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

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.

Multi-instrument observation on co-seismic ionospheric effects after great Tohoku earthquake

NASA Astrophysics Data System (ADS)

Hao, Y. Q.; Xiao, Z.; Zhang, D. H.

2012-02-01

In this paper, evidence of quake-excited infrasonic waves is provided first by a multi-instrument observation of Japan's Tohoku earthquake. The observations of co-seismic infrasonic waves are as follows: 1, effects of surface oscillations are observed by local infrasonic detector, and it seems these effects are due to surface oscillation-excited infrasonic waves instead of direct influence of seismic vibration on the detector; 2, these local excited infrasonic waves propagate upwards and correspond to ionospheric disturbances observed by Doppler shift measurements and GPS/TEC; 3, interactions between electron density variation and currents in the ionosphere caused by infrasonic waves manifest as disturbances in the geomagnetic field observed via surface magnetogram; 4, within 4 hours after this strong earthquake, disturbances in the ionosphere related to arrivals of Rayleigh waves were observed by Doppler shift sounding three times over. Two of the arrivals were from epicenter along the minor arc of the great circle (with the second arrival due to a Rayleigh wave propagating completely around the planet) and the other one from the opposite direction. All of these seismo-ionospheric effects observed by HF Doppler shift appear after local arrivals of surface Rayleigh waves, with a time delay of 8-10 min. This is the time required for infrasonic wave to propagate upwards to the ionosphere.

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.

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.

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

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

SAR imaging - Seeing the unseen

NASA Technical Reports Server (NTRS)

Kobrick, M.

1982-01-01

The functional abilities and operations of synthetic aperture radar (SAR) are described. SAR employs long wavelength radio waves in bursts, imaging a target by 'listening' to the small frequency changes that result from the Doppler shift due to the relative motion of the imaging craft and the motions of the target. The time delay of the signal return allows a determination of the location of the target, leading to the build up of a two-dimensional image. The uses of both Doppler shifts and time delay enable detailed imagery which is independent of distance. The synthetic aperture part of the name of SAR derives from the beaming of multiple pulses, which result in a picture that is effectively the same as using a large antenna. Mechanisms contributing to the fineness of SAR images are outlined.

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

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.

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. .

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

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

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.

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.

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.

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.

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.

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.

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.

Identification of atmospheric structure by coherent microwave sounding

NASA Technical Reports Server (NTRS)

Birkemeier, W. P.

1969-01-01

Two atmospheric probing experiments involving beyond-the-horizon propagation of microwave signals are reported. In the first experiment, Doppler-shift caused by the cross path wind is measured by a phase lock receiver with the common volume displaced in azimuth from the great circle. Variations in the measured Doppler shift values are explained in terms of variations in atmospheric structure. The second experiment makes use of the pseudorandom sounding signal used in a RAKE communication system. Both multipath delay and Doppler shift are provided by the receiver, permitting the cross section of the atmospheric layer structure to be deduced.

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.

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.

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

High-speed optical coherence tomography using fiberoptic acousto-optic phase modulation

NASA Astrophysics Data System (ADS)

Xie, Tuqiang; Wang, Zhenguo; Pan, Yingtian

2003-12-01

We report a new rapid-scanning optical delay device suitable for high-speed optical coherence tomography (OCT) in which an acousto-optic modulator (AOM) is used to independently modulate the Doppler frequency shift of the reference light beam for optical heterodyne detection. Experimental results show that the fluctuation of the measured Doppler frequency shift is less than +/-0.2% over 95% duty cycle of OCT imaging, thus allowing for enhanced signal-to-noise ratio of optical heterodyne detection. The increased Doppler frequency shift by AOM also permits complete envelop demodulation without the compromise of reducing axial resolution; if used with a resonant rapid-scanning optical delay, it will permit high-performance real-time OCT imaging. Potentially, this new rapid-scanning optical delay device will improve the performance of high-speed Doppler OCT techniques.

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.

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 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.

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.

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.

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.

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

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

Robust quantum logic in neutral atoms via adiabatic Rydberg dressing

DOE PAGES

Keating, Tyler; Cook, Robert L.; Hankin, Aaron M.; ...

2015-01-28

We study a scheme for implementing a controlled-Z (CZ) gate between two neutral-atom qubits based on the Rydberg blockade mechanism in a manner that is robust to errors caused by atomic motion. By employing adiabatic dressing of the ground electronic state, we can protect the gate from decoherence due to random phase errors that typically arise because of atomic thermal motion. In addition, the adiabatic protocol allows for a Doppler-free configuration that involves counterpropagating lasers in a σ +/σ - orthogonal polarization geometry that further reduces motional errors due to Doppler shifts. The residual motional error is dominated by dipole-dipolemore » forces acting on doubly-excited Rydberg atoms when the blockade is imperfect. As a result, for reasonable parameters, with qubits encoded into the clock states of 133Cs, we predict that our protocol could produce a CZ gate in < 10 μs with error probability on the order of 10 -3.« less

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.

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)

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)

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.

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.

Cooperatively coupled motion with superradiant and subradiant atoms

NASA Astrophysics Data System (ADS)

Lin, Guin-Dar; Lin, Kuan-Ting; Tang, Er-Siang

2017-04-01

We investigate the coupled motion of cooperative atoms subjected to the Doppler dissipative force. The dipole-dipole interaction introduces mutual decay channel and splits the super-radiant and sub-radiant states. The Doppler force is thus modified due to the collective emission and coupled recoil. Such a cooperative effect is more evident when the inter-atom separation is less than or comparable to a wavelength. In an optical molasses, we find that, along the axis of two atoms, there presents an effective potential with mechanically stable and unstable regions alternatively as their separation increases. Taking the cooperative Lamb shift into account, we map out the stability diagram and investigate the blockade effect. We thank the support from MOST of Taiwan under Grant No. 105-2112-M-002-015-MY3 and National Taiwan University under Grant No. NTU-ERP-105R891401.

Low-frequency gravitational wave detection via double optical clocks in space

NASA Astrophysics Data System (ADS)

Su, Jianfeng; Wang, Qiang; Wang, Qinghua; Jetzer, Philippe

2018-04-01

We propose a Doppler tracking system for gravitational wave detection via double optical clocks in space (DOCS). In this configuration two spacecrafts (each containing an optical clock) are launched to space for Doppler shift observations. Compared to the similar attempt of gravitational wave detection in the Cassini mission, the radio signal of DOCS that contains the relative frequency changes avoids completely noise effects due for instance to troposphere, ionosphere, ground-based antenna and transponder. Given the high stabilities of the two optical clocks (Allan deviation  ∼ 4.1× 10-17 @ 1000 s), an overall estimated sensitivity of 5 × 10-19 could be achieved with an observation time of 2 yr, and would allow to detect gravitational waves in the frequency range from  ∼10‑4 Hz to  ∼10‑2 Hz.

(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.

Laser and biological methods of biomonitoring of surrounding waters

NASA Astrophysics Data System (ADS)

Posudin, Yuri I.

1994-02-01

Three main methods are proposed for the biomonitoring of chemicals in water medium: laser spectrofluorometry, which is based on the excitation and recording of the spectra of fluorescence; laser scattering, which is connected with measurement of the Doppler shifts of the scattered light from the motile cells; videomicrography, which provides the analysis of parameters of photomovement of motile cells via microscope and video system. Such chemicals as surface-active substances, heavy metals and pesticides were determined in water medium due to these methods.

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.

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;

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.

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.

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).

Method and system of doppler correction for mobile communications systems

NASA Technical Reports Server (NTRS)

Georghiades, Costas N. (Inventor); Spasojevic, Predrag (Inventor)

1999-01-01

Doppler correction system and method comprising receiving a Doppler effected signal comprising a preamble signal (32). A delayed preamble signal (48) may be generated based on the preamble signal (32). The preamble signal (32) may be multiplied by the delayed preamble signal (48) to generate an in-phase preamble signal (60). The in-phase preamble signal (60) may be filtered to generate a substantially constant in-phase preamble signal (62). A plurality of samples of the substantially constant in-phase preamble signal (62) may be accumulated. A phase-shifted signal (76) may also be generated based on the preamble signal (32). The phase-shifted signal (76) may be multiplied by the delayed preamble signal (48) to generate an out-of-phase preamble signal (80). The out-of-phase preamble signal (80) may be filtered to generate a substantially constant out-of-phase preamble signal (82). A plurality of samples of the substantially constant out-of-phase signal (82) may be accumulated. A sum of the in-phase preamble samples and a sum of the out-of-phase preamble samples may be normalized relative to each other to generate an in-phase Doppler estimator (92) and an out-of-phase Doppler estimator (94).

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.

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.

Infrasonic Effect of Solar Eclipses

NASA Astrophysics Data System (ADS)

Pushin, V. F.; Chernogor, L. F.

2013-06-01

The relevance of this study is due to the need to understand, physical effects associated with rare phenomenon, solar eclipse. Until recently, the features of internal gravity wave generation, have been studied in the 10 -100 min period range, while in this, study an attempt is made to confirm the fact of generation, and estimate the general parameters of infrasound oscillations, associated with solar eclipses in the 1-10 min period range. The observations were made with the HF Doppler radar at vertical, incidence. The data were subjected to spectral analysis and, band-pass filtering. The solar eclipses that had occurred over, Kharkiv city (Ukraine) within 1999-2011 are determined to be, associated with Doppler shift of frequency oscillations in the, infrasound frequency band ( 5-8 min period range) and with, amplitude of 20 -100 mHz. The corresponding amplitude, of electron density oscillations was approximately equal to, 0.1- 0.5 %.

Radiation forces on small particles in the solar system

NASA Technical Reports Server (NTRS)

Burns, J. A.; Lamy, P. L.; Soter, S.

1979-01-01

Solar radiation forces on small particles in the solar system are examined, and the resulting orbital evolution of interplanetary and circumplanetary dust is considered. An expression is derived for the effects of radiation pressure and Poynting-Robertson drag on small, spherical particles using the energy and momentum transformation laws of special relativity, and numerical examples are presented to illustrate that radiation pressure and Poynting-Robertson drag are only important for particles within a narrow size range. The orbital consequences of these radiation forces are considered both for heliocentric and planetocentric orbiting particles, and the coupling between particle sizes and dynamics is discussed. A qualitative derivation is presented for the differential Doppler effect, which is due to the differential Doppler shifting of radiation from approaching and receding solar hemispheres, and the Yarkovsky effect, which is important for rotating meter-to kilometer-sized particles, is briefly described.

Multicomponent Arcjet plasma Parameters

NASA Astrophysics Data System (ADS)

Gorbunkov, V.; Kositsin, V. V.; Ruban, V. I.; Shalay, V. V.

2018-01-01

To determine the plasma arc parameters of an arcjet thruster, the kinetic theory of gases is used. We can find a well-known statement about the adiabatic character of the compression process due to the growth of the gas temperature in a change in its spectral composition and in the Doppler effect. The use of tungsten in the nozzle design details explains the appearance of atoms of this element in the plasma volume. The emission spectra of tungsten allow us to indirectly judge the temperature of the arc discharge and its character. Absorption of the long-wavelength wing of the line contour at λ = 465.987 nm substantiates our conclusion about the consumption of the anode material in the process of operating the arcjet. The Doppler shift of the emission lines of argon allows us to determine the rate of the gas jet escape. The results of the study can be useful in the design of aircraft.

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.

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.

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.

Hepatic vein transit time of second-generation ultrasound contrast agent: new tool in the assessment of portal hypertension.

PubMed

Luisa, Siciliani; Vitale, Giovanna; Sorbo, Anna Rita; Maurizio, Pompili; Lodovico, Rapaccini Gian

2017-03-01

It has been demonstrated that Doppler waveform of the hepatic vein (normally triphasic) is transformed into a biphasic or monophasic waveform in cirrhotic patients. The compressive mechanism of liver tissue has been considered up till now the cause of this change. Moreover, cirrhotics show, after USCA injection, a much earlier HVTT due to intrahepatic shunts. Our aim was to prospectively evaluate the correlation between Doppler pattern of hepatic vein and HVTT of a second-generation USCA; we also correlated HVTT with the most common indexes of portal hypertension. We enrolled 38 participants: 33 cirrhotics and 5 healthy controls. Doppler shift signals were obtained from the right hepatic vein. To characterize the hepatic vein pattern, we used the hepatic vein waveform index (HVWI). This index becomes >1 with the appearance of the triphasic waveform. We recorded a clip from 20 s before to 2 min after a peripheral intravenous bolus injection of 2.4 ml of USCA (sulfur hexafluoride).The time employed by USCA to cross the liver from the hepatic artery and portal vein to the hepatic vein was defined as HA-HVTT and PV-HVTT, respectively. Cirrhotics with low HVWI showed an earlier transit time; participants with higher HVWI had a longer transit time ( p  < 0.001). HVTT was earlier as MELD, Child-Pugh score and spleen diameter increased. Patients with ascites and varices of large size had significantly shorter transit times. Abnormal hepatic vein Doppler waveform in cirrhotic patients could be due to intrahepatic shunts. HVTT could be useful in the non-invasive evaluation of portal hypertension.

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

Breakdown in helium in high-voltage open discharge with subnanosecond current front rise

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

Schweigert, I. V., E-mail: ischweig@itam.nsc.ru; Alexandrov, A. L.; Bokhan, P. A.

Investigations of high-voltage open discharge in helium have shown a possibility of generation of current pulses with subnanosecond front rise, due to ultra-fast breakdown development. The open discharge is ignited between two planar cathodes with mesh anode in the middle between them. For gas pressure 6 Torr and 20 kV applied voltage, the rate of current rise reaches 500 A/(cm{sup 2} ns) for current density 200 A/cm{sup 2} and more. The time of breakdown development was measured for different helium pressures and a kinetic model of breakdown in open discharge is presented, based on elementary reactions for electrons, ions andmore » fast atoms. The model also includes various cathode emission processes due to cathode bombardment by ions, fast atoms, electrons and photons of resonant radiation with Doppler shift of frequency. It is shown, that the dominating emission processes depend on the evolution of the discharge voltage during the breakdown. In the simulations, two cases of voltage behavior were considered: (i) the voltage is kept constant during the breakdown; (ii) the voltage is reduced with the growth of current. For the first case, the exponentially growing current is maintained due to photoemission by the resonant photons with Doppler-shifted frequency. For the second case, the dominating factor of current growth is the secondary electron emission. In both cases, the subnanosecond rise of discharge current was obtained. Also the effect of gas pressure on breakdown development was considered. It was found that for 20 Torr gas pressure the time of current rise decreases to 0.1 ns, which is in agreement with experimental data.« 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.

Fundamental uncertainty limit of optical flow velocimetry according to Heisenberg's uncertainty principle.

PubMed

Fischer, Andreas

2016-11-01

Optical flow velocity measurements are important for understanding the complex behavior of flows. Although a huge variety of methods exist, they are either based on a Doppler or a time-of-flight measurement principle. Doppler velocimetry evaluates the velocity-dependent frequency shift of light scattered at a moving particle, whereas time-of-flight velocimetry evaluates the traveled distance of a scattering particle per time interval. Regarding the aim of achieving a minimal measurement uncertainty, it is unclear if one principle allows to achieve lower uncertainties or if both principles can achieve equal uncertainties. For this reason, the natural, fundamental uncertainty limit according to Heisenberg's uncertainty principle is derived for Doppler and time-of-flight measurement principles, respectively. The obtained limits of the velocity uncertainty are qualitatively identical showing, e.g., a direct proportionality for the absolute value of the velocity to the power of 32 and an indirect proportionality to the square root of the scattered light power. Hence, both measurement principles have identical potentials regarding the fundamental uncertainty limit due to the quantum mechanical behavior of photons. This fundamental limit can be attained (at least asymptotically) in reality either with Doppler or time-of-flight methods, because the respective Cramér-Rao bounds for dominating photon shot noise, which is modeled as white Poissonian noise, are identical with the conclusions from Heisenberg's uncertainty principle.

Multi-variable X-band radar observation and tracking of ash plume from Mt. Etna volcano on November 23, 2013 event

NASA Astrophysics Data System (ADS)

Montopoli, Mario; Vulpiani, Gianfranco; Riccci, Matteo; Corradini, Stefano; Merucci, Luca; Marzano, Frank S.

2015-04-01

Ground based weather radar observations of volcanic ash clouds are gaining momentum after recent works which demonstrated their potential use either as stand alone tool or in combination with satellite retrievals. From an operational standpoint, radar data have been mainly exploited to derive the height of ash plume and its temporal-spatial development, taking into account the radar limitation of detecting coarse ash particles (from approximately 20 microns to 10 millimeters and above in terms of particle's radius). More sophisticated radar retrievals can include airborne ash concentration, ash fall rate and out-flux rate. Marzano et al. developed several volcanic ash radar retrieval (VARR) schemes, even though their practical use is still subject to a robust validation activity. The latter is made particularly difficult due to the lack of field campaigns with multiple observations and the scarce repetition of volcanic events. The radar variable, often used to infer the physical features of actual ash clouds, is the radar reflectivity named ZHH. It is related to ash particle size distribution and it shows a nice power law relationship with ash concentration. This makes ZHH largely used in radar-volcanology studies. However, weather radars are often able to detect Doppler frequency shifts and, more and more, they have a polarization-diversity capability. The former means that wind speed spectrum of the ash cloud is potentially inferable, whereas the latter implies that variables other than ZHH are available. Theoretically, these additional radar variables are linked to the degree of eccentricity of ash particles, their orientation and density as well as the presence of strong turbulence effects. Thus, the opportunity to refine the ash radar estimates so far developed can benefit from the thorough analysis of radar Doppler and polarization diversity. In this work we show a detailed analysis of Doppler shifts and polarization variables measured by the X band radar working at Catania airport (Sicily, Italy) and observing the Mt. Etna fountains about 33 km far away. Collocated infrared satellite observations will be shown as well to complete the investigation. The case study on November 23rd, 2013 is taken as reference case due to its strength and its well-defined narrow plume, which is transported by the prevailing wind hundred kilometers away. For this case study, the X-band radar in Catania tracked the ash-signal from 9:40 UTC to 10:30 UTC every 10 min providing, at each acquisition step, the following variables, abbreviated as ZDR, RHV, VEL, SWD KDP and ZHH. The latter stand for differential reflectivity, correlation coefficients, radial velocity, spectral width, specific differential phase shift and reflectivity, respectively. The outcomes of this analysis reveal that the interpretation of polarization diversity and Doppler shifts might introduce new insights in the estimates of the fraction of ash mass loading due to larger particles and its rate of mass flux. This would be an important achievement for the APhoRISM Project in witch this work is framed. APHORISM is a 3 years FP7-EU project started on December 2013 that aims to develop innovative products to support the management and mitigation of the volcanic and the seismic crisis.

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.

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.

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.

A tone-aided dual vestigial sideband system for digital communications on fading channels

NASA Technical Reports Server (NTRS)

Hladik, Stephen M.; Saulnier, Gary J.; Rafferty, William

1989-01-01

A spectrally efficient tone-aided dual vestigial sideband (TA/DVSB) system for digital data communications on fading channels is presented and described analytically. This PSK (phase-shift-keying) system incorporates a feed-forward, tone-aided demodulation technique to compensate for Doppler frequency shift and channel- induced, multipath fading. In contrast to other tone-in-band-type systems, receiver synchronization is derived from the complete data VSBs. Simulation results for the Rician fading channel are presented. These results demonstrate the receiver's ability to mitigate performance degradation due to fading and to obtain proper data carrier synchronization, suggesting that the proposed TA/DVSB system has promise for this application. Simulated BER (bit-error rate) data indicate that the TA/DVSB system effectively alleviates the channel distortions of the land mobile satellite application.

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…

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.

Experimental study of dual polarized radar return from the sea surface

NASA Astrophysics Data System (ADS)

Ermakov, S. A.; Kapustin, I. A.; Lavrova, O. Yu.; Molkov, A. A.; Sergievskaya, I. A.; Shomina, O. V.

2017-10-01

Dual-polarized microwave radars are of particular interest nowadays as perspective tool of ocean remote sensing. Microwave radar backscattering at moderate and large incidence angles according to conventional models is determined by resonance (Bragg) surface waves typically of cm-scale wavelength range. Some recent experiments have indicated, however, that an additional, non Bragg component (NBC) contributes to the radar return. The latter is considered to occur due to wave breaking. At present our understanding of the nature of different components of radar return is still poor. This paper presents results of field experiment using an X-/C-/S-band Doppler radar operating at HH- and VVpolarizations. The intensity and radar Doppler shifts for Bragg and non Bragg components are retrieved from measurements of VV and HH radar returns. Analysis of a ratio of VV and HH radar backscatter - polarization ratio (PR) has demonstrated a significant role of a non Bragg component. NBC contributes significantly to the total radar backscatter, in particular, at moderate incidence angles (about 50-70 deg.) it is 2-3 times smaller than VV Bragg component and several times larger that HH Bragg component. Both NBC and BC depend on azimuth angle, being minimal for cross wind direction, but NBC is more isotropic than BC. It is obtained that velocities of scatterers retrieved from radar Doppler shifts are different for Bragg waves and for non Bragg component; NBC structures are "faster" than Bragg waves particularly for upwind radar observations. Bragg components propagate approximately with phase velocities of linear gravity-capillary waves (when accounting for wind drift). Velocities of NBC scatterers depend on radar band, being the largest for S-band and the smallest at X-band, this means that different structures on the water surface are responsible for non Bragg scattering in a given radar band.

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.

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

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.

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.

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.

Estimation of Venus wind velocities from high-resolution infrared spectra. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Smith, M. A. H.

1978-01-01

Zonal velocity profiles in the Venus atmosphere above the clouds were estimated from measured asymmetries of HCl and HF infrared absorption lines in high-resolution Fourier interferometer spectra of the planet. These asymmetries are caused by both pressure-induced shifts in the positions of the hydrogen-halide lines perturbed by CO2 and Doppler shifts due to atmospheric motions. Particularly in the case of the HCl 2-0 band, the effects of the two types of line shifts can be easily isolated, making it possible to estimate a profile of average Venus equatorial zonal velocity as a function of pressure in the region roughly 60 to 70 km above the surface of the planet. The mean profiles obtained show strong vertical shear in the Venus zonal winds near the cloud-top level, and both the magnitude and direction of winds at all levels in this region appear to vary greatly with longitude relative to the sub-solar point.

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.

Doppler synthetic aperture radar interferometry: a novel SAR interferometry for height mapping using ultra-narrowband waveforms

NASA Astrophysics Data System (ADS)

Yazıcı, Birsen; Son, Il-Young; Cagri Yanik, H.

2018-05-01

This paper introduces a new and novel radar interferometry based on Doppler synthetic aperture radar (Doppler-SAR) paradigm. Conventional SAR interferometry relies on wideband transmitted waveforms to obtain high range resolution. Topography of a surface is directly related to the range difference between two antennas configured at different positions. Doppler-SAR is a novel imaging modality that uses ultra-narrowband continuous waves (UNCW). It takes advantage of high resolution Doppler information provided by UNCWs to form high resolution SAR images. We introduce the theory of Doppler-SAR interferometry. We derive an interferometric phase model and develop the equations of height mapping. Unlike conventional SAR interferometry, we show that the topography of a scene is related to the difference in Doppler frequency between two antennas configured at different velocities. While the conventional SAR interferometry uses range, Doppler and Doppler due to interferometric phase in height mapping; Doppler-SAR interferometry uses Doppler, Doppler-rate and Doppler-rate due to interferometric phase in height mapping. We demonstrate our theory in numerical simulations. Doppler-SAR interferometry offers the advantages of long-range, robust, environmentally friendly operations; low-power, low-cost, lightweight systems suitable for low-payload platforms, such as micro-satellites; and passive applications using sources of opportunity transmitting UNCW.

