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Numerous experiments have been carried out to validate the Lorentz transformation or to find possible violations of Lorentz invariance, based on test theories to test special relativity. The test theory of Mansouri and Sexl (MS) provides a general framework for the transformation of inertial frames, presuming a preferred system of reference. Based on the MS framework, this paper systematically approaches the relativistic Doppler effect such that its dependency on transformation coefficients and parameters can be investigated. The Doppler effect is formulated in a complex Euclidean space where time is represented with imaginary numbers. Two formulae of the Doppler effect, which have been derived in an arbitrary transformation within the MS framework, are presented: one between an inertial frame and the preferred one and the other between arbitrary inertial frames. It is shown from the former formulation that the Doppler effect is independent of the synchronization of clocks, which implies that the Doppler-shifted frequency in the absolute synchronization is the same as that in the standard synchronization. The latter formula can allow us to find Doppler shifts without information on the velocities of inertial frames relative to the preferred frame. Exploiting these theoretical results, we examine the transverse and the longitudinal Doppler effects in detail. Key words: relativistic doppler effect, wave vectors, test theory, clock synchronization. Un grand nombre d'experiences ont ete faites pour valider la transformation de Lorentz ou pour trouver de possibles violations de l'invariance de Lorentz, sur la base de theories des tests visant a verifier la relativite restreinte. La theorie de Mansouri et Sexl (MS) fournit un cadre general pour la transformation de referentiels inertiels, en supposant l'existence d'un systeme de reference preferentiel. Sur la base du cadre de MS, nous etudions ici de facon systematique l'effet Doppler relativiste de facon a identifier sa dependance sur les coefficients et parametres de la transformation. L'effet Doppler est formule ici dans un espace euclidien complexe oU le temps est represente par des nombres complexes. Nous presentons deux formules de l'effet Doppler qui sont derivees dans une transformation arbitraire a l'interieur du cadre de MS : une premiere, entre un referentiel inertiel et un referentiel preferentiel et l'autre entre deux referentiels inertiels arbitraires. Nous montrons dans cette formulation que l'effet Doppler est independant de la synchronisation des horloges, ce qui implique que le deplacement en frequence de Doppler dans la synchronisation absolue est le meme que dans la synchronisation standard. Cette derniere formule peut nous permettre de trouver des deplacements de Doppler sans information sur la vitesse des referentiels inertiels relativement au referentiel preferentiel. Exploitant ces resultats theoriques, nous examinons les effets Doppler transverse et longitudinal en detail. [Traduit par la Redaction] Mots-cles : effet Doppler relativiste, vecteurs d'onde, theorie des tests, synchronisation des horloges., 1. Introduction Special relativity [1, 2] predicts time dilation. According to special relativity, Doppler shifts can occur because of the effect of time dilation as well as relative motion between [...]

Experimental results on the nature-like fishway induced flow field and its relation to fish behaviour are presented. A rocky-ramp with 5% slope was built along a8.9mx0.9mx0.6m laboratory flume, and acoustic Doppler velocity measurements were taken in a grid with 186 points for low, middle, and high discharges. The flow is characterized applying spatial and point analysis techniques. Point analysis consistently shows that the boulder to boulder distance is small enough to disrupt turbulent coherent structures. At boulder wakes no predominance of sweep and ejection events occur, evidencing a good resting place for fish migration. The nature-like rocky-ramp offers a diversity of flow conditions controlled by the boulders geometry that might allow a variety of fishes to develop their preferred paths characterized by flow properties with different magnitudes depending on the particular species. Obtained results compare well with similar ones reported for other standard fishways. Key words: ADV, fish habitat, fish passage, flow, nature-like fishways, turbulence. Cet article presente les resultats d'experiences concernant le champ de courant induit dans une passe migratoire d'aspect naturel et sa relation avec le comportement des poissons. Une rampe rocheuse ayant une pente de5%aete construite le long d'un canal jaugeur de laboratoire mesurant 8,9 x 0,9 x 0,6 m; des mesures de vitesse ont ete prises au debitmetre acoustique selon une grille de 186 points a des debits faibles moyens et eleves. L'ecoulement est caracterise en appliquant des techniques d'analyse spatiale et par points. L'analyse par points montre de maniere uniforme que la distance de rocher a rocher est suffisamment petite pour perturber les structures coherentes de turbulence. Il n'y a aucune predominance de balayage et d'ejection dans les sillages des rochers, prouvant qu'il s'agit d'un bon endroit de repos pour les poissons en migration. La rampe rocheuse d'aspect naturel offre une diversite de conditions d'ecoulement controlees par la geometrie des rochers, ce qui pourrait permettre a plusieurs especes de poissons de developper leur chemin prefere selon les proprietes d'ecoulement de differentes amplitudes propres aux especes particulieres. Les resultats obtenus se comparent bien a d'autres resultats similaires rapportes pour d'autres passes migratoires standards. [Traduit par la Redaction] Mots-cles : debitmetre acoustique, habitat du poisson, passe migratoire, ecoulement, passes migratoires d'aspect naturel, turbulence., 1. Introduction Fishways are hydraulic structures enabling fish to negotiate river obstructions such as dams, weirs, and under-road culverts. According to their design, one can distinguish standard and nature-like fishways. [...]

