-index ratio (ne/no), which work as one earthquake-station with single clock measures first-shake time and the distance to epicenter; The indirect method is that the one-way wavelength l is measured by dual-counters Ca and Cb and computer's real-time operation of reading difference (Nb - Na) of two counters, the frequency f is also simultaneously measured, then l f is just OWVL. Therefore, with classical Newtonian mechanics and ether wave optics, OWVL can be measured in the Galileo coordinate system with an isotropic length unit (1889 international meter definition). Without any hypotheses special relativity can entirely establish on the metrical results. When a certain wavelength l is defined as length unit, foregoing measurement of one-way wavelength l will become as the measurement of rod's length. Let a rigidity-rod connecting Ca and Cb moves relative to lamp-house with velocity v, rod's length L = (Nb - Na) l will change follow v by known Doppler effect, i.e., L(q) =L0 (1+ (v/c) cos q), where L0 is the proper length when v= 0, v• r = v cos q, r is the unit vector from lamphouse point to counters. Or: L (0) L (pi) =L0 (1+(v/c)) L0 (1 - (v/c)) =L0 2 y2 =L2 Or: L ≡ [L(0)L(pi)]1/2 =L0 y , which y ≡ (1 - (v/c)2 )1/2 is just Fitzgerald-Lorentzian contraction-factor. Also, when a light-wave period p is defined as time unit, from Doppler's frequency-shift the count N with p of one period T of moving-clock is: T(q) = N(q) p = T0 /(1+(v/c) cos q) Or: T ≡ (T(0) T(pi))1/2 = T 0 /y , where T0 is the proper period when v = 0, which is just the moving-clock-slower effect. Let r from clock point to lamp-house ((v/c) symbol reverse), Doppler formula in the usual form is: f (q) = 1/T(q) = f0 (1 - (v/c) cos q). Therefore, Lorentz transformation is the square root average of positive and negative directions twice metrical results of Doppler's frequency-shift, which Doppler's once items ( positive and negative v/c ) are counteract only residual twice item (v/c)2 (relativity-factor). Then Lorentz transformation can be directly measured by Doppler's frequency-shift method. The half-life of moving mu-meson is statistical average of many particles, the usual explanation using relativity-factor y is correct. An airship moving simultaneously along contrary directions is impossible, which makes that the relativity-factor y and the twin-paradox are inexistent in the macroscopical movement. Thereby, in the navigations of airship or satellite only use the measurement of Doppler's frequency-shift but have no use for Lorentz transformation.

The Amateur Scientist.

ERIC Educational Resources Information Center

Walker, Jearl

1983-01-01

Three physics experiments are described, minimizing difficulties for amateur experimenters. One experiment demonstrates the Doppler shift of light, converting the phenomenon into sound. The second measures Planck's constant. The third measures the universal gravitational constant, which does the same in Newton's theory of gravitation. (Author/JN)

Remote sensing of mesospheric winds with the High-Resolution Doppler Imager

NASA Technical Reports Server (NTRS)

Hays, Paul B.; Abreu, V. J.; Burrage, M. D.; Gell, D. A.; Grassi, H. J.; Marshall, A. R.; Morton, Y. T.; Ortland, D. A.; Skinner, W. R.; Wu, D. L.

1992-01-01

Observations of the winds in the upper atmosphere obtained with the High-Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) are discussed. This instrument is a very stable high-resolution triple-etalon Fabry-Perot interferometer, which is used to observe the slight Doppler shifts of absorption and emission lines in the O2 Atmospheric bands induced by atmospheric motions. Preliminary observations indicate that the winds in the mesosphere and lower thermosphere are a mixture of migrating and non-migrating tides, and planetary-scale waves. The mean meridional winds are dominated by the 1,1 diurnal tide which is easily extracted from the daily zonal means of the satellite observations. The daily mean zonal winds are a mixture of the diurnal tide and a zonal flow which is consistent with theoretical expectations.

Doppler Lidar Measurements of Tropospheric Wind Profiles Using the Aerosol Double Edge Technique

NASA Technical Reports Server (NTRS)

Gentry, Bruce M.; Li, Steven X.; Mathur, Savyasachee; Korb, C. Laurence; Chen, Huailin

2000-01-01

The development of a ground based direct detection Doppler lidar based on the recently described aerosol double edge technique is reported. A pulsed, injection seeded Nd:YAG laser operating at 1064 nm is used to make range resolved measurements of atmospheric winds in the free troposphere. The wind measurements are determined by measuring the Doppler shift of the laser signal backscattered from atmospheric aerosols. The lidar instrument and double edge method are described and initial tropospheric wind profile measurements are presented. Wind profiles are reported for both day and night operation. The measurements extend to altitudes as high as 14 km and are compared to rawinsonde wind profile data from Dulles airport in Virginia. Vertical resolution of the lidar measurements is 330 m and the rms precision of the measurements is a low as 0.6 m/s.

Transcutaneous measurement of volume blood flow

NASA Technical Reports Server (NTRS)

Daigle, R. E.; Mcleod, F. D.; Miller, C. W.; Histand, M. B.; Wells, M. K.

1974-01-01

Blood flow velocity measurements, using Doppler velocimeter, are described. The ability to measure blood velocity using ultrasound is derived from the Doppler effect; the change in frequency which occurs when sound is reflected or transmitted from a moving target. When ultrasound of the appropriate frequency is transmitted through a moving blood stream, the blood cells act as point scatterers of ultrasonic energy. If this scattered ultrasonic energy is detected, it is found to be shifted in frequency according to the velocity of the blood cells, nu, the frequency of the incident sound, f sub o, the speed of sound in the medium, c, and the angle between the sound beam and the velocity vector, o. The relation describing this effect is known as the Doppler equation. Delta f = 2 f sub o x nu x cos alpha/c. The theoretical and experimental methods are evaluated.

Utero-placental perfusion Doppler indices in growth restricted fetuses: effect of sildenafil citrate.

PubMed

El-Sayed, Mohamed Adel; Saleh, Said Abdel-Aty; Maher, Mohammad Ahmed; Khidre, Asmaa Mohamed

2018-04-01

To assess efficacy and tolerability of sildenafil citrate on utero-placental blood flow and fetal growth in pregnancies complicated by fetal growth restriction (FGR). From March 2015, a randomized controlled trial of 54 patients at 24 weeks or more complicated by FGR and abnormal Doppler indices were randomly allocated 1:1 into an intervention arm (receive sildenafil citrate, 50 mg) or a control arm (receive placebo). The primary outcomes were changes occurred in the Doppler parameters 2 h following drug administration. Baseline characteristics were similar between groups. Significant difference was observed in the Delta uterine and umbilical Doppler indices among sildenafil group as compared to placebo group (p < 0.001). Middle cerebral Doppler indices, however, decreased significantly after sildenafil, which could be the result of shifting more blood to improve the utero-placental perfusion. No difference regarding Delta cerebro-placental ratio among both groups (p = 0.979). Sildenafil was also associated with pregnancy prolongation (p = .0001), increased gestational age at delivery (p = .004), improved neonatal weight (p = .0001), and less admission to neonatal intensive care unit (p = .03). No adverse effects reported in both treatment arms. Sildenafil citrate, by its vasodilator effect, can improve utero-placental blood flow in pregnancies complicated by FGR and abnormal Doppler. gov Registry: NCT02362399.

The SGR-ReSI and its application for GNSS reflectometry on the NASA EV-2 CYGNSS mission

NASA Astrophysics Data System (ADS)

Unwin, M.; Jales, P.; Blunt, P.; Duncan, S.; Brummitt, M.; Ruf, C.

As part of the EV-2 Cyclone Global Navigation Satellite System (CYGNSS) mission team, Surrey will be providing the Delay Doppler Mapping Instrument (DDMI) for eight Observatories designed and built by the University of Michigan and Southwest Research Institute (SwRI). Following the success of the GPS Reflectometry Experiment on the UK-DMC 1 satellite launched in 2003, Surrey has developed the SGR-ReSI as a move towards operational reflectometry and other applications. The Space GPS Receiver Remote Sensing Instrument (SGR-ReSI) is a COTS-electronics based GNSS receiver which can support up to eight programmable front-ends. It allows collection of raw sampled data but also is capable of processing the reflections into Delay Doppler Maps in real time. The first flight of the SGR-ReSI will be on the UK TechDemoSat-1 to prove the instrument and its various applications. The SGR-ReSI on CYGNSS has a different configuration to that on TechDemoSat-1 which is needed to focus on the requirements for operational cyclone sensing.

Improved test of time dilation in special relativity.

PubMed

Saathoff, G; Karpuk, S; Eisenbarth, U; Huber, G; Krohn, S; Muñoz Horta, R; Reinhardt, S; Schwalm, D; Wolf, A; Gwinner, G

2003-11-07

An improved test of time dilation in special relativity has been performed using laser spectroscopy on fast ions at the heavy-ion storage-ring TSR in Heidelberg. The Doppler-shifted frequencies of a two-level transition in 7Li+ ions at v=0.064c have been measured in the forward and backward direction to an accuracy of Deltanu/nu=1 x 10(-9) using collinear saturation spectroscopy. The result confirms the relativistic Doppler formula and sets a new limit of 2.2 x 10(-7) for deviations from the time dilation factor gamma(SR)=(1-v2/c2)(-1/2).

Sleep deprivation decreases phase-shift responses of circadian rhythms to light in the mouse: role of serotonergic and metabolic signals.

PubMed

Challet, E; Turek, F W; Laute, M; Van Reeth, O

2001-08-03

The circadian pacemaker in the suprachiasmatic nuclei is primarily synchronized to the daily light-dark cycle. The phase-shifting and synchronizing effects of light can be modulated by non-photic factors, such as behavioral, metabolic or serotonergic cues. The present experiments examine the effects of sleep deprivation on the response of the circadian pacemaker to light and test the possible involvement of serotonergic and/or metabolic cues in mediating the effects of sleep deprivation. Photic phase-shifting of the locomotor activity rhythm was analyzed in mice transferred from a light-dark cycle to constant darkness, and sleep-deprived for 8 h from Zeitgeber Time 6 to Zeitgeber Time 14. Phase-delays in response to a 10-min light pulse at Zeitgeber Time 14 were reduced by 30% in sleep-deprived mice compared to control mice, while sleep deprivation without light exposure induced no significant phase-shifts. Stimulation of serotonin neurotransmission by fluoxetine (10 mg/kg), a serotonin reuptake inhibitor that decreases light-induced phase-delays in non-deprived mice, did not further reduce light-induced phase-delays in sleep-deprived mice. Impairment of serotonin neurotransmission with p-chloroamphetamine (three injections of 10 mg/kg), which did not increase light-induced phase-delays in non-deprived mice significantly, partially normalized light-induced phase-delays in sleep-deprived mice. Injections of glucose increased light-induced phase-delays in control and sleep-deprived mice. Chemical damage of the ventromedial hypothalamus by gold-thioglucose (600 mg/kg) prevented the reduction of light-induced phase-delays in sleep-deprived mice, without altering phase-delays in control mice. Taken together, the present results indicate that sleep deprivation can reduce the light-induced phase-shifts of the mouse suprachiasmatic pacemaker, due to serotonergic and metabolic changes associated with the loss of sleep.

Professionalism in the Twilight Zone: A Multicenter, Mixed-Methods Study of Shift Transition Dynamics in Surgical Residencies.

PubMed

Coverdill, James E; Alseidi, Adnan; Borgstrom, David C; Dent, Daniel L; Dumire, Russell D; Fryer, Jonathan; Hartranft, Thomas H; Holsten, Steven B; Nelson, M Timothy; Shabahang, Mohsen; Sherman, Stanley; Termuhlen, Paula M; Woods, Randy J; Mellinger, John D

2016-11-01

Duty hours rules sparked debates about professionalism. This study explores whether and why general surgery residents delay departures at the end of a day shift in ways consistent with shift work, traditional professionalism, or a new professionalism. Questionnaires were administered to categorical residents in 13 general surgery programs in 2014 and 2015. The response rate was 76% (N = 291). The 18 items focused on end-of-shift behaviors and the frequency and source of delayed departures. Follow-up interviews (N = 39) examined motives for delayed departures. The results include means, percentages, and representative quotations from the interviews. A minority (33%) agreed that it is routine and acceptable to pass work to night teams, whereas a strong majority (81%) believed that residents exceed work hours in the name of professionalism. Delayed departures were ubiquitous: Only 2 of 291 residents were not delayed for any of 13 reasons during a typical week. The single most common source of delay involved a desire to avoid the appearance of dumping work on fellow residents. In the interviews, residents expressed a strong reluctance to pass work to an on-call resident or night team because of sparse night staffing, patient ownership, an aversion to dumping, and the fear of being seen as inefficient. Resident behavior is shaped by organizational and cultural contexts that require attention and reform. The evidence points to the stunted development of a new professionalism, little role for shift-work mentalities, and uneven expression of traditional professionalism in resident behavior.

Dark goggles and bright light improve circadian rhythm adaptation to night-shift work.

PubMed

Eastman, C I; Stewart, K T; Mahoney, M P; Liu, L; Fogg, L F

1994-09-01

We compared the contributions of bright light during the night shift and dark goggles during daylight for phase shifting the circadian rhythm of temperature to realign with a 12-hour shift of sleep. After 10 baseline days there were 8 night-work/day-sleep days. Temperature was continuously recorded from 50 subjects. There were four groups in a 2 x 2 design: light (bright, dim), goggles (yes, no). Subjects were exposed to bright light (about 5,000 lux) for 6 hours on the first 2 night shifts. Dim light was < 500 lux. Both bright light and goggles were significant factors for producing circadian rhythm phase shifts. The combination of bright light plus goggles was the most effective, whereas the combination of dim light and no goggles was the least effective. The temperature rhythm either phase advanced or phase delayed when it aligned with daytime sleep. However, when subjects did not have goggles only phase advances occurred. Goggles were necessary for producing phase delays. The most likely explanation is that daylight during the travel-home window after a night shift inhibits phase-delay shifts, and goggles can prevent this inhibition. Larger temperature-rhythm phase shifts were associated with better subjective daytime sleep, less subjective fatigue and better mood.

Assessment of diastolic function by tissue Doppler echocardiography: comparison with standard transmitral and pulmonary venous flow

NASA Technical Reports Server (NTRS)

Farias, C. A.; Rodriguez, L.; Garcia, M. J.; Sun, J. P.; Klein, A. L.; Thomas, J. D.

1999-01-01

The objective of this study was to determine the utility of Doppler tissue echocardiography in the evaluation of diastolic filling and in discriminating between normal subjects and those with various stages of diastolic dysfunction. We measured myocardial velocities in 51 patients with various stages of diastolic dysfunction and in 27 normal volunteers. The discriminating power of each of the standard Doppler indexes of left ventricular filling, pulmonary venous flow, and myocardial velocities was determined with the use of Spearman rank correlation and analysis of variance F statistics. Early diastolic myocardial velocity (E(m)) was higher in normal subjects (16.0 +/- 3.8 cm/s) than in patients with either delayed relaxation (n = 15, 7.5 +/- 2.2 cm/s), pseudonormal filling (n = 26, 7.6 +/- 2.3 cm/s), or restrictive filling (n = 10, 7.4 +/- 2.4 cm/s, P <.0001). E(m ) was the best single discriminator between control subjects and patients with diastolic dysfunction (P =.7, F = 64.5). Myocardial velocities assessed by Doppler tissue echocardiography are useful in differentiating patients with normal from those with abnormal diastolic function. Myocardial velocity remains reduced even in those stages of diastolic dysfunction characterized by increased preload compensation.

Lifetime measurements of high-lying short lived states in {sup 69}As

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

Matejska-Minda, M.; Bednarczyk, P.; Fornal, B.

2012-10-20

Lifetimes of high-spin states in {sup 69}As have been measured using Doppler shift attenuation technique with the GASP and RFD setup. The determined transition probabilities indicate large deformation associated with some rotational bands in this nucleus.

PAU/GNSS-R: Implementation, Performance and First Results of a Real-Time Delay-Doppler Map Reflectometer Using Global Navigation Satellite System Signals

PubMed Central

Marchan-Hernandez, Juan Fernando; Camps, Adriano; Rodriguez-Alvarez, Nereida; Bosch-Lluis, Xavier; Ramos-Perez, Isaac; Valencia, Enric

2008-01-01

Signals from Global Navigation Satellite Systems (GNSS) were originally conceived for position and speed determination, but they can be used as signals of opportunity as well. The reflection process over a given surface modifies the properties of the scattered signal, and therefore, by processing the reflected signal, relevant geophysical data regarding the surface under study (land, sea, ice…) can be retrieved. In essence, a GNSS-R receiver is a multi-channel GNSS receiver that computes the received power from a given satellite at a number of different delay and Doppler bins of the incoming signal. The first approaches to build such a receiver consisted of sampling and storing the scattered signal for later post-processing. However, a real-time approach to the problem is desirable to obtain immediately useful geophysical variables and reduce the amount of data. The use of FPGA technology makes this possible, while at the same time the system can be easily reconfigured. The signal tracking and processing constraints made necessary to fully design several new blocks. The uniqueness of the implemented system described in this work is the capability to compute in real-time Delay-Doppler maps (DDMs) either for four simultaneous satellites or just one, but with a larger number of bins. The first tests have been conducted from a cliff over the sea and demonstrate the successful performance of the instrument to compute DDMs in real-time from the measured reflected GNSS/R signals. The processing of these measurements shall yield quantitative relationships between the sea state (mainly driven by the surface wind and the swell) and the overall DDM shape. The ultimate goal is to use the DDM shape to correct the sea state influence on the L-band brightness temperature to improve the retrieval of the sea surface salinity (SSS). PMID:27879862

Recent Radar Astrometry of Asteroid 2004 MN4

NASA Astrophysics Data System (ADS)

Giorgini, J. D.; Benner, L. A. M.; Nolan, M. C.; Ostro, S. J.

2005-05-01

Arecibo (2380-MHz) delay-Doppler radar astrometry obtained in late January of 2005 significantly corrected 2004 MN4's orbit. Doppler-shifted echoes were acquired 4.8-sigma away from the predicted frequency on Jan 27, while range to the object on Jan 29 was found to be 747 km (2.8-sigma) closer to Earth than the pre-radar orbit solution predicted. Incorporation of these radar measurements into least-squares orbit solution #82 resulted in a new predicted Earth encounter on 2029-Apr-13 of 36000 +/- 9900 km (3-sigma formal uncertainties), or 5.6 +/- 1.6 Earth radii, from Earth's center. This is inside geosynchronous orbit and 27700 km (4.3 Earth radii) closer to Earth than predicted by the pre-radar ephemeris -- a 5-sigma change compared to the pre-radar orbit solution, illustrating the problematic nature of prediction and statistical analysis when only single-apparition optical data-sets are available. The current data-set does not permit reliable trajectory propagation to encounters later than 2029; this may not be possible until data from 2012-2013 are available. The corrected nominal approach distance in 2029 is approximately twice the classical Roche limit and closer than any known past or future approach by a natural object larger than 10 m, other than those detected after already impacting the Earth or it's atmosphere. Such close approaches by objects as large as 2004 MN4 (D ≳ 0.3 km) are currently thought to occur at ≳ 1000-year intervals on average. 2004 MN4 is expected to reach 3rd magnitude for observers in Europe, western Asia, and Africa, and thus be visible to the unaided eye. The asteroid's disk will be 2-4 arcseconds across and potentially resolvable with small ground-based telescopes.

Time-resolved coherent Raman spectroscopy by high-speed pump-probe delay scanning.

PubMed

Domingue, S R; Winters, D G; Bartels, R A

2014-07-15

Using a spinning window pump-probe delay scanner, we demonstrate a means of acquiring time-resolved vibrational spectra at rates up to 700 Hz. The time-dependent phase shift accumulated by the probe pulse in the presence of a coherently vibrating sample gives rise to a Raman-induced frequency shifting readily detectable in a balanced detector. This rapid delay scanning system represents a 23-fold increase in averaging speed and is >10× faster than state-of-the-art voice coil delay lines. These advancements make pump-probe spectroscopy a more practical means of imaging complex media.

Scaling of echolocation call parameters in bats.

PubMed

Jones, G

1999-12-01

I investigated the scaling of echolocation call parameters (frequency, duration and repetition rate) in bats in a functional context. Low-duty-cycle bats operate with search phase cycles of usually less than 20 %. They process echoes in the time domain and are therefore intolerant of pulse-echo overlap. High-duty-cycle (>30 %) species use Doppler shift compensation, and they separate pulse and echo in the frequency domain. Call frequency scales negatively with body mass in at least five bat families. Pulse duration scales positively with mass in low-duty-cycle quasi-constant-frequency (QCF) species because the large aerial-hawking species that emit these signals fly fast in open habitats. They therefore detect distant targets and experience pulse-echo overlap later than do smaller bats. Pulse duration also scales positively with mass in the Hipposideridae, which show at least partial Doppler shift compensation. Pulse repetition rate corresponds closely with wingbeat frequency in QCF bat species that fly relatively slowly. Larger, fast-flying species often skip pulses when detecting distant targets. There is probably a trade-off between call intensity and repetition rate because 'whispering' bats (and hipposiderids) produce several calls per predicted wingbeat and because batches of calls are emitted per wingbeat during terminal buzzes. Severe atmospheric attenuation at high frequencies limits the range of high-frequency calls. Low-duty-cycle bats that call at high frequencies must therefore use short pulses to avoid pulse-echo overlap. Rhinolophids escape this constraint by Doppler shift compensation and, importantly, can exploit advantages associated with the emission of both high-frequency and long-duration calls. Low frequencies are unsuited for the detection of small prey, and low repetition rates may limit prey detection rates. Echolocation parameters may therefore constrain maximum body size in aerial-hawking bats.

Constraining hot Jupiter’s atmospheric structure and dynamics through Doppler shifted emission spectra

NASA Astrophysics Data System (ADS)

Zhang, Jisheng; Kempton, Eliza; Rauscher, Emily

2017-01-01

In recent years, astronomers have begun successfully observing the atmospheres of extrasolar planets using ground-based telescopes equipped with spectrographs capable of observing at high spectral resolution (R~105). Such studies are capable of diagnosing the atmospheric structure, composition, and dynamics (winds and rotation) of both transiting and non-transiting exoplanets. However, few studies have examined how the 3-D atmospheric dynamics could alter the emitted light of hot Jupiters at such high spectral resolution. Here, we present a model to explore such influence on the hot Jupiters’ thermal emission spectra. Our aim is to investigate the extent to which the effects of 3-D atmospheric dynamics are imprinted on planet-averaged thermal emission spectra. We couple together a 3-D general circulation model of hot Jupiter atmospheric dynamics (Rauscher & Menou, 2012) with a radiative transfer solver to predict the planet’s disk-integrated emission spectrum as a function of its orbital phase. For the first time, we self-consistently include the effects of the line-of-sight atmospheric motions (resulting from winds and rotation) in the calculation to produce Doppler-shifted spectral line profiles that result from the atmospheric dynamics. We focus our study on three benchmark hot Jupiters, HD 189733b, HD 209458b, and WASP-43b which have been the focus of previous detailed observational studies. We find that the high-resolution Doppler shifted thermal emission spectra can be used to diagnose key properties of the dynamical atmosphere - the planet’s longitudinal temperature and wind structure, and its rotation rate.

Laser cooling of nuclear spin 0 alkali 78Rb

NASA Astrophysics Data System (ADS)

Behr, J. A.; Gorelov, A.; Anholm, M.

2015-05-01

The textbook example for sub-Doppler cooling is a J = 1/2 I = 0 alkali atom in lin ⊥ lin molasses. In the σ+ σ- configuration of a standard MOT, the main sub-Doppler cooling mechanism relies on changing alignment (MF2 population) with the summed linear polarization orientation, but there is no such variation in AC Stark shift for F = 1/2. We have nevertheless looked for signs of sub-Doppler cooling by trapping I = 0 78Rb in a standard MOT and measuring the cloud size as a function of laser detuning and intensity. The 78Rb cloud size does not change significantly with lowered intensity, and expands slightly with detuning, consistent with minimal to no sub-Doppler cooling. Our geometry does show the well-known substantially smaller cloud size with detuning and intensity for I = 3/2 87Rb. Maintaining an I = 0 alkali cloud size with lowered intensity will help our planned β- ν correlation experiments in 38mK decay by suppressing possible production of photoassisted dimers. Supported by NSERC and NRC Canada through TRIUMF.

Laser Doppler flowmetry for measurement of laminar capillary blood flow in the horse

NASA Astrophysics Data System (ADS)

Adair, Henry S., III

1998-07-01

Current methods for in vivo evaluation of digital hemodynamics in the horse include angiography, scintigraphy, Doppler ultrasound, electromagnetic flow and isolated extracorporeal pump perfused digit preparations. These techniques are either non-quantifiable, do not allow for continuous measurement, require destruction of the horse orare invasive, inducing non- physiologic variables. In vitro techniques have also been reported for the evaluation of the effects of vasoactive agents on the digital vessels. The in vitro techniques are non-physiologic and have evaluated the vasculature proximal to the coronary band. Lastly, many of these techniques require general anesthesia or euthanasia of the animal. Laser Doppler flowmetry is a non-invasive, continuous measure of capillary blood flow. Laser Doppler flowmetry has been used to measure capillary blood flow in many tissues. The principle of this method is to measure the Doppler shift, that is, the frequency change that light undergoes when reflected by moving objects, such as red blood cells. Laser Doppler flowmetry records a continuous measurement of the red cell motion in the outer layer of the tissue under study, with little or no influence on physiologic blood flow. This output value constitutes the flux of red cells and is reported as capillary perfusion units. No direct information concerning oxygen, nutrient or waste metabolite exchange in the surrounding tissue is obtained. The relationship between the flowmeter output signal and the flux of red blood cells is linear. The principles of laser Doppler flowmetry will be discussed and the technique for laminar capillary blood flow measurements will be presented.