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.; Sun, Xiaoli

1993-01-01

This interim report consists of four separate reports from our research on the receivers of NASA's Gravity And Magnetic Experiment Satellite (GAMES). The first report is entitled 'Analysis of phase estimation bias of GAMES receiver due to Doppler shift.' The second report is 'Background radiation on GAMES fine ranging detector from the moon, the planets, and the stars.' The third report is 'Background radiation on GAMES receivers from the ocean sun glitter and the direct sun.' The fourth report is 'GAMES receiver performance versus background radiation power on the detectors.'

En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

NASA Astrophysics Data System (ADS)

Tan, Ou; Liu, Gangjun; Liang, Liu; Gao, Simon S.; Pechauer, Alex D.; Jia, Yali; Huang, David

2015-06-01

An automated algorithm was developed for total retinal blood flow (TRBF) using 70-kHz spectral optical coherence tomography (OCT). The OCT was calibrated for the transformation from Doppler shift to speed based on a flow phantom. The TRBF scan pattern contained five repeated volume scans (2×2 mm) obtained in 3 s and centered on central retinal vessels in the optic disc. The TRBF was calculated using an en face Doppler technique. For each retinal vein, blood flow was measured at an optimal plane where the calculated flow was maximized. The TRBF was calculated by summing flow in all veins. The algorithm tracked vascular branching so that either root or branch veins are summed, but never both. The TRBF in five repeated volumes were averaged to reduce variation due to cardiac cycle pulsation. Finally, the TRBF was corrected for eye length variation. Twelve healthy eyes and 12 glaucomatous eyes were enrolled to test the algorithm. The TRBF was 45.4±6.7 μl/min for healthy control and 34.7±7.6 μl/min for glaucomatous participants (p-value=0.01). The intravisit repeatability was 8.6% for healthy controls and 8.4% for glaucoma participants. The proposed automated method provided repeatable TRBF measurement.

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.

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.

Fixed Delay Interferometry for Doppler Extrasolar Planet Detection

NASA Astrophysics Data System (ADS)

Ge, Jian

2002-06-01

We present a new technique based on fixed delay interferometry for high-throughput, high-precision, and multiobject Doppler radial velocity (RV) surveys for extrasolar planets. The Doppler measurements are conducted by monitoring the stellar fringe phase shifts of the interferometer instead of absorption-line centroid shifts as in state-of-the-art echelle spectroscopy. High Doppler sensitivity is achieved through optimizing the optical delay in the interferometer and reducing photon noise by measuring multiple fringes over a broad band. This broadband operation is performed by coupling the interferometer with a low- to medium-resolution postdisperser. The resulting fringing spectra over the bandpass are recorded on a two-dimensional detector, with fringes sampled in the slit spatial direction and the spectrum sampled in the dispersion direction. The resulting total Doppler sensitivity is, in theory, independent of the dispersing power of the postdisperser, which allows for the development of new-generation RV machines with much reduced size, high stability, and low cost compared to echelles. This technique has the potential to improve RV survey efficiency by 2-3 orders of magnitude over the cross-dispersed echelle spectroscopy approach, which would allow a full-sky RV survey of hundreds of thousands of stars for planets, brown dwarfs, and stellar companions once the instrument is operated as a multiobject instrument and is optimized for high throughput. The simple interferometer response potentially allows this technique to be operated at other wavelengths independent of popular iodine reference sources, being actively used in most of the current echelles for Doppler planet searches, to search for planets around early-type stars, white dwarfs, and M, L, and T dwarfs for the first time. The high throughput of this instrument could also allow investigation of extragalactic objects for RV variations at high precision.

NOTE ON TRAVEL TIME SHIFTS DUE TO AMPLITUDE MODULATION IN TIME-DISTANCE HELIOSEISMOLOGY MEASUREMENTS

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

Nigam, R.; Kosovichev, A. G., E-mail: rakesh@quake.stanford.ed, E-mail: sasha@quake.stanford.ed

Correct interpretation of acoustic travel times measured by time-distance helioseismology is essential to get an accurate understanding of the solar properties that are inferred from them. It has long been observed that sunspots suppress p-mode amplitude, but its implications on travel times have not been fully investigated so far. It has been found in test measurements using a 'masking' procedure, in which the solar Doppler signal in a localized quiet region of the Sun is artificially suppressed by a spatial function, and using numerical simulations that the amplitude modulations in combination with the phase-speed filtering may cause systematic shifts ofmore » acoustic travel times. To understand the properties of this procedure, we derive an analytical expression for the cross-covariance of a signal that has been modulated locally by a spatial function that has azimuthal symmetry and then filtered by a phase-speed filter typically used in time-distance helioseismology. Comparing this expression to the Gabor wavelet fitting formula without this effect, we find that there is a shift in the travel times that is introduced by the amplitude modulation. The analytical model presented in this paper can be useful also for interpretation of travel time measurements for the non-uniform distribution of oscillation amplitude due to observational effects.« less

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.

Tangential velocity measurement using interferometric MTI radar

DOEpatents

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

2006-01-03

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

Coherent Doppler lidar for automated space vehicle, rendezvous, station-keeping and capture

NASA Technical Reports Server (NTRS)

Dunkin, James A.

1991-01-01

Recent advances in eye-safe, short wavelength solid-state lasers offer real potential for the development of compact, reliable, light-weight, efficient coherent lidar. Laser diode pumping of these devices has been demonstrated, thereby eliminating the need for flash lamp pumping, which has been a major drawback to the use of these lasers in space based applications. Also these lasers now have the frequency stability required to make them useful in coherent lidar, which offers all of the advantages of non-coherent lidar, but with the additional advantage that direct determination of target velocity is possible by measurement of the Doppler shift. By combining the Doppler velocity measurement capability with the inherent high angular resolution and range accuracy of lidar it is possible to construct Doppler images of targets for target motion assessment. A coherent lidar based on a Tm,Ho:YAG 2-micrometer wavelength laser was constructed and successfully field tested on atmospheric targets in 1990. This lidar incorporated an all solid state (laser diode pumped) master oscillator, in conjunction with a flash lamp pumped slave oscillator. Solid-state laser technology is rapidly advancing, and with the advent of high efficiency, high power, semiconductor laser diodes as pump sources, all-solid-state, coherent lidars are a real possibility in the near future. MSFC currently has a feasibility demonstration effort under way which will involve component testing, and preliminary design of an all-solid-state, coherent lidar for automatic rendezvous, and capture. This two year effort, funded by the Director's Discretionary Fund is due for completion in 1992.

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.

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.

Range-dependence of acoustic channel with traveling sinusoidal surface wave.

PubMed

Choo, Youngmin; Seong, Woojae; Lee, Keunhwa

2014-04-01

Range-dependence of time-varying acoustic channels caused by a traveling surface wave is investigated through water tank experiments and acoustic propagation analysis schemes. As the surface wave travels, surface reflected signals fluctuate and the fluctuation varies with source-receiver horizontal range. Amplitude fluctuations of surface reflected signals increase with increasing horizontal range whereas the opposite occurs in delay fluctuations. The scattered pressure field at a fixed time shows strong dependence on the receiver position because of caustics and shadow zones formed by the surface. The Doppler shifts of surface reflected signals also depend on the horizontal range. Comparison between measurement data and model results indicates the Doppler shift relies on the delay fluctuation under current experimental conditions.

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.

Photon mirror acceleration in the quantum regime

NASA Astrophysics Data System (ADS)

Mendonça, J. T.; Fedele, R.

2014-12-01

Reflection of an electron beam by an intense laser pulse is considered. This is the so-called photon mirror configuration for laser acceleration in vacuum, where the energy of the incident electron beam is nearly double-Doppler shifted due to reflection on the laser pulse front. A wave-electron optical description for electron reflection and resonant backscattering, due to both linear electric field force and quadratic ponderomotive force, is provided beyond the paraxial approximation. This is done by assuming that the single electron of the beam is spin-less and therefore its motion can be described by a quantum scalar field whose spatiotemporal evolution is governed by the Klein-Gordon equation (Klein-Gordon field). Our present model, not only confirms the classical results but also shows the occurrence of purely quantum effects, such as partial reflection of the incident electron beam and enhanced backscattering due to Bragg resonance.

Control of the electromagnetic drag using fluctuating light fields

NASA Astrophysics Data System (ADS)

Pastor, Víctor J. López; Marqués, Manuel I.

2018-05-01

An expression for the electromagnetic drag force experienced by an electric dipole in a light field consisting of a monochromatic plane wave with polarization and phase randomly fluctuating is obtained. The expression explicitly considers the transformations of the field and frequency due to the Doppler shift and the change of the polarizability response of the electric dipole. The conditions to be fulfilled by the polarizability of the dipole in order to obtain a positive, a null, and a negative drag coefficient are analytically determined and checked against numerical simulations for the dynamics of a silver nanoparticle. The theoretically predicted diffusive, superdiffusive, and exponentially accelerated dynamical regimes are numerically confirmed.

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.).

Improved performance of a digital phase-locked loop combined with a frequency/frequency-rate estimator

NASA Technical Reports Server (NTRS)

Mileant, A.; Simon, M.

1986-01-01

When a digital phase-locked loop with a long loop update time tracks a signal with high Doppler, the demodualtion losses due to frequency mismatch can become very significant. One way of reducing these Doppler-related losses is to compensate for the Doppler effect using some kind of frequency-rate estimator. The performance of the fixed-window least-squares estimator and the Kalman filter is investigated; several Doppler compensating techniques are proposed. It is shown that the variance of the frequency estimator can be made as small as desired, and with this, the Doppler effect can be effectively compensated. The remaining demodulation losses due to phase jitter in the loop can be less than 0.1 dB.

En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

PubMed Central

Tan, Ou; Liu, Gangjun; Liang, Liu; Gao, Simon S.; Pechauer, Alex D.; Jia, Yali; Huang, David

2015-01-01

Abstract. An automated algorithm was developed for total retinal blood flow (TRBF) using 70-kHz spectral optical coherence tomography (OCT). The OCT was calibrated for the transformation from Doppler shift to speed based on a flow phantom. The TRBF scan pattern contained five repeated volume scans (2×2  mm) obtained in 3 s and centered on central retinal vessels in the optic disc. The TRBF was calculated using an en face Doppler technique. For each retinal vein, blood flow was measured at an optimal plane where the calculated flow was maximized. The TRBF was calculated by summing flow in all veins. The algorithm tracked vascular branching so that either root or branch veins are summed, but never both. The TRBF in five repeated volumes were averaged to reduce variation due to cardiac cycle pulsation. Finally, the TRBF was corrected for eye length variation. Twelve healthy eyes and 12 glaucomatous eyes were enrolled to test the algorithm. The TRBF was 45.4±6.7  μl/min for healthy control and 34.7±7.6  μl/min for glaucomatous participants (p-value=0.01). The intravisit repeatability was 8.6% for healthy controls and 8.4% for glaucoma participants. The proposed automated method provided repeatable TRBF measurement. PMID:26062663

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.

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.

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.

A comparison between coherent and noncoherent mobile systems in large Doppler shift, delay spread, and C/I environment

NASA Technical Reports Server (NTRS)

Feher, Kamilo

1993-01-01

The performance and implementation complexity of coherent and of noncoherent QPSK and GMSK modulation/demodulation techniques in a complex mobile satellite systems environment, including large Doppler shift, delay spread, and low C/I, are compared. We demonstrate that for large f(sub d)T(sub b) products, where f(sub d) is the Doppler shift and T(sub b) is the bit duration, noncoherent (discriminator detector or differential demodulation) systems have a lower BER floor than their coherent counterparts. For significant delay spreads, e.g., tau(sub rms) greater than 0.4 T(sub b), and low C/I, coherent systems outperform noncoherent systems. However, the synchronization time of coherent systems is longer than that of noncoherent systems. Spectral efficiency, overall capacity, and related hardware complexity issues of these systems are also analyzed. We demonstrate that coherent systems have a simpler overall architecture (IF filter implementation-cost versus carrier recovery) and are more robust in an RF frequency drift environment. Additionally, the prediction tools, computer simulations, and analysis of coherent systems is simpler. The threshold or capture effect in low C/I interference environment is critical for noncoherent discriminator based systems. We conclude with a comparison of hardware architectures of coherent and of noncoherent systems, including recent trends in commercial VLSI technology and direct baseband to RF transmit, RF to baseband (0-IF) receiver implementation strategies.

A comparison between coherent and noncoherent mobile systems in large Doppler shift, delay spread, and C/I environment

NASA Astrophysics Data System (ADS)

Feher, Kamilo

The performance and implementation complexity of coherent and of noncoherent QPSK and GMSK modulation/demodulation techniques in a complex mobile satellite systems environment, including large Doppler shift, delay spread, and low C/I, are compared. We demonstrate that for large f(sub d)T(sub b) products, where f(sub d) is the Doppler shift and T(sub b) is the bit duration, noncoherent (discriminator detector or differential demodulation) systems have a lower BER floor than their coherent counterparts. For significant delay spreads, e.g., tau(sub rms) greater than 0.4 T(sub b), and low C/I, coherent systems outperform noncoherent systems. However, the synchronization time of coherent systems is longer than that of noncoherent systems. Spectral efficiency, overall capacity, and related hardware complexity issues of these systems are also analyzed. We demonstrate that coherent systems have a simpler overall architecture (IF filter implementation-cost versus carrier recovery) and are more robust in an RF frequency drift environment. Additionally, the prediction tools, computer simulations, and analysis of coherent systems is simpler. The threshold or capture effect in low C/I interference environment is critical for noncoherent discriminator based systems. We conclude with a comparison of hardware architectures of coherent and of noncoherent systems, including recent trends in commercial VLSI technology and direct baseband to RF transmit, RF to baseband (0-IF) receiver implementation strategies.

Effect of Multiple Scattering on the Compton Recoil Current Generated in an EMP, Revisited

DOE PAGES

Farmer, William A.; Friedman, Alex

2015-06-18

Multiple scattering has historically been treated in EMP modeling through the obliquity factor. The validity of this approach is examined here. A simplified model problem, which correctly captures cyclotron motion, Doppler shifting due to the electron motion, and multiple scattering is first considered. The simplified problem is solved three ways: the obliquity factor, Monte-Carlo, and Fokker-Planck finite-difference. Because of the Doppler effect, skewness occurs in the distribution. It is demonstrated that the obliquity factor does not correctly capture this skewness, but the Monte-Carlo and Fokker-Planck finite-difference approaches do. Here, the obliquity factor and Fokker-Planck finite-difference approaches are then compared inmore » a fuller treatment, which includes the initial Klein-Nishina distribution of the electrons, and the momentum dependence of both drag and scattering. It is found that, in general, the obliquity factor is adequate for most situations. However, as the gamma energy increases and the Klein-Nishina becomes more peaked in the forward direction, skewness in the distribution causes greater disagreement between the obliquity factor and a more accurate model of multiple scattering.« less

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…

Big Bang Titanic: New Dark Energy (Vacuum Gravity) Cosmic Model Emerges Upon Falsification of The Big Bang By Disproof of Its Central Assumptions

NASA Astrophysics Data System (ADS)

Gentry, Robert

2011-04-01

Physicists who identify the big bang with the early universe should have first noted from Hawking's A Brief History of Time, p. 42, that he ties Hubble's law to Doppler shifts from galaxy recession from a nearby center, not to bb's unvalidated and thus problematical expansion redshifts. Our PRL submission LJ12135 describes such a model, but in it Hubble's law is due to Doppler and vacuum gravity effects, the 2.73K CBR is vacuum gravity shifted blackbody cavity radiation from an outer galactic shell, and its (1 + z)-1 dilation and (M,z) relations closely fit high-z SNe Ia data; all this strongly implies our model's vacuum energy is the elusive dark energy. We also find GPS operation's GR effects falsify big bang's in-flight expansion redshift paradigm, and hence the big bang, by showing λ changes occur only at emission. Surprisingly we also discover big bang's CBR prediction is T < 2x10-8 K, not the observed 2.73K. So instead of the 2.73K affirming the big bang as cosmologists claim, it actually disproves it, to which the DAE's response is most enigmatic -- namely, CBR photons expand dλ/dt > 0, while galactic photons shrink dλ/dt < 0. Contrary to a PRL editor's claim, the above results show LJ12135 fits PRL guidelines for papers that replace established theories. For details see alphacosmos.net.

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.

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

Method for shaping and aiming narrow beams. [sonar mapping and target identification

NASA Technical Reports Server (NTRS)

Heyser, R. C. (Inventor)

1981-01-01

A sonar method and apparatus is discribed which utilizes a linear frequency chirp in a transmitter/receiver having a correlator to synthesize a narrow beamwidth pattern from otherwise broadbeam transducers when there is relative velocity between the transmitter/receiver and the target. The chirp is so produced in a generator in bandwidth, B, and time, T, as to produce a time bandwidth product, TB, that is increased for a narrower angle. A replica of the chirp produced in a generator is time delayed and Doppler shifted for use as a reference in the receiver for correlation of received chirps from targets. This reference is Doppler shifted to select targets preferentially, thereby to not only synthesize a narrow beam but also aim the beam in azimuth and elevation.

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.

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

An Acoustic OFDM System with Symbol-by-Symbol Doppler Compensation for Underwater Communication

PubMed Central

MinhHai, Tran; Rie, Saotome; Suzuki, Taisaku; Wada, Tomohisa

2016-01-01

We propose an acoustic OFDM system for underwater communication, specifically for vertical link communications such as between a robot in the sea bottom and a mother ship in the surface. The main contributions are (1) estimation of time varying Doppler shift using continual pilots in conjunction with monitoring the drift of Power Delay Profile and (2) symbol-by-symbol Doppler compensation in frequency domain by an ICI matrix representing nonuniform Doppler. In addition, we compare our proposal against a resampling method. Simulation and experimental results confirm that our system outperforms the resampling method when the velocity changes roughly over OFDM symbols. Overall, experimental results taken in Shizuoka, Japan, show our system using 16QAM, and 64QAM achieved a data throughput of 7.5 Kbit/sec with a transmitter moving at maximum 2 m/s, in a complicated trajectory, over 30 m vertically. PMID:27057558

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.

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

NASA Technical Reports Server (NTRS)

Durden, S.; Haddad, Z.

1998-01-01

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

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.

Frequency-Domain Channel Estimation and Equalization for Single Carrier Underwater Acoustic Communications

DTIC Science & Technology

2007-01-01

synchronization ; vm(k) white Gaussian noise with average power σ2. If the Doppler shift f m,k is significant, then it causes the received signal ym(k) to be time ...intersymbol interference (ISI) to extend over 20-300 symbols at a data rate of 2-10 kilosymbols per second. Another obstacle is the time -varying Doppler... synchronization that employs a phase-locked loop (PLL) or delay-locked loop (DLL). However, the DFE and PLL/DLL have to interact in a nonlinear fashion

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.

High-efficiency thermal switch based on topological Josephson junctions

NASA Astrophysics Data System (ADS)

Sothmann, Björn; Giazotto, Francesco; Hankiewicz, Ewelina M.

2017-02-01

We propose theoretically a thermal switch operating by the magnetic-flux controlled diffraction of phase-coherent heat currents in a thermally biased Josephson junction based on a two-dimensional topological insulator. For short junctions, the system shows a sharp switching behavior while for long junctions the switching is smooth. Physically, the switching arises from the Doppler shift of the superconducting condensate due to screening currents induced by a magnetic flux. We suggest a possible experimental realization that exhibits a relative temperature change of 40% between the on and off state for realistic parameters. This is a factor of two larger than in recently realized thermal modulators based on conventional superconducting tunnel junctions.

High-rate synthetic aperture communications in shallow water.

PubMed

Song, H C; Hodgkiss, W S; Kuperman, W A; Akal, T; Stevenson, M

2009-12-01

Time reversal communication exploits spatial diversity to achieve spatial and temporal focusing in complex ocean environments. Spatial diversity can be provided easily by a vertical array in a waveguide. Alternatively, spatial diversity can be obtained from a virtual horizontal array generated by two elements, a transmitter and a receiver, due to relative motion between them, referred to as a synthetic aperture. This paper presents coherent synthetic aperture communication results from at-sea experiments conducted in two different frequency bands: (1) 2-4 kHz and (2) 8-20 kHz. Case (1) employs binary-phase shift-keying modulation, while case (2) involves up to eight-phase shift keying modulation with a data rate of 30 kbits/s divided by the number of transmissions (diversity) to be accumulated. The receiver utilizes time reversal diversity combining followed by a single channel equalizer, with frequent channel updates to accommodate the time-varying channel due to coupling of space and time in the presence of motion. Two to five consecutive transmissions from a source moving at 4 kts over 3-6 km range in shallow water are combined successfully after Doppler compensation, confirming the feasibility of coherent synthetic aperture communications using time reversal.

Azimuthal resolution degradation due to ocean surface motion in focused arrays and SARS

NASA Astrophysics Data System (ADS)

1990-06-01

During the meeting at WHOI (5-18-90), a discussion arose of the ability of the focused array to simulate the R/v ratios typical of airborne and/or spaceborne SARs. In particular, the ability was questioned of the focused array to yield the same azimuthal resolution, rho, as the SAR. Although the focused array can be sampled to yield the same azimuthal resolution as the SAR, it is likely that the images generated by the focused array will not be identical to those produced by a SAR with the same azimuth resolution. For a true SAR, biases in the Doppler history of azimuthally traveling waves due to their along-track motion will cause shifts in their apparent position. This will cause waves which are physically at one location to shift over several pixel widths in the image. The limited swath width of the focused array will prevent if from observing scattered power from waves falling outside the swath, thus such waves will not affect the image formed within the swath, as would happen in the SAR. Thus, it is likely that the focused array will not yield the same image as a SAR having the same resolution.

Tropospheric Wind Profile Measurements with a Direct Detection Doppler Lidar

NASA Technical Reports Server (NTRS)

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

1998-01-01

Research has established the importance of global tropospheric wind measurements for large scale improvements in numerical weather prediction. In addition, global wind measurements provide data that are fundamental to the understanding and prediction of global climate change. These tasks are closely linked with the goals of the NASA Earth Science Enterprise and Global Climate Change programs. NASA Goddard has been actively involved in the development of direct detection Doppler lidar methods and technologies to meet the wind observing needs of the atmospheric science community. In this paper we describe a recently developed prototype wind lidar system using a direct detection Doppler technique for measuring wind profiles from the surface through the troposphere. This system uses a pulsed ND:YAG laser operating at 1064 nm as the transmitter. The laser pulse is directed to the atmosphere using a 40 cm diameter scan mirror. The portion of the laser energy backscattered from aerosols and molecules is collected by a 40 cm diameter telescope and coupled via fiber optics into the Doppler receiver. Single photon counting APD's are used to detect the atmospheric backscattered signal. The principle element of the receiver is a dual bandpass tunable Fabry Perot etalon which analyzes the Doppler shift of the incoming laser signal using the double edge technique. The double edge technique uses two high resolution optical filters having bandpasses offset relative to one another such that the 'edge' of the first filter's transmission function crosses that of the second at the half power point. The outgoing laser frequency is located approximately at the crossover point. Due to the opposite going slopes of the edges, a Doppler shift in the atmospheric backscattered laser frequency produces a positive change in signal for one filter and a negative change in the second filter. Taking the ratio of the two edge channel signals yields a result which is directly proportional to the component of the wind along the line-of-sight of the laser. Measuring the radial wind in several directions provides sufficient information to determine the true wind speed and direction. The lidar has operated from our laboratory at Goddard since June, 1997. Wind profiles have been obtained to altitudes of 12 km with a vertical resolution of 330 in. Vector wind data are obtained by rotating the scan mirror to measure line-of-sight wind profiles for at least two azimuth angles at an elevation angle of 45 degrees. The precision of the data as determined from the standard deviation of multiple independent lidar profiles is in the range of 1 to 3 m/sec up to 10 km. Good agreement is obtained when the lidar data are compared with the upper air rawinsonde soundings taken at Dulles airport. Examples of the wind lidar data will be presented along with a description of the instrument and future developments.