Measurements of the transverse Doppler effect have provided important confirmatory evidence for the validity of Einstein's theory of special relativity (SR) as it pertains to time dilation. However, these investigations fall into two distinct categories depending on whether the light source or the detector is accelerated relative to the rest frame of the observer. In their original work employing a moving light source in the laboratory, Ives and Stillwell state explicitly that they observe a wavelength shift to the red, and therefore a slowing down of the initially accelerated clock, in complete agreement with Einstein's predictions. By contrast, although both Hay et al. and Kundig also report complete agreement with SR on the basis of their ultracentrifuge experiments in which the absorber/detector is under constant high acceleration, their theoretical discussion actually contradicts this assertion. For example, Kundig states that his work demonstrates 'that the clock which experiences acceleration is retarded compared to the clock at rest,' thereby giving unequivocal support to the conclusion that it is not just a matter of perspective which of two clocks runs slower at any given time, but rather that the measurement process is perfectly objective. This experience has generally been dismissed by SR proponents, arguing that the latter theory is only to be applied for objects in uniform motion, in which case measurement is definitely subjective. It is pointed out that this conclusion overlooks the fact that a version of the Lorentz transformation exists which is consistent with both sets of measurements while still satisfying Einstein's two postulates of SR. Keywords: transverse Doppler effect, ultracentrifuge experiments, Lorentz transformation (LT), alternative Lorentz transformation (ALT), I. Introduction Before the dawn of the twentieth century there was a broad consensus among both philosophers and physicists that that the measurement of physical quantities had an absolute character. [...]

It is shown that the Pioneer anomaly is a natural consequence of variable speed of light cosmological models wherein the speed of light is assumed to be a power-law function of the scale factor (or cosmic time). In other words, the Pioneer anomaly can be regarded as a nongravitational effect of the continuously decreasing speed of light, which shows itself as an anomalous light propagation time delay in local frames. This time delay is accordingly interpreted as an additional Doppler blue shift. PACS Nos: 04.20.Cv, 95.55.Pe, 98.80.-k Nous demontrons que l'anomalie Pioneer apparait comme une consequence naturelle dans des modeles cosmologiques a vitesse de la lumiere variable, dans lesquels la vitesse de la lumiere est supposee etre une fonction en loi de puissance du facteur d'echelle (ou temps cosmique). En d'autres mots, l'anomalie de Pioneer peut etre vue comme un effet non gravitationnel de la diminution continuelle de la vitesse de la lumiere qui se presente elle-meme comme un delai anomal en temps de la propagation de la lumiere dans des referentiels locaux. Le delai en temps est alors interprete comme un deplacement additionnel vers le bleu. [Traduit par la Redaction], 1. Introduction An unexpected Doppler blue shift in the radio signals reaching the earth from the Pioneer 10 and 11 spacecrafts, when their distances from the Sun were between 20 [...]

CXO CDFS J033260.0-274748 is a quasi-stellar object (QSO) and identification of several emission lines observed in its optical spectrum has led to the determination of its redshift as 2.579. On the other hand, the Chandra ACIS-I spectrum has detected a strong absorption feature at the observed wavelength around 6.3 keV that cannot be identified under normal physical conditions. The authors have invoked an unusually large outflow bulk velocity of 0.7c-0.8c to explain the feature. However, such extraordinarily high bulk velocities are unprecedented in the extragalactic literature. We show here that the optical emission lines and the X-ray absorption feature can be identified with search lines of longer wavelengths that have been blueshifted and do not need any unusual physical conditions to be invoked. The blueshifted spectra are explained as being due to the net motion of the QSO along with the absorbing cloud towards the observer. Two scenarios are proposed, namely, the ejection mechanism and the multiverse. PACS Nos: 98.54.Aj, 98.62.Py, 98.90.-k CXO CDFS J033260.0-274748 est un quasar et l'identification de plusieurs raies d'emission observees dans son spectre optique nous indique un deplacement vers le rouge de 2,579. D'un autre cote, le spectrometre ACIS-I de Chandra a detecte une forte raie d'absorption a une longueur d'onde de 6,3 keV, qui ne peut etre identifiee dans des conditions normales. Les auteurs ont suggere une masse d'ejectats de vitesse 0,7c-0,8c, afin tenter d'expliquer ce phenomene. Cependant, une telle vitesse dans une masse d' ejectats est sans precedent dans la litterature extragalactique. Nous montrons que les raies d'emission optique et la raie d'absorption X peuvent etre expliquees comme des raies de plus grandes longueurs d'onde deplacees vers le bleu et qu' il n' est pas necessaire de faire appel a des caracteristiques physiques inhabituelles. Le deplacement vers le bleu des spectres peut s' expliquer par le mouvement net du quasar et du nuage absorbant vers l'observateur. Deux scenarios sont proposes : un mecanisme d'ejection ou un multivers. [Traduit par la Redaction], 1. Introduction The spectra of the object CXO CDFS J033260.0-274748 (hereinafter called CDFS11) are very unusual in the sense that its optical spectrum has led to the determination of its [...]

Most far-field optical imaging systems rely on lenses and spatially resolved detection to probe distinct locations on the object. We describe and demonstrate a high-speed wide-field approach to imaging that instead measures the complex spatial Fourier transform of the object by detecting its spatially integrated response to dynamic acousto-optically synthesized structured illumination. Tomographic filtered back-projection is applied to reconstruct the object in two or three dimensions. This technique decouples depth of field and working distance from resolution, in contrast to conventional imaging, and can be used to image biological and synthetic structures in fluoresced or scattered light employing coherent or broadband illumination. We discuss the electronically programmable transfer function of the optical system and its implications for imaging dynamic processes. We also explore wide-field fluorescence imaging in scattering media by coherence gating. Finally, we present two-dimensional high-resolution tomographic image reconstructions in both scattered and fluoresced light demonstrating a thousandfold improvement in the depth of field compared to conventional lens-based microscopy. [c] 2010 Optical Society of America OCIS codes: 110.0180, 110.6960, 110.4850, 180.6900, 180.1655, 180.2520.