Hyperpolarizability and Operational Magic Wavelength in an Optical Lattice Clock

NASA Astrophysics Data System (ADS)

Brown, R. C.; Phillips, N. B.; Beloy, K.; McGrew, W. F.; Schioppo, M.; Fasano, R. J.; Milani, G.; Zhang, X.; Hinkley, N.; Leopardi, H.; Yoon, T. H.; Nicolodi, D.; Fortier, T. M.; Ludlow, A. D.

2017-12-01

Optical clocks benefit from tight atomic confinement enabling extended interrogation times as well as Doppler- and recoil-free operation. However, these benefits come at the cost of frequency shifts that, if not properly controlled, may degrade clock accuracy. Numerous theoretical studies have predicted optical lattice clock frequency shifts that scale nonlinearly with trap depth. To experimentally observe and constrain these shifts in an 171Yb optical lattice clock, we construct a lattice enhancement cavity that exaggerates the light shifts. We observe an atomic temperature that is proportional to the optical trap depth, fundamentally altering the scaling of trap-induced light shifts and simplifying their parametrization. We identify an "operational" magic wavelength where frequency shifts are insensitive to changes in trap depth. These measurements and scaling analysis constitute an essential systematic characterization for clock operation at the 10-18 level and beyond.

Characterization of turbulent wake of wind turbine by coherent Doppler lidar

NASA Astrophysics Data System (ADS)

Wu, Songhua; Yin, Jiaping; Liu, Bingyi; Liu, Jintao; Li, Rongzhong; Wang, Xitao; Feng, Changzhong; Zhuang, Quanfeng; Zhang, Kailin

2014-11-01

The indispensable access to real turbulent wake behavior is provided by the pulsed coherent Doppler Light Detection and Ranging (LIDAR) which operates by transmitting a laser beam and detecting the radiation backscattered by atmospheric aerosol particles. The Doppler shift in the frequency of the backscattered signal is analyzed to obtain the line-of-sight (LOS) velocity component of the air motion. From the LOS velocities the characteristic of the turbulent wake can be deduced. The Coherent Doppler LIDAR (CDL) is based on all-fiber laser technology and fast digital-signal-processing technology. The 1.5 µm eye-safe Doppler LIDAR system has a pulse length of 200ns and a pulse repetition frequency of 10 kHz. The speed measurement range is ±50m/s and the speed measurement uncertainty is 0.3 m/s. The 2-axis beam scanner and detection range of 3000m enable the system to monitor the whole wind farming filed. Because of the all-fiber structure adoption, the system is stable, reliable and high-integrated. The wake vortices of wind turbine blades with different spatial and temporal scales have been observed by LIDAR. In this paper, the authors discuss the possibility of using LIDAR measurements to characterize the complicated wind field, specifically wind velocity deficit and terrain effects.

Holographic motion picture camera with Doppler shift compensation

NASA Technical Reports Server (NTRS)

Kurtz, R. L. (Inventor)

1976-01-01

A holographic motion picture camera is reported for producing three dimensional images by employing an elliptical optical system. There is provided in one of the beam paths (the object or reference beam path) a motion compensator which enables the camera to photograph faster moving objects.

Rotation of an optically trapped vaterite microsphere measured using rotational Doppler effect

NASA Astrophysics Data System (ADS)

Chen, Xinlin; Xiao, Guangzong; Xiong, Wei; Yang, Kaiyong; Luo, Hui; Yao, Baoli

2018-03-01

The angular velocity of a vaterite microsphere spinning in the optical trap is measured using rotational Doppler effect. The perfectly spherical vaterite microspheres are synthesized via coprecipitation in the presence of silk fibroin nanospheres. When trapped by a circularly polarized beam, the vaterite microsphere is uniformly rotated in the trap center. The probe beams containing two Laguerre-Gaussian beams of opposite topological charge l = ± 7, l = ± 8, and l = ± 9 are illuminated on the spinning vaterite. By analyzing the backscattered light, a frequency shift is observed scaling with the rotation rate of the vaterite microsphere. The multiplicative enhancement of the frequency shift proportion to the topological charge has greatly improved the measurement precision. The reliability and practicability of this approach are verified through varying the topological charge of the probe beam and the trapping laser power. In consideration of the excellent measurement precision of the rotation frequency, this technique might be generally applicable in studying the torsional properties of micro-objects.

Mass motions in the solar chromosphere and transition zone

NASA Technical Reports Server (NTRS)

Mein, P.; Simon, G.; Vial, J. C.; Shine, R. A.

1982-01-01

A comparison is made between H-alpha and C IV observations of Active Region 2717 on October 9, 1980. On the basis of this comparison, it is found that upward velocities are present above sunspots in the chromosphere-corona transition zone (20 km/s). The downward velocities are found to be well correlated in both lines. Doppler-shift ratios between C IV and H-alpha levels (approximately 10) are seen to be much smaller than expected from density ratio estimates. The comparison is seen as suggesting that flow lines are probably far from vertical in the transition zone. It is pointed out, however, that this depends on model densities that may not be correct. A simple method for comparing matter flows is presented. The best fit between H-alpha and C IV levels is obtained when C IV Doppler shifts are multiplied by the line intensity to the power 0.5 (approximately) in order to make allowance for density fluctuations.

Determination of solid-propellant transient regression rates using a microwave Doppler shift technique

NASA Technical Reports Server (NTRS)

Strand, L. D.; Schultz, A. L.; Reedy, G. K.

1972-01-01

A microwave Doppler shift system, with increased resolution over earlier microwave techniques, was developed for the purpose of measuring the regression rates of solid propellants during rapid pressure transients. A continuous microwave beam is transmitted to the base of a burning propellant sample cast in a metal waveguide tube. A portion of the wave is reflected from the regressing propellant-flame zone interface. The phase angle difference between the incident and reflected signals and its time differential are continuously measured using a high resolution microwave network analyzer and related instrumentation. The apparent propellant regression rate is directly proportional to this latter differential measurement. Experiments were conducted to verify the (1) spatial and time resolution of the system, (2) effect of propellant surface irregularities and compressibility on the measurements, and (3) accuracy of the system for quasi-steady-state regression rate measurements. The microwave system was also used in two different transient combustion experiments: in a rapid depressurization bomb, and in the high-frequency acoustic pressure environment of a T-burner.

Absolute wavelength calibration of a Doppler spectrometer with a custom Fabry-Perot optical system

NASA Astrophysics Data System (ADS)

Baltzer, M. M.; Craig, D.; Den Hartog, D. J.; Nishizawa, T.; Nornberg, M. D.

2016-11-01

An Ion Doppler Spectrometer (IDS) is used for fast measurements of C VI line emission (343.4 nm) in the Madison Symmetric Torus. Absolutely calibrated flow measurements are difficult because the IDS records data within 0.25 nm of the line. Commercial calibration lamps do not produce lines in this narrow range. A light source using an ultraviolet LED and etalon was designed to provide a fiducial marker 0.08 nm wide. The light is coupled into the IDS at f/4, and a holographic diffuser increases homogeneity of the final image. Random and systematic errors in data analysis were assessed. The calibration is accurate to 0.003 nm, allowing for flow measurements accurate to 3 km/s. This calibration is superior to the previous method which used a time-averaged measurement along a chord believed to have zero net Doppler shift.

An international review of laser Doppler vibrometry: Making light work of vibration measurement

NASA Astrophysics Data System (ADS)

Rothberg, S. J.; Allen, M. S.; Castellini, P.; Di Maio, D.; Dirckx, J. J. J.; Ewins, D. J.; Halkon, B. J.; Muyshondt, P.; Paone, N.; Ryan, T.; Steger, H.; Tomasini, E. P.; Vanlanduit, S.; Vignola, J. F.

2017-12-01

In 1964, just a few years after the invention of the laser, a fluid velocity measurement based on the frequency shift of scattered light was made and the laser Doppler technique was born. This comprehensive review paper charts advances in the development and applications of laser Doppler vibrometry (LDV) since those first pioneering experiments. Consideration is first given to the challenges that continue to be posed by laser speckle. Scanning LDV is introduced and its significant influence in the field of experimental modal analysis described. Applications in structural health monitoring and MEMS serve to demonstrate LDV's applicability on structures of all sizes. Rotor vibrations and hearing are explored as examples of the classic applications. Applications in acoustics recognise the versatility of LDV as demonstrated by visualisation of sound fields. The paper concludes with thoughts on future developments, using examples of new multi-component and multi-channel instruments.

Application of two-component phase Doppler interferometry to the measurement of particle size, mass flux, and velocities in two-phase flows

NASA Technical Reports Server (NTRS)

Mcdonell, V. G.; Samuelsen, G. S.

1989-01-01

Two-component phase Doppler interferometry is described, along with its application for the spatially-resolved measurements of particle size, velocity, and mass flux as well as continuous phase velocity. This technique measures single particle events at a point in the flow; droplet size is deduced from the spatial phase shift of the Doppler signal. Particle size influence and discrimination of continuous and discrete phases are among issues covered. Applications are presented for four cases: an example of the discrimination of two sizes of glass beads in a jet flow; a demonstration of the discrimination of phases in a spray field; an assessment of atomizer symmetry with respect to fuel distribution; and a characterization of a droplet field in a reacting spray. It is noted that the above technique is especially powerful in delineating droplet interactions in the swirling, complex flows typical of realistic systems.

Evaluation of blood microcirculation parameters by combined use of laser Doppler flowmetry and videocapillaroscopy methods

NASA Astrophysics Data System (ADS)

Volkov, M. V.; Kostrova, D. A.; Margaryants, N. B.; Gurov, I. P.; Erofeev, N. P.; Dremin, V. V.; Zharkikh, E. V.; Zherebtsov, E. A.; Kozlov, I. O.; Dunaev, A. V.

2017-03-01

Laser Doppler flowmetry (LDF) is widely used for diagnosing blood microcirculation diseases. It is well known that the Doppler shift of laser radiation scattered by moving red blood cells (RBC) can be assessed through analyzing photocurrent produced by a photodetector. LDF signal contains information about regulating blood flow rhythms: myogenic, cardiac, nervous and endothelial. The method of videocapillaroscopy (VCS) allows local capillary blood flow velocity evaluation and, using video data processing algorithms, is able to assess RBC velocity changes into capillary. We present the results of simultaneous investigations of changes in tissue perfusion of the distal phalanx of human finger by the LDF as well as changes in capillary blood flow velocity in the nail bed evaluated by the VCS method during arterial occlusion test. The experimental results confirmed the correspondence between blood perfusion and blood flow velocity.

Photonic Doppler velocimetry lens array probe incorporating stereo imaging

DOEpatents

Malone, Robert M.; Kaufman, Morris I.

2015-09-01

A probe including a multiple lens array is disclosed to measure velocity distribution of a moving surface along many lines of sight. Laser light, directed to the moving surface is reflected back from the surface and is Doppler shifted, collected into the array, and then directed to detection equipment through optic fibers. The received light is mixed with reference laser light and using photonic Doppler velocimetry, a continuous time record of the surface movement is obtained. An array of single-mode optical fibers provides an optic signal to the multiple lens array. Numerous fibers in a fiber array project numerous rays to establish many measurement points at numerous different locations. One or more lens groups may be replaced with imaging lenses so a stereo image of the moving surface can be recorded. Imaging a portion of the surface during initial travel can determine whether the surface is breaking up.

Comparison of NOAA/NMC stratospheric wind analyses with UARS high resolution Doppler Imager wind measurements

NASA Technical Reports Server (NTRS)

Miller, A. J.; Hays, P. B.; Abreu, V.; Long, C.; Kann, D.

1994-01-01

The NOAA National Weather Service currently derives global stratospheric wind analyses via several procedures. The first is the operational data assimilation system that extends from the surface up to about 50 mb and is in process of being tested to about 10 mb. In addition, a balanced wind is determined from the available Climate Analysis Center stratospheric height analyses that encompass the 70-0.4 mb region. The High Resolution Doppler Imager (HRDI) recently launched as a member of the Upper Atmosphere Research Satellite (UARS) is the first satellite instrument designed to measure winds in this stratospheric region and, thus, provide a basic evaluation of the NMC derived products. The HRDI accomplishes this by utilizing a triple-etalon Fabry-Perot interferometer that allows one to measure the Doppler shift of O2 absorption and emission features of the atmosphere, from which the wind field can be determined.

Absolute wavelength calibration of a Doppler spectrometer with a custom Fabry-Perot optical system.

PubMed

Baltzer, M M; Craig, D; Den Hartog, D J; Nishizawa, T; Nornberg, M D

2016-11-01

An Ion Doppler Spectrometer (IDS) is used for fast measurements of C VI line emission (343.4 nm) in the Madison Symmetric Torus. Absolutely calibrated flow measurements are difficult because the IDS records data within 0.25 nm of the line. Commercial calibration lamps do not produce lines in this narrow range. A light source using an ultraviolet LED and etalon was designed to provide a fiducial marker 0.08 nm wide. The light is coupled into the IDS at f/4, and a holographic diffuser increases homogeneity of the final image. Random and systematic errors in data analysis were assessed. The calibration is accurate to 0.003 nm, allowing for flow measurements accurate to 3 km/s. This calibration is superior to the previous method which used a time-averaged measurement along a chord believed to have zero net Doppler shift.

Signal processing of aircraft flyover noise

NASA Technical Reports Server (NTRS)

Kelly, Jeffrey J.

1991-01-01

A detailed analysis of signal processing concerns for measuring aircraft flyover noise is presented. Development of a de-Dopplerization scheme for both corrected time history and spectral data is discussed along with an analysis of motion effects on measured spectra. A computer code was written to implement the de-Dopplerization scheme. Input to the code is the aircraft position data and the pressure time histories. To facilitate ensemble averaging, a uniform level flyover is considered but the code can accept more general flight profiles. The effects of spectral smearing and its removal is discussed. Using data acquired from XV-15 tilt rotor flyover test comparisons are made showing the measured and corrected spectra. Frequency shifts are accurately accounted for by the method. It is shown that correcting for spherical spreading, Doppler amplitude, and frequency can give some idea about source directivity. The analysis indicated that smearing increases with frequency and is more severe on approach than recession.

Multipoint photonic doppler velocimetry using optical lens elements

DOEpatents

Frogget, Brent Copely; Romero, Vincent Todd

2014-04-29

A probe including a fisheye lens is disclosed to measure the velocity distribution of a moving surface along many lines of sight. Laser light, directed to the surface and then reflected back from the surface, is Doppler shifted by the moving surface, collected into fisheye lens, and then directed to detection equipment through optic fibers. The received light is mixed with reference laser light and using photonic Doppler velocimetry, a continuous time record of the surface movement is obtained. An array of single-mode optical fibers provides an optic signal to an index-matching lens and eventually to a fisheye lens. The fiber array flat polished and coupled to the index-matching lens using index-matching gel. Numerous fibers in a fiber array project numerous rays through the fisheye lens which in turn project many measurement points at numerous different locations to establish surface coverage over a hemispherical shape with very little crosstalk.

Great Red Spot's detection with the Juno gravity experiment

NASA Astrophysics Data System (ADS)

Parisi, M.; Folkner, W. M.

2017-12-01

The Juno spacecraft entered orbit about Jupiter in July 2016. During the perijoves (or closest approaches to Jupiter), Juno carries out observations of the magnetosphere, atmosphere and gravity field of the planet. The gravity field is estimated from precise measurements of the Doppler shift of the Juno radio signal and provides information on the Jovian interior structure.In July 2017 the 7th Juno perijove was over the Great Red Spot. The primary goal was determining differences in ammonia and water abundance in the GRS using the Microwave Radiometer instrument, while Doppler data was acquired acquired on a secondary basis. We present results of analysis of the PJ7 Doppler data to constrain the mass density variations of the GRS relative to the global average. We also present analysis to determine whether future Juno data will provide stronger constraints on the structure of the GRS.

Edge technique for measurement of laser frequency shifts including the Doppler shift

NASA Technical Reports Server (NTRS)

Korb, Larry (Inventor)

1991-01-01

A method is disclosed for determining the frequency shift in a laser system by transmitting an outgoing laser beam. An incoming laser beam having a frequency shift is received. A first signal is acquired by transmitting a portion of the incoming laser beam to an energy monitor detector. A second signal is acquired by transmitting a portion of the incoming laser beam through an edge filter to an edge detector, which derives a first normalized signal which is proportional to the transmission of the edge filter at the frequency of the incoming laser beam. A second normalized signal is acquired which is proportional to the transmission of the edge filter at the frequency of the outgoing laser beam. The frequency shift is determined by processing the first and second normalized signals.

Absolute Wavelength Calibration of the IDSII Spectrometer for Impurity Ion Velocity Measurements in the MST

NASA Astrophysics Data System (ADS)

Baltzer, M.; Craig, D.; den Hartog, D. J.; Nornberg, M. D.; MST Team

2014-10-01

The MST operates two Ion Doppler Spectrometers (IDS) for high time-resolution passive and active measurements of impurity ion emission. Absolutely calibrated measurements of flow are difficult because the spectrometers record data within 0.3 nm of the line of interest, and commercial calibration lamps do not produce lines in this narrow range . Four calibration methods were investigated. First, emission along the chord bisecting the poloidal plane was measured as it should have no time-averaged Doppler shift. Second, a calibrated CCD spectrometer and the IDSII were used to observe the same plasma from opposing sides so as to measure opposite Doppler shifts. The unshifted line is located halfway between the two opposing measurements. Third, the two fibers of the IDSI were positioned to take absolute flow measurements using opposing views. Substituting the IDSII for one of the IDSI fibers, absolute measurements of flow from the IDSI were used to calibrate the IDSII. Finally, an optical system was designed to filter an ultraviolet LED, providing a known wavelength source within the spectral range covered by the IDSII. The optical train is composed of an air-gapped etalon and fused silica lenses. The quality of calibration for each of these methods is analyzed and their results compared. Preliminary impurity ion velocity measurements are shown. This work has been supported by the US DOE and the NSF.

Light-Induced resetting of the circadian pacemaker: quantitative analysis of transient versus steady-state phase shifts.

PubMed

Watanabe, K; Deboer, T; Meijer, J H

2001-12-01

The suprachiasmatic nuclei of the hypothalamus contain the major circadian pacemaker in mammals, driving circadian rhythms in behavioral and physiological functions. This circadian pacemaker's responsiveness to light allows synchronization to the light-dark cycle. Phase shifting by light often involves several transient cycles in which the behavioral activity rhythm gradually shifts to its steady-state position. In this article, the authors investigate in Syrian hamsters whether a phase-advancing light pulse results in immediate shifts of the PRC at the next circadian cycle. In a first series of experiments, the authors aimed a light pulse at CT 19 to induce a phase advance. It appeared that the steady-state phase advances were highly correlated with activity onset in the first and second transient cycle. This enabled them to make a reliable estimate of the steady-state phase shift induced by a phase-advancing light pulse on the basis of activity onset in the first transient cycle. In the next series of experiments, they presented a light pulse at CT 19, which was followed by a second light pulse aimed at the delay zone of the PRC on the next circadian cycle. The immediate and steady-state phase delays induced by the second light pulse were compared with data from a third experiment in which animals received a phase-delaying light pulse only. The authors observed that the waveform of the phase-delay part of the PRC (CT 12-16) obtained in Experiment 2 was virtually identical to the phase-delay part of the PRC for a single light pulse (obtained in Experiment 3). This finding allowed for a quantitative assessment of the data. The analysis indicates that the delay part of the PRC-between CT 12 and CT 16-is rapidly reset following a light pulse at CT 19. These findings complement earlier findings in the hamster showing that after a light pulse at CT 19, the phase-advancing part of the PRC is immediately shifted. Together, the data indicate that the basis for phase advancing involves rapid resetting of both advance and delay components of the PRC.

The vacuum friction paradox and related puzzles

NASA Astrophysics Data System (ADS)

Barnett, Stephen M.; Sonnleitner, Matthias

2018-04-01

The frequency of light emitted by a moving source is shifted by a factor proportional to its velocity. We find that this Doppler shift requires the existence of a paradoxical effect: that a moving atom radiating in otherwise empty space feels a net or average force acing against its direction motion and proportional in magnitude to is speed. Yet there is no preferred rest frame, either in relativity or in Newtonian mechanics, so how can there be a vacuum friction force?

Low Charge States of Si and S: from Cygnus X-1 to the Lab and Back

NASA Astrophysics Data System (ADS)

Hell, Natalie; Miškovičova, I.; Hanke, M.; Brown, G. V.; Wilms, J.; Clementson, J.; Beiersdorfer, P.; Liedahl, D. A.; Pottschmidt, K.; Porter, F.; Kilbourne, C.; Kelley, R. L.; Nowak, M.; Schulz, N. S.

2013-04-01

The X-ray light curves of the high mass X-ray binary (HMXB) Cygnus X-1 are shaped by strong, relatively short, absorption dips. While spectra extracted from the dip free phases are dominated by absorption lines of the Rydberg series of H- and He-like ions, 1s-2p transitions of lower ionized Si and S appear in the dip spectra. This shift in charge balance suggests that we probe “clumps” of cold material embedded in the companion's stellar wind as they cross our line of sight. Determining the bulk motion of these clumps by measuring the Doppler shifts of these lines as a function of dipping strength and ionization state can confirm this theory. Unfortunately, the predicted uncertainty for theoretical calculations - if available at all - is of the order of the expected shifts in the system. To overcome this lack of reliable reference wavelengths, we measured the Kα spectra of H- through F-like Si and S with the EBIT Calorimeter Spectrometer (ECS) and the Lawrence Livermore National Laboratory electron beam ion trap EBIT-I. We then directly apply these new line centers to calculate the Doppler shifts of the lines observed in Cygnus X-1. With this approach, we find shifts consistent with constant velocity of the absorber throughout all ionization states and, hence, provide evidence for an onion-like ion structure of the clumps. Funded by BMWi under DLR grant 50OR1207. Work at LLNL was performed under the auspices of DOE under contract DE-AC52-07NA27344 and supported by NASA grants.

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

Hybrid catadioptric system for advanced optical cavity velocimetry

DOEpatents

Frayer, Daniel K.

2018-02-06

A probe including reflector is disclosed to measure the velocity distribution of a moving surface along many lines of sight. Laser light, directed to the surface by the probe and then reflected back from the surface, is Doppler shifted by the moving surface, collected into probe, and then directed to detection equipment through optic fibers. The received light is mixed with reference laser light and using photonic Doppler velocimetry, a continuous time record of the surface movement is obtained. An array of single-mode optical fibers provides an optic signal to one or more lens groups and a reflector, such as a parabolic reflector having a mirrored interior surface.

Exploitation of SAR data for measurement of ocean currents and wave velocities

NASA Technical Reports Server (NTRS)

Shuchman, R. A.; Lyzenga, D. R.; Klooster, A., Jr.

1981-01-01

Methods of extracting information on ocean currents and wave orbital velocities from SAR data by an analysis of the Doppler frequency content of the data are discussed. The theory and data analysis methods are discussed, and results are presented for both aircraft and satellite (SEASAT) data sets. A method of measuring the phase velocity of a gravity wave field is also described. This method uses the shift in position of the wave crests on two images generated from the same data set using two separate Doppler bands. Results of the current measurements are pesented for 11 aircraft data sets and 4 SEASAT data sets.

An Erupting Active Region Filament: Three-Dimensional Trajectory and Hydrogen Column Density

NASA Astrophysics Data System (ADS)

Penn, M. J.

2000-12-01

From 15:33 through 16:02 UT on 13 June 1998, observations of an erupting filament as it crossed solar disk center were obtained with the NSO/KPVT and SOHO/CDS instruments as part of the SOHO Joint Observing Program 70. Context observations show that this event was the eruption of the north-east section of a small active region filament associated with NOAA 8237, that the photospheric magnetic field was changing in this active region between 12-14 June 1998, and that a coronal Moreton-wave disk event occurred, as well as a white-light CME off the south-west solar limb. The NSO/KPVT imaging spectroscopy data covered 512 × 512 arc sec of the disk center and were spectrally centered at the Hei 1083 nm line and captured +/-1.0 nm of surrounding solar spectrum. The Hei absorption line is seen blue-shifted to velocities of between 200 and 300 km s^-1. The true solar trajectory of the eruption is obtained by using the projected solar coordinates and by integrating the Doppler velocity. The filament travels with a total velocity of about 300 km s^-1 along a path inclined roughly 49 deg to the solar surface and rises to a height of just over 1.5 solar radii before it becomes too diffuse to follow. The filament also shows internal motions with multiple Doppler components shifted by +/-25 km s^-1. Finally, the KPVT data show no Stokes V profiles in the Doppler-shifted Hei 1083.03 nm absorption to a limit of roughly 3×10^-3 times the continuum intensity. The SOHO/CDS scanned the center of the KPVT FOV using seven EUV lines; Doppler-shifted filament emission is seen in lines from Hei 58.4 nm, Heii 30.4 nm, Oiv 55.5 nm, Ov 63.0 nm, Nevi 56.3 nm, and Mgx 61.0 nm representing temperatures from about 2×10^4K through 1×10^6K. Bound-free continuum absorption from Hi, without confusion from foreground emission and line emission, is seen as the filament obscures underlying chromospheric emission. A fit to the wavelength dependence of the absorption from five lines between 55.5 to 63.0 nm yields a column density ξ_H I =4.8+/-2.5×10^17 cm^-2. Spatial maps show that this filament absorption is more confined than the regions which show emission.

Time-delay-induced dynamical behaviors for an ecological vegetation growth system driven by cross-correlated multiplicative and additive noises.

PubMed

Wang, Kang-Kang; Ye, Hui; Wang, Ya-Jun; Li, Sheng-Hong

2018-05-14

In this paper, the modified potential function, the stationary probability distribution function (SPDF), the mean growth time and the mean degeneration time for a vegetation growth system with time delay are investigated, where the vegetation system is assumed to be disturbed by cross-correlated multiplicative and additive noises. The results reveal some fact that the multiplicative and additive noises can both reduce the stability and speed up the decline of the vegetation system, while the strength of the noise correlation and time delay can both enhance the stability of the vegetation and slow down the depression process of the ecological system. On the other hand, with regard to the impacts of noises and time delay on the mean development and degeneration processes of the ecological system, it is discovered that 1) in the development process of the vegetation population, the increase of the noise correlation strength and time delay will restrain the regime shift from the barren state to the boom one, while the increase of the additive noise can lead to the fast regime shift from the barren state to the boom one. 2) Conversely, in the depression process of the ecological system, the increase of the strength of the correlation noise and time delay will prevent the regime shift from the boom state to the barren one. Comparatively, the increase of the additive and multiplicative noises can accelerate the regime shift from the boom state to the barren state.