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.

An comprehensive time-distance measurement of deep meridional flow and its temporal variation

NASA Astrophysics Data System (ADS)

Chen, Ruizhu; Zhao, Junwei

2016-10-01

We report our latest results on the Sun's deep solar meridional-flow measurements by time-distance helioseismology technique using 6 years of SDO/HMI Doppler-velocity data. Determination of the meridional flow by time-distance helioseismology depends on a precise measurement of the flow-induced travel-time shifts of acoustic waves traveling in the solar interior. To resolve the weak travel-time-shift signals due to deep meridional flow, we need a high signal-to-noise ratio and a robust removal of the center-to-limb (CtoL) effect, which dominates the travel-time shifts. Here we perform an ultimately comprehensive measurement that tracks acoustic waves between any two points on solar surface. The travel-time shifts are composed of CtoL effect, which is a function of disk-centric distances, and contribution from the flow component parallel to wave traveling direction, which is a function of latitude and orientation. Assuming these two effects are independent, we can derive the CtoL effect and meridional-flow contributions by solving a set of linear equations in a least-square sense. We show the solved CtoL effect and the inversion results for the solar meridional flow, and analyze the annual variation of meridional flow from May 2010 to Apr 2016.

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.

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.

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.

Adaptation of Dunn Solar Telescope for Jovian Doppler spectro imaging

NASA Astrophysics Data System (ADS)

Underwood, Thomas A.; Voelz, David; Schmider, François-Xavier; Jackiewicz, Jason; Dejonghe, Julien; Bresson, Yves; Hull, Robert; Goncalves, Ivan; Gualme, Patrick; Morand, Frédéric; Preis, Olivier

2017-09-01

This paper describes instrumentation used to adapt the Dunn Solar Telescope (DST) located on Sacramento Peak in Sunspot, NM for observations using the Doppler Spectro Imager (DSI). The DSI is based on a Mach-Zehnder interferometer and measures the Doppler shift of solar lines allowing for the study of atmospheric dynamics of giant planets and the detection of their acoustic oscillations. The instrumentation is being designed and built through a collaborative effort between a French team from the Observatoire de la Cote d'Azur (OCA) that designed the DSI and a US team at New Mexico State University (NMSU). There are four major components that couple the DSI to the DST: a guider/tracker, fast steering mirror (FSM), pupil stabilizer and transfer optics. The guider/tracker processes digital video to centroid-track the planet and outputs voltages to the DST's heliostat controls. The FSM removes wavefront tip/tilt components primarily due to turbulence and the pupil stabilizer removes any slow pupil "wander" introduced by the telescope's heliostat/turret arrangement. The light received at a science port of the DST is sent through the correction and stabilization components and into the DSI. The FSM and transfer optics designs are being provided by the OCA team and serve much the same functions as they do for other telescopes at which DSI observations have been conducted. The pupil stabilization and guider are new and are required to address characteristics of the DST.

First measurement of Lyman alpha x-ray lines in hydrogen-like vanadium: results and implications for precision wavelength metrology and tests of QED

NASA Astrophysics Data System (ADS)

Gillaspy, J. D.; Chantler, C. T.; Paterson, D.; Hudson, L. T.; Serpa, F. G.; Takács, E.

2010-04-01

The first measurement of hydrogen-like vanadium x-ray Lyman alpha transitions has been made. The measurement was made on an absolute scale, fully independent of atomic structure calculations. Sufficient signal was obtained to reduce the statistical uncertainty to a small fraction of the total uncertainty budget. Potential sources of systematic error due to Doppler shifts were eliminated by performing the measurement on trapped ions. The energies for Ly α1 (1s-2p3/2) and Ly α2 (1s-2p1/2) are found to be 5443.95(25) eV and 5431.10(25) eV, respectively. These results are within approximately 1.5 σ (experimental) of the theoretical values 5443.63 eV and 5430.70 eV. The results are discussed in terms of their relation to the Lamb shift and the development of an x-ray wavelength standard based on a compact source of trapped highly charged ions.

Precise Lamb Shift Measurements in Hydrogen-Like Heavy Ions—Status and Perspectives

NASA Astrophysics Data System (ADS)

Andrianov, V.; Beckert, K.; Bleile, A.; Chatterjee, Ch.; Echler, A.; Egelhof, P.; Gumberidze, A.; Ilieva, S.; Kiselev, O.; Kilbourne, C.; Kluge, H.-J.; Kraft-Bermuth, S.; McCammon, D.; Meier, J. P.; Reuschl, R.; Stöhlker, T.; Trassinelli, M.

2009-12-01

The precise determination of the energy of the Lyman α1 and α2 lines in hydrogen-like heavy ions provides a sensitive test of quantum electrodynamics in very strong Coulomb fields. For the first time, a calorimetric low-temperature detector was applied in an experiment to precisely determine the transition energy of the Lyman lines of lead ions 207Pb81+ at the Experimental Storage Ring (ESR) at GSI. The detectors consist of silicon thermistors, provided by the NASA/Goddard Space Flight Center, and Pb or Sn absorbers to obtain high quantum efficiency in the energy range of 40-80 keV, where the Doppler-shifted Lyman lines are located. The measured energy of the Lyman α1 line, E(Ly-α1, 207Pb81+) = (77937±12stat±23syst) eV, agrees within errors with theoretical predictions. The systematic error is mainly due to uncertainties in the non-linear energy calibration of the detectors as well as the relative position of detector and gas-jet target.

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.

MAI-free performance of PMU-OFDM transceiver in time-variant environment

NASA Astrophysics Data System (ADS)

Tadjpour, Layla; Tsai, Shang-Ho; Kuo, C.-C. J.

2005-06-01

An approximately multi-user OFDM transceiver was introduced to reduce the multi-access interference (MAI ) due to the carrier frequency offset (CFO) to a negligible amount via precoding by Tsai, Lin and Kuo. In this work, we investigate the performance of this precoded multi-user (PMU) OFDM system in a time-variant channel environment. We analyze and compare the MAI effect caused by time-variant channels in the PMU-OFDM and the OFDMA systems. Generally speaking, the MAI effect consists of two parts. The first part is due to the loss of orthogonality among subchannels for all users while the second part is due to the CFO effect caused by the Doppler shift. Simulation results show that, although OFDMA outperforms the PMU-OFDM transceiver in a fast time-variant environment without CFO, PMU-OFDM outperforms OFDMA in a slow time-variant channel via the use of M/2 symmetric or anti-symmetric codewords of M Hadamard-Walsh codes.

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.

Pulse periods and the long-term variations of the X-ray pulsars VELA X-1 and Centaurus X-3

NASA Astrophysics Data System (ADS)

Tsunemi, Hiroshi

The paper reports recent determinations of the pulse period for two X-ray pulsars, Vela X-1 and Cen X-3, made in 1987 with the All Sky Monitor (ASM) on board the Ginga satellite. The heliocentric pulse periods are 283.09 + or - 0.01 s and 4.8229 + or - 0.0001 s, respectively. These are the longest and shortest values in their respective observational histories. The random walk model for the Vela X-1 pulsar can explain this result as well as those obtained previously. It is also noted that the pulse-period change for the Cen X-3 system shows a 9-yr periodicity. This is probably due to the activity of the companion star rather than to Doppler-shift variations due to a third body or the precession of the neutron star.

Blind ICA detection based on second-order cone programming for MC-CDMA systems

NASA Astrophysics Data System (ADS)

Jen, Chih-Wei; Jou, Shyh-Jye

2014-12-01

The multicarrier code division multiple access (MC-CDMA) technique has received considerable interest for its potential application to future wireless communication systems due to its high data rate. A common problem regarding the blind multiuser detectors used in MC-CDMA systems is that they are extremely sensitive to the complex channel environment. Besides, the perturbation of colored noise may negatively affect the performance of the system. In this paper, a new coherent detection method will be proposed, which utilizes the modified fast independent component analysis (FastICA) algorithm, based on approximate negentropy maximization that is subject to the second-order cone programming (SOCP) constraint. The aim of the proposed coherent detection is to provide robustness against small-to-medium channel estimation mismatch (CEM) that may arise from channel frequency response estimation error in the MC-CDMA system, which is modulated by downlink binary phase-shift keying (BPSK) under colored noise. Noncoherent demodulation schemes are preferable to coherent demodulation schemes, as the latter are difficult to implement over time-varying fading channels. Differential phase-shift keying (DPSK) is therefore the natural choice for an alternative modulation scheme. Furthermore, the new blind differential SOCP-based ICA (SOCP-ICA) detection without channel estimation and compensation will be proposed to combat Doppler spread caused by time-varying fading channels in the DPSK-modulated MC-CDMA system under colored noise. In this paper, numerical simulations are used to illustrate the robustness of the proposed blind coherent SOCP-ICA detector against small-to-medium CEM and to emphasize the advantage of the blind differential SOCP-ICA detector in overcoming Doppler spread.

Relativistic radiative transfer in a moving stratus irradiated by a luminous flat source

NASA Astrophysics Data System (ADS)

Fukue, Jun

2015-06-01

Relativistic radiative transfer in a geometrically thin stratus (sheet-like gaseous cloud with finite optical depth), which is moving at a relativistic speed around a luminous flat source, such as accretion disks, and is irradiated by the source, is examined under the special relativistic treatment. Incident radiation is aberrated and Doppler-shifted when it is received by the stratus, and emitted radiation is also aberrated and Doppler-shifted when it leaves the stratus. Considering these relativistic effects, we analytically obtain the emergent intensity as well as other radiative quantities in the purely scattering case for both infinite and finite strati. We mainly consider the frequency-integrated case, but also briefly show the frequency-dependent one. We also solve the relativistic radiative transfer equation numerically, and compare the results with the analytical solutions. In the infinite stratus, the mean intensity in the comoving and inertial frames decreases and becomes constant, as the stratus speed increases. The flux in the comoving frame decreases exponentially with the optical depth. The emergent intensity decreases as the speed increases, since the incident photons are redshifted at the bottom-side of the stratus. In the finite stratus, the mean intensity in the comoving and inertial frames quickly increases in the top-side region due to the aberrated photons. The flux in the comoving frame is positive in the range of 0 < β ≤ 0.4, while it becomes negative for β ≳ 0.5. The behavior of the emergent intensity is similar to that of the infinite case, although there is an irradiation effect caused by the aberrated photons.

Compressional Alfvén eigenmodes in rotating spherical tokamak plasmas

DOE PAGES

Smith, H. M.; Fredrickson, E. D.

2017-02-07

Spherical tokamaks often have a considerable toroidal plasma rotation of several tens of kHz. Compressional Alfvén eigenmodes in such devices therefore experience a frequency shift, which if the plasma were rotating as a rigid body, would be a simple Doppler shift. However, since the rotation frequency depends on minor radius, the eigenmodes are affected in a more complicated way. The eigenmode solver CAE3B (Smith et al 2009 Plasma Phys. Control. Fusion 51 075001) has been extended to account for toroidal plasma rotation. The results show that the eigenfrequency shift due to rotation can be approximated by a rigid body rotationmore » with a frequency computed from a spatial average of the real rotation profile weighted with the eigenmode amplitude. To investigate the effect of extending the computational domain to the vessel wall, a simplified eigenmode equation, yet retaining plasma rotation, is solved by a modified version of the CAE code used in Fredrickson et al (2013 Phys. Plasmas 20 042112). Lastly, both solving the full eigenmode equation, as in the CAE3B code, and placing the boundary at the vessel wall, as in the CAE code, significantly influences the calculated eigenfrequencies.« less

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.

MicroV Technology to Improve Transcranial Color Coded Doppler Examinations.

PubMed

Malferrari, Giovanni; Pulito, Giuseppe; Pizzini, Attilia Maria; Carraro, Nicola; Meneghetti, Giorgio; Sanzaro, Enzo; Prati, Patrizio; Siniscalchi, Antonio; Monaco, Daniela

2018-05-04

The purpose of this review is to provide an update on technology related to Transcranial Color Coded Doppler Examinations. Microvascularization (MicroV) is an emerging Power Doppler technology which can allow visualization of low and weak blood flows even at high depths, thus providing a suitable technique for transcranial ultrasound analysis. With MicroV, reconstruction of the vessel shape can be improved, without any overestimation. Furthermore, by analyzing the Doppler signal, MicroV allows a global image of the Circle of Willis. Transcranial Doppler was originally developed for the velocimetric analysis of intracranial vessels, in particular to detect stenoses and the assessment of collateral circulation. Doppler velocimetric analysis was then compared to other neuroimaging techniques, thus providing a cut-off threshold. Transcranial Color Coded Doppler sonography allowed the characterization of vessel morphology. In both Color Doppler and Power Doppler, the signal overestimated the shape of the intracranial vessels, mostly in the presence of thin vessels and high depths of study. In further neurosonology technology development efforts, attempts have been made to address morphology issues and overcome technical limitations. The use of contrast agents has helped in this regard by introducing harmonics and subtraction software, which allowed better morphological studies of vessels, due to their increased signal-to-noise ratio. Having no limitations in the learning curve, in time and contrast agent techniques, and due to its high signal-to-noise ratio, MicroV has shown great potential to obtain the best morphological definition. Copyright © 2018 by the American Society of Neuroimaging.

Critical Spacecraft-to-Earth Communications for Mars Exploration Rover (MER) entry, descent and landing

NASA Technical Reports Server (NTRS)

Hurd, William J.; Estabrook, Polly; Racho, Caroline S.; Satorius, Edgar H.

2002-01-01

For planetary lander missions, the most challenging phase of the spacecraft to ground communications is during the entry, descent, and landing (EDL). As each 2003 Mars Exploration Rover (MER) enters the Martian atmosphere, it slows dramatically. The extreme acceleration and jerk cause extreme Doppler dynamics on the X-band signal received on Earth. When the vehicle slows sufficiently, the parachute is deployed, causing almost a step in deceleration. After parachute deployment, the lander is lowered beneath the parachute on a bridle. The swinging motion of the lander imparts high Doppler dynamics on the signal and causes the received signal strength to vary widely, due to changing antenna pointing angles. All this time, the vehicle transmits important health and status information that is especially critical if the landing is not successful. Even using the largest Deep Space Network antennas, the weak signal and high dynamics render it impossible to conduct reliable phase coherent communications. Therefore, a specialized form of frequency-shift-keying will be used. This paper describes the EDL scenario, the signal conditions, the methods used to detect and frequency-track the carrier and to detect the data modulation, and the resulting performance estimates.

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.

Helicon modes in uniform plasmas. III. Angular momentum

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

Stenzel, R. L.; Urrutia, J. M.

Helicons are electromagnetic waves with helical phase fronts propagating in the whistler mode in magnetized plasmas and solids. They have similar properties to electromagnetic waves with angular momentum in free space. Helicons are circularly polarized waves carrying spin angular momentum and orbital angular momentum due to their propagation around the ambient magnetic field B{sub 0}. These properties have not been considered in the community of researchers working on helicon plasma sources, but are the topic of the present work. The present work focuses on the field topology of helicons in unbounded plasmas, not on helicon source physics. Helicons are excitedmore » in a large uniform laboratory plasma with a magnetic loop antenna whose dipole axis is aligned along or across B{sub 0}. The wave fields are measured in orthogonal planes and extended to three dimensions (3D) by interpolation. Since density and B{sub 0} are uniform, small amplitude waves from loops at different locations can be superimposed to generate complex antenna patterns. With a circular array of phase shifted loops, whistler modes with angular and axial wave propagation, i.e., helicons, are generated. Without boundaries radial propagation also arises. The azimuthal mode number m can be positive or negative while the field polarization remains right-hand circular. The conservation of energy and momentum implies that these field quantities are transferred to matter which causes damping or reflection. Wave-particle interactions with fast electrons are possible by Doppler shifted resonances. The transverse Doppler shift is demonstrated. Wave-wave interactions are also shown by showing collisions between different helicons. Whistler turbulence does not always have to be created by nonlinear wave-interactions but can also be a linear superposition of waves from random sources. In helicon collisions, the linear and/or orbital angular momenta can be canceled, which results in a great variety of field topologies. The work will be contrasted to the research on helicon plasma sources.« less

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.

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.

A Polarization-Diversity Homodyne Image-Reject Optical Tranceiver Architecture for Improved Range and Signal Detection in Coherent Doppler Lidars

NASA Astrophysics Data System (ADS)

Abari, C. F.; Chu, X.; Mann, J.

2014-12-01

Doppler light detection and ranging (lidar) has been used for a few decades for the characterization of wind fields and turbulence structures in the atmosphere. More recently, due to the advances in fiber optic communications, all-fiber coherent Doppler lidars (CDL) have been developed and widely used as a primary instrument for probing the atmospheric boundary layer wind fields. Due to a variety of reasons, all-fiber CDLs have gradually replaced their counterparts benefiting from technologies other than fiber optics. Most CDLs suffer from a number of drawbacks inherent to their principle of operation. For instance, one of the main challenges in CDLs is extracting the signal information from noisy observations, which is common to most opto-electronic systems. Moreover, it is sometimes challenging to extract the sign of the measured radial velocity. Conventionally, CDLs have benefitted from an intermediate frequency (IF) heterodyne receiver architecture for the determination of the radial velocity. In such systems, either the transmitted or the local oscillator (LO) signal is shifted in frequency. Such architectures may suffer from increased noise and spurious effects due to the employment of additional active components, e.g., acousto-optic modulator (AOM), limited measurement bandwidth (BW), and a more sophisticated electronic front-end for signal detection. On the other hand, one of the main challenges in long-range (pulsed) CDLs is the limitations imposed on the pulse repetition rate (PRR) as well as the available transmit power. These restrictions are more significant in all-fiber pulsed CDLs in which Erbium doped fiber amplifiers (EDFA) are employed for the amplification of the optical pulses. In this study, we propose an alternative reconfigurable opto-electronic front-end transceiver architecture in all-fiber CDLs where there is no compromise in the detection BW. Additionally, by benefiting from a polarization diversity architecture we show that both the PRR and transmit optical power can be doubled. Other benefits of the proposed system include, but not limited to, capturing additional information about the nature of aerosol particles, improvement of the signal-to-estimation-noise-ratio (SENR), faster scanning of the wind field, and improved measurement range.

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

Calcino, Josh; Davis, Tamara, E-mail: j.calcino@uq.edu.au, E-mail: tamarad@physics.uq.edu.au

Recent papers have shown that a small systematic redshift shift (Δ z ∼ 10{sup −5}) in measurements of type Ia supernovae can cause a significant bias (∼1%) in the recovery of cosmological parameters. Such a redshift shift could be caused, for example, by a gravitational redshift due to the density of our local environment. The sensitivity of supernova data to redshift shifts means supernovae make excellent probes of inhomogeneities. We therefore invert the analysis, and try to diagnose the nature of our local gravitational environment by fitting for Δ z as an extra free parameter alongside the usual cosmological parameters.more » Using the Joint Light-curve SN Ia dataset we find the best fit includes a systematic redshift shift of Δ z = (2.6{sup +2.7}{sub −2.8}) × 10{sup −4}. This is a larger shift than would be expected due to gravitational redshifts in a standard Λ-Cold Dark Matter universe (though still consistent with zero), and would correspond to a monopole Doppler shift of about 100 km s{sup −1} moving away from the Milky-Way. However, since most supernova measurements are made to a redshift precision of no better than 10{sup −3}, it is possible that a systematic error smaller than the statistical error remains in the data and is responsible for the shift; or that it is an insignificant statistical fluctuation. We find that when Δ z is included as a free parameter while fitting to the JLA SN Ia data, the constraints on the matter density shifts to Ω {sub m} = 0.313{sup +0.042}{sub −0.040}, bringing it into better agreement with the CMB cosmological parameter constraints from Planck. A positive Δ z ∼ 2.6×10{sup −4} would also cause us to overestimate the supernova measurement of Hubble's constant by Δ H {sub 0} ∼ 1 kms{sup −1}Mpc{sup −1}. However this overestimation should diminish as one increases the low-redshift cutoff, and this is not seen in the most recent data.« less

Radar Doppler Processing with Nonuniform Sampling.

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

Doerry, Armin W.

2017-07-01

Conventional signal processing to estimate radar Doppler frequency often assumes uniform pulse/sample spacing. This is for the convenience of t he processing. More recent performance enhancements in processor capability allow optimally processing nonuniform pulse/sample spacing, thereby overcoming some of the baggage that attends uniform sampling, such as Doppler ambiguity and SNR losses due to sidelobe control measures.

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.

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.

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.

Wave Field Characterization Using Dual-Polarized Pulse-Doppler X-Band Radar

DTIC Science & Technology

2012-06-01

spectrum (frequencies higher than that associated with the wind wave peak) are similar for the buoy and Doppler, and likewise for the ultrasound array and...values of the RCS and ultrasound array relative to the buoy and Doppler are due to the formers’ larger energy levels at high frequencies. NSWCCD-50-TR...pp. 199- 203, 2008. [II] W. J. Plant, W. C. Keller, A. B. Reeves, E. A. Uliana, and J. W. Johnson, " Airborne microwave Doppler measurements of

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.

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.

First pressure shift measurement of ozone molecular lines at 9.54 μm using a tunable quantum cascade laser

NASA Astrophysics Data System (ADS)

Minissale, Marco; Zanon-Willette, Thomas; Jeseck, Pascal; Boursier, Corinne; Janssen, Christof

2018-06-01

Using a free-running distributed-feedback quantum cascade laser (QCL) emitting at 9.54 μm, the pressure shift parameters of four intense rovibrational transitions in the ν3 fundamental band of ozone induced by oxygen (O2), air and the noble gases helium (He), argon (Ar), and xenon (Xe) are obtained by employing second harmonic detection. The experimental analysis comprises a full uncertainty budget and provides line shift data which are traceable to SI. The high density of transitions in the ν3 spectral region of ozone make this region particularly difficult to study with more commonly used techniques such as Fourier transform spectroscopy. The comparatively high spectral resolution of the QCL in the MHz range, on the contrary, allows to measure molecular shifts at relatively low pressures (from 2 to 70 hPa), thus reducing the impact of spectral congestion due to pressure broadening of molecular lines. The comparison of our results with published data shows that presently recommended values for the pressure shift are too low in this region. This observation is corroborated by semi-classical calculations using the Robert-Bonamy formalism. A slight negative J dependence, already observed in other ozone vibrational bands, is predicted. Systematic use of our technique could be very useful to support this hypothesis and to make up for the lack of shift parameters for ozone ν3 transitions in molecular spectral databases. A subsequent stabilization of the QCL onto an optical frequency comb will open up possibilities to perform metrological measurements of Doppler-free molecular lines.

Tissue Doppler Imaging in the evaluation of abdominal aortic pulsatility: a useful tool for the neonatologist.

PubMed

Valerio, Enrico; Grison, Alessandra; Capretta, Anna; Golin, Rosanna; Ferrarese, Paola; Bellettato, Massimo

2017-03-01

Sonographic cardiac evaluation of newborns with suspected aortic coarctation (AoC) should tend to demonstrate a good phasic and pulsatile flow and the absence of pressure gradient along a normally conformed aortic arch from the modified left parasternal and suprasternal echocardiographic views; these findings, however, may not necessarily rule out a more distal coarctation in the descending aorta. For this reason, the sonographic exam of newborns with suspected AoC should always include a Doppler evaluation of abdominal aortic blood flow from the subcostal view. Occasionally, however, a clearly pulsatile Doppler flow trace in abdominal aorta may be difficult to obtain due to the bad insonation angle existing between the probe and the vessel. In such suboptimal ultrasonic alignment situation, the use of Tissue Doppler Imaging instead of classic Doppler flow imaging may reveal a preserved aortic pulsatility by sampling the aortic wall motion induced by normal flow. We propose to take advantage of the TDI pattern as a surrogate of a normal pulsatile Doppler flow trace in abdominal aorta when the latter is difficult to obtain due to malalignment with the insonated vessel.