Acoustic Doppler velocity meters (ADVMs) provide an alternative to more traditional flow measurement devices and procedures such as flumes, weirs, and stage rating for irrigation and drainage canals. However, the requirements for correct calibration are extensive and complex. A three-dimensional computational fluid dynamics (CFD) model was used to design a subcritical rapidly varied flow contraction that provides a consistent linear relationship between the upward-looking ADVM sample velocity and the cross-sectional average velocity in order to improve ADVM accuracy without the need for in situ calibration. CFD simulations validated the subcritical contraction in a rectangular and trapezoidal cross section by showing errors within +1.8 and -2.2%. Physical testing of the subcritical contraction coupled with an upward-looking ADVM in a large rectangular flume provided laboratory validation with measurement errors within [+ or -] 4% without calibration. DOI: 10.1061/(ASCE)IR.1943-4774.0000224 CE Database subject headings: Open channel flow; Subcritical flow; Flow measurement; Acoustic techniques; Doppler systems; Laboratory tests; Hydraulics. Author keywords: Open channel flow; Subcritical flow; Flow measurement; Acoustic techniques; Doppler systems; Laboratory tests; Hydraulics.

Ubiquitous radar systems look everywhere at all times and require both parallel radar processors and parallel beamformers. Current systems operate with subgigahertz bandwidths and produce a handful of angle-of-arrival (AOA) beams. We present an electro-optic radar processor that combines the multigigahertz wideband capabilities of a spectral hole burning correlator with wideband Doppler processing and the thousands of parallel channels available from an electro-optical beamformer. Preliminary experiments demonstrate 150 MHz bandwidth range correlations across 20 AOA beams. [c] 2010 Optical Society of America OCIS codes: 090.4220, 280.5110, 070.4340, 070.4550, 070.0070.

Spectral analysis of velocity signals recorded by acoustic Doppler velocimetry (ADV) and contaminated with intermittent spikes remains a challenging task. In this paper, we propose a new method for reconstructing contaminated time series which integrates two previously developed techniques for detecting and replacing spurious spikes. The spikes are first detected using a modified version of the universal phase-space-thresholding technique and subsequently replaced by the last valid data points. The accuracy of the new approach is evaluated by applying it to identify and remove spikes and reconstruct the spectra of two clean data sets which are artificially contaminated with random spikes: (1) high-quality hot-wire measurement and (2) numerically simulated velocity time series with bimodal probability density distribution. The technique is also applied to reconstruct the spectra obtained from intentionally contaminated ADV measurements and compare them with ADV spectra at the same point in the flow obtained using proper ADV settings. Special emphasis is placed on testing the ability of the technique to reproduce realistic power spectra in flows with rich coherent dynamics. The results show that the power spectra of the reconstructed time series contain a filtered white noise caused by the steps in the reconstruction technique using the last valid data point. We show that even for a severely contaminated time series, the proposed method can accurately recover the power spectra up to the frequency corresponding to the half the mean sampling rate of the valid data points. DOI: 10.1061/(ASCE)HY.1943-7900.0000202 CE Database subject headings: Acoustic techniques; Time series analysis; Open channel flow; Turbulence; Data analysis. Author keywords: Acoustic Doppler velocimetry; Time series reconstruction; Open-channel flow; Turbulence; Coherent structures.

Acoustic Doppler current profilers (ADCPs) are not able to accurately determine velocity near their transducers and near the bed. These limitations have restricted the use of ADCPs to flow depths that are large enough to allow acquisition of few directly measured velocity data that can be subsequently used to accurately estimate vertical velocity profiles and flow discharge in cross sections. While the causes that make ADCPs unable to collect data in the near-bed region are relatively well documented, the causes of near-transducer errors have not yet been fully understood and are only partly documented. We present results from an experimental study aimed at characterizing the systematic errors due to the combined effect of acoustic interference and instrument-induced flow disturbance near a Janus-configured ADCP. The study comprises: (1) concurrent measurements with an ADCP and an acoustic Doppler velocimeter (ADV) under the ADCP; (2) measurements of the flow disturbance produced by the ADCP in the vertical and horizontal planes; and (3) ADV measurements along the path of the acoustic beams ensonified by the ADCP during a measurement. Results suggest that ADCPs bias low the velocity profiles with respect to the undisturbed velocity profiles, mostly because of the flow disturbance induced by the ADCP, with acoustic effects playing a secondary role. For the range of flows we studied, both undisturbed and disturbed profiles exhibit similar shapes when plotted in dimensionless form, with the bulk flow velocity and the ADCP diameter (D) as characteristic scales. The differences between the undisturbed and the ADCP-disturbed profiles extend up to a distance of about 1.SD from the ADCP, except for the profiles measured at locations where the flow depth is close to D for which the boundary layer induced by the ADCP interacts with the one induced by the flume bed. DOI: 10.1061/(ASCE)HY.1943-7900.0000173 CE Database subject headings: Open channel flow; Flow measurement; Errors; Experimentation. Author keywords: Open-channel flow; River discharge; Flow measurements; Hydrometry; Acoustic Doppler current profilers; ADCP elemental errors; ADCP measurement uncertainty.