Optical resonators for true-time-delay beam steering

NASA Astrophysics Data System (ADS)

Gesell, Leslie H.; Evanko, Stephen M.

1996-06-01

Conventional true time delay beamforming and steering devices rely on switching between various lengths of delay line. Therefore only discrete delays are possible. Proposed is a new photonics concept for true time delay beamforming which provides a finely controlled continuum of delays with switching speeds on the order of 10's of nanoseconds or faster. The architecture uses an array of waveguide cavities with different resonate frequencies to channelize the signal. Each spectral component of the signal is phase shifted by an amount proportional to the frequency of that component and the desired time delay. These phase shifted spectral components are then summed to obtain the delayed signal. This paper provides an overview of the results of a Phase I SBIR contract where this concept has been refined and analyzed. The parameters for an operational system are determined and indication of the feasibility of this approach is given. Among the issues addressed are the requirements of the resonators and the methods necessary to implement fiber optic Bragg gratings as these resonators.

Assessment of left atrial mechanical functions and atrial electromechanical delay in Juvenile idiopathic arthritis by tissue Doppler echocardiography.

PubMed

El Eraky, Azza Z; Handoka, Nesrin M; Ghaly, Mona Sayed; Nasef, Samah Ismail; Eldahshan, Nahed A; Ibrahim, Ahmed M; Shalaby, Sherein

2016-11-24

Juvenile idiopathic arthritis (JIA) is a systemic chronic inflammatory disease. Studies using tissue Doppler imaging (TDI) for the evaluation of cardiac functions of children with JIA are limited. Thus, this study was conducted to evaluate Left ventricular function, left atrial mechanical functions and atrial electromechanical delay in JIA. This study was carried out as a across sectional study. A total of 34 patients with active JIA and 34 controls were included. Atrial electromechanical delay and left atrial (LA) mechanical functions in addition to systolic and diastolic left ventricular (LV) functions were measured by using conventional echocardiography and TDI. Assessment of disease activity was done using Juvenile arthritis disease activity score (JADAS-27). JIA patients had abnormal atrial electromechanical coupling as established from prolonged lateral mitral annulus (PA lateral), septal mitral annulus (PA septum), inter-atrial and intra-atrial electromechanical delays compared with healthy controls. Left ventricular filling abnormalities were found characterized by a reduced E/A ratio (1.07 ± 0.56 vs. 1.48 ± 0.16, p = 0.01). E/Em was significantly higher in patients with JIA (7.58 ± 1.79 vs. 4.74 ± 1.45, p = 0.003) denoting impaired diastolic function. Left atrial mechanical functions assessment showed significantly decreased LA passive emptying fraction, increased LA active emptying fraction and LA total emptying volume in JIA patients (p = 0.01, p = 0.01, p = 0.03 respectively). Atrial electromechanical coupling intervals, and LA mechanical functions were impaired which can be considered as an early form of subclinical cardiac involvement in JIA patients. Significant diastolic functional abnormalities exist in JIA.

Study of atomic coherence effects in multi-level V+Ξ system involving Rydberg state

NASA Astrophysics Data System (ADS)

Kaur, Amanjot; Singh, Neeraj; Kaur, Paramjit

2018-06-01

We present theoretical model to investigate the influence of hyperfine levels on the atomic coherences of V+Ξ Rydberg system. Using density matrix formulation, an analytical expression of atomic coherence for weak probe field is derived. The closely spaced hyperfine levels cause asymmetry and red shift while wavelength mismatching induced due to Rydberg state leads to reduction in magnitude and broadening of group index, absorption and dispersion profiles for moving atoms. Our system shows both Rydberg Electromagnetically induced transparency (EIT) with subluminal behavior and Rydberg Electromagnetically induced absorption (EIA) with superluminal propagation by adjusting the strengths of control and switching fields. Variation of group index with probe detuning reveals anomalous dispersion regions at Autler-Townes doublet positions. Group index for Doppler-broadened atoms at resonance condition has lower magnitude as compared to the stationary atoms and hence the group delay time of the pulse is also reduced. We also explore in-depth non-degenerate four-wave mixing (FWM) which is ignited due to the presence of three electromagnetic (e.m.) fields and concurrently, establish relationship between FWM and multi-photon atomic coherence. The transient behavior is also studied for practical realization of our considered system as optical switch.

How to measure a femtometer

NASA Astrophysics Data System (ADS)

Nijenhuis, Jan R.; Visser, Huib; Kruizinga, Bob

2003-10-01

Measuring the wind speed from a satellite is not new. However measuring with great precision is by far not trivial. Various methods are available for that. A common method is to use the Doppler effect. A UV-laser on board of the satellite is used to "fire" to the earth atmosphere. Some photons will be reflected back to the satellite. Because of the speed of the particles in the air the photons will experience a small Doppler shift. Wind speeds of 1 m/s are hereby equivalent to a wave length shift of 1 femtometer. The paper presents the patented method of how to measure these small wavelength shifts without running into trouble concerning the mechanical design. It will understood that such instrument will be very sensitive to thermal variations (a challenging requirement was that a temperature change of 0.2° in 7 seconds was specified at the interface surfaces). The optical system makes use of a modified Michelson interferometer while the mechanical system automatically compensates for thermal expansion effects. Originally the idea was to make a complete Zerodur structure to eliminate the thermal effects. However it appeared to be possible to use a titanium structure with certain elements made from invar and aluminium. No need to say that this reduced risk and cost of the instrument drastically.

Wind turbines and bat mortality: Doppler shift profiles and ultrasonic bat-like pulse reflection from moving turbine blades.

PubMed

Long, Chloe V; Flint, James A; Lepper, Paul A

2010-10-01

Bat mortality resulting from actual or near-collision with operational wind turbine rotors is a phenomenon that is widespread but not well understood. Because bats rely on information contained in high-frequency echoes to determine the nature and movement of a target, it is important to consider how ultrasonic pulses similar to those used by bats for echolocation may be interacting with operational turbine rotor blades. By assessing the characteristics of reflected ultrasonic echoes, moving turbine blades operating under low wind speed conditions (<6 m s(-1)) were found to produce distinct Doppler shift profiles at different angles to the rotor. Frequency shifts of up to ±700-800 Hz were produced, which may not be perceptible by some bat species. Monte Carlo simulation of bat-like sampling by echolocation revealed that over 50 rotor echoes could be required by species such as Pipistrellus pipistrellus for accurate interpretation of blade movement, which may not be achieved in the bat's approach time-window. In summary, it was found that echoes returned from moving blades had features which could render them attractive to bats or which might make it difficult for the bat to accurately detect and locate blades in sufficient time to avoid a collision.

Early Changes in Atrial Electromechanical Coupling in Patients with Hypertension: Assessment by Tissue Doppler Imaging.

PubMed

Avci, Burcak Kilickiran; Gulmez, Oyku; Donmez, Guclu; Pehlivanoglu, Seckin

2016-06-05

Hypertension (HT) is associated with atrial electrophysiological abnormalities. Echocardiographic pulsed wave tissue Doppler imaging (TDI) is one of the noninvasive methods for evaluation of atrial electromechanical properties. The aims of our study were to investigate the early changes in atrial electromechanical conduction in patients with HT and to assess the parameters that affect atrial electromechanical conduction. Seventy-six patients with HT (41 males, mean age 52.6 ± 9.0 years) and 41 controls (22 males, mean age 49.8 ± 7.9 years) were included in the study. Atrial electromechanical coupling at the right (PRA), left (PLA), interatrial septum (PIS) were measured with TDI. Intra- (right: PIS-PRA, left: PLA-PIS) and inter-atrial (PLA-PRA) electromechanical delays were calculated. Maximum P-wave duration (Pmax) was calculated from 12-lead electrocardiogram. Atrial electromechanical coupling at PLA (76.6 ± 14.1 ms vs. 82.9 ± 15.8 ms, P = 0.036), left intra-atrial (10.9 ± 5.0 ms vs. 14.0 ± 9.7 ms, P = 0.023), right intra-atrial (10.6 ± 7.8 ms vs. 14.5 ± 10.1 ms, P = 0.035), and interatrial electromechanical (21.4 ± 9.8 ms vs. 28.3 ± 12.7 ms, P = 0.003) delays were significantly longer in patients with HT. The linear regression analysis showed that left ventricular (LV) mass index and Pmax were significantly associated with PLA (P = 0.001 and P = 0.002, respectively), and the LV mass index was the only related factor for interatrial delay (P = 0.001). Intra- and interatrial electromechanical delay, PLA were significantly prolonged in hypertensive patients. LV mass index and Pmax were significantly associated with PLA, and the LV mass index was the only related factor for interatrial delay. The atrial TDI can be a valuable method to assess the early changes of atrial electromechanical conduction properties in those patients.

Early Changes in Atrial Electromechanical Coupling in Patients with Hypertension: Assessment by Tissue Doppler Imaging

PubMed Central

Avci, Burcak Kilickiran; Gulmez, Oyku; Donmez, Guclu; Pehlivanoglu, Seckin

2016-01-01

Background: Hypertension (HT) is associated with atrial electrophysiological abnormalities. Echocardiographic pulsed wave tissue Doppler imaging (TDI) is one of the noninvasive methods for evaluation of atrial electromechanical properties. The aims of our study were to investigate the early changes in atrial electromechanical conduction in patients with HT and to assess the parameters that affect atrial electromechanical conduction. Methods: Seventy-six patients with HT (41 males, mean age 52.6 ± 9.0 years) and 41 controls (22 males, mean age 49.8 ± 7.9 years) were included in the study. Atrial electromechanical coupling at the right (PRA), left (PLA), interatrial septum (PIS) were measured with TDI. Intra- (right: PIS-PRA, left: PLA-PIS) and inter-atrial (PLA-PRA) electromechanical delays were calculated. Maximum P-wave duration (Pmax) was calculated from 12-lead electrocardiogram. Results: Atrial electromechanical coupling at PLA (76.6 ± 14.1 ms vs. 82.9 ± 15.8 ms, P = 0.036), left intra-atrial (10.9 ± 5.0 ms vs. 14.0 ± 9.7 ms, P = 0.023), right intra-atrial (10.6 ± 7.8 ms vs. 14.5 ± 10.1 ms, P = 0.035), and interatrial electromechanical (21.4 ± 9.8 ms vs. 28.3 ± 12.7 ms, P = 0.003) delays were significantly longer in patients with HT. The linear regression analysis showed that left ventricular (LV) mass index and Pmax were significantly associated with PLA (P = 0.001 and P = 0.002, respectively), and the LV mass index was the only related factor for interatrial delay (P = 0.001). Conclusions: Intra- and interatrial electromechanical delay, PLA were significantly prolonged in hypertensive patients. LV mass index and Pmax were significantly associated with PLA, and the LV mass index was the only related factor for interatrial delay. The atrial TDI can be a valuable method to assess the early changes of atrial electromechanical conduction properties in those patients. PMID:27231168

Enlivening Physics, a Local Video Disc Project.

ERIC Educational Resources Information Center

McInerney, M.

1989-01-01

Describes how to make and use an inexpensive video disc of physics demonstrations. Discusses the background, production of the disc, subject of the disc including angular momentum, "monkey and the hunter" experiment, Doppler shift, pressure of a constant volume of gas thermometer, and wave effects, and using the disc in classroom. (YP)

Beam maser measurements of CH3OH rotational transitions

NASA Technical Reports Server (NTRS)

Gaines, L.; Casleton, K. H.; Kukolich, S. G.

1974-01-01

Precise measurements of rotational transitions in methanol are reported that were made by means of beam maser spectrometers. No hyperfine structure was resolved at a resonance line width of 8 kHz. Accurate center frequencies for the transitions measured are useful for determining Doppler shifts for observed interstellar lines.

Adaptation to abrupt time shifts of the oscillator(s) controlling human circadian rhythms.

PubMed Central

Mills, J N; Minors, D S; Waterhouse, J M

1978-01-01

1. Thirty-six subjects in an isolation unit were subjected to time shifts of 12 hr, or of 8 hr in either direction. 2. The rhythms of body temperature and excretion of eight urinary constituents were studied before and after the shift, both on a usual nychthemeral routine and during 24 hr when they remained under constant conditions, awake, engaged in light, mainly sedentary activity, and consuming identical food and fluid every hour. 3. The rhythms on nychthemeral routine were defined by fitting cosine curves. On constant routine the rhythm after the shift was cross-correlated with the original rhythm, either with variable delay (or advance) or with an additive mixture between this variably shifted rhythm and the unshifted or a fully shifted rhythm. The process yielding the highest correlation coefficient was accepted as the best descriptor of the nature of adaptation. 4. A combination of two rhythms was observed more often for urinary sodium, chloride and phosphate than for other variables. 5. Adaptation appeared to have proceeded further after westward than eastward shifts, and this difference was particularly noticeable for urinary potassium, sodium and chloride. 6. Partial adaptation usually involved a phase delay, even after an eastward shift when a cumulative delay of 16 hr would be needed to achieve full adaptation and re-entrainment. 7. Observations under nychthemeral conditions often gave a false idea of the degree of adaptation. In particular, after an eastward shift the phase of the rhythms appeared to shift in the appropriate direction when studied under nychthemeral conditions whereas the endogenous oscillator either showed no consistent behaviour or, in the control of urate excretion, a shift in the wrong direction. 8. The implications for people undergoing time shifts, in the course of shift work or transmeridional flights, are indicated. PMID:745108

The value of Doppler ultrasound in diagnosis in 25 cases of furunculoid myiasis.

PubMed

Quintanilla-Cedillo, Marco R; León-Ureña, Heberth; Contreras-Ruiz, José; Arenas, Roberto

2005-01-01

The larvae of the botfly Dermatobia hominis cause furunculoid myiasis in endemic areas. Lack of knowledge of this condition outside these areas leads to confusion in diagnosis and delays appropriate treatment. To describe the clinical findings of furunculoid myiasis encountered in Quintana Roo, in the south-east of Mexico. We performed an observational study on 25 cases diagnosed over a period of 4 years. Diagnosis of furunculoid myiasis was made in 14 males and 11 females with an average age of 24.5 years. Most of our patients were students, farmers, or housewives. The number of lesions varied from one to four. In 20% of cases, more than one parasite was present in each lesion. The scalp was the most commonly affected region (40%), followed by the trunk and the extremities. Doppler ultrasound study (DUSG) of the furuncle-like lesions confirmed the clinical diagnosis in all cases. Furunculoid myiasis is frequent in the state of Quintana Roo, Mexico. We found no association with occupation, gender, social background or age. DUSG can be used to evaluate the number of parasites per furunculoid lesion avoiding misdiagnoses and treatment delays.

Galileo Earth approach navigation using connected-element interferometer phase-delay tracking

NASA Technical Reports Server (NTRS)

Thurman, S. W.

1990-01-01

The application of a Connected-Element Interferometer (CEI) to the navigation of the Galileo spacecraft during its encounter with Earth in December 1990 is investigated. A CEI tracking demonstration is planned for the week of November 11 through 18, 1990, from 27 days to 20 days prior to Earth encounter on December 8. During this period, the spacecraft will be tracked daily with Deep Space Network Stations 13 and 15 at Goldstone. The purpose of this work is twofold: first, to establish and define the navigation performance expected during the tracking demonstration and, second, to study, in a more general sense, the sensitivity of orbit demonstration results obtained with CEI to the data density within CEI tracking passes and to important system parameters, such as baseline orientation errors and the phase-delay measurement accuracy. Computer simulation results indicate that the use of CEI data, coupled with conventional range and Doppler data, may reduce the uncertainty in the declination of the spacecraft's incoming trajectory by 15 to 66 percent compared with the operational solution using range and Doppler data only. The level of improvement depends upon the quantity and quality of the CEI data.

Applicability of the iterative technique for cardiac resynchronization therapy optimization: full-disclosure, 50-sequential-patient dataset of transmitral Doppler traces, with implications for future research design and guidelines.

PubMed

Jones, Siana; Shun-Shin, Matthew J; Cole, Graham D; Sau, Arunashis; March, Katherine; Williams, Suzanne; Kyriacou, Andreas; Hughes, Alun D; Mayet, Jamil; Frenneaux, Michael; Manisty, Charlotte H; Whinnett, Zachary I; Francis, Darrel P

2014-04-01

Full-disclosure study describing Doppler patterns during iterative atrioventricular delay (AVD) optimization of biventricular pacemakers (cardiac resynchronization therapy, CRT). Doppler traces of the first 50 eligible patients undergoing iterative Doppler AVD optimization in the BRAVO trial were examined. Three experienced observers classified conformity to guideline-described patterns. Each observer then selected the optimum AVD on two separate occasions: blinded and unblinded to AVD. Four Doppler E-A patterns occurred: A (always merged, 18% of patients), B (incrementally less fusion at short AVDs, 12%), C (full separation at short AVDs, as described by the guidelines, 28%), and D (always separated, 42%). In Groups A and D (60%), the iterative guidelines therefore cannot specify one single AVD. On the kappa scale (0 = chance alone; 1 = perfect agreement), observer agreement for the ideal AVD in Classes B and C was poor (0.32) and appeared worse in Groups A and D (0.22). Blinding caused the scattering of the AVD selected as optimal to widen (standard deviation rising from 37 to 49 ms, P < 0.001). By blinding 28% of the selected optimum AVDs were ≤60 or ≥200 ms. All 50 Doppler datasets are presented, to support future methodological testing. In most patients, the iterative method does not clearly specify one AVD. In all the patients, agreement on the ideal AVD between skilled observers viewing identical images is poor. The iterative protocol may successfully exclude some extremely unsuitable AVDs, but so might simply accepting factory default. Irreproducibility of the gold standard also prevents alternative physiological optimization methods from being validated honestly.

Impact of Transcranial Doppler Ultrasound on Logistics and Outcomes in Stroke Thrombolysis: Results From the SITS-ISTR.

PubMed

Mazya, Michael V; Ahmed, Niaz; Azevedo, Elsa; Davalos, Antoni; Dorado, Laura; Karlinski, Michal; Lorenzano, Svetlana; Neumann, Jiří; Toni, Danilo; Moreira, Tiago P

2018-07-01

Diagnostic transcranial Doppler ultrasound (TCD) is commonly used in patients with acute stroke before or during treatment with intravenous thrombolysis (IVT). We aimed to assess how much TCD delays IVT initiation and whether TCD influences outcomes. We analyzed data from the SITS-ISTR (Safe Implementation of Thrombolysis in Stroke-International Stroke Thrombolysis Register) collected from December 2002 to December 2011. Outcomes were door-to-needle time, symptomatic intracerebral hemorrhage, functional outcome per the modified Rankin Scale, and mortality at 3 months. In hospitals performing any TCD pre-IVT, 1701 of 11 265 patients (15%) had TCD before IVT initiation. Door-to-needle time was higher in patients with pre-IVT TCD (74 versus 60 minutes; P <0.001). At hospitals performing any TCD during IVT infusion, of 9044 patients with IVT, 747 were examined with TCD during IVT. No treatment delay was seen with TCD during IVT. After multivariate adjustment, TCD during IVT was independently associated with modestly increased excellent functional outcome (modified Rankin Scale, 0-1; adjusted odds ratio, 1.28; 95% confidence interval, 1.06-1.55; P =0.012) and lower mortality (adjusted odds ratio, 0.73; 95% confidence interval, 0.55-0.95; P =0.022). We recommend that TCD, if performed, should be done during IVT infusion, to avoid treatment delay. The association of hyperacute TCD with beneficial outcomes suggests potential impact on patient management, which warrants further study. © 2018 American Heart Association, Inc.

Atmospheric scattering effects on ground-based measurements of thermospheric winds

NASA Technical Reports Server (NTRS)

Abreu, V. J.; Schmitt, G. A.; Hays, P. B.; Meriwether, J. W., Jr.; Tepley, C. A.; Cogger, L. L.

1983-01-01

Convergent or divergent thermospheric wind patterns detected by ground-based Fabry-Perot interferometric measurements of the Doppler shifts of atomic lines are demonstrated to occur in the presence of strong intensity gradients and a scattering atmosphere. Consideration is given to the color shifts observed when sighting to the north or the south, and a numerical model is developed to describe the wind patterns which produce the recorded shifts. An account is taken of the direct and scattered components of the brightness, with the atmosphere treated as a single scattering layer with a reflecting surface underneath. A scattering coefficient is calculated, together with the line shape of the wavelength shifts. The scattered light is demonstrated, both through simulations and measurements taken near Calgary, Alberta, to produce convergence or divergence of the color shifts, depending on the line-of-sight of the viewing.

Digital tanlock loop architecture with no delay

NASA Astrophysics Data System (ADS)

Al-Kharji AL-Ali, Omar; Anani, Nader; Al-Araji, Saleh; Al-Qutayri, Mahmoud; Ponnapalli, Prasad

2012-02-01

This article proposes a new architecture for a digital tanlock loop which eliminates the time-delay block. The ? (rad) phase shift relationship between the two channels, which is generated by the delay block in the conventional time-delay digital tanlock loop (TDTL), is preserved using two quadrature sampling signals for the loop channels. The proposed system outperformed the original TDTL architecture, when both systems were tested with frequency shift keying input signal. The new system demonstrated better linearity and acquisition speed as well as improved noise performance compared with the original TDTL architecture. Furthermore, the removal of the time-delay block enables all processing to be digitally performed, which reduces the implementation complexity. Both the original TDTL and the new architecture without the delay block were modelled and simulated using MATLAB/Simulink. Implementation issues, including complexity and relation to simulation of both architectures, are also addressed.

Measurements of CO2 Concentration and Wind Profiles with A Scanning 1.6μm DIAL

NASA Astrophysics Data System (ADS)

Abo, M.; Shibata, Y.; Nagasawa, C.; Nagai, T.; Sakai, T.; Tsukamoto, M.

2012-12-01

Horizontal carbon dioxide (CO2) distribution and wind profiles are important information for understanding of the regional sink and source of CO2. The differential absorption lidar (DIAL) and the Doppler lidar with the range resolution is expected to bring several advantages over passive measurements. We have developed a new scanning 1.6μm DIAL and incoherent Doppler lidar system to perform simultaniously measurements of CO2 concentration and wind speed profiles in the atmosphere. The 1.6μm DIAL and Doppler lidar system consists of the Optical Parametric Generator (OPG) transmitter that excited by the LD pumped Nd:YAG laser with high repetition rate (500 Hz). The receiving optics include the near-infrared photomultiplier tube with high quantum efficiency operating at the photon counting mode, a fiber Bragg grating (FBG) filter to detct Doppler shift, and a 25 cm telescope[1][2]. Laser beam is transmitted coaxially and motorized scanning mirror system can scan the laser beam and field of view 0-360deg horizontally and 0-52deg vertically. We report the results of vertical CO2 scanning measurenents and vertical wind profiles. The scanning elevation angles were from 12deg to 24deg with angular step of 4deg and CO2 concentration profiles were obtained up to 1 km altitude with 200 m altitude resolution. We also obtained vertical wind vector profiles by measuring line-of-sight wind profiles at two azimuth angles with a fixed elevation angle 52deg. Vertical wind vector profiles were obtained up to 5 km altitude with 1 km altitude rasolution. This work was financially supported by the System Development Program for Advanced Measurement and Analysis of the Japan Science and Technology Agency. References [1] L. B. Vann, et al., "Narrowband fiber-optic phase-shifted Fabry-Perot Bragg grating filters for atmospheric water vapor lidar measurements", Appl. Opt., 44, pp. 7371-7377 (2005). [2] Y. Shibata, et al., "1.5μm incoherent Doppler lidar using a FBG filter", Proceedings of 25th International Laser Radar Conference (ILRC25), pp. 338-340 (2010)

Automatic retinal blood flow calculation using spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Wehbe, Hassan; Ruggeri, Marco; Jiao, Shuliang; Gregori, Giovanni; Puliafito, Carmen A.

2008-02-01

Optical Doppler tomography (ODT) is a branch of optical coherence tomography (OCT) that can measure the speed of a blood flow by measuring the Doppler shift impinged on the probing sample light by the moving blood cells. However, the measured speed of blood flow is a function of the Doppler angle, which needs to be determined in order to calculate the absolute velocity of the blood flow inside a vessel. We developed a technique that can extract the Doppler angle from the 3D data measured with spectral-domain OCT, which needs to extract the lateral and depth coordinates of a vessel in each measured ODT and OCT image. The lateral coordinates and the diameter of a blood vessel were first extracted in each OCT structural image by using the technique of blood vessel shadowgram, a technique first developed by us for enhancing the retinal blood vessel contrast in the en face view of the 3D OCT. The depth coordinate of a vessel was then determined by using a circular averaging filter moving in the depth direction along the axis passing through the vessel center in the ODT image. The Doppler angle was then calculated from the extracted coordinates of the blood vessel. The technique was applied in blood flow measurements in retinal blood vessels, which has potential impact on the study and diagnosis of blinding diseases like glaucoma and diabetic retinopathy.

Development of a mobile Doppler lidar system for wind and temperature measurements at 30-70 km

NASA Astrophysics Data System (ADS)

Yan, Zhaoai; Hu, Xiong; Guo, Wenjie; Guo, Shangyong; Cheng, Yongqiang; Gong, Jiancun; Yue, Jia

2017-02-01

A mobile Doppler lidar system has been developed to simultaneously measure zonal and meridional winds and temperature from 30 to 70 km. Each of the two zonal and meridional wind subsystems employs a 15 W power, 532 nm laser and a 1 m diameter telescope. Iodine vapor filters are used to stabilize laser frequency and to detect the Doppler shift of backscattered signal. The integration method is used for temperature measurement. Experiments were carried out using the mobile Doppler lidar in August 2014 at Qinghai, China (91°E, 38°N). The zonal wind was measured from 20 to 70 km at a 3 km spatial resolution and 2 h temporal resolution. The measurement error is about 0.5 m/s at 30 km, and 10 m/s at 70 km. In addition, the temperature was measured from 30 to 70 km at 1 km spatial resolution and 1 h temporal resolution. The temperature measurement error is about 0.4 K at 30 km, and 8.0 K at 70 km. Comparison of the lidar results with the temperature of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), the zonal wind of the Modern-Era Retrospective Analysis for Re-search and Applications (MERRA), and radiosonde zonal wind shows good agreement, indicating that the Doppler lidar results are reliable.