High-resolution Doppler model of the human gait

NASA Astrophysics Data System (ADS)

Geisheimer, Jonathan L.; Greneker, Eugene F., III; Marshall, William S.

2002-07-01

A high resolution Doppler model of the walking human was developed for analyzing the continuous wave (CW) radar gait signature. Data for twenty subjects were collected simultaneously using an infrared motion capture system along with a two channel 10.525 GHz CW radar. The motion capture system recorded three-dimensional coordinates of infrared markers placed on the body. These body marker coordinates were used as inputs to create the theoretical Doppler output using a model constructed in MATLAB. The outputs of the model are the simulated Doppler signals due to each of the major limbs and the thorax. An estimated radar cross section for each part of the body was assigned using the Lund & Browder chart of estimated body surface area. The resultant Doppler model was then compared with the actual recorded Doppler gait signature in the frequency domain using the spectrogram. Comparison of the two sets of data has revealed several identifiable biomechanical features in the radar gait signature due to leg and body motion. The result of the research shows that a wealth of information can be unlocked from the radar gait signature, which may be useful in security and biometric applications.

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)

Corruption of radio metric Doppler due to solar plasma dynamics: S/X dual-frequency Doppler calibration for these effects

NASA Technical Reports Server (NTRS)

Winn, F. B.; Reinbold, S. R.; Yip, K. W.; Koch, R. E.; Lubeley, A.

1975-01-01

Doppler data from Mariner 6, 7, 9, and 10 and Pioneer 10 and 11 were discussed and the rms noise level for various sun-earth-probe angles were shown. The noise levels of both S- and X-band Doppler data for sun-earth-probe angles smaller than 20 deg were observed to be orders of magnitude greater than nominal. Such solar plasma-related Doppler degradation reduced the Mariner 10-Mercury 11 encounter navigation accuracy by nearly a factor of 10. Furthermore, this degradation was shown to be indirectly related to plasma dynamics and not a direct measure of the dynamics.

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.

Changes in cochlear blood flow in mice due to loud sound exposure measured with Doppler optical microangiography and laser Doppler flowmetry.

PubMed

Reif, Roberto; Zhi, Zhongwei; Dziennis, Suzan; Nuttall, Alfred L; Wang, Ruikang K

2013-10-01

In this work we determined the contributions of loud sound exposure (LSE) on cochlear blood flow (CoBF) in an in vivo anesthetized mouse model. A broadband noise system (20 kHz bandwidth) with an intensity of 119 dB SPL, was used for a period of one hour to produce a loud sound stimulus. Two techniques were used to study the changes in blood flow, a Doppler optical microangiography (DOMAG) system; which can measure the blood flow within individual cochlear vessels, and a laser Doppler flowmetry (LDF) system; which averages the blood flow within a volume (a hemisphere of ~1.5 mm radius) of tissue. Both systems determined that the blood flow within the cochlea is reduced due to the LSE stimulation.

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.

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).

Ionospheric S-shaped Doppler fluctuations produced by the tornadoes

NASA Technical Reports Server (NTRS)

Hung, R. J.; Rao, G. L.; Smith, R. E.

1974-01-01

A three-dimensional nine element HF-CW Doppler sounder array has been used to detect ionospheric disturbances which may be due to tornadoes. The typical events chosen in the present study occurred on November 20 and 27, 1973. Both events are apparently associated with tornadoes sighted in the Huntsville, Alabama area. The Doppler records show S-shaped waves rather than the quasi-sinusoidal waves observed in conjunction with and apparently due to thunderstorms. The wave-periods are in the range of 6 to 8 minutes instead of the 3 to 5 minute periods associated with thunderstorms. Dissipation of waves is mostly due to the evanescent effect and they cannot propagate very far from the path of the tornado center. A theory is presented which is in good agreement with the observations.

Student Microwave Experiments Involving the Doppler Effect.

ERIC Educational Resources Information Center

Weber, F. Neff; And Others

1980-01-01

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

UV And X-Ray Emission from Impacts of Fragmented Accretion Streams on Classical T Tauri Stars

NASA Astrophysics Data System (ADS)

Colombo, Salvatore; Orlando, Salvatore; Peres, Giovanni; Argiroffi, Costanza; Reale, Fabio

2016-07-01

According to the magnetoshperic accretion scenario, during their evo- lution, Classical T Tauri stars accrete material from their circumstellar disk. The accretion process is regulated by the stellar magnetic eld and produces hot and dense post-shocks on the stellar surface as a result of impacts of the downfalling material. The impact regions are expected to strongly radiate in UV and X-rays. Several lines of evidence support the magnetospheric accretion scenario, especially in optical and infrared bands. However several points still remain unclear as, for instance,where the complex-pro le UV lines originate, or whether and how UV and X-ray emission is produced in the same shock region. The analysis of a large solar eruption has shown that EUV excesses might be e ectively produced by the impact of dense fragments onto the stellar surface. Since a steady accretion stream does not reprouce observations, in this work we investi- gate the e ects of a fragmented accretion stream on the uxes and pro les of C IV and O VIII emission lines. To this end we model the impact of a fragmented accretion stream onto the chromosphere of a CTTS with 2D axysimmetric magneto-hydrodynamic simulations. Our model takes into account of the gravity, the stellar magnetic eld, the thermal conduction and the radiative cooling from an optically thin plasma. From the model results, we synthesize the UV and X-ray emission including the e ect of Doppler shift along the line of sight. We nd that a fragmented accretion stream produces complex pro les of UV emission lines which consists of multiple components with di erent Doppler shifts. Our model predicts line pro les that are consistent with those observed and explain their origin as due to the stream fragmentation.

Calculation of extracted ion beam particle distribution including within-extractor collisions from H-alpha Doppler shift measurements.

PubMed

Kim, Tae-Seong; Kim, Jinchoon; In, Sang Ryul; Jeong, Seung Ho

2008-02-01

Prototype long pulse ion sources are being developed and tested toward the goal of a deuterium beam extraction of 120 keV/65 A. The latest prototype source consists of a magnetic bucket plasma generator and a four-grid copper accelerator system with multicircular apertures of 568 holes. To measure the angular divergence and the ion species of the ion beam, an optical multichannel analyzer (OMA) system for a Doppler-shifted H-alpha lights was set up at the end of a gas-cell neutralizer. But the OMA data are very difficult to analyze due to a large background level on the top of the three energy peaks (coming from H(+), H(2) (+), and H(3) (+)). These background spectra in the OMA signals seem to result from partially accelerated ion beams in the accelerator. Extracted ions could undergo a premature charge exchange as the accelerator column tends to have a high hydrogen partial pressure from the unused gas from the plasma generator, resulting in a continuous background of partially accelerated beam particles at the accelerator exit. This effect is calculated by accounting for all the possible atomic collision processes and numerically summing up three ion species across the accelerator column. The collection of all the atomic reaction cross sections and the numerical summing up will be presented. The result considerably depends on the background pressure and the ion beam species ratio (H(+), H(2) (+), and H(3) (+)). This effect constitutes more than 20% of the whole particle distribution. And the energy distribution of those suffering from collisions is broad and shows a broad maximum in the vicinity of the half and the third energy region.

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.

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.

Echocardiographic assessment of left ventricular diastolic function.

PubMed

Pirat, Bahar; Zoghbi, William A

2007-09-01

Assessment of diastolic function and left ventricular filling pressures in the setting of both normal and reduced systolic function is of major importance particularly in patients with dyspnea. Since multiple echocardiography parameters are used to assess diastolic function each with some limitations, a comprehensive approach should be applied. Transmitral Doppler flow should be evaluated in combination with newer, less load dependent Doppler techniques. Tissue Doppler imaging provides accurate, well validated data regarding diastolic properties and filling pressures of the left ventricle. Tissue Doppler imaging should be the part of a routine echocardiography study due to its ease of use and high reproducibility. Pulmonary vein Doppler and flow propagation velocity should be incorporated into the evaluation when needed.

Energetic-particle-modified global Alfvén eigenmodes

NASA Astrophysics Data System (ADS)

Lestz, J. B.; Belova, E. V.; Gorelenkov, N. N.

2018-04-01

Fully self-consistent hybrid MHD/particle simulations reveal strong energetic particle modifications to sub-cyclotron global Alfvén eigenmodes (GAEs) in low-aspect ratio, NSTX-like conditions. Key parameters defining the fast ion distribution function—the normalized injection velocity v0/vA and central pitch—are varied in order to study their influence on the characteristics of the excited modes. It is found that the frequency of the most unstable mode changes significantly and continuously with beam parameters, in accordance with the Doppler-shifted cyclotron resonances which drive the modes, and depending most substantially on v0/vA . This unexpected result is present for both counter-propagating GAEs, which are routinely excited in NSTX, and high frequency co-GAEs, which have not been previously studied. Large changes in frequency without clear corresponding changes in the mode structure are signatures of an energetic particle mode, referred to here as an energetic-particle-modified GAE. Additional simulations conducted for a fixed MHD equilibrium demonstrate that the GAE frequency shift cannot be explained by the equilibrium changes due to energetic particle effects.

Energetic-particle-modified global Alfven eigenmodes

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

Lestz, J. B.; Belova, E. V.; Gorelenkov, N. N.

Fully self-consistent hybrid MHD/particle simulations reveal strong energetic particle modifications to sub-cyclotron global Alfvén eigenmodes (GAEs) in low-aspect ratio, NSTX-like conditions. Key parameters defining the fast ion distribution function—the normalized injection velocity v 0/v A and central pitch—are varied in order to study their influence on the characteristics of the excited modes. It is found that the frequency of the most unstable mode changes significantly and continuously with beam parameters, in accordance with the Doppler-shifted cyclotron resonances which drive the modes, and depending most substantially on v 0/v A. This unexpected result is present for both counter-propagating GAEs, which aremore » routinely excited in NSTX, and high frequency co-GAEs, which have not been previously studied. Large changes in frequency without clear corresponding changes in the mode structure are signatures of an energetic particle mode, referred to here as an energetic-particle-modified GAE. In conclusion, additional simulations conducted for a fixed MHD equilibrium demonstrate that the GAE frequency shift cannot be explained by the equilibrium changes due to energetic particle effects.« less

Energetic-particle-modified global Alfven eigenmodes

DOE PAGES

Lestz, J. B.; Belova, E. V.; Gorelenkov, N. N.

2018-04-30

Fully self-consistent hybrid MHD/particle simulations reveal strong energetic particle modifications to sub-cyclotron global Alfvén eigenmodes (GAEs) in low-aspect ratio, NSTX-like conditions. Key parameters defining the fast ion distribution function—the normalized injection velocity v 0/v A and central pitch—are varied in order to study their influence on the characteristics of the excited modes. It is found that the frequency of the most unstable mode changes significantly and continuously with beam parameters, in accordance with the Doppler-shifted cyclotron resonances which drive the modes, and depending most substantially on v 0/v A. This unexpected result is present for both counter-propagating GAEs, which aremore » routinely excited in NSTX, and high frequency co-GAEs, which have not been previously studied. Large changes in frequency without clear corresponding changes in the mode structure are signatures of an energetic particle mode, referred to here as an energetic-particle-modified GAE. In conclusion, additional simulations conducted for a fixed MHD equilibrium demonstrate that the GAE frequency shift cannot be explained by the equilibrium changes due to energetic particle effects.« less

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.

Closed coronal structures. V - Gasdynamic models of flaring loops and comparison with SMM observations

NASA Technical Reports Server (NTRS)

Peres, G.; Serio, S.; Vaiana, G.; Acton, L.; Leibacher, J.; Rosner, R.; Pallavicini, R.

1983-01-01

A time-dependent one-dimensional code incorporating energy, momentum and mass conservation equations, and taking the entire solar atmospheric structure into account, is used to investigate the hydrodynamic response of confined magnetic structures to strong heating perturbations. Model calculation results are compared with flare observations which include the light curves of spectral lines formed over a wide range of coronal flare temperatures, as well as determinations of Doppler shifts for the high temperature plasma. It is shown that the numerical simulation predictions are in good overall agreement with the observed flare coronal plasma evolution, correctly reproducing the temporal profile of X-ray spectral lines and their relative intensities. The predicted upflow velocities support the interpretation of the blueshifts as due to evaporation of chromospheric material.

Angle-resolved Auger electron spectra induced by neon ion impact on aluminum

NASA Technical Reports Server (NTRS)

Pepper, S. V.; Aron, P. R.

1986-01-01

Auger electron emission from aluminum bombarded with 1 to 5 keV neon ions was studied by angle-resolved electron spectroscopy. The position and shape of the spectral features depended on the incident ion energy, angle of ion incidence, and electron take-off angle with respect to the aluminum surface. These spectral dependencies were interpreted in terms of the Doppler shift given to the Auger electron velocity by the excited atom ejected into the vacuum. For oblique ion incidence it is concluded that a flux of high energy atoms are ejected in a direction close to the projection of the ion beam on the target surface. In addition, a new spectral feature was found and identified as due to Auger emission from excited neon in the aluminum matrix.

Venus mesospheric winds and the carbon monoxide bulge

NASA Technical Reports Server (NTRS)

Gurwell, Mark A.; Muhleman, Duane O.; Shah, Kathryn Pierce

1992-01-01

Recently, our group mapped the CO absorption lines on the disk of Venus in 1988 using the synthetic aperture array at the Owens Valley Radio Observatory. Observations were make in the (0-1) rotational transition of CO at 115 GHz, or a wavelength of 2.6 mm. Systematic variations in the Doppler shifts of the lines (particularly near the limbs) enable the group to directly map the wind field at 100 plus or minus 10 km, the peak altitude for the experimental weighting functions used. These measurements show that the winds are indeed of the order of a 100 m/s at this altitude. Previously, many had assumed that the vertical wind profile would quickly fall to zero above the cloud tops, due to cyclostrophic breakdown. This work is reviewed.

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.

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.

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.

Detecting and mitigating wind turbine clutter for airspace radar systems.

PubMed

Wang, Wen-Qin

2013-01-01

It is well recognized that a wind turbine has a large radar cross-section (RCS) and, due to the movement of the blades, the wind turbine will generate a Doppler frequency shift. This scattering behavior may cause severe interferences on existing radar systems including static ground-based radars and spaceborne or airborne radars. To resolve this problem, efficient techniques or algorithms should be developed to mitigate the effects of wind farms on radars. Herein, one transponder-based mitigation technique is presented. The transponder is not a new concept, which has been proposed for calibrating high-resolution imaging radars. It modulates the radar signal in a manner that the retransmitted signals can be separated from the scene echoes. As wind farms often occupy only a small area, mitigation processing in the whole radar operation will be redundant and cost inefficient. Hence, this paper uses a transponder to determine whether the radar is impacted by the wind farms. If so, the effects of wind farms are then mitigated with subsequent Kalman filtering or plot target extraction algorithms. Taking airborne synthetic aperture radar (SAR) and pulse Doppler radar as the examples, this paper provides the corresponding system configuration and processing algorithms. The effectiveness of the mitigation technique is validated by numerical simulation results.

Detecting and Mitigating Wind Turbine Clutter for Airspace Radar Systems

PubMed Central

2013-01-01

It is well recognized that a wind turbine has a large radar cross-section (RCS) and, due to the movement of the blades, the wind turbine will generate a Doppler frequency shift. This scattering behavior may cause severe interferences on existing radar systems including static ground-based radars and spaceborne or airborne radars. To resolve this problem, efficient techniques or algorithms should be developed to mitigate the effects of wind farms on radars. Herein, one transponder-based mitigation technique is presented. The transponder is not a new concept, which has been proposed for calibrating high-resolution imaging radars. It modulates the radar signal in a manner that the retransmitted signals can be separated from the scene echoes. As wind farms often occupy only a small area, mitigation processing in the whole radar operation will be redundant and cost inefficient. Hence, this paper uses a transponder to determine whether the radar is impacted by the wind farms. If so, the effects of wind farms are then mitigated with subsequent Kalman filtering or plot target extraction algorithms. Taking airborne synthetic aperture radar (SAR) and pulse Doppler radar as the examples, this paper provides the corresponding system configuration and processing algorithms. The effectiveness of the mitigation technique is validated by numerical simulation results. PMID:24385880

In-process, non-destructive multimodal dynamic testing of high-speed composite rotors

NASA Astrophysics Data System (ADS)

Kuschmierz, Robert; Filippatos, Angelos; Langkamp, Albert; Hufenbach, Werner; Czarske, Jürgern W.; Fischer, Andreas

2014-03-01

Fibre reinforced plastic (FRP) rotors are lightweight and offer great perspectives in high-speed applications such as turbo machinery. Currently, novel rotor structures and materials are investigated for the purpose of increasing machine efficiency, lifetime and loading limits. Due to complex rotor structures, high anisotropy and non-linear behavior of FRP under dynamic loads, an in-process measurement system is necessary to monitor and to investigate the evolution of damages under real operation conditions. A non-invasive, optical laser Doppler distance sensor measurement system is applied to determine the biaxial deformation of a bladed FRP rotor with micron uncertainty as well as the tangential blade vibrations at surface speeds above 300 m/s. The laser Doppler distance sensor is applicable under vacuum conditions. Measurements at varying loading conditions are used to determine elastic and plastic deformations. Furthermore they allow to determine hysteresis, fatigue, Eigenfrequency shifts and loading limits. The deformation measurements show a highly anisotropic and nonlinear behavior and offer a deeper understanding of the damage evolution in FRP rotors. The experimental results are used to validate and to calibrate a simulation model of the deformation. The simulation combines finite element analysis and a damage mechanics model. The combination of simulation and measurement system enables the monitoring and prediction of damage evolutions of FRP rotors in process.

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.

Radiative amplification of sound waves in the winds of O and B stars

NASA Technical Reports Server (NTRS)

Macgregor, K. B.; Hartmann, L.; Raymond, J. C.

1979-01-01

The velocity perturbation associated with an outwardly propagating sound wave in a radiation-driven stellar wind gives rise to a periodic Doppler shifting of absorption lines formed in the flow. A linearized theory applicable to optically thin waves is used to show that the resulting fluctuation in the absorption-line force can cause the wave amplitude to grow. Detailed calculations of the acceleration due to a large number of lines indicate that significant amplification can occur throughout the high-velocity portion of winds in which the dominant force-producing lines have appreciable optical depths. In the particular case of the wind of Zeta Pup (O4f), it is found that the e-folding distance for wave growth is considerably shorter than the scale lengths over which the physical properties of the flow vary. A qualitative estimate of the rate at which mechanical energy due to nonlinear waves can be dissipated suggests that this mechanism may be important in heating the supersonic portion of winds of early-type stars.

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.

Measurement of the Stopping Power of Water for Carbon Ions Using Inverted Doppler Shift Attenuation

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

Rahm, J.M.; II. Physikalisches Institut, Universitaet Goettingen; Baek, W.Y.

2015-07-01

Carbon ion therapy has gained importance in cancer treatment due to its locally well confined dose distribution, but there is a significant lack of experimental data which is needed for dose calculations and estimation of biological damage. Since tissue is mainly comprised of water, the energy-dependent stopping power of water is the critical measure. Importantly, previous data gathered from experiments with light ions has been limited to water vapour and ice and neglected water in its liquid phase. Additionally, theoretical models regarding the stopping power cannot yet describe the complex charge transfer interactions of the projectile at velocities in themore » range of the mean velocity of the valence electrons of the traversed medium. There are also discrepancies in the amount of phase effects concerning water and water vapour cross sections. Despite its importance there exists no experimental data for the stopping power of water for carbon ions in the energy region between 1 MeV and 5 MeV. This may be due to the short track length of carbon ions which makes traditional transmission experiments unfeasible. Therefore a project was launched to measure the stopping power of liquid water for carbon ions in the vicinity of the Bragg peak which corresponds to the energy regime of the maximum stopping power. For this measurement the inverted Doppler shift attenuation method was used. This uses the gamma quanta emitted from excited carbon nuclei which are produced by means of the {sup 12}C(α,α'){sup 12}C* reaction. The recorded γ-spectra contain the information of the projectiles velocity at the time they decay to their ground state and an internal clock provided by the exponential decay law. The deceleration of the projectile is directly connected to the stopping power which can be determined with this method as a function of the projectiles kinetic energy. Further measurements have been carried out to improve the experimental method. The setup and the preliminary results of this study will be presented. (authors)« less

Functional Spectral Domain Optical Coherence Tomography imaging

NASA Astrophysics Data System (ADS)

Bower, Bradley A.

Spectral Domain Optical Coherence Tomography (SDOCT) is a high-speed, high resolution imaging modality capable of structural and functional characterization of tissue microstructure. SDOCT fills a niche between histology and ultrasound imaging, providing non-contact, non-invasive backscattering amplitude and phase from a sample. Due to the translucent nature of the tissue, ophthalmic imaging is an ideal space for SDOCT imaging. Structural imaging of the retina has provided new insights into ophthalmic disease. The phase component of SDOCT images remains largely underexplored, though. While Doppler SDOCT has been explored in a research setting, it has yet to gain traction in the clinic. Other, functional exploitations of the phase are possible and necessary to expand the utility of SDOCT. Spectral Domain Phase Microscopy (SDPM) is an extension of SDOCT that is capable of resolving sub-wavelength displacements within a focal volume. Application of sub-wavelength displacement measurement imaging could provide a new method for non-invasive optophysiological measurement. This body of work encompasses both hardware and software design and development for implementation of SDOCT. Structural imaging was proven in both the lab and the clinic. Coarse phase changes associated with Doppler flow frequency shifts were recorded and a study was conducted to validate Doppler measurement. Fine phase changes were explored through SDPM applications. Preliminary optophysiology data was acquired to study the potential of sub-wavelength measurements in the retina. To remove the complexity associated with in-vivo human retinal imaging, a first principles approach using isolated nerve samples was applied using standard SDPM and a depthencoded technique for measuring conduction velocity. Results from amplitude as well as both coarse and fine phase processing are presented. In-vivo optophysiology using SDPM is a promising avenue for exploration, and projects furthering or extending this body of work are discussed.

An airport wind shear detection and warning system using Doppler radar: A feasibility study

NASA Technical Reports Server (NTRS)

Mccarthy, J.; Blick, E. F.; Elmore, K. L.

1981-01-01

A feasibility study was conducted to determine whether ground based Doppler radar could measure the wind along the path of an approaching aircraft with sufficient accuracy to predict aircraft performance. Forty-three PAR approaches were conducted, with 16 examined in detail. In each, Doppler derived longitudinal winds were compared to aircraft measured winds; in approximately 75 percent of the cases, the Doppler and aircraft winds were in acceptable agreement. In the remaining cases, errors may have been due to a lack of Doppler resolution, a lack of co-location of the two sampling volumes, the presence of eddy or vortex like disturbances within the pulse volume, or the presence of point targets in antenna side lobes. It was further concluded that shrouding techniques would have reduced the side lobe problem. A ground based Doppler radar operating in the optically clear air, provides the appropriate longitudinal winds along an aircraft's intended flight path.

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.

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.

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.

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)

Digital Doppler measurement with spacecraft

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

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.

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

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

Recoil distance lifetime measurements in 122,124Xe

NASA Astrophysics Data System (ADS)

Govil, I. M.; Kumar, A.; Iyer, H.; Li, H.; Garg, U.; Ghugre, S. S.; Johnson, T.; Kaczarowski, R.; Kharraja, B.; Naguleswaran, S.; Walpe, J. C.