The redshift of the gamma-ray burst (GRB) GRB 011211 has been determined as 2.14 from several absorption lines seen in the spectrum of its optical afterglow. The spectrum of its X-ray afterglow exhibited several emission lines, and their identification led to a mean redshift 1.862. A supernova model has been proposed based on the redshift of the GRB as 2.141. It is shown here that the redshift interpretation cannot explain the observed spectra, as some serious inconsistencies exist in the process of redshift determinations in spectra of both optical and X-ray afterglows. In view of that, an alternative interpretation of the spectra is presented in terms of blueshifts. An ejection mechanism is proposed as a possible scenario to explain the blueshifted spectrum. PACS Nos: 98.38.Mz: 98.62Py, 98.80.-K Nous avons determine le decalage vers le rouge du sursaut gamma GRB) GRB 011211 comme etant 2,14, a partir de plusieurs lignes d'absorption dans spectre de l'emission remanente optique. Le spectre de l'emission remanente X a plusieurs lignes d'emission dont l'identification donne un decalage de 1,862. Sur la base du decalage de 2,141, il a ete propose que le sursaut etait du a une supernova. Nous montrons ici que l'interpretation du decalage ne peut expliquer le spectre observe, parce qu'il y a de serieuses incoherences dans le procede de determination des decalages des emissions remanentes optique et X. Par consequent, nous presentons une interpretation alternative des spectres a partir de decalages vers le bleu. Nous proposons un mecanisme d'ejection comme scenario d'explication du decalage vers le bleu. [Traduit par la Redaction], 1. Introduction Although the first gamma-ray burst (GRB) was discovered over thirty years ago [1], it is only in recent years that redshifts are being determined after their optical counterparts [...]

The imaging and quantification of droplet sizes in sprays is a challenging task for optical scientists and engineers. Laser sheet dropsizing (LSDS) combines the two-dimensional information of two different optical processes, one that is proportional to the droplet volume and one that depends on the droplet surface, e.g., Mie scattering. Besides Mie scattering, here we use two-dimensional Raman scattering as the volume-dependent measurement technique. Two different calibration strategies are presented and discussed. Two-dimensional droplet size distributions in a spray have been validated in comparison with the results of point-resolved phase Doppler anemometry (PDA) measurements. OCIS codes: 110.4190, 120.3940, 280.1100, 290.5850, 290.5860.

We present a dual-imaging technique combining laser speckle contrast imaging and spectral-domain Doppler optical coherence tomography to enable quantitative characterization of local cerebral blood flow (CBF) changes in rat cortex in response to drug stimulus (e.g., cocaine) at high spatiotemporal resolutions. To examine the utility of this new technique, animal experiments were performed to study the influences of anesthetic regimes (e.g., isoflurane, [alpha]-chloralose) on the pharmadynamic effects of acute cocaine challenge. The results showed that cocaine-evoked CBF patterns (e.g., increases in [alpha]-chloralose and decreases in isoflurane regimes) were quantitatively characterized, thus rendering it a potentially useful tool for imaging studies of brain functions. OCIS codes: 170.2655, 170.3340, 170.4500, 110.6150.

There are two factors responsible for the relativistic Doppler effect. One of these contributions is of first-order in the velocity of the light source relative to the observer and is non-relativistic in nature, but there is also a second-order (transverse Doppler) effect caused by the difference in rates of clocks at the source and in the laboratory (time dilation). It is pointed out that the traditional derivation for the relativistic Doppler effect based on the assumed Lorentz invariance of the phase of light waves is too restrictive. According to the latter argument, when two observers in relative motion send out signals to one another employing an identical light source, their respective measured Doppler shifts should always be the same (totally symmetric). However, an alternative derivation can also be given which indicates that the second-order contribution should in fact be anti-symmetric, although this analysis agrees with the conclusion that the corresponding first-order Doppler effect is symmetric. This is because there is a reciprocal relation between the ratios of the rates of the moving and rest clocks for the two observers. Quantitative calculations of the amount of the predicted anti-symmetry in transverse Doppler shifts are made for several examples on the basis of experimental data reported for the rates of atomic clocks carried onboard airplanes and rockets. Because of the Earth's rotation about its polar axis, the Doppler shifts can be measured in principle by using exclusively land-based atomic clocks located at widely different latitudes. Verification that the transverse Doppler frequency shifts are indeed antisymmetric would be a definitive confirmation that the oftcited symmetry principle of Einstein's special theory of relativity (STR) is incorrect, namely the claim that two observers in relative motion should each find that his/her clocks run faster than the other's. Finally, changes in the formulation of relativity theory that bring it into agreement with modern-day observations of variations in the rates of clocks with state of motion are discussed with reference to the methodology of the Global Positioning System (GPS). Keywords: transverse Doppler effect, time dilation, Global Positioning System, objectivity of measurement, remote simultaneity, Alternative Lorentz Transformation (ALT)., I. Introduction The relativistic Doppler effect differs from its classical counterpart in that there is not only a first-order effect depending on the speed of the source, but also one [...]

Two main aims of our investigation are to show differences in natural vibrations between two violins that differ in the thickness of the back plate and to determine whether they are linear systems. Two experiments were performed on the top and back plates. The first experiment was a mechanical modal analysis in a version with a fixed response point. In the second experiment optical measurements of the plate's velocities in modal frequencies obtained from the first experiment were performed by use of laser Doppler vibrometry. The second experiment was a simplified modal analysis experiment with a fixed excitation point. Changes in the thickness of the back plate caused changes in certain modal frequencies of both plates. However, no important differences in mode shapes were found in both experiments. Thus, violins can be treated as linear systems but with great care. OCIS codes: 120.7280, 280.3340.

Acousto-optic interaction between a narrow laser beam and acoustic waves in air is analyzed theoretically. The photoelastic relation in air is used to derive the phase modulation of laser light in air-coupled reflection vibrometry induced by angular spatial spectral components comprising the acoustic beam. Maximum interaction was found for the zero spatial acoustic component propagating normal to the laser beam. The angular dependence of the imaging efficiency is determined for the axial and nonaxial acoustic components with the regard for the laser beam steering in the scanning mode. The sensitivity of air-coupled vibrometry is compared with conventional 'Doppler' reflection vibrometry. Applications of the methodology for visualization of linear and nonlinear air-coupled fields are demonstrated. OCIS codes: 010.1300, 050.5080, 100.3175, 120.4290, 280.3340.