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

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

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

2014-04-28

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

Evolution of the heteroharmonic strategy for target-range computation in the echolocation of Mormoopidae

PubMed Central

Mora, Emanuel C.; Macías, Silvio; Hechavarría, Julio; Vater, Marianne; Kössl, Manfred

2013-01-01

Echolocating bats use the time elapsed from biosonar pulse emission to the arrival of echo (defined as echo-delay) to assess target-distance. Target-distance is represented in the brain by delay-tuned neurons that are classified as either “heteroharmonic” or “homoharmormic.” Heteroharmonic neurons respond more strongly to pulse-echo pairs in which the timing of the pulse is given by the fundamental biosonar harmonic while the timing of echoes is provided by one (or several) of the higher order harmonics. On the other hand, homoharmonic neurons are tuned to the echo delay between similar harmonics in the emitted pulse and echo. It is generally accepted that heteroharmonic computations are advantageous over homoharmonic computations; i.e., heteroharmonic neurons receive information from call and echo in different frequency-bands which helps to avoid jamming between pulse and echo signals. Heteroharmonic neurons have been found in two species of the family Mormoopidae (Pteronotus parnellii and Pteronotus quadridens) and in Rhinolophus rouxi. Recently, it was proposed that heteroharmonic target-range computations are a primitive feature of the genus Pteronotus that was preserved in the evolution of the genus. Here, we review recent findings on the evolution of echolocation in Mormoopidae, and try to link those findings to the evolution of the heteroharmonic computation strategy (HtHCS). We stress the hypothesis that the ability to perform heteroharmonic computations evolved separately from the ability of using long constant-frequency echolocation calls, high duty cycle echolocation, and Doppler Shift Compensation. Also, we present the idea that heteroharmonic computations might have been of advantage for categorizing prey size, hunting eared insects, and living in large conspecific colonies. We make five testable predictions that might help future investigations to clarify the evolution of the heteroharmonic echolocation in Mormoopidae and other families. PMID:23781209

Real-time high-velocity resolution color Doppler OCT

NASA Astrophysics Data System (ADS)

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

2001-05-01

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

Medical and nonmedical factors influencing utilization of delayed pushing in the second stage.

PubMed

Frey, Heather A; Tuuli, Methodius G; Cortez, Sarah; Odibo, Anthony O; Roehl, Kimberly A; Shanks, Anthony L; Macones, George A; Cahill, Alison G

2013-08-01

To evaluate factors impacting selection to delayed pushing in the second stage of labor. This case-control study was a secondary analysis of a large retrospective cohort study. Cases included women who delayed pushing for 60 minutes or more in the second stage of labor. Controls began pushing prior to 60 minutes from the time of diagnosis of complete dilation. Demographic, labor, and nonmedical factors were compared among cases and controls. Logistic regression modeling was used to identify factors independently associated with delayed pushing. We identified 471 women who delayed pushing and 4819 controls. Nulliparity, maternal body mass index > 25, high fetal station at complete dilation, regional anesthesia use, and start of second stage during staffing shift change were independent factors associated with increased use of delayed pushing. On the other hand, black race and second-stage management during night shift were associated with lower odds of employing delayed pushing. Delayed pushing was more commonly employed in nulliparous women, but 38.9% of multiparous women also delayed pushing. We identified multiple factors associated with use of delayed pushing. This study helps to define current patterns of second-stage labor management. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Medical and Non-Medical Factors Influencing Utilization of Delayed Pushing in the Second Stage

PubMed Central

FREY, Heather A.; TUULI, Methodius G.; CORTEZ, Sarah; ODIBO, Anthony O.; ROEHL, Kimberly A.; SHANKS, Anthony L.; MACONES, George A.; CAHILL, Alison G.

2014-01-01

Objective To evaluate factors impacting selection to delayed pushing in the second stage of labor. Study design This case-control study was a secondary analysis of a large retrospective cohort study. Cases included women who delayed pushing for 60 minutes or more in the second stage of labor. Controls began pushing prior to 60 minutes from the time of diagnosis of complete dilation. Demographic, labor, and nonmedical factors were compared among cases and controls. Logistic regression modelling was used to identify factors independently associated with delayed pushing. Results We identified 471 women who delayed pushing and 4,819 controls. Nulliparity, maternal body mass index > 25, high fetal station at complete dilation, regional anesthesia use, and start of second stage during staffing shift change were independent factors associated with increased use of delayed pushing. On the other hand, black race and second stage management during night shift were associated with lower odds of employing delayed pushing. Delayed pushing was more commonly employed in nulliparous women, but 38.9% of multiparous women also delayed pushing. Conclusion We identified multiple factors associated with use of delayed pushing. This study helps to define current patterns of second stage labor management. PMID:23208765

Laser Doppler flowmetry in endodontics: a review.

PubMed

Jafarzadeh, H

2009-06-01

Vascular supply is the most accurate marker of pulp vitality. Tests for assessing vascular supply that rely on the passage of light through a tooth have been considered as possible methods for detecting pulp vitality. Laser Doppler flowmetry (LDF), which is a noninvasive, objective, painless, semi-quantitative method, has been shown to be reliable for measuring pulpal blood flow. The relevant literature on LDF in the context of endodontics up to March 2008 was reviewed using PubMed and MEDLINE database searches. This search identified papers published between June 1983 and March 2008. Laser light is transmitted to the pulp by means of a fibre optic probe. Scattered light from moving red blood cells will be frequency-shifted whilst that from the static tissue remains unshifted. The reflected light, composed of Doppler-shifted and unshifted light, is returned by afferent fibres and a signal is produced. This technique has been successfully employed for estimating pulpal vitality in adults and children, differential diagnosis of apical radiolucencies (on the basis of pulp vitality), examining the reactions to pharmacological agents or electrical and thermal stimulation, and monitoring of pulpal responses to orthodontic procedures and traumatic injuries. Assessments may be highly susceptible to environmental and technique-related factors. Nonpulpal signals, principally from periodontal blood flow, may contaminate the signal. Because this test produces no noxious stimuli, apprehensive or distressed patients accept it more readily than current methods of pulp vitality assessment. A review of the literature and a discussion of the application of this system in endodontics are presented.

The stimulated Brillouin scattering during the interaction of picosecond laser pulses with moderate- scale-length plasmas

NASA Astrophysics Data System (ADS)

Gaeris, Andres Claudio

The Stimulated Brillouin Scattering (SBS) instability is studied in moderately short scale-length plasmas. The backscattered and specularly reflected light resulting from the interaction of a pair of high power picosecond duration laser pulses with solid Silicon, Gold and Parylene-N (CH) strip targets was spectrally resolved. The first, weaker laser pulse forms a short scale-length plasma while the second delayed one interacts with the isothermally expanded, underdense region of the plasma. The pulses are generated by the Table Top Terawatt (TTT) laser operating at 1054 nm (infrared) with intensities up to 5.10 16 W/cm2. Single laser pulses only show Lambertian scattering on the target critical surface. Pairs of pulses with high intensity in the second pulse show an additional backscattered, highly blueshifted feature, associated with SBS. Increasing this second pulse intensity even more leads to the appearance of a third feature, even more blueshifted than the second, resulting from the Brillouin sidescattering of the laser pulse reflected on the critical surface. The SBS threshold intensities and enhanced reflectivities for P-polarized light are determined for different plasma density scale-lengths. These measurements agree with the convective thresholds predicted by the SBS theory of Liu, Rosenbluth, and White using plasma profiles simulated by the LILAC code. The spectral position of the Brillouin back- and sidescattered features are determined. The SBS and Doppler shifts are much too small to explain the observed blueshifts. The refractive index shift is of the right magnitude, although more detailed verification is required in the future.

Cerebral blood flow autoregulation is impaired in schizophrenia: A pilot study.

PubMed

Ku, Hsiao-Lun; Wang, Jiunn-Kae; Lee, Hsin-Chien; Lane, Timothy Joseph; Liu, I-Chao; Chen, Yung-Chan; Lee, Yao-Tung; Lin, I-Cheng; Lin, Chia-Pei; Hu, Chaur-Jong; Chi, Nai-Fang

2017-10-01

Patients with schizophrenia have a higher risk of cardiovascular diseases and higher mortality from them than does the general population; however, the underlying mechanism remains unclear. Impaired cerebral autoregulation is associated with cerebrovascular diseases and their mortality. Increased or decreased cerebral blood flow in different brain regions has been reported in patients with schizophrenia, which implies impaired cerebral autoregulation. This study investigated the cerebral autoregulation in 21 patients with schizophrenia and 23 age- and sex-matched healthy controls. None of the participants had a history of cardiovascular diseases, hypertension, or diabetes. All participants underwent 10-min blood pressure and cerebral blood flow recording through finger plethysmography and Doppler ultrasonography, respectively. Cerebral autoregulation was assessed by analyzing two autoregulation indices: the mean blood pressure and cerebral blood flow correlation coefficient (Mx), and the phase shift between the waveforms of blood pressure and cerebral blood flow determined using transfer function analysis. Compared with the controls, the patients had a significantly higher Mx (0.257 vs. 0.399, p=0.036) and lower phase shift (44.3° vs. 38.7° in the 0.07-0.20Hz frequency band, p=0.019), which indicated impaired maintenance of constant cerebral blood flow and a delayed cerebrovascular autoregulatory response. Impaired cerebral autoregulation may be caused by schizophrenia and may not be an artifact of coexisting medical conditions. The mechanism underlying impaired cerebral autoregulation in schizophrenia and its probable role in the development of cerebrovascular diseases require further investigation. Copyright © 2017 Elsevier B.V. All rights reserved.

The Direct Detection and Characterization of M-dwarf Planets Using Light Echoes

NASA Astrophysics Data System (ADS)

Sparks, William B.; White, Richard L.; Lupu, Roxana E.; Ford, Holland C.

2018-02-01

Exoplanets orbiting M-dwarf stars are a prime target in the search for life in the universe. M-dwarf stars are active, with powerful flares that could adversely impact prospects for life, though there are counter-arguments. Here, we turn flaring to advantage and describe ways in which it can be used to enhance the detectability of planets, in the absence of transits or a coronagraph, significantly expanding the accessible discovery and characterization space. Flares produce brief bursts of intense luminosity, after which the star dims. Due to the light travel time between the star and planet, the planet receives the high-intensity pulse, which it re-emits through scattering (a light echo) or intrinsic emission when the star is much fainter, thereby increasing the planet’s detectability. The planet’s light-echo emission can potentially be discriminated from that of the host star by means of a time delay, Doppler shift, spatial shift, and polarization, each of which can improve the contrast of the planet to the star. Scattered light can reveal the albedo spectrum of the planet to within a size scale factor, and is likely to be polarized. Intrinsic emission mechanisms include fluorescent pumping of multiple molecular hydrogen and neutral oxygen lines by intense Lyα and Lyβ flare emission, recombination radiation of ionized and photodissociated species, and atmospheric processes such as terrestrial upper atmosphere airglow and near-infrared hydroxyl emission. We discuss the feasibility of detecting light echoes and find that light echo detection is possible under favorable circumstances.

Recoil-free Fraction in Amorphous and Nanocrystalline Aluminium Based Alloys

NASA Astrophysics Data System (ADS)

Sitek, Jozef

2008-10-01

Aluminium based rapidly quenched alloys of nominal composition Al90Fe7Nb3 and Al94Fe2V4 were studied by Mössbauer spectroscopy. We have measured the recoil-free fraction and thermal shift at room and liquid nitrogen temperature. The frequency modes of atomic vibrations were determined and consequently the characteristic Debye temperature was derived. Characteristic temperature calculated from f-factor was lower than those fitted from second order Doppler shift. This indicates the presence of different frequency modes for amorphous and nanocrystalline states.

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.

A digitally implemented preambleless demodulator for maritime and mobile data communications

NASA Astrophysics Data System (ADS)

Chalmers, Harvey; Shenoy, Ajit; Verahrami, Farhad B.

The hardware design and software algorithms for a low-bit-rate, low-cost, all-digital preambleless demodulator are described. The demodulator operates under severe high-noise conditions, fast Doppler frequency shifts, large frequency offsets, and multipath fading. Sophisticated algorithms, including a fast Fourier transform (FFT)-based burst acquisition algorithm, a cycle-slip resistant carrier phase tracker, an innovative Doppler tracker, and a fast acquisition symbol synchronizer, were developed and extensively simulated for reliable burst reception. The compact digital signal processor (DSP)-based demodulator hardware uses a unique personal computer test interface for downloading test data files. The demodulator test results demonstrate a near-ideal performance within 0.2 dB of theory.

Lifetime measurement of neutron-rich even-even molybdenum isotopes

NASA Astrophysics Data System (ADS)

Ralet, D.; Pietri, S.; Rodríguez, T.; Alaqeel, M.; Alexander, T.; Alkhomashi, N.; Ameil, F.; Arici, T.; Ataç, A.; Avigo, R.; Bäck, T.; Bazzacco, D.; Birkenbach, B.; Boutachkov, P.; Bruyneel, B.; Bruce, A. M.; Camera, F.; Cederwall, B.; Ceruti, S.; Clément, E.; Cortés, M. L.; Curien, D.; De Angelis, G.; Désesquelles, P.; Dewald, M.; Didierjean, F.; Domingo-Pardo, C.; Doncel, M.; Duchêne, G.; Eberth, J.; Gadea, A.; Gerl, J.; Ghazi Moradi, F.; Geissel, H.; Goigoux, T.; Goel, N.; Golubev, P.; González, V.; Górska, M.; Gottardo, A.; Gregor, E.; Guastalla, G.; Givechev, A.; Habermann, T.; Hackstein, M.; Harkness-Brennan, L.; Henning, G.; Hess, H.; Hüyük, T.; Jolie, J.; Judson, D. S.; Jungclaus, A.; Knoebel, R.; Kojouharov, I.; Korichi, A.; Korten, W.; Kurz, N.; Labiche, M.; Lalović, N.; Louchart-Henning, C.; Mengoni, D.; Merchán, E.; Million, B.; Morales, A. I.; Napoli, D.; Naqvi, F.; Nyberg, J.; Pietralla, N.; Podolyák, Zs.; Pullia, A.; Prochazka, A.; Quintana, B.; Rainovski, G.; Reese, M.; Recchia, F.; Reiter, P.; Rudolph, D.; Salsac, M. D.; Sanchis, E.; Sarmiento, L. G.; Schaffner, H.; Scheidenberger, C.; Sengele, L.; Singh, B. S. Nara; Singh, P. P.; Stahl, C.; Stezowski, O.; Thoele, P.; Valiente Dobon, J. J.; Weick, H.; Wendt, A.; Wieland, O.; Winfield, J. S.; Wollersheim, H. J.; Zielinska, M.; PreSPEC Collaboration

2017-03-01

Background: In the neutron-rich A ≈100 mass region, rapid shape changes as a function of nucleon number as well as coexistence of prolate, oblate, and triaxial shapes are predicted by various theoretical models. Lifetime measurements of excited levels in the molybdenum isotopes allow the determination of transitional quadrupole moments, which in turn provides structural information regarding the predicted shape change. Purpose: The present paper reports on the experimental setup, the method that allowed one to measure the lifetimes of excited states in even-even molybdenum isotopes from mass A =100 up to mass A =108 , and the results that were obtained. Method: The isotopes of interest were populated by secondary knock-out reaction of neutron-rich nuclei separated and identified by the GSI fragment separator at relativistic beam energies and detected by the sensitive PreSPEC-AGATA experimental setup. The latter included the Lund-York-Cologne calorimeter for identification, tracking, and velocity measurement of ejectiles, and AGATA, an array of position sensitive segmented HPGe detectors, used to determine the interaction positions of the γ ray enabling a precise Doppler correction. The lifetimes were determined with a relativistic version of the Doppler-shift-attenuation method using the systematic shift of the energy after Doppler correction of a γ -ray transition with a known energy. This relativistic Doppler-shift-attenuation method allowed the determination of mean lifetimes from 2 to 250 ps. Results: Even-even molybdenum isotopes from mass A =100 to A =108 were studied. The decays of the low-lying states in the ground-state band were observed. In particular, two mean lifetimes were measured for the first time: τ =29 .7-9.1+11.3 ps for the 4+ state of 108Mo and τ =3 .2-0.7+0.7 ps for the 6+ state of 102Mo. Conclusions: The reduced transition strengths B (E 2 ) , calculated from lifetimes measured in this experiment, compared to beyond-mean-field calculations, indicate a gradual shape transition in the chain of molybdenum isotopes when going from A =100 to A =108 with a maximum reached at N =64 . The transition probabilities decrease for 108Mo which may be related to its well-pronounced triaxial shape indicated by the calculations.

Coordinated satellite and incoherent scatter observations. [of the ionosphere

NASA Technical Reports Server (NTRS)

Calderon, C. H. J.

1975-01-01

Measurements taken at the Jicamarca Radar Observatory at Lima, Peru during the Cooperative Sounding Rocket Program are reported. The following types of data were acquired: (1) electron density and temperature, (2) vertical plasma drift, (3) electrojet relative echo power density, (4) electrojet Doppler shift and condition, and (5) 150 km echoing region.

(abstract) Dynamics of Meteor Trails Deposited in the Equatorial Electrojet

NASA Technical Reports Server (NTRS)

Chapin, Elaine; Kudeki, Erhan

1996-01-01

Previously we reported that the meteor echoes detected at the Jicamarca Radio Observatory exhibit some unusual properties. In summary, the echo durations are very long ..., radio wave scattering is non-specular ..., and the doppler spectra of the scattered signals contain components that are red-shifted ... immediately after the onset of the echoes.

Multi-Velocity Component LDV

NASA Technical Reports Server (NTRS)

Johnson, Dennis A. (Inventor)

1996-01-01

A laser doppler velocimeter uses frequency shifting of a laser beam to provide signal information for each velocity component. A composite electrical signal generated by a light detector is digitized and a processor produces a discrete Fourier transform based on the digitized electrical signal. The transform includes two peak frequencies corresponding to the two velocity components.

Solar Dynamics Observatory Lessons Learned

NASA Technical Reports Server (NTRS)

Rivera, Rachel; Uhl, Andrew; Secunda, Mark

2010-01-01

Mission is to study how solar activity is created and how space weather results from that activity. Atmospheric Imaging Assembly (AIA): High Resolution Images of 10 wavelengths every 10 seconds. Extreme Ultraviolet Variability Experiment (EVE): Measure Sun's brightness in EUV. Helioseismic and Magnetic Imager (HMI): Measures Doppler shift to study waves of the Sun. Launched February 11, 2010.

Integrated Modeling and Analysis of Physical Oceanographic and Acoustic Processes

DTIC Science & Technology

2013-09-30

email: swinney@chaos.utexas.edu John Wilkin Department of Marine and Coastal Sciences, Rutgers University New Brunswick, NJ 08901-8521 phone...Doppler-shift field scattered by an object moving in a stratified medium, J. Acoust. Soc. Am., 113, 223-244, 2003. [11] Tang , D. J., J. N. Moum, J. F

Ultrafast two-dimensional lithium beam emission spectroscopy diagnostic on the EAST tokamak

NASA Astrophysics Data System (ADS)

Zoletnik, S.; Hu, G. H.; Tál, B.; Dunai, D.; Anda, G.; Asztalos, O.; Pokol, G. I.; Kálvin, S.; Németh, J.; Krizsanóczi, T.

2018-06-01

A diagnostic instrument is described for the Experimental Advanced Superconducting Tokamak (EAST) for the measurement of the edge plasma electron density profile and plasma turbulence properties. An accelerated neutral lithium beam is injected into the tokamak and the Doppler shifted 670.8 nm light emission of the Li2p-2s transition is detected. A novel compact setup is used, where the beam injection and observation take place from the same equatorial diagnostic port and radial-poloidal resolution is achieved with microsecond time resolution. The observation direction is optimized in order to achieve a sufficient Doppler shift of the beam light to be able to separate from the strong edge lithium line emission on this lithium coated device. A 250 kHz beam chopping technique is also demonstrated for the removal of background light. First results show the capability of measuring turbulence and its poloidal flow velocity in the scrape-off layer and edge region and the resolution of details of transient phenomena like edge localized modes with few microsecond time resolution.

Nuclear transition moment measurements of neutron rich nuclei

NASA Astrophysics Data System (ADS)

Starosta, Krzysztof

2009-10-01

The Recoil Distance Method (RDM) and related Doppler Shift Attenuation Method (DSAM) are well-established tools for lifetime measurements following nuclear reactions near the Coulomb barrier. Recently, the RDM was implemented at National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University using NSCL/K"oln plunger device and a unique combination of the state-of-the-art instruments available there. Doppler-shift lifetime measurements following Coulomb excitation, knock-out, and fragmentation at intermediate energies of ˜100 MeV/u hold the promise of providing lifetime information for excited states in a wide range of unstable nuclei. So far, the method was used to investigate the collectivity of the neutron-rich ^16,18,20C, ^62,64,66Fe, ^70,72Ni, ^110,114Pd isotopes and also of the neutron-deficient N=Z ^64Ge. A significant fraction of these experiments was performed using NSCL's Segmented Germanium Array instrumented with the Digital Data Acquisition System which enables gamma-ray tracking. The impact of GRETINA and gamma-ray tracking on RDM and DSAM studies of neutron-rich nuclei will be discussed.

Fourier transform spectrometer observations of solar carbon monoxide. III - Time-resolved spectroscopy of the Delta V = 1 bands

NASA Astrophysics Data System (ADS)

Ayres, Thomas R.; Brault, James W.

1990-11-01

Time series of the 2100/cm Delta v = 1 absorption bands of CO at the center of the solar disk and at the extreme limb have been recorded by Fourier transform spectrometer. The photospheric 5-min oscillation appears prominently at sun center. The peak-to-peak brightness temperature amplitude is roughly 300 K, and the peak-to-peak Doppler shift is roughly 1100 m/s. The 70 deg phase lag of maximum core intensity with respect to maximum redshift for the strongest Delta v = 1 absorptions is less than the 90 deg expected in the adiabatic limit. No dominant four-minute signal in the line intensity like that reported by Deming et al. (1984, 1986, and 1987) is found, nor is evidence for extreme fluctuations on short time scales like those proposed by Kalkofen et al. (1984). The strong Delta v = 1 lines exhibit systematic Doppler shifts of less than about 1 km/s, contrary to the predictions of transonic redshifts if the CO 'clouds' are associated with a dynamic cooling phase of the Ca II 'cell flashes.'

First artificial periodic inhomogeneity experiments at HAARP

NASA Astrophysics Data System (ADS)

Hysell, D. L.; McCarrick, M. J.; Fallen, C. T.; Vierinen, J.

2015-03-01

Experiments involving the generation and detection of artificial periodic inhomogeneities have been performed at the High Frequency Active Auroral Research Program (HAARP) facility. Irregularities were created using powerful X-mode HF emissions and then probed using short (10 μs) X- and O-mode pulses. Reception was performed using a portable software-defined receiver together with the crossed rhombic antenna from the local ionosonde. Echoes were observed reliably between about 85 and 140 km altitude with signal-to-noise ratios as high as about 30 dB. The Doppler shift of the echoes can be associated with the vertical neutral wind in this altitude range. Small but persistent Doppler shifts were observed. The decay time constant of the echoes is meanwhile indicative of the ambipolar diffusion coefficient which depends on the plasma temperature, composition, and neutral gas density. The measured time constants appear to be consistent with theoretical expectations and imply a methodology for measuring neutral density profiles. The significance of thermospheric vertical neutral wind and density measurements which are difficult to obtain using ground-based instruments by other means is discussed.

A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s(-1).

PubMed

Li, Chih-Hao; Benedick, Andrew J; Fendel, Peter; Glenday, Alexander G; Kärtner, Franz X; Phillips, David F; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L

2008-04-03

Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm s(-1) (ref. 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earth-like orbit, a precision of approximately 5 cm s(-1) is necessary. The combination of a laser frequency comb with a Fabry-Pérot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40-GHz (approximately 1-A) line spacing, generated from a 1-GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or 'astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm s(-1) in astronomical radial velocity measurements.

``Simplest Molecule'' Clarifies Modern Physics II. Relativistic Quantum Mechanics

NASA Astrophysics Data System (ADS)

Harter, William; Reimer, Tyle

2015-05-01

A ``simplest molecule'' consisting of CW- laser beam pairs helps to clarify relativity from poster board - I. In spite of a seemingly massless evanescence, an optical pair also clarifies classical and quantum mechanics of relativistic matter and antimatter. Logical extension of (x,ct) and (ω,ck) geometry gives relativistic action functions of Hamiltonian, Lagrangian, and Poincare that may be constructed in a few ruler-and-compass steps to relate relativistic parameters for group or phase velocity, momentum, energy, rapidity, stellar aberration, Doppler shifts, and DeBroglie wavelength. This exposes hyperbolic and circular trigonometry as two sides of one coin connected by Legendre contact transforms. One is Hamiltonian-like with a longitudinal rapidity parameter ρ (log of Doppler shift). The other is Lagrange-like with a transverse angle parameter σ (stellar aberration). Optical geometry gives recoil in absorption, emission, and resonant Raman-Compton acceleration and distinguishes Einstein rest mass, Galilean momentum mass, and Newtonian effective mass. (Molecular photons appear less bullet-like and more rocket-like.) In conclusion, modern space-time physics appears as a simple result of the more self-evident Evenson's axiom: ``All colors go c.''

"simplest Molecule" Clarifies Modern Physics II. Relativistic Quantum Mechanics

NASA Astrophysics Data System (ADS)

Reimer, T. C.; Harter, W. G.