1998-02-01

Lifetimes of the lower-excited states in 122,124Xe are measured using the recoil-distance Doppler-shift technique. The reactions 110Pd(16O,4n)122Xe and 110Pd(18O,4n)124Xe at a beam energy of 66 MeV were used for this experiment. The lifetimes of the 2+, 4+, 6+, and 8+ states of the ground state band were extracted using the computer code LIFETIME including the corrections due to the side feeding and the nuclear deorientation effects. The lifetime of the 2+ state in 122Xe agrees with the recoil distance method (RDM) measurements but for the 124Xe it does not agree with the RDM measurements but agrees with the Coulomb-excitation experiment. The measured B(E2) values for both the nuclei are compared with the standard algebraic and the multishell models.

A search for millisecond periodic and quasi-periodic pulsations in low-mass X-ray binaries

NASA Technical Reports Server (NTRS)

Mereghetti, S.; Grindlay, J. E.

1987-01-01

The results of a Fourier analysis to detect fast periodic and quasi-periodic pulsations in the X-ray emission from the sources 4U 0614 + 091, 4U 1636 - 536, 4U 1735 - 44, 4U 1820 30, GX 5 - 1, GX 9 + 9, Ser X-1, and Cyg X-2 are presented. This search has been carried out for the first time in the soft energy band (0.2-2.0 keV), using data from the Einstein Observatory high resolution imager instrument. An approximate method of minimizing the decrease in search sensitivity produced by the Doppler shift of the pulse periods due to source orbital motion is discussed. No pulsations have been detected, and upper limits, which depend on the orbital parameters assumed for the sources, are set on the pulsed flux fraction.

Uniform laser-driven relativistic electron layer for coherent Thomson scattering.

PubMed

Wu, H-C; Meyer-ter-Vehn, J; Fernández, J; Hegelich, B M

2010-06-11

A novel scheme is proposed to generate uniform relativistic electron layers for coherent Thomson backscattering. A few-cycle laser pulse is used to produce the electron layer from an ultrathin solid foil. The key element of the new scheme is an additional foil that reflects the drive-laser pulse, but lets the electrons pass almost unperturbed. Making use of two-dimensional particle-in-cell simulations and well-known basic theory, it is shown that the electrons, after interacting with both the drive and reflected laser pulses, form a very uniform flyer freely cruising with a high relativistic γ factor exactly in the drive-laser direction (no transverse momentum). It backscatters the probe light with a full Doppler shift factor of 4γ(2). The reflectivity and its decay due to layer expansion are discussed.

Radar sensitivity and antenna scan pattern study for a satellite-based Radar Wind Sounder (RAWS)

NASA Technical Reports Server (NTRS)

Stuart, Michael A.

1992-01-01

Modeling global atmospheric circulations and forecasting the weather would improve greatly if worldwide information on winds aloft were available. Recognition of this led to the inclusion of the LAser Wind Sounder (LAWS) system to measure Doppler shifts from aerosols in the planned for Earth Observation System (EOS). However, gaps will exist in LAWS coverage where heavy clouds are present. The RAdar Wind Sensor (RAWS) is an instrument that could fill these gaps by measuring Doppler shifts from clouds and rain. Previous studies conducted at the University of Kansas show RAWS as a feasible instrument. This thesis pertains to the signal-to-noise ratio (SNR) sensitivity, transmit waveform, and limitations to the antenna scan pattern of the RAWS system. A dop-size distribution model is selected and applied to the radar range equation for the sensitivity analysis. Six frequencies are used in computing the SNR for several cloud types to determine the optimal transmit frequency. the results show the use of two frequencies, one higher (94 GHz) to obtain sensitivity for thinner cloud, and a lower frequency (24 GHz) to obtain sensitivity for thinner cloud, and a lower frequency (24 GHz) for better penetration in rain, provide ample SNR. The waveform design supports covariance estimation processing. This estimator eliminates the Doppler ambiguities compounded by the selection of such high transmit frequencies, while providing an estimate of the mean frequency. the unambiguous range and velocity computation shows them to be within acceptable limits. The design goal for the RAWS system is to limit the wind-speed error to less than 1 ms(exp -1). Due to linear dependence between vectors for a three-vector scan pattern, a reasonable wind-speed error is unattainable. Only the two-vector scan pattern falls within the wind-error limits for azimuth angles between 16 deg to 70 deg. However, this scan only allows two components of the wind to be determined. As a result, a technique is then shown, based on the Z-R-V relationships, that permit the vertical component (i.e., rain) to be computed. Thus the horizontal wind components may be obtained form the covariance estimator and the vertical component from the reflectivity factor. Finally, a new candidate system is introduced which summarizes the parameters taken from previous RAWS studies, or those modified in this thesis.

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.

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.

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.

Doppler term in the galaxy two-point correlation function: Wide-angle, velocity, Doppler lensing and cosmic acceleration effects

NASA Astrophysics Data System (ADS)

Raccanelli, Alvise; Bertacca, Daniele; Jeong, Donghui; Neyrinck, Mark C.; Szalay, Alexander S.

2018-03-01

We study the parity-odd part (that we shall call Doppler term) of the linear galaxy two-point correlation function that arises from wide-angle, velocity, Doppler lensing and cosmic acceleration effects. As it is important at low redshift and at large angular separations, the Doppler term is usually neglected in the current generation of galaxy surveys. For future wide-angle galaxy surveys, however, we show that the Doppler term must be included. The effect of these terms is dominated by the magnification due to relativistic aberration effects and the slope of the galaxy redshift distribution and it generally mimics the effect of the local type primordial non-Gaussianity with the effective nonlinearity parameter fNLeff of a few; we show that this would affect forecasts on measurements of fNL at low-redshift. Our results show that a survey at low redshift with large number density over a wide area of the sky could detect the Doppler term with a signal-to-noise ratio of ∼ 1 - 20, depending on survey specifications.

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.

Correlation of Doppler noise during solar conjunctions with fluctuations in solar activity

NASA Technical Reports Server (NTRS)

Berman, A. L.; Rockwell, S. T.

1975-01-01

Deviations betweeb observed Doppler noise and the noise model during solar conjunction were analyzed. It is tentatively concluded that these deviations are due to short-term fluctuations in solar activity as seen along the signal path, and not to solar/antenna structure effects or system noise temperature.

Interferometric imaging of acoustical phenomena using high-speed polarization camera and 4-step parallel phase-shifting technique

NASA Astrophysics Data System (ADS)

Ishikawa, K.; Yatabe, K.; Ikeda, Y.; Oikawa, Y.; Onuma, T.; Niwa, H.; Yoshii, M.

2017-02-01

Imaging of sound aids the understanding of the acoustical phenomena such as propagation, reflection, and diffraction, which is strongly required for various acoustical applications. The imaging of sound is commonly done by using a microphone array, whereas optical methods have recently been interested due to its contactless nature. The optical measurement of sound utilizes the phase modulation of light caused by sound. Since light propagated through a sound field changes its phase as proportional to the sound pressure, optical phase measurement technique can be used for the sound measurement. Several methods including laser Doppler vibrometry and Schlieren method have been proposed for that purpose. However, the sensitivities of the methods become lower as a frequency of sound decreases. In contrast, since the sensitivities of the phase-shifting technique do not depend on the frequencies of sounds, that technique is suitable for the imaging of sounds in the low-frequency range. The principle of imaging of sound using parallel phase-shifting interferometry was reported by the authors (K. Ishikawa et al., Optics Express, 2016). The measurement system consists of a high-speed polarization camera made by Photron Ltd., and a polarization interferometer. This paper reviews the principle briefly and demonstrates the high-speed imaging of acoustical phenomena. The results suggest that the proposed system can be applied to various industrial problems in acoustical engineering.

A new approach to correct yaw misalignment in the spinning ultrasonic anemometer

NASA Astrophysics Data System (ADS)

Ghaemi-Nasab, M.; Davari, Ali R.; Franchini, S.

2018-01-01

Single-axis ultrasonic anemometers are the modern instruments for accurate wind speed measurements. Despite their widespread and ever increasing applications, little attention has been paid up to now to spinning ultrasonic anemometers that can accurately measure both the wind speed and its direction in a single and robust apparatus. In this study, intensive wind-tunnel tests were conducted on a spinning single-axis ultrasonic anemometer to investigate the yaw misalignment in ultrasonic wind speed measurements during the yaw rotation. The anemometer was rotating inside the test section with various angular velocities, and the experiments were performed at several combinations of wind speed and anemometer angular velocity. The instantaneous angular position of the ultrasonic signal path with wind direction was measured using an angular position sensor. For a spinning anemometer, the circulatory wake and the associated flow distortion, along with the Doppler effect, impart a phase shift in the signals measured by the anemometer, which should be added to the position data for correcting the yaw misalignment. In this paper, the experimental data are used to construct a theoretical model, based on a response surface method, to correct the phase shift for various wind speeds and anemometer rotational velocities. This model is shown to successfully correct the velocity indicated by the spinning anemometer for the phase shift due to the rotation, and can easily be used in the calibration process for such anemometers.

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.

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.

Observations of highly sheared turbulence in the H-mode pedestal using Phase Contrast Imaging on DIII-D

NASA Astrophysics Data System (ADS)

Rost, J. C.; Marinoni, A.; Davis, E. M.; Porkolab, M.; Burrell, K. H.

2017-10-01

Highly sheared turbulence with short radial correlation lengths has been measured near the top of the H-mode pedestal, in addition to the previously measured highly-sheared turbulence measured in the Er well. Turbulence in regions of large velocity shear is characterized by radial correlation lengths shorter than the poloidal wavelength (L < λ 2 cm) and large Doppler-shifted frequencies (f > 200 kHz). The phase contrast imaging (PCI) diagnostic on DIII-D is ideally suited to measuring this density turbulence due to the measurement geometry and high frequency bandwidth. Radial localization is achieved by optical filtering, varying the ExB profile, and shifting the plasma position. Reconfiguration of the Er well, such as at the L-H transition or the transition to wide pedestal QH-mode, shows a near-instantaneous change (t < 1 ms) to the sheared turbulence in the Er well ( 1 cm inside the separatrix). In contrast, the sheared turbulence near the top of the pedestal ( 2 cm inside the separatrix) varies over times scales of tens of ms, consistent with pedestal evolution. Work supported by the US Department of Energy under DE-FG02-94ER54235 and DE-FC02-04ER54698.

Red Shifts and Existing Speculations

NASA Astrophysics Data System (ADS)

Aisenberg, Sol

2009-03-01

There are many current flaws, mysteries, and errors in the standard model of the universe - all based upon speculative interpretation of many excellent and verified observations. The most serious cause of some errors is the speculation about the meaning of the redshifts observed in the 1930s by Hubble. He ascribed the redshifts as due to ``an apparent Doppler effect''. This led to speculation that the remote stars were receding, and the universe was expanding -- although without observational proof of the actual receding velocity of the stars. The age of the universe, based upon the Hubble constant is pure speculation because of lack of velocity demonstration. The belief in expansion, the big bang, and of inflation should be reexamined. Also, the redshift cannot always be used as a distance measure, particularly for photons from quasars containing massive black holes that can reduce photon energy through gravitational attraction. If the linear Hubble constant is extrapolated to the most remote super novae and beyond, it would eventually require that the corresponding photon energy go to zero or become negative -- according to Hubble linear relationship. This should require a reexamination of the meaning of the red shift and the speculative consequences and give a model with fewer mysteries.

Robust estimation of fetal heart rate from US Doppler signals

NASA Astrophysics Data System (ADS)

Voicu, Iulian; Girault, Jean-Marc; Roussel, Catherine; Decock, Aliette; Kouame, Denis

2010-01-01

Introduction: In utero, Monitoring of fetal wellbeing or suffering is today an open challenge, due to the high number of clinical parameters to be considered. An automatic monitoring of fetal activity, dedicated for quantifying fetal wellbeing, becomes necessary. For this purpose and in a view to supply an alternative for the Manning test, we used an ultrasound multitransducer multigate Doppler system. One important issue (and first step in our investigation) is the accurate estimation of fetal heart rate (FHR). An estimation of the FHR is obtained by evaluating the autocorrelation function of the Doppler signals for ills and healthiness foetus. However, this estimator is not enough robust since about 20% of FHR are not detected in comparison to a reference system. These non detections are principally due to the fact that the Doppler signal generated by the fetal moving is strongly disturbed by the presence of others several Doppler sources (mother' s moving, pseudo breathing, etc.). By modifying the existing method (autocorrelation method) and by proposing new time and frequency estimators used in the audio' s domain, we reduce to 5% the probability of non-detection of the fetal heart rate. These results are really encouraging and they enable us to plan the use of automatic classification techniques in order to discriminate between healthy and in suffering foetus.

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.

Automated flow quantification in valvular heart disease based on backscattered Doppler power analysis: implementation on matrix-array ultrasound imaging systems.

PubMed

Buck, Thomas; Hwang, Shawn M; Plicht, Björn; Mucci, Ronald A; Hunold, Peter; Erbel, Raimund; Levine, Robert A

2008-06-01

Cardiac ultrasound imaging systems are limited in the noninvasive quantification of valvular regurgitation due to indirect measurements and inaccurate hemodynamic assumptions. We recently demonstrated that the principle of integration of backscattered acoustic Doppler power times velocity can be used for flow quantification in valvular regurgitation directly at the vena contracta of a regurgitant flow jet. We now aimed to accomplish implementation of automated Doppler power flow analysis software on a standard cardiac ultrasound system utilizing novel matrix-array transducer technology with detailed description of system requirements, components and software contributing to the system. This system based on a 3.5 MHz, matrix-array cardiac ultrasound scanner (Sonos 5500, Philips Medical Systems) was validated by means of comprehensive experimental signal generator trials, in vitro flow phantom trials and in vivo testing in 48 patients with mitral regurgitation of different severity and etiology using magnetic resonance imaging (MRI) for reference. All measurements displayed good correlation to the reference values, indicating successful implementation of automated Doppler power flow analysis on a matrix-array ultrasound imaging system. Systematic underestimation of effective regurgitant orifice areas >0.65 cm(2) and volumes >40 ml was found due to currently limited Doppler beam width that could be readily overcome by the use of new generation 2D matrix-array technology. Automated flow quantification in valvular heart disease based on backscattered Doppler power can be fully implemented on board a routinely used matrix-array ultrasound imaging systems. Such automated Doppler power flow analysis of valvular regurgitant flow directly, noninvasively, and user independent overcomes the practical limitations of current techniques.

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.

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

Transesophageal color Doppler evaluation of obstructive lesions using the new "Quasar" technology.

PubMed

Fan, P; Nanda, N C; Gatewood, R P; Cape, E G; Yoganathan, A P

1995-01-01

Due to the unavoidable problem of aliasing, color flow signals from high blood flow velocities cannot be measured directly by conventional color Doppler. A new technology termed Quantitative Un-Aliased Speed Algorithm Recognition (Quasar) has been developed to overcome this limitation. Employing this technology, we used transesophageal color Doppler echocardiography to investigate whether the velocities detected by the Quasar would correlate with those obtained by continuous-wave Doppler both in vitro and in vivo. In the in vitro study, a 5.0 MHz transesophageal transducer of a Kontron Sigma 44 color Doppler flow system was used. Fourteen different peak velocities calculated and recorded by color Doppler-guided continuous-wave Doppler were randomly selected. In the clinical study, intraoperative transesophageal echocardiography was performed using the same transducer 18 adults (13 aortic valve stenosis, 2 aortic and 2 mitral stenosis, 2 hypertrophic obstructive cardiomyopathy and 1 mitral valve stenosis). Following each continuous-wave Doppler measurement, the Quasar was activated, and a small Quasar marker was placed in the brightest area of the color flow jet to obtain the maximum mean velocity readout. The maximum mean velocities measured by Quasar closely correlated with maximum peak velocities obtained by color flow guided continuous-wave Doppler in both in vitro (0.53 to 1.65 m/s, r = 0.99) and in vivo studies (1.50 to 6.01 m/s, r = 0.97). We conclude that the new Quasar technology can accurately measure high blood flow velocities during transesophageal color Doppler echocardiography. This technique has the potential of obviating the need for continuous-wave Doppler.

Spatially Resolved MR-Compatible Doppler Ultrasound: Proof of Concept for Triggering of Diagnostic Quality Cardiovascular MRI for Function and Flow Quantification at 3T.

PubMed

Crowe, Lindsey Alexandra; Manasseh, Gibran; Chmielewski, Aneta; Hachulla, Anne-Lise; Speicher, Daniel; Greiser, Andreas; Muller, Hajo; de Perrot, Thomas; Vallee, Jean-Paul; Salomir, Rares

2018-02-01

We demonstrate the use of a magnetic-resonance (MR)-compatible ultrasound (US) imaging probe using spatially resolved Doppler for diagnostic quality cardiovascular MR imaging (MRI) as an initial step toward hybrid US/MR fetal imaging. A newly developed technology for a dedicated MR-compatible phased array ultrasound-imaging probe acquired pulsed color Doppler carotid images, which were converted in near-real time to a trigger signal for cardiac cine and flow quantification MRI. Ultrasound and MR data acquired simultaneously were interference free. Conventional electrocardiogram (ECG) and the proposed spatially resolved Doppler triggering were compared in 10 healthy volunteers. A synthetic "false-triggered" image was retrospectively processed using metric optimized gating (MOG). Images were scored by expert readers, and sharpness, cardiac function and aortic flow were quantified. Four-dimensional (4-D) flow (two volunteers) showed feasibility of Doppler triggering over a long acquisition time. Imaging modalities were compatible. US probe positioning was stable and comfortable. Image quality scores and quantified sharpness were statistically equal for Doppler- and ECG-triggering (p ). ECG-, Doppler-triggered, and MOG ejection fractions were equivalent (p ), with false-triggered values significantly lower (p < 0.0005). Aortic flow showed no difference between ECG- and Doppler-triggered and MOG (p > 0.05). 4-D flow quantification gave consistent results between ECG and Doppler triggering. We report interference-free pulsed color Doppler ultrasound during MR data acquisition. Cardiovascular MRI of diagnostic quality was successfully obtained with pulsed color Doppler triggering. The hardware platform could further enable advanced free-breathing cardiac imaging. Doppler ultrasound triggering is applicable where ECG is compromised due to pathology or interference at higher magnetic fields, and where direct ECG is impossible, i.e., fetal imaging.

Multibeam synthetic aperture radar for global oceanography

NASA Technical Reports Server (NTRS)

Jain, A.

1979-01-01

A single-frequency multibeam synthetic aperture radar concept for large swath imaging desired for global oceanography is evaluated. Each beam iilluminates a separate range and azimuth interval, and images for different beams may be separated on the basis of the Doppler spectrum of the beams or their spatial azimuth separation in the image plane of the radar processor. The azimuth resolution of the radar system is selected so that the Doppler spectrum of each beam does not interfere with the Doppler foldover due to the finite pulse repetition frequency of the radar system.

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.

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.

Venous Small Bowel Infarction: Intraoperative Laser Doppler Flowmetry Discriminates Critical Blood Supply and Spares Bowel Length

PubMed Central

Käser, S. A.; Glauser, P. M.; Maurer, C. A.

2012-01-01

Introduction. In mesenteric infarction due to arterial occlusion, laser Doppler flowmetry and spectrometry are known reliable noninvasive methods for measuring microvascular blood flow and oxygen utilisation. Case Presentation. As an innovation we used these methods in a patient with acute extensive mesenteric infarction due to venous occlusion, occurring after radical right hemicolectomy. Aiming to avoid short bowel syndrome, we spared additional 110 cm of small bowel, instead of leaving only 80 centimetres of clinically viable small bowel in situ. The pathological examination showed only 5 mm of vital mucosa to be left distal to the dissection margin. No further interventions were necessary. Conclusion. Laser doppler flowmetry and spectrometry are potentially powerful methods to assist the surgeon's decision-making in critical venous mesenteric perfusion, thus having an important impact on clinical outcome. PMID:23093968

One way Doppler Extractor. Volume 2: Digital VCO technique

NASA Technical Reports Server (NTRS)

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

1974-01-01

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

New approaches to the Doppler echocardiographic assessment of diastolic function: from research laboratory to clinical practice

NASA Technical Reports Server (NTRS)

Pasquet, A.; Garcia, M. J.; Thomas, J. D.

1999-01-01

Over the past decade, Doppler echocardiography has become a well-established tool for the diagnosis of left ventricular diastolic dysfunction. Unfortunately, in many clinical situations traditional Doppler indices of transmittal and pulmonary venous flow are inconclusive, primarily due to their dependence on left atrial pressure. Recently, new Doppler indices that are much less dependent on preload have been developed, based on intraventricular flow propagation and intrinsic myocardial velocity. These methodologies provide direct assessment of ventricular relaxation and the small intraventricular pressure gradients essential to efficient filling of the ventricle. We review in this article the theoretical and experiment background of these new echo techniques as well as how they can be implemented in routine clinical practice.

A tensor formulation of the equation of transfer for spherically symmetric flows. [radiative transfer in seven dimensional Riemannian space

NASA Technical Reports Server (NTRS)

Haisch, B. M.

1976-01-01

A tensor formulation of the equation of radiative transfer is derived in a seven-dimensional Riemannian space such that the resulting equation constitutes a divergence in any coordinate system. After being transformed to a spherically symmetric comoving coordinate system, the transfer equation contains partial derivatives in angle and frequency, as well as optical depth due to the effects of aberration and the Doppler shift. However, by virtue of the divergence form of this equation, the divergence theorem may be applied to yield a numerical differencing scheme which is expected to be stable and to conserve luminosity. It is shown that the equation of transfer derived by this method in a Lagrangian coordinate system may be reduced to that given by Castor (1972), although it is, of course, desirable to leave the equation in divergence form.

A possible detection of infrared emission from carbon monoxide in Comet Austin (1989c1)

NASA Technical Reports Server (NTRS)

Disanti, Michael A.; Mumma, Michael J.; Lacy, John H.; Parmar, Parvinder

1992-01-01

A cryogenic IR echelle grating spectrometer has been used to probe the nu = 1-0 rovibrational band of the CO molecule in Comet Austin. Line emission has been detected at the Doppler-shifted frequency expected for the cometary P(3) line, in scans which are noted to cover only the first 3000 sec of May 16, 1990 observations; this is suggested to be due to an outburst of comparable duration. No detections were made of the P(2) line, which was predicted by models to occur at the 3.5 sigma level even for relatively high coma temperatures. If the outburst was accompanied by enhanced dust production, an increase by a factor of 2.5 is consistent with the present observational data and CO/dust may have been enriched in the outbursting volume relative to the remainder of the nucleus.

Validation of fast-ion D-alpha spectrum measurements during EAST neutral-beam heated plasmas

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

Huang, J., E-mail: juan.huang@ipp.ac.cn; Wu, C. R.; Hou, Y. M.

2016-11-15

To investigate the fast ion behavior, a fast ion D-alpha (FIDA) diagnostic system has been installed on EAST. Fast ion features can be inferred from the Doppler shifted spectrum of Balmer-alpha light from energetic hydrogenic atoms. This paper will focus on the validation of FIDA measurements performed using MHD-quiescent discharges in 2015 campaign. Two codes have been applied to calculate the D{sub α} spectrum: one is a Monte Carlo code, Fortran 90 version FIDASIM, and the other is an analytical code, Simulation of Spectra (SOS). The predicted SOS fast-ion spectrum agrees well with the measurement; however, the level of fast-ionmore » part from FIDASIM is lower. The discrepancy is possibly due to the difference between FIDASIM and SOS velocity distribution function. The details will be presented in the paper to primarily address comparisons of predicted and observed spectrum shapes/amplitudes.« less

Impact of temperature-velocity distribution on fusion neutron peak shape

DOE PAGES

Munro, D. H.; Field, J. E.; Hatarik, R.; ...