Laser spectroscopy experiments are often conducted with a probe that does not significantly alter the medium's properties. For a two-level atom a clear measure of the strength of a probe beam in terms of the saturation intensity is known. We show that for a multilevel atom the situation is very different, and the effects of optical pumping are crucial to understanding the opacity of the medium. We present a simple theoretical analysis for Doppler-broadened spectroscopy of alkali metals on the [D.sub.2] line that emphasizes the importance of the transient nature of the population dynamics, and the crucial role of the distribution of the times of flight of atoms through the probe beam. Experimental results are obtained with room temperature rubidium vapor probed by an extended-cavity diode laser and confirm our theoretical prediction. [DOI: 10.1119/1.3013197]

We report successful real-time three-channel self-mixing laser-Doppler measurements with extreme optical sensitivity using a laser-diode-pumped thin-slice Nd:GdV[O.sub.4] laser in the carrier-frequency-division-multiplexing scheme with three pairs of acoustic optical modulators (i.e., frequency shifters) and a three-channel FM-wave demodulation circuit. We demonstrate (1) simultaneous independent measurement of three different nanometer-vibrating targets, (2) simultaneous measurements of small particles in Brownian motion from three directions, and (3) identification of the velocity vector of small particles moving in water flowing in a small-diameter glass pipe. OCIS codes: 140.3480, 140.3580, 120.7280, 290.7050, 120.7250.

For monitoring the position and shape of fast moving and, especially, rotating objects such as turbo machine rotors, contactless and compact sensors with a high measurement rate as well as high precision are required. We present for the first time, to the best of our knowledge, a novel laser Doppler sensor employing a single fan-shaped interference fringe system, which allows measuring for the position and shape of fast moving solid bodies with known tangential velocity. It is shown theoretically as well as experimentally that this sensor offers concurrently high position resolution and high temporal resolution in contrast to conventional measurement techniques, since its measurement uncertainty is, in principle, independent of the object velocity. Moreover, it can be built very compact, because it features low complexity. To prove its operational capability and its potential for practical applications, radial and axial shape measurements of rotating bodies are demonstrated in comparison with triangulation. An average position resolution of about 2 [micro]m could be achieved. OCIS codes: 120.0280, 120.3940, 120.6650, 150.5495, 280.3340, 280.4788.

We report a novel experimental method to measure nanometer displacements using wavelength shifts of spectral peaks around spectral switch or singular phase points in the interference spectra due to temporal correlation in a Michelson interferometer illuminated by a broadband white-light source. Dramatic changes in the spectral characteristics are recorded as a function of path difference between the interfering beams around the spectral switch position. These are then compared with measurements far from it in order to demonstrate the higher sensitivities involved in the proposed method. OCIS codes: 120.3180, 120.3940, 260.3160.

A linear frequency-modulated continuous-wave (LFMCW) synthetic aperture radar (SAR) is a highly miniaturized SAR that is suitable for use on a small unmanned aerial vehicle. In squint stripmap mode, the LFMCW SAR image quality is degraded by the presence of nonlinearities in the transmitted signal, combined with the large bandwidth introduced by the frequency scaling in the nonlinear frequency scaling (NLFS) algorithm. This paper proposes an extension of the NLFS algorithm called the Doppler-centroid-dependent frequency scaling algorithm. The algorithm introduces a new Doppler-centroid-dependent scaling factor to decrease the introduced bandwidth, effectively removing the range frequency aliasing, without extra computational load. Nonlinearity correction is performed at the same time as range cell migration correction. The validity of the proposed algorithm is demonstrated with point target simulation results. Index Terms--Doppler centroid, frequency scaling algorithm, linear frequency-modulated continuous-wave (LFMCW) radar, synthetic aperture radar (SAR).

For micromotion targets with rotating parts, the inverse synthetic-aperture-radar image of the main body may be shadowed by the micro-Doppler. To solve this problem, this paper proposes an imaging algorithm based on the complex-valued empirical-mode decomposition. First, the radar echoes are decomposed into a series of complex-valued intrinsic-mode functions (IMFs). Then, the IMFs from the rotating parts and those from the main body are separated according to the characteristics of their zero-crossings. Finally, the well-focused imaging of the main body via traditional imaging algorithm and the accurate parameter estimation of the rotating part can be obtained. Both the imaging results for the simulated and measured data are given to verify the validity of the proposed algorithm. Index Terms--Empirical-mode decomposition (EMD), inverse synthetic aperture radar (ISAR), micro-Doppler (m-D).

This paper discusses temporal and phase synchronization in bistatic synthetic aperture radar (SAR) systems that use orbital sensors as coherent sources of opportunity and receivers at a fixed location. The discussion is particularized to SAR Bistatic Receiver for INterferometric Applications (SABR1NA), a ground-based bistatic receiver that uses ENVISAT and ERS-2 as transmitters. Transmitter--receiver synchronization is hindered by the presence of independent reference oscillators at the transmit and receive end and by the lack of a common time frame. Phase synchronization and pulse alignment are achieved using a dedicated channel that receives a clean signal directly from the satellite. How to align the acquired data with the satellite orbit and how to estimate the Doppler centroid (DC) are studied. It is shown that in the bistatic configuration considered, the receiver provides an implicit control point which limits the negative impact of a DC misestimation on the resulting images. An algorithm to achieve this temporal alignment using the apparent phase history of the received pulses is proposed. Finally, this algorithm is validated through Monte Carlo simulations and experimental data acquired by SABRINA. Index Terms--Bistatic radar, phase synchronization, synchronization, synthetic aperture radar (SAR).