2014-06-01

A "simplest molecule" consisting of CW-laser beam pairs helps to clarify relativity in Talk I. In spite of a seemingly massless evanescence, an optical pair also clarifies classical and quantum mechanics of relativistic matter and anti-matter. *Logical extension of (x,ct) and (ω,ck) geometry gives relativistic action functions of Hamiltonian, Lagrangian, and Poincare that may be constructed in a few ruler-and-compass steps to relate relativistic parameters for group or phase velocity, momentum, energy, rapidity, stellar aberration, Doppler shifts, and DeBroglie wavelength. This exposes hyperbolic and circular trigonometry as two sides of one coin connected by Legendre contact transforms. One is Hamiltonian-like with a longitudinal rapidity parameter ρ (log of Doppler shift). The other is Lagrange-like with a transverse angle parameter σ (stellar aberration). Optical geometry gives recoil in absorption, emission, and resonant Raman-Compton acceleration and distinguishes Einstein rest mass, Galilean momentum mass, and Newtonian effective mass. (Molecular photons appear less bullet-like and more rocket-like.) In conclusion, modern space-time physics appears as a simple result of the more self-evident Evenson's axiom: "All colors go c."

Lifetimes of $sup 55$Co excited levels

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

Neal, G.F.; Chagnon, P.R.

1976-02-01

Gamma-rays deexciting $sup 55$CO levels have been studied in coincidence with deuterons detected in a particle telescope, in the $sup 54$Fe($sup 3$He,d$gamma$)$sup 55$Co reaction. Excitation energies, relative $gamma$-ray intensities, and Doppler-shift attenuations of 12 levels have been measured. Mean lifetimes and transition strengths are reported. The Doppler-shifted line shape of the 2164$Yields$0-keV transition has been analyzed and has been found consistent with the assumption of a single level. Lifetimes of selected levels are: 2164 keV, 125$sup +25$/sub -//sub 2//sub 0/ fs; 3301 keV, 50$sup +20$/sub -// sub 1//sub 5/ fs; 3322 keV, 45$sup +15$/sub -//sub 1//sub 0/ fs; 3641 keV,more » 300$sup +150$/sub -//sub 1//sub 0//sub 0/ fs; 4163 keV, 30$sup +15$/sub -//sub 1// sub 0/ fs; 4714 keV, 300$sup +200$/sub -//sub 1//sub 5//sub 0/ fs; 4719 keV, <30 fs; and 5172 keV, 10$sup +10$/sub -//sub 5/ fs. (AIP)« less

Doppler-shift compensation in the Taiwanese leaf-nosed bat (Hipposideros terasensis) recorded with a telemetry microphone system during flight

NASA Astrophysics Data System (ADS)

Hiryu, Shizuko; Katsura, Koji; Lin, Liang-Kong; Riquimaroux, Hiroshi; Watanabe, Yoshiaki

2005-12-01

Biosonar behavior was examined in Taiwanese leaf-nosed bats (Hipposideros terasensis; CF-FM bats) during flight. Echolocation sounds were recorded using a telemetry microphone mounted on the bat's head. Flight speed and three-dimensional trajectory of the bat were reconstructed from images taken with a dual high-speed video camera system. Bats were observed to change the intensity and emission rate of pulses depending on the distance from the landing site. Frequencies of the dominant second harmonic constant frequency component (CF2) of calls estimated from the bats' flight speed agreed strongly with observed values. Taiwanese leaf-nosed bats changed CF2 frequencies depending on flight speed, which caused the CF2 frequencies of the Doppler-shifted echoes to remain constant. Pulse frequencies were also estimated using echoes returning directly ahead of the bat and from its sides for two different flight conditions: landing and U-turn. Bats in flight may periodically alter their attended angles from the front to the side when emitting echolocation pulses.

Using Radars in Place of Magnetometers: Detection and Properties of Pc3-5 Wave Fields in HF Radar Data

NASA Astrophysics Data System (ADS)

Ponomarenko, P.; Menk, F. W.; Waters, C. L.

2004-12-01

SuperDARN HF radars are usually used to examine HF echoes from field-aligned ionospheric irregularity structures. However, ground scatter is also often recorded. Because the ground scatter signal is reflected from the ionosphere its Doppler shift is a sensitive indicator of ionospheric motions. We have used the TIGER radar, which operates at relatively low latitudes, to examine ground scatter returns with high time resolution. Ground scatter returns are present virtually every day and wave-like Doppler shift features are evident almost each time. Comparison with ground magnetometer data shows that these are the ionospheric signature of downgoing ULF waves. Several different types of wave features have been observed, including very large scale Pc5, harmonics of field line resonances in the Pc3-4 range, and bandlimited Pc4 at night. This paper presents examples and discusses the wave generation and propagation mechanisms. Furthermore, estimates of the ionospheric transfer function over the 10-110 mHz range are compared with results of numerical and analytical modelling.

Testing a dynamic-field account of interactions between spatial attention and spatial working memory.

PubMed

Johnson, Jeffrey S; Spencer, John P

2016-05-01

Studies examining the relationship between spatial attention and spatial working memory (SWM) have shown that discrimination responses are faster for targets appearing at locations that are being maintained in SWM, and that location memory is impaired when attention is withdrawn during the delay. These observations support the proposal that sustained attention is required for successful retention in SWM: If attention is withdrawn, memory representations are likely to fail, increasing errors. In the present study, this proposal was reexamined in light of a neural-process model of SWM. On the basis of the model's functioning, we propose an alternative explanation for the observed decline in SWM performance when a secondary task is performed during retention: SWM representations drift systematically toward the location of targets appearing during the delay. To test this explanation, participants completed a color discrimination task during the delay interval of a spatial-recall task. In the critical shifting-attention condition, the color stimulus could appear either toward or away from the midline reference axis, relative to the memorized location. We hypothesized that if shifting attention during the delay leads to the failure of SWM representations, there should be an increase in the variance of recall errors, but no change in directional errors, regardless of the direction of the shift. Conversely, if shifting attention induces drift of SWM representations-as predicted by the model-systematic changes in the patterns of spatial-recall errors should occur that would depend on the direction of the shift. The results were consistent with the latter possibility-recall errors were biased toward the locations of discrimination targets appearing during the delay.

Testing a Dynamic Field Account of Interactions between Spatial Attention and Spatial Working Memory

PubMed Central

Johnson, Jeffrey S.; Spencer, John P.

2016-01-01

Studies examining the relationship between spatial attention and spatial working memory (SWM) have shown that discrimination responses are faster for targets appearing at locations that are being maintained in SWM, and that location memory is impaired when attention is withdrawn during the delay. These observations support the proposal that sustained attention is required for successful retention in SWM: if attention is withdrawn, memory representations are likely to fail, increasing errors. In the present study, this proposal is reexamined in light of a neural process model of SWM. On the basis of the model's functioning, we propose an alternative explanation for the observed decline in SWM performance when a secondary task is performed during retention: SWM representations drift systematically toward the location of targets appearing during the delay. To test this explanation, participants completed a color-discrimination task during the delay interval of a spatial recall task. In the critical shifting attention condition, the color stimulus could appear either toward or away from the memorized location relative to a midline reference axis. We hypothesized that if shifting attention during the delay leads to the failure of SWM representations, there should be an increase in the variance of recall errors but no change in directional error, regardless of the direction of the shift. Conversely, if shifting attention induces drift of SWM representations—as predicted by the model—there should be systematic changes in the pattern of spatial recall errors depending on the direction of the shift. Results were consistent with the latter possibility—recall errors were biased toward the location of discrimination targets appearing during the delay. PMID:26810574

Wind profiling for a coherent wind Doppler lidar by an auto-adaptive background subtraction approach.

PubMed

Wu, Yanwei; Guo, Pan; Chen, Siying; Chen, He; Zhang, Yinchao

2017-04-01

Auto-adaptive background subtraction (AABS) is proposed as a denoising method for data processing of the coherent Doppler lidar (CDL). The method is proposed specifically for a low-signal-to-noise-ratio regime, in which the drifting power spectral density of CDL data occurs. Unlike the periodogram maximum (PM) and adaptive iteratively reweighted penalized least squares (airPLS), the proposed method presents reliable peaks and is thus advantageous in identifying peak locations. According to the analysis results of simulated and actually measured data, the proposed method outperforms the airPLS method and the PM algorithm in the furthest detectable range. The proposed method improves the detection range approximately up to 16.7% and 40% when compared to the airPLS method and the PM method, respectively. It also has smaller mean wind velocity and standard error values than the airPLS and PM methods. The AABS approach improves the quality of Doppler shift estimates and can be applied to obtain the whole wind profiling by the CDL.

Evaluation of portal venous velocity with Doppler ultrasound in patients with nonalcoholic fatty liver disease.

PubMed

Ulusan, Serife; Yakar, Tolga; Koc, Zafer

2011-01-01

We examined the relationship between portal venous velocity and hepatic-abdominal fat in patients with nonalcoholic fatty liver disease (NAFLD), using spectral Doppler ultrasonography (US) and magnetic resonance imaging (MRI). In this prospective study, 35 patients with NAFLD and 29 normal healthy adults (control group) underwent portal Doppler US. The severity of hepatic steatosis in patients with NAFLD was assessed by MRI through chemical shift imaging, using a modification of the Dixon method. Abdominal (intra-abdominal and subcutaneous) fat was measured by MRI. The difference in portal venous velocity between the patients with NAFLD and the control group was significant (p < 0.0001). There was no correlation between the degree of abdominal or hepatic fat and portal venous velocity (p > 0.05). There were strong correlations between the hepatic fat fraction and subcutaneous adiposity (p < 0.0001), intraperitoneal fat accumulation (p = 0.017), and retroperitoneal fat accumulation (p < 0.0001). Our findings suggest that patients with NAFLD have lower portal venous velocities than normal healthy subjects.

Infrasonic waves in the ionosphere generated by a weak earthquake

NASA Astrophysics Data System (ADS)

Krasnov, V. M.; Drobzheva, Ya. V.; Chum, J.

2011-08-01

A computer code has been developed to simulate the generation of infrasonic waves (frequencies considered ≤80 Hz) by a weak earthquake (magnitude ˜3.6), their propagation through the atmosphere and their effects in the ionosphere. We provide estimates of the perturbations in the ionosphere at the height (˜160 km) where waves at the sounding frequency (3.59 MHz) of a continuous Doppler radar reflect. We have found that the pressure perturbation is 5.79×10-7 Pa (0.26% of the ambient value), the temperature perturbation is 0.088 K (0.015% of the ambient value) and the electron density perturbation is 2×108 m-3 (0.12% of the ambient value). The characteristic perturbation is found to be a bipolar pulse lasting ˜25 s, and the maximum Doppler shift is found to be ˜0.08 Hz, which is too small to be detected by the Doppler radar at the time of the earthquake.

Doppler-Zeeman mapping of the magnetic CP star HD 215441

NASA Astrophysics Data System (ADS)

Khokhlova, V. L.; Vasilchenko, D. V.; Stepanov, V. V.; Tsymbal, V. V.

1997-07-01

The method of Vasilchenko et al. (1996) is used to obtain a Doppler-Zeeman map of the magnetic CP star HD 215441. The magnetic field is approximated by a magnetic dipole that is arbitrarily shifted from the star center. The solution of the inverse problem yields the dipole parameters and the maps of Si, Ti, Cr, and Fe abundance anomalies; the coordinates of local magnetic vectors on the star surface are computed. A comparison of the distribution of abundance anomalies and the magnetic-field configuration reveals that in the region where the magnetic-field lines are vertical (near the magnetic pole), Si, Ti and Cr are highly deficient, while the Fe enhancement is strongest. In the regions where the magnetic-field lines are horizontal (near the magnetic equator), Si, Ti and Cr show the greatest overabundance. In these regions, the Fe abundance is also slightly enhanced and exhibits, as it were, a secondary maximum. The factors that limit the accuracy of Doppler-Zeeman mapping are reviewed.

Recent Doppler Backscattering results from EAST tokamak

NASA Astrophysics Data System (ADS)

Zhou, Chu; Liu, Adi; Zhang, Xiaohui; Hu, Jianqiang; Wang, Mingyuan; Yu, Changxuan; Liu, Wandong; Li, Hong; Lan, Tao; Sun, Xuan; Xie, Jinlin; Ding, Weixing; CAS Key Laboratory of Geospace Environment, University of Science and Technology of China Team; Department of Physics and Astronomy, University of California at Los Angeles Collaboration

2013-10-01

A Doppler reflectometer system has recently been installed in the EAST tokamak. It includes two separated systems, one for Q-band and the other for V-band. The optical system consists of a fixed flat mirror and a steerable parabolic mirror, which enabling the measurement of perpendicular wave number in the range of 4-22/cm, with the wave number resolution around 2/cm, while the radial location can cover the whole minor radius for L mode and the whole pedestal for H mode on EAST. A 2D Gaussion Ray tracing code is used to calculate the scattering location, the perpendicular wave number and the resolution. In EAST last experimental campaign the Doppler shifted signals have been obtained and the radial profiles of the perpendicular propagation velocity during L-mode and H-mode are calculated. The Er evolution during L-H and H-L transition have also been measured. The two separated systems are also used as a poloidal coherent system together to study the GAM in EAST tokamak.

Evaluating the performance of Sentinel-3 SRAL SAR Altimetry in the Coastal and Open Ocean, and developing improved retrieval methods - The ESA SCOOP Project.

NASA Astrophysics Data System (ADS)

Benveniste, J.; Cotton, D.; Moreau, T.; Varona, E.; Roca, M.; Cipollini, P.; Cancet, M.; Martin, F.; Fenoglio-Marc, L.; Naeije, M.; Fernandes, J.; Restano, M.; Ambrozio, A.

2016-12-01

The ESA Sentinel-3 satellite, launched in February 2016 as a part of the Copernicus programme, is the second satellite to operate a SAR mode altimeter. The Sentinel 3 Synthetic Aperture Radar Altimeter (SRAL) is based on the heritage from Cryosat-2, but this time complemented by a Microwave Radiometer (MWR) to provide a wet troposphere correction, and operating at Ku and C-Bands to provide an accurate along-track ionospheric correction. Together this instrument package, including both GPS and DORIS instruments for accurate positioning, allows accurate measurements of sea surface height over the ocean, as well as measurements of significant wave height and surface wind speed. SCOOP (SAR Altimetry Coastal & Open Ocean Performance) is a project funded under the ESA SEOM (Scientific Exploitation of Operational Missions) Programme Element, started in September 2015, to characterise the expected performance of Sentinel-3 SRAL SAR mode altimeter products, in the coastal zone and open-ocean, and then to develop and evaluate enhancements to the baseline processing scheme in terms of improvements to ocean measurements. There is also a work package to develop and evaluate an improved Wet Troposphere correction for Sentinel-3, based on the measurements from the on-board MWR, further enhanced mostly in the coastal and polar regions using third party data, and provide recommendations for use. At the end of the project recommendations for further developments and implementations will be provided through a scientific roadmap. In this presentation we provide an overview of the SCOOP project, highlighting the key deliverables and discussing the potential impact of the results in terms of the application of delay-Doppler (SAR) altimeter measurements over the open-ocean and coastal zone. We also present the initial results from the project, including: Key findings from a review of the current "state-of-the-art" for SAR altimetry, Specification of the initial "reference" delay-Doppler and echo modelling /retracking processing schemes, Evaluation of the initial Test Data Set in the Open Ocean and Coastal Zone Overview of modifications planned to the reference delay-Doppler and echo modelling/ re-tracking processing schemes.

Maps of interaural delay in the owl's nucleus laminaris

PubMed Central

Shah, Sahil; McColgan, Thomas; Ashida, Go; Kuokkanen, Paula T.; Brill, Sandra; Kempter, Richard; Wagner, Hermann

2015-01-01

Axons from the nucleus magnocellularis form a presynaptic map of interaural time differences (ITDs) in the nucleus laminaris (NL). These inputs generate a field potential that varies systematically with recording position and can be used to measure the map of ITDs. In the barn owl, the representation of best ITD shifts with mediolateral position in NL, so as to form continuous, smoothly overlapping maps of ITD with iso-ITD contours that are not parallel to the NL border. Frontal space (0°) is, however, represented throughout and thus overrepresented with respect to the periphery. Measurements of presynaptic conduction delay, combined with a model of delay line conduction velocity, reveal that conduction delays can account for the mediolateral shifts in the map of ITD. PMID:26224776

A Control Allocation Technique to Recover From Pilot-Induced Oscillations (CAPIO) Due to Actuator Rate Limiting

NASA Technical Reports Server (NTRS)

Yildiz, Yildiray; Kolmanovsky, Ilya V.

2010-01-01

This paper proposes a control allocation technique that can help pilots recover from pilot induced oscillations (PIO). When actuators are rate-saturated due to aggressive pilot commands, high gain flight control systems or some anomaly in the system, the effective delay in the control loop may increase depending on the nature of the cause. This effective delay increase manifests itself as a phase shift between the commanded and actual system signals and can instigate PIOs. The proposed control allocator reduces the effective time delay by minimizing the phase shift between the commanded and the actual attitude accelerations. Simulation results are reported, which demonstrate phase shift minimization and recovery from PIOs. Conversion of the objective function to be minimized and constraints to a form that is suitable for implementation is given.

Vasospasm on transcranial Doppler is predictive of delayed cerebral ischemia in aneurysmal subarachnoid hemorrhage: a systematic review and meta-analysis.

PubMed

Kumar, Gyanendra; Shahripour, Reza Bavarsad; Harrigan, Mark R

2016-05-01

OBJECT The impact of transcranial Doppler (TCD) ultrasonography evidence of vasospasm on patient-centered clinical outcomes following aneurysmal subarachnoid hemorrhage (aSAH) is unknown. Vasospasm is known to lead to delayed cerebral ischemia (DCI) and poor outcomes. This systematic review and meta-analysis evaluates the predictive value of vasospasm on DCI, as diagnosed on TCD. METHODS MEDLINE, Scopus, the Cochrane trial register, and clinicaltrials.gov were searched through September 2014 using key words and the terms "subarachnoid hemorrhage," "aneurysm," "aneurysmal," "cerebral vasospasm," "vasospasm," "transcranial Doppler," and "TCD." Sensitivities, specificities, and positive and negative predictive values were pooled by a DerSimonian and Laird random-effects model. RESULTS Seventeen studies (n = 2870 patients) met inclusion criteria. The amount of variance attributable to heterogeneity was significant (I(2) > 50%) for all syntheses. No studies reported the impact of TCD evidence of vasospasm on functional outcome or mortality. TCD evidence of vasospasm was found to be highly predictive of DCI. Pooled estimates for TCD diagnosis of vasospasm (for DCI) were sensitivity 90% (95% confidence interval [CI] 77%-96%), specificity 71% (95% CI 51%-84%), positive predictive value 57% (95% CI 38%-71%), and negative predictive value 92% (95% CI 83%-96%). CONCLUSIONS TCD evidence of vasospasm is predictive of DCI with high accuracy. Although high sensitivity and negative predictive value make TCD an ideal monitoring device, it is not a mandated standard of care in aSAH due to the paucity of evidence on clinically relevant outcomes, despite recommendation by national guidelines. High-quality randomized trials evaluating the impact of TCD monitoring on patient-centered and physician-relevant outcomes are needed.

Turbulence and Heating in the Flank and Wake Regions of a Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Fan, Siteng; He, Jiansen; Yan, Limei; Tomczyk, Steven; Tian, Hui; Song, Hongqiang; Wang, Linghua; Zhang, Lei

2018-01-01

As a coronal mass ejection (CME) passes, the flank and wake regions are typically strongly disturbed. Various instruments, including the Large Angle and Spectroscopic Coronagraph (LASCO), the Atmospheric Imaging Assembly (AIA), and the Coronal Multi-channel Polarimeter (CoMP), observed a CME close to the east limb on 26 October 2013. A hot ({≈} 10 MK) rising blob was detected on the east limb, with an initial ejection flow speed of {≈} 330 km s^{-1}. The magnetic structures on both sides and in the wake of the CME were strongly distorted, showing initiation of turbulent motions with Doppler-shift oscillations enhanced from {≈} ± 3 km s^{-1} to {≈} ± 15 km s^{-1} and effective thermal velocities from {≈} 30 km s^{-1} to {≈} 60 km s^{-1}, according to the CoMP observations at the Fe xiii line. The CoMP Doppler-shift maps suggest that the turbulence behaved differently at various heights; it showed clear wave-like torsional oscillations at lower altitudes, which are interpreted as the antiphase oscillation of an alternating red/blue Doppler shift across the strands at the flank. The turbulence seems to appear differently in the channels of different temperatures. Its turnover time was {≈} 1000 seconds for the Fe 171 Å channel, while it was {≈} 500 seconds for the Fe 193 Å channel. Mainly horizontal swaying rotations were observed in the Fe 171 Å channel, while more vertical vortices were seen in the Fe 193 Å channel. The differential-emission-measure profiles in the flank and wake regions have two components that evolve differently: the cool component decreased over time, evidently indicating a drop-out of cool materials due to ejection, while the hot component increased dramatically, probably because of the heating process, which is suspected to be a result of magnetic reconnection and turbulence dissipation. These results suggest a new turbulence-heating scenario of the solar corona and solar wind.

Laboratory study of collisionless coupling between explosive debris plasma and magnetized ambient plasma

NASA Astrophysics Data System (ADS)

Bondarenko, A. S.; Schaeffer, D. B.; Everson, E. T.; Clark, S. E.; Lee, B. R.; Constantin, C. G.; Vincena, S.; Van Compernolle, B.; Tripathi, S. K. P.; Winske, D.; Niemann, C.

2017-08-01

The explosive expansion of a localized plasma cloud into a relatively tenuous, magnetized, ambient plasma characterizes a variety of astrophysical and space phenomena. In these rarified environments, collisionless electromagnetic processes rather than Coulomb collisions typically mediate the transfer of momentum and energy from the expanding "debris" plasma to the surrounding ambient plasma. In an effort to better understand the detailed physics of collisionless coupling mechanisms, compliment in situ measurements of space phenomena, and provide validation of previous computational and theoretical work, the present research jointly utilizes the Large Plasma Device and the Raptor laser facility at the University of California, Los Angeles to study the super-Alfvénic, quasi-perpendicular expansion of laser-produced carbon (C) and hydrogen (H) debris plasma through preformed, magnetized helium (He) ambient plasma via a variety of diagnostics, including emission spectroscopy, wavelength-filtered imaging, and a magnetic flux probe. Doppler shifts detected in a He1+ ion spectral line indicate that the ambient ions initially accelerate transverse to both the debris plasma flow and the background magnetic field. A qualitative analysis in the framework of a "hybrid" plasma model (kinetic ions and inertia-less fluid electrons) demonstrates that the ambient ion trajectories are consistent with the large-scale laminar electric field expected to develop due to the expanding debris. In particular, the transverse ambient ion motion provides direct evidence of Larmor coupling, a collisionless momentum exchange mechanism that has received extensive theoretical and numerical investigation. In order to quantitatively evaluate the observed Doppler shifts, a custom simulation utilizing a detailed model of the laser-produced debris plasma evolution calculates the laminar electric field and computes the initial response of a distribution of ambient test ions. A synthetic Doppler-shifted spectrum constructed from the simulated test ion velocities excellently reproduces the experimental measurements, verifying that the observed ambient ion motion corresponds to collisionless coupling through the laminar electric field.

Spectroscopic monitoring of SS 433: A search for long-term variations of kinematic model parameters

NASA Astrophysics Data System (ADS)

Davydov, V. V.; Esipov, V. F.; Cherepashchuk, A. M.

2008-06-01

Between 1994 and 2006, we obtained uniform spectroscopic observations of SS 433 in the region of H α. We determined Doppler shifts of the moving emission lines, H α + and H α -, and studied various irregularities in the profiles for the moving emission lines. The total number of Doppler shifts measured in these 13 years is 488 for H α - and 389 for H α +. We have also used published data to study possible long-term variations of the SS 433 system, based on 755 Doppler shifts for H α - and 630 for H α + obtained over 28 years. We have derived improved kinematic model parameters for the precessing relativistic jets of S S 433 using five-and eight-parameter models. On average, the precession period was stable during the 28 years of observations (60 precession cycles), at 162.250d ± 0.003d. Phase jumps of the precession period and random variations of its length with amplitudes of ≈6% and ≈1%, respectively, were observed, but no secular changes in the precession period were detected. The nutation period, P nut = 6.2876d ± 0.00035d, and its phase were stable during 28 years (more than 1600 nutation cycles). We find no secular variations of the nutation cycle. The ejection speed of the relativistic jets, v, was, on average, constant during the 28 years, β = v/c = 0.2561 ± 0.0157. No secular variation of β is detected. In general, S S 433 demonstrates remarkably stable long-term characteristics of its precession and nutation, as well as of the central “engine” near the relativistic object that collimates the plasma in the jets and accelerates it to v = 0.2561 c. Our results support a model with a “slaved” accretion disk in S S 433, which follows the precession of the optical star’s rotation axis.

A Novel Multiple-Access Correlation-Delay-Shift-Keying

NASA Astrophysics Data System (ADS)

Duan, J. Y.; Jiang, G. P.; Yang, H.

In Correlation-Delay-Shift-Keying (CDSK), the reference signal and the information-bearing signal are added together during a certain time delay. Because the reference signal is not strictly orthogonal to the information-bearing signal, the cross-correlation between the adjacent chaotic signal (Intra-signal Interference, ISI) will be introduced into the demodulation at the receiver. Therefore, the Bit-Error Ratio (BER) of CDSK is higher than that of Differential-Chaos-Shift-Keying (DCSK). To avoid the ISI component and enhance the BER performance of CDSK in multiuser scenario, Multiple-Access CDSK with No Intra-signal Interference (MA-CDSK-NII) is proposed. By constructing the repeated chaotic generator and applying the Walsh code sequence to modulate the reference signal, in MA-CDSK-NII, the ISI component will be eliminated during the demodulation. Gaussian approximation method is adopted here to obtain the exact performance analysis of MA-CDSK-NII over additive white Gaussian noise (AWGN) channel and Rayleigh multipath fading channels. Results show that, due to no ISI component and lower transmitting power, the BER performance of MA-CDSK-NII can be better than that of multiple-access CDSK and Code-Shifted Differential-Chaos-Shift-Keying (CS-DCSK).