2017-02-21

Doppler broadening of the 14 MeV DT and 2.45 MeV DD fusion neutron lines has long been our best measure of temperature in a burning plasma. At the National Ignition Facility (NIF), yields are high enough and our neutron spectrometers accurate enough that we see finer details of the peak shape. For example, we can measure the shift of the peak due to the bulk motion of the plasma, and we see indications of non-thermal broadening, skew, and kurtosis of the peak caused by the variations of temperature and fluid velocity during burn. We can also distinguish spectral differences amongmore » several lines of sight. Finally, this paper will review the theory of fusion neutron line shape, show examples of non-Gaussian line shapes and directional variations in NIF data, and describe detailed spectral shapes we see in radiation-hydrodynamics simulations of implosions.« less

Impact of temperature-velocity distribution on fusion neutron peak shape

NASA Astrophysics Data System (ADS)

Munro, D. H.; Field, J. E.; Hatarik, R.; Peterson, J. L.; Hartouni, E. P.; Spears, B. K.; Kilkenny, J. D.

2017-05-01

Doppler broadening of the 14 MeV DT and 2.45 MeV DD fusion neutron lines has long been our best measure of temperature in a burning plasma. At the National Ignition Facility (NIF), yields are high enough and our neutron spectrometers accurate enough that we see finer details of the peak shape. For example, we can measure the shift of the peak due to the bulk motion of the plasma, and we see indications of non-thermal broadening, skew, and kurtosis of the peak caused by the variations of temperature and fluid velocity during burn. We can also distinguish spectral differences among several lines of sight. This paper will review the theory of fusion neutron line shape, show examples of non-Gaussian line shapes and directional variations in NIF data, and describe detailed spectral shapes we see in radiation-hydrodynamics simulations of implosions.

Experimental evaluation of a system for human life detection under debris

NASA Astrophysics Data System (ADS)

Joju, Reshma; Konica, Pimplapure Ramya T.; Alex, Zachariah C.

2017-11-01

It is difficult to for the human beings to be found under debris or behind the walls in case of military applications. Due to which several rescue techniques such as robotic systems, optical devices, and acoustic devices were used. But if victim was unconscious then these rescue system failed. We conducted an experimental analysis on whether the microwaves could detect heart beat and breathing signals of human beings trapped under collapsed debris. For our analysis we used RADAR based on by Doppler shift effect. We calculated the minimum speed that the RADAR could detect. We checked the frequency variation by placing the RADAR at a fixed position and placing the object in motion at different distances. We checked the frequency variation by using objects of different materials as debris behind which the motion was made. The graphs of different analysis were plotted.

Satellite-observed cloud-top height changes in tornadic thunderstorms

NASA Technical Reports Server (NTRS)

Adler, R. F.; Fenn, D. D.

1981-01-01

Eleven tornadic storms are evaluated with respect to cloud top temperature changes relative to tornado touchdown. Digital IR data from the SMS/GOES geosynchronous satellites were employed for 10 F2 and one F1 tornadoes. A rapid ascent of the cloud tops 30-45 min before tornado touchdown, a temperature decrease of 0.4 K/min, and an ascent rate of about 3 m/sec were observed. The presence of an operating Doppler radar for three of the sample storms allowed detection of a mesocyclone coincident with the rapid cloud top ascent. The intensification and descent of the vortex to form a tornado is concluded to be due to a weakening of the updraft, the formation of a downdraft, and a shift of the vortex to the updraft-downdraft boundary, leading to dominance of the tilting term in the generation of vorticity.

Observation of copper atoms behavior in a vacuum arc discharge using laser spectroscopy

NASA Astrophysics Data System (ADS)

Sung, Y. M.; Hayashi, Y.; Okraku-Yirenkyi, Y.; Otsubo, M.; Honda, C.; Sakoda, T.

2003-01-01

In order to investigate the most important parameters influencing the breaking characteristic of a vacuum circuit breaker (VCB), the behavior of copper (Cu) particles emitted from electrodes designed as an imitation of a vacuum valve of the VCB was observed. The temporal-spatial intensity distributions due to Cu particles in an excited state or a neutral state were measured using the laser induced fluorescence (LIF) technique and a charge coupled device camera attached with a special filter. The diffusion velocity of a Cu atom was also investigated by evaluating a Doppler shift of the LIF signal. The results showed that most Cu particles were emitted from the anode and were in an excited state or an ionized state during an arc discharge. Also, Cu particles were distributed between electrodes even after the discharge chocked, and its diffusion velocity in the direction of the cathode from the anode was about 2.6 km/s.

[Extrasolar terrestrial planets and possibility of extraterrestrial life].

PubMed

Ida, Shigeru

2003-12-01

Recent development of research on extrasolar planets are reviewed. About 120 extrasolar Jupiter-mass planets have been discovered through the observation of Doppler shift in the light of their host stars that is caused by acceleration due to planet orbital motions. Although the extrasolar planets so far observed may be limited to gas giant planets and their orbits differ from those of giant planets in our Solar system (Jupiter and Saturn), the theoretically predicted probability of existence of extrasolar terrestrial planets that can have liquid water ocean on their surface is comparable to that of detectable gas giant planets. Based on the number of extrasolar gas giants detected so far, about 100 life-sustainable planets may exist within a range of 200 light years. Indirect observation of extrasolar terrestrial planets would be done with space telescopes within several years and direct one may be done within 20 years. The latter can detect biomarkers on these planets as well.

Explaining Polarization Reversals in STEREO Wave Data

NASA Technical Reports Server (NTRS)

Breneman, A.; Cattell, C.; Wygant, J.; Kersten, K.; Wilson, L, B., III; Dai, L.; Colpitts, C.; Kellogg, P. J.; Goetz, K.; Paradise, A.

2012-01-01

Recently Breneman et al. reported observations of large amplitude lightning and transmitter whistler mode waves from two STEREO passes through the inner radiation belt (L<2). Hodograms of the electric field in the plane transverse to the magnetic field showed that the transmitter waves underwent periodic polarization reversals. Specifically, their polarization would cycle through a pattern of right-hand to linear to left-hand polarization at a rate of roughly 200 Hz. The lightning whistlers were observed to be left-hand polarized at frequencies greater than the lower hybrid frequency and less than the transmitter frequency (21.4 kHz) and right-hand polarized otherwise. Only righthand polarized waves in the inner radiation belt should exist in the frequency range of the whistler mode and these reversals were not explained in the previous paper. We show, with a combination of observations and simulated wave superposition, that these polarization reversals are due to the beating of an incident electromagnetic whistler mode wave at 21.4 kHz and linearly polarized, symmetric lower hybrid sidebands Doppler-shifted from the incident wave by +/-200 Hz. The existence of the lower hybrid waves is consistent with the parametric decay mechanism of Lee and Kuo whereby an incident whistler mode wave decays into symmetric, short wavelength lower hybrid waves and a purely growing (zero-frequency) mode. Like the lower hybrid waves, the purely growing mode is Doppler-shifted by 200 Hz as observed on STEREO. This decay mechanism in the upper ionosphere has been previously reported at equatorial latitudes and is thought to have a direct connection with explosive spread F enhancements. As such it may represent another dissipation mechanism of VLF wave energy in the ionosphere and may help to explain a deficit of observed lightning and transmitter energy in the inner radiation belts as reported by Starks et al.

Evaluation of beam divergence of a negative hydrogen ion beam using Doppler shift spectroscopy diagnostics

NASA Astrophysics Data System (ADS)

Deka, A. J.; Bharathi, P.; Pandya, K.; Bandyopadhyay, M.; Bhuyan, M.; Yadav, R. K.; Tyagi, H.; Gahlaut, A.; Chakraborty, A.

2018-01-01

The Doppler Shift Spectroscopy (DSS) diagnostic is in the conceptual stage to estimate beam divergence, stripping losses, and beam uniformity of the 100 keV hydrogen Diagnostics Neutral Beam of International Thermonuclear Experimental Reactor. This DSS diagnostic is used to measure the above-mentioned parameters with an error of less than 10%. To aid the design calculations and to establish a methodology for estimation of the beam divergence, DSS measurements were carried out on the existing prototype ion source RF Operated Beam Source in India for Negative ion Research. Emissions of the fast-excited neutrals that are generated from the extracted negative ions were collected in the target tank, and the line broadening of these emissions were used for estimating beam divergence. The observed broadening is a convolution of broadenings due to beam divergence, collection optics, voltage ripple, beam focusing, and instrumental broadening. Hence, for estimating the beam divergence from the observed line broadening, a systematic line profile analysis was performed. To minimize the error in the divergence measurements, a study on error propagation in the beam divergence measurements was carried out and the error was estimated. The measurements of beam divergence were done at a constant RF power of 50 kW and a source pressure of 0.6 Pa by varying the extraction voltage from 4 kV to10 kV and the acceleration voltage from 10 kV to 15 kV. These measurements were then compared with the calorimetric divergence, and the results seemed to agree within 10%. A minimum beam divergence of ˜3° was obtained when the source was operated at an extraction voltage of ˜5 kV and at a ˜10 kV acceleration voltage, i.e., at a total applied voltage of 15 kV. This is in agreement with the values reported in experiments carried out on similar sources elsewhere.

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.

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.

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.

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

Colour Doppler ultrasound in preoperative assessment of the neck vessels in patients with tumours of the oral cavity and the neck region.

PubMed

Falkowski, Aleksander; Wilk, Grazyna; Mokrzyński, Stanisław; Dul, Przemysław; Toloczko-Grabarek, Aleksandra; Huzarski, Tomasz; Kowalczyk, Robert

2004-06-01

The aim of the study was not only to establish the applicability of color Doppler ultrasound of the neck vessels in patients with tumors of the oral cavity and the neck region but also to check whether the coexistence of sclerotic changes in the carotid arteries is essential in determination of the sequence of surgical procedure. Color Doppler ultrasound was performed on 110 patients, aged 15 -71 years with tumors of the oral cavity and the neck. The localization, size, echogenicity, as well as the tumor relationship to the surrounding structures and big vessels of the neck region was analyzed. Compression of the veins was observed in 27 cases, and of the arteries only in 20 cases. Infiltration of the jugular vein was observed in 8 patients, whereas infiltration of the carotid artery were seen only in 6 patients. Severe internal carotid artery stenosis, due to arteriosclerosis, was observed in 10 patients. Three persons were suggested to be operated on, first due to carotid artery stenosis, later on, due to the oral cavity tumor. It was found that color Doppler ultrasound is useful in deciding upon the method of treatment, while the examination of the neck vessels is helpful in establishing the sequence of surgical procedures in patients with tumors and coexisting arteriosclerosis.

Doppler Radar Vital Signs Detection Method Based on Higher Order Cyclostationary.

PubMed

Yu, Zhibin; Zhao, Duo; Zhang, Zhiqiang

2017-12-26

Due to the non-contact nature, using Doppler radar sensors to detect vital signs such as heart and respiration rates of a human subject is getting more and more attention. However, the related detection-method research meets lots of challenges due to electromagnetic interferences, clutter and random motion interferences. In this paper, a novel third-order cyclic cummulant (TOCC) detection method, which is insensitive to Gaussian interference and non-cyclic signals, is proposed to investigate the heart and respiration rate based on continuous wave Doppler radars. The k -th order cyclostationary properties of the radar signal with hidden periodicities and random motions are analyzed. The third-order cyclostationary detection theory of the heart and respiration rate is studied. Experimental results show that the third-order cyclostationary approach has better estimation accuracy for detecting the vital signs from the received radar signal under low SNR, strong clutter noise and random motion interferences.

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.

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.

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.

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.

Research Investigation Directed Toward Extending the Useful Range of the Electromagnetic Spectrum [Special Technical Report]: Further Aspects of the Theory of the Maser.

DOE R&D Accomplishments Database

Shimoda, K.; Wang, T. C.; Townes, C. H.

1956-03-01

The theory of the molecular transitions which are induced by the microwave field in a maser and the effects of various design parameters are examined in detail. It is shown that the theoretical minimum detectable beam intensity when the maser is used as a spectrometer for the 3-3 line of ammonia is about 10{sup 9} molecules/sec under typical experimental conditions. Various systematic frequency shifts and random frequency fluctuations of the maser oscillator are discussed and evaluated. The most prominent of the former are the "frequency-pulling" effect which arises from detuning of the cavity and the Doppler shift due to the asymmetrical coupling of the beam with the two travelling wave components of the standing waves which are set up in the cavity. These two effects may produce fractional shifts as large as one part in 10{sup 9}. If adequate precautions are taken, however, they can be reduced to one part in 10{sup 10} or possibly less. The random fluctuations are shown to be of the order of one part in 10{sup 13} under typical operating conditions. For molecular beams in which the electric-dipole transition is used the TM{sub 010} mode is usually the most suitable for the maser which atomic beams in which magnetic transitions are utilized, the TE{sub 011} mode is to be preferred.

Effects of Saharan Mineral Dust Aerosols on the Dynamics of an Idealized African Easterly Jet-African Easterly Wave System over North Africa

NASA Astrophysics Data System (ADS)

Grogan, Dustin Francis Phillip

The central objective of this work is to examine the direct radiative effects of Saharan mineral dust aerosols on the dynamics of African easterly waves (AEWs) and the African easterly jet (AEJ). Achieving this objective is built around two tasks that use the Weather Research and Forecasting (WRF) model coupled to an online dust model (WRF-dust model). The first task (Chapter 2) examines the linear dynamics of AEWs; the second task (Chapter 3) examines the nonlinear evolution of AEWs and their interactions with the AEJ. In Chapter 2, the direct radiative effects of dust on the linear dynamics of AEWs are examined analytically and numerically. The analytical analysis combines the thermodynamic equation with a dust continuity equation to form an expression for the generation of eddy available potential energy (APE) by the dust field. The generation of eddy APE is a function of the transmissivity and spatial gradients of the dust, which are modulated by the Doppler-shifted frequency. The expression predicts that for a fixed dust distribution, the wave response will be largest in regions where the dust gradients are maximized and the Doppler-shifted frequency vanishes. The numerical analysis calculates the linear dynamics of AEWs using zonally averaged basic states for wind, temperature and dust consistent with summertime conditions over North Africa. For the fastest growing AEW, the dust increases the growth rate from ~15% to 90% for aerosol optical depths ranging from tau=1.0 to tau=2.5. A local energetics analysis shows that for tau=1.0, the dust increases the maximum barotropic and baroclinic energy conversions by ~50% and ~100%, respectively. The maxima in the generation of APE and conversions of energy are co-located and occur where the meridional dust gradient is maximized near the critical layer, i.e., where the Doppler-shifted frequency is small, in agreement with the prediction from the analytical analysis. In Chapter 3, the direct radiative effects of dust on the evolution of AEJ-AEW system are examined using the WRF-dust model. The model is initialized with zonal-mean distributions of wind, temperature and dust used in linear study (Chapter 2). The dust modifies the lifecycle of the AEWs in the following way: the domain-averaged eddy kinetic energy (EKE) is enhanced during the linear and nonlinear growth phases, reaching a larger peak amplitude that subsequently decays more rapidly, eventually equilibrating at lower amplitude. The increase in EKE during the growth phases is due to local increases in barotropic energy conversions in the dust plume north of the AEJ. The dust-modified, rapidly decaying phase is primarily associated with enhanced barotropic decay that occurs near the top of the plume north of the AEJ. The timing of peak EKE depends on the initial dust concentration. Throughout the evolution of the AEJ-AEW system, the dust increases the maximum zonal-mean wind speeds. The increase is due to the dust-modified mean meridional circulation during the AEW growth phase and the dust-modified wave fluxes during the AEW decay phase. During AEW growth, the dust-modified maximum wind speeds are also displaced farther southward and upward, which is due to the enhanced wave fluxes decelerating the flow more efficiently north of the AEJ. These changes to the AEJ structure affect the critical surface, which expands vertically and meridionally as the AEW grows to finite amplitude. The dust-modified effects on the evolution of the AEJ-AEW system are discussed in light of tropical cyclogenesis. By better understanding the direct radiative effects of dust on the AEJ-AEW system, we can expect improvements in the modeling, forecasting and understanding of the connection between AEWs and the meteorology over North Africa and the Eastern Atlantic Ocean.

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.

Measuring Magnetic Oscillations in the Solar Photosphere: Coordinated Observations with MDI, ASP and MWO

NASA Astrophysics Data System (ADS)

Norton, A. A.; Ulrich, R. K.

2000-03-01

A comprehensive observing effort was undertaken to simultaneously obtain full Stokes profiles as well as longitudinal magnetogram maps of a positive plage region on 8 December, 1998 with the Michelson Doppler Imager, the Advanced Stokes Polarimeter and Mt. Wilson Observatory magnetograph. We compare 1.2'' spatially-averaged signals of velocities as well as filter magnetograph longitudinal flux signals with Stokes determined fluctuations in filling factor, field inclination, magnetic flux and field strength. The velocity signals are in excellent agreement. Michelson Doppler Imager magnetic flux correlates best with fluctuations in the Advanced Stokes Polarimeter filling factor, not inclination angle or field strength. A correlated flux and filling factor change in the absence of a field strength fluctuation can be understood in terms of internally unperturbed flux tubes being buffeted by external pressure fluctuations. The 12.5'' square aperture spatially averaged Mt. Wilson magnetograph signals are compared with Michelson Doppler Imager signals from the corresponding observing area. Velocity signals are in superb agreement. Magnetic signals exhibit similar oscillatory behavior. Lack of Advanced Stokes Polarimeter data for this time excludes interpretation of magnetic fluctuations as due to filling factor or field inclination angle. Mt. Wilson Observatory simultaneous sampling of the nickel and sodium spectral line profiles with several wing pairs allowed inter-comparison of signals from different heights of formation. Slight phase shifts and large propagation speeds for the velocity signals are indicative of modified standing waves. Phase speeds associated with magnetic signals are characteristic of photospheric Alfvén speeds for plage fields. The phase speed increase with height agrees with the altitude dependence of the Alfvén speed. The observed fluctuations and phases are interpreted as a superposition of signatures from the horizontal component of the driving mechanism sweeping the field lines in/out of the resolution area and the magnetic response of the flux tube to this buffeting.

EVIDENCE FOR ROTATIONAL MOTIONS IN THE FEET OF A QUIESCENT SOLAR PROMINENCE

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

Orozco Suarez, D.; Asensio Ramos, A.; Trujillo Bueno, J., E-mail: dorozco@iac.es

2012-12-20

We present observational evidence of apparent plasma rotational motions in the feet of a solar prominence. Our study is based on spectroscopic observations taken in the He I 1083.0 nm multiplet with the Tenerife Infrared Polarimeter attached to the German Vacuum Tower Telescope. We recorded a time sequence of spectra with 34 s cadence placing the slit of the spectrograph almost parallel to the solar limb and crossing two feet of an intermediate size, quiescent hedgerow prominence. The data show opposite Doppler shifts, {+-}6 km s{sup -1}, at the edges of the prominence feet. We argue that these shifts maymore » be interpreted as prominence plasma rotating counterclockwise around the vertical axis to the solar surface as viewed from above. The evolution of the prominence seen in EUV images taken with the Solar Dynamics Observatory provided us with clues to interpret the results as swirling motions. Moreover, time-distance images taken far from the central wavelength show plasma structures moving parallel to the solar limb with velocities of about 10-15 km s{sup -1}. Finally, the shapes of the observed intensity profiles suggest the presence of, at least, two components at some locations at the edges of the prominence feet. One of them is typically Doppler shifted (up to {approx}20 km s{sup -1}) with respect to the other, thus suggesting the existence of supersonic counter-streaming flows along the line of sight.« less

High-resolution optical measurements of atmospheric winds from space. I - Lower atmosphere molecular absorption

NASA Technical Reports Server (NTRS)

Hays, P. B.

1982-01-01

A high-resolution spectroscopic technique, analogous to that used in the thermosphere to measure the vector wind fields in the upper troposphere and stratosphere, is described which uses narrow features in the spectrum of light scattered from the earth's lower atmosphere to provide Doppler information on atmospheric scattering and absorption. It is demonstrated that vector winds can be measured from a satellite throughout the lower atmosphere, using a multiple-etalon Fabry-Perot interferometer of modest aperture. It is found that molecular oxygen and water vapor absorption lines in the spectrum of sunlight scattered by the atmosphere are Doppler-shifted by the line of sight wind, so that they may be used to monitor the global wind systems in the upper troposphere and stratosphere.

Use of PZT's for adaptive control of Fabry-Perot etalon plate figure

NASA Technical Reports Server (NTRS)

Skinner, WIlbert; Niciejewski, R.

2005-01-01

A Fabry Perot etalon, consisting of two spaced and reflective glass flats, provides the mechanism by which high resolution spectroscopy may be performed over narrow spectral regions. Space based applications include direct measurements of Doppler shifts of airglow absorption and emission features and the Doppler broadening of spectral lines. The technique requires a high degree of parallelism between the two flats to be maintained through harsh launch conditions. Monitoring and adjusting the plate figure by illuminating the Fabry Perot interferometer with a suitable monochromatic source may be performed on orbit to actively control of the parallelism of the flats. This report describes the use of such a technique in a laboratory environment applied to a piezo-electric stack attached to the center of a Fabry Perot etalon.

Comparison of 2- and 10-micron coherent Doppler lidar performance

NASA Technical Reports Server (NTRS)

Frehlich, Rod

1995-01-01

The performance of 2- and 10-micron coherent Doppler lidar is presented in terms of the statistical distribution of the maximum-likelihood velocity estimator from simulations for fixed range resolution and fixed velocity search space as a function of the number of coherent photoelectrons per estimate. The wavelength dependence of the aerosol backscatter coefficient, the detector quantum efficiency, and the atmospheric extinction produce a simple shift of the performance curves. Results are presented for a typical boundary layer measurement and a space-based measurement for two regimes: the pulse-dominated regime where the signal statistics are determined by the transmitted pulse, and the atmospheric-dominated regime where the signal statistics are determined by the velocity fluctuations over the range gate. The optimal choice of wavelength depends on the problem under consideration.

Development of Time-Distance Helioseismology Data Analysis Pipeline for SDO/HMI

NASA Technical Reports Server (NTRS)

DuVall, T. L., Jr.; Zhao, J.; Couvidat, S.; Parchevsky, K. V.; Beck, J.; Kosovichev, A. G.; Scherrer, P. H.

2008-01-01

The Helioseismic and Magnetic Imager of SDO will provide uninterrupted 4k x 4k-pixel Doppler-shift images of the Sun with approximately 40 sec cadence. These data will have a unique potential for advancing local helioseismic diagnostics of the Sun's interior structure and dynamics. They will help to understand the basic mechanisms of solar activity and develop predictive capabilities for NASA's Living with a Star program. Because of the tremendous amount of data the HMI team is developing a data analysis pipeline, which will provide maps of subsurface flows and sound-speed distributions inferred form the Doppler data by the time-distance technique. We discuss the development plan, methods, and algorithms, and present the status of the pipeline, testing results and examples of the data products.

Relativistic effects in earth-orbiting Doppler lidar return signals.

PubMed

Ashby, Neil

2007-11-01

Frequency shifts of side-ranging lidar signals are calculated to high order in the small quantities (v/c), where v is the velocity of a spacecraft carrying a lidar laser or of an aerosol particle that scatters the radiation back into a detector (c is the speed of light). Frequency shift measurements determine horizontal components of ground velocity of the scattering particle, but measured fractional frequency shifts are large because of the large velocities of the spacecraft and of the rotating earth. Subtractions of large terms cause a loss of significant digits and magnify the effect of relativistic corrections in determination of wind velocity. Spacecraft acceleration is also considered. Calculations are performed in an earth-centered inertial frame, and appropriate transformations are applied giving the velocities of scatterers relative to the ground.