For high-quality synthetic aperture radar (SAR) processing, Doppler centroid ambiguity resolving is an essential procedure. A novel method for the resolution of Doppler ambiguity is presented which exploits the fact that, in the compressed azimuth time and range frequency domain, all targets span the same range frequency bandwidth and exhibit the same slope which is just proportional to the Doppler ambiguity number. The slope is removed by interpolation so that a simplified Radon transform can be applied. The use of entropy to find the maximum concentration of the Radon-transformed image can improve the robustness of the method. The proposed method directly gives a reliable estimate of the Doppler ambiguity number and is not affected by the azimuth partially covered targets. Experimental results show that the proposed method works well in medium- to high-contrast scenes. Index Terms--Doppler ambiguity resolution, Doppler centroid estimation, entropy, Radon transform, synthetic aperture radar (SAR).

In this paper we present a laser sensor for highly spatially resolved flow imaging without using a camera. The sensor is an extension of the principle of laser Doppler anemometry (LDA). Instead of a parallel fringe system, diverging and converging fringes are employed. This method facilitates the determination of the tracer particle position within the measurement volume and leads to an increased spatial and velocity resolution compared to conventional LDA. Using a total number of four fringe systems the flow is resolved in two spatial dimensions and the orthogonal velocity component. Since no camera is used, the resolution of the sensor is not influenced by pixel size effects. A spatial resolution of 4 [micro]m in the x direction and 16 [micro]m in the y direction and a relative velocity resolution of 1 x [10.sup.-3] have been demonstrated up to now. As a first application we present the velocity measurement of an injection nozzle flow. The sensor is also highly suitable for applications in nano- and microfluidics, e.g., for the measurement of flow rates. OCIS codes: 120.3940, 120.7250, 170.3340.

We present a heterodyne Michelson interferometer for vibration measurement in which feedback is used to obviate the need to unwrap phase data. The Doppler shift of a vibrating target mirror is sensed interferometrically and compensated by means of a voltage-controlled oscillator driving an acousto-optic modulator. For frequencies within the servo bandwidth, the oscillator control voltage provides a direct measurement of the target velocity. Outside the servo bandwidth, phase-sensitive detection is used to evaluate high-frequency displacements. This approach is of great interest for the frequently-occurring situation where vibration amplitudes at low frequency exceed an optical wavelength, but knowledge of the vibration spectrum at high frequency is important as well. OCIS codes: 120.3180, 120.7250, 120.3930.

Under the condition of electromagnetically induced transparency, self-imaging in three-level A-type atoms at normal temperature is studied. The influences of the temperature on the position of the self-imaging and the corresponding imaging quality are discussed in detail. Numerical results show that, with the increase of the temperature, the location of the self-imaging linearly moves away from the original object, and the self-imaging quality decreases. OCIS codes: 270.5530, 080.2710, 110.2990.

The main goal of a satellite radar altimeter is to measure the height of the reflecting surface scanned by the passage of the instrument overhead. A delay/Doppler altimeter reduces the along-track footprint size by exploiting the coherence of the emitted pulses to synthetize a narrower antenna. Doppler beam formation is then a straightforward procedure that implies application of the discrete Fourier transform to time-domain bursts. Speckle and thermal noise on Doppler echoes are usually reduced using multilooking, i.e., summing incoherent contributions coming from different bursts. The summation of Doppler beams requires precise pointing toward output sample locations, particularly when highly variable topography is effective. However, the procedure of steering after beam sharpening needs a step of interpolation. In this paper, a Doppler beam sharpening and direction toward the sample position are presented which make use of the Chirp Zeta Transform to join the two operations together. This method must be compared with the existing ones to show that a little can be sacrificed to precision for computational gain. To support the discussion, experimental results will be compared with a precise--and so of reference--direct 2-D correlation algorithm over puntiform targets and more complex scenarios. Index Terms--Chirp Zeta Transform (CZT), delay/Doppler altimeter (DDA), Doppler beam sharpening.

We have implemented a tunable laser frequency lock with a wide recapture range and low sensitivity to temperature fluctuation, based on electronically power-normalized Doppler-broadened absorption spectra. The method requires no frequency modulation. A distributed-feedback diode laser locked to this system exhibits submegahertz stability over many hours. It has been used to magneto-optically trap rubidium atoms for a full day. OCIS codes: 140.3425, 300.1030, 020.7010.

Abstract: Simultaneous optical ground-based observations of auroral Balmer excited hydrogen atoms were performed during the boreal winters of 2002-2003 and 2003-2004 at Ny-Alesund, Svalbard (NYA 76.26°N 110.98°E geomagnetic) and Longyearbyen, [...]

A 4 x 4 pixel array with analog on-chip processing has been fabricated within a 0.35 [micro]m complementary metal oxide semiconductor process as a prototype sensor for laser Doppler blood flow imaging. At each pixel the bandpass and frequency weighted filters necessary for processing laser Doppler blood flow signals have been designed and fabricated. Because of the space constraints of implementing an accurate [[omega].sup.0.5] filter at the pixel level, this has been approximated using the 'roll off' of a high-pass filter with a cutoff frequency set at 10 kHz. The sensor has been characterized using a modulated laser source. Fixed pattern noise is present that is demonstrated to be repeatable across the array and can be calibrated. Preliminary blood flow results on a finger before and after occlusion demonstrate that the sensor array provides the potential for a system that can be scaled to a larger number of pixels for blood flow imaging. OCIS codes: 040.0040, 170.0170, 110.0110, 120.0120.