Resynchronization of circadian sleep-wake and temperature cycles in the squirrel monkey following phase shifts of the environmental light-dark cycle

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

Wexler, D.B.; Moore-ede, M.C.

1986-12-01

Circadian rhythms in physiological and behavioral functions gradually resynchronize after phase shifts in environmental time cues. In order to characterize the rate of circadian resynchronization in a diurnal primate model, the temperature, locomotor activity, and polygraphically determined sleep-wake states were monitored in squirrel monkeys before and after 8-h phase shifts of an environmental light-dark cycle of 12 h light and 12 h dark (LD 12:12). For the temperature rhythm, resynchronization took 4 d after phase delay shift and 5 d after phase advance shift; for the rest-activity cycle, resynchronization times were 3 d and 6 d, respectively. The activity acrophasemore » shifted more rapidly than the temperature acrophase early in the post-delay shift interval, but this internal desynchronization between rhythms disappeared during the course of resynchronization. Further study of the early resynchronization process requires emphasis on identifying evoked effects and measuring circadian pacemaker function. 13 references.« less

Resynchronization of circadian sleep-wake and temperature cycles in the squirrel monkey following phase shifts of the environmental light-dark cycle

NASA Technical Reports Server (NTRS)

Wexler, D. B.; Moore-Ede, M. C.

1986-01-01

Circadian rhythms in physiological and behavioral functions gradually resynchronize after phase shifts in environmental time cues. In order to characterize the rate of circadian resynchronization in a diurnal primate model, the temperature, locomotor activity, and polygraphically determined sleep-wake states were monitored in squirrel monkeys before and after 8-h phase shifts of an environmental light-dark cycle of 12 h light and 12 h dark (LD 12:12). For the temperature rhythm, resynchronization took 4 d after phase delay shift and 5 d after phase advance shift; for the rest-activity cycle, resynchronization times were 3 d and 6 d, respectively. The activity acrophase shifted more rapidly than the temperature acrophase early in the post-delay shift interval, but this internal desynchronization between rhythms disappeared during the course of resynchronization. Further study of the early resynchronization process requires emphasis on identifying evoked effects and measuring circadian pacemaker function.

Rapid intensity and velocity variations in solar transition region lines

NASA Astrophysics Data System (ADS)

Hansteen, V. H.; Betta, R.; Carlsson, M.

2000-08-01

We have obtained short exposure (3 s) time series of strong upper chromospheric and transition region emission lines from the quiet Sun with the SUMER instrument onboard SOHO during two 1 hour periods in 1996. With a Nyqvist frequency of 167 mHz and relatively high count rates the dataset is uniquely suited for searching for high frequency variations in intensity and Doppler velocity. From Monte-Carlo experiments taking into account the photon-counting statistics we estimate our detection limit to correspond to a wave-packet of four periods coherent over 3'' with a Doppler-shift amplitude of 2.5km s-1 in the darkest internetwork areas observed in C III. In the network the detection limit is estimated to be 1.5km s-1. Above 50 mHz we detect wave-packet amplitudes above 3km s-1 less than 0.5% of the time. Between 20 and 50 mHz we detect some wave-packets with a typical duration of four periods and amplitudes up to 8km s-1. At any given internetwork location these wave-packets are present 1% of the time. In the 10-20 mHz range we see amplitudes above 3km s-1 12% of the time. At lower frequencies our dataset is consistent with other SUMER datasets reported in the literature. The chromospheric 3-7 mHz signal is discernible in the line emission. In the internetwork this is the dominant oscillation frequency but higher frequencies (7-10 mHz) are often present and appear coherent in Doppler velocity over large spatial regions (≍ 40"). Wavelet analysis implies that these oscillations have typical durations of 1000s. The network emission also shows a 5 mHz signal but is dominated by low frequency variations (of < 4 mHz) in both intensity and velocity. The oscillations show less power in intensity than in velocity. We find that while both red and blue shifted emission is observed, the transition region lines are on average red shifted between 5-10km s-1 in the network. A net red shift is also found in the internetwork emission but it is smaller (< 4km s-1). The line widths do not differ much between the internetwork and network, the non-thermal line widths increase with increasing temperature of line formation from 30km s-1 for the C II 1334 Å line to 45km s-1 for the O VI 1032 Å line. By constructing scatterplots of velocity versus intensity we find that in the network a mean redshift is correlated with a high mean intensity. In the internetwork regions we do not find any correlation between the intensity and the Doppler velocity.

Coherent optical transients observed in rubidium atomic line filtered Doppler velocimetry experiments

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

Fajardo, Mario E., E-mail: mario.fajardo@eglin.af.mil; Molek, Christopher D.; Vesely, Annamaria L.

2015-10-14

We report the first successful results from our novel Rubidium Atomic Line Filtered (RALF) Doppler velocimetry apparatus, along with unanticipated oscillatory signals due to coherent optical transients generated within pure Rb vapor cells. RALF is a high-velocity and high-acceleration extension of the well-known Doppler Global Velocimetry (DGV) technique for constructing multi-dimensional flow velocity vector maps in aerodynamics experiments [H. Komine, U.S. Patent No. 4,919,536 (24 April 1990)]. RALF exploits the frequency dependence of pressure-broadened Rb atom optical absorptions in a heated Rb/N{sub 2} gas cell to encode the Doppler shift of reflected near-resonant (λ{sub 0} ≈ 780.24 nm) laser light onto the intensitymore » transmitted by the cell. The present RALF apparatus combines fiber optic and free-space components and was built to determine suitable operating conditions and performance parameters for the Rb/N{sub 2} gas cells. It yields single-spot velocities of thin laser-driven-flyer test surfaces and incorporates a simultaneous Photonic Doppler Velocimetry (PDV) channel [Strand et al., Rev. Sci. Instrum. 77, 083108 (2006)] for validation of the RALF results, which we demonstrate here over the v = 0 to 1 km/s range. Both RALF and DGV presume the vapor cells to be simple Beer's Law optical absorbers, so we were quite surprised to observe oscillatory signals in experiments employing low pressure pure Rb vapor cells. We interpret these oscillations as interference between the Doppler shifted reflected light and the Free Induction Decay (FID) coherent optical transient produced within the pure Rb cells at the original laser frequency; this is confirmed by direct comparison of the PDV and FID signals. We attribute the different behaviors of the Rb/N{sub 2} vs. Rb gas cells to efficient dephasing of the atomic/optical coherences by Rb-N{sub 2} collisions. The minimum necessary N{sub 2} buffer gas density ≈0.3 amagat translates into a smallest useful velocity range of 0 to 2 km/s, which can readily be extended to cover the 0 to 10 km/s range, and beyond. The recognition that coherent optical transients can be produced within low pressure vapor cells during velocimetry experiments may offer new insights into some quantitative discrepancies reported in earlier DGV studies. Future plans include “line-RALF” experiments with streak camera detection, and two-dimensional surface velocity mapping using pulsed laser illumination and/or gated intensified CCD camera detection.« less

GLOBAL SAUSAGE OSCILLATION OF SOLAR FLARE LOOPS DETECTED BY THE INTERFACE REGION IMAGING SPECTROGRAPH

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

Tian, Hui; He, Jiansen; Young, Peter R.

An observation from the Interface Region Imaging Spectrograph reveals coherent oscillations in the loops of an M1.6 flare on 2015 March 12. Both the intensity and Doppler shift of Fe xxi 1354.08 Å show clear oscillations with a period of ∼25 s. Remarkably similar oscillations were also detected in the soft X-ray flux recorded by the Geostationary Operational Environmental Satellites ( GOES ). With an estimated phase speed of ∼2420 km s{sup −1} and a derived electron density of at least 5.4 × 10{sup 10} cm{sup −3}, the observed short-period oscillation is most likely the global fast sausage mode ofmore » a hot flare loop. We find a phase shift of ∼ π /2 (1/4 period) between the Doppler shift oscillation and the intensity/ GOES oscillations, which is consistent with a recent forward modeling study of the sausage mode. The observed oscillation requires a density contrast between the flare loop and coronal background of a factor ≥42. The estimated phase speed of the global mode provides a lower limit of the Alfvén speed outside the flare loop. We also find an increase of the oscillation period, which might be caused by the separation of the loop footpoints with time.« less

Modality-specific occult intrarenal pseudoaneurysm in a renal allograft and the legacy of catheter angiography.

PubMed

Rastogi, Neeraj; Williams, Gethin; Alencar, Herlen

2013-11-01

A 69-year-old man with history of end-stage-renal disease (ESRD) underwent successful kidney transplantation from a cadaveric donor in November 2011. However, posttransplant recovery was complicated by delayed graft function and recurrent gross hematuria. Serial Doppler ultrasound (US) of the renal allograft demonstrated a pseudoaneurysm with interval increase in size. However, it could not be visualized with other modalities, including an initial angiogram (postoperative day 49) and a second angiogram (postoperative day 68), followed by surgical exploration (postoperative day 71), which demonstrated complete intra-aneurysmal thrombosis on intraoperative Doppler US. Unfortunately, the patient's hematuria continued and a repeat Doppler US 48 hours later demonstrated a persistent pseudoaneurysm. Therefore, on postoperative day 75, we performed targeted percutaneous intra-aneurysmal thrombin injection under dual image guidance, which showed complete intra-aneurysmal thrombosis on intraprocedural Doppler US. Hematuria recurred the next day. A third angiogram (postoperative day 77) finally illuminated the hidden pseudoaneurysm occult on the first and second angiographic studies (sensitivity [index case] 33%) and surgery. This allowed for successful coil embolization of a subsegmental feeding branch with an excellent outcome. We support a more aggressive management with serial angiography and embolization of the intrarenal symptomatic pseudoaneurysm rather than surgery in renal allograft recipients, with the benefits outweighing the risks. Copyright © 2013 Elsevier Inc. All rights reserved.

Impulsive choice and pre-exposure to delays: iv. effects of delay- and immediacy-exposure training relative to maturational changes in impulsivity.

PubMed

Renee Renda, C; Rung, Jillian M; Hinnenkamp, Jay E; Lenzini, Stephanie N; Madden, Gregory J

2018-04-23

Impulsive choice describes preference for smaller, sooner rewards over larger, later rewards. Excessive delay discounting (i.e., rapid devaluation of delayed rewards) underlies some impulsive choices, and is observed in many maladaptive behaviors (e.g., substance abuse, gambling). Interventions designed to reduce delay discounting may provide therapeutic gains. One such intervention provides rats with extended training with delayed reinforcers. When compared to a group given extended training with immediate reinforcers, delay-exposed rats make significantly fewer impulsive choices. To what extent is this difference due to delay-exposure training shifting preference toward self-control or immediacy-exposure training (the putative control group) shifting preference toward impulsivity? The current study compared the effects of delay- and immediacy-exposure training to a no-training control group and evaluated within-subject changes in impulsive choice across 51 male Wistar rats. Delay-exposed rats made significantly fewer impulsive choices than immediacy-exposed and control rats. Between-group differences in impulsive choice were not observed in the latter two groups. While delay-exposed rats showed large, significant pre- to posttraining reductions in impulsive choice, immediacy-exposed and control rats showed small reductions in impulsive choice. These results suggest that extended training with delayed reinforcers reduces impulsive choice, and that extended training with immediate reinforcers does not increase impulsive choice. © 2018 Society for the Experimental Analysis of Behavior.

Assimilative model for ionospheric dynamics employing delay, Doppler, and direction of arrival measurements from multiple HF channels

NASA Astrophysics Data System (ADS)

Fridman, Sergey V.; Nickisch, L. J.; Hausman, Mark; Zunich, George

2016-03-01

We describe the development of new HF data assimilation capabilities for our ionospheric inversion algorithm called GPSII (GPS Ionospheric Inversion). Previously existing capabilities of this algorithm included assimilation of GPS total electron content data as well as assimilation of backscatter ionograms. In the present effort we concentrated on developing assimilation tools for data related to HF propagation channels. Measurements of propagation delay, angle of arrival, and the ionosphere-induced Doppler from any number of known propagation links can now be utilized by GPSII. The resulting ionospheric model is consistent with all assimilated measurements. This means that ray tracing simulations of the assimilated propagation links are guaranteed to be in agreement with measured data within the errors of measurement. The key theoretical element for assimilating HF data is the raypath response operator (RPRO) which describes response of raypath parameters to infinitesimal variations of electron density in the ionosphere. We construct the RPRO out of the fundamental solution of linearized ray tracing equations for a dynamic magnetoactive plasma. We demonstrate performance and internal consistency of the algorithm using propagation delay data from multiple oblique ionograms (courtesy of Defence Science and Technology Organisation, Australia) as well as with time series of near-vertical incidence sky wave data (courtesy of the Intelligence Advanced Research Projects Activity HFGeo Program Government team). In all cases GPSII produces electron density distributions which are smooth in space and in time. We simulate the assimilated propagation links by performing ray tracing through GPSII-produced ionosphere and observe that simulated data are indeed in agreement with assimilated measurements.

Asymmetric micro-Doppler frequency comb generation via magnetoelectric coupling

NASA Astrophysics Data System (ADS)

Filonov, Dmitry; Steinberg, Ben Z.; Ginzburg, Pavel

2017-06-01

Electromagnetic scattering from moving bodies, being an inherently time-dependent phenomenon, gives rise to a generation of new frequencies, which can be used to characterize the motion. Whereas an ordinary motion along a linear path produces a constant Doppler shift, an accelerated scatterer can generate a micro-Doppler frequency comb. The spectra produced by rotating objects were studied and observed in a bistatic lock-in detection scheme. The internal geometry of a scatterer was shown to determine the spectrum, and the degree of structural asymmetry was suggested to be identified via signatures in the micro-Doppler comb. In particular, hybrid magnetoelectric particles, showing an ultimate degree of asymmetry in forward and backward scattering directions, were investigated. It was shown that the comb in the backward direction has signatures at the fundamental rotation frequency and its odd harmonics, whereas the comb of the forward scattered field has a prevailing peak at the doubled frequency and its multiples. Additional features of the comb were shown to be affected by the dimensions of the particle and by the strength of the magnetoelectric coupling. Experimental verification was performed with a printed circuit board antenna based on a wire and a split ring, while the structure was illuminated at a 2 GHz carrier frequency. Detailed analysis of micro-Doppler combs enables remote detection of asymmetric features of distant objects and could find use in a span of applications, including stellar radiometry and radio identification.

Human middle-ear nonlinearity measurements using laser Doppler vibrometry

NASA Astrophysics Data System (ADS)

Gladiné, Kilian; Muyshondt, Pieter G. G.; Dirckx, Joris J. J.

2017-12-01

It has long been supposed that the middle-ear has near to perfect linear characteristics, and several attempts have been made to investigate this hypothesis. In conclusion, the middle-ear was regarded as a linear system at least up till sound pressure levels of 120 dB. Because of the linear relationship between Doppler shift of light and the vibration velocity of the object on which the light is reflected, laser Doppler vibrometry (LDV) is an intrinsically highly linear measurement technique. Therefore it allows straightforward detection of very small nonlinearities in a vibration response. In this paper, laser Doppler vibrometry and multisine stimulation are used to detect nonlinear distortions in the vibration response at the umbo of the tympanic membrane of seven human cadaver temporal bones. Nonlinear distortions were detected starting from sound pressure levels of 99 dB and measurements were performed up to 120 dB. These distortions can be subdivided into even degree (e.g. quadratic distortion tones) and odd degree nonlinear distortions (e.g. cubic distortion tones). We illustrate that with odd multisine stimulation the level of even and odd degree nonlinear distortions can be investigated separately. In conclusion, laser Doppler vibrometry is an adequate tool to detect nonlinear distortions in the middle-ear system and to quantify the level of such distortions even at 57 dB below the vibration response. The possibility to analyze even degree and odd degree nonlinear distortion levels separately can help in future work to pinpoint the source of the nonlinearity.

Phase shifting interferometry based on a vibration sensor - feasibility study on elimination of the depth degeneracy

NASA Astrophysics Data System (ADS)

Lee, Seung Seok; Kim, Ju Ha; Choi, Eun Seo

2017-04-01

We proposed novel phase-shifting interferometry using a fiber-optic vibration sensor. The Doppler shift in the coiled fiber caused by vibrations can be used to detect the vibrations by using a fiber-optic interferometer. The principle can be applied to induce phase shifts. While applying vibrations to the coiled fiber at various vibration frequencies, we recorded the variations in the interference fringes. The interference fringe moved to longer wavelengths when a vibration frequency was increased from 38.00 to 38.40 kHz. Phase variations of 3.59 rad/kHz were obtained. The ability to accurately control the phase by using the vibrations in the coiled fiber was demonstrated by the elimination of the depth degeneracy using the complex signal generated by the phase-shifted interference fringes. Using vibrations to control phase shifting can be an acceptable alternative to conventional methods and can be applied to resolve the depth ambiguity in Fourier domain optical coherence tomography.

Impact analysis of the transponder time delay on radio-tracking observables

NASA Astrophysics Data System (ADS)

Bertone, Stefano; Le Poncin-Lafitte, Christophe; Rosenblatt, Pascal; Lainey, Valéry; Marty, Jean-Charles; Angonin, Marie-Christine

2018-01-01

Accurate tracking of probes is one of the key points of space exploration. Range and Doppler techniques are the most commonly used. In this paper we analyze the impact of the transponder delay, i . e . the processing time between reception and re-emission of a two-way tracking link at the satellite, on tracking observables and on spacecraft orbits. We show that this term, only partially accounted for in the standard formulation of computed space observables, can actually be relevant for future missions with high nominal tracking accuracies or for the re-processing of old missions. We present several applications of our formulation to Earth flybys, the NASA GRAIL and the ESA BepiColombo missions.

Range Measurement as Practiced in the Deep Space Network

NASA Technical Reports Server (NTRS)

Berner, Jeff B.; Bryant, Scott H.; Kinman, Peter W.

2007-01-01

Range measurements are used to improve the trajectory models of spacecraft tracked by the Deep Space Network. The unique challenge of deep-space ranging is that the two-way delay is long, typically many minutes, and the signal-to-noise ratio is small. Accurate measurements are made under these circumstances by means of long correlations that incorporate Doppler rate-aiding. This processing is done with commercial digital signal processors, providing a flexibility in signal design that can accommodate both the traditional sequential ranging signal and pseudonoise range codes. Accurate range determination requires the calibration of the delay within the tracking station. Measurements with a standard deviation of 1 m have been made.

Determining the Pressure Shift of Helium I Lines Using White Dwarf Stars

NASA Astrophysics Data System (ADS)

Camarota, Lawrence

This dissertation explores the non-Doppler shifting of Helium lines in the high pressure conditions of a white dwarf photosphere. In particular, this dissertation seeks to mathematically quantify the shift in a way that is simple to reproduce and account for in future studies without requiring prior knowledge of the star's bulk properties (mass, radius, temperature, etc.). Two main methods will be used in this analysis. First, the spectral line will be quantified with a continuous wavelet transformation, and the components will be used in a chi2 minimizing linear regression to predict the shift. Second, the position of the lines will be calculated using a best-fit Levy-alpha line function. These techniques stand in contrast to traditional methods of quantifying the center of often broad spectral lines, which usually assume symmetry on the parts of the lines.

Orbit-determination performance of Doppler data for interplanetary cruise trajectories. Part 2: 8.4-GHz performance and data-weighting strategies

NASA Technical Reports Server (NTRS)

Ulvestad, J. S.

1992-01-01

A consider error covariance analysis was performed in order to investigate the orbit-determination performance attainable using two-way (coherent) 8.4-GHz (X-band) Doppler data for two segments of the planned Mars Observer trajectory. The analysis includes the effects of the current level of calibration errors in tropospheric delay, ionospheric delay, and station locations, with particular emphasis placed on assessing the performance of several candidate elevation-dependent data-weighting functions. One weighting function was found that yields good performance for a variety of tracking geometries. This weighting function is simple and robust; it reduces the danger of error that might exist if an analyst had to select one of several different weighting functions that are highly sensitive to the exact choice of parameters and to the tracking geometry. Orbit-determination accuracy improvements that may be obtained through the use of calibration data derived from Global Positioning System (GPS) satellites also were investigated, and can be as much as a factor of three in some components of the spacecraft state vector. Assuming that both station-location errors and troposphere calibration errors are reduced simultaneously, the recommended data-weighting function need not be changed when GPS calibrations are incorporated in the orbit-determination process.

Ship-based Observations of Turbulence and Stratocumulus Cloud Microphysics in the SE Pacific Ocean from the VOCALS Field Program

NASA Astrophysics Data System (ADS)

Fairall, C. W.; Williams, C.; Grachev, A. A.; Brewer, A.; Choukulkar, A.

2013-12-01

The VAMOS (VOCALS) field program involved deployment of several measurement systems based on ships, land and aircraft over the SE Pacific Ocean. The NOAA Ship Ronald H. Brown was the primary platform for surface based measurements which included the High Resolution Doppler Lidar (HRDL) and the motion-stabilized 94-GHz cloud Doppler radar (W-band radar). In this paper, the data from the W-band radar will be used to study the turbulent and microphysical structure of the stratocumulus clouds prevalent in the region. The radar data consists of a 3 Hz time series of radar parameters (backscatter coefficient, mean Doppler shift, and Doppler width) at 175 range gates (25-m spacing). Several statistical methods to de-convolve the turbulent velocity and gravitational settling velocity are examined and an optimized algorithm is developed. 20 days of observations are processed to examine in-cloud profiles of mean turbulent statistics (vertical velocity variance, skewness, dissipation rate) in terms of surface fluxes and estimates of entrainment and cloudtop radiative cooling. The clean separation of turbulent and fall velocities will allow us to compute time-averaged drizzle-drop size spectra within and below the cloud that are significantly superior to previous attempts with surface-based marine cloud radar observations.

L'effet Doppler et le décalage vers le rouge en mécanique rationnelle: applications et verifications experimentales.

PubMed

Loiseaus, J

1968-07-01

Shifts z and z' toward the red of the galaxy NGC 5668 for a beam of 21 cm, z measured in radioastronomy with a frequency meter and z' measured in optics with a spectrograph, not being equal, it follows that the speed of light from a galaxy c ' is not equal to that of a galaxy c which is measured on earth from stationary source. The Doppler empirical formula cannot be explained in classical mechanics since it is in contradiction with it. As for the theory of relativity c ' = c from a postulate and z' = z. If we consider the universe represented on a three-dimensional space (H), non-Euclidian, with Euclidian connection plunged in a Riemannine four-dimension space (E), a certain universal time, like that of an astronomer, can be defined and its course calculated in relation to this time: it will necessarily be confounded with the atomic clock time, but c ' not equal c and z' not equal z: the Doppler formula is not accurate. However, c ' and c as well as z' and z are so close in all the experiments carried out on earth, even when an artificial satellite is used, that the errors made in using the Doppler formula are clearly inferior to experimental errors.

(abstract) ARGOS: a System to Monitor Ulysses Nutation and Thruster Firings from Variations of the Spacecraft Radio Signal

NASA Technical Reports Server (NTRS)

McElrath, T. P.; Cangahuala, L. A.; Miller, K. J.; Stravert, L. R.; Garcia-Perez, Raul

1995-01-01

Ulysses is a spin-stabilized spacecraft that experienced significant nutation after its launch in October 1990. This was due to the Sun-spacecraft-Earth geometry, and a study of the phenomenon predicted that the nutation would again be a problem during 1994-95. The difficulty of obtaining nutation estimates in real time from the spacecraft telemetry forced the ESA/NASA Ulysses Team to explore alternative information sources. The work performed by the ESA Operations Team provided a model for a system that uses the radio signal strength measurements to monitor the spacecraft dynamics. These measurements (referred to as AGC) are provided once per second by the tracking stations of the DSN. The system was named ARGOS (Attitude Reckoning from Ground Observable Signals) after the ever-vigilant, hundred-eyed giant of Greek Mythology. The ARGOS design also included Doppler processing, because Doppler shifts indicate thruster firings commanded by the active nutation control carried out onboard the spacecraft. While there is some visibility into thruster activity from telemetry, careful processing of the high-sample-rate Doppler data provides an accurate means of detecting the presence and time of thruster firings. DSN Doppler measurements are available at a ten-per-second rate in the same tracking data block as the AGC data.

Assessment of resting-state blood flow through anterior cerebral arteries using trans-cranial doppler recordings.

PubMed

Huang, Hanrui; Sejdić, Ervin

2013-12-01

Trans-cranial Doppler (TCD) recordings are used to monitor cerebral blood flow in the main cerebral arteries. The resting state is usually characterized by the mean velocity or the maximum Doppler shift frequency (an envelope signal) by insonating the middle cerebral arteries. In this study, we characterized cerebral blood flow in the anterior cerebral arteries. We analyzed both envelope signals and raw signals obtained from bilateral insonation. We recruited 20 healthy patients and conducted the data acquisition for 15 min. Features were extracted from the time domain, the frequency domain and the time-frequency domain. The results indicate that a gender-based statistical difference exists in the frequency and time-frequency domains. However, no handedness effect was found. In the time domain, information-theoretic features indicated that mutual dependence is higher in raw signals than in envelope signals. Finally, we concluded that insonation of the anterior cerebral arteries serves as a complement to middle cerebral artery studies. Additionally, investigation of the raw signals provided us with additional information that is not otherwise available from envelope signals. Use of direct trans-cranial Doppler raw data is therefore validated as a valuable method for characterizing the resting state. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Temporal recalibration of motor and visual potentials in lag adaptation in voluntary movement.