An Ultrasonic Contactless Sensor for Breathing Monitoring

PubMed Central

Arlotto, Philippe; Grimaldi, Michel; Naeck, Roomila; Ginoux, Jean-Marc

2014-01-01

The monitoring of human breathing activity during a long period has multiple fundamental applications in medicine. In breathing sleep disorders such as apnea, the diagnosis is based on events during which the person stops breathing for several periods during sleep. In polysomnography, the standard for sleep disordered breathing analysis, chest movement and airflow are used to monitor the respiratory activity. However, this method has serious drawbacks. Indeed, as the subject should sleep overnight in a laboratory and because of sensors being in direct contact with him, artifacts modifying sleep quality are often observed. This work investigates an analysis of the viability of an ultrasonic device to quantify the breathing activity, without contact and without any perception by the subject. Based on a low power ultrasonic active source and transducer, the device measures the frequency shift produced by the velocity difference between the exhaled air flow and the ambient environment, i.e., the Doppler effect. After acquisition and digitization, a specific signal processing is applied to separate the effects of breath from those due to subject movements from the Doppler signal. The distance between the source and the sensor, about 50 cm, and the use of ultrasound frequency well above audible frequencies, 40 kHz, allow monitoring the breathing activity without any perception by the subject, and therefore without any modification of the sleep quality which is very important for sleep disorders diagnostic applications. This work is patented (patent pending 2013-7-31 number FR.13/57569). PMID:25140632

Energetic ion, atom, and molecule reactions and excitation in low-current H2 discharges: H(alpha) Doppler profiles.

PubMed

Petrović, Z Lj; Phelps, A V

2009-12-01

Absolute spectral emissivities for Doppler broadened H(alpha) profiles are measured and compared with predictions of energetic hydrogen ion, atom, and molecule behavior in low-current electrical discharges in H2 at very high electric field E to gas density N ratios E/N and low values of Nd , where d is the parallel-plate electrode separation. These observations reflect the energy and angular distributions for the excited atoms and quantitatively test features of multiple-scattering kinetic models in weakly ionized hydrogen in the presence of an electric field that are not tested by the spatial distributions of H(alpha) emission. Absolute spectral intensities agree well with predictions. Asymmetries in Doppler profiles observed parallel to the electric field at 4

Hα Doppler shifts in a tornado in the solar corona

NASA Astrophysics Data System (ADS)

Schmieder, B.; Mein, P.; Mein, N.; Levens, P. J.; Labrosse, N.; Ofman, L.

2017-01-01

Context. High resolution movies in 193 Å from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory (SDO) show apparent rotation in the leg of a prominence observed during a coordinated campaign. Such structures are commonly referred to as tornadoes. Time-distance intensity diagrams of the AIA data show the existence of oscillations suggesting that the structure is rotating. Aims: The aim of this paper is to understand if the cool plasma at chromospheric temperatures inside the tornado is rotating around its central axis. Methods: The tornado was also observed in Hα with a cadence of 30 s by the MSDP spectrograph, operating at the Solar Tower in Meudon. The MSDP provides sequences of simultaneous spectra in a 2D field of view from which a cube of Doppler velocity maps is retrieved. Results: The Hα Doppler maps show a pattern with alternatively blueshifted and redshifted areas of 5 to 10'' wide. Over time the blueshifted areas become redshifted and vice versa, with a quasi-periodicity of 40 to 60 min. Weaker amplitude oscillations with periods of 4 to 6 min are superimposed onto these large period oscillations. Conclusions: The Doppler pattern observed in Hα cannot be interpreted as rotation of the cool plasma inside the tornado. The Hα velocity observations give strong constraints on the possible interpretations of the AIA tornado.

Force That Increases at Larger Distance Has Some Psychological and Astronomical Evidence Supporting its Existence

NASA Astrophysics Data System (ADS)

Struck, James

2011-09-01

Force that Increases with distance is different than dark energy as I am arguing for existence of force based on psychological and astronomical bases. Hubble shift, doppler shift, comet return, quasar zoo and quasars and psychological evidence of interest in distant objects lends support to a force like gravity, nuclear, weak, strong, virtual, decay, biological, growth forces which increases its intensity with distance unlike gravity which decreases in intensity with distance. Jane Frances Back Struck contributed to this finding with her request that her grandparents have "perfect justice" even though her grandparents had died before she was born; interest increasing with distance from grandparents.

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.

Method and apparatus for measuring frequency and phase difference

NASA Technical Reports Server (NTRS)

Shores, Paul (Inventor); Lichtenberg, Christopher (Inventor); Kobayashi, Herbert S. (Inventor); Cunningham, Allen R. (Inventor)

1986-01-01

The present invention is a system for deriving direct digital indications of frequency and phase difference between two incoming pulse trains adaptable for collision avoidance systems or the like. A pair of radar beams are directed toward a target and corresponding beams returning therefrom are detected. A digital difference circuit forms a pulse train from the Doppler shift frequencies of each beam pair having a repetition rate functionally related to the difference in magnitude of the shift frequencies. Pulses from the pulse train are counted as a function of time. Visual indications thereof on display are correlative to target position relative to beams.

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

NASA Technical Reports Server (NTRS)

Lee, Jonggil

1990-01-01

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

Comparison of numerical techniques for the evaluation of the Doppler broadening functions psi(x,theta) and chi(x,theta)

NASA Technical Reports Server (NTRS)

Canright, R. B., Jr.; Semler, T. T.

1972-01-01

Several approximations to the Doppler broadening functions psi(x, theta) and chi(x, theta) are compared with respect to accuracy and speed of evaluation. A technique, due to A. M. Turning (1943), is shown to be at least as accurate as direct numerical quadrature and somewhat faster than Gaussian quadrature. FORTRAN 4 listings are included.

Propagating Neural Source Revealed by Doppler Shift of Population Spiking Frequency

PubMed Central

Zhang, Mingming; Shivacharan, Rajat S.; Chiang, Chia-Chu; Gonzalez-Reyes, Luis E.

2016-01-01

Electrical activity in the brain during normal and abnormal function is associated with propagating waves of various speeds and directions. It is unclear how both fast and slow traveling waves with sometime opposite directions can coexist in the same neural tissue. By recording population spikes simultaneously throughout the unfolded rodent hippocampus with a penetrating microelectrode array, we have shown that fast and slow waves are causally related, so a slowly moving neural source generates fast-propagating waves at ∼0.12 m/s. The source of the fast population spikes is limited in space and moving at ∼0.016 m/s based on both direct and Doppler measurements among 36 different spiking trains among eight different hippocampi. The fact that the source is itself moving can account for the surprising direction reversal of the wave. Therefore, these results indicate that a small neural focus can move and that this phenomenon could explain the apparent wave reflection at tissue edges or multiple foci observed at different locations in neural tissue. SIGNIFICANCE STATEMENT The use of novel techniques with an unfolded hippocampus and penetrating microelectrode array to record and analyze neural activity has revealed the existence of a source of neural signals that propagates throughout the hippocampus. The source itself is electrically silent, but its location can be inferred by building isochrone maps of population spikes that the source generates. The movement of the source can also be tracked by observing the Doppler frequency shift of these spikes. These results have general implications for how neural signals are generated and propagated in the hippocampus; moreover, they have important implications for the understanding of seizure generation and foci localization. PMID:27013678

Combining laser frequency combs and iodine cell calibration techniques for Doppler detection of exoplanets

NASA Astrophysics Data System (ADS)

Cahoy, Kerri; Fischer, Debra; Spronck, Julien; DeMille, David

2010-07-01

Exoplanets can be detected from a time series of stellar spectra by looking for small, periodic shifts in the absorption features that are consistent with Doppler shifts caused by the presence of an exoplanet, or multiple exoplanets, in the system. While hundreds of large exoplanets have already been discovered with the Doppler technique (also called radial velocity), our goal is to improve the measurement precision so that many Earth-like planets can be detected. The smaller mass and longer period of true Earth analogues require the ability to detect a reflex velocity of ~10 cm/s over long time periods. Currently, typical astronomical spectrographs calibrate using either Iodine absorptive cells or Thorium Argon lamps and achieve ~10 m/s precision, with the most stable spectrographs pushing down to ~2 m/s. High velocity precision is currently achieved at HARPS by controlling the thermal and pressure environment of the spectrograph. These environmental controls increase the cost of the spectrograph, and it is not feasible to simply retrofit existing spectrometers. We propose a fiber-fed high precision spectrograph design that combines the existing ~5000-6000 A Iodine calibration system with a high-precision Laser Frequency Comb (LFC) system from ~6000-7000 A that just meets the redward side of the Iodine lines. The scientific motivation for such a system includes: a 1000 A span in the red is currently achievable with LFC systems, combining the two calibration methods increases the wavelength range by a factor of two, and moving redward decreases the "noise" from starspots. The proposed LFC system design employs a fiber laser, tunable serial Fabry-Perot cavity filters to match the resolution of the LFC system to that of standard astronomical spectrographs, and terminal ultrasonic vibration of the multimode fiber for a stable point spread function.

Electronic Warfare and Radar Systems Engineering Handbook

DTIC Science & Technology

2012-06-01

Airframe Missile, or Reliability, Availability, and Maintainability R&M Reliability and Maintainability RAT Ram Air Turbine RBOC Rapid Blooming...the Doppler shifted return (see Figure 10). Reflections off rotating jet engine compressor blades, aircraft propellers, ram air turbine (RAT...predict aircraft ground speed and direction of motion. Wind influences are taken into account, such that the radar can also be used to update the aircraft

Automated Detection of a Crossing Contact Based on Its Doppler Shift

DTIC Science & Technology

2009-03-01

contacts in passive sonar systems. A common approach is the application of high- gain processing followed by successive classification criteria. Most...contacts in passive sonar systems. A common approach is the application of high-gain processing followed by successive classification criteria...RESEARCH MOTIVATION The trade-off between the false alarm and detection probability is fundamental in radar and sonar . (Chevalier, 2002) A common

Model for Ultrafast Carrier Scattering in Semiconductors

DTIC Science & Technology

2012-11-14

energy transfer between semi-classical carrier drift-diffusion under an electric field and quantum kinetics of interband /intersubband transitions...from an electron during each phonon-emission event. The net rate of phonon emission is determined by the Boltzmann scattering equation which depends ...energy-drift term under a strong dc field was demonstrated to reduce the field- dependent drift velocity and mobility. The Doppler shift in the energy

Next Generation Satellite Communications: Automated Doppler Shift Compensation of PSK-31 Via Software-Defined Radio

DTIC Science & Technology

2014-05-09

Interfaces Configuration – Wired Network Connections before Editing Move the cursor to the end of the line that ends with “eth0 inet dhcp ” and type...X”. This will delete text one character back from the cursor. Delete the word “ dhcp ”. Once this is done, type “a” to begin inserting text and add

Information-Driven Blind Doppler Shift Estimation and Compensation Methods for Underwater Wireless Sensor Networks

DTIC Science & Technology

2015-08-24

SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6. AUTHORS 7. PERFORMING ORGANIZATION NAMES AND ADDRESSES 15. SUBJECT TERMS b. ABSTRACT 2...network keeping constraints such as transmission rate, transmission delay, Signal-to-Interference and Noise Ratio (SINR) under consideration. Table...distances. It is advantageous to accomplish such transmission using sensors in a multi-hop relay form keeping constraints such as transmission rate

On the Probability of Error and Stochastic Resonance in Discrete Memoryless Channels

DTIC Science & Technology

2013-12-01

Information - Driven Doppler Shift Estimation and Compensation Methods for Underwater Wireless Sensor Networks ”, which is to analyze and develop... underwater wireless sensor networks . We formulated an analytic relationship that relates the average probability of error to the systems parameters, the...thesis, we studied the performance of Discrete Memoryless Channels (DMC), arising in the context of cooperative underwater wireless sensor networks

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

NASA Astrophysics Data System (ADS)

Penn, M. J.

2000-05-01

From 15:33-16:02 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 from 12 through 14 June 1998, 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 sho the He I 1083 nm absorption line 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 degrees to the solar surface and rises to a height of just over 1.5 solar radii. The KPVT data show no Stokes V profiles in the Doppler shifted He I 1083 nm absorption to a limit of roughly 3 x 10-3 times the continuum intensity. The SoHO/CDS data scanned the center of the KPVT FOV using seven EUV lines; Doppler shifted filament emission is seen in six lines from representing temperatures from about 2 x 104K through 1 x 106K. Bound-free continuum absorption from H I, free from 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 HI = 1.7 x 1018cm-2. Spatial maps show that this filament absorption is more confined than the regions which show emission. This work was made possible by 1997 and 1999 SoHO Guest Investigator awards NASA #W-19,142 Basic and NASA NAG5-8004.

Cross Sections for Balmer-Alpha Excitation in Heavy Particle Collisions.

NASA Astrophysics Data System (ADS)

Bae, Young Kun

Doppler shifted and unshifted Balmer-alpha radiation has been observed in the absolute sense for energetic H('+), H(,2)('+) and H(,3)('+) ions incident on molecular hydrogen by the method of decay inside the target within the energy range of 20 keV to 150 keV. Most of the measurements were based on single-collision conditions, but a simple thick -target experiment has been tried for the case of dissociative excitation of the target molecules by H atoms. The Balmer-alpha radiation emitted by hydrogen and deuterium beams has been used as a diagnostic method of neutral beam parameters. One important neutral beam parameter is the species mix between H('+), H(,2)('+) and H(,3)('+) ion currents produced by the ion source and accelerator. This species mix can be resolved by analysis of the Balmer-alpha radiation if the beam is observed along an off normal axis with sufficient spectral resolution to separate the Doppler shifted radiation components from each other. An impediment to this approach to measuring the ion species is that some of the required cross sections have not been measured. This is the motivation for the presented experimental work. A home made monochromator gave enough optical throughput and spectral resolution for separation of the Doppler shifted lines from the unshifted lines. By selectively varying the target pressure and the distance of travel into the target prior to the observation region, excitation cross sections for three different angular momentum states (3s, 3p and 3d) have been determined. Combinations of a linear polarizer and a half-wave plate were used for polarization measurement. Separation of the individual Zeeman levels have been tried for the 3p state from the information obtained from the polarization. Theoretical estimates of the cascading corrections have been applied in the case of both thin and thick targets. The intensity development equations for thick targets also have been derived. Cross sections for 3s production show general agreement with previous measurements, while those for 3p and 3d differ by as much as a factor of two. Target dissociative excitation cross sections show good agreement with previous measurements except those measured by Williams, et al..

Development of algorithms for tsunami detection by High Frequency Radar based on modeling tsunami case studies in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Grilli, Stéphan; Guérin, Charles-Antoine; Grosdidier, Samuel

2015-04-01

Where coastal tsunami hazard is governed by near-field sources, Submarine Mass Failures (SMFs) or earthquakes, tsunami propagation times may be too small for a detection based on deep or shallow water buoys. To offer sufficient warning time, it has been proposed by others to implement early warning systems relying on High Frequency Surface Wave Radar (HFSWR) remote sensing, that has a dense spatial coverage far offshore. A new HFSWR, referred to as STRADIVARIUS, has been recently deployed by Diginext Inc. to cover the "Golfe du Lion" (GDL) in the Western Mediterranean Sea. This radar, which operates at 4.5 MHz, uses a proprietary phase coding technology that allows detection up to 300 km in a bistatic configuration (with a baseline of about 100 km). Although the primary purpose of the radar is vessel detection in relation to homeland security, it can also be used for ocean current monitoring. The current caused by an arriving tsunami will shift the Bragg frequency by a value proportional to a component of its velocity, which can be easily obtained from the Doppler spectrum of the HFSWR signal. Using state of the art tsunami generation and propagation models, we modeled tsunami case studies in the western Mediterranean basin (both seismic and SMFs) and simulated the HFSWR backscattered signal that would be detected for the entire GDL and beyond. Based on simulated HFSWR signal, we developed two types of tsunami detection algorithms: (i) one based on standard Doppler spectra, for which we found that to be detectable within the environmental and background current noises, the Doppler shift requires tsunami currents to be at least 10-15 cm/s, which typically only occurs on the continental shelf in fairly shallow water; (ii) to allow earlier detection, a second algorithm computes correlations of the HFSWR signals at two distant locations, shifted in time by the tsunami propagation time between these locations (easily computed based on bathymetry). We found that this second method allowed detection for currents as low as 5 cm/s, i.e., in deeper water, beyond the shelf and further away from the coast, thus allowing an earlier detection.

Remote Sensing of Wind Fields and Aerosol Distribution with Airborne Scanning Doppler Lidar

NASA Technical Reports Server (NTRS)

Rothermel, Jeffry; Cutten, Dean R.; Johnson, Steven C.; Jazembski, Maurice; Arnold, James E. (Technical Monitor)

2001-01-01

The coherent Doppler laser radar (lidar), when operated from an airborne platform, is a unique tool for the study of atmospheric and surface processes and features. This is especially true for scientific objectives requiring measurements in optically-clear air, where other remote sensing technologies such as Doppler radar are typically at a disadvantage. The atmospheric lidar remote sensing groups of several US institutions, led by Marshall Space Flight Center, have developed an airborne coherent Doppler lidar capable of mapping the wind field and aerosol structure in three dimensions. The instrument consists of an eye-safe approx. 1 Joule/pulse lidar transceiver, telescope, scanner, inertial measurement unit, and flight computer system to orchestrate all subsystem functions and tasks. The scanner is capable of directing the expanded lidar beam in a variety of ways, in order to extract vertically-resolved wind fields. Horizontal resolution is approx. 1 km; vertical resolution is even finer. Winds are obtained by measuring backscattered, Doppler-shifted laser radiation from naturally-occurring aerosol particles (of order 1 micron diameter). Measurement coverage depends on aerosol spatial distribution and composition. Velocity accuracy has been verified to be approx. 1 meter per second. A variety of applications have been demonstrated during the three flight campaigns conducted during 1995-1998. Examples will be shown during the presentation. In 1995, boundary layer winds over the ocean were mapped with unprecedented resolution. In 1996, unique measurements were made of. flow over the complex terrain of the Aleutian Islands; interaction of the marine boundary layer jet with the California coastal mountain range; a weak dry line in Texas - New Mexico; the angular dependence of sea surface scattering; and in-flight radiometric calibration using the surface of White Sands National Monument. In 1998, the first measurements of eyewall and boundary layer winds within a hurricane were made with the airborne Doppler lidar. Potential applications and plans for improvement will also be described.

EFFECT OF PREGNANCY ON AUTOREGULATION OF CEREBRAL BLOOD FLOW IN ANTERIOR VERSUS POSTERIOR CEREBRUM

PubMed Central

Cipolla, Marilyn J.; Bishop, Nicole; Chan, Siu-Lung

2012-01-01

Severe pre/eclampsia are associated with brain edema that forms preferentially in the posterior cerebral cortex possibly due to decreased sympathetic innervation of posterior cerebral arteries and less effective autoregulation during acute hypertension. In the present study, we examined the effect of pregnancy on the effectiveness of cerebral blood flow autoregulation using laser Doppler flowmetry and edema formation by wet:dry weight in acute hypertension induced by phenylephrine infusion in the anterior and posterior cerebrum from nonpregnant (n=8) and late-pregnant (n=6) Sprague Dawley rats. In addition, we compared the effect of pregnancy on sympathetic innervation by tyrosine hydroxylase staining of posterior and middle cerebral arteries (n=5–6/group) and endothelial and neuronal nitric oxide synthase expression using quantitative polymerase chain reaction (n=3/group). In nonpregnant animals, there was no difference in autoregulation between anterior and posterior cerebrum. However, in late-pregnant animals, the threshold of cerebral blood flow autoregulation was shifted to lower pressures in the posterior cerebrum, which was associated with increased neuronal nitric oxide synthase expression in the posterior cerebral cortex vs. anterior. Compared to the nonpregnant state, pregnancy increased the threshold of autoregulation in both brain regions that was related to decreased expression of endothelial nitric oxide synthase. Lastly, acute hypertension during pregnancy caused greater edema formation in both brain cortices that was not due to changes in sympathetic innervation. These findings suggest that although pregnancy shifted the cerebral blood flow autoregulatory curve to higher pressures in both the anterior and posterior cortices, it did not protect from edema during acute hypertension. PMID:22824983

[Using combined magnetotherapy in patients with acne].

PubMed

Kul'chitskaia, D B; Orekhova, E M; Vasil'eva, E S

2004-01-01

Laser Doppler flowmetry discovered microcirculatory disorders in acne patients. Affected are arterioles as well as capillaries and venules. Combination of magnetotherapy with medication improves microcirculation in acne patients. More marked positive changes occurred in the microcirculatory system due to combined treatment compared to medication therapy only. Thus, laser Doppler flowmetry is a new, noninvasive method of assessing microcirculation in acne patients and can serve an objective criterion of treatment efficacy.

Advantages and limits of hemorrhoidal dearterialization in the treatment of symptomatic hemorrhoids

PubMed Central

Giamundo, Paolo

2016-01-01

In the last two decades, hemorrhoidal dearterialization has become universally accepted as a treatment option for symptomatic hemorrhoids. The rationale for this procedure is based on the assumption that arterial blood overflow is mainly responsible for dilatation of the hemorrhoidal plexus due to the absence of capillary interposition between the arterial and venous systems within the anal canal. Dearterialization, with either suture ligation (Doppler-guided hemorrhoid artery ligation/transanal hemorrhoidal dearterialization) or laser (hemorrhoidal laser procedure), may be successfully performed alone or with mucopexy. Although the added value of Doppler-guidance in association with dearterialization has recently been challenged, this imaging method still plays an important role in localizing hemorrhoidal arteries and, therefore, minimizing the effect of anatomic variation among patients. However, it is important to employ the correct Doppler transducer. Some Doppler transducers may not easily detect superficial arteries due to inadequate frequency settings. All techniques of dearterialization have the advantage of preserving the anatomy and physiology of the anal canal, when compared to other surgical treatments for hemorrhoids. This advantage cannot be underestimated as impaired anal function, including fecal incontinence and other defecation disorders, may occur following surgical treatment for hemorrhoids. Furthermore, this potentially devastating problem can occur in patients of all ages, including younger patients. PMID:26843909

Advantages and limits of hemorrhoidal dearterialization in the treatment of symptomatic hemorrhoids.

PubMed

Giamundo, Paolo

2016-01-27

In the last two decades, hemorrhoidal dearterialization has become universally accepted as a treatment option for symptomatic hemorrhoids. The rationale for this procedure is based on the assumption that arterial blood overflow is mainly responsible for dilatation of the hemorrhoidal plexus due to the absence of capillary interposition between the arterial and venous systems within the anal canal. Dearterialization, with either suture ligation (Doppler-guided hemorrhoid artery ligation/transanal hemorrhoidal dearterialization) or laser (hemorrhoidal laser procedure), may be successfully performed alone or with mucopexy. Although the added value of Doppler-guidance in association with dearterialization has recently been challenged, this imaging method still plays an important role in localizing hemorrhoidal arteries and, therefore, minimizing the effect of anatomic variation among patients. However, it is important to employ the correct Doppler transducer. Some Doppler transducers may not easily detect superficial arteries due to inadequate frequency settings. All techniques of dearterialization have the advantage of preserving the anatomy and physiology of the anal canal, when compared to other surgical treatments for hemorrhoids. This advantage cannot be underestimated as impaired anal function, including fecal incontinence and other defecation disorders, may occur following surgical treatment for hemorrhoids. Furthermore, this potentially devastating problem can occur in patients of all ages, including younger patients.

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.

Doppler radar echoes of lightning and precipitation at vertical incidence

NASA Technical Reports Server (NTRS)

Zrnic, D. S.; Rust, W. D.; Taylor, W. L.