We demonstrate a dual wavelength acousto-optic deflector (AOD) designed to deflect two wavelengths to the same angles by driving with two RF frequencies. The AOD is designed as a beam scanner to address two-photon transitions in a two-dimensional array of trapped neutral [sup.87.Rb] atoms in a quantum computer. Momentum space is used to design AODs that have the same diffraction angles for two wavelengths (780 and 480 nm) and have nonoverlapping Bragg-matched frequency response at these wavelengths, so that there will be no cross talk when proportional frequencies are applied to diffract the two wavelengths. The appropriate crystal orientation, crystal shape, transducer size, and transducer height are determined for an AOD made with a tellurium dioxide crystal (Te[O.sub.2]). The designed and fabricated AOD has more than 100 resolvable spots, widely separated band shapes for the two wavelengths within an overall octave bandwidth, spatially overlapping diffraction angles for both wavelengths (780 and 480nm), and a 4~s or less access time. Cascaded AODs in which the first device upshifts and the second downshifts allow Doppler-free scanning as required for addressing the narrow atomic resonance without detuning. We experimentally show the diffraction-limited Doppler-free scanning performance and spatial resolution of the designed AOD. OCIS codes: 230.1040, 270.5585.

The new Doppler effect formula is derived within the framework of the recently proposed privileged system theory (PST). Comparing this formula with its SRT equivalent reveals a characteristic difference as [...]

We experimentally demonstrate two methods that improve the resolution of sub-Doppler spectroscopy using a 1 mm thick vapor cell. The linewidths of the observed spectra are approximately 1 order of magnitude narrower than the Doppler width. The first method involves using a 1 mm thick cell filled with Rb atomic vapor and two spatially separated laser beams. By employing the same principle, we also demonstrate that it is possible to achieve the same resolution by using the pump and probe pulses of a single beam. The latter method enables us to construct a simple and robust optical setup for sub-Doppler spectroscopy. OCIS codes: 300.6210, 300.6260.

The finescale structure and dynamics of cumulus, evolving from shallow to deep convection, and the accompanying changes in the environment and boundary layer over mountainous terrain were the subjects of a field campaign in July-August 2006. Few measurements exist of the transport of boundary layer air into the deep troposphere by the orographic toroidal circulation and orographic convection. The campaign was conducted over the Santa Catalina Mountains in southern Arizona, a natural laboratory to study convection, given the spatially and temporally regular development of cumulus driven by elevated heating and convergent boundary layer flow. Cumuli and their environment were sampled via coordinated observations from the surface, radiosonde balloons, and aircraft, along with airborne radar data and stereophotogrammetry from two angles. The collected dataset is expected to yield new insights in the boundary layer processes leading to orographic convection, in the cumulus-induced transport of boundary layer air into the troposphere, and in fundamental cumulus dynamics. This article summarizes the motivations, objectives, experimental strategies, preliminary findings, and the potential research paths stirred by the project.

We describe the concept of Doppler asymmetric spatial heterodyne spectroscopy (DASH) and present a laboratory Doppler-shift measurement using an infrared laser line. DASH is a modification of spatial heterodyne spectroscopy optimized for high precision, high accuracy Doppler-shift measurements of atmospheric emission lines either from the ground or a satellite. We discuss DASH design considerations, field widening, thermal stability and tracking, noise propagation, advantages, and trade-offs. DASH interferometers do not require moving optical parts and can be built in rugged, compact packages, making them suitable for space flight and mobile ground instrumentation. OCIS codes: 300.6300, 120.6200, 120.2650.

Similar in principle to recent implementations of a lidar system at 355 nm [Opt. Lett. 25, 1231 (2000), Appl. Opt. 44, 6023 (2005)], an incoherent-detection Mie Doppler wind lidar at 1064 nm was developed and deployed in 2005 [Opt. Rev. 12, 409 (2005)] for wind measurements in the low troposphere, taking advantage of aerosol scattering for signal enhancement. We present a number of improvements made to the original 1064 nm system to increase its robustness for long-period operation. These include a multimode fiber for receiving the reference signal, a mode scrambler to allow uniform illumination over the Fabry-Perot interferometer, and a fast scannable Fabry-Perot interferometer for calibration and for the determination of outgoing laser frequency during the wind observation. With these improvements in stability, the standard deviation of peak transmission and FWHM of the Fabry--Perot interferometer was determined to be 0.49% and 0.36%, respectively. The lidar wind measurements were validated within a dynamic range of [+ or -] 40 m/s. Comparison experiments with both wind profiler radar and Vaisala wiresonde show good agreement with expected observation error. An example of 24 h continuous observations of wind field and aerosol backscatter coefficients in the boundary layer with 1 min and 30 m temporal and spatial resolution and 3 m/s tolerated wind velocity error is presented and fully demonstrates the stability and robustness of this lidar. OCIS codes: 010.0010, 010.3640, 280.0280, 280.3340, 280.1100.

The performance of an approximately multiaccess interference (MAI)-free multiaccess precoded multiuser orthogonal frequency division multiplexing (PMU-OFDM) system in a mobile environment, where the channel response changes within one OFDM symbol due to the Doppler effect, is analyzed. The results have shown that the performance of PMU-OFDM is better than OFDMA in a mobile environment in terms of bit error probability (BEP) performance.

The effect of the intramolecular C-H..O contact is investigated for 3-methylacroeine and 3-(difluoromethyl)acroleine in the chelate-type (ZZ) conformation. The results are interpreted in terms of the steric compression and this mechanism has indicated that blue-shifting intramolecular interactions are not uncommon.