PubMed

Cai, Chang; Ogawa, Kenji; Kochiyama, Takanori; Tanaka, Hirokazu; Imamizu, Hiroshi

2018-05-15

Adaptively recalibrating motor-sensory asynchrony is critical for animals to perceive self-produced action consequences. It is controversial whether motor- or sensory-related neural circuits recalibrate this asynchrony. By combining magnetoencephalography (MEG) and functional MRI (fMRI), we investigate the temporal changes in brain activities caused by repeated exposure to a 150-ms delay inserted between a button-press action and a subsequent flash. We found that readiness potentials significantly shift later in the motor system, especially in parietal regions (average: 219.9 ms), while visually evoked potentials significantly shift earlier in occipital regions (average: 49.7 ms) in the delay condition compared to the no-delay condition. Moreover, the shift in readiness potentials, but not in visually evoked potentials, was significantly correlated with the psychophysical measure of motor-sensory adaptation. These results suggest that although both motor and sensory processes contribute to the recalibration, the motor process plays the major role, given the magnitudes of shift and the correlation with the psychophysical measure. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

The significance of the quadratic Doppler effect for space travel and astrophysics

NASA Astrophysics Data System (ADS)

Boehm, M.

1985-09-01

It is shown that a distinct frame of reference exists for light for which the Kennedy-Thorndike experiment provides unequivocal evidence. This leads to the postulate of a rotating instead of an expanding universe. It is shown that the cosmic red shift can be understood as the result of a Coriolis acceleration of the light propagating between two arbitrary points of different gravitational potential. Methods for determining the angular velocity of the rotating universe are given, and it is discussed whether the speed of light and the gravitational constant are universal constants or whether they are functions of distance from the center of the universe. Suggestions are made for further experimental studies and for practical application of the quadratic Doppler effect.

Temporal coherence of high-order harmonics generated at solid surfaces

NASA Astrophysics Data System (ADS)

Hemmers, D.; Behmke, M.; Karsch, S.; Keyling, J.; Major, Z.; Stelzmann, C.; Pretzler, G.

2014-07-01

We present interferometric measurements of the temporal coherence of high-order harmonics generated by reflection of a titanium sapphire laser off a solid surface. It is found that the coherence length of the harmonic emission is significantly reduced compared with the bandwidth limited case. To identify the responsible mechanism, the acquired data were analyzed by means of particle-in-cell simulations, whose results show good agreement between the calculated spectra and the measured coherence times. We show that the observed broadening can be understood consistently by the occurrence of a Doppler shift induced by the moving plasma surface, which is dented by the radiation pressure of the laser pulse. In this case, this Doppler effect would also lead to positive chirp of the emitted radiation.

Detection and counting of a submicrometer particle in liquid flow by self-mixing microchip Yb:YAG laser velocimetry.

PubMed

Ohtomo, Takayuki; Sudo, Seiichi; Otsuka, Kenju

2016-09-20

We observed intermittent modulation by scattered light from a single submicrometer particle moving in the flow channel using a self-mixing microchip Yb:YAG laser Doppler velocimeter (LDV) under lateral beam access. The Doppler-shift frequency chirping (i.e., velocity change) was identified in accordance with a particle passage through the beam focus. Single particle counting, which obeys the Poisson distribution, was performed successfully over a long period of time. The experimental results have been reproduced by a numerical simulation. The LDV signal was increased over 20 dB for a 202-nm particle without chirping by collinear beam access with the laser beam axis aligned along the flow direction.

Ultrasonically Encoded Photoacoustic Flowgraphy in Biological Tissue

NASA Astrophysics Data System (ADS)

Wang, Lidai; Xia, Jun; Yao, Junjie; Maslov, Konstantin I.; Wang, Lihong V.

2013-11-01

Blood flow speed is an important functional parameter. Doppler ultrasound flowmetry lacks sufficient sensitivity to slow blood flow (several to tens of millimeters per second) in deep tissue. To address this challenge, we developed ultrasonically encoded photoacoustic flowgraphy combining ultrasonic thermal tagging with photoacoustic imaging. Focused ultrasound generates a confined heat source in acoustically absorptive fluid. Thermal waves propagate with the flow and are directly visualized in pseudo color using photoacoustic computed tomography. The Doppler shift is employed to calculate the flow speed. This method requires only acoustic and optical absorption, and thus is applicable to continuous fluid. A blood flow speed as low as 0.24mm·s-1 was successfully measured. Deep blood flow imaging was experimentally demonstrated under 5-mm-thick chicken breast tissue.

The coating design of phase-shifting reflector array with high reflectance and specified reflection phase shifts for static Michelson interferometer

NASA Astrophysics Data System (ADS)

Zhang, Xuanni; Zhang, Hui; Wang, Yijun

2016-02-01

The optical Doppler Michelson imaging interferometer is widely used for wind measurements. Four interferograms obtained simultaneously are needed to immune to environmental disturbances. Thus, a static and divided mirror Michelson interferometer is proposed. Its highlight is the phase-shifting reflector array, which divides one mirror into four quadrants coated by different multilayer films with high reflectance, specified phase steps π/2 and little polarization effects. By combining analytical and empirical method, four coatings are designed with software TFCalc. The simulated results showed good agreement with the desired optical properties. Due to the limitation of the optical material and function of the software TFCalc, there are some design errors within tolerance.

Effects of direction of rotation in continuous and discontinuous 8 hour shift systems

PubMed Central

Tucker, P.; Smith, L.; Macdonald, I.; Folkard, S.

2000-01-01

OBJECTIVES—Previous research has produced conflicting evidence on the relative merits of advancing and delaying shift systems. The current study assessed the effects of the direction of shift rotation within 8 hour systems, upon a range of measures including sleep, on shift alertness, physical health, and psychological wellbeing.
METHODS—An abridged version of the standard shiftwork index which included retrospective alertness ratings was completed by four groups of industrial shiftworkers on relatively rapidly rotating 8 hour systems (n=611). Two groups worked continuous systems that were either advancing or delaying; the other two groups worked discontinuous systems that were either advancing or delaying.
RESULTS—Few effects were found of direction of rotation on chronic measures of health and wellbeing, even when the systems incorporated "quick returns" (a break of only 8 hours when changing from one shift to another). This was despite the use of measures previously shown to be sensitive to the effects of a broad range of features of shift systems. However, advancing continuous systems seemed to be associated with marginally steeper declines in alertness across the shift (F (3,1080)=2.87, p<0.05). They were also associated with shorter sleeps between morning shifts (F (1,404)=4.01, p<0.05), but longer sleeps between afternoons (F (1,424)=4.16, p<0.05).
CONCLUSIONS—The absence of negative effects of advancing shifts upon the chronic outcome measures accorded with previous evidence that advancing shifts may not be as harmful as early research indicated. However, this interpretation is tempered by the possibility that difficult shift systems self select those workers most able to cope with their deleterious effects. The presence of quick returns in advancing continuous systems seemed to impact upon some of the acute measures such as duration of sleep, although the associated effects on alertness seemed to be marginal.


Keywords: shift rotation; health; alertness PMID:10984340

Management of delayed cerebral ischemia after subarachnoid hemorrhage.

PubMed

Francoeur, Charles L; Mayer, Stephan A

2016-10-14

For patients who survive the initial bleeding event of a ruptured brain aneurysm, delayed cerebral ischemia (DCI) is one of the most important causes of mortality and poor neurological outcome. New insights in the last decade have led to an important paradigm shift in the understanding of DCI pathogenesis. Large-vessel cerebral vasospasm has been challenged as the sole causal mechanism; new hypotheses now focus on the early brain injury, microcirculatory dysfunction, impaired autoregulation, and spreading depolarization. Prevention of DCI primarily relies on nimodipine administration and optimization of blood volume and cardiac performance. Neurological monitoring is essential for early DCI detection and intervention. Serial clinical examination combined with intermittent transcranial Doppler ultrasonography and CT angiography (with or without perfusion) is the most commonly used monitoring paradigm, and usually suffices in good grade patients. By contrast, poor grade patients (WFNS grades 4 and 5) require more advanced monitoring because stupor and coma reduce sensitivity to the effects of ischemia. Greater reliance on CT perfusion imaging, continuous electroencephalography, and invasive brain multimodality monitoring are potential strategies to improve situational awareness as it relates to detecting DCI. Pharmacologically-induced hypertension combined with volume is the established first-line therapy for DCI; a good clinical response with reversal of the presenting deficit occurs in 70 % of patients. Medically refractory DCI, defined as failure to respond adequately to these measures, should trigger step-wise escalation of rescue therapy. Level 1 rescue therapy consists of cardiac output optimization, hemoglobin optimization, and endovascular intervention, including angioplasty and intra-arterial vasodilator infusion. In highly refractory cases, level 2 rescue therapies are also considered, none of which have been validated. This review provides an overview of current state-of-the-art care for DCI management.

Ambiguities in spaceborne synthetic aperture radar systems

NASA Technical Reports Server (NTRS)

Li, F. K.; Johnson, W. T. K.

1983-01-01

An examination of aspects of spaceborne SAR time delay and Doppler ambiguities has led to the formulation of an accurate method for the evaluation of the ratio of ambiguity intensities to that of the signal, which has been applied to the nominal SAR system on Seasat. After discussing the variation of this ratio as a function of orbital latitude and attitude control error, it is shown that the detailed range migration-azimuth phase history of an ambiguity is different from that of a signal, so that the images of ambiguities are dispersed. Seasat SAR dispersed images are presented, and their dispersions are eliminated through an adjustment of the processing parameters. A method is also presented which uses a set of multiple pulse repetition sequences to determine the Doppler centroid frequency absolute values for SARs with high carrier frequencies and poor attitude measurements.

Choroidal imaging by one-micrometer dual-beam Doppler optical coherence angiography with adjustable velocity range

NASA Astrophysics Data System (ADS)

Jaillon, Franck; Makita, Shuichi; Yasuno, Yoshiaki

2012-03-01

Ability of a new version of one-micrometer dual-beam optical coherence angiography (OCA) based on Doppler optical coherence tomography (OCT), is demonstrated for choroidal vasculature imaging. A particular feature of this system is the adjustable time delay between two probe beams. This allows changing the measurable velocity range of moving constituents such as blood without alteration of the scanning protocol. Since choroidal vasculature is made of vessels having blood flows with different velocities, this technique provides a way of discriminating vessels according to the velocity range of their inner flow. An example of choroid imaging of a normal emmetropic eye is here given. It is shown that combining images acquired with different velocity ranges provides an enhanced vasculature representation. This method may be then useful for pathological choroid characterization.

Effect of delay in hospital presentation on clinical and imaging findings in acute pulmonary thromboembolism.

PubMed

Jenab, Yaser; Alemzadeh-Ansari, Mohammad Javad; Fehri, Seyedeh Arezoo; Ghaffari-Marandi, Neda; Jalali, Arash

2014-04-01

There is limited information on the extent and clinical importance of the delay in hospital presentation of acute pulmonary thromboembolism (PTE). The aim of this study was to investigate the delay in hospital presentation of PTE and its association with clinical and imaging findings in PTE. This prospective study was conducted on patients admitted to our hospital with a diagnosis of acute PTE between September 2007 and September 2011. Relationships between delay in hospital presentation and clinical findings, risk factors, imaging findings, and in-hospital mortality were analyzed. Of the 195 patients enrolled, 84 (43.1%) patients presented 3 days after the onset of symptoms. Patients with chest pain, history of immobility for more than 3 days, recent surgery, and estrogen use had significantly less delayed presentation. Right ventricular dysfunction was significantly more frequent in patients with delayed presentation (odds ratio [OR] = 2.38; 95% confidence interval [CI] 1.27-4.44; p = 0.006); however, no relationship was found between delay in presentation and pulmonary computed tomographic angiography or color Doppler sonography findings. Patients with delayed presentation were at higher risk of in-hospital mortality (OR = 4.32; 95% CI 1.12-16.49; p = 0.021). Our study showed that a significant portion of patients with acute PTE had delayed presentation. Also, patients with delayed presentation had worse echocardiographic findings and higher in-hospital mortality. Copyright © 2014 Elsevier Inc. All rights reserved.

Performance on a strategy set shifting task during adolescence in a genetic model of attention deficit/hyperactivity disorder: Methylphenidate vs. atomoxetine treatments

PubMed Central

Harvey, Roxann C; Jordan, Chloe J; Tassin, David H; Moody, Kayla R; Dwoskin, Linda P; Kantak, Kathleen M

2013-01-01

Research examining medication effects on set shifting in teens with attention deficit/hyperactivity disorder (ADHD) is lacking. An animal model of ADHD may be useful for exploring this gap. The Spontaneously Hypertensive Rat (SHR) is a commonly used animal model of ADHD. SHR and two comparator strains, Wistar-Kyoto (WKY) and Wistar (WIS), were evaluated during adolescence in a strategy set shifting task under conditions of a 0-sec or 15-sec delay to reinforcer delivery. The task had three phases: initial discrimination, set shift and reversal learning. Under 0-sec delays, SHR performed as well as or better than WKY and WIS. Treatment with 0.3 mg/kg/day atomoxetine had little effect, other than to modestly increase trials to criterion during set shifting in all strains. Under 15-sec delays, SHR had longer lever press reaction times, longer latencies to criterion and more trial omissions than WKY during set shifting and reversal learning. These deficits were not reduced systematically by 1.5 mg/kg/day methylphenidate or 0.3 mg/kg/day atomoxetine. Regarding learning in SHR, methylphenidate improved initial discrimination, whereas atomoxetine improved set shifting but disrupted initial discrimination. During reversal learning, both drugs were ineffective in SHR, and atomoxetine made reaction time and trial omissions greater in WKY. Overall, WIS performance differed from SHR or WKY, depending on phase. Collectively, a genetic model of ADHD in adolescent rats revealed that neither methylphenidate nor atomoxetine mitigated all deficits in SHR during the set shifting task. Thus, methylphenidate or atomoxetine monotherapy may not mitigate all set shift task-related deficits in teens with ADHD. PMID:23376704

Ultraviolet Properties of Halo Coronal Mass Ejections: Doppler Shifts, Angles, Shocks, and Bulk Morphology

DTIC Science & Technology

2006-11-20

it 221036.34, 1037.02 where c is the speed of light. For spectral lines formed by scat- can pump the radiative component of the 21037 line at outflow...shift if the material is far from the plane of Li et al. 1998). In very fast CMEs pumping of the 21037 line the sky (Noci & Maccari 1999). Most of the...the plane of the sky. the 2002 July 18, 2002 July 15, and 2002 July 18 events suggest that pumping of the 0 vi 21037 line by 0 vi 21032 might be pres

Spectroscopic planetary detection

NASA Technical Reports Server (NTRS)

Deming, Drake

1988-01-01

One of the most promising methods for the detection of extra-solar planets is the spectroscopic method, where a small Doppler shift (approximately 10 meters/sec) in the spectrum of the parent star reveals the presence of planetary companions. However, solar-type stars may show spurious Doppler shifts due to surface activity. If these effects are periodic, as is the solar activity cycle, then they may masquerade as planetary companions. The goal of this investigation is to determine whether the solar cycle affects the Doppler stability of integrated sunlight. Observations of integrated sunlight are made in the near infrared (approximately 2 micrometer), using the Kitt Peak McMath Fourier transform spectrometer, with an N2O gas absorption cell for calibration. Researchers currently achieve an accuracy of approximately 5 meters/sec. Solar rotation velocities vary by plus or minus 2000 meters/sec across the solar disk, and imperfect optical integration of these velocities is the principal source of error. We have been monitoring the apparent velocity of integrated sunlight since 1983. They initially saw a decrease of approximately 30 meters/sec in the integrated light velocity from 1983 through 1985, but in 1987 to 1988 the integrated light velocity returned to its 1983 level. It is too early to say whether these changes are solar-cycle related. Although the FTS, unlike a slit spectrograph, has a large field of view, researchers are always looking for ways to improve the optical integration of the solar disk. They recently made an improvement in the method used to optically collimate the FTS, and this has reduced the error level, eliminating some systematic effects seen earlier.

A finite state machine read-out chip for integrated surface acoustic wave sensors

NASA Astrophysics Data System (ADS)

Rakshit, Sambarta; Iliadis, Agis A.

2015-01-01

A finite state machine based integrated sensor circuit suitable for the read-out module of a monolithically integrated SAW sensor on Si is reported. The primary sensor closed loop consists of a voltage controlled oscillator (VCO), a peak detecting comparator, a finite state machine (FSM), and a monolithically integrated SAW sensor device. The output of the system oscillates within a narrow voltage range that correlates with the SAW pass-band response. The period of oscillation is of the order of the SAW phase delay. We use timing information from the FSM to convert SAW phase delay to an on-chip 10 bit digital output operating on the principle of time to digital conversion (TDC). The control inputs of this digital conversion block are generated by a second finite state machine operating under a divided system clock. The average output varies with changes in SAW center frequency, thus tracking mass sensing events in real time. Based on measured VCO gain of 16 MHz/V our system will convert a 10 kHz SAW frequency shift to a corresponding mean voltage shift of 0.7 mV. A corresponding shift in phase delay is converted to a one or two bit shift in the TDC output code. The system can handle alternate SAW center frequencies and group delays simply by adjusting the VCO control and TDC delay control inputs. Because of frequency to voltage and phase to digital conversion, this topology does not require external frequency counter setups and is uniquely suitable for full monolithic integration of autonomous sensor systems and tags.

Vascular delay improves latissimus dorsi muscle perfusion and muscle function for use in cardiomyoplasty.

PubMed

Carroll, S M; Heilman, S J; Stremel, R W; Tobin, G R; Barker, J H

1997-04-01

Ischemia of the distal portion of the latissimus dorsi muscle occurs in muscle transfer for cardiomyoplasty and reduces distal muscle contractility and thus the mechanical effectiveness of cardiomyoplasty. We hypothesized that muscle function would be improved by a vascular delay procedure that increases distal muscle perfusion of the latissimus dorsi muscle. The latissimus dorsi muscles of 10 adult mongrel dogs were subjected to a vascular delay procedure on one side and a sham procedure on the other. Following 10 days of vascular delay, muscle perfusion was measured with a laser-Doppler perfusion imager before and after elevation of the muscles as flaps based only on their thoracodorsal neurovascular pedicles. The muscles were wrapped and sutured around silicone chambers (simulating cardiomyoplasty), a stimulating electrode was placed around each thoracodorsal nerve, and the muscles were stimulated to contract in both rhythmic and tetanic fashion. Circumferential (distal and middle latissimus dorsi muscle function) force generation and fatigue rates were measured independently. Circumferential muscle force, circumferential and longitudinal fatigue rate, and distal, middle, and overall perfusion were significantly (p < 0.05) improved in delayed muscle compared with nondelayed muscle. We found that a vascular delay procedure and a 10-day delay adaptation period significantly improve latissimus dorsi muscle flap perfusion and function, particularly in the distal and middle portions of the muscle. Delay should be considered as a means of improving the clinical outcome in cardiomyoplasty.

Echocardiographic Assessment of Aortic Pulse-Wave Velocity: Validation against Invasive Pressure Measurements.

PubMed

Styczynski, Grzegorz; Rdzanek, Adam; Pietrasik, Arkadiusz; Kochman, Janusz; Huczek, Zenon; Sobieraj, Piotr; Gaciong, Zbigniew; Szmigielski, Cezary

2016-11-01

Aortic pulse-wave velocity (PWV) is a measure of aortic stiffness that has a prognostic role in various diseases and in the general population. A number of methods are used to measure PWV, including Doppler ultrasound. Although echocardiography has been used for PWV measurement, to the authors' knowledge, it has never been tested against an invasive reference method at the same time point. Therefore, the aim of this study was to compare prospectively an echocardiographic PWV measurement, called echo-PWV, with an invasive study. Forty-five patients (mean age, 66 years; 60% men) underwent simultaneous intra-arterial pressure recording and echocardiographic Doppler flow evaluation during elective cardiac catheterization. Proximal pressure and Doppler waveforms were acquired in the aortic arch. Distal pressure waveforms were registered in the right and distal Doppler waveforms in the left external iliac artery. Transit time was measured as a delay of the foot of pressure or Doppler waveform in the distal relative to the proximal location. Distance was measured on the catheter for invasive PWV and over the surface for echo-PWV. Echo-PWV was calculated as distance divided by transit time. In the whole group, mean invasive PWV was 9.38 m/sec and mean echo-PWV was 9.51 m/sec (P = .78). The Pearson' correlation coefficient between methods was 0.93 (P < .0001). A Bland-Altman plot revealed a mean difference between invasive PWV and echo-PWV of 0.13 ± 0.79 m/sec. Echo-PWV, based on Doppler echocardiography, is a reliable method of aortic PWV measurement, with a close correlation with invasive assessment. Wider implementation of the echo-PWV method for the evaluation of aortic wall stiffness can further expand the clinical and scientific utility of echocardiography. Copyright © 2016 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

Infant wellbeing at 2 years of age in the Growth Restriction Intervention Trial (GRIT): multicentred randomised controlled trial.

PubMed

Thornton, J G; Hornbuckle, J; Vail, A; Spiegelhalter, D J; Levene, M

Although delivery is widely used for preterm babies failing to thrive in utero, the effect of altering delivery timing has never been assessed in a randomised controlled trial. We aimed to compare the effect of delivering early with delaying birth for as long as possible. 548 pregnant women were recruited by 69 hospitals in 13 European countries. Participants had fetal compromise between 24 and 36 weeks, an umbilical-artery doppler waveform recorded, and clinical uncertainty about whether immediate delivery was indicated. Before birth, 588 babies were randomly assigned to immediate delivery (n=296) or delayed delivery until the obstetrician was no longer uncertain (n=292). The main outcome was death or disability at or beyond 2 years of age. Disability was defined as a Griffiths developmental quotient of 70 or less or the presence of motor or perceptual severe disability. Analysis was by intention-to-treat. This trial has been assigned the International Standard Randomised Controlled Trial Number ISRCTN41358726. Primary outcomes were available on 290 (98%) immediate and 283 (97%) deferred deliveries. Overall rate of death or severe disability at 2 years was 55 (19%) of 290 immediate births, and 44 (16%) of 283 delayed births. With adjustment for gestational age and umbilical-artery doppler category, the odds ratio (95% CrI) was 1.1 (0.7-1.8). Most of the observed difference was in disability in babies younger than 31 weeks of gestation at randomisation: 14 (13%) immediate versus five (5%) delayed deliveries. No important differences in the median Griffiths developmental quotient in survivors was seen. The lack of difference in mortality suggests that obstetricians are delivering sick preterm babies at about the correct moment to minimise mortality. However, they could be delivering too early to minimise brain damage. These results do not lend support to the idea that obstetricians can deliver before terminal hypoxaemia to improve brain development.

Circadian Rhythm of Wrist Temperature among Shift Workers in South Korea: A Prospective Observational Study

PubMed Central

Kim, Hyunjoo; Kang, Suk-Hoon; Choo, Sang-Hyo; Lee, In-Seok; Choi, Kyung-Hwa

2017-01-01

Background: Human body temperature varies with circadian rhythm. To determine the effect of shift work on the circadian rhythm of the distal-skin temperature, wrist temperatures were measured. Methods: Wrist-skin temperatures were measured by an iButton® Temperature Logger. It was measured every 3 min for two and eight consecutive working days in the day and shift workers, respectively. Mesor, amplitude, and acrophase were measured by Cosinor analysis. Results: The shift-worker amplitude dropped significantly as the night shift progressed (0.92 to 0.85 °C), dropped further during rest (0.69 °C), and rose during the morning-shift days (0.82 °C). Day workers still had higher amplitudes (0.93 °C) than the morning-shift workers. The acrophase was delayed during the four night-shift days, then advanced during rest days and the morning-shift days. Nevertheless, the morning-shift worker acrophase was still significantly delayed compared to the day workers (08:03 a.m. vs. 04:11 a.m.). Conclusions: The further reduction of wrist-temperature amplitude during rest after the night shift may be due to the signal circadian rhythm disruption. Reduced amplitudes have been reported to be associated with intolerance to shift work. The findings of our study may help to design the most desirable schedule for shift workers. PMID:28946653

Circadian Rhythm of Wrist Temperature among Shift Workers in South Korea: A Prospective Observational Study.

PubMed

Jang, Tae-Won; Kim, Hyunjoo; Kang, Suk-Hoon; Choo, Sang-Hyo; Lee, In-Seok; Choi, Kyung-Hwa

2017-09-24

Background : Human body temperature varies with circadian rhythm. To determine the effect of shift work on the circadian rhythm of the distal-skin temperature, wrist temperatures were measured. Methods : Wrist-skin temperatures were measured by an iButton ® Temperature Logger. It was measured every 3 min for two and eight consecutive working days in the day and shift workers, respectively. Mesor, amplitude, and acrophase were measured by Cosinor analysis. Results : The shift-worker amplitude dropped significantly as the night shift progressed (0.92 to 0.85 °C), dropped further during rest (0.69 °C), and rose during the morning-shift days (0.82 °C). Day workers still had higher amplitudes (0.93 °C) than the morning-shift workers. The acrophase was delayed during the four night-shift days, then advanced during rest days and the morning-shift days. Nevertheless, the morning-shift worker acrophase was still significantly delayed compared to the day workers (08:03 a.m. vs. 04:11 a.m.). Conclusions : The further reduction of wrist-temperature amplitude during rest after the night shift may be due to the signal circadian rhythm disruption. Reduced amplitudes have been reported to be associated with intolerance to shift work. The findings of our study may help to design the most desirable schedule for shift workers.

Urea clearance: a new technique based on microdialysis to assess liver blood flow studied in a pig model of ischemia/reperfusion.

PubMed

Farnebo, S; Winbladh, A; Zettersten, E K; Sandström, P; Gullstrand, P; Samuelsson, A; Theodorson, E; Sjöberg, F

2010-01-01

Delayed detection of ischemia is one of the most feared postoperative complications. Early detection of impaired blood flow and close monitoring of the organ-specific metabolic status may therefore be critical for the surgical outcome. Urea clearance is a new technique for continuous monitoring of alterations in blood flow and metabolic markers with acceptable temporal characteristics. We compare this new microdialysis technique with the established microdialysis ethanol technique to assess hepatic blood flow. Six pigs were used in a liver ischemia/reperfusion injury model. Microdialysis catheters were placed in liver segment IV and all circulation was stopped for 80 min, followed by reperfusion for 220 min. Urea and ethanol clearance was calculated from the dialysate and correlated with metabolic changes. A laser Doppler probe was used as reference of restoration of blood flow. Both urea and ethanol clearance reproducibly depicted changes in liver blood flow in relation to metabolic changes and laser Doppler measurements. The two techniques highly correlated both overall and during the reperfusion phase (r = 0.8) and the changes were paralleled by altered perfusion as recorded by laser Doppler. Copyright © 2010 S. Karger AG, Basel.