1982-01-01

Digital time series data at 16 heights within two storms were collected at vertical incidence with a 10-cm Doppler radar. On several occasions during data collection, lightning echoes were observed as increased reflectivity on an oscilloscope display. Simultaneously, lightning signals from nearby electric field change antennas were recorded on an analog recorder together with the radar echoes. Reflectivity, mean velocity, and Doppler spectra were examined by means of time series analysis for times during and after lightning discharges. Spectra from locations where lightning occurred show peaks, due to the motion of the lightning channel at the air speed. These peaks are considerably narrower than the ones due to precipitation. Besides indicating the vertical air velocity that can then be used to estimate hydrometeor-size distribution, the lightning spectra provide a convenient means to estimate the radar cross section of the channel. Subsequent to one discharge, we deduce that a rapid change in the orientation of hydrometeors occurred within the resolution volume.

Laser Doppler imaging of cutaneous blood flow through transparent face masks: a necessary preamble to computer-controlled rapid prototyping fabrication with submillimeter precision.

PubMed

Allely, Rebekah R; Van-Buendia, Lan B; Jeng, James C; White, Patricia; Wu, Jingshu; Niszczak, Jonathan; Jordan, Marion H

2008-01-01

A paradigm shift in management of postburn facial scarring is lurking "just beneath the waves" with the widespread availability of two recent technologies: precise three-dimensional scanning/digitizing of complex surfaces and computer-controlled rapid prototyping three-dimensional "printers". Laser Doppler imaging may be the sensible method to track the scar hyperemia that should form the basis of assessing progress and directing incremental changes in the digitized topographical face mask "prescription". The purpose of this study was to establish feasibility of detecting perfusion through transparent face masks using the Laser Doppler Imaging scanner. Laser Doppler images of perfusion were obtained at multiple facial regions on five uninjured staff members. Images were obtained without a mask, followed by images with a loose fitting mask with and without a silicone liner, and then with a tight fitting mask with and without a silicone liner. Right and left oblique images, in addition to the frontal images, were used to overcome unobtainable measurements at the extremes of face mask curvature. General linear model, mixed model, and t tests were used for data analysis. Three hundred seventy-five measurements were used for analysis, with a mean perfusion unit of 299 and pixel validity of 97%. The effect of face mask pressure with and without the silicone liner was readily quantified with significant changes in mean cutaneous blood flow (P < .5). High valid pixel rate laser Doppler imager flow data can be obtained through transparent face masks. Perfusion decreases with the application of pressure and with silicone. Every participant measured differently in perfusion units; however, consistent perfusion patterns in the face were observed.

ORBSIM- ESTIMATING GEOPHYSICAL MODEL PARAMETERS FROM PLANETARY GRAVITY DATA

NASA Technical Reports Server (NTRS)

Sjogren, W. L.

1994-01-01

The ORBSIM program was developed for the accurate extraction of geophysical model parameters from Doppler radio tracking data acquired from orbiting planetary spacecraft. The model of the proposed planetary structure is used in a numerical integration of the spacecraft along simulated trajectories around the primary body. Using line of sight (LOS) Doppler residuals, ORBSIM applies fast and efficient modelling and optimization procedures which avoid the traditional complex dynamic reduction of data. ORBSIM produces quantitative geophysical results such as size, depth, and mass. ORBSIM has been used extensively to investigate topographic features on the Moon, Mars, and Venus. The program has proven particulary suitable for modelling gravitational anomalies and mascons. The basic observable for spacecraft-based gravity data is the Doppler frequency shift of a transponded radio signal. The time derivative of this signal carries information regarding the gravity field acting on the spacecraft in the LOS direction (the LOS direction being the path between the spacecraft and the receiving station, either Earth or another satellite). There are many dynamic factors taken into account: earth rotation, solar radiation, acceleration from planetary bodies, tracking station time and location adjustments, etc. The actual trajectories of the spacecraft are simulated using least squares fitted to conic motion. The theoretical Doppler readings from the simulated orbits are compared to actual Doppler observations and another least squares adjustment is made. ORBSIM has three modes of operation: trajectory simulation, optimization, and gravity modelling. In all cases, an initial gravity model of curved and/or flat disks, harmonics, and/or a force table are required input. ORBSIM is written in FORTRAN 77 for batch execution and has been implemented on a DEC VAX 11/780 computer operating under VMS. This program was released in 1985.

MARLI: MARs LIdar for global climate measurements from orbit

NASA Astrophysics Data System (ADS)

Allan, G. R.; Riris, H.; Sun, X.; Yu, A. W.; Abshire, J. B.

2017-12-01

NASA-GSFC is developing a pulsed multifunction lidar instrument to remotely measure winds in the Martian atmosphere from orbit. The key capabilities of this multifunctional atmospheric pulsed lidar will include continuous measurement of the aerosol backscatter profiles, the cross polarized (ice) backscatter profiles, the Doppler (wind profiles), and the range to the scattering surface from orbit. Our approach for MARLI is to use a direct detection lidar with efficient lasers, a large area low-mass telescope, a simple and rugged Doppler discriminator and with photon-sensitive detectors. The induced Doppler shifts on laser backscattered from aerosols in the Martian atmosphere will be detected using a time-resolved change in transmission through a solid etalon from two, slightly off-axis backscattered beams and the edge technique. In this presentation we report on the current progress of the core measurement of wind. We have demonstrated in the lab Doppler measurements down to 5m/s using a spinning target a pulsed lidar and edge technique. The laser is a seeded, pulsed-YAG in a MOPA configuration, operating at 1064nm producing pulses of 20ns and at a few mJ at 4KHz. Center frequency drift is less than 10MHz per minute. The Doppler discriminator is a solid etalon of 60 mm diameter and 40 mm thick with a peak transmission of over 65% and a bandpass of 100MHz FWHM. The detector is a cooled MCT array. We will also report on the deployment of the breadboard instrument to the GGAO to directly measure surface winds using the 48" telescope. The results from our field trials, the laser, detector and instrument will be more fully described in the presentation.

Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length

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

Liu, Wenzhong; Yi, Ji; Chen, Siyu

Purpose: Doppler optical coherence tomography (OCT) is widely used for measuring retinal blood flow. Existing Doppler OCT methods require the eyeball axial length, in which empirical values are usually used. However, variations in the axial length can create a bias unaccounted for in the retinal blood flow measurement. The authors plan to develop a Doppler OCT method that can measure the total retinal blood flow rate without requiring the eyeball axial length. Methods: The authors measured the retinal blood flow rate using a dual-ring scanning protocol. The small and large scanning rings entered the eye at different incident angles (smallmore » ring: 4°; large ring: 6°), focused on different locations on the retina, and detected the projected velocities/phase shifts along the probing beams. The authors calculated the ratio of the projected velocities between the two rings, and then used this ratio to estimate absolute flow velocity. The authors tested this method in both Intralipid phantoms and in vivo rats. Results: In the Intralipid flow phantom experiments, the preset and measured flow rates were consistent with the coefficient of determination as 0.97. Linear fitting between preset and measured flow rates determined the fitting slope as 1.07 and the intercept as −0.28. In in vivo rat experiments, the measured average total retinal blood flow was 7.02 ± 0.31μl/min among four wild-type rats. The authors’ measured flow rates were consistent with results in the literature. Conclusions: By using a dual-ring scanning protocol with carefully controlled incident angle difference between the two scanning rings in Doppler OCT, the authors demonstrated that it is feasible to measure the absolute retinal blood flow without knowing the eyeball axial length.« less

Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length

PubMed Central

Liu, Wenzhong; Yi, Ji; Chen, Siyu; Jiao, Shuliang; Zhang, Hao F.

2015-01-01

Purpose: Doppler optical coherence tomography (OCT) is widely used for measuring retinal blood flow. Existing Doppler OCT methods require the eyeball axial length, in which empirical values are usually used. However, variations in the axial length can create a bias unaccounted for in the retinal blood flow measurement. The authors plan to develop a Doppler OCT method that can measure the total retinal blood flow rate without requiring the eyeball axial length. Methods: The authors measured the retinal blood flow rate using a dual-ring scanning protocol. The small and large scanning rings entered the eye at different incident angles (small ring: 4°; large ring: 6°), focused on different locations on the retina, and detected the projected velocities/phase shifts along the probing beams. The authors calculated the ratio of the projected velocities between the two rings, and then used this ratio to estimate absolute flow velocity. The authors tested this method in both Intralipid phantoms and in vivo rats. Results: In the Intralipid flow phantom experiments, the preset and measured flow rates were consistent with the coefficient of determination as 0.97. Linear fitting between preset and measured flow rates determined the fitting slope as 1.07 and the intercept as −0.28. In in vivo rat experiments, the measured average total retinal blood flow was 7.02 ± 0.31μl/min among four wild-type rats. The authors’ measured flow rates were consistent with results in the literature. Conclusions: By using a dual-ring scanning protocol with carefully controlled incident angle difference between the two scanning rings in Doppler OCT, the authors demonstrated that it is feasible to measure the absolute retinal blood flow without knowing the eyeball axial length. PMID:26328984

Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length.

PubMed

Liu, Wenzhong; Yi, Ji; Chen, Siyu; Jiao, Shuliang; Zhang, Hao F

2015-09-01

Doppler optical coherence tomography (OCT) is widely used for measuring retinal blood flow. Existing Doppler OCT methods require the eyeball axial length, in which empirical values are usually used. However, variations in the axial length can create a bias unaccounted for in the retinal blood flow measurement. The authors plan to develop a Doppler OCT method that can measure the total retinal blood flow rate without requiring the eyeball axial length. The authors measured the retinal blood flow rate using a dual-ring scanning protocol. The small and large scanning rings entered the eye at different incident angles (small ring: 4°; large ring: 6°), focused on different locations on the retina, and detected the projected velocities/phase shifts along the probing beams. The authors calculated the ratio of the projected velocities between the two rings, and then used this ratio to estimate absolute flow velocity. The authors tested this method in both Intralipid phantoms and in vivo rats. In the Intralipid flow phantom experiments, the preset and measured flow rates were consistent with the coefficient of determination as 0.97. Linear fitting between preset and measured flow rates determined the fitting slope as 1.07 and the intercept as -0.28. In in vivo rat experiments, the measured average total retinal blood flow was 7.02 ± 0.31 μl/min among four wild-type rats. The authors' measured flow rates were consistent with results in the literature. By using a dual-ring scanning protocol with carefully controlled incident angle difference between the two scanning rings in Doppler OCT, the authors demonstrated that it is feasible to measure the absolute retinal blood flow without knowing the eyeball axial length.

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.

Ultrasonic ranging for the oculometer

NASA Technical Reports Server (NTRS)

Guy, W. J.

1981-01-01

Ultrasonic tracking techniques are investigated for an oculometer. Two methods are reported in detail. The first is based on measurements of time from the start of a transmit burst to a received echo. Knowing the sound velocity, distance can be calculated. In the second method, a continuous signal is transmitted. Target movement causes phase shifting of the echo. By accumulating these phase shifts, tracking from a set point can be achieved. Both systems have problems with contoured targets, but work well on flat plates and the back of a human head. Also briefly reported is an evaluation of an ultrasonic ranging system. Interface circuits make this system compatible with the echo time design. While the system is consistently accurate, it has a beam too narrow for oculometer use. Finally, comments are provided on a tracking system using the Doppler frequency shift to give range data.

Novel Optical Technique Developed and Tested for Measuring Two-Point Velocity Correlations in Turbulent Flows

NASA Technical Reports Server (NTRS)

Zimmerli, Gregory A.; Goldburg, Walter I.

2002-01-01

A novel technique for characterizing turbulent flows was developed and tested at the NASA Glenn Research Center. The work is being done in collaboration with the University of Pittsburgh, through a grant from the NASA Microgravity Fluid Physics Program. The technique we are using, Homodyne Correlation Spectroscopy (HCS), is a laser-light-scattering technique that measures the Doppler frequency shift of light scattered from microscopic particles in the fluid flow. Whereas Laser Doppler Velocimetry gives a local (single-point) measurement of the fluid velocity, the HCS technique measures correlations between fluid velocities at two separate points in the flow at the same instant of time. Velocity correlations in the flow field are of fundamental interest to turbulence researchers and are of practical importance in many engineering applications, such as aeronautics.

Doppler compensation by shifting transmitted object frequency within limits

NASA Technical Reports Server (NTRS)

Laughlin, C. R., Jr.; Hollenbaugh, R. C.; Allen, W. K. (Inventor)

1973-01-01

A system and method are disclosed for position locating, deriving centralized air traffic control data, and communicating via voice and digital signals between a multiplicity of remote aircraft, including supersonic transports, and a central station. Such communication takes place through a synchronous satellite relay station. Side tone ranging patterns, as well as the digital and voice signals, are modulated on a carrier transmitted from the central station and received on all of the supersonic transports. Each aircraft communicates with the ground stations via a different frequency multiplexed spectrum. Supersonic transport position is derived from a computer at the central station and supplied to a local air traffic controller. Position is determined in response to variable phase information imposed on the side tones at the aircrafts. Common to all of the side tone techniques is Doppler compensation for the supersonic transport velocity.

Velocity visualization in gaseous flows

NASA Technical Reports Server (NTRS)

Hanson, R. K.

1985-01-01

Techniques are established for visualizing velocity in gaseous flows. Two approaches are considered, both of which are capable of yielding velocity simultaneously at a large number of flowfield locations, thereby providing images of velocity. The first technique employs a laser to mark specific fluid elements and a camera to track their subsequent motion. Marking is done by laser-induced phosphorescence of biacetyl, added as a tracer species in a flow of N2, or by laser-induced formation of sulfur particulates in SF6-H2-N2 mixtures. The second technique is based on the Doppler effect, and uses an intensified photodiode array camera and a planar form of laser-induced fluorescence to detect 2-d velocities of I2 (in I2-N2 mixtures) via Doppler-shifted absorption of narrow-linewidth laser radiation at 514.5 nm.

New Possibilities of Positron-Emission Tomography

NASA Astrophysics Data System (ADS)

Volobuev, A. N.

2018-01-01

The reasons for the emergence of the angular distribution of photons generated as a result of annihilation of an electron and a positron in a positron-emission tomograph are investigated. It is shown that the angular distribution of the radiation intensity (i.e., the probability of photon emission at different angles) is a consequence of the Doppler effect in the center-of-mass reference system of the electron and the positron. In the reference frame attached to the electron, the angular distribution of the number of emitted photons does not exists but is replaced by the Doppler shift of the frequency of photons. The results obtained in this study make it possible to extend the potentialities of the positron-emission tomograph in the diagnostics of diseases and to obtain additional mechanical characteristics of human tissues, such as density and viscosity.

Spacecraft Doppler tracking with a VLBI antenna

NASA Technical Reports Server (NTRS)

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

1990-01-01

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

Comparison of Venous Return Characteristics with Right Ventricular Mechanics During Cephalic Fluid Shift

NASA Technical Reports Server (NTRS)

Elliott, Morgan; Martin, David

2015-01-01

For my summer internship project, I organized a pilot study to analyze the effects of a cephalic fluid shift on venous return and right ventricular mechanics to increase right ventricular and venous knowledge. To accomplish this pilot study, I wrote a testing protocol, obtained Institutional Review Board (IRB) approval, completed subject payment forms, lead testing sessions, and analyzed the data. This experiment used -20deg head down tilt (20 HDT) as the ground based simulation for the fluid shift that occurs during spaceflight and compared it to data obtained from the seated and supine positions. Using echocardiography, data was collected for the right ventricle, hepatic vein, internal jugular vein, external jugular vein, and inferior vena cava. Additionally, non-invasive venous pressure measurements, similar to those soon to be done in-orbit, were collected. It was determined that the venous return from below the heard is increased during 20 HDT, which was supported by increased hepatic vein velocities, increased right ventricular inflow, and increased right ventricular strain at 20 HDT relative to seated values. Jugular veins in the neck undergo an increase in pressure and area, but no significant increase in flow, relative to seated values when a subject is tilted 20 HDT. Contrary to the initial expectations based on this jugular flow, there was no significant increase in central venous pressure, as evidenced by no change in Doppler indices for right arterial pressure or inferior vena cava diameter. It is suspected that these differences in pressure are due to the hydrostatic pressure indifference point shifting during tilt; there is a potential for a similar phenomenon with microgravity. This data will hopefully lead to a more in-depth understanding of the response of the body to microgravity and how those relate to the previously mentioned cardiovascular risk of fluid shift that is associated with spaceflight. These results were presented in greater detail to the Cardiovascular Laboratory and the Space Life Science Summer Institute, which helped me prepare for future graduate school research presentations. This internship allowed me to apply and expand the anatomy, physiology, and mechanics information I learned during my undergraduate degree in Biomedical Engineering to the cardiovascular system with the unique zero gravity perspective. Additionally, I was able to develop skills with data analysis techniques involving speckle tracking for ventricular strain and Doppler waveforms for blood velocities. Additionally, I was able to expand upon my previous work in the Cardiovascular Laboratory by writing a literature review on a data analysis project I completed last summer. Ultimately, this internship and venous relationship comparison project provided me with a significant learning experience and additional skill sets, which are applicable to my goals of attaining a Ph.D. in biomedical engineering with a focus on tissue engineering and the cardiovascular system.

Dove prism based rotating dual beam bidirectional Doppler OCT

PubMed Central

Blatter, Cedric; Coquoz, Séverine; Grajciar, Branislav; Singh, Amardeep S. G.; Bonesi, Marco; Werkmeister, René M.; Schmetterer, Leopold; Leitgeb, Rainer A.

2013-01-01

Traditional Doppler OCT is highly sensitive to motion artifacts due to the dependence on the Doppler angle. This limits its accuracy in clinical practice. To overcome this limitation, we use a bidirectional dual beam technique equipped with a novel rotating scanning scheme employing a Dove prism. The volume is probed from two distinct illumination directions with variable controlled incidence plane, allowing for reconstruction of the true flow velocity at arbitrary vessel orientations. The principle is implemented with Swept Source OCT at 1060nm with 100,000 A-Scans/s. We apply the system to resolve pulsatile retinal absolute blood velocity by performing segment scans around the optic nerve head and circumpapillary scan time series. PMID:23847742

How to study the Doppler effect with Audacity software

NASA Astrophysics Data System (ADS)

Adriano Dias, Marco; Simeão Carvalho, Paulo; Rodrigues Ventura, Daniel

2016-05-01

The Doppler effect is one of the recurring themes in college and high school classes. In order to contextualize the topic and engage the students in their own learning process, we propose a simple and easily accessible activity, i.e. the analysis of the videos available on the internet by the students. The sound of the engine of the vehicle passing by the camera is recorded on the video; it is then analyzed with the free software Audacity by measuring the frequency of the sound during approach and recede of the vehicle from the observer. The speed of the vehicle is determined due to the application of Doppler effect equations for acoustic waves.

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.

Spin-dependent evolution of collectivity in 112Te

NASA Astrophysics Data System (ADS)

Doncel, M.; Bäck, T.; Qi, C.; Cullen, D. M.; Hodge, D.; Cederwall, B.; Taylor, M. J.; Procter, M.; Giles, M.; Auranen, K.; Grahn, T.; Greenlees, P. T.; Jakobsson, U.; Julin, R.; Juutinen, S.; HerzáÅ, A.; Konki, J.; Pakarinen, J.; Partanen, J.; Peura, P.; Rahkila, P.; Ruotsalainen, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Sorri, J.; Stolze, S.; Uusitalo, J.

2017-11-01

The evolution of collectivity with spin along the yrast line in the neutron-deficient nucleus 112Te has been studied by measuring the reduced transition probability of excited states in the yrast band. In particular, the lifetimes of the 4+ and 6+ excited states have been determined by using the recoil distance Doppler-shift method. The results are discussed using both large-scale shell-model and total Routhian surface calculations.

North Pacific Acoustic Laboratory and Deep Water Acoustics

DTIC Science & Technology

2014-09-30

collaboration with Gerald D’Spain at the Marine Physical Laboratory ( MPL ) has continued. Data from PhilSea10 during the Drift Test have corrected for...Doppler shift, processed and provided to MPL . The collaboration will continue as the analysis progresses. II. Award Number N00014-13-1-0053...Wage (George Mason Univ.), Peter Worcester (Scripps), and others. In addition, we have begun close collaboration with Gerald D’Spain ( MPL

Experiment to investigate current drive by fast Alfven waves in a small tokamak

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

Gahl, J.; Ishihara, O.; Wong, K.

1985-07-01

An experiment has been carried out to study current generation by Doppler shifted cyclotron resonance heating of minority ions with a unidirectional wave in the small tokamak at Texas Tech University. One of the objectives of the experiment is to understand in detail the wave-particle interactions through which fast (compressional) Alfven waves in the ion cyclotron range of frequencies drive currents in toroidal devices.

Lifetime measurement of high spin states in (75) Kr

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

Sheikh, Javid; Trivedi, T.; Maurya, K.

2010-01-01

The lifetimes of high spin states of {sup 75}Kr have been determined via {sup 50}Cr ({sup 28}Si, 2pn) {sup 75}Kr reaction in positive parity band using the Doppler-shift attenuation method. The transition quadrupole moments Q deduced from lifetime measurements have been compared with {sup 75}Br. Experimental results obtained from lifetime measurement are interpreted in the framework of projected shell model.

Command Wire Sensor Measurements

DTIC Science & Technology

2012-09-01

coupled with the extreme harsh terrain has meant that few of these techniques have proved robust enough when moved from the laboratory to the field...to image stationary objects and does not accurately image moving targets. Moving targets can be seriously distorted and displaced from their true...battlefield and for imaging of fixed targets. Moving targets can be detected with a SAR if they have a Doppler frequency shift greater than the

RF Bearing Estimation in Wireless Sensor Networks

DTIC Science & Technology

2010-01-01

are the main design drivers. Techniques based on ultrasonic and infrared signal modalities have short range and require line-of-sight. Clearly, RF...generating a Doppler shifted RF signal . The small frequency change can be measured even on low cost resource constrained nodes using a radio...is already included in the power budget and RF range is superior to most other signals . Radio signal strength (RSS) based approaches are the most

United States Air Force Graduate Student Summer Support Program (1987). Program Technical Report. Volume 2

DTIC Science & Technology

1987-12-01

Metabolism (VMAX) Using Quantitative Structure- Activity Relationships (QSAR) 17 Directed Motion Doppler Shift Effects on Mitric Oxide (0,0) Gamma Band...chemiluminescence values were observed at characteristic times after adding glucose to the disks. We also produced virus-sized nanoparticles (Glucose...These nanoparticles were able to penetrate a .2 um filter,and they retained their enzymatic activity for weeks. They produced 20-fold greater

Tracking Architecture Based on Dual-Filter with State Feedback and Its Application in Ultra-Tight GPS/INS Integration

PubMed Central

Zhang, Xi; Miao, Lingjuan; Shao, Haijun

2016-01-01

If a Kalman Filter (KF) is applied to Global Positioning System (GPS) baseband signal preprocessing, the estimates of signal phase and frequency can have low variance, even in highly dynamic situations. This paper presents a novel preprocessing scheme based on a dual-filter structure. Compared with the traditional model utilizing a single KF, this structure avoids carrier tracking being subjected to code tracking errors. Meanwhile, as the loop filters are completely removed, state feedback values are adopted to generate local carrier and code. Although local carrier frequency has a wide fluctuation, the accuracy of Doppler shift estimation is improved. In the ultra-tight GPS/Inertial Navigation System (INS) integration, the carrier frequency derived from the external navigation information is not viewed as the local carrier frequency directly. That facilitates retaining the design principle of state feedback. However, under harsh conditions, the GPS outputs may still bear large errors which can destroy the estimation of INS errors. Thus, an innovative integrated navigation filter is constructed by modeling the non-negligible errors in the estimated Doppler shifts, to ensure INS is properly calibrated. Finally, field test and semi-physical simulation based on telemetered missile trajectory validate the effectiveness of methods proposed in this paper. PMID:27144570