Synthetic aperture radar (SAR) provides high-resolution images of static ground scenes, whereas processing of data containing ground object motion results in varying focusing effects. Special cases of such motion are vibration and rotation, which are closely related to each other. Their patterns may be distinctly recognizable in focused SAR intensity images as well as in a time-frequency analysis. Millimeter-wave (mmW) SAR is well suited to image vibration because its wavelength is close to typical vibration amplitudes. Through a thorough motion analysis in a standard SAR system model, we show the effects of rotation and vibration in mmW SAR theoretically and in simulated and real data. Index Terms--Micro-Doppler, millimeter-wave (mmW) radar, synthetic aperture radar (SAR), time-frequency analysis.

The multilook beat frequency (MLBF) algorithm is the Doppler centroid estimator most commonly used in practice to solve the Doppler ambiguity. However, it still makes errors, notably in medium- or low-contrast scenes. In this paper, we present two ways in which the estimation sensitivity of the MLBF algorithm can be improved. First, we give a more thorough frequency-domain explanation of how the MLBF algorithm works and explain how cross beating and range migration cause estimation difficulties. The first improvement to the algorithm replaces the fast Fourier transform (FFT)-based beat frequency estimator with a more accurate one that uses phase increments. It avoids the FFT limitations of resolution and quantization, especially when the signal is discontinuous in one range cell due to range cell migration or burst mode operation (SeanSAR). A second improvement uses range cell migration correction to straighten the target trajectories before the beat frequency estimator is applied. This has the effect of narrowing the bandwidth of the beat signal and reducing the effect of cross beating. Finally, experiments with RADARSAT-I data are used to illustrate the improved estimation accuracy of the modified algorithm. Index Terms--Burst mode SAR, Doppler ambiguity resolution, Doppler centroid estimation, frequency estimation, multilook beat frequency (MLBF), range cell migration correction (RCMC), SAR antenna pointing angle, ScanSAR, synthetic aperture radar (SAR).

The Doppler broadening of audio spectral lines is demonstrated using a simple experimental setup. The sound from a vibrating loudspeaker is received by a microphone that is connected to a computer sound card. A data-acquisition program is used to acquire the sound data. Fourier analysis is done to obtain the spectral power density of the sound received by the microphone. The results demonstrate spectral broadening similar to that which takes place in atomic and molecular spectroscopy. The experiment demonstrates both the Doppler effect and spectral broadening in the undergraduate physics lab. [DOI: 10.1119/1.2372466]

The interpretation of the expanding universe as an expansion of space has recently been challenged. From the geodesic equation in Friedmann universe models and the empty Milne model, we argue that a Newtonian or special relativistic analysis is not applicable on large scales, and the general relativistic interpretation in terms of expanding space has the advantage of being globally consistent. We also show that the cosmic redshift, interpreted as an expansion effect, contains both the Doppler effect and the gravitational frequency shift. [DOI: 10.1119/1.2360990]

In this study, ophthalmic arterial Doppler signals recorded from 214 subjects were processed using classical, modelbased, and eigenvector methods. The classical method (fast Fourier transform), two model-based methods (Burg autoregressive, least squares modified Yule Walker autoregressive moving average methods), and three eigenvector methods (Pisarenko, multiple signal classification, and Minimum-Norm methods) were selected for performing spectral analysis of the ophthalmic arterial Doppler signals. Doppler power spectral density estimates of the ophthalmic arterial Doppler signals were obtained using these spectrum analysis techniques. The variations in the shape of the Doppler power spectra were examined in order to detect variabilities such as stenosis, ocular Behcet disease, and uveitis disease in the physical state of ophthalmic arterial Doppler signals. These power spectra were then used to compare the applied methods in terms of their frequency resolution and the effects in detecting stenosis, Behcet disease and uveitis disease in ophthalmic arteries. Keywords: Doppler signal; Spectral analysis; Power spectral density; Ophthalmic arterial disorders

Abstract: Backscatter data from moored acoustic Doppler current profilers (ADCPs) are analysed to quantify the diel vertical migration patterns of zooplankton on the Newfoundland Shelf, Canada. Data from 11 moorings [...]

Two model systems are designed and synthesized for neutral retinal Schiff base chromophore and a photofragmentation method is used to measure their gas-phase absorption spectra in the electrostatic storage ring Aarhus (ELISA). The effect of approaching a positive charge to the Schiff base is studied along with the susceptibility of the protonated and unprotonated chromophores to experience spectral shifts in different solvents.

Ab initio molecular orbital and density functional theory (DFT) with the 6-311++G(2d,2p) basis set is used to investigate the hydrogen bonding interactions of the HNO dimer and partial optimizations are performed to establish the interrelationship between one N-H...O hydrogen bond and the other N-H...O hydrogen bond. The NBO analysis shows that both rehybridization and electric density redistribution contribute to the large blue-shifts of the N-H stretching frequencies.

In this paper we discuss the combined use of a priori information and adaptive signal processing techniques for the design and the analysis of a knowledge-aided (KA) radar receiver for Doppler processing. To this end, resorting to the generalized likelihood function (GLF) criterion (both one-step and two-step), we design and assess data-adaptive procedures for the selection of training data. Then we introduce a KA radar detector composed of three elements: a geographic-map-based data selector, which exploits some a priori information concerning the topography of the observed scene, a data-adaptive training selector which removes dynamic outliers from the training data, and an adaptive radar detector which performs the final decision about the target presence. The performance of the KA algorithm is analyzed both on simulated as well as on real radar data collected by the McMaster University IPIX radar. The results show that the new KA system achieves a satisfactory performance level and can outperform some previously proposed adaptive detection schemes.