Hybrid space-airborne bistatic SAR geometric resolutions

NASA Astrophysics Data System (ADS)

Moccia, Antonio; Renga, Alfredo

2009-09-01

Performance analysis of Bistatic Synthetic Aperture Radar (SAR) characterized by arbitrary geometric configurations is usually complex and time-consuming since system impulse response has to be evaluated by bistatic SAR processing. This approach does not allow derivation of general equations regulating the behaviour of image resolutions with varying the observation geometry. It is well known that for an arbitrary configuration of bistatic SAR there are not perpendicular range and azimuth directions, but the capability to produce an image is not prevented as it depends only on the possibility to generate image pixels from time delay and Doppler measurements. However, even if separately range and Doppler resolutions are good, bistatic SAR geometries can exist in which imaging capabilities are very poor when range and Doppler directions become locally parallel. The present paper aims to derive analytical tools for calculating the geometric resolutions of arbitrary configuration of bistatic SAR. The method has been applied to a hybrid bistatic Synthetic Aperture Radar formed by a spaceborne illuminator and a receiving-only airborne forward-looking Synthetic Aperture Radar (F-SAR). It can take advantage of the spaceborne illuminator to dodge the limitations of monostatic FSAR. Basic modeling and best illumination conditions have been detailed in the paper.

Observation and Study of Proton Aurora by using Scanning Photometer

NASA Astrophysics Data System (ADS)

Mochizuki, T.; Ono, T.; Kadokura, A.; Sato, N.

2009-12-01

The proton auroras have significant differences from electron auroras in their spectral shape. They show Doppler-shifted and broadened spectra: the spectra have Doppler-shifted (~0.5 nm shorter) peak and both bluewing (~2-4 nm) and redwing (~1.5 nm) extending. Energy spectra of precipitating protons have been estimated from this shape. Recently it is found that the intensity in the extent of the blue wing reflects more effectively by the change of the mean energy of precipitating protons than the shift of peak wavelength [Lanchester et al., 2003]. Another character of the H-beta aurora is that it is diffuse form because a proton becomes hydrogen atom due to a charge-exchange reaction with atmospheric constituent and then possible to move across the magnetic field line. By using a scanning photometer, the movement of the proton auroral belt and change of a spectrum shape associated with the variation of proton source region due to storm and substorm were reported, however, not discussed in detail yet [Deehr and Lummerzheim, 2001]. The purpose of this study is to obtain the detail characteristics of H-beta aurora for understanding of source region of energetic protons in the magnetosphere. For this purpose, a new meridian-scanning photometer (SPM) was installed at Husafell station in Iceland in last summer season and Syowa Station, Antarctica. It will contribute to investigate the distribution of energetic protons and plasma waves which cause the pitch angle scattering in the magnetosphere. The meridian-scanning photometer is able to observe at five wavelengths for H-beta emission. One channel is to measure the background level. By analyzing the data obtained by the SPM, the H-beta spectrum can be estimated by fitting a model function with it. Then it is possible to obtain distribution of precipitating protons in north-south direction. It is also possible to estimate an energy spectrum of precipitating proton, simultaneously. The instrumental parameters of the SPM is defined by the transmission characteristics of the interference filters; they are 485.7 nm (FWHM: 3.0 nm), 484.5 nm (0.6 nm), 485.5 nm (0.6 nm), 486.5 nm (0.6 nm) and 487.5 nm (0.6 nm) for H-beta auroras, and OI 630 nm (0.6 nm), N_2 1PG 670.5 nm (5.0 nm) and OI 844.6 nm (0.6 nm) for electron auroras. We analyzed the event at 2100 UT 23rd June, 2009 observed at Syowa station. This is typical auroral breakup event. And in this event, breakup occurred in FOV of the photometer and expanded to poleward. Then NS aurora appeared and pulsating aurora occurred. We calculated Doppler profile and each parameter is below. The peak intensity is 80 R/nm, wavelength at peak intensity is 486.0 nm, HWHM of bluewing is 1.7 nm and HWHM of redwing is 0.9 nm. These value are within past studies, although the Doppler shift of peak intensity is 0.1 nm and shorter than the average of past studies (0.5 nm). And intensity and Doppler profile of proton aurora changed with eqatorward moving in substorm growth phase. This suggests that the source of precipitating proton moves Earthward and its energy increases, and correspond to the result of Deehr and Lummerzheim, 2001. We are going to report the more detailed result of this event and new events of proton aurora.

Controlled patterns of daytime light exposure improve circadian adjustment in simulated night work.

PubMed

Dumont, Marie; Blais, Hélène; Roy, Joanie; Paquet, Jean

2009-10-01

Circadian misalignment between the endogenous circadian signal and the imposed rest-activity cycle is one of the main sources of sleep and health troubles in night shift workers. Timed bright light exposure during night work can reduce circadian misalignment in night workers, but this approach is limited by difficulties in incorporating bright light treatment into most workplaces. Controlled light and dark exposure during the daytime also has a significant impact on circadian phase and could be easier to implement in real-life situations. The authors previously described distinctive light exposure patterns in night nurses with and without circadian adaptation. In the present study, the main features of these patterns were used to design daytime light exposure profiles. Profiles were then tested in a laboratory simulation of night work to evaluate their efficacy in reducing circadian misalignment in night workers. The simulation included 2 day shifts followed by 4 consecutive night shifts (2400-0800 h). Healthy subjects (15 men and 23 women; 20-35 years old) were divided into 3 groups to test 3 daytime light exposure profiles designed to produce respectively a phase delay (delay group, n=12), a phase advance (advance group, n=13), or an unchanged circadian phase (stable group, n=13). In all 3 groups, light intensity was set at 50 lux during the nights of simulated night work. Salivary dim light melatonin onset (DLMO) showed a significant phase advance of 2.3 h (+/-1.3 h) in the advance group and a significant phase delay of 4.1 h (+/-1.3 h) in the delay group. The stable group showed a smaller but significant phase delay of 1.7 h (+/-1.6 h). Urinary 6-sulfatoxymelatonin (aMT6s) acrophases were highly correlated to salivary DLMOs. Urinary aMT6s acrophases were used to track daily phase shifts. They showed that phase shifts occurred rapidly and differed between the 3 groups by the 3rd night of simulated night work. These results show that significant phase shifts can be achieved in night workers by controlling daytime light exposure, with no nighttime intervention.

How to induce multiple delays in coupled chaotic oscillators?

NASA Astrophysics Data System (ADS)

Bhowmick, Sourav K.; Ghosh, Dibakar; Roy, Prodyot K.; Kurths, Jürgen; Dana, Syamal K.

2013-12-01

Lag synchronization is a basic phenomenon in mismatched coupled systems, delay coupled systems, and time-delayed systems. It is characterized by a lag configuration that identifies a unique time shift between all pairs of similar state variables of the coupled systems. In this report, an attempt is made how to induce multiple lag configurations in coupled systems when different pairs of state variables attain different time shift. A design of coupling is presented to realize this multiple lag synchronization. Numerical illustration is given using examples of the Rössler system and the slow-fast Hindmarsh-Rose neuron model. The multiple lag scenario is physically realized in an electronic circuit of two Sprott systems.

Numerical analysis for trajectory controllability of a coupled multi-order fractional delay differential system via the shifted Jacobi method

NASA Astrophysics Data System (ADS)

Priya, B. Ganesh; Muthukumar, P.

2018-02-01

This paper deals with the trajectory controllability for a class of multi-order fractional linear systems subject to a constant delay in state vector. The solution for the coupled fractional delay differential equation is established by the Mittag-Leffler function. The necessary and sufficient condition for the trajectory controllability is formulated and proved by the generalized Gronwall's inequality. The approximate trajectory for the proposed system is obtained through the shifted Jacobi operational matrix method. The numerical simulation of the approximate solution shows the theoretical results. Finally, some remarks and comments on the existing results of constrained controllability for the fractional dynamical system are also presented.

Tunable Optical Delay in Doppler-Broadened Cesium Vapor

DTIC Science & Technology

2010-12-01

family v Acknowledgements I would like to express my sincere appreciation to my advisor Professor Glen Perram, for his guidance and support through the...including Eric Guild, Michael Cox, and Paul Stanczak. In the laboratory no experiment is complete without technical issues– I would like to thank laboratory...especially Greg Pitz and Cliff Sulham. I greatly appreciate Professor John Howell from the University of Rochester for his discussions on slow light in al

Ultraviolet Properties of Halo Coronal Mass Ejections: Doppler Shifts, Angles, Shocks, and Bulk Morphology

NASA Astrophysics Data System (ADS)

Ciaravella, A.; Raymond, J. C.; Kahler, S. W.

2006-11-01

We present UV spectral information for 22 halo or partial halo CMEs observed by UVCS. The CME fronts show broad line profiles, while the line intensities are comparable to the background corona. The Doppler shifts of the front material are generally small, showing that the motion of gas in the fronts is mostly transverse to the line of sight. This indicates that, at least in halo CMEs, the fronts generally correspond to coronal plasma swept up by a shock or compression wave, rather than plasma carried outward by magnetic loops. This favors an ice cream cone (or a spherical shell) model, as opposed to an expanding arcade of loops. We use the line widths to discriminate between shock heating and bulk expansion. Of 14 cases where we detected the CME front, the line broadening in 7 cases can be attributed to shock heating, while in 3 cases it is the line-of-sight component of the CME expansion. For the CME cores we determine the angles between the motion and the plane of the sky, along with the actual heliocentric distances, in order to provide quantitative estimates of projection effects.

Application of Spectroscopic Doppler Velocimetry for Measurement of Streamwise Vorticity

NASA Technical Reports Server (NTRS)

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

2013-01-01

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

Effects of duration and other noise characteristics on the annoyance caused by aircraft-flyover noise

NASA Technical Reports Server (NTRS)

Mccurdy, D. A.; Powell, C. A.

1979-01-01

A laboratory experiment was conducted to determine the effects of duration and other noise characteristics on the annoyance caused by aircraft-flyover noise. Duration, doppler shift, and spectra were individually controlled by specifying aircraft operational factors, such as velocity, altitude, and spectrum, in a computer synthesis of the aircraft-noise stimuli. This control allowed the separation of the effects of duration from the other main factors in the experimental design: velocity, tonal content, and sound pressure level. The annoyance of a set of noise stimuli which were comprised of factorial combinations of a 3 durations, 3 velocities, 3 sound pressure levels, and 2 tone conditions were judged. The judgements were made by using a graphical scale procedure similar to numerical category scaling. Each of the main factors except velocity was found to affect the judged annoyance significantly. The interaction of tonal content with sound pressure level was also found to be significant. The duration correction used in the effective-perceived-noise-level procedure, 3 dB per doubling of effective duration, was found to account most accurately for the effect of duration. No significant effect doppler shift was found.

Cross-shell excitations from the f p shell: Lifetime measurements in 61Zn

NASA Astrophysics Data System (ADS)

Queiser, M.; Vogt, A.; Seidlitz, M.; Reiter, P.; Togashi, T.; Shimizu, N.; Utsuno, Y.; Otsuka, T.; Honma, M.; Petkov, P.; Arnswald, K.; Altenkirch, R.; Birkenbach, B.; Blazhev, A.; Braunroth, T.; Dewald, A.; Eberth, J.; Fransen, C.; Fu, B.; Hess, H.; Hetzenegger, R.; Hirsch, R.; Jolie, J.; Karayonchev, V.; Kaya, L.; Lewandowski, L.; Müller-Gatermann, C.; Régis, J.-M.; Rosiak, D.; Schneiders, D.; Siebeck, B.; Steinbach, T.; Wolf, K.; Zell, K.-O.

2017-10-01

Lifetimes of excited states in the neutron-deficient nucleus 61Zn were measured employing the recoil-distance Doppler-shift (RDDS) and the electronic fast-timing methods at the University of Cologne. The nucleus of interest was populated as an evaporation residue in 40Ca(24Mg,n 2 p )61Zn and 58Ni(α ,n )61Zn reactions at 67 and 19 MeV, respectively. Five lifetimes were measured for the first time, including the lifetime of the 5 /21- isomer at 124 keV. Short lifetimes from the RDDS analysis are corrected for Doppler-shift attenuation (DSA) in the target and stopper foils. Ambiguous observations in previous measurements were resolved. The obtained lifetimes are compared to predictions from different sets of shell-model calculations in the f p , f5 /2p g9 /2 , and multishell f p -g9 /2d5 /2 model spaces. The band built on the 9 /21+ state exhibits a prolate deformation with β ≈0.24 . Especially, the inclusion of cross-shell excitation into the 1 d5 /2 orbital is found to be decisive for the description of collectivity in the first excited positive-parity band.

Auditory fovea and Doppler shift compensation: adaptations for flutter detection in echolocating bats using CF-FM signals.

PubMed

Schnitzler, Hans-Ulrich; Denzinger, Annette

2011-05-01

Rhythmical modulations in insect echoes caused by the moving wings of fluttering insects are behaviourally relevant information for bats emitting CF-FM signals with a high duty cycle. Transmitter and receiver of the echolocation system in flutter detecting foragers are especially adapted for the processing of flutter information. The adaptations of the transmitter are indicated by a flutter induced increase in duty cycle, and by Doppler shift compensation (DSC) that keeps the carrier frequency of the insect echoes near a reference frequency. An adaptation of the receiver is the auditory fovea on the basilar membrane, a highly expanded frequency representation centred to the reference frequency. The afferent projections from the fovea lead to foveal areas with an overrepresentation of sharply tuned neurons with best frequencies near the reference frequency throughout the entire auditory pathway. These foveal neurons are very sensitive to stimuli with natural and simulated flutter information. The frequency range of the foveal areas with their flutter processing neurons overlaps exactly with the frequency range where DS compensating bats most likely receive echoes from fluttering insects. This tight match indicates that auditory fovea and DSC are adaptations for the detection and evaluation of insects flying in clutter.

Single-element ultrasound transducer for combined vessel localization and ablation.

PubMed

Chen, Wen-Shiang; Shen, Che-Chou; Wang, Jen-Chieh; Ko, Chung-Ting; Liu, Hao-Li; Ho, Ming-Chih; Chen, Chiung-Nien; Yeh, Chih-Kuang

2011-04-01

This report describes a system that utilizes a single high-intensity focused ultrasound (HIFU) transducer for both the localization and ablation of arteries with internal diameters of 0.5 and 1.3 mm. In vitro and in vivo tests were performed to demonstrate both the imaging and ablation functionalities of this system. For imaging mode, pulsed acoustic waves (3 cycles for in vitro and 10 cycles for in vivo tests, 2 MPa peak pressure) were emitted from the 2-MHz HIFU transducer, and the backscattered ultrasonic signal was collected by the same transducer to calculate Doppler shifts in the target region. The maximum signal amplitude of the Doppler shift was used to determine the location of the target vessel. The operation mode was then switched to the therapeutic mode and vessel occlusion was successfully produced by high-intensity continuous HIFU waves (12 MPa) for 60 s. The system was then switched back to imaging mode for residual flow to determine the need for a second ablation treatment. The new system might be used to target and occlude unwanted vessels such as vasculature around tumors, and to help with tumor destruction. © 2011 IEEE

A simple model of the effects of the mid-latitude total ion trough in the bottomside F layer on HF radiowave propagation

NASA Astrophysics Data System (ADS)

Lockwood, M.

1981-06-01

Observations of the amplitudes and Doppler shifts of received HF radio waves are compared with model predictions made using a two-dimensional ray-tracing program. The signals are propagated over a sub-auroral path, which is shown to lie along the latitudes of the mid-latitude trough at times of low geomagnetic activity. Generalizing the predictions to include a simple model of the trough in the density and height of the F2 peak enables the explanation of the anomalous observed diurnal variations. The behavior of received amplitude, Doppler shift, and signal-to-noise ratio as a function of the K sub p index value, the time of day, and the season (in 17 months of continuous recording) is found to agree closely with that predicted using the statistical position of the trough as deduced from 8 years of Alouette satellite soundings. The variation in the times of the observation of large signal amplitudes with the K sub p value and the complete absence of such amplitudes when it exceeds 2.75 are two features that implicate the trough in these effects.

Can the bump in the composite spectrum of GRB 910503 be an emission line feature of gamma-ray bursts?

NASA Astrophysics Data System (ADS)

Qin, Yi-Ping; Zhang, Fu-Wen

2005-12-01

Appearing in the composite spectral data of BATSE, EGRET and COMPTEL for GRB 910503, there is a bump at around 1600 keV. We perform a statistical analysis on the spectral data, trying to find out if the bump could be accounted for by a blue-shifted and significantly broadened rest frame line due to the Doppler effect of an expanding fireball surface. We made an F-test and adopted previously proposed criteria. The study reveals that the criteria are well satisfied and the feature can be interpreted as the blue shifted 6.4 keV line. From the fit with this line taken into account, we find the Lorentz factor of this source to be Γ = 116+9-9 (at the 68% confident level, triangleχ2 = 1) and the rest frame spectral peak energy to be E0,p = 2.96+0.24-0.18 keV. Although the existence of the emission line feature requires other independent tests to confirm, the analysis suggests that it is feasible to detect emission line features in the high energy range of GRB spectra when taking into account the Doppler effect of fireball expansion.

Helioseismology of a Realistic Magnetoconvective Sunspot Simulation

NASA Technical Reports Server (NTRS)

Braun, D. C.; Birch, A. C.; Rempel, M.; Duvall, T. L., Jr.

2012-01-01

We compare helioseismic travel-time shifts measured from a realistic magnetoconvective sunspot simulation using both helioseismic holography and time-distance helioseismology, and measured from real sunspots observed with the Helioseismic and Magnetic Imager instrument on board the Solar Dynamics Observatory and the Michelson Doppler Imager instrument on board the Solar and Heliospheric Observatory. We find remarkable similarities in the travel-time shifts measured between the methodologies applied and between the simulated and real sunspots. Forward modeling of the travel-time shifts using either Born or ray approximation kernels and the sound-speed perturbations present in the simulation indicates major disagreements with the measured travel-time shifts. These findings do not substantially change with the application of a correction for the reduction of wave amplitudes in the simulated and real sunspots. Overall, our findings demonstrate the need for new methods for inferring the subsurface structure of sunspots through helioseismic inversions.

The indirect effects on the computation of geoid undulations

NASA Technical Reports Server (NTRS)

Wichiencharoen, C.

1982-01-01

The indirect effects on the geoid computation due to the second method of Helmert's condensation were studied. when Helmert's anomalies are used in Stokes's equation, there are three types of corrections to the free air geoid. The first correction, the indirect effect on geoid undulation due to the potential change in Helmert's reduction, had a maximum value of 0.51 meters in the test area covering the United States. The second correction, the attraction change effect on geoid undulation, had a maximum value of 9.50 meters when the 10 deg cap was used in Stokes' equation. The last correction, the secondary indirect effect on geoid undulatin, was found negligible in the test area. The corrections were applied to uncorrected free air geoid undulations at 65 Doppler stations in the test area and compared with the Doppler undulations. Based on the assumption that the Doppler coordinate system has a z shift of 4 meters with respect to the geocenter, these comparisons showed that the corrections presented in this study yielded improved values of gravimetric undulations.

The EMBLA 2000 Mission in Hessdalen

NASA Astrophysics Data System (ADS)

Teodorani, M.; Montebugnoli, S.; Monari, J.

2000-11-01

In August 2000 a team of italian physical scientists, working in collaboration with norwegian colleagues from Østfold College, carried out an instrumental expedition in Hessdalen (Norway), which was just the first of a series of future scientific missions planned by the joint italian-norwegian EMBLA Project. The mission was aimed at studying unexplained anomalous atmospheric luminous phenomena occurring in the Hessdalen valley since about 20 years, and it was firstly devoted to the monitor of the radio spectrum in the UHF, VLF and ELF wavelength ranges, secondly to the study of the typology of luminous phenomena. This paper presents an ample introduction describing the analysis of the data acquired in the period 1998-2000 by means of the norwegian automatic videocamera of the Hessdalen Interactive Observatory: the hourly and monthly statistics of the luminous phenomenon and its spatial distribution over the celestial sphere are shown. The paper is then focussed into the results which were obtained with the employed radio spectrum analyzers of the EMBLA team, in particular the discovery of highly anomalous periodic signals of unknown origin which were caracterized by a spike-like and a Doppler-like morphology and which were mostly detected in the VLF radio range. It is shown that the Doppler shift, supposed to be due to a `particle-like' emitting source, ranges in a very short time from 10.000 up-to 100.000 km/sec with a frequency shift which is both red-wards and blue-wards, by changing periodically. Subsequently the physical interpretation is presented and discussed: (a) the occurrence of spike-like signals may be due to the pulsation of a radio-emitting source or alternatively to the rotation of a spheroidal source with a radio-emitting spot on its surface; (b) the very high measured velocities involved in the Doppler-like signals, together with the periodic inversion of the Doppler shift, are hypothesized to be due to a physical mechanism involving the magnetically collimated acceleration of high-energy particles modulated by the rotation of a self-contained `plasma spheroid' whose magnetic axis is misaligned in comparison with its rotation axis. Moreover, a detailed description of the luminous phenomena which were sighted during the many planned skywatching sessions, is presented, together with photo-analysis and point-spread functions of enhanced frames. Finally, a detailed plan for future optical observations and analysis is shown in the appendix, in which photometric and spectroscopic techniques by means of portable scout instrumentation are described.

The variation in frequency locations in Doppler ultrasound spectra for maximum blood flow velocities in narrowed vessels.

PubMed

Zhang, Yingyun; Zhang, Yufeng; Gao, Lian; Deng, Li; Hu, Xiao; Zhang, Kexin; Li, Haiyan

2017-11-01

This study assessed the variation in the frequency locations in the Doppler ultrasound spectra for the maximum blood flow velocities of in vessels with different degrees of bilaterally axisymmetric stenosis. This was done by comparing the relationship between the velocity distributions and corresponding Doppler power spectra. First, a geometric vessel model with axisymmetric stenosis was established. This made it possible to obtain the blood flow velocity distributions for different degrees of stenosis from the solutions of the Navier-Stokes equations. Then, the Doppler spectra were calculated for the entire segment of the vessel that was covered by the sound field. Finally, the maximum frequency locations for the spectra were determined based on the intersections of the maximum values chosen from the calculated blood flow velocity distributions and their corresponding spectra. The computational analysis showed that the maximum frequencies, which corresponded to the maximum blood flow velocities for different degrees of stenosis, were located at different positions along the spectral falling edges. The location for a normal (stenosis free) vessel was in the middle of the falling edge. For vessels with increasing degrees of stenosis, this location shifted approximately linearly downward along the falling edge. For 40% stenosis, the location reached a position at the falling edge of 0.32. Results obtained using the Field II simulation tool demonstrated the validity of the theoretical analysis and calculations, and may help to improve the maximum velocity estimation accuracy for Doppler blood flow spectra in stenosed vessels. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Nonphotic phase shifting in female Syrian hamsters: interactions with the estrous cycle.

PubMed

Young Janik, L; Janik, Daniel

2003-08-01

Nonphotic phase shifting of circadian rhythms was examined in female Syrian hamsters. Animals were stimulated at zeitgeber time 4.5 by either placing them in a novel running wheel or by transferring them to a clean home cage. Placement in a clean home cage was more effective than novel wheel treatment in stimulating large (> 1.5 h) phase shifts. Peak phase shifts (ca. 3.5 h) and the percentage of females showing large phase shifts were comparable to those found in male hamsters stimulated with novel wheels. The amount of activity induced by nonphotic stimulation and the amount of phase shifting varied slightly with respect to the 4-day estrous cycle. Animals tended to run less and shift less on the day of estrus. Nonphotic stimulation on proestrus often resulted in a 1-day delay of the estrous cycle reflected in animals' postovulatory vaginal discharge and the expression of sexual receptivity (lordosis). This delay of the estrous cycle was associated with large phase advances and high activity. These results extend the generality of nonphotic phase shifting to females for the first time and raise the possibility that resetting of circadian rhythms can induce changes in the estrous cycle.

Delayed presentation of a vertebral arterio-venous fistula secondary to penetrating cervical trauma: endovascular management using coil embolisation - a case report

PubMed Central

Mortimer, Alex; Stubbs, Euan; Cookson, Daniel; Dawson, Raymond; Fleet, Mustafa

2009-01-01

Vertebro-vertebral arteriovenous fistulae occur infrequently. We report on such a case with delayed presentation following penetrating neck injury. This was successfully treated via coil embolisation. A 40-year-old woman presented with a subjective tinnitus that was abolished by turning her head to the right. She had sustained penetrating neck trauma 6 months earlier. Doppler Ultrasound and magnetic resonance angiogram confirmed the presence of a vertebral arterio-venous fistula. Using a trans-femoral arterial approach, the left vertebral artery was embolised by deployment of multiple coils. The patient had no return of symptoms at 3 months follow up. Radiological diagnosis and endovascular management of this condition is discussed. PMID:22470664

Delayed presentation of a vertebral arterio-venous fistula secondary to penetrating cervical trauma: endovascular management using coil embolisation - a case report.

PubMed

Mortimer, Alex; Stubbs, Euan; Cookson, Daniel; Dawson, Raymond; Fleet, Mustafa

2009-01-01

Vertebro-vertebral arteriovenous fistulae occur infrequently. We report on such a case with delayed presentation following penetrating neck injury. This was successfully treated via coil embolisation. A 40-year-old woman presented with a subjective tinnitus that was abolished by turning her head to the right. She had sustained penetrating neck trauma 6 months earlier. Doppler Ultrasound and magnetic resonance angiogram confirmed the presence of a vertebral arterio-venous fistula. Using a trans-femoral arterial approach, the left vertebral artery was embolised by deployment of multiple coils. The patient had no return of symptoms at 3 months follow up. Radiological diagnosis and endovascular management of this condition is discussed.